126,052 research outputs found
Oberflächenveränderung verschiedener zahnmedizinischer Werk-stoffe nach in-vitro Alterung
No full textSusceptibility of different restorative materials to toothbrush abrasion and coffee staining
Objective: The aim of this study was to evaluate the susceptibility of different restorative materials to surface alterations after an aging simulation.
Methods: Specimens (n=15 per material) of five different restorative materials (CER: ceramic/Vita Mark II; EMP: composite/Empress Direct; LAV: CAD/CAM composite/Lava Ultimate; COM: prefabricated composite/Componeer; VEN: prefabricated composite/Venear) were produced. Whereas CER was glazed, EMP and LAV were polished with silicon polishers, and COM and VEN were left untreated. Mean roughness (Ra and Rz) and colorimetric parameters (L*a*b*), expressed as colour change (E), were measured. The specimens underwent an artificial aging procedure. After baseline measurements (M1), the specimens were successively immersed for 24 hours in coffee (M2), abraded in a toothbrushing simulator (M3), immersed in coffee (M4), abraded (M5) and repeatedly abraded (M6). After each aging procedure (M2-M6), surface roughness and colorimetric parameters were recorded. Differences between the materials regarding Ra/Rz and E were analysed with a nonparametric ANOVA analysis. The level of significance was set at α=0.05.
Results: The lowest roughness values were obtained for CER. A significant increase in Ra was detected for EMP, COM and VEN compared to CER. The Ra/Rz values were found to be highly significantly different for the materials and measuring times (M) (p<0.0001). Regarding E most alterations were found for EMP and COM, whereas CER and LAV remained mostly stable. The E values were significantly different for the materials and M (p<0.0001).
Conclusion: The ceramic and the CAD/CAM composite were the most stable materials with regard to roughness and colour change and the only materials that resulted in Ra values below 0.2 μm (the clinically relevant threshold). Venears and Componeers were more inert than the direct composite material and thus might be an alternative for extensive restorations in the aesthetic zone
Melt pool detection at wire arc welding
No full textPri izdelavi 3D tiskanih kovinskih izdelkov s postopkom obločnega navarjanja z žico je težko doseči dobro dimenzijsko natančnost zaradi nestacionarnosti varilnega postopka, kar se odraža v valovitosti sten izdelkov in razliki med željeno in dejansko višino navarjenega sloja. Napaka se povečuje z večanjem števila navarjenih slojev. Z namenom povečanja dimenzijske natančnosti postopka smo razvili sistem za snemanje varjenja z visokohitrostno kamero ter algoritem za robustno in hitro zaznavo bazena taline iz dobljenih slik. Analizirali smo možnosti uporabe dobljenih podatkov o bazenu taline kot povratno zanko za krmiljenje varilnega aparata.Achieving good dimensional accuracy for 3D printed objects with the Gas metal arc welding process (Wire-arc additive manufacturing) is difficult because of the non-stationarity of the welding process, which results in object wall waviness and differences between the desired and actual layer height of the welded material. This error is cumulative and rises in proportion to the number of welded layers. To improve the dimensional accuracy of Wire-arc additively manufactured objects, we design a system to record welding using a high speed camera, and design an algorithm for robust and fast melt pool detection from the images. We analyze the possibilities of using this data as a feedback loop for controlling the welding machine parameters in real time
Decreasing of COD in wastewater with Fenton\u27s reagent
No full textCilj magistrske naloge je bil ugotoviti, ali je z uporabo Fentonovega reagenta mogoče znižati onesnaženost odpadne vode z organskimi spojinami, izraženo s kemijsko potrebo po kisiku (KPK). Fentonov reagent pomeni reakcijo med železovimi ioni Fe2+ in vodikovim peroksidom, pri čemer nastanejo visoko reaktivni hidroksilni radikali, ki razgrajujejo organske spojine.
Pripravili smo sintetične vzorce odpadne vode s huminsko kislino in tioureo. V nadaljevanju smo čistili tudi realno kompostno izcedno vodo. Eksperimente smo izvajali pri različnih pogojih Fentonove reakcije, tako da smo spreminjali maso FeSO4 × 7H2O, ki smo ga uporabili kot vir Fe2+, razmerje med reagenti, čas trajanja reakcije in pH-vrednost. Učinek čiščenja smo v glavnem spremljali z merjenjem KPK, absorbance in motnosti.
