Crystal Growth of Complex Intermetallics in Search for Heavy Electron Systems

The structural solution and physical property characterization of several Ln-T-Al/Ga and Ln-T-Al-Si contain phases, which include Ln(Cu,Al)12 (Ln = Y, Ce, Pr, Sm, and Yb), Ln(Ag,Al,Si)2 (Ln = Ce and Gd), LnCu2(Al,Si)5 (Ln = La and Ce), Ln(Cu,Al,Ga)13-x (Ln = La, Ce, Pr, and Eu), α and β LnNiGa4 (α Ln = Y and Gd – Yb; β Ln = (Tb – Er)), and Ln4FeGa12 (Ln = Tb – Er) will be presented in this work with an emphasis on crystal growth. The systems cover a large breadth of phase space and serve to illustrate the new and rich chemistry and physics that remain, to this day, to be discovered in these phase spaces. Additionally, these phases range in complexity, to the eloquently simple open network found in Ln(Ag,Al,Si)2 to the more complex 3 dimensional polyhedral environments of Ln(Cu,Al)12 (Ln = Y, Ce, Pr, Sm, and Yb) or Ln(Cu,Al,Ga)13-x. In all cases these phases were discovered from systematic progressions throughout the periodic table and can all trace their roots to one phase, CePdGa6. Chapter 1 of this document describes the logic and motivation behind the exploration of the Ln-Cu-Al phase space and alludes to some serendipitous discoveries. Additionally, it treats the issues of a failing materials science effort in America as recently outline in a recent National Academies of Science document: Frontiers in Crystalline Matter: From Discovery to Technology. Time is taken to discuss what is needed to once again assume a predominate role in these ventures and how our group aligns itself with the proposed directives Chapters 2 – 5 provide in-depth discussion of selected phases as it relates to their respective crystalline growth, structure, magnetic, and transport properties

High Surface Area Oxidation – Development of an Improved Open Cup ARC Vessel and Validation

PresentationEasily oxidized, low volatility organic liquids absorbed/dispersed on inorganic solid materials such as insulation, absorbents, and molecular sieves can result in spontaneous ignition incidents. This is due to increased rates of oxidation of the organic when it is spread out over the very high surface area inherent in these types of solid materials. Similarly, high surface area organic solids that are either self-reactive or oxidizable may self-heat when accumulated in a pile of sufficient size, resulting in thermal runaways, gas generation, and/or fire. Understanding and quantifying this behavior is critical to identifying hazards and developing appropriate mitigative measures. Previously, an Open Cup Accelerating Rate Calorimeter technique was developed at Dow using an open, stainless steel container, purged with air heated to testing temperatures to maintain adiabaticity. This method has been used for many years to understand the reaction kinetics of “auto-oxidation” reactions and high surface area runaway reactions. While the method has been shown to be reliable and able to accurately predict large scale hazards, the exposure of the gaseous decomposition and oxidation products of the reactions is destructive to the ARC calorimeter. The open-cup system vents directly into the ARC, resulting in accelerated corrosion or potentially exposing the internals to fire. A new ARC container design has been developed that has been demonstrated to produce comparable results and removes the concerns associated with damaging the equipment. The new design of the Open Cup ARC test cell, validation, and discussion of the data application will be included in this article

A Case Study: Autocatalytic Behavior and its Consideration for a Chemical Process with General application to Handling, Shipping, and Reactive Relief Design

