Physical properties of cellulose nanocrystal/magnesium oxide/chitosan transparent composite films for packaging applications.

Hitherto unreported hybrid nanofillers (CNC:MgO) reinforced chitosan (CTS) based composite (CNC:MgO)/CTS films were synthesized using a solution-casting blend technique and synergistic effect of hybrid nanofiller in terms of properties enhancement were investigated. Optical microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) technique, fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) were used to characterize the films. The hybrid nanofiller considerably changed the transparency and color of the CTS films. The tensile strengths of (3 wt%) CNC/CTS, (3 wt%) MgO/CTS, (1:1)(CNC:MgO)/CTS, (1:2)(CNC:MgO)/CTS and (2:1)(CNC:MgO)/CTS films were 27.49 %, 35.60 %, 91.62 %, 38.22 %, and 29.32 % higher than pristine CTS films respectively, while the water vapor permeation were 28.21 %, 30.77 %, 34.62 %, 38.46 %, and 37.44 % lower than pristine CTS film, respectively. Moreover, the CTS composite films exhibited an improvement in overall water barrier properties after incorporating hybrid nanofillers. Our observations suggest that chitosan-based hybrid nanofiller composite films are a good replacement for plastic-based packaging materials within the food industry.

Hydrophilicity and hydrophobicity consideration of organic surfactant compounds: Effect of alkyl chain length on corrosion protection.

Organic compounds have been recognized as one of the utmost operative corrosion protective measures. However, their usage and synthesis are allied with the consumption and release of malignant materials. More so, out of various manufactured and settled compounds, only a few are effective. Therefore, the high mandate is to design and formulate effective compounds based on literature outcomes. Literature outcomes suggest that surfactant molecules having alkyl substituent of neither too small nor too large act as effective aqueous phase corrosion inhibitors. The present review describes the effect of alkyl/hydrocarbon chain length on the corrosion inhibition potential of some series of surfactant molecules. Generally, an increase in the alkyl chain length favors inhibition performance due to enhancing the packing of surfactant molecules at the interface of metal and electrolyte, but a very high level of hydrophobicity disfavors the inhibition performance. Hydrophilicity and hydrophobicity can be suitably tailored by varying the number and size of the hydrocarbon chain. Organic compounds containing the hydrocarbon chain length of C12-C16 exhibit the best inhibition efficiency (%IE). The molecules become effective by adsorbing on the metal surface. They behave as mixed- and interface-type corrosion inhibitors.

The facile and low temperature synthesis of nanophase hydroxyapatite crystals using wet chemistry.

A simple and facile wet chemistry route was used to synthesize nanophase hydroxyapatite (HaP) crystals at low temperature. The synthesis was carried out at a pH of 11.0 and at a temperature of 37°C. The resulting samples were washed several times and subjected to further analysis. XRD studies revealed that the HaP crystals were polycrystalline in nature with a crystallite size of ~15-60 ± 5 nm. SEM-EDXA images confirmed the presence of calcium (Ca), phosphorous (P), and oxygen (O) peaks. Likewise, FTIR confirmed the presence of characteristic phosphate and hydroxyl peaks in samples. Lastly, HRTEM images clearly showed distinctive lattice fringes positioned in the 100 and 002 planes. TGA analysis shows that HaP crystals can withstand higher calcination temperatures and are thermally stable.

Effect of carbon nanotube addition on the wear behavior of basalt/epoxy woven composites.

The effect of acid-treated carbon nanotube (CNT) addition on the wear and dynamic mechanical thermal properties of basalt/epoxy woven composites was investigated in this study. Basalt/CNT/epoxy composites were fabricated by impregnating woven basalt fibers into epoxy resin mixed with 1 wt% CNTs which were acid-treated. Wear and DMA (dynamic mechanical analyzer) tests were performed on basalt/epoxy composites and basalt/CNT/epoxy composites. The results showed that the addition of the acid-treated CNTs improved the wear properties of basalt/epoxy woven composites. Specifically, the friction coefficient of the basalt/epoxy composite was stabilized in the range of 0.5-0.6 while it fell in the range of 0.3-0.4 for basalt/CNT/epoxy composites. The wear volume loss of the basalt/CNT/epoxy composites was approximately 68% lower than that of the basalt/epoxy composites. The results also showed that the glass transition temperature of basalt/CNT/epoxy composites was higher than that of basalt/epoxy composites. The improvement of wear properties of basalt/epoxy composites by the addition of acid-treated CNTs was caused by the homogeneous load transfer between basalt fibers and epoxy matrix due to the reinforcement of CNTs.

