112 research outputs found
Identification of wet areas in forest using remote sensing data
ArticleAim of this study is to evaluate different remote sensing indices to detect spatial
distribution of wet soils using GIS based algorithms. Ar
ea of this study represents different soil
types on various quaternary deposits as well as different forest types. We analyzed 25 sites with
the area of 1 km
2
each in central and western part of Latvia. Data about soil characteristics like
thickness of pea
t layer and presence of reductimorphic colors in soil was collected during field
surveys in 228 random points within study sites. ANOVA test for comparing means of different
soil wetness classes and binary logistic regression analysis for evaluating the ac
curacy of different
remote sensing indices to model spatial distribution of wet areas are used for analysis. Main
conclusion of this study is that for different quaternary deposits and soil texture classes different
algorithms for soil wetness prediction s
hould be used. Data layers for predicting soil wetness in
this study are various modifications and resolutions of digital elevation model like depressions,
slope and SAGA wetness index as well as Sentinel
-
2 multispectral satellite imagery. Accuracy of
soil
wetness classification of soils on moraine, fluvial and eolian sediments exceeds 94%, whereas
on the clayey sediments it is close to 80%
Identification of the niche and phenotype of the first human hematopoietic stem cells
SummaryIn various vertebrate species, the dorsal aorta (Ao) is the site of specification of adult hematopoietic stem cells (HSCs). It has been observed that the upregulation of essential hematopoietic transcription factors and the formation of specific intra-aortic hematopoietic cell clusters occur predominantly in the ventral domain of the Ao (AoV). In the mouse, the first HSCs emerge in the AoV. Here, we demonstrate that in the human embryo the first definitive HSCs also emerge asymmetrically and are localized to the AoV, which thus identifies aĀ functional niche for developing human HSCs. Using magnetic cell separation and xenotransplantations, we show that the first humanĀ HSCs are CD34+VE-cadherin+CD45+C-KIT+THY-1+Endoglin+RUNX1+CD38ā/loCD45RAā. This population harbors practically all committed hematopoietic progenitors and is underrepresented in the dorsal domain of the Ao (AoD) and urogenital ridges (UGRs). The present study provides a foundation for analysis of molecular mechanisms underpinning embryonic specification of human HSCs
Investigations about the impact of the sowing time and rate of the biomass yield and quality of industrial hemp
ArticleThe aim of this study was to find the optimum sowing rate of industrial hemp
(Cannabis sativa L.) and to clarify the impact of the sowing rate on the production of biofuel
from hemp biomass in Latvia. Field trials were carried out at the Research and Study Farm
āPÄterlaukiā of the Latvia University of Agriculture in 2012ā2014. The industrial hemp (Cannabis
sativa L.) āFutura 75ā was sown in a Luvic Endogleyic Stagnosol soil: pHKCl 6.7; P ā 52 mg kg-1
;
K ā 128 mg kg-1
; the organic matter content ā 21ā25 g kg-1
. Hemp was sown in 10-m2 plots,
triplicate, on May 8 and 17. The total sowing rate was 20 (100), 30 (150), 40 (200), 50 (250),
60 (300), 70 (350), 80 (400), 90 (450), and 100 (500) kg ha-1
(germinating seeds per 1 m2
). The
plots were fertilised as follows: N ā 120 kg ha-1
; P2O5 ā 80 kg ha-1
; and K2O ā 112 kg ha-1
. Hemp
was harvested when the first matured seeds appeared. The biometrical indices (height and stem
diameter), harvesting time, the amount of fresh and dry biomass, and the fibre content were
evaluated. Depending on the sowing rate, the yield of dry matter was on average 9.2ā12.1 t ha-1
when hemp was sown at the beginning of May, and 7.9ā10.0 t ha-1 when hemp was sown in the
middle of May
Assessment of the greenhouse gas emissions and energy inputs applying different weed control methods for wheat growing
Received: January 25th, 2023 ; Accepted: May 21st, 2023 ; Published: June 17th, 2023 ; Correspondence: [email protected] indicators are often used to evaluate and select technologies, determining the
production costs of the product. However, according to the EU's green course, the ecological
assessment of technologies is increasingly important. The purpose of the article is to comparatively
evaluate two winter wheat weed control methods, which are widely used in Latvia, according to
two ecological indicators - the amount of the GHG emissions and the energy consumption, to find
