Direct Surface Contact Research Articles

Validation and Comparison of Two Sampling Methods to Assess Dermal Exposure to Drilling Fluids and Crude Oil

Dermal exposure to drilling fluids and crude oil is an exposure route of concern. However, there have been no published studies describing sampling methods or reporting dermal exposure measurements. We describe a study that aimed to evaluate a wipe sampling method to assess dermal exposure to an oil-based drilling fluid and crude oil, as well as to investigate the feasibility of using an interception cotton glove sampler for exposure on the hands/wrists. A direct comparison of the wipe and interception methods was also completed using pigs' trotters as a surrogate for human skin and a direct surface contact exposure scenario. Overall, acceptable recovery and sampling efficiencies were reported for both methods, and both methods had satisfactory storage stability at 1 and 7 days, although there appeared to be some loss over 14 days. The methods' comparison study revealed significantly higher removal of both fluids from the metal surface with the glove samples compared with the wipe samples (on average 2.5 times higher). Both evaluated sampling methods were found to be suitable for assessing dermal exposure to oil-based drilling fluids and crude oil; however, the comparison study clearly illustrates that glove samplers may overestimate the amount of fluid transferred to the skin. Further comparison of the two dermal sampling methods using additional exposure situations such as immersion or deposition, as well as a field evaluation, is warranted to confirm their appropriateness and suitability in the working environment.

Horizontal transmission of bovine leukemia virus from lymphocytotic cattle, and beneficial effects of insect vector control

Bovine leukaemia virus (BLV) causes enzootic bovine leukosis (EBL) in cattle and represents a serious problem in Japanese meat and dairy industries (Ministry of Agriculture, Forestry and Fisheries). BLV can...

Squeeze film lubrication of coupled stress electrically conducting inertial fluids in wide parallel rectangular conjunctions subjected to a magnetic field

The paper presents analytical solution of squeeze film characteristics in wide parallel rectangular conjunctions with incompressible electrically conducting couple stress fluids subjected to a magnetic field. Analytical expressions are obtained by combined solution of modified Reynolds equation and Stokes micro-continuum for couple stress fluids with averaged inertia. Various cases of magneto-hydrodynamic, conducting and non-conducting fluid characteristics with and without convective inertial contributions are investigated. It is shown that, in general, couple stress fluids enhance the load carrying capacity of the contact and inhibit the incidence of thin films which can result in direct contact of surfaces. Convective inertia also significantly improves the load carrying capacity. However, with impulsive loading the response time of couple stress fluids deteriorates relative to Newtonian lubricants on account of their increased viscosity. An important conclusion of the study is that magneto-hydrodynamic couple stress fluids are best suited to applications with high relatively steady load applications.

Development and comparison of two sampling methods to assess dermal exposure to drilling fluids and crude oil

Dermal exposure to drilling fluids and crude oil is an exposure route of concern although there have been no published studies describing sampling methods or reporting dermal exposure measurements. We describe a study that aimed to evaluate further a developed wipe sampling method for assessing dermal exposure to drilling fluid and crude oil, as well as to investigate the feasibility of using an interception cotton glove sampler for the hands/wrists. A direct comparison of the wipe and interception method was also completed using surrogate human skin and a direct surface contact exposure situation. The wipe and interception sampling methods were evaluated using an oil-based drilling fluid and crude oil. Overall, acceptable recovery and sampling efficiencies were reported for both methods and both were found to show satisfactory storage stability for 1 and 7 days, although there appeared to be some loss over 14 days. The results from the side-by-side direct surface contact experiments revealed that much higher recoveries of both fluids were measured on the glove samples than on wipe samples (on average 2.5 times higher). Both evaluated sampling methods were found to be suitable for use in assessing dermal exposure to oil based drilling fluids however the comparison study clearly illustrated that the interception technique over-estimated dermal exposure. Further comparison of the two dermal sampling methods using additional exposure situations such as immersion or deposition, as well as a field evaluation, is warranted to confirm their appropriateness and suitability to assess dermal exposure to drilling fluids and crude oil in the working environment. This information, with due consideration of the sampling strategies aims and objectives, will help facilitate dermal sampler selection.

