Inhibited Inelastic Scattering of Incoherent Excitons for Near-Band Edge Excitations

A multiple pump-terahertz probe experiment enables the clear distinction between elastic and inelastic scattering of excitons with a free electron-hole plasma in (Ga,In)As multiquantum wells. Low plasma energies dictate the prevalence of elastic scattering by inhibiting inelastic processes due to the absence of final states for quasiparticles. Yet, an increased plasma energy results in a progressive destruction of excitons. Notably, despite plasma energy variations, the interaction strength between excitons and the electron-hole plasma remains unaltered.

Thermal-hydraulic insights during a main steam line break in a generic PWR KONVOI reactor with ATHLET 3.1A

The present paper gathers the main insights obtained during the numerical simulation of a 10 % main steam line break (MSLB) in a generic German PWR KONVOI reactor with the thermal-hydraulic system code ATHLET 3.1A. The contents of this paper are focused first on the transient thermal-hydraulic calculation during affected steam generator (SG) 1 boil-off and subsequently on the multidimensional fluid mixing study of the overcooled water stream and the coolant in the reactor pressure vessel. With this aim, the boundary conditions from the test PKL G3.1, carried out at the PKL test facility in the framework of the OECD/PKL-II project, are implemented in the simulation over the plant nominal parameters from the KONVOI reactor. The thermal-hydraulic and fluid mixing results obtained in the simulations are qualitatively assessed against suitable experimental data from the PKL and ROCOM test facilities, showing a good agreement between simulation and test behaviour.

Light-inducible antimiR-92a as a therapeutic strategy to promote skin repair in healing-impaired diabetic mice

MicroRNAs (miRs) are small non-coding RNAs that post-transcriptionally control gene expression. Inhibition of miRs by antisense RNAs (antimiRs) might be a therapeutic option for many diseases, but systemic inhibition can have adverse effects. Here we show that light-activatable antimiRs efficiently and locally restricted target miR activity in vivo. We use an antimiR-92a and establish a therapeutic benefit in diabetic wound healing. AntimiR-92a is modified with photolabile protecting groups, so called ‘cages'. Irradiation activates intradermally injected caged antimiR-92a without substantially affecting miR-92a expression in other organs. Light activation of caged antimiR-92a improves healing in diabetic mice to a similar extent as conventional antimiRs and derepresses the miR-92a targets Itga5 and Sirt1, thereby regulating wound cell proliferation and angiogenesis. These data show that light can be used to locally activate therapeutically active antimiRs in vivo.

Inhibition of microRNAs using antimiRs is a potential therapeutic option for a number of diseases, but systemic inhibition may cause adverse effects. Here the authors develop light-activated antimiRs directed against miR-92a, and show localized inhibition in the skin and improved wound healing in diabetic mice.

Respiration-Related Artifacts in EDA Recordings: Introducing a Standardized Method to Overcome Multiple Interpretations

When electrodermal activity (EDA) recordings are controlled for artifacts, i.e., electrodermal reactions [EDRs] elicited by breathing irregularities, several problems arise. For example, respiration is difficult to evaluate because there are no clear-cut criteria for its values, e.g., wave form, depth. Furthermore, respiration and EDA are rather complexly intertwined, and there is no established or standardized method for evaluation. Especially when subjects are not stimulated, i.e., when nonspecific EDRs are taken, EDR recordings elicited by irregular breathing may overestimate the subject's arousal and bias any given research question. Moreover, incidences of concurrent consecutive EDRs and changes in respiratory activity may encourage multicausal interpretation due to both signals' having a common central causation. To circumvent such problems, we developed a method which provides rule-based guidelines to identify potential artifacts. Two experiments ( N = 14 and N = 12) were conducted to test the accuracy of the judgments of three independent raters. The reliability coefficients for the number of electrodermal reactions and the sum of their amplitudes yielded satisfactory coefficients of convergence for each individual experiment (.87 and .82 in Exp. 1 vs .94 and .95 in Exp. 2) as well as for the two experiments combined (.92 and .91).

