Risk factors for BK viremia in kidney transplant recipients

Background. In the past 20 years, BK virus has emerged as a cause of early graft dysfunction after kidney transplantation. In the setting of chronic immunosuppression (IS), the latent virus can reactivate, leading to BK viremia (10-20%) and in 1-10% of kidney transplant recipients to BK virus nephropathy (BKVN). The early detection of BK viremia by serum DNA PCR screening allows prompt but controlled reduction of IS, which, despite numerous attempts to find specific antiviral agents, remains the mainstay therapy. So far, besides potent IS, no risk factor has been consistently associated with BK viremia/BKVN. The use of a ureteral stent at the time of transplantation to protect the ureterovesical anastomosis has been described as a potential trigger. In this study, we aimed at defining the incidence and kinetics of BK viremia in our local cohort of kidney transplant recipients, and analysed potential predictors of BK viremia/BKVN, including ureteral stents. Methods. We performed a single-centre retrospective study on consecutive patients who received a kidney transplant at the CHUV between 01.11.03 and 31.12.12, with at least 12 months follow-up. First, descriptive statistics were done to define the general characteristics of the population. From a total 308 patients, a subpopulation of 195, transplanted between 01.01.08 and 31.12.12, had enough data for relevant analysis of BK viremia status during the first year as well as the use of a ureteral stent. Statistical analyses were performed using R-software. Results. BK viremia (>1000 copies/ml at least twice) was detected in 37/195 (19%) patients within the first year post-transplantation, with an early onset in the first 4 months for 65%, whereas only 6 patients were newly diagnosed after 12 months. 28/195 (14.4%) had a peak BK viremia >10'000 copies/ml, which represents a high positive predictive value for BKVN. Patients with BK viremia had a significantly lower kidney function at one year as compared to BK viremia negative recipients (eGFR=58 vs. 67 ml/min; p=0.019), and eGFR decreased as viremia levels increased, in particular >10'000 copies/ml. We found no significant association with the type of graft (living vs. cadaveric donor), or IS protocols (Basiliximab vs. Thymoglobulin induction, tacrolimus vs. cyclosporine). Interestingly, combining recipient's age and gender, we observed a higher risk to reactivate BK virus in older men (p=0.05). Ureteral stents were placed in 76/195 patients (39%), but their use did not significantly influence BK viremia. Conclusion. Considering the incidence of BK viremia in our population (22%), the fact that BKVN represents a poor prognosis factor for graft function and that viremia detection by PCR allows early diagnosis and management, our data reinforce the importance of regular screening early after kidney transplantation and in the case of unexplained rise in serum creatinine. Based on current knowledge and on our data, a prospective randomized multicentre study with controlled variables (IS, ureteral stents) and standardized follow-up charts (including urological complications/manipulations) would help better understand the determinants of BK viremia/BKVN

Interview with Marianna Black Habisreutinger

https://digitalcommons.winthrop.edu/scmotheroftheyear/1014/thumbnail.jp

A coupled approximate deconvolution and dynamic mixed scale model for large-eddy simulation

Large-eddy simulations of incompressible Newtonian fluid flows with approximate deconvolution models based on the van Cittert method are reported. The Legendre spectral element method is used for the spatial discretization to solve the filtered Navier--Stokes equations. A novel variant of approximate deconvolution models blended with a mixed scale model using a dynamic evaluation of the subgrid-viscosity constant is proposed. This model is validated by comparing the large-eddy simulation with the direct numerical simulation of the flow in a lid-driven cubical cavity, performed at a Reynolds number of 12'000. Subgrid modeling in the case of a flow with coexisting laminar, transitional and turbulent zones such as the lid-driven cubical cavity flow represents a challenging problem. Moreover, the coupling with the spectral element method having very low numerical dissipation and dispersion builds a well suited framework to analyze the efficiency of a subgrid model. First- and second-order statistics obtained using this new model are showing very good agreement with the direct numerical simulation. Filtering operations rely on an invertible filter applied in a modal basis and preserving the C0-continuity across elements. No clipping on dynamic parameters was needed to preserve numerical stability

