Search PubMed⌕ Search

Biomedical subjects

D O'Hare

Publications and source records attributed to D O'Hare.

At least 19 recordsLinked to original sources
PubMed2006

Case-control study of risk factors for fatal and non-fatal injury in crashes of rotary-wing aircraft.

INTRODUCTION: There have been few studies of the risk factors for fatal injury in air crashes of rotary-wing aircraft, and none of risk factors for all serious injury (fatal and non-fatal) in these aircraft. The aim of the study was to identify the potentially modifiable risk factors for injury in civil rotary-wing aircraft crashes in New Zealand. METHOD: We analyzed records from all reported civil rotary-wing aircraft crashes in New Zealand between 1988 and 1994. Air crash data from the official databases were merged with nationwide injury records and information obtained from Coroner's files. Crashes where the pilot-in-command was fatally injured were compared with crashes where the pilot-in-command was not fatally injured on 50 variables, covering pilot, aircraft, environmental, and operational characteristics. A second analysis compared crashes where the pilot-in-command was seriously injured (either fatally or non-fatally) with crashes where the pilot-in-command was not hospitalized with an injury. A series of multivariate logistic regression analyses were conducted to estimate the odds associated with each of the factors identified by the univariate analyses. RESULTS: The most significant risk factors for all serious injury were: (a) not obtaining a weather briefing, (b) off-airport location of the crash site, (c) flights carried out for air transport purposes, and (d) non-solo flights. Other risk factors, significant for fatal injury only, included post-crash fire and the nature of the crash terrain. Factors within the control of the pilot, environmental, and flight characteristics are the key determinants of the injury outcome of civil rotary-wing aircraft crashes.

Accidents, Aviation↗
PubMed2005

Changes in the properties of the modulatory cerebral giant cells contribute to aging in the feeding system of Lymnaea.

This study examined whether electrophysiological changes in the endogenous properties and connectivity of the modulatory serotonergic cerebral giant cells (CGCs) contributed to the age-related changes in feeding behavior of the pond snail, Lymnaea. With increasing age there was a decrease in spontaneous CGC firing rates and decreased excitability of the CGCs to both chemosensory stimulation (0.05M sucrose applied to the lips) and direct intracellular current injection. These changes could be accounted for by a decrease in the input resistance of the neuron and an increase in the amplitude and the duration of the after-hyperpolarization. Decreases were also seen in the % of CGC pairs that were electrically coupled causing asynchronous firing. Together these changes would tend to reduce the ability of the CGCs to gate and control the frequency of the feeding behavior. Part of the ability of the CGCs to gate and frequency control the feeding network is to provide a background level of excitation to the feeding motor neurons. Recordings from B1 and B4 motor neurons showed an age-related hyperpolarization of the resting membrane potential consistent with a deficit in CGC function. Increases were seen in the strength of the evoked CGC-->B1 connection, however, this increase failed to compensate for the deficits in CGC excitability. In summary, age-related changes in the properties of the CGCs were consistent with them contributing to the age-related changes in feeding behavior seen in Lymnaea.

Aging↗
PubMed2005

Effects of age on feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis.

This study used behavioral and electrophysiological techniques to examine age-related changes in the feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis. Increasing age was associated with a 50% decrease in long-term food consumption. Analysis of short-term sucrose-evoked feeding bouts showed an age-related increase in the number of animals that failed to respond to the stimulus. Of the animals that did respond increasing age was associated with a decrease in the number of sucrose-evoked bites and a increase in the duration of the swallow phase. These changes were observed with both 0.01 and 0.05M sucrose stimuli but were not seen when 0.1M sucrose was used as the stimulus. Electrophysiological analysis of the chemosensory pathway in semi-intact lip-CNS preparations failed to demonstrate a significant change in the neuronal information entering the cerebral ganglia from the lips via the median lip nerve, but did demonstrate an age-related deficit in the neuronal output from the cerebral ganglia. This deficit was also dependent on the sucrose concentration and mirrored the concentration-dependent changes in feeding behavior. In summary, aging appeared to affect central but not peripheral processing of chemosensory information and suggests that this deficit contributes to the age-related changes in feeding behavior.

Aging↗
PubMed2002

Direct and indirect cost of general aviation crashes.

