The effect of cryotherapy on the vascular regeneration following closed soft tissue trauma

INTRODUCTION Icing (cryotherapy) is being widely used for the treatment of closed soft tissue trauma (CSTT), such as those resulting from sport injuries. It is believed that cryotherapy induces vasoconstriction and through this mechanism reduces inflammation [1]. However, the impact of this technique on the healing of impaired vasculature and muscle injuries following trauma remains controversial. Recent evidence suggests that the muscle regeneration is delayed after cryotherapy [2]. Consequently, we aimed to investigate the effect of cryotherapy on the vascular morphology following CSTT using an experimental model in rats by contrast-enhanced micro-CT imaging. METHODS Fifty four rats were divided into three main groups: control (no injury, n=6), sham (CSTT but no icing treatment, n=24) and icing (CSTT, treated with one session of ice block massaged directly on the injured muscle for 20 minutes, n=24). The CSTT was induced to the left thigh (Biceps Femoris) of anaesthetised rats (Male, Wistar) to create a standardized and reproducible vascular and muscle injury using an impact device [3]. Following trauma, animals were euthanized after 1, 3, 7, and 28 days healing time (n=6 for each time point). For a three-dimensional vascular morphological assessment, the blood vessels of euthanised rats were flushed with heparinised saline and then perfused with a radio-opaque contrast agent (Microfil, MV 122, Flowtech, USA) using an infusion pump. Both hind-limbs were dissected, and then the injured and non-injured limbs were imaged using a micro-CT scanner (µCT 40, Scanco Medical, Switzerland) and total volume of the perfused blood vessels (TVV) was calculated. More detailed morphological parameters such as vessel volume (VV), diameter (VD), spacing (VSp), number (VN) and connectivity (VConn) were quantified through high resolution (6 µm), micro-CT-scanned biopsy samples (diameter: 8mm) taken directly from the region of the injured muscles. The biopsies were then analysed histologically to confirm the results derived from contrast-enhanced micro-CT imaging. RESULTS AND DISCUSSION The TVV was significantly higher in the injured legs compared to the non-injured legs at day 1 and 7 in the sham group and at day 28 in both sham and icing groups. The biopsies from the injured legs of the icing group showed a significant reduction in VV, VN, VD, VConn and an increase in VSp compared to those in the sham and control groups at days 1, 3 and 7, post injury. While the injured legs of the sham group exhibited a decrease in VN and VConn 28 days post trauma, indicating a return to the original values prior to trauma, these parameters had increased in the icing group (Figure 1). Also, at day 1 post injury, VV and VD of the injured legs were significantly higher in the sham group compared to the icing group, which may be attributed to the effect of vasoconstriction induced by icing. Further histomorphological evaluation of day 1 post injury, indicated that although cryotherapy significantly reduced the injury size and influx of inflammatory cells, including macrophages and neutrophils, a delay in vascular and muscle fiber regeneration was found at later time points confirming other reports from the literature [2]. CONCLUSIONS We have demonstrated using micro-CT imaging that the vascular morphology changes after CSTT, and that its recovery is affected by therapeutic modalities such as icing. This may be useful for the development of future clinical monitoring, diagnosis and treatment of CSTT. While icing reduces the swelling after trauma, our results suggest that it may delay the recovery of the vasculature in the injured tissue.

