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Self-assembled monolayers (SAMs) are ordered molecular assemblies of organic molecules that form spontaneously on the substrate surface by exposing the substrate to a solution or gas containing molecules with self-assembling properties. Their application can change the surface properties of an object by forming a barrier between the substrate material and its environment. Therefore, their application has been extensively studied, including the protection of metals. Among their many advantages, studies have shown that while SAMs of many molecules exhibit good short-term protective properties, they are easily removed from the surface when exposed to corrosive media. Accordingly, many studies have focused on improving the long-term protective properties of SAMs. Crosslinking the already well- ordered molecular layer on the surface of a metal would make the film more resistant and significantly extend its lifetime by reducing the penetration of external molecules into the coatings. Radiation crosslinking is the process of using high-energy gamma rays or electron beams to initiate rapid chemical reactions between monomers and/or polymers that follow the free radical mechanism. The radiation-induced crosslinking is homogeneous, fast and can be carried out at room temperature without the use of solvents, initiators and/or catalysts. In this work, SAMs of different fatty acids were crosslinked on copper using gamma radiation. The protective properties of the crosslinked coatings were investigated by electrochemical measurements under simulated atmospheric conditions, while the surface properties of the coated metals were studied by contact angle measurements, Fourier transform infrared spectroscopy, and atomic force microscopy. The results have shown that crosslinking of the coatings significantly improves the long-term properties. Acknowledgements: We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting this research.

Corrosion causes major financial losses worldwide every year, and due to increasing air pollution, metals such as copper tend to degrade faster. Conventional methods of protecting metals, such as coatings, often contain toxic degradation products, so there is a need to develop a new environmentally friendly method of protecting metals. Fatty acids are non-toxic compounds that have an affinity for metals and self-assembling properties, forming self-assembled monolayers (SAMs) on the metal surface. In addition, SAMs from fatty acids can be crosslinked by gamma radiation, resulting in polymer nanocoatings with improved stability, durability, and other important properties. The aim of this research was to investigate the influence of double bonds and conformations of fatty acids on the protective properties of the nanocoatings obtained upon crosslinking using gamma irradiation. The influence of double bonds was investigated using two fatty acids: stearic acid, C18H36O2, a saturated fatty acid, and elaidic acid, C18H34O2, an unsaturated trans fatty acid. Two monounsaturated fatty acids with the same number of carbon atoms, C18H34O2: oleic acid, a cis-fatty acid, and elaidic acid, a trans-fatty acid, were used to study how the conformation of the fatty acids’ double bond affects the corrosion protection properties upon crosslinking. The properties of the obtained coatings under simulated atmospheric conditions were investigated using electrochemical impedance spectroscopy and Tafel extrapolation method, while the hydrophobic properties of the coated copper surface were determined using contact angle goniometry. The results showed that the saturated fatty acid (stearic acid) exhibited better protective properties compared to elaidic acid, while oleic acid showed slightly inferior properties compared to elaidic acid. We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting the research.

Rosuvastatin je lijek skupine statina koji se koristi za regulaciju visoke razine kolesterola u ljudskom tijelu. Isto tako, rosuvastatin i ostali statini pokazuju zaštitnu ulogu protiv oksidativnog stresa uzrokovanog slobodnim radikalima. Cilj ovog istraživanja bio je identificirati krajnje produkte koji su nastali radikalnom razgradnjom rosuvastatina. Kako bi se potaknula radikalna razgradnja, vodena otopina rosuvastatina ozračena je različitim dozama gama zračenja (50-1000 Gy) pri oksidativnim uvjetima. Rosuvastatin i srodni degradacijski produkti odvojeni su nanoC18 kolonom gradijentnom elucijom, a identifikacija je provedena pomoću vezanog sustava nanoUPLC i nanoESI-QTOF. Pomoću točno mjerenih masa, zajedno s algoritmom usporedbe izotopnih raspodjela, provedena je elementna analiza kojom je identificirano devet degradacijskih produkata. U ovom je istraživanju po prvi puta provedena gama-inducirana razgradnja rosuvastatina te detaljno opisana kemijska struktura, MS/MS fragmentacija te mehanizam nastanka pojedinog degradacijskog produkta. Priloženi rezultati doprinose razumijevanju razgradnog puta rosuvastatina i ostalih statina pri gama zračenju.

