Synthesis of polymers and copolymers of lactide through titanium initators

The research described in this thesis explored the synthesis tlnd characteristltion of biocompatible and biodegradable polymers of lactide through non-toxic titanium alkoxide nitiators. The research objectives focused on the preparation of polylactides in both solvent and solventless media, to produce materials with a wide range of molecular weights. The polylactides were fully characterised using gel permeation chromatography and 1H and 13C NMR spectroscopy. NMR spectroscopy was carried out in the study the reaction mechanisms. Kinetic studies of the ring opening polymerisation of lactide with titanium alkoxide initiators were also conducted using NMR spectroscopy. The objectives of this research were also focused on the enhancement of the flexibility of the polymer chains by synthesising random and block copolymers of lactide and ε-caprolactone using Ti(0-i-Pr)4 as an initiator, This work involved extensive characterisalion of the synthesised copolymers using gel permeation chromatography and 1H and 13C NMR spectroscopic analysis. Kinetic studies of the ring opening polymerisation of ε-caplrolactone and of the copolymerisation of lactide and ε-caprolactone with Ti(O-i-Pr)4 as an initiator were also carried out. The last section of this work involved the synthesis of block and star-shaped copolymers of lactide and poly(ethylene glycol) [PEG]. The preparation of lactide/PEG block copolymers was carried out by ring opening polymerisation of L-Iactide using Ti(O-i-Pr)4 as an initiator and hydroxyl-terminated PEG's with different numbers of hydroxyl groups as co-initiators both in solution and solventless media. These all-in-one polymersations yielded the synthesis of both lactide homopolymer and lactide/PEG block copolymer. In order to selectively synthesise copolymers of lactide and PEG, the experiment was carried out in two steps. The first step consisted of the synthesis of a titanium macro-initiator by exchanging the iso-propoxide ligands by PEG with different numbers of hydroxyl groups. The second step involved the ring opening polymerisation of lactide using the titanium macrocatalyst that was prepared as an initiator. The polymerisations were carried out in a solventless media. The synthesis of lactide/PEG copolymers using polyethylene glycol with amino terminal groups was also discussed. Extensive characterisation of the lactide block copolymers and macroinitiators was carried out using techniques such as, gel permeation chromatography (GPC), NMR spectroscopy and differential scanning calorimeter (DeS)

The impact of cultural dissonance and acculturation orientations on immigrant students' academic performance

Indexación: Scopus; Scielo; Redalyc.Prior research has documented meaningful differences between school performance of immigrant and native students. Multicultural education has been associated with academic failure of foreign students. e aim of this study was to examine the impact of a set of psychosocial variables on the perceived academic achievement of first generation immigrant adolescents from public secondary schools in Northern Spain. Results showed that 46% of the variability in foreign students’ perceived academic performance was explained by home-school cultural dissonance. We also explored the impact of acculturation orientation to separation, perception of discrimination from teachers, school adjustment, and psychological well-being in academic performance. Any multicultural education context should take into account psychosocial adjustment, given its influence on academic performance of all studentsSe han hallado diferencias significativas entre el rendimiento académico de los inmigrantes y el de los estudiantes nativos. Sin embargo, hay una escasa evidencia acerca de los aspectos psicosociales de este fenómeno. El objetivo de este estudio fue examinar el impacto de un conjunto de variables psicosociales: disonancia cultural y orientaciones de aculturación en el rendimiento académico percibido de adolescentes inmigrantes de primera generación de centros de Educación Secundaria en el Norte de España. Los resultados mostraron que alrededor del 46% de la variabilidad en el rendimiento era explicada por la disonancia cultural entre escuela y hogar. Cualquier contexto de educación multicultural ha de tomar en consideración el ajuste psicosocial, dada su influencia en el rendimiento académico de los estudiantes.http://www.redalyc.org/jatsRepo/647/64753989003/index.htm

Micro-Nano Technologies for Cell Manipulation and Subcellular Monitoring

Rehabilitatio

Infrared and millimetre-wavelength evidence for cold accretion within a z = 2.83 Lyman-alpha blob

