| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
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| 3. |
- Gong, Karin Anne Xia, 1965, et al.
(författare)
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Wear Evaluation on Ni3Al/MnS Composite Related to Metallurgical Processes
- 2012
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Ingår i: Journal of Iron and Steel Research International. - 1006-706X. ; 19:7, s. 46-54
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Tidskriftsartikel (refereegranskat)abstract
- Iron alloyed Ni3Al with composition of Ni-18. 8A1-10. 7Fe0. 5Mn-0. 5Ti-0.2B in atom percent (NAC alloy)showed attractive tribological properties under unlubrication condition at room temperature. The alloy was preparedby hot isostatic pressing (HIP) process. The wear properties were associated with its intrinsic deformation mechanism.Unfortunately, the single phase NAC-alloy worked inadequately with its counterpart disk, and also showed apoor machinability. In the present work, NAC-alloy matrix composite with 6% (volume percent) MnS (manganese sulfide)particle addition was studied to improve its wear behaviors and performance on machining. Two metallurgical processes of HIP and vacuum casting were applied to produce the testing materials. Pin-on-disk (POD) measurements were carried outat room temperature. A commercial vermicular graphite cast iron was selected as a reference material. The counterpartdisk was made of a grey cast iron as liner material in ship engines. The contact pressures of 2. 83 MPa and 5. 66 MPawere normally applied in the tests. The investigation indicated that MnS particle addition in the NAC-alloy compositesfunctions as an effective solid lubricant, and improved wear properties and machinability of the materials. Obviously,as-cast NAC-alloy with in-situ formed MnS phase was working more effectively with the counterpart, comparingto the HIPed NAC-alloy composite with MnS particles. At the high contact pressure of 5.66 MPa, the specificwear rate of the as-cast NAC-alloy composite was high. The phenomenon of the negative effect is mostly due to thebrittle second NiAl phase as evidenced in the microstructure analysis.
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| 4. |
- Pecunia, Vincenzo, et al.
(författare)
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Roadmap on energy harvesting materials
- 2023
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Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
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| 5. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 6. |
- Fallgren, Mikael, 1982-
(författare)
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Optimization of Joint Cell, Channel and Power Allocation in Wireless Communication Networks
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we formulate joint cell, channel and power allocation problems within wireless communication networks. The objectives are to maximize the user with mini- mum data throughput (Shannon capacity) or to maximize the total system throughput, referred to as the max-min and max-sum problem respectively. The complexity is stud- ied together with proposed optimization- and heuristic-based approaches. In the first paper an overall joint cell, channel and power allocation max-min prob- lem is formulated. We show that the decision problem is NP-hard and that the op- timization problem is not approximable unless P is equal to NP, for instances with a sufficiently large number of channels. Further, it follows that for a feasible binary cell and channel allocation, the remaining continuous power allocation optimization problem is still not approximable unless P is equal to NP. In addition, it is shown that first-order optimality conditions give global optimum of the single channel power al- location optimization problem, although the problem is in general not convex. In the following two papers heuristics for solving the overall problem are proposed. In the second paper we consider the single channel problem with convex combinations of the max-min and the max-sum objective functions. This variable utility provides the ability of tuning the amount of fairness and total throughput. The third paper investi- gates the multiple channel setting. On a system with three cells, eight mobile users and three channels, we perform an exhaustive search over feasible cell and channel alloca- tions. The exhaustive search is then compared to the less computationally expensive heuristic approaches, presenting potential earnings to strive for. A conclusion is that several of the proposed heuristics perform very well. The final paper incorporates fixed relay stations into the overall joint cell, channel and power allocation max-min problem. The complexity is inherited from the formula- tion without relay stations. Further, we propose a heuristic channel allocation approach that shows good performance, compared to an optimization based approach, in numer- ical simulations on the relay setting.
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| 7. |
- Guan, Zhi-Qiang, et al.
(författare)
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Electromechanical Behavior of Interdigitated SiO2 Cantilever Arrays
- 2010
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Ingår i: Chinese Physics Letters. - 1741-3540. ; 27:2
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Tidskriftsartikel (refereegranskat)abstract
- Bending and first flexural mode vibration behavior of electrostatic actuated nanometer-sized interdigitated cantilever arrays are characterized under vacuum conditions. The "pull-in" effect in dc driving and the "hard spring effect" in ac driving are observed. A mass sensitivity of 20 fg is expected for our devices due to the ultra-small mass of the arm and relative high.. factor. The mass-spring lump model combined with Green's function method is used to fit the dc driving behaviors including the pull-in voltage. For the ac driving case, the polynomial expansion of the capacitive force is used in the model. The successfully fittings of the pull-in voltage and the hard spring effect prove that our simulation method could be used for guiding the geometrical design of cantilever-based sensors.
