Large third-order nonlinearity of nonpolar A-plane GaN film at 800 nm determined by Z-scan technology

We report an investigation on the optical third-order nonlinear property of the nonpolar A-plane GaN film. The film sample with a thickness of ~2?μm was grown on an r-plane sapphire substrate by metal-organic chemical vapor deposition system. By performing the Z-scan method combined with a mode-locked femtosecond Ti:sapphire laser (800?nm, 50?fs), the optical nonlinearity of the nonpolar A-plane GaN film was measured with the electric vector E of the laser beam being polarized parallel (//) and perpendicular (⊥) to the c axis of the film. The results show that both the third-order nonlinear absorption coefficient β and the nonlinear refractive index n₂ of the sample film possess negative and large values, i.e. β_//?=??135?±?29?cm/GW, n_2//?=??(4.0?±?0.3)?×?10^?3?cm²/GW and β_⊥?=??234?±?29?cm/GW, n_2⊥?=??(4.9?±?0.4)?×?10^?3?cm²/GW, which are much larger than those of conventional C-plane GaN film, GaN bulk, and even the other oxide semiconductors.     

Nanospheres Containing Urea: Photothermic Properties

In the present research, nanospheres of chitosan (CS), maltodextrin, and sodium tripolyphosphate (STPP), loaded with urea, were synthesized by using an ionic gelation technique. In the nanosphere synthesis was used a central composite experimental design, obtaining nanospheres with an average size of 275?±?32 nm and 27.5 mV zeta potential. The nanospheres were characterized by their hydrodynamic diameter, polydispersity index, nitrogen content, and thermal properties such as thermal diffusivity (α), effusivity (e), and conductivity (k); also melting temperature was obtained by differential scanning calorimetry. The thermal properties of nanospheres show that the sample with the smallest size has a thermal diffusivity value of (14.4?±?0.4)?×?10^?8 m²·s^?1 and a thermal conductivity value of (6.4?±?0.1)?×?10^?1 W·m^?1·K^?1, and the obtained melting temperature was 157 °C. Higher concentrations of CS increase the values of these thermal properties, probably because chitosan interacts ionically with STPP forming a reticular network due to the opposite charges of both molecules.     

A Cross-Performance Relationship Between Carr's Index and Dissolution Rate Constant: The Study of Acetaminophen Batches

The aim of this paper is to promote a simple and scalable approach to accelerate the formulation development of wet granules using acetaminophen batches as a model system. Only two thorough experiments with five processing steps of: crystallization → dry blending → wet granulation → drying → dissolution, were required to establish a specific linear relationship between the overall effect of the particle size distribution and the dissolution performance for a given formulation of any batch of acetaminophen. With this specific linear relationship at hand, dissolution rates of the granules prepared from batches of acetaminophen with various particle size distribution could be predicted without the need of doing any wet granulation, drying and dissolution for the same formulation. It was found that the Carr's Index, C, an overall manifestation of particle size distribution, of only a few grams of the dry blended acetaminophen was good enough to be linearly related to the dissolution rate constant, k, of the formulated granules by ln k?=?α ln C?+?ln A (or exponentially by a power law of k?=?AC^α) where A was the exponential factor and α was the power index. A and α were dependent on the mass transfer of acetaminophen powders and the rheological properties of the formulated dry blended powders, respectively. The three linear relationships for 75, 62, and 30 wt % formulations were ln k?=?2.9 ln C –12.3, ln k?=?2.8 ln C –12.5, and ln k?=?4.2 ln C –18.0, respectively. The power laws for 75, 62, and 30 wt % formulations were k?=?4.7 × 10^?6 C^2.9, k?=?3.9 × 10^?6 C^2.8, and k?=?1.5 × 10^?8 C^4.2, respectively. The formulation used in our study contained acetaminophen, microcrystalline cellulose, and polyvinylpyrrolidone. The validation of the linearity between k and C was verified (1) by acetaminophen batches from different processes and sources, (2) by the various formulation compositions of acetaminophen of 75, 62, and 30 wt%, and (3) by the growth mechanisms of wet granulation and the resultant granular structures determined by dry sieve analysis, optical microscopy (OM), mercury intrusion porosimetry (MIP), the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), and Fourier transformed infrared (FT-IR) microscopic mapping. In general, granules grown from the small-size ranged acetaminophen powders of a given formulation had a higher C. Since the growth mechanism was dominated by agglomeration, the granules were more porous, higher in surface area, more homogenous, and higher in dissolution rate constant, k, as opposed to granules grown from the large-size ranged acetaminophen powders of a given formulation having a lower, C, whose growth was dominated via consolidation and layer-by-layer mechanism and resulted in a lower dissolution rate constant, k.     

