Home About us Contact
|
Home About us Contact | ||
|
|
||
mW/cm2
Selected AbstractsCover Picture: Laser Phys.LASER PHYSICS LETTERS, Issue 9 2010Lett. The parametric light can be tuned if we move the periodically-poled MgO doped lithium niobate (PPMgOLN) and change the grating period. If the working temperature of the PPMgOLN is adjusted while the grating period changes, the signal wavelength could be tuned from 1.5 to 1.6 ,m, and the idler wavelength could be tuned from 3.2 to 3.6 ,m. The optical parametric oscillator (OPO) is working at the repetition frequency of 76.8 kHz and the pump peak power density is 60 MW/cm2, while the photograph of the OPO is in cover picture. (Cover picture: J. Liu, Q. Liu, et al., pp. 630,633, in this issue) (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Strong ultraviolet emission from non-polar AlGaN/GaN quantum wells grown over r -plane sapphire substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003W. H. Sun Abstract GaN and GaN/Al0.25Ga0.75N multiple quantum wells (MQWs) over c - and r -plane sapphire substrates have been grown by metal-organic chemical vapor deposition. A comparative study of photoluminescence (PL) in GaN epitaxial layers and AlGaN/GaN MQWs on these two types of substrates is reported. At low excitation levels, the measured room temperature PL signal in GaN layers grown over r -plane sapphire was more than order of magnitude lower than in GaN on c -plane substrates. In contrast, the emission intensity from AlGaN/GaN MQWs grown over r -plane substrates was almost 30 times stronger than in the structures grown over c -plane sapphire. Furthermore, with excitation power density up to 1 MW/cm2, the PL peak position for the non-polar MQWs kept completely stable whereas the one for the c -plane structures exhibited a blue shift as large as 250 meV. We attribute this large difference in the ultraviolet emission intensity to the suppression of a strong quantum Stark effect in the AlGaN/GaN MQWs on the r -plane sapphire. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Green monolithic II,VI vertical-cavity surface-emitting laser operating at room temperaturePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004C. Kruse Abstract The realization of a monolithic all II,VI-based vertical cavity surface emitting laser (VCSEL) for the green spectral region is reported. Optically pumped lasing operation was achieved up to room temperature using a planar VCSEL structure. Taking advantage of distributed Bragg-reflectors based on MgS/Zn(Cd)Se superlattices as the low-refractive index material and ZnS0.06Se0.94 layers as the high-index material with a refractive index contrast of ,n = 0.6, a quality factor exceeding Q = 2000 is reached by using only 18 Bragg periods for the bottom DBR and 15 Bragg periods for the top DBR. The threshold power density is 0.32 MW/cm2 at a temperature of 10 K (emission wavelength 498.5 nm) and 1.9 MW/cm2 at room temperature (emission wavelength 502.3 nm). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low on-resistance of GaN p-i-n vertical conducting diodes grown on 4H-SiC substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007Atsushi Nishikawa Abstract We investigated the resistance of conductive AlGaN buffer layers and the current-voltage characteristics of GaN p-i-n vertical conducting diodes on n -type 4H-SiC substrates grown by low-pressure metalorganic vapor-phase epitaxy. High Si doping of the AlGaN buffer layer at the AlGaN/SiC interface produces ohmic current-voltage characteristics in spite of the large band offset between AlGaN and 4H-SiC. Owing to the optimization of the AlGaN buffer layer, a low on-resistance (Ron) of 1.12 m, cm2 with high breakdown voltage (VB) of 300 V is obtained for a GaN p-i-n vertical conducting diode on a 4H-SiC substrate, leading to the figure of merit (VB2/Ron) of 80 MW/cm2, which is larger than that for the diode with the same structure on a 6H-SiC substrate (62 MW/cm2). This result indicates that 4H-SiC is preferable for fabricating GaN-based electronic devices with a low on-resistance and high breakdown voltage. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] E-beam pumped resonant periodic gain GaInP/AlGaInP VCSELPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2005V. Yu. Abstract 25-period Ga0.5In0.5P/(Al0.7Ga0.3)0.5In0.5P quantum well structure was grown by MOVPE on GaAs substrates misoriented by 100 from (001) to (111)A and fabricated into a microcavities with dielectric oxide mirrors. The structure period and mirror design were chosen to provide resonant periodic gain. A non-uniformity of 5% in the total structure thickness across the 2 inch wafer was used for studying laser characteristics depending on mismatching structure period from resonance condition. The laser wavelength, threshold and output power was found to depend critically on the alignment of QW period with both the cavity and the MQW gain spectrum. Lasing in the 625,650 nm spectral range with output power up to 9 W (0.45 MW/cm2) was achieved under scanning electron beam longitudinal pumping at room temperature. The minimum threshold current density for a 40 keV electron energy was 8 A/cm2 (0.32 MW/cm2). In order to control the lasing threshold to within 10 % of its minimum, the MQW period should be tuned to the optimum value with an accuracy of about 1 %. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cryolipolysis for Noninvasive Fat Cell Destruction: Initial Results from a Pig ModelDERMATOLOGIC SURGERY, Issue 10 2009BRIAN ZELICKSON MD BACKGROUND Liposuction is one of the most frequently performed cosmetic procedures in the United States, but its cost and downtime has led to the development of noninvasive approaches for adipose tissue reduction. OBJECTIVE To determine whether noninvasive controlled and selective destruction of fat cells (Cryolipolysis) can selectively damage subcutaneous fat without causing damage to the overlying skin or rise in lipid levels. METHODS Three Yucatan pigs underwent Cryolipolysis at 22 sites: 20 at cooling intensity factor (CIF) index 24.5 (,43.8 mW/cm2), one at CIF 24.9 (,44.7 mW/cm2), and one at CIF 25.4 (,45.6 mW/cm2). Treated areas were evaluated using photography, ultrasound, and gross and microscopic pathology. Lipids were at various times points. One additional pig underwent Cryolipolysis at various days before euthanasia. RESULTS The treatments resulted in a significant reduction in the superficial fat layer without damage to the overlying skin. An inflammatory response triggered by cold-induced apoptosis of adipocytes preceded the reduction in the fat layer. Evaluation of lipids over a 3-month period following treatment demonstrated that cholesterol and triglyceride values remained normal. CONCLUSIONS Cryolipolysis is worthy of further study because it has been shown to significantly decrease subcutaneous fat and change body contour without causing damage to the overlying skin and surrounding structures or deleterious changes in blood lipids. [source] The Synthesis of the Dimethyl Ester of Quino[4,4a,5,6- efg]-Annulated 7-Demethyl-8-deethylmesoporphyrin and Three of Its Isomers with Unprecedented peri -Condensed Quinoline Porphyrin Structures.EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2004Molecules with Outstanding Properties as Sensitizers for Photodynamic Therapy in the Far-Red Region of the Visible Spectrum Abstract The mesoporphyrin dimethyl ester nickel complex has been formylated via the Vilsmeier method. The four possible mono meso-formyl derivatives were isolated and characterized. Wadsworth,Emmons coupling with the anion of (diethylphosphono)acetonitrile converted these aldehydes into the four novel meso acrylonitriles. Brief treatment of these acrylonitrile systems in hot trichloroacetic acid resulted in the formation of four achiral porphyrin derivatives with unprecedented nickel complexes of quino-fused porphyrins. Subsequent removal of the nickel gave four quino-porphyrin free bases: quino[4,4a,5,6- efg]-annulated 7-demethyl-8-deethylmesoporphyrin dimethyl ester 6a, 2,-(methoxycarbonyl)quino[4,4a,5,6- jkl]-annulated 12-demethyl-13-de[2,-(methoxycarbonyl)ethyl]mesoporphyrin dimethyl ester 6b, 2,-(methoxycarbonyl)quino[4,4a,5,6- qrs]-annulated 18-demethyl-17-de(2,-methoxycarbonylethyl)mesoporphyrin dimethyl ester 6c and quino[4,5,6,7- abt]-annulated 2-demethyl-3-deethylmesoporphyrin dimethyl ester 6d. The structures of these systems were unambiguously determined via mass spectroscopy and a plethora of NMR techniques. In the same way, etioporphyrin and octaethylporphyrin were converted into the corresponding peri -condensed quinoporphyrins as products, which shows that the formation of novel pericondensed quino-porphyrins is a general reaction in the porphyrin series and will have a wide scope in this field. Also, a plausible reaction mechanism for the formation of the quinoporphyrin systems was derived. As a first test for the use of these systems as sensitizers in far-red phototherapy, the quantum yield of singlet oxygen generation by 6a in toluene was studied. This quantum yield is 0.77, which is even higher than the singlet oxygen generation by sensitized meso-tetraphenylporphyrin. Secondly, when Chinese Hamster ovary (CHO) cells were incubated in medium which contained up to 15 ,g/ml of 6a, the survival rate of the cells in the dark is complete within experimental error, showing that under these conditions, 6a is not toxic to CHO cells. When CHO cells incubated in medium containing 6a in concentrations of 1 ,g/ml and higher were treated with white light of intensity 30 mW/cm2 for 15 minutes, complete cell death was observed. Based on these facts, we expect that all four achiral systems will show very promising properties to form the basis of a photodynamic therapy in far-red light. The fact that these systems are achiral is an additional bonus for medical applications. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Photoswitchable Gas Permeation Membranes Based on Liquid CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Eric G, owacki Abstract We have fabricated switchable gas permeation membranes in which a photoswitchable low-molecular-weight liquid crystalline (LC) material acts as the active element. Liquid crystal mixtures are doped with mesogenic azo dyes and infused into commercially available track-etched membranes with regular cylindrical pores (0.40 to 10.0 ,m). Tunability of mass transfer can be achieved through a combination of (1) LC/mesogenic dye composition, (2) surface-induced alignment, and (3) reversible photoinduced LC-isotropic transitions. Photo-induced isothermal phase changes in the imbibed material afford large and fully reversible changes in the permeability of the membrane to nitrogen. Both the LC and photogenerated isotropic states demonstrate a linear permeability/pressure relationship, but they show significant differences in their permeability coefficients. Liquid crystal compositions can be chosen such that the LC phase is more permeable than the isotropic,or vice versa , and can be further tuned by surface alignment. Permeability switching response times are 5 s, with alternating UV and >420-nm radiation at an intensity of 2 mW/cm2 