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PubMed2005

Fractal analysis of the laminar organization of spinal cord neurons.

Images of Golgi impregnated neurons from different laminae of the human and rat dorsal horns were subjected to a quantitative analysis to support the Rexed's laminar scheme in mammals. Four methods of fractal analysis were performed in the proceedings: box-counting, mass-radius, cumulative intersection, and vectorized intersection. The results show that the box-counting method is more precise than the other fractal methods performed, and offers support for the conclusion that fractal analysis can successfully discriminate the neuron populations among different laminae. The analysis supports the concept of Rexed's cytoarchitectonic lamination of the dorsal horn.

Animals↗

PubMed2006

Application of modified Sholl analysis to neuronal dendritic arborization of the cat spinal cord.

The drawings of Golgi-impregnated neurons from laminae I to VI in dorsal horn of the cat spinal cord were analysed morphometrically with a modified Sholl method of concentric circles. In order to advance the Sholl analysis of neuronal dendritic arborization patterns, we developed a new method of data presentation using polynomial regression and defining three parameters: the critical value of the circle radius (which defines the place of a possible circle intersecting maximum number of dendrites), the maximum number of dendritic intersections with the circles (counted for consecutive circles placed starting at the cell body to the border of the dendritic tree), and the mean value of the fitted polynomial function (which describes an average property concerning numbers of branches of dendritic tree over the whole region occupied by the dendritic arbor). For that purpose we also used the Sholl regression coefficient as well as the Schoenen ramification index. As an illustration of our model, we demonstrate that proposed modification of the Sholl method can successfully discriminate neuronal populations among different laminae of the cat spinal cord.

Algorithms↗

PubMedDate not supplied

Two-part surgical neck fractures of the humerus: mechanical analysis of the fixation with four Shanz-type threaded pins in four different assemblies.

The configuration of percutaneous pinning may affect the stability of the fixation of 2-part surgical neck fractures of the humerus. In this investigation, the mechanical properties of four different pin configurations were analyzed by use of 36 fresh-frozen swine femora as an experimental model. The bones were selected according to previously established morphologic parameters. A transverse osteotomy was made in the proximal metaphyseal region of the bone, and the pins were inserted according to the selected configuration (group 1, four ascending parallel pins; group 2, three ascending parallel pins and one descending intersecting pin; group 3, two ascending parallel pins and two descending parallel intersecting pins; and group 4, two ascending parallel pins and two descending converging pins, on different planes [two by two]). The assemblies were subjected to an axial load of up to 1500 N in a universal testing machine, simulating a varus stress. The parameters studied were the maximum load supported and corresponding deformation, load and deformation at the limit of proportionality, rigidity, and resilience. The results showed that all configurations were sufficiently strong, but the maximum load and load at the limit of proportionality were significantly higher (P < .05) in groups 3 and 4 (1314 and 1377 N and 950 and 923 N, respectively) than in groups 1 and 2 (1104 and 1033 N and 738 and 777 N, respectively). Rigidity was significantly higher in group 3 than in groups 1 and 2 but not in group 4. Resilience, maximum deformation, and deformation at the limit of proportionality were not significantly different between groups. We conclude that the experimental model used was reliable for the purpose of the study and that any of the configurations studied would be adequate for the percutaneous fixation of 2-part surgical neck fractures of the humerus but group 3 configuration would be the most efficient.

Animals↗

PubMed2003

Analysis of driver injury severity levels at multiple locations using ordered probit models.

PROBLEM: The occurrence and outcome of traffic crashes have long been recognized as complex events involving interactions between many factors, including the roadway, driver, traffic characteristics, and the environment. This study is concerned with the outcome of the crash. METHOD: Driver injury severity levels are analyzed using the ordered probit modeling methodology. Models were developed for roadway sections, signalized intersections, and toll plazas in Central Florida. All models showed the significance of driver's age, gender, seat belt use, point of impact, speed, and vehicle type on the injury severity level. Other variables were found significant only in specific cases. RESULTS: A driver's violation was significant in the case of signalized intersections. Alcohol, lighting conditions, and the existence of a horizontal curve affected the likelihood of injuries in the roadway sections' model. A variable specific to toll plazas, vehicles equipped with Electronic Toll Collection (ETC), had a positive effect on the probability of higher injury severity at toll plazas. Other variables that entered into some of the models were weather condition, area type, and some interaction factors. This study illustrates the similarities and the differences in the factors that affect injury severity between different locations.

