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Notes: We report a theoretical investigation of dynamic conductance G(ω), for general ac frequency ω, of two-dimensional mesoscopic waveguides whose transport is characterized by antiresonances. We calculate G(ω) by numerically evaluating nonequilibrium Green's functions. By tuning the ac frequency we observe photon-assisted resonant transport as well as a gradual smearing out of the antiresonances. The antiresonance causes the dynamic response to vary between capacitive-like behavior to that of the inductive-like behavior. © 2001 American Institute of Physics.

Notes: The role of amorphous Ni50P50 as a precoating layer in CoCrPtTa/Cr/glass substrate thin film media has been studied. It was found that the amorphous NiP layer has a strong effect on grain size reduction. Both in-plane transmission electron spectroscopy (TEM) images and atomic force microscopy images reveal a large reduction of the average grain size of the Cr underlayer deposited on the precoating Ni50P50 layer compared to the one on a glass substrate. The TEM images also show that Ni50P50 film has isolated unique granular features approximately 10 nm in diameter, consisting of grains with uniform size that could be inherited by the subsequent layers. Samples with NiP precoating layer on the glass substrate show a slightly higher surface roughness that may be attributed to the smaller Co grains induced. Magnetic force microscopy images at remanent state also indicate a much smoother micromagnetic structure for media with a NiP precoating layer. © 2000 American Institute of Physics.

Notes: The effect of CoCrTa intermediate layer and postannealing on the magnetic properties and microstructure of CoCrPt/Cr thin film media has been investigated. Through a postdeposition annealing in a vacuum oven, a tremendous increase of coercivity up to 6000 Oe was observed for these CoCrPt/CoCrTa/Cr films, in which the thickness of CoCrTa intermediate layer is about 2.6 mm. X-ray diffraction results showed that the hexagonal-close-packed crystallographic structure for the cobalt alloy did not show any change for the sample after postannealing. In-plane transmission electron microscope images for the CoCrPt/CoCrTa/Cr films showed no change of the morphology before and after annealing and about 15% increase of the grain size for the films after annealing. Delta M curves and remanent squareness results showed that intergrain diffusion may result in this improvement of magnetic properties. Atomic force microscope images showed that the surface roughness for the sample after annealing was almost the same as that before annealing. After tailoring the thickness of the magnetic layer to 10 nm, the coercivity as high as 5200 Oe and Mrt value as low as 0.24 memu/cm2 were obtained, which may support ultrahigh bit density than current media. © 2000 American Institute of Physics.

Notes: A metal layered structure consisting of Cr/Cu buffer layer and two Co layers with different thickness, separated by a Cu spacer, was deposited on Si wafers using magnetron sputtering. The influence of the individual layer's thickness on the magneto transport and magnetic hysteresis was studied. Optimization of the magnetoresistance performance was supported by the current in-plane giant magnetoresistance (GMR) modeling based on the solution to the Boltzmann transport equation. The best structures demonstrated very sharp magnetization reversal of the lower Co layer at about 100 Oe accompanied by resistivity change with a rate of 0.9%/Oe. Maximum GMR effect measured at 5 K was 9.6%. Samples with capping layers exhibited substantially smaller switching fields of the upper Co layer than the uncapped samples with a minute amount of CoO. © 2000 American Institute of Physics.

Notes: Magnetic properties and microstructure of granular CoCrPt–SiO2 thin films with Cr underlayers have been investigated for potential applications in magnetic recording media. The coercivities exceeding 2500 Oe have been obtained in the as-deposited films with SiO2 varied from 8 to 16 vol %. Remarkable improvement in magnetic properties was achieved by postdeposition annealing in vacuum. The ultrahigh coercivity up to 5640 Oe was obtained in the lower SiO2 content film (CoCrPt)96(SiO2)4 which was annealed at 580 °C for 10 min. The annealing did not induce significant grain growth. The average grain size varied from 10 to 20 nm, depending on SiO2 concentration. Grain isolation in magnetic layer was achieved by the segregated SiO2 and further enhanced by annealing. The ac demagnetized magnetic clusters, observed by magnetic force microscopy, became very fine after annealing. The peak value of delta M curves changed from positive to negative value, indicating a great reduction of intergrain magnetic exchange coupling after annealing. © 2000 American Institute of Physics.

