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.

Pneumonie grave à SARS-Cov2 chez les patients vaccinés : une étude multicentrique

Introduction

La vaccination contre le SARS-Cov2 réduit le risque d’infection, d’hospitalisation et de décès liés à l’infection. Cependant, certains patients peuvent développer une infection après une vaccination. L’objectif était de décrire les caractéristiques des patients vaccinés et qui développaient une infection grave à SARS-Cov2 nécessitant une admission en réanimation.

Patients et méthodes

Nous avons réalisé une étude de cohorte multicentrique incluant les patients vaccinés avec une infection grave à SARS-CoV2 et admis dans 15 réanimations françaises entre janvier et septembre 2021. Nous avons comparé ces patients à une cohorte publiée de patients non vaccinés avec une pneumonie grave à SARS-Cov2.

Résultats

Cent patients dont 68 (68 %) hommes avec un âge médian de 64 [57–71] ans ont été inclus. Une immunodépression était présente chez 38³8 %) des patients. Parmi les patients ayant eu une sérologie à leur admission, 64 % avait un niveau d’anticorps anti-SARS-Cov2 efficace. À l’admission en réanimation, le score SOFA médian était de 4 [4–6,3] et le rapport PaO2/FiO2 médian de 84 [69–128]mmHg. Une oxygénothérapie humidifiée à haut débit a été initiée chez 79 (79 %) patients et une ventilation non invasive chez 18 (18 %) patients. Au cours de la prise en charge, 48 (48 %) patients ont nécessité le recours à l’intubation oro-trachéale avec une durée de ventilation de 11 [5–19] jours. Sur une durée de séjout médiane de 8 [4–20] jours, 31 patients sont décédés. L’âge (OR pour 5 années supplémentaires 1,38 [1,02–1,85], p = 0,035) et le score SOFA à l’admission (OR 1,40 [1,14–1,72] par point, p = 0,002) étaient indépendamment associés à la mortalité. En comparaison avec les patients non vaccinés, les patients vaccinés présentaient moins souvent du diabète (16 [16 %] vs. 351 [27 %], p = 0,029), étaient plus souvent immunodéprimés (38 [38 %] vs. 109 (8,3 %), p < 0,0001), insuffisants rénaux chroniques (24 [24 %] vs. 89 (6,8 %), p < 0,0001), insuffisants cardiaques chroniques (16 [16 %] vs. 58 [4,4 %], p < 0,0001), and insuffisants hépatiques chroniques chronic liver disease(3 [3 %] vs. 8 [0,6 %], p = 0,037). Malgré une gravit similaire à l’admission, les patients vaccinés nécessitaient moins souvent le recours à la ventilation invasive, que ce soit à l’admission ou au cours de la prise en charge en réanimation (23 [23 %] vs. 785 [59,7 %], p < 0,0001, et 48 [48 %] vs. 930 [70,7 %], p < 0,0001, respectivement). Il n’y avait pas de différence en terme de mortalité (31 [31 %] vs. 379 [28,8 %], p = 0,64).

Conclusion

Les infections sévères à SARS-Cov2 peuvent survenir chez des patients vaccinés, principalement ceux immunodéprimés ou avec des insuffisances rénale, hépatique ou cardiaque. L’âge et la gravité à l’admission sont associés à la mortalité.

Perioperative echocardiography-guided hemodynamic therapy in high-risk patients: a practical expert approach of hemodynamically focused echocardiography

The number of high-risk patients undergoing surgery is growing. To maintain adequate hemodynamic functioning as well as oxygen delivery to the vital organs (DO2) amongst this patient population, a rapid assessment of cardiac functioning is essential for the anesthesiologist. Pinpointing any underlying cardiovascular pathophysiology can be decisive to guide interventions in the intraoperative setting. Various techniques are available to monitor the hemodynamic status of the patient, however due to intrinsic limitations, many of these methods may not be able to directly identify the underlying cause of cardiovascular impairment. Hemodynamic focused echocardiography, as a rapid diagnostic method, offers an excellent opportunity to examine signs of filling impairment, cardiac preload, myocardial contractility and the function of the heart valves. We thus propose a 6-step-echocardiographic approach to assess high-risk patients in order to improve and maintain perioperative DO2. The summary of all echocardiographic based findings allows a differentiated assessment of the patient's cardiovascular function and can thus help guide a (patho)physiological-orientated and individualized hemodynamic therapy.

