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At least 127 records · Page 7Linked to original sources
PubMed1992

Intensity artifacts in MRI caused by gradient switching in an animal-size NMR magnet.

The switching of magnetic field gradients in MRI gives rise to eddy currents in the structural components of superconducting magnet systems. The associated magnetic fields cause intensity artifacts which are particularly severe in some animal-size systems. We treat theoretically three mechanisms which cause intensity artifacts in one-dimensional projection images obtained by a spin-echo technique. The first is an off-resonance effect, caused by applying the refocusing pulse before the read compensation gradient pulse has decayed sufficiently. The other two mechanisms are caused by a spatial dependence of the phase accumulated by the spins at the time of formation of the echo, as a result of the eddy current fields. First, interference causes a loss of transverse magnetization because of a variation in the phase of spins which lie on the same isochromat during the read gradient pulse. Second, a variation of the phase of the spins in a direction orthogonal to the isochromats causes spins throughout the sample to refocus at different times. These two mechanisms are fundamentally different, since interference can occur even if the main magnetic field is homogeneous, whereas improper refocusing does not. It is shown that there is no loss of intensity by the interference mechanism if phase encoding is used to form two-dimensional images. This may well be a major reason why images obtained by 2DFT have been found to be generally superior to those obtained by projection reconstruction. Experimentally, the distribution of intensity in one-dimensional projection images of a square slice phantom is compared with theoretical intensities, estimated using eddy current field reported in the preceding paper.

Artifacts↗
PubMed2002

Enteromorpha flexuosa (Wulfen) J. Agardh (Chlorophyta: Ulvales)--evaluation as an indicator of heavy metal contamination in a tropical estuary.

The use of bioindicators for contaminant monitoring is popular in all sectors of the environment but quite often bioindicators are utilised without rigorous evaluation of their viability as an indicator. We report field and laboratory investigations into the value of a commonly found macroalga, Enteromorpha flexuosa (Wulfen) J. Agardh (Chlorophyta: Ulvales) as an indicator of copper, zinc and lead contamination in a tropical estuary in Fiji. In the laboratory, metal content of E. flexuosa after 60 days of growth in seawater containing increasing concentrations of the metals showed almost perfect correlation with metal concentrations in water for all three metals, and concentration factors obtained were generally higher than values reported for other species of Enteromorpha. Performance in the field was evaluated by a one-year monitoring of metals in E. flexuosa, water and sediments from a contaminated estuary. Metal concentrations in water were always below detection limits and field concentration factors could not be determined but the concentration of lead in E. flexuosa showed a high correlation with the lead content of sediments. Lack of such correlation for copper and zinc in the field suggests that other environmental factors besides metal load in the physical environment could be controlling the bioaccumulation of these two metals. Whilst demonstrating E. flexuosa to be a viable bioindicator for lead, these results also highlight the need for proper assessment before an organism is considered for environmental monitoring.

Chlorophyta↗
PubMed2004

Caprine hepatic lipidosis induced through the intake of low levels of dietary cobalt.

Forty-one, 10-week-old newly weaned goats were randomly allocated into two groups, namely control (n=22) and treated (n=19). Kids in both groups were fed Rhodegrass hay ad libitum that contained < 0.1 mg/kg DM cobalt and 150 g/day of a commercially prepared ruminant concentrate that contained approximately 0.12 mg/kg DM cobalt. This diet provided the minimum daily requirement of cobalt as specified for sheep. The treated goats were supplemented with bi-monthly subcutaneous injections of 2000 microg of hydroxycobalamin. All goats were weighed and blood samples collected monthly for haematological, clinical biochemical and serum vitamin B12 analysis. After a 10-month experimental period the goats were slaughtered. The control animals exhibited significantly (P<0.05) lower weight gains, and had dry scruffy hair coats. In addition, there was a decline in erythrocyte counts, mean haemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Controls also exhibited significantly (P<0.05) lower levels of total serum proteins and elevated levels of serum alkaline phosphatase compared to treated goats. Fourteen (63.6%) of the control goats developed pathology consistent with reported field cases of hepatic lipidosis associated with low liver levels of cobalt. Only one (5.3%) of the treated goats developed hepatic lipidosis. Contrary to previous reports that suggested that goats are less sensitive to low levels of dietary cobalt than sheep, it is apparent that this is not the case with Omani goats. This is the first report of the induction of hepatic lipidosis in goats due to feeding low levels of cobalt in their diet.

