Multichannel laser diode to polymer waveguide array coupling with a double-aspheric lens.

An optical system for multichannel coupling of laser arrays to polymer waveguide array probes with a single biconvex lens is developed. The developed cylindrical module with 13 mm and 20 mm in diameter and length, respectively, enables coupling of eight individual optical channels using an aspheric lens. Specific coupling with crosstalk below -13d B for each channel and quasi-uniform coupling over all channels is achieved for a waveguide array with 100 µm lateral facet pitch at the incoupling site. The polymer waveguide technology allows for tapering of the lateral waveguide pitch to 25 µm toward the tip of the flexible waveguide array. SU-8 and PMMA are used as the waveguide core and cladding, respectively. The optical coupling module is designed as a prototype for preclinical evaluation of optical neural stimulators.

Cell size and actin architecture determine force generation in optogenetically activated cells.

Adherent cells use actomyosin contractility to generate mechanical force and to sense the physical properties of their environment, with dramatic consequences for migration, division, differentiation, and fate. However, the organization of the actomyosin system within cells is highly variable, with its assembly and function being controlled by small GTPases from the Rho family. To understand better how activation of these regulators translates into cell-scale force generation in the context of different physical environments, here we combine recent advances in non-neuronal optogenetics with micropatterning and traction force microscopy on soft elastic substrates. We find that, after whole-cell RhoA activation by the CRY2/CIBN optogenetic system with a short pulse of 100 ms, single cells contract on a minute timescale in proportion to their original traction force, before returning to their original tension setpoint with near perfect precision, on a longer timescale of several minutes. To decouple the biochemical and mechanical elements of this response, we introduce a mathematical model that is parametrized by fits to the dynamics of the substrate deformation energy. We find that the RhoA response builds up quickly on a timescale of 20 s, but decays slowly on a timescale of 50 s. The larger the cells and the more polarized their actin cytoskeleton, the more substrate deformation energy is generated. RhoA activation starts to saturate if optogenetic pulse length exceeds 50 ms, revealing the intrinsic limits of biochemical activation. Together our results suggest that adherent cells establish tensional homeostasis by the RhoA system, but that the setpoint and the dynamics around it are strongly determined by cell size and the architecture of the actin cytoskeleton, which both are controlled by the extracellular environment.

Dorsal minimally invasive plate osteosynthesis of the distal tibia with regard to adjacent anatomical characteristics.

INTRODUCTION: The aim of this study was to perform MIPO of the distal tibia from a dorsomedial and dorsolateral approach and to evaluate their feasibility and risk of injury to adjacent anatomical structures. MATERIAL & METHODS: A total of 18 extremities from 9 adult human cadavers was included in the study. In each cadaver, one lower leg underwent application of a 12-hole 3.5 LCP metaphyseal plate from the medial and the further one from the lateral approach. For the medial approach, a 4 cm skin incision was performed at the tibial border of the Achilles tendon, starting from 1 cm proximal to its insertion point at the calcaneal tuberosity. Entrance was gained between the medial border of the flexor hallucis longus tendon and the medial neurovascular bundle. Regarding the lateral approach, the skin was incised over a length of about 4 cm at the lateral border of the Achilles tendon, approximately 1 cm proximal to its insertion point. Entrance was gained between the Achilles tendon and the peroneus brevis muscle. The plates were inserted in direct bone contact in a proximal direction and the proximal and distal ends were fixed. During dissection, the proximal and distal holes beneath the crossing points of the neurovascular bundle and the plate were noted. The distal and proximal intersection points of the neurovascular bundle and the plate were measured with reference to the distal border of the plate. RESULTS: Concerning the medial approach, the neurovascular bundle was on median located between the 6th and 11th plate holes starting from distal. The bundle intersected the plate distally at a mean height of 65.8 mm and proximally at 156.8 mm on average. For the lateral approach, the neurovascular bundle was situated between the 6th and the 12th plate hole from distal. It crossed the plate distally at a mean of 61.0 mm and proximal at a mean height of 153.9 mm. In none of the cases, lacerations of the neurovascular bundle were observed. CONCLUSION: In conclusion, MIPO from the dorsomedial and dorsolateral approach are both safe procedures as indicated by our study.

Electron Doping of the Iron-Arsenide Superconductor CeFeAsO Controlled by Hydrostatic Pressure.

