High--order connected moments expansion for the Rabi Hamiltonian

We analyze the convergence properties of the connected moments expansion (CMX) for the Rabi Hamiltonian. To this end we calculate the moments and connected moments of the Hamiltonian operator to a sufficiently large order. Our large--order results suggest that the CMX is not reliable for most practical purposes because the expansion exhibits considerable oscillations.Comment: 12 pages, 5 figures, 1 tabl

Investigation of AIRSAR signatures of the Gulf Stream

Extensive Airborne Synthetic Aperture Radar (AIRSAR) measurements were made on 20 July 1990 during the NRL Gulf Stream (GS) experiment which addressed a number of scientific questions relating to SAR imaging of the ocean surface in the presence of variable currents and the background thermohaline circulation. The nature of the electromagnetic (e.m.) backscatter from the North edge of the GS using polarimetric signatures and amplitude imagery from the AIRSAR data is addressed

Screening Yield of HIV Antigen/Antibody Combination and Pooled HIV RNA Testing for Acute HIV Infection in a High-Prevalence Population

Although acute HIV infection contributes disproportionately to onward HIV transmission, HIV testing has not routinely included screening for acute HIV infection. To evaluate the performance of an HIV antigen/antibody (Ag/Ab) combination assay to detect acute HIV infection compared with pooled HIV RNA testing. Multisite, prospective, within-individual comparison study conducted between September 2011 and October 2013 in 7 sexually transmitted infection clinics and 5 community-based programs in New York, California, and North Carolina. Participants were 12 years or older and seeking HIV testing, without known HIV infection. All participants with a negative rapid HIV test result were screened for acute HIV infection with an HIV Ag/Ab combination assay (index test) and pooled human immunodeficiency virus 1 (HIV-1) RNA testing. HIV RNA testing was the reference standard, with positive reference standard result defined as detectable HIV-1 RNA on an individual RNA test. Number and proportion with acute HIV infections detected. Among 86,836 participants with complete test results (median age, 29 years; 75.0% men; 51.8% men who have sex with men), established HIV infection was diagnosed in 1158 participants (1.33%) and acute HIV infection was diagnosed in 168 participants (0.19%). Acute HIV infection was detected in 134 participants with HIV Ag/Ab combination testing (0.15% [95% CI, 0.13%-0.18%]; sensitivity, 79.8% [95% CI, 72.9%-85.6%]; specificity, 99.9% [95% CI, 99.9%-99.9%]; positive predictive value, 59.0% [95% CI, 52.3%-65.5%]) and in 164 participants with pooled HIV RNA testing (0.19% [95% CI, 0.16%-0.22%]; sensitivity, 97.6% [95% CI, 94.0%-99.4%]; specificity, 100% [95% CI, 100%-100%]; positive predictive value, 96.5% [95% CI, 92.5%-98.7%]; sensitivity comparison, P < .001). Overall HIV Ag/Ab combination testing detected 82% of acute HIV infections detectable by pooled HIV RNA testing. Compared with rapid HIV testing alone, HIV Ag/Ab combination testing increased the relative HIV diagnostic yield (both established and acute HIV infections) by 10.4% (95% CI, 8.8%-12.2%) and pooled HIV RNA testing increased the relative HIV diagnostic yield by 12.4% (95% CI, 10.7%-14.3%). In a high-prevalence population, HIV screening using an HIV Ag/Ab combination assay following a negative rapid test detected 82% of acute HIV infections detectable by pooled HIV RNA testing, with a positive predictive value of 59%. Further research is needed to evaluate this strategy in lower-prevalence populations and in persons using preexposure prophylaxis for HIV prevention

Ice-Tethered Profiler observations of the double-diffusive staircase in the Canada Basin thermocline

