bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene
Authors: Arnold Donald R. , McManus Kimberly A. , Du Xinyao
Published: May 2006

Irradiation, through Pyrex, of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and meta cyclic adducts (13–16) arising from the intermediate exciplex. There was no evidence for interaction between the two double bonds of this nonconjugated diene. The oxidation potential of 9 is high enough (> 3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed. Similar irradiation of acetonitrile–methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond. The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur. In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer. There was no evidence for interaction between the two double bonds of the initially formed radical cation 10+•, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product. The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions. In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11+• to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed. This 1,6-endo, endo cyclization of 11+• must be rapid enough to compete with reaction with methanol. There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical. When the radical cation of 2,5-dimethyl-1,4-hexadiene (12+•) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24). The mechanisms for these transformations are discussed.
O(3Pj) atom formation from photodissociation of ozone in the visible and ultraviolet region
Authors: Shamsuddin Sayed Mohammed , Inagaki Yousuke , Matsumi Yutaka , Kawasaki Masahiro
Published: May 2006

The photodissociation of ozone at 266, 308, and 532 nm has been studied for [Formula: see text] probing O(3Pj) atomic photofragments by a vacuum ultraviolet laser-induced fluorescence method. Angular distributions and average kinetic energies are determined by measuring Doppler profiles of the O(3Pj) photofragments. Anisotropy parameters β for the angular distributions are 0.81 ± 0.10 at 266 nm, 0.60 ± 0.10 at 308 nm, and −0.68 ± 0.09 at 532 nm. These values are consistent with the assignment of the photoexcited states, that is, 1B2 in the ultraviolet and 1B1 in the visible region. Average center-of-mass translational energies are 44, 38, and 21 kcal/mol for photodissociation at 266, 308, and 532 nm, respectively. The j-branching ratios of O(3Pj) produced from the photodissociation at 266 nm are (j = 2)/(j = 1)/(j = 0) = (0.55 ± 0.03)/(0.32 ± 0.03)/(0.12 ± 0.03), which are close to the state degeneracy (2j + 1) ratios. At 308 and 532 nm the branching ratios are (j = 2)/(j = 1)/(j = 0) = (0.66 ± 0.03)/(0.27 ± 0.03)/(0.09 ± 0.01) and (0.74 ± 0.03)/(0.20 ± 0.02)/(0.05 ± 0.01), respectively. Population of the j = 2 level increases with decreasing photon energies. The ratios obtained are discussed in terms of the adiabaticity of the potential surfaces during bond breakup as a function of the relative speed of separation.
Crossed-beam studies of radical reaction dynamics:
Authors: Macdonald R. Glen , Argonne Kopin Liu , Sonnenfroh David M. , Liu Di-Jia
Published: May 2006

The title reaction has been studied in a crossed molecular beam apparatus. Both the product state distributions and the translational energy dependence of the reaction cross sections were measured under single collision conditions. Excellent agreement was found over a wide temperature range (26–3800 K) between rate constants deduced from the translational excitation function and recent thermal kinetic data. The rotational state distribution was found to be very cold compared to the reaction exothermicity, and could be described by a Boltzmann temperature of 110 K for all K-doublet levels. The vibronic state distribution was also found to be cold, with 70% of the products formed in the vibrational ground state. By comparing the molecular beam results for vibronic state distributions with those obtained from recent bulb experiments, it was conjectured that there appears to be a strong correlation between rotation in the reactants and bending excitation in the products.
Optical properties of poly-HCN and their astronomical applications
Authors: Khare Bishun N. , Sagan Carl , Thompson W. Reid , Arakawa Edward T. , Meisse Caroline , Tuminello Page S.
Published: May 2006

Matthews (1992) has proposed that HCN "polymer" is ubiquitous in the solar system. We apply vacuum deposition and spectroscopic techniques previously used on synthetic organic heteropolymers (tholins), kerogens, and meteoritic organic residues to the measurement of the optical constants of poly-HCN in the wavelength range 0.05–40 µm. These measurements allow quantitative comparison with spectrophotometry of organic-rich bodies in the outer solar system. In a specific test of Matthews' hypothesis, poly-HCN fails to match the optical constants of the haze of the Saturnian moon, Titan, in the visible and near-infrared, derived from astronomical observations and standard models of the Titan atmosphere. In contrast, a tholin produced from a simulated Titan atmosphere matches within the probable errors. Poly-HCN is much more N-rich than Titan tholin.
A density functional theory study of the free radicals NH2, NF2, NCl2, PH2, PF2, and PCl2
Authors: Austen Maggie A. , Eriksson Leif A. , Boyd Russell J.
Published: May 2006