Accidents, Traffic↗

PubMed2005

Road safety effects of roundabouts in Flanders.

INTRODUCTION: This paper analyzes the effect on road safety of 95 roundabouts that were built in Flanders between 1994 and 1999. RESULTS: The study shows that the effect on the number and severity of road accidents adjusted for the trend and regression to the mean is significant, but varies considerably in accordance with the speed limit regime on the intersection. Roundabouts are most effective on intersections of a main road with a high speed limit (90 km/h) and an adjacent road with a lower speed limit (50 or 70 km/h). The empirical analysis reveals a reduction of 34% (varying between 15% and 59%) for the total number of injury accidents, 30% (7%-45%) for light injury accidents, and 38% (27%-72%) for serious injury accidents. This study also takes a closer look at the impact of different post-implementation periods using accident data of 1-, 3-, or 6-years after the construction of a roundabout on the calculated effectiveness results and warns for a severe underestimation when a one-year period is used. IMPACT ON INDUSTRY: An effective traffic safety policy based on scientific results thus requires some patience from the policy-makers.

Accidents, Traffic↗

PubMed2003

Interactive specification of regions of interest on brain surfaces.

We describe Surface Editor-a tool for interactive specification of regions of interest (ROIs) on brain surfaces. The tool allows users to define subsurfaces by tracing around areas within a triangle-mesh brain surface. The input to the program is a triangle-mesh representation of a brain volume and a set of user-defined input points on the mesh. The program connects each pair of successive input points with a polyline that results from the intersection of the mesh with a plane that is approximately normal to the mesh. The polyline comprises coplanar line segments. The boundary of an ROI is a connected set of polylines that intersects triangle edges to form a continuous path. To validate Surface Editor we demonstrated that the program could be used to interactively delineate gyri on brain surfaces, and we showed that paths that the program generated were comparable to paths that a user generated and to shortest paths.

Brain↗

PubMed2005

Comparison between semiautomated kinetic perimetry and conventional Goldmann manual kinetic perimetry in advanced visual field loss.

PURPOSE: To compare quantitatively visual field (VF) results obtained using a new standardized semiautomated kinetic perimetry (SKP) with those obtained by conventional Goldmann manual kinetic perimetry (MKP) in patients with advanced VF loss. DESIGN: Prospective, single-center, observational comparative case series. SUBJECTS AND METHODS: Seventy-seven eligible patients (36 suffering from advanced retinal nerve fiber layer loss, 20 with concentric constriction of the VF, and 21 with hemianopia) were included in the study. One eye of each patient was examined on the same day with MKP and SKP. Three isopters, identical in both tests, were chosen to assess the extent of the VF loss. To compare the location and size of the corresponding isopters obtained with MKP and SKP, intersection areas of superimposed isopters were expressed as a percentage of union areas. MAIN OUTCOME MEASURES: The area and position of isopters for a defined stimulus condition obtained with both methods were compared. Test duration and patients' preference were also evaluated. RESULTS: Isopters obtained with Goldmann MKP enclosed areas smaller by 20% (confidence interval [CI], 12%-27%). The mean intersection area of Goldmann and SKP VFs was 1763.1 square degrees (CI, 1558.6-1967.7) smaller than the union for stimulus III4e over all groups of patients. Semiautomated kinetic perimetry was preferred by 60% of patients with concentric constriction of the VF. Median duration of the examination was 15 minutes and did not differ significantly between the 2 methods. CONCLUSIONS: Our results indicate that SKP isopter shape and size were very comparable to those obtained on the same eyes with MKP. Semiautomated kinetic perimetry may represent a more standardized method of kinetic perimetry, which still takes advantage of perimetrist-patient interaction to diagnose and monitor advanced VF loss in clinical practice.

Adolescent↗

PubMed2026

Discrimination, chronic stress, and multimorbidity in cohort of Black and Latina transgender women with HIV: Longitudinal findings from the LITE Plus study.

