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1.
Chemometric characterization of Slovenian red wines
Milena Ivanović, Anja Petek, Maša Islamčević Razboršek, Mitja Kolar, 2017, izvirni znanstveni članek

Opis: Total phenolic (TPC), flavonoid (TFC) and tannin (TTC) contents, total $SO_2$, total acids, pH, and reducing sugars were measured in twenty five Slovenian red wines from three key wine producing regions, Podravje, Posavje and Primorska. The results were chemometrically analysed and the wines were classified according to wine growing region and vine variety. Principal component analysis proved that TPC, TFC and TTC contents were primarily responsible for variation in the wines. Additionally, linear discriminant analysis (LDA) was performed and resulted in the satisfactory classification of samples by both vine variety and region.
Ključne besede: Slovenian red wines, quality parameters of wine, polyphenols, chemometric analysis
Objavljeno: 03.10.2017; Ogledov: 21; Prenosov: 2
.pdf Polno besedilo (119,46 KB)

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3.
Tekstim - zaščita pred elektromagnetnim sevanjem
Lucija Kobal, Iva Batič, 2002, strokovni članek

Opis: Elektromagnetna sevanja (EMS) so prisotna povsod v našem okolju in so nevidna za človeško oko. Poleg naravnih izvorov sevanj so v elektromagnetnem spektru prisotna tudi sevanja, katerih izvor je povzročil človek. Elektromagnetni spekter sestavljajo ionizirajoča sevanja, kamor spadajo gama žarki in X-žarki, ter neionizirajoča sevanja, ki nimajo dovolj energije, da bi razbila molekularne vezi. Industrializacija predstavlja glavnino umetnih izvorov elektromagnetnih sevanj (EMS) - elektrika, mikrovalovi in radiofrekvenčna sevanja - se nahajajo v relativno dolgih valovnih dolžinah in nizkih frekvencah elektromagnetnega spektra. Ti izvori nimajo dovolj energije, da bi razbijali kemične vezi. Učinki elektromagnetnih sevanj na človeško telo niso odvisni samo od stopnje sevanja ampak tudi od frekvence in energije. Če so sevanja dovolj močna, lahko inducirajo tok znotraj človeškega telesa in povzročijo vrsto efektov, kot so segrevanje in elektro šok, odvisno od amplitude in vrste frekvence. TEKSTINA d.d iz Ajdovščine je razvila novo blagovno znamko Tekstim, ki učinkovito ščiti pred EMS. Tekstim tkanine in preje bombažnega tipa imajo vgrajena nerjaveča kovinska vlakna, ki uspešno ščitijo pred škodljivimi EMS. Preje in tkanine Tekstim so namenjene izdelovanju lahkih zaščitnih oblačil, dnevnih oblek, spodnjega perila, dekorativnih tkanin in drugih zaščitnih izdelkov. Tekstim je bil testiran na Inštitutu za varovanje zdravja Republike Slovenije. Rezultati testov dokazujejo, da Tekstim zadrži nad 80 % vpadnega signala EMS v frekvenčnem območju 10-1000 MHz.
Ključne besede: elektromagnetna sevanja (EMS), zaščita, tkanine z zaščitnimi lastnostmi, Tekstim, kovinska vlakna, zaščitna oblačila, učinkovitost zaščite pred elektromagnetnim sevanjem
Objavljeno: 01.09.2017; Ogledov: 72; Prenosov: 3
.pdf Polno besedilo (342,39 KB)

4.
Obdelava tekstilnih odpadnih voda z membranskim bioreaktorjem
Irena Petrinić, Jasmina Korenak, Marjana Simonič, Mirjana Čurlin, 2010, izvirni znanstveni članek

Opis: Uporaba membranskega bioreaktorja (MBR), ki pomeni biološko razgradnjo odpadnih voda z aktivnim blatom v kombinaciji s fizikalnim procesom membranske filtracije, je postala zanimiva predvsem zaradi številnih prednosti pri čiščenju tekstilnih odpadnih voda in hitrega razvoja v zadnjem desetletju. Namen dela je bil očistiti modelno odpadno vodo z membranskim bioreaktorjem ter določiti njegovo učinkovitost čiščenja modelne tekstilne odpadne vode, pripravljene v laboratoriju po recepturi iz industrije. Cilj je bil vzpostaviti obratovalne razmere in stabilnost celotnega sistema, ki bi dal maksimalen izkoristek čiščenja z želeno kakovostjo očiščene vode. S spremljanjem obratovalnih parametrov, kot so pretok vhodne odpadne vode, dovajanje kisika v biološki del obdelave ter spremljanje tlaka ultrafiltracije, smo nameravali zagotoviti optimalne obratovalne razmere. S fizikalno-kemijskimi analizami smo dokazali, da so se vrednosti KPK in koncentracije barvila, izražene kot spektralni absorpcijski koeficient (SAK), znižale, in sicer za 70 do 90 odstotkov. Iz rezultatov je razvidno, da je bila učinkovitost znižanja KPK okoli 90-odstotna, učinkovitost znižanja vsebnosti barvil pa doseže do 97 odstotkov. Iz navedenega lahko povzamemo, da je tehnologija MBR, ki je kombinacija biološkega in fizikalnega čiščenja, zelo učinkovita pri čiščenju tekstilne odpadne vode.
Ključne besede: reaktivna azobarvila, tekstilne odpadne vode, membranski bioreaktorji, aktivno blato
Objavljeno: 31.08.2017; Ogledov: 38; Prenosov: 1
.pdf Polno besedilo (497,63 KB)