The linear combination of Gaussian-type orbitals–density functional theory (LCGTO–DFT) approach is used to study geometries and hyperfine structures of a set of neutral radicals. Each of the title molecules is investigated by means of local density approximation calculations, and using the Becke–Perdew and Perdew–Wang–Perdew corrections to the exchange and correlation functionals. The effects of local vs. non-local potentials and of various basis sets are investigated. Total densities and unpaired spin densities are compared. The isotropic couplings are found to be very dependent on the type of exchange functional used, whereas the anisotropic couplings are relatively insensitive to the choice of basis set and functional. In most cases, the Perdew–Wang exchange corrections provide isotropic couplings in satisfactory agreement with experiment.
Non-adiabatic photodissociation dynamics of BrCl
Authors: Cao Jianying , Loock Hans-Peter , Qian Charles X.W.
Published: May 2006

Nozzle-cooled BrCl was excited with tunable laser radiation at selected wavelengths between 389 and 500 nm. The chlorine atomic fragments in their Cl*(2P1/2) and Cl(2P3/2) state were stated-selectively probed by resonance-enhanced multiphoton ionization. The branching ratio (Cl*/(Cl + Cl*)) was measured as a function of the excitation wavelength. The relative Cl* yield reaches a maximum at around λphot = 460 nm. Decomposition of these branching ratios into Cl and Cl* photofragment yield spectra provides insight into the BrCl B-state 3П(0+) non-adiabatic dissociation dynamics. Our results suggest that the dissociation mechanism involves non-adiabatic transitions among 0+ potential energy curves.
Addition of alkyl radicals to C60. Part 3. The EPR spectra of R3C60 radicals and a theoretical study of HC60 and H3C60 radicals
Authors: Morton J.R. , Negri F. , Preston K.F.
Published: May 2006

The EPR spectra of a series of C60 adducts of the type R3C60 are described and discussed. In every case, two of the three ligands are equivalent, leading to the conclusion that the R3C60 radicals have a plane of symmetry. The unpaired electron distributions in mono- and trisubstituted-C60 radicals are computed with the help of the QCFF/PI and MNDO Hamiltonians. It is shown that the hyperfine constants predicted on the basis of the calculated spin densities reproduce well the values observed and suggest a reassignment of framework 13C coupling constants in RC60.
Infrared chemiluminescence in a mixed reaction situation: F + CH4 and F + CHCl3
Authors: Maneshkarimi M. , Heydtmann H.
Published: May 2006

Infrared chemiluminescence from the product molecule HF (DF) was observed for the F + CH4(CD4) and F + CHCl3 reactions under low-pressure flow conditions. The reactions with methane and deuterated methane showed the well-known vibrational inversion effect. For the mixed reaction situation F + CH4(CD4) + CHCl3 it can be shown by switching between CH4 and CD4 that no special relaxation effects are present. The HF (DF) spectra can be explained by results from the isolated reactions. A non-inverted distribution was confirmed for F + CHCl3.
Two-dimensional sublimation of CO2 on NaCl(100) with molecular reorientation as revealed by polarization infrared spectroscopy
Authors: Heidberg J. , Kampshoff E. , Kühnemuth R. , Schönekäs O.
Published: May 2006

Two-dimensional sublimation of CO2 on NaCl(100), prepared by cleaving a single crystal in situ under ultrahigh vacuum, was observed by polarization Fourier transform infrared spectroscopy. At the transition pressure pt(T) &([a-z]+); 1 × 10−10 mbar in the temperature range 45 ≤ T/K ≤ 75 the 2D solid and the ideal 2D lattice gas coexist in a 2D thermodynamic equilibrium. The temperature dependence of the spreading pressure π(T) of the coexisting 2D lattice gas yields the enthalpy of the 2D sublimation [Formula: see text] In the two-dimensional sublimation reorientation of the CO2 molecules takes place; both the polar and the azimuthal molecular angles change.
Phase-plane geometries in enzyme kinetics
Authors: Fraser Simon J. , Roussel Marc R.
Published: May 2006

The transient and steady-state behaviour of the reversible Michaelis–Menten mechanism [R] and Competitive Inhibition (CI) mechanism is studied by analysis in the phase plane. Usually, the kinetics of both mechanisms is simplified to give a modified Michaelis–Menten velocity expression; this applies to the CI mechanism with excess inhibitor and to mechanism [R] in the product inhibition limit. In this paper, [R] is treated exactly as a plane autonomous system of differential equations and its true (dynamical) steady state is described by a line-like slow manifold M. Initial velocity experiments for [R] no longer strictly correspond to the hyperbolic law (as in the irreversible Michaelis–Menten mechanism) and this leads to corrections to the standard integrated rate law. Using a new analysis, the slow dynamics of the CI mechanism is reduced from a three-dimensional system to a planar system. In this mechanism transient decay collapses the trajectory flow onto a two-dimensional "slow" surface Σ; motion on Σ can be treated exactly as projected dynamics in the plane. This projected flow may differ in important ways from that of two-step mechanisms, e.g., it may lack a proper steady state. The relevance of these more accurate dynamical descriptions is discussed in relation to experimental design and metabolic function.
Structural and substituent effects on the ketene infrared stretching frequency
Authors: McAllister Michael A. , Tidwell Thomas T.
Published: May 2006

