A drop calorimetry method was used to measure the partial and integral mixing enthalpies of Ag-Mg-Pd liquid solutions. The experiments were performed for six separate series of liquid alloys starting ...from the binary alloys with constant xAg/xMg ratios equal to 1/9, 1/3, 1/1, and 3/1 for (Ag0.10Mg0.90)1-xPdx and (Ag0.25Mg0.75)1-xPdx at 1116 K and (Ag0.50Mg0.50)1-xPdx and (Ag0.75Mg0.25)1-xPdx at 1279 K and xMg/xPd ratios of 9/1 and 4/1 for (Mg0.90Pd0.10)1-xAgx and (Mg0.80Pd0.20)1-xAgx at 1116 K. Then, using the thermodynamic properties of the binary systems in the form of the Redlich-Kister equations and the changes in mixing enthalpies provided by this study, the ternary interaction parameters were determined with the Muggianu model and our own software (TerGexHm). Based on the binary and ternary interaction parameters, the partial mixing enthalpies of Ag, Mg, and Pd were calculated for the same cross-sections where the measurements were conducted. These studies were the first step of an investigation of the Ag-Mg-Pd system before the calculation of the phase diagram for this ternary system.
Due to the development of resistance to antimicrobial agents, bacterium
is nowadays a leading cause of nosocomial outbreaks. Clinically relevant
outside hospital settings including natural soils ...affected by human waste represents a public-health risk for humans and animals. The aim of this study was to investigate the potential of metal-loaded zeolites to eliminate viable
from artificially contaminated natural soils.
isolate was subjected to the activity of natural zeolitised tuff (NZ) and Cu-modified (CuNZ) or Ag-modified zeolite (AgNZ) in wet, slightly acidic
and slightly alkaline red palaeosol.
survived in
and red palaeosol supplemented with 1 wt% of NZ for seven days and four months, respectively. The addition of 1 wt% of CuNZ to
and red palaeosol shortened the survival of
to three and 14 days, respectively. The addition of 0.1 wt% of AgNZ to both soils resulted in complete removal of viable
within 1 h of contact, while the total native heterotrophic bacterial counts remained high. Since AgNZ is prepared with a simple modification of cost-effective and environmentally friendly natural zeolite, it is a promising material for the remediation of soils contaminated with pandrug-resistant
Današnje spoznaje i dokazi o biofilmu, interakcije između različitih bakterijskih vrsta, te ukupna virulencija mikroba imaju utjecaj na odgođeno cijeljenje rane i razvoj infekcije. Kvalitetan opis ...kliničkih simptoma uz suvremena saznanja o mikrobima rane odličan su vodič za kreiranje strategije liječenja kroničnog vrijeda. Zbog sve boljeg razumijevanja uloge biofilma u produljenju vremena liječenja i znanja o sustavu i strukturi biofi lma istraživači su razvili Ag+tehnologiju. Ta tehnologija ima jake sinergističke učinke između općenite antimikrobne aktivnosti ionskog srebra i specifi čnih spojeva koji pomažu u učinkovitosti ometanja i uklanjanja biofilma.
Silver powders produced by both electrochemical (galvanostatic (DC) and potentiostatic (POT) regimes of electrolysis) and chemical processes were examined by scanning electron microscope, and ...particle size distribution (PSD) of the obtained particles was done. In the DC regime, the current densities of ?14.4 mA cm-2 for the nitrate (NIT; powder denoted with DC(NIT)) and ?13.05 mA cm-2 for the ammonium (AM; DC(AM)) electrolytes were applied. In the POT regime, the used overpotentials were ?90 mV (NIT(90)) and ?150 mV (NIT(150)) for the nitrate, and ?625 mV (AM(625)) and ?925 mV (AM(925)) for the ammonium electrolytes. Reduction with hydrazine was used for chemical synthesis (powder denoted with HYD). On the basis of SEM and PSD analysis, Ag powders were grouped into three groups. In the first group DC(AM), AM(925) and HYD powders with the (8.4?8.9 %) volume ratios were placed. In the second group were AM(625) and DC(NIT) powders with the (6.5?6.6 %) volume ratios. NIT(90) and NIT(150) powders with the volume ratios of (5.2?5.7 %) made the third group. The obtained volume ratios were correlated with the morphology of synthesized particles in order to perceive advantages and lacks of powder production via electrochemical and chemical routes.
nema
Autor na temelju novih terenskih istraživanja i prepoznavanja utisnutih žigova piše o rimskim, milanskim i engleskim umjetnički oblikovanim predmetima od srebra koji se čuvaju u samostanima, crkvama ...i zbirkama na prostoru sjeverne Dalmacije (Zadar, Nin, Novigrad, Pag, Dobropoljana na otoku Pašmanu). U radu se analiziraju radovi rimskog majstora Giuseppea Tofanellija, milanskih majstora Francesca Ceppija, Cristofora Corbelle i Emanuelea Cabera i jedan svijećnjak srebrnara Johna Parsonsa iz engleskog grada Sheffielda.
