Theoretical Study of Spin-dependent Electron Transport in Atomic Fe Nanocontacts

We present theoretical predictions of spintronic transport phenomena that should be observable in ferromagnetic Fe nanocontacts bridged by chains of Fe atoms. We develop appropriate model Hamiltonians based on semi-empirical considerations and the known electronic structure of bulk Fe derived from ab initio density functional calculations. Our model is shown to provide a satisfactory description of the surface properties of Fe nano-clusters as well as bulk properties. Lippmann-Schwinger and Green's function techniques are used together with Landauer theory to predict the current, magneto-resistance, and spin polarization of the current in Fe nanocontacts bridged by atomic chains under applied bias. Unusual device characteristics are predicted including negative magneto-resistance and spin polarization of the current, as well as spin polarization of the current for anti-parallel magnetization of the Fe nanocontacts under moderate applied bias. We explore the effects that stretching the atomic chain has on the magneto-resistance and spin polarization and predict a cross-over regime in which the spin polarization of the current for parallel magnetization of the contacts switches from negative to positive. We find resonant transmission due to dangling bond formation on tip atoms as the chain is stretched through its breaking point to play an important role in spin-dependent transport in this regime. The physical mechanisms underlying the predicted phenomena are discussed.Comment: 13 pages, 6 figures, Accepted for publication in Physical Review

Vaccines : A rapidly evolving technology - Are the hurdles being addressed?

AbstractVaccination usually works in infectious disease, why not in Cancer? Differences in the potency of microbial and cancer antigens, poor initiation of an immune response due to inadequate expression of tumour associated antigens, weak antigens or tolerance induction and local immune suppression were considered. There is a big difference between a therapeutic and a prophylactic vaccine.The opinion of the expert group was that an improved therapeutic efficacy can hardly be expected by further variation of types of vaccines, schedules, routes of administration and adjuvants alone. A major hurdle for developing therapeutic cancer vaccines is the need to effectively monitor the immune response and to be able to use this in an adaptive trial approach.End-points of assessment should be different from standard treatments as complete response or partial responses are usually low, unless combined with other therapies.In order to focus resources to overcome the hurdles of enhancing the therapeutic efficacy of cancer vaccines the Cancer Vaccine Clinical Trial Working Group, representing academia and the pharmaceutical and biotechnology industries has in a consensus process defined 'A clinical development paradigm for cancer vaccines and related biologics'

Culture and the remembering of trauma

This research investigated the influence of culture and posttraumatic stress disorder (PTSD) on global autobiographical remembering (Study 1a) and on the phenomenological properties (Study 1b) and memory-content variables (Study 1c) of trauma-specific autobiographical remembering. Australian, British, and Iranian trauma survivors with and without PTSD completed the Autobiographical Memory Test, Self-Defining Memory Task, and Autobiographical Memory Questionnaire and provided trauma- and negative-memory narratives. We found that there were pan-cultural deficits and distortions in the global autobiographical remembering of participants with PTSD (Study 1a). In addition, the presence of PTSD moderated the usual effect of culture on the phenomenological properties of the trauma memory (Study 1b). Finally, participants with PTSD, regardless of cultural background, had significantly fewer expressions of autonomy and self-determination in their autobiographical remembering than did those without PTSD (Study 1c). The findings suggest that pan-culturally, individuals with PTSD have similar disruptions and distortions in their autobiographical remembering

Research Review: The effects of mindfulness-based interventions on cognition and mental health in children and adolescents - a meta-analysis of randomized controlled trials.

