Synthesis and stable isotope dilution assay of ethanethiol and diethyl disulfide in wine using solid phase microextraction. Effect of aging on their levels in wine     

Belancic Majcenovic A  Schneider R  Lepoutre JP  Lempereur V  Baumes R 《Journal of agricultural and food chemistry》2002,50(23):6653-6658

Ethanethiol and diethyl disulfide (DEDS) most often occurred at levels above their olfactive threshold in wines with nauseous sulfur-linked smells. As ethanethiol is very oxidizable and chemically reactive, a stable isotopic dilution analysis of both ethanethiol and its disulfide in wines using solid phase microextraction and GC-MS was developed. The latter involved the determination of the proportion of DEDS formed by oxidation of the thiol during the analysis conditions, which was obtained by the use of two differently labeled disulfide standards. An original synthesis of labeled ethanethiol standards in conditions minimizing oxidation was developed, and the corresponding labeled diethyl disulfides were obtained from these thiols. This analytical method was used to follow the levels of these sulfur compounds during aging in a young red wine spiked with ethanethiol and added with enological tannins, with or without oxygen addition. The total levels of these two sulfur compounds were shown to decrease steadily after 60 days of aging, up to 83%. The effect of oxygen sped this decrease, but the effect of enological tannins was very slight. Residual ethanethiol was detected in its disulfide form from approximately 36% in the nonoxygenated wines to 69% in the oxygenated samples.  相似文献   

Electrochromatography with reversing electrophoretic field     

S Raymond  J Broome 《Science (New York, N.Y.)》1966,153(742):1381-1382

A protein mixture can be separated in a flow column by application of a transverse electrophoretic field to carry faster-migrating components of the mixture into a fixed gel bed at one side of the column, so that slower components move along in a buffer stream. The field is then reversed to returnthe faster-moving components to the buffer stream. The cycle is repeated many times to complete the separation.  相似文献   

Astronomy. Imaging the Sun's eruptions in three dimensions     

Raymond JC 《Science (New York, N.Y.)》2004,305(5680):49-50

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Ecology. Putting the heat on tropical animals     

Tewksbury JJ  Huey RB  Deutsch CA 《Science (New York, N.Y.)》2008,320(5881):1296-1297

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When fear is near: threat imminence elicits prefrontal-periaqueductal gray shifts in humans     

Mobbs D  Petrovic P  Marchant JL  Hassabis D  Weiskopf N  Seymour B  Dolan RJ  Frith CD 《Science (New York, N.Y.)》2007,317(5841):1079-1083

Humans, like other animals, alter their behavior depending on whether a threat is close or distant. We investigated spatial imminence of threat by developing an active avoidance paradigm in which volunteers were pursued through a maze by a virtual predator endowed with an ability to chase, capture, and inflict pain. Using functional magnetic resonance imaging, we found that as the virtual predator grew closer, brain activity shifted from the ventromedial prefrontal cortex to the periaqueductal gray. This shift showed maximal expression when a high degree of pain was anticipated. Moreover, imminence-driven periaqueductal gray activity correlated with increased subjective degree of dread and decreased confidence of escape. Our findings cast light on the neural dynamics of threat anticipation and have implications for the neurobiology of human anxiety-related disorders.  相似文献   

Serum dopamine-beta-hydroxylase activity: sibling-sibling correlation   总被引：7，自引：0，他引：7  

R M Weinshilboum  F A Raymond  L R Elveback  W H Weidman 《Science (New York, N.Y.)》1973,181(103):943-945

Dopamine-beta-hydroxylase activity is released into the blood with catecholamines from the adrenal medulla and sympathetic nerves. This enzyme activity has been measured in the blood of 317 normal children and 227 normal adults. A significant sibling-sibling correlation of serum dopamine-beta-hydroxylase values was found in the 94 sibling pairs tested. Frequency distributions of serum enzyme values in both children and adults suggest the existence of two populations with regard to serum activity of this enzyme.  相似文献   

Lipoprotein patterns in acrylamide gel electrophoresis   总被引：1，自引：0，他引：1  

S Raymond  J L Miles  J C Lee 《Science (New York, N.Y.)》1966,151(708):346-347

Lipoproteins of serum stained before electrophoresis gave distinct patterns in acrylamide gel of 3-percent concentration. Samples compared in parallel on gel slabs showed qualitative differences in migration rates of beta-lipoprotein bands.  相似文献   

Possible mechanism for the antiarrhythmic effect of helium in anesthetized dogs     

L Raymond  R B Weiskopf  M J Halsey  A Goldfien  E I Eger  J W Severinghaus 《Science (New York, N.Y.)》1972,176(40):1250-1252

Breathing a mixture of 75 percent helium and 25 percent oxygen instead of 75 percent nitrogen and 25 percent oxygen reduced the occurrence of dangerous cardiac arrhythmias after ligation of the circumflex coronary artery in open-chest dogs anesthetized with pentobarbital. In dogs not subjected to circumflex ligation, the sensitivity of blood pressure, heart rate, and extrasystoles to epinephrine injected intravenously was not altered by the substitution of helium for nitrogen; however, helium did reduce the baseline heart rate and the concentration of endogenous plasma catecholamines. The antiarrhythmic effect of helium may thus be mediated by changes in sympathetic activity.  相似文献   

Anterior cingulate conflict monitoring and adjustments in control     

Kerns JG  Cohen JD  MacDonald AW  Cho RY  Stenger VA  Carter CS 《Science (New York, N.Y.)》2004,303(5660):1023-1026

Conflict monitoring by the anterior cingulate cortex (ACC) has been posited to signal a need for greater cognitive control, producing neural and behavioral adjustments. However, the very occurrence of behavioral adjustments after conflict has been questioned, along with suggestions that there is no direct evidence of ACC conflict-related activity predicting subsequent neural or behavioral adjustments in control. Using the Stroop color-naming task and controlling for repetition effects, we demonstrate that ACC conflict-related activity predicts both greater prefrontal cortex activity and adjustments in behavior, supporting a role of ACC conflict monitoring in the engagement of cognitive control.  相似文献   

Pleistocene glaciation in the blue ridge province, southern appalachian mountains, north Carolina     

Berkland JO  Raymond LA 《Science (New York, N.Y.)》1973,181(4100):651-653

Glacial polish, grooves, and striations discovered at an elevation of 1370 meters in the headwaters of Boone Fork on Grandfather Mountain, North Carolina, indicate the former, existence of alpine glaciation at a latitude of 36 degrees 07'N. The Boone Fork glacier was located 890 kilometers south of the previously recognized southern limit of alpine glaciation in the Appalachian Mountains, and 350 kilometers southeast of the nearest point on the Laurentide ice sheet. This find has significant implications for studies of Pleistocene geomorphology, paleobiology, and paleoclimatology in the eastern United States.  相似文献