In the iron-pnictide material CeFeAsO not only the Fe moments, but also the local 4f moments of the Ce order antiferromagnetically at low temperatures. We elucidate on the peculiar role of the Ce on the emergence of superconductivity. While application of pressure suppresses the iron SDW ordering temperature monotonously up to 4 GPa, the Ce-4f magnetism is stabilized until both types of magnetic orders disappear abruptly and a narrow SC dome develops. With further increasing pressure characteristics of a Kondo-lattice system become more and more apparent in the electrical resistivity. This suggests a connection of the emergence of superconductivity with the extinction of the magnetic order and the onset of Kondo screening of the Ce-4f moments.

Pressure-Induced Ferromagnetism due to an Anisotropic Electronic Topological Transition in Fe_{1.08}Te.

A rapid and anisotropic modification of the Fermi-surface shape can be associated with abrupt changes in crystalline lattice geometry or in the magnetic state of a material. We show that such an electronic topological transition is at the basis of the formation of an unusual pressure-induced tetragonal ferromagnetic phase in Fe_{1.08}Te. Around 2 GPa, the orthorhombic and incommensurate antiferromagnetic ground state of Fe_{1.08}Te is transformed upon increasing pressure into a tetragonal ferromagnetic state via a conventional first-order transition. On the other hand, an isostructural transition takes place from the paramagnetic high-temperature state into the ferromagnetic phase as a rare case of a "type-0" transformation with anisotropic properties. Electronic-structure calculations in combination with electrical resistivity, magnetization, and x-ray diffraction experiments show that the electronic system of Fe_{1.08}Te is instable with respect to profound topological transitions that can drive fundamental changes of the lattice anisotropy and the associated magnetic order.

The Range of Neurological Complications in Chikungunya Fever.

BACKGROUND: Chikungunya fever is a globally spreading mosquito-borne disease that shows an unexpected neurovirulence. Even though the neurological complications have been a major cause of intensive care unit admission and death, to date, there is no systematic analysis of their spectrum available. OBJECTIVE: To review evidence of neurological manifestations in Chikungunya fever and map their epidemiology, clinical spectrum, pathomechanisms, diagnostics, therapies and outcomes. METHODS: Case report and systematic review of the literature followed established guidelines. All cases found were assessed using a 5-step clinical diagnostic algorithm assigning categories A-C, category A representing the highest level of quality. Only A and B cases were considered for further analysis. After general analysis, cases were clustered according to geospatial criteria for subgroup analysis. RESULTS: Thirty-six of 1196 studies were included, yielding 130 cases. Nine were ranked as category A (diagnosis of Neuro-Chikungunya probable), 55 as B (plausible), and 51 as C (disputable). In 15 cases, alternative diagnoses were more likely. Patient age distribution was bimodal with a mean of 49 years and a second peak in infants. Fifty percent of the cases occurred in patients <45 years with no reported comorbidity. Frequent diagnoses were encephalitis, optic neuropathy, neuroretinitis, and Guillain-Barré syndrome. Neurologic conditions showing characteristics of a direct viral pathomechanism showed a peak in infants and a second one in elder patients, and complications and neurologic sequelae were more frequent in these groups. Autoimmune-mediated conditions appeared mainly in patients over 20 years and tended to show longer latencies and better outcomes. Geospatial subgrouping of case reports from either India or Réunion revealed diverging phenotypic trends (Réunion: 88% direct viral vs. India: 81% autoimmune). CONCLUSIONS: Direct viral forms of Neuro-Chikungunya seem to occur particularly in infants and elderly patients, while autoimmune forms have to be also considered in middle-aged, previously healthy patients, especially after an asymptomatic interval. This knowledge will help to identify future Neuro-Chikungunya cases and to improve outcome especially in autoimmune-mediated conditions. The genetics of Chikungunya virus might play a key role in determining the course of neuropathogenesis. With further research, this could prove diagnostically significant.

Walking the tightrope-perspectives on local politicians' role in implementing a national social care policy on evidence-based practice.

