7,369 research outputs found
Space station integrated propulsion and fluid systems study
The program study was performed in two tasks: Task 1 addressed propulsion systems and Task 2 addressed all fluid systems associated with the Space Station elements, which also included propulsion and pressurant systems. Program results indicated a substantial reduction in life cycle costs through integrating the oxygen/hydrogen propulsion system with the environmental control and life support system, and through supplying nitrogen in a cryogenic gaseous supercritical or subcritical liquid state. A water sensitivity analysis showed that increasing the food water content would substantially increase the amount of water available for propulsion use and in all cases, the implementation of the BOSCH CO2 reduction process would reduce overall life cycle costs to the station and minimize risk. An investigation of fluid systems and associated requirements revealed a delicate balance between the individual propulsion and fluid systems across work packages and a strong interdependence between all other fluid systems
Direct-write, focused ion beam-deposited,7 K superconducting C-Ga-O nanowire
We have fabricated C-Ga-O nanowires by gallium focused ion beam-induced
deposition from the carbon-based precursor phenanthrene. The electrical
conductivity of the nanowires is weakly temperature dependent below 300 K, and
indicates a transition to a superconducting state below Tc = 7 K. We have
measured the temperature dependence of the upper critical field Hc2(T), and
estimate a zero temperature critical field of 8.8 T. The Tc of this material is
approximately 40% higher than that of any other direct write nanowire, such as
those based on C-W-Ga, expanding the possibility of fabricating direct-write
nanostructures that superconduct above liquid helium temperaturesComment: Accepted for AP
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Prospective observational study of point-of-care creatinine in trauma.
Background:Patients with trauma are at risk for renal dysfunction from hypovolemia or urological injury. In austere environments, creatinine values are not available to guide resuscitation. A new portable device, the Stat Sensor Point-of-care (POC) Whole Blood Creatinine Analyzer, provides accurate results in <30 s and requires minimal training. This device has not been evaluated in trauma despite the theoretical benefit it provides. The purpose of this study is to determine the clinical impact of the POC device in trauma. Methods:40 patients with trauma were enrolled in a prospective observational study. One drop of blood was used for creatinine determination on the Statsensor POC device. POC creatinine results were compared to the laboratory. Turnaround time (TAT) for POC and laboratory methods was calculated as well as time elapsed to CT scan if applicable. Results:Patients (n=40) were enrolled between December 2014 and March 2015. POC creatinine values were similar to laboratory methods with a mean bias of 0.075±0.27 (p=0.08). Mean analytical TATs for the POC measurements were significantly faster than the laboratory method (11.6±10.0 min vs 78.1±27.9 min, n=40, p<0.0001). Mean elapsed time before arrival at the CT scanner was 52.9±34.2 min. Conclusions:The POC device reported similar creatinine values to the laboratory and provided significantly faster results. POC creatinine testing is a promising development for trauma practice in austere environments and workup of a subset of stable patients with trauma. Further study is warranted to determine clinical impact, both in hospital-based trauma and austere environments
Marine Biodiversity and Ecosystem Health of Ilhas Selvagens, Portugal
In September 2015, National Geographic's Pristine Seas project, in conjunction with the Instituto Universitário-Portugal, The Waitt Institute, the University of Western Australia, and partners conducted a comprehensive assessment of the rarely surveyed Ilhas Selvagens to explore the marine environment, especially the poorly understood deep sea and open ocean areas, and quantify the biodiversity of the nearshore marine environment
The architectures of media power: editing, the newsroom, and urban public space
