Mathematical modeling of laser sublimation cutting

The mathematical modeling of the laser cutting of steel plates is considered here by implementing the model proposed by Niziev and Nesterov, as formulated in [1]. The 3D-cutting front is described, according to this model, by a highly nonlinear partial differential equation. A number of simplifying assumptions can be formulated, however, so that this complex equation can be handled more easily. This enables us to concentrate on the physics of the model, rather than having to struggle with its mathematical manipulations. This simple model confirms in a capturing way the conjecture originally launched in [1] that cutting speed can be increased with a factor of about 1.5 to 2 by switching over from circular to radial polarization. As a further consequence, the model predicts that a similar improvement is also found regarding the plate thickness at a constant cutting speed.     

Multiscale structure, interfacial cohesion, adsorbed layers, and thermodynamics in dense polymer-nanoparticle mixtures

We establish the existence and size of adsorbed polymer layers in miscible dense nanocomposites and their consequences on microstructure and the bulk modulus. Using contrast-matching small-angle neutron scattering to characterize all partial collective structure factors of polymers, particles, and their interface, we demonstrate qualitative failure of the random phase approximation, accuracy of the polymer reference site interaction model theory, ability to deduce the adsorbed polymer layer thickness, and high sensitivity of the nanocomposite bulk modulus to interfacial cohesion.     

Enhanced skin wound healing by a sustained release of growth factors contained in platelet-rich plasma

Platelet-rich plasma (PRP) contains growth factors that promote tissue regeneration. Previously, we showed that heparin-conjugated fibrin (HCF) exerts the sustained release of growth factors with affinity for heparin. Here, we hypothesize that treatment of skin wound with a mixture of PRP and HCF exerts sustained release of several growth factors contained in PRP and promotes skin wound healing. The release of fibroblast growth factor 2, platelet-derived growth factor-BB, and vascular endothelial growth factor contained in PRP from HCF was sustained for a longer period than those from PRP, calcium-activated PRP (C-PRP), or a mixture of fibrin and PRP (F-PRP). Treatment of full-thickness skin wounds in mice with HCF-PRP resulted in much faster wound closure as well as dermal and epidermal regeneration at day 12 compared to treatment with either C-PRP or F-PRP. Enhanced skin regeneration observed in HCF-PRP group may have been at least partially due to enhanced angiogenesis in the wound beds. Therefore, this method could be useful for skin wound treatment.     

Grape seed proanthocyanidin extract ameliorates monosodium iodoacetate-induced osteoarthritis

Osteoarthritis (OA) is an age-related joint disease that is characterized by degeneration of articular cartilage and chronic pain. Oxidative stress is considered one of the pathophysiological factors in the progression of OA. We investigated the effects of grape seed proanthocyanidin extract (GSPE), which is an antioxidant, on monosodium iodoacetate (MIA)-induced arthritis of the knee joint of rat, which is an animal model of human OA. GSPE (100 mg/kg or 300 mg/kg) or saline was given orally three times per week for 4 weeks after the MIA injection. Pain was measured using the paw withdrawal latency (PWL), the paw withdrawal threshold (PWT) and the hind limb weight bearing ability. Joint damage was assessed using histological and microscopic analysis and microcomputerized tomography. Matrix metalloproteinase-13 (MMP13) and nitrotyrosine were detected using immunohistochemistry. Administration of GSPE to the MIA-treated rats significantly increased the PWL and PWT and this resulted in recovery of hind paw weight distribution (P < 0.05). GSPE reduced the loss of chondrocytes and proteoglycan, the production of MMP13, nitrotyrosine and IL-1β and the formation of osteophytes, and it reduced the number of subchondral bone fractures in the MIA-treated rats. These results indicate that GSPE is antinociceptive and it is protective against joint damage in the MIA-treated rat model of OA. GSPE could open up novel avenues for the treatment of OA.     