PresentationAutocatalysis is a generally well understood phenomenon. However, since autocatalytic molecules do not have a fixed energy release rate for a given temperature, like nth order reactions, additional considerations are required to ensure safe shipping, handling and relief device sizing. Also, unlike nth order reactions, autocatalytic reactions have an induction time and it is associated with reaching a critical concentration of a catalytic species. Once the induction time is exhausted the reaction accelerates even under isothermal conditions (i.e. dT/dt = f (T,Ccat). Often a thermo- kinetic model is required for adequate hazard evaluation. During model development a first order reaction scheme is often used as a starting point. Such an approach typically leads to an unrealistically high apparent activation energy to get a reasonable fit to the data. Since time impacts the reaction rate, induction times need to be determined to build an accurate kinetic model. Once induction times are determined as a function of temperature, adequate layers of protection and operating discipline can be determined for safe handling. This paper describes: 1) Identification and confirmation of autocatalytic behavior, 2) Induction time model development, and 3) Application to storage, shipping, and reactive relief design. For reactive relief vent sizing, consideration is given not only to credible failure scenarios that may result in relief device activation, but also recovery from contained unplanned events

DNA Methylation Signatures of Depressive Symptoms in Middle-aged and Elderly Persons:Meta-analysis of Multiethnic Epigenome-wide Studies

IMPORTANCE Depressive disorders arise from a combination of genetic and environmental risk factors. Epigenetic disruption provides a plausible mechanism through which gene-environment interactions lead to depression. Large-scale, epigenome-wide studies on depression are missing, hampering the identification of potentially modifiable biomarkers.OBJECTIVE To identify epigenetic mechanisms underlying depression in middle-aged and elderly persons, using DNA methylation in blood.DESIGN, SETTING, AND PARTICIPANTS To date, the first cross-ethnic meta-analysis of epigenome-wide association studies (EWAS) within the framework of the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium was conducted. The discovery EWAS included 7948 individuals of European origin from 9 population-based cohorts. Participants who were assessed for both depressive symptoms and whole-blood DNA methylation were included in the study. Results of EWAS were pooled using sample-size weighted meta-analysis. Replication of the top epigenetic sites was performed in 3308 individuals of African American and European origin from 2 population-based cohorts.MAIN OUTCOMES AND MEASURES Whole-blood DNA methylation levels were assayed with Illumina-Infinium Human Methylation 450K BeadChip and depressive symptoms were assessed by questionnaire.RESULTS The discovery cohorts consisted of 7948 individuals (4104 [51.6%] women) with a mean (SD) age of 65.4 (5.8) years. The replication cohort consisted of 3308 individuals (2456 [74.2%) women) with a mean (SD) age of 60.3 (6.4) years. The EWAS identified methylation of 3 CpG sites to be significantly associated with increased depressive symptoms: cg04987734 (P = 1.57 x 10(-)(08); n = 11 256; CDC42BPB gene), cg12325605 (P = 5.24 x 10(-09); n = 11256; ARHGEF3 gene), and an intergenic CpG site cg14023999 (P = 5.99 x 10(-)(08); n = 11256; chromosome = 15q261). The predicted expression of the CDC42BPB gene in the brain (basal ganglia) (effect, 0.14; P = 2.7 x 10(-03)) and of ARHGEF3 in fibroblasts (effect. -0.48; P = 9.8 x 10(-)(04) ) was associated with major depression.CONCLUSIONS AND RELEVANCE This study identifies 3 methylated sites associated with depressive symptoms. All 3 findings point toward axon guidance as the common disrupted pathway in depression. The findings provide new insights into the molecular mechanisms underlying the complex pathophysiology of depression. Further research is warranted to determine the utility of these findings as biomarkers of depression and evaluate any potential role in the pathophysiology of depression and their downstream clinical effects. (C) 2018 American Medical Association. All lights reserved

Crystal growth, structure, and physical properties of Ln 2PdGa 12 (Ln = La, Pr, Nd, and Sm)

Single crystals of Ln 2PdGa 12 (Ln = La, Pr, Nd, Sm) were synthesized with a molten Ga flux. The intermetallic phases are isostructural to Sm 2NiGa 12 with cell dimensions of a ∼ 6.1 and c ∼ 15.5 . Pr 2PdGa 12, Nd 2PdGa 12, and Sm 2PdGa 12 order antiferromagnetically at 18, 7.5, and 7.5 K, respectively, and magnetic properties of single crystals oriented parallel and perpendicular to the magnetic field are presented. Fitting the low temperature heat capacity of Pr 2PdGa 12 gives a Sommerfeld coefficient (γ) of 250 mJ mol -1 K -2 and indicates the possibility of heavy fermion behavior. © Published by Elsevier B.V

Tetramethyl anthracene-2,3,6,7-tetracarboxylate–tetramethyl 9,10-dihydro-9,10-dioxoanthracene-2,3,6,7-tetracarboxylate (1/1)CAS 116896-77-6 and 113431-17-7.