Chitosan nanocomposite films: enhanced electrical conductivity, thermal stability, and mechanical properties.

A novel, high-performance Fe(3)O(4)/MWNT/Chitosan nanocomposite has been prepared by a simple solution evaporation method. A significant synergistic effect of Fe(3)O(4) and MWNT provided enhanced electrical conductivity, mechanical properties, and thermal stability on the nanocomposites. A 5% (wt) loading of Fe(3)O(4)/MWNT in the nanocomposite increased conductivity from 5.34×10(-5) S/m to 1.49×10(-2) S/m compared to 5% (wt) MWNT loadings. The Fe(3)O(4)/MWNT/Chitosan films also exhibited increases in tensile strength and modulus of 70% and 155%, respectively. The integral procedure decomposition temperature (IPDT) was enhanced from 501 °C to 568 °C. These effects resulted from a number of factors: generation of a greater number of conductive channels through interactions between MWNT and Fe(3)O(4) surfaces, a higher relative crystallinity, the antiplasticizing effects of Fe(3)O(4), a restricted mobility and hindrance of depolymerization of the Chitosan chain segments, as well as uniform distribution, improved dispersion, and strong interfacial adhesion between the MWNT and Chitosan matrix.

Effects of silane modification and temperature on tensile and fractural behaviors of carbon nanotube/epoxy nanocomposites.

We investigated the effects of carbon nanotube (CNT) functionalization with silanes and temperature on the tensile and fractural characteristics of CNT/epoxy nanocomposites. Three groups of nanocomposites were fabricated using unmodified, oxidized and silanized CNTs, each at 0.1 wt%. Tensile and fractural tests were performed using the three nanocomposite samples at -30 degrees C, 20 degrees C, and 45 degrees C. Results showed that the tensile strength of silanized samples at -30 degrees C was about 89% and 241% higher, respectively, than at 20 degrees C and 45 degrees C. The elastic modulus of silanized CNT nanocomposite at -30 degrees C was about 52% and 871% higher, respectively, than at 20 degrees C and 45 degrees C. The fracture toughness of silanized samples was higher than those of unmodified and oxidized samples at all temperatures. However, fracture toughness decreased with decreasing temperature. Specifically, fracture toughness of silanized nanocomposites at -30 degrees C was about 76% and 117% lower, respectively, than those at 20 degrees C and 45 degrees C.

Silane treatment of carbon nanotubes and its effect on the tribological behavior of carbon nanotube/epoxy nanocomposites.

Functionalization of carbon nanotubes (CNTs) influences dispersion and interfacial strength in CNT-reinforced nanocomposites. In this study, multi-walled CNTs were functionalized via oxidation with a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3). Then, the functionalized CNTs with oxidation were surface-modified using a coupling agent, 3-aminopropyltriethoxysilane. CNT/epoxy nanocomposites were fabricated using oxidized CNTs and silane-modified CNTs, respectively, to investigate the effect of silane treatment on the tribological behavior of CNT/epoxy nanocomposites. Wear tests were performed on oxidized and silanized CNT/epoxy nanocomposites, at three different sliding speeds. The results showed that the friction coefficient and wear rate of silanized CNT/epoxy nanocomposites were lower than those of oxidized CNT/epoxy nanocomposites, regardless of sliding speed. The improved tribological behavior of silanized CNT/epoxy nanocomposites occurred due to the improved dispersion of CNTs into the epoxy and improved adhesion with the epoxy.

Methods of endotracheal tube placement in patients undergoing pelviscopic surgery.

