1,879 research outputs found
Financing a portfolio of projects
This paper shows that investors financing a portfolio of projects may use the depth of their financial pockets to overcome entrepreneurial incentive problems. Competition for scarce informed capital at the refinancing stage strengthens investorsâ bargaining positions. And yet, entrepreneursâ incentives may be improved, because projects funded by investors with âshallow pocketsâ must have not only a positive net present value at the refinancing stage, but one that is higher than that of competing portfolio projects. Our paper may help to understand provisions used in venture capital finance that limit a fundâs initial capital and make it difficult to add more capital once the initial venture capital fund is raised
An XMM-Newton and NuSTAR study of IGR J18214-1318: a non-pulsating high-mass X-ray binary with a neutron star
IGR J18214-1318, a Galactic source discovered by the International Gamma-Ray
Astrophysics Laboratory, is a high-mass X-ray binary (HMXB) with a supergiant
O-type stellar donor. We report on the XMM-Newton and NuSTAR observations that
were undertaken to determine the nature of the compact object in this system.
This source exhibits high levels of aperiodic variability, but no periodic
pulsations are detected with a 90% confidence upper limit of 2% fractional rms
between 0.00003-88 Hz, a frequency range that includes the typical pulse
periods of neutron stars (NSs) in HMXBs (0.1-10 s). Although the lack of
pulsations prevents us from definitively identifying the compact object in IGR
J18214-1318, the presence of an exponential cutoff with e-folding energy
keV in its 0.3-79 keV spectrum strongly suggests that the compact
object is an NS. The X-ray spectrum also shows a Fe K emission line and
a soft excess, which can be accounted for by either a partial-covering absorber
with cm which could be due to the
inhomogeneous supergiant wind, or a blackbody component with
keV and km, which may originate
from NS hot spots. Although neither explanation for the soft excess can be
excluded, the former is more consistent with the properties observed in other
supergiant HMXBs. We compare IGR J18214-1318 to other HMXBs that lack
pulsations or have long pulsation periods beyond the range covered by our
observations.Comment: 15 pages, 12 figures, 4 table
A novel physiological role for ARF1 in the formation of bidirectional tubules from the Golgi.
Capitalizing on CRISPR/Cas9 gene-editing techniques and super-resolution nanoscopy, we explore the role of the small GTPase ARF1 in mediating transport steps at the Golgi. Besides its well-established role in generating COPI vesicles, we find that ARF1 is also involved in the formation of long (âŒ3 ”m), thin (âŒ110 nm diameter) tubular carriers. The anterograde and retrograde tubular carriers are both largely free of the classical Golgi coat proteins coatomer (COPI) and clathrin. Instead, they contain ARF1 along their entire length at a density estimated to be in the range of close packing. Experiments using a mutant form of ARF1 affecting GTP hydrolysis suggest that ARF1[GTP] is functionally required for the tubules to form. Dynamic confocal and stimulated emission depletion imaging shows that ARF1-rich tubular compartments fall into two distinct classes containing 1) anterograde cargoes and clathrin clusters or 2) retrograde cargoes and coatomer clusters
NuSTAR Detection Of A Cyclotron Line In The Supergiant Fast X-ray Transient IGR J17544-2619
We present NuSTAR spectral and timing studies of the Supergiant Fast X-ray
Transient (SFXT) IGR J17544-2619. The spectrum is well-described by a ~1 keV
blackbody and a hard continuum component, as expected from an accreting X-ray
pulsar. We detect a cyclotron line at 17 keV, confirming that the compact
object in IGR J17544-2619 is indeed a neutron star. This is the first
measurement of the magnetic field in a SFXT. The inferred magnetic field
strength, B = (1.45 +/- 0.03) * 10^12 G * (1+z) is typical of neutron stars in
X-ray binaries, and rules out a magnetar nature for the compact object. We do
not find any significant pulsations in the source on time scales of 1-2000 s.Comment: MNRAS Accepted. 8 pages, 4 figures, 3 table
Wild chimpanzees are infected by Trypanosoma brucei
AbstractAlthough wild chimpanzees and other African great apes live in regions endemic for African sleeping sickness, very little is known about their trypanosome infections, mainly due to major difficulties in obtaining their blood samples. In present work, we established a diagnostic ITS1-based PCR assay that allows detection of the DNA of all four Trypanosoma brucei subspecies (Trypanosoma brucei brucei, Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense, and Trypanosoma brucei evansi) in feces of experimentally infected mice. Next, using this assay we revealed the presence of trypanosomes in the fecal samples of wild chimpanzees and this finding was further supported by results obtained using a set of primate tissue samples. Phylogenetic analysis of the ITS1 region showed that the majority of obtained sequences fell into the robust T. brucei group, providing strong evidence that these infections were caused by T. b. rhodesiense and/or T. b. gambiense. The optimized technique of trypanosome detection in feces will improve our knowledge about the epidemiology of trypanosomes in primates and possibly also other endangered mammals, from which blood and tissue samples cannot be obtained.Finally, we demonstrated that the mandrill serum was able to efficiently lyse T. b. brucei and T. b. rhodesiense, and to some extent T. b. gambiense, while the chimpanzee serum failed to lyse any of these subspecies
