Monopole search below the Parker limit with the MACRO detector at Gran Sasso

The MACRO detector approved for the Gran Sasso Underground Laboratory in Italy will be the first capable of performing a definitive search for super-massive grand unified theory (GUT) monopoles at a level significantly below the Parker flux limit of 10 to the minus 15th power square centimeters Sr(-1) 5(-1). GUT monopoles will move at very low velocities (V approx. 0.001 c) relative to the Earth and a multifaceted detection technique is required to assume their unambiguous identification. Calculations of scintillator response to slow monopoles and measurements of scintillation efficiency for low energy protons have shown that bare monopoles and electrically charged monopoles moving at velocities as low as 5 x .0001 c will produce detectable scintillation signals. The time-of-flight between two thick (25 cm) liquid scintillation layers separated by 4.3m will be used in conjunction with waveform digitization of signals of extended duration in each thick scintillator to provide a redundant signature for slow penetrating particles. Limited streamer tubes filled with He and n-pentane will detect bare monopoles with velocities as low as 1 x 0.0001 c by exploiting monopole induced level mixing and the Penning effect

Track recording plastic compositions

Improved nuclear track recording plastic compositions are provided which exhibit greatly decreased surface roughness when etched to produce visible tracks of energetic nuclear particles which have passed into and/or through said plastic. The improved compositions incorporate a small quantity of a phthalic acid ester into the major plastic component which is derived from the polymerization of monomeric di-ethylene glycol bis allyl carbonate. Di-substituted phthalic acid esters are preferred as the added component, with the further perference that the ester substituent has a chain length of 2 or more carbon atoms. The inclusion of the phthalic acid ester to an extent of from about 1-2% by weight of the plastic compositions is sufficient to drastically reduce the surface roughness ordinarily produced when the track recording plastic is contacted by etchants

Near threshold response of a wave shifted Cerenkov radiator to heavy ions

The response of Pilot 425 to heavy ions with energies less than 600 MeV/amu beta approximately 0.8 is examined both theoretically and experimentally. Measurements are presented from an experiment which employed a Ne-20 beam at many energies below 575 MeV/amu. The signal is assumed to come from three sources: (1) Cerenkov light from the heavy ion, (2) Cerenkov light from secondary electrons, and (3) scintillation of the radiator. It is found that the effective index of refraction is 1.518 and that scintillation is present at a level of approximately 2.7 percent of the Cerenkov signal for beta = 1 for Ne-20. The first of these values differs from values previously quoted in the literature

Ozone Treatment of Initial Lesions

Karijes je bolest tvrdoga zubnog tkiva za koji je da bi nastao potrebno nekoliko čimebnika od kojih su najvažniji domaćin (zub), uzročnik (mikroorganizmi), utjecaj okoline i vrijeme. Razvojem tehnologije uvedene su nove suvremene metode dijagnostike karijesnih lezija. Među njima važno mjesto zauzima laserska fluorescencija. Usporedno s razvojem dijagnostike klasično “Blackovo načelo” preparacije kaviteta u terapiji karijesnih lezija ispunom zamijenila je ponajprije koncepcija “minimalno invazivne atraumatske stomatologije”, a nedavno je u svrhu terapije karijesa uporabljen i ozon. Baktericidni i dezinfekcijski učinak ozona omogućio je novu koncepciju “bezbolne terapije” karijesnih lezija.Caries is a disease of hard dental tissue caused by the following factors: host (the tooth), cause (microorganisms), environmental influence and time. With improved technology new, contemporary, methods of diagnosing caries lesions have been introduced, one of the most important being laser fluorescence. Parallel with the development of new diagnostic methods, the classical “Black’s principle” of cavity preparation, was replaced, first with “minimally invasive non-traumatic dentistry”, and more recently with “ozone therapy”. Bactericide and disinfective properties of ozone enabled a new concept of “painless therapy” in treatment of caries lesions

Investigating reciprocity failure in 1.7-micron cut-off HgCdTe detectors

Flux dependent non-linearity (reciprocity failure) in HgCdTe NIR detectors with 1.7 micron cut-off was investigated. A dedicated test station was designed and built to measure reciprocity failure over the full dynamic range of near infrared detectors. For flux levels between 1 and 100,000 photons/sec a limiting sensitivity to reciprocity failure of 0.3%/decade was achieved. First measurements on several engineering grade 1.7 micron cut-off HgCdTe detectors show a wide range of reciprocity failure, from less than 0.5%/decade to about 10%/decade. For at least two of the tested detectors, significant spatial variation in the effect was observed. No indication for wavelength dependency was found. The origin of reciprocity failure is currently not well understood. In this paper we present details of our experimental set-up and show the results of measurements for several detectors.Comment: 11 pages, 10 figures, to appear in " Astronomical Telescopes and Instrumentation: High Energy, Optical, and Infrared Detectors for Astronomy IV", Proceedings of SPIE Vol. 774

High resolution Cerenkov and range detectors for balloon-borne cosmic-ray experiment

