Colored titanium passive films preparation, characterization, applications, and surface modification

L'application de la polarisation par courant alternatif (CA) sur Ie titane dans Ie NH4BF4 aq. a permis d'obtenir des couches passives colorées brillantes et uniformes. Ces types de films révèlent une gamme de couleurs plus étendue comparativement a ceux obtenus par la technique de la passivation en phase gazeuse aux températures élevées. De plus, ces couches peuvent être formées en quelques secondes contrairement aux heures ou même aux journées nécessaires avec un traitement thermique en phase gazeuse sous atmosphère d'oxygène. Ces films démontrent de nouvelles propriétés comme protectrices et décoratives. L'influence des différents paramètres expérimentaux (ex.: Ie pH et la concentration de l'électrolyte, Ie temps de polarisation et Ie type de voltage applique) sur la coloration, l'uniformité et la brillance du film ainsi que sa morphologie a été étudiée. La comparaison avec la polarisation par courant constant (CC) était également effectuée. Les résultats expérimentaux démontrent que les couches passives colorées adhèrent bien au substrat de Ti et ne peuvent en être arrachées. Les analyses au moyen du microscope optique et du microscope a balayage électronique (MEB), confirment que la polarisation par un courant alternatif a forme des couches passives compactes ne révélant pas de fracture ou de fissure contrairement aux couches formées thermiquement en phase gazeuse. L'adhérence du film passif dépend du pré-traitement mécanique du Ti métallique avant sa formation. En général, l'adhérence est meilleure quand les films sont formés sur une surface rugueuse obtenue par décapage. Dans Ie cas d'un film formé sur une surface de Ti polie mécaniquement, l'adhérence est plus faible et Ie polissage ou Ie frottement provoque Ie détachement du film. La caractérisation par spectrométrie des photoélectrons (XPS) des couches passives colorées, révèle que la composition chimique de la surface dépend du voltage lors de la polarisation CA. Les principaux constituants de la couche passive sont Tiz+, 0 et F' (z varie de 4 a 2 selon la profondeur du film). Le fluorure dans Ie film provient de la décomposition du NH4BF4 s'accumulant a 1'interface entre Ie métal et Ie film. L'étude de la variation de la composition chimique en fonction de la profondeur nous montre que plus Ie voltage applique est élevé, plus la couche passive est épaisse.Abstract: Brightly and uniformly colored passive layers on Ti are prepared by application of AC polarization in aqueous NH4 BF4 . Such formed films reveal a wider spectrum of colors that those prepared by gas-phase techniques at elevated temperatures and can be formed within second. The influence of different experimental parameters (electrolyte pH and concentration, duration of polarization, type of applied voltage) on the coloration, uniformity, brightness, and morphology of the colored films is examined. The comparison with DC polarization was also studied. Electrochemical properties of the colored Ti passive layers are determined by recording polarization curves in the -0.8-3.2 V vs. RHE range and Tafel plots in the hydrogen evolution reaction (HER) region in 1.0 M aqueous H2 SO4 solution. Studies of morphology and electrochemical characterization of Ebonex ª are also carried out. One of the objectives of this work was the preparation of Ti-based electrode materials for Hydrogen Evolution Reaction (HER) by surface modification of colored Ti passive layers through RuO2 and/or IrO2 depositing/doping."--Résumé abrégé par UM

HRM-verktyg för minskad agentproblematik och säkrad kompetensförsörjning i IT-branschen

