1,252 research outputs found
Scaling relation for determining the critical threshold for continuum percolation of overlapping discs of two sizes
We study continuum percolation of overlapping circular discs of two sizes. We
propose a phenomenological scaling equation for the increase in the effective
size of the larger discs due to the presence of the smaller discs. The critical
percolation threshold as a function of the ratio of sizes of discs, for
different values of the relative areal densities of two discs, can be described
in terms of a scaling function of only one variable. The recent accurate Monte
Carlo estimates of critical threshold by Quintanilla and Ziff [Phys. Rev. E, 76
051115 (2007)] are in very good agreement with the proposed scaling relation.Comment: 4 pages, 3 figure
Condensation in an Economic Model with Brand Competition
We present a linear agent based model on brand competition. Each agent
belongs to one of the two brands and interacts with its nearest neighbors. In
the process the agent can decide to change to the other brand if the move is
beneficial. The numerical simulations show that the systems always condenses
into a state when all agents belong to a single brand. We study the
condensation times for different parameters of the model and the influence of
different mechanisms to avoid condensation, like anti monopoly rules and brand
fidelity.Comment: Accepted in: International Journal of Modern Physics
Single-ion anisotropy and magnetic field response in the spin-ice materials Ho2Ti2 O7 and Dy2Ti2 O7
Motivated by its role as a central pillar of current theories of dynamics of
spin ice in and out of equilibrium, we study the single-ion dynamics of the
magnetic rare earth ions in their local environments, subject to the effective
fields set up by the magnetic moments they interact with. This effective field
has a transverse component with respect to the local easy-axis of the crystal
electric field, which can induce quantum tunnelling. We go beyond the
projective spin-1/2 picture and use instead the full crystal-field Hamiltonian.
We find that the Kramers vs non-Kramers nature, as well as the symmetries of
the crystal-field Hamiltonian, result in different perturbative behaviour at
small fields ( T), with transverse field effects being more
pronounced in HoTiO than in DyTiO.
Remarkably, the energy splitting range we find is consistent with time scales
extracted from experiments. We also present a study of the static magnetic
response which highlights the anisotropy of the system in the form of an
off-diagonal tensor and we investigate the effects of thermal fluctuations
in the temperature regime of relevance to experiments. We show that there is a
narrow yet accessible window of experimental parameters where the anisotropic
response can be observed.EPSRC, STFC, HEFCE, SEPnetThis is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevB.92.15512
Documenting the Undocumented: Understanding Identity and Displacement Through U.S. Latinx Experiences
Undocumented migrants are a part of our daily lives, yet we rarely hear their stories or know who they really are; the word undocumented can have a negative connotation both within and outside the Latinx community and is often associated with criminals and various other negative stereotypes. This study aims to understand how identity is affected by documentation status and how that affects the undocumented and documented Latinx community, the experiences of Latinx people of different documentation status with connections to illegal immigration, and how they navigate through those experiences in the United States of America knowing that they are putting themselves at risk.
There is not enough representation of undocumented Latinx people and their role in society; it is important to understand the undocumented Latinx community and give them a voice because undocumented people are one of the U.S.\u27 backbones in cultural and socio-economic terms. This investigation will provide more insight into their experiences and the identity struggle within the Latinx context through a series of interviews and an in-depth literature review of other publications sharing undocumented Latinx individuals\u27 oral histories. It aims to shine a positive light on the community and contribute to future research on similar topics
Immunocytochemical demonstration of p21 ras family oncogene product in normal mucosa and in premalignant and malignant tumours of the colorectum.
