Fabrication of bismuth-oxychloride supported carbon paste electrode for sensitive Quinine sensing

Quinine is a natural white crystalline cinchona alkaloid that belongs to the aryl amino alcohol group of drugs, and it has antipyretic (fever reducing), antimalarial, analgesic, anti-inflammatory properties and a bitter taste. Today, quinine is considered as the best antimalarial drug since it is chiefly used in the treatment of falciparum malaria resistant to other antimalarials. Quinine is preferred where the disease has become highly resistant to other antimalarial drugs [1]. Quinine has a low therapeutic index, and it is potentially toxic and causes several side effects including nausea, blurred vision, diarrhea, abdominal pain, headache, fever, renal failure and asthma [2]. Since quinine is widely used as a bittering agent in tonic type drinks, a sensitive and discriminatory system for the discovery of quinine is essential for human health. In this work, a modified bismuth-oxychloride (BiOCl) carbon paste electrode was prepared for the detection of quinine. BiOCl nanoparticles were synthesized by the chemical coprecipitation method. The electrochemical properties of quinine at this electrode were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV). In addition, electrochemical impedance spectroscopy (EIS), inductively coupled plasma–optical emission spectrometry (ICP-OES), transmission and scanning electron microscopy (TEM and SEM) and X-ray diffraction (XRD) were used to characterize the synthesized materials. The prepared electrode showed better electrocatalytic response than the bare carbon paste electrode. After square wave voltammetry (SWV) optimization, the electrode showed a wide linear working range from 20 to 200 μM at pH 6 of Britton–Robinson buffer solution (BRBS) as the supporting electrolyte. The excellent selectivity of the proposed method, with good repeatability and reproducibility, strongly suggests a potential application of the method for the determination of quinine in pharmaceuticals. The practicality with good recoveries indicates that the morphology of the materials is closely related to other parameters, which in turn suggests that the developed approach can provide a cost effective, rapid, selective, and sensitive method for quinine monitoring

Analysis and design of the gas generator multifunctional bulkhead considering the thermal and structural loads

The operation of gas generators brings relatively high thermo-mechanical loads on the gas generator structure. The objective of this article is to determine the operating conditions, in terms of mechanical loads at extremely high temperatures in very limited and narrow space, of a multifunctional bulkhead for application on specific kinds of gas generators with back-to-back rotor concept. The paper contains numerical analysis and experimental investigation for determining the loads and behavior of the structure. Numerical analysis indicates that there is significant influence of the Tesla turbine effect on flow parameters. Also, uneven pressure distribution and significant thermal loads are identified. With experimental investigation and subsequent exploitation tests, it was concluded that the presented methodology identifies the operating conditions, truthfully simulates the bulkhead stress state and deformations and that the presented design solution satisfied all demands. Regarding results obtained by these numerical simulations, the innovative design solution for the multifunctional bulkhead was proposed

Buckling behaviour of dented aluminium alloy cylindrical shell subjected to uniform axial compression

Tankozide cilindrične strukture imaju veoma visoku primenu u industriji. Pošto su obično opterećene na aksijalni pritisak, najčešći uzrok njihovog otkaza je pojava izvijanja. U ovom članku se prikazuje numerička analiza izvijanja tankozide cilindrične strukture izrađene od legure aluminijuma sa imperfekcijom u vidu udubljenja na sredini strukture i eksperimentalna verifikacija rezultata dobijenih tom analizom. Numerička analiza je odrađena pomoću softvera ANSYS 16.2, a eksperimentalna ispitivanja pomoću hidraulične prese Armavir, PSU-50, na kojoj je uzorak podvrgnut aksijalnom pritisku čiji se intenzitet postepeno povećavao do pojave izvijanja. Poređenjem rezultata eksperimenta uočeno je značajno smanjenje vrednosti kritičnog napona na izvijanje između epruveta bez imperfekcije i epruveta sa imperfekcijom od 2 mm, dok su vrednosti kritičnog napona za epruvete sa imperfekcijama od 2 mm i 4 mm približne.Thin-walled cylindrical shells are commonly used in numerous branches of industry. Since they are subjected to axial load, the most common cause of their failure is buckling. This paper provides numerical analysis and experimental verification of the buckling of the thin-walled aluminium alloy cylindrical shell with special regard to the influence of dent, positioned in the middle of the shell. Numerical simulation was performed using ANSYS 16.2, and experimental verification was performed by means of hydraulic press Armavir, PSU-50, which was used to subject the specimen to the increasing axial load until the occurrence of buckling. Comparing the results it was concluded that there is significant decrease of the buckling resistance if compared the values of the specimen with no dent, and the specimen with 2 mm deep dent. On the contrary, resistance of the 2 mm and 4 mm dented specimen is quite similar. Position and shape of the deformations occurred due to buckling are matching if experimental and numerical results are compared

