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At least 793 records · Page 44Linked to original sources
PubMed1997

[Schistosomiasis imported by Spanish travelers: clinico-epidemiologic study of 80 cases].

BACKGROUND: Swimming in rivers or lakes is a risk activity, in areas where the life cycle of schistosomiasis occurs. This report presents and analyzes the clinical presentation and epidemiological data of 80 Spanish travellers. PATIENTS AND METHODS: Descriptive longitudinal and retrospective study that includes clinicoepidemiological and the laboratory data and imaging diagnosis. Patients were seen at the Section of Tropical Medicine, Hospital Clínic i Provincial, Barcelona. RESULTS: Most patients acquired the infection in the Dogon country of Mall. 25% of them presented with symptoms related to the genital tract. In some groups, 45% of travellers that swam, contracted the infection. The most prevalent species diagnosed was S. haematobium and 10 travellers presented with mixed infections. CONCLUSIONS: The trip to the Dogon country should be considered as "a risk activity". Travellers Advice Clinics should include the subject of swimming in infected waters in their routine counselling. Genital tract localizations were registered for three species of schistosome. The classical clinical presentation of schistosomiasis in the endemic areas differs considerably from that seen in travellers.

Adult↗
PubMed1997

Puerto Rican patients travel to Puerto Rico: assessing the effect on clinical care.

OBJECTIVE: To examine travel habits of Puerto Rican patients and assess the potential effect of this travel on their health care. DESIGN: Interview and survey of patients. SETTING: Urban medical clinic. PATIENTS: Two hundred consecutive, self-identified Puerto Rican patients presenting for follow-up care. INTERVENTION: Immediately prior to a follow-up office visit, patients were interviewed in either Spanish or English. MEASUREMENTS: The patients' age, sex, education level, employment status, and place of birth were recorded. The patients were asked questions concerning the principle place of residence of their family members, their ability to speak English, and their preferences in television and radio programs. Patients who had visited Puerto Rico were asked about the duration and purpose of their most recent trip and about the health care they received in Puerto Rico. Chi-square testing was applied to categorical data and t tests for continuous data; P values were calculated using the SPSS statistical analysis program. RESULTS: Of the 200 subjects, 110 (55%) had traveled to Puerto Rico in the last five years and 90 (45%) had not. The patients who traveled were more likely to have been born in Puerto Rico, less likely to speak English, and less likely to listen to English-language programs. A majority of the patients who traveled to Puerto Rico visited for a month or less (80%) and did not experience a change in health care (78%). In comparison, however, a majority (59%) of the patients who visited for longer than a month did experience a major change in their health care status (P < .00001). CONCLUSIONS: Puerto Rican patients, particularly those born in Puerto Rico with stronger cultural "ties" to the island, frequently return to Puerto Rico. Patients who visit for longer than a month often experience changes in care which are likely to have significant effect on their health. Clinicians caring for Puerto Rican patients should ask about upcoming visits to Puerto Rico and take steps to assure continuous and coordinated medical care.

Aged↗
PubMed1997

[Occurrence and management of psychiatric pathology in travelers].

The relationship between mental disorders and travel are complex and multiple. Several clinical patterns can be distinguished. Travel is a key feature in the symptomatology of some psychiatric illnesses. Psychiatric manifestations can be induced by local living conditions in subjects with declared mental illness. Disorders can occur during travel in subjects with no previous history of mental illness. Most subjects have a previous history of mental illness prior to leaving France. Attending physicians should warn patients of the possible risks of traveling and advise them concerning prevention and management. The purpose of this study is to describe the relationship between travel and mental illness and to discuss practical measures for management and medical evacuation.

Humans↗
PubMed1997

[Travel and patients with allergies].

