[en] The aim of this paper is to improve the understanding of deformation of micro medical needle and thread during assembly and then to develop an economical and flexible deformation method. Therefore, the swaging process is computationally simulated with the finite element method in this paper. A commercially available explicit nonlinear finite element analysis code, LS-Dyna, is used to model the 3-D deformation and contact problem. As the firmness of the assembly on the needle depends on the contact force and friction, the contact and the slide between the needle and thread are taken into account in the simulation. The general surface-to-surface contact algorithm (STS) is used to simulate the contact.The paper provides an insight into the deformation of the micro products

[en] Five novel coordination polymers, [Co(bpb)₂Cl₂] (1), [Co(bpb)₂(SCN)₂] (2), [Cd(H₄bpb)_0.5(dmf)(NO₃)₂] (3), [Cd₂(H₄bpb)Br₄] (4), and [Hg₂(H₄bpb)I₄] (5) [bpb=N,N'-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine, H₄bpb=N,N'-bis(3-pyridylmethyl)-1,4-benzenedimethylamine], were synthesized and their structures were determined by X-ray crystallography. In the solid state, complex 1 is a 1D hinged chain, while 2 has 2D network structure with the ligand bpb serving as a bridging ligand using its two pyridyl N atoms. The imine N atoms keep free of coordination and bpb acts as a bidentate ligand in both 1 and 2. Complexes 3, 4, and 5 with reduced bpb ligand, i.e. H₄bpb, show similar 2D network structure, in which ligand H₄bpb serves as a tetradentate ligand. Thermogravimetric analyses for complexes 1-5 were carried out and found that they have high thermal stability. The magnetic susceptibilities of compounds 1, 2 were measured over a temperature range of 75-300 K

[en] Purpose: To quantify the target volume and organ at risk of nasopharyngeal carcinoma (NPC) patients with preradiation chemotherapy based on CT scanned during intensity-modulated radiotherapy (IMRT), and recalculate the dose distribution. Methods: Seven patients with NPC and preradiation chemotherapy, treated with IMRT (35 to 37 fractions) were reviewed. Repeat CT scanning was required to all of the patients during the radiotherapy, and the number of repeat CTs varies from 2 to 6. The plan CT and repeat CT were generated by different CT scanner. To ensure crespectively on the same IMPT plan. The real dose distribution was calculated by deformable registration and weighted method in Raystation (v 4.5.1). The fraction of each dose is based on radiotherapy record. The volumetric and dose differences among these images were calculated for nascIpharyngeal tumor and retro-pharyngeal lymph nodes (GTV-NX), neck lymph nodes(GTV-ND), and parotid glands. Results: The volume variation in GTV-NX from CT1 to CT2 was 1.15±3.79%, and in GTV-LN −0.23±4.93%. The volume variation in left parotid from CT1 to CT2 was −6.79±11.91%, and in right parotid −3.92±8.80%. In patient 2, the left parotid volume were decreased remarkably, as a Result, the V30 and V40 of it were increased as well. Conclusion: The target volume of patients with NPC varied lightly during IMRT. It shows that preradiation chemotherapy can control the target volume variation and perform a good dose repeatability. Also, the decreasing volume of parotid in some patient might increase the dose of it, which might course potential complications

[en] The crystallographic structure and magnetic properties of Sm₂(Fe_1-xCo_x)₁₇C with x equal to 0.0, 0.1, 0.2, 0.3, 0.4, 0.7, and 1.0, and Y₂(Fe_1-xCo_x)₁₇C with x equal to 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 1.0 have been investigated. They crystallize in the rhombohedral Th₂Zn₁₇-type structure or the hexagonal Th₂Ni₁₇-type structure. The Curie temperatures increase with increasing cobalt content and the saturation magnetizations reach a maximum at x=0.3. All Sm₂(Fe_1-xCo_x)₁₇C compounds have an easy axis, but the anisotropy fields have a dependence on cobalt content. Both Y₂Fe₁₇C and Y₂Co₁₇C have an easy plane. However, an easy axis is found in a concentration range with 0.4< x<0.9 for the substituted Y₂(Fe_1-xCo_x)₁₇C compounds

