bluuebunny/crossref_metadata_2025 huggingface dataset:
The conformational changes of haemoglobin on its binding to haptoglobin
Authors: Dvořánková Barbora , Pavlíček Zdeněk
Published: August 2011

The binding of human haemoglobin to human haptoglobin has been found to alter the conformation of haemoglobin. Spectrophotometric measurements, measuring of peroxidase activity, thin-layer gel chromatography and modelling on an analogue computer led to the conclusion that the binding of haemoglobin to haptoglobin was associated with a change in the quaternary structure of haemoglobin, with a transition from the R state to the T state. The kinetics of the conformational changes had an autocatalytic character.
Correlation of kinetic data of 1,3-dipolar cycloadditions of C-benzoyl-N-phenylnitrones with the homo energies of furan derivatives
Authors: Fišera Lubor , Gáplovský Anton , Timpe Hans-Joachim , Kováč Jaroslav
Published: August 2011

Application of PMO treatment to 1,3-dipolar cycloaddition of C-benzoyl-N-phenylnitrone with furan derivatives is described. Ionization potentials of 2-R-substituted furan derivatives (R = H, CH3, C2H5, CH2OH, CH2OCOCH3, C6H5, CHO) and 2,5-dimethylfurane representing experimental values of the HOMO energies have been determined from energies of the respective charge-transfer complexes with TCNE. Good correlation between IP and k2 rate constants indicates that the reaction is controlled by the LUMO(nitrone)/HOMO(furan deriv.) interaction. Electron affinities of the furan derivatives were determined from IP and energies of π-π* transitions using empirical equation ΔE(π-π*) = IP-EA-450.58 kJ mol-1.
Structure and vibrational spectra of methyl benzoate and dimethyl terephthalate
Authors: Sedláček Pavel , Štokr Jan , Schneider Bohdan
Published: August 2011

Infrared and Raman spectra of the crystalline forms and of the liquid state of acetophenone, methylbenzoate and dimethyl terephthalate were measured. From these measurements it was found that acetophenone in the liquid state is present in a single conformational form, and that methyl benzoate in the liquid state contains, in addition to the major conformer with a planar structure and trans form of the ester group, also a minor conformer of different geometrical structure. Dimethyl terephthalate in the melt contains approximately equal populations of the conformers with the mutual trans and cis orientation of the two ester groups. For all the observed structures, the conformationally sensitive bands were assigned.
A new method of preparation of α,β-γ,δ-unsaturated secondary alcohols
Authors: Streinz Ludvík , Romaňuk Miroslav
Published: August 2011

A method of preparation of β-hydroxy-γ,δ-unsaturated nitriles used as intermediates for the synthesis of α,β-γ,δ-unsaturated ketones and alcohols, and having the activity of insect juvenile hormone is described.
Basicity of fuchsones. Infrared study of the ν(OH) stretching vibration in phenol-fuchsone complexes
Authors: Velek Jiří , Koutek Bohumír , Musil Lubomír , Vašíčková Soňa , Souček Milan
Published: August 2011

The hydrogen bond complexes involving phenol and carbonyl oxygen of 2- and 2,6-substituted fuchsones I and II have been studied by infrared spectroscopy in tetrachlorethylene solution. Basicities expressed as complexation enthalpies, frequency shifts and integrated intensities of the ν(OH) stretching vibrations are reported. A linear relationship was found between the frequency shift and the hydrogen bond energy. Statistical analysis of linear free energy relationships for fuchsones I and II proved the significancy of steric factor in transmission of electronic substituent effect.
Extraction of indium(III) and antimony(III) from hydrochloric acid solutions by means of some neutral organophosphorus reagents
Authors: Navrátil Oldřich , Meindl Jiří , Kos Jiří
Published: August 2011

Distribution of indium(III) and antimony(III) was examined between hydrochloric acid solutions and solutions of tri-n-butylphosphate (TBP), trialkyl- and triarylphosphine oxides (TGPO, G = phenyl (P), n-butyl (B), or n-octyl (O)), or tetra-n-butylammonium chloride (R4NCl) in benzene or other organic solvents. The extractability of indium into benzene decreases in the order TOPO > TBPO > TBP ~ TPPO. In the case of TOPO and TBPO, there is a pronounced maximum on the plots of log DIn vs c(HCl) in the region of c(HCl) = 3-6 mol l-1; this applies also to other organic solvents. The composition of the species transferred into the organic phase is probably HInCl4.2 TGPO. The distribution ratio of antimony(III) attains considerable value even in the absence of the organophosphorus reagents, which indicates that Sb chloro complexes themselves are extracted.
The synthesis of model lactones of cyclolignan type
Authors: Křepelka Jiří , Holubek Jiří
Published: August 2011

Lactones VI-IX were prepared on reduction of anhydrides of 4-aryl-1-methoxynaphthalene-2,3-dicarboxylic acids IV and V with sodium borohydride in methanol. Catalytic hydrogenation on platinum of lactones VIII and IX gave lactones with hydrogenated ring A, or A and C. Lactones XII and XIII were found to possess an inhibitory effect on the growth of the tumour S 37 in experimental animals.
Degrees of association of alkali tert-butoxides in tert-butanol in the absence and in the presence of crowns: An ebulliometric study
Authors: Pechanec Václav , Kocián Oldřich , Halaška Vlastimil , Pánková Magdalena , Závada Jiří
Published: August 2011

