Indoor exposure to particulate matter and the incidence of acute lower respiratory infections among children: A birth cohort study in urban Bangladesh

Approximately half of all children under two years of age in Bangladesh suffer from an acute lower respiratory infection (ALRI) each year. Exposure to indoor biomass smoke has been consistently associated with an increased risk of ALRI in young children. Our aim was to estimate the effect of indoor exposure to particulate matter (PM_2.5) on the incidence of ALRI among children in a low‐income, urban community in Bangladesh. We followed 257 children through two years of age to determine their frequency of ALRI and measured the PM_2.5 concentrations in their sleeping space. Poisson regression was used to estimate the association between ALRI and the number of hours per day that PM_2.5 concentrations exceeded 100 μg/m³, adjusting for known confounders. Each hour that PM_2.5 concentrations exceeded 100 μg/m³ was associated with a 7% increase in incidence of ALRI among children aged 0–11 months (adjusted incidence rate ratio (IRR) 1.07, 95% CI 1.01–1.14), but not in children 12–23 months old (adjusted IRR 1.00, 95% CI 0.92–1.09). Results from this study suggest that reducing indoor PM_2.5 exposure could decrease the frequency of ALRI among infants, the children at highest risk of death from these infections.     

High rates of discitis following surgery for prolapsed intervertebral discs at a hospital in Pakistan

OBJECTIVES: To confirm the presence of an outbreak of postoperative infections following laminectomy and to determine the infection rate after interventions were instituted. DESIGN: Retrospective cohort study. Medical records were reviewed, personnel interviewed, and premises examined. SETTING: Surgical unit of hospital A in Pakistan. SUBJECTS: Patients who had surgical laminectomy between January 1993 and July 1994. INTERVENTION: Instructive program for nursing and medical staff in December 1993. RESULTS: From January to December 1993, 6 (15%) of 41 laminectomy patients developed postoperative discitis. The risk of discitis varied significantly by surgeon (P = .016); patients who had one particular surgeon, surgeon A, were nine times more likely to develop postoperative infections than patients who did not have surgeon A. Patients were not consistently cleaned or shaved before coming to the operating room, and personnel moved back and forth between the operation theater and other parts of the hospital without changing their gowns or slippers. After the instructional intervention, between January and July 1994, 2 (6%) of 31 laminectomy patients developed postoperative discitis, a rate not significantly lower than in the preceding 12 months (P = .45). Overall, from January 1993 through July 1994, female patients were more likely to develop discitis than males (31% vs 7%; relative risk, 4.4; 95% confidence interval, 1.3-15.6; P < .032). CONCLUSION: Endemic conditions require that laminectomy at hospital A be limited to those situations where the benefits of the surgery exceed the considerable risk of postoperative discitis.     

Postexposure treatment of rabies in Pakistan

To evaluate compliance with current World Health Organization (WHO) guidelines for postexposure treatment (PET) of rabies, we interviewed all animal bite victims seeking treatment on the same day of each week from 28 December 1994 through 18 January 1995 at the Civil Hospital of Karachi (Pakistan), a major referral center. Of the 143 patients studied, 109 (76%) sustained bleeding transdermal bites (WHO category III). Overall, wounds were not washed with soap or an antiseptic in 69% of victims. All victims received 5% sheep brain-derived vaccine, and only three of the 109 victims with category III bites received rabies immune globulin. PET of rabies in Karachi was deficient by all WHO standards. Although there is a great urgency to improve PET, it will remain a costly and inefficient method of controlling rabies. Reduction of rabies reservoirs is required to decrease human deaths due to rabies in Pakistan and other developing countries in which canine rabies is endemic.     

Resistivity and structure of evaporated polycrystalline molybdenum films

Molybdenum films of thickness 20–2600 nm were evaporated at a substrate temperature of 650°C and were then vacuum annealed at 900°C. The mean grain size of films increased with increasing thickness and it became saturated at about 130 nm for films thicker than 1000 nm. Using this result, the Mayadas-Shatzkes model of grain boundary scattering was used for the interpretation of the observed thickness dependence of the resistivity of the films. Values of the grain boundary electron reflection coefficient, which increase with decreasing film thickness, were used to fit the experimental data to theoretical curves.     

Frequency dependence of the conductivity of amorphous germanium films between 20 Hz and 26 GHz

Conductivity measurements on amorphous Ge films in the frequency range 20 Hz–26 GHz are described. Above 100 MHz the frequency dependence of the conductivity at room temperature satisfied the power law σ∝ω^s with s=0.45-0.7. No saturation of the conductivity was observed. When the Ge films were doped with 0.1–1 at. % Sb the conductivity was frequency independent up to 26 GHz. A.c. hopping conduction seems to be compatible with the experimental results.     

