A dielectric theory of "multi-stratified shell" model with its application to a lymphoma cell

A theory of complex dielectric constant ($\text{ε}{}^1$) for the suspension of “multi-stratified” spherical particles is presented. Based on Maxwell's theory of interfacial polarization, we derive a general expression which correlates $\text{ε}{}^1$ with the electrical and geometrical parameters of each stratum. It can be shown that such a “multi-stratified” system in general should give rise to multiple dielectric dispersions, the number of which corresponds to the number of interfaces lying between the successive shell phases. The conditions for a full number of different “unit” dispersions to occur are also discussed. As an example, a special case of the “double-shell” model consisting of a spherical core and three layers of concentric phases is solved numerically by using a set of parameter values pertinent to a lymphoma cell. In light of the characteristic behavior of $\text{ε}{}^1$ thus revealed, we propose a scheme of procedure that applies to the determination of electrical parameters associated with the specific “double-shell” model.     

Movement of tropomyosin during regulation of vertebrate skeletal muscle: a simple physical model.

Using data obtained from (a) X-ray diffraction patterns of vertebrate skeletal muscle (b) three dimensional reconstructions from electron micrographs of in vitro aggregates of the thin filament proteins in the switched “on” and “off” positions (c) the analysis of the sequence of tropomyosin, a simple model can be proposed which may explain the geometrical arrangement of actin, tropomyosin and troponin during regulation. The “cooperative” behaviour exhibited by the thin filament can also be explained in terms of this arrangement.     

Studies on mixing in horizontal rotating tubular bioreactor

A horizontal rotating tubular bioreactor (HRTB) is a combination of a “thin-layer bioreactor” and a “biodisc” reactor. Its interior is divided by O-ring shaped partition walls. Mixing properties of this new type of the bioreactor were investigated by using a temperature step method. The mixing simulations were done by Runge-Kutta-Fehlberg numerical integration. Adjustable parameters of the “spiral flow” model were optimised by Monte-Carlo method. In this investigation, the structured “spiral flow” model (containing four adjustable parameters) was tested in a wide range of experimental conditions. The results show that the structured “spiral flow” model is capable to describe the mixing in HRTB in the whole range of both bioreactor operational parameters (n and D).     

Encapsulated fusion protein confers “sense and respond” activity to chitosan–alginate capsules to manipulate bacterial quorum sensing

We demonstrate that “nanofactory”‐loaded biopolymer capsules placed in the midst of a bacterial population can direct bacterial communication. Quorum sensing (QS) is a process by which bacteria communicate through small‐molecules, such as autoinducer‐2 (AI‐2), leading to collective behaviors such as virulence and biofilm formation. In our approach, a “nanofactory” construct is created, which comprises an antibody complexed with a fusion protein that produces AI‐2. These nanofactories are entrapped within capsules formed by electrostatic complexation of cationic (chitosan) and anionic (sodium alginate) biopolymers. The chitosan capsule shell is crosslinked by tripolyphosphate (TPP) to confer structural integrity. The capsule shell is impermeable to the encapsulated nanofactories, but freely permeable to small molecules. In turn, the capsules are able to take in substrates from the external medium via diffusion, and convert these via the nanofactories into AI‐2, which then diffuses out. The exported AI‐2 is shown to stimulate QS responses in vicinal Escherichia coli. Directing bacterial population behavior has potential applications in next‐generation antimicrobial therapy and pathogen detection. We also envision such capsules to be akin to artificial “cells” that can participate in native biological signaling and communicate in real‐time with the human microbiome. Through such interaction capabilities, these “cells” may sense the health of the microbiome, and direct its function in a desired, host‐friendly manner. Biotechnol. Bioeng. 2013; 110: 552–562. © 2012 Wiley Periodicals, Inc.     