Study of the distribution of the p21 ras oncogene product as demonstrated by monoclonal antibody Y13-259 shows this protein to be apparently present in all epithelial populations of both premalignant and malignant tumours and throughout the normal foetal and adult epithelial crypt population in the colorectum. Metastatic tumour in liver shows a similar staining pattern which is less intense however than in the surrounding normal hepatocytes. Our results suggest that the presence of this protein is a widespread feature of normal cellular metabolism in certain cell types and is not restricted to those actively involved in cellular proliferation. It appears, furthermore, that neither cells at different stages of carcinogenesis nor those representing variants of a malignant phenotype can be identified using this particular antibody
Uso de un sistema para la gestión del aprendizaje (LMS) de código libre en la Universidad Tecnológica del Suroeste de Guanajuato (UTSOE)
The use of the Information and Communication Technologies (ICT) in Learning Environment allows achieving the maximum interaction between Teachers and Students.The Virtual Learning Environments are computer programs that benefit the learning facilitating the communication between users. Open Source software allow to create the own online modular learning environment with a fast placed in service. In the present paper the use of a Learning Management Systems (LMS) as continuous education tool is proposed
Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System
It is argued that ultracold quantum degenerate gas of ytterbium Yb
atoms having nuclear spin exhibits an enlarged SU symmetry.
Within the Landau Fermi liquid theory, stability criteria against Fermi liquid
(Pomeranchuk) instabilities in the spin channel are considered. Focusing on the
SU generalizations of ferromagnetism, it is shown within mean-field
theory that the transition from the paramagnet to the itinerant ferromagnet is
generically first order. On symmetry grounds, general SU itinerant
ferromagnetic ground states and their topological excitations are also
discussed. These SU ferromagnets can become stable by increasing the
scattering length using optical methods or in an optical lattice. However, in
an optical lattice at current experimental temperatures, Mott states with
different filling are expected to coexist in the same trap, as obtained from a
calculation based on the SU Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6)
symmetry-breaking patterns; v3: added further discussion on the order of the
transition. Added Reference
Comparison of cohesive powder flowability measured by Schulze Shear Cell, Raining Bed Method, Sevilla Powder Tester and new Ball Indentation Method
Poor powder flow leads to many problems during manufacturing and can lead to inaccurate dosing and off-specification products. Powder flowability is commonly assessed under relatively high applied loads using shear cells by characterising the unconfined yield strength at a range of applied loads. For applied stresses below 1 kPa, it becomes increasingly difficult to obtain reliable values of the unconfined yield strength. The bulk cohesion and tensile strength of the powder are then obtained by extrapolating the yield locus to zero and negative loads, respectively. However, the reliability of this approximation for a given material is not known. To overcome this limitation, techniques such as the Raining Bed Method, Sevilla Powder Tester and the newly-developed Ball Indentation Method may be used. In this paper, we report our measurement results of the tensile strength of glass beads, α-lactose monohydrate and various sizes of fluid catalytic cracking powders determined by the Sevilla Powder Tester and Raining Bed Method and compare them with those inferred from the Schulze Shear Cell. The results of the latter are also compared with those of the Ball Indentation Method. The outcome suggests that in the case of shear cell tests, the extrapolation of the yield locus to lower or negative loads is unsafe. The ball indentation method enables the characterisation of highly cohesive powders at very low compressive loads; however extrapolation to negative loads is still not reliable. In contrast, the Sevilla Powder Tester and Raining Bed Methods are able to characterise the tensile strength directly, but high bulk cohesion poses difficulties as the internal bed failure needs to be analysed in order to reliably estimate the tensile strength. These methods provide a better understanding of powder flow behaviour at low stresses, thus enabling a greater control of manufacturing processes
Modeling guided elastic waves in generally anisotropic media using a spectral collocation method
Fermi surface instabilities at finite Temperature
We present a new method to detect Fermi surface instabilities for interacting
systems at finite temperature. We first apply it to a list of cases studied
previously, recovering already known results in a very economic way, and
obtaining most of the information on the phase diagram analytically. As an
example, in the continuum limit we obtain the critical temperature as an
implicit function of the magnetic field and the chemical potential
. By applying the method to a model proposed to describe reentrant
behavior in , we reproduce the phase diagram obtained
experimentally and show the presence of a non-Fermi Liquid region at
temperatures above the nematic phase.Comment: 10 pages, 10 figure
- …