Oxide nanoparticle arrays for sensors of CO and NO2 gases

Metal oxide sensors with active films from Fe₂O₃ and CoFe₂O₄ hexagonally assembled nanoparticle (NP) arrays were studied. NPs were synthesized by high-temperature solution phase reaction. Sensing NP layers were deposited by Langmuir-Blodgett (LB) technique. LB layers were characterized by XRD, SEM and magnetic measurements. NPs are monodomain and superparamagnetic at RT. Sensor active films are formed from 1 or 7 LB monolayers deposited on the alumina substrates equipped with heating meander and interdigitated contacts. LB layers were heat-treated or UV irradiated to remove the insulating surfactant. Sensing properties were studied in a test chamber containing reducing (CO) or oxidizing (NO₂) gas in concentrations between 5 and 100 ppm in the mixture with dry air. Response current signal (I_gas/I_air) vs. temperature and response vs. gas concentration calibration curves were measured. Best response values were obtained with CoFe₂O₄ devices between 300 and 400 °C, being 3 and 10 for 100 ppm of CO and 5 ppm of NO₂, respectively. The response and recovery times of sensors are between 3 and 30 min. The Fe₂O₃ and CoFe₂O₄ sensors with response of 8 or 10 to 5 ppm of NO₂ might be of practical applications in the detection of explosives.     

GISAXS analysis of 3D nanoparticle assemblies--effect of vertical nanoparticle ordering

We report on grazing-incidence small-angle x-ray scattering (GISAXS) study of 3D nanoparticle arrays prepared by two different methods from colloidal solutions-layer-by-layer Langmuir-Schaefer deposition and spontaneous self-assembling during the solvent evaporation. GISAXS results are evaluated within the distorted wave Born approximation (DWBA) considering the multiple scattering effects and employing a simplified multilayer model to reduce the computing time. In the model, particular layers are represented by nanoparticle chains where the positions of individual nanoparticles are generated following a model of cumulative disorder. The nanoparticle size dispersion is considered as well. Three model cases are distinguished-no shift between the neighboring chains (AA stacking), a shift equal to half of the mean interparticle distance (AB stacking) and random shift between the chains. The first two cases correspond to vertically correlated nanoparticle positions across different chains. A comparison of the experimental GISAXS patterns with the model cases enabled us to distinguish important differences between the 3D arrays prepared by the two methods. In particular, laterally ordered layers without vertical correlation of the nanoparticle positions were found in the nanoparticle multilayers prepared by the Langmuir-Schaefer method. On the other hand, the solvent evaporation under particular conditions produced highly ordered 3D nanoparticle assemblies where both laterally and vertically correlated nanoparticle positions were found.     

Efficient PRAM simulation on a distributed memory machine

We present algorithms for the randomized simulation of a shared memory machine (PRAM) on a Distributed Memory Machine (DMM). In a PRAM, memory conflicts occur only through concurrent access to the same cell, whereas the memory of a DMM is divided into modules, one for each processor, and concurrent accesses to the same module create a conflict. Thedelay of a simulation is the time needed to simulate a parallel memory access of the PRAM. Any general simulation of anm processor PRAM on ann processor DMM will necessarily have delay at leastm/n. A randomized simulation is calledtime-processor optimal if the delay isO(m/n) with high probability. Using a novel simulation scheme based on hashing we obtain a time-processor optimal simulation with delayO(log log(n) log*(n)). The best previous simulations use a simpler scheme based on hashing and have much larger delay: (log(n)/log log(n)) for the simulation of an n processor PRAM on ann processor DMM, and (log(n)) in the case where the simulation is time-processor optimal.Our simulations use several (two or three) hash functions to distribute the shared memory among the memory modules of the PRAM. The stochastic processes modeling the behavior of our algorithms and their analyses based on powerful classes of universal hash functions may be of independent interest.Research partially supported by NSF/DARPA Grant CCR-9005448. Work was done while at the University of California at Berkeley and the International Computer Science Institute, Berkeley, CA.Research partially supported by National Science Foundation Operating Grant CCR-9016468, National Science Foundation Operating Grant CCR-9304722, United States-Israel Binational Science Foundation Grant No. 89-00312, United States-Israel Binational Science Foundation Grant No. 92-00226, and ESPRIT BR Grant EC-US 030.Part of work was done during a visit at the International Computer Science Institute at Berkeley; supported in part by DFG-Forschergruppe Effiziente Nutzung massiv paralleler Systeme, Teilprojekt 4, and by the Esprit Basic Research Action Nr. 7141 (ALCOM II).