Conception and pilot testing of a self-management health application for patients with pollen-related allergic rhinitis and allergic asthma-the APOLLO app

It has been shown that pollen information services are an important self-management tool for patients with pollen-related allergic rhinitis (AR) and allergic asthma (AA). This study aimed to design an online application for patients with AR and AA, which supports patients to better manage their disease as well as to evaluate the app and present the first results of the pilot study. The pollen data were obtained from the electronic pollen information network of Bavaria, Germany. Participants were asked to fill in their allergy-related complaints in the app over a 60-day period. Subsequently, the app was evaluated. Indices and diagrams visualized the participants' individual complaints as well as the daily pollen concentration in the air. In order to motivate participants to complete the app on a daily basis, we used elements of gamification. Two thirds of the participants (N = 46) reported feeling better informed about pollen counts and their allergy when using the app. The app's simple and comprehensible design was rated positively. More than 80% of the participants would recommend the app to their family and friends. The app can be a tool for patients with AR and AA to better understand their disease.

Erratum: Lattice gas study of thin-film growth scenarios and transitions between them: Role of substrate [Phys. Rev. E 103, 023302 (2021)]

This corrects the article DOI: 10.1103/PhysRevE.103.023302.

EndoBarrier™ Implantation Rapidly Improves Insulin Sensitivity in Obese Individuals with Type 2 Diabetes Mellitus

The EndoBarrier™ medical device is a duodenal-jejunal bypass liner designed to mimic the effects of gastric bypass surgery to induce weight loss and glycaemic improvement. In this study, 10 participants with type 2 diabetes mellitus (T2DM), a mean body mass index (BMI) of 43.3 ± 5.0 (kg/m²) and a mean glycated haemoglobin A1c (HbA1c) of 60.6 ± 8.6 mmol/mol were examined at baseline (before implantation of EndoBarrier™), 4 weeks after implantation, at 36 weeks (right before explantation) and 24 weeks after the removal of the device to explore the short and long-term effects on glucose metabolism. Besides a significant reduction in body weight and fat mass, EndoBarrier™ treatment significantly improved insulin sensitivity during Botnia clamp investigations after four weeks of implantation. The beneficial effects decreased over time but remained significant 24 weeks after removal of the device.

Lattice gas study of thin-film growth scenarios and transitions between them: Role of substrate

Thin-film growth is investigated in two types of lattice gas models where substrate and film particles are different, expressed by unequal interaction energy parameters. The first is of solid-on-solid type, whereas the second additionally incorporates desorption, diffusion in the gas phase above the film and readsorption at the film (appropriate for growth in colloidal systems). In both models, the difference between particle-substrate and particle-particle interactions plays a central role for the evolution of the film morphology at intermediate times. The models exhibit a dynamic layering transition which occurs at generally lower substrate attraction strengths than the equilibrium layering transition. A second, flattening transition is found where initial island growth transforms to layer-by-layer growth at intermediate deposition times. Combined with the known roughening behavior in such models for very large deposition times, we present four global growth scenarios, charting out the possible types of roughness evolution.

Roughness evolution in strongly interacting donor:acceptor mixtures of molecular semiconductors. An in situ, real-time growth study using x-ray reflectivity

The evolution of surface roughness in binary mixtures of the two molecular organic semiconductors (OSCs) diindenoperylene (DIP) as electron-donor and 1, 3, 4, 5, 7, 8-hexafluoro-tetracyano naphthoquinodimethane (F6TCNNQ) as electron-acceptor is studied. We co-deposit DIP and F6TCNNQ in vacuum with varying relative molar content while keeping a molar excess of DIP in order to produce phase-heterogeneous mixtures. The excess DIP phase segregates in pristine crystallites, whereas the remaining mixed phase is constituted by DIP:F6TCNNQ co-crystallites. We calculate the surface roughness as function of film thickness by modelling x-ray reflectivity data acquired in situ and in real-time during film growth. To model the experimental data, two distinct approaches, namely the kinematic approximation and the Parratt formalism, are applied. A comparative study of surface roughness evolution as function of DIP:F6TCNNQ mixing ratio is carried out implementing the Trofimov growth model within the kinematic approximation. Depending on the thickness regime, mixing ratio-specific trends are identified and discussed. To explain them, a growth mechanism for binary heterogeneous mixtures of strongly interacting OSCs is proposed.