The frequencies and intensities of the ketene asymmetric stretching vibration near 2100 cm−1 for a series of substituted ketenes and fulvenones have been calculated using ab initio molecular orbital methods. Comparisons of the calculated values with experimentally determined results show reasonably good agreement in most cases, with a typical deviation of ± 10 cm−1 between the measured and calculated values. A test of a correlation proposed by Gano and Jacob (Spectrochim. Acta, 43A, 1023 (1987)) of the frequencies with substituent field and resonance parameters F and R shows a modest correlation coefficient of 0.86, with no significant dependence on R. These results are consistent with enhancements of ketene infrared absorption frequencies by interaction of substituents with the negative charge density at Cβ of ketenes, as indicated by the resonance structure [Formula: see text] The calculated intensities I (km/mol) for non-π acceptor substituents are correlated with the group electronegativities X by the relationship I = 1841.6 − 305.7X (r = 0.94). The π-acceptor substituents show exaltations of the intensities, and the results are interpreted as showing an enhancement of intensities by electropositive substituents increasing the normal ketene dipole directed towards oxygen, and an opposite effect by π-acceptor substituents delocalizing the negative charge at Cβ.
Cooperative mechanisms for the H + ICl reaction and their significance for the K + ICl experiment
Authors: Laganà Antonio , Gervasi Osvaldo , Crocchianti Stefano , Garcia Ernesto , Aspuru Guillermo Ochoa De , Alvariño José M.
Published: May 2006

To characterize the dynamics of halogen centre reactions, we have investigated the H + ICl system. In particular, we have focused our attention on the importance of indirect atom–diatom reactivity in determining the macroscopic and microscopic branching of a reaction. An analysis of opacity functions and trajectory plots evaluated for different collision angles and isotopic variants evidenced the occurrence of cooperative reactive mechanisms in which an atom of the target diatom favours reaction with the other end of the molecule. Two limiting cooperative mechanisms were singled out and associated with different ranges of the impact parameter. A generalization of these findings to heavier systems has been performed by considering the 39H + ICl reaction. Calculated properties of the model were found to agree with values measured for the K + ICl reaction.
Déplacements homolytiques intramoléculaires: 20. Influence de la nature de la fonction peroxyde sur la décomposition induite de peroxydes δ-insaturés
Authors: Maillard B. , Lubeigt X. , Bourgeois M-J. , Montaudon E.
Published: May 2006

Induced decomposition of δ-unsaturated peroxidic derivatives CH2=CH(CH2)3OY (Y = OtBu, OCMe2Ph, OCOEt, OCMe2OMe) in various solvents yields a heterocycle and, in some cases, a peroxidic adduct. Intramolecular homolytic substitution (SHi) leading to the cyclic ether is highly dependent on the thermal stability of the peroxidic linkage. The rate constant was determined at 60 °C for Y = OtBu, OCMe2Ph.
Structural studies of organoboron compounds. LX. Reaction of sterically hindered arylboronic acids with 2-(hydroxyamino)alkanols. Crystal and molecular structure of 2-mesityl-6,6-pentamethylene-1,3-dioxa-4-aza-2-boracyclohexane
Authors: Kliegel Wolfgang , Lubkowitz Gottfried , Rettig Steven J. , Trotter James
Published: May 2006

Three 2-(hydroxyamino)alkanols have been reacted with sterically hindered arylboronic acids, ArB(OH)2. When Ar = o-tolyl, 1:2 condensates having bicyclic structures are formed but when Ar = mesityl (2,4,6-(CH3)3C6H2), 1:1 condensates having six-membered cycloboronate structures result. These 1:1 condensates represent the first examples of N-unsubstituted 1,3-dioxa-4-aza-2-boracyclohexane derivatives. An X-ray analysis of one example provides unambiguous proof of the structure. Crystals of 2-mesityl-6,6-pentamethylene-1,3-dioxa-4-aza-2-boracyclohexane, 3c, are monoclinic, a = 11.076(9), b = 23.94(2), c = 13.414(9) Å, β = 109.40(5)°, Z = 8, space group P21/n. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R = 0.051 and Rw = 0.058 for 2037 reflections with I ≥ 3σ(F2).
Single crystal polarized spectra in the near-infrared region: a local-mode analysis of the spectra of CsMnCl3•2X2O (X = H, D)
Authors: Walker Ian M. , McCarthy Paul J.
Published: May 2006