Solid-state stability studies of crystal form of tebipenem

The aim of this study was to determine the kinetic and thermodynamic parameters of tebipenem degradation in the solid state. The process was analyzed based on the results obtained by a high performance liquid chromatography (HPLC) method using ultraviolet diode-array detector (DAD)/electrospray ionization tandem mass spectrometry (Q-TOF-MS/MS), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopic (RS) studies. In dry air, the degradation of tebipenem was a first-order reaction depending on the substrate concentration while at an increased relative air humidity tebipenem was degraded according to the kinetic model of autocatalysis. The thermodynamic parameters: energy of activation (E_a), enthalpy (ΔH^≠a) and entropy (ΔS^≠a) of tebipenem degradation were calculated. Following a spectroscopic analysis of degraded samples of tebipenem, a cleavage of the β-lactam bond was proposed as the main degradation pathway, next confirmation using HPLC-Q-TOF-MS/MS method.     

Acid-base catalysis of N-[(morpholine)methylene]daunorubicin

The stability of N-[(morpholine)methylene]-daunorubicin hydrochloride (MMD) was investigated in the pH range 0.44?13.54, at 313, 308, 303 and 298 K. The degradation of MMD as a result of hydrolysis is a pseudo-first-order reaction described by the following equation: ln c?=?ln c₀ – k_obs. t. In the solutions of hydrochloric acid, sodium hydroxide, borate, acetate and phosphate buffers, k_obs?=?k_pH because general acid-base catalysis was not observed. Specific acid-base catalysis of MMD comprises the following reactions: hydrolysis of the protonated molecules of MMD catalyzed by hydrogen ions (k₁) and spontaneous hydrolysis of MMD molecules other than the protonated ones (k₂) under the influence of water. The total rate of the reaction is equal to the sum of partial reactions: k_pH?=?k₁ ? a_H+ ? f₁ + k₂ ? f₂ where: k₁ is the second-order rate constant (mol^?1 l s^?1) of the specific hydrogen ion-catalyzed degradation of the protonated molecules of MMD; k₂ is the pseudo-first-order rate constant (s^?1) of the water-catalyzed degradation of MMD molecules other than the protonated ones, f₁ – f₂ are fractions of the compound. MMD is the most stable at approx. pH 2.5.     

Equilibria,kinetics and mechanism for the degradation of the cytotoxic compound L-NG-nitroarginine

L-N^G-nitroarginine (LNNA), an analog of L-arginine, is a competitive inhibitor of nitric oxide synthase which causes the selective reduction of blood flow to tumor cells. Despite the potential of LNNA to function as an adjuvant in cancer therapies, its poor solubility and stability have hindered the development of an injectable formulation of LNNA that is suitable for human administration. This work, for the first time, details a systematic study on the determination of equilibrium K_a constants and the rate law of LNNA degradation. The four K_a values of LNNA were determined to be 1.03, 1.10?×?10^?2, 2.51?×?10^?10, and 1.33?×?10^?13 M. From the kinetic and equilibrium studies, we have shown that the deprotonated form of LNNA is the main form of LNNA that undergoes degradation in aqueous media at room temperature. The rate law of LNNA degradation was found to be first order with respect to OH^? concentration and first order with respect to LNNA^? concentration. The rate constant at 25?°C and 1?atm was determined to be 0.04453 M^?1min^?1. A base catalyzed mechanism of LNNA degradation was proposed based on the kinetic study. The mechanism was found to be very useful in explaining the discrepancies and changes of the rate law at different pH values. It is thus recommended that LNNA should be formulated as a concentrated solution in acidic conditions for maximum chemical stability during storage and be diluted with a basic solution to near physiological pH just before administration.     

