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This study investigated the flow bifurcations of flows driven by a pressure gradient in a rectangular curved tube. When fluid flows within a curved tube, due to the centrifugal effect, secondary vortices can be induced in the cross section of the tube. The secondary flow states are dependent on the magnitude of the pressure gradient (q) and the aspect ratio (γ). In this study, the continuation method was applied to investigate the flow bifurcations in a curved tube with increasing pressure gradient (1 < q < 6000) and aspect ratio (0.9 < γ < 1.4).
The bifurcation diagrams are composed of solution branches, which are linked by limiting points or bifurcation points. The flow states in a solution branch belong to the same group. The ranges of the flow states and the relationship between the states can also be derived from the bifurcation diagrams. In this study, two types of bifurcation were found, one in the range of 0.9 < γ < 1.17, and another in the range of 1.18 < γ < 1.4. The ranges of stable flow solutions and the distributions of limit and bifurcation points in both pressure gradient and aspect ratio are derived in this study.
To assess the association between food insecurity and depression symptom severity stratified by sex, and test for evidence of effect modification by social network characteristics.
A population-based cross-sectional study. The nine-item Household Food Insecurity Access Scale captured food insecurity. Five name generator questions elicited network ties. A sixteen-item version of the Hopkins Symptom Checklist for Depression captured depression symptom severity. Linear regression was used to estimate the association between food insecurity and depression symptom severity while adjusting for potential confounders and to test for potential network moderators.
In-home survey interviews in south-western Uganda.
All adult residents across eight rural villages; 96 % response rate (n 1669).
Severe food insecurity was associated with greater depression symptom severity (b=0·4, 95 % CI 0·3, 0·5, P<0·001 for women; b=0·3, 95 % CI 0·2, 0·4, P<0·001 for men). There was no evidence of effect modification by social network factors for women. However, for men who are highly embedded within in their village social network, and (separately) for men who have few poor contacts in their personal network, the relationship between severe food insecurity and depression symptoms was stronger than for men on the periphery of their village social network, and for men with many poor personal network contacts, respectively.
In this population-based study from rural Uganda, food insecurity was associated with mental health for both men and women. Future research is needed on networks and food insecurity-related shame in relation to depression symptoms among food-insecure men.
We investigate the formation of young massive clusters near the nuclei in NGC 6946, IC 342, Maffei II, and NGC 7714, using ground-based mid-infrared [NeII] imaging. We derive the cluster formation efficiency and cluster mass function, and the results suggest that environmental effects on YMC formation may not be significant.
An uneven neurocognitive profile is a hallmark of autism spectrum disorder (ASD). Studies focusing on the visual memory performance in ASD have shown controversial results. We investigated visual memory and sustained attention in youths with ASD and typically developing (TD) youths.
We recruited 143 pairs of youths with ASD (males 93.7%; mean age 13.1, s.d. 3.5 years) and age- and sex-matched TD youths. The ASD group consisted of 67 youths with autistic disorder (autism) and 76 with Asperger's disorder (AS) based on the DSM-IV criteria. They were assessed using the Cambridge Neuropsychological Test Automated Battery involving the visual memory [spatial recognition memory (SRM), delayed matching to sample (DMS), paired associates learning (PAL)] and sustained attention (rapid visual information processing; RVP).
Youths with ASD performed significantly worse than TD youths on most of the tasks; the significance disappeared in the superior intelligence quotient (IQ) subgroup. The response latency on the tasks did not differ between the ASD and TD groups. Age had significant main effects on SRM, DMS, RVP and part of PAL tasks and had an interaction with diagnosis in DMS and RVP performance. There was no significant difference between autism and AS on visual tasks.
Our findings implied that youths with ASD had a wide range of visual memory and sustained attention impairment that was moderated by age and IQ, which supports temporal and frontal lobe dysfunction in ASD. The lack of difference between autism and AS implies that visual memory and sustained attention cannot distinguish these two ASD subtypes, which supports DSM-5 ASD criteria.
We investigated lactate dehydrogenase isoenzyme patterns in the cyst fluid of auricular pseudocysts and autogenous blood, to assist the diagnosis of auricular pseudocyst.
Twenty patients with auricular pseudocysts participated in this study conducted in Kaohsiung Medical University Hospital between February 2007 and June 2010. Patterns of lactate dehydrogenase in cyst fluid and autogenous blood were analysed.