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| 8. |
- Han, Xin-Bao, et al.
(författare)
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Fe-substituted cobalt-phosphate polyoxometalates as enhanced oxygen evolution catalysts in acidic media
- 2020
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Ingår i: Cuihuà xuébào. - : Science Press. - 0253-9837 .- 1872-2067. ; 41:5, s. 853-857
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Tidskriftsartikel (refereegranskat)abstract
- All-inorganic and earth-abundant bi-/trimetallic hydr(oxy)oxides are widely used as oxygen evolution electrocatalysts owing to their remarkable performance. However, their atomically precise structures remain undefined, complicating their optimization and limiting the understanding of their enhanced performance. Here, the underlying structure-property correlation is explored by using a well-defined cobalt-phosphate polyoxometalate cluster [{Co-4(OH)(3)(PO4)}(4)(SiW9O34)(4)](32-) (1), which may serve as a molecular model of multimetal hydr(oxy)oxides. The catalytic activity is enhanced upon replacing Co by Fe in 1, resulting in a reduced overpotential (385 mV) for oxygen evolution (by 66 mV) compared to that of the parent 1 at 10 mA cm(-2) in an acidic medium; this overpotential is comparable to that for the IrO2 catalyst. These abundant-metal-based polyoxometalates exhibit high stability, with no evidence of degradation even after 24 h of operation.
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| 9. |
- Jaldén, Joakim, 1976-
(författare)
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Detection for multiple input multiple output channels : analysis of sphere decoding and semidefinite relaxation
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The problem of detecting a vector of symbols, drawn from a finite alphabet and transmitted over a multiple-input multiple-output (MIMO) channel with Gaussian noise, is of central importance in digital communications and is encountered in several different applications. Examples include, but are not limited to; detection of symbols spatially multiplexed over a multiple-antenna channel and the multiuser detection problem in a code division multiple access (CDMA) system. Two algorithms previously proposed in the literature are considered and analyzed. Both algorithms have their origin in other fields of science but have gained mainstream recognition as efficient algorithms for the detection problem considered herein. Specifically, we consider the sphere decoder and semidefinite relaxation detector. By incorporating assumptions applicable in the communications context the performance of the two algorithms is addressed. The first algorithm, the sphere decoder, offers optimal performance in terms of its error probability. Further, the algorithm has proved extremely efficient in terms of computational complexity for moderately sized problems at high signal to noise ratio (SNR). Although it is recognized that the algorithm has an exponential worst case complexity, there has been a widespread belief that the algorithm has a polynomial average complexity at high SNR. A contribution made herein is to show that this is incorrect and that the average complexity, as the worst case complexity, is exponential in the number of symbols detected. Instead, another explanation of the observed efficiency of the algorithm is offered by deriving the exponential rate of growth and showing that this rate, although strictly positive for finite SNR, is small in the high SNR regime. The second algorithm, the semidefinite relaxation (SDR) detector, offers polynomial complexity at the expense of suboptimal performance in terms of error probability. Nevertheless, previous numerical observations suggest that error probability of the SDR algorithm is close to that of the optimal detector. Herein, the near optimality is of the SDR algorithm is given a precise meaning by studying the diversity of the SDR algorithm when applied to the (real valued) i.i.d.~Rayleigh fading channel and it is shown that the SDR algorithm achieves the same diversity order as the optimal detector. Further, criteria under which the SDR estimates coincide with the optimal estimates are derived and discussed.
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| 10. |
- Jia, Kai-Hua, et al.
(författare)
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Chromosome-scale assembly and evolution of the tetraploid Salvia splendens (Lamiaceae) genome
- 2021
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Ingår i: Horticulture Research. - : Oxford University Press (OUP). - 2052-7276 .- 2662-6810. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Polyploidization plays a key role in plant evolution, but the forces driving the fate of homoeologs in polyploid genomes, i.e., paralogs resulting from a whole-genome duplication (WGD) event, remain to be elucidated. Here, we present a chromosome-scale genome assembly of tetraploid scarlet sage (Salvia splendens), one of the most diverse ornamental plants. We found evidence for three WGD events following an older WGD event shared by most eudicots (the γ event). A comprehensive, spatiotemporal, genome-wide analysis of homoeologs from the most recent WGD unveiled expression asymmetries, which could be associated with genomic rearrangements, transposable element proximity discrepancies, coding sequence variation, selection pressure, and transcription factor binding site differences. The observed differences between homoeologs may reflect the first step toward sub- and/or neofunctionalization. This assembly provides a powerful tool for understanding WGD and gene and genome evolution and is useful in developing functional genomics and genetic engineering strategies for scarlet sage and other Lamiaceae species.
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