‘The definitive version is available at www.blackwell-synergy.com.’ Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.13580.xThis paper discusses infrared and millimetre-wavelength observations of a Lyman alpha blob (LAB) discovered by Smith & Jarvis, a candidate for ionization by the cold accretion scenario discussed in Fardal et al. and Dijkstra et al. We have observed the counterpart galaxy at infrared wavelengths in deep observations with the Spitzer Space Telescope using the IRAC 3.6, 4.5, 5.8 and 8.0 mu m and MIPS 24 mu m bands, as well as using the Max-Planck Millimeter Bolometer (MAMBO-2) at a wavelength of 1.2 mm with the IRAM 30 m telescope. These observations probe the greater than or similar to 95 kpc Lyman alpha halo for the presence of obscured active galactic nucleus (AGN) components or the presence of a violent period of star formation invoked by other models of ionization for these mysterious objects. 24 mu m observations suggest that an obscured AGN would be insufficiently luminous to ionize the halo, and that the star formation rate within the halo may be as low as < 140 M-circle dot yr(-1) depending on the model spectral energy distribution (SED) used. This is reinforced by our observations at 1.2 mm using MAMBO-2, which yield an upper limit of star formation rate < 550 M-circle dot yr(-1) from our non-detection to a 3 sigma flux limit of 0.86 mJy beam(-1). Finding no evidence for either AGN or extensive star formation, we conclude that this halo is ionized by a cold accretion process. We derive model SEDs for the host galaxy, and use the Bruzual & Charlot and Maraston libraries to show that the galaxy is well described by composite stellar populations of total mass 3.42 +/- 0.13 x 10(11) or 4.35 +/- 0.16 x 10(11) M-circle dot depending on the model SEDs used.Peer reviewe

Factores con mayor influencia sobre la elección de alimentos en la población española

Fundamentos: Encuesta poblacional dirigida a conocer los factores que influyen en la elección de los alimentos de la población española. Métodos: Análisis de una muestra de todo el territorio español compuesta por 1009 individuos y seleccionada por un procedimiento aleatorio multietápico. Este estudio corresponde a la participación española en un estudio europeo sobre las actitudes de la población frente a la alimentación, nutrición y salud dirigido por el Instituto Europeo de Estudios Nutricionales de Dublín. Se determinó el porcentaje de individuos que situó a alguno de los cinco factores mencionados con más frecuencia (calidad, precio, dieta sana, condicionantes españoles, sabor) entre las tres primeras influencias en la elección de alimentos. Se ajustó un modelo multivariante para identificar los factores asociados a la elección de una dieta sana como una de las tres primeras influencias en la alimentación.Resultados: El precio influía más en los individuos de mayor edad, en niveles socioeconómicos más bajos y en individuos con menor nivel educativo. Fue mayor el impacto del precio en las mujeres de la zona Norte, Noreste y Noroeste. El sexo, la distribución geográfica, la edad y el nivel educativo presentaron un efecto independiente y significativo sobre la importancia concedida por la población a la elección de una dieta sana. Conclusiones: Los resultados sugieren la necesidad de una mayor educación sobre dieta y salud especialmente en hombre jóvenes, personas con menor nivel educativo y mujeres del Noroeste del país

Inclusive Nucleon Emission Induced by Quasi--Elastic Neutrino--Nucleus Interactions

We study the quasi--elastic contribution to the inclusive $(\nu_l,\nu_l N)$, $(\nu_l,l^- N)$, $({\bar \nu}_l,{\bar \nu}_l N)$ and $({\bar \nu}_l,l^+ N)$ reactions in nuclei using a Monte Carlo simulation method to account for the rescattering of the outgoing nucleon. As input, we take the reaction probability from the microscopical many body framework developed in Phys. Rev. {\bf C70} (2004) 055503 for charged-current induced reactions, while for neutral currents we use results from a natural extension of the model described in that reference. The nucleon emission process studied here is a clear signal for neutral--current neutrino driven reactions, that can be used in the analysis of future neutrino experiments.Comment: 23 pages, 17 figures; Version 2: few typos correcte

Tell me your age and I tell you what you trust: the moderating effect of generations

Purpose: The proliferation of social commerce websites has allowed consumers to share and exchange information, experiences, advice and opinions. Recently, information provided by users has been considered more trustworthy than the information shared by companies. However, the way in which users interact with technology can vary with age, and generational cohorts show different shopping behaviors, interests and attitudes. Hence, the way users process information (user-generated vs company-generated) can affect trust differently. Drawing on the trust transfer theory and the generational cohort theory, the purpose of this paper is to analyze the effects on user- and company-generated information in boosting trust of three different cohorts (Generation X, Y and Z). Design/methodology/approach: The data were collected through an online survey. The sample comprised 715 users of social commerce websites, aged between 16 and 55 years old. The study was analyzed using partial least squares with the statistical software Smart PLS 3. Findings: The empirical results show that generational cohorts show different patterns. Generation X transfers trust to social commerce websites mainly from trust in information generated by companies, while Generation Z transfers trust mainly from information generated by users. Finally, Generation Y, in contrast to previous findings about millennials, develops trust based on company-generated information to an even greater extent than does Generation X. Originality/value: The originality of this study lies in its analysis of generational differences when it comes to trusting one type of information over another. This study contributes to the idea that users cannot be considered as a whole but must be segmented into generational cohorts

