Optically induced magnetization dynamics and variation of damping parameter in epitaxial Co2MnSi Heusler alloy films

Copyright © 2010 The American Physical SocietyAll-optical pump-probe measurements of magnetization dynamics have been performed upon epitaxial Co2MnSi(001) Heusler alloy thin films annealed at temperatures of 300, 400, and 450 °C. An ultrafast laser-induced modification of the magnetocrystalline anisotropy triggers precession which is detected by time-resolved magneto-optical Kerr effect measurements. From the damped oscillatory Kerr rotation, the frequency and relaxation rate of the precession is determined. Using a macrospin solution of the Landau-Lifshitz-Gilbert equation the effective fields acting upon the sample magnetization are deduced. This reveals that the magnetization is virtually independent of the annealing temperature while the fourfold magnetocrystalline anisotropy decreases dramatically with increasing annealing temperature as the film structure changes between the B2 and L21 phases. From the measured relaxation rates, the value of the apparent Gilbert damping parameter is found to depend strongly upon the static field strength and in-plane static field orientation. The variation of the apparent damping parameter is generally well reproduced by an inhomogeneous broadening model in which the presence of B2 and L21 phases leads to a large dispersion of the magnetocrystalline anisotropy. However, for the sample annealed at a temperature of 300 °C, the lack of a detailed fit to the data suggests that the apparent anisotropy of the apparent damping parameter might alternatively arise due to a network of dislocations with fourfold symmetry

Characterisation of optical phonons within epitaxial Ge2Sb2Te5/InAs(111) structures

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability; The data that support the findings of this study are available from the corresponding author upon reasonable request.Femto-second pump-probe and micro-Raman spectroscopy (RS) measurements have been made to identify optical phonons in Ge2Sb2Te5/InAs(111) and an InAs(111) substrate. A theory of transient stimulated Raman scattering (TSRS) incorporating the Raman tensor predicts which phonon modes may be observed in transient reflectance (R) and anisotropic reflectance (AR) pump-probe measurements, and how their amplitudes depend upon angles φ and θ that describe the orientation of the pump and probe beam electric fields within the sample plane. AR measurements of an InAs(111) substrate revealed the 6.5 THz transverse optical phonon with amplitude proportional to sin(2(θ−φ)), as expected for both TSRS and the specular optical Kerr effect (SOKE), confirming that TSRS and SOKE are equivalent descriptions of the same phenomenon. The AR responses of Ge2Sb2Te5/InAs(111) revealed a single coherent optical phonon (COP) mode at about 3.4 THz with sin(2(θ−φ)) amplitude variation that confirms the -like character of the mode and hence the underlying cubic structure of the epilayer. This mode was also observed in the R measurement for one sample, with amplitude independent of φ and θ as predicted by TSRS theory. Both R and AR signals were heavily damped, which is attributed to dephasing of , and modes that become non-degenerate due to structural distortions. RS measurements revealed three modes for Ge2Sb2Te5/InAs(111) and three modes for InAs(111). Taken together the TSRS and RS measurements provide rich information about optical phonons in the phase change material Ge2Sb2Te5 and the InAs(111) surface.Engineering and Physical Sciences Research Council (EPSRC

The spatial structure of lithic landscapes : the late holocene record of east-central Argentina as a case study

Fil: Barrientos, Gustavo. División Antropología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Catella, Luciana. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Oliva, Fernando. Centro Estudios Arqueológicos Regionales. Facultad de Humanidades y Artes. Universidad Nacional de Rosario; Argentin

Discovery of common and rare genetic risk variants for colorectal cancer.

To further dissect the genetic architecture of colorectal cancer (CRC), we performed whole-genome sequencing of 1,439 cases and 720 controls, imputed discovered sequence variants and Haplotype Reference Consortium panel variants into genome-wide association study data, and tested for association in 34,869 cases and 29,051 controls. Findings were followed up in an additional 23,262 cases and 38,296 controls. We discovered a strongly protective 0.3% frequency variant signal at CHD1. In a combined meta-analysis of 125,478 individuals, we identified 40 new independent signals at P < 5 × 10-8, bringing the number of known independent signals for CRC to ~100. New signals implicate lower-frequency variants, Krüppel-like factors, Hedgehog signaling, Hippo-YAP signaling, long noncoding RNAs and somatic drivers, and support a role for immune function. Heritability analyses suggest that CRC risk is highly polygenic, and larger, more comprehensive studies enabling rare variant analysis will improve understanding of biology underlying this risk and influence personalized screening strategies and drug development.Goncalo R Abecasis has received compensation from 23andMe and Helix. He is currently an employee of Regeneron Pharmaceuticals. Heather Hampel performs collaborative research with Ambry Genetics, InVitae Genetics, and Myriad Genetic Laboratories, Inc., is on the scientific advisory board for InVitae Genetics and Genome Medical, and has stock in Genome Medical. Rachel Pearlman has participated in collaborative funded research with Myriad Genetics Laboratories and Invitae Genetics but has no financial competitive interest

Identification of 12 new susceptibility loci for different histotypes of epithelial ovarian cancer.

To identify common alleles associated with different histotypes of epithelial ovarian cancer (EOC), we pooled data from multiple genome-wide genotyping projects totaling 25,509 EOC cases and 40,941 controls. We identified nine new susceptibility loci for different EOC histotypes: six for serous EOC histotypes (3q28, 4q32.3, 8q21.11, 10q24.33, 18q11.2 and 22q12.1), two for mucinous EOC (3q22.3 and 9q31.1) and one for endometrioid EOC (5q12.3). We then performed meta-analysis on the results for high-grade serous ovarian cancer with the results from analysis of 31,448 BRCA1 and BRCA2 mutation carriers, including 3,887 mutation carriers with EOC. This identified three additional susceptibility loci at 2q13, 8q24.1 and 12q24.31. Integrated analyses of genes and regulatory biofeatures at each locus predicted candidate susceptibility genes, including OBFC1, a new candidate susceptibility gene for low-grade and borderline serous EOC

Plants in aquatic ecosystems: current trends and future directions

Aquatic plants fulfil a wide range of ecological roles, and make a substantial contribution to the structure, function and service provision of aquatic ecosystems. Given their well-documented importance in aquatic ecosystems, research into aquatic plants continues to blossom. The 14th International Symposium on Aquatic Plants, held in Edinburgh in September 2015, brought together 120 delegates from 28 countries and six continents. This special issue of Hydrobiologia includes a select number of papers on aspects of aquatic plants, covering a wide range of species, systems and issues. In this paper we present an overview of current trends and future directions in aquatic plant research in the early 21st century. Our understanding of aquatic plant biology, the range of scientific issues being addressed and the range of techniques available to researchers have all arguably never been greater; however, substantial challenges exist to the conservation and management of both aquatic plants and the ecosystems in which they are found. The range of countries and continents represented by conference delegates and authors of papers in the special issue illustrate the global relevance of aquatic plant research in the early 21st century but also the many challenges that this burgeoning scientific discipline must address