42 research outputs found
Periodic Variation of Stress in Sputter Deposited Si/WSi2 Multilayers
A tension increment after sputter deposition of 1 nm of WSi2 onto sputtered
Si was observed at low Ar gas pressures. Wafer curvature data on multilayers
were found to have a periodic variation corresponding to the multilayer period,
and this permitted statistical analyses to improve the sensitivity to small
stresses. The observation of tension instead of compression in the initial
stage of growth is new and a model invoking surface rearrangement is invoked.
The data also bear on an unusual surface smoothing phenomena for sputtered Si
surfaces caused by the sputter deposition of WSi2 . We furthermore report that
for low Ar pressures the Si layers are the predominant source of built-up
stress
Pressure-dependent transition from atoms to nanoparticles in magnetron sputtering: Effect on WSi2 film roughness and stress
We report on the transition between two regimes from several-atom clusters to
much larger nanoparticles in Ar magnetron sputter deposition of WSi2, and the
effect of nanoparticles on the properties of amorphous thin films and
multilayers. Sputter deposition of thin films is monitored by in situ x-ray
scattering, including x-ray reflectivity and grazing incidence small angle
x-ray scattering. The results show an abrupt transition at an Ar background
pressure Pc; the transition is associated with the threshold for energetic
particle thermalization, which is known to scale as the product of the Ar
pressure and the working distance between the magnetron source and the
substrate surface. Below Pc smooth films are produced, while above Pc roughness
increases abruptly, consistent with a model in which particles aggregate in the
deposition flux before reaching the growth surface. The results from WSi2 films
are correlated with in situ measurement of stress in WSi2/Si multilayers, which
exhibits a corresponding transition from compressive to tensile stress at Pc.
The tensile stress is attributed to coalescence of nanoparticles and the
elimination of nano-voids.Comment: 16 pages, 10 figures; v3: published versio
Recommended from our members
Allelic Expression of Deleterious Protein-Coding Variants across Human Tissues
Personal exome and genome sequencing provides access to loss-of-function and rare deleterious alleles whose interpretation is expected to provide insight into individual disease burden. However, for each allele, accurate interpretation of its effect will depend on both its penetrance and the trait's expressivity. In this regard, an important factor that can modify the effect of a pathogenic coding allele is its level of expression; a factor which itself characteristically changes across tissues. To better inform the degree to which pathogenic alleles can be modified by expression level across multiple tissues, we have conducted exome, RNA and deep, targeted allele-specific expression (ASE) sequencing in ten tissues obtained from a single individual. By combining such data, we report the impact of rare and common loss-of-function variants on allelic expression exposing stronger allelic bias for rare stop-gain variants and informing the extent to which rare deleterious coding alleles are consistently expressed across tissues. This study demonstrates the potential importance of transcriptome data to the interpretation of pathogenic protein-coding variants
Centers For Mendelian Genomics: a Decade of Facilitating Gene Discovery
PURPOSE: Mendelian disease genomic research has undergone a massive transformation over the past decade. With increasing availability of exome and genome sequencing, the role of Mendelian research has expanded beyond data collection, sequencing, and analysis to worldwide data sharing and collaboration.
METHODS: Over the past 10 years, the National Institutes of Health-supported Centers for Mendelian Genomics (CMGs) have played a major role in this research and clinical evolution.
RESULTS: We highlight the cumulative gene discoveries facilitated by the program, biomedical research leveraged by the approach, and the larger impact on the research community. Beyond generating a list of gene-phenotype relationships and participating in widespread data sharing, the CMGs have created resources, tools, and training for the larger community to foster understanding of genes and genome variation. The CMGs have participated in a wide range of data sharing activities, including deposition of all eligible CMG data into the Analysis, Visualization, and Informatics Lab-space (AnVIL), sharing candidate genes through the Matchmaker Exchange and the CMG website, and sharing variants in Genotypes to Mendelian Phenotypes (Geno2MP) and VariantMatcher.
