300 research outputs found
Gradual Loss of Partial Denture Retentive Forces
DjelomiÄna proteza može se fizioloÅ”ki ispravno prilagoditi fundamentu samo na osnovi poznavanja biostatike stomatognatoga sustava. Velik broj Äimbenika utjeÄe hoÄe li neka sila biti u funkciji fizioloÅ”ke stimulacije ili Äe prouzroÄiti patoloÅ”ke promjene potpornoga tkiva.
Ovim istraživanjem namjerava se utvrditi poÄetna vrijednost retencijskih sila lijevanih kvaÄica, ankera i magneta, te njihov postupni gubitak sile nakon odreÄenoga broja ciklusa vaÄenja i stavljanja retencijskih elemenata.
Mjerenja su provedena u Zavodu za materijale Fakulteta za strojarstvo i brodogradnju SveuÄiliÅ”ta u Zagrebu. Ispitivani uzorci izraÄeni su od materijala i gotovih elemenata prema podatcima proizvoÄaÄa. Odgovaraju kriterijima koje zahtijeva DIN 13912 i DIN 13906-1 i ostalim internacionalnim standardima. UreÄajem za mjerenje retencijske sile može se cikliÄki ukljuÄivati i iskljuÄivati retencijske elemente i kontinuirano prikupljati mjerne podatke.
Ovim mjerenjima istraživao se postupni gubitak sila ispitivanih retncijskih elemenata. Dobivene vrijednosti kvalitativne raÅ”Älambe ispitivanih retencijskih elemenata prikazane su grafiÄki i u tablicama. Tijekom ispitivanje doÅ”lo se do spoznaje da vrijednost retencijske sile kvaÄica i ankera postupno opada, a da se sila magnetskih slitina
ne mijenja.
Temeljni Äimbenik koji bitno utjeÄe na veliÄinu retencijske sile jest troÅ”enje i zamor materijala. Spojnica uz nazoÄnost sline ima manju silu retencije, ali zbog smanjena troÅ”enja nastat Äe i sporije smanjenje retencijske sile.A partial denture can be oppropriately accommodated physiologically on the denture base only with good understanding of the stomatognathic system biostatics. A force can either act as a physiological stimulus or can lead to pathological alterations in supporting tissue, wich depends on a great number of factors.
The aim of the study was to determine the initial retentive force values of cast clasps, anchors and magnets as wel as their gradual loss of force after a certain number of retentive elements, extraction and insertion cycles.
Measurement were carried out at the Materials Department, School Engineering and Naval Architecture, University of Zagreb. The examined specimens were made of materials and ready-made elements in accordance with the manufacturerās declaration. They satisfy the DIN 13912 and DIN 13906-1 criteria and comply with other
international standards. The device for retentive force measurement can periodically both include and exclude retentive elements thus continually collecting measurement data.
Gradual loss of the examined retentive element forces was analysed by these measurings. The obtained values of the examined retentive elements qualitative analysis are presented in graphs and tables.
In the course of analysis it was dicovered that the retentive force value of both clasps and anchors gradually decreases whereas the magnetic force of the alloys remains unchanged.
The key factors which have a great impact on the retnetive force value are wear and material fatigue. A clasp in a wet environment (saliva) has less retentive force, but due to decreased wear the retnetive force decrease will progress more slowly
Maps of secular resonances in the NEO region
Context. From numerical simulations, it is known that some secular resonances
may affect the motion of near-Earth objects (NEOs). However, the specific
location of the secular resonance inside the NEO region is not fully known,
because the methods previously used to predict their location can not be used
for highly eccentric orbits and when the NEOs cross the orbits of the planets.
Aims. In this paper, we aim to map the secular resonances with the planets
from Venus to Saturn in the NEO region, even for high values of the
eccentricity.
Methods. We used an averaged semi-analytical model that can deal with orbit
crossing singularities for the computation of the secular dynamics of NEOs,
from which we can obtain suitable proper elements and proper frequencies. Then,
we computed the proper frequencies over a uniform grid in the proper elements
space. Secular resonances are thus located by the level curves corresponding to
the proper frequencies of the planets.
Results. We determined the location of the secular resonances with the
planets from Venus to Saturn, showing that they appear well inside the NEO
region. By using full numerical N-body simulations we also showed that the
location predicted by our method is fairly accurate. Finally, we provided some
indications about possible dynamical paths inside the NEO region, due to the
presence of secular resonances.Comment: Accepted for publication in A&
Tehnike raÄunarske inteligencije u modeliranju i identifikaciji indikatora ponaÅ”anja brane
Indikatori ponaÅ”anja brane su relevantne veliÄine, Äijim se praÄenjem utvrÄuje da
li je stvarno stanje brane u eksploataciji u saglasnosti sa onim Å”to je predviÄeno i oÄekivano u fazi projektovanja. VeliÄine koje se prate treba da se kreÄu u nekom unapred definisanom opsegu koji garantuje stanje stabilnosti brane.