Numerical investigation of birefringence and confinement loss formed by rectangular/elliptical/circular air holes photonic crystal fibers

In this paper, high birefringence and low confinement loss of rectangular air holes photonic crystal fibers (PCFs) are numerically investigated and compared with elliptical and circular patterns using the finite element method. The mode birefringence of the proposed PCFs with rectangular air holes at λ?=?1.55?µm reaches 8.1?×?10^?2 and the confinement loss is less than 5?×?10^?3?dB/km. Besides, a high birefringence up to 2.76?×?10^?2 is also achieved from the proposed circular air holes PCF, which is the highest value compared to conventional circular air holes PCF.     

Reaction Kinetics of C60 Fullerene Ozonation

Abstract

It has been verified that the reaction between O₃ and C₆₀ follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C?C][O₃]. The reaction rate constant k has been measured ≈(1.5 ± 0.3) × 10⁴ L mol^?1 s^?1. The value of this rate constant has the same order of magnitude of the rate constant measured for instance in the ozonation of 1,4‐diphenylbutadiene.     

Picosecond nonlinear optical studies of gold nanoparticles synthesised using coriander leaves (Coriandrum sativum)

The results are presented from the experimental picosecond nonlinear optical (NLO) studies of gold nanoparticles synthesised using coriander leaf (Coriandrum sativum) extract. Nanoparticles with an average size of ～30?nm (distribution of 5–70?nm) were synthesised according to the procedure reported by Narayanan et al. [Mater. Lett. 2008, 62, 4588–4591]. NLO studies were carried out using the Z-scan technique using 2?ps pulses near 800?nm. Open-aperture data suggested saturation absorption as the nonlinear absorption mechanism, whereas closed-aperture data suggested a positive nonlinearity. The magnitude of third-order nonlinearity was estimated to be (3.3?±?0.6)?×?10^?13?esu. A solvent contribution to the nonlinearity was also identified and estimated. A comparison is attempted with some recently reported NLO studies of similar gold nanostructures.     

Design,characterization, and evaluation of intranasal delivery of ropinirole-loaded mucoadhesive nanoparticles for brain targeting

Context: Parkinson disease (PD) is a common, progressive neurodegenerative disorder, characterized by marked depletion of striatal dopamine and degeneration of dopaminergic neurons in the substantia nigra.

Objective: The purpose of the present study was to investigate the possibility of targeting an anti-Parkinson’s drug ropinirole (RH) to the brain using polymeric nanoparticles.

Materials and methods: Ropinirole hydrochloride (RH)-loaded chitosan nanoparticles (CSNPs) were prepared by an ionic gelation method. The RH-CSNPs were characterized for particle size, polydispersity index (PDI), zeta potential, loading capacity, entrapment efficiency in vitro release study, and in vivo distribution after intranasal administration.

Results and discussion: The RH-CSNPs showed sustained release profiles for up to 18?h. The RH concentrations (% Radioactivity/g) in the brain following intranasal administration (i.n.) of RH-CSNPs were found to be significantly higher at all the time points compared with RH solution. The concentration of RH was highest in the liver (7.210?±?0.52), followed by kidneys (6.862?±?0.62), intestine (4.862?±?0.45), and lungs (4.640?±?0.92) in rats following i.n. administration of RH-CSNPs. Gamma scintigraphy imaging in rats was performed to ascertain the localization of drug in the brain following intranasal administration of formulations. The brain/blood ratios obtained (0.251?±?0.09 and 0.386?±?0.57 of RH (i.n.) and RH-CSNPs (i.n.), respectively) at 0.5?h are indicative of direct nose to brain transport, bypassing the blood–brain barrier (BBB).