Research of expendable turbojet tubular combustion chamber

This paper presents research related to the tubular combustion chamber of an expendable turbojet. Although annular combustors are dominant at present, tubular combustors are still attractive because they are simpler to produce and require lower amounts of air flow for testing. The objective of this research was to assess the combustor's primary zone configuration, and four configurations were tested to obtain experimental answers for use in future work. The configuration of the combustion chamber is a simple and classic design in line with its expendable purpose. The test methodology was to perform initial testing of the primary and secondary zones under atmospheric conditions using the four configurations, and then to subsequently complete the combustor using the best configuration. The complete combustor was then tested under both atmospheric conditions and working conditions. The results showed that the stability margin was wide enough to cover the combustor's entire working area. The measured efficiency and pressure drop were in very good agreement with the corresponding designed values. The design and testing methodology proposed here could be used for similar scientific and engineering research applications

Immunomodulatory cytokines in carotid disease

Karotidna bolest je aterosklerotsko suženje karotidnih arterija, gde inflamacija igra ključnu ulogu u patološkoj i kliničkoj progresiji razvoja aterosklerotskih plakova. Uprkos toj činjenici, precizni molekulski i ćelijski mehanizmi stvaranja karotidnog plaka i dalje nisu u potpunosti razjašnjeni. U našem istraživanju ispitivali smo serumski nivo IL-10, kao i serumski nivo i tkivnu ekspresiju IL-33 i ST2 receptora u aterosklerotskim plakovima kod pacijenata podvrgnutih operativnom lečenju aterosklerotskog oboljenja karotidnih arterija, karotidnoj endarterektromiji. U studiji su učestvovali pacijenti sa aterosklerotskom stenozom karotidne arterije i zdrave osobe. Serumske koncentracije IFN-γ, TNF-α, IL-6, IL-17, IL-1β, IL-23, IL-18, IL-10, IL-33 i ST2 su određivane ELISA metodom. Takođe, preoperativno su mereni serumski nivoi IL-33 i rastvorljivog ST2 (sST2). Izvršena je histološka klasifikacija aterosklerotskih plakova dobijenih tokom operacije, kao i imunohistohemijska analiza ekspresije IL33, IL-33R, CD68 i alfa-SMA. Prikupljeni su demografski i klinički podaci o pacijentima podvrgnutim operativnom lečenju- pol, starost, pušački status, krvni pritisak, glikemija, nivo hemoglobina i kreatinina, prateći komorbiditeti, nakon čega su poređenja među varijablama statistički analizirana. Pacijenti podrvgnuti endarterektomiji su imali značajno više serumske vrednosti IL-10 u poređenju sa zdravim kontrolama. Pacijenti sa stepenom stenoze karotidne arterije manjim od 70% ili većim od 70% se nisu razlikovali u odnosu na pol, starost, kardiovaskularne rizikofaktore izuzev hipertenzije, neurosimptoma i AHA tipa plaka. Serumski nivo IL-10 se značajno razlikuje između bolesnika sa različitim tipovima aterosklerotskog plaka. Pacijenti sa nekomplikovanim plakom su imali značajno više vrednosti serumskog IL-10 u odnosu na pacijente sa komplikovanim plakom, pa cirkulišući IL-10 može da diferencira bolesnike sa komplikovanim plakovima od onih sa nekomplikovanim plakom. Serumski nivoi IL-33 i sST2 bili su značajno veći u grupi pacijenta podvrgnutih karotidnoj endarterektomiji u poređenju sa zdravim ispitanicima. Pokazali smo obilnu tkivnu ekspresiju IL-33 i ST2 u aterosklerotskim lezijama karotidne arterije. Nivoi ekspresije IL-33 i IL-33R bili su značajno veći kod nestabilnih plakova i značajno koreliraju sa stepenom infiltracije inflamacijskih ćelija u ovim