Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510150165500
J. Mares, W. Nie, G. Boulon
Cr 3+ multisites, Cr 3+ →Nd 3+ energy transfer and spectroscopic properties of Cr 3+ codoped YAG:Nd and YAP:Nd crystals have been studied in detail. As in YAG:Cr, several multisites have been observed in YAP:Cr crystals. The Cr 3+ →Nd 3+ energy transfer is slightly more efficient in YAP:Nd, Cr than in YAG:Nd, Cr On etudie en detail les proprietes spectroscopiques, la presence de multisites relatifs a l'ion Cr 3+ et les transferts d'energie entre les ions Cr 3+ et Nd 3+ dans des cristaux lasers du type YAG:Nd et YAP:Nd. Comme pour le cristal YAG:Cr, plusieurs multisites ont en effet ete mis en evidence avec YAP:Cr. Le transfert d'energie Cr 3+ →Nd 3+ est un peu plus efficace avec YAP:Cr, Nd qu'avec YAG:Cr, Nd
{"title":"Multisites and energy transfer in Cr3+-Nd3+ codoped Y3Al5O12 and YAlO3 laser crystals","authors":"J. Mares, W. Nie, G. Boulon","doi":"10.1051/JPHYS:0199000510150165500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510150165500","url":null,"abstract":"Cr 3+ multisites, Cr 3+ →Nd 3+ energy transfer and spectroscopic properties of Cr 3+ codoped YAG:Nd and YAP:Nd crystals have been studied in detail. As in YAG:Cr, several multisites have been observed in YAP:Cr crystals. The Cr 3+ →Nd 3+ energy transfer is slightly more efficient in YAP:Nd, Cr than in YAG:Nd, Cr On etudie en detail les proprietes spectroscopiques, la presence de multisites relatifs a l'ion Cr 3+ et les transferts d'energie entre les ions Cr 3+ et Nd 3+ dans des cristaux lasers du type YAG:Nd et YAP:Nd. Comme pour le cristal YAG:Cr, plusieurs multisites ont en effet ete mis en evidence avec YAP:Cr. Le transfert d'energie Cr 3+ →Nd 3+ est un peu plus efficace avec YAP:Cr, Nd qu'avec YAG:Cr, Nd","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"96 1","pages":"1655-1669"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78054084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510150163300
D. Domínguez, C. Wiecko
The equation of motion for the wave function of the 1-d Aubry model is analyzed through a 3-d map which couples the modulation parameter γ and the integrated density of states k. Numerical results are presented for constant γ and k for energy E=0 as a function of the potential strength V. The localization transition is found at V=2 as the disappearance of a well defined curve into a cloud of points. The curves grow in complexity when approaching the critical value from below. We define a mean radius for the xy-plane projection of the 3-d map and we show numerically that it converges to a finite constant for V L'equation de mouvement pour le modele d'Aubry unidimensionnel est etudiee a l'aide d'une application 3-d qui couple le parametre de modulation γ avec la densite d'etats integree k. Nous presentons des resultats numeriques pour l'energie E=0 et pour γ et k constants en fonction du potentiel V. Pour V=2 la transition de localisation se manifeste par le passage d'une courbe bien definie a un nuage de points. La complexite des courbes augmente lorsqu'on approche par en dessous la valeur critique. Nous definissons un rayon moyen pour la projection sur le plan x-y de l'application 3-d et nous montrons numeriquement qu'il converge vers une constante finie pour V<2. D'autre part, son comportement critique est analyse pour un γ egal au nombre d'or. Finalement, nous discutons des resultats anterieurs sur la chaine desordonnee
通过耦合调制参数γ和状态积分密度k的三维映射，分析了一维Aubry模型波函数的运动方程。给出了能量E=0时恒定γ和k作为势强度V的函数的数值结果。在V=2处发现了局域化跃迁，即一条定义良好的曲线消失在点云中。当从下面接近临界值时，曲线的复杂性增加。我们定义了一个平均半径xy平面投影的三维地图,我们显示数值收敛于一个有限的常数de所属的倒V等式模型d 'Aubry unidimensionnel est学习一个应用3 d, L 'aide夫妇用拉三硝基甲苯炸药量de调制γd政变integree k。常识presentons结果numeriques倒L 'energie E = 0等倒γ等k常数与du potentiel诉倒V = 2拉过渡de本地化se manifeste par勒杜恩已经定义了一个联合国语言点。复杂的courbes增强了价值批判的方法。在平面x-y投影的情况下，三维空间的数值定义将收敛于V<2的恒定有限值。第四部分，对行为的批判与分析。最后，我们进行了大量的讨论，结果导致了我们的连锁反应
{"title":"The localization transition in the Aubry model through maps","authors":"D. Domínguez, C. Wiecko","doi":"10.1051/JPHYS:0199000510150163300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510150163300","url":null,"abstract":"The equation of motion for the wave function of the 1-d Aubry model is analyzed through a 3-d map which couples the modulation parameter γ and the integrated density of states k. Numerical results are presented for constant γ and k for energy E=0 as a function of the potential strength V. The localization transition is found at V=2 as the disappearance of a well defined curve into a cloud of points. The curves grow in complexity when approaching the critical value from below. We define a mean radius for the xy-plane projection of the 3-d map and we show numerically