Search results for "13C"
showing 10 items of 194 documents
Cribra orbitalia as a potential indicator of childhood stress: Evidence from paleopathology, stable C, N, and O isotopes, and trace element concentra…
2016
Cribra orbitalia (CO), or porotic hyperostosis (PH) of the orbital roof, is one of the most common pathological conditions found in archaeological subadult skeletal remains. Reaching frequencies higher than 50% in many prehistoric samples, CO has been generally attributed to a variety of factors including malnutrition (e.g., megaloblastic anemia) and parasitism. In this study, we tested the relationship between CO, trace element concentrations, and stable isotope values (δ13C, δ15N, δ18O) in subadult skeletons from a 17th to 18th century cemetery in the historic town of Jēkabpils, Latvia. A total of 28 subadults were examined, seven of which (25%) showed evidence of CO. Bioarchaeological ev…
Quenching of gA deduced from the β-spectrum shape of 113Cd measured with the COBRA experiment
2020
A dedicated study of the quenching of the weak axial-vector coupling strength gA in nuclear processes has been performed by the COBRA collaboration. This investigation is driven by nuclear model calculations which show that the β-spectrum shape of the fourfold forbidden non-unique decay of 113Cd strongly depends on the effective value of gA. Using an array of CdZnTe semiconductor detectors, 45 independent 113Cd spectra were obtained and interpreted in the context of three nuclear models. The resulting effective mean values are g‾A(ISM)=0.915±0.007, g‾A(MQPM)=0.911±0.013 and g‾A(IBFM-2)=0.955±0.022. These values agree well within the determined uncertainties and deviate significantly from th…
Experimental and theoretical NMR and IR studies of the side‐chain orientation effects on the backbone conformation of dehydrophenylalanine residue
2011
Conformation of N‐acetyl‐(E)‐dehydrophenylalanine N′, N′‐dimethylamide (Ac‐(E)‐ΔPhe‐NMe2) in solution, a member of (E)‐α, β‐dehydroamino acids, was studied by NMR and infrared spectroscopy and the results were compared with those obtained for (Z) isomer. To support the spectroscopic interpretation, the ϕ, ψ potential energy surfaces were calculated at the MP2/6‐31 + G(d,p) level of theory in chloroform solution modeled by the self‐consistent reaction field‐polarizable continuum model method. All minima were fully optimized by the MP2 method and their relative stabilities were analyzed in terms of π‐conjugation, internal H‐bonds and dipole interactions between carbonyl groups. The obtained N…
The metabolites of the genus onopordum (asteraceae): Chemistry and biological properties
2011
Onopordum is an interesting genus belonging to the tribe Cardueae (Asteraceae family), and the species of this genus are used as food and in the popular medicine of several countries. The present paper reviews all the metabolites present in all the species of this genus, reported up to 2009, and several chemotaxonomic consideration have been made. Furthermore, the occurrence in other genus, the spectral data, the synthetic approaches, the chemical modifications and the biological properties of the sesquiterpenes of genus Onopor- dum have been reviewed.
