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The environments in which we live, work, and play are subject to enormous variability in air pollutant concentrations. To adequately characterize air quality (AQ), measurements must be fast (real time), scalable, and reliable (with known accuracy, precision, and stability over time). Lower-cost air-quality-sensor technologies offer new opportunities for fast and distributed measurements, but a persistent characterization gap remains when it comes to evaluating sensor performance under realistic environmental sampling conditions. This limits our ability to inform the public about pollution sources and inspire policy makers to address environmental justice issues related to air quality. In this paper, initial results obtained with a recently developed lower-cost air-quality-sensor system are reported. In this project, data were acquired with the ARISense integrated sensor package over a 4.5-month time interval during which the sensor system was co-located with a state-operated (Massachusetts, USA) air quality monitoring station equipped with reference instrumentation measuring the same pollutant species. This paper focuses on validating electrochemical (EC) sensor measurements of CO, NO, NO2, and O3 at an urban neighborhood site with pollutant concentration ranges (parts per billion by volume, ppb; 5 min averages, ±1σ): [CO] = 231 ± 116 ppb (spanning 84–1706 ppb), [NO] = 6.1 ± 11.5 ppb (spanning 0–209 ppb), [NO2] = 11.7 ± 8.3 ppb (spanning 0–71 ppb), and [O3] = 23.2 ± 12.5 ppb (spanning 0–99 ppb). Through the use of high-dimensional model representation (HDMR), we show that interference effects derived from the variable ambient gas concentration mix and changing environmental conditions over three seasons (sensor flow-cell temperature = 23.4 ± 8.5 °C, spanning 4.1 to 45.2 °C; and relative humidity = 50.1 ± 15.3 %, spanning 9.8–79.9 %) can be effectively modeled for the Alphasense CO-B4, NO-B4, NO2-B43F, and Ox-B421 sensors, yielding (5 min average) root mean square errors (RMSE) of 39.2, 4.52, 4.56, and 9.71 ppb, respectively. Our results substantiate the potential for distributed air pollution measurements that could be enabled with these sensors.

Defects in semiconductors can play a vital role in the performance of electronic devices, with native defects often dominating the electronic properties of the semiconductor. Understanding the relationship between structural defects and electronic function will be central to the design of new high-performance materials. In particular, it is necessary to quantitatively understand the energy and lifetime of electronic states associated with the defect. Here, we apply first-principles density functional theory (DFT) and many-body perturbation theory within the GW approximation to understand the nature and energy of the defect states associated with a charged nitrogen vacancy on the electronic properties of gallium nitride (GaN), as a model of a well-studied and important wide gap semiconductor grown with defects. We systematically investigate the sources of error associated with the GW approximation and the role of the underlying atomic structure on the predicted defect state energies. Additionally, analysis of the computed electronic density of states (DOS) reveals that there is one occupied defect state 0.2 eV below the valence band maximum and three unoccupied defect states at energy of 0.2--0.4 eV above the conduction band minimum, suggesting that this defect in the +1 charge state will not behave as a carrier trap. Furthermore, we compare the character and energy of the defect state obtained from GW and DFT using the HSE approximate density functional and find excellent agreement. This systematic study provides a more complete understanding of how to obtain quantitative defect energy states in bulk semiconductors.

We describe the cloning of the first hymenopteran vitellogenin receptor (VgR) cDNA from the imported fire ant, Solenopsis invicta, an invasive pest. Using reverse transcription polymerase chain reaction and rapid amplification of cDNA ends, fragments encompassing the entire coding region of a putative VgR were cloned and sequenced. The complete 5764 bp cDNA encodes a 1782 residue protein with a predicted molecular mass of 201.3 kDa (=SiVgR). Northern blot analysis demonstrated that the 7.4 kb SiVgR transcript was present only in ovaries of reproductive females (virgin alates and queens). The temporal profile of transcriptional expression showed that SiVgR mRNA increased with age in virgin alate females and that this was up-regulated by methoprene, a juvenile hormone (JH) analogue. This suggests that the SiVgR gene is JH regulated.