Accidental endobronchial intubation is reported frequently during laparoscopic gynaecological surgery. We performed a prospective randomised study to compare three different methods of endotracheal tube placement in terms of susceptibility of accidental endobronchial intubation in patients undergoing laparoscopic gynaecologic surgery. The endotracheal tube was positioned by one of three methods: it was secured by palpating at the suprasternal notch while holding the pilot balloon (Group(Cuff)); by placing the 21 cm mark at the upper incisors (Group(21cm)); or by placing a guide mark, which was made on the surface of the tube 2 cm above the proximal end of the cuff at the level of the vocal cords (Group(VC)). The distance from the tip of endotracheal tube to the carina was measured with the patient in a neutral position (D(TC0)) and after the formation of pneumoperitoneum in the Trendelenburg position (D(TC1)). Eighty-eight patients were enrolled. Pneumoperitoneum and Trendelenburg position caused inward movement of the endotracheal tube toward the carina in 99%. In each group, the mean value of D(TC1) was significantly shorter than D(TC0) (Group(Cuff) 3.0 +/- 1.1 vs. 1.7 +/- 1.0, Group(21cm) 2.5 +/- 0.8 vs. 1.1 +/- 0.9, Group(VC) 3.5 +/- 0.7 vs. 2.3 +/- 0.8, D(TC0) vs. D(TC1) respectively) (all P < 0.01). Accidental endobronchial intubation occurred in 14%, with the lowest frequency in Group(VC) (2.6 %, P < 0.01) and the highest in Group(21cm), although this was not significantly (P = 0.09) different from Group(Cuff) (26.7% vs. 10.0%). The incidence of endobronchial intubation was lowest in Group(VC) but endobrochial intubation could not be avoided using any of these methods.

Transcriptional coupling between the divergent promoters of a prototypic LysR-type regulatory system, the ilvYC operon of Escherichia coli.

The twin-domain model [Liu, L. F. & Wang, J. C. (1987) Proc. Natl. Acad. Sci. USA 84, 7024-7027] suggests that closely spaced, divergent, superhelically sensitive promoters can affect the transcriptional activity of one another by transcriptionally induced negative DNA supercoiling generated in the divergent promoter region. This gene arrangement is observed for many LysR-type-regulated operons in bacteria. We have examined the effects of divergent transcription in the prototypic LysR-type system, the ilvYC operon of Escherichia coli. Double-reporter constructs with the lacZ gene under transcriptional control of the ilvC promoter and the galK gene under control of the divergent ilvY promoter were used to demonstrate that a down-promoter mutation in the ilvY promoter severely decreases in vivo transcription from the ilvC promoter. However, a down-promoter mutation in the ilvC promoter only slightly affects transcription from the ilvY promoter. In vitro transcription assays with DNA topoisomers showed that transcription from the ilvC promoter increases over the entire range of physiological superhelical densities, whereas transcription initiation from the ilvY promoter exhibits a broad optimum at a midphysiological superhelical density. Evidence that this promoter coupling is DNA supercoiling-dependent is provided by the observation that a novobiocin-induced decrease in global negative superhelicity results in an increase in ilvY promoter activity and a decrease in ilvC promoter activity predicted by the in vitro data. We suggest that this transcriptional coupling is important for coordinating basal level expression of the ilvYC operon with the nutritional and environmental conditions of cell growth.

Activation of gene expression by a ligand-induced conformational change of a protein-DNA complex.

IlvY protein binds cooperatively to tandem operator sites in the divergent, overlapping, promoter-regulatory region of the ilvYC operon of Escherichia coli. IlvY positively regulates the expression of the ilvC gene in an inducer-dependent manner and negatively regulates the transcription of its own divergently transcribed structural gene in an inducer-independent manner. Although binding of IlvY protein to the tandem operators is sufficient to repress ilvY promoter-specific transcription, it is not sufficient to activate transcription from the ilvC promoter. Activation of ilvC promoter-specific transcription requires the additional binding of a small molecule inducer to the IlvY protein-DNA complex. The binding of inducer to IlvY protein does not affect the affinity of IlvY protein for the tandem operator sites. It does, however, cause a conformational change of the IlvY protein-DNA complex, which is correlated with the partial relief of an IlvY protein-induced bend of the DNA helix in the ilvC promoter region. This structural change in the IlvY protein-DNA complex results in a 100-fold increase in the affinity of RNA polymerase binding at the ilvC promoter site. The ability of a protein to regulate gene expression by ligand-responsive modulation of a protein-DNA structure is an emerging theme in gene regulation.