Association degrees have been determined in 0.03-0.8 molal t-C4H9OLi-t-C4H9OH, t-C4H9ONa-t-C4H9OH and t-C4H9OK-t-C4H9OH solutions in the absence and also in the presence of three different crowns (18-crown-6, 15-crown-5 and 12-crown-4). It has been found that presence of any of the three crowns does not affect association degree in the alkoxide solutions. t-C4H9OLi is on average dimeric in 0.03 molal and tetrameric in 0.4-0.8 molal solution, whereas t-C4H9ONa and t-C4H9OK are in the full concentration range monomeric ion pairs, in the absence as well as in the presence of the crowns. Of the nine tert-butoxide-crown combinations studied, only two, t-C4H9OK-18-crown-6 and t-C4H9OK-15-crown-5, yielded complexes quantitatively, in the form of 1 : 1 complexed ion pairs. An incomplete complex formation (10-30%) has been observed with the combinations t-C4H9OK-12-crown-4, t-C4H9ONa-18-crown-6, t-C4H9ONa-15-crown-5, t-C4H9ONa-12-crown-4. No complex formation has been detected with t-C4H9OLi, in combination with any of the three crowns. Complex stability decreases in the order K(+) > Na(+) > Li(+), regardless of the crown cavity size. At variance with the prevailing opinion it indicates that steric fit between cation and crown is not the main factor which controls complex stability in the solution. A cooperative influence of anion on crown complex stability is considered in terms of the theory of hard and soft acids and bases.
Analysis of the precipitation reactor-separation equipment system. Continuous reactor and the rotary vacuum filter operating at the selected negative pressure drop
Authors: Söhnel Otakar
Published: August 2011

An analysis has been performed of the continuous precipitation reactor - rotary vacuum filter system (operating at the selected negative pressure drop) on the basis of the unit output. Filtration area necessary for separation of the product from the precipitation reactor is a function of the mean residence time of suspension in the reactor, concentration of the precipitating solutions, porosity of the filtration cake and the filtration negative pressure drop. Application of the derived relations is demonstrated on the continuous precipitation of Mg(OH)2.
Donor-acceptor complexes of trimethylamine with selenium trioxide, sulphur trioxide, and sulphur dioxide
Authors: Toužín Jiří , Bauer Petr
Published: August 2011

Study of reaction course of trimethylamine with selenium trioxide by conductometric titration and vibration spectra of the products proved that the reaction produces, besides the known donor-acceptor complex (CH3)3N.SeO3, also the adduct (CH3)3N.S2O6 similar to that formed in the system pyridine-selenium trioxide. Although the latter adduct could not be isolated in pure state, the results obtained indicate its structural analogy to the compound C5H5N.Se2O6. In preparation of the both DA complexes of selenium trioxide and trimethylamine the adduct (CH3)3N.SO2 is an important intermediate whose vibration spectra were measured and interpreted, too. Comparison and characterization of bonding relations in the DA complexes (CH3)3N.SeO3 and (CH3)3N.SO3 were carried out on the basis of results of normal coordinate analysis.
Electronic spectra of 2- and 4-substituted 3,5-dicyano-6-methylpyridines
Authors: Ilavský Dušan , Kuthan Josef
Published: August 2011

The PPP method has been used for calculation of theoretical spectra of the compounds III-X and IIIa-Xa, and the results obtained have been confronted with available experimental absorbance curves. It has been shown that the theoretical spectra can be used for successful interpretation of tautomeric equilibrium between 2-pyridone XI and 2-hydroxypyridine X as well as for prediction of spectral characteristics of the not yet synthetized series IIIa-Xa.
Reactions of carbonyl isothiocyanates with cyclic enamines
Authors: Uher Michal , Foltín Jozef , Floch Ľubomír
Published: August 2011

Reactions of carbonyl isothiocyanates with cyclic enamines were investigated and the IR, UV and electron impact mass spectra of the synthesized products are discussed.
Correlation and quantum-chemical interpretation of electrochemical reduction of substituted β-chlorovinyl ketones
Authors: Komenda Jaro , Roth Michal , Matschiner Hermann , Voigtländer Rolf
Published: August 2011

p-Substituted phenyl-2-chlorovinyl ketones undergo two-electron reduction at mercury dropping electrode in 0.1M-H2SO4/CH3OH medium. Localization energy calculations have shown the carbon-halogen bond to be the reaction centre in these molecules containing three potential reaction centres; in accordance with results of preparative electrolysis the first reaction step consists in reductive splitting off of the halogen. The half-wave potential values of individual derivatives correlate successfully with the calculated values of localization energies; the deviations found with the non-substituted and phenylsubstituted derivatives differing from the other compounds by magnitude of their π electron system are ascribed to the approximations involved in the simple HMO method.
Synthesis and characteristics of sulfur interligand bridge-derivatives and of some S-substituted compounds in the (C2B9H11)2Co- series. Conformations of (C2B9H11)2Mx- metallocarboranes
Authors: Janoušek Zbyněk , Plešek Jaromír , Heřmánek Stanislav , Baše Karel , Todd Lee J. , Wright W. F.
Published: August 2011

