Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TRAVEL”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMed2000

An assessment of alternate keyboards using finger motion, wrist motion and tendon travel.

OBJECTIVE: To assess the biomechanical impact of commercially available alternate keyboard designs.DESIGN. A repeated measures study was conducted in a laboratory setting, with planned comparisons of Pitch, Roll and Yaw angles of the keyboards. Ten keyboard conditions were tested. Dependent measures included tendon travel, wrist deviations, and wrist and finger kinematics.BACKGROUND. Various alternate keyboard designs have recently been introduced, which vary Pitch, Roll and Yaw angles, separation distance between keyboard halves, and include other novel features such as cup-shaped depressions for the keys. Yet little objective research has been conducted regarding the biomechanical implications of these various design features. This study attempts to quantify the keyboard designs in terms of several recognized risk factors associated with cumulative trauma disorders that arise with repetitive typing. METHODS: Wrist and finger goniometers were used to measure joint motions during a standardized typing task. 15 experienced typists (8 women, 7 men) served as subjects. Regression equations were used to generate estimates of tendon travel.RESULTS. Tendon travel was affected primarily by Pitch but not Roll or Yaw angles while wrist deviations responded to changes in all three angles. Males had significantly greater amount of tendon travel than female subjects; this difference was only partially accounted for by anthropometry. Differences in joint motion may have a greater impact on the amount of tendon travel.CONCLUSIONS. Alternate keyboard designs can affect tendon travel by as much as 11%. RelevanceAs various alternate keyboard designs are marketed, quantifiable biomechanical data such as that provided by this study, will help to assess their impact on the risk factors for cumulative trauma disorders.

Adult↗
PubMed2006

On the variety of traveling fronts in one-variable multistable reaction-diffusion systems.

The still-open problem of the variety of asymptotic solutions to one-variable, one-dimensional infinite multistable reaction-diffusion systems is solved. We show that in such systems, besides monotonic traveling fronts, nonmonotonic traveling fronts can exist for appropriate initial conditions. The dependence of numbers of various types of traveling fronts on the number of stable stationary states also is given. Examples of traveling fronts for the chemical model describing two enzymatic (catalytic) reactions inhibited by an excess of their reactant is presented.

Journal Article↗
PubMed1999

Measures of cochlear travelling wave delay in humans: I. Comparison of three techniques in subjects with normal hearing.

This study was designed to estimate and compare measures of cochlear travelling wave delay and travelling wave velocity in normally-hearing adults. Travelling wave delay and velocity measures were estimated in 23 normally-hearing adults using three different test techniques: i) derived auditory brainstem responses (ABR); ii) derived frequency-following responses (FFR); and iii) tone-burst-evoked otoacoustic emissions (TBEOAE). Estimates from ABR and TBEOAE were comparable to each other in terms of both averaged group values and associated standard deviations. Furthermore, mean cochlear travelling wave velocity estimated from ABR and TBEOAE were comparable to published estimates. Average cochlear delays obtained using the derived FFR were significantly shorter than those obtained from the other two techniques, possibly due to the effect of cochlear microphonic contamination. Among the dependent variables investigated, measures of delay are to be preferred over velocity since the latter are based on uncertain values of cochlear distance.

Acoustic Stimulation↗
PubMed2000

Dynein-mediated cargo transport in vivo. A switch controls travel distance.

Cytoplasmic dynein is a microtubule-based motor with diverse cellular roles. Here, we use mutations in the dynein heavy chain gene to impair the motor's function, and employ biophysical measurements to demonstrate that cytoplasmic dynein is responsible for the minus end motion of bidirectionally moving lipid droplets in early Drosophila embryos. This analysis yields an estimate for the force that a single cytoplasmic dynein exerts in vivo (1.1 pN). It also allows us to quantitate dynein-mediated cargo motion in vivo, providing a framework for investigating how dynein's activity is controlled. We identify three distinct travel states whose general features also characterize plus end motion. These states are preserved in different developmental stages. We had previously provided evidence that for each travel direction, single droplets are moved by multiple motors of the same type (Welte et al. 1998). Droplet travel distances (runs) are much shorter than expected for multiple motors based on in vitro estimates of cytoplasmic dynein processivity. Therefore, we propose the existence of a process that ends runs before the motors fall off the microtubules. We find that this process acts with a constant probability per unit distance, and is typically coupled to a switch in travel direction. A process with similar properties governs plus end motion, and its regulation controls the net direction of transport.

