Search

Akutno krvarenje iz gornjih partija gastrointestinalnog trakta, koje se najčešće javlja kao komplikacija peptičke ulkusne bolesti, je urgentno stanje povezano sa visokim morbiditetom i mortalitetom. Bez obzira na značajna poboljšanja u terapiji i načinu zbrinjavanja obolelih, eradikaciji Helikobakter pilori infekcije, mortalitet nije značajno opao u poslednjih 50 godina. Stariji pacijenti kao i osobe sa uznapredovalim hroničnim bolestima podnose krvarenje značajno teže, te su i izloženi većem riziku od smrtnog ishoda. Za pravilnu trijažu pacijenata sa akutnim gornjim gastrointestinalnim krvarenjem upotrebljavaju se bodovni sistemi poput Glasgow-Blatchford skora i Rockall preendoskopskog skora za procenu rizika od lošeg kliničkog toka bolesti. Transfuzija eritrocitnih krvnih produkta predstavlja vid alogene transplantacije tkiva koja je povezana sa određenim rizikom. Kod hemodinamski stabilnih pacijenata sa krvarenjem iz gornjih partija gastrointestinalnog trakta optimalnu graničnu vrednost hematokrita, kod koje je indikovana transfuzija eritrocita, potrebno je pažljivije definisati. Smatra se da restriktivna transfuzijska strategija značajno smanjuje mortalitet i morbiditet kod pacijenta sa krvarenjem iz gornjih partija gastrointestinalnog trakta. Metodologija: Ispitivanjem je obuhvaćeno 339 bolesnika, oba pola, starosti 18 godina i starijih. Retrospektivno, od 01.01.2015. do 31.12.2016. su analizirani bolesnici hospitalizovani zbog akutnog nevariksnog krvarenja iz gornjih partija gastrointestinalnog trakta u Odeljenju urgentne interne medicine Kliničkog Centra Vojvodine. Prospektivno su ispitani bolesnici koji su iz istog razloga hospitalizovani od 01.01.2017 do 31.06. 2017. Podaci koji su bili od značaja za inicijanu epizodu krvarenja, uključujući i narednih 30 dana lečenja, su prikupljeni iz istorija bolesti i kartona pacijenata. Potom su bolesnici podeljeni u grupu urgentne endoskopije, kod koje je načinjena ezofagogastroduodenoskopija unutar 12 časova od prijema i grupu rane endoskopije koja je načinjena nakon više od 12 časova od prijema. Potom je grupa urgentne endoskopije podeljena u grupu restriktivne strategije primene transfuzije (bez trasnfuzije ili transfuzija kada je vrednost hemoglobina u krvi, iznosila 70 g/L ili niže) i liberalne (transfuzija kada je vrednost hemoglobina u krvi, iznosila više od 70 g/L). Upoređivali smo endoskopske, kliničke parametre i ishod lečenja između ovih grupa bolesnika. Rezultati: Na našem uzorku dokazali smo da je liberalna strategija primene transfuzije eritrocita (primenjena transfuzija kada je vrednost hemoglobina u krvi veća od 70 g/L) u poređenju sa restriktivnom strategijom (primenjena transfuzija kada je vrednost hemoglobina u krvi manja od 70 g/L) povezana sa češćim otkrivanjem aktivnog krvarenja tokom endoskopije (p=0,010). Verovatnoća otkrivanja Forrest I a i I b lezija je veća u grupi liberalne nego u grupirestriktivne strategije primene transfuzije (3,935 puta). Nije bilo značajnih razlika u učestalosti recidiva krvarenja, mortalitetu ili potrebi za hiruškom intervencijom sa ciljem zbrinjavanja krvarenja između onih sa urgentnom i endoskopijom koja je načinjena nakon 12 časova od prijema. Stariji bolesnici, sa većim brojem komorbiditeta i nižom koncentracijom hemoglobina u krvi na prijemu, su u proseku najduže čekali na endoskopski pregled. Vrednost količnika uree (izražene u mmol/L) i koncentracije hemoglobina u krvi (izražene u g/dl) je bolja u predviđanju potrebe za primenom transfuzije krvi kod bolesnika sa akutnim gornjim nevaricealnim krvarenjem u poređenju sa Glasgow-Blatchford skorom. Zaključili smo da restriktivna strategija primene transfuzije eritrocita povoljno utiče na klinički tok akutnog gornjeg GI krvarenja. Granična vrednost koncentracije hemoglobina u krvi, kod koje je indikovana transfuzija eritrocita, kod bolesnika sa akutnim gornjim GI krvarenjem, trebalo bi da bude značajno niža od one sada ustaljene u našoj kliničkoj praksi., Acute bleeding from the upper parts of the gastrointestinal tract, which most often occurs as a complication of peptic ulcer disease, is an urgent