The Direct Sandwich Composite Molding (D-SCM) Process: Sandwich Manufacturing and Characterization

Sandwich structures benefit from the geometrical stiffening effect due to their high cross-sectional area moment of inertia. Transferred to carbon fiber-reinforced plastic (CFRP) components, the needed amount of carbon fiber (CF) material can be reduced and with it the CO$_{2}$ footprint. The combination of a light foam core with continuous fiber-reinforced face sheets is a suitable material combination for lightweight design. Traditionally, CFRP sandwich structures with a foam core are manufactured in a two-step process by combining a prefabricated foam core with fiber-reinforced face sheets. However, in addition to the reduction in the used CFRP material, manufacturing processes with a high efficiency are needed. The objective of this paper is the sandwich manufacturing and characterization by using the Direct Sandwich Composite Molding (D-SCM) process for the one-step production of CFRP sandwich structures. The D-SCM process utilizes the resulting foaming pressure during the reactive polyurethane (PUR) foam system expansion for the impregnation of the CF-reinforced face sheets. The results of this work show that the production of sandwich structures with the novel D-SCM process strategy is feasible in one single manufacturing step and achieves good impregnation qualities. The foam density and morphology significantly influence the core shear properties and thus the component behavior under a bending load

Extensive Investigations on Radial Crack Formation in Labyrinth Seals of Aircraft Engines

Labyrinth seals are due to their non-contact function and their thermal resistance the state of the art in sealing technology for thermal turbomachinery such as jet engines. The purpose of labyrinth seals is to adjust or minimize the leakage between rotor and stator. However, because of transient flight manoeuvres and the resulting mechanical and thermal loads on the components, contact between rotating and stationary parts cannot be ruled out. The aim of this study is to extend the basic understanding of the mechanisms of hot crack formation in the components of a labyrinth seal during the rubbing process. Previous investigations at the Institute of Thermal Turbomachinery have shown that the thermally induced stress caused in connection with the thermal change of the material properties can lead to formation of the cracks in the seal fin. In order to get a deeper understanding of the complex crack initiation mechanisms, it is necessary to carry out fundamental experiments on simplified geometries. For this purpose, the stress conditions of a loaded labyrinth seal are applied to a cylindrical test specimen. It is fixed on both sides and subjected to thermo-cyclic load. To model a rubbing process of a labyrinth seal, the initial temperature of the cycle corresponds to the operating temperature of the rotor in a jet engine and the final temperature corresponds to the contact temperature during the rubbing process. The temperature change causes stress in the specimen due to the rigid mounting. In literature there are analytical considerations regarding the stress-strain curve in the seal fin and a possible pre-damage of the components by remaining tensile stress after the rubbing process. In this paper, these analytical approaches are compared with the test data. Also a residual tensile strength of the seal fin which is still to be tolerated is worked out depending on the temperature load. The stress reduction during heating is very significant and is considered in detail. Due to the high mechanical and thermal loads, the stress reduction is superimposed by relaxation and plastic deformation. For a separate consideration of these basic effects, FE simulations are carried out. The main findings are that stress and strain in the component depends on both the initial and the final temperature of the specimen. The final rubbing temperature mainly influences the remaining tensile stress. With the thus calculated remaining strength of the seal fin a probable crack formation could be determined. The evaluation of this data contributes significantly to the understanding of hot crack formation in labyrinth seal fins and is therefore the basis for the optimization of the sealing system with regard to robustness against rubbing processes

Neurocan genome-wide psychiatric risk variant affects explicit memory performance and hippocampal function in healthy humans

Alterations of the brain extracellular matrix (ECM) can perturb the structure and function of brain networks like the hippocampus, a key region in human memory that is commonly affected in psychiatric disorders. Here, we investigated the potential effects of a genome‐wide psychiatric risk variant in the NCAN gene encoding the ECM proteoglycan neurocan (rs1064395) on memory performance, hippocampal function and cortical morphology in young, healthy volunteers. We assessed verbal memory performance in two cohorts (N = 572, 302) and found reduced recall performance in risk allele (A) carriers across both cohorts. In 117 participants, we performed functional magnetic resonance imaging using a novelty‐encoding task with visual scenes. Risk allele carriers showed higher false alarm rates during recognition, accompanied by inefficiently increased left hippocampal activation. To assess effects of rs1064395 on brain morphology, we performed voxel‐based morphometry in 420 participants from four independent cohorts and found lower grey matter density in the ventrolateral and rostral prefrontal cortex of risk allele carriers. In silico eQTL analysis revealed that rs1064395 SNP is linked not only to increased prefrontal expression of the NCAN gene itself, but also of the neighbouring HAPLN4 gene, suggesting a more complex effect of the SNP on ECM composition. Our results suggest that the NCAN rs1064395 A allele is associated with lower hippocampus‐dependent memory function, variation of prefrontal cortex structure and ECM composition. Considering the well‐documented hippocampal and prefrontal dysfunction in bipolar disorder and schizophrenia, our results may reflect an intermediate phenotype by which NCAN rs1064395 contributes to disease risk

