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Central nervous system infections (CNSI) are a leading cause of death and long-term disability in children. Using ICD-10 data from 2005 to 2015 from three central hospitals in Ho Chi Minh City (HCMC), Vietnam, we exploited generalized additive mixed models (GAMM) to examine the spatial-temporal distribution and spatial and climatic risk factors of paediatric CNSI, excluding tuberculous meningitis, in this setting. From 2005 to 2015, there were 9469 cases of paediatric CNSI; 33% were ⩽1 year old at admission and were mainly diagnosed with presumed bacterial CNSI (BI) (79%), the remainder were >1 year old and mainly diagnosed with presumed non-bacterial CNSI (non-BI) (59%). The urban districts of HCMC in proximity to the hospitals as well as some outer districts had the highest incidences of BI and non-BI; BI incidence was higher in the dry season. Monthly BI incidence exhibited a significant decreasing trend over the study. Both BI and non-BI were significantly associated with lags in monthly average temperature, rainfall, and river water level. Our findings add new insights into this important group of infections in Vietnam, and highlight where resources for the prevention and control of paediatric CNSI should be allocated.
Strongyloidiasis is a neglected tropical disease caused by the roundworm Strongyloides stercoralis affecting 30–100 million people worldwide. Many Southeast-Asian countries report a high prevalence of S. stercoralis infection, but there are little data from Vietnam. Here, we evaluated the seroprevalence of S. stercoralis related to geography, sex and age in Vietnam through serological testing of anonymized sera. Sera (n = 1710, 1340 adults and 270 children) from an anonymized age-stratified serum bank from four regions in Vietnam between 2012 and 2013 were tested using a commercial Strongyloides ratti immunoglobulin G ELISA. Seroreactivity was found in 29·1% (390/1340) of adults and 5·5% (15/270) of children. Male adults were more frequently seroreactive than females (33·3% vs. 24·9%, P = 0·001). The rural central highlands had the highest seroprevalence (42·4% of adults). Seroreactivity in the other regions was 29·9% (Hue) and 26·0% and 18·2% in the large urban centres of Hanoi and Ho Chi Minh City, respectively. We conclude that seroprevalence of S. stercoralis was high in the Vietnamese adult population, especially in rural areas.
We have investigated the impact broadening of the 12 μm lines. Ion broadening is found to follow the adiabatic theory, whereas electron broadening needs a non-adiabatic treatment. This relaxes the fixed width/shift ratio, as found by Chang and Schoenfeld (1991), using a pure adiabatic analysis.
Over the last 30 years organic carbon nanotube-yarn (CNTY) based dye-sensitized solar cells (DSSCs) have received considerable interest. CNTY based DSSCs have become a main focus of alternative energy source research. CNTY based PV cells have an advantage over cells based on non-flexible substrates, such as fluorine doped tin oxide glass; as a foundation for dye-sensitized solar cells, CNTYs are superior due to their low-cost, environmental sustainability, high mechanical integrity, and numerous beneficial practical applications. CNTY based DSSCs also have additional advantages because of their low electrical resistance, excellent electrocatalytic activity, and ultra-high mechanical integrity. Additionally, quantum dots and polymers have shown great promise for photovoltalic application due to their tunable bandgap and wide photon absorption range. This research explores the barrier characteristics associated with new absorbing photovoltaic materials that promote electron/hole pair separation and transportation. Utilizing the hybrid bandgap structures of quantum dots and polymers as well as the flexibility of CNTY, we reported a 3D flexible DSSC with an efficiency of 2.9%.
Non-typhoidal Salmonella are an important but poorly characterized cause of paediatric diarrhoea in developing countries. We conducted a hospital-based case-control study in children aged <5 years in Ho Chi Minh City to define the epidemiology and examine risk factors associated with Salmonella diarrhoeal infections. From 1419 diarrhoea cases and 571 controls enrolled between 2009 and 2010, 77 (5·4%) diarrhoea cases were stool culture-positive for non-typhoidal Salmonella. Salmonella patients were more likely to be younger than controls (median age 10 and 12 months, respectively) [odds ratio (OR) 0·97; 95% confidence interval (CI) 0·94–0·99], to report a recent diarrhoeal contact (8·1% cases, 1·8% controls; OR 5·98, 95% CI 1·8–20·4) and to live in a household with >2 children (cases 20·8%, controls 10·2%; OR 2·32, 95% CI 1·2–4·7). Our findings indicate that Salmonella are an important cause of paediatric gastroenteritis in this setting and we suggest that transmission may occur through direct human contact in the home.
