566 research outputs found
Real Effects of Movements in Nominal Exchange Rates: Application to the Asian Crisis
This paper analyzes the ad hoc decision of three Asian countries to peg their currency to the U.S. dollar prior to the Asian crisis. It uses the Sjaastad model to estimate the optimal basket weights for Thailand, Korea, and Singapore. The analysis in this paper differs from the optimal basket research since we are not searching for an ad hoc optimal basket; rather, the basket is the solution to the problem. For Thailand and Korea, the correct weights of the dollar in the basket are estimated to be 44 and 65 percent, respectively, which differ significantly from the actual weight of 100 percent for the U.S. dollar in their currency basket prior to the 1997 Asian crisis. Singapore, with a weight of 85 percent for the U.S. currency, is closer to a dollar peg, and therefore was less affected by the large depreciation of the European currencies and the yen toward the dollar that occurred prior to the Asian exchange rate crisis. Besides the fact that Singapore had better economic fundamentals prior to the crisis, the fact that the optimal basket for that country is closer to a dollar peg is an additional reason why its economy was less severely hit by the crisis.optimum currency area, Asian crisis, exchange rate basket, currency peg
Loop Representation of Wigner's Little Groups
Wigner's little groups are the subgroups of the Lorentz group whose
transformations leave the momentum of a given particle invariant. They thus
define the internal space-time symmetries of relativistic particles. These
symmetries take different mathematical forms for massive and for massless
particles. However, it is shown possible to construct one unified
representation using a graphical description. This graphical approach allows us
to describe vividly parity, time reversal, and charge conjugation of the
internal symmetry groups. As for the language of group theory, the two-by-two
representation is used throughout the paper. While this two-by-two
representation is for spin-1/2 particles, it is shown possible to construct the
representations for spin-0 particles, spin-1 particles, as well as for
higher-spin particles, for both massive and massless cases. It is shown also
that the four-by-four Dirac matrices constitute a two-by-two representation of
Wigner's little group.Comment: LaTex 26 pages, with 5 figure
Entangled Harmonic Oscillators and Space-time Entanglement
The mathematical basis for the Gaussian entanglement is discussed in detail,
as well as its implications in the internal space-time structure of
relativistic extended particles. It is shown that the Gaussian entanglement
shares the same set of mathematical formulas with the harmonic oscillator in
the Lorentz-covariant world. It is thus possible to transfer the concept of
entanglement to the Lorentz-covariant picture of the bound state which requires
both space and time separations between two constituent particles. These space
and time variables become entangled as the bound state moves with a
relativistic speed. It is shown also that our inability to measure the
time-separation variable leads to an entanglement entropy together with a rise
in the temperature of the bound state. As was noted by Paul A. M. Dirac in
1963, the system of two oscillators contains the symmetries of O(3,2) de Sitter
group containing two O(3,1) Lorentz groups as its subgroups. Dirac noted also
that the system contains the symmetry of the Sp(4) group which serves as the
basic language for two-mode squeezed states. Since the Sp(4) symmetry contains
both rotations and squeezes, one interesting case is the combination of
rotation and squeeze resulting in a shear. While the current literature is
mostly on the entanglement based on squeeze along the normal coordinates, the
shear transformation is an interesting future possibility. The mathematical
issues on this problem are clarified.Comment: 32 pages with 11 figure
Wigner's Space-time Symmetries based on the Two-by-two Matrices of the Damped Harmonic Oscillators and the Poincar\'e Sphere
The second-order differential equation for a damped harmonic oscillator can
be converted to two coupled first-order equations, with two two-by-two matrices
leading to the group . It is shown that this oscillator system contains
the essential features of Wigner's little groups dictating the internal
space-time symmetries of particles in the Lorentz-covariant world. The little
groups are the subgroups of the Lorentz group whose transformations leave the
four-momentum of a given particle invariant. It is shown that the damping modes
of the oscillator correspond to the little groups for massive and
imaginary-mass particles respectively. When the system makes the transition
from the oscillation to damping mode, it corresponds to the little group for
massless particles. Rotations around the momentum leave the four-momentum
invariant. This degree of freedom extends the symmetry to that of
corresponding to the Lorentz group applicable to the four-dimensional
Minkowski space. The Poincar\'e sphere contains the symmetry. In
addition, it has a non-Lorentzian parameter allowing us to reduce the mass
continuously to zero. It is thus possible to construct the little group for
massless particles from that of the massive particle by reducing its mass to
zero. Spin-1/2 particles and spin-1 particles are discussed in detail.Comment: Latex 42 pages, 7 figures, to be published in the Symmetr
Role of DNA methylation of AHR1 and AHR2 promoters in differential sensitivity to PCBs in Atlantic Killifish, Fundulus heteroclitus
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Aquatic Toxicology 101 (2011): 288-294, doi:10.1016/j.aquatox.2010.10.010.Atlantic killifish (Fundulus heteroclitus) inhabiting the PCB-contaminated Superfund site
in New Bedford Harbor (MA, USA) have evolved genetic resistance to the toxic effects of these
compounds. They also lack induction of cytochrome P4501A (CYP1A) and other aryl
hydrocarbon receptor (AHR)-dependent responses after exposure to AHR agonists, suggesting
an overall down-regulation of the AHR signaling pathway. In this study, we hypothesized that
the genetic resistance is due to altered AHR expression resulting from hypermethylation of DNA
in the promoter region of AHR genes in fish inhabiting New Bedford Harbor. To test this
hypothesis, we cloned and sequenced AHR1 and AHR2 promoter regions and employed bisulfite
conversion-polymerase chain reaction (BS-PCR) followed by clonal analysis to compare the
methylation status of CpG islands of AHR1 and AHR2 in livers of adult killifish collected from
New Bedford Harbor and a reference site (Scorton Creek, MA). No significant differences in
methylation profiles were observed in either AHR1 or AHR2 promoter regions between NBH
and SC fish. However, hypermethylation of the AHR1 promoter correlated with low expression
of transcripts in the liver in both populations. In comparison to AHR1, hepatic mRNA expression
of AHR2 is high and its promoter is hypomethylated.