U ovoj disertaciji su predloženi razliÄiti pristupi modeliranja i parametarske
identifikacije indikatora ponaŔanja brane, poput horizontalnih pomeranja i nivoa
vode u pijezometrima, tehnikama raÄunarske inteligencije. Prvi pristup je da se
linearno preslikavanje uzroÄnih veliÄina u indikatore ponaÅ”anja, koje se koristi kod viÅ”estruke linearne regresije, zameni nelinearnim. Drugi pristup, predložen u ovom radu, zasniva se na primeni postupka parametarske identifikacije nelinearnih sistema.
Horizontalna pomeranja i nivoi vode u pijezometrima su nelinearne, složene funkcije uzroÄnih veliÄina, pa je za njihovo modeliranje koriÅ”Äena NARX (Nonlinear Auto Regresive eXogenous- nelinearni auto-regresioni model sa spoljaÅ”njim ulazom)
struktura, kojom je opisana Å”iroka klasa nelinearnih dinamiÄkih procesa. Predloženi pristupi formiranja modela primenjeni su za modeliranje i parametarsku
identifikaciju horizontalnih pomeranja taÄaka brane BoÄac, kao i nivoa vode u
pijezometrima brana Äerdap II i Prvonek.
Nelinearni modeli zasnovani na tehnikama raÄunarske inteligencije
implementirani su koriÅ”Äenjem programskog jezika Java i programskog paketa Matlab.
Tehnike raÄunarske inteligencije koriÅ”Äene u ovom radu su viÅ”eslojni perceptron,
RBF (RBF - Radial Basis Function ā radijalna osnovna funkcija) neuronska mreža i ANFIS (ANFIS - Adaptive-Network-Based Fuzzy Inference System - fazi sistem za zakljuÄivanje zasnovan na adaptivnoj mreži). NedostajuÄi podaci u skupu merenja mogu biti uzrok problema u okviru procesa uÄenja i loÅ”ih performansi dobijenih modela. U cilju nadomeÅ”tanja nedostajuÄih podataka koriÅ”Äene su tehnike iz domena matematiÄke statistike. Prisustvo autlajera u mernim podacima ima veliki uticaj na predviÄanja podataka koji nedostaju, pa je njihovo prisustvo posebno analizirano. TakoÄe je analiziran i problem optimizacije ulazno-izlaznih modela, koji podrazumeva odreÄivanje broja prediktora i dimenzije regresionog vektora, kao i broja parametara neuronskih mreža i neuro-fazi sistema.
Performanse modela, formiranih na osnovu predloženog koncepta, poreÄeni su sa
rezultatima dobijenim drugim metodama modeliranja istih indikatora ponaŔanja
prikazanim u relevantoj literaturi objavljenoj u poslednjih nekoliko godina. Na osnovu rezultata zakljuÄeno je da je moguÄe kreirati i obuÄiti modele zasnovane na tehnikama raÄunarske inteligencije koji Äe sa velikom preciznoÅ”Äu predviÄati bitne indikatore ponaÅ”anja brane.The dam behavior indicators are relevant factors whose monitoring indicates whether the actual operational state of the dam is in accordance with what is expected and anticipated in the design phase. Such indicators should move in a predefined range, in order to guarantee stability of the dam.
This dissertation proposes different approaches to modeling and parametric identification of the dam behavior indicators, such as radial displacements or piezometric water levels, using the techniques of artificial intelligence. The first approach is to replace linear mapping of causal variables into behavior indicators, which is used in multiple linear regression, with nonlinear.
The second approach proposed in this paper is based on applying the method of parametric nonlinear system identification. Radial displacements and piezometric water levels are nonlinear, complex functions of causal variables, so for their modeling NARX (Nonlinear Auto Regresive eXogenous), which is employed to describe a wide class of nonlinear dynamic systems, is used.
These proposed approaches are used for modeling and parametric identification of radial displacements of dam BoÄac, and piezometric water levels of dams Iron Gate II and Prvonek.
