Novel genetic loci underlying human intracranial volume identified through genome-wide association

Intracranial volume reflects the maximally attained brain size during development, and remains stable with loss of tissue in late life. It is highly heritable, but the underlying genes remain largely undetermined. In a genome-wide association study of 32,438 adults, we discovered five novel loci for intracranial volume and confirmed two known signals. Four of the loci are also associated with adult human stature, but these remained associated with intracranial volume after adjusting for height. We found a high genetic correlation with child head circumference (ρgenetic=0.748), which indicated a similar genetic background and allowed for the identification of four additional loci through meta-analysis (Ncombined = 37,345). Variants for intracranial volume were also related to childhood and adult cognitive function, Parkinson’s disease, and enriched near genes involved in growth pathways including PI3K–AKT signaling. These findings identify biological underpinnings of intracranial volume and provide genetic support for theories on brain reserve and brain overgrowth

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg =-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness

Synthesis and Reactivity of Zn–Biphenyl Metal–Organic Frameworks, Introducing a Diphenylphosphino Functional Group

Structural features, synthesis, and reactivity of Zn–biphenyl metal–organic frameworks with MOF-5 topology are presented to show the chemical flexibility of such materials and to demonstrate the challenges that can be encountered and solved to avoid interpenetration. We introduce the synthesis of a Zn–biphenyl MOF with diphenylphosphino functionalization and illustrate its structural and chemical properties

Effect of ammonia on the decomposition of ammonium formate over Au/TiO2 under oxidizing conditions relevant to SCR: Enhancement of formic acid decomposition rate and CO2 production

Ammonium formate (AmFo) and formic acid decomposition were carried out in the presence of excess O-2 and H2O over 0.5 wt%Au/TiO2 anatase monolithic catalysts using various contact times and temperatures between 160 degrees C and 300 degrees C, under spray conditions in a dedicated setup. A systematic investigation of ammonia influence on formic acid decomposition revealed a highly beneficial influence on the reaction rate and the CO2 yield in the temperature range 160-300 degrees C. Ammonia oxidation did not occur at any of the studied temperatures and space velocities. Both AmFo and a stoichiometric ammonia formic acid mixture exhibited identical homogeneous gas phase as well as heterogeneous catalytic decomposition behavior. With the introduction of ammonia at a concentration of only 0.25 molar equivalents, the pseudo-first-order rate constants for formic acid decomposition experienced close to 110% and 15% increase at 160 degrees C and 260 degrees C, respectively and dosing 12 molar equivalents of ammonia in the gas phase, the rate constants underwent nearly 8-fold increase at 160 degrees C, while at 260 degrees C, only two times increase was achieved. Increasing the ammonia to formic acid molar ratio from 0 to 12 lead to a steep increase in the CO2 yield from 18% to 75% at 160 degrees C, while a relatively smaller rise from 60% to 75% was observed at 260 degrees C. Activity testing of bare titania revealed an inhibitory effect of ammonia on formic acid decomposition to CO. Overall, it can be concluded that the presence of gold is critical for the realization of such an ammonia-induced enhancement of rate and CO2 yield. The obtained results are relevant for the application of formate-based ammonia precursor compounds in the selective catalytic reduction of NOx in Diesel exhaust gases. (C) 2014 Elsevier B.V. All rights reserved

Water-assisted oxygen activation during gold-catalyzed formic acid decomposition under SCR-relevant conditions