Animals↗
PubMed1996

[Educational effect of field visit in the course of preventive medicine and community health-case report of the field visits to Chikuho districts (1981-89)].

The experiences over 9 years (1981-89) of field visits to the Chikuho districts as part of the preventive medicine and community health course were studied using the results of student evaluations of the educational value of such field visits conducted once or twice a year. The Chikuho district is one of the high priority regions in national public health policy since the decline of the coal mining around 1960. The field visits (an all day visit by bus) were implemented with the aim of educating doctors interested in public health by early exposure to the related establishments, such as municipal hospital, prefectural public health center, memorial museum of coal mining and regional center for vertebrate injuries, all located in this district. The students are assigned to integrate their one-day experience in evaluative report. According to the students' evaluation, just over half of the respondants supported the educational effect of this exposure positively. However, due to university policy to reduce teaching hours, this rather unique field visit had to be terminated in 1990. The advantages and disadvantages of this form of field visits were analysed for comparison with small group field trips. From these analyses the importance of developing further those programs for educating "public health minded" doctors in preparation for service in the future is clear.

Curriculum↗
PubMed1997

Development of a primary health care information system in Ghana: lessons learned.

In Ghana, between January 1990 and September 1993, a series of steps were undertaken to review the existing vertical reporting procedures and to develop an integrated Health Management Information System (HMIS) for Primary Health Care (PHC). These steps included a situation analysis of the existing reporting systems; participatory design of tools for planning, data collection, feedback and reporting; field test and revision of the modified system; training of staff at all levels; development of tools for self-assessment and stimulation of routine feedback to lower levels and reporting of analysed indicators to higher levels. There were some notable achievements which included promotion of self-reliance, improved data relevance and accuracy, as well as strengthened supervision and support. However, it was difficult to identify the most appropriate institutional location for the HMIS; over-emphasis on process leads to reduced implementation; reporting was still given greater priority than analysis and use of data, and systems for collection and use were still cumbersome and time consuming. It is also difficult to prove that having better information really improves decision-making, or even coverage and quality of PHC service delivery. These issues, as well as lessons learned, are discussed in the paper.

Ghana↗
PubMed1998

Automatic cell electrorotation measurements: studies of the biological effects of low-frequency magnetic fields and of heat shock.

A computer-aided automatic imaging technique has been developed for measuring the electrorotation spectra of up to 256 particles at the same time. This offers advantages over the conventional manual method, especially when rapidly acquired statistical data are necessary in investigations of the response of cells or test beads to chemical exposure, for example. We have applied this technique to investigate the biological effects of heat shock and low-frequency EM fields reported by others for yeast cells. Although heat shock effects were observed, no changes of the electrorotational behaviour could be detected after exposing the cells to 50 Hz, 8 and 80 microT fields. Although this does not rule out the possibility that the cells were influenced by the magnetic fields, it does limit the number of possible physicochemical changes that might have occurred to their cell walls and membranes.

Automation↗
PubMed2003

The value of community participation in disease surveillance: a case study from Niger.

