In the market of the Latvia different wood surface coating materials suitable for use in outdoor conditions are offered, but available information on the efficiency of these against direct water exposure is insufficient. For structural timber building elements, such as glued laminated timber (GLT), the surface coating should be applied taking into account technological, visual or colour changes (ISO 7724:1984) and – last, but not least – economic aspects are considered. Wood surfaces coated with coating materials, such as varnishes, paints, etc. can stabilize some properties such as movement of moisture content, dimensional changes and attack by microorganisms and fungi. The changes in the moisture content of timber may influence such important parameters as mechanical properties and the total life time of the structural timber elements. A study has been conducted with the aim of assessing the efficiency of coating materials used for wood protection against water absorption. In this study, six different commercial coating products used for the treatment of spruce (Picea Abies L. Karst.) and pine (Pinus Sylvestris L.) samples were tested. The efficiency of different coating substances was assessed using two modified test methods according to the standards EN 382-2 (1994) and EN 927-5 (2006), determining the surface water absorption after immersion in water for 24 h and the dynamics of water absorption of the glued laminated timber for 696 h kept in water. As a result of the study, it has been ascertained that organic solvent-based commercial coating products are more efficient against short-term and long-term wood water absorption compared to oil-based coating materials.

In the market of the Latvia different wood surface coating materials suitable for use in outdoor conditions are offered, but available information on the efficiency of these against direct water exposure is insufficient. For structural timber building elements, such as glued laminated timber (GLT), the surface coating should be applied taking into account technological, visual or colour changes (ISO 7724:1984) and – last, but not least – economic aspects are considered. Wood surfaces coated with coating materials, such as varnishes, paints, etc. can stabilize some properties such as movement of moisture content, dimensional changes and attack by microorganisms and fungi. The changes in the moisture content of timber may influence such important parameters as mechanical properties and the total life time of the structural timber elements. A study has been conducted with the aim of assessing the efficiency of coating materials used for wood protection against water absorption. In this study, six different commercial coating products used for the treatment of spruce (Picea Abies L. Karst.) and pine (Pinus Sylvestris L.) samples were tested. The efficiency of different coating substances was assessed using two modified test methods according to the standards EN 382-2 (1994) and EN 927-5 (2006), determining the surface water absorption after immersion in water for 24 h and the dynamics of water absorption of the glued laminated timber for 696 h kept in water. As a result of the study, it has been ascertained that organic solvent-based commercial coating products are more efficient against short-term and long-term wood water absorption compared to oil-based coating materials.

The impacts of the COVID-19 pandemic on national economies are characterized as the worst economic turmoil in recent years, as economic growth slowed to the level of the 2008 global financial crisis. At the end of 2019 and the beginning of 2020, economic growth surveys did not project that the novel virus could have a negative impact on economic growth. As a result of the rapid spread of the virus and the increase in the number of infection cases, national governments took strict measures to limit the spread of the virus, which led to a significant deterioration in the economic situation in all industries of the economy. Agriculture plays an important role in providing food to the country’s population, yet the pandemic made a negative impact on sales volumes and prices in the domestic and international markets. The research aims to assess the impacts of the pandemic on milk supply chains in Latvia and come up with solutions to stabilizing the situation in the dairy sector. The national restrictions to combat the pandemic also hampered the dairy sector concerning the sale of raw milk and finished products in foreign markets, thereby leading to overproduction and stockpiling of the finished products, price dumping and a significant decrease in milk purchase prices to or below the production cost level for many dairy farms. Although there is no indication that the pandemic would lead to a decrease in the numbers of livestock and farms or output in early 2021, it is too early to assess the overall impact of the pandemic on dairy farming, as uncertainty over the duration of pandemic restrictions is a major risk to farm survival. The operation of the dairy sector was stabilized by means of the support provided by the government, as well as the farms’ accumulated financial and feed resources. In order to identify future challenges for milk supply chains, the research performed an analysis of operational risks for milk producers and processors to identify the most important risks and design recommendations for their elimination. The longer there is uncertainty about the return of the dairy sector to pre-pandemic output levels, the more likely it is that the pandemic is going to lead to a decrease in the numbers of dairy livestock and farms.

