scholarly journals PENTAQUARKS

2004 ◽  
Vol 19 (21) ◽  
pp. 3439-3469 ◽  
Author(s):  
SHI-LIN ZHU
Keyword(s):  
Exotic State ◽  
Hadron Physics ◽  
The Past ◽  
Statistical Experiments ◽  
Low Mass ◽  
Exotic Baryon ◽  
Theoretical Developments

Since LEPS collaboration reported the first evidence of Θ+ pentaquark in early 2003, eleven other experimental groups have confirmed this exotic state while many other groups did not see any signal. If this state is further established by future high statistical experiments, its discovery shall be one of the most important events in hadron physics for the past three decades. This exotic baryon with such a low mass and so narrow a width imposes a big challenge to hadron theorists. Up to now, there have appeared more than two hundred theoretical papers trying to interpret this charming state. I will review some important theoretical developments on pentaquarks based on my biased personal views.

scholarly journals Multi-stable composite twisting structure for morphing applications

2012 ◽  
Vol 468 (2141) ◽  
pp. 1230-1251 ◽  
Author(s):  
X. Lachenal ◽  
P. M. Weaver ◽  
S. Daynes
Keyword(s):  
Analytical Model ◽  
Material Properties ◽  
Degrees Of Freedom ◽  
Design Parameters ◽  
Engineering Structures ◽  
The Past ◽  
Wide Range ◽  
Morphing Structure ◽  
Low Mass ◽  
Unstable States

Conventional shape-changing engineering structures use discrete parts articulated around a number of linkages. Each part carries the loads, and the articulations provide the degrees of freedom of the system, leading to heavy and complex mechanisms. Consequently, there has been increased interest in morphing structures over the past decade owing to their potential to combine the conflicting requirements of strength, flexibility and low mass. This article presents a novel type of morphing structure capable of large deformations, simply consisting of two pre-stressed flanges joined to introduce two stable configurations. The bistability is analysed through a simple analytical model, predicting the positions of the stable and unstable states for different design parameters and material properties. Good correlation is found between experimental results, finite-element modelling and predictions from the analytical model for one particular example. A wide range of design parameters and material properties is also analytically investigated, yielding a remarkable structure with zero stiffness along the twisting axis.

Kinematics of Meshing Surfaces Using Geometric Algebra

2003 ◽  
Author(s):  
Scott M. Miller
Keyword(s):  
Geometric Algebra ◽  
Screw Theory ◽  
Three Dimensional ◽  
Normal Vector ◽  
The Past ◽  
Geometric Concepts ◽  
Vector Algebra ◽  
The Common ◽  
Two Bodies ◽  
Theoretical Developments

As is well known, analysis of two surfaces in mesh plays a fundamental role in gear theory. In the past, special coordinate systems, vector algebra, or screw theory was used to analyze the kinematics of meshing. The approach here instead relies on geometric algebra, an extension of conventional vector algebra. The elegance of geometric algebra for theoretical developments is demonstrated by examining the so-called “equation of meshing,” which requires that the relative velocity of two bodies at a point of contact be perpendicular to the common surface normal vector. With surprisingly little effort, several alternative forms of the equation of meshing are generated and, subsequently, interpreted geometrically. Via straightforward algebraic manipulations, the results of screw theory and vector algebra are unified. Due to the simplicity with which complex geometric concepts are expressed and manipulated, the effort required to grasp the general three-dimensional meshing of surfaces is minimized.

scholarly journals The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri

2014 ◽  
Vol 14 (2) ◽  
pp. 305-312 ◽  
Author(s):  
Michael Endl ◽  
Christoph Bergmann ◽  
John Hearnshaw ◽  
Stuart I. Barnes ◽  
Robert A. Wittenmyer ◽  
...  
Keyword(s):  
High Efficiency ◽  
Detection Sensitivity ◽  
Habitable Zone ◽  
Echelle Spectrograph ◽  
Planet Detection ◽  
The Past ◽  
Temporal Sampling ◽  
Habitable Zones ◽  
Low Mass ◽  
Advanced Version

AbstractThe ‘holy grail’ in planet hunting is the detection of an Earth-analogue: a planet with similar mass as the Earth and an orbit inside the habitable zone. If we can find such an Earth-analogue around one of the stars in the immediate solar neighbourhood, we could potentially even study it in such great detail to address the question of its potential habitability. Several groups have focused their planet detection efforts on the nearest stars. Our team is currently performing an intensive observing campaign on the α Centauri system using the High Efficiency and Resolution Canterbury University Large Échelle Spectrograph (Hercules) at the 1 m McLellan telescope at Mt John University Observatory in New Zealand. The goal of our project is to obtain such a large number of radial velocity (RV) measurements with sufficiently high temporal sampling to become sensitive to signals of Earth-mass planets in the habitable zones of the two stars in this binary system. Over the past few years, we have collected more than 45 000 spectra for both stars combined. These data are currently processed by an advanced version of our RV reduction pipeline, which eliminates the effect of spectral cross-contamination. Here we present simulations of the expected detection sensitivity to low-mass planets in the habitable zone by the Hercules programme for various noise levels. We also discuss our expected sensitivity to the purported Earth-mass planet in a 3.24-day orbit announced by Dumusque et al. (2012).

