5,537 research outputs found
Clinical characteristics, evolution and prognosis of elderly patients admitted to a medical intensive care unit
Plasma-nitrided Ga2O3(Gd2O3) as interfacial passivation layer for InGaAs metal-oxide-semiconductor capacitor with HfTiON gate dielectric
published_or_final_versio
A New Parameter In Accretion Disk Model
Taking optically thin accretion flows as an example, we investigate the
dynamics and the emergent spectra of accretion flows with different outer
boundary conditions (OBCs) and find that OBC plays an important role in
accretion disk model. This is because the accretion equations describing the
behavior of accretion flows are a set of {\em differential} equations,
therefore, accretion is intrinsically an initial-value problem. We argue that
optically thick accretion flow should also show OBC-dependent behavior. The
result means that we should seriously consider the initial physical state of
the accretion flow such as its angular momentum and its temperature. An
application example to Sgr A is presented.Comment: 6 pages, 4 figures, to appear in the Proceeding of "Pacific Rim
Conference on Stellar Astrophysics", Aug. 1999, HongKong, Chin
Current measurement by real-time counting of single electrons
The fact that electrical current is carried by individual charges has been
known for over 100 years, yet this discreteness has not been directly observed
so far. Almost all current measurements involve measuring the voltage drop
across a resistor, using Ohm's law, in which the discrete nature of charge does
not come into play. However, by sending a direct current through a
microelectronic circuit with a chain of islands connected by small tunnel
junctions, the individual electrons can be observed one by one. The quantum
mechanical tunnelling of single charges in this one-dimensional array is time
correlated, and consequently the detected signal has the average frequency
f=I/e, where I is the current and e is the electron charge. Here we report a
direct observation of these time-correlated single-electron tunnelling
oscillations, and show electron counting in the range 5 fA-1 pA. This
represents a fundamentally new way to measure extremely small currents, without
offset or drift. Moreover, our current measurement, which is based on electron
counting, is self-calibrated, as the measured frequency is related to the
current only by a natural constant.Comment: 9 pages, 4 figures; v2: minor revisions, 2 refs added, words added to
title, typos correcte
Convergence from clusters to the bulk solid: an ab initio investigation of clusters NanCln (n=2-40)
The electronic structures of a series of sodium chloride clusters (NaCl)(n) (n = 2-40) cut out from the NaCl solid have been investigated by means of ab initio calculations. The calculation results demonstrated a good correlation of the topologic parameters N-d (the total amount of dangling bonds of a cut-out cluster) and beta (the average dangling bonds on each in-cluster atom) with the stability of clusters as well as an evident convergence from clusters to the bulk solid. Particularly, we found that the effective charges on the Cl anions are more site dependent than size dependent
Genetic inhibition of neurotransmission reveals role of glutamatergic input to dopamine neurons in high-effort behavior
Midbrain dopamine neurons are crucial for many behavioral and cognitive functions. As the major excitatory input, glutamatergic afferents are important for control of the activity and plasticity of dopamine neurons. However, the role of glutamatergic input as a whole onto dopamine neurons remains unclear. Here we developed a mouse line in which glutamatergic inputs onto dopamine neurons are specifically impaired, and utilized this genetic model to directly test the role of glutamatergic inputs in dopamine-related functions. We found that while motor coordination and reward learning were largely unchanged, these animals showed prominent deficits in effort-related behavioral tasks. These results provide genetic evidence that glutamatergic transmission onto dopaminergic neurons underlies incentive motivation, a willingness to exert high levels of effort to obtain reinforcers, and have important implications for understanding the normal function of the midbrain dopamine system.Fil: Hutchison, M. A.. National Institutes of Health; Estados UnidosFil: Gu, X.. National Institutes of Health; Estados UnidosFil: Adrover, Martín Federico. National Institutes of Health; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Lee, M. R.. National Institutes of Health; Estados UnidosFil: Hnasko, T. S.. University of California at San Diego; Estados UnidosFil: Alvarez, V. A.. National Institutes of Health; Estados UnidosFil: Lu, W.. National Institutes of Health; Estados Unido
Social Determinants of Community Health Services Utilization among the Users in China: A 4-Year Cross-Sectional Study