Polarized near-infrared spectra of single crystals of CsMnCl3•2X2O (X = H, D) were recorded at 10 K. Those bands which could be assigned to O—H or O—D stretch overtones were analyzed using local-mode theory specifically adapted for systems having less than C2v symmetry. Both O—H oscillators form nearly linear hydrogen bonds to neighboring chloride ions at different distances. As a result, the local-mode harmonic frequency and anharmonicity parameters show characteristic shifts from their gas-phase values. The parameter values cover an unusually narrow range in this crystal, considering the spread in hydrogen-bond distances. Assignment of stretch overtone bands to specific oscillators in the crystal was made by using the polarization behavior expected of local modes in the oriented gas model. Several of the overtone bands show combinations with lattice modes or low-energy hydrogen-bond modes in unusual detail.
Characterization and nonrigid behaviour of a carboxylate-bridged rhodium dimer
Authors: Cullen William R. , Rettig Steven J. , Wickenheiser Eugene B.
Published: May 2006

Bis(μ-t-butylacetato)bis(norbornadiene)dirhodium(I) 1 is prepared by a reaction between pivaloyl camphor and (norbornadiene)rhodium(I) chloride dimer. A molecular rearrangement takes place in which the pivaloyl groups of the pivaloyl camphor starting material are incorporated into the end product as bridging t-butylcarboxylate ligands. A variable temperature 1H NMR study and corresponding dynamic computer fit of the NMR data, and crystal structure are reported for the structurally nonrigid dimer. Crystals of 1 are triclinic, a = 10.454(1), b = 10.817(1), c = 12.424(1) Å, α = 64.904(7), β = 100.320(7), γ = 109.382(8)°, Z = 2, space group [Formula: see text] The structure was solved by heavy atom methods and was refined by full-matrix least-squares procedures to R = 0.070 and Rw = 0.081 for 3093 reflections with I ≥ 3σ(I).
Compiler-directed high-level energy estimation and optimization
Authors: Kadayif I. , Kandemir M. , Chen G. , Vijaykrishnan N. , Irwin M. J. , Sivasubramaniam A.
Published: May 2006

The demand for high-performance architectures and powerful battery-operated mobile devices has accentuated the need for power optimization. While many power-oriented hardware optimization techniques have been proposed and incorporated in current systems, the increasingly critical power constraints have made it essential to look for software-level optimizations as well. The compiler can play a pivotal role in addressing the power constraints of a system as it wields a significant influence on the application's runtime behavior. This paper presents a novel Energy-Aware Compilation (EAC) framework that estimates and optimizes energy consumption of a given code, taking as input the architectural and technological parameters, energy models, and energy/performance/code size constraints. The framework has been validated using a cycle-accurate architectural-level energy simulator and found to be within 6% error margin while providing significant estimation speedup. The estimation speed of EAC is the key to the number of optimization alternatives that can be explored within a reasonable compilation time. As shown in this paper, EAC allows compiler writers and system designers to investigate power-performance tradeoffs of traditional compiler optimizations and to develop energy-conscious high-level code transformations.
Power-performance considerations of parallel computing on chip multiprocessors
Authors: Li Jian , Martínez José F.
Published: May 2006

This paper looks at the power-performance implications of running parallel applications on chip multiprocessors (CMPs). First, we develop an analytical model that, for the first time, puts together parallel efficiency, granularity of parallelism, and voltage/frequency scaling, to establish a formal connection with the power consumption and performance of a parallel code running on a CMP. We then conduct detailed simulations of parallel applications running on a detailed power-performance CMP model to confirm the analytical results and provide further insights. Both analytical and experimental models show that parallel computing can bring significant power savings and still meet a given performance target by choosing granularity and voltage/frequency levels judiciously. The particular choice, however, is dependent on the application's parallel efficiency curve and the process technology utilized, which our model captures. Likewise, analytical model and experiments show the effect of a limited power budget on the application's scalability curve. In particular, we show that a limited power budget can cause a rapid performance degradation beyond a number of cores, even in the case of applications with excellent scalability properties. On the other hand, our experiments show that, when a limited power budget is in place, power-thrifty memory-bound applications may actually enjoy better scalability than more compute-intensive codes, even if the latter would exhibit higher scalability in a power-unconstrained scenario.
MATSLISE
Authors: Ledoux V. , Daele M. Van , Berghe G. Vanden
Published: May 2006

MATSLISE is a graphical MATLAB software package for the interactive numerical study of regular Sturm-Liouville problems, one-dimensional Schrödinger equations, and radial Schrödinger equations with a distorted Coulomb potential. It allows the fast and accurate computation of the eigenvalues and the visualization of the corresponding eigenfunctions. This is realized by making use of the power of high-order piecewise constant perturbation methods, a technique described by Ixaru. For a well-outlined class of problems, the implemented algorithms are more efficient than the well-established SL-solvers SL02f, SLEDGE, SLEIGN, and SLEIGN2, which are included by Pryce in the SLDRIVER code that has been built on top of SLTSTPAK.
Data structures for computer graphics
Authors: Abrams Marshall D.
Published: May 2006

