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1.
Isolation and characterization of nanocellulose from Polypodiophyta fern using chemo-mechanical method
Katja Vasić, Monika Dokl, Željko Knez, Maja Leitgeb, 2024, izvirni znanstveni članek

Opis: Nanocellulose is considered a promising and sustainable biomaterial, with excellent properties of biorenewability with improved mechanical properties. As a unique natural biopolymer, it has been applied to many different industries, where efficient and environmentally friendly productions are in demand. For the first time, ferns from the class Polypodiopsida were used for the isolation of cellulose fibers, which was performed using a chemo-mechanical method. As chemical treatment plays a crucial role in the isolation of nanocellulose, it affects the efficiency of the extraction process, as well as the properties of the resulting nanocellulose. Therefore, mechanical fibrillation was performed via grinding, while the chemical process consisted of three different treatments: alkali treatment, bleaching, and acid hydrolysis. In three different experiments, each treatment was separately prolonged to investigate the differing properties of isolated nanocellulose. Structural analysis and morphological analysis were investigated by SEM, EDS, FT-IR, and DLS. The thermal stability of cellulose fibers was investigated by TGA/DSC. The morphology of obtained nanocellulose was confirmed via SEM analysis for all samples, with particles ranging from 20 nm up to 600 nm, while the most consistent sizes were observed for NC3, ranging from 20 to 60 nm. FT-IR spectra showed prominent absorption peaks corresponding to cellulose, as well as the absence of absorption peaks, corresponding to lignin and hemicellulose. The EDS confirmed the elemental purity of nanocellulose, while TGA/DSC indicated higher thermal stability of nanocellulose, compared to untreated fern, which started to degrade earlier than nanocellulose. Such characteristics with unique properties make nanocellulose a versatile biomaterial for the industrial production of cellulosic materials.
Ključne besede: nanocellulose, isolation, Polypodiophyta fern, chemo-mechanical method, biomaterial, biopolymers
Objavljeno v DKUM: 31.01.2025; Ogledov: 0; Prenosov: 0
.pdf Celotno besedilo (3,75 MB)

2.
Confronting SARS-CoV-2 infection : patients’ experience in the first pandemic wave - cross-sectional study
Maja Sočan, Vanja Erčulj, 2022, izvirni znanstveni članek

Opis: The aim of the study was to investigate the real-life experience of persons infected with SARS-CoV-2 in Slovenia in the first pandemic wave and how the buffering effect of social and informational support affected negative feelings. We used a self-administrated questionnaire. There were 1182 eligible notified cases with the response rate 64.9%. At least 62% of responders were able to follow the isolation rules, while 21.1% did not or could not organize their living separately from other household members. The main providers during the isolation period were close family members. The most prevalent emotion in our study was worry (70.3%) and fear (37.6%). Worry and fear during the illness were less probable for men than women, but more probable for older patients. Participants with strong emotional support had lower odds of being sad. Those who were exposed to a larger number of sources of information had higher odds of being worried. Those patients who used a higher number of more credible sources of information had higher odds of being afraid during illness. Pets did not play a special role in psychological well-being. The role of the media and public health communications should be explored further to achieve an improved response.
Ključne besede: COVID-19, first pandemic wave, isolation, information, social support, feelings, stigma
Objavljeno v DKUM: 04.07.2024; Ogledov: 147; Prenosov: 22
.pdf Celotno besedilo (1,32 MB)
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3.
Sustainable processing of materials using supercritical fluids : doktorska disertacija
Dragana Borjan, 2022, doktorska disertacija

