Detection and features of wetwood in Quercus mongolica var. grosseserrata

To elucidate the location of water in wetwood, variations in moisture content within a tree of Quercus mongolica var. grosseserrata were observed macroscopically by determination of moisture content and by soft x-ray photography. Then the typical wetwood, which had been precisely located by such macroscopic analysis, was examined further by cryo-scanning electron microscopy. The moisture content varied considerably within the tree trunk, and typical wetwood was detected in limited regions of the heartwood. The distribution of the wetwood did not always correspond to the discoloration of the wood. In the wetwood, almost all the lumina of vessels and fibers were filled with water, while the lumina of ray and axial parenchyma cells were often cavitated. Intercellular spaces produced by deformation of cell walls and radial shakes were filled with water. In addition, tyloses were collapsed and torn in the wetwood, and they did not block the vessel lumina. These results suggest the possibility that vessels and fibers might serve as effective pathways for the accumulation of water in the wetwood.     

Ichnology of an ephemeral lacustrine/alluvial plain system: Jurassic East Berlin Formation,Hartford Basin,USA

A trace fossil assemblage from the Lower Jurassic East Berlin Formation of the Newark Supergroup, Hartford Basin, New England, USA, includes: Scoyenia gracilis, Skolithos ichnosp., Palaeophycus striatus, Planolites montanus, Fuersichnus ichnosp., fusiform burrows, pelleted material, an escape structure, and large burrows.

This assemblage is assigned to the Scoyenia ichnofacies. Specific lebensspuren are not limited to specific lithofacies; instead, their initial distribution seems to have been influenced principally by water availability within an ephemeral lacustrine/alluvial plain system. Other factors in distribution may have included amounts of organic matter, patterns of sedimentation, sediment grain size, biotic factors (settling from invertebrate drift, competition), and additional abiotic factors (wind deflation, waves, currents, desiccation, soft‐sediment deformation, evaporite formation, pedoturbation).

Extreme environmental conditions within the original depositional setting strongly influenced the availability of water which, in turn, strongly influenced the paleoecology of burrowing invertebrates in this nonmarine system.     

Grain size effect on the plastic deformation of nanocrystalline silver

The plastic deformation of nanocrystalline Ag, with columnar grains, has been studied by molecular dynamics simulations. The nanocrystalline systems show two types of deformation mechanisms. One is the split of grain boundary that occurs before the activation of the dislocation in nanocrystalline Ag, and almost no dislocation debris and twins are left in the grains. Moreover, split of grain boundary is shown between the grains of nanocrystalline Ag. Another mechanism consists in partial dislocations dominating the process of plastic deformation. Plenty of stacking faults and twins remain in the grains of nanocrystalline Ag. It is revealed that different grain aspect ratios have induced the difference in deformation mechanisms of nanocrystalline Ag. When the grain aspect ratio is less than or equal to 1, the process of plastic deformation is dominated by partial dislocations. Otherwise, the process is dominated by split of grain boundary. The grain aspect ratio is the height in z direction to length in x direction ratio, which was found to noticeably impact yield strength, grain coarsening, indicating that the observed behaviour should have contributed to the plastic deformation significantly.     

Furrows and firmgrounds: evidence for predation and implications for Palaeozoic substrate evolution in Rusophycus burrows from the Silurian of New York

Tarhan, L.G., Jensen, S. & Droser, M.L. 2011: Furrows and firmgrounds: evidence for predation and implications for Palaeozoic substrate evolution in Rusophycus burrows from the Silurian of New York. Lethaia, Vol. 45, pp. 329–341. The Silurian Herkimer Formation of east‐central New York contains abundant, exceptionally preserved composite Rusophycus‐Teichichnus burrows. We suggest that the most likely interpretation of these composite trace fossils is as structures formed by trilobites entering the sediment in search of prey. Parallel alignment of the paired traces, asymmetrical configuration of the Teichichnus along the longitudinal axis of the associated Rusophycus, depth correlation and deformation of the Teichichnus all suggest that this relationship was predatory. In addition, sectioned material indicates that these Rusophycus may have been open at the sediment‐water interface, while the crisp preservation of both Rusophycus and Teichichnus, along with the preservation of such delicate morphological details as scratch marks, suggests that the sediment must have been relatively firm at the time the traces were formed. The formation and preservation of Rusophycus in cohesive sediments located very close to the sediment‐water interface hold important implications for the manner in which we consider Palaeozoic substrates and their temporal and spatial evolution. Moreover, these findings demonstrate that the morphology and taphonomy of ichnological associations may, in the context of sedimentological relationships, prove a powerful proxy for tracking substrate conditions through both space and time. □firmgrounds, New York, predation, Rusophycus, substrate, taphonomy.     