The chondrichthyan fauna from the Middle-Late Triassic of Guanling (Guizhou province,SW China)

The Recent volutids Cymbiola and Melo burrow in a forward direction. This agrees well with the spiral terrace pattern observed in Eocene Volutidae, thus strengthening the idea that they were forward burrowers as well. The presence of collabral terraces near the aperture in the Cassidae suggests an oblique burrowing direction, by convergence with the Nassariidae. This is confirmed by observations on living cassids. The sutural canals and associated structures of the Olividae and Seraphidae are functional in detecting whether the posterior region of the shell is buried. This confirms the idea that fossil Strombidae possessing similar features were burrowers.

In contrast with these “predictable”; observations, burrowing was observed in a few gastropods the shell morphology of which would seem to exclude such behaviour, such as Architectonica, Cymatium, Volema and Bolinus. Thus, a few morphologic criteria appear to be reliable and of general applicability in inferring burrowing habits in gastropods. At the same time, the broad variety of burrowing mechanisms and life habits of gastropods makes it unlikely that general criteria will ever be found to exclude burrowing habits on the basis of shell morphology.     

COMPUTER-SIMULATED SHELL SIZE AND SHAPE VARIATION IN THE CARIBBEAN LAND SNAIL GENUS CERION: A TEST OF GEOMETRICAL CONSTRAINTS

A computer graphical model of gastropod shell form is used to test a hypothesis of geometric constraint proposed to explain the disjunct distribution of shell forms observed in Cerion, a species-rich and geometrically varied genus of terrestrial gastropods. The mapping of computer-simulated forms into a morphospace of Cerion shells produces a continuum of sizes and shapes. Therefore, the absence of particular shell forms is not explained by geometric constraints. Two proposed modes of shell morphogenesis at extreme ranges in size (“dwarfs” and “giants”) previously were thought to be exclusive routes to the construction of high-spired (“smokestack”) forms. The present study shows that there are, in fact, multiple routes of transformation. In addition, these routes are geometrically reversible and interconnect the members of the shell-form continuum. Thus, the possible pathways followed during the course of evolution within this genus cannot be determined until an adequate phylogenetic hypothesis has been proposed.     

Siphonariid development: Quintessential euthyneuran larva with a mantle fold innovation (Gastropoda; Panpulmonata)

Recent phylogenetic revisions of euthyneuran gastropods (“opisthobranchs” and “pulmonates”) suggest that clades with a planktotrophic larva, the ancestral life history for euthyneurans, are more widely distributed along the trunk of the euthyneuran tree than previously realized. There is some indication that the planktotrophic larva of euthyneurans has distinctive features, but information to date has come mainly from traditional “opisthobranch” groups. Much less is known about planktotrophic “pulmonate” larvae. If planktotrophic larvae of “pulmonates” share unique traits with those of “opisthobranchs,” then a distinctive euthyneuran larval-type has been the developmental starting template for a spectacular amount of evolved morphological and ecological disparity among adult euthyneurans. We studied development of a siphonariid by preparing sections of larval and postmetamorphic stages for histological and ultrastructural analysis, together with 3D reconstructions and data from immunolabeling of the larval apical sensory organ. We also sought a developmental explanation for the unusual arrangement of shell-attached, dorso-ventral muscles relative to the mantle cavity of adult siphonariids. Adult siphonariids (“false limpets”) have a patelliform shell but their C-shaped shell muscle partially embraces a central mantle cavity, which is different from the arrangement of these components in patellogastropods (“true limpets”). It is not obvious how shell muscles extending into the foot become placed anterior to the mantle cavity during siphonariid development from a veliger larva. We found that planktotrophic larvae of Siphonaria denticulata are extremely similar to previously described, planktotrophic “opisthobranch” larvae. To emphasize this point, we update a list of distinctive characteristics of planktotrophic euthyneuran larvae, which can anchor future studies on the impressive evolvability of this larval-type. We also describe how premetamorphic and postmetamorphic morphogenesis of larval mantle fold tissue creates the unusual arrangement of shell-muscles and mantle cavity in siphonariids. This result adds to the known postmetamorphic evolutionary innovations involving mantle fold tissue among euthyneurans.     

