1,796 research outputs found
An Effective Temperature Scale for Late M and L Dwarfs, from Resonance Absorption Lines of CsI and RbI
We present Keck HIRES spectra of 6 late-M dwarfs and 11 L dwarfs. Our goal is
to assign effective temperatures to the objects using detailed atmospheric
models and fine analysis of the alkali resonance absorption lines of CsI and
RbI. These yield mutually consistent results (+-150 K) when we use
``cleared-dust'' models, which account for the removal of refractory species
from the molecular states but do not include dust opacities. We find a tendency
for the RbI line to imply a slightly higher temperature, which we ascribe to an
incomplete treatment of the overlying molecular opacities. The final effective
temperatures we adopt are based on the CsI fits alone, though the RbI fits
support the CsI temperature sequence. This work, in combination with results
from the infrared, hints that dust in these atmospheres has settled out of the
high atmosphere but is present in the deep photosphere. We also derive radial
and rotational velocities for all the objects, finding that the previously
discovered trend of rapid rotation for very low mass objects is quite
pervasive. To improve on our analysis, there is a clear need for better
molecular line lists and a more detailed understanding of dust formation and
dynamics.Comment: 53 pages, including 20 figures and 2 Tables; accepted in Ap
Left ventricular to left atrial communication secondary to a paraaortic abscess: Color flow doppler documentation
Aortic root abscess occurs frequently in aortic prosthetic valve infective endocarditis. The present echocardiography report documents a ruptured abscess that led to a direct communication between the left ventricular outflow tract and the left atrium confirmed by real-time (color flow) Doppler imaging
Echocardiographic abnormalities and disease severity in Fabry's disease
Fabry's disease is an X-linked recessive genetic deficiency of the enzyme alpha-galactosidase A, which leads to the pathologic deposition of neutral glycosphingolipids in lysosomes of the vascular endothelium of the heart, brain and kidney. The disease is progressive in hemizygous male patients, with increasing involvement of the major organs leading to death. Because cardiac involvement is a constant feature, echocardiograms were performed on 35 patients with Fabry's disease, 23 hemizygotes (aged 28.6 ± 14 years) and 12 heterozygotes (aged 31.6 ± 6 years), to determine whether cardiac involvement could be detected noninvasively.The results demonstrated that hemizygous male patients had a greater aortic root diameter, thicker interventricular septum and greater ventricular mass than did heterozygous female patients. Left ventricular mass per square meter of body surface area correlated well with clinical disease severity (r = 0.68, p < 0.05), suggesting progressive glycosphingolipid deposition. Older heterozygotes (>25 years old) had more severe evidence of cardiac disease than did younger male patients. Although mitral valve prolapse was identified in 12 (54%) of 23 male hemizygotes and in 7 (58%) of 12 female heterozygotes, its presence did not correlate with clinical disease severity or other echocardiographic variables. Therefore, echocardiographic evidence of Fabry's disease appears to correlate with age-related disease severity and may be a useful noninvasive marker to follow disease progression and possible regression when appropriate therapy becomes available
Management of Hypertrophic Cardiomyopathy
Background: Hypertrophic cardiomyopathy (HCM) is clinically defined as unexplained myocardial hypertrophy, and it is an autosomal dominant disease of the cardiac sarcomere. It is present in 1 in 500 in the general adult population, making it the most common genetic cardiovascular disease. The pathophysiology of HCM is complex, leading to significant variability in clinical presentation. This, combined with the lack of randomized trials, makes the management of these patients difficult. Findings: The majority of patients with HCM are asymptomatic without a substantial reduction in survival. However, a considerable portion of patients will experience significant symptoms and HCM-related death, and effective therapies are available for these patients. Patients may have symptoms of heart failure from outflow tract obstruction and/or restrictive physiology. Medical therapy targeted at the underlying pathophysiology should be used, and surgical myectomy or alcohol septal ablation is available for those with refractory symptoms. While the overall risk of sudden cardiac death (SCD) is low in HCM patients, some are at elevated risk for and experience SCD, a devastating outcome in young patients. Risk stratification for SCD and treatment with implantable cardioverter-defibrillators is paramount. Many HCM patients will also develop atrial fibrillation, and this is often poorly tolerated. A rhythm control strategy with antiarrhythmic drugs or catheter ablation is often necessary, and anticoagulation should be administered to reduce the risk of thromboembolism. Finally, family members of patients with HCM should be regularly screened with electrocardiography and echocardiography. Conclusions: HCM is a complex disease with heterogeneous phenotypes and clinical manifestations. The management of HCM focuses on reducing symptoms of heart failure, preventing SCD, treating atrial fibrillation, and screening family members. Treatment should be tailored to the unique characteristics of each individual patient
Efficient algorithm to compute the Berry conductivity
We propose and construct a numerical algorithm to calculate the Berry conductivityin topological band insulators. The method is applicable to cold atomsystems as well as solid state setups, both for the insulating case where the Fermienergy lies in the gap between two bulk bands as well as in the metallic regime.This method interpolates smoothly between both regimes. The algorithm isgauge-invariant by construction, efficient, and yields the Berry conductivity withknown and controllable statistical error bars. We apply the algorithm to severalparadigmatic models in the field of topological insulators, including Haldaneʼsmodel on the honeycomb lattice, the multi-band Hofstadter model, and the BHZmodel, which describes the 2D spin Hall effect observed in CdTe/HgTe/CdTequantum well heterostructures
Uncomplicated Monochorionic Diamniotic Twins and the Timing of Delivery
Cleary-Goldman and d'Alton discuss the implications of a new study in PLoS Medicine examining the risk of fetal death in uncomplicated monochorionic diamnotic twin pregnancies
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