Publications by authors named "Christian Lehner"

InSb, a narrow-band III-V semiconductor, is known for its small bandgap, small electron effective mass, high electron mobility, large effective-factor, and strong spin-orbit interactions. These unique properties make InSb interesting for both industrial applications and quantum information processing. In this paper, we provide a review of recent progress in quantum transport research on InSb quantum well devices.

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Article Synopsis
  • Research on brain-computer interaction has advanced significantly, particularly in sight restoration for those who are profoundly blind, by stimulating the occipital cortex to create visual perceptions.
  • Recent innovations have led to the development of microelectrodes that can be implanted onto the brain's surface, with successful trials in animals already conducted.
  • The authors propose a robot-assisted technique to safely and effectively implant microelectrodes in the occipital lobe of blind volunteers, addressing various technical challenges involved in the procedure.
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Spermatozoa in animal species are usually highly elongated cells with a long motile tail attached to a head that contains the haploid genome in a compact and often elongated nucleus. In Drosophila melanogaster, the nucleus is compacted two hundred-fold in volume during spermiogenesis and re-modeled into a needle that is thirty-fold longer than its diameter. Nuclear elongation is preceded by a striking relocalization of nuclear pore complexes (NPCs).

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A change in ambient temperature is predicted to disrupt cellular homeostasis by affecting all cellular processes in an albeit non-uniform manner. Diffusion is generally less temperature-sensitive than enzymes, for example, and each enzyme has a characteristic individual temperature profile. The actual effects of temperature variation on cells are still poorly understood at the molecular level.

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Treatment refractory or recurrent trigeminal neuralgia (TN) is a severe chronic pain illness. Single-session repetitive transcranial magnetic stimulation (rTMS) has been shown to elicit analgesic effects in several craniofacial pain syndromes, including TN. However, the safety and long-term effect of multi-session rTMS for TN have yet to be fully explored.

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For meiosis I, homologous chromosomes must be paired into bivalents. Maintenance of homolog conjunction in bivalents until anaphase I depends on crossovers in canonical meiosis. However, instead of crossovers, an alternative system achieves homolog conjunction during the achiasmate male meiosis of Drosophila melanogaster.

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Meiosis in males of higher dipterans is achiasmate. In their spermatocytes, pairing of homologs into bivalent chromosomes does not include synaptonemal complex and crossover formation. While crossovers preserve homolog conjunction until anaphase I during canonical meiosis, an alternative system is used in dipteran males.

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The bivalent chromosomes that are generated during prophase of meiosis I comprise a pair of homologous chromosomes. Homolog pairing during prophase I must include mechanisms that avoid or eliminate entanglements between non-homologous chromosomes. In Drosophila spermatocytes, non-homologous associations are disrupted by chromosome territory formation, while linkages between homologous chromosomes are maintained by special conjunction proteins.

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Free-space coupling to subwavelength individual optical elements is a central theme in quantum optics, as it allows the control over individual quantum systems. Here we show that, by combining an asymmetric immersion lens setup and a complementary resonating metasurface we are able to perform terahertz time-domain spectroscopy of an individual, strongly subwavelength meta-atom. We unravel the linewidth dependence as a function of the meta-atom number indicating quenching of the superradiant coupling.

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In many species, centromere identity is specified epigenetically by special nucleosomes containing a centromere-specific histone H3 variant, designated as CENP-A in humans and CID in Drosophila melanogaster. After partitioning of centromere-specific nucleosomes onto newly replicated sister centromeres, loading of additional CENP-A/CID into centromeric chromatin is required for centromere maintenance in proliferating cells. Analyses with cultured cells have indicated that transcription of centromeric DNA by RNA polymerase II is required for deposition of new CID into centromere chromatin.

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Background: Temperature change affects the myriad of concurrent cellular processes in a non-uniform, disruptive manner. While endothermic organisms minimize the challenge of ambient temperature variation by keeping the core body temperature constant, cells of many ectothermic species maintain homeostatic function within a considerable temperature range. The cellular mechanisms enabling temperature acclimation in ectotherms are still poorly understood.

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Reduction of genome ploidy from diploid to haploid necessitates stable pairing of homologous chromosomes into bivalents before the start of the first meiotic division. Importantly, this chromosome pairing must avoid interlocking of non-homologous chromosomes. In spermatocytes of Drosophila melanogaster, where homolog pairing does not involve synaptonemal complex formation and crossovers, associations between non-homologous chromosomes are broken up by chromosome territory formation in early spermatocytes.