Absolutes und relatives Wachstum bei Ammonoideen

The following basic growth parameters of the ammonoid shell are analysed: radius of the coiling spiral; whorl width; plane of cross-section; umbilical spiral. The absolute growth of these parameters follows a general growth formula which is based on the probability theory (time-dependent stochastic processes). The in crease of all basic parameters is ruled by analogous formulas which are derived from the general growth formula; the increase of the coiling spiral results in the geometrical figure of a logarithmic spiral, because this is the only one that meets the conditions of the general growth formula. The relative growth can be described as a morphogenetic program that is subdivided in presumably three formally connected subprograms. Each subprogram is defined by specific allometry and integration constants.
Folgende Grundparameter des Wachstums von Ammonoideen-Gehäusen werden analysiert: Radius der äuβeren Spirale, Windungsbreite, Querschnittsfläche, Nabelspirale. Das absolute Wachstum dieser Parameter folgt einer allgemeinen Wachstumsformel, die sich aus der Wahrscheinlichkeitstheorie (zeitabhängige stochastische Prozesse) ergibt. Die Zunahme aller Grundparameter folgt analogen Formeln, die sich aus der allgemeinen Wachstumsformel ableiten lassen; das Anwachsen des äuβeren RadiS führt zur geometrischen Figur einer logarith-mischen Spirale, da nur diese der allgemeinen Wachstumsformel genügt. Das relative Wachstum läβt sich als ein morphogenetisches Wachstumsprogramm beschreiben, das sich in vermutlich drei formal miteinander verknüpfte Unter-programme aufteilt. Jedes Unterprogramm ist durch spezifische Allometrie- und Integrationskonstanten festgelegt.     

Finite element modeling of shell shape in the freshwater turtle Pseudemys concinna reveals a trade‐off between mechanical strength and hydrodynamic efficiency

Aquatic species can experience different selective pressures on morphology in different flow regimes. Species inhabiting lotic regimes often adapt to these conditions by evolving low‐drag (i.e., streamlined) morphologies that reduce the likelihood of dislodgment or displacement. However, hydrodynamic factors are not the only selective pressures influencing organismal morphology and shapes well suited to flow conditions may compromise performance in other roles. We investigated the possibility of morphological trade‐offs in the turtle Pseudemys concinna. Individuals living in lotic environments have flatter, more streamlined shells than those living in lentic environments; however, this flatter shape may also make the shells less capable of resisting predator‐induced loads. We tested the idea that “lotic” shell shapes are weaker than “lentic” shell shapes, concomitantly examining effects of sex. Geometric morphometric data were used to transform an existing finite element shell model into a series of models corresponding to the shapes of individual turtles. Models were assigned identical material properties and loaded under identical conditions, and the stresses produced by a series of eight loads were extracted to describe the strength of the shells. “Lotic” shell shapes produced significantly higher stresses than “lentic” shell shapes, indicating that the former is weaker than the latter. Females had significantly stronger shell shapes than males, although these differences were less consistent than differences between flow regimes. We conclude that, despite the potential for many‐to‐one mapping of shell shape onto strength, P. concinna experiences a trade‐off in shell shape between hydrodynamic and mechanical performance. This trade‐off may be evident in many other turtle species or any other aquatic species that also depend on a shell for defense. However, evolution of body size may provide an avenue of escape from this trade‐off in some cases, as changes in size can drastically affect mechanical performance while having little effect on hydrodynamic performance. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Reentry as an Origin for Rotors

