Search results

1

Theoretical construction of stable traversable wormholes

100%

Kuhfittig P.

Open Physics

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2010

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vol. 8

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issue 3

364-368

EN

It is shown in this paper that it is possible, at least in principle, to construct a traversable wormhole that is stable to linearized radial perturbations by specifying relatively simple conditions on the shape and redshift functions.

2

STABILITY STUDIES OF CEFTIOFUR SODIUM IN AQUEOUS SOLUTIONS AND IN THE SOLID PHASE

80%

Dołhań A., Sobczak A., Muszalska I., Medenecka B., Garbacki P., Tomczak S., Jelińska A.

Acta Poloniae Pharmaceutica - Drug Research

|

2018

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vol. 75

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issue 6

1279-1286

EN

Ceftiofur sodium (CFT), a third-generation cephalosporin for parenteral use, is commonly used in veterinary medicine against aerobic Gram-positive and Gram-negative bacteria as well as certain anaerobes. Its broad spectrum of activity and resistance to beta-lactamases result from the presence of methoxyimino and aminothiazole moieties at C-7 in the cephalosporin structure. The aim of this study was a comprehensive evaluation of the stability of CFT in the solid phase and in aqueous solutions. A fast and sensitive HPLC isocratic method was used for the determination of CFT degradation in the solid phase and in aqueous solutions. CFT degradation occurred according to a first-order reaction depending on the substrate concentration. The kinetic and thermodynamic parameters of CFT degradation in the solid phase were calculated. General acid-base hydrolysis of CFT was not observed in the solutions of hydrochloric acid, sodium hydroxide, phosphate (pH 5.84 – 7.25), acetate (pH 3.65 – 5.48) and borate (pH 7.49 – 10.07) buffers. CFT was the most stable in the pH range 2 – 6. The susceptibility of CFT to degradation under the influence of stress factors (pH, temperature, buffer components concentration, relative air humidity) should be considered in terms of storage conditions and the preparation of the product for administration.

3

Clinical tests for balance stability and gait assessment – bedside tests

80%

Józefowicz-Korczyńska M., Chmielecka-Rutkowska J., Mazerant A.

Polski Przegląd Otorynolaryngologiczny

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2016

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vol. 5(1)

57-63

EN

Balance and gait stability assessment is an important part of the otoneurological examination. We present the review of the clinical bedside tests procedures for diagnosis patients with balance disorders. Instability may occur not only in vestibular system dysfunction but in neurological, musculoskeletal and visual system lesions as well. An accurate clini-cal bedside ocular motor examination like, range of motion, stability of fixation, the presence of nystagmus, saccadic and smooth pursuit tests, give information about dynamic character of ocular motility. Tests of the balance system and cerebellum functioning were elaborated. Interpretations criteria for clinical bedside tests in different disease were pre-sented. Head shaking and head trust tests for vestibular system imbalance were described. Authors paid attention to the connection between examinations results and labyrinth or central nervous system disorders. Other tests are suggested to be used in benign paroxysmal positional vertigo diagnosis and ability to self-contained patients gait evaluation. There are some more complex and time-consuming tests like Dynamic Gait Index and Berg Balance Scale, measuring quanti-tative aspects of gait efficiency. The results are obtained based on points which are obtained in various tasks e.g. walking with pivot turn, stepping over and around obstacles. All of these tests are essential part of clinical examination and give preliminary information about patients functioning status and allow to focus on further diagnosis.The final results based on points which are obtained in various tasks e.g. walking with pivot turn, stepping over and around obstacles. All of these tests are essential part of clinical examination and give preliminary information about patients functioning status and allow to focus on further diagnosis.

4

Sedimentation of water dispersed systems of acrylate copolymers in xylene

80%

Makarewicz E., Zalewska A.

Polish Journal of Chemical Technology

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2008

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vol. 10

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issue 3

29-34

EN

Methyl methacrylate - butyl acrylate - methacrylic acid copolymer and butyl methacrylate - methacrylic acid amide copolymer of a different segmental structure were stabilised with non-ionic and anionic surfactants. Gel chromatography, viscosimetry, tensiometry, conductometry and sedimentation methods were applied to define the properties of the synthesized copolymers, surfactants in water solutions and water dispersions. The types and the properties of the phases being in a state of sedimentation balance were also determined. The obtained experimental data were interpreted and justified by using the copolymer and surfactants properties. The existing correlations were pointed out. The obtained results show that the stability of a disperse system considerably depends on the structure of the copolymer. The MMA/BA/MAA copolymer has monomeric units of elastic butyl acrylate. Segments containing these monomeric units adsorb surfactants much better and form more stable water disperse systems. However, the MBA/AMAA copolymer with the polarity of amide group of methacrylamide makes disperse systems less stable.

