Loop Expansion in Light-Cone ϕ4\phi^4 Field Theory

A loop expansion is implemented based on the path integral quantization of the light-cone $\phi^4$ field theory in 1+1 dimensions. The effective potential as a function of the zero-mode field $\omega$ is calculated up to two loop order and its derivative with respect to $\omega$ is used to determine the vacuum expectation value of the field $\phi$. The critical coupling constant at the spontaneous symmetry breakdown is consistent with that obtained in the ordinary instant-form field theory. The critical exponents which describe the behavior of the susceptibility and the vacuum expectation value of $\phi$ near the critical point are evaluated from the effective potential. The one loop diagrams for the connected Green's function are calculated in momentum space. The relevant equal-time correlation function is shown to be closely related.Comment: 12 pages, plain Tex, 1 table, 3 figures available from [email protected] , accepted by Phys. Rev.

Bregman distances and Chebyshev sets

A closed set of a Euclidean space is said to be Chebyshev if every point in the space has one and only one closest point in the set. Although the situation is not settled in infinite-dimensional Hilbert spaces, in 1932 Bunt showed that in Euclidean spaces a closed set is Chebyshev if and only if the set is convex. In this paper, from the more general perspective of Bregman distances, we show that if every point in the space has a unique nearest point in a closed set, then the set is convex. We provide two approaches: one is by nonsmooth analysis; the other by maximal monotone operator theory. Subdifferentiability properties of Bregman nearest distance functions are also given

A BIO-ECONOMIC DYNAMIC PROGRAMMING ANALYSIS OF THE SEASONAL SUPPLY RESPONSE BY FLORIDA DAIRY PRODUCERS

Seasonal price premiums have been proposed as a means of dampening the highly seasonal patterns of milk production in Florida. A Markov decision bio-economic model of the breeding and replacement decisions was solved via stochastic dynamic programming and used to analyze the potential supply response to seasonal price premiums. The results of the analysis suggest that the seasonal milk supply in Florida is highly price inelastic.Demand and Price Analysis,

Pathways: Augmenting interoperability across scholarly repositories

In the emerging eScience environment, repositories of papers, datasets, software, etc., should be the foundation of a global and natively-digital scholarly communications system. The current infrastructure falls far short of this goal. Cross-repository interoperability must be augmented to support the many workflows and value-chains involved in scholarly communication. This will not be achieved through the promotion of single repository architecture or content representation, but instead requires an interoperability framework to connect the many heterogeneous systems that will exist. We present a simple data model and service architecture that augments repository interoperability to enable scholarly value-chains to be implemented. We describe an experiment that demonstrates how the proposed infrastructure can be deployed to implement the workflow involved in the creation of an overlay journal over several different repository systems (Fedora, aDORe, DSpace and arXiv).Comment: 18 pages. Accepted for International Journal on Digital Libraries special issue on Digital Libraries and eScienc

Enhanced cancer therapy with cold-controlled drug release and photothermal warming enabled by one nanoplatform

Stimuli-responsive nanoparticles hold great promise for drug delivery to improve the safety and efficacy of cancer therapy. One of the most investigated stimuli-responsive strategies is to induce drug release by heating with laser, ultrasound, or electromagnetic field. More recently, cryosurgery (also called cryotherapy and cryoablation), destruction of diseased tissues by first cooling/freezing and then warming back, has been used to treat various diseases including cancer in the clinic. Here we developed a cold-responsive nanoparticle for controlled drug release as a result of the irreversible disassembly of the nanoparticle when cooled to below ∼10 °C. Furthermore, this nanoparticle can be used to generate localized heating under near infrared (NIR) laser irradiation, which can facilitate the warming process after cooling/freezing during cryosurgery. Indeed, the combination of this cold-responsive nanoparticle with ice cooling and NIR laser irradiation can greatly augment cancer destruction both in vitro and in vivo with no evident systemic toxicity

PHYLOGENETIC SYSTEMATICS OF THE BOROPHAGINAE (CARNIVORA: CANIDAE)

