Anesthetic Stability of Propofol, Dexmedetomidine, and Isoflurane by Measuring Bispectral Index (BIS) and Hemodynamic Indices: A Comparative Study.

Background Hemodynamic changes and anesthetic awareness occurring during surgery under general anesthesia is a great concern for both surgeon and anesthesiologist. Maintenance of the adequate depth of anesthesia throughout the intraoperative period is important in maintaining hemodynamic stability, preventing intraoperative awareness, and avoiding postoperative recall. Aim This study aims to predict the anesthetic stability of propofol, dexmedetomidine, and isoflurane by measuring bispectral index (BIS) and hemodynamic indices. Materials and methods This is a prospective comparative study. Sixty patients of either sex, aged 18-60 years, with American Society of Anesthesiologist (ASA) physical status classification I and II, undergoing elective surgical procedures requiring general anesthesia were allocated into three groups of 20 each. Patients in each group were administered standard general anesthesia with routine hemodynamic monitoring along with BIS, and values were recorded at baseline and thereafter at every five-minute interval for the duration of surgery. Anesthesia was maintained in Group P using a bolus dose of propofol 1 milligram.kg-1 for 10 minutes followed by propofol infusion 50-75 microgram.kg-1.minute-1, Group D with a bolus dose of dexmedetomidine 1 microgram.kg-1 for 10 minutes followed by infusion 0.2-0.7 microgram.kg-1.hour-1, and Group I with isoflurane at 1 minimum alveolar concentration (MAC) for 10 minutes and then maintained between 0.5 MAC and 1.5 MAC until the duration of surgery. To maintain the surgical plane of anesthesia, the BIS score was monitored between 40 and 65. The quantitative variables were expressed as mean±SD and compared between groups using Student's unpaired t-test. Data analysis was done using SPSS Statistics for Windows version 20.0 (IBM Corp., Armonk, NY, USA). A p-value of <0.05 was considered statistically significant. Results During intergroup comparison among study drugs, the mean BIS values were statistically significant among the groups (p<0.05). Hemodynamic indices were significantly better maintained in the dexmedetomidine group as compared to the isoflurane and propofol groups throughout the intraoperative period (p<0.05). Conclusion Dexmedetomidine is better than propofol and isoflurane in maintaining the BIS score and hemodynamic parameters during the intraoperative period.

Electronic properties of carbon nanotubes as detected by photoemission and inverse photoemission.

The relation between morphology and energy level alignment in carbon nanotubes (CNT) is a crucial information for the optimization of applications in nanoelectronics, optics, mechanics and (bio)chemistry. Here we present a study of the relation between the electronic properties and the morphology of single wall CNT (SWCNT), aligned multi wall CNT (MWCNT) and unaligned MWCNT. The CNT were synthesized via catalytic chemical vapor deposition in ultra-high vacuum conditions. Combined ultraviolet photoemission and inverse photoemission (IPES) spectra reveal a high sensitivity to the nanotube morphology. In the case of unaligned SWCNT the distinctive unoccupied Van Hove singularities (vHs) features are observed in the high resolution IPES spectra. Those features are assigned to semiconducting and metallic SWCNT states, according to calculated vHs DOS. The two MWCNT samples are similar in the diameter of the tube (about 15 nm) and present similar filled and empty electronic states, although the measured features in the aligned MWCNT are more defined. Noteworthy, interlayer states are also revealed. Their intensities are directly related to the MWCNT alignment. Focussing and geometrical effects associated to the MWCNT alignment are discussed to account the spectral differences.

Heterogeneous and Homogeneous Routes in Water Oxidation Catalysis Starting from Cu(II) Complexes with Tetraaza Macrocyclic Ligands.

Since the first report in 2012, molecular copper complexes have been proposed as efficient electrocatalysts for water oxidation reactions, carried out in alkaline/neutral aqueous media. However, in some cases the copper species have been recognized as precursors of an active copper oxide layer, electrodeposited onto the working electrode. Therefore, the question whether copper catalysis is molecular or not is particularly relevant in the field of water oxidation. In this study, we investigate the electrochemical activity of copper(II) complexes with two tetraaza macrocyclic ligands, distinguishing heterogeneous or homogeneous processes depending on the reaction media. In an alkaline aqueous solution, and upon application of an anodic bias to working electrodes, an active copper oxide layer is observed to electrodeposit at the electrode surface. Conversely, water oxidation in neutral aqueous buffers is not associated to formation of the copper oxide layer, and could be exploited to evaluate and optimize a molecular, homogeneous catalysis.

Low-Temperature Growth of Carbon Nanotube Forests Consisting of Tubes with Narrow Inner Spacing Using Co/Al/Mo Catalyst on Conductive Supports.

We grow dense carbon nanotube forests at 450 °C on Cu support using Co/Al/Mo multilayer catalyst. As a partial barrier layer for the diffusion of Co into Mo, we apply very thin Al layer with the nominal thickness of 0.50 nm between Co and Mo. This Al layer plays an important role in the growth of dense CNT forests, partially preventing the Co-Mo interaction. The forests have an average height of ∼300 nm and a mass density of 1.2 g cm(-3) with tubes exhibiting extremely narrow inner spacing. An ohmic behavior is confirmed between the forest and Cu support with the lowest resistance of ∼8 kΩ. The forest shows a high thermal effusivity of 1840 J s(-0.5) m(-2) K(-1), and a thermal conductivity of 4.0 J s(-1) m(-1) K(-1), suggesting that these forests are useful for heat dissipation devices.

