Probability distribution function of dipolar field in two-dimensional spin ensemble

We theoretically determine the probability distribution function of the net field of the random planar structure of dipoles which represent polarized particles. At small surface concentrations c of the point dipoles this distribution is expressed in terms of special functions. At the surface concentrations of the dipoles as high as 0.6 the dipolar field obey the Gaussian law. To obtain the distribution function within transitional region c<0.6, we propose the method based on the cumulant expansion. We calculate the parameters of the distributions for some specific configurations of the dipoles. The distribution functions of the ordered ensembles of the dipoles at the low and moderate surface concentrations have asymmetric shape with respect to distribution medians. The distribution functions allow to calculate various physical parameters of two-dimensional interacting nanoparticle ensembles.Comment: 9 pages, 3 figure

Numerical Study of Cosmic Censorship in String Theory

Recently Hertog, Horowitz, and Maeda have argued that cosmic censorship can be generically violated in string theory in anti-de Sitter spacetime by considering a collapsing bubble of a scalar field whose mass saturates the Breitenlohner-Freedman bound. We study this system numerically and find that for various choices of initial data black holes form rather than naked singularities, implying that in these cases cosmic censorship is upheld.Comment: 16 pages, latex, 10 figures, uses JHEP.cls, v2: minor changes, version to be published in JHE

Learner conceptions of biological processes in a content and language integrated learning context

In science education, learner conceptions concern how students interpret and understand scientific issues. Recent research into learner conceptions acknowledges students’ knowledge, experiences, language, and resources that demonstrate scientific reasoning rather than their misunderstanding. In this study, we follow a functional approach to learner conceptions and explore the functions of language in constructing and representing students’ interpretations of scientific knowledge. The major theoretical framework guiding this research is the thematic pattern analysis theory (Lemke, 1990), which views scientific phenomena as the patterning of semantic relations (i.e., the relation between scientific concepts and its function). We aim to examine the emergence of learner conceptions and potential factors informing student thematic patterning of scientific issues. This study (research ethics reference number: 20200122) is situated in an undergraduate biology course that employed Content Language Integrated Learning (CLIL) in which equal emphasis was given on learning biological concepts and learning the languaging (i.e., appropriately using the thematic patterns) of the concepts. We focus on one written assignment in which students were asked to reason about the mechanism of Antidiuretic Hormone (ADH) in water transport in the scenario of water intoxification from extensive exercise and water consumption. The primary data included students’ written responses, question prompts, and marking schemes. Other textual data including textbooks, PowerPoint slides, and teacher notes were consulted to have a contextualized understanding of students’ responses. Preliminary analysis revealed a basic thematic pattern embedded in most students’ responses: EXERCISE (condition) --\u3e SWEATING (result/condition) --\u3e WATER LOSS (result/condition) --\u3e WATER CONSUMPTION (result/condition). We also identified different thematic patterns of student conceptions along each aspect of the basic pattern. To explore factors informing learner conceptions, we then compared the thematic patterns of students’ responses and the model answer, which helped demonstrate how implicit and conflicting thematic patterns incorporated in instructional materials may hamper students’ understanding of scientific concepts. For example, the notion of water may contain an implicit semantic relation of hyponym, i.e., water (subordinate term) as a specific type of molecule (superordinate category) composed of atoms; however, students may draw from their everyday experience and view water as a free-flowing substance. This study thus calls for biology teachers’ attention to the patterning of scientific representations. It also provides implications for science education in general and stimulates science teachers’ thinking in their language use in teaching scientific concepts. Works cited Lemke, J. (1990). Talking science: Language, learning, and values. Ablex Publishing Corporation. Tang, K. S. (2020). Discourse strategies for science teaching and learning: Research and practice. Routledge

Pairing in spin polarized two-species fermionic mixtures with mass asymmetry

We discuss on the pairing mechanism of fermions with mismatch in their fermi momenta due to a mass asymmetry. Using a variational ansatz for the ground state we also discuss the BCS -BEC crossover of this system. It is shown that the breached pairing solution with a single fermi surface is stable in the BEC regime. We also include the temperatures effect on the fermion pairing within an approximation that is valid for temperatures much below the critical temperature.Comment: 8 pages and 6 figures, few typos corrected, version to appear in EPJ

Effect of substituting guinea grass with soybean hulls on production performance and digestion traits in fattening rabbits

[EN] The objective of this study was to evaluate the use of soybean hulls (SH) to substitute guinea grass (GG), traditionally used as fibre source in the diets of fattening rabbits on performance, coefficients of total tract apparent digestibility (CTTAD) of nutrients, gastrointestinal tract development and caecum fermentation. A total of 160 mixed sex Hyla commercial meat rabbits were allocated to 4 experimental groups (40 per treatment) differing in the SH level inclusion in the diet offered to rabbits from 40 to 90 d of age: 0, 50, 100 and 200 g/kg as-fed basis: SH0, SH50, SH100 and SH200 groups, respectively. Growth performance was recorded from 40 to 90 d of age, CTTAD of nutrients from 86 to 90 d of age, and gastrointestinal tract development, caecum fermentation and carcass traits were determined at 90 d of age. Average daily feed intake and the feed/gain ratio were lower in SH100 and SH200 groups than in SH0 group (P0.05). In conclusion, our results suggest that SH can substitute GG in the diets of fattening rabbits up to 200 g/kg in diet with no adverse effects on the growth performance, feed efficiency, carcass traits and meat quality.This study was supported by the earmarked fund for Modern Agro-industry Technology Research System (CARS-44-B-1).Shang, S.; Wu, Z.; Liu, G.; Sun, C.; Ma, M.; Li, FC. (2017). Effect of substituting guinea grass with soybean hulls on production performance and digestion traits in fattening rabbits. World Rabbit Science. 25(3):241-249. https://doi.org/10.4995/wrs.2017.6654SWORD24124925