The aim of the study is to understand in depth the meaning of “reentry”, and to decipher if and how it can lead to malfunctions of the heart and possibly of the brain. A simple model is used to reveal the mechanism by which a single pulse of action potential rotating around a ring of excitable medium, the latter simulating a reentry circuit, can generate spirals (single and/or double) when the pulse can emerge from and develop outside the ring. Two mechanisms of spiral generation are demonstrated: (1) a mechanism in which a source of single spirals is created at the contact with the core soon after the pulse freeing action, their chirality being due to the sense of the preceding pulse rotation. Interestingly, these spirals, adhering to the core, become “double-spiral patterns” while leaving behind the seeds of the new single spirals. (2) A second possible mechanism, similar to the known “arms encountering methods”, in which a double spiral (a figure of eight) is repeatedly created on the other side of the core. Similar procedures are assumed to occur in the heart, leading to tachycardia and fibrillation and possibly in the brain leading to epilepsy. The exact processes of the hitherto assumed spiral generations by reentry were established. The novel deep understanding of the mechanisms involved in these processes can lead to new methods of treating heart fibrillation (e.g., by judicial ablation).     

Estimation of Free Energy Systematic Errors in Molecular Simulations of Globular Proteins Surrounded by Finite Water Clusters. One Center Multipole Expansion of Reaction Field Differences

Free energy calculated in simulations on the atomic level (Monte Carlo or Molecular Dynamics) has a systematic error, if the water shell surrounding a globular protein is finite. The error (“cluster error”) is equal to a difference of free energies obtained in simulations with an infinite and finite water shell. In this work a continuum dielectric model was used to estimate the “cluster error”. A multipole expansion of the estimate was performed for a water shell with a spherical outer boundary. The expansion has very simple form. Each term is a product of two functions, one of them depending only on the charge's conformation, and the other one only on dielectric properties of the system. There are two practical uses of the expansion. First, it may be used to estimate the “cluster error” in a simulation already made; second, it may be used to plan a simulation in such a way that the “cluster error” is minimal. Numerical values of the largest terms in the multipole expansion corresponding to a typical system in simulations of globular proteins are given.     

ARCHAEOPTERIS MACILENTA,ANATOMY AND MORPHOLOGY OF ITS FROND

The stem, rachides, and pinnae of Archaeopteris macilenta, formerly considered to be a fern of Devonian age, comprise a branch system in which the ultimate divisions heretofore referred to as pinnules are the leaves. The primary vascular system of the “frond” is a lobed siphonostele from which leaf traces arise in a spiral sequence. The anatomy of the “rachis” and of the “pinnae” is shown to be similar to that of the stem, Callixylon, which bore these “fronds.” Branching, epidermal pattern and stomates are described for the spirally arranged leaves (fertile pinnules). Attachment and dehiscence of sporangia as well as their stomates are reported. Archaeopteris is retained in the Class Progymnospermopsida which includes plants with gymnospermous anatomy and pteridophytic reproduction. It is suggested that Actinopodium, Svalbardia and Siderella are related closely to Archaeopteris and that this group of genera shows evolutionary stages in webbing of leaves and planation of branch systems. The opportunities for ontogenetic studies of the arborescent genus Archaeopteris are pointed out.     

Evaluating the nucleus effect on the dynamic indentation behavior of cells

The effect of the nucleus on the cell mechanical behavior was investigated based on the dynamic indentation response of cells under a spherical tip. A “two-component” cell model (including cytoplasm and nucleus) is used, and the dynamic indentation behavior is studied by a semiempirical method, which is established based on fitting the numerical simulation results of the quasi-static indentation response of cells. We found that the “routine analysis” (based on the Hertz’s contact solution of homogeneous model) significantly overestimated the nucleus effect on the overall cell indentation response due to the effects of the Hertz contact radius and the substrate stiffening. These effects are significantly stronger in the “two-component” cell model than in the homogeneous model. The inaccuracy created by the “routine analysis” slightly increases with the modulus ratio of nucleus to cytoplasm and the volume fraction of nucleus. Finally, the error sensitivity to the geometrical parameters used in the model is discussed, which shows the indentation analysis is not very sensitive to these parameters, and the reasonable assumptions for these parameters are effective. This systematic analysis can provide a useful guideline to understanding the mechanical behavior of cells and nuclei.     

