Sum-frequency spectroscopic study of Langmuir monolayers of lipids having oppositely charged headgroups.

Sum-frequency vibrational spectroscopy, with the help of surface pressure-area (π-A) isotherm, was used to study lipid Langmuir monolayers composed of molecules with positively and negatively charged headgroups as well as a 1:1 neutral mixture of the two. The spectral profiles of the CH(x) stretch vibrations are similar for all monolayers in the liquid-condensed (LC) phase. They suggest a monolayer structure of closely packed alkyl chains that are nearly all-trans and well oriented along the surface normal. In the liquid-expanded (LE) phase, the spectra of all monolayers appear characteristic of loosely packed chains with significant gauche defects. The OH stretch spectra of interfacial water for both positively and negatively charged monolayers are significantly enhanced in comparison with a neutral water interface, but the phase measurement of SFVS indicates that OH in the two cases points toward the bulk and the interface, respectively. The enhancement results mainly from surface-field-induced polar ordering of interfacial water molecules. For a charge-neutral monolayer composed of an equal number of positively and negatively charged lipid molecules, no such enhancement is observed. This mixed monolayer exhibits a wide range of LC/LE coexistence region extended to very low surface pressure and its CH(x) spectral profile in the coexistence region resembles that of the LC phase. This result suggests that in the LC/LE coexistence region, the mixed monolayer consists of coexisting LC and LE patches in which oppositely charged lipid molecules are homogeneously mixed and dispersed.

Morphology of monolayer Cu x Au 1-x on Cu(001).

Protruding nanostructure is produced in the single layer of Cu(x)Au(1 - x) surface alloy grown on Cu(001) due to the mismatch strain which has been utilized as a template to tune the magnetic anisotropy of overlays recently. The protrusion network was investigated by in situ scanning tunneling microscopy (STM) combined with low energy electron diffraction (LEED) as a function of the stoichiometry. The measurement revealed the structure of the protrusion and its correlation with the composition. Interestingly, we observed a twin-domain phase of the protrusion when the film approaches the fully hetero-epitaxial range.

Structure and charging of hydrophobic material/water interfaces studied by phase-sensitive sum-frequency vibrational spectroscopy.

We have studied the hydrophobic water/octadecyltrichlorosilane (OTS) interface by using the phase-sensitive sum-frequency vibrational spectroscopy (PS-SFVS), and we obtained detailed structural information of the interface at the molecular level. Excess ions emerging at the interface were detected by changes of the surface vibrational spectrum induced by the surface field created by the excess ions. Both hydronium (H(3)O(+)) and hydroxide (OH(-)) ions were found to adsorb at the interface, and so did other negative ions such as Cl(-). By varying the ion concentrations in the bulk water, their adsorption isotherms were measured. It was seen that among the three, OH(-) has the highest adsorption energy, and H(3)O(+) has the lowest; OH(-) also has the highest saturation coverage, and Cl(-) has the lowest. The result shows that even the neat water/OTS interface is not neutral, but charged with OH(-) ions. The result also explains the surprising observation that the isoelectric point appeared at approximately 3.0 when HCl was used to decrease the pH starting from neat water.

Characterization of vibrational resonances of water-vapor interfaces by phase-sensitive sum-frequency spectroscopy.

Phase-sensitive sum-frequency spectroscopy provides correct characterization of vibrational resonances of water-vapor interfaces and allows better identification of interfacial water species contributing to different parts of the spectra. Iodine ions emerging at an interface create a surface field that tends to reorient the more loosely bonded water molecules below the topmost layer.

Magnetocrystalline anisotropy in permalloy revisited.

Permalloy with a body-centered-cubic structure has been grown on GaAs(001) by molecular beam epitaxy. Its magnetism, Curie temperature, and magnetic anisotropy are determined experimentally and compared to those of conventional face-centered-cubic Permalloy. Unexpectedly the vanishing magnetic cubic anisotropy in Permalloy is found to be independent of its atomic structure but depends only upon the stoichiometry of Fe and Ni in the FexNi1-x alloy. This observation is further investigated and confirmed by first-principles electronic band calculations, which help to understand the long-standing issue of why Permalloy should be a soft magnet.

Body-centered-cubic Ni and its magnetic properties.

The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

Individual and familial characteristics of youths involved in street corner gangs in Singapore.

Thirty-six youths involved in street corner gangs in Singapore were compared with 91 age-matched controls on measures of self-esteem, aggression, dysfunctional parenting and parent-adolescent communication. Results revealed that gang youths had lower self-esteem and higher levels of aggression than controls. Of note were the findings that gang youths reported a relative absence of parental abuse and indifference, and experienced less open communication and higher levels of over-control with their mothers, but not fathers. These findings diverge from anticipated familial correlates of antisocial activity in youths and were discussed with reference to cultural factors and their implications on prevention and intervention.

