| 1. |
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| 2. |
- Abramova, Anna, 1990, et al.
(författare)
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CAFE: a software suite for analysis of paired-sample transposon insertion sequencing data
- 2021
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Ingår i: Bioinformatics. - : Oxford University Press (OUP). - 1367-4803 .- 1460-2059. ; 37:1, s. 121-122
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Tidskriftsartikel (refereegranskat)abstract
- Sequencing of transposon insertion libraries is used to determine the relative fitness of individual mutants at a large scale. However, there is a lack of tools for specifically analyzing data from such experiments with paired sample designs. Here, we introduce CAFE-Coefficient-based Analysis of Fitness by read Enrichment-a software package that can analyze data from paired transposon mutant sequencing experiments, generate fitness coefficients for each gene and condition and perform appropriate statistical testing on these fitness coefficients.
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| 3. |
- Alterbeck, Max, et al.
(författare)
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Designing and Implementing a Population-based Organised Prostate Cancer Testing Programme.
- 2022
-
Ingår i: European urology focus. - : Elsevier BV. - 2405-4569. ; 8:6, s. 1568-1574
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Tidskriftsartikel (refereegranskat)abstract
- European guidelines recommend that well-informed men at elevated risk of having prostate cancer (PCa) should be offered prostate-specific antigen (PSA) testing with risk-stratified follow-up. The Swedish National Board of Health and Welfare recommends against screening for PCa but supports regional implementation of organised prostate cancer testing (OPT).To report the process for designing and implementing OPT programmes.Population-based OPT programmes in two Swedish regions, designed to include men aged between 50 and 74 yr, launched in September 2020 for 50-yr-old men.The number of men invited, the participation rate, and the numbers of magnetic resonance imaging (MRI) scans, urological visits, and biopsies from September 2020 to June 2021 were recorded.Two Swedish regions co-designed an OPT programme with a risk-stratified diagnostic algorithm based on prostate-specific antigen (PSA), PSA density, MRI findings, and age. An automated administrative system was developed on a nationwide web-based platform. Invitation letters and test results are automatically generated and sent out by post. Men with PSA ≥3ng/ml, a suspicious MRI lesion, and/or PSA density ≥0.15ng/ml/cm3 are referred for a prostate biopsy. Test results are registered for quality control and research. By June 2021, a total of 16515 men were invited, of whom 6309 (38%) participated; 147 had an MRI scan and 39 underwent prostate biopsy. The OPT framework, algorithm, and diagnostic pathways have been working well.We designed and implemented a framework for OPT with a high grade of automation. The framework and organisational experiences may be of value for others who plan a programme for early detection of PCa.We describe the implementation of an organised testing programme for early detection of prostate cancer in two Swedish regions. This model is the first of its kind and may serve as a template for similar programmes.
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| 4. |
- Andersson, Tobias, 1976, et al.
(författare)
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The effect of statins on mortality and cardiovascular disease in primary care hypertensive patients without other cardiovascular disease or diabetes.
- 2023
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Ingår i: European journal of preventive cardiology. - 2047-4881. ; 30:17, s. 1883-1894
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Tidskriftsartikel (refereegranskat)abstract
- Studies in primary health care (PHC) assessing the effect of primary prevention with statins on mortality and cardiovascular disease (CVD) are scarce. This study aimed to estimate the effect of statins on all-cause mortality, cardiovascular mortality, myocardial infarction (MI) and stroke in individuals in PHC with hypertension without CVD or diabetes.Using the Swedish PHC quality assurance register QregPV, the study included 13 193 individuals with hypertension without CVD or diabetes, who had filled a first statin prescription between 2010 and 2016, and 13 193 matched controls without a filled statin prescription at index date. Controls were matched on sex and propensity score using clinical data and data from national registers on co-morbidities, prescriptions, and socioeconomic status. The effect of statins was estimated in Cox regression models.During a median of 4.2 years of follow-up, 395 individuals in the statin group versus 475 in the control group died, 197 versus 232 died of cardiovascular disease, 171 versus 191 had a MI, and 161 versus 181 had a stroke. The treatment effect of statins was significant for all-cause mortality (HR 0.83, 95% confidence interval [CI] 0.74-0.93) and cardiovascular mortality (HR 0.85, 95% CI 0.72-0.998). Overall, no significant treatment effect of statins was seen for MI (HR 0.89, 95% CI 0.74-1.07), but there was a significant interaction with sex (p=0.008) with decreased risk of MI for women but not for men (HR 0.66, 95% CI 0.49-0.88 versus HR 1.09, 95% CI 0.86-1.38).Primary prevention with statins in PHC was associated with reduced risk of all-cause mortality, cardiovascular mortality, and in women, lower risk of MI.
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| 5. |
- Bager, Johan-Emil, et al.
(författare)
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Blood pressure levels and risk of haemorrhagic stroke in patients with atrial fibrillation and oral anticoagulants: results from The Swedish Primary Care Cardiovascular Database of Skaraborg.
- 2021
-
Ingår i: Journal of hypertension. - 1473-5598. ; 39:8, s. 1670-1677
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Tidskriftsartikel (refereegranskat)abstract
- To assess the risk of haemorrhagic stroke at different baseline SBP levels in a primary care population with hypertension, atrial fibrillation and newly initiated oral anticoagulants (OACs).We identified 3972 patients with hypertension, atrial fibrillation and newly initiated OAC in The Swedish Primary Care Cardiovascular Database of Skaraborg. Patients were followed from 1 January 2006 until a first event of haemorrhagic stroke, death, cessation of OAC or 31 December 2016. We analysed the association between continuous SBP and haemorrhagic stroke with a multivariable Cox regression model and plotted the hazard ratio as a function of SBP with a restricted cubic spline with 130mmHg as reference.There were 40 cases of haemorrhagic stroke during follow-up. Baseline SBP in the 145-180mmHg range was associated with a more than doubled risk of haemorrhagic stroke, compared with a SBP of 130mmHg.In this cohort of primary care patients with hypertension and atrial fibrillation, we found that baseline SBP in the 145-180mmHg range, prior to initiation of OAC, was associated with a more than doubled risk of haemorrhagic stroke, as compared with an SBP of 130mmHg. This suggests that lowering SBP to below 145mmHg, prior to initiation of OAC, may decrease the risk of haemorrhagic stroke in patients with hypertension and atrial fibrillation.
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| 6. |
- Bager, Johan-Emil, et al.
(författare)
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Hypertension: sex-related differences in drug treatment, prevalence and blood pressure control in primary care.
