445 research outputs found
Determination of some dominant parameters of the global dynamic sea surface topography from GEOS-3 altimetry
The 1977 altimetry data bank is analyzed for the geometrical shape of the sea surface expressed as surface spherical harmonics after referral to the higher reference model defined by GEM 9. The resulting determination is expressed as quasi-stationary dynamic SST. Solutions are obtained from different sets of long arcs in the GEOS-3 altimeter data bank as well as from sub-sets related to the September 1975 and March 1976 equinoxes assembled with a view to minimizing seasonal effects. The results are compared with equivalent parameters obtained from the hydrostatic analysis of sporadic temperature, pressure and salinity measurements of the oceans and the known major steady state current systems with comparable wavelengths. The most clearly defined parameter (the zonal harmonic of degree 2) is obtained with an uncertainty of + or - 6 cm. The preferred numerical value is smaller than the oceanographic value due to the effect of the correction for the permanent earth tide. Similar precision is achieved for the zonal harmonic of degree 3. The precision obtained for the fourth degree zonal harmonic reflects more closely the accuracy expected from the level of noise in the orbital solutions
Inflammatory cytokines in newborn infants.
Serum levels of IL-1beta, IL-6 and TNF-alpha were measured in 48 healthy, termed neonates on the 1st (N1), 5th (N5) and 40th (N40) day after birth, compared with those in maternal serum (MS), umbilical cord (UC) and adult controls. Cytokine values in N1 and N5 were significantly elevated, than those in UC and in controls (P<0.0001). IL-1beta and IL-6 declined significantly from N1 to N40 (P<0.0001), while TNF-alpha increased significantly from N1 to N5 and declined thereafter. MS infinity IL-1beta and IL-6, but not MS infinity TNF-alpha, were significantly higher than those of controls (P<0.0001). IL-1beta values depended on the mode of delivery. In conclusion, the increased concentrations of IL-1beta, IL-6 and TNF-alpha during the perinatal period might suggest their involvement in an inflammation-like process during normal parturition, and reflect also a newborn immune response to the stress of delivery and environmental changes
Suppressing dimension-5 operators in general SU(5) models
We discuss dimension-5 operators in supersymmetric models containing extra
hypercharge 1/3 color-triplets. We derive a general formula relating
dimension-5 operator to the color-triplet mass matrix. We show that certain
zeros in the triplet mass-matrix together with some triplet coupling selection
rules can lead to elimination of dimension-5 operators. In particular we focus
on SU(5) models and show that (a) Dimension-5 operators can be eliminated in
the standard SU(5) model by the introduction of an extra pair of 5+5b Higgses
with specific couplings (b) Flipped SU(5) models with extra 10+10b Higgses are
free of dimension-5 operators (c) Flipped SU(5) models with extra 5+5b and/or
extra 10+10b Higgses can be made free of dimension-5 operators for a textured
form of the triplet mass-matrix accompanied by constraints on the 5-plet
couplings to matter. Our analysis is motivated by the recently put forward
M-theory phenomenological framework that requires a strong string coupling and
reintroduces the problem of eliminating dimension-5 operators.Comment: 10 pages, Latex2e, minor changes, references adde
Sexually dimorphic gene expression in bovine conceptuses at the initiation of implantation
In cattle, maternal recognition of pregnancy occurs on Day 16 via secretion of interferon tau (IFNT) by the conceptus. The endometrium can distinguish between embryos with different developmental competencies. In eutherian mammals, X-chromosome inactivation (XCI) is required to ensure an equal transcriptional level of most X-linked genes for both male and female embryos in adult tissues, but this process is markedly different in cattle than mice. We examined how sexual dimorphism affected conceptus transcript abundance and amino acid composition as well as the endometrial transcriptome during the peri-implantation period of pregnancy. Of the 5132 genes that were differentially expressed on Day 19 in male compared to female conceptuses, 2.7% were located on the X-chromosome. Concentrations of specific amino acids were higher in the uterine luminal fluid of male compared to female conceptuses, while female conceptuses had higher transcript abundance of specific amino acid transporters (SLC6A19 and SLC1A35). Of note, the endometrial transcriptome was not different in cattle gestating a male or a female conceptus. These data support the hypothesis that, far from being a blastocyst specific phenomenon, XCI is incomplete before and during implantation in cattle. Despite differences in transcript abundance and amino acid utilization in male versus female conceptuses, the sex of the conceptus itself does not elicit a different transcriptomic response in the endometrium
