Dispersion polymerization of acrylonitrile using a poly(ethylene glycol)-b-polyacrylonitrile macro-RAFT agent

Polyacrylonitrile (PAN) nanoparticles were successfully prepared by dispersion polymerization of acrylonitrile (AN) in water using 10 and 20 wt% of the poly(ethylene oxide)-b-PAN macromolecular RAFT (PEO-b-PAN macro-RAFT) agent (M _n=5,600 g/mol, PDI=1.15). The degrees of polymerization of the PEO and PAN blocks were 113 and 16, respectively. The PAN nanoparticles had a crumpled spherical appearance and their sizes ranged from 50–80 nm. The degree of crystallinity of the PAN particles was 23 %. The M _n values of the PAN nanoparticles prepared with 10 and 20 wt% of the PEO-b-PAN macro-RAFT agent were 33,900 and 25,800 g/mol, respectively. The existence of the PEO block on the surface of the PAN nanoparticles was confirmed by ¹H NMR spectroscopy and XPS.     

Supplement of autologous ooplasm into porcine somatic cell nuclear transfer embryos does not alter embryo development

Somatic cell nuclear transfer (SCNT) is considered as the technique in which a somatic cell is introduced into an enucleated oocyte to make a cloned animal. However, it is unavoidable to lose a small amount of the ooplasm during enucleation step during SCNT procedure. The present study was aimed to uncover whether the supplement of autologous ooplasm could ameliorate the oocyte competence so as to improve low efficiency of embryo development in porcine SCNT. Autologous ooplasm‐transferred (AOT) embryos were generated by the supplementation with autologous ooplasm into SCNT embryos. They were comparatively evaluated with respect to embryo developmental potential, the number of apoptotic body formation and gene expression including embryonic lineage differentiation, apoptosis, epigenetics and mitochondrial activity in comparison with parthenogenetic, in vitro‐fertilized (IVF) and SCNT embryos. Although AOT embryos showed perfect fusion of autologous donor ooplasm with recipient SCNT embryos, the supplement of autologous ooplasm could not ameliorate embryo developmental potential in regard to the rate of blastocyst formation, total cell number and the number of apoptotic body. Furthermore, overall gene expression of AOT embryos was presented with no significant alterations in comparison with that of SCNT embryos. Taken together, the results of AOT demonstrated inability to make relevant values improved from the level of SCNT embryos to their IVF counterparts.     

Effects of a bio-assay guided fraction from Polygonum cuspidatum root on the viability,acid production and glucosyltranferase of mutans streptococci

Polygonum cuspidatum root has been traditionally used for the treatment of dental diseases in Korea. The purpose of this study was to evaluate effects of P. cuspidatum root on the development of dental caries, especially its effects against bacterial viability and caries-inducing factors of Strptococcus mutans and Strptococcus sobrinus. Among methanol extract of P. cuspidatum root and its fraction tested, ethyl acetate fraction, composed of polydatin, resveratrol, anthraglycoside B, and emodin, showed inhibitory effects on glycolytic acid production and glucosyltransferase activity of S. mutans and S. sobrinus in addition to antibacterial activities.     

Tracheal gas isufflation-aided mechanical ventilation during carbon dioxide-induced pneumoperitoneum in rabbits

Despite numerous benefits of laparoscopic procedures, the serious hypercapnia and respiratory acidosis in hypercapnic patients with decreased pulmonary compliance during carbon dioxide-induced pneumoperitoneum (CDP) may be developed. Tracheal gas insufflation (TGI) has been shown to be a useful adjunct to controlled mechanical hypoventilation. This study was undertaken to identify whether TGI superimposed on controlled mechanical ventilation (CMV) improve ventilatory efficiency during CDP in rabbits. Sixteen paralyzed and anesthetized rabbits were used. The animals were assigned to two groups-CMV group: CMV alone; TGI group: CMV superimposed by TGI with flow rate of 2L/min. The animals were insufflated to intra-abdominal pressure of 8 mmHg with CO2 gas. Then, tidal volume (V(T)) was changed to maintain the set peak inspiratory pressure (PIP) value, while other ventilatory settings were kept constant. The set PIP value corresponding to 30, 60, and 90 min after the start of peritoneal insufflation of CO2 were 15, 22, and 25 cm H2O, respectively. During CDP with TGI, PaCO2 decreased significantly (p<0.01) from CMV without TGI of 82.1 +/- 14.1 to 47.5 +/- 5.5, 58.1 +/- 9.9 to 40.0 +/- 4.6, 47.1 +/- 9.4 to 32.7 +/- 5.1 mmHg at PIP of 15, 22, and 25 cm H2O, respectively. The inspired V(T) decreased significantly (p<0.05) from CMV without TGI of 18.4 +/- 3.9 to 12.8 +/- 2.8 ml at PIP of 15 cm H2O. TGI superimposed on CMV is more effective than CMV alone in enhancing ventilatory efficiency during CDP in rabbits.     

Pathological characterization of TgElk mice injected with brain homogenate from elk with chronic wasting disease

Chronic wasting disease (CWD) is classified as a transmissible spongiform encephalopathy or prion disease that affects cervids. CWD has been reported in 15 US states, two Canadian provinces, and in imported elk on several farms in Korea. This study was conducted to examine the molecular biological and pathogenic characteristics of a CWD-associated prion isolated in Korea. The epidemiological origin of this pathogen was also determined. Homozygous TgElk mice were infected with a CWD-affected elk brain pool prepared from the brain of an imported Canadian elk. We measured the incubation time of the pathogen, neuropathological changes by immunohistochemical staining, the pattern(s) of scrapie prion protein (PrP^Sc) deposition, and PrP^Sc protein profiles by Western blotting. We found that TgElk mice infected with brain homogenate from the elk suffering from CWD showed incubation times, vacuolar degeneration, and PrP^Sc accumulation similar to those previously reported in the literature. Our results suggest that homozygous TgElk mice efficiently transmit CWD with short incubation times and that this animal can serve a valuable research model and reliable in vivo diagnostic tool.     

