Understanding the in vitro dissolution rate of glasses with respect to future clinical applications

Glass is a unique material with a long history. Several glass products are used daily in our everyday life, often unnoticed. Glass can be found not only in obvious applications such as tableware, windows, and light bulbs, but also in tennis rackets, windmill turbine blades, optical devices, and medical implants. The glasses used at present as implants are inorganic silica-based melt-derived compositions mainly for hard-tissue repair as bone graft substitute in dentistry and orthopedics. The degree of glass reactivity desired varies according to implantation situation and it is vital that the ion release from any glasses used in medical applications is controlled. Understanding the in vitro dissolution rate of glasses provides a first approximation of their behavior in vivo. Specific studies concerning dissolution properties of bioactive glasses have been relatively scarce and mostly concentrated to static condition studies. The motivation behind this work was to develop a simple and accurate method for quantifying the in vitro dissolution rate of highly different types of glass compositions with interest for future clinical applications. By combining information from various experimental conditions, a better knowledge of glass dissolution and the suitability of different glasses for different medical applications can be obtained. Thus, two traditional and one novel approach were utilized in this thesis to study glass dissolution. The chemical durability of silicate glasses was tested in water and TRIS-buffered solution at static and dynamic conditions. The traditional in vitro testing with a TRISbuffered solution under static conditions works well with bioactive or with readily dissolving glasses, and it is easy to follow the ion dissolution reactions. However, in the buffered solution no marked differences between the more durable glasses were observed. The hydrolytic resistance of the glasses was studied using the standard procedure ISO 719. The relative scale given by the standard failed to provide any relevant information when bioactive glasses were studied. However, the clear differences in the hydrolytic resistance values imply that the method could be used as a rapid test to get an overall idea of the biodegradability of glasses. The standard method combined with the ion concentration and pH measurements gives a better estimate of the hydrolytic resistance because of the high silicon amount released from a glass. A sensitive on-line analysis method utilizing inductively coupled plasma optical emission spectrometer and a flow-through micro-volume pH electrode was developed to study the initial dissolution of biocompatible glasses. This approach was found suitable for compositions within a large range of chemical durability. With this approach, the initial dissolution of all ions could be measured simultaneously and quantitatively, which gave a good overall idea of the initial dissolution rates for the individual ions and the dissolution mechanism. These types of results with glass dissolution were presented for the first time during the course of writing this thesis. Based on the initial dissolution patterns obtained with the novel approach using TRIS, the experimental glasses could be divided into four distinct categories. The initial dissolution patterns of glasses correlated well with the anticipated bioactivity. Moreover, the normalized surface-specific mass loss rates and the different in vivo models and the actual in vivo data correlated well. The results suggest that this type of approach can be used for prescreening the suitability of novel glass compositions for future clinical applications. Furthermore, the results shed light on the possible bioactivity of glasses. An additional goal in this thesis was to gain insight into the phase changes occurring during various heat treatments of glasses with three selected compositions. Engineering-type T-T-T curves for glasses 1-98 and 13-93 were stablished. The information gained is essential in manufacturing amorphous porous implants or for drawing of continuous fibers of the glasses. Although both glasses can be hot worked to amorphous products at carefully controlled conditions, 1-98 showed one magnitude greater nucleation and crystal growth rate than 13-93. Thus, 13-93 is better suited than 1-98 for working processes which require long residence times at high temperatures. It was also shown that amorphous and partially crystalline porous implants can be sintered from bioactive glass S53P4. Surface crystallization of S53P4, forming Na2O∙CaO∙2SiO2, was observed to start at 650°C. The secondary crystals of Na2Ca4(PO4)2SiO4, reported for the first time in this thesis, were detected at higher temperatures, from 850°C to 1000°C. The crystal phases formed affected the dissolution behavior of the implants in simulated body fluid. This study opens up new possibilities for using S53P4 to manufacture various structures, while tailoring their bioactivity by controlling the proportions of the different phases. The results obtained in this thesis give valuable additional information and tools to the state of the art for designing glasses with respect to future clinical applications. With the knowledge gained we can identify different dissolution patters and use this information to improve the tuning of glass compositions. In addition, the novel online analysis approach provides an excellent opportunity to further enhance our knowledge of glass behavior in simulated body conditions.

