Inverted Sugar: Generalized Ray Tracing Algorithm

Though particular algorithms utilizing Snell’s Law effectively describe most ray tracing, issues arise with infrasound applications, particularly in understanding waveguides. A more generalized differential equation derived from Fermat’s principle of least time and general functions may provide a computational solution to coupling ray tracing with wavelength related issues. However, due to its complexity, this differential equation deserves its own experimentation to confirm or deny its effectiveness. In this experiment, a gradient of index of refraction established by the diffusion of sugar emulated an atmospheric temperature inversion (hence “Inverted Sugar”) and comparison of actual rays to computer generated rays in the same gradient confirmed the accuracy of this algorithm

Complex field reversal dynamics in nanomagnetic systems

Nanomagnetic materials, built from thin, patterned films of ferromagnetic materials, began as analogues to frustrated magnetism. Their low energy of operation and emergent properties make them strong candidates for physics based devices. A recent model of how nanomagnetic domains flip, the Glauber mean-field model, is used here to understand how systems of nanomagnets evolve when opposed by external field. This reversal can be expressed in an analytical form in the case of one-dimensional chains and trees at zero temperature, where the cascade of spin flips gives rise to harmonic power spectra. The same cascades in two and three dimensions form fractal field reversal clusters whose shape depends on the strength of the field and the tuning of interactions between nanomagnets.Comment: 10 page

From Vertices to Vortices in magnetic nanoislands

Recent studies in magnetic nanolithography show that a variety of complex magnetic states emerge as a function of a single magnetic island's aspect ratio. We propose a model which, in addition to fitting experiments, predicts magnetic states with continuous symmetry at particular aspect ratios and reveals a duality between vortex and vertex states. Our model then opens new means of engineering novel types of artificial spin systems, and their application to complex magnetic textures in devices and computing.Comment: 3 pages + epsilon + 18 supplementary materia

Magnetic Charge Propagation upon a 3D Artificial Spin-ice

Magnetic charge propagation in bulk frustrated materials has yielded a paradigm-shift in science, allowing the symmetry between electricity and magnetism to be studied. Recent work is now suggesting magnetic charge dynamics upon the spin-ice surface may have important implications in determining the ordering and associated phase space. Here we detail a 3D artificial spin-ice, a 3D nanostructured array of magnetic islands which captures the exact geometry of bulk systems, allowing field-driven dynamics of magnetic charge to be directly visualized upon the surface. Using magnetic microscopy, we observe vastly different magnetic charge dynamics along two principle directions. These striking differences are found to be due to the surface-termination and associated coordination which yields different energetics and interaction strengths for magnetic charges upon the surface

Hydrogel-Based Additive Manufacturing of Lithium Cobalt Oxide

3D multicomponent metal oxides with complex architectures can enable previously impossible energy storage devices, particularly lithium‐ion battery (LIB) electrodes with fully controllable form factors. Existing additive manufacturing approaches for fabricating 3D multicomponent metal oxides rely on particle‐based or organic–inorganic binders, which are limited in their resolution and chemical composition, respectively. In this work, aqueous metal salt solutions are used as metal precursors to circumvent these limitations, and provide a platform for 3D printing multicomponent metal oxides. As a proof‐of‐concept, architected lithium cobalt oxide (LCO) structures are fabricated by first synthesizing a homogenous lithium and cobalt nitrate aqueous photoresin, and then using it with digital light processing printing to obtain lithium and cobalt ion containing hydrogels. The 3D hydrogels are calcined to obtain micro‐porous self‐similar LCO architectures with a resolution of ≈100 µm. These free‐standing, binder‐ and conductive additive‐free LCO structures are integrated as cathodes into LIBs, and exhibit electrochemical capacity retention of 76% over 100 cycles at C/10. This facile approach to fabricating 3D LCO structures can be extended to other materials by tailoring the identity and stoichiometry of the metal salt solutions used, providing a versatile method for the fabrication of multicomponent metal oxides with complex 3D architectures

Defining alcohol-related phenotypes in humans. The Collaborative Study on the Genetics of Alcoholism.

