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Sample records for biomimetic helical rosette

  1. Mechanics of tunable helices and geometric frustration in biomimetic seashells

    NASA Astrophysics Data System (ADS)

    Guo, Qiaohang; Chen, Zi; Li, Wei; Dai, Pinqiang; Ren, Kun; Lin, Junjie; Taber, Larry A.; Chen, Wenzhe

    2014-03-01

    Helical structures are ubiquitous in nature and engineering, ranging from DNA molecules to plant tendrils, from sea snail shells to nanoribbons. While the helical shapes in natural and engineered systems often exhibit nearly uniform radius and pitch, helical shell structures with changing radius and pitch, such as seashells and some plant tendrils, add to the variety of this family of aesthetic beauty. Here we develop a comprehensive theoretical framework for tunable helical morphologies, and report the first biomimetic seashell-like structure resulting from mechanics of geometric frustration. In previous studies, the total potential energy is everywhere minimized when the system achieves equilibrium. In this work, however, the local energy minimization cannot be realized because of the geometric incompatibility, and hence the whole system deforms into a shape with a global energy minimum whereby the energy in each segment may not necessarily be locally optimized. This novel approach can be applied to develop materials and devices of tunable geometries with a range of applications in nano/biotechnology.

  2. Novel injectable biomimetic hydrogels with carbon nanofibers and self assembled rosette nanotubes for myocardial applications.

    PubMed

    Meng, Xiangling; Stout, David A; Sun, Linlin; Beingessner, Rachel L; Fenniri, Hicham; Webster, Thomas J

    2013-04-01

    The objective of the present in vitro study was to investigate cardiomyocyte functions, specifically their adhesion and proliferation, on injectable scaffolds containing RNT (rosette nanotubes) and CNF (carbon nanofibers) in a pHEMA (poly(2-hydroxyethyl methacrylate)) hydrogel to determine their potential for myocardial tissue engineering applications. RNTs are novel biocompatible nanomaterials assembled from synthetic analogs of DNA bases guanine and cytosine that self-assemble within minutes when placed in aqueous solutions at body temperatures. These materials could potentially improve cardiomyocyte functions and solidification time of pHEMA and CNF composites. Because heart tissue is conductive, CNFs were added to pHEMA to increase the composite's conductivity. Our results showed that cardiomyocyte density increased after 4 h, 1 day, and 3 days with greater amounts of CNFs and greater amounts of RNTs in pHEMA (up to 10 mg mL(-1) CNFs and 0.05 mg mL(-1) RNTs). Factors that may have increased cardiomyocyte functions include greater wettability, conductivity, and an increase in surface nanoroughness with greater amounts of CNFs and RNTs. In effect, contact angles measured on the surface of the composites decreased while the conductivity and surface roughness increased as CNFs and RNTs content increased. Lastly, the ultimate tensile modulus decreased for composites with greater amounts of CNFs. In summary, the properties of these injectable composites make them promising candidates for myocardial tissue engineering applications and should be further studied. PMID:23008178

  3. Biomimetic Hierarchical Assembly of Helical Supraparticles from Chiral Nanoparticles.

    PubMed

    Zhou, Yunlong; Marson, Ryan L; van Anders, Greg; Zhu, Jian; Ma, Guanxiang; Ercius, Peter; Sun, Kai; Yeom, Bongjun; Glotzer, Sharon C; Kotov, Nicholas A

    2016-03-22

    Chiroptical materials found in butterflies, beetles, stomatopod crustaceans, and other creatures are attributed to biocomposites with helical motifs and multiscale hierarchical organization. These structurally sophisticated materials self-assemble from primitive nanoscale building blocks, a process that is simpler and more energy efficient than many top-down methods currently used to produce similarly sized three-dimensional materials. Here, we report that molecular-scale chirality of a CdTe nanoparticle surface can be translated to nanoscale helical assemblies, leading to chiroptical activity in the visible electromagnetic range. Chiral CdTe nanoparticles coated with cysteine self-organize around Te cores to produce helical supraparticles. D-/L-Form of the amino acid determines the dominant left/right helicity of the supraparticles. Coarse-grained molecular dynamics simulations with a helical pair-potential confirm the assembly mechanism and the origin of its enantioselectivity, providing a framework for engineering three-dimensional chiral materials by self-assembly. The helical supraparticles further self-organize into lamellar crystals with liquid crystalline order, demonstrating the possibility of hierarchical organization and with multiple structural motifs and length scales determined by molecular-scale asymmetry of nanoparticle interactions. PMID:26900920

  4. Biomimetic Transmembrane Channels with High Stability and Transporting Efficiency from Helically Folded Macromolecules.

    PubMed

    Lang, Chao; Li, Wenfang; Dong, Zeyuan; Zhang, Xin; Yang, Feihu; Yang, Bing; Deng, Xiaoli; Zhang, Chenyang; Xu, Jiayun; Liu, Junqiu

    2016-08-01

    Membrane channels span the cellular lipid bilayers to transport ions and molecules into cells with sophisticated properties including high efficiency and selectivity. It is of particular biological importance in developing biomimetic transmembrane channels with unique functions by means of chemically synthetic strategies. An artificial unimolecular transmembrane channel using pore-containing helical macromolecules is reported. The self-folding, shape-persistent, pore-containing helical macromolecules are able to span the lipid bilayer, and thus result in extraordinary channel stability and high transporting efficiency for protons and cations. The lifetime of this artificial unimolecular channel in the lipid bilayer membrane is impressively long, rivaling those of natural protein channels. Natural channel mimics designed by helically folded polymeric scaffolds will display robust and versatile transport-related properties at single-molecule level. PMID:27356157

  5. Triangular prism-shaped β-peptoid helices as unique biomimetic scaffolds

    PubMed Central

    Laursen, Jonas S.; Harris, Pernille; Fristrup, Peter; Olsen, Christian A.

    2015-01-01

    β-Peptoids are peptidomimetics based on N-alkylated β-aminopropionic acid residues (or N-alkyl-β-alanines). This type of peptide mimic has previously been incorporated in biologically active ligands and has been hypothesized to be able to exhibit foldamer properties. Here we show, for the first time, that β-peptoids can be tuned to fold into stable helical structures. We provide high-resolution X-ray crystal structures of homomeric β-peptoid hexamers, which reveal right-handed helical conformations with exactly three residues per turn and a helical pitch of 9.6–9.8 Å between turns. The presence of folded conformations in solution is supported by circular dichroism spectroscopy showing length- and solvent dependency, and molecular dynamics simulations provide further support for a stabilized helical secondary structure in organic solvent. We thus outline a framework for future design of novel biomimetics that display functional groups with high accuracy in three dimensions, which has potential for development of new functional materials. PMID:25943784

  6. Rosette (Double Blossom)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rosette, or double blossom, is a serious disease of erect blackberries that is limited to the genus Rubus. Rosette may occur on trailing blackberries and dewberries, but rarely on red and black raspberries. In the United States, rosette occurs from New Jersey to Illinois and southwest to Texas and i...

  7. A new rosette in retinoblastoma

    PubMed Central

    Das, Dipankar; Bhattacharjee, Kasturi; Barthakur, Sumita Sarma; Tahiliani, Prerana Sushil; Deka, Panna; Bhattacharjee, Harsha; Deka, Apurba; Paul, Rajashree

    2014-01-01

    Retinoblastoma, the most common primary malignant intraocular tumor of childhood is a great success story in pediatric and ocular oncology. Pathology of retinoblastoma is important to guide the treatment modalities. Differentiated retinoblastoma is commonly seen in younger age group. Since a hundred years, we have been observing two typical true rosettes in retinoblastoma in the form of Flexner-Wintersteiner (FW) and Homer Wright (HW) rosettes and in many occasions pseudorosettes have been documented. In the present case report, a third new type of rosette was identified in a differentiated retinoblastoma which had an unusual anterior segment involvement. PMID:24881618

  8. Probabilistic Modeling of Rosette Formation

    PubMed Central

    Long, Mian; Chen, Juan; Jiang, Ning; Selvaraj, Periasamy; McEver, Rodger P.; Zhu, Cheng

    2006-01-01

    Rosetting, or forming a cell aggregate between a single target nucleated cell and a number of red blood cells (RBCs), is a simple assay for cell adhesion mediated by specific receptor-ligand interaction. For example, rosette formation between sheep RBC and human lymphocytes has been used to differentiate T cells from B cells. Rosetting assay is commonly used to determine the interaction of Fc γ-receptors (FcγR) expressed on inflammatory cells and IgG coated on RBCs. Despite its wide use in measuring cell adhesion, the biophysical parameters of rosette formation have not been well characterized. Here we developed a probabilistic model to describe the distribution of rosette sizes, which is Poissonian. The average rosette size is predicted to be proportional to the apparent two-dimensional binding affinity of the interacting receptor-ligand pair and their site densities. The model has been supported by experiments of rosettes mediated by four molecular interactions: FcγRIII interacting with IgG, T cell receptor and coreceptor CD8 interacting with antigen peptide presented by major histocompatibility molecule, P-selectin interacting with P-selectin glycoprotein ligand 1 (PSGL-1), and L-selectin interacting with PSGL-1. The latter two are structurally similar and are different from the former two. Fitting the model to data enabled us to evaluate the apparent effective two-dimensional binding affinity of the interacting molecular pairs: 7.19 × 10−5 μm4 for FcγRIII-IgG interaction, 4.66 × 10−3 μm4 for P-selectin-PSGL-1 interaction, and 0.94 × 10−3 μm4 for L-selectin-PSGL-1 interaction. These results elucidate the biophysical mechanism of rosette formation and enable it to become a semiquantitative assay that relates the rosette size to the effective affinity for receptor-ligand binding. PMID:16603493

  9. Studies of the stability of water-soluble polypeptoid helices and investigation of synthetic, biomimetic substrates for the development of a thermally triggered, enzymatically crosslinked hydrogel for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sanborn, Tracy Joella

    Due to the unique 3D structures of proteins, these biopolymers are able to perform a myriad of vital functions and activities in vivo. Peptidomimetic oligomers are being synthesized to mimic the structure and function of natural peptides. We have examined the stability of secondary structure of a poly-N-substituted glycine (peptoid) and developed synthetic substrates for transglutaminase enzymes. We synthesized an amphipathic, helical, 36 residue peptoid to study the stability of peptoid secondary structure using circular dichroism. We saw no significant dependence of helical structure on concentration, solvent, or temperature. The extraordinary resistance of these peptoid helices to denaturation is consistent with a dominant role, of steric forces in their structural stabilization. The structured polypeptoids studied here have potential as robust mimics of helical polypeptides of therapeutic interest. The ability of transglutaminases to crosslink peptidomimetic substrates was also investigated. There is a medical need for robust, biocompatible hydrogels that can be rapidly crosslinked in situ, for application as surgical adhesives, bone-inductive materials, or for drug delivery. We have taken an enzymatic approach to the creation of a novel gelation system that fits these requirements, utilizing transglutaminase enzymes, thermo-responsive liposomes, and a biomimetic enzyme substrate based on a peptide-polymer conjugate. At room temperature, the hydrogel system is a solution. Upon heating to 37°C, the calcium-loaded liposomes release calcium that activates Factor XIII in the presence of thrombin, producing a gel within 9 minutes. Rheological studies demonstrated that the hydrogel behaves as a robust, elastic solid, while scanning electron microscopy studies revealed that the hydrogel has a very dense morphology overall. We also investigated the ability of transglutaminases to crosslink non-natural, peptoid-based substrates. The activity of five lysine

  10. Rheopathologic Consequence of Plasmodium vivax Rosette Formation.

    PubMed

    Zhang, Rou; Lee, Wenn-Chyau; Lau, Yee-Ling; Albrecht, Letusa; Lopes, Stefanie C P; Costa, Fabio T M; Suwanarusk, Rossarin; Nosten, Francois; Cooke, Brian M; Rénia, Laurent; Russell, Bruce

    2016-08-01

    Malaria parasites dramatically alter the rheological properties of infected red blood cells. In the case of Plasmodium vivax, the parasite rapidly decreases the shear elastic modulus of the invaded RBC, enabling it to avoid splenic clearance. This study highlights correlation between rosette formation and altered membrane deformability of P. vivax-infected erythrocytes, where the rosette-forming infected erythrocytes are significantly more rigid than their non-rosetting counterparts. The adhesion of normocytes to the PvIRBC is strong (mean binding force of 440pN) resulting in stable rosette formation even under high physiological shear flow stress. Rosetting may contribute to the sequestration of PvIRBC schizonts in the host microvasculature or spleen. PMID:27509168

  11. Rheopathologic Consequence of Plasmodium vivax Rosette Formation

    PubMed Central

    Lau, Yee-Ling; Albrecht, Letusa; Lopes, Stefanie C. P.; Costa, Fabio T. M.; Suwanarusk, Rossarin; Nosten, Francois; Cooke, Brian M.; Rénia, Laurent; Russell, Bruce

    2016-01-01

    Malaria parasites dramatically alter the rheological properties of infected red blood cells. In the case of Plasmodium vivax, the parasite rapidly decreases the shear elastic modulus of the invaded RBC, enabling it to avoid splenic clearance. This study highlights correlation between rosette formation and altered membrane deformability of P. vivax-infected erythrocytes, where the rosette-forming infected erythrocytes are significantly more rigid than their non-rosetting counterparts. The adhesion of normocytes to the PvIRBC is strong (mean binding force of 440pN) resulting in stable rosette formation even under high physiological shear flow stress. Rosetting may contribute to the sequestration of PvIRBC schizonts in the host microvasculature or spleen. PMID:27509168

  12. Notch Signaling Maintains Neural Rosette Polarity

    PubMed Central

    Main, Heather; Radenkovic, Jelena; Jin, Shao-bo; Lendahl, Urban; Andersson, Emma R.

    2013-01-01

    Formation of the metazoan body plan requires a complex interplay of morphological changes and patterning, and central to these processes is the establishment of apical/basal cell polarity. In the developing nervous system, apical/basal cell polarity is essential for neural tube closure and maintenance of the neural stem cell population. In this report we explore how a signaling pathway important for nervous system development, Notch signaling, impacts on apical/basal cell polarity in neural differentiation. CSL−/− mouse embryos, which are devoid of canonical Notch signaling, demonstrated a neural tube phenotype consistent with cell polarity and convergent extension defects, including deficiencies in the restricted expression of apical polarity markers in the neuroepithelium. CSL−/− mouse embryonic stem (ES) cells, cultured at low density, behaved as wild-type in the establishment of neural progenitors and apical specification, though progression through rosette formation, an in vitro correlate of neurulation, required CSL for correct maintenance of rosette structure and regulation of neuronal differentiation. Similarly, acute pharmacological inhibition of Notch signaling led to the breakdown of neural rosettes and accelerated neuronal differentiation. In addition to functional Notch signaling, rosette integrity was found to require actin polymerization and Rho kinase (ROCK) activity. Disruption of rosettes through inhibition of actin polymerization or ROCK activity, however, had no effect on neuronal differentiation, indicating that rosette maintenance is not a prerequisite for normal neuronal differentiation. In conclusion, our data indicate that Notch signaling plays a role not only in differentiation, but also in organization and maintenance of polarity during development of the early nervous system. PMID:23675446

  13. Biomimetic modelling.

    PubMed Central

    Vincent, Julian F V

    2003-01-01

    Biomimetics is seen as a path from biology to engineering. The only path from engineering to biology in current use is the application of engineering concepts and models to biological systems. However, there is another pathway: the verification of biological mechanisms by manufacture, leading to an iterative process between biology and engineering in which the new understanding that the engineering implementation of a biological system can bring is fed back into biology, allowing a more complete and certain understanding and the possibility of further revelations for application in engineering. This is a pathway as yet unformalized, and one that offers the possibility that engineers can also be scientists. PMID:14561351

  14. IUE Tomography of the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    van Buren, Dave

    We propose to obtain SWP and LWR spectra of a dozen 8th magnitude O and B stars associated with the Rosette Nebula in Monoceros for the purpose of determining the structure and kinematics of this HII region / stellar wind bubble. The ability to sense along numerous lines of sight will allow us to determine the detailed physical conditions which exist in the nebula, both inside the bubble and in the HII region exterior to it. This picture can then be compared in detail to the theory of stellar wind bubbles, HII region dynamics, photodissociation fronts and shock destruction of grains. The hot gas in the bubble has been detected in the soft x-rays by the Einstein satellite, so we anticipate a structure similar to that found by Castor, McCray and Weaver for adiabatic (non-radiative) stellar wind bubbles. Such adiabatic bubbles are ideal laboratories for the study of thermal conduction on astrophysical scales. While we will probably not be able to detect the conductive interface between the hot bubble interior and the swept up shell, we will be able to determine many properties of the bubble. These properties in turn will point to the Rosette's suitability as a cosmic laboratory for studying conductive interfaces with the Space Telescope. The energetics and mass balance of HII regions and stellar wind bubbles is important for a number of problems: the physical conditions in and near star forming regions; the structure and evolution of "superbubbles"; and galactic "ecology".

  15. Rosette globulettes and shells in the infrared

    NASA Astrophysics Data System (ADS)

    Mäkelä, M. M.; Haikala, L. K.; Gahm, G. F.

    2014-07-01

    Context. Giant galactic H ii regions surrounding central young clusters show compressed molecular shells, which have broken up into clumps, filaments, and elephant trunks interacting with UV light from central OB stars. Tiny, dense clumps of subsolar mass, called globulettes, form in this environment. Aims: We observe and explore the nature and origin of the infrared emission and extinction in these cool, dusty shell features and globulettes in one H ii region, the Rosette nebula, and search for associated newborn stars. Methods: We imaged the northwestern quadrant of the Rosette nebula in the near-infrared (NIR) through wideband JHKs filters and narrowband H2 1-0 S(1) and Pβ plus continuum filters using the Son of Isaac (SOFI) instrument at the New Technology Telescope (NTT) at European Southern Observatory (ESO). We used the NIR images to study the surface brightness of the globulettes and associated bright rims. We used the NIR JHKs photometry to create a visual extinction map and to search for objects with NIR excess emission. In addition, archival images from Spitzer Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 μm and Herschel Photoconductor Array Camera and Spectrometer (PACS) observations, covering several bands in the mid-infrared and far-infrared, were used to further analyze the stellar population, to examine the structure of the trunks and other shell structures and to study this Rosette nebula photon-dominated region in more detail. Results: The globulettes and elephant trunks have bright rims in the Ks band, which are unresolved in our images, on the sides facing the central cluster. An analysis of 21 globulettes, where surface brightness in the H2 1-0 S(1) line at 2.12 μm is detected, shows that approximately a third of the surface brightness observed in the Ks filter is due to this line: the observed average of the H2/Ks surface brightness is 0.26 ± 0.02 in the globulettes' cores and 0.30 ± 0.01 in the rims

  16. Metabolic fluxes in an illuminated Arabidopsis rosette.

    PubMed

    Szecowka, Marek; Heise, Robert; Tohge, Takayuki; Nunes-Nesi, Adriano; Vosloh, Daniel; Huege, Jan; Feil, Regina; Lunn, John; Nikoloski, Zoran; Stitt, Mark; Fernie, Alisdair R; Arrivault, Stéphanie

    2013-02-01

    Photosynthesis is the basis for life, and its optimization is a key biotechnological aim given the problems of population explosion and environmental deterioration. We describe a method to resolve intracellular fluxes in intact Arabidopsis thaliana rosettes based on time-dependent labeling patterns in the metabolome. Plants photosynthesizing under limiting irradiance and ambient CO2 in a custom-built chamber were transferred into a (13)CO2-enriched environment. The isotope labeling patterns of 40 metabolites were obtained using liquid or gas chromatography coupled to mass spectrometry. Labeling kinetics revealed striking differences between metabolites. At a qualitative level, they matched expectations in terms of pathway topology and stoichiometry, but some unexpected features point to the complexity of subcellular and cellular compartmentation. To achieve quantitative insights, the data set was used for estimating fluxes in the framework of kinetic flux profiling. We benchmarked flux estimates to four classically determined flux signatures of photosynthesis and assessed the robustness of the estimates with respect to different features of the underlying metabolic model and the time-resolved data set. PMID:23444331

  17. Rosette nanotubes inhibit bovine neutrophil chemotaxis

    PubMed Central

    Le, Minh Hong Anh; Suri, Sarabjeet Singh; Rakotondradany, Felaniaina; Fenniri, Hicham; Singh, Baljit

    2010-01-01

    Migration of activated neutrophils that have prolonged lifespan into inflamed organs is an important component of host defense but also contributes to tissue damage and mortality. In this report, we used biologically-inspired RGD-tagged rosette nanotubes (RNT) to inhibit neutrophil chemotaxis. We hypothesize that RGD-RNT will block neutrophil migration through inhibition of MAPK. In this report, RNT conjugated to lysine (K–RNT) and arginine-glycine-aspartic acid-serine-lysine (RGDSK-RNT) were co-assembled in a molar ratio of 95/5. The effect of the resulting composite RNT (RGDSK/K–RNT) on neutrophil chemotaxis, cell signaling and apoptosis was then investigated. Exposure to RGDSK/K–RNT reduced bovine neutrophil migration when compared to the non-treated group (p < 0.001). Similar effect was seen following treatment with ERK1/2 or p38 MAPK inhibitors. Phosphorylation of the ERK1/2 and p38 MAPK was inhibited at 5 min by RGDSK/K–RNT (p < 0.05). The RGDSD/K-RNT did not affect the migration of neutrophils pre-treated with αvβ3 integrin antibody suggesting that both bind to the same receptor. RGDSK/K–RNT did not induce apoptosis in bovine neutrophils, which was suppressed by pre-exposing them to LPS (p < 0.001). We conclude that RGDSK/K–RNT inhibit phosphorylation of ERK1/2 and p38 MAPK and inhibit chemotaxis of bovine neutrophils. PMID:20663476

  18. Biocatalysis and biomimetics

    SciTech Connect

    Burrington, J.D.; Clark, D.S.

    1989-01-01

    The proceedings are divided into three parts: Bioscience and biotechnology; Structure-function relationships; and Biomimetics. Topics include: the chemistry of biotechnology, biomimetics, and biocatalysts; crystallography and mutagenesis; computerized simulation of biocatalysis and biomimetic processes; enzymatic reactions in micellar systems; hydroxylation of hydrocarbons; oxidation of lignin; zeolite catalysts as enzyme mimics; and immobilization of proteins and enzymes. Some papers have been processed separately for inclusion on the data base.

  19. Spontaneous rosette formation in patients with oral cancer.

    PubMed

    Kostadinov, D A; Tzanov, T; Boeva, M; Ikonopisov, R L

    1979-06-01

    The percentage of "total" E-rosettes was studied in the peripheral blood of 38 untreated patients with squamous cell carcinoma of the oral cavity, performing the test at 4 degrees C and at 20 degrees C. At 4 degrees C the quantity of the E-rosettes was higher than at 20 degrees C. The mean value of E-rosettes was strongly reduced only in 17 of these patients with metastases in the regional lymph nodes when compared with a group of 40 normal individuals as well as with the group of remaining 21 patients with localized cancer (P less than 0.001), whatever the temperature of testing. The mean percentage of 20 degrees C E-rosettes was significantly higher in patients with localized disease than in the 22 normal donors (50.2 +/- 3.0% vs 41.8 +/- 2.0%, P less than 0.01) but in favour of 4 degrees C E-rosettes the difference was not significant (57.3 +/- 2.8% vs 54.2 +/- 2.9%). Thus there was a clear correlation between changes of the T cell level and the clinical stage of the disease. PMID:486691

  20. Biomimetic Particles as Therapeutics

    PubMed Central

    Green, Jordan J.

    2015-01-01

    In recent years, there have been major advances in the development of novel nanoparticle and microparticle-based therapeutics. An emerging paradigm is the incorporation of biomimetic features into these synthetic therapeutic constructs to enable them to better interface with biological systems. Through the control of size, shape, and material consistency, particle cores have been generated that better mimic natural cells and viruses. In addition, there have been significant advances in biomimetic surface functionalization of particles through the integration of bio-inspired artificial cell membranes and naturally derived cell membranes. Biomimetic technologies enable therapeutic particles to have increased potency to benefit human health. PMID:26277289

  1. Biomimetics of photonic nanostructures

    NASA Astrophysics Data System (ADS)

    Parker, Andrew R.; Townley, Helen E.

    2007-06-01

    Biomimetics is the extraction of good design from nature. One approach to optical biomimetics focuses on the use of conventional engineering methods to make direct analogues of the reflectors and anti-reflectors found in nature. However, recent collaborations between biologists, physicists, engineers, chemists and materials scientists have ventured beyond experiments that merely mimic what happens in nature, leading to a thriving new area of research involving biomimetics through cell culture. In this new approach, the nanoengineering efficiency of living cells is harnessed and natural organisms such as diatoms and viruses are used to make nanostructures that could have commercial applications.

  2. Biomimetic thin film synthesis

    SciTech Connect

    Graff, G.L.; Campbell, A.A.; Gordon, N.R.

    1995-05-01

    The purpose of this program is to develop a new process for forming thin film coatings and to demonstrate that the biomimetic thin film technology developed at PNL is useful for industrial applications. In the biomimetic process, mineral deposition from aqueous solution is controlled by organic functional groups attached to the underlying substrate surface. The coatings process is simple, benign, inexpensive, energy efficient, and particularly suited for temperature sensitive substrate materials (such as polymers). In addition, biomimetic thin films can be deposited uniformly on complex shaped and porous substrates providing a unique capability over more traditional line-of-sight methods.

  3. Endothelial podosome rosettes regulate vascular branching in tumour angiogenesis

    PubMed Central

    Seano, Giorgio; Chiaverina, Giulia; Gagliardi, Paolo Armando; Blasio, Laura di; Puliafito, Alberto; Bouvard, Claire; Sessa, Roberto; Tarone, Guido; Sorokin, Lydia; Helley, Dominique; Jain, Rakesh K.; Serini, Guido; Bussolino, Federico; Primo, Luca

    2015-01-01

    The mechanism by which angiogenic endothelial cells break the physical barrier of the vascular basement membrane and consequently sprout to form new vessels in mature tissues is unclear. Here, we show that the angiogenic endothelium is characterized by the presence of functional podosome rosettes. These extracellular-matrix-degrading and adhesive structures are precursors of de novo branching points and represent a key feature in the formation of new blood vessels. VEGF-A stimulation induces the formation of endothelial podosome rosettes by upregulating integrin α6β1. In contrast, the binding of α6β1 integrin to the laminin of the vascular basement membrane impairs the formation of podosome rosettes by restricting α6β1 integrin to focal adhesions and hampering its translocation to podosomes. Using an ex vivo sprouting angiogenesis assay, transgenic and knockout mouse models and human tumour sample analysis, we provide evidence that endothelial podosome rosettes control blood vessel branching and are critical regulators of pathological angiogenesis. PMID:25218639

  4. Biomimetics--a review.

    PubMed

    Vincent, J F V

    2009-11-01

    Biology can inform technology at all levels (materials, structures, mechanisms, machines, and control) but there is still a gap between biology and technology. This review itemizes examples of biomimetic products and concludes that the Russian system for inventive problem solving (teoriya resheniya izobreatatelskikh zadatch (TRIZ)) is the best system to underpin the technology transfer. Biomimetics also challenges the current paradigm of technology and suggests more sustainable ways to manipulate the world. PMID:20092091

  5. Helical equilibrium

    SciTech Connect

    Yoshikawa, S.

    1981-08-01

    A straight, helical plasma equilibrium equation is solved numerically for a plasma with a helical magnetic axis. As is expected, by a suitable choice of the plasma boundary, the vacuum configuration is made line ..integral.. dl/B stable. As the plasma pressure increases, the line ..integral.. dl/B criterion will improve (again as expected). There is apparently no limit on the plasma ..beta.. from the equilibrium consideration. Thus helical-axis stellarator ..beta.. will presumably be limited by MHD stability ..beta.., and not by equilibrium ..beta...

  6. Rosette-forming glioneuronal tumor originating in the hypothalamus.

    PubMed

    Yamamoto, Tetsuya; Matsubara, Teppei; Satomi, Kaishi; Sakamoto, Noriaki; Matsuda, Masahide; Muroi, Ai; Ishikawa, Eiichi; Akutsu, Hiroyoshi; Nakai, Kei; Matsumura, Akira

    2015-10-01

    Rosette-forming glioneuronal tumors (RGNT) of the fourth ventricle are slow-growing tumors that primarily involve the fourth ventricular region. We here report the first patient, an 8-year-old girl, with an RGNT originating in the hypothalamus and manifesting with precocious puberty. After partial removal, the remaining tumor showed rapid enlargement, and the pathologic diagnosis at the second surgery revealed histopathologic features similar to those found in the initial samples, including biphasic patterns of neurocytic rosettes and GFAP-stained astrocytic components. These tumor cells had mildly atypical nuclei; however, mitotic figures and necrosis were absent. Eosinophilic granular bodies and a glomeruloid vasculature were found, but Rosenthal fibers were absent. The Ki-67 proliferative index was 3.5 % (vs 1.1 % at the initial surgery). No recurrence was recorded during the 3-year period after the proton radiotherapy. PMID:26156565

  7. An S[II] Survey of the Rosette Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Ybarra, J. E.; Phelps, R. L.; Mahaffey, C.

    2002-12-01

    We present observations resulting from a narrow-band [SII] and continuum survey of the Rosette Molecular Cloud, using the 1.5-meter telescope at Palomar Observatory. We discuss the detection of several Herbig-Haro objects and discuss possible spatial coincidences with known star forming regions within the cloud. Research supported, in part, by a Cottrell College Science Award from the Research Corporation.

  8. Void Points, Rosettes, and a Brief History of Planetary Astronomy

    NASA Astrophysics Data System (ADS)

    Kosso, Peter

    2013-12-01

    Almost all models of planetary orbits, from Aristotle through Newton, include void points, empty points in space that have an essential role in defining the orbit. By highlighting the role of these void points, as well as the rosette pattern of the orbit that often results, I bring out different features in the history of planetary astronomy and place a different emphasis on its revolutionary changes, different from those rendered in terms of epicycles or the location of the earth.

  9. Helical logic

    NASA Astrophysics Data System (ADS)

    Merkle, Ralph C.; Drexler, K. Eric

    1996-12-01

    Helical logic is a theoretical proposal for a future computing technology using the presence or absence of individual electrons (or holes) to encode 1s and 0s. The electrons are constrained to move along helical paths, driven by a rotating electric field in which the entire circuit is immersed. The electric field remains roughly orthogonal to the major axis of the helix and confines each charge carrier to a fraction of a turn of a single helical loop, moving it like water in an Archimedean screw. Each loop could in principle hold an independent carrier, permitting high information density. One computationally universal logic operation involves two helices, one of which splits into two `descendant' helices. At the point of divergence, differences in the electrostatic potential resulting from the presence or absence of a carrier in the adjacent helix controls the direction taken by a carrier in the splitting helix. The reverse of this sequence can be used to merge two initially distinct helical paths into a single outgoing helical path without forcing a dissipative transition. Because these operations are both logically and thermodynamically reversible, energy dissipation can be reduced to extremely low levels. This is the first proposal known to the authors that combines thermodynamic reversibility with the use of single charge carriers. It is important to note that this proposal permits a single electron to switch another single electron, and does not require that many electrons be used to switch one electron. The energy dissipated per logic operation can very likely be reduced to less than 0957-4484/7/4/004/img5 at a temperature of 1 K and a speed of 10 GHz, though further analysis is required to confirm this. Irreversible operations, when required, can be easily implemented and should have a dissipation approaching the fundamental limit of 0957-4484/7/4/004/img6.

  10. Supracolloidal helices from soft Janus particles by tuning the particle softness

    NASA Astrophysics Data System (ADS)

    Zou, Qing-Zhi; Li, Zhan-Wei; Lu, Zhong-Yuan; Sun, Zhao-Yan

    2016-02-01

    Because of the unique architectures and promising potential applications of biomimetic helical structures in biotechnology and nanotechnology, the design and fabrication of these structures by experimentally realizable anisotropic colloidal particles remain one of the most challenging tasks in materials science. Here we show how soft Janus particles self-assemble into supracolloidal helices with distinctive structural characteristics, including single helices, double helices, and Bernal spirals, by appropriately tuning the particle softness. We further examine the kinetic mechanisms governing the formation of different helical structures by using particle-based dynamics simulations. Our results provide a new way for experimentally fabricating structure-controllable supracolloidal helices solely from the self-assembly of soft Janus particles.Because of the unique architectures and promising potential applications of biomimetic helical structures in biotechnology and nanotechnology, the design and fabrication of these structures by experimentally realizable anisotropic colloidal particles remain one of the most challenging tasks in materials science. Here we show how soft Janus particles self-assemble into supracolloidal helices with distinctive structural characteristics, including single helices, double helices, and Bernal spirals, by appropriately tuning the particle softness. We further examine the kinetic mechanisms governing the formation of different helical structures by using particle-based dynamics simulations. Our results provide a new way for experimentally fabricating structure-controllable supracolloidal helices solely from the self-assembly of soft Janus particles. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR07011B

  11. Novel biologically-inspired rosette nanotube PLLA scaffolds for improving human mesenchymal stem cell chondrogenic differentiation.

    PubMed

    Childs, Allie; Hemraz, Usha D; Castro, Nathan J; Fenniri, Hicham; Zhang, Lijie Grace

    2013-12-01

    Cartilage defects are a persistent issue in orthopedic tissue engineering where acute and chronic tissue damage stemming from osteoarthritis, trauma, and sport injuries, present a common and serious clinical problem. Unlike bone, cartilage repair continues to be largely intractable due to the tissue's inherently poor regenerative capacity. Thus, the objective of this study is to design a novel tissue engineered nanostructured cartilage scaffold via biologically-inspired self-assembling rosette nanotubes (RNTs) and biocompatible non-woven poly (l-lactic acid) (PLLA) for enhanced human bone marrow mesenchymal stem cell (hMSC) chondrogenic differentiation. Specifically, RNTs are a new class of biomimetic supramolecular nanomaterial obtained through the self-assembly of low-molecular-weight modified guanine/cytosine DNA base hybrids (the G∧C motif) in an aqueous environment. In this study, we synthesized a novel twin G∧C-based RNT (TB-RGDSK) functionalized with cell-favorable arginine-glycine-aspartic acid-serine-lysine (RGDSK) integrin binding peptide and a twin G∧C based RNT with an aminobutane linker molecule (TBL). hMSC adhesion, proliferation and chondrogenic differentiation were evaluated in vitro in scaffold groups consisting of biocompatible PLLA with TBL, 1:9 TB-RGDSK:TBL, and TB-RGDSK, respectively. Our results show that RNTs can remarkably increase total glycosaminoglycan, collagen, and protein production when compared to PLLA controls without nanotubes. Furthermore, the TB-RGDSK with 100% well-organized RGDSK peptides achieved the highest chondrogenic differentiation of hMSCs. The current in vitro study illustrated that RNT nanotopography and surface chemistry played an important role in enhancing hMSC chondrogenic differentiation thus making them promising for cartilage regeneration. PMID:24225196

  12. Macro-fiber composite piezoelectric rosettes for acoustic source location in complex structures

    NASA Astrophysics Data System (ADS)

    Matt, Howard; Lanza di Scalea, Francesco

    2007-04-01

    An approach based upon the employment of piezoelectric transducer rosettes is proposed for passive damage or impact location in anisotropic or geometrically-complex structures. The rosettes are comprised of rectangular Macro-Fiber Composite (MFC) transducers which exhibit a highly directive response to ultrasonic guided waves. The MFC response to flexural (A 0) motion is decomposed into axial and transverse sensitivity factors, which allow extraction of the direction of an incoming wave using rosette principles. The wave source location in a plane is then simply determined by intersecting the wave directions detected by two rosettes. The rosette approach is applicable to anisotropic or geometrically-complex structures where conventional time-of-flight source location is challenging due to the direction-dependent wave velocity. The performance of the rosettes for source location is validated through pencil-lead breaks performed on an aluminum plate, an anisotropic CFRP laminate, and a complex CFRP-honeycomb sandwich panel.

  13. Biomimetic remineralization of dentin

    PubMed Central

    Niu, Li-na; Zhang, Wei; Pashley, David H.; Breschi, Lorenzo; Mao, Jing; Chen, Ji-hua; Tay, Franklin R.

    2013-01-01

    Objectives Remineralization of demineralized dentin is important for improving dentin bonding stability and controlling primary and secondary caries. Nevertheless, conventional dentin remineralization strategy is not suitable for remineralizing completely-demineralized dentin within hybrid layers created by etch-and-rinse and moderately aggressive self-etch adhesive systems, or the superficial part of a caries-affected dentin lesion left behind after minimally invasive caries removal. Biomimetic remineralization represents a different approach to this problem by attempting to backfill the demineralized dentin collagen with liquid-like amorphous calcium phosphate nanoprecursor particles that are stabilized by biomimetic analogs of noncollagenous proteins. Methods This paper reviewed the changing concepts in calcium phosphate mineralization of fibrillar collagen, including the recently discovered, non-classical particle-based crystallization concept, formation of polymer-induced liquid- precursors (PILP), experimental collagen models for mineralization, and the need for using phosphate-containing biomimetic analogs for biomimetic mineralization of collagen. Published work on the remineralization of resin-dentin bonds and artificial caries-like lesions by various research groups was then reviewed. Finally, the problems and progress associated with the translation of a scientifically-sound concept into a clinically-applicable approach are discussed. Results and Significance The particle-based biomimetic remineralization strategy based on the PILP process demonstrates great potential in remineralizing faulty hybrid layers or caries-like dentin. Based on this concept, research in the development of more clinically feasible dentin remineralization strategy, such as incorporating poly(anionic) acid-stabilized amorphous calcium phosphate nanoprecursor-containing mesoporous silica nanofillers in dentin adhesives, may provide a promising strategy for increasing of the

  14. Helical filaments

    NASA Astrophysics Data System (ADS)

    Barbieri, Nicholas; Hosseinimakarem, Zahra; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Johnson, Eric; Richardson, Martin

    2014-06-01

    The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

  15. Amelogenin and Enamel Biomimetics

    PubMed Central

    Ruan, Qichao; Moradian-Oldak, Janet

    2015-01-01

    Mature tooth enamel is acellular and does not regenerate itself. Developing technologies that rebuild tooth enamel and preserve tooth structure is therefore of great interest. Considering the importance of amelogenin protein in dental enamel formation, its ability to control apatite mineralization in vitro, and its potential to be applied in fabrication of future bio-inspired dental material this review focuses on two major subjects: amelogenin and enamel biomimetics. We review the most recent findings on amelogenin secondary and tertiary structural properties with a focus on its interactions with different targets including other enamel proteins, apatite mineral, and phospholipids. Following a brief overview of enamel hierarchical structure and its mechanical properties we will present the state-of-the-art strategies in the biomimetic reconstruction of human enamel. PMID:26251723

  16. Biomimetic Scaffolds for Osteogenesis

    PubMed Central

    Yuan, Nance; Rezzadeh, Kameron S.; Lee, Justine C.

    2015-01-01

    Skeletal regenerative medicine emerged as a field of investigation to address large osseous deficiencies secondary to congenital, traumatic, and post-oncologic conditions. Although autologous bone grafts have been the gold standard for reconstruction of skeletal defects, donor site morbidity remains a significant limitation. To address these limitations, contemporary bone tissue engineering research aims to target delivery of osteogenic cells and growth factors in a defined three dimensional space using scaffolding material. Using bone as a template, biomimetic strategies in scaffold engineering unite organic and inorganic components in an optimal configuration to both support osteoinduction as well as osteoconduction. This article reviews the various structural and functional considerations behind the development of effective biomimetic scaffolds for osteogenesis and highlights strategies for enhancing osteogenesis. PMID:26413557

  17. Biomimetic sensor design

    NASA Astrophysics Data System (ADS)

    Lee, Ju Hun; Jin, Hyo-Eon; Desai, Malav S.; Ren, Shuo; Kim, Soyoun; Lee, Seung-Wuk

    2015-11-01

    Detection of desired target chemicals in a sensitive and selective manner is critically important to protect human health, environment and national security. Nature has been a great source of inspiration for the design of sensitive and selective sensors. In this mini-review, we overview the recent developments in bio-inspired sensor development. There are four major components of sensor design: design of receptors for specific targets; coating materials to integrate receptors to transducing machinery; sensitive transducing of signals; and decision making based on the sensing results. We discuss the biomimetic methods to discover specific receptors followed by a discussion about bio-inspired nanocoating material design. We then review the recent developments in phage-based bioinspired transducing systems followed by a discussion of biomimetic pattern recognition-based decision making systems. Our review will be helpful to understand recent approaches to reverse-engineer natural systems to design specific and sensitive sensors.

  18. Biomimetic sensor design.

    PubMed

    Lee, Ju Hun; Jin, Hyo-Eon; Desai, Malav S; Ren, Shuo; Kim, Soyoun; Lee, Seung-Wuk

    2015-11-28

    Detection of desired target chemicals in a sensitive and selective manner is critically important to protect human health, environment and national security. Nature has been a great source of inspiration for the design of sensitive and selective sensors. In this mini-review, we overview the recent developments in bio-inspired sensor development. There are four major components of sensor design: design of receptors for specific targets; coating materials to integrate receptors to transducing machinery; sensitive transducing of signals; and decision making based on the sensing results. We discuss the biomimetic methods to discover specific receptors followed by a discussion about bio-inspired nanocoating material design. We then review the recent developments in phage-based bioinspired transducing systems followed by a discussion of biomimetic pattern recognition-based decision making systems. Our review will be helpful to understand recent approaches to reverse-engineer natural systems to design specific and sensitive sensors. PMID:26498660

  19. Development of a biomimetic swimmer and the flow pattern surrounding the filament

    NASA Astrophysics Data System (ADS)

    Ha, Ngoc-San; Goo, Nam-Seo

    2010-04-01

    We have studied a biomimetic swimmer inspired by the motility mechanisms of bacteria such as E. coli theoretically and experimentally. Even though E. coli uses one or several rotating helical filaments to swim, a single rotating helical filament swimmer is considered in this work. The performance of this swimmer was estimated by modeling the dynamics of a swimmer in viscous fluid. The model has an ellipsoidal cell body propelled by a helical filament. We applied the resistive force theory on this model to calculate the linear swimming speed and the efficiency of the model. A parametric study on the swimming velocity was performed. To validate the theoretical results, a biomimetic swimmer was fabricated and an experiment setup was prepared to measure the swimming speed in silicone oil. In addition, we have studied the flow patterns surrounding the filament with a finite element simulation to understand the mechanism of propulsion.

  20. Biomimetic hydrogel materials

    DOEpatents

    Bertozzi, Carolyn; Mukkamala, Ravindranath; Chen, Qing; Hu, Hopin; Baude, Dominique

    2000-01-01

    Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

  1. Biomimetic Hydrogel Materials

    DOEpatents

    Bertozzi, Carolyn , Mukkamala, Ravindranath , Chen, Oing , Hu, Hopin , Baude, Dominique

    2003-04-22

    Novel biomimetic hydrogel materials and methods for their preparation. Hydrogels containing acrylamide-functionalized carbohydrate, sulfoxide, sulfide or sulfone copolymerized with a hydrophilic or hydrophobic copolymerizing material selected from the group consisting of an acrylamide, methacrylamide, acrylate, methacrylate, vinyl and a derivative thereof present in concentration from about 1 to about 99 wt %. and methods for their preparation. The method of use of the new hydrogels for fabrication of soft contact lenses and biomedical implants.

  2. Self-sorting regioisomers through the hierarchical organization of hydrogen-bonded rosettes.

    PubMed

    Aratsu, Keisuke; Prabhu, Deepak D; Iwawaki, Hidetaka; Lin, Xu; Yamauchi, Mitsuaki; Karatsu, Takashi; Yagai, Shiki

    2016-07-01

    The self-assembly of two regioisomeric hydrogen-bonding naphthalenes was studied in mixed states in different polarity solvents. The regioisomers co-assemble to form heteromeric rosettes in chloroform. Upon injecting this solution into methylcyclohexane the heteromeric rosettes kinetically form amorphous aggregates, which over time differentiate into thermodynamically stable distinct nanostructures through self-sorting. PMID:27211509

  3. A Lightweight Vertical Rosette for Deployment in Ice Covered Water

    NASA Astrophysics Data System (ADS)

    Smethie, W. M.; Chayes, D. N.; Perry, R. S.; Schlosser, P.

    2009-12-01

    Although remote sensing technology provides measurement capability for a number of water properties, there are important substances for which this technology does not currently exist and the only way to measure these substances is to collect water samples and return the samples to the lab. In the Arctic Ocean water samples are difficult to obtain from ships because of the extensive ice cover and thick pressure ridges. However, the ice provides a landing platform for aircraft, which can rapidly cover long distances. Aircraft have been used for sampling the Arctic Ocean for the past half-century using bottles and internally recording CTDs attached to a cable and lowered through leads or holes drilled in the ice. The routine CTD/rosette technology used for sampling from ships measures profiles of temperature, salinity, oxygen as well as other substances in situ, displays the data in real time for choosing depths to obtain water samples and the water samples are then collected with the rosette. These systems are too heavy and bulky to deploy from aircraft. We have developed a lightweight modular CTD/rosette system that is deployed through a 12-inch diameter hole drilled in the ice. The modules are connected together physically and electrically with the water bottle modules, which contain four 4-liter bottles each, stacked on top of the CTD module. The CTD traces are displayed on a laptop computer and the bottles are tripped using modified Seabird controllers and a melt-lanyard tripping mechanism. We have used this system for several years with Twin Otter fixed wing aircraft as part of the Switchyard Project, sampling a line of stations annually in the heavily ice covered region between Alert and the North Pole. Casts are carried out in a tent connected to the airplane using a lightweight winch mounted in the airplane. At the completion of a cast, the water modules are placed in a cooler with bags of snow to provide thermal stability at about 0°C and the end caps

  4. THE YOUNG INTERSTELLAR BUBBLE WITHIN THE ROSETTE NEBULA

    SciTech Connect

    Bruhweiler, F. C.; Bourdin, M. O.; Gull, T. R. E-mail: theodore.r.gull@nasa.go

    2010-08-20

    We use high-resolution International Ultraviolet Explorer (IUE) data and the interstellar (IS) features of highly ionized Si IV and C IV seen toward the young, bright OB stars of NGC 2244 in the core of the Rosette Nebula to study the physics of young IS bubbles. Two discrete velocity components in Si IV and C IV are seen toward stars in the 6.2 pc radius central cavity, while only a single velocity component is seen toward those stars in the surrounding H II region, at the perimeter and external to this cavity. The central region shows characteristics of a very young, windblown bubble. The shell around the central hot cavity is expanding at 56 km s{sup -1} with respect to the embedded OB stars, while the surrounding H II region of the Rosette is expanding at {approx}13 km s{sup -1}. Even though these stars are quite young ({approx}2-4 Myr), both the radius and expansion velocity of the 6.2 pc inner shell point to a far younger age; t{sub age} {approx} 6.4 x 10{sup 4} years. These results represent a strong contradiction to theory and present modeling, where much larger bubbles are predicted around individual O stars and O associations. Specifically, the results for this small bubble and its deduced age extend the 'missing wind luminosity problem' to young evolving bubbles. These results indicate that OB star winds mix the surrounding H II regions and the wind kinetic energy is converted to turbulence and radiated away in the dense H II regions. These winds do not form hot, adiabatically expanding cavities. True IS bubbles appear only to form at later evolutionary times, perhaps triggered by increased mass loss rates or discrete ejection events. Means for rectifying discrepancies between theory and observations are discussed.

  5. Templated biomimetic multifunctional coatings

    NASA Astrophysics Data System (ADS)

    Sun, Chih-Hung; Gonzalez, Adriel; Linn, Nicholas C.; Jiang, Peng; Jiang, Bin

    2008-02-01

    We report a bioinspired templating technique for fabricating multifunctional optical coatings that mimic both unique functionalities of antireflective moth eyes and superhydrophobic cicada wings. Subwavelength-structured fluoropolymer nipple arrays are created by a soft-lithography-like process. The utilization of fluoropolymers simultaneously enhances the antireflective performance and the hydrophobicity of the replicated films. The specular reflectivity matches the optical simulation using a thin-film multilayer model. The dependence of the size and the crystalline ordering of the replicated nipples on the resulting antireflective properties have also been investigated by experiment and modeling. These biomimetic materials may find important technological application in self-cleaning antireflection coatings.

  6. Biomimetic Receptors and Sensors

    PubMed Central

    Dickert, Franz L.

    2014-01-01

    In biomimetics, living systems are imitated to develop receptors for ions, molecules and bioparticles. The most pertinent idea is self-organization in analogy to evolution in nature, which created the key-lock principle. Today, modern science has been developing host-guest chemistry, a strategy of supramolecular chemistry for designing interactions of analytes with synthetic receptors. This can be realized, e.g., by self-assembled monolayers (SAMs) or molecular imprinting. The strategies are used for solid phase extraction (SPE), but preferably in developing recognition layers of chemical sensors. PMID:25436653

  7. Biomimetics in Tribology

    NASA Astrophysics Data System (ADS)

    Gebeshuber, I. C.; Majlis, B. Y.; Stachelberger, H.

    Science currently goes through a major change. Biology is evolving as new Leitwissenschaft, with more and more causation and natural laws being uncovered. The term `technoscience' denotes the field where science and technology are inseparably interconnected, the trend goes from papers to patents, and the scientific `search for truth' is increasingly replaced by search for applications with a potential economic value. Biomimetics, i.e. knowledge transfer from biology to technology, is a field that has the potential to drive major technical advances. The biomimetic approach might change the research landscape and the engineering culture dramatically, by the blending of disciplines. It might substantially support successful mastering of current tribological challenges: friction, adhesion, lubrication and wear in devices and systems from the meter to the nanometer scale. A highly successful method in biomimectics, the biomimicry innovation method, is applied in this chapter to identify nature's best practices regarding two key issues in tribology: maintenance of the physical integrity of a system, and permanent as well as temporary attachment. The best practices identified comprise highly diverse organisms and processes and are presented in a number of tables with detailed references.

  8. A Small Diameter Rosette for Sampling Ice Covered Waters

    NASA Astrophysics Data System (ADS)

    Chayes, D. N.; Smethie, W. M.; Perry, R. S.; Schlosser, P.; Friedrich, R.