Suomen peliteollisuuden kasvu ja kansainvälistyminen

Suomen peliteollisuus on ollut erittäin puhuttu aihe mediassa viime vuosien ajan. Työmme pyrkii selvittämään Suomen peliteollisuuden kasvun ja kansainvälistymisprosessin taustalla olleita tekijöitä sekä niiden suhteita toisiinsa. Työssä keskitytään analysoimaan jo tapahtunutta kasvua ja kansainvälistymistä, joiden tarkastelussa käytetään hyväksi Porterin jalostamaa Klusteri -teoriaa sekä kasvuyritysten uutta kansainvälistymisilmiötä, Born Global -teoriaa. Suomen peliteollisuuden klusterista esitetään hahmotelma pelialan kattavan kokonaiskuvan rakentamiseksi. Lopuksi kootaan havaintoja ja johtopäätöksiä Suomen peliteollisuusalan kasvuprosessista eri aikakausilta sekä analysoidaan kansainvälistymisprosessin kulkua ja metodologiaa. Myös näkemyksiä Suomen peliteollisuuden tulevaisuudesta esitetään. Suomen peliteollisuuden kasvua arvioidessa voidaan havaita, että sen kasvunopeus on lisääntynyt huomattavasti viimeisen muutaman vuoden aikana. Alan yritysten kasvu painottuu erittäin vahvasti globaaleille markkinoille. Peliteollisuus on kuitenkin edelleen erittäin pieni teollisuudenala Suomessa. Tulevaisuudessa sen koko ja merkitys tulevat kasvamaan, ja varsinkin Suomen mobiilipeliteollisuuden tulevaisuus näyttää valoisalta.

The 5alpha-reductase type 1, but not type 2, gene is expressed in anagen hairs plucked from the vertex area of the scalp of hirsute women and normal individuals

The aim of the present study was to determine the expression of the genes for type 1 (SDR5A1) and type 2 (SDR5A2) 5alpha-reductase isoenzymes in scalp hairs plucked from 33 hirsute patients (20 with polycystic ovary syndrome and 13 with idiopathic hirsutism) and compare it with that of 10 men and 15 normal women. SDR5A1 and SDR5A2 expression was estimated by RT-PCR using the gene of the ubiquitously expressed protein ß2-microglobulin as an internal control. The results are expressed as arbitrary units in relation to ß2-microglobulin absorbance (mean ± SEM). SDR5A2 expression was not detected in any hair samples analyzed in this study. No differences were found in SDR5A1 mRNA levels between men and normal women (0.78 ± 0.05 vs 0.74 ± 0.06, respectively). SDR5A1 gene expression in the cells of hair plucked from the scalp of normal women (0.85 ± 0.04) and of women with polycystic ovary syndrome (0.78 ± 0.05) and idiopathic hirsutism (0.80 ± 0.06) was also similar. These results indicate that SDR5A1 gene expression in the follicular keratinocytes from the vertex area of the scalp seems not to be related to the differences in hair growth observed between normal men and women and hirsute patients. Further studies are needed to investigate the expression of the 5alpha-reductase genes in other scalp follicular compartments such as dermal papillae, and also in hair follicles from other body sites, in order to elucidate the mechanism of androgen action on the hair growth process and related diseases.

Uma análise da estratégia nacional de desenvolvimento da Malásia

This paper aims at studying Malaysia's national development strategy in the last three decades. Firstly, we will give emphasis to the country's economic planning development, its medium-term and long-term plans, as well as Mahathir's political influence. Secondly, we will try to identify key elements in the Malaysian growth process, such as its exchange rate and current account policies, the participation of the government in the whole process and matters related to domestic savings and foreign direct investment. We will also talk about the 1997 financial crisis.

Há compatibilidade entre a "tecnologia social" de Nelson e a "causalidade vebleniana" de Hodgson?

