Vibration-Driven Self-Doping of Dangling-Bond Wires on Si(553)-Au Surfaces.

Density-functional theory is used to explore the Si(553)-Au surface dynamics. Our study (i) reveals a complex two-stage order-disorder phase transition where with rising temperature first the ×3 order along the Si step edges and, subsequently, the ×2 order of the Au chains is lost, (ii) identifies the transient modification of the electron chemical potential during soft Au chain vibrations as instrumental for disorder at the step edge, and (iii) shows that the transition leads to a self-doping of the Si dangling-bond wire at the step edge. The calculations are corroborated by Raman measurements of surface phonon modes and explain previous electron diffraction, scanning tunneling microscopy, and surface transport data.

Adolescent friendships predict later resilient functioning across psychosocial domains in a healthy community cohort.

BACKGROUND: Adolescence is a key time period for the emergence of psychosocial and mental health difficulties. To promote adolescent adaptive ('resilient') psychosocial functioning (PSF), appropriate conceptualisation and quantification of such functioning and its predictors is a crucial first step. Here, we quantify resilient functioning as the degree to which an individual functions better or worse than expected given their self-reported childhood family experiences, and relate this to adolescent family and friendship support. METHOD: We used Principal Component and regression analyses to investigate the relationship between childhood family experiences and PSF (psychiatric symptomatology, personality traits and mental wellbeing) in healthy adolescents (the Neuroscience in Psychiatry Network; N = 2389; ages 14-24). Residuals from the relation between childhood family experiences and PSF reflect resilient functioning; the degree to which an individual is functioning better, or worse, than expected given their childhood family experiences. Next, we relate family and friendship support with resilient functioning both cross-sectionally and 1 year later. RESULTS: Friendship and family support were positive predictors of immediate resilient PSF, with friendship support being the strongest predictor. However, whereas friendship support was a significant positive predictor of later resilient functioning, family support had a negative relationship with later resilient PSF. CONCLUSIONS: We show that friendship support, but not family support, is an important positive predictor of both immediate and later resilient PSF in adolescence and early adulthood. Interventions that promote the skills needed to acquire and sustain adolescent friendships may be crucial in increasing adolescent resilient PSF.

Oxygen and potassium vacancies in KTP calculated from first principles.

The atomic geometry and energetics of oxygen and potassium vacancies in potassium titanyl phosphate (KTP) as well as their electronic and optical properties are studied within density-functional theory in dependence of their charge state. Oxygen vacancies formed between Ti and P are characterized by a negative-U behavior. Their neutral charge state is favored for Fermi levels near the conduction band and gives rise to a defect level in the band gap, which leads to an additional optical absorption peak. In contrast, the two-fold positive charge state, stable for low and intermediate values of the Fermi level, modifies the KTP optical response only slightly. Oxygen vacancies formed between two Ti atoms are two-fold positively charged, while potassium vacancies are negatively charged irrespective of the Fermi level position. In both these cases, the KTP optical response is essentially not affected.

Reproducing movement in the lower extremity using kinesthetic cues of distance and location.

The purpose of this study was to determine if kinesthetic cues of distance or location serve as references in motor memory for reproducing movement in the lower extremity. Thirty normal subjects randomly reproduced criterion movements of 30, 60, and 90 degrees of knee flexion. Starting positions of the criterion and reproduction movements were varied. Reproducing distance required that subjects move the same amplitude as the criterion movement, while reproducing location involved moving to the end position of the criterion movement. Results showed that reproductions based on location were significantly (p less than .05) more accurate than those based on distance cues. Reproductions of 30 and 60 degrees were found to be significantly (p less than .05) less variable than 90-degree reproduction movements. The results were explained according to the theories that have been proposed for retention of kinesthetic distance and location cues in motor memory.

Self-care independence after spinal cord injury: patient and therapist expectations and real life performance.

