Global and local contributions to the optical specification of time to contact: Observer sensitivity to composite tau

First-order time remaining until a moving observer will pass an environmental element is optically specified in two different ways. The specification provided by global tau (based on the pattern of change of angular bearing) requires that the element is stationary and that the direction of motion is accurately detected, whereas the specification provided by composite tau (based on the patterns of change of optical size and optical distance) does not require either of these. We obtained converging evidence,for our hypothesis. that observers are sensitive to composite tau in four experiments involving, relative judgments of, time to, passage with forced-choice methodology. Discrimination performance was enhanced in the presence of a local expansion component, while being unaffected when the detection of the direction of heading was impaired. Observers relied on the information carried in composite tau rather than on the information carried in its constituent components. Finally, performance was similar under conditions of observer motion and conditions of object motion. Because composite tau specifies first-order time remaining for a large number of situations, the different ways in which it may be detected are discussed.

Tight-binding simulation of current-carrying nanostructures

The tight-binding (TB) approach to the modelling of electrical conduction in small structures is introduced. Different equivalent forms of the TB expression for the electrical current in a nanoscale junction are derived. The use of the formalism to calculate the current density and local potential is illustrated by model examples. A first-principles time-dependent TB formalism for calculating current-induced forces and the dynamical response of atoms is presented. An earlier expression for current-induced forces under steady-state conditions is generalized beyond local charge neutrality and beyond orthogonal TB. Future directions in the modelling of power dissipation and local heating in nanoscale conductors are discussed.

Information used in detecting upcoming collisions.

In four experiments we examined the nature of the information used in judging whether events would or would not give rise to a collision in the near future. Observers were tested in situations depicting approaches between two objects (lateral approaches) and approaches between an object and the point of observation (head-on approaches), with objects moving according to constant deceleration or sinusoidal deceleration patterns. Judgments were found to be based, to a large extent, on the (in)sufficiency of current deceleration to avoid upcoming collision, as specified optically by tau-dot (tau over dot). However, the information specified, by tau (tau), that is the current (first-order) time remaining until contact, was also found to play a significant role. We deduce that judgment of upcoming collision is based on the detection Of T and its evolution over time, suggesting that observers are sensitive to Deltatau rather than to tau over dot itself.

How to estimate scavenger fish abundance using baited camera data

Baited cameras are often used for abundance estimation wherever alternative techniques are precluded, e.g. in abyssal systems and areas such as reefs. This method has thus far used models of the arrival process that are deterministic and, therefore, permit no estimate of precision.
Furthermore, errors due to multiple counting of fish and missing those not seen by the camera have restricted the technique to using only the time of first arrival, leaving a lot of data redundant. Here, we reformulate the arrival process using a stochastic model, which allows the precision of abundance
estimates to be quantified. Assuming a non-gregarious, cross-current-scavenging fish, we show that prediction of abundance from first arrival time is extremely uncertain. Using example data, we show
that simple regression-based prediction from the initial (rising) slope of numbers at the bait gives good precision, accepting certain assumptions. The most precise abundance estimates were obtained
by including the declining phase of the time series, using a simple model of departures, and taking account of scavengers beyond the camera’s view, using a hidden Markov model.

Effect of coinfection with genogroup 1 porcine torque teno virus on porcine circovirus type 2-associated postweaning multisystemic wasting syndrome in gnotobiotic pigs

Objective—To determine whether genogroup 1 porcine torque teno virus (g1-TTV) can potentiate clinical disease associated with porcine circovirus type 2 (PCV2).

Sample population—33 gnotobiotic baby pigs.

Procedures—Pigs were allocated into 7 groups: group A, 5 uninoculated control pigs from 3 litters; group B, 4 pigs oronasally inoculated with PCV2 alone; group C, 4 pigs inoculated IP with first-passage g1-TTV alone; group D, 4 pigs inoculated IP with fourth-passage g1-TTV alone; group E, 6 pigs inoculated IP with first-passage g1-TTV and then oronasally inoculated with PCV2 7 days later; group F, 6 pigs inoculated IP with fourth-passage g1-TTV and then inoculated oronasally with PCV2 7 days later; and group G, 4 pigs inoculated oro-nasally with PCV2 and then inoculated IP with fourth-passage g1-TTV 7 days later.

Results—6 of 12 pigs inoculated with g1-TTV prior to PCV2 developed acute onset of postweaning multisystemic wasting syndrome (PMWS). None of the pigs inoculated with g1-TTV alone or PCV2 alone or that were challenge exposed to g1-TTV after establishment of infection with PCV2 developed clinical illness. Uninoculated control pigs remained healthy.