Is there compatibility between Nelson's 'Social Technology' and Hodgson's 'Veblenian Causality'? This paper aims to discuss the role and the relationship among the concept of institutions and the economic growth process, through the Neo-Schumpeterian and Institutionalist approaches. Both of them constitute a new research agenda differentiated and opposite to the mainstream. In the first part of the paper we discuss the research agenda proposed by Richard Nelson who emphasizes the necessity to unpack the institution concept throughout the social technology notion. In the second part we discuss Geoffrey Hodgson's contribution that suggests inserting this process in an evolutionary perspective, which has in habits, norms and social behavior his major characteristic.

Étude par dynamique moléculaire de l'ablation par impulsions laser ultrabrèves de cibles nanocristallines

L’ablation de cibles d’Al nanocristallines (taille moyenne des cristallites d = 3,1 et 6,2 nm) par impulsions laser ultrabrèves (200 fs) a été étudiée par l’entremise de si- mulations combinant la dynamique moléculaire et le modèle à deux températures (two- temperature model, TTM) pour des fluences absorbées allant de 100 à 1300 J/m2. Nos simulations emploient un potentiel d’interaction de type EAM et les propriétés électro- niques des cibles en lien avec le TTM sont représentées par un modèle réaliste possédant une forme distincte dans le solide monocristallin, le solide nanocristallin et le liquide. Nous avons considéré l’effet de la taille moyenne des cristallites de même que celui de la porosité et nous avons procédé à une comparaison directe avec des cibles mono- cristallines. Nous avons pu montrer que le seuil d’ablation des métaux nanocristallins est significativement plus bas, se situant à 400 J/m2 plutôt qu’à 600 J/m2 dans le cas des cibles monocristallines, l’écart étant principalement dû à l’onde mécanique plus im- portante présente lors de l’ablation. Leur seuil de spallation de la face arrière est aussi significativement plus bas de par la résistance à la tension plus faible (5,40 GPa contre 7,24 GPa) des cibles nanocristallines. Il est aussi apparu que les contraintes résiduelles accompagnant généralement l’ablation laser sont absentes lors de l’ablation de cibles d’aluminium nanocristallines puisque la croissance cristalline leur permet d’abaisser leur volume spécifique. Nos résultats indiquent aussi que le seuil de fusion des cibles nano- cristallines est réduit de façon marquée dans ces cibles ce qui s’explique par la plus faible énergie de cohésion inhérente à ces matériaux. Nos simulations permettent de montrer que les propriétés structurelles et électroniques propres aux métaux nanocristallins ont toutes deux un impact important sur l’ablation.

Isolation and Characterization of Agglutinin in the Hemolymph of Penaeus indicus H. Milne Edwards

The present study is an attempt to find out the ralation between RNA/DNA ratio, protein,percentage growth rate and specific growth rate of prawn,Penaeus indicus with respect to Nervous system, Eyestalk and Muscle tissues during ontogenesis. We have isolated and purified a natural agglutinin in the hemolymph of P.indicus with antigenecity, agglutinating, hemolytic and antibacterial properties. The influence of growth and environmental parameters on the level of agglutinin in the hemolymph was studied. Agglutinin concentration during normal growth process was compared. The agglutinin concentration in the hemolymph was quantified through developing ELISA, which is useful in health monitoring studies of individual species. Complete amino acid composition of both the subunits of P.indicus agglutinin were analysed. P.indicus agglutinin showed similarity to those proteins having antigenecity,hemolytic and agglutinating properties.Hence, agglutinin was considered as a natural defence protein in the hemolymph of P.indicus responsible for immune surveillance. The humoral defence mechanism of agglutinin was a co-operative effort with hemocytes and complement system. The composition of isolated agglutinin of P.indicus amino acids will be helpful in the synthesis of new antibacterial analogues which can be used against disease causing organisms.

