Adlayer influence on Dirac-type surface state at W(110).

In a combined experimental and theoretical study, we investigated how Fe and Co adlayers on W(110) affect the Dirac-type surface state (DSS). Angle-resolved photoelectron spectroscopy data show an increase in binding energy of 75 meV and 107 meV for Fe and Co, respectively. In order to identify the origin of the energy shift we performed first-principles calculations of the surface electronic structure. The inward surface relaxation of the uncovered W(110) surface is lifted by the adlayers. This structural change is one reason of the energy shift of the DSS. Furthermore, the Fe and Co adlayers change the surface potential, which results in an additional energy shift of the DSS.

Spin-dependent electron reflection at W(110).

Spin-dependent reflection of low-energy electrons at the W(110) surface caused by spin-orbit interaction was studied experimentally and theoretically. Comprehensive information for a wide range of electron incidence angles and energies was collected via maps for the reflectivity, the spin-dependent reflection asymmetry, and the figure of merit of the spin separation. The experimental results are compared with calculations of the scattering process using a realistic surface potential barrier. The results are discussed in view of possible applications of W(110) as a scattering target in spin-polarization detectors. Possible working points for use in single- as well as multi-channel spin-polarization-detection devices are identified and discussed.

Circular-polarized-light-induced spin polarization characterized for the Dirac-cone surface state at W(110) with C2v symmetry.

The C2v surface symmetry of W(110) strongly influences a spin-orbit-induced Dirac-cone-like surface state and its characterization by spin- and angle-resolved photoelectron spectroscopy. In particular, using circular polarized light, a distinctive k-dependent spin texture is observed along the [Formula: see text] direction of the surface Brillouin zone. For all spin components Px, Py, and Pz, non-zero values are detected, while the initial-state spin polarization has only a Py component due to mirror symmetry. The observed complex spin texture of the surface state is controlled by transition matrix element effects, which include orbital symmetries of the involved electron states as well as the geometry of the experimental set-up.

[Abdominal pain and hypertension in a 55-year-old male patient]. / Abdominale Beschwerden und Hypertonus bei einem 55­jährigen Patienten.

A 55-year-old male patient under permanent testosterone therapy for hypogonadism presented with abdominal pain and increased blood pressure values. In the physical examination a plethora was noted and laboratory examinations revealed polyglobulia. In the subsequent diagnostic process polycythemia vera and cancer could be excluded as the cause. A secondary polyglobulia due to testosterone substitution was diagnosed. Unphysiologically high testosterone levels represent a rare cause of secondary polyglobulia and with an appropriate medical history should be taken into account at an early stage.

Momentum resolution in inverse photoemission.

We present a method to determine the electron beam divergence, and thus the momentum resolution, of an inverse-photoemission setup directly from a series of spectra measured on Cu(111). Simulating these spectra with different beam divergences shows a distinct influence of the divergence on the appearance of the Shockley surface state. Upon crossing the Fermi level, its rise in intensity can be directly linked with the beam divergence. A comparison of measurement and simulation enables us to quantify the momentum resolution independent of surface quality, energy resolution, and experimental geometry. With spin resolution, a single spectrum taken around the Fermi momentum of a spin-split surface state, e.g., on Au(111), is sufficient to derive the momentum resolution of an inverse-photoemission setup.

Ambiguity of experimental spin information from states with mixed orbital symmetries.

The spin texture of the unoccupied bands of the surface alloy Bi/Ag(111) is investigated with spin- and angle-resolved inverse photoemission and first-principles calculations. Surprisingly, the measured spin character does not always reflect the calculated spin texture of the bands. With the help of photoemission calculations within the one-step model, however, the discrepancy is traced back to the influence of the orbital symmetry of the respective states in combination with the experimental geometry. In particular, the calculations show that the spin texture of a surface band with mixed orbital symmetries may neither be recovered with s- nor p- nor unpolarized light. In general, spin information from direct or inverse photoemission experiments on electronic states with mixed orbital symmetries at spin-orbit-influenced surfaces has to be taken with a pinch of salt, while it remains reliable for states with pure symmetry.

