13,509 research outputs found
Precision Measurement of sin^2 theta_W at a Reactor
This paper presents a strategy for measuring sin^2 theta_W to ~1% at a
reactor-based experiment, using antineutrinos electron elastic scattering. This
error is comparable to the NuTeV, SLAC E158, and APV results on sin^2 theta_W,
but with substantially different contributions to the systematics. An improved
method for identifying antineutrino proton events, which serve both as a
background and as a normalization sample, is described. The measurement can be
performed using the near detector of the presently proposed reactor-based
oscillation experiments. We conclude that an absolute error of delta(sin^2
theta_W)=0.0019 may be achieved.Comment: To be Submitted to Phys. Rev.
Using Reactors to Measure
A next-generation neutrino oscillation experiment using reactor neutrinos
could give important information on the size of mixing angle . The
motivation and goals for a new reactor measurement are discussed in the context
of other measurements using off-axis accelerator neutrino beams. The reactor
measurements give a clean measure of the mixing angle without ambiguities
associated with the size of the other mixing angles, matter effects, and
effects due to CP violation. The key question is whether a next-generation
experiment can reach the needed sensitivity goals to make a measurement for
at the 0.01 level. The limiting factors associated with
a reactor disappearance measurement are described with some ideas of how
sensitivities can be improved. Examples of possible experimental setups are
presented and compared with respect to cost and sensitivity
A strong correlation in radio pulsars with implications for torque variations
We present an analysis of the spin-down parameters for 131 radio pulsars for
which has been well determined. These pulsars have characteristic
ages ranging from yr and spin periods in the range 0.4--30 s;
nearly equal numbers of pulsars have as . We find a
strong correlation of with , {\em independent of the sign
of} . We suggest that this trend can be accounted for by small,
stochastic deviations in the spin-down torque that are directly proportional
(in magnitude) to the spin-down torque.Comment: MNRAS, 4 pages, 2 figures. Minor editorial changes and typos
correcte
Differential thresholds for motions in the periphery
Differential thresholds for rotary and linear motion in the peripher
Creativity and the Family Tree: Human Capital Endowments and the Propensity of Entrepreneurs to Patent
In this paper we show that the patenting behavior of creative entrepreneurs is correlated with the patenting behavior of their fathers, which we refer to as a source of the entrepreneurs' human capital endowments. Our argument for this relationship follows from established theories of developmental creativity, and our empirical analysis is based on survey data collected from MIT's Technology Review winners.patents, entrepreneurship, human capital endowments
Oxytocin at physiological concentrations evokes adrenocorticotropin (ACTH) release from corticotrophs by increasing intracellular free calcium mobilized mainly from intracellular stores. Oxytocin displays synergistic or additive effects on ACTH-releasing factor or arginine vasopressin-induced ACTH secretion, respectively
The potency of oxytocin (OT) in evoking ACTH secretion by isolated, superfused rat adenohypophyseal corticotrophs and its enhancement by CRF and arginine vasopressin (AVP) were analyzed. Each secretagogue effectively released ACTH from adenohypophyseal cells when added separately in pulsatile fashion in physiological concentrations based on hypophyseal portal blood (OT, 10 nM; AVP, 0.5 nM; CRF, 0.1 nM). OT released ACTH at concentrations as low as 1 nM. Moreover, a dose- response relationship up to 10 microM was revealed. Combinations of a constant amount of CRF (0.1 nM) with increasing concentrations of OT exerted a synergistic effect on ACTH release. In contrast, OT given in various concentrations in combination with AVP (0.5 nM) produced an additive effect on ACTH release. To study the mechanism of action of OT on ACTH secretion, cytosolic free calcium levels in single pituitary cells exposed to OT or AVP were measured using the calcium-sensitive fluorescent indicator Fura-2. Corticotrophs among mixed adenohypophyseal cell types in the primary cultures were identified by immunocytochemistry. More than 500 cells were individually stimulated with OT or AVP. Basal cytosolic free calcium levels ranged between 80- 130 nM free calcium. The addition of 100 nM OT or 1 microM AVP increased the cytosolic free calcium concentration within 3 sec to values ranging from 500-800 nM. An increase in intracellular calcium ranging from 200-500 nM due to OT could still be observed after extracellular calcium depletion. Taken together, our data demonstrate that physiological concentrations of OT stimulate ACTH secretion, independent of the other ACTH secretagogues, by mobilizing calcium mainly from intracellular stores
Evolution of a fluorinated green fluorescent protein
The fluorescence of bacterial cells expressing a variant (GFPm) of the green fluorescent protein (GFP) was reduced to background levels by global replacement of the leucine residues of GFPm by 5,5,5-trifluoroleucine. Eleven rounds of random mutagenesis and screening via fluorescence-activated cell sorting yielded a GFP mutant containing 20 amino acid substitutions. The mutant protein in fluorinated form showed improved folding efficiency both in vivo and in vitro, and the median fluorescence of cells expressing the fluorinated protein was improved {approx}650-fold in comparison to that of cells expressing fluorinated GFPm. The success of this approach demonstrates the feasibility of engineering functional proteins containing many copies of abiological amino acid constituents
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