BACKGROUND: Despite national policy recommending evidence-based practice (EBP), its application in social care has been limited. While local politicians can affect the process, little is known about their knowledge, attitudes and roles regarding EBP. The aim here is twofold: to explore the role of local politicians in the implementation of EBP in social care from both their own and a management perspective; and to examine factors politicians perceive as affecting their decisions and actions concerning the implementation of EBP policy. METHODS: Local politicians (N = 13) and managers (N = 22) in social care were interviewed. Qualitative thematic analysis with both inductive and deductive codes was used. RESULTS: Politicians were rather uninformed regarding EBP and national policy. The factors limiting their actions were, beside the lack of awareness, lack of ability to question existing working methods, and a need for support in the steering of EBP. Thus, personal interest played a significant part in what role the politicians assumed. This resulted in some politicians taking a more active role in steering EBP while others were not involved. From the managers' perspective, a more active steering by politicians was desired. Setting budget and objectives, as well as active follow-up of work processes and outcomes, were identified as means to affect the implementation of EBP. However, the politicians seemed unaware of the facilitating effects of these actions. CONCLUSIONS: Local politicians had a possibility to facilitate the implementation of EBP, but their role was unclear. Personal interest played a big part in determining what role was taken. The results imply that social care politicians might need support in the development of their steering of EBP. Moving the responsibility for EBP facilitation upwards in the political structure could be an important step in developing EBP in social care.

Genetic Predictors of Azathioprine Toxicity and Clinical Response in Patients with Inflammatory Bowel Disease.

BACKGROUND: Thiopurines (Azathioprine (AZA) and 6-Mercaptopurine (6-MP) are considered a well-established therapy for patients with Inflammatory Bowel Disease (IBD) including ulcerative colitis (UC) and Crohn's Disease (CD). However, nearly 20% of patients discontinue thiopurines due to adverse events. Functional polymorphisms of several enzymes involved in the metabolism of thiopurines have been linked with toxicity. The clinical value of variant carriers such as TPMT, ITPA and GSTs in predicting toxicity and adverse events for IBD patients treated with thiopurines remains to be clarified. OBJECTIVES: To determine if variation in TPMT, ITPA and GST genotypes can predict adverse effects such as neutropenia, pancreatitis, liver enzyme elevation, as well as clinical response for patients with IBD treated with thiopurines. METHODS: Patients known to have IBD and treated with AZA or 6MP were enrolled. Adverse effects were calculated and their correlation with TPMT, ITPA and GST genotypes was evaluated. Further, the correlation between clinical response and TPMT, ITPA and GST genotypes were assessed. RESULTS: A total of 53 patients were enrolled. 16/53 patients (28.6%) responded to AZA therapy. 17 patients experienced adverse events with 10 having to discontinue treatment. Three patients (5.4%) developed severe myelosuppression (WBC< 2.0 or neutrophils <1.0). Loss of function TPMT genotype was associated with adverse events (OR 3.64, 95% CI 0.55 - 24.23, p=0.0313). ITPA and GST polymorphisms were not associated with toxicity. GSTM1 deletion was associated with poor clinical response to therapy (OR 3.75, 95% CI 0.940 - 14.97, p=0.1028), however, neither TPMT*3A nor ITPA polymorphisms were associated with clinical response. CONCLUSION: In addition to TPMT for adverse events, genotyping for GSTM1 appears to predict clinical response in IBD patients treated with thiopurines.

Solitonic Spin-Liquid State Due to the Violation of the Lifshitz Condition in Fe(1+y)Te.

A combination of phenomenological analysis and Mössbauer spectroscopy experiments on the tetragonal Fe(1+y)Te system indicates that the magnetic ordering transition in compounds with higher Fe excess, y≥0.11, is unconventional. Experimentally, a liquidlike magnetic precursor with quasistatic spin order is found from significantly broadened Mössbauer spectra at temperatures above the antiferromagnetic transition. The incommensurate spin-density wave order in Fe(1+y)Te is described by a magnetic free energy that violates the weak Lifshitz condition in the Landau theory of second-order transitions. The presence of multiple Lifshitz invariants provides the mechanism to create multidimensional, twisted, and modulated solitonic phases.

Integration of an opto-chemical detector based on group III-nitride nanowire heterostructures.