Spectroscopic properties of Sm3+ doped lead bismosilicate glasses using Judd-Ofelt theory.

The spectroscopic properties of Sm(3+) ions in lead bismosilicate glasses (PBSS) as a function of bismuth oxide were investigated using optical absorption and fluorescence spectra. These glasses have shown strong absorption and emission bands in the near infrared and visible region respectively. From the measured absorption spectra, Judd-Ofelt intensity parameters Ω2, Ω4 and Ω6 were determined by applying least square analysis method. The variation of Ω2 and Ω6 with Bi2O3 content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in the rare earth oxygen (RE-O) covalency. The variation of Ω4 with Bi2O3 content has been attributed to rigidity of the samples. Using the Judd Ofelt intensity parameters the other radiative properties like radiative transition probability, radiative life time, branching ratio and the stimulated emission cross-sections of prepared PBSS glasses have been calculated. The values of radiative properties indicate that Sm(3+) ions emit intense reddish-orange emission ((4)G5/2→(6)H7/2) under excitation at 450 nm wavelength.

In situ observations of the atomistic mechanisms of Ni catalyzed low temperature graphene growth.

The key atomistic mechanisms of graphene formation on Ni for technologically relevant hydrocarbon exposures below 600 °C are directly revealed via complementary in situ scanning tunneling microscopy and X-ray photoelectron spectroscopy. For clean Ni(111) below 500 °C, two different surface carbide (Ni2C) conversion mechanisms are dominant which both yield epitaxial graphene, whereas above 500 °C, graphene predominantly grows directly on Ni(111) via replacement mechanisms leading to embedded epitaxial and/or rotated graphene domains. Upon cooling, additional carbon structures form exclusively underneath rotated graphene domains. The dominant graphene growth mechanism also critically depends on the near-surface carbon concentration and hence is intimately linked to the full history of the catalyst and all possible sources of contamination. The detailed XPS fingerprinting of these processes allows a direct link to high pressure XPS measurements of a wide range of growth conditions, including polycrystalline Ni catalysts and recipes commonly used in industrial reactors for graphene and carbon nanotube CVD. This enables an unambiguous and consistent interpretation of prior literature and an assessment of how the quality/structure of as-grown carbon nanostructures relates to the growth modes.

Drug salt formation via mechanochemistry: the case study of vincamine.

In the present research a salt of vincamine, a poorly bioavailable indole alkaloid derived from the leaves of Vinca minor L., was synthesized in the solid state by means of a mechanochemical process employing citric acid as a reagent. The mechanochemical process was adopted as a solvent-free alternative to classical citrate synthetic route that involves the use of solvents. Since the mechanochemical salification is little studied to date and presents the disadvantage of offering a low yield, in this work, the influence of three process and formulation variables on the percentage of vincamine citrate was studied. In particular, the time of mechanical treatment (in planetary mill Fritsch P5) and the amount of citric acid were varied in order to evaluate their effect on the yield of the process, and the introduction of a solid solvent, a common pharmaceutical excipient (sodium carboxymethylcellulose, NaCMC), was considered. Due to the complexity of the resulting samples' matrix, an appropriate experimental design was employed to project the experimental trials and the influence of the three variables on the experimental response was estimated with the help of a statistical analysis. The experimental response, that is, the yield of the process corresponding to the percentage of vincamine in the protonated form, was unconventionally calculated by means of X-ray photoelectron spectroscopy analysis (XPS). Out of 16 samples, the one with the highest yield was the coground sample containing vincamine and citric acid in a 1:2 molar ratio, treated for 60 min in the presence of NaCMC. Under the above conditions the salification reaction was completed highlighting the importance of a proper selection of process and formulation variables of the mechanochemical salification, and emphasizing the crucial role of the solid solvent in facilitating the salification. The second step of the research encompassed the characterization of the citrate salt obtained by solid excipient assisted mechanochemical salification (SEAMS) in comparison with the vincamine citrate obtained by classical synthetic route. The samples were characterized by, besides XPS, high resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRPD), in vitro solubilization kinetics and in vivo oral pilot study in rats. Finally, in order to monitor over time possible disproportionation phenomena, stability studies have been performed by repeating XPS analysis after 8 months. As expected, the the SEAMS-vincamine salt consisted of particles both crystalline and amorphous. The solubilization kinetics was superior to the corresponding salt probably thanks to the favorable presence of the hydrophilic excipient although the two salts were bioequivalent in rats after oral administration. Furthermore, no evidence of disporportionation phenomena in the SEAMS-vincamine salt was found after storage. In conclusion, in the case of forming salts of poorly soluble drugs, the SEAMS process may be an interesting alternative to both classical synthetic routes, eliminating the need for solvent removal, and simple neat mechanochemical salification, overcoming the problem of limited process yield.