Ionic conductivity and relaxation dynamics in plastic crystals with nearly globular molecules

We have performed a dielectric investigation of the ionic charge transport and the relaxation dynamics in plastic crystalline 1-cyano-adamantane (CNA) and in two mixtures of CNA with the related plastic crystals adamantane or 2-adamantanon. Ionic charge carriers were provided by adding 1% of Li salt. The molecules of these compounds have nearly globular shape and, thus, the so-called revolving-door mechanism assumed to promote ionic charge transport via molecular reorientations in other PC electrolytes should not be active here. Indeed, a comparison of the dc resistivity and the reorientational α-relaxation times in the investigated PCs reveals complete decoupling of both dynamics. Similar to other PCs, we find a significant mixing-induced enhancement of the ionic conductivity. Finally, these solid-state electrolytes reveal a second relaxation process, slower than the α-relaxation, which is related to ionic hopping. Due to the mentioned decoupling, it can be unequivocally detected and is not superimposed by the reorientational contributions as found for most other ionic conductors.

Plastic-crystalline solid-state electrolytes: Ionic conductivity and orientational dynamics in nitrile mixtures

Many plastic crystals, molecular solids with long-range, center-of-mass crystalline order but dynamic disorder of the molecular orientations, are known to exhibit exceptionally high ionic conductivity. This makes them promising candidates for applications as solid-state electrolytes, e.g., in batteries. Interestingly, it was found that the mixing of two different plastic-crystalline materials can considerably enhance the ionic dc conductivity, an important benchmark quantity for electrochemical applications. An example is the admixture of different nitriles to succinonitrile, the latter being one of the most prominent plastic-crystalline ionic conductors. However, until now, only few such mixtures were studied. In the present work, we investigate succinonitrile mixed with malononitrile, adiponitrile, and pimelonitrile to which 1 mol. % of Li ions was added. Using differential scanning calorimetry and dielectric spectroscopy, we examine the phase behavior and the dipolar and ionic dynamics of these systems. We especially address the mixing-induced enhancement of the ionic conductivity and the coupling of the translational ionic mobility to the molecular reorientational dynamics, probably arising via a "revolving-door" mechanism.

Nimotuzumab and radiotherapy for treatment of newly diagnosed diffuse intrinsic pontine glioma (DIPG): a phase III clinical study

BACKGROUND

Diffuse intrinsic pontine glioma (DIPG) is a devastating cancer of childhood and adolescence.

METHODS

The study included patients between 3 and 20 years with clinically and radiologically confirmed DIPG. Primary endpoint was 6-month progression-free survival (PFS) following administration of nimotuzumab in combination with external beam radiotherapy (RT). Nimotuzumab was administered intravenously at 150 mg/m² weekly for 12 weeks. Radiotherapy at total dose of 54 Gy was delivered between week 3 and week 9. Response was evaluated based on clinical features and MRI findings according to RECIST criteria at week 12. Thereafter, patients continued to receive nimotuzumab every alternate week until disease progression/unmanageable toxicity. Adverse events (AE) were evaluated according to Common Terminology Criteria for Adverse Events (CTC-AE) Version 3.0 (CTC-AE3).

RESULTS

All 42 patients received at least one dose of nimotuzumab in outpatient settings. Two patients had partial response (4.8%), 27 had stable disease (64.3%), 10 had progressive disease (23.8%) and 3 patients (7.1%) could not be evaluated. The objective response rate (ORR) was 4.8%. Median PFS was 5.8 months and median overall survival (OS) was 9.4 months. Most common drug-related AEs were alopecia (14.3%), vomiting, headache and radiation skin injury (7.1% each). Therapy-related serious adverse events (SAEs) were intra-tumoral bleeding and acute respiratory failure, which were difficult to distinguish from effects of tumor progression.

CONCLUSIONS

Concomitant treatment with RT and nimotuzumab was feasible in an outpatient setting. The PFS and OS were comparable to results achieved with RT and intensive chemotherapy in hospitalized setting.

Gemcitabine combined with the monoclonal antibody nimotuzumab is an active first-line regimen in KRAS wildtype patients with locally advanced or metastatic pancreatic cancer: a multicenter, randomized phase IIb study

Background

This randomized study was designed to investigate the superiority of gemcitabine (gem) plus nimotuzumab (nimo), an anti-epidermal growth factor receptor monoclonal antibody, compared with gem plus placebo as first-line therapy in patients with advanced pancreatic cancer.

Patients and methods

Patients with previously untreated, unresectable, locally advanced or metastatic pancreatic cancer were randomly assigned to receive gem: 1000 mg/m2, 30-min i.v. once weekly (d1, 8, 15; q29) and nimo: fixed dose of 400 mg once weekly as a 30-min infusion, or gem plus placebo, until progression or unacceptable toxicity. The primary end point was overall survival (OS), secondary end points included time to progression, overall response rate, safety and quality of life.

