BER Performance of IM/DD FSO System with OOK using APD Receiver

In this paper, the performance of intensity-modulated with direct detection (IM/DD) free space optical (FSO) system using the on-off keying (OOK) and avalanche photodiode (APD) receiver is observed. The gamma-gamma model is used to describe the effect of atmospheric turbulence since it provides good agreement in the wide range of atmospheric conditions. In addition, the same FSO system with equal gain combining applied at the reception is analyzed. After theoretical derivation of the expression for the bit error rate (BER), the numerical integration with previously specified relative calculation error is performed. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of the FSO link and receiver parameters on the BER performance are discussed. The results illustrate that the optimal APD gain in the minimum BER sense depends considerably on the link distance, atmospheric turbulence strength and receiver temperature. In addition, the value of this optimal gain is slightly different in the case of spatial diversity application compared with single channel reception

Impact of climatic factors to the percentage of young in the population of brown hare (Lepus europaeus P) in the Bačka district

Climatic factors, especially temperature and precipitations, greatly affect the dynamics of the hare number and population. Climatic factors directly affect the physiological and reproductive processes of both individuals and entire populations, or indirectly, through the availability of food, competition with other species, predators and other. The age structure of the hare population at the end of the period of reproduction is an important indicator of the population growth that is used for planning the level of explotation of the hare population (hunting). The rational use of the hare's population is one of the most important protection procedures and it should be well monitored and controlled by the hunting professionals. We used the average monthly temperature and the sum of monthly precipitations in the hare reproductive period (March-September) during ten years (2000 - 2009), together with the percent of young in the hare population, on the territory of Bačka, for multiple regression (stepwise) analysis. Results of the regression analysis show an association between the percentage of young hares and the influence of climatic factors. The average temperature and sum of precipitation in June, are the strongest predictor of the percent of young in the hare’s population in Bačka. According to the coefficient of determination (R2=0.50) climatic parameters account for 50% of variance in the percentage of young hares in Bačka. The regression correlation coefficient of all factors was R=0.70, which is on the border line between medium and high correlation

HPLC analysis of technetium(I)-99m labelled C60(OH)22

Fullerenols, water-soluble polihydroxylated fullerenes, are very important kinds of fullerene derivatives because it is suitable for biological study. In order to get convenient substance for studies (in vivo and in vitro) we investigate possibilities of labeling fullerenol. The HPLC results performed by isocratic HPLC, confirmed that hydrophilic organometallic [99mTc(CO)3(H2O)3]+ precursor allows forming of 99mTc(I) complexes with fullerenol.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200

Benefits of inoculation with azotobacter in the growth and production of tomato and peppers

The aim of this research was to investigate the effects of Azotobacter chroococcum in tomato and pepper growth and production by using two types of inoculation - seed inoculation and seedling inoculation. The effect of inoculation was observed thirty days after sowing, thirty days after transplanting, and in the phase of technological maturity. The following were measured: height of the plants, dry matter of the plants and number and the weight of the fruits. Inoculation had a positive effect on these in both plants. With tomato, better results were achieved when seedlings were inoculated. With pepper, the length of the plant and the dry matter were greater with seedling inoculation, whereas the number and the weight of the fruits were greater with seed inoculation

Novi pristupi u razvoju talasnog modela šuma mikrotalasnih tranzistora

The microwave transistor noise wave model is defined by the parameters called the noise wave temperatures. These temperatures are determined based on the measured transistor noise parameters, mostly by using optimization procedures in the microwave circuit simulators. The main disadvantage of the optimization procedures is that they are usually time-consuming. Therefore, the aim of the research presented in this dissertation is to find the new extraction methods for more efficient determination of the noise wave temperatures. New extraction methods both for the indirect and direct determination of the noise wave temperatures are developed. In the first case, the noise wave temperatures are calculated on the basis of the extracted noise parameters of the transistor intrinsic circuit, by using appropriate equations. The noise parameters of the transistor intrinsic circuit are extracted on the basis of the measured transistor noise parameters, by applying one of the following three de-embedding procedures: analytical de-embedding procedure, de-embedding procedure within the microwave circuit simulator or de-embedding procedure based on artificial neural networks. In the second case, the determination of the noise wave temperatures is performed directly, on the basis of the measured transistor noise parameters. For the purpose of the direct determination of the noise wave temperatures, four extraction methods based on artificial neural networks, as well as semi-analytical extraction method based on polynomials are developed. In order to provide their validation, all proposed extraction methods are used for the modeling of noise characteristics of the specific GaAs HEMT component in the wide range of operating temperatures. In addition, the noise wave model application for the noise parameter modeling in the case of GaN HEMT, illuminated GaAs HEMT, and three different GaAs HEMTs with the scaled gate width is presented in the dissertation. In all cases, some of the extraction methods for the indirect determination of the noise wave temperatures is used. Hence, the reliability of the noise wave model is proved in terms of the new generation of components, the components exposed to various light conditions as well as the same class components with different gate widths

