2,930 research outputs found

    Diagonalization Procedure for a Bose System Hamiltonian

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    Organic milk supply in Poland: market and policy developments

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    Purpose Global demand for organic milk products gives an opportunity to Polish organic farmers and dairies to supply national, European Union and international milk markets. The aim of this study is to review the historic and contemporary changes in organic milk production and processing in Poland, in order to identify the main factors of influence and to propose the direction of future market and policy development in the sector. Design/methodology/approach In this study, secondary data from a range of literature sources and databases is analysed. The Lorenz’s concentration ratio is applied to the data derived to evaluate the degree of concentration of certified organic farms in the different regions of Poland and conclusions are drawn as a result. Findings Organic dairy farm operations in Poland are small scale and territorially dispersed. Although there is some evidence of growing supply concentration, Polish processors of organic milk face multiple barriers to development not least a lack of continuity of supplies. Whilst global markets are of interest, the development of alternative, innovative food networks in Poland that focus on provenance, integrity and promoting the special health benefits of organic milk would be of value to the sector, but further co-operation and integration is essential to take advantage of these market opportunities. Originality This research underpins the need for appropriate national policies in Poland for the development and actualisation of a dynamic organic milk supply system that delivers value to local, regional and international markets

    Scaling of human behavior during portal browsing

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    We investigate transitions of portals users between different subpages. A weighted network of portals subpages is reconstructed where edge weights are numbers of corresponding transitions. Distributions of link weights and node strengths follow power laws over several decades. Node strength increases faster than linearly with node degree. The distribution of time spent by the user at one subpage decays as power law with exponent around 1.3. Distribution of numbers P(z) of unique subpages during one visit is exponential. We find a square root dependence between the average z and the total number of transitions n during a single visit. Individual path of portal user resembles of self-attracting walk on the weighted network. Analytical model is developed to recover in part the collected data.Comment: 6 pages, 7 figure

    Oznaczanie poziomów zawartości surfaktantów w próbkach środowiskowych. Część 3. Niejonowe związki

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    Non-ionic surface active agents are a diverse group of chemicals which have an uncharged polar head and a non-polar tail. They have different properties due to amphiphilic structure of their molecules. Commercial available non-ionic surfactants consist of the broadest spectrum of compounds in comparison with other types of such agents. Typically, non-ionic compounds found applications in households and industry during formulation of cleaning products, cosmetics, paints, preservative coatings, resins, textiles, pulp and paper, petroleum products or pesticides. Their are one of the most common use class of surfactants which can be potential pollution sources of the different compartment of environment (because of they widely application or discharging treated wastewaters to surface water and sludge in agricultural). It is important to investigate the behavior, environmental fate of non-ionic surfactants and their impact on living organisms (they are toxic and/or can disrupt endocrine functions). To solve such problems should be applied appropriated analytical tools. Sample preparation step is one of the most critical part of analytical procedures in determination of different compounds in environmental matrices. Traditional extraction techniques (LLE - for liquid samples; SLE - for solid samples) are time and solvent-consuming. Developments in this field result in improving isolation efficiency and decreasing solvent consumption (eg SPE and SPME - liquid samples or PLE, SFE and MAE - solid samples). At final determination step can be applied spectrophotometric technique, potentiometric titrametration or tensammetry (determination total concentration of non-ionic surfactants) or chromatographic techniques coupled with appropriated detection techniques (individual analytes). The literature data concerning the concentrations of non-ionic surfactants in the different compartments of the environment can give general view that various ecosystems are polluted by those compounds

    Uticaj -hidroksi--metilbutirata (hmb) dodavanog u hranu na imunitet i otpornost na bakterijske infekcije kod smuđa (sander lucioperca)