- 2023
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Ingår i: Journal of human hypertension. - : Springer Science and Business Media LLC. - 1476-5527. ; 37, s. 662-670
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Forskningsöversikt (refereegranskat)abstract
- Antihypertensive treatment is equally beneficial for reducing cardiovascular risk in both men and women. Despite this, the drug treatment, prevalence and control of hypertension differ between men and women. Men and women respond differently, particularly with respect to the risk of adverse events, to many antihypertensive drugs. Certain antihypertensive drugs may also be especially beneficial in the setting of certain comorbidities - of both cardiovascular and extracardiac nature - which also differ between men and women. Furthermore, hypertension in pregnancy can pose a considerable therapeutic challenge for women and their physicians in primary care. In addition, data from population-based studies and from real-world data are inconsistent regarding whether men or women attain hypertension-related goals to a higher degree. In population-based studies, women with hypertension have higher rates of treatment and controlled blood pressure than men, whereas real-world, primary-care data instead show better blood pressure control in men. Men and women are also treated with different antihypertensive drugs: women use more thiazide diuretics and men use more angiotensin-enzyme inhibitors and calcium-channel blockers. This narrative review explores these sex-related differences with guidance from current literature. It also features original data from a large, Swedish primary-care register, which showed that blood pressure control was better in women than men until they reached their late sixties, after which the situation was reversed. This age-related decrease in blood pressure control in women was not, however, accompanied by a proportional increase in use of antihypertensive drugs and female sex was a significant predictor of less intensive antihypertensive treatment.
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| 7. |
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| 8. |
- Bengtsson, Mats, et al.
(författare)
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CELTIC CP5-026 WINNER+, D1.4 Initial Report on Advanced Multiple Antenna Systems
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable captures the first set of best innovative concepts identified in the field of Advanced Multiple Antenna Systems for potential inclusion into the WINNER+ system concept. The concepts consist of promising principles or ideas as well as detailed innovative techniques. For each concept, the associated benefits as well as the corresponding requirements on the system architecture and protocols, measurements and signalling, are considered. The document involves two main tracks: development of new advanced antenna schemes in the context of conventional cellular networks, and a study of coordinated multipoint transmission and reception, where multiple network nodes cooperate to enhance system performance.
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| 9. |
- Björnson, Emil, et al.
(författare)
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Capacity Limits and Multiplexing Gains of MIMO Channels with Transceiver Impairments
- 2013
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Ingår i: IEEE Communications Letters. - : IEEE Communications Society. - 1089-7798 .- 1558-2558. ; 17:1, s. 91-94
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Tidskriftsartikel (refereegranskat)abstract
- The capacity of ideal MIMO channels has a high-SNR slope that equals the minimum of the number of transmit and receive antennas. This letter analyzes if this result holds when there are distortions from physical transceiver impairments. We prove analytically that such physical MIMO channels have a finite upper capacity limit, for any channel distribution and SNR. The high-SNR slope thus collapses to zero. This appears discouraging, but we prove the encouraging result that the relative capacity gain of employing MIMO is at least as large as with ideal transceivers.
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| 10. |
- Björnson, Emil, 1983-, et al.
(författare)
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Computational Framework for Optimal Robust Beamforming in Coordinated Multicell Systems
- 2011
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Ingår i: Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP). - : IEEE Signal Processing Society. - 9781457721045 ; , s. 245-248
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Konferensbidrag (refereegranskat)abstract
- Coordinated beamforming can significantly improvethe performance of cellular systems through joint interferencemanagement. Unfortunately, such beamforming optimization problems are typically NP-hard in multicell scenarios, making heuristic beamforming the only feasible choice in practice. Thispaper proposes a new branch-reduce-and-bound algorithm thatsolves such optimization problems globally, with a complexitysuitable for benchmarking and analysis. Compared to priorwork, the framework handles robustness to uncertain intercell interference and numerical analysis shows higher efficiency.
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| 11. |
- Björnson, Emil, 1983-, et al.
(författare)
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Feedback design in multiuser MIMO systems using quantization splitting and hybrid instantaneous/statistical channel information
- 2008
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Ingår i: ICT-MobileSummit 2008 Conference Proceedings. - : IIMC International Information Management Corporation. - 9781905824083
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Konferensbidrag (refereegranskat)abstract
- In the design of next generation multiuser communication systems, multiple antenna transmission is an essential part providing spatial multiplexing gain and allowing efficient use of resources. A major limiting factor in the resource allocation is the amount of channel state information (CSI) available at the transmitter, particularly in multiuser systems where the feedback from each user terminal must be limited. To this effect we propose two independent approaches for an efficient representation of the channel in multiuser MIMO systems. In the first approach, channel quantization is considered where the total number of feedback bits is limited. A resource allocation scheme is proposed where the available rate is split between the scheduling phase, where all users feed back a coarse CSI quantization, and the precoding phase where the selected receivers refine their CSI. The optimum splitting of the available feedback rate provides a large increase in performance and even simple heuristic splitting gives a noticeable advantage. In the second approach, we exploit a combination of instantaneous and statistical channel information. For spatially correlated Rayleigh and Ricean channels, it is shown that the CSI to large extent can be represented by the channel norm when the long-term channel statistics are known. Within a minimum mean square error (MMSE) estimation framework, feedback of a few bits of the quantized channel norm is sufficient to perform efficient resource allocation and achieve performance close to that of full CSI.
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| 12. |
- Björnson, Emil, 1983-
(författare)
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Multiantenna Cellular Communications : Channel Estimation, Feedback, and Resource Allocation
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of multiple antennas at base stations and user devices is a key component in the design of cellular communication systems that can meet the capacity demands of tomorrow. The downlink transmission from base stations to users is particularly limiting, both from a theoretical and a practical perspective, since user devices should be simple and power-efficient, and because many applications primarily create downlink traffic (e.g., video streaming). The potential gain of employing multiple antennas for downlink transmission is well recognized: the total data throughput increases linearly with the number of transmit antennas if the spatial dimension is exploited for simultaneous transmission to multiple users. In the design of practical cellular systems, the actual benefit of multiuser multiantenna transmission is limited by a variety of factors, including acquisition and accuracy of channel information, transmit power, channel conditions, cell density, user mobility, computational complexity, and the level of cooperation between base stations in the transmission design. The thesis considers three main components of downlink communications: 1) estimation of current channel conditions using training signaling; 2) efficient feedback of channel estimates; and 3) allocation of transmit resources (e.g., power, time and spatial dimensions) to users. In each area, the thesis seeks to provide a greater understanding of the interplay between different system properties. This is achieved by generalizing the underlying assumptions in prior work and providing both extensions of previous outcomes and entirely new mathematical results, along with supporting numerical examples. Some of the main thesis contributions can be summarized as follows. A framework is proposed for estimation of different channel quantities using a common optimized training sequence. Furthermore, it is proved that each user should only be allocated one data stream and utilize its antennas for receive combining and interference rejection, instead of using the antennas for reception of multiple data streams. This fundamental result is proved under both exact channel acquisition and under imperfections from channel estimation and limited feedback. This also has positive implications on the hardware and system design. Next, a general mathematical model is proposed for joint analysis of cellular systems with different levels of base station cooperation. The optimal multicell resource allocation can in general only be found with exponential computational complexity, but a systematic algorithm is proposed to find the optimal solution for the purpose of offline benchmarking. A parametrization of the optimal solution is also derived, creating a foundation for heuristic low-complexity algorithms that can provide close-to-optimal performance. This is exemplified by proposing centralized and distributed multicell transmission strategies and by evaluating these using multicell channel measurements.
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| 13. |
- Björnson, Emil, 1983-, et al.
