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Corynebacterium jeikeium, a resident of human skin, is often associated with multidrug resistant nosocomial infections in immunodepressed patients. C. jeikeium K411 belongs to mycolic acid-containing actinomycetes, the mycolata and contains a channel-forming protein as judged from reconstitution experiments with artificial lipid bilayer experiments. The channel-forming protein was present in detergent treated cell walls and in extracts of whole cells using organic solvents. A gene coding for a 40 amino acid long polypeptide possibly responsible for the pore-forming activity was identified in the known genome of C. jeikeium by its similar chromosomal localization to known porH and porA genes of other Corynebacterium strains. The gene jk0268 was expressed in a porin deficient Corynebacterium glutamicum strain. For purification temporarily histidine-tailed or with a GST-tag at the N-terminus, the homogeneous protein caused channel-forming activity with an average conductance of 1.25 nS in 1M KCl identical to the channels formed by the detergent extracts. Zero-current membrane potential measurements of the voltage dependent channel implied selectivity for anions. This preference is according to single-channel analysis caused by some excess of cationic charges located in the channel lumen formed by oligomeric alpha-helical wheels. The channel has a suggested diameter of 1.4 nm as judged from the permeability of different sized hydrated anions using the Renkin correction factor. Surprisingly, the genome of C. jeikeium contained only one gene coding for a cell wall channel of the PorA/PorH type found in other Corynebacterium species. The possible evolutionary relationship between the heterooligomeric channels formed by certain Corynebacterium strains and the homooligomeric pore of C. jeikeium is discussed.
Objective. Current evidence indicates that there is no single ideal treatment for fibromyalgia syndrome (FMS). First choice treatment options remain debatable, especially concerning the importance of complementary and alternative medicine (CAM) treatments. Methods. Three evidence-based interdisciplinary guidelines on FMS in Canada, Germany, and Israel were compared for their first choice and CAM-recommendations. Results. All three guidelines emphasized a patient-tailored approach according to the key symptoms. Aerobic exercise, cognitive behavioral therapy, and multicomponent therapy were first choice treatments. The guidelines differed in the grade of recommendation for drug treatment. Anticonvulsants (gabapentin, pregabalin) and serotonin noradrenaline reuptake inhibitors (duloxetine, milnacipran) were strongly recommended by the Canadian and the Israeli guidelines. These drugs received only a weak recommendation by the German guideline. In consideration of CAM-treatments, acupuncture, hypnosis/guided imagery, and Tai Chi were recommended by the German and Israeli guidelines. The Canadian guidelines did not recommend any CAM therapy. Discussion. Recent evidence-based interdisciplinary guidelines concur on the importance of treatment tailored to the individual patient and further emphasize the need of self-management strategies (exercise, and psychological techniques).
The Chlamydiae constitute an evolutionary well separated group of intracellular bacteria comprising important pathogens of humans as well as symbionts of protozoa. The amoeba symbiont Protochlamydia amoebophila lacks a homologue of the most abundant outer membrane protein of the Chlamydiaceae, the major outer membrane protein MOMP, highlighting a major difference between environmental chlamydiae and their pathogenic counterparts. We recently identified a novel family of putative porins encoded in the genome of P. amoebophila by in silico analysis. Two of these Protochlamydia outer membrane proteins, PomS (pc1489) and PomT (pc1077), are highly abundant in outer membrane preparations of this organism. Here we show that all four members of this putative porin family are toxic when expressed in the heterologous host Escherichia coli. Immunofluorescence analysis using antibodies against heterologously expressed PomT and PomS purified directly from elementary bodies, respectively, demonstrated the location of both proteins in the outer membrane of P. amoebophila. The location of the most abundant protein PomS was further confirmed by immuno-transmission electron microscopy. We could show that pomS is transcribed, and the corresponding protein is present in the outer membrane throughout the complete developmental cycle, suggesting an essential role for P. amoebophila. Lipid bilayer measurements demonstrated that PomS functions as a porin with anion-selectivity and a pore size similar to the Chlamydiaceae MOMP. Taken together, our results suggest that PomS, possibly in concert with PomT and other members of this porin family, is the functional equivalent of MOMP in P. amoebophila. This work contributes to our understanding of the adaptations of symbiotic and pathogenic chlamydiae to their different eukaryotic hosts.
