Diffraction-induced instability of coupled dark solitary waves.

We report on a novel instability arising from the propagation of coupled dark solitary beams governed by coupled defocusing nonlinear Schrödinger equations. Considering dark notches on backgrounds with different wavelengths, hence different diffraction coefficients, we find that the vector dark soliton solution is unstable to radiation modes. Using perturbation theory and numerical integration, we demonstrate that the component undergoing stronger diffraction radiates away, leaving a single dark soliton in the other mode/wavelength.

Fatal methemoglobinemia: A case series highlighting a new trend in intentional sodium nitrite or sodium nitrate ingestion as a method of suicide.

Unintentional exposure to nitrite- or nitrate-containing toxic salts is a recognized cause of acquired methemoglobinemia (MetHb). This systemic alteration of the blood can be fatal if not recognized and treated promptly. The intentional ingestion of sodium nitrite (NaNO2) or sodium nitrate (NaNO3), causing MetHb, is an uncommon and recently identified method of suicide, with the first reported case in the literature occurring in New Zealand in 2010. In this case series we present 28 cases of sudden death of individuals with evidence of MetHb and/or toxic salt ingestion, occurring in the Province of Ontario, Canada, between the years 1980 and 2020, inclusive. Of the 28 deaths in our case series, 25 showed evidence of intentional ingestion of sodium nitrite or sodium nitrate salts. Our year-over-year data demonstrated this is an increasingly used method of suicide in our provincial population, with the majority of cases occurring in the final two years of our study. Postmortem detection of MetHb is typically established via screening techniques such as scene evidence suggesting fatal consumption of a toxic salt in addition to the characteristic grey-purple lividity observed upon the body. The diagnosis can be established via postmortem blood testing demonstrating elevated methemoglobin saturation. Additionally, we have confirmed that postmortem MRI in cases of MetHb demonstrates a T1-bright (hyperintense) signal of the blood; both within intracardiac blood on chest MRIs and postmortem blood samples in tubes.

NEUROSCIENCE: Neural Net Contest Draws Online Crowd.

When two computational neuroscientists announced an online contest last September to reverse-engineer a simulated set of neurons, neither thought the event would attract much attention beyond a small group of their colleagues. But The New York Times ran an article on the competition, and 25,000 people visited the site. Now, the researchers think they may have found a new method for stimulating scientific communication.

ECOLOGY: Forest Fire Plan Kindles Debate.

Forest fires burning in the western United States have already scorched over 2.5 million hectares this summer. Now a federal proposal to prevent them by paying loggers to cut smaller trees is generating heat among ecologists, who say the approach may not be right for all forests--or all fires.

Mars exploration. Plan for two rovers squeezes NASA budget.

NASA's decision last week to send two rovers to Mars in 2003 is being hailed by researchers as affirming the agency's commitment to exploring the Red Planet. But once the applause dies down, cash-strapped space science managers will be forced to make tough decisions about how to shoulder the added $200 million cost of a second mission, starting with $96 million that must come out of NASA's 2001 budget.

Beyond the dichotomy: linking HIV prevention with care.

In the past decade, the global strategy against AIDS has focused primarily upon prevention. Regardless of the effectiveness of prevention efforts being made today and advances in treatments, the numbers of persons infected globally continues to grow at an alarming rate, especially in developing countries. With numbers of infections increasing, and the trend to more people learning their HIV status earlier, demands for care will mount dramatically into the next century. This paper examines the virtually unexplored role care can play in prevention and its potential to have a mitigating effect on the pandemic. Critical issues addressed include (i) the relationship between care, HIV and productivity; (ii) the role of both care and prevention in promoting acceptance of HIV/AIDS as a community problem; (iii) the role of care in decreasing the vulnerability to HIV in specific populations such as women and children; (iv) the role of care in sustaining behavior change over time for infected persons; and (v) the synergy between improved treatments and prevention. Future areas of research are proposed examining these prevention and care issues that move beyond the traditional dichotomy.

