Shining a light on the photochemistry of methylammonium lead iodide perovskite for solar cell application

Since their first use in solar cells in 2009, lead halide perovskites have been employed in a wide variety of solar cell architectures leading to an impressive 25.5 % power conversion efficiency in 2020. However, the complex properties of perovskite materials as well as their instability in ambient atmosphere is impeding their development. In particular, trap states, through their formation and passivation, are believed to be responsible for the instability and subsequent degradation of the perovskite, as well as decreasing the device performances. In this work, 3 aspects of the methylammonium lead iodide (MAPI) perovskite are investigated. First, the steady-state photoluminescence and degradation of MAPI were investigated using fluorescence spectroscopy, microscopy, and X-ray diffractometry. Photobrightening, due to the passivation of trap states, and photodarkening, due to the degradation of the perovskite by moisture and oxygen, are found to be competing processes, making the onset of degradation difficult to accurately determine. Second, two models used to simulate charge carrier recombination and time-resolved photoluminescence (TRPL) in perovskite materials, and extract information related to trap states are investigated. The importance of the excitation fluence and repetition period used is highlighted. The models are then used to fit TRPL decays of a MAPI thin-film and a bimolecular rate constant of ∼ 50 × 10−20 cm3/ns is obtained. Finally, the optical, morphological, photoluminescence and crystallographic properties, and stability of MAPI and 5-aminovaleric acid iodide-modified MAPI (AVA-MAPI) infiltrated in mesoporous carbon perovskite solar cells are investigated. Superoxide formation was measured using the dihydroethidium fluorescence probe and AVA-MAPI is shown to generate less superoxide than MAPI when infiltrated in mesoporous layers (ZrO2, TiO2/ZrO2 and TiO2/ZrO2/C). This is partially explained by the presence of a uniform capping layer in AVA-MAPI, hindering oxygen diffusion in the film hence reducing superoxide formation

PEARS: A Web Tool for Fitting Time-Resolved Photoluminescence Decays of Perovskite Materials

Time-resolved photoluminescence (TRPL) is a powerful tool to investigate charge carrier recombination processes in emissive materials. Perovskite materials are extremely promising for applications in solar cells; however, the interpretation of their TRPL is arduous due to the complicated nature of the recombination processes occurring in these materials. We present here the PErovskite cArrier Recombination Simulator (PEARS) web tool for effortlessly and quickly fitting TRPL of perovskite materials using advanced charge carrier recombination models, allowing for the extraction of recombination rate constants and trap state concentration. PEARS is flexible and can adapt to different situations, by ignoring recombination processes or fixing known parameters (e.g., the doping concentration). The tool is publicly available at https://pears-tool.herokuapp.com

Oral bioavailability and drug/carrier particulate systems

The oral route remains the preferred route of administration to ensure patient satisfaction and compliance. However, new chemical entities may exhibit low bioavailability after oral administration because of poor stability within the gastrointestinal tract, poor solubility in gastrointestinal fluids, low mucosal permeability, and/or extensive first-pass metabolism. Consequently, these new drug substances cannot be further developed using conventional oral formulations. This issue is addressed by an innovative approach based on the entrapment of drug molecules in drug/carrier assembling systems. The carrier materials are lipids, naturally occurring polymers or synthetic polymers, which are considered as nontoxic and biocompatible materials. Drug entrapment is intended to protect drug substances against degradation by gastrointestinal fluids. Fine drug/carrier particle size ensures increased drug dissolution rates. Carriers and particle supramolecular organization can be designed to enhance drug absorption through the intestinal epithelium and lymphatic transport. Promising preclinical results have been obtained with model drugs like paclitaxel, insulin, calcitonin, or cyclosporin. Attention has focused on mucoadhesive carriers like chitosan that favor an intimate and extended contact between drugs and intestinal cells, thus enhancing absorption. Addition of ligands such as lectins improves intestinal drug absorption through specific binding of the carrier to intestinal cell carbohydrates. In conclusion, drug/carrier particulate systems are an attractive and exciting drug delivery strategy for highly potent drug substances unsuitable for oral use. Further evidence will determine whether this approach has marked therapeutic benefits over conventional drug formulations and is compatible with large-scale industrial production and stringent registration requirements. Producing highly effective particulate systems requiring low-complexity manufacturing processes is therefore an ongoing challenge

