Wyniki wyszukiwania - Biblioteka Nauki

1

Two-phase gas-liquid flow in conditions of expansion and contraction of channel

100%

Witczak S. , Wiśniowska J.

Journal of Energy Science

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2012

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tom Vol. 1, nr 2

135--143

EN

The paper presents the results of studies concerning the effects of sudden change of cross-sectional area on the flow patterns and local pressure losses in the horizontal flow of two-phase mixture. The scope of research include the observation of flow patterns of flowing mixture and their disturbances caused sudden change in cross-section of the pipeline. In addition, flow resistance affecting pressure change before and after the local obstacle were measured. The experiment was conducted in a horizontal flow through the measuring channel with a local obstacle in the form of a sudden change in channel cross-sectional area. Measurement channel was a system of two interconnected tubes with internal diameters of 40 and 22 mm and a total length of 7 m. The air, water and oil were used in the experiments. Analysis of the experimental data leads to the conclusion that the mathematical model for calculating the two-phase flow pattern disturbance areas and their impact on the value of the pressure drop in the pipe with a sudden expansion and contraction should take into account both the parameters of the liquid phase and gas phase.

2

Matroids And Greedy Algorithms. A Deeper Justification of Using Greedy Approach To Find A Maximal set of a Matroid

100%

Haider S. A.

Annales Universitatis Mariae Curie-Skłodowska. Sectio AI, Informatica

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2016

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tom Vol. 16, no. 2

48--50

EN

Greedy algorithms are used in solving a diverse set of problems in small computation time. However, for solving problems using greedy approach, it must be proved that the greedy strategy applies. The greedy approach relies on selection of optimal choice at a local level reducing the problem to a single sub problem, which actually leads to a globally optimal solution. Finding a maximal set from the independent set of a matroid M(S, I) also uses greedy approach and justification is also provided in standard literature (e.g. Introduction to Algorithms by Cormen et .al.). However, the justification does not clearly explain the equivalence of using greedy algorithm and contraction of M by the selected element. This paper thus attempts to give a lucid explanation of the fact that the greedy algorithm is equivalent to reducing the Matroid into its contraction by selected element. This approach also provides motivation for research on the selection of the test used in algorithm which might lead to smaller computation time of the algorithm.

3

Structural determinants of cooperativity in acto-myosin interactions.

100%

Moraczewska J.

Acta Biochimica Polonica

|

2002

|

tom 49

|

nr 4

805-812

EN

Regulation of muscle contraction is a very cooperative process. The presence of tropomyosin on the thin filament is both necessary and sufficient for cooperativity to occur. Data recently obtained with various tropomyosin isoforms and mutants help us to understand better the structural requirements in the thin filament for cooperative protein interactions. Forming an end-to-end overlap between neighboring tropomyosin molecules is not necessary for the cooperativity of the thin filament activation. When direct contacts between tropomyosin molecules are disrupted, the conformational changes in the filament are most probably transmitted cooperatively through actin subunits, although the exact nature of these changes is not known. The function of tropomyosin ends, alternatively expressed in various isoforms, is to confer specific actin affinity. Tropomyosin's affinity or actin is directly related to the size of the apparent cooperative unit defined as the number of actin subunits turned into the active state by binding of one myosin head. Inner sequences of tropomyosin, particularly actin-binding periods 3 to 5, play crucial role in myosin-induced activation of the thin filament. A plausible mechanism of tropomyosin function in this process is that inner tropomyosin regions are either specifically recognized by myosin or they define the right actin conformation required for tropomyosin movement from its blocking position.

4

L-approach merotopies and their categorical perspective

88%

Khare M. , Tiwari S.

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2012

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tom Vol. 45, nr 3

699-716

EN

In the present paper, we have made a category theoretic and lattice theoretic study of some nearness-like structures in the L-approach theory. Using L-grills, the notion of L-approach grill structure is introduced as a characterization of L-approach grill merotopy on X; their categorical perspectives and implications are also investigated. A number of illustrative examples are included.

5

The simplest shadowing

88%

Ombach J.

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1993

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tom 58

|

nr 3

253-258

EN

Two different and easy proofs are presented that a hyperbolic linear homeomorphism of a Banach space admits the shadowing.

6

88%

Sisneros K. , Maurya P. , Johnson E. , Ford B. , Palmer T.