Effect of mobile phone distraction on car-following behaviour

Multitasking, such as the concurrent use of a mobile phone and operating a motor vehicle, is a significant distraction that impairs driving performance and is becoming a leading cause of motor vehicle crashes. This study investigates the impact of mobile phone conversations on car-following behaviour. The CARRS-Q Advanced Driving Simulator was used to test a group of young Australian drivers aged 18 to 26 years on a car-following task in three randomised phone conditions: baseline (no phone conversation), hands-free and handheld. Repeated measure ANOVA was applied to examine the effect of mobile phone distraction on selected car-following variables such as driving speed, spacing, and time headway. Overall, drivers tended to select slower driving speeds, larger vehicle spacings, and longer time headways when they were engaged in either hands-free or handheld phone conversations, suggesting possible risk compensatory behaviour. In addition, phone conversations while driving influenced car-following behaviour such that variability was increased in driving speeds, vehicle spacings, and acceleration and decelerations. To further investigate car-following behaviour of distracted drivers, driver time headways were modelled using Generalized Estimation Equation (GEE). After controlling for various exogenous factors, the model predicts an increase of 0.33 seconds in time headway when a driver is engaged in hands-free phone conversation and a 0.75 seconds increase for handheld phone conversation. The findings will improve the collective understanding of distraction on driving performance, in particular car following behaviour which is most critical in the determination of rear-end crashes.

On the effect of Reynolds number for flow past three side-by-side square cylinders for unequal gap spacings

Flow patterns and aerodynamic characteristics behind three side-by-side square cylinders has been found depending upon the unequal gap spacing (g1 = s1/d and g2 = s2/d) between the three cylinders and the Reynolds number (Re) using the Lattice Boltzmann method. The effect of Reynolds numbers on the flow behind three cylinders are numerically studied for 75 ≤ Re ≤ 175 and chosen unequal gap spacings such as (g1, g2) = (1.5, 1), (3, 4) and (7, 6). We also investigate the effect of g2 while keeping g1 fixed for Re = 150. It is found that a Reynolds number have a strong effect on the flow at small unequal gap spacing (g1, g2) = (1.5, 1.0). It is also found that the secondary cylinder interaction frequency significantly contributes for unequal gap spacing for all chosen Reynolds numbers. It is observed that at intermediate unequal gap spacing (g1, g2) = (3, 4) the primary vortex shedding frequency plays a major role and the effect of secondary cylinder interaction frequencies almost disappear. Some vortices merge near the exit and as a result small modulation found in drag and lift coefficients. This means that with the increase in the Reynolds numbers and unequal gap spacing shows weakens wakes interaction between the cylinders. At large unequal gap spacing (g1, g2) = (7, 6) the flow is fully periodic and no small modulation found in drag and lift coefficients signals. It is found that the jet flows for unequal gap spacing strongly influenced the wake interaction by varying the Reynolds number. These unequal gap spacing separate wake patterns for different Reynolds numbers: flip-flopping, in-phase and anti-phase modulation synchronized, in-phase and anti-phase synchronized. It is also observed that in case of equal gap spacing between the cylinders the effect of gap spacing is stronger than the Reynolds number. On the other hand, in case of unequal gap spacing between the cylinders the wake patterns strongly depends on both unequal gap spacing and Reynolds number. The vorticity contour visualization, time history analysis of drag and lift coefficients, power spectrum analysis of lift coefficient and force statistics are systematically discussed for all chosen unequal gap spacings and Reynolds numbers to fully understand this valuable and practical problem.

Row spacing and planting density effects on the growth and yield of sugarcane. 2. Strategies for the adoption of controlled traffic.

Controlled traffic (matching wheel and row spacing) is being promoted as a means to manage soil compaction in the Australian sugar industry. However, machinery limitations dictate that wider row spacings than the standard 1.5-m single row will need to be adopted to incorporate controlled traffic and many growers are reluctant to widen row spacing for fear of yield penalties. To address these concerns, contrasting row configuration and planting density combinations were investigated for their effect on cane and sugar yield in large-scale experiments in the Gordonvale, Tully, Ingham, Mackay, and Bingera (near Bundaberg) sugarcane-growing regions of Queensland, Australia. The results showed that sugarcane possesses a capacity to compensate for different row configurations and planting densities through variation in stalk number and individual stalk weight. Row configurations ranging from 1.5-m single rows (the current industry standard) to 1.8-m dual rows (50 cm between duals), 2.1-m dual (80 cm between duals) and triple ( 65 cm between triples) rows, and 2.3-m triple rows (65 cm between triples) produced similar yields. Four rows (50 cm apart) on a 2.1-m configuration (quad rows) produced lower yields largely due to crop lodging, while a 1.8-m single row configuration produced lower yields in the plant crop, probably due to inadequate resource availability (water stress/limited radiation interception). The results suggest that controlled traffic can be adopted in the Australian sugar industry by changing from a 1.5-m single row to 1.8-m dual row configuration without yield penalty. Further, the similar yields obtained with wider row configurations (2 m or greater with multiple rows) in these experiments emphasise the physiological and environmental plasticity that exists in sugarcane. Controlled traffic can be implemented with these wider row configurations (>2 m), although it will be necessary to carry out expensive modifications to the current harvester and haul-out equipment. There were indications from this research that not all cultivars were suited to configurations involving multiple rows. The results suggest that consideration be given to assessing clones with different growth habits under a range of row configurations to find the most suitable plant types for controlled traffic cropping systems.