Severe accident research activities at Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

In the frame of the nuclear safety research program of the Helmholtz Association HZDR performs fundamental and applied research to assess and to reduce the risks related to the nuclear fuel cycle and the production of electricity in nuclear power plants. One of the research topics focuses on the safety aspects of current and future reactor designs. This includes the development and application of methods for analyses of transients and postulated accidents, covering the whole spectrum from normal operation till severe accident sequences including core degradation. This paper gives an overview of the severe accident research activities at the Reactor Safety Division at the Institute of Resource Ecology.

Cardiac RKIP induces a beneficial β-adrenoceptor-dependent positive inotropy

In heart failure therapy, it is generally assumed that attempts to produce a long-term increase in cardiac contractile force are almost always accompanied by structural and functional damage. Here we show that modest overexpression of the Raf kinase inhibitor protein (RKIP), encoded by Pebp1 in mice, produces a well-tolerated, persistent increase in cardiac contractility that is mediated by the β1-adrenoceptor (β1AR). This result is unexpected, as β1AR activation, a major driver of cardiac contractility, usually has long-term adverse effects. RKIP overexpression achieves this tolerance via simultaneous activation of the β2AR subtype. Analogously, RKIP deficiency exaggerates pressure overload-induced cardiac failure. We find that RKIP expression is upregulated in mouse and human heart failure, indicative of an adaptive role for RKIP. Pebp1 gene transfer in a mouse model of heart failure has beneficial effects, suggesting a new therapeutic strategy for heart failure therapy.

Experimental realization of quantum zeno dynamics

It is generally impossible to probe a quantum system without disturbing it. However, it is possible to exploit the back action of quantum measurements and strong couplings to tailor and protect the coherent evolution of a quantum system. This is a profound and counterintuitive phenomenon known as quantum Zeno dynamics. Here we demonstrate quantum Zeno dynamics with a rubidium Bose–Einstein condensate in a five-level Hilbert space. We harness measurements and strong couplings to dynamically disconnect different groups of quantum states and constrain the atoms to coherently evolve inside a two-level subregion. In parallel to the foundational importance due to the realization of a dynamical superselection rule and the theory of quantum measurements, this is an important step forward in protecting and controlling quantum dynamics and, broadly speaking, quantum information processing.

While a quantum system is always disturbed by any observation, one can exploit the back action of measurements and strong couplings to tailor the system evolution via quantum Zeno dynamics. Schäfer et al. demonstrate quantum Zeno dynamics in a five-level Hilbert space using a ⁸⁷Rb Bose–Einstein condensate.

Scattering experiments with microwave billiards at an exceptional point under broken time-reversal invariance

Scattering experiments with microwave cavities were performed and the effects of broken time-reversal invariance (TRI), induced by means of a magnetized ferrite placed inside the cavity, on an isolated doublet of nearly degenerate resonances were investigated. All elements of the effective Hamiltonian of this two-level system were extracted. As a function of two experimental parameters, the doublet and the associated eigenvectors could be tuned to coalesce at a so-called exceptional point (EP). The behavior of the eigenvalues and eigenvectors when encircling the EP in parameter space was studied, including the geometric amplitude that builds up in the case of broken TRI. A one-dimensional subspace of parameters was found where the differences of the eigenvalues are either real or purely imaginary. There, the Hamiltonians were found to be PT invariant under the combined operation of parity (P) and time reversal (T) in a generalized sense. The EP is the point of transition between both regions. There a spontaneous breaking of PT occurs.

Regulating angiogenesis with light-inducible AntimiRs

The inhibition of microRNAs (miRs) in a spatiotemporally defined manner by an exogenous trigger would help to specifically target the biological activity and avoid off-target effects. Novel antimiRs directed against miR-92a can be activated by irradiation (see scheme; 3'-UTR=3'-untranslated region) In this way miR-92a is inhibited, the miR-92a target integrin α5 is derepressed, and angiogenesis of endothelial cells is enhanced.