Strategies of burrowing in soft muddy sediments by diverse polychaetes

Muddy sediments are elastic solids through which morphologically diverse animals extend burrows by fracture. Muddy sediments inhabited by burrowing infauna vary considerably in mechanical properties, however, and at high enough porosities, muds can be fluidized. In this study, we examined burrowing behaviors and mechanisms of burrow extension for three morphologically diverse polychaete species inhabiting soft muddy sediments. Worms burrowed in gelatin, a transparent analog for muddy sediments, and in natural sediments in a novel viewing box enabling visualization of behaviors and sediment responses. Individuals of Scalibregma inflatum and Sternaspis scutata can extend burrows by fracture, but both also extended burrows by plastic deformation and by combinations of fracture and plastic deformation. Mechanical responses of sediments corresponded to different burrowing behaviors in Scalibregma; direct peristalsis was used to extend burrows by fracture or a combination of plastic deformation and fracture, whereas a retrograde expansive peristaltic wave extended burrows by plastic deformation. Burrowing speeds differed between behaviors and sediment mechanical responses, with slower burrowing associated with plastic deformation. Sternaspis exhibited less variability in behavior and burrowing speed but did extend burrows by different mechanisms consistent with observations of Scalibregma. Individuals of Ophelina acuminata did not extend burrows by fracture; rather individuals plastically deformed sediments similarly to individuals of the related Armandia brevis. Our results extend the range of natural sediments in which burrowing by fracture has been observed, but the dependence of burrow extension mechanism on species, burrowing behavior, and burrowing speed highlights the need for better understanding of mechanical responses of sediments to burrowers.     

Deciphering the shape and deformation of secondary structures through local conformation analysis

Background  

Protein deformation has been extensively analysed through global methods based on RMSD, torsion angles and Principal Components Analysis calculations. Here we use a local approach, able to distinguish among the different backbone conformations within loops, α-helices and β-strands, to address the question of secondary structures' shape variation within proteins and deformation at interface upon complexation.     

A multidisciplinary approach to the study of the plasma membrane of Zea mays pollen during controlled dehydration

A multidisciplinary approach (freeze-fracture, nuclear magnetic resonance, differential scanning calorimetry, isoelectric focusing and fluorochromatic reaction test) has been used to follow the behaviour of Zea mays pollen during dehydration - and to estimate its quality. At anthesis, the water content of maize pollen is 57–58% and the vegetative plasma membrane is continous and well structured with a very low density of intramembraneous particles on the extraplasmic fracture face. Maize pollen grains can withstand the drying process until a water content of 28% is reached, at which point 60–80% of the individuals show a negative reaction in the fluorochromatic test. At this water content, there is no more crystallizable water and thus metabolism decreases, leading to oxidative damage and the formation of gelphase microdomains in the plasma membrane. Consequently, the plasma-membrane permeability is modified. At 15–13% water content, all pollen grains show a negative fluorochromatic reaction, and gel-phase microdomains are more numerous but membranes still have a bilayer structure. Relaxation-time experiments indicate the occurrence of water replacement at the membrane level. Thus, sugar may stabilize the membrane structure at water contents as low as 3%. During the dehydration process, pollen walls act as elastic structures and remain closely applied to the protoplast. The combination of wall deformation and water replacement would permit pollen survival until oxidative damage occurs in the dehydrated grain.Abbreviations EF extraplasmic fracture face - FCR fluorochromatic reaction - IMP intramembraneous particle - NMR nuclear magnetic resonance - PF protoplasmic fracture face - T₂ relaxation time     

New details of the neural architecture of the salmonid adipose fin

The adipose fin of salmonids, once widely regarded as vestigial and lacking in function, was shown to be important to swimming efficiency in juvenile brown trout Salmo trutta. Examination with confocal microscopy of adipose fins of S. trutta stained with various antibodies targeting the nervous system revealed several large nerves entering the fin and anastomosing throughout its length. The branching nerves form a plexus with specific patterns of fine terminal branches in the leading and trailing edges. A network of astrocyte‐like cells (ALCs) that is linked through cell processes to nerves and structural collagen reacted positively with antibodies to glial cells. No other fish fins, including other adipose fins, have been shown to exhibit this type of neural architecture. Many vertebrate mechanoreceptors rely on collagen deformation to stimulate responses in afferent nerves; similarly, the adipose fin also may function as a mechanosensor, where passive mechanical deflection by water currents stimulates afferent nerves.     

