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A simple numerical model has been proposed for laser cladding. The model does not involve complex techniques such as cell addition, moving mesh, or prescribing a clad profile with a certain polynomial function. Instead, a mass function has been introduced to register the clad mass deposition on substrate, and from which the clad-track height can be estimated. The model takes several operational parameters, laser power, laser-head speed, and clad powder feeding rate, into consideration and predicts clad-track geometry, dilution, and substrate temperature. Experiments using two different combinations of substrate and clad powder materials to lay single and multiple clad tracks were conducted to provide data for model validation. The results show that the present model returns good agreement with experimental clad profiles for single and multiple tracks.
Relativistic collisionless shock charged particle acceleration is considered as a possible origin of high-energy cosmic rays. However, it is hard to explore the nature of relativistic collisionless shock due to its low occurring frequency and remote detecting distance. Recently, there are some works attempt to solve this problem by generating relativistic collisionless shock in laboratory conditions. In laboratory, the scheme of generation of relativistic collisionless shock is that two electron–positron pair plasmas knock each other. However, in laboratory, the appropriate pair plasmas have been not generated. The 10 PW laser pulse maybe generates the pair plasmas that satisfy the formation condition of relativistic collisionless shock due to its ultrahigh intensity and energy. In this paper, we study the positron production by ultraintense laser high Z target interaction using numerical simulations, which consider quantum electrodynamics effect. The simulation results show that the forward positron beam up to 1013/kJ can be generated by 10 PW laser pulse interacting with lead target. The estimation of relativistic collisionless shock formation shows that the positron yield satisfies formation condition and the positron divergence needs to be controlled. Our results indicate that the generation of relativistic collisionless shock by 10 PW laser facilities in laboratory is possible.
In this paper, an ultra-wideband (UWB) filter with a notch band using T-shaped step impedance resonator loaded with cross-shaped open stubs has been presented. The notch band is formed by utilizing intrinsic zero. The characteristics of the new quad-mode resonator have been analyzed using odd-even mode analysis method. It can be shown that it is the intrinsic zero that generates the notch band. In addition, wide tunable notch band form 5–9.3 GHz can be achieved. A UWB filter with a notch band centered at 6.25 GHz using the proposed quad-mode resonator has been designed, fabricated, and tested. Experiment results show that the attenuation in notch frequency is >22 dB while the return loss of the simulation and measurement results are 22 dB/20 dB and 14.5 dB/11.2 dB in the lower and upper passband, respectively, which illustrate that the simulation and measurement results are in agreement.
Toxoplasma gondii is a major cause of congenital brain disease; however, the underlying mechanism of neuropathogenesis in brain toxoplasmosis remains elusive. To explore the role of T. gondii in the development of neural stem cells (NSCs), NSCs were isolated from GD14 embryos of ICR mice and were co-cultured with tachyzoites of T. gondii RH strain. We found that apoptosis levels of the NSCs co-cultured with 1×106 RH tachyzoites for 24 and 48 h significantly increased in a dose-dependent manner, as compared with the control. Western blotting analysis displayed that the protein level of C/EBP homologous protein (CHOP) was up-regulated, and caspase-12 and c-Jun N-terminal kinase (JNK) were activated in the NSCs co-cultured with the parasites. Pretreatment with endoplasmic reticulum stress (ERS) inhibitor (TUDCA) and caspase-12 inhibitor (Z-ATAD-FMK) inhibited the expression or activation of the key molecules involved in the ERS-mediated apoptotic pathway, and subsequently decreased the apoptosis levels of the NSCs induced by the T. gondii. The findings here highlight that T. gondii induced apoptosis of the NSCs through the ERS signal pathway via activation of CHOP, caspase-12 and JNK, which may constitute a potential molecular mechanism responsible for the cognitive disturbance in neurological disorders of T. gondii.
Beidou is the Global Navigation Satellite System (GNSS) being developed in China, with the aim to provide a global navigation service that is similar to the Global Positioning System (GPS) and Galileo navigation systems. In this paper, it is demonstrated that through the flexibility and re-configurability of a PC-based software receiver in which the baseband operations are realized in terms of software, it is possible to acquire, track, and demodulate Beidou satellite signals even when only a limited amount of information is known. Further, with the Beidou interface control document now available, the proposed PC-based software receiver can be easily adapted to perform navigation functions. This research lays the foundation for the further development of navigation receivers and exploration of multi-GNSS applications.