Effect of magnetic and electrical fields on dendritic freezing of aqueous solutions of sodium chloride

Aqueous solutions of sodium chloride were solidified under the influence of magnetic and electrical fields using two different freezing systems. In the droplet system, small droplets of the solution are introduced in an organic liquid column at −20°C which acts as the heat sink. In the unidirectional freezing system the solutions are poured into a tygon tube mounted on a copper chill, maintained at −70°C, from which the freezing initiates. Application of magnetic fields caused an increase in the spacing and promoted side branching of primary ice dendrites in the droplet freezing system, but had no measurable effect on the dendrites formed in the unidirectional freezing system. The range of electric fields applied in this investigation had no measurable effect on the dendritic structure. Possible interactions between external magnetic and electrical fields have been reviewed and it is suggested that the selective effect of magnetic fields on dendrite spacings in a droplet system could be due to a change in the nucleation behaviour of the solution in the presence of a magnetic field.

Effect of laser processing parameters on the structure of ductile iron

Laser processing of structure sensitive hypereutectic ductile iron, a cast alloy employed for dynamically loaded automative components, was experimentally investigated over a wide range of process parameters: from power (0.5-2.5 kW) and scan rate (7.5-25 mm s(-1)) leading to solid state transformation, all the way through to melting followed by rapid quenching. Superfine dendritic (at 10(5) degrees C s(-1)) or feathery (at 10(4) degrees C s(-1)) ledeburite of 0.2-0.25 mu m lamellar space, gamma-austenite and carbide in the laser melted and martensite in the transformed zone or heat-affected zone were observed, depending on the process parameters. Depth of geometric profiles of laser transformed or melt zone structures, parameters such as dendrile arm spacing, volume fraction of carbide and surface hardness bear a direct relationship with the energy intensity P/UDb2, (10-100 J mm(-3)). There is a minimum energy intensity threshold for solid state transformation hardening (0.2 J mm(-3)) and similarly for the initiation of superficial melting (9 J mm(-3)) and full melting (15 J mm(-3)) in the case of ductile iron. Simulation, modeling and thermal analysis of laser processing as a three-dimensional quasi-steady moving heat source problem by a finite difference method, considering temperature dependent energy absorptivity of the material to laser radiation, thermal and physical properties (kappa, rho, c(p)) and freezing under non-equilibrium conditions employing Scheil's equation to compute the proportion of the solid enabled determination of the thermal history of the laser treated zone. This includes assessment of the peak temperature attained at the surface, temperature gradients, the freezing time and rates as well as the geometric profile of the melted, transformed or heat-affected zone. Computed geometric profiles or depth are in close agreement with the experimental data, validating the numerical scheme.

Effect of substrate on particle arrangement in arrays formed by self-assembly of polymer grafted nanoparticles

We show that the substrate affects the interparticle spacing in monolayer arrays with hexagonal order formed by self-assembly of polymer grafted nanoparticles. Remarkably, arrays with square packing were formed due to convective shearing at a liquid surface induced by miscibility of colloidal solution with the substrate.

