Role of Surfactants in Carbon Nanotubes Density Gradient Separation

Several strategies aimed at sorting single-walled carbon nanotubes (SWNT) by diameter and/or electronic structure have been developed in recent years. A nondestructive sorting method was recently proposed in which nanotube bundles are dispersed in water-surfactant solutions and submitted to ultracentrifugation in a density gradient. By this method, SWNTs of different diameters are distributed according to their densities along the centrifuge tube. A mixture of two anionic amphiphiles, namely sodium dodecylsulfate (SIDS) and sodium cholate (SC), presented the best performance in discriminating nanotubes by diameter. We present molecular dynamics studies of the water-surfactant-SWNT system. The simulations revealed one aspect of the discriminating power of surfactants: they can actually be attracted toward the interior of the nanotube cage. The binding energies of SDS and SC on the outer nanotube surface are very similar and depend weakly on diameter. The binding inside the tubes, on the contrary, is strongly diameter dependent: SDS fits best inside tubes with diameters ranging from 8 to 9 angstrom, while SC is best accommodated in larger tubes, with diameters in the range 10.5-12 angstrom. The dynamics at room temperature showed that, as the amphiphile moves to the hollow cage, water molecules are dragged together, thereby promoting the nanotube filling. The resulting densities of filled SWNT are in agreement with measured densities.

Evidence for magnetic phase separation in La(0.86)Sr(0.14)Mn(1-x)Cu(x)O(3+delta) manganites from NMR and magnetic measurements

Polycrystalline La(0.86)Sr(0.14)Mn(1-x)Cu(x)O(3+delta) (x = 0, 0.05, 0.10, 0.15, 0.20) manganites were investigated by means of magnetic measurements and zero-field (139)La and (55)Mn nuclear magnetic resonance (NMR) spectroscopy. Magnetization versus temperature measurements revealed a paramagnetic to ferromagnetic transition in most samples, with lower Curie temperatures and broader transitions for samples with higher Cu contents. The details of the magnetization measurements suggested a phase-separated scenario, with ferromagnetic clusters embedded in an antiferromagnetic matrix, especially for the samples with large Cu contents (x = 0.15 and 0.20). Zero-field (139)La NMR measurements confirmed this finding, since the spectral features remained almost unchanged for all Cu-doped samples, whereas the bulk magnetization was drastically reduced with increasing Cu content. (55)Mn NMR spectra were again typical of ferromagnetic regions, with a broadening of the resonance line caused by the disorder introduced by the Cu doping. The results indicate a coexistence of different magnetic phases in the manganites studied, with the addition of Cu contributing to the weakening of the double-exchange interaction in most parts of the material.

Environmental formaldehyde analysis by active diffusive sampling with a bundle of polypropylene porous capillaries followed by capillary zone electrophoretic separation and contactless conductivity detection

Compared to other volatile carbonylic compounds present in outdoor air, formaldehyde (CH2O) is the most toxic, deserving more attention in terms of indoor and outdoor air quality legislation and control. The analytical determination of CH2O in air still presents challenges due to the low-level concentration (in the sub-ppb range) and its variation with sampling site and time. Of the many available analytical methods for carbonylic compounds, the most widespread one is the time consuming collection in cartridges impregnated with 2,4-dinitrophenylhydrazine followed by the analysis of the formed hydrazones by HPLC. The present work proposes the use of polypropylene hollow porous capillary fibers to achieve efficient CH2O collection. The Oxyphan (R) fiber (designed for blood oxygenation) was chosen for this purpose because it presents good mechanical resistance, high density of very fine pores and high ratio of collection area to volume of the acceptor fluid in the tube, all favorable for the development of air sampling apparatus. The collector device consists of a Teflon pipe inside of which a bundle of polypropylene microporous capillary membranes was introduced. While the acceptor passes at a low flow rate through the capillaries, the sampled air circulates around the fibers, impelled by a low flow membrane pump (of the type used for aquariums ventilation). The coupling of this sampling technique with the selective and quantitative determination of CH2O, in the form of hydroxymethanesulfonate (HMS) after derivatization with HSO3-, by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-(CD)-D-4) enabled the development of a complete analytical protocol for the CH2O evaluation in air. (C) 2008 Published by Elsevier B.V.

