Photothermal and Reorientational Contributions to the Photomechanical Response of DR1 Azo Dye-Doped PMMA Fibers

This work is a comprehensive experimental and theoretical study aimed at understanding the photothermal and molecular shape-change contributions to the photomechanical effect of polymers doped with azo dyes. Our prototypical system is the azobenzene dye Disperse Red 1 (DR1) doped into poly (methyl methacrylate) (PMMA) polymer formed into optical fibers. We start by determining the thermo-mechanical properties of the materials with a temperature-dependent stress measurement. The material parameters, so determined, are used in a photothermal heating model—with no adjustable parameters—to predict its contribution. The photothermal heating model predicts the observations, ruling out mechanisms originating in light-induced shape changes of the dopant molecules. The photomechanical tensor response along the two principle axes in the uniaxial approximation is measured and compared with another independent theory of photothermal heating and angular hole burning/reorientation. Again, the results are consistent only with a purely thermal response, showing that effects due to light-induced shape changes of the azo dyes are negligible. The measurements are repeated as a function of polymer chain length and the photomechanical efficiencies determined. We find the results to be mostly chain-length independent.

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Autonomy and non-autonomy in Drosophila mesoderm determination and morphogenesis

Development ◽

10.1242/dev.120.4.853 ◽

1994 ◽

Vol 120 (4) ◽

pp. 853-859 ◽

Cited By ~ 3

Author(s):

M. Leptin ◽

S. Roth

Keyword(s):

Cell Shape ◽

Shape Change ◽

Developmental Program ◽

Cell Shape Change ◽

Ventral Furrow ◽

Large Numbers ◽

The Individual ◽

Mutant Cells ◽

Transplantation Experiments ◽

Shape Changes

The mesoderm in Drosophila invaginates by a series of characteristic cell shape changes. Mosaics of wild-type cells in an environment of mutant cells incapable of making mesodermal invaginations show that this morphogenetic behaviour does not require interactions between large numbers of cells but that small patches of cells can invaginate independent of their neighbours' behaviour. While the initiation of cell shape change is locally autonomous, the shapes the cells assume are partly determined by the individual cell's environment. Cytoplasmic transplantation experiments show that areas of cells expressing mesodermal genes ectopically at any position in the egg form an invagination. We propose that ventral furrow formation is the consequence of all prospective mesodermal cells independently following their developmental program. Gene expression at the border of the mesoderm is induced by the apposition of mesodermal and non-mesodermal cells.

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An Experimental Study on the Shape Changes of TiO2Nanocrystals Synthesized by Microemulsion-Solvothermal Method

Journal of Nanomaterials ◽

10.1155/2011/467083 ◽

2011 ◽

Vol 2011 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Wei Kong ◽

Bo Liu ◽

Bo Ye ◽

Zhongping Yu ◽

Hua Wang ◽

...

Keyword(s):

Experimental Study ◽

Stainless Steel ◽

Oleic Acid ◽

Solvothermal Method ◽

Shape Change ◽

Tetrabutyl Titanate ◽

Microemulsion System ◽

Solvothermal Process ◽

Shape Changes ◽

Shape And Size

Titanium dioxide (TiO2) nanocrystals of different shape were successfully synthesized in a new microemulsion system through a solvothermal process. The TiO2nanocrystals were prepared from the reaction of tetrabutyl titanate (TBT),H2O, and oleic acid (OA), which were used as solvent and surfactant at 300∘Cand 240∘Cin a stainless steel autoclave. The sphere, polygon, and rhombus-shaped nanocrystals have been prepared at 300∘Cand the dot- and- rod shaped nanocrystals have been synthesized at 240∘C. The effect of the reaction time on the shape and size of TiO2nanocrystals in this method was studied in the present paper. The size distribution of TiO2nanocrystals prepared at 300∘Cfor different hours is also studied. In addition, an attempt to describe the mechanism of shape change of TiO2nanocrystals was presented in this paper.