Rotatable spin-polarized electron source for inverse-photoemission experiments.

We present a ROtatable Spin-polarized Electron source (ROSE) for the use in spin- and angle-resolved inverse-photoemission (SR-IPE) experiments. A key feature of the ROSE is a variable direction of the transversal electron beam polarization. As a result, the inverse-photoemission experiment becomes sensitive to two orthogonal in-plane polarization directions, and, for nonnormal electron incidence, to the out-of-plane polarization component. We characterize the ROSE and test its performance on the basis of SR-IPE experiments. Measurements on magnetized Ni films on W(110) serve as a reference to demonstrate the variable spin sensitivity. Moreover, investigations of the unoccupied spin-dependent surface electronic structure of Tl/Si(111) highlight the capability to analyze complex phenomena like spin rotations in momentum space. Essentially, the ROSE opens the way to further studies on complex spin-dependent effects in the field of surface magnetism and spin-orbit interaction at surfaces.

Targeting inflammation in the treatment of type 2 diabetes.

Islets of patients with type 2 diabetes display the typical features of an inflammatory process characterized by the presence of cytokines, chemokines, immune cell infiltration, impaired function and tissue destruction with fibrotic areas. Functional studies have shown that targeting inflammation may improve insulin secretion and sensitivity. In particular clinical proof of concept studies using modulators of the interleukin-1ß (IL-1ß)-nuclear factor--κB (NF-κB) pathway demonstrated the role of the innate immune system in type 2 diabetes. This programme has now entered the phase 3 of clinical development. Other targets such as tumour necrosis factor α (TNFα) may be equally important but have been neglected based on poorly designed studies. In this article we discuss the mechanisms of islet inflammation in type 2 diabetes and review the opportunity of clinical translation.

Cannabis exposure associated with weight reduction and ß-cell protection in an obese rat model.

The aim of this study was to investigate the effect of an organic cannabis extract on ß-cell secretory function in an in vivo diet-induced obese rat model and determine the associated molecular changes within pancreatic tissue. Diet-induced obese Wistar rats and rats fed on standard pellets were subcutaneously injected with an organic cannabis extract or the vehicle over a 28-day period. The effect of diet and treatment was evaluated using the intraperitoneal glucose tolerance tests (IPGTTs) and qPCR analysis on rat pancreata harvested upon termination of the experiment. The cafeteria diet induced an average weight difference of 32g and an overall increase in body weight in the experimental groups occurred at a significantly slower rate than the control groups, irrespective of diet. Area under the curve for glucose (AUC(g)) in the obese group was significantly lower compared to the lean group (p<0.001), with cannabis treatment significantly reducing the AUC(g) in the lean group (p<0.05), and remained unchanged in the obese group, relative to the obese control group. qPCR analysis showed that the cafeteria diet induced down-regulation of the following genes in the obese control group, relative to lean controls: UCP2, c-MYC and FLIP. Cannabis treatment in the obese group resulted in up-regulation of CB1, GLUT2, UCP2 and PKB, relative to the obese control group, while c-MYC levels were down-regulated, relative to the lean control group. Treatment did not significantly change gene expression in the lean group. These results suggest that the cannabis extract protects pancreatic islets against the negative effects of obesity.

Spin-polarized Dirac-cone-like surface state with d character at W(110).

The surface of W(110) exhibits a Dirac-cone-like state with d character within a spin-orbit-induced symmetry gap. As a function of the wave vector parallel to the surface, it shows a nearly massless energy dispersion and a pronounced spin polarization, which is antisymmetric with respect to the Brillouin zone center. In addition, the observed constant energy contours are strongly anisotropic for all energies. This discovery opens new pathways to the study of surface spin-density waves arising from a strong Fermi surface nesting as well as d-electron-based topological properties.