Levels of lactate dehydrogenase 1 and 2 were lower in auricular pseudocysts than in autogenous blood, whereas levels of lactate dehydrogenase 4 and 5 were higher; this difference was statistically significant (p < 0.001).
Lactate dehydrogenase isoenzyme patterns in auricular pseudocyst fluid indicated higher percentage distributions of lactate dehydrogenase 4 and 5 and lower percentage distributions of lactate dehydrogenase 1 and 2. An effective laboratory method of evaluating the different lactate dehydrogenase isoenzyme components was developed; this method may improve the accuracy of auricular pseudocyst diagnosis.
We describe trends in incidence rates of methicillin-resistant Staphylococcus aureus (MRSA) in HIV-infected and HIV-uninfected patients enrolled in a large northern California Health Plan, and the ratio of MRSA to methicillin-susceptible S. aureus (MSSA) case counts. Between 1995 and 2010, 1549 MRSA infections were diagnosed in 14060 HIV-infected patients (11·0%) compared to 89546 MRSA infections in 6597396 HIV-uninfected patients (1·4%) (P = 0·00). A steady rise in MRSA infection rates began in 1995 in HIV-uninfected patients, peaking at 396·5 infections/100000 person-years in 2007. A more rapid rise in MRSA infection rates occurred in the HIV-infected group after 2000, peaking at 3592·8 infections/100000 in 2005. A declining trend in MRSA rates may have begun in 2008–2009. Comparing the ratio of MRSA to MSSA case counts, we observed that HIV-infected patients shouldered a greater burden of MRSA infection during most years of study follow-up compared to HIV-uninfected patients.
We report production of a self-injected, collimated (8 mrad divergence), 600 pC bunch of electrons with energies up to 350 MeV from a petawatt laser-driven plasma accelerator in a plasma of electron density ne = 1017 cm−3, an order of magnitude lower than previous self-injected laser-plasma accelerators. The energy of the focused drive laser pulse (150 J, 150 fs) was distributed over several hot spots. Simulations show that these hot spots remained independent over a 5 cm interaction length, and produced weakly nonlinear plasma wakes without bubble formation capable of accelerating pre-heated (~1 MeV) plasma electrons up to the observed energies. The required pre-heating is attributed tentatively to pre-pulse interactions with the plasma.
An innovative tri-axes micro-power receiver is proposed and studied for wireless magnetic energy transmission. The tri-axes micro-power receiver mainly consists of two sets of 3D micro-solenoids and one set of planar micro-coils in which individually iron core is all embedded. The three sets of micro-coils/micro-solenoids are designed to be orthogonal to each other. Therefore, no matter which direction the input magnetic flux is present along, the supplied magnetic energy can be harvested and transformed into electric power by the proposed micro-power receiver in wireless sense. Not only dead zone of receiving power is greatly reduced, but also transformation efficiency of magnetic energy into electric power can be much enhanced. By Biot-Savart law and Faraday’s law, the mathematical description upon power transmission from transmitter to receiver is developed. By employing commercial software, Ansoft Maxwell, based on finite element method, the estimation error on power transmission by mathematical description is revealed. Besides, the preliminary simulation results by Ansoft Maxwell show that the proposed micro-power receiver can efficiently harvest the energy supplied by magnetic power source. The design parameters of tri-axes micro-receiver are hence examined and verified for follow-up fabrication. At last, for the MEMS process, the isotropic etching technique is employed to micro-machine the inverse-trapezoid fillister so that the copper wire can be successfully electroplated. The adhesion between micro-coils and fillister is hence much enhanced as well.
CdTe nanocrystal quantum dots sequestered in TiO2 thin film matrix have been synthesized by r.f. sputtering from a composite CdTe/TiO2 target. CdTe nanocrystal formation is nucleation controlled as their size (11-25 nm), dispersion and volume fraction (0.065-0.2) increases with film thickness, substrate temperature (100°C) and thermal treatment. The optical band gap derived from the onset of absorption coefficient showed blue shifts concurrent with the CdTe nanocrystal size reduction due to quantum size effects. These shifts, not consistent with theoretical models based on strong or weak confinement regimes, are explained on the basis of anisotropic growth and formation of CdTe nanocrystal clusters. TiO2, in addition to being an ideal passivator and providing a barrier for carrier confinement to observe quantum effects, shows O2 vacancy dependent conductivity modulation. Electrical conductivity variation with CdTe nanocrystal size and density is attributed to electrical coupling and tunneling behavior of carriers between CdTe nanocrystallites.