Lipid lowering drugs lower the risk of ischaemic cardiovascular events. The absolute benefit is highest in people at greatest risk of having an event in the near future, but adverse effects and costs are similar whatever the baseline risk. The decision to treat entails balancing expected benefits with expected harms,1 but is essentially a value judgement. Treatment preferences may vary systematically between groups of people either because they have different levels of baseline risk, or because they have different values and priorities. Current UK guidelines recommend treatment for those whose 10 year risk of coronary heart disease is at least 30%.2,3 Assuming a relative risk reduction of one third this is an absolute benefit of about 10% over 10 years (or 5% over five years). Very little is known about the level of coronary risk at which either doctors or patients want treatment.4 One small study suggested that patients and nurses would choose higher risk thresholds (larger absolute benefits) than doctors.5 The policy to treat a risk of 30% over …

The Localized Wave project of the Strategic System Support Program has recently finished an experiment in cooperation with the Advanced SONAR group of the Applied Research Laboratory of the University of Texas at Austin. The purpose of the experiment was three-fold. They wanted to see if (1) the LW pulse could propagate over significant distances, to see if (2) a new type of array and drive system specifically designed for the pulse would increase efficiency over single frequency tone bursts, and to see if (3) the complexity of our 24 channel drivers resulted in better efficiency than a single equivalent pulse driving a piston. In the experiment, several LW pulses were launched from the Lake Travis facility and propagated over distances of either 100 feet or 600 feet, through a thermocline for the 600 foot measurements. The results show conclusively that the Localized Wave will propagate past the near field distance. The LW pulses resulted in extremely broad frequency band width pulses with narrow spatial beam patterns and unmeasurable side lobes. Their array gain was better than most tone bursts and further, were better than their equivalent piston pulses. This marks the first test of several Low Diffraction beams against their equivalent piston pulses, as well as the first propagation of LW pulses over appreciable distances. The LW pulse is now proven a useful tool in open water, rather than a laboratory curiosity. The experimental system and array were built by ARL, and the experiments were conducted by ARL staff on their standard test range. The 600 feet measurements were made at the farthest extent of that range.

Sexual behavioral data from a survey of 396 male drug injectors showed that 301 (76%) were behavioral heterosexuals, 49 (12.45%) were bisexuals, and 46 (11.6%) were homosexuals over the previous 5 years. Among those sexually active during the 6 months before the interview, bisexuals were similar to heterosexuals and homosexuals in reporting two or more female or male partners, respectively. Overall, almost three fourths of the bisexuals had two or more sexual partners. Bisexuals were also similar to heterosexuals in reported heterosexual and intercourse (16 and 15%, respectively), and to homosexuals in reported homosexual insertive anal intercourse (33 and 54%, respectively). They were less likely than heterosexuals to engage in vaginal and insertive oral sex with women and than homosexuals to practice receptive and and oral sex with men. The three groups all practiced high levels of unprotected sex. Almost half the behavioral bisexuals identified themselves as heterosexuals. Self-identified heterosexuals in the sample were less likely than self-identified gays or bisexuals to state they reduced sexual risk; however, reported condom use was low for all three groups. With human immunodeficiency virus infection rates of 54% (21 of 39) for behavioral homosexuals, 24% (11 of 45) for bisexuals, and 9% (24 of 260) for heterosexuals, these findings indicate an urgent need for more effective sexual risk reduction among injection drug users and their partners.

A sample of 149 (70 White, 79 Black) male intravenous drug users with steady female sexual partners was interviewed in 1987, in treatment and street settings, about sexual practices during the previous five years. Eighty-three percent had multiple partners, 15 percent reported male sexual contact, 38 percent reported heterosexual anal intercourse, and 73 percent never used condoms. Thirty-seven White and 30 Black subjects reported bisexuality or heterosexual and intercourse or both.

The frequency dependence of the phase velocity and attenuation of ultrasonic waves were measured as a function of time during the polymerization (curing) reaction of epoxy resins. The phase velocity and attenuation were evaluated from the amplitude and phase spectra of ultrasonic signals transmitted through a layer of curing epoxy resin. The measurements were made in the frequency range of 2–20 MHz. From the experimental data follows an important conclusion: The attenuation coefficient increases linearly with frequency at all stages of the curing reaction from the viscous liquid to the solid state. The slope of the attenuation coefficient as a function of frequency is strongly dependent on the time of cure (degree of cure). The linear behavior of attenuation versus frequency suggests that the attenuation effect cannot be explained by classical viscothermal absorption or relaxation theory. This type of behavior (so‐called hysteresis behavior) is poorly understood on the molecular level and was found previo...