PURPOSE: To evaluate changes in self-care performance between rehabilitation discharge and 1 year follow-up and to compare patients' and therapists' expectations of self-care independence with actual self-care performance after discharge. METHODS: Prospective study of 55 patients with tetraplegia (21 complete and 34 incomplete) after spinal cord injury (SCI) consecutively admitted to a large urban rehabilitation hospital [injury levels: C4 (5), C5 (33), C6 (9), C7 (4), and C8 (4)]. Data were collected using structured patient interviews, occupational therapists' predictions of patients' self care, and Functional Independence Measure ratings by rehabilitation staff. RESULTS: Analysis showed that for all skills, expectations of patients (mainly African American men) were higher than therapists' predictions, and for 3 of these skills, the differences were statistically significant: eating (Z = -4.47, P < .001 ); bathing (Z = -3.67, P < .001 ); and dressing (Z = -3.16, P = .002). Occupational therapists were better predictors of patients' actual self-care performance at discharge than were patients, although both tended to overestimate patients' performance. There was no evidence that self-care capability declined between discharge and 12 months follow-up, but routine self-care performance varied widely across patient and personal circumstances. CONCLUSIONS: Differential attrition reduced the study sample to 25 SCI patients who were primarily more severely injured African American men. Results showed that these patients maintained their self-care performance 1 year after discharge, but more innovative strategies must be developed to customize self-care retraining to address the unique needs of this patient population.

Complications of surgical treatments for adult flatfoot deformities.

Numerous surgical procedures have been proposed for reconstructing and correcting adult flatfoot deformity. Most procedures include lengthening of the tight Achilles tendon and transferring the FDL tendon to substitute for a dysfunctional PTT. These procedures commonly are combined with a bone procedure to stabilize the correction and correct the pathologic anatomy. All of these procedures have the potential for a range of complications, many of them serious. In general, the clinician should perform the least invasive procedure that decreases pain and improves function. The effects of each procedure and the associated morbidity and complications must be considered.

Total ankle arthroplasty: indications, results, and biomechanical rationale.

Total ankle replacement was developed in the 1970s after the success of total hip and knee arthroplasty. The goal of total ankle arthroplasty is to decrease pain and improve function in the lower limb. Ideally, to be superior to an arthrodesis, the ankle replacement should provide the patient with good patterns of joint motion and the ability to walk and run and should have low complication rates. Unfortunately, total ankle arthroplasty has not been as successful as replacement of other joints. Published studies of early series with greater follow-up show that ankle arthroplasties did not provide lasting pain relief or improve function, and most ultimately failed. During the 1980s, many authors concluded that a total ankle arthroplasty was not warranted because of the generally poor long-term results and the high rate of complications. However, newer second-generation design techniques, innovative operative procedures, and dissatisfaction with the results of ankle arthrodesis have renewed interest in total ankle arthroplasties. This review describes the numerous types of ankle joint replacements, critically reviews the results, and reports on newer prostheses that incorporate more anatomic designs.

Ulnar ray deficiency.

Longitudinal deficiencies of the ulna are very rare deformities. Despite the cosmetic appearance, patients usually have very functional extremities. The limb function has been adversely related to ipsilateral hand deformities and radiohumeral synostosis. Surgical treatment should be aimed at correcting such deformities. It is prudent to wait and observe patients before definitive wrist or forearm treatment is recommended.

What to do about flat heads: preventing and treating positional occipital flattening.

Across Canada there has been an increasing incidence of positional occipital flattening. This increase appears to be related to the recent change in infant sleep position to supine. In this paper, two patterns of positional occipital flattening, positional plagiocephaly and positional brachycephaly, are outlined. While there is no evidence of long-term developmental or neurological problems that result from positional occipital flattening, the infant's appearance can be distressing to parents who will then seek treatment. Prevention of positional occipital flattening requires a community approach with timely screening and early intervention should the infant's skull appear flat. Treatment involves repositioning the infant coupled with physiotherapy if there is neck muscle involvement. Should repositioning alone be ineffective, a helmet or headband program may be implemented. Neuroscience nurses can work in partnership with the community to ensure prevention strategies are implemented and timely interventions initiated.

What is a missed dose? Implications for construct validity and patient adherence.

