17 research outputs found
Estimation of Standards for Gold and Silver Sampling
U protetskoj se terapiji upotrebljava vrlo mnogo plemenitih
slitina razliÄita sastava. Plemeniti metali su sinonim za biokompatibilnost. Zlato je jedna od najinertnijih plementih kovina, a srebro jedna od najreaktivnijih.
Cilj rada bio je razvijanje i raÅ”Älamba kromatografskih mrlja Äistoga zlata i srebra (Aurodent, Celje, Slovenija).
Kovine su uzorkovane na sobnoj temperaturi otopinom voda-HCl(conc.) (v/v 10:1) tijekom 10 s pri stalnom naponu struje od 4,5 V. Otopine kationa iz Äistih kovina i 10 Āµl standardnih otopina soli nanesene su na HPTLC kromatografske ploÄe (Merck, Darmstadt, NjemaÄka) 10 x 10 cm presvuÄene celulozom. PloÄe su razvijene u staklenoj kromatografskoj komori zasiÄenoj mobilnom fazom izo-amilni alkohol: HCl(conc.) : acetonitril u omjeru 5,4 : 4,3 : 0,3
do visine od približno 8 cm. Kada su razvijene suÅ”ene su u struji vruÄega zraka, a kationi su vizualizirani prskanjem zasiÄenim etanolnim otopinama difenilkarbazida, alizarina, kvercetina te 0,1% otopinom ditizona u kloroformu. Nakon prskanja i suÅ”enja ploÄe su izložene parama amonijaka i uÄinjena je vizualizacija.
Uzorkovano zlato i srebro meÄusobno se razlikuje bojom kromatografskih mrlja i utvrÄenim Rf vrijednostima. Metodom anodnoga uzorkovanja slitina i identifikacijom kationa tankoslojnom kromatogafijom moguÄe je dokazati postojanje odreÄenih kationa s udjelom mase veÄim od 1%, ne oÅ”teÄujuÄi pritom sam uzorak. Metoda se pokazala prikladnom za uzorkovanje kovina zlata i srebra,
Å”to je nastavak dosadaÅ”nih istraživanja u identifikaciji odreÄenih sastavnica u pojedinim slitinama ili u inkorporiranome protetskom radu.Different precious dental alloys are used in prosthodontic therapy. Precious metals are the synonym for biocompatibility. Gold is one of the most inert and silver the most active presious metals.
The purpose of this study was to develop an analyze the chromatographic spots of pure gold and silver (Aurodent, Celje, Slovenia).
The sampling was performed in a water-HCl(conc.) solution in a 10 : 1 volume ratio at room temperature using a 4,5 V battery. Dissoluted cations and solutions of standard elements (salts of gold and silver) were applied to HPTLC plates (Mareck, Darmstadt, Germany) 10 x 10 cm precoated with cellulose. Plates were developed in a vertical
separating chamber to a height of approximately 8 cm saturated with iso-amyl (3.methyl-1-butanol) - HCl (36,5%) - acetonitrile in a volume ratio 5,4 : 4,3 : 0,3. After development, plates were dried in (a steam of) hot air and the cations were visualized by spraying with the saturated ethanolic solutions of alizarin, diphenylcarbazide,
quercetin and 0,1% chlorophorm solution of dithizone. After drying, plates were exposed to NH3 vapor.
According to the Rf value and the color of the spots, the difference between gold and silver were obtained.
Anodic sampling with thin-layer chromatography is a suitable, nondestructive method for identification of cations presents in different dental alloys. It is possible to identify the cations with their mass ratio W > 1%. The results have shown that the described method is suitable for analysis of gold and silver and it can be used in future work to identify those cations in dental alloys of unknown
composition
Hydropyrimidines. V. Isomeric Dihydro 2- and 4-0xopyrimidines
Desulfurization of, thio analogs of 5,f.-dihydrouracil and partial
hydrogenation of oxopyrimidines* were investigated as synthetic
routes for the preparation of isomeric dihydropyrimidines.
The synthesis of unstable 1-methyl-5,6-dihydro-4-oxopyrimidine
(IX) from 1-methyl-5,6-dihydro-2-thiouracil (X) is described.