Imaging of the Acetabular Labrum

The evaluation and proposed relevance of acetabular labral tears has rapidly evolved over the last decade due to the recognition of femoroacetabular impingement, an increase in the number of surgical options, and improved imaging of the hip with MR arthrography and 3-T MR protocols. The acetabular labrum, stabilizing the hip joint, provides a seal, enhancing fluid lubrication, maintains synovial pressure, and prevents direct contact of the articular surfaces. The labrum takes on a weightbearing role at the extremes of motion with excessive forces seen in a great number of athletic activities thought to contribute to tearing. Approximately 25% of labral tears are not associated with any specific injury or traumatic event with the underlying etiology thought to be repetitive microtrauma. This article reviews the anatomy of the acetabular labrum and discusses the five most commonly occurring etiologies of labral tears: trauma, femoroacetabular impingement, hip hypermobility, dysplasia, and degeneration. We also review the surgical and MR classification of labral tears and describe potential pitfalls in image interpretation.

Prediction of wind turbine gear micropitting under variable load and speed conditions using ISO/TR 15144-1: 2010

Wind turbine gearbox operates under a wide array of highly fluctuating and dynamic load conditions caused by the stochastic nature of wind and operational wind turbine controls. Micropitting damage is one of failure modes commonly observed in wind turbine gearboxes. This article investigates gear micropitting of high-speed stage gears of a wind turbine gearbox operating under nominal and varying load and speed conditions. Based on the ISO standard of gear micropitting (ISO/TR 15144-1:2010) and considering the operating load and speed conditions, a theoretical study is carried out to assess the risk of gear micropitting by determining the contact stress, sliding parameter, local contact temperature and lubricant film thickness along the line of action of gear tooth contact. The non-uniform distributions of temperature and lubricant film thickness over the tooth flank are observed due to the conditions of torque and rotational speed variations and sliding contact along the gear tooth flanks. The lubricant film thickness varies along the tooth flank and is at the lowest when the tip of the driving gear engages with the root of the driven gear. The lubricant film thickness increases with the increase of rotational speed and decreases as torque and sliding increase. It can be concluded that micropitting is most likely to initiate at the addendum of driving gear and the dedendum of driven gear. The lowest film thickness occurs when the torque is high and the rotational speed is at the lowest which may cause direct tooth surface contact. At the low-torque condition, the varying rotational speed condition may cause a considerable variation of lubricant film thickness thus interrupting the lubrication which may result in micropitting.

Improved survival following cerebral edema using a novel hollow fiber-hydrogel device

Cerebral edema is a significant cause of morbidity and mortality in many disease states. Current therapies of cerebral edema are often ineffective in treating severe edema. Here, the authors develop a hollow fiber-hydrogel device (HFHD) for direct surface contact-based treatment of severe cerebral edema. Brain edema was induced in adult mice via water intoxication by intraperitoneal water administration (30% body weight). Control mice received no treatment. A distinct group of mice was treated with craniectomy but no device application (craniectomy only). A third experimental group was treated with craniectomy and HFHD application. The HFHD contained a lumen solution of 350 g/L bovine serum albumin in room-temperature artificial CSF at pH 7.4. Survival and brain water content were assessed as end points. Craniectomy and application of the HFHD enhanced survival in animals with severe cerebral edema. Animals treated with a craniectomy and HFHD (n = 5) survived up to 5 hours longer than animals treated with craniectomy only (n = 5) (p < 0.001) or no treatment (n = 5) (p < 0.001). Animals treated with craniectomy and HFHD (n = 5) had a survival rate of 80% within the observation period (360 minutes), whereas no animal treated with craniectomy only (n = 5) or no treatment (n = 5) survived longer than 50 and 33 minutes, respectively. Statistical significance was observed for the survival rate between the animals treated with a craniectomy + HFHD (n = 5) versus those treated with craniectomy only (n = 5) (p < 0.001), and craniectomy + HFHD versus no treatment (n = 5) (p < 0.001). Histological analysis demonstrated no significant cell loss in the cortex subjacent to HFHD application. Here, the authors demonstrate the feasibility of their HFHD to treat cerebral edema in this model. These results indicate that controlled water extraction from edematous brain tissue can be performed and can lead to increased survival compared with craniectomy only. Further studies remain to be performed to further optimize the HFHD and to test it in more clinically relevant models, such as traumatic brain injury.