Materials and processes issues in fine pitch eutectic solder flip chip interconnection

New product designs within the electronics packaging industry continue to demand interconnects at microscopic geometry, both at the Integrated Circuit (IC) and supporting board level, thereby creating numerous manufacturing challenges. Flip Chip On Board (FCOB) applications are currently being driven by competitive manufacturing costs and the need for higher volume and robust production capabilities. One of today’s low cost FCOB solutions has emerged as an extension of the existing infrastructure for Surface Mount Technology (SMT) and combines an Under Bump Metallisation (UBM) with a stencil printing solder bumping process, to generate mechanically robust joint structures with low electrical resistance between chip and board. Although electroless Ni plating of the UBM, and stencil printing for solder paste deposition, have been widely used in commercial industrial applications, there still exists a number of technical issues related to these materials and processes as the joint geometry is further reduced. This paper reports on trials with electroless Ni plating and stencil paste printing and the correlation between process variables in the formation of bumps and the shear strength of such bumps at different geometries. The effect of precise control of the tolerances of squeegees, stencils and wafer fixtures was examined to enable the optimisation of the materials, processes and tooling for reduction of bumping defects

Materials and processes issues in fine pitch eutectic solder flip chip interconnection

New product designs within the electronics packaging industry continue to demand interconnects at shrinking geometry, both at the integrated circuit and supporting circuit board substrate level, thereby creating numerous manufacturing challenges. Flip chip on board (FCOB) applications are currently being driven by the need for reduced manufacturing costs and higher volume robust production capability. One of today’s low cost FCOB solutions has emerged as an extension of the existing infrastructure for surface mount technology and combines an under bump metallization (UBM) with a stencil printing solder bumping process, to generate mechanically robust joint structures with low electrical resistance between chip and board. Although electroless Ni plating of the UBM, and stencil printing for solder paste deposition have been widely used in commercial industrial applications, there still exists a number of technical issues related to these materials and processes as the joint geometry is further reduced. This paper reports on trials with electroless Ni plating and stencil paste printing and the correlation between process variables in the formation of bumps and the shear strength of said bumps at different geometries. The effect of precise control of tolerances in squeegees, stencils and wafer fixtures was examined to enable the optimization of the materials, processes, and tooling for reduction of bumping defects

Nonlinear hyperbolic systems: Non-degenerate flux, inner speed variation, and graph solutions

We study the Cauchy problem for general, nonlinear, strictly hyperbolic systems of partial differential equations in one space variable. First, we re-visit the construction of the solution to the Riemann problem and introduce the notion of a nondegenerate (ND) system. This is the optimal condition guaranteeing, as we show it, that the Riemann problem can be solved with finitely many waves, only; we establish that the ND condition is generic in the sense of Baire (for the Whitney topology), so that any system can be approached by a ND system. Second, we introduce the concept of inner speed variation and we derive new interaction estimates on wave speeds. Third, we design a wave front tracking scheme and establish its strong convergence to the entropy solution of the Cauchy problem; this provides a new existence proof as well as an approximation algorithm. As an application, we investigate the time-regularity of the graph solutions $(X,U)$ introduced by the second author, and propose a geometric version of our scheme; in turn, the spatial component $X$ of a graph solution can be chosen to be continuous in both time and space, while its component $U$ is continuous in space and has bounded variation in time.Comment: 74 page

The correction of the littlest Higgs model to the Higgs production process e−γ→νeW−He^{-}\gamma\to \nu_{e}W^{-}H in e−γe^{-}\gamma collisions

The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs(LH) model, we study the process $e^{-}\gamma\to \nu_{e}W^{-}H$ and calculate the contributions of the LH model to the cross section of this process. The results show that, in most of parameter spaces preferred by the electroweak precision data, the value of the relative correction is larger than 10%. Such correction to the process $e^{-}\gamma\to \nu_{e}W^{-}H$ is large enough to be detected via $e^{-}\gamma$ collisions in the future high energy linear $e^{+}e^{-}$ collider($LC$) experiment with the c.m energy $\sqrt{s}$=500 GeV and a yearly integrated luminosity $\pounds=100fb^{-1}$, which will give an ideal way to test the model.Comment: 13 pages, 4 figure

Mode-hop-free tuning over 135 GHz of external cavity diode lasers without anti-reflection coating

We report an external cavity diode laser (ECDL), using a diode whose front facet is not antireflection (AR) coated, that has a mode-hop-free (MHF) tuning range greater than 135 GHz. We achieved this using a short external cavity and by simultaneously tuning the internal and external modes of the laser. We find that the precise location of the pivot point of the grating in our laser is less critical than commonly believed. The general applicability of the method, combined with the compact portable mechanical and electronic design, makes it well suited for both research and industrial applications.Comment: 5 pages, 5 figure