(författare)
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Optimal Coordinated Beamforming in the Multicell Downlink with Transceiver Impairments
- 2012
-
Ingår i: 2012 IEEE Global Telecommunications Conference (GLOBECOM). - New York : IEEE conference proceedings. - 9781467309219 ; , s. 4775-4780
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Konferensbidrag (refereegranskat)abstract
- Physical wireless transceivers suffer from a variety of impairments that distort the transmitted and received signals. Their degrading impact is particularly evident in modern systems with multiuser transmission, high transmit power, and low-cost devices, but their existence is routinely ignored in the optimization literature for multicell transmission. This paper provides a detailed analysis of coordinated beamforming in the multicell downlink. We solve two optimization problems under a transceiver impairment model and derive the structure of the optimal solutions. We show numerically that these solutions greatly reduce the impact of impairments, compared with beamforming developed for ideal transceivers. Although the so-called multiplexing gain is zero under transceiver impairments, we show that the gain of multiplexing can be large at practical SNRs.
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| 14. |
- Björnson, Emil, et al.
(författare)
-
Optimal Multiuser Transmit Beamforming : A Difficult Problem with a Simple Solution Structure
- 2014
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Ingår i: IEEE signal processing magazine (Print). - : Institute of Electrical and Electronic Engineers. - 1053-5888 .- 1558-0792. ; 31:4, s. 142-148
-
Tidskriftsartikel (refereegranskat)abstract
- Transmit beamforming is a versatile technique for signal transmission from an array of antennas to one or multiple users [1]. In wireless communications, the goal is to increase the signal power at the intended user and reduce interference to nonintended users. A high signal power is achieved by transmitting the same data signal from all antennas but with different amplitudes and phases, such that the signal components add coherently at the user. Low interference is accomplished by making the signal components add destructively at nonintended users. This corresponds mathematically to designing beamforming vectors (that describe the amplitudes and phases) to have large inner products with the vectors describing the intended channels and small inner products with nonintended user channels.
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| 15. |
- Björnson, Emil, 1983-, et al.
(författare)
-
Optimality Properties and Low-Complexity Solutions to Coordinated Multicell Transmission
- 2010
-
Ingår i: 2010 IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE GLOBECOM 2010. - : IEEE. - 9781424456383 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Base station cooperation can theoretically improve the throughput of multicell systems by coordinating interference and serving cell edge terminals through multiple base stations. In practice, the extent of cooperation is limited by the increase in backhaul signaling and computational demands. To address these concerns, we propose a novel distributed cooperation structure where each base station has responsibility for the interference towards a set of terminals, while only serving a subset of them with data. Weighted sum rate maximization is considered, and conditions for beamforming optimality and the optimal transmission structure are derived using Lagrange duality theory. This leads to distributed low-complexity transmission strategies, which are evaluated on measured multiantenna channels in a typical urban multicell environment.
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| 16. |
- Björnson, Emil, 1983-, et al.
(författare)
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Optimality Properties, Distributed Strategies, and Measurement-Based Evaluation of Coordinated Multicell OFDMA Transmission
- 2011
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 59:12, s. 6086-6101
-
Tidskriftsartikel (refereegranskat)abstract
- The throughput of multicell systems is inherently limited by interference andthe available communication resources. Coordinated resource allocation is the key to efficient performance, but the demand on backhaul signaling andcomputational resources grows rapidly with number of cells, terminals, andsubcarriers. To handle this, we propose a novel multicell framework with dynamic cooperation clusters where each terminal is jointly served by a small set of base stations. Each base station coordinates interference to neighboring terminals only, thus limiting backhaul signalling and making the framework scalable. This framework can describe anything from interference channels to ideal joint multicell transmission. The resource allocation (i.e., precoding and scheduling) is formulated as an optimization problem (P1) with performance described by arbitrary monotonic functions of the signal-to-interference-and-noise ratios (SINRs) and arbitrary linear power constraints. Although (P1) is nonconvex and difficult to solve optimally, we are able to prove: 1) optimalityof single-stream beamforming; 2) conditions for full power usage; and 3) a precoding parametrization based on a few parameters between zero and one. These optimality properties are used to propose low-complexity strategies: both a centralized scheme and a distributed version that only requires local channel knowledge and processing. We evaluate the performance on measuredmulticell channels and observe that the proposed strategies achieve close-to-optimal performance among centralized and distributed solutions, respectively. In addition, we show that multicell interference coordination can give substantial improvements in sum performance, but that joint transmission is very sensitive to synchronization errors and that some terminals can experience performance degradations.
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| 17. |
- Björnson, Emil, et al.
(författare)
-
Pareto characterization of the multicell MIMO performance region with simple receivers
- 2012
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 60:8, s. 4464-4469
-
Tidskriftsartikel (refereegranskat)abstract
- We study the performance region of a general multicell downlink scenario with multiantenna transmitters, hardware impairments, and low-complexity receivers that treat interference as noise. The Pareto boundary of this region describes all efficient resource allocations, but is generally hard to compute. We propose a novel explicit characterization that gives Pareto optimal transmit strategies using a set of positive parameters-fewer than in prior work. We also propose an implicit characterization that requires even fewer parameters and guarantees to find the Pareto boundary for every choice of parameters, but at the expense of solving quasi-convex optimization problems. The merits of the two characterizations are illustrated for interference channels and ideal network multiple-input multiple-output (MIMO).
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| 18. |
- Björnson, Emil, et al.
(författare)
-
Receive Combining vs. Multi-Stream Multiplexing in Downlink Systems With Multi-Antenna Users
- 2013
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 61:13, s. 3431-3446
-
Tidskriftsartikel (refereegranskat)abstract
- In downlink multi-antenna systems with many users, the multiplexing gain is strictly limited by the number of transmit antennas and the use of these antennas. Assuming that the total number of receive antennas at the multi-antenna users is much larger than, the maximal multiplexing gain can be achieved with many different transmission/reception strategies. For example, the excess number of receive antennas can be utilized to schedule users with effective channels that are near-orthogonal, for multi-stream multiplexing to users with well-conditioned channels, and/or to enable interference-aware receive combining. In this paper, we try to answer the question if the data streams should be divided among few users (many streams per user) or many users (few streams per user, enabling receive combining). Analytic results are derived to show how user selection, spatial correlation, heterogeneous user conditions, and imperfect channel acquisition (quantization or estimation errors) affect the performance when sending the maximal number of streams or one stream per scheduled user-the two extremes in data stream allocation. While contradicting observations on this topic have been reported in prior works, we show that selecting many users and allocating one stream per user (i.e., exploiting receive combining) is the best candidate under realistic conditions. This is explained by the provably stronger resilience towards spatial correlation and the larger benefit from multi-user diversity. This fundamental result has positive implications for the design of downlink systems as it reduces the hardware requirements at the user devices and simplifies the throughput optimization.
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| 19. |
- Björnson, Emil, 1983-, et al.
(författare)
-
Receive combining vs. multistream multiplexing in multiuser MIMO systems
- 2011
-
Ingår i: Communication Technologies Workshop (Swe-CTW), 2011 IEEE Swedish. - : IEEE Communications Society. - 9781457718779 ; , s. 103-108
-
Konferensbidrag (refereegranskat)abstract
- In single-user transmission, the receive antennas should preferably be used to enable multiplexing. The situation is different under multiuser transmission, where only the number of transmit antennas limits the multiplexing gain. The system therefore has the choice between sending one stream per scheduled user (i.e., combining receive antennas for diversity) or selecting a smaller number of users and multiplex multiple streams to each of them. This tradeoff is investigated herein, based on zero-forcing (with receive antenna combining) and block-diagonalization precoding which represents the two extremes. Based on asymptotic analysis and numerical examples, the unexpected conclusion is that each user only should receive one stream and use its antennas to achieve a receive combining gain. This is explained by zero-forcing having a stronger resilience towards spatial correlation and larger benefit from multiuser diversity. This fundamental result has positive implications for the design of multiuser systems as it reduces the hardware constraints at the user devices.
