Breaking the Speed Limits of Phase-Change Memory Loke, D.; Lee, T. H.; Wang, W. J. ...
Science (American Association for the Advancement of Science),
06/2012, Letnik:
336, Številka:
6088
Journal Article
Recenzirano
Phase-change random-access memory (PCRAM) is one of the leading candidates for next-generation data-storage devices, but the trade-off between crystallization (writing) speed and amorphous-phase ...stability (data retention) presents a key challenge. We control the crystallization kinetics of a phase-change material by applying a constant low voltage via prestructural ordering (incubation) effects. A crystallization speed of 500 picoseconds was achieved, as well as high-speed reversible switching using 500-picosecond pulses. Ab initio molecular dynamics simulations reveal the phase-change kinetics in PCRAM devices and the structural origin of the incubation-assisted increase in crystallization speed. This paves the way for achieving a broadly applicable memory device, capable of nonvolatile operations beyond gigahertz data-transfer rates.
Reports of ChAdOx1 vaccine-associated thrombocytopenia and vascular adverse events have led to some countries restricting its use. Using a national prospective cohort, we estimated associations ...between exposure to first-dose ChAdOx1 or BNT162b2 vaccination and hematological and vascular adverse events using a nested incident-matched case-control study and a confirmatory self-controlled case series (SCCS) analysis. An association was found between ChAdOx1 vaccination and idiopathic thrombocytopenic purpura (ITP) (0-27 d after vaccination; adjusted rate ratio (aRR) = 5.77, 95% confidence interval (CI), 2.41-13.83), with an estimated incidence of 1.13 (0.62-1.63) cases per 100,000 doses. An SCCS analysis confirmed that this was unlikely due to bias (RR = 1.98 (1.29-3.02)). There was also an increased risk for arterial thromboembolic events (aRR = 1.22, 1.12-1.34) 0-27 d after vaccination, with an SCCS RR of 0.97 (0.93-1.02). For hemorrhagic events 0-27 d after vaccination, the aRR was 1.48 (1.12-1.96), with an SCCS RR of 0.95 (0.82-1.11). A first dose of ChAdOx1 was found to be associated with small increased risks of ITP, with suggestive evidence of an increased risk of arterial thromboembolic and hemorrhagic events. The attenuation of effect found in the SCCS analysis means that there is the potential for overestimation of the reported results, which might indicate the presence of some residual confounding or confounding by indication. Public health authorities should inform their jurisdictions of these relatively small increased risks associated with ChAdOx1. No positive associations were seen between BNT162b2 and thrombocytopenic, thromboembolic and hemorrhagic events.
Intense, millisecond-duration bursts of radio waves (named fast radio bursts) have been detected from beyond the Milky Way
. Their dispersion measures-which are greater than would be expected if they ...had propagated only through the interstellar medium of the Milky Way-indicate extragalactic origins and imply contributions from the intergalactic medium and perhaps from other galaxies
. Although several theories exist regarding the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetized plasma
. Two of these bursts have been observed to repeat
, and one repeater (FRB 121102) has been localized to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 (refs.
). However, the host galaxies and distances of the hitherto non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer that has sufficient spatial resolution for arcsecond localization at the time of discovery. Here we report the localization of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is different from the host of FRB 121102, as it is a thousand times more massive, with a specific star-formation rate (the star-formation rate divided by the mass) a hundred times smaller.
Topological Kondo insulators have been proposed as a new class of topological insulators in which non-trivial surface states reside in the bulk Kondo band gap at low temperature due to strong ...spin-orbit coupling. In contrast to other three-dimensional topological insulators, a topological Kondo insulator is truly bulk insulating. Furthermore, strong electron correlations are present in the system, which may interact with the novel topological phase. By applying spin- and angle-resolved photoemission spectroscopy, here we show that the surface states of SmB6 are spin polarized. The spin is locked to the crystal momentum, fulfilling time reversal and crystal symmetries. Our results provide strong evidence that SmB6 can host topological surface states in a bulk insulating gap stemming from the Kondo effect, which can serve as an ideal platform for investigating of the interplay between novel topological quantum states with emergent effects and competing orders induced by strongly correlated electrons.
