Surface roughness modeling of CBN hard steel turning

Study in the paper investigate the influence of the cutting conditions parameters on surface roughness parameters during turning of hard steel with cubic boron nitrite cutting tool insert. For the modeling of surface roughness parameters was used central compositional design of experiment and artificial neural network as well. The values of surface roughness parameters Average mean arithmetic surface roughness (Ra) and Maximal surface roughness (Rmax) were predicted by this two-modeling methodology and determined models were then compared. The results showed that the proposed systems can significantly increase the accuracy of the product profile when compared to the conventional approaches. The results indicate that the design of experiments modeling technique and artificial neural network can be effectively used for the prediction of the surface roughness parameters of hard steel and determined significantly influential cutting conditions parameters

Isolation of Active Substances from the Seeds of the Milk Thistle Plant (Silybum marianum) and Determination of Antioxidant Activity

Opisana je izolacija silimarina, smjese dobro definiranih flavonolignana, iz sjemena biljke sikavice (Silybum marianum). Silimarin je ekstrahiran acetonom iz deoleinizirana sjemena bez zagrijavanja. Iskorištenje je iznosilo Y = 4,1 %. Antioksidacijska aktivnost silimarina određena je na sobnoj temperaturi kolorimetrijski 2,2-difenil-1-pikrilhidrazilom (DPPH) pri λ = 515 nm. Aktivnost je određena na temelju smanjenja apsorbancije, kao rezultat promjene boje DPPH iz purpurne u žutu. Dobiveni rezultati pokazuju da je askorbinska kiselina znatno jači antioksidans od ispitivana silimarina, ali je silimarin znatno jači hvatač radikala DPPH od standarda silibinina.Isolation of silymarin, a mixture of well-defined flavonolignans, from the seeds of milk thistle (Silybum marianum) was achieved. Silymarin was extracted from defatted seed with acetone without heating; the yield was Y=4.1 %. The antioxidant activity of silymarin was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydrazyl (DPPH) colorimetry with a detection scheme at λ= 515 nm. The activity was evaluated by the decrease in absorbance as the result of a DPPH radical color change from purple to yellow. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than silymarin, but silymarin was a significantly stronger quencher of DPPH radical than the standard silibinin

Intenzitet habanja kod različito toplinski poboljšanog nodularnog lijeva

In the paper we investigate the relationship between the wear intensity of two nodular cast irons and their heat treatment conditions. Disks tempered by austempering and isothermal procedure were used. The wear test was realized by using Pin and Disk tribometer. Measurement of the disks wear, after the contact for duration of 30 min, was done by the PQ meter. The quantity of the wear products in lubricant is determined by the PQ index. The best wear resistance posses the disk isothermally tempering with 30 minutes holding at 390 °C temperature.U ovom radu je ispitivana zavisnost između intenziteta habanja dva nodularna lijeva kao i uvjeta pri njihovoj toplinskoj obradi. Uzorci za ispitivanje nodularnog lijeva su bili poboljšani klasičnim i izotermalnim postupkom. Ispitivanje intenziteta habanja je realizirano uz pomoć Pin on Disc tribometra. Mjerenje pohabanosti diska, nakon trenja u trajanju od 30 minuta, je obavljeno na PQ metru. Količina čestica nastalih kao produkti habanja, u sredstvu za hlađenje i podmazivanje je određena PQ indexom. Najveću otpornost na habanje posjeduje disk izotermalno temperovan na 390 °C u trajanju od 30 minuta

Utjecaj mikrostrukture na proces nastajanja strugotine za konvencionalnu i polutekuću lijevanu Al-Cu leguru

For many metal alloys, the process of metal cutting is accompanied by extensive plastic deformation and fracture. To study this process, quick stop sectional samples of hypoeutectic Al-Cu alloy chip formation, either as conventionally cast alloy or as “semi solid metal” are used. The type of chip formation is classified according to crack formation mechanism and propagation. During cutting, in all specimens used, quasi-continuous chips with built-up edge (BUE) are obtained. The formation of BUE is undesirable since it is a highly deformed body with a semi stable top which periodically breaks away giving rise to poor workpiece surface quality.Za mnoge metalne legure, proces rezanja je praćen intenzivnom plastičnom deformacijom i lomom. Za istraživanje tog procesa u radu je korištena metoda brzog zaustavljanja procesa rezanja. Materijal uzorka je podeutektička Al-Cu legura, lijevana konvencionalno i kao „polu čvrsti metal“ (semi solid metal-SSM). Vrsta strugotine koja je obrazovana klasifi cirana je prema mehanizmu nastajanja i širenja pukotina. Tokom rezanja, u svim uzorcima nastajala je, kvazi-kontinuirano strugotina sa naslagama (BUE). Stvaranje BUE je nepoželjan proces, jer je to jako deformirani volumen sa polu stabilnim oblikom, koji povremeno raste i odvaja se, što dovodi do lošeg kvaliteta obrađene površine

