700 research outputs found
Amino acid racemization dating of marine shells: a mound of possibilities
Shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments. Establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal. This paper explores the potential application of a new methodology of amino acid racemization(AAR) dating of shell middens and describes a simple protocol to test the suitability of different molluscanspecies. This protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins(by bleaching experiments and subsequent heating at high temperature), checking the closed system behaviour of this fraction during diagenesis. Only species which pass both tests can be considered suitable for further studies to obtain reliable age information. This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea.Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world
Amino acid racemization dating of marine shells: a mound of possibilities
Shell middens are one of the most important and widespread indicators for human exploitation of marine resources and occupation of coastal environments. Establishing an accurate and reliable chronology for these deposits has fundamental implications for understanding the patterns of human evolution and dispersal. This paper explores the potential application of a new methodology of amino acid racemization(AAR) dating of shell middens and describes a simple protocol to test the suitability of different molluscanspecies. This protocol provides a preliminary test for the presence of an intracrystalline fraction of proteins(by bleaching experiments and subsequent heating at high temperature), checking the closed system behaviour of this fraction during diagenesis. Only species which pass both tests can be considered suitable for further studies to obtain reliable age information. This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea.Results obtained in this study indicate that the application of this new method of AAR dating of shells has the potential to aid the geochronological investigation of shell mounds in different areas of the world
Mass accretion rates from multi-band photometry in the Carina Nebula: the case of Trumpler 14
We present a study of the mass accretion rates of pre-Main Sequence (PMS)
stars in the cluster Trumpler 14 (Tr14) in the Carina Nebula. Using optical
multi-band photometry we were able to identify 356 PMS stars showing H-alpha
excess emission with equivalent width EW(H-alpha)>20\AA. We interpret this
observational feature as indication that these objects are still actively
accreting gas from their circumstellar medium. From a comparison of the HR
diagram with PMS evolutionary models we derive ages and masses of the PMS
stars. We find that most of the PMS objects are younger than 10 Myr with a
median age of ~3 Myr. Surprisingly, we also find that ~20% of the mass
accreting objects are older than 10 Myr. For each PMS star in Trumpler 14 we
determine the mass accretion rate () and discuss its dependence
on mass and age. We finally combine the optical photometry with near-IR
observations to build the spectral energy distribution (SED) for each PMS star
in Tr14. The analysis of the SEDs suggests the presence of transitional discs
in which a large amount of gas is still present and sustains accretion onto the
PMS object at ages older than 10 Myr. Our results, discussed in light of recent
recent discoveries with Herschel of transitional discs containing a massive gas
component around the relatively old PSM stars TW Hydrae, 49 Ceti, and HD 95086,
support a new scenario in which old and evolved debris discs still host a
significant amount of gas.Comment: 12 pages, 13 figures, accepted for publication on A&
Population structure and genetic differentiation among the substructured Vysya caste population in comparison to the other populations of Andhra Pradesh, India
The present paper focuses on the study of the patterns of genetic microdifferentiation among one of the substructured caste populations of Andhra Pradesh, namely Vysya, with reference to 17 other Telugu speaking populations from the same region of India. A total of 302 individuais from the three Vysya subgroups (101 of Arya Vysya, 100 from Kalinga Vysya and 101 from Thrivarnika) were typed in 17 blood groups and protein polymorphisms. Nei's gene diversity analysis, as well as neighbour-joining tree and UPGMA cluster diagrams, derived from standard genetic distances, R-matrix analysis and a regression model for investigating the patterns of external gene flow and genetic drift due to isolation under the island model, were done at two levels: (1) considering only the three Vysya populations and (2) considering common loci among 20 populations of Andhra Pradesh. Seven of the 17 systems investigated were found to be monomorphic among all the three Vysya groups. The UPGMA tree and bidimensional scaling of the D2 distances derived from R-matrix analysis show a very distinct cluster of Vysya populations. Application of the model of regression of average heterozygosity versus the distance of populations from the centroid shows the three Vysya populations placed as clear outliers above the theoretical regression line. Different approaches employed in this study give support to the hypothesis of different origin and/or demographic story for the three Vysya groups compared with other populations of Andhra Pradesh.Fil: Lakshmi, N.. Andhra University; IndiaFil: Demarchi, Dario. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Instituto de AntropologĂa de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de FilosofĂa y Humanidades. Instituto de AntropologĂa de CĂłrdoba; ArgentinaFil: Veerraju, P.. Andhra University; IndiaFil: Rao, T. V.. Andhra University; Indi
Efeitos de doses de resĂduos orgânicos e tipos de adubação na biomassa microbiana do solo cultivado com milho.