Selection of resistance by antimicrobial coatings in the healthcare setting

Antimicrobial touch surfaces have been introduced in healthcare settings with the aim of supporting existing hygiene procedures, and to help combat the increasing threat of antimicrobial resistance. However, concerns have been raised over the potential selection pressure exerted by such surfaces, which may drive the evolution and spread of antimicrobial resistance. This review highlights studies that indicate risks associated with resistance on antimicrobial surfaces by different processes, including evolution by de-novo mutation and horizontal gene transfer, and species sorting of inherently resistant bacteria dispersed on to antimicrobial surfaces. The review focuses on antimicrobial surfaces made of copper, silver and antimicrobial peptides because of the practical application of copper and silver, and the promising characteristics of antimicrobial peptides. The available data point to a potential for resistance selection and a subsequent increase in resistant strains via cross-resistance and co-resistance conferred by metal and antibiotic resistance traits. However, translational studies describing the development of resistance to antimicrobial touch surfaces in healthcare-related environments are rare, and will be needed to assess whether and how antimicrobial surfaces lead to resistance selection in these settings. Such studies will need to consider numerous variables, including the antimicrobial concentrations present in coatings, the occurrence of biofilms on surfaces, and the humidity relevant to dry-surface environments. On-site tests on the efficacy of antimicrobial coatings should routinely evaluate the risk of selection associated with their use.

Induction chemotherapy (IC) followed by radiotherapy (RT) versus cetuximab plus IC and RT in advanced laryngeal/hypopharyngeal cancer resectable only by total laryngectomy-final results of the larynx organ preservation trial DeLOS-II

Background

The German multicenter randomized phase II larynx organ preservation (LOP) trial DeLOS-II was carried out to prove the hypothesis that cetuximab (E) added to induction chemotherapy (IC) and radiotherapy improves laryngectomy-free survival (LFS; survival with preserved larynx) in locally advanced laryngeal/hypopharyngeal cancer (LHSCC).

Patients and methods

Treatment-naïve patients with stage III/IV LHSCC amenable to total laryngectomy (TL) were randomized to three cycles IC with TPF [docetaxel (T) and cisplatin (P) 75 mg/m2/day 1, 5-FU (F) 750 mg/m2/day days 1-5] followed by radiotherapy (69.6 Gy) without (A) or with (B) standard dose cetuximab for 16 weeks throughout IC and radiotherapy (TPFE). Response to first IC-cycle (IC-1) with ≥30% endoscopically estimated tumor surface shrinkage (ETSS) was used to define early responders; early salvage TL was recommended to non-responders. The primary objective was 24 months LFS above 35% in arm B.

Results

Of 180 patients randomized (July 2007 to September 2012), 173 fulfilled eligibility criteria (A/B: larynx 44/42, hypopharynx 41/46). Because of 4 therapy-related deaths among the first 64 randomized patients, 5-FU was omitted from IC in the subsequent 112 patients reducing further fatal toxicities. Thus, IC was TPF in 61 patients and TP in 112 patients, respectively. The primary objective (24 months LFS above 35%) was equally met by arms A (40/85, 47.1%) as well as B (41/88, 46.6%). One hundred and twenty-three early responders completed IC+RT; their overall response rates (TPF/TP) were 94.7%/87.2% in A versus 80%/86.0% in B. The 24 months overall survival (OS) rates were 68.2% and 69.3%.

Conclusions

Despite being accompanied by an elevated frequency in adverse events, the IC with TPF/TP plus cetuximab was feasible but showed no superiority to IC with TPF/TP regarding LFS and OS at 24 months. Both early response and 24 months LFS compare very well to previous LOP trials and recommend effective treatment selection and stratification by ETSS.

Clinical trial information

NCT00508664.

Invited Review: The spectrum of age-related small vessel diseases: potential overlap and interactions of amyloid and nonamyloid vasculopathies

Deep perforator arteriopathy (DPA) and cerebral amyloid angiopathy (CAA) are the commonest known cerebral small vessel diseases (CSVD), which cause ischaemic stroke, intracebral haemorrhage (ICH) and vascular cognitive impairment (VCI). While thus far mainly considered as separate entities, we here propose that DPA and CAA share similarities, overlap and interact, so that 'pure' DPA or CAA are extremes along a continuum of age-related small vessel pathologies. We suggest blood-brain barrier (BBB) breakdown, endothelial damage and impaired perivascular β-amyloid (Aβ) drainage are hallmark common mechanisms connecting DPA and CAA. We also suggest a need for new biomarkers (e.g. high-resolution imaging) to deepen understanding of the complex relationships between DPA and CAA.

