Elevation of plasma levels of L-dopa in transdermal administration of L-dopa-butylester in rats

To increase delivery of L-dopa in its transdermal absorption, a new lipophilic derivative of L-dopa, L-dopa-butylester, was synthesized. An in-vitro study employing two-chamber diffusion cells, in which the excised rat abdominal skin was mounted, revealed that, in the presence of L-menthol and ethanol, L-dopa-butylester penetrated in its original form more effectively than L-dopa. L-Dopa-butylester sheets were made by immersing wiper sheets in methanol containing the compound, and then evaporating the methanol. An extraction study of the compound from the sheets revealed that its stability was maintained for at least 12 weeks. In an in-vivo cutaneous absorption study, an L-dopa-butylester sheet was attached to the shaved rat abdominal skin. A hydrogel containing L-menthol and ethanol was spread on vinyl tape, and this sheet was placed over it. In plasma, the L-dopa level rose linearly between 30 and 180 min after the cutaneous application; L-dopa-butylester was not detected. The L-dopa level was higher than that in which L-dopa was applied. These findings indicated that the lipophilic nature of L-dopa-butylester further increased its penetration through the skin, and that L-dopa-butylester that was taken up into the general circulation system was rapidly converted to L-dopa by hydrolysis in the body.     

Strain sensing in composites using aligned carbon nanotube sheets embedded in the interlaminar region

This paper introduces a novel technique for embedding aligned sheets of two millimeters long, interconnected CNTs into the interlaminar region of composite structures. The potential of these embedded CNT sheets to function as damage detecting and strain sensing elements was demonstrated via various mechanical tests that were accompanied by real time electrical resistance change data acquisition. The experimental results suggested that the CNT sheet sensitivity could be further enhanced by an oxygen plasma treatment and also by pre-straining the CNT sheets before embedding them. The samples containing two CNT sheets layers exhibited long term stability, sensitivity and repeatability which are vital features for health monitoring.     

Silver nanoparticles enhanced luminescence of terbium complex in solution for L-dopa determination

Luminescent properties of a terbium (Tb3+)-L-3, 4-dihydroxyphenylalanine (L-dopa) complex by binding to colloidal silver nanoparticles (Ag NPs) have been presented. Luminescence intensity of the L-dopa complex was dramatically enhanced about 6-7 times by introducing Ag NPs. The Ag NPs concentration on the luminescent intensity was regarded as a main factor that balancing between an enhancing and a quenching effect of the Ag NPs. It was observed that changing the concentration of L-dopa causes the change in luminescence intensity. Under the optimized condition, the luminescence intensity of the system was linearly related to the concentration of L-dopa. Based on this observation, L-dopa-Tb3+ complex containing Ag NPs has been applied for the determination of L-dopa in pharmaceutical formulation. Linear responses of luminescence intensity were observed in the concentration range of 0.25 to 1.5 nM (r = 0.9934) of L-dopa with limit of detection 0.042 nM. The performance of the system was tested using 1.0 x 10(-9) M of L-dopa, yielding a precision of 1.21% RSD for nine replicate measurements. The present method has been successfully applied to determine L-dopa in pharmaceutical samples.     

Preparation and properties of collagen/modified hyaluronic acid hydrogel for biomedical application

Hydrogels composed of collagen and hyaluronic acid are types of crosslinked water-swellable polymers and possess vast potential for applications in the medical industry. Collagen (Co) is the major structural protein of connective tissues such as skin, tendon and cartilage. Hyaluronic acid (HA) is a non-immunogenic, non-adhesive glycosaminoglycan that has a high water absorption property and plays significant roles in several cellular processes. The purpose of this study is to prepare a collagen (Co)-modified hyaluronic acid (MHA) hydrogel and investigate its potential utility for biomedical products such as wound dressing materials. Collagen (Co, type I) was obtained from pig skin and mucopolysaccharide-HA was modified by a poly (ethylene glycol) diglycidyl ether (PEGDGE) crosslinker. Thermal stability, swelling behavior, and mechanical strength of Co-MHA hydrogel according to different mass ratios of Co and MHA in hydrogel networks were investigated. The physical properties of the hydrogel were measured by SEM, Differential Scanning Calorimetry (DSC), Thermal Gravity Analysis (TGA), and a Universal Testing Machine (UTM). The cell viability of Co-MHA hydrogel was also evaluated using an in vitro MTT assay.     

