1,191 research outputs found
OdreÄivanje indeksa seroloÅ”ke razlike meÄu sojevima virusa žutog mozaika postrne repe (TYMV) tehnikom Ā»raketneĀ« imunoelektroforeze
An attempt was made to apply rocket immunoelectro- phoresis (RIE) technique for the determination of serological differentiation index (SDI) values between three British strains of turnip yellow mosaic virus (TYMV) based on the height of Ā»rocketĀ« precipitates. The experiments were conducted in lĀ°/o agar gel containing antiserum to Edinburgh (E) strain of the virus, the holes being charged separately with purified E and two other strains. Following experiments with E strain in several subsequent twofold dilutions, a calibration graph showing linear proportionality was drawn in a coordinate system determined by steps of virus dilutions and logarithm of Ā»rocketsĀ« heights. By interpolation procedure SDIs of two heterologous strains against E were found fairly comparable with SDI values obtained by double radial immunodiffusion technique.Indeks seroloÅ”ke razlike (SDI), jedinica koja pokazuje stupanj seroloÅ”- ke razlike izmeÄu virusa i njihovih sojeva, može se manje ili viÅ”e precizno odrediti pomoÄu nekih standardnih seroloÅ”kih tehnika. U toku ovog rada pokuÅ”ali smo taj indeks izmjeriti Ā»raketnomĀ« (kvantitativnom) imu- noelektroforezom (RIE) na osnovi veliÄine (visine) imunoprecipitata oblika rakete. U pokusima smo koristili purificirane sojeve E (tipiÄni soj), N i S virusa žutog mozaika postrne repe (turnip yellow mosaic virus; TYMV) koji potjeÄu iz V. Britanije i imuni serum protiv soja E koji je bio pomijeÅ”an s lĀ°/o agarskim gelom. Na osnovi pokusa sa sojem E u nekoliko uzastopnih dvostrukih razrjeÄenja (1 do 1/8 mg/ml) naÅ”li smo linearnu ovisnost izmeÄu stupnja razrjeÄenja virusa i logaritma visine Ā»raketaĀ«. Interpolacijskim postupkom naÅ”li smo da su SDI vrijednosti heterolognih sojeva bile priliÄno podudarne s onima koje su bile izmjerene tehnikom dvostruke radijalne imunodifuzije
Identifikacija virusnog izolata iz vrste Tropaeolum majus L.
An isolate (TK) from a virus-infected Tropaeolum majus specimen found on the island of Korcula (Jugoslavia) was investigated for purpose of identification. The virus was identified as an isolate of turnip mosaic virus (TuMV) on the basis on the following results:
Isolate TK caused only local lesions in N. tabacum cvs. āWhite Burleyā and āXanthiā-nc and C. quinoa, local lesions and sporadic systemic symptoms in C. amar anticolor, as well as systemic symptoms in N. glutinosa and B. rapa var. rapa. Infected N. glutinosa and B. rapa var. rapa plants contained elongated flexuous particles with an average length of 728 nm. Isolate TK gave a positive serological reaction with the antiserum to TuMV. It provoked the building of cytoplasmic inclusion bodies composed of a great number of needle-shaped crystals which are characteristic of TuMV. Thermal inactivation point of isolate TK was between 52Ā° and 54Ā° C. Isolate TK may belong to the ordinary strain of TuMV. This is the first finding of TuMV in a non-cruciferous species in Jugoslavia.
Infective sap of N. glutinosa contained occasionally tubular structures of submicroscopic dimensions.
