Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials.

Disentangling electronic and thermal effects in photoexcited perovskite materials is crucial for photovoltaic and optoelectronic applications but remains a challenge due to their intertwined nature in both the time and energy domains. In this study, we employed temperature-dependent variable-angle spectroscopic ellipsometry, density functional theory calculations, and broadband transient absorption spectroscopy spanning the visible to mid-to-deep-ultraviolet (UV) ranges on MAPbBr3 thin films. The use of deep-UV detection opens a new spectral window that enables the exploration of high-energy excitations at various symmetry points within the Brillouin zone, facilitating an understanding of the ultrafast responses of the UV bands and the underlying mechanisms governing them. Our investigation reveals that the photoinduced spectral features remarkably resemble those generated by pure lattice heating, and we disentangle the relative thermal and electronic contributions and their evolutions at different delay times using combinations of decay-associated spectra and temperature-induced differential absorption. The results demonstrate that the photoinduced transients possess a significant thermal origin and cannot be attributed solely to electronic effects. Following photoexcitation, as carriers (electrons and holes) transfer their energy to the lattice, the thermal contribution increases from ∼15% at 1 ps to ∼55% at 500 ps and subsequently decreases to ∼35-50% at 1 ns. These findings elucidate the intricate energy exchange between charge carriers and the lattice in photoexcited perovskite materials and provide insights into the limited utilization efficiency of photogenerated charge carriers.

Charge Carrier Screening in Photoexcited Epitaxial Semiconductor Nanorods Revealed by Transient X-ray Absorption Linear Dichroism.

Understanding the electronic structure and dynamics of semiconducting nanomaterials at the atomic level is crucial for the realization and optimization of devices in solar energy, catalysis, and optoelectronic applications. We report here on the use of ultrafast X-ray linear dichroism spectroscopy to monitor the carrier dynamics in epitaxial ZnO nanorods after band gap photoexcitation. By rigorously subtracting out thermal contributions and conducting ab initio calculations, we reveal an overall depletion of absorption cross sections in the transient X-ray spectra caused by photogenerated charge carriers screening the core-hole potential of the X-ray absorbing atom. At low laser excitation densities, we observe phase-space filling by excited electrons and holes separately. These results pave the way for carrier- and element-specific probing of charge transfer dynamics across heterostructured interfaces with ultrafast table-top and fourth-generation X-ray sources.

Quantifying Photoinduced Polaronic Distortions in Inorganic Lead Halide Perovskite Nanocrystals.

The development of next-generation perovskite-based optoelectronic devices relies critically on the understanding of the interaction between charge carriers and the polar lattice in out-of-equilibrium conditions. While it has become increasingly evident for CsPbBr3 perovskites that the Pb-Br framework flexibility plays a key role in their light-activated functionality, the corresponding local structural rearrangement has not yet been unambiguously identified. In this work, we demonstrate that the photoinduced lattice changes in the system are due to a specific polaronic distortion, associated with the activation of a longitudinal optical phonon mode at 18 meV by electron-phonon coupling, and we quantify the associated structural changes with atomic-level precision. Key to this achievement is the combination of time-resolved and temperature-dependent studies at Br K and Pb L3 X-ray absorption edges with refined ab initio simulations, which fully account for the screened core-hole final state effects on the X-ray absorption spectra. From the temporal kinetics, we show that carrier recombination reversibly unlocks the structural deformation at both Br and Pb sites. The comparison with the temperature-dependent XAS results rules out thermal effects as the primary source of distortion of the Pb-Br bonding motif during photoexcitation. Our work provides a comprehensive description of the CsPbBr3 perovskites' photophysics, offering novel insights on the light-induced response of the system and its exceptional optoelectronic properties.

Interfacial Electron Injection Probed by a Substrate-Specific Excitonic Signature.