Opis: Supercritical fluids (SCFs) are powerful solvents with many unique properties. They have great potential for many processes, from extraction to chemical reactions and recycling. Accordingly, phase equilibrium data and thermodynamic and transport properties measurements in systems with a supercritical phase, as well as reliable and versatile mathematical models of the phase equilibrium thermodynamics, are needed for the process design and economic feasibility studies. The dissertation focuses on the benefits of supercritical fluid technology and consists of three main sections. The first section includes studies of the phase equilibria of the binary gas-alcohol and gas-urea derivatives. The influence of pressure and temperature on the system behaviour (solubility, viscosity, density, interfacial tension, melting point curve) was investigated. Most of the experiments were carried out with a high-pressure optical view cell, with minor modifications of the apparatus and measurement principle to determine mentioned thermodynamic and transport properties. The second part of the dissertation deals with the recovery of extracts from natural materials. Special interest is oriented towards supercritical fluid extracts, characterised by strong biological activities, especially antimicrobial and antioxidant properties. Supercritical fluid extraction has been performed on a semi-continuous apparatus (at pressures of 150 bar and 250 bar and temperatures of 313.15 K and 333.15 K for oregano extraction; and at pressures of 100 bar and 300 bar and temperatures of 313.15 K and 333.15 K for red beetroot extraction) and various methods such as the microdilution method and the DPPH method were used to determine antimicrobial and antioxidant activity. In the third part, an overview of different methods for recycling carbon fibre reinforced composites is given, including chemical recycling with supercritical fluids. This field has not been well explored, and the approach is relatively new but very interesting from a sustainable point of view. For an economically feasible process design, the thermodynamic and mass transfer data have to be determined. The principles of the future lab- and pilot-scale operations demand these supporting data be known. The results obtained in the frame of this study represent the high added value in the scientific field. They are essential to design and modify processes that yield products that cannot be achieved with conventional production processes.
Ključne besede: supercritical fluids, alcohols, urea, phase equilibria, viscosity, density, interfacial tension, modified capillary method, isolation methods, supercritical fluid extraction, pharmacological activity, carbon fiber reinforced composites, recycling techniques
Objavljeno v DKUM: 11.10.2022; Ogledov: 1029; Prenosov: 143
.pdf Celotno besedilo (4,64 MB)

4.
Optimizacija postopka ekstrakcije učinkovin iz arnike arnica montana in formulacija produktov : master's thesis
Álvaro Pequeno Alonso, 2022, magistrsko delo

Opis: Arnica Montana je obetaven vir bioaktivnih spojin, predvsem fenolov, ki zaradi svoje antioksidativne aktivnosti izkazujejo koristi za zdravje ljudi. Da bi dosegli stopnjo farmacevtske uporabe, je treba cvetove Arnice Montana predelati v izdelek, ki je primeren za preživetje. V ta namen so bile izvedene različne ekstrakcijske tehnike z različnimi topili: hladna maceracija, ultrazvok, Soxhlet in superkritični CO2; uporabljena topila so bila etanol, metanol in mešanica etanola in vode 95:5 (v:v). Analiza, ki je vključevala ultravijolično/vidno spektrometrijo, je bila opravljena za merjenje antioksidativne aktivnosti in celotne vsebnosti fenolov v ekstraktih. Končno je bil organogel oblikovan z uporabo izvlečka, olja konoplje in voska riževih otrobov ter testiran glede njegove stabilnosti. V okviru tega dela je bil prvič formuliran organogel z visoko stabilnostjo, saj do sedaj v znanstveni literaturi ni bilo podatkov o tovrstni formulaciji. Za določitev njegovih reoloških lastnosti in topnosti v različnih topilih pri različnih temperaturnih pogojih bodo potrebne dodatne študije.
Ključne besede: Arnica Montana, organogels, solvent extraction, phenolic compounds, isolation, formulation
Objavljeno v DKUM: 13.07.2022; Ogledov: 584; Prenosov: 40
.pdf Celotno besedilo (2,03 MB)

5.
For safety and security reasons : The cost of component-isolation in IoT
Alexander Zuepke, Kai Beckmann, Andreas Zoor, Reinhold Kroeger, 2016, izvirni znanstveni članek

Opis: The current development trend of Internet of Things (IoT) aims for a tighter integration of mobile and stationary devices via various networks. This includes communication of vehicles to roadside infrastructure (V2I), as well as intelligent sensors / actors in Logistics and smart home environments. Compared to isolated traditional embedded systems, the exposure to open networks increases the attack surface, and errors in the networking components could compromise the safety and security of the embedded application or the whole network. But often current system architectures for mass-market IoT devices lack the required isolation concepts. Using a partitioning microkernel and enforcing the use of a microcontroller’s memory protection unit (MPU) facilities, we compare different isolation concepts for a publish/subscribe middleware implementing OMG’s Data Distribution Service (DDS) standard and we evaluate our results on an STM32F4 microcontroller. The results of this case study show moderate costs for increased memory usage and additional context switches.
Ključne besede: component-isolation, microkernel, partitioning, IoT
Objavljeno v DKUM: 17.11.2017; Ogledov: 1116; Prenosov: 277
.pdf Celotno besedilo (456,12 KB)
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6.
Financial aspects of a seismic base isolation system for a steel high-rack structure
Vojko Kilar, Simon Petrovčič, Simon Šilih, David Koren, 2013, izvirni znanstveni članek

