1,269 research outputs found
Objective constraints of figural goodness
The effects of uniformity, compactness and symmetry on pattern goodness estimates were evaluated in three experiments. Ss were asked to choose the pattern which looks the best in respect to other patterns from given set. Patterns within sets differed from each other in uniformity (Experiment 1), compactness (Experiment 2) and symmetry (Experiment 3). Regression analyses indicated that symmetry was a single good predictor of the frequency of good pattern choice. This result is connected with Koffka's concept of perceptual economy: uniformity and compactness have perceptual advantages in the restricted situations (low energy disposal), while symmetry prevails in unrestricted conditions (high energy disposal)
Current and Shot Noise Measurements in a Carbon Nanotube-Based Spin Diode
Low-temperature measurements of asymmetric carbon nanotube (CNT) quantum dots
are reported. The CNTs are end-contacted with one ferromagnetic and one
normal-metal electrode. The measurements show a spin-dependent rectification of
the current caused by the asymmetry of the device. This rectification occurs
for gate voltages for which the normal-metal lead is resonant with a level of
the quantum dot. At the gate voltages at which the current is at the maximum
current, a significant decrease in the current shot noise is observed
Intrinsic adaptation in autonomous recurrent neural networks
A massively recurrent neural network responds on one side to input stimuli
and is autonomously active, on the other side, in the absence of sensory
inputs. Stimuli and information processing depends crucially on the qualia of
the autonomous-state dynamics of the ongoing neural activity. This default
neural activity may be dynamically structured in time and space, showing
regular, synchronized, bursting or chaotic activity patterns.
We study the influence of non-synaptic plasticity on the default dynamical
state of recurrent neural networks. The non-synaptic adaption considered acts
on intrinsic neural parameters, such as the threshold and the gain, and is
driven by the optimization of the information entropy. We observe, in the
presence of the intrinsic adaptation processes, three distinct and globally
attracting dynamical regimes, a regular synchronized, an overall chaotic and an
intermittent bursting regime. The intermittent bursting regime is characterized
by intervals of regular flows, which are quite insensitive to external stimuli,
interseeded by chaotic bursts which respond sensitively to input signals. We
discuss these finding in the context of self-organized information processing
and critical brain dynamics.Comment: 24 pages, 8 figure
Effects of Developmental Training of Basketball Cadets Realised in the Competitive Period
The analysis of effects of a two-month developmental training cycle realised within a
basketball season revealed statistically significant positive changes at the multivariate
level in components of motor-functional conditioning (fitness) status of the sample of
talented basketball cadets (15–16 years). The greatest correlations with discriminant
function were found in variables with statistically significant changes at the univariate
level, more explicitly in variables of explosive and repetitive power of the upper body and
trunk, anaerobic lactic endurance, as well as in jumping type explosive leg power. The
presented developmental conditioning training programme, although implemented within
the competitive period, induced multiple positive fitness effects between the two control
time points in this sample of basketball players. The authors suggest that, to assess
power of shoulders and upper back, the test overgrip pull-up should not be applied to
basketball players of this age due to its poor sensitivity. Instead, they propose the undergrip
pull-up test , which is a facilitated version of the same test. The results presented in
this article reinforce experienced opinion of experts that, in the training process with
youth teams, the developmental conditioning training programme is effectively applicable
throughout the entire competitive season. The proposed training model is a system
of various training procedures, operating synergistically, aimed at enhancing integral
fitness (preparedness) of basketball players. Further investigations should be focused on
assessing effects of both the proposed and other developmental training cycle programmes,
by means of assessing and monitoring actual quality (overall performance) of players,
on the one hand, and, on the other, by following-up hormonal and biochemical
changes over multiple time points
Ispitivanje antioksidativnih mehanizama kempferola sa hidroksi radikalom i superoksid radikal anjonom
Kaempferol, one of the most bioactive plant flavonoids was theoretically (at M05-2X/6-311G(d,p) level of theory) investigated for its ability scavange potentially highly damaging hydroxyl and superoxide anion radicals. Theoretical calculations point to HAT and SPLET mechanisms as operative for kaempferol in all solvents under investigations.Teoretski (na M05-2X/6-311G(d,p) nivou teorije) je ispitivana sposobnost kempferola, važnog bioaktivnog biljnog jedinjenja flavonoida, da reaguje sa potencijalno veoma štetnim hidroksi radikalom i superoksid radikal anjonom. Proračuni su pokazali da su HAT i SPLET mogući mehanizmi u svim rastvaračima
