scholarly journals Study of the Abundance Patterns in the Metal-Poor Stellar Stream

2013 ◽  
Vol 30 ◽  
Author(s):  
Hongjie Li ◽  
Shuai Liang ◽  
Wenyuan Cui ◽  
Bo Zhang
Keyword(s):  
Gradual Increase ◽  
Type Ii ◽  
Constant Mass ◽  
Chemical Abundances ◽  
Abundance Patterns ◽  
The Difference ◽  
The Masses ◽  
Process Component ◽  
Process Elements ◽  
Early Galaxy

AbstractThe chemical abundances of the metal-poor stars in the stellar stream provide important information for setting constraints on models of neutron-capture processes. The study of these stars could gives us a better understanding of the r-process nucleosynthesis and chemical composition of the early Galaxy. Using the updated main r-process and weak r-process patterns, we fit abundances in the stellar stream stars. The weak r-process component coefficients are almost constant for the sample stars, including r-rich stars, which means that both the weak r-process and Fe are produced as primary elements from Type II supernovae and their yields have nearly a constant mass fraction. The difference between the stream stars and r-rich stars is obvious. For the stream stars, the fact that the increased trend in the main r-process component coefficients as metallicity increases means a gradual increase in the production of main r-process elements relative to iron. This behaviour implies that the masses of progenitors for the main r-process are smaller than those of the weak r-process. Furthermore, we find that the metal-poor stream star HD 237846 is a weak r-process star.

scholarly journals A Spectroscopic Study of Barium Stars

2008 ◽  
Vol 4 (S252) ◽  
pp. 425-426
Author(s):  
G. Q. Liu ◽  
Y. C. Liang ◽  
L. Deng
Keyword(s):  
Neutron Capture ◽  
Binary Systems ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Agb Stars ◽  
Atmospheric Parameters ◽  
Chemical Abundances ◽  
Capture Process ◽  
Abundance Patterns ◽  
Process Elements

AbstractWe present an analysis of eight barium stars, providing their atmospheric parameters (Teff, log g, [Fe/H], ξt) and chemical abundances, based on the high signal-to-noise ratio and high resolution Echelle spectra. The s-process elements Y, Zr, Ba, La, Eu show obvious overabundance relative to the Sun. And Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Ni show comparable abundances to the Solar ones. The results of theoretical model of wind accretion for binary systems can explain the observed abundance patterns of the neutron capture process elements in these Ba stars, which means that their overabundant heavy-elements could be caused by accreting the ejecta of AGB stars, the progenitors of the present white dwarf companions in the binary systems.

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

scholarly journals Identification of Glu-519 as the catalytic nucleophile in β-mannosidase 2A from Cellulomonas fimi

2000 ◽  
Vol 351 (3) ◽  
pp. 833-838 ◽  
Author(s):  
Dominik STOLL ◽  
Shouming HE ◽  
Stephen G. WITHERS ◽  
R. Antony J. WARREN
Keyword(s):  
Peptide Bond ◽  
Enzyme Inactivation ◽  
Ionization Mass ◽  
Glycosyl Hydrolases ◽  
Cellulomonas Fimi ◽  
Inactivation Rate Constant ◽  
Dependent Inactivation ◽  
The Difference ◽  
The Masses ◽  
Covalent Intermediate

Incubation of the β-mannosidase Man2A from Cellulomonas fimi with 2-deoxy-2-fluoro-β-d-mannosyl fluoride (2FManβF) resulted in time-dependent inactivation of the enzyme (inactivation rate constant ki = 0.57min-1, dissociation constant for the inactivator Ki = 0.41mM) through the accumulation of a covalent 2-deoxy-2-fluoro-α-d-mannosyl–β-mannosidase 2A (2FMan–Man2A) enzyme intermediate, as observed by electrospray ionization mass spectrometry. The stoichiometry of inactivation was 1:1. Removal of excess inactivator and regeneration of active enzyme by transglycosylation of the covalently attached inhibitor to gentiobiose [Glcβ(1–6)Glc] demonstrated that the covalent intermediate was catalytically competent. Comparison by MS of the peptic digests of 2FMan–Man2A with peptic digests of native Man2A revealed a peptide of m/z 1520 that was unique to 2FMan–Man2A, and one of m/z 1036.5 that was unique to a Man2A peptide. Their sequences, determined by collision-induced fragmentation, were CSEFGFQGPPTW and FGFQGPPTW, corresponding to residues 517–528 and 520–528 of Man2A respectively. The difference in mass of 483.5 between the two peptides equals the sum of the masses of the tripeptide CSE plus that of 2-fluoromannose. It was concluded that in 2FMan–Man2A, the 2-fluoromannose esterified to Glu-519 blocks hydrolysis of the Glu-519–Phe-520 peptide bond, and that Glu-519 is the catalytic nucleophile in this enzyme. This residue is conserved in all members of family 2 of the glycosyl hydrolases. This represents the first ever labelling and identification of an active-site nucleophile in a β-mannosidase.

