Chaotic behavior in Casimir oscillators: A case study for phase change materials

Casimir forces between material surfaces at close proximity of less than 200 nm can lead to increased chaotic behavior of actuating devices depending on the strength of the Casimir interaction. We investigate these phenomena for phase change materials in torsional oscillators, where the amorphous to crystalline phase transitions lead to transitions between high and low Casimir force and torque states respectively, without material compositions. For a conservative system bifurcation curve and Poincare maps analysis show the absence of chaotic behavior but with the crystalline phase (high force/torque state) favoring more unstable behavior and stiction. However, for a non-conservative system chaotic behavior can occur introducing significant risk for stiction, which is again more pronounced for the crystalline phase. The latter illustrates the more general scenario that stronger Casimir forces and torques increase the possibility for chaotic behavior. The latter is making impossible to predict whether stiction or stable actuation will occur on a long term basis, and it is setting limitations in the design of micro/nano devices operating at short range nanoscale separations.Comment: 30 pages, 13 figure

Prevalence of Coenurus cerebralis in sheep in Northwest of Iran

AbstractThis survey was carried out to determine the infection rate of Coenurus cerebralis in Urmiaabattoir, West Azerbaijan, Iran. A total of 402 sheep heads were examined and the number ofC. cerebralis cysts per each head was recorded. Thirty three sheep heads were examined eachmonth during 12 months from 2006 to 2007. Of 402 heads, a number of 75 heads (18.65%)were infected with C. cerebralis. The cysts located in the left and right hemispheres andcerebellum were 54.63%, 40.20% and 5.15%, respectively. The infected heads contained 1-4cysts. The highest and lowest prevalence were detected in sheep in March (42.42%) and in July(2.94%), respectively. The infection rates according to age of sheep were 42.02% in 0.5 to 2years, 22.50% in 2 to 4 years and 8.92% in older than 4 years. The age specific infection ratesamong age groups were significantly differed (P < 0.05). Infection rate in Haraki breed(27.77%) was higher comparing to the rate in the Ghezel breed (21.13%) and Makoie breed(23.91%). However differences between sheep breeds were not statistically significant (P > 0.05)

Dependence of chaotic actuation dynamics of Casimir oscillators on optical properties and electrostatic effects

With Casimir and electrostatic forces playing a crucial role for the performance and stability of microelectromechanical systems (MEMS), the presence of chaotic behavior, which is often unavoidable, leads to device malfunction due to stiction. Therefore, we investigate here how the optical properties of different materials influence the chaotic behavior of electrostatic torsional MEMS due to changes in magnitude of the Casimir forces and torques. We consider the materials Au, which is a good conductor, AIST, which is a phase change material being close to metal in the crystalline state, and finally doped SiC as a very poor conductor. For the conservative systems, there is no chaotic behavior and the analysis of phase portraits and bifurcation diagrams reveal the strong sensitivity of stable actuation dynamics on the material optical properties, while applied electrostatic potentials lead faster to instability and stiction for higher conductivity materials. For the driven systems, the Melnikov method is used to study the chaotic behavior. The results from this method are supported by the study of the contours of the transient time to stiction in the phase plane, which reveal a substantially increased chaotic behavior for higher conductivity materials, associated with stronger Casimir torques and applied electrostatic potentials

Depression and its associated factors among secondary school students in Malaysia

Research in the field of factors associated with depression among adolescents is lacking in Malaysia. The aims of the present study were to assess the current prevalence of depression and its related factors among secondary school students in Pasir Gudang, South Malaysia. In this cross sectional study, 2,927 secondary school students (13-17 years old) from urban areas were screened for symptoms of mental disorder as well as demographic and risk behaviors using a validated Depression, Anxiety and Stress Scale (DASS) 12 questionnaire. The majority of the respondents (53.8%) were Malay, of which 53.1% were female. Symptoms of mild depression were found in 33.2% of the respondents, while the prevalence of the symptoms of moderate, severe, and extremely severe depression was 21.5%, 18.1%, and 3.0%, respectively. Logistic regression suggested that participants who were Chinese or had a lower average grade were three times more likely to have depression, while those who came from a single-parent family were twice as likely to have this condition. This study indicated that academic performance and risk behaviors along with the demographic characteristics are important contributors to adolescent depression

The Relationship Between Post-Traumatic Stress Disorder After Childbirth and Social Support and Marital Satisfaction

