5,028 research outputs found
The 1996 Soft State Transitions of Cygnus X-1
We report continuous monitoring of Cygnus X-1 in the 1.3 to 200 keV band
using ASM/RXTE and BATSE/CGRO for about 200 days from 1996 February 21 to 1996
early September. During this period Cygnus X-1 experienced a hard-to-soft and
then a soft-to-hard state transition. The low-energy X-ray (1.3-12 keV) and
high-energy X-ray (20-200 keV) fluxes are strongly anti-correlated during this
period. During the state transitions flux variations of about a factor of 5 and
15 were seen in the 1.3-3.0 keV and 100-200 keV bands, respectively, while the
average 4.8-12 keV flux remains almost unchanged. The net effect of this
pivoting is that the total 1.3-200 keV luminosity remained unchanged to within
about 15%. The bolometric luminosity in the soft state may be as high as 50-70%
above the hard state luminosity, after color corrections for the luminosity
below 1.3 keV. The blackbody component flux and temperature increase in the
soft state is probably caused by a combination of the optically thick disk mass
accretion rate increase and a decrease of the inner disk radius.Comment: 18 pages, 1 PostScript figure. Accepted for ApJ
Inhibition of Rice Germination by Ustiloxin A Involves Alteration in Carbon Metabolism and Amino Acid Utilization
Ustiloxins are the main mycotoxin in rice false smut, a devastating disease caused by Ustilaginoidea virens. A typical phytotoxicity of ustiloxins is strong inhibition of seed germination, but the physiological mechanism is not clear. Here, we show that the inhibition of rice germination by ustiloxin A (UA) is dose-dependent. The sugar availability in UA-treated embryo was lower while the starch residue in endosperm was higher. The transcripts and metabolites responsive to typical UA treatment were investigated. The expression of several SWEET genes responsible for sugar transport in embryo was down-regulated by UA. Glycolysis and pentose phosphate processes in embryo were transcriptionally repressed. Most of the amino acids detected in endosperm and embryo were variously decreased. Ribosomal RNAs for growth was inhibited while secondary metabolites salicylic acid was also decreased under UA. Hence, we propose that the inhibition of seed germination by UA involves the block of sugar transport from endosperm to embryo, leading to altered carbon metabolism and amino acids utilization in rice plants. Our analysis provides a framework for understanding of the molecular mechanisms of ustiloxins on rice growth and in pathogen infection
Anatomska rekonstrukcija prednjeg kriĹľnog ligamenta
Tears of the anterior cruciate ligament (ACL) are one of the most common injuries to active individuals. The history of reconstructing a ruptured ACL has undergone many advances from open, extra-articular reconstructions, to modern day advanced arthroscopic techniques. Some of these new arthroscopic techniques use small incisions and standardized instruments reducing the surgical time, however, they fail to restore the native ACL anatomy. Recent studies have shown that non-anatomical reconstruction might result in suboptimal clinical outcomes. As a result, anatomic ACL reconstruction has gained popularity. The cornerstone of anatomic ACL reconstruction is the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites. This article is meant to provide the most up-to-date literature review regarding anatomic ACL reconstruction.Ozljede prednjeg križnog ligament (PKL) spadaju među najčešće sportske ozljede koljena. Povijest rekonstrukcije PKL-a prešla je dug put od otvorenih metoda do današnji modernih artroskopskih tehnika. Pri nekim artroskopskim tehnikama koriste se male incizije uz upotrebu standardiziranih instrumenata, čime se značajno skraćuje vrijeme operacije, ali se ne uspijeva u cijelosti rekonstruirati anatomsko hvatište PKL-a. Novije studije pokazale su da se takvim rekonstrukcijama ne uspijevaju postići zadovoljavajući klinički rezultati. Cilj anatomske rekonstrukcije jest rekonstukcija prirodne duljine i promjera PKL-a, orijetnacije kolagenih vlakana i anatomskih hvatišta. U ovom radu dajemo pregled najnovije literature koja se bavi anatomskom rekonstrukcijom PKL-a
Bistable molecular conductors with a field-switchable dipole group
A class of bistable "stator-rotor" molecules is proposed, where a stationary
bridge (stator) connects the two electrodes and facilitates electron transport
between them. The rotor part, which has a large dipole moment, is attached to
an atom of the stator via a single sigma bond. Hydrogen bonds formed between
the rotor and stator make the symmetric orientation of the dipole unstable. The
rotor has two potential minima with equal energy for rotation about the sigma
bond. The dipole orientation, which determines the conduction state of the
molecule, can be switched by an external electric field that changes the
relative energy of the two potential minima. Both orientation of the rotor
correspond to asymmetric current-voltage characteristics that are the reverse
of each other, so they are distinguishable electrically. Such bistable
stator-rotor molecules could potentially be used as parts of molecular
electronic devices.Comment: 8 pages, 7 figure
X-Ray Flares of Gamma-Ray Bursts: Quakes of Solid Quark Stars?
