Reološko ponašanje termoplastičnih poli(estar-siloksana)

Two series of thermoplastic elastomers (TPES), based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were analyzed by dynamic mechanical spectroscopy. In the first TPES series the lengths of both hard and soft segments were varied while the mass ratio of the hard to soft segments was nearly constant (about 60 mass%). In the second series, the mass ratio of hard and soft segments was varied in the range from 60/40 to 40/60, with a constant length of soft PDMS segments. The influence of the structure and composition of TPESs on the rheological properties, such as complex dynamic viscosity, μ*, the storage, G', and loss, G', shear modulus as well as the microphase separation transition temperature, TMST, was examined. The obtained results showed that the storage modulus of the TPESs increased in a rubbery plateau region with increase in degree of crystallinity. The rheological measurements of TPESs also showed that a microphase reorganization occurred during the melting process. The microphase separation transition temperatures were in the range from 220 to 234°C. In the isotropic molten state, the complex dynamic viscosity increased with increasing both the content and length of hard PBT segments.Dve serije termoplastičnih elastomera (TPES) na bazi poli(dimetilsiloksana) kao mekog segmenta i poli(butilentereftalata) kao tvrdog segmenta su analizirane dinamičko-mehaničkom spektroskopijom. U prvoj TPES seriji varirane su dužine tvrdih i mekih segmenata dok je njihov maseni odnos bio skoro konstantan (oko 60 mas%). U drugoj seriji, odnos tvrdih i mekih segmenata je variran u opsegu od 60/40 do 40/60, dok je dužina mekih PDMS segmenata bila konstantna. Ispitan je uticaj strukture i sastava TPES kopolimera na reološka svojstva, kao što su kompleksni dinamički viskozitet, μ*, moduli sačuvane, G', i izgubljene energije, G', i temperatura mikrofaznog razdvajanja, TMST. Dobijeni rezultati su pokazali da su uzorci sa većim stepenom kristaliničnosti imali i veće module sačuvane energije u gumolikom platou. Reološka merenja su takođe pokazala da svi TPES uzorci ispoljavaju mikrofaznu reorganizaciju u procesu topljenja. Temperature mikrofaznog razdvajanja su bile u opsegu od 220 do 234°C. U izotropskom rastopu, kompleksni dinamički viskoziteti su rasli sa povećanjem sadržaja i dužine PBT segmenata

Typical errors in presenting concepts in textbooks for the first four grades of primary school

