Every symplectic toric orbifold is a centered reduction of a Cartesian product of weighted projective spaces

We prove that every symplectic toric orbifold is a centered reduction of a Cartesian product of weighted projective spaces. A theorem of Abreu and Macarini shows that if the level set of the reduction passes through a non-displaceable set then the image of this set in the reduced space is also non-displaceable. Using this result we show that every symplectic toric orbifold contains a non-displaceable fiber and we identify this fiber.Comment: 20 pages, 11 figures; Final version. Accepted at IMRN. Comments from the referees included. Section about Gromov width added. Moreover we fixed some small mistakes that unfortunately made it to the published version (moment polytope for the weighted projective space was not fully correct; at some point a not connected subgroup was called a torus

C-myc misregulation triggers complex process of genomic instability

Genetic stability is an essential factor for the cellular integrity. Failure in its maintenance leads to accumulation of errors derived from the process of DNA replication, cellular metabolism, action of endogenous and exogenous DNA damaging factors and eventually, as a final outcome tumor initiation and progression occur. Overall manifestation of c-Myc deregulation in many tumors and different mechanisms of Myc's action toward genomic stability suggest that this gene plays a central role in destabilization of genome. Microarray studies and functional genomics approach led us to conclusion that c-Myc can control nuclear architecture in global fashion since about 15% of all cellular genes are regulated by this transcription factor. Deregulation of c-illyc gene triggers a composite network of genomic instability that may result in several different outcomes as: locus-specific amplification, formation of extrachromosomal elements (EEs), chromosomal instability, long-range illegitimate recombination, point mutations, DNA breakage and nuclear structure reorganization This review outlines the growing evidence that c-Myc oncogene induces a complex network of genomic instability and describes systems and circumstances under which deregulation of c-Myc results in specific types of genomic alteration

KE-formulacija za aplikacije virtualne stvarnosti

Virtual reality (VR), as a novel technology, represents one of the most powerful tools to assist or even play the major role in many areas, such as development of new designs, training medical practitioners or assembly operators, entertaining industry, etc. On the other hand, the finite element method (FEM) imposed itself as an essential technical support for the needs of computing flexible bodies’ deformational behavior. FEM together with CAD are important ingredients of VR. In the VR applications that imply interactive simulations with flexible bodies included, the efficiency of FEM formulations is of crucial importance. The paper presents a co-rotational FEM-formulation developed to meet the needs of simulating geometrically nonlinear deformational behavior at interactive frame rates. It is presented here in combination with a rather simple linear tetrahedral element. The formulation is enriched with a coupled-mesh technique to enable the usage of rougher FEM models to compute deformational behavior of complex geometries. The advantages of an iterative solver and the solution procedure for both static and dynamic analyses are discussed.Virtualna stvarnost (VR), kao nova tehnologija, predstavlja jednu od najmoćnijih alatki koje podržavaju rad ili čak igraju glavnu ulogu u mnogim područjima, kao što su razvoj novih dizajna, trening liječnika ili montažera, industrija zabave, itd. S druge strane, metoda konačnih elemenata (MKE) se nametnula kao osnovna tehnička podrška za potrebe proračunavanja deformacijskog ponašanja elastičnih tijela. MKE je zajedno s CAD-om, važan dio VR-a. U VR aplikacijama koje podrazumijevaju interaktivnu simulaciju s elastičnim tijelima, efikasnost MKE formulacije je od presudne važnosti. Rad predstavlja korotacijsku MKE formulaciju razvijenu s ciljem simuliranja geometrijski nelinearnog ponašanja u interaktivnoj domeni. Formulacija je predstavljena u kombinaciji s vrlo jednostavnim linearnim elementom tipa tetraedra. Formulacija je proširena tehnikom spregnutih mreža kako bi se omogućilo korištenje grubljih MKE modela za određivanje deformacijskog ponašanja složenih geometrija. Razmotrene su prednosti iterativnog solvera kao i procedura rješavanja statičke i dinamičke analize

THE ANALYSIS OF FEM RESULTS CONVERGENCE IN MODELLING PIEZOELECTRIC ACTIVE SHELL STRUCTURES

The field of active/adaptive structures has been the subject of intense interest over the past couple of decades. The progress in this research field strongly depends on the availability of adequate and reliable modelling tools. Regarding structural analysis in general, the finite element method (FEM) has imposed itself as the method of choice for modelling and simulation. Piezoelectric active structures are characterized by strong enough coupling between the mechanical field and the electric field, which is further used for the realization of active structural behaviour. The descriptions of the mechanical and electrical field as well as their coupling significantly affect the convergence of the FEM results with mesh refinement, which may proceed in a trend different to what is commonly expected when FEM is applied to purely mechanical problems. The paper considers this aspect by using two quadratic shell type finite elements developed for modelling piezoelectric composite laminates. Both full and uniformly reduced integration techniques are taken into consideration in a set of examples involving composite laminates with active piezoelectric layers

THE ANALYSIS OF FEM RESULTS CONVERGENCE IN MODELLING PIEZOELECTRIC ACTIVE SHELL STRUCTURES

The field of active/adaptive structures has been the subject of intense interest over the past couple of decades. The progress in this research field strongly depends on the availability of adequate and reliable modelling tools. Regarding structural analysis in general, the finite element method (FEM) has imposed itself as the method of choice for modelling and simulation. Piezoelectric active structures are characterized by strong enough coupling between the mechanical field and the electric field, which is further used for the realization of active structural behaviour. The descriptions of the mechanical and electrical field as well as their coupling significantly affect the convergence of the FEM results with mesh refinement, which may proceed in a trend different to what is commonly expected when FEM is applied to purely mechanical problems. The paper considers this aspect by using two quadratic shell type finite elements developed for modelling piezoelectric composite laminates. Both full and uniformly reduced integration techniques are taken into consideration in a set of examples involving composite laminates with active piezoelectric layers

Razvoj kalupa za injekcijsko prešanje polimernog ispitka za ispitivanje skupljanja

Ispravna konstrukcija kalupa je od velike važnosti za injekcijsko prešanje polimera, jer u velikoj mjeri određuje kvalitetu, strukturu i dimenzije gotovog proizvoda. Ona se sastoji u rješavanju niza problema pri čemu je najvažnije poznavanje materijala kojeg se prerađuje. Pri konstruiranju kalupa za injekcijsko prešanje vrlo je bitan podatak o skupljanju polimernog materijala koji je vrlo često, posebice pri uporabi novih materijala, nedostupan. U cilju određivanja skupljanja otpreska u kalupu definirana je norma HRN EN ISO 294-4 koja propisuje oblik i izmjere ispitaka s pomoću kojih se određuje skupljanje, smjernice za konstruiranje i izradu kalupa za ispitke te parametre prerade (injekcijskog prešanja) pri izradi ispitaka. Na temelju navedene norme te spoznaje o metodičkom konstruiranju kalupa, potrebno je konstruirati kalup za izradu ispitaka za određivanje skupljanja polimernih otpresaka