Studies on the physiology of moulting in the penaeid prawn, penaeius indicius h. Milne edwards

Penaeid prawns form the most economically significant group in the marine and brackishwater fishery resources of India. This particular group contributes about 62% of the total prawn landings of the country. At present prawns have assumed an important place especially as a commodity supporting an export trade of sizable magnitude. Considerable interest has been shown in the last decade to increase prawn production through various culture practices, mainly due to the high demand for good quality prawns for export coupled with the stagnant and even depleting nature of marine catches. Available informations suggest that among the 15 species of shrimps and prawns occurring in Indian waters, which are deemed suitable for aquaculture, the Indian white prawn §.indicus is identified as one of the most important commercial species. Considering the increasing importance as an accepted species for prawn culture, £.indicus was selected for the present study. In the life history of prawns, moulting is an important event, which enables the animal to achieve growth. This dynamic physiological event continues through out the life span ofthe prawn, linking almost all biological activities with this process. Hence, a good knowledge pertaining to the physiology of moulting is imperative to understand the growth process. This knowledge will be of great use in the scientific prawn farming, so as to achieve high prawn production.

Investigations on some amino acid based single crystals for nonlinear optical applications and amino acid capped nanocrystals

Organic crystals possess extremely large optical nonlinearity compared to inorganic crystals. Also organic compounds have the amenability for synthesis and scope for introducing desirable characteristics by inclusions. A wide variety of organic materials having electron donor and acceptor groups, generate high order of nonlinearity. In the present work, a new nonlinear optical crystal, L-citrulline oxalate (LCO) based on the aminoacid L-citrulline was grown using slow evaporation technique. Structural characterization was carried out by single crystal XRD. It crystallizes in the noncentrosymmetric, orthorhombic structure with space group P21 P21 P21. Functional groups present in the sample were identified by Fourier transform infra red (FTIR) and FT-Raman spectral analysis. On studying the FTIR and Raman spectra of the precursors L-citrulline and oxalic acid, used for growing L-citrulline oxalate crystal, it is found that the significant peaks of the precursors are present in the spectra of the L-citrulline oxalate crystal . This observation along with the presence of NH3 + group in the spectra of L-citrulline oxalate, confirms the formation of the charge transfer complex

Characterization and FTIR spectral studies of human urinary stones from Southern India

Urinary stones resected from urinary bladders of patients hailing from Kollam district of Kerala State, India were analyzed by SEM, XRD and by thermal analysis techniques. The analytical results indicate that, stones have different composition, i.e., calcium phosphate, calcium phosphate hydroxide and sodium calcium carbonate. Infrared spectral studies also reveal the presence of phosphates or carbonates in these samples. Further, IR spectral investigations have revealed that amorphous carbonated species are occupied in PO4 sites in calcium phosphate type stone and OH sites in calcium phosphate hydroxide sample. Thermal studies of these samples also reveal that, carbon dioxide is released from carbonated samples upon heating which is related to amount of carbon content and bond strength. Crystals with defects and irregular morphology are grown inside the urinary bladder due to variation in crystal growth conditions

Defects in Self Assembled Colloidal Crystals

Colloidal self assembly is an efficient method for making 3-D ordered nanostructures suitable for materials such as photonic crystals and macroscopic solids for catalysis and sensor applications. Colloidal crystals grown by convective methods exhibit defects on two different scales. Macro defects such as cracks and void bands originate from the dynamics of meniscus motion during colloidal crystal growth while micro defects like vacancies, dislocation and stacking faults are indigenous to the colloidal crystalline structure. This paper analyses the crystallography and energetics of the microscopic defects from the point of view of classical thermodynamics and discusses the strategy for the control of the macroscopic defects through optimization of the liquid-vapor interface.

Biological Routes to Gold Nanoplates

Much effort has been devoted to the synthesis of gold nanoparticles with different shapes, including the zero-dimensional nanospheres, one dimensional nanorods, and two-dimensional nanoplates. Compared to zero or one dimensional nanostructures, the synthesis of two-dimensional nanostructures in high yield has always been more involved, often requiring complex and time-consuming steps such as morphology transformation from the nanospheres, or the seeded growth process. Herein we report a high yield method for gold nanoplate synthesis using the extract of unicellular green alga Chlorella vulgaris, which can be carried out under ambient conditions. More than 90% of the total nanoparticle population is of the platelet morphology, surpassing the previously reported value of 45%. The control of the anisotropic growth of different planes; as well as the lateral size, has also been partially optimized.