[Drug-drug interactions with HIV treatments]. / Medikamenteninteraktion bei HIV-Therapien.

We develop a differential diagnosis and diagnostic approach to a possible drug-drug interaction between a cART based on boosted atazanavir and newly given drugs. History taking should not only encompass prescribed but also over-the-counter medication. Exchange of information between attending physicians as to therapeutic changes, documented side effects and adherence, therapeutic drug monitoring of cART and evaluation by pharmacologist in complex situations are the diagnostic tools at hand.

Role of spin-flip exchange scattering for hot-electron lifetimes in cobalt.

The spin-dependent lifetimes of hot electrons in fcc Co films were studied by spin- and time-resolved two-photon photoemission. Even for excitation energies close to the Fermi level, we find almost identical lifetimes for majority and minority electrons. This result contradicts ab initio theories predicting 5 to 10 times longer lifetimes for the majority electrons in 3d ferromagnets. We provide direct experimental evidence that this discrepancy is caused by the dominance of exchange scattering in inelastic electron decay, in combination with the excitation of secondary electrons. The latter are inherent for all real materials and devices.

Magnetic exchange splitting in Fe above the Curie temperature.

The magnetic exchange splitting of electronic states in a 7 monolayer Fe film on Cu(001) was investigated below and above the Curie temperature T(C), using image-potential surface states as sensor. At T(C), the long-range magnetic order breaks down as reflected by a vanishing spin splitting and vanishing spin polarization. The exchange splitting, in contrast, does not change abruptly at T(C) but persists up to T=1.2T(C). Equally, the spin-integrated linewidth shows no signature of the magnetic phase transition but smoothly decreases with increasing temperature. Our experimental results confirm theoretical expectations that, at T(C), the long-range magnetic order disappears but the local magnetic moments and, in particular, the valence electronic structure are unaffected by the phase transition.

Ultrafast magnon generation in an Fe film on Cu(100).

We report on a combined experimental and theoretical study of the spin-dependent relaxation processes in the electron system of an iron film on Cu(100). Spin-, time-, energy- and angle-resolved two-photon photoemission shows a strong characteristic dependence of the lifetime of photoexcited electrons on their spin and energy. Ab initio calculations as well as a many-body treatment corroborate that the observed properties are determined by relaxation processes involving magnon emission. Thereby we demonstrate that magnon emission by hot electrons occurs on the femtosecond time scale and thus provides a significant source of ultrafast spin-flip processes. Furthermore, engineering of the magnon spectrum paves the way for tuning the dynamic properties of magnetic materials.

IL-1 antagonism reduces hyperglycemia and tissue inflammation in the type 2 diabetic GK rat.

Recent studies suggest an inflammatory process, characterized by local cytokine/chemokine production and immune cell infiltration, regulates islet dysfunction and insulin resistance in type 2 diabetes. However, the factor initiating this inflammatory response is not known. Here, we characterized tissue inflammation in the type 2 diabetic GK rat with a focus on the pancreatic islet and investigated a role for IL-1. GK rat islets, previously characterized by increased macrophage infiltration, displayed increased expression of several inflammatory markers including IL-1beta. In the periphery, increased expression of IL-1beta was observed primarily in the liver. Specific blockade of IL-1 activity by the IL-1 receptor antagonist (IL-1Ra) reduced the release of inflammatory cytokines/chemokines from GK islets in vitro and from mouse islets exposed to metabolic stress. Islets from mice deficient in IL-1beta or MyD88 challenged with glucose and palmitate in vitro also produced significantly less IL-6 and chemokines. In vivo, treatment of GK rats with IL-1Ra decreased hyperglycemia, reduced the proinsulin/insulin ratio, and improved insulin sensitivity. In addition, islet-derived proinflammatory cytokines/chemokines (IL-1beta, IL-6, TNFalpha, KC, MCP-1, and MIP-1alpha) and islet CD68(+), MHC II(+), and CD53(+) immune cell infiltration were reduced by IL-1Ra treatment. Treated GK rats also exhibited fewer markers of inflammation in the liver. We conclude that elevated islet IL-1beta activity in the GK rat promotes cytokine and chemokine expression, leading to the recruitment of innate immune cells. Rather than being directly cytotoxic, IL-1beta may drive tissue inflammation that impacts on both beta cell functional mass and insulin sensitivity in type 2 diabetes.