Histopathological evaluation of caffeine-loaded solid lipid nanoparticles in efficient treatment of cellulite

Context: Cellulite refers to dimpled appearance of the skin, usually located in the thighs and buttocks regions of most adult women.

Objective: The aim of this study was to formulate topically used caffeine-loaded solid lipid nanoparticle (SLN) for the treatment of cellulite.

Methods: SLNs were prepared by hot homogenization technique using Precirol® as lipid phase. The physical characterization and stability studies of SLNs as well as in vitro skin permeation and histological studies in rat skin were conducted.

Results: The mean particle size, encapsulation efficiency and loading efficiency percentages for optimized SLN formulation were 94?nm, 86 and 28%, respectively. In vitro drug release demonstrated that caffeine-loaded SLN incorporated into carbopol made hydrogel (caffeine-SLN-hydrogel) exhibited a sustained drug release compared to the caffeine hydrogel over 24?h. Caffeine-loaded SLNs showed a good stability during 12 months of storage at room temperature. The DSC and XRD results showed that caffeine was dispersed in SLN in an amorphous state. In vitro permeation studies illustrated higher drug accumulation in the skin with caffeine-SLN-hydrogel compared to caffeine hydrogel. The flux value of caffeine through rat skin in caffeine-SLN-hydrogel was 3.3 times less than caffeine hydrogel, representing lower systemic absorption. In contrast with caffeine hydrogel, the histological studies showed the complete lysis of adipocytes by administration of caffeine-SLN-hydrogel in the deeper skin layers.

Conclusion: Results of this study indicated that SLNs are promising carrier for improvement of caffeine efficiency in the treatment of cellulite following topical application on the skin.     

Formability of continuous cast 5052 alloy thin sheets

The formability of continuous cast 5052 alloy thin sheets from two different process schedules was examined. One was prepared in the laboratory by cold-rolling from a continuous cast thick plate followed by annealing (lab-processed sheet), and the other was produced by a new process involving hot-rolling followed immediately by in-line annealing (in-line annealed sheet). Tensile test results indicate that all the lab-processed sheets exhibit evident yield behavior. Increasing rolling reduction results in an increase of strength and a decrease of ductility in the lab-processed sheets due to increasing contribution of centerline segregation of second-phase particles. Both the lab-processed sheets annealed at 400 °C for 90 min and the in-line annealed sheets exhibit tensile elongation of more than 20% and two-stage strain hardening behavior. Compared with the lab-processed sheets, the in-line annealed sheet annealed at 454 °C has higher values of UTS and elongation. Furthermore, forming limit curves were determined. It is found that the level of the forming limit curve of the lab-processed thin sheet is lower than that of conventionally produced 5052-O Al, but close to that of 6111-T4 Al sheet. Moreover, the in-line annealed sheets have higher limit strains than the lab-processed sheets. These results demonstrate that the in-line annealing process results in the production of continuous cast alloy sheet with improved formability.     

Few layers of graphene as transparent electrode from botanical derivative camphor

Here, we report synthesis of large area graphene sheets by control pyrolysis of solid botanical derivative camphor (C₁₀H₁₆O) and fabrication of transparent electrodes. Raman study shows highly ordered graphene sheet with minimum defects. Second order Raman spectrum shows that graphene layers are more than single layer and can be controlled with amount of camphor pyrolyzed. Transmission electron microscopic images show presence of 4 layers for thinner and 13 layers for thicker graphene sheets. Transferred graphene sheets on glass substrates show very good transparency in wide range of wavelength (0.3-2 μm). Electrical measurements of the graphene sheets show thickness dependent sheet resistance. A sheet resistance of 203 Ω/sq is obtained at a transmittance of 63.5% of the graphene sheet. The technique to fabricate few layer of graphene as transparent electrode from camphor is both viable and scalable for potential large area optoelectronic applications.     