out whether these indicators can serve as a criterion for the selection of technologies. These two
methods are HA (harrowing), in which weeds are controlled by harrowing and herbicides, HE
(herbicides), in which weeds are controlled only by herbicides. The methodology for calculating the
mentioned indicators was developed by analyzing several studies by other authors. The total GHG
emissions generated are calculated as the sum of five components: emissions, generated for the
manufacture and delivery of the machinery used; emissions, generated by the fuel, consumed for
implementation of the technology; emissions, generated for the production, delivery and installation
of fertilizers; emissions, generated for the production, delivery and installation of pesticides, seed
production, delivery and installation emissions. Analogously, the total energy consumption is
calculated by summing the components The technologies were implemented on a specific farm,
with the machinery of this farm, labor, fertilizers and the plant protection products. It has been
established that the technologies differ by the calculated ecological indicators within the range of
1.2ā2.6%; moreover, these indicators are lower for the technology with the herbicide spraying, and
the technology is simpler to implement. Therefore, it is also more widely used. Since the coefficients
for the calculation of the ecological indicators can be applied by the methodology of this article, the
characteristics of the technique and the doses of fertilizers and the plant protection agents, used on
the farms, are known, the ecological indicators can be used as an additional criterion for the selection
of technologies on the farms. The ratio of the energy value and energy consumption of the produced
product (the output and the input ratio) was also determined, this indicator for technologies HA and
HE being, respectively, 8.30 and 8.41. In comparison with the research by the authors in other
countries, from the point of view of the amount of the generated CO2-eq emissions and rational
consumption of energy, the analysed winter wheat production technologies are evaluated as
moderately efficient, but from the point of view of the energy value of the product produced and the
ratio of the energy consumption (the output and the input ratio) - as efficient
The efficiency of nitrogen fertilizer on the dry matter yield of tall fescue and festulolium grown as feedstock for combustion
ArticleGrass biomass grows during one vegetation season and can be cultivated and consumed
at the place of breeding. Grass biomass can be used not only in traditional feed, but, recently, also
for energy production (biogas, solid fuels). The most important economic indicator for any crop
is its productivity. The study found that it is important to use nitrogen fertilizer to increase the
productivity of tall fescue and festulolium. A significant increase (p < 0.05) in the yield of tall
fescue was observed starting from the nitrogen norm of 60 kg ha-1 N. Further increase in nitrogen
fertilizer norm provides a significant increase in dry mater yield of tall fescue (reaching
8.64 t ha-1
) and festulolium (reaching 8.11 t ha-1
) at 180 kg ha-1 N. The analysis of linear
regression coefficients of polynomials showed that the highest nitrogen efficiency in the first year
of the use of tall fescue was achieved at the norm of 180 kg ha-1 N, but for festulolium ā at the
norm of 120 kg ha-1 N. In the following years of tall fescue use, the highest efficiency of nitrogen
norms differed: in the 2nd and 4th year of use ā at 60 kg ha-1 N, in the 3rd year of use ā at
30 kg ha-1 N, and in the 5th year of use ā at 120 kg ha-1 N. In contrast, for festulolium, in the 2nd
year of use, the highest nitrogen efficiency was reached at the norm of 30 kg ha-1 N, and in the
3rdā5th year of use ā at the norm of 60 kg ha-1 N
Low temperature BMP tests using fish waste from invasive Round goby of the Baltic Sea
ArticleRound goby
(Neogobius melanostomus
) is an
invasive fish species in the Baltic Sea.
While meat can be used for human consumption, fish processing residues are considered as a
waste. Within circular economy and bio
-
economy perspectives fish waste could be used as a
valuable feedstock for biogas prod
uction. However, the research is mostly focused on evaluating
biogas yield at mesophilic conditions (i.e. 37
Ā°C
). In this study the impact of low temperature on
Biochemical Methane Potential (BMP) tests has been investigated. Round gobyās processing
leftov
ers
-
heads, intestines and skin/bone mixture were tested in codigestion with sewage sludge.