Results

A total of 192 patients were randomized, with 186 of them being assessable for efficacy and safety (average age 63.6 years). One-year OS/progression-free survival (PFS) was 34%/22% for gem plus nimo compared with 19%/10% for gem plus placebo (HR = 0.69; P = 0.03/HR = 0.68; P = 0.02). Median OS/PFS was 8.6/5.1 months for gem plus nimo versus 6.0/3.4 mo in the gem plus placebo group (HR = 0.69; P = 0.0341/HR = 0.68; P = 0.0163), with very few grade 3/4 toxicities. KRAS wildtype patients experienced a significantly better OS than those with KRAS mutations (11.6 versus 5.6 months, P = 0.03).

Conclusion

This randomized study showed that nimo in combination with gem is safe and well tolerated. The 1-year OS and PFS rates for the entire population were significantly improved. Especially, those patients with KRAS wildtype seem to benefit. The study was registered as protocol ID OSAG101-PCS07, NCT00561990 and EudraCT 2007-000338-38.

Glycerol Hydrogen-Bonding Network Dominates Structure and Collective Dynamics in a Deep Eutectic Solvent

The deep eutectic solvent glyceline formed by choline chloride and glycerol in 1:2 molar ratio is much less viscous compared to glycerol, which facilitates its use in many applications where high viscosity is undesirable. Despite the large difference in viscosity, we have found that the structural network of glyceline is completely defined by its glycerol constituent, which exhibits complex microscopic dynamic behavior, as expected from a highly correlated hydrogen-bonding network. Choline ions occupy interstitial voids in the glycerol network and show little structural or dynamic correlations with glycerol molecules. Despite the known higher long-range diffusivity of the smaller glycerol species in glyceline, in applications where localized dynamics is essential (e.g., in microporous media), the local transport and dynamic properties must be dominated by the relatively loosely bound choline ions.

201Thallium Scintigraphy – a New Method for Radionuclide Imaging of the Uterus

A new radionuclide method for uterus imaging is described. After intravenous application of 201T1 chloride the myometrium can be displayed by means of a gamma camera and a small digital computer. Early results suggest that T1 accumulation by the uterus depends on its histopathologic structure. After intra-uterine injection of 133Xe in saline demarcation between myometrium and uterine cavity is possible.

Variation of ionic conductivity in a plastic-crystalline mixture

Ionically conducting plastic crystals (PCs) are possible candidates for solid-state electrolytes in energy-storage devices. Interestingly, the admixture of larger molecules to the most prominent molecular PC electrolyte, succinonitrile, was shown to drastically enhance its ionic conductivity. Therefore, binary mixtures seem to be a promising way to tune the conductivity of such solid-state electrolytes. However, to elucidate the general mechanisms of ionic charge transport in plastic crystals and the influence of mixing, a much broader database is needed. In the present work, we investigate mixtures of two well-known plastic-crystalline systems, cyclohexanol and cyclooctanol, to which 1 mol. % of Li ions were added. Applying differential scanning calorimetry and dielectric spectroscopy, we present a thorough investigation of the phase behavior and the ionic and dipolar dynamics of this system. All mixtures reveal plastic-crystalline phases with corresponding orientational glass-transitions. Moreover, their conductivity seems to be dominated by the "revolving-door" mechanism, implying a close coupling between the ionic translational and the molecular reorientational dynamics of the surrounding plastic-crystalline matrix. In contrast to succinonitrile-based mixtures, there is no strong variation of this coupling with the mixing ratio.

Dielectric study on mixtures of ionic liquids

Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.

Detection and Control of Spin-Orbit Interactions in a GaAs Hole Quantum Point Contact

We investigate the relationship between the Zeeman interaction and the inversion-asymmetry-induced spin-orbit interactions (Rashba and Dresselhaus SOIs) in GaAs hole quantum point contacts. The presence of a strong SOI results in the crossing and anticrossing of adjacent spin-split hole subbands in a magnetic field. We demonstrate theoretically and experimentally that the anticrossing energy gap depends on the interplay between the SOI terms and the highly anisotropic hole g tensor and that this interplay can be tuned by selecting the crystal axis along which the current and magnetic field are aligned. Our results constitute the independent detection and control of the Dresselhaus and Rashba SOIs in hole systems, which could be of importance for spintronics and quantum information applications.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Polaron-induced lattice distortion of (In,Ga)As/GaAs quantum dots by optically excited carriers

We report on a high resolution x-ray diffraction study unveiling the effect of carriers optically injected into (In,Ga)As quantum dots on the surrounding GaAs crystal matrix. We find a tetragonal lattice expansion with enhanced elongation along the [001] crystal axis that is superimposed on an isotropic lattice extension. The isotropic contribution arises from excitation induced lattice heating as confirmed by temperature dependent reference studies. The tetragonal expansion on the femtometer scale is tentatively attributed to polaron formation by carriers trapped in the quantum dots.

