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://plato.stanford.edu/archives/fall2011/entries/time-thermo/ >. Dunn, Jeffrey (2011) “Fried Eggs, Thermodynamics, and the Special Sciences”, The British Journal for the Philosophy of Science , 62, pp. 71–98. Elga, Adam (2001) “Statistical Mechanics and the Asymmetry of Counterfactual Dependence”, Philosophy of Science , 68, pp. S313-S324. Frigg, Roman, Hoefer, Carl (2010) “Determinism and Chance from a Humean Perspective”, in: Friedrich Stadler et al. (ed.), The Present Situation in the Philosophy of Science , F. Stadler et al (Ed.), Dordrecht: Springer, pp. 351–371. Hitchcock, Christopher (2011

In recent years, due to the health problems and better life expectancy, natural sources of bioactive substances have gained wide interest. Sea buckthorn is well known as a valuable plant and is widely used in traditional medicine for the treatment of diseases and disorders. A considerable amount of literature has been published on sea buckthorn berries, although all parts of sea buckthorn plant are considered as a source of a large amount of biological active substances, and believed to have beneficial health effects. Therefore, vegetative parts would be a good raw material not only for medicinal, cosmetic and pharmaceutical properties, but also for the food industry. This has increased the research on different sea buckthorn vegetative parts and their extract activity and toxicity. Sea buckthorn leaves have attracted interest during the past few years as the most promising source of active compounds after berries. They contain a wide range of hydrophilic and lipophilic bioactive compounds, which exhibit remarkable anti-oxidant potential together with anti-bacterial, anti-viral, anti-tumour and anti-inflammatory activity. Therefore, extracts of the plant leaves could be used as natural replacements for synthetic additives and for food products with functional properties. This creates the need to investigate the biochemical content of sea buckthorn vegetative parts grown in Latvia.

Abstract

This paper presents the results of the study of long-term changes of Daugava River ice phenology, i.e. the freeze-up date, the break-up date, and the duration of ice cover from 1919/1920 to 2011/2012, under the impact of the cascade of hydro power plants. The long-term changes of ice phenology were determined by global climate warming at the turn of the 20th and the 21st centuries and anthropogenic activities after the year 1939. The Mann-Kendall test showed that the ice freeze-up date has a positive trend, while the ice break-up date and the duration of ice cover had negative trends. The changes were statistically significant. Data series covering twenty years before and after construction of the hydro power plants were used for assessing the impact of each hydro power plant on changes of Daugava River ice phenology parameters. The study results showed that the duration of ice cover was significantly longer in water reservoirs, i.e. the freeze-up date was earlier and the break-up date was later. Downstream of dams duration of ice cover was shorter with later freeze-up dates and earlier break-up dates. The impact of hydro power plants on ice phenology parameters gradually decreased with distance down from the dams.

Application of Conceptual Rainfall-Runoff Model METQ for Simulation of Daily Runoff and Water Level: The case of the Lake Burtnieks Watershed

In this study a conceptual rainfall-runoff METQ model—the latest version METQ2007BDOPT—was applied to simulate the daily runoff and water level of the Lake Burtnieks watershed from 1990 to 1999. The model structure and parameters were basically the same as in the METQ98, with some additional improvements and semi-automatical calibration performance. Model calibration was done for four rivers and one lake gauging station. The results of calibration showed a good correlation between the measured and simulated daily discharges. The Nash-Sutcliffe efficiency R 2 varied from 0.90 to 0.58 and correlation coefficient r from 0.95 to 0.83. The highest values of R 2 = 0.90 and r = 0.95 were obtained for the River Salaca and the lowest R 2 = 0.53 and r = 0.83 for Lake Burtnieks. We observed some relationships between the model parameter values and physiographic characteristic of the sub-catchments.

Changes of total annual runoff distribution, high and low discharges in Latvian rivers

The paper examines climate change impacts on the hydrological regime of nineteen different river basins in Latvia. Hydrological data series for the period of 1951-2006 were analysed for river basins of four hydrological districts: Western, Central, Northern and Eastern. Climate change has influenced the temporal and spatial distribution of total annual river runoff and high and low flows in Latvia at the turn of century. The results confirm the hypothesis that the main tendency in the run-off change is a decrease in spring floods and increase in winter. Generally, statistically insignificant long-term trends were observed for summer and autumn.