[en] We present a novel approach to the synthesis of inorganic sol-gel microspheres for encapsulating organic and bioactive molecules, and controlling their subsequent release kinetics. The bioactive species are incorporated, at ambient temperature, into the inorganic particles using an emulsion gelation process. Independent control of the release rate (by adapting the nanostructure of the internal pore network to the physico-chemical properties of the bioactive molecules) and particle size (by tailoring the emulsion chemistry) is demonstrated. Sol-gel chemistry has been shown to be a flexible technique for producing inorganic silica matrices with tailored microstructures, which can be used for the encapsulation and controlled release of organic and bioactive molecules. The present paper extends this concept by combining sol-gel chemistry with an emulsion approach for producing inorganic particles with controlled dimensions, and demonstrates how the particle size and microstructure can be independently controlled. Sol-Gel Chemistry and Encapsulation of Model Compounds. A stock solution of 4-(2-hydroxy-l-naphthylazo) benzene sulfonic acid (Orange II) was produced by dissolving Orange II in water (0.1 wt%), and adjusting the pH to the required value. Sol-gel solutions were subsequently prepared by mixing the aqueous solution with tetramethylorthosilicate (TMOS) and methanol (MeOH), to achieve H₂O:TMOS (W] and MeOH:TMOS mole ratios (D) of four. The resulting solution was stirred and left to age at ambient temperature for one day. A transparent emulsion was prepared by mixing selected surfactants and organic solvents. The surfactants used included sorbitan monooleate, sorbitan monolaurate and bis-2-ethylhexylsulfo-succinate (AOT), while the organic phase was typically chosen from the group consisting of kerosene, hexane, heptane, octane, decane, dodecane and cyclohexane. The sol-gel solution was added to the emulsion, and the resulting mixture was stirred at 500 rpm for one hour. The particles thus produced were washed with cyclohexane and carefully dried. Release Kinetics. The release of the encapsulated species from the particles was monitored by placing a fixed quantity of the sample in water or physiological saline, and monitoring the concentration of the released species using UV/Vis spectroscopy. The fraction released was normalised to the total mass initially encapsulated. The influence of the emulsion chemistry on the size of the microspheres obtained at pH 2 is illustrated in Figure 1 for microspheres containing encapsulated Orange II Using essentially identical sol-gel chemistries, particles with dimensions ranging from 50 nm to 50 μm can be readily obtained. The size of the particles is controlled by the size of the emulsion droplets, which act as micro-reactors for the sol-gel reactions. In turn, the size of the droplets is determined predominantly by the hydrophile/lipophile balance of the surfactant/ solvent couple and by processing parameters such as the water to surfactant ratio and the concentration of surfactant. The effect of sol-gel processing parameters on the morphology and associated release kinetics is illustrated in Figure 2. Although both samples have essentially identical particle sizes (not shown), their morphologies are significantly different. Processing under acidic conditions leads to the formation of nanosized linear silicate 'building block' which are woven tightly together in the final gel matrix, to produce a microporous material (pore diameters < 2 run). In contrast, three-dimensional fundamental particles are produced under basic conditions, leading to the formation of mesoporous gels (pore diameters > 2 nm). The different morphologies are clearly reflected in the release rate of the encapsulated species from the respective matrices; rapid release kinetics are evident for the mesoporous material (high pH), while significantly slower release rates are obtained for the microporous material (low pH). A combined sol-gel/emulsion processing method has been developed to produce inorganic matrices with tailored nanostructures containing encapsulated organic and bioactive molecules. Control of the release kinetics is achieved by tailoring the internal nanostructure of the matrix during synthesis and encapsulation, while the particle size of the matrices is controlled through the emulsion chemistry. This approach enables the size and internal structure of the matrices to be independently controlled. The wide range of particle size (from nanometers to microns), combined with the potential to control the release kinetics independently from the particle size, make this technology very attractive for a wide range of therapeutic applications