Conclusion: The novel formulation showed the superiority of nose to brain delivery of RH using mucoadhesive nanoparticles compared with other delivery routes reported earlier.     

A facile synthesis of silver nanoparticle with SERS and antimicrobial activity using Bacillus subtilis exopolysaccharides

In this study, we report a facile synthesis of silver nanoparticle having SERS and antimicrobial activity using bacterial exopolysaccharide (EPS). Bacillus subtilis (MTCC 2422) was grown in nutrient broth and the extracellular EPS secreted by the organism was extracted and purified. The purified EPS was used for the synthesis of silver nanoparticles. The kinetics of silver nanoparticle synthesis was deduced by varying the exposure time and the concentration of EPS. The rate constant (k) for the synthesis of silver nanoparticle was calculated from the slope of ln(A^∞ ? A^t) versus time plot. The k value was found to be 3.49 × 10^?3, 5.81 × 10^?3 and 5.03 × 10^?3 per min for particle synthesis using 2, 5 and 10 mg/mL EPS, respectively. The nanoparticles synthesised had an average particle size of 5.18 ± 1.49 nm, 1.96 ± 0.77 nm and 2.08 ± 0.88 nm for 2, 5 and 10 mg/mL EPS, respectively. The synthesised particles were characterised using UV-Vis absorbance spectroscopy, high-resolution transmission electron microscopy (HRTEM) attached to EDS (energy dispersive spectroscopy), Fourier transform infrared spectroscopy (FTIR), surface enhanced Raman spectroscopy (SERS) and zeta potential analyser. To our knowledge, this is the first study to report SERS activity of microbial Bacillus subtilis EPS-based synthesis of silver nanoparticle. HRTEM images showed silver nanoparticle entrapped in polysaccharide nanocages. Silver nanoparticle showed higher adherence towards the bacterial surface, with good bactericidal activity against Pseudomonas aeroginosa and Staphylococcus aureus.     

The usefulness of diffusion-weighted imaging for differentiating portal vein thrombus from tumour embolus

To investigate the usefulness of diffusion-weighted imaging (DWI) for differentiating bland portal vein thrombus from tumour thrombus. Fifteen patients with clinical comprehensive diagnoses of portal vein thrombus were analysed retrospectively. The thrombus signal intensity on 21 DWI slices and apparent diffusion coefficient (ADC) values were analysed quantitatively. The portal vein thrombus was divided into four types (low/low, high/low, low/high, and high/high) based on the DWI/ADC ratios between the thrombus and liver parenchyma (rDWI and rADC, respectively). Twenty patients with portal vein tumour thrombi were used for comparison as controls. The average ADC value for the bland thrombus was 1.84?±?0.70?×?10^?3?mm²?s^?1 (range: 0.46–2.77?×?10^?3?mm²?s^?1), and was 2.18?±?0.51?×?10^?3?mm²?s^?1 (range: 1.39–2.82?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.90?±?0.45 (range: 0.26–1.86). The tumour thrombi were high/low and high/high type. The average ADC for the tumour thrombus was 1.25?±?0.26?×?10^?3?mm²?s^?1 (range: 0.68–1.67?×?10^?3?mm²?s^?1), and 1.56?±?0.33?×?10^?3?mm²?s^?1 (range: 1.11–2.34?×?10^?3?mm²?s^?1) for the liver parenchyma; the rADC was therefore 0.82?±?0.16 (range: 0.39–1.08). There was no statistical difference in rADC values and rDWI/rADC classification performance between the bland and tumour thrombi. The ADC difference between portal vein bland and tumour thrombi was statistically significant, but the ADC values of bland thrombi have a wider range, which contains the ADC values of tumour thrombi with a narrower range. The elevated ADC values of the liver parenchyma adjacent to portal vein emboli may be helpful for the diagnosis of bland thrombi.     