    2011-12-01

    A gas tight, small diameter, lightweight rosette, supporting equipment and an effective operational protocol has been developed for aircraft supported sampling of sea water across the Lincoln Sea. The system incorporates a commercial off the shelf CTD electronics (SBE19+ sensor package and SBE33 deck unit) to provide real-time measurement data at the surface. We designed and developed modular water sample units and custom electronics to decode the bottle firing commands and close the sample bottles. For a typical station, we land a ski-equipped deHaviland Twin Otter (DHC-6) aircraft on a suitable piece of sea-ice, drill a 12" diameter hole through the ice next to the cargo door and set up a tent to provide a reasonable working environment over the hole. A small winch with 0.1" diameter single conductor cable is mounted in the aircraft by the cargo door and a tripod supports a sheave above the hole. The CTD module is connected to the end of the wire and the water sampling modules are stacked on top as the system is lowered. For most stations, three sample modules are used to provide 12 four (4) liter sample bottles. Data collected during the down-cast is used to formulate the sampling plan which is executed on the up-cast. The system is powered by a 3,700 Watt, 120VAC gasoline generator. After collection, the sample modules are stored in passively temperature stabilized ice chests during the flight back to the logistics facility at Alert where a broad range of samples are drawn and stored for future analysis. The transport mechanism has a good track record of maintaining water samples within about two degrees of the original collection temperature which minimizes out-gassing. The system has been successfully deployed during a field program each spring starting in 2004 along a transect between the north end of Ellesmere Island (Alert, Nunavut) and the North Pole. During the eight field programs we have taken 48 stations with twelve bottles at most stations (eight at

  9. Isolation and Synthesis of a Bacterially Produced Inhibitor of Rosette Development in Choanoflagellates.

    PubMed

    Cantley, Alexandra M; Woznica, Arielle; Beemelmanns, Christine; King, Nicole; Clardy, Jon

    2016-04-01

    The choanoflagellate Salpingoeca rosetta is a microbial marine eukaryote that can switch between unicellular and multicellular states. As one of the closest living relatives of animals, this organism has become a model for understanding how multicellularity evolved in the animal lineage. Previously our laboratories isolated and synthesized a bacterially produced sulfonolipid that induces S. rosetta to form multicellular "rosettes." In this study, we report the identification of a bacterially produced inhibitor of rosettes (IOR-1) as well as the total synthesis of this molecule and all of its stereoisomers. Our results confirm the previously noted specificity and potency of rosette-modulating molecules, expand our understanding of the complex chemical ecology between choanoflagellates and rosette-inducing bacteria, and provide a synthetic probe template for conducting further mechanistic studies on the emergence of multicellularity. PMID:26998963

  10. Isolation and Synthesis of a Bacterially Produced Inhibitor of Rosette Development in Choanoflagellates

    PubMed Central

    2016-01-01

    The choanoflagellate Salpingoeca rosetta is a microbial marine eukaryote that can switch between unicellular and multicellular states. As one of the closest living relatives of animals, this organism has become a model for understanding how multicellularity evolved in the animal lineage. Previously our laboratories isolated and synthesized a bacterially produced sulfonolipid that induces S. rosetta to form multicellular “rosettes.” In this study, we report the identification of a bacterially produced inhibitor of rosettes (IOR-1) as well as the total synthesis of this molecule and all of its stereoisomers. Our results confirm the previously noted specificity and potency of rosette-modulating molecules, expand our understanding of the complex chemical ecology between choanoflagellates and rosette-inducing bacteria, and provide a synthetic probe template for conducting further mechanistic studies on the emergence of multicellularity. PMID:26998963

  11. Bioactive rosette nanotube-hydroxyapatite nanocomposites improve osteoblast functions.

    PubMed

    Sun, Linlin; Zhang, Lijie; Hemraz, Usha D; Fenniri, Hicham; Webster, Thomas J

    2012-09-01

    Inspired from biological systems, small synthetic organic molecules expressing the hydrogen bonding arrays of the DNA bases guanine and cytosine were prepared, and their self-assembly into rosette nanotubes (RNTs) was investigated. Due to their unique biological, physicochemical, and mechanical properties, RNTs could serve as the next generation of injectable orthopedic materials. In this study, a self-assembling module (termed twin base linkers or TBL) was synthesized, and the corresponding RNTs were used as bioactive components in composites of poly (2-hydroxyethyl methacrylate) (pHEMA) and hydroxyapatite (HA) nanoparticles (termed TBL/HA/pHEMA). The properties of these composites were characterized for solidification time, surface morphology, mechanical properties, and cytocompatibility. The experimental conditions were optimized to achieve solidification within 2-40 min, offering a range of properties for orthopedic applications. Composites with 20 wt% HA nanoparticles had a compressive strength (37.1 MPa) and an ultimate tensile stress (14.7 MPa) similar to that of a natural vertebral disc (5-30 MPa). Specifically, the TBL (0.01 mg/mL)/HA(20 wt%)/pHEMA composites improved long-term functions of osteoblasts (or bone-forming cells) in terms of collagen synthesis, alkaline phosphatase activity, and calcium deposition. Moreover, this composite inhibited fibroblast adhesion, thus decreasing the potential for undesirable fibrous tissue formation. In summary, this in vitro study provided evidence that TBL/HA/pHEMA composites are promising injectable orthopedic implant materials that warrant further mechanistic and in vivo studies. PMID:22530958

  12. Metabolic Fluxes in an Illuminated Arabidopsis Rosette[W][OA

    PubMed Central

    Szecowka, Marek; Heise, Robert; Tohge, Takayuki; Nunes-Nesi, Adriano; Vosloh, Daniel; Huege, Jan; Feil, Regina; Lunn, John; Nikoloski, Zoran; Stitt, Mark; Fernie, Alisdair R.; Arrivault, Stéphanie

    2013-01-01

    Photosynthesis is the basis for life, and its optimization is a key biotechnological aim given the problems of population explosion and environmental deterioration. We describe a method to resolve intracellular fluxes in intact Arabidopsis thaliana rosettes based on time-dependent labeling patterns in the metabolome. Plants photosynthesizing under limiting irradiance and ambient CO2 in a custom-built chamber were transferred into a 13CO2-enriched environment. The isotope labeling patterns of 40 metabolites were obtained using liquid or gas chromatography coupled to mass spectrometry. Labeling kinetics revealed striking differences between metabolites. At a qualitative level, they matched expectations in terms of pathway topology and stoichiometry, but some unexpected features point to the complexity of subcellular and cellular compartmentation. To achieve quantitative insights, the data set was used for estimating fluxes in the framework of kinetic flux profiling. We benchmarked flux estimates to four classically determined flux signatures of photosynthesis and assessed the robustness of the estimates with respect to different features of the underlying metabolic model and the time-resolved data set. PMID:23444331

  13. Sympodial Construction of Fibonacci-type Leaf Rosettes in Pinguicula moranensis (Lentibulariaceae)

    PubMed Central

    Grob, Valentin; Pfeifer, Evelin; Rutishauser, Rolf

    2007-01-01

    Background and Aims The leaf rosettes of the carnivorous Pinguicula moranensis follow a spiral phyllotaxis approaching a Fibonacci pattern while the stalked flowers arise from extra-axillary sites between the leaves. The organization of this rosette has been discussed by various authors, with various results. The aim of the present study was to clarify the development of the flowering rosettes of this species. Methods The formation of the rosettes is shown with the aid of scanning electron microscopy. Key Results and Conclusions The scanning electron micrographs show that each flower terminates an article (sympodial unit). The leaves of consecutive articles of such sympodially constructed rosettes are arranged along a spiral Fibonacci pattern (with divergence angles around 137°). This results from homodromy of leaf initiation in consecutive articles with the first leaf (prophyll) of a new article inserted in an obliquely transverse position next to the floral scape that terminates the former article. Sympodial construction of flowering shoots and leaf rosettes is also known from Aloe, Gunnera and Philodendron. As a by-product of this study, the unidirectional development of the Pinguicula flower is confirmed and discussed. PMID:17720680

  14. Biomimetic thin film deposition

    SciTech Connect

    Rieke, P.R.; Graff, G.E.; Campbell, A.A.; Bunker, B.C.; Baskaran, S.; Song, L.; Tarasevich, B.J.; Fryxell, G.E.

    1995-09-01

    Biological mineral deposition for the formation of bone, mollusk shell and other hard tissues provides materials scientists with illustrative materials processing strategies. This presentation will review the key features of biomineralization and how these features can be of technical importance. We have adapted existing knowledge of biomineralization to develop a unique method of depositing inorganic thin films and coating. Our approach to thin film deposition is to modify substrate surfaces to imitate the proteins found in nature that are responsible for controlling mineral deposition. These biomimetic surfaces control the nucleation and growth of the mineral from a supersaturated aqueous solution. This has many processing advantages including simple processing equipment, environmentally benign reagents, uniform coating of highly complex shapes, and enhanced adherence of coating. Many different types of metal oxide, hydroxide, sulfide and phosphate materials with useful mechanical, optical, electronic and biomedical properties can be deposited.

  15. Rosette-forming glioneuronal tumour of the fourth ventricle: case report and review of the literature.

    PubMed

    Hakan, T; Aker, F V

    2016-01-01

    Rosette-forming glioneuronal tumour (RGNT) of the fourth ventricle is one of the newly described primary tumours of the central nervous system. These tumours have two components of both neurocytic and glial areas but usually the glial component of the tumour predominates. They have biphasic cytoarchitecture with two elements; neurocytic rosettes resembling Homer-Wright rosettes, and astrocytic component resembling a pilocytic astrocytoma. They are low-grade tumours with lack of histopathological signs of malignancy. Here, clinical, magnetic resonance, computed tomography (CT) and pathological features of rosette-forming glioneuronal tumour of posterior fossa are presented. A 29-year-man was admitted with an acute neurological deterioration. A three ventricular hydrocephalus and a hypo-density around vermis in the posterior fossa were seen in his CT scans. He did well after an emergency external ventricular drainage. He had an elective operation and a mass that was reported to be a rosette-forming glioneuronal tumour of the fourth ventricle was excised. PMID:27179225

  16. Immunogold labeling of rosette terminal cellulose-synthesizing complexes in the vascular plant vigna angularis

    PubMed Central

    Kimura, S; Laosinchai, W; Itoh, T; Cui, X; Linder, CR; Brown, RM

    1999-01-01

    The catalytic subunit of cellulose synthase is shown to be associated with the putative cellulose-synthesizing complex (rosette terminal complex [TC]) in vascular plants. The catalytic subunit domain of cotton cellulose synthase was cloned using a primer based on a rice expressed sequence tag (D41261) from which a specific primer was constructed to run a polymerase chain reaction that used a cDNA library from 24 days postanthesis cotton fibers as a template. The catalytic region of cotton cellulose synthase was expressed in Escherichia coli, and polyclonal antisera were produced. Colloidal gold coupled to goat anti-rabbit secondary antibodies provided a tag for visualization of the catalytic region of cellulose synthase during transmission electron microscopy. With a freeze-fracture replica labeling technique, the antibodies specifically localized to rosette TCs in the plasma membrane on the P-fracture face. Antibodies did not specifically label any structures on the E-fracture face. Significantly, a greater number of immune probes labeled the rosette TCs (i.e., gold particles were 20 nm or closer to the edge of the rosette TC) than did preimmune probes. These experiments confirm the long-held hypothesis that cellulose synthase is a component of the rosette TC in vascular plants, proving that the enzyme complex resides within the structure first described by freeze fracture in 1980. In addition, this study provides independent proof that the CelA gene is in fact one of the genes for cellulose synthase in vascular plants. PMID:10559435

  17. Image reconstruction for single detector rosette scanning systems based on compressive sensing theory

    NASA Astrophysics Data System (ADS)

    Uzeler, Hande; Cakir, Serdar; Aytaç, Tayfun

    2016-02-01

    Compressive sensing (CS) is a signal processing technique that enables a signal that has a sparse representation in a known basis to be reconstructed using measurements obtained below the Nyquist rate. Single detector image reconstruction applications using CS have been shown to give promising results. In this study, we investigate the application of CS theory to single detector infrared (IR) rosette scanning systems which suffer from low performance compared to costly focal plane array (FPA) detectors. The single detector pseudoimaging rosette scanning system scans the scene with a specific pattern and performs processing to estimate the target location without forming an image. In this context, this generation of scanning systems may be improved by utilizing the samples obtained by the rosette scanning pattern in conjunction with the CS framework. For this purpose, we consider surface-to-air engagement scenarios using IR images containing aerial targets and flares. The IR images have been reconstructed from samples obtained with the rosette scanning pattern and other baseline sampling strategies. It has been shown that the proposed scheme exhibits good reconstruction performance and a large size FPA imaging performance can be achieved using a single IR detector with a rosette scanning pattern.

  18. [Biomimetic sensors in biomedical research].

    PubMed

    Gayet, Landry; Lenormand, Jean-Luc

    2015-01-01

    The recent research on both the synthesis of membrane proteins by cell-free systems and the reconstruction of planar lipid membranes, has led to the development of a cross-technology to produce biosensors or filters. Numerous biomimetic membranes are currently being standardized and used by the industry, such as filters containing aquaporin for water desalination, or used in routine at the laboratory scale, for example the bacteriorhodopsin as a light sensor. In the medical area, several fields of application of these biomimetic membranes are under consideration today, particularly for the screening of therapeutic molecules and for the developing of new tools in diagnosis, patient monitoring and personalized medicine. PMID:26152170

  19. Low anticoagulant heparin disrupts Plasmodium falciparum rosettes in fresh clinical isolates.

    PubMed

    Leitgeb, Anna M; Blomqvist, Karin; Cho-Ngwa, Fidelis; Samje, Moses; Nde, Peter; Titanji, Vincent; Wahlgren, Mats

    2011-03-01

    The binding of Plasmodium falciparum parasitized erythrocytes to uninfected erythrocytes (rosetting) is associated with severe malaria. The glycosaminoglycan heparan sulfate is an important receptor for rosetting. The related glycosaminoglycan heparin was previously used in treatment of severe malaria, although abandoned because of the occurrence of severe bleedings. Instead, low anticoagulant heparin (LAH) has been suggested for treatment. LAH has successfully been evaluated in safety studies and found to disrupt rosettes and cytoadherence in vitro and in vivo in animal models, but the effect of LAH on fresh parasite isolates has not been studied. Herein, we report that two different LAHs (DFX232 and Sevuparin) disrupt rosettes in the majority of fresh isolates from Cameroonian children with malaria. The rosette disruption effect was more pronounced in isolates from complicated cases than from mild cases. The data support LAH as adjunct therapy in severe malaria. PMID:21363975

  20. Low Anticoagulant Heparin Disrupts Plasmodium falciparum Rosettes in Fresh Clinical Isolates

    PubMed Central

    Leitgeb, Anna M.; Blomqvist, Karin; Cho-Ngwa, Fidelis; Samje, Moses; Nde, Peter; Titanji, Vincent; Wahlgren, Mats

    2011-01-01

    The binding of Plasmodium falciparum parasitized erythrocytes to uninfected erythrocytes (rosetting) is associated with severe malaria. The glycosaminoglycan heparan sulfate is an important receptor for rosetting. The related glycosaminoglycan heparin was previously used in treatment of severe malaria, although abandoned because of the occurrence of severe bleedings. Instead, low anticoagulant heparin (LAH) has been suggested for treatment. LAH has successfully been evaluated in safety studies and found to disrupt rosettes and cytoadherence in vitro and in vivo in animal models, but the effect of LAH on fresh parasite isolates has not been studied. Herein, we report that two different LAHs (DFX232 and Sevuparin) disrupt rosettes in the majority of fresh isolates from Cameroonian children with malaria. The rosette disruption effect was more pronounced in isolates from complicated cases than from mild cases. The data support LAH as adjunct therapy in severe malaria. PMID:21363975

  1. [A specific rosette formation method in assessing the immunological status of acute leukemia patients].

    PubMed

    Moroz, I A

    1985-01-01

    The paper deals with the evaluation of immunologic vigor in 88 patients suffering acute lymphoblastic leukemia. It involved a modified test of specific rosette formation of blood-circulating lymphocytes and those of the bone marrow with erythrocytes bearing leukemia cell extracts. The highest levels of rosette-forming lymphocytes were registered in the acute period prior to treatment and in recurrence. The said levels decreased gradually following chemoimmunotherapy, falling to nil in complete remission. Patients in whom the treatment had failed revealed no changes in lymphocyte response. The control group (healthy subjects and cases of nonmalignant hematologic pathology) showed levels of rosette-forming lymphocytes similar to those in acute lymphoblastic leukemia patients in remission. PMID:3861026

  2. Repairable, nanostructured biomimetic hydrogels

    NASA Astrophysics Data System (ADS)

    Firestone, M.; Brombosz, S.; Grubjesic, S.

    2013-03-01

    Proteins facilitate many key cellular processes, including signal recognition and energy transduction. The ability to harness this evolutionarily-optimized functionality could lead to the development of protein-based systems useful for advancing alternative energy storage and conversion. The future of protein-based, however, requires the development of materials that will stabilize, order and control the activity of the proteins. Recently we have developed a synthetic approach for the preparation of a durable biomimetic chemical hydrogel that can be reversibly swollen in water. The matrix has proven ideal for the stable encapsulation of both water- and membrane-soluble proteins. The material is composed of an aqueous dispersion of a diacrylate end-derivatized PEO-PPO-PEO macromer, a saturated phospholipid and a zwitterionic co-surfactant that self-assembles into a nanostructured physical gel at room temperature as determined by X-ray scattering. The addition of a water soluble PEGDA co-monomer and photoinitator does not alter the self-assembled structure and UV irradiation serves to crosslink the acrylate end groups on the macromer with the PEGDA forming a network within the aqueous domains as determined by FT-IR. More recently we have begun to incorporate reversible crosslinks employing Diels-Alder chemistry, allowing for the extraction and replacement of inactive proteins. The ability to replenish the materials with active, non-denatured forms of protein is an important step in advancing these materials for use in nanostructured devices This work was supported by the Office of Basic Energy Sciences, Division of Materials Sciences, USDoE under Contract No. DE-AC02-06CH11357.

  3. Biomimetic Production of Hydrogen

    NASA Astrophysics Data System (ADS)

    Gust, Devens

    2004-03-01

    The basic reaction for hydrogen generation is formation of molecular hydrogen from two electrons and two protons. Although there are many possible sources for the protons and electrons, and a variety of mechanisms for providing the requisite energy for hydrogen synthesis, the most abundant and readily available source of protons and electrons is water, and the most attractive source of energy for powering the process is sunlight. Not surprisingly, living systems have evolved to take advantage of these sources for materials and energy. Thus, biology provides paradigms for carrying out the reactions necessary for hydrogen production. Photosynthesis in green plants uses sunlight as the source of energy for the oxidation of water to give molecular oxygen, protons, and reduction potential. Some photosynthetic organisms are capable of using this reduction potential, in the form of the reduced redox protein ferredoxin, to reduce protons and produce molecular hydrogen via the action of an hydrogenase enzyme. A variety of other organisms metabolize the reduced carbon compounds that are ultimately the major products of photosynthesis to produce molecular hydrogen. These facts suggest that it might be possible to use light energy to make molecular hydrogen via biomimetic constructs that employ principles similar to those used by natural organisms, or perhaps with hybrid "bionic" systems that combine biomimetic materials with natural enzymes. It is now possible to construct artificial photosynthetic systems that mimic some of the major steps in the natural process.(1) Artificial antennas based on porphyrins, carotenoids and other chromophores absorb light at various wavelengths in the solar spectrum and transfer the harvested excitation energy to artificial photosynthetic reaction centers.(2) In these centers, photoinduced electron transfer uses the energy from light to move an electron from a donor to an acceptor moiety, generating a high-energy charge-separated state

  4. Bio-mimetic Flow Control

    NASA Astrophysics Data System (ADS)

    Choi, Haecheon

    2009-11-01

    Bio-mimetic engineering or bio-mimetics is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology (from Wikipedia). The concept itself is old, but successful developments have been made recently, especially in the research field of flow control. The objective of flow control based on the bio-mimetic approach is to develop novel concepts for reducing drag, increasing lift and enhancing aerodynamic performance. For skin friction reduction, a few ideas have been suggested such as the riblet from shark, compliant surface from dolphin, microbubble injection and multiple front-body curvature from penguin, and V-shaped protrusion from sailfish. For form drag reduction, several new attempts have been also made recently. Examples include the V-shaped spanwise grooves from saguaro cactus, overall shape of box fish, longitudinal grooves on scallop shell, bill of swordfish, hooked comb on owl wing, trailing-edge protrusion on dragonfly wing, and fillet. For the enhancement of aerodynamic performance, focuses have been made on the birds, fish and insects: e.g., double layered feather of landing bird, leading-edge serration of humpback-whale flipper, pectoral fin of flying fish, long tail on swallowtail-butterfly wing, wing flapping motion of dragonfly, and alula in birds. Living animals adapt their bodies to better performance in multi purposes, but engineering requires single purpose in most cases. Therefore, bio-mimetic approaches often produce excellent results more than expected. However, they are sometimes based on people's wrong understanding of nature and produce unwanted results. Successes and failures from bio-mimetic approaches in flow control will be discussed in the presentation.

  5. Biomimetic catalysis of metal-organic frameworks.

    PubMed

    Chen, Yao; Ma, Shengqian

    2016-06-14

    Metal-organic frameworks (MOFs) have attracted great attention as a new type of prospective material with various merits and functionalities. MOFs can either act as biomimetic catalysts to mimic enzymatic activities or serve as hosts to encapsulate bio-active species for biomimetic catalysis. However, in comparison with the dramatic development of MOFs in other catalytic fields, MOF-based biomimetic catalysis is still in its infancy and is yet to be systematically and comprehensively explored. Herein, the principles and strategies for the design and synthesis of MOF-based biomimetic catalysts, especially the structural features of representative MOFs that are related to biomimetic catalysis, are summarized and reviewed. In addition, recent advances in biomimetic catalysis of MOFs and the relationships between their catalytic performances and the structural specificities are discussed in detail as well. PMID:27041152

  6. Comparison of Strain Rosettes and Digital Image Correlation for Measuring Vertebral Body Strain.

    PubMed

    Gustafson, Hannah; Siegmund, Gunter; Cripton, Peter

    2016-05-01

    Strain gages are commonly used to measure bone strain, but only provide strain at a single location. Digital image correlation (DIC) is an optical technique that provides the displacement, and therefore strain, over an entire region of interest on the bone surface. This study compares vertebral body strains measured using strain gages and DIC. The anterior surfaces of 15 cadaveric porcine vertebrae were prepared with a strain rosette and a speckled paint pattern for DIC. The vertebrae were loaded in compression with a materials testing machine, and two high-resolution cameras were used to image the anterior surface of the bones. The mean noise levels for the strain rosette and DIC were 1 με and 24 με, respectively. Bland-Altman analysis was used to compare strain from the DIC and rosette (excluding 44% of trials with some evidence of strain rosette failure or debonding); the mean difference ± 2 standard deviations (SDs) was -108 με ± 702 με for the minimum (compressive) principal strain and -53 με ± 332 με for the maximum (tensile) principal strain. Although the DIC has higher noise, it avoids the relatively high risk we observed of strain gage debonding. These results can be used to develop guidelines for selecting a method to measure strain on bone. PMID:26902321

  7. Helicity in superfluids

    NASA Astrophysics Data System (ADS)

    Kedia, Hridesh; Kleckner, Dustin; Proment, Davide; Irvine, William T. M.

    Ideal fluid flow conserves a special quantity known as helicity, in addition to energy, momentum and angular momentum. Helicity can be understood as a measure of the knottedness of vortex lines of the flow, providing an important geometric tool to study diverse physical systems such as turbulent fluids and plasmas. Since superfluids flow without resistance just like ideal (Euler) fluids, a natural question arises: Is there an extra conserved quantity akin to helicity in superfluids? We address the question of a ''superfluid helicity'' theoretically and examine its consequences in numerical simulations.

  8. Mass and motion of globulettes in the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    Gahm, G. F.; Persson, C. M.; Mäkelä, M. M.; Haikala, L. K.

    2013-07-01

    Context. Tiny molecular clumps are abundant in many H ii regions surrounding newborn stellar clusters. In optical images these so-called globulettes appear as dark patches against the background of bright nebulosity. The majority of the globulettes were found to be of planetary mass in a previous optical investigation, while the largest objects may contain more than half a solar mass. Aims: We aim to clarify the physical nature of globulettes by deriving densities and masses, and to determine their velocities as a function of position over the nebula. This information will provide clues to the question of origins, evolution, and fate of globulettes. The Rosette Nebula is relatively rich in globulettes, and we selected a sample of well-confined objects of different sizes for the present investigation. Methods: Radio observations were made of molecular line emission from 16 globulettes combined with near-infrared (NIR) broad-band JHKs and narrow-band Paschen β and H2 imaging. Ten objects, for which we collected information from several transitions in 12CO and 13CO, were modelled using a spherically symmetric model. Results: Practically all globulettes were detected in our CO survey. The observed 12CO (3-2) and (2-1) line temperatures range from 0.6 K to 6 K, the 13CO being a third of this. As a rule, the lines are narrow, ~1.0 km s-1. The best fit to observed line ratios and intensities was obtained by assuming a model composed of a cool and dense centre and warm and dense surface layer. This model provides estimates of maximum and minimum mass; the average masses range from about 50 to 500 Jupiter masses, which is similar to earlier estimates based on extinction measures. The selected globulettes are dense, nH ~ 104 cm-3, with very thin layers of fluorescent H2 emission, showing that the gas is in molecular form just below the surface. The NIR data show that several globulettes are very opaque and contain dense cores. No infrared-excess stars in the fields are

  9. Nanotechnology Biomimetic Cartilage Regenerative Scaffolds

    PubMed Central

    Sardinha, Jose Paulo; Myers, Simon

    2014-01-01

    Cartilage has a limited regenerative capacity. Faced with the clinical challenge of reconstruction of cartilage defects, the field of cartilage engineering has evolved. This article reviews current concepts and strategies in cartilage engineering with an emphasis on the application of nanotechnology in the production of biomimetic cartilage regenerative scaffolds. The structural architecture and composition of the cartilage extracellular matrix and the evolution of tissue engineering concepts and scaffold technology over the last two decades are outlined. Current advances in biomimetic techniques to produce nanoscaled fibrous scaffolds, together with innovative methods to improve scaffold biofunctionality with bioactive cues are highlighted. To date, the majority of research into cartilage regeneration has been focused on articular cartilage due to the high prevalence of large joint osteoarthritis in an increasingly aging population. Nevertheless, the principles and advances are applicable to cartilage engineering for plastic and reconstructive surgery. PMID:24883273

  10. Biomimetic Materials for Tissue Engineering

    PubMed Central

    Ma, Peter X

    2008-01-01

    Tissue engineering and regenerative medicine is an exciting research area that aims at regenerative alternatives to harvested tissues for transplantation. Biomaterials play a pivotal role as scaffolds to provide three-dimensional templates and synthetic extracellular-matrix environments for tissue regeneration. It is often beneficial for the scaffolds to mimic certain advantageous characteristics of the natural extracellular matrix, or developmental or would healing programs. This article reviews current biomimetic materials approaches in tissue engineering. These include synthesis to achieve certain compositions or properties similar to those of the extracellular matrix, novel processing technologies to achieve structural features mimicking the extracellular matrix on various levels, approaches to emulate cell-extracellular matrix interactions, and biologic delivery strategies to recapitulate a signaling cascade or developmental/would-healing program. The article also provides examples of enhanced cellular/tissue functions and regenerative outcomes, demonstrating the excitement and significance of the biomimetic materials for tissue engineering and regeneration. PMID:18045729

  11. Distortions in protein helices.

    PubMed

    Geetha, V

    1996-08-01

    alpha-helices are the most common secondary structures in observed proteins. However, they are not always found in ideal helical conformation and they often exhibit structural distortions. Quantification of these irregularities become essential in understanding the packing of helices and therefore, their role in the functional characteristics of the protein. The backbone torsions phi, psi are of limited utility in this endeavor, because distorted helices often maintain the backbone geometry. The local compensatory effects are responsible for the preservation of the entire hydrogen bond network of the helical stretch. Earlier descriptions of helical linearity and curvature rest mostly on approximation, thus motivating the search for a better method for understanding and quantifying helical irregularities. We developed a method which involves the rotation and superposition of identical repeating units of the protein by the quaternion method. The set of parameters derived from the rotation-superposition algorithm helps in identifying the bends and kinks which are not necessarily induced by unusual amino acids like proline. The quantification of irregularities of observed helices might lead to a better understanding of their packing interactions. PMID:8842770

  12. A Helical Stairway Project

    ERIC Educational Resources Information Center

    Farmer, Tom

    2008-01-01

    We answer a geometric question that was raised by the carpenter in charge of erecting helical stairs in a 10-story hospital. The explanation involves the equations of lines, planes, and helices in three-dimensional space. A brief version of the question is this: If A and B are points on a cylinder and the line segment AB is projected radially onto…

  13. Emerging double helical nanostructures

    NASA Astrophysics Data System (ADS)

    Zhao, Meng-Qiang; Zhang, Qiang; Tian, Gui-Li; Wei, Fei

    2014-07-01

    As one of the most important and land-mark structures found in nature, a double helix consists of two congruent single helices with the same axis or a translation along the axis. This double helical structure renders the deoxyribonucleic acid (DNA) the crucial biomolecule in evolution and metabolism. DNA-like double helical nanostructures are probably the most fantastic yet ubiquitous geometry at the nanoscale level, which are expected to exhibit exceptional and even rather different properties due to the unique organization of the two single helices and their synergistic effect. The organization of nanomaterials into double helical structures is an emerging hot topic for nanomaterials science due to their promising exceptional unique properties and applications. This review focuses on the state-of-the-art research progress for the fabrication of double-helical nanostructures based on `bottom-up' and `top-down' strategies. The relevant nanoscale, mesoscale, and macroscopic scale fabrication methods, as well as the properties of the double helical nanostructures are included. Critical perspectives are devoted to the synthesis principles and potential applications in this emerging research area. A multidisciplinary approach from the scope of nanoscience, physics, chemistry, materials, engineering, and other application areas is still required to the well-controlled and large-scale synthesis, mechanism, property, and application exploration of double helical nanostructures.

  14. Synthetic Biomimetic Membranes and Their Sensor Applications

    PubMed Central

    Kim, Young-Rok; Jung, Sungho; Ryu, Hyunil; Yoo, Yeong-Eun; Kim, Sun Min; Jeon, Tae-Joon

    2012-01-01

    Synthetic biomimetic membranes provide biological environments to membrane proteins. By exploiting the central roles of biological membranes, it is possible to devise biosensors, drug delivery systems, and nanocontainers using a biomimetic membrane system integrated with functional proteins. Biomimetic membranes can be created with synthetic lipids or block copolymers. These amphiphilic lipids and polymers self-assemble in an aqueous solution either into planar membranes or into vesicles. Using various techniques developed to date, both planar membranes and vesicles can provide versatile and robust platforms for a number of applications. In particular, biomimetic membranes with modified lipids or functional proteins are promising platforms for biosensors. We review recent technologies used to create synthetic biomimetic membranes and their engineered sensors applications. PMID:23012557

  15. The formation of elephant-trunk globules in the Rosette nebula: CO observations

    SciTech Connect

    Schneps, M.H.; Ho, P.T.P.; Barrett, A.H.

    1980-08-15

    The prominent elephant-trunk globules in the northwest quadrant of the Rosette nebula have been observed in the microwave lines of CO and /sup 13/CO (J=1..-->..0). The CO emission closely follows the optical outline of the obscuring material and leaves little doubt that the emission is associated with the globules. The physical characteristics derived are typical of those observed in other dust globules which are not necessarily associated with H II regions.

  16. Fiber Optic Rosette Strain Gauge Development and Application on a Large-Scale Composite Structure

    NASA Technical Reports Server (NTRS)

    Moore, Jason P.; Przekop, Adam; Juarez, Peter D.; Roth, Mark C.

    2015-01-01

    A detailed description of the construction, application, and measurement of 196 FO rosette strain gauges that measured multi-axis strain across the outside upper surface of the forward bulkhead component of a multibay composite fuselage test article is presented. A background of the FO strain gauge and the FO measurement system as utilized in this application is given and results for the higher load cases of the testing sequence are shown.

  17. Molecular Profiling of a Rare Rosette-Forming Glioneuronal Tumor Arising in the Spinal Cord

    PubMed Central

    Bidinotto, Lucas Tadeu; Scapulatempo-Neto, Cristovam; Mackay, Alan; de Almeida, Gisele Caravina; Berardinelli, Gustavo Noriz; Torrieri, Raul; Clara, Carlos Afonso; Feltrin, Leonir Terezinha; Viana-Pereira, Marta; Varella-Garcia, Marileila; Jones, Chris; Reis, Rui Manuel

    2015-01-01

    Rosette-forming glioneuronal tumor (RGNT) of the IV ventricle is a rare and recently recognized brain tumor entity. It is histologically composed by two distinct features: a glial component, resembling pilocytic astrocytoma, and a component forming neurocytic rosettes and/or perivascular rosettes. Herein, we describe a 33-year-old man with RGNT arising in the spinal cord. Following an immunohistochemistry validation, we further performed an extensive genomic analysis, using array-CGH (aCGH), whole exome and cancer-related hotspot sequencing, in order to better understand its underlying biology. We observed the loss of 1p and gain of 1q, as well as gain of the whole chromosomes 7, 9 and 16. Local amplifications in 9q34.2 and 19p13.3 (encompassing the gene SBNO2) were identified. Moreover, we observed focal gains/losses in several chromosomes. Additionally, on chromosome 7, we identified the presence of the KIAA1549:BRAF gene fusion, which was further validated by RT-PCR and FISH. Across all mutational analyses, we detected and validated the somatic mutations of the genes MLL2, CNNM3, PCDHGC4 and SCN1A. Our comprehensive molecular profiling of this RGNT suggests that MAPK pathway and methylome changes, driven by KIAA1549:BRAF fusion and MLL2 mutation, respectively, could be associated with the development of this rare tumor entity. PMID:26371886

  18. Identifying developmental phases in the Arabidopsis thaliana rosette using integrative segmentation models.

    PubMed

    Lièvre, Maryline; Granier, Christine; Guédon, Yann

    2016-06-01

    The change in leaf size and shape during ontogeny associated with heteroblastic development is a composite trait for which extensive spatiotemporal data can be acquired using phenotyping platforms. However, only part of the information contained in such data is exploited, and developmental phases are usually defined using a selected organ trait. We here introduce new methods for identifying developmental phases in the Arabidopsis rosette using various traits and minimum a priori assumptions. A pipeline of analysis was developed combining image analysis and statistical models to integrate morphological, shape, dimensional and expansion dynamics traits for the successive leaves of the Arabidopsis rosette. Dedicated segmentation models called semi-Markov switching models were built for selected genotypes in order to identify rosette developmental phases. Four successive developmental phases referred to as seedling, juvenile, transition and adult were identified for the different genotypes. We show that the degree of covering of the leaf abaxial surface with trichomes is insufficient to define these developmental phases. Using our pipeline of analysis, we were able to identify the supplementary seedling phase and to uncover the structuring role of various leaf traits. This enabled us to compare on a more objective basis the vegetative development of Arabidopsis mutants. PMID:26853434

  19. Embryonal tumors with abundant neuropil and true rosettes: a distinctive CNS primitive neuroectodermal tumor.

    PubMed

    Gessi, Marco; Giangaspero, Felice; Lauriola, Libero; Gardiman, Marina; Scheithauer, Bernd W; Halliday, William; Hawkins, Cynthia; Rosenblum, Marc K; Burger, Peter C; Eberhart, Charles G

    2009-02-01

    Embryonal neoplasms of the central nervous system (CNS) generally arise in the early years of life and behave in a clinically aggressive manner, but vary somewhat in their microscopic appearance. Several groups have reported examples of an embryonal tumor with combined histologic features of ependymoblastoma and neuroblastoma, a lesion referred to as "embryonal tumor with abundant neuropil and true rosettes" (ETANTR). Herein, we present 22 new cases, and additional clinical follow-up on our 7 initially reported cases, to better define the histologic features and clinical behavior of this distinctive neoplasm. It affects infants and arises most often in cerebral cortex, the cerebellum and brainstem being less frequent sites. Unlike other embryonal tumors of the CNS, girls are more commonly affected than boys. On neuroimaging, the tumors appear as large, demarcated, solid masses featuring patchy or no contrast enhancement. Five of our cases (18%) were at least partly cystic. Distinctive microscopic features include a prominent background of mature neuropil punctuated by true rosettes formed of pseudo-stratified embryonal cells circumferentially disposed about a central lumen (true rosettes). Of the 25 cases with available follow-up, 19 patients have died, their median survival being 9 months. Performed on 2 cases, cytogenetic analysis revealed extra copies of chromosome 2 in both. We believe that the ETANTR represents a histologically distinctive form of CNS embryonal tumor. PMID:18987548

  20. Genetic reprogramming of human amniotic cells with episomal vectors: neural rosettes as sentinels in candidate selection for validation assays

    PubMed Central

    Payne, Tiffany

    2014-01-01

    The promise of genetic reprogramming has prompted initiatives to develop banks of induced pluripotent stem cells (iPSCs) from diverse sources. Sentinel assays for pluripotency could maximize available resources for generating iPSCs. Neural rosettes represent a primitive neural tissue that is unique to differentiating PSCs and commonly used to identify derivative neural/stem progenitors. Here, neural rosettes were used as a sentinel assay for pluripotency in selection of candidates to advance to validation assays. Candidate iPSCs were generated from independent populations of amniotic cells with episomal vectors. Phase imaging of living back up cultures showed neural rosettes in 2 of the 5 candidate populations. Rosettes were immunopositive for the Sox1, Sox2, Pax6 and Pax7 transcription factors that govern neural development in the earliest stage of development and for the Isl1/2 and Otx2 transcription factors that are expressed in the dorsal and ventral domains, respectively, of the neural tube in vivo. Dissociation of rosettes produced cultures of differentiation competent neural/stem progenitors that generated immature neurons that were immunopositive for βIII-tubulin and glia that were immunopositive for GFAP. Subsequent validation assays of selected candidates showed induced expression of endogenous pluripotency genes, epigenetic modification of chromatin and formation of teratomas in immunodeficient mice that contained derivatives of the 3 embryonic germ layers. Validated lines were vector-free and maintained a normal karyotype for more than 60 passages. The credibility of rosette assembly as a sentinel assay for PSCs is supported by coordinate loss of nuclear-localized pluripotency factors Oct4 and Nanog in neural rosettes that emerge spontaneously in cultures of self-renewing validated lines. Taken together, these findings demonstrate value in neural rosettes as sentinels for pluripotency and selection of promising candidates for advance to validation

  1. Genetic reprogramming of human amniotic cells with episomal vectors: neural rosettes as sentinels in candidate selection for validation assays.

    PubMed

    Wilson, Patricia G; Payne, Tiffany

    2014-01-01

    The promise of genetic reprogramming has prompted initiatives to develop banks of induced pluripotent stem cells (iPSCs) from diverse sources. Sentinel assays for pluripotency could maximize available resources for generating iPSCs. Neural rosettes represent a primitive neural tissue that is unique to differentiating PSCs and commonly used to identify derivative neural/stem progenitors. Here, neural rosettes were used as a sentinel assay for pluripotency in selection of candidates to advance to validation assays. Candidate iPSCs were generated from independent populations of amniotic cells with episomal vectors. Phase imaging of living back up cultures showed neural rosettes in 2 of the 5 candidate populations. Rosettes were immunopositive for the Sox1, Sox2, Pax6 and Pax7 transcription factors that govern neural development in the earliest stage of development and for the Isl1/2 and Otx2 transcription factors that are expressed in the dorsal and ventral domains, respectively, of the neural tube in vivo. Dissociation of rosettes produced cultures of differentiation competent neural/stem progenitors that generated immature neurons that were immunopositive for βIII-tubulin and glia that were immunopositive for GFAP. Subsequent validation assays of selected candidates showed induced expression of endogenous pluripotency genes, epigenetic modification of chromatin and formation of teratomas in immunodeficient mice that contained derivatives of the 3 embryonic germ layers. Validated lines were vector-free and maintained a normal karyotype for more than 60 passages. The credibility of rosette assembly as a sentinel assay for PSCs is supported by coordinate loss of nuclear-localized pluripotency factors Oct4 and Nanog in neural rosettes that emerge spontaneously in cultures of self-renewing validated lines. Taken together, these findings demonstrate value in neural rosettes as sentinels for pluripotency and selection of promising candidates for advance to validation

  2. Biomimetics: its practice and theory.

    PubMed

    Vincent, Julian F V; Bogatyreva, Olga A; Bogatyrev, Nikolaj R; Bowyer, Adrian; Pahl, Anja-Karina

    2006-08-22

    Biomimetics, a name coined by Otto Schmitt in the 1950s for the transfer of ideas and analogues from biology to technology, has produced some significant and successful devices and concepts in the past 50 years, but is still empirical. We show that TRIZ, the Russian system of problem solving, can be adapted to illuminate and manipulate this process of transfer. Analysis using TRIZ shows that there is only 12% similarity between biology and technology in the principles which solutions to problems illustrate, and while technology solves problems largely by manipulating usage of energy, biology uses information and structure, two factors largely ignored by technology. PMID:16849244

  3. Biomimetics: its practice and theory

    PubMed Central

    Vincent, Julian F.V; Bogatyreva, Olga A; Bogatyrev, Nikolaj R; Bowyer, Adrian; Pahl, Anja-Karina

    2006-01-01

    Biomimetics, a name coined by Otto Schmitt in the 1950s for the transfer of ideas and analogues from biology to technology, has produced some significant and successful devices and concepts in the past 50 years, but is still empirical. We show that TRIZ, the Russian system of problem solving, can be adapted to illuminate and manipulate this process of transfer. Analysis using TRIZ shows that there is only 12% similarity between biology and technology in the principles which solutions to problems illustrate, and while technology solves problems largely by manipulating usage of energy, biology uses information and structure, two factors largely ignored by technology. PMID:16849244

  4. Biomimetic graphene films and their properties

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Lai; Chen, Qi-Dai; Jin, Zhi; Kim, Eunkyoung; Sun, Hong-Bo

    2012-07-01

    Biomimetic fabrication has long been considered a short cut to the rational design and production of artificial materials or devices that possess fascinating properties, just like natural creatures. Considering the fact that graphene exhibits a lot of exceptional properties in a wide range of scientific fields, biomimetic fabrication of graphene multiscale structures, denoted as biomimetic graphene, is of great interest in both fundamental research and industrial applications. Especially, the combination of graphene with biomimetic structures would realize structural and functional integrity, and thus bring a new opportunity of developing novel graphene-based devices with remarkable performance. In this feature article, we highlight the recent advances in biomimetic graphene films and their structure-defined properties. Functionalized graphene films with multiscale structures inspired from a wide range of biomaterials including rose petals, butterfly wings, nacre and honeycomb have been collected and presented. Moreover, both current challenges and future perspectives of biomimetic graphene are discussed. Although research of the so-called ``biomimetic graphene'' is still at an early stage, it might become a ``hot topic'' in the near future.

  5. Planck intermediate results. XXXIV. The magnetic field structure in the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Arzoumanian, D.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Ferrière, K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Juvela, M.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Noviello, F.; Novikov, D.; Novikov, I.; Oppermann, N.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Pettorino, V.; Piacentini, F.; Piat, M.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Soler, J. D.; Spencer, L. D.; Stolyarov, V.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Wiesemeyer, H.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-02-01

    Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). We combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and the formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm-3. The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered asa whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette's parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45° on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4%. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 6.5-9 μG. The present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the mean dust polarization properties of the

  6. Biomimetic vibrissal sensing for robots

    PubMed Central

    Pearson, Martin J.; Mitchinson, Ben; Sullivan, J. Charles; Pipe, Anthony G.; Prescott, Tony J.

    2011-01-01

    Active vibrissal touch can be used to replace or to supplement sensory systems such as computer vision and, therefore, improve the sensory capacity of mobile robots. This paper describes how arrays of whisker-like touch sensors have been incorporated onto mobile robot platforms taking inspiration from biology for their morphology and control. There were two motivations for this work: first, to build a physical platform on which to model, and therefore test, recent neuroethological hypotheses about vibrissal touch; second, to exploit the control strategies and morphology observed in the biological analogue to maximize the quality and quantity of tactile sensory information derived from the artificial whisker array. We describe the design of a new whiskered robot, Shrewbot, endowed with a biomimetic array of individually controlled whiskers and a neuroethologically inspired whisking pattern generation mechanism. We then present results showing how the morphology of the whisker array shapes the sensory surface surrounding the robot's head, and demonstrate the impact of active touch control on the sensory information that can be acquired by the robot. We show that adopting bio-inspired, low latency motor control of the rhythmic motion of the whiskers in response to contact-induced stimuli usefully constrains the sensory range, while also maximizing the number of whisker contacts. The robot experiments also demonstrate that the sensory consequences of active touch control can be usefully investigated in biomimetic robots. PMID:21969690

  7. Challenges in Commercializing Biomimetic Membranes.

    PubMed

    Perry, Mark; Madsen, Steen Ulrik; Jørgensen, Tine; Braekevelt, Sylvie; Lauritzen, Karsten; Hélix-Nielsen, Claus

    2015-01-01

    The discovery of selective water channel proteins-aquaporins-has prompted growing interest in using these proteins, as the building blocks for designing new types of membranes. However, as with any other new and potentially disruptive technology, barriers for successful market entry exist. One category includes customer-related barriers, which can be influenced to some extent. Another category includes market-technical-related barriers, which can be very difficult to overcome by an organization/company aiming at successfully introducing their innovation on the market-in particular if both the organization and the technology are at early stages. Often, one faces barriers from both these categories at the same time, which makes it necessary to gain insight of the particular market when introducing a new innovative product. In this review we present the basic concepts and discuss some of these barriers and challenges associated with introducing biomimetic aquaporin membranes. These include technical issues in membrane production and product testing. Then we discuss possible business models for introducing new technologies in general, followed by a presentation of beach-head market segments relevant for biomimetic aquaporin membranes. PMID:26556379

  8. Challenges in Commercializing Biomimetic Membranes

    PubMed Central

    Perry, Mark; Madsen, Steen Ulrik; Jørgensen, Tine; Braekevelt, Sylvie; Lauritzen, Karsten; Hélix-Nielsen, Claus

    2015-01-01

    The discovery of selective water channel proteins—aquaporins—has prompted growing interest in using these proteins, as the building blocks for designing new types of membranes. However, as with any other new and potentially disruptive technology, barriers for successful market entry exist. One category includes customer-related barriers, which can be influenced to some extent. Another category includes market-technical-related barriers, which can be very difficult to overcome by an organization/company aiming at successfully introducing their innovation on the market—in particular if both the organization and the technology are at early stages. Often, one faces barriers from both these categories at the same time, which makes it necessary to gain insight of the particular market when introducing a new innovative product. In this review we present the basic concepts and discuss some of these barriers and challenges associated with introducing biomimetic aquaporin membranes. These include technical issues in membrane production and product testing. Then we discuss possible business models for introducing new technologies in general, followed by a presentation of beach-head market segments relevant for biomimetic aquaporin membranes. PMID:26556379

  9. Biomimetics: determining engineering opportunities from nature

    NASA Astrophysics Data System (ADS)

    Fish, Frank E.

    2009-08-01

    The biomimetic approach seeks to incorporate designs based on biological organisms into engineered technologies. Biomimetics can be used to engineer machines that emulate the performance of organisms, particularly in instances where the organism's performance exceeds current mechanical technology or provides new directions to solve existing problems. For biologists, an adaptationist program has allowed for the identification of novel features of organisms based on engineering principles; whereas for engineers, identification of such novel features is necessary to exploit them for biomimetic development. Adaptations (leading edge tubercles to passively modify flow and high efficiency oscillatory propulsive systems) from marine animals demonstrate potential utility in the development of biomimetic products. Nature retains a store of untouched knowledge, which would be beneficial in advancing technology.

  10. Biomimetic catalysis: Taking on the turnover challenge

    NASA Astrophysics Data System (ADS)

    Hooley, Richard J.

    2016-03-01

    Emulating the efficiency with which enzymes catalyse reactions has often been used as inspiration to develop self-assembled cages. Now two studies present approaches to achieving catalyst turnover -- one of the biggest challenges in achieving truly biomimetic catalysis.

  11. Helical plasma thruster

    NASA Astrophysics Data System (ADS)

    Beklemishev, A. D.

    2015-10-01

    A new scheme of plasma thruster is proposed. It is based on axial acceleration of rotating magnetized plasmas in magnetic field with helical corrugation. The idea is that the propellant ionization zone can be placed into the local magnetic well, so that initially the ions are trapped. The E × B rotation is provided by an applied radial electric field that makes the setup similar to a magnetron discharge. Then, from the rotating plasma viewpoint, the magnetic wells of the helically corrugated field look like axially moving mirror traps. Specific shaping of the corrugation can allow continuous acceleration of trapped plasma ions along the magnetic field by diamagnetic forces. The accelerated propellant is expelled through the expanding field of magnetic nozzle. By features of the acceleration principle, the helical plasma thruster may operate at high energy densities but requires a rather high axial magnetic field, which places it in the same class as the VASIMR® rocket engine.

  12. Helical screw viscometer

    DOEpatents

    Aubert, J.H.; Chapman, R.N.; Kraynik, A.M.

    1983-06-30

    A helical screw viscometer for the measurement of the viscosity of Newtonian and non-Newtonian fluids comprising an elongated cylindrical container closed by end caps defining a circular cylindrical cavity within the container, a cylindrical rotor member having a helical screw or ribbon flight carried by the outer periphery thereof rotatably carried within the cavity whereby the fluid to be measured is confined in the cavity filling the space between the rotor and the container wall. The rotor member is supported by axle members journaled in the end caps, one axle extending through one end cap and connectable to a drive source. A pair of longitudinally spaced ports are provided through the wall of the container in communication with the cavity and a differential pressure meter is connected between the ports for measuring the pressure drop caused by the rotation of the helical screw rotor acting on the confined fluid for computing viscosity.

  13. Helical plasma thruster

    SciTech Connect

    Beklemishev, A. D.

    2015-10-15

    A new scheme of plasma thruster is proposed. It is based on axial acceleration of rotating magnetized plasmas in magnetic field with helical corrugation. The idea is that the propellant ionization zone can be placed into the local magnetic well, so that initially the ions are trapped. The E × B rotation is provided by an applied radial electric field that makes the setup similar to a magnetron discharge. Then, from the rotating plasma viewpoint, the magnetic wells of the helically corrugated field look like axially moving mirror traps. Specific shaping of the corrugation can allow continuous acceleration of trapped plasma ions along the magnetic field by diamagnetic forces. The accelerated propellant is expelled through the expanding field of magnetic nozzle. By features of the acceleration principle, the helical plasma thruster may operate at high energy densities but requires a rather high axial magnetic field, which places it in the same class as the VASIMR{sup ®} rocket engine.

  14. Biomimetic Active Touch with Fingertips and Whiskers.

    PubMed

    Lepora, Nathan F

    2016-01-01

    This study provides a synthetic viewpoint that compares, contrasts, and draws commonalities for biomimetic perception over a range of tactile sensors and tactile stimuli. Biomimetic active perception is formulated from three principles: (i) evidence accumulation based on leading models of perceptual decision making; (ii) action selection with an evidence-based policy, here based on overt focal attention; and (iii) sensory encoding of evidence based on neural coding. Two experiments with each of three biomimetic tactile sensors are considered: the iCub (capacitive) fingertip, the TacTip (optical) tactile sensor, and BIOTACT whiskers. For each sensor, one experiment considers a similar task (perception of shape and location) and the other a different tactile perception task. In all experiments, active perception with a biomimetic action selection policy based on focal attention outperforms passive perception with static or random action selection. The active perception also consistently reaches superresolved accuracy (hyperacuity) finer than the spacing between tactile elements. Biomimetic active touch thus offers a common approach for biomimetic tactile sensors to accurately and robustly characterize and explore non-trivial, uncertain environments analogous to how animals perceive the natural world. PMID:27168603

  15. Contact kinematics of biomimetic scales

    SciTech Connect

    Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan

    2014-12-08

    Dermal scales, prevalent across biological groups, considerably boost survival by providing multifunctional advantages. Here, we investigate the nonlinear mechanical effects of biomimetic scale like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element (FE) analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial overlap of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking material level complexities of either the scales or the substrate.

  16. Contact kinematics of biomimetic scales

    NASA Astrophysics Data System (ADS)

    Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan

    2014-12-01

    Dermal scales, prevalent across biological groups, considerably boost survival by providing multifunctional advantages. Here, we investigate the nonlinear mechanical effects of biomimetic scale like attachments on the behavior of an elastic substrate brought about by the contact interaction of scales in pure bending using qualitative experiments, analytical models, and detailed finite element (FE) analysis. Our results reveal the existence of three distinct kinematic phases of operation spanning linear, nonlinear, and rigid behavior driven by kinematic interactions of scales. The response of the modified elastic beam strongly depends on the size and spatial overlap of rigid scales. The nonlinearity is perceptible even in relatively small strain regime and without invoking material level complexities of either the scales or the substrate.

  17. Biomimetic mechanism for micro aircraft

    NASA Technical Reports Server (NTRS)

    Pines, Darryll J. (Inventor); Bohorquez, Felipe A. (Inventor); Sirohi, Jayant (Inventor)

    2005-01-01

    A biomimetic pitching and flapping mechanism including a support member, at least two blade joints for holding blades and operatively connected to the support member. An outer shaft member is concentric with the support member, and an inner shaft member is concentric with the outer shaft member. The mechanism allows the blades of a small-scale rotor to be actuated in the flap and pitch degrees of freedom. The pitching and the flapping are completely independent from and uncoupled to each other. As such, the rotor can independently flap, or independently pitch, or flap and pitch simultaneously with different amplitudes and/or frequencies. The mechanism can also be used in a non-rotary wing configuration, such as an ornithopter, in which case the rotational degree of freedom would be suppressed.

  18. Biological and biomimetic molecular machines.

    PubMed

    Huang, Tony J; Juluri, Bala K

    2008-02-01

    The evolution of life facilitates the creation of biological molecular machines. In these so-called 'nanomachines,' nature elegantly shows that when precisely organized and assembled, simple molecular mechanical components can link motions efficiently from the nanometer scale to the macroscopic world, and achieve complex functions such as powering skeletal muscles, synthesizing ATP and producing DNA/RNA. Inspired by nature, researchers are creating artifical molecular machines with tailored structures and properties, with the aim of realizing man-made active nanosystems that operate with the same efficiency and complexity as biological nanomachines. It is anticipated that in the not-too-distant future, unique applications of biological and biomimetic molecular machines will emerge in areas such as biochemical instrumentation and nanomedicine. PMID:18393670

  19. Biomimetic bonelike polymer cementitious composite

    NASA Astrophysics Data System (ADS)

    Dry, Carolyn M.; Warner, Carrie

    1997-02-01

    This paper outlines the progress in the development of a biomimetic, prefabricated synthetic building material that is to have the superior properties of bone. The goal was to make polymer/ceramic composite which mimics bone in both process of fabrication and resultant properties and bond between phases, because bones and shells have been found to have greater toughness and strength than conventional ceramics alone due to the presence of organic bonding materials. The intimate connection between material phases is due to careful growth sequences, i.e. the fibers are made first and the matrix grown around them as opposed to conventional ceramics in which any fibers are added to the matrix. We followed the rules under which bone material naturally forms albeit at a macroscale, as spelled out by researchers in biological materials.

  20. A lightweight vertical rosette for deployment in ice-covered waters

    NASA Astrophysics Data System (ADS)

    Smethie, William M., Jr.; Chayes, Dale; Perry, Richard; Schlosser, Peter

    2011-04-01

    A lightweight modular rosette system has been developed that can be launched and recovered from aircraft in ice-covered waters through a 12 in. diameter hole in the ice. The small diameter is achieved by the modular design, in which a CTD module is attached to the end of a conducting cable and water bottle modules (four 4-L bottles per module) are positioned vertically above it. A novel tripping mechanism based on melting a link of monofilament line is used to close the water bottles at the desired depths. After launching the rosette, the cast proceeds like a normal rosette cast with the traces of temperature, salinity, oxygen and other desired sensors being displayed on a computer screen during the down and up casts and tripping the bottles electronically at the desired depths on the up cast. A Seabird 19+ CTD and Seabird 43 oxygen sensor are mounted in the CTD module and data acquisition and bottle tripping are controlled using a Seabird 33 deck unit and Seabird's SeaSave software run on a laptop computer. Deployment and recovery are done in a heated tent attached to the aircraft to prevent the water from freezing. After recovery the bottle modules are placed in coolers with bags of snow to stabilize the cooler temperature close to 0 °C, which is within ±1.8 °C of the in situ temperature, and the modules are transported back to a base camp for subsampling and sample processing. This system has been used to collect over 250 water samples in the ice-covered Lincoln Sea and the quality of the samples for dissolved gases and other constituents has been excellent.

