275 research outputs found
Evaluating the Effect of Ambient and Scanning Lights on the Trueness of the Intraoral Scanner
No full textPurpose To determine the influence of different scanning and ambient light conditions on the trueness values of an intraoral scanning (IOS) device. Material and methods The present study was conducted among 20 complete dentate volunteers. After making complete maxillary arch impressions with vinyl polysiloxane material, type IV dental stone was poured, and working casts were obtained. Then, the models were digitized using a dental laboratory scanner (LS) and standard tessellation language (STL) files were acquired. Full arch digital scans of the volunteers were also performed using an IOS device with 2 ambient light conditions (RL: room light, 1003 lux, and ZL: zero light, 0 lux) and 2 scanning light modes (blue [B] and white [W]). Twenty digital scans per group at each light condition were consecutively obtained. Discrepancy between the digital scans and digitized working casts was analyzed using a 3D inspection software. The obtained data were analyzed using one-way ANOVA and Tukey tests (alpha = 0.05). Results Significant differences were obtained among different light conditions for the IOS device (p < 0.0001, F = 42.958 for positive deviations and F = 29.278, for negative deviations). The room light and blue mode (RLB) condition had the lowest deviation values compared with the other light conditions, followed by room light and white mode (RLW), zero light and blue mode (ZLB), and zero light and white mode (ZLW; p = 0.008, p < 0.0001, and p < 0.0001, respectively). Conclusion Lighting conditions are effective in assessing the trueness of the digital impressions made with an IOS device. RLB conditions are recommended for taking a digital impression
Growth and structure of authorship and co-authorship network in the strategic management realm: Evidence from the Strategic Management Journal
No full textAbstractThe main objective of this study is to investigate the intellectual structure and evolution of author collaborations from articles published in the Strategic Management Journal between 1980 and 2014. This assessment includes the general view of authorship, authorship patterns, author productivity, ranking of authors, visualization of the co-authorship network, comparison of strategic management co-authorship network attributes with those of other disciplines, the evolution of main components and core authors in the networks by period, discussions on whether the strategic management network fits with the small world network theory, individual network attributes such as degree centrality, Bonacich's power index, closeness centrality, and betweenness centrality. Finally, the authors provide an inclusive evaluation of the results, limitations, and suggestions for future research
Detection of free radicals in gamma-irradiated seasnail hard tissues by electron paramagnetic resonance
No full textGamma-irradiated seasnail (from family of Helix lukortium) hard tissues (CaCO3) were investigated by electron paramagnetic resonance (EPR) at room temperature. The radicals produced by gamma-irradiation in seasnail were attributed to orthorhombic C-. O-2(-), freely rotating C-. O-2(-), orthorhombic C-. O-3(-), axial C-. O-3(-), and axial C-. O-3(3-) free radicals. Unirradiated seasnail hard tissues also feature Mn2+ ions in their EPR spectra. The hyperfine values were determined for the C-13 nucleus in the orthorhombic C-. O-2(-) and axial C-. O-3(3-) free radicals and for the manganese impurity ions. The g values of all the free radicals have been measured. The results were compared with the literature data for similar defects. (C) 2003 Elsevier Ltd. All rights reserved
Solvent and substituent effects on the protonation of anilines in dioxane-water mixtures
No full textProtonation constants of a number of mono-substituted anilines were determined potentiometrically in 0, 20, 30, 40, 50, and 60% (v/v) dioxane - water mixtures at (25.00 +/- 0.0.02). degreesC at an ionic strength of 0.1 mol-dm(-3) in sodium perchlorate. The data from the potentiometric titrations were evaluated using the BEST computer program. The trends in the values of the protonation constants of anilines were explained in terms of the nature of substituent and the solute - solvent and solvent - solvent interactions. Furthermore, the effects of the substituents on the basicity of aniline, the additivies of these effects, and the applicability of the Hammett equation to the behavior of these substituents are discussed
Stability of copper(II), nickel(II) and zinc(II) binary and ternary complexes of histidine, histamine and glycine in aqueous solution