The construct 'missed dose' is central to many assessments of medication adherence. However, few studies have investigated how patients or clinicians conceptualize missed doses or the extent of the concordance or discordance between clinicians and patients. To address this gap we conducted semi-structured interviews with 45 sero-positive African American adults taking HAART and 17 of their clinicians. Results reveal large variability in missed dose conceptions among both patients and physicians and significant differences between the two groups. Overall, patients reported a stricter definition of missed dose than did clinicians. Fifty-five percent of patients thought that a pill-taking delay of six hours beyond the prescribed dosing time constituted a missed dose, by comparison, only one physician agreed with this assessment. More than one-third of patients thought that the proper response to a missed dose would be to skip it altogether, but only about 12% of clinicians agreed. These findings have implications for the construct validity of self-report measures of adherence, for patient adherence behaviours based on missed dose conceptions and for patient-physician relationships and communication within the clinical environment.

Contrast detection and discrimination in young and older adults.

PURPOSE: To determine if age differences in contrast detection thresholds extend to suprathreshold contrast discrimination. METHODS: Psychophysical contrast detection and discrimination thresholds were determined in 56 adults ranging in age from 22 to 72 years. In experiment 1, thresholds were measured using a two-interval forced-choice procedure across a range of pedestal grating contrasts. In experiment 2, detection and discrimination thresholds were measured at two spatial frequencies and two luminance levels. RESULTS: When normalized to the contrast detection threshold, contrast discrimination thresholds were similar in young and older adults. This result is akin to previous findings for clinical patients with contrast detection deficits. In addition, contrast discrimination in the elderly is independent of mean display luminance as has been found in young adults. CONCLUSIONS: Normalized contrast discrimination functions have the same shape in young and older adults and show no change with a 4-fold reduction in luminance.

Respite care users who have children with chronic conditions: are they getting a break?

Caregiving for children with chronic illness and disabilities by family caregivers at home is widely recognized as an optimal choice for the child and family. To promote and maintain the health of the child, primary caregiver, and entire family, respite care has been established as an important caregiving resource. The purpose of this study was to describe primary caregivers' respite service use, perceptions of actual respite, and barriers to respite and respite care. A descriptive design with written survey methods and convenience sampling techniques was used. We found that, despite accessing a variety of respite services, the participants perceived limited actual respite from caregiving. Increased preparation of respite care providers and revision of available services may be means for achieving respite for primary caregivers and their families.

On the functional significance of the polypeptide PsbY for photosynthetic water oxidation in the cyanobacterium Synechocystis sp. strain PCC 6803.

Recent investigations have revealed that the cyanobacterial photosystem II complex contains more than 26 polypeptides. The functions of most of the low-molecular-mass polypeptides, including PsbY, have remained elusive. Here we present a comparative characterization of the wild-type Synechocystis sp. strain PCC 6803 and a PsbY-free mutant derived from it. The results show that growth of the PsbY-free mutant was comparable to that of the wild-type when cells were cultivated in complete BG11 medium or under initial manganese or chloride limitation, and when illuminated at 20 or 200 microE m(-2) s(-1). However, while growth rates of both the wild-type and the PsbY-free mutant were reduced when cells were cultivated in BG11 medium in the absence of calcium, the reduction was significantly greater in the case of the PsbY-free mutant. This differential effect on growth of the mutant relative to the wild-type in CaCl(2) deficient medium was detected when the cells were illuminated with high-intensity light (200 microE m(-2) s(-1)) but not when light levels were lower (20 microE m(-2) s(-1)). The differential effect on growth was associated with lower O(2) evolving activity in the mutant compared to wild-type cells. The mutant was also found to be more sensitive to photoinhibition, and showed an altered pattern of fluorescence emission at 77 K. In addition, mass spectrometric analysis revealed that PsbY-free cells cultivated in CaCl(2) sufficient medium (in which no growth reduction was observed) had a significantly higher O(2) evolution from hydrogen peroxide and a lower O(2) evolution from water under flash light illumination than wild-type cells. These results imply that photosystem II is slightly impaired in the PsbY-free mutant, and that the mutant is less capable of coping with low levels of Ca(2+) than the wild-type.