Black and Latina transgender women with HIV (BLTWH) are exposed to repeated, intersecting discrimination based on race, gender, and serostatus. Minority stress theory conceptualizes discrimination as minority-specific stressors that drive health inequities. Allostatic load theory posits a pathway between discrimination and chronic disease through multisystem physiological dysregulation caused by chronic stress. To test this pathway, a longitudinal cohort of 108 BLTWH, enrolled December 2020 - June 2022 in Boston, New York City, and Washington, DC, were followed for 24 months, with biomarkers measured at baseline, 12, and 24 months. Questionnaires administered every 6 months assessed anticipated discrimination, everyday discrimination, perceived stress, and other psychosocial factors. Multimorbidity was measured via self-reported non-HIV chronic conditions. In mixed-effects mediation models, allostatic load did not mediate relationships between multimorbidity outcomes and anticipated discrimination (β: -0.0004 [95% CI: -0.004, 0.003]) nor everyday discrimination (β: -0.002 [95%CI: -0.009, 0.003]). Perceived stress demonstrated indirect effects on multimorbidity in unadjusted models of anticipated discrimination (β: 0.024, [95% CI: 0.015, 0.081]) and everyday discrimination (β: 0.021 [95%CI: 0.016, 0.077]). Indirect effects remained significant, with attenuated effects (β: 0.020 for anticipated discrimination; β: 0.017 for everyday discrimination) after adjusting for social support, community connection, and resilient coping. Total effects were only significant for the adjusted model of everyday discrimination (β: 0.056 [0.014, 0.099]). Findings suggest discrimination impacted health through specific psychosocial pathways. Alongside efforts to eliminate intersectional discrimination, stress-lowering interventions and increased access to social support and community connection may be effective approaches to reducing multimorbidity in this highly marginalized group.

Humans↗

PubMed2005

Infrared reflectance spectra of some optically biaxial crystals: on the origin of isosbestic-like points in the polarized reflectance spectra.

An investigation of the IR polarized reflectance spectra of the orthorhombic K2SO4, KHSO4 and monoclinic CaSO4 x 2H2O, K2Ni(SO4)2 x 6H2O, (NH4)2Ni(SO4)2 x 6H2O was performed in order to explain the appearance of particular intersection points in their spectra. The analogy in the origin of the appearance of intersection points and the well-known isosbestic points in UV-vis and IR spectra was discussed. The reason for such an appearance was identified in the way that the individual reflectances (for radiation polarized along principal dielectric axes) sum up to give the reflectance under arbitrary polarization. This summation may also produce supplementary bands in the reflectance spectra, not predicted by the group theory. It was shown that relatively large LO-TO splitting is needed for the supplementary band(s) to appear, but also the overlapping region must be taken into account.

Crystallization↗

PubMed2004

Introduction to the DAPPLE Air Pollution Project.

The Dispersion of Air Pollution and its Penetration into the Local Environment (DAPPLE) project brings together a multidisciplinary research group that is undertaking field measurements, wind tunnel modelling and computer simulations in order to provide better understanding of the physical processes affecting street and neighbourhood-scale flow of air, traffic and people, and their corresponding interactions with the dispersion of pollutants at street canyon intersections. The street canyon intersection is of interest as it provides the basic case study to demonstrate most of the factors that will apply in a wide range of urban situations. The aims of this paper are to introduce the background of the DAPPLE project, the study design and methodology for data collection, some preliminary results from the first field campaign in central London (28 April-24 May 2003) and the future for this work. Updated information and contact details are available on the web site at http://www.dapple.org.uk.

Air Pollution↗

PubMed2005

Geochemical fingerprints and controls in the sediments of an urban river: River Manzanares, Madrid (Spain).

