Single photoeffect on helium-like ions in the non-relativistic region

We present a generalization of the pioneering results obtained for single K-shell photoionization of H-like ions by M. Stobbe [Ann. Phys. 7 (1930) 661] to the case of the helium isoelectronic sequence. The total cross section of the process is calculated, taking into account the correlation corrections to first order of the perturbation theory with respect to the electron-electron interaction. Predictions are made for the entire non-relativistic energy domain. The phenomenon of dynamical suppression of correlation effects in the ionization cross section is discussed.Comment: to be published in Physics Letters

Expression of the serotonin receptor type 2C gene in sublines of the Wistar-Zagreb 5HT rat

Serotonin (5-hidroksitriptamin, 5HT) je važna signalna molekula uključena u brojne fiziološke funkcije, uključujući i regulaciju energetske ravnoteže organizma. Učinci serotonina posredovani su njegovim membranskim receptorima kojih ima ukupno 14 tipova. Serotoninski receptor tipa 2C (5HT-2C) igra važnu ulogu u regulaciji tjelesne mase i metabolizma glukoze te predstavlja farmakološku metu za tretman pretilosti i kontrolu glikemije. Wistar-Zagreb 5HT (WZ-5HT) štakor je animalni model razvijen usmjerenom selekcijom životinja prema ekstremnim vrijednostima trombocitnih serotoninskih parametra. Sastoji se od dviju podlinija štakora, hiposerotonergične (5HT-niske) i hiperserotonergične (5HT-visoke) podlinije. Životinje iz 5HT-niske i 5HT-visoke podlinije štakora WZ-5HT značajno se razlikuju u tjelesnoj masi, nakupljanju masnog tkiva, unosu hrane i metabolizmu glukoze. Cilj ovog rada bio je usporediti ekspresiju gena za 5HT-2C (Htr2c) između 5HT-niske i 5HT-visoke podlinije WZ-5HT štakora. Ekspresiju Htr2c analizirali smo u hipotalamusu i gonadalnom bijelom masnom tkivu mužjaka iz navedenih podlinija (n=10 po podliniji) metodom kvantitativne lančane reakcije polimerazom nakon reverzne transkripcije (RT-qPCR). Rezultati ovog rada pokazali su da životinje iz 5HT-visoke podlinije imaju, u odnosu na životinje iz 5HT-niske podlinije višu relativnu ekspresiju mRNA za receptor 5HT-2C u gonadalnom bijelom masnom tkivu, što upućuje na potencijalnu ulogu ovog receptora u regulaciji količine masnog tkiva. U hipotalamusu nismo opazili statistički značajne razlike u ekspresiji gena Htr2c između životinja iz dviju podlinija štakora WZ-5HT pa možemo zaključiti da hipotalamička ekspresija mRNA za receptor 5HT-2C ne pridonosi razlici u tjelesnoj masi između ovih podlinija.Serotonin (5-hydroxytryptamine, 5-HT) is an important signaling molecule involved in numerous physiological functions, including regulation of the energy balance of the organism. The effects of serotonin are mediated by 14 different types of its membrane receptors. Serotonin receptor type 2C (5HT-2C) plays an important role in regulation of body weight and glucose metabolism and represents a pharmacological target for the treatment of obesity and control of glycemia. Wistar-Zagreb 5HT (WZ-5HT) rat is an animal model developed by selective breeding according to extreme values of platelet serotonin parameters. It consists of two sublines of the rat, hyposerotonergic (5HT-low) and hyperserotonergic (5HT-high) subline. Animals from the 5HT-low and 5HT-high sublines of the WZ-5HT rats differ significantly in body mass, adiposity, food intake, and glucose metabolism. The aim of this paper was to compare expression of the 5HT-2C receptore gene (Htr2c) between 5HT-low and 5HT-high subline of WZ-5HT rats. Expression of the Htr2c was analyzed in the hypothalamus and gonadal white adipose tissue of males from the above mentioned sublines (n = 10 per subunit) by the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method. Results of this study showed that animals from the 5HT-high subline, as compared to animals from the 5HT-low subline, had a higher relative expression of mRNA encoding 5HT-2C receptor in gonadal white adipose tissue, suggesting the potential role of this receptor in the regulation of adiposity. In the hypothalamus we did not notice statistically significant differences in the expression of the Htr2c gene between animals from the two sublines of the WZ-5HT rat, so we can conclude that hypothalamic expression of the mRNA for the 5HT-2C receptor does not contribute to the differences in the body mass regulation between these sublines