The photoluminescence intensity of group III nitrides, nanowires, and heterostructures (NWHs) strongly depends on the environmental H(2) and O(2) concentration. We used this opto-chemical transducer principle for the realization of a gas detector. To make this technology prospectively available to commercial gas-monitoring applications, a large-scale laboratory setup was miniaturized. To this end the gas-sensitive NWHs were integrated with electro-optical components for optical addressing and read out within a compact and robust sensor system. This paper covers the entire realization process of the device from its conceptual draft and optical design to its fabrication and assembly. The applied approaches are verified with intermediate results of profilometric characterizations and optical performance measurements of subsystems. Finally the gas-sensing capabilities of the integrated detector are experimentally proven and optimized.

Intermetallic germanides with non-centrosymmetric structures derived from the Yb3Rh4Sn13 type.

New germanides with composition RE3Pt4Ge13 (RE = Y, Pr, Sm, Gd, Tb, Tm) have been prepared by high-pressure, high-temperature synthesis. Their crystal structures have been refined, and the relationship of this new rhombohedral and monoclinic structure types with the primitive cubic Yb3Rh4Sn13 prototype is discussed. Band structure calculations within density functional theory confirm the distorted rhombohedral and monoclinic structural arrangements to be energetically more favorable than the simple cubic one. X-ray absorption spectroscopy and magnetic susceptibility measurements indicate that the RE-atoms are in the +3 oxidation state in all studied compounds.

CoBi3--the first binary compound of cobalt with bismuth: high-pressure synthesis and superconductivity.

The first compound in the cobalt bismuth system was synthesized by high-pressure high-temperature synthesis at 5 GPa and 450 °C. CoBi3 crystallizes in space group Pnma (no. 62) with lattice parameters of a = 8.8464(7) Å, b = 4.0697(4) Å and c = 11.5604(9) Å adopting a NiBi3-type crystal structure. CoBi3 undergoes a superconducting transition at Tc = 0.48(3) K as evidenced by electrical-resistivity and specific-heat measurements. Based on the anomaly of the specific heat at Tc and considering the estimated electron-phonon coupling, the new Bi-rich compound can be classified as a Bardeen-Cooper-Schrieffer-type superconductor with weak electron-phonon coupling. Density-functional theory calculations disclose a sizable influence of the spin-orbit coupling to the valence states and proximity to a magnetic instability, which accounts for a significantly enhanced Sommerfeld coefficient.

Nanostructure and strain in InGaN/GaN superlattices grown in GaN nanowires.

The structural properties and the strain state of InGaN/GaN superlattices embedded in GaN nanowires were analyzed as a function of superlattice growth temperature, using complementary transmission electron microscopy techniques supplemented by optical analysis using photoluminescence and spatially resolved microphotoluminescence spectroscopy. A truncated pyramidal shape was observed for the 4 nm thick InGaN inclusions, where their (0001¯) central facet was delimited by six-fold {101¯l} facets towards the m-plane sidewalls of the nanowires. The defect content of the nanowires comprised multiple basal stacking faults localized at the GaN base/superlattice interface, causing the formation of zinc-blende cubic regions, and often single stacking faults at the GaN/InGaN bilayer interfaces. No misfit dislocations or cracks were detected in the heterostructure, implying a fully strained configuration. Geometrical phase analysis showed a rather uniform radial distribution of elastic strain in the (0001¯) facet of the InGaN inclusions. Depending on the superlattice growth temperature, the elastic strain energy is partitioned among the successive InGaN/GaN layers in the case of low-temperature growth, while at higher superlattice growth temperature the in-plane tensile misfit strain of the GaN barriers is accommodated through restrained diffusion of indium from the preceding InGaN layers. The corresponding In contents of the central facet were estimated at 0.42 and 0.25, respectively. However, in the latter case, successful reproduction of the experimental electron microscopy images by image simulations was only feasible, allowing for a much higher occupancy of indium adatoms at lattice sites of the semipolar facets, compared to the invariable 25% assigned to the polar facet. Thus, a high complexity in indium incorporation and strain allocation between the different crystallographic facets of the InGaN inclusions is anticipated and supported by the results of photoluminescence and spatially resolved microphotoluminescence spectroscopy.

Isotopic phonon effects in LaB6-LaB6 do not possess cubic symmetry and show a non-random isotope distribution.