This paper introduces data structures as applied to computer graphics. Design criteria for computer graphics data structures are discussed, followed by a comparison of general-purpose and tailored graphic data structures. A general graphic data structure is introduced as an example of a structure meeting the preceding criteria. The L6language is then examined as a tool for implementing the above data structure, and is compared to a few other language systems.
Modern Performance Monitoring
Authors: Purdy Mark
Published: May 2006

The modern Unix server floor can be a diverse universe of hardware from several vendors and software from several sources. Often, the personnel needed to resolve server floor performance issues are not available or, for security reasons, not allowed to be present at the very moment of occurrence. Even when, as luck might have it, the right personnel are actually present to witness a performance "event," the tools to measure and analyze the performance of the hardware and software have traditionally been sparse and vendor-specific. Because few real Unix cross-platform toolkits exist, there is no standard method for administrators to accurately view an event, record it for later analysis, or share it with additional qualified personnel for an efficient resolution.
Mobile web surfing is the same as web surfing
Authors: Halvey Martin , Keane Mark T. , Smyth Barry
Published: May 2006

Even in the new context, users surf in the usual way.
Women in computer science
Authors: Othman Mazliza , Latih Rodziah
Published: May 2006

The dwindling number of women pursuing a degree in CS is a growing frustration for many countries around the globe, but in Malaysia female CS/IT students outnumber the males. What accounts for this dichotomy?
Performance modeling and prediction of enterprise JavaBeans with layered queuing network templates
Authors: Xu Jing , Oufimtsev Alexandre , Woodside Murray , Murphy Liam
Published: May 2006

Component technologies, such as Enterprise Java Beans (EJB) and .NET, are used in enterprise servers with requirements for high performance and scalability. This work considers performance prediction from the design of an EJB system, based on the modular structure of an application server and the application components. It uses layered queueing models, which are naturally structured around the software components. This paper describes a framework for constructing such models, based on layered queue templates for EJBs, and for their inclusion in the server. The resulting model is calibrated and validated by comparison with an actual system.
A component-based specification approach for embedded systems using FDTs
Authors: Guerrouat Abdelaziz , Richter Harald
Published: May 2006

This paper presents a framework for specification and testing of component-based embedded systems using formal description techniques (FDTs). We deal with embedded systems from the point of view of communication and thus we propose a communication model for them. We further explain the meaning of component-based embedded systems and how these can be specified using FDTs. FDTs such as Estelle and SDL are based on EFSMs (Extended finite State Machines) and have been widely used in the automation of the development process of protocols and communicating systems, i.e. for specification, analysis and validation purposes. The main goal of this work is to demonstrate the reusability of FDTs for component-based systems.
A dichotomy theorem for constraint satisfaction problems on a 3-element set
Authors: Bulatov Andrei A.
Published: May 2006

The Constraint Satisfaction Problem (CSP) provides a common framework for many combinatorial problems. The general CSP is known to be NP-complete; however, certain restrictions on a possible form of constraints may affect the complexity and lead to tractable problem classes. There is, therefore, a fundamental research direction, aiming to separate those subclasses of the CSP that are tractable and those which remain NP-complete.Schaefer gave an exhaustive solution of this problem for the CSP on a 2-element domain. In this article, we generalise this result to a classification of the complexity of the CSP on a 3-element domain. The main result states that every subproblem of the CSP is either tractable or NP-complete, and the criterion separating them is that conjectured in Bulatov et al. [2005] and Bulatov and Jeavons [2001b]. We also characterize those subproblems for which standard constraint propagation techniques provide a decision procedure. Finally, we exhibit a polynomial time algorithm which, for a given set of allowed constraints, outputs if this set gives rise to a tractable problem class. To obtain the main result and the algorithm, we extensively use the algebraic technique for the CSP developed in Jeavons [1998b], Bulatov et al.[2005], and Bulatov and Jeavons [2001b].
High-cost banner blindness
Authors: Burke Moira , Hornof Anthony , Nilsen Erik , Gorman Nicholas
Published: May 2006

The seeming contradiction between “banner blindness” and Web users' complaints about distracting advertisements motivates a pair of experiments into the effect of banner ads on visual search. Experiment 1 measures perceived cognitive workload and search times for short words with two banners on the screen. Four kinds of banners were examined: (1) animated commercial, (2) static commercial, (3) cyan with flashing text, and (4) blank. Using NASA's Task Load Index, participants report increased workload under flashing text banners. Experiment 2 investigates search through news headlines at two levels of difficulty: exact matches and matches requiring semantic interpretation. Results show both animated and static commercial banners decrease visual search speeds. Eye tracking data reveal people rarely look directly at banners. A post hoc memory test confirms low banner recall and, surprisingly, that animated banners are more difficult to remember than static look-alikes. Results have implications for cognitive modeling and Web design.
From fingerprint to writeprint
Authors: Li Jiexun , Zheng Rong , Chen Hsinchun
Published: May 2006

Identifying the key features to help identify and trace online authorship.
Exploratory search
Authors: Marchionini Gary
Published: May 2006

