ENHANCING MECHANICAL PROPERTIES OF COLD-SPRAYED ALUMINUM COATINGS USING GRAPHENE-NANOPLATELET AND MICRO-BORON-CARBIDE REINFORCEMENTS

This study explores the individual and combined reinforcement effects of graphene nanoplatelets (GNP) and micro-boron carbide (µB4C) in cold-sprayed Al matrix composite coatings. High energy ball milling was used to create compositions of 2 vol.% GNP, 2 vol.% µB4C, and one of 1 vol.% GNP with 1 vol.% µB4C. All reinforced compositions consisted of a total of 2 vol.% reinforcement to compare the effectiveness of single and dual reinforcement and not the amount of total reinforcement. Coatings were heat treated for 1 h at 400◦C to improve coating densification. Each coating was evaluated using microhardness tests, nanoindentation, dry-sliding wear tests, and adhesion tests. The coatings were also qualitatively evaluated using optical and scanning electron microscopy. All three reinforced coatings experienced a greater than 47% increase in microhardness after heat treatment than the control Al coating. Adhesion testing revealed that 2 vol.% µB4C and the dual-particle coatings had a 40% and 29% increase in adhesion strength, respectively. Most notably, nanoindentation showed that the dual-particle coating experienced a 17% increase in hardness and a 13% increase in elastic modulus compared to the unreinforced coating. The singly reinforced coatings either had the same or lower hardness and elastic modulus than the unreinforced coating.ONR, Washington DC, 22217Outstanding ThesisEnsign, United States NavyApproved for public release. Distribution is unlimited

In vitro and in vivo analysis of the effects of dehydroepiandrosterone on metabolic and vascular risk

DHEA is an adrenal derived hormone with a unique secretory pattern with highest serum concentrations observed in middle age. Individuals with adrenal insufficiency exhibit gross DHEA deficiency though its replacement in this context is not commonplace. DHEA is known to behave as a pro-hormone with the ability to be converted into either androgenic or oestrogenic terminal hormones whether this is its sole physiological role still remains unclear. Various animal and in vitro studies have suggested that treatment with DHEA can precipitate improvements in body fat, adipocytokine profiles, insulin resistance and estimates of vascular disease. Human studies have demonstrated inconsistent results and have tended to focus on the physiological deficiency of DHEA associated with normal aging and not the pathological DHEA deficiency seen in adrenal insufficiency. The aims of this thesis were: (1) To determine the effect of DHEA on preadipocyte (cell line and primary) proliferation and differentiation and to examine the mechanisms behind any observed effects. (2) To evaluate the effect of replacing DHEA on vascular function and body composition in subjects with primary and secondary adrenal insufficiency. (1) DHEA inhibited proliferation in all preadipocytes examined secondary, at least in part, to cell cycle blockade. DHEA inhibited adipogenesis in omental but not subcutaneous derived preadiocytes. (2) Arterial stiffness and endothelial function was not affected the total population but stratification by study group showed that DHEA replacement reduced central blood pressure in patients with secondary adrenal insufficiency. Body composition was not affected in either subject group.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

In vitro and in vivo analysis of the effects of dehydroepiandrosterone on metabolic and vascular risk

DHEA is an adrenal derived hormone with a unique secretory pattern with highest serum concentrations observed in middle age. Individuals with adrenal insufficiency exhibit gross DHEA deficiency though its replacement in this context is not commonplace. DHEA is known to behave as a pro-hormone with the ability to be converted into either androgenic or oestrogenic terminal hormones whether this is its sole physiological role still remains unclear. Various animal and in vitro studies have suggested that treatment with DHEA can precipitate improvements in body fat, adipocytokine profiles, insulin resistance and estimates of vascular disease. Human studies have demonstrated inconsistent results and have tended to focus on the physiological deficiency of DHEA associated with normal aging and not the pathological DHEA deficiency seen in adrenal insufficiency. The aims of this thesis were: (1) To determine the effect of DHEA on preadipocyte (cell line and primary) proliferation and differentiation and to examine the mechanisms behind any observed effects. (2) To evaluate the effect of replacing DHEA on vascular function and body composition in subjects with primary and secondary adrenal insufficiency. (1) DHEA inhibited proliferation in all preadipocytes examined secondary, at least in part, to cell cycle blockade. DHEA inhibited adipogenesis in omental but not subcutaneous derived preadiocytes. (2) Arterial stiffness and endothelial function was not affected the total population but stratification by study group showed that DHEA replacement reduced central blood pressure in patients with secondary adrenal insufficiency. Body composition was not affected in either subject group

