Effects of early-postmortem glycolytic rate on beef tenderness

Electrical stimulation (ES) was applied at 500 V to one side from each of 60 beef carcasses at 30 to 40 min postmortem. Wide ranges of early-postmortem glycolytic and cooling rates were produced in the musculature by use of three different forms of ES (in addition to non-ES treatment of the contralateral sides) and application of chilling routines of four different degrees of severity. Panel and Warner-Bratzler shear evaluations of loin steaks from all 120 sides showed that tenderness was highest when glycolysis had proceeded at an intermediate rate (corresponding to the attainment of a 3-h pH of about 6·1) and was appreciably lower on both sides of this mid-value. The toughening effect of rapid glycolysis (relative to that of a moderately increased glycolytic rate) persisted through 14 days of aging at 2°C.

These observations appear to be incompatible with the view that lysosomal enzymes contribute significantly to ES-induced tenderization. They also indicate that the effect of ES on tenderness is highly dependent on the subsequent cooling rate, very slow chilling sometimes accelerating the already high rate of pH fall to such an extent that the tissue is significantly toughened. Finally, they suggest that the goal of maximizing the early-postmortem rate of pH decline in bovine muscle is misguided and, if attained, will cause sub-optimal tenderness.     

Effects of 2-Hz and 60-Hz electrical stimulation on the microstructure of beef

A comparative electron-microscope study was made of the structural changes brought about in bovine longissimus dorsi muscle by 2-Hz and 60-Hz electrical stimulation. Apart from the frequency difference, the two treatments were identical: 500V AC, 600 pulses (2Hz × 300s and 60 Hz × 10 s), and a time of application of about 40 min post mortem. The low-frequency current produced no detectable tissue disruption or irregularity in sarcomere length, whereas the 60-Hz treatment caused widespread supercontraction and the formation of contraction nodes; many sarcomeres in the internodal zones were stretched or fractured. The observations confirm and extend those of our earlier light-microscope study, and support the view that fiber disruption contributes significantly to the tenderizing effect of high-voltage electrical stimulation.     

The medial scaffold of 3D unorganized point clouds

We introduce the notion of the medial scaffold, a hierarchical organization of the medial axis of a 3D shape in the form of a graph constructed from special medial curves connecting special medial points. A key advantage of the scaffold is that it captures the qualitative aspects of shape in a hierarchical and tightly condensed representation. We propose an efficient and exact method for computing the medial scaffold based on a notion of propagation along the scaffold itself, starting from initial sources of the flow and constructing the scaffold during the propagation. We examine this method specifically in the context of an unorganized cloud of points in 3D, e.g., as obtained from laser range finders, which typically involve hundreds of thousands of points, but the ideas are generalizable to data arising from geometrically described surface patches. The computational bottleneck in the propagation-based scheme is in finding the initial sources of the flow. We thus present several ideas to avoid the unnecessary consideration of pairs of points which cannot possibly form a medial point source, such as the "visibility of a point from another given a third point and the interaction of clusters of points. An application of using the medial scaffold for the representation of point samplings of real-life objects is also illustrated     

TreePlus: interactive exploration of networks with enhanced tree layouts

Despite extensive research, it is still difficult to produce effective interactive layouts for large graphs. Dense layout and occlusion make food Webs, ontologies and social networks difficult to understand and interact with. We propose a new interactive visual analytics component called TreePlus that is based on a tree-style layout. TreePlus reveals the missing graph structure with visualization and interaction while maintaining good readability. To support exploration of the local structure of the graph and gathering of information from the extensive reading of labels, we use a guiding metaphor of "plant a seed and watch it grow." It allows users to start with a node and expand the graph as needed, which complements the classic overview techniques that can be effective at (but often limited to) revealing clusters. We describe our design goals, describe the interface and report on a controlled user study with 28 participants comparing TreePlus with a traditional graph interface for six tasks. In general, the advantage of TreePlus over the traditional interface increased as the density of the displayed data increased. Participants also reported higher levels of confidence in their answers with TreePlus and most of them preferred TreePlus     

Electrical stimulation, muscle tension and glycolysis in bovine Sternomandibularis