Grid Filter Models for the Large Eddy Simulation of Fluid Flows

In fluid mechanics, turbulence can occur in very simple flow geometries, for Newtonian fluids and without the need for additional flow conditions such as temperature gradients or chemical reactions. In standard cases, intuitive assumptions on the physics of the subgrid scales coupled with the classical theories of turbulence can be well suited for subgrid modelling in large eddy simulation. However, considering more complex situations such as elastic or plasmas turbulence, the behaviour of the subgrid scales is not clearly identified, certainly not as intuitive and the corresponding theories are not available yet. The question is how to proceed when the functional modelling, which imposes a known behaviour to the subgrid scales of the flow, is not possible. For instance, this issue could be overcome using deconvolution-based subgrid models which aim at a partial recovery of the original quantities from their filtered counterpart. In principle, functional modelling is avoided by attempting to invert the filtering operator applied to the governing equations. However, this apparent advantage is completely lost since these models are usually coupled with auxiliary approaches, directly based on functional modelling, in order to account for the interactions with the scales which are not representable on the coarse spatial discretization used for large eddy simulation. The driving motivation of this work is to suppress the need for this secondary modelling which would allow to extend the use of deconvolution-based models to the large eddy simulation of flows whose behaviour of subgrid scales is not identified. Considering the effects of the coarse numerical discretization as the only effective filter applied to the macroscopic equations, an interpretation of the deconvolution models as a way to approximate the effect of the scales lost by numerical discretization on the resolved scales of the flow is demonstrated. Consequently, a new category of subgrid models, the grid filter models, is defined and gives a theoretical justification to the use of deconvolution models for the entire subgrid modelling process. In this perspective, a general method for the computation of the convolution filter which models the effect of the grid filter on the computable scales of the solution is proposed, thereby addressing the key issue of the numerical discretization in large eddy simulation. This modelling approach is validated performing the large eddy simulation of the incompressible flow of a Newtonian fluid in a lid-driven cubical cavity. Comparisons with classical subgrid models allow to assess the validity of this modelling approach and the suppression of the need for functional modelling. In order to extend the validity domain of the grid filter models, the large eddy simulation of an elastic turbulence problem is envisaged. Numerical simulations of elastic turbulence are limited by numerical instabilities which are particularly stringent at high elasticity. Moreover, the computational burden resulting from the required space-time resolutions is significantly increased as compared to the Newtonian case. Consequently, available direct numerical simulations are restricted to periodic and two-dimensional cases. Among these studies, the large eddy simulation of the viscoelastic Kolmogorov flow is chosen as benchmark problem

Oxygen Degradation in Mesoporous Al<inf>2</inf>O<inf>3</inf>/CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3-</inf><inf>x</inf>Cl<inf>x</inf> Perovskite Solar Cells: Kinetics and Mechanisms

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market-competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen-induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build-up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge-extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen.This work was supported by SABIC and by the EPSRC, including by the Supergen Supersolar Consortium (EP/J017361/1) and the European Union Seventh Framework Program [FP7 2007-2003] under grant agreement 604032 of the MESO project. GE is supported by the EPSRC and Oxford Photovoltaics Ltd. through a Nanotechnology KTN CASE award. JW acknowledges the Swire Educational Trust for supporting his D.Phil. study at Oxford. We thank Sian Dutton (University of Cambridge) for access to XRD facilities and Felix Deschler (University of Cambridge) for helpful discussions.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aenm.20160001

To form a union without having a child. The lengthening of the initial period of life in union before parenthood. A study based on European FFS data

