Human knowing and perceived complexity: implications for systems practice

Complexity has been understood in different ways since its (re) introduction into scientific discourse. Therefore, instead of proposing a definition of complexity, we group the existing explanations about it into two distinct categories: descriptive and perceived complexity. The main features of these categories are described and how they arise as the result of the adoption of contrasting epistemologies is discussed. These categories together with their implications for our doing in the world are explored under the rubric of the 'epistemological problem of complexity'. The practical significance of the issues we address, especially as they relate to building capacity for systems practice, understood as a way of managing in situations of complexity, is also of concern. "Even when the individual trees are highly interesting and picturesque, it has use to see what the forest looks like in the large" (Rescher, 199S; xvii)

Application of the Two-Scale Model to the HERMES Data on Nuclear Attenuation

The Two-Scale Model and its improved version were used to perform the fit to the HERMES data for $\nu$ (the virtual photon energy) and z (the fraction of $\nu$ carried by hadron) dependencies of nuclear multiplicity ratios for $\pi^+$ and $\pi^-$ mesons electro-produced on two nuclear targets ($^{14}$N and $^{84}$Kr). The quantitative criterium $\chi ^2$ was used for the first time to analyse the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gives satisfactory agreement with the HERMES data. Best values of the parameters were then used to calculate the $\nu$- and $z$ - dependencies of nuclear attenuation for $\pi^0$, K$^+$, K$^-$ and $\bar{p}$ produced on $^{84}$Kr target, and also make a predictions for $\nu$, z and the Q$^2$ (the photon virtuality) - dependencies of nuclear attenuation data for those identified hadrons and nuclea, that will be published by HERMES

The Value of STEM as an Educational Tool for Enhancing Cognitive Development

STEM is an acronym for Science, Technology, Engineering, and Math. The focus of STEM education is to provide a holistic approach through hands-on, problem-based learning where students are able to take what they learn in the classroom and apply it to real world problems.https://digital.sandiego.edu/npi-sdclimate/1034/thumbnail.jp

Uncertainty and Risk in Financial Markets

This paper considers a general equilibrium model in which the=20 distinction between un-certainty and risk is formalized by assuming agents= =20 have incomplete preferences over state-contingent consumption bundles, as=20 in Bewley (1986). Without completeness, individual decision making depends= =20 on a set of probability distributions over the state space. A bundle is=20 preferred to another if and only if it has larger expected utility for all= =20 probabilities in this set. When preferences are complete this set is a=20 singleton, and the model reduces to standard expected utility. In this=20 setting, we characterize Pareto optima and equilibria, and show that the=20 presence of uncertainty generates robust indeterminacies in equilibrium=20 prices and allocations for any speci=AFcation of initial endowments. We=20 derive comparative statics results linking the degree of uncertainty with=20 changes in equilibria. Despite the presence of robust indeterminacies, we=20 show that equilibrium prices and allocations vary continuously with=20 underlying fundamentals. Equilibria in a standard risk economy are thus=20 robust to adding small degrees of uncertainty. Finally, we give conditions= =20 under which some assets are not traded due to uncertainty aversion.

High-contrast dark resonance on the D2 - line of 87Rb in a vapor cell with different directions of the pump - probe waves

We propose a novel method enabling to create a high-contrast dark resonance in the 87Rb vapor D2-line. The method is based on an optical pumping of atoms into the working states by a two-frequency, linearly-polarized laser radiation propagating perpendicularly to the probe field. This new scheme is compared to the traditional scheme involving the circularly-polarized probe beam only, and significant improvement of the dark resonance parameters is found. Qualitative considerations are confirmed by numerical calculations.Comment: 7 pages, 4 figure

On different qq-systems in nonextensive thermostatistics

It is known that the nonextensive statistics was originally formulated for the systems composed of subsystems having same $q$. In this paper, the existence of composite system with different $q$ subsystems is investigated by fitting the power law degree distribution of air networks with $q$-exponential distribution. Then a possible extension the nonextensive statistics to different $q$ systems is provided on the basis of an entropy nonadditivity rule and an unnormalized expectation of energy.Comment: 17 pages, 4 figures, will be published in Euro. Phys. J. B (2006

Two-pion Bose-Einstein correlations in central Pb-Pb collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV

The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV at the Large Hadron Collider is presented. We observe a growing trend with energy now not only for the longitudinal and the outward but also for the sideward pion source radius. The pion homogeneity volume and the decoupling time are significantly larger than those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/388

Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV

We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (|$\eta$|<0.8) and transverse momentum range 0.2< $p_{\rm T}$< 5.0 GeV/$c$. The elliptic flow signal v$_2$, measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 $\pm$ 0.002 (stat) $\pm$ 0.004 (syst) in the 40-50% centrality class. The differential elliptic flow v$_2(p_{\rm T})$ reaches a maximum of 0.2 near $p_{\rm T}$ = 3 GeV/$c$. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/389

Strange particle production in proton-proton collisions at s=0.9\sqrt{s}=0.9 TeV with ALICE at the LHC

The production of mesons containing strange quarks (K$^0_s$, $\phi$) and both singly and doubly strange baryons ($\Lambda$, Anti-$\Lambda$, and $\Xi$+Anti-$\Xi$) are measured at central rapidity in pp collisions at $\sqrt{s}$ = 0.9 TeV with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250 k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at central rapidities for inelastic pp collisions are presented. For mesons, we report yields () of 0.184 $\pm$ 0.002 stat. $\pm$ 0.006 syst. for K$^0_s$ and 0.021 $\pm$ 0.004 stat. $\pm$ 0.003 syst. for $\phi$. For baryons, we find = 0.048 $\pm$ 0.001 stat. $\pm$ 0.004 syst. for $\Lambda$, 0.047 $\pm$ 0.002 stat. $\pm$ 0.005 syst. for Anti-$\Lambda$ and 0.0101 $\pm$ 0.0020 stat. $\pm$ 0.0009 syst. for $\Xi$+Anti-$\Xi$. The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline for comparisons with both future pp measurements at higher energies and heavy-ion collisions.Comment: 33 pages, 21 captioned figures, 10 tables, authors from page 28, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/387

Dihadron fragmentation: in vacuum and in matter

Two particle correlations within a single jet produced in deeply inelastic scattering (DIS) off a large nucleus as well as in heavy-ion collisions are explored. This is performed within the framework of the medium modified dihadron fragmentation functions. The modification occurs due to gluon bremsstrahlung induced by multiple scattering. The modified fragmentation functions for dihadrons are found to follow closely that of single hadrons leading to a weak nuclear suppression of their ratios as measured by HERMES in DIS experiments. Meanwhile, a moderate medium enhancement of the near-side correlation of two high $p_T$ hadrons is found in central heavy-ion collisions, partially due to trigger bias caused by the competition between parton energy loss and the initial Cronin effect.Comment: 4 pages, 2 figures, LATEX, talk given at Hard Probes 200