scholarly journals The ages of Galactic globular clusters in the context of self-enrichment

2008 ◽  
Vol 4 (S258) ◽  
pp. 265-274 ◽  
Author(s):  
T. Decressin ◽  
H. Baumgardt ◽  
P. Kroupa ◽  
G. Meynet ◽  
C. Charbonnel
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Second Generation ◽  
Age Determination ◽  
Dynamical Evolution ◽  
Low Velocity ◽  
Tidal Forces ◽  
History Of ◽  
First And Second Generation

AbstractA significant fraction of stars in globular clusters (about 70%-85%) exhibit peculiar chemical patterns, with strong abundance variations in light elements along with constant abundances in heavy elements. These abundance anomalies can be created in the H-burning core of a first generation of fast-rotating massive stars, and the corresponding elements are conveyed to the stellar surface thanks to rotational induced mixing. If the rotation of the stars is fast enough, this material is ejected at low velocity through a mechanical wind at the equator. It then pollutes the interstellar medium (ISM) from which a second generation of chemically anomalous stars can be formed. The proportion of anomalous stars to normal stars observed today depends on at least two quantities: (1) the number of polluter stars; (2) the dynamical history of the cluster, which may lose different proportions of first- and second-generation stars during its lifetime. Here we estimate these proportions, based on dynamical models for globular clusters. When internal dynamical evolution and dissolution due to tidal forces are accounted for, starting from an initial fraction of anomalous stars of 10% produces a present-day fraction of about 25%, still too small with respect to the observed 70-85%. In the case of gas expulsion by supernovae, a much higher fraction is expected to be produced. In this paper we also address the question of the evolution of the second-generation stars that are He-rich, and deduce consequences for the age determination of globular clusters.

Increased rate of psychosis among African–Caribbeans in Britain is not due to an excess of pregnancy and birth complications

1997 ◽  
Vol 171 (2) ◽  
pp. 145-147 ◽  
Author(s):  
G. Hutchinson ◽  
N. Takei ◽  
D. Bhugra ◽  
T. A. Fahy ◽  
C. Gilvarry ◽  
...  
Keyword(s):  
Odds Ratio ◽  
First Generation ◽  
Second Generation ◽  
Psychotic Illness ◽  
Comparable Group ◽  
Birth Complications ◽  
African Caribbean ◽  
History Of ◽  
First And Second Generation ◽  
Pregnancy And Birth

BackgroundIt has been suggested that the increased rate of psychotic illness among African–Caribbeans living in Britain is due to an excess of pregnancy and birth complications (PBCs).MethodWe therefore compared the frequency of PBCs in a group of White psychotic patients (n=103) and a comparable group of patients of African–Caribbean origin (n=61); the latter consisted of 30 first-generation (born in the Caribbean) and 31 second-generation (born in Britain) individuals.ResultsWhite psychotic patients were more than twice as likely to have a history of PBCs as their African–Caribbean counterparts (odds ratio=2.34, 95% confidence interval (CI) 0.88–6.47, P=0.062). The same trend was observed among patients with a DSM–III diagnosis of schizophrenia (odds ratio=l.65, 95% CI 0.56–4.97, P=0.32). The rate of PBCs was similar among the first- and second-generation Caribbean psychotic patients.ConclusionsThe increased rate of psychotic illness that has been reported among the African–Caribbean population in Britain is not due to an increased prevalence of PBCs.

scholarly journals Massive stars in globular clusters: drivers of chemical and dynamical evolution

2010 ◽  
Vol 6 (S272) ◽  
pp. 227-232
Author(s):  
Thibault Decressin
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Second Generation ◽  
Massive Stars ◽  
Dynamical Evolution ◽  
Strong Impact ◽  
Low Velocity ◽  
Cluster Evolution ◽  
The One ◽  
Mechanical Mass

AbstractMassive stars have a strong impact on globular cluster evolution. First providing they rotate initially fast enough they can reach the break-up velocity during the main sequence and a mechanical mass-loss will eject matter from the equator at low velocity. Rotation-induced mixing will also bring matter from the convective core to the surface. From this ejected matter loaded in H-burning material a second generation of stars will born. The chemical pattern of these second generation stars are similar to the one observed for stars in globular cluster with abundance anomalies in light elements. Then during the explosion as supernovae the massive stars will also clear the cluster of the remaining gas. If this gas expulsion process acts on short timescale it can strongly modify the dynamical properties of clusters by ejecting preferentially first generation stars.

scholarly journals Different sodium enhancements among multiple populations of Milky Way globular clusters

