Search

Microalgae are considered an accurate indicator of ecosystem perturbations induced by global climate change. The present work aims to investigate the alteration of temperature on surface properties and behaviour of three algal species using the complementary surface methods (electrochemical and atomic force microscopy). The results showed that the temperature-induced response of algae is species-specific due to the structural features of the cell envelope. Wall-less algae experience the largest nanomechanical and chemical change, while algae with silicified walls show the pronounced chemical change in the degree of hydrophobicity. Alterations of surface properties suggest a molecular modification of the algal barrier and cytoskeletal rearrangements due to a change in cell size, while algal morphology reveals no change. The physiological activity of cells showed a different organisation of released extracellular substances in the form of fine fibrillar structures, aggregated particles, and dense networks. Both types of algal responses, physiological activity, and molecular modification of the cell barrier determine the cell adhesion and motility. This study highlights the role of surface properties in cell-substrate and cell–cell interactions, which is important for the understanding of algal behaviour at natural interfaces and the mechanism of algal biofilm and aggregate formation in aquatic systems under the stress. Graphical abstract

The aim of our study is to expand the world-wide knowledge about pollutant transport in sediments of medium-sized meandering rivers and to explain barium distribution in Kupa River (Croatia), which showed as an ideal "natural laboratory". Sampling was performed twice at the same places with the time span of 15 years to see the changes in Ba concentrations after that period. Ba was analyzed using ICP-MS method on clay + silt sediment fraction (< 63 mu m). Modelling was performed in R environment. After barite mine ceased operation in 1990, Ba is still entering Kupica and Kupa rivers, as karstic underground still contains large amounts of barite waste. Ba concentrations in Kupa River sediments are still increasing consequently along the whole river length, except in Kupica River and first downstream sample in Kupa River. It seems that in this part of the river course erosion exceeded deposition processes. Also, there is an indication of changing the way of underground Ba transport. Erosion and deposition processes lead to formation of peak of Ba concentrations in the lower course of the Kupa River. The most important conclusion is that the peak was formed under one or two flood episodes, when sediment eroded from the upstream locations and was brought and deposited in the lower course of the river. Our modelling predicts that Ba source will not cease during the next 20 years. Additional sampling of river- and ground-water showed that the correlation between Ba in sediment and river water is statistically significant (0.79, p < 0.05). This might be result of Ba dissolution from the sediment and dilution with waters entering from Kupa River tributaries.

Purpose The objective of this study was to provide insights into the most recent responses of sediments to climate change and their capability to sequester atmospheric carbon (C). Methods Three sediment cores were collected, one from the western Black Sea, and two from the southern Adriatic Sea. Cores were extruded and sectioned into 1 cm or 0.5 cm intervals. Sections were frozen, weighed, freeze-dried, and then weighed again to obtain dry weights. Freeze-dried samples were dated by using lead 210 (Pb-210) and cesium 137/ americium 241 (Cs-137/Am-241). Organic and inorganic C were determined by combustion. Particle size distribution was determined using a Beckman Coulter particle size analyzer (LS 13,320; Beckman Coulter Inc.). Mineralogical analyses were carried out by a Philips X'Pert powder diffractometer. Results Sedimentation and organic and inorganic C accumulation rates increased with time in both the Black Sea and the Adriatic Sea. The increase in accumulation rates continued after the global introduction in the early 1970s of controls on the release of phosphorus (P) into the environment and despite the reduced sediment yield of major rivers (Po and Danube). Therefore, the increased accumulation of organic and inorganic C in the sediments cannot be assigned only to nutrient availability. Instead, we suggest that the increase in organic C is the consequence of the increase in atmospheric C, which has made more carbon dioxide (CO2) available to phytoplankton, thus enabling more efficient photosynthesis. This process known as CO2 fertilization may increase the organic C accumulation in sediments. Simultaneously, the increase of sea temperatures decreases the calcite solubility resulting in increases of the inorganic C accumulation. Conclusion Our results suggest that long-term, general increases in accumulation rates of organic and inorganic C in sediments are the consequence of increases in atmospheric C. This shows that coastal sediments play an important role in C uptake and thus in regulating the Earth's climate., Croatian Science Foundation-Youth Careers Development Project [ESF-DOK-1-2018]; Croatian Science Foundation [IP-01-2018], AV acknowledges the support of the Croatian Science Foundation-Youth Careers Development Project (ESF-DOK-1-2018). JO and TK acknowledge the support of the Croatian Science Foundation project IP-01-2018.

Training neural networks with faster gradient methods brings them to the edge of stability, proximity to which improves their generalization capability. However, it is not clear how to stably approach the edge. We propose a new activation function to model inner processes inside neurons with single-species population dynamics. The function induces essential dynamics in neural networks with a growth and harvest rate to improve their generalization capability.

Convergence and generalization are two crucial aspects of performance in neural networks. When analyzed separately, these properties may lead to contradictory results. Optimizing a convergence rate yields fast training, but does not guarantee the best generalization error. To avoid the conflict, recent studies suggest adopting a moderately large step size for optimizers, but the added value on the performance remains unclear. We propose the LIGHT function with the four configurations which regulate explicitly an improvement in convergence and generalization on testing. This contribution allows to: 1) improve both convergence and generalization of neural networks with no need to guarantee their stability; 2) build more reliable and explainable network architectures with no need for overparameterization. We refer to it as step size self-adaptation.

