Several species of Heracleum have been introduced as a cultivated plant and is out of human control in Latvia. Heracleum is a very harmful to humans, especially to children because of causing skin burn. Eradication of the established plant colonies is practically impossible therefore individual efforts are not successful. In Latvia, botanists, plant protection experts and practicians are involved in the solution of this problem. The tasks of the project were as follows: recognising hogweed spread in Latvia; elaboration of temporary recommendations and establishing trials, and performance of observations with the target on science based weed localising measures. After request of the Ministry of Agriculture in 2001, Latvia University of Agriculture collaborating with Latvian Agricultural Advisory and Training Centre performed questionnaire of local power about the spreading of hogweed. Results of the questionnaire showed that total polluted area in Latvia was 12225 ha.

Evaluation of virulences of Blumeria graminis f.sp. hordei was started in Latvia in 1981, first in the Baltic States. Until 1994 the observations were carried out only in the central part of Latvia - Salaspils. As the climatic factors and the used barley varieties in various parts of Latvia are different, in 1995 we started regular observations of the particularities of the genetic structure of the pathogen population also in Daugavpils. The aim of this investigation was to detect particularities of the genetic structure of the pathogen population in different parts of Latvia in 1996-2000.

The main aim of the paper is to analyse influence of the real exchange rate on competitiveness of Latvia. Using fundamental equilibrium exchange rate methodology the equilibrium real exchange rate for Latvia is estimated. According the model's results the real exchange rate was overvalued almost during all the reporting period and therefore it could be used as one of the factors influencing competitiveness of Latvia.

In order to identify the quality of natural Silver birch stands in Latvia, fifteen sample plots covering all country's regions were established. Stem quality affecting morphological traits - stem straightness, branch angle, branching thickness and branching patterns were measured and assessed to all birches in sample plots. To compare the stand's quality, the integral quality indicator was introduced. According to results obtained in plots, most quality birch stands in Latvia are located in East and North parts of Latvia. The best stands proved to be in Aluksne and Smiltene. Birch stands in West part of Latvia had stems of substantially lower quality. The best quality stand in this region was birch stand located in Tukuma's head forestry.

The article presents as information on the essential changes which have taken place in strategy of crop protection and agronomy in Latvia during the last five years. Up to 1995 crop protection in Latvia was based only on the experience of experts. Weather based computer programmes have not been used for prediction of pest and disease outbreaks. For the present moment, weather - based system for calculating accumulated risk values of certain cereal pests and diseases and potato late blight is under evaluation in Latvia.

Current demographical situation in Latvia, together with unrestricted labour flow between countries of European Union creates a lack of labour. Employees are becoming more selective and are not ready to work on any job or under old-fashioned autocratic management. This article is an analytical report on a survey of managerial attitudes in Latvia conducted in 2006, revised in 2008. The survey represents the evaluations of 886 respondents on management methods used at their workplace - in organizations in Latvia.

Overall, 932 828 cars are registered in Latvia as per 01 January 2009, and only 534 489 of them are suitable for road traffic. Some cars of specific brand and model year are more popular and widespread in Latvia than others, and many cars at the same time have similar or same fuel systems. The objective of the study is to determine the most widespread fuel systems for cars with diesel fuel and gasoline engines in Latvia. The study is based on the analysis of the Road Traffic Safety Authority data, specific car model manuals and information provided by car dealers.

The current work is dedicated to electrochemical impedance spectra analysis of the fine and coarse airborne particulate matter sampled on the glass fibre filters in Riga city air. The cyclic voltammograms, impedance spectra and double layer capacitance spectra of particulate matter were obtained after the pre-treatment of samples. The equivalent circuit method and the statistical method were used for impedance spectra analysis. Analyzing the impedance spectra, it was concluded that the impedance of both – fine and coarse particles heated in N2 flow does not change by aerosol mass concentration variations. On the other hand, the impedance of particulate matter heated in O2 flow increases, by increasing PM10 mass concentration. Describing the spectra of double layer capacitance, it was observed that the double layer capacitance of aerosols heated in N2 flow did not change, by mass concentration and size variations. However, by increasing mass concentration of coarse aerosols heated in O2 flow, the double layer capacitance reduced. | Pētījumā veikta elektroķīmiskās impedances un dubultslāņa kapacitātes spektru analīze Rīgas pilsētvides gaisa smalkajām un rupjajām aerosolu daļiņām, kas uzkrātas uz stikla šķiedras filtriem. Veicot frakcionēto aerosolu daļiņu ņemšanu vienādu stundu skaitu, smalko daļiņu daudzums bija krietni augstāks par rupjo daļiņu daudzumu gaisā. Pēc aerosolu daļiņu paraugu karsēšanas dažādas vidēs tika uzņemtas cikliskās voltamperogrammas, impedances spektri un dubultslāņa kapacitātes spektri. Kvalitatīvu impedances spektru uzņemšanai izmantoja „sviestmaizes” veida elektroķīmisku šūnu. Pēc uzņemtām voltamperogrammām tika noteikti nepieciešamie parametri aerosolu daļiņu paraugu impedances mērījumiem. Impedances spektru analīzei izmantota ekvivalento shēmu metode un statistiskā metode. Mērījumu precizitāte un ticamība pirms analīzes pārbaudīta ar Krāmera-Kroniga testu. Analizējot impedances spektrus, tika konstatēts, ka gan smalkajām, gan rupjajām, slāpekļa vidē karsētām aerosolu daļiņām impedance nemainās, mainoties daļiņu masas koncentrācijai. Savukārt, gaisā karsētiem paraugiem impedance pieaug, pieaugot rupjo daļiņu masas koncentrācijai. Analizējot dubultslāņa kapacitātes spektrus tika novērots, ka dubultslāņa kapacitāte slāpekļa plūsmā karsētām aerosolu daļiņām nemainās, mainoties daļiņu izmēram un masas koncentrācijai, bet pieaugot skābekļa plūsmā karsēto, rupjo aerosolu daļiņu masas koncentrācijai, dubultslāņa kapacitāte samazinās. Kopumā iegūtie dati liecina par ogles, galvenā aerosolu daļiņu komponenta, virsmas rakstura nemainīgumu, mainoties aerosolu daļiņu izmēram un masas koncentrācijai. Analizējot impedances spektrus augsto frekvenču apgabalā tika noteikta nehomogēna, bez noteikta poru izmēra, trīsstūrveida vai rombveida stikla šķiedru filtra uzbūve.

This article describes reasons of power system disturbance occurrences and problems of its prevention. Instead of using large electro power systems it is offered to use centralized multistage hierarchical system of operative and technological management, which could reduce the number of possible failures. Issues of scientific works reaching conformity of the centralized multistage control system under conditions and requirements of the liberalized electro power market are also included.

The aim of this research is to study the economic aspect of the objective regionalization process (not regional reform) in Latvia. The following tasks are planed in order to reach the aim: (1) to observe the development of regional direction and formation of regional economics in the world's general economic theory, (2) to give methodological grounds for investigating the process of regionalisation in Latvia exactly from the economic aspect, (3) to carry out an original empiric research in order to find out the number of the economic regions of Latvia and to state what they are.