The impacts of the COVID-19 pandemic on national economies are characterized as the worst economic turmoil in recent years, as economic growth slowed to the level of the 2008 global financial crisis. At the end of 2019 and the beginning of 2020, economic growth surveys did not project that the novel virus could have a negative impact on economic growth. As a result of the rapid spread of the virus and the increase in the number of infection cases, national governments took strict measures to limit the spread of the virus, which led to a significant deterioration in the economic situation in all industries of the economy. Agriculture plays an important role in providing food to the country’s population, yet the pandemic made a negative impact on sales volumes and prices in the domestic and international markets. The research aims to assess the impacts of the pandemic on milk supply chains in Latvia and come up with solutions to stabilizing the situation in the dairy sector. The national restrictions to combat the pandemic also hampered the dairy sector concerning the sale of raw milk and finished products in foreign markets, thereby leading to overproduction and stockpiling of the finished products, price dumping and a significant decrease in milk purchase prices to or below the production cost level for many dairy farms. Although there is no indication that the pandemic would lead to a decrease in the numbers of livestock and farms or output in early 2021, it is too early to assess the overall impact of the pandemic on dairy farming, as uncertainty over the duration of pandemic restrictions is a major risk to farm survival. The operation of the dairy sector was stabilized by means of the support provided by the government, as well as the farms’ accumulated financial and feed resources. In order to identify future challenges for milk supply chains, the research performed an analysis of operational risks for milk producers and processors to identify the most important risks and design recommendations for their elimination. The longer there is uncertainty about the return of the dairy sector to pre-pandemic output levels, the more likely it is that the pandemic is going to lead to a decrease in the numbers of dairy livestock and farms.

This paper investigates the effect of separated exhaust expansion chamber parameters on pressure oscillations in spark-ignited internal combustion (IC) gasoline engines. It is known that exhaust expansion chambers are becoming increasingly more popular among both – original equipment (OE) and aftermarket equipment (AE) exhaust system manufacturers for performance-oriented motorcycles equipped with mainly single cylinder engines, but the companies are reluctant to reveal any detailed principles of operation of the mentioned expansion chambers. The subject of this research is the type of expansion chamber (separate) as used on performance-oriented motorcycles, particularly its’ effect on exhaust pressure pulsations as different chamber volumes, locations and passage sizes are tested. Time-dependent computational fluid dynamics (CFD) analysis was carried out in Solidworks Flow Simulation environment on a simplified exhaust header pipe model imitating engine operation at full load and steady speed. Honda CRF450R motorcycle engine was used as the example and fully defined using a 1D engine performance calculator software to determine the combustion chamber pressure and exhaust valve lift at any given crankshaft position. Volume flow rate of exhaust gasses at the header pipe inlet was calculated based on engine parameters and operating speed. The average pressure values with respect to physical time were measured and graphed across the header pipe inlet cross-section. Eight different header pipe and exhaust expansion chamber combinations were modelled, tested, and results compared at low, medium and high engine speeds. It was found that the presence of exhaust expansion chamber tends to dampen the amplitude and decrease the frequency of pressure oscillations generated at the opening of the exhaust valve(s). Observations show that the addition of an expansion chamber as per design of performance-oriented motorcycles helps to decrease the negative effect of engine tuning while also dampening the positive effect.

This paper investigates the effect of separated exhaust expansion chamber parameters on pressure oscillations in spark-ignited internal combustion (IC) gasoline engines. It is known that exhaust expansion chambers are becoming increasingly more popular among both – original equipment (OE) and aftermarket equipment (AE) exhaust system manufacturers for performance-oriented motorcycles equipped with mainly single cylinder engines, but the companies are reluctant to reveal any detailed principles of operation of the mentioned expansion chambers. The subject of this research is the type of expansion chamber (separate) as used on performance-oriented motorcycles, particularly its’ effect on exhaust pressure pulsations as different chamber volumes, locations and passage sizes are tested. Time-dependent computational fluid dynamics (CFD) analysis was carried out in Solidworks Flow Simulation environment on a simplified exhaust header pipe model imitating engine operation at full load and steady speed. Honda CRF450R motorcycle engine was used as the example and fully defined using a 1D engine performance calculator software to determine the combustion chamber pressure and exhaust valve lift at any given crankshaft position. Volume flow rate of exhaust gasses at the header pipe inlet was calculated based on engine parameters and operating speed. The average pressure values with respect to physical time were measured and graphed across the header pipe inlet cross-section. Eight different header pipe and exhaust expansion chamber combinations were modelled, tested, and results compared at low, medium and high engine speeds. It was found that the presence of exhaust expansion chamber tends to dampen the amplitude and decrease the frequency of pressure oscillations generated at the opening of the exhaust valve(s). Observations show that the addition of an expansion chamber as per design of performance-oriented motorcycles helps to decrease the negative effect of engine tuning while also dampening the positive effect.

