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PubMed2000

A simple control law generates Listing's positions in a detailed model of the extraocular muscle system.

The neural commands for maintaining static Listing's positions were identified using a detailed model of extraocular muscle based on Miller and Shamaeva (Orbit 1.5 gaze mechanics simulation 1995). The commands were approximately separable, suggesting a simple control law whereby independent horizontal and vertical commands are combined to generate tertiary positions. Tests showed that this control law (i) generated Listing' s positions to reasonable accuracy over+/-30 deg, provided pulleys were represented in the model; (ii) if driven by retinal coordinates, produced errors close to the theoretical minimum for a commutative system. The proposed commands appear consistent with electrophysiological evidence.

Biomechanical Phenomena↗

PubMed2001

Hydrocarbon source apportionment for the 1996 Paso del Norte Ozone Study.

The 1996 Paso del Norte (PdN) ozone study was conducted to improve current understanding of the significant meteorological and air quality processes that lead to high concentrations of ozone in El Paso, Texas (USA) and Ciudad Juárez, Chihuahua (Mexico). Two-hour canister samples were collected five times daily at 05.00-07.00 h, 07.00-09.00 h, 09.00-11.00 h, 11.00-13.00 h, and 15.00-17.00 h MST during intensive study periods at one urban and one rural site on each side of the border. An automated gas chromatograph was operated at one site in central El Paso. Source profiles (the fractional chemical composition of emissions) from motor vehicles, gasoline, liquefied petroleum gas, and commercial natural gas were combined with source profiles from other studies for input to the Chemical Mass Balance (CMB) receptor model to apportion the measured non-methane hydrocarbons (NMHC) to sources. On-road vehicle emissions accounted for one-half to two-thirds of the NMHC in Ciudad Juárez and El Paso with the highest contributions occurring during the morning and afternoon commute periods. Emissions from diesel exhaust contributed approximately 2-3% of NMHC in Ciudad Juárez and less than 2% in El Paso. The average sum of liquid gasoline and gasoline vapor increased during the day in Ciudad Juárez from 2% at 06.00 h to approximately 12% at 16.00 h. Diurnal and day-of-the-week patterns in the liquid gasoline contributions are essentially identical to the corresponding patterns for motor vehicle exhaust, which suggest that a large fraction of the liquid gasoline contribution may be associated with tailpipe emissions rather than evaporative emissions from motor vehicles or industrial sources. Including the sum of the two sources put the upper limit for tailpipe contributions at 60-70% of NMHC.

Environmental Monitoring↗

PubMed2003

Neural control of 3-D gaze shifts in the primate.

The neural mechanisms that specify target locations for gaze shifts and then convert these into desired patterns of coordinated eye and head movements are complex. Much of this complexity is only revealed when one takes a realistic three-dimensional (3-D) view of these processes, where fundamental computational problems such as kinematic redundancy, reference-frame transformations, and non-commutativity emerge. Here we review the underlying mechanisms and solutions for these problems, starting with a consideration of the kinematics of 3-D gaze shifts in human and non-human primates. We then consider the neural mechanisms, including cortical representation of gaze targets, the nature of the gaze motor command used by the superior colliculus, and how these gaze commands are decomposed into brainstem motor commands for the eyes and head. A general conclusion is that fairly simple coding mechanisms may be used to represent gaze at the cortical and collicular level, but this then necessitates complexity for the spatial updating of these representations and in the brainstem sensorimotor transformations that convert these signals into eye and head movements.

Animals↗

PubMed1996

Meeting the challenge of railway injury in a South African city.

BACKGROUND: Efficient and safe transport infrastructure is vital for economic growth in developing countries. The city of Cape Town, South Africa, has an extensive rail network with high levels of injury and violence. We investigated the reporting and frequency of railway injuries and examined their reduction through a range of interventions. METHODS: We analysed railway injury and death reporting by Cape Town's rail utility, state mortuaries, and a regional trauma survey. The data were obtained over 2.5 years, and the use of more than one data source was necessary to increase the size of the data pool and to determine under-reporting. FINDINGS: There were 379 railway-related deaths and 505 serious injuries during the study period. Most death (190) were train-pedestrian collisions, and the fatality rate on the metropolitan lines was about 60 per 100 million passenger journeys. There was substantial under-reporting by the rail utility of both fatal (20% under-reported) and non-fatal injuries (at least 24%). Many injuries occurred during peak commuting times and alcohol played an important part, especially in pedestrian fatalities. INTERPRETATION: Our results demonstrate the importance of a comprehensive, sustainable railway injury surveillance system to promote safety engineering and law enforcement in a metropolitan rail system.