Distribution of scattering matrix elements in quantum chaotic scattering

Scattering is an important phenomenon which is observed in systems ranging from the micro- to macroscale. In the context of nuclear reaction theory, the Heidelberg approach was proposed and later demonstrated to be applicable to many chaotic scattering systems. To model the universal properties, stochasticity is introduced to the scattering matrix on the level of the Hamiltonian by using random matrices. A long-standing problem was the computation of the distribution of the off-diagonal scattering-matrix elements. We report here an exact solution to this problem and present analytical results for systems with preserved and with violated time-reversal invariance. Our derivation is based on a new variant of the supersymmetry method. We also validate our results with scattering data obtained from experiments with microwave billiards.

Study on severe accidents and countermeasures for VVER-1000 reactors using the integral code ASTEC

The research field focussing on the investigations and the analyses of postulated severe accidents is an important part of the nuclear safety. To maintain the safety barriers as long as possible and to retain the radioactivity within the airtight premises of the containment, to avoid or mitigate the consequences of such events and to assess the risk, thorough studies are needed. This paper is focused on the possibilities for accident management measures in case of severe accidents. The analyses performed with the integral code ASTEC cover two accident sequences which could lead to a severe accident: a small break loss of coolant accident and a station blackout. The discussed issues concern the main phenomena during the early and late in-vessel phase of the accidents, the time to core heat-up, the hydrogen production, the mass of corium in the reactor pressure vessel lower plenum and the failure of the reactor pressure vessel. Additionally, possible operator's actions and countermeasures in the preventive or mitigative domain are addressed.

Automated coaching to help parents increase their children's brushing frequency: an exploratory trial

Advances in digital communication, such as the internet, now provide a cost effective channel to reach and help families struggling to establish good oral hygiene in their homes. This paper describes a novel internet based oral hygiene intervention whose design draws from advances in social cognitive models of behaviour change. Intervention components included role-modelling cartoons for children, a guide for parents on using rewards, a personalised plan with clear steps, tips to follow and a weekly 10-minute review of progress.

OBJECTIVE

To evaluate the efficacy of the online coaching programme; specifically we expected that those in the intervention group would brush their teeth more frequently during the intervention period than those in the control group.

BASIC RESEARCH DESIGN

An exploratory trial using a randomised controlled parallel approach.

PARTICIPANTS

Children aged 5 to 9 years from 44 families (23 control and 21 intervention).

MAIN OUTCOME MEASURE

An objective monitoring of tooth brushing.

RESULTS

In the 3-week intervention period, children from families assigned to the coaching programme brushed their teeth 38% more often than those in the control group.

CONCLUSIONS

The programme was effective in a number of respects. Opportunities for further research are discussed, including the need to create a more engaging system and so increase compliance.

Investigation on primary side oriented accident management measures in a hypothetical station blackout scenario for a VVER-1000 pressurized water reactor

As a consequence of a total loss of AC power supply (station blackout) at a VVER-1000 leading to unavailability of major active safety systems, the safety criteria ensuring the safe operation of the nuclear power plant would be violated and core heat-up with possible core degradation could occur. A dedicated accident management measure (primary side depressurization) can be applied to reduce the primary pressure and to activate the injection from the passive emergency core cooling systems (accumulators). The analyses presented in this paper are aiming at both a detailed investigation of the accident sequence, taking into account the depressurization of the primary circuit, and the possibilities to prevent or at least to mitigate a damage of the reactor core so as to gain additional time for taking necessary countermeasures. The analyses are performed using the codes ASTEC and ATHLET developed by IRSN (Institut de Radioprotection et de Sûreté Nucléaire) and GRS (Gesellschaft für Anlagen- und Reaktorsicherheit mbH).