The experiment was conducted to analyse the effect of fermented acid whey permeate on milk yield and composition in the lactating cows. Propionic acid bacteria and their metabolites have been used in the lactating cows feeding over decades, primarily to improve growth performance, feed conversation and milk production efficiency. Two groups of the lactating cows were arranged in the study: control group (n=50) and experimental group (n=50). Experimental group’s animals received 0.5 L of fermented whey permeate daily. Acid whey permeate was inoculated with the freeze-dried PS-4 (Propionibacterium freudenreichii subsp. shermanii, Chr.Hansen, Denmark) starter and fermented anaerobically for 48 hours at 20±2 ᵒC. Fat, protein, lactose and total solids concentration in acid whey permeate and fermented acid whey permeate was analysed by the standard methods, but propionic acid was detected by HPLC. Milk composition and quality indices were determined at the beginning of the study and each month during 6 months period. At the end of the study the feeding of fermented acid whey permeate was stopped, but milk composition and quality data were monitored additionally after one month. Milk fat, protein, lactose, total solids, urea concentration and somatic cell count were analysed by a near infrared spectroscopy. The variability in milk composition and quality data across trial was greater in the experiment group than in the control. Milk fat and somatic cell count were significantly different (p<0.05) than other studied parameters in the experimental group cows’ milk. Milk yield and lactose concentration were tended to increase during feeding of fermented acid whey permeate in the lactating cows without significant differences between control and experimental groups. Fermented acid whey permeate as feed supplement improves energy metabolism for dairy cows which results in the higher milk yield and fat concentration.

The experiment was conducted to analyse the effect of fermented acid whey permeate on milk yield and composition in the lactating cows. Propionic acid bacteria and their metabolites have been used in the lactating cows feeding over decades, primarily to improve growth performance, feed conversation and milk production efficiency. Two groups of the lactating cows were arranged in the study: control group (n=50) and experimental group (n=50). Experimental group’s animals received 0.5 L of fermented whey permeate daily. Acid whey permeate was inoculated with the freeze-dried PS-4 (Propionibacterium freudenreichii subsp. shermanii, Chr.Hansen, Denmark) starter and fermented anaerobically for 48 hours at 20±2 ºC. Fat, protein, lactose and total solids concentration in acid whey permeate and fermented acid whey permeate was analysed by the standard methods, but propionic acid was detected by HPLC. Milk composition and quality indices were determined at the beginning of the study and each month during 6 months period. At the end of the study the feeding of fermented acid whey permeate was stopped, but milk composition and quality data were monitored additionally after one month. Milk fat, protein, lactose, total solids, urea concentration and somatic cell count were analysed by a near infrared spectroscopy. The variability in milk composition and quality data across trial was greater in the experiment group than in the control. Milk fat and somatic cell count were significantly different (p is less than 0.05) than other studied parameters in the experimental group cows’ milk. Milk yield and lactose concentration were tended to increase during feeding of fermented acid whey permeate in the lactating cows without significant differences between control and experimental groups. Fermented acid whey permeate as feed supplement improves energy metabolism for dairy cows which results in the higher milk yield and fat concentration.

