1,689 research outputs found
Victims of Progress: Economic Integration, Specialization, and Wages for Unskilled Labor
In this paper we demonstrate that intra-industry trade (or FDI) between identical countries could produce the observed deterioration in the relative wages of unskilled workers. This involves a model of North-North integration through either increased trade flows or increased MNE- based production. Our motivation in this regard is arguments to the effect that trade cannot be responsible for the observed labour market trends because trade with developing countries is quantitatively too small to have significant labour market effects. We also introduce a relatively unexploited class of model that possesses attractive properties with respect to the explicit incorporation of firm-theoretic considerations in trade models
The metallogenic evolution of the Greater Antilles
The Greater Antilles host some of the world's most important deposits of bauxite and lateritic nickel as well as significant resources of gold and silver, copper, zinc, manganese, cobalt and chromium. Beginning in Jurassic time, sedimentary exhalative base metal deposits accumulated in marine sedimentary rift basins as North and South America drifted apart. With the onset of intraoceanic subduction during the Early Cretaceous, a primitive (tholeiitic) island arc formed above a southwesterly-dipping subduction zone. Podiform chromite deposits formed in the mantle portion of the supra-subduction zone, directly above subducted Proto-Caribbean oceanic lithosphere. Within the nascent island arc, bimodal-mafic volcanogenic massive sulfide deposits formed in a fore-arc setting; mafic volcanogenic massive sulfide deposits formed later in mature back-arc basins. The Pueblo Viejo gold district, with five million ounces in production and twenty million ounces in mineable reserves, formed at 108-112Ma, in an apical rift or back-arc setting. By Late Cretaceous time, calc-alkaline volcanism was well established along the entire length of the Greater Antilles. Volcanogenic massive sulfide deposits including shallow submarine deposits characteristic of the primitive island arc gave way to porphyry copper and epithermal precious metal deposits typical of the mature island arc. Oblique collision of the Greater Antilles with North America began in the Late Cretaceous in Cuba and migrated eastward. Orogenic gold and tungsten deposits that formed during the collision event are preserved in ophiolites and in metamorphic core complexes. Since the Eocene, regional tectonism has been dominated by strike-slip motion as the North American continent moved westward relative to the Caribbean Plate. Large nickel-cobalt laterite deposits were formed when serpentinites were exposed to weathering and erosion during the mid-Tertiary. Bauxite deposits were derived from the weathering of volcanic ash within a carbonate platform of Eocene to Miocene age
External cadmium and internal calcium block of single calcium channels in smooth muscle cells from rabbit mesenteric artery
The patch clamp technique was used to record unitary currents through single calcium channels from smooth muscle cells of rabbit mesenteric arteries. The effects of external cadmium and cobalt and internal calcium, barium, cadmium, and magnesium on single channel currents were investigated with 80 mM barium as the charge carrier and Bay K 8644 to prolong openings. External cadmium shortened the mean open time of single Ca channels. Cadmium blocking and unblocking rate constants of 16.5 mM-1 ms-1 and 0.6 ms-1, respectively, were determined, corresponding to dissociation constant Kd of 36 microM at -20 mV. These results are very similar to those reported for cardiac muscle Ca channels (Lansman, J. B., P. Hess, and R. W. Tsien. 1986. J. Gen. Physiol. 88:321â347). In contrast, Cd2+ (01â10 mM), when applied to the internal surface of Ca channels in inside-out patches, did not affect the mean open time, mean unitary current, or the variance of the open channel current. Internal calcium induced a flickery block, with a Kd of 5.8 mM. Mean blocking and unblocking rate constants for calcium of 0.56 mM-1 ms-1 and 3.22 ms-1, respectively, were determined. Internal barium (8 mM) reduced the mean unitary current by 36%. We conclude that under our experimental conditions, the Ca channel is not symmetrical with respect to inorganic ion block and that intracellular calcium can modulate Ca channel currents via a low-affinity binding site
Magnetic field induced rotation of the d-vector in Sr_2RuO_4
The superconductor Sr_2RuO_4 is widely believed to be a spin triplet system
with a chiral order parameter analogous to the A phase of superfluid helium-3.