Crosslinking of a well-ordered layer of self- assembled molecules (SAMs) on the surface of copper additionally enhances SAMs protective properties by improving their functional properties as well as reducing penetration of external molecules into the coatings [1]. Thus, the obtained polymer nanocoating (PNC) has significantly higher stability and better protective properties while retaining SAMs numerous advantages. In this work elaidic acid (EA), a non-toxic unsaturated fatty acid (FA) was used as the self-assembling molecule, while crosslinking was initiated by ionizing irradiation. By using irradiation toxic agents that are used for classical crosslinking can be avoided, while on the other hand the process is homogeneous, fast and simple to perform. Since FAs are environment friendly molecules and crosslinking is performed without toxic agents the process can be considered as a Green Technology [2]. The aim of this work was to reduce the irradiation dose needed for successful crosslinking of a SAM of EA on copper by changing the irradiation media from air to water. Namely, previous research has shown that EA SAMs can be successfully crosslinked in air with 110 kGy. Reducing the applied irradiation dose would reduce the treatment price. This work has shown that when irradiated in water doses can be reduced to 40 kGy, but the polymer coatings obtained by crosslinking in air have somewhat better properties. The obtained coatings properties were investigated by contact angle measurements and FTIR Spectroscopy, while their behavior in atmospheric conditions was studied by electrochemical methods (Tafel extrapolation method and electrochemical impedance spectroscopy). ACKNOWLEDGEMENTS: We thank the Croatian Science Foundation (HRZZ IP-2020-02-4344) for supporting the research. REFERENCES [1] A. Pathania, J. Sharma, R. K. Arya, S. Ahuja. Prog. Org. Coat. 2018, 114, 78. [3] Woods, R.J. & Pikaev, A.L. Applied Radiation Chemistry: Radiation Processing (John Wiley & Sons, Inc., 1994).

Photodynamic therapy (PDT) is a cancer treatment that has been increasingly investigated. Photosensitizer (PS), light and oxygen are main components of PDT, and in their combination reactive oxygen species (ROS) are produced, which can lead to cytotoxic effect within the cell and consequent destruction of cancerous tissue [1]. The desired characteristics of the PS include stability of the molecule, high production of singlet oxygen and other ROS, good absorption in red or infrared region, negligible toxicity without irradiation and relative fast excretion from the body [2]. Porphyrins are often used as PSs because their structure can be relatively easily modified to achieve adequate lipophilicity of the molecule, or chelated by different cations, such as Zn(II) in our work. Amphiphilic molecules can facilitate cellular uptake while maintaining good water solubility [3], and Zn(II) is expected to increase the lifetime of the excited triplet state (3PS*), and thus the production of singlet oxygen [4]. In addition to the PS, light also plays an important role in PDT, so the optimal dose of light and the appropriate irradiation wavelenght should be selected [5]. Here we will present two groups of tripyridylporphyrins, Zn(II) and free-based, both conjugated with chains of different length. Spectroscopic properties of the ground state, as well as the excited state, of the obtained compounds were studied by using laser flash photolysis (LFP) and time-resolved single photon counting (TC-SPC). Lipophilicity and singlet oxygen production, which was investigated by using modified relative methods, will also be presented. In vitro studies of the PSs’ biological properties included evaluation of cytotoxicity on melanoma cell line (MeWo) and human foreskin fibroblasts (HFF), with two light sources used for photoactivation, with irradiation wavelength at 605 nm (orange light) and 645 nm (red light).

A big part of our cultural heritage (CH) is made from natural materials which are very sensitive to surrounding conditions and thus get easily infected. Disinfection through ionizing radiation has been proven to be very effective, because it is based on electromagnetic radiation from radioactive 60Co, which causes chemical damage of DNA molecules of all biological pollutants, while on the other hand in most cases leaving the materials constituting the object intact. Contrary to all other methods gamma rays are highly penetrating acting on all pests present in the whole volume of a treated object in their whole life cycles ; from spores to grown pests. Among all the advantages of radiation technology it needs to be outlined that it is harmless for humans and damage of the material is minimal, when using optimal conditions. In the process of irradiating a CH object the most important parameter to pay special attention to is the irradiation dose. The used dose depends on the type and degree of contamination, the desired reduction of pests and their radio sensitivity, as well as type of material and its condition. It is necessary to apply the smallest possible dose for deactivation of biological contaminants, which should also be smaller than the dose that would induce any changes in the material or change its appearance. In this work, we investigated the influence of radiation on natural leather which is used for restoring leather book covers using gama rays. With this research, we wanted to investigate the effect ionizing radiation has on natural leather, treated and non-treated. The main objective was to determine can radiation technology be used for preservation of cultural heritage made of leather and in which conditions. Applying radiation to objects made of leather, such as clothing, book covers or furniture is still rare due to insufficient research into the effects of radiation on leather. This work investigates the effect of ionizing radiation on natural leather, unimpregnated and impregnated, in order to determine whether radiation technology can be used for protection and preservation of CH made from leather. Goatskin was used for the investigations with two types of common impregnation agents: Leather preservative and Talas SC600 preservative. The samples were tested by colorimetry and pH measurements, as well as FTIR. In the dose range used on cultural heritage at both investigated dose rates no observable changes were noticed, according to colorimetry, pH or FTIR.