Improving Communication between Doctors and Parents after Newborn Screening

Background: Newborn screening (NBS) enables early treatment, and some consider it a natural vehicle for genetic screening. Bioethicists argue for caution since families of infants with carrier status can develop psychosocial complications. This paper describes the methods and feasibility of Wisconsin’s statewide project for quality improvement of communication and psychosocial outcomes after NBS. Methods: When NBS identifies carrier status for cystic fibrosis or sickle cell, we contact primary care providers (PCPs), answer questions, and invite them to rehearse informing the parents. Three months later, we telephone the parents, assess knowledge and psychosocial outcomes, provide counseling, and assist with self-referral to further resources. Afterward, evaluation surveys are provided to the parents, to be returned anonymously. Results: Birthing facilities provided accurate PCP names for 73% of 817 infants meeting inclusion criteria; we identified PCPs for 21% more. We reached 47.3% of PCPs in time to invite a rehearsal; 60% of these accepted. We successfully called 50.2% of eligible parents; 61% recalled a PCP explanation, and 48.5% evaluated the explanation favorably. Evaluations by parents with limited health literacy were less favorable. Conclusion: It is feasible to follow parents for psychosocial outcomes after NBS. Preliminary data about communication is mixed, but further data will describe psychosocial outcomes and investigate outcomes’ associations with communication

Hepatic encephalopathy complicated by decompensated alcoholic liver cirrhosis in a Hispanic male

Introduction: Alcohol can directly affect the brain via neuroinflammation or alter the gut microbiome which concomitantly results in hepatic encephalopathy. Hepatic encephalopathy can cause altered mental status from liver dysfunction with or without portal-systemic blood shunting. Chronic alcohol use has been associated with dementia, cirrhosis, and hepatic encephalopathy. This case report highlights the prognosis of hepatic encephalopathy in the setting of decompensated liver cirrhosis complicated by acute alcohol intoxication. Case report: A 35-year-old Hispanic man with history of alcohol use disorder, decompensated alcoholic liver cirrhosis with ascites, severe anemia secondary to upper GI bleeding with underlying esophageal varices who was accompanied to the ED via EMS after being found obtunded and nonresponsive on the floor. Upon arrival to ED, ethanol level was 178. The patient was intubated for airway protection due to two episodes of large volume hematemesis. Two units of PRBCs were ordered and an upper EGD showed two nonbleeding varices which were banded; however, the source of bleeding was not confirmed or arrested. The patient’s ICU course included eleven units of PRBCs, two units of cryoprecipitate and ten units of fresh frozen plasma. Despite emergent dialysis and intensive care interventions, the patient has not been able to be extubated despite being off sedation and paralytics. Conclusion: Alcohol can directly affect the brain via neuroinflammation or alter the gut microbiome which concomitantly results in hepatic encephalopathy. In patients with acute alcohol intoxication, prompt assessment of ammonia levels and gastroenterology recommendations are warranted to improve patient outcome

A Method to Assess the Organizing Behaviors Used in Physicians\u27 Counseling of Standardized Parents after Newborn Genetic Screening

Well-organized conversation can improve people’s ability to comprehend and retain information. As part of a long-term effort to adapt Quality Improvement techniques for communication, we developed an explicit criteria method to assess usage of three organizing behaviors (OBs): ‘opening behaviors’ to establish goals; ‘structuring behaviors’ to guide patients through conversation; and ‘emphasizing behaviors’ that signal a need for attention. Pairs of abstractors independently reviewed transcripts in a demonstration sample of conversations between physicians and standardized parents after newborn screening identifies carrier status for sickle cell disease. Criteria for at least one OB were identified in 50/84 transcripts (60%), including 27 with at least one opening behavior (32%), 5 with at least one structuring behavior (6%), and 38 with at least one emphasizing behavior (45%). The limited number of OBs raises concern about communication after newborn screening. Assessment and improvement of OB usage may improve understanding and allow parents to more actively participate in health care

A Case Study of Excreta Disposal Following the 2006 Java Earthquake*

Providing safe excreta disposal following disasters is important for disease prevention and the safety and dignity of the affected population. This is challenging because every emergency varies due to the nature of the disaster, local conditions and the characteristics of the affected population. This paper investigates the impact of the 2006 Java earthquake on excreta disposal needs and the response to those needs. Relevant documents were retrieved from the ReliefWeb database, complemented by a literature search. The case study highlights gaps in rapidly providing latrines on a large scale. Three months after the disaster, only 57% of the latrines targeted had been provided. One way to address this problem is to better understand the factors affecting excreta disposal needs and response, allowing appropriate solutions to be identified more effectively