By changing their surroundings and lifestyle, travelers with allergic conditions exposed themselves to new risks. The main perennial allergens are house dust mites which thrive in tropical areas and can be especially sensitizing. The risk of seasonal reactions to grass-pollens varies from region to region. Reactions to some highly sensitizing respiratory allergens can occur in travelers who return to regions where they were previously exposed. Subjects with food allergies should beware of possible reactions to ingredients in exotic dishes. The bites of several insects can cause anaphylactic reactions. Some medications required for tropical travel (e.g. antimalarial drugs) can trigger severe hypersensitivity reactions. Avoidance of allergens is more difficult during travel. Travelers with allergic conditions should carry alert identification cards and medications for routine as well as emergency treatment including self-injectable adrenaline.

Humans↗
PubMed1997

[Malaria and travelers: protection and information].

With the increasing drug resistance of Plasmodium falciparum especially to agents used for chemoprophylaxis, every precaution must be taken to protect travelers from contracting malaria. Prevention of mosquito bites is a fundamental goal that can be achieved by a variety of means including pyrethrinoid-impregnated bed nets, insecticide strips, liquid vaporizers, repellents, insecticide-impregnated garments, and air-conditioning. There are no contraindications for vector control. Chemoprophylaxis depends of individual criteria as determined by clinical and laboratory examinations and on travel conditions (destination, season, duration of stay, and local living conditions). Stand-by medication should be prescribed for self-treatment of fever in areas where medical care is not readily available. Chemoprophylaxis must be continued after the traveler returns and medical attention should be sought if symptoms occur. To ensure proper compliance with preventive measures, pre-travel counseling is a mandatory and integral part of prevention. Information provided to travelers must be clear, reliable, and up-to-date.

Antimalarials↗
PubMed2003

Effects and costs of requiring child-restraint systems for young children traveling on commercial airplanes.

CONTEXT: The US Federal Aviation Administration is planning a new regulation requiring children younger than 2 years to ride in approved child-restraint seats on airplanes. OBJECTIVES: To estimate the annual number of child air crash deaths that might be prevented by the proposed regulation, the threshold proportion of families switching from air to car travel above which the risks of the policy would exceed its benefits, and the cost per death prevented. DESIGN: Risk and economic analyses. RESULTS: Child-restraint seat use could prevent about 0.4 child air crash deaths per year in the United States. Increased deaths as a result of car travel could exceed deaths prevented by restraint seat use if the proportion of families switching from air to car travel exceeded about 5% to 10%. The estimate for this proportion varied with assumptions about trip distance, driver characteristics, and the effectiveness of child-restraint seats but is unlikely to exceed 15%. Assuming no increase in car travel, for each dollar increase in the cost of implementing the regulation per round trip per family, the cost per death prevented would increase by about $6.4 million. CONCLUSIONS: Unless space for young children in restraint seats can be provided at low cost to families, with little or no diversion to automobile travel, a policy requiring restraint seat use could cause a net increase in deaths. Even excluding this possibility, the cost of the proposed policy per death prevented is high.

Accident Prevention↗
PubMed1992

Discrete-time travelling waves: ecological examples.

Integrodifference equations are discrete-time models that possess many of the attributes of continuous-time reaction-diffusion equations. They arise naturally in population biology as models for organisms with discrete nonoverlapping generations and well-defined growth and dispersal stages. I examined the varied travelling waves that arise in some simple ecologically-interesting integro-difference equations. For a scalar equation with compensatory growth, I observed only simple travelling waves. For carefully chosen redistribution kernels, one may derive the speed and approximate the shape of the observed waveforms. A model with overcompensation exhibited flip bifurcations and travelling cycles in addition to simple travelling waves. Finally, a simple predator-prey system possessed periodic wave trains and a variety of travelling waves.

Ecology↗
PubMed2003

Locomotor adjustments for circumvention of an obstacle in the travel path.