Sammanfattning Examensarbetets titel: HRM för minskad agentproblematik och bättre kompetensförsörjning inom IT-branschen Seminariedatum: 2016-01-14 Ämne/kurs: FEKH19, Examensarbete på kandidatnivå i Strategic Management Författare: Charlotte Karlsson, Ena Hrapovic, William Wallin Handledare: Christine Blomqvist Nyckelord: HRM, IT-branschen, agent-principal-teorin, kompetensbrist, Knowledge Management Syfte: Denna uppsats ämnar studera om agent-principal-teorin kan förklara hur situationen gällande kompetensbrist i IT-branschen kan hanteras. Det leder oss till att undersöka vilka HRM-verktyg som är centrala för att attrahera, behålla och utveckla sin personal i IT-branschen. Metod: Vi har gjort en fallstudie med kvalitativ ansats, där intervjuer har använts för att samla in empirisk primärdata. Intervjuerna var semi-strukturerade för att ge respondenterna möjlighet att fritt utveckla sina svar och påverka diskussionens riktning under intervjutillfället. Teoretiska perspektiv: Agent-principal-teorin beskriver arbetsgivar- och arbetstagarrelationer, hur löneincitament, risk för uppsägning och kontrollsystem används för att säkerställa att medarbetare utför sitt arbete (Eisenhardt, 1989). Wiseman, Rodrìguez & Gomez-Meija (2012) framför att teorin måste anpassas beroende på kontext och att andra mekanismer kan påverka relationen. Stewardshipteorin beskriver att medarbetare och arbetsgivare har gemensamma målsättningar (Donaldson & Davis, 1991). Human Resource Management (HRM) behandlar hur företag arbetar med att attrahera, utveckla och behålla personal (Wikström & Henrik, 2012). Resursbaserad teori (RBV) beskriver konkurrensfördelar genom olika resurser eller kapabiliteter (Barney, 1991). I vår studie gestaltas hur HRM kan vara en eventuell konkurrensfördel. Knowledge Management redogör kring hur företag kan jobba för att sprida kunskap i organisationer (Ikujiro, 1994), vilket är högst centralt i kunskapsintensiva organisationer. Empiri: För insamling av empirisk data utfördes totalt nio intervjuer med tio personer i olika befattning på fyra fallföretag, som är verksamma inom IT-branschen. Analytisk slutsats: Vi kunde bekräfta att löneincitament och kontroll inte är primära faktorer, som teorin traditionellt sätt beskriver, för att hantera agentkostnader och säkra kompetensbehov i den studerade branschen. Den studerade kontexten kräver andra mekanismer som kompetensutveckling, flexibilitet, Knowledge Management och värderingar.Summary Title: HRM for reduced agency problems and better competence skills in the IT industry Seminar date: 2016-01-14 Course: FEKH19, Degree project Undergraduate level, Strategic Management Authors: Charlotte Karlsson, Ena Hrapovic, William Wallin Advisor: Christine Blomqvist Keywords: HRM, IT industry, principal agency theory, competence deficiency, knowledge management Purpose: This study intends to research whether the principal agency theory can explain how the competence deficiency situation in the IT industry should be managed. And clarify which central HRM tools that could be used to attract, retain and develop staff within the IT industry. Methodology: This is a case study with a qualitative approach. Interviews were done to collect empirical primary data. The interviews were semi-structured to give the respondents the opportunity to freely express their answers and influence the discussion through our interview. Theoretical perspectives: Principal agency theory describes empolyer and employee relations, and how salary, risks of being fired and control systems are used to ensure empolyees work performance (Eisenhardt, 1989). Wiseman, Rodrìguez & GomezMeija (2012) concludes that the theory needs to be adjusted depended on the social context and that other mechanisms could be relevant in that specific context. Stewardship theory focuses on how employees and employers strive for a common target (Donaldson & Davis, 1991). Human Resource Management (HRM) explicate how companies are attracting, developing and retaining their employees (Wikström & Henrik, 2012). Resource Based View of Theory (RBV) declare competitive advantage through different resources or capabilities (Barney, 1991), where our study figures how HRM could be a potential competitive advantage. Knowledge Management describes how companies can work to spread knowledge inside their organizations (Ikujiro, 1994), which is an important perspective in knowledge intensive organizations. Empirical foundation: Empirical data was collected through nine interviews with ten employees in different positions in our four research companies that are operating in the IT industry. Conclusions: We could confirm wage incentives and control not being primary factors, as the theory traditionally describes, for handling agency costs and secure required competence in the studied industry. This context requires other mechanisms such as: competence development, flexibility, Knowledge Management and values