Assessment of environmental quality within marinas is essential to validate implemented environmental protection measures and to adopt appropriate action plans. Here we present temporal trends over the period from 2009 to 2018 using seasonal analysis of physico-chemical and microbiological parameters in seawater column and measurements of elements’ concentrations in surface sediments of the Marina Punat, located in the northern Adriatic Sea, in order to evaluate improvements and deteriorations in marine environmental quality. Environmental monitoring in Marina Punat is carried out four times per year (in May, July, August, and October) at four sampling points (three are within the marina and one is an outside control point). The parameters analysed in situ in a bottom and surface seawater layer are conductivity, dissolved oxygen (DO), pH, mineral oil, total coliform bacteria, faecal coliforms, and intestinal enterococci. The concentrations of elements K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, Zr, Sn, Hg, and Pb in surface sediments collected twice per year (in May and August) were analysed in the laboratory by the EDXRF technique. The concentrations of elements in sediments are compared to results from 2005, i.e. prior to full operation of wastewater treatment plants deployed in service areas where boats are repaired and antifouling paints (AFPs) are removed from boats’ hulls. There has been a significant improvement in sediment quality in Marina Punat after deployment of the wastewater treatment plants, especially with respect to Cu concentrations close to service areas. An increase in concentrations of V, Fe, Cu, Zn, As, and Pb in surface sediments within the marina due to passive leaching from AFPs is still present. On the whole data set, there were no trends in pH and DO values, however, strongly correlated seasonal trends were observed. The seasonal increase and decrease of DO and pH values in the seawater column are unlikely to be related to the marina’s activities. A quick overview of the status of the environmental monitoring in the marinas in Montenegro has been given. This study provides support data for further improvement of management practices in marinas, both in Croatia and Montenegro.

The present work aims to develop a fast and reliable procedure for motility analysis of a short-term effect of heavy metal cadmium on the algal cell response in laboratory conditions. Three unicellular motile species similar in cell length, while differing in the cell wall and the flagellar system are used as model algae. We quantitatively characterise motility in terms of swimming speed and search radius following addition of 1 mg Cd L−1. Both swimming speed and search radius determined in control algal cultures reflect morphological features of the corresponding flagellated system. After 1 h of cell exposure to a toxic concentration of cadmium, a statistically significant decrease in swimming speed is determined with predominant erratic cell movement on the spot in all examined cultures. After 3 h of cell exposure to cadmium, swimming speed in most of the examined cell cultures recovered close to the control value, indicating quick cell adaptation to elevated cadmium concentration. The results support the implementation of swimming speed and search radius as motility parameters for direct screening of cell physiological state, which is applicable to ecotoxicological studies providing insight into the mechanism of cell adaptation under stress, as well as a better understanding of the spatial distribution of algal cells in aquatic systems.

Results from a 3D numerical simulation of wind-induced currents and pollution spreading from a sewage outfall are described.The goal was to predict seawater sanitary quality in the Rijeka Bay, Adriatic Sea. A sea motion model was coupled with a modelof transport and chemical reactions of fecal coliforms (FC), fecal streptococci (FS) and dissolved oxygen. The selected simulationperiod of 36 hours following wastewater discharge was found to be sufficient for a significant extinction of bacteria. The simulationwas carried out for eight wind directions and two intensities (moderate and high). Mesh convergence was obtained. Twomesh sizes were coupled: coarse, for the whole Bay, and fine, for the northern part of the Bay, close to the sewage discharge ofthe Rijeka city.For all considered wind directions, the pollution plume with a concentration higher than 100 FC and 100 FS per 100 ml of seawateris conveyed mostly parallel to the coast in either north-west or south-east directions. The plume does not rise to the surfacebut stays at the depth of 10 to 20 meters. This is a consequence of the hydrodynamics of the Rijeka Bay: the bora wind carriesthe surface water layer out of the Bay through the Middle and Great Gates, while cold water enters the Bay from the layer belowthe thermocline. During the southern wind (jugo), the situation is reversed: warmer surface water enters the Bay through eitherthe Middle Gate or the Great Gate, while cold seawater exits through the bottom layer, accumulating warmer seawater in the Bay.The conclusion is that the Rijeka city sewage discharge Delta is well-designed, and the microorganism concentration is wellwithin the suggested regulatory range. The discharge site is far enough from the coast, where local streamlines are mostly parallelto the coast, hence the elevated pollution concentration does not come close to swimming and recreational areas. Even if thedischarge increases by 50%, which is unlikely in the near future, the pollution at beaches will stay within regulatory boundaries.