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Compaction-related deformation in Cambrian olenelloid trilobites and its implications for fossil morphometry

Journal of Paleontology ◽

10.1017/s0022336000027827 ◽

1999 ◽

Vol 73 (2) ◽

pp. 355-371 ◽

Cited By ~ 40

Author(s):

Mark Webster ◽

Nigel C. Hughes

Keyword(s):

Lower Cambrian ◽

Shape Change ◽

Anterior Lobe ◽

Interspecific Differences ◽

Fracture Patterns ◽

Morphometric Analyses ◽

Ontogenetic Trajectories ◽

Metric Distances ◽

Relative Convexity ◽

Shape Changes

Morphometric analyses of silicified and nonsilicified (preserved in shale) specimens of the olenelloid trilobites Olenellus (Olenellus) gilberti Meek (in White, 1874) and Nephrolenellus geniculatus Palmer, 1998, from the Lower Cambrian C-Shale Member of the Pioche Formation show that even well-preserved specimens in shales have undergone significant changes in lateral as well as vertical dimensions as a result of compaction. Analyses of cephalic landmarks show that in both species compaction causes posteriordirected collapse of the anterior lobe of the glabella, adaxial deformation of the ocular lobes, and abaxial and anterior splaying of genal regions. These shape changes are explicable in terms of observed exoskeletal fracture patterns. Landmarks show an increase in scatter around their ontogenetic trajectories that is generally proportional to the degree of lateral shift each landmark has undergone. Interspecific differences in compactional response may depend on the relative convexity of the cephalon. Olenellus (Olenellus) gilberti is a low-convexity species and shows marked lateral shape change, particularly in the genal region. Nephrolenellus geniculatus is more convex and shows less severe lateral shape change. Landmarks of both species exhibit an average trebling of the degree of scatter around their average ontogenetic trajectories in compacted samples. Because even well-preserved specimens in shales differ in shape from their precompactional appearance, results of morphometric studies utilizing metric distances between landmarks in trilobites where compaction can be detected must be interpreted with caution.

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A dominant inhibitory version of the small GTP-binding protein Rac disrupts cytoskeletal structures and inhibits developmental cell shape changes in Drosophila

Development ◽

10.1242/dev.121.3.903 ◽

1995 ◽

Vol 121 (3) ◽

pp. 903-914 ◽

Cited By ~ 9

Author(s):

N. Harden ◽

H.Y. Loh ◽

W. Chia ◽

L. Lim

Keyword(s):

Epidermal Cell ◽

Cell Shape ◽

Shape Change ◽

Yeast Cells ◽

Cell Shape Change ◽

Gtp Binding ◽

Wide Range ◽

Cell Shape Changes ◽

Germband Retraction ◽

Shape Changes

The Rho subfamily of Ras-related small GTP-binding proteins is involved in regulation of the cytoskeleton. The cytoskeletal changes induced by two members of this subfamily, Rho and Rac, in response to growth factor stimulation, have dramatic effects on cell morphology. We are interested in using Drosophila as a system for studying how such effects participate in development. We have identified two Drosophila genes, DRacA and DRacB, encoding proteins with homology to mammalian Rac1 and Rac2. We have made transgenic flies bearing dominant inhibitory (N17DRacA), and wild-type versions of the DRacA cDNA under control of an Hsp70 promoter. Expression of the N17DRacA transgene during embryonic development causes a high frequency of defects in dorsal closure which are due to disruption of cell shape changes in the lateral epidermis. Embryonic expression of N17DRacA also affects germband retraction and head involution. The epidermal cell shape defects caused by expression of N17DRacA are accompanied by disruption of a localized accumulation of actin and myosin thought to be driving epidermal cell shape change. Thus the Rho subfamily may be generating localized changes in the cytoskeleton during Drosophila development in a similar fashion to that seen in mammalian and yeast cells. The Rho subfamily is likely to be participating in a wide range of developmental processes in Drosophila through its regulation of the cytoskeleton.