Exploring Liquid Sequential Injection Chromatography To Teach Fundamentals of Separation Methods: A Very Fast Analytical Chemistry Experiment

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)

Automated two-dimensional separation flow system with electrochemical preconcentration, stripping, capillary electrophoresis and contactless conductivity detection for trace metal ion analysis

This paper describes the automation of a fully electrochemical system for preconcentration, cleanup, separation and detection, comprising the hyphenation of a thin layer electrochemical flow cell with CE coupled with contactless conductivity detection (CE-C(4)D). Traces of heavy metal ions were extracted from the pulsed-flowing sample and accumulated on a glassy carbon working electrode by electroreduction for some minutes. Anodic stripping of the accumulated metals was synchronized with hydrodynamic injection into the capillary. The effect of the angle of the slant polished tip of the CE capillary and its orientation against the working electrode in the electrochemical preconcentration (EPC) flow cell and of the accumulation time were studied, aiming at maximum CE-C(4)D signal enhancement. After 6 min of EPC, enhancement factors close to 50 times were obtained for thallium, lead, cadmium and copper ions, and about 16 for zinc ions. Limits of detection below 25 nmol/L were estimated for all target analytes but zinc. A second separation dimension was added to the CE separation capabilities by staircase scanning of the potentiostatic deposition and/or stripping potentials of metal ions, as implemented with the EPC-CE-C(4)D flow system. A matrix exchange between the deposition and stripping steps, highly valuable for sample cleanup, can be straightforwardly programmed with the multi-pumping flow management system. The automated simultaneous determination of the traces of five accumulable heavy metals together with four non-accumulated alkaline and alkaline earth metals in a single run was demonstrated, to highlight the potentiality of the system.

Fast separation of selective serotonin reuptake inhibitors antidepressants in plasma sample by nonaqueous capillary electrophoresis

A simple, fast, and sensitive liquid-liquid extraction method followed by nonaqueous capillary electrophoresis (LLE/NACE) was developed and validated for Simultaneous determination of four antidepressants (fluoxetine, sertraline, citalopram and paroxetine) in human plasma. Several experimental separation conditions using aqueous and nonaqueous media separation were tested by varying the electrolyte pH value (for aqueous medium) and the ionic strength concentration considering the similar mobility of the compounds. High-resolution separation was achieved with a mixture of 1.25 mol L(-1) of phosphoric acid in acetonitrile. The quantification limits of the LLE/CE method varied between 15 and 30 ng mL(-1), with a relative standard deviation (RSD) lower than 10.3%. The method was successfully applied in therapeutic drug monitoring and should be employed in the evaluation of plasma levels in urgent toxicological analysis. (C) 2009 Elsevier B.V. All rights reserved.

TLC Separation and Identification of the Essential Oil Constituents from Aloysia gratissima

The present work had as objective the isolation of the five compounds by thin-layer Chromatography (TLC) from the essential oil of the Aloysia gratissima. For this, a number of systems of eluents were used for its separation, indicating that through the system acetone/hexane in proportions (v/v) 1:30 it was possible to isolate guaiol, elemol, pinocanphone (trans-3-pinanone), cis-pinocarvyl, and acorenone. The isolation of the compound acorenone from the other compounds was possible with the mixture of solvents hexane/dichloromethane in proportions (v/v) (1:1,3).

A Contour-based Separation of VerticallyAttached Traffic Signs

This report presents an algorithm for locating the cut points for and separatingvertically attached traffic signs in Sweden. This algorithm provides severaladvanced digital image processing features: binary image which representsvisual object and its complex rectangle background with number one and zerorespectively, improved cross correlation which shows the similarity of 2Dobjects and filters traffic sign candidates, simplified shape decompositionwhich smoothes contour of visual object iteratively in order to reduce whitenoises, flipping point detection which locates black noises candidates, chasmfilling algorithm which eliminates black noises, determines the final cut pointsand separates originally attached traffic signs into individual ones. At each step,the mediate results as well as the efficiency in practice would be presented toshow the advantages and disadvantages of the developed algorithm. Thisreport concentrates on contour-based recognition of Swedish traffic signs. Thegeneral shapes cover upward triangle, downward triangle, circle, rectangle andoctagon. At last, a demonstration program would be presented to show howthe algorithm works in real-time environment.