Impact of Duodeno-Jejunal Bypass Liner (EndoBarrierTM) Implantation on Insulin Sensitivity in Patients with Type 2 Diabetes Mellitus (T2DM): A Study Protocol for a Pilot Trial

INTRODUCTION

A 60-cm endoscopically implantable duodenal-jejunal bypass liner (Endobarrier™, GI Dynamics, Lexington, MA, USA) has been introduced as a therapeutic option to support weight loss for a selected group of obese subjects with type 2 diabetes mellitus (T2DM). The sleeve prevents contact between chyme and the intestinal mucosa of the upper gastrointestinal tract. The primary aim of this study is to elucidate the changes in insulin sensitivity and beta-cell function after EndoBarrier™ implantation in obese patients with T2DM; changes in gut permeability and gut microbiome are also to be examined.

METHODS

This is an open, single-center, prospective trial in which ten obese subjects with T2DM and suboptimal glycemic control (glycosylated hemoglobin A1_c (HbA1c) level > 48 mmol/mol) are investigated with regards to EndoBarrier™ implantation. The Endobarrier™ is implanted shortly after baseline and left in situ for a period of 36 weeks. Dual-energy X-ray absorptiometry measurement, assessment of beta-cell function and insulin sensitivity as measured by a Botnia clamp procedure, and a mixed-meal tolerance test are performed prior to implantation and at 4, 36, and 64 weeks after implantation. The composition of the gut microbiota is characterized from stool using 454 pyrosequencing of 16S rRNA genes. Gut permeability is assessed by a differential sugar absorption method.

PLANNED OUTCOME

This study will give mechanistic insights in particulr into changes of insulin sensitivity, beta-cell function or microbiome changes over time in subjects implanted with an Endobarrier^TM device.

TRIAL REGISTRATION

NCT02769728, Registered 12 May 2016. Current Protocol Date/Version: 04 September 2017/Version 1.9.

Two time scales for self and collective diffusion near the critical point in a simple patchy model for proteins with floating bonds

Using dynamic Monte Carlo and Brownian dynamics, we investigate a floating bond model in which particles can bind through mobile bonds. The maximum number of bonds (here fixed to 4) can be tuned by appropriately choosing the repulsive, nonadditive interactions among bonds and particles. We compute the static and dynamic structure factor (intermediate scattering function) in the vicinity of the gas-liquid critical point. The static structure exhibits a weak tetrahedral network character. The intermediate scattering function shows a temporal decay deviating from a single exponential, which can be described by a double exponential decay where the two time scales differ approximately by one order of magnitude. This time scale separation is robust over a range of wave numbers. The analysis of clusters in real space indicates the formation of noncompact clusters and shows a considerable stretch in the instantaneous size distribution when approaching the critical point. The average time evolution of the largest subcluster of given initial clusters with 10 or more particles also shows a double exponential decay. The observation of two time scales in the intermediate scattering function at low packing fractions is consistent with similar findings in globular protein solutions with trivalent metal ions that act as bonds between proteins.

Efficacy and safety of a new low-volume PEG with citrate and simethicone bowel preparation for colonoscopy (Clensia): a multicenter randomized observer-blind clinical trial vs. a low-volume PEG with ascorbic acid (PEG-ASC)

BACKGROUND AND STUDY AIMS

Quality of inspection during colonoscopy is strictly related to the level of cleansing. High-volume (PEG-based) solutions are highly effective and safe, but their high volume affects tolerability and compliance. The aim of this study was to compare a new low-volume PEG with citrate and simethicone solution (PMF 104,Clensia) with a low-volume PEG with ascorbic acid solution (PEG-ASC; Moviprep).

PATIENTS AND METHODS

 This was a multicenter, randomized, observer-blind, parallel-group, phase 3 clinical trial, where patients were randomized between PMF 104 and PEG-ASC. In both groups, patients were instructed to take a full-dose regimen the evening before if colonoscopy was scheduled before 11 am to 12 pm, or to take a split regimen if colonoscopy was scheduled after 11 am to 12 pm. The primary end-point was an equivalence between PMF104 and PEG-ASC in the rate of adequate level of cleansing (Ottawa scale ≤ 6), with safety, mucosal visibility, tolerability, acceptance and compliance being also assessed.

