Cink je esencijalni biljni hranjivi element s vrlo opsežnom i značajnom ulogom. Uključen je u više metabolitičkih procesa i sudjeluje u razvoju reproduktivnih dijelova vinove loze. Količina cinka u ...biljci je niska, te se značajno razlikuje između pojedinih biljnih vrsta. Kod vinove loze, optimalna opskrbljenost cinkom u listu kreće se u rasponu od 25-150 mg kg-1. Nedostatak cinka najčešći je na tlima s pH 7.0-8.0, a u slučaju karbonatnih tala nedostatak cinka često je povezan s nedostatkom željeza (‘vapnena kloroza’). Gnojiva na bazi cinka sadrže različite vrijednosti cinka ovisno o njegovom obliku u gnojivu. Postojei nekoliko najznačajnijih kemijskih oblika cinka od kojih ćemo spomenuti cink-oksid, cink-helat, cink-sulfat i cink-fosfit. Svaki od njih ciljano se koristi za rješavanje određenih nedostataka ili potiče razvoj metabolizma vinove loze. Prema rezultatima istraživanja većine autora vidljivo je da u većini vinogradarskih tala nedostaje cinka, te se preporuča dodatna gnojidba vinove loze. Ovisno o stanju cinka u tlu, gnojidba se može provesti preko lista (kod manjih nedostataka cinka) ili u kombinaciji tlo-folijarna gnojidba (kod većih nedostataka cinka), upotrebom različitih gnojiva na bazi cinka. Na taj način može se postići dobra opskrbljenost vinove loze cinkom te ujednačen rast i razvoj vinove loze tijekom vegetacije.
Hydropower plants (HPP) are considered to be one of the major threats to the survival of European eels when they migrate downstream along inland water bodies during the early part of their annual ...journey to the spawning area in the Sargasso Sea. There are 98 HPPs in Lithuania and thousands throughout Europe. Numerous studies describe HPP induced mortality rates among European eels as variable depending on local, environmental, and technical factors. This heterogeneity in effect complicates theoretical extrapolation to eel mortality arising from specific types of HPP, necessary for effective management of local stocks. Silver eel mortality was estimated for 4 different HPPs in Lithuania. Mortality was estimated using RFID (Radio Frequency Identification, passive integrated transponders) tags and acoustic telemetry in a large HPP (>100 MW) with Kaplan turbines, a small HPP (<1 MW) with a Kaplan turbine and a fish passage, and for the first time in two small HPPs (<1 MW) with CINK turbines. The results supported a hypothesis that the mortality rate of migrating eels depends mainly on the type and size of the turbine. HPP induced mortality varied from 100% in a small CINK turbine down to 25% in the large HPP with Kaplan turbines. The importance of simple mitigation measures was highlighted by 34% of all tagged eels bypassing one of the HPP via an adjacent fish passage constructed for upstream migration of salmonids. The observed differences in mortality provide essential information for long term strategies designed to restore depleted eel populations in Lithuania and other European countries.
Svrha: Iz postojeće literature poznato je da metalni ioni iz ortodontskih naprava mogu korodirati zbog djelovanja sline i bakterija u usnoj šupljini. Rezultati većine studija upućuju na to da se ...razina nikla i kroma u slini ne povisuje nakon postavljanja ortodontskih naprava. No nema istraživanja o razini titanija, kobalta, bakra i cinka u slini ortodontskih pacijenata. Ispitanici i postupci: Razina nikla (Ni), titanija (Ti), kroma (Cr), kobalta (Co), bakra (Cu) i cinka (Zn) mjerena je u slini četrdeset i dvoje pacijenta s keramičkim metalnim bravicama i isto toliko njih s konvencionalnima i to prije postavljanja ortodontskih naprava s pomoću induktivne spregnute plazme/masene spektrometrije i šest mjeseci poslije toga. U statističkoj analizi korištena su dva testa – Wilcoxonov signed rank i Mann-Whitneyev s razinom značajnosti od 0,05. Rezultati: Rezultati su pokazali da se razina titana u slini povisila šest mjeseci nakon postavljanja ortodontskih naprava. Razina kroma i cinka, pak, značajno se snizila nakon postavljanja ortodonskih naprava. Nije bilo statistički značajne razlike u razini nikla, titanija, kroma, bakra, kobalta i cinka u slini između pacijenata s metalnim i keramičkim ortotontskim
bravicama. Zaključak: Možemo zaključiti da se razina titanija u slini značajno povisila šest mjeseci nakon postavljanja ortodontskih naprava za razliku od razine kroma i cinka koja se značajno snizila šest mjeseci poslije njihova postavljanja, bez obzira na vrstu korištenih bravica.
