Generation of Haploid Spermatids on Silk Fibroin-Alginate-Laminin-Based Porous 3D Scaffolds

In vitro production of sperm is a desirable idea for fertility preservation in azoospermic men and prepubertal boys suffering from cancer. In this study, a biocompatible porous scaffold based on a triad mixture of silk fibroin (SF), alginate (Alg), and laminin (LM) is developed to facilitate the differentiation of mouse spermatogonia stem cells (SSCs). Following SF extraction, the content is analyzed by SDS-PAGE and stable porous 3D scaffolds are successfully prepared by merely Alg, SF, and a combination of Alg-SF, or Alg-SF-LM through freeze-drying. Then, the biomimetic scaffolds are characterized regarding the structural and biological properties, water absorption capacity, biocompatibility, biodegradability, and mechanical behavior. Neonatal mice testicular cells are seeded on three-dimensional scaffolds and their differentiation efficiency is evaluated using real-time PCR, flow cytometry, immunohistochemistry. Blend matrices showed uniform porous microstructures with interconnected networks, which maintained long-term stability and mechanical properties better than homogenous structures. Molecular analysis of the cells after 21 days of culture showed that the expression of differentiation-related proteins in cells that are developed in composite scaffolds is significantly higher than in other groups. The application of a composite system can lead to the differentiation of SSCs, paving the way for a novel infertility treatment landscape in the future.     

The Fermi-Walker Derivative on the Spherical Indicatrix of a Space Curve

In this paper Fermi-Walker derivative and Fermi-Walker parallelism and non-rotating frame concepts are given along the spherical indicatrix of a curve in E ³. First, we consider a curve in Euclid space and investigate the Fermi-Walker derivative along the tangent. The concepts which Fermi-Walker derivative are analyzed along its tangent. Then, the Fermi-Walker derivative and its theorems are analyzed along the principal normal indicatrix and the binormal indicatrix of any curve in E ³.     

Pyrolysis of polyphenylenes with PCL or/and PSt side chains

Thermal degradation characteristic of polyphenylenes is an important issue for developing a rational technology of polymer processing and applications. In this study, we discussed thermal degradation of polyphenylenes (PP) with poly(-caprolactone) (PCL) and/or PCL/polystyrene copolymers (PSt) prepared by combined controlled polymerization and cross-coupling processes via direct pyrolysis mass spectrometry. When PP-graft-PCL/PSt copolymers were considered, thermally less stabile PCL side chains decomposed in the first step. In the second stage of pyrolysis, the decomposition of the polystyrene chains has taken place. A slight increase in thermal stability of PCL chains for PP-graft-PCL/PSt copolymers was noted compared to copolymer PP-graft-PCL due to the interaction between PSt and PCL chains. This interaction was stronger when PSt chains were linked to the 2-position of the 1,4-phenylene ring.     

Development of agriculture biotechnology in Pakistan

Agriculture plays an important role in the national economy of Pakistan, where most of the rapidly increasing population resides in rural areas and depends on agriculture for subsistence. Biotechnology has considerable potential for promoting the efficiency of crop improvement, food production, and poverty reduction. Use of modern biotechnology started in Pakistan since 1985. Currently, there are 29 biotech centers/institutes in the country. However, few centers have appropriate physical facilities and trained manpower to develop genetically modified (GM) crops. Most of the activities have been on rice and cotton, which are among the top 5 crops of Pakistan. Biotic (virus/bacterial/insect) and abiotic (salt) resistant and quality (male sterility) genes have already been incorporated in some crop plants. Despite acquiring capacity to produce transgenic plants, no GM crops, either produced locally or imported, have been released in the country. Pakistan is signatory to the World Trade Organization, Convention on Biological Diversity, and Cartagena protocols. Several legislations under the Agreement on Trade-Related Aspects of Intellectual Property Rights have been promulgated in the country. National Biosafety Guidelines have been promulgated in April 2005. The Plant Breeders Rights Act, Amendment in Seed Act-1976, and Geographical Indication for Goods are still passing through discussion, evaluation, and analysis phases. Meanwhile, an illegal GM crop (cotton) has already sneaked into farmer's field. Concerted and coordinated efforts are needed among various ministries for implementation of regulation and capacity building for import/export and local handling of GM crops. Pakistan could easily benefit from the experience of Asian countries, especially China and India, where conditions are similar and the agriculture sector is almost like that of Pakistan. Thus, the exchange of information and experiences is important among these nations.     