Non-equilibrium dynamics in the form of oscillations or chaos is often found to be a natural phenomenon in complex ecological systems. In this paper, we first analyze a tri-trophic food chain, which is an extension of the Rosenzweig-MacArthur di-trophic food chain. We then explore the impact of harvesting individual trophic levels to answer the following questions : a) when a non-equilibrium dynamics persists, b) whether it can locally be stabilized to a steady state, c) when the system switches from a stable steady state to a non-equilibrium dynamics and d) whether the Maximum Sustainable Yield (MSY) always exists when the top predator is harvested. It is shown that searching for a general theory to unify the harvesting induced stability must take into account the number of trophic levels and the degree of species enrichment, the outcomes that cannot be obtained from the earlier reports on prey-predator models. We also identify the situation where harvesting induces instability switching: the non-equilibrium state enters into a stable steady-state and then, upon more intensive harvesting, the steady-state again loses its stability. One of the new and important results is also that the MSY may not exist for harvesting the top predator. In general, our results contribute to biological conservation theory, fishery and ecosystem biodiversity management.

The goal of this paper is to quantify the atmospheric influence, i.e. the influence of wind in particular, on the sea dynamics in the Rijeka Bay (Adriatic Sea). This quantification is important for city sewage disposal and dispersion as well as surface pollution dispersion. We compare the effect of jugo (sirocco) and bora winds on a calm period. The resulting simulations show that the bora conveys the surface layer of sea water out of the bay through the Middle and the Great Gate while deep cold water enters the bay through the same gates. The mean vertical upward velocity component close to the coast is about 1 mm s-1. This is sufficient to rise cold water near the city of Rijeka to the surface in three hours and to significantly cool the surface layer during summer. For the south-east wind (jugo) the situation is reverse: the warmer surface sea water enters the bay through the Middle and the Great Gate, while the colder bottom sea water exits the bay through the Middle and the Great Gate, accumulating the warmer sea water in the bay. In the case of no wind the surface velocity vectors (at depths of 0.5 m) are disordered and do not follow any particular pattern while the movements at 12 m, 24 m, 36 m, 48 m, and 60 m show dominant flow from the western coast (of the island Krk) toward the eastern coast of the Istrian peninsula.

Understanding the relationship between the environmental conditions and life-history traits (such as growth, reproduction, and size at specific life stages) is important for understanding the population dynamics of a species and for constructing adaptable, relevant, and efficient conservation measures. For the endangered loggerhead turtle, characterizing effects of environmental conditions on the life-history traits is complicated by this species’ longevity, global distribution, and migratory way of life. Two significant environmental factors – temperature and available food – often account for most of observed intra-population variability in growth and reproduction rates, suggesting that those two factors determine the biological responses of an individual. Adopting this hypothesis, we simulate a range of the two environmental factors to quantify effects of changes in temperature and food availability on an individual's physiology (energy investment into processes such as growth, maturation, and reproduction) and the resulting life-history traits. To represent an individual, we use a previously developed mechanistic dynamic energy budget (DEB) model for loggerhead turtles. DEB models rely on one of the empirically best validated general ecological theories, which captures rules of energy acquisition and utilization. We found that the ultimate size (length and mass) is primarily affected by food availability, whereas growth and maturation are primarily affected by temperature whilst also showing positive correlation with available food. Reproduction increases with both food availability and temperature because food availability determines energy investment into egg production, and temperature affects the rate of related processes (such as vitellogenesis). Length at puberty varies between simulated scenarios by only a small proportion, suggesting that inter-individual variability plays a larger role for length at puberty than the environmental factors do.

Loggerhead turtle is an endangered sea turtle species with a migratory lifestyle and worldwide distribution, experiencing markedly different habitats throughout its lifetime. Environmental conditions, especially food availability and temperature, constrain the acquisition and the use of available energy, thus affecting physiological processes such as growth, maturation, and reproduction. These physiological processes at the population level determine survival, fecundity, and ultimately the population growth rate—a key indicator of the success of conservation efforts. As a first step towards the comprehensive understanding of how environment shapes the physiology and the life cycle of a loggerhead turtle, we constructed a full life cycle model based on the principles of energy acquisition and utilization embedded in the Dynamic Energy Budget (DEB) theory. We adapted the standard DEB model using data from published and unpublished sources to obtain parameter estimates and model predictions that could be compared with data. The outcome was a successful mathematical description of ontogeny and life history traits of the loggerhead turtle. Some deviations between the model and the data existed (such as an earlier age at sexual maturity and faster growth of the post-hatchlings), yet probable causes for these deviations were found informative and discussed in great detail. Physiological traits such as the capacity to withstand starvation, trade-offs between reproduction and growth, and changes in the energy budget throughout the ontogeny were inferred from the model. The results offer new insights into physiology and ecology of loggerhead turtle with the potential to lead to novel approaches in conservation of this endangered species.

Recent research in machine learning pointed to the core problem of state-of-the-art models which impedes their widespread adoption in different domains. The models' inability to differentiate between noise and subtle, yet significant variation in data leads to their vulnerability to adversarial perturbations that cause wrong predictions with high confidence. The study is aimed at identifying whether the algorithms inspired by biological evolution may achieve better results in cases where brittle robustness properties are highly sensitive to the slight noise. To answer this question, we introduce the new robust gradient descent inspired by the stability and adaptability of biological systems to unknown and changing environments. The proposed optimization technique involves an open-ended adaptation process with regard to two hyperparameters inherited from the generalized Verhulst population growth equation. The hyperparameters increase robustness to adversarial noise by penalizing the degree to which hardly visible changes in gradients impact prediction. The empirical evidence on synthetic and experimental datasets confirmed the viability of the bio-inspired gradient descent and suggested promising directions for future research. The code used for computational experiments is provided in a repository at https://github.com/yukinoi/bio_gradient_descent.