A combination of an active Cerenkov detector and passive range detectors is proposed for the high resolution measurement of isotopic composition in the neighborhood of iron in the galactic cosmic rays. A large area (4,300 sq cm) Cerenkov counter and passive range detectors were tested. Tests with heavy ions (2.1 GeV/amu C-12, 289 MeV/amu Ar-40, and 594 MeV/amu Ne-20) revealed the spatial uniformity of response of the Cerenkov counter to be better than 1% peak-to-peak. Light collection efficiency is independent of projectile energy and incidence angle to within at least 0.5%. Passive Lexan track recorders to measure range in the presence of the nuclear interaction background which results from stopping particles through 0.9 interaction lengths of matter were also tested. It was found that nuclear interactions produce an effective range straggling distribution only approximately 75% wider than that expected from range straggling alone. The combination of these tested techniques makes possible high mass resolution in the neighborhood of iron

Digital Holographic Interferometry - A New Method for Measuring Polymerization Shrinkage of Composite Materials

Polimerizacija kompozitnih materijala smatra se iznimno važnim čimbenikom dugotrajnosti kompozitnog ispuna. Kakvoća polimerizacije utječe na fizičko-mehanička svojstva, stabilnost boje, volumetrijske promjene restoracije te na biokompatibilnost samoga materijala. Neizbježna posljedica stvrdnjavanja kompozitnih materijala jest polimerizacijsko skupljanje. Iznos polimerizacijskoga skupljanja do sada se je mjerio s viπe različitih postupaka. Digitalna holografska interferometrija, opisana u ovome radu, jedini je postupak koji omogućuje da se izravno prati polimerizacijsko skupljanje u svakoj sekundi osvjetljavanja kompozitnog materijala. Vrijednosti polimerizacijskoga skupljanja dobivene ovim postupkom u okviru su veličina polimerizacijskoga skupljanja izmjerenih drugim postupcima.Polymerization of composite filling is considered to be an important factor in achieving longevity of the restorative treatment. Quality of the polymerization influences physico-mechanical characteristics, color stability, volumetric changes of restoration and biocompatibility of the material itself. Polymerization shrinkage is an unavoidable consequence of setting of the composite material. So far, it has been measured by several different methods. Digital holographic interferometry, a method described in this study, is the only procedure that enables direct monitoring of the polymerization shrinkage for every second of polymerization of the composite material. Values of the polymerization shrinkage obtained by this method correspond with the values obtained by other methods

Esthetic Reconstruction of the Incisal Edge of Upper Central Incisors

Oštećeni incizijski bridovi središnjih gornjih sjekutića smatraju se značajnim i razmerno složenim problemom u restorativnoj stomatologiji zbog minimalnoga stupnja oštećenja, složenih estetskih zahtijeva te zbog osiguravanja dugotrajnosti provedene rekonstrukcije. Za opskrbu incizijskih defekata postoji niz tehnika. Među njima je najmanje invanzivna izravna tehnika kompozitnim smolama. Svrha rad bila je prikazati jednu od mogućnosti rekonstrukcije traumom oštećenog incizijskoga brida. Pacijent K.R., u dobi od 22 godine, imao je nakon udarca tvrdim predmetom frakture cakline i dijela dentina na incizijskome bridu. Prijašnji restorativni zahvat nije bio odgovarajući pa se proveo nov postupak uporabom Artemis (Vivadent, Schaan, Liechtenstein) mikrohibridnoga kompozitnoga materijala s paletom estetskih nijansi za stimuliranje cakline, dentina i posebnih efekata. Opakne nijanse boja stimulirale su izgubljeni dentin, prozirne caklinske boje caklinu, a mamelonske i jasne transparentne boje posebne efekte. Rekonstrukcija je provedena u slojevitoj tehnici uz uporabu instrumenata za plasticiranje i odgovarajućih kistova uz polimerizaciju svakoga sloja posebno.Damaged incisal edges of the upper central incisors are considered to be an important as well as a relatively complex problem in restorative dentistry because the degree of damage is minimal yet esthetical demand provision of long-lasting reconstruction complex. There are several techniques for provision of incisal defects, the least invasive being direct technique with composite resins. The purpose of this study was to present one of the possibilities for reconstruction of trauma damaged incisal edge. A 22 year old patient after being strike by a hard object, sustained fractures od enamel and part of the dentin on the incisal edge. Previously performed restorative treatment was not satisfactory, so a new procedure was undertaken, using Artemis (Vivadent, Schaan, Liechtenstein) microhybrid composite material with a wide spectrum of shades for enamel and dentin simulation as well as special effects. Opaque shades of colours simulated lost dentin, transparent enamel shades enamel, and mammelon and clear transparent shades special effects. Reconstruction was performed in layer technique with the use of instruments for plasticizing including responding brushes and polymerization of each layer separately

Constraints on the Intergalactic Transport of Cosmic Rays

Motivated by recent experimental proposals to search for extragalactic cosmic rays (including anti-matter from distant galaxies), we study particle propagation through the intergalactic medium (IGM). We first use estimates of the magnetic field strength between galaxies to constrain the mean free path for diffusion of particles through the IGM. We then develop a simple analytic model to describe the diffusion of cosmic rays. Given the current age of galaxies, our results indicate that, in reasonable models, a completely negligible number of particles can enter our Galaxy from distances greater than $\sim 100$ Mpc for relatively low energies ($E$ $< 10^6$ GeV/n). We also find that particle destruction in galaxies along the diffusion path produces an exponential suppression of the possible flux of extragalactic cosmic rays. Finally, we use gamma ray constraints to argue that the distance to any hypothetical domains of anti-matter must be roughly comparable to the horizon scale.Comment: 24 pages, AAS LaTex, 1 figure, accepted to Ap