446 research outputs found
Benchmark of the FLUKA model of crystal channeling against the UA9-H8 experiment
AbstractChanneling in bent crystals is increasingly considered as an option for the collimation of high-energy particle beams. The installation of crystals in the LHC has taken place during this past year and aims at demonstrating the feasibility of crystal collimation and a possible cleaning efficiency improvement. The performance of CERN collimation insertions is evaluated with the Monte Carlo code FLUKA, which is capable to simulate energy deposition in collimators as well as beam loss monitor signals. A new model of crystal channeling was developed specifically so that similar simulations can be conducted in the case of crystal-assisted collimation. In this paper, most recent results of this model are brought forward in the framework of a joint activity inside the UA9 collaboration to benchmark the different simulation tools available. The performance of crystal STF 45, produced at INFN Ferrara, was measured at the H8 beamline at CERN in 2010 and serves as the basis to the comparison. Distributions of deflected particles are shown to be in very good agreement with experimental data. Calculated dechanneling lengths and crystal performance in the transition region between amorphous regime and volume reflection are also close to the measured ones
Design optimization of multibody systems by sequential approximation
Abstract. Design optimization of multibody systems is usually established by a direct coupling of multibody system analysis and mathematical programming algorithms. However, a direct coupling is hindered by the transient and computationally complex behavior of many multibody systems. In structural optimization often approximation concepts are used instead to interface numerical analysis and optimization. This paper shows that such an approach is valuable for the optimization of multibody systems as well. A design optimization tool has been developed for multibody systems that generates a sequence of approximate optimization problems. The approach is illustrated by three examples: an impact absorber, a slider-crank mechanism, and a stress-constrained four-bar mechanism. Furthermore, the consequences for an accurate and efficient accompanying design sensitivity analysis are discussed
Synaptic transmission parallels neuromodulation in a central food-intake circuit
NeuromedinU is a potent regulator of food intake and activity in mammals. In Drosophila, neurons producing the homologous neuropeptide hugin regulate feeding and locomotion in a similar manner. Here, we use EM-based reconstruction to generate the entire connectome of hugin-producing neurons in the Drosophila larval CNS. We demonstrate that hugin neurons use synaptic transmission in addition to peptidergic neuromodulation and identify acetylcholine as a key transmitter. Hugin neuropeptide and acetylcholine are both necessary for the regulatory effect on feeding. We further show that subtypes of hugin neurons connect chemosensory to endocrine system by combinations of synaptic and peptide-receptor connections. Targets include endocrine neurons producing DH44, a CRH-like peptide, and insulin-like peptides. Homologs of these peptides are likewise downstream of neuromedinU, revealing striking parallels in flies and mammals. We propose that hugin neurons are part of an ancient physiological control system that has been conserved at functional and molecular level.SFB 645 and 704, DFG Cluster of Excellence ImmunoSensation, DFG grant PA 787, HHMI Janeli
Assessing complex PTSD and PTSD: validation of the German version of the International Trauma Interview (ITI)
Background: With the introduction of the ICD-11 into clinical practice, the reliable distinction between Posttraumatic Stress Disorder (PTSD) and Complex Posttraumatic Stress Disorder (CPTSD) becomes paramount. The semi-structured clinician-administered International Trauma Interview (ITI) aims to close this gap in clinical and research settings.
Objective: This study investigated the psychometric properties of the German version of the ITI among trauma-exposed clinical samples from Switzerland and Germany.
Method: Participants were 143 civilian and 100 military participants, aged M = 40.3 years, of whom 53.5% were male. Indicators of reliability and validity (latent structure, internal reliability, inter-rater agreement, convergent and discriminant validity) were evaluated. Confirmatory factor analysis (CFA) and partial correlation analysis were conducted separately for civilian and military participants.
Results: Prevalence of PTSD was 30% (civilian) and 33% (military) and prevalence of CPTSD was 53% (civilians) and 21% (military). Satisfactory internal consistency and inter-rater agreement were found. In the military sample, a parsimonious first-order six-factor model was preferred over a second-order two-factor CFA model of ITI PTSD and Disturbances in Self-Organization (DSO). Model fit was excellent among military participants but no solution was supported among civilian participants. Overall, convergent validity was supported by positive correlations of ITI PTSD and DSO with DSM-5 PTSD. Discriminant validity for PTSD symptoms was confirmed among civilians but low in the military sample.
Conclusions: The German ITI has shown potential as a clinician-administered diagnostic tool for assessing ICD-11 PTSD and CPTSD in primary care. However, further exploration of its latent structure and discriminant validity are indicated
Comparison of size distribution and (Pro249-Ser258) epitope exposure in in vitro and in vivo derived Tau fibrils
Background: Although several studies demonstrate prion-like properties of Tau fibrils, the effect of size in the seeding capacity of these aggregates is not fully understood. The aim of this study is to characterize Tau seeds by their size and seeding capacity. Methods: Tau aggregates were isolated from postmortem AD brain tissue and separated from low molecular weight species by sucrose gradient ultracentrifugation. Biochemical characterization of the different fractions was done by non-reducing Western blotting and aggregate-specific immuno-assays using in house developed anti-Tau monoclonal antibodies, including PT76 which binds to an epitope close to the microtubule-binding domain and, hence, also to K18. Seeding efficiency was then assessed in HEK293 cells expressing K18 FRET sensors. Results: We observed that upon sonication of Tau aggregates different size-distributed tau aggregates are obtained. In biochemical assays, these forms show higher signals than the non-sonicated material in some aggregation-specific Tau assays. This could be explained by an increased epitope exposure of the smaller aggregates created by the sonication. By analyzing human brain derived and recombinant (K18) Tau aggregates in a cellular FRET assay, it was observed that, in the absence of transfection reagent, sonicated aggregates showed higher aggregation induction. Preparations also showed altered profiles on native PAGE upon sonication and we could further separate different aggregate species based on their molecular weight via sucrose gradients. Conclusions: This study further elucidates the molecular properties regarding relative aggregate size and seeding efficiency of sonicated vs. non-sonicated high molecular weight Tau species. This information will provide a better knowledge on how sonication, a commonly used technique in the field of study of Tau aggregation, impacts the aggregates. In addition, the description of PT76-based aggregation specific assay is a valuable tool to quantify K18 and human AD Tau fibrils
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