Hyperglycaemia but not hyperlipidaemia causes beta cell dysfunction and beta cell loss in the domestic cat.

AIMS/HYPOTHESIS: In vitro studies point to a toxic effect of high glucose and non-esterified fatty acids on beta cells. Whether elevated levels of glucose and lipids induce beta cell loss in vivo is less clear. The domestic cat has recently been proposed as a valuable animal model for human type 2 diabetes because feline diabetes shows several similarities with diabetes in humans, including obesity-induced insulin resistance, impaired beta cell function, decreased number of beta cells and pancreatic amyloid deposition. METHODS: We infused healthy cats with glucose or lipids for 10 days to clamp their blood concentrations at the approximate level found in untreated feline diabetes (glucose: 25-30 mmol/l; triacylglycerols: 3-7 mmol/l). RESULTS: Glucose and lipid levels were adequately targeted. Plasma non-esterified fatty acids were increased by lipid infusion 1.7-fold. A dramatic and progressive decline of plasma insulin levels was observed in glucose-infused cats beginning after 2 days of hyperglycaemic clamp. In contrast, plasma insulin concentration and glucose tolerance test were not affected by hyperlipidaemia. Compared with controls, glucose-infused cats had a 50% decrease in beta cells per pancreatic area. Apoptotic islet cells and cleaved caspase-3-positive beta cells were observed in glucose-infused cats only. CONCLUSIONS/INTERPRETATION: Sustained hyperglycaemia but not hyperlipidaemia induces early and severe beta cell dysfunction in cats, and excess glucose causes beta cell loss via apoptosis in vivo. Hyperglycaemic clamps in cats may provide a good model to study the pathogenesis of glucose toxicity in beta cells.

Ferromagnetic Fe on Cu(001) throughout the fcc-like phase: arguing from the viewpoint of the electronic structure.

The scientific enthusiasm for ultrathin Fe films on Cu(001) has now lasted for more than 20 years. Is there ferromagnetic iron with a face-centred cubic (fcc) structure? Does ferromagnetism in Fe hinge on the body-centred cubic (bcc) structure? In this contribution, we try to establish that the electron system gives evidence of ferromagnetic behaviour with fcc-like electronic bands. We examine a crystal-induced surface state, which is characteristic of fcc surface order. Furthermore, we compare electronic signatures of fcc and bcc: the d-band exchange splitting, image-potential-state energies and the work function. We conclude that, from the viewpoint of the electronic structure, Fe on Cu(001) is found to be ferromagnetic throughout the fcc-like phase. This result raises a new question: how much deviation from the relaxed fcc order is acceptable without losing the electronic signature of fcc?

Insulitis in type 2 diabetes.

Islets of patients with type 2 diabetes have the feature of an inflammatory process reflected by the presence of cytokines, immune cells, beta-cell apoptosis, amyloid deposits and fibrosis. Indeed, beta-cells from patients with type 2 diabetes display inflammatory markers, including increased interleukin (IL)-1 beta expression. Furthermore, increased islet-associated macrophages are observed in human type 2 diabetic patients and in most animal models of diabetes. Importantly, increased numbers of macrophages are detectable very early in high fat-fed mice islets, before the onset of diabetes. These immune cells are most likely attracted by islet-derived chemokines, produced in response to metabolic stress, and under the control of IL-1 beta. It follows that modulation of intra-islet inflammatory mediators, in particular IL-1 beta, may prevent insulitis in type 2 diabetes and therefore presents itself as a possible causal therapy with disease-modifying potential.