W3233 -- Networks and Complexity in Social Systems (Collective Dynamics Group ISERP -- Columbia University) Course Syllabus

The Networks and Complexity in Social Systems course commences with an overview of the nascent field of complex networks, dividing it into three related but distinct strands: Statistical description of large scale networks, viewed as static objects; the dynamic evolution of networks, where now the structure of the network is understood in terms of a growth process; and dynamical processes that take place on fixed networks; that is, "networked dynamical systems". (A fourth area of potential research ties all the previous three strands together under the rubric of co-evolution of networks and dynamics, but very little research has been done in this vein and so it is omitted.) The remainder of the course treats each of the three strands in greater detail, introducing technical knowledge as required, summarizing the research papers that have introduced the principal ideas, and pointing out directions for future development. With regard to networked dynamical systems, the course treats in detail the more specific topic of information propagation in networks, in part because this topic is of great relevance to social science, and in part because it has received the most attention in the literature to date.

Vida y muerte empresarial, estudios empíricos de perdurabilidad

Servientrega S.A. es una empresa exitosa y perdurable. Por medio del presente trabajo se pretendió analizar qué factores le han permitido a Servientrega que ésta sea su realidad, bajo el marco expuesto por la investigación de la Facultad de Administración de la Universidad del Rosario que determina los 13 componentes de la perdurabilidad empresarial. Un acercamiento a los niveles de la gerencia y dirección de la organización permitieron identificar a partir de su proceso de crecimiento, las crisis que ha enfrentado y cómo ha logrado recuperarse de ellas, al mismo tiempo que los aspectos más destacados que hacen a Servientrega perdurable en el tiempo. Para lograr el análisis y desarrollo del presente trabajo, se obtuvo información primaria y secundaria por medio de 54 encuestas entre los empleados de la compañía, dónde se indagaba por los atributos que la Facultad de Administración, consideró eran claves para la perdurabilidad de una empresa. De igual forma, se realizó una entrevista personal con los fundadores de la compañía, la Señora Luz Mary Guerrero y el Señor Jesús Guerrero.

Análisis comparativo financiero de las empresas galardonadas y nominadas al premio Mariposa Lorenz.

El estudio de la perdurabilidad empresarial permite pensar cómo sobreviven las empresas a variables endógenas cómo exógenas de su entorno. Una de las variables exógenas de alta importancia son los créditos financieros. El acceso al crédito para empresas que están en constante inversión, crecimiento, desarrollo, transformación cultural como también la internacionalización, son fundamentales para poder convertirse en empresas perdurables en el tiempo, y es aquí donde otras variables exógenas del mercado, como crisis, expansión, tratados de libre comercio, entre otras, juegan un papel fundamental en su proceso de crecimiento haciendo indispensable el financiamiento de sus proyectos y el apalancamiento de los mismos. Uno de los problemas de las empresas del mercado financiero Colombiano son las altas tasas de interés, las cuales han ocasionado las empresas se vean en la obligación de tener un respaldo financiero alto para poder reaccionar ante sus deudas y cualquier imprevisto en el mercado cambiante y sin paradigmas en el que nos desarrollamos. La presente investigación, busca hacer un acercamiento al comportamiento financiero de las empresas perdurables que obtuvieron el premio Empresario Colombiano del Año Mariposa Lorenz de la Universidad del Rosario , teniendo en cuenta el análisis comparativo de indicadores financieros como Liquidez, Endeudamiento, Actividad y Rentabilidad, ligados a áreas estratégicas como lo son Dirección y Gerencia a partir de la exploración de una encuesta que consta de 47 preguntas en dónde se destacan las que tienen mayor relación con los aspectos anteriormente mencionados.