The effect of SiC particles on the size and morphology of eutectic silicon in cast A356/SiCp composites

Properties of cast aluminium matrix composites are greatly influenced by the nature of distribution of reinforcing phase in the matrix and matrix microstructural length scales, such as grain size, dendrite arm spacing, size and morphology of secondary matrix phases, etc. Earlier workers have shown that SIC reinforcements can act as heterogeneous nucleation sites for Si during solidification of Al-Si-SiC composites. The present study aims at a quantitative understanding of the effect of SiC reinforcements on secondary matrix phases, namely eutectic Si, during solidification of A356 Al-SiC composites. Effect of volume fraction of SiC particulate on size and shape of eutectic Si has been studied at different cooling rates. Results indicate that an increase in SiC volume fraction leads to a reduction in the size of eutectic Si and also changes its morphology from needle-like to equiaxed. This is attributed to the heterogeneous nucleation of eutectic Si on SiC particles. However, SiC particles are found to have negligible influence on DAS. Under all the solidification conditions studied in the present investigation, SiC particles are found to be rejected by the growing dendrites. (C) 1999 Elsevier Science Ltd. All rights reserved.

Effect of Gallium on microstructure and mechanical properties of Nb-Si eutectic alloy

In this paper, we report a significant improvement in mechanical properties of near eutectic Nb-Si alloys by addition of Gallium (Ga) and control of microstructural length scale. A comparative study of two alloys Nb-18.79 at.%Si and Nb-20.2 at.%Si-2.7 at.%Ga were carried out. The microstructure refinements were carried out by vacuum suction casting in water cooled thick copper mold. It is shown that addition of Ga suppresses Nb(3)Si phase and promotes beta-Nb(5)Si(3) phase. The microstructural length scale and in particular eutectic spacing reduces significantly to 50-100 nm in suction cast ternary alloys. Compression test shows a strength of 2.8 +/- 0.1 GPa and plasticity of 4.3 +/- 0.03%. In comparison, the binary Nb-18.79 at.%Si alloy processed under identical conditions exhibit coarser length scale (300-400 nm) and brittle behavior. The fracture toughness of Ga containing suction cast alloy shows a value of 24.11 +/- 0.5 MPa root m representing a major improvement for bulk Nb-Si eutectic alloy. (C) 2011 Elsevier Ltd. All rights reserved.

Effect of temperature on the plastic zone size and the shear band density in a bulk metallic glass

High temperature bonded interface indentation experiments are carried out on a Zr based bulk metallic glass (BMG) to examine the plastic deformation characteristics in subsurface deformation zone under a Vickers indenter. The results show that the shear bands are semi-circular in shape and propagate in radial direction. At all temperatures the inter-band spacing along the indentation axis is found to increase with increasing distance from the indenter tip. The average shear band spacing monotonically increases with temperature whereas the shear band induced plastic deformation zone is invariant with temperature. These observations are able to explain the increase in pressure sensitive plastic flow of BMGs with temperature. (C) 2011 Elsevier B.V. All rights reserved.

Effect of Input Source Energy on SASW Evaluation of Cement Concrete Pavement

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter (D) varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance (S) and receiver spacing (X), and (2) for two different heights (H) of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength (lambda(max)) and minimum wavelength (lambda(min)) associated with the combined dispersion curve, corresponding to a particular combination of D and H, were noted to increase almost linearly with an increase in the magnitude of the input source energy (E). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of D. Based on statistical analysis, two regression equations have been proposed to determine lambda(max) and lambda(min) for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. (C) 2014 American Society of Civil Engineers.

Effect of viscosity contrast on plume formation in density stratified fluids

We perform two and three dimensional numerical simulations of plume formation in density and viscosity stratified fluid systems. We show that the ambient to plume fluid viscosity ratio strongly affects the near wall plume structures (line or sheet plumes) such as plume spacing and shape of plumes. We observe that where mushroom-like plumes are observed for lower viscosity ratios, taller plumes with bulbous heads form for high viscosity ratios. Plume structure and spacing are in good agreement with experimental results. By studying the geometry of the line plumes and the flow in the circulation cells, we discuss the mechanisms of their formation and the dynamics of merging. We show that an increase in the viscosity ratio decreases the total length of line plumes in the planform which indicates a decreased mixing at higher viscosity ratios. (C) 2015 Elsevier Ltd. All rights reserved.

