Assessing neuromuscular block at the larynx: the effect of change in resting cuff pressure and a comparison with video imaging in anesthetized humans

Neuromuscular block (NMB) at the larynx has been assessed by measuring the cuff pressure (CP) in an endotracheal tube (ETT) placed between the vocal cords. In this study, we evaluated the decrease in resting cuff pressure (RCP) after the administration of rocuronium and the effect of this decrease on the assessment of NMB, and we compared CP measurement with an alternative technique, video imaging (VI). In 20 patients, NMB was determined at the hand by mechanomyography and at the larynx initially by CP and subsequently by VI, recording images using a fiberoptic bronchoscope via a laryngeal mask. Train-of-four stimuli were applied at both sites. After baseline measurements, the ETT was replaced, and rocuronium was infused to achieve a steady-state 50% (n = 10) or 75% (n = 10) block at the hand. CP measurements were recorded before and after restoration of RCP to prerocuronium pressure, followed by further VI measurements. The mean RCP decreased from 21 +/- 4 to 12 +/- 5 mm Hg after rocuronium. At 50% block at the hand, the CP estimate of block at the larynx with reduced RCP was 62% +/- 18%, and that after restoring RCP was 29% +/- 13%; VI estimated 27% +/- 14% block. At 75% block at the hand, CP and VI estimated 52% +/- 11% and 46% +/- 9% block, respectively (RCP maintained). We conclude that RCP decreases after the administration of rocuronium, that restoring RCP significantly alters CP estimates of NMB, and that VI is in agreement with CP measurement if RCP is maintained at prerelaxant values. Implications: In this study, we show that a muscle relaxant-induced decrease in resting tension at the larynx may confound the assessment of neuromuscular block by cuff pressure measurement. The preliminary data suggest that video imaging may provide a suitable alternative to cuff pressure measurement to assess neuromuscular block at the larynx.     

Guest–host interaction in ferroelectric liquid crystal–nanoparticle composite system

The present paper deals with the characterization of a ferroelectric liquid crystal–nanoparticle (FLC–NP) composite system. The dielectric, electrical and polarization property of the FLC–NP composite system have been studied as a function of temperature and frequency. Ferroelectric Cu-doped ZnO (Cu–ZnO) nanoparticles have been added to the pure ferroelectric liquid crystal (FLC) Felix 17/100. The nanoparticles are bigger in size as compared to FLC molecules; therefore, they distort the existing geometry of FLC matrix and set up an antiparallel correlation with the dipole moments of the host FLC molecules. This antiparallel correlation of guest–host geometry reduces the net ferroelectricity of the composite system and modifies all the physical properties of the pure FLC. The change in properties has been analysed and explained in the light of guest–host interaction.     

TETRA-BUTYL-MALONAMIDE AND TETRA-ISOBUTYL MALONAMIDE AS EXTRACTANTS FOR URANIUM(VI) AND PLUTONIUM(IV)

ABSTRACT

Two new symmetrical diamides, namely straight-chain alkyl substituted neutral tetra-butyl-malonamide(TBMA) and sterlcally hindered branched-chain alkyl substituted tetra-isobutyl malonamide(TIBMA) were synthesised, characterised and used for the extraction of U(VI) and Pu(IV) from nitric acid media into n-dodecane. Both the cations were found to be extracted as their disolvates. Interestingly TBMA extracted more efficiently than TIBMA but afforded poor selectivity for Pu/U separation. The thermodynamic parameters involved in the extraction, determined by the temperature variation method, indicated the reactions in all cases to be enthalpy favoured. Entropy was found to be counteracting the extraction of U(VI) and favouring the extraction of Pu(IV). The recovery of diamides from the loaded actinides could be easily accomplished by using dilute oxalic acid or dilute U(IV) as the strippant for Pu(IV) and using dilute Na₂C0₃ as that for U(VI).     

An experimental investigation of mixed-mode fracture

In this paper, mixed-mode fracture is investigated experimentally. In the first part, critical conditions for initiation of crack growth are explored. The method of caustics was used in conjunction with a high speed video system to determine critical stress intensity factors at initiation of crack growth. It was found that the maximum tangential stress criterion originally proposed by Erdogan and Sih [1] was the best criterion in terms of predictive capability. Polymethylmethacrylate and Homalite-100 were used in the experiments and Homalite-100 was found to exhibit significant rate dependence. In the second part, crack growth initiated under mixed-mode loading is addressed. It is shown that subsequent slow crack growth in PMMA is under pure mode-I conditions.