There is a strong correlation between diet and mental health, and malnutrition can contribute to the development of various psycho-neurological diseases. Fatty acid profile plays an important role in the treatment of psycho-neurological diseases; therefore, the aim of the current study was to evaluate fatty acid profile in the diet of patients in three Latvian psycho-neurological hospitals. Latvian psycho-neurological hospitals submitted a detailed one-week menu. The information in the menus was processed using the Fineli program. Each menu identified the composition of fatty acids. The average fat concentration in different hospital menus ranged from 74.8 g to 96.1 g per day, where the concentration of saturated fatty acids ranged from 37.5 g to 47.7 g per day and the unsaturated fat concentration ranged from 35.9 g to 47 g per day. The n-3 PUFA content was consistent with the recommendations of a healthy individual, but it did not meet the needs of patients in a psycho-neurological hospital. The total eicosapentaenoic acid and docosahexaenoic acid concentration in the hospital menus ranged from 0.03 to 0.13 g, which was significantly lower than recommended, whereas LA and ALA concentration in hospital menus is close to optimal. The trans-fatty acids concentration in hospital menus did not exceed 2.5 g per day, with the exception of one day in hospital No. 2. The impact of diet on the treatment of psycho-neurological diseases in Latvian psycho-neurological hospitals has not been sufficiently assessed.

There is a strong correlation between diet and mental health, and malnutrition can contribute to the development of various psycho-neurological diseases. Fatty acid profile plays an important role in the treatment of psycho-neurological diseases; therefore, the aim of the current study was to evaluate fatty acid profile in the diet of patients in three Latvian psycho-neurological hospitals. Latvian psycho-neurological hospitals submitted a detailed one-week menu. The information in the menus was processed using the Fineli program. Each menu identified the composition of fatty acids. The average fat concentration in different hospital menus ranged from 74.8 g to 96.1 g per day, where the concentration of saturated fatty acids ranged from 37.5 g to 47.7 g per day and the unsaturated fat concentration ranged from 35.9 g to 47 g per day. The n-3 PUFA content was consistent with the recommendations of a healthy individual, but it did not meet the needs of patients in a psycho-neurological hospital. The total eicosapentaenoic acid and docosahexaenoic acid concentration in the hospital menus ranged from 0.03 to 0.13 g, which was significantly lower than recommended, whereas LA and ALA concentration in hospital menus is close to optimal. The trans-fatty acids concentration in hospital menus did not exceed 2.5 g per day, with the exception of one day in hospital No. 2. The impact of diet on the treatment of psycho-neurological diseases in Latvian psycho-neurological hospitals has not been sufficiently assessed.

An urgent problem is drying and processing of the wet dispersed waste, obtained in the production of food products, which can then be efficiently used as a fertiliser, for feeding livestock or as biofuel. A new design of a vibrating fluidised bed dryer has been developed, which, with low energy consumption, provides a pre-set productivity and the required final moisture content. The process of vertical oscillations of the body of a vibration dryer, together with the food waste contained in it, is analysed analytically, the necessary equivalent scheme is built, on the basis of which differential equations of the vertical oscillations of the body are compiled, their analytical solutions are obtained, and a numerical calculation is performed on a PC using the developed program. Rational parameters of the vibration dryer, providing vibroboiling of the mass of the food waste, have been determined: the body mass m = 250 ... 510 kg; the debalance mass md = 10… 15 kg; the number of revolutions of the debalance electric motor nd = 1950 ... 2650 rpm ∙ min ∙¹; maximum stiffness of the support springs Cₚ = 8∙10⁵ N∙m–¹; the diameter of the centre of mass of the debalances dd = 0.01 m. In addition, as a result of the thermophysical theoretical and experimental studies of the vibration drying process, the following optimal design and technological parameters of the vibration dryer were obtained: the heat transfer area Sₜ.ₚ.ₙ= 4.15 m²; the radius of the heating pipe rₜ= 0.1 m; the length of the heating pipe lₜ = 3 m; the number of heating pipes nₜ= 50; the heat transfer coefficient Kₚ= 2500; the final temperature of the dried waste tₒ₂ = 100 ºС.

An urgent problem is drying and processing of the wet dispersed waste, obtained in the production of food products, which can then be efficiently used as a fertiliser, for feeding livestock or as biofuel. A new design of a vibrating fluidised bed dryer has been developed, which, with low energy consumption, provides a pre-set productivity and the required final moisture content. The process of vertical oscillations of the body of a vibration dryer, together with the food waste contained in it, is analysed analytically, the necessary equivalent scheme is built, on the basis of which differential equations of the vertical oscillations of the body are compiled, their analytical solutions are obtained, and a numerical calculation is performed on a PC using the developed program.