In Vietnam, highly pathogenic avian influenza (HPAI) H5N1 infections in poultry often occur without concomitant clinical signs and outbreaks are not consistently reported. Live bird markets represent a convenient site for surveillance that does not rely on farmers' notifications. Two H5N1 surveys were conducted at live bird markets/slaughter points in 39 districts (five provinces) in the Red River, Mekong delta, and central Vietnam during January and May 2011. Oropharyngeal and rectal swab samples from 12 480 ducks were tested for H5N1 by reverse transcription–polymerase chain reaction in pools of five. Traders and stallholders were interviewed using standardized questionnaires; 3·3% of pools tested positive. The highest prevalence (6·6%) corresponded to the Mekong delta, and no H5N1 was detected in the two Red River provinces. The surveys identified key risk behaviours of traders and stallholders. It is recommended that market surveys are implemented over time as a tool to evaluate progress in HPAI control in Vietnam.
This work investigates the reliability issues associated with an aluminum sputter process, called the Al-plug process, that results in the complete filling of submicron contacts and vias of various sizes. The state-of-the-art Al-plug technology has proven its superiority over conventional processes due to its process simplicity and complete elimination of metal step-coverage problems and dielectric voiding over contacts/vias, resulting in higher reliability. Materials and electrical characterization of this metal process are presented.
The effects of the space environment on polytetrafluorethylene and some fluorinated polymers, copolymers, and blends are critically reviewed. It is shown that in low altitude orbits such as Low Earth Orbit and Geostationary Orbit the presence of both ionizing radiation and atomic oxygen triggers a synergetic degradation of materials based on fluorinated polymers. The behavior is due to the lability of the in-chain alkyl radical to oxygen attack. It is concluded that fluorinated polymers should not be used as materials for space applications, as long as the mission implies low Earth orbits.
Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been produced by consolidation of mechanical alloyed powders. Powders with composition Al90Mg10 and Al80Mg20 were consolidated into highly dense specimens by hot extrusion. Room temperature compression tests for the Al90Mg10 specimen reveal interesting mechanical properties, namely, a high strength of 630 MPa combined with a plastic strain of about 4 %. The increase of the Mg content to 20 at.% increases the strength by about 100 MPa but it suppresses plastic deformation. The Al60Mg40 powder was consolidated at different temperatures by spark plasma sintering and the effect of the sintering temperature on microstructure, density and hardness have been studied. The results reveal that both density and hardness of the consolidated samples increase with increasing sintering temperature, while retaining a nanocrystalline structure. These results indicate that powder metallurgy is a suitable processing route for the production of nanocrystalline Al-Mg alloys with promising mechanical properties.
Nanoporous devices constitute emerging platforms for selective molecule separation and sensing, with great potential for high throughput and economy in manufacturing and operation. Acting as mass transfer diodes similar to a solid-state device based on electron conduction, conical pores are shown to have superior performance characteristics compared to traditional cylindrical pores. Such phenomena, however, remain to be exploited for molecular separation. Here we present performance results from silicon membranes created by a new synthesis technique based on interferometric lithography. This method creates millimeter sized planar arrays of uniformly tapered nanopores in silicon with pore diameter 100 nm or smaller, ideally-suited for integration into a multi-scale microfluidic processing system. Molecular transport properties of these devices are compared against state-of-the-art polycarbonate track etched (PCTE) membranes. Mass transfer rates of up to fifteen-fold greater than commercial sieve technology are obtained. Complementary results from molecular dynamics simulations on molecular transport are reported.
The volume of a Wiener sausage constructed from a diffusion process with periodic, mean-zero, divergence-free velocity field, in dimension 3 or more, is shown to have a non-random and positive asymptotic rate of growth. This is used to establish the existence of a homogenized limit for such a diffusion when subject to Dirichlet conditions on the boundaries of a sparse and independent array of obstacles. There is a constant effective long-time loss rate at the obstacles. The dependence of this rate on the form and intensity of the obstacles and on the velocity field is investigated. A Monte Carlo algorithm for the computation of the volume growth rate of the sausage is introduced and some numerical results are presented for the Taylor–Green velocity field.