The paper contains literature data on occurrence of TuMV in non- cruciferous plants, on spontaneous infections of T. majus with viruses, and data on the viruses which have been experimentally transmitted to T. majus.Istraživanja, koja smo iznijeli u ovom radu, vrÅ”ena su na virusnom izolatu (TK) iz vrste Tropaeolum majus radi njegove identifikacije. Spontano inficirani primjerak T. majus potjecao je iz Jugoslavije (Vela Luka, otok KorÄula). Na listovima prirodno inficirane biljke bili su uoÄljivi jako Å”arenilo, mozaik i deformacije. Na temelju istraživanja utvrdili smo da izolat TK predstavlja virus mozaika postrne repe (TuMV). To su, Äini se, ujedno prvi podaci o nalazu TuMV u Jugoslaviji na biljci izvan porodice krstaÅ”ica.
Rad predstavlja rijetku, ako ne i jedinu, identifikaciju TuMV iz vrste T. majus, koja osim simptoma na pokusnim biljkama (N. tabacum, N. glutinosa, C. amar anticolor, C. quinoa, B. rapa var. rapa) uzima u obzir i rezultate seroloŔkih, elektronskomikroskopskih i drugih istraživanja.
Zanimljivo je da smo u soku inficirane N. glutinosa mogli ponekad opaziti cjevaste strukture submikroskopskih dimenzija koje se mogu dovesti u vezu s virusnom infekcijom.
U radu je iznesen veÄi broj podataka iz literature o prirodnoj raÅ”irenosti TuMV na biljkama iz viÅ”e biljnih porodica, o virusima koji su prirodno raÅ”ireni na vrsti T. majus, te o virusima koji su na tu vrstu preneseni eksperimentalno
Prvi nalaz furovirusa nekrotiÄnog žutila Å”eÄerne repe u Hrvatskoj
In fields of sugar beet (Beta vulgaris L. var. saccharifera) near Osijek and Županja (eastern Croatia) virus symptoms similar to those of beet necrotic yellow vein furovirus (BNYW) were observed on plant specimens in 1997. The main symptoms were pale greenish yellow foliage, upright leaves, reduced root size and root proliferation characteristic of rhizomania. Samples of sugar beet collected in the fields during June, July and August 1997 were checked for BNYW. In these samples BNYW v as revealed. This was established on the basis of test plant reactions, serology, electron microscope analysis of virus particles and soil transmission experiments. That is the first certain finding of rhizomania caused by BNYW in sugar beet in Croatia. Attempts to isolate BNYW from sugar beet growing in fields near Äakovec and Virovitica (northwestern and central Croatia, respectively), which also showed rhizomania symptoms, were unsuccessful.ViÅ”e faktora utjeÄe na urod Å”eÄerne repe u Hrvatskoj. Dosad nije bilo poznato je li meÄu tim faktorima i Å”tetna virusna bolest poznata pod imenom rizomanija koju uzrokuje virus nekrotiÄnog žutila žila Å”eÄerne repe (beet necrotic yellow vein virus; BNYW). Taj virus pripada furovirusima (Rush i Heidel 1995). Prema Horvathu (1994) BNYW može smanjiti urod Å”eÄerne repe i do 90%. Virus je rasprostranjen Å”irom svijeta: otkriven je i u preko 20 europskih zemalja meÄu kojima su i zemlje s kojima Hrvatska graniÄi.
IstražujuÄi virusne bolesti Å”eÄerne repe u okolici Äakovca, Virovitice, Osijeka i Županje, opazili smo tijekom 1997. godine na listovima Å”eÄerne repe na sva Äetiri lokaliteta simptome sliÄne onima koje uzrokuje BNYW. Najupadljiviji simptomi bili su: usmjerenost listova prema gore a na njima su se tu i tamo zapažala zelenkastožuta podruÄja (si. 1). NekrotiÄno žuÄenje žila nije opaže- no. Zapazili smo takoÄer da biljke s promjenama na listu imaju smanjen glavni korijen a na vrÅ”nom dijelu tog korijena redovito je nazoÄan abnormalno velik broj sitnih korjenÄiÄa; ti su korjenÄiÄi bili meÄusobno tijesno isprepleteni tako da su oblikovali gusti splet koji je nalikovao bradi (si. 2, 3). Zbog toga se ta bolest Å”eÄerne repe naziva rizomanija ili bradatost korijena.
