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Abstract Background Aging is associated with many personal, social, and environmental challenges that increase the risk of loneliness. Loneliness is a painful emotional experience associated with a perceived lack of connection and intimacy. Loneliness accelerates health deterioration, but the presence of chronic health conditions (comorbidities) in older individuals may potentiate the feeling of loneliness. The relationships between health status and loneliness in older individuals have not been assessed in an integrated manner, although it is necessary for planning efficient interventions. The aim of this study was to fill in this knowledge gap, by attempting to create an integrated model of loneliness in older individuals. Methods The sample consisted of 189 (58% F) older individuals (> 60 years) (mean ± SD, 78.47 ± 6.65), attendees in Primary Health Care. Different factors associated with loneliness in the older population were assessed, and classified as demographic, environmental, physical (health-related), and psychological, in addition to functional abilities. A set of standard questionnaires was used to assess psychological factors and functional abilities. The hierarchical regression model assessed the effect of particular blocks of factors on status loneliness. The second aim was to analyze how psychological factors mediate associations between health status (comorbidity level) and loneliness. Results Indicated that increasing comorbidity, anxiety, lack of positive moods, not having hobbies/activities, low perception of social support, impaired cognitive function, and suppression of emotion expression, are significant predictors of loneliness. Mediation analysis informed us of how to help patients with comorbidities feel less lonely. Interventions that were suggested were those that can reduce anxiety and depression, improve cognitive abilities and emotional regulation control, and enhance social support. Conclusions Results can help understand the pathophysiology loops linking poor health status (comorbidity level) of older individuals and loneliness, and have significant potentials from the translational perspectives, as a decision-support tool.

In the last decade, due to climate change concerns and new environmental regulations in the EU, there was a tremendous rise in installed heat pump systems in new homes and buildings. The majority of these installed units are related to air-source heat pumps, as they offer a good trade-off between capital and operating expenses. However, when analysing heating and cooling heat pump systems from the primary energy consumption and ecological aspects, groundwater and shallow geothermal heat pump systems offer superior efficiency, compared to all market-available thermo-technical systems today. In the last decade, ground-source systems have seen some technological improvement by employing new borehole heat exchanger designs, such as piping with internal fins and a wider diameter (so called Turbocollector) to enhance the heat transfer between fluid and rock, as well as to reduce the pressure drop in the system. Furthermore, the process of drilling deeper offers higher ground temperatures and consequently higher seasonal performance factors in the heating cycle, due to the effect of the geothermal gradient. Nevertheless, although deeper boreholes provide better heat extraction rates per meter during the heat pump heating cycle, at the same time, it reduces heat rejection rates during the heat pump cooling cycle. The objective of this paper is to analyse and evaluate benefits and downsides of a new approach in the heat pump system design with deeper borehole heat exchangers of up to 300 m, comparing it to the traditional design of double-loop exchangers with 100 m depth. The geothermal borehole grid design simulation model, along with heat extraction and rejection, is performed on a yearly basis. The results are showing that the benefits of shallow geothermal boreholes, from the hydraulic and thermodynamic point of view, still dominate over deeper solutions.

The possibilities of using geothermal energy are slowly expanding to all areas of energy consumption, so the assessment of geothermal potential has become the backbone of energy policies in countries that have the potential. Countries and companies that have experience in the oil and gas industry are increasingly exploring the possibilities of first using the acquired knowledge, and then using the existing oil and gas infrastructure for the use of geothermal energy. For this reason, it is necessary to analyse the possibilities of using the existing infrastructure with all its limitations to maximise the energy potential of geothermal energy. The existing oil infrastructure, especially the wells, is in many cases not suitable for the production of brine and it is necessary to analyse the maximum impact of each well for the production of geothermal energy, with particular attention to the equipment installed in the well and the thickness of the geothermal reservoir in the oil and gas fields that would be suitable for the production of brine.