Effects of stage, intercalant species and expansion technique on exfoliation of graphite intercalation compound into graphene sheets

Graphite is composed of a series of stacked parallel graphene layers bonded by weak van der Waals forces. Although the weak interactions that hold the graphene sheets together allow them to slide readily over each other, the numerous weak bonds make it difficult to separate the sheets. A graphene sheet is a two-dimensional platelet consisting of a few graphene layers with an overall thickness in nanometer scale. Graphene sheets can be obtained from intercalation and subsequent exfoliation of graphite. To realize the expansion and exfoliation behaviors of graphite, graphite intercalation compound (GIC) is produced using an electrochemical method and three important factors, namely stage structure of GIC, intercalant species and expansion techniques, are taken into account. Graphene sheets produced from a lower stage FeCl3-GIC display the best exfoliation behavior in terms of specific surface area, total pore volume and expansion volume. Microwave irradiation gives rise to a more explosive expansion than heating in a furnace.     

Fabrication of multilayered titanium aluminide sheets by self-propagating high-temperature synthesis reaction using hot rolling and heat treatment

This study is concerned with the fabrication of multilayered and bulk Ti aluminide sheets by self-propagating high-temperature synthesis (SHS) reaction using hot rolling and heat treatment. A multilayered Ti/Al sheet was prepared by stacking thin Ti and Al sheets alternatively. When this sheet was hot-rolled and heat-treated at 1000°C, a multilayered sheet composed of Ti₃Al and TiAl was made through the process of formation and growth of intermetallic phases at Ti/Al interfaces and porosity reduction. A bulk Ti aluminide sheet having a lamellar structure of TiAl and Ti₃Al was also fabricated successfully by heat treatment at 1400°C.     

Stress intensity factors for a crack in two intersecting uniformly stressed sheets

A model is considered for a crack growing simultaneously in the stiffener and the main sheet of a panel in which the stiffener is continuously attached. Stress intensity factors are determined for various ratios in the stiffnesses of the sheet and the stiffener. The panel is modelled with two uniformly stressed mutually perpendicular infinite sheets each containing a crack perpendicular to and bisected by the line of intersection of the sheets. Compatibility of displacements is maintained along the line of intersection of the sheets and the problem is reduced to the solution of a singular integral equation.     

Physically cross-linked polyvinyl alcohol for the topical delivery of fluconazole

The aim of this study was to develop fluconazole in an ultrapure polyvinyl alcohol (PVA) hydrogel able to deliver the drug in a sustained release pattern for local treatment of skin fungal infections. The topical fluconazole hydrogels were prepared using PVA hydrogels physically cross-linked by freeze-thaw technique. Polyethylene glycol (PEG) was added as a hydrophilic excipient as a release enhancer of fluconazole. The effects of PVA molecular weight, PEG molecular weight, and PEG concentration were studied using a 2 x 4 x 2 factorially designed experiment. The selected fluconazole hydrogel proved to be physically stable over a period of 6 months and to be effective in the topical treatment of cutaneous candidiasis. Therefore, it could be concluded that the formula composed of 10% PVA 205000 and 1.5% PEG 4000 and 2% fluconazole and prepared by three cycles of freezing, and thawing is very promising in the local treatment of skin fungal infection as an alternative to the systemic use of fluconazole.     

Co-firing of PZN-PZT/Ag multilayer actuator prepared by tape-casting method

A large-area multilayer ceramic actuator composed of piezoelectrically active Pb(Zn_1/3Nb_2/3)_0.2(Zr_1/2Ti_1/2)_0.8 (PZN-PZT) layers and silver metal layers was fabricated by the tape-casting method. Low-temperature sinterable PZN-PZT ceramics were used as piezoelectric layers, and silver paste containing PZN-PZT ceramic frits was used as conductive inner-electrode layers. PZN-PZT powder was prepared by conventional mechanical mixing of the raw powders in ethanol. The green sheet was fabricated using methyl ethyl ketone (MEK) as a solvent, polyvinyl butyral (PVB) as a binder, dibutyl phthalate (DBP) as a plasticizer, and KD-1 as a dispersant. Silver inner-electrode containing ceramic frits was pasted on the green-tape sheets and the sheets were stacked, warm-pressed, and sintered at 900 °C for 4 h after burn-out. The thickness of the piezoelectric and electrode layers was about 120 and 20 μm, respectively. The electrical properties and piezoelectric displacement of the actuator were characterized.     