Notes: Magnetic and structural properties of hexagonal-close-packed-(CoCrPt)100−xCx thin films for potential applications in magnetic recording media have been investigated. CrTi and Cr underlayers were used to improve the in-plane preferred orientation. High coercivity of 4.4 kOe and anisotropy of 3.6×106 erg/cm3 have been achieved in films with a CrTi underlayer after postdeposition annealing. The addition of Ti to the Cr underlayer results in lower annealing temperature and shorter annealing time, while retaining higher coercivity. Vibrating sample magnetometer measurements showed that the magnetic moment lies fairly well in the film plane under proper preparation conditions; while x-ray diffraction measurements showed that the CrTi underlayer promoted Co (10.0) in-plane preferred orientation. Grain isolation in the magnetic layer was improved by the segregated C and further enhanced by postdeposition annealing. The peak value of δM curves decreased upon annealing and changed to a negative value when higher annealing temperatures were applied, indicating that strong exchange coupling in as-deposited film decreased and changed to dipolar interaction dominance upon annealing. © 2000 American Institute of Physics.

Notes: Previous studies in a pig model of skin wound healing showed a coordinate expression of transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF), and exposure of porcine skin fibroblasts in vitro to recombinant human CTGF significantly up-regulated mRNA levels for a number of molecules. Therefore, based on recent reports that small interfering RNA (siRNA; double-stranded RNA) can effect silencing of the expression of gene(s), this approach has now been used with CTGF-specific siRNA to better understand the function of this growth factor in regulating matrix homeostasis and repair. Normal skin fibroblasts from Yorkshire pigs were treated with 0.1–0.8 µM CTGF siRNA, TGF-β, or TGF-β plus CTGF siRNA for 12–48 hours. Total RNA was isolated and quantified, and then mRNA levels for specific molecules were analyzed by reverse transcription-polymerase chain reaction. Protein levels for CTGF and HSP47 were assessed by Western-blot analysis. CTGF siRNA transfection led to significant decreases in mRNA and protein levels for CTGF in both a dose- and time-dependent manner. mRNA levels for types I and III procollagen, decorin, HSP47, tissue inhibitor of metalloproteinase -1, -2, -3, and basic fibroblast growth factor were also significantly and uniquely decreased following exposure of cells to CTGF siRNA. Addition of TGF-β to the cells led to increases in CTGF mRNA levels that were blocked by CTGF siRNA. CTGF siRNA exposure also significantly and selectively down-regulated TGF-β–mediated increases in mRNA levels for types I and III procollagen. The results indicate that CTGF can regulate extracellular matrix molecule, growth factor, and proteinase inhibitor gene expression, and that some of the TGF-β effects on skin fibroblasts are via a CTGF-dependent pathway. (WOUND REP REG 2004;12:–)

