keyword
MENU ▼
Read by QxMD icon Read
search

Isotope

keyword
https://www.readbyqxmd.com/read/28812741/persistent-tropical-foraging-in-the-highlands-of-terminal-pleistocene-holocene-new-guinea
#1
Patrick Roberts, Dylan Gaffney, Julia Lee-Thorp, Glenn Summerhayes
The terminal Pleistocene/Holocene boundary (approximately 12-8 thousand years ago) represented a major ecological threshold for humans, both as a significant climate transition and due to the emergence of agriculture around this time. In the highlands of New Guinea, climatic and environmental changes across this period have been highlighted as potential drivers of one of the earliest domestication processes in the world. We present a terminal Pleistocene/Holocene palaeoenvironmental record (12-0 thousand years ago ) of carbon and oxygen isotopes in small mammal tooth enamel from the site of Kiowa...
February 6, 2017: Nature ecology & evolution
https://www.readbyqxmd.com/read/28812683/megafaunal-isotopes-reveal-role-of-increased-moisture-on-rangeland-during-late-pleistocene-extinctions
#2
M Timothy Rabanus-Wallace, Matthew J Wooller, Grant D Zazula, Elen Shute, A Hope Jahren, Pavel Kosintsev, James A Burns, James Breen, Bastien Llamas, Alan Cooper
The role of environmental change in the late Pleistocene megafaunal extinctions remains a key question, owing in part to uncertainty about landscape changes at continental scales. We investigated the influence of environmental changes on megaherbivores using bone collagen nitrogen isotopes (n = 684, 63 new) as a proxy for moisture levels in the rangelands that sustained late Pleistocene grazers. An increase in landscape moisture in Europe, Siberia and the Americas during the Last Glacial-Interglacial Transition (LGIT; ~25-10 kyr bp) directly affected megaherbivore ecology on four continents, and was associated with a key period of population decline and extinction...
April 18, 2017: Nature ecology & evolution
https://www.readbyqxmd.com/read/28812639/late-pliocene-environmental-change-during-the-transition-from-australopithecus-to-homo
#3
Joshua R Robinson, John Rowan, Christopher J Campisano, Jonathan G Wynn, Kaye E Reed
It has long been hypothesized that the transition from Australopithecus to Homo in eastern Africa was linked to the spread of open and arid environments near the Plio-Pleistocene boundary, but data for the latest Pliocene are scarce. Here we present new stable carbon isotope data from the late Pliocene mammalian fauna from Ledi-Geraru, in the lower Awash Valley (LAV), Ethiopia, and mammalian community analyses from the LAV and Turkana Basin. These data, combined with pedogenic carbonate stable isotopes, indicate that the two regions were largely similar through the Plio-Pleistocene, but that important environmental differences existed during the emergence of Homo around 2...
May 15, 2017: Nature ecology & evolution
https://www.readbyqxmd.com/read/28812278/monomer-dependent-secondary-nucleation-in-amyloid-formation
#4
REVIEW
Sara Linse
Secondary nucleation of monomers on the surface of an already existing aggregate that is formed from the same kind of monomers may lead to autocatalytic amplification of a self-assembly process. Such monomer-dependent secondary nucleation occurs during the crystallization of small molecules or proteins and self-assembled materials, as well as in protein self-assembly into fibrous structures. Indications of secondary nucleation may come from analyses of kinetic experiments starting from pure monomers or monomers supplemented with a low concentration of pre-formed aggregates (seeds)...
August 15, 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28812082/a-broader-view-on-ion-heating-in-traveling-wave-devices-using-fragmentation-of-csi-clusters-and-extent-of-h%C3%AB-migration-as-molecular-thermometers
#5
Frederik Lermyte, Frank Sobott
Electron transfer dissociation (ETD) is becoming increasingly important in mass spectrometry-based analysis of peptides and proteins. Supplemental collisional activation of undissociated electron transfer products can significantly increase fragmentation yield and sequence coverage, but hydrogen rearrangements - specifically, transfer of a hydrogen radical from a c to a z fragment - lead to distorted isotope distributions and increased potential for signal overlap. Concomitant collisional activation during the ion/ion reaction significantly reduces these rearrangements, but, in ion traps, also leads to lower reaction rates and reduced overlap of anion and cation clouds...