Electrostatic deposition of graphene

Loose graphene sheets, one to a few atomic layers thick, are often observed on freshly cleaved HOPG surfaces. A straightforward technique using electrostatic attraction is demonstrated to transfer these graphene sheets to a selected substrate. Sheets from one to 22?layers thick have been transferred by this method. One sheet after initial deposition is measured by atomic force microscopy to be only an atomic layer thick (～0.35?nm). A few weeks later, this height is seen to increase to ～0.8?nm. Raman spectroscopy of a single layer sheet shows the emergence of an intense D band which dramatically decreases as the number of layers in the sheet increase. The intense D band in monolayer graphene is attributed to the graphene conforming to the roughness of the substrate. The disruption of the C-C bonds within the single graphene layer could also contribute to this intense D band as evidenced by the emergence of a new band at 1620?cm(-1).     

An analytical approach to determination of bending modulus of a multi-layered graphene sheet

In this paper, the bending modulus of a multi-layered graphene sheet is investigated using a geometrically based analytical approach. For this purpose, a bending potential energy is derived, based on the van der Waals interactions of atoms belonging to the two neighboring sheets of a double-layered graphene sheet. The inter-atomic spacing between the adjacent layers is determined along the line of action of the applied bending moments. The bending potential of the double-layered sheet is calculated by summing up the potentials at discrete hexagons over the length and width of the sheet. A multi-layered graphene sheet is considered as consisting of many stacking double-layers. It is observed that the bending modulus of a multi-layered graphene sheet does not depend on the length of the sheet and is a property for the multi-layered sheet.     

电弧放电法制备石墨烯及其在导电油墨中的应用

导电油墨是印刷电子技术中使用的关键电子材料, 而导电填料作为导电油墨的主要成分要求其化学性能稳定且电导率高。其中, 基于石墨烯的导电油墨因为其、透射电子显微镜、拉曼光谱等手段对制备的石墨烯进行了表征。结果表明: 直流电弧放电法制备的石墨烯为2~10层、尺寸在100~200 nm范围且纯度高、结晶性好。在此基础上, 研究了涂层厚度、热处理温度以及弯曲角度等对石墨烯导电油墨导电性能的影响。研究发现, 石墨烯导电油墨电阻率与涂层厚度、热处理温度成反比, 且随着厚度、温度的增加石墨烯导电油墨的电阻率逐渐降低。并且样品在柔性基底上经过不同角度的弯曲折叠后电阻率没有明显变化。当厚度为170 μm的样品经过360℃ (30 min) 热处理后, 石墨烯导电油墨的电阻率仅为0.003 Ω·cm。上述结果表明, 电弧法制备的石墨烯导电油墨有望成为未来印制电子领域的关键材料。     

Formulation and rheological evaluation of ethosome-loaded carbopol hydrogel for transdermal application

Objective: To select a suitable ethosome-loaded Carbopol hydrogel formulation, specifically tailored for transdermal application that exhibits (i) plastic flow with yield stress of approximately 50–80?Pa at low polymer concentration, (ii) relatively frequency independent elastic (G′) and viscous (G″) properties and (iii) thermal stability.

Methods: Carbopol (C71, C934, C941, C971 or C974) hydrogels were prepared by dispersing Carbopol in distilled water followed neutralization by sodium hydroxide. The effects of Carbopol grade, Carbopol concentration, ethosome addition and temperature on flow (yield stress and viscosity) and viscoelastic (G′ and G″) properties of Carbopol hydrogel were evaluated. Based on the aforementioned rheological properties evaluated, suitable ethosome-loaded Carbopol hydrogel was selected. In-vitro permeation studies of diclofenac using rat skin were further conducted on ethosome-loaded Carbopol hydrogel along with diclofenac-loaded ethosomal formulation as control.

Results: Based on preliminary screening, C934, C971 and C974 grades were selected and further evaluated for flow and viscoelastic properties. It was observed that ethosome-loaded C974 hydrogel at concentration of 0.50 and 0.75% w/w, respectively, demonstrated acceptable plastic flow with distinct yield stress and a frequency independent G′ and G″. Furthermore, the flow and viscoelastic properties were maintained at the 4, 25 and 32?°C. The results from in vitro skin permeation studies indicate that ethosome-loaded C974 hydrogel at 0.5% w/w polymer concentration exhibited similar skin permeation as that of ethosomal formulation.