A team of researchers, including one behavioral scientist (S.M.N.) and three epidemiologists (L.Q., O.S. and S.N.) conducted community analyses to assess the social and cultural factors that affect the detection and reporting of disease cases in a surveillance system, using acute flaccid paralysis (AFP) surveillance in Niger as a case study. Over a 60-day period in the country, the research team reviewed written field reports and interviewed epidemiologists, nurses, community members and persons in governmental and non-governmental organizations. Overall, we found that the logistical difficulties of travel and communication, which are common in developing countries, constrain the conventional surveillance system that relies on epidemiologists visiting sites to discover and investigate cases, particularly in rural areas. Other challenges include: community members' lack of knowledge about the possible link between a case of paralysis and a dangerous, communicable disease; lack of access to health care, including the low number of clinics and health care workers; cultural beliefs that favor seeking a local healer before consulting a nurse or physician; and health workers' lack of training in AFP surveillance. The quality of surveillance in developing countries can improve if a community-based approach is adopted. Such a system has been used successfully in Niger during smallpox-eradication and guinea worm-control campaigns. In a community-based system, community members receive basic education or more extensive training to motivate and enable them to notify health care staff about possible cases of disease in a timely fashion. Local organizations, local projects and local leaders must be included to ensure the success of such a program. In Niger we found sufficient quantities of this type of social capital, along with enough local experience of past health campaigns, to suggest that a community-based approach can improve the level of comprehensiveness and sensitivity of surveillance.

Adolescent↗
PubMed1997

Experimental induction of the "sensed presence" in normal subjects and an exceptional subject.

9 of the 15 volunteers who were exposed to successive 3-min. durations of bursts of different types of weak (1 microT) complex magnetic fields or sham-fields reported the sense of a presence as indicated by a button press at the time of the experience. Reports of subjective experiences indicated that attempts to "focus" cognitively upon the location of the presence altered its location or induced its "movement." An exceptional subject who had a history of experiencing within his upper left peripheral visual field "flashing images" concerning the health and history of people [when handling their photographs] was also exposed to the burst sequences. Numbers of button presses associated with the experiences of a mystical presence, to whom the subject attributed his capacity, increased when the complex magnetic fields were applied without the subject's knowledge. The results support the hypothesis that the sense of a presence, which may be the common phenomenological base from which experiences of gods, spirits, angels, and other entities are derived, is a right hemispheric homologue of the left hemispheric sense of self.

Adult↗
PubMed2006

Local morphology predicts functional organization of the dorsal premotor region in the human brain.

A confusing picture of the functional organization of the dorsal premotor region of the human brain emerged when functional neuroimaging studies that either examined visuomotor hand conditional activity or attempted to localize the human frontal eye field reported activity increases at the same general location, namely the junction of the superior precentral sulcus with the superior frontal sulcus. The present functional magnetic resonance imaging study examined visuomotor hand conditional activity and the locus of the frontal eye field as defined by a standard task, on a subject-by-subject basis, to clarify their location and reveal relationships between the pattern of local morphology and functional activity. The results demonstrate that visuomotor hand conditional activity and the frontal eye field lie within distinct parts of the superior precentral sulcus, revealing an organization of the human premotor cortex consistent with that observed in experimental studies in the monkey.

Adult↗
PubMed1992

Mortality rates and aggression management among Native Americans.

Using data from the general USA population, Field reported that various causes of death correlated with measures of aggression management obtained from suicide and homicide rates. Since in this study replication of these findings cross-culturally was not successful with data for US Indian Health Service areas and Field did not explain his ecological correlations, the reliability and validity of his findings may be questioned.

Aggression↗
PubMed1976

Academic tenure and collective bargaining in American dental schools.

In thier survey of organizational structures in American dental schools, Dilts and Fields reported that the organization and administration of dental schools are of importance in the operation and attainment of educational goals. If one institutional goal is to provide faculty with attractive working conditions, then academic tenure and collective bargaining are important. In this respect, dental schools run true to higher education form. Having great variability, tenure systems were reported to be universal in dental schools. On the other hand, collective bargaining was found to be a new phenomenon on trial. The experience of dental schools with academic tenure and the trial of collective bargaining are of some interest to all college educators. Dilts and Fields concluded that "Although dental education is traditional in nature, resisting changes as do other phases of higher education, the results indicate that dental education is dynamic and is responding to internal as well as external needs." Dental educators may wish to follow these tenure and union issues to help determine successful policies for the conditions of dental faculty employment.

Collective Bargaining↗
PubMed2001

Why integrated health networks have failed.

