4,638 research outputs found
Auroral zone absorption of radio waves transmitted via the ionosphere
A discussion of the design for a new antenna system for the transmitter stations is presented together with the measurements and power computation made on the old and new antennas. In the 12 mc back-scatter program at College, the technique used to measure the amplitude of each individual echo and reanalysis of the range distribution previously reported are discussed. Revisions in the techniques of observation of visual auroras and the methods of recording the data for analysis are described in detail.Section I Purposes – Section II Abstract – Section III Publications, Lectures, Reports and Conferences – Section IV Factual Data : Task A ; Task B – Section V Conclusions and Recommendations – Section VI Plans for Next Quarter – Section VII Personnel – Section VIII Appendix : Visual Observations of Aurora in Alaska 1953-1954 / C.T. Elvey ; References ; Figures 1 to 17Ye
Integral Farkas type lemmas for systems with equalities and inequalities
A central result in the theory of integer optimization states that a system of linear diophantine equations Ax = b has no integral solution if and only if there exists a vector in the dual lattice, y T A integral such that y T b is fractional. We extend this result to systems that both have equations and inequalities {Ax = b, Cx d}. We show that a certificate of integral infeasibility is a linear system with rank(C) variables containing no integral point.
An analysis of mixed integer linear sets based on lattice point free convex sets
Split cuts are cutting planes for mixed integer programs whose validity is
derived from maximal lattice point free polyhedra of the form called split sets. The set obtained by adding all
split cuts is called the split closure, and the split closure is known to be a
polyhedron. A split set has max-facet-width equal to one in the sense that
. In this paper
we consider using general lattice point free rational polyhedra to derive valid
cuts for mixed integer linear sets. We say that lattice point free polyhedra
with max-facet-width equal to have width size . A split cut of width
size is then a valid inequality whose validity follows from a lattice point
free rational polyhedron of width size . The -th split closure is the set
obtained by adding all valid inequalities of width size at most . Our main
result is a sufficient condition for the addition of a family of rational
inequalities to result in a polyhedral relaxation. We then show that a
corollary is that the -th split closure is a polyhedron. Given this result,
a natural question is which width size is required to design a finite
cutting plane proof for the validity of an inequality. Specifically, for this
value , a finite cutting plane proof exists that uses lattice point free
rational polyhedra of width size at most , but no finite cutting plane
proof that only uses lattice point free rational polyhedra of width size
smaller than . We characterize based on the faces of the linear
relaxation
Congruence of chloroplast- and nuclear-encoded DNA sequence variations used to assess species boundaries in the soil microalga Heterococcus (Stramenopiles, Xanthophyceae).
BackgroundHeterococcus is a microalgal genus of Xanthophyceae (Stramenopiles) that is common and widespread in soils, especially from cold regions. Species are characterized by extensively branched filaments produced when grown on agarized culture medium. Despite the large number of species described exclusively using light microscopic morphology, the assessment of species diversity is hampered by extensive morphological plasticity.ResultsTwo independent types of molecular data, the chloroplast-encoded psbA/rbcL spacer complemented by rbcL gene and the internal transcribed spacer 2 of the nuclear rDNA cistron (ITS2), congruently recovered a robust phylogenetic structure. With ITS2 considerable sequence and secondary structure divergence existed among the eight species, but a combined sequence and secondary structure phylogenetic analysis confined to helix II of ITS2 corroborated relationships as inferred from the rbcL gene phylogeny. Intra-genomic divergence of ITS2 sequences was revealed in many strains. The 'monophyletic species concept', appropriate for microalgae without known sexual reproduction, revealed eight different species. Species boundaries established using the molecular-based monophyletic species concept were more conservative than the traditional morphological species concept. Within a species, almost identical chloroplast marker sequences (genotypes) were repeatedly recovered from strains of different origins. At least two species had widespread geographical distributions; however, within a given species, genotypes recovered from Antarctic strains were distinct from those in temperate habitats. Furthermore, the sequence diversity may correspond to adaptation to different types of habitats or climates.ConclusionsWe established a method and a reference data base for the unambiguous identification of species of the common soil microalgal genus Heterococcus which uses DNA sequence variation in markers from plastid and nuclear genomes. The molecular data were more reliable and more conservative than morphological data