Light emitting devices (LEDs) based on porous polysilicon (PPS) have been fabricated on a transparent quartz substrate. Several structures have been developed, each consisting of a backside contact (ITO or p+ polysilicon), a light emitting PPS layer, a capping layer, and a metal top contact. Photoluminescence (PL) from PPS is similar to that of etched crystalline Si, peaking near 750 nn and showing degradation during 515 nm laser excitation with intensity <100 mW/cm2. This degradation disappears if PPS is oxidized after formation. Visible electroluminescence (EL) has been achieved in both oxidized and non-oxidized PPS devices with voltages under 10 V and current densities <200 mA/cm2.
Radiation hard monolithic particle sensors can be fabricated by a vertical integration of amorphous silicon particle sensors on top of CMOS readout chip. Two types of such particle sensors are presented here using either thick diodes or microchannel plates. The first type based on amorphous silicon diodes exhibits high spatial resolution due to the short lateral carrier collection. Combination of an amorphous silicon thick diode with microstrip detector geometries permits to achieve micrometer spatial resolution beneficial for high accuracy beam positioning. Microchannel plates based on amorphous silicon were successfully fabricated and multiplication of electrons was observed. This material may solve some of the problems related to conventional microchannel devices. Issues, potential and limits of these detectors are presented and discussed.
Single crystal-silicon quantum well layers with SiO2 barriers were grown from silicon-on-insulator substrates. Photoluminescence in the red and near-infrared was observed for average layer thickness < 8 nm, with peak signal for 2-nm thickness. The luminescence spectrum was essentially independent of well width for SiO2 barriers, but the photoluminescence intensity decreased sharply after annealing in Ar. These results suggest the importance of radiation from surface states. In contrast to oxide-passivated silicon nanocrystals and to porous silicon, the room-temperature photoluminescence quantum efficiency is low (10-4-10-5), probably due to variations in layer thickness and to diffusion of photoexcited carriers to fast nonradiative recombination centers.
We discuss a process for selective area deposition of microcrystalline silicon (μc-Si) using plasma enhanced chemical vapor deposition at low substrate temperature (<300°C) using time modulated silane flow in a hydrogen plasma. We discuss selectivity and deposition rate on a variety of substrates with process conditions important for manufacturing applications, and show a distinct microstructural evolution in the initial nucleation layers using Raman spectroscopy that correlates with the transition from selective to non-selective growth. Atomic hydrogen discriminates between different degrees of bond strain in the nucleii formed on different substrates, and can increase the crystallinity fraction in films deposited at low temperatures by modifying the kinetics of bulk-like bond formation.
Small-angle neutron scattering (SANS) measurements of four electrochemically etched, porous silicon (PS) samples have been performed over a wide wavevector transfer (Q) range. The intermediate to high Q results can be modeled with a non-particulate, random phase model. Correlation length scales on the order of 1 to 2 nm thought to characterize the PS skeleton have been deduced from the SANS data. The microstructural anisotropy was studied tilting two of the samples with respect to the neutron beam. These samples exhibited an asymmetric scattering pattern at intermediate Q (0.1 ≤ Q ≥ 0.6 nm-1) in this condition. Photoluminescence spectra from all four samples have been recorded as well. A correlation appears to exist between the SANS and photoluminescence measurements. An x-ray diffraction measurement of one sample demonstrates that the PS layer retains the silicon lattice structure. Significant peak broadening is observed that we interpreted as a quasi-particle size effect The PS particle size calculated from the x-ray diffraction measurement is equal to the correlation length obtained in the SANS measurement.
We have developed three classes of techniques to produce micron-size and submicron-size light emitting porous Si (LEPSi) patterns and to protect the rest of the wafer. In the 1st class, LEPSi lines down to 2 µm width have been made using a photoresist/silicon nitride trilayer mask, followed by anodization. PL mapping of the structures indicates that the protected regions have not been etched. Using electron beam lithography sub-0.5 micron porous Si lines have been generated. In the 2nd class, formation of porous Si is inhibited by amorphizing Si using ion implantation followed by anodization and annealing. The crystallinity and electrical properties of the implanted region have been fully characterized after annealing. Using focussed ion-beam implantation, LEPSi patterns of the order of 100 nm have been obtained. The 3rd class consists of enhancing the formation of porous Si by a low energy/low dose bombardment (ion-milling) with argon ions prior to anodization. Under appropriate conditions, we have observed a strong enhancement of the formation rate of LEPSi where bombardment took place, possibly due to the generation of a large number of defects on the wafer surface.