PREDATOR-INDUCED SHELL DIMORPHISM IN THE ACORN BARNACLE CHTHAMALUS ANISOPOMA

Field experiments were conducted in order to determine the nature of shell dimorphism in the acorn barnacle Chthamalus anisopoma and the adaptive significance of the atypical form. The typical morph has the conical shape which is characteristic of acorn barnacles, while the atypical morph appears bent over, with the rim of its aperture oriented perpendicular to its base. The experiments showed that: 1) the bent-over morphology is an environmentally-induced developmental response to the presence of a carnivorous gastropod (Acanthina angelica) and 2) that “bents” are more resistant than “conics” to specialized predation by this snail. The results also showed that predation by A. angelica is patchy and heaviest in the near vicinity of cracks and crevices, which it uses as refuges during periods of tidal inundation. Because predation is patchy and bents are less fecund and grow slower than conics, the conditional developmental strategy is likely to be favored over strict genetical control of shell morphology.     

The development of specific visual connections in the monkey and the goldfish: outline of a geometric theory of receptotopic structure.

The anatomical structure of the primate retino-striate system and the goldfish retino-tectal system are characterized by idealized geometrical domains. The physiological retinotopic mappings are then shown to be determined by the boundary conditions of the respective anatomical surfaces. This fact is interpreted as support for the “systems-matching” hypothesis of neural development of Gaze &; Keating. It is suggested that the development of specific neural mappings may be, in part, a variational problem in which two neural surfaces establish connections as “smoothly” as possible. Dirichlet's Principle supplies a quantitative definition of the term “smooth”—the average physiological magnification factor of the neural mapping is minimized, subject to the boundary conditions of the available tissue. Three developmental rules are formulated, which deal respectively with gross specificity, polarity, and detailed map construction. The latter rule, based on Dirichlet's Principle, supplies a link between the classical theory of fields and developmental neurobiology. Specific experimental tests are outlined in the goldfish visual system, and a general discussion of global approaches to neural structure and function is presented.     

Zoologische und paläontologische Ostracoden-Systematik

Systematic rules for the OrdoOstracoda are results of two different ways of study. Palaeontologists consider for systematic purpose the shell to be of the highest importance whereas zoologists prefer to use the differences of the interior. These two different ways of consideration are of no significance for the Palaeozoic and Mesozoic species, however of greatest importance for the Cenozoic ostracoda. There are many species with “homoeomorph” shells which are stated by zoologists according to the form of their interior only. On hand of the genusCandona, the author tries to explain that “homoeomorphism” is not present if the form of the shell would be studied in a more subtile way. Negligence of the form of the shell in the zoological system is not justified. Species which differ in the form of their members have sufficiently distinct differences with regard to their shells too.It is emphasized that each of the two analytists, the palaeontological as well as the zoological one, may pay more attention to the fact that, after all, one has to deal with one and the same animal group.     

Decorated Core-Shell Architectures: Influence of the Dimensional Properties on Hybrid Resonances

Emerging nanoplasmonics utilizing asymmetric core-shell architectures present opportunities to precisely control the plasmon position and signal amplification within a single particle. In particular, asymmetric gold nanorods, assembled into a “matryoshka” structure (gold nanorod core, silica spacer shell, and outer gold shell) have the unique ability to enhance and precisely manipulate the plasmonic signature when compared to single gold nanorods via the generation of hybridized plasmonic modes. Currently, the fundamental understanding of the impact of the gold nanorod matryoshka dimensional parameters on the subsequent resonance behavior is incomplete. In this work, we elucidate the structural-hybridized resonance relationship of gold nanorod nanomatryoshka designs by experimentally varying the key geometrical properties; including silica spacer thickness, gold nanorod core size, and gold shell thickness/continuity.     