A comprehensive score reflecting memory-related fMRI activations and deactivations as potential biomarker for neurocognitive aging

Older adults and particularly those at risk for developing dementia typically show a decline in episodic memory performance, which has been associated with altered memory network activity detectable via functional magnetic resonance imaging (fMRI). To quantify the degree of these alterations, a score has been developed as a putative imaging biomarker for successful aging in memory for older adults (Functional Activity Deviations during Encoding, FADE; Düzel et al., Hippocampus, 2011; 21: 803–814). Here, we introduce and validate a more comprehensive version of the FADE score, termed FADE-SAME (Similarity of Activations during Memory Encoding), which differs from the original FADE score by considering not only activations but also deactivations in fMRI contrasts of stimulus novelty and successful encoding, and by taking into account the variance of young adults' activations. We computed both scores for novelty and subsequent memory contrasts in a cohort of 217 healthy adults, including 106 young and 111 older participants, as well as a replication cohort of 117 young subjects. We further tested the stability and generalizability of both scores by controlling for different MR scanners and gender, as well as by using different data sets of young adults as reference samples. Both scores showed robust agegroup-related differences for the subsequent memory contrast, and the FADE-SAME score additionally exhibited age-group-related differences for the novelty contrast. Furthermore, both scores correlate with behavioral measures of cognitive aging, namely memory performance. Taken together, our results suggest that single-value scores of memory-related fMRI responses may constitute promising biomarkers for quantifying neurocognitive aging

CDH12 as a Candidate Gene for Kidney Injury in Posterior Urethral Valve Cases:A Genome-wide Association Study Among Patients with Obstructive Uropathies

Background: Posterior urethral valves (PUVs) and ureteropelvic junction obstruction (UPJO) are congenital obstructive uropathies that may impair kidney development. Objective: To identify genetic variants associated with kidney injury in patients with obstructive uropathy. Design, setting, and participants: We included 487 patients born in 1981 or later who underwent pyeloplasty or valve resection before 18 yr of age in the discovery phase, 102 PUV patients in a first replication phase, and 102 in a second replication phase

Graph Regionalization with Clustering and Partitioning: an Application for Daily Commuting Flows in Albania

The paper presents an original application of the recently proposed spatial data mining method named GraphRECAP on daily commuting flows using 2011 Albanian census data. Its aim is to identify several clusters of Albanian municipalities/communes; propose a classification of the Albanian territory based on daily commuting flows among municipalities/communes. Starting from 373 local units, we first applied a spatial clustering technique without imposing any constraining strategy. Based on the input variables, we obtained 16 clusters. In the second step of our analysis, we impose a set of constraining parameters to identify intermediate areas between the local level (municipality/commune) and the national one. We have defined 12 derived regions (same number as the actual Albanian prefectures but with different geographies). These derived regions are quite different from the traditional ones in terms of both geographical dimensions and boundarie