Frequency, severity, and geographic range of harmful blooms caused by a dinoflagellate Prorocentrum minimum have been increasing significantly over the past few decades. The ability to adapt nutrient quotas and carbon content to a wide range of environmental conditions is one of the key factors for the proliferation of P. minimum. Understanding the limits of stoichiometric variability in terms of nutrient quotas and carbon content would help explain the observed trends and assist in P. minimum growth model creation. This manuscript aggregates information from 15 studies to investigate variability in nutrient quotas and carbon content for a broad range of P. minimum isolates and clonal lines. Nitrogen quota, phosphorus quota, and carbon content in the studies varied between 11–107.5 pgN cell−1, 1.45–17.58 pgP cell−1, and 70–656.36 pgC cell−1, respectively. Regression analysis was used to estimate average nitrogen and phosphorus quotas as functions of carbon, and to show that carbon content variability explains 55% of nitrogen and 23% of phosphorus quota variability. Confidence intervals for data (CID) found during the analysis were used to define maximal and minimal nutrient quotas as functions of carbon content. The ratios of the upper and lower CID ranges can, therefore, be used to estimate nutrient storage capacity as a function of carbon content. The new results and comparison with other species show that, at least for P. minimum, carbon-based quotas are more suitable for modelling than cell-based quotas. Finally, results indicate that environmental nutrient availability affects quotas more than light does: while quota variability due to light remains within 80% CID, nutrient variability covers the 95% CID.

The paper considers the problem of accelerating the convergence of stochastic gradient descent (SGD) in an automatic way. Previous research puts forward such algorithms as Adagrad, Adadelta, RMSprop, Adam and etc. to adapt both the updates and learning rates to the slope of a loss function. However, these adaptive methods do not share the same regret bound as the gradient descent method. Adagrad provably achieves the optimal regret bound on the assumption of convexity but accumulates the squared gradients in the denominator that dramatically shrinks the learning rate. This research is aimed at introducing a generalized logistic map directly into the SGD method in order to automatically set its parameters to the slope of the logistic loss function. The optimizer based on the population may be considered as a meta-learner that learns how to tune both the learning rate and gradient updates with respect to the rate of population growth. The present study yields the “growing” descent method and a series of computational experiments to point out the benefits of the proposed meta-learner.

Some of the major European oil supply routes pass through the Adriatic Sea representing a potential to endanger the whole basin with an oil spill. Particularly high ecological vulnerability of Rijeka Bay is due to its geospatial characteristics as semi-enclosed basin. The simulated onemonth sea surface velocity field of Rijeka Bay was analyzed using Lagrangian coherent structures (LCSs) to assess the diffusion and chaotic advection of passive pollutants (dye). LCSs were extracted by the Finite-Time Lyapunov Exponents (FTLE), hypergraphs, Lagrangian advection alone and advection-diffusion methods. Results show relatively complex nonstationary flow dynamics in Rijeka Bay. Areas of ridges and valleys of FTLE fields spread in north-south and northeast-southwest directions, and they move toward east. Similarly, the hypergraphs method shows areas of attraction and areas of mixing that can be observed in stripes that stretch in directions north-south and northeast-southwest. In addition, the stripes of mesohyperbolic area spread toward east. To assess the potential of passive pollutant spreading, Gaussian pollutant source was simulated at the middle of the bay. The pollutant spreads in the same direction (north-south and northeast-southwest) with lateral diffusion of material proportional to diffusion coefficient.

This paper examines the application of maximum sustainable yield (MSY) policy in ecosystem and indicates when the ecosystem based fisheries management approach is required for conservation purpose. To describe the possible impacts of applying global MSY policy in an ecosystem, we have considered both specialist and generalist prey–predator models with different fishing efforts. It is found that harvesting both prey and predator species in specialist prey–predator systems, to achieve global maximum sustainable total yield (MSTY) under independent efforts, will cause the extinction of the predator species. In contrast, the global MSTY may exist in a generalist prey–predator system. If global MSTY does not exist, then it is due to the extinction of predator species. Hence, the prey species never goes to extinction under independent efforts and this scenario is quite different from the one found under combined harvesting effort.

The decomposition of the organic matter, in the form of excess feed and excreted faeces, introduced to the environment by aquaculture can endanger living organisms by lowering oxygen levels. To increase the accuracy of the oxygen utilization assessment, we developed linear (L-MOD) and non-linear models (NL-MOD) for the dynamics of decomposition and accumulation of the organic matter, oxygen utilization and ammonium production. The models are based on mass-balance stoichiometric reactions for conversion of organic matter into bacterial biomass under aerobic conditions. Organic matter is represented by a general chemical formula sensitive to protein, carbohydrate and lipid content. The mass of organic matter is expressed in chemical oxygen demand (COD) units, providing more convenient tracking of oxygen utilization. Degradable part of the organic matter is distinguished from a non-degradable part. The model results are compared with the data sets from simulated aquaculture pond experiment.

