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Indoor transmission of respiratory droplets bearing influenza within humans poses high risks to respiratory function deterioration and death. Therefore, we aimed to develop a framework for quantifying the influenza infection risk based on the relationships between inhaled/exhaled respiratory droplets and airborne transmission dynamics in a ventilated airspace. An experiment was conducted to measure the size distribution of influenza-containing droplets produced by coughing for a better understanding of potential influenza spread. Here we integrated influenza population transmission dynamics, a human respiratory tract model, and a control measure approach to examine the indoor environment–virus–host interactions. A probabilistic risk model was implemented to assess size-specific infection risk for potentially transmissible influenza droplets indoors. Our results found that there was a 50% probability of the basic reproduction number (R0) exceeding 1 for small-size influenza droplets of 0·3–0·4 µm, implicating a potentially high indoor infection risk to humans. However, a combination of public health interventions with enhanced ventilation could substantially contain indoor influenza infection. Moreover, the present dynamic simulation and control measure assessment provide insights into why indoor transmissible influenza droplet-induced infection is occurring not only in upper lung regions but also in the lower respiratory tract, not normally considered at infection risk.
The purpose of this paper was to determine how contact behaviour change influences the indoor transmission of influenza A(H1N1)pdm09 among school children. We incorporated transmission rate matrices constructed from questionnaire responses into an epidemiological model to simulate contact behaviour change during an influenza epidemic. We constructed a dose–response model describing the relationships between contact rate, viral load, and respiratory symptom scores using published experimental human infection data for A(H1N1)pdm09. Findings showed that that mean numbers of contacts were 5·66 ± 6·23 and 1·96 ± 2·76 d−1 in the 13–19 and 40–59 years age groups, respectively. We found that the basic reproduction number (R0) was <1 during weekends in pandemic periods, implying that school closures or class suspensions are probably an effective social distancing policy to control pandemic influenza transmission. We conclude that human contact behaviour change is a potentially influential factor on influenza infection rates. For substantiation of this effect, we recommend a future study with more comprehensive control measures.
Influenza poses a significant public health burden worldwide. Understanding how and to what extent people would change their behaviour in response to influenza outbreaks is critical for formulating public health policies. We incorporated the information-theoretic framework into a behaviour-influenza (BI) transmission dynamics system in order to understand the effects of individual behavioural change on influenza epidemics. We showed that information transmission of risk perception played a crucial role in the spread of health-seeking behaviour throughout influenza epidemics. Here a network BI model provides a new approach for understanding the risk perception spread and human behavioural change during disease outbreaks. Our study allows simultaneous consideration of epidemiological, psychological, and social factors as predictors of individual perception rates in behaviour-disease transmission systems. We suggest that a monitoring system with precise information on risk perception should be constructed to effectively promote health behaviours in preparation for emerging disease outbreaks.
To examine the effects of complex cognitive (mahjong) and physical (Tai Chi) activities on dementia severity in nursing home residents with dementia.
Cluster-randomized open-label controlled design. 110 residents were randomized by nursing home into three conditions: mahjong, Tai Chi, and simple handicrafts (control). Activities were conducted three times a week for 12 weeks. Clinical Dementia Rating (CDR) was taken at 0 (baseline), 3 (post-treatment), 6, and 9 months. The outcome measure was CDR sum-of-box, which is a composite measure of both cognitive and functional deterioration in dementia.
Intent-to-treat analyses were performed using multilevel regression models. Apolipoprotein E ε4 allele and education were included as covariates. Neither treatments had effects on the cognitive and functional components of the CDR, but mahjong had a significant interaction with time on the CDR sum-of-box total, suggesting a slower rate of global deterioration in the mahjong group as compared with the control group.
Mahjong led to a gradual improvement in global functioning and a slightly slower rate of dementia progression over time. The effect was generalized and was not specific to cognition or daily functioning.
To examine potential clinical outcomes and cost of active methicillin-resistant Staphylococcus aureus (MRSA) surveillance with and without decolonization in neonatal intensive care units (NICUs) from the perspective of healthcare providers in Hong Kong.
Decision analysis modeling.
Hypothetical cohort of patients admitted to an NICU.
We designed a decision tree to simulate potential outcomes of active MRSA surveillance with and without decolonization in patients admitted to an NICU. Outcome measures included total direct medical cost per patient, MRSA infection rate, and MRSA-associated mortality rate. Model inputs were derived from the literature. Sensitivity analyses evaluated the impact of uncertainty in all model variables.
In the base-case analysis, active surveillance plus decolonization showed a lower expected MRSA infection rate (0.911% vs 1.759%), MRSA-associated mortality rate (0.223% vs 0.431%), and total cost per patient (USD 47,294 vs USD 48,031) compared with active surveillance alone. Sensitivity analyses showed that active surveillance plus decolonization cost less and had lower event rates if the incidence risk ratio of acquiring MRSA infections in carriers after decolonization was less than 0.997. In 10,000 Monte Carlo simulations, active surveillance plus decolonization was significantly less costly than active surveillance alone 99.9% of the time, and both the MRSA infection rate and the MRSA-associated mortality rate were significantly lower 99.9% of the time.