Presynaptic CRF1 Receptors Mediate the Ethanol Enhancement of GABAergic Transmission in the Mouse Central Amygdala

Corticotropin-releasing factor (CRF) is a 41-amino-acid neuropeptide involved in stress responses initiated from several brain areas, including the amygdala formation. Research shows a strong relationship between stress, brain CRF, and excessive alcohol consumption. Behavioral studies suggest that the central amygdala (CeA) is significantly involved in alcohol reward and dependence. We recently reported that the ethanol augmentation of GABAergic synaptic transmission in rat CeA involves CRF1 receptors, because both CRF and ethanol significantly enhanced the amplitude of evoked GABAergic inhibitory postsynaptic currents (IPSCs) in CeA neurons from wild-type (WT) and CRF2 knockout (KO) mice, but not in neurons of CRF1 KO mice. The present study extends these findings using selective CRF receptor ligands, gene KO models, and miniature IPSC (mIPSC) analysis to assess further a presynaptic role for the CRF receptors in mediating ethanol effects in the CeA. In whole-cell patch recordings of pharmacologically isolated GABAAergic IPSCs from slices of mouse CeA, both CRF and ethanol augmented evoked IPSCs in a concentration-dependent manner, with low EC50s. A CRF1 (but not CRF2) KO construct and the CRF1-selective nonpeptide antagonist NIH-3 (LWH-63) blocked the augmenting effect of both CRF and ethanol on evoked IPSCs. Furthermore, the new selective CRF1 agonist stressin1, but not the CRF2 agonist urocortin 3, also increased evoked IPSC amplitudes. Both CRF and ethanol decreased paired-pulse facilitation (PPF) of evoked IPSCs and significantly enhanced the frequency, but not the amplitude, of spontaneous miniature GABAergic mIPSCs in CeA neurons of WT mice, suggesting a presynaptic site of action. The PPF effect of ethanol was abolished in CeA neurons of CRF1 KO mice. The CRF1 antagonist NIH-3 blocked the CRF- and ethanol-induced enhancement of mIPSC frequency in CeA neurons. These data indicate that presynaptic CRF1 receptors play a critical role in permitting or mediating ethanol enhancement of GABAergic synaptic transmission in CeA, via increased vesicular GABA release, and thus may be a rational target for the treatment of alcohol abuse and alcoholism

Late Cretaceous-Early Eocene tectonic development of the Tethyan suture zone in the Erzincan area, Eastern Pontides, Turkey

Six individual tectonostratigraphic units are identified within the Izmir-Ankara-Erzincan Suture Zone in the critical Erzincan area of the Eastern Pontides. The Ayikayasi Formation of Campanian-Maastrichtian age is composed of bedded pelagic limestones intercalated with polymict, massive conglomerates. The Ayikayasi Formation conformably overlies the Tauride passive margin sequence in the Munzur Mountains to the south and is interpreted as an underfilled foredeep basin. The Refahiye Complex, of possible Late Cretaceous age, is a partial ophiolite composed of similar to 75 % (by volume) serpentinized peridotite (mainly harzburgite), similar to 20 % diabase and minor amounts of gabbro and plagiogranite. The complex is interpreted as oceanic lithosphere that formed by spreading above a subduction zone. Unusual screens of metamorphic rocks (e.g. marble and schist) locally Occur between sheeted diabase dykes. The Upper Cretaceous Karayaprak Melange exhibits two lithological associations: (1) the basalt + radiolarite + serpentinite association, including depleted arc-type basalts; (2) the massive neritic limestone + lava + volcaniclastic association that includes fractionated, intermediate-composition lavas, and is interpreted as accreted Neotethyan seamount(s). The several-kilometre-thick Karadag Formation, of Campanian-Maastrichtian age, is composed of greenschist-facies volcanogenic rocks of mainly basaltic to andesitic composition, and is interpreted as an emplaced Upper Cretaceous volcanic arc. The Campanian-Early Eocene Sutpinar Formation (similar to 1500 m thick) is a coarsening-Upward succession of turbiditic calcarenite, sandstone, laminated mudrock, volcaniclastic sedimentary rocks that includes rare andesitic lava, and is interpreted as a regressive forearc basin. The Late Paleocene-Eocene Sipikor Formation is a laterally varied succession of shallow-marine carbonate and siliciclastic lithofacies that overlies deformed Upper Cretaceous units with an angular unconformity. Structural study indicates that the assembled accretionary prism, supra-subduction zone-type oceanic lithosphere and volcanic are units were emplaced northwards onto the Eurasian margin and also southwards onto the Tauride (Gondwana-related) margin during Campanian-Maastrichtian time. Further, mainly southward thrusting took place during the Eocene in this area, related to final closure of Tethys. Our preferred tectonic model involves northward subduction, supra-subduction zone ophiolite genesis and arc magmatism near the northerly, Eurasian margin of the Mesozoic Tethys

