In vivo measurement of mechanical impedance of bone

System of measurement provides indications of ulnar properties independent of characteristics of surrounding soft tissue and other bones. Mechanical modal approximated ulnar response so average bending rigidity could be determined to provide direct index of bone resistance to bending loading

The effect of different combinations of boundary conditions on the average radiation efficiency of rectangular plates

The boundary conditions of a vibrating plate are known to have an influence on its sound radiation for frequencies below the critical frequency. To investigate this effect in a systematic way, the average radiation efficiency and radiated power are calculated for a rectangular plate set in an infinite baffle using a modal summation approach. Whereas analytical expressions exist for simply supported boundary conditions, a numerical approach is required for other cases. Nine combinations of boundary conditions are considered, consisting of simply supported, clamped and free edges on different plate edges. The structural vibration is approximated by using independent beam functions in orthogonal directions allowing simple approximate formulae for mode shapes and natural frequencies. This assumption is checked against a finite element model and shown to give reliable results. It is shown that a free plate has the lowest radiation efficiency and a clamped plate the highest for most frequencies between the fundamental panel natural frequency and the critical frequency. Other combinations of boundary condition give intermediate results according to the level of constraint introduced. The differences depend on frequency: excluding the extreme case of a fully free plate all the other boundary conditions give results within a range of 8 dB in the middle part of the short-circuiting region, decreasing towards the critical frequency. At low frequency the differences can be even greater, in some cases up to 20 dB. These conclusions are shown to hold for a range of plate thicknesses and dimensions

Long-term Global Agricultural Output Supply-Demand Balance and Real Farm and Food Prices

Global food demand is estimated from population projections of the United Nations and food supply is projected from Food and Agriculture Organization yield data to quantify the global food supply-demand balance for 2025 and 2050. The eight food categories examined account for 95 percent of global food consumption. Results indicate that the historic era of secularly falling real food prices is over. The real price of corn, for example, is not expected to fall over the next four decades at the annual rate of 1.3 percent that it fell annually from 1960 to 2006. The analysis foresees future real food prices fluctuating around a flat or rising trend. Slowed national economic growth from flat or rising real food prices may be little more than an irritant for consumers in affluent countries, but will entail severe hardship for consumers in the many countries currently troubled by poverty and hunger. Opportunities exist to expand food output by adding cropland in Brazil and irrigation in Africa, for example, but in the long term such developments will be offset by cropland removed from production by urban and industrial development, soil degradation, and the like. Although cropland can be expanded through higher real farm and food prices, higher yields rather than added cropland offer the most attractive opportunities for farm output expansion at low cost to consumers and the environment. The slowing rate of increase in crop and livestock yields corresponds with a slowing rate of increase in public and in private agricultural research and development spending. The world will not have the luxury of curtailing spending on agricultural technology and rejecting promising technologies such as genetically modified organisms (GMOs) if is to keep real food costs from rising. Productive new cropland, irrigation, genetically modified varieties, and other technologies will be hard pressed indeed to match the massive historic gains from hybrid varieties, irrigation, synthetic fertilizers, and mechanization. On the demand side, subsidies to expand demand for farming resources such as biofuels will need revisiting if rising food costs are to be contained.World Food Supply-Demand, Food Prices, Agricultural Markets, Crop and Livestock Yields, Agricultural and Food Policy, Demand and Price Analysis, International Development, Q11, Q18,

Country of Origin Advertising and U.S. Wine Imports

The objective of this paper is to investigate the impact of media advertising on the US consumption of imported wine. A panel data of seven countries and twelve years from 1994-2005 is used to estimate the demand function for US wine imports. Our empirical analysis reveals evidence of strong price and advertising effects of domestic and imported wines on imported quantities; the advertising of imported wines significantly increases the quantity of imports while the advertising of domestic wines has a strong depressing effect on imported wine volumes. Our short-run import demand price and advertising elasticity estimates are -0.406 and 0.109 for imports and 0.654 and -0.370 for domestic wines, respectively. Other determinants such as population, real income and country specific fixed effects are also found significant. Based on our model estimates, we compute the marginal return to advertising to be $2.68 on average for the six importing countries and$3.40 for the U.S.International Relations/Trade, Marketing,