Optical properties of strain-compensated CdSe/ZnSe/(Zn,Mg)Se quantum well microdisks

Strain-compensated CdSe/ZnSe/(Zn,Mg)Se quantum well structures that were grown on (In,Ga)As allow for efficient room-temperature photoluminescence and spectral tuning over the whole visible range. We fabricated microdisk cavities from these samples by making use of a challenging chemical structuring technique for selective and homogeneous removal of the (In,Ga)As sacrificial layer below the quantum structure. The observed whispering gallery modes in our microdisks are mainly visible up to photon energies of ~ 2.3 eV due to strong self-absorption. As extinction coefficients and effective refractive indices are dominated by the quantum well material CdSe, thick quantum wells (> 3 monolayer) are necessary to observe resonances in the corresponding quantum well emission.

Life-threatening complications and outcomes in patients with malignancies and severe pulmonary embolism

BACKGROUND

Data are scarce about ICU patients with malignancy and severe pulmonary embolism. Here, our main objective was to identify risk factors for life-threatening complications, organ failures, and death in ICU patients with severe pulmonary embolism, with special attention to the impact of malignancy. We also described the clinical features of PE in patients with and without malignancies.

METHODS

Data from consecutive adults admitted to our ICU in 2002-2011 with severe pulmonary embolism were collected retrospectively. Multivariate analysis was performed to look for factors associated with death, organ failures, or life-threatening complications (major bleeding, recurrent PE, and cardiac arrest).

RESULTS

Of 119 included patients (42 [35%] with bilateral pulmonary embolism), 41 had solid malignancies, 27 hematological malignancies, and 51 no malignancies. The most common symptoms were syncope (40%) and hemoptysis (18%) in patients with solid and hematological malignancies, respectively. Life-threatening complications occurred in 23 (19%) patients; risk factors were obesity (OR, 13.22; 1.93-90.70), disseminated intravascular coagulation/ischemic hepatitis (OR, 27.06; 5.14-142.46), fluid load ≥1000 mL/24 h (OR, 6.42; 1.60-25.76), and solid malignancy (OR, 5.45; 1.15-25.89). Inhospital mortality was 27/119 (23%) and respiratory or circulatory failure developed in 36 (30%) patients. Risk factors for these adverse outcomes were older age (OR, 1.04/year; 1.01-1.07), higher oxygen flow rate (OR, 1.28/L; 1.13-1.45); and renal failure (OR, 8.08; 2.50-26.11); whereas chest pain was protective (OR, 0.13; 0.04-0.48).

CONCLUSION

In this study, solid malignancy was a risk factor for life-threatening complications but not for death.

Severe infections requiring intensive care unit admission in kidney transplant recipients: impact on graft outcome

BACKGROUND

Kidney transplant recipients are at risk for life-threatening infections, which may affect the long-term prognosis.

METHODS

We retrospectively included all kidney transplant recipients admitted for sepsis, severe sepsis, or septic shock to the medical intensive care unit (ICU) of the Saint-Louis Hospital, Paris, France, between 2000 and 2010. The main objective was to identify factors associated with survival without graft impairment 90 days after ICU discharge.

RESULTS

Data were available for 83 of 100 eligible patients. The main sites of infection were the lungs (54%), urinary tract (24%), and bloodstream (22%). Among documented infections (55/83), 80% were bacterial. Fungal infections were more common among patients transplanted after 2005 (5% vs. 23%, P = 0.02). Mechanical ventilation was used in 46 (56%) patients, vasopressors in 39 (47%), and renal replacement therapy (RRT) in 34 (41%). In-hospital and day-90 mortality rates were 20% and 22%, respectively. On day 90, among the 65 survivors, 39 (47%) had recovered their previous graft function and 26 (31%) had impaired graft function, including 16 (19%) who were dependent on RRT. Factors independently associated with day-90 survival and graft function recovery were baseline serum creatinine (odds ratio [OR] for a 10 μmol/L increase 0.94, 95% confidence interval [CI] 0.88-1.00) and cyclosporine therapy (OR 0.30, 95% CI 0.11-0.79).

CONCLUSION

Sepsis was chiefly related to bacterial pneumonia or urinary tract infection. Pneumocystis jirovecii was the leading opportunistic agent, with a trend toward an increase over time. Infections often induced severe graft function impairment. Baseline creatinine and cyclosporine therapy independently predicted the outcome.

Direct quantitative electrical measurement of many-body interactions in exciton complexes in InAs quantum dots

We present capacitance-voltage spectra for the conduction band states of InAs quantum dots obtained under continuous illumination. The illumination leads to the appearance of additional charging peaks that we attribute to the charging of electrons into quantum dots containing a variable number of illumination-induced holes. By this we demonstrate an electrical measurement of excitonic states in quantum dots. Magnetocapacitance-voltage spectroscopy reveals that the electron always tunnels into the lowest electronic state. This allows us to directly extract, from the highly correlated many-body states, the correlation energy. The results are compared quantitatively to state of the art atomistic configuration interaction calculations, showing very good agreement for a lower level of excitations and also limitations of the approach for an increasing number of particles. Our experiments offer a rare benchmark to many-body theoretical calculations.

