423 research outputs found
Nomenclature note: ICTAC Nomenclature of Thermal Analysis (IUPAC Recommendations 2014)
RaÅ”irena primjena toplinske analize kao znanstvene laboratorijske tehnike dovela je do razvoja radnih naziva. Nakana je ovog dokumenta pružiti svima koji se bave toplinskom analizom meÄusobno usklaÄene definicije koje Äe omoguÄiti jasnu i preciznu komunikaciju i sporazumijevanje. Dokument sadrži definicije 13 tehnika, 54 pojma u glosaru te simbole i jedinice.The widespread use of thermal analysis (TA) by scientists as a laboratory technique carries with it a working vocabulary. This document is intended to provide those working in the field with a consistent set of definitions to permit clear and precise communication as well as understanding. Included in the document are the definitions of 13 techniques, 54 terms within the glossary, as well as symbols and units
Sol-gel Process in Preparation of Organic-inorganic Hybrid Materials
Organsko-anorganski hibridni materijali vrsta su nanostrukturnih materijala u kojima su organska i anorganska faza meÄusobno pomijeÅ”ane na molekulnoj razini. Anorganska faza u hibridnim materijalima pripravlja se sol-gel postupkom koji obuhvaÄa reakcije hidrolize i kondenzacije metalnih (veÄinom silicijevih) alkoksida. Da bi se sprijeÄilo razdvajanje faza tijekom priprave hibrida, poželjno je poboljÅ”ati meÄudjelovanje faza stvaranjem vodikovih ili kovalentnih veza meÄu njima. Kovalentna veza najjednostavnije se uvodi uporabom organski modificiranih alkoksisilana s reaktivnom organskom skupinom koja može reagirati s organskom fazom. Da bi se pripravili hibridni materijali željene strukture, potrebno je podrobno poznavanje mehanizama reakcija hidrolize i kondenzacije. U ovom radu izložit Äe se utjecaji reakcijskih uvjeta na hidrolizu i kondenzaciju silicijevih alkoksida i organski modificiranih alkoksisilana.Organic-inorganic hybrid materials are a sort of nanostructured material in which the organic and inorganic phases are mixed at molecular level. The inorganic phase in hybrid materials is formed by the sol-gel process, which consists of reactions of hydrolysis and condensation of metal (usually silicon) alkoxides. Flexibility of sol-gel process enables creation of hybrid materials with varying organic and inorganic phases in different ratios, and consequently fine-tuning of their properties. In order to obtain true hybrid materials, contact between the phases should be at molecular level, so phase separation between thermodynamically incompatible organic and inorganic phases has to be prevented. Phase interaction can be improved by formation of hydrogen or covalent bonds between them during preparation of hybrid materials. Covalent bond can be introduced by organically modified silicon alkoxides containing a reactive organic group (substituent) capable of reacting with the organic phase. In order to obtain hybrid materials with desired structures, a detailed knowledge of hydrolysis and condensation mechanism is necessary. The choice of catalyst, whether acid or base, has the most significant influence on the structure of the inorganic phase. Other important parameters are alkoxide concentration, water: alkoxide ratio, type of alkoxide groups, solvent used, temperature, purity of chemicals used, etc. Hydrolysis and condensation of organically modified silicon alkoxides are additionally influenced by nature and size of the organic supstituent
Imenje i nazivlje u kemiji i kemijskom inženjerstvu: Enciklopedijski rjeÄnik analitiÄkoga nazivlja (M. KaÅ”telan-Macan)
Glossary of Terms Relating to Thermal and Thermomechanical Properties of Polymers (IUPAC Recommendations 2013)
Dokument definira nazive vezane uz ustaljenu toplinsku i termomehaniÄku karakterizaciju polimernih materijala.The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials
Definitions of Terms Relating to the Structure and Processing of Sols, Gels, Networks, and Inorganic-Organic Hybrid Materials
U ovom dokumentu definirani su pojmovi vezani uz strukturu, pripravu i obradu anorganskih, polimernih i anorgansko-organskih hibridnih materijala, polazeÄi od polaznih tvari (prekursora) preko gelova do Ävrstih proizvoda. Podijeljen je na Äetiri dijela - polazne tvari, gelovi, Ävrste tvari i postupci - a pojmovi su ograniÄeni na one koji se najÄeÅ”Äe upotrebljavaju.
