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We performed a combination of experiments and mechanical simulations to assess the importance of cell geometry and wall structure in tissue and cell mechanics. Osmotic treatments combined with live imaging were used to quantify deformations at the tissue, cellular, and subcellular levels. We used the adaxial epidermis of onion scale as a model system. We found that the osmotically induced surface strain in onion is small because outer periclinal walls are thick and stiff, requiring bending stiffness to be considered in our mechanical models. As expected, the mechanical behaviors of the tissue and its component cells are related. Upon changes in internal pressure, cells embedded in the tissue undergo deformation that is different from isolated cells, while the tissue undergoes a somewhat counterintuitive deformation, e.g., shrinking upon pressurization, that depends on cell geometry. At the subcellular level, the amount of deformation and its anisotropy vary within the walls of individual cells, and are affected by the cell shape and vicinity of three-way wall junctions. When the turgor pressure is lost, the protoplast-facing wall surface wrinkles due to buckling, with the pattern of wrinkles depending on the strain anisotropy and the local wall geometry. Key words: cell wall buckling, cell wall curvature and strain, mechanical model, onion epidermis, osmotic treatment. Les auteurs ont realise une combinaison d'experiences et de simulations mecaniques pour evaluer l'importance de la geometrie et de la structure de la paroi des cellules dans la mecanique cellulaire et tissulaire. Des traitements osmotiques combines a l'imagerie ven temps reel ont ete utilises pour quantifier les deformations aux niveaux tissulaire, cellulaire et subcellulaire. Ils ont utilise, comme systeme modele, l'epiderme adaxial de l'ecaille de l'oignon. Ils ont trouve que la deformation de la surface induite de maniere osmotique chez l'oignon est petite, car les parois externes periclinales sont epaisses et rigides, necessitant une rigidite mecanique pour etre prises en compte dans leurs modeles mecaniques. Comme prevu, les comportements mecaniques du tissu et de ses cellules constituantes sont relies. En fonction des changements de pression interne, les cellules integrees dans le tissu subissent une deformation differente de celle des cellules isolees, alors que le tissu subit une deformation quelque peu contre-intuitive, c'est-a-dire un retrecissement en fonction de la pressurisation qui depend de la geometrie cellulaire. A l'echelle subcellulaire, l'amplitude de la deformation et son anisotropie varient a l'interieur des parois des cellules individuelles et elles sont affectees par la forme de la cellule et la proximite de jonctions tripartites de la paroi. Lorsque la pression de la turgescence est perdue, la surface de la paroi qui fait face au protoplaste se ride a cause de la deformation, le patron des rides dependant de l'anisotropie de la deformation et la geometrie locale de la paroi. Mots-cles : deformation de la paroi cellulaire, deformation et courbure de la paroi cellulaire, modele mecanique, epiderme de l'oignon, traitement osmotique., Introduction Walls of living plant cells are under considerable stress that originates from the turgor pressure within, which is a result of the higher osmotic potential in the protoplast compared [...]

Elbrusite-(Zr) [Ca.sub.3]([U.sup.6+]Zr)([Fe.sup.3+.sub.2] [Fe.sup.2+])[O.sub.12], a new uranian garnet (Ia[bar.3]d, a [approximately equal to] 12.55 [Angstrom], V [approximately equal to] 1977 [[Angstrom].sup.3], Z= 8), within the complex solid solution elbmsite-kimzeyite-toturite [Ca.sub.3][(U,Zr, Sn, Ti, Sb, Sc, Nb ...).sub.2] [(Fe,Al,Si,Ti).sub.3] [O.sub.12] was discovered in spurrite zones in skarn xenoliths of the Upper Chegem caldera. The empirical formula of holotype elbrusite-(Zr) with 25.14 wt% U[O.sub.3] is [([Ca.sub.3.040][Th.sub.0.018][Y.sub.0.001]).sub.[summation]3.059] [([U.sup.6+.sub.0.658][Zr.sub.1.040][Sn.sub.0.230] [Hf.sub.0.009][Mg.sub.0.004]).sub.[summation]1.941] [([Fe.sup.3+.sub.1.575][Fe.sup.2+.sub.0.559][Al.sub.0.539] [Ti.sup.4+.sub.0.199][Si.sub.0.099][Sn.sub.0.025] [V.sup.5+.sub.0.004]).sub.[summation]3][O.sub.12]. Associated minerals are spurrite, rondorfite, wadalite, kimzeyite, perovskite, lakargiite, ellestadite-(OH), hillebrandite, afwillite, hydrocalumite, ettringite group minerals, and hydrogrossular. Elbrusite-(Zr) forms grains up to 10-15 [micro]m in size with dominant {110} and minor {211} forms. It often occurs as zones and spots within [Fe.sup.3+]-dominant kimzeyite crystals up to 20-30 [micro]m in size. The mineral is dark-brown to black with a brown streak. The density calculated on the basis of the empirical formula is 4.801 g/[cm.sup.3] The following broad bands are observed in the Raman spectra of elbrusite-(Zr): 730, 478, 273,222, and 135 [cm.sup.-1]. Elbrusite-(Zr) is radioactive and nearly completely metamict. The calculated cumulative dose ([alpha]-decay events/mg) of the studied garnets varies from 2.50 x [10.sup.14] [is equivalent to 0.04 displacement per atom (dpa)] for uranian kimzeyite (3.36 wt% U[O.sub.3]), up to 2.05 x [10.sup.15] (0.40 dpa) for elbrusite-(Zr) with 27.09 wt% U[O.sub.3]. Keywords: Elbrusite-(Zr), new garnet, uranium, solid solution, metamictization, Raman spectroscopy, EBSD, Upper Chegem caldera DOI: 10.2138/am.2010.3507