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| 20. |
- Björnson, Emil, 1983-, et al.
(författare)
-
Robust Monotonic Optimization Framework for Multicell MISO Systems
- 2012
-
Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 60:5, s. 2508-2523
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Tidskriftsartikel (refereegranskat)abstract
- The performance of multiuser systems is both difficult to measure fairly and to optimize. Most resource allocation problems are nonconvex and NP-hard, even under simplifying assumptions such as perfect channel knowledge, homogeneous channel properties among users, and simple power constraints. We establish a general optimization framework that systematically solves these problems to global optimality. The proposed branch-reduce-and-bound (BRB) algorithm handles general multicell downlink systems with single-antenna users, multiantenna transmitters, arbitrary quadratic power constraints, and robustness to channel uncertainty. A robust fairness-profile optimization (RFO) problem is solved at each iteration, which is a quasiconvex problem and a novel generalization of max-min fairness. The BRB algorithm is computationally costly, but it shows better convergence than the previously proposed outer polyblock approximation algorithm. Our framework is suitable for computing benchmarks in general multicell systems with or without channel uncertainty. We illustrate this by deriving and evaluating a zero-forcing solution to the general problem.
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| 21. |
- Bohlin, Alexis, et al.
(författare)
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Direct measurement of S-branch N(2)-H(2) Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy.
- 2012
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:7
-
Tidskriftsartikel (refereegranskat)abstract
- S-branch N(2)-H(2) Raman linewidths have been measured in the temperature region 294-1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N(2) RCARS spectra recorded in binary mixtures of N(2) and H(2) at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N(2) CARS thermometry on the fuel-side of H(2) diffusion flames.
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| 22. |
- Bohlin, Alexis, et al.
(författare)
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On the sensitivity of rotational O2 CARS thermometry to the Herman-Wallis factor
- 2012
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- Contributions of vibrationrotation interaction to line intensities of pure rotational coherent anti-Stokes Raman scattering (CARS) of oxygen are here considered in the perspective of what was remarked by us recently for nitrogen. The interaction is conventionally evaluated by means of the so-called HermanWallis (HW) factor, the need of which is conceptually clear but the theoretical expression is debatable, as shown in the literature of this field. In this work, the various solutions for the anisotropic HW factor of pure rotational Raman transitions are compared in light of the implications for the corresponding CARS spectral line intensities. The results show that neglecting the use of HW factors in rotational N2 and O2 CARS thermometry leads to systematic overestimation of temperatures; on the order of 1.5% in the temperature range 300-2100K in comparison with the use of the most plausible HW factors. The results also suggest that, in general, oxygen is more sensitive than nitrogen to the HW correction, and in particular, different S-branch HW expressions for oxygen are responsible for thermometric uncertainties between 0.5% and 1% at flame temperatures. Copyright (c) 2012 John Wiley & Sons, Ltd.
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| 23. |
- Bohlin, Alexis, et al.
(författare)
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Pure rotational CARS measurements of temperature and O2-concentration in a low swirl turbulent premixed flame
- 2013
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 34, s. 3629-3636
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedTemperature and relative O-2-concentrations have been measured using pure rotational coherent anti-Stokes Raman spectroscopy (RCARS) in a low swirl turbulent premixed flame. This lean flame burning methane has previously been investigated using laser diagnostic techniques and numerical modeling of flame characteristics. In the present work, single-shot RCARS measurements were performed and analysed statistically to obtain temperature and O-2-concentration probability density functions. The results were compared with large eddy simulations (LES) showing fairly good agreement. The rotational CARS technique was successfully applied in the whole range of temperatures (300-1700 K) and relative O-2-concentrations (9-21%), and based on the simultaneous measurements of temperature and O-2-concentration an improved understanding of the reaction progress and air entrainment from the surroundings can be achieved. From the evaluated O-2-concentration, the H2O mole fraction could be estimated, which subsequently made an important thermometric correction possible of up to similar to 40 K at 1700 K by inclusion of N-2-H2O line-broadening coefficients in the theoretical spectral calculations. Spatial averaging effects were observed in a fraction of spectra where both hot and cold spectral envelopes were detected, most often with corresponding peaks displaced relative to each other. The large range of CARS signal intensities (about 3 orders of magnitude) when intermittently probing low and high temperature gases was dealt with by using a multi-track function of the CCD camera that increased the dynamic range. Merits and limitations of pure rotational CARS for diagnostics in turbulent flames are discussed and comparison is made with vibrational CARS. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 24. |
- Bohlin, Alexis, et al.
(författare)
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Validation of a rotational coherent anti-Stokes Raman scattering model for N2O at temperatures from 295K to 796K
- 2012
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 604-610
-
Tidskriftsartikel (refereegranskat)abstract
- Pure rotational coherent anti-Stokes Raman scattering (CARS) spectra of N2O was recorded in a series of temperature calibrated cell measurements in the region 295-796K. A theoretical rotational CARS code for N2O was implemented and temperature analysis was performed by fitting the modeled theoretical spectra to the experimental spectra. Excellent agreement between the experimental and modeled spectra was obtained and the thermometric accuracy for the measurements was evaluated to be better than 1%. Also, rotational N2 CARS spectra were recorded at the same measurement conditions and the temperature analysis performed on these spectra resulted in the same accuracy. The peak signal strength was found to be similar to 5 times stronger for N2O than for N2 at ambient temperature and pressure. The temperature precision was evaluated to a relative standard deviation of 2.0%-2.7% in the studied temperature range, about half of the values for N2, which is attributed to the larger number of spectral lines for N2O. Rotational N2O CARS thermometry show great potential, because of a high Raman cross-section and large number of populated rotational states at any temperature. Copyright (c) 2012 John Wiley & Sons, Ltd.
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| 25. |
- Brackmann, Christian, et al.
(författare)
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Structure of premixed ammonia plus air flames at atmospheric pressure: Laser diagnostics and kinetic modeling
- 2016
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 163, s. 370-381
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of premixed ammonia air flames, burning at atmospheric pressure under strain-stabilized conditions on a porous-plug burner, has been investigated using laser-diagnostic methods. Profiles of OH, NH, and NO were acquired by laser-induced fluorescence (LIF) and quantitative concentrations of OH and NO were retrieved using a concept for calibration versus absorption utilizing the LIF-signal itself, whereas NH concentrations were evaluated employing a saturated fluorescence signal. In addition, temperatures and relative oxygen concentrations were measured by rotational Coherent Anti-stokes Raman Spectroscopy (CARS). The new experimental data for flames with equivalence ratios of 0.9, 1.0, and 1.2 were used to validate and rank the performance of four contemporary detailed kinetic models. Simulations were carried out using experimental temperature profiles as well as by solving the energy equation. Two models of the same origin, developed by Mendiara and Glarborg (2009) and by Klippenstein et al. (2011), in most cases showed good agreement in terms of radical concentrations, however, the model of Mendiara and Glarborg had better prediction of temperatures and flame front positions. The model by Shmakov et al. (2010) had comparable performance concerning radical species, but significant discrepancies appeared in the prediction of flame front positions. The model of Duynslaegher et al. (2012), in addition to the flame front positions, deviated from experiments or other models in terms of NH and NO concentrations. A sensitivity analysis for the Mendiara-Glarborg mechanism indicated that remaining uncertainties of the rate constants implemented in the recent H/N/O models are difficult to scrutinize unambiguously due to experimental uncertainties. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 26. |
- Brandt, Rasmus, 1985-, et al.