Ultrafast interfacial electron transfer in sensitized solar cells has mostly been probed by visible-to-terahertz radiation, which is sensitive to the free carriers in the conduction band of the semiconductor substrate. Here, we demonstrate the use of deep-ultraviolet continuum pulses to probe the interfacial electron transfer, by detecting a specific excitonic transition in both N719-sensitized anatase TiO2 and wurtzite ZnO nanoparticles. Our results are compared to those obtained on bare nanoparticles upon above-gap excitation. We show that the signal upon electron injection from the N719 dye into TiO2 is dominated by long-range Coulomb screening of the final states of the excitonic transitions, whereas in sensitized ZnO it is dominated by phase-space filling. The present approach offers a possible route to detecting interfacial electron transfer in a broad class of systems, including other transition metal oxides or sensitizers.

Somatic Testing on Gynecological Cancers Improve the Identification of Lynch Syndrome.

OBJECTIVE: Recent data from the literature indicate gynecological cancers (GCs) as sentinel cancers for a diagnosis of Lynch syndrome (LS). Clinical approaches to identifying LS have low sensitivity, whereas somatic tests on GCs may be a more sensitive and cost-effective strategy. METHODS: A series of 78 GCs belonging to 74 patients sent to the Genetic Counselling Service were investigated using microsatellite instability, immunohistochemical expression of mismatch repair (MMR) genes, and MLH1 promoter methylation. RESULTS: The presence of microsatellite instability was observed in 67.5% of GCs, and the absence of immunohistochemical expression of at least 1 of the 4 MMR proteins was observed in 71.4% of GCs, showing 96.1% concordance between the methods. Methylation analysis using methylation specific multiplex ligation-dependent probe amplification performed on 35 samples revealed MLH1 promoter hypermethylation in 18 cases (54%). Molecular analysis identified 36 LS carriers of MMR variants (27 pathogenetic and 9 variants of uncertain significance), and, interestingly, 3 LS patients had MLH1 methylated GC.With regard to histological features, LS-related GCs included endocervical cancers and also histological types different from the endometrioid cancers. The presence of peritumoral lymphocytes in GCs was statistically associated with LS tumors. CONCLUSIONS: Somatic analysis is a useful strategy to distinguish sporadic from LS GC. Our data allow the identification of a subset of LS patients otherwise unrecognized on the basis of clinical or family history alone. In addition, our results indicate that some clinicopathological features including age of GC diagnosis; presence of peritumoral lymphocytes; isthmic, endocervical sites, and body mass index value could be useful criteria to select patients for genetic counseling.

Time-resolved Element-selective Probing of Charge Carriers in Solar Materials.

We review our recent results on the implementation of picosecond (ps) X-ray absorption spectroscopy to probe the electronic and geometric structure of centres formed by photoexcitation of solar materials such as TiO2 polymorphs and inorganic Cs-based perovskites. The results show electron localization at Ti defects in TiO2 anatase and rutile and small hole polaron formation in the valence band of CsPbBr3, all within 80 ps. This method is promising for the study of the ultrafast time scales of such processes, especially with the advent of the Swiss X-ray Free Electron Laser (SwissFEL).

The LOUVRE Laboratory: State-of-the-Art Ultrafast Ultraviolet Spectroscopies for Molecular and Materials Science.

We describe the facilities for ultraviolet studies in the femtosecond to nanosecond time domain. These facilities consist of: i) a set-up for deep-ultraviolet spectroscopy in the 260-380 nm range in both pump and probe pulses for transient absorption/reflectivity or two-dimensional spectroscopy studies; ii) a set-up for ultrafast fluorescence measurements with detection down to 300 nm. The capabilities of these set-ups are demonstrated by examples on molecular systems, biosystems, nanoparticles and solid materials.

Brown bowel syndrome: a rare complication in diseases associated with long-standing malabsorption.