The growing interest in Radio Frequency Identification (RFID) technology in recent years has sparked an intensive debate on the benefits to be expected. With the growth of RFID implementations in size and scope comes a shift away from infrastructural aspects to the question of how to draw value from the large amounts of collected data. However, the necessary procedures for the handling of massive RFID data sets are still an under-researched issue. Against this background, the study presents results from a real-world trial conducted by a large apparel retailer. The objective of the trial was to explore the opportunities for generating novel performance indicators and reports on the reality of store processes and customer behavior on the sales floor. We give an overview of the algorithms used for RFID data processing and the interpretation of the resulting insights from a practitioner’s point of view. The case example thus provides an overview of the potential of RFID as a powerful tool for assortment optimization, customer research, store layout design, and other management tasks in retail.
Introduction
Juvenile idiopathic arthritis is a heterogeneous T cell-mediated autoimmune disease with symptoms of premature aging of the immune system (immunosenescence). The present work is an investigation of immunosenescence parameters, such as quantity of naive and CD28- T cells, T cell receptor excision circles, relative telomere length and alterations of peripheral T cell replication, and was performed via comparison of a case of acute exacerbation of juvenile idiopathic arthritis against six patients with juvenile idiopathic arthritis with disease remission and six age-matched healthy donors over a follow-up course of 12 months.
Case presentation
Phenotypical T cell characterization and intracellular interferon γ, tumor necrosis factor α, and interleukin 2 production were studied in peripheral blood mononuclear cells from seven patients with juvenile idiopathic arthritis and six healthy control donors, with findings determined by flow cytometry. T cell receptor excision circles and relative telomere length quantification were performed on deoxyribonucleic acid isolated from naive (CD4+CD28+CD45RA+) T cells and investigated via reverse transcription polymerase chain reaction. Ki67 expression was studied by immunohistochemistry on naive T cells. The non-parametric Mann-Whitney U test and Wilcoxon test for two independent groups of variables were used to compare healthy donors with patients with juvenile idiopathic arthritis. During follow-up, patients with juvenile idiopathic arthritis showed lower total counts of naive and CD28-expressing T cells compared to healthy donors. Acute exacerbation led to low naive and CD28+ T cell populations and elevated proportions of Ki67-expressing CD4+ naive T cells. In conditions of exacerbation, T cell receptor excision circle numbers were in the lower range in patients with juvenile idiopathic arthritis and increased after follow-up. Healthy donors showed significantly higher relative telomere lengths compared to patients with juvenile idiopathic arthritis.
Conclusions
This investigation illustrates that the changes in T cell homeostasis in patients with juvenile idiopathic arthritis may be the result of several mechanisms, such as diminished thymus function and peripheral exertions to maintain the peripheral T cell pool. The results also demonstrate that hallmarks of immunosenescence such as decreased naive T cell levels and lower T cell receptor excision circle numbers can only be interpreted together with replication markers such as relative telomere length or Ki67 expression.
The nuclear lamina is the structural scaffold of the nuclear envelope and is well known for its central role in nuclear organization and maintaining nuclear stability and shape. In the past, a number of severe human disorders have been identified to be associated with mutations in lamins. Extensive research on this topic has provided novel important clues about nuclear lamina function. These studies have contributed to the knowledge that the lamina constitutes a complex multifunctional platform combining both structural and regulatory functions. Here, we report that, in addition to the previously demonstrated significance for somatic cell differentiation and maintenance, the nuclear lamina is also an essential determinant for germ cell development. Both male and female mice lacking the short meiosis-specific A-type lamin C2 have a severely defective meiosis, which at least in the male results in infertility. Detailed analysis revealed that lamin C2 is required for telomere-driven dynamic repositioning of meiotic chromosomes. Loss of lamin C2 affects precise synapsis of the homologs and interferes with meiotic double-strand break repair. Taken together, our data explain how the nuclear lamina contributes to meiotic chromosome behaviour and accurate genome haploidization on a mechanistic level.