This paper offers a systematization of typical errors in presenting scientific concepts in textbooks for the first four grades of primary school. The subject of our analysis and systematization were presentations of concepts which deviate from or violate the internal cognitive and logical nature of a scientific concept, thus representing a source of potential difficulties for students in understanding scientific knowledge. Starting from Vygotsky's theory of the development of scientific concepts, as well as the general standards of textbook quality and a review of studies analyzing textbooks in this field, we have made a systematization of typical errors in the presentation of scientific terms. Five typical errors are explained and elucidated: a simple description of a phenomenon or the statement of its function, use or usefulness; a simple establishment of connections between a concept (word) and an object (image); offering ready-made phrases and scientific statements without relating them to a system of concepts; providing only typical examples or providing examples that lack variety, and presenting important and unimportant facts on the same level, without pointing out the differences. Every typical error is explained using examples from textbooks in which scientific concepts relevant to grades 1-4 are introduced (settlement, village, city, plants, relief, historical figure and birds). In the absence of scientific principles in presenting concepts in textbooks, their authors rely on implicit assumptions about concepts as phenomenal or factual kinds of knowledge. Due to the importance of acquiring scientific concepts for the cognitive development of the individual, the practical implications of the findings are that in textbook design but also in teacher education particular attention must be devoted to the area of teaching and learning scientific concepts.В статье систематизированы типичные ошибки изложения научных понятий в учебниках для младших классов основной школы. Предметом анализа и систематизации являются способы изложения понятий, которые отклоняют или нарушают внутреннюю когнитивно-логическую природу научного понятия и, таким образом, представляют собой источник потенциальных трудностей, которые могут возникнуть у учеников при понимании научного знания. Исходя из теории развития научных понятий Льва Выготского, общих стандартов качества учебников и обзора результатов научных исследований учебников, авторами проведена систематизация типичных ошибок в изложении научных понятий. В статье приводится и объясняется пять типичных ошибок: простое описание явления или его функции, использования или пользы; простое установление связи между понятием (словом) и предметом (изображением); представление готовых фраз и научных высказываний вне связи с системой понятий; задержка на представлении типичных примеров или недостаточного разнообразия представленных примеров и изложение важного и неважного в одной плоскости, без указания различий. Каждая типичная ошибка объясняется примером из учебника, в котором вводятся научные понятия, относящиеся к младшим классам (поселок, деревня, город, растения, рельеф, историческая личность, птицы). В отсутствии научных принципов в представлении понятий в учебниках, авторы учебников полагаются на неявные предположения о понятии как явлении или фактическом типе знания. Имея в виду важность усвоения научных понятий для когнитивного развития ученика, практическое значение выводов исследования состоит в том, что при создании учебников, а также в образовании преподавателей, особое внимание следует уделять преподаванию и изучению научных понятий.U radu se izvodi sistematizacija tipičnih grešaka u prezentovanju naučnih pojmova u udžbenicima za mlađe razrede osnovne škole. Predmet analize i sistematizacije su postupci prezentacije pojmova koji odstupaju ili krše unutrašnju saznajno-logičku prirodu naučnog pojma i time predstavljaju izvor potencijalnih teškoća koje učenici mogu imati u razumevanju naučnih znanja. Polazeći od teorije razvoja naučnih pojmova Lava Vigotskog, opštih standarda kvaliteta udžbenika i pregleda istraživanja analiza udžbenika u ovom domenu, napravili smo sistematizaciju tipičnih grešaka u prezentovanju naučnih pojmova. U radu je eksplicirano i pojašnjeno pet tipičnih grešaka: jednostavna deskripcija fenomena ili navođenje njegove funkcije, upotrebe ili koristi; jednostavno uspostavljanje odnosa između pojma (reči) i objekta (slike); izlaganje gotovih fraza i naučnih konstatacija izvan odnosa sa sistemom pojmova; zadržavanje na izlaganju tipičnih primera ili nedovoljna raznovrsnost izloženih primera i prezentovanje važnog i nevažnog u istoj ravni, bez ukazivanja na razlike. Svaka tipična greška je pojašnjena na primeru iz udžbenika u kojima su uvođeni naučni pojmovi relevantni za mlađe razrede (naselje, selo, grad, biljke, reljef, istorijska ličnost i ptice). U odsustvu naučnih načela u prezentaciji pojmova u udžbenicima, autori udžbenika se oslanjaju na implicitne pretpostavke o pojmovima kao pojavnoj ili činjeničkoj vrsti znanja. Zbog značaja usvajanja naučnih pojmova za kognitivni razvoj jedinke, praktične implikacije dobijenih nalaza su da se u konstrukciji udžbenika ali i u obrazovanju nastavnika posebna pažnja mora posvetiti oblasti nastave i učenja naučnih pojmova

Kvantitativno određivanje poli(vinilpirolidona) primenom 'On-line' pirolize kuplovane sa gasnom hromatografijom

