8,875 research outputs found
Detection of Lyman-alpha Emitting Galaxies at Redshift z=4.55
Studies of the formation and early history of galaxies have been hampered by
the difficulties inherent in detecting faint galaxy populations at high
redshift. As a consequence, observations at the highest redshifts (3.5 < z < 5)
have been restricted to objects that are intrinsically bright. These include
quasars, radio galaxies, and some Ly alpha-emitting objects that are very close
to (within ~10 kpc) -- and appear to be physically associated with -- quasars.
But the extremely energetic processes which make these objects easy to detect
also make them unrepresentative of normal (field) galaxies. Here we report the
discovery using Keck spectroscopic observations of two Ly alpha-emitting
galaxies at redshift z = 4.55, which are sufficiently far from the nearest
quasar (~700 kpc) that radiation from the quasar is unlikely to provide the
excitation source of the Ly alpha emission. Instead, these galaxies appear to
be undergoing their first burst of star formation, at a time when the Universe
was less than one billion years old.Comment: 8 pages, 1 landscape table, and 3 PostScript figures. Uses
aaspp4.sty, flushrt.sty, aj_pt4.sty, overcite.sty (style macros available
from xxx.lanl.gov) Figure 1 is bitmapped to 100 dpi. The original PostScript
version of Fig. 1 is available via anonymous ftp to
ftp://hubble.ifa.hawaii.edu/pub/preprints To appear in Natur
Hydrodynamics of a 5D Einstein-dilaton black hole solution and the corresponding BPS state
We apply the potential reconstruction approach to generate a series of
asymptotically AdS (aAdS) black hole solutions, with a self-interacting bulk
scalar field. Based on the method, we reproduce the pure AdS solution as a
consistency check and we also generate a simple analytic 5D black hole
solution. We then study various aspects of this solution, such as temperature,
entropy density and conserved charges. Furthermore, we study the hydrodynamics
of this black hole solution in the framework of fluid/gravity duality, e.g. the
ratio of the shear viscosity to the entropy density. In a degenerate case of
the 5D black hole solution, we find that the c function decreases monotonically
from UV to IR as expected. Finally, we investigate the stability of the
degenerate solution by studying the bosonic functional energy of the gravity
and the Witten-Nester energy . We confirm that the degenerate solution
is a BPS domain wall solution. The corresponding superpotential and the
solution of the killing spinor equation are found explicitly.Comment: V2: 23 pages, no figure, minor changes, typos corrected, new
references and comments added, version accepted by JHE
Measuring Metacognition in Cancer: Validation of the Metacognitions Questionnaire 30 (MCQ-30)
Objective
The Metacognitions Questionnaire 30 assesses metacognitive beliefs and processes which are central to the metacognitive model of emotional disorder. As recent studies have begun to explore the utility of this model for understanding emotional distress after cancer diagnosis, it is important also to assess the validity of the Metacognitions Questionnaire 30 for use in cancer populations.
Methods
229 patients with primary breast or prostate cancer completed the Metacognitions Questionnaire 30 and the Hospital Anxiety and Depression Scale pre-treatment and again 12 months later. The structure and validity of the Metacognitions Questionnaire 30 were assessed using factor analyses and structural equation modelling.
Results
Confirmatory and exploratory factor analyses provided evidence supporting the validity of the previously published 5-factor structure of the Metacognitions Questionnaire 30. Specifically, both pre-treatment and 12 months later, this solution provided the best fit to the data and all items loaded on their expected factors. Structural equation modelling indicated that two dimensions of metacognition (positive and negative beliefs about worry) were significantly associated with anxiety and depression as predicted, providing further evidence of validity.
