| 1631. |
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| 1632. |
- Koul, R., et al.
(författare)
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The TACTIC atmospheric Cherenkov imaging telescope
- 2007
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 578:3, s. 548-564
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Tidskriftsartikel (refereegranskat)abstract
- The TACTIC (TeV Atomospheric Cherenkov Telescope with Imaging Camera) γγ-ray telescope, equipped with a light collector of area ∼9.5m2 and a medium resolution imaging camera of 349 pixels, has been in operation at Mt. Abu, India, since 2001. This paper describes the main features of its various subsystems and its overall performance with regard to (a) tracking accuracy of its two-axes drive system, (b) spot size of the light collector, (c) back-end signal processing electronics and topological trigger generation scheme, (d) data acquisition and control system and (e) relative and absolute gain calibration methodology. Using a trigger field-of-view of 11×1111×11 pixels (∼3.4∘×3.4∘)(∼3.4∘×3.4∘), the telescope records a cosmic ray event rate of ∼2.5Hz at a typical zenith angle of 15∘15∘. Monte Carlo simulation results are also presented in the paper for comparing the expected performance of the telescope with actual observational results. The consistent detection of a steady signal from the Crab Nebula above ∼1.2TeV energy, at a sensitivity level of ∼5.0σ∼5.0σ in ∼25h, alongwith excellent matching of its energy spectrum with that obtained by other groups, reassures that the performance of the TACTIC telescope is quite stable and reliable. Furthermore, encouraged by the detection of strong γγ-ray signals from Mrk 501 (during 1997 and 2006 observations) and Mrk 421 (during 2001 and 2005–2006 observations), we believe that there is considerable scope for the TACTIC telescope to monitor similar TeV γγ-ray emission activity from other active galactic nuclei on a long-term basis.
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| 1633. |
- Krebs, Alice, et al.
(författare)
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The EU-ToxRisk method documentation, data processing and chemical testing pipeline for the regulatory use of new approach methods
- 2020
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Ingår i: Archives of Toxicology. - : Springer Science and Business Media LLC. - 0340-5761 .- 1432-0738. ; 94:7, s. 2435-2461
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Tidskriftsartikel (refereegranskat)abstract
- Hazard assessment, based on new approach methods (NAM), requires the use of batteries of assays, where individual tests may be contributed by different laboratories. A unified strategy for such collaborative testing is presented. It details all procedures required to allow test information to be usable for integrated hazard assessment, strategic project decisions and/or for regulatory purposes. The EU-ToxRisk project developed a strategy to provide regulatorily valid data, and exemplified this using a panel of > 20 assays (with > 50 individual endpoints), each exposed to 19 well-known test compounds (e.g. rotenone, colchicine, mercury, paracetamol, rifampicine, paraquat, taxol). Examples of strategy implementation are provided for all aspects required to ensure data validity: (i) documentation of test methods in a publicly accessible database; (ii) deposition of standard operating procedures (SOP) at the European Union DB-ALM repository; (iii) test readiness scoring accoding to defined criteria; (iv) disclosure of the pipeline for data processing; (v) link of uncertainty measures and metadata to the data; (vi) definition of test chemicals, their handling and their behavior in test media; (vii) specification of the test purpose and overall evaluation plans. Moreover, data generation was exemplified by providing results from 25 reporter assays. A complete evaluation of the entire test battery will be described elsewhere. A major learning from the retrospective analysis of this large testing project was the need for thorough definitions of the above strategy aspects, ideally in form of a study pre-registration, to allow adequate interpretation of the data and to ensure overall scientific/toxicological validity.
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| 1634. |
- Krishnaswamy, Jayendra Kumar, et al.
(författare)
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Migratory CD11b+ conventional dendritic cells induce T follicular helper cell-dependent antibody responses.
- 2017
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Ingår i: Science immunology. - : American Association for the Advancement of Science (AAAS). - 2470-9468. ; 2:18
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Tidskriftsartikel (refereegranskat)abstract
- T follicular helper (Tfh) cells are a subset of CD4+ T cells that promote antibody production during vaccination. Conventional dendritic cells (cDCs) efficiently prime Tfh cells; however, conclusions regarding which cDC instructs Tfh cell differentiation have differed between recent studies. We found that these discrepancies might exist because of the unusual sites used for immunization in murine models, which differentially bias which DC subsets access antigen. We used intranasal immunization as a physiologically relevant route of exposure that delivers antigen to all tissue DC subsets. Using a combination of mice in which the function of individual DC subsets is impaired and different antigen formulations, we determined that CD11b+ migratory type 2 cDCs (cDC2s) are necessary and sufficient for Tfh induction. DC-specific deletion of the guanine nucleotide exchange factor DOCK8 resulted in an isolated loss of CD11b+ cDC2, but not CD103+ cDC1, migration to lung-draining lymph nodes. Impaired cDC2 migration or development in DC-specific Dock8 or Irf4 knockout mice, respectively, led to reduced Tfh cell priming, whereas loss of CD103+ cDC1s in Batf3-/- mice did not. Loss of cDC2-dependent Tfh cell priming impaired antibody-mediated protection from live influenza virus challenge. We show that migratory cDC2s uniquely carry antigen into the subanatomic regions of the lymph node where Tfh cell priming occurs-the T-B border. This work identifies the DC subset responsible for Tfh cell-dependent antibody responses, particularly when antigen dose is limiting or is encountered at a mucosal site, which could ultimately inform the formulation and delivery of vaccines.
