Mikroplastika (MP) posljednjih desetak godina izaziva zabrinutost znanstvene zajednice zbog velike prisutnosti u okolišu, dok mogući štetni učinci još nisu u potpunosti poznati. MP su čvrste, ...polimerne čestice, s dodanim aditivima, netopljive u vodi dimenzija od 1µm do 5mm. Dosad je dokazana prisutnost MP-a u različitim dijelovima okoliša, poput tla, oceana, jezera, sedimenata i izoliranih područja poput Marijanske brazde. Ljudi su izloženi MP-u unosom kontaminirane hrane. Mnogobrojna istraživanja rezultirala su pronalaskom znatne količine MP-a u pitkoj vodi, flaširanim pićima, soli, morskoj hrani i sl. Zakonska ograničenja i dalje nisu na izravan način obuhvatila MP kao skupinu onečišćivala, ali se direktivom EU-a do 2024. godine želi usvojiti metodologija za kvantificiranje MP-a s ciljem uvrštavanja MP-a na popis praćenih onečišćavala. Postojeće metode analize MP-a, iako u razvoju, najčešće uključuju spektroskopske metode poput infracrvene spektroskopije s Furierovom transformacijom (FTIR) i Ramanove spektroskopije, koje mogu pružiti informaciju o veličini, broju i obliku čestice, ali i o tipu polimera. No, unatoč napretku, još uvijek ne postoje standardizirane metode za usporedbu rezultata različitih istraživanja. U ovom preglednom radu glavni je cilj pružiti pregled metoda analize i izazova s kojima se istraživači suočavaju. Kroz analizu raznih metoda, poput destruktivnih (pirolize) i nedestruktivnih (kao što su spektroskopske metode), dobiva se širi uvid u tipove polimera, broj, veličinu i oblik čestica. Međutim, nedostatak standardiziranih protokola za pripremu uzorka, analizu i obradu podataka otežava usporedbu rezultata i smanjuje pouzdanost istraživanja. Stoga je ključno propisati eksperimentalne uvjete da bi se osigurala kvaliteta istraživanja i omogućila meta-analiza te pregled prisutnosti MP-a u različitim okolišnim matricama.
Održavanje adekvatne opskrbe mozga kisikom sukladno metaboličkim potrebama ključan je korak u zbrinjavanju pacijenta s akutnom ozljedom mozga u okviru Jedinice intenzivnog liječenja (JIL), bilo da se ...radi o pacijentima s traumatskom ozljedom mozga (eng. Traumatic brain injury, TBI), intracerebralnim (ICH) ili subarahnoidalnim krvarenjem (SAH), odnosno o perioperativnom zbrinjavanju pacijenata u okviru neurokirurških, kardiokirurških ili zahvata vaskularne kirurgije. Ti su pacijenti pod povećanim rizikom razvoja sekudarne ozljede mozga posljedično hipoksiji i ishemiji. Upravo je s ciljem sprječavanja sekundarne ozljede mozga započeto s monitoriranjem moždane oksigenacije. Dostupne se metode mogu podijeliti na neinvazivne – trenutno je jedina dostupna near-infracrvena spektroskopija (NIRS), i invazivne poput monitoriranja jugularne venske saturacije kisikom (SjvO2) i monitoriranja parcijalnog tlaka kisika u moždanom parenhimu (PtiO2). Svaka od metoda ima svoje prednosti, ali i nedostatke, uz mjesto u kliničkom radu, te će isti uz opis metode i kliničku primjenu biti prikazani u ovome radu.
Cilj ovog rada bio je pripremiti poli(3-hidroksibutirat)/montmorilonit (PHB/MMT) kompozite na laboratorijskoj preši uz zagrijavanje te odrediti utjecaj različitih modelnih otopina na kompozite i ...migraciju punila. Analiza modelnih otopina nakon ispitivanja migracije provedena je pomoću UV/Vis spektroskopije. Zbog utvrđene hidrolize PHB-a pod utjecajem modelnih otopina nemoguće je odrediti migraciju MMT-a iz kompozita PHB/MMT. Diferencijalna pretražna kalorimetrija (DSC) potvrdila je razgradnju PHB-a. Provedenim istraživanjem ukazalo se na potencijal uporabe UV/Vis spektroskopije kod ispitivanja utjecaja modelnih otopina na polimerne kompozite.