A new Sn-rich garnet, toturite [Ca.sub.3][Sn.sub.2][Fe.sub.2]Si[O.sub.12], occurs as an accessory mineral in high- temperature altered carbonate-silicate xenoliths in ignimbrite of the Upper Chegem structure in the Northern Caucasus, Kabardino-Balkaria, Russia. The empirical formula of toturite from the holotype sample is ([Ca.sub.2.989][Fe.sup.2+.sub.0.011])[summation]3 ([Sn.sup.4+.sub.1.463][Sb.sup.5+.sub.0.325][Ti.sup.4+.sub.0.193] [Zr.sub.0.013][Mg.sub.0.003][Nb.sup.5+.sub.0.002] [Cr.sub.0.001])[summation]2(Fe.sup.3+.sub.1.633][Al.sub.0.609][Si.sub. 0.552][Ti.sup.4+.sub.0.166][Fe.sup.2+.sub.0.039][V.sup.5+.sub.0.001]) [summation]3[O.sub.12]. The mineral forms thin regular growth zones and irregular spots in the [Fe.sup.3+]-dominant analog of kimzeyite. Toturite is cubic, Ia[bar.3]d, a [approximately equal to] 12.55 [Angstrom], as is confirmed by electron backscatter diffraction (EBSD) data. The strongest lines of the calculated powder diffraction pattern are [d, [Angstrom] (hkl)/]: 2.562 (422) 100, 1.677 (642) 91, 3.138 (400) 74, 4.437 (220) 67, 1.146 (10.4.2) 31, 1.046 (884) 25, 1.984 (620) 23. Raman spectra of toturite are analogous to those of kimzeyite and shows the following diagnostic bands ([cm.sup.-1]): 244, 301,494, 497, 575, 734. The association of toturite with larnite, rondorfite, wadalite, magnesioferrite, lakargiite, and cuspidine indicates a high temperature (>800 [degrees]C) of formation. The mineral name is given after the Totur River situated in Eltyubyu village, also Totur is the name of a Balkarian god. Keywords: Garnet, toturite, [Fe.sup.3+]-dominant analog of kimzeyite, Sn, Sb, Raman spectroscopy, EBSD, Lakargi Mountain, Russia DOI: 10.2138/am.2010.3421