Abstract

The study describes the trends of monthly mean water temperature (from May to October) and the annual maximum water temperature of the rivers in Latvia during the time period from 1945 to 2000. The results demonstrated that the mean water temperatures during the monitoring period from May to October were higher in the largest rivers (from 13.6 °C to 16.1 °C) compared to those in the smallest rivers (from 11.5 °C to 15.7 °C). Similar patterns were seen for the maximum water temperature: in large rivers from 22.9 °C to 25.7 °C, and in small rivers from 20.8 °C to 25.8 °C. Generally, lower water temperatures occurred in rivers with a high groundwater inflow rate, for example, in rivers of the Gauja basin, in particular, in the Amata River. Mann-Kendall test results demonstrated that during the monitoring period from May to October, mean water temperatures had a positive trend. However, the annual maximum temperature had a negative trend.

Changes in the hydrological regime of the lakes of Latvia have been caused by several natural and human factors. This publication summarises the results of research on the long-term and seasonal changes in the water level, and thermal and ice regimes of the three biggest lakes of Latvia (Usma, Burtnieks, and Râzna) and their regional features in the period from 1926 to 2002. The levels of the lakes Usma and Râzna have been controlled, but it can be considered that changes of the water level in Lake Burtnieks have been due to the impact of natural factors during the period from 1947 to 2002. Global climate warming has caused considerable changes in the hydrological regime of the lakes during the last decades, as the water level and temperature have increased and the number of days with ice cover and the thickness of ice have decreased. A positive trend in the freezing data and statistically reliable negative trend for the ice break-up date were observed for all the lakes. Lake Usma is located in the western part of Latvia, therefore, its hydrological regime, in particular, the thermal and ice regime, differs from those of lakes Burtnieks and Râzna which are located in the northern and eastern part of Latvia, respectively.

Abstract

All parts of the sea buckthorn (Hippophae rhamnoides L.) plant are considered to contain large amounts of compounds that are believed to have beneficial health effects. Till now, different parts of sea buckthorn plant have been used for the treatment of diseases in traditional medicine in various countries. Nevertheless, sea buckthorn parts would be a good raw material not only for medicinal properties but also for food products with functional properties; therefore, the aim of the research was to determine the concentration of different phenolic compounds and antioxidant activity in various sea buckthorn parts. The study was conducted on parts of female and male sea buckthorn bushes. Phenolic compounds (total phenols, total flavonoids and condensed tannins) and antioxidative activity (ferric reducing antioxidant power (FRAP) free radical scavenging activity (using 2.2-diphenyl-1-picrylhydrazyl, DPPH)) in ethanolic extracts of leaves, shoots, flowers, and berries were determined using various spectrophotometric methods. The study showed that concentration of phenolic compounds differed among parts of sea buckthorn plant and among gender. Leaves of female plants proved to be the most valuable, as they contained the highest total phenol concentration (165.76 mg/g) and antioxidant activity (220.97 mg/g for FRAP and 43.76 mg/g for DPPH), while lowest values were found in young shoots of male plants (84.94 mg/g, 94.24 mg/g and 24.63 mg/g, respectively). The significant differences in chemical composition and biological activity of sea buckthorn leaves, shoots, berries, and buds indicate a need for detailed studies of their extracts, specific fractions and compounds during a whole vegetative season.

Abstract

Rowanberries (Sorbus aucuparia) are small orange-red fruits of a rowan tree. They have been described as an important source of flavonoids, and their antioxidant activity affects reactive oxygen species and lipid peroxidation. Cultivars of sweet rowanberries and hybrids with other species are sweeter and less astringent than wild rowanberries. The aim of the current study was to determine physical and chemical properties of sauces from various cultivars of wild and sweet rowanberries, and mixes of sweet rowanberries with pumpkins, and to assess their degree of acceptance. The experiments were carried out at the Faculty of Food Technology of the Latvia University of Agriculture. The sauces were made from purees of wild rowanberry and sweet rowanberry cultivars and purees of sweet rowanberry with apple or pumpkin using different species. The content of total dry matter, soluble solids, total carotene, pH, colour L* a* b* values and texture parameters were determined in samples of the sauces. The results showed large variability between the rowanberry and rowanberry-pumpkin sauces. The total dry matter content of sauce samples varied from 25.92 to 31.38%, the total carotene content from 3.94 ± 0.40 to 7.34 ± 0.57 mg 100 g-1 DM, and firmness from 0.5 to 2.2 N. According with sensory evaluation the panellists liked (P < 0.05) sauces samples made from rowanberry ‘Michurinskaya krasnaya’ puree and from ‘Granatnaya’ and pumpkin purees.

Long-term Development of the Hydroecosystem of the Lake Engure and its Influencing Factors

Investigations of water chemical composition and biota of Lake Engure have been carried out since 1995 by using standard methods for inland surface waters. Time series of air temperature and precipitation for the Mersrags meteorological station for the period 1928 to 2009 are used for the trend analysis. The results show that the long-term development of the hydroecosystem is related to such environmental factors as the lake's geographical location, basin and morphology, as well as the lake's history and relationship of biotic and abiotic factors.