In VitroAntimicrobial Effect of a Cold Plasma Jet againstEnterococcus faecalisBiofilms

The hypothesis that a cold plasma jet has the antimicrobial effect against Enterococcus faecalis biofilms was tested in vitro. 27 hydroxyapatite discs were incubated with E. faecalis for six days to form a monoculture biofilm on the disc surface. The prepared substrata were divided into three groups: the negative control, the positive control (5.25% NaOCl solution), and the plasma treatment group. Resultant colony-forming unit counts were associated with observations of bacterial cell morphology changes using scanning electron microscopy (SEM). Treatment of E. faecalis biofilm with the plasma and 5.25% NaOCl for 5 min resulted in 93.1% and 90.0% kill (P < 0.0001), respectively. SEM detected that nearly no intact bacteria were discernible for the plasma-exposed HA disc surfaces. The demonstrated bactericidal effect of the plasma with direct surface contact may be due to the enhanced oxidation by the locally produced reactive plasma species.

A micromechanism study of thermosonic gold wire bonding on aluminum pad

A micromechanism of thermosonic gold wire bonding was elaborated by examining its interfacial characteristics as a result of the bonding process, including the fragmentation of the native aluminum oxide layer on Al pads, and formation of initial intermetallic compounds (IMCs). It is found that the existence of an approximately 5 nm thick native oxide layer on original Al pads has a significant effect on the bonding, and the nucleation of IMCs during the bonding process must overcome this relatively inert thin film. Bonding strength was fundamentally determined by the degree of fragmentation of the oxide films, through which the formation of IMCs can be initiated due to the direct contact of the metal surfaces to be bonded. The extent of fracture the oxide layer was strongly influenced by the level of ultrasonic power, as at its high level alumina fragmentation becomes pervasive resulting in contiguous alloy interfaces and robust bonds. The IMCs formed at the interfaces were identified as Al4Al and AuAl2 with a thickness of 150–300 nm. The formation mechanism of such IMCs was explained by the effective heat of formation theory.

Identification of Up-regulated Genes of Bacillus amyloliquefaciens B55 During the Early Stage of Direct Surface Contact with Rice R109 Root

The early stage of plant-rhizobacteria interaction, affected by plant root exudates and plant-rhizobacteria surface contact, is considered to be critical for plant growth-promoting rhizobacteria colonizing plant roots and initiating the beneficial effects on plant growth. However, little is known about the mechanisms of plant-rhizobacteria surface contact involved in early stage of plant-rhizobacteria interaction. In order to reveal the molecular mechanisms of the surface contact, a rhizobacterium Bacillus amyloliquefaciens B55 was interacted with plant roots of rice R109 and used to perform a cDNA-based suppression-subtractive hybridization. Seven differentially expressed DNA fragments were identified. Except for the two fragments showing no matches to any known sequences in the Genbank, the other five fragments were found to have high homologies with the genes encoding 2-oxoglutarate dehydrogenase E1 component OdhA, aspartate ammonia-lyase AnsB, and hypothetical protein proposed to be involved in surface adhesion, acetolactate decarboxylase AlsD, and DNA mismatch repair protein MutL, respectively. The induced RNA expression levels of two putative genes ansB and odhA and an unmatched DNA fragment BD33 were verified by RT-PCR analysis.

Effect of relative humidity and disk acceleration on tribocharge build-up at a slider–disk interface

High performance disk drives require high spindle speed. The spindle speed of typical hard disk drives has increased in recent years from 5400 to 15000 rpm and even higher speeds are anticipated in the near future. The increasing disk velocity leads to increasing disk acceleration and slider–disk interaction. As the head-to-disk spacing continues to decrease to facilitate increasing recording densities in disk drives, the slider–disk interaction has become much more severe due to the direct contact of head and disk surfaces in both start/stop and flying cases. The slider–disk interaction in contact-start-stop (CSS) mode is an important source of particle generation and tribocharge. Charge build-up in the slider–disk interface can cause electrostatic discharge (ESD) damage and lubricant decomposition. In turn, ESD can cause severe melting damage to MR or GMR heads. We measured the tribocurrent/voltage build-up generated at increasing disk acceleration. In addition, we examined the effects of relative humidity on the tribocharge build-up. We found that the tribocurrent/voltage was generated during pico-slider/disk interaction and that its level was below 250 pA and 0.5 V, respectively. Tribocurrent/voltage build-up was reduced with increasing disk acceleration. Higher humidity conditions (75–80%) yielded lower levels of tribovoltage/current. Therefore, a higher tribocharge is expected at a lower disk acceleration and lower relative humidity condition.