Accidental Falls↗

PubMed1999

Contextualizing the effects of childhood sexual abuse on adult self- and social functioning: an attachment theory perspective.

OBJECTIVE: This retrospective survey study explored the hypothesis that multiple maltreatment and loss experiences in early childhood would interfere with the formation of secure attachments, creating (1) an increased vulnerability to childhood sexual abuse (CSA), and (2) adult problems in self- and social functioning. METHOD: Data were collected from 687 undergraduates on an urban, commuter campus. They were analyzed by means of between group (individuals with and without CSA histories) and within group (individuals with CSA histories) path analytic models. RESULTS: The number of maltreatment and loss experiences encountered in early childhood predicted greater CSA frequency in childhood and increased maltreatment in adulthood in the form of more frequent reports of sexual, physical, and emotional abuse. Childhood maltreatment and loss experiences also predicted poor adult self-functioning in the form of higher levels of depression and lower levels of self-esteem. Self-blame in response to CSA and maltreatment in adult relationships also predicted poorer adult self- and social functioning for individuals with CSA histories. CONCLUSIONS: Findings support both direct and mediational effects of childhood maltreatment and loss experiences on adult self- and social functioning and are consistent with predictions derived from attachment theory.

Adaptation, Psychological↗

PubMed2002

Estimating the total exposure to air pollutants for different population age groups in Hong Kong.

Given that Hong Kong is one of the most densely populated cities in the world, the exposure of the Hong Kong people is one of the interesting research areas. In this study, an indirect approach was used to estimate the exposure to nitrogen dioxide (NO2), respiratory dust (PM10) and carbon monoxide (CO) pollutants experienced by different age groups of people in Hong Kong. The average concentrations of the 20 major microenvironments obtained from our measurement survey data, together with the people activity pattern data obtained from 7-day recall questionnaires, were used to predict frequency distributions to exposure assessment. Our results showed that Hong Kong people spent more than 86% of their time indoors. Homes were shown to be the one of the major exposure sites to NO2, CO and PM10 for all age groups. Our results also indicate that the 24-h NO2 exposure for individuals, irrespective of age, spending more than 2 h in commuting daily, was observed to be exceeding the 24-h NO2 exposure standards. This study was one of the pioneering studies with valuable contribution for modeling the estimates of exposures to NO2, PM10 and CO of different age groups in Hong Kong.

Adolescent↗

PubMed1999

Methodology for coupling local application of dopamine and other chemicals with rapid in vivo electrochemical recordings in freely-moving rats.

Methodology is presented for constructing and using an electrode/microcannulae assembly that allows in vivo electrochemical measurements coupled with local application of dopamine (DA) and other chemicals in the unanesthetized freely-moving rat. Rats were implanted with a voltammetric electrode constructed of a carbon fiber sealed in fused silica tubing attached to a pair of stainless steel guide cannulae, into which fused silica injection cannulae were inserted for local application of DA and other chemicals. Precise delivery of nanoliter volumes was accomplished using a syringe drive combined with a fluid swivel to deliver the solutions to the injection cannulae. A newly-designed miniature potentiostat connected to a commutator via a modular telephone jack assembly allowed for high-speed chronoamperometric electrochemical recordings in freely-moving rats. Initial experiments characterized the in vitro electrochemical recording characteristics of the voltammetric electrode. In vivo studies were also carried out to study clearance of locally-applied DA and of potassium-evoked endogenous DA in the striatum and nucleus accumbens of freely-moving rats. In addition, the effects of chloral hydrate anesthesia on DA clearance signals in the nucleus accumbens were investigated. Moreover, the stability and reproducibility of this recording technique for measuring exogenous DA clearance was verified over a period of 5 days. Finally, the concurrent effects of systemic cocaine injection on DA uptake in nucleus accumbens and locomotor activity were examined. These studies support the conclusion that the methodology described herein allows for rapid chronoamperometric electrochemical recordings in freely-moving rats with precise microapplications of DA and other chemicals combined with concurrent measures of animal behavior.

Anesthesia↗

PubMed1998

Exaptation and torsion: toward a theory of natural information processing.