Na temelju simptoma opaženih na Å”eÄernoj repi u polju, reakcija na pokusnim biljkama, elektronskomikroskopskih istraživanja te seroloÅ”ke identifikacije ustanovili smo da opisanu bolest na Å”eÄernoj repi u okolici Osijeka i Županje uzrokuje BNYW. To su potvrdili i pokusi prijenosa bolesti uzorcima tla u kojem su u polju rasli inficirani primjerci Å”eÄerne repe. Naime, naÅ”i su se virusni izdati, kao i svi dosad opisani izolati BNYW-a, prenosili tlom. Iz literature je poznato da je prenosilac virusa u tlu gljivica Polymyxa betae (Abe i Tamada 1986). NaÅ”i pokusi pomoÄu kojih smo nastojali dokazati BNYVV u Å”eÄernoj repi te u pripadajuÄem tlu s podruÄja Äakovca i Virovitice nisu dali pozitivan rezultat.
Izloženi rezultati nedvojbeno pokazuju da je i na podruÄju Hrvatske rasprostranjen BNYW Å”to je ujedno i prvi sigurni nalaz ovog virusa u naÅ”oj zemlj
Modelling international tourism demand using seasonal ARIMA models
Purpose ā The purpose of this study is to establish a seasonal autoregressive integrated moving
average model able to capture and explain the patterns and the determinants of German tourism
demand in Croatia.
Design ā The present study is based on the Box-Jenkins approach in building a seasonal
autoregressive integrated moving average model intend to describe the behaviour of the German
touristsā flows to Croatia.
Approach ā The proposed model is a seasonal ARIMA(0,0,0)(1,1,3)4 model.
Findings ā The diagnostic checking and the performed tests showed that the estimated seasonal
ARIMA(0,0,0)(1,1,3)4 model is adequate in modelling and analysing the number of German
tourists āarrivals to Croatia.
Originality of the paper ā This study provides a seasonal ARIMA model helpful to analyse,
understand and forecast German touristsā flows to Croatia. Such, more detailed and systematic
studies should be considered as starting points of future macroeconomic development strategies,
pricing strategies and tourism sector routing strategies in Croatia, as a predominantly tourism
oriented country
Identifikacija tobamovirusa izoliranog iz vrste Roripa amphibia
On the basis of the investigations presented it has been established that RMVāK isolate from Roripa amphibia belongs to tobamoviruses. This virus is symptomatologically and serologically more closely related to the type strain of ribgrass mosaic virus (RMV) than to the common tobacco mosaic virus. Consequently, the virus which was isolated and investigated is a strain of RMV.ProÅ”le godine izolirali smo virus iz divlje krucifere Roripa amphi- bia (L.) Bcss. u blizini Zagreba i dali mu oznaku RMVāK. Inficirane biljke imale su simptome u obliku blage iÅ”aranosti i nekrotiÄnih linija na listovima (si. 1A).
Elektronsko-mikroskopska analiza purificirane virusne suspenzije pokazala je da RMVāK ima Äestice približno 300 nm duge (si. 4). Apsorpcija virusne suspenzije dosizala je maksimum u ultravioletnom dijelu spektra kod 260 nm (si. 5).
Izolirani virus prenijeli smo na 12 zeljastih biljaka (tablica 1). Virus je prouzrokovao lokalne lezije na listovima vrsta Nicotiana silves- tris, N. glutinosa, D. stramonium i vrlo jake sistemiÄne simptome na vrsti N. tabacum, tip Samsun (si. 1). Na osnovi simptoma na tim vrstama bilo je oÄito da je RMVāK vrlo sliÄan obiÄnom virusu mozaika trpuca.