BACKGROUND: Mindfulness based interventions (MBIs) are an increasingly popular way of attempting to improve the behavioural, cognitive and mental health outcomes of children and adolescents, though there is a suggestion that enthusiasm has moved ahead of the evidence base. Most evaluations of MBIs are either uncontrolled or nonrandomized trials. This meta-analysis aims to establish the efficacy of MBIs for children and adolescents in studies that have adopted a randomized, controlled trial (RCT) design. METHODS: A systematic literature search of RCTs of MBIs was conducted up to October 2017. Thirty-three independent studies including 3,666 children and adolescents were included in random effects meta-analyses with outcome measures categorized into cognitive, behavioural and emotional factors. Separate random effects meta-analyses were completed for the seventeen studies (n = 1,762) that used an RCT design with an active control condition. RESULTS: Across all RCTs we found significant positive effects of MBIs, relative to controls, for the outcome categories of Mindfulness, Executive Functioning, Attention, Depression, Anxiety/Stress and Negative Behaviours, with small effect sizes (Cohen's d), ranging from .16 to .30. However, when considering only those RCTs with active control groups, significant benefits of an MBI were restricted to the outcomes of Mindfulness (d = .42), Depression (d = .47) and Anxiety/Stress (d = .18) only. CONCLUSIONS: This meta-analysis reinforces the efficacy of using MBIs for improving the mental health and wellbeing of youth as assessed using the gold standard RCT methodology. Future RCT evaluations should incorporate scaled-up definitive trial designs to further evaluate the robustness of MBIs in youth, with an embedded focus on mechanisms of action

Asymmetrical transfer effects of cognitive bias modification: Modifying attention to threat influences interpretation of emotional ambiguity, but not vice versa.

BACKGROUND AND OBJECTIVES: It is well established that attention bias and interpretation bias each have a key role in the development and continuation of anxiety. How the biases may interact with one another in anxiety is, however, poorly understood. Using cognitive bias modification techniques, the present study examined whether training a more positive interpretation bias or attention bias resulted in transfer of effects to the untrained cognitive domain. Differences in anxiety reactivity to a real-world stressor were also assessed. METHODS: Ninety-seven first year undergraduates who had self-reported anxiety were allocated to one of four groups: attention bias training (n = 24), interpretation bias training (n = 26), control task training (n = 25) and no training (n = 22). Training was computer-based and comprised eight sessions over four weeks. Baseline and follow-up measures of attention and interpretation bias, anxiety and depression were taken. RESULTS: A significant reduction in threat-related attention bias and an increase in positive interpretation bias occurred in the attention bias training group. The interpretation bias training group did not exhibit a significant change in attention bias, only interpretation bias. The effect of attention bias training on interpretation bias was significant as compared with the two control groups. There were no effects on self-report measures. LIMITATIONS: The extent to which interpretive training can modify attentional processing remains unclear. CONCLUSIONS: Findings support the idea that attentional training might have broad cognitive consequences, impacting downstream on interpretive bias. However, they do not fully support a common mechanism hypothesis, as interpretive training did not impact on attentional bias

Effect of fluorination on the crystal and electronic structure of organometallic cyclopentadienyl-phenylenediamino-cobalt complexes

The fluorinated half sandwich complex [CpCoLF] (Cp = cyclopentadiene; LF = o-perfluoro-phenylenediimine; 2F) shows a T-shaped geometry with the LF ligand coplanar with the metallocycle. The molecules are dimerized in a head-to-tail fashion and arranged in a herringbone manner in the crystal packing. The crystal structure of 2F is different from that of the corresponding hydrocarbon compound (2H). Moreover, the differences due to the presence of fluorine atoms are also highlighted by the analysis of the intermolecular contacts, which show that 2F exhibits several F⋯F contacts, as well as aromatic intra-dimer π … π interactions in addition to C–H … π and C–H⋯F contacts. No relevant π … π interactions are observed in the case of 2H. Hirshfeld Surface (HS) analysis also depicted well the differences in the solid state interactions between the different crystal structures. In particular, HS has been useful in highlighting the differences observed between the crystal structure of 2H obtained from Rietveld refinement and that measured on single crystal (2HP and 2HSCH, respectively). The effect of the fluorination on the electronic structure has been investigated also by CV measurements and Density Functional Theory calculations. Both are consistent with a lowering in energy of the molecular orbitals. Data Mining Force Field calculations clearly indicate that the 2HSCH structure is more stable than the 2HP one. These findings can be explained in terms of the energy of the intermolecular interactions. The enhanced stability of the fluorine substitute can be easily explained by the large number of strong interactions involving fluorine atoms

