Preoperative radiosurgery for brain metastases (PREOP-1): A feasibility trial.

Purpose: Preoperative radiosurgery (SRS) of brain metastases (BM) aims to achieve cavity local control with a reduction in leptomeningeal relapse (LMD) and without additional radionecrosis compared to postoperative SRS. We present the final results of a prospective feasibility trial of linac-based stereotactic radiosurgery (SRS) prior to neurosurgical resection of a brain metastasis (PREOP-1). Methods: Eligibility criteria included a BM up to 4 cm in diameter for elective resection. The primary endpoint was the feasibility of delivering linac-based preoperative SRS in all patients prior to anticipated gross tumour resection. Secondary endpoints included rates of LMD, local control and overall survival. Exploratory endpoints were the level of expression of immunological and proliferative markers. Results: Thirteen patients of median age 65 years (range 41-77) were recruited. Twelve patients (92 %) received preoperative radiosurgery and metastasectomy and one patient went directly to surgery and received postoperative SRS, thus the primary endpoint was not met. The median time between referral and preoperative SRS was 6.5 working days (1-10) and from SRS to neurosurgery was 1 day (0-5). The median prescribed dose was 16 Gy (14-19) to a median planning target volume of 12.7 cm3 (5.9-26.1). Five patients completed 12-month follow-up after preoperative SRS without local recurrence or leptomeningeal disease. The patient who received postoperative FSRT developed LMD after six months. There was one transient toxicity (grade 2 alopecia) and nine patients have died from extracranial causes. Patients reported significant improvement in motor weakness at 6 months (P = 0.04). No pattern in changes of marker expression was observed. Conclusion: In patients with large brain metastasis without raised intracranial pressure, linac-based preoperative SRS was feasible in 12/13 patients and safe in 12/12 patients without any surgical delay or intracranial complications.

The Electronic Structures of Azaphenanthrenes and Their Dimers.

Insertion of a nitrogen atom modifies the electronic structures and photochemistry of polycyclic aromatic hydrocarbons by introducing nπ* states into the molecules. To better understand the electronic structures of isolated polycyclic aromatic nitrogen-containing hydrocarbons (PANHs) and their dimers as well as the influence of the position of the nitrogen atom in the molecule, we investigate three different azaphenanthrenes, benzo[f]quinoline, benzo[h]quinoline, and phenanthridine, in a joint experimental and computational study. Experimentally, resonance-enhanced multiphoton ionization (REMPI) spectroscopy is applied to characterize the excited electronic states. The REMPI spectra of the azaphenanthrene monomers have a rather similar appearance, with origins between 3.645 and 3.670 eV for the 1ππ* ← S0 transition. In contrast to the phenanthrene parent, 2ππ* ← S0 is broad and unstructured even at the band origin. The experiments are accompanied by density functional theory computation, and vibrationally resolved spectra are simulated using a time-independent approach. The differences between phenanthrene and the azaphenanthrenes are assigned to perturbations due to the low-lying 1(nπ*) state, which accelerates nonradiative deactivation. For the dimers, it is found that two π-stacked isomers with two electronic transitions each contribute to the electronic spectrum, leading to overlapping bands that are difficult to assign.

The development of a hiPSC-based platform to identify tissue-dependencies of IDH1 R132H.

The application of patient-derived (PD) in vitro tumor models represents the classical strategy for clinical translational oncology research. Using these cellular heterogeneous cultures for the isolation of cancer stem cells (CSCs), suggested to be the main driver for disease malignancy, relies on the use of surrogate biomarkers or is based on CSC-enriching culture conditions. However, the ability of those strategies to exclusively and efficiently enrich for CSC pool has been questioned. Here we present an alternative in vitro CSC model based on the oncogenic transformation of single clone-derived human induced pluripotent stem cells (hiPSC). Hotspot mutations in the DNA encoding for the R132 codon of the enzyme isocitrate dehydrogenase 1 (IDH1) and codon R175 of p53 are commonly occurring molecular features of different tumors and were selected for our transformation strategy. By choosing p53 mutant glial tumors as our model disease, we show that in vitro therapy discovery tests on IDH1-engineered synthetic CSCs (sCSCs) can identify kinases-targeting chemotherapeutics that preferentially target tumor cells expressing corresponding genetic alteration. In contrast, neural stem cells (NSCs) derived from the IDH1R132H overexpressing hiPSCs increase their resistance to the tested interventions indicating glial-to-neural tissue-dependent differences of IDH1R132H. Taken together, we provide proof for the potential of our sCSC technology as a potent addition to biomarker-driven drug development projects or studies on tumor therapy resistance. Moreover, follow-up projects such as comparing in vitro drug sensitivity profiles of hiPSC-derived tissue progenitors of different lineages, might help to understand a variety of tissue-related functions of IDH1 mutations.