that it converges to a finite constant for V L'equation de mouvement pour le modele d'Aubry unidimensionnel est etudiee a l'aide d'une application 3-d qui couple le parametre de modulation γ avec la densite d'etats integree k. Nous presentons des resultats numeriques pour l'energie E=0 et pour γ et k constants en fonction du potentiel V. Pour V=2 la transition de localisation se manifeste par le passage d'une courbe bien definie a un nuage de points. La complexite des courbes augmente lorsqu'on approche par en dessous la valeur critique. Nous definissons un rayon moyen pour la projection sur le plan x-y de l'application 3-d et nous montrons numeriquement qu'il converge vers une constante finie pour V<2. D'autre part, son comportement critique est analyse pour un γ egal au nombre d'or. Finalement, nous discutons des resultats anterieurs sur la chaine desordonnee","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"6 1","pages":"1633-1643"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87267288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160176900
I. S. Gersht, V. Pershin
Terms nonlinear with respect to the wave vector at translational oscillation frequencies have been taken into account for a layer system of uniaxial molecules and it has been proved that crystal order can coexist with a shear instability. On this basis a new model of smectic B phase has been proposed where the structure possessed long range translational order in all directions. At the same time interlayer dynamical shear modulus decreases at lower ω ap frequencies of an applied strain and equals zero in the static case (ω ap →0)
{"title":"Smectic B : long range translational order and static shear instability. Nonlinear effects","authors":"I. S. Gersht, V. Pershin","doi":"10.1051/JPHYS:0199000510160176900","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160176900","url":null,"abstract":"Terms nonlinear with respect to the wave vector at translational oscillation frequencies have been taken into account for a layer system of uniaxial molecules and it has been proved that crystal order can coexist with a shear instability. On this basis a new model of smectic B phase has been proposed where the structure possessed long range translational order in all directions. At the same time interlayer dynamical shear modulus decreases at lower ω ap frequencies of an applied strain and equals zero in the static case (ω ap →0)","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"44 1","pages":"1769-1776"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88140827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160175900
K. Nishinari, S. Koide, Peter A. Williams, G. Phillips
Le modele propose permet de simuler les endothermes observes en DSC lors de la transition gel-sol si la liberte rotationnelle des liaisons, l'energie de liaison et le nombre de liaisons dans les gels sont correctement choisis. Le modele est applique a des gels de poly(vinyl alcool), de carraghenane et de melange carraghenane-glucomannane
{"title":"A zipper model approach to the thermoreversible gel-sol transition","authors":"K. Nishinari, S. Koide, Peter A. Williams, G. Phillips","doi":"10.1051/JPHYS:0199000510160175900","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160175900","url":null,"abstract":"Le modele propose permet de simuler les endothermes observes en DSC lors de la transition gel-sol si la liberte rotationnelle des liaisons, l'energie de liaison et le nombre de liaisons dans les gels sont correctement choisis. Le modele est applique a des gels de poly(vinyl alcool), de carraghenane et de melange carraghenane-glucomannane","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"4 1","pages":"1759-1768"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87509936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160170300
P. Ribière, P. Oswald
We have studied the behavior of a cholesteric liquid crystal sandwiched between two plates, with homeotropic anchoring, in the presence of an electric field. By changing two control parameters, namely the sample thickness and the electric field magnitude, we were able to characterize different types of solutions: a nematic phase (unwound cholesteric), isolated doubly twisted fingers, a periodic pattern of fingers arranged side by side, and a transient singly twisted translationally invariant configuration. Including the electric field contribution to the calculations of reference [3], we have computed a theoretical phase diagram that agrees well with the experimental data. The consideration of anisotropic elasticity in our calculations was essential in explaining our observations
