1,884 research outputs found
Non-Bunch-Davies Initial State Reconciles Chaotic Models with BICEP and Planck
The BICEP2 experiment has announced a signal for primordial gravity waves
with tensor-to-scalar ratio [arXiv:1403.3985]. There
are two ways to reconcile this result with the latest Planck experiment
[arXiv:1303.5082]. One is by assuming that there is a considerable tilt of ,
, with a positive sign, corresponding to a blue tilt for the tensor modes of
order , assuming the Planck experiment best-fit
value for tilt of scalar power spectrum . The other possibility is to
assume that there is a negative running in the scalar spectral index,
which pushes up the upper bound on from up
to in the Planck analysis assuming the existence of a tensor spectrum.
Simple slow-roll models fail to provide such large values for
or negative runnings in [arXiv:1403.3985]. In this note we show that a
non-Bunch-Davies initial state for perturbations can provide a match between
large field chaotic models (like ) with the latest Planck result
[arXiv:1306.4914] and BICEP2 results by accommodating either the blue tilt of
or the negative large running of .Comment: v1:5 pages, double column; v2: 6 pages, double column, the option of
negative running of scalar spectral index and some references were added; v3:
Matched the PLB versio
ELECTRON BEAM INDUCED DEPOSITION OF HIGHLY CONDUCTIVE COPPER NANOWIRES FROM BULK LIQUIDS
Electron-beam induced deposition (EBID) is a position-controlled technique that can directly fabricate nanometer-sized structures in functional materials. In the standard process, a gaseous precursor delivers the desired substance to the substrate for deposition. However, the material purity from these precursors is typically poor, which often negatively affects the functional properties of the deposit. Recently, bulk liquid precursors have been investigated as promising reactants for high purity deposition without the need for post-processing. In this work, EBID from bulk liquids is shown to yield highly conductive nanowire deposits. Aqueous solutions containing copper sulfate (CuSO4) and sulfuric acid (H2SO4) are used as precursors to deposit copper nanowires on oxidized silicon substrates in an environmental scanning electron microscope (ESEM). Using four point I-V measurement, our results show a copper resistivity as low as 67 μΩ⦁cm, which is 6-8 orders of magnitude lower than that of as-deposited copper from gas phase reactants, 4-5 orders of magnitude lower than that of annealed materials, and within 1 order of magnitude of bulk copper. The low resistivity of these deposits without post-processing highlights the importance of further research to overcome challenges associated with deposition via liquid precursors, such as collateral deposition; local delivery of the reactant; and control of liquid thickness
Developmentally regulated SUMOylation in the ciliate Tetrahymena thermophila
The Small Ubiquitin-like MOdifier (SUMO) protein regulates numerous nuclear events such as transcription, mitosis and meiosis and DNA repair. These processes are critical to the programmed nuclear events of conjugation in ciliates and provide the potential to investigate developmentally regulated SUMOylation. We predicted a developmental increase in SUMOylation during late conjugation based on the extensive genome remodeling in the developing macronucleus (anlagen) ofTetrahymena thermophila. Immunoblotting of cell lysates from vegetative and mating cells using anti-SUMO antibodies revealed distinct developmental differences and an increased signal correlated with formation of the anlagen. Immunofluorescence of mating Tetrahymena cells with the same antibody revealed an increase in staining of the parental macronucleus until the signal shifts to the anlagen at 7 hours post-mixing. This along with the finding that GFP-Uba2 fusion proteins localize to the anlagen is consistent with a major nuclear role for SUMOylation during conjugation. Germ-line knockout mutants of SUMO (SMT3) and UBA2 are vegetative lethal and conditional mutants dependent on a cadmium-inducible metallothionein promoter exhibit reduced cell growth and increased sensitivity to DNA damaging agents upon cadmium withdrawal. Interestingly, mating of Uba2p conditional lines leads to a cadmium-dependent delay after meiosis but prior to macronuclear development predicting a SUMOylation-dependent event. Additionally, in an effort to provide further insight into the various processes affected by SUMO modification, we utilized a proteomics-based approach to generate an unbiased spectrum of SUMO protein substrates from vegetativeTetrahymena. We used a two-step affinity purification scheme to isolate SUMO substrates from a tagged Tetrahymena strain. Proteins from the purification were then identified by subsequent LC-MS.MS analysis using a QuadTOF mass spectrometer. We identified 110 candidate proteins that were identified by 2 or more peptides. The nature of the protein substrates that were identified is consistent with roles of SUMOylation in modulating diverse cellular processes including transcriptional regulation, protein folding and translation, metabolism and crosstalk with other post-translational modifications. These results support multiple roles of SUMOylation in regulating various cellular processes in eukaryotic cells. Taken together, our findings provide the foundation for additional studies of SUMOylation during conjugation in Tetrahymen
