On the Existence of Linearly Oscillating Galaxies

We consider two classes of steady states of the three-dimensional, gravitational Vlasov-Poisson system: the spherically symmetric Antonov-stable steady states (including the polytropes and the King model) and their plane symmetric analogues. We completely describe the essential spectrum of the self-adjoint operator governing the linearized dynamics in the neighborhood of these steady states. We also show that for the steady states under consideration, there exists a gap in the spectrum. We then use a version of the Birman-Schwinger principle first used by Mathur to derive a general criterion for the existence of an eigenvalue inside the first gap of the essential spectrum, which corresponds to linear oscillations about the steady state. It follows in particular that no linear Landau damping can occur in the neighborhood of steady states satisfying our criterion. Verification of this criterion requires a good understanding of the so-called period function associated with each steady state. In the plane symmetric case we verify the criterion rigorously, while in the spherically symmetric case we do so under a natural monotonicity assumption for the associated period function. Our results explain the pulsating behavior triggered by perturbing such steady states, which has been observed numerically

Učešće i ekonomski značaj velikih mljekara za snabdjevanje gradova i razvoj stočarstva

Snabdijevanje velikih gradova mlijekom mliječnim proizvodima, kao jednom od osnovnih namirnica ishrane, zahtijeva dobro organiziranu i uhodanu službu nabavke, dovoza i dostave ovih artikala do prodajnih centara ili neposredno potrošaču, najbržim putem i u određeno vrijeme s obzirom na ritam života i rada našeg zaposlenog čovjeka i njegove porodice

Učešće i ekonomski značaj velikih mljekara za snabdjevanje gradova i razvoj stočarstva

Snabdijevanje velikih gradova mlijekom mliječnim proizvodima, kao jednom od osnovnih namirnica ishrane, zahtijeva dobro organiziranu i uhodanu službu nabavke, dovoza i dostave ovih artikala do prodajnih centara ili neposredno potrošaču, najbržim putem i u određeno vrijeme s obzirom na ritam života i rada našeg zaposlenog čovjeka i njegove porodice

Uticaj cijanobakterija (cyanophyta) na svojstva različitih tipova zemljišta Vojvodine

To examine the effect of cyanobacteria on the properties of different soil types of the Vojvodina Province soil samples were inoculated with a mixture of two cyanobacteria cultures. The experiment was conducted in greenhouse. It included two treatments, With and Without cyanobacteria. Each experiment unit (soil genetic horizon of layer) was replicated four times. It may be concluded on the basic of the obtained results that the cyanobacteria did not have a pronounced effect on the water-physical and basic chemical properties of the soils. Increases in the content of mineral nitrogen in all soil horizon and layers were observed. Soil inoculation with cyanobacteria decreased the level of electric conductivity in saturated water extract (Amo,p subhorizon in chernozem and Aoh,na/E horizon) and the content of Na in saturated water extract (Aoh,na/E horizon in solenetz).U cilju istraživanja uticaja cijanobakterija na promené svojstava različitih tipova zemljišta Vojvodine. Uzorci ispitivanih genetičkih horizonata i slojeva zemljišta su inokulisani inokulumom koji je predstavljao združenu kulturu cijanobakterija. Ogled je postavljen u stakleniku u dva tretmana (inokulisano cijanobakterijama i kontrola), u četiri ponavljanja. Na osnovu rezultata ogleda može se zaključiti da uticaj cijanobakterija na vodno fizička i većinu osnovnih hemijskih osobina zemljišta nije bio izražen. Zabeleženo je povećanje sadržaja mineralnog azota u svim genetičkim horizontima i slojevima ispitivanih zemljišta inokulisanog tretmana u odnosu na kontrolni. Inokulacija zemljišta cijanobakterijama je kod nekih genetičkih horizonata uticalo na statistički značajno smanjenje vrednosti električne provodljivosti u saturisanom vodnom ekstraktu (Amo,p podhorizonta černozema i Aoh,na/E horizonta solonjeca) i sadržaja Na+ jona vodnog ekstrakta (Aoh,na/E horizonta solonjeca)

On the steady states of the spherically symmetric Einstein-Vlasov system

Using both numerical and analytical tools we study various features of static, spherically symmetric solutions of the Einstein-Vlasov system. In particular, we investigate the possible shapes of their mass-energy density and find that they can be multi-peaked, we give numerical evidence and a partial proof for the conjecture that the Buchdahl inequality $\sup_{r > 0} 2 m(r)/r < 8/9$, $m(r)$ the quasi-local mass, holds for all such steady states--both isotropic {\em and} anisotropic--, and we give numerical evidence and a partial proof for the conjecture that for any given microscopic equation of state--both isotropic {\em and} anisotropic--the resulting one-parameter family of static solutions generates a spiral in the radius-mass diagram.Comment: 34 pages, 18 figures, LaTe

Dental Hypersensitivity as a Consequence of the Initial Course of Periodontal Treatment