No full textThe binary and mixed-ligand complexes formed between ligands (histidine (His), histamine (Him) and glycine (Gly)) and some transition metals (Cu(II), Ni(II) and Zn(II)) were studied potentiometrically in aqueous solution at (25.0 +/- 0.1)degrees C and I = 0.10 M KCl in order to determine the protonation constants of the free ligands and stability constants of binary and ternary complexes. The complexation model for each system has been established by the software program "BEST" from the potentiometric data. The most probable binding mode for each binary species of histidine and for all mixed species was also discussed based upon derived equilibrium constants and stability constants related to the binary species. The ambidentate nature of the histidine ligand, i.e. the ability to coordinate histamine-like, imidazolepropionic acid-like and glycine-like modes was indicated from the results obtained. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters, Delta log K, log X and Delta(1110). The concentration distributions of various species formed in solution were also evaluated. In terms of the nature of metal ion, the complex stability follows the trend Cu(II) > Ni(II) > Zn(II), which is in agreement with the Irving-Williams' order of metal ions. Thus, the results obtained were compared and evaluated with those in the literature
Equilibrium studies of schiff bases and their complexes with Ni(II), Cu(II) and Zn(II) derived from salicylaldehyde and some alpha-amino acids
No full textThe acid-base equilibria of Schiff bases derived from salicylaldehyde, glycine, alanine, serine, tyrosine, and phenylalanine, and their Ni(II), Cu(II) and Zn(II) complex formation equilibria were investigated by a potentiometric method in aqueous solution (t = 25 degrees C, mu = 0.1 M, KCl). The data from the potentiometric titrations were evaluated by means of the BEST computer program. The order of the formation constant values of the Schiff bases was Sal-Ala > Sal-Gly > Sal-Ser > Sal-Phe > Sal-Tyr, which is the same order as the increasing log K-1 values of amino acids (and the log K-2 values of tyrosine) with the exception of an inversion between serine and phenylalanine. Also, it was seen that the stability constants, log beta(1) and log beta(2), of Schiff base-metal complexes vary for all the metal ions investigated, viz., Sal-Gly > Sal-Ala > Sal-Ser > Sal-Tyr > Sal-Phe with the exception of Sal-Gly in the copper complex. The effect of the nature of the amino acids on their formation, protonation and stability constants was also discussed
Women's perception of male facial attractivness in association with handgrip strength
No full textDas menschliche Gesicht zeigt Emotionen und Persönlichkeitsmerkmale und diese Vielfalt ist beobachtbar und quantifizierbar. Menschen können sogar körperliche Stärke ihrer Artgenossen erkennen und wahrgenommene Stärke kann mit körperlicher Attraktivität als bedeutender Indikator bei Männern in Zusammenhang gebracht werden. Andererseits sind extreme Merkmale generell weniger erwünscht. Dies könnte durch die Kultur, den Beziehungsstatus und das Empfängnisrisiko weiblicher Bewerterinnen moduliert werden. Für Frauen, die männliche Gesichter bewerten, wurden die Hypothesen aufgestellt, dass (1) die wahrgenommene Stärke mit der tatsächlichen Stärke übereinstimmt, (2) dass der durchschnittliche Morph am attraktivsten ist, (3) österreichische und türkische Frauen in ihren Attraktivitätsbewertungen übereinstimmen, (4) während einer Phase eines hohen Empfängnisrisikos, werden stärkere Männer attraktiver wahrgenommen als schwächere und (5) Frauen in einer Beziehung bevorzugen stärkere Männer im Gegensatz zu alleinstehenden Frauen.
Fünf frontale Gesichtsmorphs junger deutscher Männer (Durchschnittsalter = 24 Jahre, SD = 3,7 Jahre) aus einer früheren Studie, kalibriert nach Handgriffstärke, wurden 104 österreichischen (Durchschnittsalter = 22 Jahre, SD = 2,5 Jahre) und 109 türkischen (Durchschnittsalter = 20 Jahre, SD = 1,9 Jahre) Studentinnen in Wien und Istanbul in zufälliger Reihenfolge präsentiert. Mithilfe von Bildschirmreglern bewerteten sie jedes Morph zu verschiedenen Merkmalen, von denen in der aktuellen Studie nur die wahrgenommene Attraktivität und die empfundene Stärke verwendet wurden. Zusätzlich wurden die Teilnehmerinnen nach ihrer Länge und dem aktuellen Status der Beziehung zu Männern sowie nach ihrer Regelmäßigkeit, Länge und dem letzten Datum ihres Menstruationszyklus befragt. Für den Nullhypothesentest wurde ein Varianzanalyse-Test (ANOVA) mit wiederholten Messungen durchgeführt.
