The Boson peak in supercooled water

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line TW. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.We thank S. V. Buldyrev and S. Sastry for helpful discussions. The simulations were in part performed using resources provided by the Swedish National Infrastructure for Computing (SNIC) at the NSC and HPC2N centers. LGMP, KTW and DS were supported by the Swedish Research Council. KTW is also supported by the Icelandic Research Fund through the START programme. PK acknowledges the support of National Academies Keck Future Initiatives award. HES thanks NSF Grants No. CHE0911389, No. CHE0908218, and No. CHE-1213217. (Swedish Research Council; Icelandic Research Fund through the START programme; National Academies Keck Future Initiatives award; CHE0911389 - NSF; CHE0908218 - NSF; CHE-1213217 - NSF)Published versio

The Boson peak in supercooled water

We perform extensive molecular dynamics simulations of the TIP4P/2005 model of water to investigate the origin of the Boson peak reported in experiments on supercooled water in nanoconfined pores, and in hydration water around proteins. We find that the onset of the Boson peak in supercooled bulk water coincides with the crossover to a predominantly low-density-like liquid below the Widom line $T_W$. The frequency and onset temperature of the Boson peak in our simulations of bulk water agree well with the results from experiments on nanoconfined water. Our results suggest that the Boson peak in water is not an exclusive effect of confinement. We further find that, similar to other glass-forming liquids, the vibrational modes corresponding to the Boson peak are spatially extended and are related to transverse phonons found in the parent crystal, here ice Ih.Comment: 25 pages, 9 figure

Current AATS guidelines on surgical treatment of infective endocarditis

© Annals of Cardiothoracic Surgery. The 2016 American Association for Thoracic Surgery (AATS) guidelines for surgical treatment of infective endocarditis (IE) are question based and address questions of specific relevance to cardiac surgeons. Clinical scenarios in IE are often complex, requiring prompt diagnosis, early institution of antibiotics, and decision-making related to complications, including risk of embolism and timing of surgery when indicated. The importance of an early, multispecialty team approach to patients with IE is emphasized. Management issues are divided into groups of questions related to indications for and timing of surgery, pre-surgical work-up, preoperative antibiotic treatment, surgical risk assessment, intraoperative management, surgical management, surveillance, and follow up. Standard indications for surgery are severe heart failure, severe valve dysfunction, prosthetic valve infection, invasion beyond the valve leaflets, recurrent systemic embolization, large mobile vegetations, or persistent sepsis despite adequate antibiotic therapy for more than 5-7 days. The guidelines emphasize that once an indication for surgery is established, the operation should be performed as soon as possible. Timing of surgery in patients with strokes and neurologic deficits require close collaboration with neurological services. In surgery infected and necrotic tissue and foreign material is radically debrided and removed. Valve repair is performed whenever possible, particularly for the mitral and tricuspid valves. When simple valve replacement is required, choice of valve-mechanical or tissue prosthesis-should be based on normal criteria for valve replacement. For patients with invasive disease and destruction, reconstruction should depend on the involved valve, severity of destruction, and available options for cardiac reconstruction. For the aortic valve, use of allograft is still favored

On the bond distance in methane

The equilibrium bond distance in methane was optimized using coupled-pair functional and contracted CI wave functions, and a Gaussian basis that includes g-type functions on carbon and d-type functions on hydrogen. The resulting bond distance, when corrected for core-valence correlation effects, agrees with the experimental value of 2.052 a(0) to within the experimental uncertainty of 0.002 a(0). The main source of error in the best previous studies, which showed discrepancies with experiment of 0.007 a(0) is shown to be basis set incompleteness. In particular, it is important that the basis set be close to saturation, at least for the lower angular quantum numbers

Who Wants to Work in a Rural Health Post? The Role of Intrinsic Motivation, Rural Background and Faith-Based Institutions in Rwanda and Ethiopia

Most developing countries face shortages of health workers in rural areas. This has profound consequences for health service delivery, and ultimately for health outcomes. To design policies that rectify these geographic imbalances it is vital to understand what factors determine health workers' choice to work in rural areas. But empirical analysis of health worker preferences has remained limited due to the lack of data. Using unique contingent valuation data from a cohort survey of 412 nursing and medical students in Rwanda, this paper examines the determinants of future health workers' willingness to work in rural areas, as measured by rural reservation wages, using regression analysis. These data are also combined with those from an identical survey in Ethiopia to enable a two-country analysis. We find that health workers with higher intrinsic motivation – measured as the importance attached to helping the poor – as well as those who have grown up in a rural area, and Adventists who participate in a local bonding scheme are all significantly more willing to work in a rural area. The main Rwanda result for intrinsic motivation is strikingly similar to that obtained for Ethiopia and Rwanda together. These results suggest that in addition to economic incentives, intrinsic motivation and rural origin play an important role in health workers' decisions to work in a rural area, and that faith-based institutions matter.health care delivery, health workers, labour supply, public service

Who Wants to Work in a Rural Health Post? The Role of Intrinsic Motivation, Rural Background and Faith-Based Institutions in Rwanda and Ethiopia

Background: Most developing countries face shortages of health workers in rural areas. This has profound consequences for health service delivery, and ultimately for health outcomes. To design policies that rectify these geographic imbalances it is vital to understand what factors determine health workers’ choice to work in rural areas. But empirical analysis of health worker preferences has remained limited due to the lack of data. Methods: Using unique contingent valuation data from a cohort survey of 412 nursing and medical students in Rwanda, this paper examines the determinants of future health workers’ willingness to work in rural areas, as measured by rural reservation wages, using regression analysis. These data are also combined with those from an identical survey in Ethiopia to enable a two-country analysis. Results: Health workers with higher intrinsic motivation - measured as the importance attached to helping the poor - as well as those who have grown up in a rural area, and Adventists who participate in a local bonding scheme are all significantly more willing to work in a rural area. The main Rwanda result for intrinsic motivation is strikingly similar to that obtained for Ethiopia and Rwanda together. Discussion: The results suggest that in addition to economic incentives, intrinsic motivation and rural origin play an important role in health workers’ decisions to work in a rural area, and that faith-based institutions matter.