The geochemical fingerprint of sediment retrieved from the banks of the River Manzanares as it passes through the City of Madrid is presented here. The river collects the effluent water from several Waste Water Treatment (WWT) plants in and around the city, such that, at low flows, up to 60% of the flow has been treated. A total of 18 bank-sediment cores were collected along the course of the river, down to its confluence with the Jarama river, to the south-east of Madrid. Trace and major elements in each sample were extracted following a double protocol: (a) "Total" digestion with HNO3, HClO4 and HF; (b) "Weak" digestion with sodium acetate buffered to pH=5 with acetic acid, under constant stirring. The digests thus obtained were subsequently analysed by ICP-AES, except for Hg which was extracted with aqua regia and sodium chloride-hydroxylamine sulfate, and analysed by Cold Vapour-AAS. X-ray diffraction was additionally employed to determine the mineralogical composition of the samples. Uni- and multivariate analyses of the chemical data reveal the influence of Madrid on the geochemistry of Manzanares' sediments, clearly manifested by a marked increase in the concentration of typically "urban" elements Ag, Cr, Cu, Pb and Zn, downstream of the intersection of the river with the city's perimeter. The highest concentrations of these elements appear to be associated with illegal or accidental dumping of waste materials, and with the uncontrolled incorporation of untreated urban runoff to the river. The natural matrix of the sediment is characterised by fairly constant concentrations of Ce, La and Y, whereas changes in the lithology intersected by the river cause corresponding variations in Ca-Mg and Al-Na contents. In the final stretch of the river, the presence of carbonate materials seems to exert a strong geochemical control on the amount of Zn and, to a lesser extent, Cu immobilised in the sediments. This fact suggests that a variable but significant proportion of both elements may be susceptible to reincorporation in the aqueous phase under realistic environmental conditions.

Journal Article↗

PubMed2005

Comparison of linear tomography and direct ridge mapping for the determination of edentulous ridge dimensions in human cadavers.

OBJECTIVE: The purpose of this study was to compare the accuracy of linear tomography (LT) and direct ridge mapping (RM) for determining alveolar ridge dimensions. STUDY DESIGN: One site in the posterior mandible was selected for evaluation in each of 5 cadaver heads. Vacuum-formed stents made from models of the cadaver ridges were used to identify 3 sets of measurement points for each specimen: coronal (intersection of coronal and middle third of ridge), middle (intersection of middle and apical third), and apical (base of vestibule). The imaging stent contained 2-mm metal balls at each point, while the RM stent had holes drilled at corresponding locations. Linear tomograms and periapical radiographs (PA) were taken of the selected sites. RM measurements were made with calipers. Five blinded examiners measured ridge width at the designated measurement points with both LT and RM as well as distance from the ridge crest to mandibular canal (using PAs for RM group). Mandibles were then sectioned and an independent examiner made direct measurements (DM). MANOVA was used to determine whether LT and RM differed significantly from DM. RESULTS: There were no significant differences between LT and RM for ridge width measurements. However, both techniques underestimated ridge dimensions compared to DM ( P < .05). Measurement of mandibular canal height was accurate when determined by periapical radiographs but not by LT. CONCLUSION: Neither LT nor RM proved to be completely accurate in determining ridge width in the posterior mandible.

Alveolar Process↗

PubMed2004

Metabolic dysfunction and depletion of mitochondria in hearts of septic rats.

Our previous studies indicate that hearts from septic rats have decreased work with oxygen wasting. The present studies test if there is energy deficit, changes in cardiac mitochondrial content and caspase activation during sepsis. Anesthetized, male Sprague-Dawley rats received no surgical treatment (control), laparotomy (sham), or laparotomy with cecal ligation and puncture (CLP) to induce polymicrobial septic shock. Hearts were isolated 12-14 h later. Cardiac work, oxygen consumption, substrate oxidation and energy stores were measured in perfused hearts. Normalized density of mitochondria was determined in ventricles without perfusion by morphometric analysis with electron microscopy. Citrate synthase activity was assessed in homogenates and isolated mitochondria. Cardiac work decreased significantly in CLP (47%), while oxygen consumption and glucose oxidation were unchanged compared with control or sham hearts (oxygen and substrate wasting). Tissue adenosine triphosphate, creatine phosphate and glycogen were lower in CLP hearts (energy deficit). Mitochondrial grid intersects decreased significantly from 151 +/- 8 sham to 130 +/- 4 CLP out of 361 possible intersects and autophagy was observed in CLP hearts. Total activity of citrate synthase decreased in homogenates (99 +/- 8 micromol/min/g wet weight sham vs. 62 +/- 7 CLP, P < 0.05) and in the mitochondrial fraction (27 +/- 1 micromol/min/g wet weight sham to 22 +/- 1 CLP, P < 0.05). Calculated mitochondrial content decreased from 63 +/- 4 mg protein/g wet weight sham to 46 +/- 5 CLP, P < 0.05 (mitochondrial depletion). Caspase-3 activity doubled and tumor necrosis factor alpha content tripled in CLP hearts. CONCLUSIONS. - Oxygen and substrate wasting in CLP occurs with fewer mitochondria and energy deficit, processes that are coincident with caspase-3 activation.