The aim of this work was to prepare poly(3-hydroxybutyrate)/montmorillonite (PHB/MMT) composites on the laboratory press with heating, and to determine the influence of different food simulants on the composites and the filler migration. Analysis of the food simulants after migration testing was conducted with UV/Vis spectroscopy. Due to the established hydrolysis of PHB under the influence of the food simulants, it was impossible to determine the migration of MMT from PHB/MMT composites. Differential scanning calorimetry (DSC) confirmed the degradation of PHB. This research showed the potential of UV/Vis spectroscopy in dealing with the influence of food simulants on polymer composites.
Proces štavljenja ima najvažniju ulogu u postizanju trajnosti kože, čemu pridonosi umrežavanje stabilizirajući trostruku spiralnu strukturu kolagena. Čvrstoća nastalih veza ovisi o vrsti sredstva za ...štavljenje. Zbog dobrih svojstava kože nakon štavljenja, kao i same učinkovitosti, danas se najčešće koriste mineralna štavna sredstva. Međutim, zbog ekoloških aspekata vegatabilno štavljenje još uvijek je značajno prisutno. Mehanizam stabilizacije vegetabilnih štavnih sredstava temelji se na vodikovim vezama između polifenola i kolagena. Posljednjih godina sintetski zeoliti korišteni su u predštavnom procesu proizvodnje "wet-white" koža bez kroma, pokazujući bolja svojstva od drugih metoda "wet-white" predštave. Proces nadoštave omogućuje proizvodnju kože različitih karakteristika i svojstava. Štavna svojstva sintetskih zeolita i njihova učinkovitost u iscrpljivanju kroma iz štavne kupelji već su istraživana. Kombinirana uporaba zeolita i kroma rezultira većim iscrpljenjem kupelji i višim temperaturama skupljanja u kraćem vremenu, nego kod konvencionalnog procesa kromnog štavljenja. U ovom radu istražena je mogućnost štavljenja goveđe kože primjenom vegetabilne štave uz dodatak zeolita. Analiza fizikalno-kemijskih svojstava uzoraka izvedena je pomoću Fourierove transformacijske infracrvene spektroskopije (FT-IR). Uzorci su podvrgnuti termogravimetrijskoj analizi (TGA) s ciljem praćenja toplinske stabilnosti tako štavljenog uzorka goveđe kože. Također su na tako pripremljenim uzorcima provedena ispitivanje otpornosti na savijanje metodom fleksometra prema HRN EN ISO 5402-1:2017, propusnost vodene pare prema HRN EN ISO 14268:2012 te je utvrđena rastezljivost uzoraka i čvrstoća površine uzoraka prema HRN EN ISO 3379:2015.
Tanning plays the most important role in leather durability, stabilizing the triple helical structure of the collagen. It has been proven that the strength of the resulting bonds depends on the type of tanning agent. Today, mineral tanning is particularly popular due to tanning results. However, vegetable tanning is still used for certain purposes due to the environmental aspect. Mechanism of their stabilization is based on multi-hydrogen links between the polyphenols and collagen. In recent years, synthetic zeolite has been used in "wet white" pretanning and pretanned leather exhibiting better properties than other "wet white" pretanning methods. Subsequent tanning processes makes it possible to manufacture leather with different properties and characteristics. The tanning properties of synthetic zeolites and their effectiveness in the exhaustion of chrome tanning float have been previously investigated. Combined use of zeolite and chrome results in both higher float exhaustion and higher shrinkage temperatures in shorter time than in conventional chrome tanning. In this paper, the possibility of tanning beef leather using vegetable tanning with the addition of zeolite was investigated. The analysis of physicochemical properties of samples was performed using Fourier transform infrared (FT-IR) spectroscopy. The samples were subjected to thermogravimetric analysis (TGA) with the aim of monitoring the thermal stability of the tanned bovine leather sample. The samples thus prepared were also tested for flex resistance by the flexometer method according to HRN EN ISO 5402-1:2017 and for water vapor permeability according to HRN EN ISO 14268:2012, and the distension and surface strength of the samples were determined according to HRN EN ISO 3379:2015.