Research tools critical for exploratory search success involve the creation of new interfaces that move the process beyond predictable fact retrieval.
Query reformulation with constraints
Authors: Deutsch Alin , Popa Lucian , Tannen Val
Published: May 2006

Let Σ
1
, Σ
2
be two schemas, which may overlap,
C
be a set of constraints on the joint schema Σ
1
∪ Σ
2
, and
q
1
be a Σ
1
-query. An
(equivalent) reformulation
of
q
1
in the presence of
C
is a Σ
2
-query,
q
2
, such that
q
2
gives the same answers as
q
1
on any Σ
1
∪ Σ
2
-database instance that satisfies
C
. In general, there may exist multiple such reformulations and choosing among them may require, for example, a cost model.
Reducing parameter uncertainty for stochastic systems
Authors: Ng Szu Hui , Chick Stephen E.
Published: May 2006

The design of many production and service systems is informed by stochastic model analysis. But the parameters of statistical distributions of stochastic models are rarely known with certainty, and are often estimated from field data. Even if the mean system performance is a known function of the model's parameters, there may still be uncertainty about the mean performance because the parameters are not known precisely. Several methods have been proposed to quantify this uncertainty, but data sampling plans have not yet been provided to reduce parameter uncertainty in a way that effectively reduces uncertainty about mean performance. The optimal solution is challenging, so we use asymptotic approximations to obtain closed-form results for sampling plans. The results apply to a wide class of stochastic models, including situations where the mean performance is unknown but estimated with simulation. Analytical and empirical results for the
M/M/1
queue, a quadratic response-surface model, and a simulated critical care facility illustrate the ideas.
'Programming language paradigms' instruction through designing a new paradigm
Authors: Standley Hilda M.
Published: May 2006

Undergraduate and master's students enrolled in a programming language paradigms class are given the assignment to design a new programming language paradigm. The students are asked to develop a paradigm concept, demonstrate the utility of the paradigm for programmed solutions, and outline a sample programming language. Resulting student-designed paradigms from this class fall into three loosely defined categories: connection with a physical item, modeling a process, and representing program structure. The resulting class experience demonstrates that students can think and create beyond existing paradigms and features of languages to the level of abstraction that defines a new paradigm.
On using scheme to introduce prolog
Authors: Wick Michael R. , Stevenson Daniel E.
Published: May 2006

The traditional way to teach Prolog is to have students start by writing recursive mathematical definitions of the problems they are trying to solve. While this is an effective technique, it does not fit well into a Programming Languages course that uses a single demonstration language to illustrate the different paradigms. Thus, we have developed an approach to introduce students to Prolog via our demonstration language, Scheme. Additionally, we performed an experiment to determine if the Scheme to Prolog approach is as effective at introducing Prolog as the more traditional recursive mathematical definition approach.
The open network laboratory
Authors: DeHart John , Kuhns Fred , Parwatikar Jyoti , Turner Jonathan , Wiseman Charlie , Wong Ken
Published: May 2006

The
Open Network Laboratory
(ONL) is a remotely accessible network testbed of high performance routers which has been designed with an eye towards ease of use for users from the naïve to the expert. The system is built around a set of high-performance routers that are extendible and easily configurable through the
Remote Laboratory Interface
(RLI), an intuitive graphical interface. The RLI also makes it easy to configure packet filters in the routers, assign flows or flow aggregates to separate queues with configurable QoS and attach hardware monitoring points to real-time charts. The RLI's real-time charts and user data facility make it easy to directly view the effects of traffic as it moves through a router, allowing the user to gain better insight into system behavior and create compelling demonstrations. Each port of the router is equipped with an embedded processor that supports software plugins which allow users to extend the system's functionality. This paper describes the ONL and how it can be used in networking education. Our web site onl.arl.wustl.edu includes a short video and a tutorial.
Virtual classroom pedagogy
Authors: Bower Matt
Published: May 2006

For lecturers who are used to presenting face-to-face, facilitating online classes through a virtual classroom interface proposes several new challenges. At the same time the affordances of the media offer many opportunities to improve the quality of students' learning. This paper outlines the pedagogical lessons derived from convening a first year introductory programming unit through a series of twelve, two-hour online classes. General virtual classroom strategies as well as those particular to computer science are described. Approaches to developing students' virtual classroom competencies, approaches to groupwork, and the implications of virtual classrooms for professional development and research are also discussed.
GSPIM
Authors: Borunda Patrick , Brewer Chris , Erten Cesim
Published: May 2006

We describe our system, GSPIM, used for visualization of low-level MIPS Assembly programming and simulation. Although many visualization tools for algorithms and high-level programs have been considered in educational settings, visualization specific to low-level programs have not received enough consideration. One desirable property of such a visualization is that it should close the gap between high-level programming constructs and the sequential nature of low-level programs. Secondly it should provide techniques to present information specific to the simulation of the code. GSPIM supports both properties and is publicly available at http://www.cs.arizona.edu/~cesim/gspim.tar.gz
Back to basics in CS1 and CS2
Authors: Reges Stuart
Published: May 2006