Background: Childbirth is among the most significant and pleasant events in a woman’s life. This event can be a traumatic event and a threat to the mother’s mental health. This study recognizes the relationship between Post-Traumatic Stress Disorder (PTSD) after childbirth and social support and marital satisfaction.Methods: This Cross-sectional analytical study was performed on a sample of 400 mothers who had delivered at Shohadaye-15-Khordad Hospital in Varamin (in two groups with &amp; without PTSD). The research instruments include the Demographic, Midwifery, Neonatal Factors checklist, Enrich Marital Satisfaction, Weinfeld and Tigman Social Support, and the PTSD Symptoms Scale. We used SPSS to analyze the descriptive and Pearson correlation and logistic regression data. A P&lt;0.05 was considered significant.Results: The prevalence of PTDS in this study was equal to 16.8%. There was no significant correlation between the mean of the total score of PTSD in all dimensions with social support (P&gt;0.05). Marital satisfaction significantly affected the probability of PTSD after childbirth (P=0.001). There was a significant correlation between PTSD total score and dimension of avoidance symptoms and infant gender (P=0.038). There was also a significant correlation between gestational age and avoidance symptoms (P=0.001) and type of nutrition feeding and motivational symptoms (P=0.041) of PTSD dimensions.Conclusion: According to the relationship between marital satisfaction and PTSD, it is recommended to design suitable interventions to improve the marital status and promptly diagnose the susceptible mothers to prevent the spread of this complication

Psychosocial problem and its associated factors among adolescents in the secondary schools in Pasir Gudang, Johor

Introduction: Adolescence is a crucial period with impressive emotional changes. Emotional disorders such as depression, anxiety and stress are high among adolescents worldwide; however the psychosocial changes are often neglected. The aim of the current study was to determine the depression, anxiety and stress symptoms and their associated factors among adolescents. Methods: A cross-sectional study using cluster sampling was carried out among school-going adolescents in 10 secondary schools in Pasir Gudang, Johor, Malaysia. Respondents answered a self-administered questionnaire including socio-demographic, Inventory of Parent and Peer Attachment (IPPA), Depression Anxiety Stress Scale-21 (DASS-21) and Strength and Difficulties Questionnaire (SDQ). Using SPSS-21, chi-square test and binomial logistic regression were conducted to examine the associations between dependent and independent variables. Results: Respondents (52.6% female and 53.9% Malay) had 46.0% prevalence of depression symptoms, 59.1% anxiety, 38.1% stress and 45.6% psychosocial status (internalizing and externalizing problems). Age, father occupation and parental bonding were significantly predicted having moderate to extremely severe depression symptom (p<0.05). Younger adolescents (13-14 years old) were 1.42 times more likely to have anxiety symptom. In addition, respondents with insecure father attachment were 1.5 times more likely to have stress symptom (p<0.05). Respondents with insecure parental attachment were more likely to have psychosocial problem (p<0.05). Conclusions: Depression, anxiety and stress of adolescents were influenced by the sociodemographic of adolescents and their parents. Age, gender and parental attachment were the significant predictors in the current study which should be the center of attention for the future studies to reduce the psychological disorders among adolescents

APPLICABILITY OF MIXED DENTITION PREDICTION EQUATIONS IN CONTEMPORARY POPULATION OF PASHTUNS

OBJECTIVE: To determine the accuracy of Tanaka and Johnston and Bherwani’s prediction equations when applied to a sample of Pashtun population of Pakistan. METHODS: Odontometric data from casts of 180 subjects (90 males and 90 females, ages 13-19 years) of Pashtun origin was collected using digital callipers. Mesiodistal widths of mandibular incisors, mandibular and maxillary canines and premolars were measured. Data was analysed using SPSS software version 20. RESULTS: Data was analysed for 90 male and 90 female subjects with a mean age of 15.7±1.7years and 15.4±1.5 years, respectively. Statistically significant right and left tooth size difference was found only for upper arch in males (mean 0.08, p=0.027). Statistically significant gender dimorphism was noted for tooth sizes tooth sizes with males showing larger tooth sizes. Tanaka and Johnston equations significantly overestimated the sizes of canine and premolars segments for upper (mean difference=0.72+0.96, p=0.000) and lower (mean difference=0.75+0.94, p=0.000) arches when applied to ethnic Pashtun population. Customized Regression equations represented by y=a+b(x) were derived for unerupted canine and premolars segments of Pashtun population. The values for coefficient of correlation (r) ranged from 0.59 to 0.73 and the coefficient of determination (r2) ranged from 0.36-0.52. CONCLUSION: Tanaka and Johnston equations developed for North American population (at 75th percentile) should be used with caution for mixed dentition analyses in local Pashtun population as it overestimates tooth sizes in males and females. Regression equations developed in this study can be used for diagnostic planning in local Pashtun children