Kukuruzna silaža (KS) je glavna energetska komponenta obroka u hranidbi goveda za meso i mlijeko. Cilj rada bio je utvrditi kvalitetu KS s područja Sisačko–moslavačke županije proizvedenih tijekom ...2016. godine na deset obiteljskih poljoprivrednih gospodarstava (OPG). Analizirano je 65 uzoraka KS na organoleptičke, fizikalne, kemijske i biološke parametre kvalitete. Boja analiziranih uzoraka KS se kretala od normalne i zelenkaste do tamno smeđe, a miris od mirisa po alkoholu i maslačnoj kiselini do mirisa po karamelu. Najzastupljenija je bila duljina sječke od 0,8-1,9 cm (55 % analiziranih uzoraka), a zatim od 0,4-0,8 cm (31 % analiziranih uzoraka). Proizvedene KS su u prosjeku imale sadržaj suhe tvari (ST) 378,31 g kg-1 svježeg uzorka, neutralnih detergent vlakana (NDV) 407,78 g kg-1 ST, pH vrijednost 4,37, sadržaj sirovih proteina (SP) 72,81 g kg-1 ST, sadržaj škroba 343,3 g kg-1 ST, sadržaj metaboličke energije (ME) 10,85 MJ kg-1 ST, neto energije laktacije (NEL ) 6,56 MJ kg-1 ST i probavljivost organske tvari (POT) 71,1 %. Od ukupno analiziranih uzoraka se u optimalnu kvalitetu KS prema sadržaju ST može svrstati 23 % KS, sadržaju SP 46 %, škroba 18 %, pH vrijednosti 23 % analiziranih uzoraka dok prema POT 0% analiziranih uzoraka. Zaključeno je da su analizirane KS proizvedene su od usjeva kukuruza siliranih u kasnijim fazama fenološke zrelosti od optimalne za proizvodnju KS visoke kvalitete. Nadalje, vrijednosti sadržaja ST, NDV, pH i škroba su veće, a vrijednosti sadržaja SP, ME, NEL i POT niže od vrijednosti utvrđenih ranijim monitorinzima kvalitete KS na OPG-ima kao i poželjnih vrijednosti za KS. Varijabilna kvaliteta proizvedenih KS ukazuje na primijenjenu različitu tehnologiju uzgoja i siliranja usjeva kukuruza u istim mikroklimatskim uvjetima.
Corn silage (CS) is the main energy component of the ration in feeding cattle for meat and milk. The objective of this study was to determine the quality of CS from the Sisak-Moslavina County produced in 2016 on ten family farms. Total of 65 CS samples were analyzed for organoleptic, physical, chemical and biological quality parameters. The color of the analyzed CS ranged from normal and greenish to dark brown, and the smell from the smell of alcohol and butyric acid to the smell of caramel. The most common was the chopping length of 0.8-1.9 cm (55% of the analyzed samples), followed by 0.4-0.8 cm (31% of the analyzed samples). The CS produced had on average dry matter (DM) content 378.31 g kg-1 fresh sample, neutral detergent fiber (NDF) 407.78 g kg-1 DM and pH value 4.37, crude protein (CP) 72.81 g kg-1 DM, starch 343.3 g kg-1 DM, metabolic energy (ME) 10.85 MJ kg-1 DM, net energy for lactation (NEL ) 6.56 MJ kg-1 DM and digestibility of organic matter (OMD) 711 g kg-1 DM. Out of the total of analyzed samples, the optimal quality was determined in 23% of CS for DM, 46% for CP content, 18% for starch, 23% for pH value and 0% for OMD. It was concluded that the analyzed CS were produced from corn crops ensiled in later stages of phenological maturity than optimal for the production of high quality CS. Also, the values determined for DM, NDF, pH, starch were higher while the values for CP, ME, NEL i OMD lower than reported by previous monitoring of CS quality on family farms as well as the desired values for CS. The variable quality of the produced CS indicates applied different technology of cultivation and ensiling of corn crops in the same microclimatic conditions.