SeroloÅ”ki pokusi vrÅ”eni su metodom dvostruke difuzije u agaru te unakrsnim zasiÄavanjem u agaru. Ti su pokusi pokazali da je istraživani virus srodniji virusu mozaika trpuca nego virusu mozaika duhana (si. 3)
Sentiment analysis and artificial neural networks-based econometric models for tourism demand forecasting
Purpose \u2013 This is the second step of a previous paper (Folgieri et al., 2017), where we modelled and applied a backpropagation Artificial Neural Network (ANN) to forecast tourists arrivals in Croatia. Tourism is a very important sector of current Countries\u2019 economies, and forcasting assumes even more an significant issue to lead the local tourist offer. In this context, early prediction on the tourist inflow represents a challenge as it is an opportunity in developing tourist income. Applying a Machine Learning Method for Decision Support and Pattern Discovery such as ANN, represents an occasion to achieve a greater accuracy if compared to results usually obtained by other methods, such as Linear Regression.
Design \u2013 In this paper, we extended the model of the previously used backpropagation Artificial Neural Network, including data from sentiment analysis collected through social networks on the Internet.
Methodology \u2013The accuracy of the neural network has been measured by the Mean Squared Error (MSE) and compared to results obtained applying the ANN without data coming from the sentiment analysis.
Approach \u2013 Our approach consists in combining ideas from Tourism Economics and Information Technology, in particular Artificial Intelligence methods, such as Machine Learning and sentiment analysis, throught the Artificial Neural Networks (ANN) we used in our study.
Findings \u2013 The results showed that including also data from sentiment analysis, the neural network model to predict tourists arrivals outperforms the previous obtained results.
Originality of the research \u2013The idea to use ANN as a Decision Making tool to improve tourist services in a proactive way or in case of unexpected events is innovative. Adding data from sentiment analysis, we can add also tourists' preferences so considering collective intelligence and collective trends as factors which could influence a prediction
DOPRINOS MODELIRANJU E-TURISTIÄKE POTRAŽNJE
The tourism sector has experienced several significant changes over the past decades due to the strong development of the information and communication technologies (ICT). The technological revolution experienced through the development of the Internet has changed dramatically the market conditions for tourism organizations. ICTs evolve rapidly providing new tools for tourism development and rerouting. As known, tourism is defined and characterized by the demand side, it is therefore important to detect and define the various factors that determine it. Tourism demand modeling and forecasting have been an issue under examination in many researches. A large number of econometrics studies used, both time series and econometric approaches to model and forecast tourism demand and its various determinants. As known, tourism demand can be defined as a set of goods and services that people acquire to accomplish their journeys, expressed in term of quantity. Among different factors that influence tourism demand income, prices, substitute pries, and other variable are mentioned as determining measures or explanatory variables that affect the quantity of goods or services purchased. On the other side of the tourism demand function, as the dependent variable, most commonly the number of tourists or the number of tourists overnights are investigated. The paper presents the authors endeavor to express a theoretical e ā tourism demand model, as a mathematical function that indicates the presence of a relationship between the dependent variable, expressed by the number of touristsā overnight stays and a number of commonly used explanatory variables. Due to the growing importance of the information and communication technology and its great influence