Various aspects of dryness in Serbia

In this manuscript we analyze daily rainfall observational records from 22 weather stations located in different regions over Serbia in the period 1949–2007. We examine the characteristics of dryness by using the Dry Days Since Last Rain – DDSLR approach. In order to quantify the DDSLR we use three metrics for each weather station: severity, consistency and uncertainty. Results show that these three metrics vary independently of each other as well as that there is a weak relationship between them. Weather stations in the northern parts of Serbia, with moderate annual amount of rainfall less than 650 mm, present higher dryness conditions whereas the lowest values were obtained for central parts in Serbia. Limited number of studies examined drying tendencies in Serbia and neighboring countries so far. We consider Serbia as an area of particular interest because of its position in a frontier between Mediterranean conditions on the southwest and the continental inland

Mapping probabilities of precipitation occurrence on the territory of the Republic of Serbia by the method of indicator kriging

This paper presents the application of indicator kriging as a geostatistical method for the purpose of creating maps of precipitation occurrence probabilities on the territory of the Republic of Serbia for distinctive months during 2009. The difference between this approach to mapping and standard isohyetal maps, which describe precipitation intensity, lies in the fact that this approach points to the potential of the occurrence of a certain amount of precipitation at a specific location for a given time period. [Projekat Ministarstva nauke Republike Srbije, br. III 47014, br. TR 36009 i br. III 43007

Klima i nestanak civilizacije Maja

Istovremenost suše i nestanka civilizacije Maja je samo jedan primer od mnogih. Na jugozapadu SAD podaci godova drveća ukazuju na uslove suve klime u periodu od 1275 do 1300, koji su bili dovoljni da odigraju ulogu u nestajanju Anasazi naroda. Takođe postoje indikacije da su slične promene klime mogle da budu odgovorne i za druga velika zbivanja u istoriji društva. Nestanak imperije Akada u Mesopotamiji pre 4200 godine, nestanak kulture Mohika na obalama Perua pre 1500 godina kao i kraj kulture Tiuanako na Bolivijsko-peruanskom altiplanu pre 1000 godina, danas se povezuju sa dugotrajnim sušama u ovim oblastima. Pre nego su geološki dokazi o sušama u prošlosti postali dostupni svaki od ovih civilizacijskih nestanaka kao i nestanak Maja, objašnjavan je ljudskim faktorima-ratovima i porastom stanovništva. Uspon i pad civilizacije Maja svojevrstan je primer društvene evolucije. U tom smislu je značajan u otkrivanju povezanosti istorije Maja i prirodnih uslova. Ako je civilizacija Maja mogla da nestane pod uticajem prirodnih faktora, onda je veoma značajno pitanje na koji način moderno društvo može da bude suočeno sa nepredvidivim uslovima klime. Razumevanje načina na koji su stare civilizacije odgovorile na promene klime u prošlosti može nam obezbediti važne lekcije za čovečanstvo u budućnosti

Synthesis and caracterisation of tungsteen based refractory materials

Ideja ove doktorske disertacije je pronalaženje optimalnih uslova sinteze vatrostalnih materijala na bazi volframa: volfram karbida (WC) i volframovih silicida (volfram disilicida - WSi2, i pentavolfram trisilicida W5Si3) od elementarnih prahova...The focus of this doctoral dissertation is finding the optimal parameters for the synthesis of tungsten-based refractory materials: tungsten carbide (WC) and tungsten silicides (tungsten disilicide-wSi2, and pentatungsten trisilicide - W5Si3) starting fom the elementary powders..

Uporedna analiza promena temperature vazduha u Srbiji na osnovu satelitskih i prizemnih merenja

In this paper the air temperature changes on the territory of Serbia were investigated, on the basis of data from ground-based and satellite measurements, for the period 1979-2006. The trend analysis has shown that there is no amplification of trend of air temperature increase with altitude. The conclusion imposes itself that the air temperature increase in the researched area as well as on the Earth can not be only explained by models which presume domination of anthropogenic greenhouse effect.U radu je vršena uporedna analiza promene temperature vazduha na teritoriji Srbije, na osnovu setova podataka prizemnih i satelitskih osmatranja, u periodu od 1979. do 2006. godine. Analiza trenda je pokazala da nema amplifikacije trenda porasta temperature sa visinom. Nameće se zaključak da se porast temperature vazduha na istraživanom prostoru kao i na planeti u celini ne može isključivo objasniti modelima dominacije antropogenog efekta staklene bašte

