Testing of electrochemical supercapacitors

U ovom radu provedeno je testiranje superkondenzatora proizvođača Bussman By Eaton, nazivnog napona od 2,5 V i kapaciteta 6 F. Testiranje je provedeno metodom punjenja i pražnjenja konstantnom strujom. Korištene su struje od 10, 20, 50 i 100 mA. Iz dobivenih rezultata koji su prikazani kao ovisnosti napona o vremenu punjenja ili pražnjenja izračunati su kapacitet kondenzatora u ovisnosti o naponu, energija, snaga te energetska učinkovitost. Rezultati pokazuju da kapacitet superkondenzatora ovisi o naponu, ali i o struji punjenja i pražnjenja. Ispitivanjem stabilnosti superkondenzatora njegovim punjenjem i pražnjenjem kroz 2000 sukcesivna ciklusa nađeno je da kapacitet superkondenzatora naglo pada u prvih 500 ciklusa nakon čega se stabilizira i poprima konstantnu vrijednost neovisnu o broju ciklusa. Provedeno je također i testiranje individualnih elektroda superkondenzatora metodom cikličke voltametrije i nađeno je da nema značajne razlike u elektrokemijskom ponašanju pozitivne i negativne elektrode.In this work the testing of supercapacitor Bussman By Eaton with nominal voltage of 2,5 V and capacitance of 6 F was carried out by constant current charging/discharging method. The currents of 10, 20, 50 and 100 mA were used. The obtained results were graphed as the dependence of voltage on time of charge/discharge and the capacitance, energy, power and energy efficiency were determined. The results showed that capacitance depended on the voltage and discharge/charge current. The stability of supercapacitor was investigated by successively charging/discharging it over 2000 cycles. It was found that the capacitance of supercapacitor rapidly deteriorated in the first 500 cycles after which it assumed constant value. Testing of individual supercapacitor electrodes by cyclic voltammetry was also carried out and it was found that there was no significant different in the electrochemical behaviour of positive and negative electrodes

Preparation of ink-jet printable solid state reference electrode

Predmet ovog rada bila je priprema plošne Ag|AgCl referentne elektrode printanjem ink-jet printerom. Ag tinta (NovaCentrix / ZOAK) otisnuta je na fleksibilnu površinu pomoću modificiranog ink–jet printera. Površine Ag elektroda zatim su modificirane kemijski, otopinom FeCl3 te elementarnim klorom, i elektrokemijski, cikličkom voltametrijom te potenciostatski što je rezultiralo nastankom AgCl sloja na Ag površini. Tako priređene elektrode ispitivane su potenciometrijski u neprotočnim ćelijama u nizu standardnih otopina KCl-a sa i bez podešene ionske jakosti. Ionska jakost podešena je otopinama Na2SO4 i NaNO3. Na iste elektrode nanesene su membrane na bazi ionskih tekućina (IL) i na bazi epoksida te su dulje ili kraće vrijeme močene u 10^-3 M otopini KCl-a. Potom su ponovo podvrgnute potenciometrijskim mjerenjima unutar neprotočne ćelije u nizu istih standardnih otopina. Također, testirana je i stabilnost pojedine referentne elektrode u 10^-3 M otopini KCl-a s podešenom ionskom jakosti kako bi se pratio odziv elektrode (potencijal) u vremenu. Najbolje rezultate pokazala je referentna elektroda dobivena modifikacijom sa željezovim (III) kloridom i IL membranom nakon petodnevnog kondicioniranja.In this work an alternative strategy for manufacturing all-solid-state reference electrodes was carried out. Planar Ag electrodes were printed using ink-jet printer which was followed by surface modification. The modification processes involved electrochemical potentiostatic and potentiodynamic methods such as cycliyc voltammetry, and also chemical methods where FeCl3 an Cl2 were used in order to obtain AgCl thin layer on the printed Ag electrode. For keeping a steady potential of quasi-reference electrodes, two kinds of membranes were prepared, first one based on ionic liquids (IL) and the second one based on epoxy resin. Potentiometric measurements were applied for calibration curves determination of printed Ag|AgCl electrodes with and without membrane. Measurements were performed in KCl standard solutions prepared in 50 mM solution of Na2SO4 and NaNO3. Electrode with IL-based membrane, the surface of which was previously modified with FeCl3 solution, exhibited the best potential stability among all other manufactured electrodes

