The Experts below are selected from a list of 2940 Experts worldwide ranked by ideXlab platform
Jeffrey L Bada - One of the best experts on this subject based on the ideXlab platform.
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new method for estimating bacterial cell abundances in natural samples by use of sublimation
Applied and Environmental Microbiology, 2004Co-Authors: Daniel P Glavin, James H Cleaves, Michael Schubert, A D Aubrey, Jeffrey L BadaAbstract:We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The Sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.
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new method for estimating bacterial cell abundances in natural samples by use of sublimation
Applied and Environmental Microbiology, 2004Co-Authors: Daniel P Glavin, James H Cleaves, Michael Schubert, A D Aubrey, Jeffrey L BadaAbstract:We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500°C for several seconds under reduced pressure. The Sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from ∼105 to 109 E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.
Edwin A Bergin - One of the best experts on this subject based on the ideXlab platform.
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molecule sublimation as a tracer of protostellar accretion evidence for accretion bursts from high angular resolution c18o images
Astronomy and Astrophysics, 2015Co-Authors: J K Jorgensen, R Visser, J Williams, Edwin A BerginAbstract:Context. The accretion histories of embedded protostars are an integral part of descriptions of their physical and chemical evolution. In particular, we want to know whether the accretion rates smoothly decline from earlier to later stages or whether they are in fact characterized by variations such as intermittent bursts. Aims. We aim to characterize the impact of possible accretion variations for a sample of embedded protostars by measuring the sizes of the inner regions of their envelopes where CO is Sublimated and relate these extents to the temperature profiles dictated by the current luminosities of the protostars. Methods. Using observations from the Submillimeter Array we measure the extent of the emission from the C 18 O isotopologue toward 16 deeply embedded protostars. We compare these measurements to the predicted extent of the emission given the current luminosities of the sources through dust and line radiative transfer calculations. Results. Eight out of sixteen sources show more extended C 18 O emission than predicted by the models. The modeling shows that the likely culprit for these signatures is sublimation due to increases in luminosities of the sources by about a factor of five or more during the recent 10 000 yr, i.e., the time it takes for CO to freeze-out again on dust grains. For four of these sources the increase must have been a factor of 10 or more. The compact emission seen toward the other half of the sample suggests that C 18 O only Sublimates when the temperature exceeds 30 K ‐ as expected if CO is mixed with H2O in the grain ice-mantles. Conclusions. The results from this survey suggest that protostars undergo significant bursts about once every 20 000 yr, although the statistics su er from the small sample size. The results illustrate the importance of taking the physical evolutionary histories into account for descriptions of the chemical structures of embedded protostars.
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molecule sublimation as a tracer of protostellar accretion evidence for accretion bursts from high angular resolution c18o images
arXiv: Solar and Stellar Astrophysics, 2015Co-Authors: J K Jorgensen, R Visser, Jonathan P Williams, Edwin A BerginAbstract:The accretion histories of embedded protostars are an integral part of descriptions of their physical and chemical evolution. In particular, are the accretion rates smoothly declining from the earlier toward later stages or in fact characterized by variations such as intermittent bursts? We aim to characterize the impact of possible accretion variations in a sample of embedded protostars by measuring the size of the inner regions of their envelopes where CO is Sublimated and relate those to their temperature profiles dictated by their current luminosities. Using observations from the Submillimeter Array we measure the extents of the emission from the C18O isotopologue toward 16 deeply embedded protostars. We compare these measurements to the predicted extent of the emission given the current luminosities of the sources through dust and line radiative transfer calculations. Eight out of sixteen sources show more extended C18O emission than predicted by the models. The modeling shows that the likely culprit for these signatures is sublimation due to increases in luminosities of the sources by about a factor five or more during the recent 10,000 years - the time it takes for CO to freeze-out again on dust grains. For four of those sources the increase would have had to have been a factor 10 or more. The compact emission seen toward the other half of the sample suggests that C18O only Sublimates when the temperature exceeds 30 K - as one would expect if CO is mixed with H2O in the grain ice-mantles. The small-number statistics from this survey suggest that protostars undergo significant bursts about once every 20,000 years. This also illustrates the importance of taking the physical evolutionary histories into account for descriptions of the chemical structures of embedded protostars.
Junhai Yang - One of the best experts on this subject based on the ideXlab platform.