EFFECT OF AGING ON IMPRESSION CREEP BEHAVIOR OF Pb-FREE SOLDERS

During service and/or storage, Sn-Ag-Cu (SAC) solder alloys are subjected to temperatures ranging from 0.4 to 0.8 Tm (where Tm is the melting temperature of SAC alloys), making them highly prone to significant microstructural coarsening. The microstructures of these low melting point alloys continuously evolve during service. This results in evolution of creep properties of the joint over time, thereby influencing the long-term reliability of microelectronic packages. Here, we study microstructure evolution and creep behavior of two Sn-Ag-Cu (SAC) alloys, namely Sn-3.0Ag-0.5Cu and Sn-1.0Cu-0.5Cu, isothermally aged at 150 degrees C for various lengths of time. Creep behavior of the two SAC solders after different aging durations was systematically studied using impression creep technique. The key microstructural features that evolve during aging are Ag3Sn particle size and inter-particle spacing. Creep results indicate that the creep rate increases considerably with increasing inter-particle spacing although the creep stress exponent and creep activation energy are independent of the aging history.

Effect of particle size of sand and surface asperities of reinforcement on their interface shear behaviour

This paper investigates the effect of particle size of sand and the surface asperities of reinforcing material on their interlocking mechanism and its influence on the interfacial shear strength under direct sliding condition. Three sands of different sizes with similar morphological characteristics and four different types of reinforcing materials with different surface features were used in this study. Interface direct shear tests on these materials were performed in a specially developed symmetric loading interface direct shear test setup. Morphological characteristics of sand particles were determined from digital image analysis and the surface roughness of the reinforcing materials was measured using an analytical expression developed for this purpose. Interface direct shear tests at three different normal stresses were carried out by shearing the sand on the reinforcing material fixed to a smooth surface. Test results revealed that the peak interfacial friction and dilation angles are hugely dependent upon the interlocking between the sand particles and the asperities of reinforcing material, which in turn depends on the relative size of sand particles and asperities. Asperity ratio (AS/D-50) of interlocking materials, which is defined as the ratio of asperity spacing of the reinforcing material and the mean particle size of sand was found to govern the interfacial shear strength with highest interfacial strength measured when the asperity ratio was equal to one, which represents the closest fitting of sand particles into the asperities. It was also understood that the surface roughness of the reinforcing material influences the shear strength to an extent, the influence being more pronounced in coarser particles. Shear bands in the interface shear tests were analysed through image segmentation technique and it was observed that the ratio of shear band thickness (t) to the median particle size (D-50) was maximum when the AS/D-50 was equal to one. (C) 2015 Elsevier Ltd. All rights reserved.

The Effect of Periodic Segmentation Cracks on the Interfacial Debonding: Study on Interfacial Stresses

Hard coatings on relatively soft substrate always face the danger of debonding along the interface. Interfacial stresses are considered to be the initial driving force for the interfacial debonding of the relatively strong bonded coatings. Interfacial stresses due to the mismatch of strain between the coating and substrate are simulated with FEM firstly. The distribution of the interfacial stresses is achieved, which confirms an excessive stresses concentration near the interface end. Subsequently, the redistribution of interfacial stresses is calculated for a coating with periodic segmentation cracks. Results indicate that the distribution of interfacial stresses is altered greatly with the periodic segmentation cracks. To reveal the effect of the spacing of the periodic segmentation cracks on the distribution of interfacial stresses, different crack density is modeled within the coating. It is found that that the peak values of the interfacial stresses decrease with the increase of crack density, i.e. with reduction of spacing of segmentation cracks.