Formulation and Comparative Characterization of Chitosan,Gelatin, and Chitosan–Gelatin-Coated Liposomes of CPT-11–HCl

Liposomes containing phosphatidylcholine and cholesterol (uncoated) and coated by chitosan, gelatin, and combination of chitosan and gelatin were prepared by the modified ethanol injection method. The aim of this work was to formulate and characterize liposomes of camptothecin (CPT)-11–HCl (Irinotecan HCl) containing chitosan, gelatin, and both polymers as coating materials; and also to increase its circulation longevity when compared with the free drug while maintaining the agent in its active lactone form. Size, shape, zeta potential, encapsulation efficiency, stability study, in vitro, and in vivo release study were used for characterization of liposomes. The size of liposomes was in the order of uncoated?<?chitosan coated?<?gelatin coated?<?combination of chitosan and gelatin coated. The zeta potential of liposomes was in the order of combination of chitosan and gelatin coated?>?chitosan coated?>?gelatin coated?>?uncoated. The formulations showed the long-term stability. The encapsulation efficiency of liposomes was in order of combination of chitosan and gelatin coated?>?gelatin coated?>?chitosan coated?>?uncoated. The in vitro and in vivo release of drug was observed in the order of combination chitosan and gelatin coated?>?gelatin coated?>?chitosan coated?>?uncoated.     

Thermal Conductivity and Thermal Diffusivity of Liquid Indium–Tin Alloys

Thermal-conductivity and thermal-diffusivity coefficients of indium–tin alloys have been determined using the laser flash method over the temperature range from the liquidus line to 1173 K. Measurements were performed using the setup LFA-427 of NETZSCH company in an argon protective atmosphere, and cells were produced from molybdenum. The equations for temperature dependences of the thermal conductivity and thermal diffusivity of In–Sn alloys have been obtained. The results of measurements were compared with data available in the literature.     

Structural, Dielectric, and Magnetic Characterization of Nanocrystalline Ni–Co Ferrites

Spinel ferrites containing Nickel and Cobalt of composition with nominal formula Ni_(1?x)Co_(x)Fe₂O₄ (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) prepared by the coprecipitation method are reported. The single phase spinel formation of ferrites was confirmed by X-ray diffraction techniques. The lattice constants (a _th) were calculated based on the ionic radii of the constituents. The calculated lattice constants are smaller than the measured, because for calculations ideal ionic radii are used. The particle size calculated from the Scherrer formula varied within 15 to 33?nm. The dielectric constant and dielectric loss tangent measurement were carried out at room temperature as a function of frequency from 100 Hz to 3 MHz. Both the dielectric constant and dielectric loss tangent increased with increase in cobalt concentration. Ferrimagnetic transition temperature as a function of Co?concentration was measured with the low field ac susceptibility apparatus. The ferrimagnetic transition (T _c ) was observed in the temperature range 573 to 720?K. The T _c decreased with the addition of Co?concentration. The effect of Co?concentration on the magnetic properties was investigated using a vibrating sample magnetometer (VSM). It was found that both magnetic saturation (M _s ) and coercivity (H _c ) increase with Co?concentration.     

Optical absorption,P NMR,and photoluminescence spectroscopy study of copper and tin co-doped barium–phosphate glasses

The optical and structural properties of 50P₂O₅:50BaO glasses prepared by melting have been investigated for additive concentrations of 10 and 1 mol% of CuO and SnO dopants. Absorption and photoluminescence spectroscopies were employed in the optical characterization, whereas structural properties were assessed by ³¹P nuclear magnetic resonance (NMR) spectroscopy. Residual Cu²⁺ was detectable by absorption spectroscopy for the highest concentration of CuO and SnO. More prominently, the optical data suggests contributions from both twofold-coordinated Sn centers and Cu⁺ ions to light absorption and emission in the glasses. The luminescence depends strongly on excitation wavelength for the highest concentration of dopants where a blue–white emission is observed under short-wavelength excitation (e.g., 260 nm) largely due to tin, while an orange luminescence is exhibited for longer excitation wavelengths (e.g., 360 nm) essentially due to Cu⁺ ions. On the other hand, dissimilar luminescent properties were observed in connection to Cu⁺ ions for the lowest concentration studied, as the copper ions were preferentially excited in a narrower range at shorter wavelengths near tin centers absorption. The structural analyses revealed the glass matrix to be composed essentially of Q² (two bridging oxygens) and Q¹ (one bridging oxygen) phosphate tetrahedra. A slight increase in the Q¹/Q² ratio reflected upon SnO doping alone suggests a major incorporation of tin into the glass network via P–O–Sn bonds, compatible with the 2-coordinated state attributed to the luminescent Sn centers. However, a significant increase in the Q¹/Q² ratio was indicated with the incorporation of copper at the highest concentration, consistent with a key role of the metal ions as network modifiers. Thus, the change in Cu⁺ optical properties concurs with different distributions of local environments around the ions induced by variation in metal ion concentration. Luminescence decay curve analyses were found in agreement with the presence of Cu⁺ ions in the glasses suggesting their existence in tetragonally-distorted octahedral sites.     