India-2021: Middle class in pandemic conditions

2021 ◽  
pp. 14
Author(s):  
Elena A. Bragina
Keyword(s):  
Developing Countries ◽  
Middle Class ◽  
Gradual Increase ◽  
Population Group ◽  
Special Significance ◽  
Statistical Estimates ◽  
National Characteristics ◽  
The Difference ◽  
Definition Of ◽  
Sociological Studies

The article analyzes the conditions for the formation of the middle class in India. Shown is its important balancing role in the politics and economy of the country. The nature of the definition of "middle class", its special significance in developing countries is considered. Due to the difference in the applied criterion - the initial unit of account (employee, family, population group), due to the weakness of statistical services, the results of sociological studies, statistical estimates of the size of the middle class are often approximate. The work shows that the official and infor-mal (shadow) parts of the middle class coexist in the economies of developing countries in parallel.  The pressure of the COVID-19 pandemic on the development of the Indian middle class is taken into account.  The article examines the national characteristics of the formation of the middle class inherent in India. Due to the unclear definition of the criteria, the inconsistency of its assessments, the insufficient level of work of statistical organizations, information on the size of the middle class is inaccurate (according to various estimates, about 210-360 million people). Attention is paid to the formation of the rural middle class in India, rural residents make up a significant part of it (estimated at 48-66%).The forecast of the recovery of the Indian middle class ispresented. It is assumed that its quantitative growth, which was observed before the pandemic, and a gradual increase in influence will continue and will allow in the future. The topic is relevant, in demand by the Russian reader.

Responses of Medullary Dorsal Horn Neurons to Corneal Stimulation by CO2 Pulses in the Rat

1999 ◽  
Vol 82 (5) ◽  
pp. 2092-2107 ◽  
Author(s):  
Harumitsu Hirata ◽  
James W. Hu ◽  
David A. Bereiter
Keyword(s):  
Thalamic Nucleus ◽  
Receptive Fields ◽  
Male Rats ◽  
Cervical Cord ◽  
Type I ◽  
Type Ii ◽  
Upper Cervical ◽  
The Difference ◽  
Evoked Activity ◽  
Stimulation Of

