Kinetics of the homogeneous freezing of water.

Rates of homogeneous nucleation of ice in micrometre-sized water droplets are reported. Measurements were made using a new system in which droplets were supported on a hydrophobic substrate and their phase was monitored using optical microscopy as they were cooled at a controlled rate. Our nucleation rates are in agreement, given the quoted uncertainties, with the most recent literature data. However, the level of uncertainty in the rate of homogeneous freezing remains unacceptable given the importance of homogeneous nucleation to cloud formation in the Earth's atmosphere. We go on to use the most recent thermodynamic data for cubic ice (the metastable phase thought to nucleate from supercooled water) to estimate the interfacial energy of the cubic ice-supercooled water interface. We estimate a value of 20.8 +/- 1.2 mJ m(-2) in the temperature range 234.9-236.7 K.

Critical roles for the netrin receptor deleted in colorectal cancer in dopaminergic neuronal precursor migration, axon guidance, and axon arborization.

DCC (deleted in colorectal cancer), a receptor for the axon guidance cue netrin-1, is highly expressed by mesencephalic dopaminergic (DA) neurons during development; however, the contribution of DCC to DA development remains largely uncharacterized. DA neurons in ventral mesencephalic nuclei also express UNC5 homologue netrin receptors from late embryogenesis to adulthood, raising the possibility that DA axons could be attracted or repelled by netrins. Examining newborn dcc null mice, we report that loss of DCC function results in profound alterations of DA circuitry, including DA progenitor cell migration defects, reduced numbers of DA cells in midbrain nuclei, an anomalous DA ventral commissure, malformed DA innervation of the ventral striatum, and reduced DA innervation of the cerebral cortex. Caspase-3 activation was detected in inappropriately localized DA cells, consistent with apoptosis contributing to reduced cell numbers. Dcc heterozygous mice express reduced levels of DCC protein. Although less severely disrupted than dcc nulls, newborn and adult dcc heterozygotes also have fewer DA neurons in ventral mesenscephalic nuclei. Despite the reduced numbers of DA neurons, newborn dcc heterozygotes and nulls exhibit similar DA innervation density as wild-type littermates in the nucleus accumbens core, and adult dcc heterozygotes exhibit increased DA innervation in medial prefrontal cortex. A trend towards increased innervation of medial prefrontal cortex was detected in newborn dcc heterozygotes, but did not reach statistical significance, suggesting that the increase in adult heterozygotes results from enhanced DA arborization during postnatal development. Consistent with the hypothesis that DCC regulates DA axonal projections, disrupting DCC function in culture inhibits netrin-1 induced DA axon extension and axon branching. Furthermore, disrupting DCC function in isolated DA neurons grown as micro-island cultures reduces the number of autaptic synapses per cell. We conclude that DCC regulates appropriate precursor cell migration, axon guidance, and terminal arborization by DA neurons.

Nanomechanical characterization of tissue engineered bone grown on titanium alloy in vitro.

Intensive work has been performed on the characterization of the mechanical properties of mineralised tissues formed in vivo. However, the mechanical properties of bone-like tissue formed in vitro have rarely been characterised. Most research has either focused on compact cortical bone or cancellous bone, whilst leaving woven bone unaddressed. In this study, bone-like mineralised matrix was produced by osteoblasts cultured in vitro on the surface of titanium alloys. The volume of this tissue-engineered bone is so small that the conventional tensile tests or bending tests are implausible. Therefore, nanoindentation techniques which allow the characterization of the test material from the nanoscale to the microscale were adopted. These reveal the apparent elastic modulus and hardness of the calcospherulite crystals (a representative element for woven bone) are 2.35 +/- 0.73 and 0.41 +/- 0.15 GPa, respectively. The nanoscale viscoelasticity of such woven bone was further assessed by dynamic indentation analysis.

Functional polymorphisms in the interleukin-6 and serotonin transporter genes, and depression and fatigue induced by interferon-alpha and ribavirin treatment.

Depression and fatigue are frequent side effects of interferon-alpha (IFN-alpha) treatment, and there is compelling evidence that the inflammatory response system (including interleukin-6, IL-6) and the serotonergic system is important in the pathophysiology of such symptoms. Functional polymorphisms in the promoter region of the IL-6 gene (rs1800795) and serotonin transporter gene (5-HTTLPR) have been identified as regulating these systems. The present study aimed to determine if these polymorphisms were associated with the development of depression and fatigue during IFN-alpha and ribavirin treatment. Ninety-eight Caucasian patients receiving pegylated IFN-alpha and ribavirin treatment for chronic hepatitis C virus at King's College Hospital, London, and Emory University Hospital, Atlanta, participated in this prospective cohort study. Symptoms of depression and fatigue were measured before treatment and at weeks 4, 8, 12 and 24 during treatment. The 'low IL-6' synthesizing genotype (CC) was associated with significantly fewer symptoms of depression (effect size = 0.7 at week 24; F = 9.4, d.f. = 436, P = 0.002). The 'high transcription' serotonin transporter (5-HTT) genotype (LL) was also associated with significantly fewer symptoms of depression, but with a much smaller effect (effect size = 0.2 at week 24; F = 4.5, d.f. = 436, P = 0.03). Neither polymorphisms were associated with symptoms of fatigue (IL-6: F = 1.2, d.f. = 430, P = 0.2; 5-HTT: F = 0.5, d.f. = 430, P = 0.5). The smaller effects of the 5-HTT polymorphism on depression may be explained by an interaction between the genes (F = 5.0, d.f. = 434, P = 0.02): the 'protective' effect of the 5-HTTLPR polymorphism was evident only in the presence of the 'low IL-6' genotype (F = 5.4, d.f. = 64, P = 0.02), not in the presence of the 'high IL-6' genotype (F = 2.2, d.f. = 369, P = 0.1). The association between the IL-6 polymorphism and reduced risk of depressive symptoms confirms the role of the inflammatory response system in the pathophysiology of IFN-alpha-induced depression; in contrast, the effect of the 5-HTT gene was small and perhaps dependent on the status of the inflammatory response.