Animals↗
PubMed1998

Effects of lavender straw on stress and travel sickness in pigs.

OBJECTIVE: To observe pigs during road journeys in order to establish whether lavender straw was likely to decrease stress and incidence of travel sickness. SUBJECTS: Forty 70-kg Large White pigs were transported by road for 2 hours, 20 animals each day, over a 2-day period. DESIGN: On day 1, ample wheat straw was provided as bedding such that the floor of the vehicle was entirely covered (straw condition). On day 2, lavender straw was provided as bedding (lavender condition). During the journey, direct behavioral observations of the individually marked pigs were made by scanning every 10 minutes for incidence of standing and lying along with the less severe symptoms of travel sickness (foaming at the mouth and repetitive chomping). Incidences of retching and vomiting were noted as they occurred. A general activity index was also scored every 10 minutes (5 = high activity, 1 = low activity). Saliva samples were taken from each animal at different stages of the journey for analysis of cortisol. RESULTS: Pigs stood more when in the straw condition, but were more active when standing in the lavender condition. Symptoms of travel sickness appeared to be less acute in the lavender condition, with more animals exhibiting the less severe symptom, foaming and chomping (a total of 3 in straw compared with 6 in lavender), but fewer animals showing the more severe symptoms of retching and vomiting (in straw, 3 retched, 6 vomited; in lavender 0 retched, 3 vomited). A total of 6 animals retched or vomited in the straw condition but only 3 in the lavender. There was a significant difference in mean concentrations of cortisol between conditions but this was due to a difference in mean baseline concentrations between groups. CONCLUSION: Addition of lavender straw appeared to decrease incidence and severity of travel sickness but not overall levels of stress (as measured by concentrations of salivary cortisol).

Animals↗
PubMed1985

Travel sickness in patients attending a geriatric day hospital.

A survey of 172 patients attending a geriatric day hospital revealed that 33 patients (19%) suffered travel sickness at some time. Sixteen (49%) of these patients also had a past history of travel sickness, while only 10 (7%) of those who were not sick gave a positive past history. The use of emergency vehicles for transporting patients may have increased the level of travel sickness. Seven (4%) of the patients had defaulted or considered defaulting on attendance because of the fear of travel sickness. Patients commenced on drug therapy for sickness responded well and experienced few side-effects and no interference with rehabilitation.

Aged↗
PubMed1999

Space travel directly induces skeletal muscle atrophy.

Space travel causes rapid and pronounced skeletal muscle wasting in humans that reduces their long-term flight capabilities. To develop effective countermeasures, the basis of this atrophy needs to be better understood. Space travel may cause muscle atrophy indirectly by altering circulating levels of factors such as growth hormone, glucocorticoids, and anabolic steroids and/or by a direct effect on the muscle fibers themselves. To determine whether skeletal muscle cells are directly affected by space travel, tissue-cultured avian skeletal muscle cells were tissue engineered into bioartificial muscles and flown in perfusion bioreactors for 9 to 10 days aboard the Space Transportation System (STS, i.e., Space Shuttle). Significant muscle fiber atrophy occurred due to a decrease in protein synthesis rates without alterations in protein degradation. Return of the muscle cells to Earth stimulated protein synthesis rates of both muscle-specific and extracellular matrix proteins relative to ground controls. These results show for the first time that skeletal muscle fibers are directly responsive to space travel and should be a target for countermeasure development.

Animals↗
PubMed1976

Geographic access to hospital care: a 30-minute travel time standard.

A review of literature focusing upon geographic accessibility to health facilities indicates that while distance has been the traditional measure, travel time may now be a more meaningful indicator. Applying a 30-minute travel time standard to general hospitals, as advocated by various health plans, this paper illustrates an approach to the determination of geographic accessibility through a combination of a travel time file and sociodemographic profiles. Focusing upon all residents of West Virginia, the study identifies the number and characteristics of persons who reside within and beyond the 30-minute standard. More than 10 per cent of the entire population and nearly 20 per cent of the rural residents live in areas which are, by this standard, inaccessible to general hospitals. The "inaccessible" populations are characterized as having sociodemographic attributes associated with high medical needs. Other applications of travel time data are discussed.