Conclusions and Clinical Relevance—These data implicated g1-TTV as another viral infection that facilitates PCV2-induced PMWS. This raises the possibility that torque teno viruses in swine may contribute to disease expression currently associated with only a single infectious agent.

The first time: young people and sex in Northern Ireland.

The sexual health of people, particularly young people, in Northern Ireland is currently poor. Yet there has been little research conducted on sexual attitudes and lifestyles. This paper is based on data from the first ever major research project in this field in Northern Ireland. Using quantitative and qualitative methods, it targeted young people aged 14-25. A combination of a self-administered survey questionnaire, focus group discussions and one-to-one interviews was found to be most suitable for the collection of sensitive data on sexuality in a country where the social and moral climate had previously prevented studies of this nature. Information was collected on sexual attitudes and behaviour generally. This paper focuses on one crucial issue: the age of first sexual encounter. It explores the attitudes of young people to that experience and the use of contraception. Many of the findings match those of similar large-scale surveys in England and Wales, including the modal age of first sexual encounter and the influence of peer pressure on decision-making about first sex. There were significant gender differences in both behaviour and attitudes. It is hoped that the research results will influence future education and health policy, which has all too often been based on ignorance.

Peer-mentoring for first-time mothers from areas of socio-economic disadvantage: a qualitative study within a randomised controlled trial

Objective: To explore the difficulties experienced by lay-workers, women and health professionals involved in a peer-mentoring programme for first-time mothers living in socially disadvantaged areas. Design: Qualitative study; semi-structured interviews with lay-worker peer-mentoring programme participants at two separate stages of the programme (antenatal and postnatal). Setting: Community based. Participants: 11 women receiving peer-mentoring support (from first hospital antenatal visit to one year postnatal); 11 lay-workers; 2 research midwives. Results: Lay-workers had difficulty initiating contact with women and failure to establish contact affected their morale adversely. They felt that women understood their intended role poorly and attempted to develop relationships with them by sharing personal experiences and offering friendship; women who participated in the programme appreciated this. Developing a peer-mentor relationship was difficult if women lacked interest in the programme or in continuing contact. External influences on peer-mentoring uptake and delivery included family and friends who could prevent or encourage women’s participation and cause difficulties for the lay-worker both in delivering support and arranging follow-up. Lay-workers providing support to women from a different ethnic background experienced difficulties relating to both language and culture: these were perceived to affect peer-mentor relationships adversely. Major personal difficulties for lay-workers related to time constraints in reconciling mentoring requirements with demands of family and other work. Informing midwives of these difficulties helped identify solutions through training and ongoing professional support for the lay-workers. Conclusions: Lay-worker peer support is appreciated by first time mothers but difficulties in initiating contact, developing peer-mentor relationships and external influences such as family, ethnicity and time constraints are relevant to poor uptake and high staff turnover. In developing peer support programmes, awareness of potential difficulties and of how professional support can help resolve these should improve uptake and thus optimise the evaluations of their effectiveness.

A RCT of peer-mentoring for first-time mothers in socially disadvantaged areas (the moments study)

Objective: Interventions to reduce health inequalities for young children and their mothers are important: involving peers is recommended, but evidence of value for this approach is limited. The authors aimed to examine the effect of an innovative tailored peer-mentoring programme, based on perceived needs, for first-time mothers in socio-economically deprived communities. Design: Randomised controlled trial; parallel qualitative study with purposive samples using semistructured interviews. Setting: Socio-economically disadvantaged areas, Belfast. Participants: Primigravidae, aged 16-30 years, without significant co-morbidity. Intervention: Peer-mentoring by a lay-worker fortnightly during pregnancy and monthly for the following year, tailored to participants' wishes (home visits/telephone contacts), additional to usual care. Main outcome measures: Infant psychomotor and mental development (Bayley Scales of Infant Development (BSID-II)) at 1 year, assessed by an observer blinded to group allocation. Mothers' health at 1 year postnatal (SF-36). Results: Of 534 women invited, 343(64%) participated; 85%, with their children, completed outcome assessments (140 of 172 intervention; 152 of 171 controls). Intervention and control groups did not differ in BSID-II psychomotor (mean difference 1.64, 95% CI -0.94 to 4.21) or mental (-0.81, -2.78 to 1.16) scores, nor SF-36 physical functioning (-5.4, -11.6 to 0.7) or mental health (-1.8, -6.1 to 2.6). Women valued advice given in context of personal experience of child-rearing. Mentors gained health-related knowledge, personal skills and new employment opportunities. Conclusions: Despite possible longer-term social advantage, this peer-mentoring programme showed no benefit for infant development or maternal health at 1 year. Further rigorous evaluation of important outcomes of complex interventions promoting health for children in socially disadvantaged communities is warranted. Trial registration no: ISRCTN 55055030.