PIP: The global strategy against AIDS over the past decade has focused mainly upon preventing the spread of HIV infection to additional populations and individuals. However, despite such prevention efforts and advances made in treatment, the number of people infected globally with HIV continues to grow at an alarming rate, especially in developing countries. The provision of care for HIV-infected people has historically not been viewed as a component of the overall strategy to reduce the incidence of HIV infection. However, HIV-infected people are important partners in preventing the spread of the virus. If they feel abandoned by care services, they may be less likely to understand the need for prevention and therefore less motivated to protect others. Demands for HIV/AIDS care will grow dramatically into the next century. The authors examine the largely unexplored role care can play in prevention and its potential to have a mitigating effect upon the pandemic. Main issues addressed include the relationship between care, HIV, and productivity; the role of care and prevention in promoting acceptance of HIV/AIDS as a community problem; the role of care in decreasing the vulnerability to HIV in populations such as women and children; the role of care in sustaining behavior change over time for infected persons; and the synergy between improved treatments and prevention. Future areas of research into prevention and care are proposed.

Applying social, behavioral and evaluation research to developing country HIV prevention programs.

OBJECTIVE: To examine the role that social, behavioral and evaluation research played in a 6-year global HIV prevention program working in 45 developing countries. METHODS: Computerized review of project database inventories: 320 research abstracts, 591 subproject abstracts, on-line literature search of project peer-reviewed literature, and hand review of 390 final project reports and country evaluations. DESIGN: Research included descriptive, correlational, ethnographic, survey, quasi-experimental and experimental designs. RESULTS: Over 400 social, behavioral and evaluation studies were conducted and consisted of program-related research, controlled intervention research and multi-year competitive research grants to advance the science of HIV prevention. Program research involved extensive use of qualitative methodologies and the development of innovative research tools such as rapid ethnographic assessments, behavioral surveillance surveys, and targeted intervention research. Intervention studies and multilevel evaluations of prevention programs in 19 countries demonstrated that HIV prevention has changed knowledge, attitudes, and behavior in target groups. Triangulating the results of a variety of data sources and methodologies, and increasing reliance on surveillance of behavioral trends among targeted population groups helped to circumvent numerous methodological problems. CONCLUSION: Linking research to program interventions is a critical component of effective HIV prevention but operationalizing the linking process remains a major challenge.

PIP: The campaign against HIV/AIDS has been hindered by a disjunction between behavioral research and the design of preventive interventions. A review was conducted of over 400 social, behavioral, and evaluation studies conducted as part of Family Health International's AIDS Control and Prevention Project in 45 countries in Latin America, Africa, and Asia in 1992-1997. Program-related research showed a shift from repetitive studies of knowledge, attitudes, and practice (KAP) to studies that yielded tangible information on how people change. Extensive use was made of findings from focus group discussions, key informant interviews, and baseline and follow-up KAP surveys to design culturally relevant interventions. Behavioral research evolved over time from a focus on traditional high-risk groups to broader populations such as adolescents and women. Most research continues to be descriptive, conducted in response to urgent program needs (e.g., for baseline data), and focused on individuals rather than social organizations. Valid assessment of the effectiveness of behavior change interventions presents numerous methodological and evaluation problems, including the bias inherent in self-report data, an inability to attribute behavioral changes to specific interventions, and the insensitivity of HIV prevalence as an indicator of short-term behavior change. However, the results of controlled intervention studies attest that prevention had had a substantial impact on HIV knowledge, attitudes toward those infected with HIV, perceptions of individual risk, and sex behavior among target groups. Continued triangulation of the results of a variety of sources and methodologies will reduce systemic bias in the research data.

Identification of time-varying biological systems from ensemble data.

The theory underlying a new method for the identification of time-varying systems is described. The method uses singular value decomposition to obtain least-squares estimates of time-varying impulse response functions from an ensemble of input-output realizations. No a priori assumptions regarding the system structure or form of the time-variation are required and there are few restrictions on the input signal. Simulation studies, using a model of time-varying joint dynamics, show that the method can track rapid changes in system dynamics accurately and is robust in the presence of output noise. An application of the method is demonstrated by using it to track dynamic ankle stiffness during a rapid, voluntary, isometric contraction. During the transient phase of the contraction, low-frequency ankle stiffness gain decreased in a manner which could not be described with the second-order model of joint dynamics often used under stationary conditions.

Long-term trends and sources of organochlorine contamination in Canadian tundra Peregrine Falcons, Falco peregrinus tundrius.