CVD diamond films prepared under varying conditions have been investigated with IR and Raman spectroscopy. Raman spectroscopy was used to characterize the crystal structure, and ir absorption was used to determine the H bonding environments. The growth temperatures were varied in one series, while the CH4/H2 ratio was varied in another. The IR absorption of all the samples showed a weak broad band extending from approximately 2800 to 2970 cm−1 which was attributed to H bonded to sp3 C sites. There was no evidence of ir absorption at 3000 to 3200 cm−1 which would indicate H bonded to sp2 or sp1 C sites. For both series, the Raman measurements showed progression from diamond-like films to diamond films. The ir absorption showed a general trend of less H with more well ordered diamond structures. No sharp transition of the H incorporation vs the growth parameters was observed.
The preparation of amorphous insulating films containing nanometer-scaled structures of semiconductors has attracted increased attention since the observation of room temperature emission of light from films containing indirect-bandgap semiconductors such as Ge and Si. While most experimental reports on these Si and Ge nano-scale structures have been based on thin films created using sputter-deposition, in this study we have used conventional ion implantation of Ge to create the non-equilibrium mixture of materials that, upon annealing, develops a nano-crystallite phase embedded in the amorphous matrix. The presence of clusters that are difficult to image in TEM, in addition to microcrystallites, is an issue of interest since the source of light emission is still controversial. The second phase is formed from excess amounts of the semiconductor, in this case added by implantation. In this paper the formation and size distribution of the Ge nano-structures was characterized using Raman scattering and transmission electron microscopy (TEM). Similarly to reported sputtered film results, Raman spectra suggest Ge clusters that are not well formed crystallites may be present for anneals at low temperatures and in unannealed films. For annealing temperatures exceeding 600°C, a mixture of amorphous-like clustering and nano-crystallites may result, depending on the volume fraction of Ge. For low dose samples it was found that temperature and time of annealing could be used to manipulate the nucleation behavior of the nano-crystallites.
A porous polymer material, which is made of a two-phase composite and contains 35% porosity with a pore size less than 50Å, is found to have a dielectric constant of 1.8. It absorbs almost no water. The electrical properties, such as capacitance and leakage current, do not change with time and temperature.
A novel embedded cylindrical-array magnetic actuator (ECAMA) is proposed and
verified by experiments to provide sufficient magnetic force for spindle
deviation regulation of high-speed milling process. Four I-shape silicon
steel columns enclosing the spindle constitute the backbone of the ECAMA.
The shape of modified concave-type yokes is designed to reduce the average
air gap between magnetic poles and the spindle. In contrast to the
conventional AMB (active magnetic bearing) design for which coils are
usually wound on the yokes, the copper wire is wound on the I-shape silicon
steel columns. As a result, the overall wound coil turns can be much
increased. In other words, stronger magnetic force can be induced by ECAMA.
On the other hand, to reduce the cost of ECAMA, two pairs of self-sensing
modules are employed to replace the gap sensors for measurement of spindle
position deviation. In order to verify the efficacy of the proposed ECAMA
and the self-sensing module, high-speed milling tests are undertaken. By
inspection on the precision and quality of the finish surface of workpiece,
the superiority of ECAMA and the self-sensing module are assured.
This study examines the parallel computing as a means to minimize the execution time in the optimization applied to thermohydrodynamic (THD) lubrication. The objective of the optimization is to maximize the load capacity of a slider bearing with two design variables. A global optimization method, DIviding RECTangle (DIRECT) algorithm, is used. The first approach was to apply the parallel computing within the THD model in a shared-memory processing (SMP) environment to examine the parallel efficiency of fine-grain computation. Next, a distributed parallel computing in the search level was conducted by use of the standard DIRECT algorithm. Then, the algorithm is modified to provide a version suitable for effective parallel computing. In the latter coarse-grain computation the speedups obtained by the DIRECT algorithms are compared with some previous studies using other parallel optimization methods. In the fine-grain computation of the SMP machine, the communication and overhead time costs prohibit high speedup in the cases of four or more simultaneous threads. It is found that the standard DIRECT algorithm is an efficient sequential but less parallel-computing-friendly method. When the modified algorithm is used in the slider bearing optimization, a parallel efficiency of 96.3% is obtained in the 16-computing-node cluster. This study presents the modified DIRECT algorithm, an efficient parallel search method, for general engineering optimization problems.