The subfamily Borophaginae (Canidae, Carnivora, Mammalia) was erected by G. G. Simpson in 1945 to include seven genera of large, bonecrushing ‘‘dogs’’ in the late Tertiary of the northern continents. As a monophyletic group of canids, the Borophaginae is now known to be much more diverse than was originally envisioned but is confined within the middle to late Tertiary of North America. Fossil records of the borophagines are well represented and members of this prolific clade are often the most common predators in the late Tertiary deposits. Largely due to the Childs Frick Collection at the American Museum of Natural History, borophagines are represented by some of the best materials among fossil carnivorans in anatomical representation, sample size, and stratigraphic density. As a result of this explosive growth of new information, borophagine systematics is now in need of a complete rethinking at a level that could not have been attempted by previous studies. A detailed study of borophagine phylogenetic systematics is presented here, publishing for the first time the entire Frick Collection. A total of 66 species of borophagines, including 18 new species, ranging from Orellan through Blancan ages, are presently recognized. A phylogenetic analysis of these species is performed using cladistic methods, with Hesperocyoninae, an archaic group of canids, as an outgroup. At its base, the Borophaginae has a sister relationship with the subfamily Caninae, which includes all living canids and their most recent fossil relatives. The Borophaginae– Caninae clade is in turn derived from the subfamily Hesperocyoninae. Apart from some transitional forms, most of the Borophaginae can be organized in four major clades (all erected as new tribes or subtribes): Phlaocyonini, Cynarctina, Aelurodontina, and Borophagina. The Borophaginae begins with a group of small fox-sized genera, such as Archaeocyon, Oxetocyon, Otarocyon, and Rhizocyon, in the Orellan through early Arikareean. Relationships among these genera are difficult to resolve due to their primitiveness. Slightly more derived, but still near the base of the Borophaginae, is the Phlaocyonini, a hypocarnivorous clade of the Arikareean and Hemingfordian that includes Cynarctoides and Phlaocyon. These two genera represent divergent approaches toward hypocarnivory. Species of Cynarctoides trend toward selenodonty and remain small in size, whereas species of Phlaocyon specialize toward bunodont dentitions but of increasing size, with an unusual trend toward hypercarnivory by two terminal species in the clade. Four transitional taxa (species of Cormocyon and Desmocyon) occupy intermediate positions between the Phlaocyonini and Cynarctina, and represent a gradual size increase toward mediumsize individuals. The subtribe Cynarctina, the second hypocarnivorous clade, includes Paracynarctus and Cynarctus in the Hemingfordian through Clarendonian, and represents a larger size group than the Phlaocyonini, although there is a tendency toward size reduction among advanced species of Cynarctus. The cynarctines feature the most bunodont dentition known among canids. The next series of transitional taxa (Metatomarctus, Euoplocyon, Psalidocyon, Microtomarctus, Protomarctus, and Tephrocyon) are of medium size and occupy a pectinated sequence that contains a rather diverse set of dental morphology. These include the most hypercarnivorous borophagine Euoplocyon, the peculiarly trenchant Psalidocyon, and the dwarf lineage Microtomarctus. The next clade, Aelurodontina, is the first major hypercarnivorous group and is represented by Tomarctus and Aelurodon in the Barstovian and Clarendonian. The aelurodontines evolve around a more consistent theme of increasingly more hypercarnivorous dentitions with strong premolars, forming a rather linear series from Tomarctus to various species of Aelurodon. The terminal clade Borophagina, sister to the Aelurodontina, begins with the mostly mesocarnivorous Paratomarctus and Carpocyon in the late Barstovian through late Hemphillian. The terminal species of Carpocyon, C. limosus, shows some hypocarnivorous adaptations. Protepicyon in the Barstovian initiates the hypercarnivorous trend in the terminal clade. Epicyon, the largest known canid, is the dominant predator in the Clarendonian and Hemphillian. Finally, an enlarged concept of Borophagus consists of a series of pectinated species terminated by B. diversidens in the late Blancan. Epicyon and Borophagusare the most highly evolved in their capacity to crush bones. Phylogenetic reconstruction was greatly aided by the high quality of fossil records and the large number of transitional forms. The latter ensures a morphological continuity that facilitates the identification of homoplasies that otherwise could easily be mistaken as synapomorphies. Confidence in the phylogeny is further enhanced by a high congruence between the cladistic rank and the stratigraphic sequence. The temporal and morphological continuity in many borophagine lineages also permits further postulation about their evolutionary processes, such as cladogenetic and anagenetic events. Our considerably enlarged concept of the Borophaginae indicates a much broader trophic diversity than has previously been envisioned. In addition to the commonly recognized hyenalike forms, members of the Borophaginae acquired a wider spectrum of morphologies that surpassed either the hesperocyonine or canine canids. The Borophaginae played broad ecological roles that are performed by at least three living carnivoran families, Canidae, Hyaenidae, and Procyonidae

Dynamic Fluid Flow In Heterogeneous Porous Media And Through A Single Fracture With Rough Surfaces

This study investigates the frequency-dependence of fluid flow in heterogeneous porous media using the theory of dynamic permeability and a finite-difference method. Given a permeability distribution, the dynamic permeability is applied locally to calculate the frequency-dependence of fluid flow at each local point. An iterative Alternating Direction Implicit finite-difference technique is applied to calculate the flow field in the frequency domain. We compare the flow through a 2-D heterogeneous porous medium and that through an equivalent homogeneous medium and find that the two media do not behave equivalently as a function of frequency. At very low-frequencies, the heterogeneous medium is less conductive than the homogeneous medium, However, in the transition region from quasi-static to dynamic regimes, the former medium becomes more conductive than the latter medium, with the ratio of the former flow over the latter flow reaching a maximum in this region. The larger the scale, or the higher the degree of the heterogeneity, the higher this maximum is. This finding is important for studying the interaction of a borehole stoneley wave with a heterogeneous porous formation. The finite-difference technique is also applied to simulate frequency-dependent flow through a single fracture with rough surfaces. It is shown that the flow exhibits strong frequency-dependence even for small fractures with contacting surfaces. The amount of flow through the fracture is reduced by the surface roughness .Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumUnited States. Dept. of Energy (Grant DE-FG02-86ERI3636