Robust estimation of charge carrier diffusivity using transient photoluminescence microscopy.

Transient microscopy has emerged as a powerful tool for imaging the diffusion of excitons and free charge carriers in optoelectronic materials. In many excitonic materials, extraction of diffusion coefficients can be simplified because of the linear relationship between signal intensity and local excited state population. However, in materials where transport is dominated by free charge carriers, extracting diffusivities accurately from multidimensional data is complicated by the nonlinear dependence of the measured signal on the local charge carrier density.

Colloidal nano-MOFs nucleate and stabilize ultra-small quantum dots of lead bromide perovskites.

The development of synthetic routes to access stable, ultra-small ( <5 nm) lead halide perovskite (LHP) quantum dots (QDs) is of fundamental and technological interest. The considerable challenges include the high solubility of the ionic LHPs in polar solvents and aggregation to form larger particles. Here, we demonstrate a simple and effective host-guest strategy for preparing ultra-small lead bromide perovskite QDs through the use of nano-sized MOFs that function as nucleating and host sites.

Tunable exciton binding energy in 2D hybrid layered perovskites through donor-acceptor interactions within the organic layer.

The strength of electrostatic interactions within semiconductors strongly affects their performance in optoelectronic devices. An important target is the tuning of a material's exciton binding energy-the energy binding an electron-hole pair through the electrostatic Coulomb force-independent of its electronic band gap. Here, we report on the doping of a family of two-dimensional hybrid perovskites, in which inorganic lead halide sheets alternate with naphthalene-based organic layers, with tetrachloro-1,2-benzoquinone (TCBQ).

Multi-cation perovskites prevent carrier reflection from grain surfaces.

The composition of perovskite has been optimized combinatorially such that it often contains six components (ABCPbXY) in state-of-art perovskite solar cells. Questions remain regarding the precise role of each component, and the lack of a mechanistic explanation limits the practical exploration of the large and growing chemical space. Here, aided by transient photoluminescence microscopy, we find that, in perovskite single crystals, carrier diffusivity is in fact independent of composition.

Dynamics of the triplet-pair state reveals the likely coexistence of coherent and incoherent singlet fission in crystalline hexacene.

The absorption of a photon usually creates a singlet exciton (S) in molecular systems, but in some cases S may split into two triplets (2×T) in a process called singlet fission. Singlet fission is believed to proceed through the correlated triplet-pair (TT) state. Here, we probe the (TT) state in crystalline hexacene using time-resolved photoemission and transient absorption spectroscopies.

Direct Time-Domain View of Auger Recombination in a Semiconductor.

The radiationless recombination of electron-hole pairs in semiconductors is detrimental to optoelectronic technologies. A prominent mechanism is Auger recombination, in which nonradiative recombination occurs efficiently by transferring the released energy-momentum to a third charge carrier. Here we use femtosecond photoemission to directly detect Auger electrons as they scatter into energy and momentum spaces from Auger recombination in a model semiconductor, GaSb.

Screening in crystalline liquids protects energetic carriers in hybrid perovskites.

Hybrid lead halide perovskites exhibit carrier properties that resemble those of pristine nonpolar semiconductors despite static and dynamic disorder, but how carriers are protected from efficient scattering with charged defects and optical phonons is unknown. Here, we reveal the carrier protection mechanism by comparing three single-crystal lead bromide perovskites: CHNHPbBr, CH(NH)PbBr, and CsPbBr We observed hot fluorescence emission from energetic carriers with ~10-picosecond lifetimes in CHNHPbBr or CH(NH)PbBr, but not in CsPbBr The hot fluorescence is correlated with liquid-like molecular reorientational motions, suggesting that dynamic screening protects energetic carriers via solvation or large polaron formation on time scales competitive with that of ultrafast cooling. Similar protections likely exist for band-edge carriers.

Direct Observation of Entropy-Driven Electron-Hole Pair Separation at an Organic Semiconductor Interface.

How an electron-hole pair escapes the Coulomb potential at a donor-acceptor interface has been a key issue in organic photovoltaic research. Recent evidence suggests that long-distance charge separation can occur on ultrafast time scales, yet the underlying mechanism remains unclear. Here we use charge transfer excitons (CTEs) across an organic semiconductor-vacuum interface as a model and show that nascent hot CTEs can spontaneously climb up the Coulomb potential within 100 fs.

Charge Transfer Excitons at van der Waals Interfaces.

The van der Waals interfaces of molecular donor/acceptor or graphene-like two-dimensional (2D) semiconductors are central to concepts and emerging technologies of light-electricity interconversion. Examples include, among others, solar cells, photodetectors, and light emitting diodes. A salient feature in both types of van der Waals interfaces is the poorly screened Coulomb potential that can give rise to bound electron-hole pairs across the interface, i.

Impact of implementing an electronic health record on surgical resident work flow, duty hours, and operative experience.

Our objective was to assess the effect of implementing an electronic health record (EHR) on surgical resident work flow, duty hours, and operative experience at a large teaching hospital. In May 2012, an EHR was put into effect at our institution replacing paper documentation and orders. Resident time to complete patient documentation, average duty hours, and operative experience before EHR and afterward (at 1, 4, 6, 8, and 24 weeks) were surveyed.

Outcomes of pancreatic debridement in acute pancreatitis: analysis of the nationwide inpatient sample from 1998 to 2010.

