How the cucumber tendril coils and overwinds     

SJ Gerbode  JR Puzey  AG McCormick  L Mahadevan 《Science (New York, N.Y.)》2012,337(6098):1087-1091

The helical coiling of plant tendrils has fascinated scientists for centuries, yet the underlying mechanism remains elusive. Moreover, despite Darwin's widely accepted interpretation of coiled tendrils as soft springs, their mechanical behavior remains unknown. Our experiments on cucumber tendrils demonstrate that tendril coiling occurs via asymmetric contraction of an internal fiber ribbon of specialized cells. Under tension, both extracted fiber ribbons and old tendrils exhibit twistless overwinding rather than unwinding, with an initially soft response followed by strong strain-stiffening at large extensions. We explain this behavior using physical models of prestrained rubber strips, geometric arguments, and mathematical models of elastic filaments. Collectively, our study illuminates the origin of tendril coiling, quantifies Darwin's original proposal, and suggests designs for biomimetic twistless springs with tunable mechanical responses.  相似文献   

Night-time sap flow is parabolically linked to midday water potential for field-grown almond trees     

S. Fuentes  M. Mahadevan  M. Bonada  M. A. Skewes  J. W. Cox 《Irrigation Science》2013,31(6):1265-1276

To quantify night-time (S _n) and diurnal (S _d) tree water uptake, two sets of sap flow sensors (heat-pulse compensated) were installed per tree in the north-east and south-west sides of the trunk in three trees per treatment. There were two treatments: (1) control, irrigated with 100 % ETc (T₁₀₀), and (2) deficit, irrigated at 60 % ETc (T₆₀) with daily irrigations at the peak atmospheric demand (December–January). Normalised S _n by trees was in the range of 15–25 % throughout the season, compared to normalised S _d, for T₁₀₀ and T₆₀, respectively. Furthermore, S _n was parabolically correlated to plant water status from the previous day, measured as midday stem water potential. We also found strong correlations between S _n and nocturnal vapour pressure deficit for T₁₀₀ and T₆₀, indicating that nocturnal transpiration was significant for both treatments. Differences in S _n were observed for the NE and SW sensors for T₆₀, being significantly less for the NE side (sunny side) compared to the SW side (more shaded). No differences were observed for T₁₀₀ regarding probe positioning.  相似文献   

Efficacy of Liriope platyphylla on Hematology and Immune Response in Olive Flounder,Paralichthys olivaceus,Against Flexibacter maritimus Infection     

Ramasamy Harikrishnan  Ju‐Sang Kim  Man‐Chul Kim  Moon‐Soo Heo  Chellam Balasundaram 《Journal of the World Aquaculture Society》2012,43(2):259-269

The effect of different solvent‐based (methanol, ethanol, and aqueous) extracts of Liriope platyphylla at 0, 0.1, 1.0, and 2.0 mg doses on hematology and innate immune response in olive flounder, Paralichthys olivaceus, against Flexibacter maritimus is reported. The red blood cells and white blood cells significantly increased with ethanol and aqueous extracts with any dose against F. maritimus while the hematocrit level significantly increased with methanol or ethanol extracts. However, the hemoglobin content significantly increased irrespective of the doses and type of extracts, whereas the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration significantly decreased. The lymphocytes and monocytes significantly increased in all doses and extracts, whereas neutrophils increased in ethanol or aqueous extracts. However, the thrombocytes level neither the doses nor extracts did not significant changes to the control against pathogen. Total protein and globulin levels significantly increased with all the doses of ethanol extract while does not significant change in methanol extract. The phagocytic activity and complement activity were significantly enhanced with any dose of ethanol extract while with aqueous extract it was only at 1.0 and 2.0 mg doses. At all the doses of each extract significantly enhanced the leucocytes activity against F. maritimus. The results confirm that the ethanolic and aqueous extracts of L. platyphylla stimulate the immune response against F. maritimus in P. olivaceus.  相似文献   

Eddy-driven stratification initiates North Atlantic spring phytoplankton blooms     

A Mahadevan  E D'Asaro  C Lee  MJ Perry 《Science (New York, N.Y.)》2012,337(6090):54-58

Springtime phytoplankton blooms photosynthetically fix carbon and export it from the surface ocean at globally important rates. These blooms are triggered by increased light exposure of the phytoplankton due to both seasonal light increase and the development of a near-surface vertical density gradient (stratification) that inhibits vertical mixing of the phytoplankton. Classically and in current climate models, that stratification is ascribed to a springtime warming of the sea surface. Here, using observations from the subpolar North Atlantic and a three-dimensional biophysical model, we show that the initial stratification and resulting bloom are instead caused by eddy-driven slumping of the basin-scale north-south density gradient, resulting in a patchy bloom beginning 20 to 30 days earlier than would occur by warming.  相似文献   

In vitro and in vivo studies of the use of some medicinal herbals against the pathogen Aeromonas hydrophila in goldfish     