Submarine Karst of Croatia - Evidence of Former Lower Sea Levels

Med zadnjo, to je pleistocensko-holocensko transgresijo, je naraščajoča morska gladina zalila velike dele dinarskega krasa. Ker porečja rek na vzhodni jadranski obali sestavljajo pretežno karbonatne kamnine, te reke prenašajo le okoli 20 % sedimentov v obliki suspenza, vse ostalo pa kot raztopljeni tovor. Zaradi tega je pod morsko gladino še vedno mogoče ugotavljati značilne kraške oblike, kot so škraplje, vrtače, polja, jame in brezna, kot tudi rečne doline in soteske. Poleg teh preprostih potopljenih oblik so zaradi dvigajoče se gladine nastale tudi nove: podmorski izviri imenovani vrulje, zaslanjeni obalni izviri in morska jezera. Najpomembnejši dokazi o nekdanjem kopnem okolju so kapniki v potopljenih jamah in lehnjak v potopljenih nekdanjih rekah. Te oboje je mogoče uporabiti za ugotavljanje nekdanje niæje morske gladine.During the last, Late Pleistocene-Holocene transgression, rising sea flooded a vast part of the Dinaric karst. Due to prevalence of carbonate rocks in the drainage area of most of the rivers on Eastern Adriatic coast, those rivers carry only approximately 20% of particulates as suspended matter and the rest is dissolved. Consequently, many typical karst features such as karrens, dolines, poljes, caves, pits and river valleys and canyons as well, presently under the sea, can still be recognized. Beside these simply drowned features, some new ones were formed by the sea level rise. Those are submarine springs, so called vruljas, brackish coastal springs and marine lakes. The most significant evidences of former subaerial conditions are speleothems in submerged caves and calc tufa deposits of drowned paleo rivers. Both of them could be used for determination of the former low sea level stands

Algoritmi za problem toka kroz mrežu

U ovom radu govorimo o problemu toka kroz mrežu. Najprije definiramo neke osnovne pojmove koji su nam potrebni za daljnje razmatranje problema. Potom opisujemo Ford-Fulkersonov algoritam, koji je jedan od najznačajnijih algoritama za rješavanje problema toka kroz mrežu. Analiziramo složenost algoritma te na primjeru pokazujemo kako se može izračunati maksimalan tok kroz mrežu pomoću ovog algoritma. Prije same analize, navodimo teorem maksimalnog toka, odnosno, minimalnog reza, koji govori o odnosu ta dva problema. Nakon Ford-Fulkersonovog algoritma, opisujemo Edmonds-Karpov algoritam, koji je, zapravo, jedno poboljšanje Ford-Fulkersonovog algoritma. Zatim uvodimo neka proširenja problema toka kroz mrežu, poput cirkulacija sa zahtjevima i cirkulacija sa zahtjevima i donjim granicama. Navedena proširenja poslužit će nam kod rješavanja problema provođenja nadzora i određivanja rasporeda letenja. Problem provođenja nadzora i problem određivanja rasporeda letenja samo su neke od primjena problema toka kroz mrežu.In this paper we talk about the network flow problem. First of all, we define some of the basic terms needed for the future analysis of the problem. Then we describe the Ford-Fulkerson algorithm, which is one of the most important algorithms for solving the network flow problem. We analyse the complexity of the Ford-Fulkerson algorithm and also demonstrate by example how to compute the maximum flow by using this algorithm. Before the complexity analysis, we first talk about Max-Flow/Min-Cut Theorem, that talks about the relationship between maximum flow and minimum cut problems. After describing Ford-Fulkerson’s algorithm, we describe the Edmonds-Karp algorithm, which is, actually, one of improvements of the Ford-Fulkerson algorithm. Finally, we introduce some extensions of the maximum flow problem, like circulations with demands and circulations with demands and lower bounds. Above mentioned extensions of the maximum flow will be used to solve the problem of survey design and airline scheduling. Survey design and airline scheduling are just some applications of the maximum flow problem

Challenges in cave monitoring and sampling – experiences from speleothem-based researches in Croatian caves

Speleothem-based research aimed to the reconstruction of the Quaternary environment in Dinaric karst has been conducted in several Croatian caves. As the interpretation of the palaeoenvironmental signal archived in speleothems relies on identifying and understanding processes between atmosphere and cave precipitates, especially hydrological behaviour, cave monitoring is crucial. Despite relatively simple sampling and monitoring protocols, series of problems and complications has arisen, caused by different natural and technical reasons. Extreme weather events such as enormous precipitation, prolonged drought or snow drifts, each in their own way can cause sample loss, while technical issues associated with equipment failures can lead to data loss. Even biological threats occurred, both man-induced and of natural origin. Although the later cannot be eliminated, as well as extreme weather, experience gained substantially helps to minimize negative effects. On the other hand, most of the technical issues are resolvable, and suggested solutions have been regularly implemented