Gray's Model of Personality and Signal Detection Theory: Uncovering New Relationships of Impulsivity and Anxiety with Learning and Performance Criteria

Research in learning and performance using Gray's (1972, 2001) theory of personality has increased substantially in the last decade. Gray's key postulations, that impulsive individuals are most sensitive to reward while anxious people are most sensitive to punishment, have been investigated using a number of learning and performance paradigms. This paper introduces a prgram of research in progress using Signal Detection Theory to examine learning and performance relationships with Gray's model

Supernatants from lymphocytes stimulated with Bacillus Calmette-Guerin can modify the antigenicity of tumours and stimulate allogeneic T-cell responses

BACKGROUND: Reduced expression of class 1 human leucocyte antigens (HLA1) is often a mechanism by which tumours evade surveillance by the host immune system. This is often associated with an immune function that is unable to mount appropriate responses against disease, which can result in a state that favours carcinogenesis. METHODS: In the current study, we have explored the effects of Bacillus Calmette-Guerin (BCG) on the cytokine output of leucocytes, which is a key determinant in generating antitumour action, and have also assessed the effect of these cytokine cocktails on HLA1 expression in solid tumour cell lines. RESULTS: BCG potently activated a broad range of leucocytes, and also enhanced the production of cytokines that were Th(1)-predominant. Supernatants from BCG-treated leucocytes significantly increased the expression of HLA1 on the surface of cancer cell lines, which correlated with increased cytolytic T-cell activity. We also showed that the increased HLA1 expression was associated with activation of intracellular signalling pathways, which was triggered by the increases in the Th(1)-cytokines interferon-γ and tumour necrosis factor-α, as counteracting their effects negated the enhancement. CONCLUSION: These studies reaffirm the role of BCG as a putative immunotherapy through their cytokine-modifying effects on leucocytes and their capacity to enhance tumour visibility

A phase II study of continuous-infusion 5-fluorouracil with cisplatin and epirubicin in inoperable pancreatic cancer.

Carcinomas of the exocrine pancreas respond poorly to most chemotherapy regimens. Recently continuous infusional 5-fluorouracil (200 mg m-(2)day-1) with 3 weekly cisplatin (60 mg m-2) and epirubicin (50 mg m-2) (the ECF regimen) has proven to be an active regimen in gastric and breast cancer and consequently worthy of further study in pancreatic cancer. Thirty-five patients were treated with the ECF regimen as above, of whom 29 were evaluable for response and 32 were evaluable for toxicity. The mean age was 59 years (range 37-75). Sixteen patients had locally advanced disease at presentation and 19 had metastases. Objective tumour responses were documented in five (17.3%) patients who achieved a partial response; in 18 (62%) patients there were no change and six (20.7%) patients progressed on therapy. Patients with either stable disease or partial response had a significantly improved overall survival (median = 253 days) compared with patients who progressed (median = 170 days; P = 0.01). Grade 3/4 (WHO) toxicity (all cycles) included alopecia in 18 (56%) patients, nausea/vomiting in eight (25%) stomatitis in three (9%) and diarrhoea in seven (22%) patients, with rhinorrhoea and excessive lacrimation in one patient each. Neutropenic sepsis occurred in 13 cycles in ten patients, and there was one toxic death due to sepsis. There were eight other episodes of non-neutropenic sepsis requiring hospital admission. Fourteen patients (40%) experienced complications with their Hickman lines, including thrombotic episodes (six patients) or their line falling out (five patients). ECF can prolong survival in patients with locally advanced or metastatic pancreatic cancer who demonstrate a response or stabilisation of their disease. However, this is associated with considerable toxicity