A novel antibacterial titania coating: Metal ion toxicity and in vitro surface colonization

Postoperative implant-associated infection is still an unresolved and serious complication in modern surgery. Antibacterial and biocompatible surfaces could both reduce infection rates and promote tissue integration. In this respect, a comparative study of the antibacterial as well as the biocompatible potential of different metal ions in vitro is presented. The assays used were growth inhibition tests with different metal salts carried out with tissue cells and bacteria under corresponding culture conditions. Additionally, in vitro tests in direct surface contact with tissue cells and bacteria onto a novel copper containing sol-gel derived titanium dioxide coating (Cu-TiO2) and a fourfold Cu-TiO2 coating were performed. The values were compared to a non-filled titanium dioxide coating and standard Ti6Al4V alloy. SEM-investigations were performed to approve the results of the in vitro tests. Among Ag+, Zn2+, Co2+, Al3+ and Hg2+, the growth inhibition tests revealed an outstanding position of copper ions as antibacterial but nevertheless bio-tolerant additive. These results were affirmed by the cell tests in direct surface contact and SEM-investigations, where best cell growth was found on the Cu-TiO2 coatings. Highest antibacterial properties with a tolerable cytocompatibility could be observed on the fourfold Cu-TiO2 coatings. Consequently, surfaces with custom-tailored antibacterial properties may be established and could be of particular interest in revision and tumor arthroplasty.

Classification of dermal exposure modifiers and assignment of values for a risk assessment toolkit.

This paper describes how default dermal exposure values can be adjusted with modifier values for specific work situations. The work presented here is supplementary to a toolkit developed for the EU RISKOFDERM project. This toolkit is intended for the assessment and management of dermal risks in small and medium sized enterprises. Potential dermal exposure (on the outer envelope of the body) is estimated with an algorithm whereby modifier values are applied multiplicatively to dermal default exposure values. These exposure modifiers with their assigned factors are intended to increase or decrease the potential (default) dermal exposure accordingly. Default estimates are modified to obtain two modified defaults: potential exposure rate to the hands and to the body. Quantitative exposure data is at present inadequate and insufficient to derive meaningful information that can be used for the selection of independent modifiers and the assignment of appropriate values. Instead, available information from the literature was considered and, in combination with expert judgement, 15 potential dermal modifiers were selected. Modifiers were classified and grouped into non-overlapping groups in order to avoid double scoring. Values were assigned to modifiers in three different exposure routes, i.e. direct contact, surface contact and deposition. Depending on the significance of a modifier, the values assigned to modifiers were weighted in equal steps on a log-scale. The values assigned to modifiers as presented in this paper are open to validation and revision once new data become available.

Index of Suspicion

Index of Suspicion

Direct Surface Force and Contact Angle Measurements of an Adsorbed Polymer with a Lower Critical Solution Temperature

As an example of a polymer with a lower critical solution temperature, TLC, in water, we studied the phase behavior of a poly(N-isopropylacrylamide) copolymer. To adsorb it to a negatively charged surface, we introduced a positively charged comonomer. The combination of direct force measurements with the surface forces apparatus (SFA) and contact angle measurements reveal a lower TLC of the adsorbed layer than in bulk solution. At and above TLC the adsorbed polymer chains collapse and the adsorbed layers on the two opposing surfaces attract each other. The resulting adhesion is strongly dependent on the applied speed of separation, emphasizing the role of slow molecular relaxations and rearrangements above TLC. The results also point to the validity of the time−temperature superposition principle to this polymer system at T > TLC: at a low speed of separation the polymer layer is “liquid-like”, and at high speeds its behavior is more “solid-like”.

Macrophage-like-cell-induced growth regulation of lymphoma cells.

Since hematopoietic stromal cells play a major role in regulating the growth and differentiation of hematopoietic cells, we have studied the effects of stromal cells on the in vitro growth of highly malignant murine RAW117-H10 lymphoma cells. These cells, when grown on a preformed layer of syngeneic Balb/c macrophage/monocyte cell line, J774A.1, stop proliferating 48 h after coculture. This stromal-cell-mediated growth regulation appears to require cell-to-cell contact between stromal cells and RAW117-H10 cells, since the J774A.1 cell supernatant did not significantly inhibit the in vitro growth of RAW117-H10 cells. Because one of the cytokines produced by the macrophages is tumor necrosis factor (TNF)-alpha, which is known to inhibit certain tumor cells, we also studied the effects of various concentrations of TNF-alpha on the in vitro growth of RAW117-H10 lymphoma cells. TNF-alpha did not significantly affect the growth of these cells in vitro. However, TNF-alpha induced significant morphologic changes in these cells similar to those seen in plasma cytoid differentiation. Thus, our results indicate that the macrophage-like stromal cells regulate the in vitro growth of malignant lymphoma cells, and that direct cell surface contact between stromal and lymphoma cells is necessary for the growth regulation, and the growth inhibition is not due to TNF-alpha secreted by the macrophages. TNF-alpha is associated with differentiation of these lymphoma cells.

