1,984 research outputs found
Size effects of nanoindentation creep
The size effects on indentation creep were studied on single-crystal Ni3Al, polycrystalline pure Al, and fused quartz samples at room temperature. The stress exponents were measured by monitoring the displacement during constant indentation loads after correction for thermal drift effects. The stress exponents were found to exhibit a very strong size effect. In the two metals Al and Ni3Al, the stress exponent for very small indents is very small, and for Al, this even approaches unity, suggesting that linear diffusional flow may be the controlling mechanism. The stress exponents in these two metals rise rapidly to over 100 as the indent size gets larger, indicating a rapid change of the dominating mechanism to climb-controlled to eventually glide-controlled events. In fused quartz, the stress exponent also exhibits a sharply rising trend as the indent size increases. The stress exponent is also close to unity at the smallest indents studied, and it rises rapidly to a few tens as the indent size gets larger.published_or_final_versio
Probing neutrino and Higgs sectors in model with lepton-flavor non-universality
The neutrino and Higgs sectors in the \mbox{SU(2)}_1 \times \mbox{SU(2)}_2
\times \mbox{U(1)}_Y model with lepton-flavor non-universality are discussed.
We show that active neutrinos can get Majorana masses from radiative
corrections, after adding only new singly charged Higgs bosons. The mechanism
for generation of neutrino masses is the same as in the Zee models. This also
gives a hint to solving the dark matter problem based on similar ways discussed
recently in many radiative neutrino mass models with dark matter. Except the
active neutrinos, the appearance of singly charged Higgs bosons and dark matter
does not affect significantly the physical spectrum of all particles in the
original model. We indicate this point by investigating the Higgs sector in
both cases before and after singly charged scalars are added into it. Many
interesting properties of physical Higgs bosons, which were not shown
previously, are explored. In particular, the mass matrices of charged and
CP-odd Higgs fields are proportional to the coefficient of triple Higgs
coupling . The mass eigenstates and eigenvalues in the CP-even Higgs
sector are also presented. All couplings of the SM-like Higgs boson to normal
fermions and gauge bosons are different from the SM predictions by a factor
, which must satisfy the recent global fit of experimental data, namely
. We have analyzed a more general diagonalization of gauge boson
mass matrices, then we show that the ratio of the tangents of the and
mixing angles is exactly the cosine of the Weinberg angle, implying that
number of parameters is reduced by 1. Signals of new physics from decays of new
heavy fermions and Higgs bosons at LHC and constraints of their masses are also
discussed.Comment: 40 pages, 1 figure; Journal vesio
Evaluation of human epididymal secretory protein E4 (HE4) for monitoring for ovarian cancer recurrence
INTRODUCTION: Serum HE4, a new biomarker for ovarian cancer, was shown to have a better sensitivity for detecting ovarian cancer compared to Ca 125, especially in early disease. In this study, we measured the HE4 levels in patients who had relapsed ovarian cancer in an attempt to elucidate its role in disease monitoring and recurrence detection. METHODS: HE4 levels were measured at pre-treatment, immediately post ...postprin
Hard multilayered thin films of metal–intermetallic Ni/Ni3Al
Metal-intermetallic Ni/Ni3Al multilayered thin films were synthesized by the magnetron sputtering technique. The synthesized films possessed high hardness that could be compared with intermetallic Ni3Al films. The constituent layers of Ni and Ni3Al were fully adherent to one another at the multilayered boundaries. The fracture surface of the multilayered films on bending showed the characteristics of local ductile fracture. This novel type of multilayered thin films is expected to be used as hard coatings and miniaturized parts of apparatus in micro-electromechanical systems.published_or_final_versio
Continuous strain bursts in crystalline and amorphous metals during plastic deformation by nanoindentation