5

Antioxidant effects of carotenoids in a model pigment-protein complex

80%

Fiedor J., Sulikowska A., Orzechowska A., Fiedor L., Burda K.

Acta Biochimica Polonica

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2012

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vol. 59

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issue 1

61-64

EN

The effect of carotenoids on stability of model photosynthetic pigment-protein complexes subjected to chemical oxidation with hydrogen peroxide or potassium ferricyanide was investigated. The oxidation of carotenoid-less and carotenoid-containing complexes was conducted in the presence or absence of ascorbic acid. The progress of the reactions was monitored by use of absorption and fluorescence spectroscopy. Our results show that carotenoids may significantly enhance the stability of photosynthetic complexes against oxidation and their protective (antioxidant) effect depends on the type of the oxidant.

6

Stability conditions for fractional-order linear equations with delays

80%

Mozyrska D., Ostalczyk P., Wyrwas M.

Bulletin of the Polish Academy of Sciences: Technical Sciences

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2018

|

issue 4

7

Finite difference scheme for the time-space fractional diffusion equations

80%

Cao J., Li C.

Open Physics

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2013

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vol. 11

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issue 10

1440-1456

EN

In this paper, we derive two novel finite difference schemes for two types of time-space fractional diffusion equations by adopting weighted and shifted Grünwald operator, which is used to approximate the Riemann-Liouville fractional derivative to the second order accuracy. The stability and convergence of the schemes are analyzed via mathematical induction. Moreover, the illustrative numerical examples are carried out to verify the accuracy and effectiveness of the schemes.

8

Do Ergogenic Aids Alter Lower Extremity Joint Alignment During a Functional Movement Lunge Prior to and Following an Exercise Bout?

80%

Mills C., Knight J., Milligan G.

Journal of Human Kinetics

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2015

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vol. 45

|

issue 1

9-17

EN

Ergogenic aids have been used to alter joint kinematics in an attempt to minimise injury risk, yet the effectiveness of these aids may be compromised following a bout of exercise. This preliminary study aimed to measure the effect of compression garments and Kinesio Tape® on lower extremity joint alignment prior to and following an exercise bout. Eight male athletes (age = 24.1 ± 3.0 years, body height = 177.4 ± 5.2 cm, body mass = 72.3 ± 7.2 kg) volunteered to participant in this study. Joint kinematics were recorded whilst all participants performed three rotational lunges, in three conditions (control, compression garment, Kinesio Tape®), prior to and following a 10 minute exercise bout. Frontal plane kinematics (lateral pelvic tilt, knee valgus, ankle inversion/eversion) were used to assess ergogenic aid effectiveness during the lunge. Participants exhibited no significant differences in joint kinematics between ergogenic aid conditions prior to the exercise bout. Following exercise the only significant difference occurred within the Kinesio Tape® condition where maximum knee valgus angle significantly increased from 6.5° prior to exercise, to 7.7° following the exercise bout. The results of this study suggest joint kinematics are not affected by the ergogenic aids in this study prior to an exercise bout. However, there is evidence to suggest that the application of Kinesio Tape® may allow an increase in knee valgus angle following a bout of exercise, yet, compression garments are effective at maintaining joint alignment following a bout of exercise.

9

Pelvis motion characteristics in case of induced gait perturbation in male and female adults

80%

Łysoń B., Bienias K., Ścibek J., Wit A.

Advances in Rehabilitation

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2019

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vol. 33

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issue 3

27-33

EN

Introduction Falls are a serious social problem. The risk of falling is higher for women compared to the male population, which may be resulting from differences in anatomy of the pelvis. Even though there are papers describing pelvis reaction to perturbation differentiating males and females, the perturbation is usually applied in standing position. The study’s aim was to compare selected values describing the pelvis motion while gait perturbation and normal walking, having regard to sex differences. Material and methods The study group included 43 young healthy adults (27 women and 16 men) aged 23±4 years. Motek Grail system was used to record the position of reflective markers placed on subjects’ body. Gait perturbation (trip) was induced by decelerating one of the belts of the treadmill integrated with the system. Three-dimensional kinematic parameters for the left leg stance phase, when the perturbation occurred, and the next stance phase of the contralateral leg was analyzed. Statistical analysis was conducted in STATISTICA software using a two-way analysis of variance and Pearson correlation. Results Statistically significant differences between gait and perturbation were found for each of the analyzed planes. It was also observed that gender influenced the results. Females had greater maximum pelvic tilt and greater rotation to the right compared to men, both for gait and perturbation. Conclusions Based on the obtained results it can be suggested that differences in the anatomy and biomechanics of the pelvis between male and female may be the reason of higher risk of falling while walking in women compared to the men.

10

Influence of Passive Stiffness of Hamstrings on Postural Stability

80%

Kuszewski M., Gnat R., Sobota G., Myśliwiec A.