Opis: The paper deals with the effects and costs of implementing a base isolation system for the mitigation of the seismic risk of an existing steel rack structure. Different realistic distributions of the payload mass and occupancy levels, which form different plan asymmetric variants, have been analysed. The results obtained by the pushover analysis (N2 method) are presented as top floor envelopes and as plastic hinge damage patterns. In the presented cost study, the cost of the implementation of the proposed base isolation system is compared with the estimated costs of structural repairs to the damaged structural members of the superstructure, as well as with estimated expenses of the downtime period. The results have shown that base isolation is, in general, not economically feasible for lower ground motion intensities, whereas it could be of great benefit in the case of moderate and high intensities, especially if the downtime period is taken into account.
Ključne besede: rack structures, seismic behaviour, base isolation, cost efficiency, mass eccentricity, pushover analysis
Objavljeno v DKUM: 07.08.2017; Ogledov: 1316; Prenosov: 161
.pdf Celotno besedilo (999,00 KB)
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7.
Isolation and characterization of human articular chondrocytes from surgical waste after total knee arthroplasty (TKA)
Jakob Naranđa, Lidija Gradišnik, Mario Gorenjak, Matjaž Vogrin, Uroš Maver, 2017, izvirni znanstveni članek

Opis: BACKGROUND: Cartilage tissue engineering is a fast-evolving field of biomedical engineering, in which the chondrocytes represent the most commonly used cell type. Since research in tissue engineering always consumes a lot of cells, simple and cheap isolation methods could form a powerful basis to boost such studies and enable their faster progress to the clinics. Isolated chondrocytes can be used for autologous chondrocyte implantation in cartilage repair, and are the base for valuable models to investigate cartilage phenotype preservation, as well as enable studies of molecular features, nature and scales of cellular responses to alterations in the cartilage tissue. METHODS: Isolation and consequent cultivation of primary human adult articular chondrocytes from the surgical waste obtained during total knee arthroplasty (TKA) was performed. To evaluate the chondrogenic potential of the isolated cells, gene expression of collagen type 2 (COL2), collagen 1 (COL1) and aggrecan (ACAN) was evaluated. Immunocytochemical staining of all mentioned proteins was performed to evaluate chondrocyte specific production. RESULTS: Cartilage specific gene expression of COL2 and ACAN has been shown that the proposed protocol leads to isolation of cells with a high chondrogenic potential, possibly even specific phenotype preservation up to the second passage. COL1 expression has confirmed the tendency of the isolated cells dedifferentiation into a fibroblast-like phenotype already in the second passage, which confirms previous findings that higher passages should be used with care in cartilage tissue engineering. To evaluate the effectiveness of our approach, immunocytochemical staining of the evaluated chondrocyte specific products was performed as well. DISCUSSION: In this study, we developed a protocol for isolation and consequent cultivation of primary human adult articular chondrocytes with the desired phenotype from the surgical waste obtained during TKA. TKA is a common and very frequently performed orthopaedic surgery during which both femoral condyles are removed. The latter present the ideal source for a simple and relatively cheap isolation of chondrocytes as was confirmed in our study.
Ključne besede: aggrecan, collagen 2, gene expression, human articular chondrocytes, isolation protocol, phenotype preservation, TKA, total knee arthroplasty
Objavljeno v DKUM: 02.08.2017; Ogledov: 1730; Prenosov: 656
.pdf Celotno besedilo (42,50 MB)
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8.
Social isolation during puberty affects female sexual behavior in mice
Jasmina Kerčmar, Stuart Tobet, Gregor Majdič, 2014, izvirni znanstveni članek