This article deals with hydrometallurgical treatment with the subsequent precipitation of zinc from hazardous waste Sal- Ammoniac Skimming produced in wet hot-dip galvanizing process. Chemical ...analysis showed that skimming contained 46.64% Zn. X-ray diffraction analysis identified the Zn(OH)Cl phase (96.36%) and NH4Cl (3.64%) in Sal-Ammoniac Skimming. The skimming was first subjected to leaching in order to extract zinc into the solution containing HCl, followed by precipitation of the zinc. The experiments were performed in a medium of HCl at concentrations of 0.25, 0.5, 1 and 2M. Complete dissolution of zinc was achieved in 0.5M HCl solution, at 40?C, L:S=20, max. 30 min. The apparent activation energy of leaching reaction by hydrochloric acid solution was Ea=5.543 kJ mol-1. Zn precipitation was carried out using Na2CO3 and NaOH. Zinc oxide with a purity of about 99% was obtained directly from the solution of 6M NaOH at a temperature of 60?C ? 80?Cat pH 8.8.
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Universal Mobile Telecommunication Systems Authentication and Key Agreement (UMTS-AKA) protocol is an enhanced Authentication and Key Agreement (AKA) protocol of Global System for Mobile (GSM) ...communications. The UMTS-AKA has weaknesses in bandwidth consumption, authentication message overhead and mutual authentication. This paper analyzes UMTS-AKA protocol and proposes a new Enhanced Secured Universal Mobile Telecommunication System Authentication and Key Agreement (ESUMTS-AKA) protocol with additional security features. All the messages exchanged between different entities with International Mobile Subscriber Identity (IMSI) are encrypted so that it would be less vulnerable to attacks. Private keys and public keys of different entities are used during encryption of messages. A temporary key in the proposed ESUMTS-AKA protocol reduces the bandwidth consumption between different entities. The computation of hash functions in Home Network (HN) decreases by increasing the hash functions generated in Serving Network (SN). The proposed ESUMTS-AKA protocol is more secured due to Combined Cipher Key (CCiK) and Combined Integrity Key (CInK). Analysis and simulated results prove that the proposed ESUMTS-AKA protocol is more enhanced and highly protected.
Pyrogallol-type phenolic compounds are widespread in nature and may have significant impact on human health. As Zn(II) ion was proved to be capable of enhancing some biological activities of ...pyrogallol-type natural phenolic compounds, we decided to study its influence on the autoxidation of pyrogallol and gallic acid in weakly acidic aqueous solutions.
UV-Vis spectrophotometric measurements showed that autoxidation of pyrogallol was initiated by the influence of Zn(II) ions at pH 5.5 and pH 6.5. The differences in UV-Vis spectra of the first autoxidation products resolved by the application of multivariate curve resolution - alternating least squares (MCR-ALS) method indicated that pH change also changed the mechanism of autoxidation process. Formation of stable Zn(II) ion spin stabilized free radical obtained during the autoxidation of pyrogallol at pH 6.5 was confirmed by using electron spin resonance (ESR) spectroscopy and its structure was determined. Both UV-Vis spectrophotometric and ESR spectroscopic measurements did not give any evidence that gallic acid autoxidation was initiated by the influence of Zn(II) ions in weakly acidic aqueous solutions.
The results of this study may be used for explaining possible differences in the Zn(II) ion influence on various biological activities of pyrogallol-type phenolic compounds containing simple pyrogallol moiety and the ones containing gallate moiety as a part of the molecule
Fenolna jedinjenja sa strukturom pirogalola su široko rasprostranjena u prirodi i mogu da imaju značajan uticaj na ljudsko zdravlje. Kako je pokazano da Zn(II) jon ima sposobnost da pojačava neke biološke aktivnosti prirodnih fenolnih jedinjenja sa strukturom pirogalola, odlučili smo da ispitamo njegov uticaj na autooksidaciju pirogalola i galne kiseline u slabo kiselim vodenim rastvorima.
