669 research outputs found
Unusual hemiacetal structure derived from Salvinorin A
The salvinorin A analog dimethyl (2R,3aR,4R,6aR,7R,9S,9aS,9bS)-2-(3-furyl)-9,9a-dihydroxy-3a,6a-dimethyldodecahydrobenzo[de]chromene-4,7-dicarboxylate, C22H30O8, has a relatively simple spatial arrangement in which molecules are linked into layers by two pairs of O—H⋯O hydrogen bonds. Each molecule has as the central feature a dodecahydro-1H-phenalene ring system. Its three six-membered rings are in the chair conformation, with two axial methyl groups, one axial OH, and one equatorial OH, these OH groups being directly responsible for linking of the molecules in the crystal structure
(2S,4aR,6aR,7R,9S,10aS,10bR)-7-Carboxy-2-(3-furyl)-6a,10b-dimethyl-4,10-dioxoperhydrobenzo[f]isochromen-9-yl acetate
The asymmetric unit of the title compound, C22H26O8, contains two crystallographically independent molecules with closely comparable conformations (r.m.s. overlay = 0.54 Å for 30 non-H atoms). All six-membered rings display chair conformations, with a slight distortion for the lactone ring. The molecules are connected by O—H⋯O hydrogen bonds into chains along [010], with the independent molecules segregated into separate chains. The two molecules in the asymmetric unit face each other in a head-to-tail fashion, with the furan ring of one molecule turned towards the carboxylic acid terminal of the other molecule
Electron multiplication CCD detector technology advancement for the WFIRST-AFTA coronagraph
The WFIRST-AFTA (Wide Field InfraRed Survey Telescope-Astrophysics Focused Telescope Asset) is a NASA space observatory. It will host two major astronomical instruments: a wide-field imager (WFI) to search for dark energy and carry out wide field near infrared (NIR) surveys, and a coronagraph instrument (CGI) to image and spectrally characterize extrasolar planets. In this paper, we discuss the work that has been carried out at JPL in advancing Electron Multiplying CCD (EMCCD) technology to higher flight maturity, with the goal of reaching a NASA technology readiness level of 6 (TRL-6) by early-to-mid 2016. The EMCCD has been baselined for both the coronagraph's imager and integral field spectrograph (IFS) based on its sub-electron noise performance at extremely low flux levels - the regime where the AFTA CGI will operate. We present results from a study that fully characterizes the beginning of life performance of the EMCCD. We also discuss, and present initial results from, a recent radiation test campaign that was designed and carried out to mimic the conditions of the WFIRST-AFTA space environment in an L2 orbit, where we sought to assess the sensor's end of life performance, particularly degradation of its charge transfer efficiency, in addition to other parameters such as dark current, electron multiplication gain, clock induced charge and read noise
Concert recording 2017-10-11
[Track 1]. Fantasy on Acteon / J.B. Arban -- [Track 2]. Fantasiestücke. I. Zart und mit Ausdruck [Track 3]. II. Lebhaft, leicht / Robert Schumann -- [Track 4]. El Moncayo / Jan Hadermann -- [Track 5]. Concerto for tuba. I. Allegro moderato / John Williams -- [Track 6]. Sonata in F minor. I. Triste [Track 7]. II. Allegro / G.F. Telemann -- [Track 8]. Suite no. 3 for solo cello, BWV 1009. Prelude / J.S. Bach -- [Track 9]. Fantasy for tuba / Malcolm Arnold -- [Tracks 10-12]. Sonata in F major / Benedetto Marcello
Cryogenic irradiation of an EMCCD for the WFIRST coronagraph: preliminary performance analysis
The Wide Field Infra-Red Survey Telescope (WFIRST) is a NASA observatory scheduled to launch in the next decade that will settle essential questions in exoplanet science. The Wide Field Instrument (WFI) offers Hubble quality imaging over a 0.28 square degree field of view and will gather NIR statistical data on exoplanets through gravitational microlensing. An on-board coronagraph will for the first time perform direct imaging and spectroscopic analysis of exoplanets with properties analogous to those within our own solar system, including cold Jupiters, mini Neptunes and potentially super Earths.
The Coronagraph Instrument (CGI) will be required to operate with low signal flux for long integration times, demanding all noise sources are kept to a minimum. The Electron Multiplication (EM)-CCD has been baselined for both the imaging and spectrograph cameras due its ability to operate with sub-electron effective read noise values with appropriate multiplication gain setting. The presence of other noise sources, however, such as thermal dark signal and Clock Induced Charge (CIC), need to be characterized and mitigated. In addition, operation within a space environment will subject the device to radiation damage that will degrade the Charge Transfer Effciency (CTE) of the device throughout the mission lifetime. Irradiation at the nominal instrument operating temperature has the potential to provide the best estimate of performance degradation that will be experienced in-flight, since the final population of silicon defects has been shown to be dependent upon the temperature at which the sensor is irradiated.
