Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite Family

We describe the crystal growth, crystal structure, and basic electrical properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material differs from other Tetradymites studied as topological insulators due to the increased ionic character that arises from its significant S content. Bi2Te1.6S1.4 forms high quality crystals from the melt and is the S-rich limit of the ternary Bi-Te-S {\gamma}-Tetradymite phase at the melting point. The native material is n-type with a low resistivity; Sb substitution, with adjustment of the Te to S ratio, results in a crossover to p-type and resistive behavior at low temperatures. Angle resolved photoemission study shows that topological surface states are present, with the Dirac point more exposed than it is in Bi2Te3 and similar to that seen in Bi2Te2Se. Single crystal structure determination indicates that the S in the outer chalcogen layers is closer to the Bi than the Te, and therefore that the layers supporting the surface states are corrugated on the atomic scale.Comment: To be published in Physical Review B Rapid Communications 16 douuble spaced pages. 4 figures 1 tabl

HIV and HTLV-I antibody studies: pregnant women in the 1960s, patients with AIDS, homosexuals, and individuals with tropical spastic paraparesis.

To investigate the possible occurrence of human immunodeficiency virus (HIV) or human T-cell lymphotropic virus, type I (HTLV-I) infections in the United States prior to 1979-1981, when acquired immune deficiency syndrome (AIDS) was first recognized, we tested sera from 310 pregnant women who participated in the Collaborative Perinatal Project during the period 1959-1964 for HIV and HTLV-I antibody. These samples included sera from 53 pregnant women who were intravenous drug users. The remainder were from women who had cervical epithelial abnormalities, who developed cervical carcinomas, who had had children with erythroblastosis fetalis, who had had children that developed malignant neoplasms early in life, or normal pregnant women. None of the 310 women had confirmed HIV or HTLV-I antibody. The rate of false-positive reactions with the HIV enzyme-linked immunosorbent assay (ELISA) antibody test in these long-frozen samples was similar to that observed in fresh sera. HIV antibody was detected in homosexual patients with AIDS; HTLV-I antibody was not detected in any of these sera. HTLV-I antibody was detected in 17 of 20 patients with tropical spastic paraparesis (TSP) and in two of seven patients with other neurological diseases diagnosed as transverse myelopathy and multiple sclerosis, and in none of nine normal controls; HIV antibody was not detected in any of these sera patients. Thus, we conclude that there was no serological evidence of infection with HIV or HTLV-I in the pregnant women studied; however, HIV antibody was present in all AIDS patients tested, and HTLV-I antibody was found in the majority of patients with TSP

Advanced Differentiated Thyroid Cancer. A Complex Condition Needing a Tailored Approach

Differentiated thyroid cancers (DTCs) are slow-growing malignant tumours, including papillary and follicular carcinomas. Overall, prognosis is good, although it tends to worsen when local invasion occurs with bulky cervical nodes, or in the case of distant metastases. Surgery represents the main treatment for DTCs. However, radical excision is challenging and significant morbidity and functional loss can follow the treatment of the more advanced forms. Literature on advanced thyroid tumours, both differentiated and undifferentiated, does not provide clear and specific guidelines. This emerges the need for a tailored and multidisciplinary approach. In the present study, we report our single-centre experience of 111 advanced (local, regional, and distant) DTCs, investigating the rate of radical excision, peri-procedural and post-procedural complications, quality of life, persistence, recurrence rates, and survival rates. Results are critically appraised and compared to the existing published evidence review

Cholesterol Metabolism Is Required for Intracellular Hedgehog Signal Transduction In Vivo

We describe the rudolph mouse, a mutant with striking defects in both central nervous system and skeletal development. Rudolph is an allele of the cholesterol biosynthetic enzyme, hydroxysteroid (17-beta) dehydrogenase 7, which is an intriguing finding given the recent implication of oxysterols in mediating intracellular Hedgehog (Hh) signaling. We see an abnormal sterol profile and decreased Hh target gene induction in the rudolph mutant, both in vivo and in vitro. Reduced Hh signaling has been proposed to contribute to the phenotypes of congenital diseases of cholesterol metabolism. Recent in vitro and pharmacological data also indicate a requirement for intracellular cholesterol synthesis for proper regulation of Hh activity via Smoothened. The data presented here are the first in vivo genetic evidence supporting both of these hypotheses, revealing a role for embryonic cholesterol metabolism in both CNS development and normal Hh signaling

Citizen science breathes new life into participatory agricultural research : A review

Participatory research can improve the efficiency, effectiveness, and scope of research processes, and foster social inclusion, empowerment and sustainability. Yet despite four decades of agricultural research institutions exploring and developing methods for participatory research, it has never become mainstream in the agricultural technology development cycle. Citizen science promises an innovative approach to participation in research, using the unique facilities of new digital technologies, but its potential in agricultural research participation has not been systematically probed. To this end, we conducted a critical literature review. We found that citizen science opens up four opportunities for creatively reshaping research: i) new possibilities for interdisciplinary collaboration, ii) rethinking configurations of socio-computational systems, iii) research on democratization of science more broadly, and iv) new accountabilities. Citizen science also brings a fresh perspective on the barriers to institutionalizing participation in the agricultural sciences. Specifically, we show how citizen science can reconfigure cost-motivation-accountability combinations using digital tools, open up a larger conceptual space of experimentation, and stimulate new collaborations. With appropriate and persistent institutional support and investment, citizen science can therefore have a lasting impact on how agricultural science engages with farming communities and wider society, and more fully realize the promises of participation

Male-specific deficits in natural reward learning in a mouse model of neurodevelopmental disorders

Neurodevelopmental disorders, including autism spectrum disorders, are highly male biased, but the underpinnings of this are unknown. Striatal dysfunction has been strongly implicated in the pathophysiology of neurodevelopmental disorders, raising the question of whether there are sex differences in how the striatum is impacted by genetic risk factors linked to neurodevelopmental disorders. Here we report male-specific deficits in striatal function important to reward learning in a mouse model of 16p11.2 hemideletion, a genetic mutation that is strongly associated with the risk of neurodevelopmental disorders, particularly autism and attention-deficit hyperactivity disorder. We find that male, but not female, 16p11.2 deletion animals show impairments in reward-directed learning and maintaining motivation to work for rewards. Male, but not female, deletion animals overexpress mRNA for dopamine receptor 2 and adenosine receptor 2a in the striatum, markers of medium spiny neurons signaling via the indirect pathway, associated with behavioral inhibition. Both sexes show a 50% reduction of mRNA levels of the genes located within the 16p11.2 region in the striatum, including the kinase extracellular-signal related kinase 1 (ERK1). However, hemideletion males show increased activation in the striatum for ERK1, both at baseline and in response to sucrose, a signaling change associated with decreased striatal plasticity. This increase in ERK1 phosphorylation is coupled with a decrease in the abundance of the ERK phosphatase striatum-enriched protein-tyrosine phosphatase in hemideletion males. In contrast, females do not show activation of ERK1 in response to sucrose, but notably hemideletion females show elevated protein levels for ERK1 as well as the related kinase ERK2 over what would be predicted by mRNA levels. These data indicate profound sex differences in the impact of a genetic lesion linked with neurodevelopmental disorders, including mechanisms of male-specific vulnerability and female-specific resilience impacting intracellular signaling in the brain