Taken together, our results suggest that
genetic resistance to contaminants in NBH fish is not due to altered methylation of AHR
promoter regions, but that promoter methylation may control tissue-specific expression of AHR
genes in killifish.This work is funded in part by the Superfund Basic Research Program at Boston
University to MEH (NIH Grant P42ES007381) and the postdoctoral scholar program at WHOI,
with funding provided by the Dr. George D. Grice Postdoctoral Scholarship Fund to NA
Biobased Sprayable Mulch Films Suppressed Annual Weeds in Vegetable Crops
Biobased sprayable mulch (BSM) films are a potential alternative to herbicides, polyethylene plastic mulch film, and hand weeding for specialty crops. We developed a series of BSM films using locally available biomaterials [including corn (Zea mays) starch, glycerol, keratin hydrolysate, corn gluten meal, corn zein, eggshells, and isolated soy (Glycine max) protein] and tested their effects on weeds and crop yield during a total of seven greenhouse or field trials between 2017 and 2019 in Nebraska, USA. Application rates of BSM films applied in pots (greenhouse), planting holes in plastic film (field), or bed tops (field) ranged from 0.9 to 18.2 L•m-2 ; they were applied before and after the emergence of weeds. Weed control efficacy was variable, and results of greenhouse pots were rarely replicated under field conditions. Increasing the viscosity of the final suspension tested [BSM7; a mix of corn starch (72.8 g•L-1 ), glycerol (184.7 mL•L-1 ), keratin hydrolysate (733.3 mL•L-1 ), corn zein (19.8 g•L-1 ), and isolated soy protein (19.8 g•L-1 )] reduced weed biomass by more than 96% in field-grown kale (Brassica oleracea var. sabellica) when applied to bare soil bed tops before or after weed emergence, but kale yield in treated plots was not different from the weedy control. The results demonstrated the potential for postemergence applications of BSM films, which increase application timing flexibility for growers. Further research is needed to explore the effects of BSM films on soil properties and crop physiology and yield
Nrf2 and Nrf2-related proteins in development and developmental toxicity : insights from studies in zebrafish (Danio rerio)
© The Author(s), 2015. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Free Radical Biology and Medicine 88B (2015): 275-289, doi:10.1016/j.freeradbiomed.2015.06.022.Oxidative stress is an important mechanism of chemical toxicity, contributing to developmental
toxicity and teratogenesis as well as to cardiovascular and neurodegenerative diseases and
diabetic embryopathy. Developing animals are especially sensitive to effects of chemicals that
disrupt the balance of processes generating reactive species and oxidative stress, and those
anti-oxidant defenses that protect against oxidative stress. The expression and inducibility of
anti-oxidant defenses through activation of NFE2-related factor 2 (Nrf2) and related proteins is
an essential process affecting the susceptibility to oxidants, but the complex interactions of Nrf2
in determining embryonic response to oxidants and oxidative stress are only beginning to be
understood. The zebrafish (Danio rerio) is an established model in developmental biology and
now also in developmental toxicology and redox signaling. Here we review the regulation of
genes involved in protection against oxidative stress in developing vertebrates, with a focus on
Nrf2 and related cap’n’collar (CNC)-basic-leucine zipper (bZIP) transcription factors. Vertebrate
animals including zebrafish share Nfe2, Nrf1, Nrf2, and Nrf3 as well as a core set of genes that
respond to oxidative stress, contributing to the value of zebrafish as a model system with which
to investigate the mechanisms involved in regulation of redox signaling and the response to
oxidative stress during embryolarval development. Moreover, studies in zebrafish have revealed
nrf and keap1 gene duplications that provide an opportunity to dissect multiple functions of
vertebrate NRF genes, including multiple sensing mechanisms involved in chemical-specific
effects.This work was
supported in part by National Institutes of Health grants R01ES016366 (MEH), R01ES015912
(JJS), and F32ES017585 (ART-L).2016-06-2
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