'On-line' pyrolysis coupled with gas chromatography (GC) was performed for quantitative determination of poly(vinylpyrrolidone) (PVP) in wastewater sample. Gas chromatography-mass spectrometry (GC-MS) showed that the main product of pyrolysis of PVP, at high temperatures, was N-vinylpyrrolidone (NVP). After that, different amounts of commercial PVP were pyrolyzed in order to establish the correlation between the amount of generated NVP (its GC peak area) and the initial mass of pyrolyzed PVP. GC-FID analysis was used for construction of the calibration curve and for quantitative determination of PVP. Very good linear correlation was obtained between the area of NVP peak, generated during pyrolysis, and the initial mass of PVP (r2 = 0.998). Further, solutions of known concentration of PVP were prepared in destilled water ('spiked samples'). Spiked samples were preextracted with diethyl ether and n-hexane, after which the water-layer was evaporated and dissolved again in methanol. Analysis of pyrolysates of preextracted spiked samples showed that the 'recovery' of PVP was above 96 mass%. This finding suggested that pre-extraction could be applied to reduce the concentration of organic substances that could also be pyrolyzed, and thus hinder identification and quantitative determination of PVP, without significant loss of polymer. The sample of an industrial wastewater from Pančevo, Serbia was investigated in the last part of this work. The sample was preextracted in the same way as the spiked samples and than pyrolyzed. NVP was identified by GC-MS in obtained pyrolysate, which was the evidence that PVP was present in the wastewater sample. NVP was quantified on the basis of the peak area in GC-FID chromatogram, and than the concentration of PVP in wastewater sample was calculated based on calibration curve. Concentration of PVP in industrial wastewater amounted 2.5 mg/L.U ovom radu je primenjena metoda 'on-line' pirolize u sprezi sa gasnom hromatografijom (GC) za kvantitativno određivanje poli(vinilpirolidona) (PVP) u uzorku otpadne vode. Najpre je gasnomhromatografsko-masenospektrometrijskom analizom (GC-MS) utvrđeno da pirolizom PVP na visokim temperaturama kao glavni proizvod degradacije nastaje monomer, N-vinilpirolidon (NVP). Nakon toga su različite količine komercijalnog PVP pirolizovane da bi se uspostavila korelacija između količine nastalog NVP i inicijalne mase pirolizovanog polimera. Za konstruisanje kalibracione krive i kvantitativno određivanje PVP u rastvorima poznate koncentracije u destilovanoj vodi ('spiked samples'), kao i u uzorku otpadne vode, korišćena je GC analiza. Analizom rastvora komercijalnog PVP poznate koncentracije ustanovljeno je da PVP 'recovery', nakon ekstrakcije n-heksanom i dietil-etrom, iznosi iznad 96 mas.%. U poslednjem delu rada ispitan je uzorak industrijske otpadne vode iz Pančeva, Srbija. Pokazano je da je PVP bio prisutan u otpadnoj vodi i da je njegova koncentracija bila daleko iznad uobičajenih koncentracija niskomolekularnih organskih zagađivača

Wpływ kształcenia ustawicznego i doskonalenia zawodowego pielęgniarek na proces opieki nad pacjentami neurologicznymi

Introduction. Nurses distinguish continuous professional development intended for career improvement and personal development from continuous professional development intended for improvement of skills and knowledge. Too many requests are put in front of an individual unacceptably stretching it onto the life outside work. Nurses and students have various expectations from their education.Aim. The aim of the study was to recognize the motivation and expectations of nurses undertaking further nursing education.Material and Methods. A three-phase study was conducted in 2007, 2009 and 2010 and included 622 nurses, 132 head nurses and 106 nursing undergraduate students at the University of Applied Health Studies in Zagreb, respectively. Anonymous questionnaire was used in the study.Results. Factors that motivate nurses to study are to improve knowledge, patient care and professional relations. Factors connected to personal development include boost of confidence and embracing of other values. Motivation for additional education is also connected to the change of work, practice improvement, self-confidence improvement, nursing career plans, and necessary intellectual stimulation. The reasons for which nurses decide to undertake further education are also desire for maintenance of clinical competence, but also enjoyment in studying itself.Conclusions. A permanently educated nurse will be able to assess the needs of patients of health care on time and consequently organize the provision of health care by using all human and technical resources. (JNNN 2014;3(1):10–14)Wprowadzenie. Pielęgniarki dostrzegają różnicę między kształceniem ustawicznym dającym szansę rozwoju osobistego i lepszej kariery w zawodzie a ciągłym doskonaleniem zawodowym, którego celem jest pogłębianie wiedzy i podnoszenie umiejętności zawodowych. Pielęgniarkom stawiane są zbyt wysokie wymagania, które rozciągają się poza sferę zawodową. Pielęgniarki i studenci pielęgniarstwa mają różne oczekiwania związane z procesem kształcenia.Cel. Głównym celem badań było poznanie i określenie motywacji oraz oczekiwań osób kontynuujących naukę w zawodzie pielęgniarki.Materiał i metody. Przeprowadzono trzyfazowe badania w latach 2007, 2009 i 2010, które objęły kolejno: 622 pielęgniarki, 132 siostry przełożone oraz 106 studentów pielęgniarstwa na University of Applied Health Studies w Zagrzebiu. Badania przeprowadzono za pomocą anonimowego kwestionariusza ankiety.Wyniki. Czynnikami, które motywują pielęgniarki do studiowania są: chęć pogłębiania wiedzy, poprawa opieki nad pacjentem oraz udoskonalenie relacji zawodowych. Czynniki związane z rozwojem osobistym obejmują wzmocnienie pewności siebie. Motywacją do dalszej edukacji jest chęć zmiany pracy, udoskonalenie umiejętności zawodowych, umocnienie pewności siebie, plany rozwinięcia kariery oraz stymulacja intelektualna. Innymi czynnikami, dla których pielęgniarki decydują się na dalszą naukę są potrzeba utrzymania kompetencji klinicznych oraz chęć uczenia się dla przyjemności.Wnioski. Dobrze wykształcona i ciągle kształcąca się pielęgniarka będzie w stanie na czas ocenić potrzeby pacjenta, a co za tym idzie, będzie potrafiła wykorzystać wszelkie zasoby ludzkie i techniczne, by jakość jej opieki była na najwyższym poziomie. (PNN 2014;3(1):10–14