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C00A02, doi:10.1029/2008JC004829.Six Ice-Tethered Profilers (ITP), deployed in the central Canada Basin of the Arctic Ocean between 2004 and 2007, have provided detailed potential temperature and salinity measurements of a double-diffusive staircase at about 200–300 m depth. Individual layers in the staircase are of order 1 m in vertical height but appear to extend horizontally for hundreds of kilometers, with along-layer gradients of temperature and salinity tightly related. On the basis of laboratory-derived double-diffusive flux laws, estimated vertical heat fluxes through the staircase are in the range 0.05–0.3 W m−2, only about one tenth of the estimated mean surface mixed layer heat flux to the sea ice. It is thus concluded that the vertical transport of heat from the Atlantic Water in the central basin is unlikely to have a significant impact to the Canada Basin ocean surface heat budget. Icebreaker conductivity-temperature-depth data from the Beaufort Gyre Freshwater Experiment show that the staircase is absent at the basin periphery. Turbulent mixing that presumably disrupts the staircase might drive greater flux from the Atlantic Water at the basin boundaries and possibly dominate the regionally averaged heat flux.Funding for construction and deployment of the prototype ITPs was provided by the National Science Foundation Oceanographic Technology and Interdisciplinary Coordination (OTIC) Program and Office of Polar Programs (OPP) under grant OCE-0324233. Continued support for the ITP field program and data analysis has been provided by the OPP Arctic Sciences Section under awards ARC-0519899, ARC-0631951, ARC-0713837, and internal WHOI funding

First-line FOLFIRI and bevacizumab in patients with advanced colorectal cancer prospectively stratified according to serum LDH: Final results of the GISCAD (Italian Group for the Study of Digestive Tract Cancers) CENTRAL (ColorEctalavastiNTRiAlLdh) trial

Background:Previous findings suggested that bevacizumab might be able to improve response rate (RR) in colorectal cancer patients with high lactic dehydrogenase (LDH) basal levels.Methods:We conducted a phase II trial to prospectively ascertain whether bevacizumab in combination with FOLFIRI could have an improved clinical activity in patients with high LDH serum levels. Primary end point of the study was RR; secondary end points were median overall survival and median progression-free survival (mPFS).Results:A total of 81 patients were enrolled. No difference in terms of ORR (39% vs 31% for low vs high LDH level stratum, P=0.78) and mPFS (14.16 vs 10.29 months, HR: 1.07, 95% CI: 0.51-2.24, P=0.83) between the strata was observed, whereas overall survival (OS) was significantly longer for patients with low LDH (24.85 vs 15.14 months, HR: 4.08, 95% CI: 1.14-14.61, P=0.0004). In a not-pre-planned exploratory analysis using different cut-off ranges for LDH, we observed RR up to 70%, with no improvement in progression-free survival or OS.Conclusions:The CENTRAL trial failed to demonstrate that high LDH levels were related to a significantly improved RR in patients receiving first-line FOLFIRI and bevacizumab. The LDH serum levels should then no further be investigated as a predictive factor in this setting

On the detectability of internal waves by an imaging lidar

The first results of a multisensor airborne survey conducted off the western Iberian Coast are presented (including visible, lidar, and infrared imagery) and reveal the presence of internal solitary waves (ISWs) propagating into the nearshore region. For the first time, two-dimensional lidar imagery is shown to detect the presence of ISWs, and the results are interpreted in a more comprehensive framework provided by the remaining instrumentation. Sea surface roughness patterns, resulting from the ISWs, are found to be imaged in the lidar data, where specular reflection causes slicks to appear as areas of significantly reduced backscatter. Moreover, the lidar data reveal an unprecedented view into the ISW surface and subsurface structures. Possible interpretations are discussed based on the accumulation of surfactants and air bubble entrainment at the leading edge of the ISWs (where maximum convergence occurs)

Amide proton exchange rates of oxidized and reduced Saccharomyces cerevisiae iso-1-cytochrome c.

Proton NMR spectroscopy was used to determine the rate constant, kobs, for exchange of labile protons in both oxidized (Fe(III)) and reduced (Fe(II)) iso-1-cytochrome c. We find that slowly exchanging backbone amide protons tend to lack solvent-accessible surface area, possess backbone hydrogen bonds, and are present in regions of regular secondary structure as well as in omega-loops. Furthermore, there is no correlation between kobs and the distance from a backbone amide nitrogen to the nearest solvent-accessible atom. These observations are consistent with the local unfolding model. Comparisons of the free energy change for denaturation, delta Gd, at 298 K to the free energy change for local unfolding, delta Gop, at 298 K for the oxidized protein suggest that certain conformations possessing higher free energy than the denatured state are detected at equilibrium. Reduction of the protein results in a general increase in delta Gop. Comparisons of delta Gd to delta Gop for the reduced protein show that the most open states of the reduced protein possess more structure than its chemically denatured form. This persistent structure in high-energy conformations of the reduced form appears to involve the axially coordinated heme