This paper describes a significant redesign of the introductory courses at the University of Washington that has led to increased enrollments, increased student satisfaction and an increase in the number of women admitted to the CS major. The new courses are still taught in Java, but they represent a return to the basics that were emphasized in the pre-Java era. The biggest changes have occurred in the CS1 course where we have replaced an "objects early" curriculum with a more traditional procedural approach using static methods in Java. The new CS1 course emphasizes problem solving, procedural decomposition and mastery of basic skills (e.g., loops, conditionals and arrays). The new CS2 course emphasizes data structures, linked lists, binary trees and recursion.
Programming fundamentals and innovation taught through windows media player skin creation
Authors: Shurn Todd
Published: May 2006

Windows Media Player user interface "skin" creation has proven an extremely effective method to reinforce practical object oriented programming techniques. Skin creation motivated non-engineers, women and even high school students to learn XML, and Jscript scripting language. Non-computer science students were especially excited when their custom media player user interface operated as intended. Many students demonstrated their skin to potential employers as evidence of their creativity and programming prowess.This paper discusses how skin programming is related to the object oriented paradigm and may be used as an exemplary collegiate interdisciplinary design project. Examples illustrate how skin creation can emphasize design principles, fundamental programming concepts, and group software development. Software innovation is advanced via novel windows media player skins incorporating recently released features to provide an enhanced user interface for a target domain.
Student progress monitoring tool using treeview
Authors: Yoo Jungsoon , Yoo Sung , Lance Chris , Hankins Judy
Published: May 2006

In this paper, we present an extensible visualization tool that is being used in a web-based closed laboratory system. The goal of this project is to provide a tool for both students and teachers that can help trace deficiencies in a student's understanding back to individual concepts. This visualization tool has been developed by using the tree abstract data type (ADT) which is built from the concepts to be covered in a lab, lecture, or course. Once the tree ADT is built, each node can be associated with different entities such as student performance, class performance, or lab development. Using this tool, a teacher can help students by discovering concepts that need additional lecture coverage, and students may discover concepts for which they need to spend additional time working on reinforcement exercises.
jFAST
Authors: White Timothy M. , Way Thomas P.
Published: May 2006

Visualization and interactivity are valuable active learning techniques that can improve mastery of difficult concepts. In this paper we describe jFAST, an easy-to-use graphical software tool for teachers and students, with an emphasis on introductory level finite state machine topics. The jFAST software enables visual design, exploration and simulation of a variety of finite state machines, with a primary goal of enhancing teaching effectiveness in this subject, particularly for less advanced computer science students. The architecture and functionality of jFAST are explained, and results of preliminary evaluation are provided.
Reduction -- an abstract thinking pattern
Authors: Armoni Michal , Gal-Ezer Judith
Published: May 2006

Abstraction has been the focus of many researches in mathematics education and to some extent in computer science education. Abstract thinking characterizes the theoretical foundations of computer science, where reduction is one important abstract thinking pattern. In a previous work, we discussed the issue of reductive thinking among high school students in relation to computational models -- a theoretical unit. This unit requires abstract thinking in many aspects. Our findings in relation to reductive thinking showed that many students preferred direct, non-reductive solutions, even if reductive solutions could have significantly decreased the design complexity of the solution. This study motivated the current study where we examine the issue of reductive thinking among university students. The findings of this preliminary study are demonstrated by students' solutions to questions in assignments given in the computational models course. We found that even among university students in a very prestigious academic institution with very high entrance requirements abstraction is a real obstacle as reduction is not easily understood and used. This encourages us to further investigate this phenomenon.
Overview of the cyberTech-ITEST project
Authors: Peterson Laurence I. , Benham Dale
Published: May 2006

This paper describes an NSF-funded initiative involving 600 underrepresented high school students and 60 teachers designed to introduce underrepresented students to the numerous and varied career opportunities in the computing sciences, prepare them to succeed in college degree programs, and prepare their teachers to be effective in the computer science class room. The initiative has five components: 1) CyberTech I (Principles of Computing): An online introductory course for second-semester sophomores, 2) CyberTech II: A twenty day on-campus intense summer programming experience between the sophomore and junior year, 3) CT Games: A junior year video game programming experience to apply the programming knowledge gaining in CyberTech II, 4) AP Computer Science (using Java 5 as the programming language) taken during the senior year, and 5) training workshops for teachers to prepare them to teach computer programming. The overarching goal is to prepare students for a college-level degree program in the computing sciences by having them successfully complete the AP Computer Science course and exam while teaching the soft skills, such as team work, oral communication and problem solving necessary in a professional career. Additionally, role models from various industry sectors are utilized to introduce students to the exciting career opportunities in the computing sciences.
Practice what you preach
Authors: Roumani Hamzeh
Published: May 2006