  1. Deep sequencing reveals a novel closterovirus associated with wild rose leaf rosette disease.

    PubMed

    He, Yan; Yang, Zuokun; Hong, Ni; Wang, Guoping; Ning, Guogui; Xu, Wenxing

    2015-06-01

    A bizarre virus-like symptom of a leaf rosette formed by dense small leaves on branches of wild roses (Rosa multiflora Thunb.), designated as 'wild rose leaf rosette disease' (WRLRD), was observed in China. To investigate the presumed causal virus, a wild rose sample affected by WRLRD was subjected to deep sequencing of small interfering RNAs (siRNAs) for a complete survey of the infecting viruses and viroids. The assembly of siRNAs led to the reconstruction of the complete genomes of three known viruses, namely Apple stem grooving virus (ASGV), Blackberry chlorotic ringspot virus (BCRV) and Prunus necrotic ringspot virus (PNRSV), and of a novel virus provisionally named 'rose leaf rosette-associated virus' (RLRaV). Phylogenetic analysis clearly placed RLRaV alongside members of the genus Closterovirus, family Closteroviridae. Genome organization of RLRaV RNA (17,653 nucleotides) showed 13 open reading frames (ORFs), except ORF1 and the quintuple gene block, most of which showed no significant similarities with known viral proteins, but, instead, had detectable identities to fungal or bacterial proteins. Additional novel molecular features indicated that RLRaV seems to be the most complex virus among the known genus members. To our knowledge, this is the first report of WRLRD and its associated closterovirus, as well as two ilarviruses and one capilovirus, infecting wild roses. Our findings present novel information about the closterovirus and the aetiology of this rose disease which should facilitate its control. More importantly, the novel features of RLRaV help to clarify the molecular and evolutionary features of the closterovirus. PMID:25187347

  2. Biomimetic catalysts responsive to specific chemical signals

    SciTech Connect

    Zhao, Yan

    2015-03-04

    Part 1. Design of Biomimetic Catalysts Based on Amphiphilic Systems The overall objective of our research is to create biomimetic catalysts from amphiphilic molecules. More specifically, we aim to create supramolecular systems that can be used to control the microenvironment around a catalytic center in a biomimetic fashion and apply the learning to construct supramolecular catalysts with novel functions found in enzymatic catalysts. We have prepared synthetic molecules (i.e., foldamers) that could fold into helical structures with nanometer-sized internal hydrophilic cavities. Cavities of this size are typically observed only in the tertiary and quaternary structures of proteins but were formed in our foldamer prepared in just a few steps from the monomer. Similar to many proteins, our foldamers displayed cooperativity in the folding/unfolding equilibrium and followed a two-state conformational transition. In addition, their conformational change could be triggered by solvent polarity, pH, or presence of metal ions and certain organic molecules. We studied their environmentally dependent conformational changes in solutions, surfactant micelles, and lipid bilayer membranes. Unlike conventional rigid supramolecular host, a foldamer undergoes conformational change during guest binding. Our study in the molecular recognition of an oligocholate host yielded some extremely exciting results. Cooperativity between host conformation and host–guest interactions was found to “magnify” weak binding interactions. In other words, since binding affinity is determined by the overall change of free energy during the binding, guest-induced conformational change of the host, whether near or far from the binding site, affects the binding. This study has strong implications in catalysis because enzymes have been hypothesized to harvest similar intramolecular forces to strengthen their binding with the transition state of an enzyme-catalyzed reaction. The supramolecular and

  3. Fire adaptation in Neblinaria celiae (Theaceae), a high-elevation rosette shrub endemic to a wet equatorial tepui

    USGS Publications Warehouse

    Givnish, T.J.; McDiarmid, R.W.; Buck, W.R.

    1986-01-01

    Neblinaria celiae (Theaceae), a rosette shrub endemic to the exceedingly rainy summit of remote Cerro de la Neblina in southern Venezuela, has a previously undescribed set of adaptations to fire. Its growth form entails sparse branching, massive terminal leaf rosettes, and thick bark. It is highly fire-tolerant, with a survival rate of 93% in a stand recently ignited by lightning, vs. 0% in seven co-occurring woody species. Survival increases sharply with rosette height, favoring a sparsely branched habit that would maximize the rate of upward growth through the sparse fuel layer supported by a sterile substrate. Thick bark and massive rosettes help protect cambial and foliar meristems from brief exposure to high temperatures. Rosettes on shorter plants are exposed to greater damage from fire near the ground and, as expected, are bigger and impound more rainwater; the greater number of leaves nearly balances the greater leaf mortality caused by fire. We relate Neblinaria's growth form to its dominance atop Neblina, to a general model for the evolution of sparse branching, and to the evolution of growth form in other tepui plants.

  4. Cell electrophoretic characterization of peripheral blood lymphocyte subpopulations enriched by rosette formation, from normal individuals and CLL patients.

    PubMed

    Rychly, J; Babusíková, O; Koníková, E; Anders, O

    1984-01-01

    Peripheral blood lymphocytes from healthy subjects and patients with chronic lymphatic leukemia (CLL) were isolated and their subpopulations enriched through formation of spontaneous rosettes with sheep or mouse red blood cells, respectively. Electrophoretic measurements were performed in unseparated as well as in fractionated cell populations. Normal blood lymphocytes showed two clearly distinguishable populations of different electrophoretic mobilities. After separation by SRBC rosette formation the rosette-forming cells could be identified as high mobility cells. CLL lymphocytes showed in most cases an unimodally distributed cytopherogram, the mean electrophoretic mobility being intermediate between the low and high mobility cells of control persons. After separation through mouse erythrocytes rosette formation these cells contained two cell fractions differing in their electrophoretic mobility: a fraction of slower mouse rosette-forming cells and a fraction of the non-MRFC which contained mainly cells of higher mobility that could be identified as enriched T cells. These both fractions showed unimodal distributions. This study shows that CLL lymphocyte subpopulations can be further characterized by surface charge density. PMID:6700796

  5. Regrowth patterns and rosette attributes contribute to the differential compensatory responses of Arabidopsis thaliana genotypes to apical damage.

    PubMed

    Scholes, D R; Wszalek, A E; Paige, K N

    2016-03-01

    A plant's compensatory performance refers to its ability to maintain or increase its reproductive output following damage. The ability of a plant to compensate depends on numerous factors including the type, severity, frequency and timing of damage, the environmental conditions and the plant's genotype. Upon apical damage, a cascade of hormonal and genetic responses often produces dramatic changes in a plant's growth, development, architecture and physiology. All else being equal, this response is largely dependent on a plant's genotype, with different regrowth patterns displayed by different genotypes of a given species. In this study, we compare the architectural and growth patterns of two Arabidopsis thaliana genotypes following apical damage. Specifically, we characterise regrowth patterns of the genotypes Columbia-4 and Landsberg erecta, which typically differ in their compensation to apical meristem removal. We report that Landsberg erecta suffered reductions in the number of stems produced, maximum elongation rate, a delay in reaching this rate, lower average rosette quality throughout the growing period, and ultimately, less aboveground dry biomass and seed production when damaged compared to undamaged control plants. Columbia-4 had no reductions in any of these measures and maintained larger rosette area when clipped relative to when unclipped. Based on the apparent influence of the rosette on these genotypes' compensatory performances, we performed a rosette removal experiment, which confirmed that the rosette contributes to compensatory performance. This study provides a novel characterisation of regrowth patterns following apical damage, with insights into those measures having the largest effect on plant performance. PMID:26434737

  6. Calcifying tissue regeneration via biomimetic materials chemistry

    PubMed Central

    Green, David W.; Goto, Tazuko K.; Kim, Kye-Seong; Jung, Han-Sung

    2014-01-01

    Materials chemistry is making a fundamental impact in regenerative sciences providing many platforms for tissue development. However, there is a surprising paucity of replacements that accurately mimic the structure and function of the structural fabric of tissues or promote faithful tissue reconstruction. Methodologies in biomimetic materials chemistry have shown promise in replicating morphologies, architectures and functional building blocks of acellular mineralized tissues dentine, enamel and bone or that can be used to fully regenerate them with integrated cell populations. Biomimetic materials chemistry encompasses the two processes of crystal formation and mineralization of crystals into inorganic formations on organic templates. This review will revisit the successes of biomimetics materials chemistry in regenerative medicine, including coccolithophore simulants able to promote in vivo bone formation. In-depth knowledge of biomineralization throughout evolution informs the biomimetic materials chemist of the most effective techniques for regenerative framework construction exemplified via exploitation of liquid crystals (LCs) and complex self-organizing media. Therefore, a new innovative direction would be to create chemical environments that perform reaction–diffusion exchanges as the basis for building complex biomimetic inorganic structures. This has evolved widely in biology, as have LCs, serving as self-organizing templates in pattern formation of structural biomaterials. For instance, a study is highlighted in which artificially fabricated chiral LCs, made from bacteriophages are transformed into a faithful copy of enamel. While chemical-based strategies are highly promising at creating new biomimetic structures there are limits to the degree of complexity that can be generated. Thus, there may be good reason to implement living or artificial cells in ‘morphosynthesis’ of complex inorganic constructs. In the future, cellular construction is

  7. Objective Definition of Rosette Shape Variation Using a Combined Computer Vision and Data Mining Approach

    PubMed Central

    Camargo, Anyela; Papadopoulou, Dimitra; Spyropoulou, Zoi; Vlachonasios, Konstantinos; Doonan, John H.; Gay, Alan P.

    2014-01-01

    Computer-vision based measurements of phenotypic variation have implications for crop improvement and food security because they are intrinsically objective. It should be possible therefore to use such approaches to select robust genotypes. However, plants are morphologically complex and identification of meaningful traits from automatically acquired image data is not straightforward. Bespoke algorithms can be designed to capture and/or quantitate specific features but this approach is inflexible and is not generally applicable to a wide range of traits. In this paper, we have used industry-standard computer vision techniques to extract a wide range of features from images of genetically diverse Arabidopsis rosettes growing under non-stimulated conditions, and then used statistical analysis to identify those features that provide good discrimination between ecotypes. This analysis indicates that almost all the observed shape variation can be described by 5 principal components. We describe an easily implemented pipeline including image segmentation, feature extraction and statistical analysis. This pipeline provides a cost-effective and inherently scalable method to parameterise and analyse variation in rosette shape. The acquisition of images does not require any specialised equipment and the computer routines for image processing and data analysis have been implemented using open source software. Source code for data analysis is written using the R package. The equations to calculate image descriptors have been also provided. PMID:24804972

  8. Objective definition of rosette shape variation using a combined computer vision and data mining approach.

    PubMed

    Camargo, Anyela; Papadopoulou, Dimitra; Spyropoulou, Zoi; Vlachonasios, Konstantinos; Doonan, John H; Gay, Alan P

    2014-01-01

    Computer-vision based measurements of phenotypic variation have implications for crop improvement and food security because they are intrinsically objective. It should be possible therefore to use such approaches to select robust genotypes. However, plants are morphologically complex and identification of meaningful traits from automatically acquired image data is not straightforward. Bespoke algorithms can be designed to capture and/or quantitate specific features but this approach is inflexible and is not generally applicable to a wide range of traits. In this paper, we have used industry-standard computer vision techniques to extract a wide range of features from images of genetically diverse Arabidopsis rosettes growing under non-stimulated conditions, and then used statistical analysis to identify those features that provide good discrimination between ecotypes. This analysis indicates that almost all the observed shape variation can be described by 5 principal components. We describe an easily implemented pipeline including image segmentation, feature extraction and statistical analysis. This pipeline provides a cost-effective and inherently scalable method to parameterise and analyse variation in rosette shape. The acquisition of images does not require any specialised equipment and the computer routines for image processing and data analysis have been implemented using open source software. Source code for data analysis is written using the R package. The equations to calculate image descriptors have been also provided. PMID:24804972

  9. The Herschel view of star formation in the Rosette molecular cloud under the influence of NGC 2244

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Motte, F.; Bontemps, S.; Hennemann, M.; di Francesco, J.; André, Ph.; Zavagno, A.; Csengeri, T.; Men'shchikov, A.; Abergel, A.; Baluteau, J.-P.; Bernard, J.-Ph.; Cox, P.; Didelon, P.; di Giorgio, A.-M.; Gastaud, R.; Griffin, M.; Hargrave, P.; Hill, T.; Huang, M.; Kirk, J.; Könyves, V.; Leeks, S.; Li, J. Z.; Marston, A.; Martin, P.; Minier, V.; Molinari, S.; Olofsson, G.; Panuzzo, P.; Persi, P.; Pezzuto, S.; Roussel, H.; Russeil, D.; Sadavoy, S.; Saraceno, P.; Sauvage, M.; Sibthorpe, B.; Spinoglio, L.; Testi, L.; Teyssier, D.; Vavrek, R.; Ward-Thompson, D.; White, G.; Wilson, C. D.; Woodcraft, A.

    2010-07-01

    Context. The Rosette molecular cloud is promoted as the archetype of a triggered star-formation site. This is mainly due to its morphology, because the central OB cluster NGC 2244 has blown a circular-shaped cavity into the cloud and the expanding H II-region now interacts with the cloud. Aims: Studying the spatial distribution of the different evolutionary states of all star-forming sites in Rosette and investigating possible gradients of the dust temperature will help to test the “triggered star-formation” scenario in Rosette. Methods: We use continuum data obtained with the PACS (70 and 160 μm) and SPIRE instruments (250, 350, 500 μm) of the Herschel telescope during the science demonstration phase of HOBYS. Results: Three-color images of Rosette impressively show how the molecular gas is heated by the radiative impact of the NGC 2244 cluster. A clear negative temperature gradient and a positive density gradient (running from the H II-region/molecular cloud interface into the cloud) are detected. Studying the spatial distribution of the most massive dense cores (size scale 0.05 to 0.3 pc), we find an age-sequence (from more evolved to younger) with increasing distance to the cluster NGC 2244. No clear gradient is found for the clump (size-scale up to 1 pc) distribution. Conclusions: The existence of temperature and density gradients and the observed age-sequence imply that star formation in Rosette may indeed be influenced by the radiative impact of the central NGC 2244 cluster. A more complete overview of the prestellar and protostellar population in Rosette is required to obtain a firmer result. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Figures [see full textsee full text] and [see full textsee full text] are only available in electronic form at http://www.aanda.org

  10. Forisome as biomimetic smart materials

    NASA Astrophysics Data System (ADS)

    Shen, Amy; Hamlington, Benjamin; Knoblauch, Michael; Peters, Winfried; Pickard, William

    2005-05-01

    With the discovery in plants of the proteinaceous forisome crystalloid (Knoblauch et al. 2003), a novel nastic non-living, ATP-independent biological material became available to the designer of smart materials for advanced actuating and sensing. The in vitro studies of Knoblauch et al. show that forisomes (1-3 micron wide and 10-30 micron long) can be repeatedly stimulated to contract and expand anisotropically by shifting either the ambient pH or the ambient calcium ion concentration. In a device, the energy required for the transformations would be provided electrochemically by mini-electrodes inducing pH variation. Because of their unique abilities to develop and reverse strains greater than 20% in time periods less than 1s , forisomes have the potential to outperform current smart materials (such as ATP-dependent actuators or synthetic hydrogels/polymers) as advanced, biomimetic, multi-functional, smart sensors or valves or actuators. To date, studies have been limited to questions of protein engineering explored by Knaublach et al. Probing forisome material properties is therefore an immediate need to lay the foundation for synthesizing forisome-based smart materials for health monitoring of structural integrity in civil infrastructure and aerospace hardware. Here, we use microfluidics to study the surface interaction between forisome and substrate and the conformational dynamics of forisomes within a confined geometry to lay the foundation for forisome-based smart materials synthesis with controlled and repeatable environment.

  11. Biomimetic Analogs for Collagen Biomineralization

    PubMed Central

    Gu, L.; Kim, Y.K.; Liu, Y.; Ryou, H.; Wimmer, C.E.; Dai, L.; Arola, D.D.; Looney, S.W.; Pashley, D.H.; Tay, F.R.

    2011-01-01

    Inability of chemical phosphorylation of sodium trimetaphosphate to induce intrafibrillar mineralization of type I collagen may be due to the failure to incorporate a biomimetic analog to stabilize amorphous calcium phosphates (ACP) as nanoprecursors. This study investigated adsorption/desorption characteristics of hydrolyzed and pH-adjusted sodium trimetaphosphate (HPA-Na3P3O9) to collagen. Based on those results, a 5-minute treatment time with 2.8 wt% HPA-Na3P3O9 was used in a single-layer reconstituted collagen model to confirm that both the ACP-stabilization analog and matrix phosphoprotein analog must be present for intrafibrillar mineralization. The results of that model were further validated by complete remineralization of phosphoric-acid-etched dentin treated with the matrix phosphoprotein analog and lined with a remineralizing lining composite, and with the ACP-stabilization analog supplied in simulated body fluid. An understanding of the basic processes involved in intrafibrillar mineralization of reconstituted collagen fibrils facilitates the design of novel tissue engineering materials for hard tissue repair and regeneration. PMID:20940362

  12. Biomimetic endodontics: the final evolution?

    PubMed

    Clark, David J

    2007-07-01

    We are seeing a gradual evolution by a small but growing number of endodontists and general dentists toward delicate biomimetic, microscope-based shaping. This old-fashioned respect for periradicular dentin is paired with microscopes, ultrasonics, and an appreciation for root morphology. Although no 2 roots are the same, general anatomic patterns allow the microscope-equipped clinician to search for major pulpal regions that will yield a high probability of cleaning and shaping the clinically available pulpal zones. There are complex, anatomically improbable, and clinically impossible areas of pulp that are beyond the reach of even the most gifted hands. Regardless, the clinician has the responsibility to begin each procedure seeking perfection and joyfully finishing with excellence. The shapes that were introduced during the Schilder (crown-down) era have served as a transitional technique to allow the first real 3-dimensional compaction of gutta-percha. Nonetheless, endodontics is in the end a restoratively driven procedure. Large, arbitrary, round shapes create beautiful endodontics but can dramatically weaken the tooth. The shaping philosophy advanced in this treatise allows perfectly adequate shapes to achieve the hydraulics needed for modern obturation. It will require different skills and materials to shape, pack, and restore the exotic architecture of nature. (See Tables 1 to 3.). PMID:17708316

  13. Biomimetics, color, and the arts

    NASA Astrophysics Data System (ADS)

    Schenk, Franziska

    2015-03-01

    Color as dramatic, dynamic and dazzling as the iridescent hues on the wings of certain butterflies has never been encountered in the art world. Unlike and unmatched by the chemical pigments of the artists' palette, this changeable color is created by transparent, colorless nanostructures that, as with prisms, diffract and reflect light to render spectral color visible. Until now, iridescent colors, by their very nature, have defied artists' best efforts to fully capture these rainbow hues. Now, for the first time, the artist and researcher Franziska Schenk employs latest nature-inspired color-shift technology to actually simulate the iridescence of butterflies and beetles on canvas. Crucially, studying the ingenious ways in which a range of such displays are created by insects has provided the artist with vital clues on how to adapt and adopt these challenging optical nano-materials for painting. And indeed, after years of meticulous and painstaking research both in the lab and studio, the desired effect is achieved. The resulting paintings, like an iridescent insect, do in fact fluctuate in perceived color - depending on the light and viewing angle. In tracing the artist's respective biomimetic approach, the paper not only provides an insight into the new color technology's evolution and innovative artistic possibilities, but also suggests what artists can learn from nature.

  14. Helically linked mirror arrangement

    SciTech Connect

    Ranjan, P.

    1986-08-01

    A scheme is described for helical linking of mirror sections, which endeavors to combine the better features of toroidal and mirror devices by eliminating the longitudinal loss of mirror machines, having moderately high average ..beta.. and steady state operation. This scheme is aimed at a device, with closed magnetic surfaces having rotational transform for equilibrium, one or more axisymmetric straight sections for reduced radial loss, a simple geometrical axis for the links and an overall positive magnetic well depth for stability. We start by describing several other attempts at linking of mirror sections, made both in the past and the present. Then a description of our helically linked mirror scheme is given. This example has three identical straight sections connected by three sections having helical geometric axes. A theoretical analysis of the magnetic field and single-particle orbits in them leads to the conclusion that most of the passing particles would be confined in the device and they would have orbits independent of pitch angle under certain conditions. Numerical results are presented, which agree well with the theoretical results as far as passing particle orbits are concerned.

  15. Energy transfer and photochemistry in biomimetic solar conversion

    NASA Astrophysics Data System (ADS)

    Boxer, S. G.

    1987-09-01

    Electron transfer is being studied in several well-defined molecular systems, and techniques for studying electron transfer are being developed. Photo-induced electron transfer lies at the heart of photosynthesis and forms the basis for the approach to biomimetic solar conversion. Electron donors and acceptors are covalently connected to molecular frameworks which permit variation of the distance between sites and the nature of the intervening medium. Myoglobin produced by recombinant DNA methods was modified to place a free sulfhydryl group at various positions on the surface for attachment of electron acceptors. Surface histidine residues are modified with Ru-reagents. Electron donors and acceptors were also attached to double-helical DNA as a first approach to polymer-based donor/acceptor systems. The effects of applied electric fields on the absorption and emission spectra of compounds undergoing electron transfer were studied. The Stark effect spectra of several Ru-complexes were obtained, from which quantitative information on changes in the permanent dipole moment between the ground and the excited state was extracted. It was also shown that, under certain conditions, the electric field can change the rate of electron transfer reactions, and that the effect is easily detected in the electric-field-modulated fluorescence spectrum. These effects were demonstrated for bacterial reaction centers and certain Ru-complexes.

  16. Biomimetic Delivery with Micro- and Nanoparticles

    PubMed Central

    Balmert, Stephen C.; Little, Steven R.

    2013-01-01

    The nascent field of biomimetic delivery with micro- and nanoparticles (MNP) has advanced considerably in recent years. Drawing inspiration from the ways that cells communicate in the body, several different modes of “delivery” (i.e. temporospatial presentation of biological signals) have been investigated in a number of therapeutic contexts. In particular, this review focuses on (1) controlled release formulations that deliver natural soluble factors with physiologically relevant temporal context, (2) presentation of surface-bound ligands to cells, with spatial organization of ligands ranging from isotropic to dynamically anisotropic, and (3) physical properties of particles, including size, shape and mechanical stiffness, which mimic those of natural cells. Importantly, the context provided by multimodal, or multifactor delivery represents a key element of most biomimetic MNP systems, a concept illustrated by an analogy to human interpersonal communication. Regulatory implications of increasingly sophisticated and “cell-like” biomimetic MNP systems are also discussed. PMID:22528985

  17. Antigenic Modification, Rosette-Forming Cells, and Salmonella typhimurium Resistance in Outbred and Inbred Mice

    PubMed Central

    Bigley, Nancy J.; Kreps, David P.; Smith, Randall A.; Esa, Ahmed

    1981-01-01

    To assess the separate contributions of host T cells and the physical state of the antigen in the development of effective. Salmonella resistance, glutaraldehyde-treated and untreated protein- and ribonucleic acid-rich extracts (E-RNA extracts) of virulent Salmonella typhimurium SR-11 or attenuated S. typhimurium RIA were used to immunize Salmonella-resistant Salmonella-susceptible strains of mice for the purpose of determining whether antigen-specific T-cell or B-cell responses were formed and, if so, which responses predominated. The resistance imparted to each mouse strain after vaccination with S. typhimurium RIA was used as the standard for comparison. The inbred mouse strains C57BL/6 and DBA/2 and their F1 hybrid (strain BDF1), outbred ICR Swiss mice, and endotoxin-resistant C3H/HeJ mice were examined for the capacity to develop resistance to lethal Salmonella infections, as well as the ability to generate antigen-reactive T cells. Only the BDF1, C3H/HeJ, and ICR Swiss mice were able to develop resistance to challenge infections mediated by the virulent SR-11 strain of S. typhimurium after vaccination with the living, attenuated RIA strain of S. typhimurium or immunization with E-RNA extracts. We developed an assay to identify the antigen-reactive rosette-forming lymphocytes present in lymph nodes and spleens of immunized mice. Levels of 0.2% or higher of theta antigen-bearing, antigen-reactive rosette-forming cells were found in the lymph nodes or spleens or both of only the BDF1, C3H/HeJ, and ICR Swiss mice (i.e., in the “Salmonella responder” strains). Mouse strains C57BL/6 and DBA/2, which failed to develop resistance to lethal infections after immunization with the S. typhimurium RIA vaccine or with the E-RNA extracts, lacked effective numbers of antitheta antigen-sensitive rosette-forming cells. Modification of the effective E-RNA extracts by polymerization with glutaraldehyde resulted in a marked diminution in their abilities to induce resistance

  18. Dental cell sheet biomimetic tooth bud model.

    PubMed

    Monteiro, Nelson; Smith, Elizabeth E; Angstadt, Shantel; Zhang, Weibo; Khademhosseini, Ali; Yelick, Pamela C

    2016-11-01

    Tissue engineering and regenerative medicine technologies offer promising therapies for both medicine and dentistry. Our long-term goal is to create functional biomimetic tooth buds for eventual tooth replacement in humans. Here, our objective was to create a biomimetic 3D tooth bud model consisting of dental epithelial (DE) - dental mesenchymal (DM) cell sheets (CSs) combined with biomimetic enamel organ and pulp organ layers created using GelMA hydrogels. Pig DE or DM cells seeded on temperature-responsive plates at various cell densities (0.02, 0.114 and 0.228 cells 10(6)/cm(2)) and cultured for 7, 14 and 21 days were used to generate DE and DM cell sheets, respectively. Dental CSs were combined with GelMA encapsulated DE and DM cell layers to form bioengineered 3D tooth buds. Biomimetic 3D tooth bud constructs were cultured in vitro, or implanted in vivo for 3 weeks. Analyses were performed using micro-CT, H&E staining, polarized light (Pol) microscopy, immunofluorescent (IF) and immunohistochemical (IHC) analyses. H&E, IHC and IF analyses showed that in vitro cultured multilayered DE-DM CSs expressed appropriate tooth marker expression patterns including SHH, BMP2, RUNX2, tenascin and syndecan, which normally direct DE-DM interactions, DM cell condensation, and dental cell differentiation. In vivo implanted 3D tooth bud constructs exhibited mineralized tissue formation of specified size and shape, and SHH, BMP2 and RUNX2and dental cell differentiation marker expression. We propose our biomimetic 3D tooth buds as models to study optimized DE-DM cell interactions leading to functional biomimetic replacement tooth formation. PMID:27565550

  19. Differential Gene Expression in Liver, Gill, and Olfactory Rosettes of Coho Salmon (Oncorhynchus kisutch) After Acclimation to Salinity

    PubMed Central

    Lavado, Ramon; Bammler, Theo K.; Gallagher, Evan P.; Stapleton, Patricia L.; Beyer, Richard P.; Farin, Federico M.; Hardiman, Gary; Schlenk, Daniel

    2015-01-01

    Most Pacific salmonids undergo smoltification and transition from freshwater to saltwater, making various adjustments in metabolism, catabolism, osmotic, and ion regulation. The molecular mechanisms underlying this transition are largely unknown. In the present study, we acclimated coho salmon (Oncorhynchus kisutch) to four different salinities and assessed gene expression through microarray analysis of gills, liver, and olfactory rosettes. Gills are involved in osmotic regulation, liver plays a role in energetics, and olfactory rosettes are involved in behavior. Between all salinity treatments, liver had the highest number of differentially expressed genes at 1616, gills had 1074, and olfactory rosettes had 924, using a 1.5-fold cutoff and a false discovery rate of 0.5. Higher responsiveness of liver to metabolic changes after salinity acclimation to provide energy for other osmoregulatory tissues such as the gills may explain the differences in number of differentially expressed genes. Differentially expressed genes were tissue- and salinity-dependent. There were no known genes differentially expressed that were common to all salinity treatments and all tissues. Gene ontology term analysis revealed biological processes, molecular functions, and cellular components that were significantly affected by salinity, a majority of which were tissue-dependent. For liver, oxygen binding and transport terms were highlighted. For gills, muscle, and cytoskeleton-related terms predominated and for olfactory rosettes, immune response-related genes were accentuated. Interaction networks were examined in combination with GO terms and determined similarities between tissues for potential osmosensors, signal transduction cascades, and transcription factors. PMID:26260986

  20. Long-term culture and differentiation of CNS precursors derived from anterior human neural rosettes following exposure to ventralizing factors

    SciTech Connect

    Colleoni, Silvia; Giannelli, Serena G.; Armentero, Marie-Therese; Blandini, Fabio; Broccoli, Vania; Lazzari, Giovanna

    2010-04-15

    In this study we demonstrated that neural rosettes derived from human ES cells can give rise either to neural crest precursors, following expansion in presence of bFGF and EGF, or to dopaminergic precursors after exposure to ventralizing factors Shh and FGF8. Both regionalised precursors are capable of extensive proliferation and differentiation towards the corresponding terminally differentiated cell types. In particular, peripheral neurons, cartilage, bone, smooth muscle cells and also pigmented cells were obtained from neural crest precursors while tyrosine hydroxylase and Nurr1 positive dopaminergic neurons were derived from FGF8 and Shh primed rosette cells. Gene expression and immunocytochemistry analyses confirmed the expression of dorsal and neural crest genes such as Sox10, Slug, p75, FoxD3, Pax7 in neural precursors from bFGF-EGF exposed rosettes. By contrast, priming of rosettes with FGF8 and Shh induced the expression of dopaminergic markers Engrailed1, Pax2, Pitx3, floor plate marker FoxA2 and radial glia markers Blbp and Glast, the latter in agreement with the origin of dopaminergic precursors from floor plate radial glia. Moreover, in vivo transplant of proliferating Shh/FGF8 primed precursors in parkinsonian rats demonstrated engraftment and terminal dopaminergic differentiation. In conclusion, we demonstrated the derivation of long-term self-renewing precursors of selected regional identity as potential cell reservoirs for cell therapy applications, such as CNS degenerative diseases, or for the development of toxicological tests.

  1. ROSETTE GLANDS IN THE GILLS OF THE GRASS SHRIMP, 'PALAEMONETES PUGIO' I. COMPARATIVE MORPHOLOGY, CYCLICAL ACTIVITY, AND INNERVATION

    EPA Science Inventory

    Two types of exocrine rosette glands (type A and type B), located in the gill axes of the grass shrimp, Palaemonetes pugio, are described. The type A glands are embedded within the longitudinal median spetum of the gill axes, whereas the type B glands typically project into the e...

  2. Differential Gene Expression in Liver, Gill, and Olfactory Rosettes of Coho Salmon (Oncorhynchus kisutch) After Acclimation to Salinity.

    PubMed

    Maryoung, Lindley A; Lavado, Ramon; Bammler, Theo K; Gallagher, Evan P; Stapleton, Patricia L; Beyer, Richard P; Farin, Federico M; Hardiman, Gary; Schlenk, Daniel

    2015-12-01

    Most Pacific salmonids undergo smoltification and transition from freshwater to saltwater, making various adjustments in metabolism, catabolism, osmotic, and ion regulation. The molecular mechanisms underlying this transition are largely unknown. In the present study, we acclimated coho salmon (Oncorhynchus kisutch) to four different salinities and assessed gene expression through microarray analysis of gills, liver, and olfactory rosettes. Gills are involved in osmotic regulation, liver plays a role in energetics, and olfactory rosettes are involved in behavior. Between all salinity treatments, liver had the highest number of differentially expressed genes at 1616, gills had 1074, and olfactory rosettes had 924, using a 1.5-fold cutoff and a false discovery rate of 0.5. Higher responsiveness of liver to metabolic changes after salinity acclimation to provide energy for other osmoregulatory tissues such as the gills may explain the differences in number of differentially expressed genes. Differentially expressed genes were tissue- and salinity-dependent. There were no known genes differentially expressed that were common to all salinity treatments and all tissues. Gene ontology term analysis revealed biological processes, molecular functions, and cellular components that were significantly affected by salinity, a majority of which were tissue-dependent. For liver, oxygen binding and transport terms were highlighted. For gills, muscle, and cytoskeleton-related terms predominated and for olfactory rosettes, immune response-related genes were accentuated. Interaction networks were examined in combination with GO terms and determined similarities between tissues for potential osmosensors, signal transduction cascades, and transcription factors. PMID:26260986

  3. Hydrogen-bonded oligothiophene rosettes with a benzodithiophene terminal unit: self-assembly and application to bulk heterojunction solar cells.

    PubMed

    Ouchi, Hayato; Lin, Xu; Kizaki, Takahiro; Prabhu, Deepak D; Silly, Fabien; Kajitani, Takashi; Fukushima, Takanori; Nakayama, Ken-Ichi; Yagai, Shiki

    2016-06-14

    Benzodithiophene-functionalized oligothiophene with barbituric acid hydrogen-bonding unit self-assembles into nanoscopic structures via the formation of rosettes. The nanostructures show a power conversion efficiency of 3% upon mixing with PC61BM in bulk-heterojunction solar cells without thermal annealing. PMID:27251116

  4. The genome organization of lucerne transient streak and turnip rosette sobemoviruses revisited.

    PubMed

    Sõmera, Merike; Truve, Erkki

    2013-03-01

    Unlike other sobemoviruses, lucerne transient streak virus (LTSV) and turnip rosette virus (TRoV) have been reported to contain two successive ORF1s (denoted as ORF1a and ORF1b) instead of a single ORF1. Also, their next ORF (ORF2a/2a2b) has been mapped to a region ca. 200 nucleotides downstream from that of other sobemoviruses, leading to the lack of transmembrane segments at the N-termini of P2a/2a2b. In the current study, we resequenced this region for TRoV and LTSV. The hypothetical beginning of ORF1b was mapped as the beginning of ORF2a/2a2b for both TRoV and LTSV. Computional analysis revealed transmembrane segments at the N-termini of the TRoV and LTSV polyproteins. PMID:23111554

  5. Whole field displacement and strain rosettes by grating objective speckle method

    NASA Astrophysics Data System (ADS)

    Tu, Meirong; Gielisse, Peter J.; Xu, Wei

    1991-12-01

    The grating objective speckle method was applied for whole field displacement measurements to a high transition temperature superconductor (YBa2Cu3Ox) disk under diametral-compression. Four fringe patterns were obtained from one single specklegram, indicating the displacement components along four different directions, with 45 degree intervals. The spatial frequencies, which represent the sensitivities of the fringe intervals, were 2400 lines/mm for Ux and Uy, and 1697 lines/mm for U45 and U135, respectively. The normal strain components, (epsilon) x, (epsilon) y, (epsilon) 135, can be directly transformed. The shear strain, (gamma) xy, can therefore be calculated by the rosette equations without the need for first cross-derivatives from two displacement contour maps, which is highly sensitive to accidental rigid-body rotations. The technique provides an extremely simple set-up for the recording system. There is no laser, no camera, no laborious optical alignment, and no requirement for vibration isolation.

  6. Novel FBG rosette for determining impact location in thin plate-like structure

    NASA Astrophysics Data System (ADS)

    Majewska, K.; Opoka, S.; Kudela, P.; Ostachowicz, W.

    2015-07-01

    The paper consists of two interdependent parts. The first part presents numerical simulations of output response of single Fibre Bragg Grating (FBG) sensor which is driven by homogeneous deformation along sensor length. The example of such sensor is FBG sensor glued at only two points. The grating length and modulation depth of the refractive index are the critical parameters contributing to performance of the FBG sensors. Numerical analysis allowed to select an appropriate FBG sensors which will be used in the impact detection problem. In the second part of the paper a novel strain rosette with specific sensor array used in impact localisation problem is discussed and presented. The experiment was carried out on thin composite plate with the use of pulse force excitation. The method is based on estimation of principal direction of perturbed travelling wave initiated at impact point and does not use any information about wave propagation velocity.

  7. NIR and MM observations of the globulettes in the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    Mäkelä, Minja; Haikala, Lauri; Gahm, Gösta; Persson, Carina

    2013-07-01

    Globulettes are tiny, optically dark molecular clouds, most likely detached from eroding elephant trunks. They form a class of objects whose shape resembles that of starless globules but their size is considerably smaller with masses ranging from 1 to about 500M_Jup. We have observed the globulette and shell system in the northwestern region of the Rosette Nebula in near-infrared and mm. We present NIR JHKs, Paschen beta and H2 2.12 micron observations obtained with the NTT/SOFI and CO observations done with the APEX and Onsala 20m radio telescopes. Combined with Spitzer archival data, we can study the physical properties such as mass, velocity and the visual extinction of the globulettes. We can also identify possible star formation. The Ks and H2 observations suggest fluorescent H2 emission is seen in the region.

  8. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    DOE PAGESBeta

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; Walko, Donald A.; Landahl, Eric C.

    2016-01-11

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Finally, using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acousticmore » oscillations at frequencies of several GHz.« less

  9. Picosecond x-ray strain rosette reveals direct laser excitation of coherent transverse acoustic phonons

    PubMed Central

    Lee, Sooheyong; Williams, G. Jackson; Campana, Maria I.; Walko, Donald A.; Landahl, Eric C.

    2016-01-01

    Using a strain-rosette, we demonstrate the existence of transverse strain using time-resolved x-ray diffraction from multiple Bragg reflections in laser-excited bulk gallium arsenide. We find that anisotropic strain is responsible for a considerable fraction of the total lattice motion at early times before thermal equilibrium is achieved. Our measurements are described by a new model where the Poisson ratio drives transverse motion, resulting in the creation of shear waves without the need for an indirect process such as mode conversion at an interface. Using the same excitation geometry with the narrow-gap semiconductor indium antimonide, we detected coherent transverse acoustic oscillations at frequencies of several GHz. PMID:26751616

  10. Modelling an advanced ManPAD with dual band detectors and a rosette scanning seeker head

    NASA Astrophysics Data System (ADS)

    Birchenall, Richard P.; Richardson, Mark A.; Butters, Brian; Walmsley, Roy

    2012-01-01

    Man Portable Air Defence Systems (ManPADs) have been a favoured anti aircraft weapon since their appearance on the military proliferation scene in the mid 1960s. Since this introduction there has been a 'cat and mouse' game of Missile Countermeasures (CMs) and the aircraft protection counter counter measures (CCMs) as missile designers attempt to defeat the aircraft platform protection equipment. Magnesium Teflon Viton (MTV) flares protected the target aircraft until the missile engineers discovered the art of flare rejection using techniques including track memory and track angle bias. These early CCMs relied upon CCM triggering techniques such as the rise rate method which would just sense a sudden increase in target energy and assume that a flare CM had been released by the target aircraft. This was not as reliable as was first thought as aspect changes (bringing another engine into the field of view) or glint from the sun could inadvertently trigger a CCM when not needed. The introduction of dual band detectors in the 1980s saw a major advance in CCM capability allowing comparisons between two distinct IR bands to be made thus allowing the recognition of an MTV flare to occur with minimal false alarms. The development of the rosette scan seeker in the 1980s complemented this advancement allowing the scene in the missile field of view (FOV) to be scanned by a much smaller (1/25) instantaneous FOV (IFOV) with the spectral comparisons being made at each scan point. This took the ManPAD from a basic IR energy detector to a pseudo imaging system capable of analysing individual elements of its overall FOV allowing more complex and robust CCM to be developed. This paper continues the work published in [1,2] and describes the method used to model an advanced ManPAD with a rosette scanning seeker head and robust CCMs similar to the Raytheon Stinger RMP.

  11. Hydrodynamic interactions between rotating helices.

    PubMed

    Kim, MunJu; Powers, Thomas R

    2004-06-01

    Escherichia coli bacteria use rotating helical flagella to swim. At this scale, viscous effects dominate inertia, and there are significant hydrodynamic interactions between nearby helices. These interactions cause the flagella to bundle during the "runs" of bacterial chemotaxis. Here we use slender-body theory to solve for the flow fields generated by rigid helices rotated by stationary motors. We determine how the hydrodynamic forces and torques depend on phase and phase difference, show that rigid helices driven at constant torque do not synchronize, and solve for the flows. We also use symmetry arguments based on kinematic reversibility to show that for two rigid helices rotating with zero phase difference, there is no time-averaged attractive or repulsive force between the helices. PMID:15244620

  12. Biomimetic control for DEA arrays

    NASA Astrophysics Data System (ADS)

    O'Brien, Benjamin; Gisby, Todd; Xie, Sheng Q.; Calius, Emilio; Anderson, Iain

    2010-04-01

    Arrays of actuators are ubiquitous in nature for manipulation, pumping and propulsion. Often these arrays are coordinated in a multi-level fashion with distributed sensing and feedback manipulated by higher level controllers. In this paper we present a biologically inspired multi-level control strategy and apply it to control an array of Dielectric Elastomer Actuators (DEA). A test array was designed consisting of three DEA arranged to tilt a set of rails on which a ball rolls. At the local level the DEA were controlled using capacitive self-sensing state machines that switched the actuator off and on when capacitive thresholds were exceeded, resulting in the steady rolling of the ball around the rails. By varying the voltage of the actuators in the on state, it was possible to control the speed of the ball to match a set point. A simple integral derivative controller was used to do this and an observer law was formulated to track the speed of the ball. The array demonstrated the ability to self start, roll the ball in either direction, and run at a range of speeds determined by the maximum applied voltage. The integral derivative controller successfully tracked a square wave set point. Whilst the test application could have been controlled with a classic centralised controller, the real benefit of the multi-level strategy becomes apparent when applied to larger arrays and biomimetic applications that are ideal for DEA. Three such applications are discussed; a robotic heart, a peristaltic pump and a ctenophore inspired propulsion array.

  13. Conservation of helicity in superfluids

    NASA Astrophysics Data System (ADS)

    Kedia, Hridesh; Kleckner, Dustin; Proment, Davide; Irvine, William T. M.

    2015-03-01

    Helicity arises as a special conserved quantity in ideal fluids, in addition to energy, momentum and angular momentum. As a measure of the knottedness of vortex lines, Helicity provides an important tool for studying a wide variety of physical systems such as plasmas and turbulent fluids. Superfluids flow without resistance just like ideal (Euler) fluids, making it natural to ask whether their knottedness is similarly preserved. We address the conservation of helicity in superfluids theoretically and examine its consequences in numerical simulations.

  14. Foldamers: Biomimetic and built to order

    NASA Astrophysics Data System (ADS)

    Horne, W. Seth

    2015-11-01

    Synthetic oligomers could potentially expand beyond the functions offered by proteins and nucleic acids. However, this requires precise methods for controlling their folding and self-assembly. Now, it is shown that two drastically different supramolecular architectures can be fabricated from closely related sequences using a single biomimetic scaffold.

  15. Evolving application of biomimetic nanostructured hydroxyapatite

    PubMed Central

    Roveri, Norberto; Iafisco, Michele

    2010-01-01

    By mimicking Nature, we can design and synthesize inorganic smart materials that are reactive to biological tissues. These smart materials can be utilized to design innovative third-generation biomaterials, which are able to not only optimize their interaction with biological tissues and environment, but also mimic biogenic materials in their functionalities. The biomedical applications involve increasing the biomimetic levels from chemical composition, structural organization, morphology, mechanical behavior, nanostructure, and bulk and surface chemical–physical properties until the surface becomes bioreactive and stimulates cellular materials. The chemical–physical characteristics of biogenic hydroxyapatites from bone and tooth have been described, in order to point out the elective sides, which are important to reproduce the design of a new biomimetic synthetic hydroxyapatite. This review outlines the evolving applications of biomimetic synthetic calcium phosphates, details the main characteristics of bone and tooth, where the calcium phosphates are present, and discusses the chemical–physical characteristics of biomimetic calcium phosphates, methods of synthesizing them, and some of their biomedical applications. PMID:24198477

  16. Major intrinsic proteins in biomimetic membranes.

    PubMed

    Nielsen, Claus Hélix

    2010-01-01

    Biological membranes define the structural and functional boundaries in living cells and their organelles. The integrity of the cell depends on its ability to separate inside from outside and yet at the same time allow massive transport of matter in and out the cell. Nature has elegantly met this challenge by developing membranes in the form of lipid bilayers in which specialized transport proteins are incorporated. This raises the question: is it possible to mimic biological membranes and create a membrane based sensor and/or separation device? In the development of a biomimetic sensor/separation technology, a unique class of membrane transport proteins is especially interesting-the major intrinsic proteins (MIPs). Generally, MIPs conduct water molecules and selected solutes in and out of the cell while preventing the passage of other solutes, a property critical for the conservation of the cells internal pH and salt concentration. Also known as water channels or aquaporins they are highly efficient membrane pore proteins some of which are capable of transporting water at very high rates up to 10(9) molecules per second. Some MIPs transport other small, uncharged solutes, such as glycerol and other permeants such as carbon dioxide, nitric oxide, ammonia, hydrogen peroxide and the metalloids antimonite, arsenite, silicic and boric acid depending on the effective restriction mechanism of the protein. The flux properties of MIPs thus lead to the question ifMIPs can be used in separation devices or as sensor devices based on, e.g., the selective permeation of metalloids. In principle a MIP based membrane sensor/separation device requires the supporting biomimetic matrix to be virtually impermeable to anything but water or the solute in question. In practice, however, a biomimetic support matrix will generally have finite permeabilities to both electrolytes and non-electrolytes. The feasibility of a biomimetic MIP device thus depends on the relative transport

  17. Helical tomotherapy quality assurance.

    PubMed

    Balog, John; Soisson, Emilie

    2008-01-01

    Helical tomotherapy uses a dynamic delivery in which the gantry, treatment couch, and multileaf collimator leaves are all in motion during treatment. This results in highly conformal radiotherapy, but the complexity of the delivery is partially hidden from the end-user because of the extensive integration and automation of the tomotherapy control systems. This presents a challenge to the medical physicist who is expected to be both a system user and an expert, capable of verifying relevant aspects of treatment delivery. A related issue is that a clinical tomotherapy planning system arrives at a customer's site already commissioned by the manufacturer, not by the clinical physicist. The clinical physicist and the manufacturer's representative verify the commissioning at the customer site before acceptance. Theoretically, treatment could begin immediately after acceptance. However, the clinical physicist is responsible for the safe and proper use of the machine. In addition, the therapists and radiation oncologists need to understand the important machine characteristics before treatment can proceed. Typically, treatment begins about 2 weeks after acceptance. This report presents an overview of the tomotherapy system. Helical tomotherapy has unique dosimetry characteristics, and some of those features are emphasized. The integrated treatment planning, delivery, and patient-plan quality assurance process is described. A quality assurance protocol is proposed, with an emphasis on what a clinical medical physicist could and should check. Additionally, aspects of a tomotherapy quality assurance program that could be checked automatically and remotely because of its inherent imaging system and integrated database are discussed. PMID:18406907

  18. Helical Tomotherapy Quality Assurance

    SciTech Connect

    Balog, John Soisson, Emilie

    2008-05-01

    Helical tomotherapy uses a dynamic delivery in which the gantry, treatment couch, and multileaf collimator leaves are all in motion during treatment. This results in highly conformal radiotherapy, but the complexity of the delivery is partially hidden from the end-user because of the extensive integration and automation of the tomotherapy control systems. This presents a challenge to the medical physicist who is expected to be both a system user and an expert, capable of verifying relevant aspects of treatment delivery. A related issue is that a clinical tomotherapy planning system arrives at a customer's site already commissioned by the manufacturer, not by the clinical physicist. The clinical physicist and the manufacturer's representative verify the commissioning at the customer site before acceptance. Theoretically, treatment could begin immediately after acceptance. However, the clinical physicist is responsible for the safe and proper use of the machine. In addition, the therapists and radiation oncologists need to understand the important machine characteristics before treatment can proceed. Typically, treatment begins about 2 weeks after acceptance. This report presents an overview of the tomotherapy system. Helical tomotherapy has unique dosimetry characteristics, and some of those features are emphasized. The integrated treatment planning, delivery, and patient-plan quality assurance process is described. A quality assurance protocol is proposed, with an emphasis on what a clinical medical physicist could and should check. Additionally, aspects of a tomotherapy quality assurance program that could be checked automatically and remotely because of its inherent imaging system and integrated database are discussed.

  19. Magnetic design constraints of helical solenoids

    SciTech Connect

    Lopes, M. L.; Krave, S. T.; Tompkins, J. C.; Yonehara, K.; Flanagan, G.; Kahn, S. A.; Melconian, K.

    2015-01-30

    Helical solenoids have been proposed as an option for a Helical Cooling Channel for muons in a proposed Muon Collider. Helical solenoids can provide the required three main field components: solenoidal, helical dipole, and a helical gradient. In general terms, the last two are a function of many geometric parameters: coil aperture, coil radial and longitudinal dimensions, helix period and orbit radius. In this paper, we present design studies of a Helical Solenoid, addressing the geometric tunability limits and auxiliary correction system.

  20. Helicity patterns on the Sun

    NASA Astrophysics Data System (ADS)

    Pevtsov, A.

    Solar magnetic fields exhibit hemispheric preference for negative (pos- itive) helicity in northern (southern) hemisphere. The hemispheric he- licity rule, however, is not very strong, - the patterns of opposite sign helicity were observed on different spatial scales in each hemisphere. For instance, many individual sunspots exhibit patches of opposite he- licity inside the single polarity field. There are also helicity patterns on scales larger than the size of typical active region. Such patterns were observed in distribution of active regions with abnormal (for a give hemisphere) helicity, in large-scale photospheric magnetic fields and coronal flux systems. We will review the observations of large-scale pat- terns of helicity in solar atmosphere and their possible relationship with (sub-)photospheric processes. The emphasis will be on large-scale pho- tospheric magnetic field and solar corona.

  1. Systematic characterization of polycrystalline silica-carbonate helices.

    PubMed

    Nakouzi, Elias; Knoll, Pamela; Hendrix, Kenzie B; Steinbock, Oliver

    2016-08-17

    Biomorphs are complex, life-like structures that emerge from the precipitation of barium carbonate and amorphous silica in alkaline media. Despite their inorganic nature, these microstructures have non-crystallographic morphologies such as helices and cardioid sheets. At the nanoscale, biomorphs arrange thousands of crystalline nanorods as hierarchical assemblies that resemble natural biominerals suggesting novel approaches towards the production of biomimetic materials. We report the synthesis of silica-carbonate biomorphs in single-phase, gradient-free solutions that differ markedly from the typical solution-gas or gel-solution setups. Our experimental approach significantly increases the duration of biomorph growth and hence assembles networks in which individual helices extend to several millimeters. These unusually long biomorphs allow the first quantitative measurements of mesoscopic parameters such as the helix wavelength, period, width, and linear as well as tangential growth velocities. We find that the latter quantities are system-specific and tightly conserved during many hours of growth. Moreover, the average double helix wavelength of (19 ± 3) μm and width of (9.6 ± 0.8) μm vary by less than 12% when the initial carbonate concentration is changed by three orders of magnitude. We also delineate the single helix growth mechanism and report the occurrence of ribbon-like structures and highly regular "superhelices". Our experiments clearly demonstrate the robustness and consistency of biomorph growth under stable chemical conditions. PMID:27492708

  2. The Advanced Helical Generator

    SciTech Connect

    Reisman, D B; Javedani, J B; Ellsworth, G F; Kuklo, R M; Goerz, D A; White, A D; Tallerico, L J; Gidding, D A; Murphy, M J; Chase, J B

    2009-10-26

    A high explosive pulsed power (HEPP) generator called the Advanced Helical Generator (AHG) has been designed, built, and successfully tested. The AHG incorporates design principles of voltage and current management to obtain a high current and energy gain. Its design was facilitated by the use of modern modeling tools as well as high precision manufacture. The result was a first-shot success. The AHG delivered 16 Mega-Amperes of current and 11 Mega-Joules of energy to a quasi-static 80 nH inductive load. A current gain of 154 times was obtained with a peak exponential rise time of 20 {micro}s. We will describe in detail the design and testing of the AHG.

  3. Biochemical evaluation of borage (Borago officinalis) rosette leaves through their essential oil and fatty acid composition.

    PubMed

    Mhamdi, Baya; Aidi Wannes, Wissem; Marzouk, Brahim

    2007-06-01

    Borago officinalis rosette leaves were sampled in the region of Amdoun (Tunisia) during different stages of their development. Essential oil contents varied from 0.01% to 0.13% respectively in young and adult leaves. Twenty three volatile compounds were identified. Hydrocarbons, mainly represented by nonadecane (29.8%), tetracosane (11.3%) and heptacosane (4.7%), constituted the major class in the young leaves (45.8%), followed by aldehydes (22.4%). The percentages of these two classes decreased to reach respectively 15% and 8.1% in adult leaves in favour of alcohols (57.9%) where cis-3-hexenol (29.6%) and hexanol (14.5%) were the main compounds. Total fatty acids amounts increased from 5.03 mg/g DW in young leaves to 32.23 mg/g DW in adult ones. The predominant fatty acids were alpha-linolenic (C18:3 n-3), stearidonic (C18:4 n-3), gamma-linolenic (C18:3 n-6), palmitic (C16: 0) and linoleic (C18:2 n-6) acids. PMID:17722661

  4. Evaluation of the good tumor response of embryonal tumor with abundant neuropil and true rosettes (ETANTR).

    PubMed

    Mozes, Petra; Hauser, Péter; Hortobágyi, Tibor; Benyó, Gábor; Peták, István; Garami, Miklós; Cserháti, Adrienne; Bartyik, Katalin; Bognár, László; Nagy, Zoltán; Turányi, Eszter; Hideghéty, Katalin

    2016-01-01

    The embryonal tumor with abundant neuropil and true rosettes is a rare and highly malignant variant of embryonal brain tumors. It usually affects infants and young children under the age of 4 years and exhibits a very aggressive course with a dismal prognosis. For the 68 cases reported to date the mean age at diagnosis was 25.42 months (range 3-57 months). Survival data are available for 48 children (including our case): the median overall survival is 13.0 months, though 6 (9%) of the children have had a relative long survival (>30 months). The aggressive combined treatment, involving primary surgical tumor removal, adjuvant polychemotherapy, including high-dose chemotherapy with stem cell transplantation, radiotherapy and radiochemotherapy, might play an important role in the longer survival. We have performed a literature review and we present here a multimodal-treated case of a 2- year-old girl with a long survival, who was reoperated when recurrence occurred. The residual tumor demonstrated a good response to temozolomide radiochemotherapy (craniospinal axis + boost) and followed by maintenance temozolomide. The described complex aggressive treatment option might be considered for future cases of this tumor entity. PMID:26373296

  5. Acoustic Emission Source Location Using a Distributed Feedback Fiber Laser Rosette

    PubMed Central

    Huang, Wenzhu; Zhang, Wentao; Li, Fang

    2013-01-01

    This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage in structures such as those found in civil applications. The directional sensitivity of DFB fiber laser is investigated by calculating location coefficient using a method of digital signal analysis. In this, autocorrelation is used to extract the location coefficient from the periodic AE signal and wavelet packet energy is calculated to get the location coefficient of a burst AE source. Normalization is processed to eliminate the influence of distance and intensity of AE source. Then a new location algorithm based on the location coefficient is presented and tested to determine the location of AE source using a Delta (Δ) DFB fiber laser rosette configuration. The advantage of the proposed algorithm over the traditional methods based on fiber Bragg Grating (FBG) include the capability of: having higher strain resolution for AE detection and taking into account two different types of AE source for location. PMID:24141266

  6. Growth rates, reproductive phenology, and pollination ecology of Espeletia grandiflora (Asteraceae), a giant Andean caulescent rosette.