Adherence of prebiotic fibers, antioxidants and B complex vitamins on the survival of probiotics

The studies on the relationship between probiotics and prebiotics as well as probiotics and antioxidants have gained significant increase in popularity over the past decade. However, exposure to antibiotics can result in disrupting the human microbiome, causing several related diseases. Additionally, probiotics can lose some of their beneficial effects when in contact with stomach acid which has a pH between 2 and 3. The purpose of this study was to examine the effects of prebiotic fibres and antioxidants and B complex vitamins on the survival of probiotics. When combined with those, a sufficient amount of probiotics survives and carries out their beneficial functions. This study points out the importance of mentioned compounds in maintaining a healthy organism as well as their role in preserving the life of probiotics in our gut

Intrinsic electrochemical activity of single walled carbon nanotube–Nafion assemblies

The intrinsic electrochemical properties and activity of single walled carbon nanotube (SWNT) network electrodes modified by a drop-cast Nafion film have been determined using the one electron oxidation of ferrocene trimethyl ammonium (FcTMA+) as a model redox probe in the Nafion film. Facilitated by the very low transport coefficient of FcTMA+ in Nafion (apparent diffusion coefficient of 1.8 × 10−10 cm2 s−1), SWNTs in the 2-D network behave as individual elements, at short (practical) times, each with their own characteristic diffusion, independent of neighbouring sites, and the response is diagnostic of the proportion of SWNTs active in the composite. Data are analysed using candidate models for cases where: (i) electron transfer events only occur at discrete sites along the sidewall (with a defect density typical of chemical vapour deposition SWNTs); (ii) all of the SWNTs in a network are active. The first case predicts currents that are much smaller than seen experimentally, indicating that significant portions of SWNTs are active in the SWNT–Nafion composite. However, the predictions for a fully active SWNT result in higher currents than seen experimentally, indicating that a fraction of SWNTs are not connected and/or that not all SWNTs are wetted completely by the Nafion film to provide full access of the redox mediator to the SWNT surface

The effect of carbon nanotube aspect ratio and loading on the elastic modulus of electrospun poly(vinyl alcohol)-carbon nanotube hybrid fibers

The reinforcement effect of carbon nanotubes (CNTs) has been examined as a function of their loading and aspect ratio in poly(vinyl alcohol) (PVA) based hybird fibers. Lignosulfonic acid sodium salt (LSA) was used to disperse CNTs to produce consistently high CNT loaded PVA-LSA-CNT hybrid fibers using an electrospinning process. The elastic modulus of individual fibers was measured using atomic force microscopy. The presence of CNTs significantly increased the average elastic modulus of PVA-LSA-CNT fibers compared to PVA-LSA fibers. The elastic modulus, however, exhibited no fiber diameter dependency. Transmission electron microscopy (TEM) was used to determine the loading and the aspect ratio of CNTs in each hybrid fiber. The CNT loading in PVA-LSA-CNT fibers varied widely due to non-uniform CNT dispersion and displayed no relationship with the elastic modulus. Our results also demonstrated that the average value of CNT aspect ratio significantly affected the elastic modulus of the hybrid fibers. Such a result was in agreement with theoretical prediction in which the stress transfer efficiency in a composite matrix is strongly dependent on the CNT aspect ratio.NRC publication: Ye

Preparation of a Polypyrrole-Polyvinylsulphonate Composite Film Biosensor for Determination of Cholesterol Based on Entrapment of Cholesterol Oxidase