The microstructure infl uence on the chip formation process of Al-Cu alloy cast conventionally and in semi solid state

For many metal alloys, the process of metal cutting is accompanied by extensive plastic deformation and fracture. To study this process, quick stop sectional samples of hypoeutectic Al-Cu alloy chip formation, either as conventionally cast alloy or as “semi solid metal” are used. The type of chip formation is classifi ed according to crack formation mechanism and propagation. During cutting, in all specimens used, quasi-continuous chips with built-up edge (BUE) are obtained. The formation of BUE is undesirable since it is a highly deformed body with a semi stable top which periodically breaks away giving rise to poor workpiece surface quality

Stanje površinskog sloja materijala obratka kod visokoučinskog brušenja

This paper focuses on the development of high temperatures in the cutting zone during high performance grinding. In order to identify the influence of grinding temperature on surface integrity, temperatures were measured in the workpiece surface layer under different machining conditions. Beside this, under the same conditions, the surface layer properties of the workpiece material were determined through metallographic examination. Microstructureand microhardness of the workpiece surface layer, as well as the burned surfaces and microcracks phenomena were investigated. The conducted experimental investigations allow the surface layer properties of the workpiece material in high performance grinding to be defined.U članku se ukazuje na pojavu visokih temperatura u zoni rezanja pri visokoučinskom brušenju. Da bi se ustanovio utjecaj temperature brušenja na kvalitet obrađene površine, izmjerene su temperature u površinskom sloju materijala obratka pri različitim uvjetima obrade. Ujedno je pri istim uvjetima obrade određeno stanje površinskog sloja materijala obratka metalografskim ispitivanjima. Ispitane su mikrostruktura i mikrotvrdoća površinskog sloja obratka i pojava nagorjelih površina i mikropukotina. Izvedena eksperimentalna istraživanja defi niraju stanje površinskog sloja materijala obratka kod visokoučinskog brušenja

Kineziographic Research of Patients with Cross Bite

The paper describes the use of an objective method for the quantitative analysis of the relationship between the posterior cross-bite and the occurrence of occlusive interferences and damages to the mandible muscle elevator. Two groups of subjects were selected for the analysis: 10 patients with unilateral cross-bite and 10 students without any symptoms of temporomandibular disorders (TMD). By means of the Robert Jenkelson K5A kinesiograph we measured maximal – opening velocity of the mandible (mm/s), maximal- closing velocity (mm/s), first tooth contact velocity and displacement in the vertical plane at the maximal intercuspidation (mm). The following values were obtained: maximal-opening velocity in the first group was 349 mm/s and 380 mm/s in the control group. This difference was incidental. The maximal closing velocity in the study group was 204.9 and 345.2 in the control group (p < 0.05). The first tooth contact velocity in the study group was 75.93 and 325 in the control group (p < 0.01). Displacements in the vertical plane at the maximal intercuspidation in the investigated group was 0.240.01 mm, while in control group that value was 0120.012 mm