Preparation,Characterization, and Bioavailability of Ursodeoxycholic Acid–Phospholipid Complex In Vivo

The aim of this study was to prepare ursodeoxycholic acid–phospholipid complex (UDCA-PLC) to enhance oral bioavailability of UDCA, and the physicochemical properties of the complex were studied. Compared with those of UDCA tablet after oral administration in rats, the main pharmacokinetic characteristics and bioavailability of UDCA-PLC orally administered were evaluated. Tetrahydrofuran was used as a reaction medium, UDCA and phospholipids were resolved into the medium, and UDCA-PLC was formed after the organic solvent was evaporated off under vacuum condition. The physicochemical properties of the complex were evaluated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), X-ray diffraction, particle size distribution analysis, and n-octanol/water partition coefficient (P) study. The blood concentrations of UDCA-PLC and UDCA tablet at different time points after oral administration in rats were assayed by high-performance liquid chromatography (HPLC) after derivatization. The pharmacokinetic parameters were computed by software program 3p87. The X-ray diffraction and DSC studies showed that UDCA and phospholipids in the UDCA-PLC were combined by noncovalent bond, not forming a new compound, and n-octanol/water partition coefficient (P) of UDCA-PLC was effectively enhanced. The mean serum concentration–time curves of UDCA after oral administration of UDCA-PLC and UDCA tablet in rats were both in accordance with open two-compartment model. Pharmacokinetic parameters of UDCA tablet and the PLC in rats were T_max 1.9144 and 1.5610 h, C_max 0.0576 and 0.1346 μg/mL, and AUC_0–∞ 4.736 and 11.437 μg h/mL, respectively. The bioavailability of UDCA in rats was significantly different (p < .05) compared with those of UDCA tablet after administration. The UDCA-PLC would be more prospective formulation in future.     

Characterization of Ge–Bi–S glass by thermal, electrical, switching and optical measurements

A study of the synthesized Ge22.5Bi7S70.5 glassy system has been carried out. Differential thermal analysis data indicate the retention in the as-quenched sample of two amorphous phases. Thermal conductivity, , measurements on bulk sample reveal that the main contribution to is due to phonon thermal conductivity. Thermal evaporation of the synthesized ingot gives films with Ge20.7Bi6.8S72.5 as composition. The values of the activation energy and the pre-exponential factor calculated from the direct current electrical conductivity above 53 °C suggest that carrier conduction occurred between extended states in these films. The I–V characteristics in the off-state and the switching phenomenon are investigated. A memory switch with a threshold voltage decreasing with temperature is detected for the studied films. Optical parameters such as absorption coefficient, optical gap and refractive index are also determined. Comparison with binary Ge–S glass reveals that the addition of Bi introduces additional absorbing states at band edges. © 1998 Kluwer Academic Publishers     

Synthesis and Characterization of Aluminum–Zirconium Intermetallic Composites

The search for composite materials comes from a necessity of improving properties of conventional materials. The reaction synthesis process frequently gives products with some level of porosity that may be improved through the use of hot pressing routes. The combination of aluminum and zirconia in controlled conditions has led to a metal matrix composite with a dispersion of intermetallics, especially Al₃Zr. Temperature, pressure, and chemical composition were the main parameters varied during the production of the samples. The experimental procedures consisted initially of the mixing and homogenization of the powders in three proportions (5, 10, and 20 in zirconia wt. %). The powders were pressed for the production of green bodies, cylinders of 9 × 9 mm, with the application of three pressures (150, 250, and 300 MPa). Synthesis was carried out in a tubular furnace (1073, 1173, and 1273 K) using a helium atmosphere. Reactive hot pressing was carried out in a MTS machine. The densification process in the simultaneous hot pressing was observed with the use of mercury picnometry to measure the densities and confirmed with the help of an image analyzer. The temperatures were monitored by a thermocouple connected to an A/D interface. Determination of Vickers microhardness was carried out in the aluminum matrix and in the intermetallic particles; hardness was determined in all samples. The identification of the phases was obtained utilizing XRD, optical, and SEM microscopy.     

