1,055 research outputs found
Generation of spiral bevel gears with conjugate tooth surfaces and tooth contact analysis
A new method for generation of spiral bevel gears is proposed. The main features of this method are as follows: (1) the gear tooth surfaces are conjugated and can transform rotation with zero transmission errors; (2) the tooth bearing contact is localized; (3) the center of the instantaneous contact ellipse moves in a plane that has a fixed orientation; (4) the contact normal performs in the process of meshing a parallel motion; (5) the motion of the contact ellipse provides improved conditions of lubrication; and (6) the gears can be manufactured by use of Gleason's equipment
A Series of 4- and 5-Coordinate Ni(II) Complexes: Synthesis, Characterization, Spectroscopic, and DFT Studies
A series of four- and five-coordinate Ni(II) complexes CztBu(PyriPr)2NiX (1–3 and 1·THF–3·THF), where X = Cl, Br, and I, were synthesized and fully characterized by NMR and UV–vis spectroscopy, X-ray crystallography, cyclic voltammetry, and density functional theory calculations. The solid-state structures of 1–3 reveal rare examples of seesaw Ni(II) complexes. In solution, 1–3 bind reversibly to a THF molecule to form five-coordinate adducts. The electronic transitions in the visible region (630–680 nm), attributed to LMCT bands, for 1 → 3 exhibit a bathochromic shift. The thermochromic tendency of the five-coordinate complexes implies the loss of THF coordination at elevated temperatures. Finally, the electronic properties of all Ni(II) complexes were studied by time-dependent density functional theory calculations to characterize the nature of the excited states
Influence on electron coherence from quantum electromagnetic fields in the presence of conducting plates
The influence of electromagnetic vacuum fluctuations in the presence of the
perfectly conducting plate on electrons is studied with an interference
experiment. The evolution of the reduced density matrix of the electron is
derived by the method of influence functional. We find that the plate boundary
anisotropically modifies vacuum fluctuations that in turn affect the electron
coherence. The path plane of the interference is chosen either parallel or
normal to the plate. In the vicinity of the plate, we show that the coherence
between electrons due to the boundary is enhanced in the parallel
configuration, but reduced in the normal case. The presence of the second
parallel plate is found to boost these effects. The potential relation between
the amplitude change and phase shift of interference fringes is pointed out.
The finite conductivity effect on electron coherence is discussed.Comment: 29 pages, 3 figure
Stochastic Lorentz forces on a point charge moving near the conducting plate
The influence of quantized electromagnetic fields on a nonrelativistic
charged particle moving near a conducting plate is studied. We give a
field-theoretic derivation of the nonlinear, non-Markovian Langevin equation of
the particle by the method of Feynman-Vernon influence functional. This
stochastic approach incorporates not only the stochastic noise manifested from
electromagnetic vacuum fluctuations, but also dissipation backreaction on a
charge in the form of the retarded Lorentz forces. Since the imposition of the
boundary is expected to anisotropically modify the effects of the fields on the
evolution of the particle, we consider the motion of a charge undergoing
small-amplitude oscillations in the direction either parallel or normal to the
plane boundary. Under the dipole approximation for nonrelativistic motion,
velocity fluctuations of the charge are found to grow linearly with time in the
early stage of the evolution at the rather different rate, revealing strong
anisotropic behavior. They are then asymptotically saturated as a result of the
fluctuation-dissipation relation, and the same saturated value is found for the
motion in both directions. The observational consequences are discussed. plane
boundary. Velocity fluctuations of the charge are found to grow linearly with
time in the early stage of the evolution at the rate given by the relaxation
constant, which turns out to be smaller in the parallel case than in the
perpendicular one in a similar configuration. Then, they are asymptotically
saturated as a result of the fluctuation-dissipation relation. For the
electron, the same saturated value is obtained for motion in both directions,
and is mainly determined by its oscillatory motion. Possible observational
consequences are discussed.Comment: 33 pages, 2 figure
Photothermal optical coherence tomography in ex vivo human breast tissues using gold nanoshells