Sterilizacija je postupak u kojem se uništavaju svi mikroorganizmi pa i oni najrezistentniji poput bakterijskih spora. Kontrola sterilizacije provodi se fizikalnim, kemijskim i biološkim postupcima. Međutim, kemijski i fizikalni parametri sterilizacije ne pokazuju uspješnost procesa sterilizacije već potvrđuju da je materijal bio podvrgnut sterilizaciji odabranim postupkom. Jedna od najpouzdanijih, najprikladnijih i najjednostavnijih načina kojim se dokazuje učinkovitost sterilizacije je biološka kontrola. Jedna od često korištenih metoda za sterilizaciju različitih materijala i proizvoda poput medicinskog pribora za jednokratnu upotrebu, farmaceutskih sirovina, gotovih proizvoda i ambalaže je gama zračenje. To je efikasna, brza i sigurna metoda za inaktivaciju i eliminaciju svih bioloških kontaminanata u svim životnim ciklusima. U suradnji Nastavnog zavoda za javno zdravstvo Andrija Štampar i Instituta Ruđer Bošković provedeno je istraživanje djelotvornosti ionizirajućeg zračenja u postupku sterilizacije TSA i Sabouraud Dextrose agar Petrijevih zdjelica uz praćenje utjecaja gama zračenja na njihove fizikalno-kemijske parametre i mikrobiološke karakteristike u prisustvu bioloških indikatora koji sadrže spore Bacillus pumilus. Rezultati provedenih ispitivanja su pokazali da je primjena gama zračenja za postizanje sterilnih Petrijevih zdjelica kao gotovog proizvoda učinkovita budući su zahtjevi za sterilnost sukladno smjernicama EU i odgovarajućim europskim normama, u potpunosti zadovoljeni. Biološki indikatori koji su pritom bili upotrijebljeni dokazuju da su vegetativni oblici spora uništeni u procesu sterilizacije.

One of the largest health issue in modern society is increased frequency of hard tissues chronic diseases. Often the only treatment of such diseases is implementation with the aim to regenerate damaged or diseased tissue. Considering that the main inorganic component of hard tissue is biological apatite, form of calcium phosphate (CaP), composite materials based on calcium phosphate and different inorganic nanomaterials attracts attentions as possible new and innovative implant materials. Among different nanomaterials, TiO2 nanomaterials stand out because they can improve mechanical properties of CaP. Albumine is one of three soluble proteins which adsorbs on the surface of implant materialsright after its implantation and affect their behavior in vivo. But, its role in formation of calcium phosphates on titanium implants is still not clarified. Therefore, the aim of this study is to investigate the adsorption of bovine serum albumin (BSA) on nanocomposites of calcium phosphate (CaP) and TiO2 nanoparticles (CaP/TiNP) or nanotubes (CaP/TiNT). In order to do that, the kinetics of BSA adsorption kinetics of BSA adsorption on TiO2 nanoparticles (TiNP), titanate nanotubes (TiNT), calcium deficient hydoxiapatite (CaDHA) obtained in control system, CaP/TiNP and CaP/TiNT was measured in situ on UV/VIS scanning spectrophotomer. Samples obtained after adsorption were filtered and given for further analysis which included Fourier- transform infrared apectroscopy (FTIR), powder x-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of kinetics measurements were modeled using kinetics models of pseudo-first, pseudo-second rate and interparticle diffusion model. From the results of various kinetic models, the adsorption kinetics were found to follow pseudo-second- order rate kinetic model for CaP/TiNT nanocomposites, respectively pseudo-second- order rate and interparticle diffusion model for CaP/TiNP nanocomposites. Results obtained from FTIR, XRD and SEM analysis showed that albumin did not influence the composition and solid phase morphology

The Ruđer Bošković Institute (RBI) is the largest and most multidisciplinary scientific research institution in the Republic of Croatia. While the RBI is primarily concerned with fundamental research in fields ranging from theoretical physics to environmental research, its presence in applied science is currently expanding. The present contribution will demonstrate how fundamental concepts in physics and chemistry can be applied to the areas of food safety and quality. For example, the RBI's historical expertise with ionising radiation can be harnessed for the purpose of controlled sterilisation. Such treatments, as well as other processes can, however, lead to the formation of free-radical species with unpaired electrons. High-sensitivity detection of free radicals is possible in the presence of strong magnetic fields using electron paramagnetic resonance (EPR) spectroscopy, a technique which the RBI has used for fundamental research for many years. On the other end of the spectrum, the demand for products low in sugar is increasing markedly in recent times. This has led to an increased use of artificial sweeteners. Such substitutions, however, can have a dramatic influence on the physical and chemical properties of certain preparations. This situation opens new ways of leveraging RBI's fundamental knowledge of physical chemistry for concrete applications in the food industry.

Food irradiation is a physical method for food treatment comparable to processing food by heating or freezing it. Processing of food with low levels of radiation has the potential to contribute to reducing both spoilage of food during storage and the high incidence of food-borne diseases. The process involves intentionally exposed food, either prepackaged or in bulk, to gamma rays- X-rays or electrons. The most common and approved sources of gamma rays for food and industrial processing are radioisotope sources of cobalt-60 and caesium-137 and lineat accelerators of electrons. Different doses of gamma radiation can be used for different purposes in food preservation. At present, the dose of radiation recommended by the FAO/WHO Codex Alimentarius Commission must not exceed 10 kGy, at which irradiated food is considered safe for human consumption. This is actually a very small amount of energy equal to the amount of heat required to raise the temperature of 1 l of water by only 2.4 C. Food processing by irradiation can solve specific problems of food losses and could complement other established technologies, in improving the quality and wholesomeness of food as well as well as in expanding trade in certain foods and agricultural products. In this lecture the effects of irradiation on the physicochemical properties of food will be described. The legislation and control mechanisms required to ensure the safety of food irradiation facilities will also be discussed. Education is seen as the key to promoting the understanding of the benefits that irradiation can provide.

