945 research outputs found
High-precision Photometric Redshifts from Spitzer/IRAC: Extreme [3.6]-[4.5] Colors Identify Galaxies in the Redshift Range z~6.6-6.9
One of the most challenging aspects of studying galaxies in the z>~7 universe
is the infrequent confirmation of their redshifts through spectroscopy, a
phenomenon thought to occur from the increasing opacity of the intergalactic
medium to Lya photons at z>6.5. The resulting redshift uncertainties inhibit
the efficient search for [C II] in z~7 galaxies with sub-mm instruments such as
ALMA, given their limited scan speed for faint lines. One means by which to
improve the precision of the inferred redshifts is to exploit the potential
impact of strong nebular emission lines on the colors of z~4-8 galaxies as
observed by Spitzer/IRAC. At z~6.8, galaxies exhibit IRAC colors as blue as
[3.6]-[4.5] ~-1, likely due to the contribution of [O III]+Hb to the 3.6 mum
flux combined with the absence of line contamination in the 4.5 mum band. In
this paper we explore the use of extremely blue [3.6]-[4.5] colors to identify
galaxies in the narrow redshift window z~6.6-6.9. When combined with an
I-dropout criterion, we demonstrate that we can plausibly select a relatively
clean sample of z~6.8 galaxies. Through a systematic application of this
selection technique to our catalogs from all five CANDELS fields, we identify
20 probable z~6.6-6.9 galaxies. We estimate that our criteria select the ~50%
strongest line emitters at z~6.8 and from the IRAC colors we estimate a typical
[O III]+Hb rest-frame equivalent width of 1085A for this sample. The small
redshift uncertainties on our sample make it particularly well suited for
follow-up studies with facilities such as ALMA.Comment: In submission to the Astrophysical Journal, updated in response to
the referee report, 13 pages, 11 figures, 1 tabl
Biolistic-mediated genetic transformation of cowpea (Vigna unguiculata) and stable Mendelian inheritance of transgenes.
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Previous issue date: 2009-01-1
Nano-Hall sensors with granular Co-C
We analyzed the performance of Hall sensors with different Co-C ratios,
deposited directly in nano-structured form, using gas molecules,
by focused electron or ion beam induced deposition. Due to the enhanced
inter-grain scattering in these granular wires, the Extraordinary Hall Effect
can be increased by two orders of magnitude with respect to pure Co, up to a
current sensitivity of . We show that the best magnetic field
resolution at room temperature is obtained for Co ratios between 60% and 70%
and is better than . For an active area of the sensor of , the room temperature magnetic flux resolution is , in the thermal noise frequency range, i.e. above 100
kHz.Comment: 5 pages, 4 figure
Flexible, photonic films of surfactant-functionalized cellulose nanocrystals for pressure and humidity sensing
Most paints contain pigments that absorb light and fade over time. A robust
alternative can be found in nature, where structural coloration arises from the
interference of light with submicron features. Plant-derived, cellulose
nanocrystals (CNCs) mimic these features by self-assembling into a cholesteric
liquid crystal that exhibits structural coloration when dried. While much
research has been done on CNCs in aqueous solutions, less is known about
transferring CNCs to apolar solvents that are widely employed in paints. This
study uses a common surfactant in agricultural and industrial products to
suspend CNCs in toluene that are then dried into structurally colored films.