We demonstrate photothermal optical coherence tomography (OCT) imaging in highly scattering human breast tissue ex vivo. A 120 kHz axial scan rate, swept-source phase-sensitive OCT system at 1300 nm was used to detect phase changes induced by 830 nm photothermal excitation of gold nanoshells. Localized phase modulation was observed 300–600 μm deep in scattering tissue using an excitation power of only 22 mW at modulation frequencies up to 20 kHz. This technique enables integrated structural and molecular-targeted imaging for cancer markers using nanoshells.National Institutes of Health (U.S.) (Grant Number R01- CA75289-13)United States. Air Force Office of Scientific Research (Contract Number FA9550-07-1-0014)MFELP (Contract Number FA9550-07-1-0101)Natural Sciences and Engineering Research Council of Canada (NSERC) Heritage Scholarship FundCenter for Integration of Medicine and Innovative TechnologyNational Science council of Taiwan. Taiwan Merit Scholarshi
Linking the effects of helminth infection, diet and the gut microbiota with human whole-blood signatures
Helminth infection and dietary intake can affect the intestinal microbiota, as well as the immune system. Here we analyzed the relationship between fecal microbiota and blood profiles of indigenous Malaysians, referred to locally as Orang Asli, in comparison to urban participants from the capital city of Malaysia, Kuala Lumpur. We found that helminth infections had a larger effect on gut microbial composition than did dietary intake or blood profiles. Trichuris trichiura infection intensity also had the strongest association with blood transcriptional profiles. By characterizing paired longitudinal samples collected before and after deworming treatment, we determined that changes in serum zinc and iron levels among the Orang Asli were driven by changes in helminth infection status, independent of dietary metal intake. Serum zinc and iron levels were associated with changes in the abundance of several microbial taxa. Hence, there is considerable interplay between helminths, micronutrients and the microbiota on the regulation of immune responses in humans
High-Energy Symmetry of Bosonic Open String Theory in the Light-like Linear Dilaton Background
High-energy limits of fixed-angle tree-level stringy scattering amplitudes in
the light-like linear dilaton background are calculated. Treating the time
component of the gradient of light-like dilaton field (V_0) as a moduli
parameter, we show that: (1) there exists a new fixed-point (V_0/E \to \infty)
in the moduli space of the bosonic open string theory, where a new high-energy
symmetry among scattering amplitudes can be identified, (2) this new symmetry
can be interpreted as a deformation of the flat-space high-energy symmetry, as
proposed by D. Gross. Hence, our results give a concrete illustration about the
relation between high-energy stringy symmetry and the background independent
formulation of string theory.Comment: 42pages, 3figures, 5tables, typos corrected, commments and reference
added
Changes in the expression of the Alzheimer's disease-associated presenilin gene in drosophila heart leads to cardiac dysfunction
Mutations in the presenilin genes cause the majority of early-onset familial Alzheimer’s disease.
Recently, presenilin mutations have been identified in patients with dilated cardiomyopathy
(DCM), a common cause of heart failure and the most prevalent diagnosis in cardiac
transplantation patients. However, the molecular mechanisms, by which presenilin mutations lead
to either AD or DCM, are not yet understood. We have employed transgenic Drosophila models
and optical coherence tomography imaging technology to analyze cardiac function in live adult
Drosophila. Silencing of Drosophila ortholog of presenilins (dPsn) led to significantly reduced
heart rate and remarkably age-dependent increase in end-diastolic vertical dimensions. In contrast,
overexpression of dPsn increased heart rate. Either overexpression or silencing of dPsn resulted in
irregular heartbeat rhythms accompanied by cardiomyofibril defects and mitochondrial
impairment. The calcium channel receptor activities in cardiac cells were quantitatively
determined via real-time RT-PCR. Silencing of dPsn elevated dIP[subscript 3]R expression, and reduced dSERCA expression; overexprerssion of dPsn led to reduced dRyR expression. Moreover,
overexpression of dPsn in wing disc resulted in loss of wing phenotype and reduced expression of
wingless. Our data provide novel evidence that changes in presenilin level leads to cardiac
dysfunction, owing to aberrant calcium channel receptor activities and disrupted Wnt signaling
transduction, indicating a pathogenic role for presenilin mutations in DCM pathogenesis.Cure Alzheimer’s FundNational Institutes of Health (U.S.) (Grant R01AG014713)National Institutes of Health (U.S.) (Grant R01MH60009)National Institutes of Health (U.S.) (Grant R01CA75289)National Institutes of Health (U.S.) (Grant R01HL095717)National Institutes of Health (U.S.) (Grant FA9550-07-1-0014
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