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    U ovoj studiji je ispitivan uticaj metabolita leucina β-hidroksi-β-metilbutirata (HMB) na imunitet i zaštitu od enterične bolesti crvenih usta (ERM) i furunkuloze kod smuđa (Sander lucioperca). Ribe su bile hranjene 18 sati dnevno komercijalnom hranom za pastrmke. Hrana je formulisana tako da obezbedi ili 0 (kontrolna grupa) ili 50 mg HBM/kg telesne težine na dan (grupa hranjena sa HBM) tokom 4 nedelje. Posle hranjenja sa HBM 20 zdravih smuđeva prosečne težine 35 g je anestezirano i uzeta je krv iz kaudalne vene u heparizovane špriceve. Takođe je aseptično izdvojen pronefros svake ribe i dobijena suspenzija pojedinačnih ćelija za izolovanje ćelija koristeći ili Gradisol (Polfa) ili Percoll (Pharmacia) gradijent. Test na izazivanje bolesti upotrebom Yersinia ruckeri ili Aeromonas salmonicida je obavljen 4 nedelje posle hranjenja. Ukratko, svakoj od 20 riba svake grupe data je jedna intraperitonealna injekcija 48 sati kulture Y.ruckeri ili A. salmonicida (0,2 ml). Zabeležen je mortalitet, a prisustvo patogena potvrđeno izolacijom iz bubrega. Rezultati ovog ogleda pokazuju da HBM u dozi od 50 mg/kg telesne težine statistički značajno stimuliše nespecifične ćelijske i humoralne odbrambene mehanizme i zaštitu od Yersinia ruckeri i Aeromonas salmonicida

    Radiation pressure acting on the neutral He atoms in the Heliosphere

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    The Interstellar Neutral Helium (ISN He) is an important source of information on the physical state of the Local Interstellar Medium. Radiation pressure acting on the neutral helium atoms in the heliosphere has always been neglected, its effect has been considered insignificant compared to gravitational force. The most advanced numerical models of ISN He take into account more and more subtle effects, therefore it is important to check if the effect of radiation pressure is still negligible. In this paper, we use the most up-to-date version of the Warsaw Test Particle Model (WTPM) to calculate the expected helium distribution in the heliosphere, and simulate the flux of ISN He observed by the Interstellar Boundary Explorer (IBEX) and in the future by the Interstellar Mapping and Acceleration Probe (IMAP). We compare results calculated with and without radiation pressure during low and high solar activity. The results show that in the analysis of IBEX-Lo observations the radiation pressure acting on typical helium causes flux differences at a level of 1-4% and is comparable to the observational errors. For the more sensitive IMAP-Lo instrument, there are some regions in the considered observations configurations where radiation pressure causes potentially statistically significant changes in the calculated fluxes. The effect can be up to 9% for the indirect beam and is likely to be higher than the estimated errors. Therefore, we claim that in the future analysis of the IMAP-Lo observations radiation pressure acting on ISN He should be considered.Comment: Accepted to Ap

    Oznaczanie poziomów zawartości surfaktantów w próbkach środowiskowych. Część 2. Związki anionowe

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    Surface active agents (SAA) with negative charge of polar group are named as anionic compounds. They are the main constituent of most products containing synthetic surfactants. The linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) are typically applied from this class of compounds. Those surfactants are ingredients of household detergents and cleaners, laundry detergents, cosmetic etc. Moreover they can be applied in the paper, textile and tanning industry as optical brighteners, dispersant, wetting and suspending agents. They can be substrates in the formulation of different products like dyes, pigments, pesticides, exchange resins, plasticizers and pharmaceuticals. Anionic surfactants after use are passed into sewage-treatment plants, where they are partially degraded and adsorbed to sewage sludge (applied in agriculture fields). Finally, the anionic SAA or their degradation products are discharged into surface waters and onto bottom sediments, soils or living organisms. Therefore, it is important (widely application, bioaccumulation, toxicity for living organisms) to investigate the environmental fate of those class of compounds in more details. This research involves determination the concentration of anionic surfactants with use appropriated analytical techniques in environmental samples The official methodology for determination of anionic SAA in liquid samples is based on the ion-pair reaction of these analytes compounds with methylene blue (MB) and an extraction with toxic solvent chloroform. During isolation step of anionic compounds from solid samples are employed Soxhlet and ultrasonic-assisted extraction techniques with use of methanol or mixture of other organic solvents as extraction medium. To overcome disadvantages of those traditional techniques were applied following techniques at sample preparation step from liquid and solid matrices: solid-phase extraction (SPE) and solid-phases microextraction (SPME); accelerated solvent extraction (ASE), microwave-assisted extraction (MAE), supercritical fluid extraction (SFE), respectively. For estimate total concentration of anionic analytes in extracts the spectrophotometric technique is used (as official regulation). For determination concentration of individual analytes were applied gas (derivatization step requires) and liquid chromatography mainly with mass spectrometry technique. The presence of anionic surface active agents was confirmed in various ecosystems (liquid and solid environmental samples)
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