We investigate a community of independent logistically growing populations under a common harvesting effort which leads to the total maximum sustainable yield (TMSY). It is surprising that in the case of two populations with approximately equal carrying capacities, TMSY is reached while both populations persist, although their biotic potential may differ substantially. In general, however, TMSY with a common harvesting effort implies suboptimal fishing of some populations, overfishing of others and extinction of the rest of the populations. Since extinction of populations is a rule rather than an exception and since a community of independent populations is more robust than an ecosystem with multiple trophic levels, we call for urgent retraction of all legal documents advocating MSY in ecosystems.

With intent to help fisherman catch the most fish in the long run and to protect fish populations from extinction, major world fisheries regulation agencies have passed recommendations to implement sustainability in fisheries through the application of "maximum sustainable yield" (MSY). We show that application of MSY policy will lead to extinction of a large number of fish species in a majority of ecosystems. More precisely, we prove the following law: approaching MSY in ecosystems means that fish species will be driven to extinction for every fishery that includes fishing of at least one trophic level which is directly or indirectly used as food for a higher trophic level. Because such single and multispecies fisheries make a great majority of existing fisheries, attempts to reach MSY should be discouraged instead of being legally prescribed as a goal. Based on the above result, we offer a simple advice on how to manage a fishery in agreement with the Convention on Biological Diversity.

We conducted a 60-day experiment to investigate whether compensatory growth can fully compensate for reduced growth during food deprivation, and whether food deprivation improves feed conversion ratio (FCR) in gilthead sea bream (Sparus aurata L). During the first half of the experiment, four groups of fish were subjected to feeding levels ranging from starvation to satiation. All groups were fed to satiation during the second half of the experiment. As expected, the three food-deprived groups showed smaller growth rates during the first half, and compensatory growth in weight during the second half of the experiment. Although this may suggest complete compensation is possible, our analysis of length data suggests otherwise. The analysis shows that von Bertalanffy growth rates in length during the second half of the experiment did not differ significantly among groups. This leads us to conclude that fish did not compensate growth in length, and that the observed compensatory growth is mainly due to the rapid increase in condition of the fish. Because the maximum condition for any given length is limited, length limits the maximum weight of each fish. It follows that any retardation of growth in length implies a permanent loss of the weight increase potential which we defined as the maximum attainable increase in weight in a given period. Therefore, our results suggest that reduction in feeding which reduces growth also permanently reduces maximum attainable weight of gilthead sea bream in any given period. Considering the theoretical background we argue that, in addition to weight, one should always analyze length (or some other measure that incorporates length, such as condition) when characterizing compensatory growth. Finally, to facilitate comparison of our experiments to previous work in the field, we estimate gilthead sea bream maintenance ratio at 0.3% of body weight per day, and the optimum feeding ratio at 1.06% of body weight per day based on specific growth rate.

In order to be used within Environmental Impact Assessment study, we have developed a three-dimensional particle tracking model for prediction of benthic carbon loading (BCL) caused by fish farms. The model is based on stochastic differential equations for particle transport consistent with the well-known semi-empirical advection/diffusion equation. It requires only easily obtainable input data in the form of measured current record, the source location and a specification of local bathymetry. The model accounts for advection by long-term residual and tidal currents, turbulent diffusion, realistic bathymetry and variations in daily (monthly or yearly) emissions from fish farm. Here, we concentrate on the changes in sedimentation pattern caused by various bathymetric shapes. Examination of idealized cases reveals where and why we can expect the worst impact on benthic communities. For future reference, these results will be included into guidelines for fish farming.