{"title":"Nucleation and growth of cholesteric fingers under electric field","authors":"P. Ribière, P. Oswald","doi":"10.1051/JPHYS:0199000510160170300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160170300","url":null,"abstract":"We have studied the behavior of a cholesteric liquid crystal sandwiched between two plates, with homeotropic anchoring, in the presence of an electric field. By changing two control parameters, namely the sample thickness and the electric field magnitude, we were able to characterize different types of solutions: a nematic phase (unwound cholesteric), isolated doubly twisted fingers, a periodic pattern of fingers arranged side by side, and a transient singly twisted translationally invariant configuration. Including the electric field contribution to the calculations of reference [3], we have computed a theoretical phase diagram that agrees well with the experimental data. The consideration of anisotropic elasticity in our calculations was essential in explaining our observations","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"88 1","pages":"1703-1720"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90669173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160168300
J. Carton, L. Leibler
We define local order parameters to take into account the orientation of monomers and molecules in polymer systems. These fields are naturally coupled to density gradients. Such couplings lead to interesting effects in the neighbourhood of interfaces (polymer-solvent and polymer-polymer cases are considered): macromolecules are prolate on one side, oblate on the other
{"title":"Density-conformation coupling in macromolecular systems: polymer interfaces","authors":"J. Carton, L. Leibler","doi":"10.1051/JPHYS:0199000510160168300","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160168300","url":null,"abstract":"We define local order parameters to take into account the orientation of monomers and molecules in polymer systems. These fields are naturally coupled to density gradients. Such couplings lead to interesting effects in the neighbourhood of interfaces (polymer-solvent and polymer-polymer cases are considered): macromolecules are prolate on one side, oblate on the other","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"103 1","pages":"1683-1691"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80641391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510150159500
G. Parisi
In this note we study directed polymers in a two dimensional random medium with short range noise using the replica approach. We find the predictions of the replica symmetric theory and we compare them with exact results. We consider the possibility of spontaneous symmetry breaking and we suggest that replica symmetry is weakly broken also in this two dimensional model
{"title":"On the replica approach to random directed polymers in two dimensions","authors":"G. Parisi","doi":"10.1051/JPHYS:0199000510150159500","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510150159500","url":null,"abstract":"In this note we study directed polymers in a two dimensional random medium with short range noise using the replica approach. We find the predictions of the replica symmetric theory and we compare them with exact results. We consider the possibility of spontaneous symmetry breaking and we suggest that replica symmetry is weakly broken also in this two dimensional model","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"5 1","pages":"1595-1606"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80069439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160167100
B. Thudic, J. Gallier, M. Boumaza, H. Cailleau
The neutral to ionic transition of tetrathiafulvalene-p-chloranil is studied by nuclear magnetic resonance. Whereas the second moment of the 1 H resonance line is not appreciably sensitive to this phase transition, because no large amplitude motions are concerned, the proton spin-lattice relaxation time T 1 presents an obvious discontinuity at T N−I . This behaviour is discussed in terms of the created paramagnetic species related to the dimerization in the ionic phase Nous presentons une etude par RMN de la transition neutre-ionique du tetrathiafulvalene-p-chloranile. Alors que le second moment de la raie de resonance du proton n'est pas sensiblement affecte par cette transition de phase ne concernant pas de mouvement de grandes amplitudes, le temps de relaxation spin-reseau presente une nette discontinuite a T N−I . Ce comportement est discute en considerant les centres paramagnetiques crees en relation avec la dimerisation de la phase ionique
用核磁共振技术研究了四硫丁烯-对氯胺的中性向离子转变。而H共振线的第二矩对这种相变并不敏感，因为不涉及大振幅运动，质子自旋-晶格弛豫时间t1在T N−I处表现出明显的不连续。这种行为是根据与离子相中二聚化有关的产生的顺磁物质来讨论的。Nous表示一种过渡中性离子，即四噻吩-对氯苯胺。二次矩de la raie号那么质子共振du不sensiblement affecte这个过渡de阶段不concernant de所属的大的振幅,le temps de放松spin-reseau介绍一个nette discontinuite T n−我。考虑到双中心、顺磁性、二聚相和离子的关系，对其性能进行了讨论