Odd and even Kondo effects from emergent localization in quantum point contacts

A quantum point contact (QPC) is a basic nanometre-scale electronic device: a short and narrow transport channel between two electron reservoirs. In clean channels, electron transport is ballistic and the conductance is then quantized as a function of channel width with plateaux at integer multiples of 2e(2)/h (where e is the electron charge and h is Planck's constant). This can be understood in a picture where the electron states are propagating waves, without the need to account for electron-electron interactions. Quantized conductance could thus be the signature of ultimate control over nanoscale electron transport. However, even studies with the cleanest QPCs generically show significant anomalies in the quantized conductance traces, and there is consensus that these result from electron many-body effects. Despite extensive experimental and theoretical studies, understanding these anomalies is an open problem. Here we report that the many-body effects have their origin in one or more spontaneously localized states that emerge from Friedel oscillations in the electron charge density within the QPC channel. These localized states will have electron spins associated with them, and the Kondo effect--related to electron transport through such localized electron spins--contributes to the formation of the many-body state. We present evidence for such localization, with Kondo effects of odd or even character, directly reflecting the parity of the number of localized states; the evidence is obtained from experiments with length-tunable QPCs that show a periodic modulation of the many-body properties with Kondo signatures that alternate between odd and even Kondo effects. Our results are of importance for assessing the role of QPCs in more complex hybrid devices and for proposals for spintronic and quantum information applications. In addition, our results show that tunable QPCs offer a versatile platform for investigating many-body effects in nanoscale systems, with the ability to probe such physics at the level of a single site.

The effect of (NH4)2Sx passivation on the (311)A GaAs surface and its use in AlGaAs/GaAs heterostructure devices

We have studied the efficacy of (NH4)2Sx surface passivation on the (311)A GaAs surface. We report XPS studies of simultaneously-grown (311)A and (100) heterostructures showing that the (NH4)2Sx solution removes surface oxide and sulfidizes both surfaces. Passivation is often characterized using photoluminescence measurements; we show that while (NH4)2Sx treatment gives a 40-60 ×  increase in photoluminescence intensity for the (100) surface, an increase of only 2-3 ×  is obtained for the (311)A surface. A corresponding lack of reproducible improvement in the gate hysteresis of (311)A heterostructure transistor devices made with the passivation treatment performed immediately prior to gate deposition is also found. We discuss possible reasons why sulfur passivation is ineffective for (311)A GaAs, and propose alternative strategies for passivation of this surface.

Optical spectroscopy of spin noise

Spontaneous fluctuations of the magnetization of a spin system in thermodynamic equilibrium (spin noise) manifest themselves as noise in the Faraday rotation of probe light. We show that the correlation properties of this noise over the optical spectrum can provide clear information about the composition of the spin system that is largely inaccessible for conventional linear optics. Such optical spectroscopy of spin noise, e.g., allows us to clearly distinguish between optical transitions associated with different spin subsystems, to resolve optical transitions that are unresolvable in the usual optical spectra, to unambiguously distinguish between homogeneously and inhomogeneously broadened optical bands, and to evaluate the degree of inhomogeneous broadening. These new possibilities are illustrated by theoretical calculations and by experiments on paramagnets with different degrees of inhomogeneous broadening of optical transitions [atomic vapors of 41K and singly charged (In,Ga)As quantum dots].

Confinement and interaction of single indirect excitons in a voltage-controlled trap formed inside double InGaAs quantum Wells

Voltage-tunable quantum traps confining individual spatially indirect and long-living excitons are realized by providing a coupled double quantum well with nanoscale gates. This enables us to study the transition from confined multiexcitons down to a single, electrostatically trapped indirect exciton. In the few exciton regime, we observe discrete emission lines identified as resulting from a single dipolar exciton, a biexciton, and a triexciton, respectively. Their energetic splitting is well described by Wigner-like molecular structures reflecting the interplay of dipolar interexcitonic repulsion and spatial quantization.

Using a tunable quantum wire to measure the large out-of-plane spin splitting of quasi two-dimensional holes in a GaAs nanostructure

The out-of-plane g-factor g([perpendicular])(*) for quasi two-dimensional (2D) holes in a (100) GaAs heterostructure is studied using a variable width quantum wire. A direct measurement of the Zeeman splitting is performed in a magnetic field applied perpendicular to the 2D plane. We measure an out-of-plane g-factor up to g([perpendicular])(*) = 5, which is larger than previous optical studies of g([perpendicular])(*) and is approaching the long predicted but never experimentally verified out-of-plane g-factor of 7.2 for heavy holes.