Synthesis, properties and chemical behaviour of the (C2B9H11)2Co- derivatives, namely anions with -S- or -SS- bridges and of neutral species with -SR- (R = H, alkyl, aryl) or -S-SR- bridges as well as with -(+)S(CH3)2 group are described. The analysis of 11B NMR spectra indicates in solution and in the 11B NMR time scale a free rotation at (C2B9H11)2Co-, oscillations at -S2-, -S=CH=S- and rigid conformations at -S- or -(+)SR-, (CH3)2S(+)- and -S-SR(+)- derivatives. For description of different conformations a combination of locants and descriptors e (eclipsed), s (staggered) is proposed. The (s-1,4',2,1') conformation was found by X-ray study of (8-CH3OC2B9H10)2Ni.
Wavy flow along oscillating wall
Authors: Sobolík Václav , Drahoš Jiří
Published: August 2011

A capacitance probe for the measurement of a local liquid film thickness was developed and tested. Characteristics of wavy flows of Newtonian (glycerol) and non-Newtonian liquids (aqueous solution of carboxymethylcellulose and kaolin suspension in water) along a vertical wall were measured by the probe. Attention was also devoted to the influence of wall oscillations upon waves on the film surface. The measured data on wavy flow of glycerine and partially also on carboxymethylcellulose (flow behaviour index n = 0.86) were in a good agreement with Kapitsa theory based, besides others, on the assumption of the sine shape of waves. However the theory cannot be used even as the first approximation for description of wavy flow of kaolin suspension (n = 0.14).
Mathematical simulation of the formation of small holes during electrochemical machining
Authors: Novák Petr , Roušar Ivo , Kimla Arnošt , Mejta Vladimír , Cezner Václav
Published: August 2011

For the purpose of studying the formation of small holes during electrochemical machining, a two-fold transformation of the interelectrode space to a rectangle was used (threedimensional system symmetrical around the axis of the hole) and a superrelaxation method for the calculation of the potentials in this region was proposed. The results for the case of primary current distribution are compared with those involving polarization of the electrodes, heating of the streaming electrolyte by the Joule heat, and the formation of the gas phase. It is shown that the primary current distribution represents a sufficient approximation of the situation during machining.
The search for the active base operating in alkoxide promoted E2 reactions in low polar solvents: A kinetic analysis of the elusive problem
Authors: Závada Jiří , Pánková Magdalena , Vítek Antonín
Published: August 2011

Partial kinetic orders in base for 1-decene, cis-2-decene and trans-2-decene formation from the reaction of 2-decyl bromide with t-C4H9OK in tetrahydrofuran and in tert-butanol and with t-C4H9ONa in tert-butanol have been determined and their significance for assessment of active base has been probed. It has been ascertained that assessment of active base in alkoxide promoted E2 reactions is model-dependent. An unambiguous evidence has been provided by a kinetic analysis of the effect of base concentration on olefin-isomer distribution in the reaction. Two alternative kinetic models of this effect have been devised, the one assuming a competition of several active base species for a single substrate and the other a competition between an uncomplexed and alkoxide-complexed substrate for a single active base. Compatibility of both kinetic models with experimental data has been demonstrated.
Characterization of polysaccharides from various varieties of peach trees (Prunus persica (L.) BATSCH.)
Authors: Rosík Jozef , Kardošová Alžbeta
Published: August 2011

Methylation analysis of 6 polysaccharides of gums from various varieties of peach trees was carried out. Different methylation methods were used. The results are correlated with the presently known structural characteristics of the peach gum polysaccharide.
Isolation and characterization of cathepsin D from human gastric mucosa
Authors: Pohl Jan , Bureš Ladislav , Slavík Karel
Published: August 2011

The molecular weight of the enzyme, purified by ion-exchange chromatography and affinity chromatography, was determined by gel filtration on Sephadex G-100 as 49 000. After treatment with 2-mercaptoethanol, polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate resolved the enzyme into two chains, of molecular weights 33 000 and 18 000. This shows that in the native state the enzyme is composed of one light and one heavy chain. Isoelectric focusing in polyacrylamide gel gave four bands, the isoelectric points being 5.5, 6.1, 6.5 and 7.1. The optimum protein substrate (pH optimum 3.2-3.6) was haemoglobin. The best synthetic substrate was methyl ester of pyroglutamyl-histidyl-phenylalanyl-phenylalanyl-alanyl-leucine. The protease was inhibited by the inhibitor of cathepsin D from the potato tubers. It is concluded that the enzyme is cathepsin D from gastric mucosa.
The effect of community and family interventions on young people's physical activity levels: a review of reviews and updated systematic review
Authors: van Sluijs Esther M F , Kriemler Susi , McMinn Alison M
Published: August 2011

Background

Next to the school environment, the family and community environment are key for young people's behaviour and for promoting physical activity (PA).

Methods

A review of reviews was conducted, after which a literature search was conducted (in PubMed, Scopus and PsychInfo) from August 2007 (search date of the most recent review) to October 2010. Inclusion criteria were study population aged 18 years or younger, controlled trial, no PA control condition, PA promotion intervention and reported analyses of a PA-related outcome. Methodological quality was assessed, and data on intervention details, methods and effects on primary and secondary outcomes (PA, body composition and fitness) were extracted.

Results

Three previous reviews were reviewed, including 13 family-based and three community-based interventions. Study inclusion differed for each review, but all concluded that the evidence was limited, although the potential of family-based interventions delivered in the home and including self-monitoring was highlighted. A further six family-based and four community-based interventions were included in the updated review, with a methodological quality score ranging from 2 to 10 and five studies scoring 6 or higher. Significant positive effects on PA were observed for one community-based and three family-based studies. No distinctive characteristics of the effective interventions compared with those that were ineffective were identified.