Notes: Connective tissue growth factor (CTGF) is a 38 Kda cysteine-rich, heparin-binding peptide that has been implicated in several normal and abnormal physiological processes. CTGF has been shown to be induced by transforming growth factor-β. Previous studies in our pig model of skin wound healing showed a coordinate expression of transforming growth factor-β and CTGF during the healing process. To better understand the function of CTGF during wound healing, normal porcine fibroblasts were isolated from skin samples from SPF Yorkshire pigs. At fourth passage the cells were cultured in Dulbecco's modified Eagle's medium supplemented with fetal calf serum and at 80% confluence the medium was replaced with supplemented serum-free medium. After a further 24 hours, cells were treated with 0, 10, 25, 50, 100, and 500 ng/ml of 38 Kda or 16–20 Kda (C-terminal truncated form) recombinant expressed human CTGF for 24 hours or treated with 100 ng/ml for 0, 12, 24, and 48 hours. Subsequently, CTGF effects on cell DNA synthesis and mRNA levels for a subset of relevant molecules were assessed. The results showed that in cells treated with 38 Kda rhCTGF, mRNA levels for types I and III collagen, fibromodulin, and basic fibroblast growth factor were significantly up-regulated, but mRNA levels for HSP47, decorin, biglycan, and versican were not significantly altered. mRNA levels for CTGF were also significantly increased, indicating autoregulation of expression. However, mRNA levels for transforming growth factor-β, inteleukins 1 and 6, tumor necrosis factor-α, and nerve growth factor did not change. Interestingly, mRNA levels for the tissue inhibitors of metalloproteinase-1, -2, -3 and -4 were observed to significantly increase, but in contrast, mRNA levels for matrix metalloproteinases-1, -2, -9 were not significantly altered by exposure of the cells to the 38 Kda form of CTGF. In addition, DNA synthesis was augmented in the presence of 38 Kda rhCTGF. However, the truncated 16–20 Kda form of rhCTGF appeared to have none of these effects on porcine fibroblasts. These results indicate that in order to induce changes in porcine fibroblasts a molecule with an intact C-terminal domain is required, and that CTGF regulates porcine fibroblast extracellular matrix molecule, growth factor, and proteinase inhibitor gene expression without apparently affecting matrix metalloproteinase mRNA levels. These findings suggest that CTGF contributes to the anabolic environment during skin wound healing via selective modulation of fibroblast proliferation and changes to gene expression. (WOUND REP REG 2003;11:220–229)

Notes: Heat shock protein (HSP) 47 is a major stress-inducible protein that is localized to the endoplasmic reticulum of avian and mammalian cells and is thought to act as a molecular chaperone specific for the processing of procollagen. However, limited information is available regarding the regulation of HSP47 during wound healing. Using a polymerase chain reaction strategy, screening of a cDNA library, and RACE-polymerase chain reaction approaches, the sequence of a full-length porcine HSP47 cDNA has been identified. The cDNA contained 2096 bp that encodes for an 18 amino acid signal peptide and a mature protein coding region consisting of 401 amino acid residues. It also included 108 bp of the 5′ noncoding region and a 731-bp 3′ noncoding region. The deduced amino acid is 83% identical to chicken, 87% identical to mouse, 88% identical to rat, and 91% identical to human HSP47. It also shares between 26% and 30% identity with different members of the serine protease inhibitor superfamily. The protein contains a RDEL endoplasmic reticulum retention signal, and two potential glycosylation sites. All of these features are characteristic of HSP47 in higher vertebrates. Heat shock treatment of porcine fibroblasts led to up-regulation of HSP47 at both the transcriptional and translational levels. HSP47 protein levels were also up-regulated during skin wound healing in a pig model. Moreover, a higher molecular weight complex at approximately 140 Kda containing HSP47 was detected at the stage of healing that was coincident with the maximal transcriptional expression of HSP47 during wound healing in this animal model. Further investigation of how HSP47 is regulated during normal and abnormal skin wound healing may lead to new therapeutic approaches to improve the healing process. (WOUND REP REG 2002;10:230–240)

Notes: In this article, we report the magnetic properties of surfactant coated γ-Fe2O3 nanoparticles which are pressed under different pressures. With increasing pressure, the sample volume decreases, density increases, and a 55% density change has been achieved. The blocking temperature is increased from 50 to 80 K. Analyzing the data of blocking temperature versus densities, which exhibits linear relationship, and comparing the magnetic properties, the increase in blocking temperature is understood in terms of increased magnetic interactions between neighboring nanoparticles, which is due to the reduced average interparticle distance by the applied pressure. © 2000 American Institute of Physics.