Nonlinear interplay of Alfven instabilities and energetic particles in tokamaks

The confinement of energetic particles (EP) is crucial for an efficient heating of tokamak plasmas. Plasma instabilities such as Alfven Eigenmodes (AE) can redistribute the EP population making the plasma heating less effective, and leading to additional loads on the walls. The nonlinear dynamics of toroidicity induced AE (TAE) is investigated by means of the global gyrokinetic particle-in-cell code ORB5, within the NEMORB project. The nonperturbative nonlinear interplay of TAEs and EP due to the wave-particle nonlinearity is studied. In particular, we focus on the nonlinear modification of the frequency, growth rate and radial structure of the TAE, depending on the evolution of the EP distribution in phase space. For the ITPA benchmark case, we find that the frequency increases when the growth rate decreases, and the mode shrinks radially. This nonlinear evolution is found to be correctly reproduced by means of a quasilinear model, namely a model where the linear effects of the nonlinearly modified EP distribution function are retained.Comment: Submitted to Plasma Phys. Control. Fusio

Defects of steroidogenesis

In the biosynthesis of steroid hormones the neutral lipid cholesterol, a normal constituent of lipid bilayers is transformed via a series of hydroxylation, oxidation, and reduction steps into a vast array of biologically active compounds: mineralocorticoids, glucocorticoids, and sex hormones. Glucocorticoids regulate many aspects of metabolism and immune function, whereas mineralocorticoids help maintain blood volume and control renal excretion of electrolytes. Sex hormones are essential for sex differentiation in male and support reproduction. They include androgens, estrogens, and progestins. A block in the pathway of steroid biosynthesis leads to the lack of hormones downstream and accumulation of the upstream compounds that can activate other members of the steroid receptor family. This review deals with the clinical consequences of these block

Endocrine and molecular investigations in a cohort of 25 adolescent males with prominent/persistent pubertal gynecomastia

Pubertal gynecomastia is a common condition observed in up to 65% of adolescent males. It is usually idiopathic and tends to regress within 1–2 years. In this descriptive cross-sectional study, we investigated 25 adolescent males with prominent (>B3) and/or persistent (>2 years) pubertal gynecomastia (P/PPG) to determine whether a hormonal/genetic defect might underline this condition. Endocrine investigation revealed the absence of hormonal disturbance for 18 boys (72%). Three patients presented Klinefelter syndrome and three a partial androgen insensitivity syndrome (PAIS) as a result of p.Ala646Asp and p.Ala45Gly mutations of the androgen receptor gene. The last patient showed a 17α-hydroxylase/17,20-lyase deficiency as a result of a compound heterozygous mutation of the CYP17A1 gene leading to p.Pro35Thr(P35T) and p.Arg239Stop(R239X) in the P450c17 protein. Enzymatic activity was analyzed: the mutant protein bearing the premature stop codon R239X showed a complete loss of 17α-hydroxylase and 17,20-lyase activity. The mutant P35T seemed to retain 15–20% of 17α-hydroxylase and about 8–10% of 17,20-lyase activity. This work demonstrates that P/PPG had an endocrine/genetic cause in 28% of our cases. PAIS may be expressed only by isolated gynecomastia as well as by 17α-hydroxylase/17,20-lyase deficiency. Isolated P/PPG is not always a ‘physiological’ condition and should thus be investigated through adequate endocrine and genetic investigations, even though larger studies are needed to better determine the real prevalence of genetic defects in such patients

Age-period-cohort analysis of Swiss suicide data, 1881-2000

At the end of the 19th century, male suicide rates in Switzerland were as high as the respective rates in recent decades, whereas female suicide rates were distinctly lower. An age-period-cohort analysis was performed to provide more information about the genderspecific changes over the last century. Suicide mortality has been reported in Switzerland since 1876 when the standardised registration of mortality data began. The analysed data cover the period 1881-2000. The statistical analyses were based on log-linear models and data aggregated by 10-year age-intervals and 10-year periodintervals. The results indicate similar age and period effects in males and females. The estimates representing age-specific risk increase steadily with age, with intermediate plateaus in the 20s and the 50s. The period-specific estimates follow the economic cycles. The birth cohort effects are stronger in males and weaker in females. In the males' estimates, there is a peak in cohorts born around 1840 and a low in cohorts born some 60-100 years later. The estimates increased again in generations born after World War II. In females, the birth cohort estimates are low in cohorts born in the first half of the 19th century and increase until the first half of the 20th century. Birth cohort effects remain an intriguing topic in epidemiology of suicide. A better understanding of birth cohort effects might open new doors to suicide preventio

Suicide after bereavement: an overlooked problem

Background To examine the effect of time on suicide after bereavement among widowed persons. Method The data were extracted from Swiss mortality statistics for the period 1987-2005. The time between bereavement and subsequent death, specifically by suicide, was determined by linkage of individual records of married persons. The suicide rates and the standardized mortality ratios in the first week/month/year of widowhood were calculated based on person-year calculations. Results The annualized suicide rates in widowed persons were highest in the first week after bereavement: 941 males and 207 females per 100 000. The corresponding standardized mortality ratios were approximately 34 and 19 respectively. In the first month(s) after bereavement, the rates and the ratios decreased, first rapidly, then gradually. Except in older widows, they did not reach the baseline levels during the first year after bereavement. Conclusions The suicide risk of widowed persons is increased in the days, weeks and months after bereavement. Widowed persons are a clear-cut risk group under the aegis of undertakers, priests and general practitioner