Cilj ovog stručnog rada je prikazati osnove razvoja kalibracijskih modela za procjenu fizikalnih, kemijskih i/ili bioloških parametara voluminozne krme bliskom infracrvenom spektroskopijom (NIR ...spektroskopijom). U usporedbi s klasičnim kemijskim metodama, NIR spektroskopija je multianalitička, ekološki potpuno prihvatljiva i brza metoda, jednostavna za primjenu i interpretaciju rezultata. Za korištenje NIR spektroskopije u svrhu procjene hranidbene vrijednosti voluminozne krme, neophodne su razvijene kalibracijske jednadžbe. Uzorci korišteni za razvoj primjenjivih kalibracija moraju biti dovoljno slični da pripadaju istom kalibracijskom setu, ali i dovoljno različiti da pokrivaju očekivane fizikalne, kemijske i/ili biološke varijabilnosti uzoraka nepoznatog kemijskog sastava. Razvoj kalibracija se sastoji od niza aktivnosti od prikupljanja/odabira uzoraka i njihove analize klasičnim kemijskim/fizikalnim i/ili biološkim metodama do predobrade i skeniranja uzoraka, razvoja kalibracijske jednadžbe primjenom neke od regresijskih metoda na spektralne podatke uzoraka, te primjene i kontrole razvijenog kalibracijskog modela procjene. Razvijena kalibracija koja ima stupanj korelacije (R2) što bliži 1.00, nisku standardnu grešku kalibracije (SEC), standardnu grešku unakrsne validacije (SECV) i standardnu grešku procjene (SEP) može se primjenjivati u praksi. Daljnja istraživanja su usmjerena na korištenje mobilne NIR spektroskopije za svakodnevnu primjenu na farmama.
The aim of this article is to present the basics of the development of calibration models for the estimation of the physical, chemical and / or biological parameters of forage by NIR spectroscopy. Compared to conventional chemical methods, NIR spectroscopy is a multianalytical, environmentally friendly and fast method, easy to apply and interpret results. For the use of NIR spectroscopy for the prediciton of the nutritional value of forages, developed calibration equations are necessary. The samples used to develop applicable calibrations must be similar enough to belong to the same calibration set but also sufficiently different to cover the expected physical, chemical and / or biological variability of samples of unknown chemical composition. Calibration development consists of a range of activities from collecting / selecting samples and analyzing them by classical chemical / physical and / or biological methods to pre-processing and scanning, developing a calibration equation and finally applying and controlling the developed calibration prediction model. A developed calibration with a degree of correlation (R2) closer to 1.00, a low standard error of calibration (SEC), a standard error of cross-validation (SECV), and a standard error of prediction (SEP) can be applied in practice. Further research is focused on the use of mobile NIR spectroscopy for daily on-farm application.
Al-Si/Al-Mn composites are commonly used in aluminum heat exchangers. Improving their corrosion resistance is the key for prolonging their service life and reducing their costs. In this paper, an ...artificial salt spray corrosion test was adopted in accordance with the ASTM G85 standard to evaluate the atmospheric corrosion resistance of Al-Si/Al-Mn composites. The corroded samples were tested with electrochemical impedance spectroscopy (EIS). Microstructure evolution and their corrosion mechanism were discussed after the use of OM, SEM, EPMA and XRD. The results showed two corrosion mechanisms, including the pitting-induction mechanism and intergranular-development mechanism: pitting is induced by the destruction of the passive film as Cl– is adsorbed at the defects, while the corrosive medium in the pitting pores expands along the grain boundaries where eutectic Si is enriched. A corrosion process can be divided into three periods: the pitting-induction period, pitting-propagation period and matrix-corrosion period. The equivalent circuit models established sequentially were consistent with the actual macroscopic and microscopic observations.