The isotopic phonon effects in LaB(6) are investigated on the Raman spectra of a series of high-quality single crystals with systematically varied contents of (10)B and (11)B isotopes. A detailed group theoretical analysis enlightens the correlation between distortions of the B(6) octahedra and the splitting or broadening of phonon modes. It is evident that LaB(6) does not have cubic symmetry as assumed so far. A further symmetry reduction of the B(6) octahedra occurs in isotopically mixed crystals. There, the distribution of isotopes is not random as commonly assumed; the probability of associating equal isotopes increases with their mass decreasing.

Isotopic phonon effects in ß-rhombohedral boron--non-statistical isotope distribution.

On the basis of the spectra of IR- and Raman-active phonons, the isotopic phonon effects in ß-rhombohedral boron are analysed for polycrystalline (10)B- and (11)B-enriched samples of different origin and high-purity (nat)B single crystals. Intra- and inter-icosahedral B-B vibrations are harmonic, hence meeting the virtual crystal approximation (VCA) requirements. Deviations from the phonon shift expected according to the VCA are attributed to the anharmonic share of the lattice vibrations. In the case of icosahedral vibrations, the agreement with calculations on α-rhombohedral boron by Shirai and Katayama-Yoshida is quite satisfactory. Phonon shifts due to isotopic disorder in (nat)B are separated and determined. Some phonon frequencies are sensitive to impurities. The isotopic phonon effects yield valuable specific information on the nature of the different phonon modes. The occupation of regular boron sites by isotopes deviates significantly from the random distribution.

Contractile network models for adherent cells.

Cells sense the geometry and stiffness of their adhesive environment by active contractility. For strong adhesion to flat substrates, two-dimensional contractile network models can be used to understand how force is distributed throughout the cell. Here we compare the shape and force distribution for different variants of such network models. In contrast to Hookean networks, cable networks reflect the asymmetric response of biopolymers to tension versus compression. For passive networks, contractility is modeled by a reduced resting length of the mechanical links. In actively contracting networks, a constant force couple is introduced into each link in order to model contraction by molecular motors. If combined with fixed adhesion sites, all network models lead to invaginated cell shapes, but only actively contracting cable networks lead to the circular arc morphology typical for strongly adhering cells. In this case, shape and force distribution are determined by local rather than global determinants and thus are suited to endow the cell with a robust sense of its environment. We also discuss nonlinear and adaptive linker mechanics as well as the relation to tissue shape.

Influence of plaque volume on hemodynamic response and stress hormone release in patients undergoing carotid artery stenting.

AIM: Carotid artery stenting (CAS) may cause bradycardia and hypotension due to barostimulation. The impact of periprocedural hypotension on CAS outcome remains controversial. The role of carotid plaque volume and catecholamine hormone release during CAS on hemodynamic changes has not been investigated so far. The aim of this prospective study was to evaluate if carotid artery plaque characteristics are predictive for stress hormone release or for postprocedural hemodynamic instability. METHODS: In 26 patients undergoing CAS, carotid plaque volume and morphology were assessed by two- and three-dimensional (3D)-Duplex sonography prior to the procedure. Arterial plasma adrenaline, noradrenaline and renin concentrations were measured at the time of sheath insertion and 5 minutes after stent placement. ECG, heart rate, and invasive blood pressure were monitored throughout the procedure. RESULTS: CAS caused no significant changes in hormone release, but increasing plaque volume was related to the degree of bradycardia following stent deployment (r=0.57; P=0.01). Plaque size was not associated with postprocedural hypotension. Plaque echogenicity (echolucent, heterogeneous or echogenic) did not correlate with changes in systolic blood pressure, heart rate or catecholamine hormone release. CONCLUSION: CAS caused bradycardia in relation to plaque size, but did not cause catecholamine release which may indicate that the endovascular procedure is not associated with a relevant stress reaction.

Raman scattering and isotopic phonon effects in dodecaborides.

The Raman spectra of numerous dodecaborides have been measured on high-quality single crystals at ambient conditions with high spectral resolution and signal-to-noise ratio. Besides the strong Raman-active modes, numerous Raman-inactive modes occur in the spectra, indicating distortions of the structures. Ab initio calculation of the phonon spectra on ZrB(12) excellently agrees with the experimental results. Force constants are theoretically calculated and force parameters are estimated from the Raman frequencies. The influence of the surface range on the Raman spectra is evident. The different isotopic effects (virtual crystal approximation, the polarization effect and the effect of isotopic disorder) on the phonon frequencies are determined, separated and discussed.