Low-Energy Electron Potentiometry: Contactless Imaging of Charge Transport on the Nanoscale.

Charge transport measurements form an essential tool in condensed matter physics. The usual approach is to contact a sample by two or four probes, measure the resistance and derive the resistivity, assuming homogeneity within the sample. A more thorough understanding, however, requires knowledge of local resistivity variations. Spatially resolved information is particularly important when studying novel materials like topological insulators, where the current is localized at the edges, or quasi-two-dimensional (2D) systems, where small-scale variations can determine global properties. Here, we demonstrate a new method to determine spatially-resolved voltage maps of current-carrying samples. This technique is based on low-energy electron microscopy (LEEM) and is therefore quick and non-invasive. It makes use of resonance-induced contrast, which strongly depends on the local potential. We demonstrate our method using single to triple layer graphene. However, it is straightforwardly extendable to other quasi-2D systems, most prominently to the upcoming class of layered van der Waals materials.

Systolic blood pressure differences among pediatric epidemiological studies.

This report reviews the results of six large blood pressuree surveys done on pediatric populations and points out factors responsible for differences in the blood pressure norms. The studies were selected on the basis of there being recent examinations of large numbers of children. Important differences in mean systolic pressures and 95th percentile values were found among the studies, which may be attributed to: 1) actual differences among the populations; 2) biases due to methodological differences; or 3) increased sampling variability with small sample sizes. Actual differences in pressures among the populations surveyed may be due to differences in geographic location, racial composition, or average body sizes. Discrepancies due to methodological biases may have occurred because of associated venipuncture or exercise stress on the day of the examination; differences in selection of blood pressure cuff sizes; differences in the number of measurements averaged. In several studies, small sample sizes for each age-race-sex subclass accounted for considerable variability of the 95th percentile value. The implication of this analysis is that before the 95th percentile norms for children of different ages, races, and sexes can be more firmly established, it is necessary to collect larger sample sizes controlling for known biasing factors and using a standardized methodology.

The predictive value of resting electrocardiograms for 12-year incidence of coronary heart disease in the Honolulu Heart Program.

The predictive value of electrocardiographic (ECG) abnormalities at baseline for subsequent risk of fatal and total coronary heart disease (CHD) was analyzed in a 12-year follow-up of 7682 men in the Honolulu Heart Program aged 45-68 who were free of CHD at baseline. Univariate analysis showed that men with major or minor ECG abnormalities, ST depression, high R wave, T-wave inversion, left ventricular hypertrophy or strain and premature ventricular contractions had considerably higher (2-10 fold) CHD incidence rates than those with normal ECG. When blood pressure, cigarette smoking, body mass index, alcohol use, physical activity, serum glucose, serum cholesterol, serum uric acid, age and years lived in Japan were taken into consideration through multivariate analysis, the ECG abnormalities retained significant associations with fatal and total CHD. This study demonstrated that resting ECG abnormalities were independent predictors of both total and fatal CHD.

Plasma lipids and lipoproteins in elderly Japanese-American men.

Knowledge about blood lipids in older individuals is limited. In the Lipoprotein Study of the Honolulu Heart Program, plasma cholesterol, triglyceride, and high-density lipoprotein (HDL) were measured during 1980 and 1981 in Japanese-American men over 60 years of age. In addition, low-density lipoprotein cholesterol (LDL-C) was estimated via a regression model. Age-related differences in mean lipid levels between the youngest (60 to 64 years) and the oldest (75 years and older) groups included a decrease in total cholesterol from 214 to 207 mg/dL and plasma triglyceride from 188 to 144 mg/dL. High density lipoprotein cholesterol rose from 47 to 49 mg/dL and LDL was relatively stable (137 and 135 mg/dL, respectively). Age-adjusted total cholesterol tended to significantly increase with increasing body mass index and hematocrit but was not significantly related with systolic blood pressure, physical activity index, cigarettes per day, or alcohol intake. Among those variables HDL-C decreased significantly with increasing body mass index and hematocrit and increased significantly with increasing alcohol intake. Compared with elderly white men in the Lipid Research Clinic Program, total cholesterol values tended to be slightly higher and triglyceride values were substantially higher, whereas HDL and LDL values were appreciably lower. Both cholesterol and triglyceride values were substantially higher than values reported from Japan from men in these age groups.

Purification and properties of 5,6-dihydropyrimidine amidohydrolase from calf liver.