condition associated with high morbidity and mortality. Despite significant improvements in therapy and the patient care, as well as the eradication of Helicobacter pylori infection, mortality has not decreased significantly in the last 50 years. Elderly patients, as well as patients with late stages of chronic diseases, have a significantly reduced tolerability towards bleeding and are thus at higher risk of death. In order to properly triage patients with acute upper gastrointestinal bleeding, scoring systems such as the Glasgow-Blatchford score and the Rockall preendoscopic score are used to assess the risk of poor clinical course of the disease. Transfusion of erythrocyte blood products represents a type of allogenic tissue transplantation, which is associated with a certain risk. In hemodynamically stable patients with acute upper gastrointestinal bleeding, the optimal limit value of hematocrit, in which erythrocyte transfusion is indicated, needs to be defined more carefully. A restrictive transfusion strategy is considered to have significantly reduced mortality and morbidity in s patients with upper gastrointestinal bleeding. Methodology: The study included 339 patients, male and female, aged 18 years and older. Retrospective analysis was performed, and included patients who were admitted in the period of 01.01.2015. to 31.12.2016. to the Department of Emergency Internal Medicine, Clinical Center of Vojvodina, due to acute non-varicose bleeding from the upper lobes of the gastrointestinal tract. Patients who were hospitalized for the same reason from 01.01.2017 to 31.06.2017 were prospectively examined. Data that were relevant to the initial bleeding episode, including the following 30 days of treatment, were collected from medical histories and patient records. The patients were afterwards split into two groups: first on being emergency endoscopy group, in which an esophagogastroduodenoscopy was performed within 12 hours of admission, and the second one being the early endoscopy group, which was performed more than 12 hours after admission. The emergency endoscopy group was then further divided into a group of restrictive transfusion strategies (no transfusion or transfusion when the hemoglobin value in the blood was 70 g / L or lower) and liberal (transfusion when the hemoglobin value in the blood was more than 70 g / L). ). We compared endoscopic, clinical parameters and treatment outcome between these groups of patients. Results: Our study demonstrated that the liberal strategy of erythrocyte transfusion (applied transfusion when the value of hemoglobin in the blood is greater than 70 g / L) compared to the restrictive strategy (applied transfusion when the value of hemoglobin in the blood is less than 70 g / L) ) is associated with more frequent detection of active bleeding during endoscopy (p = 0.010). The probability of detecting Forrest I a and I b lesions is higher in the group of liberal than in the group of restrictive transfusion application strategies (3,935 times). There were no statistically significant differences in the frequency of bleeding recurrence, mortality, or the need for surgical intervention to manage bleeding between those with emergency endoscopy and endoscopy performed 12 hours after admission. Elderly patients, who have a greater number of comorbidities and a lower concentration of hemoglobin in the blood at admission, waited on average the longest for an endoscopic examination. The value of urea quotient (expressed in mmol / L) and hemoglobin concentration in blood (expressed in g / dl) is better in predicting the need for blood transfusion in patients with acute upper nonvariceal hemorrhage compared to the Glasgow-Blatchford score. We concluded that the restrictive strategy of erythrocyte transfusion has a favorable effect on the clinical course of acute upper GI bleeding. The cut-off value of hemoglobin concentration in the blood, in which erythrocyte transfusion is indicated, in patients with acute upper GI bleeding, should be significantly lower than the one established and used today in our clinical practice.