Acta of Bioengineering and Biomechanics

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2023

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tom Vol. 25, no. 1

19--26

EN

This study aimed to examine the effects of age on vertical jump height and handgrip strength measurements in women. A secondary aim was to investigate the correlations between vertical jump height and handgrip strength. Methods: Twenty young (21.5 ± 2.8 years) and twenty older (67.0 ± 5.5 years) healthy women participated in this study. Handgrip contractions were used to assess strength measurements of peak force and rate of force development at different time intervals. Vertical jumps were performed on a jump mat. The jump mat measured vertical jump height based on flight time. Results: The older women had lower vertical jump height (P < 0.001) and handgrip peak force (P = 0.028) and rate of force development values (P = 0.003–0.016) than the younger women. A larger difference was observed between the groups for vertical jump height (41%) than handgrip peak force and rate of force development (12–17%). Of all the strength measurements, handgrip rate of force development at 200 ms in the young (r = 0.502, P = 0.024) and older (r = 0.446, P = 0.049) women exhibited the strongest correlation with vertical jump height. Conclusions: This investigation showed significantly lower vertical jump height and handgrip peak force and rate of force development values in older compared to younger women. Interestingly, the difference between age groups was larger for jump height than handgrip peak force and rate of force development. This suggests that vertical jump performance may be more severely affected by age than handgrip strength characteristics.

7

Comparative Analysis of the Course of Business Cycles and Thermodynamic Cycles

88%

Włodarczyk J.

Equilibrium. Quarterly Journal of Economics and Economic Policy

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2011

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tom 6

|

nr 1

EN

Mainstream economics tends to perceive economic systems in a mechanistic way, which makes it impossible to grasp the notion of the irreversibility of real economic processes and thus encourages referring to the achievements of thermodynamics.Although economic equivalents of thermodynamic quantities have been discussed for more than a hundred years, a significant development of thermodynamic techniques of modeling economic phenomena, that could complement standard econometric methods, has not been observed.It seems that a comparative analysis of the course of thermodynamic and business cycles could enhance the understanding of the mechanisms underlying business cycles, especially in the context of mutual relations between economy and its environment.The aim of this article is to discuss some similarities and differences between economic and thermodynamic systems (heat engines and heat pumps). In particular, the problem of performing positive or negative work by an economy is considered and illustrated by the analysis of statistical data referring to the American and Polish economies.

8

The tetanic depression in unfused tetani of fast motor units in mammalian muscle

75%

Celichowski J.

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tom Vol. 25, no. 4

27-35

EN

Tetanic depression is a phenomenon that limits the force of unfused tetani in contractions evoked at unstable stimulation frequencies. In our experiments this phenomenon was visible in tetani evoked at two frequencies of stimulation: the lower immediately followed by the higher one. The force at the higher stimulation frequency was evidently depressed in relation to the force achieved during the control constant-frequency stimulations. This depression concerned the fast motor units and it was not observed in the slow units. The tetanic depression was initially found in the rat medial gastrocnemius muscle. However, it is not clear whether this phenomenon is specific only to the rat muscle or it concerns all mammals. Therefore, in the subsequent series of experiments, the tetanic depression was investigated in the motor units of the feline medial gastrocnemius, and the effect was also observed in all fast units. The maximum evoked depression exceeded 50% of the control values. Moreover, the analysis of the relationship between the amplitude of the tetanic depression and the degree of the tetanic fusion revealed that the strongest amplitude of depression was observed in the middle-fused tetani (with the fusion index in the range 0.5-0.7). The third experimental series proved that the tetanic depression could be visible in tetani evoked at a progressively increasing frequency of stimulation. Moreover, it was found that the effect of the force decrease could result from the prolongation of only one, the first interpulse interval. The amplitude of this decrease exceeded 20% of the control values. Summarizing, the tetanic depression is a phenomenon influencing the force of unfused tetani of the fast motor units at an increasing stimulation frequency. The depressive effect is present in various species of mammals, probably, including human. The amplitude of the depression depends on the fusion of the tetanic contraction. The physiological significance of tetanic depression is closely related to reduction of the importance of the motoneuronal firing rate.

9

Rough Set Characterization for 2-circuit Matroid

75%

Wang S. , Zhu Q. , Zhu W. , Min F.