BACKGROUND: There have been few well-designed studies which estimate the costs inflicted on society from injuries, fatalities, and property damage caused by aviation crashes. Furthermore, indirect cost estimates from the human capital (HC) approach tend to be substantially smaller than those obtained from the willingness-to-pay (WTP) approach. OBJECTIVES: To estimate the direct and indirect costs of general aviation crashes in New Zealand, and to contrast the HC and WTP approaches used to estimate indirect costs. METHODS: The incidence, morbidity, and mortality from aviation crashes between 1988 and 1997 were estimated from national health and aviation records. Direct costs included medical treatment, damage to aircraft and property, and the cost of crash investigation. For the HC approach, we valued losses to society as the value of lost production from both employed work and household activity. For the WTP approach, we used the Land Transport Safety Authority's estimated values of society's willingness to pay to avoid a fatality or injury. RESULTS: The annual average direct cost of aviation crashes was $9.1 m (range: $8.0 m to $11.4 m). The annual average indirect cost using the HC approach was $13.6 m ($5.6 m to $32.2 m). Using the WTP approach the annual average indirect costs was $49.3 m ($20.6 m to $106.5 m). Indirect costs from premature deaths were the key cost drivers. A sensitivity analysis showed that these values were relatively robust to changes in parameters. CONCLUSION: The annual average cost of general aviation crashes in New Zealand was between $22.6 m and $58.4 m. Indirect costs using the WTP approach were 3.5 times greater than those estimated using the HC approach.

Accidents, Aviation↗
PubMed2001

Real time observation of the hydrothermal crystallization of barium titanate using in situ neutron powder diffraction.

The hydrothermal crystallization of barium titanate, BaTiO3, has been studied in situ by time-resolved powder neutron diffraction methods using the recently developed Oxford/ISIS hydrothermal cell. This technique has allowed the formation of the ferroelectric ceramic to be followed in a noninvasive manner in real time and under genuine reaction conditions. In a first set of experiments, Ba(OD)2-8D2O was reacted with two different titanium sources, either crystalline TiO2 (anatase) or amorphous TiO2-H2O in D2O, at 100-140 degrees C and the reaction studied using the POLARIS time-of-flight neutron powder diffractometer, at the ISIS Facility. In a second series of experiments, the reaction between barium chloride and crystalline TiO2 (anatase) in NaOD/D2O was studied at temperatures between 100 and 200 degrees C and at different deuterioxide concentrations using the constant-wavelength D20 neutron powder diffractometer at the Institut Laue Langevin. Quantitative growth and decay curves were determined from analysis of the integrated intensities of Bragg reflections of starting materials and product phases. In both sets of experiments the rapid dissolution of the barium source was observed, followed by dissolution of the titanium source before the onset of crystallization of barium titanate. Using a nucleation-growth model we are able to simulate the growth curve of barium titanate at three temperatures. Our results indicate the predominance of a homogeneous dissolution-precipitation mechanism for the hydrothermal formation of barium titanate, rather than other possible mechanisms that have been discussed in the literature. Analysis of the line widths of the Bragg reflections in the neutron diffraction data indicates that the particle size of the BaTiO3 product phase prepared from the amorphous TiO2-H2O is smaller than that prepared from crystalline TiO2 (anatase).

Journal Article↗
PubMed2001

Intercalation and controlled release of pharmaceutically active compounds from a layered double hydroxide.

A series of pharmaceutically active compounds including diclofenac, gemfibrozil, ibuprofen, naproxen, 2-propylpentanoic acid, 4-biphenylacetic acid and tolfenamic acid can be reversibly intercalated into a layered double hydroxide, initial studies suggest that these materials may have application as the basis of a novel tuneable drug delivery system.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

High resolution imaging of the distribution and permeability of methyl viologen dication in bovine articular cartilage using scanning electrochemical microscopy.

