Perturbation analysis of the limit cycle of the free van der Pol equation

A power series expansion in the damping parameter, epsilon, of the limit cycle of the free van der Pol equation is constructed and analyzed. Coefficients in the expansion are computed in exact rational arithmetic using the symbolic manipulation system MACSYMA and using a FORTRAN program. The series is analyzed using Pade approximants. The convergence of the series for the maximum amplitude of the limit cycle is limited by two pair of complex conjugate singularities in the complex epsilon-plane. A new expansion parameter is introduced which maps these singularities to infinity and leads to a new expansion for the amplitude which converges for all real values of epsilon. Amplitudes computed from this transformed series agree very well with reported numerical and asymptotic results. For the limit cycle itself, convergence of the series expansion is limited by three pair of complex conjugate branch point singularities. Two pair remain fixed throughout the cycle, and correspond to the singularities found in the maximum amplitude series, while the third pair moves in the epsilon-plane as a function of t from one of the fixed pairs to the other. The limit cycle series is transformed using a new expansion parameter, which leads to a new series that converges for larger values of epsilon

Psychometric Properties of the Persian Version of the Short Beck Depression Inventory with Iranian Psychiatric Outpatients

The short form of the Beck Depression Inventory (BDI-13) is useful for the screening and assessment of depression in clinical and research settings. The aim of the present study was to investigate the psychometric properties of the Persian (Farsi) version of BDI-13 in an Iranian clinical sample. The sample consisted of 52 Iranian psychiatric outpatients who received services at psychiatric and psychological clinics at the School of Behavioral Sciences & Mental Health-Tehran Institute of Psychiatry, Iran University of Medical Sciences (IUMS) in Tehran, Iran. The study examined the reliability, construct validity, and factor structure of the instrument. The instrument indicated good reliability with Cronbach's alpha of.85 and strong construct validity based on moderate to strong positive correlations with other measures of mental health issues. Using a Principal Component Analysis and Varimax Rotation with Kaiser Normalization, three factors were identified and labeled Affective (F1), Somatic/Vegetative (F2), and Cognitive/Loss of Functioning (F3). The current factor structure suggests that depression is a multidimensional construct in an Iranian clinical sample. This study provides further evidence that the Persian version of the BDI-13 is a psychometrically sound instrument that can be used for clinical and research purposes in Iran. Copyright © 2016 M. Dadfar and Z. Kalibatseva

Reliability and factorial structure of the farsi version of the Arabic scale of death anxiety in an iranian middle-aged sample

The present study aimed to explore the psychometric properties of the Arabic Scale of Death Anxiety (ASDA) in an Iranian middle-aged sample. A sample of 55 volunteer Iranian persons took part in the study. Cronbach's alpha of the ASDA was found to be high (0.91) and Spearman-Brown and Guttman Split-Half coefficients were 0.86. The factor analysis of the ASDA items yielded five factors accounting for 72.49 of the total variance and labeled (F1) fear of death and fear of dead people; (F2) fear of postmortem events and fear of tombs; (F3) fear of lethal disease; (F4) preoccupation with after death, and death fear in sleep; and (F5) fear of deprivation of own ones. The ASDA has a good validity and reliability, and it can be used in clinical, educational, and research settings. © 2016 Mahboubeh Dadfar and Fazel Bahrami

Death Anxiety, Reliability, Validity, and Factorial Structure of the Farsi Form of the Arabic Scale of Death Anxiety in Iranian Old-Aged Persons