Despite accumulating evidence of structural deficits in individuals with
psychopathy, especially in frontal regions, our understanding of
systems-level disturbances in cortical networks remains limited. We applied
novel graph theory-based methods to assess information flow and connectivity
based on cortical thickness measures in 55 individuals with psychopathy and
47 normal controls. Compared with controls, the psychopathy group showed
significantly altered interregional connectivity patterns. Furthermore,
bilateral superior frontal cortices in the frontal network were identified
as information flow control hubs in the psychopathy group in contrast to
bilateral inferior frontal and medial orbitofrontal cortices as network hubs
of the controls. Frontal information flow and connectivity may have a
significant role in the neuropathology of psychopathy.
Broadband spectral conversion from visible light to near-infrared radiation in Ce3+–Nd3+/Yb3+ codoped yttrium aluminum garnet is reported. Excitation, emission spectra, and decay curves have been measured to prove the energy transfer from Ce3+ to Nd3+ or Yb3+. The energy transfer efficiencies have been estimated, and the mechanisms of the energy transfer between Ce3+ and Nd3+/Yb3+ have been proposed. Ce3+–Nd3+ codoped YAG can obtain more effective emission in the desired near-infrared region (around 1100 nm) through broadband conversion, showing potential application to improve the conversion efficiency of Si solar cells.
Transparent glass ceramics containing Li2MgSiO4: Cr4+ nanocrystallites were prepared. Intense broadband near-infrared emission with full width at half-maximum larger than 200 nm and long fluorescence lifetime (τ > 100 μs) were observed. The temperature-dependent optical characteristics of the glass ceramics containing Li2MgSiO4: Cr4+ crystallites were compared to those of Li2MgSiO4: Cr4+ single crystals. The reason for extra-long near-infrared fluorescence lifetime was illuminated by the mixed effect between 3T2 and 1E levels. The crystal-filed-induced particular energy-level scheme makes the fluorescence lifetime of the glass ceramics containing Li2MgSiO4: Cr4+ crystallites one order longer than those of other Cr4+-doped glass ceramics.
The Orai1-STIM1 constructed store-operated Ca2+ channels (SOCs) have been found to exert several essential Ca2+ entry/signaling cascades, e.g., the generation of immune response in T lymphocytes. Although biochemical and novel imaging evidence appear to indicate that Orai1 and STIM1 interact with each other to achieve store-operated Ca2+ entry (SOCE), the detailed mechanism of functional SOCE in situ has yet to be fully understood. In this study, green fluorescence protein (EGFP as donor) targeted to either the N- or C-terminal of Orai1 (wild type or ▵1-90+▵267-301 double deletion type) and mOrange (as acceptor) tagged STIM1 were used to comprise a fluorescence resonance energy transfer (FRET) pair within living PC12 cells. The fluorescence lifetime map and histogram/distribution of each single cell, determined by one-photon excitation fluorescence lifetime imaging microscopy (FLIM), was used to visualize FRET and show the Orai1 homodimer and Orai1-STIM1 binding. Both the color-coded lifetime map and the distribution of EGFP-tagged Orai1 significantly changed after the administration of thapsigargin, the SOCE stimulating agent. The FRET efficiency from each experimental set was also calculated and compared using double exponential analysis. In summary, we show the detailed interactions Orai1-Orai1 and Orai1-STIM1 within intact living cells by using the FLIM-FRET technique.
Cr3+-doped LiInSiO4 phosphors were prepared by a solid-state reaction method. X-ray diffraction measurement was carried out for crystalline phase identification. Absorption, photoluminescence, excitation, and time-resolved spectra were measured to investigate the optical properties of the phosphors. Two broadband near-infrared emissions centered at 920 and 1172 nm were observed. Time-resolved spectra show that the emission at 1172 nm decays more quickly than the emission at 920 nm. The electron spin resonance spectra exhibit a broad resonance signal at g = 1.96 because of exchange-coupled Cr3+ pairs. The value of Dq/B for low and intermediate crystal fields was evaluated. We suggest that Cr3+ incorporated into different octahedral sites of the crystal is responsible for the different near-infrared luminescence.
Sm3+, Ce3+ codoped Al2O3–La2O3–SiO2 glasses were prepared and their luminescence properties were characterized. Blue-cyan to orange-red tunable luminescence was observed from these glasses with different excitation wavelengths ranging from 385 to 410 nm. White light emission with internal luminescence efficiency 42% has been observed using commercially available purple light-emitting-diode excitation. The energy transfer between Ce3+ and Sm3+ has also been investigated from fluorescence decay curves and spectral properties.