Preparation of ink-jet printable solid state reference electrode

Predmet ovog rada bila je priprema plošne Ag|AgCl referentne elektrode printanjem ink-jet printerom. Ag tinta (NovaCentrix / ZOAK) otisnuta je na fleksibilnu površinu pomoću modificiranog ink–jet printera. Površine Ag elektroda zatim su modificirane kemijski, otopinom FeCl3 te elementarnim klorom, i elektrokemijski, cikličkom voltametrijom te potenciostatski što je rezultiralo nastankom AgCl sloja na Ag površini. Tako priređene elektrode ispitivane su potenciometrijski u neprotočnim ćelijama u nizu standardnih otopina KCl-a sa i bez podešene ionske jakosti. Ionska jakost podešena je otopinama Na2SO4 i NaNO3. Na iste elektrode nanesene su membrane na bazi ionskih tekućina (IL) i na bazi epoksida te su dulje ili kraće vrijeme močene u 10^-3 M otopini KCl-a. Potom su ponovo podvrgnute potenciometrijskim mjerenjima unutar neprotočne ćelije u nizu istih standardnih otopina. Također, testirana je i stabilnost pojedine referentne elektrode u 10^-3 M otopini KCl-a s podešenom ionskom jakosti kako bi se pratio odziv elektrode (potencijal) u vremenu. Najbolje rezultate pokazala je referentna elektroda dobivena modifikacijom sa željezovim (III) kloridom i IL membranom nakon petodnevnog kondicioniranja.In this work an alternative strategy for manufacturing all-solid-state reference electrodes was carried out. Planar Ag electrodes were printed using ink-jet printer which was followed by surface modification. The modification processes involved electrochemical potentiostatic and potentiodynamic methods such as cycliyc voltammetry, and also chemical methods where FeCl3 an Cl2 were used in order to obtain AgCl thin layer on the printed Ag electrode. For keeping a steady potential of quasi-reference electrodes, two kinds of membranes were prepared, first one based on ionic liquids (IL) and the second one based on epoxy resin. Potentiometric measurements were applied for calibration curves determination of printed Ag|AgCl electrodes with and without membrane. Measurements were performed in KCl standard solutions prepared in 50 mM solution of Na2SO4 and NaNO3. Electrode with IL-based membrane, the surface of which was previously modified with FeCl3 solution, exhibited the best potential stability among all other manufactured electrodes

Testing of electrochemical supercapacitors

U ovom radu provedeno je testiranje superkondenzatora proizvođača Bussman By Eaton, nazivnog napona od 2,5 V i kapaciteta 6 F. Testiranje je provedeno metodom punjenja i pražnjenja konstantnom strujom. Korištene su struje od 10, 20, 50 i 100 mA. Iz dobivenih rezultata koji su prikazani kao ovisnosti napona o vremenu punjenja ili pražnjenja izračunati su kapacitet kondenzatora u ovisnosti o naponu, energija, snaga te energetska učinkovitost. Rezultati pokazuju da kapacitet superkondenzatora ovisi o naponu, ali i o struji punjenja i pražnjenja. Ispitivanjem stabilnosti superkondenzatora njegovim punjenjem i pražnjenjem kroz 2000 sukcesivna ciklusa nađeno je da kapacitet superkondenzatora naglo pada u prvih 500 ciklusa nakon čega se stabilizira i poprima konstantnu vrijednost neovisnu o broju ciklusa. Provedeno je također i testiranje individualnih elektroda superkondenzatora metodom cikličke voltametrije i nađeno je da nema značajne razlike u elektrokemijskom ponašanju pozitivne i negativne elektrode.In this work the testing of supercapacitor Bussman By Eaton with nominal voltage of 2,5 V and capacitance of 6 F was carried out by constant current charging/discharging method. The currents of 10, 20, 50 and 100 mA were used. The obtained results were graphed as the dependence of voltage on time of charge/discharge and the capacitance, energy, power and energy efficiency were determined. The results showed that capacitance depended on the voltage and discharge/charge current. The stability of supercapacitor was investigated by successively charging/discharging it over 2000 cycles. It was found that the capacitance of supercapacitor rapidly deteriorated in the first 500 cycles after which it assumed constant value. Testing of individual supercapacitor electrodes by cyclic voltammetry was also carried out and it was found that there was no significant different in the electrochemical behaviour of positive and negative electrodes