Drought-induced structural alterations at the mycobiont-photobiont interface in a range of foliose macrolichens

Summary Cryotechniques, such as low temperature scanning electron microscopy (LTSEM) and freeze-substitution for transmission electron microscopy (TEM), were applied to two cyanobacterial and three green algal macrolichens in order to locate free water and to visualize drought-induced structural alterations at the mycobiont—photobiont interface. The following species were examined:Peltigera canina/Nostoc punctiforme, Sticta sylvatica/Nostoc sp. (both Peltigerales),Parmelia sulcata/Trebouxia impressa, Hypogymnia physodes/Trebouxia sp. (both Lecanorales), andXanthoria parietina/Trebouxia arboricola (Teloschistales). In all species free water was confined to the symplast and the apoplast. No intercellular water reservoirs were found in the gas-filled thallus interior. Thalline fluctuations in water content reflect fluctuations in apoplastic and symplastic water. All the taxonomically diverse lichen photobionts have access to water and dissolved nutrients via the fungal apoplast only. Drought stress (i.e., water content 20%/dw and below) caused dramatic shrinkage and deformation in all cell types. At any level of hydration the fungal and algal protoplast maintained close contact with the cell wall. This applied to the cyanobacterial photobionts and their murein sacculus and gelatinous sheath too. Although the cytoplasm of both partners was strongly condensed in desiccated lichens the cellular membrane systems, usually negatively contrasted, were very well preserved. The significance of these data is discussed with regard to the functioning of the symbiotic relationship.     

Dynamic surface deformation of silicone elastomers for management of marine biofouling: laboratory and field studies using pneumatic actuation

Many strategies have been developed to improve the fouling release (FR) performance of silicone coatings. However, biofilms inevitably build on these surfaces over time. Previous studies have shown that intentional deformation of silicone elastomers can be employed to detach biofouling species. In this study, inspired by the methods used in soft-robotic systems, controlled deformation of silicone elastomers via pneumatic actuation was employed to detach adherent biofilms. Using programmed surface deformation, it was possible to release > 90% of biofilm from surfaces in both laboratory and field environments. A higher substratum strain was required to remove biofilms accumulated in the field environment as compared with laboratory-grown biofilms. Further, the study indicated that substratum modulus influences the strain needed to de-bond biofilms. Surface deformation-based approaches have potential for use in the management of biofouling in a number of technological areas, including in niche applications where pneumatic actuation of surface deformation is feasible.     

Elastin as a rubber

The thermoelastic behavior of water solvated elastin has been investigated in simple tension, in the temperature range 0–70°C. Specimens purified from both the ox ligamentum nuchae and pig thoracic aorta have been studied. Force data obtained by cycling the temperature for various constant specimen lengths display a separated variable dependence of the form f = A(T)B(α), where T is absolute temperature and α the extension ratio. For ligament elastin B(α) is a linear function whereas for aortic elastin it is a nonlinear function. The applicability of the rubber elasticity theory to elastin has been tested by setting A(T) equal to the temperature-dependent front factor for simple tension of a homogeneous rubber whilst B(α) is left undefined. In this way it has been possible to take into account the fibrous nonhomogeneity of the polymer, and also to avoid any inconsistency within the theory of attributing a dependence of the variable fe/f upon extension ratio. The behavior of both ligament and aortic elastin agrees well with the conclusion that the dominant deformation mechanism is entropy elastic, fe/f ? 1. The linearity of the load isotherm for ligament elastin permits a particularly simple experimental procedure using a single force-temperature plot for one value of interclamp length. Using this procedure high precision has been obtainble, and the data shows a close adherence to the theory with fe/f = 0.1. The relationship between this result and current controversy over the molecular conformation of elastin is discussed.     

