645 research outputs found
Boomerang returns unexpectedly
Experimental study of the anisotropy in the cosmic microwave background (CMB)
is gathering momentum. The eagerly awaited Boomerang results have lived up to
expectations. They provide convincing evidence in favor of the standard
paradigm: the Universe is close to flat and with primordial fluctuations which
are redolent of inflation. Further scrutiny reveals something even more
exciting however -- two hints that there may be some unforeseen physical
effects. Firstly the primary acoustic peak appears at slightly larger scales
than expected. Although this may be explicable through a combination of mundane
effects, we suggest it is also prudent to consider the possibility that the
Universe might be marginally closed. The other hint is provided by a second
peak which appears less prominent than expected. This may indicate one of a
number of possibilities, including increased damping length or tilted initial
conditions, but also breaking of coherence or features in the initial power
spectrum. Further data should test whether the current concordance model needs
only to be tweaked, or to be enhanced in some fundamental way.Comment: 11 pages, 3 figures, final version accepted by Ap
The variable X-ray light curve of GRB 050713A: the case of refreshed shocks
We present a detailed study of the spectral and temporal properties of the
X-ray and optical emission of GRB050713a up to 0.5 day after the main GRB
event. The X-ray light curve exhibits large amplitude variations with several
rebrightenings superposed on the underlying three-segment broken powerlaw that
is often seen in Swift GRBs. Our time-resolved spectral analysis supports the
interpretation of a long-lived central engine, with rebrightenings consistent
with energy injection in refreshed shocks as slower shells generated in the
central engine prompt phase catch up with the afterglow shock at later times.
Our sparsely-sampled light curve of the optical afterglow can be fitted with a
single power law without large flares. The optical decay index appears flatter
than the X-ray one, especially at later times.Comment: few changes, to be published in A&
A Case of Drug-Induced Hepatitis due to Lenalidomide
Lenalidomide is a recent thalidomide analog used for the treatment of refractory multiple myeloma. The main toxicity of this drug consists in severe neutropenia and thrombocytopenia. Lenalidomide-associated liver injury is rare, manifesting itself as elevated liver enzymes and hyperbilirubinemia reversible upon weeks after drug withdrawal. We report here in detail the clinical course as well as the biological and histological alterations of an acute lenalidomide-induced liver injury. Findings on liver biopsy allowed us to discriminate acute inflammatory changes due to the drug and minor associated lesions of graft-versus-host disease in this patient with recurrent myeloma after allogeneic bone marrow transplantation
Basics of Generalized Unitarity
We review generalized unitarity as a means for obtaining loop amplitudes from
on-shell tree amplitudes. The method is generally applicable to both
supersymmetric and non-supersymmetric amplitudes, including non-planar
contributions. Here we focus mainly on N=4 Yang-Mills theory, in the context of
on-shell superspaces. Given the need for regularization at loop level, we also
review a six-dimensional helicity-based superspace formalism and its
application to dimensional and massive regularizations. An important feature of
the unitarity method is that it offers a means for carrying over any identified
tree-level property of on-shell amplitudes to loop level, though sometimes in a
modified form. We illustrate this with examples of dual conformal symmetry and
a recently discovered duality between color and kinematics.Comment: 37 pages, 10 figures. Invited review for a special issue of Journal
of Physics A devoted to "Scattering Amplitudes in Gauge Theories", R.
Roiban(ed), M. Spradlin(ed), A. Volovich(ed
Effect of Intraduodenal Bile and Na-Taurodeoxycholate on Exocrine Pancreatic Secretion and on Plasma Levels of Secretin, Pancreatic Polypeptide, and Gastrin in Man
The effect of intraduodenally administered cattle bile (CB) and Na-taurodeoxycholate (TDC) on basal pancreatic secretion and plasma levels of secretin, pancreatic polypeptide (PP), and gastrin were investigated on two separate days in 10 fasting volunteers. Doses of 2-6 g CB and 20&600 mg TDC were given intraduodenally at 65-min intervals. Volume, bicarbonate, lipase, trypsin, amylase, and bilirubin were measured in 10-min fractions of duodenal juice, and GI peptides determined by radioimmunoassay. CB and TDC enhanced significantly and dose-dependently volume, bicarbonate and enzyme secretion, and plasma secretin and PP levels. In contrast, plasma gastrin showed only a marginal increase. We conclude that the hydrokinetic effect of intraduodenal CB and TDC is at least partially mediated by secretin. Gastrin could be ruled out as a mediator of the ecbolic effect, whereas other GI peptides, primarily CCK, and/or neural mechanisms must be considered possible mediators. Both pathways may also play a role in the PP release
Pion production in the inner disk around Cygnus X-1
Neutron production via ^{4}He breakup and p(p, n{pi}^+)p is considered in the
innermost region of an accretion disk surrounding a Kerr Black Hole. These
reactions occur in a plasma in Wien equilibrium, where (radiatively produced)
pair production equals annihilation. Cooling of the disk is assumed to be due
to unsaturated inverse Comptonization of external soft photons and to the
energy needed to ignite both nuclear reactions. Assuming matter composition of
90% Hydrogen and 10% He, it is shown that, close to the border of this region,
neutron production is essentially from ^{4}He breakup. Close to the horizon,
the contribution from p(p, n{pi}^+)p to the neutron production is comparable to
that from the breakup. It is shown that the viscosity generated by the
collisions of the accreting matter with the neutrons may drive stationary