Adolescent↗
PubMed2003

Traveling waves in phase-separating reactive mixtures.

A model of phase separation of chemically reactive ternary mixtures is constructed. In this model, spatially periodic structures that coherently propagate at a constant speed emerge through a Hopf bifurcation at a finite wave number. It is shown by computer simulations that both lamellar and hexagonal structures undergo a coherent propagating motion in two dimensions, and there are two types of traveling hexagons depending on the relative direction between the traveling velocity and the lattice vectors of the hexagonal structure. Amplitude equations for the traveling waves are derived, and the stability of the traveling and standing waves is discussed.

Journal Article↗
PubMed2004

Electro-osmotic streaming on application of traveling-wave electric fields.

We describe ac electro-osmotic flow of an aqueous electrolyte on application of a traveling-wave electric field. Depending on the frequency of the applied traveling wave, the interaction of the electric double layer charge and the tangential electric field leads to fluid flow in the direction of the traveling wave. We have derived two theoretical models that describe this flow as a function of the amplitude of the applied electric potential, the signal frequency, and the material properties of the system. The first is based on a capacitative model and is limited to frequencies much lower than the double layer relaxation frequency. The second is an analytical solution of the electrokinetic equations and is also valid at higher frequencies. We provide experimental evidence that streaming takes place on application of a traveling wave of potential by tracing the movements of fluorescent latex beads over a spiral electrode structure. Streaming takes place at applied potentials low enough for the method to be easily integrated into lab-on-a-chip devices.

Journal Article↗
PubMed2006

Robust hierarchical state-space models reveal diel variation in travel rates of migrating leatherback turtles.

1. Biological and statistical complexity are features common to most ecological data that hinder our ability to extract meaningful patterns using conventional tools. Recent work on implementing modern statistical methods for analysis of such ecological data has focused primarily on population dynamics but other types of data, such as animal movement pathways obtained from satellite telemetry, can also benefit from the application of modern statistical tools. 2. We develop a robust hierarchical state-space approach for analysis of multiple satellite telemetry pathways obtained via the Argos system. State-space models are time-series methods that allow unobserved states and biological parameters to be estimated from data observed with error. We show that the approach can reveal important patterns in complex, noisy data where conventional methods cannot. 3. Using the largest Atlantic satellite telemetry data set for critically endangered leatherback turtles, we show that the diel pattern in travel rates of these turtles changes over different phases of their migratory cycle. While foraging in northern waters the turtles show similar travel rates during day and night, but on their southward migration to tropical waters travel rates are markedly faster during the day. These patterns are generally consistent with diving data, and may be related to changes in foraging behaviour. Interestingly, individuals that migrate southward to breed generally show higher daytime travel rates than individuals that migrate southward in a non-breeding year. 4. Our approach is extremely flexible and can be applied to many ecological analyses that use complex, sequential data.

Animal Migration↗
PubMed1998

Prevalence of diarrheagenic Escherichia coli strains detected by PCR in patients with travelers' diarrhea.

OBJECTIVE: To determine the prevalence of the different categories of diarrheagenic Escherichia coli, enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), verotoxin-producing E. coli (VTEC), enteroaggregative E. coli (EAggEC), diffusely adherent E. coli (DAEC), and enteropathogenic E. coli (EPEC), associated with travelers' diarrhea. METHODS: Stool specimens from 350 patients with travelers' diarrhea were collected between 1994 and 1996. The virulence factors of the diarrheagenic E. coli isolated were detected by PCR technique, in subcultures of single colonies of all morphotypes of E. coli observed in culture on MacConkey agar. RESULTS: ETEC (15.7%), EAggEC (13.4%) and DAEC (9.14%) are significantly more prevalent than EIEC (3.4%), EPEC (2.86%) and VTEC (0.86%) (p<0.05; z-test). The prevalence of ETEC and EAggEC was similar in all geographic areas visited. CONCLUSIONS: PCR is a rapid and specific technique to use in the identification of the different categories of diarrheagenic E. coli and greatly increases the yield of potential enteropathogens from cases of travelers' diarrhea. Not only ETEC but also EAggEC and DAEC strains play a major role in the etiology of travelers' diarrhea, whereas EIEC, EPEC, and VTEC strains play a minor role, leading to the question of whether it is necessary to search routinely for these three types of E. coli in diagnostic laboratories.