Isolation and physiology of a manganese-reducing Bacillus polymyxa from an Oligocene silver-bearing ore and sediment with reference to Precambrian biogeochemistry

Abstract Samples from an Oligocene silver-bearing manganese ore mining site in Saguochi country, Colorado were screened for bacteria which solubilize manganese in the refractory ore thus making the silver more amenable to standard extraction techniques. Over 300 bacterial isolates were tested. Manganese reduction was detected by growing the organisms in a mineral salts medium supplemented with the insoluble MnO2 (pyrolusite). Reduction of the black MnO2 resulted in the formation of colorless solubilized Mn2+. One of the most efficient manganese reducers was a Bacillus polymyxa strain D1. This bacterium was isolated from the ore heap and from a zone 5 cm below the sediment surface of the inlet which drained ore heap leachate into a holding pond. Isolate D1 has a unique mode of manganese reduction as shown by the following combination of characteristics: (1) anaerobiosis is absolutely necessary; (2) direct surface contact with the mineral particle is required; (3) facultative fermentation occurs concomitantly with manganese reduction; and (4) Mn4+ does not substitute for O2 at the end of the respiratory electron transport chain. Although the ore deposit is approximately 35-30 Ma old, D1 probably have first appeared at the site contemporaneous with mining activities as evidenced by its resistance to exogenous zinc used in the silver extractive process. If organisms such as D1 were present > 600 Ma ago they could have played a role in the Precambrian manganese cycle as they do in the Holocene. Encrustations of MnO2 have been found in Precambrian sediments which are thought to be biogenic in origin. Solubilized reduced Mn2+ must also have been present to serve as a substrate. Anaerobic conditions alone are insufficient for the reduction of manganese dioxide, therefore, it is likely that manganese reduction was due, in part, to microbial activity. Solubilization of manganese occurs via microbial dissimilatory reduction as seen with isolate D1. Precipitation results from oxidation of manganese coupled to ATP synthesis as described by Ehrlich (1976, 1983).

Characteristics of Ni-Ti surface alloys formed by electrospark deposition

Electrospark deposition is a microwelding technique of overlaying a metallic substrate with a conducting electrode. The revolving electrode is in direct surface contact and is rapidly scanned over the substrate to cover the entire surface area. Using this surfacing process Ni-Ti alloys were formed on a Ti-6Al-4V substrate by using a pure nickel electrode. Continuous, crack-free surfaces metallurgically bonded to the substrate were formed. Unlike carbide coatings, this coating exhibited intermediate hardness; nevertheless, an enhancement of wear properties is expected in certain applications. Crossed-cylinder wear tests (ASTM G 83-83) did not confirm this expectation for a variety of reasons. Efforts to spall or delaminate the coating were unsuccessful. X-ray diffraction shows that the deposited coating surface and new surfaces obtained by sequential polishing of the coating are predominantly the disordered NiTi phase. Some claims have been made in the literature of amorphous or near-amorphous depositions by electrospark deposition. The presence of amorphous NiTi phase was not identified by the diffraction method.

Novel Techniques and Their Applications for Measuring Out-of-Plane Distortion of Welded Structures

Whether or not a certain-amount of planar distortion is critical, a point of consistency in the ship fabrication process is the need to accurately assess an existing degree of distortion in both local and global domains. At the Massachusetts Institute of Technology, three novel measurement devices have been developed as an adjunct to ongoing research. Distortion can now be evaluated either through laser interferometry, low-power laser beam triangulation, or direct surface contact. In addition to describing the operation and construction of the devices, this paper details their particular applications from a ship production/plate forming perspective.

Observation of Micro-Structure in Seized Portion and Mechanism of Seizure

A pin-on-disk and a rod-in-bush apparatus were used to investigate the seizure mechanism of sliding components. Sliding was conducted in a dry condition in room air until the sliding components seized. X-ray micro analysis was made in the vertical section of the seized elements after the sliding system was stopped by the seizure. It was found that very high friction leading to seizure is the result of bonding of the rubbing elements by the transfer particles generated through the mutual transfer and growth process of wear particles. The particles are large and flattened and they form adhesive links between the rubbing components. Experimental results indicated that the seizure is not inherent to direct contact of the mating surfaces but is a result of the formation process of wear particles.