5,6-Dihydropyrimidine amidohydrolase was isolated from an acetone powder of calf liver and purified to homogeneity. Purification made use of heat treatment, ammonium sulfate fractionation and chromatography on Chelating Sepharose and DEAE-Sepharose with 44% recovery of total activity. The native enzyme has a molecular mass of 217 kDa consisting of four subunits with a molecular mass of 54 kDa each. The amidohydrolase is a metalloenzyme containing one zinc atom/subunit. The enzyme can slowly be inactivated by chelating agents. The kinetic parameters for substrates, 5,6-dihydrouracil, 5,6-dihydrothymine and glutarimide were determined. From log Vmax/KM data, a pKa of 7.6 could be calculated suggesting the formation of a zinc-bound hydroxyl ion which carries out the nucleophilic attack on the C-4 of dihydrouracil.

Trends in cardiovascular mortality in Spanish-surnamed, other white, and black persons in Texas, 1970--1975.

Certain categories of cardiovascular disease have significantly declined recently as causes of death. In the present investigation we describe the variation in cardiovascular mortality in Texas by ethnicity, age and sex during 1970--1975 using age-standardized proportional mortality ratios. Specifically, the question of whether the three major ethnic groups in Texas have shared equally in any changes in cardiovascular mortality is examined. Several subcategories of cardiovascular mortality are considered. Among the sex-ethnic groups both ischemic heart disease and acute myocardial infarction mortality declined less among Spanish-surnamed males and females than in their other white and black counterparts. Chronic ischemic heart disease increased in relative importance for all groups except Spanish-surnamed females, in whom it decreased. There was no significant decrease in cerebrovascular disease mortality among Spanish-surnamed males or females as there was in the other groups. These results suggest that important differences in cause-structure of mortality are occurring in the ethnic subpopulations of Texas.

Changes in life expectancy in the United States due to declines in mortality, 1968-1975.

This study examines the gains in life expectancy for four race/sex groups of the US population between 1968 and 1975. An increase of 2.3 years in life expectancy at birth and 1.7 years in life expectancy at age 45 years has occurred for all race/sex groups combined. The added years of life for the normal working ages (15-70 years) is only 0.6 years for the total US population, 0.3 years for white females, 0.6 years for white males, 1.5 years for nonwhite males, and 1.7 years for nonwhite females. The relative contribution of the five leading causes of death to this gain varies at different ages. For example, more than 50% of the increase in life expectancy at age 45 years was due to a lower mortality rate in diseases of the heart which is still the leading cause of death among each of the race/sex groups. Other contributions to the increase in life expectancy at age 45 years are: cerebrovascular diseases, 16%; accidents, 6%; influenza and pneumonia, 7%; and all other causes, 16%. The increase in the malignant neoplasms mortality rate had a negative effect, -2%, on the gain of life expectancy.

Volunteer and paid long term care ombudsmen: differences in complaint resolution.

Data are reported from a pilot study of the ombudsman reporting system in one southeastern state. The focus of this article is the relationship between types of complaints investigated and resolved by both paid and volunteer long-term care ombudsmen operating under various auspices. Statistically significant differences exist between the resolution of complaints by volunteer and paid ombudsmen. Data are discussed in terms of the implications of these differences for the implementation of a federal mandate to increase citizen participation in long-term care facilities.

Elder rights and the Long-Term Care Ombudsman Program.

Since 1975 the Long-Term Care Ombudsman Program has grown and developed under the Older Americans Act (OAA) of 1965. With the passage of the Older Americans Act Amendments of 1992, this program was combined with other advocacy functions and placed in Title VII--Vulnerable Elder Rights Protection Activities. This article provides a historical overview of the policy, programmatic, and research issues that surround OAA and explains the activities of ombudsmen in their local communities and the roles many social workers perform under the auspices of long-term care ombudsman programs.

Relationship of plasma lipoprotein Lp(a) levels to race and to apolipoprotein B.

Lipoprotein Lp(a) is an atherogenic subfraction of plasma lipoproteins which has been studied predominantly in white populations. We quantified Lp(a) by electroimmunoassay in plasma from 105 black and 134 white healthy men and women. Results were correlated with clinical variables and plasma levels of lipids, other lipoproteins, and apolipoprotein (apo) B determined by radioimmunoassay. Black subjects had levels of Lp(a) that averaged twice those of whites (p less than 0.001). Among blacks, Lp(a) levels showed a bell-shaped frequency distribution, while among whites the distribution was strongly skewed, with the highest frequencies at low levels. Contrary to previously published results, the apo B levels in our study correlated significantly, though weakly, with Lp(a) (r = 0.21, p = 0.001 among whites, and r = 0.15, p = 0.02 among blacks, Kendall rank correlation). The regression slopes and variances suggested that apo B in the Lp(a) lipoprotein could account for the correlation. Lp(a) levels did not correlate significantly with any other plasma lipoprotein or lipid levels. The implications of this study are as follows: Despite the high levels of Lp(a) among blacks in the Houston area, these blacks do not experience greatly increased atherosclerotic progression and mortality. Thus, the atherogenicity of Lp(a) in blacks must be decreased or counterbalanced by other factors. The correlation between Lp(a) and apo B should be taken into account when analyzing atherogenic risk, but this correlation is not strong enough to dispute the independence of Lp(a) and apo B as risk factors.