Over the last two decades, hospitals, physicians, and nursing homes have rushed to merge or partner with one another, cheered on by consultants, academics, and experts who claimed that such networking was imperative for these organizations to survive in an increasingly competitive environment. In the 1990s, however, reports of the major difficulties encountered by the merged entities began to dampen the industry's enthusiasm for integration, causing some to even question the value of the integration "revolution." This article will review the primary rationale behind integration and will assess its success to date. Based on field reports and the available evidence, the authors conclude that IHNS have not delivered on their promise. While each network should be considered in its unique market and contextual situation, the enormous financial, human, and clinical resources devoted to integration have not borne much fruit. Evidence of quantifiable, sustained financial or clinical value is scant.

Communication↗
PubMed2006

Quality of life of nasopharyngeal carcinoma survivors in Mainland China.

The aim of this study is to evaluate the quality of life (QoL) of nasopharyngeal carcinoma (NPC) survivors. 192 NPC survivors treated in 1999 and 2000 were enrolled in this study. Median follow up was 3.6 years (range 2.4-4.6 years). The Chinese SF-36 questionnaire and a self-reported symptom checklist consisting of 14 items were completed at clinics. Sociodemographic factors and clinical information were also collected. Most functional domains of the Chinese SF-36 were significantly worse in NPC survivors compared to the normal population. Xerostomia, hearing loss, hypomnesia, dysphagia, and trismus were frequently reported symptoms. Sociodemographic variables including gender, age, dialect, educational level, monthly income, economic status, and number of comorbidities were univariate predictors of different SF-36 domains and symptoms. Patients with earlier T and N stage, irradiated by linear accelerator, with lower dose and weekly dose to nasopharynx and neck, and those who had anterior nasal radiation field reported better QoL. Multiple stepwise regression analysis showed that the number of comorbidities, monthly income, age, and T stage were independent factors affecting global QoL. We concluded that NPC survivors had worse QoL than the normal population and improving radiotherapy might increase physical and functional domain of QoL.

Adolescent↗
PubMed1993

A model for autumn outbreaks of Legionnaires' disease associated with cooling towers, linked to system operation and size.

Cooling towers have been demonstrated to be amplifiers and disseminators of legionella, the causative organism of Legionnaires' disease. Community outbreaks associated with cooling towers have been reported with several common factors. Small towers (< 300 kW) have predominantly been implicated in outbreaks. Cooling tower-associated outbreaks are most frequent in autumn, and frequently implicated systems have been operated after a period of shutdown. This paper reports field study data relating system operation to legionella colonization of systems. Operating systems have been shown to be more frequently colonized by legionella than shutdown systems. In some cases operation of systems after periods of shutdown raised legionella concentrations from below detection limits to between 50 and 950 c.f.u./ml within 10 min. These data and previously reported data relating to biofilm and sediment colonization of the systems, and community outbreaks of Legionnaires' disease, have been used to develop a model explaining the seasonal nature of outbreaks associated with irregularly operated, small cooling tower systems.

Air Conditioning↗
PubMed2002

Management preferences following radical inguinal orchidectomy for Stage I testicular seminoma in Australasia.

A survey to evaluate the preferred patterns of management of Stage I seminoma was conducted during March 2001. The questionnaire was distributed by the Royal Australian and New Zealand College of Radiologists to all qualified radiation oncologists, 74 out of 170 responded. All performed a staging CT scan of the abdomen and pelvis. Thoracic imaging consisted of either chest X-ray (29%) or chest CT (38%) while 33% performed both. Fifty-four percent of radiation oncologists discussed surveillance with their patients but estimated that 5% or less would choose this option. The most commonly prescribed dose was 25 Gy in 15 or 20 fractions (79%). Sixty-five percent of respondents treated the para-aortic (PA) nodes alone. Forty-two of 48 clinicians treating the PA field reported a change in practice after publication of the Medical Research Council study in 1999. Of these, 40 and 23% perform CT scans of the pelvis annually and every 6 months. Thirty-one percent did no follow-up CT scan. Compared to a similar survey from North America, we are more likely to use PA fields and less likely to discuss surveillance. As in the USA, and in contrast to Canada, few patients choose surveillance. There is no consensus regarding the frequency of follow-up scans in either North America or Australasia.