UV-Vis spektrofotometrijska merenja su pokazala da prisustvo Zn(II) jona inicira autooksidaciju piroglola na pH 5,5 i pH 6,5. Razlike u UV-Vis spektrima koji su dobijeni hemometrijskom obradom spektrofotometrijskih podataka metodom MCR-ALS za prve proizvode autooksidacije ukazuju da promena pH vrednosti dovodi i do promene mehanizma autooksidacije. Formiranje slobodnog radikala, koji je stabilisan prisustvom Zn(II) jona, potvrđeno je metodom elektronske spinske rezonance (ESR) i određena je njegova struktura. Obe primenjene metode nisu pokazale da prisustvo Zn(II) jona inicira autooksidaciju galne kiseline u slabo kiselim vodenim rastvorima.
Rezultati ovog ispitivanja mogu se koristiti za objašnjenje mogućih razlika u uticaju Zn(II) jona na biološku aktivnost fenolnih jedinjenja pirogalolske strukture koja imaju samo jednostavne strukturne jedinice pirogalola i onih koje u molekulu sadrže ostatke galne kiseline
Currently, the commercial antimony metallurgy is mainly based on pyrometallurgical processes and oxidative volatilization of Sb2S3 is an essential step. This step includes the problems of high energy ...consumption and low concentration of SO2 pollution. Aiming at these problems, we present a new method of sulfur-fixing roasting of antimony sulfide. This method uses ZnO as a sulfur-fixing agent, and roasting with Sb2S3 was carried out at 673 K~1073 K to produce Sb2O3 and ZnS. By calculating the thermodynamics of the reactions, we can conclude that the Gibbs Free Energy Change (?G?) of roasting reaction is below -60 kJ/mol and the predominance areas of Sb2O3 and ZnS are wide and right shifting with the temperature increase, which all indicates that this method is theoretically feasible. The reacted products between Sb2S3 and ZnO indicated that the reaction began at 773 K and finished approximately at 973K. We used the Ozawa-Flynn-Wall, Kissinger and Coats-Redfern method to calculate the kinetics of the roasting reaction. The conclusion is as follows: The average values of apparent activation energy (E) and natural logarithmic frequency factor (lnA) calculated by Ozawa-Flynn-Wall, Kissinger and Coats-Redfern were 189.72 kJ?mol-1 and 35.29 s-1, respectively. The mechanism of this reaction was phase boundary reaction model. The kinetic equation is shown as follow, where ? represents reaction fraction: 1-(1-?)1/3 = 2.12 x1015 exp(-1.90x105/RT) t.
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This study examined the uptake, translocation, distribution and accumulation of Cd, Zn and Fe and the interaction of these elements in winter wheat. The objectives were: (1) to characterise ...specificity among winter wheat genotypes in terms of accumulation of Cd, Zn and Fe in various organs and identify genotypes combining low accumulation of Cd with high accumulation of Zn and/or Fe, (2) to determine genetic specificity of winter wheat genotypes in terms of translocation of Cd, Zn and Fe from the vegetative parts to the grain, and (3) elucidate an effect of soil cadmium contamination on the distribution and accumulation of Cd, Zn and Fe in various organs of wheat. In the 2007/2008 vegetation season, 52 winter wheat varieties (34 Croatian, 7 Austrian, 5 Hungarian, 3 French and one variety of Russian, Italian and German descent) were investigated. The pots were arranged, according to a completely randomized design with two levels of soil Cd contamination (0 and 20 mg kg-1 soil) in four replicates. In the vegetation season of 2008/2009 the experiment was set up to a completely randomized block design with 10 varieties of wheat and three levels of soil Cd contamination (0, 2 and 5 mg kg-1 soil) in four replicates. The concentration of Cd, Zn and Fe in the solution of plant samples was determined by ICP-OES. The concentration of Cd, Zn and Fe was determined at the flowering stage in the root, stem,leaves, flag leaf and spike and in a full maturity in the straw, leaves, glumes and grain. Collected data were statistically analyzed with SAS software 9.1.3. Analysis of variance identified a statistically significant difference in the concentrations of Cd, Zn and Fe in vegetative parts and grain between the tested wheat varieties at all levels of soil Cd contamination. It was also found that the soil Cd contamination had a significant effect on the accumulation of Cd in grain while the accumulation of Zn and Fe in the grain hasn’t been influenced by soil Cd contamination. The tested genotypes differed significantly in the Cd, Zn and Fe plant uptake factor as well as in the coefficient of translocation from roots to stems and from roots to the flag leaf. According to correlation coefficient between the concentrations of Cd, Zn and Fe in the grain, the tested cultivars were divided into six groups which differ in the interrelation of these elements. Obtained results may serve as a starting point for investigation of the mechanisms of uptake, translocation and accumulation of Cd, Zn and Fe in winter wheat as well as for the selection of genotypes with increased concentrations of Zn and Fe and decreased Cd concentration in the grain.
