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Biomedical subjects

D Shahar

Publications and source records attributed to D Shahar.

16 recordsLinked to original sources
PubMed2005

Nanowire acting as a superconducting quantum interference device.

We present the results from an experimental study of the magnetotransport of superconducting wires of amorphous indium-oxide having widths in the range 40-120 nm. We find that, below the superconducting transition temperature, the wires exhibit clear, reproducible, oscillations in their resistance as a function of magnetic field. The oscillations are reminiscent of those that underlie the operation of a superconducting quantum interference device.

Journal Article↗
PubMed2005

Experimental evidence for a collective insulating state in two-dimensional superconductors.

We present the results of an experimental study of the current-voltage characteristics in a strong magnetic field (B) of disordered, superconducting, thin films of amorphous indium oxide. As the B strength is increased superconductivity degrades, until a critical field (B(c)) where the system is forced into an insulating state. We show that the differential conductance measured in the insulating phase vanishes abruptly below a well-defined temperature, resulting in a clear threshold for conduction. Our results indicate that a new collective state emerges in two-dimensional superconductors at high B.

Journal Article↗
PubMed2004

Superconductivity-related insulating behavior.

We present the results of an experimental study of superconducting, disordered, thin films of amorphous indium oxide. These films can be driven from the superconducting phase to a reentrant insulating state by the application of a perpendicular magnetic field (B). We find that the high-B insulator exhibits activated transport with a characteristic temperature, TI. TI has a maximum value (TpI) that is close to the superconducting transition temperature (Tc) at B=0, suggesting a possible relation between the conduction mechanisms in the superconducting and insulating phases. Tp(I) and Tc display opposite dependences on the disorder strength.

Journal Article↗
PubMed2003

Near-perfect correlation of the resistance components of mesoscopic samples at the quantum Hall regime.

We study the four-terminal resistance fluctuations of mesoscopic samples near the transition between the nu=2 and the nu=1 quantum Hall states. We observe near-perfect correlations between the fluctuations of the longitudinal and Hall components of the resistance. These correlated fluctuations appear in a magnetic-field range for which the two-terminal resistance of the samples is quantized. We discuss these findings in light of edge-state transport models of the quantum Hall effect. We also show that our results lead to an ambiguity in the determination of the width of quantum Hall transitions.

Journal Article↗
PubMed2003

Observation of a quantized hall resistivity in the presence of mesoscopic fluctuations.

We present an experimental study of mesoscopic, two-dimensional electronic systems at high magnetic fields. Our samples, prepared from a low-mobility InGaAs/InAlAs wafer, exhibit reproducible, sample specific, resistance fluctuations. Focusing on the lowest Landau level, we find that, while the diagonal resistivity displays strong fluctuations, the Hall resistivity is free of fluctuations and remains quantized at its nu=1 value, h/e(2). This is true also in the insulating phase that terminates the quantum Hall series. These results extend the validity of the semicircle law of conductivity in the quantum Hall effect to the mesoscopic regime.

Journal Article↗
PubMed2003

Dietary intake and eating patterns of elderly people in Israel: who is at nutritional risk?

OBJECTIVE: To determine dietary intake and eating patterns of older persons in Israel and to identify factors associated with low intake. DESIGN: A cross-sectional study. SETTING: Community-dwelling participants living in the Beer-Sheva area were interviewed at home, using a 24 h food questionnaire with additional questions regarding health and eating habits. Dietary intake was compared between people aged 65-74 and 75 y and older. SUBJECTS: A total of 377 people over the age of 65 224 aged 65-74 and 153>75, were randomly selected from the Negev population. RESULTS: Dietary intake of energy, fat, carbohydrates, vitamins E, C and B(1) were significantly lower for people aged 75 and older compared with people aged 65-74. Low energy intake was associated with lower subjective health status for men (P<0.01), poor appetite (P<0.01) and more gastrointestinal problems (P<0.05) for women and lower snack consumption (P<0.01) for both genders. In a multivariate model, low energy intake was associated with low appetite and higher use of medication for both sexes and with frequency of eating alone and not consuming snacks for men. CONCLUSIONS: Dietary intake is lower among individuals older than 75 than in 65-74 y old. Risk factors for low intake include poor appetite and health status, gastrointestinal problems, and eating alone. Snacking enhanced dietary intake and should be encouraged in this group.

Age Factors↗
PubMed2003

[Prevalence and characteristics of myocardial infarction, diabetes and hypertension in the adult Jewish population: results from the Negev Nutritional Study].