being sufficient for complete and reversible switching. Thermal and kinetic properties of the confined LC materials are evaluated and correlated with the observed permeation properties. We demonstrate for the first time reversible permeation control of a membrane with light irradiation. [source] Solid Composite Polymer Electrolytes with High Cation Transference NumberISRAEL JOURNAL OF CHEMISTRY, Issue 3-4 2008Hadar Mazor This work presents the electrochemical and structural study of the dual modified composite LiBOB-based polymer electrolyte. Modification has been carried out by calix[6]pyrrole (CP) anion trap and nanosize silica filler. The main advantage of the use of LiBOB salt is the high ionic conductivity at near-ambient temperatures and low solid-electrolyte interphase (SEI) resistance. The conductivity of LiBOB:PEO20:CP0.125 with SiO2 is slightly lower than 10,5 Scm,1 at 30 °C, a value higher by about two orders of magnitude than that of the semi-crystalline LiCF3SO3 (LiTf)-PEO system. At 75 to 90 °C the bulk ionic conductivity of modified LiBOB polymer electrolyte approaches 1 mScm,1. The transference number of dual-modified LiBOB-polymer electrolyte is about 0.8 at 75 °C. Cyclic voltammetry tests showed a wide electrochemical stability window of the composite polymer electrolyte. The peak power of Li/MoOxSy cell with the polymer electrolyte film containing CP and SiO2 reaches 2.2 mW/cm2 and 3.0 mW/cm2 at 90 and 110 °C, respectively. [source] Solubility, salivary sorption and degree of conversion of dimethacrylate-based polymeric matrixesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Luana Gonçalves Abstract This study investigated the relationship between the solubility, salivary sorption, and degree of conversion of dimethacrylate-based polymeric matrixes. Six polymeric matrixes produced by mixing bis-GMA, TEGDMA and UDMA dimethacrylate monomers were studied. Photoactivation was induced by camphoroquinone/ethyl N,N-dimethyl-4-aminobenzoate. The specimens were light-cured using an irradiance of 850 mW/cm2 for 20 s. The solubility and sorption (,g/mm3) were measured after immersion in artificial saliva (neutral pH) for 7 days. The degree of conversion (%) was obtained by using a FT-IR spectrometer equipped with an attenuated total reflectance crystal (ATR). The degree of conversion varied from 39.15 ± 6.30 to 65.57± 4.80, and was influenced by the viscosity of the monomers present in the polymeric matrixes. The solubility of polymeric matrixes varied between 13.64 ± 0.39 and 25.08 ± 0.83, and was strongly influenced by the degree of conversion (Pearson, r = ,0.9587, p < 0.01). No correlation was found between salivary sorption and the degree of conversion (p = 0.3918). Salivary sorption was only dependent on the chemical and physical structures of the monomers presented in the polymeric matrixes. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Low-intensity pulsed ultrasound (LIPUS) increases the articular cartilage type II collagen in a rat osteoarthritis modelJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2010Kiyohito Naito Abstract In this study, the effect of low-intensity pulsed ultrasound (LIPUS) on cartilage was evaluated in a rat osteoarthritis (OA) model using serum biomarkers such as CTX-II (type II collagen degradation) and CPII (type II collagen synthesis) as well as histological criteria (Mankin score and immunohistochemical type II collagen staining). OA was surgically induced in the knee joint of rats by anterior cruciate/medial collateral ligament transection and medial meniscus resection (ACLT,+,MMx). Animals were divided into three groups: sham-operated group (Sham), ACLT,+,MMx group without LIPUS (,LIPUS), and ACLT,+,MMx group with LIPUS (+LIPUS; 30 mW/cm2, 20 min/day for 28 days). CTX-II levels were elevated in both ,LIPUS and +LIPUS groups compared to that in the Sham group after the operation, but there was no significant difference between +LIPUS and ,LIPUS groups, suggesting that LIPUS does not affect the degradation of type II collagen in this model. In contrast, CPII was significantly increased in +LIPUS group compared to ,LIPUS and Sham. Moreover, histological damage on the cartilage (Mankin score) was ameliorated by LIPUS, and type II collagen was immunohistochemically increased by LIPUS in the cartilage of an OA model. Of interest, mRNA expression of type II collagen was enhanced by LIPUS in chondrocytes. Together these observations suggest that LIPUS is likely to increase the type II collagen synthesis in articular cartilage, possibly via the activation of chondrocytes and induction of type II collagen mRNA expression, thereby exhibiting chondroprotective action in a rat OA model. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:361,369, 2010 [source] Low intensity pulsed ultrasound accelerated bone remodeling during consolidation stage of distraction osteogenesisJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2006Chun Wai Chan Abstract Bone regeneration in distraction osteogenesis occurs under tensile stress with axial rhythmic distraction after osteotomy. In this study, we evaluated if the low intensity pulsed ultrasound (LIPUS) was also effective on enhancement of bone remodeling during consolidation stage of distraction osteogenesis. Open osteotomy of seventeen 18-week-old female New Zealand rabbit tibiae were performed. The distraction was applied with the rate of 1 mm per day. LIPUS (30 mW/cm2, 1.5 MHz) was delivered for 20 min per day during 4-week consolidation stage (n,=,10). The animals without treatment served as sham group (n,=,7). Plain X-ray, peripheral