on the tourism sector, the authors research the possibilities of adding some additional supplementary independent variables i.e. the number of internet users, the number of overnights stays that were booked online or the number of online reservations to stress and represent the significant role play by the information and communication technology in determining the e-tourism demand.Zbog snažnog razvoja informacijskih i komunikacijskih tehnologija (ICT) turistiÄki sektor je u posljednjih nekoliko desetljeÄa doživio nekoliko znaÄajnih promjena. TehnoloÅ”ka revolucija prouzroÄena razvojem interneta dramatiÄno je promijenila tržiÅ”ne uvjete poslovanja svih turistiÄkih organizacija. ICT se brzo razvija, pružajuÄi nove alate za preusmjeravanje i razvoj turizma.Kao Å”to je poznato, turizam je determiniran i karakteriziran prvenstveno od strane potražnje, stoga je važno definirati i pronaÄi razliÄite faktore koji ju odreÄuju. Modeliranje i prognoziranje turistiÄke potražnje tema je mnogih istraživanja. Veliki broj ekonometrijskih istraživanja koristi pristup analize vremenskih serija kao i ekonometrijski pristup za modeliranje i prognoziranje turistiÄke potražnje i njezinih razliÄitih odrednica. Kao Å”to je poznato, turistiÄka potražnja može se definirati kao skup dobara i usluga koje ljudi koriste za vrijeme svojeg putovanja, izražen u smislu kvalitete. IzmeÄu razliÄitih Äimbenika koji utjeÄu na turistiÄku potražnju prihod, cijene, cijene supstituta i druge varijable spominju se kao mjere odrednice ili eksplanatorne varijable koje utjeÄu na kvantitetu kupljenih dobara i usluga. S druge strane, u funkciji turistiÄke potražnje kao zavisna varijabla najÄeÅ”Äe se istražuje broj turista ili broj ostvarenih turistiÄkih noÄenja. PolazeÄi od snažnog utjecaja, kojega dramatiÄni razvoj ICTa, ima na cjelokupni turistiÄki sektor, ad prikazuje nastojanje autorica da izraze teorijski model e-turistiÄke potražnje, kao matematiÄku funkciju koja izražava prisutnost veze izmeÄu zavisne varijable, izražene brojem turistiÄkih dolazaka i najÄeÅ”Äe koriÅ”tenih eksplanatornih varijabli, ali i ukljuÄivanjem dodatne nezavisne varijable, primjerice broj internet korisnika, broj noÄenja ostvarenih online bookingom ili broj online rezervacija da bi se istaknula i prikazala znaÄajna uloga informacijske i komunikacijske tehnologije u odreÄivanje e-turistiÄke potražnje
Neka svojstva virusa crtiÄavog mozaika ovsika
Virus crtiÄavog mozaika ovsika (VCMO = brome streak mosaic virus) naÄen je prije viÅ”e godina na vrsti Bromus mollis L. u okolici Zagreba. To je virus koji ima produženu i savitljivu Äesticu, dugu oko 693 nm. Virus je na mehaniÄki naÄin prenesen na otprilike 20 vrsta iz porodice Poaceae, meÄu njima i na žitarice Avena sativa L., Triticum vulgar e Vili. i Hordeum vulgare L. KarakteristiÄno je da taj virus stvara cilindriÄne citoplazmatske inkluzije (pin-wheels) koje pripadaju drugoj podskupini prema razdiobi Edwardsona (1974).
Vrlo je pogodna pokusna biljka za VCMO Briza maxima L. koja reagira na infekciju vrlo jakim simptomima, a ponekad i nekrozama. U listovima te vrste stvaraju se takoÄer karakteristiÄne cilindriÄne cito- piazmatske inkluzije s laminatnim agregatima ali bez smotaka.
Da bismo bolje karakterizirali virus, purificirali smo ga na dva razliÄita naÄina. Prvi naÄin sastojao se najprije od homogeniziranja listova pomoÄu fosfatnog pufera uz dodatak potrebnih sastojina. Poslije toga je suspenzija bila dvaput obraÄena kloroformom i izložena dvokratnom diferencijalnom centrifugiranju.
Drugu upotrebijenu metodu opisao je Slykhuis (1973), a koriÅ”tena je samo za purifikaciju inficiranih listova biljke B. maxima L. DosadaÅ”nja iskustva pokazuju da Äe i ta metoda biti upotrebljiva.
Spektrofotometrijska istraživanja obavljena su pomoÄu UV svjetla u podruÄju od 220 do 300 nm i pri tom je utvrÄen apsorpcijski kvocijent A 260/A 280 = 1,28. Na osnovi tih istraživanja ustanovljeno je da se pomoÄu upotrebljene metode iz 1 kg listova inficiranog jeÄma dobiva oko 5 mg virusa
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