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.

Back Muscle Mass as a Predictor of Postoperative Complications in Posterior Lumbar Interbody Fusion Surgery

BACKGROUND

There is a lack of studies on utilising skeletal muscle mass via preoperative lumbar computed tomography or magnetic resonance imaging as a predictor of postoperative complications of posterior lumbar interbody fusion (PLIF) surgery in elderly patients.

METHODS

Patients aged >65 years who underwent PLIF were enrolled. The sum of the cross-sectional areas of the erector spinae muscles (CSABoth) was presented as the skeletal muscle mass. Postoperative complications were assessed using CSABoth, pulmonary function testing, and prognostic nutritional index (PNI).

RESULTS

Patients with postoperative complications showed significantly lower values of CSABoth (median 2266.70 (2239.73-2875.10) mm2 vs. 3060.30 (2749.25-3473.30) mm2, p < 0.001), functional vital capacity, forced expiratory volume at 1 s, and PNI. However, multiple logistic regression analysis identified American Society of Anaesthesiologists Physical Status (ASA PS) I (odds ratio 0.307 (95% confidence interval 0.110-0.852), p = 0.023), ASA PS III (4.033 (1.586-10.254), p = 0.003), CSABoth (0.999 (0.999-1.000), p < 0.001), and postoperative red blood cell (RBC) transfusion (1.603 (1.193-2.152), p = 0.002) as risk factors for postoperative complications after PLIF surgery.

CONCLUSIONS

CSABoth, ASA PS III, and postoperative RBC transfusion might be used as predictors of postoperative complications after PLIF in patients aged >65 years.

High-dose ulinastatin improves postoperative oxygenation in patients undergoing aortic valve surgery with cardiopulmonary bypass: A retrospective study

Objective

To determine whether pre-treatment with high-dose ulinastatin provides enhanced postoperative oxygenation in patients who have undergone aortic valve surgery with moderate hypothermic cardiopulmonary bypass (CPB).

Methods

Patients who underwent aortic valve surgery with moderate hypothermic CPB were retrospectively evaluated. In total, 94 of 146 patients were included. The patients were classified into one of two groups: patients in whom ulinastatin (10,000 U/kg followed by 5,000 U/kg/h) was administered during CPB (Group U, n = 38) and patients in whom ulinastatin was not administered (Group C, n = 56). The PaO₂/FiO₂ ratio was calculated at the following time points: before CPB (pre-CPB), 2 h after weaning from CPB (post-CPB), and 6 h after arrival to the intensive care unit (ICU-6). The incidence of a low PaO₂/FiO₂ ratio was also compared among the time points.

Results

Group U showed a significantly higher PaO₂/FiO₂ ratio (F(4, 89.0) = 657.339) and a lower incidence of lung injury (PaO₂/FiO₂ ratio < 300) than Group C at the post-CPB and ICU-6 time points.

Conclusion

High-dose ulinastatin improved pulmonary oxygenation after CPB and in the early stages of the ICU stay in patients undergoing aortic valve surgery with CPB.

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.

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.

Comparison of analgesic efficacy between single interscalene block combined with a continuous intra-bursal infusion of ropivacaine and continuous interscalene block after arthroscopic rotator cuff repair

Background

This study evaluated the effectiveness of a continuous interscalene block (CISB) by comparing it with that of a single interscalene block combined with a continuous intra-bursal infusion of ropivacaine (ISB-IB) after arthroscopic rotator cuff repair.

Methods

Patients who had undergone CISB (CISB group; n = 25) were compared with those who had undergone ISB-IB (ISB-IB group; n = 25) for more than 48 hours after surgery. The visual analog scale (VAS) for pain, motor and/or sensory deficit, supplementary analgesics and adverse effects were recorded.

Results

There were no significant differences between the postoperative VAS of the CISB and ISB-IB groups, except at 1 hour after surgery. Their supplementary analgesics of the two groups were similar. Transient motor weakness (52%) and sensory disturbance (40%) of the affected arm were observed in patients in the CISB group. The catheters came out accidentally in 22% of the CISB group but in only 4% of the ISB-IB group.

Conclusions

ISB-IB provides similar analgesia to CISB. However, the ISB-IB group had a lower incidence of neurological deficits and better catheter retention.

A heated humidifier does not reduce laryngopharyngeal complaints after brief laryngeal mask anesthesia

PURPOSE

Warming and humidification of inspired gases is standard care for intubated patients whose lungs are ventilated mechanically for prolonged periods. We examined whether active humidification of inspired gases might reduce laryngo-pharyngeal discomfort in patients undergoing brief laryngeal mask airway (LMA) anesthesia.

METHODS

In a prospective trial, 200 adult patients undergoing elective surgery under general anesthesia were randomly assigned to receive ventilation without airway warming and exogenous humidification (Group C-control), or active warming and humidification of inspired gases (Group HUM-humidified), using a humidifier with a heated wire circuit. Inhalational anesthesia was maintained via a circle system. The temperatures and relative humidities of inspired gases were monitored continuously throughout surgery. Postoperative sore throat, dysphonia, and dysphagia were assessed one and 24 hr after anesthesia. Whenever symptoms were present, their severities were graded using a 101-point numerical rating scale.

RESULTS

The mean temperature and relative humidity of the inspired gases in Group HUM were greater compared to Group C (36.1+/-0.4 degrees C and 99.5+/-0.5% vs 26.9+/-0.8 degrees C and 76.4+/-10.9%, respectively). Postoperatively, the overall frequencies of laryngeal and pharyngeal discomfort were similar in the two groups (53.8% and 54.9% in Group C vs 51.6% and 41.9% in Group HUM at one and 24 hr respectively, P>0.05). The groups were also similar with respect to the severity scores of laryngo-pharyngeal discomfort.

CONCLUSION

Active warming and humidification of inspired gases has no clinically appreciable effect in reducing the incidence and severity of laryngo-pharyngeal complaints after brief (<two hours) LMA anesthesia.

Continuous mixed venous oxygen saturation, not mean blood pressure, is associated with early bupivacaine cardiotoxicity in dogs

PURPOSE

To investigate changes of continuous mixed venous oxygen saturation (cSvO(2)) and mean arterial blood pressure (MBP) in dogs with bupivacaine-induced cardiac depression.

METHODS

Bupivacaine was infused into pentobarbital-anesthetized mongrel dogs (n = 8) at a rate of 0.5 mg.kg(-1).min(-1) until the MBP was 40 mmHg or less (end of bupivacaine infusion; BIE). The infusion time was divided into the early period, first 30 min of bupivacaine infusion and the late period, which was from 30 min of bupivacaine infusion until BIE. cSvO(2) was monitored using a fibreoptic pulmonary artery catheter, and MBP and cardiac output (CO) were measured every ten minutes after the initiation of bupivacaine infusion. Arterial blood gas, serum electrolyte and bupivacaine concentration were measured simultaneously. The relationships between CO and cSvO(2), and of CO vs MBP were compared by regression analysis in the early and late periods.

RESULTS

The Pearson's correlation coefficients between CO and cSvO(2) were 0.782 (P = 2.1 x 10(-7)) in the early period and 0.824 (P = 1.3 x 10(-6)) in the late period. The correlation coefficients between CO and MBP were 0.019 (P = 0.921) in the early period and 0.799 (P = 4.8 x 10(-6)) in the late period.

CONCLUSIONS

cSvO(2), but not MBP, is associated with CO changes in bupivacaine-induced cardiac depression during the early period of bupivacaine intoxication. Decrease of MBP with low cSvO(2) observed during the late period might imply severe cardiac depression induced by bupivacaine infusion.

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.