Mechanical Scratching Research Articles

Effects of indomethacin and dexamethasone on mechanical scratching‐induced cutaneous barrier disruption in mice

Effects of indomethacin and dexamethasone on recovery of cutaneous barrier disruption induced by mechanical scratching were examined. Cutaneous barrier was disrupted by scratching using a stainless-steel wire brush (mechanical scratching) and compared to cutaneous application of acetone/ether (1:1) mixture (AE) and tape-stripping. Increase of transepidermal water loss (TEWL), as an indicator of a broken skin barrier, and recovery period for mechanical scratching were higher and longer than those for AE treatment and tape-stripping and we also confirmed the severity of skin damage in a histological study. Topical application of moisturizers showed a temporal effect, rapidly decreased TEWL on mechanical scratching- or AE treatment-induced cutaneous barrier disruption, and gradually increased base levels from 4 to 12 h after treatment. Topical application of indomethacin or dexamethasone prolonged the recovery period for the cutaneous barrier, and concomitant use further worsened the status of the barrier. Additionally, we examined the effects of prostaglandins (PGs) and inflammatory cytokine on mechanical scratching-induced cutaneous barrier disruption pretreated with indomethacin and dexamethasone. As a results, PGD2 and interleukin (IL)-1beta significantly accelerated the recovery of cutaneous barrier disruption by mechanical scratching but such was not the case with PGE2, IL-1alpha, and tumor necrosis factor-alpha treatment. These results suggest that indomethacin and dexamethasone prolonged the recovery period caused by inhibition of PGD2 and IL-1beta. Mechanical scratching-induced cutaneous barrier disruption may be a useful method for evaluating means of recovery from skin damage.

Characterization of age-hardening behavior of eutectic region in squeeze-cast A356-T5 alloy using nanoindenter and atomic force microscope

The nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in squeeze-cast A356 alloy parts were investigated using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. In addition, the eutectic region showed lower pile-up and higher elastic recovery than the primary Al region. The aging responses of the eutectic regions in the squeeze-cast A356 alloys aged at 150 °C for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. As the aging time increased, acicular Si particles in the eutectic regions gradually came to a fine structure. Both Vickers hardness ( H V) and indentation ( H IT) test results showed almost the same trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

Bone Marrow Cell Differentiation Induced by Mechanically Damaged Osteocytes in 3D Gel-Embedded Culture

Osteocytes are suggested to have a crucial role in the initial resorptive phase of bone turnover after microdamage. To study the role of osteocytes in targeted remodeling, we developed an in vitro model, in which osteocytes can be locally damaged and their interactions with bone marrow cells studied. Our results show that the damaged osteocytes activate the osteoclast precursors by soluble factors and thus can control the initial phase of targeted remodeling. Microdamage in bone contributes to fractures and acts as a stimulus for bone remodeling. Besides the targeted remodeling, some remodeling may also be random to serve metabolic purposes. Osteocytes have been considered to provide a crucial role in the activation of osteoclastic bone resorption adjacent to the damaged site. This study was aimed to develop a relevant in vitro model of the targeted remodeling and to show that damaged osteocytes can induce the initial bone resorptive stage. We developed a new device, in which osteocyte-like cell line MLO-Y4 cells were 3D cultured, subjected to local scratching, and assayed for cell viability. NIH3T3-3 cells were used as a control. Bone marrow cells were cultured on the top of the mechanically damaged MLO-Y4 cells, and the formation of TRACP+ cells was assayed. Additionally, the conditioned medium from scratched cultures was added to bone marrow cultures, and the TRACP activity in cell lysates was quantified. The macrophage-colony stimulating factor (M-CSF) and RANKL secretion in the conditioned medium was assayed by ELISA. Scratching induced the death of MLO-Y4 cells. When bone marrow cells were cultured over the gel-embedded MLO-Y4 cells, the application of mechanical scratching induced TRACP+ cell differentiation on gel surface. The cells with TRACP+ could be observed in the very restricted region along the scratching path. Additionally, mechanically damaged osteocytes secreted M-CSF and RANKL, and the conditioned medium showed the potential to induce TRACP+ cells in bone marrow culture. These findings indicate that soluble factors secreted from damaged osteocytes can locally induce and activate the initial phase of osteoclastic cell formation. This study directly shows the association between the damaged osteocytes and the initiation of resorptive stage in bone remodeling.