Several conundrums are provoked by attempts to provide algorithmic descriptions of natural phenomena. A characteristic feature of natural computation is a breakdown in the formal simulation relation. This is called hermeneutic torsion, and is formally the failure to commute of a diagram describing homomorphisms between dynamical systems. This torsion is a source of computational power. For example, it is deeply involved with phenomena such as exaptation, wherein an existing structure is recruited for a novel function. Exaptation occurs continually at the macromolecular level and is fundamentally nonalgorithmic; our system-theoretic models of computation deal with structural descriptions for which a functional semantics must be assigned in advance, and a natural system continually 'diagonalizes out' of this semantics. This perspective clarifies the nature of computing power and encourages consideration of a new kind of transcomputational complexity.

Algorithms↗

PubMed1978

Therapeutic consequences of antitumour drug interactions: methotrexate and 5-fluorouracil in the chemotherapy of C3H mice with transplanted mammary adenocarcinoma.

Methotrexate and 5-fluorouracil at fixed dosages of 1.5 mg/kg and 50 mg/kg, respectively, were employed in combination chemotherapy for transplanted mammary adenocarcinoma in C3H mice. Tumour regression analyses demonstrated the importance of drug sequence and scheduling. Significantly, a drug synergism and antagonism was exhibited under certain conditions. Results indicated a superior therapeutic efficacy when methotrexate was administered 6-12 h before 5-fluorouracil; the reverse proved antagonistic. However, at longer intervals a commutative additivity was apparent. Judicious scheduling of methotrexate and 5-fluorouracil would seem appropriate, as both drugs are widely employed in the current management of neoplasms, such as breast carcinoma.

Adenocarcinoma↗

PubMed2003

Testing the utility of a geographical profiling approach in three rape series of a single offender: a case study.

The purpose of the study was to test the potential utility of a geographical profiling approach for three separate series of rapes committed by a single offender. Two different mathematical distance-decay functions using either a normal distribution with a mean distance and standard deviation based on previous research or a truncated negative exponential function based on distances between crime sites in the series under investigation were applied to each of the series giving prioritised search areas the accuracy of which was then assessed. The prioritised area that had to be searched before the home base of the offender could be located varied from 7.60 km(2) or 2.15% of the total search area at its best to 15 1.10 km(2) or 42.66% at its worst for the normal distribution based on previous research and from 42.06 km(2) or 11.88% to no improvement when the truncated negative exponential function was used. The functions used showed less predictive ability when the offender was a commuter. Explanations for the variations in the findings as well as suggestions for improvements were outlined in the discussion.

Forecasting↗

PubMed2003

Multi-pumping flow system for the spectrophotometric determination of dipyrone in pharmaceutical preparations.

A novel flow system for the spectrophotometric determination of dipyrone with p-dimethylaminobenzaldehyde exploiting the multi-pumping approach was developed. The proposed methodology utilises several micro-pumps for propelling the involved fluids under improved mixing conditions, introducing sample/reagent aliquots and providing commuting facilities. As a consequence the multi-pumping system presents high versatility and manifold simplicity, as well as a straightforward operational control and enhanced analytical capabilities. Linearity of the analytical curve was observed within 10 and 400 mg l(-1) dipyrone (r=0.9997; n=6), results were precise (r.s.d.<0.12%; n=20) and sampling rate was 50 h(-1). Detection limit was estimated as 1 mg l(-1) dipyrone. The method was applied to pharmaceutical preparations and the results were in agreement with those obtained by the reference procedure with relative deviations within -1.7 and +2.2%.

Dipyrone↗

PubMed1996

Sadness, tragedy and mass disaster in Oklahoma City: providing critical incident stress debriefings to a community in crisis.

Shortly after 09:00 h on 19 April 1995, the Alfred P. Murrah Federal Building, located in downtown Oklahoma City, was devastated with a bomb blast of such gigantic proportions that it was heard 60 miles away in neighbouring Norman, Oklahoma. Oklahomans routinely commuting to work on that sunny Wednesday morning went about their business as usual. A crude bomb chemically comprised of various organic compounds, chemical fertilizer, ammonium nitrate and diesel fuel, weighing an estimated 4800 pounds or more, was transported in a vehicle the size of a truck. It blew open a crater 6-8 ft deep in the street floor. The Murrah Federal Building was impacted immediately; floors, windows, communication equipment and almost all the innocent victims inside were razed to the ground. Outside the building, as far as 10 blocks away or more, hundreds of victims lay hurt, seriously injured or dead from shards of glass that flew from office windows hundreds of feet above the street floor. Without warning, the initial impact of the bomb immediately devastated the entire city. People were in a state of shock, disbelief and denial; acute symptoms of post traumatic stress disorder (PTSD) were commonplace. Oklahomans, 'numb' from the impact of the critical incident and ill-equipped to handle the chaos of such catastrophic proportions, struggled to regain control of their lives as friends, family and loved ones went unaccounted for or were found critically injured, dying or already dead. The critical incident on 19 April demanded the immediate attention of the nation, to come to the aid of the Oklahomans who were in desperate need. By 1 June, the exhaustive investigations revealed that 30 office buildings in downtown Oklahoma City had to be condemned, and as many as 300 others were damaged. In addition, 168 people had been found dead including 19 children and one nurse working as an emergency services rescue worker. Approximately 490 other victims had been reported injured from the blast. Countless others have been traumatised by the critical event and will need professional attention and care for weeks, months and years to come. The final extent of the impact on Oklahoma City is yet unknown and may never realistically be estimated in terms of personal trauma, loss and grief.