Conclusions
These findings provide initial evidence that the Metacognitions Questionnaire 30 is a valid measure for use in cancer populations
Rapid EST isolation from chromosome 1R of rye
<p>Abstract</p> <p>Background</p> <p>To obtain important expressed sequence tags (ESTs) located on specific chromosomes is currently difficult. Construction of single-chromosome EST library could be an efficient strategy to isolate important ESTs located on specific chromosomes. In this research we developed a method to rapidly isolate ESTs from chromosome 1R of rye by combining the techniques of chromosome microdissection with hybrid specific amplification (HSA).</p> <p>Results</p> <p>Chromosome 1R was isolated by a glass needle and digested with proteinase K (PK). The DNA of chromosome 1R was amplified by two rounds of PCR using a degenerated oligonucleotide 6-MW sequence with a <it>Sau</it>3AI digestion site as the primer. The PCR product was digested with <it>Sau</it>3AI and linked with adaptor HSA1, then hybridized with the <it>Sau</it>3AI digested cDNA with adaptor HSA2 of rye leaves with and without salicylic acid (SA) treatment, respectively. The hybridized DNA fragments were recovered by the HSA method and cloned into pMD18-T vector. The cloned inserts were released by PCR using the partial sequences in HSA1 and HSA2 as the primers and then sequenced. Of the 94 ESTs obtained and analyzed, 6 were known sequences located on rye chromosome 1R or on homologous group 1 chromosomes of wheat; all of them were highly homologous with ESTs of wheat, barley and/or other plants in <it>Gramineae</it>, some of which were induced by abiotic or biotic stresses. Isolated in this research were 22 ESTs with unknown functions, probably representing some new genes on rye chromosome 1R.</p> <p>Conclusion</p> <p>We developed a new method to rapidly clone chromosome-specific ESTs from chromosome 1R of rye. The information reported here should be useful for cloning and investigating the new genes found on chromosome 1R.</p
Detection of Massive Forming Galaxies at Redshifts Greater than One
The complex problem of when and how galaxies formed has not until recently
been susceptible of direct attack. It has been known for some time that the
excessive number of blue galaxies counted at faint magnitudes implies that a
considerable fraction of the massive star formation in the universe occurred at
z < 3, but, surprisingly, spectroscopic studies of galaxies down to a B
magnitude of 24 found little sign of the expected high-z progenitors of current
massive galaxies, but rather, in large part, small blue galaxies at modest
redshifts z \sim 0.3. This unexpected population has diverted attention from
the possibility that early massive star-forming galaxies might also be found in
the faint blue excess. From KECK spectroscopic observations deep enough to
encompass a large population of z > 1 field galaxies, we can now show directly
that in fact these forming galaxies are present in substantial numbers at B
\sim 24, and that the era from redshifts 1 to 2 was clearly a major period of
galaxy formation. These z > 1 galaxies have very unusual morphologies as seen
in deep HST WFPC2 images.Comment: 10 pages LaTeX + 5 PostScript figures in uuencoded gzipped tar file;
aasms4.sty, flushrt.sty, overcite.sty (the two aastex4.0 and overcite.sty
macros are available from xxx.lanl.gov) Also available (along with style
files) via anonymous ftp to ftp://hubble.ifa.hawaii.edu/pub/preprints .
E-print version of paper adds citation cross-references to other archived
e-prints, where available. To appear in Nature October 19, 199
Selective serotonin reuptake inhibitors in the treatment of generalized anxiety disorder
Selective serotonin reuptake inhibitors have proven efficacy in the treatment of panic disorder, obsessive–compulsive disorder, post-traumatic stress disorder and social anxiety disorder. Accumulating data shows that selective serotonin reuptake inhibitor treatment can also be efficacious in patients with generalized anxiety disorder. This review summarizes the findings of randomized controlled trials of selective serotonin reuptake inhibitor treatment for generalized anxiety disorder, examines the strengths and weaknesses of other therapeutic approaches and considers potential new treatments for patients with this chronic and disabling anxiety disorder
Variable-temperature, variable-field magnetic circular dichroism spectroscopic study of NifEN-bound precursor and “FeMoco”