Conclusions

The effect of family- and community-based interventions remains uncertain despite improvements in study quality. Of the little evidence of effectiveness, most comes from those targeted at families and set in the home. Further detailed research is needed to identify key approaches for increasing young people's PA levels in family and community settings.
What proportion of youth are physically active? Measurement issues, levels and recent time trends
Authors: Ekelund Ulf , Tomkinson Grant , Armstrong Neil
Published: August 2011

Aim

The aim of this review is to summarise issues surrounding the measurement of physical activity (PA) by self-report and accelerometry in youth (2–18 years old). Current levels and temporal trends in PA and sport participation and the effect of assessment method on data interpretation will be summarised.

Methods

Relevant papers were extracted from a computerised literature search of MEDLINE and personal databases. Additional papers were extracted from reference lists of recently published reviews.

Results

The criterion validity (direct comparison with an objective method) of self-reported instruments is low to moderate, with correlation coefficients generally between 0.3 and 0.4. Self-report instruments overestimate the intensity and duration of PA and sport participation. The interpretation of PA data from accelerometry is a challenge, and specific issues include the definition of intensity thresholds and the influence of age on intensity thresholds.

Recent data on self-reported PA in youth suggest that between 30% and 40% are sufficiently active. Prevalence values for sufficiently active youth measured by accelerometry range between 1% and 100%, depending on the intensity thresholds used. Sport participation is likely to contribute to higher levels of PA. The available evidence does not support the notion that PA levels and sport participation in youth have declined in recent decades.

Conclusion

The number of youth meeting current PA guidelines varies by assessment method and the intensity thresholds used when PA is measured by accelerometry. The available evidence does not firmly support the notion that PA in young people has declined during the last decades. It is unlikely that any self-report method is sufficiently accurate for examining cross-cultural differences and temporal trends in young people's PA and sport participation over time. Surveillance systems therefore need to strive for an international standardisation using objective measurements of PA to complement existing self-report instruments.
Training the child athlete: physical fitness, health and injury
Authors: Carter Cordelia W , Micheli Lyle J
Published: August 2011

The number of children and adolescents participating in organised athletic activities worldwide is increasing. However, physical fitness levels among youth are lower today than in previous decades. The combination of increased exposure and decreased preparedness for sports participation has led to an epidemic of both acute and chronic sports-related injuries in this population. Poor physical fitness, in addition to having negative health consequences, seems to be a risk factor for sports-related injury. Accurate injury surveillance data are required to better define the magnitude of the problem of injury in youth sports, as well as to identify specific risk factors for injury. From these data, targeted intervention strategies incorporating fitness training may be developed with the goal of preventing sports-related injury. Preliminary experience with several specific injury patterns—anterior cruciate ligament injuries and ankle sprains—has demonstrated the efficacy of such targeted prevention strategies.
The Model for Understanding Success in Quality (MUSIQ): building a theory of context in healthcare quality improvement
Authors: Kaplan Heather C , Provost Lloyd P , Froehle Craig M , Margolis Peter A
Published: August 2011

Background

Quality improvement (QI) efforts have become widespread in healthcare, however there is significant variability in their success. Differences in context are thought to be responsible for some of the variability seen.

Objective

To develop a conceptual model that can be used by organisations and QI researchers to understand and optimise contextual factors affecting the success of a QI project.

Methods

10 QI experts were provided with the results of a systematic literature review and then participated in two rounds of opinion gathering to identify and define important contextual factors. The experts subsequently met in person to identify relationships among factors and to begin to build the model.

Results

The Model for Understanding Success in Quality (MUSIQ) is organised based on the level of the healthcare system and identifies 25 contextual factors likely to influence QI success. Contextual factors within microsystems and those related to the QI team are hypothesised to directly shape QI success, whereas factors within the organisation and external environment are believed to influence success indirectly.

Conclusions

The MUSIQ framework has the potential to guide the application of QI methods in healthcare and focus research. The specificity of MUSIQ and the explicit delineation of relationships among factors allows a deeper understanding of the mechanism of action by which context influences QI success. MUSIQ also provides a foundation to support further studies to test and refine the theory and advance the field of QI science.
Comparison of a chlorhexidine and a benzoyl peroxide shampoo as sole treatment in canine superficial pyoderma
Authors: Loeffler A. , Cobb M. A. , Bond R.
Published: August 2011

The clinical and antibacterial efficacy of two shampoos used as a sole antibacterial treatment in dogs with superficial pyoderma were investigated and compared. In a randomised, partially blinded study, a 3 per cent chlorhexidine gluconate shampoo (Chlorhex 3; Leo Animal Health) was compared against a 2.5 per cent benzoyl peroxide shampoo (Paxcutol; Virbac) in 22 dogs with superficial pyoderma. Dogs were washed two to three times weekly with a 10‐minute contact time over 21 days. Clinical scores and bacterial counts were assessed on days 1, 8 and 22 and compared within and between treatment groups; overall response was assessed at the end of the study. Twenty dogs completed the study; 15 (68.2 per cent) showed an overall clinical improvement and the clinical signs resolved in three chlorhexidine‐treated dogs. In the chlorhexidine‐treated group, scores for papules/pustules (P<0.001), investigator‐assessed pruritus (P=0.003), total bacterial counts (P=0.003) and counts for coagulase‐positive staphylococci (P=0.003) were reduced after three weeks. Scores and bacterial counts did not vary significantly in the benzoyl peroxide‐treated group.
Use of radiography to identify keel bone fractures in laying hens and assess healing in live birds
Authors: Richards G. J. , Nasr M. A. , Brown S. N. , Szamocki E. M. G. , Murrell J. , Barr F. , Wilkins L. J.
Published: August 2011