Coffee, caffeine, and serum cholesterol in Japanese men in Hawaii.

The relationship between coffee consumption and serum cholesterol was investigated in a cohort of 5,858 Japanese males born in 1900-1919 and living in Hawaii in 1965 who are currently followed by the Honolulu Heart Program. Data on coffee consumption, other dietary variables from a 24-hour dietary recall, and other potentially confounding variables collected in 1965 were correlated with serum cholesterol at that examination and at examination six years later. The mean coffee and tea consumption was 3.4 and 1.8 cups/day, respectively. Those consuming no coffee had a mean serum cholesterol of 210 mg/dl, while that of those drinking 9+ cups/day was 220 mg/dl (no such relationship was apparent with tea or cola). The relationship of coffee consumption and serum cholesterol with potentially confounding variables including body mass index, cigarette smoking, diastolic blood pressure, alcohol consumption, physical activity index, serum glucose, serum uric acid, education, age, and fat consumption was examined. When these variables were entered into a multiple regression equation with coffee consumption, a significant relationship between coffee consumption and serum cholesterol (p less than 0.001) persisted, as did that between baseline coffee consumption and serum cholesterol six years later (p less than 0.001). There was no significant relationship between tea or cola, the other major caffeine contributors to the diet, and baseline serum cholesterol. Thus, this analysis indicates a significant positive relationship between coffee consumption and serum cholesterol which is not present with other sources of caffeine.

Synthesis and reactivity of the monocarbon molybdenacarborane anion [1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-MoCB(10)H(10)](-).

The reagent Li[7-NHBu(t)()-nido-7-CB(10)H(12)] reacts with [Mo(CO)(6)] in NCMe at reflux temperatures, followed by addition of [N(PPh(3))(2)]Cl, to give [N(PPh(3))(2)][1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-MoCB(10)H(10)] (1). The tungsten (2) and chromium (3) analogues were similarly obtained, but the latter is unstable and was isolated in low yield. An X-ray diffraction study of 2 confirmed that the exo-polyhedral NHBu(t) group forms a bridge between the cage-carbon atom and the tungsten. For 1, this intramolecular donor bond is lifted on protonation in the presence of donor molecules L (CO, PPh(3), PMe(3), PEt(3), PMe(2)Ph) when zwitterionic complexes [1-NH(2)Bu(t)()-2,2,2-(CO)(3)-2-L-closo-2,1-MoCB(10)H(10)] (4) are formed. In contrast, protonation with HCl gives a salt [N(PPh(3))(2)][1-NH(2)Bu(t)()-2,2,2-(CO)(3)-2-Cl-closo-2,1-MoCB(10)H(10)] (5). Complex 1 in CH(2)Cl(2) with CNBu(t) is oxidized by iodine, affording [1,2-mu-NHBu(t)()-2,2,2-(CNBu(t)())(3)-2-I-closo-2,1-MoCB(10)H(10)] (6a). Treatment of 1 with [CuCl(PPh(3))](4) in the presence of Tl[PF(6)] yields the bimetallic compound [exo-[Cu(PPh(3))]-1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-MoCB(10)H(10)] (8), whereas reaction with [AuCl(PPh(3))] and Tl[PF(6)] affords a mixture of [1,2-mu-NHBu(t)-2-[Au(PPh(3))]-2,2,2-(CO)(3)-closo-2,1-MoCB(10)H(10)] (9) and [Au(PPh(3))(2)][2,2'-mu-Au-[1,2-mu-NHBu(t)-2,2,2-(CO)(3)-closo-2,1-MoCB(1)(0)H(10)](2)] (10a). In solution, 9 disproportionates, giving 10a. The [N(PPh(3))(2)](+) salt (10b) is readily prepared by treating 1 with [AuCl(THT)] (THT = tetrahydrothiophene) and Tl[PF(6)], and its structure was determined by X-ray diffraction.

Acid-base catalytic mechanism of dihydropyrimidinase from pH studies.