5.
Čiščenje odpadnih voda iz industrijske pralnice z uporabo membranske tehnologije
Marjana Simonič, Irena Petrinić, Sonja Šostar-Turk, 2004, izvirni znanstveni članek

Opis: Industrijske in obrtne pralnice onesnažujejo okolje z odpadno vodo, ki nastane po pranju različnih vrst perila. Predpisi in uredbe za odvajanje odpadnih voda iz industrijskih in obrtnih pralnic v komunalne čistilne naprave ali pa iztok neposredno v reko so čedalje strožji, kar morajo upoštevati tudi pralnice. Sedanje sodobne čistilne naprave vključujejo poleg čiščenja vode še možnost ponovne uporabe vode. Za dosego tega cilja je najprimernejša membranska filtracija. V prispevku smo podrobno prikazali proces čiščenja vode iz pralnice z ultrafiltracijo in reverzno osmozo. Rezultati analiz odpadne vode so pokazali, da so se vsi merjeni parametri znižali v tolikšni meri, da ima voda zelo visoko kakovost in z njenim recikliranjem prihranimo do 90 % sveže vode.
Ključne besede: odpadne vode, čiščenje odpadnih vod, pralnice, membranska tehnologija, ultrafiltracija, reverzna ozmoza
Objavljeno: 31.08.2017; Ogledov: 46; Prenosov: 4
.pdf Polno besedilo (574,89 KB)

6.
The magnetic and colloidal properties of $CoFe_2O_4$ nanoparticles synthesized by co-precipitation
Sašo Gyergyek, Mihael Drofenik, Darko Makovec, 2014, izvirni znanstveni članek

Opis: Magnetic $CoFe_2O_4$ nanoparticles were synthesized by co-precipitation at 80 °C. This co-precipitation was achieved by the rapid addition of a strong base to an aqueous solution of cations. The investigation of the samples that were quenched at different times after the addition of the base, using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS) and X-ray powder diffractometry, revealed the formation of a Co-deficient amorphous phase and $Co(OH)_2$, which rapidly reacted to form small $CoFe_2O_4$ nanoparticles. The nanoparticles grew with the time of aging at elevated temperature. The colloidal suspensions of the nanoparticles were prepared in both an aqueous medium and in a non-polar organic medium, with the adsorption of citric acid and ricinoleic acid on the nanoparticles, respectively. The measurements of the room-temperature magnetization revealed the ferrimagnetic state of the $CoFe_2O_4$ nanoparticles, while their suspensions displayed superparamagnetic behaviour.
Ključne besede: cobalt ferrite, nanoparticles, co-precipitation, colloidal suspensions, magnetic properties
Objavljeno: 30.08.2017; Ogledov: 41; Prenosov: 2
.pdf Polno besedilo (279,23 KB)

7.
The curing of diallylterephthalate determination of the kinetic triplet A, Ea,app, ƒ(α) using the isoconversional method
Dušan Klinar, Janvit Golob, Matjaž Krajnc, 2003, izvirni znanstveni članek

Opis: Allyl polymers are important materials for the production of high performance ophthalmic lenses by free-radical bulk polymerization in the casting process. Isoconversional model-free analysis was applied to the isothermal and nonisothermal curing of diallylterephthalate performed by DSC at different sets of heating rates. The results of the kinetic analysis in a form of kinetic triplet $(Ea, A, ƒ(α))$ present the variation of the Arrhenius parameters with the calculation method, reaction extent, process mode and heating rates applied. This variation is a sign of the complex and multi-step reaction mechanism. Such a mechanism was approximated with one step $(1-α)^n$ reaction model. With the isokinetic relationship - IKR (compensation effect) in the form of $lnA=aEa,app+b$ it was found out that the isothermal and nonisothermal IKR lines converge to different singular points. From the correlation procedure with the experimental data isothermal narrowest point – NPI was selected as a common point. The curing process in the isothermal and nonisothermal process conditions, respectively, was successfully simulated with the obtained kinetic parameters. The possible alternative reaction paths and the partial diffusion control of the curing process are the reasons for the limiting usage of the model-free kinetic analysis method. This method was mainly used as a preliminary step for further analysis with other methods.
Ključne besede: DSC, DAT, curing kinetics, compensation effect
Objavljeno: 29.08.2017; Ogledov: 36; Prenosov: 3
.pdf Polno besedilo (158,92 KB)