[en] Neutron diffraction experiments on Y(Ti,Fe)₁₂ have been carried out to investigate the crystallographic structure and magnetic properties of these compounds. In the ThMn₁₂-type structure, with a space group of I4/mmm, Fe and Ti atoms are distributed on three nonequivalent crystallographic sites. A preferential site occupation for Fe and Ti is observed. The detailed analysis of crystallographic and magnetic arrangement are reported

[en] The RTiFe₁₁N_x compounds have higher Curie temperatures, larger saturation magnetization, and entirely different magnetocrystalline anisotropy behavior as compared with the RTiFe₁₁ compounds. In contrast to RTiFe₁₁, the c axis becomes the easy magnetization direction of RTiFe₁₁N_x when R=Nd, Tb, Dy, and Ho, while SmTiFe₁₁N_x has an easy plane and ErTiFe₁₁N_x presents a spin reorientation at about 45 K. Theoretical calculations were made to explain those anisotropy behaviors. The calculation results show that the changes in anisotropy behaviors could be attributed to the large positive contribution of nitrogen atoms located at 2b interstitial sites to the second-order crystal-field coefficient A₂₀

[en] An effective method for the development of magnetic materials with high microwave permeability on the basis of carbonyl iron powders has been proposed. This method consists in the modification of particle morphology from the spherical shape into flaky one with subsequent silica coating of the flakes by sol-gel method. Composites with submicron flaky iron powders (thickness < 1 μm) exhibit remarkable improvement in the microwave magnetic spectra compared to the spherical powder based composites. Even a thin silica overlayer provides a sufficient insulation of the metal particle and decreases the permittivity values.

[en] Full text: The controlled release of drugs, encapsulated within nanoparticles, has been achieved by a variety of microencapsulation techniques, including, liposomes, hydrogels and polymeric materials, which are based on organic carrier systems. We have been studying inorganic nanoparticles as they possess several intrinsic advantages as drug carriers for in-vivo applications. In particular, they are biologically inert, intrinsically hydrophilic and exhibit a long shelf life in the 'dry' state. Recently, we have developed a suite of sol-gel techniques for producing nanoparticulate silica containing encapsulated bioactive species using water-in-oil microemulsions. The internal nanostructure of the gels (pore volume, size and tortuosity, and surface chemistry), which controls the release kinetics of the bioactive species, can be precisely tailored by varying such sol-gel processing parameters as the water-to-alkoxide ratio, pH, alkoxide concentration, ageing, and drying conditions. Prior to encapsulation of the drug it is vital to understand the mechanism of particle formation. The effect of processing parameters, such as the pH of the aqueous core on the mechanism and kinetics of reactions occurring during nanoparticle evolution, have been investigated. Scattering methods including SANS, SAXS and light scattering, in conjunction with complementary spectroscopic techniques, have been used to probe the evolution of silica nanoparticle structure during the hydrolysis and condensation of tetramethylorthosilicate (TMOS) within the aqueous core of the w/o microemulsions. Photon correlation spectroscopy has revealed the micelle diameter to be 10-12nm. Particle evolution at various pH was monitored using SANS and the rate of hydrolysis has been studied with FTIR, revealing that particle formation appears to be more rapid in base than in acid conditions

[en] We investigate superconductivity in the compound FeSe_0.5Te_0.5 and in its transition-metal-substituted derivatives Fe_1-xTM_xSe_0.5Te_0.5, where x = 5% and the substituent ions studied were Mn, Co, Ni, Cu and Zn. Electronic and magnetic measurements indicate that doping with Mn or by Co acts respectively to cause a slight enhancement or suppression of the transition temperature. However, doping with this concentration of Ni or Cu destroys the superconductivity completely, and leads to semiconducting behaviour. Zn ions cannot be incorporated properly into the parent compound. The reasons for these contrasting effects are associated with the differing magnetic properties of the substituent ions, which determine their local impurity moments and the net carrier concentrations in the doped 11 system. The effects of magnetic ion substitution on superconductivity suggest that the pairing symmetry may not be either pure s wave or pure d wave.