Two new antimonian garnets--bitikleite-(SnAl) [Ca.sub.3]SbSn[Al.sub.3][O.sub.12] and bitikleite-(ZrFe) [Ca.sub.3]SbZr[Fe.sub.3][O.sub.12]--have been found as accessory minerals in the cuspidine zone of high-temperature skarns in a carbonate-silicate xenolith at the contact with ignimbrites within the Upper Chegem structure in the Northern Caucasus, Kabardino-Balkaria, Russia. The bitikleite series forms a solid solution with garnets of the kimzeyite-schorlomite and toturite type. Antimony-garnets form crystals up to 50 [micro]m across containing kimzeyite cores and thin subsequent zones of complex lakargiite-tazheranite-kimzeyite pseudomorphs after zircon. Bitikleite-(SnAl) has a = 12.5240(2) [Angstrom], V = 1964.40(3) [[Angstrom].sup.3] and bitikleite-(ZrFe) has a = 12.49 [Angstrom], V = 1948.4 [[Angstrom].sup.3] (la[bar.3]d, Z = 8). The strongest powder diffraction lines of bitikleite-(SnAl) are [d, [Angstrom] (hkl)]: 4.407 (220), 3.118 (440), 2.789 (420), 2.546 (422), 1.973 (620), 1.732 (640), 1.668 (642), and 1.396 (840). The strongest calculated powder diffraction lines of bitikleite-(ZrFe) are [d, [Angstrom] (hkl)]: 4.416 (220), 3.123 (440), 2.793 (420), 2.550 (422), 1.975 (620), 1.732 (640), 1.669 (642), and 1.396 (840). The Raman spectra of bitikleite garnets are similar to the spectra of kimzeyite and toturite. Larnite, rondorfite, wadalite, magnesioferrite, tazheranite, lakargiite, kimzeyite, and toturite associated with bitikleite garnets are typical of high-temperature (>800[degrees]C) formation. Keywords: Bitikleite-(SnAl), bitikleite-(ZrFe), new garnet, antimony, solid solution, single-crystal diffraction, Raman spectroscopy, Caucasus DOI: 10.2138/am.2010.3458

Kumtyubeite, [Ca.sub.5][(Si[O.sub.4]).sub.2][F.sub.2]--the fluorine analog of reinhardbrannsite with a chondrodite-type structure--is a rock-forming mineral found in skarn carbonate-xenoliths in ignimbrites of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northem Caucasus, Russia. The new mineral occurs in spurrite-rondorfite-ellestadite zones of skam. The empirical formula of kumtyubeite from the holotype sample is [Ca.sub.5][([Si.sub.1.99][Ti.sub.0.01]).sub.[integral] 2[O.sub.8][(F.sub.1.39]O[H.sub.0.6]).sub.[integral]. Single-crystal X-ray data were collected for a grain of Cas(Si[O.sub.4])2([F.sub.13]O[H.sub.0.7]) composition, and the structure refmement, including a partially occupied H position, converged to R = 1.56%: monoclinic, space group P[2.sub.1]/a, Z = 2, a = 11.44637(18), b = 5.05135(8), c = 8.85234(13) [Angstrom], [beta] = 108.8625(7)[degrees], V = 484.352(13) [[Angstrom].sup.3] For direct comparison, the structure of reinhardbraunsite Cas(Si[O.sub.4])2(OH1.3F0.7) from the same locality has also been refmed to R = 1.9%, and both symmetry independent, partially occupied H sites were determined: space group P[2.sub.1]/a, Z = 2, C/= 11.4542(2), b = 5.06180(10), c = 8.89170(10) [Angstrom], [beta] = 108.7698(9)[degrees], V = 488.114(14) [[Angstrom].sup.3]. The following main absorption bands were observed in kumtyubeite FTIR spectra ([cm.sup.-1]): 427, 507, 530, 561,638, 779, 865,934, 1113, and 3551. Raman spectra are characterized by the following strong bands ([cm.sup.-1]) at: 281,323, 397 ([v.sub.2]), 547 ([v.sub.4]), 822 ([v.sub.1]), 849 ([v.sub.1]), 901 ([v.sub.3]), 925 ([v.sub.3]), 3553 (VOH). Kumtyubeite with compositions between [Ca.sub.5][(Si[O.sub.1/2]).sub.[sigma]] [F.sub.2] and [Ca.sub.5](Si[O.sub.4])2(O[H.sub.1.0][F.sub.1.0]) has only the hydrogen bond O5-H1 ... F5', whereas reinhardbraunsite with compositions between [Ca.sub.5][(Si[O.sub.4]).sub.2](O[H.sub.1.0][F.sub.1.0]) and [Ca.sub.5][(Si[O.sub.1/4]).sub.2][(OH).sub.2] has the following hydrogen bonds: O5-HI ... F5', O5-HI ... O5', and O5-H2 ... 02. Keywords: Kumtyubeite, new mineral, reinhardbraunsite, crystal structure, chondrodite, composition, Raman, FTIR, Northem Caucasus, Russia

