Primjena tetrahoričkog i polihoričkog koeficijenta korelacijeu verifikaciji prognoza

The measure of association in 2 x 2 (K x K) contingency tables known as tetrachoric (polychoric) correlation coefficient is recalled. These measures rely on two assumptions: 1) there exist continuous latent variables underlying the contingency table and 2) joint distribution of corresponding standard normal deviates is bivariate normal. It is shown that, in practice, the tetrachoric (polychoric) correlation coefficient is an estimate of Pearson correlation coefficient between the latent variables. Consequently, these measures do not depend on bias nor on marginal frequencies of the table, which implies a natural and convenient partition of information (carried by the contingency table), between association, bias and probability of the event and subsequently enables the analysis of how other scores depend on bias and marginal frequencies. Results extended to K x K tables lead to eventual reduction in dimensionality from K2 to 2K. The theoretical findings are illustrated through analysis of real-life, 6 x 6 contingency tables on verification of quantitative precipitation forecasts.Tetrahorički (polihorički) koeficijent korelacije dobro je poznata mjera asocijacije u kontingencijskim tablicama veličine 2 x 2 (K x K). Ove mjere počivaju na dvjema pretpostavkama: 1) U pozadini kontingencijske tablice nalaze se neprekidne latentne varijable, te 2) zajednička funkcija distribucije pripadnih standardnih normalnih devijata je bivarijantna normalna razdioba. Pokazano je da tetrahorički, odnosno polihorički koeficijent korelacije predstavlja procjenu Pearsonovog koeficijenta korelacije izmedju latentnih varijabli. Posljedično, ove mjere ne ovise o pristranosti, kao ni o marginalnim čestinama, što rezultira rasčlambom informacije sadržane u kontingencijskoj tablici na tri dijela. Prvi se odnosi na povezanost, drugi na pristranost, a treći daje čestinu razmatrane pojave. Korištenjem dobivenog rastava analizirana je ovisnost drugih verifikacijskih mjera o pristranosti i o marginalnim čestinama. Rezultati su prirodno prošireni na tablice oblika K x K, pri čemu se dimenzija problema smanjuje s K2 na 2K. Teorija je primjenjena u analizi tablica veličine 6 x 6 koje opisuju kvantitativne prognoze oborine

Evaluation of 1961-1990 Standard Climatological Normals

The comparison of standard climatological normals for the periods 1931-1960 and 1961-90 indicates a certain increase in winter temperatures and a decrease in summer temperatures in Croatia. ln the monthly precipitation totals there is an opposite trend. Weakening of the continental climate characteristics has recently been accompanied by a decrease of interannual variability of mean monthly temperatures. Temperature normals for the 1961-90 period approach more closely the mean values for the entire period of observation in Zagreb than any other standard normals. lt is shown that the often advocated advantage of short period (5 or 10 years) normals as a more reliable basis for future value estimations, has no justification

On the stochastic model for the temporal persistence of cloud cover

The considered stochastic model is based on the assumption that the series of observations of cloud cover can be represented by the series of normal variates which have properties of the Markov process. This assumption made possible the estimation of the joint probabilities for 1331 (=113) possible combinations of observations on the basis of frequency distribution of cloud cover at 7, 14, and 21 local time. The theoretical frequency distribution of mean daily cloud amount is obtained by adding the joint probabilities which contribute to the corresponding class (nearest tenth). The autocorrelation coefficient, which is the only free model parameter, has been determined in the way that the theoretical distribution fits the observed distribution in the best way. The differences between these two distributions could be partly explained by the contributions of mesoscale processes (convective storm, radiation fog) which have a much lower persistence than the prevailing large scale processes. Finally, there is a brief survey of possible applications of the results on the data control, the evolution of weather modification and the verification of forecast

Some characteristics of climatic change at Zagreb during the last thirty years

On the basis of changes in the seasonal variations of pressure, precipitation and temperaturte at the Zagreb-Grič Observatory in the 1862 – 1980 period, we can distinguish four periods of an approximate duration of thirty years each, within which seasonal variations of climatic elements show some specific characteristics. Periods with somewhat stronger characteristics of continental climate (1862– 1890, 1920– 1950) alternate with periods during which continental characteristics are considerably weakened (1890– 1920, 1951– 1980). As a consequence of these climatic oscillations, it has been pointed out that the climatological normals determined on the basis of 30-year record are not necessarily reliable. The relative significance of these climatological fluctuations has been estimated on the basis of comparisons with spatial variations of previously used indicators in the area of Northern Croatia, which can be considered as an area with a uniform climate. The comparisons have shown that although the temporal variations of the climatic characteristics of Zagreb (and probably even a wider area) are relatively small, they cannot be neglected