Fundamenta Informaticae

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2014

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tom Vol. 129, nr 4

377--393

EN

Rough sets are efficient to extract rules from information systems. Matroids generalize the linear independency in vector spaces and the cycle in graphs. Specifically, matroids provide well-established platforms for greedy algorithms, while most existing algorithms for many rough set problems including attribute reduction are greedy ones. Therefore, the combination between rough sets and matroids may bring new efficient solutions to those important and difficult problems. In this paper, 2-circuit matroids, abstracted from matroidal characteristics of rough sets, are studied and axiomatized. A matroid is induced by an equivalence relation, and its characteristics including the independent set and duality are represented with rough sets. Based on these rough set representations, this special type of matroid is defined as 2-circuit matroids. Conversely, an equivalence relation is induced by a matroid, and its relationship with the above induction is further investigated. Finally, a number of axioms of the 2-circuit matroid are obtained through rough sets. These interesting and diverse axioms demonstrate the potential for the connection between rough sets and matroids.

10

Contractive projections on the fixed point set of $L_∞$ contractions

75%

Lin M. , Sine R.

Colloquium Mathematicum

|

1991

|

tom 62

|

nr 1

91-96

11

Experimental and numerical investigation of scour downstream contracted spillways

75%

Nasralla T. H.

Journal of Water and Land Development

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2022

|

tom no. 52

53--59

EN

A study of scour downstream of free hydraulic jump in stilling basin of stepped spillways was carried out. This paper employed an experimental study to investigate the stepped spillway with the movable bed material of D50= 3.1 mm. The effect of the contraction ratio of the stepped spillway was highlighted. Different downstream divergent angle was studied to minimise the scour depth, the results showed that the relative scour depth was reduced by 23% for divergent angle is equal to 170°, different shapes of buffer in stilling basin were also studied to reduce the scour depth where the considered buffer decrease the relative scour depth up to 84%. This study was simulated by Flow 3D program to analyse the scour hole formed using velocity vectors at the bed. The simulated results well agreed with the measured data.

12

Krystalizacja i skurcz stopu AK9 (AISi9Mg)

75%

Dudyk M. , Kosibor K.

Archiwum Odlewnictwa

|

2004

|

tom R. 4, nr 14

138-145

PL

W artykule przedstawiono wpływ uszlachetniania (rafinacji, modyfikacji Sr lub Sb) siluminu AK9 (AISi9Mg) na zmiany kinetyki procesów krystalizacji, określanych na urządzeniu CRISTALDIMAT (ATD). Dla badanych siluminów przedstawiono oryginalne wyniki dotyczące skurczu w czasie krystalizacji oraz wyniki badań dylatometrycznych po zastosowanych zabiegach rafinacji i modyfikacji. Określono wpływ krystalizacji podstawowych faz (alfa i eutektyki alfa + Si) na zmiany wydłużenia badanych próbek. Na DYLATOMETRZE AUTOMATYCZNYM DA - 2 sporządzono dylatogramy i określono ich wpływ na skurcz w stanie stałym badanych siluminów.

EN

In the article introduced influence of enriching (refinement, modification Sr or Sb) aluminium alloy AK9 (AISi9Mg) on changes of kinetic crystallization proceses defined on device CRISTALDIMAT (ATD). For investigated alluminium alloy introduced oryginal results relating contraction during of crystallization and results dylatometric researches after used interventions of refinement and of modification. Qualified influence crystallization of basic phases (alfa and eutektic alfa + Si) on changes of extension investigated sampIes. On automatic dilatometer DA-2 prepared dilatogrames and defined their influence on contraction in solid state investigated aluminium alloys.

13

The influence of increasing and decreasing frequency of stimulation on the contraction of motor units in rat medial gastrocnemius muscle

75%

Celichowski J. , Bichler E.

|

2000

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tom 51

|

nr 4,2

14

Effect of adrenalin, insulin and contractions on the content of the free fatty acid fraction in skeletal muscle

75%

Chabowski A. , Baranczuk E. , Gorski J.

Journal of Physiology and Pharmacology

|

2005

|

tom 56

|

nr 3

EN

The fraction of free fatty acids (FFA) is present in skeletal muscles. However, there is almost no data regarding regulation in the content of this intramuscular lipid pool. We took advantage of the isolated muscle preparation to examine whether: a) increasing exogenous concentration of FFA (500µM or 700µM, 30min) b) insulin (10.00 I.U./L, 30min), c) adrenalin (4.4 nM, 30min), or d) contractions (200ms, tetani, 1Hz, 30min), affect the FFA content inside myocytes. Incubation of soleus (S) and extensor digitorum longus (EDL) with increasing concentrations of exogenous FFA (from 500µM to 700µM) resulted in an increase in the total FFA fraction in both muscles studied (by 280.2% and 259.1%, respectively). In contracting muscles FFA pool was significantly reduced both in S (by 73.1%) and in EDL (by 31.1%). Neither stimulation by adrenalin nor insulin affected the total content of FFA fraction in the muscles examined. We conclude that a) increased availability of exogenous FFA at the sarcolemma level results in an increase in the size of intramuscular FFA fraction b) the intracellular FFA fraction is utilized by contracting muscles with regard to the fiber composition and to a greater extent in more oxidative muscles, c) FFA fraction remains stable upon stimulation by insulin or adrenalin.