RESULTS

Of the 403 enrolled, 367 patients (Mean age [SD]: 55.6 (14.4) years; male:166 [45.2 %]) were included in the per protocol (PP) analysis: 184 being randomized in the PMF 104 group and 183 in the PEG-ASC group. Successful bowel cleansing was 78.3 % and 74.3 % in PMF104 and in PEG-ASC, respectively ( P  = 0.37). Both preparations were equally safe (mild adverse events were observed in 9.2 % and 9.3 % of patients in the PMF104 and in the PEG-ASC group, respectively) and acceptable (no or mild distress during the intake in 81.4 % and 80.8 % in the PMF104 in the PEG-ASC, respectively [ P  = 0.74]).

CONCLUSION

The new low-volume product Clensia is equivalent to the reference low-volume PEG-ASC in terms of bowel cleansing, safety and acceptance.

Substrate and electron donor limitation induce phenotypic heterogeneity in different metabolic activities in a green sulphur bacterium

Populations of genetically identical cells can display marked variation in phenotypic traits; such variation is termed phenotypic heterogeneity. Here, we investigate the effect of substrate and electron donor limitation on phenotypic heterogeneity in N₂ and CO₂ fixation in the green sulphur bacterium Chlorobium phaeobacteroides. We grew populations in chemostats and batch cultures and used stable isotope labelling combined with nanometer-scale secondary ion mass spectrometry (NanoSIMS) to quantify phenotypic heterogeneity. Experiments in H₂ S (i.e. electron donor) limited chemostats show that varying levels of NH4+ limitation induce heterogeneity in N₂ fixation. Comparison of phenotypic heterogeneity between chemostats and batch (unlimited for H₂ S) populations indicates that electron donor limitation drives heterogeneity in N₂ and CO₂ fixation. Our results demonstrate that phenotypic heterogeneity in a certain metabolic activity can be driven by different modes of limitation and that heterogeneity can emerge in different metabolic processes upon the same mode of limitation. In conclusion, our data suggest that limitation is a general driver of phenotypic heterogeneity in microbial populations.

Robust singlet fission in pentacene thin films with tuned charge transfer interactions

Singlet fission, the spin-allowed photophysical process converting an excited singlet state into two triplet states, has attracted significant attention for device applications. Research so far has focused mainly on the understanding of singlet fission in pure materials, yet blends offer the promise of a controlled tuning of intermolecular interactions, impacting singlet fission efficiencies. Here we report a study of singlet fission in mixtures of pentacene with weakly interacting spacer molecules. Comparison of experimentally determined stationary optical properties and theoretical calculations indicates a reduction of charge-transfer interactions between pentacene molecules with increasing spacer molecule fraction. Theory predicts that the reduced interactions slow down singlet fission in these blends, but surprisingly we find that singlet fission occurs on a timescale comparable to that in pure crystalline pentacene. We explain the observed robustness of singlet fission in such mixed films by a mechanism of exciton diffusion to hot spots with closer intermolecular spacings.

Secondary tumours of the ampulla of Vater: Case report and review of the literature

Secondary tumours of the ampulla of Vater are rare. Underlying primary tumours, clinical presentation, macroscopic appearance, treatment strategies and outcome of secondary ampullary lesions have not been systematically analysed. The present case study reported a 57-year old patient with an ampullary metastasis from renal cancer and a literature review was performed in which a further 32 patients were included. The most common responsible primary tumours were malignant melanoma and renal clear cell carcinoma, followed by breast cancer. The time interval between the diagnosis of the primary tumour and the ampullary metastasis was highly variable, and may be as long as 10 years, particularly for renal cancer. Patients may present with unspecific abdominal discomfort, jaundice or upper gastrointestinal bleeding. The gross appearance was largely indistinguishable from that of a primary tumour. Lesions may present as polypoid or irregular, soft and friable tumour mass, in certain cases with superficial ulceration. In ~50% of cases, the ampullary metastasis was the only metastatic lesion, while in the remaining cases, the cancer had spread to one or more organs. The prognosis was generally poor. The management requires a multi-modal approach, including endoscopic, surgical and oncological procedure.