On the stochastic model for the temporal persistence of cloud cover

The considered stochastic model is based on the assumption that the series of observations of cloud cover can be represented by the series of normal variates which have properties of the Markov process. This assumption made possible the estimation of the joint probabilities for 1331 (=113) possible combinations of observations on the basis of frequency distribution of cloud cover at 7, 14, and 21 local time. The theoretical frequency distribution of mean daily cloud amount is obtained by adding the joint probabilities which contribute to the corresponding class (nearest tenth). The autocorrelation coefficient, which is the only free model parameter, has been determined in the way that the theoretical distribution fits the observed distribution in the best way. The differences between these two distributions could be partly explained by the contributions of mesoscale processes (convective storm, radiation fog) which have a much lower persistence than the prevailing large scale processes. Finally, there is a brief survey of possible applications of the results on the data control, the evolution of weather modification and the verification of forecast

O MODELIRANJU BINARNIH METEOROLOŠKH SLJEDOVA S POSEBNIM OSVRTOM NA ČESTINE TOPLIH I HLADNIH RAZDOBLJA

Prikazani su razni pristupi pri analizi čestina toplih i hladnih razdoblja koji su korišteni u literaturi. Ukazano je na relativno mali broj radova na ovom području u usporedbi s velikim brojem modela za kišna i sušna razdoblja. Glavne teškoće pri modeliranju temperaturnih nizova posljedica su njihove nestacionarnosti. Također, statistička struktura nizova koji su dobijeni kategorizacijom (u dvije kategorije) iz kontinuiranih vrijednosti nekog meteorološkog elementa vrlo je složena, iako struktura izvornog vremenskog niza ima jednostavni oblik autoregresije. U radu se ukazuje na to da zbog sličnosti autokorelacionih funkcija diskretiziranog procesa autoregresije prvog reda AR (1) i modela DARMA (1,1) postoji mogućnost da se kvalitativni (diskretni) nizovi meteoroloških veličina (koje su u svojoj osnovi kontinuirane) uspješno modeliraju pomoću modela DARMA (1,1). Čak što više, dva parametra koji određuju oblik autokorelacione funkcije ovog modela mogu se procijeniti iz koeficijenta autokorelacije osnovnog niza. Na nekim primjerima prikazane su mogućnosti ovog modela i uspoređene s drugim metodama uobičajenim pri modeliranju diskretnih vremenskih nizova

Pathological pregnancy and psychological symptoms in women [Patološka trudnoća i psihički simptomi u žena]

Pregnancy is followed by many physiologic, organic and psychological changes and disorders, which can become more serious in pregnancy followed by complications, especially in women with pathological conditions during pregnancy. The purpose of this study was to find out and analyze the prevalence and intensity of psychological disorders in women with pathological conditions during pregnancy and compare it with conditions in pregnant women who had normal development of pregnancy. The research is approved by the Ethical committee of the Mostar University Hospital Center, and it was made in accordance with Helsinki declaration and good clinical practices. The research conducted section for pathology of pregnancy of Department for gynecology and obstetrics of the Mostar University Hospital Center. It included 82 pregnant women with disorders in pregnancy developement and control group consisted of pregnant women who had normal development of pregnancy. The research work was conducted from September 2007 to August 2008 in Mostar University Hospital Center. Pregnant women had Standard and laboratory tests, Ultrasound. CTG examinations were done for all pregnant women and additional tests for those women with complications during pregnancy. Pregnant women completed sociobiographical, obstetrical-clinical and psychological SCL 90-R questionnaire. Pregnant women with pathological pregnancy exibited significantly more psychological symptoms in comparison to pregnant women with normal pregnancy (p < 0.001 to p = 0.004). Frequency and intensity of psychical symptoms and disorders statisticly are more characteristic in pathological pregnancy (61%/40.6%). The statistical data indicate a significantly higher score of psychological disorders in those pregnant women with primary school education (p = 0.050), those who take more than 60% carbohydrates (p = 0.001), those with pathological CTG records (p < 0.001), those with pathological ultrasound results (p < 0.001 to 0.216) and those pregnant women with medium obesity and obesity (p = 0.046). Body mass index (BMI) during normal pregnancy development is lower (p = 0.002) but the levels of glucose, triglycerides, cholesterol, HDL and LDL in blood are higher Blood pressure in pregnant women with pathological pregnancy was statistically significantly higher (p < 0.001). Diagnostic criteria for the metabolic syndrome were found in 19 pregnant women with the pathological pregnancy. Statistically, in those women, a significantly higher appearance of psychological symptoms and disorders was observed in comparison to the pregnant women without metabolic syndrome (p < 0.001). The research has shown that 87.8% from all pregnant women included in this study have been hospitalized due to premature birth, hypertensive disorders, and diabetes in pregnancy, and also due to bleeding in the second and third trimester of pregnancy