Recikliranje nus proizvoda čeličanskih procesa u elektro lučnim pećima (ELP) je važna aktivnost sa gledišta zaštite okoliša kao i osobno za čeličansku industriju. Ovaj članak se tiče rasprave ...selektivnih rezultata istraživanja sa gledišta rabljene čeličanske prašine sa sadržajem 4-12 % cinka pri proizvodnji cementnih blokova, keramičkih materijala kao i obojenih staklenih proizvoda. Provedena istraživanja su ukazala da rabljenje čeličanske prašine u nemetalurškoj industriji je moguće i razborito.
Tin-zinc alloy deposits are recognized as a potential alternative to toxic cadmium as corrosion resistant coatings. Tin-zinc alloy layers offer outstanding corrosion protection for steel by combining ...the barrier protection of tin with the galvanic protection of zinc. Tin-zinc coatings have been used on the chassis of electrical and electronic apparatus and on critical automotive parts such as fuel and brake line components. In this study, tin-zinc alloy deposits were successfully prepared from alkaline, pyrophosphate-based electrolytes. The plating process gives a compact and fine grained deposit. The desired proportions of tin and zinc in the deposited alloy are determined by the bath composition and the operating conditions during plating. Three electrode systems were used for the electrochemical investigation. The mechanism of Sn-Zn electrodeposition was studied by linear and cyclic voltammetry. The corrosion parameters, including open-circuit potential-time curves, corrosion potential and corrosion current density of electrodeposited tin-zinc alloys of different compositions have been examined in a brine medium containing 3 wt. % NaCl. The corrosion resistance depends on the plating composition. The Sn-28Zn deposit showed the best anticorrosive properties. / Покрытия из олова и цинка являются потенциальным аналогом токсичного кадмия для антикоррозийной защиты. Покрытия на основе сплава олово-цинк являются отличной антикоррозийной защитой для стальных изделий. При осаждениев качестве барьерного слоя используется олово, а в качестве гальванического защитного слоя–цинк. Покрытия на основе олово-цинк первоначально применялись для защиты шасси электрооборудования и электронной техники, а также для защиты критических автодеталей, например, тормозной системы. В данной работе приведены результаты успешного применения сплава на основе олово-цинк в качестве покрытия пирофосфатных ванн. Соответствующие пропорции сплава олова и цинка определены составом ванны и операционных параметров нанесения каждого отдельного слоя покрытия. Для электрохимических испытаний применялась ячейка из трех электродов. Испытания механизма электрохимического осаждения Sn-Zn покрытия проводились линейной и циклической вольтаммограммой. Параметры коррозии, включая влияние потенциал-время, коррозийный потенциал и плотность тока коррозии электрохимические осаждения сплава олово-цинк различного состава тестировались в растворе с содержанием 3% NaCl. Коррозийная стойкость зависит от состава отдельных слоев. Слой, содержащий Sn-28Zn отличается лучшими антикоррозийными свойствами. / Slojevi kalaja i cinka označeni su kao potencijalna alternativa za otrovni kadmijum korišćen kao zaštitni korozivni sloj. Slojevi na bazi legure kalaj-cinka poseduju izuzetnu korozivnu zaštitu za čelik, kombinujući zaštitu korišćenog kalaja kao barijere zajedno sa galvanskom zaštitom od cinka. Prevlake na bazi kalaja i cinka prvobitno su korišćene za šasije električnih i elektronskih aparatura ili za kritične delove i kočione sisteme. U ovom radu legure na bazi kalaja i cinka uspešno su proizvedene iz baznih pirofosfatnihkupatila. Proces izdvajanja metala daje kompaktan i finozrnasti deposit. Željeni odnosi cinka i kalaja u nanesenoj leguri odredjeni su od sastava kupatila i operacionih parametara tokom izdvajanja slojeva. Sistem od tri elektrode korišćen je za elektrohemijska istraživanja. Mehanizam elektrohemijskog taloženja Sn-Zn sloja ispitivan je linearnom i cikličnom voltametrijom. Parametri korozije, uključujući zavisnosti potencija-vreme, korozivni potencijal i gustinu struje korozije elektrohemijski taložene kalaj-cink legure različitih sastava izvođeni su u rastvoru koji sadrži 3% NaCl. Korozívna otpornost zavisi od sastava izdvojenog sloja, a sloj koji sadrži Sn-28 Zn pokazao je najbolja antikorozivna svojstva.
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