The aim of this study was to use radiography to assess and characterise naturally occurring keel bone fractures in laying hens and monitor live birds over several weeks to examine the healing process. Twenty‐four Lohmann brown commercial laying hens with varying degrees of keel bone fracture were used in the study. Birds were radiographed regularly over six weeks and the radiographic features and changing appearance of keel bone fractures were evaluated. The radiographic characteristics of old and new fractures were categorised and indicated that 80 per cent of birds entering the study with new fractures had healed after 35 days and five birds had incurred new fractures irrespective of their original fracture status.
Review of seven cases of granulosa cell tumour of the equine ovary
Authors: Crabtree J.
Published: August 2011

This paper reviews the equine granulosa cell tumour (GCT) and describes the clinicopathological features, treatment and outcome in seven cases of GCT in mares. Mares were presented with unilateral ovarian enlargement during the 2007 to 2010 breeding seasons. The mean (sd) age of the mares was 11.7 (5.96) years. Three mares were multiparous barren, three were nulliparous and one was primigravida. Behaviour at presentation was 57 per cent anoestrus, 28 per cent with stallion‐like behaviour and 14 per cent with persistent oestrus. All mares had unilateral ovarian enlargement. Six non‐pregnant mares had a small and inactive contralateral ovary; the pregnant mare had a single small corpus luteum on the contralateral ovary and was at three‐and‐a‐half months' gestation. Enlarged ovaries measured 7 cm to an estimated 30 cm in diameter. 28 per cent had a multicystic ultrasound appearance, 57 per cent were dense structures and 14 per cent were of mixed appearance. Mean concentrations of progesterone were <1 ng/ml, oestrone sulphate 3.06 (2.32) ng/ml and testosterone 0.58 (0.64) nmol/l in non‐pregnant mares. Inhibin was elevated in all non‐pregnant cases at 7.6 (12.45) ng/ml. The pregnant mare had concentrations of progesterone 2.5 ng/ml, oestrone sulphate 81.0 ng/ml, testosterone 1.9 nmol/l and inhibin 1.31 ng/ml. Mares demonstrating stallion‐like behaviour had a significantly higher (P<0.001) testosterone concentration (1.85 [0.07] nmol/l) than those that did not (0.34 [0.26] nmol/l). Three mares underwent unilateral ovariectomy and resumed cyclic ovarian activity within nine months of surgery.
NON-MINIMAL COSMOLOGICAL MODEL IN MODIFIED YANG–MILLS THEORY
Authors: SHCHIGOLEV V. K. , OREKHOVA G. N.
Published: August 2011

In this paper, we consider a model of non-minimal modified Yang–Mills (Y-M) theory in the Friedmann–Robertson–Walker (FRW) cosmology, in which the Y-M field couples to the scalar curvature through a function of its first invariant. We show that cosmic acceleration can be realized due to non-minimal gravitational coupling of the modified Y-M theory. Besides general study, we consider in detail the case of power-law coupling function. We derive the basic equations for the cosmic scale factor in our model, and provide several examples of their solutions.
GENERICITY OF FILLING ELEMENTS
Authors: SOLIE BRENT B.
Published: August 2011

An element of a finitely generated non-Abelian free group F(X) is said to be filling if that element has positive translation length in every very small minimal isometric action of F(X) on an ℝ-tree. We give a proof that the set of filling elements of F(X) is exponentially F(X)-generic in the sense of Arzhantseva and Ol'shanskiı. We also provide an algebraic sufficient condition for an element to be filling and show that there exists an exponentially F(X)-generic subset consisting only of filling elements and whose membership problem has linear time complexity.
PHYSICAL ASPECTS OF QUASI-LOCAL BLACK HOLE HORIZONS
Authors: NIELSEN ALEX B.
Published: August 2011

We discuss some of the physical aspects expected to be associated with black holes. These include Hawking radiation, horizon entropy and cosmic censorship. In particular we focus on whether these properties are more naturally associated to causally defined horizons or quasi-local horizons.
DETERMINATION OF OPTIMUM REFLECTANCE OF OUTPUT COUPLER IN NANOSECOND SINGLY-RESONANT OPTICAL PARAMETRIC OSCILLATOR
Authors: AHN WHA-KEUN , RHEE BUM KU , CHA MYOUNGSIK
Published: August 2011

We investigated the signal output efficiency of a singly-resonant ns-optical parametric oscillator based on LiNbO3 with the double-pass pump as a function of reflectance (R) of the output coupler. The measured signal output exhibited a broad maximum around R ~ 35% at a fixed pump energy of 100 mJ/pulse, yielding a maximum signal output efficiency of ~ 38%. The experimental results were well-supported by the numerical calculation using a split-step beam propagation model. We also found that the same beam propagation model with one-dimensional diffraction predicts nearly the same results, enabling fast numerical determination of the optimum reflectance of the output coupler.
Zn1-xMgxSe: A PROMISING MATERIAL FOR NON-LINEAR OPTICS
Authors: KOVALENKO N.
Published: August 2011