Corneal-responsive neurons were recorded extracellularly in two regions of the spinal trigeminal nucleus, subnucleus interpolaris/caudalis (Vi/Vc) and subnucleus caudalis/upper cervical cord (Vc/C1) transition regions, from methohexital-anesthetized male rats. Thirty-nine Vi/Vc and 26 Vc/C1 neurons that responded to mechanical and electrical stimulation of the cornea were examined for convergent cutaneous receptive fields, responses to natural stimulation of the corneal surface by CO2 pulses (0, 30, 60, 80, and 95%), effects of morphine, and projections to the contralateral thalamus. Forty-six percent of mechanically sensitive Vi/Vc neurons and 58% of Vc/C1 neurons were excited by CO2 stimulation. The evoked activity of most cells occurred at 60% CO2 after a delay of 7–22 s. At the Vi/Vc transition three response patterns were seen. Type I cells ( n = 11) displayed an increase in activity with increasing CO2 concentration. Type II cells ( n = 7) displayed a biphasic response, an initial inhibition followed by excitation in which the magnitude of the excitatory phase was dependent on CO2 concentration. A third category of Vi/Vc cells (type III, n = 3) responded to CO2 pulses only after morphine administration (>1.0 mg/kg). At the Vc/C1 transition, all CO2-responsive cells ( n = 15) displayed an increase in firing rates with greater CO2 concentration, similar to the pattern of type I Vi/Vc cells. Comparisons of the effects of CO2 pulses on Vi/Vc type I units, Vi/Vc type II units, and Vc/C1 corneal units revealed no significant differences in threshold intensity, stimulus encoding, or latency to sustained firing. Morphine (0.5–3.5 mg/kg iv) enhanced the CO2-evoked activity of 50% of Vi/Vc neurons tested, whereas all Vc/C1 cells were inhibited in a dose-dependent, naloxone-reversible manner. Stimulation of the contralateral posterior thalamic nucleus antidromically activated 37% of Vc/C1 corneal units; however, no effective sites were found within the ventral posteromedial thalamic nucleus or nucleus submedius. None of the Vi/Vc corneal units tested were antidromically activated from sites within these thalamic regions. Corneal-responsive neurons in the Vi/Vc and Vc/C1 regions likely serve different functions in ocular nociception, a conclusion reflected more by the difference in sensitivity to analgesic drugs and efferent projection targets than by the CO2 stimulus intensity encoding functions. Collectively, the properties of Vc/C1 corneal neurons were consistent with a role in the sensory-discriminative aspects of ocular pain due to chemical irritation. The unique and heterogeneous properties of Vi/Vc corneal neurons suggested involvement in more specialized ocular functions such as reflex control of tear formation or eye blinks or recruitment of antinociceptive control pathways.

scholarly journals Demography and feeding behavior of Stenostomum leucops (Dugés, 1828)

2016 ◽  
Vol 75 (s1) ◽  
Author(s):  
Alma R. Núñez-Ortiz ◽  
Sarma Nandini ◽  
S.S.S. Nandini
Keyword(s):  
Functional Response ◽  
Food Preference ◽  
Type Ii ◽  
Final Density ◽  
Two Temperatures ◽  
The Difference ◽  
Growth Experiments ◽  
Pelagic Communities ◽  
Type Ii Functional Response ◽  
Planktonic Communities

<p>Freshwater turbellarians, despite their mainly benthic habits, interact with pelagic communities of rotifers and cladocerans. However, very little is known about their demographic characteristics, food preference and functional response. To fill that gap we studied one of the most widely spread species, <em>Stenostomum leucops</em>.  We conducted population growth experiments using abundant food (several rotifer and cladocerans species). To evaluate possible impact of <em>S. leucops</em> on planktonic communities, we conducted prey preference experiments at two temperatures: 18 and 23°C. The number of rotifers and cladocerans consumed was calculated by the difference between the initial and final density. We found that diets supplemented with fresh algae achieved higher <em>S. leucops</em> densities than those with detritus supplements in their diets. In the case of animal diets, <em>Euchlanis dilatata</em> allowed <em>S. leucops</em> reach higher densities than the other zooplankton species; <em>E. dilatata</em> was positively selected for in the selectivity study at both 18 and 23°C.  <em>Stenostomum leucops</em> showed a type II functional response on rotifers and the cladoceran <em>Alona glabra</em>. Our results suggest that <em>S. leucops</em> select their prey according to their vulnerability using different mechanisms, which optimize their food intake.</p>

scholarly journals Number of fiber bundles in the fetal anterior talofibular ligament

2021 ◽  
Author(s):  
Mutsuaki Edama ◽  
Tomoya Takabayashi ◽  
Hirotake Yokota ◽  
Ryo Hirabayashi ◽  
Chie Sekine ◽  
...  
Keyword(s):  
Fiber Bundle ◽  
Fiber Bundles ◽  
Anterior Talofibular Ligament ◽  
Type I ◽  
Type Ii ◽  
Crown Rump Length ◽  
Type Iii ◽  
The Difference ◽  
And Inversion