Surprisingly, a stable liquid crystal phase is formed within hours, even with
concentrations of up to 50 wt.-%. Evaporating the apolar CNC suspensions
results in photonic films with peak wavelengths ranging from 660 to 920 nm. The
resulting flexible films show increased mechanical strength, enabling a
blue-shift into the visible spectrum with applied force. The films also act as
humidity sensors, with increasing relative humidity yielding a red-shift. With
the addition of a single surfactant, CNCs can be made compatible with existing
production methods of industrial coatings, while improving the strength and
responsiveness of structurally-colored films to external stimuli.Comment: 11 pages, 4 figure
Microfibril-associated glycoprotein 4 (Mfap4) regulates haematopoiesis in zebrafish
Microfibril-associated glycoprotein 4 (MFAP4) is an extracellular matrix protein belonging to the fibrinogen-related protein superfamily. MFAP4 is produced by vascular smooth muscle cells and is highly enriched in the blood vessels of the heart and lung, where it is thought to contribute to the structure and function of elastic fibers. Genetic studies in humans have implicated MFAP4 in the pathogenesis of Smith-Magenis syndrome, in which patients present with multiple congenital abnormalities and mental retardation, as well as in the severe cardiac malformation left-sided congenital heart disease. Comprehensive genetic analysis of the role of MFAP4 orthologues in model organisms during development and tissue homeostasis is however lacking. Here, we demonstrate that zebrafish mfap4 transcripts are detected embryonically, resolving to the macrophage lineage by 24 h post fertilization. mfap4 null mutant zebrafish are unexpectedly viable and fertile, without ostensible phenotypes. However, tail fin amputation assays reveal that mfap4 mutants have reduced numbers of macrophages, with a concomitant increase in neutrophilic granulocytes, although recruitment of both cell types to the site of injury was unaffected. Molecular analyses suggest that loss of Mfap4 alters the balance between myeloid and lymphoid lineages during both primitive and definitive haematopoiesis, which could significantly impact the downstream function of the immune system
Stringy NJL and Gross-Neveu models at finite density and temperature
Nonlocal stringy versions of the Nambu-Jona-Lasinio and Gross-Neveu models
arise in a certain limit of holographic QCD. We analyze the phase structure at
finite density and temperature at strong coupling in terms of probe branes in
the gravity dual. Comparison with the phase structure of the local field theory
models shows qualitative agreement with some aspects, and disagreement with
others. Finally, we explain how to construct the Landau potentials for these
models by taking the probe branes off-shell.Comment: 32 pages, uses JHEP3.cls; v2, references added, version to be
submitted to JHE
Conformal Field Theory Interpretation of Black Hole Quasi-normal Modes
We obtain exact expressions for the quasi-normal modes of various spin for
the BTZ black hole. These modes determine the relaxation time of black hole
perturbations. Exact agreement is found between the quasi-normal frequencies
and the location of the poles of the retarded correlation function of the
corresponding perturbations in the dual conformal field theory. This then
provides a new quantitative test of the AdS/CFT correspondence.Comment: 4 pages, RevTeX, references adde
Variable Ratio Hydrostatic Transmission Simulator for Optimal Wind Power Drivetrains
This work presents a hydromechanical transmission coupled to an electric AC motor and DC generator to simulate a wind power turbine drive train. The goal of this project was to demonstrate and simulate the ability of a hydrostatic variable ratio system to produce constant electric power at varying wind speeds. The experimental results show that the system can maintain a constant voltage when a 40% variation in input speed is produced. An accompanying computer simulation of the system was built and experimentally validated showing a discrete error no larger than 12%. Both the simulation and the experimental results show that the electrical power output can be regulated further if an energy storage device is used to absorb voltage spikes produced by abrupt changes in wind speed or wind direction
Intelligence within BAOR and NATO's Northern Army Group
During the Cold War the UK's principal military role was its commitment to the North Atlantic Treaty Organisation (NATO) through the British Army of the Rhine (BAOR), together with wartime command of NATO's Northern Army Group. The possibility of a surprise attack by the numerically superior Warsaw Pact forces ensured that great importance was attached to intelligence, warning and rapid mobilisation. As yet we know very little about the intelligence dimension of BAOR and its interface with NATO allies. This article attempts to address these neglected issues, ending with the impact of the 1973 Yom Kippur War upon NATO thinking about warning and surprise in the mid-1970s. It concludes that the arrangements made by Whitehall for support to BAOR from national assets during crisis or transition to war were - at best - improbable. Accordingly, over the years, BAOR developed its own unique assets in the realm of both intelligence collection and special operations in order to prepare for the possible outbreak of conflict
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