Barn och ungdomars upplevelser av separation sett ur ett omvårdnadsperspektiv. : Systematisk litteraturstudie.

Syftet med denna studie var att belysa barn och ungdomars erfarenheter, upplevelser och eventuella risk-och skyddsfaktorer i samband med föräldrarnas separation. Undersöka betydelsen av goda familjerelationer och vilka möjliga stödåtgärder sjuksköterskor kan använda för att hjälpa barn och ungdomar som inte mår bra av en separation.Metoden var utformad som en retrospektiv systematisk litteraturstudie och sökningar gjordes i databaser, framförallt via Högskolan Dalarna bibliotek. I resultatet framkommer hur barn upplever separationer, både positiva och negativa aspekter. Bra relationer både inom och utom familjen är viktiga för barnen vilket framkommer genomgående i arbetet. Umgängesföräldern har en viktig roll för barnen. Själva boendet spelar oftast inte så stor roll så länge barnen har bra relation till, regelbundet umgänge med, båda föräldrarna. Många riskfaktorer för barnen är ändå kopplade till separationer och barnen kan må psykiskt dåligt ända upp i vuxen ålder. Sjuksköterskan i barn- och skolhälsovården kan använda sig av olika verktyg för att hjälpa barn och föräldrar efter en separation. Familjefokuserad omvårdnad är en omvårdnadsmodell som lämpar sig väl för familjer i svåra och konfliktfyllda situationer.

Nyblivan föräldrars upplevelser av separation från sitt nyfödda barn efter förlossningen : en systematisk litteraturstudie

I olika sammanhang och i olika omfattning separeras mor och barn idag inom den perinatala vården. Då barnet behöver vård på neonatalavdelning leder det ofta till upprepad och långvarig separation mellan föräldrarna och barnet. Syftet med denna litteraturstudie är att beskriva föräldrars upplevelse av separation från sitt nyfödda barn efter förlossningen. Metod- studien är en systematisk litteraturstudie där 15 vetenskapliga artiklar ingår. Resultat- situationer som leder till separation mellan mamma och barn kan utgöra ett unikt tillfälle för pappan till nära kontakt och tidig anknytning mellan honom och barnet. Behovet att vara nära sitt barn är starkt och finns hos båda föräldrarna och separation leder till många negativa känslor och ökad stress hos föräldrarna samt utgör ett hinder för den tidiga anknytningen till barnet. Skillnader i behovet att vara nära barnet i den tidiga nyföddhetsperioden kan ses mellan mammor och pappor och mellan föräldrar till prematura barn och fullgångna. Nära hudkontakt och samvård mellan föräldrar och barn har visat sig ha många positiva effekter. Slutsatser- separation mellan föräldrar och barn har många negativa konsekvenser, såväl fysiska, psykiska som sociala. Kontinuerlig närhet efter förlossningen mellan mamman och det nyfödda barnet är viktigt och närhet mellan pappan och det nyfödda barnet är att föredra vid de tillfällen mor och barn måste separeras. Neonatal samvård skapar förutsättningar för en god anknytning mellan föräldrar och barn och ger möjlighet att påbörja föräldraskapet under optimala förutsättningar.

