1,706 research outputs found
Modelling quasicrystals at positive temperature
We consider a two-dimensional lattice model of equilibrium statistical
mechanics, using nearest neighbor interactions based on the matching conditions
for an aperiodic set of 16 Wang tiles. This model has uncountably many ground
state configurations, all of which are nonperiodic. The question addressed in
this paper is whether nonperiodicity persists at low but positive temperature.
We present arguments, mostly numerical, that this is indeed the case. In
particular, we define an appropriate order parameter, prove that it is
identically zero at high temperatures, and show by Monte Carlo simulation that
it is nonzero at low temperatures
KESAN PEMBANGUNAN KAWASAN PERINDUSTRIAN TERHADAP KOMUNITI PESISIR PANTAI DI PASIR GUDANG, JOHOR
Kawasan perindustrian Pasir Gudang merupakan sebuah kawasan perindustrian yang sedang
giat membangun di Johor. Kawasan perindustrian Pasir Gudang dahulunya merupakan sebuah
kawasan pedalaman yang hasil ekonominya bergantung kepada komoditi getah. Kini,
pembangunan dalam sektor perindustrian telah membawa kepada pertambahan peluang
pekerjaan dan pertumbuhan penduduk yang pesat. Hal ini secara langsung telah memberi kesan
ke atas taraf hidup dan keadaan sosioekonomi masyarakat setempat khususnya terhadap
komuniti pesisir pantai di kawasan Pasir Gudang. Meskipun pembangunan kawasan
perindustrian rancak berlaku di sekeliling mereka, namun masih terdapat perkampungan di
kawasan pesisir pantai yang masih mengekalkan nilai, tradisi dan amalan ekonomi masyarakat
desa. Sehubungan dengan itu, kajian ini dijalankan bertujuan untuk menilai kesan
pembangunan kawasan perindustrian terhadap tahap sosioekonomi komuniti pesisir pantai di
kawasan Pasir Gudang. Kajian ini dijalankan dengan menggunakan kaedah kuantitatif
deskriptif melibatkan seramai 60 orang ketua isi rumah yang terdiri daripada komuniti pesisir
pantai di Kampung Tanjung Langsat dan Kampung Perigi Acheh. Hasil kajian ini mendapati
terdapat perubahan yang ketara ke atas status sosioekonomi komuniti pesisir pantai akibat
pembangunan kawasan perindustrian di Pasir Gudang. Antara perubahan positif yang diterima
adalah dari aspek pekerjaan dan pendapatan. Manakala kesan negatif akibat pembangunan
pesat kawasan perindustrian adalah dari aspek kesejahteraan sosial dan persekitaran
Local Complexity of Delone Sets and Crystallinity
This paper characterizes when a Delone set X is an ideal crystal in terms of
restrictions on the number of its local patches of a given size or on the
hetereogeneity of their distribution. Let N(T) count the number of
translation-inequivalent patches of radius T in X and let M(T) be the minimum
radius such that every closed ball of radius M(T) contains the center of a
patch of every one of these kinds. We show that for each of these functions
there is a `gap in the spectrum' of possible growth rates between being bounded
and having linear growth, and that having linear growth is equivalent to X
being an ideal crystal. Explicitly, for N(T), if R is the covering radius of X
then either N(T) is bounded or N(T) >= T/2R for all T>0. The constant 1/2R in
this bound is best possible in all dimensions. For M(T), either M(T) is bounded
or M(T) >= T/3 for all T>0. Examples show that the constant 1/3 in this bound
cannot be replaced by any number exceeding 1/2. We also show that every
aperiodic Delone set X has M(T) >= c(n)T for all T>0, for a certain constant
c(n) which depends on the dimension n of X and is greater than 1/3 when n > 1.Comment: 26 pages. Uses latexsym and amsfonts package
Extinctions and Correlations for Uniformly Discrete Point Processes with Pure Point Dynamical Spectra
The paper investigates how correlations can completely specify a uniformly
discrete point process. The setting is that of uniformly discrete point sets in
real space for which the corresponding dynamical hull is ergodic. The first
result is that all of the essential physical information in such a system is
derivable from its -point correlations, . If the system is
pure point diffractive an upper bound on the number of correlations required
can be derived from the cycle structure of a graph formed from the dynamical
and Bragg spectra. In particular, if the diffraction has no extinctions, then
the 2 and 3 point correlations contain all the relevant information.Comment: 16 page
Anatomy and physiology of the mineralized tissues: Role in the pathogenesis of osteoarthrosis
AbstractSynovial joints are composed of several different kinds of tissue that interact to protect normal joint function. Three subchondral mineralized tissues can be identified–calcified cartilage, subchondral cortical bone, and subchondral trabecular bone–which are distinguished morphologically, physiologically, and mechanically. Each responds to mechanical and pharmaceutical stimuli in different ways through processes of growth, modeling, and remodeling, and changes in each may have a distinct effect on the health of the joint. It is important to distinguish between the structural properties of these tissues and their material properties as these change differently in osteoarthrosis (OA). It is likely that changes in the mineral content and thickness of the calcified cartilage play a greater role in the pathogenesis of OA than has been realized, whereas changes in trabecular bone are probably not causative. Changes in the subchondral cortical bone may accelerate progression of pre-existing disease, but the combined effects of increased subchondral bone turnover and greater subchondral bone volume are not at all clear. Ultimately, the efficacy of bone anti-resorptive therapies for OA will depend upon whether the increased structural stiffness of the subchondral mineralized tissues predisposes the cartilage to deteriorate, whether the increased bone turnover that occurs in OA is itself a causative factor, or whether the lower tissue elastic modulus offsets the increased structural stiffness of the subchondral plate in an attempt to protect the cartilage from damage
Fluid/solid transition in a hard-core system
We prove that a system of particles in the plane, interacting only with a
certain hard-core constraint, undergoes a fluid/solid phase transition
Statistical mechanics of glass transition in lattice molecule models
Lattice molecule models are proposed in order to study statistical mechanics
of glass transition in finite dimensions. Molecules in the models are
represented by hard Wang tiles and their density is controlled by a chemical
potential. An infinite series of irregular ground states are constructed
theoretically. By defining a glass order parameter as a collection of the
overlap with each ground state, a thermodynamic transition to a glass phase is
found in a stratified Wang tiles model on a cubic lattice.Comment: 18 pages, 8 figure
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