Acute Cholangitis: An Update in Management Based on Severity Assessment
Acute cholangitis (AC) is a biliary tract emergency which causes significant morbidity and mortality. The direct cause of death in AC is sepsis that leads to irreversible shock and multiple organ failure. The most common predisposition are bile duct stones and previous invasive manipulation of the biliary tree. Biliary infection and biliary obstruction are the two main factors in pathophysiology of AC. Gram-negative bacteria are isolated frequently from bile and blood culture in cholangitis. The most common cause of biliary obstruction is gallstone.The Charcot’s triad which commonly has been used to diagnose AC is severely limited and the clinical presentation of the disease has wide spectrum ranging from mild symptoms to severe life-threatening disease. Thus, the use of the most updated Tokyo Guidelines (TG18) is imperative to diagnose the disease and to assess the severity. The TG18 diagnostic criteria is based on the presence of systemic inflammmation, cholestasis, and evidence on imaging studies of biliary tract. The prompt treatment is tailored according to severity assessed by TG18. Initial treatment includes sufficient fluid replacement, hemodynamic control, electrolyte compensation, intravenous antibiotic administration, and intravenous analgesic administration. The definitive treatment which related to the pathophysiology of the disease are biliary drainage and antibiotic administration
Effective Theory of Wilson Lines and Deconfinement
To study the deconfining phase transition at nonzero temperature, I outline
the perturbative construction of an effective theory for straight, thermal
Wilson lines. Certain large, time dependent gauge transformations play a
central role. They imply the existence of interfaces, which can be used to
determine the form of the effective theory as a gauged, nonlinear sigma model
of adjoint matrices. Especially near the transition, the Wilson line may
undergo a Higgs effect. As an adjoint field, this can generate eigenvalue
repulsion in the effective theory.Comment: 6 pages, LaTeX. Final, published version. Refs. 7, 39, and 40 added.
In Ref. 37, there is an expanded discussion of a "fuzzy" bag mode
Models of discretized moduli spaces, cohomological field theories, and Gaussian means
We prove combinatorially the explicit relation between genus filtrated
-loop means of the Gaussian matrix model and terms of the genus expansion of
the Kontsevich--Penner matrix model (KPMM). The latter is the generating
function for volumes of discretized (open) moduli spaces
given by for
. This generating function therefore enjoys
the topological recursion, and we prove that it is simultaneously the
generating function for ancestor invariants of a cohomological field theory
thus enjoying the Givental decomposition. We use another Givental-type
decomposition obtained for this model by the second authors in 1995 in terms of
special times related to the discretisation of moduli spaces thus representing
its asymptotic expansion terms (and therefore those of the Gaussian means) as
finite sums over graphs weighted by lower-order monomials in times thus giving
another proof of (quasi)polynomiality of the discrete volumes. As an
application, we find the coefficients in the first subleading order for
in two ways: using the refined Harer--Zagier recursion and
by exploiting the above Givental-type transformation. We put forward the
conjecture that the above graph expansions can be used for probing the
reduction structure of the Delgne--Mumford compactification of moduli spaces of punctured Riemann surfaces.Comment: 36 pages in LaTex, 6 LaTex figure
The boundary length and point spectrum enumeration of partial chord diagrams using cut and join recursion
We introduce the boundary length and point spectrum, as a joint
generalization of the boundary length spectrum and boundary point spectrum in
arXiv:1307.0967. We establish by cut-and-join methods that the number of
partial chord diagrams filtered by the boundary length and point spectrum
satisfies a recursion relation, which combined with an initial condition
determines these numbers uniquely. This recursion relation is equivalent to a
second order, non-linear, algebraic partial differential equation for the
generating function of the numbers of partial chord diagrams filtered by the
boundary length and point spectrum.Comment: 16 pages, 6 figure
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