One of the important sources of renewable energy is geothermal heat. Its special feature of being independent 24/7 ensures the stability and security of the system, either for electricity or heat production. Geothermal energy has a local character and is limited by the geological characteristics of each state. In the Republic of Croatia, the development of geothermal energy is closely related to the development of the oil industry, as geothermal deposits were discovered during oil and gas exploration. Considering the established temperature gradients in Croatia, there is a greater possibility of using geothermal energy, and for this, it is necessary to evaluate its full potential and possibilities of use. The aim of this research is to determine the heat potential of the Croatian part of the Pannonian Basin System (CPBS), a part of Croatia with exceptional geothermal potential, based on the analysis of a large amount of well data with confirmed water inflow. In order to estimate the heat in place, the available data on the presence of inflow, temperature, and porosity, as well as permeability and volume for each well/reservoir included in the assessment, were considered. In geothermal reservoirs, one of the most important pieces of data besides petrophysical and thermodynamic data is the potential of the well, i.e., the maximum flow under certain permeability and porosity conditions. To define this, the productivity index was made dependent on the permeability of each well, and the inflow in each well was risked using Monte Carlo for three main geological phases in CPBS, which subsequently influenced inflow and spacing between production and injection wells. The beta-PERT distribution for permeability is used in Monte Carlo simulation to determine the most likely values and produce a distribution that resembles the real probability distribution. As a result, geothermal potential was mapped according to the obtained values of heat in place for part of the CPBS covered with analysed wells.

Kindergarten Grdelin in the city of Buzet, Istria, Croatia, was chosen to undergo a deep retrofit of the current thermotechnical system, as a part of the HORIZON 2020 HAPPEN project1. The existing shallow spiral heat exchanger field is insufficient to cover heating loads of the building. Therefore, additional BHEs were drilled and completed to determine optimal borehole heat exchanger type within the same geological environment. Four BHEs, either single U (1U) or double U (2U), with different geometrical setting and depth were tested: BHE-1 (50 m, 2U DN32 ribbed), BHE-2 (75 m, 2U DN40 ribbed), BHE-3 (100 m, 2U DN32 smooth) and BHE-4 (150 m, 1U DN45 ribbed). A thermal response test (TRT) was performed to obtain the ground thermal properties. Furthermore, synthetic TRT curves were calculated to describe temperature response in the case of different heat pulses. This was done to determine heat extraction rates and the capacity of each BHE type, according to EN14511 norm. It was established that the BHE-4 is the optimal design for heating and cooling purposes on the selected site due to positive impact of the geothermal gradient, higher initial borehole temperature and a positive effect of the ribbed inner wall.

Aim: The goal of this research is to examine the biofilm forming ability of Staphylococcus aureus and Pseudomonas aeruginosa clinical isolates in different in vitro conditions using Meuller-Hinton and Luria-Bertani broths. Material and methods: 30 strains of Pseudomonas aeruginosa and 30 strains of Staphylococcus aureus obtained from clinical specimens were used. After preparing the suspensions of bacteria inoculated on broths, they were set on microtiter plates and the biofilm production was measured using the spectrophotometric reader on 550 nm. Strains were classified into four categories: non producing, weak producers, moderate and strong producers, based on the comparison of the optical density of samples and negative control. Results: Both of the tested strains, successfully formed a biofilm in both broths (p

At three locations in Zagreb, classical and extended thermal response test (TRT) was conducted on installed coaxial heat exchangers. With classic TR test, thermogeological properties of the ground and thermal resistance of the borehole were determined at each location. It is seen that thermal conductivity of the ground varies, due to difference in geological profile of the sites. In addition, experimental research of steady-state thermal response step test (SSTRST) was carried out to determine heat rejection rates for passive and active cooling in steady state regime. Results showed that heat rejection rate is only between 8-11 W/m, which indicates that coaxial system is not suitable for passive cooling demands. Furthermore, the heat pump in passive cooling mode uses additional plate heat exchanger where there is additional temperature drop of working fluid by approximately 1,5 °C. Therefore, steady-state rejection rate for passive cooling is even lower for a real case project. Coaxial heat exchanger should be always designed for an active cooling regime with an operation of a heat pump compressor in a classical vapour compression refrigeration cycle.

The present work focuses on the determination of absolute permeability in an oil reservoir whose pressure is under the bubble point. The simulation of the reservoir and well with the simultaneous flow of oil and gas is performed using the Eclipse100 software. The main purpose of the simulation is to obtain pressure build-up tests for two reservoir systems, as the well testing technology requires the shut-in period, which increases the costs of the real well production cycle. In the first simulation it is presumed that the well is not damaged, having the skin effect equal to zero, while in the second one, the skin effect of the well in the same reservoir is 9,44. The aim is to compare the results of the pressure build-up test analysis for both cases. In each case, permeability is firstly calculated using four methods, given by different authors. The theoretical background and the process of obtaining the required results are given for each approach. Results are compared with the permeability as determined by the pressure transient analysis, using the Saphir software, for both the ideal and the damaged well. Differences in results are presented and discussed. Conclusions can be applied to real reservoir systems with the multiphase fluid flow in the porous media.