August 16, 2017: Analyst
https://www.readbyqxmd.com/read/28811883/effect-of-habitat-degradation-on-competition-carrying-capacity-and-species-assemblage-stability
#6
Edoardo Calizza, Maria Letizia Costantini, Giulio Careddu, Loreto Rossi
Changes in species' trophic niches due to habitat degradation can affect intra- and interspecific competition, with implications for biodiversity persistence. Difficulties of measuring species' interactions in the field limit our comprehension of competition outcomes along disturbance gradients. Thus, information on how habitat degradation can destabilize food webs is scarce, hindering predictions regarding responses of multispecies systems to environmental changes. Seagrass ecosystems are undergoing degradation...
August 2017: Ecology and Evolution
https://www.readbyqxmd.com/read/28811874/functional-roles-of-an-engineer-species-for-coastal-benthic-invertebrates-and-demersal-fish
#7
Aurélie Chaalali, Anik Brind'Amour, Stanislas F Dubois, Hervé Le Bris
Through their tissues or activities, engineer species create, modify, or maintain habitats and alter the distribution and abundance of many plants and animals. This study investigates key ecological functions performed by an engineer species that colonizes coastal ecosystems. The gregarious tubiculous amphipod Haploops nirae is used as a biological model. According to previous studies, the habitat engineered by H. nirae (i.e., Haploops habitat) could provide food and natural shelter for several benthic species such as benthic diatoms belonging to the gender Navicula, the micrograzer Geitodoris planata, or the bivalve Polititapes virgineus...
August 2017: Ecology and Evolution
https://www.readbyqxmd.com/read/28811573/simultaneous-separation-of-actinium-and-radium-isotopes-from-a-proton-irradiated-thorium-matrix
#8
Tara Mastren, Valery Radchenko, Allison Owens, Roy Copping, Rose Boll, Justin R Griswold, Saed Mirzadeh, Lance E Wyant, Mark Brugh, Jonathan W Engle, Francois M Nortier, Eva R Birnbaum, Kevin D John, Michael E Fassbender
A new method has been developed for the isolation of (223,224,225)Ra, in high yield and purity, from a proton irradiated (232)Th matrix. Herein we report an all-aqueous process using multiple solid-supported adsorption steps including a citrate chelation method developed to remove >99.9% of the barium contaminants by activity from the final radium product. A procedure involving the use of three columns in succession was developed, and the separation of (223,224,225)Ra from the thorium matrix was obtained with an overall recovery yield of 91 ± 3%, average radiochemical purity of 99...
August 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28811532/protein-expression-changes-caused-by-spaceflight-as-measured-for-18-russian-cosmonauts
#9
Irina M Larina, Andrew J Percy, Juncong Yang, Christoph H Borchers, Andrei M Nosovsky, Anatoli I Grigoriev, Evgeny N Nikolaev
The effects of spaceflight on human physiology is an increasingly studied field, yet the molecular mechanisms driving physiological changes remain unknown. With that in mind, this study was performed to obtain a deeper understanding of changes to the human proteome during space travel, by quantitating a panel of 125 proteins in the blood plasma of 18 Russian cosmonauts who had conducted long-duration missions to the International Space Station. The panel of labeled prototypic tryptic peptides from these proteins covered a concentration range of more than 5 orders of magnitude in human plasma...
August 15, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28811296/a-novel-d2o-tracer-method-to-quantify-rna-turnover-as-a-biomarker-of-de-novo-ribosomal-biogenesis-in-vitro-in-animal-models-and-in-human-skeletal-muscle
#10
Matthew S Brook, Daniel J Wilkinson, W Kyle Mitchell, Jonathan L Lund, Bethan E Phillips, Nathaniel J Sweczyk, Heikki Kainulainen, Sanna Lensu, Lauren G Koch, Steve L Britton, Paul L Greenhaff, Kenneth Smith, Philip J Atherton
Current methods to quantify RNA dynamics are beset with limitations. Here, we developed a novel stable isotope (D2O)-methodology to quantify RNA synthesis (i.e. ribosomal biogenesis) in cells, animal models, and humans. Firstly, proliferating C2C12 cells were incubated in D2O-enriched media and myotubes (±) 50ng.ml(-1) IGF-1. Secondly, rat quadriceps [untrained n=9; 7-wks interval-"like" training n=13] were collected after ~3-wks D2O (70-Atom%) administration, with body-water enrichment (BWE) monitored via blood sampling...
