Do-it-yourself microfluidics and possibilities for micro PIV

U odnosu na najčešće korišćene metode za proizvodnju mikrokanala, postupak koji je izložen u ovom radu ima sledeće prednosti: jednostavnost, niža cena potrebne opreme i velika ušteda u vremenu. Korišćenjem laserskog štampača moguće je ostaviti trag mastila na listu od termoplastičnog materijala, u obliku željenog mikrokanala. Zatim se list ubacuje u zagrejano ulje gde dolazi do izotropnog smanjivanja njegove dužine i širine, i istovremeno do povećavanja debljine. Na taj način se dobija kalup. Pripremljena PDMS masa se izliva na kalup i zatim peče. Nakon pečenja, kalup se odvaja od PDMS mase u kojoj se sada nalazi udubljenje koje predstavlja mikrokanal. Kada se uređaj pričvrsti za podlogu, i kada se naprave ulazni i izlazni otvori, spreman je za korišćenje. Na ovaj način moguće je napraviti veoma složene mikrokanale promenljivih dimenzijama, korišćenjem opreme koja nije skupa i u veoma kratkom vremenskom roku. U okviru rada su prikazane i vizualizacije strujanja u kanalima koji su napravljeni u okviru radionice 'Do-it-yourself Microfluidics Workshop' koja je održana na Mašinskom fakultetu Univerziteta u Beogradu. Dat je i kratak osvrt na mogućnosti primene mikro PIV merne tehnike.We present a method for microfluidic channel fabrication that has the following advantages compared to conventionally-used methods: technical simplicity, dramatically lower fabrication costs, and fabrication time. The method entails printing channel designs on a thermoplastic film from a LaserJet printer. Exposure to high temperatures elicits isotropic shrinkage of the film (in the x-y plane), in addition to thickening (in the z-direction), resulting in a positive relief mold. The microfluidic channel design of the mold is then transferred to a polydimethyl siloxane (PDMS) chip through soft lithography, resulting in a ready-to-use microfluidic chip. Through this approach, chips with complex channel geometries can be generated with low cost equipment and in as little as a couple hours. Flow visualizations from several chips from the 'Do-it-yourself Microfluidics Workshop', held at the Faculty of Mechanical Engineering Univeristy of Belgrade, are presented in this paper. We also discuss possibilities for adapting micro particle image velocimetry (PIV) measurements to channel designs on PDMS-based microfluidic chips using the fabrication method delineated here

EVALUATION OF FORESTS IN THE AREA OF MOUNTAIN KOSMAJ IN RELATION TO THEIR ENVIRONMENTAL, SOCIAL AND ECONOMIC FUNCTIONS

The paper presents a special evaluation of environmental, social and economic functions of forests by applying Vyskot's methodologies of objectification, systematization and evaluation of forest functions. To the method utilization, area of Mountain Kosmaj is chosen, where the processes of urbanization have caused the greatest change in use of natural resources, especially forests. For this reason, the need for multi-functional use of forests is justified. Applying the methodology of objectivity, systematization and evaluation of forest functions (Vyskot et al, 2003), a financial evaluation of forest functions is carried out. As a special part of the research, determination of the level of contamination by heavy metals (Pb, Ni, Mn, Zn and Fe, ), and their accumulation in plants on the mountain Kosmaj was carried out. Evaluation of forest functions of the study area have been based on data on forest area that have taken from the General management plan for “Posavsko – podunavsko forest area (2001-2010)“ The financial value of each function is expressed in € per m3, which is currently the only reliable method of assessing functions. Use of this method, and data received form this research in area of Mountain Kosmaj creates the basis for the implementation of the concept of functionally integrated forest management. We will receive a more reliable data for managing state forests, as well as data to perform inspection of the state forests. There will be more reliable data to be used for forest management planning, silviculture, forest objective categorization

Growth rings width of bald cypress stems from two alluvial sites in Serbia

The paper shows the differences in growth rings width between bald cypress stems grown on two alluvial sites in Serbia - Veliko ratno ostrvo and Backa Palanka. Performing this anatomical research included falling of overall six trunks (3 from one and 3 from another location). After that, appropriate wood cross-sections were made and they served for making permanent anatomical preparations. Obtained results proved a big dependence between radial increment from one side and available water content together with nutrients content on the other side. It caused a very significant correlation between growth rings width and qualitative site features. Bearing on mind this fact, it was established that Veliko ratno ostrvo is more suitable for bald cypress growing. As for behavior of radial increment with ages, there are some differences between these locations, first of all because stems from Veliko ratno ostrvo still did not reach its culmination