Late Pleistocene – Holocene environmental changes – records from submerged speleothems along the Eastern Adriatic coast (Croatia)

U-Th and 14C dating, and X-ray diffraction of the parts of 16 submerged speleothems taken from the depths of 1.5−41.5 m from 7 submarine caves and pits along the Eastern Adriatic coast, provided insight to the sea-level fluctuations during the last 220 ka and to the palaeogeographic changes caused by sea-level changes. Due to the climate changes, palaeoenvironmental settings also varied, but not so abrupt and intensive as in the rest of Europe. Namely, owing to the Alps and Dinarides acting as orographic barriers, Eastern Adriatic coast was the border region between periglacial Europe and temperate Mediterranean region. It was, also, refuge area for plant species from the north. This study showed that appropriate temperature, humidity and vegetation cover ensured favourable conditions for karstification and speleothems formation processes even during Last Glacial Maximum.</p

Kraška hidrologija hrvaške obale v delih Alberta Fortisa (1741-1803)

Alberto Fortis (1741-1803) was an Italian naturalist who had a wide range of scientific interests from linguistics and ethnology to geology, geography and hydrology. This paper presents an overview of hydrological features that Fortis recorded in two of his works: Saggio d'Osservazzioni sopra l'Isola di Cherso ed Osero (1771) and Viaggio in Dalmazia (1774). These works were a result of several Fortis' travels in the region and were noted in European scientific literature of that time. Fortis revealed to European public the eastern Adriatic coast, a then little-known part of Europe with its wide variety of natural features. Despite the scarce appearance of surface water in karst, numerous interpretations of hydrological features can be found in Fortis’ descriptions of the East Adriatic coast. He often shows a remarkable understanding of karst hydrology even though some of his ideas and explanations are dubious from the present point of view. Although Fortis is not considered a karstologist in the strict sense, his works contain elements of what will eventually become karstology.Alberto Fortis (1741-1803) je bil italijanski naravoslovec s širokim razponom znanstvenih interesov od jezikoslovja in etnologije do geologije, geografije in hidrologije. V članku predstavljava pregled hidroloških pojavov, ki jih je Fortis opisal v dveh svojih delih: Saggio d'Osservazzioni sopra l'Isola di Cherso ed Osero (1771) in Viaggio in Dalmazia (1774). Deli, ki sta rezultat Fortisovih potovanj po vzhodni jadranski obali, sta  bili opaženi v evropski znanstveni literaturi tistega časa. Fortis je z njima evropski javnosti predstavil naravno pestrost tega, takrat malo poznanega območja. Kljub odsotnosti površinskih voda, Fortis predstavi in razloži  številne hidrološke pojave in pri tem pokaže  za tisti čas izjemno razumevanja kraške hidrologije. Seveda pa so nekatere ideje in razlage z današnjega vidika naivne. Fortisa sicer ne velja za krasoslovca v ožjem pomenu besede, a njegova dela nedvomno vsebujejo  gradnike bodočega krasoslovja

Comparison of 14C and 230Th/234U Dating of Speleothems from Submarine Caves in the Adriatic Sea (Croatia)

Z metodama 14C oziroma U-Th smo datirali 16 sig iz sedmih podmorskih jam v Jadranu. Dve sigi smo datirali z obema metodama. Primernost metod za datacijo sig je različna zaradi različnih okoljskih pogojev, ki so vladali med izločanjem sige oziroma po zalitju jame. Obe metodi sta zanesljivi na dobro ohranjenih sigah. U-Th metoda je slabša, ko so karbonati onesnaženi z detritičnim materialom oz. preraščeni s plastjo morskega izvora . Vendar metoda U-Th z uporabo MC ICPMS analize, kjer potrebujemo le 100-300mg vzorca (namesto 30 g pri metodi 14C), omogoča boljšo časovno ločljivost datacij, kar je pri datiranju sig zelo pomembno.Among the 16 speleothems that were collected from 7 submarine caves and pits for the purpose of 14C and U-Th dating and reconstructing sea-level changes, two speleothems were dated by both methods. Different environmental conditions during the speleothem deposition and after the submergence resulted with different appropriateness for speleothem dating by these techniques. Well preserved speleothems gave reliable results by both methods, while U-Th method showed disadvantage in the case of carbonates contaminated with detrital material, as well as in the case of carbonate from marine overgrowth that covers the speleothems. However, U-Th method using MC ICPMS technique which requires only 100-300 mg of sample per analysis (instead of ca. 30 g for 14C conventional method), offers better age resolution that is essential for speleothem dating