August 15, 2017: American Journal of Physiology. Endocrinology and Metabolism
https://www.readbyqxmd.com/read/28811145/characterization-of-methane-oxidation-in-a-simulated-landfill-cover-system-by-comparing-molecular-and-stable-isotope-mass-balances
#11
Marcel Schulte, Maik A Jochmann, Tobias Gehrke, Andrea Thom, Tim Ricken, Martin Denecke, Torsten C Schmidt
Biological methane oxidation may be regarded as a method of aftercare treatment for landfills to reduce climate relevant methane emissions. It is of social and economic interest to estimate the behavior of bacterial methane oxidation in aged landfill covers due to an adequate long-term treatment of the gas emissions. Different approaches assessing methane oxidation in laboratory column studies have been investigated by other authors recently. However, this work represents the first study in which three independent approaches, ((i) mass balance, (ii) stable isotope analysis, and (iii) stoichiometric balance of product (CO2) and reactant (CH4) by CO2/CH4-ratio) have been compared for the estimation of the biodegradation by a robust statistical validation on a rectangular, wide soil column...
August 12, 2017: Waste Management
https://www.readbyqxmd.com/read/28810782/first-principles-molecular-dynamics-study-of-deuterium-diffusion-in-liquid-tin
#12
Xiaohui Liu, Daye Zheng, Xinguo Ren, Lixin He, Mohan Chen
Understanding the retention of hydrogen isotopes in liquid metals, such as lithium and tin, is of great importance in designing a liquid plasma-facing component in fusion reactors. However, experimental diffusivity data of hydrogen isotopes in liquid metals are still limited or controversial. We employ first-principles molecular dynamics simulations to predict diffusion coefficients of deuterium in liquid tin at temperatures ranging from 573 to 1673 K. Our simulations indicate faster diffusion of deuterium in liquid tin than the self-diffusivity of tin...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28810732/tracking-radionuclide-fractionation-in-the-first-atomic-explosion-using-stable-elements
#13
Chloe E Bonamici, Richard L Hervig, William S Kinman
Compositional analysis of post-detonation fallout is a tool for forensic identification of nuclear devices. However, the relationship between device composition and fallout composition is difficult to interpret because of the complex combination of physical mixing, nuclear reactions, and chemical fractionations that occur in the chaotic nuclear fireball. Using a combination of in situ microanalytical techniques - electron microprobe analysis and secondary ion mass spectrometry - we show that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd, Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test, Trinity, are reliable chemical proxies for radionuclides generated during the explosion...
August 16, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28810730/hydrogen-isotope-fractionation-during-biodegradation-of-1-2-dichloroethane-potential-for-pathway-identification-using-a-multi-element-c-cl-and-h-isotope-approach
#14
Jordi Palau, Orfan Shouakar-Stash, Siti Hatijah Mortan, Rong Yu, Monica Rosell, Ernest Marco-Urrea, David L Freedman, Ramon Aravena, Albert Soler, Daniel Hunkeler
Even though multi-element isotope fractionation patterns provide crucial information to identify contaminant degradation pathways in the field, those involving hydrogen are still lacking for many halogenated groundwater contaminants and degradation pathways. This study investigates for the first time hydrogen isotope fractionation during both aerobic and anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) using five microbial cultures. Transformation-associated isotope fractionation values (ε_bulk^H) were: -115 ± 18‰ (aerobic C-H bond oxidation), -34 ± 4‰ and -38 ± 4‰ (aerobic C-Cl bond cleavage via hydrolytic dehalogenation), -57 ± 3‰ and -77 ± 9‰ (anaerobic C-Cl bond cleavage via reductive dihaloelimination)...
August 16, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28810225/critical-evaluation-of-distillation-procedure-for-the-determination-of-methylmercury-in-soil-samples
#15
Pablo A Perez, Holger Hintelman, Waldo Quiroz, Manuel A Bravo
In the present work, the efficiency of distillation process for extracting monomethylmercury (MMHg) from soil samples was studied and optimized using an experimental design methodology. The influence of soil composition on MMHg extraction was evaluated by testing of four soil samples with different geochemical characteristics. Optimization suggested that the acid concentration and the duration of the distillation process were most significant and the most favorable conditions, established as a compromise for the studied soils, were determined to be a 70 min distillation using an 0...