The pH dependence of kinetic parameters and solvent deuterium isotope effects have been used to probe the mechanism of the dihydropyrimidinase from the liver of pig and calf. The V/K for 5,6-dihydrouracil (DHU) (or the alternative substrate glutarimide) measured with either the native zinc or cadmium-substituted enzymes decreases at both low and high pH giving pK values of about 7.5-8 and 9-10. The low pK value observed in V is perturbed significantly to lower pH (approximately 6), and the high pK is not observed. The binding of glutarate monoamide is optimum when the group with a pK of 7.7 is protonated, and this same group must be protonated for the reverse reaction, that is, formation of DHU from N-carbamoyl-beta-alanine. These data are consistent with a general base mechanism and in addition suggest that the enzyme is present initially with a water bound to the active site zinc. The enzymic general base with a pK of 7.5-8 is required to activate water for nucleophilic attack on the C-4 of 5,6-dihydrouracil which is directly coordinated to the active site zinc. The second group with a pK of 9-10 likely reflects Zn-water ionization of the free enzyme. The water bound to the active site Zn is displaced by reactant binding, and thus the pK of 9-10 is not observed in the V profile. Solvent deuterium isotope effects are near unity on the V/K for the natural substrate 5,6-dihydrouracil, but a finite effect of 1.6 is observed on V.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive value of resting electrocardiograms for 12-year incidence of stroke in the Honolulu Heart Program.

The importance of electrocardiographic (ECG) abnormalities at baseline examination for subsequent risk of stroke was analyzed in a 12-year follow-up of 7,560 men in the Honolulu Heart Program, aged 45-68 years, who were free of coronary heart disease and stroke at baseline. Age-adjusted univariate analysis showed that men with major ST depression, left ventricular strain, left ventricular hypertrophy, major T wave inversion, and overall major ECG abnormalities had considerably higher (2.5-5.4 times) incidence rates of both thromboembolic and hemorrhagic stroke than those with normal baseline ECG. When blood pressure, age, cigarette smoking, alcohol consumption, fat intake, serum glucose concentration, serum uric acid concentration, years of education, and years lived in Japan were taken into consideration through multivariate analysis, the ECG abnormalities retained a significant relation with stroke. Our study demonstrates that resting ECG abnormalities are independent predictors of both thromboembolic and hemorrhagic stroke.

Communicating health information to urban Mexican Americans: sources of health information.

Data from a six-week hypertension campaign aimed at urban Mexican Americans were analyzed to document how they receive their health information and to identify the communication channels most likely to reach different segments of the Mexican-American community. The nine sources of information examined were doctor, nurse, pharmacist, family, friends, radio, newspaper, television, and magazine. The most common source of health information reported was doctor, followed by television, newspapers, magazines, family, and radio. Interview language (Spanish or English) was a significant predictor of the amount of health information received from all nine sources. Sex, family income, education, and age also were shown to affect the amount of health information received from various sources. Profiles of respondents most likely to use each source of health information are presented and implications for health educators are discussed.

Association of levels of lipoprotein Lp(a), plasma lipids, and other lipoproteins with coronary artery disease documented by angiography.

In a study of 307 white patients who underwent coronary angiography, the relationship of coronary artery disease (CAD) to plasma levels of lipoprotein Lp(a) and other lipid-lipoprotein variables was examined. Lp(a) resembles low-density lipoprotein (LDL) in several ways, but can be distinguished and quantified by electroimmunoassay. CAD was rated as present or absent and was also represented by a quantitative lesion score derived from estimates of stenosis in four major coronary vessels. Coronary lesion scores significantly correlated with Lp(a), total cholesterol, triglycerides, LDL cholesterol, and high-density lipoprotein (HDL) cholesterol levels by univariate statistical analysis. By multivariate analysis levels of Lp(a) were associated significantly and independently with the presence of CAD (p less than .02), and tended to correlate with lesion scores (p = .06). Among subgroups Lp(a) level was associated with CAD in women of all ages and in men 55 years old or younger. An apparent threshold for coronary risk occurred at Lp(a) lipoprotein mass concentrations of 30 to 40 mg/dl, corresponding to Lp(a) cholesterol concentrations of approximately 10 to 13 mg/dl. Plasma Lp(a) in white patients appears to be a major coronary risk factor with an importance approaching that of the level of LDL or HDL cholesterol.

Silver as an exopolyhedral auxiliary to the rhenacarborane anion [Re(CO)3(eta5-7,8-C2B9H11)]-.