Relationship between genetic divergence and hybrid performance in japonica rice grown in a cold water-irrigated field

The present study was carried out to evaluate genetic divergence among eleven japonica rice cultivars and to assess the relationship between genetic distance and hybrid performance in partial non-reciprocal crosses among them. The 44 F1 hybrids along with the eleven parents were evaluated for five cold tolerance-related traits; discoloration at seedling stage, days to heading, culm length, fertility, and spikelets per panicle in a cold water screening nursery (17 ^°C). The eleven parents were examined for DNA polymorphism using amplified fragment length polymorphisms(AFLPs). A total of 855 polymorphic variants were generated and based on the polymorphism data, genetic distances (GDs) ranged from 0.023 to0.524. Very little heterosis was observed in hybrids for most of the traits,whereas heterosis was high for fertility. The correlation values of GDs with F1 performance were mostly non-significant except for discoloration and fertility. The correlations of GDs with mid-parent and better-parent heterosis were not significant and proved to be of no predictive value. Our results indicate that GDs based on AFLP markers are not useful for predicting heterosis for cold tolerance in japonica hybrids. This revised version was published online in August 2006 with corrections to the Cover Date.     

Predicting the tensile strength of needle-punched nonwoven mats using X-ray computed tomography and a statistical model

As nonwoven mats are randomly oriented fiber assemblies, the tensile strength of nonwoven mats is determined by their microstructural factors, such as fiber orientation, fiber volume fraction, and fiber-fiber contact level. The complex microstructure of nonwoven mats must be reasonably simplified to properly predict their mechanical properties within affordable efforts. In this study, a new parameter, so called contact efficiency, is defined to describe the fiber-fiber contact level of nonwoven mats. Micro X-ray computer tomography (CT) is employed to characterize the microstructure of needlepunched nonwoven mats made of polypropylene short fibers. The fiber orientation and volume fraction are obtained by analyzing 2D sectional CT image of the nonwoven mat, while the contact efficiency is determined from 3D CT image. A statistical model, developed originally for staple yarns, is modified to predict the tensile strength of the nonwoven mat using the microstructural factors obtained from CT analysis. The prediction is then compared with experiments to validate that the current model incorporating the contact efficiency is highly suitable for predicting the tensile strength of nonwoven mats.     

Preparation,chemical, and thermal characterization of nylon 4/6 copolymers by anionic ring opening polymerization of 2-Pyrrolidone and ε-Caprolactam

Nylon 4/6 copolymers based on 2-pyrrolidone (C4) and ε-caprolactam (C6) were synthesized and characterized as part of ongoing efforts to develop thermally stable, melt-processable 2-pyrrolidone (C4) based Nylons. Copolymers of various compositions were synthesized at between 50 and 100 °C via the anionic ring opening polymerization of C4 and C6 using a potassium tert-butoxide catalyst and a benzoyl chloride initiator. The polymers were characterized by NMR spectroscopy, DSC, TGA, GPC, intrinsic viscosity measurements, and X-ray scattering (SAXS and WAXS). Their chemical compositions and sequence distributions were obtained by ¹H- and ¹³C-NMR spectroscopies, respectively. X-ray scattering was used to investigate the lamellar morphologies and the crystal structures of solvent cast films of the copolymers. WAXS revealed the presence of α-phase crystals in the copolymers. TGA data coupled with molecular weight and sequence distribution information indicated that the polymers’ thermal stability depended on both their chemical composition and their sequence distribution.     

Enhanced electrical properties of electrospun nylon66 nanofibers containing carbon nanotube fillers and Ag nanoparticles

In this study, we describe the preparation and characterization of electrospun Nylon66 composite nanofibers incorporated with carbon nanotubes (CNT) fillers and silver nanoparticles. We have incorporated the composites in to Nylon66 nanofibers to enhance the characteristics of the resultant composite nanofibers. The resultant composite nanofibers were characterized by using field-emission scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, X-ray diffraction, and current-voltage (I–V) measurement analysis. The morphology of the composite nanofibers exhibited densely arranged mesh-like ultrafine nanofibers which were strongly bound in between the main fibers. From I–V characteristics, it was observed that the incorporation of CNT fillers and Ag nanoparticles in to electrospun Nylon66 composite nanofibers can be significantly enhanced the electrical properties.     

Dimensional stability of cotton-spandex interlock structures under relaxation

In this study, dimensional characteristics of core spun cotton/spandex interlock structures with high, medium and low tightness factors were studied under dry-, wet-, and full relaxation conditions. Results are compared with those for similar fabrics knitted from 100 % cotton. Dimensional characteristics of samples of core-spun cotton/spandex and cotton are measured by considering the changing of course-, wale- densities and stitch densities under dry, wet and full relaxation conditions. Based on these data, dimensional constants (U-values) were predicted under 95 % significance level. Higher U-values are reported with cotton/spandex interlocks than 100 % cotton and under full relaxation, cotton/spandex shows the U-values with lesser CV%. Stitch density growth is linearly correlated with tightness factor for both interlock material structures. Excellent resiliency property of cotton/spandex yarns increases tightness factors at machine off state and during relaxation states. Cotton/spandex interlock structures show more prominent co-relationship with their tightness factors on their dimensional parameters.