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

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

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

P25@CoAl layered double hydroxide heterojunction nanocomposites for CO2 photocatalytic reduction

Artificial photosynthesis driven by inorganic photocatalysts offers a promising route to renewable solar fuels, however efficient CO2 photoreduction remains a challenge. A family of hierarchical nanocomposites, comprising P25 nanoparticles encapsulated within microporous CoAl-layered double hydroxides (CoAl-LDHs) were prepared via a one-pot hydrothermal synthesis. Heterojunction formation between the visible light absorbing CoAl-LDH and UV light absorbing P25 semiconductors extends utilisation of the solar spectrum, while the solid basicity of the CoAl-LDH increases CO2 availability at photocatalytic surfaces. Matching of the semiconductor band structures and strong donor–acceptor coupling improves photoinduced charge carrier separation and transfer via the heterojunction. Hierarchical P25@CoAl-LDH nanocomposites exhibit good activity and selectivity (>90%) for aqueous CO2 photoreduction to CO, without a sacrificial hole acceptor. This represents a facile and cost-effective strategy for the design and development of LDH-based nanomaterials for efficient photocatalysis for renewable solar fuel production from particularly CO2 and aqueous water

Direct measurement of the exciton binding energy and effective masses for charge carriers in organic–inorganic tri-halide perovskites

Solar cells based on the organic-inorganic tri-halide perovskite family of materials have shown remarkable progress recently, offering the prospect of low-cost solar energy from devices that are very simple to process. Fundamental to understanding the operation of these devices is the exciton binding energy, which has proved both difficult to measure directly and controversial. We demonstrate that by using very high magnetic fields it is possible to make an accurate and direct spectroscopic measurement of the exciton binding energy, which we find to be only 16 meV at low temperatures, over three times smaller than has been previously assumed. In the room temperature phase we show that the binding energy falls to even smaller values of only a few millielectronvolts, which explains their excellent device performance due to spontaneous free carrier generation following light absorption. Additionally, we determine the excitonic reduced effective mass to be 0.104me (where me is the electron mass), significantly smaller than previously estimated experimentally but in good agreement with recent calculations. Our work provides crucial information about the photophysics of these materials, which will in turn allow improved optoelectronic device operation and better understanding of their electronic properties

Interfacial charge-transfer doping of metal halide perovskites for high performance photovoltaics

We demonstrate a method for controlled p-doping of the halide perovskite surface using molecular dopants, resulting in reduced non-radiative recombination losses and improved device performance.</p

Interfacial charge-transfer doping of metal halide perovskites for high performance photovoltaics

We demonstrate a method for controlled p-doping of the halide perovskite surface using molecular dopants, resulting in reduced non-radiative recombination losses and improved device performance.</p