August 9, 2017: Chemosphere
https://www.readbyqxmd.com/read/28809117/n5-in-solution-isotopic-labeling-and-further-details-of-its-synthesis-by-phenyl-pentazole-reduction
#16
Boris Bazanov, Uzi Geiger, Dan Grinstein, Shmuel Welner, Yehuda Haas
The cyclopentazolate anion, N5-, has been researched extensively over the years and detected in the gas phase more than a decade ago, but was only recently measured in solution. The process whereby aryl pentazole reduction leads to the production of N5- is still not fully understood. Here, the production of N5- in solution was investigated using isotopic labeling techniques while implementing changes to the synthesis methodologies. 15N labeled phenyl pentazole produced appropriately labeled phenyl pentazole radical anions and N5- which, upon collision induced dissociation, produced the expected N3- signals...
August 15, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28809062/carbon-nitrogen-and-sulphur-isotopic-fractionation-in-captive-juvenile-hooded-seal-cystophora-cristata-application-for-diet-analysis
#17
Marianna Pinzone, Mario Acquarone, Loreen Huyghebaert, Nicolas Sturaro, Loïc N Michel, Ursula Siebert, Krishna Das
RATIONALE: Intrinsic biogeochemical markers, such as stable isotope ratios of carbon, nitrogen and sulphur are increasingly used to trace the trophic ecology of marine top predators. However, insufficient knowledge of fractionation processes in tissues continues to hamper the use of these markers. METHODS: We performed a controlled feeding experiment with eight juvenile hooded seals (Cystophora cristata) that were held on a herring-based diet (Clupea harengus) for two years...
August 15, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28808779/optimisation-of-extraction-methods-and-quantification-of-benzo-a-pyrene-and-benz-a-anthracene-in-yerba-mat%C3%A3-tea-by-isotope-dilution-mass-spectrometry
#18
Ee Mei Gui, Ting Lu, Tang Lin Teo, Pui Sze Cheow, Tong Kooi Lee
A gas chromatography-isotope dilution mass spectrometry (GC-IDMS) technique was developed for the quantification of two heavy polyaromatic hydrocarbons (PAHs), benz[a]anthracene and benzo[a]pyrene, in yerba maté tea (maté). The optimisation of two extraction methods, namely liquid-liquid extraction and accelerated solvent extraction, was carried out. Both optimised methods were validated using a certified reference material of fine dust and the results were within the expanded uncertainties at 95% confidence level...
August 14, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28808741/stable-isotope-raman-microspectroscopy-for-the-analysis-of-soil-organic-matter
#19
Alexandra C Wiesheu, Ramona Brejcha, Carsten W Mueller, Ingrid Kögel-Knabner, Martin Elsner, Reinhard Niessner, Natalia P Ivleva
We examined the potential of stable-isotope Raman microspectroscopy (SIRM) for the evaluation of differently enriched (13)C-labeled humic acids as model substances for soil organic matter (SOM). The SOM itself can be linked to the soil water holding capacity. Therefore, artificial humic acids (HA) with known isotopic compositions were synthesized and analyzed by means of SIRM. By performing a pregraphitization, a suitable analysis method was developed to cope with the high fluorescence background. Results were verified against isotope ratio mass spectrometry (IRMS)...
August 14, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28808731/biomacromolecules-as-tools-and-objects-in-nanometrology-current-challenges-and-perspectives
#20
Payam Hashemi, Luise Luckau, Petra Mischnick, Sarah Schmidt, Rainer Stosch, Bettina Wünsch
Nucleic acids, proteins, and polysaccharides are the most important classes of biopolymers. The inherent properties of biomacromolecules are contrary to those of well-defined small molecules consequently raising a number of specific challenges which become particularly apparent if biomacromolecules are treated as objects in quantitative analysis. At the same time, their specific functional ability of molecular recognition and self-organization (e.g., enzymes, antibodies, DNA) enables us to make biomacromolecules serving as molecular tools in biochemistry and molecular biology, or as precisely controllable dimensional platforms for nanometrological applications...
August 14, 2017: Analytical and Bioanalytical Chemistry
keyword
keyword
115571
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"