BACKGROUND/AIMS: Longtime chronic malabsorption may among other things cause a lack of liposoluble vitamins. Vitamin E deficiency can lead to formation of lipofuscin aggregates. Its deficiency is also associated with an increased lipofuscinosis of the bowel, i.e. brown bowel syndrome. METHODS: Systematic research via Medline on brown bowel syndrome, lipofuscinosis, and vitamin E deficiency was performed. We combined our own clinical experience and a review of the literature for this paper. Its goal is to inform about the possible consequences of severe malabsorption and brown bowel syndrome. RESULTS: Systematic data about the occurrence of severe malabsorption and brown bowel syndrome are rare. Only about 27 scientific reports can be found on this subject. Brown bowel syndrome is found mostly in conjunction with vitamin E deficiency and lipofuscinosis of the bowel. The clinical findings are caused by both malabsorption and lipofuscinosis. Case reports show a therapeutic effect of vitamin E. CONCLUSION: Vitamin deficiency caused by longtime chronic malabsorption can lead to the development of brown bowel syndrome, which is seen as the expression of lipofuscinosis of the bowel, and can cause further clinical disorders. Patients with malabsorption should therefore be monitored regarding their vitamin E levels.

Excited-State Identification of a Nickel-Bipyridine Photocatalyst by Time-Resolved X-ray Absorption Spectroscopy.

Photoassisted catalysis using Ni complexes is an emerging field for cross-coupling reactions in organic synthesis. However, the mechanism by which light enables and enhances the reactivity of these complexes often remains elusive. Although optical techniques have been widely used to study the ground and excited states of photocatalysts, they lack the specificity to interrogate the electronic and structural changes at specific atoms. Herein, we report metal-specific studies using transient Ni L- and K-edge X-ray absorption spectroscopy of a prototypical Ni photocatalyst, (dtbbpy)Ni(o-tol)Cl (dtb = 4,4'-di-tert-butyl, bpy = bipyridine, o-tol = ortho-tolyl), in solution. We unambiguously confirm via direct experimental evidence that the long-lived (∼5 ns) excited state is a tetrahedral metal-centered triplet state. These results demonstrate the power of ultrafast X-ray spectroscopies to unambiguously elucidate the nature of excited states in important transition-metal-based photocatalytic systems.

Disentangling the evolution of electrons and holes in photoexcited ZnO nanoparticles.

The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and ab initio molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions. The x-ray absorption measurements, obtained upon excitation close to the band edge at 3.49 eV, are sensitive to the migration and trapping of holes. They reveal that the 2 ps transient largely reproduces the previously reported transient obtained at 100 ps time delay in synchrotron studies. In addition, the x-ray absorption signal is found to rise in ∼1.4 ps, which we attribute to the diffusion of holes through the lattice prior to their trapping at singly charged oxygen vacancies. Indeed, the MD simulations show that impulsive trapping of holes induces an ultrafast expansion of the cage of Zn atoms in <200 fs, followed by an oscillatory response at a frequency of ∼100 cm-1, which corresponds to a phonon mode of the system involving the Zn sub-lattice.

Incidental follicular cholecystitis with periductal fibrosis on liver biopsy: Rare findings.

INTRODUCTION AND IMPORTANCE: Follicular cholecystitis (FC) is a rare entity found, it is found in 0.1-1 % of patients with chronic cholecystitis. 1,2 This pathologic finding has been associated with extrahepatic biliary obstruction distal to the gallbladder, such as primary sclerosing cholangitis, choledocholithiasis, and distal biliary strictures. CASE PRESENTATION: Our patient is a 32-year-old female with a past medical history significant for obesity presented with symptoms of postprandial nausea and spasmodic abdominal pain. An abdominal ultrasound was performed with findings adenomyosis and possible gallbladder polyps or adherent stones. The patient was referred to surgery and a routine laparoscopic cholecystectomy with liver biopsy was performed. On pathology, the gallbladder was found to have chronic, active follicular cholecystitis with cholelithiasis. Percutaneous needle liver biopsy revealed the following: focal, mild periductal fibrosis, mild portal fibrosis with minimal mixed micro- and macrovesicular steatosis, and no significant steatohepatitis. CLINICAL DISCUSSION: To the best of our knowledge, this is the first documented case of follicular cholecystitis with associated hepatic findings on pathology. Follicular cholecystitis is strongly associated with extrahepatic biliary obstruction distal to the gallbladder, but it has not been previously associated with liver fibrosis. We hope to bring awareness to this rare but significant pathology. CONCLUSION: Our case is unusual due to the findings of hepatic periductal fibrosis with follicular cholecystitis. Follicular cholecystitis is strongly associated with extrahepatic biliary obstruction distal to the gallbladder but it has not been documented it to be associated with any hepatic findings or pathology.