Desulfurization of 5,6-dihydro-2-thiouracil (XV) and its 3-methyl
derivative (XI) afforded the corresponding dihydro-4-oxo-pyrimidines
XVI and XII having the double bond at 1V.2 position. The
structures of XII and XVI were confirmed by hydrogenation to the
tetrahydro compounds XVII and XIII.
The more stable dihydro-2-oxopyrimidines III, IV and XIX were
prepared from the corresponding 4-thiouracils XX, XXI and
XVIII. The NMR spectra of 2- and 4-oxopyrimidines, their dihydro
and tetrahydro derivatives as well as of 5,6-dihydrouracil and its
thio analogs are discussed
Relationship Between Orthodontic and Articulatory Impairments in Adolosecents
RazliÄita su istraživanja pokazala da je broj izgovornih poremeÄaja veÄi u populaciji s ortodontskim anomalijama nego u osoba bez njih. Odnos izmeÄu anatomskih struktura u orofacijalnoj regiji i izgovornih kompenzacijskih mehanizama u osoba s ortodontskim anomalijama zanimljiv je i s teoretskoga i s praktiÄnoga stajaliÅ”ta. U ovom je istraživanju na uzorku od 282 srednjoÅ”kolca (203 - 72% djevojaka i 79 - 28% djeÄaka) u dobi od 15 do 18 godina istražen odnos izmeÄu ortodontskih i izgovornih poremeÄaja. Procjenom ortodontskog i izgovornoga statusa , koju je uÄinilo dvoje specijalista, svaki za svoje podruÄje, dobiveni su sljedeÄi postotci ortodontskih anomalija: primarna kompresija - 43,6%, otvoreni zagriz - 11,0%, pokrovni zagriz - 8,5% , progenijski kompleks - 5,7%, križni zagriz - 3,5%, diastema medijana - 0,0%. TakoÄer je naÄeno 41,4% ispitanika s kratkim frenulumom linguae i 25,2% s gotskim nepcem. Izgovorni su poremeÄaji registrirani u sljedeÄim postotcima: sigmatizam - 64,9%, rotacizam- 36,5% i lambdacizam - 39,0%. Ukupno 78% ispitanika imalo je ortodontske anomalije, a 72% izgovorne poremeÄaje, a njih je 52% imalo kombinirane ortodontske i izgovorne poremeÄaje. Samo je 9% ispitanika bilo s urednim ortodontskim i izgovornim statusom. TakoÄer je pokazano da su sve tri kategorije izgovornih poremeÄaja najviÅ”e povezane s primarnom kompresijom (oko 30%), praÄeno s kratkim frenulumom linguae (oko 30%) i gotskim nepcem (od 15 do 20%). TakoÄer je oÄito da postoji 19% ispitanika koji imaju ortodontsku anomaliju ali i normalni izgovorni status, Å”to potvrÄuje da su oni razvili djelotvorne kompenzacijske izgovorne mehanizme. S druge strane, postoji 13% ortodontski normalnih ispitanika koji imaju izgovorne poremeÄaje, uzrokovane nekim drugim razlozima a ne ortodontskim statusom. Iako postoji jaka povezanost izmeÄu ortodontskih i izgovornih poremeÄaja, moguÄe je zakljuÄiti da njihov odnos nije neposredan ta da se drugi psiholingvistiÄki, razvojni, neurogeni i ostali parametri moraju uzeti u razmatranje u daljnjem objaÅ”njenju toga odnosa.Various investigations have shows that the number of articulatory impairments is greater in a population with orthodontic anomalies than in eugnathic subjects. The relationship between anatomic structures in the orofacial region and articulatory compensatory mechanisms in persons with orthodontic anomalies is interesing from the theoretical and practical point of view. In the present investigation on a sample of 282 high school adolescents (203 - 72% male and 79 - 28% female) aged from 15 to 18 years the relationship between orthodontic and articulatory impairments was investigated. Assessment of the orthodontic and articulatory status, judged two specialists in the fields, showed the following percentages of orthodontic anomalies : primary compression -43,6%, open bite - 11,0%, closed bite -8,5%, progenia complex -5,7%, cross bite 3,5%, diastema media - 0,0%, short frenulum linguae - 41,5%, gothic palate -25,2% and tthe following percentages of ariculatory impairments: sigmatism - 64,9%, rhotacism - 36,5% and lambdacism - 39,9%. 