accretion, for accretion rates below a critical value. In this case, solution
to the disk equations is double-valued and for both solutions protons
overnumber the pairs. It is claimed that these solutions may mimic the states
of high and low luminosity observed in Cygnus X-1 and related sources. This
would be explained either by the coupling of thermal instability to the
peculiar behavior of the viscosity parameter alpha with the ion temperature
that may intermittently switch accretion off or by the impossibility of a
perfect tuning for both thermal and pair equilibrium in the disk, a fact that
forces the system to undergo a kind of limit cycle behavior around the upper
solution.Comment: 23 pages, 11 figure
Clear cell chondrosarcoma of the head and neck
Clear cell chondrosarcoma is a rare variant of chondrosarcoma that mostly involves the end of long bones. However, nine cases have been reported in the head and neck: four in larynx, two in nasal septum, two in maxilla and one in the skull. These cases form the basis of this review. Head and neck cases accounts for less than 5% of Clear cell chondrosarcomas in the whole body and the larynx is the most common place. The histological findings of head and neck cases are consistent with general features of this entity in the whole body and nearly all tumors in this case series had a component of conventional chondrosarcoma. Clear cell chondrosarcoma is an intracompartmental tumor and retains "Grenz zone" just beneath the epithelium. Therefore, the overlying mucosa remained intact in all laryngeal cases. Nasal tumor caused ballooning of the septum and the maxillary lesion did not involve the oral mucosa. This tumor presents various radiographic features in the head and neck area. Chondroblastoma, chondroma, osteoblastoma, osteosarcoma and metastatic renal cell carcinoma are included in the histologic differential diagnoses. Differentiation from chondroblastic osteosarcoma is important in the maxilla. A wide resection is adequate in most cases. However, some laryngeal cases show tendency to recur. Clear cell chondrosarcoma is a slow growing tumor and this necessitates a long time follow-up of patients. Due to the extreme rarity in the head and neck, diagnosis of Clear cell chondrosarcoma in this area, must be confirmed by histochemical and immunohistochemical studies
Obesity and nocturnal gastro-oesophageal reflux are related to onset of asthma and respiratory symptoms
Several studies have identified obesity as a risk factor for asthma in both children and adults. An increased prevalence of asthma in subjects with gastro-oesophageal reflux (GOR) and obstructive sleep apnoea syndrome has also been reported. The aim of this investigation was to study obesity, nocturnal GOR and snoring as independent risk factors for onset of asthma and respiratory symptoms in a Nordic population. In a 5-10 yr follow-up study of the European Community Respiratory Health Survey in Iceland, Norway, Denmark, Sweden and Estonia, a postal questionnaire was sent to previous respondents. A total of 16,191 participants responded to the questionnaire. Reported onset of asthma, wheeze and night-time symptoms as well as nocturnal GOR and habitual snoring increased in prevalence along with the increase in body mass index (BMI). After adjusting for nocturnal GOR, habitual snoring and other confounders, obesity (BMI >30) remained significantly related to the onset of asthma, wheeze and night-time symptoms. Nocturnal GOR was independently related to the onset of asthma and in addition, both nocturnal GOR and habitual snoring were independently related to onset of wheeze and night-time symptoms. This study adds evidence to an independent relationship between obesity, nocturnal gastro-oesophageal reflux and habitual snoring and the onset of asthma and respiratory symptoms in adults
Fabrication of three-dimensional hydrogel scaffolds for modeling shunt failure by tissue obstruction in hydrocephalus
MMP-3 in the peripheral serum as a biomarker of knee osteoarthritis, 40Â years after open total knee meniscectomy.
BACKGROUND: To explore potential biomarkers in a meniscectomy-induced knee osteoarthritis model, at forty years after meniscectomy. METHODS: We carried out a forty-year study of 53 patients who, as adolescents, underwent open total meniscectomy and assessed two potential synovial and serum biomarkers, namely glycosaminoglycan (GAG) and matrix metalloproteinase-3 (MMP-3). Of the 30 patients available for review, 8 had contralateral knee operations and were excluded. Of the remaining 22 patients, 17 had successful operated knee synovial fluid aspirations and 8 also had successful contralateral control knee aspirations. GAG and MMP3 levels in the synovial fluid and peripheral serum was measured using Alcian blue precipitation and ELISA quantification, respectively. Patients also had their knee radiographs assessed and their radiographic osteoarthritis classified as per the Kellgren-Lawrence and Ahlbӓck systems. RESULTS: At forty years after meniscectomy, synovial MMP-3 levels remain increased (p = 0.0132) while GAG levels were reduced (p = 0.0487) when compared to controls and these two levels correlate inversely. Furthermore, levels of synovial MMP-3 significantly correlated (p = 0.0032, r = 0.7734; p = 0.0256, r = 0.5552) and GAG levels significantly inversely correlated (p = 0.0308, r = - 0.6220; p = 0.0135, r = - 0.6024), respectively, with both radiological scoring systems. Interestingly, we found that the levels of serum MMP-3 correlated only with the synovial fluid levels of MMP-3 in the operated knee and not with the non-operated joint (p = 0.0252, r = 0.7706 vs. p = 0.0764, r = 0.6576). Multiple regression analysis for patient's quality of life based on these biomarkers revealed an almost perfect result with an R2 of 0.9998 and a p value = 0.0087. CONCLUSION: Our results suggest that serum levels of MMP3 could be used as a potential biomarker for knee osteoarthritis, using a simple blood test. Larger cohorts are desirable in order to prove or disprove this finding
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