Scanning electrochemical microscopy (SECM) has been used in the induced transfer (SECMIT) mode to image the permeability of a probe cation, methyl viologen (MV(2+)), in samples of articular cartilage. An ultramicroelectrode (UME), scanned just above the surface of a sample, is used to amperometrically detect the probe solute. The resulting depletion of MV(2+) in solution induces the transfer of this cation from the sample into the solution for detection at the UME. The current provides quantitative information on local permeability, provided that the sample-UME distance is known. It is shown that the necessary topographical information can be obtained using the amperometric response for the oxidation of Ru(CN)(4-)(6), which does not permeate into the cartilage matrix. This procedure was validated by marking samples in situ, after electrochemical imaging, with subsequent examination by ex situ interferometry and optical microscopy. Wide variations in the permeability of MV(2+) have been detected by SECMIT. These observations represent the first demonstration of the inhomogeneous permeability of a cation in cartilage on a micrometre scale. The permeability maps show similar features to the proteoglycan distribution, identified by toluidine blue staining, and it is likely that proteoglycans are the main determinant of MV(2+) permeability in articular cartilage.

Animals↗
PubMed2001

Variable coordination modes of hydrotris(3-isopropyl-4-bromopyrazolyl)borate (Tp') in Fe(II), Mn(II), Cr(II), and Cr(III) Complexes: formation of MTp'Cl (M = Fe and Mn), structural isomerism in CrTp'(2), and the observation of Tp' (-) as an uncoordinated anion.

The syntheses of the 4-coordinate Tp'MCl complexes (where M = Fe (1), Mn (2); and Tp' = hydrotris(3-isopropyl-4-bromopyrazolyl)borate) are described. The single-crystal X-ray structures show that the metal centers have distorted tetrahedral coordination. Analogous reaction of CrCl(2)(MeCN)(2) with TlTp' gave Cr(kappa(3)-Tp')(kappa(2)-Tp') (3) as the initial product. The 5-coordinate structure was assigned by single-crystal X-ray crystallography, and it was found that the kappa(3) ligand had isomerized to hydro(3-isopropyl-4-bromopyrazolyl)(2)(5-isopropyl-4-bromopyrazolyl)borate). 3 is labile in solution: in pentane it slowly converts to the 6-coordinate isomer Cr(kappa(3)-Tp')(2) (4), whose structure was determined by X-ray crystallography. In 4 both ligands are isomerized. Both 3 and 4 display Jahn-Teller distorted structures expected for high-spin d(4) configurations. Variable temperature magnetic susceptibility measurements confirm that 1, 2, and 3 all have high-spin electronic configurations in the range 5-300 K. In benzene solution 3 decomposes; one product [Cr(kappa(3)-Tp')(2)](+)[Tp'](-) (5), was identified by X-ray crystallography. 5 contains a pseudooctahedral Cr(III) cation with both ligands in the isomerized form and an uncoordinated Tp' ligand as counterion. Mechanistic studies reveal that this reaction is light rather than heat induced. IR spectroscopy is utilized to confirm the ligand hapticity in all complexes from the value of nu(B)(-)(H), and comparison is made with similar compounds.

Journal Article↗
PubMed2001

Arterial blood sampling practices in intensive care units in England and Wales.

A postal survey of arterial blood sampling practices in 280 intensive care units throughout England and Wales found that very few measures are taken to reduce diagnostic blood loss in adult intensive care patients from arterial sampling. The average volume of blood withdrawn to clear the arterial line before sampling is 3.2 ml; subsequently returned to the patient in only 18.4% of intensive care units. Specific measures to reduce the blood sample size by the routine use of paediatric sample tubes in adult patients occurs in only 9.3% of intensive care units. In paediatric units, the average volume withdrawn was 1.9 ml and this was routinely returned in 67% of units. Some aspects of arterial blood sampling practices identified in this survey may contribute to iatrogenic anaemia in intensive care patients.

Adult↗
PubMed2001

The use of botulinum toxin in otorhinolaryngology.

In recent years, the use of botulinum toxin has become more popular for the treatment of a wide variety of diseases in the head and neck. It offers the possibility of non-invasive treatment of conditions whose aetiology lies in neuromuscular dyskinesis.

Botulinum Toxins, Type A↗
PubMed2000

Hydrothermal synthesis of (C6N2H14)2(UVI2UIVO4F12), a mixed-valent one-dimensional uranium oxyfluoride.

