Ground state and glass transition of the RNA secondary structure

RNA molecules form a sequence-specific self-pairing pattern at low temperatures. We analyze this problem using a random pairing energy model as well as a random sequence model that includes a base stacking energy in favor of helix propagation. The free energy cost for separating a chain into two equal halves offers a quantitative measure of sequence specific pairing. In the low temperature glass phase, this quantity grows quadratically with the logarithm of the chain length, but it switches to a linear behavior of entropic origin in the high temperature molten phase. Transition between the two phases is continuous, with characteristics that resemble those of a disordered elastic manifold in two dimensions. For designed sequences, however, a power-law distribution of pairing energies on a coarse-grained level may be more appropriate. Extreme value statistics arguments then predict a power-law growth of the free energy cost to break a chain, in agreement with numerical simulations. Interestingly, the distribution of pairing distances in the ground state secondary structure follows a remarkable power-law with an exponent -4/3, independent of the specific assumptions for the base pairing energies

Commercialization of Food Consumption in Rural China

Rural households in China have traditionally consumed food mostly grown on their own farms. While they continue to rely on self-produced grains, vegetables, meats, and eggs for a large portion of their diet, rural households are now purchasing more of their food as they enter the mainstream of the Chinese economy. Cash purchases of food by rural Chinese households increased 7.4 percent per year from 1994 to 2003. Consumption has shifted from self-produced to purchased food at a rate faster than can be explained by income growth or changes in other household characteristics. The move away from self-produced food is associated with lower consumption of staple grains, the most important self produced food in rural Chinese diets. Food consumed away from home is one of the fastest growing categories of rural household expenditures, doubling in budget share from 1995 to 2001. Commercialization of food consumption is diversifying Chinese diets, broadening food markets, and creating new opportunities for retailers and product distributors.China, food, consumption, expenditures, rural, commercialization, subsistence agriculture, Engel analysis, Food Consumption/Nutrition/Food Safety,

Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots

Fluorescence blinking in nanocrystal quantum dots is known to exhibit power-law dynamics, and several different mechanisms have been proposed to explain this behavior. We have extended the measurement of quantum-dot blinking by characterizing fluctuations in the fluorescence of single dots over time scales from microseconds to seconds. The power spectral density of these fluctuations indicates a change in the power-law statistics that occurs at a time scale of several milliseconds, providing an important constraint on possible mechanisms for the blinking. In particular, the observations are consistent with the predictions of models wherein blinking is controlled by diffusion of the energies of electron or hole trap states

Comment on "Atomic Scale Structure and Chemical Composition across Order-Disorder Interfaces"

Interfaces have long been known to be the key to many mechanical and electric properties. To nickel base superalloys which have perfect creep and fatigue properties and have been widely used as materials of turbine blades, interfaces determine the strengthening capacities in high temperature. By means of high resolution scanning transmission electron microscopy (HRSTEM) and 3D atom probe (3DAP) tomography, Srinivasan et al. proposed a new point that in nickel base superalloys there exist two different interfacial widths across the {\gamma}/{\gamma}' interface, one corresponding to an order-disorder transition, and the other to the composition transition. We argue about this conclusion in this comment

The reform of Chinese state-owned ship crewing agencies and implications for China’s seafaring labour export

peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=tmpm2

Comparison of various methods to delineate blood vessels in retinal images

The blood vessels in the human retina are easily visualisable via digital fundus photography and provide an excellent window to the health of a patient affected by diseases of blood circulation such as diabetes. Diabetic retinopathy is identifiable through lesions of the vessels such as narrowing of the arteriole walls, beading of venules into sausage like structures and new vessel growth as an attempt to reperfuse ischaemic regions. Automated quantification of these lesions would be beneficial to diabetes research and to clinical practice, particularly for eye-screening programmes for the detection of eye-disease amongst diabetic persons

MRI and image quantitation for assessment of the growth effects of anabolic steroid precursors in a guinea pig model

MRI and image quantitation play an expanding role in modern drug research. With effective image segmentation and analysis methods, in vivo and longitudinal tissue growth can be assessed. The effects of the nandrolone and testosterone steroids on muscle growth have been investigated previously, in which MRI acquisition and analysis protocol were established, and excellent correlations were found between MRI measurement and dissection analyzes. In this study, the MRI protocol was used to evaluate the anabolic potential of 4 steroid precursors. The effects on muscle growth in castrated guinea pigs, in comparison with that of respective positive control steroids were determined.MRI and image quantitation play an expanding role in modern drug research. With effective image segmentation and analysis methods, in vivo and longitudinal tissue growth can be assessed. The effects of the nandrolone and testosterone steroids on muscle growth have been investigated previously, in which MRI acquisition and analysis protocol were established, and excellent correlations were found between MRI measurement and dissection analyzes. In this study, the MRI protocol was used to evaluate the anabolic potential of 4 steroid precursors. The effects on muscle growth in castrated guinea pigs, in comparison with that of respective positive control steroids were determined.published_or_final_versio

MRI and image quantitation for drug assessment - Growth effects of anabolic steroids and precursors

MRI and image quantitation play an expanding role in modern drug research, because MRI offers high resolution and non-invasive ability, and provides excellent soft tissue contrast. Moreover, with development of effective image segmentation and analysis methods, in-vivo and serial tissue growth measurements could be assessed. In the study, MR image acquisition and analysis protocol were established and validated for investigating the effects of anabolic steroids and precursors on muscle growth and body composition in a guinea pig model. Semi-automatic and interactive segmentation methods were developed to accurately label the tissue of interest for tissue volume estimation. In addition, a longitudinal tissue area outlining procedure was proposed for study of tissue geometric features in relation to tissue growth. Finally, a fully automatic data retrieval and analysis scheme was implemented to facilitate the overall huge amount of image quantitation, statistical analysis, as well as study group comparisons. As a result, highly significant differences in muscle and organ growth were detected between intact and castrated guinea pigs using the selected anabolic steroids, indicating the viability of employing such protocol to assess other anabolic steroids. Furthermore, the anabolic potential of selected steroid precursors and their effects on muscle growth, in comparison with that in respective positive control groups of castrated guinea pigs, were evaluated with the proposed protocol. © 2005 IEEE.published_or_final_versio

Housing Subsidies: A Closer Look at the Issues

To improve poor household’s access to housing, the government has provided subsidies to lower production costs and make housing units more affordable to low-income groups. However, mechanisms should be implemented to ensure that the intended targets are the ones who receive it. This issue reviews the beneficiaries of subsidies, its transfer mechanisms and its budgetary implications. This hopes to eliminate the mismatch between what the government should provide and the estimated housing targets.housing finance, housing subsidy, subsidy

Simulation and analysis of in vitro DNA evolution

We study theoretically the in vitro evolution of a DNA sequence by binding to a transcription factor. Using a simple model of protein-DNA binding and available binding constants for the Mnt protein, we perform large-scale, realistic simulations of evolution starting from a single DNA sequence. We identify different parameter regimes characterized by distinct evolutionary behaviors. For each regime we find analytical estimates which agree well with simulation results. For small population sizes, the DNA evolutional path is a random walk on a smooth landscape. While for large population sizes, the evolution dynamics can be well described by a mean-field theory. We also study how the details of the DNA-protein interaction affect the evolution.Comment: 11 pages, 11 figures. Submitted to PNA