Copper has been widely used in construction of sculptures and other works of art for ages. When exposed to air a thin oxide layer is formed. This layer offers natural protection to copper. Due to increased environmental pollution copper’s natural protection is not enough. In order to preserve cultural heritage in these conditions it is necessary to apply additional protection from corrosion. Formation of a thin self-assembled protective film (SAM) on the surface of the natural oxide film is a good and practical way to enhance the metal’s natural protective properties. Fatty acids are non-toxic compounds which have an affinity for adsorbing on metals with their hydrophobic end, the carboxyl group. The other end of fatty acids chain has hydrophobic properties and when adsorbed on the metal surface it makes the whole surface of the metal appear hydrophobic. Thus by blocking access for water to the surface the dissolution of the metal is disabled. In this work elaidic acid (EA), a monounsaturated C18 trans fatty acid is used. Because of the specific shape due to the trans form of the double bond EA molecules are close-packed on the copper surface making the coating very compact and water difficult to approach the surface. The EA coating is convenient to be used for cultural heritage protection, because it is very thin and does not change the appearance of the surface. Unfortunately, when exposed to urban outdoors fatty acids tend to degrade and wash-off, and so the protective properties of the SAM are not long-lasting. The aim of this research is to investigate the possibility of using ionizing radiation to modify the structure of the elaidic acid SAM on copper’s surface. By radiation-induced crosslinking the coating would become more stable and durable, while it still would be only physically adsorbed on the surface.

Gamma irradiation method is efficient, safe and fast method for inactivation of all biological contaminants at all stages of their life cycle. This method is based on the ability of high-energy photons generated by radioactive 60Co to induce chemical DNA damage in biological contaminants such as insects, moulds, yeasts and bacteria. Therefore, γ-irradiation finds its use in sterilization of different materials such as medical supplies and pharmaceuticals and in food quality preservation. The aim of this research work was to investigate the physico-chemical parametars and microbiological characteristics of Tryptone soya and Sabouraud Dextrose agar media on Petri dishes after irradiation in dependence on the irradiation dose. Microbiological media (20 Petri dishes) packed in thermalshrinking foil were put in cardbox in the presence of biological indicators (spores of Bacillus pumilus). The three irradiation cycles were performed on the panoramic 60Co source at the Ruđer Bošković Institute. Dosimetry were established with the ethanol- chlorobenzene dosimetry system (ISO/ASTM 51538: 2017). Quality control of microbiological media was perfomed before and after irradiation according HRN EN ISO 11133. Physico-chemical parameters (appearance, color, homogeneity, agar consistency) and microbiological characteristics of culture media (sterility and productivity) were tested. Since the results of performed tests meet the requirements in accordance of guidelines of EU and corresponding standards we recommend these plates to be used for microbiological methods, validation of aseptic procedures control of safe operation under clean conditions. This research is result of collaboration of the Radiation Chemistry and Dosimetry Laboratory and the Department of Clinical Microbiology, Andrija Štampar Teaching Institute of Public Health in Zagreb

Background of the study Various metals and alloys are commonly used in medicine. As such they are often exposed to aggressive environments and thus subjected to corrosion, i.e. dissolution. Thus, modification of the metal surface is interesting since this way the resistance to corrosion can be increased and the durability of the object can be prolonged. Medical equipment, in most cases, must be sterilized and a common method is using ionizing radiation. While ionizing radiation does not markedly influence the properties of the metal it can influence the protective layer that is formed on its surface. Fatty acids are non-toxic compounds which have an affinity for self-assembling on metals and therefore lately they have been investigated as possible protective layers on metals. The influence of ionizing radiation on the formation of such a layer is needed to determine weather it changes the properties of the protective layer or maybe even enhances them. Methodology Procedures for adsorption of self-assembling layers of fatty acids on metals exist in literature. This work studies influence of ionizing gamma-radiation on the process of assembling such a layer and the efficiency of the outcoming layers in corrosion protection. Various variables are studied. The most important variables are the applied dose of gamma irradiation, as well as the dose rate at which it is applied. The quality and efficiency of the obtained layers in corrosion protection are studied by electrochemical methods. Results The results have shown that the layer of fatty acid that forms on the surface of the metal using ionizing radiation offers additional protection to the bare metal making it more resistive to corrosion. Conclusion For successful formation of a protective layer on the metal it is essential to determine the proper molecule which has good adhesive properties and to irradiate with an appropriate dose, at an optimal dose rate.