Influence of Smoking on the Stomatognathic System in Women With Diabetes

Šećerna je bolest metabolička bolest koja nastaje kao posljedica poremećaja u stvaranju i lučenju inzulina ili njegovu djelovanju. Kod tako oslabljena organizma pušenje duhana vjerojatno više oštećuje stomatognati sustav nego u zdravih osoba. Žene s potvrđenom dijagnozom šećerne bolesti (N = 90) podijeljene su u dvije skupine: žene fertilne dobi (N = 51) te žene u menopauzi i postmenopauzi (N = 39). Sve su žene ispunile anketni list s općim podatcima i pitanjem o pušenju. Izvršen je klinički pregled s pomoću stomatološkoga zrcala i parodontne sonde. Vrjednovan je klinički nalaz zubnoga statusa, gingive i parodonta (indeks krvarećeg sulkusa i dubina parodontnih džepova) te stanje oralne sluznice. Pušenje nije statistički znatno utjecalo na zubni status ni u fertilnih žena ni u žena u menopauzi i postmenopauzi. (p > 0,05). Klinički nalaz gingive i parodonta statistički se znatno razlikovao samo u žena u menopauzi i postmenopauzi (*p 0,05). Klinički nalaz oralne sluznice analiziran je samo u dobnoj skupini menopauza i postmenopauza. Razlika je bila statistički znatna (*p < 0,05). U skupini fertilnih žena raščlamba nije izvršena zbog premalog broja podataka. Oslabljeni imunološki sustav zbog zajedničkoga djelovanja šećerne bolesti, pušenja i nedostatka ženskih spolnih hormona (u menopauzi i postmenopauzi) znatno oštećuje oralnu sluznicu, gingivu i parodont. Vjerojatni razlog tomu je njihova čvrsta povezanost osobito hematogenim putem s ostalim dijelovima organizma. Pušenje nije znatno utjecalo na tvrda zubna tkiva vjerojatno zbog njihove anorganske naravi i kompaktnosti građe.The aim of the study was to check the influence of smoking on the stomatognathic system in women with diabetes. Diabetes is metabolic disease that occurs as a result of disorders in creation or secretion of insulin, or its effect. On a weakened organism smoking will probably do more harm on the stomatognathic system then on a healthy one. Women with confirmed diagnosis of diabetes (N = 90) were divided into 2 groups: fertile women (N = 51) and women in the menopause and postmenopause (N = 39). All women completed the given paper forms on general data and their smoking habits. A clinical examination was performed using a stomatological mirror and parodontal probe. Clinical findings of the dental status, gingiva, parodontal tissue (bleeding sulcus index and depth of parodontal pockets) and the status of oral muscosa were evalued. Smoking did not show statistically significant influence on the dental status either on fertile women or on women in the menopause and postmenopause (p > 0.05). Clinical findings of the gingiva and parodontal tissue showed statistically significant difference in women in the menopause and postmenopause (*p 0.05). Clinical findings of oral muscosa were only analyzed in the age group of menopausal and postmenopausal women. The difference was statistically significant (*p < 0.05). In the group of fertile women analysis was not performed due to the small number of specimens. Weakened immunological system due to the synergistic influence of diabetes, smoking and the lack of feminine sex hormones (in the menopause and postmenopause) significantly damages oral muscosa, gingiva and parodontal tissue. The probable explanation was their firm correlation especially throughtout the blood circulation with the other parts of the organism. Smoking did not significantly influence the hard dental tissue, probably because of its inorganic origin and compact structure