Dioksini i njihova toksičnost za ljude

The term dioxins usually refers to polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). As 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) has the highest toxic potential, the toxic potentials of other PCDDs and PCDFs are defined in comparison with it. Human exposure to dioxins can be environmental (background), occupational, or accidental pollution. In the human body, dioxins are in part metabolised and eliminated, and the rest is stored in body fat. People vary in their capacity to eliminate TCDD, but it is also dose-dependent; the elimination rate is much faster at higher than lower levels. The liver microsomal P4501A1 enzyme oxygenates lipophilic chemicals such as dioxins. It is encoded by the CYP1A1 gene. Cytosolic aryl hydrocarbon receptor (AhR) mediates their carcinogenic action. It binds to dioxin, translocates to nucleus and together with hydrocarbon nuclear translocator (ARNT) and xenobiotic responsive element (XRE) increases the expression of CYP1A1. Dioxins are classified as known human carcinogens, but they also cause noncancerous effects like atherosclerosis, hypertension, and diabetes. Long-term exposures to dioxins cause disruption of the nervous, immune, reproductive, and endocrine system. Short-term exposure to high levels impairs the liver function and causes chloracne. The most sensitive population to dioxin exposure are the foetuses and infants. A large number of health effects have been documented in the scientific literature, and they all place dioxins among the most toxic chemicals known to man.Dioksini su skupina kemijskih spojeva koji obuhvaćaju poliklorirane dibenzo-dioksine (PCDD) i poliklorirane dibenzo-furane (PCDF). Najveći toksični potencijal (faktor ekvivalentne toksičnosti) ima 2,3,7,8-TCDD, dok su toksični potencijali drugih PCDD i PCDF određeni u odnosu na njega. Izloženost dioksinima može biti izravna: izloženost dioksinima emitiranim u okoliš kao posljedica nesreće, profesionalna izloženost te neizravna, tzv. pozadinska. Nakon ulaska u ljudski organizam dioksini se djelomično metaboliziraju i eliminiraju, a ostatak se pohranjuje u adipozno tkivo. Postoji određena varijabilnost između ljudi u kapacitetu eliminacije TCDD. Eliminacija TCDD ovisna je o dozi – kod veće izloženosti (izloženost višim koncentracijama) brzina eliminacije je viša nego kod manje izloženosti (izloženost nižim koncentracijama). Enzim P4501A1 najvažniji je u oksigenaciji lipofi lnih supstrata poput dioksina. Kodiran je genom CYP1A1. AhR je stanični receptor koji djeluje kao transkripcijski faktor koji posreduje u njihovu karcinogenom učinku. AhR veže dioksin te se premješta u jezgru gdje zajedno s ARNT (engl. aryl hydrocarbon nuclear translocator) i XRE (engl. xenobiotic responsive element), smještenim u promotorskoj regiji gena za CYP1A1, uzrokuje povećani izražaj CYP1A1. Dioksini su karcinogeni spojevi, ali imaju i nekarcinogene učinke poput ateroskleroze, hipertenzije, dijabetesa, poremećaj živčanog, imunosnog, reproduktivnog i endokrinog sustava, posebice kod kronične izloženosti. Akutna izloženost uzrokuje oštećenja jetre i klorakne. Najosjetljivija skupina izloženosti dioksinu je dojenčad u prenatalnom i postnatalnom razdoblju. U znanstvenoj i stručnoj literaturi dokumentirani su brojni zdravstveni učinci kao posljedice izloženosti dioksinima te ih svi ističu kao jedne od najtoksičnijih kemijskih spojeva

Bar-Coded Pyrosequencing Reveals the Responses of PBDE-Degrading Microbial Communities to Electron Donor Amendments

Polybrominated diphenyl ethers (PBDEs) can be reductively degraded by microorganisms under anaerobic conditions. However, little is known about the effect of electron donors on microbial communities involved in PBDEs degradation. Here we employed 454 Titanium pyrosequencing to examine the phylogenetic diversity, composition, structure and dynamics of microbial communities from microcosms under the conditions of different electron donor amendments. The community structures in each of the five alternate electron donor enrichments were significantly shifted in comparison with those of the control microcosm. Commonly existing OTUs between the treatment and control consortia increased from 5 to 17 and more than 50% of OTUs increased around 13.7 to 186 times at least in one of the microcosms after 90-days enrichment. Although the microbial communities at different taxonomic levels were significantly changed by different environmental variable groups in redundancy analysis, significant correlations were observed between the microbial communities and PBDE congener profiles. The lesser-brominated PBDE congeners, tri-BDE congener (BDE-32) and hexa-BDE, were identified as the key factors shaping the microbial community structures at OTU level. Some rare populations, including the known dechlorinating bacterium, Dehalobacter, showed significant positive-correlation with the amounts of PBDE congeners in the consortia. The same results were also observed on some unclassified bacteria. These results suggest that PBDEs-degrading microbial communities can be successfully enriched, and their structures and compositions can be manipulated through adjusting the environmental parameters