A theoretical analysis of the condition of scalar phase-matched second harmonic generation and optical parametric oscillation (OPO) in single-crystalline samples Zn0.52Mg0.48Se is presented. The calculated range of pumping for second harmonic generation with phase matching is 5.1-13 μm. The tuning range of the optical parametric oscillator based on Zn0.52Mg0.48Se is determined. The combination of active media and nonlinear converter for OPO in the same optical element are proposed.
INTERFACE WAVE COMPRESSION IN NONLINEAR BI-DISPERSIVE HETERO-STRUCTURE WAVEGUIDE ARRAYS
Authors: WANG HONGCHENG
Published: August 2011

The propagation behavior of an optical pulse is investigated at the interface of two different nonlinear bi-dispersive waveguide arrays. It is found that the peak power has a great impact on the propagation of the pulse. When the peak power is high enough, the major part of the initial pulse can be guided and confined in the interface of this waveguide array. Because of the interplay between asymmetry discrete diffraction, dispersion and Kerr nonlinearity of hetero-structure waveguide array, the output pulse develops a rectangular-like intensity profile with richer bandwidth, and its power spectrum in the frequency domain is rather uniform, i.e., less modulated. Therefore, the output pulse from the hetero-structure waveguide array can be compressed more efficiently than that of a homogeneous element.
POLARIZATION INSENSITIVE QUASI-PHASE-MATCHED SECOND HARMONIC GENERATION
Authors: SONG XIAO-SHI , WANG QIN , YU ZI-YAN , XU FEI , LU YAN-QING
Published: August 2011

Polarization insensitive second harmonic generation (SHG) is proposed in an electro-optic (EO) tunable periodically poled Lithium Niobate (PPLN). The PPLN consists of four sections. External electric fields could be selectively applied to them to induce polarization rotation between the ordinary and extraordinary waves. If the domain structure is well-designed, the fundamental wave with an arbitrary polarization state can be frequency doubled efficiently in this special PPLN.
CONCENTRATION DEPENDENT OPTICAL PROPERTIES OF PORPHYRINS IN NAFION MATRIX
Authors: TESSEMA GENENE , HAILU GIRMA , MAAZA MALIK
Published: August 2011

Concentration dependent optical properties of the various types of porphyrin compounds were studied using optical absorbance and Z-scan measurements. Enhanced absorbance width of the Soret and Q-bands have been observed by blending three different porphyrin molecules in Nafion column matrix membrane. This is an important development towards achieving efficient photon-harvesting medium for possible application in photonic devices. Moreover, new evidences have been found on the concentration dependance of the nonlinear absorption coefficient (β) of the VTPP in Nafion.
THE TRANSMISSION OF QUASI-DISCRETE SOLITONS IN RESONANT WAVEGUIDE ARRAYS ACTIVATED BY THE ELECTROMAGNETICALLY INDUCED TRANSPARENCY
Authors: WU JIANXIONG , FENG MINGNENG , PANG WEI , FU SHENHE , LI YONGYAO
Published: August 2011

We introduce a model of resonant optical systems: a waveguide array doped periodically with resonant four-level N-type atoms. The dopant atoms are driven by external fields which induce the effect of the electromagnetically induced transparency (EIT). In this resonant waveguide arrays (RWA) system, the optical field propagates as quasi-discrete diffraction, breathing beam or stable spatial soliton when different initial amplitude and width of the probe are given. The critical values representing these transformations are obtained by the numerical simulations. In a further study of the oblique incidence, the soliton loses a portion of its energy while a kick (i.e., a transverse wave vector) is initially introduced. As the value of the kick becomes larger than a critical value, the soliton collapses.
A THEORETICAL INVESTIGATION ON PROPAGATION CHARACTERISTICS AND COUPLING EFFICIENCIES OF A COUPLING SYSTEM
Authors: LI SHUPING , ZHU JINGPING , SUN YUZHOU , QIN WANGUANG , TANG TIANTONG
Published: August 2011

In a butt-joint coupling system, a fiber is coupled to a slab waveguide by a fiber ended micro-lens (FEML), so that the electromagnetic field emerging from the FEML is completely different from the fiber mode. The conventional method for calculations of the coupling efficiency, such as the overlap integral method, is not valid. In this paper, a Monte Carlo model for the coupling system is proposed, based not only on the principles of reflection and refraction at media interface plane, but also on the diffractions of micro lens. This model incorporates the geometrical surface of both the fiber end-face micro-lens and slab waveguide, the relative position of the fiber and slab waveguide, and also takes into consideration both the aberration and diffraction effects. The propagation characteristics and coupling efficiencies of the system are simulated. The losses caused by misalignment of the system are also discussed.
A NONUNIFORM HIGH-QUALITY IMAGE COMPRESSION METHOD TO PRESERVE USER-SPECIFIED COMPRESSION RATIO
Authors: BONYADI MOHAMMAD REZA , MOGHADDAM MOHSEN EBRAHIMI
Published: August 2011

Most of image compression methods are based on frequency domain transforms that are followed by a quantization and rounding approach to discard some coefficients. It is obvious that the quality of compressed images highly depends on the manner of discarding these coefficients. However, finding a good balance between image quality and compression ratio is an important issue in such manners. In this paper, a new lossy compression method called linear mapping image compression (LMIC) is proposed to compress images with high quality while the user-specified compression ratio is satisfied. This method is based on discrete cosine transform (DCT) and an adaptive zonal mask. The proposed method divides image to equal size blocks and the structure of zonal mask for each block is determined independently by considering its gray-level distance (GLD). The experimental results showed that the presented method had higher pick signal to noise ratio (PSNR) in comparison with some related works in a specified compression ratio. In addition, the results were comparable with JPEG2000.
BINARY-UNCODED IMAGE AND VIDEO COMPRESSION USING SPIHT-ZTR CODING
Authors: CHIA WAI CHONG , CHEW LI WERN , ANG LI-MINN , SENG KAH PHOOI
Published: August 2011