The present study is aimed at examining the level of death anxiety and the sex-related differences among old-aged Iranian individuals sample to compare the old-aged persons with young college students and to explore the psychometric properties of the Arabic Scale of Death Anxiety (ASDA) factors in old-aged sample. A sample of 146 volunteer Iranian individuals took part in the study. The mean ages were 68.58 (SD = 7.10), men 68.81 (SD = 7.44) and women 68.28 (SD = 6.76), respectively. The mean score of the ASDA was 51.09 (SD = 20.19). Cronbach's alpha of the ASDA was found to be high (0.94); and Spearman-Brown coefficient was 0.92. Women had a significantly higher mean total score on the ASDA. Old-aged individuals had a significantly higher mean ASDA total score than younger college students (M age = 25.77). The factor analysis of the ASDA items yielded three factors accounting for 67.88 of the total variance labeled (F1) fear of dead people and tombs; (F2) fear of lethal disease and postmortem events; and (F3) death fear. These factors were highly replicable with previous factors extracted from a middle-aged Kuwaiti sample. On the basis of the present results, there are the following three general conclusions: death anxiety is not significantly correlated with age; the sex-related differences on death anxiety are striking in the Iranian samples; and the ASDA has a highly replicable factor structure among two Iranian and Arab countries. © 2016 Mahboubeh Dadfar et al

Perturbation Analysis of the Limit Cycle of the Free Van Der Pol Equation

. A power series expansion in the damping parameter E of the limit cycle U(t; E) of the free van der Pol equation Ul + E( U2 _1) U + U =0 is constructed and analyzed. Coefficients in the expansion are computed up to 0(E24) in exact rational arithmetic using the symbolic manipulation system MACSYMA and up to O(E163) using a FORTRAN program. The series is analyzed using Pade approximants. The convergence of the series for the maximum amplitude of the limit cycle is limited by two pairs of complex conjugate singularities in the complex e-plane. These singularities are the same as those which limit the convergence of the series expansion of the frequency of the limit cycle. A new expansion parameter is introduced which maps these singularities to infinity and leads to a new expansion for the amplitude which converges for all real values of E. Amplitudes computed from this transformed series agree very well with reported numerical and asymptotic results. For the limit cycle itself, convergence of the series expansion is limited by three pairs of complex conjugate branch point singularities. Two pairs remain fixed throughout the cycle and correspond to the singularities found in the maximum amplitude series, while the third pair moves in the E-plane as a function of t from one of the fixed pairs to the other. This moving pair of singularities dominate the fixed singularities for certain ranges of t and hence account for a nonuniformity in the convergence of the series. The limit cycle series is transformed using a new expansion parameter, which leads to a new series that converges for larger values of E

Death distress constructs: A preliminary empirical examination of the Farsi form in nurses: A brief note

Aim: Death distress can increase mental health problems. The aim of the present study was to develop a measure of death distress and evaluate the reliability of this Death Distress Scale-Farsi (DDS-F) among nurses. The hypotheses were that death distress has three components and that the DDS-F would have desirable psychometric properties. Design: A descriptive cross-sectional study. Methods: A convenience sample of 106 Iranian nurses from two hospitals at Tehran city, Iran was recruited. They completed the Death Anxiety Scale (DAS), the Death Depression Scale (DDS) and the Death Obsession Scale (DOS). Results: Cronbach's α for the DDS-F was 0.71. As expected, the DDS-F had three independent components: death obsession, death depression and death anxiety. A principle component analysis with a varimax rotation of the DDS-F items identified three factors accounting for 66.13 of the variance. Factor 1 was labelled �Death Obsession� (31.3 of the variance), Factor 2 was labelled �Death Depression� (21.9 of the variance), and Factor 3 was labelled �Death Anxiety� (12.8 of the variance). Discussion: Death distress has three components: death obsession, death depression and death anxiety. The DDS-F which measures these has good psychometric properties, and it can be used in hospital settings to assess death distress among Iranian nurses. © 2020 The Authors. Nursing Open published by John Wiley & Sons Lt

The farsi translation, reliability and validity of the death concern scale Tradução, confiabilidade e validade da death concern death para a língua persa