PSSOH paper on free software for analog and digital design. The lecture was recorded and the video of presentation held by Assist. Prof. Dušan Grujić together with the Q&A session is available at https://youtu.be/fCSQRYTIDSI., Title in Serbian language: "Slobodni softver za projektovanje analognih i digitalnih kola".

Detection of infrared radiation using the biological structures gathered increasing attention over the last decade [1, 2], as the need for faster, more sensitive infrared imaging sensors grows ever stronger. Among the proposed techniques for the interrogation of the radiation-induced effects, digital holographic interferometry stands out as the simplest method for obtaining the spatio-temporal information about the response [3]. Using similar methods as described previously [3], with the radiation wavelengths of 405 nm, 450 nm, 660 nm and 980 nm, we prove that the natural structures found on the wing scales of the Morpho Didius butterfly can be used for the detection of radiation throughout the visible and near-infrared part of the optical spectrum

Vibrating diaphragms have become an important component of acoustics technology, with nearly all commercial microphones and speakers of the past half a century relying on diaphragm vibration. Although few select materials (such as nickel and boPET) are predominantly used because of their favorable properties such as small mass density and large tensile strength, the rise of new materials with superior properties such as graphene demands an assessment of their potential use in acoustic diaphragms. Here we evaluate various forms of graphene as an acoustic diaphragm material. We fabricate diaphragms from graphene paper and multilayer (~60 layers) CVD graphene and measure their response to acoustic stimuli either in capacitance mode, which most closely resembles actual use in electrostatic condenser microphones, or with digital holography, which allows for physical studies of diaphragm vibration modes [1]. We find that multilayer graphene diaphragms outperform traditional nickel membranes in terms of responsivity, up to 12 dB at audio frequencies [2]. For large- diameter (25 mm) diaphragms that can be made from graphene paper, we detect a rich array of acoustic vibration modes that point to the diaphragms’ potential use in pressure sensing or for detection of weak acoustic signals in quiet environments. Our findings are supported with numerical COMSOL calculations that also reveal that a thicker multilayer diaphragm made of 300 layers of CVD graphene would in theory sustain tension forces that allow ultrasonic reach. Hence we conclude that graphene diaphragms hold potential for miniature low- cost ultrasonic transducers that compete with current piezoelectric technology.

Paper – like materials are becoming an important component of industrial technology. Their applications are numerous, starting from protective and adhesive layers, chemical filters to electronic or optoelectronic components. Graphene paper, as one of the youngest paper – like materials has favorable properties for all those applications, but also for novel applications in acoustics. Graphene paper is superior to other acoustic materials because it is lightweight, stiff, and has a large tensile strength. The aim of our project is to investigate the real – world potential of graphene – based acoustic membranes. Here we report acoustic membranes made of graphene paper. We use time – averaged digital holography to study the vibrational modes of the membranes. Graphene paper shows a rich modal behaviour in the audible part of the spectrum with multiple interesting and complex modes at frequencies between 40 Hz and 4 kHz. Numerical calculations confirm our experimental data, indicating a low pre – tension force (12.5 – 75 Nm-1). For comparison, we performed the same holographic measurements on membranes made of Mylar polyester film, paraffin film, aluminium foil and different kinds of filter paper. We have found resonant modes for each tested membrane, with graphene paper showing the richest behaviour. Our calculations indicate that more tightly pulled graphene paper membranes could be useful for applications in acoustics.