Hranidbeno ponašanje pasa lutalica u javnom prihvatilištu

Feeding time of stray dogs on the first, second, third, fifth and seventh day of captivity in a municipal shelter was studied. The average value of the feeding time of dogs decreased from the first day (429.07±107.08 seconds) to the third day in captivity when it reached the lowest average value (229.53±95.18 seconds). The feeding time of dogs on the third day in captivity differs significantly from the same parameter on the first (429.07±107.08 seconds) and second day (372.73±100.58 seconds) in captivity (p lt 0.01). The highest average value of feeding time of stray dogs in the shelter was recorded on the first day. On the fifth and seventh day the feeding time of dogs increased compared to the third day. However, there were no significant differences of the average value of feeding time on the third day comparing with the fifth day (260.8±111.06 seconds) or the seventh day (301.33±119.89 seconds). Dogs ate their food more slowly on the fifth and the seventh day than on the third day, but more quickly than on the first and the second day (372.73±100.58 seconds). Significant differences were estimated comparing the feeding time of dogs on the first day with the third (p lt 0.01), fifth (p lt 0.01), and seventh day (p lt 0.05) of housing in the municipal shelter. Also, the feeding time of dogs on the second day differed significantly from the third (p lt 0.01) and the fifth day (p lt 0.05).U radu su prikazani rezultati proučavanja brzine unošenja hrane kod pasa lutalica u javnom prihvatilištu u Beogradu prvog, drugog, trećeg, petog i sedmog dana boravka. Prosečna brzina unošenja hrane je opadala počev od prvog dana (429,07±107,08 sekundi) do trećeg dana boravka pasa u zatočeništvu kada je ovaj pokazatelj dostigao najnižu vrednost (229,53±95,18 sec). Brzina unošenja hrane trećeg dana se statistički značajno razlikovala u poređenju sa prvim danom (429,07±107,08 sec) i drugim danom (372,73±100,58 sec) boravka pasa u prihvatilištu (p lt 0,01). Najveća prosečna vrednost brzine unošenja hrane zabeležena je prvog dana boravka u prihvatilištu. Petog i sedmog dana boravka u prihvatilištu brzina unošenja hrane se povećala u poređenju sa trećim danom. Međutim, nisu uočene statistički značajne razlike u poređenju brzine unošenja hrane između trećeg i petog (260,8±111,06 sec) i trećeg I sedmog dana (301,33±119,89 sec). Psi su mnogo sporije unosili hranu petog i sedmog dana nego trećeg dana, ali brže nego prvog i drugog dana boravka u prihvatilištu (372,73±100,58 seconds). Značajne razlike su utvrđene u brzini unošenja hrane između prvog i trećeg (p lt 0,01), petog (p lt 0,01), sedmog dana (p lt 0,05) boravka pasa u prihvatilištu. Takođe, brzina unošenja hrane se značajno razlikovala i drugog dana u poređenju sa trećim (p lt 0,01) i petim danom (p lt 0,05)

Effects of interleukin-17 on functional properties of human periodontal ligament mesenchymal stem cells

