2,892 research outputs found
Yule’s “nonsense correlation” for Gaussian random walks
This paper provides an exact formula for the second moment of the empirical correlation (also known as Yule’s “nonsense correlation”) for two independent standard Gaussian random walks, as well as implicit formulas for higher moments. We also establish rates of convergence of the empirical correlation of two independent standard Gaussian random walks to the empirical correlation of two independent Wiener processes
Low Resistance Polycrystalline Diamond Thin Films Deposited by Hot Filament Chemical Vapour Deposition
Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH4) highly diluted with H2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications
Electronic measurement and control of spin transport in Silicon
The electron spin lifetime and diffusion length are transport parameters that
define the scale of coherence in spintronic devices and circuits. Since these
parameters are many orders of magnitude larger in semiconductors than in
metals, semiconductors could be the most suitable for spintronics. Thus far,
spin transport has only been measured in direct-bandgap semiconductors or in
combination with magnetic semiconductors, excluding a wide range of
non-magnetic semiconductors with indirect bandgaps. Most notable in this group
is silicon (Si), which (in addition to its market entrenchment in electronics)
has long been predicted a superior semiconductor for spintronics with enhanced
lifetime and diffusion length due to low spin-orbit scattering and lattice
inversion symmetry. Despite its exciting promise, a demonstration of coherent
spin transport in Si has remained elusive, because most experiments focused on
magnetoresistive devices; these methods fail because of universal impedance
mismatch obstacles, and are obscured by Lorentz magnetoresistance and Hall
effects. Here we demonstrate conduction band spin transport across 10 microns
undoped Si, by using spin-dependent ballistic hot-electron filtering through
ferromagnetic thin films for both spin-injection and detection. Not based on
magnetoresistance, the hot electron spin-injection and detection avoids
impedance mismatch issues and prevents interference from parasitic effects. The
clean collector current thus shows independent magnetic and electrical control
of spin precession and confirms spin coherent drift in the conduction band of
silicon.Comment: Single PDF file with 4 Figure
Geographic and research center origins of rice resistance to asian planthoppers and leafhoppers: Implications for rice breeding and gene deployment
2017 by the authors. This study examines aspects of virulence to resistant rice varieties among planthoppers and leafhoppers. Using a series of resistant varieties, brown planthopper, Nilaparvata lugens, virulence was assessed in seedlings and early-tillering plants at seven research centers in South and East Asia. Virulence of the whitebacked planthopper, Sogatella furcifera, in Taiwan and the Philippines was also assessed. Phylogenetic analysis of the varieties using single-nucleotide polymorphisms (SNPs) indicated a clade of highly resistant varieties from South Asia with two further South Asian clades of moderate resistance. Greenhouse bioassays indicated that planthoppers can develop virulence against multiple resistance genes including genes introgressed from wild rice species. Nilaparvata lugens populations from Punjab (India) and the Mekong Delta (Vietnam) were highly virulent to a range of key resistance donors irrespective of variety origin. Sogatella furcifera populations were less virulent to donors than N. lugens; however, several genes for resistance to S. furcifera are now ineffective in East Asia. A clade of International Rice Research Institute (IRRI)-bred varieties and breeding lines, without identified leafhopper-resistance genes, were highly resistant to the green leafhopper, Nephotettix virescens. Routine phenotyping during breeding programs likely maintains high levels of quantitative resistance to leafhoppers. We discuss these results in the light of breeding and deploying resistant rice in Asia
Ultrasensitive force and displacement detection using trapped ions
The ability to detect extremely small forces is vital for a variety of
disciplines including precision spin-resonance imaging, microscopy, and tests
of fundamental physical phenomena. Current force-detection sensitivity limits
have surpassed 1 (atto ) through coupling of micro or
nanofabricated mechanical resonators to a variety of physical systems including
single-electron transistors, superconducting microwave cavities, and individual
spins. These experiments have allowed for probing studies of a variety of
phenomena, but sensitivity requirements are ever-increasing as new regimes of
physical interactions are considered. Here we show that trapped atomic ions are
exquisitely sensitive force detectors, with a measured sensitivity more than
three orders of magnitude better than existing reports. We demonstrate
detection of forces as small as 174 (yocto ), with a
sensitivity 390 using crystals of Be
ions in a Penning trap. Our technique is based on the excitation of normal
motional modes in an ion trap by externally applied electric fields, detection
via and phase-coherent Doppler velocimetry, which allows for the discrimination
of ion motion with amplitudes on the scale of nanometers. These experimental
results and extracted force-detection sensitivities in the single-ion limit
validate proposals suggesting that trapped atomic ions are capable of detecting
of forces with sensitivity approaching 1 . We anticipate that
this demonstration will be strongly motivational for the development of a new
class of deployable trapped-ion-based sensors, and will permit scientists to
access new regimes in materials science.Comment: Expanded introduction and analysis. Methods section added. Subject to
press embarg
Physical and immunological aspects of exercise in chronic diseases.
Physical inactivity and sedentary lifestyles are believed to be independent risk factors for the occurrence of numerous diseases, including, obesity, Type 2 diabetes, metabolic syndrome, cardiovascular disease, cancer and mental health, all leading to substantial morbidity and/or premature death. It has been found that regular exercise, is associated with better quality of life and health outcomes, and reduces the risk of cardiovascular disease and cancer. Here, we review the effects regular exercise has on mental health and well-being, on the immune system and in cancer, cardiovascular disease, autoimmunity and metabolic syndrome. Is exercise the new immunotherapy to treat diseases
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Bulk properties of the system formed in Au+Au collisions at sNN =14.5 GeV at the BNL STAR detector
We report systematic measurements of bulk properties of the system created in Au+Au collisions at sNN=14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum spectra of π±, K±, and p(p) are studied at midrapidity (|y|<0.1) for nine centrality intervals. The centrality, transverse momentum (pT), and pseudorapidity (η) dependence of inclusive charged particle elliptic flow (v2), and rapidity-odd charged particles directed flow (v1) results near midrapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at sNN=2.76 TeV. The results at sNN=14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. These results are important as the 14.5-GeV energy fills the gap in μB, which is of the order of 100 MeV, between sNN=11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general
Lycopene Protects the Diabetic Rat Kidney Against Oxidative Stress-mediated Oxidative Damage Induced by Furan
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