Novel individualized power training protocol preserves physical function in adult and older mice

Sarcopenia, the age-related loss of muscle mass and strength, contributes to frailty, functional decline, and reduced quality of life in older adults. Exercise is a recognized therapy for sarcopenia and muscle dysfunction, though not a cure. Muscle power declines at an increased rate compared to force, and force output declines earlier than mass. Thus, there is a need for research of exercise focusing on improving power output and functionality in older adults. Our primary purpose was proof-of-concept that a novel individualized power exercise modality would induce positive adaptations in adult mice, before the exercise program was applied to an aged cohort. We hypothesized that after following our protocol, both adult and older mice would show improved function, though there would be evidence of anabolic resistance in the older mice. Male C57BL/6 mice (12 months of age at study conclusion) were randomized into control (n = 9) and exercise (n = 6) groups. The trained group used progressive resistance (with a weighted harness) and intensity (~ 4-10 rpm) on a custom motorized running wheel. The mice trained similarly to a human workout regimen (4-5 sets/session, 3 sessions/week, for 12 weeks). We determined significant (p < 0.05) positive adaptations post-intervention, including: neuromuscular function (rotarod), strength/endurance (inverted cling grip test), training physiology (force/power output per session), muscle size (soleus mass), and power/velocity of contraction (in vitro physiology). Secondly, we trained a cohort of older male mice (28 months old at conclusion): control (n = 12) and exercised (n = 8). While the older exercised mice did preserve function and gain benefits, they also demonstrated evidence of anabolic resistance.F31 AG044108 - NIA NIH HHS; R01 AG017768 - NIA NIH HHS; TL1 TR001440 - Institute for Translational Sciences, University of Texas Medical BranchAccepted manuscrip

The Algebra of Strand Splitting. II. A Presentation for the Braid Group on One Strand

Presentations are computed for a braided version BV of Thompson's group V and for V itself showing that there is an Artin group/Coxeter group relation between them. The presentation for V is obtained from that for BV by declaring all that all generators are involutions.Comment: 15 page

Nonparametric maximum likelihood estimation of probability densities by penalty function methods

When it is known a priori exactly to which finite dimensional manifold the probability density function gives rise to a set of samples, the parametric maximum likelihood estimation procedure leads to poor estimates and is unstable; while the nonparametric maximum likelihood procedure is undefined. A very general theory of maximum penalized likelihood estimation which should avoid many of these difficulties is presented. It is demonstrated that each reproducing kernel Hilbert space leads, in a very natural way, to a maximum penalized likelihood estimator and that a well-known class of reproducing kernel Hilbert spaces gives polynomial splines as the nonparametric maximum penalized likelihood estimates

Determination of mechanical properties of excised dog radii from lateral vibration experiments

Experimental data which can be used as a guideline in developing a mathematical model for lateral vibrations of whole bone are reported. The study used wet and dry dog radii mounted in a cantilever configuration. Data are also given on the mechanical, geometric, and viscoelastic properties of bones

Laser cooling in the Penning trap: an analytical model for cooling rates in the presence of an axializing field

Ions stored in Penning traps may have useful applications in the field of quantum information processing. There are, however, difficulties associated with the laser cooling of one of the radial motions of ions in these traps, namely the magnetron motion. The application of a small radio-frequency quadrupolar electric potential resonant with the sum of the two radial motional frequencies has been shown to couple these motions and to lead to more efficient laser cooling. We present an analytical model that enables us to determine laser cooling rates in the presence of such an 'axializing' field. It is found that this field leads to an averaging of the laser cooling rates for the two motions and hence improves the overall laser cooling efficiency. The model also predicts shifts in the motional frequencies due to the axializing field that are in qualitative agreement with those measured in recent experiments. It is possible to determine laser cooling rates experimentally by studying the phase response of the cooled ions to a near resonant excitation field. Using the model developed in this paper, we study the expected phase response when an axializing field is present.Comment: 22 pages, 7 figure