(författare)
-
Weighted Sum Rate Optimization for Multicell MIMO Systems with Hardware-Impaired Transceivers
- 2014
-
Konferensbidrag (refereegranskat)abstract
- Physical transceivers exhibit distortions from hardware impairments, of which traces remain even after compensation and calibration. Multicell MIMO coordinated beamforming methods that ignore these residual impairments may suffer from severely degraded performance. In this work, we consider a general model for the aggregate effect of the residual hardware impairments, and propose an iterative algorithm for finding locally optimal points to a weighted sum rate optimization problem. The importance of accounting for the residual hardware impairments is verified by numerical simulation, and a substantial gain over traditional time-division multiple access with impairments-aware resource allocation is observed.
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| 27. |
- Burman, Emil, et al.
(författare)
-
Microbial Community Interactions Are Sensitive to Small Changes in Temperature
- 2021
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Microbial communities are essential for human and environmental health, often forming complex interaction networks responsible for driving ecosystem processes affecting their local environment and their hosts. Disturbances of these communities can lead to loss of interactions and thereby important ecosystem functionality. The research on what drives interactions in microbial communities is still in its infancy, and much information has been gained from the study of model communities. One purpose of using these model microbial communities is that they can be cultured under controlled conditions. Yet, it is not well known how fluctuations of abiotic factors such as temperature affect their interaction networks. In this work, we have studied the effect of temperature on interactions between the members of the model community THOR, which consists of three bacterial species: Pseudomonas koreensis, Flavobacterium johnsoniae, and Bacillus cereus. Our results show that the community-intrinsic properties resulting from their interspecies interactions are highly dependent on incubation temperature. We also found that THOR biofilms had remarkably different abundances of their members when grown at 11, 18, and 25 degrees C. The results suggest that the sensitivity of community interactions to changes in temperature is influenced, but not completely dictated, by different growth rates of the individual members at different temperatures. Our findings likely extend to other microbial communities and environmental parameters. Thus, temperature could affect community stability and may influence diverse processes including soil productivity, bioprocessing, and disease suppression. Moreover, to establish reproducibility between laboratories working with microbial model communities, it is crucial to ensure experimental stability, including carefully managed temperature conditions.
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| 28. |
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| 29. |
- Carlsson, Henning, et al.
(författare)
-
Numerical and experimental study of flame propagation and quenching of lean premixed turbulent low swirl flames at different Reynolds numbers
- 2015
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 162:6, s. 2582-2591
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a joint experimental and large eddy simulation (LES) study of lean premixed low swirl stabilized methane/air flames at different Reynolds numbers (Re similar to 20,000-100,000). The aims are to investigate the sensitivity of the structures and dynamics of low swirl flames to the inflow boundary conditions and to evaluate the capability of an LES flamelet model in predicting the stabilization and local extinction of the flames. Chemiluminescence measurements are carried out for Re - 20,000-50,000 and further detailed oxygen concentration and temperature fields are measured using rotational coherent anti-Stokes Raman spectroscopy (RCARS) for Re - 20,000 and 30,000 along the centerline of the burner and at various radial positions at different heights above the burner. The data are used first for validation of the combustion LES model employed in the numerical simulations, and then the RCARS and LES results are used to delineate the effect of ambient air entrainment on the flame structure at various burner exit velocities. A three-scalar flamelet model based on a level-set G-equation shows excellent predictions of the lift-off positions and the structures of the flames, including quenching at the trailing edge of the flame. The results show that the flame lift-off height varies only slightly when the burner exit velocity is increased, which is consistent with a shear-layer flame stabilization mechanism reported previously. The volume of the flame decreases substantially with increasing burner exit velocity at relatively low Reynolds numbers, as a result of flame quenching at the trailing edge of the flame caused by entrainment of the ambient air into the fuel/air stream and the flame itself. At high Reynolds numbers the flame structures become fairly self-similar with the flame volume nearly independent of the Reynolds number. (C) 2015 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 30. |
- Carlsson Tedgren, Åsa, et al.
(författare)
-
Experience from long-term monitoring of RAKR ratios in Ir-192 brachytherapy
- 2008
-
Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 89:2, s. 217-221
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Ratios of values of brachytherapy source strengths, as measured by hospitals and vendors, comprise constant differences as, e.g., systematic errors in ion chamber calibration factors and measurement setup. Such ratios therefore have the potential to reveal the systematic changes in routines or calibration services at either the hospital or the vendor laboratory, which could otherwise be hidden by the uncertainty in the source strength values. Methods: The RAKR of each new source in 13 afterloading units at five hospitals were measured by well-type ion chambers and compared to values for the same source stated on vendor certificates. Results: Differences from unity in the ratios of RAKR values determined by hospitals and vendors are most often small and stable around their mean values to within +/- 11.5%. Larger deviations are rare but occur. A decreasing ratio, seen at two hospitals for the same source, was useful in detecting an erroneous pressure gauge at the vendors site. Conclusions: Establishing a mean ratio of RAKR values, as measured at the hospital and supplied on the vendor certificate, and monitoring this as a function of time are an easy way for the early detection of problems with equipment or routines at either the hospital or the vendor site.
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| 31. |
- Chongtham Iman, Raj, et al.
(författare)
-
Factors influencing crop rotation strategies on organic farms with different time periods since conversion to organic production
- 2017
-
Ingår i: Biological Agriculture and Horticulture. - : Informa UK Limited. - 0144-8765 .- 2165-0616. ; 33, s. 14-27
-
Tidskriftsartikel (refereegranskat)abstract
- Productive crop rotations are central to the success of organic production systems. The selection and sequence of crops are determined by a combination of agronomic and economic factors as well as the principles and standards of organic farming. Semi-structured interviews were conducted with sixteen organic farmers in Central-east Sweden to explore the factors that influence the design of crop rotations and the trade-offs between these factors, taking into account the length of time since conversion to organic production. We discerned three crop rotation strategies: strict, flexible and liberal, based on how crop(s) are repeated over time. A major trade-off for arable farmers was between perennial leys to provide nitrogen and control weeds, and the use of more inputs such as purchased nutrients and mechanical weed control to allow continuous cereal production. Critical considerations for livestock farmers were the length of ley for feed production and weed control, cost of re-seeding leys and decisions about whether to grow crops to feed animals or cereals to sell. Farmers practicing organic for a long time (more than 10years) often had flexible rotations to adapt to changing conditions, but they generally included leys and a selection of annual crops in line with the principles of crop rotation and organic farming. Recently converted organic farmers usually concentrated on controlling weeds and producing sufficient livestock feed by following strict crop rotations. We conclude that farm type and experience strongly influenced rotation strategies and that weed management and market prices were the most important influences.
