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Mississauga, Canada

McGee W.K.,Oregon National Primate Research Center | McGee W.K.,Oregon Health And Science University | Bishop C.V.,Oregon National Primate Research Center | Bahar A.,Oregon Health And Science University | And 9 more authors.
Human Reproduction

BACKGROUND: Hyperandrogenemia is associated with several clinical disorders in which both reproductive dysfunction and metabolic changes may coexist [i.e. polycystic ovary syndrome (PCOS), obesity and congenital adrenal hyperplasia]. Moreover, there is growing evidence that the elevated levels of circulating androgens in obese girls may lead to an increased neuroendocrine drive to the reproductive axis, similar to that associated with PCOS. METHODS: To test whether androgen exposure in the childhood and adolescent period could lead to pubertal alterations in LH secretory patterns, female rhesus monkeys received subcutaneous testosterone implants prepubertally beginning at 1 year of age, maintaining a 3.7-fold increase (P = 0.001) in circulating testosterone levels over cholesterol-implant controls (n = 6/group) into the post-pubertal period. In early adulthood, pulsatile secretion of LH was measured over 12 h during the early follicular phase of a menstrual cycle, and responsiveness of the pituitary to gonadotrophin-releasing hormone was determined. In addition, ultrasounds were performed to assess ovarian morphology and glucose tolerance testing was performed to assess insulin sensitivity. RESULTS: The timing of menarche was similar between groups. Testosterone-treated animals had a significantly greater LH pulse frequency during the early follicular phase compared with controls (P = 0.039) when measured at 5 years of age. There was a larger LH response to GnRH when testosterone-treated animals were 4 years of age (P = 0.042), but not when the animals were 5 years old (P = 0.57). No differences were seen in insulin sensitivity or ovarian morphology, and the groups showed similar rates of ovulation in early adulthood. CONCLUSIONS: Exposure to increased levels of androgens over the course of pubertal development appears to trigger physiological changes in the neural drive to the reproductive axis that resemble those of obese hyperandrogenemic girls in early adulthood and are characteristic of PCOS. © The Author 2011. Published by Oxford University Press. All rights reserved. Source

Parvin S.,Curtin University Australia | Hussain F.K.,Lab Tech Support | Hussain O.K.,Curtin University Australia | Han S.,Curtin University Australia | And 2 more authors.
Journal of Network and Computer Applications

Recent advancements in wireless communication are creating a spectrum shortage problem on a daily basis. Recently, Cognitive Radio (CR), a novel technology, has attempted to minimize this problem by dynamically using the free spectrum in wireless communications and mobile computing. Cognitive radio networks (CRNs) can be formed using cognitive radios by extending the radio link features to network layer functions. The objective of CRN architecture is to improve the whole network operation to fulfil the users demands anytime and anywhere, through accessing CRNs in a more efficient way, rather than by just linking spectral efficiency. CRNs are more flexible and exposed to wireless networks compared with other traditional radio networks. Hence, there are many security threats to CRNs, more so than other traditional radio environments. The unique characteristics of CRNs make security more challenging. Several crucial issues have not yet been investigated in the area of security for CRNs. A typical public key infrastructure (PKI) scheme which achieves secure routing and other purposes in typical ad hoc networks is not enough to guarantee the security of CRNs under limited communication and computation resources. However, there has been increasing research attention on security threats caused specifically by CR techniques and special characteristics of CR in CRNs. Therefore, in this research, a survey of CRNs and their architectures and security issues has been carried out in a broad way in this paper. © 2012 Elsevier Ltd. All rights reserved. Source

Morgado E.,University of Veracruz | Meza E.,University of Veracruz | Gordon M.K.,University of Delaware | Pau F.K.Y.,Lab Tech Support | And 2 more authors.
Hormones and Behavior

Rabbit does nurse their litter once every 24. h during the night. We hypothesized that corticosterone, ghrelin, leptin, and metabolites such as glucose, liver glycogen, and free fatty acids could be affected in the pups by the time at which does nurse them. Therefore, we measured these parameters in pups nursed at 02:00. h (nighttime for the doe) to compare them with results from a previous study where does nursed at 10:00. h, during daytime. From postnatal day 7, pups were sacrificed either just before their scheduled time of nursing or at 4, 8, 12, 16, or 20. h after nursing (n=6 at each time point); additional pups were sacrificed at 4. h intervals between 48 and 72. h after nursing to study the persistence of oscillations during fasting. All pups developed locomotor anticipatory activity to nursing. Corticosterone, ghrelin, and free fatty acids exhibited a rhythm that persisted in fasted pups. Glucose concentrations were lower in fasted than in nursed pups, and glycogen was only detected in nursed subjects. Leptin values were stable and low in nursed subjects but increased significantly in fasted subjects up to 72. h after the expected nursing time. The rhythm of ghrelin persisted during fasting, contrary to our previous findings in pups nursed during daytime (i.e., outside the natural time of nursing for this species). Therefore, in 7-day-old rabbit pups, night nursing is a strong zeitgeber for corticosterone, ghrelin, free fatty acids, and energy metabolites but not for leptin. © 2010 Elsevier Inc. Source

Sousa M.R.,University of Porto | Gama J.,University of Porto | Gama J.,Lab Tech Support | Brandao E.,University of Porto
Expert Systems with Applications

We propose a new dynamic modeling framework for credit risk assessment that extends the prevailing credit scoring models built upon historical data static settings. The driving idea mimics the principle of films, by composing the model with a sequence of snapshots, rather than a single photograph. In doing so, the dynamic modeling consists of sequential learning from the new incoming data. A key contribution is provided by the insight that different amounts of memory can be explored concurrently. Memory refers to the amount of historic data being used for estimation. This is important in the credit risk area, which often seems to undergo shocks. During a shock, limited memory is important. Other times, a larger memory has merit. An application to a real-world financial dataset of credit cards from a financial institution in Brazil illustrates our methodology, which is able to consistently outperform the static modeling schema. © 2015 Elsevier Ltd. Source

Wang N.,Tianjin Polytechnic University | Li G.,Tianjin Polytechnic University | Zhang X.,Tianjin Polytechnic University | Qi X.,Lab Tech Support
RSC Advances

A dodecylbenzene sulfonic acid (DBSA) doped-polyaniline (PANI) coated conductive viscose fiber (VCF) was prepared by chemical oxidation polymerization in an ethanol/water solution. Fourier transform infrared spectra (FTIR) and XPS proved that an interaction between PANI and VCF formed in the PANI/VCF composites. The mild treatment did not result in the oxidation and degradation of VCF detected by thermal gravimetric analysis (TGA) and mechanical testing. Moreover, the influence of the reaction conditions including reaction time, aniline monomer (ANI) concentration, ammonium persulfate (APS) concentration and DBSA concentration on the morphology and the conductivity of the PANI/VCF composites were investigated in detail. The orthogonal experiments were designed to determine the optimal reaction conditions as follows: ethanol/water ratio (30/70), reaction time (18 h), ANI concentration (0.1 mol L-1), APS concentration (0.125 mol L-1) and DBSA concentration (0.1 mol L-1). When the PANI/VCF composite was washed 40 times in water, the conductivity still remained at 2.5 × 10-2 S cm-1, and this value was stable for more washing. © 2015 Royal Society of Chemistry. Source

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