Surface contact and design of fibrillar 'friction pads' in stick insects (Carausius morosus): mechanisms for large friction coefficients and negligible adhesion.

Many stick insects and mantophasmids possess tarsal 'heel pads' (euplantulae) covered by arrays of conical, micrometre-sized hairs (acanthae). These pads are used mainly under compression; they respond to load with increasing shear resistance, and show negligible adhesion. Reflected-light microscopy in stick insects (Carausius morosus) revealed that the contact area of 'heel pads' changes with normal load on three hierarchical levels. First, loading brought larger areas of the convex pads into contact. Second, loading increased the density of acanthae in contact. Third, higher loads changed the shape of individual hair contacts gradually from circular (tip contact) to elongated (side contact). The resulting increase in real contact area can explain the load dependence of friction, indicating a constant shear stress between acanthae and substrate. As the euplantula contact area is negligible for small loads (similar to hard materials), but increases sharply with load (resembling soft materials), these pads show high friction coefficients despite little adhesion. This property appears essential for the pads' use in locomotion. Several morphological characteristics of hairy friction pads are in apparent contrast to hairy pads used for adhesion, highlighting key adaptations for both pad types. Our results are relevant for the design of fibrillar structures with high friction coefficients but small adhesion.

Effect of pH, temperature and surface contact on the elaboration of fimbriae and flagella by Salmonella serotype Enteritidis

Survival of enteric pathogens exposed to various environmental stresses depends upon a number of protective responses, some of which are associated with induction of virulence determinants. Flagella and fimbriae are putative virulence determinants of Salmonella spp, and ELISAs specific for the detection of flagella and SEF21, SEF14 and SEF17 fimbriae were used to assess the effect of temperature and pH upon their elaboration by isolates of Salmonella serotype Enteritidis in planktonic growth and on the surface of two-dimensional gradient agar plates, For three phage type 4 isolates of Enteritidis of comparative clinical provenance, similar phenotypes for the elaboration of these surface antigens were observed. SEF14 fimbriae were elaborated in planktonic growth at 37 degrees C, but not 20 degrees C, at pH 4.77 and above but not at pH 4.04; whereas on agar gradient plates SEF14 fimbriae were elaborated poorly but with best yields at pH 4.04, SEF17 fimbriae were elaborated in planktonic growth at 20 degrees C, but not at 37 degrees C, at pH 6.18 and above but not at pH 5.09 or below; whereas on agar gradient plates SEF17 fimbriae were elaborated well even at pH 4.65, SEF21 fimbriae were expressed very poorly under all conditions tested, Planktonic growth at 37 degrees C induced least flagella whereas growth at 20 degrees C, and particularly surface growth at lower pH values, induced a 'hyper-flagellate' phenotype, Single colonies allowed to form on gradient agar plates were shown to generate different colonial morphologies which were dependent on initial pH. These results demonstrate that the physicochemical environment is an important determinant of bacterial response, especially the induction of putative virulence factors.

Application of Three-Dimensional Discrete Element Face-to-Face Contact Model with Fissure Water Pressure to Stability Analysis of Landslide in Panluo Iron Mine

Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stage process of landslide under fissure water pressure in the opencast mine, according to the actual state of landslide in Panluo iron mine where landslide happened in 1990 and was fathered in 1999. The calculation results show that fissure water pressure on the sliding surface is the main reason causing landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in good agreement; while if the assumption is not adopted in the discrete element method, the critical phi numerically calculated is less than the one calculated by use of the limit equilibrium method for the same C. Thus, from an engineering point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.

Effect of solder volume on joint shape with variable chip-to-board contact pad ratio

The objective of this paper is to investigate the effect of the pad size ratio between the chip and board end of a solder joint on the shape of that solder joint in combination with the solder volume available. The shape of the solder joint is correlated to its reliability and thus of importance. For low density chip bond pad applications Flip Chip (FC) manufacturing costs can be kept down by using larger size board pads suitable for solder application. By using “Surface Evolver” software package the solder joint shapes associated with different size/shape solder preforms and chip/board pad ratios are predicted. In this case a so called Flip-Chip Over Hole (FCOH) assembly format has been used. Assembly trials involved the deposition of lead-free 99.3Sn0.7Cu solder on the board side, followed by reflow, an underfill process and back die encapsulation. During the assembly work pad off-sets occurred that have been taken into account for the Surface Evolver solder joint shape prediction and accurately matched the real assembly. Overall, good correlation was found between the simulated solder joint shape and the actual fabricated solder joint shapes. Solder preforms were found to exhibit better control over the solder volume. Reflow simulation of commercially available solder preform volumes suggests that for a fixed stand-off height and chip-board pad ratio, the solder volume value and the surface tension determines the shape of the joint.

An evidence-based brochure to educate contact lens wearers about safe contact lens wear

Contact lenses are a successful and popular means to correct refractive error and are worn by just under 700,000 Australians1 and approximately 125 million people worldwide. The most serious complication of contact lens wear is microbial keratitis, a potentially sight-threatening corneal infection most often caused by bacteria. Gram-negative bacteria, in particular pseudomonas species, account for the majority of severe bacterial infections. Pathogens such as fungi or amoebae, which feature less often, are associated with significant morbidity. These unusual pathogens have come into the spotlight in recent times with an apparent association with specific lens cleaning solutions...

Cell-to-cell contact-independent regulatory T cells in human tuberculosis

info:eu-repo/semantics/nonPublished

Skin-to-Skin contact

Skin to skin contact facilitates the initiation of breast feeding, neonatal thermoregulation and the promotion of maternal-infant attachment. However, there are cultural influences in society and in the labour ward that may make implemention of skin to skin contact difficult.

Measurement of Polymer-to-Polymer Contact Friction in Thermoforming

Contact friction plays a critical role in all the major thermoforming processes for polymers. However, these effects are very difficult to measure in practice and, as a result, have received little scientific investigation. In this work, two independently developed test methods for the measurement of elevated temperature polymer-to-polymer contact friction are presented, and their results are compared in detail for the first time. One is based on a modified moving sled friction test, whereas the other uses a rotational rheometer. In each case, friction tests were conducted between two plug and two sheet materials. The results show that broadly similar coefficients of friction were obtained from the two test methods. The measured values were quite low (<0.3) at lower temperatures and typically were higher for polypropylene (PP) sheet than for polystyrene (PS). On approaching the glass transition temperature for PS (95°C) and the crystalline melting point for PP (165°C), the friction coefficients rose very sharply, and both test techniques became increasingly unreliable. It was concluded that despite their physical differences, both test techniques were able to capture the highly temperature sensitive nature of friction between polymer materials used in thermoforming.

Registered Nurses' Perceptions about Facilitators and Barriers to Maternal Skin to Skin Contact in the Operating Room

Abstract It is recommended that all new mothers experience skin-to-skin contact (SSC) with their newborns immediately after birth. However, SSC is not commonly practiced after cesarean deliveries. To understand facilitators and barriers regarding SSC in the operating room (OR), a descriptive online and paper survey was conducted with 68 Registered Nurses from four hospitals in Ontario. The theory of planned behavior framed the study. Nurses had positive attitudes, and believed most health care team members supported SSC in the OR, but were uncertain about their control over the behavior. Nurses who had practiced the behavior in the past had more positive attitudinal and normative beliefs, and perceived some barriers as less difficult. Attitude and past behavior were the only significant multivariate predictors of intention to practice SSC in the future. Results suggest that shifting attitude and supporting more experience with the practice may increase nurses’ implementation of SSC in the OR.