Sol-Gel Synthesis and Thermal Evaluation of Cordierite–Zirconia Composites (Ce–ZrO2, Y–Ce–ZrO2)

Cordierite and cordierite–zirconia composites (ceria- and yttria–ceria-stabilized zirconia) were prepared by sol-gel processing for different compositions. The precursor powders of these composites were studied using analytical techniques such as thermogravimetric analysis, differential thermal analysis, X-ray diffraction, and infrared spectroscopy for different temperatures to investigate the crystallization behavior of the material. It was observed that the cordierite–zirconia composite powders are crystallized as -cordierite and tetragonal zirconia when sintered at a temperature above 1200°C in the presence of zircon in the cordierite matrix. Powder morphologies of cordierite–zirconia composites have also been investigated.     

Erbium–ytterbium microlasers: optical properties and lasing characteristics

In this paper we present a comprehensive review of the work done by our group on diode-pumped bulk erbium–ytterbium microlasers. Starting from an analysis of the optical properties of Er–Yb doped phosphate glasses, addressed to the modeling of the active material and to the design and optimization of laser cavities, different operating regimes and peculiar properties of these novel laser devices are described and discussed, including multi-longitudinal mode and single-frequency operation, frequency tuning and stabilization, intensity stabilization, Q-switching, mode-locking and frequency-modulation operation. Due to the high performance in terms of emission characteristics and potential low cost, these microlasers are attractive for a large number of applications and, in particular, for optical communications at 1530–1560 nm wavelengths, metrology, and telemetry at an eye-safe wavelength.     

Electrical and Dielectric Characterization of Bi–La Ion-Substituted Barium Hexaferrites

BaLa _x Bi _x Fe_12?2xO₁₉ (0.0 ≤ x ≤ 0.5) hexaferrites were produced by solid-state synthesis route, and the effect of Bi³⁺ and La³⁺ substitutions on electrical and dielectric properties of barium hexaferrite material were investigated. It is noticed that ac conductivity of barium (BaM) increases slightly with ionic substitutions of both La³⁺ and Bi³⁺ and then decreases. Ac conductivity is increased with increasing frequency at lower temperatures then remains constant for higher temperatures. This type of conductivity attitude could be originated from the indication of both electronics and polaron hopping mechanisms. The dielectric properties of BaLa _x Bi _x Fe_12?2xO₁₉ (0.0 ≤ x ≤ 0.5) hexaferrites represent a very interesting tunability as functions of frequency, temperature, and Bi³⁺ and La³⁺ ions.     

Synthesis and Characterization of PEG-Sr Hexaferrite by Sol–Gel Conversion

Sr-M-type hexagonal ferrites have been prepared via a sol?Cgel route, and the effects of addition of different molecular weight polyethylene glycol (PEG) into the sol solutions on the static magnetic properties and particle morphology have been studied. Crystalline phases of the samples were determined by XRD analysis. FT-IR and TG analyses were used to prove the presence of PEG on SrFe₁₂O₁₉. The results showed that adding PEG with different molecular weight into the sol solutions affected the formation mechanism of SrFe₁₂O₁₉. Sr-M precursors prepared by various PEG types show different magnetic behaviors after pre-calcination at 150?^°C. This discrepancy is explained by the formation of a different phase during the synthesis of SrM particles.     