scholarly journals High Pressure Experiments for Astrophysics

1994 ◽  
Vol 147 ◽  
pp. 239-271
Author(s):  
P. Loubeyre
Keyword(s):  
High Pressures ◽  
Dense Matter ◽  
Planetary Interiors ◽  
The Past ◽  
Dynamic Methods ◽  
Great Progress ◽  
Astrophysical Objects ◽  
Low Mass ◽  
Plasma Phase ◽  
Very High

AbstractIn the past decade, measurements of the properties of H2 and He systems at very high pressures have made great progress, now reaching density at the limit of the plasma phase transition of hydrogen. The potentialities and limits of static and dynamic methods will be reviewed. Then, a survey of the major experimental results is presented. It is the intention of this article to show how these measurements can bring information to model low-mass astrophysical objects. Three levels of usefulness are distinguished on selected examples: data for codes of planetary interiors, constraints for theoretical descriptions of dense matter, observations of unsuspected properties at very high density.

scholarly journals On the ultra-compact nature of the neutron star system 1RXS J170854.4−321857: insights from X-ray spectroscopy

2019 ◽  
Vol 488 (4) ◽  
pp. 5014-5019 ◽  
Author(s):  
M Armas Padilla ◽  
E López-Navas
Keyword(s):  
Neutron Star ◽  
Spectral Study ◽  
Binary Systems ◽  
Absorption Model ◽  
Star System ◽  
X Ray ◽  
Emission Component ◽  
The Past ◽  
Solar Composition ◽  
Low Mass

ABSTRACT The relatively small family of ultra-compact X-ray binary systems is of great interest for many areas of astrophysics. We report on a detailed X-ray spectral study of the persistent neutron star low-mass X-ray binary 1RXS J170854.4−321857. We analysed two XMM–Newton observations obtained in late 2004 and early 2005 when, in agreement with previous studies, the system displayed an X-ray luminosity (0.5–10 keV) of ${\sim} 1\times 10^{36}\, \mathrm{erg~s}^{-1}$. The spectrum can be described by a Comptonized emission component with Γ ∼ 1.9 and a distribution of seed photons with a temperature of ∼0.23 keV. A prominent residual feature is present at soft energies, which is reproduced by the absorption model if overabundances of Ne and Fe are allowed. We discuss how similar observables, which might be attributed to the peculiar (non-solar) composition of the plasma donated by the companion star, are a common feature in confirmed and candidate ultra-compact systems. Although this interpretation is still under debate, we conclude that the detection of these features along with the persistent nature of the source at such low luminosity and the intermediate–long burst that it displayed in the past confirms 1RXS J170854.4−321857 as a solid ultra-compact X-ray binary candidate.

scholarly journals Magnetic Massive Stars

2007 ◽  
Vol 3 (S250) ◽  
pp. 577-586 ◽  
Author(s):  
Rich Townsend ◽  
David H. Cohen ◽  
Luc Dessart ◽  
Swetlana Hubrig ◽  
Yaël Nazé ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Significant Influence ◽  
Massive Star ◽  
Massive Stars ◽  
Structure Evolution ◽  
Special Session ◽  
The Past ◽  
Recent Developments ◽  
Circumstellar Environments ◽  
Theoretical Developments

AbstractMagnetic fields are unexpected in massive stars, due to the absence of a sub-surface convective dynamo. However, advances in instrumentation over the past three decades have led to their detection in a small but growing subset of these stars. Moreover, complementary theoretical developments have highlighted their potentially significant influence over the structure, evolution and circumstellar environments of massive stars. Here, we summarize a special session convened prior to the main conference, focused on presenting recent developments in the study of massive-star magnetic fields.

