401 research outputs found
Use of Ultrasound Imaging to Determine Sex of Shovelnose Sturgeon
During November 2002, 51 shovelnose sturgeon Scaphirhynchus platorynchus were sexed by ultrasound imaging using a portable ultrasonograph. We identified males with 96% accuracy (N = 25) and females with 80% accuracy (N = 25); one hermaphroditic individual was misidentified as a male. Overall, ultrasound imaging was 86% accurate. Sex in postspawned females was difficult to determine, 60% being misidentified as males (N = 5). Ultrasonography is an effective noninvasive method for sex determination that can be applied to other species of Acipenseriformes. Modern portable equipment expands its utility to field studies
Field induced magnetic order in the frustrated magnet Gadolinium Gallium Garnet
Gd3Ga5O12, (GGG), has an extraordinary magnetic phase diagram, where no long
range order is found down to 25 mK despite \Theta_CW \approx 2 K. However, long
range order is induced by an applied field of around 1 T. Motivated by recent
theoretical developments and the experimental results for a closely related
hyperkagome system, we have performed neutron diffraction measurements on a
single crystal sample of GGG in an applied magnetic field. The measurements
reveal that the H-T phase diagram of GGG is much more complicated than
previously assumed. The application of an external field at low T results in an
intensity change for most of the magnetic peaks which can be divided into three
distinct sets: ferromagnetic, commensurate antiferromagnetic, and
incommensurate antiferromagnetic. The ferromagnetic peaks (e.g. (112), (440)
and (220)) have intensities that increase with the field and saturate at high
field. The antiferromagnetic reflections have intensities that grow in low
fields, reach a maximum at an intermediate field (apart from the (002) peak
which shows two local maxima) and then decrease and disappear above 2 T. These
AFM peaks appear, disappear and reach maxima in different fields. We conclude
that the competition between magnetic interactions and alternative ground
states prevents GGG from ordering in zero field. It is, however, on the verge
of ordering and an applied magnetic field can be used to crystallise ordered
components. The range of ferromagnetic and antiferromagnetic propagation
vectors found reflects the complex frustration in GGG.Comment: 6 pages, 7 figures, HFM 2008 conference pape
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Co3(SO4)3(OH)2[enH2]: a newS= 3/2 Kagome-type layered sulfate with a unique connectivity
The Kagome lattice, comprising a two-dimensional array of corner-sharing equilateral triangles, is central to the exploration of magnetic frustration. In such a lattice, antiferromagnetic coupling between ions in triangular plaquettes prevents all of the exchange interactions being simultaneously satisfied and a variety of novel magnetic ground states may result at low temperature. Experimental realization of a Kagome lattice remains difficult. The jarosite family of materials of nominal composition AM3(SO4)2(OH)6 (A = monovalent cation; M= Fe3+, Cr3+), offers perhaps one of the most promising manifestations of the phenomenon of magnetic frustration in two dimensions. The magnetic properties of jarosites are however extremely sensitive to the degree of coverage of magnetic sites. Consequently, there is considerable interest in the use of soft chemical techniques for the design and synthesis of novel materials in which to explore the effects of spin, degree of site coverage and connectivity on magnetic frustration
A strained alkyne-containing bipyridine reagent ; synthesis, reactivity and fluorescence properties
We report the synthesis of a bipyridyl reagent containing a strained alkyne, which significantly restricts its flexibility. Upon strain-promoted alkyne-azide cycloaddition (SPAAC) with an azide, which does not require a Cu catalyst, the structure becomes significantly more flexible and an increase in fluorescence is observed. Upon addition of Zn(II), the fluorescence is enhanced further. The reagent has the potential to act as a fluorescent labelling agent with azide-containing substrates, including biological molecules
Intra-night Optical Variability of BL Lacs, Radio-Quiet Quasars and Radio-Loud Quasars
We report optical monitoring observations of 20 high-luminosity AGN, 12 of
which are radio-quiet quasars (RQQs). Intra-night optical variability (INOV)
was detected for 13 of the 20 objects, including 5 RQQs. The variations are
distinctly stronger and more frequent for blazars than for the other AGN
classes. By combining these data with results obtained earlier in our program,
we have formed an enlarged sample consisting of 9 BL Lacs, 19 RQQs and 11
lobe-dominated radio-loud quasars. The moderate level of rapid optical
variability found for both RQQs and radio lobe-dominated quasars argues against
a direct link between INOV and radio-loudness. We supplemented the present
observations of 3 BL Lacs with additional data from the literature. In this
extended sample of 12 well observed BL Lacs, stronger INOV is found for the
EGRET detected BL Lacs.Comment: 8 pages, 3 Postscript figures, Accepted for publication in MNRAS,
uses mn2e.cl
Unification of Luminous Type 1 Quasars through CIV Emission
Using a sample of 30,000 quasars from SDSS-DR7, we explore the range of
properties exhibited by high-ionization, broad emission lines, such as CIV