Wider Zagreb city area, capital city of Republic of Croatia, has significant potential for major implementation of geothermal heat pump systems in not just the residential sector, but in commercial sector as well. Geothermal heat pumps often cumulatively describes different earth energy heat exchanger installations, from groundwater up to shallow ground horizontal and borehole heat exchangers installations. Zagreb area has especially favourable both hydrogeological and thermogeological parameters, which allows implementation of different designs for residential and commercial heating and cooling. Analysis of comparative energy and economy advantages of heating and cooling with heat pump systems (air, ground or groundwater) was made for capital city of Zagreb. Since heat pump systems in residential area is always higher-class investment, there is often a need for whole year heating since projects increasingly incorporate outside swimming pool. Up till now, many authors investigated comparison of winter heating energy cost for different heat pump systems. However, outdoor swimming pool sometimes consumes as much heating energy during spring-summer-autumn season, as do house in autumn-winter-spring season. Since air temperatures during spring-summer season are much more favourable then sub-cooled ground or groundwater temperatures, air-source heat pumps when used in whole year round for heating, could offset economically unfavourable coefficient of performance (COP) during coldest days of winter. On a real residential home, currently in construction phase, techno-economic analysis was performed comparing seasonal performance factor (SPF) for different heat pump systems during whole year round heating.

Utilization of shallow geothermal energy is well known in several European countries. Even though large parts of Republic of Croatia show significant potential for it use, installation of ground source heat pump systems (heat pump and heat exchangers) is slowly progressing. Therefore, a short overview of so far published research concerning utilization and assessments of shallow geothermal potential for Croatia was done. In Croatia there is no agency or government department in charge of collecting and publishing data concerning installations of heat exchangers. Therefore, a study was done to collect available data of installed closed-loop heat exchangers either from scientific research or from personal contacts with drilling companies. Based on collected data a map was produced that shows general locations of installed heat exchangers. From obtained data of installed heat exchanger length, a first assessment of utilizing shallow geothermal potential in Croatia was given.

Based on the statistical analysis of the time series of data, the influence of the change of Sava River temperature and geothermal anomalies on the changes of the groundwater temperature of the Zagreb and Samobor-Zaprešić aquifers is described. In the analysis, data were used from daily measurements of the Sava River temperature and from the quarterly measurements of the groundwater temperature. Statistical methods of correlation, cross-correlation and linear regression were applied and the maximum, mean and minimum groundwater temperatures were analysed. Obtained results are presented in the form of statistical parameters, diagrams and maps of isotherms. This data is indispensable for development of shallow geothermal applications related to open loop groundwater heat pump systems. Since efficiency of the heat pump is directly dependent source temperature, presented analyses is necessary for prefeasibility study of geothermal projects and comparison between different designs. Furthermore, currently operating projects in the Zagreb and Samobor-Zaprešić are systematically elaborated, giving first approximation of energy consummation from this renewable energy resource.

The term resilience, which has been present in science for almost half a century, stands for the capacity of some system needed to overcome an amount of disturbance from the environment in order to avoid a change to another stable state. In medicine, the concept of resilience means the ability to deal with daily stress and disturbance to our homeostasis with the intention of protecting it from disturbance. With aging, the organism becomes more sensitive to environmental impacts and more susceptible to changes. Mental disturbances and a decline in psychological resilience in older people are potentiated with many social and environmental factors along with a subjective perception of decreasing health. Distinct from findings in younger age groups, mental and physical medical conditions in older people are closely associated with each other, sharing common mechanisms and potentiating each other’s development. Increased inflammation and oxidative stress have been recognized as the main driving mechanisms in the development of aging diseases. This paper aims to reveal, through a translational approach, physiological and molecular mechanisms of emotional distress and low psychological resilience in older individuals as driving mechanisms for the accelerated development of chronic aging diseases, and to systematize the available information sources on strategies for mitigation of low resilience in order to prevent chronic diseases.