Analyzing Thiol-Dependent Redox Networks in the Presence of Methylene Blue and Other Antimalarial Agents with RT-PCR-Supported in silico Modeling

Background

In the face of growing resistance in malaria parasites to drugs, pharmacological combination therapies are important. There is accumulating evidence that methylene blue (MB) is an effective drug against malaria. Here we explore the biological effects of both MB alone and in combination therapy using modeling and experimental data.

Results

We built a model of the central metabolic pathways in P. falciparum. Metabolic flux modes and their changes under MB were calculated by integrating experimental data (RT-PCR data on mRNAs for redox enzymes) as constraints and results from the YANA software package for metabolic pathway calculations. Several different lines of MB attack on Plasmodium redox defense were identified by analysis of the network effects. Next, chloroquine resistance based on pfmdr/and pfcrt transporters, as well as pyrimethamine/sulfadoxine resistance (by mutations in DHF/DHPS), were modeled in silico. Further modeling shows that MB has a favorable synergism on antimalarial network effects with these commonly used antimalarial drugs.

Conclusions

Theoretical and experimental results support that methylene blue should, because of its resistance-breaking potential, be further tested as a key component in drug combination therapy efforts in holoendemic areas.

Cannabinoid receptor subtypes 1 and 2 mediate long-lasting neuroprotection and improve motor behavior deficits after transient focal cerebral ischemia

The endocannabinoid system is crucially involved in the regulation of brain activity and inflammation. We have investigated the localization of cannabinoid CB1 and CB2 receptors in adult rat brains before and after focal cerebral ischemia due to endothelin-induced transient occlusion of the middle cerebral artery (eMCAO). Using immunohistochemistry, both receptor subtypes were identified in cortical neurons. After eMCAO, neuronal cell death was accompanied by reduced neuronal CB1 and CB2 receptor-linked immunofluorescence. In parallel, CB1 receptor was found in activated microglia/macrophages 3 days post eMCAO and in astroglia cells at days 3 and 7. CB2 receptor labeling was identified in activated microglia/macrophages or astroglia 3 and 7d ays post ischemia, respectively. In addition, immune competent CD45-positive cells were characterized by pronounced CB2 receptor staining 3 and 7 days post eMCAO. KN38-72717, a potent and selective CB1 and CB2 receptor agonist, revealed a significant, dose-dependent and long-lasting reduction of cortical lesion sizes due to eMCAO, when applied consecutively before, during and after eMCAO. In addition, severe motor deficits of animals suffering from eMCAO were significantly improved by KN38-7271. KN38-7271 remained effective, even if its application was delayed up to 6h post eMCAO. Finally, we show that the endocannabinoid system assembles a comprehensive machinery to defend the brain against the devastating consequences of cerebral ischemia. In summary, this study underlines the therapeutic potential of CB1 and/or CB2 receptor agonists against neurodegenerative diseases or injuries involving acute or chronic imbalances of cerebral blood flow and energy consumption.

In vivo cardiac anatomical and functional effects of wheel running in mice by magnetic resonance imaging

Physical activity is frequently used as a strategy to decrease pathogenesis and improve outcomes in chronic pathologies such as metabolic or cardiac diseases. In mice, it has been shown that voluntary wheel running (VWR) could induce an aerobic training effect and may provide a means of exploring the relationship between physical activity and the progression of pathology, or the effect of a drug on locomotor activity. To the best of our knowledge, in vivo magnetic resonance imaging (MRI) and other non-invasive methods had not been investigated for training evaluation in mice; therefore, it was proposed to test an MRI method coupled with a cardiorespiratory gating system on C57Bl/6 mice for in vivo heart anatomical and functional characterization in both trained and untrained animals. Twenty mice were either assigned to a 12-week VWR program or to a control group (CON - no wheel in the cage). At week 12, MRI scans showed an increase in the left ventricular (LV) wall mass in the VWR group compared with the CON group. The ex vivo measurements also found an increase in the heart and LV weight, as well as an increase in oxidative enzyme activities (i.e. cytochrome c oxidase [COx] in the soleus). In addition, correlations have been observed between ex vivo LV/body weight ratio, COx activity in the soleus and in vivo MRI LV wall mass/body weight. In conclusion, mouse cardiac MRI methods coupled with a cardio-respiratory gating system are sufficiently effective and feasible for non-invasive, training-induced heart hypertrophy characterization, and may be used for longitudinal training level follow-up in mouse models of cardiovascular and metabolic diseases.