Classical stability and quantum instability of black-hole Cauchy horizons
For a certain region of the parameter space , the Cauchy
horizon of a (charged) black hole residing in de Sitter space is classically
stable to gravitational perturbations. This implies that, when left to its own
devices, classical theory is unable to retain full predictive power: the
evolution of physical fields beyond the Cauchy horizon is not uniquely
determined by the initial conditions. In this paper we argue that the Cauchy
horizon of a Reissner-Nordstr\"om-de Sitter black hole must always be unstable
quantum mechanically.Comment: 4 pages; uses ReVTeX; figure available upon request to
[email protected]
First record of the Northern brown shrimp, Farfantepenaeus aztecus (Ives, 1891) (Crustacea: Decapoda: Penaeidae) in the South Adriatic Sea, Montenegro
A single adult female specimen of the Northern brown shrimp, Farfantepenaeus aztecus, a species native to the western Atlantic coasts, was caught in Boka kotorska bay (southern Adriatic Sea) on 19 September 2013. This is the first record of this alien species in the Adriatic Sea
DFT ispitivanje antioksidativne aktivnosti alizarina Red S
Density functional theory calculations were performed to evaluate the antioxidant activity of alizarin red S molecule. The conformational behavior of molecule were analysed at the M06-2X/6-311++G(d,p) method. The most stable conformer of alizarin red S has two IHBs. The expected antioxidant activity of alizarin red S was justified from ionization potential (IPs) and homolytic O-H bond dissociation enthalpy (BDEs) values. Heterolytic O-H bond cleavages (proton dissociation enthalpies, PDEs) were also computed. Calculated IP, BDE, and PA values suggested that one-step H atom transfer (HAT), rather than SPLET or SET-PT, would be the most favored mechanism for explaining the antioxidant activity of alizarin red S in gas phase. In aqueous solution all of three mechanisms were competitive.Upotrebom DFT metode vršena su izračunavanja u cilju određivanja antioksidativne aktivnosti alizarina red S. Konformaciona priroda molekula analizirana ispitana je primenom M06-2X/6-311++G(d,p) metoda. Najstabilniji konformer alizarina red S ima dve unutrašnje vodonične veze. Očekivana antioksidativna aktivnost alizarina red S određena je izračunavanjem vrednosti jonizacionih potencijala (IP) i i vrednosti entalpija homolitičkog raskidanja O-H veza (BDE). Vrednosti entalpije heterolitičkog raskidanja O-H veza (entalpije disocijacije protona, PDE), su takođe izračunate. Izračunate IP, BDE i PA vrednosti ukazuju na to da je jednostepeni transfer H-atoma (HAT), pre nego SPLET ili SET-PT mehanizam, favorizovan u pogledu antioksidativne aktivnosti alizarina red S u gasnoj fazi. U vodenom rastvoru, sva tri mehanizma su konkurentna
Structure and dielectric caracteristics of BaTi1-xSnxO3 ceramic powders
BaTi1-xSnxO3 (BTS) ceramic powders, with different tin content (x = 0-1) were prepared. The BTS powders were calcined at 1370 °C for 4 hours. The structure of these powders was characterized by XRPD method, tetragonal and cubic crystal structures were noticed. Powders were pressed in pellets and sintered at 1370 °C for 1 hour. The dielectric properties of BTS ceramics were measured and the results were reported.Physical chemistry 2004 : 7th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 21-23 September 200
Mesenchymal Stem Cells from Periapical Lesions Upregulate the Production of Immunoregulatory Cytokines by Inflammatory Cells in Culture
The pathophysiology of periapical lesions (PLs) is under control of pro-inflammatory and anti-inflammatory (mainly immunoregulatory) cytokines. We have recently established mesenchymal stem cells (MSCs) from PLs and showed their suppressive effects on the production of proinflammatory cytokines from PLs inflammatory cells (ICs). In this work we studied the production of interleukin (IL)-10, IL-27 and transforming growth factor (TGF)-β, by PL-ICs in direct or indirect contacts with PL-MSCs. PL-ICs, which were isolated from four different asymptomatic PLs, predominantly composed of lymphocytes, followed by neutrophil granulocytes, macrophages and plasma cells. PLMSCs, expressing typical MSC markers, were co-cultivated with PL-ICs at 1:10 ratio, either in direct contact or in a transwell-system, for 24 hours. The levels of cytokines in cell-culture supernatants were tested by ELISA. The results showed that PL-MSCs up-regulated the production of all three immunoregulatory cytokines by PL-ICs. PL-MSCs stimulated the production of IL-10 and IL-27 via soluble factors, whereas the up-regulation of TGF-β required direct cell-to-cell contacts. In conclusion, our results showed for the first time the involvement of PL-MSCs in restriction of inflammation in PLs by up-regulation of immunoregulatory cytokines
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