We propose a star-quake model to understand X-ray flares of both long and
short Gamma-ray bursts (GRBs) in a solid quark star regime. Two kinds of
central engines for GRBs are available if pulsar-like stars are actually
(solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found
that a quark star could be solidified about 10^3 to 10^6 s later after its
birth if the critical temperature of phase transition is a few MeV, and then a
new source of free energy (i.e., elastic and gravitational ones, rather than
rotational or magnetic energy) could be possible to power GRB X-ray flares.Comment: 8 pages, latex file. 2 figures. To appear in Science in China Series
Metabolomics Investigation Reveals Metabolite Mediators Associated with Acute Lung Injury and Repair in a Murine Model of Influenza Pneumonia
Influenza virus infection (IVI) can cause primary viral pneumonia, which may progress to acute lung injury (ALI) and respiratory failure with a potentially fatal outcome. At present, the interactions between host and influenza virus at molecular levels and the underlying mechanisms that give rise to IVI-induced ALI are poorly understood. We conducted a comprehensive mass spectrometry-based metabolic profiling of serum, lung tissue and bronchoalveolar lavage fluid (BALF) from a non-lethal mouse model with influenza A virus at 0, 6, 10, 14, 21 and 28 days post infection (dpi), representing the major stages of IVI. Distinct metabolite signatures were observed in mice sera, lung tissues and BALF, indicating the molecular differences between systematic and localized host responses to IVI. More than 100 differential metabolites were captured in mice sera, lung tissues and BALF, including purines, pyrimidines, acylcarnitines, fatty acids, amino acids, glucocorticoids, sphingolipids, phospholipids, etc. Many of these metabolites belonged to pulmonary surfactants, indicating IVI-induced aberrations of the pulmonary surfactant system might play an important role in the etiology of respiratory failure and repair. Our findings revealed dynamic host responses to IVI and various metabolic pathways linked to disease progression, and provided mechanistic insights into IVI-induced ALI and repair process.National Science Foundation (U.S.)Singapore-MIT Alliance for Research and Technology (SMART
A gene signature of loss of oestrogen receptor (ER) function and oxidative stress links ER-positive breast tumours with an absent progesterone receptor and a poor prognosis
Prognostic gene signatures like the wound and hypoxia signature differ by assumptions of cellular growth. Although gene signatures show little overlap, they also track within the group of luminal breast tumours those with a high proliferation and poor prognosis. Oxidative stress is another assumption of cellular growth. It affects several pathological conditions through its influence on the regulation of protein kinases and signal transduction pathways. A comprehensive set of 62 core genes from cultured oestrogen- and oestrogen receptor-deprived epithelial breast cancer cells is responsive to three forms of oxidative stress. Evidence is presented that oxidative stress involves the development of an aggressive subset of primary oestrogen receptor-positive breast tumours
Serum Metabolomics Reveals Serotonin as a Predictor of Severe Dengue in the Early Phase of Dengue Fever
Effective triage of dengue patients early in the disease course for in- or out-patient management would be useful for optimal healthcare resource utilization while minimizing poor clinical outcome due to delayed intervention. Yet, early prognosis of severe dengue is hampered by the heterogeneity in clinical presentation and routine hematological and biochemical measurements in dengue patients that collectively correlates poorly with eventual clinical outcome. Herein, untargeted liquid-chromatography mass spectrometry metabolomics of serum from patients with dengue fever (DF) and dengue hemorrhagic fever (DHF) in the febrile phase (1.5) in the serum, among which are two products of tryptophan metabolism–serotonin and kynurenine. Serotonin, involved in platelet aggregation and activation decreased significantly, whereas kynurenine, an immunomodulator, increased significantly in patients with DHF, consistent with thrombocytopenia and immunopathology in severe dengue. To sensitively and accurately evaluate serotonin levels as prognostic biomarkers, we implemented stable-isotope dilution mass spectrometry and used convalescence samples as their own controls. DHF serotonin was significantly 1.98 fold lower in febrile compared to convalescence phase, and significantly 1.76 fold lower compared to DF in the febrile phase of illness. Thus, serotonin alone provided good prognostic utility (Area Under Curve, AUC of serotonin = 0.8). Additionally, immune mediators associated with DHF may further increase the predictive ability than just serotonin alone. Nine cytokines, including IFN-γ, IL-1β, IL-4, IL-8, G-CSF, MIP-1β, FGF basic, TNFα and RANTES were significantly different between DF and DHF, among which IFN-γ ranked top by multivariate statistics. Combining serotonin and IFN-γ improved the prognosis performance (AUC = 0.92, sensitivity = 77.8%, specificity = 95.8%), suggesting this duplex panel as accurate metrics for the early prognosis of DHF
GaN and InN nanowires grown by MBE: a comparison
Morphological, optical and transport properties of GaN and InN nanowires
grown by molecular beam epitaxy (MBE) have been studied. The differences
between the two materials in respect to growth parameters and optimization
procedure was stressed. The nanowires crystalline quality has been investigated
by means of their optical properties. A comparison of the transport
characteristics was given. For each material a band schema was shown, which
takes into account transport and optical features and is based on Fermi level
pinning at the surface.Comment: 5 pages, 5 figure
RXTE Observation of Cygnus X-1 In Its High State
We present the results from the RXTE observations of Cygnus X-1 in its high
state. In the energy range of 2-200 keV, the observed X-ray spectrum can be
described by a model consisting of a soft blackbody component and a broken
power-law with a high energy cutoff. The low energy spectrum (below about 11
keV) varies significantly from observation to observation while the high energy
portion changes little. The X-ray flux varies on all timescales down to
milliseconds. The power density spectrum (PDS) can be characterized by excess
red noise (``1/f'') at low frequencies and a white noise component that extends
to 1-3 Hz before being cut off. At higher frequencies, the PDS becomes
power-law again, with a slope of roughly -2 (i.e., ``1/f^2''). Broad peaks in
the range of 3-9 Hz are present, and might be due to quasi-periodic
oscillations. The PDS shows interesting spectral dependence: the 1/f component
becomes more prominent when the low-energy spectrum becomes softer. The
difference in the observed spectral and timing properties between the low and
high states is qualitatively consistent with a simple ``fluctuating corona''
model.Comment: 11 pages including 3 figures, LaTeX (aaspp4.sty). Accepted for
publication in ApJ Letter
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