PT symmetry and spontaneous symmetry breaking in a microwave billiard

We demonstrate the presence of parity-time (PT) symmetry for the non-Hermitian two-state Hamiltonian of a dissipative microwave billiard in the vicinity of an exceptional point (EP). The shape of the billiard depends on two parameters. The Hamiltonian is determined from the measured resonance spectrum on a fine grid in the parameter plane. After applying a purely imaginary diagonal shift to the Hamiltonian, its eigenvalues are either real or complex conjugate on a curve, which passes through the EP. An appropriate basis choice reveals its PT symmetry. Spontaneous symmetry breaking occurs at the EP.

Vapor diffusion-controlled meso crystallization of membrane proteins

The presented method to crystallize membrane proteins combines the advantages of the meso-phase crystallization method and the classical vapor diffusion crystallization. It allows fast screening of crystallization conditions employing automated liquid handlers suited for the 96-well crystallization format.

Double-slit experiments with microwave billiards

Single and double-slit experiments are performed with two microwave billiards with the shapes of a rectangle and a quarter stadium, respectively. The classical dynamics of the former is regular, whereas that of the latter is chaotic. Microwaves can leave the billiards via slits in the boundary, forming interference patterns on a screen. The aim is to determine the effect of the billiard dynamics on their structure. For this the development of a method for the construction of a directed wave packet by means of an array of multiple antennas was crucial. The interference patterns show a sensitive dependence not only on the billiard dynamics but also on the initial position and direction of the wave packet.

Exceptional points in a microwave billiard with time-reversal invariance violation

We report on the experimental study of an exceptional point (EP) in a dissipative microwave billiard with induced time-reversal invariance (T) violation. The associated two-state Hamiltonian is non-Hermitian and nonsymmetric. It is determined experimentally on a narrow grid in a parameter plane around the EP. At the EP the size of T violation is given by the relative phase of the eigenvector components. The eigenvectors are adiabatically transported around the EP, whereupon they gather geometric phases and in addition geometric amplitudes different from unity.

Wavelength-selective uncaging of dA and dC residues

Nitrodibenzofuran (NDBF) groups are used as photolabile "caging" groups to temporarily mask the Watson-Crick interaction of dA and dC residues. They show improved masking capabilities and are photodeprotected 12 times more efficiently than 1-(o-nitrophenyl)-ethyl (NPE) caging groups in these positions. Furthermore, NDBF groups can be removed wavelength-selectively in the presence of NPE groups. This will allow more complex (un)caging strategies of oligonucleotides--beyond the usual irreversible triggering.

Comparison of the duplex-destabilizing effects of nucleobase-caged oligonucleotides

Nucleobase-caged oligonucleotide residues have photolabile "caging groups" that prevent the formation of Watson-Crick base pairs until the unmodified nucleobase is restored in a photolysis event. This principle can be used to put a growing variety of powerful nucleic acid-based applications under the precise spatiotemporal control using light as an addressing mechanism. Examples for applications include light control of transcription, RNAi, nucleic acid folding, primer extension, and restriction endonuclease as well as DNAzyme, aptamer, and antisense activity. However, a comparison of the duplex-destabilization properties of the various caged residues that have been used up to date and rules for achieving a maximal duplex destabilization with a minimum amount of modified residues are still missing. We present both a comparison of the duplex-destabilizing capabilities of various nucleobase-caged residues and address the question of influence on neighboring base pairs.