Preosjetljivost dentina često je i bolno patološko stanje koje se javlja kao posljedica različitih provokacijskih čimbenika. Dentinska preosjetljivost očituje se kratkom i jakom boli koja se javlja u području ogoljela dentina kao odgovor na tipične stimuluse, kao što su: toplotni, evaporativni, taktilni, osmotski, ili kemijski, a koji se ne mogu pripisati ni jednom drugom obliku dentalnoga defekta ili dentalne patologije. (Addy M, 2002). To patološko stanje još uvijek nije potpuno razjašnjeno, ali ga treba razlikovati od boli kod zubnoga karijesa, boli kod oštećenih zuba, frakturiranih restauracija, nedovoljnoga zubnog zatvora te palatogingivnih fisura i udubina. Jedina sličnost s dentinskom preosjetljivošću jest osjetljivost zuba koja se javlja nakon profesionalne inicijalne parodontalne terapije. Čestoća dentinske preosjetljivosti varira od 3 - 57% (Verzak Ž et al. 1998, Ress JS 2000), a preosjetljivost u sklopu parodontalnih bolesti može doseći znantno veći postotak (72 - 98% (Chabanski MB et al 1996). U studiju je bilo uključeno 60 slučajno odabranih pacijenata, liječenih na klinikama našega fakulteta. Pacijenti su podijeljeni u 4 skupine prema stanju parodontalnog zdravlja. Dentalna preosjetljivost bila je ispitana s pomoću taktilne osjetljivosti, osjetljivosti na hladan zrak i vodu, prije i poslije inicijalnog parodontalnog tretmana, koji je obavljen ultrazvukom. Stupanj boli izražavan je vrijednošću od 0 - 3 (0- nema boli, 1 - blaga osjetljivost, 2 - umjerena osjetljivost, 3 - jaka bol. Preosjetljivost zuba bila je najizražene bez obzira na vrstu provokacijskoga čimbenika bol postupno smanjivala krajem prvoga tjedna. Upotreba ultrazvuka u terapiji parodontalnih bolesti može izazvti preosjetljivost zuba. Služeći se različitim provokacijskim čimbenicima utija ako se kao provokacijski čimbenik upotrebljavao hladan zrak. Također je ustanovljeno da svrdili smo da je hladan zrak izazivao naj jaču osjetljivost. Bol se obično javljala neposredno nakon uporabe ultrazvuka, ali je trajanje boli bilo razmjerno kratko.Dentin hypersensitivity is a common and painful condition, wich can occur on different kinds of provocation factors. Dental hypersensitivitiy is characterized by short sharp pain arising from exposed dentine in response to stimuli typically thermal, evaporative, tactile, osmotic or chemical and wich cannot be ascribed to any other form of dental defect or pathology (Addy M, 2002). Until today this pathological condition is still unclear but should be deffered from dental caries, chipped teeth, fractured restorations, marginal leakage around restoration, palatogingival fissures and grooves. The only similarity to the dentin hypersensitivity is teeth sensitivity, wich follows the professional initial course of periodontal therapy. The frequency of dentin hypersensitivity varies from 3 - 57% (Verzak Ž et al, 1998, Ress JS 2000), while sensitivity in periodontal diseases could reach a higher percentage: 72-98% (Chabanski MB et al 1996). 60 randomly selected patients from our Clinic were included in the study. All patients were divided into 4 groups according to the grade of pathological periodontal condition. Dental hypersensitivity was investigated by tactile and by cold air/water provocation factors before and after initial periodontal treatment using ultrsound scaling. Pain was scored by 0 - 3 scoring system ( 0 - no pain, 1 - mild pain, 2 - moderate pain, 3 - severe pain). Teeth hypersensitivity was most pronounced if cold air was used as the provocative factor. Regardless of the sort of provocative factor the pain subsided gradually within one week. Ultrasound usage in periodontal treatment may cause teeth hypersensitivity. The hypersensitivity was provoked by mechanical od psysical provocative factors. The most painful sensation was related to cold air. The pain started early after treatment and lasted for a relatively short period of time

Ellipsometric measurements of plastically deformed copper

Chemically pure copper (99.99) prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm was extremely plastically deformed with the repeated application of equal channel angular pressing. Equal channel angular pressing was applied as an effective technique for producing bulk nanoscaled structures. It is well known that severe plastic deformation of metallic materials often leads to microstructure with ultrafine grains and cross-sections which remain about equal before and after deformation. Optical properties of the sample were studied using spectroscopic ellipsometry in UV-VIS range. The parameters of the sample like copper oxide and surface roughness overlayer were calculated using two-film model together with the Bruggeman effective medium approximation

Optical properties of plastically deformed copper

Pure copper (99.99), prepared in the sample of square cross-section (10 x 10 mm2) and length about 50 mm, was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing (ECAP). ECAP was applied as an effective technique for producing bulk nano-scaled structures. Optical properties of the sample were investigated using Raman spectroscopy. Two types of lines: narrow (with width of 7 cm¡1) and wide ( 40 cm¡1) are registered. Existence of two types of lines indicates that in the specimen exists nano-sized crystal structures of both Cu and CuO related with three dimensional amorphous boundary spaces, which indicates that plastic deformation of the sample did not lead to total amorphisation of the specimen