Differential diagnosis problem of pulmonary changes in ulcerative colitis

Introduction. Inflammatory intestinal diseases are often accompanied with extraintestinal and even pulmonary manifestations. The treatment of these intestinal diseases includes sulphasalazine and mesalazine, which may have undesirable allergic and other side effects, including hypersensitive pneumonitis. Case report. Having performed colonoscopy due to abdominal pains and mushy stools, the diagnosis of ulcerous colitis was established in a 20-year old female patient and the treatment with mesalazine initiated. However, the patient developed slimy and bloody stools, slightly increased body temperature, dry cough and bilateral lung lesions. The bronchological exploration established interstitial and organizing pneumonia. Despite the treatment with antibiotics, corticosteroids and mesalazine, dry cough, fever and bloody stools persisted, accompanied with bilateral inhomogeneous lesions of the pulmonary parenchyma. Upon discontinuation of the treatment with mesalazine, clinical symptoms and pulmonary lesions disappeared. Conclusion. The differential diagnosis of pulmonary lesions in patients with ulcerous colitis may be a problem. In the reported case, pulmonary lesions were interpreted as interstitial pneumonitis accompanying ulcerous colitis. However, they are most probably a consequence of allergic response to mesalazine

MRTVO DRVO U GOSPODARENIM BUKOVIM ŠUMAMA NA PODRUČJU SRBIJE

Dead wood in forests of Serbia hasn`t been studied so far, although it is an important component of forest ecosystems. This paper presents results of investigating volume, biomass, and carbon stock bound in the dead wood of beech high forests. The sample includes eleven pure beech stands selected in six forest regions. They are all uneven-aged stands that have been managed for the last several decades, mostly under selection or group-selection. Their site class is I/II–III/IV. The altitude ranges from 400 to 1380 m. One stand belongs to submontane (Fagetum moesiacae submontanum B. Jov. 1967) and ten to montane (Fagetum moesiacae montanum B. Jov. 1953) beech forests. A systematic sample was used to determine the presence, quantity, diameter structure of volume, and state of dead wood considering its degree of decomposition both in standing and lying position. Sample plots of 500 m2, at a distance of 100 x 100 m were used as elements of the sample. Altogether 242 sample plots were established. The volume of aboveground dead wood was determined by applying familiar dendrometric methods, while the dry biomass was calculated on the basis of its volume and wood density at different degrees of decomposition. The biomass of belowground dead wood i.e. roots of stumps and snags was obtained directly using the relevant regression equations. The quantity of the carbon bound in dead wood was calculated by multiplying dry biomass of dead wood by 0.5 coefficient. A simple and a stratified sample were used for the purposes of estimating the average and total volume, biomass, and carbon stock of dead wood. It was concluded that the average aboveground deadwood volume in all studied stands amounted to 19.24 m3 ha–1. The aboveground biomass of dead wood was 6.06 t ha–1 and belowground 17.34 t ha–1, or 23.40 t ha–1 in total. The carbon-bound stock in the total estimated dry biomass of dead wood was 11.70 t C ha–1.U cilju rješavanja problema energetske krize i klimatskih promjena u svijetu se pridaje veliko značenje proučavanju biomase, odnosno zalihe i kruženja ugljika u šumskim ekosustavima. Proučavan je najčešće utjecaj klimatskih promjena i načina gospodarenja na razvoj i stabilnost šumskih ekosustava, kao i njihov doprinos ublažavanju negativnih utjecaja klimatskih promjena na životni okoliš (Cannell 1995., Lebaube et al. 2000., Joosten et al. 2004., Mund 2004., Mund and Schulze 2006., Liski et al. 2006). Mrtvo drvo je najviše proučavano u prašumama, odnosno rezervatima bukovih šuma (Christensen et al. 2005). Uz to, proučavano je u približno prirodnim bukovim šumama (Beneke and Manning 2003., Mountford 2002) i u gospodarenim bukovim šumama (Green and Peterken 1997., Fridman and Walheim 2000., Ferguson and Archibald 2002., Mund 2004., Mund and Schulze 2006). Rađena je i komparacija karakteristika mrtvog drveta u prirodnim – negospodarenim i gospodarenim šumama (Andersson and Hytteborn 1991., Kirby et al. 1998). U Europi, volumen dubećeg i ležećeg mrtvog drveta u uređivanim – proizvodnim šumama označena je kao važan indikator za održivo gospodarenje i očuvanje biodiverziteta (MCPFE 2003). Prema tomu, mrtvo drvo je važna komponenta šumskih ekosustava. Međutim, u šumama Srbije do sada nije detaljnije proučavano. Zbog toga, cilj ovog rada bio je dobivanje pouzdanih informacija o najznačajnijim