8.
Synthesis, crystal structure and magnetic properties of a new hydroxylammonium fluoroferrate
Brina Dojer, Matjaž Kristl, Zvonko Jagličić, Amalija Golobič, Marta Kasunič, Mihael Drofenik, 2012, izvirni znanstveni članek

Opis: This paper reports on the synthesis of a new hydroxylammonium fluoroferrate, with the formula $(NH_3OH)_3FeF_6$, obtained after dissolving iron powder in hydrofluoric acid and adding solid $NH_3OHF$. This new compound has been characterized by chemical and thermal analysis, single-crystal X-ray diffraction, and magnetic measurements. The title compound crystallizes trigonal, R3c, with cell parameters a = 11.4154(2) Å, c = 11.5720(2) Å, Z = 6. The structure consists of $NH_3OH^+$ cations and isolated $FeF_6^{3–}$ octahedra in which the central ion lies on a threefold axis. The oxygen and nitrogen atoms of the hydroxylammonium cations are donors of hydrogen bonds to fluoride anions, resulting in a network of hydrogen bonds between counterions. The effective magnetic moment $µ_{eff}$ = 5.8 BM was calculated and perfectly matches the expected value of high-spin Fe(III) ions. The thermal decomposition of the compound was studied by TG, DSC, and X-ray powder diffraction.
Ključne besede: inorganic chemistry, crystallography, coordination compounds, synthesis, crystal structure, characterization of compounds, determination of the structure of compounds, X-ray diffraction, magnetic measurements, thermal analysis, TG, DSC, hydrogen bond, metal complexes, hydroxylammonium fluoromethalatehydroxylammonium, fluoroferrate
Objavljeno: 25.08.2017; Ogledov: 85; Prenosov: 3
.pdf Polno besedilo (198,42 KB)

9.
Synthesis and characterisation of hydroxylammonium fluorochromate
Matjaž Kristl, Mihael Drofenik, Ljubo Golič, Amalija Golobič, 2003, izvirni znanstveni članek

Opis: Reactions in the system $Cr – NH_3OHF – HF – H_2O$ were investigated. Green crystals of a new compound with the formula $(NH_3OH)_3CrF_6$ have been isolated from the water solution and characterized by chemical analysis. The compound crystallizes as triclinic, P-1, with cell parameters: a = 6.5461(2) Å, b = 6.9347(2) Å, c = 9.4072(3) Å, α = 86.772(1)°, β = 83.804(1)°, γ = 70.283(1)°. The effective magnetic moment, $µ_{eff}$ = 3.82 BM, was calculated from magnetic susceptibility measurements in the temperature range 80-290 K. The thermal decomposition of the compound was studied by TG and DSC analysis. $(NH_3OH)_3CrF_6$ decomposes above 125 °C in three steps and the residue has been identified by X-ray powder diffraction as $α – Cr_2O_3$.
Ključne besede: inorganic chemistry, structural chemistry, crystalline structure, coordination compounds, synthesis, inorganic reactions, thermal decomposition, characterization of compounds, TG, DSC, X-ray diffraction, chromium complexes, hydroxylammonium fluoro chromates, crystals
Objavljeno: 25.08.2017; Ogledov: 77; Prenosov: 3
.pdf Polno besedilo (206,45 KB)

10.
Simultaneous GC-MS determination of free and bound phenolic acids in Slovenian red wines and chemometric characterization
Milena Ivanović, Maša Islamčević Razboršek, Mitja Kolar, 2016, izvirni znanstveni članek

Opis: Several phenolic acids (PAs), caffeic, vanillic, syringic, p-coumaric and ferulic acid, found in Slovenian red wines were studied using gas chromatography and mass spectrometry (GC-MS). For isolation of the PAs from wine samples, solid phase extraction (SPE) using hydrophilic modified styrene - HLB cartridges was used. The bound PAs were extracted after basic hydrolysis and o-coumaric acid was used as the internal standard (ISTD). The method developed was validated and the linear concentration range for all analytes was from 1 to 100 mg L$^{-1}$ with correlation coefficients above 0.999. We show that the method is repeatable (RSD<2%), recoveries were above 96%, and LOD and LOQ values were acceptable. In all of the wine samples tested, caffeic and p-coumaric acid were determined to be the predominant PAs (17-72 mg L$^{-1}$), while other compounds were found in lower concentrations. Principal Component Analysis (PCA) and Cluster Analysis (CLU) were used to study differences between wines related towards varieties and Slovenian wine regions. The results demonstrate that variety has more influence on PAs content than wine regions in Slovenian red wines.
Ključne besede: phenolic acids, Slovenian red wines, gas chromatography, mass spectrometry, PCA, CLU
Objavljeno: 25.08.2017; Ogledov: 47; Prenosov: 2
.pdf Polno besedilo (222,27 KB)

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