Molecular Determinants of Juvenile Hormone Action as Revealed by 3D QSAR Analysis in Drosophila

BACKGROUND:Postembryonic development, including metamorphosis, of many animals is under control of hormones. In Drosophila and other insects these developmental transitions are regulated by the coordinate action of two principal hormones, the steroid ecdysone and the sesquiterpenoid juvenile hormone (JH). While the mode of ecdysone action is relatively well understood, the molecular mode of JH action remains elusive. METHODOLOGY/PRINCIPAL FINDINGS:To gain more insights into the molecular mechanism of JH action, we have tested the biological activity of 86 structurally diverse JH agonists in Drosophila melanogaster. The results were evaluated using 3D QSAR analyses involving CoMFA and CoMSIA procedures. Using this approach we have generated both computer-aided and species-specific pharmacophore fingerprints of JH and its agonists, which revealed that the most active compounds must possess an electronegative atom (oxygen or nitrogen) at both ends of the molecule. When either of these electronegative atoms are replaced by carbon or the distance between them is shorter than 11.5 A or longer than 13.5 A, their biological activity is dramatically decreased. The presence of an electron-deficient moiety in the middle of the JH agonist is also essential for high activity. CONCLUSIONS/SIGNIFICANCE:The information from 3D QSAR provides guidelines and mechanistic scope for identification of steric and electrostatic properties as well as donor and acceptor hydrogen-bonding that are important features of the ligand-binding cavity of a JH target protein. In order to refine the pharmacophore analysis and evaluate the outcomes of the CoMFA and CoMSIA study we used pseudoreceptor modeling software PrGen to generate a putative binding site surrogate that is composed of eight amino acid residues corresponding to the defined molecular interactions

First report on PVL-positive methicillin-resistant Staphylococcus aureus of SCCmec type V, spa type t441 in Croatia

Purpose The aim of the study was to investigate the molecular epidemiology of community- associated MRSA in Primorsko-Goranska County of Croatia during a six-year period(2001-2007). Methods In period from 2001 and 2007, 46 MRSA isolates were collected in Rijeka, strains were subjected to susceptibility testing according to CLSI guidelines, mecA gene detection and SCCmec typing as well as detection of PVL. Strains were typed by Pulse Field Gel Electrophoresis (PFGE) and spa typing. Results All isolates were susceptible to vancomycin, linezolid, mupirocin, nitrofurantoin, only one strain was resistant to fusidic acid and co-trimoxazole. Results of SCCmec typing showed the presence of SCCmec type IV in 26 MRSA strains, SCCmec type V in three strains, and 13 strains comprised SCCmec I. SCCmec type II and III were not observed. Four MRSA strains were non-typeable by applied SCCmec typing methods. PVL was detected in 4 strains, two SCCmec IV and two SCCmec V. PFGE analysis, grouped MRSA strains into six similarity groups and 18 singletons. Dominating spa types in this collection of strains were t015, with 15 strains, followed by t041(N=7), t051,(N=2 ), t2850(N=2), t008(N=2)and single isolates t441, t002, t448, t018, t019, t355, t390, t026, t449, t148. We also detected two new spa types, t3510 and t3509, respectively. Conclusions This is the first report on SCCmec type V in Croatia, and, to our knowledge, first report of PVL-positive mehicillin-resistant Staphylococcus aureus SCCmec type V and t441(ST59-MRSA-V) in this part of Europe

First report on PVL-positive methicillin-resistant Staphylococcus aureus of SCCmec type V, spa type T441 in Croatia [Prvi izolat staphylococcus auerus rezistentnog na meticilin SCCmec tipa V, pozitivan na PVL]

