3,420 research outputs found
Ordering dynamics of the driven lattice gas model
The evolution of a two-dimensional driven lattice-gas model is studied on an
L_x X L_y lattice. Scaling arguments and extensive numerical simulations are
used to show that starting from random initial configuration the model evolves
via two stages: (a) an early stage in which alternating stripes of particles
and vacancies are formed along the direction y of the driving field, and (b) a
stripe coarsening stage, in which the number of stripes is reduced and their
average width increases. The number of stripes formed at the end of the first
stage is shown to be a function of L_x/L_y^\phi, with \phi ~ 0.2. Thus,
depending on this parameter, the resulting state could be either single or
multi striped. In the second, stripe coarsening stage, the coarsening time is
found to be proportional to L_y, becoming infinitely long in the thermodynamic
limit. This implies that the multi striped state is thermodynamically stable.
The results put previous studies of the model in a more general framework
Electron Tomography Analysis of Thylakoid Assembly and Fission in Chloroplasts of a Single-Cell C4 plant, Bienertia sinuspersici
Bienertia sinuspersici is a single-cell C4 plant species of which chlorenchyma cells have two distinct groups of chloroplasts spatially segregated in the cytoplasm. The central vacuole encloses most chloroplasts at the cell center and confines the rest of the chloroplasts near the plasma membrane. Young chlorenchyma cells, however, do not have large vacuoles and their chloroplasts are homogenous. Therefore, maturing Bienertia chlorenchyma cells provide a unique opportunity to investigate chloroplast proliferation in the central cluster and the remodeling of chloroplasts that have been displaced by the vacuole to the cell periphery. Chloroplast numbers and sizes increased, more notably, during later stages of maturation than the early stages. Electron tomography analyses indicated that chloroplast enlargement is sustained by thylakoid growth and that invaginations from the inner envelope membrane contributed to thylakoid assembly. Grana stacks acquired more layers, differentiating them from stroma thylakoids as central chloroplasts matured. In peripheral chloroplasts, however, grana stacks stretched out to a degree that the distinction between grana stacks and stroma thylakoids was obscured. In central chloroplasts undergoing division, thylakoids inside the cleavage furrow were kinked and severed. Grana stacks in the division zone were disrupted, and large complexes in their membranes were dislocated, suggesting the existence of a thylakoid fission machinery.11Ysciescopu
Observing two dark accelerators around the Galactic Centre with Fermi Large Area Telescope
We report the results from a detailed ray investigation in the field
of two "dark accelerators", HESS J1745-303 and HESS J1741-302, with years
of data obtained by the Fermi Large Area Telescope. For HESS J1745-303, we
found that its MeV-GeV emission is mainly originated from the "Region A" of the
TeV feature. Its ray spectrum can be modeled with a single power-law
with a photon index of from few hundreds MeV to TeV. Moreover,
an elongated feature, which extends from "Region A" toward northwest for
, is discovered for the first time. The orientation of this
feature is similar to that of a large scale atomic/molecular gas distribution.
For HESS J1741-302, our analysis does not yield any MeV-GeV counterpart for
this unidentified TeV source. On the other hand, we have detected a new point
source, Fermi J1740.1-3013, serendipitously. Its spectrum is apparently curved
which resembles that of a ray pulsar. This makes it possibly
associated with PSR B1737-20 or PSR J1739-3023.Comment: 11 pages, 7 figures, 2 tables, accepted for publication in MNRA
Phase Separation Kinetics in a Model with Order-Parameter Dependent Mobility
We present extensive results from 2-dimensional simulations of phase
separation kinetics in a model with order-parameter dependent mobility. We find
that the time-dependent structure factor exhibits dynamical scaling and the
scaling function is numerically indistinguishable from that for the
Cahn-Hilliard (CH) equation, even in the limit where surface diffusion is the
mechanism for domain growth. This supports the view that the scaling form of
the structure factor is "universal" and leads us to question the conventional
wisdom that an accurate representation of the scaled structure factor for the
CH equation can only be obtained from a theory which correctly models bulk
diffusion.Comment: To appear in PRE, figures available on reques
Spinodal Decomposition and the Tomita Sum Rule
The scaling properties of a phase-ordering system with a conserved order
parameter are studied. The theory developed leads to scaling functions
satisfying certain general properties including the Tomita sum rule. The theory
also gives good agreement with numerical results for the order parameter
scaling function in three dimensions. The values of the associated
nonequilibrium decay exponents are given by the known lower bounds.Comment: 15 pages, 6 figure
Evolution of speckle during spinodal decomposition
Time-dependent properties of the speckled intensity patterns created by
scattering coherent radiation from materials undergoing spinodal decomposition
are investigated by numerical integration of the Cahn-Hilliard-Cook equation.