15

Changes in fusion index during the fatigue test of fast motor units in the medial gastrocnemius muscle of the rat

75%

Celichowski J. , Grottel K. , Bichler E.

|

nr 4

16

Structural determinants of cooperativity in acto-myosin interactions

75%

Moraczewska J.

Acta Biochimica Polonica

|

2002

|

tom 49

|

nr 4

EN

Regulation of muscle contraction is a very cooperative process. The presence of tropomyosin on the thin filament is both necessary and sufficient for cooperativity to occur. Data recently obtained with various tropomyosin isoforms and mutants help us to understand better the structural requirements in the thin filament for cooperative protein interactions. Forming an end-to-end overlap between neighboring tropomyosin molecules is not necessary for the cooperativity of the thin filament activation. When direct contacts between tropomyosin molecules are disrupted, the conformational changes in the filament are most probably transmitted cooperatively through actin subunits, although the exact nature of these changes is not known. The function of tropomyosin ends, alternatively expressed in various isoforms, is to confer specific actin affinity. Tropomyosin's affinity or actin is directly related to the size of the apparent cooperative unit defined as the number of actin subunits turned into the active state by binding of one myosin head. Inner sequences of tropomyosin, particularly actin-binding periods 3 to 5, play crucial role in myosin-induced activation of the thin filament. A plausible mechanism of tropomyosin function in this process is that inner tropomyosin regions are either specifically recognized by myosin or they define the right actin conformation required for tropomyosin movement from its blocking position.

17

Fatigability of motor units estimated by changes in work performed during their repetitive stimulation during the fatigue test

75%

Celichowski J. , Grottel K. , Bichler E.

Acta Neurobiologiae Experimentalis

|

1999

|

tom 59

|

nr 1

18

The time course of the last contractions during incompletely fused tetani of motor units in rat skeletal muscle

75%

Celichowski J. , Bichler E.

|

nr 1

19

The effect of vasoconstrictors on oxygen consumption in resting and contracting skeletal muscle of the autologous pump-perfused rat hindlimb

63%

Hoy A. J. , Peoples G. E. , McLennan P. L.

Journal of Physiology and Pharmacology

|

2009

|

tom 60

|

nr 3

155-160

EN

This study used a novel in vivo model to test the hypothesis that nutritive and non-nutritive blood flow distribution can still be observed under conditions of high vascular tone and oxygen delivery at rest and in metabolically active (twitch contracting) skeletal muscle. Experiments were performed in a constant flow autologous pump-perfused hindlimb in anaesthetised male Wistar rats. Agonists were tested at rest with a flow rate of 1ml•min-1, and during hindlimb muscle twitch contractions (sciatic nerve stimulation: 6V, 1Hz, 0.05ms, 3min) at a flow rate of 2ml•min-1. Oxygen consumption was determined from hindlimb venous and arterial blood samples. Resting perfusion pressure at 1ml•min-1 was 92±3 mmHg (N=15) and oxygen consumption was 0.41±0.05 µmol•min-1•g-1. Serotonin increased perfusion pressure and significantly decreased basal hindlimb oxygen consumption at rest. During acute muscle contraction this effect on oxygen consumption was diminished. Noradrenaline significantly increased perfusion pressure but had no significant effect on basal hindlimb oxygen consumption. Vasoconstriction that impacts upon muscle metabolism occurs in vivo, which potentially could be due to selective redistribution of blood flow. However, during muscle contraction local release of vasodilatory regulation can overcome exogenously-induced vasoconstriction. These results support the hypothesis that dual vascular pathways may explain differential vasoconstriction and how it impacts upon muscle metabolism.

20

Miejscowe straty ciśnienia przy przewężeniu kanału poziomego podczas przepływu dwufazowego ciecz - ciecz

63%

Witczak S. , Wiśniowska J.

Inżynieria i Aparatura Chemiczna

|

2010

|

tom Nr 4

88-89