Alcoholism is a disease that runs in families and results at least in part from genetic risk factors. The Collaborative Study on the Genetics of Alcoholism (COGA) is a Federally funded effort to identify and characterize those genetic factors. The study involves more than 1,000 alcoholic subjects and their families, with researchers conducting comprehensive psychological, physiological, electrophysiological, and genetic analyses of the participants. These analyses have identified several traits, or phenotypes, that appear to be genetically determined, such as the presence of alcohol dependence, the level of response to alcohol, the presence of coexisting depression, or the maximum number of drinks a person consumes per occasion. Genetic analyses have identified regions on several chromosomes that are associated with these phenotypes and need to be studied further

Supplementing High-Density SNP Microarrays for Additional Coverage of Disease-Related Genes: Addiction as a Paradigm

Commercial SNP microarrays now provide comprehensive and affordable coverage of the human genome. However, some diseases have biologically relevant genomic regions that may require additional coverage. Addiction, for example, is thought to be influenced by complex interactions among many relevant genes and pathways. We have assembled a list of 486 biologically relevant genes nominated by a panel of experts on addiction. We then added 424 genes that showed evidence of association with addiction phenotypes through mouse QTL mappings and gene co-expression analysis. We demonstrate that there are a substantial number of SNPs in these genes that are not well represented by commercial SNP platforms. We address this problem by introducing a publicly available SNP database for addiction. The database is annotated using numeric prioritization scores indicating the extent of biological relevance. The scores incorporate a number of factors such as SNP/gene functional properties (including synonymy and promoter regions), data from mouse systems genetics and measures of human/mouse evolutionary conservation. We then used HapMap genotyping data to determine if a SNP is tagged by a commercial microarray through linkage disequilibrium. This combination of biological prioritization scores and LD tagging annotation will enable addiction researchers to supplement commercial SNP microarrays to ensure comprehensive coverage of biologically relevant regions

ANKK1, TTC12, and NCAM1 polymorphisms and heroin dependence: importance of considering drug exposure

Context: The genetic contribution to liability for opioid dependence is well established; identification of the responsible genes has proved challenging. Objective: To examine association of 1430 candidate gene single-nucleotide polymorphisms (SNPs)with heroin dependence, reporting here only the 71 SNPs in the chromosome 11 gene cluster (NCAM1, TTC12, ANKK1, DRD2) that include the strongest observed associations. Design: Case-control genetic association study that included 2 control groups (lacking an established optimal control group). Setting: Semistructured psychiatric interviews. Participants: A total of 1459 Australian cases ascertained from opioid replacement therapy clinics, 531 neighborhood controls ascertained from economically disadvantaged areas near opioid replacement therapy clinics, and 1495 unrelated Australian Twin Registry controls not dependent on alcohol or illicit drugs selected from a twin and family sample. Main Outcome Measure: Lifetime heroin dependence. Results: Comparison of cases with Australian Twin Registry controls found minimal evidence of association for all chromosome 11 cluster SNPs (P≥.01); a similar comparison with neighborhood controls revealed greater differences (P≥1.8×10-4). Comparing cases (n=1459) with the subgroup of neighborhood controls not dependent on illicit drugs (n=340), 3 SNPs were significantly associated (correcting for multiple testing): ANKK1 SNP rs877138 (most strongly associated; odds ratio=1.59; 95% CI, 1.32-1.92; P=9.7×10-7), ANKK1 SNP rs4938013, and TTC12 SNP rs7130431. A similar pattern of association was observed when comparing illicit drug-dependent (n=191) and nondependent (n=340) neighborhood controls, suggesting that liability likely extends to nonopioid illicit drug dependence. Aggregate heroin dependence risk associated with 2 SNPs, rs877138 and rs4492854 (located in NCAM1), varied more than 4-fold (P=2.7×10-9 for the risk-associated linear trend). Conclusions: Our results provide further evidence of association for chromosome 11 gene cluster SNPs with substance dependence, including extension of liability to illicit drug dependence. Our findings highlight the necessity of considering drug exposure history when selecting control groups for genetic investigations of illicit drug dependence