Utjecaj trajne stručne izobrazbe i usavršavanja na proces sestrinske skrbi za neurološke bolesnike

Nurses distinguish continuous professional development intended for career improvement and personal development from continuous professional development intended for improvement of skills and knowledge. Too many requests are put in front of an individual unacceptably stretching it onto the life outside work. Students have various expectations from their education. Factors that motivate nurses to study are to improve knowledge, patient care and professional relations. Factors connected to personal development include boost of confidence and embracing of other values. Motivation for additional education is also connected to the change of work, practice improvement, self-confidence improvement, nursing career plans, and necessary intellectual stimulation. The reasons for which nurses decide to undertake further education are also desire for maintenance of clinical competence, but also enjoyment in studying itself. An employer who expects from nurses to opt for such a type of education or stimulate it is another common reason.Medicinske sestre razlikuju kontinuirani profesionalni razvoj namijenjen unapređenju karijere i osobnog razvoja od kontinuiranog profesionalnog razvoja namijenjenog unapređenju znanja i vještina. Previše zahtjeva stavlja se pred pojedinca koji se neprihvatljivo protežu na život izvan radne sredine. Studenti imaju različita očekivanja od obrazovanja. Čimbenici koji motiviraju medicinske sestre za studiranje uključuju unapređenje znanja, skrbi o bolesnicima i profesionalnih veza. Čimbenici povezani s osobnim razvojem uključuju povećanje povjerenja i otvaranje drugih mogućnosti. Motivacija za dodatno obrazovanje povezana je i s promjenom poslova, unapređivanjem prakse, unapređivanjem samopouzdanja, planova za sestrinsku karijeru i potrebnu intelektualnu stimulaciju. Razlozi zbog kojih se medicinske sestre odlučuju na daljnje obrazovanje su i želja za održavanjem kliničke stručnosti, ali i uživanje u samom studiranju. Čest razlog je i poslodavac koji očekuje da se medicinske sestre odluče na takvu vrstu usavršavanja ili ju i sami potiču

Synthesis, structure and thermogravimetric analysis of alpha,omega-telechelic polydimethylsiloxanes of low molecular weight

A series of alpha,omega-telechelic polydimethylsiloxanes (PDMS), with predetermined molecular weights of about 2500 g mol(-1), was synthesized by siloxane equilibration reaction. Syntheses were performed using octamethylcyclotetrasiloxane (D-4) and various disiloxanes: hexamethyldisiloxane (HMDS), 1,1,3,3-tetramethyldisiloxane (TMDS), 1,3-divinyltetramethyldisiloxane (DVTMDS), 1,3-bis(3-carboxypropyl) tetramethyldisiloxane (DCPTMDS) and 1,3-bis(3-aminopropyl) tetramethyldisiloxane (DAPTMDS). The role of the disiloxane was to introduce terminal functional groups at the end of the polymer chains and to control the molecular weight of the polymers. Polymers with trimethyl, hydrido, vinyl, carboxypropyl and aminopropyl end-groups were obtained in this way. The structure of the alpha,omega-telechelic PDMSs was confirmed by NMR and IR spectroscopy. The molecular weights of the polymers were determined by H-1-NMR, gel permeation chromatography (GPC) and dilute solution viscometry. Thermogravimetric analysis (TGA) under nitrogen and air showed that the type of the terminal groups significantly influenced the thermal and thermo-oxidative stability, as well as the degradation mechanism of the alpha,omega-telechelic PDMSs