PERCOLATION AND TUNNELING IN COMPOSITE MATERIALS

2004 ◽  
Vol 18 (15) ◽  
pp. 2091-2121 ◽  
Author(s):  
I. BALBERG ◽  
D. AZULAY ◽  
D. TOKER ◽  
O. MILLO
Keyword(s):  
Electrical Transport ◽  
Disordered Systems ◽  
Microcrystalline Silicon ◽  
Physical Processes ◽  
Electrical Transport Properties ◽  
Metal Insulator ◽  
The Past ◽  
Bona Fide ◽  
The Difference ◽  
Theoretical Developments

Classical percolation theory is concerned with the onset of geometrical connectivity and the accompanied onset of electrical connectivity in disordered systems. It was found, however, that in many systems, such as various composites, the geometrical and electrical onsets of the connectivity are not simultaneous and the correlation between them depends on physical processes such as tunneling. The difference between the above two types of systems and the consequences for the electrical transport properties of the latter composites have been largely ignored in the past. The application of scanning local probe microscopies and some recent theoretical developments have enabled a better understanding of the latter systems and their sometimes "strange" behavior as bona fide percolation systems. In this review we consider the above issues and their manifestation in three types of systems: Carbon Black–Polymer composites, metal–insulator cermets and hydrogenated microcrystalline silicon.

Globalization, Transnationalism, and “Mobile Societies” from a Sociological Perspective: Comments on Engseng Ho's “Inter-Asian Concepts for Mobile Societies”

2017 ◽  
Vol 76 (4) ◽  
pp. 935-941
Author(s):  
Jaeeun Kim
Keyword(s):  
Sociological Perspective ◽  
Area Studies ◽  
The Past ◽  
Theoretical Developments ◽  
Do So ◽  
Broad Overview

Speaking across disciplines is always easier said than done. Engseng Ho's thought-provoking article strives to do just that (and achieves the goal nicely), with its broad overview of the literature, the numerous examples that it draws on, and the ambitious conceptual innovations it proposes. As the only sociologist invited to comment on Ho's article, I see my task as bringing Ho's article into fruitful conversation with my own discipline, which is known to be indifferent (if not hostile) to area studies and which (unfortunately) remains largely missing in Ho's imagined audience. I do so by drawing on my own work and some of the theoretical developments in the broader discipline in the past two decades or so. To make intelligible where my comments are coming from, let me begin by briefly introducing what sorts of questions interest me as a sociologist.

scholarly journals Inspiration from the Development of Public Administration in the West for Studies of Public Administration in China

2019 ◽  
Vol 19 (1) ◽  
pp. 23-51
Author(s):  
Lisheng Dong
Keyword(s):  
Public Administration ◽  
The West ◽  
Teaching And Research ◽  
The Past ◽  
Government Role ◽  
Research Programmes ◽  
Chinese Scholars ◽  
Chinese Public ◽  
Theoretical Developments

Many Western-based theories of public administration have had some traction in the Chinese setting. However, they also point to the importance of context and the need to ensure that the theory is relevant to the setting. In this regard, theory needs to be both clearly developed and there are various routes that can be taken. In this article, I share with readers some of my thoughts emanating from my teaching and research over the past two decades, namely, inspiration from the development of public administration in the West for studies of public administration in China. The two analytical lenses that I use for this article are the five essential attributes of public administration and the instrumental and value rationalities as the fundamental nature of the various schools of thought in the development of public administration in the West. The five essential attributes refer to core value, assumptions about human nature, methodology, government role, and disciplinary positioning. They serve as references for my review of the field of public administration in China. Over the last four decades, public administration research in China has resulted in the restoration of the discipline, the flourishing of teaching and research programmes, and active exchanges with colleagues around the world. However, Chinese public administration is facing an “identity crisis”. Chinese scholars have become used to playing the role of consumers of imported concepts, theories, and methods. At this stage it is urgent that they develop their own unique paradigm, including concepts, theories, and methodologies, and contribute to the progress of the whole discipline. The goal of forming their own theoretical framework is urging our Chinese colleagues to challenge themselves to consciously engage in independent theoretical thought. More specifically, they should try to keep abreast of the theoretical developments in the West and lay emphasis on cutting-edge research, avoid not seeing the forest for the trees, and practise timely adoption of dominant theories.

scholarly journals Massive Star Formation: Observational Constraints

1997 ◽  
Vol 182 ◽  
pp. 525-536
Author(s):  
Ed Churchwell
Keyword(s):  
Star Formation ◽  
Accretion Disks ◽  
Massive Star ◽  
Young Stellar Objects ◽  
Mass Star ◽  
Structure And Properties ◽  
Low Mass Stars ◽  
Stellar Objects ◽  
The Past ◽  
Low Mass

Observations during the past several years strongly imply that virtually every star, independent of final mass, goes through a phase of rapid outflow simultaneously with rapid accretion during formation. The structure and properties of outflows and accretion disks associated with low-mass star formation has received intensive observational attention during the past several years (see the reviews and references in Lada 1985; Edwards, Ray, and Mundt 1993; Fukui et al. 1993; and this symposium). Young stellar objects (YSOs) with Lbol < 103 L⊘ will be referred to as “low-mass” stars in this review. The range of physical properties of CO outflows associated with YSOs of all masses are enormous, see Fukui et al. (1993). I will focus attention in this review on what we know about massive YSOs and their environments.

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