Orientation-Dependent Work-Function Modification Using Substituted Pyrene-Based Acceptors

The adsorption of molecular acceptors is a viable method for tuning the work function of metal electrodes. This, in turn, enables adjusting charge injection barriers between the electrode and organic semiconductors. Here, we demonstrate the potential of pyrene-tetraone (PyT) and its derivatives dibromopyrene-tetraone (Br-PyT) and dinitropyrene-tetraone (NO₂-PyT) for modifying the electronic properties of Au(111) and Ag(111) surfaces. The systems are investigated by complementary theoretical and experimental approaches, including photoelectron spectroscopy, the X-ray standing wave technique, and density functional theory simulations. For some of the investigated interfaces the trends expected for Fermi-level pinning are observed, i.e., an increase of the metal work function along with increasing molecular electron affinity and the same work function for Au and Ag with monolayer acceptor coverage. Substantial deviations are, however, found for Br-PyT/Ag(111) and NO₂-PyT/Ag(111), where in the latter case an adsorption-induced work function increase of as much as 1.6 eV is observed. This behavior is explained as arising from a face-on to edge-on reorientation of molecules in the monolayer. Our calculations show that for an edge-on orientation much larger work-function changes can be expected despite the prevalence of Fermi-level pinning. This is primarily ascribed to a change of the electron affinity of the adsorbate layer that results from a change of the molecular orientation. This work provides a comprehensive understanding of how changing the molecular electron affinity as well as the adsorbate structure impacts the electronic properties of electrodes.

Limits of size scalability of diffusion and growth: Atoms versus molecules versus colloids

Understanding fundamental growth processes is key to the control of nonequilibrium structure formation for a wide range of materials on all length scales, from atomic to molecular and even colloidal systems. While atomic systems are relatively well studied, molecular and colloidal growth are currently moving more into the focus. This poses the question to what extent growth laws are size scalable between different material systems. We study this question by analyzing the potential energy landscape and performing kinetic Monte Carlo simulations for three representative systems. While submonolayer (island) growth is found to be essentially scalable, we find marked differences when moving into the third (vertical) dimension.

Structure, transport and photoconductance of PbS quantum dot monolayers functionalized with a copper phthalocyanine derivative

We simultaneously surface-functionalize PbS nanocrystals with Cu 4,4′,4′′,4′′′-tetraaminophthalocyanine and assemble this hybrid material into macroscopic monolayers.

Mefenamic acid: A possible cause of drug-induced acute pancreatitis

INTRODUCTION

Drug-induced acute pancreatitis (AP) is rare, but as there are no systematic data on it, the true incidence is not known.

CASE REPORT

This case report is a first description of two episodes of AP occurring after administration and subsequent re-administration of mefenamic acid to a young woman without comorbidities. Other common causes of AP could be ruled out. With both episodes, the latency of AP was less than 24 h after drug intake.

CONCLUSION

Mefenamic acid should be considered as a possible cause of drug-induced AP.

Coupled organic–inorganic nanostructures (COIN)

Materials to devices: coupled organic–inorganic nanostructures provide versatile perspectives for quantum dot-based optoelectronic devices.

Unravelling the multilayer growth of the fullerene C60 in real time

Molecular semiconductors are increasingly used in devices, but understanding of elementary nanoscopic processes in molecular film growth is in its infancy. Here we use real-time in situ specular and diffuse X-ray scattering in combination with kinetic Monte Carlo simulations to study C60 nucleation and multilayer growth. We determine a self-consistent set of energy parameters describing both intra- and interlayer diffusion processes in C60 growth. This approach yields an effective Ehrlich-Schwoebel barrier of EES=110 meV, diffusion barrier of ED=540 meV and binding energy of EB=130 meV. Analysing the particle-resolved dynamics, we find that the lateral diffusion is similar to colloids, but characterized by an atom-like Schwoebel barrier. Our results contribute to a fundamental understanding of molecular growth processes in a system, which forms an important intermediate case between atoms and colloids.