Ubrzo nakon uvođenja komercijalnih automatskih detektora bojnih otrova, većinom temeljenih na spektrometriji ionske pokretljivosti, krajem 20. stoljeća razvijaju se terenski uređaji koji primjenjuju ...i druge tehnike kemijske detekcije (FTIR, Raman, GC-MS, površinski akustični val, fotoakustične, elektrokemijske, biosenzorske i ostale). Od navedenih tehnika, prijenosni GC-MS detektori omogućuju vrlo pouzdanu kvalitativnu i kvantitativnu kemijsku analizu, no problem predstavljaju visoka cijena tih uređaja, zahtjevnost u rukovanju s njima te kompleksna priprema uzoraka. Neke tehnike kemijske detekcije nisu primjenjive za razvoj pouzdanog ručnog kemijskog detektora, a niti jedna tehnika, zasad, ne omogućuje razvoj univerzalnog kemijskog detektora. Potencijalno rješenje je razvoj višestrukog senzorskog uređaja koji bi kompenzirao negativne strane svakog od senzora. U ovom radu dan je pregled komercijalno dostupnih kemijskih detektora temeljenih na novim generacijama tehnika detekcije te pregled znanstvenih istraživanja usmjerenih na daljnji razvoj detekcije bojnih otrova s jednostavnijim, pouzdanijim i poželjno jeftinijim rješenjima.
Mikroplastika predstavlja ozbiljan problem u morskom i priobalnom okolišu. Analiziran je uzorak mikroplastike iz sedimenta plaže Prapratno na poluotoku Pelješcu, Hrvatska. Uzorkovanje i ...laboratorijsko odvajanje provedeni su prema DeFishGear protokolu. Svaki ispitak svrstan je u određenu kategoriju te je svakom određena masa, boja, prozirnost, maksimalna dimenzija i površina. Identifikacija je provedena infracrvenom spektroskopijom (FTIR) – HATR tehnikom. Otpad s plaže Prapratno sastoji se uglavnom od polietilena te, u manjem udjelu, od polistirena i polipropilena.
Microplastics represent a major problem in the marine and coastal environment. In this work, microplastics from the sediment of Prapratno beach on the Pelješac Peninsula (Croatia) were analysed. Sampling and laboratory separation were performed according to the DeFishGear protocol ( Derelict Fishing Gear Management System in the Adriatic Region ). The microplastic waste from Prapratno beach sediment consisted of 116 specimens, which could be classified into 6 micro litter categories according to EU TG ML Master List (Fig. 1). Fragments were found to be the predominant category of microplastic waste from the sediment of Prapratno beach, followed by granules, films, pellets and foams, which were present in approximately the same number, while filaments were the least represented category (Fig. 2). The most important categories by mass were granules and fragments, followed by pellets, while films, foams and filaments made up a very small content of the total sample mass (Fig. 3). The numerical contents (Fig. 4), did not correspond to the mass contents (Fig. 3) of individual categories due to the different densities and thicknesses of the specimens in each category. Almost all the base colours were present in the analysed samples (Fig. 5), while 90.52 % of specimens were opaque (Fig. 6). The maximum dimension and surface area of each specimen was determined by Digimizer Image Analysis Software . Maximum dimensions in the range of 1–5 mm were observed in 52.59 % of the specimens, thus belonging to large microplastics (LMP), while 47.41 % of the specimens had maximum dimensions in the range of 5–20 mm, thus belonging to so-called mezzo litter. The distribution of specimen dimensions within LMP is shown in Fig. 8, and within mezzo litter in Fig. 9. The fraction of each category in the total sample surface area is shown in Fig. 10. These results are similar to the numerical fractions of categories, since the samples were generally in the narrow range of maximum dimensions, and thus their numerical fractions corresponded to their fraction in the total surface of the sample. Identification of plastic material was performed by infrared spectroscopy, HATR technique. The obtained spectra were compared with the spectra in the database (Fig. 11–13). The results showed (Fig. 14) that the microplastic waste from Prapratno beach was made of polyethylene (82.46 %), polystyrene (11.40 %) and polypropylene (6.14 %). These polymers came from plastic packaging since polyethylene, polystyrene and polypropylene are the most used polymers for plastic packaging.