Independent living requires the navigation of a surrounding environment which is often cluttered with obstacles. When walking around an obstacle in the travel path, safe clearance requires some degree of body-segment reorientation. While body-segmental coordination strategies have been well studied for steering tasks that require moving the body in a new walking direction, it has never been established just what coordination strategies are used in different walking tasks. To address this issue, the current study was designed to investigate the timing of body segment coordination strategies and whole-body anticipatory locomotor adjustments employed when circumventing an obstacle placed in the travel path. Six healthy adults were asked to walk at their natural pace during unobstructed walking, as well as during avoidance to the right or left of a cylindrical obstacle (OBS) located in the travel path. Data analyzed were center of mass (COM) clearance from the OBS, forward velocity, step length and width, yaw angles of the head and trunk, roll angle of the trunk, and medial-lateral COM displacement. Onset of change in these variables from unobstructed walking was calculated as the time from OBS crossing. Avoidance involved two equally used strategies: lead limb close to or away from the OBS during the crossing step. Medial-lateral COM deviations were controlled by changes in step width without changes in trunk roll. There were no differences in the onset times of body segment reorientation for path deviation. These results are in contrast to previous studies on change in travel direction where the head segment initiates the body reorientation. Contrary to a steering task, circumventing an obstacle requires a different coordination for a transient change in COM trajectory with the underlying travel-direction maintained.

Adult↗
PubMed2005

Children use different anticipatory control strategies than adults to circumvent an obstacle in the travel path.

Carrying out the daily activities of work and play requires the ability to integrate available sensory information in order to navigate complex, potentially cluttered, environments. The expression of locomotor adjustment behaviour is still maturing during mid- to late-childhood (Grasso et al. in Neurosci Biobehav Rev 22(4): 533-539, 1998a; McFadyen et al. in Gait Posture 13:7-16, 2001), which raises the question, do children coordinate their body segments differently than adults when circumventing an obstacle in their travel path? Healthy young children (n=5; age 10.3+/-1.5 years) and adults (n=6; age 26.3+/-2.9 years) were asked to walk at their natural pace during unobstructed walking, as well as during the avoidance to the right or left of a cylindrical obstacle located in the travel path 3 m from the initial starting position. Fourteen infrared markers were fixed to participants and tracked using the Optotrak motion analysis system (60 Hz; Northern Digital Inc, Canada). Data analyses included center of mass (COM) clearance from the obstacle, gait speed, angular movement of the head and trunk (yaw, pitch and roll) and medial-lateral (M-L) COM displacement. Onset of change in these variables from unobstructed walking was also calculated as the time from OBS crossing. Although there were no differences in when adults or children altered their M-L COM trajectory, adults reoriented their head and trunk segments at the same time as their COM while children reoriented their head and trunk prior to changing COM direction. A comparison of foot placement data for this task indicated that while adults changed their gait patterns well in advance of obstacle crossing, children initiated M-L adjustments to gait patterns just prior to OBS crossing. Vallis and McFadyen (Exp Brain Res 152 (3):409-414, 2003) indicated that during circumvention of an obstacle, adults coordinate body segments for a single transient change in COM trajectory while maintaining the underlying travel direction. The present data suggest, however, that children partition obstacle avoidance into two tasks, initially steering with proactive movement of the head and trunk segments and finally making adjustments to their gait trajectory, via stride and step width changes, to ensure adequate obstacle clearance just prior to obstacle crossing. This study demonstrates different anticipatory control strategies used by children as compared to adults to circumvent obstacles in the travel path. The different head and trunk anticipatory segmental coordination suggests that children gather visual information differently when circumventing an obstacle in their travel path and are more dependent on visual input to guide their circumvention strategy.

Adult↗
PubMed2004

Do forward- and backward-traveling waves occur within the cochlea? Countering the critique of Nobili et al.