Evidence for kinetically limited thickness dependent phase separation in organic thin film blends

We present depth-resolved grazing incidence x-ray diffraction, grazing incidence small angle scattering and x-ray reflectivity studies on the structure of mixed C(60) and diindinoperylene (DIP) films as a function of the mixing ratio. We observe enhanced out-of-plane order and smoothing of the mixed films compared to pure films upon coevaporation of DIP:C(60) thin films (in different mixing ratio) which otherwise phase separate. The mixing ratio of molecules can be tuned to alter the in-plane crystallite size as well as the interisland distances of the mixing molecules. Real-time in situ grazing incidence x-ray diffraction measurements show the kinetics and thickness dependence of phase separation, which appears to proceed only after a certain thickness. The crystallite grain size of the individual phase separated components is significantly larger at the top of the film than at the bottom with implications for the understanding of devices.

Mixing-induced anisotropic correlations in molecular crystalline systems

We investigate the structure of mixed thin films composed of pentacene and diindenoperylene using x-ray reflectivity and grazing incidence x-ray diffraction. For equimolar mixtures we observe vanishing in-plane order coexisting with an excellent out-of-plane order, a yet unreported disordering behavior in binary mixtures of organic semiconductors, which are crystalline in their pure form. One approach to rationalize our findings is to introduce an anisotropic interaction parameter in the framework of a mean field model. By comparing the structural properties with those of other mixed systems, we discuss the effects of sterical compatibility and chemical composition on the mixing behavior, which adds to the general understanding of interactions in molecular mixtures.

Structure and morphology of coevaporated pentacene-perfluoropentacene thin films

The structural properties of coevaporated thin films of pentacene (PEN) and perfluoropentacene (PFP) on SiO(2) were studied using x-ray reflectivity and grazing incidence x-ray diffraction. Reciprocal space maps of the coevaporated thin films with different volume fractions reveal the coexistence of two different molecular mixed PEN-PFP phases together with the pure PEN and PFP crystallites. The crystal structure of PEN:PFP blends does not change continuously with volume fraction, instead the proportion of the appropriate phases changes, as seen from the diffraction analysis. Additional temperature dependent experiments reveal that the fraction of the two mixed PEN-PFP phases varies with growth temperature. The λ-phase (molecular plane parallel to the substrate) is metastable and induced by low growth temperature. The σ-phase (molecular plane nearly perpendicular to the substrate) is thermally stable and nucleates predominantly at high growth temperatures.

Detecting artery occlusion and critical flow diminution in the case of an acute ischemic stroke--methodological pitfalls of common vascular diagnostic methods

PURPOSE

None of the vascular emergency diagnostic methods commonly used in the case of acute ischemic stroke, i. e. CTA, color-coded duplex sonography (CCDS), MRA, and DSA, is free of restrictions due to physical and physiological characteristics. As a result, misleading results initiating an inappropriate acute therapeutic intervention or hampering a promising one cannot be excluded. We aimed to assess the type and frequency of methodological pitfalls occurring in this situation.

MATERIALS AND METHODS

We retrospectively analyzed data of 269 consecutive patients admitted to our stroke unit with a clinical syndrome of an acute stroke. All patients underwent one or more vascular emergency diagnostic methods on a routine basis.

RESULTS

37 patients were excluded because of a final diagnosis other than ischemic stroke. 76 of 232 ischemic stroke patients underwent emergency diagnostic methods with two or more vascular examination techniques. Controversial results occurred in 20 patients and related to the detection and localization of large artery occlusion and its differentiation from a low/slow flow situation and the identification of critical cerebral flow diminution distal to large artery occlusion/severe stenosis. Methodological pitfalls were able to be most reliably resolved by CCDS. Within the whole cohort of ischemic stroke patients, vascular constellations susceptible to misinterpretation were diagnosed in 40 (17.2 %) patients.

CONCLUSION

We recommend providing several techniques including CCDS in an emergency stroke setting and applying techniques with respect to diagnostic findings.

Orientational ordering of nonplanar phthalocyanines on Cu(111): strength and orientation of the electric dipole moment

In order to investigate the orientational ordering of molecular dipoles and the associated electronic properties, we studied the adsorption of chlorogallium phthalocyanine molecules (GaClPc, Pc=C32N8H16(-2) on Cu(111) by using the x-ray standing wave technique, photoelectron spectroscopy, and quantum mechanical calculations. We find that for submonolayer coverages on Cu(111) the majority of GaClPc molecules adsorb in a Cl-down configuration by forming a covalent bond to the substrate. For bilayer coverages the x-ray standing wave data indicate a coexistence of the Cl-down and Cl-up configurations on the substrate. The structural details established for both cases and supplementary calculations of the adsorbate system allow us to analyze the observed change of the work function.