Comunicació presentada a l'European Population Conference: "Migration and Migrants in Europe"(Sessió 53). Organitzat per l'European Association for Population Studies (EAPS); Centre d'Estudis Demogràfics. Barcelona, del 9 al 12 de juliol de 2008.The authors of the Second Demographic Transition scheme single out the postponement of the age at first childbearing as the main effect of the changes in habits of young adults associated with this transition. This postponement is accompanied by an increase in the length of the initial period of life in partnership when the couple has no plan yet to have children. This change is made possible by the use of contraceptive means by people living in partnerships in order to delay first childbearing. This is in sharp contrast with the First Demographic Transition, which was also characterized by the extension of the use of contraceptive means, but only after the birth of children. So contraception was used then to control fertility, when it is used nowadays to extend the period of life when no irreversible decisions, like having a child, have been made yet. In this work, we study various dimensions of this postponement of childbearing by couples. First, we try to quantify the magnitude of the increase in the duration of this initial period, when the couple delays parenthood. Second we have a look at the way this change in fertility behaviours in the first years of union change the duration model that was typical at the end of the First Demographic Transition. Finally, we investigate the possible determinants of the increase of this initial period using data on time spent by women studying and working, and of the transition from cohabitation to marriage. We use data from Fertility and Families Surveys for 17 countries and apply life table techniques and proportional hazard modelling.Un dels principals canvis associats a la Segona Transició Demogràfica és el retard en l'edat de tenir el primer fill, allargant-se el període d'unió sense plans de tenir-los. El retard és possible gràcies a la utilització dels mitjans anticonceptius, fet que contrasta amb la Primera Transició Demogràfica, a on els mitjans anticonceptius s'empraven després del naixement dels fills. En aquest estudi s'analitzen les diverses dimensions d'aquest ajornament. En primer lloc, es quantifica l'augment temporal d'aquest període inicial sense fills; en segon lloc s'analitza la forma en què aquest canvi modifica el model de la Primera Transició Demogràfica; finalment, s'apunten possibles determinants, emprant dades sobre el temps dedicat per les dones a estudiar i a treballar, i de la transició de la cohabitació al matrimoni. La font bàsica d'informació és la Fertility and Families Surveys , per a 17 països.Uno de los principales cambios asociados a la Segunda Transición Demográfica, es el aplazamiento en la edad de tener el primer hijo, ampliándose el período de unión sin planes de tenerlos. La demora es posible gracias a la utilización de los medios anticonceptivos, hecho que contrasta con la Primera Transición Demográfica, donde los medios anticonceptivos se utilizaban después del nacimiento de los hijos. En este estudio se analizan las dimensiones de este aplazamiento. En primer lugar, se cuantifica el aumento temporal de esta etapa inicial sin hijos; en segundo lugar, se analiza la forma en que este cambio modifica el modelo de la Primera Transición Demográfica; finalmente, se apuntan posibles determinantes utilizando datos sobre el tiempo dedicado por las mujeres a estudiar y a trabajar, y de la transición de la cohabitación al matrimonio. La fuente básica de información es la Fertility and Families Surveys, para 17 países

Assessing health and environmental impacts of solvents for producing perovskite solar cells

Halide perovskites are poised as a game-changing semiconductor system with diverse applications in optoelectronics. Industrial entities aim to commercialize perovskite technologies because of high performance but also because this type of semiconductor can be processed from solution, a feature enabling low cost and fast production. Here, we analyse the health and environmental impacts of eight solvents commonly used in perovskite processing. We consider first- and higher-order ramifications of each solvent on an industrial scale such as solvent production, use/removal, emissions and potential end-of-life treatments. Further, we consider the energy of evaporation for each solvent, air emission, condensation and subsequent incineration, reuse or distillation for solvent recycling, and apply a full end-of-life analysis. For human health impact, we use the ‘USEtox’ method but also consider toxicity data beyond carcinogenic classifications. We find that dimethyl sulfoxide has the lowest total impact, by being the most environmentally friendly and least deleterious to human health of the solvents considered. The analysis of the effects of these solvents on human health and the environment provides guidance for sustainable development of this new technology

CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites

The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI3. In this work, inorganic perovskite composition CsPbI3 is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI2–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.It is found that unique adducts form between CsI and dimethyl sulfoxide (DMSO) and certain antisolvents, such as methyl acetate, during film formation of the all‐inorganic perovskite CsPbI3. These adducts significantly influence crystallization and the power conversion efficiency of the resulting solar cells.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/1/aenm201903365-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/2/aenm201903365.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154525/3/aenm201903365_am.pd