411 research outputs found
Specialized physiological studies in support of manned space flight
The effects of a diuretic (Lasix) induced dehydration on the cardiovascular and hematological responses to lower body negative pressure (LBNP) were analyzed and compared to previous observations on dehydration following exercise in the heat. During LBNP runs the subjects were monitored for changes in blood volume, heart rate, blood pressure, and variations in the volume of the left calf. It was concluded that Lasix dehydration produced a depletion of the body electrolytes at the expense of both the plasma and extravascular compartments. Striking differences were found between those subjects who were physically active (Runners: R) and those who did not engage in any regular physical activity (Non-runners: NR). Tolerance to LBNP (Torr x min) was significantly lower in the R's than the NR's before and after dehydration, however the R's lost more of their tolerance after dehydration with Lasix than after exercise in the heat for about the same fluid loss. The opposite was true for the NR's. Two factors appear to be responsible for the lower LBNP tolerance in R's: parasympathetic inhibition of cardiac activity during LBNP and a greater propensity to pool blood in the lower extremities
The case of Scott Ortiz: a clash between criminal justice and public health
The criminal justice system creates particular challenges for persons with HIV and Hepatitis C, many of whom have a history of injection drug use. The case of Scott Ortiz, taken from public trial and sentencing transcripts, reveals the manner in which incarceration may delay learning of important health problems such as Hepatitis C infection. In addition, the case of Mr. Ortiz suggests the bias in sentencing that a former injection drug user may face. Collaboration between the Montefiore Medical Center residency in Social Medicine and a Bronx legal services agency, Bronx Defenders, yielded the discovery that a decade after diagnosis with HIV and after long term incarceration, Mr. Ortiz was infected with Hepatitis C. Mr. Ortiz only became aware of his advanced Hepatitis C and liver damage during his trial. The second important aspect of this case centers on the justification for lengthy sentence for a burglary conviction. The presiding Judge in Mr. Ortiz's case acknowledged that because of his advanced illness, Mr. Ortiz posed no threat to society as a burglar (the crime for which he was convicted). But the Judge elected to use his discretion to sentence Mr. Ortiz to a term of 15 years to life (as opposed to a minimum of two to four years) based on the idea that the public health would be served by preventing Mr. Ortiz from returning to the life of a street addict, sharing dirty needles with others. Mr. Ortiz reports distant injection drug use, no evidence of current or recent drug use was presented during Mr. Ortiz's trial and he reports no injection drug use for over a decade. In this case, bias against a former injection drug user, masquerading as concern for public health, is used to justify a lengthier sentence. Mr. Ortiz's lack of awareness of his Hepatitis C infection despite long term incarceration, combined with the justification for his dramatically increased sentence, provide examples of how persons within the criminal justice system may face particular challenges to their health
A Hard X-ray Study of the Normal Star-Forming Galaxy M83 with NuSTAR
We present results from sensitive, multi-epoch NuSTAR observations of the
late-type star-forming galaxy M83 (d=4.6 Mpc), which is the first investigation
to spatially resolve the hard (E>10 keV) X-ray emission of this galaxy. The
nuclear region and ~ 20 off-nuclear point sources, including a previously
discovered ultraluminous X-ray (ULX) source, are detected in our NuSTAR
observations. The X-ray hardnesses and luminosities of the majority of the
point sources are consistent with hard X-ray sources resolved in the starburst
galaxy NGC 253. We infer that the hard X-ray emission is most likely dominated
by intermediate accretion state black hole binaries and neutron star low-mass
X-ray binaries (Z-sources). We construct the X-ray binary luminosity function
(XLF) in the NuSTAR band for an extragalactic environment for the first time.
The M83 XLF has a steeper XLF than the X-ray binary XLF in NGC 253, consistent
with previous measurements by Chandra at softer X-ray energies. The NuSTAR
integrated galaxy spectrum of M83 drops quickly above 10 keV, which is also
seen in the starburst galaxies NGC253, NGC 3310 and NGC 3256. The NuSTAR
observations constrain any AGN to be either highly obscured or to have an
extremely low luminosity of 10 erg/s (10-30 keV), implying it
is emitting at a very low Eddington ratio. An X-ray point source consistent
with the location of the nuclear star cluster with an X-ray luminosity of a few
times 10 erg/s may be a low-luminosity AGN but is more consistent with
being an X-ray binary.Comment: Accepted for publication in ApJ (25 pages, 17 figures
To Trust or Not to Trust? Developing Trusted Digital Spaces through Timely Reliable and Personalized Provenance
Organizations are increasingly dependent on data stored and processed by distributed, heterogeneous services to make
critical, high-value decisions. However, these service-oriented computing environments are dynamic in nature and are becoming
ever more complex systems of systems. In such evolving and dynamic eco-system infrastructures, knowing how data was derived
is of significant importance in determining its validity and reliability. To address this, a number of advocates and theorists postulate
that provenance is critical to building trust in data and the services that generated it as it provides evidence for data consumers to
judge the integrity of the results. This paper presents a summary of the STRAPP (trusted digital Spaces through Timely Reliable
And Personalised Provenance) project, which is designing and engineering mechanisms to achieve a holistic solution to a number
of real-world service-based decision-support systems
Performance and science reach of the Probe of Extreme Multimessenger Astrophysics for ultrahigh-energy particles
The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a potential
NASA Astrophysics Probe-class mission designed to observe ultra-high energy
cosmic rays (UHECRs) and cosmic neutrinos from space. POEMMA will monitor
colossal volumes of the Earth's atmosphere to detect extensive air showers
(EASs) produced by extremely energetic cosmic messengers: UHECRs above 20 EeV
over the full sky and cosmic neutrinos above 20 PeV. We focus most of this
study on the impact of POEMMA for UHECR science by simulating the detector
response and mission performance for EAS from UHECRs. We show that POEMMA will
provide a significant increase in the statistics of observed UHECRs at the
highest energies over the entire sky. POEMMA will be the first UHECR
fluorescence detector deployed in space that will provide high-quality
stereoscopic observations of the longitudinal development of air showers.