Microstructure and Electrical Conductivity of Yttria Stabilized Zirconia （8Y-CSZ） Containing Small NiO Addition

In this study, the effect of addition in small contents of NiO on microstructure and electrical conductivity properties of 8 mol% yittria stabilized cubic zirconia （8Y-CSZ） were investigated. Specimens were produced by colloidal processing from 1 wt% NiO and 99 wt% 8Y-CSZ powders. Specimens were pressurelless sintered at 1,400 ℃ for 10 h. Scanning Electron Microscope （SEM） and EDS analysis results showed that an amount of 1 wt% NiO dissolved in the 8Y-CSZ and insoluble NiO in the 8Y-CSZ precipitated at the grain boundaries. Electrical conductivities of undoped and 1 wt% NiO doped 8Y-CSZ specimens were measured using a frequency response analyzer （impedance spectroscopy） in the frequency range of 100 mHz-13 MHz and at 300-800 ℃. Electrical conductivity results showed that grain interior, grain boundary and total conductivity of 8Y-CSZ increased with 1 wt% NiO addition. The reason for increase of electrical conductivity in NiO doped 8Y-CSZ, due to create oxygen vacancies in the crystal lattice of dissolved NiO in 8Y-CSZ and the ion transfer of the oxygen vacancies at high temperatures.     

Characterization of corrosion phenomena of Zr–Ti–Cu–Al–Ni metallic glass by SEM and TEM

Corrosion phenomena are investigated for a Zr₅₉Ti₃Cu₂₀Al₁₀Ni₈ metallic glass immersed in hydrofluoric acid (HF) in open-circuit conditions and by means of electron microscopies (SEM and TEM). Several morphologies develop on the corroded surface and especially large and deep pits. TEM study demonstrates that Cu-rich nanocrystals of 5–10 nm are formed inside the corrosion pits (on their walls) during the corrosion process. These nanocrystals are not only by-products of the corrosion process but they very likely play a role in the development of the corrosion pitting morphology. They could have a dual role: (i) protecting the capped areas against dissolution and (ii) speeding the dissolution of neighboring uncapped areas by the creation of local galvanic cells.     

Characterization and photocatalytic activities of C, N and S co-doped TiO(2) with 1D nanostructure prepared by the nano-confinement effect

A novel method was developed for preparing high specific surface area (156.2?m(2)?g(-1)) one-dimensional TiO(2) nanostructures co-doped with C, N and S by the nano-confinement effect. A nonmetal doping source (thiourea) was first intercalated into the inner space of H-titanate nanotubes prepared by the hydrothermal method, and then calcined at 450?°C for 2?h in air. The as-prepared C, N and S co-doped TiO(2) nanowires exhibited high visible light and enhanced UV-vis activities in photocatalytic degradation of toluene in the gas phase. The samples were characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, fast Fourier transform analysis, x-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra and photoluminescence. The?results indicated that the anatase nanowires grew along the [101] direction. Doping TiO(2) nanowires with C, N and S could not only broaden the light adsorption spectra into the visible region (400-600?nm), but also inhibit the recombination of photo-induced carriers. A?mechanism is proposed to elucidate the nano-confinement effect of H-titanate nanotubes in the formation of C, N and S co-doping. Based on this mechanism, the effect of C, N and S co-doping on the band structure of TiO(2) nanowires is also discussed.     

Characterization and catalytic activity studies of sol–gel Co–SiO2 nanocomposites

Silica embedded with transition metals exhibits adequate properties for applications in catalysis, sensors and optics. Cobalt–silica (Co–SiO₂) nanocomposites were prepared by the sol–gel method and thermally treated at 700, 900, 1100 and 1250 °C. Characterization of the samples was performed by XRD and BET nitrogen adsorption. The performance of the nanocomposites was investigated by catalysis reactions of oxidation. These catalysts were found to be recyclable showing a catalytic activity even after a third recovering. The results indicate that thermal treatment of sol–gel nanocomposites at temperatures higher than 900 °C is essential for the preparation of active heterogeneous catalysts.     