The question of whether or not forward- and backward-traveling waves occur within the cochlea constitutes a long-standing controversy in cochlear mechanics recently brought to the fore by the problem of understanding otoacoustic emissions. Nobili and colleagues articulate the opposition to the traveling-wave viewpoint by arguing that wave-equation formulations of cochlear mechanics fundamentally misrepresent the hydrodynamics of the cochlea [e.g., Nobili et al. (2003) J. Assoc. Res. Otolaryngol. 4:478-494]. To correct the perceived deficiencies of the wave-equation formulation, Nobili et al. advocate an apparently altogether different approach to cochlear modeling--the so-called "hydrodynamic" or "Green's function" approach--in which cochlear responses are represented not as forward- and backward-traveling waves but as weighted sums of the motions of individual basilar membrane oscillators, each interacting with the others via forces communicated instantaneously through the cochlear fluids. In this article, we examine Nobili and colleagues' arguments and conclusions while attempting to clarify the broader issues at stake. We demonstrate that the one-dimensional wave-equation formulation of cochlear hydrodynamics does not misrepresent long-range fluid coupling in the cochlea, as claimed. Indeed, we show that the long-range component of Nobili et al.'s three-dimensional force propagator is identical to the hydrodynamic Green's function representing a one-dimensional tapered transmission line. Furthermore, simulations that Nobili et al. use to discredit wave-equation formulations of cochlear mechanics (i.e., cochlear responses to excitation at a point along the basilar membrane) are readily reproduced and interpreted using a simple superposition of forward- and backward-traveling waves. Nobili and coworkers' critique of wave-equation formulations of cochlear mechanics thus appears to be without compelling foundation. Although the traveling-wave and hydrodynamic formulations impose strikingly disparate conceptual and computational frameworks, the two approaches ultimately describe the same underlying physics.

Animals↗
PubMed2003

Emerging Causes of Traveler's Diarrhea: Cryptosporidium, Cyclospora, Isospora, and Microsporidia.

Travel is a risk factor for acquiring infection with a spore-forming protozoa: Cryptosopridium, Cyclospora, Microsporidia, and Isospora. Certain travel destinations have a high disease burden and intense exposure. Patients present with persistent diarrhea and a history of recent travel to a developing country in the tropics. Very mild infections may be underdiagnosed and may cause typical traveler's diarrhea. In a patient with a history of travel and persistent diarrhea unresponsive to the usual antibiotic and antidiarrhea treatment, stool studies for all four of these protozoa infections should be performed. If immune status is normal and the disease is mild, symptomatic therapy may suffice. Effective treatment is available for Cyclospora, Microsporidia, and Isospora.

Journal Article↗
PubMed2004

International Travel: Recommendations for the HIV-infected Patient.

In order to prevent travel-related diseases in patients infected with HIV, pretravel planning that includes vaccination, chemoprophylaxis, and behavioral modification is recommended. Many HIV-infected individuals successfully treated with highly active antiretroviral therapy may travel safely. However, patients with reduced CD4 lymphocyte counts are at increased risk for bacterial, mycobacterial, viral, fungal, and parasitic infections. Recommendations for vaccination and chemoprophylaxis are based on immune status and risk of infection. The efficacy of vaccination is dependant on CD4 lymphocyte count; inactivated and polysaccharide vaccines are considered safe in this population. Behavioral modifications to prevent food- and waterborne disease are an important component of disease prevention. A travel-health practitioner should review travel duration, destination, and activities, and assess the risk-benefit ratio of vaccination and chemoprophylaxis, in order to reduce the likelihood of travel-associated illness.

Journal Article↗
PubMed2007

Strategies used by older adults to change travel direction.

INTRODUCTION: A distinct body reorientation strategy during steering tasks has been reported in young adults. As challenges to whole-body stability in older adults occur when navigating complex environments, this study was designed to examine control strategies used by older adults to initiate a voluntary change in travel direction. METHODS: Thirteen older adults, recruited from an independent living division of a local retirement residence, were instrumented with reflective markers and whole-body kinematic data were monitored using a video camera (30 Hz). Participants executed self-paced walking trials 3-m along a straight path and were instructed prior to the trial to continue either straight ahead or randomly turn 40 degrees left or right and continue walking for an additional 2-m. Timing of changes with respect to when the trunk crossed the turning point were calculated for deviations in head and trunk position and foot rotation in the medial-lateral plane. RESULTS: Older adults reoriented themselves into the new travel direction in a top-down, segmental sequence, beginning with head reorientation followed by trunk reorientation, foot rotation and foot displacement into the new travel direction. These changes were initiated over two or more steps 69% of the time and over one step 31% of the time. A significant relationship between turning strategy used and balance confidence was observed; the frequency of using a turning strategy involving two or more steps to initiate a change in travel direction increased as balance confidence decreased. DISCUSSION AND CONCLUSION: Older adults made segmental changes to voluntarily reorient themselves in a new travel direction in a similar sequence to that observed in young adults. Older adults chose primarily to initiate these changes two or more steps prior to the turn; the selection of this strategy was related to balance confidence.