Role of diffusion-annealing temperature on the microstructural and superconducting properties of Cu-doped MgB2 superconductors

This study deals with not only investigate the effect of the copper diffusion on the microstructural and superconducting properties of MgB₂ superconducting samples employing dc resistivity as a function of temperature, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements but also calculate the diffusion coefficient and the activation energy of copper for the first time. Electrical-resistivity measurements indicate that both the room-temperature resistivity value and zero resistivity transition temperatures (T _c ) increase with increasing the diffusion-annealing temperature from 650 to 850?°C. SEM measurements show that not only the surface morphology and grain connectivity improve but also the grain size of the samples increases with the increase in the diffusion-annealing temperature up to 850?°C. As for the XRD results, all the samples contain the MgB₂ phase only and exhibit the polycrystalline superconducting phase with more intensity of diffraction lines, leading to the increasement in the lattice parameter a and c. Additionally, the diffusion coefficient is observed to increase from 6.81?×?10^?8 to 4.69?×?10^?7?cm²?s^?1 as the diffusion-annealing temperature increases, confirming that the Cu diffusion at lower temperatures is much less significant. Temperature dependence of the Cu diffusion coefficient is described with the aid of the Arrhenius relation D?=?3.75?×?10^?3 exp (?1.15?±?0.10?eV/k _B T) and the corresponding activation energy of copper in MgB₂ system is found to be about 1.15?eV. The possible reasons for the observed improvement in microstructural and superconducting properties of the samples due to Cu diffusion are also discussed.     

Active wrapping paper against mango anthracnose fungi and its releasing profiles

Active wrapping papers varied in bio‐based coating materials (chitosan and carboxymethyl cellulose) and vanillin concentrations (0.5%, 1.0%, 2.0%, and 4.0% (w/v)) were prepared to study their antifungal effects and release properties. Chitosan‐coated paper with 1% (w/v) vanillin gave the best inhibition against mycelial growth of mango anthracnose fungi and could inhibit its conidiospores germination. The release of vanillin from a chitosan‐coated paper under different conditions of temperatures (13°C, 25°C, and 37°C), relative humidity (RH) (75%, 86%, and 96% RH), and pH values (pH 3.8, 5.2, and 6.2) was studied. Moreover, the vanillin release from the paper to mango fruit under an actual commercial storage condition (13°C, 90% RH) was also investigated. The predominant mechanism of vanillin release under low temperatures (13‐25°C) and all RH studied was a Fickian diffusion, whereas the high temperature (37°C) and in all buffers varying pH showed a non‐Fickian behaviour. Increasing temperature and RH enhanced in diffusion coefficient (D value) from 78.24 × 10^?10 to 162.10 × 10^?10 cm²/s and 42.87 × 10^?10 to 59.98 × 10^?10 cm²/s, respectively. Meanwhile, the increasing pH value reduced the D value from 233.87 × 10^?10 to 122.74 × 10^?10 cm²/s. The kinetic of vanillin release under an actual wrapping application exhibited a non‐Fickian behaviour, and the D value was considerably low (approximately 65.36 × 10^?12 cm²/s). The developed active wrapping paper can be great interest for food industry and is practically reasonable for postharvest mango fruits.     

Thermal Characterization of PZT Ceramics Obtained by Mechanically Activated Mixed Oxides Using Different Pb Sources

In this study, three sets of PZT samples with compositions 57/43 and 55/45 (rhombohedral phase), 53/47 and 51/49 (tetragonal phase) prepared by mechanochemical activation of powder mixtures (during 4?h of milling) and thermal treatment (sintered at 1200?°C for 4?h) were thermally characterized. The three sets of compositions were prepared using different Pb sources (A-PbO, B-PbO₂, and C-Pb₃O₄). The thermal characterization of sintered samples was carried out by photoacoustic spectroscopy and differential scanning calorimetry, to obtain the thermal diffusivity and specific heat (c _p ). The DSC thermograms also allowed the determination of the Curie temperature, and the thermal conductivity was calculated combining the results of the thermal diffusivity, specific heat, and density. The samples obtained with Pb₃O₄ showed a theoretical density higher than 95?%, whereas those obtained from PbO₂ precursors showed a lower densification rate (around 89?%). The samples obtained with Pb₃O₄ with compositions 53/47 and 51/49 also showed the highest values of thermal diffusivity (7.3 ± 0.4)?× 10^?7m²· s^?1 and (6.6 ± 0.3)?× 10^?7m²· s^?1, respectively.     