CONCLUSION: The work is far from complete; strengthening communication between research and clinical realms, continued development and sharing of knowledge and tools, and improving access to richly characterized data sets are all required to diagnose the remaining molecularly undiagnosed patients
Can Inoculation Withstand Multiple Attacks?: An Examination of the Effectiveness of the Inoculation Strategy Compared to the Supportive and Restoration Strategies
This investigation introduced multiple competitive attacks in order to assess the effectiveness of inoculation treatments in protecting established attitudes in a natural setting. A four-phase experiment was conducted involving 433 participants. The results revealed that the effectiveness of refutational inoculation messages dissipated some in the face of an additional attack. Still, refutational inoculation messages proved to be more effective than supportive, restoration, and control (no message) conditions in protecting established attitudes in the face of multiple attacks. The content of an additional attack (the same as the first attack or different) did not affect the capacity of inoculation refutational messages to confer resistance to competitive attacks.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Genetic effects on gene expression across human tissues
Characterization of the molecular function of the human genome and its variation across individuals is essential for identifying the cellular mechanisms that underlie human genetic traits and diseases. The Genotype-Tissue Expression (GTEx) project aims to characterize variation in gene expression levels across individuals and diverse tissues of the human body, many of which are not easily accessible. Here we describe genetic effects on gene expression levels across 44 human tissues. We find that local genetic variation affects gene expression levels for the majority of genes, and we further identify inter-chromosomal genetic effects for 93 genes and 112 loci. On the basis of the identified genetic effects, we characterize patterns of tissue specificity, compare local and distal effects, and evaluate the functional properties of the genetic effects. We also demonstrate that multi-tissue, multi-individual data can be used to identify genes and pathways affected by human disease-associated variation, enabling a mechanistic interpretation of gene regulation and the genetic basis of diseas
Population- and individual-specific regulatory variation in Sardinia
Genetic studies of complex traits have mainly identified associations with noncoding variants. To further determine the contribution of regulatory variation, we combined whole-genome and transcriptome data for 624 individuals from Sardinia to identify common and rare variants that influence gene expression and splicing. We identified 21,183 expression quantitative trait loci (eQTLs) and 6,768 splicing quantitative trait loci (sQTLs), including 619 new QTLs. We identified high-frequency QTLs and found evidence of selection near genes involved in malarial resistance and increased multiple sclerosis risk, reflecting the epidemiological history of Sardinia. Using family relationships, we identified 809 segregating expression outliers (median z score of 2.97), averaging 13.3 genes per individual. Outlier genes were enriched for proximal rare variants, providing a new approach to study large-effect regulatory variants and their relevance to traits. Our results provide insight into the effects of regulatory variants and their relationship to population history and individual genetic risk.M.P. is supported by the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement 633964 (ImmunoAgeing). Z.Z. is supported by the National Science Foundation (NSF) GRFP (DGE- 114747) and by the Stanford Center for Computational, Evolutionary, and Human Genomics (CEHG). Z.Z., J.R.D., and G.T.H. also acknowledge support from the Stanford Genome Training Program (SGTP; NIH/NHGRI T32HG000044). J.R.D. is supported by the Stanford Graduate Fellowship. K.R.K. is supported by Department of Defense, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEQ) Fellowship 32 CFR 168a. S.J.S. is supported by the NIHR Cambridge Biomedical Research Centre. The SardiNIA project is supported in part by the intramural program of the National Institute on Aging through contract HHSN271201100005C to the Consiglio Nazionale delle Ricerche of Italy. The RNA sequencing was supported by the PB05 InterOmics MIUR Flagship grant; by the FaReBio2011 “Farmaci e Reti Biotecnologiche di Qualità” grant; and by Sardinian Autonomous Region (L.R. no. 7/2009) grant cRP3-154 to F. Cucca, who is also supported by the Italian Foundation for Multiple Sclerosis (FISM 2015/R/09) and by the Fondazione di Sardegna (ex Fondazione Banco di Sardegna, Prot. U1301.2015/AI.1157.BE Prat. 2015-1651). S.B.M. is supported by the US National Institutes of Health through R01HG008150, R01MH101814, U01HG007436, and U01HG009080. All of the authors would like to thank the CRS4 and the SCGPM for the computational infrastructure supporting this project
Genetic effects on gene expression across human tissues
Characterization of the molecular function of the human genome and its variation across individuals is essential for identifying the cellular mechanisms that underlie human genetic traits and diseases. The Genotype-Tissue Expression (GTEx) project aims to characterize variation in gene expression levels across individuals and diverse tissues of the human body, many of which are not easily accessible. Here we describe genetic effects on gene expression levels across 44 human tissues. We find that local genetic variation affects gene expression levels for the majority of genes, and we further identify inter-chromosomal genetic effects for 93 genes and 112 loci. On the basis of the identified genetic effects, we characterize patterns of tissue specificity, compare local and distal effects, and evaluate the functional properties of the genetic effects. We also demonstrate that multi-tissue, multi-individual data can be used to identify genes and pathways affected by human disease-associated variation, enabling a mechanistic interpretation of gene regulation and the genetic basis of disease
Fabrication and Characterization of Vertically Aligned Carbon Nanofibers (VACNF) as Amperometric Biosensors on a Silicon-Compatible Platform
This thesis presents fabrication, characterization and initial results of vertically aligned carbon nanofibers (VACNF)-based electrodes for use as electrochemical sensors. VACNFs are nanostructures that can be fabricated to the desired specifications using a plasma-enhanced chemical-vapor deposition process and are ideal candidates for electrode material because of their excellent electrical and structural properties. The first step of the fabrication of VACNFs on silicon substrates involved photolithography to pattern the interconnects and the catalysts (nickel dots). VACNFs were then grown on silicon substrates from the nickel catalysts, whose size determines the growth of a single nanofiber or a forest of nanofibers. This work presents a method for growth of nanofiber forest for redundancy and uniform vertical growth.
A reservoir was built around the nanofibers to keep the liquid samples in contact with the nanofibers during testing. Nanofiber electrodes were characterized electrochemically using ruthenium hexamine trichloride to ensure proper functionality. The biosensor is customizable to selectively detect various elements or compounds depending on the binding materials used on the nanofibers. One example of a sample that can be detected with VACNF electrodes is glucose. The enzymes, horseradish peroxidase and glucose oxidase, were applied to the nanofibers and were immobilized for the testing of glucose. The reference electrode of the electrochemical analyzer was inserted into the reservoir containing the glucose and multiple analyses were performed. The nanofiber electrodes were able to collect the electrons from the electrochemical reactions of glucose and the enzymes. Amperometric data was gathered for the oxidation and reduction potentials and the current was measured as a function of the glucose concentration.
Vertically aligned carbon nanofibers fabricated on silicon substrates are ideal electrodes for integration with silicon compatible structures such as complementary metal-oxide-semiconductor (CMOS) microelectronics based transmitting and signal processing integrated circuits