Evolution of point defects in pulsed-laser-melted Ge1-xSnxprobed by positron annihilation lifetime spectroscopy.

Direct-band-gap Germanium-Tin alloys (Ge1-xSnx) with high carrier mobilities are promising materials for nano- and optoelectronics. The concentration of open volume defects in the alloy, such as Sn and Ge vacancies, influences the final device performance. In this article, we present an evaluation of the point defects in molecular-beam-epitaxy grown Ge1-xSnxfilms treated by post-growth nanosecond-range pulsed laser melting (PLM). Doppler broadening - variable energy positron annihilation spectroscopy and variable energy positron annihilation lifetime spectroscopy are used to investigate the defect nanostructure in the Ge1-xSnxfilms exposed to increasing laser energy density. The experimental results, supported with ATomic SUPerposition calculations, evidence that after PLM, the average size of the open volume defects increases, which represents a raise in concentration of vacancy agglomerations, but the overall defect density is reduced as a function of the PLM fluence. At the same time, the positron annihilation spectroscopy analysis provides information about dislocations and Ge vacancies decorated by Sn atoms. Moreover, it is shown that the PLM reduces the strain in the layer, while dislocations are responsible for trapping of Sn and formation of small Sn-rich-clusters.

Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting.

The pseudomorphic growth of Ge1-xSnxon Ge causes in-plane compressive strain, which degrades the superior properties of the Ge1-xSnxalloys. Therefore, efficient strain engineering is required. In this article, we present strain and band-gap engineering in Ge1-xSnxalloys grown on Ge a virtual substrate using post-growth nanosecond pulsed laser melting (PLM). Micro-Raman and x-ray diffraction (XRD) show that the initial in-plane compressive strain is removed. Moreover, for PLM energy densities higher than 0.5 J cm-2, the Ge0.89Sn0.11layer becomes tensile strained. Simultaneously, as revealed by Rutherford Backscattering spectrometry, cross-sectional transmission electron microscopy investigations and XRD the crystalline quality and Sn-distribution in PLM-treated Ge0.89Sn0.11layers are only slightly affected. Additionally, the change of the band structure after PLM is confirmed by low-temperature photoreflectance measurements. The presented results prove that post-growth ns-range PLM is an effective way for band-gap and strain engineering in highly-mismatched alloys.

Threshold Photoelectron Spectrum of m-Benzyne.

Due to their unusual electronic structure, the biradical m-benzyne, C6H4, and its cation are of considerable interest in chemistry. Here, the photoion mass-selected threshold photoelectron spectrum of the m-benzyne biradical is presented. An adiabatic ionization energy of 8.65 ± 0.015 eV is derived, while a vibrational progression of 0.10 eV is assigned to the ν9+ ring breathing mode, in excellent agreement with computations. The experimental spectrum was reproduced well by Franck-Condon spectral modeling of the 2A1 ← X 1A1 transition, in which the cation retains a monocyclic C6 framework. The energetically close-lying bicyclic 2A2 cation state exhibits low Franck-Condon factors, due to the large change in geometry, and thus cannot be observed.

The MCP2 and the wrist plus two extensor compartments are the most affected and responsive joints/tendons out of the US7 score in patients with rheumatoid arthritis-an observational study.