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| 32. |
- Holgersen, Ståle, 1980-, et al.
(författare)
-
13 myter om bostadsfrågan
- 2016
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- I tretton kapitel utmanas rådande problemformuleringar om vad som utgör hindren för att skapa en mer tillgänglig bostadsmarknad och rimligare boendesituation åt alla. Är ökad marknadsekonomi lösningen på bostadsbristen? Måste vi sänka kvalitetskraven för att alla ska få tak över huvudet? Hur hänger bostadsfrågan och frågan om integration och segregation ihop? Är gentrifiering en naturlig förändring av staden? Rådande "sanningar" om fler avregleringar, lägre skatter och ökad marknadsfrihet har kommit att stå i vägen för nytänkande. Det behövs fler röster i debatten. 13 myter om bostadsfrågan ger alternativa tolkningar som kan föra in nya perspektiv på bostadskrisen. Boken ges ut av Förlag Dokument Press, med illustrationer av Sara Granér.
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| 33. |
- Hosseinnia, Ali, et al.
(författare)
-
Ethane thermometry using rotational coherent anti-Stokes Raman scattering (CARS)
- 2017
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 36:3, s. 4461-4468
-
Tidskriftsartikel (refereegranskat)abstract
- The complete rotational CARS (coherent anti-Stokes Raman scattering) spectrum of ethane (C2H6) has for the first time been recorded instantaneously under high spectral resolution, and the potential for thermometry has been investigated. Experiments were performed in the temperature range 292-650K in pure ethane and in binary mixtures with nitrogen. A polarization technique was used to suppress the non-resonant contribution to the CARS signal. The ethane RCARS spectra show both S- and R-branch lines, which are more closely spaced than for the well-known nitrogen spectrum and located at much smaller Raman shifts. The peak signal strength was found to be around 240 times lower for ethane than for nitrogen (at 292K). Two main approaches for ethane thermometry are evaluated, which both show high potential. The first is a method in which a spectrum with unknown temperature is fitted using a library of experimental spectra recorded at various temperatures. The second is a method based on ratios of integrated signals in different spectral regions. A theoretical model for simulation of theoretical spectra is under development.
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| 34. |
- Hosseinnia, Ali, et al.
(författare)
-
Rotational CARS thermometry and concentration measurements in ethane-nitrogen mixtures using Fourier analysis
- 2018
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486. ; 49:7, s. 1096-1108
-
Tidskriftsartikel (refereegranskat)abstract
- Rotational coherent anti-Stokes Raman scattering (CARS) is an established diagnostic technique for thermometry and species concentration measurements of di-atomics and tri-atomics in combustion processes; however, studies on hydrocarbon fuel molecules have been scarce. In this work, we have investigated the diagnostic potential for rotational CARS on ethane with emphasis on concentration measurements in mixtures with nitrogen. Rotational CARS spectra have periodic line structures, and because ethane and nitrogen spectra partially overlap, a novel Fourier analysis approach was developed and applied to facilitate evaluation of relative concentrations and temperatures. Instead of the standard procedure of spectral fitting using libraries of theoretically calculated spectra, the fitting was based on an experimental database of temperatures and relative ethane/nitrogen concentrations. The method was successfully demonstrated in an ethane diffusion flame where ethane, initially at room temperature, is heated downstream as well as mixed with increasing amounts of nitrogen. The evaluated temperatures and concentrations are in good agreement with computational fluid dynamic model simulations.
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| 35. |
- Hou, Xueying, et al.
(författare)
-
Cell-Grouping Based Distributed Beamforming and Scheduling for Multi-cell Cooperative Transmission
- 2011
-
Ingår i: Proceedings 22nd IEEE Symposium on Personal, Indoor, Mobile and Radio Communications (PIMRC). - : IEEE conference proceedings. - 9781457713477 - 9781457713460 ; , s. 1929-1933
-
Konferensbidrag (refereegranskat)abstract
- Base station cooperative transmission is an effective strategy to mitigate inter-cell interference. Centralized multicell transmission provides considerable performance gains but is impractical in large cellular systems, due to its prohibitive complexity and large amount of overhead. Dividing cells into small clusters enables practical channel acquisition and coordination within each cluster but still suffers from out-of-cluster interference. In this paper, we propose a dynamic cooperative framework for large cellular systems, which divides cells into groups such that neighboring cells belong to different groups. Based on the cell-grouping, a distributed scheduling strategy is proposed which can effectively coordinate the interference between cell-groups. With limited signalling among BSs and lower complexity, the cell-grouping based distributed scheduling and beamforming shows performance advantages over the fixed clustering based centralized scheduling and beamforming.
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| 36. |
- Jorge, Emilio, 1992, et al.
(författare)
-
Reinforcement learning in real-time geometry assurance
- 2018
-
Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 72, s. 1073-1078
-
Konferensbidrag (refereegranskat)abstract
- To improve the assembly quality during production, expert systems are often used. These experts typically use a system model as a basis for identifying improvements. However, since a model uses approximate dynamics or imperfect parameters, the expert advice is bound to be biased. This paper presents a reinforcement learning agent that can identify and limit systematic errors of an expert systems used for geometry assurance. By observing the resulting assembly quality over time, and understanding how different decisions affect the quality, the agent learns when and how to override the biased advice from the expert software.
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| 37. |
- Katselis, Dimitrios, et al.
(författare)
-
Training sequence design for MIMO channels: an application-oriented approach
- 2013
-
Ingår i: EURASIP Journal on Wireless Communications and Networking. - : Springer Science and Business Media LLC. - 1687-1472 .- 1687-1499. ; 2013, s. 245-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the problem of training optimization for estimating a multiple-input multiple-output (MIMO) flat fading channel in the presence of spatially and temporally correlated Gaussian noise is studied in an application-oriented setup. So far, the problem of MIMO channel estimation has mostly been treated within the context of minimizing the mean square error (MSE) of the channel estimate subject to various constraints, such as an upper bound on the available training energy. We introduce a more general framework for the task of training sequence design in MIMO systems, which can treat not only the minimization of channel estimator's MSE but also the optimization of a final performance metric of interest related to the use of the channel estimate in the communication system. First, we show that the proposed framework can be used to minimize the training energy budget subject to a quality constraint on the MSE of the channel estimator. A deterministic version of the 'dual' problem is also provided. We then focus on four specific applications, where the training sequence can be optimized with respect to the classical channel estimation MSE, a weighted channel estimation MSE and the MSE of the equalization error due to the use of an equalizer at the receiver or an appropriate linear precoder at the transmitter. In this way, the intended use of the channel estimate is explicitly accounted for. The superiority of the proposed designs over existing methods is demonstrated via numerical simulations.
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| 38. |
- Kliewer, C. J., et al.