Introduction: Death concern is a conscious contemplation of the reality of death combined with a negative evaluation of that reality. The Death Concern Scale (DCS) is related to thinking, and death fear or anxiety about death. The aim of the present study was to develop a Farsi version of the DCS and to explore its psychometric properties in a sample of Iranian nurses. Methods: A cross-sectional study was conducted to investigate the reliability, validity, and factorial structure of the Farsi version of the DCS in a convenience sample of 106 Iranian nurses in two hospitals in Tehran, Iran. The nurses completed the DCS, the Collett-Lester Fear of Death Scale (CLFDS), the Death Anxiety Scale (DAS), the Reasons for Death Fear Scale (RDFS), the Death Depression Scale (DDS), and the Death Obsession Scale (DOS). Results: For the DCS, Cronbach�s α was 0.77, the Spearman-Brown coefficient 0.63, the Guttman split-half coefficient 0.62, and two-week test-retest reliability 0.77. The DCS correlated at 0.51 with the CLFDS, 0.52 with the DAS, 0.34 with the RDFS, 0.40 with the DDS, and 0.48 with the DOS, indicating good construct and criterion-related validity. The results of an exploratory factor analysis for the DCS identified seven factors, accounting for 64.30 of the variance and indicating considerable heterogeneity in the content of the items. Conclusions: The Farsi version of the DCS has good validity and reliability, and it can be used in clinical, educational, and research settings to assess death concerns in the Iranian society. © 2018, Sociedade de Psiquiatria do Rio Grande do Sul. All rights reserved

Reliability and validity of the farsi version of the patient health questionnaire-9 (PHQ-9) with iranian psychiatric outpatients Confiabilidade e validade da versão persa do patient health questionnaire-9 (PHQ-9) em pacientes psiquiátricos ambulatoriais iranianos

Introduction: The Patient Health Questionnaire-9 (PHQ-9) is a brief screening and diagnostic tool for depression. It has been used in research and clinical practice in primary care and other clinical and non-clinical settings. The PHQ-9 has not had its validity examined in psychiatric and psychological settings in Iran. Methods: A cross-sectional study was conducted to investigate the validation of the Farsi version of the PHQ-9. A convenience sample of 130 Iranian volunteer psychiatric outpatients was selected from psychiatric and psychological clinics. They completed the PHQ-9, the Patient Health Questionnaire-15 (PHQ-15), the World Health Organization-five Well-Being Index (WHO-5), and the short form of the Beck Depression Inventory-13 (BDI-13). Data were analyzed by descriptive statistics, Cronbach�s α, Pearson correlation coefficient, principal component analysis, exploratory factor analysis, and confirmatory factor analysis. Results: Mean score of the PHQ-9 was 12.83 (standard deviation=6.25), indicating moderately severe depression in the sample. Cronbach�s α coefficient for PHQ-9 was 0.88, and one-week test-retest reliability 0.79. The PHQ-9 correlated 0.64 with PHQ-15,-0.35 with WHO-5, and 0.70 with BDI-13, indicating good construct and criterion-related validity. The results of the factor analysis of PHQ-9 items identified and confirmatory factor analysis confirmed a single factor labeled general depression. Conclusions: The PHQ-9 appears to have a unidimensional structure, adequate validity and reliability, and can be useful in epidemiological/research settings. Based on previous literature and on the present findings, the PHQ-9 may have applicability to other contexts in the studied population, but this needs to be confirmed by other studies. © 2018, Sociedade de Psiquiatria do Rio Grande do Sul. All rights reserved

Psychometric Characteristics of the Wish to Be Dead Scale (WDS) in Iranian Psychiatric Outpatients

The Wish to be Dead Scale (WDS) was administered to a convenience sample of 200 Iranian psychiatric outpatients. Using a Principal Component Analysis, two factors were identified, labeled Lack of purpose in life (F1), and Lack of interest in living (F2). The WDS had good reliability and significant positive correlations with scores on the Beck Suicide Ideation Scale and with other measures of mental ill-health. This study provides evidence of the usefulness of the WDS for assessing psychiatric patients. © 2016 The Author(s