quantitative computational tomography (pQCT), and torsional test were performed. Results showed that smaller radiolucent interzone of LIPUS treatment group was gradually occupied by calcified tissue in plain X-ray at week 2. The bone mineral density (BMD) measured on radiographs increased by 9.18% in the LIPUS group. Bone mineral content (BMC), hard callus volume, and bone strength index (BSI) measured by pQCT were 83%, 116%, and 94%, respectively, in LIPUS group that were significantly greater than those of the controls. At the 4th week, LIPUS-treated callus showed the development of neocorticalization in the proximal and distal region. The BMC, hard callus volume, and BSI of LIPUS group decreased and was not significantly different from control. This was also confirmed by the maximum torque of LIPUS-treated callus (1424.2,±,457.3 N,·,mm) obtained at week 4, which did not differ from that of the sham group (1968.8,±,895.1 N,·,mm). In conclusion, the effective period of LIPUS treatment was at the initial stage of consolidation, with accelerated bone formation and remodeling. © 2005 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Lethal photosensitization of periodontal pathogens by a red-filtered Xenon lamp in vitroJOURNAL OF PERIODONTAL RESEARCH, Issue 4 2003Donco Matevski Background:, The ability of Helium,Neon (He,Ne) laser irradiation of a photosensitizer to induce localized phototoxic effects that kill periodontal pathogens is well documented and is termed photodynamic therapy (PDT). Objectives:, We investigated the potential of a conventional light source (red-filtered Xenon lamp) to activate toluidine blue O (TBO) in vitro and determined in vitro model parameters that may be used in future in vivo trials. Materials and methods:,Porphyromonas gingivalis 381 was used as the primary test bacterium. Results:, Treatment with a 2.2 J/cm2 light dose and 50 µg/ml TBO concentration resulted in a bacterial kill of 2.43 ± 0.39 logs with the He,Ne laser control and 3.34 ± 0.24 logs with the lamp, a near 10-fold increase (p = 0.028). Increases in light intensity produced significantly higher killing (p = 0.012) that plateaued at 25 mW/cm2. There was a linear relationship between light dose and bacterial killing (r2 = 0.916); as light dose was increased bacterial survival decreased. No such relationship was found for the drug concentrations tested. Addition of serum or blood at 50% v/v to the P. gingivalis suspension prior to irradiation diminished killing from approximately 5 logs to 3 logs at 10 J/cm2. When serum was washed off, killing returned to 5 logs for all species tested except Bacteroides forsythus (3.92 ± 0.68 logs kill). Conclusions:, The data indicate that PDT utilizing a conventional light source is at least as effective as laser-induced treatment in vitro. Furthermore, PDT achieves significant bactericidal activity in the presence of serum and blood when used with the set parameters of 10 J/cm2, 100 mW/cm2 and 12.5 µg/ml TBO. [source] Synthesis and applications of low-bandgap conjugated polymers containing phenothiazine donor and various benzodiazole acceptors for polymer solar cellsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Harihara Padhy Abstract A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (Mn) in the range of 3.85,5.13 × 104 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300,750 nm with optical bandgaps of 1.80,1.93 eV. Both the HOMO energy level (,5.38 to ,5.47 eV) and LUMO energy level (,3.47 to ,3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C61 -butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71 -butyric acid methyl ester (PC71BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC71BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (Voc) value of 0.75 V, a short-circuit current (Jsc) value of 4.60 mA/cm2, and a fill factor (FF) value of 35.0% were achieved. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Novel two-dimensional donor,acceptor conjugated polymers containing quinoxaline units: Synthesis, characterization, and photovoltaic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Lijun Huo Abstract Novel two-dimensional donor,acceptor (D,A) structured conjugated polymers, P1,P4, were designed and synthesized by introducing electron-deficient quinoxaline as core and electron-rich alkoxyl-phenylenevinylene in side chains and p -phenylenevinylene, triphenylamine, or thiophene in main chain. Benefited from the D,A structures, the polymers possess low bandgaps of 1.75 eV, 1.86 eV, 1.59 eV, and 1.58 eV for P1, P2, P3, and P4, respectively, and show broad absorption band in the visible region: the shorter wavelength absorption peak at ,400 nm ascribed to the conjugated side chains and the longer wavelength absorption peak between 500 nm and 750 nm belonging to the absorption of the conjugated main chains. Especially, the absorption band of P4 film covers the whole visible range from 300 nm to 784 nm. The power conversion efficiencies of the polymer solar cells based on P1,P4 as donor and PCBM as acceptor are 0.029%, 0.14%, 0.46%, and 0.57%, respectively, under the illumination of AM 1.5, 100 mW/cm2. The polymers with the low bandgap and broad absorption band are promising photovoltaic materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4038,4049, 2008 [source] Enhancement of photocurrent of polymer-gelled dye-sensitized solar cell by incorporation of exfoliated montmorillonite nanoplateletsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Chi-Wei Tu Abstract Poly(n -isopropylacrylamide) (PNIPAAm) and its nanocomposite with exfoliated montmorillonite (MMT) were prepared by soap-free emulsion polymerization and individually applied to gel the electrolyte systems for the dye-sensitized solar cells (DSSCs). Each exfoliated MMT nanoplatelet had a thickness of , 1 nm, carried , 1.8 cation/nm2, and acted like a two-dimensional electrolyte. The DSSC with the LiI/I2/tertiary butylpyridine electrolyte system gelled by this polymer nanocomposite had higher short-circuit current density (Jsc) compared to that gelled by the neat PNIPAAm. The former has a Jsc of 12.6 mA/cm2, an open circuit voltage (Voc) of 0.73 V, and a fill factor (FF) of 0.59, which harvested 5.4% electricity conversion efficiency (,) under AM 1.5 irradiation at 100 mW/cm2, whereas the latter has Jsc = 7.28 mA/cm2, Voc = 0.72 V, FF = 0.60, and , = 3.17%. IPCE of the nanocomposite-gelled DSSC were also improved. Electrochemical impedance spectroscopy of the DSSCs revealed that the nanocomposite-gelled electrolytes significantly decreased the impedances in three major electric current paths of DSSCs, that is, the resistance of electrolytes and electric contacts, impedance across the electrolytes/dye-coated TiO2 interface, and Nernstian diffusion within the electrolytes. The results were also consistent with the increased molar conductivity of nanocomposite-gelled electrolytes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 47,53, 2008 [source] UV-photodimerization in uracil-substituted dendrimers for high density data storageJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2007Brian Lohse Abstract Two series of uracil-functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2-bis(hydroxymethylpropionic acid) bis-MPA backbones were prepared and their photoinduced (2,+2,) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th generation were synthesized and investigated as potential materials for high capacity optical data storage with their dimerization efficiency compared to uracil as a reference compound. This allows the impact of increasing the generation number of the dendrimers, both the number of chromophores, as well as the different steric environments, on the performance of each series of dendrimers to be investigated. The (uracil)12 -[G-2]-bis-MPA and (uracil)8 -[G-1]-PAMAM were observed to have high dimerization efficiency in solution with different behavior being observed for the PAMAM and bis-MPA dendrimers. The dendrimers with the best dimerization efficiency in solution were then examined in the solid state as thin films cast on quartz plates, and their film qualities along with their photodimerization performance studied. High quality films with a transmission response of up to 70% in 55 s. when irradiated at 257 nm with an intensity of 70 mW/cm2 could be obtained suggesting future use as recording media for optical data storage. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4401,4412, 2007 [source] Effect of Light-Curing Method and Cement Activation Mode on Resin Cement Knoop HardnessJOURNAL OF PROSTHODONTICS, Issue 6 2007Rubens Nisie Tango Purpose: To evaluate the Knoop hardness (KHN) of the resin cement Enforce activated by chemical/physical mode or physical mode solely; light-cured directly or through a 1.5 mm thick ceramic disc (HeraCeram) on shade DD2. Materials and Methods: Light-curing was carried out using a conventional quartz tungsten halogen light (QTH) (XL2500) for 40 seconds at 700 mW/cm2; light-emitting diodes (LED) (Ultrablue Is) for 40 seconds at 440 mW/cm2; and Xenon plasma arc (PAC) (Apollo 95E) for 3 seconds at 1600 mW/cm2. Bovine incisors had their buccal faces flattened and hybridized. A mold was seated on these surfaces and filled with cement. A disc of the acid-etched and silanized veneering material was seated over this set for light-curing. After dry storage (24 hours at 37°C), specimens (n= 10) were sectioned for KHN measurements performed in a microhardness tester (50 gf load for 15 seconds). Data were submitted to ANOVA and Tukey's test (,= 0.05). Results: The highest KHN values were obtained with LED, for both dual-cured and light-cured cement. The lowest KHN value was obtained with light-cured PAC. Light-curing with QTH resulted in hardness values similar to PAC in dual-cured groups. Conclusions: Light-curing through HeraCeram can influence resin cement hardness. [source] Electrode Properties of the Ruddlesden,Popper Series, Lan+1NinO3n+1 (n=1, 2, and 3), as Intermediate-Temperature Solid Oxide Fuel CellsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010Suguru Takahashi The Ruddlesden,Popper phases, Lan+1NinO3n+1 (n=1, 2, and 3), were synthesized by a solid-state reaction for use as cathodes in an intermediate-temperature (500°,700°C) solid oxide fuel cell. The samples crystallized into an orthorhombic layered perovskite structure. The overall electrical conductivity increased with the increase of n in the intermediate temperature range. Single test-cells, which consisted of samarium-oxide-doped ceria (SDC; Sm0.2Ce0.8Ox) as an electrolyte, Ni,SDC cermet (Ni,SDC) as an anode, and Lan+1NinO3n+1 as a cathode, were fabricated for measurements of cell performance at 500°,700°C. Current interruption measurements revealed that both the ohmic and overpotential losses at 700°C decreased with the increase of n. La4Ni3O10 was found to exhibit the best cathode characteristics in the Lan+1NinO3n+1 series. Maximum test-cell power densities with La4Ni3O10 (n=3) were 10.2, 36.5, and 88.2 mW/cm2 at 500°, 600°, and 700°C, respectively. [source] Fabrication and Characterization of Anode-Supported Tubular Solid-Oxide Fuel Cells by Slip Casting and Dip Coating TechniquesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009Lan Zhang High-performance anode-supported tubular solid-oxide fuel cells (SOFCs) have been successfully developed and fabricated using slip casting, dip coating, and impregnation techniques. The effect of a dispersant and solid loading on the viscosity of the NiO/Y2O3,ZrO2 (NiO/YSZ) slurry is investigated in detail. The viscosity of the slurry was found to be minimum when the dispersant content was 0.6 wt% of NiO/YSZ. The effect of sintering temperature on the shrinkage and porosity of the anode tubes, densification of the electrolyte, and performance of the cell at different solid loadings is also investigated. A Ni/YSZ anode-supported tubular cell fabricated from the NiO/YSZ slurry with 65 wt% solid loading and sintered at 1380°C produced a peak power output of ,491 and ,376 mW/cm2 at 800°C in wet H2 and CH4, respectively. With the impregnation of Ce0.8Gd0.2O2 (GDC) nanoparticles, the peak power density increased to ,1104 and ,770 mW/cm2 at 800°C in wet H2 and CH4, respectively. GDC impregnation considerably enhances the electrochemical performance of the cell and significantly reduces the ohmic and polarization resistances of thin solid electrolyte cells. [source] Electrophoretic Deposition of YSZ Particles on Non-Conducting Porous NiO,YSZ Substrates for Solid Oxide Fuel Cell ApplicationsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2006Laxmidhar Besra This paper reports a method of performing electrophoretic deposition (EPD) on non-conducting substrates overcoming the requirement of a conducting substrate through the use of porous substrates. The conductivity of the substrate is therefore no longer a limiting factor in the application of EPD. This method is applicable to the fabrication of thick or thin layers of ceramic or metal for various applications. As an example, thin and dense yttria-stabilized zirconia (YSZ) layers have been deposited on a non-conducting NiO,YSZ substrate by EPD from a non-aqueous suspension. A solid oxide fuel cell constructed on these sintered bilayers exhibited power densities of 384 and 611 mW/cm2 at 750° and 850°C, respectively. [source] Photodynamic therapy with topical 5-aminolevulinic acid as a post-operative adjuvant therapy for an incompletely resected primary nasopharyngeal papillary adenocarcinoma: A case reportLASERS IN SURGERY AND MEDICINE, Issue 5 2006Cheng-Ping Wang MD Abstract Background and Objectives Surgical excision of primary nasopharyngeal papillary adenocarcinoma is sometimes incomplete with remaining microscopic disease. Post-operative radiotherapy only has limited efficacy but may cause many complications. Study Design/Materials and Methods Photodynamic therapy (PDT) was used as a post-operative adjuvant therapy for an incompletely resected primary nasopharyngeal papillary adenocarcinoma. A special form of 20% topical 5-aminolevulinic acid (5-ALA), which was originally a liquid form and became a gel form after applied on the nasopharynx, was used as the photosensitizer. A 2-mm optic fiber delivered the light (633 nm wavelength) to the lesion with a fluence rate of 100 mW/cm2 generated by a diode laser under 5 mm 0° endoscope assistance. The total energy delivered was 150 joules/cm2. Results No significant acute side effect was noted and the nasopharyngeal wound healed rapidly. The patient is alive without locoregional recurrence or distant metastasis for 5 years. Articulation, salivation, and swallowing functions are all well preserved. Conclusion Post-operative adjuvant PDT can successfully cure an otherwise difficult to treat disease with preservation of good life quality of the patient. Potential complications of PDT (e.g., photosensitivity) can be prevented by a special formulation of topical 5-ALA preparation. Lasers Surg. Med. © 2006 Wiley-Liss, Inc. [source] Attenuation of infarct size in rats and dogs after myocardial infarction by low-energy laser irradiationLASERS IN SURGERY AND MEDICINE, Issue 3 2001Uri Oron PhD Abstract Background and Objective The aim of the present study was to investigate the possibility that low-energy laser irradiation attenuates infarct size formation after induction of chronic myocardial infarction (MI) in small and large experimental animals. Study Design/Materials and Methods Laser irradiation was applied to the infarcted area of rats and dogs at various power densities (2.5 to 20 mW/cm2) after occlusion of the coronary artery. Results In infarcted laser-irradiated rats that received laser irradiation immediately and 3 days after MI at energy densities of 2.5, 6, and 20 mW/cm2, there was a 14%, 62% (significant; P,<,0.05), and 2.8% reduction of infarct size (14 days after MI) relative to non,laser-irradiated rats, respectively. In dogs, a 49% (significant; P,<,0.01) reduction of infarct size was achieved. Conclusion The results of the present study indicate that delivery of low-energy laser irradiation to infarcted myocardium in rats and dogs has a profound effect on the infarct size after MI. Lasers Surg. Med. 28:204,211, 2001. © 2001 Wiley-Liss, Inc. [source] Chemical and morphological features of dental composite resin: Influence of light curing units and immersion mediaMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2010Patrícia Aleixo Dos Santos Abstract Aims: The study evaluated the influence of light curing units and immersion media on superficial morphology and chemistry of the nanofilled composite resin Supreme XT (3M) through the EDX analysis and SEM evaluation. Light curing units with different power densities and mode of application used were XL 3000 (480 mW/cm2), Jet