A hierarchical self-assembly route to three-dimensional polymer-quantum dot photonic arrays

We demonstrate a new hierarchical self-assembly strategy for the formation of photonic arrays containing quantum dots (QDs), in which sequential self-assembly steps introduce organization on progressively longer length scales, ranging from the nanoscale to the microscale regimes. The first step in this approach is the self-assembly of diblock copolymers to form block ionomer reverse micelles (SA1); within each micelle core, a single CdS QD is synthesized to yield the hybrid building block BC-QD. Once SA1 is completed, the hydrophobic BD-QD building blocks are blended with amphiphilic block copolymer stabilizing chains in an organic solvent; water addition induces secondary self-assembly (SA2) to form quantum dot compound micelles (QDCMs). Finally, aqueous dispersions of QDCMs are slowly evaporated to induce the formation of three-dimensional (3D) close-packed arrays in a tertiary self-assembly step (SA3). The resulting hierarchical assemblies, consisting of a periodic array of hybrid spheres each containing multiple CdS QDs, exhibit the collective property of a photonic stop band, along with photoluminescence arising from the constituent QDs. A high degree of structural control is possible at each level of organization by judicious selection of experimental variables, allowing various parameters governing the collective optical properties, including QD size, nanoparticle spacing, and mesocale periodicity, to be independently tuned. The resulting control over optical properties via successive self-assembly steps should provide new opportunities for hierarchical materials for QD lasers and all-optical switching.     

Wavelength Flexibility in Photoinitiated Cationic Polymerization

The spectral sensitivity of onium salt photoinitiators in cationic polymerization can be tuned from the short wavelength region of the UV spectrum to wavelengths up to the visible region by using direct and indirect activation, respectively. Indirect activation is based on the electron transfer reactions between onium salts and free radical photoinitiators, appropriate sensitizers and compounds capable of forming charge transfer complexes. Bisacylphosphine oxides, dimanganese decacarbonyl in conjunction with alkyl halides and titanocene type photoinitiators such as Irgacure 784 were shown to be useful free radical promoters providing the possibility of performing cationic polymerization in the long wavelength and visible region. The synthetic routes to prepare block copolymers by using electron transfer photosensitization and free radical promoted cationic polymerization are also described.     

Synthesis and Characterization of α,ω‐Heterofunctional Poly(ethylene oxide) Macromonomers

A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of ¹H NMR analysis.

     

Block copolymers of thiophene-capped poly(methyl methacrylate) with pyrrole

Poly(methyl methacrylate) with a thiophene end group having narrow polydispersity was prepared by the Atom Transfer Radical Polymerization (ATRP) technique. Subsequently, electrically conducting block copolymers of thiophene-capped poly(methyl methacrylate) with pyrrole were synthesized by using p-toluene sulfonic acid and sodium dodecyl sulfate as the supporting electrolytes via constant potential electrolysis. Characterization of the block copolymers were performed by CV, FTIR, SEM, TGA, and DSC analyses. Electrical conductivities were evaluated by the four-probe technique. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4218–4225, 1999     

New exact solutions of the space-time fractional cubic Schrodinger equation using the new type F-expansion method

In this study, a more general version of F-expansion method is proposed. With this offered method, more than one Jacobi elliptic functions are located in the solution function. We seek analytical solutions of the space-time fractional cubic Schrodinger equation by use of the new type of F-expansion method. Consequently, multifarious exact analytical solutions consisting of single, double, and multiple combined Jacobi elliptic functions solutions are acquired.