Staklo je materijal koji se upotrebljava još od Antike pa sve do danas, ali je razvojem tehnologije postalo dostupno svima i sveprisutno je u industriji. Za proizvodnju stakla važan je sastav ...sirovina, a svojstva stakla ovise i o procesu proizvodnje. U članku je opisan proces proizvodnje stakla kroz povijest i razvoj novih vrsta stakla s boljim svojstvima. Također, uspoređeno je antropogeno s prirodnim staklima kao što su opsidijani i tektiti. Opisana su stakla koja se upotrebljavaju za izradu velikih teleskopa i u svemirskoj tehnologiji. U nastavnom dijelu opisani su jednostavni pokusi koji se mogu napraviti u učionici u sklopu STEM-orijentirane nastave.
Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna .
In this study, the effects of Zr, Zn and Cu additions on the microstructure, room-temperature and high-temperature mechanical properties of an Mg-3Sn-1Ca alloy (from 25 °C to 250 °C) were studied. ...The results reveal that additions of Zr and Zn do not change the phase composition of the alloy, composed of CaMgSn and Mg2Sn phases. After the addition of Zn, the grains are significantly refined, the volume fraction of the second phase is increased and dispersed, and the Mg2Ca phase is precipitated. The grain refinement of Zr is better than that of Zn. After adding the Cu element, the Mg2Cu phase precipitates besides the CaMgSn phase. A comparison of mechanical properties shows that the alloy with Zr (TXK311) has the best mechanical properties at room temperature and high temperature, and the elongation of the TXK311 alloy can reach 68.3 % at 250 °C. The TXK311 alloy was comprehensively considered to find its optimum mechanical properties. The analysis shows that fine grains, a uniform phase distribution and texture play important roles in the deformation of the alloy.
Bakterije i kvasci, a ponekad i filamentozne plijesni u kefirnim zrnima žive u složenom simbiotskom odnosu koji kefirna zrna čini jedinstvenom mikrobnom zajednicom u prirodi. Složenost i kompleksnost ...njihove fizičke i mikrobne strukture razlogom su što su kefirna zrna još uvijek mikrobiološki nedovoljno i nepotpuno istražena. U istraživanju mikrobnog sastava kefirnih zrna koriste se različiti mikrobiološki i molekularni pristupi. Razvojem metagenomike, bazirane na identifikaciji bez kultivacije, otvaraju se nove mogućnosti identifikacije do sada još neidentificiranih mikrobnih vrsta sadržanih u kefirnom zrnu. Do sada je identificirano preko 50 vrsta mikroorganizama prisutnih u kefirnom zrnu. U radu su prikazane do danas identificirane mikrobne vrste sadržane u kefirnim zrnima različitog podrijetla. Također, radi tehnološkog i mikrobiološkog značenja koja imaju kefirna zrna sama po sebi, u radu su detaljnije prikazani molekularni eksperimentalni pristupi koji se koriste u istraživanju njihove mikrobne bioraznolikosti.
Med arheološkimi izkopavanji na najdišču Kleszewo, enem izmed grobišč przeworske kulture na območju vzhodne Mazovije na vzhodu Poljske, so bile v dveh grobovih iz konca poznega predrimskega ...obdobja odkrite tri fibule vrste Jezerine. Vse tri so atipične oblike s trikotnim lokom in v enem primeru z rebrom na spodnjem delu loka. Primerjave jim lahko iščemo v severovzhodni Italiji in južni Panoniji (današnji Slovenija in Hrvaška). Najdbe tovrstnih fibul na območjih severno od Karpatov lahko povezujemo s stiki na dolge razdalje, domnevno v zvezi s trgovino z jantarjem.