It is shown that corannulene‐based strained π‐surfaces can be obtained through the use of mechanochemical Suzuki and Scholl reactions. Besides being solvent‐free, the mechanochemical synthesis is ...high‐yielding, fast, and scalable. Therefore, gram‐scale preparation can be carried out in a facile and sustainable manner. The synthesized nanographene structure carries positive (bowl‐like) and negative (saddle‐like) Gaussian curvatures and adopts an overall quasi‐monkey saddle‐type of geometry. In terms of properties, the non‐planar surface exhibits a high electron affinity that was measured by cyclic voltammetry, with electrolysis and in situ UV/vis spectroscopy experiments indicating that the one‐electron reduced state displays a long lifetime in solution. Overall, these results indicate the future potential of mechanochemistry in accessing synthetically challenging and functional curved π‐systems.
Mechanochemistry is demonstrated to be an effective and sustainable synthetic tool in the preparation of curved π‐materials with high electron affinity and a highly reversible nature of the electron‐transfer process.
We applied ozone source apportionment technology (OSAT) with tagged tracers coupled within the Comprehensive Air Quality Model with Extensions (CAMx) to study the region and source category ...contribution to surface ozone in the Yangtze River Delta area in summer of 2013. Results indicate that the daytime ozone concentrations in the YRD region are influenced by emissions both locally, regionally and super-regionally. At urban Shanghai, Hangzhou and Suzhou receptors, the ozone formation is mainly VOC-limited, precursor emissions form Zhejiang province dominate their O3 concentrations. At the junction area among two provinces and Shanghai city, the ozone is usually influenced by all the three areas. The daily max O3 at the Dianshan Lake in July are contributed by Zhejiang (48.5%), Jiangsu (11.7%), Anhui (11.6%) and Shanghai (7.4%), long-range transport constitutes around 20.9%. At Chongming site, the BVOC emissions rate is higher than urban region. Regional contribution results show that Shanghai constitutes 15.6%, Jiangsu contributes 16.2% and Zhejiang accounts for 25.5% of the daily max O3. The analysis of the source category contribution to high ozone in the Yangtze River Delta region indicates that the most significant anthropogenic emission source sectors contributing to O3 pollution include industry, vehicle exhaust, although the effects vary with source sector and selected pollution episodes. Emissions of NOx and VOCs emitted from the fuel combustion of industrial boilers and kilns, together with VOCs emissions from industrial process contribute a lot to the high concentrations in urban Hangzhou, Suzhou and Shanghai. The contribution from regional elevated power plants cannot be neglected, especially to Dianshan Lake. Fugitive emissions of volatile pollution sources also have certain contribution to regional O3. These results indicate that the regional collaboration is of most importance to reduce ambient ozone pollution, particularly during high ozone episodes.
•A high O3 episode over the YRD was simulated using the CAMx modeling system.•Ozone source apportionment technology was applied to study the formation mechanism and sources of O3.•Contributions of different source regions and source categories to O3 were analyzed.
Accurate prediction of in vivo hepatic drug clearance using in vitro assays is important to properly estimate clinical dosing regimens. Clearance of low-turnover compounds is especially difficult to ...predict using short-lived suspensions of unpooled primary human hepatocytes (PHHs) and functionally declining PHH monolayers. Micropatterned cocultures (MPCCs) of PHHs and 3T3-J2 fibroblasts have been shown previously to display major liver functions for several weeks in vitro. In this study, we first characterized long-term activities of major cytochrome P450 enzymes in MPCCs created from unpooled cryopreserved PHH donors. MPCCs were then used to predict the clearance of 26 drugs that exhibit a wide range of turnover rates in vivo (0.05-19.5 ml/min per kilogram). MPCCs predicted 73, 92, and 96% of drug clearance values for all tested drugs within 2-fold, 3-fold, and 4-fold of in vivo values, respectively. There was good correlation (R(2) = 0.94, slope = 1.05) of predictions between the two PHH donors. On the other hand, suspension hepatocytes and conventional monolayers created from the same donor had significantly reduced predictive capacity (i.e., 30-50% clearance values within 4-fold of in vivo), and were not able to metabolize several drugs. Finally, we modulated drug clearance in MPCCs by inducing or inhibiting P450s. Rifampin-mediated CYP3A4 induction increased midazolam clearance by 73%, while CYP3A4 inhibition with ritonavir decreased midazolam clearance by 79%. Similarly, quinidine-mediated CYP2D6 inhibition reduced clearance of dextromethorphan and desipramine by 71 and 22%, respectively. In conclusion, MPCCs created using cryopreserved unpooled PHHs can be used for drug clearance predictions and to model drug-drug interactions.
