122 research outputs found
Hadronic decays of in the perturbative QCD approach
We calculate the branching ratios and polarization fractions of the decays in the perturbative QCD(pQCD) approach at leading order, where
() stands for the axial-vector state. By
combining the phenomenological analyses with the perturbative calculations, we
find the following results: (a) the large decay rates around to
of the decays dominated by the longitudinal
polarization(except for the mode) are predicted and
basically consistent with those in the QCD factorization(QCDF) within errors,
which are expected to be tested by the Large Hadron Collider and Belle-II
experiments. The large branching ratio could provide
hints to help explore the mechanism of the color-suppressed decays. (b) the
rather different QCD behaviors between the and mesons result in the
destructive(constructive) contributions in the nonfactorizable spectator
diagrams with emission. Therefore, an interesting pattern of the
branching ratios appears for the color-suppressed and modes in the pQCD approach, , which is different
from in the QCDF and would be verified at future experiments. (c) the
large naive factorization breaking effects are observed in these decays. Specifically, the large nonfactorizable spectator(weak
annihilation) amplitudes contribute to the mode(s), which demand confirmations
via the precise measurements.Comment: 13 pages, 1 figure, 5 tables, revtex fil
Aminolevulinate synthase 2 mediates erythrocyte differentiation by regulating larval globin expression during Xenopus primary hematopoiesis
AbstractHemoglobin synthesis by erythrocytes continues throughout a vertebrate’s lifetime. The mechanism of mammalian heme synthesis has been studied for many years; aminolevulinate synthase 2 (ALAS2), a heme synthetase, is associated with X-linked dominant protoporphyria in humans. Amphibian and mammalian blood cells differ, but little is known about amphibian embryonic hemoglobin synthesis. We investigated the function of the Xenopus alas2 gene (Xalas2) in primitive amphibian erythrocytes and found that it is first expressed in primitive erythroid cells before hemoglobin alpha 3 subunit (hba3) during primary hematopoiesis and in the posterior ventral blood islands at the tailbud stage. Xalas2 is not expressed during secondary hematopoiesis in the dorsal lateral plate. Hemoglobin was barely detectable by o-dianisidine staining and hba3 transcript levels decreased in Xalas2-knockdown embryos. These results suggest that Xalas2 might be able to synthesize hemoglobin during hematopoiesis and mediate erythrocyte differentiation by regulating hba3 expression in Xenopus laevis
High-speed metasurface modulator using critically coupled bimodal plasmonic resonance
Free-space electro-optic (EO) modulators operating at gigahertz and beyond
are attractive for a wide range of emerging applications, including high-speed
imaging, free-space optical communication, microwave photonics, and diffractive
computing. Here we experimentally demonstrate a high-speed plasmonic
metasurface EO modulator operating at a near-infrared wavelength range with a
gigahertz modulation bandwidth. To achieve efficient intensity modulation of
reflected light from an ultrathin metasurface layer, we utilize the bimodal
plasmonic resonance inside a subwavelength metal-insulator-metal grating, which
is precisely tuned to satisfy the critical coupling condition. As a result,
perfect absorption of -27 dB (99.8%) and a high quality (Q) factor of 113 are
obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer
inside the grating, we achieve a modulation depth of up to 9.5 dB under an
applied voltage of 30 V. The 3-dB modulation bandwidth is confirmed to be
1.25 GHz, which is primarily limited by the undesired contact resistance. Owing
to the high electrical conductivity of metallic gratings and a compact device
structure with a minimal parasitic capacitance, the demonstrated device can
potentially operate at several tens of gigahertz, which opens up exciting
opportunities for ultrahigh-speed active metasurface devices in various
applications.Comment: Main text: 18 pages, 3 figures, 39 references Supplementary material:
3 pages, 2 figures
3Rd-Order Nonlinearity Of 4-Dialkylamino-4\u27Nitro-Stilbene Wave-Guides At 1319 Nm
The intensity dependent optical properties of 4-dialkylamino-4\u27nitro-stilbene polymer channel waveguides were measured at 1319 nm with a pulse modulated Mach-Zehnder interferometer to be n2 = 0.8 x 10(-13) cm2/W and beta2 \u3c 0.08 cm/GW. This material is promising for all-optical switching at 1319 nm because it satisfies both the W and T figures of merit