Opis: Exposure to stress during puberty can lead to long-term behavioral alterations in adult rodents coincident with sex steroid hormone-dependent brain remodeling and reorganization. Social isolation is a stress for social animals like mice, but little is known about the effects of such stress during adolescence on later reproductive behaviors. The present study examined sexual behavior of ovariectomized, estradiol and progesterone primed female mice that were individually housed from 25 days of age until testing at approximately 95 days, or individually housed from day 25 until day 60 (during puberty), followed by housing in social groups. Mice in these isolated groups were compared to females that were group housed throughout the experiment. Receptive sexual behaviors of females and behaviors of stimulus males were recorded. Females housed in social groups displayed greater levels of receptive behaviors in comparison to both socially isolated groups. Namely, social females had higher lordosis quotients (LQs) and more often displayed stronger lordosis postures in comparison to isolated females. No differences between female groups were observed in stimulus male sexual behavior suggesting that female “attractiveness” was not affected by their social isolation. Females housed in social groups had fewer cells containing immunoreactive estrogen receptor (ER) α in the anteroventral periventricular nucleus (AVPV) and in the ventromedial nucleus of the hypothalamus (VMH) than both isolated groups. These results suggest that isolation during adolescence affects female sexual behavior and re-socialization for 1 month in adulthood is insufficient to rescue lordosis behavior from the effects of social isolation during the pubertal period.
Ključne besede: mice, social isolation, female sexual behavior, estrogen receptor α, puberty, adolescence
Objavljeno v DKUM: 10.07.2017; Ogledov: 1508; Prenosov: 465
.pdf Celotno besedilo (944,61 KB)
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9.
Highly divergent Clostridium difficile strains isolated from the environment
Sandra Janežič, Mojca Potočnik, Valerija Tkalec, Maja Rupnik, 2016, izvirni znanstveni članek

Opis: Clostridium difficile is one of the most important human and animal pathogens. However, the bacterium is ubiquitous and can be isolated from various sources. Here we report the prevalence and characterization of C. difficile in less studied environmental samples, puddle water (n = 104) and soil (n = 79). C. difficile was detected in 14.4% of puddle water and in 36.7% of soil samples. Environmental strains displayed antimicrobial resistance patterns comparable to already published data of human and animal isolates. A total of 480 isolates were grouped into 34 different PCR ribotypes. More than half of these (52.9%; 18 of 34) were already described in humans or animals. However, 14 PCR ribotypes were new in our PCR ribotype library and all but one were non-toxigenic. The multilocus sequence analysis of these new PCR ribotypes revealed that non-toxigenic environmental isolates are phylogenetically distinct and belong to three highly divergent clades, two of which have not been described before. Our data suggest that environment is a potential reservoir of genetically diverse population of C. difficile.
Ključne besede: clostridium difficile, environment, isolation
Objavljeno v DKUM: 19.06.2017; Ogledov: 1565; Prenosov: 388
.pdf Celotno besedilo (1,13 MB)
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10.
Isolation of chlorophylls from stinging nettle (Urtica dioica L.)
Maša Hojnik Niderl, Mojca Škerget, Željko Knez, 2007, izvirni znanstveni članek

Opis: This study was aimed to assess the feasibility of extracting chlorophylls fromstinging nettle (Urtica dioica L.) by solvent extraction. In preliminary, the investigation concerned three parts of raw material (leaves, stalk and whole plant), different preservation techniques (blanching and drying) and different storage temperatures of preserved material ( |20 C for blanched and 4 C for dried sample). Extracts were analysed for chlorophyll A and chlorophyll B, respectively, by means of HPLC method. Afterwards, optimizationof single-step conventional extraction was carried out by examining the influence of the following process parameters on the extraction yield and isolation efficiency of chlorophylls: type of organic solvent, content of water in ethanol/water mixtures, ratio solvent/material, temperature, time of extraction and pH of the extraction mixture. Furthermore,to improve the yield and/or the selectivity of the extraction, multi-step conventional extraction experiments as well as other solid ]liquid extraction techniques (soxhlet and ultra-sound assisted) were performed and compared. c 2007 Elsevier B.V. All rights reserved.
Ključne besede: chemical processing, extraction, nettle, isolation of chlorophyll, chlorophyll content, solvent extraction
Objavljeno v DKUM: 31.05.2012; Ogledov: 2872; Prenosov: 118
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