Imaging magnetic vortex configurations in ferromagnetic nanotubes

We image the remnant magnetization configurations of CoFeB and permalloy nanotubes (NTs) using x-ray magnetic circular dichroism photo-emission electron microscopy. The images provide direct evidence for flux-closure configurations, including a global vortex state, in which magnetization points circumferentially around the NT axis. Furthermore, micromagnetic simulations predict and measurements confirm that vortex states can be programmed as the equilibrium remnant magnetization configurations by reducing the NT aspect ratio.Comment: 14 pages, 4 figures, link to supplementary informatio

Magnetization reversal of an individual exchange biased permalloy nanotube

We investigate the magnetization reversal mechanism in an individual permalloy (Py) nanotube (NT) using a hybrid magnetometer consisting of a nanometer-scale SQUID (nanoSQUID) and a cantilever torque sensor. The Py NT is affixed to the tip of a Si cantilever and positioned in order to optimally couple its stray flux into a Nb nanoSQUID. We are thus able to measure both the NT's volume magnetization by dynamic cantilever magnetometry and its stray flux using the nanoSQUID. We observe a training effect and temperature dependence in the magnetic hysteresis, suggesting an exchange bias. We find a low blocking temperature $T_B = 18 \pm 2$ K, indicating the presence of a thin antiferromagnetic native oxide, as confirmed by X-ray absorption spectroscopy on similar samples. Furthermore, we measure changes in the shape of the magnetic hysteresis as a function of temperature and increased training. These observations show that the presence of a thin exchange-coupled native oxide modifies the magnetization reversal process at low temperatures. Complementary information obtained via cantilever and nanoSQUID magnetometry allows us to conclude that, in the absence of exchange coupling, this reversal process is nucleated at the NT's ends and propagates along its length as predicted by theory.Comment: 8 pages, 4 figure

Bridging the Mid-Infrared-to-Telecom Gap with Silicon Nanophotonic Spectral Translation

Expanding far beyond traditional applications in optical interconnects at telecommunications wavelengths, the silicon nanophotonic integrated circuit platform has recently proven its merits for working with mid-infrared (mid-IR) optical signals in the 2-8 {\mu}m range. Mid-IR integrated optical systems are capable of addressing applications including industrial process and environmental monitoring, threat detection, medical diagnostics, and free-space communication. Rapid progress has led to the demonstration of various silicon components designed for the on-chip processing of mid-IR signals, including waveguides, vertical grating couplers, microcavities, and electrooptic modulators. Even so, a notable obstacle to the continued advancement of chip-scale systems is imposed by the narrow-bandgap semiconductors, such as InSb and HgCdTe, traditionally used to convert mid-IR photons to electrical currents. The cryogenic or multi-stage thermo-electric cooling required to suppress dark current noise, exponentially dependent upon the ratio Eg/kT, can limit the development of small, low-power, and low-cost integrated optical systems for the mid-IR. However, if the mid-IR optical signal could be spectrally translated to shorter wavelengths, for example within the near-infrared telecom band, photodetectors using wider bandgap semiconductors such as InGaAs or Ge could be used to eliminate prohibitive cooling requirements. Moreover, telecom band detectors typically perform with higher detectivity and faster response times when compared with their mid-IR counterparts. Here we address these challenges with a silicon-integrated approach to spectral translation, by employing efficient four-wave mixing (FWM) and large optical parametric gain in silicon nanophotonic wires

Birth after TESE–ICSI in a man with hypogonadotropic hypogonadism and congenital adrenal hypoplasia linked to a DAX-1 (NR0B1) mutation

DAX1/NR0B1 mutations are responsible for X-linked congenital adrenal hypoplasia (AHC) associated with hypogonadotropic hypogonadism (HH). Few data are available concerning testicular function and fertility in men with DAX1 mutations. Azoospermia as well as failure of gonadotrophin treatment have been reported. We induced spermatogenesis in a patient who has a DAX1 mutation (c.1210C>T), leading to a stop codon in position 404 (p.Gln404X). His endocrine testing revealed a low testosterone level at 1.2 nmol/l (N: 12–40) with low FSH and LH levels at 2.1 IU/l (N: 1–5 IU/l) and 0.1 IU/l (N: 1–4 IU/l), respectively. Baseline semen analysis revealed azoospermia. Menotropin (Menopur®:150 IU, three times weekly) and human chorionic gonadotrophin (1500 IU, twice weekly) were used. After 20 months of treatment, as azoospermia persisted, bilateral multiple site testicular biopsies were performed. Histology revealed severe hypospermatogenesis. Rare spermatozoa were extracted from the right posterior fragment and ICSI was performed. Four embryos were obtained and, after a frozen–thawed single-embryo transfer, the patient's wife became pregnant and gave birth to a healthy boy. We report the first case of paternity after TESE–ICSI in a patient with DAX1 mutation, giving potential hope to these patients to father non-affected children. Furthermore, this case illustrates the fact that patients with X-linked AHC have a primary testicular defect in addition to HH