Owing to the problems associated with the use of urea as an ammonia precursor compound in the selective catalytic reduction process in automobiles, alternative compounds such as ammonium formate, methanamide, and guanidinium formate have been suggested as more efficient and cleaner candidates. For the application of such formate-based ammonia precursors, a fundamental understanding of catalytic formic acid decomposition in the presence of the diesel exhaust components water and oxygen is required. Oxygen activation is a reaction step common to many catalytic processes. We observed that oxygen activation over titania and base-modified titania-supported gold catalysts is greatly enhanced in the presence of water, resulting in a significant increase in carbon dioxide production from the decomposition of formic acid. Unlike the supports, gold catalyzed the selective production of carbon dioxide. Monodentate and bidentate formates are the kinetically relevant surface species for carbon monoxide and carbon dioxide production, respectively. The support acts as a reservoir, storing bidentate formates that do not react in the steady state when formic acid and oxygen (and water) are co-fed. However, during transient experiments, when the feed is switched from formic acid to oxygen (and water), they are reactivated upon reverse spillover to the active site associated with gold, where they decompose to carbon dioxide. In the presence of oxygen and water, carbon monoxide oxidation and the water gas shift reaction do not produce carbon dioxide. Instead, a direct oxidative-dehydrogenation-type pathway proceeds, which strongly differs from stoichiometric formic acid decomposition. A kinetically consistent mechanism is proposed in which the hydroperoxy species facilitate the C-H bond cleavage of formates to release carbon dioxide and water in the rate-determining step. (C) 2017 Elsevier Inc. All rights reserved

Ammonium formate decomposition over Au/TiO2: a unique case of preferential selectivity against NH3 oxidation

The unique selectivity of Au/TiO2 for converting ammonium formate to CO2 in the presence of excess O2 and H2O without oxidising NH3 up to 300 °C is reported. The catalyst is highly stable and selective even after severe hydrothermal aging

Thermal degradation of defective high-surface-area UiO-66 in different gaseous environments

UiO-66 is a versatile zirconium-based MOF, which is thermally stable up to 500 °C. In the present work, the thermal degradation of UiO-66 with a high number of defects has been studied in inert, oxidative and reductive environments. A sample of UiO-66 with a high BET surface area of 1827 m2 g−1 was prepared, which contains 2.3 missing linkers per hexa-zirconium node, as calculated by the thermogravimetric curve. The crystalline framework of this UiO-66 sample collapses at 250 °C, while thermal decomposition starts at 450 °C in the oxidative environment and at 500 °C in the reductive and inert environments. The BET surface area of the MOF is affected variably by heating under different gaseous conditions. Under inert conditions, porosity is maintained up to 711 m2 g−1, which is quite high when compared to that under reductive (527 m2 g−1) or oxidative (489 m2 g−1) conditions. Upon complete thermal decomposition at 600 °C, the MOF produces predominantly tetragonal zirconia. TEM images of the thermally decomposed samples show that the shape of the original MOF crystal is maintained during the heating process in the inert and reductive environments, whereas under oxidative conditions, all of the carbon is burnt to carbon dioxide, leaving no carbon matrix as the support.ISSN:2046-206

Promotion of Ammonium Formate and Formic Acid Decomposition over Au/TiO2 by Support Basicity under SCR-Relevant Conditions

This work demonstrates the rational design of a dedicated hydrolysis catalyst for application in the selective catalytic reduction (SCR) of NOx. Modification of titania by lanthanum prior to gold deposition entailed highly improved catalytic activities for ammonium formate (AmFo) and formic acid decomposition under SCR-relevant conditions stemming from dual phenomena: particle size effect and base effect. Smaller gold particles were stabilized, and there was higher uptake of CO2 and formic acid, as demonstrated by HAADF-STEM and in situ DRIFT analyses, respectively. The difference in the activities between the lanthanum-modified, unmodified, and tungsten-modified catalysts was implicitly dictated by the formic acid coverage, which was in turn greatly increased in the presence of base. In situ DRIFT studies under reaction conditions identified formate as a relevant reaction intermediate, under reaction conditions. Higher E-a,E-app alongside a higher pre-exponential factor (A), describe an underlying compensation effect originating from the contribution of enthalpy associated with the desorption of the strongly adsorbed formate, which is consistent with the highly negative formic acid orders observed in the case of the lanthanum-modified catalysts. Gold is essential to achieve selectivity to CO2; its absence yields CO. The introduction of lanthanum to the catalytic system preferentially promoted the CO2 formation mechanism, enabling complete decomposition of formic acid selectively to CO2 at significantly lower gold loading and lower contact times, making it a promising candidate for decomposition of formate-based ammonia precursors in the SCR process

Palladium Catalysts for Methane Oxidation: Old Materials, New Challenges

ISSN:0001-4842ISSN:1520-489