The Prediction of the Dissolution Rate Constant by Mixing Rules: The Study of Acetaminophen Batches

The purpose of this article is to promote two simple and scalable methods to accelerate the formulation development of formulated granules using acetaminophen as a model system. In method I, formulated granules made from the batch of small particle–sized acetaminophen (1) by ball milling the batch of large particle–sized acetaminophen (2), and the mixture of the two batches at equal weights (mix) gave the dissolution rate constants (k) of k₁?=?0.43 ± 0.15 minutes^?1, k₂?=?0.18 ± 0.01 minutes^?1, and k_mix?=?0.30 ± 0.03 minutes^?1 for 75 wt percent formulation; k₁?=?0.75 ± 0.01 minutes^?1, k₂?=?0.18 ± 0.01 minutes^?1, and k_mix?=?0.34 ± 0.03 minutes^?1 for 62 wt percent formulation; and k₁?=?0.28 ± 0.01 minutes^?1, k₂?=?0.16 ± 0.01 minutes^?1, and k_mix?=?0.22 ± 0.02 minutes^?1 for 30 wt percent formulation. In method II, the mixture of the formulated granules produced by mixing the formulated granules from the two batches at equal weights gave dissolution rate constants of k_mix?=?0.30 ± 0.03 minutes^?1, 0.30 ± 0.02 minutes^?1, and 0.22 ± 0.01 minutes^?1 for 75 wt percent, 62 wt percent, and 30 wt percent formulations, respectively. After fitting the three data points of k₁, k₂, and k_mix to the 10 mixing rules in materials science—series mixing rule, Hashin and Shtrikman upper bound, logarithmic mixing, Looyenga mixing rule, effective media approximation (EMA), three-point lower bound, Torquato approximation, three-point upper bound, Maxwell mixing rule, and parallel mixing rule—we found that the selection of the best suited mixing rules based on k₁, k₂, and k_mix was solely dependent on the formulations under a given operating condition and regardless of whether the system was a powder mixture or a granular mixture. The values of k₁, k₂, and k_mix in both the 75 wt percent and 30 wt percent formulations were enveloped by the parallel mixing rule and Maxwell mixing rule, whereas the values of k₁, k₂, and k_mix for the 62 wt percent formulation were encompassed by the logarithmic mixing rule, Hashin and Shtrikman upper bound, and the series mixing rule. Apparently, the best suited mixing rules could be used to predict the right proportions of either the powder mixture (Method I) or the granular mixture (Method II) for obtaining any other desired dissolution rate constant, k_mix, whose value fell in between the values of k₁ and k₂.     

Structural design of Cr/GLC films for high tribological performance in artificial seawater: Cr/GLC ratio and multilayer structure

In this paper,graphite-like carbon(GLC)films with Cr buffer layer were fabricated by DC magnetron sputtering technique with the thickness ratio of Cr to GLC films varying from 1:2 to 1:20.The effect of Cr/GLC modulation ratio on microstructure,mechanical and tribological properties in artificial seawater was mainly investigated by scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),nano-indenter and a reciprocating sliding tribo-meter.The propagation of defects plays an important role in the evolution of delamination,which is critical to wear failure of GLC films in artificial seawater.Designing the proper multilayer structure could inhibit the defects propagation and thus protect the basis material.The multilayer Cr/GLC film with optimized ratio of 1:3 demonstrates a low average friction coefficient of 0.08±0.006 and wear rate of(2.3±0.3)×10~(-8)mm~3/(N m)in artificial seawater,respectively.     