Potreba za bežicnim komunikacioniom linkovima velikih brzina prenosa podataka je podstaknuta ekspanzijom prenosivih uređaja i multimedijalnih servisa, uz pogodnost da priroda korišcenja dozvoljava a ponekad i zahteva ogranicen domet. Problem kapaciteta komunikacionih linkova i sve veceg broja korisnika se može rešiti prelaskom u opseg ucestanosti od 30 do 300 GHz, koji se naziva i milimetarski opseg. Visoka radna ucestanost pruža mogucnost korišcenja kanala velikog kapaciteta, kao i fizicki malih antenskih nizova za fokusiranje i prostornu lokalizaciju prijemnog i predajnog snopa. Milimetarski opseg nalazi primene i u ostalim oblastima, kao što su industrijske, medicinske i bezbednosne. U komercijalnim primenama od interesa je opseg ucestanosti oko 60 GHz, koji je dodeljen za nelicenciranu upotrebu širom sveta. Razvoj CMOS i BiCMOS tehnologija je omogucio da se sistemi u 60 GHz-om opsegu mogu integrisati u standardnim procesima. Pored viših radnih ucestanosti, skaliranje tehnologija uvodi i tehnološka ogranicenja koja degradiraju performanse ukoliko se njihov uticaj zanemari. Zanemareni efekti mogu doprineti vecim gubicima, koji povecavaju faktor šuma prijemnika i degradiraju efikasnost predajnika, ali i parazitnim preslušavanjima koja rezultuju neželjenim spektralnim komponentama. Stoga je potrebno razmotriti kvalitativne i kvantitativne pokazatelje uticaja tehnoloških ogranicenja na performanse i prilagoditi postupak projektovanja. Kriticni blokovi za domet primopredajnika su malošumni pojacavac na prijemnoj strani i pojacavac snage na predajnoj strani. U okviru teze predstavljen je postupak projektovanja malošumnog pojacavaca i pojacavaca snage za rad u 60 GHz-om opsegu i širokopojasnog delitelja ucestanosti. Uvedene su nove smernice projektovanja koje uzimaju u obzir tehnološka ogranicenja. Pokazano je da se pravilnim particionisanjem elektromagnetskog modela može postici dobro slaganje rezultata simulacije i merenja. Projektovana kola su fabrikovana u IHP Microelectronics korišcenjem 0.25 mm SiGe:C BiCMOS procesa (fT/fmax = 200 GHz). Parametri fabrikovanih kola su izmereni i verifikovani na stopicama cipa, upotrebom mikrotalasnih sondi... The need for high capacity wireless data links is driven by expansion of mobile devices and multimedia services, with the advantage that a typical use case allows, and sometimes demands, a limited range. Problems of limited communication link capacity and growing number of users can be solved by moving to frequency range of 30 - 300 GHz, also known as millimeter range. High operating frequency allows the use of high capacity channels, and physically small antenna arrays for beam steering and spatial localization. Millimeter region of spectrum is also suitable for industrial, scientific and security applications. Unlicensed 60 GHz band is available worldwide, and is attractive for commercial applications. Development of CMOS and BiCMOS technologies has enabled the integration of complete 60 GHz systems in standard processes. Technology scaling enables the use of higher operating frequencies, but imposes new design constraints which may degrade the performance if their effect is neglected. Neglected effects may contribute to higher losses, which increase the noise figure of receiver and degrade transmitter efficiency, and also to parasitic coupling which results in undesired spectral components. Therefore, qualitative and quantitative measure of technology constraints impact on performance degradation needs to be evaluated, and applied to circuit design process. Critical blocks for transceiver range are low noise amplifier on receiver, and power amplifier on transmitter side. Design procedures for 60 GHz low noise and power amplifiers, and wideband frequency divider are presented in this thesis. Guidelines for technology constraints aware design are used in the presented design flow. Good agreement of experimental and simulation results is achieved by proper electromagnetic model partitioning. Designed circuits have been fabricated in IHP Microelectronics 0.25 mm SiGe:C BiCMOS process (fT/fmax = 200 GHz). Test chip parameters have been measured and verified on-wafer by using microwave probes...

