Metaanyagok Homogenizálása Transzmissziós és Reflexiós Adatokból

A metaanyagok olyan hullámhossz alatti méretekkel rendelkező periodikus szerkezetek, amelyeknek különleges elektromágneses tulajdonságaik vannak, úgymint negatív vagy nulla törésmutató. Mivel a metaanyagok jellemző méretei nem sokkal kisebbek a vezetett hullámhossznál, ezért nincs általánosan alkalmazható módszer az effektív anyagparaméterek számítására, a homogenizálás körülményes és nagykörültekintést igényel. Ebben a cikkben két transzmissziós és reflexiós adatokat felhasználó homogenizálási eljárást vizsgálunk és hasonlítunk össze. A módszereket FishNet típusú metaanyagok effektív anyagparamétereinek kiszámításával szemléltetjük

Calculation of Imaging Properties of Metamaterials

Metamaterials have extraordinary optical properties, which can be utilized in novel imaging systems. Their imaging properties, however, cannot be determined by simple geometrical optics. Here we propose a method that combines full wave simulation, transfer matrix method and geometrical optics to efficiently simulate imaging systems containing metamaterials. The dispersion relation of a periodic metamaterial slab is retrieved from the S-parameters obtained from full wave simulation of the unit cell. The dispersion relation can be connected with numerical field solvers, e.g. the transfer matrix method, to calculate the field produced by a point source placed behind a metamaterial slab. Finally, light rays are derived from the full wave solution to obtain the virtual image of the point source. From the virtual distance an effective geometrical refractive index is determined, which characterizes the imaging properties of the metamaterial. Using the developed procedure, imaging possibilities with fishnet metamaterials are investigated

ANALIZA IZOTROPII METAMATERIAŁÓW

Metamaterials – artificial periodic structures with subwavelength feature sizes – can be characterized with macroscopic electromagnetic properties, like refractive index and wave impedance, just like homogeneous materials. However, in contrast to homogeneous materials, their properties depend strongly on the angle of incidence. 3D metamaterial structures can exhibit homogeneous behaviour, but their fabrication is challenging compared to layered (2D) metamaterials. Here we demonstrate with an example, that layered (2D) metamaterials can also exhibit homogeneous behaviour despite of their anisotropic geometry.Metamateriały – sztuczne struktury periodyczne o wymiarze charakterystycznym porównywalnym z długością fali – można scharakteryzować za pomocą tych samych właściwości jak dla materiałów homogenicznych np. współczynnikiem załamania czy impedancją falową. Jednakże, w przeciwieństwie do materiałów homogenicznych, ic parametry silnie zależą od kąta padania fali. Trójwymiarowe struktury metamateriałów mogą wykazywać jednorodne zachowanie, ale ich wykonanie jest trudne w porównaniu do metamateriałów warstwowych (2D). W artykule pokazujemy na przykładzie, że metamateriały warstwowe (2D) mogą również wykazywać jednorodne zachowanie pomimo ich anizotropowej geometrii

3D Imaging With Metamaterials

Here we present a new kind of 3D display using near zero index (NZI) metamaterial in front of a 2D display. The virtual distance of a pixel is controlled by the refractive index of the metamaterial. As near zero index metamaterials are highly dispersive, a minor shift in the frequency can cause a big change in the virtual distance, hence enabling the control of depth with fine frequency tuning. We derive closed form expression for the virtual distance of a point source in case of lossless isotropic materials and provide a procedure to calculate virtual distance for arbitrary material with given material parameters. A double negative metamaterial working in the microwave regime is demonstrated as proof of the concept

New methods of in vivo monitoring and management of colonic anastomoses leak in experimental study

Primárním cílem projektu bylo zhodnotit efektivitu minimálně invazivních technik (transanální minimálně invazivní chirurgický přístup - TAMIS a endoskopický uzávěr) ošetření dehiscence střevní anastomózy na experimentálním modelu. Sekundárním cílem bylo zhodnotit 2 nové metody (mikrodialýza, konfokální laserová endomikroskopie - CLE) pooperační monitorace kolorektální anastomózy. V první fázi projektu byl vytvořen model dehiscentní kolorektální anastomózy na velkém laboratorním zvířeti. Následně byly v randomizované studii srovnány výše uvedené techniky ošetření dehiscence s přímou chirurgickou suturou a standardním ošetřením v podobě laparotomie s rozpojením anastomózy a vyvedením stomie. Celkem se tedy jednalo o 4 intervenční skupiny a skupinu kontrolní, ve které byla dehiscence ponechána bez léčby. V rámci sekundárního cíle byl vytvořen model kolorektální anastomózy s možností vyvolání ischemie. Na tomto modelu byla následně zhodnocena účinnost monitorace změn v anastomóze pomocí mikrodializačních čidel umístěných intramurálně a na seróze střeva a pomocí endomikroskopie prováděné v pravidelných intervalech. V experimentální randomizované studii bylo prokázáno, že transanální ošetření dehiscence pomocí TAMIS a endoskopického uzávěru jsou technicky proveditelné a zaručují vysokou šanci na zhojení....The primary aim of the project was to assess two different minimally invasive techniques (Transanal minimally invasive surgical approach - TAMIS and endoscopic closure) in the treatment of colorectal anastomosis dehiscence on an experimental model. The secondary aim was to evaluate microdialysis (MD), and confocal laser endomicroscopy (CLE) as novel methods potentially suitable for postoperative monitoring of colo-rectal anastomosis. In the first step, large animal model of dehiscent colo-rectal anastomosis was developed. Two novel techniques of dehiscence closure were then compared with conventional surgical repair and laparotomy with anastomotic diversion. Thus 4 intervention groups and one untreated control group were included. Transanal repair using TAMIS and endoscopic closure were technically feasible with high healing rate. Both techniques reduced the incidence of intra- abdominal septic complications compared to control. With regards to secondary aim, colorectal anastomosis was monitored using MD and CLE before and after the induction of ischaemia. Moreover, intramural and serosal positioning of MD sensors were compared. Both methods revealed hypoperfusion of anastomosis promptly and were proven as suitable for early detection of impaired healing. Based on the results of this project, a...Chirurgická klinika ÚVNDepartment of Surgery (Central Military Hospital)2. lékařská fakultaSecond Faculty of Medicin