Spatial pattern of climate change in Serbia in the instrumental period

Последњих година, у стручној литератури из области климатологије све више је радова у којима се анализира просторни распоред температуре ваздуха и/или падавина на одређеној територији. У том смислу, све чешћа је примена ГИС-а и, у оквиру њих, употреба метода интерполације. Коришћење ГИС-а у климатологији пре свега има примену у изради климатолошких карата, на којима је приказан просторни распоред неког климатског елемента Како је основни циљ тезе увођење просторне димензије у проучавање промена климе у Србији у инструменталном периоду, то је акценат био на просторној анализи климатских елемената и вредности њихових трендова. Разматран је просторни распоред падавина, температуре ваздуха, инсолације, облачности и релативне влажности ваздуха у Србији у периоду од 1949. до 2010. године. Анализиран је распоред тренда падавина и температуре ваздуха у Србији на годишњем, месечном и сезонском нивоу, просторни распоред трендова уз помоћ тематских мапа направљених применом web картирања. У циљу детаљније анализе режима и његове несигурности падавина извршен је анализа дневних падавина по кишним епизодама, њиховим карактеристикама и утицају на годишњу суму падавина. Резултати тренда падавина не показују статистичку значајност, као и просторну кохерентност. Уочена је, међутим, веома блага тенденција ка снижавању падавина на сезонском нивоу, током зиме и пролећа, као и ка повећању током јесени. Значајан пораст температуре ваздуха присутан је на већини анализираних станица током последње две деценије. Резултати добијени за Србију у складу са оним за Европу. На многим станицама у Србији уочен је тренд отопљавања почев од краја 1970-их година. Негативан тренд карактеристичан је за инсолацију, облачност и релативну влажност ваздуха...Recently, there are many papers analyzing the spatial pattern of air temperature and / or precipitation over the particular area. In this sense, there is very often use of GIS tools and interpolation methods. The use of GIS in climatology is primarily used in climatological maps, depicting the spatial distribution of certain climatic elements. Since the main objective of the thesis is introduction of the spatial approach in the study of climate change in Serbia in the instrumental period, the focus was on the spatial analysis of climatic elements (rainfall, temperature, solar radiation, cloud cover and humidity) and their trends in Serbia in the period 1949-2010. Precipitation and air temperature trend an annual, monthly and seasonal level has been analyzed, applying thematic maps made using web mapping tools. In order to get insight the analysis of the rainfall regime and its uncertainty, rain-spell analysis was performed. General results are showing absence of statistically significant rainfall trends and their spatial coherence. There is, however, slight tendency towards drier conditions during the winter and spring, and the opposite one in the autumn. A significant increase in temperature is detected during the last two decades. The results obtained for Serbia are in line with those obtained for Europe. At many stations in Serbia, there has been a warming trend from 1970s. The negative trend is also calculated for number of sunshine hours, cloud cover and relative humidity. Results generally suggest very weak trends all over the Serbia at annual scale, but show significant spatial patterns..

Uporedna analiza promena temperature vazduha u Srbiji na osnovu satelitskih i prizemnih merenja

In this paper the air temperature changes on the territory of Serbia were investigated, on the basis of data from ground-based and satellite measurements, for the period 1979-2006. The trend analysis has shown that there is no amplification of trend of air temperature increase with altitude. The conclusion imposes itself that the air temperature increase in the researched area as well as on the Earth can not be only explained by models which presume domination of anthropogenic greenhouse effect.U radu je vršena uporedna analiza promene temperature vazduha na teritoriji Srbije, na osnovu setova podataka prizemnih i satelitskih osmatranja, u periodu od 1979. do 2006. godine. Analiza trenda je pokazala da nema amplifikacije trenda porasta temperature sa visinom. Nameće se zaključak da se porast temperature vazduha na istraživanom prostoru kao i na planeti u celini ne može isključivo objasniti modelima dominacije antropogenog efekta staklene bašte

Moguća veza između kolebanja proticaja Dunava i sunčeve aktivnosti

Relations between discharge changes and solar activity are very complex and this is the reason why the obtained results are often contradictory. In this paper we tray to explore possible relation between Danube river discharge elements and parameters of solar activity. The best result has been found between flow index and latitude of sunspots. According to literature we propose possible mechanism of solar activity influence on the discharge.Veze između promena proticaja i sunčeve aktivnosti veoma su složene, zbog čega su dobijeni rezultati često protivrečni. U radu smo pokušali da ispitamo moguću vezu između elemenata proticaja Dunava i parametara sunčeve aktivnosti. Najbolji rezultat dobijen je za vezu između indeksa vodnosti i asimetrije heliografske širine sunčevih pega. Na osnovu literature predložen je mogući mehanizam uticaja sunčeve aktivnosti na proticaj

Impact of reduced thyroid function of mothers on development of rat offspring ovaries in the early postnatal period