BACKGROUND: There is no international consensus on an optimal ultrasound score for monitoring of rheumatoid arthritis (RA) on patient-level yet. Our aim was to reassess the US7 score for the identification of the most frequently pathologic and responsive joint/tendon regions, to optimize it and contribute to an international consensus. Furthermore, we aimed to evaluate the impact of disease duration on the performance of the score. METHODS: RA patients were assessed at baseline and after 3 and 6 months of starting/changing DMARD therapy by the US7 score in greyscale (GS) and power Doppler (PD). The frequency of pathologic joint/tendon regions and their responsiveness to therapy were analyzed by Friedman test and Cochrane-Q test respectively, including the comparison of palmar vs. dorsal regions (chi-square test). The responsiveness of different reduced scores and the amount of information retained from the original US7 score were assessed by standardized response means (SRM)/linear regression. Analyses were also performed separately for early and established RA. RESULTS: A total of 435 patients (N = 138 early RA) were included (56.5 (SD 13.1) years old, 8.2 (9.1) years disease duration, 80% female). The dorsal wrist, palmar MCP2, extensor digitorum communis (EDC) and carpi ulnaris (ECU) tendons were most frequently affected by GS/PD synovitis/tenosynovitis (wrist: 45%/43%; MCP2: 35%/28%; EDC: 30%/11% and ECU: 25%/11%) and significantly changed within 6 months of therapy (all p ≤0.003 by GS/PD). The dorsal vs. palmar side of the wrist by GS/PD (p < 0.001) and the palmar side of the finger joints by PD (p < 0.001) were more frequently pathologic. The reduced US7 score (GS/PD: palmar MCP2, dorsal wrist, EDC and ECU, only PD: dorsal MCP2) showed therapy response (SRM 0.433) after 6 months and retained 76% of the full US7 score's information. No major differences between the groups of early and established RA could be detected. CONCLUSIONS: The wrist, MCP2, EDC, and ECU tendons were most frequently pathologic and responsive to therapy in both early and established RA and should therefore be included in a comprehensive score for monitoring RA patients on patient-level.

Pelvic lymphadenectomy in vulvar cancer and its impact on prognosis and outcome.

BACKGROUND: The value of pelvic lymphadenectomy (LAE) has been subject of discussions since the 1980s. This is mainly due to the fact that the relation between lymph node involvement of the groin and pelvis is poorly understood and therewith the need for pelvic treatment in general. PATIENTS AND METHODS: N = 514 patients with primary vulvar squamous cell cancer (VSCC) FIGO stage ≥ IB were treated at the University Medical Center Hamburg-Eppendorf between 1996 and 2018. In this analysis, patients with pelvic LAE (n = 21) were analyzed with regard to prognosis and the relation of groin and pelvic lymph node involvement. RESULTS: The majority had T1b/T2 tumors (n = 15, 78.9%) with a median diameter of 40 mm (11-110 mm). 17/21 patients showed positive inguinal nodes. Pelvic nodal involvement without groin metastases was not observed. 6/17 node-positive patients with positive groin nodes also had pelvic nodal metastases (35.3%; median number of affected pelvic nodes 2.5 (1-8)). These 6 patients were highly node positive with median 4.5 (2-9) affected groin nodes. With regard to the metastatic spread between groins and pelvis, no contralateral spread was observed. Five recurrences were observed after a median follow-up of 33.5 months. No pelvic recurrences were observed in the pelvic nodal positive group. Patients with pelvic metastasis at first diagnosis had a median progression-free survival of only 9.9 months and overall-survival of 31.1 months. CONCLUSION: A relevant risk for pelvic nodal involvement only seems to be present in highly node-positive disease, therefore pelvic staging (and radiotherapy) is probably unnecessary in the majority of patients with node-positive VSCC.

MTT Heterogeneity in Perfusion CT Imaging as a Predictor of Outcome after Aneurysmal SAH.

