Synthesis and luminescence properties of some Ce3+ doped silica sols

Ce -doped silica sols samples were prepared by acid, or two steps catalyzed sol-gel process, at different concentration of Ce3+ dopant. As silica precursors, tetraetoxysilane, or tetrametoxysilane, or a precursors mixture consisting of tetraetoxysilane and isobuthyltrietoxysilane, were used. By UV excitation, all synthesized samples presented strong luminescence emission with maxima situated at ~ 386 nm. Regarding the emission efficiency, better results were achieved at lower Ce3+ concentrations. Depending on precursors nature, a favorable influence had the use of precursors mixture

Influence of synthesis parameters on luminescence emission properties of some sol-gel derived Eu3+ doped willemite phosphors

Europium doped zinc silicate phosphor sample, corresponding to general formula, Zn2-(x+y)EuxLiySi0 4 , (where x = 0.01 or 0.02 and y = 0, 0.01, or 0, 02), have been synthesized by acid, or two steps (acid-base) catalyzed sol-gel processing, in the presence, or absence of Li+ ions, as charge compensator. The obtained xerogel samples was successively annealed, at different steps, up to 1000°C, for 180 minutes time soaking for each temperature. Starting from 700°C temperature, the formation of Si-O-Zn linkage was put in evidence by FT-IR spectra. The appearance of IR signals corresponding to willemite vibration modes has been observed for 900°C calcined samples. At UV excitation beam, the luminescence spectra of Zn2Si0 4 :Eu3+ synthesized phosphors samples show some emission peaks in the red region of spectra, assigned to 5Do—> Fj (j = 0, 1, 2, 3, 4 and 5) spin forbidden f-f transitions of Eu3+ ions, respectively. Specifically they were situated around 575 nm, 590 nm, 615 nm, 624 nm, 650 nm and 700 nm. The most intense emission was observed for the 1000°C calcined sample, with 0.02 moles Eu3+ activator content, prepared with charge compensator

5-(4-Pyridyl)dipyrromethane-silica sol synthesis and luminescent properties

Methodologies for the immobilization and characterization of 5(4-pyridyl)dipyrromethane into silica gel are described. The corresponding spectroscopic, thermal, and photochemical properties are used for their characterization and study

Mesoporous silica matrices derived from sol-gel process assisted by low power ultrasonic activation

The present work contributes to elucidating the differences between silica gels obtained by low doses ultrasonic activation, and those obtained by the conventional method, termed as classical sol gel. Silica matrices were produced by sol-gel synthesis process, assisted and non-assisted by an ultrasonic field, and subsequently characterized by various methods. Nitrogen adsorption and small-angle neutron scattering (SANS) measurements provided texture and microstructure of the dried gels. The adsorption results show that the sample sonicated for 2 hours presents the most ordered microstructure, characterized by pore shape close to spherical and the narrowest size distribution – about 90 % of the pores for this sample fall into the mesopore range (2–50 nm). SANS data reveal the formation of primary structural units of sizes around 1.5–2 nm which are small linear or branched polymeric species of roughly spherical shape and with rough surface. They are generated in the very early stage of sol gel process, as a result of hydrolysis and condensation reactions. The aggregated primary units form the secondary porous structure which can be described as a rough surface with fractal dimension above 2. The best porosity characteristics were obtained for the sample activated for 2 hours, indicating the optimal doses of sonication in the present conditions. Our results demonstrate the possibility of tailoring the pore size distribution using a low power ultrasonic bath

Exemptions Resulting from the International Public Sector Accounting Standards (IPSAS) and European Standards for Intangible Investment, Inventories and Personnel Expenditures in Public Entities

Simultaneously with the globalization of economies, it was necessary the adoption and implementation of international accounting standards for the public sector also. In 1996 a set of accounting standards for public sector entities was developed, namely International Public Sector Accounting Standards (IPSAS). After 31st July 1998, 32 IPSAS standards, mostly inspired by IASs, centered on model and engagement-based accounting, were issued. IPSAS 1 – Presentation of financial statements relating to the place of intangible assets, inventories and personnel expenses in the content and format of the financial statements is applied to all general purpose financial statements realized under accrual accounting. The IPSAS 12 – Inventory objective is to state the stock accounting treatment. The IPSAS 25 objective – Employee benefits is to state the employee benefits from an accounting perspective

Software Tools Used for Continuous Assessment

he present paper addresses the subject of continuous evaluation and of the IT tools that support it. The approach starts from the main concepts and methods used in the teaching process, according to the assessment methodology and, then, it focuses on their implementation in the Wondershare QuizCreator software

Social Business Models

A Social Business embraces networks of people to create business value. A Social Business connects people to expertise. It enable individuals – whether customers, partners or employees – to form networks to generate new sources of innovation, foster creativity, and establish greater reach and exposure to new business opportunities. It establishes a foundational level of trust across these business networks and, thus, a willingness to openly share information. It empowers these networks with the collaborative, gaming and analytical tools needed for members to engage each other and creatively solve business challenges. A Social business strives to remove unnecessary boundaries between experts inside the company and experts in the marketplace. It embraces the tools and leadership models that support capturing knowledge and insight from many sources, allowing it to quickly sense changes in customer mood, employee sentiment or process efficiencies. It utilizes analytics and social connections inside and outside the company to solve business problems and capture new business opportunities. A Social Business leverages these social networks to speed up business, gaining real time insight to make quicker and better decisions. It gets information to customers and partners in new ways -- faster. Supported by ubiquitous access on mobile devices and new ways of connecting and working together in the Cloud and on open platforms, a Social Business turns time and location from constraints into advantages. Business is free to occur when and where it delivers the greatest value, allowing the organization to adapt quickly to the changing marketplace. We believe the most effective approach to enabling a Social Business centers around helping people discover expertise, develop social networks and capitalize on relationships

The IT Impact on the Productivity and the Organizational Performance of Firms in Romania. A model of Empirical Analysis

The paper propose an analysis based on an empirical model of IT impact on firms performances of Romania. There are presented the model, the equations of the model and the results of statistical processing. All these shown that the ICT impact on firm performance is greater and positive if the information technologies are accompanied by a proactive management policy and an organizational culture

The Internal Audit in Private Companies

One of the major characteristics of the audit is to permanently resort to various criteria, norms and standards. This attitude is, on the other hand, much more systematic as the audit is applied as professional norms. It is of a major importance to respect the stages of the financial-accounting audit, both for the auditors and for the patrimonial audited unit whose administration can be defined as a totality of decisions that apply its strategy. We may consider that when the financial audit gets support from the internal control it appears as an operational audit, and when it determines the application of the strategy it appears as the audit of the administration control.linternal audit, private companies, strategy, control;