Background: The objective of this study was to perform a national review of patients with acute pancreatitis (AP) who undergo pancreatic debridement (PD) to evaluate for risk factors of in-hospital mortality.

Methods: The Nationwide Inpatient Sample was used to identify patients with AP who underwent PD between 1998 and 2010. Risk factors for in-hospital mortality were assessed with multivariate logistic regression.

Arterial vs venous blood gas differences during hemorrhagic shock.

Aim: To characterize differences of arterial (ABG) and venous (VBG) blood gas analysis in a rabbit model of hemorrhagic shock.

Methods: Following baseline arterial and venous blood gas analysis, fifty anesthetized, ventilated New Zealand white rabbits were hemorrhaged to and maintained at a mean arterial pressure of 40 mmHg until a state of shock was obtained, as defined by arterial pH ≤ 7.2 and base deficit ≤ -15 mmol/L.

Impact of the establishment of a specialty hernia referral center.

Background: Creating a surgical specialty referral center requires a strong interest, expertise, and a market demand in that particular field, as well as some form of promotion. In 2004, we established a tertiary hernia referral center. Our goal in this study was to examine its impact on institutional volume and economics.

The first nationwide evaluation of robotic general surgery: a regionalized, small but safe start.

Background: The purpose of this study was to evaluate the outcomes of the most commonly performed robotic-assisted general surgery (RAGS) procedures in a nationwide database and compare them with their laparoscopic counterparts.

Methods: The Nationwide Inpatient Sample was queried from October 2008 to December 2010 for patients undergoing elective, abdominal RAGS procedures. The two most common, robotic-assisted fundoplication (RF) and gastroenterostomy without gastrectomy (RG), were individually compared with the laparoscopic counterparts (LF and LG, respectively).

Postoperative quality of life after open transinguinal preperitoneal inguinal hernia repair using memory ring or three-dimensional devices.

A transinguinal preperitoneal (TIPP) approach has become a common technique for inguinal hernia repair. Our goal was to compare the impact of the two mesh designs for this operation: a flat mesh with a memory ring device (MRD) or a three-dimensional device (3DD) containing both onlay and preperitoneal mesh components. The prospective International Hernia Mesh Registry (2007 to 2012) was queried for MRD and 3DD inguinal hernia repairs.

Does ventral hernia defect length, width, or area predict postoperative quality of life? Answers from a prospective, international study.

Background: The goal of this study was to determine if ventral hernia defect length, width, or area predict postoperative pain and quality of life following ventral hernia repair (VHR).

Methods: The International Hernia Mesh Registry, a prospective database from 40 institutions worldwide, was queried for patients undergoing VHR from October 2007 to June 2012. Laparoscopic and open VHR were evaluated separately.

Preliminary results of surgical and quality of life outcomes of Physiomesh in an international, prospective study.

Physiomesh is a novel, lightweight, large pore, polypropylene mesh designed to have flexibility that matches the compliance of the abdominal wall in an effort to improve patient quality of life (QOL). The International Hernia Mesh Registry was queried for ventral hernia repair (VHR) and inguinal hernia repair (IHR) with Physiomesh. Demographics, operative and postoperative details, and the Carolinas Comfort Scale (CCS) as a measure of QOL were recorded.

Surgical relief work in Haiti: a practical resident learning experience.

Introduction: A once-a-year, week-long surgical missionary trip to Haiti has become incorporated into our residency experience on a voluntary basis since 2007. The purpose of this article is to describe our experience with this mission effort during the last 4 years.

Methods: Since 2007, at least one PGY 3-5 surgical resident from our program has traveled to the Hôpital Sacré Coeur in Milot, Haiti for a voluntary, week-long surgical mission working with the local health care providers.

Regioselective esterification of vicinal diols on monosaccharide derivatives via Mitsunobu reactions.

We have carried out a series of esterification reactions of secondary alcohols derived from d-glucose, d-mannose, and d-galactose via the Mitsunobu reaction. The benzoylation reaction of vicinal diols derived from monosaccharides under Mitsunobu conditions afforded monobenzoates with retention of stereochemistry only. The regioselectivity of these reactions depends on the stereochemistry of the sugar starting material.

Neuroma of the infrapatellar branch of the saphenous nerve a cause of reversible knee stiffness after total knee arthroplasty.

Injury of the infrapatellar branch of the saphenous nerve (ISN) may be caused by a surgical laceration or trauma about the knee and can result in formation of a painful neuroma. There has been no report of knee stiffness after a total knee arthroplasty secondary to a painful neuroma of the ISN. In this report, we present a patient with pain and severe stiffness of her knee after a total knee arthroplasty.

Synthesis and characterization of monosaccharide lipids as novel hydrogelators.

Self-assembly of small molecules is a useful strategy for forming functional supramolecular structures. Three new series of methyl alpha-D-glucopyranoside derivatives, including esters and carbamates, have been synthesized and characterized. Several of these compounds are excellent hydrogelators and formed interesting self-assembled network structures, including birefringent fibers and tubules.

Development and application of a polymerase chain reaction assay for the detection and enumeration of bile acid 7alpha-dehydroxylating bacteria in human feces.

Background: Secondary bile acids are synthesized in the human colon from the bacterial 7alpha-dehydroxylation of primary bile acids. Increased levels of secondary bile acids have been correlated with an increased risk of colon cancer and cholesterol gallstone disease. Based on 16s rDNA sequence analysis, stock cultures of bacterial strains with bile acid 7alpha-dehydroxylation all belong to the genus Clostridium.