Multidisciplinary Approach in the Implementation of ATL Methods in Teaching of Animal Sciences I. Presentation of Scenarios

One of the problems Serbian HE faces is summing up of knowledge thaught in different courses and its application in real life by professional decision making. In order to give an example of possibilities of interactive teaching methodology and contribute to the transformation of students from knowledge recipients to knowledge co-constructors, a set of scenarios for a multidisciplinary approach in teaching/learning is presented. The set consists of 4 scenarios for knowledge refreshment followed by a final workshop – a debate similar to the real life situation. A multidisciplinary approach to the topic of aquaculture development, water and fish quality in aquaculture is presented in this case. By participating interactive classes and a debate, 4 year students in animal sciences work in groups to exercise solving problems, to make professional decision, and develop other professional and generic skills. This paper presents the result of the process of development o scenarios for such exercise and results of the exercise will be presented in another paper (Part 2)

Sinteza estar-siloksanskih multiblok kopolimera

U radu je opisana sinteza blok kopolimera sa poli(butilentereftalatnim) tvrdim segmentima i poli(dimetilsiloksanskim) mekim segmentima. Cilj rada je da se ispita iproveri da lije primenljiva klasična metoda dvostepene transesterifikacije/polikondenzacije u rastopu, koja se koristi za dobijanje estar-etarskih blok kopolimera i u slučaju estar-siloksanskih blok kopolimera. Pošto reaktant koji sadrži siloksansku komponentu može da ima različite završne grupe, ispitana su dva karakteristična slučaja: a) reaktant sa estarskim završnim grupama, dimetil-estar a, (ù-dikarboksipropil-poli(dimetilsil oksana), i b) reaktant sa hidroksilnim završnim grupama, α, ω-dihidroksi-poli(propilenoksid-di metilsiloksan-propilenoksid). Sintetizovane su tri serije kopolimera, pri čemu su kao reaktanti korišćeni poli(dimetilsiloksani) sa estarskim (dve serije) i hidroksilnim završnim grupama. Struktura i sastav kopolimera određeni su 1H NMR spektroskopijom. Predložen je mehanizam, odnosno redosled reakcionih koraka koji vode formiranju kopolimera

Structural, thermal and surface characterization of thermoplastic polyurethanes based on poly(dimethylsiloxane)

In this study, the synthesis, structure and physical properties of two series of thermoplastic polyurethanes based on hydroxypropyl-terminated poly(dimethylsiloxane) (HP-PDMS) or hydroxyethoxypropyl-terminated poly(dimethylsiloxane) (EO-PDMS) as soft segments, and 4,4'-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments were investigated. The polyurethanes were synthesized by two-step polyaddition in solution. The effects of the type and content of PDMS segments on the structure, thermal and surface properties of copolymers were studied by H-1-, C-13-nuclear magnetic resonance (NMR) spectroscopy and two-dimensional NMR spectroscopies (heteronuclear multiple bond correlation (HMBC) and rotating-frame nuclear Overhauser effect (ROESY)), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and water contact angle and water absorption measurements. Thermal properties investigated by DSC indicated that the presence of soft PDMS segments lowers the glass transition and melting temperatures of the hard phase as well as the degree of crystallinity. SEM analysis of the copolymers with a lower soft segment content confirmed the presence of spherulite superstructures, which arise from the crystallization of the hard segments. When compared with polyurethanes prepared from HP-PDMS, the copolymers synthesized from EO-PDMS with the same content of the soft segments had a higher degree of crystallinity, better thermal stability and a less hydrophobic surface. The obtained results showed that the synthesized polyurethanes had good thermal and surface properties, which could be further modified by changing the type or content of the soft segments