Large scale development of tight oil resources in US started after 2010. with following five-year period of favorable steady increase in crude oil price. During this relatively short expansion cycle, operating and capital expenses changed drastically for main tight oil plays due to technological improvements in both well drilling and completion, expansion of service sector as well as loose government monetary policy which allowed favorable financing. This paper analyzed trends in costs during expansion period, as well as correlation of oil price to number of operating rigs and production quotas. After 2008/2009. world financial crisis economy recovery in US was somewhat sluggish and it caused extreme volatile environment in both equity and commodity markets. In such volatile environment intra-day crude oil prices, as well as other commodities and equities, show significant reaction to monthly published macroeconomic indicator reports, which give better overviews of trends in economic recovery. Prior to announcement, these reports always have forecasted value determined by consensus among market analysts. Therefore, any positive or negative surprise in real value tends to influence price of oil. This paper investigated influence of such macroeconomic reports to closing intraday oil price, as well as effect of other important daily market indices. Analysis showed that only Producer Price Index (PPI), among other indicators, has statistical significance of affecting intraday closing oil price.

ndisturbed ground temperature is one of the most crucial thermogeological parameters needed for shallow geothermal resources assessment. Energy considered to be geothermal is energy stored in the ground at depths where solar radiation has no effect. At depth where undisturbed ground temperature occurs there is no influence of seasonal variations in air temperature from surface. Exact temperature value, and depth where it occurs, is functionally dependent on surface climate parameters and thermogeologic properties of ground. After abovementioned depth, increase of ground temperature is solely dependent on geothermal gradient. Accurately determined value of undisturbed ground temperature is beneficial for proper sizing of borehole heat exchangers. On practical example of building which is being heated and cooled with shallow geothermal resource, influences of undisturbed ground temperature and geothermal gradient, on size of borehole heat exchanger are going to be presented. Sizing of borehole heat exchanger was calculated with commercial software Ground Loop Designer (GLD), which uses modified line source and cylinder source solutions of heat conduction in solids.

When considering implementation of shallow geothermal energy as a renewable source for heating and cooling of buildings, special care should be taken in the hydraulic design of the borehole heat exchanger system. Laminar flow can occur in pipes due to the usage of glycol mixtures at low temperature or inadequate flow rates. This can lead to lower heat extraction and rejection rates of the exchanger because of higher thermal resistance. Furthermore, by increasing the flow rate to achieve turbulent flow and satisfactory heat transfer rate can lead to an increase in the pressure drop of the system and oversizing of the circulation pump which leads to impairment of the seasonal coefficient of performance at the heat pump. The most frequently used borehole heat exchanger system in Europe is a double-loop pipe system with a smooth inner wall. Lately, development is focused on the implementation of a different configuration as well as with ribbed inner walls which ensures turbulent flow in the system, even at lower flow rates. At a location in Zagreb, standard and extended thermal response tests were conducted on three different heat exchanger configurations in the same geological environment. With a standard TRT test, thermogeological properties of the ground and thermal resistance of the borehole were determined for each smooth or turbulator pipe configuration. On the other hand, extended Steady-State Thermal Response Step Test (TRST) incorporates a series of power steps to determine borehole extraction rates at the defined steady-state heat transfer conditions of 0/−3 °C. When comparing most common exchanger, 2U-loop D32 smooth pipe, with novel 1U-loop D45 ribbed pipe, an increase in heat extraction of 6.5% can be observed. Also, when the same comparison is made with novel 2U-loop D32 ribbed pipe, an increase of 18.7% is achieved. Overall results show that heat exchangers with ribbed inner pipe wall have advantages over classic double-loop smooth pipe designs, in terms of greater steady-state heat extraction rate and more favorable hydraulic conditions.

Nuclear waste repositories should be designed in order to mantain the waste for several thousand years. Although the waste is stored in tanks that can persist the most extreme conditions, it is necessary to ensure that gases that can come into existence nearby the storage tank will not spread far from the repository well. Technology that was developed by petroleum exploration and production industry is at sofisticated enough to determine all geological and petrophysical aspects of the waste disposal. The main task is to determine if there is possibility of leakage pathways in the repository rock. That requires exploration in order to define geological model, by utilisation of well logging, 3D and 4D seismic measurements. Petrophysical measurements give data required for well-log calibration and input data for reservoir flow calculations and simulations. Well testing of pressure changes can give validation of lab data, and can be use din order to correct input data for flow calculations. Because of semi-empirical nature of the measured data interpretation, some testing and calculation methods should be slightly modified for nuclear waste repository (the paper is published in Croatian).