Therefore, it will be able to provide event-by-event estimates of the
calorimetric energy and nuclear mass of UHECRs. The particle physics in the
interactions limits the interpretation of the shower maximum on an event by
event basis. In contrast, the calorimetric energy measurement is significantly
less sensitive to the different possible final states in the early
interactions. We study the prospects to discover the origin and nature of
UHECRs using expectations for measurements of the energy spectrum, the
distribution of arrival direction, and the atmospheric column depth at which
the EAS longitudinal development reaches maximum. We also explore supplementary
science capabilities of POEMMA through its sensitivity to particle interactions
at extreme energies and its ability to detect ultra-high energy neutrinos and
photons produced by top-down models including cosmic strings and super-heavy
dark matter particle decay in the halo of the Milky Way.Comment: 40 pages revtex, with 42 figure
POEMMA: Probe Of Extreme Multi-Messenger Astrophysics
The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission is being
designed to establish charged-particle astronomy with ultra-high energy cosmic
rays (UHECRs) and to observe cosmogenic tau neutrinos (CTNs). The study of
UHECRs and CTNs from space will yield orders-of-magnitude increase in
statistics of observed UHECRs at the highest energies, and the observation of
the cosmogenic flux of neutrinos for a range of UHECR models. These
observations should solve the long-standing puzzle of the origin of the highest
energy particles ever observed, providing a new window onto the most energetic
environments and events in the Universe, while studying particle interactions
well beyond accelerator energies. The discovery of CTNs will help solve the
puzzle of the origin of UHECRs and begin a new field of Astroparticle Physics
with the study of neutrino properties at ultra-high energies.Comment: 8 pages, in the Proceedings of the 35th International Cosmic Ray
Conference, ICRC217, Busan, Kore
Entrepreneurial Value Creation in the Cloud: Exploring the Value Dimensions of the Business Model
Part 5: Research in ProgressInternational audienceCloud computing’s potential in creating and capturing business value is being increasingly acknowledged. Existing empirical studies of business value in cloud computing have focused on user organizations and large enterprises with legacy systems. Acknowledging the innovation opportunities created by cloud, we study entrepreneurial cloud service providers. In this paper we conduct an exploratory study of six cloud-based start-up firms in India. We examine the value dimensions of the business model concept to study entrepreneurial value creation in the cloud. We find that cloud is a key resource in the structural configuration of their business model and enables the value proposition
A Focused, Hard X-ray Look at Arp 299 with NuSTAR
We report on simultaneous observations of the local starburst system Arp 299
with NuSTAR and Chandra, which provides the first resolved images of this
galaxy up to energies of ~ 45 keV. Fitting the 3-40 keV spectrum reveals a
column density of ~ 4 x10^{24} cm^{-2}, characteristic of a
Compton-thick AGN, and a 10-30 keV luminosity of 1.2x 10^{43} ergs s^{-1}. The
hard X-rays detected by NuSTAR above 10 keV are centered on the western
nucleus, Arp 299-B, which previous X-ray observations have shown to be the
primary source of neutral Fe-K emission. Other X-ray sources, including Arp
299-A, the eastern nucleus which is also thought to harbor an AGN, as well as
X-ray binaries, contribute to the 10-20 keV emission from the
Arp 299 system. The lack of significant emission above 10 keV other than that
attributed to Arp 299-B suggests that: a) any AGN in Arp 299-A must be heavily
obscured ( > 10^{24} cm^{-2}) or have a much lower luminosity than
Arp 299-B and b) the extranuclear X-ray binaries have spectra that cut-off
above ~10 keV. Such soft spectra are characteristic of ultraluminous X-ray
(ULX) sources observed to date by NuSTAR.Comment: 9 pages; accepted for publication in Astrophysical Journa
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