{"title":"Proton spin-lattice relaxation study of the neutral-to-ionic transition in TTF-chloranil","authors":"B. Thudic, J. Gallier, M. Boumaza, H. Cailleau","doi":"10.1051/JPHYS:0199000510160167100","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160167100","url":null,"abstract":"The neutral to ionic transition of tetrathiafulvalene-p-chloranil is studied by nuclear magnetic resonance. Whereas the second moment of the 1 H resonance line is not appreciably sensitive to this phase transition, because no large amplitude motions are concerned, the proton spin-lattice relaxation time T 1 presents an obvious discontinuity at T N−I . This behaviour is discussed in terms of the created paramagnetic species related to the dimerization in the ionic phase Nous presentons une etude par RMN de la transition neutre-ionique du tetrathiafulvalene-p-chloranile. Alors que le second moment de la raie de resonance du proton n'est pas sensiblement affecte par cette transition de phase ne concernant pas de mouvement de grandes amplitudes, le temps de relaxation spin-reseau presente une nette discontinuite a T N−I . Ce comportement est discute en considerant les centres paramagnetiques crees en relation avec la dimerisation de la phase ionique","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"22 1","pages":"1671-1678"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78833438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160167900
A. Baumgärtner, B. Chakrabarti
Self-avoiding polymer chains trapped in annealed random media have been investigated by Monte Carlo methods. It is found that the configurational characteristics of a polymer are not affected by the media and are independent of the concentration of the impurities. This is in agreement with an early conjecture, but in disagreement with recent analytical results
{"title":"Polymer chain in annealed random media","authors":"A. Baumgärtner, B. Chakrabarti","doi":"10.1051/JPHYS:0199000510160167900","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160167900","url":null,"abstract":"Self-avoiding polymer chains trapped in annealed random media have been investigated by Monte Carlo methods. It is found that the configurational characteristics of a polymer are not affected by the media and are independent of the concentration of the impurities. This is in agreement with an early conjecture, but in disagreement with recent analytical results","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"108 1","pages":"1679-1682"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76274008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1990-08-01DOI: 10.1051/JPHYS:0199000510160174900
Cheng-Cher Huang, T. Min, Deng-Sung Lin, B. Zhou, J. Goodby
Temperature variations of heat capacity, optical tilt angle, polarization, and helical pitch have been measured in the vicinity of the smectic-A (SmA)-chiral-smectic-C (SmC*) transition of one liquid-crystal compound which exhibits an unusual reversal behavior in polarization at about 25°C while the SmA-SmC* transition occurs at 50°C. Unexpectedly, from our detailed calorimetric and optical microscopy studies, we have found that the recrystallization also occurs around 25°C during a reasonably slow cooling experimental run
在一种液晶化合物的smic - a (SmA)-手性- smic -C (SmC*)转变附近，测量了热容量、光学倾斜角、极化和螺旋节距的温度变化，该化合物在约25℃时表现出不寻常的极化反转行为，而SmA-SmC*转变发生在50℃。出乎意料的是，从我们详细的量热和光学显微镜研究中，我们发现在相当缓慢的冷却实验运行中，再结晶也发生在25°C左右
{"title":"Electro-optical and thermal studies of one ferroelectric liquid-crystal compound with a polarization sign reversal","authors":"Cheng-Cher Huang, T. Min, Deng-Sung Lin, B. Zhou, J. Goodby","doi":"10.1051/JPHYS:0199000510160174900","DOIUrl":"https://doi.org/10.1051/JPHYS:0199000510160174900","url":null,"abstract":"Temperature variations of heat capacity, optical tilt angle, polarization, and helical pitch have been measured in the vicinity of the smectic-A (SmA)-chiral-smectic-C (SmC*) transition of one liquid-crystal compound which exhibits an unusual reversal behavior in polarization at about 25°C while the SmA-SmC* transition occurs at 50°C. Unexpectedly, from our detailed calorimetric and optical microscopy studies, we have found that the recrystallization also occurs around 25°C during a reasonably slow cooling experimental run","PeriodicalId":14747,"journal":{"name":"Journal De Physique","volume":"20 1","pages":"1749-1757"},"PeriodicalIF":0.0,"publicationDate":"1990-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83312750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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