Adaptation, Physiological↗
PubMed2005

Travel time and trajectory moments of conservative solutes in two-dimensional convergent flows.

We address advective transport of a solute traveling toward a single pumping well in a two-dimensional randomly heterogeneous aquifer. The two random variables of interest are the trajectory followed by an individual particle from the injection point to the well location and the particle travel time under steady-state conditions. Our main objective is to derive the predictors of trajectory and travel time and the associated uncertainty, in terms of their first two statistical moments (mean and variance). We consider a solute that undergoes mass transfer between a mobile and an immobile zone. Based on Lawrence et al. [Lawrence, A.E., Sánchez-Vila, X., Rubin, Y., 2002. Conditional moments of the breakthrough curves of kinetically sorbing solute in heterogeneous porous media using multirate mass transfer models for sorption and desorption. Water Resour. Res. 38 (11), 1248, doi:10.1029/2001WR001006.], travel time moments can be written in terms of those of a conservative solute times a deterministic quantity. Moreover, the moments of solute particles trajectory do not depend on mass transfer processes. The resulting mean and variance of travel time and trajectory for a conservative species can be written as functions of the first, second moments and cross-moments of trajectory and velocity components. The equations are developed from a consistent second order expansion in sigmaY (standard deviation of the natural logarithm of hydraulic conductivity). Our solution can be completely integrated with the moment equations of groundwater flow of Guadagnini and Neuman [Guadagnini, A., Neuman, S.P., 1999a. Nonlocal and localized analyses of conditional mean steady state flow in bounded, randomly non uniform domains 1. Theory and computational approach. Water Resour. Res. 35(10), 2999-3018.,Guadagnini, A., Neuman, S.P., 1999b. Nonlocal and localized analyses of conditional mean steady state flow in bounded, randomly non uniform domains 2. Computational examples. Water Resour. Res. 35(10), 3019-3039.], it is free of distributional assumptions regarding the log conductivity field, and formally includes conditioning. We present analytical expressions for the unconditional case by making use of the results of Riva et al. [Riva, M., Guadagnini, A., Neuman, S.P., Franzetti, S., 2001. Radial flow in a bounded randomly heterogeneous aquifer. Transport in Porous Media 45, 139-193.]. The quality of the solution is supported by numerical Monte Carlo simulations. Potential uses of this work include the determination of aquifer reclamation time by means of a single pumping well, and the demarcation of the region potentially affected by the presence of a contaminant in the proximity of a well, whenever the aquifer is very thin and Dupuit-Forchheimer assumption holds.

Kinetics↗
PubMed2003

Discrimination of travel distances from 'situated' optic flow.

Effective navigation requires knowledge of the direction of motion and of the distance traveled. Humans can use visual motion cues from optic flow to estimate direction of self-motion. Can they also estimate travel distance from visual motion?Optic flow is ambiguous with regard to travel distance. But when the depth structure of the environment is known or can be inferred, i.e., when the flow can be calibrated to the environmental situation, distance estimation may become possible. Previous work had shown that humans can discriminate and reproduce travel distances of two visually simulated self-motions under the assumption that the environmental situation and the depth structure of the scene is the same in both motions. Here we ask which visual cues are used for distance estimation when this assumption is fulfilled. Observers discriminated distances of visually simulated self-motions in four different environments with various depth cues. Discrimination was possible in all cases, even when motion parallax was the only depth cue available. In further experiments we ask whether distance estimation is based directly on image velocity or on an estimate of observer velocity derived from image velocity and the structure of the environment. By varying the simulated height above ground, the visibility range, or the simulated gaze angle we modify visual information about the structure of the environment and alter the image velocity distribution in the optic flow. Discrimination ability remained good. We conclude that the judgment of travel distance is based on an estimate of observer speed within the simulated environment.