Nonlinear models based on artificial intelligence techniques have been implemented using the Java programming language and MATLAB. Artificial intelligence techniques used in this work are the multilayer perceptron, RBF (Radial Basis Function) neural network and ANFIS (Adaptive-Network-Based Fuzzy Inference System). The presence of missing data in a set of measurements may be causing problems in the learning process and the poor performance of the obtained models. In order to predict the missing data, the techniques of mathematical statistics
have been used. Outliers present in a set of measurements have a big effect on the prediction of missing data, and their presence is specifically analyzed. The problem of optimizing the inputoutput model, which involves determining the number of predictors and dimensions of the regression vector, and the number of parameters of neural networks and neuro-fuzzy systems, is also analyzed.
The performance of the models, formed on the basis of the proposed concept, are compared with those obtained by other methods of modeling the same behavioral indicators presented in relevant accompanying literature published in the last few years. Based on the results, it was concluded that it is possible to create and train models based on computational intelligence techniques to predict with great accuracy the essential dam behavior indicators
Supplementary data for the article: DimitrijeviÄ, T.; NovakoviÄ, I.; RadanoviÄ, D.; NovakoviÄ, S. B.; RodiÄ, M. V.; AnÄelkoviÄ, K.; Å umar-RistoviÄ, M. Synthesis, Spectral and Structural Characterization and Biological Activity of Cu(II) Complexes with 4-(Diethylamino)Salicylaldehyde and Ī±-Diimines. Journal of Coordination Chemistry 2020, 73 (4), 702ā716. https://doi.org/10.1080/00958972.2020.1740212
Supplementary material for: [https://doi.org/10.1080/00958972.2020.1740212]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/4025
The effect of the polyphenols of natural origin and the synthetic potassium channel openers on contractility of the isolated uterus
Prirodni polifenoli su zastupljeni u velikom broju biljnih vrsta. Kao posebni izvori rezveratrola moglo bi se izdvojiti grožÄe i vino, kao njegov produkt, a naringenina grejpfrut, njegov sok, hmelj i pivo.
Tokom poslednje decenije rezveratrol se naÅ”ao u žiži nauÄne i Å”ire javnosti kao supstanca koja usporava starenje, ima antikancerogena, antiinflamatorna, kardioprotektivna svojstva. Kao moguÄa mesta dejstva pokazan je veliki broj Äelijskih struktura, stoga je rezveratrol oznaÄen kao "jedan molekul - mnogo meta". IzmeÄu ostalog, pokazano je da rezveratrol dovodi do relaksacije glatkih miÅ”iÄa mnogobrojnih krvnih sudova kao i glatkih miÅ”iÄa žuÄne kese. Kalijumovi kanali su direktno ili indirektno ukljuÄeni u mehanizam dejstva rezveratrola.
Za razliku od njega, naringenin, pripada manje prouÄavanoj grupi, flavonoidima. Njegov mehanizam inhibicije kontrakcija glatkih miÅ”iÄa uterusa joÅ” uvek nije prouÄen. Pored velikog interesovanja za rezveratrol, njegov uticaj na kontraktilnost glatke muskulature uterusa nije izuÄavan. Stoga su ciljevi ove studije bili da ispitimo moguÄe inhibitorno dejstvo rezveratrola i naringenina na nekoliko eksperimentalnih modela negravidnog i gravidnog uterusa i da definiÅ”emo ulogu kalijumovih kanala u tim mehanizmima dejstva. Nepoželjna kontraktilnost uterusa je uzrok poremeÄaja kao Å”to su dismenoreja, kod negravidnog, a prevremeni poroÄaj, kod gravidnog uterusa. Do danas, ni jedan od ovih problema nije farmakoloÅ”ki reÅ”en. Dismenoreja se uglavnom tretira nesteroidnim antiinflamatornim lekovima, koji nisu uspeÅ”ni kod svih pacijenata i imaju izrazite neželjene efekte. Dodatno, prevremeni poroÄaj je uzrok morbiditeta novoroÄenÄati u 50 % sluÄajeva. Malo je dokaza da lekovi koji se koriste za suzbijanje prevremenih kontrakcija zaista efikasni. Prevremeni poroÄaj je ÄeÅ”Äi i ozbiljniji problem u grupi pacijenkinja iz progrma in vitro oplodnje. Shodno tome, idealno sredstvo za prevenciju i leÄenje neželjene
kontraktilnosti uterusa joÅ” uvek nije pronaÄen..