1549. Specifically we investigate the anti-correlation between L_UV and
emission line EQW (the Baldwin Effect) and the "blueshifting" of
high-ionization emission lines. The blueshift of the CIV emission line is
nearly ubiquitous, with a mean shift of 810 km/s for radio-quiet (RQ) quasars
and 360 km/s for radio-loud (RL) quasars, and the Baldwin Effect is present in
both RQ and RL samples. Composite spectra are constructed as a function of CIV
emission line properties in attempt to reveal empirical relationships between
different line species and the SED. Within a two-component disk+wind model of
the broad emission line region (BELR), where the wind filters the continuum
seen by the disk component, we find that RL quasars are consistent with being
dominated by the disk component, while BALQSOs are consistent with being
dominated by the wind component. Some RQ objects have emission line features
similar to RL quasars; they may simply have insufficient black hole (BH) spin
to form radio jets. Our results suggest that there could be significant
systematic errors in the determination of L_bol and BH mass that make it
difficult to place these findings in a more physical context. However, it is
possible to classify quasars in a paradigm where the diversity of BELR
parameters are due to differences in an accretion disk wind between quasars
(and over time); these differences are underlain primarily by the SED, which
ultimately must be tied to BH mass and accretion rate.Comment: 51 pages, 18 figures, accepted by AJ, revised version includes
various modifications based on the referee's comment
Locating the Youngest HII Regions in M82 with 7 mm Continuum Maps
We present 7mm Very Large Array continuum images of the starburst galaxy M82.
On arcsecond scales, two-thirds of the 7mm continuum consists of free-free
emission from HII regions. In the subarcsecond resolution map, we identify 14
compact sources, including 9 bright HII regions with N_Lyc > 10^51 sec^-1. Four
of the HII regions have rising spectra, implying emission measures > 10^8 cm^-6
pc. Except for one compact source with peculiar features, all other compact
radio sources are found in dust lanes and do not have optical or near-infrared
continuum counterparts. Four regions of extended, high brightness (EM > 10^7
cm-6 pc) radio emission are found in our high resolution map, including some as
large as ~2", or 30 pc, representing either associations of small HII regions,
or sheetlike structures of denser gas. The good correlation between 7 mm
emission and Spitzer IRAC 8 micron continuum-removed PAH feature suggests that
PAH emission may track the recently formed OB stars. We find an excellent
correlation between molecular gas and star formation, particularly dense gas
traced by HCN, down to the ~ 45 pc scale in M82. We also find star formation
efficiencies (SFEs) of 1-10% on the same scale, based on CO maps. The highest
SFE are found in regions with the highest dense gas fractions.Comment: 18 pages, 10 figures. Accepted for publication in A
In the Murine and Bovine Maternal Mammary Gland Signal Transducer and Activator of Transcription 3 is Activated in Clusters of Epithelial Cells around the Day of Birth
Signal transducers and activators of transcription (STAT) proteins regulate mammary development. Here we investigate the expression of phosphorylated STAT3 (pSTAT3) in the mouse and cow around the day of birth. We present localised colocation analysis, applicable to other mammary studies requiring identification of spatially congregated events. We demonstrate that pSTAT3-positive events are multifocally clustered in a non-random and statistically significant fashion. Arginase-1 expressing cells, consistent with macrophages, exhibit distinct clustering within the periparturient mammary gland. These findings represent a new facet of mammary STAT3 biology, and point to the presence of mammary sub-microenvironments.</p
Optical variability properties of high luminosity AGN classes
We present the results of a comparative study of the intra-night optical
variability (INOV) characteristics of radio-loud and radio-quiet quasars, which
involves a systematic intra-night optical monitoring of seven sets of high
luminosity AGNs covering the redshift range {\it z} to {\it z}
. The sample, matched in the optical luminosity -- redshift (M
-- z) plane, consists of seven radio-quiet quasars (RQQs), eight radio
lobe-dominated quasars (LDQs), six radio core-dominated quasars (CDQs) and five
BL Lac objects (BLs). Systematic CCD observations, aided by a careful data
analysis procedure, have allowed us to detect INOV with amplitudes as low as
1%. Present observations cover a total of 113 nights (720 hours) with only a
single quasar monitored as continuously as possible on a night. Considering
cases of only unambiguous detections of INOV we have estimated duty cycles
(DCs) of 17%, 12%, 20% and 72% respectively for RQQs, LDQs, CDQs, and BLs. The
low amplitude and low DC of INOV shown by RQQs compared to BLs can be
understood in terms of their having optical synchrotron jets which are modestly
misdirected from us. From our fairly extensive dataset, no unambiguous general
trend of a correlation between the INOV amplitude and the apparent optical
brightness of the quasar is noticed.Comment: 36 pages, 14 Figures, due to large size Fig. 5,6,11 and 12 are not
included. Intersted people contact to [email protected]. Submitted to
Journal of Astrophysics and Astronom
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