Validity and efficiency issues are considered with regard to the use of matching and random sampling as alternative methods of subject selection in follow-up and case-control studies. We discuss the simple situation involving dichotomous disease and exposure variables and a single dichotomous matching factor, and we consider the influence on efficiency of a possible loss of subjects due to matching constraints. The decision to match or not should be motivated by efficiency considerations. An efficiency criterion based on a comparison of confidence intervals under matching and random sampling for the effect measure of interest (the risk ratio and risk difference in follow-up studies, and the odds ratio in case-control studies) leads to the following conclusions when the sampling method does not influence the size of the comparison group. In follow-up studies, matching on a confounder is expected to lead to a gain in efficiency over random sampling, while matching on a nonconfounder is not expected to result in a loss of efficiency. In case-control studies, the same conclusions hold, except that matching is not as advantageous as in follow-up studies and can lead to a loss of efficiency in some situations (usually of little practical importance). When matching reduces the size of the comparison group, there is likely to be a meaningful gain in efficiency due to random sampling only when the matched comparison group is at most 40-50% the size of the randomly-sampled comparison group is a follow-up study, and at most 50-65% the size in a case-control study.

THERE is no adequate method to determine the biological availability of the sulphur-containing amino-acids in the chick, but Schweigert and Guthneck1 have described a technique for the rat A method has therefore been developed for the bioassay of methionine using White Leghorn chicks at 11–18 days of age: it can readily be modified to determine methionine plus cystine in terms of methionine equivalence. By difference an indication can be obtained of available cystine. The basal ration contains (per cent) 48.6 maize starch, 35 extracted soybean meal, 5 dried whey, 5 beef tallow, 6 mineral and vitamin mixture2, 0.2 choline chloride and 0.2 glycine. All supplements to this ration replace part of the maize starch. Where test materials are calculated to contribute less ‘metabolizable’ energy than starch additional tallow is included to correct for the difference.

COLHOUN1 showed that many water-miscible organic solvents increased the activity of cholinesterase (ChE) preparations from the cockroach Periplaneta americana. Shatoury2,3 showed that a similar activation occurred in the case of the housefly Musca domestica, though here n-butanol only was used as “activator”, and the effect was far less marked. It has now been found that an even larger activation than that recorded by Colhoun can be achieved by addition of certain water-miscible organic solvents, notably n-butanol and n-pentanol, to ChE preparations from heads of the honeybee Apis mellifera.

In an attempt to develop models for nondestructive testing of flaw characterization we have simulated “flaws” by using metal circular reflectors in water. A broad‐band ultrasonic beam was incident on the reflectors. The scattered wave amplitudes were measured as a function of frequency for fixed angles and as a function of angles for several frequencies. In our previous work [Laszlo Adler and H.L. Whaley, J. Acoust. Soc. Am. 51, 881 (1972)], the frequency distribution of the scattered sound wave was related to the size and orientation of the reflector by an approximate theory. This theory assumed that the wavelets originating from the extreme edges of the reflector will interfere. Now we have adopted a theory from the diffraction of electromagnetic waves by aperture [Keller, Appl. Phys. 28, 426 (1957)]. An expression for the diffracted amplitude was calculated as a function of frequency and angle for several reflector sizes. The result compares favorably with our experiments. [This research was sponsored ...

THE insecticidal activity of certain N-acyl N-methyl-carbamate insecticides has been reported recently by Fraser et al.1. Reay and Lewis2 showed that the N-acetyl derivative of 1-naphthyl N-methylcarbamate (carbaryl) was nearly 100 times less inhibitory towards honeybee head cholinesterase (ChE) in vitro than the parent compound (see also Table 1). It is the purpose of this communication to report that the N-acylation of several other N-methylcarbamates leads to a marked reduction in in vitro anticholinesterase activity against honeybee head ChE.