BACKGROUND AND PURPOSE: Impairment of tissue oxygenation caused by inhomogeneous microscopic blood flow distribution, the so-called capillary transit time heterogeneity, is thought to contribute to delayed cerebral ischemia after aneurysmal SAH but has so far not been systematically evaluated in patients. We hypothesized that heterogeneity of the MTT, derived from CTP parameters, would give insight into the clinical course of patients with aneurysmal SAH and may identify patients at risk of poor outcome. MATERIALS AND METHODS: We retrospectively analyzed the heterogeneity of the MTT using the coefficient of variation in CTP scans from 132 patients. A multivariable logistic regression model was used to model the dichotomized mRS outcome. Linear regression was used to eliminate variables with high linear dependence. T tests were used to compare the means of 2 groups. Furthermore, the time of the maximum coefficient of variation for MTT after bleeding was evaluated for correlation with the mRS after 6 months. RESULTS: On average, each patient underwent 5.3 CTP scans during his or her stay. Patients with high coefficient of variation for MTT presented more often with higher modified Fisher (P = .011) and World Federation of Neurosurgical Societies grades (P = .014). A high coefficient of variation for MTT at days 3-21 after aneurysmal SAH correlated significantly with a worse mRS score after 6 months (P = .016). We found no correlation between the time of the maximum coefficient of variation for MTT after bleeding and the patients' outcomes after 6 months (P = .203). CONCLUSIONS: Heterogeneity of MTT in CTP after aneurysmal SAH correlates with the patients' outcomes. Because the findings are in line with the pathophysiologic concept of the capillary transit time heterogeneity, future studies should seek to verify the coefficient of variation for MTT as a potential imaging biomarker for outcome.

Plectin dysfunction in neurons leads to tau accumulation on microtubules affecting neuritogenesis, organelle trafficking, pain sensitivity and memory.

AIMS: Plectin, a universally expressed multi-functional cytolinker protein, is crucial for intermediate filament networking, including crosstalk with actomyosin and microtubules. In addition to its involvement in a number of diseases affecting skin, skeletal muscle, heart, and other stress-exposed tissues, indications for a neuropathological role of plectin have emerged. Having identified P1c as the major isoform expressed in neural tissues in previous studies, our aim for the present work was to investigate whether, and by which mechanism(s), the targeted deletion of this isoform affects neuritogenesis and proper nerve cell functioning. METHODS: For ex vivo phenotyping, we used dorsal root ganglion and hippocampal neurons derived from isoform P1c-deficient and plectin-null mice, complemented by in vitro experiments using purified proteins and cell fractions. To assess the physiological significance of the phenotypic alterations observed in P1c-deficient neurons, P1c-deficient and wild-type littermate mice were subjected to standard behavioural tests. RESULTS: We demonstrate that P1c affects axonal microtubule dynamics by isoform-specific interaction with tubulin. P1c deficiency in neurons leads to altered dynamics of microtubules and excessive association with tau protein, affecting neuritogenesis, neurite branching, growth cone morphology, and translocation and directionality of movement of vesicles and mitochondria. On the organismal level, we found P1c deficiency manifesting as impaired pain sensitivity, diminished learning capabilities and reduced long-term memory of mice. CONCLUSIONS: Revealing a regulatory role of plectin scaffolds in microtubule-dependent nerve cell functions, our results have potential implications for cytoskeleton-related neuropathies.

Metachronous hepatic resection for liver only pancreatic metastases.

BACKGROUND: The value of liver resection (LR) for metachronous pancreatic ductal adenocarcinoma (PDAC) metastases remains controversial. However, in light of increasing safety of liver resections, surgery might be a valuable option for metastasized PDAC in selected patients. METHODS: We performed a retrospective, multicenter study including patients undergoing hepatectomy for metachronous PDAC liver metastases between 2004 and 2015 to analyze postoperative outcome and overall survival. All patients were operated with curative intent. Patients with oligometastatic metachronous liver metastasis with definitive chemotherapy (n = 8) served as controls. RESULTS: Overall 25 patients in seven centers were included in this study. The median age at the time of LR was 63.8 years (56.9-69.9) and the median number of metastases in the liver was 1 (IQR 1-2). There were eight non-anatomical resections (32%), 15 anatomical minor (60%) and 2 major LR (8%). Postoperative complications occurred in eleven patients (eight Clavien-Dindo grade I complications (32%) and three grade IIIa complications (12%), respectively). The 30-day mortality was 0%. The median length of stay was 8.6 days (IQR 5-11). Median overall survival following LR was 36.8 months compared to 9.2 months in patients with metachronous liver metastasis with chemotherapy (p = 0007). DISCUSSION: Liver resection for metachronous PDAC metastasis is safe and feasible in selected patients. To address general applicability and to find factors for patient selection, larger trials are urgently warranted.

Photoelectron spectroscopy of boron-containing reactive intermediates using synchrotron radiation: BH2, BH, and BF.

