Rubber friction: role of the flash temperature

When a rubber block is sliding on a hard rough substrate, the substrate asperities will exert time-dependent deformations of the rubber surface resulting in viscoelastic energy dissipation in the rubber, which gives a contribution to the sliding friction. Most surfaces of solids have roughness on many different length scales, and when calculating the friction force it is necessary to include the viscoelastic deformations on all length scales. The energy dissipation will result in local heating of the rubber. Since the viscoelastic properties of rubber-like materials are extremely strongly temperature dependent, it is necessary to include the local temperature increase in the analysis. At very low sliding velocity the temperature increase is negligible because of heat diffusion, but already for velocities of order 0.01 m/s the local heating may be very important. Here I study the influence of the local heating on the rubber friction, and I show that in a typical case the temperature increase results in a decrease in rubber friction with increasing sliding velocity for v > 0.01 m/s. This may result in stick-slip instabilities, and is of crucial importance in many practical applications, e.g., for the tire-road friction, and in particular for ABS-breaking systems.Comment: 22 pages, 27 figure

Olprinone Attenuates the Acute Inflammatory Response and Apoptosis after Spinal Cord Trauma in Mice

BACKGROUND: Olprinone hydrochloride is a newly developed compound that selectively inhibits PDE type III and is characterized by several properties, including positive inotropic effects, peripheral vasodilatory effects, and a bronchodilator effect. In clinical settings, olprinone is commonly used to treat congestive cardiac failure, due to its inotropic and vasodilating effects. The mechanism of these cardiac effects is attributed to increased cellular concentrations of cAMP. The aim of the present study was to evaluate the pharmacological action of olprinone on the secondary damage in experimental spinal cord injury (SCI) in mice. METHODOLOGY/PRINCIPAL FINDINGS: Traumatic SCI is characterized by an immediate, irreversible loss of tissue at the lesion site, as well as a secondary expansion of tissue damage over time. Although secondary injury should be preventable, no effective treatment options currently exist for patients with SCI. Spinal cord trauma was induced in mice by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy. SCI in mice resulted in severe trauma characterized by edema, neutrophil infiltration, and production of inflammatory mediators, tissue damage, apoptosis, and locomotor disturbance. Olprinone treatment (0.2 mg/kg, i.p.) 1 and 6 h after the SCI significantly reduced: (1) the degree of spinal cord inflammation and tissue injury (histological score), (2) neutrophil infiltration (myeloperoxidase activity), (3) nitrotyrosine formation, (4) pro-inflammatory cytokines, (5) NF-kappaB expression, (6) p-ERK1/2 and p38 expression and (7) apoptosis (TUNEL staining, FAS ligand, Bax and Bcl-2 expression). Moreover, olprinone significantly ameliorated the recovery of hind-limb function (evaluated by motor recovery score). CONCLUSIONS/SIGNIFICANCE: Taken together, our results clearly demonstrate that olprinone treatment reduces the development of inflammation and tissue injury associated with spinal cord trauma

Application of SeaXerocks on habitat mapping for the deep-sea megabenthos around cobalt-rich ferromanganese crusts in Arnold Guyot of the northwestern Pacific - from the perspective of "whale's eye view"

In this study, to improve image acquisitions in the deep-sea environments, we performed habitat mapping by visualizing distribution patterns of benthic organisms and environments around cobalt-rich ferromanganese crusts by using a state-of-the-art 3-D mapping device SeaXerocks system. We applied SeaXerocks mounted on the skid of an underwater remotely operated vehicle (ROV) along a survey line (about 1.4 km) on the flat top of the Arnold Guyot in the International Seabed Authority (ISA) licensed exploration area for Japan in the northwestern Pacific. As the result, we succeeded in grasping the distributions of microtopography and benthic organisms based on whale's eye view of the sea floor of ~1,400 m depth. The distributions of sessile organisms such as Porifera and Gorgonacea were aggregated on the surface of hard substrates as expected, indicating bottom conditions restrict the distribution of megabenthos. Our observation also clarified the pattern of sand ripples suggesting the direction of dominant bottom water current from northeast to southwest or vice versa. The SeaXerocks system enables us to grasp the relationship between distribution of organisms and environmental factors in more details than the previous methods. Knowledge of these patterns is essential not only for understanding biodiversity patterns but also for the selection of possible mining sites and preservation reference zones, which are required by the ISA environmental guidelines. Thus, the application of SeaXerocks would contribute to the environmental baseline studies and impact assessments relating to future deep-sea mining activities