Journal Article↗
PubMed1994

Meningococcal Disease in Travelers: Vaccination Recommendations.

The object of the study was to determine the incidence rate of meningococcal disease in travelers originating in industrialized countries and visiting developing countries. Subjects were intercontinental travelers with meningococcal diseases acquired from 1986 to 1989. Health authorities in 108 countries were contacted; data obtained by postal survey were analyzed. The 56 replying health authorities reported 13 cases of meningococcal disease in tourist or business persons as well as 40 primary and 26 secondary cases in pilgrims in Mecca. The majority of cases were due to serogroup A. The case fatality rate in both groups of patients slightly exceeded 20%. Among the tourists and business persons, several patients had stayed in hotels; in several the onset of symptoms occurred during the flight home. The incidence rate per month of stay was estimated to be 0.4 per million travelers in this group, but 2000 per million in pilgrims to Mecca. Vaccination of pilgrims to Mecca is highly recommended, presently even compulsory. For the usual traveler to endemic countries, the risk of infection abroad seems not to exceed the one at home, thus vaccination may be limited to high-risk groups, such as trekkers.

Journal Article↗
PubMed1994

Prevention of Travelers' Diarrhea: Ciprofloxacin versus Trimethoprim/Sulfamethoxazole in Adult Volunteers Working in Latin America and the Caribbean.

The objective of the study was to compare the safety and efficacy of three treatment protocols for the prevention of travelers' diarrhea: once-daily ciprofloxacin versus trimethoprim/sulfamethoxazole (TMP/SMZ) once daily versus placebo for the prevention of travelers' diarrhea. The study population was comprised of participants in 2-week medical-missions projects based in Latin America and the Caribbean. The diverse age group and varied study sites closely resembles the population of travelers who seek pretravel advice from physicians. A prospective, randomized, double-blind, placebo-controlled comparison was designed. Subjects who developed diarrhea, defined as three stools in 8 hours plus one or more signs of an enteric infection, were considered prophylaxis failures. Stool specimens were collected and examined for the presence of enteric pathogens. DNA probes were used to determine the presence of diarrheagenic E. coli. Bacterial colony blots were used. Adverse events were recorded by participants in a diary. Three hundred and forty-four subjects were entered in the study, of which two hundred and seventy-eight subjects met the criteria for the efficacy and safety review. Subjects were randomly assigned to receive ciprofloxacin (500 mg), TMP/SMZ (160/800 mg), or placebo. Five of the 99 (5%) subjects taking ciprofloxacin, 14 of the 87 (16%) taking TMP/SMZ, and 30 of the 92 (33%) taking placebo experienced diarrhea. Bacterial pathogens were identified more commonly in the TMP/SMZ and placebo groups than in the ciprofloxacin-treated group. The incidence of adverse reactions was 9.0%, 14.8%, and 7.5% for ciprofloxacin, TMP/SMZ, and placebo subjects, respectively (p =.287). Ciprofloxacin 500 mg once daily provides safe and effective prophylaxis for travelers' diarrhea and is superior to TMP/SMZ (160/800 mg).

Journal Article↗
PubMed1997

Mediterranean Spotted Fever in Travelers from the United States.