The aim of the study was to investigate the molecular epidemiology of community- associated MRSA in Primorsko-Goranska County of Croatia during a six-year period(2001-2007). In period from 2001 and 2007, 46 MRSA isolates were collected in Rijeka, strains were subjected to susceptibility testing according to CLSI guidelines, mecA gene detection and SCCmec typing as well as detection of PVL. Strains were typed by Pulse Field Gel Electrophoresis (PFGE) and spa typing. All isolates were susceptible to vancomycin, linezolid, mupirocin, nitrofurantoin, only one strain was resistant to fusidic acid and co-trimoxazole. Results of SCCmec typing showed the presence of SCCmec type IV in 26 MRSA strains, SCCmec type V in three strains, and 13 strains comprised SCCmec I. SCCmec type II and III were not observed. Four MRSA strains were non-typeable by applied SCCmec typing methods. PVL was detected in 4 strains, two SCCmec IV and two SCCmec V. PFGE analysis, grouped MRSA strains into six similarity groups and 18 singletons. Dominating spa types in this collection of strains were t015, with 15 strains, followed by t041(N=7), t051,(N=2 ), t2850(N=2), t008(N=2)and single isolates t441, t002, t448, t018, t019, t355, t390, t026, t449, t148. We also detected two new spa types, t3510 and t3509, respectively. This is the first report on SCCmec type V in Croatia, and, to our knowledge, first report of PVL-positive mehicillin-resistant Staphylococcus aureus SCCmec type V and t441(ST59-MRSA-V) in this part of Europe

Legionella pneumophila infections in Primorsko-goranska county

Cilj: Bakterije roda Legionella značajni su uzročnici nozokomijalnih pneumonija, kao i pneumonija koje se javljaju u zajednici. U većini slučajeva klinički nije moguće razlikovati pneumonije uzrokovane legionelama od onih nastalih ostalim atipičnim uzročnicima. Etiološka dijagnoza zasniva se prije svega na kultivaciji, detekciji antigena, serodijagnostici i molekularnim testovima. Metode: U radu smo retrospektivno analizirali rezultate pretraga izvršenih na Mikrobiološkom odjelu Nastavnog zavoda za javno zdravstvo u Rijeci od 2003. do 2008. godine. U našim laboratorijima u većini slučajeva legioneloza je dijagnosticirana detekcijom Legionella antigena u urinu i/ili imunoenzimskim (EIA) anti Legionella IgM pretragama kao najranijim serološkim pokazateljem infekcije. Rezultati: Sveukupno je obrađeno 97 uzoraka urina i 112 seruma prikupljenih od bolesnika s područja Primorsko-goranske županije. L. pneumophila O1 antigen otkriven je u 5 (5 %) od 97 uzoraka urina. Serološki je EIA metodom utvrđena prisutnost IgM protutijela u ukupno 13 obrađenih uzoraka (12 %). Samo IgM detektiran je u 4 (21 %), IgM plus IgA i IgG u 5 (26 %), IgM i IgA u 3 (16 %), IgM i IgG u 1 (5 %), i samo IgG protutijela u 6 (32 %) od 19 pozitivnih uzoraka seruma. U konačnici, u razdoblju od 2003. do 2008. godine pozitivni nalazi na bakteriju L. pneumophila utvrđeni su u uzorcima od ukupno 8 bolesnika. Rasprava i zaključci: Detekcija IgM protutijela primjenom osjetljive metode kao što je imunoenzimski test – EIA pokazala se pogodnom u kombinaciji s detekcijom antigena u urinu za dijagnostiku legioneloza. EIA za otkrivanje L. pneumophila seroskupine O1 antigena u urinu predstavlja specifičnu metodu koja je osobito značajna za brzu dijagnostiku legionarske bolesti.Aim: Bacteria of the genus Legionella are important causes of both community-acquired and nosocomial pneumonia. However, the majority of cases are clinically indistinguishable from other causes of pneumonia and it cannot be reliably diagnosed on clinical grounds alone. The etiological diagnosis depends mostly on culture, antigen detection, serological or molecular tests. Methods: Present paper represents the results of retrospective analysis of tests performed at the Department of Microbiology the Teaching Institute of Public Health in Rijeka between 2003 to 2008. In our laboratories most of the cases were diagnosed by the detection of Legionella antigen in urine and/or serological determination with enzyme immunoassay (EIA) test of the anti-Legionella IgM fraction as the most recent answer to infection. Results: Overall 97 urine samples and 112 sera of patients from Primorsko-Goranska County were analysed. L. pneumophila O1 antigen in urine was detected in 5 (5 %) of 97 samples. Serologically EIA detected IgM in overall 13 (12 %) of all samples tested. IgM only was found in 4 (21 %) samples, IgM plus IgA and IgG in 5 (26 %), IgM plus IgA in 3 (16 %), IgM plus IgG in 1 (5 %), and IgG alone was found in 6 (32 %) of 19 positive samples. Overall, from 2003 to 2008 L. pneumophila positive results were found in samples from 8 patients. Discussion and Conclusions: Detection of IgM using a sensitive technique such as EIA seems to be a suitable complement to antigenuria detection for the diagnosis of legionellosis. EIA for the detection of L. pneumophila serogroup O1 antigen in urine specimens is a specific assay which is of great importance in providing a rapid diagnosis of Legionnaires’ disease