2020 ◽  
Vol 643 ◽  
pp. A77
Author(s):  
Andrés E. Piatti
Keyword(s):  
Galaxy Formation ◽  
Globular Clusters ◽  
First Generation ◽  
Second Generation ◽  
Milky Way ◽  
Recent Literature ◽  
Orbital Parameters ◽  
The Difference ◽  
First And Second Generation

We searched for clues to understand the different Na abundances measured in first and second generation stars of ancient Milky Way globular clusters. For that purpose, from the recent literature, we gathered the aforementioned Na abundances, orbital parameters, and structural and internal dynamical properties and ages in a homogeneous scale of 28 globular clusters. We found that the intra-cluster Na enrichment, which is measured by the difference of Na abundances between first and second generation stars, exhibits a trend as a function of the Na abundances of first generation stars, in the sense that the more Na-poor the first generation stars are, the larger the Na enrichment is. By using the inclinations of the globular clusters’ orbits, the analyzed Na enrichments also hinted at a boundary at ∼0.3 dex to differentiate globular clusters with an accreted or in situ origin, the accreted globular clusters having larger Na enrichments. Because relatively larger intra-cluster Na enhancements are seen in accreted globular clusters and small Na enhancements are observed in globular clusters formed in situ, although not exclusively, we speculate that the amplitude of the Na enrichment may be linked with the building block paradigm. Globular clusters at the time of formation of first and second generation stars would seem to keep a memory of this hierarchical galaxy formation process.

scholarly journals Second-Generation Antipsychotics and Extrapyramidal Adverse Effects

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Nevena Divac ◽  
Milica Prostran ◽  
Igor Jakovcevski ◽  
Natasa Cerovac
Keyword(s):  
Adverse Effects ◽  
First Generation ◽  
Second Generation ◽  
Great Expectations ◽  
Extrapyramidal Syndrome ◽  
Generation Agent ◽  
Second Generation Antipsychotics ◽  
History Of ◽  
High Doses ◽  
First And Second Generation

Antipsychotic-induced extrapyramidal adverse effects are well recognized in the context of first-generation antipsychotic drugs. However, the introduction of second-generation antipsychotics, with atypical mechanism of action, especially lower dopamine receptors affinity, was met with great expectations among clinicians regarding their potentially lower propensity to cause extrapyramidal syndrome. This review gives a brief summary of the recent literature relevant to second-generation antipsychotics and extrapyramidal syndrome. Numerous studies have examined the incidence and severity of extrapyramidal syndrome with first- and second-generation antipsychotics. The majority of these studies clearly indicate that extrapyramidal syndrome does occur with second-generation agents, though in lower rates in comparison with first generation. Risk factors are the choice of a particular second-generation agent (with clozapine carrying the lowest risk and risperidone the highest), high doses, history of previous extrapyramidal symptoms, and comorbidity. Also, in comparative studies, the choice of a first-generation comparator significantly influences the results. Extrapyramidal syndrome remains clinically important even in the era of second-generation antipsychotics. The incidence and severity of extrapyramidal syndrome differ amongst these antipsychotics, but the fact is that these drugs have not lived up to the expectation regarding their tolerability.

scholarly journals Dynamical evolution of multiple-population globular clusters

2021 ◽  
Vol 502 (3) ◽  
pp. 4290-4304
Author(s):  
Enrico Vesperini ◽  
Jongsuk Hong ◽  
Mirek Giersz ◽  
Arkadiusz Hypki
Keyword(s):  
Structural Properties ◽  
Globular Clusters ◽  
First Generation ◽  
Radial Profile ◽  
Dynamical Evolution ◽  
Evolutionary Phase ◽  
Dynamical Parameters ◽  
Energy Equipartition

ABSTRACT We have carried out a set of Monte Carlo simulations to study a number of fundamental aspects of the dynamical evolution of multiple stellar populations in globular clusters with different initial masses, fractions of second generation (2G) stars, and structural properties. Our simulations explore and elucidate: (1) the role of early and long-term dynamical processes and stellar escape in the evolution of the fraction of 2G stars and the link between the evolution of the fraction of 2G stars and various dynamical parameters; (2) the link between the fraction of 2G stars inside the cluster and in the population of escaping stars during a cluster’s dynamical evolution; (3) the dynamics of the spatial mixing of the first-generation (1G) and 2G stars and the details of the structural properties of the two populations as they evolve toward mixing; (4) the implications of the initial differences between the spatial distribution of 1G and 2G stars for the evolution of the anisotropy in the velocity distribution and the expected radial profile of the 1G and 2G anisotropy for clusters at different stages of their dynamical history; and (5) the variation of the degree of energy equipartition of the 1G and the 2G populations as a function of the distance from the cluster’s centre and the cluster’s evolutionary phase.