Conclusion: The results indicate that suitable rheological properties of C974 could facilitate in achieving desired skin permeation of diclofenac while acting as an efficient carrier system for ethosomal vesicles.     

Dry forming of aluminum alloys – Wear mechanisms and influencing factors

Tribological contacts in sheet metal forming are accompanied by several wear phenomena. One of which is the transfer of material from the softer sheet material to the harder tool surface, namely adhesive wear. Forming of aluminum alloys makes high demands on forming processes. Aluminum alloys show a strong tendency of adhesion on common tool materials. Adhesions on tools reduce the surface quality, the dimensional accuracy of the parts and the process stability. In order to avoid adhesive wear during forming, nowadays a high amount of lubricant is applied to the aluminum sheets. Though economically and ecologically attractive, dry forming processes with aluminum sheets seem not to be possible. In order to develop advantageous tribological systems a comprehensive understanding of the acting mechanisms is necessary. This paper discusses the influence of the alloy composition and the influence of oxide layers on the adhesive wear in aluminum forming.     

Formation of {111} fibre texture in recrystallised aluminium sheet

Abstract

The deep drawability of commercial purity aluminium sheets is improved by introducing a (in fcc materials rather unusual) {111} fibre texture in the sheet surface layers. An additional step of warm rolling after the conventional hot and cold rolling leads to the formation of a pronounced shear texture in the sheet surface layers. During the final recrystallisation annealing, the desired {111} texture prevails at the expense of the other shear texture components. The present paper aims to clarify the mechanisms of the formation of {111}∥ND orientations during both warm rolling and recrystallisation. The effect of the {111} surface texture on the plastic anisotropy of the resulting sheets is discussed.     

Response of thin-skinned sandwich panels to contact loading with flat-ended cylindrical punches: Experiments,numerical simulations and neutron diffraction measurements

The response of aluminium foam-cored sandwich panels to localised contact loading was investigated experimentally and numerically using flat-ended cylindrical punch of four varying sizes. ALPORAS and ALULIGHT closed-cell foams of 15 mm thickness with 0.3 mm thick aluminium face sheets (of 236 MPa yield strength) were used to manufacture the sandwich panels. Face sheet fracturing at the perimeter of the indenter, in addition to foam cells collapse beneath the indenter and tearing of the cell walls at the perimeter of the indenter were the major failure mechanisms of the sandwich panels, irrespective of the strength and density of the underlying foam core. The authors employed a 3D model in ABAQUS/Explicit to evaluate the indentation event, the skin failure of the face sheets and carry out a sensitivity study of the panel's response. Using the foam model of Deshpande and Fleck combined with the forming limit diagram (FLD) of the aluminium face sheet, good quantitative and qualitative correlations between experiments and simulations were achieved. The higher plastic compliance of the ALPORAS led to increased bending of the sheet metal and delayed the onset of sheet necking and failure. ALULIGHT-cored panels exhibited higher load bearing and energy absorption capacity, compared with ALPORAS cores, due to their higher foam and cell densities and higher yield strength of the cell walls. Additionally, they exhibited greater propensity for strain hardening as evidenced by mechanical testing and the neutron diffraction measurements, which demonstrated the development of macroscopically measurable stresses at higher strains. At these conditions the ALULIGHT response upon compaction becomes akin to the response of bulk material with measurable elastic modulus and evident Poisson effect.     

Textures and Magnetic Properties of Grain Oriented ElectricalSteel Produced by Cross Shear Rolling

Commercial grain oriented electrical steels were made by cross shear rolling (CSR) with a chosen mismatch speed ratio 1.1. Original sheets of 0.75 mm thick, which had been produced by conventional cold rolling and intermediate annealing were rolled to thickness from 0.35 mm to 0.15 mm, and followed by industry annealing. The deformation texture and the magnetic properties were measured. Results indicate that: in the condition of the CSR, the deformation texture of rolled sheet is generally similar to that of conventional rolled sheet; for sheets with the thicknesses from 0.35 mm to 0.25 mm, favorable deformation textures, mainly consisting of {111} <112>, are also found at subsudece layers, which may help produce sharp Goss texture, and after the final annealing, the magnetic properties of sheets are not lower than that of conventional rolled sheets