Abstract
Sulphur is an essential element that all pathogens have to absorb from their surroundings in order to grow inside their infected host. Despite its importance, the relevance of sulphur assimilation in fungal virulence is largely unexplored. Here we report a role of the bZIP transcription factor MetR in sulphur assimilation and virulence of the human pathogen Aspergillus fumigatus. The MetR regulator is essential for growth on a variety of sulphur sources; remarkably, it is fundamental for assimilation of inorganic S-sources but dispensable for utilization of methionine. Accordingly, it strongly supports expression of genes directly related to inorganic sulphur assimilation but not of genes connected to methionine metabolism. On a broader scale, MetR orchestrates the comprehensive transcriptional adaptation to sulphur-starving conditions as demonstrated by digital gene expression analysis. Surprisingly, A. fumigatus is able to utilize volatile sulphur compounds produced by its methionine catabolism, a process that has not been described before and that is MetR-dependent. The A. fumigatus MetR transcriptional activator is important for virulence in both leukopenic mice and an alternative mini-host model of aspergillosis, as it was essential for the development of pulmonary aspergillosis and supported the systemic dissemination of the fungus. MetR action under sulphur-starving conditions is further required for proper iron regulation, which links regulation of sulphur metabolism to iron homeostasis and demonstrates an unprecedented regulatory crosstalk. Taken together, this study provides evidence that regulation of sulphur assimilation is not only crucial for A. fumigatus virulence but also affects the balance of iron in this prime opportunistic pathogen.
Author Summary
Invasive pulmonary aspergillosis (IPA) is a life-threatening disease that affects primarily immunosuppressed patients. During the last decades the incidence of this disease that is accompanied by high mortality rates has increased. Since opportunistic pathogenic fungi, unlike other pathogens, do not express specific virulence factors, it is becoming more and more clear that the elucidation of fungal metabolism is an essential task to understand fungal pathogenicity and to identify novel antifungal targets. In this work we report genetic inactivation of the sulphur transcription regulator MetR in Aspergillus fumigatus and subsequent study of the resulting phenotypes and transcriptional deregulation of the mutant. Here we show that regulation of sulphur assimilation is an essential process for the manifestation of IPA. Moreover, a regulatory connection between sulphur metabolism and iron homeostasis, a further essential virulence determinant of A. fumigatus, is demonstrated in this study for the first time. A deeper knowledge of sulphur metabolism holds the promise of increasing our understanding of fungal virulence and might lead to improved antifungal therapy.
Heparins are one of the most used class of anticoagulants in daily clinical practice. Despite their widespread application immune-mediated hypersensitivity reactions to heparins are rare. Among these, the delayed-type reactions to s.c. injected heparins are well-known usually presenting as circumscribed eczematous plaques at the injection sites. In contrast, potentially life-threatening systemic immediate-type anaphylactic reactions to heparins are extremely rare. Recently, some cases of non-allergic anaphylaxis could be attributed to undesirable heparin contaminants.
A 43-year-old patient developed severe anaphylaxis symptoms within 5–10 minutes after s.c. injection of enoxaparin. Titrated skin prick testing with wheal and flare responses up to an enoxaparin dilution of 1:10.000 indicated a probable allergic mechanism of the enoxaparin-induced anaphylaxis. The basophil activation test as an additional in-vitro test method was negative. Furthermore, skin prick testing showed rather broad cross-reactivity among different heparin preparations tested.
In the presented case, history, symptoms, and results of skin testing strongly suggested an IgE-mediated allergic hypersensitivity against different heparins. Therefore, as safe alternative anticoagulants the patient could receive beneath coumarins the hirudins or direct thrombin inhibitors. Because these compounds have a completely different molecular structure compared with the heparin-polysaccharides.