A new hybrid organic-inorganic mixed-valent uranium oxyfluoride, (C6N2H14)2(U3O4F12), UFO-17, has been synthesized under hydrothermal conditions using uranium dioxide as the uranium source, hydrofluoric acid as mineralizer, and 1,4-diazabicyclo[2.2.2]octane as template. The single-crystal X-ray structure was determined. Crystals of UFO-17 belonged to the orthorhombic space group Cmcm (no. 63), with a = 14.2660(15) A, b = 24.5130(10) A, c = 7.201(2) A, and Z = 4. The structure reveals parallel uranium-containing chains of two types: one type is composed of edge-sharing UO2F5 units; the other has a backbone of edge-sharing UF8 units, each sharing an edge with a pendant UO2F5 unit. Bond-valence calculations suggest the UF8 groups contain UIV, while the UO2F5 groups contain UVI. EXAFS data give results consistent with the single-crystal X-ray structure determination, while comparison of the uranium LIII-edge XANES of UFO-17 with that of related UIV and UVI compounds supports the oxidation-state assignment. Variable-temperature magnetic susceptibility measurements on UFO-17 and a range of related hybrid organic-inorganic uranium(IV) and uranium(VI) fluorides and oxyfluorides further support the formulation of UFO-17 as a mixed-valent UIV/UVI compound.

Journal Article↗
PubMed2000

Scanning electrochemical microscopy as a local probe of oxygen permeability in cartilage.

The use of scanning electrochemical microscopy, a high-resolution chemical imaging technique, to probe the distribution and mobility of solutes in articular cartilage is described. In this application, a mobile ultramicroelectrode is positioned close ( approximately 1 microm) to the cartilage sample surface, which has been equilibrated in a bathing solution containing the solute of interest. The solute is electrolyzed at a diffusion-limited rate, and the current response measured as the ultramicroelectrode is scanned across the sample surface. The topography of the samples was determined using Ru(CN)(6)(4-), a solute to which the cartilage matrix was impermeable. This revealed a number of pit-like depressions corresponding to the distribution of chondrocytes, which were also observed by atomic force and light microscopy. Subsequent imaging of the same area of the cartilage sample for the diffusion-limited reduction of oxygen indicated enhanced, but heterogeneous, permeability of oxygen across the cartilage surface. In particular, areas of high permeability were observed in the cellular and pericellular regions. This is the first time that inhomogeneities in the permeability of cartilage toward simple solutes, such as oxygen, have been observed on a micrometer scale.

Animals↗
PubMed2000

The 'Wheel of Misfortune': a taxonomic approach to human factors in accident investigation and analysis in aviation and other complex systems.

The analysis and reporting of the human factors aspects of accidents in aviation and other complex systems continues to present difficulties for investigators and analysts alike. Reason's 'latent conditions' model has had a major impact on the way accidents are conceptualized but it has proven difficult to apply as a practical tool. Recent attempts to overcome these difficulties are discussed and an alternative conceptualization is proposed. This conceptualization is based on a blend of several well-supported theoretical models in cognitive engineering and can be used to formulate a parsimonious analysis system for the investigation and reporting of the human factors aspects of accidents. Two well-known examples of transportation disasters are briefly described and related to the proposed conceptual framework. The proposed framework serves three important functions in accident investigation and analysis: a heuristic function, an investigative function, and an integrative function.

Accidents, Aviation↗
PubMed1998

Measurement of the charge properties of articular cartilage by an electrokinetic method.

The charge structure of the surface of articular cartilage determines its interactions with the macromolecules and cells of synovial fluid. It may thereby be important to the physiological function and pathological degeneration of the tissue. To determine whether the electrokinetic properties of the surface differ from those of the bulk tissue, we measured the streaming potential generated by the flow of electrolyte over the surface of a cartilage plug mounted in a chamber built for that purpose. We then calculated the effective surface charge density. In nonfibrillated cartilage from the human femoral head, the surface charge density, 0.037+/-0.004 Cm(-2) (mean+/-SD), was approximately half that measured at the surface of slices cut from the middle and deep zones. In addition, the surface charge density fell relatively little at low pH; this is consistent with a higher proportion of strongly acidic groups. The variations in surface charge density were found to be similar to those in total fixed charge density in the slices by the tracer cation method. Therefore, no evidence exists that the actual surface differs in composition from the immediately underlying matrix. The addition of synovial fluid (0.0025 ml/ml) to the superfusing solution reduced the surface charge density by 25+/-9% (n=5), and we attributed this to the binding of synovial-fluid macromolecules.

Animals↗