Crisis Intervention↗

PubMed2003

Transverse magnetization transfer under planar mixing conditions in spin systems consisting of three coupled spins 1/2.

Polarization transfer under planar mixing conditions is a widely used tool in modern NMR-experiments. In the case of two coupled spins 1/2 or a chain of three or more spins 1/2 with only nearest neighbor couplings, it is only possible to transfer a single magnetization component (longitudinal magnetization in the principle axis system of the planar coupling tensors). However, if all couplings in a three-spin system are non-zero, it turns out that all magnetization components can be efficiently transferred even under strictly planar mixing conditions. In this article a detailed theoretical analysis is presented based on analytical transverse coherence transfer functions and on the underlying commutator algebra. In addition, transverse magnetization transfer is demonstrated experimentally. The results show that in highly coupled spin systems, as for example in the case of partially aligned samples with many residual dipolar couplings, special care has to be taken to avoid phase distortions if planar mixing steps are used.

Algorithms↗

PubMed2001

The glycine decarboxylase system: a fascinating complex.

The mitochondrial glycine decarboxylase multienzyme system, connected to serine hydroxymethyltransferase through a soluble pool of tetrahydrofolate, consists of four different component enzymes, the P-, H-, T- and L-proteins. In a multi-step reaction, it catalyses the rapid destruction of glycine molecules flooding out of the peroxisomes during the course of photorespiration. In green leaves, this multienzyme system is present at tremendously high concentrations within the mitochondrial matrix. The structure, mechanism and biogenesis of glycine decarboxylase are discussed. In the catalytic cycle of glycine decarboxylase, emphasis is given to the lipoate-dependent H-protein that plays a pivotal role, acting as a mobile substrate that commutes successively between the other three proteins. Plant mitochondria possess all the necessary enzymatic equipment for de novo synthesis of tetrahydrofolate and lipoic acid, serving as cofactors for glycine decarboxylase and serine hydroxymethyltransferase functioning.

Amino Acid Oxidoreductases↗

PubMedDate not supplied

Get off the bus: sound strategy for injury prevention during a tornado?

INTRODUCTION: On 08 May 2003, a tornado categorized as an F-3 on the Fujita Tornado Scale (the "F Scale") struck an Oklahoma City, Oklahoma commuter bus carrying 24 passengers. The driver evacuated several passengers before the tornado struck. The tornado rolled the bus, and pelted it with debris. METHODS: A case-series investigation of tornado-related injuries was conducted among passengers who were evacuated to a ditch and those who remained on the bus when the tornado struck. RESULTS: Nineteen of 24 passengers sought care for injuries at hospital emergency departments (injury rate = 79.2%). While a greater number of passengers who were outside the bus when the tornado struck (11) sought care for injuries than did those who remained on the bus (8); passengers outside of the bus suffered fewer injuries than did those who remained on the bus (median number of injuries 3 versus 4), and their injuries were less severe (median injury severity score (ISS) 1 versus 4). CONCLUSION: For persons caught in motor vehicles during tornado events, this study supports currently accepted recommendations to immediately evacuate and lie in a low-lying area away from motor vehicles if other shelter is unavailable. However, generalizing the experience of bus passengers to automobile drivers might be inappropriate because buses lack the safety features that might protect automobile drivers from tornado-related injuries.

Adolescent↗

PubMed2002

Speciated ambient carbonyls in Rio de Janeiro, Brazil.