MRI in diagnostics of failing cerebral perfusion

Background and Purpose: The employment of Magnetic resonance (MR) in investigations of cerebral tissue in health and disease achieved during the last 3 decades great appreciation. Its spectacular results in MR imaging and spectroscopy are especially useful in the domain of brain ischaemia. Materials and Methods: We have combined practical experience with search in literature to create a review of possible examinations in the field of stroke and chronic cerebrovascular insufficiency. Results and Conclusions: Our survay contains chapters on the causes of cerebral ischaemia, described in methods ofMR angiography and Perfusion weighted imaging and chapters on the consequences of ischaemia: Imaging of the ischaemic cascade by classical spin echo sequences, imaging of diffusion, of contrast enhancement and distinction of the surviving parts in the hypoperfused regions. Magnetic resonance spectroscopy is reported in its proton and phosphorus examinations. Longlasting diminushion of cerebral blood flow with aging is reviewed in the last chapter

Logistics in the process of evacuation of the population in the finding of a booby-trapped explosive system

Every day, emergencies endanger people who are at risk of injury and, in worse cases, death. It is even worse when another person is responsible for the loss of human life. In recent years, we have encountered attacks on places where a large number of people gather, such as concerts, shopping malls, or even Christmas markets. This work focuses on logistics in the process of evacuating the population when finding a booby-trapped explosive system that aims to injure as many people as possible. For better orientation, a model situation is created in the Zlin Malenovice Shopping Center, during which the routes of the IRS to the place of intervention and their dislocation are also outlined. The work aims to point out the model situation of the attack in the Shopping Center Zlín Malenovice and the logistics of the IRS. © 2021 Elsevier B.V.. All rights reserved.IGA/FAI/2021/00

Liječenje i troškovi moždanog udara u kasnim devedesetim: Sveučilišna bolnica u Pragu

Analysis of 224 stroke admissions during the year 1997 was performed to contribute to the international comparisons in the management of acute stroke. The analysis revealed 83% of patients with cerebral hemorrhage and 37% of those with cerebral infarction to have spent at least several days in the intensive care unit (ICU). The mean length of the hospital stay of 12.7 days differed between men and women, while the mean length of ICU stay differed between cerebral hemorrhage and cerebral ischemia. The intervals between stroke onset and admission and between stroke onset and computed tomography (CT) as well as the percentual employment of various diagnostic methods were evaluated in a subset of 156 cases. Hospital admission with a median of 4 hours and management in case of hemorrhage compared relatively well with international standards, whereas in case of cerebral infarction the use of CT was found to be insufficient, also showing a delay from hospital admission. The overall mortality rate of 10.7% revealed a relatively young mean age of our cohort (61.2 years). The expenses of stroke hospitalization of 1,390 USD were strikingly low as compared with other industrialized countries, which was mainly due to the current exchange rate.Analiza 224 prijma zbog moždanog udara tijekom 1997. godine provedena je kao doprinos međunarodnim usporedbama liječenja akutnog moždanog udara. Analiza je pokazala da je 83% bolesnika s krvarenjem i 37% onih s moždanim infarktom provelo barem nekoliko dana u jedinici intenzivnog liječenja ( JIL). Prosječna duljina boravka u bolnici od 12,7 dana razlikovala se između muškaraca i žena, a prosječna duljina boravka u JIL razlikovala se između bolesnika s krvarenjem i onih s ishemijom. Vremenski razmak od nastupa moždanog udara do prijma u bolnicu te između nastupa moždanog udara i pregleda pomoću kompjutorske tomografije (CT), kao i postotak primjene različitih dijagnostičkih metoda procijenjeni su u podskupini od 156 slučajeva. Prijam u bolnicu s medijanom od 4 sata i liječenje u slučaju krvarenja pokazali su se relativno povoljnima u usporedbi s međunarodnim standardima, dok se u slučaju infarkta naša primjena CT-a pokazala nedostatnom i zakašnjelom u odnosu na prijam u bolnicu. Sveukupna stopa smrtnosti od 10,7% odražava razmjerno mlađu prosječnu životnu dob naših bolesnika (61,2 godine). Izdaci za bolničko liječenje bolesnika s moždanim udarom od 1390 USD vrlo su niski u odnosu na industrijski razvijene zemlje, i to uglavnom zbog sadašnjeg valutnog tečaja