Using depth-sensing indentation with sub-nanometer displacement resolution, the plastic deformation of a range of materials, including a metallic glass, amorphous selenium, Ni3Al, pure Nb, Al, Cu, and Zn metals, and an Al-Mg alloy, has been investigated at room temperature. In amorphous selenium, even the sub-nanometer displacement resolution of the nanoindentation technique cannot reveal any strain burst during deformation at room temperature. In all other metals studied, what may appear to be smooth load-displacement curves at macroscopic scale during indentation deformation in fact turn out to consist of a continuous series of random bursts of the nanometer scale. The occurrence probability of the bursts is found to decrease at increasing burst size. In all of the crystalline metals and alloys studied, the size distribution of the strain bursts seems to follow an exponential law with a characteristic length scale. The absence of the self-organized critical behavior is likely a result of the small size of the strained volume in the nanoindentation situation, which gives rise to a constraint of a characteristic strain. In the metallic glass sample, due to the limited range of the burst sizes encountered, whether the deformation bursts follow an exponential or a power-law behavior corresponding to self-organized criticality is inconclusive. From a theoretical viewpoint based on the Shannon entropy, the exponential distribution is the most likely distribution at a given mean burst size, and this is thought to be the reason for its occurrence in different materials. © 2005 Materials Research Society.published_or_final_versio
Spectra of axions emitted from main sequence stars
We compute the detailed energy spectra of axions with two-photon coupling
produced in stellar cores over a wide range of stellar masses. We focus on main
sequence stars and base our calculations on the stellar interior profiles from
MESA, for which we provide simple fits in an appendix. The obtained stellar
axion spectra, combined with recent models of star formation history and
stellar initial mass function, enable us to estimate the properties of the
diffuse axion background sourced by all the stars in the universe. The fluxes
of this stellar axion background and its decay photons are subdominant to but
can in principle be disentangled from those expected from the Sun and the early
universe based on their different spectral and spatial profiles
Fractography, elastic modulus and oxidation resistance of novel metal-intermetallic Ni/Ni 3Al multilayer films
Novel metal–intermetallic Ni/Ni3Al multilayer films are synthesized by a magnetron sputtering technique. The fractography, elastic modulus, and the oxidation resistance of the multilayer films are studied by a series of experimental tests. The scanning electron microscopy fractography of the films shows that both Ni and Ni3Al layers fracture with the appearance of ductile metal failure. No metal–intermetallic delamination appears in the multilayered films. Fluted dimpling in each Ni and Ni3Al layer is
evident and continuous, layer through layer, illustrating very good adherence among the constituent layers. Such adherence makes the toughness of the Ni layers capable of transferring into the Ni3Al layers. Young’s modulus of the Ni/Ni3Al film is found to be 226 and 253 ± 10 GPa by nanoindentation and laser acoustic techniques, respectively. The continuity of elastic modulus between the two phases is revealed by nanoindentation test. The modulus continuity indicates an excellent integration of the
constituent layers with similar crystal structure and close lattice constants. This integration makes the multilayers unsurpassed in comprehensive mechanical properties. Sheet resistance measurements show a good protective ability of the Ni/Ni3Al
multilayers during high temperature oxidation. X-ray photoelectron spectroscopy spectra suggest that crystallized Al2O3 /Ni scales formed during the deposition and subsequent annealing processes are apparently responsible for the stability of these
films under oxidative conditions. The appearance of the crystallized Al2O3 /Ni thin scales on the top of Ni3Al layers provides the Ni/Ni3Al multilayers good thermal oxidation resistance without lowering the fracture toughness.published_or_final_versio
Imaging and radiological intervention in hepatocellular carcinoma
Hepatocellular carcinoma is the second most common cause of death from malignancy in Hong Kong. The prognosis of patients with hepatocellular carcinoma depends on the hepatic function, tumour size, and tumour extent at diagnosis. Ultrasound, computed tomography, Lipiodal computed tomography, hepatic angiography, and magnetic resonance imaging are useful imaging modalities for the diagnosis of hepatocellular carcinomas and in assessing their operability. Transcatheter arterial chemoembolization, selective internal radiation therapy, and percutaneous transhepatic ethanol injection are promising interventional radiological techniques that have been introduced in the treatment of patients with inoperable disease. The indications for these treatment modalities and their efficacy are discussed.published_or_final_versio
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