Animals↗

PubMed2002

Changes in crash risk following re-timing of traffic signal change intervals.

More than I million motor vehicle crashes occur annually at signalized intersections in the USA. The principal method used to prevent crashes associated with routine changes in signal indications is employment of a traffic signal change interval--a brief yellow and all-red period that follows the green indication. No universal practice exists for selecting the duration of change intervals, and little is known about the influence of the duration of the change interval on crash risk. The purpose of this study was to estimate potential crash effects of modifying the duration of traffic signal change intervals to conform with values associated with a proposed recommended practice published by the Institute of Transportation Engineers. A sample of 122 intersections was identified and randomly assigned to experimental and control groups. Of 51 eligible experimental sites, 40 (78%) needed signal timing changes. For the 3-year period following implementation of signal timing changes, there was an 8% reduction in reportable crashes at experimental sites relative to those occurring at control sites (P = 0.08). For injury crashes, a 12% reduction at experimental sites relative to those occurring at control sites was found (P = 0.03). Pedestrian and bicycle crashes at experimental sites decreased 37% (P = 0.03) relative to controls. Given these results and the relatively low cost of re-timing traffic signals, modifying the duration of traffic signal change intervals to conform with values associated with the Institute of Transportation Engineers' proposed recommended practice should be strongly considered by transportation agencies to reduce the frequency of urban motor vehicle crashes.

Accidents, Traffic↗

PubMed2000

Factors affecting the severity of motor vehicle traffic crashes involving elderly drivers in Ontario.

A population-based cross-sectional study was conducted to examine factors affecting the severity of motor vehicle traffic crashes (MVTCs) involving elderly drivers in Ontario. The study population included drivers aged 65 and over involved in injury-producing MVTCs between 1988 and 1993 on Ontario public roads. Information was obtained from the Canadian Traffic Accident Information Databank (TRAID) compiled from police reports. The severity of MVTC was classified as fatal, major, minor or minimal. Comparisons between fatal-, major-, minor- and minimal-injury crashes were conducted. Percentage distributions of crashes at each level of severity involving elderly drivers were examined according to specific factors and tested using the X2 test. Multivariate unconditional logistic regression was used to calculate the estimated relative risk as odds ratios (ORs) while controlling for confounding factors. A number of factors were significantly related to the increased risk of fatal-injury in crashes compared with a reference category for each variable. These included age (OR = 1.4 for 70-79 and OR = 2.3 for 80 + ), sex (OR = 1.4 for males), failing to yield right-of-way/disobeying traffic signs (OR = 1.7), non-use of seat belts (OR = 4.0), ejection from vehicle (OR = 11.3), intersection without traffic controls (OR = 1.7), roads with higher speed limits (OR = 7.9 for 70-90 km/h; OR= 5.8 for 100 km/h), snowy weather (OR= 1.6), head-on collisions (OR=55.1), two-vehicle turning collisions (OR = 3.1 for left-turn, OR = 8.7 for right-turn), overtaking (OR = 5.6), and changing lanes (OR = 2.1). Adverse medical/physical conditions increased the risk of fatality by a factor of 5 for drivers 75-79 years of age and a factor of 3.5 for those 80 years and over. However, in the age group 65-74, medical/physical condition did not appear to be related to risk of fatality. Similar but weaker associations between these factors and risk of major- and minor-injury in crashes were also observed. To reduce the severity of crashes involving elderly drivers, strategies could target specific factors such as head-on collisions, single-vehicle collisions, and traffic controls at intersections. Driver conditions such as medical/physical conditions and driver actions such as failing to yield right-of-way/disobeying traffic signs should be examined further.

