Comparison of next-generation portable pollution monitors to measure exposure to PM2.5 from household air pollution in Puno,Peru

Assessment of personal exposure to PM_2.5 is critical for understanding intervention effectiveness and exposure-response relationships in household air pollution studies. In this pilot study, we compared PM_2.5 concentrations obtained from two next-generation personal exposure monitors (the Enhanced Children MicroPEM or ECM; and the Ultrasonic Personal Air Sampler or UPAS) to those obtained with a traditional Triplex Cyclone and SKC Air Pump (a gravimetric cyclone/pump sampler). We co-located cyclone/pumps with an ECM and UPAS to obtain 24-hour kitchen concentrations and personal exposure measurements. We measured Spearmen correlations and evaluated agreement using the Bland-Altman method. We obtained 215 filters from 72 ECM and 71 UPAS co-locations. Overall, the ECM and the UPAS had similar correlation (ECM ρ = 0.91 vs UPAS ρ = 0.88) and agreement (ECM mean difference of 121.7 µg/m³ vs UPAS mean difference of 93.9 µg/m³) with overlapping confidence intervals when compared against the cyclone/pump. When adjusted for the limit of detection, agreement between the devices and the cyclone/pump was also similar for all samples (ECM mean difference of 68.8 µg/m³ vs UPAS mean difference of 65.4 µg/m³) and personal exposure samples (ECM mean difference of −3.8 µg/m³ vs UPAS mean difference of −12.9 µg/m³). Both the ECM and UPAS produced comparable measurements when compared against a cyclone/pump setup.     

Effects of Temperature and Humidity on the Characterization of C-4 Explosive Threats

Both the quantity and the amount of time that an explosive is present on the surface of a material is dependent upon the amount of explosive originally deposited on the surface, the adhesive forces, temperature and humidity, as well as other environmental factors. This laboratory study focused on evaluating RDX crystal morphology changes resulting from variations in temperature and humidity conditions of the sample. The temperature and humidity conditions were controlled using a Tenney THRJ environmental chamber and a Tenney T11RC-1.5 environmental chamber. These chambers allow the temperature and humidity to be held within ±3?°C and ±5?% RH. The temperature and humidity conditions used for this test series were: 4?°C/40?%RH, 21?°C/20?%RH (samples left on benchtop), 21?°C/70?%RH, 21?°C/95?%RH, 35?°C/40?%RH, 35?°C/70?%RH, and 35?°C/95?%RH. These temperature and humidity set points were chosen to represent a wide range of conditions that may be found in real world scenarios. C-4 (RDX crystals and binder material) was deposited on the surface of one of six substrates by placing a fingerprint from the explosive block onto the matrix surface. The substrates were chosen to provide a range of items that are commonly used. Six substrate types were used during these tests: 50?% cotton/50?% polyester as found in T-shirts, 100?% cotton with a smooth surface such as that found in a cotton dress shirt, 100?% cotton on a rough surface such as that found on canvas or denim, suede leather such as might be found on jackets, purses, or shoes, painted metal obtained from a car hood, and a computer diskette. The samples were not pre-cleaned prior to testing and contained sizing agents, and in the case of the metal: oil, dirt, scratches, and rust spots. The substrates were photographed at various stages of testing, using a Zeiss Discover V12 stereoscope with Axiocam ICc1 3 megapixel digital camera, to determine any changes in the crystalline morphology. Some of the samples were examined using scanning electron microscopy and atomic force microscopy in an attempt to determine how the explosive was bound to the substrate. This is the second article in a series on the effects of temperature and relative humidity on trace explosive threats.     

Observation and Prediction of Cavities in a Lubricant Between Non-Parallel Disks in Relative Rotation

Observed and predicted cavity shapes in a lubricant between two disks are presented. The geometry is similar to that of a thrust bearing or a face seal having non-parallel rotating surfaces. Photographs of cavitated regions are shown and compared with predictions of cavity shapes obtained by an approximate calculation method analogous to the short bearing analysis used for journal bearings. The calculation and the experiment show steady state cavities that are symmetric about the maximum gap thickness. For small angles of disk inclination a single exterior cavity is seen and for larger values of inclination both an interior and an exterior cavity are present. The predicted cavity shape in a given case is a function of the disk inclination, the lower bound pressure for the oil film and rotor speed. General agreement on the cavity shape is obtained between theory and experiment.     

Residential lighting load profile modelling: ANFIS approach using weighted and non-weighted data

This study involves the use of adaptive neural fuzzy inference system (ANFIS) for residential lighting load profile development and evaluation of energy and demand side management (DSM) initiatives. Three variable factors are considered in this study namely, natural light, occupancy (active), and income level. A better correlation of fit and reduced root mean square error was obtained after validation of the developed model using the investigative data—weighted and non-weighted approach (natural lighting). The technique showed that income level of the class in relation to the area (location), working lifestyle of individuals in relation to behavioural pattern, and effect of natural lighting are highly essential and need to be incorporated in any load profile development. The generalisation of income needs to be revisited; emerging middle and realised middle-income predictors have shown that their behavioural pattern differs. Forecast based on averages of lamps per households from a survey of an income class to determine lighting usage is prone to high errors. The developed methodology of the ANFIS gives better lighting prediction accuracy in accordance with the learning characteristics of light usage complexities.     

Electrothermal analysis of AlGaN/GaN high electron mobility transistors

Efficiency of AlGaN/GaN HEMTs used in high power, high frequency applications is thought to be limited by parasitic thermal effects. In this study, we investigate coupled electrical and thermal transport in AlGaN/GaN HEMTs using an ensemble Monte Carlo model. Calculation of the non-equilibrium phonon population reveals a hot spot in the channel that is localized at low drain-source bias, but expands towards the drain at higher bias, significantly degrading channel mobility.     

Identification of human and mouse hematopoietic stem cell populations expressing high levels of mRNA encoding retrovirus receptors

One obstacle to retrovirus-mediated gene therapy for human hematopoietic disorders is the low efficiency of gene transfer into pluripotent hematopoietic stem cells (HSC). We have previously shown a direct correlation between retrovirus receptor mRNA levels in mouse HSC and the efficiency with which they are transduced. In the present study, we assayed retrovirus receptor mRNA levels in a variety of mouse and human HSC populations to identify HSC which may be more competent for retrovirus transduction. The highest levels of amphotropic retrovirus receptor (amphoR) mRNA were found in cryopreserved human cord blood HSC. The level of amphoR mRNA in Lin- CD34(+) CD38(-) cells isolated from frozen cord blood was 12-fold higher than the level in fresh cord blood Lin- CD34(+) CD38(-) cells. In mice, the level of amphoR mRNA in HSC from the bone marrow (BM) of mice treated with stem cell factor and granulocyte-colony stimulating factor was 2.8- to 7.8-fold higher than in HSC from the BM of untreated mice. These findings suggest that HSC from frozen cord blood and cytokine-mobilized BM may be superior targets for amphotropic retrovirus transduction compared with HSC from untreated adult BM.