Assimilation of the Puerto Ricans on the Mainland

1968 ◽  
Vol 2 (2) ◽  
pp. 21-39
Author(s):  
John J. Macisco
Keyword(s):  
United States ◽  
First Generation ◽  
Second Generation ◽  
Puerto Ricans ◽  
The United States ◽  
Social Scientists ◽  
First Marriage ◽  
Labor Force Status ◽  
Age At First Marriage ◽  
First And Second Generation

Social scientists have repeatedly tried to specify the process whereby assimilation takes place. This article points out the value of socio-demographic analysis in the study of assimilation, by describing the characteristics of Puerto Ricans on the United States mainland. In order to assess the direction of change between the first and second generation Puerto Ricans, data for the total United States population are also presented. Most of the data are drawn from the 1960 Census. First generation Puerto Ricans are compared with the second generation along the following dimensions: age, education, labor force status, income, occupation, age at first marriage, percent outgroup marriage and fertility. The Author concludes that second generation Puerto Ricans are moving in the direction of total United States averages.

scholarly journals Why do first and second-generation young migrants volunteer? The Migrant Volunteerism Motivation Model (MVMM)

2019 ◽  
Vol 7 (2) ◽  
pp. 1089-1107 ◽  
Author(s):  
Sara Alfieri ◽  
Daniela Marzana ◽  
Sara Martinez Damia
Keyword(s):  
Transition To Adulthood ◽  
Process Model ◽  
First Generation ◽  
Second Generation ◽  
Maintenance Phase ◽  
Structured Interviews ◽  
Sub Saharan ◽  
Italian Context ◽  
First And Second Generation ◽  
Motivation Model

The following study aims at inquiring into the motivations behind young migrants’ volunteerism in civic organizations in Italy, namely in starting and maintaining their engagement (preliminary vs. maintenance phase). The term “young migrants” refers to first and second generation of migrants who deal with two challenges: the transition to adulthood and the acquisition of a cultural identity. We conducted semi-structured interviews with 37 Sub-Saharan young migrants living in Italy (18-32 years old), 19 of first generation (1G) and 18 of second generation (2G). The Omoto and Snyder’s Volunteer Process Model (VPM, 1995) was used as an underpinning theoretical framework and a guide for the interpretations of the results. The findings indicate that a) motivations included in the VPM are also found for young migrants, b) some of these motivations take particular meaning for young migrants, c) some motivations are not included in the VPM and are specific of this sample. We named these last motivations: social norms, advocacy and ethno-cultural. In addition, some considerations may be advanced regarding the generation and the phase of motivation: 1G migrants are particularly moved by the importance of integration in the Italian context and by the promotion of their ethnic group while 2G migrants reported mostly the desire to understand their roots. The values, the concern for the community and the longing to develop relationships are the motivations for which all young migrants continue to volunteer; however, 1G migrants are also sustained by advocacy and ethno-cultural motivations. Implications and future directions are discussed.

scholarly journals The performance and genetic variation of first and second generation tropical alfalfa (Medicago sativa)

2021 ◽  
Vol 22 (6) ◽  
Author(s):  
Bambang Suwignyo ◽  
LUKMANA ARIFIN ◽  
NAFIATUL UMAMI ◽  
MUHLISIN MUHLISIN ◽  
BAMBANG SUHARTANTO
Keyword(s):  
Organic Matter ◽  
Genetic Variation ◽  
Medicago Sativa ◽  
Crude Protein ◽  
Dry Matter ◽  
First Generation ◽  
Second Generation ◽  
Seed Viability ◽  
Nutrient Content ◽  
First And Second Generation

Abstract. Suwignyo B, Arifin L, Umami N, Muhlisin, Suhartanto B. 2021. The performance and genetic variation of first and second generation tropical alfalfa (Medicago sativa). Biodiversitas 22: 3265-3270. This study aimed to compare the growth performance, nutrient content, seed viability, and genetic variation of first- and second-generation alfalfa (Medicago sativa L.). First and second-generation alfalfa seeds were obtained from the Forage and Pasture Science Laboratory, Department of Animal Nutrition and Feed Science, Faculty of Animal Science, Universitas Gadjah Mada (UGM), Yogyakarta, Indonesia. First generation alfalfa (F1) seeds were obtained from cross breeding of two different parental alfalfa varieties, namely, Canadian and local. The second-generation (F2) seeds were obtained from plants of the first-generation alfalfa (F1). A randomized design experiment was conducted using the two types of alfalfa (first- and second generation). Alfalfa from Canada as female parent was used as the baseline in the genetic masker test. Seeds were planted in a polybag, watered twice a day, and received 12 hours of daylight and 4 hours of artificial light. Plants were then harvested 8 weeks after planting by cutting the plant canopy. Genetic variation was examined using the Inter Simple Sequence Repeat (ISSR) method followed by descriptive analysis. Germination, plant height, dry matter content, organic matter, and crude protein were assessed as variables using a Student’s T-test. Our results showed that germination, plant height, leaf color, and nutrient content (dry matter, organic matter, and crude protein) of the first- and second-generation alfalfa plants were not significantly different. However, the second-generation alfalfa demonstrated better seed viability than the first generation plants, then it can be categorized as a new genotype (tropical alfalfa) based on genetic variation analysis.