    PubMed

    Fagua, J C; Gonzalez, V H

    2007-01-01

    From March 2001 to December 2002, we studied the reproductive phenology, pollination ecology, and growth rates of Espeletia grandiflora Humb. and Bonpl. (Asteraceae), a giant caulescent rosette from the Páramos of the Eastern Andes of Colombia. Espeletia grandiflora was found to be predominantly allogamous and strongly self-incompatible. Bumblebees (Bombus rubicundus and B. funebris) were the major pollinators of E. grandiflora, although moths, hummingbirds, flies, and beetles also visited flowers. Inflorescence development began in March and continued through August to September. Plants flowered for 30 - 96 days with a peak from the beginning of October through November. The percentage of flowering plants strongly differed among size classes and between both years. Seed dispersal occurred as early as September through May of the following year. The average absolute growth rate for juveniles and adults rate was 7.6 cm/year. Given the scarcity of floral visitors at high altitudes due to climatic conditions, we suggest that even small contributions from a wide range of pollinators might be advantageous for pollination of E. grandiflora. Long-term studies on different populations of E. grandiflora are required to determine if the high growth rates are representative, to quantify the variation in the flowering behavior within and among populations, and to establish if nocturnal pollination is a trait that is exclusive to our population of E. grandiflora. PMID:17066366

  7. Freezing avoidance mechanisms in juveniles of giant rosette plants of the genus Espeletia

    NASA Astrophysics Data System (ADS)

    García-Varela, Sonia; Rada, Fermín

    2003-07-01

    Along soil-air gradients in tropical high mountains, plants growing at soil level tolerate frost while those growing well above ground, including all species in the genus Espeletia, use freezing avoidance mechanisms to survive low nighttime temperatures. The question that arises and the objective of this work were: What are the low temperature resistance mechanisms in giant rosettes when they are within the juvenile stages, i.e. closer to the ground? Juveniles of Espeletia spicata and Espeletia timotensis, dominant plants of the high Venezuelan Andes, were chosen for this study. To determine resistance mechanisms for these species, air and leaf temperatures were recorded in the field in 24 h cycles, while thermal analysis and injury temperature were determined in the laboratory. Both E. spicata and E. timotensis juveniles depend on avoidance mechanisms through a high supercooling capacity, permitting leaves to resist low nighttime temperatures. Minimum leaf temperatures were -4.9 and -5.1 °C, for E. spicata and E. timotensis, respectively, occurring during the dry season. Ice formation occurred at -14.3 and -15.3 °C for E. spicata and E. timotensis, respectively. Injury occurred at approximately -15 °C in both species. Low temperature resistance mechanisms in juveniles are similar to those in adult plants.

  8. Demodulation of a fiber Fabry-Perot strain rosette using white light interferometry

    NASA Astrophysics Data System (ADS)

    Zuliani, Gary Louis

    Fiber optic sensors are starting to be used in specialty application areas where electrical sensors are usually found, such as in aircraft and spacecraft. Fiber optic sensor technology has advantages over its electronic counterparts including small size and weight, immunity to electromagnetic interference, and ruggedness. The use of fiber interferometers as sensors is reviewed along with methods for demodulating their signals. The principles of path-matched differential interferometry and coherence multiplexing are demonstrated and applied to the design and construction of a system that simultaneously demodulates three fiber Fabry-Perot (FFP) interferometers. The FFP's formed the arms of a delta rosette which were bonded to the surface of an aluminum cantilevered beam and were illuminated with one broadband light source. The receiving interferometer consisted of a bulk Michelson interferometer with three distinct optical paths. A charge coupled device array was used as the detector allowing fringe shifts to be counted on a television monitor. Tensor measurements were made and found to be in good agreement when compared to those obtained from electrical strain gages.

  9. A suspended-particle rosette multi-sampler for discrete biogeochemical sampling in low-particle-density waters

    SciTech Connect

    Breier, J. A.; Rauch, C. G.; McCartney, K.; Toner, B. M.; Fakra, S. C.; White, S. N.; German, C. R.

    2010-06-22

    To enable detailed investigations of early stage hydrothermal plume formation and abiotic and biotic plume processes we developed a new oceanographic tool. The Suspended Particulate Rosette sampling system has been designed to collect geochemical and microbial samples from the rising portion of deep-sea hydrothermal plumes. It can be deployed on a remotely operated vehicle for sampling rising plumes, on a wire-deployed water rosette for spatially discrete sampling of non-buoyant hydrothermal plumes, or on a fixed mooring in a hydrothermal vent field for time series sampling. It has performed successfully during both its first mooring deployment at the East Pacific Rise and its first remotely-operated vehicle deployments along the Mid-Atlantic Ridge. It is currently capable of rapidly filtering 24 discrete large-water-volume samples (30-100 L per sample) for suspended particles during a single deployment (e.g. >90 L per sample at 4-7 L per minute through 1 {mu}m pore diameter polycarbonate filters). The Suspended Particulate Rosette sampler has been designed with a long-term goal of seafloor observatory deployments, where it can be used to collect samples in response to tectonic or other events. It is compatible with in situ optical sensors, such as laser Raman or visible reflectance spectroscopy systems, enabling in situ particle analysis immediately after sample collection and before the particles alter or degrade.

  10. Rosette-Disrupting Effect of an Anti-Plasmodial Compound for the Potential Treatment of Plasmodium falciparum Malaria Complications

    PubMed Central

    Ch’ng, Jun-Hong; Moll, Kirsten; Quintana, Maria del Pilar; Chan, Sherwin Chun Leung; Masters, Ellen; Moles, Ernest; Liu, Jianping; Eriksson, Anders B.; Wahlgren, Mats

    2016-01-01

    The spread of artemisinin-resistant parasites could lead to higher incidence of patients with malaria complications. However, there are no current treatments that directly dislodge sequestered parasites from the microvasculature. We show that four common antiplasmodial drugs do not disperse rosettes (erythrocyte clusters formed by malaria parasites) and therefore develop a cell-based high-throughput assay to identify potential rosette-disrupting compounds. A pilot screen of 2693 compounds identified Malaria Box compound MMV006764 as a potential candidate. Although it reduced rosetting by a modest 20%, MMV006764 was validated to be similarly effective against both blood group O and A rosettes of three laboratory parasite lines. Coupled with its antiplasmodial activity and drug-likeness, MMV006764 represents the first small-molecule compound that disrupts rosetting and could potentially be used in a resource-limited setting to treat patients deteriorating rapidly from malaria complications. Such dual-action drugs that simultaneously restore microcirculation and reduce parasite load could significantly reduce malaria morbidity and mortality. PMID:27403804

  11. Protein fraction isolated from epididymal fluid re-associates sperm in vitro: possible role of serpins in rat rosettes assembly.

    PubMed

    Monclus, María A; Andreina, Cesari; Cabrillana, María E; Lancellotti, Tania E Saez; Rensetti, Daniel E; Clementi, Marisa A; Boarelli, Paola V; Vincenti, Amanda E; Fornés, Miguel W

    2010-05-01

    In many mammalian species, sperm associate as a consequence of the epididymal transit. From the classic Rouleaux in guinea pig to the most recent work in mouse and echidna, authors have focused mainly on a detailed morphological description of this phenomenon. Some of these articles have also begun to describe the nature of the material present between sperm heads. Here, we try to better understand the factor/s involved in rat sperm association (Rosette). Based on previous work describing the appearance of Rosettes in the distal segments of the rat epididymis, we consider that sperm during their transit must be in contact with factor/s present in the caudal lumen in order to associate with each other. By an in vitro sperm re-associating assay, we try to determine the in vivo phenomenon observed in the lumen. The assay consists of co-incubating non-associated sperm with several protein fractions obtained from epididymal caudal fluid. After establishing the most active fraction, the proteins were characterized by MALDI-TOF mass spectrometry. Among the proteins we found two members of the serine protease inhibitors family; an alpha-1 antitrypsin and a new protein with an alpha-1 antitrypsin like domain which includes a sequence compatible with the serpins' reactive center loop. These serpins may play a role in the assembly/disassembly process of Rosettes by modulating lumenal protease activity. Finally, a biochemical-morphological model which explains the sperm-proteases interaction was proposed. PMID:20143401

  12. Rosette-Disrupting Effect of an Anti-Plasmodial Compound for the Potential Treatment of Plasmodium falciparum Malaria Complications.

    PubMed

    Ch'ng, Jun-Hong; Moll, Kirsten; Quintana, Maria Del Pilar; Chan, Sherwin Chun Leung; Masters, Ellen; Moles, Ernest; Liu, Jianping; Eriksson, Anders B; Wahlgren, Mats

    2016-01-01

    The spread of artemisinin-resistant parasites could lead to higher incidence of patients with malaria complications. However, there are no current treatments that directly dislodge sequestered parasites from the microvasculature. We show that four common antiplasmodial drugs do not disperse rosettes (erythrocyte clusters formed by malaria parasites) and therefore develop a cell-based high-throughput assay to identify potential rosette-disrupting compounds. A pilot screen of 2693 compounds identified Malaria Box compound MMV006764 as a potential candidate. Although it reduced rosetting by a modest 20%, MMV006764 was validated to be similarly effective against both blood group O and A rosettes of three laboratory parasite lines. Coupled with its antiplasmodial activity and drug-likeness, MMV006764 represents the first small-molecule compound that disrupts rosetting and could potentially be used in a resource-limited setting to treat patients deteriorating rapidly from malaria complications. Such dual-action drugs that simultaneously restore microcirculation and reduce parasite load could significantly reduce malaria morbidity and mortality. PMID:27403804

  13. Biomimetic synthesis of materials for technology.

    PubMed

    Galloway, Johanna M; Bramble, Jonathan P; Staniland, Sarah S

    2013-07-01

    In a world with ever decreasing natural reserves, researchers are striving to find sustainable methods of producing components for technology. Bioinspired, biokleptic and biomimetic materials can be used to form a wide range of technologically relevant materials under environmentally friendly conditions. Here we investigate a range of biotemplated and bioinspired materials that can be used to develop components for devices, such as optics, photonics, photovoltaics, circuits and data storage. PMID:23761195

  14. Embedded SMA wire actuated biomimetic fin: a module for biomimetic underwater propulsion

    NASA Astrophysics Data System (ADS)

    Wang, Zhenlong; Hang, Guanrong; Wang, Yangwei; Li, Jian; Du, Wei

    2008-04-01

    An embedded shape memory alloy (SMA) wire actuated biomimetic fin is presented, and based on this module for biomimetic underwater propulsion, a micro robot fish (146 mm in length, 30 g in weight) and a robot squid (242 mm in length, 360 g in weight) were developed. Fish swim by undulating their body and/or fins. Squid and cuttlefish can also swim by undulating their fins. To simplify engineering modeling, the undulating swimming movement is assumed to be the integration of the movements of many flexible bending segments connected in parallel or in series. According to this idea, a biomimetic fin which can bend flexibly was developed. The musculature of a cuttlefish fin was investigated to aid the design of the biomimetic fin. SMA wires act as 'muscle fibers' to drive the biomimetic fin just like the transverse muscles of the cuttlefish fin. During the bending phase, elastic energy is stored in the elastic substrate and skin, and during the return phase, elastic energy is released to power the return movement. Theorem analysis of the bending angle was performed to estimate the bending performance of the biomimetic fin. Experiments were carried out on single-face fins with latex rubber skin and silicone skin (SF-L and SF-S) to compare the bending angle, return time, elastic energy storage and reliability. Silicone was found to be the better skin. A dual-face fin with silicone skin (DF-S) was tested in water to evaluate the actuating performance and to validate the reliability. Thermal analysis of the SMA temperature was performed to aid the control strategy. The micro robot fish and robot squid employ one and ten DF-S, respectively. Swimming experiments with different actuation frequencies were carried out. The speed and steering radius of the micro robot fish reached 112 mm s-1 and 136 mm, respectively, and the speed and rotary speed of the robot squid reached 40 mm s-1 and 22° s-1, respectively.

  15. Biomimetic nanoparticles: preparation, characterization and biomedical applications.

    PubMed

    Carmona-Ribeiro, Ana Maria

    2010-01-01

    Mimicking nature is a powerful approach for developing novel lipid-based devices for drug and vaccine delivery. In this review, biomimetic assemblies based on natural or synthetic lipids by themselves or associated to silica, latex or drug particles will be discussed. In water, self-assembly of lipid molecules into supramolecular structures is fairly well understood. However, their self-assembly on a solid surface or at an interface remains poorly understood. In certain cases, hydrophobic drug granules can be dispersed in aqueous solution via lipid adsorption surrounding the drug particles as nanocapsules. In other instances, hydrophobic drug molecules attach as monomers to borders of lipid bilayer fragments providing drug formulations that are effective in vivo at low drug-to-lipid-molar ratio. Cationic biomimetic particles offer suitable interfacial environment for adsorption, presentation and targeting of biomolecules in vivo. Thereby antigens can effectively be presented by tailored biomimetic particles for development of vaccines over a range of defined and controllable particle sizes. Biomolecular recognition between receptor and ligand can be reconstituted by means of receptor immobilization into supported lipidic bilayers allowing isolation and characterization of signal transduction steps. PMID:20463941

  16. Kirigami design and fabrication for biomimetic robotics

    NASA Astrophysics Data System (ADS)

    Rossiter, Jonathan; Sareh, Sina

    2014-03-01

    Biomimetics faces a continual challenge of how to bridge the gap between what Nature has so effectively evolved and the current tools and materials that engineers and scientists can exploit. Kirigami, from the Japanese `cut' and `paper', is a method of design where laminar materials are cut and then forced out-of-plane to yield 3D structures. Kirimimetic design provides a convenient and relatively closed design space within which to replicate some of the most interesting niche biological mechanisms. These include complex flexing organelles such as cilia in algae, energy storage and buckled structures in plants, and organic appendages that actuate out-of-plane such as the myoneme of the Vorticella protozoa. Where traditional kirigami employs passive materials which must be forced to transition to higher dimensions, we can exploit planar smart actuators and artificial muscles to create self-actuating kirigami structures. Here we review biomimetics with respect to the kirigami design and fabrication methods and examine how smart materials, including electroactive polymers and shape memory polymers, can be used to realise effective biomimetic components for robotic, deployable structures and engineering systems. One-way actuation, for example using shape memory polymers, can yield complete self-deploying structures. Bi-directional actuation, in contrast, can be exploited to mimic fundamental biological mechanisms such as thrust generation and fluid control. We present recent examples of kirigami robotic mechanisms and actuators and discuss planar fabrication methods, including rapid prototyping and 3D printing, and how current technologies, and their limitations, affect Kirigami robotics.

  17. Twist Helicity in Classical Vortices

    NASA Astrophysics Data System (ADS)

    Scheeler, Martin W.; Kedia, Hridesh; Kleckner, Dustin; Irvine, William T. M.

    2015-11-01

    Recent experimental work has demonstrated that a partial measure of fluid Helicity (the sum of linking and writhing of vortex tubes) is conserved even as those vortices undergo topology changing reconnections. Measuring the total Helicity, however, requires additional information about how the vortex lines are locally twisted inside the vortex core. To bridge this gap, we have developed a novel technique for experimentally measuring twist Helicity. Using this method, we are able to measure the production and eventual decay of twist for a variety of vortex evolutions. Remarkably, we observe twist dynamics capable of conserving total Helicity even in the presence of rapidly changing writhe. This work was supported by the NSF MRSEC shared facilities at the University of Chicago (DMR-0820054) and an NSF CAREER award (DMR-1351506). W.T.M.I. further acknowledges support from the A.P. Sloan Foundation and the Packard Foundation.

  18. Helicity multiplexed broadband metasurface holograms

    PubMed Central

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Yue Bun Pun, Edwin; Zhang, Shuang; Chen, Xianzhong

    2015-01-01

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices. PMID:26354497

  19. Helicity multiplexed broadband metasurface holograms.

    PubMed

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

    2015-01-01

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices. PMID:26354497

  20. Biomimetic Taste Receptors with Chiral Recognition by Photoluminescent Metal-Organic Frameworks Chelated with Polyaniline Helices.

    PubMed

    Lee, Tu; Lin, Tsung Yan; Lee, Hung Lin; Chang, Yun Hsuan; Tsai, Yee Chen

    2016-01-22

    The adsorption of phenylaniline (Phe) enantiomers on (+)-polyaniline (PAN)-chelated [In(OH)(bdc)]n microcrystals was carefully designed and studied by using the Job titration, circular dichroism, X-ray photoelectron spectroscopy, and photoluminescence to mimic heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors in selective, but not specific, ligand binding with chiral recognition and signal transduction. Six essential working principles across different length scales are unraveled: 1) a chiral (+)-PAN (host), 2) specific sites for Phe-(+)/PAN (guest-host) binding, 3) a conformational change of (+)-PAN after binding with Phe enantiomers, 4) different degrees of packing for (+)-PAN, 5) interactions between (+)-PAN and the underlying signal-generating framework (i.e., [In(OH)(bdc)]n microcrystals), and 6) a systematic photoluminescent signal combination by using principal-component analysis from the other three polymer-chelated metal-organic frameworkds (MOFs), such as poly(acrylic acid) (PAA), sodium alginate (SA), and polyvinylpyrrolidone (PVP) to enhance the selectivity and discrimination capabilities. PMID:26670931

  1. Employing helicity amplitudes for resummation

    NASA Astrophysics Data System (ADS)

    Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.

    2016-05-01

    Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in 4- and d -dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard matching coefficients, for p p →H +0 , 1, 2 jets, p p →W /Z /γ +0 , 1, 2 jets, and p p →2 , 3 jets. These operator bases are completely crossing symmetric, so the results can easily be applied to processes with e+e- and e-p collisions.

  2. Cleavage strain in the Variscan fold belt, County Cork, Ireland, estimated from stretched arsenopyrite rosettes

    USGS Publications Warehouse

    Ford, M.; Ferguson, C.C.

    1985-01-01

    In south-west Ireland, hydrothermally formed arsenopyrite crystals in a Devonian mudstone have responded to Variscan deformation by brittle extension fracture and fragment separation. The interfragment gaps and terminal extension zones of each crystal are infilled with fibrous quartz. Stretches within the cleavage plane have been calculated by the various methods available, most of which can be modified to incorporate terminal extension zones. The Strain Reversal Method is the most accurate currently available but still gives a minimum estimate of the overall strain. The more direct Hossain method, which gives only slightly lower estimates with this data, is more practical for field use. A strain ellipse can be estimated from each crystal rosette composed of three laths (assuming the original interlimb angles were all 60??) and, because actual rather than relative stretches are estimated, this provides a lower bound to the area increase in the plane of cleavage. Based on the average of our calculated strain ellipses this area increase is at least 114% and implies an average shortening across the cleavage of at least 53%. However, several lines of evidence suggest that the cleavage deformation was more intense and more oblate than that calculated, and we argue that a 300% area increase in the cleavage plane and 75% shortening across the cleavage are more realistic estimates of the true strain. Furthermore, the along-strike elongation indicated is at least 80%, which may be regionally significant. Estimates of orogenic contraction derived from balanced section construction should therefore take into account the possibility of a substantial strike elongation, and tectonic models that can accommodate such elongations need to be developed. ?? 1985.

  3. Biomimetics: forecasting the future of science, engineering, and medicine

    PubMed Central

    Hwang, Jangsun; Jeong, Yoon; Park, Jeong Min; Lee, Kwan Hong; Hong, Jong Wook; Choi, Jonghoon

    2015-01-01

    Biomimetics is the study of nature and natural phenomena to understand the principles of underlying mechanisms, to obtain ideas from nature, and to apply concepts that may benefit science, engineering, and medicine. Examples of biomimetic studies include fluid-drag reduction swimsuits inspired by the structure of shark’s skin, velcro fasteners modeled on burrs, shape of airplanes developed from the look of birds, and stable building structures copied from the backbone of turban shells. In this article, we focus on the current research topics in biomimetics and discuss the potential of biomimetics in science, engineering, and medicine. Our report proposes to become a blueprint for accomplishments that can stem from biomimetics in the next 5 years as well as providing insight into their unseen limitations. PMID:26388692

  4. Biomimetics: forecasting the future of science, engineering, and medicine.

    PubMed

    Hwang, Jangsun; Jeong, Yoon; Park, Jeong Min; Lee, Kwan Hong; Hong, Jong Wook; Choi, Jonghoon

    2015-01-01

    Biomimetics is the study of nature and natural phenomena to understand the principles of underlying mechanisms, to obtain ideas from nature, and to apply concepts that may benefit science, engineering, and medicine. Examples of biomimetic studies include fluid-drag reduction swimsuits inspired by the structure of shark's skin, velcro fasteners modeled on burrs, shape of airplanes developed from the look of birds, and stable building structures copied from the backbone of turban shells. In this article, we focus on the current research topics in biomimetics and discuss the potential of biomimetics in science, engineering, and medicine. Our report proposes to become a blueprint for accomplishments that can stem from biomimetics in the next 5 years as well as providing insight into their unseen limitations. PMID:26388692

  5. Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes.

    PubMed

    Knaus, Tanja; Paul, Caroline E; Levy, Colin W; de Vries, Simon; Mutti, Francesco G; Hollmann, Frank; Scrutton, Nigel S

    2016-01-27

    The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the "ene" reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. "Better-than-Nature" biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost. PMID:26727612

  6. Selective control for helical microswimmers

    NASA Astrophysics Data System (ADS)

    Katsamba, Panayiota; Lauga, Eric

    2015-11-01

    One of the greatest aspirations for artificial microswimmers is their application in non-invasive medicine. For any practical use, adequate mechanisms enabling control of multiple artificial swimmers is of paramount importance. Here we propose a multi-helical, freely-jointed motor as a novel selective control mechanism. We show that the nonlinear step-out behavior of a magnetized helix driven by a rotating magnetic field can be exploited, when used in conjunction with other helices, to obtain a velocity profile that is non-negligible only within a chosen interval of operating frequencies. Specifically, the force balance between the competing opposite-handed helices is tuned to give no net motion at low frequencies while in the middle frequency range, the swimming velocity increases monotonically with the driving frequency if two opposite helices are used, thereby allowing speed adjustment by varying the driving frequency. We illustrate this idea in detail on a two-helix system, and demonstrate how to generalize to N helices, both numerically and theoretically. We finish by explaining how to solve the inverse problem and design an artificial swimmer with an arbitrarily-complex velocity vs. frequency relationship.

  7. Flexible helical-axis stellarator

    DOEpatents

    Harris, Jeffrey H.; Hender, Timothy C.; Carreras, Benjamin A.; Cantrell, Jack L.; Morris, Robert N.

    1988-01-01

    An 1=1 helical winding which spirals about a conventional planar, circular central conductor of a helical-axis stellarator adds a significant degree of flexibility by making it possible to control the rotational transform profile and shear of the magnetic fields confining the plasma in a helical-axis stellarator. The toroidal central conductor links a plurality of toroidal field coils which are separately disposed to follow a helical path around the central conductor in phase with the helical path of the 1=1 winding. This coil configuration produces bean-shaped magnetic flux surfaces which rotate around the central circular conductor in the same manner as the toroidal field generating coils. The additional 1=1 winding provides flexible control of the magnetic field generated by the central conductor to prevent the formation of low-order resonances in the rotational transform profile which can produce break-up of the equilibrium magnetic surfaces. Further, this additional winding can deepen the magnetic well which together with the flexible control provides increased stability.

  8. Helicity Injected Torus Program Overview

    NASA Astrophysics Data System (ADS)

    Redd, A. J.; Jarboe, T. R.; Aboulhosn, R. Z.; Akcay, C.; Hamp, W. T.; Marklin, G.; Nelson, B. A.; O'Neill, R. G.; Raman, R.; Sieck, P. E.; Smith, R. J.; Sutphin, G. L.; Wrobel, J. S.; Mueller, D.; Roquemore, L.

    2006-10-01

    The Helicity Injected Torus with Steady Inductive Helicity Injection (HIT--SI) spheromak experiment [Sieck, Nucl. Fusion v.46, p.254 (2006)] addresses critical issues for spheromaks, including current drive, high-beta operation, confinement quality and efficient steady-state operation. HIT--SI has a ``bow-tie'' shaped axisymmetric confinement region (major radius R=0.33 m, axial extent of 0.57 m) and two half-torus helicity injectors, one mounted on each end of the flux conserver. HIT--SI has produced spheromaks with up to 30 kA of toroidal current, using less than 4 MW of applied power, demonstrating that Steady Inductive Helicity Injection can generate and sustain discharges with modest power requirements. Fast camera images of HIT--SI discharges indicate a toroidally rotating n=1 structure, driven by the helicity injectors. The direction of the toroidal current is determined by the direction of rotation of the driven n=1. Measured surface and internal magnetic fields in HIT--SI discharges are consistent with that of the true 3D Taylor state, including the injectors. Recent HIT--SI physics studies, diagnostic improvements and machine upgrades will also be summarized.

  9. Effect of urea on biomimetic aggregates.

    PubMed

    Florenzano, F H; Politi, M J

    1997-02-01

    The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities. PMID:9239302

  10. Biomimetic Strategies for Bone Repair and Regeneration

    PubMed Central

    Raucci, Maria G.; Guarino, Vincenzo; Ambrosio, Luigi

    2012-01-01

    The osseointegration rate of implants is related to their composition and surface roughness. Implant roughness favors both bone anchoring and biomechanical stability. Osteoconductive calcium phosphate (Ca-P) coatings promote bone healing and apposition, leading to the rapid biological fixation of implants. It has been clearly shown in many publications that Ca-P coating accelerates bone formation around the implant. This review discusses two main routes for the manufacturing of polymer-based osteoconductive scaffolds for tissue engineering, namely the incorporation of bioceramic particles in the scaffold and the coating of a scaffold with a thin layer of apatite through a biomimetic process. PMID:24955638

  11. Biomimetic synthesis: discovery of xanthanolide dimers.

    PubMed

    Shang, Hai; Liu, Junhua; Bao, Ruiyang; Cao, Yu; Zhao, Kun; Xiao, Chengqian; Zhou, Bing; Hu, Lihong; Tang, Yefeng

    2014-12-22

    Starting from xanthatin, the biomimetic synthesis of 4β,5β-epoxyxanthatin-1α,4α-endoperoxide, a novel monomeric xanthanolide, has been achieved. Moreover, four unprecedented xanthanolide dimers were synthesized by three different dimerizations of xanthatin, either in a head-to-head or head-to-tail fashion. Notably, these dimeric compounds were firstly identified as artifacts in the laboratory, and two of them, mogolides A and B, proved to be natural products present in the Xanthium mogolium Kitag plant. PMID:25430055

  12. Biomimetic total synthesis of santalin Y.

    PubMed

    Strych, Sebastian; Journot, Guillaume; Pemberton, Ryan P; Wang, Selina C; Tantillo, Dean J; Trauner, Dirk

    2015-04-20

    A biomimetic total synthesis of santalin Y, a structurally complex but racemic natural product, is described. The key step is proposed to be a (3+2) cycloaddition of a benzylstyrene to a "vinylogous oxidopyrylium", which is followed by an intramolecular Friedel-Crafts reaction. This cascade generates the unique oxafenestrane framework of the target molecule and sets its five stereocenters in one operation. Our work provides rapid access to santalin Y and clarifies its biosynthetic relationship with other colorants isolated from red sandalwood. PMID:25858797

  13. Generalized helicity and Beltrami fields

    SciTech Connect

    Buniy, Roman V.; Kephart, Thomas W.

    2014-05-15

    We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫{sub Ω}trF{sub μν}F{sup μν}d{sup 4}x subject to the local constraint ε{sup μναβ}trF{sub μν}F{sub αβ}=0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity.

  14. Rational design of helical architectures

    PubMed Central

    Chakrabarti, Dwaipayan; Fejer, Szilard N.; Wales, David J.

    2009-01-01

    Nature has mastered the art of creating complex structures through self-assembly of simpler building blocks. Adapting such a bottom-up view provides a potential route to the fabrication of novel materials. However, this approach suffers from the lack of a sufficiently detailed understanding of the noncovalent forces that hold the self-assembled structures together. Here we demonstrate that nature can indeed guide us, as we explore routes to helicity with achiral building blocks driven by the interplay between two competing length scales for the interactions, as in DNA. By characterizing global minima for clusters, we illustrate several realizations of helical architecture, the simplest one involving ellipsoids of revolution as building blocks. In particular, we show that axially symmetric soft discoids can self-assemble into helical columnar arrangements. Understanding the molecular origin of such spatial organisation has important implications for the rational design of materials with useful optoelectronic applications.

  15. Biomimetic High-Density Lipoproteins from a Gold Nanoparticle Template

    NASA Astrophysics Data System (ADS)

    Luthi, Andrea Jane

    For hundreds of years the field of chemistry has looked to nature for inspiration and insight to develop novel solutions for the treatment of human diseases. The ability of chemists to identify, mimic, and modifiy small molecules found in nature has led to the discovery and development of many important therapeutics. Chemistry on the nanoscale has made it possible to mimic natural, macromolecular structures that may also be useful for understanding and treating diseases. One example of such a structure is high-density lipoprotein (HDL). The goal of this work is to use a gold nanoparticle (Au NP) as a template to synthesize functional mimics of HDL and characterize their structure and function. Chapter 1 details the structure and function of natural HDL and how chemistry on the nanoscale provides new strategies for mimicking HDL. This Chapter also describes the first examples of using nanoparticles to mimic HDL. Chapter 2 reports the synthesis and characterization of biomimetic HDL using different sizes of Au NPs and different surface chemistries and how these variables can be used to tailor the properties of biomimetic HDL. From these studies the optimal strategy for synthesizing biomimetic HDL was determined. In Chapter 3, the optimization of the synthesis of biomimetic HDL is discussed as well as a full characterization of its structure. In addition, the work in this chapter shows that biomimetic HDL can be synthesized on a large scale without alterations to its structure or function. Chapter 4 focuses on understanding the pathways by which biomimetic HDL accepts cholesterol from macrophage cells. The results of these studies demonstrate that biomimetic HDL is able to accept cholesterol by both active and passive pathways of cholesterol efflux. In Chapter 5 the preliminary results of in vivo studies to characterize the pharmacokinetics and pharmacodynamics of biomimetic HDL are presented. These studies suggest that biomimetic HDL traffics through tissues prone to

  16. Helical axis stellarator equilibrium model

    SciTech Connect

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift.

  17. Brownian motion of helical flagella.

    PubMed

    Hoshikawa, H; Saito, N

    1979-07-01

    We develops a theory of the Brownian motion of a rigid helical object such as bacterial flagella. The statistical properties of the random forces acting on the helical object are discussed and the coefficients of the correlations of the random forces are determined. The averages , and are also calculated where z and theta are the position along and angle around the helix axis respectively. Although the theory is limited to short time interval, direct comparison with experiment is possible by using the recently developed cinematography technique. PMID:16997210

  18. OPE for all helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Basso, Benjamin; Caetano, João; Córdova, Lucía; Sever, Amit; Vieira, Pedro

    2015-08-01

    We extend the Operator Product Expansion (OPE) for scattering amplitudes in planar SYM to account for all possible helicities of the external states. This is done by constructing a simple map between helicity configurations and so-called charged pentagon transitions. These OPE building blocks are generalizations of the bosonic pentagons entering MHV amplitudes and they can be bootstrapped at finite coupling from the integrable dynamics of the color flux tube. A byproduct of our map is a simple realization of parity in the super Wilson loop picture.

  19. Engineering Biomimetic Materials for Islet Transplantation

    PubMed Central

    Yang, Ethan Y.; Kronenfeld, Joshua P.; Stabler, Cherie L.

    2015-01-01

    A closed-loop system that provides both the sensing of glucose and the appropriate dosage of insulin could dramatically improve treatment options for insulin-dependent diabetics. The intrahepatic implantation of allogeneic islets has the potential to provide this intimate control, by transplanting the very cells that have this inherent sensing and secretion capacity. Limiting islet transplantation, however, is the significant loss and dysfunction of islets following implantation, due to the poor engraftment environment and significant immunological attack. In this review, we outline approaches that seek to address these challenges via engineering biomimetic materials. These materials can serve to mimic natural processes that work toward improving engraftment, minimizing inflammation, and directing immunological responses. Biomimetic materials can serve to house cells, recapitulate native microenvironments, release therapeutic agents in a physiological manner, and/or present agents to direct cells towards desired responses. By integrating these approaches, superior platforms capable of improving long-term engraftment and acceptance of transplanted islets are on the horizon. PMID:25776871

  20. Biomimetic Strategies for Sensing Biological Species

    PubMed Central

    Hussain, Munawar; Wackerlig, Judith; Lieberzeit, Peter A.

    2013-01-01

    The starting point of modern biosensing was the application of actual biological species for recognition. Increasing understanding of the principles underlying such recognition (and biofunctionality in general), however, has triggered a dynamic field in chemistry and materials sciences that aims at joining the best of two worlds by combining concepts derived from nature with the processability of manmade materials, e.g., sensitivity and ruggedness. This review covers different biomimetic strategies leading to highly selective (bio)chemical sensors: the first section covers molecularly imprinted polymers (MIP) that attempt to generate a fully artificial, macromolecular mold of a species in order to detect it selectively. A different strategy comprises of devising polymer coatings to change the biocompatibility of surfaces that can also be used to immobilized natural receptors/ligands and thus stabilize them. Rationally speaking, this leads to self-assembled monolayers closely resembling cell membranes, sometimes also including bioreceptors. Finally, this review will highlight some approaches to generate artificial analogs of natural recognition materials and biomimetic approaches in nanotechnology. It mainly focuses on the literature published since 2005. PMID:25587400

  1. Biomimetic phantom for cardiac diffusion MRI

    PubMed Central

    Teh, Irvin; Zhou, Feng‐Lei; Hubbard Cristinacce, Penny L.; Parker, Geoffrey J.M.

    2015-01-01

    Purpose Diffusion magnetic resonance imaging (MRI) is increasingly used to characterize cardiac tissue microstructure, necessitating the use of physiologically relevant phantoms for methods development. Existing phantoms are generally simplistic and mostly simulate diffusion in the brain. Thus, there is a need for phantoms mimicking diffusion in cardiac tissue. Materials and Methods A biomimetic phantom composed of hollow microfibers generated using co‐electrospinning was developed to mimic myocardial diffusion properties and fiber and sheet orientations. Diffusion tensor imaging was carried out at monthly intervals over 4 months at 9.4T. 3D fiber tracking was performed using the phantom and compared with fiber tracking in an ex vivo rat heart. Results The mean apparent diffusion coefficient and fractional anisotropy of the phantom remained stable over the 4‐month period, with mean values of 7.53 ± 0.16 × 10‐4 mm2/s and 0.388 ± 0.007, respectively. Fiber tracking of the 1st and 3rd eigenvectors generated analogous results to the fiber and sheet‐normal direction respectively, found in the left ventricular myocardium. Conclusion A biomimetic phantom simulating diffusion in the heart was designed and built. This could aid development and validation of novel diffusion MRI methods for investigating cardiac microstructure, decrease the number of animals and patients needed for methods development, and improve quality control in longitudinal and multicenter cardiac diffusion MRI studies. J. MAGN. RESON. IMAGING 2016;43:594–600. PMID:26213152

  2. The state of the art in biomimetics.

    PubMed

    Lepora, Nathan F; Verschure, Paul; Prescott, Tony J

    2013-03-01

    Biomimetics is a research field that is achieving particular prominence through an explosion of new discoveries in biology and engineering. The field concerns novel technologies developed through the transfer of function from biological systems. To analyze the impact of this field within engineering and related sciences, we compiled an extensive database of publications for study with network-based information analysis techniques. Criteria included publications by year and journal or conference, and subject areas judged by popular and common terms in titles. Our results reveal that this research area has expanded rapidly from less than 100 papers per year in the 1990s to several thousand papers per year in the first decade of this century. Moreover, this research is having impact across a variety of research themes, spanning robotics, computer science and bioengineering. In consequence, biomimetics is becoming a leading paradigm for the development of new technologies that will potentially lead to significant scientific, societal and economic impact in the near future. PMID:23302259

  3. Biomimetic multifunctional surfaces inspired from animals.

    PubMed

    Han, Zhiwu; Mu, Zhengzhi; Yin, Wei; Li, Wen; Niu, Shichao; Zhang, Junqiu; Ren, Luquan

    2016-08-01

    Over millions of years, animals have evolved to a higher intelligent level for their environment. A large number of diverse surface structures on their bodies have been formed to adapt to the extremely harsh environment. Just like the structural diversity existed in plants, the same also applies true in animals. Firstly, this article provides an overview and discussion of the most common functional surface structures inspired from animals, such as drag reduction, noise reduction, anti-adhesion, anti-wear, anti-erosion, anti-fog, water capture, and optical surfaces. Then, some typical characteristics of morphologies, structures, and materials of the animal multifunctional surfaces were discussed. The adaptation of these surfaces to environmental conditions was also analyzed. It mainly focuses on the relationship between their surface functions and their surface structural characteristics. Afterwards, the multifunctional mechanisms or principles of these surfaces were discussed. Models of these structures were provided for the development of structure materials and machinery surfaces. At last, fabrication techniques and existing or potential technical applications inspired from biomimetic multifunctional surfaces in animals were also discussed. The application prospects of the biomimetic functional surfaces are very broad, such as civil field of self-cleaning textile fabrics and non-stick pots, ocean field of oil-water separation, sports field of swimming suits, space development field of lens arrays. PMID:27085632

  4. The transport of relative canonical helicity

    SciTech Connect

    You, S.

    2012-09-15

    The evolution of relative canonical helicity is examined in the two-fluid magnetohydrodynamic formalism. Canonical helicity is defined here as the helicity of the plasma species' canonical momentum. The species' canonical helicity are coupled together and can be converted from one into the other while the total gauge-invariant relative canonical helicity remains globally invariant. The conversion is driven by enthalpy differences at a surface common to ion and electron canonical flux tubes. The model provides an explanation for why the threshold for bifurcation in counter-helicity merging depends on the size parameter. The size parameter determines whether magnetic helicity annihilation channels enthalpy into the magnetic flux tube or into the vorticity flow tube components of the canonical flux tube. The transport of relative canonical helicity constrains the interaction between plasma flows and magnetic fields, and provides a more general framework for driving flows and currents from enthalpy or inductive boundary conditions.

  5. Conservation of magnetic helicity during plasma relaxation

    SciTech Connect

    Ji, H.; Prager, S.C.; Sarff, J.S.

    1994-07-01

    Decay of the total magnetic helicity during the sawtooth relaxation in the MST Reversed-Field Pinch is much larger than the MHD prediction. However, the helicity decay (3--4%) is smaller than the magnetic energy decay (7--9%), modestly supportive of the helicity conservation hypothesis in Taylor`s relaxation theory. Enhanced fluctuation-induced helicity transport during the relaxation is observed.

  6. Denser Sampling of the Rosette Nebula with Faraday Rotation Measurements: Improved Estimates of Magnetic Fields in H II Regions

    NASA Astrophysics Data System (ADS)

    Costa, Allison H.; Spangler, Steven R.; Sink, Joseph R.; Brown, Shea; Mao, Sui Ann

    2016-04-01

    We report Faraday rotation measurements of 11 extragalactic radio sources with lines of sight through the Rosette Nebula, a prominent H ii region associated with the star cluster NGC 2244. The goal of these measurements is to better determine the strength and structure of the magnetic field in the nebula. We calculate the rotation measure (RM) through two methods, a least-squares fit to χ ({λ }2) and Rotation Measure Synthesis. In conjunction with our results from Savage et al., we find an excess RM due to the shell of the nebula of +40 to +1200 rad m-2 above a background RM of +147 rad m-2. We discuss two forms of a simple shell model intended to reproduce the magnitude of the observed RM as a function of distance from the center of the Rosette Nebula. The models represent different physical situations for the magnetic field within the shell of the nebula. The first assumes that there is an increase in the magnetic field strength and plasma density at the outer radius of the H ii region, such as would be produced by a strong magnetohydrodynamic shock wave. The second model assumes that any increase in the RM is due solely to an increase in the density, and the Galactic magnetic field is unaffected in the shell. We employ a Bayesian analysis to compare the two forms of the model. The results of this analysis were inconclusive, although the model without amplification of the interstellar magnetic field is weakly favored.

  7. Identification and characterization of two novel genomic RNA segments RNA5 and RNA6 in rose rosette virus infecting roses.

    PubMed

    Babu, B; Washburn, B K; Poduch, K; Knox, G W; Paret, M L

    2016-06-01

    Rose rosette virus (RRV), a negative-strand RNA virus belonging to the genus Emaravirus, has recently been characterized to be the causal agent of rose rosette disease. Roses showing typical symptoms of RRV collected from a rose nursery in Florida were subjected to reverse transcription-PCR (RT-PCR) assay using primers corresponding to the conserved inverted 13 nucleotide long stretches found at the termini of the RRV genomic RNA segments. RT-PCR analysis yielded two novel genomic RNA segments, RNA5 and RNA6, in addition to the previously identified four RNA segments. The RNA5 is 1650 bp long and encodes for a polypeptide of 465 amino acids (54.3 K), while RNA6 is 1400 bp long and encodes for a polypeptide of 233 amino acids (27.05 K). RACE analysis showed that, both the RNA segments posses at their 5' and 3' termini, stretches of conserved inverted complementary13 nucleotides long sequence with two nucleotide mismatches as previously identified in other genomic RNA segments. Northern blot analysis as well as RT-PCR using specific primers showed the presence of the novel genomic RNA segments in infected plants, but absent in the non-infected plants. The GenBank Acc. Nos. for the sequences reported in this paper are KT007556 and KT007557. PMID:27265465

  8. A simplified strategy for sensitive detection of Rose rosette virus compatible with three RT-PCR chemistries.

    PubMed

    Dobhal, Shefali; Olson, Jennifer D; Arif, Mohammad; Garcia Suarez, Johnny A; Ochoa-Corona, Francisco M

    2016-06-01

    Rose rosette disease is a disorder associated with infection by Rose rosette virus (RRV), a pathogen of roses that causes devastating effects on most garden cultivated varieties, and the wild invasive rose especially Rosa multiflora. Reliable and sensitive detection of this disease in early phases is needed to implement proper control measures. This study assesses a single primer-set based detection method for RRV and demonstrates its application in three different chemistries: Endpoint RT-PCR, TaqMan-quantitative RT-PCR (RT-qPCR) and SYBR Green RT-qPCR with High Resolution Melting analyses. A primer set (RRV2F/2R) was designed from consensus sequences of the nucleocapsid protein gene p3 located in the RNA 3 region of RRV. The specificity of primer set RRV2F/2R was validated in silico against published GenBank sequences and in-vitro against infected plant samples and an exclusivity panel of near-neighbor and other viruses that commonly infect Rosa spp. The developed assay is sensitive with a detection limit of 1fg from infected plant tissue. Thirty rose samples from 8 different states of the United States were tested using the developed methods. The developed methods are sensitive and reliable, and can be used by diagnostic laboratories for routine testing and disease management decisions. PMID:26850142

  9. Note: Helical nanobelt force sensors

    SciTech Connect

    Hwang, G.; Hashimoto, H.

    2012-12-15

    We present the fabrication and characterization of helical nanobelt force sensors. These self-sensing force sensors are based on the giant piezoresistivity of helical nanobelts. The three-dimensional helical nanobelts are self-formed from 27 nm-thick n-type InGaAs/GaAs bilayers using rolled-up techniques, and assembled onto electrodes on a micropipette using nanorobotic manipulations. The helical nanobelt force sensors can be calibrated using a calibrated atomic force microscope cantilever system under scanning electron microscope. Thanks to their giant piezoresistance coefficient (515 Multiplication-Sign 10{sup -10} Pa{sup -1}), low stiffness (0.03125 N/m), large-displacement capability ({approx}10 {mu}m), and good fatigue resistance, they are well suited to function as stand-alone, compact ({approx}20 {mu}m without the plug-in support), light ({approx}5 g including the plug-in support), versatile and large range ({approx}{mu}N) and high resolution ({approx}nN) force sensors.

  10. Helicity Generation by Heat Pulses

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    1996-11-01

    In a large laboratory plasma (ne ~= 10^12 cm-3, k Te ~= 2 eV, B0 ~= 30 G, 1 m ⊥ B_0, 2.5 m allel B_0), the electrons are heated locally by a short intense current pulse (100 A, 0.2 μs) using a magnetic loop antenna or a biased electrode. The heat transport along the field establishes a flux tube with strong radial and weak axial temperature gradients. The time scale of temperature relaxation (Δ t ~= 50 μs) is much longer than that of the transient whistler wave pulse excited by the initial current pulse (Δ t < 2 μs). The temperature gradients drive linked field-aligned and diamagnetic currents which, due to their linkage, exhibit helicity and form a flux rope with J × B ~= 0.(R. L. Stenzel and J. M. Urrutia, Phys. Rev. Lett. 76), 1469 (1996). Alternatively, the helicity generation can be understood by the twisting of magnetic field lines which, in the parameter regime of electron MHD, are frozen into the electron fluid. The electron heating at one end of the flux tube causes a nonuniform diamagnetic rotation, hence the helicity. The heat transport by helical convection and conduction is investigated. The slowly time-varying magnetic field may excite Alfvénic perturbations.

  11. Note: Helical nanobelt force sensors

    NASA Astrophysics Data System (ADS)

    Hwang, G.; Hashimoto, H.

    2012-12-01

    We present the fabrication and characterization of helical nanobelt force sensors. These self-sensing force sensors are based on the giant piezoresistivity of helical nanobelts. The three-dimensional helical nanobelts are self-formed from 27 nm-thick n-type InGaAs/GaAs bilayers using rolled-up techniques, and assembled onto electrodes on a micropipette using nanorobotic manipulations. The helical nanobelt force sensors can be calibrated using a calibrated atomic force microscope cantilever system under scanning electron microscope. Thanks to their giant piezoresistance coefficient (515 × 10-10 Pa-1), low stiffness (0.03125 N/m), large-displacement capability (˜10 μm), and good fatigue resistance, they are well suited to function as stand-alone, compact (˜20 μm without the plug-in support), light (˜5 g including the plug-in support), versatile and large range (˜μN) and high resolution (˜nN) force sensors.

  12. Note: helical nanobelt force sensors.

    PubMed

    Hwang, G; Hashimoto, H

    2012-12-01

    We present the fabrication and characterization of helical nanobelt force sensors. These self-sensing force sensors are based on the giant piezoresistivity of helical nanobelts. The three-dimensional helical nanobelts are self-formed from 27 nm-thick n-type InGaAs/GaAs bilayers using rolled-up techniques, and assembled onto electrodes on a micropipette using nanorobotic manipulations. The helical nanobelt force sensors can be calibrated using a calibrated atomic force microscope cantilever system under scanning electron microscope. Thanks to their giant piezoresistance coefficient (515 × 10(-10) Pa(-1)), low stiffness (0.03125 N/m), large-displacement capability (~10 μm), and good fatigue resistance, they are well suited to function as stand-alone, compact (~20 μm without the plug-in support), light (~5 g including the plug-in support), versatile and large range (~μN) and high resolution (~nN) force sensors. PMID:23278031

  13. Research trends in biomimetic medical materials for tissue engineering: commentary.

    PubMed

    Park, Ki Dong; Wang, Xiumei; Lee, Jae Young; Park, Kyung Min; Zhang, ShengMin; Noh, Insup

    2016-01-01

    We introduce our active experts' communications and reviews (Part II) of 2015 Korea-China Joint Symposium on Biomimetic Medical Materials in Republic of Korea, which reflect their perspectives on current research trends of biomimetic medical materials for tissue regeneration in both Korea and China. The communications covered three topics of biomimetics, i.e., 1) hydrogel for therapeutics and extracellular matrix environments, 2) design of electrical polymers for communications between electrical sources and biological systems and 3) design of biomaterials for nerve tissue engineering. The reviews in the Part II will cover biomimetics of 3D bioprinting materials, surface modifications, nano/micro-technology as well as clinical aspects of biomaterials for cartilage. PMID:27026826

  14. Biomimetics - using nature as an inspiring model for innovation

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    2006-01-01

    In this presentation, various aspects of the field of biomimetics will be reviewed, examples of inspiring biological models and practical applications will be described, and challenges and potential direction of the field will be discussed.

  15. Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier.

    PubMed

    Li, Jing; Xu, Lu; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming

    2015-10-01

    This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. PMID:26117767

  16. [Biomimetic nanosystems and novel composite nanobiomaterials].

    PubMed

    Khomutov, G B

    2011-01-01

    Biophysicochemical approaches to the solution of nanotechnology problems associated with the design of functional biomimetic nanosystems, hybrid and composite nanobiomaterials and study of their structure-function relationships. The results of studies concerned with physicochemical mechanisms of the formation of organized biomimetic nanostructures and bioinorganic nanomaterials in systems involving a bulky liquid phase and the interface (gas-liquid, solid-liquid, liquid-liquid) during the synthesis and structure formation with the participation of the components of colloid systems, inorganic nanoparticles of various composition and clusters of metals, surfactants, polyelectrolytes and their complexes are discussed. In the development of the methods for the formation of composite bioinorganic nanosystems containing inorganic nanocomponents, two major approaches were used: adsorption and incorporation into the biomolecular matrix or colloid system of presynthesized inorganic nanoparticles, as well as the synthesis of the inorganic nanophase immediately in the biomolecular system. The methods of obtaining biomaterials and nanosystems are based on the principles of biomimetics, biomineralization, self-assembly and self-organization, combination and integration of a number of synthetic and physicochemical methods (physical and chemical adsorption, Langmuir technique, the formation of polycomplexes, chemical linking, competitive interactions, and substitution of ligands in supramolecular and coordination complexes) and nanocomponents of different nature. In particular, a novel approach to the preparation of highly organized nanofilm materials was developed, which is based on the effect of self-assembly and self-organization of colloid nanoparticles during the formation of their complexes with polyfunctional biogenic ligands in the volume of the liquid phase in the absence of any surfaces and interfaces. The physical and chemical factors responsible for the formation of

  17. Progress of Biomimetic Artificial Nose and Tongue

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Liu, Qingjun

    2009-05-01

    As two of the basic senses of human beings, olfaction and gustation play a very important role in daily life. These two types of chemical sensors are important for recognizing environmental conditions. Electronic nose and electronic tongue, which mimics animals' olfaction and gustation to detect odors and chemical components, have been carried out due to their potential commercial applications for biomedicine, food industry and environmental protection. In this report, the biomimetic artificial nose and tongue is presented. Firstly, the smell and taste sensors mimicking the mammalian olfaction and gustation was described, and then, some mimetic design of electronic nose and tongue for odorants and tastants detection are developed. Finally, olfactory and gustatory biosensors are presented as the developing trends of this field.

  18. Biomimetic superelastic graphene-based cellular monoliths.

    PubMed

    Qiu, Ling; Liu, Jeffery Z; Chang, Shery L Y; Wu, Yanzhe; Li, Dan

    2012-01-01

    Many applications proposed for graphene require multiple sheets be assembled into a monolithic structure. The ability to maintain structural integrity upon large deformation is essential to ensure a macroscopic material which functions reliably. However, it has remained a great challenge to achieve high elasticity in three-dimensional graphene networks. Here we report that the marriage of graphene chemistry with ice physics can lead to the formation of ultralight and superelastic graphene-based cellular monoliths. Mimicking the hierarchical structure of natural cork, the resulting materials can sustain their structural integrity under a load of >50,000 times their own weight and can rapidly recover from >80% compression. The unique biomimetic hierarchical structure also provides this new class of elastomers with exceptionally high energy absorption capability and good electrical conductivity. The successful synthesis of such fascinating materials paves the way to explore the application of graphene in a self-supporting, structurally adaptive and 3D macroscopic form. PMID:23212370

  19. Conducting IPN actuators for biomimetic vision system

    NASA Astrophysics Data System (ADS)

    Festin, Nicolas; Plesse, Cedric; Chevrot, Claude; Teyssié, Dominique; Pirim, Patrick; Vidal, Frederic

    2011-04-01

    In recent years, many studies on electroactive polymer (EAP) actuators have been reported. One promising technology is the elaboration of electronic conducting polymers based actuators with Interpenetrating Polymer Networks (IPNs) architecture. Their many advantageous properties as low working voltage, light weight and high lifetime (several million cycles) make them very attractive for various applications including robotics. Our laboratory recently synthesized new conducting IPN actuators based on high molecular Nitrile Butadiene Rubber, poly(ethylene oxide) derivative and poly(3,4-ethylenedioxithiophene). The presence of the elastomer greatly improves the actuator performances such as mechanical resistance and output force. In this article we present the IPN and actuator synthesis, characterizations and design allowing their integration in a biomimetic vision system.