Electroplating of mild steel by aluminium in a first generation ionic liquid: A green alternative to commercial Al-plating in organic solvents

In this paper we report on the electroplating of mild steel by aluminium in a first generation ionic liquid [EMIm]Cl/AlCl 3 (40/60 mol.-%). The study was performed by means of cyclic voltammetry and galvanostatic polarization complemented by SEM/EDAX and optical microscopy. The results show that the pretreatment of the substrates plays a key role in the coating adhesion. The aluminium coating made on a conventionally pretreated mild steel substrate is of high quality but it does not exhibit good adherence to the substrate. However, we have found that an in situ electrochemical etching of the substrate by anodic polarization prior to electrodeposition leads to well adherent Al coatings of mild steel which resist even mechanical scratching. This is due to dissolution of the pre-formed iron oxide layer and the subsequent re-deposition of iron or Fe–Al alloy formation prior to Al bulk deposition resulting in excellent adhesion. It is also shown that with the electrochemical pretreatment in the ionic liquid not only steel sheets but also complex shapes like e.g. screws can be coated with well adherent aluminium.

Characterization of age-hardening behavior of eutectic surface on rheo-cast A356-T5 alloy by using nano/micro-indentation, scratching and atomic force microscopy

This study investigates the nano/microstructure, the aging response (in T5 heat treatment), and the mechanical/tribological properties of the eutectic regions in rheo-cast A356 alloy parts using nano/micro-indentation and mechanical scratching, combined with optical microscopy and atomic force microscope (AFM). Most eutectic Si crystals in the A356 alloy showed a modified morphology as fine-fibers. The loading curve for the eutectic region was more irregular than that of the primary Al region due to the presence of various particles of varying strength. The aging responses of the eutectic regions in the rheo-cast A356 alloys aged at 150 °C for different times (0, 2, 4, 8, 10, 16, 24, 36, and 72 h) were investigated. Both Vickers hardness and indentation test results showed a similar trend of aging curves, and the peak was obtained at the same aging time of 10 h. A remarkable size-dependence of the tests was found. The friction coefficient for the eutectic region was lower than that for the primary Al region.

Tumorigenesis of the Oral Mucosa and Skin in Athymic Nude Mice: DMBA, Trp-P-2 and ENU Applications

This investigation was carried out to study tumorigenesis in the tongue of athymic nude mice by painting with carcinogens such as DMBA, Trp-P-2 and ENU after mechanical scratching. Tumorigenesis in the skin of the same animals was also investigated by painting with the above-mentioned carcinogens. In athymic nude mice, severe dysplasia of the tongue was induced by a combination of mechanical trauma and applications of DMBA, and the expression pattern for PCNA indicated that dysplastic cells were more proliferative and of a higher malignant potential than those induced by applications of Trp-P-2 or ENU. Squamous cell carcinoma was produced in the skin of the same athymic nude mice by application of DMBA only, indicating that the skin of nude mice was more sensitive than the tongue to DMBA. Our results indicated that the mechanical trauma was very significant in producing oral epithelial dysplasia after application of carcinogens.

Increased scratching counts depend on a decrease in ability of cutaneous prostaglandin D2 biosynthesis in NC/Nga mice with atopic dermatitis