Intrinsic spin fluctuations reveal the dynamical response function of holes coupled to nuclear spin baths in (In,Ga)As quantum dots

The problem of how single central spins interact with a nuclear spin bath is essential for understanding decoherence and relaxation in many quantum systems, yet is highly nontrivial owing to the many-body couplings involved. Different models yield widely varying time scales and dynamical responses (exponential, power-law, gaussian, etc.). Here we detect the small random fluctuations of central spins in thermal equilibrium [holes in singly charged (In,Ga)As quantum dots] to reveal the time scales and functional form of bath-induced spin relaxation. This spin noise indicates long (400 ns) spin correlation times at a zero magnetic field that increase to ∼5  μs as dominant hole-nuclear relaxation channels are suppressed with small (100 G) applied fields. Concomitantly, the noise line shape evolves from Lorentzian to power law, indicating a crossover from exponential to slow [∼1/log(t)] dynamics.

Photoluminescence lineshape features of carbon δ-doped GaAs heterostructures

Photoluminescence lineshape properties of quasi-two-dimensional electron systems in setback δ-doped GaAs heterostructures are studied at liquid helium temperature. Contributions from the ground and the first excited two-dimensional subband are clearly observed. A simple fit to the lineshape including broadening demonstrates that there is an exponential low-energy tail associated with the ground subband. No such tail is observed for the first excited subband. The fit precisely reveals the subband bottom energies, the Fermi energy, the electron temperature and the recombination intensities. A self-consistent calculation of subband properties including the potential contribution of the setback δ-doping reproduces well the subband properties and the recombination intensities.

All-optical tunability of microdisk lasers via photo-adressable polyelectrolyte functionalization

Photoactive materials are highly promising candidates for novel applications as they enable all-optical control of photonic devices. Photochromic molecules exhibit a reversible change of their dielectric function upon irradiation with light of proper wavelength. The trans- and cis-isomers of azobenzene exhibit different absorption properties due to the effect of the configuration on the polarizability of the molecule. Here, we introduce a novel molecular/semiconductor hybrid device which is fully tunable by all-optical means via the integration of a semiconductor microdisk into a photo-adressable polyelectrolyte material. We demonstrate that such polyelectrolyte superlattices can be used to tune semiconductor photonic resonators with high precision and without any significant degeneration of device performance. Moreover, we demonstrate an all-optically tunable laser based on this hybrid concept.

Probing single-charge fluctuations at a GaAs/AlAs interface using laser spectroscopy on a nearby InGaAs quantum dot

We probe local charge fluctuations in a semiconductor via laser spectroscopy on a nearby self-assembled quantum dot. We demonstrate that the quantum dot is sensitive to changes in the local environment at the single-charge level. By controlling the charge state of localized defects, we are able to infer the distance of the defects from the quantum dot with ±5  nm resolution. The results identify and quantify the main source of charge noise in the commonly used optical field-effect devices.

Dynamic nuclear spin resonance in n-GaAs

The dynamics of optically detected nuclear magnetic resonance is studied in n-GaAs via time-resolved Kerr rotation using an on-chip microcoil for rf field generation. Both optically allowed and optically forbidden NMR are observed with a dynamics controlled by the interplay between dynamic nuclear polarization via hyperfine interaction with optically generated spin-polarized electrons and nuclear spin depolarization due to magnetic resonance absorption. Comparing the characteristic nuclear spin relaxation rate obtained in experiment with master equation simulations, the underlying nuclear spin depolarization mechanism for each resonance is extracted.

Optical control of coherent interactions between electron spins in InGaAs quantum dots

Coherent interactions between spins in quantum dots are a key requirement for quantum gates. We have performed pump-probe experiments in which pulsed lasers emitting at different photon energies manipulate two distinct subsets of electron spins within an inhomogeneous InGaAs quantum dot ensemble. The spin dynamics are monitored through their precession about an external magnetic field. These measurements demonstrate spin precession phase shifts and modulations of the magnitude of one subset of oriented spins after optical orientation of the second subset. The observations are consistent with results from a model using a Heisenberg-like interaction with μeV strength.

Observation of the Kondo effect in a spin-3/2 hole quantum dot

We report the observation of Kondo physics in a spin-3/2 hole quantum dot. The dot is formed close to pinch-off in a hole quantum wire defined in an undoped AlGaAs/GaAs heterostructure. We clearly observe two distinctive hallmarks of quantum dot Kondo physics. First, the Zeeman spin splitting of the zero-bias peak in the differential conductance is independent of the gate voltage. Second, this splitting is twice as large as the splitting for the lowest one-dimensional subband. We show that the Zeeman splitting of the zero-bias peak is highly anisotropic and attribute this to the strong spin-orbit interaction for holes in GaAs.