The rhenacarborane salt Cs[Re(CO)3(eta5-7,8-C2B9H11)] (1) has been used to synthesize the tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Ph2P(CH2)2PPh2]] (3) where two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments have been shown by X-ray crystallography to be bridged by a single 1,2-bis(diphenylphosphino)ethane ligand. Reaction of 1 with Ag[BF4] in the presence of the ligands bis- or tris(pyrazol-1-yl)methane yields the complexes [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-CH2(C3H3N2-1)2]] (4) or [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-kappa1,kappa2-CH(C3H3N2-1)3]] (5), respectively. From X-ray studies, the former comprises a Re-Ag bond bridged by the carborane cage and with the bis(pyrazol-1-yl)methane coordinating the silver(I) center in an asymmetric kappa(2) mode. Complex 5 was unexpectedly found to contain a tris(pyrazol-1-yl)methane bridging two [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] fragments in a kappa1,kappa2 manner. Treatment of 1 with Ag[BF4] in the presence of 2,2'-dipyridyl and 2,2':6',2' '-terpyridyl yields [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa2-(C5H4N-2)(2)]] (6) and [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3[kappa3-C5H3N(C5H4N-2)2-2,6]] (7). The X-ray structure determination of 7 revealed an unusual pentacoordinated silver(I) center, asymmetrically ligated by a kappa3-2,2':6',2' '-terpyridyl molecule. The same synthetic procedure using N,N,N',N'-tetramethylethylenediamine gave a tetranuclear metal complex [[ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3]2[mu-Me2N(CH2)2NMe2]2] (8) which is believed, in the solid state, to be bridged between the silver atoms by two of the diamine molecules. The salt 1 with Ag[BF4] in the absence of any added ligand gave the tetrameric cluster [ReAg[mu-5,6,10-(H)3-eta5-7,8-C2B9H8](CO)3]4 (9) where, in the solid state, four [ReAg(mu-10-H-eta5-7,8-C2B9H10)(CO)3] units are held together by long interunit B-H right harpoon-up Ag bonds.

An epidemiologic study on carcinoma of the breast following irradiation for benign conditions in infancy and childhood.

To investigate the relationship of irradiation during infancy and childhood to the subsequent development of carcinoma of the breast, 996 eligible patients were studied at Evanston Hospital, Evanston, Illinois, and Northwestern Memorial Hospital, Chicago. This was a case-control study, with those in the control group being selected from concurrent hospital admissions for nonmalignant surgical conditions. A second group consisting of those with benign biopsy results was also studied. The Mantel-Haenszel method of analysis, controlling for age and race, was used to estimate the approximate relative risk of carcinoma of the breast in the irradiated group compared with that for the nonirradiated group. The type of radiation history included radiotherapy for mastitis or enlarged thymus (nine patients), irradiation of the head and neck (69 patients), diagnostic fluoroscopies (ten patients) and miscellaneous irradiation (52 patients) for bursitis, eczema or keloid. Based upon the data obtained from the results of this study and its analysis, we conclude that there is little evidence of increased risk of carcinoma of the breast after irradiation about the head, neck and chest areas for benign conditions in the population being studied herein. Such a risk, if indeed it exists at all for this population, is estimated to be about 10 per cent.

Indicators of response to a mass media CPR recruitment campaign.

Respondents to a mass media cardiopulmonary resuscitation (CPR) recruitment campaign in Harris County, Texas were more likely than non-respondents to be White, female, and under 45 years of age, to have had previous CPR training, experienced an incident in which knowledge of CPR might have been useful, or to have a friend or relative with a relevant medical history. The majority of the respondents were housewives, and professionals or technical workers, particularly in the health field. Findings can be used to identify audiences for future mass media CPR campaigns.

Retrolental fibroplasia: efficacy of vitamin E in a double-blind clinical study of preterm infants.

We performed a double-blind study in 101 preterm infants who weighed less than or equal to 1500 g at birth, who had respiratory distress, and who survived for at least four weeks, to evaluate the efficacy of oral vitamin E in preventing the development of retrolental fibroplasia. Weekly indirect ophthalmologic examinations begun when the infants were three weeks old revealed a significant decrease in the incidence of retrolental fibroplasia greater than or equal to Grade III (P less than 0.03) and greater than or equal to Grade II (P less than 0.05) (McCormick classification) in the 50 infants given 100 mg of vitamin E per kilogram of body weight per day as compared with 51 given 5 mg per kilogram per day (controls). When multivariate analysis was applied to the controls, five risk factors were identified: gestational age, level and duration of administration oxygen, intraventricular hemorrhage, sepsis, and birth weight. When multivariate analysis was applied to both control and treatment groups, the severity of retrolental fibroplasia was found to be significantly reduced in infants given 100 mg of vitamin E (P = 0.012).