Psychosocial assessment of children with short stature: a preliminary report.

Previous studies that have examined the psychosocial adjustment of children with short stature have often been flawed, for two main reasons: first, a lack of sample homogeneity and, secondly, the measures of adjustment used have been limited in terms of their sensitivity. This paper examines psychological functioning in the following four broad areas: cognition, social behaviour, emotional adjustment and self-concept. A sample of children referred to growth clinics (mean height below -2 SDS) and a comparison group, recruited from the referred childrens' classes at school, were assessed. Children were prepubertal (age range, 6-11 years) and had no organic cause for their short stature. Parent, teacher and peer reports were used in the assessment, which included sociometric measures in the classroom. The children with short stature described themselves as equally well supported as the comparison children in terms of social support by parents, teachers, peers and friends. Peers reported the short children to be well accepted within their class. Compared with control children, there was a trend for short children to be described by their peers as socially better adjusted than average. Teacher and parental accounts revealed significant group differences in terms of reported behaviour, with poorer attention and more thought problems among the children with short stature. Further analysis suggested, however, that their slightly lower IQ than children of normal height (95.8 +/- 18.7 (mean +/- SD) compared with 105 +/- 15.4) accounted for a greater proportion of the variance in these findings than short stature per se. There is little evidence to indicate that short prepubertal children are psychosocially maladjusted.(ABSTRACT TRUNCATED AT 250 WORDS)

Susceptibility of Singapore Chinese schoolgirls to anorexia nervosa--part II. (family factors).

It was found that of a group of 656 GCE 'O' level Chinese Singapore schoolgirls in schools of good academic standing, where pressure was expected to be high, 15 (6%) had high drive for thinness (DT) scores. The families of these latter girls were not perceived to be significantly more enmeshed or rigid than those with low DT scores, and other family functioning was also not significantly different.

Susceptibility of Singapore Chinese schoolgirls to anorexia nervosa--Part I (Psychological factors).

Of 656 GCE "O" level Chinese Singapore schoolgirls, it was found that 56% perceived themselves as being too fat, and 38% had been teased about being overweight. On the Eating Disorders Inventory (EDI), 15 (2%) had a score at the anorectic range. Compared to a group of American undergraduates, Singaporean subjects had no significant difference on the drive for thinness scores, but had significantly higher scores on bulimia, ineffectiveness, body dissatisfaction, interpersonal distress and greater maturity fears. In a population which appears to be susceptible to anorexia nervosa, possible reasons for the low incidence of this disorder is discussed.

Neurobehavioral functions among workers exposed to manganese ore.

The Neurobehavioral Core Test Battery of the World Health Organization was performed on 17 baggers (mean age 36.6 years) in a manganese ore milling plant and 17 referents (mean age 35.7 years). The baggers had a mean exposure period of 7.4 (range 1-14) years with a mean blood manganese concentration of 25.3 (range 15-92.5) micrograms.l-1 [0.46 (0.27-1.68) mumol.l-1]. Of the 37 symptoms related to the nervous system, 20 were more frequently reported by the exposed workers. No significant differences were noted between the nerve conduction of the median and ulnar nerves of the dominant forearm of the two groups. The exposed workers had significantly poorer motor speed, visual scanning, visuomotor coordination, visuomotor and response speed, and visuomotor coordination and steadiness. A clinical examination did not reveal any abnormality among the two groups. Hence a neurobehavioral test battery may be a more sensitive method than a clinical examination in detecting early changes in motor function among manganese-exposed workers.

Drinking problems.

This is a study of 54 patients referred for treatment of drinking problems. They were from two age groups--20 to 39 years and 40 to 59 years. More of the younger patients were referred by their families and older patients by their doctors or other health professionals. The younger patients had a mean duration of 8.2 years of drinking and were more severely dependent on alcohol (higher mean SADQ score). The older patients' mean duration of drinking was 14.1 years and had a lower mean SADQ score. More younger patients had work and family problems, but did not differ significantly from the older patients in alcohol-related physical or mental disabilities.

Work stress and mental distress.

In a study of 14 managers and 25 workers who were referred for psychiatric treatment, the majority suffered from depressive illness (60%) or anxiety neurosis (28%). The main work problem of the managers was conflict with the employers (or directors), but for the workers the main problem was difficulty with fellow workers. The patients' scores on the Work Environment Scale (WES) indicated that the managers felt they had little supervisor support and work pressure was great. However the workers complained of poor peer cohesion but could get on well with the employers, and their work was not too taxing.