Combinations of ZAP-70, CD38 and IGHV mutational status as predictors of time to first treatment in CLL.

ZAP-70, CD38 and IGHV mutations have all been reported to have prognostic impact in chronic lymphocytic leukemia (CLL), both individually and in paired combinations. We aimed to determine whether the combination of all three factors provided more refined prognostic information concerning the treatment-free interval (TFI) from diagnosis. ZAP-70, CD38 and IGHV mutations were evaluated in 142 patients. Combining all three factors, the ZAP-70-/CD38-/Mutated group showed the longest median TFI (62 months, n = 37), ZAP-70+/CD38+/Unmutated cases the shortest (11 months, n = 37) and cases discordant for > or = 1 factor, an intermediate TFI (27 months, n = 68) (p = 0.006). Analysis of discordant cases revealed values that were otherwise masked when measuring single prognostic factors. The presence or absence of cytogenetic abnormalities did not explain the variability among discordant cases. Simultaneous analysis of ZAP-70, CD38 and IGHV mutations in CLL provides more discriminatory prediction of TFI than any factor alone.

Sexual behaviour of young people in Northern Ireland: First sexual experience

Two National Surveys of Sexual Attitudes and Lifestyles in Britain (Natsal) were conducted, one in 1990 and one in 2000. Northern Ireland was excluded from both studies. Now, for the first time, comparable data about sexual attitudes and lifestyles of young people (14- to 25-year-olds) in Northern Ireland are available. Data were collected through self-administered questionnaires, one-to-one interviews and focus-group discussions. As in Natsal 1990 and 2000, young people were asked about their sexual attitudes towards sex, experiences of sex education, knowledge of sexually transmitted infections (STIs) and, if sexually active, about the circumstances in which sexual intercourse occurred. A total of 1013 young people in the target age group completed the self-administered questionnaire. Young people in Northern Ireland do not differ significantly from their counterparts in Britain in terms of sexual lifestyles and attitudes. Some 53.3% of all respondents reported that they had had sexual intercourse. Condom use at first sex was reported by 64% of sexually active respondents; 27.4% said they used no contraception; 26.7% of all respondents said they had sex before age 16. Respondents who first had sex when they were 15 or 16 years were more likely than other respondents to say that 'being drunk' was the main reason why intercourse occurred. Peer pressure to engage in sex was more prevalent among males than females. Young people in Northern Ireland regard friends as their most important source of sex education. School is the second most important source but most respondents wanted more sex education in school. It is important that it is needs focused and includes potentially sensitive and contentious information.

First EXAFS studies on aurophilic interactions in solution

EXAFS has been used to directly show the existence of Au…Au interactions in dissolved Au(I) complexes for the first time; the information has been used to understand the optical properties of these materials.

Surface alloying and mixing at the Mn/Fe(001) interface: Real-time photoelectron spectroscopy and modified embedded atom simulations

Structural and magnetic properties of thin Mn films on the Fe(001) surface have been investigated by a combination of photoelectron spectroscopy and computer simulation in the temperature range 300 Kless than or equal toTless than or equal to750 K. Room-temperature as deposited Mn overlayers are found to be ferromagnetic up to 2.5-monolayer (ML) coverage, with a magnetic moment parallel to that of the iron substrate. The Mn atomic moment decreases with increasing coverage, and thicker samples (4-ML and 4.5-ML coverage) are antiferromagnetic. Photoemission measurements performed while the system temperature is rising at constant rate (dT/dtsimilar to0.5 K/s) detect the first signs of Mn-Fe interdiffusion at T=450 K, and reveal a broad temperature range (610 Kless than or equal toTless than or equal to680 K) in which the interface appears to be stable. Interdiffusion resumes at Tgreater than or equal to680 K. Molecular dynamics and Monte Carlo simulations allow us to attribute the stability plateau at 610 Kless than or equal toTless than or equal to680 K to the formation of a single-layer MnFe surface alloy with a 2x2 unit cell and a checkerboard distribution of Mn and Fe atoms. X-ray-absorption spectroscopy and analysis of the dichroic signal show that the alloy has a ferromagnetic spin structure, collinear with that of the substrate. The magnetic moments of Mn and Fe atoms in the alloy are estimated to be 0.8mu(B) and 1.1mu(B), respectively.