Ugotovili smo, da je bila Fentonova reakcija primerna za čiščenje sintetičnih vzorcev odpadne vode s huminsko kislino in kompostne izcedne vode, medtem ko za sintetične vzorce odpadne vode s tioureo znižanja KPK nismo dosegli. Najbolj učinkovito znižanje KPK je pri obdelavi sintetične odpadne vode s huminsko kislino znašalo 97,40 %, dosegli pa smo ga pri pogojih reakcije: "mFeSO4 × 7H2O " = 0,2 g, "nFeSO4 × 7H2O∶ nH2O2 " = 1 : 3, pH = 3, t = 60 min. Najučinkovitejše znižanje KPK pri obdelavi kompostne izcedne vode je doseglo 64,08 % pri pogojih reakcije: "mFeSO4 × 7H2O " = 0,6 g, "nFeSO4 × 7H2O∶ nH2O2 " = 1 : 5, pH = 4,5, t = 30 min.The aim of the master thesis was to determine whether the use of Fenton\u27s reagent can reduce pollution of wastewater with organic compounds, expressed as the chemical oxygen demand (COD). Fenton\u27s reagent means the reaction between iron ions Fe2+ and hydrogen peroxide, whereby highly reactive hydroxyl radicals, which decompose organic compounds are formed.
We prepared synthetic wastewater samples containing humic acid and thiourea. Hereinafter, we also cleaned a real compost leachate. Experiments were carried out under different conditions of Fenton\u27s reaction by varying the ratio of the reagents, the reaction time, the pH value and the mass of FeSO4 × 7H2O, which was used as a source of Fe2+. The cleaning efficiency was mainly monitored by measuring COD, absorbance and turbidity.
We have found that Fenton\u27s reaction was suitable for treatment of synthetic wastewater containing humic acid and for treatment of compost leachate, while in the case of synthetic wastewater containing thiourea COD reduction was not achieved. The maximum reduction of COD for the treatment of wastewater containing humic acid stood at 97.40%, achieved at following conditions: "mFeSO4 × 7H2O " = 0,2 g, "nFeSO4 × 7H2O∶ nH2O2 " = 1 : 3, pH = 3, t = 60 min. The maximum reduction of COD for the treatment of compost leachate has reached 64.08 % at the reaction conditions: "mFeSO4 × 7H2O " = 0,6 g, "nFeSO4 × 7H2O∶ nH2O2 " = 1 : 5, pH = 4,5, t = 30 min
THE INFLUENCE OF INTERMOLECULAR VAN DER WAALS FORCES ON THE FORMATION OF ASSOCIATED MOLECULES
No full textNamen diplomske naloge je preučiti vpliv van der Waalsovih sil na tvorbo asociiranih molekul. V ta namen smo izbrali površinsko aktivne snovi, ki imajo amfifilne lastnosti in vplivajo na povšinske in medfazne napetosti ter pri določeni koncentraciji, imenovani kritična micelna koncentracija (CMC), tvorijo molekulske skupke, ki jim pravimo micele. Kritično micelno koncentracijo smo določili trem površinsko aktivnim snovem: heksadeciltrimetilamonijevemu bromidu, tetradeciltrimetilamonijevemu bromidu in n dodeciltrimetilamonijevemu bromidu. Eksperimente smo izvajali pri temperaturah 25 °C, 30 °C in 35 °C s klasično konduktometrično metodo. Na osnovi rezultatov smo analizirali vpliv van der Waalsovih sil na proces asociacije molekul v micele.