(författare)
-
Time-domain measurements of S-branch N-2-N-2 Raman linewidths using picosecond pure rotational coherent anti-Stokes Raman spectroscopy
- 2012
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 108:2, s. 419-426
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved dual-broadband picosecond pure rotational CARS has been applied to measure self-broadened S-branch N-2-N-2 Raman linewidths in the temperature range 294-1466 K. The coherence decays were detected directly in the time domain by following the J-dependent CARS signal decay as a function of probe delay. The rotational Raman N-2-N-2 linewidths were derived from these time-dependent decays and evaluated for thermometric accuracy. Comparisons were made to the energy-corrected sudden (ECS) and modified exponential gap (MEG) dynamical scaling laws, and the results were used to quantify the sensitivity of nanosecond rotational CARS thermometry to the linewidth model employed. The uncertainty based on the linewidth model used in pure N-2 was found to be 2 %. The merits and limitations of this rapid method for the determination of accurate Raman linewidths are discussed.
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| 39. |
- Komulainen, Petri, et al.
(författare)
-
CSI acquisition concepts for advanced antenna schemes in the WINNER+ project
- 2010
-
Ingår i: Future Network and MobileSummit 2010 Conference Proceedings. - : IIMC International Information Management Corporation. - 9781905824182 ; , s. 5722348-
-
Konferensbidrag (refereegranskat)abstract
- This paper summarizes four novel advanced antenna concepts explored in the framework of the WINNER+ project. The concepts are related to multiuser MIMO communication in cellular networks, focusing on the acquisition and application of channel state information (CSI) at the transmitter in time-division-duplex (TDD) mode. The concepts include new ideas for CSI modeling and sounding for the purposes of multiuser precoding, and methods for pilot signal design with the aim to support the estimation of different CSI quantities. Furthermore, a new relaying strategy for terminal-to-terminal communication is described. All the ideas are feasible for adoption into practical upcoming communication systems such as LTE-Advanced, and most of the proposed concepts have only a minor impact on standards.Our study indicates that the CSI at its best is not only about estimating the channel responses between different antenna pairs. What counts is the nature of the intended communication link as well as the form in which CSI is applied.
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| 40. |
- Kristensson, Elias, et al.
(författare)
-
Stray light suppression in spectroscopy using periodic shadowing
- 2014
-
Ingår i: Optics Express. - 1094-4087. ; 22:7, s. 7711-7721
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity. (C) 2014 Optical Society of America
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| 41. |
- Kristensson, Elias, et al.
(författare)
-
Stray light suppression in spectroscopy using periodic shadowing
- 2014
-
Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 22:7, s. 7711-7711
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity.
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| 42. |
- Marrocco, Michele, et al.
(författare)
-
Sensitivity of coherent anti-Stokes Raman lineshape to time asymmetry of laser pulses
- 2014
-
Ingår i: Optics Letters. - 0146-9592. ; 39:19, s. 5748-5751
-
Tidskriftsartikel (refereegranskat)abstract
- We show that coherent anti-Stokes Raman lineshapes do not follow known spectral profiles if the time asymmetry of realistic laser pulses is taken into account. Examples are given for nanosecond and picosecond laser pulses commonly employed in frequency-resolved coherent anti-Stokes Raman scattering. More remarkably, the analysis suggests an effect of line narrowing in comparison to the customary approach, based primarily on the Voigt lineshape. (C) 2014 Optical Society of America
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| 43. |
- Mochaourab, Rami, et al.
(författare)
-
Adaptive Pilot Clustering in Heterogeneous Massive MIMO Networks
- 2016
-
Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 15:8, s. 5555-5568
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the uplink of a cellular massive multiple-input multiple-output network. Acquiring channel state information at the base stations (BSs) requires uplink pilot signaling. Since the number of orthogonal pilot sequences is limited by the channel coherence, pilot reuse across cells is necessary to achieve high spectral efficiency. However, finding efficient pilot reuse patterns is non-trivial, especially in practical asymmetric BS deployments. We approach this problem using the coalitional game theory. Each BS has a few unique pilots and can form coalitions with other BSs to gain access to more pilots. The BSs in a coalition, thus, benefit from serving more users in their cells at the expense of higher pilot contamination and interference. Given that a cell's average spectral efficiency depends on the overall pilot reuse pattern, the suitable coalitional game model is in the partition form. We develop a low-complexity distributed coalition formation based on individual stability. By incorporating a BS intercommunication budget constraint, we are able to control the overhead in message exchange between the BSs and ensure the algorithm's convergence to a solution of the game called individually stable coalition structure. Simulation results reveal fast algorithmic convergence and substantial performance gains over the baseline schemes with no pilot reuse, full pilot reuse, or random pilot reuse pattern.
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| 44. |
- Mochaourab, Rami, et al.
(författare)
-
Pilot clustering in asymmetric massive MIMO networks
- 2015
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - : IEEE conference proceedings. - 9781479919307 - 9781479919314 ; , s. 231-235
-
Konferensbidrag (refereegranskat)abstract
- We consider the uplink of a cellular massive MIMO network. Since the spectral efficiency of these networks is limited by pilot contamination, the pilot allocation across cells is of paramount importance. However, finding efficient pilot reuse patterns is non-trivial especially in practical asymmetric base station deployments. In this paper, we approach this problem using coalitional game theory. Each cell has its own unique pilots and can form coalitions with other cells to gain access to more pilots. We develop a low-complexity distributed algorithm and prove convergence to an individually stable coalition structure. Simulations reveal fast algorithmic convergence and substantial performance gains over one-cell coalitions and full pilot reuse.
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| 45. |
- Mohajershojai, Tabassom, et al.
(författare)
-
PD-1 blockade enhances therapeutic effects of 177Lu-DOTA-M5A in colorectal cancer CEA-transgenic mice
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Radioimmunotherapy (RIT) is emerging as an effective treatment for metastatic solid tumors by coupling radionuclides with tumor-targeting molecules, precisely directing radiation to cancer cells while sparing healthy tissue. Carcinoembryonic antigen (CEA) is a promising target for RIT in CEA-expressing cancers, including colorectal cancers (CRCs). Recent studies highlight radiotherapy's role in enhancing the immune response against cancer. Combining RIT with immune checkpoint inhibitors, such as anti-PD-1 antibodies, may further enhance anti-tumor immunity and improve outcomes. This study aimed to investigate, for the first time, the in vivo effects of CEA-targeted RIT using the novel humanized anti-CEA antibody hT84.66-M5A labeled with 177Lu (177Lu-DOTA-M5A), combined with PD-1 blockade. Radioconjugate uptake and therapeutic effects were first assessed in vitro using the CRC spheroid model MC38-CEA1. The therapeutic effects of 177Lu-DOTA-M5A and PD-1 blockade were then evaluated alone or in combination in CEA-transgenic mice bearing CEA-transduced CRC xenografts, with radioconjugate uptake validated in biodistribution studies and visualized via SPECT/CT imaging. Dose-dependent therapeutic effects of 177Lu-DOTA-M5A were demonstrated in the 3D spheroid model. In vivo studies showed that both 177Lu-DOTA-M5A and PD-1 antibody monotherapies effectively reduced tumor growth rates compared to the control group, but the combination therapy had the most significant impact. Combination therapy resulted in a dramatic tumor growth inhibition rate of -6% average daily, compared to +7%, +7.9%, and +13.5% in the PD-1 blockade, 177Lu-DOTA-M5A (2.5 MBq), and control groups, respectively. Median survival increased by 31% in the PD-1 blockade group and by 52% in the 177Lu-DOTA-M5A (2.5 MBq) group compared to the control group, while median survival was not reached in the corresponding combination group. Radioconjugate monotherapies and combination therapies did not introduce any bone marrow toxicity. 177Lu-DOTA-M5A slightly altered the immune cell profile in the tumor microenvironment, increasing cytotoxic and helper T cells. Notably, pro-inflammatory macrophages became dominant over tumor-promoting ones in the tumor microenvironment of combination-treated mice. These findings highlight the promise of 177Lu-DOTA-M5A as a CRC therapeutic agent and its enhanced efficacy when combined with an immune checkpoint inhibitor. Further in vivo studies are needed to fully validate these findings and explore the treatment’s potential for clinical use.