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| 1635. |
- Krog, Jens, et al.
(författare)
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Stochastic unfolding of nanoconfined DNA: Experiments, model and Bayesian analysis
- 2018
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149:21
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Tidskriftsartikel (refereegranskat)abstract
- Nanochannels provide a means for detailed experiments on the effect of confinement on biomacro-molecules, such as DNA. Here we introduce a model for the complete unfolding of DNA from the circular to linear configuration. Two main ingredients are the entropic unfolding force and the friction coefficient for the unfolding process, and we describe the associated dynamics by a non-linear Langevin equation. By analyzing experimental data where DNA molecules are photo-cut and unfolded inside a nanochannel, our model allows us to extract values for the unfolding force as well as the friction coefficient for the first time. In order to extract numerical values for these physical quantities, we employ a recently introduced Bayesian inference framework. We find that the determined unfolding force is in agreement with estimates from a simple Flory-type argument. The estimated friction coefficient is in agreement with theoretical estimates for motion of a cylinder in a channel. We further validate the estimated friction constant by extracting this parameter from DNA's center-of -mass motion before and after unfolding, yielding decent agreement. We provide publically available software for performing the required image and Bayesian analysis. Published by AIP Publishing.
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| 1636. |
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| 1637. |
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| 1638. |
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| 1639. |
- Kumar, A., et al.
(författare)
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A Scalable Feedback Mechanism for Distributed Nullforming with Phase-Only Adaptation
- 2015
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Ingår i: IEEE Transactions on Signal and Information Processing over Networks. - : Institute of Electrical and Electronics Engineers Inc.. - 2373-776X. ; 1:1, s. 58-70
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers a problem of distributed nullforming, in which multiple wireless transmitters steer a null toward a designated receiver by only adjusting their carrier phases. Since each transmitter transmits at full power, the system maximizes 'power pooling' gains for cooperative communication or jamming, while simultaneously protecting a designated receiver. Analysis in a noiseless setting shows that, while the received power at the designated receiver, as a function of the transmitted phases, is nonconvex with multiple critical points, all of its local minima are also global minima. This implies that a null can be formed using a distributed, scalable protocol based on gradient descent: each transmitter adapts its phase based only on aggregate feedback broadcast by the receiver (so that feedback overhead does not increase with the number of transmitters), along with an estimate of its own channel gain (which can be obtained, e.g., via reciprocity). Simulations show that the convergence rate actually improves with the number of transmitters, and that the algorithm is robust to noise, substantial channel estimation errors, and oscillator drift.
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| 1640. |
- Kumar, Amit, et al.
(författare)
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Astroglial tracer BU99008 detects multiple binding sites in Alzheimer's disease brain
- 2021
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Ingår i: Molecular psychiatry. - : Springer Science and Business Media LLC. - 1476-5578 .- 1359-4184. ; 26:10, s. 5833-5847
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Tidskriftsartikel (refereegranskat)abstract
- With reactive astrogliosis being established as one of the hallmarks of Alzheimer’s disease (AD), there is high interest in developing novel positron emission tomography (PET) tracers to detect early astrocyte reactivity. BU99008, a novel astrocytic PET ligand targeting imidazoline-2 binding sites (I2BS) on astrocytes, might be a suitable candidate. Here we demonstrate for the first time that BU99008 could visualise reactive astrogliosis in postmortem AD brains and propose a multiple binding site [Super-high-affinity (SH), High-affinity (HA) and Low-affinity (LA)] model for BU99008, I2BS specific ligands (2-BFI and BU224) and deprenyl in AD and control (CN) brains. The proportion (%) and affinities of these sites varied significantly between the BU99008, 2-BFI, BU224 and deprenyl in AD and CN brains. Regional binding studies demonstrated significantly higher 3H-BU99008 binding in AD brain regions compared to CN. Comparative autoradiography studies reinforced these findings, showing higher specific binding for 3H-BU99008 than 3H-Deprenyl in sporadic AD brain compared to CN, implying that they might have different targets. The data clearly shows that BU99008 could detect I2BS expressing reactive astrocytes with good selectivity and specificity and hence be a potential attractive clinical astrocytic PET tracer for gaining further insight into the role of reactive astrogliosis in AD.
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