Microstratigraphy and taphonomy of rudist shell concentrations in Upper Cretaceous limestones,Cilento area (central-southern Italy)

Rudist bed type and distribution has been investigated in Upper Cretaceous limestones cropping out in the northern Cilento area (southern Italy). These limestones are dominated by fine-grained, peloidal, silty packstone in which rudist-rich beds are intercalated. An inner shelf environment may be inferred on the basis of the recognized sedimentary and taphonomic features. The rudist shell beds are characterized by low species diversity, with slight differences in abundance of a few species belonging to the Durania, Bournonia, Sauvagesia, Gorjanovicia and Biradiolites genera, which usually form oligo- or monospecific congregations. The internal fabric of these levels (i.e. orientation, arrangement, packing and sorting of the skeletal elements; internal microstratigraphy) has permitted us to distinguish two broad shell bed categories: (a) shell beds considered as “Primary Shell Concentration”, in which the shell concentration is essentially created by the behaviour of local shell producers, preserved in situ and in growth position; (b) shell beds considered as “Hydraulic Shell Concentration”, which were deposited under the influence of hydraulic processes and/or input of surrounding bioclastic sediments. The taphonomic analyses allowed us to highlight the role of some of the biotic and abiotic factors that controlled the distribution of the rudists in the various habitats. The increase of physical disturbance (especially hydrodynamism) is the primary difference between these shell bed categories. The establishment and development of the densest rudist congregations appear to be related to the accommodation space made available by means of relative sea level rise. The lowering of the sea level was often accompanied by the increased influence of waves and/or currents on the seabed and the consequent sediment disturbance and demise of the rudist lithosome, although other factors cannot be excluded.     

FINE STRUCTURE OF THE SPERMATOZOID OF ZAMIA WITH SPECIAL REFERENCE TO THE FLAGELLAR APPARATUS

The locomotor apparatus of the spermatozoid of Zamia integrifolia consists of numerous flagella having the typical 9 + 2 substructure connected through basal bodies to a spiral band of complex structure. Basal bodies have a fine structure somewhat resembling that found in algae, mosses, and ferns, but they are much longer. They are composed of a circle of 9 double fibers just beneath the plasma membrane, changing to 9 doublets interconnected by fibrils in a star-pattern, giving over to a centriolar type of 9 triplet fibers embedded in an electron-dense layer of the spiral band, and ending in a “cartwheel” configuration. A system of microtubules arranged in a spiral, secondary to the flagellated spiral, is thought to underlie the plasma membrane in flagellated regions. It is suggested that this system accounts for “euglenoid” movements of the sperm. Other details of cellular fine structure are described.     

Fascicled Androecia in Dilleniidae and Some Remarks on the Garcinia Androecium

In Dilleniidae, stamen fascicles are interpreted either as phylogenetically secondary structures (derived from a single stamen primordium by dédoublement), or as the most archaic type of androecial organs in angiosperms. In context with an assumed high plasticity in the flowers at the beginning of angiosperm evolution (Endress, 1987 a, b), fascicled androecia can also be regarded as having coexisted with “magnolioid” spiral androecia since early in the evolution. On the basis of this assumption, it is easy to link the Dilleniidae, via their basal group, the Paeoniaceae, to the Magnoliidae. In Paeonia, the stamen clusters continue the spiral arrangement of the perianth members, with “limiting divergence” (Hiepko, 1964). Our investigations of Paeonia officinalis show that the fascicle primordia follow the spiral not only in their position, but also in their temporal sequence. In some Theaceae (Stewartia) and Clusiaceae (species of Garcinia) the divergence angle changes to 2/5, resulting in an epipetalous position of the stamen fascicles. The transition from fascicled (complex) androecia to simple ones (one- or two-whorled) has occurred repeatedly within the Dilleniidae. A great diversity of androecial structures, based on a fascicled androecium, can be found in the palaeotropical genus Garcinia (Clusiaceae), which comprises about 200 species. Some of these forms, including exceptional ones, are presented in this article. The diversity in the androecium in Garcinia can be interpreted phylogenetically as a secondarily increased plasticity, resulting in morphological curiosities.