Resistively detected nuclear magnetic resonance in n- and p-type GaAs quantum point contacts

We present resistively detected NMR measurements in induced and modulation-doped electron quantum point contacts, as well as induced hole quantum point contacts. While the magnitude of the resistance change and associated NMR peaks in n-type devices is in line with other recent measurements using this technique, the effect in p-type devices is too small to measure. This suggests that the hyperfine coupling between holes and nuclei in this type of device is much smaller than the electron hyperfine coupling, which could have implications in quantum information processing.

Putative biomarker genes for grading clear cell renal cell carcinoma

OBJECTIVE

The initial objective of this renal cancer study was to identify gene sets in clear cell renal cell carcinoma (ccRCC) to support grading of ccRCC histopathology.

MATERIALS AND METHODS

Preselected ccRCC tumor tissues of grade 1 (G1, n = 14) and grade 3 (G3, n = 15) as well es 14 normal kidney tissues thereof were subjected to microarray expression analysis using Human Genome U133 Plus 2.0 Array. Event ratio scoring, hierarchical clustering and principal component analysis were used to determine gene sets that distinguish expression profiles from normal kidney tissue, G1 and G3 tumor tissues.

RESULTS

An initial set of 73 genes provided seven gene subclusters (SC01 to SC07) that distinguish RNA expression profiles from G1, G3 tumor and normal kidney tissues. A ranked list of 24 genes was determined that separated G1 from G3 tumors in high concordance with histopathological grading confirmed by immunohistochemical analysis of ceruloplasmin protein expression.

CONCLUSION

A final set of 24 genes has been determined awaiting further validation on the RNA as well as on the protein level by studying an additional cohort of ccRCC patients. A reliable separation of G1 and G3 tumor grades will be instrumental to foster and direct the administration of upcoming targeted therapeutics of ccRCC tumors in a more predictive and reliable manner.

Polarization-preserving confocal microscope for optical experiments in a dilution refrigerator with high magnetic field

We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film.

Gene expression analysis in clear cell renal cell carcinoma using gene set enrichment analysis for biostatistical management

OBJECTIVE

To improve the workflow for standardizing the statistical interpretation provides an opportunity for the analysis of gene expression in clear cell renal cell carcinoma (ccRCC). RCC as a solid tumour entity represents a very suitable tumour model for such investigations. Although it is possible to investigate expression profiles by microarray technologies, the main problem is how to adequately interpret the accumulated mass of data derived from microarray technologies. There is a clear lack of a defined, consistent and comparable biostatistical analysis system, with no specific biostatistical standard methodology being available to compare the results of microarray analyses. We used the gene set enrichment analysis (GSEA) method to analyze microarray data from RCC tissue. The present study aimed to analyze differential expression profiles and establish biomarkers suitable for prognostication at the time of renal surgery by comparing RCC patients with long-term survival data against RCC samples of patients with poorly differentiated (grade 3) RCC, concomitant metastatic disease and short survival.

PATIENTS AND METHODS

In the present study, a total of 29 ccRCC fresh-frozen tissue samples were used; 14 samples from grade 1 (G1) RCC patients without metastatic disease and 15 from grade 3 (G3) RCC patients with synchronous metastatic disease. Expression profiling was performed with the Human Genome U133 Plus 2.0 Array (Affymetrix Corp., Santa Clara, CA, USA). Clinical data and long-term follow-up were obtained for all patients. The primary probe level analysis was performed using the Affymetrix MAS 5 algorithm. Further statistical processing was carried out by GSEA, using the Molecular Signatures Database, MSigDB (http://www.broad.mit.edu/gsea/msigdb/index.jsp). After selecting gene sets with the highest leading edge subsets, a cluster and a further analyses based on MSigDB data bank analysis was performed.

RESULTS

In total, 15 poorly G3 ccRCC, 14 well differentiated G1 ccRCC and 14 normal renal tissue samples were analyzed for comparative gene expression profiling. There were 12 of 15 G3 ccRCC patients who had synchronous metastatic disease at the time of surgery (pN+ and/or distant metastases: pN+ only = 4, M+ only = 11 and pN+M+ = 3). The GSEA identified 700 gene sets. Out of these, 120 sets with the highest leading edge subset were selected monitored by hierarchical clustering G1 vs G3. Comparative analysis using the the MSigDB data bank for pathway network identified 16 gene sets that were differentially strongly over- or underexpressed in G3 vs G1 tumours and are involved in various aspects of tumour physiology, such as metastases and cell motility, signalling and cell proliferation, as well as gene products that are involved in the building of the extracellular matrix and as cell surface markers.