The synthesis of gold and silver nanoparticles by the blue-green algae Spirulina platensis for medical purposes was studied. A complex of optical and analytical methods was used in order to ...characterize produced nanoparticles. It was shown that the extracellular formation of metal nanoparticles of spherical shape with sizes in the range between 8 and 40 nm (the average size of 20-30 nm) takes place. The characteristics of gold and silver nanoparticles in the Spirulina biomass were compared. The role of biosorption processes in the synthesis of nanoparticles was estimated by using equilibrium dialysis. A positive influence of sonication on the process of microbial synthesis and yield of nanoparticles were demonstrated. The neutron activation analysis and the atomic absorption spectrometry were applied for characterizing the dynamics of gold and silver nanoparticles formation in the Spirulina platensis biomass. The neutron activation analysis was used for studying the elemental content of the Spirulina platensis biomass.
A bacterial model system (Pseudomonas putida DSM 50026) was used in this research to assess toxicity of the environmentally relevant concentrations of mercury species (MeHg and Hg(II)) that represent ...important pollutants of aquatic ecosystems at sites of industrial or mining activities. In addition to direct monitoring of bacterial growth, we also analyzed fatty acid profiles of exposed and non-exposed cultures to determine possible toxic effects manifested on membrane level. The results showed that exposure of P. putida to Hg(II) in concentrations of 0.2-200 μg/L did not have any significant effects on growth nor fatty acid composition of exposed bacterial culture. On the other hand, when bacteria were exposed to up to 1600-times lower concentrations of MeHg (0.12-12.5 μg/L), growth inhibition as well as significant changes in fatty acid composition were detected. Observed adaptive membrane changes due to MeHg exposure were similar to those associated with responses to organic solvents and some other membrane-disrupting compounds.
V raziskavi smo na bakterijskem modelu (Pseudomonas putida DSM 50026) analizirali strupenost okoljskih koncentracij anorganske (Hg(II)) in organske (MeHg) oblike živega srebra, ki predstavljata pomembna vira onesnaženja vodnih ekosistemov v bližini nekaterih industrijskih in rudarskih območij. Poleg neposrednega spremljanja bakterijske rasti smo analizirali tudi maščobnokislinske profile izpostavljenih bakterijskih kultur in jih primerjali s tistimi, ki živosrebrovima spojinama niso bili izpostavljeni. Rezultati so pokazali, da izpostavitev P. putida Hg(II) v koncentracijah med 0,2 in 200 μg/L ne inhibira rasti, niti ne vpliva na maščobnokislinsko sestavo bakterijskih membran. Nasprotno pa je izpostavitev celic do 1600-krat nižjim koncentracijam MeHg povzročila tako upočasnitev rasti kot tudi prilagoditvene spremembe na membranskem nivoju. Slednje so bile podobne kot tiste, opažene ob izpostavitvi bakterij organskim topilom in nekaterim drugim spojinam, ki motijo integriteto membran.
U sklopu izložbe Making Marvels: Science and Splendor at the Courts of Europe („Stvaranje ushićenja: znanost i raskoš na europskim dvorovima“, koja se održavala od 25. studenoga 2019. do 1. ožujka ...2020.) u The Metropolitan Museum of Art u New Yorku, SAD, izloženi su umivaonik i vrč iz vlasništva Dubrovačke biskupije – Dioecesis Ragusina. Ta dva dragocjena primjera renesansne zlatarske umjetnosti njemačkoga grada Nürnberga izradio je oko 1550. godine Peter Kuster. Iako se radi o stolnom uresu i jedinim predmetima bez vidljive liturgijske namjene, umivaonik i vrč su do navedenoga projekta bili spremljeni i izloženi u Moćniku dubrovačke katedrale Uznesenja Blažene Djevice Marije. Posudba predmeta iskorištena je kao prilika i povod za opsežne znanstveno-tehnološke analize materijala i primijenjenih tehnika izrade tih iznimnih djela nirnberškog renesansnog zlatarstva. Na temelju istraživanja i stečenih informacija o tehničkom sklopu, upotrijebljenim materijalima, njihovu zatečenom stanju i prijašnjim zahvatima osmišljen je koncept za daljnje konzervatorsko-restauratorske zahvate. U radu su predstavljeni rezultati opsežnih istraživačkih radova. Njihova interpretacija donosi nove spoznaje o tehnici izrade naturalističkih odljeva biljaka i životinja, kao i o životu, stilskim obilježjima, tehnologiji i značenju rada Petera Kustera. Također je dan uvid u nirnberško zlatarstvo 16. stoljeća, te djelovanje njegova najpoznatijega predstavnika – Wenzela Jamnitzera.