Gravitational Waves from Preheating in M-flation
Matrix inflation, or M-flation, is a string theory motivated inflationary
model with three scalar field matrices and gauge fields in the adjoint
representation of the gauge group. One of these scalars
appears as the effective inflaton while the rest of the fields (scalar and
gauge fields) can play the role of isocurvature fields during inflation and
preheat fields afterwards. There is a region in parameter space and initial
field values, "the hilltop region," where predictions of the model are quite
compatible with the recent Planck data. We show that in this hilltop region, if
the inflaton ends up in the supersymmetric vacuum, the model can have an
embedded preheating mechanism. Couplings of the preheat modes are related to
the inflaton self-couplings and therefore are known from the CMB data. Through
lattice simulations performed using a symplectic integrator, we numerically
compute the power spectra of gravitational waves produced during the preheating
stage following M-flation. The preliminary numerical simulation of the spectrum
from multi-preheat fields peaks in the GHz band with an amplitude
, suggesting that the model has
concrete predictions for the ultra-high frequency gravity-wave probes. This
signature could be used to distinguish the model from rival inflationary modelsComment: v1:27 pages and 7 figures; v2: typos corrected; v3: references added;
v4: matched the JCAP versio
Two new species and two new reports of Ulva L. (Ulvophyceae) from the coast of Karachi, Pakistan
Morphology and taxonomy of four species of Ulva i.e. U. anandii Amjad et Shameel sp. nov., U. bifrons Ardre, U. saifullahii Amjad et Shameel sp. nov. and U. taeniata (Setchell) et Gardner were described for the first time from Pakistan. Their anatomy has been investigated in detail and compared with the allied species. A taxonomic comment has been written on U. grandis Saifullah et Nizamuddin
Comparative haemagglutinic activity in the species of Caulerpa and Ulva (Chlorophyta) of Karachi coast
Aquous extracts of 24 species of green seaweeds, 13 of Caulerpa Lamour and 11 of Ulva Linn, were collected from the coastal areas near Karachi, Pakistan and tested for haemagglutination against human erythrocytes of blood groups A,B,AB and O and compared. All the species of Caulerpa and seven of Ulva exhibited a positive activity, the former genus (a member of Bryopsidophyceae) appeared to possess more phycohaemagglutinins than the latter (a member of Ulvophyceae). The haemagglutinic activity proved to be quite helpful in the distinction of various species of both the genera
The Efficiency of Professional Development Programs based on Social Constructivism in Improving Teaching Practices of Mathematics Teachers in Jordan
The purpose of this study was to investigate the efficiency of professional development programs based on social constructivism in improving the teaching practices of mathematics teachers. The research team developed a training program based on social constructivism in teacher education. The participants of this program included nine mathematics teachers from the Um Al-Basateen school district located in the south of the capital city, Amman. Data was collected before and after the program and certain tools of qualitative research were employed in the study. These tools included observation, interviews, and documentation. Moreover, the research team developed a measurement to evaluate the participants’ teaching practices. The measurement consisted of five levels (novice, advanced beginner, competent, proficient and expert) indicating the improvement in teaching practices. The teaching practices under evaluation were composed of six areas: teaching, learning, evaluation, classroom dialogue, knowledge resources, and mathematical content. Research findings indicated that there was a noticeable improvement in the participants’ teaching practices during the two stages of the study. Prior to the program, the teaching practices in the areas of classroom dialogue and knowledge resources were classified at the first level (novice) and in the remaining four areas, the teaching practices were classified at level two (advanced beginner). However, in the post-program stage, teaching practices in the areas of teaching, learning and classroom dialogue reached level five (expert) whereas mathematical content achieved level four (proficient). Furthermore, teaching practices in the areas of evaluation and resources reached level three (competent)
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