VENA CAVA AS AN ALTERNATIVE TO PERICARDIUM IN BIOPROSTHETIC PERCUTANEOUS HEART VALVES

Valve disease is a specialized form of cardiovascular disease that specifically affects the heart valves. Heart valves serve the vital function of maintaining unidirectional blood flow through the chambers of the heart during the cardiac cycle; however, as valve disease progresses, this function can become severely compromised [1]. Currently, the only cure for valve disease is to replace the defective valve with an engineered substitute. Each year, over 300,000 heart valve replacement surgeries are performed worldwide [2], and this number is expected to continue growing as life expectancies increase [3]. In the United States, the most common form of valve disease is aortic stenosis [4], which can become severe enough to necessitate valve replacement surgery. Although the demand for replacement valves is growing, current clinically available valve substitutes have still not been perfected. Mechanical valves present problems with thrombosis and necessitate lifetime anticoagulation therapy, whereas bioprosthetic valves have limited durability [1, 5]. Furthermore, valve replacement surgery is very invasive, and high risk patient populations are often denied surgery. Over 50% of elderly populations with aortic stenosis are not offered surgery because the mortality risk is too great [6, 7]. Due to the limitations of traditional heart valve replacement surgery, a new, less invasive option, percutaneous aortic valve replacement (PAVR), has been developed [8, 9]. PAVR involves transcatheter delivery of a crimped, stented valve to the aortic annulus. The valve is deployed by a balloon catheter or self-expansion. While not yet commercially available, two percutaneous heart valves (PVRs) are currently in clinical trials [9]. These models are composed of glutaraldehyde-fixed pericardial tissue. A major limitation of PVRs is the diameter to which the stent can be crimped. The device profile precludes use in small or tortuous vascular systems, limiting the candidate patient pool for PAVR [10]. An alternative material for PHVs may be porcine vena cava, as this tissue may provide enhanced flexibility and resilience. This study evaluates the feasibility of utilizing vena cava as a bioprosthetic tissue in PHVs by comparing its structural, mechanical, and in vivo properties to those of bovine pericardium. While the extracellular matrix fibers of pericardium are randomly oriented, the vena cava contains highly aligned collagen and elastin fibers that impart strength to the vessel in the circumferential direction and elasticity in the longitudinal. Mechanically, the vena cava is significantly less stiff than the pericardium, even after crosslinking with glutaraldehyde (GLUT) or combined neomycin and glutaraldehyde (NG) protocols. Furthermore, the vena cava\u27s mechanical compliance is preserved after compression under forces similar to those exerted by a stent, whereas pericardium is significantly stiffened by this process. However, the high elastin content of the vena cava may be responsible for enhanced calcification as compared to the pericardium, and an effective anticalcification strategy is necessary if the vena cava is to be clinically useful. Taken together, these results suggest that the vena cava may enhance leaflet flexibility, tissue resilience, and tissue integrity in PHVs, ultimately reducing the device profile while improving the durability of these valves

Fishes Associated with Oil and Gas Platforms in Louisiana\u27s River-Influenced Nearshore Waters

A distinctive feature of coastal Louisiana is the unrivaled network of oil and gas installations (platforms) extending from inshore waters to the deep Gulf of Mexico. Since 2007 there has been a 38% reduction in platform numbers with the highest removal rates occurring in shallow (\u3c 18 m) nearshore waters. Many fishes and invertebrates are attracted to platforms, presenting a unique opportunity to study detailed species-specific responses to the river-influenced hydrographic characteristics of Louisiana’s nearshore zone (5–25 km water depth). Prior studies of fishes around platforms focused on a few relatively large platforms in water depths ≥ 18 m. However, about one-third of all platforms are small, unmanned and non-drilling platforms located in waters \u3c 18 m depth. Paired video and hydrographic data were collected at 150 small platforms in \u3c 18 m water depth during the summers of 2013–2014. Fifty-four species of fishes were associated with small platforms. The assemblage(s) included juveniles of 29 species, indicating the importance of nearshore platforms as diverse nursery habitat. The coastal zone was divided into three regions based on broad-scale interactions between freshwater input and bathymetry driving major distinctions in interregional hydrography and fish assemblages. Co-occurring within this expansive artificial reef network is the second largest hypoxic area (dissolved oxygen (DO) \u3c 2.0 mg l−1) on Earth. Platforms offer reef-like habitat features in the upper water column that may offer refugia for some reef-associated species during hypoxic events. Significant intraregional differences in physicochemical features were related to the presence of hypoxia (defined as DO \u3c 50% saturation), as well as the distribution of sandy shoals. Eleven species accounted for most of the assemblage dissimilarities, composing ~93% of fishes observed. Habitat suitability indices for these 11 species provided information about habitat selection across horizontal and vertical physicochemical gradients throughout the coastal zone, and within hypoxic and well-oxygenated stratified water columns. East Bay, near the outlet of the Mississippi River, exhibited less hypoxia and a distinct fauna that included four adult goliath grouper (Epinephelus itajara). This endangered fish was observed during spawning season (summer), suggesting that East Bay might support a spawning aggregation