Journal of Human Kinetics

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2015

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vol. 45

|

issue 1

49-57

EN

The aim of the study was to explore whether passive stiffness of the hamstrings influences the strategy of maintaining postural stability. A sample of 50 subjects was selected; the final analyses were based on data of 41 individuals (33 men, 8 women) aged 21 to 29 (mean = 23.3, SD = 1.1) years. A quasi- experimental ex post facto design with repeated measures was used. Categories of independent variables were obtained directly prior to the measurement of the dependent variables. In stage one of the study, passive knee extension was measured in the supine position to assess hamstring stiffness. In stage two, the magnitude of postural sway in antero-posterior direction was measured, while varying the body position on a stabilometric platform, both with and without visual control. The margin of safety was used as a measure of postural control. The magnitude of the margin of safety increased significantly between the open-eye and closed-eye trials. However, although we registered a visible tendency for a larger increase of the margin of safety associated with lower levels of passive hamstrings stiffness, no significant differences were found. Therefore, this study demonstrated that hamstring stiffness did not influence the strategy used to maintain postural stability.

11

Control and correction of horse rider's body posture

80%

Mrozkowiak M., Ambroży D.

Central European Journal of Sport Sciences and Medicine

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2014

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vol. 6

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issue 2

21-33

EN

Centre of gravity represents the point where the net force of gravity of all the body parts is applied. Balance is a specific state of the postural control system, being a vertical orientation of human body maintained through balancing the forces and moments of forces that act on the body. Stability is understood to mean the ability to recover the state of balance and typical body position in the space. The concept of division of the rider's posture into 5 blocks that has been used in the literature seems to be legitimate. However, due to the natural shape of spinal curvature, the division of body into opposing truncated pyramids (a trapezoid in the sagittal plane and a rectangle with longer horizontal sides in the frontal plane) appears to be more accurate. The eight-segment model is dynamic and illustrates all the shallowed or deepened spinal curvatures very well while maintaining alternate sagittal curvatures with regard to the deficits of motion in the joints. It is also correct in anatomical terms since it contains all the sections and joints in the kinematic chain. Body posture, considered under conditions of the equestrian pair (a rider and a horse) as a motor task, will be adjusted using the continuous control. This control works within the tracking system and consistently adjusts the activity of different muscles to current needs. These needs result from a specific program encoded in the central nervous system and, more specifically, from the difference between the program and current state of the equestrian pair. This program is developed during equestrian training and it represents a demanded situation.

12

Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

80%

Zun M., Dwornicka D., Wojciechowska K., Swiader K., Kasperek R., Rzadkowska M., Poleszak E.

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vol. 27

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issue 4

213-216

EN

In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w) of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w) of urea had the best constancy.

13

Stability of positive linear discrete-time systems

80%

James G., Rumchev V.

Bulletin of the Polish Academy of Sciences: Technical Sciences

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2005

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vol. 53

|

issue 1

14

The Influence of the Geometrical Construction of the Powered Roof Support on the Loss of a Longwall Working Stability Based on the Practical Experience

71%

Rajwa S., Rajwa S.

Archives of Mining Sciences

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2020

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vol. 65

|

issue 3

15

Phenolics, antioxidative activity and characterization of anthocyanins in berries of blackcurrant interspecific hybrids

71%

Anisimovienė N., Jankauskienė J., Jodinskienė M., Bendokas V., Stanys V., Šikšnianas T.

Acta Biochimica Polonica

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2013

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vol. 60

|

issue 4

767-772

EN

The interest in phenols and anthocyanins has increased due to their antioxidant properties and to their potential usage as dietary antioxidants in human nutrition. Total phenols and anthocyanin content, composition and stability in berry extracts of blackcurrant interspecific hybrids, and antioxidative activity of extracts was evaluated. Berries of interspecific hybrids accumulated 530 to 614 mg 100 g-1 FW of total phenolic compounds, while 621 mg 100 g-1 FW of phenolics was established in berries of control Ribes nigrum cultivar 'Ben Tirran'. 'Ben Tirran' berries accumulated 444 mg 100 g-1 FW of anthocyanins and higher amount was identified in berries of interspecific hybrids No. 11-13 (R. nigrum × R. petraeum) and No. 57 (R. nigrum × R. aureum), 522 and 498 mg100 g-1 FW respectively. Berry extracts of hybrid No. 11-13 distinguished by the highest antioxidative activity (80%) and it was higher than antioxidant activity of 'Ben Tirran' (70%). Antioxidative activity of all tested berry extracts (70-80%) was twice higher compared to synthetic antioxidant BHT (39%). However correlation between phenolics or total anthocyanin content and antioxidative activity degree was not established. Amount of cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside in berries of hybrids No. 57, No. 11-13 and No. 8 ((R. nigrum × R. americanum) × (R. nigrum × R. americanum)) was higher than in berries of 'Ben Tirran'. It was established that cyanidins are more stable anthocyanins in all studied temperature and irradiation conditions. Therefore interspecific hybrids No. 57 and No. 11-13 were the most agronomically valuable hybrids.