Derogation of student female athletes who consult a sport psychologist: an alternative perspective on the negative halo effect.

This study attempts to further research female student athletes' perceptions of the sport psychologist and other sport and mental health professionals. 90 British student athletes from 17 different sports completed a two-part questionnaire to examine the potential derogation effect as a result of consulting one of three identified professionals and to explore the perceived definition and role of the sport psychologist. A fictitious selection report of a female field hockey player was presented to subjects with coach, sport psychologist and psychotherapist as the three professionals. It was hypothesised that subjects' recommendations regarding selection would differ depending on the consultant used. No differences were found which suggests the absence of a negative halo effect and that derogation would not occur within this sample group. Definitions and perceived role of the sport psychologist varied with the subjective tone of the responses from participants being mainly positive (74%). These results indicate that this female student athlete sample has a moderated, even a positive, perception of the sport psychologist. A general acceptance of the sport psychologist falls in line with the suggestions of Murstein and Fontaine (1993) concerning a reported increase in acceptance of mental health professionals.

Perceptions of the sport psychologist by female university athletes.

In this study we explored the existence of a favourable attitude towards sport psychologists by female athletes in relation to other sport-oriented and mental health professionals. Ninety female student athletes made judgements of similarity between 11 practitioner terms using the triad method. A rank-order task was also completed, where the 11 professionals were ranked on three expertise variables in sporting, mental and physical issues. The results were analysed using (1) the metric scaling procedure of correspondence analysis, (2) cultural consensus analysis and (3) PROperty FITting analysis. A two-dimensional solution provided the best interpretation of the similarity judgements. The correspondence analysis configuration positioned the sport psychologist centrally between a sport-oriented pair and the cluster of mental health professionals. Participants reported adequate consensus on all three expertise variables, which is consistent with the assumptions of Cultural Consensus Theory. Consistent with earlier research, the three variables were salient in the participants' similarity judgements of sport and mental health professionals. Our results suggest the existence of a more favourable perception of the sport psychologist and a distancing from a direct association with mental health practitioners. However, the centrality of the term may indicate a more cloudy distinction as to where the sport psychologist exists in relation to other professionals.

The use of a single case design to investigate the effect of a pre-performance routine on the water polo penalty shot.

The pre-performance routine (PPR) is proposed to assist the performance of closed skills by enhancing concentration (Crews and Boutcher, 1987) and the recall of optimal psychological and physiological states (Cohn, 1990). A multiple-baseline-across-individuals design was utilised to assess the effect of PPRs on water polo penalty shot performance. Three experienced male water polo players were assisted in designing a personalised multi-component PPR, which was rehearsed in accordance with a training program, and implemented prior to performing penalty shots in simulated trials. Mean performance scores increased for all players between pre and post intervention phases. A Split Middle analysis (White, 1974) further described performance trends and changes. Players 1 and 2 reversed negative baseline trends of -1.071 and -1.031 to positive post intervention trends of +1.011 and +1.011, producing respective positive changes in slope of +1.08 and +1.042. Player 3's baseline trend of +1.008 was reversed post intervention to -1.004, causing a negative change in slope of -1.012. Respective ratios of 1.38, 1.36 and 1.20, suggest a positive change in trend level immediately following PPR introduction. Binomial tests revealed improvements in all participant performances between stages (p<0.001). Results are reviewed in light of previous research and the utilisation of single-subject designs is discussed.

Standardized mortality from cervical cancer: a measure of performance?

A retrospective cohort analysis, using data extracted from clinical notes, examined the validity of standardized mortality ratios (SMRs) for cervical cancer as an indicator of the quality of health services by exploring the mortality at five years of patients presenting with cervical cancer, identifying factors associated with survival, and studying the relationship of those factors to SMRs for the disease. The subjects were 1038 women aged 15-64 registered at the Yorkshire Cancer Registry as having invasive cervical cancer between 1979 and 1983. It was found that independent risk factors for mortality within five years of presentation were stage at diagnosis and smoking habit. Method of treatment had an effect that failed to reach statistical significance. Independent risk factors for late stage at presentation were absence of a history of cervical smear and increasing age. Considerable variation remained unexplained in both models. District SMRs were not related to five-year survival, stage at presentation or screening history. SMRs were related to proportions of smokers. It is concluded that SMRs are subject to considerable influence from a range of unidentified factors, as well as identified risk factors. They are too broad an indicator to be a valid measure of health service performance. The health service's ability to reduce case fatality does not outweigh the effects of incidence and severity. Better indicators would be survival to five years of those presenting at stage II or less and distribution of stage at presentation.