Background: We wish to increase awareness by U.S. physicians of the clinical manifestations and diagnosis of Mediterranean spotted fever (MSF), and to determine the incidence of MSF among travelers returning to the United States from endemic areas. Methods: We report a case of a 56-year-old female physician from New Orleans who returned from a 3-week safari trip to Zimbabwe and Zambia with clinical findings of MSF. The diagnosis was confirmed with a greater than fourfold rise in titer of IgM and IgG antibody to Rickettsia conorii on acute and convalescent sera (16 days apart) using indirect immunofluorescence technique. In addition, we conducted a MEDLINE computer search of published MSF cases in U.S. travelers returning to the United States and obtained the United States data over the past 20 years from the Centers for Disease Control and Prevention (CDC). Results: Less than 50 imported cases of MSF have been reported and confirmed by the CDC. Only seven cases have been published in the literature and none in the last 7 years. Conclusions: Despite the increasing incidence of MSF in Europe, Asia and Africa, and the high number of U.S. citizens traveling to these endemic areas, only a few imported cases of MSF in travelers have been reported in the United States. Physicians in the United States are not familiar with the clinical findings and diagnosis of MSF; therefore this disease is underrecognized in the majority of cases.

Journal Article↗
PubMedDate not supplied

Fractal travel time estimates for dispersive contaminants.

Alternative fractional models of contaminant transport lead to a new travel time formula for arbitrary concentration levels. For an evolving contaminant plume in a highly heterogeneous aquifer, the new formula predicts much earlier arrival at low concentrations. Travel times of contaminant fronts and plumes are often obtained from Darcy's law calculations using estimates of average pore velocities. These estimates only provide information about the travel time of the average concentration (or peak, for contaminant pulses). Recently, it has been shown that finding the travel times of arbitrary concentration levels is a straightforward process, and equations were developed for other portions of the breakthrough curve for a nonreactive contaminant. In this paper, we generalize those equations to include alternative fractional models of contaminant transport.

Models, Theoretical↗
PubMedDate not supplied

On using simple time-of-travel capture zone delineation methods.

As part of its Wellhead Protection Program, the U.S. EPA mandates the delineation of "time-of-travel capture zones" as the basis for the definition of wellhead protection zones surrounding drinking water production wells. Depending on circumstances the capture zones may be determined using methods that range from simply drawing a circle around the well to sophisticated ground water flow and transport modeling. The simpler methods are attractive when faced with the delineation of hundreds or thousands of capture zones for small public drinking water supply wells. On the other hand, a circular capture zone may not be adequate in the presence of an ambient ground water flow regime. A dimensionless time-of-travel parameter T is used to determine when calculated fixed-radius capture zones can be used for drinking water production wells. The parameter incorporates aquifer properties, the magnitude of the ambient ground water flow field, and the travel time criterion for the time-of-travel capture zone. In the absence of interfering flow features, three different simple capture zones can be used depending on the value of T . A modified calculated fixed-radius capture zone proves protective when T < 0.1, while a more elongated capture zone must be used when T > 1. For values of T between 0.1 and 1, a circular capture zone can be used that is eccentric with respect to the well. Finally, calculating T allows for a quick assessment of the validity of circular capture zones without redoing the delineation with a computer model.

Environmental Monitoring↗
PubMed1980

Systematic errors in indirect estimates of basilar membrane travel times.

There exist in the literature three attempts to derive basilar membrane travel times from the phase versus frequency characteristics of responses to tones in the auditory nerve [Anderson et al., J. Acoust. Soc. Am. 4., 1131-1139 (1971)], cochlear nucleus [Gibson et al., in Psychophysics and Physiology of Hearing, edited by Evans and Wilson (Academic, New York, 1977), pp. 57-68], and basilar membrane [Robles et al., J. Acoust. Soc. Am. 59, 926-939 (1976)]. It is argued in this paper that these derivations probably have overestimated the actual mechanical travel times. Travel time was originally defined by von Békésy as the latency between the onset of a click stimulus and the onset of basilar membrane vibration. For a linear bandpass system, the frequency-domain equivalent of this latency is the high-frequency asymptotoic slope of the phase lag versus frequency characteristic, which is not generally a linear function. In the neural studies (auditory nerve and cochlear nucleus) it was assumed that the phase versus frequency characteristic was a straight line. Slopes derived under a linear assumption are probably closer to the weighted average group delay (i.e., the center of gravity of the click response) than they are to travel time. In the Mössbauer study of basilar membrane mechanics the latency of the response to clicks was compared with the low-frequency slope of the phase characteristic. The comparison should have been made with the high-frequency slope.

Basilar Membrane↗