The best evidence for this pairing state is that the Knight shift or spin
susceptibility measured in neutron scattering is constant below T_c, unlike in
a spin-singlet superconductor. The original Knight shift and neutron scattering
measurements were performed for magnetic fields aligned in the ruthenate a-b
plane. These would be consistent with a triplet d-vector d{k} aligned along the
c-axis. However recently the Knight shift for fields along c was also found to
be constant below T_c, which is not expected for this symmetry state. In this
paper we show that while spin-orbit interaction stabilises the c-axis oriented
d-vector, it is possible that only a very small external B field may be
sufficient to rotate the d-vector into the a-b plane. In this case the triplet
pairing model remains valid. We discuss characteristics of the transition and
the prospects to detect it in thermodynamic quantities.Comment: 2 pages, 1 figure, Proceedings of the M2S-HTSC conference in Dresden.
Requires elsart.sty (included
The Littlest Higgs
We present an economical theory of natural electroweak symmetry breaking,
generalizing an approach based on deconstruction. This theory is the smallest
extension of the Standard Model to date that stabilizes the electroweak scale
with a naturally light Higgs and weakly coupled new physics at TeV energies.
The Higgs is one of a set of pseudo Goldstone bosons in an
nonlinear sigma model. The symmetry breaking scale is around a TeV, with
the cutoff \Lambda \lsim 4\pi f \sim 10 TeV. A single electroweak doublet,
the ``little Higgs'', is automatically much lighter than the other pseudo
Goldstone bosons. The quartic self-coupling for the little Higgs is generated
by the gauge and Yukawa interactions with a natural size ,
while the top Yukawa coupling generates a negative mass squared triggering
electroweak symmetry breaking. Beneath the TeV scale the effective theory is
simply the minimal Standard Model. The new particle content at TeV energies
consists of one set of spin one bosons with the same quantum numbers as the
electroweak gauge bosons, an electroweak singlet quark with charge 2/3, and an
electroweak triplet scalar. One loop quadratically divergent corrections to the
Higgs mass are cancelled by interactions with these additional particles.Comment: 15 pages. References added. Corrected typos in the discussion of the
top Yukawa couplin
Unzipping Dynamics of Long DNAs
The two strands of the DNA double helix can be `unzipped' by application of
15 pN force. We analyze the dynamics of unzipping and rezipping, for the case
where the molecule ends are separated and re-approached at constant velocity.
For unzipping of 50 kilobase DNAs at less than about 1000 bases per second,
thermal equilibrium-based theory applies. However, for higher unzipping
velocities, rotational viscous drag creates a buildup of elastic torque to
levels above kBT in the dsDNA region, causing the unzipping force to be well
above or well below the equilibrium unzipping force during respectively
unzipping and rezipping, in accord with recent experimental results of Thomen
et al. [Phys. Rev. Lett. 88, 248102 (2002)]. Our analysis includes the effect
of sequence on unzipping and rezipping, and the transient delay in buildup of
the unzipping force due to the approach to the steady state.Comment: 15 pages Revtex file including 9 figure
Influence of enrollment sequence effect on observed outcomes in the ADDRESS and PROWESS studies of drotrecogin alfa (activated) in patients with severe sepsis
INTRODUCTION: We performed a study to determine whether an enrollment sequence effect noted in the PROWESS (recombinant human activated Protein C Worldwide Evaluation in Severe Sepsis) trial exists in the ADDRESS (Administration of Drotrecogin Alfa [Activated] [DrotAA] in Early Stage Severe Sepsis) trial. METHODS: We evaluated prospectively defined subgroups from two large phase 3 clinical trials: ADDRESS, which included 516 sites in 34 countries, and PROWESS, which included 164 sites in 11 countries. ADDRESS consisted of patients with severe sepsis at low risk of death not indicated for treatment with DrotAA. PROWESS consisted of patients with severe sepsis with one or more organ dysfunctions. DrotAA (24 microg/kg per hour) or placebo was infused for 96 hours. RESULTS: In ADDRESS and PROWESS, there was a statistically significant interaction between the DrotAA treatment