Coherent addition of laser beams in resonant passive optical cavities

An optical resonator, designed for frequency doubling of cw single-frequency radiation, is simultaneously injected by two phase-coherent laser beams with the same frequency. By using standard methods in laser-cavity stabilization, we are able to stabilize the cavity length on resonance with the laser, as well as the relative phase of the fundamental beams, to fulfill the optimum coupling conditions simultaneously on the two input couplers. By using this method, we generate reliably more than 220 mW of single-frequency radiation at 399 nm using two 0.5 W semiconductor tapered amplifiers at 798 nm. This method can be generalized to a larger number of input couplers and holds promise for improving the performances of extreme-UV frequency combs.

Experimental test of a trace formula for two-dimensional dielectric resonators

Resonance spectra of two-dimensional dielectric microwave resonators of circular and square shapes have been measured. The deduced length spectra of periodic orbits were analyzed and a trace formula for dielectric resonators recently proposed by Bogomolny [Phys. Rev. E 78, 056202 (2008)] was tested. The observed deviations between the experimental length spectra and the predictions of the trace formula are attributed to a large number of missing resonances in the measured spectra. We show that by taking into account the systematics of observed and missing resonances the experimental length spectra are fully understood. In particular, a connection between the most long-lived resonances and certain periodic orbits is established experimentally.

Quantum chaotic scattering in microwave resonators

In a frequency range where a microwave resonator simulates a chaotic quantum billiard, we have measured moduli and phases of reflection and transmission amplitudes in the regimes of both isolated and of weakly overlapping resonances and for resonators with and without time-reversal invariance. Statistical measures for S -matrix fluctuations were determined from the data and compared with extant and/or newly derived theoretical results obtained from the random-matrix approach to quantum chaotic scattering. The latter contained a small number of fit parameters. The large data sets taken made it possible to test the theoretical expressions with unprecedented accuracy. The theory is confirmed by both a goodness-of-fit-test and the agreement of predicted values for those statistical measures that were not used for the fits, with the data.

Dependence of aptamer activity on opposed terminal extensions: improvement of light-regulation efficiency

Aptamers that can be regulated with light allow precise control of protein activity in space and time and hence of biological function in general. In a previous study, we showed that the activity of the thrombin-binding aptamer HD1 can be turned off by irradiation using a light activatable 'caged' intramolecular antisense-domain. However, the activity of the presented aptamer in its ON state was only mediocre. Here we studied the nature of this loss in activity in detail and found that switching from 5'- to 3'-extensions affords aptamers that are even more potent than the unmodified HD1. In particular we arrived at derivatives that are now more active than the aptamer NU172 that is currently in phase 2 clinical trials as an anticoagulant. As a result, we present light-regulatable aptamers with a superior activity in their ON state and an almost digital ON/OFF behavior upon irradiation.

Friedel oscillations in microwave billiards

Friedel oscillations of electron densities near step edges have an analog in microwave billiards. A random plane-wave model, normally only appropriate for the eigenfunctions of a purely chaotic system, can be applied and is tested for non-purely-chaotic dynamical systems with measurements on pseudointegrable and mixed dynamics geometries. It is found that the oscillations in the pseudointegrable microwave cavity match the random plane-wave modeling. Separating the chaotic from the regular states for the mixed system requires incorporating an appropriate phase-space projection into the modeling in multiple ways for good agreement with experiment.

Nonperiodic echoes from quantum mushroom-billiard hats

Nonperiodic tunable quantum echoes have been observed in experiments with an open microwave billiard whose geometry under certain conditions provides Fibonacci-like sequences of classical delay times. These sequences combined with the reflection at the opening induced by the wave character of the experiment and the size of the opening allow to shape quantum pulses. The pulses are obtained by response of an integrable scattering system.