Levels of eggshell thinning, and organochlorine residues in egg contents, blood plasma of adults and juveniles, tissue samples, and prey species were determined for a population of migratory Peregrine Falcons (Falco peregrinus tundrius) breeding in the Canadian Arctic. Temporal trends were assessed by comparing data collected during 1991-1994, with data from 1982-1986, for the same population. Shells (n=54) from 1991-1994 averaged 15% thinner than eggs produced prior to the introduction of DDT. No improvement in shell thickness was detected between decades. Mean DDE residue levels in eggs showed a decline from 7.6 mg kg (1982-1986) to 4.5 mg kg (1991-1994), but there was no significant change in SigmaPCB residues. Moreover, the proportion of clutches with eggs exceeding critical SigmaPCB, DDE, and dieldrin residue levels (10%) did not change between decades. Relative to Greenland and Alaskan populations, F. p. tundrius at Rankin Inlet show high levels of organochlorine contamination and little reduction in residues over the last decade. These Tundra Peregrines continue to be exposed to organochlorines in Latin America; however, results also link relatively high levels in the study population with waterfowl species that do not leave Canada in winter.

Persistence of chloramphenicol residues in calf tissues.

Twenty-one 5 to 18 day old calves were administered 11 mg chloramphenicol in propylene glycol per kg body weight intramuscularly twice daily for three days. Groups of calves were euthanized with a barbiturate overdose at 5, 21, 42 and 70 days after the last dose was administered. Serum, kidney, analyzed for the drug using a quantitative gas chromatographic method with a detection limit of five parts per billion. After five days of withdrawal, chloramphenicol was detected in all the injection sites and in 6 out of 16 of the other samples. After 21 days of withdrawal, chloramphenicol was detected in all the injection sites and in one each of the serum, liver and muscle samples. After 42 days of withdrawal, chloramphenicol was detected in the injection sites only, and after 70 days of withdrawal it was not detected in any of the samples.

Survey of chloramphenicol residues in diseased swine.

Tissue samples from 279 hogs suspected of having received antibiotic treatment were collected at federally-inspected abattoirs and submitted for chloramphenicol residue analysis during August and September 1984. Injection sites (when present), kidneys or muscle samples were tested by one of two gas chromatographic methods. Kidney samples were also tested at the abattoirs by the Swab Test On Premises. Thirty-one animals (11%) were found with detectable levels ranging from 1 part per billion to 5727 ppb. Highest levels were found at the injection sites, while levels in muscle tissue did not exceed 500 ppb. None of the kidneys from animals found to contain chloramphenicol residues produced a positive Swab Test On Premises result attributable to the presence of chloramphenicol. Twelve kidneys from animals free of chloramphenicol residues produced positive Swab Test On Premises results. Of these, five contained penicillin or streptomycin, but antibiotic residues were not detected in the remaining seven. In addition to the samples collected for this survey, samples from eight hogs representing a herd which had been treated for pneumonia were submitted by an abattoir in Manitoba in November 1984. Chloramphenicol levels in these animals ranged from 0.1 to 73 parts per million in the injection sites, and from 0.04 to 21 ppm in the muscle tissues. The survey data indicated that there were a significant number of animals reaching the abattoirs with detectable chloramphenicol residues, and that the Swab Test On Premises procedure was ineffective in detecting these animals.

Depletion of intramuscularly and subcutaneously injected procaine penicillin G from tissues and plasma of yearling beef steers.

Withdrawal periods required when doses of 24,000 IU and 66,000 IU of procaine penicillin G/kg body weight were administered to yearling beef steers by intramuscular injection daily for five consecutive days were investigated. These dosages are in excess of product label recommendations, but are in the range of procaine penicillin G dosages that have been administered for the treatment of some feedlot bacterial diseases. The approved dose in Canada is 7,500 IU/kg body weight intramuscularly, once daily, with a withdrawal period of five days. Based on the tissue residue data from this study, the appropriate withdrawal period is ten days for the 24,000 IU/kg body weight dose and 21 days for the 66,000 IU/kg body weight dose when administered intramuscularly to yearling beef steers. In a related study, 18 yearling beef steers received 66,000 IU of procaine penicillin G/kg body weight administered by subcutaneous injection, an extra-label treatment in terms of both dose and route of administration, typical of current practice in some circumstances. Deposits of the drug were visible at subcutaneous injection sites up to ten days after injection, with more inflammation and hemorrhage observed than for intramuscular injections of the same dose. These results suggest that procaine penicillin G should not be administered subcutaneously at high doses; and therefore a withdrawal period was not established for subcutaneous injection.

Determination of neomycin in animal tissues by liquid chromatography.

