Single ion implantation for single donor devices using Geiger mode detectors

Electronic devices that are designed to use the properties of single atoms such as donors or defects have become a reality with recent demonstrations of donor spectroscopy, single photon emission sources, and magnetic imaging using defect centers in diamond. Improving single ion detector sensitivity is linked to improving control over the straggle of the ion as well as providing more flexibility in lay-out integration with the active region of the single donor device construction zone by allowing ion sensing at potentially greater distances. Using a remotely located passively gated single ion Geiger mode avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency at a distance of >75 um from the center of the collecting junction. This detection efficiency is achieved with sensitivity to ~600 or fewer electron-hole pairs produced by the implanted ion. Ion detectors with this sensitivity and integrated with a thin dielectric, for example 5 nm gate oxide, using low energy Sb implantation would have an end of range straggle of <2.5 nm. Significant reduction in false count probability is achieved by modifying the ion beam set-up to allow for cryogenic operation of the SIGMA detector. Using a detection window of 230 ns at 1 Hz, the probability of a false count was measured as 1E-1 and 1E-4 for operation temperatures of 300K and 77K, respectively. Low temperature operation and reduced false, dark, counts are critical to achieving high confidence in single ion arrival. For the device performance in this work, the confidence is calculated as a probability of >98% for counting one and only one ion for a false count probability of 1E-4 at an average ion number per gated window of 0.015.Comment: 10 pages, 5 figures, submitted to Nanotechnolog

Improving stool sample processing and pyrosequencing for quantifying benzimidazole resistance alleles in Trichuris trichiura and Necator americanus pooled eggs

Background: There is an urgent need for an extensive evaluation of benzimidazole efcacy in humans. In veterinary science, benzimidazole resistance has been mainly associated with three single-nucleotide polymorphisms (SNPs) in the isotype-1 β-tubulin gene. In this study, we optimized the stool sample processing methodology and resistance allele frequency assessment in Trichuris trichiura and Necator americanus anthelmintic-related SNPs by pyrosequenc‑ ing, and standardized it for large-scale benzimidazole efcacy screening use. Methods: Three diferent protocols for stool sample processing were compared in 19 T. trichiura-positive samples: fresh stool, egg concentration using metallic sieves with decreasing pore size, and egg concentration followed by fotation with saturated salt solution. Yield of each protocol was assessed by estimating the load of parasite DNA by real-time PCR. Then, we sequenced a DNA fragment of the β-tubulin gene containing the putative benzimidazole resistance SNPs in T. trichiura and N. americanus. Afterwards, resistant and susceptible-type plasmids were produced and mixed at diferent proportions, simulating diferent resistance levels. These mixtures were used to compare previ‑ ously described pyrosequencing assays with processes newly designed by our own group. Once the stool sample processing and the pyrosequencing methodology was defned, the utility of the protocols was assessed by measur‑ ing the frequencies of putative resistance SNPs in 15 T. trichiura- and 15 N. americanus-positive stool samples. Results: The highest DNA load was provided by egg concentration using metallic sieves with decreasing pore size. Sequencing information of the β-tubulin gene in Mozambican specimens was highly similar to the sequences previ‑ ously reported, for T. trichiura and N. americanus, despite the origin of the sample. When we compared pyrosequenc‑ ing assays using plasmids constructs, primers designed in this study provided the most accurate SNP frequencies. When pooled egg samples were analysed, none of resistant SNPs were observed in T. trichiura, whereas 17% of the resistant SNPs at codon 198 were found in one N. americanus sample

A Negotiated Approach

We propose in this paper a negotiated approach for the bilateral optimal selection problem (BOSP). The problem is defined as a dynamic process that includes two decision makers (DMs) in the selection of the same o#er. A sequence of a prefixed number of n o#ers is observed, one at a time, randomly. The arrival of o#ers does not follow any probability distribution. Hence, each DM should rank the currently observed o#ers among those already observed. Two kinds of ranks follow: relative and absolute ranks [2]

Respecting tribal voices in the development of a gestational diabetes risk reduction preconception counseling program for American Indian/Alaska Native adolescent females: a qualitative study

Abstract Background American Indians and Alaska Natives (AI/AN) are disproportionately affected by adolescent obesity, adolescent pregnancy and gestational diabetes mellitus (GDM). GDM is associated with increased risk for perinatal death, obesity, and subsequent type 2 diabetes (T2D) for the offspring. Moreover, mothers with GDM are also at increased risk for T2D post-partum. Yet few lifestyle interventions exist to reduce GDM risk prior to pregnancy. We describe the process of adapting an existing validated preconception counseling intervention for AI/AN adolescent girls at-risk for GDM and their mothers. Perspectives and recommendations were gathered from a diverse array of stakeholders to assure the new program called Stopping GDM was culturally responsive and developed with tribal voices and perspectives represented. Methods We conducted focus groups and individual interviews with multiple AI/AN stakeholders (n = 55). Focus groups and interviews were digitally recorded, transcribed verbatim, and analyzed using a thematic content approach to construct cross-cutting themes across the focus groups and interviews. Results Four key themes emerged reflecting issues important to planning a reproductive health intervention: 1) Limited awareness, knowledge, and health education resources about GDM; 2) The importance of acknowledging traditional AI/AN values and the diversity of traditions and culture among AI/AN tribes; 3) The need to cultivate healthy decision-making skills and empower girls to make safe and healthy choices; and 4) Lack of communication about reproductive health between AI/AN mothers and daughters and between AI/AN women and health care professionals. Conclusion Findings have been used to inform the cultural tailoring and adaptation of an existing preconception counseling program, originally designed for non-AI/AN adolescent girls with diabetes, for AI/AN adolescents at-risk for GDM in future pregnancies