This paper considers the relation of the newsroom and the city as a lens into the more general relation of production spaces and mediated publics. Leading theoretically from Lee and LiPuma’s (2002) notion of ‘cultures of circulation’, and drawing on an ethnography of the Toronto Star, the paper focuses on how media forms circulate and are enacted through particular practices and material settings. With its attention to the urban milieus and orientations of media organizations, this paper exhibits both affinities with but also differences to current interests in the urban architectures of media, which describe and theorize how media get ‘built into’ the urban experience more generally. In looking at editing practices situated in the newsroom, an emphasis is placed on the phenomenological appearance of media forms both as objects for material assembly as well as more abstracted subjects of reflexivity, anticipation and purposiveness. Although this is explored with detailed attention to the settings of the newsroom and the city, the paper seeks to also provide insight into the more general question of how publicness is material shaped and sited
Dynamic Spin Response for Heisenberg Ladders
We employ the recently proposed plaquette basis to investigate static and
dynamic properties of isotropic 2-leg Heisenberg spin ladders. Simple
non-interacting multi-plaquette states provide a remarkably accurate picture of
the energy/site and dynamic spin response of these systems. Insights afforded
by this simple picture suggest a very efficient truncation scheme for more
precise calculations. When the small truncation errors are accounted for using
recently developed Contractor Renormalization techniques, very accurate results
requiring a small fraction of the computational effort of exact calculations
are obtained. These methods allow us to determine the energy/site, gap, and
spin response of 2x16 ladders. The former two values are in good agreement with
density matrix renormalization group results. The spin response calculations
show that nearly all the strength is concentrated in the lowest triplet level
and that coherent many-body effects enhance the response/site by nearly a
factor of 1.6 over that found for 2x2 systems.Comment: 9 pages with two enclosed postscript figure
A Plaquette Basis for the Study of Heisenberg Ladders
We employ a plaquette basis-generated by coupling the four spins in a
lattice to a well-defined total angular momentum-for the study of
Heisenberg ladders with antiferromagnetic coupling. Matrix elements of the
Hamiltonian in this basis are evaluated using standard techniques in
angular-momentum (Racah) algebra. We show by exact diagonalization of small
( and ) systems that in excess of 90% of the ground-state
probability is contained in a very small number of basis states. These few
basis states can be used to define a severely truncated basis which we use to
approximate low-lying exact eigenstates. We show how, in this low-energy basis,
the isotropic spin-1/2 Heisenberg ladder can be mapped onto an anisotropic
spin-1 ladder for which the coupling along the rungs is much stronger than the
coupling between the rungs. The mapping thereby generates two distinct energy
scales which greatly facilitates understanding the dynamics of the original
spin-1/2 ladder. Moreover, we use these insights to define an effective
low-energy Hamiltonian in accordance to the newly developed COntractor
REnormalization group (CORE) method. We show how a simple range-2 CORE
approximation to the effective Hamiltonian to be used with our truncated basis
reproduces the low-energy spectrum of the exact theory at the \alt
1% level.Comment: 12 pages with two postscript figure
Metal-to-insulator transition and magnetic ordering in CaRu_{1-x}Cu_xO_3
CaRuO_3 is perovskite with an orthorhombic distortion and is believed to be
close to magnetic ordering. Magnetic studies of single crystal and
polycrystalline CaRu_{1-x}Cu_xO_3 (0\le x \le 15 at.%Cu) reveal that
spin-glass-like transition develops for x\le 7 at.%Cu and obtained value for
effective magnetic moment p_{eff}=3.55 mu_B for x=5 at.% Cu, single crystal,
indicates presence of Ru^{5+}. At higher Cu concentrations more complex
magnetic behaviors are observed. Electrical resistivity measured on
polycrystalline samples shows metal-to-insulator transition (MIT) at 51 K for
only 2 at.% Cu. Charge compensation, which is assumed to be present upon
Cu^{2+/3+} substitution, induces appearance of Ru^{5+} and/or creation of
oxygen vacancies in crystal structure. Since the observed changes in physical
properties are completely attributable to the charge compensation, they cannot
be related to behaviors of pure compound where no such mechanism is present.
This study provides the criterion for "good" chemical probes for studying
Ru-based perovskites.Comment: 12 pages, 7 figure
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