Ģimenes ārstu un speciālistu nozīmēto H.pylori eradikācijas shēmu salīdzinājums; to atbilstība vadlīnijām un efektivitāte
2016
Helicobacter pylori kolonizē kuņģa gļotādu vairāk nekā pusei pasaules iedzīvotāju. Pasaules Veselības organizācija ir pasludinājusi H. pylori par 1. grupas kancerogēno vielu. Latvijā H. pylori eradikācijas shēmas nozīmē atbilstoši Māstrihtas IV vadlīnijām. Pētījuma mērķis – salīdzīnāt ģimenes ārstu un speciālistu nozīmēto H. pylori eradikācijas shēmu efektivitāti un atbilstību vadlīnijām. Pētījumā piedalījās 550 pacienti, kuri bija ieradušies uz eradikācijas efektivitātes testa veikšanu. Ģimenes ārsti vadlīnijām atbilstošas eradikācijas shēmas bija nozīmējuši 85,8% gadījumu, bet gastroenterologi – 96,8% gadījumu. Ģimenes ārsti efektīvu H. pylori eradikācijas terapiju nozīmējuši 77,6% gadīju…
H.pylori eradikācijas shēmas un to efektivitāte Latvijas ģimenes ārstu un gastroenterologu praksēs
2017
H. pylori ir kuņģī mītošs patogēns, kurš visiem inficētajiem izsauc aktīvu hronisku gastrītu. V Māstrihtas vadlīnijas nosaka, ka vajadzētu piedāvāt veikt H. pylori eradikāciju visiem pacientiem, lai novērstu risku nākotnē attīstīties nopietnākām komplikācijām, piemēram, kuņģa vēzim. Pētījumā analizētas Latvijas ģimenes ārstu un gastroenterologu nozīmētās eradikācijas terapijas. Iesaistīti 670 pacienti un kopumā izvērtētas 753 terapijas. Kopējā eradikācijas terapiju efektivitāte sasniedz tikai 73.31% un tā ir zemāka par vadlīnijās noteikto minimālo vēlamo efektivitātes rādītāju (80%). Gastroenterologi biežāk (85.14% gadījumu) kā ģimenes ārsti (70.96% gadījumu) nozīmē efektīvas eradikācijas t…
Nonlinear Raman Spectroscopy in Gases
1992
0022-2860; Recent progress in high-resolution non-linear coherent Raman spectroscopy in the gas phase is reviewed. An instrumental spectral resolution of less than 100 MHz can be routinely achieved. It is limited by the convoluted linewidths of the lasers used for excitation and is of particular advantage in the gas phase, where the rotational structure of vibrational bands is to be resolved. It also allows the measurement of linewidths and line positions with an accuracy of 60 MHz when an appropriate wavemeter is used for calibration. After a short overview of the various techniques being used, examples of recent results of the evaluation of measurements on nitrogen, oxygen, carbon dioxide…
1,3-Dipolar Cycloaddition Reactions of Indan-1-one Enamines across Arylnitrile Oxides Leading to Novel Cyclic Isoxazoline Derivatives
2013
Synthesis of a series of cyclic fused-isoxazolines has been accomplished by regioselective and diastereoselective 1,3-dipolar cycloaddition of 3-methylindan-1-one enamines (1a, 1b, 1c) and 3-phenylindan-1-one enamines (2a, 2b, 2c) to arylnitrile oxides (3d, 3e, 3f, 3g, 3h). The structure of the cycloadducts was elucidated by 1H and 13C NMR spectroscopy. The proposed regio- and stereochemistry of fused-compounds (4) and (5) has also been corroborated by two single-crystal X-ray diffraction studies carried out on 4-methyl-8b-morpholinyl-3-(p-tolyl)-4H-3a,8b-dihydroindeno[2,3-d]isoxazoline (4be) and 3-(p-anisyl)-4-phenyl-8b-pyrrolidinyl-4H-3a,8b-dihydroindeno[2,3-d]isoxazoline (5af) and by mea…
Parasite infection alters host stable-isotope composition under controlled feeding
2016
1) Stable isotopes are widely used for studying trophic relationships, but variation driven by environmental conditions or food availability complicates the interpretation of trophic dynamics. Parasites are ubiquitous and known to affect physiological functions of their hosts, but only few studies have assessed the effects of parasites on isotope composition of hosts. 2) We measured the changes in two of the most commonly used stable isotopes in food-web studies, nitrogen (i.e. 15N:14N ratio; denoted as δ15N) and carbon (13C:12C; δ13C) in Daphnia hosts exposed to infection by a parasitic micosporidian in the laboratory. Isotopic signatures of hosts fed a standardised controlled diet were co…
Effect of cactus pear cultivation after Mediterranean maquis on soil carbon stock, δ13C spatial distribution and root turnover
2014
Abstract Mediterranean ecosystems are characterized by nearly complete replacement of natural vegetation by intensive croplands and orchards leading to strong soil degradation. Organic carbon is usually accumulated in soils under maquis leading to partial regeneration of fertility for future agricultural use. The aim of this work was to investigate the effect of land use change from maquis to agriculture on soil organic carbon (SOC) stock and its spatial distribution in a Mediterranean system. Three Mediterranean land use systems (seminatural vegetation, cactus pear crop and olive grove) were selected in Sicily and analysed for soil C stocks and their δ13C. Total SOC and δ13C were measured …