When the embedded zerotree wavelet (EZW) algorithm was first introduced by Shapiro, four types of symbols (zerotree (ZTR), isolated zero (IZ), positive (POS), and negative (NEG)) were used to represent the tree structure. An improved version of EZW, the set partitioning in hierarchical trees (SPIHT) algorithm was later proposed by Said and Pearlman. SPIHT removed the ZTR symbol, while keeping the other three symbols in a slightly different form. In the SPIHT algorithm, the coding of the parent node is isolated from the coding of its descendants in the tree structure. Therefore, it is no longer possible to encode the parent and its descendants with a single symbol. When both the parent and its descendants are insignificant (forming a degree-0 zerotree (ZTR)), it cannot be represented using a ZTR symbol. From our observation, the number of degree-0 ZTRs can occur very frequently not only in natural and synthesis images, but also in video sequences. Hence, the ZTR symbol is reintroduced into SPIHT in our proposed SPIHT-ZTR algorithm. In order to achieve this, the order of sending the output bits was modified to accommodate the use of ZTR symbol. Moreover, the significant offspring were also encoded using a slightly different method to further enhance the performance. The SPIHT-ZTR algorithm was evaluated on images and video sequences. From the simulation results, the performance of binary-uncoded SPIHT-ZTR is higher than binary-uncoded SPIHT and close to SPIHT with adaptive arithmetic coding.
VECTORIZATION AND LINE DETECTION FOR AUTOMATIC IMAGE RECOGNITION
Authors: ALVAREZ MIGUEL , ALGORRI MARÍA-ELENA
Published: August 2011

We propose an algorithm for creating line graphs from binary images. The algorithm consists of a vectorizer followed by a line detector that can handle a large variety of binary images and is tolerant to noise. The proposed algorithm can accurately extract higher-level geometry from the images lending itself well to automatic image recognition tasks. Our algorithm revisits the technique of image polygonization proposing a very robust variant based on subpixel resolution and the construction of directed paths along the center of the border pixels where each pixel can correspond to multiple nodes along one path. The algorithm has been used in the areas of chemical structure and musical score recognition and is available for testing at www.docnition.com. Extensive testing of the algorithm against commercial and noncommercial methods has been conducted with favorable results.
A NOVEL TWO-LEVEL COLOR IMAGE RETRIEVAL METHOD
Authors: WANG XING-YUAN , CHEN ZHI-FENG , YUN JIAO-JIAO
Published: August 2011

This paper presents an effective two-level color image retrieval method based on the RGB color model. For the purpose of effectively retrieving more similar images from the digital image databases, we divide the image into different regions and set bigger weight for the region we focus on. In addition, we set different weights for each RGB component of the color image according to the main hue of it. As a result, this scheme can enhance the retrieval accuracy that is measured in terms of the recall and precision.
ON COVERAGE BOUNDS OF UNSTRUCTURED PEER-TO-PEER NETWORKS
Authors: CHANDRA JOYDEEP , GANGULY NILOY
Published: August 2011

In this paper, we develop methods to estimate the network coverage of a TTL-bound query packet undergoing flooding on an unstructured p2p network. The estimation based on the degree distribution of the networks, reveals that the presence of certain cycle-forming edges, that we name as cross and back edges, reduces the coverage of the peers in p2p networks and also generate a large number of redundant messages, thus wasting precious bandwidth. We therefore develop models to estimate the back/cross edge probabilities and the network coverage of the peers in the presence of these back and cross edges. Extensive simulation is done on random, power-law and Gnutella networks to verify the correctness of the model. The results highlight the fact that for real p2p networks, which are large but finite, the percentage of back/cross edges can increase enormously with increasing distance from a source node, thus leading to huge traffic redundancy.
MIXING PATTERNS AMONG EPIDEMIC GROUPS
Authors: KAMP CHRISTEL
Published: August 2011

Epidemic modeling has a long tradition in facilitating an understanding of the spread of infectious agents with direct impact on public health. Recent modeling approaches have specifically improved our understanding of the connections between transmission network topology and epidemic spread: Host populations are generally not well mixed and show heterogeneous and dynamic contact behavior. This results in a broad range of epidemic patterns regarding both speed and width of epidemic expansion. However, there is also a mutual influence between transmission network structure, mixing between susceptible and infected hosts and the epidemic process: epidemic control gets more difficult if infected hosts mix well within the susceptible population. We present a new mathematical framework which allows for a study of mixing patterns between susceptible and infected hosts in populations with very general structural features. While clustering of infected hosts is a qualitatively well known phenomenon, our approach allows for its quantification and puts it in relation to the hosts' overall contact behavior. It shows that different degrees of assortativity emerge depending on the transmission network structure and epidemic stage. This method's use is demonstrated for synthetic populations. It can however easily be transferred to more realistic settings in which information about mixing patterns of epidemic groups is vital for improved epidemic control.
BOUNDARIES BETWEEN ANCIENT CULTURES: ORIGINS AND PERSISTENCE
Authors: COHEN MORREL H. , ACKLAND GRAEME J.
Published: August 2011