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Collagenase secretion accompanying changes in cell shape occurs only in the presence of a biologically active cytokine

Journal of Cell Science ◽

10.1242/jcs.92.3.473 ◽

1989 ◽

Vol 92 (3) ◽

pp. 473-485

Author(s):

I. Kuter ◽

B. Johnson-Wint ◽

N. Beaupre ◽

J. Gross

Keyword(s):

Cell Cultures ◽

Cell Shape ◽

Cell Function ◽

Shape Change ◽

Biologically Active ◽

Target Cells ◽

Mixed Cell ◽

Cell Shape Change ◽

Cell Shape Changes ◽

Shape Changes

We have investigated the relationship between collagenase production, cell shape and stimulatory factors in cell culture. In a homogeneous culture of primary rabbit corneal stromal cells, shape change induced by a variety of agents was not effective in stimulating collagenase secretion. Only in the presence of a biologically active cytokine or phorbol myristate acetate was a correlation seen between changes in cell shape (induced by a second agent) and collagenase secretion by these primary cells. Cell shape changes were not, however, necessary for collagenase secretion, since certain concentrations of endotoxin or lactalbumin hydrolysate effected secretion of the enzyme in the absence of morphological changes. With passaged cells or mixed cell cultures, where cell shape change did correlate with collagenase secretion without the addition of an exogenous agent, the production of an effective cytokine (autocrine or paracrine) was demonstrated. Thus cell shape change seems to be neither universally necessary nor sufficient for the stimulation of collagenase secretion. It is proposed that the function of cytokines may be more immediately related to gene expression in this system than is change in the shape of the cell. The hypothesis is presented that cell shape changes may render the target cells receptive to cytokines, perhaps by replacing the need for a natural cytokine cofactor. It is also demonstrated here that the use of passaged cells, mixed cell cultures containing endogenous cytokine-secreting cells or tissue culture additives can profoundly affect the interpretation of the effect of various agents on collagenase secretion, and may lead to observations that are not directly relevant to cell function in vivo.

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Mechanical evaluation of theories of neurulation using computer simulations

Development ◽

10.1242/dev.118.3.1013 ◽

1993 ◽

Vol 118 (3) ◽

pp. 1013-1023 ◽

Cited By ~ 4

Author(s):

D. A. Clausi ◽

G. W. Brodland

Keyword(s):

Computer Simulations ◽

Driving Forces ◽

Shape Change ◽

Three Dimensional ◽

Dorsal Surface ◽

Neural Plate ◽

Neural Tube Closure ◽

Amphibian Embryo ◽

Axial Elongation ◽

Shape Changes

Current theories about the forces that drive neurulation shape changes are evaluated using computer simulations. Custom, three-dimensional, finite element-based computer software is used. The software draws on current engineering concepts and makes it possible to construct a ‘virtual’ embryo with any user-specified mechanical properties. To test a specific hypothesis about the forces that drive neurulation, the whole virtual embryo or any selected part of it is ascribed with the force generators specified in the hypothesis. The shape changes that are produced by these forces are then observed and compared with experimental data. The simulations demonstrate that, when uniform, isotropic circumferential microfilament bundle (CMB) constriction and cephalocaudal (axial) elongation act together on a circular virtual neural plate, it becomes keyhole shaped. When these forces act on a spherical (amphibian) embryo, dorsal surface flattening occurs. Simulations of transverse sections further show that CMB constriction, acting with or without axial elongation, can produce numerous salient transverse features of neurulation. These features include the sequential formation of distinct neural ridges, narrowing and thickening of the neural plate, skewing just medial to the ridges, ‘hinge’ formation and neural tube closure. No region-specific ‘programs’ or non-mechanical cell-cell communications are used. The increase in complexity results entirely from mechanical interactions. The transverse simulations show how changes to the driving forces would affect the patterns of shape change produced. Hypotheses regarding force generation by microtubules, intercellular adhesions and forces extrinsic to the neural plate are also evaluated. The simulations show that these force-generating mechanisms do not, by themselves, produce shape changes that are consistent with normal development. The simulations support the concept of cooperation of forces and suggest that neurulation is robust because redundant force generating mechanisms exist.