Spontaneous and 2,4,6-trinitrochlorobenzene (TNCB)-induced dermatitis models using NC/Nga mice have been recognized as animal models of atopic dermatitis. We reported that scratching behavior leads to dermatitis in a spontaneous dermatitis but not in a TNCB-induced dermatitis. Prostaglandin D2 (PGD2) suppressed the scratching behavior of NC/Nga mice, suggesting that PGD2 plays a physiological role on inhibiting pruritus. We studied whether there was a difference in skin PG contents between spontaneous and TNCB-induced dermatitis. Spontaneous dermatitis was induced by cohabitation with NC/Nga mice having severe skin lesions. TNCB-induced dermatitis was caused by applications of TNCB. PGD2, PGE2, 6keto-PGF1alpha, and PGF2alpha contents in the skin were examined using enzyme-immunoassay kits. For studying ability to produce skin PGs, PG contents were evaluated after topical treatment of arachidonic acid (AA) or mechanical scratching. In spontaneous dermatitis, PGE2, 6keto-PGF1alpha, and PGF2alpha contents increased with dermatitis, but only PGD2 did not do so. In TNCB-induced dermatitis, PGD2, PGE2, 6keto-PGF1alpha, and PGF2alpha increased. Determination of skin PG contents after AA treatment or mechanical scratching revealed that skin PGD2 production of conventional group of spontaneous dermatitis was lower than the specific pathogen-free group. It seemed that ability of skin PGD2 production was attenuated in spontaneous dermatitis. These results suggest that enhancement of scratching behavior in spontaneous dermatitis was caused by the defect of ability to produce PGD2, which plays a physiological role in inhibiting pruritus, resulting in development of dermatitis.

The effect of substrate surface roughness on the nucleation of cubic boron nitride films

Boron nitride (BN) films have been deposited on silicon (Si) substrates with a root-mean-square surface roughness between 0.2 and 170 nm using mass-selected ion beam deposition (MSIBD). Mechanical scratching by either diamond or alumina powders with different powder sizes was used for substrate pretreatment. The effect of substrate surface roughness on the subsequent growth of BN films at different ion energies (75–500 eV) was investigated by Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and transmission electron microscopy (TEM). For rough substrates the surface morphology of the BN films changes from a granular structure at low ion energies to a flat and featureless surface at 500 eV ion energy. In the latter case grooves and valleys are first filled up with amorphous BN before turbostratic BN (t-BN) is formed. Eventually c-BN nucleates on the t-BN interfacial layer. The c-BN nucleation threshold energy of about 125 eV remains unchanged. Surface-like growth processes dominate at low ion energy, leading to the granular morphology. The observations are explained by ion impact on inclined micro-surfaces, leading to reduced projected ion ranges and enhanced sputtering and re-deposition into surface grooves and valleys.

Patterned growth of carbon nanotubes on Si substrates without predeposition of metal catalysts

Aligned carbon nanotubes (CNTs) can be readily synthesized on quartz or silicon-oxide-coated Si substrates using a chemical vapor deposition method, but it is difficult to grow them on pure Si substrates without predeposition of metal catalysts. We report that aligned CNTs were grown by pyrolysis of iron phthalocyanine at 1000°C on the templates created on Si substrates with simple mechanical scratching. Scanning electron microscopy and x-ray energy spectroscopy analysis revealed that the trenches and patterns created on the surface of Si substrates were preferred nucleation sites for nanotube growth due to a high surface energy, metastable surface structure, and possible capillarity effect. A two-step pyrolysis process maintained Fe as an active catalyst.

Prostaglandin D 2 and prostaglandin E 2 accelerate the recovery of cutaneous barrier disruption induced by mechanical scratching in mice

The role of prostaglandins in mechanical scratching-induced cutaneous barrier disruption in mice was investigated. Skin prostaglandins contents were measured after cutaneous barrier function was disrupted by scratching using a stainless-steal wire brush (mechanical scratching), then effects of prostanoids on recovery of cutaneous barrier functions were examined. This mechanical scratching increased transepidermal water loss and skin prostaglandins (prostaglandin D 2, prostaglandin E 2, 6-keto-prostaglandin F 1α and prostaglandin F 2α) contents, count-dependently. Topical application of indomethacin immediately after cutaneous barrier disruption delayed the recovery period of cutaneous barrier disruption. We examined effects of several prostanoids (prostaglandin D 2, prostaglandin E 2, prostaglandin F 2α, prostaglandin I 2 and U46619) on delay of the recovery process of mechanical scratching-induced cutaneous barrier disruption with treatment of indomethacin. Topically applied prostaglandin D 2 and prostaglandin E 2 accelerated the recovery of cutaneous barrier disruption and topical application of prostaglandin J 2, limaprost, sulprostone and ONO-4819, but not 13,14-dihydro-15-keto-prostaglandin D 2, 15-deoxy-Δ 12,14-prostaglandin J 2, 17-phenyl-trinor-prostaglandin E 2 or butaprost had effects on recovery of the cutaneous barrier. These results suggest that prostaglandin D 2 and prostaglandin E 2 accelerate the recovery process of cutaneous barrier disruption caused by mechanical scratching, via specific prostanoid DP 1, EP 3 and EP 4 receptors.