Differential Impairments in Incentive Learning Caused by First‐ and Second‐ Generation Antipsychotic Drugs

2016 ◽  
Author(s):  
Matthew Florczynski
Keyword(s):  
Neural Control ◽  
First Generation ◽  
Antipsychotic Drugs ◽  
Second Generation ◽  
Operant Chamber ◽  
Incentive Learning ◽  
Dopamine Receptor Antagonists ◽  
Natural Response ◽  
Second Generation Antipsychotic ◽  
First And Second Generation

Schizophrenia is a neuropsychiatric disorder characterized by increased function of dopamine in the brain.  Dopamine release is a natural response to reward.  It promotes incentive learning (IL), a process by which neutral stimuli acquire the ability to elicit approach and other responses.  A recent model characterizes dopamine‐mediated IL as a progressive process with early and late stages accompanied by a shift in neural control from the nucleus accumbens (NAc) to the dorsolateral striatum (DLS).  A parallel can be drawn to differences in regionally specific neural responses generated by first‐ and second‐generation antipsychotic drugs (APDs) used to treat schizophrenia.  APDs are dopamine receptor antagonists, but first‐generation APDs affect the NAc and DLS while second‐generation APDs affect primarily the NAc.  We compared the effects of APDs on IL. Rats (N = 48) were trained to press a lever forfood pellets in an operant chamber.  Intraperitoneal injections (1 hr before testing) of the first‐generation APD haloperidol (0,0.05,0.10,0.20 mg/kg) or of the second‐generation APD risperidone (0,0.20,0.40,0.80 mg/kg) induced dose‐dependent suppression of lever pressing on days 1‐4, with the highest dose groups failing to demonstrate any evidence of previous learning on day 5 when tested drug‐free.  On days 16‐20 haloperidol induced a day‐to‐day suppression not seen with risperidone.  The results suggest that the effects of first‐ and second‐generation APDs on learning processes putatively mediated by the NAc and DLS can be differentiated experimentally.  The findings imply that APDs may differentially affect IL inpatients with schizophrenia.  

4.  Differential Impairments in Incentive Learning Caused by First‐ and Second‐ Generation Antipsychotic Drugs

2016 ◽  
Author(s):  
Matthew Florczynski
Keyword(s):  
Neural Control ◽  
First Generation ◽  
Antipsychotic Drugs ◽  
Second Generation ◽  
Operant Chamber ◽  
Incentive Learning ◽  
Dopamine Receptor Antagonists ◽  
Natural Response ◽  
Second Generation Antipsychotic ◽  
First And Second Generation

Schizophrenia is a neuropsychiatric disorder characterized by increased function of dopamine in the brain.  Dopamine release is a natural response to reward.  It promotes incentive learning (IL), a process by which neutral stimuli acquire the ability to elicit approach and other responses.  A recent model characterizes dopamine‐mediated IL as a progressive process with early and late stages accompanied by a shift in neural control from the nucleus accumbens (NAc) to the dorsolateral striatum (DLS).  A parallel can be drawn to differences in regionally specific neural responses generated by first‐ and second‐generation antipsychotic drugs (APDs) used to treat schizophrenia.  APDs are dopamine receptor antagonists, but first‐generation APDs affect the NAc and DLS while second‐generation APDs affect primarily the NAc.  We compared the effects of APDs on IL. Rats (N = 48) were trained to press a lever for food pellets in an operant chamber.  Intraperitoneal injections (1 hr before testing) of the first‐generation APD haloperidol (0,0.05,0.10,0.20 mg/kg) or of the second‐generation APD risperidone (0,0.20,0.40,0.80 mg/kg) induced dose‐dependent suppression of lever pressing on days 1‐4, with the highest dose groups failing to demonstrate any evidence of previous learning on day 5 when tested drug‐free.  On days 16‐20, haloperidol induced a day‐to‐day suppression not seen with risperidone.  The results suggest that the effects of first‐ and second‐generation APDs on learning processes putatively mediated by the NAc and DLS can be differentiated experimentally.  The findings imply that APDs may differentially affect IL inpatients with schizophrenia.

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