Successful Delivery of Fetus with Fetal Inherited Thrombophilia After Two Fetal Deaths

A pregnant woman with inherited thrombophilia (factor II mutation – 20210A) had two late pregnancy losses. The first pregnancy was not well documented, but the second pregnancy was complicated by fetal thrombophilia and umbili- cal artery thrombosis, proven after fetal death. During the third pregnancy enoxaparine was introduced in the therapy and early amniocentesis was performed. Fetal thrombophilia was proven again. Early delivery was induced and per- formed with no complications, resulting in a live healthy infant. A history of miscarriages or recurrent fetal loss should raise suspicion of thrombophilia as a potential cause. It is debatable whether amniocentesis in pursuit of fetal thrombo- philia should be performed and whether this will lead to a better perinatal outcome. When fetal thrombophilia is diag- nosed, an earlier induction of delivery should be considered, taking into account the fetal extrauterine viability. The aforementioned approach of early delivery in cases of inherited fetal thrombophilia could be a possible solution for better perinatal outcomes

STATISTIČKA ANALIZA SUŠNIH I KIŠNIH RAZDOBLJA PRIMJENOM MODELA MARKOVLJEVIH LANACA

Primjenom statističkog modela Markovljevih lanaca odredjene su teoretske čestine sušnih i kišnih razdoblja, povratni periodi sušnih razdoblja i koeficijenti perzistencije u gornjem slivu rijeke Save za sve mjesece razdoblja I947-71. Rezultati pokazuju da se najveće čestine sušnih razdoblja, kao i najveća perzistencija, javljaju za vrijeme hladnog doba godine i na većim visinama. Dana je usporedba rezultata sa dugogodišnjim nizom za Zagreb- Grič (1862-1971), i sa raspodjelom perzistencije za cijelo područje Jugoslavije

Impact of intravenous oxytocin on lung haemodynamics and gas exchange during caesarean section under general and spinal anaesthesia

Numerous studies have proven haemodynamic effects of oxytocin, yet there is not much knowledge about the impact of oxytocin on lung haemodynamics and gas exchange. Our goal was to determine the potential impact of intravenous oxytocin on lung haemodynamics and arterial oxygen saturation in patients undergoing Caesarean delivery and to determine the possible difference in arterial oxygen saturation between general and spinal anaesthesia after intravenous administration of oxytocin. Methods. Total of 215 patients scheduled for elective Caesarean delivery were included in the study and randomised into two groups: Caesarean section under spinal anaesthesia and Caesarean section under general anaesthesia. After excluding the patients with severe intraoperative blood loss and those given the standard doses of oxytocin, 70 patients (35 per group) were left for statistical analysis. Patients in both groups were given 10 international units (IU) of oxytocin as a bolus dose plus 10 IU of oxytocin in infusion through 3 minutes, after clamping and cutting of the umbilical cord. Oxygen saturation values throughout the whole procedure were compared between the two groups. Results. Oxygen saturation values decreased more often and to a greater degree in general anaesthesia group than in the spinal anaesthesia group after intravenous administration of oxytocin (all P < 0.05). Conclusion. Drop in arterial oxygen saturation after intravenous oxytocin is inside the safety range among full-term healthy partiurents undergoing spinal or general anaesthesia for Caesarean section. Larger studies on patients with risk factors are needed to conclude the safety of oxytocin in those patients