Fusion of sacrals and anatomy in Champsosaurus (Diapsida,Choristodera)

Sacral centra are occasionally fused with or without severe deformation in Champsosaurus (Diapsida, Choristodera). The sympatrical occurrence of fusion and non-fusion of sacra in adults through their evolution questions that sacral fusion represents the final form of a simple ontogenetic change or specific variation. Females are proposed to possess more robust limb bones than males because they are considered to have been more terrestrial due to the nesting behaviour on land. The coincidental occurrence of fusion of sacral centra without severe deformation and more robust limb bones in same individuals suggests that sacral fusion is a phenomenon occurring in females as a result of terrestrial adaptation for reproductive activities. Sacral fusion associated with severe deformation is considered a pathological condition although its etiology and factors remain undefined.     

An affine micro-sphere-based constitutive model,accounting for junctional sliding,can capture F-actin network mechanics

Actin filaments are a major component of the cytoskeleton and play a crucial role in cell mechanotransduction. F-actin networks can be reconstituted in vitro and their mechanical behaviour has been studied experimentally. Constitutive models that assume an idealised network structure, in combination with a non-affine network deformation, have been successful in capturing the elastic response of the network. In this study, an affine network deformation is assumed, in which we propose an alternative 3D finite strain constitutive model. The model makes use of a micro-sphere to calculate the strain energy density of the network, which is represented as a continuous distribution of filament orientations in space. By incorporating a simplified sliding mechanism at the filament-to-filament junctions, premature filament locking, inherent to affine network deformation, could be avoided. The model could successfully fit experimental shear data for a specific cross-linked F-actin network, demonstrating the potential of the novel model.     

An ionised/non-ionised dual porosity model of intervertebral disc tissue

The volume of the intrafibrillar water space – i.e. the water contained inside the collagen fibres – is a key parameter that is relevant to concepts of connective tissue structure and function. Confined compression and swelling experiments on annulus fibrosus samples are interpreted in terms of a dual porosity model that distinguishes between a non-ionised intrafibrillar porosity and an ionised extrafibrillar porosity. Both porosities intercommunicate and are saturated with a monovalent ionic solution, i.c. NaCl. The extrafibrillar fixed charge density of the samples is assessed using radiotracer techniques and the collagen content is evaluated by measurement of hydroxyproline concentration. The interpretation of the experimental data yields values for the intrafibrillar water content, the average activity coefficient of the ions, the Donnan osmotic coefficient, the fraction of intrafibrillar water, the stress-free deformation state, and an effective stress–strain relationship as a function of the radial position in the disc. A linear fit between the second Piola–Kirchhoff effective stress and Green–Lagrange strain yielded an effective stiffness: H_e=1.087 ± 0.657 MPa. The average fraction of intrafibrillar water was 1.16 g/g collagen. The results were sensitive to changes in the activity and osmotic coefficients and the fraction of intrafibrillar water. The fixed charge density increased with distance from the outer edge of the annulus, whereas the hydroxyproline decreased.The authors wish to thank Dr. Jill Urban for her advice concerning fixed charge density measurements, and Ing. Paul Willems for his assistance with the experiments. The research of Dr. J. M. Huyghe has been made possible through a fellowship of the Royal Netherlands Academy of Arts and Sciences.     

Hinge-bending deformation of enzyme observed by microwave dielectric measurement

A dielectric relaxation peak due to an intramolecular motion in the active site of trypsin was first observed in aqueous solution below the freezing temperature of bulk water by a time domain reflectometry method. If trypsin inhibitor is added to the solution, it vanishes. It is suggested that the motion observed is a hinge-bending deformation giving rise to the enzymatic activity of trypsin, which is prohibited by linkage of the trypsin inhibitor. Relaxation time of the motion is 3 × 10² ns at − 10°C. © 1996 John Wiley & Sons, Inc.     