In the title co-crystal, C22H16O10·C22H18O8, the independent tetramethyl 9,10-dihydro-9,10-dioxoanthracene-2,3,6,7-tetracarboxylate, (I), and tetramethyl anthracene-2,3,6,7-tetracarboxylate, (II), components occupy separate crystallographic inversion centers. In (II), the dihedral angles between the mean aromatic plane and the two independent carboxylate planes are 41.32 (10) and −38.35 (10)°. The methylcarboxylate groups of (I) are disordered, with each resolvable into two groups. In the least disordered carboxylate, the apparent angles between the mean aromatic plane and the two partial carboxylate planes [site occupations = 0.510 (3) and 0.490 (3)] are 16.8 (3) and 23.3 (3)°. In the highly disordered group, the apparent angles between the mean aromatic plane and the two partial carboxylate planes [site occupations = 0.510 (3) and 0.490 (3)] are 78.3 (3) and −74.1 (3)°. In addition, this extreme disorder leads to an artificially elongated C(aromatic)—C(carboxyl) bond

Crystal growth, structure, and physical properties of Ln(Ag, Al, Si) 2 (Ln = Ce and Gd)

Single crystals of CeM2 and GdM2 (M = Ag, Al, and Si) were grown by the flux growth technique and characterized by means of single crystal X-ray diffraction, magnetic susceptibility, resistivity, and heat capacity measurements. CeM2 and GdM2 crystallize in the tetragonal I41/amd space group with the α-ThSi2 structure type with lattice parameters a ∼ 4.2 Å and c ∼ 14.4 Å. Curie-Weiss behavior is observed for both analogues with CeM 2 ordering first ferromagnetically at 11 K with a second antiferromagnetic transition at 8.8 K while GdM2 orders antiferromagnetically at 24 K. Heat capacity measurements on CeM2 show two magnetic transitions at 10.8 and 8.8 K with an electronic specific heat coefficient, γ0, of ∼53 mJ K-2 mol-1. The entropy at the magnetic transition is less than the expected R ln 2 for CeM2, reinforcing the assertions of an enhanced mass state and Kondo behavior being observed in the resistivity. © 2010 IOP Publishing Ltd

Crystal growth and properties of Ln2Ag1-xGa 10-y (Ln=La, Ce), a disordered variant of the Ce2NiGa 10-structure type

We report the flux growth and characterization of Ln2Ag 1-xGa10-y (Ln=La, Ce), a disordered variant of the Ce 2NiGa10 structure type. Single crystals of La 2Ag1-xGa10-y (x∼0.3; y∼0.6) and Ce 2Ag1-xGa10-y (x∼0.3; y∼0.9) were grown by the self-flux method and characterized using single-crystal X-ray diffraction. Transport measurements of Ce2Ag1-xGa 10-y (x∼0.3; y∼0.9) reveal metallic behavior with a transition at 3 K. Magnetic measurements indicate antiferromagnetic ordering at 3 K of localized Ce3 moments for Ce2Ag 1-xGa10-y. Magnetoresistance is positive with a maximum value of 16% at 9 T. La2Ag1-xGa10-y exhibits metallic behavior with magnetic susceptibility showing temperature independent paramagnetism. We will compare Ce2Ag1-xGa10-y (x∼0.3; y∼0.9) to Ce2NiGa10 to examine the effects of transition metal substitution and to the related Ce(Ag,Ga)4 phase to examine the effects of crystal structure on the physical properties. © 2010 Elsevier Inc. All rights reserved