Lite 4000 Plus (1230mW/cm2), and Ultralume Led 5 (790 mW/cm2) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10 mm × 2 mm) were immersed in each respective solution for 5 min, three times a day, during 60 days and stored in artificial saliva at 37°C ± 1°C between immersion periods. Topography and chemical analysis was qualitative. Findings: Groups immersed in artificial saliva, showed homogeneous degradation of matrix and deposition of calcium at the material surface. Regarding coffee, there was a reasonable chemical degradation with loss of load particles and deposition of ions. For tea, superficial degradation occurred in specific areas with deposition of calcium, carbon, potassium and phosphorus. For Coke®, excessive matrix degradation and loss of load particles with deposition of calcium, sodium, and potassium. Conclusion: Light curing units did not influence the superficial morphology of composite resin tested, but the immersion beverages did. Coke® affected material's surface more than did the other tested drinks. Microsc. Res. Tech., 2010. © 2009 Wiley-Liss, Inc. [source] WST11, A Novel Water-soluble Bacteriochlorophyll Derivative; Cellular Uptake, Pharmacokinetics, Biodistribution and Vascular-targeted Photodynamic Activity Using Melanoma Tumors as a Model,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Ohad Mazor ABSTRACT WST11 is a novel negatively charged water-soluble palladiumbacteriochlorophyll derivative that was developed for vascular-targeted photodynamic therapy (VTP) in our laboratory. The in vitro results suggest that WST11 cellular uptake, clearance and phototoxicity are mediated by serum albumin trafficking. In vivo, WST11 was found to clear rapidly from the circulation (t1/2= 1.65 min) after intravenous bolus injection in the mouse, whereas a longer clearance time (t1/2= 7.5 min) was noted in rats after 20 min of infusion. The biodistribution of WST11 in mouse tissues indicates hepatic clearance (t1/2= 20 min), with minor (kidney, lung and spleen) or no intermediary accumulation in other tissues. As soon as 1 h after injection, WST11 had nearly cleared from the body of the mouse, except for a temporal accumulation in the lungs from which it cleared within 40 min. On the basis of these results, we set the VTP protocol for a short illumination period (5 min), delivered immediately after WST11 injection. On subjecting M2R melanoma xenografts to WST11-VTP, we achieved 100% tumor flattening at all doses and a 70% cure with 9 mg/kg and a light exposure dose of 100 mW/cm2. These results provide direct evidence that WST11 is an effective agent for VTP and provide guidelines for further development of new candidates. [source] Determination of the Minimal Erythema Dose and Colorimetric Measurements as Indicators of Skin Sensitivity to UV-B Radiation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2004Sérgio Dornelles ABSTRACT There is a strong relation between chronic UV-B-induced sunburns and the development of skin cancer. Therefore, it is important to obtain a method that can be reproduced easily to detect individuals with similar skin color but different sensitiveness to sun exposure. The study evaluated 193 healthy volunteers (68% women; the average age was 38 years). They were divided into six groups of at least 30 subjects, according to skin type. The minimal erythema dose (MED) was assessed in two non-sun-exposed areas (thorax-infra-axillary area and on the buttocks), using a UV-B source (0.5 mW/cm2), with openings of 1 cm2, in increasing doses. The same areas were evaluated with a Minolta CR 300 Chromameter (L*a*b* system). The MED values ranged from 13 to 156 mJ/cm2; the coordinate L* (brightness) ranged from 75.96 to 30.15. The correlation between the MED and the brightness was negative in both areas (Pearson's correlation r =,0.91, P < 0.05). Color measurements, especially brightness, can be used to quickly assess skin sensibility. Considering the MED, there is a substantial overlapping of adjacent phototypes, but they could be separated into two groups: more sensitive individuals (Types I, II, III and IV) and less sensitive ones (Types V and VI). [source] 5-Aminolevulinic Acid-Based Photodynamic Therapy in Leukemia Cell HL60,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2004Su-Juan Zhang ABSTRACT A study to explore the optimal experimental parameters and the photosensitization of 5-aminolevulinic acid (ALA)-based photodynamic therapy (PDT) in promyelocytic leukemia cell HL60 has been conducted, in which HL60 cells and their control groups, peripheral blood mononuclear cell (PBMC), first are incubated with different concentrations of ALA in dark for different periods of time and then followed by irradiating with different wavebands for different fluences. Fluorescence microscope and spectrofluorometer have been used to detect the fluorescence of protoporphyrin IX (PpIX) endogenously produced by ALA. The response of the cells to ALA-PDT was evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2-5-diphenyl-2H-tetrazolium bromide (MTT) assay (interval between irradiation and the MTT assay is 24 h) and by flow cytometry (the length of time between irradiation and the flow assay is 30 min). MTT results will reflect the relative number of metabolically active mitochondria in the population. Propidium iodide uptake in flow cytometry will test for membrane damage. The results of parameter experiments were obtained: 1 × 105/mL HL60 cell was first incubated with 1 mmol/L ALA in dark for 4 h and the maximum fluorescence of PpIX level appeared; then irradiated with 410 nm (4 mW/cm2) for 14.4 