  20. Biomimetic gyroid nanostructures exceeding their natural origins

    PubMed Central

    Gan, Zongsong; Turner, Mark D.; Gu, Min

    2016-01-01

    Using optical two-beam lithography with improved resolution and enhanced mechanical strength, we demonstrate the replication of gyroid photonic nanostructures found in the butterfly Callophrys rubi. These artificial structures are shown to have size, controllability, and uniformity that are superior to those of their biological counterparts. In particular, the elastic Young’s modulus of fabricated nanowires is enhanced by up to 20%. As such, the circular dichroism enabled by the gyroid nanostructures can operate in the near-ultraviolet wavelength region, shorter than that supported by the natural butterfly wings of C. rubi. This fabrication technique provides a unique tool for extracting three-dimensional photonic designs from nature and will aid the investigation of biomimetic nanostructures. PMID:27386542

  1. Biomimetic superhydrophobic and highly oleophobic cotton textiles.

    PubMed

    Hoefnagels, H F; Wu, D; de With, G; Ming, W

    2007-12-18

    We report a biomimetic procedure to prepare superhydrophobic cotton textiles. By in situ introducing silica particles to cotton fibers to generate a dual-size surface roughness, followed by hydrophobization with polydimethylsiloxane (PDMS), normally hydrophilic cotton has been easily turned superhydrophobic, which exhibits a static water contact angle of 155 degrees for a 10 microL droplet. The roll-off angle of water droplets depends on the droplet volume, ranging from 7 degrees for a droplet of 50 microL to 20 degrees for a 7 microL droplet. When a perfluoroalkyl chain is introduced to the silica particle surface, the superhydrophobic textile also becomes highly oleophobic, as demonstrated by a static contact angle of 140 degrees and a roll-off angle of 24 degrees for a 15 microL sunflower oil droplet. PMID:17985939

  2. Biomimetic silicification of demineralized hierarchical collagenous tissues

    PubMed Central

    Ryou, Heonjune; Diogenes, Anibal; Yiu, Cynthia K.Y.; Mazzoni, Annalisa; Chen, Ji-hua; Arola, Dwayne D.; Hargreaves, Kenneth M.; Pashley, David H.; Tay, Franklin R.

    2013-01-01

    Unlike man-made composite materials, natural biominerals containing composites usually demonstrate different levels of sophisticated hierarchical structures which are responsible for their mechanical properties and other metabolic functions. However, the complex spatial organizations of the organic-inorganic phases are far beyond what they be achieved by contemporary engineering techniques. Here, we demonstrate that carbonated apatite present in collagen matrices derived from fish scale and bovine bone may be replaced by amorphous silica, using an approach that simulates what is utilized by phylogenetically ancient glass sponges. The structural hierarchy of these collagen-based biomaterials is replicated by the infiltration and condensation of fluidic polymer-stabilized silicic acid precursors within the intrafibrillar milieu of type I collagen fibrils. This facile biomimetic silicification strategy may be used for fabricating silica-based, three-dimensional functional materials with specific morphological and hierarchical requirements. PMID:23586938

  3. Clues for biomimetics from natural composite materials

    PubMed Central

    Lapidot, Shaul; Meirovitch, Sigal; Sharon, Sigal; Heyman, Arnon; Kaplan, David L; Shoseyov, Oded

    2013-01-01

    Bio-inspired material systems are derived from different living organisms such as plants, arthropods, mammals and marine organisms. These biomaterial systems from nature are always present in the form of composites, with molecular-scale interactions optimized to direct functional features. With interest in replacing synthetic materials with natural materials due to biocompatibility, sustainability and green chemistry issues, it is important to understand the molecular structure and chemistry of the raw component materials to also learn from their natural engineering, interfaces and interactions leading to durable and highly functional material architectures. This review will focus on applications of biomaterials in single material forms, as well as biomimetic composites inspired by natural organizational features. Examples of different natural composite systems will be described, followed by implementation of the principles underlying their composite organization into artificial bio-inspired systems for materials with new functional features for future medicine. PMID:22994958

  4. Biomimetic Hybrid Nanocontainers with Selective Permeability.

    PubMed

    Messager, Lea; Burns, Jonathan R; Kim, Jungyeon; Cecchin, Denis; Hindley, James; Pyne, Alice L B; Gaitzsch, Jens; Battaglia, Giuseppe; Howorka, Stefan

    2016-09-01

    Chemistry plays a crucial role in creating synthetic analogues of biomacromolecular structures. Of particular scientific and technological interest are biomimetic vesicles that are inspired by natural membrane compartments and organelles but avoid their drawbacks, such as membrane instability and limited control over cargo transport across the boundaries. In this study, completely synthetic vesicles were developed from stable polymeric walls and easy-to-engineer membrane DNA nanopores. The hybrid nanocontainers feature selective permeability and permit the transport of organic molecules of 1.5 nm size. Larger enzymes (ca. 5 nm) can be encapsulated and retained within the vesicles yet remain catalytically active. The hybrid structures constitute a new type of enzymatic nanoreactor. The high tunability of the polymeric vesicles and DNA pores will be key in tailoring the nanocontainers for applications in drug delivery, bioimaging, biocatalysis, and cell mimicry. PMID:27560310

  5. Biomimetic biphasic scaffolds for osteochondral defect repair

    PubMed Central

    Li, Xuezhou; Ding, Jianxun; Wang, Jincheng; Zhuang, Xiuli; Chen, Xuesi

    2015-01-01

    The osteochondral defects caused by vigorous trauma or physical disease are difficult to be managed. Tissue engineering provides a possible option to regenerate the damaged osteochondral tissues. For osteochondral reconstruction, one intact scaffold should be considered to support the regeneration of both cartilage and subchondral bone. Therefore, the biphasic scaffolds with the mimic structures of osteochondral tissues have been developed to close this chasm. A variety of biomimetic bilayer scaffolds fabricated from natural or synthetic polymers, or the ones loading with growth factors, cells, or both of them make great progresses in osteochondral defect repair. In this review, the preparation and in vitro and/or in vivo verification of bioinspired biphasic scaffolds are summarized and discussed, as well as the prospect is predicted. PMID:26816644

  6. Clues for biomimetics from natural composite materials.

    PubMed

    Lapidot, Shaul; Meirovitch, Sigal; Sharon, Sigal; Heyman, Arnon; Kaplan, David L; Shoseyov, Oded

    2012-09-01

    Bio-inspired material systems are derived from different living organisms such as plants, arthropods, mammals and marine organisms. These biomaterial systems from nature are always present in the form of composites, with molecular-scale interactions optimized to direct functional features. With interest in replacing synthetic materials with natural materials due to biocompatibility, sustainability and green chemistry issues, it is important to understand the molecular structure and chemistry of the raw component materials to also learn from their natural engineering, interfaces and interactions leading to durable and highly functional material architectures. This review will focus on applications of biomaterials in single material forms, as well as biomimetic composites inspired by natural organizational features. Examples of different natural composite systems will be described, followed by implementation of the principles underlying their composite organization into artificial bio-inspired systems for materials with new functional features for future medicine. PMID:22994958

  7. Swimming like algae: biomimetic soft artificial cilia.

    PubMed

    Sareh, Sina; Rossiter, Jonathan; Conn, Andrew; Drescher, Knut; Goldstein, Raymond

    2013-01-01

    Cilia are used effectively in a wide variety of biological systems from fluid transport to thrust generation. Here, we present the design and implementation of artificial cilia, based on a biomimetic planar actuator using soft-smart materials. This actuator is modelled on the cilia movement of the alga Volvox, and represents the cilium as a piecewise constant-curvature robotic actuator that enables the subsequent direct translation of natural articulation into a multi-segment ionic polymer metal composite actuator. It is demonstrated how the combination of optimal segmentation pattern and biologically derived per-segment driving signals reproduce natural ciliary motion. The amenability of the artificial cilia to scaling is also demonstrated through the comparison of the Reynolds number achieved with that of natural cilia. PMID:23097503

  8. Swimming like algae: biomimetic soft artificial cilia

    PubMed Central

    Sareh, Sina; Rossiter, Jonathan; Conn, Andrew; Drescher, Knut; Goldstein, Raymond E.

    2013-01-01

    Cilia are used effectively in a wide variety of biological systems from fluid transport to thrust generation. Here, we present the design and implementation of artificial cilia, based on a biomimetic planar actuator using soft-smart materials. This actuator is modelled on the cilia movement of the alga Volvox, and represents the cilium as a piecewise constant-curvature robotic actuator that enables the subsequent direct translation of natural articulation into a multi-segment ionic polymer metal composite actuator. It is demonstrated how the combination of optimal segmentation pattern and biologically derived per-segment driving signals reproduce natural ciliary motion. The amenability of the artificial cilia to scaling is also demonstrated through the comparison of the Reynolds number achieved with that of natural cilia. PMID:23097503

  9. Biomimetic gyroid nanostructures exceeding their natural origins.

    PubMed

    Gan, Zongsong; Turner, Mark D; Gu, Min

    2016-05-01

    Using optical two-beam lithography with improved resolution and enhanced mechanical strength, we demonstrate the replication of gyroid photonic nanostructures found in the butterfly Callophrys rubi. These artificial structures are shown to have size, controllability, and uniformity that are superior to those of their biological counterparts. In particular, the elastic Young's modulus of fabricated nanowires is enhanced by up to 20%. As such, the circular dichroism enabled by the gyroid nanostructures can operate in the near-ultraviolet wavelength region, shorter than that supported by the natural butterfly wings of C. rubi. This fabrication technique provides a unique tool for extracting three-dimensional photonic designs from nature and will aid the investigation of biomimetic nanostructures. PMID:27386542

  10. Osteoblast response to biomimetically altered titanium surfaces.

    PubMed

    Nebe, J Barbara; Müller, Lenka; Lüthen, Frank; Ewald, Andrea; Bergemann, Claudia; Conforto, Egle; Müller, Frank A

    2008-11-01

    Bioinert titanium (Ti) materials are generally encapsulated by fibrous tissue after implantation into the living body. To improve the bone-bonding ability of Ti implants, we activated commercially pure titanium (cpTi) by a simple chemical pre-treatment in HCl and NaOH. Subsequently, we exposed the treated samples to simulated body fluid (SBF) for 2 (TiCT) and 14 days (TiHCA), respectively, to mimic the early stages of bone bonding and to investigate the in vitro response of osteoblasts on thus altered biomimetic surfaces. Sample surfaces were characterized by scanning electron microscopy, energy-dispersive X-ray analysis, cross-sectional transmission electron microscopy analyses, Fourier transform infrared and Raman spectroscopy. It was shown that the efflorescence consisting of sodium titanate that is present on pre-treated cpTi surfaces transformed to calcium titanate after 2 days in SBF. After 14 days in SBF a homogeneous biomimetic apatite layer precipitated. Human osteoblasts (MG-63) revealed a well spread morphology on both functionalized Ti surfaces. On TiCT, the gene expression of the differentiation proteins alkaline phosphatase (ALP) and bone sialo protein was increased after 2 days. On both TiCT and TiHCA, the collagen I and ALP expression on the protein level was enhanced at 7 and 14 days. The TiCT and the TiHCA surfaces reveal the tendency to increase the differentiated cell function of MG-63 osteoblasts. Thus, chemical pre-treatment of titanium seems to be a promising method to generate osteoconductive surfaces. PMID:18595788

  11. Biomimetic oral mucin from polymer micelle networks

    NASA Astrophysics Data System (ADS)

    Authimoolam, Sundar Prasanth

    Mucin networks are formed by the complexation of bottlebrush-like mucin glycoprotein with other small molecule glycoproteins. These glycoproteins create nanoscale strands that then arrange into a nanoporous mesh. These networks play an important role in ensuring surface hydration, lubricity and barrier protection. In order to understand the functional behavior in mucin networks, it is important to decouple their chemical and physical effects responsible for generating the fundamental property-function relationship. To achieve this goal, we propose to develop a synthetic biomimetic mucin using a layer-by-layer (LBL) deposition approach. In this work, a hierarchical 3-dimensional structures resembling natural mucin networks was generated using affinity-based interactions on synthetic and biological surfaces. Unlike conventional polyelectrolyte-based LBL methods, pre-assembled biotin-functionalized filamentous (worm-like) micelles was utilized as the network building block, which from complementary additions of streptavidin generated synthetic networks of desired thickness. The biomimetic nature in those synthetic networks are studied by evaluating its structural and bio-functional properties. Structurally, synthetic networks formed a nanoporous mesh. The networks demonstrated excellent surface hydration property and were able capable of microbial capture. Those functional properties are akin to that of natural mucin networks. Further, the role of synthetic mucin as a drug delivery vehicle, capable of providing localized and tunable release was demonstrated. By incorporating antibacterial curcumin drug loading within synthetic networks, bacterial growth inhibition was also demonstrated. Thus, such bioactive interfaces can serve as a model for independently characterizing mucin network properties and through its role as a drug carrier vehicle it presents exciting future opportunities for localized drug delivery, in regenerative applications and as bio

  12. Predictive supracolloidal helices from patchy particles

    NASA Astrophysics Data System (ADS)

    Guo, Ruohai; Mao, Jian; Xie, Xu-Ming; Yan, Li-Tang

    2014-11-01

    A priori prediction of supracolloidal architectures from nanoparticle and colloidal assembly is a challenging goal in materials chemistry and physics. Despite intense research in this area, much less has been known about the predictive science of supracolloidal helices from designed building blocks. Therefore, developing conceptually new rules to construct supracolloidal architectures with predictive helicity is becoming an important and urgent task of great scientific interest. Here, inspired by biological helices, we show that the rational design of patchy arrangement and interaction can drive patchy particles to self-assemble into biomolecular mimetic supracolloidal helices. We further derive a facile design rule for encoding the target supracolloidal helices, thus opening the doors to the predictive science of these supracolloidal architectures. It is also found that kinetics and reaction pathway during the formation of supracolloidal helices offer a unique way to study supramolecular polymerization, and that well-controlled supracolloidal helices can exhibit tailorable circular dichroism effects at visible wavelengths.

  13. Predictive supracolloidal helices from patchy particles

    PubMed Central

    Guo, Ruohai; Mao, Jian; Xie, Xu-Ming; Yan, Li-Tang

    2014-01-01

    A priori prediction of supracolloidal architectures from nanoparticle and colloidal assembly is a challenging goal in materials chemistry and physics. Despite intense research in this area, much less has been known about the predictive science of supracolloidal helices from designed building blocks. Therefore, developing conceptually new rules to construct supracolloidal architectures with predictive helicity is becoming an important and urgent task of great scientific interest. Here, inspired by biological helices, we show that the rational design of patchy arrangement and interaction can drive patchy particles to self-assemble into biomolecular mimetic supracolloidal helices. We further derive a facile design rule for encoding the target supracolloidal helices, thus opening the doors to the predictive science of these supracolloidal architectures. It is also found that kinetics and reaction pathway during the formation of supracolloidal helices offer a unique way to study supramolecular polymerization, and that well-controlled supracolloidal helices can exhibit tailorable circular dichroism effects at visible wavelengths. PMID:25387544

  14. An experimental superconducting helical undulator

    SciTech Connect

    Caspi, S.; Taylor, C.

    1995-12-31

    Improvements in the technology of superconducting magnets for high energy physics and recent advancements in SC materials with the artificial pinning centers (APC){sup 2}, have made a bifilar helical SC device an attractive candidate for a single-pass free electron laser (FEL){sup 3}. Initial studies have suggested that a 6.5 mm inner diameter helical device, with a 27 mm period, can generate a central field of 2-2.5 Tesla. Additional studies have also suggested that with a stored energy of 300 J/m, such a device can be made self-protecting in the event of a quench. However, since the most critical area associated with high current density SC magnets is connected with quenching and training, a short experimental device will have to be built and tested. In this paper we discuss technical issues relevant to the construction of such a device, including a conceptual design, fields, and forces.

  15. Helical screw expander evaluation project

    NASA Technical Reports Server (NTRS)

    Mckay, R.

    1982-01-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  16. Lamb Wave Helical Ultrasonic Tomography

    NASA Astrophysics Data System (ADS)

    Leonard, K. R.; Hinders, M. K.

    2004-02-01

    Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT). This new technique, among other things, has direct application to advanced pipe inspection. HUT uses guided ultrasonic waves along with an adaptation of the tomographic reconstruction algorithms developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel in various helical crisscross paths between two parallel circumferential transducer arrays instead of the planar crisscross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. We demonstrate the feasibility of the HUT technique via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.

  17. Helical screw expander evaluation project

    NASA Astrophysics Data System (ADS)

    McKay, R.

    1982-03-01

    A one MW helical rotary screw expander power system for electric power generation from geothermal brine was evaluated. The technology explored in the testing is simple, potentially very efficient, and ideally suited to wellhead installations in moderate to high enthalpy, liquid dominated field. A functional one MW geothermal electric power plant that featured a helical screw expander was produced and then tested with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing, operation on two-phase geothermal fluids. The Project also produced a computer equipped data system, an instrumentation and control van, and a 1000 kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  18. Emulsification-Induced Homohelicity in Racemic Helical Polymer for Preparing Optically Active Helical Polymer Nanoparticles.

    PubMed

    Zhao, Biao; Deng, Jinrui; Deng, Jianping

    2016-04-01

    Optically active nano- and microparticles have constituted a significant category of advanced functional materials. However, constructing optically active particles derived from synthetic helical polymers still remains as a big challenge. In the present study, it is attempted to induce a racemic helical polymer (containing right- and left-handed helices in equal amount) to prefer one predominant helicity in aqueous media by using emulsifier in the presence of chiral additive (emulsification process). Excitingly, the emulsification process promotes the racemic helical polymer to unify the helicity and directly provides optically active nanoparticles constructed by chirally helical polymer. A possible mechanism is proposed to explain the emulsification-induced homohelicity effect. The present study establishes a novel strategy for preparing chirally helical polymer-derived optically active nanoparticles based on racemic helical polymers. PMID:26829250

  19. Topology of modified helical gears

    NASA Technical Reports Server (NTRS)

    Litvin, F. L.; Zhang, J.; Handschuh, R. F.; Coy, J. J.

    1989-01-01

    The topology of several types of modified surfaces of helical gears is proposed. The modified surfaces allow absorption of a linear or almost linear function of transmission errors. These errors are caused by gear misalignment and an improvement of the contact of gear tooth surfaces. Principles and corresponding programs for computer aided simulation of meshing and contact of gears have been developed. The results of this investigation are illustrated with numerical examples.

  20. Helical Antimicrobial Sulfono- {gamma} -AApeptides

    SciTech Connect

    Li, Yaqiong; Wu, Haifan; Teng, Peng; Bai, Ge; Lin, Xiaoyang; Zuo, Xiaobing; Cao, Chuanhai; Cai, Jianfeng

    2015-06-11

    Host-defense peptides (HDPs) such as magainin 2 have emerged as potential therapeutic agents combating antibiotic resistance. Inspired by their structures and mechanism of action, herein we report the fi rst example of antimicrobial helical sulfono- γ - AApeptide foldamers. The lead molecule displays broad-spectrum and potent antimicrobial activity against multi-drug-resistant Gram- positive and Gram-negative bacterial pathogens. Time-kill studies and fl uorescence microscopy suggest that sulfono- γ -AApeptides eradicate bacteria by taking a mode of action analogous to that of HDPs. Clear structure - function relationships exist in the studied sequences. Longer sequences, presumably adopting more-de fi ned helical structures, are more potent than shorter ones. Interestingly, the sequence with less helical propensity in solution could be more selective than the stronger helix-forming sequences. Moreover, this class of antimicrobial agents are resistant to proteolytic degradation. These results may lead to the development of a new class of antimicrobial foldamers combating emerging antibiotic-resistant pathogens.

  1. Isolation and identification of an anti-bolting compound, hexadecatrienoic acid monoglyceride, responsible for inhibition of bolting and maintenance of the leaf rosette in radish plants.

    PubMed

    Yoshida, Yuko; Takada, Noboru; Koda, Yasunori

    2010-08-01

    Generally, the bolting (stem elongation from rosette plants) of winter annuals is believed to be induced by an increase in the levels of gibberellin that occurs after a certain period of chilling (vernalization), and a deficiency of gibberellin allows the plant to maintain a rosette style. Lack of direct evidence proving the above assumption in radish plants (Raphanus sativus L.) encouraged us to assume the presence of an anti-bolting compound actively maintaining the rosette habit through inhibition of bolting. Anti-bolting activity was detected in an extract of rosette shoots of radish plants by an assay using seedlings cultured in vitro. The causal compound that strongly inhibited bolting was isolated and identified as alpha-(7Z,10Z,13Z)-hexadecatrienoic acid monoglyceride (16:3 monoglyceride). This compound did not inhibit leaf production at the apical meristem, indicating that it merely inhibits growth at the internode. The compound disappeared completely after vernalization, and bolting occurred thereafter. The results suggest that the release from inhibition by 16:3 monoglyceride induces the initiation of bolting. The possible mechanism by which the compound exerts the activity is discussed. PMID:20601431

  2. High Field Solid-State NMR Spectroscopy Investigation of (15)N-Labeled Rosette Nanotubes: Hydrogen Bond Network and Channel-Bound Water.

    PubMed

    Fenniri, Hicham; Tikhomirov, Grigory A; Brouwer, Darren H; Bouatra, Souhaila; El Bakkari, Mounir; Yan, Zhimin; Cho, Jae-Young; Yamazaki, Takeshi

    2016-05-18

    (15)N-labeled rosette nanotubes were synthesized and investigated using high-field solid-state NMR spectroscopy, X-ray diffraction, atomic force microscopy, and electron microscopy. The results established the H-bond network involved in the self-assembly of the nanostructure as well as bound water molecules in the nanotube's channel. PMID:27141817

  3. Simulated binding of transcription factors to active and inactive regions folds human chromosomes into loops, rosettes and topological domains

    PubMed Central

    Brackley, Chris A.; Johnson, James; Kelly, Steven; Cook, Peter R.; Marenduzzo, Davide

    2016-01-01

    Biophysicists are modeling conformations of interphase chromosomes, often basing the strengths of interactions between segments distant on the genetic map on contact frequencies determined experimentally. Here, instead, we develop a fitting-free, minimal model: bivalent or multivalent red and green ‘transcription factors’ bind to cognate sites in strings of beads (‘chromatin’) to form molecular bridges stabilizing loops. In the absence of additional explicit forces, molecular dynamic simulations reveal that bound factors spontaneously cluster—red with red, green with green, but rarely red with green—to give structures reminiscent of transcription factories. Binding of just two transcription factors (or proteins) to active and inactive regions of human chromosomes yields rosettes, topological domains and contact maps much like those seen experimentally. This emergent ‘bridging-induced attraction’ proves to be a robust, simple and generic force able to organize interphase chromosomes at all scales. PMID:27060145

  4. Simulated binding of transcription factors to active and inactive regions folds human chromosomes into loops, rosettes and topological domains.

    PubMed

    Brackley, Chris A; Johnson, James; Kelly, Steven; Cook, Peter R; Marenduzzo, Davide

    2016-05-01

    Biophysicists are modeling conformations of interphase chromosomes, often basing the strengths of interactions between segments distant on the genetic map on contact frequencies determined experimentally. Here, instead, we develop a fitting-free, minimal model: bivalent or multivalent red and green 'transcription factors' bind to cognate sites in strings of beads ('chromatin') to form molecular bridges stabilizing loops. In the absence of additional explicit forces, molecular dynamic simulations reveal that bound factors spontaneously cluster-red with red, green with green, but rarely red with green-to give structures reminiscent of transcription factories. Binding of just two transcription factors (or proteins) to active and inactive regions of human chromosomes yields rosettes, topological domains and contact maps much like those seen experimentally. This emergent 'bridging-induced attraction' proves to be a robust, simple and generic force able to organize interphase chromosomes at all scales. PMID:27060145

  5. Development of Nested PCR-Based Specific Markers for Detection of Peach Rosette Mosaic Virus in Plant Quarantine.

    PubMed

    Lee, S; Kim, C S; Shin, Y G; Kim, J H; Kim, Y S; Jheong, W H

    2016-03-01

    The Peach rosette mosaic virus (PRMV) is a plant pathogen of the genus Nepovirus, and has been designated as a controlled quarantine virus in Korea. In this study, a specific reverse transcription (RT)-PCR marker set, nested PCR marker set, and modified-plasmid positive control were developed to promptly and accurately diagnose PRMV at plant-quarantine sites. The final selected PRMV-specific RT-PCR marker was PRMV-N10/C70 (967 bp), and the nested PCR product of 419 bp was finally amplified. The modified-plasmid positive control, in which the SalI restriction-enzyme region (GTCGAC) was inserted, verified PRMV contamination in a comparison with the control, enabling a more accurate diagnosis. It is expected that the developed method will continuously contribute to the plant-quarantine process in Korea. PMID:26843704

  6. The morphology transformation from helical nanofiber to helical nanotube in a diarylethene self-assembly system.

    PubMed

    Duan, Yulong; Yan, Shihai; Zhou, Xinhong; Xu, Wei; Xu, Hongxia; Liu, Zhihong; Zhang, Lixue; Zhang, Chuanjian; Cui, Guanglei; Yao, Lishan

    2014-08-01

    A helical nanostructure can be obtained by self-assembly of a diarylethene derivative that bears two malononitrile substitutes in a tetrahydrofuran/water medium. It is revealed that the helical nanostructure changed from helical nanofiber to helical nanotube when the diarylethene monomer changed from the open-ring isomer to the closed-ring isomer upon irradiation with 365 nm ultraviolet light, meanwhile, the helix angle of the nanostructure changed from 50° ± 5° to 75° ± 5°. There is a great possibility that the helical nanofibers and helical nanotubes are assembled from dimers as base units based on theoretical calculation and experimental results. PMID:24940732

  7. Tubular inverse opal scaffolds for biomimetic vessels

    NASA Astrophysics Data System (ADS)

    Zhao, Ze; Wang, Jie; Lu, Jie; Yu, Yunru; Fu, Fanfan; Wang, Huan; Liu, Yuxiao; Zhao, Yuanjin; Gu, Zhongze

    2016-07-01

    There is a clinical need for tissue-engineered blood vessels that can be used to replace or bypass damaged arteries. The success of such grafts depends strongly on their ability to mimic native arteries; however, currently available artificial vessels are restricted by their complex processing, controversial integrity, or uncontrollable cell location and orientation. Here, we present new tubular scaffolds with specific surface microstructures for structural vessel mimicry. The tubular scaffolds are fabricated by rotationally expanding three-dimensional tubular inverse opals that are replicated from colloidal crystal templates in capillaries. Because of the ordered porous structure of the inverse opals, the expanded tubular scaffolds are imparted with circumferentially oriented elliptical pattern microstructures on their surfaces. It is demonstrated that these tailored tubular scaffolds can effectively make endothelial cells to form an integrated hollow tubular structure on their inner surface and induce smooth muscle cells to form a circumferential orientation on their outer surface. These features of our tubular scaffolds make them highly promising for the construction of biomimetic blood vessels.There is a clinical need for tissue-engineered blood vessels that can be used to replace or bypass damaged arteries. The success of such grafts depends strongly on their ability to mimic native arteries; however, currently available artificial vessels are restricted by their complex processing, controversial integrity, or uncontrollable cell location and orientation. Here, we present new tubular scaffolds with specific surface microstructures for structural vessel mimicry. The tubular scaffolds are fabricated by rotationally expanding three-dimensional tubular inverse opals that are replicated from colloidal crystal templates in capillaries. Because of the ordered porous structure of the inverse opals, the expanded tubular scaffolds are imparted with circumferentially

  8. Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes

    PubMed Central

    2016-01-01

    The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the “ene” reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. “Better-than-Nature” biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost. PMID:26727612

  9. A Review Paper on Biomimetic Calcium Phosphate Coatings

    PubMed Central

    Lin, X.; de Groot, K.; Wang, D.; Hu, Q.; Wismeijer, D.; Liu, Y.

    2015-01-01

    Biomimetic calcium phosphate coatings have been developed for bone regeneration and repair because of their biocompatibility, osteoconductivity, and easy preparation. They can be rendered osteoinductive by incorporating an osteogenic agent, such as bone morphogenetic protein 2 (BMP-2), into the crystalline lattice work in physiological situations. The biomimetic calcium phosphate coating enables a controlled, slow and local release of BMP-2 when it undergoes cell mediated coating degradation induced by multinuclear cells, such as osteoclasts and foreign body giant cells, which mimics a physiologically similar release mode, to achieve sustained ectopic or orthotopic bone formation. Therefore, biomimetic calcium phosphate coatings are considered to be a promising delivery vehicle for osteogenic agents. In this review, we present an overview of biomimetic calcium phosphate coatings including their preparation techniques, physico-chemical properties, potential as drug carrier, and their pre-clinical application both in ectopic and orthotopic animal models. We briefly review some features of hydroxyapatite coatings and their clinical applications to gain insight into the clinical applications of biomimetic calcium phosphate coatings in the near future. PMID:25893016

  10. Sustainability assessment of a lightweight biomimetic ceiling structure.

    PubMed

    Antony, Florian; Grießhammer, Rainer; Speck, Thomas; Speck, Olga

    2014-03-01

    An intensive and continuous debate centres on the question of whether biomimetics has a specific potential to contribute to sustainability. In the context of a case study, the objective of this paper is to contribute to this debate by presenting the first systematic approach to assess the sustainability of a complex biomimetic product. The object of inquiry is a lecture hall's ribbed slab. Based on criteria suggested by the Association of German Engineers (VDI), it has been verified that the slab has been correctly defined as biomimetic. Moreover, a systematic comparative product sustainability assessment has been carefully carried out. For purposes of comparison, estimated static calculations have been performed for conceivable current state-of-the-art lightweight ceiling structures. Alternative options are a hollow article slab and a pre-stressed flat slab. Besides a detailed benefit analysis and a discussion of social effects, their costs have also been compared. A particularly detailed life cycle assessment on the respective environmental impacts has also been performed. Results show that the biomimetic ribbed slab built in the 1960s is able to keep up with the current state-of-the-art lightweight solutions in terms of sustainability. These promising results encourage a systematic search for a broad range of sustainable biomimetic solutions. PMID:24503487

  11. Conventional vs Biomimetic Approaches to the Exploration of Mars

    NASA Astrophysics Data System (ADS)

    Ellery, A.

    It is not usual to refer to convention in planetary exploration missions by virtue of the innovation required for such projects. The term conventional refers to the methodologies, tools and approaches typically adopted in engineering that are applied to such missions. Presented is a "conventional" Mars rover mission in which the author was involved - ExoMars - into which is interspersed references to examples where biomimetic approaches may yield superior capabilities. Biomimetics is a relatively recently active area of research which seeks to examine how biological systems solve the problem of survival in the natural environment. Biological organisms are autonomous entities that must survive in a hostile world adapting both adaptivity and robustness. It is not then surprising that biomimetics is particularly useful when applied to robotic elements of a Mars exploration mission. I present a number of areas in which biomimetics may yield new solutions to the problem of Mars exploration - optic flow navigation, potential field navigation, genetically-evolved neuro-controllers, legged locomotion, electric motors implementing muscular behaviour, and a biomimetic drill based on the wood wasp ovipositor. Each of these techniques offers an alternative approach to conventional ones. However, the perceptive hurdles are likely to dwarf the technical hurdles in implementing many of these methods in the near future.

  12. BatSLAM: Simultaneous localization and mapping using biomimetic sonar.

    PubMed

    Steckel, Jan; Peremans, Herbert

    2013-01-01

    We propose to combine a biomimetic navigation model which solves a simultaneous localization and mapping task with a biomimetic sonar mounted on a mobile robot to address two related questions. First, can robotic sonar sensing lead to intelligent interactions with complex environments? Second, can we model sonar based spatial orientation and the construction of spatial maps by bats? To address these questions we adapt the mapping module of RatSLAM, a previously published navigation system based on computational models of the rodent hippocampus. We analyze the performance of the proposed robotic implementation operating in the real world. We conclude that the biomimetic navigation model operating on the information from the biomimetic sonar allows an autonomous agent to map unmodified (office) environments efficiently and consistently. Furthermore, these results also show that successful navigation does not require the readings of the biomimetic sonar to be interpreted in terms of individual objects/landmarks in the environment. We argue that the system has applications in robotics as well as in the field of biology as a simple, first order, model for sonar based spatial orientation and map building. PMID:23365647

  13. BatSLAM: Simultaneous Localization and Mapping Using Biomimetic Sonar

    PubMed Central

    Steckel, Jan; Peremans, Herbert

    2013-01-01

    We propose to combine a biomimetic navigation model which solves a simultaneous localization and mapping task with a biomimetic sonar mounted on a mobile robot to address two related questions. First, can robotic sonar sensing lead to intelligent interactions with complex environments? Second, can we model sonar based spatial orientation and the construction of spatial maps by bats? To address these questions we adapt the mapping module of RatSLAM, a previously published navigation system based on computational models of the rodent hippocampus. We analyze the performance of the proposed robotic implementation operating in the real world. We conclude that the biomimetic navigation model operating on the information from the biomimetic sonar allows an autonomous agent to map unmodified (office) environments efficiently and consistently. Furthermore, these results also show that successful navigation does not require the readings of the biomimetic sonar to be interpreted in terms of individual objects/landmarks in the environment. We argue that the system has applications in robotics as well as in the field of biology as a simple, first order, model for sonar based spatial orientation and map building. PMID:23365647

  14. Helicity in dynamical processes in the atmosphere

    NASA Astrophysics Data System (ADS)

    Kurgansky, Michael; Maksimenkov, Leonid; Khapaev, Alexey; Chkhetiani, Otto

    2016-04-01

    In modern geophysical fluid dynamics and dynamic meteorology, a notable interest is observed to the notion of helicity ("kinetic helicity" to be distinguished from "magnetic helicity" widely used in magnetohydrodynamics, astrophysics and Solar physics), which is defined by the scalar product of 3D vectors of velocity and vorticity. In this contribution, we bring together different, both known in the literature and novel formulations of the helicity balance equation, by also taking into account the effects of air compressibility and Earth rotation. Equations and relationships are presented that are valid under different approximations customarily made in the dynamic meteorology, e.g. Boussinesq approximation, quasi-static approximation, quasi-geostrophic approximation. An emphasis is placed on the helicity budget analysis in large-scale atmospheric motions. An explicit expression is presented for the rate of helicity injection from the free atmosphere into a non-linear Ekman boundary layer. This injection is shown to be exactly balanced by the helicity viscous destruction within the boundary layer. It is conjectured that this helicity injection may characterize the intensity of atmospheric circulation in extratropical latitudes of both terrestrial hemispheres. Examples are provided based on re-analyses data. Vertical distribution of helicity and superhelicity in different Ekman boundary layers is also discussed.

  15. Building blocks for subleading helicity operators

    NASA Astrophysics Data System (ADS)

    Kolodrubetz, Daniel W.; Moult, Ian; Stewart, Iain W.

    2016-05-01

    On-shell helicity methods provide powerful tools for determining scattering amplitudes, which have a one-to-one correspondence with leading power helicity operators in the Soft-Collinear Effective Theory (SCET) away from singular regions of phase space. We show that helicity based operators are also useful for enumerating power suppressed SCET operators, which encode subleading amplitude information about singular limits. In particular, we present a complete set of scalar helicity building blocks that are valid for constructing operators at any order in the SCET power expansion. We also describe an interesting angular momentum selection rule that restricts how these building blocks can be assembled.

  16. Magnetic helicity in emerging solar active regions

    SciTech Connect

    Liu, Y.; Hoeksema, J. T.; Bobra, M.; Hayashi, K.; Sun, X.; Schuck, P. W.

    2014-04-10

    Using vector magnetic field data from the Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory, we study magnetic helicity injection into the corona in emerging active regions (ARs) and examine the hemispheric helicity rule. In every region studied, photospheric shearing motion contributes most of the helicity accumulated in the corona. In a sample of 28 emerging ARs, 17 follow the hemisphere rule (61% ± 18% at a 95% confidence interval). Magnetic helicity and twist in 25 ARs (89% ± 11%) have the same sign. The maximum magnetic twist, which depends on the size of an AR, is inferred in a sample of 23 emerging ARs with a bipolar magnetic field configuration.

  17. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, Allan; Boozer, Allen H.

    1987-01-01

    A helical axis stellarator using only noninterlocking planar, non-circular coils, generates magnetic fields having a magnetic well and large rotational transform with resultant large equilibrium beta.

  18. Helical tomotherapy superficial dose measurements

    SciTech Connect

    Ramsey, Chester R.; Seibert, Rebecca M.; Robison, Benjamin; Mitchell, Martha

    2007-08-15

    Helical tomotherapy is a treatment technique that is delivered from a 6 MV fan beam that traces a helical path while the couch moves linearly into the bore. In order to increase the treatment delivery dose rate, helical tomotherapy systems do not have a flattening filter. As such, the dose distributions near the surface of the patient may be considerably different from other forms of intensity-modulated delivery. The purpose of this study was to measure the dose distributions near the surface for helical tomotherapy plans with a varying separation between the target volume and the surface of an anthropomorphic phantom. A hypothetical planning target volume (PTV) was defined on an anthropomorphic head phantom to simulate a 2.0 Gy per fraction IMRT parotid-sparing head and neck treatment of the upper neck nodes. A total of six target volumes were created with 0, 1, 2, 3, 4, and 5 mm of separation between the surface of the phantom and the outer edge of the PTV. Superficial doses were measured for each of the treatment deliveries using film placed in the head phantom and thermoluminescent dosimeters (TLDs) placed on the phantom's surface underneath an immobilization mask. In the 0 mm test case where the PTV extends to the phantom surface, the mean TLD dose was 1.73{+-}0.10 Gy (or 86.6{+-}5.1% of the prescribed dose). The measured superficial dose decreases to 1.23{+-}0.10 Gy (61.5{+-}5.1% of the prescribed dose) for a PTV-surface separation of 5 mm. The doses measured by the TLDs indicated that the tomotherapy treatment planning system overestimates superficial doses by 8.9{+-}3.2%. The radiographic film dose for the 0 mm test case was 1.73{+-}0.07 Gy, as compared to the calculated dose of 1.78{+-}0.05 Gy. Given the results of the TLD and film measurements, the superficial calculated doses are overestimated between 3% and 13%. Without the use of bolus, tumor volumes that extend to the surface may be underdosed. As such, it is recommended that bolus be added for these

  19. Biomimetic synthesis of aragonite superstructures using hexamethylenetetramine

    SciTech Connect

    Chen Long; Huang Fangzhi; Li Shikuo; Shen Yuhua; Xie Anjian; Pan Jian; Zhang Yaping; Cai Yan

    2011-11-15

    In this paper, biomimetic synthesis of aragonite superstructures using a low molecular weight organic-hexamethylenetetramine (HMT) as an additive in the presence of CO{sub 2} supplied by an ammonium carbonate ((NH{sub 4}){sub 2}CO{sub 3}) diffusion method at room temperature was studied. The products were characterized by scanning or transmission electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray powder diffractometry, and selected area electron diffraction. The results showed the aragonite superstructures especially dumbbell-flower-like ones were obtained. The formation process of calcium carbonate (CaCO{sub 3}) in HMT aqueous solution was investigated, suggesting that the products transformed from calcite to vaterite primarily, and then changed into a mixture of aragonite and calcite with an increase of reaction time. The formation mechanism of CaCO{sub 3} in HMT solution was also discussed, revealing that aragonite might be controlled by HMT molecules and NH{sub 4}{sup +} ions together. - Graphical abstract: The well-defined aragonite hierarchical superstructures are formed using hexamethylenetetramine in aqueous solution. Highlights: > Aragonite superstructures are formed with hexamethylenetetramine at about 25 deg. C. > Dumbbell-flower-like aragonite produces when hexamethylenetetramine/Ca{sup 2+}=10:1. > CaCO{sub 3} formation in hexamethylenetetramine solution violates the Ostwald ripening. > Hexamethylenetetramine and NH{sub 4}{sup +} might control the growth of aragonite together.

  20. BIOMIMETIC GRADIENT HYDROGELS FOR TISSUE ENGINEERING

    PubMed Central

    Sant, Shilpa; Hancock, Matthew J.; Donnelly, Joseph P.; Iyer, Dharini; Khademhosseini, Ali

    2011-01-01

    During tissue morphogenesis and homeostasis, cells experience various signals in their environments, including gradients of physical and chemical cues. Spatial and temporal gradients regulate various cell behaviours such as proliferation, migration, and differentiation during development, inflammation, wound healing, and cancer. One of the goals of functional tissue engineering is to create microenvironments that mimic the cellular and tissue complexity found in vivo by incorporating physical, chemical, temporal, and spatial gradients within engineered three-dimensional (3D) scaffolds. Hydrogels are ideal materials for 3D tissue scaffolds that mimic the extracellular matrix (ECM). Various techniques from material science, microscale engineering, and microfluidics are used to synthesise biomimetic hydrogels with encapsulated cells and tailored microenvironments. In particular, a host of methods exist to incorporate micrometer to centimetre scale chemical and physical gradients within hydrogels to mimic the cellular cues found in vivo. In this review, we draw on specific biological examples to motivate hydrogel gradients as tools for studying cell–material interactions. We provide a brief overview of techniques to generate gradient hydrogels and showcase their use to study particular cell behaviours in two-dimensional (2D) and 3D environments. We conclude by summarizing the current and future trends in gradient hydrogels and cell–material interactions in context with the long-term goals of tissue engineering. PMID:21874065

  1. Tubular inverse opal scaffolds for biomimetic vessels.

    PubMed

    Zhao, Ze; Wang, Jie; Lu, Jie; Yu, Yunru; Fu, Fanfan; Wang, Huan; Liu, Yuxiao; Zhao, Yuanjin; Gu, Zhongze

    2016-07-14

    There is a clinical need for tissue-engineered blood vessels that can be used to replace or bypass damaged arteries. The success of such grafts depends strongly on their ability to mimic native arteries; however, currently available artificial vessels are restricted by their complex processing, controversial integrity, or uncontrollable cell location and orientation. Here, we present new tubular scaffolds with specific surface microstructures for structural vessel mimicry. The tubular scaffolds are fabricated by rotationally expanding three-dimensional tubular inverse opals that are replicated from colloidal crystal templates in capillaries. Because of the ordered porous structure of the inverse opals, the expanded tubular scaffolds are imparted with circumferentially oriented elliptical pattern microstructures on their surfaces. It is demonstrated that these tailored tubular scaffolds can effectively make endothelial cells to form an integrated hollow tubular structure on their inner surface and induce smooth muscle cells to form a circumferential orientation on their outer surface. These features of our tubular scaffolds make them highly promising for the construction of biomimetic blood vessels. PMID:27241065

  2. Biomimetic optical sensor for aerospace applications

    NASA Astrophysics Data System (ADS)

    Frost, Susan A.; Gorospe, George E.; Wright, Cameron H. G.; Barrett, Steven F.

    2015-05-01

    We report on a fiber optic sensor based on the physiological aspects of the eye and vision-related neural layers of the common housefly (Musca domestica) that has been developed and built for aerospace applications. The intent of the research is to reproduce select features from the fly's vision system that are desirable in image processing, including high functionality in low-light and low-contrast environments, sensitivity to motion, compact size, lightweight, and low power and computation requirements. The fly uses a combination of overlapping photoreceptor responses that are well approximated by Gaussian distributions and neural superposition to detect image features, such as object motion, to a much higher degree than just the photoreceptor density would imply. The Gaussian overlap in the biomimetic sensor comes from the front-end optical design, and the neural superposition is accomplished by subsequently combining the signals using analog electronics. The fly eye sensor is being developed to perform real-time tracking of a target on a flexible aircraft wing experiencing bending and torsion loads during flight. We report on results of laboratory experiments using the fly eye sensor to sense a target moving across its field of view.

  3. Biomimetic visual detection based on insect neurobiology

    NASA Astrophysics Data System (ADS)

    O'Carroll, David C.

    2001-11-01

    With a visual system that accounts for as much as 30% of the lifted mass, flying insects such as dragonflies and hoverflies invest more in vision than any other animal. Impressive visual performance is subserved by a surprisingly simple visual system. In a typical insect eye, between 2,000 and 30,000 pixels in the image are analyzed by fewer than 200,000 neurons in underlying neural circuits. The combination of sophisticated visual processing with an approachable level of complexity has made the insect visual system a leading model for biomimetic approaches to computer vision. Much neurobiological research has focused on neural circuits used for detection of moving patterns (e.g. optical flow during flight) and moving targets (e.g. prey). Research from several labs has led to great advances in our understanding of the neural mechanisms involved, and has spawned neuromorphic hardware based on key processes identified in neurobiological experiments. Despite its attractions, the highly non-linear nature of several key stages in insect visual processing presents a challenge to understanding. I will describe examples of adaptive elements of neural circuits in the fly visual system which analyze the direction and velocity of wide-field optical flow patterns and the result of experiments that suggest that these non-linearities may contribute to robust responses to natural image motion.

  4. Hydrogen Tunneling in Enzymes and Biomimetic Models

    SciTech Connect

    Layfield, Joshua P.; Hammes-Schiffer, Sharon

    2013-12-20

    Hydrogen transfer reactions play an important role throughout chemistry and biology. In general, hydrogen transfer reactions encompass proton and hydride transfer, which are associated with the transfer of a positively or negatively charged species, respectively, and proton-coupled electron transfer (PCET), which corresponds to the net transfer of one electron and one proton in the simplest case. Such PCET reactions can occur by either a sequential mechanism, in which the proton or electron transfers first, or a concerted mechanism, in which the electron and proton transfer in a single kinetic step with no stable intermediate. Furthermore, concerted PCET reactions can be subdivided into hydrogen atom transfer (HAT), which corresponds to the transfer of an electron and proton between the same donor and acceptor (i.e., the transfer of a predominantly neutral species), and electron-proton transfer (EPT), which corresponds to the transfer of an electron and proton between different donors and acceptors, possibly even in different directions. In all of these types of hydrogen transfer reactions, hydrogen tunneling could potentially play a signficant role. The theoretical development portion of this Review was supported by the National Science Foundation under CHE-10-57875. The biological portion of this Review was funded by NIH Grant No. GM056207. The biomimetic portion was supported as part of the Center for Molecular Electro-catalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  5. Hydrogen Tunneling in Enzymes and Biomimetic Models

    SciTech Connect

    Layfield, Joshua P.; Hammes-Schiffer, Sharon

    2014-04-09

    Hydrogen transfer reactions play an important role throughout chemistry and biology. In general, hydrogen transfer reactions encompass proton and hydride transfer, which are associated with the transfer of a positively or negatively charged species, respectively, and proton-coupled electron transfer (PCET), which corresponds to the net transfer of one electron and one proton in the simplest case. Such PCET reactions can occur by either a sequential mechanism, in which the proton or electron transfers first, or a concerted mechanism, in which the electron and proton transfer in a single kinetic step with no stable intermediate. Furthermore, concerted PCET reactions can be subdivided into hydrogen atom transfer (HAT), which corresponds to the transfer of an electron and proton between the same donor and acceptor (i.e., the transfer of a predominantly neutral species), and electron-proton transfer (EPT), which corresponds to the transfer of an electron and proton between different donors and acceptors, possibly even in different directions. In all of these types of hydrogen transfer reactions, hydrogen tunneling could potentially play a significant role. The biomimetic portion was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  6. A multi-electrode biomimetic electrolocation sensor

    NASA Astrophysics Data System (ADS)

    Mayekar, K.; Damalla, D.; Gottwald, M.; Bousack, H.; von der Emde, G.

    2012-04-01

    We present the concept of an active multi-electrode catheter inspired by the electroreceptive system of the weakly electric fish, Gnathonemus petersii. The skin of this fish exhibits numerous electroreceptor organs which are capable of sensing a self induced electrical field. Our sensor is composed of a sending electrode and sixteen receiving electrodes. The electrical field produced by the sending electrode was measured by the receiving electrodes and objects were detected by the perturbation of the electrical field they induce. The intended application of such a sensor is in coronary diagnostics, in particular in distinguishing various types of plaques, which are major causes of heart attack. For calibration of the sensor system, finite element modeling (FEM) was performed. To validate the model, experimental measurements were carried out with two different systems. The physical system was glass tubing with metal and plastic wall insertions as targets. For the control of the experiment and for data acquisition, the software LabView designed for 17 electrodes was used. Different parameters of the electric images were analyzed for the prediction of the electrical properties and size of the inserted targets in the tube. Comparisons of the voltage modulations predicted from the FEM model and the experiments showed a good correspondence. It can be concluded that this novel biomimetic method can be further developed for detailed investigations of atherosclerotic lesions. Finally, we discuss various design strategies to optimize the output of the sensor using different simulated models to enhance target recognition.

  7. Biomimetic Polymers for Cardiac Tissue Engineering

    PubMed Central

    2016-01-01

    Heart failure is a morbid disorder characterized by progressive cardiomyocyte (CM) dysfunction and death. Interest in cell-based therapies is growing, but sustainability of injected CMs remains a challenge. To mitigate this, we developed an injectable biomimetic Reverse Thermal Gel (RTG) specifically engineered to support long-term CM survival. This RTG biopolymer provided a solution-based delivery vehicle of CMs, which transitioned to a gel-based matrix shortly after reaching body temperature. In this study we tested the suitability of this biopolymer to sustain CM viability. The RTG was biomolecule-functionalized with poly-l-lysine or laminin. Neonatal rat ventricular myocytes (NRVM) and adult rat ventricular myocytes (ARVM) were cultured in plain-RTG and biomolecule-functionalized-RTG both under 3-dimensional (3D) conditions. Traditional 2D biomolecule-coated dishes were used as controls. We found that the RTG-lysine stimulated NRVM to spread and form heart-like functional syncytia. Regarding cell contraction, in both RTG and RTG-lysine, beating cells were recorded after 21 days. Additionally, more than 50% (p value < 0.05; n = 5) viable ARVMs, characterized by a well-defined cardiac phenotype represented by sarcomeric cross-striations, were found in the RTG-laminin after 8 days. These results exhibit the tremendous potential of a minimally invasive CM transplantation through our designed RTG-cell therapy platform. PMID:27073119

  8. Bactericidal activity of biomimetic diamond nanocone surfaces.

    PubMed

    Fisher, Leanne E; Yang, Yang; Yuen, Muk-Fung; Zhang, Wenjun; Nobbs, Angela H; Su, Bo

    2016-03-01

    The formation of biofilms on implant surfaces and the subsequent development of medical device-associated infections are difficult to resolve and can cause considerable morbidity to the patient. Over the past decade, there has been growing recognition that physical cues, such as surface topography, can regulate biological responses and possess bactericidal activity. In this study, diamond nanocone-patterned surfaces, representing biomimetic analogs of the naturally bactericidal cicada fly wing, were fabricated using microwave plasma chemical vapor deposition, followed by bias-assisted reactive ion etching. Two structurally distinct nanocone surfaces were produced, characterized, and the bactericidal ability examined. The sharp diamond nanocone features were found to have bactericidal capabilities with the surface possessing the more varying cone dimension, nonuniform array, and decreased density, showing enhanced bactericidal ability over the more uniform, highly dense nanocone surface. Future research will focus on using the fabrication process to tailor surface nanotopographies on clinically relevant materials that promote both effective killing of a broader range of microorganisms and the desired mammalian cell response. This study serves to introduce a technology that may launch a new and innovative direction in the design of biomaterials with capacity to reduce the risk of medical device-associated infections. PMID:26992656

  9. Membrane activity of biomimetic facially amphiphilic antibiotics.

    PubMed

    Arnt, Lachelle; Rennie, Jason R; Linser, Sebastian; Willumeit, Regine; Tew, Gregory N

    2006-03-01

    Membranes are a central feature of all biological systems, and their ability to control many cellular processes is critically important. As a result, a better understanding of how molecules bind to and select between biological membranes is an active area of research. Antimicrobial host defense peptides are known to be membrane-active and, in many cases, exhibit discrimination between prokaryotic and eukaryotic cells. The design of synthetic molecules that capture the biological activity of these natural peptides has been shown. In this report, the interaction between our biomimetic structures and different biological membranes is reported using both model vesicle and in vitro bacterial cell experiments. Compound 1 induces 12% leakage at 20 microg/mL against phosphatidylglycerol (PG)-phosphatidylethanolamine (PE) vesicles vs only 3% leakage at 200 microg/mL against phosphatidyl-L-serine (PS)-phosphatidylcholine (PC) vesicles. Similarly, a 40% reduction in fluorescence is measured in lipid movement experiments for PG-PE compared to 10% for PS-PC at 600 s. A 30 degrees C increase in the phase transition of stearoyl-oleoyl-phosphatidylserine is observed in the presence of 1. These results show that lipid composition is more important for selectivity than overall net charge. Additionally, the overall concentration of a given lipid is another important factor. An effort is made to connect model vesicle studies with in vitro data and naturally occurring lipid compositions. PMID:16494408

  10. BIOMIMETIC GRADIENT HYDROGELS FOR TISSUE ENGINEERING.

    PubMed

    Sant, Shilpa; Hancock, Matthew J; Donnelly, Joseph P; Iyer, Dharini; Khademhosseini, Ali

    2010-12-01

    During tissue morphogenesis and homeostasis, cells experience various signals in their environments, including gradients of physical and chemical cues. Spatial and temporal gradients regulate various cell behaviours such as proliferation, migration, and differentiation during development, inflammation, wound healing, and cancer. One of the goals of functional tissue engineering is to create microenvironments that mimic the cellular and tissue complexity found in vivo by incorporating physical, chemical, temporal, and spatial gradients within engineered three-dimensional (3D) scaffolds. Hydrogels are ideal materials for 3D tissue scaffolds that mimic the extracellular matrix (ECM). Various techniques from material science, microscale engineering, and microfluidics are used to synthesise biomimetic hydrogels with encapsulated cells and tailored microenvironments. In particular, a host of methods exist to incorporate micrometer to centimetre scale chemical and physical gradients within hydrogels to mimic the cellular cues found in vivo. In this review, we draw on specific biological examples to motivate hydrogel gradients as tools for studying cell-material interactions. We provide a brief overview of techniques to generate gradient hydrogels and showcase their use to study particular cell behaviours in two-dimensional (2D) and 3D environments. We conclude by summarizing the current and future trends in gradient hydrogels and cell-material interactions in context with the long-term goals of tissue engineering. PMID:21874065

  11. Biomimetic Control of Calcite Morphology with Homopolyanions

    PubMed Central

    McKenna, Brandon J.; Waite, J. Herbert; Stucky, Galen D.