Demonstration of the multimaterial coating concept to reduce thermal noise in gravitational-wave detectors
Thermal noise associated with the mechanical loss of current highly reflective mirror coatings is a critical limit to the sensitivity of gravitational-wave detectors. Several alternative coating materials show potential for reducing thermal noise, but cannot be used due to their high optical absorption. Multimaterial coatings have been proposed to enable the use of such materials to reduce thermal noise while minimizing their impact on the total absorption of the mirror coating. Here we present experimental verification of the multimaterial concept, by integrating aSi into a highly reflective SiO2 and Ta2O5 multilayer coating. We show a significant thermal noise improvement and demonstrate consistent optical and mechanical performance. The multimaterial coating survives the heat treatment required to minimize the absorption of the aSi layers, with no adverse effects from the different thermomechanical properties of the three materials
Advancing Our Functional Understanding of HostâMicrobiota Interactions: A Need for New Types of Studies
Multicellular life evolved in the presence of microorganisms and formed complex associations with their microbiota, the sum of all associated archaea, bacteria, fungi, and viruses. These associations greatly affect the health and life history of the host, which led to a new understanding of âselfâ and establishment of the âmetaorganismâ concept.1 The Collaborative Research Centre (CRC) 1182 aims at elucidating the evolution and function of metaorganisms. Its annual conference, the Young Investigator Research Day (YIRD), serves as a platform for scientists of various disciplines to share novel findings on hostâmicrobiota interactions, thereby providing a comprehensive overview of recent developments and new directions in metaorganism research. Even though we have gained tremendous insights into the composition and dynamics of hostâassociated microbial communities and their correlations with host health and disease, it also became evident that moving from correlative toward functional studies is needed to examine the underlying mechanisms of interactions within the metaorganism. Nonâclassical model organisms in particular possess significant potential to functionally address many open questions in metaorganism research. Here, we suggest and introduce a roadmap moving from correlation toward a functional understanding of hostâmicrobiota interactions and highlight its potential in emerging ecological, agricultural, and translational medical applications
Maternal hemoglobin concentration during pregnancy and risk of infant leukaemia: a children's oncology group study
In contrast to the positive association found in three studies between maternal anaemia during pregnancy and childhood leukaemia, no such association was found in infant leukaemia (odds ratio 0.85, 95% confidence interval 0.53â1.37)
Design and performance of the multiplexing spectrometer CAMEA
The cold neutron multiplexing secondary spectrometer CAMEA (Continuous Angle
Multiple Energy Analysis) was commissioned at the Swiss spallation neutron
source SINQ at the Paul Scherrer Institut at the end of 2018. The spectrometer
is optimised for an efficient data collection in the horizontal scattering
plane, allowing for detailed and rapid mapping of excitations under extreme
conditions. The novel design consists of consecutive, upward scattering
analyzer arcs underneath an array of position sensitive detectors mounted
inside a low permeability stainless-steel vacuum vessel. The construction of
the world's first continuous angle multiple energy analysis instrument required
novel solutions to many technical challenges, including analyzer mounting,
vacuum connectors, and instrument movement. These were solved by extensive
prototype experiments and in-house developments. Here we present a technical
overview of the spectrometer describing in detail the engineering solutions and
present our first experimental data taken during the commissioning. Our results
demonstrate the tremendous gains in data collection rate for this novel type of
spectrometer design
BioRock:new experiments and hardware to investigate microbeâmineral interactions in space
In this paper, we describe the development of an International Space Station experiment,
BioRock. The purpose of this experiment is to investigate biofilm formation and microbeâmineral
interactions in space. The latter research has application in areas as diverse as regolith amelioration and
extraterrestrial mining. We describe the design of a prototype biomining reactor for use in space
experimentation and investigations on in situ Resource Use and we describe the results of pre-flight tests
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