Nonlinear excitations in CsNiF3 in magnetic fields perpendicular to the easy plane

Experimental and numerical studies of the magnetic field dependence of the specific heat and magnetization of single crystals of CsNiF3 have been performed at 2.4 K, 2.9 K, and 4.2 K in magnetic fields up to 9 T oriented perpendicular to the easy plane. The experimental results confirm the presence of the theoretically predicted double peak structure in the specific heat arising from the formation of nonlinear spin modes. The demagnetizing effects are found to be negligible, and the overall agreement between the data and numerical predictions is better than reported for the case when the magnetic field was oriented in the easy plane. Demagnetizing effects might play a role in generating the difference observed between theory and experiment in previous work analyzing the excess specific heat using the sine-Gordon model.Comment: 6 pages, 5 figures, submitted to Phys. Rev.

Flowering of kiwifruit (Actinidia deliciosa) is reduced by long photoperiods

Mature kiwifruit (Actinidia deliciosa ‘Hayward’) vines grown under standard orchard management were exposed to 16-h photoperiods from the longest day in summer until after leaf fall in autumn. Photoperiod extension was achieved with tungsten halogen lamps that produced 2–8 µmols m–2 s–1 photosynthetically active radiation. Long day treatments did not affect fruit dry matter or fruit weight at harvest during the growing season that the treatments were applied or during the following growing season. However, flowering was reduced by 22% during the spring following treatment application. As this reduction in flowering was not accompanied by a decrease in budbreak, the long day effect is not consistent with a delay in the onset of winter chilling. It is suggested therefore, that the observed reduction in flowering may be because of a diminution of floral evocation

Influence of linear and nonlinear excitations in the ferromagnetic S = 1/2 chain system [C6H11NH3]CuBr3 (CHAB)

The magnetic properties of the title compound have been studied by measurements of the nuclear spin-lattice relaxation time T1, the uniform magnetization M, and by quasielastic and inelastic neutron scattering. The field and temperature dependence of T1 and the wave-number dependence of the magnon excitation energy can be satisfactorily described by linear spin-wave theory. A good description of M, however, requires a contribution from kink solitons. The available evidence suggests that, in contrast to the linear excitations, the nonlinear excitations in CHAB for B¿c can be described very well by a classical model, which is consistent with the interpretation of earlier heat-capacity measurements

Cold hardiness and transplant response of Juglans nigra seedlings subjected to alternative storage regimes

$\bullet$ Effects of overwinter storage regimes on seedling cold hardiness and physiological vigor are relatively unexplored, particularly for temperate deciduous forest tree species. $\bullet$ We evaluated influence of storage duration (0, 66, 119, or 175 d) on electrolyte leakage of stem and root collar tissues following exposure to a series of freeze-test temperatures in black walnut (Juglans nigra L.) seedlings sampled from cold (3 °C) or freezer (–2 °C) storage. Seedlings were subsequently transplanted into a controlled growth chamber environment for two months. $\bullet$ Regardless of storage temperature, mean LT$_{50}$ was lowest for seedlings stored for 66 d ($\leq$ –34 °C) and increased dramatically after 119 d ($\geq$ –13 °C). $\bullet$ Root collar tissue had lower LT$_{50}$ than stem tissue after 119 d for cold-stored seedlings, reflecting importance of evaluative tissue type. Days to bud break shortened with increasing storage duration up to 119 d and stabilized thereafter for both storage regimes. Root growth potential was maximized after 119 d of storage, and subsequently declined for cold-stored seedlings. Height growth increased following storage, regardless of duration. $\bullet$ To promote stress resistance and transplant growth response, we recommend that black walnut seedlings from this genetic source be outplanted after approximately 66–119 d of storage.Endurcissement au froid et réponse des semis de Juglans nigra transplantés après exposition à différentes modalités de stockage. $\bullet$ Les effets de différentes modalités de stockage hivernal sur la résistance au froid des semis et sur leur vigueur physiologique ont été relativement inexplorés, en particulier pour les arbres forestiers décidus tempérés. $\bullet$ Nous avons évalué l'influence de la durée de stockage (0, 66, 119 ou 175 jours) sur la perte d'électrolyte de la tige et des tissus du collet racinaire exposés à une série de tests (témoin 4 %C, –10 °C, –20 °C, –40 °C) de température de congélation de semis de noyer noir (Juglans nigra L.), après stockage au froid (3 °C) ou au gel (–2 °C). Les semis étaient ensuite transplantés dans une chambre climatisée pour une durée de deux mois. Indépendamment de la température de stockage, la moyenne de LT50 (température létale correspondant à un endommagement de 50 % des plants) a été plus basse pour les semis stockés pendant 66 jours ($\leq$ –34 °C) et s'est accrue de façon spectaculaire après 119 jours ($\geq$ –13 °C). $\bullet$ Les tissus du collet racinaire avaient un plus bas LT50 que les tissus de la tige, après 119 jours pour les semis stockés au froid, reflétant l'importance du type de tissu pour l'évaluation. Le nombre de jours jusqu'au débourrement a été raccourci avec l'accroissement de la durée de stockage jusqu'à 119 jours et s'est stabilisé par la suite pour les deux modalités de stockage. Le potentiel de croissance racinaire a été maximisé après 119 jours de stockage et a décliné par la suite, pour les semis stockés au froid. La croissance en hauteur s'est accrue à la suite du stockage, indépendamment de sa durée. $\bullet$ Pour promouvoir une résistance élevée au stress et une forte reprise de croissance des semis transplantés, nous recommandons que les semis de noyer noir de cette source génétique soient plantés après approximativement 66 à 119 jours de stockage