Effect of interchain coupling on conducting polymer luminescence: excimers in derivatives of poly(phenylene vinylene)

Optical excitation of a chain in a polymer film may result in formation of an excimer, a superposition of on-chain excitons and charge-transfer excitons on the originally excited chain and a neighboring chain. The excimer emission is red-shifted compared to that of an on-chain exciton by an amount depending on the interchain coupling $t_\perp$. Setting up the excimer wavefunction and calculating the red shift, we determine average $t_\perp$ values, referred to a monomer, of 0.52 eV and 0.16 eV for poly(2,5-hexyloxy $p$-phenylene cyanovinylene), CN-PPV, and poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1, 4 p-phenylene vinylene], MEH-PPV, respectively, and use them to determine the effect of interchain distance on the emission.Comment: 10 pages, RevTeX, 1 PS figure, replaced version of cond-mat/9707095, accepted for publication in Phys. Rev. B, Rapid Communicatio

Development of Alcohol Use Disorder as a Function of Age, Severity, and Comorbidity with Externalizing and Internalizing Disorders in a Young Adult Cohort

Background: As part of the ongoing Collaborative Study of the Genetics of Alcoholism, we performed a longitudinal study of a high risk cohort of adolescents/young adults from families with a proband with an alcohol use disorder, along with a comparison group of age-matched controls. The intent was to compare the development of alcohol problems in subjects at risk with and without comorbid externalizing and internalizing psychiatric disorders. Methods: Subjects (N = 3286) were assessed with a structured psychiatric interview at 2 year intervals over 10 years (2004–2017). The age range at baseline was 12–21. Results: Subjects with externalizing disorders (with or without accompanying internalizing disorders) were at increased risk for the onset of an alcohol use disorder during the observation period. Subjects with internalizing disorders were at greater risk than those without comorbid disorders for onset of a moderate or severe alcohol use disorder. The statistical effect of comorbid disorders was greater in subjects with more severe alcohol use disorders. The developmental trajectory of drinking milestones and alcohol use disorders was also accelerated in those with more severe disorders. Conclusions: These results may be useful for counseling of subjects at risk who present for clinical care, especially those subjects manifesting externalizing and internalizing disorders in the context of a positive family history of an alcohol use disorder. We confirm and extend findings that drinking problems in subjects at greatest risk will begin in early adolescence

Does age matter? The impact of rodent age on study outcomes

Rodent models produce data which underpin biomedical research and non-clinical drug trials, but translation from rodents into successful clinical outcomes is often lacking. There is a growing body of evidence showing that improving experimental design is key to improving the predictive nature of rodent studies and reducing the number of animals used in research. Age, one important factor in experimental design, is often poorly reported and can be overlooked. The authors conducted a survey to assess the age used for a range of models, and the reasoning for age choice. From 297 respondents providing 611 responses, researchers reported using rodents most often in the 6–20 week age range regardless of the biology being studied. The age referred to as ‘adult’ by respondents varied between six and 20 weeks. Practical reasons for the choice of rodent age were frequently given, with increased cost associated with using older animals and maintenance of historical data comparability being two important limiting factors. These results highlight that choice of age is inconsistent across the research community and often not based on the development or cellular ageing of the system being studied. This could potentially result in decreased scientific validity and increased experimental variability. In some cases the use of older animals may be beneficial. Increased scientific rigour in the choice of the age of rodent may increase the translation of rodent models to humans