karakteristikama mrtvog drveta (volumenu, biomasi i ugljiku) u visokim gospodarenim bukovim šumama koje su u državnom vlasništvu.Istraživane sastojine bukve po strukturnoj su izgrađenosti specifične, a početkom dvadesetog stoljeća bile su pretežito prašume, pa su neurednim prebornim sječama prevedene u privredne šume. Radi se o izrazito raznodobnim sastojinama bukve, specifične starosne strukture. Uzorkom je obuhvaćeno jedanaest čistih sastojina bukve izabranih u šest šumskih područja (Slika 1). Jedna sastojina pripada brdskoj (Fagetum moesiacae submontanum B. Jov. 1967) a deset sastojina planinskoj šumi bukve (Fagetum moesiacae montanum B. Jov. 1953). Klima je umjereno kontinentalna. Površina sastojina je 9,8–32,3 ha (ukupno 241,9 ha). Bonitet staništa je I/II–III/IV, nadmorska visina 400–1380 m, prosječan nagib terena 11–27°, najčešća ekspozicija sjeverozapadna, stupanj sklopa 69–94 %, srednji promjer po temeljnici 30–42 cm, srednja visina po Loraju 22–34 m, broj stabala 214–308 po ha, temeljnica 22–33 m2 ha–1, volumen 290–522 m3 ha–1 i volumni prirast 5,0–10,5 m3 ha–1. Kvalitativna i sortimentna struktura istraživanih sastojina bukve bila je loša (Koprivica et al. 2010b).Za utvrđivanje prisutnosti, količine, debljinske strukture volumena i stanja mrtvog drveta glede stupnja raspadanja u dubećem i ležećem položaju primijenjen je sistematski uzorak. Kao elementi uzorka u sastojinama korištene su probne plohe veličine 500 m2, raspoređene na rastojanju 100 x 100 m. Postavljene su ukupno 242 probne plohe. Volumen mrtvog drveta na probnim plohama iznad zemlje određen je po klasičnim dendrometrijskim metodama, a suha biomasa na bazi njegovog volumena i gustoće drveta pri različitom stupnju raspadanja (Marjanović et al. 2010). Biomasa mrtvog drveta ispod zemlje (korijena panjeva i suhih stabala) određena je izravno po regresijskoj jednadžbi (Wutzler et al. 2008). Sadržaj vezanog ugljika u mrtvom drvetu dobijen je množenjem suhe biomase mrtvog drveta s koeficijentom 0,5 (IPCC 2003). Za procjenu prosječnog i ukupnog volumena, biomase i zalihe ugljika primijenjen je jednostavni i stratifikacijski uzorak.Prosječan volumen živog i mrtvog drveta iznad zemlje po hektaru u sastojinama i za sve istraživane sastojine zajedno prikazan je u tablici 2. Za sastojine dobiveni su podaci nedovoljne točnosti. Međutim, podaci dobiveni za sve istraživane sastojine zajedno su dovoljno točni – pouzdani. Prosječan volumen mrtvog drveta iznad zemlje svih istraživanih sastojina bukve zajedno (p = 0,95, n-1 = 241) je 19,24 +/– 2,63 m3 ha–1 ili 5,01 % od prosječnog volumena živog drveta (383,9 +/– 20,58 m3 ha–1). Metodom analize varijance utvrđeno je da je razlika između sastojina, s obzirom na prosječan volumen mrtvog drveta po hektaru, statistički značajna. Volumen mrtvog drveta s obzirom na način javljanja i stupanj raspadanja prikazan je u tablici 5, a s obzirom na debljinsku strukturu volumena u tablici 6. Na osnovi jednostavnog uzorka od 242 probne plohe utvrđeno je da je raspored mrtvog drveta iznad zemlje po hektaru jako pozitivno asimetričan i jako izdužen u odnosu na normalni raspored. Koeficijent varijacije je 108 %. Relativna greška uzorka (p = 0,95) je +/– 13,61 %. Primjenom stratifikacijskog uzorka dobivena je relativna greška uzorka +/– 13,01 %. Na osnovi stratifikacijskog uzorka, interval povjerenja (p = 0,95, n-4 =238) za prosječan volumen mrtvog drveta je 16,74–21,74 m3/ha. Prosječna suha biomasa mrtvog drveta i zaliha ugljika po hektaru u istraživanim sastojinama bukve prikazana je u tablici 7. Biomsa istraživanih sastojina zajedno iznad zemlje je 6,06 t ha–1, a ispod zemlje 17,34 t ha–1, odnosno ukupno 23,40 t ha–1. Zaliha vezanog ugljika u ukupno procijenjenoj suhoj biomasi mrtvog drveta iznad zemlje je 3,03 t C ha–1 a ispod zemlje 8,67 t C ha–1, odnosno ukupno 11,70 t C ha–1.Gospodarene visoke sastojine bukve u Srbiji imaju veći volumen, biomasu i zalihu vezanog ugljika u mrtvom drvetu po hektaru u odnosu na intenzivno gospodarene sastojine bukve u Europi. Sadašnje stanje je posljedica dugogodišnjeg provođenja neurednog gospodarenja i česte promjene načina gospodarenja bukovim šumama (preborni, grupimični, naplodni i sl.). Na bazi provedenog istraživanja procijenjeno je (p= 0,95, n-1 = 241) da se u visokim gospodarenim bukovim šumama na području Srbije (350.000 ha) nalazi 6,73+/– 0,92 milijuna m3 mrtvog drveta iznad zemlje, čija je suha biomasa 2,12 +/– 0,29 milijuna tona a uskladišteni ugljik u ovoj biomasi 1,06 +/– 0,14 milijun tona. Biomasa mrtvog drveta ispod zemlje je 6,07 +/– 0,73 milijuna tona, a uskladišteni ugljika u ovoj biomasi 3,03 +/– 0,36 milijuna tona. Prema tomu, ukupna procijenjena biomasa mrtvog drveta iznad i ispod zemlje je 8,19 +/– 0,82 milijuna tona, a uskladišteni ugljik 4,10 +/– 0,41 milijuna tona