In this paper, a novel amperometric cholesterol biosensor with immobilization of cholesterol oxidase on electrochemically polymerized polypyrrole–polyvinylsulphonate (PPy–PVS) films has been accomplished via the entrapment technique on the surface of a platinum electrode. Electropolymerization of pyrrole and polyvinylsulphonate on the Pt surface was carried out by cyclic voltammetry between −1.0 and +2.0 V (vs. Ag/AgCl) at a scan rate of 100 mV upon the Pt electrode with an electrochemical cell containing pyrrole and polyvinylsulphonate. The amperometric determination is based on the electrochemical detection of H2O2 generated in the enzymatic reaction of cholesterol. Determination of cholesterol was carried out by the oxidation of enzymatically produced H2O2 at 0.4 V vs. Ag/AgCl. The effects of pH and temperature were investigated and optimum parameters were found to be 7.25 and 35 °C, respectively. The storage stability and operational stability of the enzyme electrode were also studied. The results show that 32% of the response current was retained after 19 activity assays. The prepared cholesterol biosensor retained 43% of initial activity after 45 days when stored in 0.1 M phosphate buffer solution at 4 °C

Versatile Sarcosine Biosensing Schemes Utilizing Layer-by-Layer Construction of Carbon Nanotube-Chitosan Composite Films

Layer-by-layer composite films of carbon nanotubes (CNTs) within a chitosan matrix with sarcosine oxidase enzyme and capped with Nafion have been developed and optimized as a versatile 1st generation amperometric sarcosine biosensing platform that operates successfully both as an isolated sarcosine sensor as well as a functional component within a creatinine sensor. Accurate measurement of sarcosine in urine and creatinine in blood may help with early diagnosis of diseases such as prostate cancer and renal failure, respectively. In this study, each material within the film is systematically optimized toward sarcosine sensitivity, including a critical evaluation of different CNTs effect on sensing performance. Films featuring carboxylic acid–modified single–walled carbon nanotubes and strategic enzyme doping were shown to be most effective sarcosine sensing platforms, exhibiting excellent sensitivity (~0.5 μA/mM), a linear response (≤ 0.75 mM), fast response time (8 s), low limits of detection (~6 μM), as well as both continuous use stability (7 days) and effective shelf life (\u3e 12 days). Operation of the sarcosine sensor was demonstrated in a urine matrix, detecting sarcosine at physiologically relevant concentrations and successfully quantifying sarcosine-spiked urine samples with high percent recovery and low relative error. The sarcosine sensing platform was also adapted to a 1st generation creatinine biosensing scheme in which the sarcosine enzymatic reaction is critical to a trienzymatic cascade event. The creatinine sensor yielded sensitivity of ~0.6 μA/mM, similar sensing performance parameters to the sarcosine sensor, and was effectively operated in blood serum at physiologically relevant creatinine concentrations. The demonstrated functionality of these sensors in their respective biological fluids at physiological concentrations of the analyte species suggests potential clinical application as diagnostic tools

Selective nanomolar detection of dopamine using a boron-doped diamond electrode modified with an electropolymerized sulfobutylether-\u3b2- cyclodextrin-doped poly(N-acetyltyramine) and polypyrrole composite film

N-Acetyltyramine was synthesized and electropolymerized together with a negatively charged sulfobutylether-\u3b2-cyclodextrin on a boron-doped diamond (BDD) electrode followed by the electropolymerization of pyrrole to form a stable and permselective film for selective dopamine detection. The selectivity and sensitivity of the formed layer-by-layer film was governed by the sequence of deposition and the applied potential. Raman results showed a decrease in the peak intensity at 1329 cm-1 (sp\ub3), the main feature of BDD, upon each electrodeposition step. Such a decrease was correlated well with the change of the charge-transfer resistance derived from impedance data, i.e., reflecting the formation of the layer-by-layer film. The polycrystalline BDD surface became more even with lower surface roughness as revealed by scanning electron and atomic force microscopy. The modified BDD electrode exhibited rapid response to dopamine within 1.5-2 s and a low detection limit of 4-5 nM with excellent reproducibility. Electroactive interferences caused by 4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, ascorbic acid, and uric acid were completely eliminated, whereas the signal response of epinephrine and norepinephrine was significantly suppressed by the permselective film.NRC publication: Ye