Primene prenosivih beskontaktnih radarskih senzora kratkog dometa, koji daju informacije o prisustvu, položaju i relativnoj brzini, prakticno su neprebrojive. Ovi radarski sistemi ne samo da imaju potencijal da poboljšaju kvalitet usluga u mnogim oblastima, vec se ocekuje da budu pokretac mnogih inovativnih rešenja ubuduce... Applications of portable short-range noncontact radar sensors, which provide information on presence, position, and relative speed, are virtually countless. These radar systems not only have the potential to improve the service quality in numerous existing fields, but are also expected to be the driving force for many novel applications in the near future...

Disertacija se bavi razvojem metodologije projektovanja i unapre enjem topologija pojacavaca snage u klasi A sa istovremenim konjugovanim prilago enjem i prilago enjem po snazi pri velikim signalima na izlaznom pristupu. Jedan od osnovnih zahteva za svaki pojacavac snage jeste efikasnost. U slucaju pojacavaca snage u klasi A, tranzistor treba prilagoditi po snazi pri velikim signalima na izlaznom pristupu da bi se opterecenju predala maksimalna moguca snaga. Osim prilago enja po snazi, pojacavaci male i srednje snage cesto moraju biti i konjugovano-kompleksno prilago eni na izlaznom pristupu. Ovaj zahtev je bitan pošto je uobicajeno da je sledeci stepen projektovan tako da optimalno radi kada je konjugovano-kompleksno prilago en na ulaznom pristupu. Pojacavaci male i srednje snage su obicno implementirani u standardnoj complementary metal-oxide semiconductor (CMOS) tehnologiji, dok naredni stepen može biti filtar za potiskivanje neželjenih harmonika ili pojacavac snage napravljen u nekoj od III-V generacija poluprovodnicke tehnologije sa znatno vecom izlaznom snagom. Standardni pojacavac sa zajednickim sorsom može biti prilago en po snazi pri velikim signalima ili konjugovano prilago en na izlaznom pristupu, ali se oba prilago enja ne mogu, u opštem slucaju, ostvariti istovremeno. Da bi se prevazišlo pomenuto ogranicenje, predložena je topologija pojacavaca sa drejn-gejt povratnom spregom kao i kompletna metodologija projektovanja. U svrhu verifikacije razvijene teorije, projektovan je širokopojasni pojacavac snage u 130 nm RFCMOS tehnologiji. Postignuta je maksimalna izlazna snaga od 7 dBm i efikasnost od 20%, u opsegu ucestanosti od 6 do 9 GHz. Koeficijent refleksije na ulaznom i izlaznom pristupu je manji od -8,5 dB i -9,5 dB, redom. The dissertation deals with the development of design methodology and the enhancement of topology of power amplifiers in class A with simultaneous conjugate and power matching for large signals at the output port. One of the major demands for any power amplifier is power efficiency. In the case of a power amplifier in Class A, the transistor needs to be power matched for large signals at the output port in order to deliver maximum power to the load. This criterion is particularly important in the case of an amplifier with an output power of the order of 30 dBm or more. In addition to power matching, small and medium power amplifiers often have to be conjugately matched at the output port as well. This requirement is important because it is quite common that the next stage is designed so that it works optimally when it is conjugately matched at the input port. Small and medium power amplifiers are usually implemented in standard complementary metal-oxide semiconductor CMOS technology, while the next stage can be a filter for suppressing unwanted harmonics or a power amplifier made in one of the III-V generations of semiconductor technology with significantly higher output power. A standard common-source amplifier can be designed to be either large signal power matched or conjugately matched at the output port, but not both of them at the same time. In order to overcome the mentioned limit, we propose a simple topology based on a drain-gate feedback amplifier, together with a complete design methodology. For the purpose of verifying the developed theory, a broadband power amplifier is designed in 130 nm RFCMOS technology. The amplifier achieves 7 dBm peak output power and maximum power efficiency of about 20% in the frequency range from 6 to 9 GHz. Input and output return loss are better than 8.5 and 9.5 dB, respectively.