plakovima. Imunohistohemijskom analizom je takođe otkriveno da ćelije odgovorne za ekspresiju IL-33 nisu samo mononuklearne ćelije ograničene na inflamacijske aterosklerotske lezije, već i glatkomišićne ćelije koje su stekle fenotipske karakteristike penastih ćelija i ispunile se lipidnim kapljicama. Dobijeni rezultati potvrđuju značaj IL33/ST2 osovine u procesu ateroskleroze i ukazuju na njenu dvosmislenu funkciju u imunskom odgovoru, bilo kao proinflamacijski citokin u uznapredovalim aterosklerotskim lezijama, ili kao profibrotičan, u ranim fazama lezija. Serumski IL-10 može biti potencijalni biomarker za razlikovanje bolesnika sa karotidnom bolešću od zdravih osoba. Niži nivoi IL-10 su povezani sa prisustvom komplikovanih plakova.Carotid atherosclerosis is manifested by atherosclerotic narrowing of the carotid arteries where inflammation plays a key role in the progression of atherosclerotic plaques. Despite this fact, the precise molecular and cellular mechanisms of carotid plaque formation are still not fully elucidated. The role of IL-10 in carotid disease has not been fully investigated. In our study, we examined serum IL-10 levels, as well as serum levels and tissue expression of IL-33 and ST2 receptors in atherosclerotic plaques in patients undergoing carotid endarterectomy. Patients with atherosclerotic carotid stenosis and healthy controls were enrolled in this study. Serum IFN-γ, TNF-α, IL-6, IL-17, IL-1β, IL-23, IL-18, IL-10, IL-33 and ST2 levels were determined by ELISA. Also, serum levels of IL-33 and soluble ST2 (sST2) were measured preoperatively. Atherosclerotic plaques obtained during surgery were initially histologically classified and immunohistochemical analyzes of IL-33, IL-33R, CD68, and alpha-SMA expression was performed. Demographic and clinical data such as gender, age, smoking status, blood pressure, glycaemia, hemoglobin and creatinine levels and comorbidities were collected and the comparisons between variables were statistically evaluated. Patients undergoing endarterectomy had significantly higher circulating IL-10 levels in comparison with healthy controls and IL-10 has good discriminatory efficacy between these two groups. Patients with 70% of carotid stenosis did not differ in terms of age, sex, cardiovascular risk factors except hypertension, neurosymptoms, and AHA plaque types. Circulating IL-10 levels differed significantly among patients with different carotid plaque types. Patients with uncomplicated plaques had significantly higher serum levels of IL-10 compared to those with complicated plaques. Serum levels of IL-33 and sST2 were significantly higher in the group of patients undergoing carotid endarterectomy compared to healthy subjects. We demonstrated abundant tissue expression of IL-33 and ST2 in atherosclerotic carotid artery lesions. The levels of IL-33 and IL-33R expression were significantly higher in vulnerable plaques and significantly correlated with the degree of inflammatory cells infiltration in these plaques. Immunohistochemical analysis also revealed that cells responsible for IL-33 expression are not only mononuclear cells confined to inflammatory atherosclerotic lesions but also smooth muscle cells which gained phenotypic characteristics of foam cells and were loaded with lipid droplets. The obtained results confirm the importance of IL-33/ST2 axis in the process of atherosclerosis, and indicate its ambiguous function in immune response, whether as proinflammatory cytokine in advanced atherosclerotic lesions or as profibrotic, in early lesions. IL-10 might be a potential biomarker in discriminating patients with carotid disease from healthy controls. Decreased serum levels of IL-10 are related to complicated carotid plaques