Active surveillance plus decolonization for patients admitted to NICUs appears to be cost saving and effective in reducing the MRSA infection rate and the MRSA-associated mortality rate if addition of decolonization to active surveillance reduces the risk of MRSA infection.
Infect Control Hosp Epidemiol 2012;33(10):1024-1030
Undoped 69GaAs/71GaAs isotope superlattice structures grown by MBE on n-type GaAs substrates, doped by Si to ∼3×1018 cm−3, have been used to study Ga self-diffusion in GaAs by disordering reactions. In the temperature range of 850–960°C, the SIMS measured Ga self-diffusivity values showed an activation enthalpy of 4 eV, and are larger than previously compiled Ga self-diffusivity and Al-Ga interdiffusivity values obtained under thermal equilibrium and intrinsic conditions, which are characterized by a 6 eV activation enthalpy. SIMS, CV, and TEM characterizations showed that the as-grown superlattice layers were intrinsic which became p-type with hole concentrations up to ∼2×1017 cm−3 after annealing, because the layers contain carbon. Dislocations of a density of ∼106-107 cm−2 were also present. However, the factor responsible for the presently observed larger Ga self-diffusivity values appears to be Si outdiffusion from the substrate, which was determined using CV measurements. Outdiffusion of Si decreases the n value in the substrate which causes the release of excess Ga vacancies into the superlattice layers where the supersaturated Ga vacancies enhance Ga self-diffusion.
The aim of this work was to use experimental infection data of human influenza to assess a simple viral dynamics model in epithelial cells and better understand the underlying complex factors governing the infection process. The developed study model expands on previous reports of a target cell-limited model with delayed virus production. Data from 10 published experimental infection studies of human influenza was used to validate the model. Our results elucidate, mechanistically, the associations between epithelial cells, human immune responses, and viral titres and were supported by the experimental infection data. We report that the maximum total number of free virions following infection is 103-fold higher than the initial introduced titre. Our results indicated that the infection rates of unprotected epithelial cells probably play an important role in affecting viral dynamics. By simulating an advanced model of viral dynamics and applying it to experimental infection data of human influenza, we obtained important estimates of the infection rate. This work provides epidemiologically meaningful results, meriting further efforts to understand the causes and consequences of influenza A infection.
Co-sputtering has been used to fabricate equiatomic thin films of TiNi, a shape memory alloy, which form the basis of microactuators with many applications in MEMS. The stress evolution of TiNi films will be described. The performance of the TiNi actuators has been characterized, with regards to actuation force, recoverable strain, time response, and fatigue resistance. The performance of microvalves using these actuators will also be presented.
A new structure of triode type field emission displays based on single-walled carbon nanotube emitters is demonstrated. In this structure, gate electrodes are situated under cathode electrodes with an in-between insulating layer, so called under-gate type triode. Electron emission from the carbon nanotube emitters is modulated by changing gate voltages. A threshold voltage is approximately 70 V at the anode bias of 275 V.
Ag films deposited on Si(111) substrates by partially ionized beam (PIB) under conventional vacuum conditions were studied by MeV ion channeling techniques. In spite of their large lattice mismatch (24.8%), Ag films were still found to be epitaxial. With a deposition temperature of 350°C and without post-annealing, the Xmin value at the surface of a 2550 A° thick Ag film was found to be 10%. The azimuthal angular scan and the measured axial channeling dip showed that the Ag film was (111) oriented. The lattice quality of the films was comaparable to that deposited by MBE techniques. Dislocations were found in the PIB deposited Ag films. Lattice damage due to the bombardment of energetic ions was also observed. The thickness of the Ag film was found to have a pronounced effect on the crystalline quality at the surface. With the thickness increasing from 1240 A° to 2550 A°, the lattice quality at the Ag surface improved significantly, but not much change in the defect density in the Ag films was obseved.
The combination of Cu and parylene (poly-p-xylylene) for metallization and insulator in integrated circuit or packaging multilayer interconnection systems gives one of the lowest resistance and capacitance values per unit length. In this paper we present a detailed study of the diffusion characteristics of Cu in parylene-n (PA-n) substrates. PA-n was vapor-deposited and Cu metallization performed at room temperature using the Partially Ionized Beam (PIB) technique. Rutherford Backscattering (RBS) technique has been used to study the diffusion of Cu in PA-n substrate after annealing the samples to elevated temperatures in vacuum. We found no sign of Cu diffusion after the Cu/PA-n sample was annealed at 300°C for 6 hours. Diffusion occurs at 350 °C. However, preannealed PA-n substrate prior to Cu deposition can prevent the diffusion even at a temperatures above 350°C. Also we found that amorphous carbon and chromium are good diffusion barriers of Cu on PA-n. The dry adhesion between PA-n deposited on Al, Cu and Ag was found to be good. The adhesion of these PIB deposited metals on PA-n in high vacuum was also very good.