U radu je dan pregled pojmova i jednadžbi vezanih uz određivanje zabranjene zone metodom difuzne refleksijske spektroskopije i uporabu Taucova grafičkog prikaza. Kako bi se demonstrirao postupak i ...vrednovala sama metoda, primjenom metode određena je zabranjena zona komercijalnih uzoraka anatasa, rutila, cinkita i hematita. Na temelju eksperimentalno dobivenih vrijednosti širine zabranjene zone komentirana je točnost metode te osjetljivost pri razlikovanju poluvodiča s direktnim i indirektnim prijelazima. Pokazano je da Taucova metoda nije besprijekorna niti u pogledu točnosti niti razlikovanja indirektnih i direktnih elektronskih prijelaza u poluvodičkim materijalima, ali je vrlo praktičan način određivanja širine zabranjene zone poluvodiča budući da ne zahtijeva pretjerano skupu instrumentaciju a obrada eksperimentalnih podataka relativno je jednostavna.
For the application of semiconductors, an important factor is the band gap,
i.e.
, the minimum
energy required for the transfer of electrons from the valence to the conduction band. One of the
possible methods for band gap determination is diffuse reflectance spectroscopy and Tauc plot. In
this paper, an overview of the terms and equations related to the said method is given, as well as
its utilization in the determination of band gaps of commercial samples of various metal oxides.
Thus, the procedure is demonstrated and evaluated through the determination of indirect and
direct band gap values of anatase (TiO2), rutile (TiO2), zincite (ZnO), and hematite (Fe2O3). All
samples were beforehand analysed and identified by X-ray powder diffraction on Shimadzu XRD
6000 diffractometer with CuKα radiation working in a step scan mode with steps of 0.02° and
counting time of 0.6 s. It was determined that all samples are well crystallized with relatively large
crystallite sizes. UV-Vis spectra of the samples, as well as barite, which was used as a reference,
were obtained on the UV-Vis spectrometer with an integrating sphere in total reflectance mode.
The UV-Vis DRS spectra were transformed to Kubelka-Munk function, after which Tauc plot was
used for the determination of the indirect and direct band gap values of all samples. The obtained
values for anatase were 3.20 eV for indirect transition and 3.41 eV for direct transition, and for
rutile 3.00 eV for indirect transition and 3.11 eV for direct transition. The zincite sample showed
an indirect band gap of 3.19 eV and direct band gap of 3.25 eV, while the obtained indirect band
gap value for hematite was 1.96 eV and direct band gap value 2.15 eV. As may be seen, the method is not particularly useful when distinguishing direct from indirect semiconductors, since, for all
samples, the curves in Tauc plot for both indirect and direct electron transitions possess a linear
dependence region from which the band gap value is estimated. However, the obtained band
gap values for all the studied semiconductors are in relatively good concordance with literature
references. The method is perhaps most useful in monitoring the variation of band gap depending
on the dopant content. Namely, the studied metal oxides are used in photocatalysis where the
addition of dopants is expected to reduce the band gap to visible light area, and thus improve
the photocatalytic activity of the semiconductor. It can be concluded that the Tauc method is not
perfect in terms of accuracy and differentiation between indirect and direct electron transitions in
semiconductors. Nevertheless, it is a very practical way of band gap assessment for semiconducting materials, because it requires no excessively expensive instrumentation, and the processing of
experimental data is rather simple.
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