Parenteral fish oil-associated burr cell anemia.

We report the development of burr cell anemia in an infant with short bowel syndrome who received parenteral fish oil (Omegaven, Fresenius-Kabi, Graz, Austria) after development of total parenteral nutrition-associated liver disease. Parenteral fish oil was discontinued, and the burr cell anemia disappeared, suggesting that parenteral fish oil might be associated with hemolytic anemia.

The use of Lactobacillus rhamnosus in the therapy of bacterial vaginosis. Evaluation of clinical efficacy in a population of 40 women treated for 24 months.

BACKGROUND: Bacterial vaginosis (BV) is the most prevalent vaginal disorder in adult women worldwide. A number of clinical studies indicate that re-establishment of the physiological ecosystem by re-colonization of vaginal mucosa by lactobacilli may be an effective therapy for BV both after initial antimicrobial therapy or when given alone. A vaginal pH <4.5 is considered physiological and its measurement has been reported as an objective parameter, very sensitive to alterations of vaginal microflora and correlated with clinically relevant BV. OBJECTIVE: The aims of this work were to assess the effectiveness of a long-term (24 months) intravaginal treatment with Lactobacillus rhamnosus (NORMOGIN) on the vaginal pH and on the clinical symptoms in a group of 40 women affected by BV diagnosed by the Amsel criteria. METHOD: A prospective open clinical trial was performed in 40 consecutive cases evaluated for B.V. by the Amsel criteria. RESULTS: Vaginal pH was above the physiological value of 4.5 in 36 out of 40 patients at the first visit. It returned under 4.5 value in 24/40 and 32/40 women after 12 and 24 months of treatment, respectively. pH values were significantly decreased at 12 month treatment (P < 0.001) and further reduction in pH values was found at 24 months of treatment (P < 0.02 vs. 12 months). The gradual return to a vaginal physiological pH was associated with a reduction of the intensity of symptoms as shown by the decrease in the symptoms score. CONCLUSIONS: The present study supports the use of pH measurement for sensitive, objective, and simple therapy follow-up in women with BV and shows that long-term administration of vaginal tablets containing Lactobacillus rhamnosus represents an effective and safe treatment for restoring the physiological vaginal pH and controlling BV symptoms.

Pediatric gastroenterology fellows, class of 2007: how well are they prepared for the future?

OBJECTIVES: Pediatric gastroenterology fellows are expected to acquire skills as clinicians, researchers, and educators. An e-mail survey was conducted to examine training experiences of individual fellows; to understand how graduating fellows rate their abilities as clinicians, researchers, and teachers; and to answer whether the size of a pediatric gastroenterology training program affects a fellow's training and future position choice. MATERIALS AND METHODS: A survey was e-mailed to 76 third-year pediatric gastroenterology fellows. Respondents were ranked according to the size of their training program. RESULTS: Completed surveys were returned by 50 respondents. Of these, 75% planned to pursue careers in academic medicine and 16% in private practice. In all, 68% of trainees participated in some type of basic research and 64% in clinical research. As attending physicians, 22% of fellows hoped to conduct basic science research and 74% clinical research. The majority thought they were competent or proficient teachers, and rated themselves as advanced beginners or competent when asked to evaluate their research skills. The North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition recommends that fellows perform 100 colonoscopies, 20 liver biopsies, and 5 paracenteses to be considered competent. We found that regardless of program size, 48% of fellows performed fewer than 100 colonoscopies, 62% performed fewer than 20 liver biopsies, and 80% performed fewer than 5 paracenteses. CONCLUSIONS: The majority of fellows will pursue academic careers. Trainees may not be performing sufficient numbers of procedures. The number of procedures performed during fellowship was independent of program size.