Diagnostik arbeitsbedingter Erkrankungen und arbeitsmedizinisch-diagnostische Tabellen

Eine ganze Reihe von beruflichen Belastungen und ungünstigen Arbeitsbedingungen kann zu zahlreichen berufsbedingten Erkrankungen und Beschwerden führen, von denen nur ein kleiner Teil als Berufskrankheit oder Arbeitsunfall anerkannt wird. Der größere, versicherungsrechtlich nicht anerkannte Teil gilt als "arbeitsbedingte Erkrankung" im engeren Sinne. Es sind Erkrankungen und Beschwerden, die beruflich verursacht, teilweise beruflich verursacht oder in ihrer Dynamik beeinflusst werden. Neue Technologien und andere Arbeitsanforderungen führen zu einem geänderten Spektrum und zur Zunahme der arbeitsbedingten Erkrankungen und Beschwerden. Während einzelne Berufskrankheiten aufgrund der Präventionsmaßnahmen seltener geworden sind, verbergen sich viele arbeitsbedingte Erkrankungen im allgemeinen Krankheitsspektrum der Bevölkerung und sind bei der hausärztlichen und klinischen Betreuung zunehmend zu berücksichtigen. Unsere "Diagnostik arbeitsbedingter Erkrankungen und arbeitsmedizinisch-diagnostische Tabellen" gehen einerseits von allgemeinen und speziellen Krankheitsbildern aus und geben eine Übersicht über die möglichen Ursachen. Andererseits werden bestimmte Gefährdungen und die möglichen Beschwerden und Erkrankungen aufgeführt. Bei ausgewählten Erkrankungen werden Hinweise zur spezifischen Diagnostik und Differentialdiagnostik gegeben. Die Darstellungen orientieren sich daher auch am allgemeinen Krankheitsspektrum und sind nicht nur auf die anerkannten Berufskrankheiten eingeengt. Unsere Ausführungen und Tabellen, die in Kooperation mit den jeweiligen Fachvertretern der Medizinischen Fakultät in Homburg erarbeitet wurden, umfassen arbeitsbedingte Atemwegs- und Lungenkrankheiten, Herz- und Kreislaufkrankheiten, Karzinome, Leberkrankheiten, neurologische Krankheiten, Nieren- und Harnwegserkrankungen, ophthalmologische Krankheiten, orthopädisch-chirurgische Erkrankungen der Bewegungsorgane, sensibilisierende Arbeitsstoffe, Virus- und Infektionskrankheiten und verschiedene aktuelle Kurzinformationen. Aufgrund unserer besonderen poliklinischen Tätigkeit haben wir über Jahrzehnte Informationen über arbeitsbedingte Erkrankungen gesammelt und im Jahr 2000 in einer ersten Form zusammen gestellt und im Internet veröffentlicht. Die jetzige Fassung 2007 gehört längst zur Pflichtlektüre für unsere Studierenden und für die Facharztweiterbildung. Die Aktualisierung und Ergänzung ist laufend vorgesehen

Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

Urticaria and infections

Urticaria is a group of diseases that share a distinct skin reaction pattern. Triggering of urticaria by infections has been discussed for many years but the exact role and pathogenesis of mast cell activation by infectious processes is unclear. In spontaneous acute urticaria there is no doubt for a causal relationship to infections and all chronic urticaria must have started as acute. Whereas in physical or distinct urticaria subtypes the evidence for infections is sparse, remission of annoying spontaneous chronic urticaria has been reported after successful treatment of persistent infections. Current summarizing available studies that evaluated the course of the chronic urticaria after proven Helicobacter eradication demonstrate a statistically significant benefit compared to untreated patients or Helicobacter-negative controls without urticaria (p < 0.001). Since infections can be easily treated some diagnostic procedures should be included in the routine work-up, especially the search for Helicobacter pylori. This review will update the reader regarding the role of infections in different urticaria subtypes