Remote Labs and Problem Oriented Engineering Education

This paper describes a study case of student production of laboratory model for engineering education and its integration in the local remote laboratory. Students guided by teaching staff are passing through all phases of development and testing of engineering product. In our case, student should produce and test a fan. This part of case study concerning with courses in Hydraulic and Pneumatic Machinery, which incorporates, besides fundamental courses, subjects related to the theory, construction, design and testing of the hydraulic machines (pumps, fans, turbines) and turbo-compressors. After this, students should produce fan and plate system, which is well-known a laboratory model for Control Engineering education. In this paper, are also described procedures and benefits of integration of a laboratory model in Go-Lab Portal as a remote controlled experimental setup with materials for teaching and learning

Zinc concentration in woody and herbaceous plants at Kosmaj area, Serbia

In the paper, the content of heavy metal (Zn) in plants of Kosmaj area was analyzed. Concentration of Zn was measured at four locations, in vegetative parts - leaves of ten plants (eight of them were woody plants and the other two were herbaceous plants). Results showed that samples of plant material from all locations are not contaminated with heavy metal and, at the same time, the results show lack of Zn at some locations, as well. It is important to emphasize that Zn does not endanger the area of Kosmaj

concentration of pollutants in the air, soil and plants in the area of the national park "Fruska Gora" - Serbia

Fruska gora is a mountain situated in the northern part of the Republic of Serbia in the province of Vojvodina. The purpose of this study was to determine the degree to which soil and plants are burdened with certain heavy metals (Pb, Ni, Zn, Fe, Mn, and others usually present in polluted atmosphere), then the accumulation of heavy metals in the National Park "Fruska gora" was detected and the interdependence of pollution among all three media of the environment determined. This paper analyzes the heavy metal contents within a 2-years period in air, soil and plants at the beginning of the vegetation period. The presence of Pb, Ni, Zn, Fe and Mn in the samples was analyzed using flame atomic absorption spectrophotometry. Measurements of heavy metal contents were performed at 7 locations in soil and vegetative parts of 17 plant types (woody plants, herbs and lianas), and analysis of the air was performed at 2 locations (through placement of sedimentators) within a 3-months period during winter. One of the major findings is that the dominant emission of pollutants at the analyzed locations is anthropogenic and originates from traffic

Hybrid procedure for a descending thoracic and subclavian artery aneurysm in a patient with previous abdominal aortic surgery: Case report

Introduction. Hybrid procedures represent staged or simultaneous endovascular and open surgical techniques in the treatment of complex pathologies of the thoracic and abdominal aorta. We are presenting a patient with previous abdominal aortic surgery in whom hybrid vascular procedure for descending aorta and left subclavian artery aneurysm was performed. Case Outline. A 63-year-old female patient was admitted for computed tomography angiography. Descending aorta aneurysm (7.6 cm) as well as aneurysm of the left subclavian artery (LSA) was noted. Eight years ago she underwent abdominal aortic aneurysm resection and aortoiliac bypass. Standard TEVAR (thoracic endovascular aortic repair) procedure couldn’t be done due to small dimensions of previous “Y” graft (12.6 mm), so first we did LSA transposition and after three days hybrid procedure. After “Y” graft exposure, anastomosis between the corps of “Y” graft and tubular graft 10 mm was created and through this conduit thoracic stent-graft was placed followed by complete “Y” graft replacement. After 6 months angiography showed regular postoperative findings. Conclusion. Combined surgical and endovascular procedures in thoracic aorta pathology treatment could be useful solutions with favorable outcome. [Projekat Ministarstva nauke Republike Srbije, br. 41002