The Upper Miocene lignite from the Main coal seam in the D field, Kolubara basin, is a typical humic coal with huminite, liptinite and inertinite concentrations of up to 83.7vol.%, 17.2vol.% and ...15.5vol.%, respectively. In the huminite group, textinite and ulminite are the most abundant macerals with variable amounts of densinite and attrinite. Liptodetrinite and sporinite are the most common macerals of the liptinite group, while inertodetrinite is the most abundant maceral of the inertinite group. The mineral matter consists mostly of clay minerals. The main sources of organic matter were gymnosperms (conifers) and microbial biomass, followed by angiosperms. Based on composition of saturated and aromatic diterpenoids it has been established that coal forming plants belonged to the gymnosperm families Taxodiaceae, Podocarpaceae, Cupressaceae, Araucariaceae, Phyllocladaceae and Pinaceae. Peatification occurred in neutral to slightly acidic, fresh water environment. Composition and distribution of biomarkers show that diagenetic changes of the organic matter were mainly governed by bacterial activity in a suboxic to oxic environment. Based on distribution of aromatic diterpenoids a novel diagenetic pathway for transformation of abietane-type precursors under suboxic to oxic conditions is proposed. Variations in compositions of macerals and biomarkers are in concordance with pronounced seasonality during Pontian, which caused changes in the water level, redox conditions during peatification, and to some extent vegetation differences in the paleo-plant communities.
► Palaeoenvironment of lignite precursor material was determined. ► Differences in the palaeo-plant communities are caused by pronounced seasonality. ► Diagenetic changes of the organic matter were mainly governed by bacterial activity. ► Novel diagenetic pathway for transformation of abietane-type precursors proposed.
This paper is a study of the chemical composition of Hyssopus officinalis ssp. officinalis grown during three years (2017–2019) at the Institute of Field and Vegetable Crops Novi Sad (Vojvodina ...Province, Serbia). Furthermore, comparisons with ISO standards during the years were also investigated, as well as a prediction model of retention indices of compounds from the essential oils. An essential oil obtained by hydrodistillation and analysed by GC-FID and GC-MS was isopinocamphone chemotype. The gathered information about the volatile compounds from H. officinalis was used to classify the samples using the unrooted cluster tree. The correlation analysis was applied to investigate the similarity of different samples, according to GC-MS data. The quantitative structure–retention relationship (QSRR) was also employed to predict the retention indices of the identified compounds. A total of 74 experimentally obtained retention indices were used to build a prediction model. The coefficient of determination for the training cycle was 0.910, indicating that this model could be used for the prediction of retention indices for H. officinalis essential oil compounds.
Roots of wild growing Angelica archangelica L. from Mt. Ozren (Serbia) were subjected to hydrodistillation and GC-MS analysis. The roots contained 0.10% of essential oil with α-pinene (29.7%), ...δ-3-carene (14.2%), and a mixture of β-phellandrene and limonene (13.2%) as main compounds. The modified resazurin microtiter-plate assay was used to evaluate the antibacterial activity of the essential oil against Staphylococcus aureus and Escherichia coli. The minimum inhibitory concentration (MIC) values were 14.2 μL/mL for S. aureus and 28.4 μL/mL for E. coli, while the minimum bactericidal concentrations (MBC) were 56.8 μL/mL and 113.6 μL/mL, respectively. According to the obtained results, the angelica root essential oil can be applied as a natural preservative in food and as a natural antibiotic for the treatment of several infectious diseases caused by these two bacteria.
In this paper, for given operators
,
and
, we completely describe the set of all
such that the operator
is injective, in the case when
is closed. Then, we give necessary and sufficient conditions for ...the existence of some
such that
is not dense in
. The results are then used to draw some additional conclusions about the residual spectrum of the operator matrix
.
An algorithm for computing minimal Geršgorin sets Kostic, Vladimir R; Midlar, Agnieszka; Cvetkovic, Ljiljana
Numerical linear algebra with applications,
March 2016, Letnik:
23, Številka:
2
Journal Article
In this paper we present a nonsingularity result which is a generalization of Nekrasov property by using two different permutations of the index set. The main motivation comes from the following ...observation: matrices that are Nekrasov matrices up to the same permutations of rows and columns, are nonsingular. But, testing all the permutations of the index set for the given matrix is too expensive. So, in some cases, our new nonsingularity criterion allows us to use the results already calculated in order to conclude that the given matrix is nonsingular. Also, we present new max-norm bounds for the inverse matrix and illustrate these results by numerical examples, comparing the results to some already known bounds for Nekrasov matrices.
Background: The quality of life in patients undergoing hemodialysis is significantly disturbed. There are data that hemodiafiltration (HDF) may be more effective than conventional hemodialysis in the ...removal of uremic toxins and may reduce frequency and severity of intradialytic and postdialysis adverse symptoms in patients. Also, some researchers suggest advantages of using high-flux membranes compared with low-flux. Objective: The aim of this study was to examine whether hemodialysis modality and membrane flux, independent of membrane biocompatibility, make differences in quality of life in patients. Methods: In our cross-sectional study, we evaluated 124 patients who were divided, based on therapy, into three groups: online HDF, high-flux hemodialysis, and low-flux hemodialysis. Data were collected using the Short Form-36 questionnaire combined with special questionnaire, which included demographic and clinically related questions. Results: Health-related quality of life was better in patients on HDF compared with patients on hemodialysis, especially compared with low-flux hemodialysis patients in most of the scales and in both dimensions: physical component scale and mental component scale. There were no statistically significant differences in Short Form-36 domains between high-flux hemodialysis and low-flux hemodialysis. Conclusion: Our data suggest the potential advantages of HDF with regard to influence on quality of life, which is sufficient to justify further research in prospective and longitudinal study design.
A new subclass of H-matrices CVETKOVIC, Ljiljana; KOSTIC, Vladimir; RAUSKI, Sonja
Applied mathematics and computation,
02/2009, Letnik:
208, Številka:
1
Journal Article
Recenzirano
Class of
H-matrices plays an important role in various scientific disciplines, in economics, for example. However, this class could be used in order to get various benefits in other linear algebra ...fields, like determinant estimation, Perron root estimation, eigenvalue localization, improvement of convergence area of relaxation methods, etc. For that reason, it seems important to find a subclass of
H-matrices, as wide as possible, and expressed by explicit conditions, involving matrix elements only. One step forward in this direction, starting from Gudkov matrices, from one side, and
S-SDD matrices, from the other side, will be presented in this paper.
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