Monte Carlo Simulation of Hydration of the Nucleic Acid Fragments

Abstract

Systems containing a base or a base pair and 25 water molecules, as well as a helical stack and 30 water molecules per base pair, have been simulated. Changes in the base hydration shell structure, after the bases have been included into the pair and then into the base pair stack are discussed. Hydration shells of several configurations of the base pair stacks are discussed. Probabilities of formation of the hydrogen-bonded bridges of 1, 2 and 3 water molecules between hydrophilic centres have been estimated. The hydration shell structure was shown to depend on the nature of the base pair and on the stack configuration, while dependence of the global hydration shell characteristics on the stack configuration has been proved to be rather slight. The most typical structural elements of hydration shells, in the glycosidic (minor in B-like conformation) and non-glycosidic (major) grooves, for different configurations of AU and GC stacks, have been found and discussed. The number of hydrogen bonds between water molecules and bases per water molecule was shown to change upon transformation of the stack from A to B configuration. This result is discussed in connection with the reasons for B to A conformational transition and the concept of “water economy”. Hydration shell patterns of NH₂-groups of AU and GC helical stacks differ significantly.     

FRESHWATER DINOFLAGELLATES OF BELIZE,C.A.

Freshwater dinoflagellates have not previously been reported from Belize, although there has been extensive work with marine dinoflagellates and some work with other freshwater groups. Freshwater dinoflagellates are more frequently observed in standing water and none have been observed in the several streams and rivers sampled since 1990. The goal in 1998 was to examine water samples from small ponds within hours of collection to improve the chance of observing swimming dinoflagellates. A plankton net was used and whole water samples also were collected. A small brown water pond on a peninsula and 30m from the Caribbean yielded a bloom of Thompsodinium intermedium. Dinoflagellates, including Peridinium centenniale, Katodinium sp., and Peridinium sp. in the Umbonatum Group, were observed within “Crocodile pond” and “Lily pond” on the mainland.     

Developmental failure after experimental activation of insect eggs

Summary

Eggs taken from the genital tracts of Venturia (Nemeritis) canescens (Hym., Ichneum.) and Psychoda cinerea (Dipt., Psychod.) can be activated by brief exposure to distilled water. However, embryogenesis fails soon unless some other conditions are met. These are mechanical deformation of the egg in Venturia, and mating in Psychoda. Development ceases at or soon after meiosis in Psychoda and in most Venturia eggs; the remaining Venturia eggs fail to form an orderly blastoderm although they contain hundreds of nuclei. In Venturia the anomalies are probably due to insufficient activation of some cytoplasmic component(s) while Psychoda eggs fail in the absence of some paternal contribution, possibly the sperm which in this case must enter the oocyte within the follicle.     

Contributo alla Conoscenza dell'idratazione e della Pressione Osmotica Nelle Specie di Tre Associazioni Forestali delle Marche: I° - L'idratazione

Abstract

Researches on the water content and osmotic pressure in plants of three forest associations in the Marche. I° - The water content. — The main forest associations of the Umbro-Marchigiani Appennines are the Orneto-Quercetum ilicis, the Quercetum pubescentis (s. l.) and the Fagetum. In each of these associations a typical station has been chosen where the most important species have been followed from March to November 1963 in order to determine the seasonal variations of their water content (« T.I. »)expressed as percentage of fresh weight.

The annual curves show that the water content reaches very high levels in the early stages of plant development while it falls to lower levels later in the season when the leaves are full grown. The water content of each species follows a different course and can be considered a specific character. Taking into account the maximum and minimum levels of water content of the three groups of species a « hydric spectrum » has been worked out for the three associations.

The water content of each species has also been calculated as percentage of dry weight (imbibition percentage: « G.I. »).     

Variations in response to induced stem bending in seedlings of Pinus radiata

Summary The occurrence of stem deformation in Pinus radiata plantations has been examined previously in terms of the factors leading to the onset of bending symptoms. In this study the influence of seedling family and nitrogen availability on the ability of seedlings to recover from deformation was investigated under glasshouse conditions. Seedlings from four families ranging from resistant to susceptible to stem deformation were used. Stem deformation was induced by loading stems with a known weight and comparing bending moments and rates of recovery. Significant differences between families were found with more susceptible families exhibiting greater initial magnitudes of stem lean. Similarly these families also exhibited greater rates of apical elongation following bending despite the larger stem leans. This resulted in more exaggerated stem bends as a consequence of the recovery of the lower stem pushing the upper stem away from the vertical. The strength characteristics of the stems could not explain differences between families. Susceptibility to stem deformation was explained more by stem slenderness expressed as stem height to root collar diameter.