Za izbrano temperaturno območje smo ugotovili, da vrednosti kritične micelne koncentracije rastejo s povišanjem temperature in da se z višanjem števila C atomov v molekuli površinsko aktivne snovi kritične micelne koncentracije znižujejo. Po izračunu stopnje ionizacije micele α, stopnje vezave protiiona β in standardne Gibbsove proste energije pri micelizaciji 〖∆G〗_mic^°, smo ugotovili, da so vrednosti standardne Gibbsove proste energije pri micelizaciji v vseh primerih negativne in s podaljševanjem alkilne verige v molekuli padajo, kar si razlagamo kot krepitev privlačnih van der Waalsovih sil, ki posledično povzročijo nastanek micele pri nižji vrednosti kritične micelne koncentracije.The aim of the diploma thesis was to investigate the influence of van der Waals forces on formation of the associated molecules. For this purpose we chose surface active agents, which have amphiphilic properties and they affect on surface and interface tensions and on the certain concentration, called critical micelle concentration (CMC), they form molecular assemblies, known as micelles. We determined critical micelle concentration to three surfactants: hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and n-dodecyltrimethylammonium bromide. We executed the experiment at temperatures 25 °C, 30 °C and 35 °C with clasic conductometry method. On the basis of the results, we analysed the influence of van der Waals forces on the process of association of molecules to micelles.
For chosen temperature range, we found out, that values of critical micelle concentration increase with increasing temperature and with the extension of the number of C atoms in molecule of surfactant critical micelle concentration decreases. According to calculation of ionization degree α, degree of binding counterion β and standard Gibbs energy of micellization 〖∆G〗_mic^°, we found out, that values of standard Gibbs energy of micellization are in all cases negative and with extending alkyl chain in molecule, decrease, what we explain as enhancement of attractive van der Waals forces, which consequentially cause formation of micelle at lower value of critical micelle concentration
Use of biosensors for SARS-CoV-2 virus detection
No full textPandemija, ki jo je povzročil virus SARS-CoV-2, zahteva hitre, zanesljive, stroškovno sprejemljive in enostavne načine detekcije, da bi se z boleznijo COVID-19 učinkovito spopadli in preprečili njeno širjenje. Obratna transkripcija in verižna reakcija s polimerazo (RT-PCR) je trenutno referenčna metoda in velja za zlati standard v klinični diagnozi. Metoda pa ni najbolj primerna zaradi dolgotrajnih analiz in zahtevne drage opreme ter potreb po usposobljenemu osebju. Tako v klinični praksi kot v domači uporabi je zato zelo razširjena tudi uporaba testov lateralnega toka (LFIA), med katere spadajo tudi hitri antigenski testi (HAGT). Biosenzorji, ki predstavljajo tretjo možnost za detekcijo, so se izkazali kot zmogljiva in učinkovita orodja, saj so sposobni odkrivanja virusnih antigenov, protiteles, RNA celih virusnih delcev in drugih potencialnih biomarkerjev. Nanomateriali, kot so nano zlato, srebro in nikelj, se lahko uporabijo za znatno izboljšanje delovanja biosenzorjev, če pa v biosenzorje vključimo še grafen, ki je čista oblika ogljika, se sposobnost zaznavanja izboljša na bistveno višjo raven. Grafenski tranzistor (Gr-FET), ki je zasnovan kot tranzistor na poljski pojav, je eden od primerov aplikacije grafena, ki je sposoben ultra občutljive detekcije z nizkimi šumi, kar omogoča meritve tudi v primeru prisotnosti majhne količine analitov. Novejše tehnologije predstavljajo velik napredek in izboljšavo v primerjavi s tradicionalnimi metodami detekcije, saj jih lahko uspešno in z večjo mero učinkovitosti, natančnosti, hitrosti in priročnosti uporabljamo tudi za detekcijo SARS-CoV-2.The pandemic, caused by the SARS-CoV-2 virus, requires fast, reliable, cost-effective and simple detection methods in order to effectively deal with the COVID-19 disease and prevent its spread. Reverse Transcription Polymerase Chain Reaction (RT-PCR) is currently the reference method and is considered the gold standard in clinical diagnosis. However, the method is not the most suitable due to the time-consuming analyses and sophisticated, expensive equipment and the need for qualified personnel. The use of lateral flow tests (LFIA), which also includes rapid antigen tests (RAT), is widely used both in clinical practice and at home. Biosensors, which