NifEN plays a key role in the biosynthesis of the iron–molybdenum cofactor (FeMoco) of nitrogenase. A scaffold protein that hosts the conversion of a FeMoco precursor to a mature cofactor, NifEN can assume three conformations during the process of FeMoco maturation. One, designated ΔnifB NifEN, contains only two permanent [Fe4S4]-like clusters. The second, designated NifENPrecursor, contains the permanent clusters and a precursor form of FeMoco. The third, designated NifEN“FeMoco”, contains the permanent [Fe4S4]-like clusters and a fully complemented, “FeMoco”-like structure. Here, we report a variable-temperature, variable-field magnetic circular dichroism spectroscopic investigation of the electronic structure of the metal clusters in the three forms of dithionite-reduced NifEN. Our data indicate that the permanent [Fe4S4]-like clusters are structurally and electronically conserved in all three NifEN species and exhibit spectral features of classic [Fe4S4]+ clusters; however, they are present in a mixed spin state with a small contribution from the S > ½ spin state. Our results also suggest that both the precursor and “FeMoco” have a conserved Fe/S electronic structure that is similar to the electronic structure of FeMoco in the MoFe protein, and that the “FeMoco” in NifEN“FeMoco” exists, predominantly, in an S = 3/2 spin state with spectral parameters identical to those of FeMoco in the MoFe protein. These observations provide strong support to the outcome of our previous EPR and X-ray absorption spectroscopy/extended X-ray absorption fine structure analysis of the three NifEN species while providing significant new insights into the unique electronic properties of the precursor and “FeMoco” in NifEN
Combinations of β-lactam or aminoglycoside antibiotics with plectasin are synergistic against methicillin-sensitive and methicillin-resistant Staphylococcus aureus.
Bacterial infections remain the leading killer worldwide which is worsened by the continuous emergence of antibiotic resistance. In particular, methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) are prevalent and the latter can be difficult to treat. The traditional strategy of novel therapeutic drug development inevitably leads to emergence of resistant strains, rendering the new drugs ineffective. Therefore, rejuvenating the therapeutic potentials of existing antibiotics offers an attractive novel strategy. Plectasin, a defensin antimicrobial peptide, potentiates the activities of other antibiotics such as β-lactams, aminoglycosides and glycopeptides against MSSA and MRSA. We performed in vitro and in vivo investigations to test against genetically diverse clinical isolates of MSSA (n = 101) and MRSA (n = 115). Minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. The effects of combining plectasin with β-lactams, aminoglycosides and glycopeptides were examined using the chequerboard method and time kill curves. A murine neutropenic thigh model and a murine peritoneal infection model were used to test the effect of combination in vivo. Determined by factional inhibitory concentration index (FICI), plectasin in combination with aminoglycosides (gentamicin, neomycin or amikacin) displayed synergistic effects in 76-78% of MSSA and MRSA. A similar synergistic response was observed when plectasin was combined with β-lactams (penicillin, amoxicillin or flucloxacillin) in 87-89% of MSSA and MRSA. Interestingly, no such interaction was observed when plectasin was paired with vancomycin. Time kill analysis also demonstrated significant synergistic activities when plectasin was combined with amoxicillin, gentamicin or neomycin. In the murine models, plectasin at doses as low as 8 mg/kg augmented the activities of amoxicillin and gentamicin in successful treatment of MSSA and MRSA infections. We demonstrated that plectasin strongly rejuvenates the therapeutic potencies of existing antibiotics in vitro and in vivo. This is a novel strategy that can have major clinical implications in our fight against bacterial infections
Cosmic Hydrogen Was Significantly Neutral a Billion Years After the Big Bang
The ionization fraction of cosmic hydrogen, left over from the big bang,
provides crucial fossil evidence for when the first stars and quasar black
holes formed in the infant universe. Spectra of the two most distant quasars
known show nearly complete absorption of photons with wavelengths shorter than
the Ly-alpha transition of neutral hydrogen, indicating that hydrogen in the
intergalactic medium (IGM) had not been completely ionized at a redshift z~6.3,
about a billion years after the big bang. Here we show that the radii of
influence of ionizing radiation from these quasars imply that the surrounding
IGM had a neutral hydrogen fraction of tens of percent prior to the quasar
activity, much higher than previous lower limits of ~0.1%. When combined with
the recent inference of a large cumulative optical depth to electron scattering
after cosmological recombination from the WMAP data, our result suggests the
existence of a second peak in the mean ionization history, potentially due to
an early formation episode of the first stars.Comment: 14 Pages, 2 Figures. Accepted for publication in Nature. Press
embargo until publishe
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