Carbonyls in urban air continue to receive scientific and regulatory attention as toxic air contaminants and for their important role in photochemical smog. However, few data are available for speciated carbonyls in urban air. Ambient concentrations of up to 61 carbonyls have been measured in Rio de Janeiro, Brazil. The most abundant carbonyls were formaldehyde and acetaldehyde (study-averaged concentrations of 10.8 +/- 4.1 and 10.4 +/- 4.6 microg m(-3), respectively, in samples of 3-h duration collected from May to November 2000 at a downtown location during the morning vehicle commute) followed by acetone, 2-butanone, and benzaldehyde. Ambient concentrations of other carbonyls (except acetophenone) correlated well with those of acetaldehyde and of formaldehyde. This study examines the ambient acetaldehyde/ambient formaldehyde concentration ratio in Brazilian cities since the mid-1980s in the context of changes in Brazil's reliance on ethanol as a vehicle fuel. This ratio has begun to decrease in recent years due to fleet turnover and is likely to decrease further as older cars fueled with ethanol are replaced by lower-emitting models that run on a gasoline-ethanol blend. The carbonyls measured are ranked with respect to ozone formation potential (using MIR coefficients) and reaction with OH (using carbonyl-OH reaction rate constants). Ozone formation is dominated by formaldehyde (43% of total) followed by acetaldehyde (32%) and methylglyoxal (8%); other carbonyls each contributed < or = 4% of total. For reaction with OH, acetaldehyde ranks first closely followed by formaldehyde.

Air Pollutants↗

PubMed2003

Persistent organic pollutants in the dusts that settled across lower Manhattan after September 11, 2001.

The explosion and collapse of the World Trade Center (WTC) was a catastrophic event that produced an aerosol impacting many workers, residents, and commuters during the first few days after September 11, 2001. During the initial days that followed, 14 bulk samples of the settled dust were collected at locations surrounding the epicenter of the disaster, including one indoor location. Some samples were analyzed for many potential hazards, including inorganic and organic constituents as well as morphology. The results of the analyses for persistent organic pollutants are described herein, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and select organochlorine pesticides on settled dust samples. The sigma86-PCBs comprising less than 0.001% by mass of the bulk in the three bulk samples analyzed indicated that PCBs were of limited significance in the total settled dust across lower Manhattan. Likewise, organochlorine pesticides, including chlordanes, hexachlorobenzene, heptachlor, 4,4'-DDE, 2,4'-DDT, 4,4'-DDT, and Mirex, were found at low concentrations in the bulk samples. Conversely, the sigma37-PAHs comprised up to nearly 0.04% (<0.005-0.039%) by mass of the bulk settled dust in the six bulk samples. Further size segregation of these three initial bulk samples and seven additional samples indicates that sigma37-PAHs were found in higher concentrations on relatively large particles (10-53 microm), representing up to 0.04% of the total dust mass. Significant concentrations were also found on fine particles (<2.5 microm), often accounting for approximately 0.005% by mass. We estimate that approximately 100-1000 tons of sigma37-PAHs were spread over a localized area immediately after the WTC disaster on September 11.

Aircraft↗

PubMed2005

Vehicle self-pollution intake fraction: children's exposure to school bus emissions.

Vehicle self-pollution occurs when a vehicle's emissions migrate to inside that vehicle's passenger compartment. This paper presents values fortwo new parameters: vehicle self-pollution intake fraction (iF(SP)), which is the total fraction of a vehicle's emissions inhaled by all people in the vehicle, and vehicle self-pollution individual intake fraction (iF1SP), which is the fraction of a vehicle's emissions inhaled by an individual in the vehicle. We use results from tracer-gas experiments in California's South Coast Air Basin (SoCAB) to quantify students' iF(SP) and iF1SP for school bus emissions. Six buses were studied during nine runs with windows open and seven runs with windows closed. Reported iF(SP) values (units: per million; min = 10, max = 94, mean = 27) indicate that the total mass of a bus' exhaust inhaled by students commuting on it is comparable in magnitude to the total mass of that bus' exhaust inhaled by all other people in the SoCAB. Reported iF1SP values (units: per million; min = 0.2, max = 2.4, mean = 0.7) indicate that average per capita inhalation of emissions from any single bus is 10(5)-10(6) times greater for a student on that school bus than for a typical resident in the SoCAB. Vehicle self-pollution rate varies with bus window position (open or closed) and bus manufacture year. Our results can be used to develop cost-effective strategies to reduce children's exposure to school bus emissions. Our results indicate, for example, that even if emission reductions were many times more expensive per gram emitted for school buses than for an average vehicle, it would still be less expensive per gram inhaled by a student to reduce emissions from school buses than from an average vehicle.

Air Pollutants↗