Electrical parameters previously employed to hasten the onset of rigor mortis in carcasses were derived empirically. Various parameters have been studied to determine their relationship to the two-stage fall of muscle pH resulting from stimulation. At any given stimulation period pulse frequency had a considerable effect on the magnitude of the pH fall that occurs during stimulation, the greatest falls, ～ 0·7 pH units in a 120 sec period, being achieved with 5 to 16·6 pulses. sec(-1). The same total number of pulses delivered at differing frequencies did not produce pH falls of equal magnitude. Variation in pulse shape and polarity caused minor changes. Increased energy levels per pulse increases the magnitude of the pH fall during stimulation. All stimulation parameters tested resulted in the rate of pH fall after stimulation being one and a half times to twice that of non-stimulated muscle. The tension-time curves obtained with lower frequencies (< 10 pulses . sec(-1)) show incomplete summation of pulses with sustained tension. At higher frequencies a complete tetanus develops, while tension falls rapidly soon after achieving the peak tension. The relationship between the mechanical and biochemical responses and the implications for stimulation as a practical processing method are discussed.     

Residual blood in lamb muscles

The effect of slaughter method on the residual blood content of the M. longissimus dorsi, the microbiological status of the meat and its tenderness was examined with lambs. There were no differences in any of the characteristics examined between the various stunning procedures used, even though there were marked differences in the amount of blood collected after slaughter.     

High-throughput detection and sizing of individual low-index nanoparticles and viruses for pathogen identification

Rapid, chip-scale, and cost-effective single particle detection of biological agents is of great importance to human health and national security. We report real-time, high-throughput detection and sizing of individual, low-index polystyrene nanoparticles and H1N1 virus. Our widefield, common path interferometer detects nanoparticles and viruses over a very large sensing area, orders of magnitude larger than competing techniques. We demonstrate nanoparticle detection and sizing down to 70 nm in diameter. We clearly size discriminate nanoparticles with diameters of 70, 100, 150, and 200 nm. We also demonstrate detection and size characterization of hundreds of individual H1N1 viruses in a single experiment.     

湿度对近地面大气湍流测量不确定性影响研究

采用多项式法模拟近地面大气湍流,并与实验现场基于温度脉动原理的双点法实测近地面大气湍流进行比对,一方面可以充分利用实验现场的实测温湿压等气象参数进行模拟实验,为研究工作的开展提供便利条件;另一方面可以使研究工作达到科学实际的效果。文中着重研究了在相对湿度较高的环境里实测湍流与多项式法模拟湍流之间的相关性、以及在重新拟合多项式系数后两者之间的相关性变化,从中研究了双点法测量近地面大气湍流的不确定性。分析结果表明:多项式法模拟近地面大气湍流与双点法实测湍流之间在湿度相对较高的环境里相关性较强,且能够维持较高的稳定性,但在相对湿度达到80%以上的环境里两者之间的相关性则明显降低,甚至于出现负值,由此证明双点法测量近地面大气湍流在相对湿度大(80%以上)的环境里存在较大的不确定性。     

Runoff of pharmaceuticals and personal care products following application of biosolids to an agricultural field

Municipal biosolids are a source of nutrients for crop production. Beneficial Management Practices (BMPs) can be used to minimize the risk of contamination of adjacent water resources with chemical or microbial agents that are of public or environmental health concern. In this field study, we applied biosolids slurry at a commercial rate using either subsurface injection or broadcast application followed by incorporation. Precipitation was simulated at 1, 3, 7, 22, 36 and 266 days post-application on 2 m² microplots to evaluate surface runoff of 9 model pharmaceuticals and personal care products (PPCPs), atenolol, carbamazepine, cotinine, gemfibrozil, naproxen, ibuprofen, acetaminophen, sulfamethoxazole and triclosan. In runoff from the injected plots, concentrations of the model PPCPs were generally below the limits of quantitation. In contrast, in the broadcast application treatment, the concentrations of atenolol, carbamazepine, cotinine, gemfibrozil, naproxen, sulfamethoxazole and triclosan on the day following application ranged from 70-1477 ng L^− 1 in runoff and generally declined thereafter with first order kinetics. The total mass of PPCPs mobilized in surface runoff per m² of the field ranged from 0.63 µg for atenolol to 21.1 µg for ibuprofen. For ibuprofen and acetaminophen, concentrations in runoff first decreased and then increased, suggesting that these drugs were initially chemically or physically sequestered in the biosolids slurry, and subsequently released in the soil. Carbamazepine and triclosan were detected at low concentrations in a runoff event 266 days after broadcast application. Overall, this study showed that injection of biosolids slurry below the soil surface could effectively eliminate surface runoff of PPCPs.