Stability of an electroweak string with a fermion condensate

A solution of the standard electroweak theory with a single lepton family is constructed, consisting of a cosmic string and a fermion condensate within its core. The stability of this system to small perturbations is examined, and it is found that stability is not enhanced relative to the bare electroweak string. The presence of quark zero modes is shown to violate the existence criteria for embedded defects.Comment: 13 pages, preprint DAMTP 94-9, SWAT/2

On the structure and spectrum of classical two-dimensional clusters with a logarithmic interaction potential

We present a numerical study of the effect of the repulsive logarithmic inter-particle interaction on the ground state configuration and the frequency spectrum of a confined classical two-dimensional cluster containing a finite number of particles. In the case of a hard wall confinement all particles form one ring situated at the boundary of the potential. For a general r^n confinement potential, also inner rings can form and we find that all frequencies lie below the frequency of a particular mode, namely the breathing-like mode. An interesting situation arises for the parabolic confined system(i.e. n=2). In this case the frequency of the breathing mode is independent of the number of particles leading to an upper bound for all frequencies. All results can be understood from Earnshaw's theorem in two dimensions. In order to check the sensitivity of these results, the spectrum of vortices in a type II superconductor which, in the limit of large penetration depths, interact through a logarithmic potential, is investigated.Comment: 11 pages, 6 figure

Performance of the Colorado wind-profiling network, part 1.5A

The Wave Propagation Laboratory (WPL) has operated a network of radar wind Profilers in Colorado for about 1 year. The network consists of four VHF (50-MHz) radars and a UHF (915-MHz) radar. The Platteville VHF radar was developed by the Aeronomy Laboratory (AL) and has been operated jointly by WPL and AL for several years. The other radars were installed between February and May 1983. Experiences with these radars and some general aspects of tropospheric wind measurements with Doppler radar are discussed

Membranes in the two-Higgs standard model

We present some non-topological static wall solutions in two-Higgs extensions of the standard model. They are classically stable in a large region of parameter space, compatible with perturbative unitarity and with present phenomenological bounds.Comment: 7 pages, latex, 3 figures available upon reques

Food Matters: Food Insecurity among Pregnant Adolescents and Infant Birth Outcomes

Objectives: The objectives of this study are to: (1) document prevalence of food insecurity among pregnant adolescents; (2) determine if food insecurity is associated with adverse birth outcomes (i.e., lower birth weight, earlier gestational age) among their newborns; and (3) examine whether depressive symptoms, anxiety, nutrition and/or weight gain mediate these associations. Methods: Pregnant adolescents (14-21 years old; N-881) in prenatal care at community hospitals and health centers in New York City completed a health and psychosocial survey during second and third trimesters of pregnancy. Birth weight and gestational age were recorded from medical records. Results: Over one-half of the adolescents reported food insecurity. Path analyses demonstrated that food insecurity was associated with lower birth weight and earlier gestational age. Depressive symptoms mediated these associations. Conclusions: Pregnant adolescents experience high rates of food insecurity. Those who were food insecure experienced more depressive symptoms, which in turn predicted adverse birth outcomes. Programs and policies should target these vulnerable children to stem the multi-generational effects of food insecurity

European Antibiotic Awareness Day: a five-year perspective of Europe-wide actions to promote prudent use of antibiotics.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.Following the European Union (EU) Council Recommendation on prudent use of antimicrobial agents in human medicine in 2001, and the success of national campaigns, i.e. Belgium and France, the European Centre for Disease Prevention and Control (ECDC) decided to establish the European Antibiotic Awareness Day (EAAD) on 18 November as platform to support national campaigns across Europe. This article provides an overview of EAAD tools, materials, and activities developed during the first five years. It shows that EAAD has been successful due to good cooperation between ECDC and national institutions, strong political and stakeholder support and evidence-based development of campaign materials. EAAD has provided a platform for pre-existing national campaigns and encouraged similar campaigns to develop where neither political support had been secured, nor financial support had been available. As a result, participating countries have continuously expressed strong support for ECDC to continue its work on EAAD. This has been endorsed by a steadily increasing number of countries participating and the growing interest of varied professional and stakeholder organisations. We conclude that EAAD should continue to act as catalyst for discussion and as mechanism to raise awareness of the public and prescribers about prudent use of antibiotics

Supersymmetric Electroweak Cosmic Strings

We study the connection between $N=2$ supersymmetry and a topological bound in a two-Higgs-doublet system with an $SU(2)\times U(1)_Y\times U(1)_{Y^{\prime}}$ gauge group. We derive the Bogomol'nyi equations from supersymmetry considerations showing that they hold provided certain conditions on the coupling constants, which are a consequence of the huge symmetry of the theory, are satisfied. Their solutions, which can be interpreted as electroweak cosmic strings breaking one half of the supersymmetries of the theory, are studied. Certain interesting limiting cases of our model which have recently been considered in the literature are finally analyzed.Comment: 20 pages, RevTe

Scattering from Electroweak Strings

The scattering of a charged fermion from an electroweak string is studied. Owing to an amplification of the wave function at the core radius, the cross sections for helicity flip processes can be largely enhanced. For $0 <\sin^2 \theta_w < 1/2$ (where $\theta_w$ is the Weinberg angle), $\omega \sim k \sim m_e$ and $kR \ll 1$, we show that the helicity flip differential cross section for electrons is of the order $m_e^{-1}$ and is independent of angle. We compare our results with those obtained in calculations of rates for baryon number violating processes in the core of a cosmic string. In that case, while the enhancement is a general phenomenon, its actual magnitude is extremely sensitive to the fractional flux carried by the string core. Apart from showing the existence of a similar enhancement effect for non-topological strings, our results indicate that in some models the magnitude of enhancement can be rendered much less sensitive to the value of the parameters in the theories. Scattering of particles off semi-local strings and axion strings are also considered.Comment: Replaced with revised version "Tex with phyzzx, 18 pages, CALT-68-1921 Non-trivial changes made: discussion on axion strings corrected. Overlap with a recently revised version of hep-ph/9311202 note

Probing liquid surface waves, liquid properties and liquid films with light diffraction

Surface waves on liquids act as a dynamical phase grating for incident light. In this article, we revisit the classical method of probing such waves (wavelengths of the order of mm) as well as inherent properties of liquids and liquid films on liquids, using optical diffraction. A combination of simulation and experiment is proposed to trace out the surface wave profiles in various situations (\emph{eg.} for one or more vertical, slightly immersed, electrically driven exciters). Subsequently, the surface tension and the spatial damping coefficient (related to viscosity) of a variety of liquids are measured carefully in order to gauge the efficiency of measuring liquid properties using this optical probe. The final set of results deal with liquid films where dispersion relations, surface and interface modes, interfacial tension and related issues are investigated in some detail, both theoretically and experimentally. On the whole, our observations and analyses seem to support the claim that this simple, low--cost apparatus is capable of providing a wealth of information on liquids and liquid surface waves in a non--destructive way.Comment: 25 pages, 12 figures, to appear in Measurement Science and Technology (IOP