Bakterija Acinetobacter baumannii u današnje je vrijeme vodeći uzročnik bolničkih infekcija, ponajprije zbog brzoga razvoja otpornosti te bakterije na antimikrobne lijekove. Klinički značajni A. ...baumannii izvan bolničkoga okružja, kao što su prirodna tla pod utjecajem ljudskoga otpada, javnozdravstveni su rizik za ljude i životinje. Cilj ovoga rada bio je istražiti potencijal zeolita modificiranih metalima za uklanjanje vijabilnih A. baumannii iz umjetno zagađenih prirodnih tala. Izolat A. baumannii u vlažnoj blago kiseloj terra rossa (pH 5,40) i blago lužnatom crvenom paleotlu (pH 8,43) podvrgnut je djelovanju prirodnoga zeolitnoga tufa (NZ) te NZ-a modificiranoga bakrom (CuNZ) ili srebrom (AgNZ). U slučaju dodatka 1 wt% NZ-a, A. baumannii je preživio u terra rossa sedam dana, a u crvenom paleotlu čak četiri mjeseca. Dodatak 1 wt% CuNZ-a u tla skratio je preživljavanje A. baumannii na tri dana u terra rossa i 14 dana u crvenom paleotlu. Dodatak samo 0,1 wt% AgNZ-a u tla rezultirao je kompletnim uklanjanjem vijabilnih A. baumannii tijekom jednoga sata kontakta, pri čemu je brojnost ukupnih heterotrofnih bakterija, prirodno prisutnih u tlu, ostala visoka. Čestice AgNZ-a pripremaju se jednostavnom modifikacijom jeftinoga i okolišno prihvatljivoga prirodnoga zeolita. Mala koncentracija (1 g AgNZ-a po 1 kg tla) mogla bi se jednostavno raspršiti po tlu koje je zagađeno bakterijom A. baumannii. Stoga je AgNZ obećavajući materijal za remedijaciju tala zagađenih tom bakterijom koja je otporna na sve dostupne antibiotike.
Provider: - Institution: - Data provided by Europeana Collections- In this doctoral dissertation, we present the results of the investigations of the nanocomposite systems obtained by in situ ...synthesis of metal (Ag), semiconductor (ZnO) and hybrid (ZnO/Ag) nanoparticles in the presence of synthetic- and biopolymers. Poly (?-(dimethylamino) ethyl methacrylate-co-acrylic acid) (pDMAEMAco- AA) was used as a synthetic matrix, while biopolymer matrices were alginate and agar-agar. The mentioned polymers were characterized by using absorption, emission and FTIR spectroscopies. The numerical simulation of the IR-spectra showed that certain IR-lines originate from the vibration of several diUerent groups of the particular macromolecule. All three polymers were employed as stabilization matrices for the synthesis of silver nanoparticles, while zinc-oxide was synthesized in biopolymers (alginate and agar-agar). The alginate-ZnO nanocomposite was further used as a starting material for the preparation of hybrid zinc-oxide/silver nanoparticles. The synthetic procedure usually resulted with spherical particles but the nanoparticles of the other geometrical shapes were noticed as well (decahedrons and thin triangular prisms for Ag and cubes for ZnO). Besides diUerent morphology of the obtained nanoparticles, the nanocomposites also exhibited a number of additional properties. It was shown that the nanocomposites induce the inhibition of the pathogenic microorganisms (Escherichia coli, Staphylococcus aureus i Candida albicans). Also, in the case of hybrid ZnO/Ag nanoparticles, it was observed that photocatalitic activity increases with increasing in concentration of silver.- U ovoj doktorskoj disertaciji su prikazani rezultati ispitivanja nanokompozitnih sistema dobijenih in situ sintezom metalnih (Ag), poluprovodnickih (ZnO) i hibridnih (ZnO/Ag) nanocestica u prisustvu sintetickih- i bio-polimera. Kao predstavnik sintetickih polimera, korišcen je kopolimer poli(?-(dimetilamino)etil metakrilat-koakrilna kiselina) (PDMAEMA-ko-AK), dok su alginat i agar-agar predstavnici biopolimera. Svi navedeni polimeri su karaterisani apsorpcionom, emisionom i infracrvenom spektroskopijom. Numericke simulacije infracrvenih spektara polimera su pokazale da pojedine IC-linije poticu od vibracija nekoliko razlicitih grupa datog makromolekula. Sva tri polimera su korišcena kao matrice za stabilizaciju i sintezu srebrnih nanocestica; nanocestice cink-oksida su sintetisane u biopolimerima (alginat i agar-agar). Korišcenjem nanokompozita alginat-ZnO kao polaznog materijala, sintetisane su i hibridne ZnO/Ag cestice. U toku sinteze najcešce su dobijane sferne cestice, ali su dobijane i nanocestice drugih oblika, kao što su dekahedroni i tanke trougaone prizme (Ag) i kocke (ZnO). Pored toga što su dobijene nanocestice razlicitih morfologija, ispitivanja su pokazala da nanokompoziti pokazuju i niz drugih osobina. Pokazano je da nanokompoziti znacajno uticu na inhibiciju patogenih mikroorganizama (Escherichia coli, Staphylococcus aureus i Candida albicans). Takoe, uoceno je da u slucaju hibridnih ZnO/Ag nanocestica, fotokataliticka aktivnost raste sa porastom koncentracije srebra.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
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