Separation and Execution of graphical engine on a cross platform IDE to enhance performance

“Biosim” is a simulation software which works to simulate the harvesting system.This system is able to design a model for any logistic problem with the combination of several objects so that the artificial system can show the performance of an individual model. The system will also describe the efficiency, possibility to be chosen for real life application of that particular model. So, when any one wish to setup a logistic model like- harvesting system, in real life he/she may be noticed about the suitable prostitution for his plants and factories as well as he/she may get information about the least number of objects, total time to complete the task, total investment required for his model, total amount of noise produced for his establishment in advance. It will produce an advance over view for his model. But “Biosim” is quite slow .As it is an object based system, it takes long time to make its decision. Here the main task is to modify the system so that it can work faster than the previous. So, the main objective of this thesis is to reduce the load of “Biosim” by making some modification of the original system as well as to increase its efficiency. So that the whole system will be faster than the previous one and performs more efficiently when it will be applied in real life. Theconcept is to separate the execution part of ”Biosim” form its graphical engine and run this separated portion in a third generation language platform. C++ is chosenhere as this external platform. After completing the proposed system, results with different models have been observed. The results show that, for any type of plants of fields, for any number of trucks, the proposed system is faster than the original system. The proposed system takes at least 15% less time “Biosim”. The efficiency increase with the complexity of than the original the model. More complex the model, more efficient the proposed system is than original “Biosim”.Depending on the complexity of a model, the proposed system can be 56.53 % faster than the original “Biosim”.

Violence and reproductive health preceding flight from war : accounts from Somali born women in Sweden

Background: Political violence and war are push factors for migration and social determinants of health among migrants. Somali migration to Sweden has increased threefold since 2004, and now comprises refugees with more than 20 years of war experiences. Health is influenced by earlier life experiences with adverse sexual and reproductive health, violence, and mental distress being linked. Adverse pregnancy outcomes are reported among Somali born refugees in high-income countries. The aim of this study was to explore experiences and perceptions on war, violence, and reproductive health before migration among Somali born women in Sweden. Method: Qualitative semi-structured individual interviews were conducted with 17 Somali born refugee women of fertile age living in Sweden. Thematic analysis was applied. Results: Before migration, widespread war-related violence in the community had created fear, separation, and interruption in daily life in Somalia, and power based restrictions limited access to reproductive health services. The lack of justice and support for women exposed to non-partner sexual violence or intimate partner violence reinforced the risk of shame, stigmatization, and silence. Social networks, stoicism, and faith constituted survival strategies in the context of war. Conclusions: Several factors reinforced non-disclosure of violence exposure among the Somali born women before migration. Therefore, violence-related illness might be overlooked in the health care system. Survival strategies shaped by war contain resources for resilience and enhancement of well-being and sexual and reproductive health and rights in receiving countries after migration.

Violence and reproductive health preceding flight from war : accounts from Somali born women in Sweden

Background: Political violence and war are push factors for migration and social determinants of health among migrants. Somali migration to Sweden has increased threefold since 2004, and now comprises refugees with more than 20 years of war experiences. Health is influenced by earlier life experiences with adverse sexual and reproductive health, violence, and mental distress being linked. Adverse pregnancy outcomes are reported among Somali born refugees in high-income countries. The aim of this study was to explore experiences and perceptions on war, violence, and reproductive health before migration among Somali born women in Sweden. Method: Qualitative semi-structured individual interviews were conducted with 17 Somali born refugee women of fertile age living in Sweden. Thematic analysis was applied. Results: Before migration, widespread war-related violence in the community had created fear, separation, and interruption in daily life in Somalia, and power based restrictions limited access to reproductive health services. The lack of justice and support for women exposed to non-partner sexual violence or intimate partner violence reinforced the risk of shame, stigmatization, and silence. Social networks, stoicism, and faith constituted survival strategies in the context of war. Conclusions: Several factors reinforced non-disclosure of violence exposure among the Somali born women before migration. Therefore, violence-related illness might be overlooked in the health care system. Survival strategies shaped by war contain resources for resilience and

Financial distress as a collapse of incentive scheme

This paper explaina why workers lack motivation near bankruptcy, why they tend to leave companies in financiai distreas, and why thoae who remam require higher compensation. Theae indirect costa of financiai diatresa adie becauae the optimal combination of debt and incentive achem.ea, deaigned to minimize agency costa, ends up underpaying managers when there ia a bankruptcy threat. The paper a1so providea new empirica1 implications on the intera.ction between financiai reatructuring and changea in managerial compensation. Theae predictions are supported by the findings of Gilson and Vetsuypens (1992).