Comparative study of nonlinear-optical polymers for guided-wave second-harmonic generation at telecommunication wavelengths
International audiencex
Solid state diffusion bonding of doped tungsten alloys with different thermo-mechanical properties
To develop joints using W materials with different thermo-mechanical properties, solid state diffusion bonding involving two different W materials (pure W, K-doped W, or K-doped W-3%Re) and using a pure V interlayer (1.5 mm, 0.5 mm, or 0.05 mm thick) were carried out at 1250 °C for 1 h. The use of a thin interlayer was found to be effective from the point of optimizing the strength and thermal diffusivity. Diffusion bonding at lower temperatures or utilizing W materials with higher recrystallization temperatures were also determined to be effective because pure W can recrystallize at 1250 °C. Further evaluation of a wide range of interlayer thicknesses and thermo-mechanical test conditions is necessary based on the present work to obtain optimum W/V/W joints
Loss of ALS2/Alsin Exacerbates Motor Dysfunction in a SOD1H46R-Expressing Mouse ALS Model by Disturbing Endolysosomal Trafficking
BACKGROUND: ALS2/alsin is a guanine nucleotide exchange factor for the small GTPase Rab5 and involved in macropinocytosis-associated endosome fusion and trafficking, and neurite outgrowth. ALS2 deficiency accounts for a number of juvenile recessive motor neuron diseases (MNDs). Recently, it has been shown that ALS2 plays a role in neuroprotection against MND-associated pathological insults, such as toxicity induced by mutant Cu/Zn superoxide dismutase (SOD1). However, molecular mechanisms underlying the relationship between ALS2-associated cellular function and its neuroprotective role remain unclear. METHODOLOGY/PRINCIPAL FINDINGS: To address this issue, we investigated the molecular and pathological basis for the phenotypic modification of mutant SOD1-expressing mice by ALS2 loss. Genetic ablation of Als2 in SOD1(H46R), but not SOD1(G93A), transgenic mice aggravated the mutant SOD1-associated disease symptoms such as body weight loss and motor dysfunction, leading to the earlier death. Light and electron microscopic examinations revealed the presence of degenerating and/or swollen spinal axons accumulating granular aggregates and autophagosome-like vesicles in early- and even pre-symptomatic SOD1(H46R) mice. Further, enhanced accumulation of insoluble high molecular weight SOD1, poly-ubiquitinated proteins, and macroautophagy-associated proteins such as polyubiquitin-binding protein p62/SQSTM1 and a lipidated form of light chain 3 (LC3-II), emerged in ALS2-deficient SOD1(H46R) mice. Intriguingly, ALS2 was colocalized with LC3 and p62, and partly with SOD1 on autophagosome/endosome hybrid compartments, and loss of ALS2 significantly lowered the lysosome-dependent clearance of LC3 and p62 in cultured cells. CONCLUSIONS/SIGNIFICANCE: Based on these observations, although molecular basis for the distinctive susceptibilities to ALS2 loss in different mutant SOD1-expressing ALS models is still elusive, disturbance of the endolysosomal system by ALS2 loss may exacerbate the SOD1(H46R)-mediated neurotoxicity by accelerating the accumulation of immature vesicles and misfolded proteins in the spinal cord. We propose that ALS2 is implicated in endolysosomal trafficking through the fusion between endosomes and autophagosomes, thereby regulating endolysosomal protein degradation in vivo
Determinação de plastificantes em água potável utilizando cromatografia gasosa e espectrometria de massas
This study investigated the levels of plasticizer endocrine disruptors (diethyl phthalate, dibutyl phthalate, and bisphenol A) in drinking water at Paraíba do Sul River region and release of these compounds from bottled water. An analytical method employing solid phase extraction and GC/MS was optimized and validated. The results showed that the method is selective, linear (r² > 0.99), precise (RSD <12%), accurate (recoveries between 62 and 105%), sensitive and robust. Applying the method, the presence of all studied pollutants in drinking water was observed for the three sampled plasticizers. These plasticizers were not found in mineral bottled water, before or after storage
2Nd-Harmonic Generation By Counter Propagating Beams In 4-Dimethylamino-4\u27-Nitrostilbene Side-Chain Polymer Channel Wave-Guides
We demonstrate surface emitted second harmonic generation due to mixing of counter propagating waves in in-plane poled, low loss, channel waveguides of 4-dimethylamino-4\u27-nitrostilbene (DANS) side-chain polymers. Single film DANS side-chain polymer waveguides yield high conversion efficiency devices
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