Molecular Imaging Mass Spectrometry

Molecular imaging mass spectrometry (IMS) is a recently developed method for direct determination of spatial distribution of biopolymers, preferably proteins on cell surface and tissues. Imaging mass spectrometry data are mainly based on Matrix-Assisted Laser Desorption/Ionization- Time of Flight (MALDI TOF). The MALDI TOF based imaging mass spectrometry was applied for determination of changes in kidney tissue of sensitive mice after poisoning with aristolochic acid I. The second application presented here were changes in the gastric tissue in mice after infection with Helicobacter pylori, as a model of gastric cancer in humans caused by this pathogen microorganism. Molecular imaging mass spectrometry can be applied in medicine, mostly for identification of candidate biomarkers for malignant and non-malignant diseases. Furthermore, imaging MS has almost unlimited capacity in agriculture, food technology and biotechnology, e. g. for monitoring, process development and quality control of manufactured tissue of animal, plant and microbial origin.Razvoj masene spektrometrije u posljednjih 20 godina i primjena ove metode u analitici makromolekula, prije svega proteina i ugljikohidrata, otvorio je nove perspektive za uporabu ove metode u medicini, biotehnologiji i ostalim biodisciplinama. Ova se metoda može primijeniti i u novim područjima, kao što su mikroelektronika, geokemija i površinska analitika, posebice nanotehnologija.1 Imaging mass spectrometry (IMS) je jedna vrsta sinteze dviju tehnika, histokemije i masene spektrometrije. Ova metoda omogućava optički prikaz rasporeda raspodjele malih i velikih molekula u uzorku, pa čak i makromolekula kao što su proteini i polisaharidi. 2 Optimalizacija masene spektrometrije, ali također i veliki napredak u razvoju instrumentacije dodatni su razlog za sve veći interes za ovu metodu u mnogim interdisciplinarnim područjima medicine, biotehnologije, ali ianorganskim tehnologijama i znanosti o materijalima (material science).1 Imaging MS daje mogućnost izravnog praćenja prostorne raspodjele molekula u stanicama ili tkivu. Za dobivanje molekularne distribucije u adekvatno pripravljenom uzorku najčešće se primjenjuju Matrix-Assisted Laser Deionisation (MALDI) Time of Flight (TOF) ili Secondary Ion Mass Spectrometry (SIMS)4. Pomoću MALDI TOF dobiva se slika prostorne raspodjele velikih molekula, prije svega proteina. Rezolucija ove metode je 25 μm, što je još uvijek nedovoljno da se prati raspored komponenata na razini stanice, ali novi instrumenti omogućavaju i bolju rezoluciju u području od oko 10 μm. SIMS je metoda koja se primjenjuje za praćenje prostorne raspodjele malih molekula, najčešće biološki aktivnih supstancija. 1,5,6 MALDI TOF je pak metoda izbora za analizu prostorne distribucije makromolekula, najčešće proteina i polipeptida. IMS se do sada primjenjivala za patološke studije i analizu biomarkera,3,7-10 za analizu tumora, kao glioblastoma,3 karcinoma debeloga crijeva,11 metastaza u jetri,12 kod praćenja promjena u moždanom tkivu kod Alzheimerove bolesti10 i ostalih promjena u živčanom tkivu,14 kod nefrotoksiciteta13 itd. Na sl. 1 prikazan je princip određivanja raspodjele makromolekula pomoću MALDI TOF masene spektrometrije. Nakon rezanja tankog sloja i fiksiranja, tkivu se dodaje određena supstancija (matrix) koja omogućava optimalnu ionizaciju i mobilizaciju makromolekula. Vrijeme letenja (time of flight) je obrnuto proporcionalno vrijednosti kvocijenta fragmentirane mase i (pozitivnog) naboja m/z. Računalo automatski upravlja sveobuhvatnim snimanjem površine (screening) i daje površinsku sliku rasporeda molekule određene m/z vrijednosti. To se vidi i na slici 4 koja daje raspodjelu molekule s m/z vrijednosti od 7.791 u uzorku bubrega miša otrovanog aristolohijskom kiselinom I (AA I). Na slici 4 je prikazan raspored triju različitih molekula u istim uzorcima. Model miša tretiranog s AA I i AA II je izoliran jer postoje opravdani pokazatelji da je kronično trovanje ovom suspstancijom jedan od uzroka endemskog nefritisa (EN). Endemski nefritis je kronično oboljenje bubrega, proširen u endemskim područjima u donjem toku rijeke Dunava. U Hrvatskoj se ova bolest pojavljuje u određenim selima Brodske Posavine zapadno od Slavonskog Broda. Bakterija Helicobacter pylori je uzročnik infekcije želuca, koja dovodi do kroničnoga gastritisa i, godinama nakon infekcije, do karcinoma. Model miša, inficiranog s Helicobacter pylori pokazuje da 15 dana nakon infekcije dolazi do promjene u raspodjeli proteina, i da protein s m/z vrijednosti 9,962 gotovo nestaje s maseno-spekrometrijskog profila. Ovi pokusi su prvi koraci u definiranju molekulskih promjena kod karcinogeneze želuca, definiciji novih biomarkera za otkrivanje rizika i prognozu kod ove zloćudne bolesti. - IMS je tehnika kojom se kombinira histologija i masena spektrometrija MALDI TOF. - IMS trenutačno nalazi primjenu u medicini, za identifikaciju kandidata za biomarkere za maligne i druge bolesti. - Kao tehnika, imaging mass spectrometry ima velike perspektive za primjenu u agrikulturi, prehrambenoj tehnologiji i biotehnologiji i to za kontrolu kvalitete i praćenja promjena u biljnim, životinjskim tkivima i mikrobnim stanicama tijekom procesa proizvodnje

Anterior Tooth Relationship in Cuspid Protected and Group Function Occlusion

OBJECTIVE OF INVESTIGATION: The aim of the study was to determine anterior tooth relationship (overbite and overjet) according to the type of occlusion (canine guided, group function). METHODS: A total of 111 test subjects (56 men and 55 women, mean 23.9 years of age) were examined, and it was determined that they have occlusional conception. The relationship of the front teeth in the position of maximum intercuspidation was evaluated by a portable meter. RESULTS: By analysing the obtained results of vertical overjet and horizontal overbite of the front teeth, we concluded that there was significant statistic difference in the amount of the vertical overjet with regard to occlusional conception (t=6.669, p=0.00001). Average value of the vertical overjet in examinees with occlusion lead by the canine was 2.22+0.09 mm, while in examinees with group function it was 1.58+0.26 mm. No significant statistical difference was found by analysing vertical overjet with regard to gender. No significant statistical difference between the groups was found by comparing the results of horizontal overbite of frontal teeth with regard to occlusional concepcion and gender. Average value of horizontal overjet was 1.62+0.29 mm. CONCLUSION: Subjects with canine guided occlusion have significantly and statistically bigger overjet of frontal teeth