CONCLUSIONS

We analyzed microarray data of gene expression in ccRCC comparing poorly differentiated and well differentiated tumour tissue samples. Using GSEA, we found a number of genes set candidates relevant to biological network processes with high complexity; conspicuously, these comprised members of the interleukin- and chemokine-family, cyclin-dependent kinases, angiogenic growth factors and transcriptional factors. This suggests that, in poorly differentiated aggressive ccRCC, there may be a limited number of gene sets that are responsible for the very aggressive biological behaviour. This comparison performed at a gene set level enables the identification of such congruency between different gene sets and whole data sets with respect to a specific biological question. GSEA embedded in the statistical workflow procedure for the suitable preparation of expression data may improve the analysis and avoid missing changes at the molecular level. A systematic approach such as GSEA is clearly needed to analyze raw data from microarray analyses, although these data can only be descriptive and the mass of raw data is derived from a relatively small number of tissue samples. However, consistent alterations of gene expression found in specific tumour entities may allow a better understanding of certain aspects of specific tumour biology. Therefore, the molecular characterization of individual tumours may potentially be useful for the better individual assessment of prognosis and, finally, the identification of biomarkers and targets of specific treatments may eventually help to improve treatment.

S3 guidelines for intensive care in cardiac surgery patients: hemodynamic monitoring and cardiocirculary system

Hemodynamic monitoring and adequate volume-therapy, as well as the treatment with positive inotropic drugs and vasopressors are the basic principles of the postoperative intensive care treatment of patient after cardiothoracic surgery. The goal of these S3 guidelines is to evaluate the recommendations in regard to evidence based medicine and to define therapy goals for monitoring and therapy. In context with the clinical situation the evaluation of the different hemodynamic parameters allows the development of a therapeutic concept and the definition of goal criteria to evaluate the effect of treatment. Up to now there are only guidelines for subareas of postoperative treatment of cardiothoracic surgical patients, like the use of a pulmonary artery catheter or the transesophageal echocardiography. The German Society for Thoracic and Cardiovascular Surgery (Deutsche Gesellschaft für Thorax-, Herz- und Gefässchirurgie, DGTHG) and the German Society for Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und lntensivmedizin, DGAI) made an approach to ensure and improve the quality of the postoperative intensive care medicine after cardiothoracic surgery by the development of S3 consensus-based treatment guidelines. Goal of this guideline is to assess the available monitoring methods with regard to indication, procedures, predication, limits, contraindications and risks for use. The differentiated therapy of volume-replacement, positive inotropic support and vasoactive drugs, the therapy with vasodilatators, inodilatators and calcium sensitizers and the use of intra-aortic balloon pumps will also be addressed. The guideline has been developed following the recommendations for the development of guidelines by the Association of the Scientific Medical Societies in Germany (AWMF). The presented key messages of the guidelines were approved after two consensus meetings under the moderation of the Association of the Scientific Medical Societies in Germany (AWMF).

Quantized magnetic confinement in quantum wires

Ballistic quantum wires are exposed to longitudinal profiles of perpendicular magnetic fields composed of a spike and a homogeneous part. An asymmetric magnetoconductance peak as a function of the homogeneous magnetic field is found, comprising quantized conductance steps in the interval where the homogeneous magnetic field and the magnetic barrier have identical polarities, and a characteristic shoulder with several resonances in the interval of opposite polarities. The observations are interpreted in terms of inhomogeneous diamagnetic shifts of the quantum wire modes leading to magnetic confinement.

Spin noise of electrons and holes in self-assembled quantum dots

We measure the frequency spectra of random spin fluctuations, or "spin noise," in ensembles of (In,Ga)As/GaAs quantum dots (QDs) at low temperatures. We employ a spin noise spectrometer based on a sensitive optical Faraday rotation magnetometer that is coupled to a digitizer and field-programmable gate array, to measure and average noise spectra from 0-1 GHz continuously in real time with subnanoradian/sqrt[Hz] sensitivity. Both electron and hole spin fluctuations generate distinct noise peaks, whose shift and broadening with magnetic field directly reveal their g factors and dephasing rates within the ensemble. A large, energy-dependent anisotropy of the in-plane hole g factor is clearly exposed, reflecting systematic variations in the average QD confinement potential.

Long-term hole spin memory in the resonantly amplified spin coherence of InGaAs/GaAs quantum well electrons

Pulsed optical excitation of the negatively charged trion has been used to generate electron spin coherence in an n-doped (In,Ga)As/GaAs quantum well. The coherence is monitored by resonant spin amplification detected at times exceeding the trion lifetime by 2 orders of magnitude. Still, even then signatures of the hole spin dynamics in the trion complex are imprinted in the signal leading to an unusual batlike shape of the magnetic field dispersion of spin amplification. From this shape information about the spin relaxation of both electrons and holes can be derived.