The undisturbed ground temperature is one of the key thermogeological parameters for the assessment and utilization of shallow geothermal resources. Geothermal energy is the type of energy which is stored in the ground where solar radiation has no effect. The depth at which the undisturbed ground temperature occurs, independent of seasonal changes in the surface air temperature, is functionally determined by climate parameters and thermogeological properties. In deeper layers, the increase of ground temperature depends solely on geothermal gradient. Determining accurate values of undisturbed ground temperature and depth of occurrence is crucial for the correct sizing of a borehole heat exchanger as part of the ground-source heat pump system, which is considered the most efficient technology for utilising shallow geothermal resources. The purpose of this paper is to define three specific temperature regions, based on the measured ground temperature data collected from the main meteorological stations in Croatia. The three regions are: Northern Croatia, Adriatic region, and the regions of Lika and Gorski Kotar.

The theory of Thermal Response Testing (TRT) is a well-known part of the sizing process of the geothermal exchange system. Multiple parameters influence the accuracy of effective ground thermal conductivity measurement; like testing time, variable power, climate interferences, groundwater effect, etc. To improve the accuracy of the TRT, we introduced a procedure to additionally analyze falloff temperature decline after the power test. The method is based on a premise of analogy between TRT and petroleum well testing, since the origin of both procedures lies in the diffusivity equation with solutions for heat conduction or pressure analysis during radial flow. Applying pressure build-up test interpretation techniques to borehole heat exchanger testing, greater accuracy could be achieved since ground conductivity could be obtained from this period. Analysis was conducted on a coaxial exchanger with five different power steps, and with both direct and reverse flow regimes. Each test was set with 96 h of classical TRT, followed by 96 h of temperature decline, making for almost 2000 h of cumulative borehole testing. Results showed that the ground conductivity value could vary by as much as 25%, depending on test time, seasonal period and power fluctuations, while the thermal conductivity obtained from the falloff period provided more stable values, with only a 10% value variation.

According to European Strategy for sustainable, competitive and secure energy, which guidelines are described in two documents: ‘’Green Paper: a European Strategy for Sustainable, Competitive and Secure Energy’’ and ‘’White Paper: Energy for the Future: Renewable Sources of Energy’’, it is predicted that share of renewable energy resources in total energy balance will raise from present 6% up to 15% until 2015. Croatia, as candidate country for EU admittance, with growing dependency upon imported energy because of continuous depletion of own energy resources, prior oil and gas, needs to follow EU strategic aims to achieve diversification of energy sources and implement and promote renewable energy resources. This paper presents strategy of geothermal resources development in Republic of Croatia for the period of 2007-2030 in cascade and cogeneration principle of energy utilization. These projections of geothermal energy development are part of comprehensive Strategy of Mineral Resources Development which is made by Faculty of Mining, Geology and Petroleum Engineering for Ministry of Economy, Labour and Entrepreneurship.

Production of synthetic diesel fuel through Fischer-Tropsch process is a well known technology which dates from II World War, when Germany was producing transport fuel from coal. This process has been further improved in the South Africa due to period of international isolation. Today, with high crude oil market cost and increased demand of energy from China and India, as well as global ecological awareness and need to improve air quality in urban surroundings, many projects are being planned regarding production of synthetic diesel fuel, known as GTL (Gas To Liquid). Most of the future GTL plants are planned in oil exporting countries, such are Qatar and Nigeria, where natural gas as by-product of oil production is being flared, losing in that way precious energy and profit. In that way, otherwise flared natural gas, will be transformed into synthetic diesel fuel which can be directly used in all modern diesel engines. Furthermore, fossil fuel transportation and distribution technology grid can be used without any significant changes. According to lower emissions of harmful gasses during combustion than fossil diesel, this fuel could in the future play a significant part of EU efforts to reach 23% of alternative fuel share till 2020., which are now mostly relied on biodiesel, LPG (liquefied petroleum gas) and CNG (compressed natural gas).

Optimization of geothermal energy production process means the minimization of all energy losses from the reservoir conditions to the user. As the available energy is being utilized mostly in the wellbore and in the surface equipment, process optimization requires scientific access including the extraction technology parameters.Specific energy on the geothermal wellhead is calculated for two possible cases. The first embraces only geothermal water production, while the other takes into account the saturated steam production as well. Each of these working conditions defines unambiguously designed pressure on the wellhead.The steam and water energy ratio, in function of predicted sink temperature for reinjection of geothermal water, points out the possibilities for commercialization of reservoir Velika Ciglena.