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Repetitive transcranial stimulation (rTMS) has been shown to produce an analgesic effect and therefore has a potential for treating chronic refractory pain. However, previous studies used various stimulation parameters (including cortical targets), and the best stimulation protocol is not yet identified. The present study investigated the effects of multi-session 20 Hz (2000 pulses) and 5 Hz (1800 pulses) rTMS stimulation of left motor cortex (M1-group) and left dorsolateral prefrontal cortex (DLPFC-group), respectively.

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Objectives: The aim of this retrospective clinical study was to investigate the survival rate, technical and biologic complications of leucite-reinforced glass-ceramic crowns after a follow-up time of 13-15 years.

Material And Methods: Fifty-three patients with 131 crowns were invited to the follow-up visit. The reconstructions were re-examined clinically and radiographically using the modified USPHS criteria and periodontal parameters of probing pocket depth (PPD), plaque index (PI), sulcus bleeding index (SBI).

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Objective: To evaluate the frequency, type and indications of nasal turbinate (NT) resection during endoscopic, anterior skull base surgery and to analyze factors that may have an impact on the need of NT removal.

Methods: In this retrospective cohort study, 306 subjects (150 males and 156 females, mean age 55.4 ± 15.

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Regular chromosome segregation during the first meiotic division requires prior pairing of homologous chromosomes into bivalents. During canonical meiosis, linkage between homologous chromosomes is maintained until late metaphase I by chiasmata resulting from meiotic recombination in combination with distal sister chromatid cohesion. Separase-mediated elimination of cohesin from chromosome arms at the end of metaphase I permits terminalization of chiasmata and homolog segregation to opposite spindle poles during anaphase I.

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Objectives: Long-term retrospective evaluation of the survival rate and the technical and biologic outcomes of all-ceramic inlays and onlays in premolars and molars.

Method And Materials: Fifty-four patients treated as part of a prospective clinical trial and having received 157 inlays and 27 onlays made out of a leucite-reinforced glass-ceramic (IPS Empress) in premolars and molars, were invited to the present follow-up examination. The survival of the restorations was evaluated.

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The first meiotic division reduces genome ploidy. This requires pairing of homologous chromosomes into bivalents that can be bi-oriented within the spindle during prometaphase I. Thereafter, pairing is abolished during late metaphase I, and univalents are segregated apart onto opposite spindle poles during anaphase I.

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Sister kinetochores are connected to the same spindle pole during meiosis I and to opposite poles during meiosis II. The molecular mechanisms controlling the distinct behavior of sister kinetochores during the two meiotic divisions are poorly understood. To study kinetochore behavior during meiosis, we have optimized time lapse imaging with Drosophila spermatocytes, enabling kinetochore tracking with high temporal and spatial resolution through both meiotic divisions.

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Oxygen concentrations vary between tissues of multicellular organisms and change under certain physiological or pathological conditions. Multiple methods have been developed for measuring oxygenation of biological samples and However, most require complex equipment, are laborious and have significant limitations. Here we report that oxygen concentration determines the choice between two maturation pathways of DsRed FT (Timer).

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Cells in ectotherms function normally within an often wide temperature range. As temperature dependence is not uniform across all the distinct biological processes, acclimation presumably requires complex regulation. The molecular mechanisms that cope with the disruptive effects of temperature variation are still poorly understood.

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The terminal differentiation of adult stem cell progeny depends on transcriptional control. A dramatic change in gene expression programs accompanies the transition from proliferating spermatogonia to postmitotic spermatocytes, which prepare for meiosis and subsequent spermiogenesis. More than a thousand spermatocyte-specific genes are transcriptionally activated in early Drosophila spermatocytes.

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Spatially controlled release of sister chromatid cohesion during progression through the meiotic divisions is of paramount importance for error-free chromosome segregation during meiosis. Cohesion is mediated by the cohesin protein complex and cleavage of one of its subunits by the endoprotease separase removes cohesin first from chromosome arms during exit from meiosis I and later from the pericentromeric region during exit from meiosis II. At the onset of the meiotic divisions, cohesin has also been proposed to be present within the centromeric region for the unification of sister centromeres into a single functional entity, allowing bipolar orientation of paired homologs within the meiosis I spindle.

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The analysis of consequences resulting after experimental elimination of gene function has been and will continue to be an extremely successful strategy in biological research. Mutational elimination of gene function has been widely used in the fly Drosophila melanogaster. RNA interference is used extensively as well.

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