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Diacylglycerols and PMA induce actin polymerization and distinct shape changes in lymphocytes: relation to fluid pinocytosis and locomotion

Journal of Cell Science ◽

10.1242/jcs.93.3.457 ◽

1989 ◽

Vol 93 (3) ◽

pp. 457-465

Author(s):

H.U. Keller ◽

V. Niggli ◽

A. Zimmermann

Keyword(s):

Actin Polymerization ◽

Shape Change ◽

Second Messengers ◽

Cell Periphery ◽

Response Curves ◽

Blood Lymphocytes ◽

Different Types ◽

Net Uptake ◽

Very High ◽

Shape Changes

Shape changes have been determined in human blood lymphocytes stimulated with OAG, diC8, PMA, colchicine or the hexapeptide fNLPNTL in short-term assays (30 min). Distinct types of shape-change responses were observed. Colchicine was active in generating a relatively small proportion of polarized lymphocytes (front-tail polarity). OAG, diC8 and PMA produced different types of shape change (non-polar cells with surface projections), and these were closely associated with an increase in actin polymerization and a shift of F-actin into the projections at the cell periphery. The diacylglycerols OAG and diC8 produced biphasic dose-response curves leading to rounding up of cells at very high stimulant concentrations. PMA produced no comparable biphasic response when tested over a much wider concentration range. Though the nonpolar cells with surface projections generated by OAG, diC8 or PMA showed vigorous shape changes, they lacked significant locomotor activity. alpha-Phorbol, 4 alpha-PDD, lumicolchicine or fNLPNTL were inactive. Small blood lymphocytes stimulated by OAG, diC8 or PMA showed a very small increase in the net uptake of FITC-dextran by fluid pinocytosis. Unlike neutrophils, which show a high net uptake, lymphocytes did not concentrate FITC-dextran in large granules, indicating that they do not develop a ‘storage’ compartment in the form of large vesicles. However, small fluorescent spots were consistently found in at least a fraction of blood lymphocytes. The results indicate that stimulated surface movement may be instrumental in fluid pinocytosis. Diacylglycerols may act as second messengers to induce pinocytosis, shape changes and altered actin polymerization in lymphocytes.

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Visualization of Individual Growth-Related Craniofacial Changes Based on Cephalometric Landmark Data: A Pilot Study

The Cleft Palate-Craniofacial Journal ◽

10.1597/1545-1569_2002_039_0341_voigrc_2.0.co_2 ◽

2002 ◽

Vol 39 (3) ◽

pp. 341-352 ◽

Cited By ~ 1

Author(s):

Christopher J. Lux ◽

Jens Starke ◽

Jan Rübel ◽

Angelika Stellzig ◽

Gerda Komposch

Keyword(s):

Dynamic Behavior ◽

Growth Process ◽

Shape Change ◽

Individual Growth ◽

Craniofacial Skeleton ◽

Size And Shape ◽

Lateral Cephalograms ◽

Landmark Data ◽

The Individual ◽

Shape Changes

Objective: An approach based on Euclidean distances between cephalometric landmarks is presented (1) to visualize and localize the individual shape changes of the complex craniofacial skeleton during growth and (2) to depict the individual dynamic behavior of developmental size and shape changes. Patients and Method: Growth-related craniofacial changes were investigated exemplarily for two male orthodontically untreated subjects from the Belfast Growth Study on the basis of lateral cephalograms at 7, 9, 11, 13, and 15 years. The interlandmark distances among seven skeletal cephalometric landmarks served as a database for the study. A modified Karhunen-Loèvedecomposition based on orthogonal modes and time-dependent scalar amplitudes was used to describe the growth process. The individual shape changes of the various craniofacial regions were visualized by allocation of colors to the respective distances, and overdrawn representations were reconstructed by means of multidimensional scaling. Results and Conclusions: This visualization technique allows anatomical regions to be characterized with respect to reduced or strengthened growth, compared with pure size changes. The clinically relevant mechanisms of craniofacial changes are visualized (e.g., shifts in the anteroposterior or vertical dimensions of the jaws in relation to cranial base and structural imbalances during development). In addition, overdrawing the effects of shape change on the skeletal structures gives a more readily comprehensible impression of the growth process. Taking account of the methodical limitations of this approach (e.g., the restrictions concerning the number of landmarks), the clinician may take advantage of this technique in orthodontic or surgical diagnostics to gain additional insight into the individual complex size and shape changes during development along with their dynamic behavior.