Accidents, Traffic↗

PubMed2000

The effects on safety, time consumption and environment of large scale use of roundabouts in an urban area: a case study.

An experiment with small roundabouts-as speed reducing measures-was carried out in a Swedish city. The purpose of the study was to test the large scale and long term effects of the roundabouts. The results showed that the roundabouts reduced the speed considerably at the junctions and on links between roundabouts. The lateral displacement the roundabout forces the driver to has a great importance for the speed of approaching cars to a roundabout. The speed-reducing effect is large already at a 2 m deflection. A larger deflection does not result in a larger effect. Conflict studies indicated an overall decrease in accident risk by 44%. Vulnerable road-users' risk was reduced significantly, while there was no reduction for car occupants. There is a relation between the reduction of approach speed and the reduction of injury accident risk. The time consumption at a time operated signal was reduced heavily by the instalment of a roundabout at a signalised intersection. On average, emissions (CO and NOx) at roundabouts replacing non-signalised junctions increased by between 4 and 6%, while a roundabout replacing a signalised intersection led to a reduction by between 20 and 29%. The noise level was reduced at junctions that were provided with roundabout. Car drivers were less positive to the roundabouts than bicyclists. In the long term, the unchanged roundabouts worked almost as good as they did shortly after the rebuilding. The study showed that details in the design are of decisive importance for road-users' safety. Special attention has to be paid to the situation of bicyclists. The transition between the cycle path/lane and the junction has to be designed with care-the bicyclists should be integrated with motorised traffic before they enter the roundabout. There should be only one car lane both on the approach, in the circulating area and on the exit. The size of the roundabout shall be as small as possible.

Acceleration↗

PubMed2000

Road safety engineering: an effective tool in the fight against whiplash injuries.

Road safety engineering can play an integral part in the prevention of whiplash injuries. While improvements to vehicle design can reduce the severity of whiplash injuries when a crash occurs, improvements to road safety can prevent whiplash-inducing crashes from occurring in the first place. Whiplash injuries are most commonly associated with rear end crashes. Unfortunately, rear end crashes are also the most common type of crash at urban signalized intersections, where the majority of crashes occur in British Columbia, Canada. The Insurance Corporation of British Columbia (ICBC), through the road improvement program, has been funding road improvements in order to reduce the frequency of collisions at high crash locations in British Columbia. Several road safety engineering countermeasures specifically targeted at rear end collisions have been researched and deployed. These countermeasures include simple and affordable solutions such as signal visibility enhancements, as well as complex and expensive solutions such as intersection geometric upgrades. When appropriately used, these countermeasures have proven to be extremely cost-effective in reducing the frequency of rear end collisions. Widespread application of signal visibility enhancements is now being pursued to further decrease the risk of rear end collisions and whiplash injuries. Costs are the direct cost of the ICBC portion of the investment and benefits are only those associated with reduced insurance claims over a 2-year period.

Accidents, Traffic↗

PubMed2003

Synthesis and characterization of goethite and goethite-hematite composite: experimental study and literature survey.

Aging of synthetic goethite at 140 degrees C overnight leads to a composite material in which hematite is detectable by Mössbauer spectroscopy, but X-ray diffraction does not reveal any hematite peaks. The pristine point of zero charge (PZC) of synthetic goethite was found at pH 9.4 as the common intersection point of potentiometric titration curves at different ionic strengths and the isoelectric point (IEP). For the goethite-hematite composite, the common intersection point (pH 9.4), and the IEP (pH 8.8) do not match. The electrokinetic potential of goethite at ionic strengths up to 1 mol dm(-3) was determined. Unlike metal oxides, for which the electrokinetic potential is reversed to positive over the entire pH range at sufficiently high ionic strength, the IEP of goethite is rather insensitive to the ionic strength. A literature survey of published PZC/IEP values of iron oxides and hydroxides indicated that the average PZC/IEP does not depend on the degree of hydration (oxide or hydroxide). Our material showed a higher PZC and IEP than most published results. The present results confirm the allegation that electroacoustic measurements produce a higher IEP than the average IEP obtained by means of classical electrokinetic methods.

Journal Article↗