    2009-01-01

    Biomineralization is an intricate process that relies on precise physiological control of solution and interface properties. Despite much research of the process, mechanistic details of biomineralization are only beginning to be understood, and studies of additives seldom investigate a wide space of chemical conditions in mineralizing solutions. We present a ternary diagram-based method that globally identifies the changing roles and effects of polymer additives in mineralization. Simple polyanions were demonstrated to induce a great variety of morphologies, each of which can be selectively and reproducibly fabricated. This chemical and physical analysis also aided in identifying conditions that selectively promote heterogeneous nucleation and controlled cooperative assembly, manifested here in the form of highly organized cones. Similar complex shapes of CaCO3 have previously been synthesized using double hydrophilic block copolymers. We have found the biomimetic mineralization process to occur interfacially and by the assembly of precursor modules, which generate large mesocrystals with high dependence on pH and substrate surface. PMID:20161392

  12. The biomimetic apatite-cefalotin coatings on modified titanium.

    PubMed

    Kang, Min-Kyung; Lee, Sang-Bae; Moon, Seung-Kyun; Kim, Kwang-Mahn; Kim, Kyoung-Nam

    2012-02-01

    Dental implant failure often occurs due to oral bacterial infection. The aim of this study was to demonstrate that antibiotic efficacy could be enhanced with modified titanium. First, the titanium was modified by anodization and heat-treatment. Then, a biomimetic coating process was completed in two steps. Surface characterization was performed with scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Release of antibiotic was evaluated by UV/VIS spectrometry, and the antibacterial effect was evaluated on Streptococcus mutans. After the second coating step, we observed a thick homogeneous apatite layer that contained the antibiotic, cefalotin. The titanium formed a rutile phase after the heat treatment, and a carbonated apatite phase appeared after biomimetic coating. We found that the modified titanium increased the loading of cefalotin onto the hydroxyapatite coated surface. The results suggested that modified titanium coated with a cefalotin using biomimetic coating method might be useful for preventing local post-surgical implant infections. PMID:22277612

  13. Biomimetic Magnetite Formation: From Biocombinatorial Approaches to Mineralization Effects

    PubMed Central

    2014-01-01

    Biological materials typically display complex morphologies and hierarchical architectures, properties that are hardly matched by synthetic materials. Understanding the biological control of mineral properties will enable the development of new synthetic approaches toward biomimetic functional materials. Here, we combine biocombinatorial approaches with a proteome homology search and in vitro mineralization assays to assess the role of biological determinants in biomimetic magnetite mineralization. Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro. Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface. In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron. PMID:24499323

  14. A biomimetic synthesis of (±)-basiliolide B.

    PubMed

    Min, Long; Zhang, Yang; Liang, Xuefeng; Huang, Junrong; Bao, Wenli; Lee, Chi-Sing

    2014-10-13

    A highly diastereoselective and practical biomimetic total synthesis of (±)-basiliolide B has been achieved through the study of the two proposed biosynthetic pathways (O-methylation and O-acylation) for the unprecedented 7-methoxy-4,5-dihydro-3H-oxepin-2-one (C ring). The synthesis featured a cyclopropanation/ring opening strategy for establishing the stereogenic centers at C8 and C9, a biomimetic 2-pyrone Diels-Alder cycloaddition for the synthesis of the ABD ring system, and finally a highly efficient biomimetic intramolecular O-acylation for the C ring formation. This result provides an important perspective on the biosynthetic origin of the unprecedented 7-membered acyl ketene acetal moiety of the C ring. PMID:25159722

  15. Superhydrophobic surfaces: from natural to biomimetic to functional.

    PubMed

    Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

    2011-01-15

    Nature is the creation of aesthetic functional systems, in which many natural materials have vagarious structures. Inspired from nature, such as lotus leaf, butterfly' wings, showing excellent superhydrophobicity, scientists have recently fabricated a lot of biomimetic superhydrophobic surfaces by virtue of various smart and easy routes. Whilst, many examples, such as lotus effect, clearly tell us that biomimicry is dissimilar to a simple copying or duplicating of biological structures. In this feature article, we review the recent studies in both natural superhydrophobic surfaces and biomimetic superhydrophobic surfaces, and highlight some of the recent advances in the last four years, including the various smart routes to construct rough surfaces, and a lot of chemical modifications which lead to superhydrophobicity. We also review their functions and applications to date. Finally, the promising routes from biomimetic superhydrophobic surfaces in the next are proposed. PMID:20846662

  16. PEM Fuel Cells Redesign Using Biomimetic and TRIZ Design Methodologies

    NASA Astrophysics Data System (ADS)

    Fung, Keith Kin Kei

    Two formal design methodologies, biomimetic design and the Theory of Inventive Problem Solving, TRIZ, were applied to the redesign of a Proton Exchange Membrane (PEM) fuel cell. Proof of concept prototyping was performed on two of the concepts for water management. The liquid water collection with strategically placed wicks concept demonstrated the potential benefits for a fuel cell. Conversely, the periodic flow direction reversal concepts might cause a potential reduction water removal from a fuel cell. The causes of this water removal reduction remain unclear. In additional, three of the concepts generated with biomimetic design were further studied and demonstrated to stimulate more creative ideas in the thermal and water management of fuel cells. The biomimetic design and the TRIZ methodologies were successfully applied to fuel cells and provided different perspectives to the redesign of fuel cells. The methodologies should continue to be used to improve fuel cells.

  17. Spheromak Power and Helicity Balance

    SciTech Connect

    Thomassen, K.I.

    2000-05-18

    This note addresses the division of gun power and helicity between the open line volume and the closed flux surface volume in a steady state flux core spheromak. Our assumptions are that fine scale turbulence maintains each region close to a Taylor state, {mu}{sub o}J = {lambda}B. The gun region that feeds these two volumes surrounded by a flux conserver is shown topologically below. (The actual geometry is toroidal). Flux and current from the magnetized gun flow on open lines around the entire closed surface containing the spheromak. The gun current flows down the potential gradient, the potential difference between the two ends of each line being the gun voltage. Here, the gun voltage excludes the sheath drops at each end. When these volumes have different values of {lambda} (ratio of {mu}{sub o}B{sup -2}j {center_dot} B in each region) in the open line volume V{sub 1} and the closed spheromak volume V{sub 2} the efficiency of transferring the gun power to the spheromak to sustain the ohmic loss is the {lambda}-ratio of these regions, in the limit V{sub 1} << V{sub 2}. This result follows immediately from helicity balance in that limit. Here we give an accounting of all the gun power, and do not assume a small edge (open line) region.

  18. Helical coil thermal hydraulic model

    NASA Astrophysics Data System (ADS)

    Caramello, M.; Bertani, C.; De Salve, M.; Panella, B.

    2014-11-01

    A model has been developed in Matlab environment for the thermal hydraulic analysis of helical coil and shell steam generators. The model considers the internal flow inside one helix and its associated control volume of water on the external side, both characterized by their inlet thermodynamic conditions and the characteristic geometry data. The model evaluates the behaviour of the thermal-hydraulic parameters of the two fluids, such as temperature, pressure, heat transfer coefficients, flow quality, void fraction and heat flux. The evaluation of the heat transfer coefficients as well as the pressure drops has been performed by means of the most validated literature correlations. The model has been applied to one of the steam generators of the IRIS modular reactor and a comparison has been performed with the RELAP5/Mod.3.3 code applied to an inclined straight pipe that has the same length and the same elevation change between inlet and outlet of the real helix. The predictions of the developed model and RELAP5/Mod.3.3 code are in fairly good agreement before the dryout region, while the dryout front inside the helical pipes is predicted at a lower distance from inlet by the model.

  19. Biomimetic actuators using electroactive polymers (EAP) as artificial muscles

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    2006-01-01

    Evolution has resolved many of nature's challenges leading to lasting solutions with maximal performance and effective use of resources. Nature's inventions have always inspired human achievements leading to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems and many other benefits. The field of mimicking nature is known as Biomimetics and one of its topics includes electroactive polymers that gain the moniker artificial muscles. Integrating EAP with embedded sensors, self-repair and many other capabilities that are used in composite materials can add greatly to the capability of smart biomimetic systems. Such development would enable fascinating possibilities potentially turning science fiction ideas into engineering reality.

  20. The AGS synchrotron with four helical magnets

    SciTech Connect

    Tsoupas N.; Huang, H.; Roser, T.; MacKay, W.W.; Trbojevic, D.

    2012-05-20

    The idea of using two partial helical magnets was applied successfully to the AGS synchrotron to preserve the proton beam polarization. In this paper we explore in details the idea of using four helical magnets placed symmetrically in the AGS ring. The placement of four helical magnets in the AGS ring provides many advantages over the present setup of the AGS which uses two partial helical magnets. First, the symmetric placement of the four helical magnets allows for a better control of the AGS optics with reduced values of the beta functions especially near beam injection, second, the vertical spin direction during beam injection and extraction is closer to vertical, and third, it provides for a larger 'spin tune gap', which allows the vertical and horizontal tunes to be placed, and prevent the horizontal and vertical intrinsic spin resonances of the AGS to occur during the acceleration cycle. Although the same spin gap can be obtained with a single or two partial helices, the required high field strength of a single helix makes its use impractical, and that of the double helix rather difficult. In this paper we will provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and compare these results with the present setup of the AGS that uses two partial helical magnets.

  1. Magnetic Helicity and the Solar Dynamo

    NASA Technical Reports Server (NTRS)

    Canfield, Richard C.

    1997-01-01

    The objective of this investigation is to open a new window into the solar dynamo, convection, and magnetic reconnection through measurement of the helicity density of magnetic fields in the photosphere and tracing of large-scale patterns of magnetic helicity in the corona.

  2. Hydrodynamic characteristics of the helical flow pump.

    PubMed

    Ishii, Kohei; Hosoda, Kyohei; Nishida, Masahiro; Isoyama, Takashi; Saito, Itsuro; Ariyoshi, Koki; Inoue, Yusuke; Ono, Toshiya; Nakagawa, Hidemoto; Sato, Masami; Hara, Sintaro; Lee, Xinyang; Wu, Sheng-Yuan; Imachi, Kou; Abe, Yusuke

    2015-09-01

    The helical flow pump (HFP) was invented to be an ideal pump for developing the TAH and the helical flow TAH (HFTAH) using two HFPs has been developed. However, since the HFP is quite a new pump, hydrodynamic characteristics inside the pump are not clarified. To analyze hydrodynamic characteristics of the HFP, flow visualization study using the particle image velocimetry and computational fluid dynamics analysis were performed. The experimental and computational models were developed to simulate the left HFP of the HFTAH and distributions of flow velocity vectors, shear stress and pressure inside the pump were examined. In distribution of flow velocity vectors, the vortexes in the vane were observed, which indicated that the HFP has a novel and quite unique working principle in which centrifugal force rotates the fluid in the helical volutes and the fluid is transferred from the inlet to the outlet helical volutes according to the helical structure. In distribution of shear stress, the highest shear stress that was considered to be occurred by the shunt flow across the impeller was found around the entrance of the inlet helical volute. However, it was not so high to cause hemolysis. This shunt flow is thought to be improved by redesigning the inlet and outlet helical volutes. In distribution of pressure, negative pressure was found near the entrance of the inlet helical volute. However, it was not high. Negative pressure is thought to be reduced with an improvement in the design of the impeller or the vane shape. PMID:25784463

  3. Simplified Fabrication of Helical Copper Antennas

    NASA Technical Reports Server (NTRS)

    Petro, Andrew

    2006-01-01

    A simplified technique has been devised for fabricating helical antennas for use in experiments on radio-frequency generation and acceleration of plasmas. These antennas are typically made of copper (for electrical conductivity) and must have a specific helical shape and precise diameter.

  4. Chiral self-assembly of helical particles.

    PubMed

    Kolli, Hima Bindu; Cinacchi, Giorgio; Ferrarini, Alberta; Giacometti, Achille

    2016-04-12

    The shape of the building blocks plays a crucial role in directing self-assembly towards desired architectures. Out of the many different shapes, the helix has a unique position. Helical structures are ubiquitous in nature and a helical shape is exhibited by the most important biopolymers like polynucleotides, polypeptides and polysaccharides as well as by cellular organelles like flagella. Helical particles can self-assemble into chiral superstructures, which may have a variety of applications, e.g. as photonic (meta)materials. However, a clear and definite understanding of these structures has not been entirely achieved yet. We have recently undertaken an extensive investigation on the phase behaviour of hard helical particles, using numerical simulations and classical density functional theory. Here we present a detailed study of the phase diagram of hard helices as a function of their morphology. This includes a variety of liquid-crystal phases, with different degrees of orientational and positional ordering. We show how, by tuning the helix parameters, it is possible to control the organization of the system. Starting from slender helices, whose phase behaviour is similar to that of rodlike particles, an increase in curliness leads to the onset of azimuthal correlations between the particles and the formation of phases specific to helices. These phases feature a new kind of screw order, of which there is experimental evidence in colloidal suspensions of helical flagella. PMID:26767786

  5. [Loss of pubescence and their physiological effects on endangered rosette Espeletia paipana (Asteraceae), Boyacá-Colombia].

    PubMed

    Buitrago, Sindy; Vanegast, Leidy; Ramos, Carolina

    2015-09-01

    Espeletia paipana is an endangered giant caulescent rosette endemic to (Asteraceae), Boyacdi-Colombia. Espelelia paipana is an endangered giant caulescent rosette endemic to Boyacá department. In order to establish whether a plant disease, characterized by the loss of leaf pubescence (PPF) and attributed to the pathogenic action of endophytic microorganisms, is the cause of the increasing mortality of population, the physiological performance of the species was evaluated with and without PPF. The incidence (% leaves affected in each of the 27 individuals in the current population) and severity (% leaf area affected on 135 leaves) of the PPF were monitored over a period of nine months, in three topographic zones of different heights. During four consecutive days in both dry and wet season, physiological parameters as chlorophyll content index (ICC), stomatal conductance (Gs) and leaf temperature (Tfol) were measured in healthy and affected leaves. The study was complemented with isolations and pathogenicity tests to identify the causal agent of the PPF. Overall, although the disease incidence in E. paipana was constant over time, the severity progressed surpassing 60 % of the leaf area. The increasing of severity in the upper side of leaves was attributed to the photo-oxidative effect of high radiation between 11:00 h and 14:00 h of the day. The reduction of functional leaf area because of the PPF, led to low Gs with serious implications for carbon fixation and thus limiting growth and biomass renewal. The effect of season in Tfol varied according to the topographic zone, while the ICC did not present a defined pattern with respect to the PPF; its low values could be associated with the production of other pigments. Finally, although it is not possible to ensure that Botrytis sp. is the causative of the loss of leaf pubescence, it is postulated as the most probably causal agent due to its high representativeness in the isolates and its infectious potential during

  6. Polarized neural stem cells derived from adult bone marrow stromal cells develop a rosette-like structure.

    PubMed

    Darabi, Shahram; Tiraihi, Taki; Ruintan, Atefeh; Abbaszadeh, Hojatt Allah; Delshad, AliReza; Taheri, Taher

    2013-09-01

    Bone marrow stromal cells (BMSCs) were reported to form floating aggregation of cells with expression of nestin, a marker for neural stem cells (NSCs). The purpose of this investigation is to evaluate the morphology and the molecular markers expressed by NSCs derived from these neurospheres. The BMSCs were isolated from Sprague Dawley rats and evaluated for osteogenesis, lipogenesis, and expression of fibronectin, CD90, CD106, CD31, and Oct4. The BMSCs were cultured with Dulbecco's modified Eagle's medium (DMEM)/F12 containing 15% fetal bovine serum, then with DMEM/F12 containing 2% B27, basic fibroblast growth factor, and epidermal growth factor. The cell aggregates or spheres were stained with acridine orange, which showed that the neurospheres comprised aggregated cells at either premitotic/postsynthetic (PS), postmitotic/presynthetic (PM) phases of cell cycle, or a mixture of both. The NSCs harvested from the neurospheres were polar with eccentric nucleus, and at either a PS or a PM cell cycle phases, some cells at the latter phase tended to form rosette-like structures. The cells were immunostained for molecular markers such as nestin, neurofilament 68 (NF68), NF160, and NF200 and glial fibrillary acidic protein (GFAP). Myelin basic protein (MBP), the pluripotency (Oct4, Nanog, and SOX2), and the differentiation genes (NeuroD1, Tubb4, and Musashi I) were also evaluated using reverse transcription polymerase chain reaction (RT-PCR). Nestin, NF68, NF160, NF200, GFAP, O4, and N-cadherin were expressed in the NSCs. The percentage of immunoreactive cells to nestin was significantly higher than that of the other neuronal markers. MBP was not expressed in BMSCs, neurospheres, and NSCs. The neurospheres were immunoreactive to GFAP. RT-PCR showed the expression of NeuroD1 and Musashi I. The pluripotency gene (SOX2) was expressed in NSCs. Oct4 and Nanog were expressed in BMSCs, while Oct4 and SOX2 were expressed in the neurosphere. This indicates that a pluripotency

  7. Structure and interactions of biological helices

    NASA Astrophysics Data System (ADS)

    Kornyshev, Alexei A.; Lee, Dominic J.; Leikin, Sergey; Wynveen, Aaron

    2007-07-01

    Helices are essential building blocks of living organisms, be they molecular fragments of proteins ( α -helices), macromolecules (DNA and collagen), or multimolecular assemblies (microtubules and viruses). Their interactions are involved in packing of meters of genetic material within cells and phage heads, recognition of homologous genes in recombination and DNA repair, stability of tissues, and many other processes. Helical molecules form a variety of mesophases in vivo and in vitro. Recent structural studies, direct measurements of intermolecular forces, single-molecule manipulations, and other experiments have accumulated a wealth of information and revealed many puzzling physical phenomena. It is becoming increasingly clear that in many cases the physics of biological helices cannot be described by theories that treat them as simple, unstructured polyelectrolytes. The present article focuses on the most important and interesting aspects of the physics of structured macromolecules, highlighting various manifestations of the helical motif in their structure, elasticity, interactions with counterions, aggregation, and poly- and mesomorphic transitions.

  8. Optical and Calorimetric Studies of Cholesterol-Rich Filamentous, Helical Ribbon and Crystal Microstructures

    SciTech Connect

    Miroshnikova, Y. A.; Elsenbeck, M.; Zastavker, Y. V.; Kashuri, K; Iannacchione, G. S.

    2009-04-19

    Formation of biological self-assemblies at all scales is a focus of studies in fields ranging from biology to physics to biomimetics. Understanding the physico-chemical properties of these self-assemblies may lead to the design of bio-inspired structures and technological applications. Here we examine self-assembled filamentous, helical ribbon, and crystal microstructures formed in chemically defined lipid concentrate (CDLC), a model system for cholesterol crystallization in gallbladder bile. CDLC consists of cholesterol, bilayer-forming amphiphiles, micelle-forming amphiphiles, and water. Phase contrast and differential interference contrast (DIC) microscopy indicate the presence of three microstructure types in all samples studied, and allow for an investigation of the structures' unique geometries. Additionally, confocal microscopy is used for qualitative assessment of surface and internal composition. To complement optical observations, calorimetric (differential-scanning and modulation) experiments, provide the basis for an in-depth understanding of collective and individual thermal behavior. Observed ''transition'' features indicate clustering and ''straightening'' of helical ribbons into short, increasingly thickening, filaments that dissolve with increasing temperature. These results suggest that all microstructures formed in CDLC may coexist in a metastable chemical equilibrium. Further investigation of the CDLC thermal profile should uncover the process of cholesterol crystallization as well as the unique design and function of microstructures formed in this system.

  9. Biomimetic processing of oriented crystalline ceramic layers

    SciTech Connect

    Cesarano, J.; Shelnutt, J.A.

    1997-10-01

    The aim of this project was to develop the capabilities for Sandia to fabricate self assembled Langmuir-Blodgett (LB) films of various materials and to exploit their two-dimensional crystalline structure to promote the growth of oriented thin films of inorganic materials at room temperature. This includes the design and synthesis of Langmuir-active (amphiphilic) organic molecules with end groups offering high nucleation potential for various ceramics. A longer range goal is that of understanding the underlying principles, making it feasible to use the techniques presented in this report to fabricate unique oriented films of various materials for electronic, sensor, and membrane applications. Therefore, whenever possible, work completed in this report was completed with the intention of addressing the fundamental phenomena underlying the growth of crystalline, inorganic films on template layers of highly organized organic molecules. This problem was inspired by biological processes, which often produce exquisitely engineered structures via templated growth on polymeric layers. Seashells, for example, exhibit great toughness owing to their fine brick-and-mortar structure that results from templated growth of calcium carbonate on top of layers of ordered organic proteins. A key goal in this work, therefore, is to demonstrate a positive correlation between the order and orientation of the template layer and that of the crystalline ceramic material grown upon it. The work completed was comprised of several parallel efforts that encompassed the entire spectrum of biomimetic growth from solution. Studies were completed on seashells and the mechanisms of growth for calcium carbonate. Studies were completed on the characterization of LB films and the capability developed for the in-house fabrication of these films. Standard films of fatty acids were studied as well as novel polypeptides and porphyrins that were synthesized.

  10. Vickers indentation on the {l_brace}001{r_brace} faces of ZnS sphalerite under UV illumination and in darkness. Crack patterns and rosette microstructure

    SciTech Connect

    Koubaieti, S.; Couderc, J.J.; Levade, C.; Vanderschaeve, G.

    1996-08-01

    Vickers microhardness indentations are performed on the (001) surface of ZnS sphalerite single crystals in darkness and under UV illumination, close to the band absorption edge. For low applied loads, the crack length and the rosette size confirm the hardening effect of illumination (positive photoplastic effect) that causes a lowering of the dislocation mobility. For high applied loads the positive photoplastic effect is masked by a strong workhardening in the highly strained zone. In darkness as well as under irradiation, perpendicular rosette arms have the same length, showing that {alpha} and {beta} perfect dislocations have similar mobilities at variance with III-V compounds. However, the observed asymmetry in the dissociation behavior suggests that partial dislocations have different mobilities.

  11. Synthesis of N-substituted pyrido[4,3-d]pyrimidines for the large-scale production of self-assembled rosettes and nanotubes.

    PubMed

    Durmus, Asuman; Gunbas, Gorkem; Farmer, Steven C; Olmstead, Marilyn M; Mascal, Mark; Legese, Belete; Cho, Jae-Young; Beingessner, Rachel L; Yamazaki, Takeshi; Fenniri, Hicham

    2013-11-15

    N-substituted pyrido[4,3-d]pyrimidines are heterocycles which exhibit the asymmetric hydrogen bonding codes of both guanine and cytosine at 60° angles to each other, such that the molecules self-organize unambiguously into a cyclic hexamer, assembled via 18 intermolecular hydrogen bonds. The synthesis is straightforward and can be concluded in six steps from the commercially available malononitrile dimer. X-ray crystallographic analysis of the supermacrocyclic structure shows an undulating disk with a ca. 10.5 Å cavity, the centers of which do not overlap sufficiently to describe a channel in the solid state. However, AFM, SEM, and TEM imaging in solution reveals the formation of 1D nanostructures in agreement with their self-assembly into rosette supermacrocycles, which then stack linearly to form rosette nanotubes. PMID:24131036

  12. Helices of fractionalized Maxwell fluid

    NASA Astrophysics Data System (ADS)

    Jamil, Muhammad; Abro, Kashif Ali; Khan, Najeeb Alam

    2015-12-01

    In this paper the helical flows of fractionalized Maxwell fluid model, through a circular cylinder, is studied. The motion is produced by the cylinder that at the initial moment begins to rotate around its axis with an angular velocity Omegatp, and to slide along the same axis with linear velocity Utp. The solutions that have been obtained using Laplace and finite Hankel transforms and presented in series form in terms of the newly defined special function M(z), satisfy all imposed initial and boundary conditions. Moreover, the corresponding solutions for ordinary Maxwell and Newtonian fluid obtained as special cases of the present general solution. Finally, the influence of various pertinent parameters on fluid motion as well as the comparison among different fluids models is analyzed by graphical illustrations.

  13. Thermal deformation of helical gears

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Fei, Ye-tai; Liu, Shan-lin

    2010-08-01

    The analytical equation for the thermal field of a helical gear under normal working condition in a stable thermal field is established using mathematical physics, and the thermal deformation of the gear can be computed using this equation. The variations of gear geometric parameters, such as radial dimension, tooth depth, spiral angle, pressure angle, flank clearance and etc., are investigated with respect to the temperature change. According to the analytical and computational results obtained using the equation, the thermal deformation of the gear is strongly dependent on the choice of parameters, which is also confirmed using simulation software (COMSOL Multiphysic software). This is significant for the improvement of the rotation precision and working efficiency of screw gears.

  14. The quantum Hall effect helicity

    SciTech Connect

    Shrivastava, Keshav N.

    2015-04-16

    The quantum Hall effect in semiconductor heterostructures is explained by two signs in the angular momentum j=l±s and g=(2j+1)/(2l+1) along with the Landau factor (n+1/2). These modifications in the existing theories explain all of the fractional charges. The helicity which is the sign of the product of the linear momentum with the spin p.s plays an important role for the understanding of the data at high magnetic fields. In particular it is found that particles with positive sign in the spin move in one direction and those with negative sign move in another direction which explains the up and down stream motion of the particles.

  15. Adding helicity to inflationary magnetogenesis

    SciTech Connect

    Caprini, Chiara; Sorbo, Lorenzo E-mail: sorbo@physics.umass.edu

    2014-10-01

    The most studied mechanism of inflationary magnetogenesis relies on the time-dependence of the coefficient of the gauge kinetic term F{sub μν} F{sup μν}. Unfortunately, only extremely finely tuned versions of the model can consistently generate the cosmological magnetic fields required by observations. We propose a generalization of this model, where also the pseudoscalar invariant F{sub μν}  F-tilde {sup μν} is multiplied by a time dependent function. The new parity violating term allows more freedom in tuning the amplitude of the field at the end of inflation. Moreover, it leads to a helical magnetic field that is amplified at large scales by magnetohydrodynamical processes during the radiation dominated epoch. As a consequence, our model can satisfy the observational lower bounds on fields in the intergalactic medium, while providing a seed for the galactic dynamo, if inflation occurs at an energy scale ranging from 10{sup 5} to 10{sup 10} GeV. Such energy scale is well below that suggested by the recent BICEP2 result, if the latter is due to primordial tensor modes. However, the gauge field is a source of tensors during inflation and generates a spectrum of gravitational waves that can give a sizable tensor to scalar ratio r=O(0.2) even if inflation occurs at low energies. This system therefore evades the Lyth bound. For smaller values of r, lower values of the inflationary energy scale are required. The model predicts fully helical cosmological magnetic fields and a chiral spectrum of primordial gravitational waves.

  16. Biochemical studies of olfaction: isolation, characterization, and odorant binding activity of cilia from rainbow trout olfactory rosettes.

    PubMed

    Rhein, L D; Cagan, R H

    1980-08-01

    The role of cilia in recognition of olfactory stimuli has been controversial. Cilia from the intact olfactory rosettes of the rainbow trout Salmo gairdneri were isolated, characterized biochemically, and examined by electron microscopy. The markers studied are those associated with cilia in other organisms. Dynein arms contain Mg2+-AtPase; this enzyme was enriched in the isolated cilia preparation. Guanine nucleotides are associated with the outer microtubule doublets of cilia but adenine nucleotides are not; a substantial enrichment in guanine, relative to adenine, was found in the cilia preparation. Tubulin, the structural protein component of microtubules, occurs in large amounts in cilia. Disc gel electrophoresis indicated tubulin in the cilia preparation. Electron microscopy confirmed the presence of cilia in the isolated preparation. Rainbow trout have an acute sense of smell and many amino acids are odorants to this species. Functional activity of the cilia preparation relevant to odorant recognition was assessed by using binding of radioactively labeled odorant amino acids. L-Alanine, L-serine, L-threonine, L-lysine, and D-alanine bound to the cilia preparation. This study provides direct biochemical evidence that olfactory cilia bind odorant molecules and supports the hypothesis that odorant recognition sites are integral parts of the cilia. PMID:6449006

  17. Biochemical studies of olfaction: binding specificity of odorants to a cilia preparation from rainbow trout olfactory rosettes.

    PubMed

    Rhein, L D; Cagan, R H

    1983-08-01

    Cilia isolated from the olfactory epithelium (olfactory rosettes) of rainbow trout (Salmo gairdneri) bind amino acids, which are odor stimuli to this species. We demonstrate that L-threonine, L-serine, and L-alanine bind to a common site, TSA, in the cilia preparation. All possible mixtures of two of the amino acids as competitors, with the third as the 3H-labeled ligand, were studied. The effect of two combined (unlabeled) competitors was always substantially less than additive compared with their actions singly. Along with additional inhibition studies using mixtures of inhibitors, the data show that the three odorants must interact with at least one common binding site, TSA. Binding of L-[3H]lysine to site L was unaffected by addition of L-threonine, L-serine, or L-alanine, establishing its independence from site TSA. L-Arginine inhibited binding of L-[3H]lysine, showing that both of these basic amino acids interact with site L. The data establish the presence, in trout olfactory cilia, of at least two separate and noninteracting populations of odorant binding sites, TSA and L. PMID:6409997

  18. SPITZER AND NEAR-INFRARED OBSERVATIONS OF A NEW BIPOLAR PROTOSTELLAR OUTFLOW IN THE ROSETTE MOLECULAR CLOUD

    SciTech Connect

    Ybarra, Jason E.; Lada, Elizabeth A.; Fleming, Scott W.; Balog, Zoltan; Phelps, Randy L.

    2010-05-01

    We present and discuss Spitzer and near-infrared H{sub 2} observations of a new bipolar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four InfraRed Array Camera (IRAC) bands and partially as diffuse emission in the MIPS 24 {mu}m band. An embedded MIPS 24 {mu}m source bisects the outflow and appears to be the driving source. This source is coincident with a dark patch seen in absorption in the 8 {mu}m IRAC image. Spitzer IRAC color analysis of the shocked emission was performed from which thermal and column density maps of the outflow were constructed. Narrowband near-infrared (NIR) images of the flow reveal H{sub 2} emission features coincident with the high temperature regions of the outflow. This outflow has now been given the designation MHO 1321 due to the detection of NIR H{sub 2} features. We use these data and maps to probe the physical conditions and structure of the flow.

  19. Spitzer And Near-infrared Observations Of A Bi-polar Outflow In The Rosette Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Ybarra, Jason E.; Lada, E. A.; Balog, Z.; Fleming, S. W.; Phelps, R. L.

    2010-01-01

    We present and discuss Spitzer and near-infrared H2 observations of a bi-polar protostellar outflow in the Rosette Molecular Cloud. The outflow is seen in all four IRAC bands and partially in the MIP 24 micron band. A dark cloud seen in absorption in the 8 micron image bisects the outflow and contains an embedded Class 0 object that appears to be the outflow source. Near-infrared narrow-band H2 observations were obtained using the Infrared Side Port Imager (ISPI) on the CTIO 4 meter telescope. Spitzer IRAC color analysis of the shocked emission was performed from which thermal and density maps of the outflow were constructed. We use these data and maps to probe the physical conditions and structure of the flow. This work is based in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by an award issued by JPL/Caltech, NASA LTSA Grant NNG05GD66G, and the Florida Space Grant Consortium

  20. Biomimetic smart sensors for autonomous robotic behavior I: acoustic processing

    NASA Astrophysics Data System (ADS)

    Deligeorges, Socrates; Xue, Shuwan; Soloway, Aaron; Lichtenstein, Lee; Gore, Tyler; Hubbard, Allyn

    2009-05-01

    Robotics are rapidly becoming an integral tool on the battlefield and in homeland security, replacing humans in hazardous conditions. To enhance the effectiveness of robotic assets and their interaction with human operators, smart sensors are required to give more autonomous function to robotic platforms. Biologically inspired sensors are an essential part of this development of autonomous behavior and can increase both capability and performance of robotic systems. Smart, biologically inspired acoustic sensors have the potential to extend autonomous capabilities of robotic platforms to include sniper detection, vehicle tracking, personnel detection, and general acoustic monitoring. The key to enabling these capabilities is biomimetic acoustic processing using a time domain processing method based on the neural structures of the mammalian auditory system. These biologically inspired algorithms replicate the extremely adaptive processing of the auditory system yielding high sensitivity over broad dynamic range. The algorithms provide tremendous robustness in noisy and echoic spaces; properties necessary for autonomous function in real world acoustic environments. These biomimetic acoustic algorithms also provide highly accurate localization of both persistent and transient sounds over a wide frequency range, using baselines on the order of only inches. A specialized smart sensor has been developed to interface with an iRobot Packbot® platform specifically to enhance its autonomous behaviors in response to personnel and gunfire. The low power, highly parallel biomimetic processor, in conjunction with a biomimetic vestibular system (discussed in the companion paper), has shown the system's autonomous response to gunfire in complicated acoustic environments to be highly effective.

  1. On the Biomimetic Design of Agile-Robot Legs

    PubMed Central

    Garcia, Elena; Arevalo, Juan Carlos; Muñoz, Gustavo; Gonzalez-de-Santos, Pablo

    2011-01-01

    The development of functional legged robots has encountered its limits in human-made actuation technology. This paper describes research on the biomimetic design of legs for agile quadrupeds. A biomimetic leg concept that extracts key principles from horse legs which are responsible for the agile and powerful locomotion of these animals is presented. The proposed biomimetic leg model defines the effective leg length, leg kinematics, limb mass distribution, actuator power, and elastic energy recovery as determinants of agile locomotion, and values for these five key elements are given. The transfer of the extracted principles to technological instantiations is analyzed in detail, considering the availability of current materials, structures and actuators. A real leg prototype has been developed following the biomimetic leg concept proposed. The actuation system is based on the hybrid use of series elasticity and magneto-rheological dampers which provides variable compliance for natural motion. From the experimental evaluation of this prototype, conclusions on the current technological barriers to achieve real functional legged robots to walk dynamically in agile locomotion are presented. PMID:22247667

  2. Biomimetic flavin-catalysed reactions for organic synthesis.

    PubMed

    Iida, H; Imada, Y; Murahashi, S-I

    2015-07-28

    Using simple riboflavin related compounds as biomimetic catalysts, catalytic oxidation of various substrates with hydrogen peroxide or molecular oxygen can be performed selectively under mild conditions. The principle of these reactions is fundamental and will provide a wide scope for environmentally benign future practical methods. PMID:26077635

  3. Biomimetic cilia arrays generate simultaneous pumping and mixing regimes

    PubMed Central

    Shields, A. R.; Fiser, B. L.; Evans, B. A.; Falvo, M. R.; Washburn, S.; Superfine, R.

    2010-01-01

    Living systems employ cilia to control and to sense the flow of fluids for many purposes, such as pumping, locomotion, feeding, and tissue morphogenesis. Beyond their use in biology, functional arrays of artificial cilia have been envisaged as a potential biomimetic strategy for inducing fluid flow and mixing in lab-on-a-chip devices. Here we report on fluid transport produced by magnetically actuated arrays of biomimetic cilia whose size approaches that of their biological counterparts, a scale at which advection and diffusion compete to determine mass transport. Our biomimetic cilia recreate the beat shape of embryonic nodal cilia, simultaneously generating two sharply segregated regimes of fluid flow: Above the cilia tips their motion causes directed, long-range fluid transport, whereas below the tips we show that the cilia beat generates an enhanced diffusivity capable of producing increased mixing rates. These two distinct types of flow occur simultaneously and are separated in space by less than 5 μm, approximately 20% of the biomimetic cilium length. While this suggests that our system may have applications as a versatile microfluidics device, we also focus on the biological implications of our findings. Our statistical analysis of particle transport identifying an enhanced diffusion regime provides novel evidence for the existence of mixing in ciliated systems, and we demonstrate that the directed transport regime is Poiseuille–Couette flow, the first analytical model consistent with biological measurements of fluid flow in the embryonic node. PMID:20798342

  4. Textile Processes for Engineering Tissues with Biomimetic Architectures and Properties.

    PubMed

    Fallahi, Afsoon; Khademhosseini, Ali; Tamayol, Ali

    2016-09-01

    Textile technologies in which fibers containing biological factors and cells are formed and assembled into constructs with biomimetic properties have attracted significant attention in the field of tissue engineering. This Forum article highlights the most prominent advances of the field in the areas of fiber fabrication and construct engineering. PMID:27499277

  5. Structural Design and Sealing Performance Analysis of Biomimetic Sealing Ring.

    PubMed

    Han, Chuanjun; Zhang, Han; Zhang, Jie

    2015-01-01

    In order to reduce the failure probability of rubber sealing rings in reciprocating dynamic seal, a new structure of sealing ring based on bionics was designed. The biomimetic ring has three concave ridges and convex bulges on each side which are very similar to earthworms. Bulges were circularly designed and sealing performances of the biomimetic ring in both static seal and dynamic seal were simulated by FEM. In addition, effects of precompression, medium pressure, speed, friction coefficient, and material parameters on sealing performances were discussed. The results show that von Mises stress of the biomimetic sealing ring distributed symmetrically in no-pressure static sealing. The maximum von Mises stress appears on the second bulge of the inner side. High contact stress concentrates on left bulges. Von Mises stress distribution becomes uneven under medium pressure. Both von Mises stress and contact stress increase when precompression, medium pressure, and rubber hardness increase in static sealing. Biomimetic ring can avoid rolling and distortion in reciprocating dynamic seal, and its working life is much longer than O-ring and rectangular ring. The maximum von Mises stress and contact stress increase with the precompression, medium pressure, rubber hardness, and friction coefficient in reciprocating dynamic seal. PMID:27019582

  6. A biomimetic tactile sensing system based on polyvinylidene fluoride film.

    PubMed

    Xin, Yi; Tian, Hongying; Guo, Chao; Li, Xiang; Sun, Hongshuai; Wang, Peiyuan; Qian, Chenghui; Wang, Shuhong; Wang, Cheng

    2016-02-01

    Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensing material due to its outstanding properties such as biocompatibility, high thermal stability, good chemical resistance, high piezo-, pyro- and ferro-electric properties. This paper reports on the design, test, and analysis of a biomimetic tactile sensor based on PVDF film. This sensor consists of a PVDF film with aluminum electrodes, a pair of insulating layers, and a "handprint" friction layer with a copper foil. It is designed for easy fabrication and high reliability in outputting signals. In bionics, the fingerprint of the glabrous skin plays an important role during object handling. Therefore, in order to enhance friction and to provide better manipulation, the ridges of the fingertips were introduced into the design of the proposed tactile sensor. And, a basic experimental study on the selection of the high sensitivity fingerprint type for the biomimetic sensor was performed. In addition, we proposed a texture distinguish experiment to verify the sensor sensitivity. The experiment's results show that the novel biomimetic sensor is effective in discriminating object surface characteristics. Furthermore, an efficient visual application program (LabVIEW) and a quantitative evaluation method were proposed for the verification of the biomimetic sensor. The proposed tactile sensor shows great potential for contact force and slip measurements. PMID:26931883

  7. A biomimetic tactile sensing system based on polyvinylidene fluoride film

    NASA Astrophysics Data System (ADS)

    Xin, Yi; Tian, Hongying; Guo, Chao; Li, Xiang; Sun, Hongshuai; Wang, Peiyuan; Qian, Chenghui; Wang, Shuhong; Wang, Cheng

    2016-02-01

    Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensing material due to its outstanding properties such as biocompatibility, high thermal stability, good chemical resistance, high piezo-, pyro- and ferro-electric properties. This paper reports on the design, test, and analysis of a biomimetic tactile sensor based on PVDF film. This sensor consists of a PVDF film with aluminum electrodes, a pair of insulating layers, and a "handprint" friction layer with a copper foil. It is designed for easy fabrication and high reliability in outputting signals. In bionics, the fingerprint of the glabrous skin plays an important role during object handling. Therefore, in order to enhance friction and to provide better manipulation, the ridges of the fingertips were introduced into the design of the proposed tactile sensor. And, a basic experimental study on the selection of the high sensitivity fingerprint type for the biomimetic sensor was performed. In addition, we proposed a texture distinguish experiment to verify the sensor sensitivity. The experiment's results show that the novel biomimetic sensor is effective in discriminating object surface characteristics. Furthermore, an efficient visual application program (LabVIEW) and a quantitative evaluation method were proposed for the verification of the biomimetic sensor. The proposed tactile sensor shows great potential for contact force and slip measurements.

  8. Biomimetic robots using EAP as artificial muscles - progress and challenges

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    2004-01-01

    Biology offers a great model for emulation in areas ranging from tools, computational algorithms, materials science, mechanisms and information technology. In recent years, the field of biomimetics, namely mimicking biology, has blossomed with significant advances enabling the reverse engineering of many animals' functions and implementation of some of these capabilities.

  9. Structural Design and Sealing Performance Analysis of Biomimetic Sealing Ring

    PubMed Central

    Han, Chuanjun

    2015-01-01

    In order to reduce the failure probability of rubber sealing rings in reciprocating dynamic seal, a new structure of sealing ring based on bionics was designed. The biomimetic ring has three concave ridges and convex bulges on each side which are very similar to earthworms. Bulges were circularly designed and sealing performances of the biomimetic ring in both static seal and dynamic seal were simulated by FEM. In addition, effects of precompression, medium pressure, speed, friction coefficient, and material parameters on sealing performances were discussed. The results show that von Mises stress of the biomimetic sealing ring distributed symmetrically in no-pressure static sealing. The maximum von Mises stress appears on the second bulge of the inner side. High contact stress concentrates on left bulges. Von Mises stress distribution becomes uneven under medium pressure. Both von Mises stress and contact stress increase when precompression, medium pressure, and rubber hardness increase in static sealing. Biomimetic ring can avoid rolling and distortion in reciprocating dynamic seal, and its working life is much longer than O-ring and rectangular ring. The maximum von Mises stress and contact stress increase with the precompression, medium pressure, rubber hardness, and friction coefficient in reciprocating dynamic seal. PMID:27019582

  10. A Laboratory Exercise to Introduce Inorganic Biomimetic Compounds.

    ERIC Educational Resources Information Center

    Baird, Donald M.

    1985-01-01

    Biomimetic chemistry is concerned with the synthesis of small, molecular weight molecules which mimic the properties of metal-containing sites within certain biologically significant species. A series of experiments for an advanced undergraduate laboratory is described as a way to introduce this area into the chemistry curriculum. (JN)

  11. Bio-Mimetic Sensors Based on Molecularly Imprinted Membranes

    PubMed Central

    Algieri, Catia; Drioli, Enrico; Guzzo, Laura; Donato, Laura

    2014-01-01

    An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. By means of this technology, selective molecular recognition sites are introduced in a polymer, thus conferring it bio-mimetic properties. The potential applications of these systems include affinity separations, medical diagnostics, drug delivery, catalysis, etc. Recently, bio-sensing systems using molecularly imprinted membranes, a special form of imprinted polymers, have received the attention of scientists in various fields. In these systems imprinted membranes are used as bio-mimetic recognition elements which are integrated with a transducer component. The direct and rapid determination of an interaction between the recognition element and the target analyte (template) was an encouraging factor for the development of such systems as alternatives to traditional bio-assay methods. Due to their high stability, sensitivity and specificity, bio-mimetic sensors-based membranes are used for environmental, food, and clinical uses. This review deals with the development of molecularly imprinted polymers and their different preparation methods. Referring to the last decades, the application of these membranes as bio-mimetic sensor devices will be also reported. PMID:25196110

  12. Natural variation in rosette size under salt stress conditions corresponds to developmental differences between Arabidopsis accessions and allelic variation in the LRR-KISS gene.

    PubMed

    Julkowska, Magdalena M; Klei, Karlijn; Fokkens, Like; Haring, Michel A; Schranz, M Eric; Testerink, Christa

    2016-04-01

    Natural variation among Arabidopsis accessions is an important genetic resource to identify mechanisms underlying plant development and stress tolerance. To evaluate the natural variation in salinity stress tolerance, two large-scale experiments were performed on two populations consisting of 160 Arabidopsis accessions each. Multiple traits, including projected rosette area, and fresh and dry weight were collected as an estimate for salinity tolerance. Our results reveal a correlation between rosette size under salt stress conditions and developmental differences between the accessions grown in control conditions, suggesting that in general larger plants were more salt tolerant. This correlation was less pronounced when plants were grown under severe salt stress conditions. Subsequent genome wide association study (GWAS) revealed associations with novel candidate genes for salinity tolerance such as LRR-KISS (At4g08850),flowering locus KH-domain containing protein and a DUF1639-containing protein Accessions with high LRR-KISS expression developed larger rosettes under salt stress conditions. Further characterization of allelic variation in candidate genes identified in this study will provide more insight into mechanisms of salt stress tolerance due to enhanced shoot growth. PMID:26873976

  13. Structure of a Plasmodium falciparum PfEMP1 rosetting domain reveals a role for the N-terminal segment in heparin-mediated rosette inhibition

    PubMed Central

    Juillerat, Alexandre; Lewit-Bentley, Anita; Guillotte, Micheline; Gangnard, Stéphane; Hessel, Audrey; Baron, Bruno; Vigan-Womas, Inès; England, Patrick; Mercereau-Puijalon, Odile; Bentley, Graham A.

    2011-01-01

    The human malaria parasite Plasmodium falciparum can cause infected red blood cells (iRBC) to form rosettes with uninfected RBC, a phenotype associated with severe malaria. Rosetting is mediated by a subset of the Plasmodium falciparum membrane protein 1 (PfEMP1) variant adhesins expressed on the infected host-cell surface. Heparin and other sulfated oligosaccharides, however, can disrupt rosettes, suggesting that therapeutic approaches to this form of severe malaria are feasible. We present a structural and functional study of the N-terminal domain of PfEMP1 from the VarO variant comprising the N-terminal segment (NTS) and the first DBL domain (DBL1α1), which is directly implicated in rosetting. We demonstrate that NTS-DBL1α1-VarO binds to RBC and that heparin inhibits this interaction in a dose-dependent manner, thus mimicking heparin-mediated rosette disruption. We have determined the crystal structure of NTS-DBL1α1, showing that NTS, previously thought to be a structurally independent component of PfEMP1, forms an integral part of the DBL1α domain. Using mutagenesis and docking studies, we have located the heparin-binding site, which includes NTS. NTS, unique to the DBL α-class domain, is thus an intrinsic structural and functional component of the N-terminal VarO domain. The specific interaction observed with heparin opens the way for developing antirosetting therapeutic strategies. PMID:21402930

  14. Natural variation in rosette size under salt stress conditions corresponds to developmental differences between Arabidopsis accessions and allelic variation in the LRR-KISS gene

    PubMed Central

    Julkowska, Magdalena M.; Klei, Karlijn; Fokkens, Like; Haring, Michel A.; Schranz, M. Eric; Testerink, Christa

    2016-01-01

    Natural variation among Arabidopsis accessions is an important genetic resource to identify mechanisms underlying plant development and stress tolerance. To evaluate the natural variation in salinity stress tolerance, two large-scale experiments were performed on two populations consisting of 160 Arabidopsis accessions each. Multiple traits, including projected rosette area, and fresh and dry weight were collected as an estimate for salinity tolerance. Our results reveal a correlation between rosette size under salt stress conditions and developmental differences between the accessions grown in control conditions, suggesting that in general larger plants were more salt tolerant. This correlation was less pronounced when plants were grown under severe salt stress conditions. Subsequent genome wide association study (GWAS) revealed associations with novel candidate genes for salinity tolerance such as LRR-KISS (At4g08850), flowering locus KH-domain containing protein and a DUF1639-containing protein. Accessions with high LRR-KISS expression developed larger rosettes under salt stress conditions. Further characterization of allelic variation in candidate genes identified in this study will provide more insight into mechanisms of salt stress tolerance due to enhanced shoot growth. PMID:26873976

  15. A strong loss-of-function mutation in RAN1 results in constitutive activation of the ethylene response pathway as well as a rosette-lethal phenotype

    NASA Technical Reports Server (NTRS)

    Woeste, K. E.; Kieber, J. J.; Evans, M. L. (Principal Investigator)

    2000-01-01

    A recessive mutation was identified that constitutively activated the ethylene response pathway in Arabidopsis and resulted in a rosette-lethal phenotype. Positional cloning of the gene corresponding to this mutation revealed that it was allelic to responsive to antagonist1 (ran1), a mutation that causes seedlings to respond in a positive manner to what is normally a competitive inhibitor of ethylene binding. In contrast to the previously identified ran1-1 and ran1-2 alleles that are morphologically indistinguishable from wild-type plants, this ran1-3 allele results in a rosette-lethal phenotype. The predicted protein encoded by the RAN1 gene is similar to the Wilson and Menkes disease proteins and yeast Ccc2 protein, which are integral membrane cation-transporting P-type ATPases involved in copper trafficking. Genetic epistasis analysis indicated that RAN1 acts upstream of mutations in the ethylene receptor gene family. However, the rosette-lethal phenotype of ran1-3 was not suppressed by ethylene-insensitive mutants, suggesting that this mutation also affects a non-ethylene-dependent pathway regulating cell expansion. The phenotype of ran1-3 mutants is similar to loss-of-function ethylene receptor mutants, suggesting that RAN1 may be required to form functional ethylene receptors. Furthermore, these results suggest that copper is required not only for ethylene binding but also for the signaling function of the ethylene receptors.

  16. Spontaneous sense inversion in helical mesophases

    NASA Astrophysics Data System (ADS)

    Wensink, H. H.

    2014-08-01

    We investigate the pitch sensitivity of chiral nematic phases of helicoidal patchy cylinders as a generic model for chiral (bio-)polymers and helix-shaped colloidal rods. The behaviour of the macroscopic helical pitch is studied from microscopic principles by invoking a simple density functional theory generalised to accommodate weakly twisted director fields. Upon changing the degree of alignment along the local helicoidal director we find that chiral nematic phases exhibit a sudden sense inversion whereby the helical symmetry changes from left- to right-handed and vice versa. Since the local alignment is governed by thermodynamic variables such as density, temperature or the amplitude of an external directional field, such pitch sense inversions can be expected in systems of helical mesogens of both thermotropic and lyotropic origin. We show that the spontaneous change of helical symmetry is a direct consequence of an antagonistic effective torque between helical particles with a certain prescribed internal helicity. The results may help opening up new routes towards precise control of the helical handedness of chiral assemblies by a judicious choice of external control parameters.

  17. Magnetic Helicity in a Cyclic Convective Dynamo

    NASA Astrophysics Data System (ADS)

    Miesch, Mark S.; Zhang, Mei; Augustson, Kyle C.

    2016-05-01

    Magnetic helicity is a fundamental agent for magnetic self-organization in magnetohydrodynamic (MHD) dynamos. As a conserved quantity in ideal MHD, it establishes a strict topological coupling between large and small-scale magnetic fields. The generation of magnetic fields on scales larger than the velocity field is linked to an upscale transfer of magnetic helicity, either locally in spectral space as in the inverse cascade of magnetic helicity in MHD turbulence or non-locally, as in the turbulent alpha-effect of mean-field dynamo theory. Thus, understanding the generation, transport, and dissipation of magnetic helicity is an essential prerequisite to understanding manifestations of magnetic self-organization in the solar dynamo, including sunspots, the prominent dipole and quadrupole moments, and the 22-year magnetic activity cycle. We investigate the role of magnetic helicity in a convective dynamo model that exhibits regular magnetic cycles. The cycle is marked by coherent bands of toroidal field that persist within the convection zone and that are antisymmetric about the equator. When these toriodal bands interact across the equator, it initiates a global restructuring of the magnetic topology that contributes to the reversal of the dipole moment. Thus, the polar field reversals are preceeded by a brief reversal of the subsurface magnetic helicity. There is some evidence that the Sun may exhibit a similar magnetic helicity reversal prior to its polar field reversals.

  18. Magnetic Helicity in Solar Dynamo Simulations

    NASA Astrophysics Data System (ADS)

    Miesch, Mark; Augustson, Kyle C.; Zhang, Mei

    2015-08-01

    Magnetic helicity is a fundamental agent for magnetic self-organization in magnetohydrodynamic (MHD) dynamos. As a conserved quantity in ideal MHD, it establishes a strict topological coupling between large and small-scale magnetic fields. The generation of magnetic fields on scales larger than the velocity field is linked to an upscale transfer of magnetic helicity, either locally in spectral space as in the inverse cascade of magnetic helicity in MHD turbulence or non-locally, as in the turbulent alpha-effect of mean-field dynamo theory. Thus, understanding the generation, transport, and dissipation of magnetic helicity is an essential prerequisite to understanding manifestations of magnetic self-organization in the solar dynamo, including sunspots, the prominent dipole and quadrupole moments, and the 22-year magnetic activity cycle. Yet, despite its significance, magnetic helicity is often neglected in observational and theoretical studies of solar magnetism. This can be attributed to two factors; First, the calculation of the magnetic helicity is not unique; in general it depends on an electromagnetic guage through the magnetic vector potential. Second, unless it is explicitly calculated as part of the computational algorithm in numerical models, it is not always straightforward to obtain the magnetic vector potential. Here we consider gauge-invariant measures of the magnetic helicity and magnetic helicity flux and we describe how they can be computed from measurable quantities such as the magnetic field, the bulk plasma velocity, and the electrical current density. These measures can be applied to local Cartesian geometries as well as global spherical shells. Here we apply them to two global dynamo simulations, each exhibiting regular magnetic cycles. These include a convective MHD dynamo model and a 3-D Babcock-Leighton dynamo model. Both exhibit patterns of magnetic helicity evolution that reflect the global restructuring of the magnetic field over the

  19. Enhanced helical swimming in Boger fluids

    NASA Astrophysics Data System (ADS)

    Godinez, Francisco; Mendez-Rojano, Rodrigo; Zenit, Roberto; Lauga, Eric

    2014-11-01

    We conduct experiments with force-free magnetically-driven helical swimmers in Newtonian and viscoelastic (Boger) fluids. In order assess the effect of viscoelasticity on the swimming performance, we conduct experiments for swimmers with different helical tail geometries. We use helices with the same wave length and total length but vary the angle of the helix. As previously reported by the computational study of Spagniole and collaborators, we found that the swimming performance can either increase, decrease or remain unchanged, depending on the geometry of the tail. With the right geometry, the enhancement can be up to a factor of two.