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Platelet Shape Change Evoked by Selective Activation of P2X1 Purinoceptors with α,β-Methylene ATP

Thrombosis and Haemostasis ◽

10.1055/s-0037-1615684 ◽

2001 ◽

Vol 85 (02) ◽

pp. 303-308 ◽

Cited By ~ 100

Author(s):

Michael Rolf ◽

Charles Brearley ◽

Martyn Mahaut-Smith

Keyword(s):

Inhibitory Action ◽

Light Transmission ◽

Shape Change ◽

Second Messengers ◽

Receptor Activation ◽

Selective Activation ◽

The Relationship ◽

Shape Changes ◽

Platelet Shape

SummarySimultaneous measurements of [Ca2+]i and light transmission were used to examine the relationship between P2X1 receptor activation and functional platelet responses. The P2X1 agonist α,β-MeATP evoked a transient [Ca2+]i increase and a reversible decrease in light transmission; both responses required external Ca2+ and the nucleotidase apyrase. The transmission response was due to shape change only, verified by scanning electron microscopy and insensitivity to Reopro, a GPIIbIIIa antagonist. α,β-MeATP stimulated smaller shape changes than ADP, however P2X1 responses had a lifespan of <2 h following resuspension in saline and may be considerably larger in vivo. A peak [Ca2+]i increase of >50 nM was required for detectable shape change. Overlap of concentration-response relationships for α,β-MeATP-evoked [Ca2+]i and shape change suggests that other second messengers are not involved. Therefore, the physiological P2X1 agonist ATP can contribute to platelet activation, in contrast to its previously described inhibitory action at metabotropic platelet purinoceptors.

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Roles of SLP-76, phosphoinositide 3-kinase, and gelsolin in the platelet shape changes initiated by the collagen receptor GPVI/FcRγ-chain complex

Blood ◽

10.1182/blood.v96.12.3786 ◽

2000 ◽

Vol 96 (12) ◽

pp. 3786-3792 ◽

Cited By ~ 38

Author(s):

Hervé Falet ◽

Kurt L. Barkalow ◽

Vadim I. Pivniouk ◽

Michael J. Barnes ◽

Raif S. Geha ◽

...

Keyword(s):

Platelet Activation ◽

Shape Change ◽

Chain Complex ◽

Actin Assembly ◽

Coated Surface ◽

Phosphoinositide 3 Kinase ◽

Collagen Receptor ◽

Shape Changes ◽

Platelet Shape

Abstract How platelet shape change initiated by a collagen-related peptide (CRP) specific for the GPVI/FcRγ-chain complex (GPVI/FcRγ-chain) is coupled to SLP-76, phosphoinositide (PI) 3-kinase, and gelsolin is reported. As shown by video microscopy, platelets rapidly round and grow dynamic filopodial projections that rotate around the periphery of the cell after they contact a CRP-coated surface. Lamellae subsequently spread between the projections. All the actin-driven shape changes require SLP-76 expression. SLP-76 is essential for the Ca++mobilization induced by CRP, whereas PI 3-kinase only modulates it. The extension of lamellae requires net actin assembly and an exposure of actin filament barbed ends downstream of PI 3-kinase. Gelsolin expression is also required for the extension of lamellae, but not for the formation of filopodia. Altogether, the data describe the role of SLP-76 in the platelet activation initiated by GPVI/FcRγ-chain and the roles of PI 3-kinase and gelsolin in lamellae spreading.

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