In a recent work on the wave of advance of a beneficial technology and associated hitchhiking of cultural and biological traits, we simulated the advance of neolithic agriculture into Europe. That model embraced geographical variation of land fertility and human mobility, conversion of indigenous mesolithic hunter-gatherers to agriculture, and competition between invading farmers and indigenous converts. A key result is a sharp cultural boundary across which the agriculturalists' heritage changes from that of the invading population to that of the converts. Here we present an analytical study of the cultural boundary for some simple cases. We show that the width of the boundary is determined by human mobility and the strength of competition. Simulations for the full model give essentially the same result. The finite width facilitates irreversible gene flow between the populations, so over time genetic differences appear as gradients while e.g. linguistic barriers may remain sharp. We also examine the various assumptions of the model relating to purposeful versus. random movement of peoples and the competition between cultures, demonstrating its richness and flexibility.
THE COEVOLUTION OF GROUP SIZE AND LEADERSHIP: AN AGENT-BASED PUBLIC GOODS MODEL FOR PREHISPANIC PUEBLO SOCIETIES
Authors: KOHLER TIMOTHY A. , COCKBURN DENTON , HOOPER PAUL L. , BOCINSKY R. KYLE , KOBTI ZIAD
Published: August 2011

We present an agent-based model for voluntaristic processes allowing the emergence of leadership in small-scale societies, parameterized to apply to Pueblo societies of the northern US Southwest between AD 600 and 1300. We embed an evolutionary public-goods game in a spatial simulation of household activities in which agents, representing households, decide where to farm, hunt, and locate their residences. Leaders, through their work in monitoring group members and punishing defectors, can increase the likelihood that group members will cooperate to achieve a favorable outcome in the public-goods game. We show that under certain conditions households prefer to work in a group with a leader who receives a share of the group's productivity, rather than to work in a group with no leader. Simulation produces outcomes that match reasonably well those known for a portion of Southwest Colorado between AD 600 and 900. We suggest that for later periods a model incorporating coercion, or inter-group competition, or both, and one in which tiered hierarchies of leadership can emerge, would increase the goodness-of-fit.
INTERACTIONS IN SPACE FOR ARCHAEOLOGICAL MODELS
Authors: EVANS T. S. , RIVERS R. J. , KNAPPETT C.
Published: August 2011

In this article, we examine a variety of quantitative models for describing archaeological networks, with particular emphasis on the maritime networks of the Aegean Middle Bronze Age. In particular, we discriminate between those gravitational networks that are most likely (maximum entropy) and most efficient (best cost/benefit outcomes).
QUICKEST PATHS IN SIMULATIONS OF PEDESTRIANS
Authors: KRETZ TOBIAS , GROßE ANDREE , HENGST STEFAN , KAUTZSCH LUKAS , POHLMANN ANDREJ , VORTISCH PETER
Published: August 2011

This contribution proposes a method to make agents in a microscopic simulation of pedestrian traffic walk approximately along a path of estimated minimal remaining travel time to their destination. Usually models of pedestrian dynamics are (implicitly) built on the assumption that pedestrians walk along the shortest path. Model elements formulated to make pedestrians locally avoid collisions and intrusion into personal space do not produce motion on quickest paths. Therefore a special model element is needed, if one wants to model and simulate pedestrians for whom travel time matters most (e.g. travelers in a station hall who are late for a train). Here such a model element is proposed, discussed and used within the Social Force Model.
MULTI-WEIGHTED MONETARY TRANSACTION NETWORK
Authors: WANG H. , VAN BOVEN E. , KRISHNAKUMAR A. , HOSSEINI M. , VAN HOOFF H. , TAKEMA T. , BAKEN N. , VAN MIEGHEM P.
Published: August 2011

This paper aims to both develop and apply advances from the field of complex networks to large economic systems and explore the (dis)similarities between economic systems and other real-world complex networks. For the first time, the nature and evolution of the Dutch economy are captured by means of a data set analysis that describes the monetary transactions among 105 economical activity clusters over the period 1987–2007. We propose to represent this data set as a multi-weighted network, called the monetary transaction network. Each node represents a unique activity cluster. Nodes are interconnected via monetary transactions. The millions of euros that traverse the links and that circulate inside each activity cluster are denoted by a link weight and a node weight respectively. By applying innovative methodologies from network theory, we observe important features of the monetary transaction network as well as its evolution: (a) Activity clusters with a large internal flow tend to cooperate with many other clusters via high volume monetary transactions. (b) Activity clusters with a lower internal transaction volume prefer to transact with fewer neighboring nodes that have a higher internal flow. (c) The node weights seem to follow a power law distribution. Surprisingly, (b) and (c) have been observed in community structures of many real-world networks as well. (d) Activity clusters tend to balance the monetary volume of their transactions with their neighbors, reflected by a positive link weight correlation around each node. This correlation becomes stronger over time while the number of links increases over time as well.
THE IMPORTANCE OF SPACE IN MODELS OF SOCIAL LEARNING, CULTURAL EVOLUTION AND NICHE CONSTRUCTION
Authors: FOGARTY LAUREL , RENDELL LUKE , LALAND KEVIN N.
Published: August 2011

This article focusses on the importance of space in mathematical models of cultural evolution, cooperation, niche construction and social learning. We discuss the benefits of including spacial effects in these evolutionary models and illustrate how the inclusion of space has changed accepted and long-standing results. We also briefly discuss the spatial dynamics of these systems and suggest future directions for research investigating spatial evolution.