We consider the problem of the existence and characterization of a homogenized limit for advection-diffusion in a perforated domain. This problem was initially motivated for us as a model for the transport of water vapour in the atmosphere, subject to molecular diffusion and turbulent advection, where the vapour is also lost by condensation on suspended ice crystals. It is of interest to determine the long-time rate of loss and in particular whether this is strongly affected by the advection. In this article we address a simple version of this set-up, where the advection is periodic in space and constant in time and where the ice crystals remain fixed in space.
Structural properties of liquid and amorphous Al2O3.2SiO2
(denoted as AS2) have been studied in a model containing 3025 particles
under periodic boundary conditions with the Born-Mayer type pair potentials.
Models have been obtained by cooling from the melt via molecular dynamics
(MD) simulation. Structural properties of an amorphous model obtained at the
temperature of 350 K have been analyzed in details through the partial
radial distribution functions (PRDF), coordination number distribution,
bond-angle distributions and interatomic distances. Calculations show that
calculated data agree well with the experimental ones and with those
obtained previously in other simulation works. The evolution of structure
upon cooling from the melt was observed and discussed. We found a clear
evidence of the existence of triclusters in the system. Diffusion constant
of particles has been calculated and discussed. Calculations presented that
the temperature dependence of diffusion constant D of components in the
system shows an Arrhenius law at temperatures ranged from 2450 K to 4200 K
and it shows a power law,
$D\propto (T-T_C )^\gamma$
, at higher
Few studies have been conducted in Vietnam on the epidemiology of healthcare-associated infections or antimicrobial use. Thus, we sought to determine the prevalence of and risk factors for surgical-site infections (SSIs) and to document antimicrobial use in surgical patients in a large healthcare facility in Vietnam.
We conducted a point-prevalence survey of SSIs and antimicrobial use at Cho Ray Hospital, Ho Chi Minh City, a 1,250-bed inpatient facility. All patients on the 11 surgical wards and 2 intensive care units who had surgery within 30 days before the survey date were included.
Of 391 surgical patients, 56 (14.3%) had an SSI. When we compared patients with and without SSIs, factors associated with infection included trauma (relative risk [RR], 2.65; 95% confidence interval [CI95], 1.60 to 4.37; P < .001), emergency surgery (RR, 2.74; CI95, 1.65 to 4.55; P < .001), and dirty wounds (RR, 3.77; CI95, 2.39 to 5.96; P < .001). Overall, 198 (51%) of the patients received antimicrobials more than 8 hours before surgery and 390 (99.7%) received them after surgery. Commonly used antimicrobials included third-generation cephalosporins and aminoglycosides. Thirty isolates were identified from 26 SSI patient cultures; of the 25 isolates undergoing antimicrobial susceptibility testing, 22 (88%) were resistant to ceftriaxone and 24 (92%) to gentamicin.
Our data show that (1) SSIs are prevalent at Cho Ray Hospital; (2) antimicrobial use among surgical patients is widespread and inconsistent with published guidelines; and (3) pathogens often are resistant to commonly used antimicrobials. SSI prevention interventions, including appropriate use of antimicrobials, are needed in this population.
For flood protection against storm tides, barriers of box-like
hinged along a
bottom axis have been designed to span the three inlets of the Venice Lagoon.
on calm days the gates are ballasted to rest horizontally on the seabed,
weather they are raised by buoyancy to act as a dam which is expected to
and fro in unison in response to the normally incident sea waves. Previous
experiments with sinusoidal waves have revealed however that neighbouring
oscillate out of phase, at one half the wave frequency, in a variety of
ways, and hence
would reduce the effectiveness of the barrier. Extending the linear theory
waves by Mei et al. (1994), we present here a nonlinear
theory for subharmonic
resonance of mobile gates allowed to oscillate about a vertical plane of
In this part (1) the evolution equation of the Landau–Stuart type
is first derived for
the gate amplitude. The effects of gate geometries on the coefficients
in the equation
are examined. After accounting for dissipation effects semi-empirically
results on the equilibrium amplitude excited by uniform incident waves
with laboratory experiments.
In order to examine the effects of finite bandwidth of the
incident sea spectrum on
the resonance of the articulated storm gates for Venice Lagoon, we consider
band consisting of the carrier frequency and two sidebands. The evolution
for the gate oscillations now has a time-periodic coefficient, and is
equivalent to a non-autonomous dynamical system. For small damping and
analysis for local and global bifurcations are carried out, and extended
numerical simulation. Typical bifurcation scenarios are also examined by
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