Bolno rame jedan je od najčešćih bolnih sindroma u fizijatrijsko-reumatološkoj ambulanti. Fizikalna terapija je metoda izbora u konzervativnom liječenju bolnog ramena. Rani početak liječenja i mogućnost izbora neke od terapijskih procedura fizikalne terapije otvaraju mogućnost dobrog rezultata liječenja. Cilj ovoga rada je prikazati rezultate učinka radiofrekventne rezonance (RFR) na smanjenje boli i poboljšanje funkcionalnog statusa u liječenju pacijenata sa sindromom bolnog ramena. Ispitanici i metode: u ispitivanje je bilo uključeno 37 bolesnika sa sindromom bolnog ramena, koji su unatoč primijenjenoj medikamentoznoj terapiji i ranije primjenjivanih uobičajenih modaliteta fizikalne terapije, imali trajne bolove u ramenom zglobu, prosječno 3,5 mjeseca. Metode rada orijentirane na analizu bolnosti i funkcionalni status, uključivale su primjenu vizualne analogne skale (VAS) za ocjenu bolnosti, te primjenu Roles-Maudsley specifičnog upitnika za ocjenu funkcionalnog statusa. Za primjenu radiofrekeventne terapije korišten je uređaj Physio Wave Prestige. Modalitet fizikalne terapije apliciran je tijekom dva tjedna svaki drugi dan u trajanju od 40 minuta. Analize su izvršene prije tretmana RFR, te nakon prvog i drugog tjedna od primjene iste. Rezultati: nakon primjenjene RFR postigli smo značajnu redukciju bolnosti u svih ispitanika, te poboljšanje funkcionalnog statusa. Prosječna bolnost prije tretmana RFR iznosila je 67 mm (u rasponu od 50 do 85 mm), nakon tretmana bila je značajno manja (p < 0,01) i iznosila je 25,5 mm (u rasponu od 0 do 50 mm). Prije tretmana prosječna vrijednost funkcionalnog statusa iznosila je 3,1 (slab), a nakon tretmana 2,3 (vrlo dobar: p < 0,05). U 16 % ispitanika postigli smo potpunu odsutnost bolova i potpuni opseg pokreta, ocjena funkcionalnog statusa 1 (odličan). Zaključak: radiofrekventna rezonanca je učinkovita, sigurna, neinvazivna fizikalno- terapijska procedura koja u bolesnika sa sindromom bolnog ramena može smanjiti bolove i poboljšati funkcionalni status., Painful shoulder is one of the most common pain syndromes in physiatrist and rheumatological practice. Physical therapy is the method of choice in the conservative treatment of painful shoulder. Early initiation of treatment and choice of some of the treatment procedures of physical therapy opens the possibility of good treatment outcomes. The aim of this paper is to present the results of the effect of radio-frequency resonance (RFR) to reduce pain and improve functional status in the treatment of patients with the syndrome of painful shoulder. Patients and methods: the study included 37 patients with the syndrome of painful shoulder, who in spite of the applied medical therapy and applied before the usual modalities of physical therapy, had persistent pain in the shoulder joint for an average of 3.5 months. Methods of work-oriented analysis of pain and functional status included the implementation of a visual analogue scale (VAS) for pain assessment and application of Roles-Maudsley specific questionnaire for the assessment of functional status. The device that is used to apply radiofrequent therapy was the Physio Wave Prestige. The modality of physical therapy was administered for two weeks, every second day for 40 minutes. Analyses were performed before treatment and RFR after the first and second weeks of the their application Results: after applied RFR, we achieved a significant reduction in pain and improvement in the functional status of all patients. The average pain before AFA treatment was 67 mm (in the range of 50 to 85 mm), after treatment it was significantly lower (p < 0.01) and amounted to 25.5 mm (in the range 0 to 50 mm). Before treatment the average value of the functional status was 3.1 (weak), after treatment it was 2.3 (very good: p

Irrigation efficiency improvement requires optimization of its parameters like irrigation scheduling, threshold and amount of water usage. If these parameters are not satisfactorily optimized, negative consequences for the plantsoil system can occur with decreased yield and hence economic viability of the agricultural production. Numerical modelling represents an efficient, i.e. simple and fast method for optimizing and testing different irrigation scenarios. In this study HYDRUS-1D model assuming single- and dual- porosity systems was used to evaluate a triggered irrigation module for irrigation scheduling in maize/soybean cropping trials. Irrigation treatment consisted of two irrigation regimes (A2 = 60–100% field capacity (FC) and A3 = 80–100% FC) and control plot (A1) without irrigation. The model showed a very good fit to the measured data with satisfactory model efficiency values of 0.77, 0.69, and 0.93 (single-porosity model) and 0.84, 0.67, and 0.92 (dual-porosity model) for A1, A2, and A3 plots, respectively. The single-porosity model gave a slightly better fit in the irrigated plots while the dual-porosity model gave better performance in the control plot. This inconsistency between the two approaches is due to the manual irrigation triggering and uncertainty in field data timing collection. Using the triggered irrigation module provided more irrigation events during maize and soybean crop rotation and consequently increased cumulative amounts of irrigated water. However, that increase resulted in more water available in the root zone during high evapotranspiration period. The HYDRUS code can be used to optimize irrigation threshold values further by assuming different scenarios (e.g. different irrigation threshold or scheduling) or a different crop.

One of the consequences of the anticipated growth of tourist industry on the island Rab (Adriatic Sea) is that the source of wastewater will increase. Jf preselit practice of releasing wastewaters in to the sea were to continue, sea water quality in recreational zones would worsen. This forced Rab municipality to consider options for expansion of canalization, waste treatment and submarine outfalls. Three options were put forth. Analysis and model ing reported here were used to choose the most acceptable among proposed options. Based on estimates of wastewater sources and oceanographic properties, water quality around island Rab is predicted. It is concluded that in princip le each option could satisfy water quality criteria specified by the lawmaker. The option, which is chosen as the best solution, satisfies additional ecological as well as socially acceptable conditions.