Mass selected slow photoelectron spectra (SPES) of three boron-containing reactive species, BH2, BH, and BF were recorded by double imaging photoion-photoelectron coincidence spectroscopy (i2PEPICO) using synchrotron radiation. All species were generated in a flow reactor from the H-abstraction of B2H6 by F atoms created in a F2 microwave discharge. The spectrum of BH2+ exhibits a long bending mode progression with a 970 cm-1 spacing due to the large geometry change from bent to linear upon ionization. Its ionization energy was determined as 8.12 ± 0.02 eV. For BH, photoionisation from both X1Σ+ singlet and a3Π triplet state was observed, permitting the experimental determination of the singlet/triplet gap (ΔEST) from the observed IE's of 9.82 eV and 8.48 eV. In addition, a threshold photoelectron spectrum of BF was recorded, which leads to an IE of 11.11 eV and an improved value for νBF+ of 1690 cm-1. All spectra were simulated by calculating Franck-Condon factors from optimised structures based on quantum chemical calculations.

Cross-predicting the dynamics of an optically injected single-mode semiconductor laser using reservoir computing.

In real-world dynamical systems, technical limitations may prevent complete access to their dynamical variables. Such a lack of information may cause significant problems, especially when monitoring or controlling the dynamics of the system is required or when decisions need to be taken based on the dynamical state of the system. Cross-predicting the missing data is, therefore, of considerable interest. Here, we use a machine learning algorithm based on reservoir computing to perform cross-prediction of unknown variables of a chaotic dynamical laser system. In particular, we chose a realistic model of an optically injected single-mode semiconductor laser. While the intensity of the laser can often be acquired easily, measuring the phase of the electric field and the carriers in real time, although possible, requires a more demanding experimental scheme. We demonstrate that the dynamics of two of the three dynamical variables describing the state of the laser can be reconstructed accurately from the knowledge of only one variable, if our algorithm has been trained beforehand with all three variables for a limited period of time. We analyze the accuracy of the method depending on the parameters of the laser system and the reservoir. Finally, we test the robustness of the cross-prediction method when adding noise to the time series. The suggested reservoir computing state observer might be used in many applications, including reconstructing time series, recovering lost time series data and testing data encryption security in cryptography based on chaotic synchronization of lasers.

[Identification of patients with axial spondylarthritis in primary care (AWARE study)]. / Identifikation von Patienten mit axialer Spondyloarthritis in der Primärversorgung (AWARE-Studie).

BACKGROUND: Early detection of patients with axial spondylarthritis (axSpA) in primary care is difficult. The combination of various parameters indicative of inflammatory back pain (AWARE criteria) was found to be beneficial in an initial study. OBJECTIVE: Review of the criteria for the identification of young patients with axSpA and chronic back pain (≥3 months of back pain). MATERIAL AND METHODS: In adult patients with chronic back pain and age at onset of symptoms <45 years, orthopedic surgeons documented various possible axSpA characteristics before referral to the rheumatologist. RESULTS: Overall, the data from 1306 patients were recorded. Of these, ultimately 500 patients were also seen by rheumatologists, 199 patients (39.8%) were diagnosed with axSpA while 301 (60.2%) had non-specific back pain. A total of 87 patients had ankylosing spondylitis (44%) and 112 non-radiographic axSpA (56%). The ASAS classification criteria were fulfilled by 226 patients (45.2%). The mean age of axSpA patients was 38 years, 56% were male with a mean duration of back pain of 98 months. The AWARE criteria had a sensitivity and specificity of 69.3% and 40.3% (n = 343), respectively, when ≥4/5 criteria were chosen. Positive imaging for sacroiliitis using magnetic resonance imaging (MRI) or X­ray was present in 77% of patients and positive HLA-B27 was identified in 59% of axSpA patients. The combination of positive imaging and HLA-B27 had the highest likelihood ratio for diagnosis of axSpA. CONCLUSION: Although the study design used here led to a preselection and thus to a bias in the statistical evaluation, the study confirmed the benefit of the AWARE criteria for the early detection of patients with axSpA. In further studies, the 2­stage approach with initially 3 clinical questions and then an optional HLA-B27 test is currently being investigated further.

Normal and resonant Auger spectroscopy of isocyanic acid, HNCO.