Background of the study. A common carrier for paintings is glue-coated linen that is vulnerable to fungal biodeterioration. The study aimed to assess antifungal effect of gamma-irradiation doses and dose rates against naturally occurring mycobiota and artificially inoculated primary, secondary and tertiary fungal colonizers common for cellulose materials like linen. The composition of natural mycobiota on glue-coated linen (initial level) and eventual post-irradiation recovery of mycobiota were analyzed. Methodology. The initial level of common fungal colony-forming mycobiota on model glue-coated linen textile was determined by plate count method upon 7 days of incubation (at 25°C and 70-80% r.h.) and the data expressed as the number of colony-forming units per gram (CFU/g). Next, linen samples were separately inoculated with selected primary (Aspergillus jensenii), secondary (Cladosporium spaherospermum) and tertiary colonizers (Trichoderma harzianum) at concentration of 104 CFU/g. Inoculated linen and controls were incubated as described. One group of samples was analysed immediately upon the incubation while the rest of the samples were irradiated at 60-Co gamma source at RCDL to doses of 2, 7, 20 and 50 kGy, at dose rates of 0.1 and 9.8 Gy/s and analysed after incubation for 0, 7, 14 and 28 days. Results. Alternaria spp., Aspergillus spp., Cladosporium spp. Fusarium spp., Penicillium spp. and yeasts comprised naturally occurring mycobiota, in initial concentrations of 103 CFU/g (molds) and 104 CFU/g (yeasts). These fungi were non-homogeneously dispersed on glue-coated linen. On incubation in humid atmosphere the concentration of mycobiota increased for four orders of magnitude. Similar increase was obtained for non-irradiated artificially inoculated samples. All applied doses and dose rates were effective against primary and tertiary colonizers but not for secondary colonizers and linen mycobiota. Doses of 2 and 7 kGy was ineffective in reduction of linen mycobiota to the initial level ; after 28 days of incubation fungi were recovered in concentrations up to 106 and 105 CFU/g, respectivelly. Dose of 20 kGy (0.1 Gy/s) reduced Cladosporium spp., and Alternaria spp. to 104 CFU/g ; Penicillium spp. was reduced to the initial level while yeasts, Aspergillus spp., and Fusarium spp. recovered in concentrations below initial. For both 7 and 20 kGy dose rate of 9.8 Gy/s was more effective in fungal elimination than 0.1. Gy/s while for 2 kGy the dose rate effect was inconsistent. Upon exposure to 50 kGy sterile white mycelia was recovered on few plates after incubation periods. Secondary colonizer, C. sphaerospermum survived radiation with 2, 7 and 20 kGy, and showed the similar recovery pattern as obtained for Cladosporium spp. After treatment with 7 and 20 kGy (0.1 Gy/s) cladosporia recovered between 7th (or 14th) and 28th day in concentrations between 103 and 106 CFU/g. The same doses with dose rate 9.8 Gy/s inhibited recovery of C. sphaerospermum. Conclusion. For successful gamma-radiation reduction of fungal contamination on cultural heritage it is essential to determine mycobiota composition and to irradiate at an appropriate dose rate.

Cultural heritage artefacts of organic origins are susceptible to deterioration by the action of insects, moulds, fungi and bacteria. The infestation of museum store rooms, collections and sacral places is a serious permanent worldwide problem to the safekeeping of such objects. Protecting cultural heritage objects against biodeterioration becomes especially urgent when provoked by sudden changes of their stable and optimum storage conditions, caused either by natural catastrophes (floods, earthquakes, tempests, etc.) or by human activities (wars, riots, street unrest, etc.). The emergency recovery of many objects in the course of a rescue operations can bring infested and non-infested objects into contact, engendering an abrupt development of pests and endangerment of whole collections. The commonly used methods for suppressing massive biocontamination (capable of fast processing of large numbers of objects), are treatment with poisonous gasses and treatment with ionizing radiation. While the use of ethylene oxide gas is now severely restricted, irradiation has proven an effective physical, noncontact method of preservation, applicable to massive treatment of cultural heritage objects. In its ~ 50 years of application to cultural heritage preservation, the irradiation method has most often been used for disinsection, i.e., eradication of insect pests from objects. In the course of safekeeping, massive treatments of entire museum collections during regular and/or urgent maintenance and clean-up procedures provide examples of especially appropriate applications of irradiation method. Likewise, in cases of simultaneous endangerment of many objects by mold, literally for entire collections caught up in catastrophes, the irradiation method has proven to be the method of choice. Professional literature presents some especially successful cases of massive decontamination by irradiation and it will be briefly presented in the lecture. Croatian experience in the field gained at the irradiation facility of the Radiation Chemistry and Dosimetry Laboratory of the Ruđer Bošković Institute in Zagreb during the past 25 years will be illustrated by two groups of examples of successful application of irradiation to the protection of large numbers of cultural heritage objects endangered by massive biocontamination: a) Massive radiation desinsection in the process of maintenance of museum collection and interventive treatment of an entire polychromic altar ; b) Radiation treatment in the massive process of rescuing and protecting art objects endangered during the war in Croatia (1991–1995). In co-operation with the Croatian Conservation Institute, one third of evacuated objects, mostly polychromic wooden sculptures, parts of altars and other wooden pieces, comprising almost 1500 complete altars, were irradiated for disinsection, or disinfection by the RBI facility. Besides halting degradation, irradiation was used as the first step of conservation to enable safe object storage without the risk of cross-contamination before final conservation and restoration.