Long-term partial remission of autoimmune thrombocytopenia in a patient treated with the anti-tumor necrosis factor-alpha antibody infliximab for refractory fistulizing Crohn's disease.

BACKGROUND: Up to the present date, the treatment of recurrent chronic fistulas occurring with Crohn's disease represents a challenging task for both internists and surgeons alike. METHODS: Conservative methods of treatment using steroids, dietotherapy, antibiotics or immunosuppressive agents are not particularly effective in treating fistulas. Treatment with anti-tumor necrosis factor-alpha (TNFalpha) antibodies results in more remissions of fistulas. However, its use requires appropriate medical experience and causes substantial costs. Surgical procedures such as fistula sanitation or protective ileostomy are often obfuscated by the recurrence of the condition. The efficiency of anti-TNFalpha antibodies for the treatment of active Crohn's disease has been evidenced through several multicenter, double-blind, placebo-controlled studies. RESULTS: Here we report the successful anti-TNFalpha treatment of a patient suffering from chronic, fistulizing, therapy-resistant Crohn's disease and a concomitant chronic autoimmune thrombocytopenia. The chimeric anti-TNFalpha antibody infliximab markedly reduced the disease activity of Crohn's disease, and, in addition, substantially increased the platelet counts. After infliximab application, no other treatment of autoimmune thrombocytopenia was required. After infliximab therapy, autoantibodies to dsDNS could be observed. However, there were no signs of a lupus-like disease. CONCLUSION: This report indicates a favorable therapeutic response of autoimmune thrombocytopenia associated to Crohn's disease.

Quiescence of human muscle stem cells is favored by culture on natural biopolymeric films.

BACKGROUND: Satellite cells are quiescent resident muscle stem cells that present an important potential to regenerate damaged tissue. However, this potential is diminished once they are removed from their niche environment in vivo, prohibiting the long-term study and genetic investigation of these cells. This study therefore aimed to provide a novel biomaterial platform for the in-vitro culture of human satellite cells that maintains their stem-like quiescent state, an important step for cell therapeutic studies. METHODS: Human muscle satellite cells were isolated from two donors and cultured on soft biopolymeric films of controlled stiffness. Cell adhesive phenotype, maintenance of satellite cell quiescence and capacity for gene manipulation were investigated using FACS, western blotting, fluorescence microscopy and electron microscopy. RESULTS: About 85% of satellite cells cultured in vitro on soft biopolymer films for 3 days maintained expression of the quiescence marker Pax7, as compared with 60% on stiffer films and 50% on tissue culture plastic. The soft biopolymeric films allowed satellite cell culture for up to 6 days without renewing the media. These cells retained their stem-like properties, as evidenced by the expression of stem cell markers and reduced expression of differentiated markers. In addition, 95% of cells grown on these soft biopolymeric films were in the G0/G1 stage of the cell cycle, as opposed to those grown on plastic that became activated and began to proliferate and differentiate. CONCLUSIONS: Our study identifies a new biomaterial made of a biopolymer thin film for the maintenance of the quiescence state of muscle satellite cells. These cells could be activated at any point simply by replating them onto a plastic culture dish. Furthermore, these cells could be genetically manipulated by viral transduction, showing that this biomaterial may be further used for therapeutic strategies.

Localized holes and delocalized electrons in photoexcited inorganic perovskites: Watching each atomic actor by picosecond X-ray absorption spectroscopy.

We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge, and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes is observed at the Cs L2-edge. The results at the Br and Pb edges suggest the existence of a weakly localized exciton, while the absence of signatures at the Cs edge indicates that the Cs+ cation plays no role in the charge transport, at least beyond 80 ps. This first, time-resolved element-specific study of perovskites helps understand the rather modest charge carrier mobilities in these materials.