This paper presents an invasive plant species that occur in the forests of Kalnik. It also presents the state of the distribution and their impact on forests of Kalnik. A total of 14 invasive species ...in the forests of Kalnik and these are –
Acer negundo
L.,
Ailanthus altissima
(Mill.) Swingle,
Ambrosia artemisiifolia
L.,
Amorpha fruticosa
L.,
Asclepias syriaca
L.,
Conyza canadensis
(L.) Cronquist,
Echinocystis lobata
(Michx.) Torr. et Gray,
Erigeron annuus
(L.) Pers.,
Impatiens glandulifera
Royle,
Juncus tenuis
Willd.),
Phytolacca americana
L.,
Reynoutria japonica
Houtt.,
Robinia pseudoacacia
L.,
Solidago gigantea
Aiton. Alochtonous vegetation is not only inevitable, but it also appears to be a constant future challenge in the globalizing world which communicates on all levels with every means possible. Its influence should not by any means be marginalized. Its importance and influence is not completely negative and there are possible benefits and dangers which should be controlled by the preventive measures and physical regulation. The most important species in Kalnik forest vegetation is definitely acacia. It is especially important for private forest lands where acacia tree has become very popular because of its characteristics as a fast growing tree species without any special requirements with relation to growth and it gives fast results concerning timber and firewood. Private lots are usually very small and fragmented. There is a growing need for timber, therefore the trees are grown extensively, from stumps and roots. Other woody species still do not pose a serious threat in economical or biological sense. The impact of herbaceous plants differs in various areas. The most problematic issues for the forestersare thick layers of unwanted specieswhich grow in young forest stands or in forests in the phase of restorationwhere these unwanted speciesinvasively compete with autochthonous species. In biological sense, invasive species pose a constant threat not only to domestic vegetation and biodiversity, but also to human health. We should also mention apiculture, a very important and well developed activity on Kalnik. Above mentioned species are very important and interesting for apiculture as a type of rich bee pasturage. Apiculture in this area depends on acacia pasturage and it is one of very important reasons for growing acacia tree. Other tree species are also valuable for bee pasturage, especially late in autumn when there is no other bee pasturage available and they are mostly species which blossom in autumn and represent a valuable source of pollen (Japanese Knotweed, Prickly cucumber and European goldenrod). Generally speaking, the biggest responsibility for possible consequences of invasive plant species to the vegetation of Kalnik lies on foresters who have to recognize and monitor the appearance of invasive species, especially in state forest lands where they grow and directly influence their composition and state.
U radu se navode invazivne biljne vrste koje se javljaju u šumama Kalnika. Također se navodi i stanje njihove rasprostranjenosti u Hrvatskoj i njihov utjecaj na šume Kalnika. Ukupno je zabilježeno 14 invazivnih vrsta koje u šumama Kalnika stvaraju probleme, a to su –
Acer negundo
L. (negundovac),
Ailanthus altissima
(Mill.) Swingle (pajasen),
Ambrosia artemisiifolia
L. (ambrozija),
Amorpha fruticosa
L. (čivitnjača),
Asclepias syriaca
L. (cigansko perje),
Conyza canadensis
(L.) Cronquist (kanadska hudoljetnica),
Echinocystis lobata
(Michx.) Torr. et Gray (divlji krastavac),
Erigeron annuus
(L.) Pers. (krasolika),
Impatiens glandulifera
Royle (žljezdasti nedirak),
Juncus tenuis
Willd. (nježni sit),
Phytolacca americana
L. (vinobojka),
Reynoutria japonica
Houtt. (japanski dvornik),
Robinia pseudoacacia
L. (bagrem),
Solidago gigantea
Aiton (velika zlatnica). Najviše problema u šumama Kalnika čini bagrem, i to na svim tipovima staništa i u sastojinama svih starosnih skupina, a posebno su štete značajne u mladim sastojinama te u sastojinama u fazi obnove. Na površinama nakon čistih sječa a prije pošumljavanja, u mladim sastojinama i osunčanim čistinama starih sastojina u fazi obnove, štetu čine i gusti sklopovi krasolike, ambrozije, žljezdastoga nedirka i vinobojke. Ostale navedene vrste za sada nalazimo uz rubove šuma, cesta, vlaka, obalama vodotoka te na šumskim čistinama, gdje dolaze u manjim skupinama ili pojedinačno te za sada ne čine ozbiljne štete, ali su stalna prijetnja autohtonim vrstama, kao i bioraznovrsnosti.