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| 46. |
- Munir, Hussan, Assistant Professor, et al.
(författare)
-
Management tools for business model innovation : a review
- 2022
-
Ingår i: Innovation. - London : Routledge. - 9780429346033 - 9780367343026 - 9780367364427 - 9781000641134 ; , s. 141-158
-
Bokkapitel (refereegranskat)abstract
- The purpose of this chapter is to identify and classify proposed business model innovation tools through a literature review of academic publications. We classified the tools into three categories: innovation process stage, strategic objective and size of firm. Our main findings are that the overall number of business model innovation (BMI) tools described in the research literature is limited mostly to facilitate design processes rather than for test or implementation purposes. Moreover, the identified tools are based on conceptual reasoning and not on empirical studies of tools used by managers. Implications for managers are that most BMI tools are intended for, and have their strength in, experimenting with the design or redesign of a business model, placing it in a value chain and value network ecosystem. As most of these BMI tools have a visual representation, such as the business model canvas, they facilitate creativity and analysis work in management groups with different functions, e.g., in workshops with visual boards. Moreover, while most BMI tools assume the profit objective it is important for managers to make the objective of the BMI process explicit as many of the tools may be used also for growth or creating new businesses. Making the objective explicit might be especially important for managers in government or non-profit organizations as these organizations often have other objectives than profit and growth. A final implication for managers is that BMI tools are mainly developed to support managers when established companies need to change their business model in three types of situations; changes due to digitalization, to develop and sharpen the company’s competitive advantages and when developing new businesses, i.e., corporate venturing.
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| 47. |
- Nilsson, Emil, et al.
(författare)
-
A low power-long range active RFID-system consisting of active RFID backscatter transponders
- 2010
-
Ingår i: 2010 IEEE International Conference on RFID-Technology and Applications (RFID-TA). - Piscataway, N.J. : IEEE Press. - 9781424466986 ; , s. 26-30, s. 26-30
-
Konferensbidrag (refereegranskat)abstract
- In this paper we present a novel active radio frequency identification system consisting of transponders with low complexity, low power consumption, and long system reading range. The transponder’s low complexity and small circuit integration area indicate that the production cost is comparable to the one of a passive tag. The hardware keystone is the transponder’s radio wake-up transceiver, which is a single oscillator with very low power consumption. The communication protocol, based on frequency signalling binary tree, contributes to the low complexity of the tag architecture. More than 1500 tags can be read per second. The average transponder ID read-out delay is 319 ms when there are 1000 transponders within reach of the interrogator. The calculated expected life time for a transponder is estimated to be almost three years.
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| 48. |
- Nilsson, R. Henrik, 1976, et al.
(författare)
-
Improving ITS sequence data for identification of plant pathogenic fungi
- 2014
-
Ingår i: Fungal Diversity. - : Springer Science and Business Media LLC. - 1560-2745 .- 1878-9129. ; 67:1, s. 11-19
-
Tidskriftsartikel (refereegranskat)abstract
- Plant pathogenic fungi are a large and diverse assemblage of eukaryotes with substantial impacts on natural ecosystems and human endeavours. These taxa often have complex and poorly understood life cycles, lack observable, discriminatory morphological characters, and may not be amenable to in vitro culturing. As a result, species identification is frequently difficult. Molecular (DNA sequence) data have emerged as crucial information for the taxonomic identification of plant pathogenic fungi, with the nuclear ribosomal internal transcribed spacer (ITS) region being the most popular marker. However, international nucleotide sequence databases are accumulating numerous sequences of compromised or low-resolution taxonomic annotations and substandard technical quality, making their use in the molecular identification of plant pathogenic fungi problematic. Here we report on a concerted effort to identify high-quality reference sequences for various plant pathogenic fungi and to re-annotate incorrectly or insufficiently annotated public ITS sequences from these fungal lineages. A third objective was to enrich the sequences with geographical and ecological metadata. The results – a total of 31,954 changes – are incorporated in and made available through the UNITE database for molecular identification of fungi (http://unite.ut.ee), including standalone FASTA files of sequence data for local BLAST searches, use in the next-generation sequencing analysis platforms QIIME and mothur, and related applications. The present initiative is just a beginning to cover the wide spectrum of plant pathogenic fungi, and we invite all researchers with pertinent expertise to join the annotation effort.
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| 49. |
- Nordström, Emil, et al.
(författare)
-
Fourier-based approach to overcome anomalies in high-resolution spectra of vibrational CARS measurements of gases
- 2014
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 45:7, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report on an unconventional experimental procedure useful for thermometric measurements on the basis of high-resolution vibrational coherent anti-Stokes Raman scattering (CARS) generated using conventional lasers. The high spectral dispersion of 0.02 cm(-1)/pixel is achieved by means of some specific spectral arrangements (single-mode pump laser and diffraction grating providing spectra at the sixth order) and is further strengthened by the use of a relay lens system mounted before the charge-coupled device camera. Surprisingly, at the high spectral dispersion of our measurements, a significant and persistent thermometric inaccuracy is observed. The effect arises from an inevitable spectral modulation of defined frequency hidden in the main CARS signal of the gas under study, and to secure a good thermometric evaluation, we describe a Fourier approach that is experimentally demonstrated for the typical nitrogen CARS spectrum measured at room temperature. Copyright (C) 2014 John Wiley & Sons, Ltd.
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- Nordström, Emil, et al.
(författare)
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Local gas heating in sooting flames by heat transfer from laser-heated particles investigated using rotational CARS and LII
- 2015
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 35, s. 3707-3713
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Tidskriftsartikel (refereegranskat)abstract
- Soot particles strongly absorb radiation in the visible and infrared spectral regions, and the soot interaction with laser light during laser diagnostic interrogation leads to particle heating and often to subsequent sublimation. Consequently, laser-heated particles transfer heat to the ambient gas leading to local gas heating, a process that has received minor attention so far in the diagnostic community. In the present work, this specific local gas heating is measured in a pump-probe-type experiment. A 1064-nm laser beam heated the soot particles in an ethylene/ air diffusion flame (on a Gulder-burner) with known soot volume fraction, and a two-beam rotational coherent anti-Stokes Raman spectroscopy (CARS) setup was used to probe the local gas temperature on time scales from nanoseconds to milliseconds. The temperature of the heated particles was simultaneously probed using a two-color laser-induced incandescence (2C-LII) detection system. The results show that laser heating of soot particles from flame temperatures to sublimation temperatures leads to local gas heating of similar to 100 K at a soot volume fraction of 4 ppm, in good agreement with theoretical predictions. The implication of these results to the application of laser diagnostic techniques is briefly discussed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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