represent a third option for detection, have proven to be powerful and effective tools, as they are capable of detecting viral antigens, antibodies, RNA, entire viral particles and other potential biomarkers. Nanomaterials such as nano gold, silver and nickel can be used to significantly improve the performance of biosensors, and if graphene, which is a pure form of carbon, is incorporated into the biosensors, the sensing ability is improved to a significantly higher level. The graphene transistor (Gr-FET), which is designed as a field-effect transistor, is one example of the application of graphene, which is capable of ultra-sensitive detection with low noise, enabling measurements also in the presence of small amounts of analytes. Newer technologies represent a major advancement and improvement over traditional detection methods, as they can be successfully used to detect SARS-CoV-2 with greater efficiency, accuracy, speed and convenience
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
SHOX duplications found in some cases with type I Mayer-Rokitansky-Kuster-Hauser syndrome
No full textPurpose: The Mayer-Rokitansky-Kuster-Hauser syndrome is defined as congenital aplasia of mullerian ducts derived structures in females with a normal female chromosomal and gonadal sex. Most cases with Mayer-Rokitansky-Kuster-Hauser syndrome are sporadic, although familial cases have been reported. The genetic basis of Mayer-Rokitansky-Kuster-Hauser syndrome is largely unknown and seems heterogeneous, and a small number of cases were found to have mutations in the WNT4 gene. The aim of this study was to identify possible recurrent submicroscopic imbalances in a cohort of familial and sporadic cases with Mayer-Rokitansky-Kuster-Hauser syndrome. Methods: Multiplex ligation-dependent probe amplification was used to screen the subtelomeric sequences of all chromosomes in 30 patients with Mayer-Rokitansky-Kuster-Hauser syndrome (sporadic, n = 27 and familial, n = 3). Segregation analysis and pyrosequencing were applied to validate the MLPA results in the informative family. Results: Partial duplication of the Xpter pseudoautosomal region 1 containing the short stature homeobox (SHOX) gene was detected in five patients with Mayer-Rokitansky-Kuster-Hauser syndrome (familial, n = 3 and sporadic, n = 2) and not in 53 healthy controls. The duplications were not overlapping, and SHOX was never entirely duplicated. Haplotyping in the informative family revealed that SHOX gene duplication was inherited from the unaffected father and was absent in two healthy sisters. Conclusions: Partial duplication of SHOX gene is found in some cases with both familial and sporadic Mayer-Rokitansky-Kuster-Hauser type I syndrome
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
<Special Contribution>Bringen die Reproduktionstechnologien die Familie zum Verschwinden?
No full text岡崎 佑香 訳原著作の書誌事項: Kuster, Friederike. (2020). „Bringen die Reproduktionstechnologien die Familie zum Verschwinden?“. In: C. Mahs, B. Rendtorff, A. Warmuth (Hg.), Geschlechterverwirrungen. Was wir wissen, was wir glauben und was nicht stimmt, Frankfurt a. M./New York: Campus, 237-243.「正誤表」を追加（2022-04-28）Translated by Yuka OKAZAK
NADPH oxidase (NOX) in the heart : the interplay of NOX-derived ROS in β1-integrin-induced survival signalling
No full textModerate levels of reactive oxygen species (ROS) act as mediators in cellular signalling processes. An important source of cardiac ROS is the highly expressed NADPH oxidase (NOX) family isoform NOX2. However, little is known about whether NOX-derived ROS are protective in the heart.
In this study we show that CD29 (β1-integrin), a cell adhesion receptor highly expressed on cardiac muscle cells, induces NOX-dependent ROS. CD29 is known to be mandatory in cell growth and survival, and non-functional CD29 causes severe heart disease. We demonstrate that NOX2-derived ROS are essential for CD29-induced survival signalling, including the PI3K/PKB and MEK/ERK pathways. Furthermore, CD29-induced NOX-derived ROS are indispensible in the inhibition of the pro-apoptotic kinase GSK-3β, which we uncovered as a downstream target of both the ERK and PKB survival pathways in cardiac muscle cells. These findings clearly add to the growing body of evidence suggesting that moderate ROS levels are beneficial to the cell and highlight the crucial role of NOX2-derived ROS for cell survival in the heart
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