Large-scale anatomical and functional analyses of the connectivity in both invertebrate and mammalian brains have gained intense attention in recent years. At the same time, the understanding of synapses on a molecular level still lacks behind. We have only begun to unravel the basic mechanisms of how the most important synaptic proteins regulate release and reception of neurotransmitter molecules, as well as changes of synaptic strength. Furthermore, little is known regarding the stoichiometry of presynaptic proteins at different synapses within an organism. An assessment of these characteristics would certainly promote our comprehension of the properties of different synapse types. Presynaptic proteins directly influence, for example, the probability of neurotransmitter release as well as mechanisms for short-term plasticity. We have examined the strength of expression of several presynaptic proteins at different synapse types in the central nervous system of Drosophila melanogaster using immunohistochemistry. Clear differences in the relative abundances of the proteins were obvious on different levels: variations in staining intensities appeared from the neuropil to the synaptic level. In order to quantify these differences, we have developed a ratiometric analysis of antibody stainings. By application of this ratiometric method, we could assign average ratios of presynaptic proteins to different synapse populations in two central relays of the olfactory pathway. In this manner, synapse types could be characterized by distinct fingerprints of presynaptic protein ratios. Subsequently, we used the method for the analysis of aberrant situations: we reduced levels of Bruchpilot, a major presynaptic protein, and ablated different synapse or cell types. Evoked changes of ratio fingerprints were proportional to the modifications we had induced in the system. Thus, such ratio signatures are well suited for the characterization of synapses. In order to contribute to our understanding of both the molecular composition and the function of synapses, we also characterized a novel synaptic protein. This protein, Drep-2, is a member of the Dff family of regulators of apoptosis. We generated drep-2 mutants, which did not show an obvious misregulation of apoptosis. By contrast, Drep-2 was found to be a neuronal protein, highly enriched for example at postsynaptic receptor fields of the input synapses of the major learning centre of insects, the mushroom bodies. Flies mutant for drep-2 were viable but lived shorter than wildtypes. Basic synaptic transmission at both peripheral and central synapses was in normal ranges. However, drep-2 mutants showed a number of deficiencies in adaptive behaviours: adult flies were locomotor hyperactive and hypersensitive towards ethanol-induced sedation. Moreover, the mutant animals were heavily impaired in associative learning. In aversive olfactory conditioning, drep-2 mutants formed neither short-term nor anaesthesia-sensitive memories. We could demonstrate that Drep-2 is required in mushroom body intrinsic neurons for normal olfactory learning. Furthermore, odour-evoked calcium transients in these neurons, a prerequisite for learning, were reduced in drep-2 mutants. The impairment of the mutants in olfactory learning could be fully rescued by pharmacological application of an agonist to metabotropic glutamate receptors (mGluRs). Quantitative mass spectrometry of Drep-2 complexes revealed that the protein is associated with a large number of translational repressors, among them the fragile X mental retardation protein FMRP. FMRP inhibits mGluR-mediated protein synthesis. Lack of this protein causes the fragile X syndrome, which constitutes the most frequent monogenic cause of autism. Examination of the performance of drep-2 mutants in courtship conditioning showed that the animals were deficient in both short- and long-term memory. Drep-2 mutants share these phenotypes with fmrp and mGluR mutants. Interestingly, drep-2; fmrp double mutants exhibited normal memory. Thus, we propose a model in which Drep-2 antagonizes FMRP in the regulation of mGluR-dependent protein synthesis. Our hypothesis is supported by the observation that impairments in synaptic plasticity can arise if mGluR signalling is imbalanced in either direction. We suggest that Drep-2 helps in establishing this balance.