Istraživanja regenerativnih i modulatornih uloga mezenhimskih matičnih ćelija (MMĆ) u poslednjih nekoliko decenija su zaokupirala pažnju naučnika s obzirom da ove ćelije ispoljavaju karakteristike koje ukazuju na mogućnosti njihove primene u regenerativnoj medicini, kao i na polju ćelijske terapije. Iako MMĆ izolovane iz različitih adultnih i neonatalnih izvora ispoljavaju potencijal samoobnove i multipotentne diferencijacije (u ćelije mezodermalnog, ali i ektodermalnog i endodermalnog porekla), mnoga istraživanja koja se tiču funkcionalnih karakteristika ovih ćelija tek predstoje kako bi njihova primena bila efikasna i bezbedna. Jedan od novije otkrivenih izvora MMĆ je i tkivo periodoncijuma koje predstavlja bogat i lako dostupan izvor MMĆ, s obzirom da se ovo tkivo dobija nakon ekstrakcije zuba iz ortodontskih razloga. Periodoncijum je vezivno tkivo čija je glavna uloga uspostavljanje čvrste veze između korena zuba i alveolarne kosti. Regenerativni potencijal MMĆ periodoncijuma (PD-MMĆ) ogleda se u njihovom potencijalu samoobnove i multipotentne diferencijacije, kao i sposobnosti formiranja tkiva sličnih potpornom tkivu zuba, uključujući periodoncijum i cement. Ove osobine čine PD-MMĆ dobrim kandidatima za primenu u regeneraciji potpornog tkiva zuba u parodontopatiji, hroničnom inflamatornom oboljenju uzrokovanom bakterijama zubnog plaka. Razvoj hronične parodontopatije podrazumeva procese remodelovanja koštanog tkiva pod uticajem brojnih faktora u koje su uključeni osteoblasti i osteoklasti koji ostvaruju recipročne interakcije sa ćelijama imunskog odgovora regulišući inflamaciju i degradaciju koštanog tkiva. Uloga lokalne mikrosredine u parodontopatiji predstavlja jedan od ključnih faktora u kontekstu ćelijskog odgovora tkiva periodoncijuma na perzistentnu infekciju. U okviru parodontalnih lezija potvrđeno je prisustvo Th17 (od engl. T helper cells17) ćelija, značajnih regulatora tkivnog razaranja u toku zapaljenskih procesa, koje produkuju proinflamatorni citokin interleukin (IL)-17. U kontekstu parodontopatije, do sada je pokazano da IL-17 ostvaruje svoju ulogu stimulišući privlačenje neutrofila na mesto inflamacije kao i direktnim stimulatornim delovanjem Th17 ćelija na diferencijaciju osteoklasta...In the last few decades regenerative and modulatory properties of mesenchymal stem cells (MSCs) have gained the attention of scientists since their characteristics indicated the possibility of their use in regenerative medicine and cell therapy. Although MSCs isolated from various adult and neonatal tissues exhibit the potential of self-renewal and multipotent differentiation (towards cells of mesodermal, ectodermal and endodermal origin), many aspects concerning their functional characteristics are yet to be explored. One of the recently discovered sources of MSCs is easily accessible tissue of periodontal ligament, obtained after tooth extraction for orthodontic reasons. Periodontal ligament tissue strengthens the root of the tooth in the alveolar bone. The regenerative potential of periodontal ligament MSCs (PDLSCs) is reflected in self-renewal and multipotent differentiation ability, as well as potency for the formation of tissues which support the teeth, including the periodontal ligament and cement. These features make the PDLSCs good candidates for use in the regeneration/reconstruction of supporting tissue of teeth in periodontal disease, a chronic inflammatory disease caused by bacterial plaque. The development of chronic periodontal disease includes the process of bone tissue remodeling governed by a number of factors, including osteoblasts and osteoclasts, which reciprocally interact with cellular and humoral compartments of the immune system, thus regulating inflammation, degradation and renewal of bone tissue. The role of the local microenvironment in the periodontal disease is one of the key factors in the context of periodontal ligament tissue response to persistent infection. The presence of T helper cells17 (Th17) cells, important regulators of tissue destruction during inflammatory processes has been confirmed in periodontal lesions. Th17 cells produce proinflammatory cytokine interleukin (IL)-17. In the context of periodontal disease, as well as in other inflammatory diseases, IL-17 stimulates the activation and migration of neutrophils to the site of inflammation. Additionally, IL-17 directly stimulates differentiation of osteoclasts and contributes to the alveolar bone resorption..

The influence of vitamin E supplementation on the oxidative status of rat liver

We tested to see if the additional intake of vitamin E in the form of α-tocopheryl-succinate would improve liver antioxidative protection. Thus, we studied the tissue oxidative status in rats supplemented by two doses of the antioxidant over a four week period of time. Our results confirmed that the additional intake of vitamin E decreased the liver lipid peroxidation level and SOD activity level and preserved its vitamin C content. However, the hydrogen peroxide content and catalase activity remained unchanged, probably due to the mechanism of vitamin E liver metabolism.

AUTOMATIC DETERMINATION OF FILTER COEFFICIENTS FOR LOCAL CONTRAST ENHANCEMENT

This study proposes an algorithm whose main advantage is in enabling the automatic determination of non-linear homomorphic filter coefficients used for local contrast enhancement in digital image processing. The presented algorithm is tested in a real production environment. The obtained results are compared with relevant examples in literature, showing the advantages of the achieved results or a relatively high level of their correspondence with reference results. The proposed procedure can be used for various applications in mechatronics, robotics and automatized production systems