Synthesis and luminescence properties of Yb3+–Er3+ co-doped LaOCl nanostructures

LaOCl:Yb³⁺, Er³⁺ nanofibers and hollow nanofibers were prepared by electrospinning combined with a double-crucible chlorination technique using NH₄Cl as chlorinating agent. X-ray powder diffraction analysis indicated that LaOCl:Yb³⁺, Er³⁺ nanostructures were tetragonal with space group P4/nmm. Scanning electron microscope analysis and histograms revealed that diameters of LaOCl:Yb³⁺, Er³⁺ nanofibers and hollow nanofibers, respectively, were 117.87 ± 15.48 and 141.09 ± 17.10 nm under the 95 % confidence level. Up-conversion (UC) emission spectra analysis manifested that LaOCl:Yb³⁺, Er³⁺ nanostructures exhibited strong green and red UC emission centering at 526, 548, and 671 nm, respectively, attributed to ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_l5/2 transitions of Er³⁺ ions under the excitation of a 980-nm diode laser. It was found that the relative intensities of green and red emissions vary obviously with the addition of Yb³⁺ ions, and the optimized molar ratio of Yb³⁺ to Er³⁺ was 10:1 in the as-prepared nanofibers. Moreover, the near-infrared characteristic emissions of LaOCl:Yb³⁺, Er³⁺ nanostructures were achieved under the excitation of a 532-nm laser. CIE analysis demonstrated that color-tuned luminescence can be obtained by changing doping concentration of Yb³⁺ (and/or Er³⁺) ions and morphologies of nanomaterials, which could be applied in the fields of optical telecommunication and optoelectronic devices. The UC luminescent mechanism and the formation mechanisms of LaOCl:Yb³⁺, Er³⁺ nanofibers and hollow nanofibers were also proposed.     

Characterization of polypropylene–polyethylene blends made of waste materials with compatibilizer and nano-filler

Waste polypropylene and polyethylene were blended by a twin-screw extruder with two compatibilizers (PE-g-MAH and EPDM) and an additive (O-MMT). The mechanical properties were measured firstly. By adding O-MMT, the tensile strength showed a decline while the impact strength made a promotion. The phase morphology was observed by scanning electron microscopy (SEM) to explore the fracture toughness of blends. The blend with EPDM had a better compatibilization than PE-g-MAH. X-ray diffraction was used to investigate the crystallization behavior and the result showed no change by blending. Moreover, further measurements such as thermogravimetric (TGA) and differential scanning calorimetry (DSC) were taken to show the thermal stability and crystallization temperature of the blend. Additionally, the storage modulus and loss modulus are measured by dynamic mechanical analysis (DMA), the presence of O-MMT caused the increases of the storage modulus and loss modulus.     

Synthesis and Characterization of Electrochromic Polyimides

Following the initial work by Haushalter and Krause,1 the redox properties of some common phthalimides and naphthalimides as well as phthalimide polymers have been described.2,3 Owing to its electron affinity, an imide can undergo the electrochemical reduction.     

Characterization and numerical evaluation of vibration on elastic–viscoelastic sandwich structures

The objective of this paper is to study the vibration characteristic for a sandwich beam with silica/polymer blend as principal material, and pure polymer matrix as surface laminate. It is anticipated that high stiffness and structure damping of viscoelastic layer can be obtained by taking advantage of fascinating network of densely packed between silica and polymer matrix. Spherical particles of size 12–235 nm at various filler fraction (10–50 wt.%) and three different polymer matrices, polyacrylate, polyimide and polypropylene, were selected as the matrix materials. The mechanical damping and stiffness of the sandwich cantilever beam are recorded by using a Dynamic Mechanical Thermal Analyzer (DMTA). The silica’s small particle size feature and strain difference between principal and surface layers could highly enhance the energy dissipation ability of the beam structure. A numerical model is then developed and validated for the vibration of a symmetric elastic–viscoelastic sandwich beam. Experimental results show that the structure deformation for these sandwich beams with contiguous and constraining layers are in reasonable agreement with the prediction of the model. Both higher resonant vibrations are well damped in accordance with the symmetric motion of the elastic layers and relative little motion of the constraining layer.     

Temperature Dependent I–V and Resistance Characterization of SuperCDMS Germanium Crystals

We have built a versatile, compact ³He test facility to evaluate high-purity Ge (HPGe) SuperCDMS (Cryogenic Dark Matter Search) detectors. We are able to rapidly identify photolithographic or other defects in the thousands of W-Al transition edge sensors (TESs) on each detector and to evaluate the performance of the underlying substrate. We describe our simple method to measure current-voltage (I–V) characteristics and R vs. T behavior of HPGe detector crystals with resistances up to 100?GΩ. This provides a way to quickly perform diagnostic physics studies. Results provide critical data that give early warning that a crystal may not be suitable for the SuperCDMS underground experiment. Data from tests made on several kg-scale detectors are presented.