Human resources needs for universal access to antiretroviral therapy in South Africa: a time and motion study

<p>Background - Although access to life-saving treatment for patients infected with HIV in South Africa has improved substantially since 2004, treating all eligible patients (universal access) remains elusive. As the prices of antiretroviral drugs have dropped over the past years, availability of human resources may now be the most important barrier to achieving universal access to HIV treatment in Africa. We quantify the number of HIV health workers (HHWs) required to be added to the current HIV workforce to achieve universal access to HIV treatment in South Africa, under different eligibility criteria.</p> <p>Methods - We performed a time and motion study in three HIV clinics in a rural, primary care-based HIV treatment program in KwaZulu-Natal, South Africa, to estimate the average time per patient visit for doctors, nurses, and counselors. We estimated the additional number of HHWs needed to achieve universal access to HIV treatment within one year.</p> <p>Results - For universal access to HIV treatment for all patients with a CD4 cell count of ≤350 cells/μl, an additional 2,200 nurses, 3,800 counselors, and 300 doctors would be required, at additional annual salary cost of 929 million South African rand (ZAR), equivalent to US$141 million. For universal treatment (‘treatment as prevention’), an additional 6,000 nurses, 11,000 counselors, and 800 doctors would be required, at an additional annual salary cost of ZAR 2.6 billion (US$ 400 million).</p> <p>Conclusions - Universal access to HIV treatment for patients with a CD4 cell count of ≤350 cells/μl in South Africa may be affordable, but the number of HHWs available for HIV treatment will need to be substantially increased. Treatment as prevention strategies will require considerable additional financial and human resources commitments.</p&gt

On-chip light detection using monolithically integrated quantum dot micropillars

This work was supported by the German Research Foundation (DFG) under Grants RE2974/9-1 and SCHN1376/1-1. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework ERC Grant Agreement No. 615613.We demonstrate the on-chip detection of light using photosensitive detectors based on quantum dot (QD) micropillar cavities. These microscale detectors are applied exemplarily to probe the emission of a monolithically integrated, electrically pumped whispering gallery mode microlaser. Light is detected via the photocurrent induced in the electrically contacted micropillar detectors under reverse-bias. In order to demonstrate the high potential and applicability of the microdetector presented, we determine the threshold current of an integrated microlaser to be (54 ± 4) μA, in very good agreement with the value of (53 ± 4) μA inferred from optical data. Within this work we realize the monolithic integration of a laser and a detector in a single device operating in the regime of cavity-quantum electrodynamics. Our results thus advance the research on microscale sensor technology towards the few-photon quantum limit and pave the way for on-chip opto-electronic feedback experiments.PostprintPeer reviewe

An electrically driven cavity-enhanced source of indistinguishable photons with 61% overall efficiency

This work was financially supported by the German Research Foundation (DFG) under Grants RE2974/9-1 and SCHN1376/1-1 as well as the German Federal Ministry of Education and Research (BMBF) through the VIP-project “QSOURCE”.We report on an electrically driven efficient source of indistinguishable photons operated at pulse-repetition rates f up to 1.2 GHz. The quantum light source is based on a p-i-n-doped micropillar cavity with integrated self-organized quantum dots, which exploits cavity quantum electrodynamics effects in the weak coupling regime to enhance the emission of a single quantum emitter coupled to the cavity mode. We achieve an overall single-photon extraction efficiency of (61 ± 11) % for a device triggered electrically at f = 625 MHz. Analyzing the suppression of multi-photon emission events as a function of excitation repetition rate, we observe single-photon emission associated with g(2)HBT(0) values between 0.076 and 0.227 for f ranging from 373 MHz to 1.2 GHz. Hong-Ou-Mandel-type two-photon interference experiments under pulsed current injection at 487 MHz reveal a photon-indistinguishability of (41.1 ± 9.5) % at a single-photon emission rate of (92 ± 23) MHz.Publisher PDFPeer reviewe