Die Ergebnisse zeigten, dass der schwächste Morph signifikant schwächer wahrgenommen wurde als der zweitschwächste und alle anderen signifikant höher abschnitten (F = 43,7, p <0,001). In Bezug auf Attraktivität wurde der durchschnittliche Morph mit Ausnahme des zweitschwächsten Morphs (F = 59,8, p <0,001) erheblich attraktiver wahrgenommen als die anderen (p <0,001). Wahrnehmungen von Österreicherinnen und Türkinnen waren systematisch unterschiedlich (F = 8,9, p = 0,003): Im Durchschnitt gaben
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österreichische Teilnehmerinnen jedem Morph höhere Bewertungen. Bei den Attraktivitätsbewertungen gab es weder Unterschiede zwischen Frauen, die sich in einer Beziehung befanden und alleinstehenden österreichischen (p = 0,708) und türkischen (p = 0,878) Frauen noch bei österreichischen (p = 0,405) und türkischen (p = 0,184) Teilnehmerinnen in verschiedenen Menstruationszyklusphasen.
Diese Studie bestätigte, dass Frauen die körperliche Stärke weitgehend anhand der Gesichtsform beurteilen konnten, die über kalibrierte Morphe präsentiert wurde. In Übereinstimmung mit Vorhersagen von Trade-offs, die in der evolutionären Ästhetik geprägt wurden, bevorzugten die weiblichen Teilnehmerinnen die durchschnittlichen Morphen gegenüber den stärkeren und schwächeren, unabhängig von ihren kulturellen Hintergründen. Dies könnte ein Gleichgewicht zwischen Aggressionsvermeidung, körperlicher Fitness, Ressourcenhaltepotential und Elternqualitäten darstellen. Unterschiedliche Interpretationen des hellen Hautfarbtons könnten für die etwas niedrigere Attraktivitätsbewertung in der Türkei verantwortlich sein. Die Menstruationszyklusphase hatte keinen Einfluss auf die Wahrnehmung der männlichen Gesichtsattraktivität in Bezug auf die Körperkraft. Dies könnte jedoch auf eine sehr geringe Anzahl von Frauen im Empfängnisrisiko zurückzuführen sein. Auch die subjektive Interpretation des Beziehungsstatus sowie individuelle Unterschiede in der Soziosexualität könnten Gesichtspräferenzen vermitteln und somit zum Nullbefund in dieser Studie beitragen. Im Allgemeinen bestätigte die Anwendung der kalibrierten Morphe die Durchschnittlichkeit als Säule in evolutionären Erklärungen der Attraktivität.The human face shows emotions and personality traits, and this diversity is observable and quantifiable. Humans can even recognise physical strength in face of a conspecific and perceived strength may be related to physical attractiveness as formidability indicator in men. On the other hand, extreme features are usually less desirable. This might be modulated by culture, relationship status and conception risk of female raters. For women rating male faces, it was hypothesized that (1) perceived strength matches actual strength, (2) that the average morph is most attractive, (3) Austrian and Turkish women agree in their attractiveness assessments, (4) during a phase of high conception risk, stronger men are perceived more attractive than weaker ones, and (5) partnered women prefer stronger men than single women.
Five frontal facial morphs of young adult German men (mean age= 24 y., SD = 3.7 y.) from a previous study calibrated by handgrip strength were presented in random order to 104 Austrian (mean age = 22 y., SD = 2.5 y.) and 109 Turkish (mean age = 20 years, SD = 1.9 y.) female university students in Vienna and Istanbul. Using on-screen sliders, they rated each morph for various traits of which only perceived attractiveness and perceived strength was used in the current study. Additionally, the participants were asked about their length and current status of relationship with men, as well as their regularity, length and last date of their menstrual cycle. A repeated-measures analysis of variance (ANOVA) test was performed for null hypothesis testing.
The results showed that the weakest morph was perceived significantly weaker than the second weakest, and all others scored significantly higher (F = 43.7, p < 0.001). For attractiveness, the average morph was perceived considerably (p <0.001) more attractive than the others except for the second weakest morph (F = 59.8, p < 0.001). Austrian and Turkish perceptions were systematically different (F = 8.9, p = 0.003): On average, Austrian participants gave higher ratings to every morph. There were no differences between partnered and single Austrian (p= 0.708) and Turkish (p = 0.878) women in the attractiveness ratings as well as within Austrian (p = 0.405) and Turkish (p = 0.184) participants in different menstrual cycle phases.