Development and uniform evaluation of ropinirole osmotic pump tablets with REQUIP XL both in vitro and in beagle dogs

REQUIP XL, prolonged release formulation of ropinirole hydrochloride (RH) in market, could release ropinirole constantly and showed satisfactory therapeutic effect and good compliance. REQUIP XL was composed of more than 10 kinds of excipients and prepared by Geomatrix technology, which was complex and laborious. The purpose of this study was to obtain a dosage form of RH with similar in vitro release profile and bioequivalence in vivo compared to REQUIP XL. Osmotic pump tablet combined with fast release phase was selected as the delivery system of RH and similar release curves were obtained in different media. The tablets were also administered to beagle dogs and the pharmacokinetic parameters were calculated using a non-compartmental model. C_max, t_max, mean residence time (MRT), and area under the curve from 0 to 24?h (AUC_0–24) were 3.97?±?0.53?ng/mL, 3.58?±?0.49?h, 8.29?±?0.93?h, and 35.20?±?8.11?ng/mL???h for ropinirole osmotic pump tablets (ROPT) and 4.15?±?1.07?ng/mL, 2.92?±?0.49?h, 7.84?±?1.09?h, and 34.34?±?10.06?ng/mL???h for REQUIP XL. The log-transformed mean C_max and AUC_0–24 of ROPT were about 92.15% and 102.49% relative to that of REQUIP XL, respectively. The 90% confidence intervals of C_max and AUC_0–24 for ROPT were 75.69–115.31% and 88.89–122.30%, respectively. So it could be concluded that ROPT was uniform with REQUIP XL both in vitro and in beagles and the release profiles of Geomatrix technology may be obtained by osmotic pump combined with fast release technology.     

Near‐threshold fatigue crack growth properties of wrought magnesium alloy AZ61 in ambient air,dry air,and vacuum

Environmental influences on near‐threshold fatigue crack growth in wrought magnesium alloy AZ61 were investigated. Fatigue tests were performed in ambient (humid) air, dry air, vacuum, and dry nitrogen gas at 19 kHz cycling frequency and load ratio R = ?1. Threshold stress intensity factor amplitudes, K_th, determined for limiting growth rates below 5 × 10^?13 m/cycle were 1.1 MPam^1/2 in ambient air and 1.2 MPam^1/2 in dry air. A much higher K_th of 1.9 MPam^1/2 was measured in vacuum and dry nitrogen gas. This suggests oxygen to be the most detrimental constituent of ambient air that increases near‐threshold crack propagation rates and decreases K_th. The deleterious effect of humidity is comparatively small. Corrosive influences are effective at ultrasonic cycling frequency for growth rates below approximately 3 × 10^?9 m/cycle. The crack propagation curves in ambient and dry air show a plateau‐like regime where the fracture mode changes from purely ductile to a mixed ductile and brittle mode. In vacuum and dry nitrogen gas, a ductile crack path is found for all investigated crack growth rates.     

Biodegradable nanoparticles for improved kidney bioavailability of rhein: preparation,characterization, plasma,and kidney pharmacokinetics

The aim of this work is to develop biodegradable nanoparticles for improved kidney bioavailability of rhein (RH). RH-loaded nanoparticles were prepared using an emulsification solvent evaporation method and fully characterized by several techniques. Kidney pharmacokinetics was assessed by implanting a microdialysis probe in rat's kidney cortex. Blood samples were simultaneously collected (via femoral artery) for assessing plasma pharmacokinetics. Optimized nanoparticles were small, with a mean particle size of 132.6?±?5.95?nm, and homogeneously dispersed. The charge on the particles was nearly zero, the encapsulation efficiency was 62.71?±?3.02%, and the drug loading was 1.56?±?0.15%. In vitro release of RH from the nanoparticles showed an initial burst release followed by a sustained release. Plasma and kidney pharmacokinetics showed that encapsulation of RH into nanoparticles significantly increased its kidney bioavailability (AUC_kidney/AUC_plasma?=?0.586?±?0.072), clearly indicating that nanoparticles are a promising strategy for kidney drug delivery.