In this paper, we investigate HNCO by resonant and nonresonant Auger electron spectroscopy at the K-edges of carbon, nitrogen, and oxygen, employing soft X-ray synchrotron radiation. In comparison with the isosteric but linear CO2 molecule, spectra of the bent HNCO molecule are similar but more complex due to its reduced symmetry, wherein the degeneracy of the π-orbitals is lifted. Resonant Auger electron spectra are presented at different photon energies over the first core-excited 1s → 10a' resonance. All Auger electron spectra are assigned based on ab initio configuration interaction computations combined with the one-center approximation for Auger intensities and moment theory to consider vibrational motion. The calculated spectra were scaled by a newly introduced energy scaling factor, and generally, good agreement is found between experiment and theory for normal as well as resonant Auger electron spectra. A comparison of resonant Auger spectra with nonresonant Auger structures shows a slight broadening as well as a shift of the former spectra between -8 and -9 eV due to the spectating electron. Since HNCO is a small molecule and contains the four most abundant atoms of organic molecules, the reported Auger electron decay spectra will provide a benchmark for further theoretical approaches in the computation of core electron spectra.

Critical evaluation of an innovative mesh for bilateral transabdominal preperitoneal (TAPP) repair of inguinal hernias.

PURPOSE: Transabdominal preperitoneal hernia mesh plasty (TAPP) offers significant benefits to patients undergoing bilateral inguinal hernia repair. We evaluated a novel pre-shaped, large-pored, titanium-coated, lightweight polypropylene mesh for bilateral placement as an alternative to two separate meshes. METHODS: Thirty-six patients underwent elective surgical repair of bilateral inguinal hernias with the new mesh at three departments of surgery in Linz and Graz, Austria, between May 1, 2015 and June 30, 2017. RESULTS: All operations were completed without intraoperative complications or conversion to open procedures. The mean operation time was 74 min. There were no postoperative procedure-related complications with the exception of one hematoseroma of the spermatic cord. Two symptomatic medial recurrences (2/36 patients = 5.6%, 2/72 hernia repairs = 2.8%, respectively) after supravesical and medial hernia repair with the bilateral mesh were seen at structured follow-up examinations 6 and 12 months postoperatively. CONCLUSION: Treatment of bilateral inguinal hernias with the newly designed bilateral mesh for TAPP theoretically brings benefits in terms of resistance to forces acting on the mesh. The larger area may decrease the risk for mesh bulging and recurrence, and one large mesh might provide more stable support than two separate meshes overlapping at the midline. The results of our study do not confirm these theoretical benefits regarding a high recurrence rate (2.8%) after treatment of medial hernia defects. We recommend re-designing the mesh with only a small central slit, which would provide a broader mesh bridge with sufficient overlap for all types of inguinal and femoral hernias, including medial and supravesical defects. After the mesh has been re-designed, a new study should evaluate its real benefits before it is marketed.

Consistency properties of chaotic systems driven by time-delayed feedback.

Consistency refers to the property of an externally driven dynamical system to respond in similar ways to similar inputs. In a delay system, the delayed feedback can be considered as an external drive to the undelayed subsystem. We analyze the degree of consistency in a generic chaotic system with delayed feedback by means of the auxiliary system approach. In this scheme an identical copy of the nonlinear node is driven by exactly the same signal as the original, allowing us to verify complete consistency via complete synchronization. In the past, the phenomenon of synchronization in delay-coupled chaotic systems has been widely studied using correlation functions. Here, we analytically derive relationships between characteristic signatures of the correlation functions in such systems and unequivocally relate them to the degree of consistency. The analytical framework is illustrated and supported by numerical calculations of the logistic map with delayed feedback for different replica configurations. We further apply the formalism to time series from an experiment based on a semiconductor laser with a double fiber-optical feedback loop. The experiment constitutes a high-quality replica scheme for studying consistency of the delay-driven laser and confirms the general theoretical results.

Accelerated barrier recovery and enhancement of the barrier integrity and properties by topical application of a pH 4 vs. a pH 5·8 water-in-oil emulsion in aged skin.