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matrix sublimation recrystallization for imaging proteins by mass spectrometry at high spatial resolution
Analytical Chemistry, 2011Co-Authors: Junhai YangAbstract:We have employed matrix deposition by sublimation for protein image analysis on tissue sections using a hydration/recrystallization process that produces high-quality MALDI mass spectra and high-spatial-resolution ion images. We systematically investigated different washing protocols, the effect of tissue section thickness, the amount of Sublimated matrix per unit area, and different recrystallization conditions. The results show that an organic solvent rinse followed by ethanol/water rinses substantially increased sensitivity for the detection of proteins. Both the thickness of the tissue section and the amount of sinapinic acid Sublimated per unit area have optimal ranges for maximal protein signal intensity. Ion images of mouse and rat brain sections at 50, 20, and 10 μm spatial resolution are presented and are correlated with hematoxylin and eosin (H&E)-stained optical images. For targeted analysis, histology-directed imaging can be performed using this protocol where MS analysis and H&E staining are ...
Daniel P Glavin - One of the best experts on this subject based on the ideXlab platform.
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new method for estimating bacterial cell abundances in natural samples by use of sublimation
Applied and Environmental Microbiology, 2004Co-Authors: Daniel P Glavin, James H Cleaves, Michael Schubert, A D Aubrey, Jeffrey L BadaAbstract:We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The Sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.
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new method for estimating bacterial cell abundances in natural samples by use of sublimation
Applied and Environmental Microbiology, 2004Co-Authors: Daniel P Glavin, James H Cleaves, Michael Schubert, A D Aubrey, Jeffrey L BadaAbstract:We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500°C for several seconds under reduced pressure. The Sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from ∼105 to 109 E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.
J K Jorgensen - One of the best experts on this subject based on the ideXlab platform.
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molecule sublimation as a tracer of protostellar accretion evidence for accretion bursts from high angular resolution c18o images
Astronomy and Astrophysics, 2015Co-Authors: J K Jorgensen, R Visser, J Williams, Edwin A BerginAbstract:Context. The accretion histories of embedded protostars are an integral part of descriptions of their physical and chemical evolution. In particular, we want to know whether the accretion rates smoothly decline from earlier to later stages or whether they are in fact characterized by variations such as intermittent bursts. Aims. We aim to characterize the impact of possible accretion variations for a sample of embedded protostars by measuring the sizes of the inner regions of their envelopes where CO is Sublimated and relate these extents to the temperature profiles dictated by the current luminosities of the protostars. Methods. Using observations from the Submillimeter Array we measure the extent of the emission from the C 18 O isotopologue toward 16 deeply embedded protostars. We compare these measurements to the predicted extent of the emission given the current luminosities of the sources through dust and line radiative transfer calculations. Results. Eight out of sixteen sources show more extended C 18 O emission than predicted by the models. The modeling shows that the likely culprit for these signatures is sublimation due to increases in luminosities of the sources by about a factor of five or more during the recent 10 000 yr, i.e., the time it takes for CO to freeze-out again on dust grains. For four of these sources the increase must have been a factor of 10 or more. The compact emission seen toward the other half of the sample suggests that C 18 O only Sublimates when the temperature exceeds 30 K ‐ as expected if CO is mixed with H2O in the grain ice-mantles. Conclusions. The results from this survey suggest that protostars undergo significant bursts about once every 20 000 yr, although the statistics su er from the small sample size. The results illustrate the importance of taking the physical evolutionary histories into account for descriptions of the chemical structures of embedded protostars.
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molecule sublimation as a tracer of protostellar accretion evidence for accretion bursts from high angular resolution c18o images
arXiv: Solar and Stellar Astrophysics, 2015Co-Authors: J K Jorgensen, R Visser, Jonathan P Williams, Edwin A BerginAbstract:The accretion histories of embedded protostars are an integral part of descriptions of their physical and chemical evolution. In particular, are the accretion rates smoothly declining from the earlier toward later stages or in fact characterized by variations such as intermittent bursts? We aim to characterize the impact of possible accretion variations in a sample of embedded protostars by measuring the size of the inner regions of their envelopes where CO is Sublimated and relate those to their temperature profiles dictated by their current luminosities. Using observations from the Submillimeter Array we measure the extents of the emission from the C18O isotopologue toward 16 deeply embedded protostars. We compare these measurements to the predicted extent of the emission given the current luminosities of the sources through dust and line radiative transfer calculations. Eight out of sixteen sources show more extended C18O emission than predicted by the models. The modeling shows that the likely culprit for these signatures is sublimation due to increases in luminosities of the sources by about a factor five or more during the recent 10,000 years - the time it takes for CO to freeze-out again on dust grains. For four of those sources the increase would have had to have been a factor 10 or more. The compact emission seen toward the other half of the sample suggests that C18O only Sublimates when the temperature exceeds 30 K - as one would expect if CO is mixed with H2O in the grain ice-mantles. The small-number statistics from this survey suggest that protostars undergo significant bursts about once every 20,000 years. This also illustrates the importance of taking the physical evolutionary histories into account for descriptions of the chemical structures of embedded protostars.