  20. Helicity oscillations of Dirac and Majorana neutrinos

    NASA Astrophysics Data System (ADS)

    Dobrynina, Alexandra; Kartavtsev, Alexander; Raffelt, Georg

    2016-06-01

    The helicity of a Dirac neutrino with mass m evolves under the influence of a B field because it has a magnetic dipole moment proportional to m . Moreover, it was recently shown that a polarized or anisotropic medium engenders the same effect for both Dirac and Majorana neutrinos. Because a B field polarizes a background medium, it instigates helicity oscillations even for Majorana neutrinos unless the medium is symmetric between matter and antimatter. Motivated by these observations, we review the impact of a B field and of an anisotropic or polarized medium on helicity oscillations for Dirac and Majorana neutrinos from the common perspective of in-medium dispersion.

  1. Steering Chiral Swimmers along Noisy Helical Paths

    NASA Astrophysics Data System (ADS)

    Friedrich, Benjamin M.; Jülicher, Frank

    2009-08-01

    Chemotaxis along helical paths towards a target releasing a chemoattractant is found in sperm cells and many microorganisms. We discuss the stochastic differential geometry of the noisy helical swimming path of a chiral swimmer. A chiral swimmer equipped with a simple feedback system can navigate in a concentration gradient of chemoattractant. We derive an effective equation for the alignment of helical paths with a concentration gradient which is related to the alignment of a dipole in an external field and discuss the chemotaxis index.

  2. Thermally activated helicity reversals of skyrmions

    NASA Astrophysics Data System (ADS)

    Yu, X. Z.; Shibata, K.; Koshibae, W.; Tokunaga, Y.; Kaneko, Y.; Nagai, T.; Kimoto, K.; Taguchi, Y.; Nagaosa, N.; Tokura, Y.

    2016-04-01

    Magnetic bubbles with winding number S =1 are topologically equivalent to skyrmions. Here we report the discovery of helicity (in-plane magnetization-swirling direction) reversal of skyrmions, while keeping their hexagonal lattice form, at above room temperature in a thin hexaferrite magnet. We have observed that the frequency of helicity reversals dramatically increases with temperature in a thermally activated manner, revealing that the generation energy of a kink-soliton pair for switching helicity on a skyrmion rapidly decreases towards the magnetic transition temperature.

  3. Helical flux ropes in solar prominences

    NASA Technical Reports Server (NTRS)

    Martens, P. C. H.; Van Ballegooijen, A. A.

    1990-01-01

    The present numerical method for the computation of force-free, cancelling magnetic structures shows that flux cancellation at the neutral line in a sheared magnetic arcade generates helical field lines that can support a prominence's plasma. With increasing flux cancellation, the axis of the helical fields moves to greater heights; this is suggestive of a prominence eruption. Two alternative scenarios are proposed for the formation of polar crown prominences which yield the correct axial magnetic field sign. Both models are noted to retain the formation of helical flux tubes through flux cancellation as their key feature.

  4. Design and Dynamic Analysis of a Novel Biomimetic Robotics Hip Joint.

    PubMed

    Cui, Bingyan; Chen, Liwen; Wang, Zhijun; Zhao, Yuanhao; Li, Zhanxian; Jin, Zhenlin

    2015-01-01

    In order to increase the workspace and the carrying capacity of biomimetic robotics hip joint, a novel biomimetic robotics hip joint was developed. The biomimetic robotics hip joint is mainly composed of a moving platform, frame, and 3-RRR orthogonal spherical parallel mechanism branched chains, and has the characteristics of compact structure, large bearing capacity, high positioning accuracy, and good controllability. The functions of the biomimetic robotics hip joint are introduced, such as the technical parameters, the structure and the driving mode. The biomimetic robotics hip joint model of the robot is established, the kinematics equation is described, and then the dynamics are analyzed and simulated with ADAMS software. The proposed analysis methodology can be provided a theoretical base for biomimetic robotics hip joint of the servo motor selection and structural design. The designed hip joint can be applied in serial and parallel robots or any other mechanisms. PMID:27018226

  5. Design and Dynamic Analysis of a Novel Biomimetic Robotics Hip Joint

    PubMed Central

    Cui, Bingyan; Chen, Liwen; Wang, Zhijun; Zhao, Yuanhao; Li, Zhanxian; Jin, Zhenlin

    2015-01-01

    In order to increase the workspace and the carrying capacity of biomimetic robotics hip joint, a novel biomimetic robotics hip joint was developed. The biomimetic robotics hip joint is mainly composed of a moving platform, frame, and 3-RRR orthogonal spherical parallel mechanism branched chains, and has the characteristics of compact structure, large bearing capacity, high positioning accuracy, and good controllability. The functions of the biomimetic robotics hip joint are introduced, such as the technical parameters, the structure and the driving mode. The biomimetic robotics hip joint model of the robot is established, the kinematics equation is described, and then the dynamics are analyzed and simulated with ADAMS software. The proposed analysis methodology can be provided a theoretical base for biomimetic robotics hip joint of the servo motor selection and structural design. The designed hip joint can be applied in serial and parallel robots or any other mechanisms. PMID:27018226

  6. On helical vortex motions of moist air

    NASA Astrophysics Data System (ADS)

    Kurgansky, M. V.

    2013-09-01

    Two results that are fundamentally different from what takes place in a dry atmosphere have been obtained for adiabatic motions of unsaturated moist air: (1) the steady helical motion of moist air with collinear velocity and vorticity vectors everywhere is dynamically impossible; (2) the spontaneous amplification (generation) of helicity in a moist air due to baroclinicity is dynamically and thermodynamically feasible. In the absence of helicity flux through the boundary of the domain occupied by air flows, the difference between the values of integral helicity H at time instant t delaying at a small time interval from the initial instant t 0 (at which the instantaneous state of air motion is isomorphic either to a steady Beltrami flow or to an irrotational flow) and the initial value of H increases proportionally to ( t - t 0)4. The nonzero value of the proportionality factor is ensured by the difference in values of the Poisson ratio for dry air and water vapor, respectively.

  7. Passive micromixers with dual helical channels

    NASA Astrophysics Data System (ADS)

    Liu, Keyin; Yang, Qing; Chen, Feng; Zhao, Yulong; Meng, Xiangwei; Shan, Chao; Li, Yanyang

    2015-02-01

    In this study, a three-dimensional (3D) micromixer with cross-linked double helical microchannels is studied to achieve rapid mixing of fluids at low Reynolds numbers (Re). The 3D micromixer takes full advantages of the chaotic advection model with helical microchannels; meanwhile, the proposed crossing structure of double helical microchannels enables two flow patterns of repelling flow and straight flow in the fluids to promote the agitation effect. The complex 3D micromixer is realized by an improved femtosecond laser wet etching (FLWE) technology embedded in fused silica. The mixing results show that cross-linked double helical microchannels can achieve excellent mixing within 3 cycles (300 μm) over a wide range of low Re (1.5×10-3~600), which compare well with the conventional passive micromixers. This highly-effective micromixer is hoped to contribute to the integration of microfluidic systems.

  8. Emergence of helicity in rotating stratified turbulence

    NASA Astrophysics Data System (ADS)

    Marino, Raffaele; Mininni, Pablo D.; Rosenberg, Duane; Pouquet, Annick

    2013-03-01

    We perform numerical simulations of decaying rotating stratified turbulence and show, in the Boussinesq framework, that helicity (velocity-vorticity correlation), as observed in supercell storms and hurricanes, is spontaneously created due to an interplay between buoyancy and rotation common to large-scale atmospheric and oceanic flows. Helicity emerges from the joint action of eddies and of inertia-gravity waves (with inertia and gravity with respective associated frequencies f and N), and it occurs when the waves are sufficiently strong. For N/f<3 the amount of helicity produced is correctly predicted by a quasilinear balance equation. Outside this regime, and up to the highest Reynolds number obtained in this study, namely Re≈10000, helicity production is found to be persistent for N/f as large as ≈17, and for ReFr2 and ReRo2, respectively, as large as ≈100 and ≈24000.

  9. Evolution of helicities in dynamo problems

    NASA Astrophysics Data System (ADS)

    Reshetnyak, M. Yu.

    2015-07-01

    The properties of wavelet spectra of kinetic and magnetic energies, as well as of helicities, are considered by the example of a three-dimensional dynamo model in a rapidly rotating a plane layer and heated from below. It is shown that the transition from the kinematic mode to the full dynamo mode is accompanied by a decrease in the magnetic energy of the system. The hydrodynamic helicity changes its sign by height and has the same sign for all scales. The current and magnetic helicities also have the dipole form of symmetry in the physical space; however, their sign at small and large scales is different—the so-called effect of separation in scales. The cross-helicity has no separation in scales, but it can change the sign with time so that its averaged value is small.

  10. Helical vortices: viscous dynamics and instability

    NASA Astrophysics Data System (ADS)

    Rossi, Maurice; Selcuk, Can; Delbende, Ivan; Ijlra-Upmc Team; Limsi-Cnrs Team

    2014-11-01

    Understanding the dynamical properties of helical vortices is of great importance for numerous applications such as wind turbines, helicopter rotors, ship propellers. Locally these flows often display a helical symmetry: fields are invariant through combined axial translation of distance Δz and rotation of angle θ = Δz / L around the same z-axis, where 2 πL denotes the helix pitch. A DNS code with built-in helical symmetry has been developed in order to compute viscous quasi-steady basic states with one or multiple vortices. These states will be characterized (core structure, ellipticity, ...) as a function of the pitch, without or with an axial flow component. The instability modes growing in the above base flows and their growth rates are investigated by a linearized version of the DNS code coupled to an Arnoldi procedure. This analysis is complemented by a helical thin-cored vortex filaments model. ANR HELIX.

  11. CURRENT HELICITY OF ACTIVE REGIONS AS A TRACER OF LARGE-SCALE SOLAR MAGNETIC HELICITY

    SciTech Connect

    Zhang, H.; Gao, Y.; Xu, H.; Moss, D.; Kleeorin, N.; Rogachevskii, I.; Kuzanyan, K.; Sokoloff, D.

    2012-05-20

    We demonstrate that the current helicity observed in solar active regions traces the magnetic helicity of the large-scale dynamo generated field. We use an advanced two-dimensional mean-field dynamo model with dynamo saturation based on the evolution of the magnetic helicity and algebraic quenching. For comparison, we also studied a more basic two-dimensional mean-field dynamo model with simple algebraic alpha-quenching only. Using these numerical models we obtained butterfly diagrams both for the small-scale current helicity and also for the large-scale magnetic helicity, and compared them with the butterfly diagram for the current helicity in active regions obtained from observations. This comparison shows that the current helicity of active regions, as estimated by -A {center_dot} B evaluated at the depth from which the active region arises, resembles the observational data much better than the small-scale current helicity calculated directly from the helicity evolution equation. Here B and A are, respectively, the dynamo generated mean magnetic field and its vector potential. A theoretical interpretation of these results is given.

  12. Planetary dynamos driven by helical waves - II

    NASA Astrophysics Data System (ADS)

    Davidson, P. A.; Ranjan, A.

    2015-09-01

    In most numerical simulations of the Earth's core the dynamo resides outside the tangent cylinder and may be crudely classified as being of the α2 type. In this region the flow comprises a sea of thin columnar vortices aligned with the rotation axis, taking the form of alternating cyclones and anticyclones. The dynamo is thought to be driven by these columnar vortices within which the flow is observed to be highly helical, helicity being a crucial ingredient of planetary dynamos. As noted in Davidson, one of the mysteries of this dynamo cartoon is the origin of the helicity, which is observed to be positive in the south and negative in the north. While Ekman pumping at the mantle can induce helicity in some of the overly viscous numerical simulations, it is extremely unlikely to be a significant source within planets. In this paper we return to the suggestion of Davidson that the helicity observed in the less viscous simulations owes its existence to helical wave packets, launched in and around the equatorial plane where the buoyancy flux is observed to be strong. Here we show that such wave packets act as a potent source of planetary helicity, constituting a simple, robust mechanism that yields the correct sign for h north and south of the equator. Since such a mechanism does not rely on the presence of a mantle, it can operate within both the Earth and the gas giants. Moreover, our numerical simulations show that helical wave packets dispersing from the equator produce a random sea of thin, columnar cyclone/anticyclone pairs, very like those observed in the more strongly forced dynamo simulations. We examine the local dynamics of helical wave packets dispersing from the equatorial regions, as well as the overall nature of an α2-dynamo driven by such wave packets. Our local analysis predicts the mean emf induced by helical waves, an analysis that rests on a number of simple approximations which are consistent with our numerical experiments, while our global

  13. Spheromak Power and Helicity Balance

    SciTech Connect

    Thomassen, K.I.

    2000-05-18

    This note addresses the division of gun power and helicity between the open line volume and the closed flux surface volume in a steady state flux core spheromak. Our assumptions are that fine scale turbulence maintains each region close to an axisymmetric Taylor state, {mu}{sub o}j = {lambda}B. The gun region that feeds these two volumes surrounded by a flux conserver is shown topologically below. (The actual geometry is toroidal). Flux and current from the magnetized gun flow on open lines around the entire closed surface containing the spheromak. The gun current flows down the potential gradient, the potential difference between the two ends of each line being the gun voltage. Here, the gun voltage excludes the sheath drops at each end. These volumes have different values of {lambda} in each region (open line volume V{sub 1} and closed spheromak volume V{sub 2}) and we want to calculate the efficiency of transferring the gun power to the spheromak to sustain the ohmic loss in steady state.

  14. Evasion of Immunity to Plasmodium falciparum: Rosettes of Blood Group A Impair Recognition of PfEMP1

    PubMed Central

    Moll, Kirsten; Palmkvist, Mia; Ch'ng, Junhong; Kiwuwa, Mpungu Steven; Wahlgren, Mats

    2015-01-01

    The ABO blood group antigens are expressed on erythrocytes but also on endothelial cells, platelets and serum proteins. Notably, the ABO blood group of a malaria patient determines the development of the disease given that blood group O reduces the probability to succumb in severe malaria, compared to individuals of groups A, B or AB. P. falciparum rosetting and sequestration are mediated by PfEMP1, RIFIN and STEVOR, expressed at the surface of the parasitized red blood cell (pRBC). Antibodies to these antigens consequently modify the course of a malaria infection by preventing sequestration and promoting phagocytosis of pRBC. Here we have studied rosetting P. falciparum and present evidence of an immune evasion mechanism not previously recognized. We find the accessibility of antibodies to PfEMP1 at the surface of the pRBC to be reduced when P. falciparum forms rosettes in blood group A RBC, as compared to group O RBC. The pRBC surrounds itself with tightly bound normal RBC that makes PfEMP1 inaccessible to antibodies and clearance by the immune system. Accordingly, pRBC of in vitro cloned P. falciparum devoid of ABO blood group dependent rosetting were equally well detected by anti-PfEMP1 antibodies, independent of the blood group utilized for their propagation. The pathogenic mechanisms underlying the severe forms of malaria may in patients of blood group A depend on the ability of the parasite to mask PfEMP1 from antibody recognition, in so doing evading immune clearance. PMID:26714011

  15. Leaf gas exchange in Espeletia schultzii Wedd, a giant caulescent rosette species, along an altitudinal gradient in the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Rada, Fermin; Azocar, Aura; Gonzalez, Juan; Briceño, Benito

    1998-02-01

    Gas exchange studies along low altitudinal gradients (0-2 500 metres above sea level) suggest an increase in plant CO 2 assimilation with increasing altitude. The question arises however, will this hold true for higher altitudinal ranges? The purpose of this work was to characterize carbon and water relationships in Espeletia schultzii along an extreme altitudinal gradient. Gas exchange characteristics under field conditions during wet and dry seasons were documented for Espeletia schultzii, a giant caulescent rosette species, along an altitudinal gradient (2 950, 3 550 and 4 200 m) in the Venezuelan Andes. Significant differences in CO 2 assimilation rates between seasons were found for all studied sites. Low assimilation rates obtained during the dry season were a consequence of: low leaf conductances to counteract low leaf water potentials and/or high vapour pressure differences between leaf and air, and to high leaf temperatures measured during the dry season. Important differences in A/P i curve parameters were obtained between wet and dry seasons. A decrease in A max was observed for the two lower populations, while a similar value was obtained for both wet and dry seasons at the higher altitude. A decrease in the relation P i/P a and an increase in stomatal limitation and leaf temperature were measured from wet to dry season. There was a differentiation in CO 2 assimilation with increasing altitude. At 2 950 m, maximum rates were above 5 μmol · m -2 · s -1, at 3 550 m 3 μmol · m -2 · s -1, while at 4 200 m maximum CO 2 assimilation rate was below 3 μmol ·m -2 · s -1. This decrease may be explained by: an increase in leaf pubescence, lower leaf conductances and/or lower leaf nitrogen content at higher altitude.

  16. Helical rotary screw expander power system

    NASA Technical Reports Server (NTRS)

    Mckay, R. A.; Sprankle, R. S.

    1974-01-01

    An energy converter for the development of wet steam geothermal fields is described. A project to evaluate and characterize a helical rotary screw expander for geothermal applications is discussed. The helical screw expander is a positive displacement machine which can accept untreated corrosive mineralized water of any quality from a geothermal well. The subjects of corrosion, mineral deposition, the expansion process, and experience with prototype devices are reported.

  17. Studies of Solar Helicity Using Vector Magnetograms

    NASA Technical Reports Server (NTRS)

    Hagyard, Mona J.; Pevstov, Alexei A.

    1999-01-01

    observations of photospheric magnetic fields made with vector magnetographs have been used recently to study solar helicity. In this paper we indicate what can and cannot be derived from vector magnetograms, and point out some potential problems in these data that could affect the calculations of 'helicity'. Among these problems are magnetic saturation, Faraday rotation, low spectral resolution, and the method of resolving the ambiguity in the azimuth.

  18. Bioinspired helical microswimmers based on vascular plants.

    PubMed

    Gao, Wei; Feng, Xiaomiao; Pei, Allen; Kane, Christopher R; Tam, Ryan; Hennessy, Camille; Wang, Joseph

    2014-01-01

    Plant-based bioinspired magnetically propelled helical microswimmers are described. The helical microstructures are derived from spiral water-conducting vessels of different plants, harnessing the intrinsic biological structures of nature. Geometric variables of the spiral vessels, such as the helix diameter and pitch, can be controlled by mechanical stretching for the precise fabrication and consistent performance of helical microswimmers. Xylem vessels of a wide variety of different plants have been evaluated for the consistency and reproducibility of their helical parameters. Sequential deposition of thin Ti and Ni layers directly on the spiral vessels, followed by dicing, leads to an extremely simple and cost-efficient mass-production of functional helical microswimmers. The resulting plant-based magnetic microswimmers display efficient propulsion, with a speed of over 250 μm/s, as well as powerful locomotion in biological media such as human serum. The influence of actuation frequencies on the swimming velocity is investigated. Such use of plant vessels results in significant savings in the processing costs and provides an extremely simple, cost-effective fabrication route for the large-scale production of helical magnetic swimmers. PMID:24283342

  19. The AGS with four helical magnets

    SciTech Connect

    Tsoupas, N.; Huang, H.; MacKay, W.W.; Roser, T.; Trbojevic, D.

    2010-02-25

    The idea of using multiple partial helical magnets was applied successfully to the AGS synchrotron, to preserve the proton beam polarization. In this paper we explore in details the idea of using four helical magnets placed symmetrically in the AGS ring. This modification provides many advantages over the present setup of the AGS that uses two partial helical magnets. First, it provides a larger 'spin tune gap' for the placement of the vertical betatron tune of the AGS during acceleration, second, the vertical spin direction during the beam injection and extraction is closer to vertical, third, the symmetric placement of the snakes allows for a better control of the AGS optics, and for reduced values of the beta and eta functions, especially near injection, fourth, the optical properties of the helical magnets also favor the placement of the horizontal betatron tune in the 'spin tune gap', thus eliminating the horizontal spin resonances. In this paper we provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and we compare these results with the present setup of the AGS that uses two partial helical magnets.

  20. On the helicity of open magnetic fields

    SciTech Connect

    Prior, C.; Yeates, A. R.

    2014-06-01

    We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

  1. Alternative Methods for Field Corrections in Helical Solenoids

    SciTech Connect

    Lopes, M. L.; Krave, S. T.; Tompkins, J. C.; Yonehara, K.; Flanagan, G.; Kahn, S. A.; Melconian, K.

    2015-05-01

    Helical cooling channels have been proposed for highly efficient 6D muon cooling. Helical solenoids produce solenoidal, helical dipole, and helical gradient field components. Previous studies explored the geometric tunability limits on these main field components. In this paper we present two alternative correction schemes, tilting the solenoids and the addition of helical lines, to reduce the required strength of the anti-solenoid and add an additional tuning knob.

  2. Biomimetic, polymer-based microcantilever infrared sensors

    NASA Astrophysics Data System (ADS)

    Mueller, Michael Thomas

    angle to determine the degree of hydrophobicity or hydrophilicity at the chitosan or chitin surface. Chitin in the infrared sensor of Melanophila acuminata functions as a thermomechanical material that has a high coefficient of thermal expansion and strong optical absorption in the infrared due to its chemical composition and organic bonds (absorption which matches its forest fire target). Based on this infrared detection mechanism, the potential exists to develop a broad, novel class of polymer-based, biomimetic infrared sensors having high CTE and spectral absorption tuned to a target of interest. Towards this objective, a photoresist-polysilicon cantilever bimorph prototype was designed, fabricated, and tested. Two types of this device were formed with different readouts; one required an optical readout while the other used a capacitive readout. Devices were characterized using optical and thermal methods. Prototypes were found to suffer from the presence of residual stress which caused significant out-of-plane deflections upon release. Such strain gradients should be minimized (by modifying the thermal processing steps or by annealing) to maximize the capacitive output signal. The optically-interrogated cantilever was observed to bend due to both stimulation with heat and with infrared radiation. The presence of a human finger in the vicinity of the silicon die was sufficient to cause cantilever deflection that was readily observable using optical techniques. The interdigitated cantilever array using capacitive readout was found to be highly sensitive, with a dynamic range >500:1, a peak spectral sensitivity from 600 nm to 1.2 mum, and a threshold sensitivity of 2 muW/cm2.

  3. Computational design of microvascular biomimetic materials

    NASA Astrophysics Data System (ADS)

    Aragon, Alejandro Marcos

    Biomimetic microvascular materials are increasingly considered for a variety of autonomic healing, cooling and sensing applications. The microvascular material of interest in this work consists of a network of hollow microchannels, with diameters as small as 10 mum, embedded in a polymeric matrix. Recent advances in the manufacturing of this new class of materials have allowed for the creation of very complex 2D and 3D structures. The computational design of such network structures, which is the focus of this work, involves a set of particular challenges, including a large number of design variables (e.g., topology of the network, number of diameters to consider and their sizes) that define the network, and a large number of multidisciplinary objective functions and constraints that drive the optimization process. The computational design tool to be developed must be capable of capturing the trade-off between the different objective and constraint functions, as, for example, networks designed for flow efficiency are likely to have a topology that is very different from those designed for structural integrity or thermal control. In this work, we propose to design these materials using Genetic Algorithms (GAs), the most common methodology within a broader category of Evolutionary Algorithms (EAs). GAs can be combined with a Pareto-selection mechanism to create Multi-Objective Genetic Algorithms (MOGAs), which enable the optimization of an arbitrary number of objective functions. As a result, a Pareto-optimal front is obtained, where all candidates are optimal solutions to the optimization problem. Adding a procedure to deal with constraints results in a powerful tool for multi-objective constrained optimization. The method allows the use of discrete variable problems and it does not require any a priori knowledge of the optimal solution. Furthermore, GAs search the entire decision space so the optimal solutions found are likely to be global. The

  4. Special section on biomimetics of movement.

    PubMed

    Carpi, Federico; Erb, Rainer; Jeronimidis, George

    2011-11-29

    Movement in biology is an essential aspect of survival for many organisms, animals and plants. Implementing movement efficiently to meet specific needs is a key attribute of natural living systems, and can provide ideas for man-made developments. If we had to find a subtitle able to essentially convey the aim of this special section, it could read as follows: 'taking inspiration from nature for new materials, actuators, structures and controls for systems that move'. Our world is characterized by a huge variety of technical, engineering systems that move. They surround us in countless products that integrate actuators for different kinds of purposes. Basically, any kind of mechatronic system, such as those used for consumer products, machines, vehicles, industrial systems, robots, etc, is based on one or more devices that move, according to different implementations and motion ranges, often in response to external and internal stimuli. Despite this, technical solutions to develop systems that move do not evolve very quickly as they rely on traditional and well consolidated actuation technologies, which are implemented according to known architectures and with established materials. This fact limits our capability to overcome challenges related to the needs continuously raised by new fields of application, either at small or at large scales. Biomimetics-based approaches may provide innovative thinking and technologies in the field, taking inspiration from nature for smart and effective solutions. In an effort to disseminate current advances in this field, this special section collects some papers that cover different topics. A brief synopsis of the content of each contribution is presented below. The first paper, by Lienhard et al [1], deals with bioinspiration for the realization of structural parts in systems that passively move. It presents a bioinspired hingeless flapping mechanism, considered as a solution to the kinematics of deployable systems for

  5. A unified convention for biological assemblies with helical symmetry

    SciTech Connect

    Tsai, Chung-Jung; Nussinov, Ruth

    2011-08-01

    A new representation of helical structure by four parameters, [n{sub 1}, n{sub 2}, twist, rise], is able to generate an entire helical construct from asymmetric units, including cases of helical assembly with a seam. Assemblies with helical symmetry can be conveniently formulated in many distinct ways. Here, a new convention is presented which unifies the two most commonly used helical systems for generating helical assemblies from asymmetric units determined by X-ray fibre diffraction and EM imaging. A helical assembly is viewed as being composed of identical repetitive units in a one- or two-dimensional lattice, named 1-D and 2-D helical systems, respectively. The unification suggests that a new helical description with only four parameters [n{sub 1}, n{sub 2}, twist, rise], which is called the augmented 1-D helical system, can generate the complete set of helical arrangements, including coverage of helical discontinuities (seams). A unified four-parameter characterization implies similar parameters for similar assemblies, can eliminate errors in reproducing structures of helical assemblies and facilitates the generation of polymorphic ensembles from helical atomic models or EM density maps. Further, guidelines are provided for such a unique description that reflects the structural signature of an assembly, as well as rules for manipulating the helical symmetry presentation.

  6. Tetracycline-loaded biomimetic apatite: an adsorption study.

    PubMed

    Cazalbou, Sophie; Bertrand, Ghislaine; Drouet, Christophe

    2015-02-19

    Biomimetic apatites are appealing compounds for the elaboration of bioactive bone-repair scaffolds due to their intrinsic similarity to bone mineral. Bone surgeries are however often heavy procedures, and the infiltration of pathogens may not be totally avoided. To prevent their development, systemic antibiotic prophylaxis is widespread but does not specifically target surgical sites and involves doses not always optimized. A relevant alternative is a preliminary functionalization by an infection-fighting agent. In this work, we investigated from a physicochemical viewpoint the association of a wide-spectrum antibiotic, tetracycline (TC), and a biomimetic nanocrystalline apatite previously characterized. TC adsorption kinetics and isotherm were thoroughly explored. Kinetic data were fitted to various models (pseudo-first-order, pseudo-second-order, general kinetic model of order n, Elovich, double-exponential, and purely diffusive models). The best fit was found for a double-exponential kinetic model or with a decimal reaction order of 1.4, highlighting a complex process with such TC molecules which do not expose high-affinity end groups for the surface of apatite. The adsorption isotherm was perfectly fitted to the Sips (Langmuir-Freundlich) model, while other models failed to describe it, and the Sips exponent greater than unity (1.08) suggested a joint impact of surface heterogeneity and positive cooperativity between adsorbed molecules. Finally, preliminary insights on TC release from pelletized nanocrystalline apatite, in aqueous medium and neutral pH, were obtained using a recirculation cell, indicating a release profile mainly following a Higuchi-like diffusion-limited rate. This work is intended to shed more light on the interaction between polar molecules not exhibiting high-affinity end groups and biomimetic apatites and is a starting point in view of the elaboration of biomimetic apatite-based bone scaffolds functionalized with polar organic drugs for a

  7. UV photofunctionalization promotes nano-biomimetic apatite deposition on titanium

    PubMed Central

    Saita, Makiko; Ikeda, Takayuki; Yamada, Masahiro; Kimoto, Katsuhiko; Lee, Masaichi Chang-Il; Ogawa, Takahiro

    2016-01-01

    Background Although biomimetic apatite coating is a promising way to provide titanium with osteoconductivity, the efficiency and quality of deposition is often poor. Most titanium implants have microscale surface morphology, and an addition of nanoscale features while preserving the micromorphology may provide further biological benefit. Here, we examined the effect of ultraviolet (UV) light treatment of titanium, or photofunctionalization, on the efficacy of biomimetic apatite deposition on titanium and its biological capability. Methods and results Micro-roughed titanium disks were prepared by acid-etching with sulfuric acid. Micro-roughened disks with or without photofunctionalization (20-minute exposure to UV light) were immersed in simulated body fluid (SBF) for 1 or 5 days. Photofunctionalized titanium disks were superhydrophilic and did not form surface air bubbles when immersed in SBF, whereas non-photofunctionalized disks were hydrophobic and largely covered with air bubbles during immersion. An apatite-related signal was observed by X-ray diffraction on photofunctionalized titanium after 1 day of SBF immersion, which was equivalent to the one observed after 5 days of immersion of control titanium. Scanning electron microscopy revealed nodular apatite deposition in the valleys and at the inclines of micro-roughened structures without affecting the existing micro-configuration. Micro-roughened titanium and apatite-deposited titanium surfaces had similar roughness values. The attachment, spreading, settling, proliferation, and alkaline phosphate activity of bone marrow-derived osteoblasts were promoted on apatite-coated titanium with photofunctionalization. Conclusion UV-photofunctionalization of titanium enabled faster deposition of nanoscale biomimetic apatite, resulting in the improved biological capability compared to the similarly prepared apatite-deposited titanium without photofunctionalization. Photofunctionalization-assisted biomimetic apatite

  8. The influence of helical background fields on current helicity and electromotive force of magnetoconvection

    NASA Astrophysics Data System (ADS)

    Rüdiger, G.; Küker, M.

    2016-07-01

    Motivated by the empirical finding that the known hemispheric rules for the current helicity at the solar surface are not strict, we demonstrate the excitation of small-scale current helicity by the influence of large-scale helical magnetic background fields on nonrotating magnetoconvection. This is shown within a quasilinear analytic theory of driven turbulence and by nonlinear simulations of magnetoconvection that the resulting small-scale current helicity has the same sign as the large-scale current helicity, while the ratio of both pseudoscalars is of the order of the magnetic Reynolds number of the convection. The same models do not provide finite values of the small-scale kinetic helicity. On the other hand, a turbulence-induced electromotive force is produced including the diamagnetic pumping term, as well as the eddy diffusivity but, however, no α effect. It has thus been argued that the relations for the simultaneous existence of small-scale current helicity and α effect do not hold for the model of nonrotating magnetoconvection under consideration. Calculations for various values of the magnetic Prandtl number demonstrate that, for the considered diffusivities, the current helicity increases for growing magnetic Reynolds number, which is not true for the velocity of the diamagnetic pumping, which is in agreement with the results of the quasilinear analytical approximation.

  9. Ceramic adhesive restorations and biomimetic dentistry: tissue preservation and adhesion.

    PubMed

    Tirlet, Gil; Crescenzo, Hélène; Crescenzo, Dider; Bazos, Panaghiotis

    2014-01-01

    Thanks to sophisticated adhesive techniques in contemporary dentistry, and the development of composite and ceramic materials, it is possible to reproduce a biomimetic match between substitution materials and natural teeth substrates. Biomimetics or bio-emulation allows for the association of two fundamental parameters at the heart of current therapeutic treatments: tissue preservation and adhesion. This contemporary concept makes the retention of the integrity of the maximum amount of dental tissue possible, while offering exceptional clinical longevity, and maximum esthetic results. It permits the conservation of the biological, esthetic, biomechanical and functional properties of enamel and dentin. Today, it is clearly possible to develop preparations allowing for the conservation of the enamel and dentin in order to bond partial restorations in the anterior and posterior sectors therefore limiting, as Professor Urs Belser from Geneva indicates, "the replacement of previous deficient crowns and devitalized teeth whose conservation are justified but whose residual structural state are insufficient for reliable bonding."1 This article not only addresses ceramic adhesive restoration in the anterior area, the ambassadors of biomimetic dentistry, but also highlights the possibility of occasionally integrating one or two restorations at the heart of the smile as a complement to extensive rehabilitations that require more invasive treatment. PMID:25126616

  10. Methods for biomimetic remineralization of human dentine: a systematic review.

    PubMed

    Cao, Chris Ying; Mei, May Lei; Li, Quan-Li; Lo, Edward Chin Man; Chu, Chun Hung

    2015-01-01

    This study aimed to review the laboratory methods on biomimetic remineralization of demineralized human dentine. A systematic search of the publications in the PubMed, TRIP, and Web of Science databases was performed. Titles and abstracts of initially identified publications were screened. Clinical trials, reviews, non-English articles, resin-dentine interface studies, hybrid layer studies, hybrid scaffolds studies, and irrelevant studies were excluded. The remaining papers were retrieved with full texts. Manual screening was conducted on the bibliographies of remaining papers to identify relevant articles. A total of 716 studies were found, and 690 were excluded after initial screening. Two articles were identified from the bibliographies of the remaining papers. After retrieving the full text, 23 were included in this systematic review. Sixteen studies used analogues to mimic the functions of non-collagenous proteins in biomineralization of dentine, and four studies used bioactive materials to induce apatite formation on demineralized dentine surface. One study used zinc as a bioactive element, one study used polydopamine, and another study constructed an agarose hydrogel system for biomimetic mineralization of dentine. Many studies reported success in biomimetic mineralization of dentine, including the use of non-collagenous protein analogues, bioactive materials, or elements and agarose hydrogel system. PMID:25739078

  11. Methods for Biomimetic Remineralization of Human Dentine: A Systematic Review

    PubMed Central

    Cao, Chris Ying; Mei, May Lei; Li, Quan-Li; Lo, Edward Chin Man; Chu, Chun Hung

    2015-01-01

    This study aimed to review the laboratory methods on biomimetic remineralization of demineralized human dentine. A systematic search of the publications in the PubMed, TRIP, and Web of Science databases was performed. Titles and abstracts of initially identified publications were screened. Clinical trials, reviews, non-English articles, resin-dentine interface studies, hybrid layer studies, hybrid scaffolds studies, and irrelevant studies were excluded. The remaining papers were retrieved with full texts. Manual screening was conducted on the bibliographies of remaining papers to identify relevant articles. A total of 716 studies were found, and 690 were excluded after initial screening. Two articles were identified from the bibliographies of the remaining papers. After retrieving the full text, 23 were included in this systematic review. Sixteen studies used analogues to mimic the functions of non-collagenous proteins in biomineralization of dentine, and four studies used bioactive materials to induce apatite formation on demineralized dentine surface. One study used zinc as a bioactive element, one study used polydopamine, and another study constructed an agarose hydrogel system for biomimetic mineralization of dentine. Many studies reported success in biomimetic mineralization of dentine, including the use of non-collagenous protein analogues, bioactive materials, or elements and agarose hydrogel system. PMID:25739078

  12. Direct laser writing: biomimetic photonics and superresolution nanolithography

    NASA Astrophysics Data System (ADS)

    Gu, Min

    2014-03-01

    Biomimetic photonics is inspired by nature's ability to self-assemble complex nanostructured materials with superior properties to that of conventional materials. Biomimetic engineering of novel nanophotonic devices has led to optical nano-fountains, artificial compound eyes and optical gas sensors. Direct laser writing (DLW) is a powerful tool toward the development of ultimate three-dimensional (3D) biomimetic photonic devices. Here we demonstrate the fabrication (DWL) of a novel class of 3D photonic microstructures inspired by a recent finding in butterfly wing-scales and show that these nano-engineered 3D gyroid structures have the ability to redirect circularly polarized light as a chiral beamsplitter. Because of the increasing demand for realising nanogeometries, the diffraction-limited resolution associated with DLW, should be overcomed to access to the nanoscale. We will report on our recent progress on optical beam nanolithography by using the superresolution photoinduction-inhibited nanolithography (SPIN) technique. The smallest feature size of 9 nm for free-standing lines has been demonstrated.

  13. Strategies in biomimetic surface engineering of nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Gong, Yong-Kuan; Winnik, Françoise M.

    2012-01-01

    Engineered nanoparticles (NPs) play an increasingly important role in biomedical sciences and in nanomedicine. Yet, in spite of significant advances, it remains difficult to construct drug-loaded NPs with precisely defined therapeutic effects, in terms of release time and spatial targeting. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Upon injection in the blood stream or following oral administation, NPs have to bypass numerous barriers prior to reaching their intended target. A particularly successful design strategy consists in masking the NP to the biological environment by covering it with an outer surface mimicking the composition and functionality of the cell's external membrane. This review describes this biomimetic approach. First, we outline key features of the composition and function of the cell membrane. Then, we present recent developments in the fabrication of molecules that mimic biomolecules present on the cell membrane, such as proteins, peptides, and carbohydrates. We present effective strategies to link such bioactive molecules to the NPs surface and we highlight the power of this approach by presenting some exciting examples of biomimetically engineered NPs useful for multimodal diagnostics and for target-specific drug/gene delivery applications. Finally, critical directions for future research and applications of biomimetic NPs are suggested to the readers.

  14. ENDOXY - Development of a Biomimetic Oxygenator-Test-Device

    PubMed Central

    Dietrich, Maren; Finocchiaro, Nicole; Olszweski, Sebastian; Arens, Jutta; Schmitz-Rode, Thomas; Sachweh, Joerg; Jockenhoevel, Stefan; Cornelissen, Christian G.

    2015-01-01

    Objective This study focusses on the development of a biomimetic oxygenator test device. Due to limited biocompatibility, current oxygenators do not allow mid- to long-term therapy. Tissue engineering uses autologous cell sources to overcome the immunogenic barriers of biomaterials. Surface coating with endothelial cells might improve hemocompatibility and thus prevent immunogenic reactions of the body. In this study this concept is applied to endothelialise a gas-permeable membrane to develop a biomimetic oxygenator test-device (ENDOXY). Methods ENDOXY—a multifunctional test-system was developed to endothelialise a gas-permeable membrane suitable for cell culture and to test the cell retention under shear stress and to measure gas transfer through it. Results Successful endothelialisation of the membrane was achieved and cells showed characteristic endothelial morphologies. They stained positive for endothelial markers. The number of cells aligned with shear stress and cell retention after blood perfusing experiments was high. Gas transfer is observed via uncoated and endothelialised membranes. Conclusion The study showed promising results with regard to system design, endothelialisation, and cell retention under shear stress conditions. It strongly encourages further research into the system by testing different membrane materials to design a biomimetic membrane surface and pave way for a fully hemocompatible oxygenator. PMID:26682907

  15. Aloe vera Induced Biomimetic Assemblage of Nucleobase into Nanosized Particles

    PubMed Central

    Chauhan, Arun; Zubair, Swaleha; Sherwani, Asif; Owais, Mohammad

    2012-01-01

    Aim Biomimetic nano-assembly formation offers a convenient and bio friendly approach to fabricate complex structures from simple components with sub-nanometer precision. Recently, biomimetic (employing microorganism/plants) synthesis of metal and inorganic materials nano-particles has emerged as a simple and viable strategy. In the present study, we have extended biological synthesis of nano-particles to organic molecules, namely the anticancer agent 5-fluorouracil (5-FU), using Aloe vera leaf extract. Methodology The 5-FU nano- particles synthesized by using Aloe vera leaf extract were characterized by UV, FT-IR and fluorescence spectroscopic techniques. The size and shape of the synthesized nanoparticles were determined by TEM, while crystalline nature of 5-FU particles was established by X-ray diffraction study. The cytotoxic effects of 5-FU nanoparticles were assessed against HT-29 and Caco-2 (human adenocarcinoma colorectal) cell lines. Results Transmission electron microscopy and atomic force microscopic techniques confirmed nano-size of the synthesized particles. Importantly, the nano-assembled 5-FU retained its anticancer action against various cancerous cell lines. Conclusion In the present study, we have explored the potential of biomimetic synthesis of nanoparticles employing organic molecules with the hope that such developments will be helpful to introduce novel nano-particle formulations that will not only be more effective but would also be devoid of nano-particle associated putative toxicity constraints. PMID:22403622

  16. Enhanced Osteogenicity of Bioactive Composites with Biomimetic Treatment

    PubMed Central

    Meretoja, Ville V.; Tirri, Teemu; Seppälä, Jukka V.; Närhi, Timo O.

    2014-01-01

    Purpose. This study aimed to explore if initiation of biomimetic apatite nucleation can be used to enhance osteoblast response to biodegradable tissue regeneration composite membranes. Materials and Methods. Bioactive thermoplastic composites consisting of poly(ε-caprolactone/DL-lactide) and bioactive glass (BAG) were prepared at different stages of biomimetic calcium phosphate deposition by immersion in simulated body fluid (SBF). The modulation of the BAG dissolution and the osteogenic response of rat mesenchymal stem cells (MSCs) were analyzed. Results. SBF treatment resulted in a gradual calcium phosphate deposition on the composites and decreased BAG reactivity in the subsequent cell cultures. Untreated composites and composites covered by thick calcium phosphate layer (14 days in SBF) expedited MSC mineralization in comparison to neat polymers without BAG, whereas other osteogenic markers—alkaline phosphatase activity, bone sialoprotein, and osteocalcin expression—were initially decreased. In contrast, surfaces with only small calcium phosphate aggregates (five days in SBF) had similar early response than neat polymers but still demonstrated enhanced mineralization. Conclusion. A short biomimetic treatment enhances osteoblast response to bioactive composite membranes. PMID:24812608

  17. Evaluation of helicity generation in the tropical storm Gonu

    NASA Astrophysics Data System (ADS)

    Farahani, Majid M.; Khansalari, Sakineh; Azadi, Majid

    2016-06-01

    Helicity is a valuable dynamical concept for the study of rotating flows. Consequently helicity flux, indicative of the source or sink of helicity, owns comparable importance. In this study, while reviewing the existing methods, a mathematical relation between helicity and helicity-flux is introduced, discussed and examined. The computed values of helicity and helicity fluxes in an actual case, using the classical and this proposed method are compared. The down-stream helicity flux including sources and sinks of helicity is considered for the tropical storm Gonu that occurred over the coasts of Oman and Iran on June 2-7, 2007. Results show that the buoyancy, through the upper troposphere down to a height within boundary layer, is the main source in producing helicity, and surface friction from earth surface up to a height within boundary layer, is the main dissipating element of helicity. The dominance of buoyancy forcing over the dissipative friction forcing results in generation of vortex or enhancement of it after bouncing the land. Furthermore, the increase (decrease) of helicity results in an increase (decrease) in the height of the level in which maximum helicity flux occurs. It is suggested that the maximum helicity flux occurs at the top of the turbulent boundary layer, so that the height of boundary layer could be obtained.

  18. Replication and encapsidation of the viroid-like satellite RNA of lucerne transient streak virus are supported in divergent hosts by cocksfoot mottle virus and turnip rosette virus.

    PubMed

    Sehgal, O P; Sinha, R C; Gellatly, D L; Ivanov, I; AbouHaidar, M G

    1993-04-01

    Cocksfoot mottle sobemovirus supports replication and encapsidation of the viroid-like satellite RNA (sat-RNA) of lucerne transient streak virus (LTSV) in two monocotyledonous species, Triticum aestivum and Dactylis glomerata. Additionally, LTSV sat-RNA replicates effectively in the presence of turnip rosette sobemovirus in Brassica rapa, Raphanus raphanistrum and Sinapsis arvensis, but not in Thlaspi arvense or Nicotiana bigelovii, indicating that host species markedly influence this interaction. Previous reports of the association between LTSV sat-RNA and helper sobemoviruses were limited to dicotyledonous hosts. Our results demonstrate that the biological interaction between these two entities spans divergent dicotyledonous and monocotyledonous species. PMID:7682254

  19. Antialiasing backprojection for helical MDCT.

    PubMed

    Mori, I

    2008-03-01

    Helical CTs are well known to suffer from aliasing artifacts because of their finite longitudinal sampling pitch. The artifact pattern is typically strong streaks from bone edges in clinical images. Especially in the case of multidetector row CT, the artifact resulting from longitudinal aliasing is often called a windmill artifact because the visible streaks form a windmill pattern when the object is of a particular shape. The scan must be performed using a very thin slice thickness, i.e., fine sampling in the longitudinal direction, with a longer scan time to mitigate this aliasing artifact. Some elaborate longitudinal interpolation methods to remediate longitudinal aliasing have been proposed, but they have not been successful in practice despite their theoretical importance. A periodic swing of the focal spot in the longitudinal direction, a so-called z-flying focal spot, was introduced recently to achieve finer sampling. Although it is a useful technique, some important deficiencies exist: It is sufficiently effective only near the isocenter and is difficult to apply to a scan using a thick slice thickness, even though longitudinal aliasing is more serious at the thicker scan. In this paper, the author addresses the nature of interlaced (or unequally spaced) sampling and derives a new principle of data treatment that can suppress the aliased spectra selectively. According to this principle, the common practice of image reconstruction, which backprojects data along the original sampling ray path, is never the best choice. The author proposes a new scheme of backprojection, which involves the longitudinal shift of projection data. A proper choice of longitudinal shift for backprojection provides effective and selective suppression of aliased spectra, with retention of the original frequency spectrum depending on the level of focus swing. With this shifted backprojection, the swing of focus can be made much smaller than for a conventional z-flying focal spot. The

  20. Working member of a helical downhole motor for drilling wells

    SciTech Connect

    Kochnev, A.M.; Vshivkov, A.N.; Goldobin, V.B.

    1993-06-22

    A working member of a helical downhole motor is described for drilling wells comprising: separate tubular sections having helical teeth arranged in succession and interconnected by connecting elements, each connecting element having the form of a ring, rigidly secured at the tubular sections and having helical teeth of a pitch and a direction equal to a pitch and a direction, respectively, of the helical teeth of the tubular sections, whereas a profile of the helical teeth of the ring is equidistant to a profile of the helical teeth of the sections.

  1. Biomimetically inspired short access to the 2-aminoimidazole-fused tetracyclic core of (+/-)-dibromoagelaspongin.

    PubMed

    Picon, Sylvain; Tran, Huu Dau Elise; Martin, Marie-Thérèse; Retailleau, Pascal; Zaparucha, Anne; Al-Mourabit, Ali

    2009-06-18

    A six-step synthesis of the tetracyclic core of the natural compound (+/-)-dibromoagelaspongin, isolated from Agelas sp. Sponge, was achieved from the commercially available 5-aminopentan-1-ol, 2-trichloroacetylpyrrole, and 2-aminopyrimidine. Following a biomimetic inspired approach, successive oxidative reactions including the final DMDO biomimetic oxidation gave the interesting triaminomethane-fused core. PMID:19445491

  2. A future of living machines?: International trends and prospects in biomimetic and biohybrid systems

    NASA Astrophysics Data System (ADS)

    Prescott, Tony J.; Lepora, Nathan; Vershure, Paul F. M. J.

    2014-03-01

    Research in the fields of biomimetic and biohybrid systems is developing at an accelerating rate. Biomimetics can be understood as the development of new technologies using principles abstracted from the study of biological systems, however, biomimetics can also be viewed from an alternate perspective as an important methodology for improving our understanding of the world we live in and of ourselves as biological organisms. A biohybrid entity comprises at least one artificial (engineered) component combined with a biological one. With technologies such as microscale mobile computing, prosthetics and implants, humankind is moving towards a more biohybrid future in which biomimetics helps us to engineer biocompatible technologies. This paper reviews recent progress in the development of biomimetic and biohybrid systems focusing particularly on technologies that emulate living organisms—living machines. Based on our recent bibliographic analysis [1] we examine how biomimetics is already creating life-like robots and identify some key unresolved challenges that constitute bottlenecks for the field. Drawing on our recent research in biomimetic mammalian robots, including humanoids, we review the future prospects for such machines and consider some of their likely impacts on society, including the existential risk of creating artifacts with significant autonomy that could come to match or exceed humankind in intelligence. We conclude that living machines are more likely to be a benefit than a threat but that we should also ensure that progress in biomimetics and biohybrid systems is made with broad societal consent.

  3. S-duality and helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Colwell, Kitran; Terning, John

    2016-03-01

    We examine interacting Abelian theories at low energies and show that holomorphically normalized photon helicity amplitudes transform into dual amplitudes under SL(2, {Z} ) as modular forms with weights that depend on the number of positive and negative helicity photons and on the number of internal photon lines. Moreover, canonically normalized helicity amplitudes transform by a phase, so that even though the amplitudes are not duality invariant, their squares are duality invariant. We explicitly verify the duality transformation at one loop by comparing the amplitudes in the case of an electron and the dyon that is its SL(2, {Z} ) image, and extend the invariance of squared amplitudes order by order in perturbation theory. We demonstrate that S-duality is a property of all low-energy effective Abelian theories with electric and/or magnetic charges and see how the duality generically breaks down at high energies.

  4. Heat Loss by Helicity Injection II

    SciTech Connect

    Fowler, T K

    2006-04-25

    Arguments are reviewed showing that helicity transport always flattens the temperature profile, yielding unit current amplification in SSPX and flat temperature profiles in RFP's whenever the dynamo is active. The argument is based on transport theory yielding a hyper-resistivity {Lambda} {approx} (c{sup 2}/{omega}{sub pc}{sup 2}){chi}{sub c} with electron thermal diffusivity {chi}{sub c}, valid for any process producing a random-walk in electron constants of motion in the unperturbed field. The theory could be tested by deriving {Lambda} from helicity transport in SSPX, by analogy with recent analysis yielding {chi}{sub c} from heat transport. If the predicted ratio {Lambda}/{chi}{sub c} is confirmed, efforts to increase current amplification in SSPX must be based on scenario scenarios consistent with slow helicity transport compared to heat s transport (pulsed reactor, multipulse, neutral beam injection).

  5. Single-superfield helical-phase inflation

    NASA Astrophysics Data System (ADS)

    Ketov, Sergei V.; Terada, Takahiro

    2016-01-01

    Large-field inflation in supergravity requires the approximate global symmetry needed to protect flatness of the scalar potential. In helical-phase inflation, the U(1) symmetry of the Kähler potential is assumed, the phase part of the complex scalar of a chiral superfield plays the role of inflaton, and the radial part is strongly stabilized. The original model of helical phase inflation, proposed by Li, Li and Nanopoulos (LLN), employs an extra (stabilizer) superfield. We propose a more economical new class of the helical phase inflationary models without a stabilizer superfield. As the specific examples, the quadratic, the natural, and the Starobinsky-type inflationary models are studied in our approach.

  6. Demonstration of steady inductive helicity injection

    NASA Astrophysics Data System (ADS)

    Sieck, P. E.; Jarboe, T. R.; Izzo, V. A.; Hamp, W. T.; Nelson, B. A.; O'Neill, R. G.; Redd, A. J.; Smith, R. J.

    2006-02-01

    Initial results demonstrating the concept of constant inductive helicity injection are presented. Constant helicity injection is achieved using two oscillating inductive helicity injectors, with the goal of producing a bow tie spheromak. Each injector is a 180° segment of a reverse field pinch and they are driven 90° out of phase. Approximately 5 MW of power is injected during the 6 ms pulse, and the input power has been maintained at a fairly constant value by directly fuelling the injectors with neutral gas. Motivation for the experiment is given, including beta-limit calculations for the bow tie spheromak. Fuelling the injectors with neutral gas during the discharge is shown to produce injector parameters that are more constant in time. A series of discharges with increasing power input shows a promising increase in toroidal current. Unique construction techniques of the experiment are also described.

  7. Helical motion of chiral liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takaki; Sano, Masaki

    Artificial swimmers have been intensively studied to understand the mechanism of the locomotion and collective behaviors of cells and microorganisms. Among them, most of the artificial swimmers are designed to move along the straight path. However, in biological systems, chiral dynamics such as circular and helical motion are quite common because of the chirality of their bodies, which are made of chiral biomolecules. To understand the role of the chirality in the physics of microswimmers, we designed chiral artificial swimmers and the theoretical model for the chiral motion. We found that chiral liquid crystal droplets, when dispersed in surfactant solutions, swim in the helical path induced by the Marangoni effect. We will discuss the mechanism of the helical motion with our phenomenological model. This work is supported by Grant-in-Aid for JSPS Fellows (Grant No. 26.9814), and MEXT KAKENHI Grant No. 25103004.

  8. Structural Transition from Helices to Hemihelices

    PubMed Central

    Su, Tianxiang; Bertoldi, Katia; Clarke, David R.