Policy and Mechanism in Adaptive Protocols

Adaptive protocols are protocols which automatically adjust their behavior to runtime phenomena such as traffic or link characteristics. For such protocols, the behavioral adjustment is accomplished with some mechanism; the decision as to how much (if any) adjustment is needed is made under control of a policy. Design and implementation of policies has often proven more challenging than that of mechanisms. We make three contributions in this paper. First, we develop a rule of thumb for policy/ mechanism separation and lay out a general set of challenges in policy module design. Second, as an illustration, we have analyzed a Forward-Error Correcting Code (FEC) for ATM supporting TCP/IP, and analytically identified a small robust set of tunable parameters to delineate regions where the code should be applied. Third, we exploited the analytic results and policy/mechanism separation to implement an adaptive protocol for network errors using programmable hardware to obtain high performance. Measurements of TCP/IP traffic over a 155 Mbps ATM link augmented with two cooperating Programmable Protocol Processing Pipelines were made with ttcp. The new policy module improves through-put by up to 50% over an unaugmented TCP/IP in the face of increasing bit errors rates, and continue operation into a range of bit error rates where an unmodified TCP practically ceases to function

Assessment of the Patient\u27s Education and Motivation in the Maintaince of Oral Hygiene

Zadovoljavajuća oralna higijena je conditio sine qua non u prevenciji karijesa i parodontnih bolesti. Prihvaćanje informacija za održavanje oralne higijene ovisi o više čimbenika među kojima su: pacijentova dob, stupanj naobrazbe, inteligencija, druπtveno-ekonomski status itd. Prijašnje studije su utvrdile da se gotovo 50% ljudi u održavanju oralne higijene služi samo četkicom (Karihovski B et al., 2001). Malendijk B et al 1995. Koivusilt A et al. 2003, pokazali su da ljudi s nižim stupnjem naobrazbe rijetko ili nikako ne čiste svoje zube. Ukupno 117 slučajno odabranih pacijenata koji su liječeni na klinikama Stomatološkog fakulteta uključeno je u ovu studiju. Svi pacijenti su uredno ispunili upitnik koji je posebno pripremljen za tu prigodu. Najveći dio pacijenata u našoj studiji imali su visoku i srednju školsku naobrazbu (33,3%, odnosno 43,6%). Visok postotak ispitanika već je prije dobio upute kako održavati oralnu higijenu i to od: stomatologa i medija 63,8%, stomatologa i laika 54,6%, dok je stomatolog sa stomatološkom sestrom bio zastupljen u 47 % slučajeva. Više od 61% ispitanika smatra da je dobilo dovoljno uputa u održavanju oralne higijene i da ih nije potrebno ponavljati. Ispitanici su upotrebljavali samo četkicu za zube u održavanju higijene usta u 50% slučajeva. Najveći broj pacijenata koristio se je četkicom dva puta na dan (79,5%), a četkicu pacijenti najčešće mijenjaju unutar tri mjeseca. U slučaju kada nastane neki stomatološki problem jedna četvrtina pacijenata odgađa intervenciju. Dobiveni su rezultati pokazali da je održavanje oralne higijene u naših pacijenata bilo na zadovoljavajućem stupnju. Ovakav rezultat mogao bi proizlaziti iz visoke opće razine naobrazbe naših ispitanika i iz već prije dobivenih naputaka kako održavati oralnu higijenu.Good oral hygiene is conditio sine qua non in prevention of dental caries and periodontal diseases. The acceptance of obtained information related to maintain good oral hygiene depends on several factors such as: age, educational level, personal skill, socioeconomic level etc. Previous studies revealed that almost 50 % of the general population use a toothbrush only to maintain their oral hygiene (Karihovski B et al., 2001). Malendijk B et al 1995, Koivulsit A et al., 2003, showed that people with a lower level of general education very rarely, or not at all, brush their teeth. A total of 117 randomly selected patients who attend the Clinics at our Faculty was enrolled in our study. All of them agreed to fulfill the questionaire designed by the investigators. The majority of our patients were highly educated (high school and university degree; 33.3 % and 43.6% respectively). A high percentage of the investigated patients were already educated in oral hygiene through their dentist and media (63.8%), dentist and non-preofessionals (54.6%) and dentist and dental nursing stuff in 47% of cases. A relatively high percentage (61.5%) of the investigated patients consider that there is no need for additional instructions related to oral hygiene. More than 50% of our cases only use toothbrush in their oral hygiene. The frequency of brushing the teeth was twice daily in the majority of the investigated patients, while replacements of an old toothbrush with a new one within a period of 3 months was in 79.5% of cases. One quater of the investigated patients who suffer from some kind of dental problem do not ask immediately for dental intervention. Our results have shown that the level of maintenanace of oral hygiene is rather high. Such results could be related to the high level of general education of the subjects enrolled in the study, and previously obtained education in oral hygiene