Neutrophils and neutrophil extracellular traps (NETs) have been shown to be involved in coagulation. However, the interactions between neutrophils or NETs and fibrin(ogen) in clots, and the ...mechanisms behind these interactions are not yet fully understood. In this in vitro study, the role of neutrophils or NETs on clot structure, formation and dissolution was studied with a combination of confocal microscopy, turbidity and permeation experiments. Factor (F)XII, FXI and FVII-deficient plasmas were used to investigate which factors may be involved in the procoagulant effects. We found both neutrophils and NETs promote clotting in plasma without the addition of other coagulation triggers, but not in purified fibrinogen, indicating that other factors mediate the interaction. The procoagulant effects of neutrophils and NETs were also observed in FXII- and FVII-deficient plasma. In FXI-deficient plasma, only the procoagulant effects of NETs were observed, but not of neutrophils. NETs increased the density of clots, particularly in the vicinity of the NETs, while neutrophils-induced clots were less stable and more porous. In conclusion, NETs accelerate clotting and contribute to the formation of a denser, more lysis resistant clot architecture. Neutrophils, or their released mediators, may induce clotting in a different manner to NETs, mediated by FXI.
Medical cyber-physical systems: A survey Dey, Nilanjan; Ashour, Amira S.; Shi, Fuqian ...
Journal of medical systems,
04/2018, Letnik:
42, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Medical cyber-physical systems (MCPS) are healthcare critical integration of a network of medical devices. These systems are progressively used in hospitals to achieve a continuous high-quality ...healthcare. The MCPS design faces numerous challenges, including inoperability, security/privacy, and high assurance in the system software. In the current work, the infrastructure of the cyber-physical systems (CPS) are reviewed and discussed. This article enriched the researches of the networked Medical Device (MD) systems to increase the efficiency and safety of the healthcare. It also can assist the specialists of medical device to overcome crucial issues related to medical devices, and the challenges facing the design of the medical device’s network. The concept of the social networking and its security along with the concept of the wireless sensor networks (WSNs) are addressed. Afterward, the CPS systems and platforms have been established, where more focus was directed toward CPS-based healthcare. The big data framework of CPSs is also included.
Field measurements of aboveground net primary productivity (ANPP) in
temperate grasslands suggest that both positive and negative asymmetric
responses to changes in precipitation (P) may occur. Under ...normal range of
precipitation variability, wet years typically result in ANPP gains being
larger than ANPP declines in dry years (positive asymmetry), whereas
increases in ANPP are lower in magnitude in extreme wet years compared to
reductions during extreme drought (negative asymmetry). Whether the current
generation of ecosystem models with a coupled carbon–water system in
grasslands are capable of simulating these asymmetric ANPP responses is an
unresolved question. In this study, we evaluated the simulated responses of
temperate grassland primary productivity to scenarios of altered
precipitation with 14 ecosystem models at three sites: Shortgrass
steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a
rainfall gradient from dry to moist. We found that (1) the spatial slopes
derived from modeled primary productivity and precipitation across sites were
steeper than the temporal slopes obtained from inter-annual variations, which
was consistent with empirical data; (2) the asymmetry of the responses of
modeled primary productivity under normal inter-annual precipitation
variability differed among models, and the mean of the model ensemble
suggested a negative asymmetry across the three sites, which was contrary to
empirical evidence based on filed observations; (3) the mean sensitivity of
modeled productivity to rainfall suggested greater negative response with
reduced precipitation than positive response to an increased precipitation
under extreme conditions at the three sites; and (4) gross primary productivity
(GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground
NPP (BNPP) all showed concave-down nonlinear responses to altered
precipitation in all the models, but with different curvatures and mean
values. Our results indicated that most models overestimate the negative
drought effects and/or underestimate the positive effects of increased
precipitation on primary productivity under normal climate conditions,
highlighting the need for improving eco-hydrological processes in those
models in the future.
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