Tribological characteristcs of the composite sliding bearings with the polimer as the base material

Osnovna ideja ove disertacije je izrada numeričkog modela habanja kliznih ležaja u kontaktu sa rukavcem vratila. Numerički model je u poređenju sa postojećim eksperimentalnim metodama u vremenskom smislu brži, a u ekonomskom isplativiji, pa je uspostavljanje ovog modela od velikog, kako naučnog, tako i praktičnog značaja. Kako bi se došlo do krajnjeg cilja, bilo je neophodno primeniti i kombinovati nekoliko različitih metoda: eksperimentalnu, analitičku i statističku i numeričku. Predložena je metodologija za određivanje pohabane zapremine tela prstenastog poprečnog preseka (klizni ležaj) u kontaktu sa cilindrom (vratilo), kombinovanjem eksperimentalnog i analitičkog postupka, a na osnovu promene debljine zida uzorka. Metodologija se može primenjivati za bilo koji materijal uzorka gorenavedene geometrije. Zapremina pohabanog materijala se dalje koristi za izračunavanje Arčardove konstante, koja je neophodan ulazni podatak za simulaciju habanja. Jedan od doprinosa disertacije je tačna vrednost Arčardove konstante za materijal PTFE poliamid. Dobijena vrednost je verifikovana poređenjem sa materijalima sličnih karakteristika iz literature. Vrednosti imaju visok stepen korelacije. U uslovima dovođenja polimernog uzorka u kontakt sa tečnošću (inicijalno podmazivanje, čišćenje u ultrazvučnoj kadi), utvrđeno je da se ne može uspostaviti veza između masenog i zapreminskog habanja, zbog osobine polimera da upija tečnost, čija masa tako nadomešta deo mase pohabanog materijala. Stoga se uvek poređenjem masenog i zapreminskog habanja događa da je zapreminsko habanje daleko veće. Analitičkim i numeričkim putem je određen kontaktni pritisak tribo-para. Rezultati dobijeni dvema metodama su približni.The concept of this dissertation is to develop the numerical model of the wearing process of the sliding bearing in contact with the shaft. If compared to the experimental methods, the numerical method is significantly faster and more cost-effective, thus the development of this model is of great scientific, as well as practical importance. In order to achieve the ultimate goal – the development of the numerical model, it was necessary to apply and combine several different scientific methods: experimental, analytical, statistical and numerical. Combining the experimental and analytical procedure, based on the change in the thickness of the samples’ wall, the methodology for determining the worn volume of the ring (sliding bearing) in contact with the cylinder (shaft) is proposed. This methodology can be applied for the sample made of any material with above mentioned geometry. The worn volume is further used to calculate the Archard coefficient, which is a necessary input value for the wear simulation. Among others, one contribution of this dissertation is the exact value of the Archard coefficient for the material PTFE polyamide. The value obtained by the experiments is verified by comparing it with the Archard coefficients of the similar materials, obtained from the literature. Bringing the polymer sample in contact with the fluid (by initial lubrication, cleaning in the ultrasonic bath, etc.), it absorbs certain amount of the fluid. The mass of the absorbed fluid compensates an amount of the worn mass. Hence, if compared volumetric loss with the mass loss, the volumetric loss will always appear significantly higher, and these two approaches of the loss measurements cannot be correlated. This is also proved in this thesis. The contact pressure of the tribo-pair is determined by analytically and numerically. The results obtained by two different methods are in high correlation

Comparison of gamma ray effects on EPROMs and E2PROMs

This paper compares the reliability of standard commercial Erasable Programmable Read Only Memory (EPROM) and Electrically Erasable Programmable Read Only Memory (E2PROM) components exposed to gamma rays. The results obtained for CMOS-based EPROM (NM27C010) and E2PROM (NM93CS46) components provide the evidence that EPROMs have greater radiation hardness than E2PROMs. Moreover, the changes in EPROMs are reversible, and after erasure and reprogramming all EPROM components restore their functionality. On the other hand, changes in E2PROMs are irreversible. The obtained results are analyzed and interpreted on the basis of gamma ray interaction with the CMOS structure