For binary systems which obey a local conservation law, the characteristic
domain size is known to grow in time as with n=1/3,
where B is a constant. The intensities of individual speckles are found to be
nonstationary, persistent time series. The two-time intensity covariance at
wave vector can be collapsed onto a scaling function , where and . Both analytically and numerically, the covariance
is found to depend on only through in the
small- limit and in the large-
limit, consistent with a simple theory of moving interfaces that applies to any
universality class described by a scalar order parameter. The speckle-intensity
covariance is numerically demonstrated to be equal to the square of the
two-time structure factor of the scattering material, for which an analytic
scaling function is obtained for large In addition, the two-time,
two-point order-parameter correlation function is found to scale as
, even for quite large
distances . The asymptotic power-law exponent for the autocorrelation
function is found to be , violating an upper bound
conjectured by Fisher and Huse.Comment: RevTex: 11 pages + 12 figures, submitted to PR
Stereotactic ablative radiotherapy for medically inoperable early stage lung cancer: early outcomes
Objective To evaluate the clinical outcome and safety of stereotactic ablative radiotherapy for medically inoperable stage I non- small-cell lung carcinoma. Design Retrospective case series. Setting Pamela Youde Nethersole Eastern Hospital, Hong Kong. Patients All patients with medically inoperable stage I non-small-cell lung carcinoma receiving stereotactic ablative radiotherapy since its establishment in 2008. Main outcome measures Disease control rate, overall survival, and treatment toxicities. Results Sixteen stage I non-small-cell lung carcinoma patients underwent the procedure from June 2008 to November 2011. The median patient age was 82 years and the majority (81%) had moderate-tosevere co-morbidity based on the Adult Comorbidity Evaluation 27 index. With a median follow-up of 22 months, the 2-year primary tumour control rate, disease-free survival and overall survival rates were 91%, 71% and 87%, respectively. No grade 3 (National Cancer Institute Common Terminology Criteria for Adverse Events) or higher treatment-related complications were reported. Conclusion Stereotactic ablative radiotherapy can achieve a high degree of local control safely in medically inoperable patients with early lung cancer.published_or_final_versio
Networking - A Statistical Physics Perspective
Efficient networking has a substantial economic and societal impact in a
broad range of areas including transportation systems, wired and wireless
communications and a range of Internet applications. As transportation and
communication networks become increasingly more complex, the ever increasing
demand for congestion control, higher traffic capacity, quality of service,
robustness and reduced energy consumption require new tools and methods to meet
these conflicting requirements. The new methodology should serve for gaining
better understanding of the properties of networking systems at the macroscopic
level, as well as for the development of new principled optimization and
management algorithms at the microscopic level. Methods of statistical physics
seem best placed to provide new approaches as they have been developed
specifically to deal with non-linear large scale systems. This paper aims at
presenting an overview of tools and methods that have been developed within the
statistical physics community and that can be readily applied to address the
emerging problems in networking. These include diffusion processes, methods
from disordered systems and polymer physics, probabilistic inference, which
have direct relevance to network routing, file and frequency distribution, the
exploration of network structures and vulnerability, and various other
practical networking applications.Comment: (Review article) 71 pages, 14 figure
Wnt activation downregulates olfactomedin-1 in Fallopian tubal epithelial cells:a microenvironment predisposed to tubal ectopic pregnancy
Ectopic pregnancy (EP) occurs when the embryo fails to transit to the uterus and attach to the luminal epithelium of the Fallopian tube (FT). Tubal EP is a common gynecological emergency and more than 95% of EP occurs in the ampullary region of the FT. In humans, Wnt activation and downregulation of olfactomedin-1 (Olfm-1) occur in the receptive endometrium and coincided with embryo implantation in vivo. Whether similar molecular changes happen in the FT leading to EP remains unclear. We hypothesized that activation of Wnt signaling downregulates Olfm-1 expression predisposes to EP. We investigated the spatiotemporal expression of Olfm-1 in FT from non-pregnant women and women with EP, and used a novel trophoblastic spheroid (embryo surrogate)-FT epithelial cell co-culture model (JAr and OE-E6/E7 cells) to study the role of Olfm-1 on spheroid attachment. Olfm-1 mRNA expression in the ampullary region of non-pregnant FT was higher (P0.05) in the follicular phase than in the luteal phase. Ampullary tubal Olfm-1 expression was lower in FT from women with EP compared to normal controls at the luteal phase (histological scoring (H-SCORE)1.30.2 vs 2.40.5; P0.05). Treatment of OE-E6/E7 with recombinant Olfm-1 (0.2-5 g/ml) suppressed spheroid attachment to OE-E6/E7 cells, while activation of Wnt-signaling pathway by Wnt3a or LiCl reduced endogenous Olfm-1 expression and increased spheroid attachment. Conversely, suppression of Olfm-1 expression by RNAi increased spheroid attachment to OE-E6/E7 cells. Taken together, Wnt activation suppresses Olfm-1 expression, and this may predispose a favorable microenvironment of the retained embryo in the FT, leading to EP in humans. © 2012 USCAP, Inc All rights reserved.link_to_OA_fulltex
Engaging service users and carers in health and social care education: : challenges and opportunities in the Chinese Community
This is an accepted manuscript of an article published by Taylor & Francis Group in Social Work Education on 25 June 2010, available online at: http://dx.doi.org/10.1080/02615479.2010.491542.Service users' and carers' involvement in health and social care education has become a mainstream activity in Britain. However, members from black and minority ethnic communities (BME) remain under-represented in this area of participation. In this article, we will take the readers across the globe to explore the difficulties and opportunities of engaging such an under-represented group, the Chinese community. The journey will begin in Britain where barriers to engagement of service users and carers from the Chinese community will be discussed. We will then travel to Hong Kong, a cosmopolitan city, where successful engagement in work with Chinese service users and carers will be explored. Throughout the journey, we will highlight the importance of the consideration of cultural factors, particularly Confucian beliefs such as social harmony and collectivism, when working with Chinese people. We will also fully explore the issue of ‘trust’ as a culturally laden concept in Chinese societies and its significance for successful engagement in work with Chinese service users and carers in different parts of the world.Peer reviewedFinal Accepted Versio
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