Anaerobic digestion (AD) was carried out in 100
mL batch tests at low temperature 23
Ā°C
and
37
Ā°C
conditions, over an incubation period of 31 days. The results sho
w that AD at low
temperature occurs twice as slowly as under 37
Ā°C
conditions. However, after 31 days the BMP
values for 23
Ā°C
samples were only 2% lower than for high temperature samples. Heads and skins
showed similar BMP values
reaching on average 502
L
CH
4
kg
VS
-
1
and 556
L
CH
4
kg
VS
-
1
respectively. BMP for fish intestines was higher, reaching on average 870
L
CH
4
kg
VS
-
1
. Average
BMP for mixes of fish heads, skins, intestines and bones was 660
L
CH
4
kg
VS
-
1
. Acquired BMPs
were further compared with the theoretical BMPs from Buswell's formula. Research results
suggests that anaerobic digestion of fish waste under low temperature conditions could be feasible
as the process still efficiently occurs, in fact ope
ning a new opportunity to explore the overall
sustainability of technologies based on these conversion processes
Mapping drainage ditches in agricultural landscapes using LiDAR data
Received: December 8th, 2021 ; Accepted: January 30th, 2022 ; Published: March 22nd, 2022 ; Correspondence: mailto:[email protected] aim of this study is to develop a method for identification of the drainage ditch
network, which can be used for surface runoff modeling and to increase accuracy of estimation
of greenhouse gas (GHG) emissions in croplands and grasslands, using remote sensing data. The
study area consists of 11 objects throughout Latvia with a total area of 145 km2
. Digital elevation
models (DEMs) in two resolutions, which were created using three different interpolation
methods, were used for the analysis. Several multi-level data filtering methods were applied to
identify ditch network, including flow patterns, which can be used in surface runoff process. The
method we developed correctly identified 85ā89% of ditches, depending on the DEM used, in
comparison to the reference data. Mapped ditches are located within 3 m range of the reference
data in 89ā93% of cases. The elaborated model is robust and uses openly available source data
and can be used for large scale ditch mapping with sufficient accuracy necessary for hydrological
modelling and GHG accounting in the national inventories
Development of Latvian land use and land use change matrix using geospatial data of National forest inventory
ArticleLand use and land use change calculation matrix is one of the most important parts of
the national greenhouse gas (GHG) inventory in land use, land use change and forestry
(LULUCF) sector providing information of an overall summary and changes in land use at a
national level over a specified period of time. Information on land use and land use changes are
further used to calculate other parameters important for determination of GHG emissions and
carbon stock changes in living and dead biomass, soil and litter, as well as basic information on
the impact of applied climate change mitigation measures. Calculations of land use change can
be carried out in a partly automated process using GIS tools, which makes calculations easier to
perform, reduces time consumption for this task and occasional mistakes due to manual
operations. The aim of this study is to improve the methodology for development of land use and
land use change matrix in the national GHG inventory system using geospatial data of National
forest inventory (NFI) and auxiliary data sources. The developed system uses geospatial NFI data
and auxiliary information provided by the land parcel information system (LPIS) and stand-wise
forest inventory, and it improves accuracy and consistency of the land use and land use change
matrix, providing the ability to apply the same land use accounting method for the whole reporting
period since 1990 without a significant increase of uncertainty. The developed method determines
land use changes in a 5-year period by comparing three successive NFI cycles. To determine the
actual land use category in a particular year, we adjusted weights for different land use categories.
Interpolation is used to determine year-by-year transitions
Approximate approach of research and assessment of crack resistance of cylindrical housings
In this work, we propose a procedure that allows us to quickly, without involving finite-element packages at the execution stage, evaluate the state of postulated cracks in cylindrical structural elements with internal anticorrosion cladding under pressure and unsteady temperature loading. The procedure contains three components. The first component of the procedure is based on the analytical solution of the unsteady thermal conductivity problem. The second component of the procedure is also analytical relations specifying circumferential and longitudinal stresses in a two-layer cylinder as a function of internal pressure and temperature distribution along the depth of the wall. In the third stage of the procedure, the coefficients of stress intensity along the crack front are determined by the method of influence functions using the known distribution of stresses. To implement this part of the procedure, the influence functions must first be calculated by the finite element method. In this work the example of calculating the functions of influence for longitudinal semi-elliptical cracks of 1/8 wall thickness depth and with the ratio of the principal half-diameters 0.3 and 0.7 is presented. As an example of the implementation of the procedure, comparative calculations were carried out and the elastic-plastic calculation of a cylindrical shell containing longitudinal cracks was given. Stress intensity coefficients along the part of the front located in the base metal were calculated. The results of analytical calculations were conservative until plastic deformations developed in the cladding. At significant plastic strains, the values of the stress intensity coefficients calculated by the proposed procedure, on the contrary, are significantly inferior. This demonstrates once again the fact that calculations in the framework of linear fracture mechanics are not always conservative in relation to calculations in the elastic-plastic formulation. The paper gives an explanation of the reason for the obtained effect
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