Abstract Background For the anterior talofibular ligament (ATFL), a three-fiber bundle has recently been suggested to be weaker than a single or double fiber bundle in terms of ankle plantarflexion and inversion braking function. However, the studies leading to those results all used elderly specimens. Whether the difference in fiber bundles is a congenital or an acquired morphology is important when considering methods to prevent ATFL damage. The purpose of this study was to classify the number of fiber bundles in the ATFL of fetuses. Methods This study was conducted using 30 legs from 15 Japanese fetuses (mean weight, 1764.6 ± 616.9 g; mean crown-rump length, 283.5 ± 38.7 mm; 8 males, 7 females). The ATFL was then classified by the number of fiber bundles: Type I, one fiber bundle; Type II, two fiber bundles; and Type III, three fiber bundles. Results Ligament type was Type I in 5 legs (16.7%), Type II in 21 legs (70%), and Type III in 4 legs (13.3%). Conclusions The present results suggest that the three fiber bundles of the structure of the ATFL may be an innate structure.

scholarly journals GRO J1744-28 and the Rapid Burster; Bizarre Objects!

1998 ◽  
Vol 188 ◽  
pp. 111-111
Author(s):  
Walter H.G. Lewin
Keyword(s):  
Type Ii ◽  
Time Intervals ◽  
Periodic Oscillations ◽  
X Ray ◽  
Magnetic Dipole Field ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Type Ii Bursts ◽  
The Difference ◽  
X Ray Binaries

The bursts from GRO J1744-28 are due to accretion instabilities as is the case for type II bursts in the Rapid Burster. Both sources are transient Low-Mass X-ray Binaries, and they both exhibit unusual quasi-periodic-oscillations in their persistent X-ray flux following several (not all) of the type II bursts. There are important differences too. GRO J1744-28 is an X-ray pulsar; the Rapid Burster is not. In addition, the pattern of bursts and the burst peak luminosities are very different for the two sources. Time intervals between the rapidly repetitive bursts in the Rapid Burster can be as short as 10 sec, in 1744-28 they are as short as 200 sec. The peak luminosities of the bursts from GRO J1744-28 can exceed the Eddington luminosity (for assumed isotropic emission) by one to two orders of magnitude. The QPO centroid frequencies (see above) differ by an order of magnitude (~0.04 Hz for the Rapid Burster, and 0.3 Hz for GRO J1744-28). The difference in behavior p obably lies in the difference in the magnetic dipole field strength of the accreting neutron stars (for GRO J1744-28 it is almost certainly much higher than for the Rapid Burster). It remains puzzling, why GRO J1744-28 and the Rapid Burster are the only known sources which exhibit rapidly repetitive type II bursts.

scholarly journals Chemical Evolution of Galaxies: Abundance Trends and Implications

1991 ◽  
Vol 145 ◽  
pp. 13-19
Author(s):  
James W. Truran
Keyword(s):  
Massive Stars ◽  
Current Knowledge ◽  
Spectroscopic Studies ◽  
Early History ◽  
Elemental Abundance ◽  
Type Ii ◽  
Halo Stars ◽  
Abundance Patterns ◽  
Abundance Trends ◽  
History Of

Recent spectroscopic studies of the elemental abundance patterns associated with extremely metal deficient field halo stars and globular cluster stars are briefly reviewed. These metal deficient stellar populations have been found to be characterized by abundance patterns which differ quite distinctly from those of solar system abundances, but are consistent with the view that they reflect primarily the nucleosynthesis products of the evolution of massive stars and associated Type II supernovae. Guided by our current knowledge of nucleosynthesis as a function of stellar mass occurring in stars and supernovae, we identify some interesting constraints upon theories of the formation and early history of our Galaxy.

scholarly journals Physical parameters and chemical abundances of Planetary Nebulae in the large Magellanic Cloud

1997 ◽  
Vol 180 ◽  
pp. 471-471 ◽  
Author(s):  
R. E. Carlos Reyes ◽  
J. E. Steiner ◽  
F. Elizalde
Keyword(s):  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Physical Parameters ◽  
Chemical Abundances ◽  
The Difference

In the present work we have computed the physical parameters and chemical abundances for 45 planetary nebulae (PN) in the Large Magellanic Cloud (LMC) using the photoionization code CLOUDY, developed by Ferland (1993). CLOUDY is used as a subroutine in the code DIANA, developed by Elizalde & Steiner (1996), which minimises indices that measures the difference between the calculated and real nebula.

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