J/cm2 and maximum photodamage to membrane and mitochondrial function of HL60 cell resulted. With the normal granulocytes, such response was not detected. Therefore a hypothetical idea can be brought forward that ALA-based PDT can be used for inactivation of leukemia cell HL60 and these optimal parameters may be useful for clinical application. [source] Eradication of Multiple Myeloma and Breast Cancer Cells by TH9402-mediated Photodynamic Therapy: Implication for Clinical Ex Vivo Purging of Autologous Stem Cell Transplants,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2000N. Brasseur ABSTRACT High-dose chemotherapy combined with autologous transplantation using bone marrow or peripheral blood-derived stem cells (PBSC) is now widely used in the treatment of hematologic malignancies as well as some solid tumors like breast cancer (BC). However, some controversial results were recently obtained in the latter case. The presence of malignant cells in the autograft has been associated with the recurrence of the disease, and purging procedures are needed to eliminate this risk. The aim of this study was to evaluate the potential of the photosensitizer 4,5-dibromorhodamine methyl ester (TH9402), a dibrominated rhodamine derivative, to eradicate multiple myeloma (MM) and BC cell lines, while sparing more than 50% of normal pluripotential blood stem cells from healthy volunteers. The human BC MCF-7 and T-47D and MM RPMI 8226 and NCI-H929 cell lines were used to optimize the photodynamic purging process. Cell concentration and the cell suspension thickness as well as the dye and light doses were varied in order to eventually treat 1,2 L of apheresis. The light source consisted of two fluorescent scanning tubes emitting green light centered about 515 nm. The cellular uptake of TH9402 was measured during the incubation and washout periods and after photodynamic treatment (PDT) using spectrofluorometric analysis. The limiting dilution assay showed that an eradication rate of more than 5 logs is obtained when using a 40 min incubation with 5,10 ,M dye followed by a 90 min washout period and a light dose of 5,10 J/cm2 (2.8 mW/cm2) in all cell lines. Agitating the 2 cm thick cell suspension containing 20 × 106 cells/mL during PDT was essential for maximal photoinactivation. Experiments on mobilized PBSC obtained from healthy volunteers showed that even more drastic purging conditions than those found optimal for maximal eradication of the malignant cell lines were compatible with a good recovery of hematopoietic progenitors cells. The absence of significant toxicity towards normal hematopoietic stem cells, combined with the 5 logs eradication of cancer cell lines induced by this procedure suggests that TH9402 offers an excellent potential as an ex vivo photodynamic purging agent for autologous transplantation in MM and BC treatment. [source] Complete resolution of a squamous cell carcinoma of the skin using intralesional 5-aminolevulinic acid photodynamic therapy intralesional PDT for SCCPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 5 2010Eleni Sotiriou We present an 82-year-old female patient with a 2-year history of an infiltrative squamous cell carcinoma (SCC) on her right cheek. The patient was treated with one intralesional photodynamic therapy (PDT) session using 10% 5-aminolevulinic acid solution. We used red light by a non-coherent light source at a light dose of 100 J/cm2 and a fluency rate of 100 mW/cm2. Complete clinical and histological response was achieved 3 months after the treatment procedure. Cosmetic outcome was evaluated as fair. The patient remains disease free with the absence of any clinical sign of recurrence 16 months after PDT. Long-term follow-up is needed for assessment of recurrences. Optimization of the therapeutic protocol, as well as justification of our results in larger studies are needed in order to elicit safe conclusions. [source] 013 Effect of UV on the susceptibility of acid-soluble Skh-1 hairless mouse collagen to collagenasePHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 2 2002J.M. Menter To test the hypothesis that UV could alter collagen susceptibility to interstitial collagenase, acid-extracted Skh-1 hairless mouse collagen samples were (un)irradiated with 0,140 J/cm2 of radiation from bank of filtered FS lamp (UVB/UVA = 0.33, fluence rate = 0.81 mW/cm2). Subsequent to UV irradiation, collagen samples were coupled with fluorescein isothiocyanate (FITC) and assayed for its susceptibility to bacterial collagenase by monitoring the appearance of supernatant FITC fluorescence (a measure of lysed collagen) over time of incubation. As a reference. unirradiated commercial FITC , labeled collagen (Elastin Products) was similarly analyzed. Mouse collagen had a lower rate of cleavage than did the calf skin sample. Mouse collagen initial cleavage followed a quasi-linear time course over the first 5 h. Calf-skin collagen displayed a ,sigmoidal' time course, reminiscent of a cooperative mechanism. UV irradiation afforded no significant effect on the ability of collagenase to cleave mouse collagen, although a small effect could be discerned after 48 h (140 J/cm2). On the other hand, these samples exhibited significant chain degradation. cross-linking and loss of intrinsic collagen fluorescence on UV photolysis. It appears that the rate of cleavage depends on the superstructure of the collagen, and that the collagen fluorophores are not in proximity to the specific site of collagenase cleavage. Supported in part by NIH/MBRS Grant #GM 08248 and RCMI Grant #RR 03034. [source] | ||||||||||||||||||||||