Relief from pain is positively valenced and entails reward-like properties. Notably, stimuli that became associated with pain relief elicit reward-like implicit responses too, but are explicitly evaluated by humans as aversive. Since the unpredictability of pain makes pain more aversive, this study examined the hypotheses that the predictability of pain also modulates the valence of relief-associated stimuli. In two studies, we presented one conditioned stimulus \((_{FORWARD}CS+)\) before a painful unconditioned stimulus (US), another stimulus \((_{BACKWARD}CS+)\) after the painful US, and a third stimulus (CS−) was never associated with the US. In Study 1, \(_{FORWARD}CS+\) predicted half of the USs while the other half was delivered unwarned and followed by \(_{BACKWARD}CS+\). In Study 2, all USs were predicted by \(_{FORWARD}CS+\) and followed by \(_{BACKWARD}CS+\). In Study 1 both \(_{FORWARD}CS+\) and \(_{BACKWARD}CS+\) were rated as negatively valenced and high arousing after conditioning, while \(_{BACKWARD}CS+\) in Study 2 acquired positive valence and low arousal. Startle amplitude was significantly attenuated to \(_{BACKWARD}CS+\) compared to \(_{FORWARD}CS+\) in Study 2, but did not differ among CSs in Study 1. In summary, predictability of aversive events reverses the explicit valence of a relief-associated stimulus.
Since its creation in 1966, Star Trek has been a dominant part of popular culture and as thus served as the source for many cultural references. Star Trek’s creator Gene Roddenberry wanted to realize his vision of a utopia but at the same time, he used the futuristic setting of the show to comment on the present time, on actual social and political circumstances. This means that each series can be regarded as a mirror image of the time in which it was created. The clothing of the characters in the different series is one part of that image. The uniforms of The Original Se-ries show influences of the 1960s pop art movement as well as the mini-skirt trend that experienced its peak in that decade. In the course of almost 40 years, howev-er, many things changed. In the 1990s, in Deep Space Nine and Voyager, a unisex uniform replaced the mini-dresses, with few exceptions; the colorful shirts gave way to ones that were mostly black. This trend continues into the new century. This essay interprets the evolution of the female officers’ uniforms from femi-nized dresses to androgynous clothing over the development of the series as a reflection of the change of gender roles in contemporary American society. The general functions of the female characters’ uniforms are the central object of its analysis while the few, but noteworthy exceptions to this pattern are given specif-ic attention. Finally, one of the most intriguing lines of enquiry is, how the pre-quel series Enterprise, supposed to be set before The Original Series, but pro-duced and aired from 2001 to 2005, fits in the picture.
Serotonin (5-HT) has been implicated in the regulation of emotions as well as in its pathological states, such as anxiety disorders and depression. Mice with targeted deletion of genes encoding various mediators of central serotonergic neurotransmission therefore provides a powerful tool in understanding contributions of such mediators to homeostatic mechanisms as well as to the development of human emotional disorders. Within this thesis a battery of electrophysiological recordings were conducted in the dorsal raphe nucleus (DRN) and the hippocampus of two murine knockout lines with deficient serotonergic systems. Serotonin transporter knockout mice (5-Htt KO), which lack protein responsible for reuptake of 5-HT from the extracellular space and tryptophan hydroxylase 2 knockout (Tph2 KO) mice, which lack the gene encoding the neuronal 5-HT-synthesising enzyme. First, 5-HT1A receptor-mediated autoinhibition of serotonergic neuron firing in the DRN was assessed using the loose-seal cell-attached configuration. Stimulation of 5-HT1A receptors by a selective agonist, R-8-hydroxy-2-(di-n-propylamino)tetralin (R-8-OH-DPAT), showed a mild sensitisation and a marked desensitisation of these receptors in Tph2 KO and 5-Htt KO mice, respectively. While application of tryptophan, a precursor of 5-HT and a substrate of Tph2, did not cause autoinhibition in Tph2 KO mice due to the lack of endogenously produced 5-HT, data from 5-Htt KO mice as well as heterozygous mice of both KO mice lines demonstrated the presence of autoinhibitory mechanisms as normal as seen in wildtype (WT) controls. When the Tph2-dependent step in the 5-HT synthesis pathway was bypassed by