78% of the subjects had orthodontic anomalies and 72% had articulatory impairments while 52% had combined orthodontic and articulatory impairments and only 9% were eugnathic subjects with normal articulatory status. It was also show that all three categories of articulatory impairments are mostly combined with primary compression (approximately 30%) accompanied by short frenulum linguae (approximately 30%) and gothic palate (approximately 15 to 20%). It is also obvious that there are 19% of subjetcts with orthodontic anomalies who have normal articulatory status, meaning that they developed efficient compensatory mechanisms in articulation and also that there are 13% of eugnathic subjects who have articulatory imapirments, consequently, caused by some other reasons and not by the orthodontic status. Although there is a strong connection between orthodontica and articulatory characteristics it can be concluded that the relationship between them is not straight forward and that other psycholinguistic, developmental, neurogenic and other parameters should be taken into consideration in further explication of that relationship
Group tonal audiometry
Iznosi se važnost sistematskih audioloÅ”kih pregleda Å”kolske populacije i, osobito, radnika koji rade u buci. Opisuje se jedan novi postupak grupnog tonalnog audiometriranja koji se u dosadaÅ”njem iskuÅ”avanju pokazao koliko jednostavan i jeftin toliko osjetljiv i efikasan. Tim se postupkom ne samo pouzdano selekcioniraju mali i parcijalni sluÅ”ni gubici nego se odmah dobija i orijentacijska slika tonalnog audiograma.Systematic examinations of hearing are indispensable especially when the populations of school children and workers exposed to noise are concerned. The latter should undergo regular check-ups every three to six months at the beginning and later at least once a year. So far this has been the only reliable method of discovening excessive sensitivity to noise and protecting workers from noise before their hearing is considerably impaired. As such audio-logical check-ups are rather expensive they are undertaken for the time being only for demonstration and research sake and do not make part of a routine procedure. The existing group audiometry which is baked on signals-numbers is not very useful for such systematic check-ups; it has two shortcomings: a) it does not register small and partial defficiencies typical for the initial stage of a hearing impairment and b) it does not provide us with a tonal audiogram on which audiology has based its criteria for the interpretation of the hearing status. This was the reason why we made up a kind of group tonal audiometry. While experimenting with this new procedure we realized that it was as simple to carry out as it was sensitive and efficient. The time usually needed for individual audiometry is here shortened up to fifty times: the whole testing procedure lasts about 25 minutes and about SO people can be tested at a time. The equipment needed for this new audiometry is extremely simple: a tape-recorder, a test-tape and a test-form (Fig. 1). On the test-tape are recorded the same (pure tone) signals the routine tonal audiometry uses (250, 500, 1 000, 2 000, 4 000, 6 000, 8 000 cycles). Each of these tones is recorded at seven different intensity levels (50 dB above the threshold, 40 dB, 30 dB, 20 dB, 10 dB, 5 dB and O dB). The decision on the number of impulses (1, 2 or 3) in each item is left to chance. The examinee is supposed to draw as many lines on the paper as there are impulses he can perceive. In case he does not make any mark or draws the wrong number of lines it will mean that he did not hear (Fig. 1). Before each signal is heard the number corresponding to the numbers on the form will be announced. This kind of audiometry can be carried out in any room or hall (classroom, conference hall etc), the only condition being that the stationary noise level should not exceed 35 phons. The signals are perceived directly from the tape-recorder without earphones. After having listened to the whole of the 12 minute long test the examinees are given the correct answers. They will encircle the wrong answers and make a cross in the Ā»AudiogramĀ«. The audiogram obtained by linking together the crosses is more or less the same as the one obtained in individual testing. It can serve very well not only as a Ā»screeningĀ« test but also as a final picture of the hearing status which is accurate enough to enable a longitudinal observation of the hearing status of workers exposed to noise