Follow-Up Studies↗
PubMed1985

A computer-assisted quality assurance system for an emergency medical service.

A busy urban emergency medical service answering more than 50,000 calls each year developed a plan for quality assurance using a computer-assisted model designed to employ a full-time quality assurance officer whose work was supplemented with computer evaluation of EMS field reports. The development of standardized reporting formats, protocols and computer programs enabled a significant improvement in detection of errors of documentation and patient care. Investigated cases rose dramatically in the month following implementation of the system, from five patient care errors per month to 35 (P less than .05), and from 50 documentation errors to 265 per month (P less than .05). Our experience indicates that computer-assisted evaluation of field performance, as judged by prehospital records, is a useful tool to ensure standards in patient care and EMS recordkeeping.

Allied Health Personnel↗
PubMed2002

Insecticide use and organophosphate resistance in the coffee leaf miner Leucoptera coffeella (Lepidoptera: Lyonetiidae).

Increasing rates of insecticide use against the coffee leaf minerLeucoptera coffeella(Guérin-Méneville) and field reports on insecticide resistance led to an investigation of the possible occurrence of resistance of this species to some of the oldest insecticides used against it in Brazil: chlorpyrifos, disulfoton, ethion and methyl parathion. Insect populations were collected from ten sites in the state of Minas Gerais, Brazil and these populations were subjected to discriminating concentrations established from insecticide LC99s estimated for a susceptible standard population. Eight of the field-collected populations showed resistance to disulfoton, five showed resistance to ethion, four showed resistance to methyl parathion, and one showed resistance to chlorpyrifos. The frequency of resistant individuals in each population ranged from 10 to 93% for disulfoton, 53 to 75% for ethion, 23 to 76% for methyl parathion, and the frequency of resistant individuals in the chlorpyrifos resistant population was 35%. A higher frequency of individuals resistant to chlorpyrifos, disulfoton and ethion was associated with greater use of insecticides, especially other organophosphates. This finding suggests that cross-selection, mainly between organophosphates, played a major role in the evolution of insecticide resistance in Brazilian populations of L. coffeella. Results from insecticide bioassays with synergists (diethyl maleate, piperonyl butoxide and triphenyl phosphate) suggested that cytochrome P450-dependent monooxygenases may play a major role in resistance with minor involvement of esterases and glutathione S-transferases.

Animals↗
PubMed2006

[Bitemporal hemianopia in road traffic].

BACKGROUND: Patients suffering from pituitary adenomas and diseases of the chiasma typically show a bitemporal hemianopia. The residual undisturbed nasal visual fields of both eyes should have an extension of (at least) 120 degrees and are according to the actual German traffic rules (FeVAndV) for cars of the classes A, B, M, L and T. The intact half fields fit geometrically to one virtual normal field, that seems to correspond in the centre of a normal field. Reports on this problem often do not address correctly the questions of suitability for participation in road traffic. PATIENTS: The case of a patient with typical bitemporal hemianopia illustrates the sensorial peculiarities: the functioning temporal retinal halves do not correspond. This patient suffered additionally from disturbing diplopia due to a small-angle exotropia. The extent of the performed eye muscle surgery was selected to induce a slight overcorrection, i. e., resulting in 3 to 5 degrees esotropia. This eliminated the diplopia, but resulted in a vertical scotoma of the extension of the esotropia. CONCLUSIONS: In bitemporal hemianopia the undisturbed nasal visual half fields do not add up to a "nearly normal field of one eye". Moreover, either diplopia or--much more dangerous in traffic--a central vertical scotoma is the result. The explanation for this is a sliding of the hemifields of each eye without stabilisation by corresponding areas of the retinas of the right and left eyes. The peripheral extension of the visual field is not the key to the problem to imagine how a patient with typical bitemporal hemianopia will visualise daily life and traffic. In bitemporal hemianopia there is substantially no eligibility for driving a car or motor bicycle in road traffic.

Adult↗