Dynamic Behavior of Organic Thin Films Attached to Carbon Surfaces

The electrochemical reduction of 4-nitrobenzene diazonium salt has been investigated at carbon electrodes. Glassy carbon and pyrolyzed photoresist films were used as substrates to examine the attached nitrophenyl (NP) thin films using electrochemistry and atomic force microscopy (AFM). NP-films were treated to negative potential excursions in aqueous acidic conditions to electrochemically reduce the NP groups. The voltammetric responses of Fe(CN)_{6}^{3-} redox probe were recorded, and the film thicknesses monitored by an AFM mechanical scratching method that involves removing a section of the film with an AFM tip and measuring the depth profile of the trench created. A mechanism is proposed to account for the observed film changes. [DOI: 10.1380/ejssnt.2005.294]

Nontraditional manufacturing technique??Nano machining technique based on SPM

Nano machining based on SPM is a novel, nontraditional advanced manufacturing technique. There are three main machining methods based on SPM, i.e. single atom manipulation, surface modification using physical or chemical actions and mechanical scratching. The current development of this technique is summarized. Based on the analysis of mechanical scratching mechanism, a 5 μm micro inflation hole is fabricated on the surface of inertial confinement fusion (ICF) target. The processing technique is optimized. The machining properties of brittle material, single crystal Ge, are investigated. A micro machining system combining SPM and a high accuracy stage is developed. Some 2D and 3D microstructures are fabricated using the system. This method has broad applications in the field of nano machining.

Effect of Surface Treatment on Interfacial Strength between Bamboo Fiber and PP Resin

The interfacial shear strength (IFSS) between a bamboo fiber bundle and maleic anhydride polypropylene (MAPP) was examined for various kinds of surface treatments in conjunction with ultrasonic washing. Bamboo fiber bundles were extracted from Chinese bamboo by either mechanical scratching or steam explosion. The effect of fiber bundle diameter on IFSS was measured by using the micro-droplet test. The test results showed that higher IFSS was observed for bundles having smaller diameter. Isocyanate silane treatment improved IFSS in the case of raw bamboo fibers while it was less effective to improve IFSS for steam exploded fibers. The highest tensile strength of bamboo fiber reinforced polypropylene was obtained when steam exploded bamboo fibers were used as the reinforcement.

Scanning tunneling microscope modifications of amorphous Ge–Sb–Te films

Surface modifications produced in Ge–Sb–Te films by a scanning tunneling microscope have been studied. Three kinds of modifications appear to depend upon the applied voltages to the tip. Positive tip voltages of about 2 V produce depressions accompanying peripheral mounds, which can be accounted for as mechanical scratching by the tip. When the humidity is higher than ∼50%, tip voltages between 5 and 10 V produce depressions with no peripheral mounds, and negative tip voltages of about −10 V produce expansions. These humidity-assisted depression and expansion are assumed to be caused by electrochemical etchings and anodic oxidation processes.

Shock–induced brittle failure of boron carbide

The mechanism for the failure of brittle materials during uniaxial compressive shockloading has been the subject of much discussion. In particular, the physical interpretation of the yield point, t...