The supramolecular arrangement in the Ni(II) complexes of isothiosemicarbazide
The molecules of two complexes [Ni(ITSC)2(H2O)2](tere)Ī2H2O and [Ni(ITSC)2(NO3)2] (ITSC = S-methylisothiosemicarbazide; tere = terephthalate) tend to associate trough the hydrogen bonding interactions into the characteristic 2D blocks separated by the S-methyl moieties. The different coordination mode of the isothiosemicarbazide comparing to thiosemicarbazide (TSC) prevents the formation of the complementary hydrogen bonds with dicarboxylate important for selfassambly of TSC complexes, however in these ITSC the terephthalate anion has role in connection of the blocks and transformation of the 2D into the 3D supramolecular structure. The similar crystal arrangement is found in two earlier reported complexes of Ni(II) with ITSC.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200
Comparison of two views regarding the nature of the X-Hā¦phenyl interaction
There are two approaches in the analysis of the nature of the X-Hā¦phenyl interactions. One is based on the assumption that atoms, bonds and the Ļ plane belonging to the phenyl ring, are the points which can be involved in the interaction. The other states that center of the phenyl ring is the point acceptor. In this paper we compare two views using the directionality of the X-H vector and length/angle correlations relative to both assumed point acceptors. The results suggest that on the basis of this methodology there is no clear answer regarding the nature of the acceptor site in the phenyl ring.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200
Transition metal complexes with Girard reagents and their hydrazones
This is the first review dealing with the coordination chemistry of metal complexes with Girard's reagents and their hydrazones. The short introduction points out to chemical properties and significance of these organic compounds. The next section briefly describes synthetic methods for preparing complexes with Girard's reagents, as well as modes of coordination of these ligands. The last two extensive sections review the preparation, stereochemistry and structural characteristics of metal complexes with Girard's hydrazones, including some newer non-hydrazonic derivatives of Girard's reagents, also.[Acknowledgments. Projekat Ministarstva nauke Republike Srbije, br. 172014
Schizophyllum commune: The main cause of dying trees of the Banja Luka arbored walks and parks
In the frame of investigation of the main cause of dying trees of the main arbored walks (Mladena StojanoviÄa Aley and Park), the investigation of the presence and diversity of macrofungi in Banja Luka City were undertaken in the period 2006-2011. Relatively poor generic diversity of lignicolous (pathogenic or potentially pathogenic and saprotrophic) macrofungi with only 16 species representing this group (13 basidiomycets: Schizophyllum commune, Fomes fomentarius, Stereum hirsutum, Coriolus versicolor, Flammulina velutipes, Pseudotrametes gibbosa, Ganoderma applanatum, G. lucidum, G. adspersum, Polyporus squamosus, Meripilus giganteus, Laetiporus sulphureus, AuricuĀlaria auricula-judae, and 3 ascomycets: Nectria cinnabarina, Xylaria hypoxylon, X. polyĀmorpha) were recorded. Such a poor qualitative composition of this very important fungal group could be explained by the reduction in the number of plant species in arbored walks and alleys, as well as the reduction in the number of fungi resistant to heavy air pollution caused by nearby (1-5m) fuel combustion in engines. Although only preliminary, our results pointed to the necessity of conservation and protection of the most beautiful features of Banja Luka and its alleys and arbored walks, by undertaking the measures of curing damaged trees and treating them with fungicides in order to wipe out the epiphytia caused in more than 95% of cases (dated May 2011) by Split-gill (Schizophyllum commune), present on dead wood but also on damaged trees of Aesculus hyppocastaneum (127 trees), Tilia cordata (124 trees), Tilia platyphyllos (36 trees), Tilia argentea (40 trees), Acer negundo (20 trees), Platanus acerifolia (2 trees), Robinia pseudoacacia (3 trees), Fraxinus ornus (1 tree), Betula pendula (1 tree), Catalpa sp. (2 trees), etc. Altogether, during the last decade, around 200 trees collapsed or were sanitary cut in Banja Luka arbored walk from the Malta site to the Green bridge, a total length around 5 km. The reason for this was primarily due to Split-gill fungus and the restoration of arbored walks in the streets extremely polluted by engine fuel consumption in the zone of Mladena StojanoviÄa street. By analyzing the trees along the City of Banja Luka main street it could be concluded that, besides the appearance of suffocation of plants, due to wide asphalt surfaces that are located immediately next to the tree-trunks and heavy air pollution, fungi caused illnesses are the most important cause of the decline of trees. With its great adaptation to arid climate and ability to resist to the air pollution, Schizophyllum commune turned out to be the most aggressive and successful universal fungal invader of trees from old alleys, even threatening immunoĀcompromised human individuals. However, man and his direct or indirect impacts contribĀute to the dying of trees much faster than the fungal pathogens in the busiest and most polluted Mladena StojanoviÄa street
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