A theoretical model of a life support system, composed of a cascade of well-mixed continuous culture reactors, is investigated (e.g. photoautotroph, herbivore and carnivore). Simple one limiting nutrient reactor equations provide a starting point for the analysis. Optimum surface illumination intensity for a given reactor depth and population density has been calculated. Linking reactors in a cascade enables decoupling of equations, easier analysis, control and optimisation. Greater stability is thereby also achieved. Maximum sustainable yield for a given nutrient input is found in a general cascade. Needed nutrient input for desired output from each reactor has been calculated as well. In contrast to a single reactor food chain, we found linear dependence of the highest trophic level in each reactor on the nutrient input. Model provides a theoretical basis for acquiring desired yield from each reactor, thus enabling formation of balanced diet for users (e.g. a spaceship crew). Nutrient cycling is achieved with bacterial degradation. A buffer, which acts as a low pass filter, is inserted in a cycle.

A representation of nutrients uptake and grazing processes, based on the specific uptake rate of multiple nutrients and specific predation rate in 1-predator_ n -prey systems, is applied to a model for simulation of deep-chlorophyll maximum (DCM) in seas. In the original model a formulation for uptake processes was obtained from a mononutrient system. A detailed analysis of differences between the original and a modified model is performed. The modification increases the peak, but does not change the depth of DCM. Replacing the expression for grazing processes contributed to the differences between results more than a change in the uptake formulation. This is a consequence of two facts, (a) nutrient cycling plays a secondary role in the model, making nitrate dominant and ammonium a superfluous variable; while (b) prey concentrations are closer to their half-saturation constants. Since the original model was calibrated using improper formulations in uptake and grazing processes, a new calibration was performed.

We give answers to two important problems arising in current fisheries: (i) how maximum sustainable yield (MSY) policy is influenced by the initial population level, and (ii) how harvesting, oscillation and MSY are related to each other in prey–predator systems. To examine the impact of initial population on exploitation, we analyze a single species model with strong Allee effect. It is found that even when the MSY exists, the dynamic solution may not converge to the equilibrium stock if the initial population level is higher but near the critical threshold level. In a prey–predator system with Allee effect in the prey species, the initial population does not have such important impact neither on MSY nor on maximum sustainable total yield (MSTY). However, harvesting the top predator may cause extinction of all species if odd number of trophic levels exist in the ecosystem. With regard to the second problem, we study two prey–predator models and establish that increasing harvesting effort either on prey, predator or both prey and predator destroys previously existing oscillation. Moreover, equilibrium stock both at MSY and MSTY level is stable. We also discuss the validity of found results to other prey–predator systems.

A new method is described for estimating the direction of an unknown air pollution source. A heterogeneous topographic exposure to the wind on the polluted surface is assumed. Hence, the method is applicable to mountainous or hilly areas. Estimators of the topographic exposure to wind are modelled using a digital elevation model for different hypothetical directions of wind using an azimuthal step. These estimators are correlated to soil pollution but any other relevant field sampling can be used. If significant, maximum positive correlation indicates the direction towards pollution source(s). When spatial sampling intensity is low, estimators of topographic exposure can be used to significantly improve spatial interpolation of measured values. The first application of the method were performed on a sample of heavy metals soil concentrations in the Risnjak National Park in Croatia. Maximum correlations between soil pollution and topographic exposure are obtained toward the west. This is the main direction of incoming cyclones and also the direction toward major industrial pollution sources.

Toxic substances in wastewaters that are released into the aquatic environment cause reduction of phytoplankton uptake up to 50 km away from the sources depending on the geometry of the coastal sea and the intensity of existing sources. This conclusion follows from an unusual application of the advection-diffusion-interaction equation to the transport of unknown toxic substances. The consequence is that if existing eutrophication models (without a toxicity submodel) reproduce phytoplankton densities in the coastal sea, then probably they have been miscalibrated. The problem could be solved by coupling transport of toxic substances to an eutrophication model given that results of uptake experiments are available.

We demonstrate how searching for the extrema of the rotational kinetic energy can be exploited to introduce the idea of the principal axes of inertia in a general and intuitive way. To that end, we propose a motivational starting point for a discussion with students, followed by a physical problem that, in its simplest form, can be handled using only basic calculus. Principal axes and moments of inertia arise seamlessly as solutions to the proposed problem. A numerical example is provided to emphasize key ideas. To encourage alternative ways of thinking, we also show how similar conclusions can be derived from the square of the angular momentum. A generalized procedure, appropriate for a classical mechanics course, is outlined in the Appendix.

Elements needed to obtain mass balance of a nutrient in a coastal sea by direct methods are: movement of water masses (current field), estimates of location and intensity of all major nutrient sources, estimate of nutrient inflow from the neighboring sea and a reliable estimate of the nutrient extinction in the water column. In practice, the intensity of major sources and extinction of nutrient water column are seldom known. Therefore inverse methods for the transport equation are employed to obtain mass balance. Mass balance of total phosphorus in the Izmit Bay for March 1994 suggests that total source from the coast is about 1.3 t P/day. The extinction constant is 12 days. The majority of TP originating from the land-based sources of the bay proper ends up in the lower layer of the bay. A small part is transported into the Marmara sea.

