2,251 research outputs found
Warm and Cold Denaturation in the Phase Diagram of a Protein Lattice Model
Studying the properties of the solvent around proteins, we propose a much
more sophisticated model of solvation than temperature-independent pairwise
interactions between monomers, as is used commonly in lattice representations.
We applied our model of solvation to a 16-monomer chain constrained on a
two-dimensional lattice. We compute a phase diagram function of the temperature
and a solvent parameter which is related to the pH of the solution. It exhibits
a native state in which the chain coalesces into a unique compact conformation
as well as a denatured state. Under certain solvation conditions, both warm and
cold denaturations occur between the native and the denatured states. A good
agreement is found with the data obtained from calorimetric experiments,
thereby validating the proposed model.Comment: 7 pages, 2 figure
Benign Bilateral Adenomyoepithelioma of the Mammary Gland in a Ring-tailed Lemur (Lemur catta)
Naturally occurring mammary tumours are uncommon in prosimians. A 20-year-old female ring-tailed lemur (Lemur catta) developed bilateral enlargement of the mammary glands. Surgical removal revealed that both masses were comprised of multiple nodules and cystic areas that entirely replaced the normal glands. Histologically, a benign neoplastic biphasic cellular proliferation, composed of luminalâepithelial and basalâmyoepithelial components, was identified. Immunohistochemical analysis for expression of cytokeratin (CK) AE1/AE3, CK7, CK5 + 8, CK14, vimentin, p63 and 14-3-3Ï highlighted the biphasic nature of the neoplasm. A low mitotic count, low Ki67 labelling index, expression of oestrogen receptor-α, lack of expression of human epidermal growth factor receptor and a 3-year disease-free period without recurrence supported the benign nature of the tumour. Macroscopically, histologically and immunohistochemically this neoplasm resembled benign adenomyoepithelioma of the breast in women. This is the first complete report of a naturally occurring mammary tumour in a ring-tailed lemur
Critical wetting of a class of nonequilibrium interfaces: A mean-field picture
A self-consistent mean-field method is used to study critical wetting
transitions under nonequilibrium conditions by analyzing Kardar-Parisi-Zhang
(KPZ) interfaces in the presence of a bounding substrate. In the case of
positive KPZ nonlinearity a single (Gaussian) regime is found. On the contrary,
interfaces corresponding to negative nonlinearities lead to three different
regimes of critical behavior for the surface order-parameter: (i) a trivial
Gaussian regime, (ii) a weak-fluctuation regime with a trivially located
critical point and nontrivial exponents, and (iii) a highly non-trivial
strong-fluctuation regime, for which we provide a full solution by finding the
zeros of parabolic-cylinder functions. These analytical results are also
verified by solving numerically the self-consistent equation in each case.
Analogies with and differences from equilibrium critical wetting as well as
nonequilibrium complete wetting are also discussed.Comment: 11 pages, 2 figure
Pulsar Prospects for the Cherenkov Telescope Array
In the last few years, the Fermi-LAT telescope has discovered over a 100
pulsars at energies above 100 MeV, increasing the number of known gamma-ray
pulsars by an order of magnitude. In parallel, imaging Cherenkov telescopes,
such as MAGIC and VERITAS, have detected for the first time VHE pulsed
gamma-rays from the Crab pulsar. Such detections have revealed that the Crab
VHE spectrum follows a power-law up to at least 400 GeV, challenging most
theoretical models, and opening wide possibilities of detecting more pulsars
from the ground with the future Cherenkov Telescope Array (CTA). In this
contribution, we study the capabilities of CTA for detecting Fermi pulsars. For
this, we extrapolate their spectra with "Crab-like" power-law tails in the VHE
range, as suggested by the latest MAGIC and VERITAS results.Comment: 4 pages, 3 figures. In Proceedings of the 2012 Heidelberg Symposium
on High Energy Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.184
The role of clustering and gridlike ordering in epidemic spreading
The spreading of an epidemic is determined by the connectiviy patterns which
underlie the population. While it has been noted that a virus spreads more
easily on a network in which global distances are small, it remains a great
challenge to find approaches that unravel the precise role of local
interconnectedness. Such topological properties enter very naturally in the
framework of our two-timestep description, also providing a novel approach to
tract a probabilistic system. The method is elaborated for SIS-type epidemic
processes, leading to a quantitative interpretation of the role of loops up to
length 4 in the onset of an epidemic.Comment: Submitted to Phys. Rev. E; 15 pages, 11 figures, 5 table
On the structure of non-full-rank perfect codes
The Krotov combining construction of perfect 1-error-correcting binary codes
from 2000 and a theorem of Heden saying that every non-full-rank perfect
1-error-correcting binary code can be constructed by this combining
construction is generalized to the -ary case. Simply, every non-full-rank
perfect code is the union of a well-defined family of -components
, where belongs to an "outer" perfect code , and these
components are at distance three from each other. Components from distinct
codes can thus freely be combined to obtain new perfect codes. The Phelps
general product construction of perfect binary code from 1984 is generalized to
obtain -components, and new lower bounds on the number of perfect
1-error-correcting -ary codes are presented.Comment: 8 page
Renormalisation group determination of the order of the DNA denaturation transition
We report on the nature of the thermal denaturation transition of homogeneous
DNA as determined from a renormalisation group analysis of the
Peyrard-Bishop-Dauxois model. Our approach is based on an analogy with the
phenomenon of critical wetting that goes further than previous qualitative
comparisons, and shows that the transition is continuous for the average
base-pair separation. However, since the range of universal critical behaviour
appears to be very narrow, numerically observed denaturation transitions may
look first-order, as it has been reported in the literature.Comment: 6 pages; no figures; to appear in Europhysics Letter
Prosodia y discurso en el español rioplatense
IntroducciĂłnLa prosodia estĂĄ compuesta por un conjunto de rasgos âel tono, el timbre, laintensidad y la duraciĂłn, y sus correspondientes variacionesâ que estĂĄnvinculados con estados emocionales de los emisores, estableciĂ©ndose un vĂnculonatural entre ciertos rasgos prosĂłdicos y ciertos estados de ĂĄnimo. En cuantovĂnculo natural, la prosodia tiene un carĂĄcter indicial o sintomĂĄtico, y forma partede un conjunto mĂĄs amplio de rasgos paralingĂŒĂsticos, que comprenden tambiĂ©nlos gestos y las expresiones faciales. Pero los rasgos prosĂłdicos tambiĂ©n puedenfuncionar como sĂmbolos lingĂŒĂsticos, asociĂĄndose de manera convencional a unsignificado, y por consiguiente formar parte de la gramĂĄtica de una lengua
Nonequilibrium wetting
When a nonequilibrium growing interface in the presence of a wall is
considered a nonequilibrium wetting transition may take place. This transition
can be studied trough Langevin equations or discrete growth models. In the
first case, the Kardar-Parisi-Zhang equation, which defines a very robust
universality class for nonequilibrium moving interfaces, with a soft-wall
potential is considered. While in the second, microscopic models, in the
corresponding universality class, with evaporation and deposition of particles
in the presence of hard-wall are studied. Equilibrium wetting is related to a
particular case of the problem, it corresponds to the Edwards-Wilkinson
equation with a potential in the continuum approach or to the fulfillment of
detailed balance in the microscopic models. In this review we present the
analytical and numerical methods used to investigate the problem and the very
rich behavior that is observed with them.Comment: Review, 36 pages, 16 figure
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