The panoramic 60Co source at the Ruđer Bošković Institute is the only facility in Croatia suitable for variety of applications: from medium range of doses used in radiobiology and accident dosimetry to the high doses pertain to radiation processing and research in radiation chemistry. In November 2015 thanks to IAEA support the source was upgraded with additional 3.5 PBq. The results of precise dosimetric calibration and determination of the dose distribution curves typical for the cylindrical gamma ray panoramic source geometry are presented. Because of the cylindrical shape of the source, the radiation field also has a cylindrical symmetry and is best described by cylindrical coordinates. Radiation field mapping was performed with ethanol-chlorobenzene (ECB) dosimetry system which was discovered 50 years ago in Radiation Chemistry and Dosimetry Laboratory and developed later for scientific radiation research and dosimetry in radiation processing (ISO/ASTM 51538:2009). The commercial 5 cm3 pharmaceutical ampoules were used for irradiations. Irradiated ECB dosimeters were analysed for chloride ion concentration by two methods: oscillometry before opening ; after opening aliquots were taken for mercurimetric titration. Oscillometry was performed by oscillotitrator Model OK-302/1 (Radelkis Electrochemical Onstruments, Budapest). After measurements, the doses were evaluated from the previously determinated calibration curves. For mercurimetric titration, the standardization of Hg+2 solution used for titration with standard NaCl solutions was performed before the analysis of irradiated dosimetric solutions. All doses were expressed as “absorbed dose to water”, obtained from doses absorbed in ECB solutions multiplied with appropriate ratios of mass energy absorption coefficients for water and ECB. For dosimetry calibration and “transit” dose measurements an ionization chamber type 2581 and a Farmer Dosimeter type 2570 (NE Technology Limited, England) were used. Dose mapping in horizontal and vertical planes was performed with ECB dosimetry system, as it follows: (a) The check for the angular symmetry of the radiation field was performed inside the annular space enclosed by the source rack. (b) The dependence of the dose rate on the radius r from the plane axes of the cylinder, was measured at two heights: at h = 0 cm, which is in the horizontal plane passing through the centre of the source cylinder and at h = 100 cm. (c) The dependence of dose rate on the height h was measured at two radii: at r = 50 cm from the axis of the source, and at r = 100 cm from the axis, both in a vertical plane through the axis. The “transit dose” was measured at different radii at h = 0. In this work it was shown that the radiation field of the cylindrical gamma ray panoramic source geometry is fully described by using only two parameters, a radius r and distance h from the reference horizontal plane. Acknowledgment: The support of the IAEA in ensuring the timely supplies of the radioactive 60 Co over the years, especially through the recent Technical Co-operation Project CRO/1/006 (2014-2015) is gratefully acknowledged.

Background of the study. Polyunsaturated fatty acids (PUFA), major constituents of biological membranes are sensitive to a free radical attack. The reactions of PUFA with free radicals are known to occur via two main processes: (i) lipid peroxidation and (ii) cis– trans isomerization. Lipid peroxidation can be inhibited by thiols, due to their H-donation ability. On the other hand, thiyl radicals are known to catalyse the double bond isomerization in PUFA. Both processes have damaging potential that must be carefully considered for its consequences in a biological systems. Therefore, the protection against lipid degradation under oxidative and free radical conditions is of special interest. The aim of this study is to elucidate the influence of different naturally occurring antioxidants on lipid peroxidation and cis–trans isomerization processes in biomimetic model system under different conditions. Methodology. Model system containing mixed surfactant micelles and buffer was prepared by slow solubilization of linoleic acid (LH) in non-ionic surfactant micelles previously formed by mixing Tween®-20 and PB, pH 6.5. The composition of the investigated systems was typically 0.5 mM LH, 0.28 mM Tween®-20 and 5 mM PB (pH ~ 5). Ascorbic acid (AscH), -tocopherol (α-TOH) and resveratrol (ResOH)) of defined concentrations were added during preparation of model systems. The addition of the amphiphilic 2.8 mM 2- mercaptoethanol was added to previously prepared micelles just before irradiation. Model lipid systems were irradiated up to the dose of 400 Gy, in equilibrium with air or after saturation with N2O at room temperature using panoramic 60Co source at the Ruđer Bošković Institute. Accurate dose rates in the irradiating positions were established with the ethanol-chlorobenzene dosimetry system (ISO/ASTM 51538:2009). The concentrations of hydroperoxides of linoleic acid were determined by the spectrophotometric ferric thiocyanate method, and the geometrical isomerization of LH methyl ester was studied by capillary gas chromatography. Results. Under air-equlibrated conditions, the addition of different natural occuring antioxidants retarded the process of lipid peroxidation among which ResOH showed the best antioxidative property. In model systems where process of cis–trans isomerization prevailed, the presence of antioxidants influenced on a decrease of the trans isomerization level ; AscH was the the most effective inhibitor of radiation-induced trans- isomer formation. Among the natural compounds analyzed in this work an amphiphilic ResOH has proven to be the most effective antioxidant, also significant inhibitor for cis–trans isomerization process in conditions of low irradiation dose rates with formation of low initial radical species concentration. Conclusion. Results indicate that the cis–trans isomerization and lipid peroxidation processes level could be dependent on the hydrophilic/lipophilic properties of particular antioxidant and its localization in model lipid system. This study contributes to the understanding of the role of antioxidants in radical processes which are not only able to prevent peroxidation but can also behave as anti-isomerizing compounds.