Al-Ga interdiffusion, carbon acceptor diffusion, and hole reduction were studied in carbondoped Al0.4Ga0.6As/GaAs superlattices (SL). Al-Ga interdiffusion was found to be most prominent for Ga-rich annealing, with the hole concentrations in the SL almost intact during annealing. For As-rich annealing, the interdiffusivity values, DAI.Ga, are in approximate agreement with those predicted by the Fermi-level effect model, and the hole concentrations in the SL decreased dramatically after annealing. By analyzing the measured hole concentration profiles, it was found that both carbon acceptor diffusion and reduction have occurred during annealing, with both depending on As4 pressure values to the one quarter power. These As4 pressure dependencies indicate that carbon diffuses via the interstitial-substitutional mechanism while hole reduction is governed by a precipitation mechanism.
We performed in-situ x-ray reflectivity measurements to study the growth dynamics of gold sputter deposited onto silicon using an x-ray scattering chamber equipped with a faced magnetron source where the substrate is held at a right angle relative to the sputtering guns. By operating the guns at low power (1 watt) and under 20 mTorr Ar, we could control the gold deposition rate to less than 1Å/sec. The observed x-ray reflectivity for gold deposited onto a silicon substrate at 300 K and 400 K is consistent with nucleated island growth for average gold particle sizes less than 50 Å. Above 50 Å, the reflectivity data indicates that the gold film uniformly covers the silicon surface, and that as the film thickness is increased the gold-vacuum interface gets progressively rougher. Detailed analysis of room temperature data is in progress, as is the temperature dependence on the roughness of the gold vacuum interface.
We studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO2 films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO2 films with out-of plane particle size ranging from 60–310Å. Each VO2 film was grown on a thin TiO2 buffer layer, which in turn was grown by MOCVD on a polished sapphire (1120) substrate. The transition was found to be first order. As the out-of plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60Å film the transition was observed at ∼61°C with a transition width of ∼10°C, while for the 310Å film the transition temperature was ∼59°C and the transition width ∼2°C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.
Alloys, with six different compositions in the system Mg-Ca-Zn were produced by melt spinning. The aging behavior of alloys was investigated by measuring the changes in microhardness after isochronal aging and the microstructure was analyzed by means of Transmission Electron Microscopy(TEM), Energy Dispersive X-ray Spectrometry (EDS), Scanning Transmission Electron Microscopy (STEM) and Scanning Electron Microscopy (SEM). All six compositions in the as-solidified condition show a difference in microstructure between the wheel contact side (zone A) and the free surface side (zone B) as a result of the differences in the solidification rate across the ribbons. One of the alloys was chosen to be more deeply investigated in this work as it exhibited grain boundary films and presented the highest peak hardness among the low Ca alloys. The comparison between the two microstructural zones in this alloy can aid in understanding of the phase transformation steps during cooling with a model which is proposed here.
The nanoporous materials prepared from iron-iron oxide core-shell nanoparticles are of great interest due to their enhanced possibilities for distribution in the environment, a high rate of chemical reactivity and also the possibility to enhance environmentally friendly reaction paths. However, production of these nanoparticle porous materials by conventional methods is difficult. Therefore, we use a cluster deposition system, which prepares the iron nanoclusters and iron-iron oxide core shell nanoclusters at room temperature. The nanoporous films are synthesized by using the nanoclusters as building blocks. These films are characterized using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and the Brunauer-Emmett-Teller (BET) method for surface area determination.
Color phosphors have been deposited on indium-tin glasses by utilizing an electrophoretic process for the application to prototype 4-inch full color FED devices. The deposition suspension is prepared with color phosphors of l-3um size, isopropanol, charger and binder. Various parameters, such as deposition time and applied voltages, are systematically performed to this end. As a result, each phosphor exhibited uniform thickness of about 6–10um over the whole plate. Electrical properties of the deposited phosphors are investigated and compared both in the vacuum chamber and in fully-sealed 4” FED conditions. In addition, they are extensively characterized by the SEM and 3-dimentional analysis. Experimental results confirm that the phosphor quality in real FED devices is significantly affected by deposition conditions.
We report an investigation of optical-limiting behavior in two neutral nickel complexes with multi-sulfur 1,2 dithiolene ligands, [Ni(medt)2] I (medt = 5,6-dihydro-6-methyl-1,4-dithiin-2,3- dithiolate) and [Ni(phdt)2] 2 (phdt = 5,6-dihydro-5-phenyl-l,4-dithiin-2,3-dithiolate) in benzene solution. The fluence-dependent transmission of the complexes was observed with nanosecond and picosecond laser pulses at 532-nm wavelength. The limiting thresholds of the complexes were ˜0.3 J/cm2, when measured with the picosecond pulses. Both picosecond time-resolved pump-probe and Z-scan measurement revealed that the limiting effects should originate from excited-state absorption and refraction. The transparency window (400˜900 nm), observed in the linear absorption spectra of the complexes, indicated that their limiting response should cover a wider range than those of fullerenes and phthalocyanines.