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Résumé On étudie par voie expérimentale les ruptures selon un mode mixte. On explore, dans une première partie, les conditions d'amorçage de la croissance d'une fissure. En utilisant la méthode des caustiques en association avec un système vidéo à grande vitesse, on détermine les facteurs critiques d'intensité de contraintes correspondant à l'amorçage de la fissure. On trouve que le critère de contrainte maximum tangentielle, proposé à l'origine par Erdogan et Sih, est le meilleur en termes de capacité de prédiction. Pour les essais, on a utilisé du plyméthylméthacrylate et de l'Homalite-100, et on a trouvé que ce dernier matériau faisait état d'une sensibilité importante à la vitesse. La deuxième partie du travail est consacrée à la croissance d'une fissure sous un mode de sollicitations mixte. On montre que la propagation lente de la fissure dans le PMMA se produit sous des conditions de pur Mode I.

     

Synthesis and characterization of aromatic-alipathic polyamides containing tetraphenylthiophene units into the backbone

Summary Aromatic-aliphatic polyamides were prepared from 2, 5-bis(4-carboxyethylcarbonylphenyl)-3,4-diphenylthiophene (BCDT) with few commercial diamines by using Yamazaki's phosphorylation reaction. The polymers were obtained in good yields and were characterized by solubility tests, viscosity measurements, IR spectroscopy, thermal analysis and X-ray diffraction studies. These polyamides had inherent viscosities in the range of 0.35 to 0.70 dl/g and were amorphous in nature. All the polyamides were readily soluble in solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinone, N,N-dimethylformamide, nitrobenzene, hexamethylphosphoramide, m-cresol, sulphuric acid and did not lose weight below 300°C in air. NCL Communication No:-4815     

Mechanical behaviour of Ti<Subscript>5</Subscript>Si<Subscript>3</Subscript> based alloys and composites

The demand for materials to be used in the components operating above 1100°C in advanced aero-engines drives the development of the silicide-based intermetallic alloys and composites, including the titanium silicides. The mechanical behaviour of Ti₅Si₃ and its composites has been reviewed with emphasis on the microstructure-property relationships. It is found that the grain size is a critical parameter, and smaller grain sizes are desirable for reducing the magnitude of internal residual stress caused by the crystallographic anisotropy in coefficients of thermal expansion. The reduction in grain size leads to significant improvement in hardness, room temperature flexural strength and fracture toughness. On the other hand, the high temperature strength observed at slow strain rates and creep resistance are higher in the samples with the coarser grain sizes. Further improvements in the strength, fracture toughness and high temperature creep resistance are possible, either through the development of multiphase alloys, or by the use of ceramic reinforcements in composites.     

Remediation of Cd(II) Metal Ion from Aqueous Systems by Using Calcium Alginate Modified (CAM) Acacia saligna and Delbergia sisso Pods Composite Beads

The present investigation reports the possibility of using Acacia saligna and Delbergia sisso pods to remove Cd(II) from aquatic systems in the form of calcium alginate modified immobilized composite beads (CAM-ASPCB and CAM-DSPCB). Batch and fixed bed column studies were carried out under various process affecting parameters. Maximum metal removal efficiency of 92% by CAM-ASPCB and 85% by CAM-DSPCB was observed under optimized conditions. Pseudo-second-order kinetic model, intra-particle diffusion, and Freundlich isotherm were found fitted well. The regeneration of the sorbents were found effectively high showing up to 10 cycles for simulated solution and up to 3 cycles for industrial effluent.     

Phytic acid and extractable phosphorus of pearl millet flour as affected by natural lactic acid fermentation

Lactic acid fermentation of pearl millet flour decreased its phytic acid content and increased extractable phosphorus. Fermentation at 40 and 50°C for 72 h or longer eliminated phytic acid almost completely; extractable phosphorus was more than doubled. Lower temperatures (20 and 30°C) were less effective. The changes in concentration of phytic acid and extractable phosphorus may be attributed partly to phytase activity inherent in pearl millet flour.     

Effect of Zr on dielectric, ferroelectric and impedance properties of BaTiO3 ceramic

A polycrystalline sample of Zr-doped barium titanate (BaTiO₃) was prepared by conventional solid state reaction method. The effect of Zr (0·15) on the structural and microstructural properties of BaTiO₃ was investigated by XRD and SEM. The electrical properties (dielectric, ferroelectric and impedance spectroscopy) were measured in wide range of frequency and temperature. With substitutions of Zr, the structure of BaTiO₃ changes from tetragonal to rhombohedral. Lattice parameters were found to increase with substitution. The room temperature dielectric constant increases from ～ 1675 to ～ 10586 and peak dielectric constant value increases from ～ 13626 to ～ 21023 with diffuse phase transition. Impedance spectroscopy reveals the formation of grain and grain boundary in the material and found to decrease with increase in temperature.