Leucine-responsive regulatory protein-DNA interactions in the leader region of the ilvGMEDA operon of Escherichia coli.

The leucine-responsive regulatory protein (Lrp) regulates the expression of many operons in Escherichia coli including several involved in the metabolism of the branched-chain amino acids, L-isoleucine, L-valine, and L-leucine. The ilvGMEDA operon contains the genes for four of the five enzymes of the common pathway for the biosynthesis of these amino acids. A high affinity, consensus-like Lrp-DNA binding site has been identified at an unusual position in the leader region of this operon 226 base pairs downstream of the transcriptional initiation site between the attenuator and the ilvG gene. Binding to this site facilitates the cooperative binding of a second Lrp protomer to an adjacent, upstream, secondary site. At higher Lrp concentrations, binding to a third site is observed. Chemical, enzymatic, and alkylation protection and interference footprinting experiments demonstrate that the Lrp homodimer contacts the DNA helix at symmetrical half-sites present in adjacent major grooves and that the primary and secondary binding sites are separated by one helical turn and aligned along the same face of the DNA helix. In vivo, Lrp represses transcription through the leader-attenuator region of the ilvGMEDA operon. Lrp-dependent production of attenuated RNA transcripts is also observed in vitro. No transcriptional effects are observed, in vivo or in vitro, in the absence of an intact Lrp primary binding site. A possible physiological role for Lrp in the regulation of ilvGMEDA operon expression is discussed.

Lead concentrations in blood among the general population of Korea.

The purpose of this survey was to obtain information on the overall blood lead concentrations of the Korean population due to environmental exposure. Five hundred and twenty-five Korean adults from four provinces who had no previous occupational exposure to lead were chosen by random sampling to represent the general (normal) population. Blood lead determinations were performed by atomic absorption spectrometry with a graphite furnace. Interlaboratory quality control for analysis of blood lead was carried out in seven laboratories in Korea and Europe. The geometric mean were 6.36 micrograms/dl for males and 5.09 micrograms/dl for females. There was no correlation between blood lead concentration and age. The mean concentration of blood lead in smokers was higher than that in nonsmokers (P < 0.0005). The mean blood lead concentration in male nonsmokers was higher than that in female nonsmokers (P < 0.0005). Differences in mean blood lead values according to residential area were observed, and this result showed good agreement with the results of ambient monitoring.

The 'unreached' in family planning: a case study of the Republic of Korea.

PIP: The family planning program of the Republic of Korea has been quite successful, yet it has not been able to extend its services to all couples of childbearing age. There still exists a group of couples who want no more children and yet are not currently using any contraceptive method. The word pong-eem which literally means being neglected, i.e. untouched by the family planning program, was coined to describe this group. National surveys have shown that the proportion of women of reproductive age in this group is significant. The study on which this article is based focuses on the psychosocial characteristics of the group to provide policy makers, family planning administrators and workers with the specific information they need in order to reduce its size. Among the factors affecting the family planning decisions of couples is demographic pressure. However, there was no statistically significant relationship between demographic pressure and family planning status. With regard to the couples' knowledge about contraception, the higher the respondents' level of knowledge was, the lower was their proportion in the pong-eem group. In both the urban and rural areas, the proportion of women in the pong-eem group was higher among those who disapproved of the Government's population policies. The proportion of women in the pong-eem group was much higher among those who were least motivated to limit family size. The lower the level of social support for family planning, the higher was the proportion of women in the pong-eem group in both the urban and rural areas. Among the psychosocial characteristics, social support for family planning was the most closely related to the family planning status of couples no matter what measure of social support was used.^ieng