Harikrishnan R  Balasundaram C 《Journal of aquatic animal health》2008,20(3):165-176

Aeromonas hydrophila is a ubiquitous and opportunistic bacterial pathogen that produces ulcerative dermatitis under stress conditions and inflicts severe losses on global fisheries and fish culture. This study evaluates the antimicrobial potency of aqueous and ethanolic decoction (individual extract) and concoction (mixed extract) of three common medicinal herbs, turmeric Curcuma longa, Tulsi plant Ocimum sanctum, and neem Azadirachta indica, against the in vitro growth of A. hydrophila. Among the decoctions, A. indica exhibited the most potent antibacterial property (P < 0.05) against A. hydrophila. Among the concoctions, both the aqueous and ethanolic triherbal extracts mixed in the ratio of 1:1:1 had higher antibacterial activity (P < 0.05) than the other concoctions and decoctions. Goldfish Carassius auratus (10 +/- 2 g) were challenged with A. hydrophila intramuscularly in the caudal region with two separate doses (days 1 and 3) of 50 microL/fish (1.8 x 10(3) colony-forming units per milliliter). On days 9 (early) and 15 (late) of infection, fish were held in a net and dip treated for 5 min daily in a 1-L solution of 1% aqueous triherbal concoction. Red blood cell (RBC) count, hemoglobin, and hematocrit levels of the infected group were significantly higher (P < 0.05) than those of the control group. In the early treated group, all of the affected profile values returned to near normal, while the late-treated group registered a partial recovery, such as improved RBC count. The derived hematological values, such as mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration, of the early and late-treated groups also significantly declined (P < 0.05) but were restored to near normal (P > 0.05) only in the early treated group. The results suggest that dip treatment of A. hydrophila-infected goldfish in an aqueous triherbal concoction had a synergistic restorative effect on the hematological variables.  相似文献   

Chemical composition and nutritive value of Bijada cake (Citrulus vulgaris)     

R N Pal  V Mahadevan 《The Indian veterinary journal》1968,45(5):433-439

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'Spent aniseed' (Pimpenella anisum) as a cattle feed     

K Nath  O N Agarwala  V Mahadevan 《The Indian veterinary journal》1966,43(10):908-912

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The levels of some minerals in the sera of growing buffalo calves     

A R Rao  D N Mullick  V Mahadevan 《The Indian veterinary journal》1966,43(1):55-60

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Elastic behavior of cross-linked and bundled actin networks     

Gardel ML  Shin JH  MacKintosh FC  Mahadevan L  Matsudaira P  Weitz DA 《Science (New York, N.Y.)》2004,304(5675):1301-1305

Networks of cross-linked and bundled actin filaments are ubiquitous in the cellular cytoskeleton, but their elasticity remains poorly understood. We show that these networks exhibit exceptional elastic behavior that reflects the mechanical properties of individual filaments. There are two distinct regimes of elasticity, one reflecting bending of single filaments and a second reflecting stretching of entropic fluctuations of filament length. The mechanical stiffness can vary by several decades with small changes in cross-link concentration, and can increase markedly upon application of external stress. We parameterize the full range of behavior in a state diagram and elucidate its origin with a robust model.  相似文献   

Effect of a mixed herb-enriched diet on the innate immune response and disease resistance of Paralichthys olivaceus against Philasterides dicentrarchi infection     

Harikrishnan R  Balasundaram C  Kim MC  Kim JS  Han YJ  Heo MS 《Journal of aquatic animal health》2010,22(4):235-243

We investigated the effect of a mixed herb-enriched diet obtained from pomegranate Punica granatum, Dalmatian chrysanthemum Chrysanthemum cinerariaefolium, and mastic-leaved prickly-ash Zanthoxylum schinifolium on innate immune mechanisms (e.g., phagocytosis activity, respiratory burst activity, alternative complement activity, lysozyme activity, and disease resistance) of olive flounder Paralichthys olivaceus against the scuticociliate Philasterides dicentrarchi. All experimental groups were challenged with P. dicentrarchi (1 x 10(5) ciliates/mL) through intraperitoneal administration of the pathogen (50 microL) on day 1. On day 7, the infected groups were fed 0, 5, 50, and 100 mg/kg of the enriched diets. The innate immune parameters, cumulative mortality, and relative percent survival (RPS) were assessed at weeks 1, 2, 3, and 4. Administration of 50 or 100 mg/kg of the herbal-enriched diet enhanced immunity throughout the experimental period. However, at the 5-mg/kg dosage, the enriched diet did not enhance the innate immune estimates at any time. At doses of 50 and 100 mg/kg, administration of the diet preceding the challenge with P. dicentrarchi decreased the percentage cumulative mortality in the experimental groups and thereby increased RPS values. This study reports that administration of 50 or 100 mg/kg mixed herbal-enriched diet could positively influence the innate immune response to P. dicentrarchi and enhance the health status of olive flounder with respect to this microbe.  相似文献