Copper is a reddish-gold metal that is easily worked and drawn, it conducts both heat and electricity very well. Because of its very good properties it has a wide range of applications and is exposed to various often aggressive environments. Therefore, additional protection is required to enhance the protective properties of its naturally formed oxide film. Formation of a thin protective film on the copper surface is a good and practical way to enhance the metal’s natural protective properties. Fatty acids are non-toxic compounds which have an affinity for adsorbing on metals with their hydrophobic end, the carboxyl group. The other end of fatty acids, the methyl group, has hydrophobic properties and when adsorbed on the metal surface it makes the whole surface of the metal appear hydrophobic. Thus by blocking access for water to the surface the dissolution of the metal is disabled [2]. Elaidic acid is a monounsaturated fatty acid found in hydrogenated vegetable oils. Because of its specific shape that it has thanks to the trans form of the double bond its molecules are close-packed on the surface of copper making the coating very compact and water difficult to approach the surface.

Radiation decontamination offers fast and effective protection to damaged cultural heritage (CH) objects. Due to wider availability of irradiation sources like 60Co gamma radiation the treatment of CH objects became important in 1970's. At Laboratory for Radiation Chemistry and Dosimetry, (LRCD), Ruđer Bošković Institute, Zagreb, Croatia where CH objects are being treated for almost 25 years [1]. Linear accelerator of electrons (LINAC) is another common type of irradiator that is somewhat less suitable for heritage treatment because of lower penetration and homogeneity of electron beam. Radiation treatment has numerous advantages like radiation being a very effective and universal biocide with almost unlimited penetration, temperature independent, leaving no residues and not inducing secondary radioactivity. CH objects may be packed during treatment to protect them and to prevent recontamination. Radiation consolidation is also an option. In disastrous situations decontamination of CH objects may be necessary to ensure safety of restores and other personnel that handles it. Contaminant response to irradiation is based on experiences attained in radiation sterilization and sanitization of medical materials, pharmaceuticals, food and the like. In processing of CH objects doses are selected according to contamination - up to 0.5 kGy for disinsection, 4-10 kGy for fungi control while 5-20 kGy ensures microbiological decontamination. The dose may be fine tuned depending on the materials that constitute the object and its state. The decision is usually made by irradiation plant staff, in cooperation with restorer and other specialists. In radiation treatment of heritage objects special consideration should be given to protection from any unwanted side effects. In disastrous circumstances fungi and bacteria are likely contaminants so higher doses may be required. In order to meet the high standards of conservators and restores the effects of such doses should be assessed for a particular cultural heritage object. Because of that the knowledge of the material response to irradiation is of utmost importance. The most recent knowledge on the subject will be presented. For example, plain wooden objects can withstand any desired radiation dose other materials are less radiation resistant, especially paper and some textiles. Pigments, varnishes, glass, decorative stones and other ornaments made of various materials that have diverse radiation sensitivities are often present on the same object. The extent of inflicted damage to the heritage object has also to be taken into account when deciding on the radiation dose to be applied. At LRCD we are recently begun investigation of radiation effects in selected materials that are common constituents of CH objects like textiles since sensitivity of natural fibers to biological deteriorants is a serious problem. Examples of studies [2, 3] performed on model and authentic CH textiles will be presented. The tests were conducted on model samples of the most common textile materials in CH items. To ensure that the radiation effects will be observed a high dose in contact with air was applied. A part of the model samples were heat- or UV -aged before exposure to γ-irradiation. Changes were determined by a number of analytical techniques The results indicated that even a dose more than 20 times higher than otherwise recommended caused only slight changes comparable to or lesser than those caused artificial aging. That is another confirmation that textile CH items can be safely radiation treated for fungi control and probably microbiological decontaminated what is especially important in catastrophic circumstances. [1] B. Katušin-Ražem, D. Ražem, M. Braun, Radiat. Phys. Chem. 78 (2009), 7/8 ; 729-731. [2] K. Kavkler, A. Demšar, Polym. Degrad. Stab. 97 (2012), 5 ; 786-792. [3] I. Pucić, K. Kavkler, B. Mihaljević, to be published

