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.
Rad analizira prelijevanja volatilnosti cijena između tržišta dobara i financijskih tržišta u svrhu istraživanja međusobne povezanosti i integracije tržišta te njihovog potencijala pri ...diverzifikaciji rizika portfelja. U radu su analizirane cijene zlata i srebra, cijene nafte te devizni tečajevi eura i britanske funte te je korištena Diebold-Yilmaz metodologija indeksa prelijevanja za visokofrekventne tjedne podatke od 1988. do 2020. godine. Utvrđeno je kako su ukupna prelijevanja među dobrima i deviznim tečajevima 25.7% te se indeks prelijevanja volatilnosti tijekom analiziranog perioda kreće većinom između 25% i 50% s ekstremima tijekom globalne financijske krize i za vrijeme pandemije COVIDa-19. To ukazuje na snažnu integraciju tržišta dobara i financijskih tržišta, pogotovo u kriznim razdobljima. Također, rezultati rada sugeriraju da su kretanja cijene srebra pod najmanjim utjecajem prelijevanja s ostalih tržišta te stoga srebro može poslužiti pri diverzifikaciji rizika. Doprinos rada postojećoj literaturi je sljedeći: Prvo, analizom transmisijskih procesa pokazana su značajna prelijevanja volatilnosti između tržišta roba i deviznih tečajeva, što ukazuje na postojanje integracije između različitih tržišta. Također, analizira se dugi vremenski period te dinamička analiza pokazuje pojačana prelijevanja volatilnosti u periodima globalnih kriza. Drugo, rezultati analize mogu pomoći profesionalnim prognostičarima pri prognoziranju te financijskim analitičarima za pružanje sveobuhvatne investicijske analize. Menadžeri i investitori tako mogu dizajnirati optimalne instrumente zaštite od neželjenih kretanja na financijskim tržištima i tržištima dobara. Investitori imaju koristi od diverzifikacije portfelja, a informacijski sadržaj dobiven analizom prelijevanja volatilnosti može se koristiti za procjenu potencijalnih determinanti budućih povrata prilagođenih riziku, što bi im pomoglo u donošenju odluka o ulaganju.
The paper analyzes price volatility spillovers between commodity and financial markets in order to investigate the interconnectedness and market integration and their potential in portfolio risk diversification. The paper analyzes gold and silver prices, oil prices, and the exchange rates of the Euro and British pound using the Diebold-Yilmaz spillover index methodology for high-frequency weekly data from 1988 to 2020. The total spillovers between commodities and exchange rates were found to be 25.7% and the volatility spillover index during the analyzed period mostly ranged between 25% and 50% with extremes during the global financial crisis and during the COVID-19 pandemic. This indicates a strong integration of commodity and financial markets, especially in crisis periods. Also, the results of the work suggest that silver price movements are least affected by spillovers from other markets and therefore silver can be used to diversify risks. The contribution of the paper to the existing literature is as follows: Firstly, the analysis of transmission processes showed significant volatility spillovers between commodity markets and exchange rates, indicating the existence of integration between different markets. Furthermore, a long period of time is analyzed and the dynamic analysis shows intensified volatility spillovers in global crises periods. Secondly, the results of the analysis can help professional forecasters in forecasting and financial analysts to provide a comprehensive investment analysis. Managers and investors can thus design optimal protection instruments against unwanted movements in the financial and commodity markets. Investors benefit from portfolio diversification, and the information content obtained from volatility spillover analysis can be used to assess potential determinants of future risk-adjusted returns, which would help them make investment decisions.
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.
The valuable
ensemble of an ewer and basin owned by the Diocese of Dubrovnik -
Dioecesis
Ragusina
was exhibited as part of the “Making Marvels: Science and Splendor
at the Courts of Europe” exhibition (November 25, 2019 – March 1, 2020) at The
Metropolitan Museum of Art in New York, USA. These two Renaissance examples of
goldsmith art from the German city of Nuremberg were made around 1550 by Peter
Kuster. Although these are the only objects with no apparent liturgical
purpose, before this project, the ewer and basin were stored in the treasury of
the Cathedral of the Assumption of the Blessed Virgin Mary in Dubrovnik. When
they return from New York, the Renaissance basin and ewer will become part of
the exhibition at the Sorkočević Palace or the Bishop’s Palace in Dubrovnik. The basin and ewer
were loaned for the exhibition as an opportunity and motivation for a
comprehensive scientific and technological analysis of the materials and
techniques used to manufacture these exceptional works of Nuremberg Renaissance
goldsmith art. In order to learn more about the production technique, as well
as the nature of the surface and its ageing phenomena, a systematic examination
of the entire surface was carried out. Based on the information obtained
through the research, a concept for the necessary conservation was drawn up.
Images from an
optical microscope in combination with z-scan techniques allowed precise
characterization of the surface topography as well as insights into the
construction, preparation of animals and the casting technique. The colours of
the natural casts as well as later layers of overpaint were identified and
dated through energy dispersive X-ray microanalysis in the scanning electron microscope.
The use of micro-computer tomography on several animal and plant figures
provided interesting insights about the construction and techniques used to
make this outstanding Renaissance artwork, since only a few comparable objects
have been preserved and researched worldwide.
Scientific and
technological research also showed the skilled craftsmanship involved in making
such unique creations of silverware destined for the cabinets of curiosities.
It takes months of intensive work to make this type of item, during which the
master must anticipate countless details and have a very broad knowledge of
materials and techniques. In many cases he must also be lucky, especially in
working with new techniques such as natural casts. The production of natural
casts of plants and animals has been a great challenge, starting with catching
and collecting the animals and plants for casting, making moulds, preparing the
animals, casting in metal, colouring and imitating their appearance. Although Peter
Kuster's ewer and basin seem to lag behind the elegant works of Wenzel
Jamnitzer in the sophistication of composition, this work combines an
emblematic Renaissance approach to science and luxury at the same time. At the
beginning of his career, the young goldsmith Kuster attempted to compete with,
or even surpass, his well-known and respected neighbour Jamnitzer with an
incomparable number of natural casts of flora and fauna. Kuster deviated from
Jamnitzer's symmetry and tried to integrate elements of flora and fauna into the
natural environment. As this is Kuster’s
only known work, it is difficult to compare his creativity and the quality of
his craftsmanship with Jamnitzer’s. Kuster never used a mould twice - all his
natural casts of animals are unique, which can be attributed to the difficult
production of negative moulds. However, even after very extensive research, it
is not possible to judge why a small number of the naturalistic outflows are
technically less accurate than others. The fact that only a few animals were gilded
before painting may be an indication of a change in the aesthetic concept
during the long-term production of this series. Furthermore, it is possible
that part of the casting was made later, during a different stage, or under
different working conditions. In the case of turtles that were cast after he
had carved the wooden models, it cannot be said with certainty whether Kuster
tried to simplify his work, or whether these animals were made by someone else.
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.
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