BACKGROUND: Monitoring the prevalence of chronic conditions such as chronic heart disease, diabetes and hypertension in adult populations is essential for health services planning and identification of populations at high risk. OBJECTIVES: To describe the prevalence of self-reported conditions such as myocardial infarction, diabetes mellitus and hypertension in the Jewish Negev population and the patterns of use of health services and dietary behavior of persons suffering from these conditions. METHODS: A random proportional geographic cluster sample of the adult Jewish population (n = 1159, age 35+) from the Negev area was interviewed at home between 1998 and 1999. The interview included questions regarding chronic conditions, patterns of health services use and dietary behavior. RESULTS: Men had twice the prevalence of myocardial infarction and underwent more invasive cardiac procedures than women. The highest prevalence of myocardial infarction and hypertension were found in Central- and Eastern European-born persons while the highest prevalence of diabetes was found in Western-born participants. Of the participants < 61 years of age, 19% reporting diabetes and 33% reporting hypertension did not use medication and were not adhering to an appropriate diet. Thus, one-third of those with reported hypertension and 15% of those reported as diabetics were not adhering to any treatment. The prevalence reported in this study was higher than the national data. CONCLUSIONS: The data collected showed a higher prevalence of chronic diseases among the southern Israeli population as compared with the national data. Among people with chronic diseases, high percentages are not treated. The information reported here may help in the allocation of health services for the south of Israel and in the identification of populations at risk.

Adult↗
PubMed2001

Attitudes of physicians and medical students toward nutrition's place in patient care and education at Ben-Gurion University.

OBJECTIVES: To describe attitudes of physicians and medical students at one medical school toward the role of dietetic treatment in patient care and toward adding nutritional education into the medical school curriculum. STUDY DESCRIPTION: A cross sectional survey was conducted at Soroka University Medical Center and Ben-Gurion University's School of Medicine. The attitudes of 67 physicians and 62 medical students toward nutritional treatment were determined using an attitudes questionnaire. RESULTS: Despite recommendations in medical treatment protocols to use dietary intervention as the primary treatment for several chronic diseases, physicians did not rate nutritional treatment as the most important treatment for these conditions. Students rated the importance of nutritional treatment significantly higher for each of the medical conditions presented than did practicing physicians (p=0.001). Almost 50% of the physicians reported not using nutritional treatment due to lack of time and awareness of the available options. Physicians and students rated the importance of nutrition education in the curriculum equally. Physicians who rated nutrition treatment as important also felt the need to add this subject to the medical education curriculum. CONCLUSION: Physicians and medical students agreed that dietary treatment and nutrition education are important. Our results suggest that there is good reason to introduce nutrition topics into medical school curricula. Improved nutritional knowledge in physicians would improve the teamwork capacity between physicians and dieticians in the realms of curative care and public health.

Journal Article↗
PubMed2000

Negev nutritional studies: nutritional deficiencies in young and elderly populations.

The importance of nutrition to public health and preventive medicine is evident. Undernutrition is a main nutritional risk factor in the elderly and has been established as a cause of excess morbidity and mortality in different segments of the older population. In the infant population, inadequate nutrition is one of the causes of iron-deficiency anemia, which is associated with impaired physical and cognitive development and lowered immunity. The aim of this paper was to estimate the nutritional pattern and micronutrient deficiencies in elderly and young populations in the Negev. In southern Israel, 351 subjects over 64 years old reported mean dietary intake that was lower than that in younger persons and was independent of the presence of chronic diseases. Current data from southern Israel on healthy Jewish children revealed anemia prevalence of 15% in the second year of life. Data from recent prospective study on Bedouin children showed that anemia affected one quarter of children at age one year. Thus, infants in this area are at high risk for iron deficiency. The findings require the attention of public health authorities and food manufacturers, and should result in a range of activities including publicity and educational programs, fortification of foods, and supplementation programs in high risk-groups.

Age Factors↗
PubMedDate not supplied

Factors associated with low reported energy intake in the elderly.

BACKGROUND: Underreporting of dietary intake can be estimated by the Energy Ratio (ER) between reported energy intake (EI) and calculated total energy expenditure (TEE). The gap between EI and TEE is usually attributed to underreporting. In elderly populations, compromised dietary intake and health status may offer alternative explanations to this gap. OBJECTIVE: This study aimed to characterize "underreporting" of dietary intake and low energy reporters (LER) among the elderly. DESIGN: Participants aged 65 years and over, were recruited using random population sampling of the Negev population. Data were collected using the 24-h recall method with additional demographic and age-specific health questionnaires. ER was calculated using the ratio between reported energy intake and calculated TEE computed by the Schofield formula. LER were defined as those with reported energy intake of less than 0.8 calculated BMR using the Schofield formula. RESULTS: We restricted our analysis to 191 elderly aged 65-74 y and 177 aged 75 y and older who reported their diet to be "as usual." In univariate analyses, BMI < 22, better health status, use of fewer than four medications and good reported appetite were significantly related to higher ER. No difference was shown in ER by gender, level of education, and family status. Weight loss superior 5 kg was associated with low ER (p = 0.049). In a linear regression model, low ER (indicating "underreporting") was significantly associated with higher activity level and use of over four medications. Using a dichotomous approach, Low Energy Reporters (LER) used a higher number of medications, ate fewer food items per day and suffered from poorer appetite. CONCLUSIONS: In the elderly, ER < 1 may indicate underreporting in dietary intake, and indeed, is frequent among the obese. Nonetheless, among the elderly, ER < 1 may reflect truly low caloric intake. Our results suggest that, to some degree, health status variables are associated with decreased ER, supporting a true caloric deprivation state.

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