The susceptibility of natural fibers to biological damage is a serious problem in the protection of cultural heritage (CH) objects made of textile [1]. The treatment with ionizing radiation has been widely used for disinfestation and decontamination of CH artifacts and necessary doses established: up to 0.5 kGy for insect control, 4-10 kGy for fungi control, and 5-20 kGy for microbial decontamination. A number of wooden, paper, textile and leather items have been treated over the past 20 years at the 60Co gamma irradiation facility of the Ruđer Bošković Institute in Zagreb, Croatia [2]. Textile artifacts, mostly of ethnological significance, were efficiently disinfected by irradiation to less than 2 kGy dose. However, the application of higher doses for the control of fungi needs to be justified by investigating the effects of irradiation on textile fibers and to determine whether the treatment complies to the high standards of conservator specialists considering undesirable changes. The most common textile materials in CH artifacts - silk, cotton, linen and wool were chosen and model samples were γ-irradiated to D=120 kGy in contact with air. Such high dose ensures that all radiation effects are detected and could be later recognized in textiles samples irradiated to doses needed for fungi control. A lot on information on structural and chemical effects brought into a material on irradiation can be quickly determined assessing its thermal properties using DSC and TGA. DSC thermograms of irradiated model textile samples were monitored immediately on irradiation and after a 6-day postirradiation period and compared to those of unirradiated samples and of the same materials that were artificially aged. In spite of high dose the changes due to irradiation were comparable or lesser that those brought in by artificial ageing. Based on this results it can be proposed that radiation treatment is efficient and safe for fungi control of CH textile materials. [1] K. Kavkler, A. Demšar, Polym. Degrad. Stab. 97 (2012) 5, 786−792. [2] B. Katušin-Ražem, D. Ražem, M. Braun, Radiat. Phys. Chem. 78 (2009), 7/8 ; 729-731.

Complexation of Fe-III ion with thiocyanate in dichloromethane-methanol solvent mixture was studied because of our interest in the analytical uses of Fe-II-to-Fe-III transformations in non-aqueous media. Molar absorptivity and composition of the complex, as well as the solvolysis constant and the stability constant of the complex as a function of the solution composition were determined by spectrophotometry. The composition of the complex throughout the solubility range of the components was that of a monocomplex, [FeNCS](2+). In highly acidic solutions, molar absorptivity of the complex was not influenced by acid concentration and was (13 700 +/- 700) dm(3) mol(-1) cm(-1). The solvolysis constant was similar to the value in water, K-s = 7.0 x 10(-3) mol dm(-3). The stability constant of the complex, on the other hand, was strongly influenced by acid concentration. Extrapolation to the infinite acid concentration yielded the stability constant 40 500 dm(3) mol(-1), which is adequate for analytical uses of the complex in non-aqueous media.

Uzročno-posljedične veze između slobodnih radikala u biološkim sustavima i različitih patoloških stanja omogućavaju da se radijacijsko-kemijske metode koriste za pripravu i praćenje njihovih reakcija u kontroliranim uvjetima. U ovom su radu istraživani radikali višenezasićene masne kiseline, prekursori za dvije vrste procesa, peroksidaciju i, posebno u prisustvu biološki važnih tiola, cis, trans-izomerizaciju na dvostrukoj vezi linolne kiseline, LiH. Pritom je razvijen modelni sustav micela LiH u kojemu se radikalski procesi mogu selektivno pratiti u uvjetima koji se, za razliku od fizioloških uvjeta, mogu prilagođavati potrebama eksperimentiranja. Prvi put se istražila povezanost tih dvaju radikalima induciranih procesa u biomimetičkim uvjetima te je pokazano da hidroperoksidi (LiOOH) i transkonfiguracija LiH nastaju i u oksidacijskim uvjetima. Biomimetički model priređen je s dodatkom 2-merkaptoetanola kao amfifilnog tiola, a inicijacija radikalskih procesa provedena gama zračenjem s dozama zračenja do 400 Gy u različitim uvjetima. U uvjetima ravnoteže sa zrakom uz značajnu koncentraciju LiOOH (~105 mol dm3) odvijao se i proces cis, transizomerizacije s katalitičkim ciklusom 370. Kako bi se predvidio utjecaj samoorganiziranih supramolekulskih struktura LiH na ispitivane procese istražen je i utjecaj veličine micela te prisutnost prirodnih antioksidansa. The cause-effect relationship between free radicals in biological systems and the various pathological conditions enable us to use the radiation-chemical methods for preparation and determination these reactions under controlled conditions. In this paper we investigated polyunsaturated fatty acid radicals which are precursors for the two types of processes, peroxidation and, especially in the presence of biologically relevant thiol, cis, transisomerization of linoleic acid (LiH). A model micellar system was developed in which radical processes of LiH were selectively determined under conditions that, in contrast to the physiological, could be adapted to the experiments requirements. These two radical-induced processes were compared for the first time under biomimetic conditions demonstrating that hydroperoxides (LiOOH) and trans-lipids can be formed under oxidizing conditions. Biomimetic model was prepared with the addition of 2-mercaptoethanol as amphiphilic thiol, and radical processes initiation was performed by -radiation up to 400 Gy under different conditions. In air-equilibrated solutions, together with substantial amount of LiOOH (~10-5 mol dm3), the cis, trans-isomerization process was also observed with a catalytic cycle of 370. In order to envisage the impact of self-organized supramolecular organization of LiH on the outcome of lipid peroxidation and cis, trans-isomerization processes, the influence of the micelle size and the presence of natural antioxidants were also studied.