application of 5-hydroxytryptophan (5-HTP), serotonergic neurons of both Tph2 KO and 5-Htt KO mice showed decrease in firing rates at lower concentrations of 5-HTP than in WT controls. Elevated responsiveness of serotonergic neurons from Tph2 KO mice correspond to mild sensitisation of 5-HT1A receptors, while responses from 5-Htt KO mice suggest that excess levels of extracellular 5-HT, created by the lack of 5-Htt, stimulates 5-HT1A receptors strong enough to overcome desensitisation of these receptors. Second, the whole-cell patch clamp recording data from serotonergic neurons in the DRN showed no differences in basic electrophysiological properties between Tph2 KO and WT mice, except lower membrane resistances of neurons from KO mice. Moreover, the whole-cell patch clamp recording from CA1 pyramidal neurons in the hippocampus of 5-Htt KO mice showed increased conductance both at a steady state and at action potential generation. Lastly, magnitude of long-term potentiation (LTP) induced by the Schaffer collateral/commissural pathway stimulation in the ventral hippocampus showed no differences among Tph2 KO, 5-Htt KO, and WT counterparts. Taken together, lack and excess of extracellular 5-HT caused sensitisation and desensitisation of autoinhibitory 5-HT1A receptors, respectively. However, this may not directly translate to the level of autoinhibitory regulation of serotonergic neuron firing when these receptors are stimulated by endogenously synthesised 5-HT. In general, KO mice studied here showed an astonishing level of resilience to genetic manipulations of the central serotonergic system, maintaining overall electrophysiological properties and normal LTP inducibility. This may further suggest existence of as-yet-unknown compensatory mechanisms buffering potential alterations induced by genetic manipulations.
Firing activity of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) is controlled by inhibitory somatodendritic 5-HT1A autoreceptors. This autoinhibitory mechanism is implicated in the etiology of disorders of emotion regulation, such as anxiety disorders and depression, as well as in the mechanism of antidepressant action. Here, we investigated how persistent alterations in brain 5-HT availability affect autoinhibition in two genetically modified mouse models lacking critical mediators of serotonergic transmission: 5-HT transporter knockout (Sert-/-) and tryptophan hydroxylase-2 knockout (Tph2-/-) mice. The degree of autoinhibition was assessed by loose-seal cell-attached recording in DRN slices. First, application of the 5-HT1A-selective agonist R(+)-8-hydroxy-2-(di-n-propylamino)tetralin showed mild sensitization and marked desensitization of 5-HT1A receptors in Tph2-/- mice and Sert-/- mice, respectively. While 5-HT neurons from Tph2-/- mice did not display autoinhibition in response to L-tryptophan, autoinhibition of these neurons was unaltered in Sert-/- mice despite marked desensitization of their 5-HT1A autoreceptors. When the Tph2-dependent 5-HT synthesis step was bypassed by application of 5-hydroxy-L-tryptophan (5-HTP), neurons from both Tph2-/- and Sert-/- mice decreased their firing rates at significantly lower concentrations of 5-HTP compared to wildtype controls. Our findings demonstrate that, as opposed to the prevalent view, sensitivity of somatodendritic 5-HT1A receptors does not predict the magnitude of 5-HT neuron autoinhibition. Changes in 5-HT1A receptor sensitivity may rather be seen as an adaptive mechanism to keep autoinhibition functioning in response to extremely altered levels of extracellular 5-HT resulting from targeted inactivation of mediators of serotonergic signaling.
Organic semiconductors are attractive for optical sensing applications due to the effortless processing on large active area of several \(cm^2\), which is difficult to achieve with solid-state devices. However, compared to silicon photodiodes, sensitivity and dynamic behavior remain a major challenge with organic sensors. Here, we show that charge trapping phenomena deteriorate the bandwidth of organic photodiodes (OPDs) to a few Hz at low-light levels. We demonstrate that, despite the large OPD capacitances of similar to 10 nF \(cm^{-2}\), a frequency response in the kHz regime can be achieved at light levels as low as 20 nW \(cm^{-2}\) by appropriate interface engineering, which corresponds to a 1000-fold increase compared to state-of-the-art OPDs. Such device characteristics indicate that large active area OPDs are suitable for industrial sensing and even match medical requirements for single X-ray pulse detection in the millisecond range.