Tiroidni hormoni (TH) su od ključnog značaja za razviće sisara u prenatalnom periodu. Prethodne studije pokazuju da subklinički hipotiroidizam ima za posledicu povećanu stopu atrezije u jajnicima mladunaca u prepubertalnom i pubertalnom uzrastu. Uticaj smanjene koncentracije TH na ranu postnatalnu folikulogenezu i razviće jajnika nije do sada ispitano. Ova disertacija ima za predmet istraživanja uticaj hipotiroidizma majki indukovanog 6-n-propil-2- tiouracilom (PTU) na folikulogenezu mladunaca pacova (n=15) 0, 4. i 7. dana po rođenju. Kod mladunaca 0. dana određivani su broj karakteristike oogonija i oocita normalne i izmenjene morfologije svetlosnom i elektronskom mikroskopijom. Pomenutim metodima kod mladunaca 4. i 7. dana starosti u jajnicima je određivan broj nestova, oogonija i oocita po nestu, primordijalnih, primarnih, sekundarnih i preantralnih folikula. Prisustvo glikogena i mukopolisaharida u tkivu jajnika mladunaca 0. dana određivano je PAS (eng. Periodic Acid Shiff) histohemijskim bojenjem, a prisustvo kalcijuma u tkivu jajnika pacova 4. i 7. dana Alizarin Red bojenjem. Volumenska gustina nukleusa, mitohondrija i glatkog endoplazmatičnog retikuluma u oocitama primordijalnih folikula analizirana je u jajnicima pacova 4. i 7. dana starosti. Imunohistohemijskom metodom detektovana je imunoekspresija PCNA (eng. proliferating cell nuclear antigen) kao markera proliferacije, dva markera apoptoze (kaspaza 3 i TUNEL (eng. terminaldeoxynucleotidyl transferase dUTP nick end labelling)) kao i dva markera autofagijе (ATG7 i LC3I/II). Hipotiroidni pacovi na rođenju imali su smanjen broj oogonija u mitozi i u mirovanju, kao i povećan broj atipičnih oogonija/oocita. Na ultrastukturnom nivou pokazano je prisustvo degenerisanih ćelija u pahitenu (Z-ćelije), oogonija/oocita u autofagiji, apoptozi i kombinaciji ova dva tipa ćelijske smrti, kod obe grupe životinja ovog uzrasta. Najbrojniji tipovi atipičnih ćelija kod hipotiroidnih pacova 0. dana su bile oogonije/oocite u autofagiji i Z-ćelije. U prilog ubrzanoj maturaciji neizmenjenih oogonija/oocita kod ove grupe životinja ide zapaženo prisustvo prominentnih organela i ekspresija PCNA. Broj TUNEL pozitivnih oogonija/oocita je bio manji kod hipotiroidnih pacova 0. dana, dok nije bilo razlike kada je u pitanju imunoekspresija kaspaze 3, ATG7 i LC3. Kod hipotiroidnih pacova starih 4 dana smanjen je broj oogonija i oocita po nestu, primarnih i sekundarnih folikula, a povećan je broj primordijalnih folikula. Kod hipotiroidnih pacova starih 7 dana prisutan je veći broj primarnih, sekundarnih i preantralnih folikula. Alizarin Red bojenje i elektronska mikroskopija su ukazali na prisustvo prominentnog endoplazminog retikuluma kod hipotiroidnih pacova starih 4 dana...Thyroid hormones (TH) are essential for mammals’ development in the prenatal period. Previous studies have shown that subclinical hypothyroidism results in an increased rate of atresia in the pups ovaries in prepubertal and pubertal age. The impact of reduced concentration of TH on the early postnatal folliculogenesis and development of ovarian cancer has not been studied until now. The aim of the current thesis is to explain the influence of maternal hypothyroidism induced by 6-n-propyl-2-thiouracil (PTU) on folliculogenesis of rat offspring (n = 15) of at the rat at the day of birth (0. day) and 4 and 7 days old. The number and morphological characteristics of oogonia and oocytes of normal and altered morphology was determined using light and electron microscopy. These methods were applied to determine the number of germ cell nests, oogonia and oocytes within nest, primordial, primary, secondary and preantral follicles in the ovaries of 4 and 7 days old pups. The presence of glycogen and mucopolysaccharides in the ovary tissue of the pups at the 0. day was detected using PAS (Periodic Acid Shiff) histochemical staining and the presence of calcium by Alizarin Red staining in the ovary tissue of 4 and 7 days old pups. The volume density of nucleus, mitochondria and smooth endoplasmic reticulum in oocytes of primordial follicles was obtained in the ovaries 4 and 7 days old rats. Immunohistochemistry was used to detect the expression of PCNA (proliferating cell nuclear antigen), as a marker of proliferation, two markers of apoptosis (caspase-3 and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling)) as well as two markers for autophagy (ATG7 LC3I / II). Hypothyroid rats at birth had reduced number of resting oogonia and oogonia undergoing mitosis, as well as the increased number of atypical oogonia/oocytes. Ultrastructural analyses showed the presence of degenerated cells in pachytene (Z-cell), oogonia/oocytes in autophagy, apoptosis and the combination of these two types of cell death in both groups of animals of this age. The most common types of atypical cells in hypothyroid rats at birth were oogonia/oocytes autophagy and Z-cell. In addition to the accelerated maturation morphologically unchanged oogonia/oocytes in this group of animals was the finding of the presence of prominent organelles in oocyte cytoplasm, followed with the increased expression of PCNA. Number of oogonia/oocytes labeled with TUNEL was lower in hypothyroid rats at birth, while there was no difference when it comes to expression of caspase-3, ATG7 and LC3..