A system of n competing logistical species of the Volterra type under proportional harvesting strategy is analyzed. In case of selective harvesting, when the effort is adjusted to each species, the optimum effort may result in the total maximum sustainable yield (TMSY 1 ). When it exists, reaching TMSY 1 does not affect the system stability character, but it does affect the state, and hence some populations may reach too small a value to persist in nature. If competition is strong, species with smaller biotic potential may be driven to extinction. In case the system is harvested with a common harvesting effort, such as in trawler fishery, the total maximum sustainable yield (TMSY 2 ) is smaller than TMSY 1 , and all the species with lower or equal biotic potential to the optimum harvesting effort will be driven to extinction. In this case a call for implementation of the MSY is equivalent to a call for the extermination of some species and it runs directly against the Convention on Biological Diversity ( CBD, 1992 ). Therefore, all legal documents advocating MSY in ecosystems starting with the Johannesburg Plan of Implementation ( JPI, 2002 ) must be urgently retracted and replaced with adaptive management which will respect CBD.

Changes in longitudinal distribution of eutrophication parameters in brackish and marine layers of a stratified karstic estuary have been investigated from December 1988 until October 1989 on a gradient between a pristine and a moderately polluted area. In the estuary, only marine phytoplankton blooms were found to develop. Near the head of the estuary, blooms develop below the halocline. Marine phytoplankton is fed by nutrients released from the decay of sinking freshwater phytoplankton. Phytoplankton growth is P-limited. Hypoxia near the bottom follows the decay of occasionally large quantities of allochtonous freshwater and of autochthonous marine phytoplankton. In the lower estuary, blooms have been observed to develop in the brackish layer above the halocline due to high salinity in the layer and the existence of a local anthropogenic nutrient input.

The increase in intensive aquaculture production in the Bolinao Bay, Philippines reached the point of harmful influence to production stock. Up to the present, there has been no estimation of aquaculture carrying capacity which is based on quantification of processes responsible for (a) water quality inside the units, (b) impact to the seabed and (c) water quality in the whole Bolinao Bay. The numerical estimation of tidal circulation, which is the most dominant part of the hydrodynamical regime in the Bolinao Bay, represents an unavoidable step in the carrying capacity determination considering points (a), (b) and (c). The hydrodynamical model we apply is a free surface, 3D finite element tidal model, forced with sea elevation dynamics at three open boundaries. It incorporates an increase in bottom stress drag coefficients in the coral areas and advanced transport corrected advection scheme. The model simulations of water flow show good agreement with measured currents in the central part of the Bolinao Bay, southern and northeastern channel, while agreement in the areas in vicinity of northern channel is not as tight. In order to provide an insight into the water exchange in aquaculture units, to support local water quality models and seabed deposition models (points (a) and (b)), the area is mapped with neap tide mean, spring tide mean and 14-day mean current velocity contours. The highest 14-day mean velocities are attained in the southern channel (>17 cm s−1), while the mean velocities characteristic for northern part (

Chronoamperometry is proposed as a novel experimental technique for determination of the size of individual surface active particles in aquatic systems by analysis of their heterocoalescence signals at the dropping mercury electrode. Using model dispersions of methyl oleate and squalene in artificial seawater it was found that a range of volumes of surface active particles between 1 and 3000 μm3 is accessible to electrochemical analysis.

The Commission of the European Communities passed a resolution in 2006 to implement sustainability in EU fisheries through application of the maximum sustainable yield (MSY) based policy. It is shown here that attempts to reach MSY will lead towards extinction of species for every fishery that includes fishing of at least one trophic level which is directly or indirectly used as food for a higher trophic level. Because this condition is met by most single and multispecies fisheries, attempts to reach MSY should be discouraged instead of being legally prescribed as a goal. Based upon above result advice is given on how to manage a fishery which will not drive species to extinction.

The Commission of the European Communities passed a resolution in 2006 to implement sustainability in EU fisheries through application of the maximum sustainable yield (MSY) based policy. It is shown here that attempts to reach MSY will lead towards extinction of species for every fishery that includes fishing of at least one trophic level which is directly or indirectly used as food for a higher trophic level. Because this condition is met by most single and multispecies fisheries, attempts to reach MSY should be discouraged instead of being legally prescribed as a goal. Based upon above result advice is given on how to manage a fishery which will not drive species to extinction.

A sediment trap validation study was conducted near the commercial sea bass and sea bream fish farm in order to assess the predictive capability of a particle tracking deposition model. The validation procedure consisted of two distinct phases. First, the deposition of particulate waste (i.e. fecal pellets and excess feed) was measured near a single net pen containing 19 tons of sea bass. Afterwards, the model quality was determined by statistical comparison of predicted and observed values. Goodness of fit analysis indicates that the model successfully accounts for more than 75% of variance in the observed deposition. At 5% significance level, predictions do not underestimate or overestimate observations and there is no bias. Mean absolute relative error of ±48.9% compares favorably to other published deposition models. Obtained results affirm the reliability of particle tracking techniques in modeling the aquaculture-derived benthic organic enrichment.

Suppose that an arbitrary electric circuit with a network of capacitors is connected to a d.c. e.m.f. device. Herein we address several related questions. What is the equivalent capacitance of the network? What is the voltage and charge on each capacitor? How long will it take to charge the network and will all capacitors be charged at the same time? Finally, the most challenging among these questions: how, in fact, are capacitors being charged? We answer these questions using theory and experiment adapted to the undergraduate level.