Distribution and determinants of sedentary lifestyles in the European Union

Background Many studies have shown the health burden of a sedentary lifestyle. The main goal of this study was to determine the prevalence of sedentary lifestyles in the 15 Member States of the European Union (EU) and to identify the main correlates of a sedentary lifestyle. Methods Nationally representative samples (n ≈ 1000 subjects in each country; >15 years) completed a questionnaire concerning attitudes to physical activity, body weight, and health; in total 15 239 subjects. Sedentary people were defined in two ways: (1) those expending less than 10% of their leisure time expenditure in activities involving ≥4 metabolic equivalents (MET). (2) Those who did not practice any leisure-time physical activity and who also were above the median in the number of hours spent sitting down during leisure time. Logistic regression models were fitted to analyse the association between sedentary lifestyles and gender, age, body mass index (BMI), educational level, weight change in the last 6 months, and marital and smoking status. Results Percentages of sedentary lifestyles across European countries ranged between 43.3% (Sweden) and 87.8% (Portugal) according to the first definition. According to both definitions, a lower prevalence of sedentary lifestyle was found in Northern countries (especially Scandinavian countries) as compared with Mediterranean countries, whereas the prevalence was higher among older, obese, less educated, widowed/divorced individuals, and current smokers. Similar relative differences between countries and socio-demographic groups were found independently of the method used to define a sedentary lifestyle. Conclusion Prevalence of sedentary lifestyle in the EU is high, especially among inhabitants of some Mediterranean countries, obese subjects, less-educated people, and current smokers. This high prevalence involves important public health burdens and preventive strategies are urgently needed

From sPassion to sWOM: The role of flow

Purpose - Social commerce websites entail a completely new scenario for sharing experiences and opinions due to its richness in terms of social interactions. Nowadays, users can interact with the company and with other users; hence, it seems important to study how social stimuli affect users. Drawing on the stimulus-organism-response framework and flow theory, the purpose of this paper is to propose that the social stimulus (named social passion (sPassion)) has a positive effect on the organism (state of flow), which leads to a users' positive response (via social word of mouth (sWOM)). Design/methodology/approach - The data were collected through an online survey in 2015. The sample consists of 771 users of social commerce websites, of which 51 percent are male and 49 percent female, aged between 16 and 80 years old. Structural equation modeling was used to analyze the data with the statistical software SPSS version 22 and EQS 6. Findings - The empirical results confirm that passionate users are prone to experience a state of flow and, as a consequence, share positive sWOM. Originality/value - This study contributes to the literature on customers' online participation, and the findings are hoped to help companies in developing social commerce websites that boost users' exchange of information

Social commerce users'' optimal experience: stimuli, response and culture

Social commerce users' experience is generated during socio-commercial interactions. Therein, users receive utilitarian and hedonic stimuli that form their experience and influence their responses. However, research is needed to understand how this experience is generated. Based on the stimulus-organism-response framework and flow theory, this study analyzes how hedonic stimulus (here called sPassion) and utilitarian stimulus (usability) affect users' flow experience (organism) to positively impact emotional and behavioral loyalty (users' responses). Furthermore, as social commerce users are culturally diverse, the moderating effect of cultural background is studied, drawing on Hofstede's cultural dimensions. Findings show that hedonic stimulus more strongly impacts social commerce users' flow experience versus utilitarian stimulus. Once users reach the state of optimal experience, their positive responses are reflected in their increased intention to spread social word of mouth, to return to the website and to repurchase on it. Additionally, optimal user experience in social commerce is generated mainly through hedonic stimuli and, while social commerce environments can be culturally diverse, cultural background does not imply changes in users' behavioral patterns. This study theoretically advances research on social commerce users' experience. Likewise, the findings guide online retailers in optimizing user experience via hedonic stimuli to enhance loyalty