We applied the deactivation treatments to p-type single crystalline silicon solar cells for deactivating the recombination-active boron-oxygen complex. The methods we used include thermal annealing treatment, capacitively couple plasma (CCP) treatment, and plasma immersion ion implantation (PIII) treatment. The results showed that all the deactivation treatments were working and the energy transfer efficiency (Eff) was thereby increased by more than 1% absolute compared to the degraded state base on the increasing of the open-circular voltage (Voc) and short-current density (Jsc). The CCP deactivated treatment got better efficiencies than PIII treatment because the PIII treatment damaged the surface of solar cells. After the forming gas treatment, the samples could be improved to close to the PIII samples due to the surface damage repairing. However, the increased efficiency could not be kept and would be degraded again after illumination.
GaN film grown on Si substrate with AlN/AlxGa1−xN buffer is studied by low pressure metal organic chemical vapor deposition (MOCVD) method. The AlxGa1−xN film with Al composition varying from 0∼ 0.66 was used. The correlation of the Al composition in the AlxGa1−xN film with the stress of the GaN film grown was studied using high resolution X-ray diffraction including symmetrical and asymmetrical ω/2θscans and reciprocal space maps. It is found that with proper design of the Al composition in the AlxGa1−xN buffer layer, crack-free GaN films can be successfully grown on Si (111) substrates using AlN and AlxGa1−xN buffer layers.
Bifunctional electrocatalytic films were prepared employing a layer-by-layer assembly approach. The cation, metalloporphyrin (MP), and the anion, potassium tetrachloroaurate (KAuCl4) were alternatively assembled on glass or indium-doped tin oxide (ITO) supports. The assembled AuCl4- ions were then converted to gold nanoparticles (Aun) under the exposure to ultraviolet light. Film growth at each adsorption step was monitored by UV-Vis absorption spectroscopy and cyclic voltammetry (CV). The formation of gold nanoparticles was characterized by UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Bifunctional electrocatalytic activity of the film was demonstrated in the oxidative detection of nitric oxide (NO) over Aun and the reductive detection of oxygen (O2) over Co(II)P in the same CV scan.
Fluorescent polystyrene microparticles with different sizes were produced by the consecutive assembly of fluorescently labeled polyelectrolytes using the layer-by-layer self-assembly method. Film growth was characterized by microelectrophoresis and fluorescence microscopic image (FMI) analysis. Alternating negative and positive ζ-potentials with deposition of each successive polyelectrolyte layer demonstrated that the alternate adsorption of polyelectrolytes was achieved. FMI analysis provided direct measurement of the fluorescence intensity of single microparticles. The subsequent deposition of a protein (immunoglobulin G, IgG) layer onto the fluorescent microparticles was confirmed by a sandwich immunoassay.
To describe the epidemiology of vancomycin-resistant enterococci (VRE) in a university hospital in Taipei, Taiwan.
Retrospective review over a 27-month period, from March 1996 to May 1998.
A tertiary-care teaching hospital in Taiwan.
Patients with VRE isolated from any body site.
Patients were identified through hospital microbiology and infection control records. Patient charts were reviewed for clinical and epidemiology data, including age, gender, previous hospital admissions, underlying diseases, types of infection, and recent antibiotic use. VRE isolates were characterized by their typical biochemical reactions, cellular fatty acid profiles, and the presence of van genes. Antibiotypes using the E-test and randomly amplified polymorphic DNA (RAPD) patterns of these isolates were used to determine the clonality.
Twenty-five isolates of VRE recovered from 12 patients were identified. One patient with a perianal abscess had 12 isolates of VRE (4 Enterococcus faecalis, 7 Enterococcus faecium, and 1 Enterococcus casseliflavus) recovered from perianal lesions. Among 3 patients who were hospitalized in the same room, 1 had a community-acquired cellulitis over the left leg caused by E faecalis, and the other 2 patients both had anal colonization with 2 isolates of E faecalis. The other 8 patients had 1 E faecalis isolate each from various clinical specimens. All isolates possessed vanA resistance phenotype and vanA genes. Different antibiotypes and RAPD patterns of the isolates from different patients excluded the possibility of nosocomial spread at the hospital.
Multiple species of VRE (E faecalis, E faecium, and E casseliflavus) and multiple clones of E faecium could colonize or infect hospitalized patients. In addition, clones of VRE can persist long-term in patients' lower gastrointestinal tracts. These results extend our knowledge of the coexistence and the persistence of multiple species and multiple clones of VRE in hospitalized patients.