O trabalho foi conduzido na fazenda escola da UEL com o objetivo de avaliar os efeitos de doses de resĂduos orgânicos e de tipos de adubação na biomassa microbiana do solo cultivado com milho. O carbono da biomassa microbiana do solo foi avaliado em cada Ă©poca de floração e colheita do milho em duas safras, considerando-se o delineamento experimental de blocos casualizados em esquema fatorial 4 x 2, com trĂŞs repetições, em que os fatores foram quatro doses de resĂduos (O, 15, 30 e 45 Mg ha-1), e dois tipos de adubação (AO: adubação orgânica e OM: adubação organomineral). A adubação mineral empregada na semeadura do milho nas duas safras correspondeu Ă aplicação de 40, 60 e 40 kg ha-1 de N, P2O5 e K2O, respectivamente. O conteĂşdo de carbono da biomassa microbiana do solo aumentou com as doses de resĂduo na primeira safra de milho. O ponto de máximo (777 mg Kg-1 de solo) foi observado na floração do milho da segunda safra e para a dose de 23 Mg ha-1 de resĂduo. Na colheita da segunda safra reduziu linearmente com as doses de resĂduos nas parcelas que receberam adubação organomineral
The subscapular artery and the thoracodorsal branch: an anatomical study
The motive for this research was the use of the muscles of the scapular region
in transposition, transplantation and reparative surgery and the need for more
detailed knowledge of the blood supply to these muscles. In addition, the subscapular
arterial tree may be used as a source of microvascular grafts to replace
damaged or diseased portions of arteries, particularly in the hand and forearm.
The research was conducted on 60 sides of corpses of adults of both sexes.
It was noticed that the subscapular artery was present in 96.7% of cases and
originated laterally to the pectoralis minor muscle in 76.7% of cases. The average
calibre was 5.0 mm, and in 73.2% of cases it measured between 4.0 and
5.9 mm. The average length was 18.0 mm, ranging from 10.0 to 29.9 mm
(76.7%). It presented in its course important relations with the axillary nerve
(69%) and with the radial nerve (82.8%). Its branches were collateral (subscapular
muscle - 61.3%) and terminal (except for the circumflex scapular artery),
leading to the following muscles: serratus anterior (43.9%), latissimus dorsi
(27.6%), and subscapular (23.3%). The thoracodorsal artery, one of the terminal
branches, most frequently showed a calibre of between 2.0 and 3.9 mm
(70.3%), collateral branches in 85.0%, was mainly distributed to the subscapular
muscle (36.7%) and to the serratus anterior muscle (29.0%) and had terminal
branches to the following muscles: latissimus dorsi (44.1%), serratus anterior
(40.5%) and the subscapular (12.5%). The serratus anterior muscle received
one branch in 39.5% and two branches in 41.9%, while the latissimus dorsi
muscle received one branch in 66.7% and two branches in 23.1%. (Folia Morphol
2008; 67: 58-62
Silicon nanofluidic membrane for electrostatic control of drugs and analytes elution
Individualized long-term management of chronic pathologies remains an elusive goal despite recent progress in drug formulation and implantable devices. The lack of advanced systems for therapeutic administration that can be controlled and tailored based on patient needs precludes optimal management of pathologies, such as diabetes, hypertension, rheumatoid arthritis. Several triggered systems for drug delivery have been demonstrated. However, they mostly rely on continuous external stimuli, which hinder their application for long-term treatments. In this work, we investigated a silicon nanofluidic technology that incorporates a gate electrode and examined its ability to achieve reproducible control of drug release. Silicon carbide (SiC) was used to coat the membrane surface, including nanochannels, ensuring biocompatibility and chemical inertness for long-term stability for in vivo deployment. With the application of a small voltage (≤ 3 V DC) to the buried polysilicon electrode, we showed in vitro repeatable modulation of membrane permeability of two model analytes—methotrexate and quantum dots. Methotrexate is a first-line therapeutic approach for rheumatoid arthritis; quantum dots represent multi-functional nanoparticles with broad applicability from bio-labeling to targeted drug delivery. Importantly, SiC coating demonstrated optimal properties as a gate dielectric, which rendered our membrane relevant for multiple applications beyond drug delivery, such as lab on a chip and micro total analysis systems (µTAS)
Intra-crystalline protein diagenesis (IcPD) in Patella vulgata. Part I: Isolation and testing of the closed system
This study successfully isolates a fraction of intra-crystalline proteins from shells of the marine gastropod Patella vulgata and assesses the suitability of these proteins for IcPD (Intra-crystalline Protein Diagenesis) geochronology. We discuss the mineralogical composition of this gastropod, investigated for the first time by X-ray diffraction mapping, and use the results to inform our sampling strategy. The potential of the calcitic rim and of a bulk sample (containing both apex and rim) of the shell to act as stable repositories for the intra-crystalline proteins during diagenesis is examined. The composition and the diagenetic behaviour of the intra-crystalline proteins isolated from different locations within the shell are compared, highlighting the necessity of targeting consistent sampling positions. We induced artificial diagenesis of both intra-crystalline and whole-shell proteins by conducting high-temperature experiments in hydrous environment; this allowed us to quantify the loss of amino acids by leaching and therefore evaluate the open- or closed-system behaviour of the different fractions of proteins. The results obtained provide further confirmation that patterns of diagenesis vary according to the protein sequence, structure, and location within or outside the intra-crystalline fraction. As Patella is frequently found in the fossil record, both in archaeological and geological contexts, the application of IcPD geochronology to this biomineral opens up the possibility to obtain reliable age information from a range of sites in different areas of the world
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