The adiabatic insertion of a \(\pi\) flux into a quantum spin Hall insulator gives rise to localized spin and charge fluxon states. We demonstrate that \(\pi\) fluxes can be used in exact quantum Monte Carlo simulations to identify a correlated \(Z_2\) topological insulator using the example of the Kane-Mele-Hubbard model. In the presence of repulsive interactions, a \(\pi\) flux gives rise to a Kramers doublet of spin-fluxon states with a Curie-law signature in the magnetic susceptibility. Electronic correlations also provide a bosonic mode of magnetic excitons with tunable energy that act as exchange particles and mediate a dynamical interaction of adjustable range and strength between spin fluxons. \(\pi\) fluxes can therefore be used to build models of interacting spins. This idea is applied to a three-spin ring and to one-dimensional spin chains. Because of the freedom to create almost arbitrary spin lattices, correlated topological insulators with \(\pi\) fluxes represent a novel kind of quantum simulator, potentially useful for numerical simulations and experiments.
Pinning the Order: The Nature of Quantum Criticality in the Hubbard Model on Honeycomb Lattice
(2013)
In numerical simulations, spontaneously broken symmetry is often detected by computing two-point correlation functions of the appropriate local order parameter. This approach, however, computes the square of the local order parameter, and so when it is small, very large system sizes at high precisions are required to obtain reliable results. Alternatively, one can pin the order by introducing a local symmetrybreaking field and then measure the induced local order parameter infinitely far from the pinning center. The method is tested here at length for the Hubbard model on honeycomb lattice, within the realm of the projective auxiliary-field quantum Monte Carlo algorithm. With our enhanced resolution, we find a direct and continuous quantum phase transition between the semimetallic and the insulating antiferromagnetic states with increase of the interaction. The single-particle gap, measured in units of Hubbard U, tracks the staggered magnetization. An excellent data collapse is obtained by finite-size scaling, with the values of the critical exponents in accord with the Gross-Neveu universality class of the transition.
Silicon carbide light-emitting diode as a prospective room temperature source for single photons
(2013)
Generation of single photons has been demonstrated in several systems. However, none of them satisfies all the conditions, e.g. room temperature functionality, telecom wavelength operation, high efficiency, as required for practical applications. Here, we report the fabrication of light-emitting diodes (LEDs) based on intrinsic defects in silicon carbide (SiC). To fabricate our devices we used a standard semiconductor manufacturing technology in combination with high-energy electron irradiation. The room temperature electroluminescence (EL) of our LEDs reveals two strong emission bands in the visible and near infrared (NIR) spectral ranges, associated with two different intrinsic defects. As these defects can potentially be generated at a low or even single defect level, our approach can be used to realize electrically driven single photon source for quantum telecommunication and information processing.