Regulation of B cell activating factor (BAFF) receptor expression by NF-ΚB signaling in rheumatoid arthritis B cells

B cells play an important role in the pathogenesis of rheumatoid arthritis (RA). High levels of B cell activating factor (BAFF) are detected in autoimmune diseases. BAFF and BAFF receptor (BAFF-R) are expressed in B and T cells of RA synovium. The study was undertaken to identify the NF-ΚB signal pathway involved in the induction of BAFF-R in human B cells. Immunohistochemical staining of NF-ΚB p65, NF-ΚB p50, BAFF, and BAFF-R was performed on sections of synovium from severe and mild RA and osteoarthritis (OA) patients. Peripheral blood mononuclear cells (PBMCs) were isolated from control and RA patients and B cells were isolated from controls. BAFF-R was analyzed by flow cytometry, realtime PCR and confocal staining after treatment with NF-ΚB inhibitors. NF-ΚB p65, NF-ΚB p50, BAFF, and BAFF-R were highly expressed in severe RA synovium relative to mild RA synovium or OA synovium. BAFF-R expression was reduced by NF-ΚB inhibitors in PBMCs and B cells from normal controls. We also showed reduction in expression of BAFF-R via inhibition of the NF-ΚB pathway in PBMCs of RA patients. BAFF/BAFF-R signaling is an important mechanism of pathogenesis in RA and that BAFF-R reduction by NF-ΚB blocking therapy is another choice for controlling B cells in autoimmune diseases such as RA.     

Direct electrical junction formation of highly vertical aligned zinc oxide nanorods

A two dimensionally assembled monolayer of hexagonal convexo-convex β-cobalt hydroxide nanoplates as a self-disposable sacrificial epi-template leads to a highly vertical alignment of zinc oxide nanorods array having a good electrical contact with metal or semiconductor layer on a substrate in a hydrothermal process.     

Application of cyclic biamperometry to viability and cytotoxicity assessment in human corneal epithelial cells

The application of cyclic biamperometry to viability and cytotoxicity assessments of human corneal epithelial cells has been investigated. Electrochemical measurements have been compared in PBS containing 5.0 mM glucose and minimal essential growth medium. Three different lipophilic mediators including dichlorophenol indophenol, 2-methyl-1,4-naphthoquinone (also called menadione or vitamin K₃) and N,N,N′,N′-tetramethyl-p-phenylenediamine have been evaluated for shuttling electrons across the cell membrane to the external medium. Transfer of these electrons to ferricyanide in the extra cellular medium results in the accumulation of ferrocyanide. The amount of ferrocyanide is then determined using cyclic biamperometry and is related to the extent of cell metabolic activity and therefore cell viability. To illustrate cytotoxicity assessment of chemicals, hydrogen peroxide, benzalkonium chloride and sodium dodecyl sulfate have been chosen as sample toxins, the cytotoxicities of which have been evaluated and compared to values reported in the literature. Similar values have been reported using colorimetric assays; however, the simplicity of this electrochemical assay can, in principle, open the way to miniaturization onto lab-on-chip devices and its incorporation into tiered-testing approaches for cytotoxicity assessment.

An azo dye-coupled tripodal chromogenic sensor for cyanide

A tripodal receptor bearing phenol as a hydrogen bond donor site and azo dye as the signaling subunit was synthesized. The receptor had a high binding affinity for CN⁻ as signaled by the change in the color of a solution of sensor 4 upon addition of CN⁻. Using UV-Vis spectroscopy, the system can be used to quantify 0-19 × 10⁻⁵ mol L⁻¹ of CN⁻, and the sensor was found to successfully function in the presence of other anions.     

A DFT study on the reaction mechanism of the gold(I)-catalyzed cycloisomerization of alkynylhydroxyallylamides to 4-Oxa-6-azatricyclo[3.3.0.02,8]octane and 3-Acyl-4-alkenylpyrrolidine

In this study, we use density functional theory calculations to investigate the discrepancy between two experimental results of Au(I)-catalyzed cycloisomerization reactions of alkynylhydroxyallyl tosylamide under similar reaction conditions, with the only variations being reaction temperature and time. The experimental results reported by Yeh and Chung groups, respectively, showed that 3-acyl-4-alkenylpyrrolidines are produced dominantly at ambient temperature, while 4-aza-6-oxatricyclo[3.3.0.0^2,8]octanes are produced in higher yield at elevated temperature. Using (Z)-4-([3-phenylprop-2-yn-1-yl]amino)but-2-en-1-ol and [Au(PPh₃)]⁺ as the model starting material and active catalyst species, respectively, we identified two major pathways leading to 4-aza-6-oxatricyclo[3.3.0.0^2,8]octane (pathway I ) and 3-acyl-4-alkenylpyrrolidine (pathway II ). The overall free energy barrier (ΔG^‡_max) and the energetic span (ΔG^‡_span) of each pathway were 38.3 and 48.4 kcal/mol for pathway I and 29.0 and 37.1 kcal/mol for pathway II . Our analysis shows that the disparate outcomes observed in the experiments by two separate groups mainly originate in the reaction kinetics, with both the overall activation barrier and energetic span being the important factor.