Antibiotic use and antimicrobial resistance in school children

Uvod: Neracionalna uporaba antibiotika je zasigurno složen problem kojem doprinosi više čimbenika, ali i jedan od glavnih pokretača za pojavu i širenje rezistencije bakterija na antibiotike. Metode: U prospektivnom istraživanju obrađeni su obrisci ždrijela i nazofarinksa 450 djece školske dobi, 6-15 godina, Grada Rijeke i okolice. Dva presječna istraživanja su provedena pomoću strukturiranih upitnika o znanju, stavovima i praksi o uporabi antibiotika na 1000 roditelja djece osnovnih škola i 230 liječnika dentalne medicine Primorsko-goranske županije, Hrvatska. Rezultati: Izloženost antibioticima u djece školske dobi u prethodnih šest mjeseci je bila povezana s pojavom bakterija rezistentnih na antibiotike. Uporaba uskospektralnih penicilina je bila rjeđa nego uporaba amoksicilina (26% školska djeca, 33.1% liječnici dentalne medicine) i amoksicilina s klavulanskom kiselinom (26% školska djeca, 65% liječnici dentalne medicine). Roditelji i liječnici dentalne medicine su imali visoku svjesnost o rezistenciji bakterija na antibiotike. Zaključci: Uporaba antibiotika je povezana s višom stopom rezistencije u respiratornih patogena. Sociodemografske karakteristike roditelja nisu utjecale na uporabu antibiotika. Iako liječnici dentalne medicine posjeduju visoku svjesnost o rezistenciji bakterija na antibiotike, i dalje postoji prevelika uporaba antibiotika, naročito širokospektralnih te treba povećati osobnu odgovornost za racionalnu uporabu antibiotika.Introduction: Irrational antibiotic use is certainly complex and multifactorial problem, but also one of the major drivers for the emergence and spread of antimicrobial resistance. Methods: In prospective study throat and nasopharyngeal swabs from 450 school children, 6-15 years of age, from the city of Rijeka and the surrounding area, were processed. Two cross-sectional studies based on a structured questionnaire about knowledge, attitudes and practice regarding antibiotic use, that were given to 1000 parents of children attending elementary schools and 230 dental practitioners in outpatient settings of Primorsko-Goranska County, Croatia. Results: Antibiotic exposure in school children in the previous six months was associated with the carriage of antibiotic-resistant bacteria. The use of narrow spectrum penicillins was less common than the use of amoxicillin (26% school children, 33.1% dental practitioners) and amoxicillin with clavulanic acid (26% school children, 65% dental practitioners). Parents and dental practitioners had a high awareness of antimicrobial resistance. Conclusions: Antibiotic use is linked with higher resistance rates of respiratory tract pathogens. Parents' background did not influence the frequency of antibiotic use. Although there is a high level of antimicrobial resistance awareness among dental practitioners, there is still too much overuse of antibiotics, especially broad spectrum, and personal responsibility for rational antibiotic use should be increased