Do sada su u Glasniku Hrvatskog botaničkog društva objavljena četiri priloga koja popis flore Hrvatske i bazu podataka Flora Croatica (
https://hirc.botanic.hr/fcd/
) dopunjuju s novoopisanim i ...novootkrivenim biljnim svojtama te se provode nomenklaturne preinake već postojećih svojti. Kako bi se taj niz i dalje nastavio, ovaj prilog je peti u nizu te su u bazu podataka Flora Croatica dodane tri nove biljne svojte (
Veronica dalmatica
Padilla-García, Rojas-Andrés, López-González et M.M.Mart.Ort.,
Betula
×
aurata
Borkh. i
Alnus
×
pubescens
Tausch) koje su zabilježene po prvi puta za Hrvatsku. Osim toga, izvršena je jedna nomenklaturna preinka koja se odnosi na vrstu
Veronica orbiculata
A. Kern., a vrsta
Asyneuma pichelrii
(Vis.) Lakušić et Conti je izbačena iz popisa hrvatske flore.
an update of the Flora Croatica Database (
https://hirc.botanic.hr/fcd/
) with new entries of a newly described plant taxa and new discovered taxa in the flora, as well as nomenclatural changes were applied on already existing plant taxa. In order to continue this series, this contribution is the fifth in a series and three new plant taxa (
Veronica dalmatica
Padilla-García, Rojas-Andrés, López-González et M.M.Mart. Ort.,
Betula
×
aurata
Borkh. and
Alnus
×
pubescens
Tausch) have been added to the Flora Croatica Database, which are being recorded for the first time in Croatia. Besides, one nomenclatural change was made that refers to the species
Veronica orbiculata
A. Kern., and the species
Asyneuma pichleri
(Vis.) Lakušić et Conti is excluded from the checklist of the Croatian flora.
Electrochemical micromachining (ECMM) is a well know for manufacturing hard-to-cut materials, e.g., nickel-based alloys, titanium alloys and metal-matrix composites. For this reason it finds ...application in aerospace, automobile and biomedical industries. In this research Hastelloy C-276 is used as a workpiece and stainless-steel electrode coated with polytetrafluoroethylene (PTFE) to avoid stray current. The effect of process parameters such as voltage, duty cycle and electrolyte concentration on the machining speed and the surface-corrosion factor were studied. The range of 9–11 V has an impact on the machining speed. The electrolyte concentration range of 25–35 g/L shows a linear increase in the machining speed and the surface-corrosion factor is found to be highest at 1.1449 for an electrolyte concentration of 15g/L. The surface roughness depth profile depicts the values of Rz, Rt, Ra are 16.3 µm, 99.1 µm and 1.90 µm, and 15.4 µm, 50.6 µm and 1.49 µm, respectively.
U ovom tekstu biće reči o Blanšoovom (Maurice Blanchot) konceptu odnosa treće vrste i njegovim političkim implikacijama. Ove odnose ne karakteriše neko specifično svojstvo, već upravo odsustvo tih ...svojstava. Na taj način, autrui izmiče svim tradicionalnim dihotomijama karakterističnim za zapadnoevropsku tradiciju mišljenja: biće i ništavilo, subjekt i objekt, ja i drugi, prisustvo i odsustvo. Rečima Roberta Esposita (Roberto Esposito), Blanšoov autrui je možda najbolje definisati kao ono što je smešteno „na mestu ukrštanja na kom se jedno neprestano prevodi u drugo: ništavilo se prevodi u biće, prisustvo je ispražnjeno odsustvom, unutrašnjost se izliva u spoljašnjost“. Mišljenje i politika koji nisu oruđa moći, vlasti i održanja statusa quo čini se da su, danas više nego ikad, u rukama odnosa „treće vrste“, mesta na kojima se ukrštaju, prepliću i poništavaju pozicije subjekta i objekta, „nečasnih ljudi“, Lokovog (John Locke) papagaja, Deridine (Jacques Derrida) mačke, Nansijevih (Jean-Luc Nancy) „srca“, Melvilovog (Herman Melville) pisara Bartlbija i drugih. Jedino sa ovih mesta moguće je postaviti, toliko neophodna, drugačija pitanja – pitanja na koja su iz današnje perspektive odgovori još uvek nemislivi.