Tissue samples are digested under hot alkaline conditions after initial conditioning at room temperature with phosphate-buffered saline. The cooled digest is deproteinated with concentrated perchloric acid. After centrifugation and pH adjustment, the clear supernatant is applied to an ion-exchange cartridge, and after the cartridge is washed, the neomycin is eluted with dilute perchloric acid. This eluate is derivatized with 9-fluorenylmethyl chloroformate prior to liquid chromatography using a wide-pore spherical silica C4 column and fluorescence detection. Recovery and repeatability are calculated from tissue extract standard calibration curves produced from the same assay. Recoveries ranged from 80 to 120% for fortifications of 0.25-1.00 mg/kg for muscle tissue and from 80 to 100% for fortifications of 0.50-10.0 mg/kg for kidney tissue. Limits of quantitation were 0.25 and 0.50 mg/kg, respectively, for muscle and kidney tissues. Limits of detection were 0.125 and 0.20 mg/kg, respectively, for muscle and kidney tissues.

Analysis of penicillin G in milk by liquid chromatography.

A liquid chromatographic (LC) method that was previously developed for penicillin G residues in animal tissues has been adapted to milk and milk products. After protein precipitation with sodium tungstate, samples are applied to a C18 solid-phase extraction cartridge, from which penicillin is eluted, derivatized with 1,2,4-triazole-mercuric chloride solution, and analyzed by isocratic liquid chromatography (LC) on a C18 column with UV detection at 325 nm. Quantitation is done with reference to penicillin V as an internal standard. Penicillin G recoveries were determined to be > 70% on standards fortified at 3-60 ppb. Accuracy approached 100% using the penicillin V internal standard. The detection limit for penicillin G residues was 3 ppb in fluid milk. Samples may be confirmed by thermospray/LC at concentrations approaching the detection limit of the UV method.

Analysis of streptomycin and dihydrostreptomycin in milk by liquid chromatography.

A method developed for the determination of the aminoglycoside antibiotics streptomycin and dihydrostreptomycin in tissues was applied to the analysis of fluid milk. Samples are extracted with 3.6% perchloric acid, and then injected onto a trace enrichment column, from which they are eluted onto a reversed-phase analytical column. The analytes are detected by fluorescence following postcolumn derivatization with 1,2-naphthoquinone-4-sulfonic acid. Recovery of analytes was in the range of 50-65% for skim or partially defatted fluid milk, while recoveries for homogenized whole milk were lower. Limits of quantitation were 10 ppb for streptomycin and 20 ppb for dihydrostreptomycin.

Determination of streptomycin and dihydrostreptomycin in animal tissue by on-line sample enrichment liquid chromatography.

A method for the determination of streptomycin and dihydrostreptomycin in pork and bovine muscle and kidney was developed. Dilute perchloric acid solution is used to precipitate proteins and extract the analytes from the tissue. The extract is loaded onto a cation-exchange, solid-phase extraction column, and the drugs are eluted with pH 8 phosphate buffer. The eluant is chromatographed by using an on-line column enrichment liquid chromatographic system with postcolumn derivatization using 1,2-naphthoquinone-4-sulfonic acid and detection by fluorescence. The recoveries were 61.1% (coefficient of variation [CV], 7.3%) for streptomycin and 55.3% (CV, 8.2%) for dihydrostreptomycin. The detection limits were 10 ppb for streptomycin and 20 ppb for dihydrostreptomycin.

Comparison of four commercially available rapid test kits with liquid chromatography for detecting penicillin G residues in bovine plasma.

Four commercially available rapid tests (Brilliant Black reduction test, LacTek test, Charm Farm test, and Charm Test II receptor assay) were compared with a liquid chromatographic (LC) method (lowest quantitatable level of 5 ng/mL) in their efficiency, reliability, and sensitivity to detect penicillin G in bovine plasma. Samples were obtained from 16 steers treated with procaine penicillin G alone or in combination with its long-acting form, benzathine penicillin G. The steers were injected intramuscularly with penicillin G doses ranging from label dose to about 9 times label dose. When results of the Brilliant Black reduction, LacTek, Charm Test II, and Charm Farm tests for penicillin G in plasma (with detection sensitivities of 5, 10, 20, and 30 ng/mL, respectively) were compared with results of LC, none of the rapid tests gave false-positive results. Each rapid test elicited a positive response when used to test bovine plasma containing penicillin G residues at concentrations above the test's detection sensitivity. The simplicity, selectivity, and sensitivity of the rapid tests, coupled with rapidity with which results are obtained, make them suitable for use in large-volume preslaughter screening of penicillin-treated cattle.