We argue that the failure to separate the concerns in CS1 is the leading cause of difficulty in teaching OOP in the first year. We show how the concerns can be detangled and present a detailed reorganization of contents for CS1/CS2 with CS1 exposing only the client view. We also report on our experience with this new pedagogy after three years of implementation at our institution.
Graphical game development in CS2
Authors: Lewis Mark C. , Massingill Berna
Published: May 2006

This paper discusses a project that has been used to teach CS2 for six semesters at Trinity University. The project spans the full semester, and all eight of the assignments students turn in are part of the project. For this project, the students develop a 2-D game using a framework written by one of the authors. The framework is intended to allow students to produce some results early in the semester before they have significant knowledge without constraining them or doing too much for them. It was originally written for Java 1.3 and has evolved for Java 1.4 and now Java 5. We discuss the details of this project, the benefits it provides, and our experience with it.
The art and science of game programming
Authors: Parberry Ian , Kazemzadeh Max B. , Roden Timothy
Published: May 2006

The University of North Texas has for many years offered classes in game programming to Computer Science students and classes in game art and design to art students. A key feature of these classes is the opportunity for these diverse communities of students to collaborate on joint projects. We describe the features that make these classes unique.
Web servers under overload
Authors: Schroeder Bianca , Harchol-Balter Mor
Published: May 2006

This article provides a detailed implementation study on the behavior of web serves that serve static requests where the load fluctuates over time (transient overload). Various external factors are considered, including WAN delays and losses and different client behavior models. We find that performance can be dramatically improved via a kernel-level modification to the web server to change the scheduling policy at the server from the standard FAIR (processor-sharing) scheduling to SRPT (shortest-remaining-processing-time) scheduling. We find that SRPT scheduling induces no penalties. In particular, throughput is not sacrificed and requests for long files experience only negligibly higher response times under SRPT than they did under the original FAIR scheduling.
A space-partitioning-based indexing method for multidimensional non-ordered discrete data spaces
Authors: Qian Gang , Zhu Qiang , Xue Qiang , Pramanik Sakti
Published: May 2006

There is an increasing demand for similarity searches in a multidimensional non-ordered discrete data space (NDDS) from application areas such as bioinformatics and data mining. The non-ordered and discrete nature of an NDDS raises new challenges for developing efficient indexing methods for similarity searches. In this article, we propose a new indexing technique, called the
NSP-tree
, to support efficient similarity searches in an NDDS. As we know, overlap causes a performance degradation for indexing methods (e.g., the R-tree) for a continuous data space. In an NDDS, this problem is even worse due to the limited number of elements available on each dimension of an NDDS. The key idea of the NSP-tree is to use a novel discrete space-partitioning (SP) scheme to ensure no overlap at each level in the tree. A number of heuristics and strategies are incorporated into the tree construction algorithms to deal with the challenges for developing an SP-based index tree for an NDDS. Our experiments demonstrate that the NSP-tree is quite promising in supporting efficient similarity searches in NDDSs. We have compared the NSP-tree with the ND-tree, a data-partitioning-based indexing technique for NDDSs that was proposed recently, and the linear scan using different NDDSs. It was found that the search performance of the NSP-tree was better than those of both methods.
The deep structure of business processes
Authors: Dietz Jan L.G.
Published: May 2006

Delving beneath organizational surface structure to reveal the essential structure of business processes.
Pattern matching for arc-annotated sequences
Authors: Gramm Jens , Guo Jiong , Niedermeier Rolf
Published: May 2006

We study pattern matching for arc-annotated sequences. An
O
(
nm
) time algorithm is given for the problem to determine whether a length
m
sequence with nested arc annotation is an arc-preserving subsequence (aps) of a length
n
sequence with nested arc annotation, called APS(NESTED,NESTED). Arc-annotated sequences and, in particular, those with nested arc annotation are motivated by applications in RNA structure comparison. Our algorithm generalizes results for ordered tree inclusion problems and it is useful for recent fixed-parameter algorithms for LAPCS(NESTED,NESTED), which is the problem of computing a longest arc-preserving common subsequence of two sequences with nested arc annotations. In particular, the presented dynamic programming methodology implies a quadratic-time algorithm for an open problem posed by Vialette.
The Story Picturing Engine---a system for automatic text illustration
Authors: Joshi Dhiraj , Wang James Z. , Li Jia
Published: May 2006

We present an unsupervised approach to automated story picturing. Semantic keywords are extracted from the story, an annotated image database is searched. Thereafter, a novel image ranking scheme automatically determines the importance of each image. Both lexical annotations and visual content play a role in determining the ranks. Annotations are processed using the Wordnet. A mutual reinforcement-based rank is calculated for each image. We have implemented the methods in our Story Picturing Engine (SPE) system. Experiments on large-scale image databases are reported. A user study has been performed and statistical analysis of the results has been presented.