Pripravljena je serija ferocenom supstituiranih purinskih nukleobaza 1-10 te su izmjereni njihovi redoks-potencijali metodom cikličke voltametrije. Svi ispitani spojevi pokazali su reverzibilnu ...jednoelektronsku oksidaciju u rasponu potencijala od 330 do 470 mV. Također je uočena razlika redoks-potencijala od 100 mV između N7 i N9 regioizomera ispitivanih nukleobaza. Ispitana je i acelularna aktivnost stvaranja reaktivnih kisikovih vrsta (ROS) kolorimetrijskom metodom s DCFH 2 -DA te je utvrđeno da konjugati generiraju ROS, dok su ferocen i nukleobaze neaktivni. Različiti supstituenti na purinskom prstenu utječu na stvaranje ROS-a, što omogućuje dizajn biološki aktivnih konjugata ferocena i prikladnih nukleobaza.
A series of ferrocene-substituted purine-nucleobase derivatives 1-10 were synthesized and their redox potential was measured by cyclic voltammetry. Measured compounds showed a reversible one-electron oxidation in the range of 330–470 mV. A difference of 100 mV between N7 and N9 regioisomers was observed. In order to examine the tendency of ferrocene-nucleobase conjugates to produce reactive oxygen species (ROS), an acellular screening with DCFH 2 -DA assay was carried out. The nucleobases coupled with ferrocene generated ROS, while neither ferrocene itself nor the nucleobases were active. Changing the substituents on the purine ring can significantly influence the ROS generation of ferrocene-substituted nucleobases, which support design of biologically active ferrocene-nucleobase conjugates.
Dosad su u Glasniku Hrvatskog botaničkog društva objavljena tri priloga koja popis flore Hrvatske i bazu podataka Flora Croatica (http://hirc.botanic.hr/fcd) dopunjuju s novoopisanim i novootkrivenim ...biljnim svojtama te se provode nomenklaturne preinake već postojećih svojti. Kako bi se taj niz i dalje nastavio, ovaj prilog je četvrti u nizu te je u bazu podataka Flora Croatica dodano sedam novih biljnih svojti (Glaux maritima L., Cystopteris dickieana R. Sim, Teucrium x rohlenae K. Malý, Helianthemum jonium Lacaita & Grosser ex Bég., Ornithogalum sibthorpii Greuter, Carex phyllostachys C. A. Mey. i Amaranthus tuberculatus (Moq.) J.D. Sauer) koje se po prvi puta bilježe za Hrvatsku.
Till now in the Journal of the Croatian Botanical Society three contributions were published that serve as an update of the Flora Croatica Database (http://hirc.botanic.hr/fcd) with new entries of a newly described plant taxa and new discovered taxa in the flora, as well as nomenclatural changes were applied on already existing plant taxa. In order to continue this series, this contribution is the fourth in a series and seven new plant taxa (Glaux maritima L., Cystopteris dickieana R. Sim, Teucrium x rohlenae K. Malý, Helianthemum jonium Lacaita & Grosser ex Bég., Ornithogalum sibthorpii Greuter, Carex phyllostachys C. A. Mey. i Amaranthus tuberculatus (Moq.) J.D. Sauer) have been added to the Flora Croatica Database, which are being recorded for the first time in Croatia.
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