Plug actuation and active manipulation in closed monolithic fluidics using backpressure
We explore the mechanisms to actuate and manipulate liquid plugs in monolithic closed channel fluidics with porous hydrophobic walls. Applying a small pressure, as much as 10 mbar, from the rear side of the porous wall, hereafter backpressure, the inherently pinned plug is depinned and flows through downwards the fluidic. The method is reversible in that by removing the backpressure the plug sticks back again to the fluidic. 3D numerical simulations with the volume of fluid method, presented here for the first time, show that the velocity of the plug can be manipulated by adjusting the backpressure. The movement of the plug results from deformation – displacement phases which are observed in the simulation and are corroborated by experimental results, recorded inside fluidics. A simplified model based on measurements of back and front contact angles under backpressure is developed
Dilatonic Black Holes in Higher Curvature String Gravity
We give analytical arguments and demonstrate numerically the existence of
black hole solutions of the Effective Superstring Action in the presence
of Gauss-Bonnet quadratic curvature terms. The solutions possess non-trivial
dilaton hair. The hair, however, is of ``secondary" type", in the sense that
the dilaton charge is expressed in terms of the black hole mass. Our solutions
are not covered by the assumptions of existing proofs of the ``no-hair"
theorem. We also find some alternative solutions with singular metric
behaviour, but finite energy. The absence of naked singularities in this system
is pointed out.Comment: 22 pages, Latex file, 7 Latex figures already include
Left-Right Symmetric Heterotic-String Derived Models
Recently it was demonstrated that free fermionic heterotic-strings can
produce models with solely the Minimal Supersymmetric Standard Model states in
the low energy spectrum. This unprecedented result provides further strong
evidence for the possibility that the true string vacuum shares some of the
properties of the free fermionic models. Past free fermionic models have
focused on several possible unbroken observable SO(10) subgroups at the string
scale, which include the flipped SU(5) (FSU5), the Pati-Salam (PS) string
models, and the string Standard-like Models (SLM). We extend this study to
include the case in which the SO(10) symmetry is broken to the Left-Right
Symmetric (LRS) gauge group, SO(10) -> SU(3)_C X U(1)_{B-L} X SU(2)_L X
SU(2)_R. We present several models of this type and discuss their
phenomenological features. The most striking new outcome of the LRS string
models, in contrast to the case of the FSU5, the PS, and the SLM string models,
is that they can produce effective field theories that are free of Abelian
anomalies. We discuss the distinction between the two types of free fermionic
models which result in the presence, or absence, of an anomalous U(1). As a
counter example we also present a LRS model that does contain an anomalous
U(1). Additionally, we discuss how in string models the Standard Model spectrum
may arise from the three \mbf 16 representations of SO(10), while the
weak-hypercharge does not have the canonical SO(10) embedding.Comment: 39 pages. Standard Latex. Version to appear in PR
Gauge Unification and Quark Masses in a Pati-Salam Model from Branes
We investigate the phase space of parameters in the Pati-Salam model derived
in the context of D-branes scenarios, requiring low energy string scale. We
find that a non-supersymmetric version complies with a string scale as low as
10 TeV, while in the supersymmetric version the string scale raises up to ~2 x
10^7 TeV. The limited energy region for RGE running demands a large tan(beta)
in order to have experimentally acceptable masses for the top and bottom
quarks.Comment: 11 pages, LaTeX, 7 figures include
Static dilaton solutions and singularities in six dimensional warped compactification with higher derivatives
Static solutions with a bulk dilaton are derived in the context of six
dimensional warped compactification. In the string frame, exponentially
decreasing warp factors are identified with critical points of the low energy
-functions truncated at a given order in the string tension corrections.
The stability of the critical points is discussed in the case of the first
string tension correction. The singularity properties of the obtained solutions
are analyzed and illustrative numerical examples are provided.Comment: 35 pages. Revised version. Accepted in Phys. Rev.
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