Background To identify social factors determining the frequency of community health service (CHS) utilization among CHS users in China. Methods Nationwide cross-sectional surveys were conducted in 2008, 2009, 2010, and 2011. A total of 86,116 CHS visitors selected from 35 cities were interviewed. Descriptive analysis and multinomial logistic regression analysis were employed to analyze characteristics of CHS users, frequency of CHS utilization, and the socio-demographic and socio-economic factors influencing frequency of CHS utilization. Results Female and senior CHS clients were more likely to make 3–5 and ≥6 CHS visits (as opposed to 1–2 visits) than male and young clients, respectively. CHS clients with higher education were less frequent users than individuals with primary education or less in 2008 and 2009; in later surveys, CHS clients with higher education were the more frequent users. The association between frequent CHS visits and family income has changed significantly between 2008 and 2011. In 2011, income status did not have a discernible effect on the likelihood of making ≥6 CHS visits, and it only had a slight effect on making 3–5 CHS visits. Conclusion CHS may play an important role in providing primary health care to meet the demands of vulnerable populations in China. Over time, individuals with higher education are increasingly likely to make frequent CHS visits than individuals with primary school education or below. The gap in frequency of CHS utilization among different economic income groups decreased from 2008 to 2011
Scallop swimming kinematics and muscle performance: modelling the effects of "within-animal" variation in temperature sensitivity
Escape behaviour was investigated in Queen scallops (Aequipecten opercularis) acclimated to 5, 10 or 15 degrees C and tested at their acclimation temperature. Scallops are active molluscs, able to escape from predators by jet-propelled swimming using a striated muscle working in opposition to an elastic hinge ligament. The first cycle of the escape response was recorded using high-speed video ( 250 Hz) and whole-animal velocity and acceleration determined. Muscle shortening velocity, force and power output were calculated using measurements of valve movement and jet area, and a simple biomechanical model. The average shortening speed of the adductor muscle had a Q(10) of 2.04, significantly reducing the duration of the jetting phase of the cycle with increased temperature. Muscle lengthening velocity and the overall duration of the clap cycle were changed little over the range 5 - 15 degrees C, as these parameters were controlled by the relatively temperature-insensitive, hinge ligament. Improvements in the average power output of the adductor muscle over the first clap cycle ( 222 vs. 139 W kg(-1) wet mass at 15 and 5 degrees C respectively) were not translated into proportional increases in overall swimming velocity, which was only 32% higher at 15 degrees C ( 0.37m s(-1)) than 5 degrees C (0.28 m s(-1))
Conditional statistics of electron transport in interacting nanoscale conductors
Interactions between nanoscale semiconductor structures form the basis for
charge detectors in the solid state. Recent experimental advances have
demonstrated the on-chip detection of single electron transport through a
quantum dot (QD). The discreteness of charge in units of e leads to intrinsic
fluctuations in the electrical current, known as shot noise. To measure these
single-electron fluctuations a nearby coherent conductor, called a quantum
point contact (QPC), interacts with the QD and acts as a detector. An important
property of the QPC charge detector is noninvasiveness: the system physically
affects the detector, not visa-versa. Here we predict that even for ideal
noninvasive detectors such as the QPC, when a particular detector result is
observed, the system suffers an informational backaction, radically altering
the statistics of transport through the QD as compared to the unconditional
shot noise. We develop a theoretical model to make predictions about the joint
current probability distributions and conditional transport statistics. The
experimental findings reported here demonstrate the reality of informational
backaction in nanoscale systems as well as a variety of new effects, such as
conditional noise enhancement, which are in essentially perfect agreement with
our model calculations. This type of switching telegraph process occurs
abundantly in nature, indicating that these results are applicable to a wide
variety of systems.Comment: 16 pages, 3 figures, to appear in Nature Physic
Measurement of finite-frequency current statistics in a single-electron transistor
Electron transport in nano-scale structures is strongly influenced by the
Coulomb interaction which gives rise to correlations in the stream of charges
and leaves clear fingerprints in the fluctuations of the electrical current. A
complete understanding of the underlying physical processes requires
measurements of the electrical fluctuations on all time and frequency scales,
but experiments have so far been restricted to fixed frequency ranges as
broadband detection of current fluctuations is an inherently difficult
experimental procedure. Here we demonstrate that the electrical fluctuations in
a single electron transistor (SET) can be accurately measured on all relevant
frequencies using a nearby quantum point contact for on-chip real-time
detection of the current pulses in the SET. We have directly measured the
frequency-dependent current statistics and hereby fully characterized the
fundamental tunneling processes in the SET. Our experiment paves the way for
future investigations of interaction and coherence induced correlation effects
in quantum transport.Comment: 7 pages, 3 figures, published in Nature Communications (open access
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