Here we present initial findings from pre- and post- cryogenic irradiation testing of the e2v CCD201-20 BI EMCCD sensor, baselined for the WFIRST coronagraph instrument. The motivation for irradiation at cryogenic temperatures is discussed with reference to previous investigations of a similar nature. The results are presented in context with those from a previous room temperature irradiation investigation that was performed on a CCD201-20 operated under the same conditions. A key conclusion is that the measured performance degradation for a given proton fluence is seen to measurably differ for the cryogenic case compared to the room temperature equivalent for the conditions of this study
Molecular characterization of 5-chlorophyll a/b-binding protein genes from Panax ginseng Meyer and their expression analysis during abiotic stresses
The chlorophyll a/b-binding protein (CAB) serves in both photosystems (PS), I and II, as a coordinator of antenna pigments in the light-harvesting complex (LHC). The CABs constitute abundant and important proteins in the thylakoid membrane of higher plants. In our study, five CAB genes, which contained full-length cDNA sequences from the 4-year-old ginseng leaves (Panax ginseng Meyer), were isolated and named PgCAB. Phylogenetic comparison of the members of the subfamily between ginseng and higher plants, including Arabidopsis, revealed that the putative functions of these ginseng CAB proteins were clustered into the different family of Arabidopsis CABs; two PgCABs in LHCII family and three PgCABs in LHCI family. The expression analysis of PgCABs consistently showed dark-dependent inhibition in leaves. Expression analysis during abiotic stress identified that PgCAB genes responded to heavy metal, salinity, chilling, and UV stresses differently, suggesting their specific function during photosynthesis. This is the first comprehensive study of the CAB gene family in P. ginseng
Concert recording 2018-04-24b
[Track 1]. Six studies in English folksong. I. Adagio [Track 2]. II. Andante sostenuto [Track 3]. III. Andante tranquillo [Track 4]. IV. Allegro vivace / Ralph Vaughan Williams -- [Track 5]. Sonata in F minor. I. Andante [Track 6]. II. Allegro / G.F. Teleman -- [Track 7]. Allerseelen / Richard Strauss arranged by Stuckemeyer/Bottorf -- [Track 8]. Bride of the waves / Herbert L. Clarke -- [Track 9]. Suite. I. Allegor marcato [Track 10]. III. Allegretto [Track 11]. IV. Slow / Vaclav Nelhybel -- [Track 12]. A walk in the woods / Jiro Censhu -- [Track 13]. Concerto in one movement / Alexy Lebedev -- [Track 14]. By gaslight / Tadeusz Kassatti -- [Track 15]. Child\u27s play. I. ♩=132 / Barbara York
The impact of radiation damage on photon counting with an EMCCD for the WFIRST-AFTA coronagraph
WFIRST-AFTA is a 2.4m class NASA observatory designed to address a wide range of science objectives using two complementary scientific payloads. The Wide Field Instrument (WFI) offers Hubble quality imaging over a 0.28 square degree field of view, and will gather NIR statistical data on exoplanets through gravitational microlensing. The second instrument is a high contrast coronagraph that will carry out the direct imaging and spectroscopic analysis of exoplanets, providing a means to probe the structure and composition of planetary systems. The coronagraph instrument is expected to operate in low photon flux for long integration times, meaning all noise sources must be kept to a minimum. In order to satisfy the low noise requirements, the Electron Multiplication (EM)-CCD has been baselined for both the imaging and spectrograph cameras. The EMCCD was selected in comparison with other candidates because of its low effective electronic read noise at sub-electron values with appropriate multiplication gain setting. The presence of other noise sources, however, such as thermal dark signal and Clock Induced Charge (CIC), need to be characterised and mitigated. In addition, operation within a space environment will subject the device to radiation damage that will degrade the Charge Transfer Efficiency (CTE) of the device throughout the mission lifetime. Here we present our latest results from pre- and post-irradiation testing of the e2v CCD201-20 BI EMCCD sensor, baselined for the WFIRST-AFTA coronagraph instrument. A description of the detector technology is presented, alongside considerations for operation within a space environment. The results from a room temperature irradiation are discussed in context with the nominal operating requirements of AFTA-C and future work which entails a cryogenic irradiation of the CCD201-20 is presented
Concert recording 2017-11-28
[Track 1]. Bill Bailey / Hughie Cannon arranged by James Garrett -- [Track 2]. Second suite. I. March [Track 3]. II. Song without words, I\u27ll love my love / Gustav Holst arranged by Cody Hutchison -- [Track 4]. Deutschland uber alles / Franz Joseph Haydn arranged by Eugene Anderson -- [Track 5]. Geleit from Three pieces / Johannes Brahms translated by William R. Lee -- [Track 6]. Belle of Chicago march / John Philip Sousa arranged by Skip Gray -- [Track 7]. Three preludes from op. 34. No. 14 [Track 8]. No. 7 [Track 9]. No. 16 / Dmitri Shostakovich arranged by Rauch -- [Track 10]. Tuba Sunday / traditional arranged by Gerald Sloan -- [Track 11]. Quartet for tubas / Sy Brandon -- [Track 12.] Cherokee / John Schooley -- [Track 13]. Moondance / John Stevens -- [Track 14]. Amazing grace / traditional arranged by David Uber
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