Dosljednosti radi preuzeti su pojmovi iz drugih IUPAC-ovih publikacija, ako su im definicije zadovoljavajuÄe za potrebe ovog dokumenta. Pojmovi i definicije sabrani su uz savjetovanje sa struÄnjacima iz odgovarajuÄih podruÄja. Namjera je da definicije pomognu Äitatelju koji nije upoznat sa sol-gel postupkom, keramizacijom te srodnim materijalima i tehnologijama, a da istraživaÄima u tim podruÄjima posluže kao vodiÄ za ustaljenu terminologiju.This document defines terms related to the structure and processing of inorganic, polymeric, and inorganic-organic hybrid materials from precursors, through gels to solid products. It is divided into four sections ā precursors, gels, solids, and processes ā and the terms have been restricted to those most commonly encountered. For the sake of completeness and where they are already satisfactorily defined for the scope of this document, terms from other IUPAC publications have been used. Otherwise, the terms and their definitions have been assembled in consultation with experts in the relevant fields. The definitions are intended to assist the reader who is unfamiliar with sol-gel processing, ceramization, and related technologies and materials, and to serve as a guide to the use of standard terminology by those researching in these areas
Analysis of the Financial Support by the Croatian Ministry of Science, Education and Sports to Croatian Scientific Journals
UsporeÄeni su podaci o novÄanoj potpori izdavanju hrvatskih znanstvenih i znanstveno-struÄnih Äasopisa te Äasopisa namijenjenih promicanju znanosti koju osigurava Ministarstvo znanosti, obrazovanja i Å”porta RH (MZOÅ ) prema znanstvenom podruÄju koje Äasopisi pokrivaju. Detaljnije su analizirani Äasopisi iz podruÄja prirodnih znanosti u odnosu na broj objavljenih znanstvenih radova, broj objavljenih brojeva Äasopisa, kao i postojanje mrežnih stranica Äasopisa. Poseban osvrt dan je Äasopisima koji su zastupljeni u jednoj od dvije promatrane baze podataka Thomson Scientifica (Current Contents i Web of Science), kao i Äasopisima koji nude cjeloviti tekst objavljenih radova u otvorenom pristupu putem vlastitih mrežnih stranica ili Portala znanstvenih Äasopisa RH - HrÄak
Cutaneous reactivity to grass pollen and house dust mite in prick test with two types of allergen extracts
Upotrebljivost domaÄih nestandardiziranih pripravaka za prick-test htjela se provjeriti usporedbom s internacionalno priznatim standardiziranim pripravcima aktivnosti 100 000 BU. Komparativna su upotrijebljeni alergeni grinje Dermatophagoides pteronyssinus kod 107 ispitanika te pojedinaÄni poleni trava, i to: Dactylis glomerata, Poa pratensis, Phleum pratense i Secale cereale kod 39 ispitanika. KliniÄka znaÄajnost kožne reakcije odreÄena je usporedbom veliÄine urtike izazvane alergenom s onom izazvanom negativnom kontrolom (puferom) te pozitivnom kontrolom (otopinom histamina koncentracije 1 mg/ml). UtvrÄeno je da domaÄi preparat grinje od 3000 PNU/ml ne daje podjednake kožne reakcije kao standardizirani pripravak te ne daje kliniÄki vjerodostojne rezultate, dok su pripravci polena trave, s izuzetkom trave Poa pratensis, vrlo dobri i usporedivi sa standardnim pripravcima, te se mogu pouzdano upotrebljavati u praksi. Na temelju rezultata ovog istraživanja zakljuÄuje se da treba postrožiti kriterije za ocjenu kliniÄki znaÄajno pozitivne kožne reakcije na alergenske pripravke.The reliability of prick testing with allergen preparations produced in Yugoslavia was assessed by comparison to the internationally accepted ones (Pharmacia Diagnostica) of 100 000 BU activity. The following allergens were used: the mite Dermatophagoides pteronyssinus in 107 subjects, and grass pollens: Dactylis glomerata, Poa pratensis, Pbleum pratense and Secale cereale in 39 subjects. The clinical significance of the response was assessed in relation to the skin reaction to the negative control solution and positive histamine control (in concentration of 1 mg/ml). The results indicate that the allergen extract of Dermatophagoides pteronyssinus (3000 PNU/ml) produced in Yugoslavia does not provoke skin reactions comparable to those provoked by the standardized extract of 100 000 BU in contrast to the grass pollen allergens, with the exception of Poa pratensis, which evokes equivalent skin reactions. Thus grass pollen allergens are reliable extracts and can be applied with good confidence in routine work. The need to set more rigorous criteria for assessing skin prick reactions, when domestic, unstandardized products are used, emerged as a result of this study
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