Scientific surveys provide sufficient evidence that anxiety disorders are one of the most common psy-chiatric disorders in the world. The lifetime prevalence rate of anxiety disorder is 28.8% (Kessler, et al., 2005). The most widely studied anxiety disorders are as follows panic disorder (PD), post-traumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), social phobia (or social anxiety disorder), specific phobias, and generalized anxiety disorder (GAD). (NIMH Article, 2009). Classical conditioning is the stable paradigm used from the last one century to understand the neurobi-ology of fear learning. Neurobiological mechanism of fear learning is well documented with the condi-tioning studies. In the therapy of anxiety disorders, exposure based therapies are known to be the most effective approaches. Flooding is a form of exposure therapy in which a participant is exposed to the fear situation and kept in that situation until their fear dissipates. The exposure therapy is based on the phenomena of extinction; this means that a conditioned response diminishes if the conditioned stimulus (CS) is repeatedly presented without an unconditioned stimulus (UCS). One problem with extinction as well as with exposure-based therapy is the problem of fear return (for e.g. renewal, spontaneous recov-ery and reinstatement) after successful extinction. Therefore, extinction does not delete the fear memory trace. It has been well documented that memory processes can be modulated or disrupted using several sci-entific paradigms such as behavioral (for e.g. exposure therapy), pharmacological (for e.g. drug manipu-lation), non-invasive stimulation (for e.g. non-invasive stimulation such as electroconvulsive shock (ECS), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), etc. However, modulation of memory processes after reactivation or via non-invasive stimulation is still not clear, which is the focus of the current study. In addition, study of genetic variant suggests that genetic differences play a vital role in the psychiatric disorder especially in fear learning. Hence, it is also one of the concerns of the current dissertation to investigate the interaction between gene and reconsolidation of memory. With respect to fear-conditioning, there are three findings in the current dissertation, which are as fol-lows: (i) In the first study we investigated that non-invasive weak electrical stimulation interferes with the consolidation process and disrupts the fear consolidation to attain stable form. This might offer an effective treatment in the pathological memories, for e.g. PTSD, PD, etc. (ii) In the second study we demonstrated whether a brief single presentation of the CS will inhibit the fear recovery. Like earlier studies we also found that reactivation followed by reconsolidation douses fear return. Attenuation of fear recovery was observed in the reminder group compared to the no-reminder group. (iii) Finally, in our third study we found a statistically significant role of brain derived neurotrophic factor (BDNF) polymorphism in reconsolidation. Results of the third study affirm the involvement of BDNF variants (Met vs. Val) in the modulation of conditioned fear memory after its reactivation. In summary, we were able to show in the current thesis modulation of associative learning and recon-solidation via transcranial direct current stimulation and genetic polymorphism.
Human alveolar echinococcosis (AE) is a potentially deadly disease; recent studies have shown that the endemic area of Echinococcus multilocularis, its causative agent, is larger than previously known. This disease has low prevalence and remains underreported in Europe. Emerging clinical data show that diagnostic difficulties are still common. We report on a 76-year old patient suffering from AE lesions restricted to the left lobe of the liver who underwent a curative extended left hemihepatectomy. Prior to the resection a liver biopsy under the suspicion of an atypical malignancy was performed. After the intervention he developed a pseudoaneurysm of the hepatic artery that was successfully coiled. Surprisingly, during surgery, the macroscopic appearance of the tumour revealed a growth pattern that was rather typical for cystic echinococcosis (CE), i.e., a gross tumour composed of multiple large vesicles with several centimeters in diameter. In addition, there were neither extensive adhesions nor infiltrations of the neighboring pancreas and diaphragm as was expected from previous imaging results. The unexpected diagnosis of AE was confirmed by definite histopathology, specific polymerase chain reaction and serology results. This is a rare case of unusual macroscopic presentation of AE that posed immense diagnostic challenges and had an eventful course. To our knowledge this is the first case of an autochthonous infection in this particular geographic area of Germany, the federal state of Saxony. This report may provide new hints for an expanding area of risk for AE and emphasizes the risk of complications in the scope of diagnostic procedures and the limitations of modern radiological imaging.
Baclofen (1) is a potent and selective agonist for bicuculline-insensitive GABAB receptors and is used clinically as an antispastic and muscle relaxant agent. In the search for new bioactive chemical entities that bind specifically to GABAB receptors, we report here the synthesis of certain baclofen homologues, namely (R,S)-5-amino-3-arylpentanoic acid hydrochlorides (R,S)-1a–h as well as (R,S)-5-amino-3-methylpentanoic acid [(RS)-1i] to be evaluated as GABABR agonists. Compound 1a is an agonist to GABAB receptors with an EC50 value of 46 μM on tsA201 cells transfected with GABAB1b/GABAB2/Gqz5, being the most active congener among all the synthesized compounds.