This study confirmed that women could largely assess physical strength from facial shape presented via calibrated morphs. In line with predictions of trade-offs coined in
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evolutionary aesthetics, the female participants preferred the average morphs over the stronger and weaker ones, irrespective of their cultural background. This might represent a balance between aggression avoidance, physical fitness, resource holding potential and parenting qualities. Different interpretations of the light skin tone might account for the slightly lower attractiveness rating in Turkey. Menstrual cycle phase had no impact on perception of male facial attractiveness in relation to body strength but this might be due to very low numbers of women at high conception risk. Also, the subjective interpretation of relationship status as well as individual differences in sociosexuality might mediate facial preferences, and thus contribute to the null finding in this study. Generally, the application of the calibrated morphs confirmed averageness as a pillar in evolutionary explanations of attractivenes
EPR study of radicals produced by gamma-irradiation in marine mollusc (Venus sp.) fossils
No full textIn this study, gamma-irradiated marine mollusc (Venus sp.) fossils were investigated by electron paramagnetic resonance (EPR) at ambient temperature. Powder X-ray diffraction technique indicates that the Venus sp. fossils were made mainly of CaCO3. Before gamma-irradiation, the EPR lines of the powder of fossil samples showed the existence of Mn2+ (I = 5/2, 100% natural abundance) ions with g(av) = 2.0055 and A(av) = 9.4 mT gamma-Irradiation-induced additional defects in Venus sp. fossil were attributed to axial CO3- (gperpendicular to = 2.0171, g// = 2.0048), orthorhombic CO2- (g(x) = 2.0030, g(z) = 2.0018, g(y) = 1.9973, g(av) = 2.0007), freely rotating CO2- (g(iso) = 2.0007), isotropic SO2- (g = 2.0057), axial SO3- (g perpendicular to = 2.0036, g// = 2.0024) and isotropic SO3- (g = 2.0032) free radicals. The g-values of these free radicals were compared with the literature data belonging to similar defects
Ferromagnetic resonance studies of Co nanowire arrays
No full textCo nanowires grown by electrodeposition technique on di-block copolymers composed of polystyrene and polymethylmethacrylate, P(S-B-MMA), have been studied. Two samples with the same wire length of I pm and different wire diameters of 12 and 24nm have been prepared. The nanowires are perpendicular to the film plane and arrayed in hexagonal symmetry in the lateral dimensions. Ferromagnetic resonance (FMR) technique has been used to investigate magnetic parameters of the system. The FMR spectra are very broad (a few kG) for every direction of the external field with respect to the sample plane. The FMR spectra exhibit considerable anisotropic behavior as the field is rotated both in sample plane and from the film plane towards the film normal direction. (C) 2003 Elsevier B.V. All rights reserved
Effect of pirenzepine, a muscarinic M-1 receptor antagonist, on amygdala kindling in rat
No full textKindling, an animal model of complex partial seizures with secondary generalization, is performed by daily application of low-intensity electrical brain stimulation. The purpose of this study was to investigate the role of muscarinic M-1 receptors on amygdala kindling in the rat. Bipolar nichrome stimulation and recording electrodes were stereotaxically implanted into the right and left basolateral amygdala. Extradural recording electrodes were also placed bilaterally in the skull over the cortex. Amygdala stimulation was applied twice daily at the current intensity of afterdischarge threshold. Seizure intensity was graded by using Racine's standard five-stage scale. In the first group of experiments, saline or pirenzepine (10, 25, 50 and 100 nmol), a muscarinic M-1 receptor antagonist, was injected intracerebroventricularly 1 h before the electrical stimulation. In the second group of experiments, rats were kindled to full stage 5 seizures. After a recovery period, 50 nmol of pirenzepine was administered intracerebroventricularly to kindled animals. In the first group of experiments, none of the animals pretreated with the doses of 50 and 100 nmol of pirenzepine reached a stage 5 seizure. Pirenzepine significantly retarded kindling seizure development and increased the total number of stimulations required to reach the first stage 5 seizure. Afterdischarge duration was also reduced in the pirenzepine 10 nmol group as compared with that in the saline-pretreated group. In the second group, seizure stage and afterdischarge duration were not affected by pirenzepine in fully-kindled animals. The findings of this study suggest that muscarinic M-1 receptors may have a critical role in the development of kindling epileptic activity, but not in already kindled seizures. (C) 1999 Elsevier Science B.V. All rights reserved
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