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 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.

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.

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.

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).

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.

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.

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.

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.

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.

Collagenous colitis associated with protein losing enteropathy in a toddler.

Collagenous mucosal inflammatory disease is a rare gastrointestinal disorder that involves the columnar lining of gastric and intestinal mucosa and is characterized by a distinct subepithelial collagen deposition. Recent clinical and pathological evidence have indicated that collagenous mucosal inflammatory disease can be extensive disease that may concomitantly involve several gastrointestinal sites at the same time. This entity, however, occurs infrequently in children. It is even less common to find concomitant depositions of collagen in the mucosa of gastrointestinal sites other than the colon. Only two cases in pediatric literature reported concomitant involvement, one with gastric and colonic involvement and the other one with gastroduodenocolitis. We are reporting a 15-month-old boy who presented with severe diarrhea and diffuse edema secondary to hypoalbuminemia. Further testing documented protein losing enteropathy (PLE) associated with collagenous colitis.

Local anesthetic versus forced coughing at colposcopic-guided biopsy: a prospective study.

OBJECTIVE: To evaluate whether the administration of local anesthetic (LA) reduces pain in comparison with forced coughing (FC) for the execution of colposcopically guided biopsies (CGBs). STUDY DESIGN: Data of 100 consecutive patients undergoing CGBs with the use of LA or FC were prospectively evaluated. Procedure-related pain was assessed with the use of a 100-mm visual analogue scale. RESULTS: Fifty-one and 49 patients had CGBs using LA and FC, respectively. No between-group differences were observed in terms of pain related to speculum insertion, CGBs and pain recorded after the procedures (p>0.05). However, patients in the LA group experienced pain related to cervical injection for administration of anesthesia (mean (±SD): 12.4 (±1.6)). Operative time was longer in the LA than in the FC group (7.2 (±0.2) vs. 5.0 (±0.1)min; p<0.001). CONCLUSIONS: FC should be preferred over LA. Although CGB-related pain levels do not differ, the omission of intracervical injection is associated with undoubted advantages.

Colon capsule endoscopy: detection of colonic polyps compared with conventional colonoscopy and visualization of extracolonic pathologies.

BACKGROUND: Conventional colonoscopy (CC) is the gold standard for diagnostic examination of the colon. However, the overall acceptance of this procedure is low due to patient fears of complications or embarrassment. Colon capsule endoscopy (CCE) represents a minimally invasive, patient-friendly procedure that offers complete visualization of the entire intestine. OBJECTIVE: To assess the PillCam Colon 2 (Given Imaging Ltd, Israel) capsule with regard to feasibility, sensitivity and specificity for the detection of colonic pathologies and additional recorded extracolonic findings. METHODS: CCE was performed before CC in patients indicated for CC for known or suspected colonic disease. The results of both techniques were compared with regard to polyp detection. Additionally, bowel preparation and extracolonic pathologies were analyzed. RESULTS: Twenty-four patients (mean age 51.1 years) were included in the analysis. Visualization of the colon was complete in 23 CCs and 17 CCEs. No adverse events or major technical failures occurred. CC detected 47 polyps and CCE detected 43 polyps of any size (per-finding sensitivity 90.9%, specificity 67.6%). The accuracy of CCE in detecting polyp carriers was 81.5% (per-patient analysis). On average, the colon was adequately cleansed in 90.1% of patients. CCE identified esophageal, gastric and small bowel pathologies in seven (24%), nine (38%) and 14 (58%) patients, respectively. CONCLUSIONS: CCE proved to be technically feasible and safe. Acceptable sensitivity and moderate specificity levels in polyp detection were recorded. Bowel preparation was adequate in most patients. Because extracolonic pathologies were effectively visualized, new indications for the PillCam Colon 2 may be defined.

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.

Massive panniculectomy results in improved functional outcome.

BACKGROUND: Panniculus morbidus is a large abdominal apron found in morbidly obese patients. This condition creates a vicious cycle of weight gain and functional incapacity. Our study assessed the functional improvement in patients undergoing massive panniculectomy. METHODS: A retrospective review of panniculectomies performed from 1994 to 2012 was conducted. Twenty-seven patients with resections >20 lbs were selected. Data on demographics, operative details, complications, and pre- and postoperative functional capacity (using the Steinbrocker Functional Classification) were collected. RESULTS: The preoperative mean body mass index was 58 kg/m(2), with a mean resection weight of 33 lbs. The overall complication rate was 74%. A statistically significant improvement in functional capacity (preop mean 3.7 vs postop mean 2.0; P < .0001) was identified. CONCLUSIONS: Panniculus morbidus is a functionally debilitating condition and massive panniculectomy is often the only treatment available. Our data suggest that massive panniculectomy is a viable option for patients functionally incapacitated by panniculus morbidus.

Body composition analysis in bariatric surgery: use of air displacement plethysmograph.

Body weight, body mass index (BMI), and percent excess weight loss are used to assess patient outcomes after bariatric surgery; however, they provide little insight into the true nature of the patient's weight loss. Body composition measurements monitor fat versus lean mass losses to permit interventions to reduce or avoid lean body mass loss after bariatric surgery. A retrospective review of patients who underwent bariatric surgery between 2002 and 2008 was performed. Patients underwent body composition testing via air displacement plethysmography before and after surgery (6 and 12 months). Body composition changes were assessed and compared with the BMI. Results include 330 patients (54 male, 276 female). Average preoperative weight was 139 kg, BMI was 50 kg/m(2), fat percentage was 55 per cent, and lean mass percent was 45 per cent. Twelve months after surgery average weight was 90 kg, mean BMI was 32 kg/m(2), fat percentage was 38 per cent, and lean mass percent was 62 per cent. Body composition measurements help monitor fat losses versus lean mass gains after bariatric surgery. This may give a better assessment of the patient's health and metabolic state than either BMI or excess weight loss and permits intervention if weight loss results in lean mass losses.

Capsule endoscopy in patients with cardiac pacemakers and implantable cardioverter-defibrillators - a retrospective multicenter investigation.

BACKGROUND & AIMS: Capsule endoscopy (CE) is an established tool for the investigation of the small intestine. The Food and Drug Administration, Given Imaging and Olympus have not recommended the use of capsule endoscopy in patients with cardiac pacemakers and implantable cardioverter defibrillators (ICDs). The aim of this retrospective study was to investigate the safety of capsule endoscopy systems (Given Imaging and Olympus) when applied in patients with different types of pacemakers/ICDs in vivo. METHODS: A standardized questionnaire was sent to high volume centers in Germany and in Austria. The questionnaire covered the age and gender of the examined patients, indication of CE, brand and type of CE, brand and model of pacemaker/ICD, check of the devices before and after CE, monitoring during CE, possible interference between CE and cardiac pacemakers/ICDs and possible adverse events during CE. RESULTS: Data from 62 patients were retrieved for this study. Capsules used were Given Imaging (n=58; M2A, M2Aplus, PillCam SB2), Olympus EndoCapsule (n=3), Given PillCam Colon (n=1). The collective included patients with pacemakers/ICDS from seven brands (Biotronik, Medtronic, St. Jude Medical, Guidant, Boston Scientific, Ela Sorin, Vitatron) with a total of 19/8 (pacemaker/ICD) different types. In two patients interference between capsule endoscopy and telemetry (loss of images/gaps in video) was recorded. None of the cardiac pacemakers or ICDs was impaired in function. No clinically evident event was observed in any of these patients. CONCLUSIONS: Clinical use of these CE types is safe in patients with cardiac pacemakers and ICDs. Interference can occur between CE and ECG-telemetry leading to loss of images or impaired quality of video.