Dependence of the longitudinal resistance on edge potential and electron density in quantum Hall systems

Differently prepared mesas of the same wafer yield different longitudinal resistances ρ xx (B) in the quantum Hall regime. The ratio of two neighboring spin-split maxima is constant for one sample, but varies from sample to sample. We assume an exponential law for the short-range elastic edge channel scattering rate 1/τ el n,n+1∝ exp(− const·γn 2 D l depl ) where γ is spin-dependent, l depl the depletion length and n 2 D the electron density. Different depletion lengths can explain the measurements mentioned above. Furthermore, experiments with in-plane gates defined with focussed ion beam writing or mechanical scratching verify this dependence. Measurements under illumination confirm the dependence on l depl and n 2 D .

Effect of Scratching on Galvanic Corrosion in Oil and Gas Environments

Galvanic corrosion behavior in stagnant oil and gas environments, when the metal specimens were mechanically scratched, was investigated by electrochemical methods using material combinations ranging from carbon steels to duplex stainless steels. Galvanic currents and coupled potentials increased rapidly upon mechanical scratching, immediately started to decrease, and finally returned to the values before scratching in sweet and sour environments. Therefore, an increase in the galvanic corrosion rate caused by scratching was negligibly small for the long term, and localized corrosion as a result of mechanical scratching did not occur in these stagnant solutions. The change in coupled potential immediately after scratching was small in sweet environments and large in sour environments. For rapidly forming corrosion films on less noble metals, the galvanic current after scratching decreased rapidly; however, for slowly forming corrosion films on less noble specimens, galvanic current after scratching decreased gradually.

Microscopic Stripe Formation and Adhesion Force Increase Introduced by Local Shear-Stress Deformation of Polypropylene Film

Localized shear deformation of biaxially oriented polypropylene (PP) film using a stylus force of 0.4 mN results in a reorientation of polymer strands in the shear-force direction, which appears as a striped region. This change in surface structure, which was observed by atomic force microscopy (AFM), resulted in an increase in the adhesion force as determined from the interaction between the AFM tip and the sample surface. This increase in adhesion force results from an increase in surface energy, which is thought to be caused by an increase in density and closer ordering of the polymer strands on the film surface. We demonstrate that the surface energy of PP film can be increased either by this mechanical scratching on the surface or by adding oxidation-induced chemical functional groups to the surface. The increase in surface energy from mechanical scratching of the PP surface is comparable to that introduced by surface oxidation of the unscratched PP surface after 1-min UV/ozone exposure.

Adherence experiments on cBN films

Boron nitride thin films were deposited by tuned substrate rf magnetron sputtering from an h-BN target. Pure Ar, 85% Ar + 15% N2 and Ar + 10% < H2 < 30% were used as processing gases. A threshold value of momentum per deposited atom was found, around 600 eV12amu12, to obtain films with a high content of the cubic phase (between 70 and 90%). By introducing H2 into the gas mixture, an attempt was made to improve stability of the films exposed to the air atmosphere, which was achieved at 18% H2 content. However, a decrease in cBN percentage, deduced from IR spectra, was observed. A 50% Ar + 50% N2 gas mixture was also used for “in situ” deposition of hBN coatings on cBN films. The resulting films exhibited longer lifetimes and different methods of delamination, observed by SEM, than films without hBN coatings. Besides these attempts, different substrates were tested. B-doped (100)-Si showed greater stability than P-doped (100)-Si, and a buffer layer of 40 A Ni improved the adherence of 18% H2 film. However, neither buffer layers consisting of diamond nor other Ni thickness, nor mechanical scratching of silicon with diamond and cBN powders, were successful. From XPS analysis, the B/N atomic ratio was estimated to be in the range of 1.05–1.10 for films obtained with 85% Ar + 15% N2 and 1.15–1.20 for films deposited in pure Ar and in an Ar + H2 atmosphere.

Cladding-surrounding interface insensitive long-periodgrating

A long period grating is presented, the resonant peak of which is not sensitive to the interface between the cladding and the surrounding media of a fibre. The spectral behaviour of the resonant peak is investigated using index matching oils and mechanical scratching on the cladding surface of the fibre.