Adult↗
PubMed2002

In vitro thrombolysis enhanced by standing and travelling ultrasound wave fields.

Success of thrombolytic therapy depends on penetration of recombinant tissue plasminogen activator (rt-PA) into clots. Ultrasound (US) of therapeutic quality accelerates thrombolysis in vitro. As yet, only the effects of travelling acoustic waves on thrombolysis have been investigated, and the impact of standing acoustic waves has been neglected. In the present study, we examined the effects of standing and travelling US wave fields applied continuously for 1 h (frequency 2 MHz, acoustic intensity 1.2 W/cm(2)) on thrombolysis enhancement by measuring clot weight reduction and concentration of fibrin degradation product D-dimer (FDP-DD) produced from clots subjected to rt-PA. The level of FDP-DD was 1.8 times greater in travelling than in standing acoustic waves. Thrombolysis enhancement was 46.0 +/- 20.8% in standing and 116.8 +/- 23.1% in travelling acoustic waves. Travelling waves enhanced thrombolysis significantly more (p < 0.0001) than did standing waves.

Culture Techniques↗
PubMed2002

An analysis of travel costs on transport of load and nest building in golden hamster.

We investigated the effects of travel costs on transporting nest material and nest-building activity in golden hamsters. Nest-deprived animals were submitted to run alleys 30, 90 and 180 cm long to access a source containing paper strips as nest material (Experiment 1) or were submitted to the same travel costs in 24-h experimental sessions (Experiment 2). We noted that increased travel costs were related to a decreased number of trips to the source, larger amounts (cm(2)) of nest material transported per trip (although total loads also decreased in longer alleys), longer intervals between trips, and increased time spent at the source and in nest building activity. Foraging efficiency (i.e. size of load divided by the time spent at the source) decreased as a function of travel costs, and animals transported their loads in two fundamental ways: in 30-cm alleys, they simply used their mouth to pull the paper strips, but in 90- or 180-cm alleys they transported the loads in their cheek pouches. The animals were faster when returning to the home-cage and their running speed (cm/s) increased as a function of the length of the alley, showing that animals are under different environmental pressures when searching for resources and subsequently running back with the load to the nest. Both male and female subjects were sensitive to travel costs, but males engaged in nest building activity more promptly and exhibited higher mean performances in most measures. We conclude that nest material is a good reinforcer, and our major results are in accordance with the predictions of microeconomic and optimal foraging theories.

Journal Article↗
PubMed1992

An audit of travel and waiting times for outpatient radiotherapy.

The object of this study was to assess the non-medical factors which detract from the quality of outpatient receiving service to a population of 2.7 million in a wide geographical area. We conducted a survey by patient questionnaire of all outpatients receiving radiotherapy in the West of Scotland on a single day in 1990. A total of 216 outpatients attended for radiotherapy with a 92% response rate to the questionnaire being achieved. Median values (and ranges) were: age 58 (4-85) years, number of daily treatments 20 (4-33), distance travelled in one direction 10 (1-60) miles, travelling time 45 (5-130) minutes, waiting time in the unit for treatment 60 (0-200) minutes, and a time away from home of 2 hours 50 minutes (35 minutes-7 hours). Sixteen per cent of patients had a relative who lost time from work by transporting the patient and only 12 of 60 patients who were away from home over a meal time were offered a hospital meal. Sixteen per cent of patients came by ambulance and 73% by motor car. Of 146 travelling by car 27% used a charity service and 20% a volunteer driver ambulance service car. It is concluded that long travelling distances, travelling times and treatment waiting times for many patients require revision of transport provision, a strict appointment system, more treatment machines and hostel accommodation.

Adolescent↗