BACKGROUND: Increased skin-surface pH is an important host-related factor for deteriorated barrier function in aged skin. OBJECTIVES: We investigated whether restoration of skin pH through topical application of a water-in-oil emulsion with pH 4 improved the barrier homeostasis in aged skin, and compared the effects with an identical galenic formulation with pH 5·8. METHODS: The effects of the test formulations on barrier recovery were investigated by repeated measurements of transepidermal water loss (TEWL) and skin pH 3 h, 6 h and 24 h after acetone-induced impairment of barrier function in aged skin. The long-term effects of the pH 4 and pH 5·8 emulsions were analysed by investigation of the barrier integrity and cohesion, the skin-surface pH and the skin roughness and scaliness before and after a 4-week, controlled application of the formulations. RESULTS: The application of the pH 4 emulsion accelerated barrier recovery in aged skin: 3 h and 6 h after acetone-induced barrier disruption the differences in the TEWL recovery between the pH 4 treated and acetone control fields were significant. Furthermore, long-term application of the pH 4 formulation resulted in significantly decreased skin pH, enhanced barrier integrity and reduced skin-surface roughness and scaliness. At the same time points, the pH 5·8 formulation exerted only minor effects on the barrier function parameters. CONCLUSIONS: Exogenous acidification through topical application of a water-in-oil emulsion with pH 4 leads to improvement of the skin barrier function and maintenance of the barrier homeostasis in aged skin.

Kinetics of the a-C3H5 + O2 reaction, investigated by photoionization using synchrotron radiation.

The kinetics of the combustion-relevant reaction of the allyl radical, a-C3H5, with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring, using the CRF-PEPICO (Combustion Reactions Followed by Photoelectron Photoion Coincidence Spectroscopy) setup. The ability to measure threshold photoelectron spectra enables a background-free detection of reactive species as well as an isomer-specific analysis of reaction products. Allyl was generated by direct photodissociation of allyl iodide at 266 nm and 213 nm and indirectly by the reaction of propene with Cl atoms, which were generated by photolysis from oxalyl chloride at 266 nm. Experiments were conducted at room temperature at low pressures between 0.8 and 3 mbar using Ar as the buffer gas and with excess O2 to maintain nearly pseudo-first-order reaction conditions. Whereas allyl was detected by photoionisation using synchrotron radiation, the main reaction product allyl peroxy was not observed due to dissociative ionisation of this weakly bound species. From the concentration-time profiles of the allyl signal, second-order rate constants between 1.35 × 1011 cm3 mol-1 s-1 at 0.8 mbar and 1.75 × 1011 cm3 mol-1 s-1 at 3 mbar were determined. The rates obtained for the different allyl radical generation schemes agree well with each other, but are about a factor of 2 higher than the ones reported previously using He as a buffer gas. The discrepancy is partly attributed to the higher collision efficiency of Ar causing a varying fall-off behavior. When allyl is produced by the reaction of propene with Cl atom, an unexpected product is observed at m/z = 68, which was identified as 1,3-butadienal in the threshold photoelectron spectrum. It is formed in a secondary reaction of allyl with the OCCl radical, which is generated in the 266 nm photolysis of oxalyl chloride.

The ortho-benzyne cation is not planar.

A recent review on the photoionisation of the C6H4 isomer ortho-benzyne suggests that bands reported in earlier photoelectron spectra might be due to side products or contaminations, while computations raise doubts, whether the cation has a planar geometry. We therefore reinvestigate the photoionisation of ortho-benzyne, generated by pyrolysis from benzocyclobutenedione, by photoion mass-selected threshold photoelectron (ms-TPE) spectroscopy using synchrotron radiation. The experiments are accompanied by a theoretical study that investigates the structure of the ortho-benzyne cation systematically as a function of the computational method, up to CASPT2(11,14) ab initio computations. Our study leads to a re-evaluation of the ionisation energy of ortho-benzyne. It reveals that the ortho-benzyne cation has indeed a twisted C2 geometry rather than a C2v structure. A vertical ionisation energy IEvert of 9.77 eV and an adiabatic ionisation energy of IEad = 9.56 eV are computed for ortho-benzyne. A Franck-Condon simulation of the photoelectron spectrum based on the CASPT2 results and including three electronic states of the cation is in agreement with the experiment and yields IEad = 9.51 eV (+50 meV/-100 meV). Since this value is in contrast with previous work, the ionisation energy has to be revised based on our study. Computational methods based on density functional theory give a reasonable description of the cationic ground state, but fail for the corresponding excited electronic states that are indispensible for a proper assignment of the photoelectron spectrum.