9,213 research outputs found
Laboratory assessment of antibacterial activity of zwitterionic 7-methoxyimino cephalosporins
Zwitterionic 7-methoxyimino cephalosporins (cefpirome, cefepime, cefclidin, DQ2556, FKO37 and SCE2787) possess a variable substitution at C3 which contains a quarernary nitrogen. These cephalosporins display low affinities for Class I /7-lactamase and rapid penetration through the outer membrane of Gram-negative bacilli, so that an increased number of periplasmic β-lactam molecules interact with PBP's per unit of time. As a consequence, the new zitterionic compounds remain active against some, but not all, ceftazidime-resistant Enterobacteriaceae producing high levels of Class Iβlactamase or Bush type 2bβlactamases. Antipseudomonas activities are generally similar to that of ceftazidime except that cefclidin is more active. The new zwitterionic compounds, especially cefpirome and FK037, express greater antistaphylococcal potency than does ceftazidime. A variety of animal models including meningitis and endocarditis have confirmed the potential of these compounds in-vivo. On the basis of structural and antibacterial characteristics, the expression ‘forth generation' is acceptable to describe the zwitterionic 7-methoxyimino cephalosporin
Experimental metrics for detection of detailed balance violation
We report on the measurement of detailed balance violation in a coupled,
noise-driven linear electronic circuit consisting of two nominally identical RC
elements that are coupled via a variable capacitance. The state variables are
the time-dependent voltages across each of the two primary capacitors, and the
system is driven by independent noise sources in series with each of the
resistances. From the recorded time histories of these two voltages, we
quantify violations of detailed balance by three methods: 1) explicit
construction of the probability current density, 2) by constructing the
time-dependent stochastic area, and 3) by constructing statistical fluctuation
loops. In comparing the three methods, we find that the stochastic area is
relatively simple to implement, computationally inexpensive, and provides a
highly sensitive means for detecting violations of detailed balance.Comment: 12 pages, 6 figures, this version contains additional material
relative to the previous on
Practical management of heterogeneous neuroimaging metadata by global neuroimaging data repositories
Rapidly evolving neuroimaging techniques are producing unprecedented quantities of digital data at the same time that many research studies are evolving into global, multi-disciplinary collaborations between geographically distributed scientists. While networked computers have made it almost trivial to transmit data across long distances, collecting and analyzing this data requires extensive metadata if the data is to be maximally shared. Though it is typically straightforward to encode text and numerical values into files and send content between different locations, it is often difficult to attach context and implicit assumptions to the content. As the number of and geographic separation between data contributors grows to national and global scales, the heterogeneity of the collected metadata increases and conformance to a single standardization becomes implausible. Neuroimaging data repositories must then not only accumulate data but must also consolidate disparate metadata into an integrated view. In this article, using specific examples from our experiences, we demonstrate how standardization alone cannot achieve full integration of neuroimaging data from multiple heterogeneous sources and why a fundamental change in the architecture of neuroimaging data repositories is needed instead
Validation of northern latitude Tropospheric Emission Spectrometer stare ozone profiles with ARC-IONS sondes during ARCTAS: sensitivity, bias and error analysis
We compare Tropospheric Emission Spectrometer (TES) versions 3 and 4, V003 and V004, respectively, nadir-stare ozone profiles with ozonesonde profiles from the Arctic Intensive Ozonesonde Network Study (ARCIONS, http://croc.gsfc.nasa.gov/arcions/ during the Arctic Research on the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field mission. The ozonesonde data are from launches timed to match Aura's overpass, where 11 coincidences spanned 44° N to 71° N from April to July 2008. Using the TES "stare" observation mode, 32 observations are taken over each coincidental ozonesonde launch. By effectively sampling the same air mass 32 times, comparisons are made between the empirically-calculated random errors to the expected random errors from measurement noise, temperature and interfering species, such as water. This study represents the first validation of high latitude (>70°) TES ozone. We find that the calculated errors are consistent with the actual errors with a similar vertical distribution that varies between 5% and 20% for V003 and V004 TES data. In general, TES ozone profiles are positively biased (by less than 15%) from the surface to the upper-troposphere (~1000 to 100 hPa) and negatively biased (by less than 20%) from the upper-troposphere to the lower-stratosphere (100 to 30 hPa) when compared to the ozonesonde data. Lastly, for V003 and V004 TES data between 44° N and 71° N there is variability in the mean biases (from −14 to +15%), mean theoretical errors (from 6 to 13%), and mean random errors (from 9 to 19%)
Microstructure-sensitive fatigue modelling of medical-grade fine wire
This work presents a modelling methodology to assess the sensitivity to microstructure in high‐cycle fatigue performance of fine wires made from MP35N alloy (35Ni‐35Co‐20Cr‐10Mo in wt%) used as conductors in cardiac leads. The model consists of a microstructure generator that creates a mesh of a statistically representative microstructure, a finite element analysis using a crystal plasticity constitutive model to determine the local response behaviour of the microstructure, and a postprocesser using fatigue indicating parameters to assess the likelihood of fatigue crack initiation. The fatigue crack initiation potency for selected microstructure attributes, boundary and interface conditions, and loading profiles is determined by computing the Fatemi‐Socie fatigue indicating parameter over a physically relevant volume of scale. Case studies are used to investigate (1) the influence of nonmetallic inclusion proximity to the wire surface on fatigue potency and (2) the transition life demarcating lives primarily controlled by fatigue crack initiation versus microcrack fatigue growth
Ultra-bright and efficient single photon generation based on N-V centres in nanodiamonds on a solid immersion lens
Single photons are fundamental elements for quantum information technologies
such as quantum cryptography, quantum information storage and optical quantum
computing. Colour centres in diamond have proven to be stable single photon
sources and thus essential components for reliable and integrated quantum
information technology. A key requirement for such applications is a large
photon flux and a high efficiency. Paying tribute to various attempts to
maximise the single photon flux we show that collection efficiencies of photons
from colour centres can be increased with a rather simple experimental setup.
To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colour
centres on the flat surface of a ZrO2 solid immersion lens. We found stable
single photon count rates of up to 853 kcts/s at saturation under continuous
wave excitation while having excess to more than 100 defect centres with count
rates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we found
count rates up to 2.4 Mcts/s for time intervals of several ten seconds. It
seems to be a general feature that very high rates are accompanied by a
blinking behaviour. The overall collection efficiency of our setup of up to
4.2% is the highest yet reported for N-V defect centres in diamond. Under
pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a
click on the detector adding to 221 kcts/s thus opening the way towards diamond
based on-demand single photon sources for quantum applications
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