Lakargiite CaZr[O.sub.3]--the zirconium analog of perovskite [Pbnm, a = 5.556(1), b = 5.715(1), c = 7.960(1) [Angstrom], V252.7(1) [[Angstrom].sup.3], Z = 4]--was discovered as an accessory mineral in high-temperature skarns in carbonate-silicate rocks occurring as xenoliths in ignimbrites of the Upper-Chegem (Verkhniy Chegem) volcanic structure, the North Caucasus, Kabardino-Balkaria, Russia. Lakargiite forms pseudo-cubic crystals up to 30-35 [micro]m in size and aggregates up to 200 [micro]m. Lakargiite is associated with spurrite, larnite, calcio-olivine, calcite, cuspidine, rondorfite, reinhardbraunsite, wadalite, perovskite, and minerals of the ellestadite group. The new perovskite mineral belongs to the ternary solid solution CaZr[O.sub.3]-CaTi[O.sub.3]-CaSn[O.sub.3] with a maximum CaZr[O.sub.3] content of ca. 93%, maximum CaTi[O.sub.3] content of 22%, and maximum CaSn[O.sub.3] content of 20%. Significant impurities are Sc, Cr, Fe, Ce, La, Hf, Nb, U, and Th. Raman spectra of lakargiite are similar to those of the synthetic phase Ca(Zr, Ti)[O.sub.3] with strong bands at 352, 437, 446, 554, and 748 [cm.sup.-1]. Lakargiite crystallized under sanidinite-facies conditions of contact metamorphism characterized by very high temperatures and low pressures. Keywards: Lakargiite, perovskite group, solid solution, CaZr[O.sub.3], CaSn[O.sub.3], Raman spectroscopy, skarn, Caucasus

The average structure, space group Pnnm [subcell: A = 5.666(16), B = 18.844(5), C = 3.728(11) [Angstrom], V = 398.0(2) [[Angstrom].sup.3], Z= 1], of the new mineral dovyrenite [Ca.sub.6]Zr[[[Si.sub.2][O.sub.7]].sup.2] [(OH).sub.4] has been refined from single-crystal X-ray data to R = 7.97%. The modular structure of dovyrenite is build by alternate stacking of Ca-polyhedral layers characteristic of the tobermorite structure and octahedral layers with attached disilicate groups known from the rosenbuschite group of minerals. No indications of ordered polytypes were detected for the potential OD-structure. Either the small crystal size producing only weak diffraction intensities did not allow detecting diffuse diffraction features (or 'super-structure' reflections) or the structure is build by disordered stacks of OD layers. Nevertheless, the resolved average structure allowed unraveling the possible order patterns within the rosenbuschite-like octahedral layers. The key for understanding the polytypic character of this structure is the short periodicity of the tobermorite-like Ca polyhedral layer of only 3.73 [Angstrom] along c, whereas the periodicity of the attached rosenbuschite-like octahedral layer is doubled. In dovyrenite Ca occurs in sixfold-, sevenfold-, and eightfold-coordination. The octahedral Ca site is only half occupied and may reveal additional vacancies, which must be charge balanced by disordered OH-groups replacing O. A corresponding modular structure with the same subunits but different composition and without octahedral vacancies exists for rinkite (Ti,Nb,Al,Zr)[(Na,Ca).sub.3] [(Ca,Ce).sub.4][[[Si.sub.2][O.sub.7]].sup.2][(OH).sub.4], which has hitherto been considered as heterophyllosilicate. Keywords: Dovyrenite, zirconosilicates, single-crystal X-ray diffraction, structure solution, modular structure, tobermorite, rinkite, heterophyllosilicate

The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 → S2 transition which could not be determined experimentally. [ABSTRACT FROM AUTHOR]

IR vibrational spectroscopy has been employed to study liquid-liquid phase transitions of trans-1,2-dichloroethylene (TDCE). The temperature dependence of the vibrational frequency, band absorbance, and band broadening has been analyzed in the temperature range of 293–237 K. All peaks show distinct increases in their absorbancies at the temperature of 246.7 K accompanied by a frequency shift and bandwidth changes. Weak H...Cl hydrogen bonding has been suggested as the explanation for the overall behavior in a wide temperature range, whereas the significant changes in the spectrum at 246.7 K are probably due to molecular ordering originating from electrostatic interactions. The transition is well described by the model of the cooperative formation of locally favored structures. [ABSTRACT FROM AUTHOR]