16

Phase space analysis of interacting dark energy in f(T) cosmology

71%

Jamil M., Yesmakhanova K., Momeni D., Myrzakulov R.

Open Physics

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2012

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vol. 10

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issue 5

1065-1071

EN

In this paper, we examine the interacting dark energy model in f(T) cosmology. We assume dark energy as a perfect fluid and choose a specific cosmologically viable form f(T) = β√T. We show that there is one attractor solution to the dynamical equation of f(T) Friedmann equations. Further we investigate the stability in phase space for a general f(T) model with two interacting fluids. By studying the local stability near the critical points, we show that the critical points lie on the sheet u* = (c − 1)v* in the phase space, spanned by coordinates (u, v, Ω, T). From this critical sheet, we conclude that the coupling between the dark energy and matter c ∈ (−2, 0).

17

Numerical solutions and analysis of diffusion for new generalized fractional advection-diffusion equations

71%

Xu Y., Agrawal O.

Open Physics

|

2013

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vol. 11

|

issue 10

1178-1193

EN

In this paper we study a class of new Generalized Fractional Advection-Diffusion Equations (GFADEs) with a new Generalized Fractional Derivative (GFD) proposed last year. The new GFD is defined in the Caputo sense using a weight function and a scale function. The GFADE is discussed in a bounded domain, and numerical solutions for two examples consisting of a linear and a nonlinear GFADE are obtained using an implicit finite difference approach. The stability of the numerical scheme is investigated, and the order of convergence is estimated numerically. Numerical results illustrate that the finite difference scheme is simple and effective for solving the GFADEs. We investigate the influence of weight and scale functions on the diffusion of GFADEs. Linear and nonlinear stretching and contracting functions are considered. It is found that an increasing weight function increases the rate of diffusion, and a scale function can stretch or contract the diffusion on the time domain.

18

Stability of discrete-time fractional linear systems with delays

71%

Ruszewski A., Ruszewski A.

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2019

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vol. 29

|

issue 3

19

The Effects of Wetted Ice on Dynamic Stability over a Rewarming Period

71%

Alexander J., Mawene Y., Alexanders J., Jeffery J., Rhodes D.

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vol. 41

13-23

EN

BACKGROUND During half time or breaks in play cryotherapy is often applied for analgesia for minor musculoskeletal sport injury, however the effect of cryotherapy on dynamic stability is debated. A risk factor for further lower limb injury may be heightened due to a reduction in dynamic postural stability. OBJECTIVES The purpose of the current study was to investigate the effects of wetted-ice applied for 20-minutes at the ankle on dynamic stability using the star excursion balance test, immediately-post exposure and over a rewarming period of 30-minutes. MATERIALS AND METHODS Twenty-two healthy male athletes that regular took part in land-based sport were assessed on reach directions of Anterior (Ant), Posteromedial (PM), and Posterolateral (PL) using the modified star excursion balance test (mSEBT) on the non-dominant limb. Thermal imaging quantified skin surface temperature (Tsk) over lateral and medial regions. Participants were tested pre-intervention, exposed to 15-minutes wetted-ice cryotherapy application, immediately-post and up to 30-minutes post intervention at 10-minute intervals. RESULTS Significant decreases in Tsk over the medial and lateral regions of the ankle (p < 0.05) not returning to pre-cooling temperatures at 30-minutes post. Significant decrease in reach -distance scores (ANT, PL and PM) pre-immediately post and at 10, 20 and 30-minutes post cryotherapy exposure. CONCLUSION Following wetted ice application to the non-dominant ankle, dynamic postural stability was adversely affected for up to 30-minutes post exposure demonstrated through a decrease in reach scores for ANT, PL and PM directions. Functional performance which requires stabilising mechanisms may be negatively affected and contribute to a heightened risk of injury or further injury in consideration of the findings.

20

Practical and asymptotic stabilities for a class of delayed fractional discrete-time linear systems

71%

Ruszewski A.

Bulletin of the Polish Academy of Sciences: Technical Sciences

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2019

|

issue 3

Refine search results

Theoretical construction of stable traversable wormholes

STABILITY STUDIES OF CEFTIOFUR SODIUM IN AQUEOUS SOLUTIONS AND IN THE SOLID PHASE

Clinical tests for balance stability and gait assessment – bedside tests

Sedimentation of water dispersed systems of acrylate copolymers in xylene

Antioxidant effects of carotenoids in a model pigment-protein complex