effect and the sequence in which patients were enrolled. In both trials, higher mortality was associated with DrotAA use in the subgroup of patients enrolled first at study sites. Compared with placebo, PROWESS mortality was lower with DrotAA treatment for the second and subsequent patients enrolled, whereas in ADDRESS, mortality remained higher for the second patient enrolled but thereafter was lower for DrotAA-treated patients. Comparison of patients enrolled first with subsequent patients enrolled indicated that the characteristics of patients changed. Subsequently enrolled patients were treated earlier, were less likely to suffer nonserious bleeds (ADDRESS), and experienced fewer protocol violations (PROWESS). CONCLUSIONS: Analyses suggest that an enrollment sequence effect was present in the ADDRESS and PROWESS trials. Analysis of this effect on outcomes suggests that it is most apparent in patients at lower risk of death. In PROWESS, this effect appeared to be associated with a reduction of the DrotAA treatment effect for the first patients enrolled at each site. In ADDRESS, this effect may have contributed to early termination of the study. The finding of an enrollment sequence effect in two separate trials suggests that trial designs, site selection and training, data collection and monitoring, and statistical analysis plans may need to be adjusted for these potentially confounding events. TRIAL REGISTRATION: ADDRESS trial registration number: NCT00568737. PROWESS was completed before trial registration was required
Gluino Pair Production at Linear e^+e^- Colliders
We study the potential of high-energy linear colliders for the
production of gluino pairs within the Minimal Supersymmetric Standard Model
(MSSM). In this model, the process is mediated by
quark/squark loops, dominantly of the third generation, where the mixing of
left- and right-handed states can become large. Taking into account realistic
beam polarization effects, photon and -boson exchange, and current mass
exclusion limits, we scan the MSSM parameter space for various
center-of-mass energies to determine the regions, where gluino production
should be visible.Comment: 22 pages, 9 figure
Theory of High-Force DNA Stretching and Overstretching
Single molecule experiments on single- and double stranded DNA have sparked a
renewed interest in the force-extension of polymers. The extensible Freely
Jointed Chain (FJC) model is frequently invoked to explain the observed
behavior of single-stranded DNA. We demonstrate that this model does not
satisfactorily describe recent high-force stretching data. We instead propose a
model (the Discrete Persistent Chain, or ``DPC'') that borrows features from
both the FJC and the Wormlike Chain, and show that it resembles the data more
closely. We find that most of the high-force behavior previously attributed to
stretch elasticity is really a feature of the corrected entropic elasticity;
the true stretch compliance of single-stranded DNA is several times smaller
than that found by previous authors. Next we elaborate our model to allow
coexistence of two conformational states of DNA, each with its own stretch and
bend elastic constants. Our model is computationally simple, and gives an
excellent fit through the entire overstretching transition of nicked,
double-stranded DNA. The fit gives the first values for the elastic constants
of the stretched state. In particular we find the effective bend stiffness for
DNA in this state to be about 10 nm*kbt, a value quite different from either
B-form or single-stranded DNAComment: 33 pages, 11 figures. High-quality figures available upon reques
Trends in the Statistical Assessment of Reliability
Changes in technology have had and will continue to have a strong effect on changes in the area of statistical assessment of reliability data. These changes include higher levels of integration in electronics, improvements in measurement technology and the deployment of sensors and smart chips into more products, dramatically improved computing power and storage technology, and the development of new, powerful statistical methods for graphics, inference, and experimental design and reliability test planning. This paper traces some of the history of the development of statistical methods for reliability assessment and makes some predictions about the future
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