Stricture dilation after laparoscopic Roux-en-Y gastric bypass.

BACKGROUND: In surgical treatment of morbid obesity, maintaining a restrictive anastomosis is key to long-range success. However, laparoscopic Roux-en-Y gastric bypass (LRYGB) may result in gastrojejunal (GJ) stricture, requiring treatment in up to 27% of patients. METHODS: This is a retrospective review of the outcome of 223 consecutive LRYGB patients. Patients developing stricture received standard endoscopic balloon dilation by the same surgeon. Stricture and nonstricture groups were compared for excess body weight loss (EBWL) at 1, 3, 6, and 12 months. RESULTS: GJ stricture requiring dilation occurred in 38 patients (17%). After dilation all patients were relieved of stricture symptoms and none required revision. By 12 months, patients with stricture had an EBWL of 86% compared with nonstrictured patients at 75%. CONCLUSION: Endoscopic balloon dilation is a safe and effective treatment option for GJ stricture. Improved weight loss occurred for patients with stricture requiring dilation.

Jejunitis and brown bowel syndrome with multifocal carcinogenesis of the small bowel.

This is the first report describing a case where prolonged, severe malabsorption from brown bowel syndrome progressed to multifocally spread small bowel adenocarcinoma. This case involves a female patient who was initially diagnosed with chronic jejunitis associated with primary diffuse lymphangiectasia at the age of 26 years. The course of the disease was clinically, endoscopically, and histologically followed for 21 years until her death at the age 47 due to multifocal, metastasizing adenocarcinoma of the small bowel. Multiple lipofuscin deposits (so-called brown bowel syndrome) and severe jejunitis were observed microscopically, and sections of the small bowel showed dense lymphoplasmacytic infiltration of the lamina propria as well as blocked lymphatic vessels. After several decades, multifocal nests of adenocarcinoma cells and extensive, flat, neoplastic mucosal proliferations were found only in the small bowel, along with a loss of the mismatch repair protein MLH1 as a long-term consequence of chronic jejunitis with malabsorption. No evidence was found for hereditary nonpolyposis colon carcinoma syndrome. This article demonstrates for the first time multifocal carcinogenesis in the small bowel in a malabsorption syndrome in an enteritis-dysplasia-carcinoma sequence.

Roux-en-Y gastric bypass leak complications.

HYPOTHESIS: Enteric leakage is a significant complication of the Roux-en-Y gastric bypass (RYGB) procedure that can be treated successfully. DESIGN: Retrospective study of 400 consecutive RYGB patients from 1999-2002. SETTING: Community hospital with a university surgical residency. PATIENTS: Hospital records of 400 morbidly obese patients who underwent gastric bypass surgery were reviewed. MAIN OUTCOME MEASURES: Time of discovery of leak, location of leak, treatment, hospital stay, and mortality. RESULTS: Twenty-one patients (5.25%) developed leaks. The mean body mass index (calculated as weight in kilograms divided by the square of height in meters) was 54.2. Thirteen patients were noted to develop a leak at the gastrojejunal anastomosis, with an average time to diagnosis of 7.0 days. Five of these patients underwent reexploration, and 8 were successfully treated with percutaneous drainage alone. Four patients developed leaks at the jejunojejunal anastomosis (mean time to diagnosis, 2.0 days). All of these patients required exploration, and 2 patients died. Four patients were noted to have leaks in other areas (average time to diagnosis, 3.5 days). Two patients were treated with drainage, and 2 underwent exploration. The average hospital stay of all patients was 33 days. CONCLUSIONS: Enteric leakage is a significant complication of the RYGB. Patients who are suspected of having an enteric leak because of signs of sepsis or hemodynamic instability require emergent exploration. Leaks that are more insidious may be treated successfully with percutaneous drainage. Aggressive exploration of patients who appear to be septic, and percutaneous drainage of insidiously developing leaks may decrease patients' morbidity and mortality.