    2014-01-01

    Helices are amongst the most common structures in nature and in some cases, such as tethered plant tendrils, a more complex but related shape, the hemihelix forms. In its simplest form it consists of two helices of opposite chirality joined by a perversion. A recent, simple experiment using elastomer strips reveals that hemihelices with multiple reversals of chirality can also occur, a richness not anticipated by existing analyses. Here, we show through analysis and experiments that the transition from a helical to a hemihelical shape, as well as the number of perversions, depends on the height to width ratio of the strip's cross-section. Our findings provides the basis for the deterministic manufacture of a variety of complex three-dimensional shapes from flat strips. PMID:24759785

  9. Helicity and singular structures in fluid dynamics

    PubMed Central

    Moffatt, H. Keith

    2014-01-01

    Helicity is, like energy, a quadratic invariant of the Euler equations of ideal fluid flow, although, unlike energy, it is not sign definite. In physical terms, it represents the degree of linkage of the vortex lines of a flow, conserved when conditions are such that these vortex lines are frozen in the fluid. Some basic properties of helicity are reviewed, with particular reference to (i) its crucial role in the dynamo excitation of magnetic fields in cosmic systems; (ii) its bearing on the existence of Euler flows of arbitrarily complex streamline topology; (iii) the constraining role of the analogous magnetic helicity in the determination of stable knotted minimum-energy magnetostatic structures; and (iv) its role in depleting nonlinearity in the Navier-Stokes equations, with implications for the coherent structures and energy cascade of turbulence. In a final section, some singular phenomena in low Reynolds number flows are briefly described. PMID:24520175

  10. Primordial magnetic helicity from stochastic electric currents

    NASA Astrophysics Data System (ADS)

    Calzetta, Esteban; Kandus, Alejandra

    2014-04-01

    We study the possibility that primordial magnetic fields generated in the transition between inflation and reheating posses magnetic helicity, HM. The fields are induced by stochastic currents of scalar charged particles created during the mentioned transition. We estimate the rms value of the induced magnetic helicity by computing different four-point scalar quantum electrodynamics Feynman diagrams. For any considered volume, the magnetic flux across its boundaries is in principle not null, which means that the magnetic helicity in those regions is gauge dependent. We use the prescription given by Berger and Field and interpret our result as the difference between two magnetic configurations that coincide in the exterior volume. In this case, the magnetic helicity gives only the number of magnetic links inside the considered volume. We calculate a concrete value of HM for large scales and analyze the distribution of magnetic defects as a function of the scale. Those defects correspond to regular as well as random fields in the considered volume. We find that the fractal dimension of the distribution of topological defects is D=1/2. We also study if the regular fields induced on large scales are helical, finding that they are and that the associated number of magnetic defects is independent of the scale. In this case, the fractal dimension is D=0. We finally estimate the intensity of fields induced at the horizon scale of reheating and evolve them until the decoupling of matter and radiation under the hypothesis of the inverse cascade of magnetic helicity. The resulting intensity is high enough and the coherence length long enough to have an impact on the subsequent process of structure formation.

  11. Au nanorod helical superstructures with designed chirality.

    PubMed

    Lan, Xiang; Lu, Xuxing; Shen, Chenqi; Ke, Yonggang; Ni, Weihai; Wang, Qiangbin

    2015-01-14

    A great challenge for nanotechnology is to controllably organize anisotropic nanomaterials into well-defined three-dimensional superstructures with customized properties. Here we successfully constructed anisotropic Au nanorod (AuNR) helical superstructures (helices) with tailored chirality in a programmable manner. By designing the 'X' pattern of the arrangement of DNA capturing strands (15nt) on both sides of a two-dimensional DNA origami template, AuNRs functionalized with the complementary DNA sequences were positioned on the origami and were assembled into AuNR helices with the origami intercalated between neighboring AuNRs. Left-handed (LH) and right-handed (RH) AuNR helices were conveniently accomplished by solely tuning the mirrored-symmetric 'X' patterns of capturing strands on the origami. The inter-rod distance was precisely defined as 14 nm and inter-rod angle as 45°, thus a full helix contains 9 AuNRs with its length up to about 220 nm. By changing the AuNR/origami molar ratio in the assembly system, the average number of AuNR in the helices was tuned from 2 to 4 and 9. Intense chiroptical activities arose from the longest AuNR helices with a maximum anisotropy factor of ∼0.02, which is highly comparable to the reported macroscopic AuNR assemblies. We expect that our strategy of origami templated assembly of anisotropic chiral superstructures would inspire the bottom-up fabrication of optically active nanostructures and shed light on a variety of applications, such as chiral fluids, chiral signal amplification, and fluorescence combined chiral spectroscopy. PMID:25516475

  12. Two-impurity helical Majorana problem

    NASA Astrophysics Data System (ADS)

    Eriksson, Erik; Zazunov, Alex; Sodano, Pasquale; Egger, Reinhold

    2015-02-01

    We predict experimentally accessible signatures for helical Majorana fermions in a topological superconductor by coupling to two quantum dots in the local moment regime (corresponding to spin-1 /2 impurities). Taking into account Ruderman-Kittel-Kasuya-Yosida interactions mediated by bulk and edge modes, where the latter cause a long-range antiferromagnetic Ising coupling, we formulate and solve the low-energy theory for this two-impurity helical Majorana problem. In particular, we show that the long-time spin dynamics after a magnetic field quench displays weakly damped oscillations with universal quality factor.

  13. The effect of a rosette-crown fly, Botanophila turcica, on growth,biomass allocation and reproduction of the thistle Carthamus lanatus

    NASA Astrophysics Data System (ADS)

    Sheppard, Andrew W.; Vitou, Janine

    2000-12-01

    Plant growth and reproductive output of the winter annual invasive thistle, Carthamus lanatus was characterised in relation to plant size in three native populations in southern France. The effects of the rosette-crown feeding fly Botanophila turcica on these plant characteristics were assessed by comparing unattacked with naturally attacked plants at each site and by a field experiment. Indirect effects of B. turcica on plant seed production were also compared with direct seed loss caused by a guild of capitulum-feeding insects that incidentally attacked the marked plants at these sites. C. lanatus showed no size or weight requirement for flowering, but larger flowering plants produced less total receptacle surface and less seed production (female reproductive potential) in proportion to plant weight than smaller flowering plants. B. turcica did not select hosts on the basis of size or density. B. turcica reduced plant relative growth rate (RGR) in all situations, but attacked plants compensated fully at two of three sites as attack failed to halt rosette growth. Attacked plants suffered 12 % mortality, and 71 % lower seed production than unattacked plants at the site with the lowest RGR. This corresponded to 9 % lower seed production for the whole thistle population compared to 8.6-19.5 % direct seed loss to capitulum insects across all sites.

  14. ARF6 promotes the formation of Rac1 and WAVE-dependent ventral F-actin rosettes in breast cancer cells in response to epidermal growth factor.

    PubMed

    Marchesin, Valentina; Montagnac, Guillaume; Chavrier, Philippe

    2015-01-01

    Coordination between actin cytoskeleton assembly and localized polarization of intracellular trafficking routes is crucial for cancer cell migration. ARF6 has been implicated in the endocytic recycling of surface receptors and membrane components and in actin cytoskeleton remodeling. Here we show that overexpression of an ARF6 fast-cycling mutant in MDA-MB-231 breast cancer-derived cells to mimick ARF6 hyperactivation observed in invasive breast tumors induced a striking rearrangement of the actin cytoskeleton at the ventral cell surface. This phenotype consisted in the formation of dynamic actin-based podosome rosette-like structures expanding outward as wave positive for F-actin and actin cytoskeleton regulatory components including cortactin, Arp2/3 and SCAR/WAVE complexes and upstream Rac1 regulator. Ventral rosette-like structures were similarly induced in MDA-MB-231 cells in response to epidermal growth factor (EGF) stimulation and to Rac1 hyperactivation. In addition, interference with ARF6 expression attenuated activation and plasma membrane targeting of Rac1 in response to EGF treatment. Our data suggest a role for ARF6 in linking EGF-receptor signaling to Rac1 recruitment and activation at the plasma membrane to promote breast cancer cell directed migration. PMID:25799492

  15. WVD2 and WDL1 modulate helical organ growth and anisotropic cell expansion in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Yuen, Christen Y L.; Pearlman, Rebecca S.; Silo-Suh, Laura; Hilson, Pierre; Carroll, Kathleen L.; Masson, Patrick H.

    2003-01-01

    Wild-type Arabidopsis roots develop a wavy pattern of growth on tilted agar surfaces. For many Arabidopsis ecotypes, roots also grow askew on such surfaces, typically slanting to the right of the gravity vector. We identified a mutant, wvd2-1, that displays suppressed root waving and leftward root slanting under these conditions. These phenotypes arise from transcriptional activation of the novel WAVE-DAMPENED2 (WVD2) gene by the cauliflower mosaic virus 35S promoter in mutant plants. Seedlings overexpressing WVD2 exhibit constitutive right-handed helical growth in both roots and etiolated hypocotyls, whereas the petioles of WVD2-overexpressing rosette leaves exhibit left-handed twisting. Moreover, the anisotropic expansion of cells is impaired, resulting in the formation of shorter and stockier organs. In roots, the phenotype is accompanied by a change in the arrangement of cortical microtubules within peripheral cap cells and cells at the basal end of the elongation zone. WVD2 transcripts are detectable by reverse transcriptase-polymerase chain reaction in multiple organs of wild-type plants. Its predicted gene product contains a conserved region named "KLEEK," which is found only in plant proteins. The Arabidopsis genome possesses seven other genes predicted to encode KLEEK-containing products. Overexpression of one of these genes, WVD2-LIKE 1, which encodes a protein with regions of similarity to WVD2 extending beyond the KLEEK domain, results in phenotypes that are highly similar to wvd2-1. Silencing of WVD2 and its paralogs results in enhanced root skewing in the wild-type direction. Our observations suggest that at least two members of this gene family may modulate both rotational polarity and anisotropic cell expansion during organ growth.

  16. The effect of cytochalasin B and vinca alkaloids on EA- and EAC-rosette formation and on the binding of heat-aggregated human IgG by human lymphocytes

    PubMed Central

    Gutierrez, Carmen; Papamichail, M.; Faulk, W. Page

    1976-01-01

    We report the effect of cytochalasin B and vinca alkaloids on EA- and EAC-rosette formation and on the binding of heat-aggregated human IgG by human lymphocytes. Cytochalasin B inhibits EA- but not EAC-rosette formation, and neither colchicine nor vinblastine have a measurable effect on either reaction. Also, cytochalasin B inhibits the binding of heat-aggregated IgG by human lymphocytes. The inhibition caused by cytochalasin B is reversible, and the cells recover to normal values within 30 min.

  17. QCD Evolution of Helicity and Transversity TMDs

    SciTech Connect

    Prokudin, Alexei

    2014-01-01

    We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.

  18. Theory of helical electron beams in gyrotrons

    SciTech Connect

    Kuftin, A.N.; Lygin, V.K.; Manuilov, V.N.; Raisky, B.V.; Solujanova, E.A.; Tsimring, S.E.

    1993-04-01

    Helical electron beams (HEB) with disturbed axial symmetry of currents density and HEB with locking electrons in magnetic trap are described. The theory of magnetron injection gun (MIG) in space-charge limited current is developed. Systems on permanent magnets forming HEB are considered. 30 refs., 12 figs., 5 tabs.

  19. Dynamics of helical states in MST

    NASA Astrophysics Data System (ADS)

    Munaretto, Stefano; Auriemma, F.; Brower, D.; Chapman, B. E.; den Hartog, D. J.; Ding, W. X.; Duff, J.; Franz, P.; Goetz, J. A.; Holly, D.; Lin, L.; McCollam, K. J.; McGarry, M.; Morton, L.; Nornberg, M. D.; Parke, E.; Sarff, J. S.

    2014-10-01

    The thermal and the magnetic dynamics of quasi-single-helicity (QSH) plasmas evolve independently during the formation and sustainment of the core helical structure. At higher plasma current (and Lundquist number) MST plasmas transition from an axisymmetric multi-helicity state to a QSH state characterized by a strong core helical mode and reduced secondary mode amplitudes. Plasmas in the QSH state tend to wall-lock, often in an orientation that is unfavorable for optimized measurements of the 3D structure using MST's advanced diagnostics. Recently a technique to control the locking position through an applied resonant magnetic perturbation has been developed. Using this technique it is possible to adjust the 3D phase more optimally for specific diagnostics, to study the dynamics of the QSH structure and thermal features. The multi-chord FIR interferometer shows the presence of a density structure for the duration of the QSH state. Measurements of the time evolution of the electron temperature profile using the Thomson Scattering diagnostic reveal that the transition to QSH allows the presence of a 3D thermal structure, but this structure is intermittent. Understanding the mechanism(s) driving these dynamics is the goal of this work. Work supported by the US DOE and NSF.

  20. Deformation of flexible micro helices under flow

    NASA Astrophysics Data System (ADS)

    Daieff, Marine; Lindner, Anke; Du Roure, Olivia; Morozov, Alexander; Pham, Jonathan; Crosby, Alfred

    The interaction of small helices with fluids is important because of its relevance to both fundamental science and technological applications, such as swimming microrobots or microflow sensors. Helically shaped flagella are also exploited by swimming microorganisms to move through their surrounding fluids. Here we study experimentally the deformation of flexible helical ribbons under flow in a microfluidic channel. The size of the helix is typically microscale for the diameter and nanoscale for the thickness. We focus on two different aspects: the overall shape of the helix and the viscous frictional properties. The frictional coefficients determined by our experiments are consistent with calculated values in the context of resistive force theory. Deformation of helices by viscous flow is well-described by non-linear finite extensibility. Due to the non-uniform distribution of the pitch under distributed loading, we identify both linear and nonlinear behavior along the contour length of a single helix. Utilizing our system, we explore the impact of non-Newtonian fluid properties on the mechanics of helix-fluid interactions.

  1. Vibration of thin, tensioned, helically wrapped plates

    NASA Astrophysics Data System (ADS)

    Lopez, Ernesto; Müftü, Sinan

    2011-02-01

    Free vibration analysis of a thin tensioned plate, wrapped around a cylindrical guide in a helical manner is presented. The system is a model of a thin, flexible web wrapped around a turn-bar. The equation of motion of the wrapped plate is derived by using the energy method and with the Kirchhoff-Love assumptions. The weak form of the equation of motion was obtained by the finite element method and the eigenvalue problem was solved numerically. The effects of parameters such as plate tension, guide radius, longitudinal and helical wrap angles, plate width, and the lengths of the non-wrapped segments were investigated. Eigenmodes with same mode numbers were observed in symmetric and anti-symmetric fashion about the center of the plate, for symmetrically wrapped plates. It was shown that the plate/shell boundary of the wrapped plate effectively acts like a support. For non-helically wrapped plates the free edges cause a frequency clustering of the lateral modes about the dominant longitudinal mode. The frequency clustering diminishes when helical wrap is introduced.

  2. Bunch Coalescing in a Helical Channel

    SciTech Connect

    Neuffer, D.V.; Yonehara, K.; Ankenbrandt, C.M.; Yoshikawa, C.Y.; /MUONS Inc., Batavia

    2012-05-01

    A high-luminosity Muon Collider requires bunch recombination for optimal luminosity. In this paper, we take advantage of the large slip factor attainable in a helical transport channel (HTC) to coalesce bunches of muons into a single one over a shorter distance than can be achieved over a straight channel.

  3. Filament Channel Formation by Helicity Condensation

    NASA Astrophysics Data System (ADS)

    Knizhnik, K. J.; Antiochos, S. K.; DeVore, C.

    2013-12-01

    A major unexplained feature of the solar atmosphere is the accumulation of magnetic shear, in the form of filament channels, at photospheric polarity inversion lines (PILs). In addition to free energy, this shear also represents magnetic helicity, which is conserved under reconnection. Consequently, the observations raise the question: Why is helicity observed to be concentrated along PILs? Preliminary results of 3D MHD simulations using the Adaptively Refined MHD Solver (ARMS) are presented that support the magnetic-helicity condensation model of filament-channel formation (Antiochos 2013). In this work, we address the problem of filament-channel formation by considering supergranular twisting of a quasi-potential flux system, bounded by a PIL and containing a coronal hole (CH). The magnetic helicity injected by small-scale photospheric motions is shown to inverse-cascade up to the largest allowable scales that define the closed flux system: the PIL and the CH boundary. This, in effect, produces field lines that are both sheared and smooth and, in agreement with Antiochos (2013), are sheared in opposite senses at the PIL and the CH. We present a detailed analysis of our simulation results and discuss their implications for observations.

  4. Muon Beam Helical Cooling Channel Design

    SciTech Connect

    Johnson, Rolland; Ankenbrandt, Charles; Flanagan, G; Kazakevich, G M; Marhauser, Frank; Neubauer, Michael; Roberts, T; Yoshikawa, C; Derbenev, Yaroslav; Morozov, Vasiliy; Kashikhin, V S; Lopes, Mattlock; Tollestrup, A; Yonehara, Katsuya; Zloblin, A

    2013-06-01

    The Helical Cooling Channel (HCC) achieves effective ionization cooling of the six-dimensional (6d) phase space of a muon beam by means of a series of 21st century inventions. In the HCC, hydrogen-pressurized RF cavities enable high RF gradients in strong external magnetic fields. The theory of the HCC, which requires a magnetic field with solenoid, helical dipole, and helical quadrupole components, demonstrates that dispersion in the gaseous hydrogen energy absorber provides effective emittance exchange to enable longitudinal ionization cooling. The 10-year development of a practical implementation of a muon-beam cooling device has involved a series of technical innovations and experiments that imply that an HCC of less than 300 m length can cool the 6d emittance of a muon beam by six orders of magnitude. We describe the design and construction plans for a prototype HCC module based on oxygen-doped hydrogen-pressurized RF cavities that are loaded with dielectric, fed by magnetrons, and operate in a superconducting helical solenoid magnet.

  5. Phase diagram of two interacting helical states

    NASA Astrophysics Data System (ADS)

    Santos, Raul A.; Gutman, D. B.; Carr, Sam T.

    2016-06-01

    We consider two coupled time-reversal-invariant helical edge modes of the same helicity, such as would occur on two stacked quantum spin Hall insulators. In the presence of interaction, the low-energy physics is described by two collective modes, one corresponding to the total current flowing around the edge and the other one describing relative fluctuations between the two edges. We find that quite generically, the relative mode becomes gapped at low temperatures, but only when tunneling between the two helical modes is nonzero. There are two distinct possibilities for the gapped state depending on the relative size of different interactions. If the intraedge interaction is stronger than the interedge interaction, the state is characterized as a spin-nematic phase. However, in the opposite limit, when the interaction between the helical edge modes is strong compared to the interaction within each mode, a spin-density wave forms, with emergent topological properties. First, the gap protects the conducting phase against localization by weak nonmagnetic impurities; second, the protected phase hosts localized zero modes on the ends of the edge that may be created by sufficiently strong nonmagnetic impurities.

  6. Helically corrugated circular waveguides as antenna feeders

    NASA Astrophysics Data System (ADS)

    Jecko, F.; Papiernik, A.

    1983-07-01

    Rotation of the plane of polarization of the TE(11)-mode is predicted and observed in a helically corrugated circular waveguide. Rotation is suppressed by a longitudinal deformation produced on the corrugation. This modified structure can be used as an antenna feeder with low losses.

  7. Exabyte helical scan devices at Fermilab

    SciTech Connect

    Constanta-Fanourakis, P.; Kaczar, K.; Oleynik, G.; Petravick, D.; Votava, M.; White, V.; Hockney, G.; Bracker, S.; de Miranda, J.M.

    1989-05-01

    Exabyte 8mm helical scan storage devices are in use at Fermilab in a number of applications. These devices have the functionality of magnetic tape, but use media which is much more economical and much more dense than conventional 9 track tape. 6 refs., 3 figs.

  8. Magnetic stripes and skyrmions with helicity reversals.

    PubMed

    Yu, Xiuzhen; Mostovoy, Maxim; Tokunaga, Yusuke; Zhang, Weizhu; Kimoto, Koji; Matsui, Yoshio; Kaneko, Yoshio; Nagaosa, Naoto; Tokura, Yoshinori

    2012-06-01

    It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion--a nano-sized bundle of noncoplanar spins--that by virtue of its nontrivial topology acts as a flux of magnetic field on spin-polarized electrons. Lorentz transmission electron microscopy recently emerged as a powerful tool for direct visualization of skyrmions in noncentrosymmetric helimagnets. Topologically, skyrmions are equivalent to magnetic bubbles (cylindrical domains) in ferromagnetic thin films, which were extensively explored in the 1970s for data storage applications. In this study we use Lorentz microscopy to image magnetic domain patterns in the prototypical magnetic oxide-M-type hexaferrite with a hint of scandium. Surprisingly, we find that the magnetic bubbles and stripes in the hexaferrite have a much more complex structure than the skyrmions and spirals in helimagnets, which we associate with the new degree of freedom--helicity (or vector spin chirality) describing the direction of spin rotation across the domain walls. We observe numerous random reversals of helicity in the stripe domain state. Random helicity of cylindrical domain walls coexists with the positional order of magnetic bubbles in a triangular lattice. Most unexpectedly, we observe regular helicity reversals inside skyrmions with an unusual multiple-ring structure. PMID:22615354

  9. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, A.; Boozer, A.H.

    1984-03-06

    The present invention generates stellarator fields having favorable properties (magnetic well and large rotational transform) by a simple coil system consisting only of unlinked planar non-circular coils. At large rotational transform toroidal effects on magnetic well and rotational transform are small and can be ignored. We do so herein, specializing in straight helical systems.

  10. Chiral transport of neutrinos in supernovae: Neutrino-induced fluid helicity and helical plasma instability

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki

    2016-03-01

    Chirality of neutrinos modifies the conventional kinetic theory and hydrodynamics, leading to unusual chiral transport related to quantum anomalies in field theory. We argue that these corrections have new phenomenological consequences for hot and dense neutrino gases, especially in core-collapse supernovae. We find that the neutrino density can be converted to the fluid helicity through the chiral vortical effect. This fluid helicity effectively acts as a chiral chemical potential for electrons via the momentum exchange with neutrinos and induces a "helical plasma instability" that generates a strong helical magnetic field. This provides a new mechanism for converting the gravitational energy released by the core collapse to the electromagnetic energy and potentially explains the origin of magnetars. The other possible applications of the neutrino chiral transport theory are also discussed.

  11. PREFACE: Symposium 13: Ceramics for Medicine, Biotechnology and Biomimetics

    NASA Astrophysics Data System (ADS)

    Ohtsuki, Chikara

    2011-10-01

    Preface to Symposium 13 (Ceramics for Medicine, Biotechnology and Biomimetics) of the International Congress on Ceramics III, 14-18 November 2010, Osaka, Japan Ceramic materials are now widely used in biomedical fields, such as applications of artificial bones, joints and teeth. The high potential of ceramics to exhibit biological functionality is expected to produce novel materials supporting biotechnology. These applications are governed by the interactions of materials and biological molecules. So far, 'bioceramics' is a type of biomaterial used for repairing damaged tissues. The orthopaedic application of bioceramics has advanced rapidly since the invention of Bioglass® that was found to encourage direct bonding with living bone. Hydroxyapatite and calcium phosphate ceramics are now popular bioceramics for use in artificial bones. While the bone-bonding behavior of materials was understood phenomenologically, very little has been known about the mechanism of either hard or soft tissue attachment or tissue growth on ceramic-based materials, such as glasses, glass-ceramics, ceramic composites and organic-inorganic hybrids. This symposium discussed the scientific understanding of the interface between biomedical materials and soft/hard tissues, and the design and construction of nanoscopic interfaces. It also involved establishment of biomimetic structures, characterization of natural life-related hard and soft tissues, and their formation mechanisms for a wide range of applications in biotechnology through 45 oral presentations including 5 invited lectures and 45 posters. I wish to express my sincere appreciation to the organizers of this symposium in the ICC3 conference. I am also grateful to the invited speakers, all the participants and organizing committee of the ICC3. It is my great pleasure that this proceedings could be published as the fruit of this symposium's achievement, which includes the contributions in all aspect of scientific understanding and

  12. A Novel Soft Biomimetic Microrobot with Two Motion Attitudes

    PubMed Central

    Shi, Liwei; Guo, Shuxiang; Li, Maoxun; Mao, Shilian; Xiao, Nan; Gao, Baofeng; Song, Zhibin; Asaka, Kinji

    2012-01-01

    A variety of microrobots have commonly been used in the fields of biomedical engineering and underwater operations during the last few years. Thanks to their compact structure, low driving power, and simple control systems, microrobots can complete a variety of underwater tasks, even in limited spaces. To accomplish our objectives, we previously designed several bio-inspired underwater microrobots with compact structure, flexibility, and multi-functionality, using ionic polymer metal composite (IPMC) actuators. To implement high-position precision for IPMC legs, in the present research, we proposed an electromechanical model of an IPMC actuator and analysed the deformation and actuating force of an equivalent IPMC cantilever beam, which could be used to design biomimetic legs, fingers, or fins for an underwater microrobot. We then evaluated the tip displacement of an IPMC actuator experimentally. The experimental deflections fit the theoretical values very well when the driving frequency was larger than 1 Hz. To realise the necessary multi-functionality for adapting to complex underwater environments, we introduced a walking biomimetic microrobot with two kinds of motion attitudes: a lying state and a standing state. The microrobot uses eleven IPMC actuators to move and two shape memory alloy (SMA) actuators to change its motion attitude. In the lying state, the microrobot implements stick-insect-inspired walking/rotating motion, fish-like swimming motion, horizontal grasping motion, and floating motion. In the standing state, it implements inchworm-inspired crawling motion in two horizontal directions and grasping motion in the vertical direction. We constructed a prototype of this biomimetic microrobot and evaluated its walking, rotating, and floating speeds experimentally. The experimental results indicated that the robot could attain a maximum walking speed of 3.6 mm/s, a maximum rotational speed of 9°/s, and a maximum floating speed of 7.14 mm/s. Obstacle

  13. Biomimetics and Tubercles on Flippers for Hydrodynamic Flow Control

    NASA Astrophysics Data System (ADS)

    Fish, Frank E.

    2011-11-01

    The biomimetic approach seeks to incorporate designs based on biological organisms into engineered technologies. Biomimetics can be used to engineer machines that emulate the performance of organisms, particularly in instances where the organism's performance exceeds current mechanical technology or provides new directions to solve existing problems. The ability to control the flow of water around the body dictates the performance of marine mammals in the aquatic environment. Morphological specializations of marine mammals afford mechanisms for passive flow control. Aside from the design of the body, which minimizes drag, the morphology of the appendages provide hydrodynamic advantages with respect to drag, lift, thrust, and stall. Of particular interest are the pectoral flippers of the humpback whale (Megaptera novaeangliae). These flippers act as wing-like structures to provide hydrodynamic lift for maneuvering. The use of any such wing-like structure in making small radius turns to enhance both agility and maneuverability is constrained by performance associated with stall. Delay of stall can be accomplished passively by modification of the flipper leading edge. The design of the flippers includes prominent leading edge bumps or tubercles. Such a design is exhibited by the leading edge tubercles on the flippers of humpback whales. These novel morphological structures induce a spanwise flow field of separated vortices alternating with regions of accelerated flow. The coupled flow regions maintain areas of attached flow and delay stall to high angles of attack. The morphological features of humpback whales for flow control can be utilized in the biomimetic design of engineered structures and commercial products for increased hydrodynamic performance. Nature retains a store of untouched knowledge, which would be beneficial in advancing technology.

  14. A novel soft biomimetic microrobot with two motion attitudes.

    PubMed

    Shi, Liwei; Guo, Shuxiang; Li, Maoxun; Mao, Shilian; Xiao, Nan; Gao, Baofeng; Song, Zhibin; Asaka, Kinji

    2012-01-01

     A variety of microrobots have commonly been used in the fields of biomedical engineering and underwater operations during the last few years. Thanks to their compact structure, low driving power, and simple control systems, microrobots can complete a variety of underwater tasks, even in limited spaces. To accomplish our objectives, we previously designed several bio-inspired underwater microrobots with compact structure, flexibility, and multi-functionality, using ionic polymer metal composite (IPMC) actuators. To implement high-position precision for IPMC legs, in the present research, we proposed an electromechanical model of an IPMC actuator and analysed the deformation and actuating force of an equivalent IPMC cantilever beam, which could be used to design biomimetic legs, fingers, or fins for an underwater microrobot. We then evaluated the tip displacement of an IPMC actuator experimentally. The experimental deflections fit the theoretical values very well when the driving frequency was larger than 1 Hz. To realise the necessary multi-functionality for adapting to complex underwater environments, we introduced a walking biomimetic microrobot with two kinds of motion attitudes: a lying state and a standing state. The microrobot uses eleven IPMC actuators to move and two shape memory alloy (SMA) actuators to change its motion attitude. In the lying state, the microrobot implements stick-insect-inspired walking/rotating motion, fish-like swimming motion, horizontal grasping motion, and floating motion. In the standing state, it implements inchworm-inspired crawling motion in two horizontal directions and grasping motion in the vertical direction. We constructed a prototype of this biomimetic microrobot and evaluated its walking, rotating, and floating speeds experimentally. The experimental results indicated that the robot could attain a maximum walking speed of 3.6 mm/s, a maximum rotational speed of 9°/s, and a maximum floating speed of 7.14 mm/s. Obstacle

  15. Touch stimulated pulse generation in biomimetic single-layer graphene

    NASA Astrophysics Data System (ADS)

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-01

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour.Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac

  16. Multiwalled carbon nanotube reinforced biomimetic bundled gel fibres.

    PubMed

    Kim, Young-Jin; Yamamoto, Seiichiro; Takahashi, Haruko; Sasaki, Naruo; Matsunaga, Yukiko T

    2016-08-19

    This work describes the fabrication and characterization of hydroxypropyl cellulose (HPC)-based biomimetic bundled gel fibres. The bundled gel fibres were reinforced with multiwalled carbon nanotubes (MWCNTs). A phase-separated aqueous solution with MWCNT and HPC was transformed into a bundled fibrous structure after being injected into a co-flow microfluidic device and applying the sheath flow. The resulting MWCNT-bundled gel fibres consist of multiple parallel microfibres. The mechanical and electrical properties of MWCNT-bundled gel fibres were improved and their potential for tissue engineering applications as a cell scaffold was demonstrated. PMID:27200527

  17. Biomimetic surface patterning for long-term transmembrane access

    PubMed Central

    VanDersarl, Jules J.; Renaud, Philippe

    2016-01-01

    Here we present a planar patch clamp chip based on biomimetic cell membrane fusion. This architecture uses nanometer length-scale surface patterning to replicate the structure and function of membrane proteins, creating a gigaohm seal between the cell and a planar electrode array. The seal is generated passively during cell spreading, without the application of a vacuum to the cell surface. This interface can enable cell-attached and whole-cell recordings that are stable to 72 hours, and generates no visible damage to the cell. The electrodes can be very small (<5 μm) and closely packed, offering a high density platform for cellular measurement. PMID:27577519

  18. Polycyclic Polyprenylated Xanthones from Symphonia globulifera: Isolation and Biomimetic Electrosynthesis.

    PubMed

    Cottet, Kevin; Neudörffer, Anne; Kritsanida, Marina; Michel, Sylvie; Lallemand, Marie-Christine; Largeron, Martine

    2015-08-28

    Two regioisomeric polycyclic xanthones, 3,16-oxyguttiferone A (2) and 1,16-oxyguttiferone A (3), which are polyprenylated acylphloroglucinol-derived analogues, were isolated from the seeds of Symphonia globulifera, together with their presumed o-dihydroxybenzoyl precursor, guttiferone A (1). Anodic oxidation of 1 into the corresponding o-quinone species proved to be an efficient biomimetic method to generate xanthones 2 and 3 in high overall yield and to confirm their structures. Both compounds displayed cytotoxicity against the HCT 116 colon carcinoma cell line with IC₅₀ values of 8 and 3 μM, respectively. PMID:26221771

  19. Biomimetic Approaches to Control Soluble Concentration Gradients in Biomaterials

    PubMed Central

    Nguyen, Eric H.; Schwartz, Michael P.

    2013-01-01

    Soluble concentration gradients play a critical role in controlling tissue formation during embryonic development. The importance of soluble signaling in biology has motivated engineers to design systems that allow precise and quantitative manipulation of gradient formation in vitro. Engineering techniques have increasingly moved to the third dimension in order to provide more physiologically relevant models to study the biological role of gradient formation and to guide strategies for controlling new tissue formation for therapeutic applications. This review provides an overview of efforts to design biomimetic strategies for soluble gradient formation, with a focus on microfluidic techniques and biomaterials approaches for moving gradient generation to the third dimension. PMID:21265021

  20. Biomimetic surface patterning for long-term transmembrane access.

    PubMed

    VanDersarl, Jules J; Renaud, Philippe

    2016-01-01

    Here we present a planar patch clamp chip based on biomimetic cell membrane fusion. This architecture uses nanometer length-scale surface patterning to replicate the structure and function of membrane proteins, creating a gigaohm seal between the cell and a planar electrode array. The seal is generated passively during cell spreading, without the application of a vacuum to the cell surface. This interface can enable cell-attached and whole-cell recordings that are stable to 72 hours, and generates no visible damage to the cell. The electrodes can be very small (<5 μm) and closely packed, offering a high density platform for cellular measurement. PMID:27577519

  1. Membrane Assembly Driven by a Biomimetic Coupling Reaction

    PubMed Central

    Budin, Itay; Devaraj, Neal K.

    2012-01-01

    One of the major goals of synthetic biology is the development of non-natural cellular systems. In this work we describe a catalytic biomimetic coupling reaction capable of driving the de novo self-assembly of phospholipid membranes. Our system features a copper catalyzed azide-alkyne cycloaddition that results in the formation of a triazole containing phospholipid analog. Concomitant assembly of membranes occurs spontaneously, not requiring preexisting membranes to house catalysts or precursors. The substitution of efficient synthetic reactions for key biochemical processes may offer a general route toward synthetic biological systems. PMID:22239722

  2. Advances in modelling of biomimetic fluid flow at different scales

    PubMed Central

    2011-01-01

    The biomimetic flow at different scales has been discussed at length. The need of looking into the biological surfaces and morphologies and both geometrical and physical similarities to imitate the technological products and processes has been emphasized. The complex fluid flow and heat transfer problems, the fluid-interface and the physics involved at multiscale and macro-, meso-, micro- and nano-scales have been discussed. The flow and heat transfer simulation is done by various CFD solvers including Navier-Stokes and energy equations, lattice Boltzmann method and molecular dynamics method. Combined continuum-molecular dynamics method is also reviewed. PMID:21711847

  3. A Biomimetic Modular Polymer with Tough and Adaptive Properties

    PubMed Central

    Kushner, Aaron M.; Vossler, John; Williams, Gregory A.; Guan, Zhibin

    2009-01-01

    Natural materials employ many elegant strategies to achieve mechanical properties required for survival under varying environmental conditions. Thus these remarkable biopolymers and nanocomposites often not only have a combination of mechanical properties such as high modulus, toughness, and elasticity, but also exhibit adaptive and stimuli-responsive properties. Inspired by skeletal muscle protein titin, we have synthesized a biomimetic modular polymer that not only closely mimics the modular multi-domain structure of titin, but also manifests an exciting combination of mechanical properties, as well as adaptive properties such as self-healing and temperature-responsive shape-memory properties. PMID:19505144

  4. Biomimetic optical directional microphone with structurally coupled diaphragms

    NASA Astrophysics Data System (ADS)

    Liu, H. J.; Yu, M.; Zhang, X. M.

    2008-12-01

    A biomimetic directional microphone based on structurally coupled diaphragms and a fiber-optic detection system is presented. The microphone design aims to mimic the fly Ormia Ochracea's ear structure and capture its performance. Experiments show that the designed microphone amplifies the interaural time difference (ITD) by 4.4 times and has a directional sensitivity of 6.5 μs/deg. An important finding is that one needs to utilize both the rocking and translational vibration modes to obtain the appropriate ITD amplification without sacrifice of directional sensitivity. This work can serve as a foundation for realizing fly-ear inspired miniature directional microphones.

  5. Selective Change Driven Imaging: A Biomimetic Visual Sensing Strategy

    PubMed Central

    Boluda, Jose A.; Zuccarello, Pedro; Pardo, Fernando; Vegara, Francisco

    2011-01-01

    Selective Change Driven (SCD) Vision is a biologically inspired strategy for acquiring, transmitting and processing images that significantly speeds up image sensing. SCD vision is based on a new CMOS image sensor which delivers, ordered by the absolute magnitude of its change, the pixels that have changed after the last time they were read out. Moreover, the traditional full frame processing hardware and programming methodology has to be changed, as a part of this biomimetic approach, to a new processing paradigm based on pixel processing in a data flow manner, instead of full frame image processing. PMID:22346684

  6. Biomimetic on-a-chip platforms for studying cancer metastasis

    PubMed Central

    Lee, Esak; Song, H-H Greco; Chen, Christopher S

    2016-01-01

    Cancer metastasis is a multi-step, secondary tumor formation that is responsible for the vast majority of deaths in cancer patients. Animal models have served as one of the major tools for studying metastatic diseases. However, these metastasis models inherently lack the ability to decouple many of the key parameters that might contribute to cancer progression, and therefore ultimately limit detailed, mechanistic investigation of metastasis. Recently, organ-on-a-chip model systems have been developed for various tissue types with the potential to recapitulate major components of metastasis. Here, we discuss recent advances in in vitro biomimetic on-a-chip models for cancer metastasis.

  7. Acoustic beam control in biomimetic projector via velocity gradient

    NASA Astrophysics Data System (ADS)

    Gao, Xiaowei; Zhang, Yu; Cao, Wenwu; Dong, Erqian; Song, Zhongchang; Li, Songhai; Tang, Liguo; Zhang, Sai

    2016-07-01

    A biomimetic projector (BioP) based on computerized tomography of pygmy sperm whale's biosonar system has been designed using gradient-index (GRIN) material. The directivity of this BioP device was investigated as function of frequency and the velocity gradient of the GRIN material. A strong beam control over a broad bandwidth at the subwavelength scale has been achieved. Compared with a bare subwavelength source, the main lobe pressure of the BioP is about five times as high and the angular resolution is one order of magnitude better. Our results indicate that this BioP has excellent application potential in miniaturized underwater sonars.

  8. The Effects of Spatial Smoothing on Solar Magnetic Helicity and the Hemispheric Helicity Sign Rule

    NASA Astrophysics Data System (ADS)

    Koch Ocker, Stella; Petrie, Gordon

    2016-05-01

    The hemispheric sign rule for solar magnetic helicity, which states that negative/positive helicity occurs preferentially in the northern/southern hemisphere, provides clues to the causes of twisted, flaring magnetic fields. However, previous studies on the hemisphere rule may have been significantly affected by seeing from atmospheric turbulent motions. Using Hinode/SOT-SP data spanning from 2006 to 2012, we studied the effects of two important data processing steps that imitate the effects of atmospheric seeing: noise reduction by ignoring pixel values that are weaker than the estimated noise threshold, and Gaussian spatial smoothing. We applied these processing techniques to the helicity distribution maps for active regions NOAA 11158 and NOAA 11243, along with the average helicities of 36 active regions, in order to imitate and understand the effects of seeing from atmospheric turbulence. We found that rather than changing trends in the helicity distributions, Gaussian smoothing and noise reduction enhanced existing trends by pushing outliers towards the mean or removing them altogether. We also found that, when separated for weak and strong magnetic fields, the average helicities of the 36 active regions conformed to the hemisphere rule for weak field helicities and breached the rule for strong field helicities. In general, we found that data processing did not affect whether the hemisphere rule held for data taken from space-based instruments, and thus that seeing from atmospheric turbulence did not significantly affect previous studies' ground-based results on the hemisphere rule. This work was carried out through the National Solar Observatory Research Experiences for Undergraduates (REU) Program, which is funded by the National Science Foundation (NSF). The National Solar Observatory is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the NSF.

  9. Shaping quaternary assemblies of water-soluble non-peptide helical foldamers by sequence manipulation.

    PubMed

    Collie, Gavin W; Pulka-Ziach, Karolina; Lombardo, Caterina M; Fremaux, Juliette; Rosu, Frédéric; Decossas, Marion; Mauran, Laura; Lambert, Olivier; Gabelica, Valérie; Mackereth, Cameron D; Guichard, Gilles

    2015-11-01

    The design and construction of biomimetic self-assembling systems is a challenging yet potentially highly rewarding endeavour that contributes to the development of new biomaterials, catalysts, drug-delivery systems and tools for the manipulation of biological processes. Significant progress has been achieved by engineering self-assembling DNA-, protein- and peptide-based building units. However, the design of entirely new, completely non-natural folded architectures that resemble biopolymers ('foldamers') and have the ability to self-assemble into atomically precise nanostructures in aqueous conditions has proved exceptionally challenging. Here we report the modular design, formation and structural elucidation at the atomic level of a series of diverse quaternary arrangements formed by the self-assembly of short amphiphilic α-helicomimetic foldamers that bear proteinaceous side chains. We show that the final quaternary assembly can be controlled at the sequence level, which permits the programmed formation of either discrete helical bundles that contain isolated cavities or pH-responsive water-filled channels with controllable pore diameters. PMID:26492006

  10. Peptoids that mimic the structure, function, and mechanism of helical antimicrobial peptides

    SciTech Connect

    Chongsiriwatana, Nathaniel P.; Patch, James A.; Czyzewski, Ann M.; Dohm, Michelle T.; Ivankin, Andrey; Gidalevitz, David; Zuckermann, Ronald N.; Barron, Annelise E.

    2008-04-02

    Antimicrobial peptides (AMPs) and their mimics are emerging as promising antibiotic agents. We present a library of 'ampetoids' (antimicrobial peptoid oligomers) with helical structures and biomimetic sequences, several members of which have low-micromolar antimicrobial activities, similar to cationic AMPs like pexiganan. Broad-spectrum activity against six clinically relevant BSL2 pathogens is also shown. This comprehensive structure-activity relationship study, including circular dichroism spectroscopy, minimum inhibitory concentration assays, hemolysis and mammalian cell toxicity studies, and specular x-ray reflectivity measurements shows that the in vitro activities of ampetoids are strikingly similar to those of AMPs themselves, suggesting a strong mechanistic analogy. The ampetoids' antibacterial activity, coupled with their low cytotoxicity against mammalian cells, make them a promising class of antimicrobials for biomedical applications. Peptoids are biostable, with a protease-resistant N-substituted glycine backbone, and their sequences are highly tunable, because an extensive diversity of side chains can be incorporated via facile solid-phase synthesis. Our findings add to the growing evidence that nonnatural foldamers will emerge as an important class of therapeutics.

  11. Shaping quaternary assemblies of water-soluble non-peptide helical foldamers by sequence manipulation

    NASA Astrophysics Data System (ADS)

    Collie, Gavin W.; Pulka-Ziach, Karolina; Lombardo, Caterina M.; Fremaux, Juliette; Rosu, Frédéric; Decossas, Marion; Mauran, Laura; Lambert, Olivier; Gabelica, Valérie; Mackereth, Cameron D.; Guichard, Gilles

    2015-11-01

    The design and construction of biomimetic self-assembling systems is a challenging yet potentially highly rewarding endeavour that contributes to the development of new biomaterials, catalysts, drug-delivery systems and tools for the manipulation of biological processes. Significant progress has been achieved by engineering self-assembling DNA-, protein- and peptide-based building units. However, the design of entirely new, completely non-natural folded architectures that resemble biopolymers (‘foldamers’) and have the ability to self-assemble into atomically precise nanostructures in aqueous conditions has proved exceptionally challenging. Here we report the modular design, formation and structural elucidation at the atomic level of a series of diverse quaternary arrangements formed by the self-assembly of short amphiphilic α-helicomimetic foldamers that bear proteinaceous side chains. We show that the final quaternary assembly can be controlled at the sequence level, which permits the programmed formation of either discrete helical bundles that contain isolated cavities or pH-responsive water-filled channels with controllable pore diameters.

  12. Hydrodynamics of helical-shaped bacterial motility

    NASA Astrophysics Data System (ADS)

    Wada, Hirofumi; Netz, Roland R.

    2009-08-01

    To reveal the underlying hydrodynamic mechanism for the directed propulsion of the bacterium Spiroplasma, we formulate a coarse-grained elastic polymer model with domains of alternating helicities along the contour. Using hydrodynamic simulations and analytic arguments, we show that the propagation of helical domain walls leads to the directed propulsion of the cell body opposite to the domain-wall traveling direction. Several key features of Spiroplasma motility are reproduced by our model. We in particular show that the helical pitch angle observed for Spiroplasma meliferum, ψ=35° , is optimized for maximal swimming speed and energy-conversion efficiency. Our analytic theory based on the slender-body hydrodynamic approximation agrees very well with our numerical data demonstrating how the chirality switch propagating along the helical cell body is converted to a translational thrust for the cell body itself. We in detail consider thermal effects on the propulsion efficiency in the form of orientational fluctuations and conformational fluctuations of the helix shape. The body length dependence of the cell motility is studied numerically and compared to our approximate analytic theory. For fixed pitch angle ψ=35° , the swimming speed is maximized at a ratio of cell-body length to domain length of about 2-3, which are typical values for real cells. We also propose simple analytic arguments for an enhancement of the swimming velocity with increasing solution viscosity by taking into account the effects of transient confinement of a helical cell body in a polymeric meshwork. Comparison with a generalized theory for the swimming speed of flagellated bacteria in polymeric meshworks shows that the presence of a finite-sized bacterial head gives rise to a maximal swimming speed at a finite solution viscosity, whereas in the absence of a head the swimming speed monotonically increases with increasing viscosity.

  13. Preparation, anti-biofouling and drag-reduction properties of a biomimetic shark skin surface.

    PubMed

    Pu, Xia; Li, Guangji; Huang, Hanlu

    2016-01-01

    Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydrophobic mechanism of the shark skin surface microstructure, the effect of biomimetic shark skin surface microstructure on surface wettability was evaluated by recording water contact angle. Additionally, protein adhesion experiments and anti-algae adhesion performance testing experiments were used to investigate and evaluate the anti-biofouling properties of the surface microstructure of biomimetic shark skin. The recorded values of the water contact angle of differently microstructured surfaces revealed that specific microstructures have certain effects on surface wettability. The anti-biofouling properties of the biomimetic shark skin surface with microstructures were superior to a smooth surface using the same polymers as substrates. Moreover, the air layer fixed on the surface of the biomimetic shark skin was found to play a key role in their antibiont adhesion property. An experiment into drag reduction was also conducted. Based on the experimental results, the microstructured surface of the prepared biomimetic shark skin played a significant role in reducing drag. The maximum of drag reduction rate is 12.5%, which is higher than the corresponding maximum drag reduction rate of membrane material with a smooth surface. PMID:26941105

  14. Preparation, anti-biofouling and drag-reduction properties of a biomimetic shark skin surface

    PubMed Central

    Pu, Xia; Li, Guangji; Huang, Hanlu

    2016-01-01

    ABSTRACT Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydrophobic mechanism of the shark skin surface microstructure, the effect of biomimetic shark skin surface microstructure on surface wettability was evaluated by recording water contact angle. Additionally, protein adhesion experiments and anti-algae adhesion performance testing experiments were used to investigate and evaluate the anti-biofouling properties of the surface microstructure of biomimetic shark skin. The recorded values of the water contact angle of differently microstructured surfaces revealed that specific microstructures have certain effects on surface wettability. The anti-biofouling properties of the biomimetic shark skin surface with microstructures were superior to a smooth surface using the same polymers as substrates. Moreover, the air layer fixed on the surface of the biomimetic shark skin was found to play a key role in their antibiont adhesion property. An experiment into drag reduction was also conducted. Based on the experimental results, the microstructured surface of the prepared biomimetic shark skin played a significant role in reducing drag. The maximum of drag reduction rate is 12.5%, which is higher than the corresponding maximum drag reduction rate of membrane material with a smooth surface. PMID:26941105

  15. Biot-Savart helicity versus physical helicity: A topological description of ideal flows

    NASA Astrophysics Data System (ADS)

    Sahihi, Taliya; Eshraghi, Homayoon

    2014-08-01

    For an isentropic (thus compressible) flow, fluid trajectories are considered as orbits of a family of one parameter, smooth, orientation-preserving, and nonsingular diffeomorphisms on a compact and smooth-boundary domain in the Euclidian 3-space which necessarily preserve a finite measure, later interpreted as the fluid mass. Under such diffeomorphisms the Biot-Savart helicity of the pushforward of a divergence-free and tangent to the boundary vector field is proved to be conserved and since these circumstances present an isentropic flow, the conservation of the "Biot-Savart helicity" is established for such flows. On the other hand, the well known helicity conservation in ideal flows which here we call it "physical helicity" is found to be an independent constant with respect to the Biot-Savart helicity. The difference between these two helicities reflects some topological features of the domain as well as the velocity and vorticity fields which is discussed and is shown for simply connected domains the two helicities coincide. The energy variation of the vorticity field is shown to be formally the same as for the incompressible flow obtained before. For fluid domains consisting of several disjoint solid tori, at each time, the harmonic knot subspace of smooth vector fields on the fluid domain is found to have two independent base sets with a special type of orthogonality between these two bases by which a topological description of the vortex and velocity fields depending on the helicity difference is achieved since this difference is shown to depend only on the harmonic knot parts of velocity, vorticity, and its Biot-Savart vector field. For an ideal magnetohydrodynamics (MHD) flow three independent constant helicities are reviewed while the helicity of magnetic potential is generalized for non-simply connected domains by inserting a special harmonic knot field in the dynamics of the magnetic potential. It is proved that the harmonic knot part of the vorticity

  16. A biomimetic projector with high subwavelength directivity based on dolphin biosonar

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Gao, Xiaowei; Zhang, Sai; Cao, Wenwu; Tang, Liguo; Wang, Ding; Li, Yan

    2014-09-01

    Based on computed tomography of a Yangtze finless porpoise's biosonar system, a biomimetic structure was designed to include air cavity, gradient-index material, and steel outer-structure mimicking air sacs, melon, and skull, respectively. The mainlobe pressure was about three times higher, the angular resolution was one order of magnitude higher, and the effective source size was orders of magnitude larger than those of the subwavelength source without the biomimetic structure. The superior subwavelength directivity over a broad bandwidth suggests potential applications of this biomimetic projector in underwater sonar, medical ultrasonography, and other related applications.

  17. Touch stimulated pulse generation in biomimetic single-layer graphene.

    PubMed

    Sul, Onejae; Chun, Hyunsuk; Choi, Eunseok; Choi, Jungbong; Cho, Kyeongwon; Jang, Dongpyo; Chun, Sungwoo; Park, Wanjun; Lee, Seung-Beck

    2016-02-14

    Detecting variation in contact pressure is a separate sensing mode in the human somatosensory system that differs from the detection of pressure magnitude. If pressure magnitude and variation sensing can be achieved simultaneously, an advanced biomimetic tactile system that better emulates human senses may be developed. We report on a novel single-layer graphene based artificial mechanoreceptor that generates a resistance pulse as the contact stimulus passes a specific threshold pressure, mimicking the generation of action potentials in a biological fast-adapting mechanoreceptor. The electric field from a flexible membrane gate electrode placed above a graphene channel raises the Fermi level from the valence band as pressure deflects the membrane. The threshold pressure is reached when the Fermi level crosses the Dirac point in the graphene energy band, which generates a sharp peak in the measured resistance. We found that by changing the gate potential it was possible to modulate the threshold pressure and using a series of graphene channels, a train of pulses were generated during a transient pressurizing stimulus demonstrating biomimetic behaviour. PMID:26790981

  18. Biomimetic Extracellular Environment Based on Natural Origin Polyelectrolyte Multilayers.

    PubMed

    Silva, Joana M; Reis, Rui L; Mano, João F

    2016-08-01

    Surface modification of biomaterials is a well-known approach to enable an adequate biointerface between the implant and the surrounding tissue, dictating the initial acceptance or rejection of the implantable device. Since its discovery in early 1990s layer-by-layer (LbL) approaches have become a popular and attractive technique to functionalize the biomaterials surface and also engineering various types of objects such as capsules, hollow tubes, and freestanding membranes in a controllable and versatile manner. Such versatility enables the incorporation of different nanostructured building blocks, including natural biopolymers, which appear as promising biomimetic multilayered systems due to their similarity to human tissues. In this review, the potential of natural origin polymer-based multilayers is highlighted in hopes of a better understanding of the mechanisms behind its use as building blocks of LbL assembly. A deep overview on the recent progresses achieved in the design, fabrication, and applications of natural origin multilayered films is provided. Such films may lead to novel biomimetic approaches for various biomedical applications, such as tissue engineering, regenerative medicine, implantable devices, cell-based biosensors, diagnostic systems, and basic cell biology. PMID:27435905

  19. Advances in surfaces and osseointegration in implantology. Biomimetic surfaces

    PubMed Central

    Albertini, Matteo; Fernandez-Yague, Marc; Lázaro, Pedro; Herrero-Climent, Mariano; Bullon, Pedro; Gil, Francisco-Javier

    2015-01-01

    The present work is a revision of the processes occurring in osseointegration of titanium dental implants according to different types of surfaces -namely, polished surfaces, rough surfaces obtained from subtraction methods, as well as the new hydroxyapatite biomimetic surfaces obtained from thermochemical processes. Hydroxyapatite’s high plasma-projection temperatures have proven to prevent the formation of crystalline apatite on the titanium dental implant, but lead to the formation of amorphous calcium phosphate (i.e., with no crystal structure) instead. This layer produce some osseointegration yet the calcium phosphate layer will eventually dissolve and leave a gap between the bone and the dental implant, thus leading to osseointegration failure due to bacterial colonization. A new surface -recently obtained by thermochemical processes- produces, by crystallization, a layer of apatite with the same mineral content as human bone that is chemically bonded to the titanium surface. Osseointegration speed was tested by means of minipigs, showing bone formation after 3 to 4 weeks, with the security that a dental implant can be loaded. This surface can be an excellent candidate for immediate or early loading procedures. Key words:Dental implants, implants surfaces, osseointegration, biomimetics surfaces. PMID:25662555

  20. Scaling Up Nature: Large Area Flexible Biomimetic Surfaces.

    PubMed

    Li, Yinyong; John, Jacob; Kolewe, Kristopher W; Schiffman, Jessica D; Carter, Kenneth R

    2015-10-28

    The fabrication and advanced function of large area biomimetic superhydrophobic surfaces (SHS) and slippery lubricant-infused porous surfaces (SLIPS) are reported. The use of roll-to-roll nanoimprinting techniques enabled the continuous fabrication of SHS and SLIPS based on hierarchically wrinkled surfaces. Perfluoropolyether hybrid molds were used as flexible molds for roll-to-roll imprinting into a newly designed thiol-ene based photopolymer resin coated on flexible polyethylene terephthalate films. The patterned surfaces exhibit feasible superhydrophobicity with a water contact angle around 160° without any further surface modification. The SHS can be easily converted into SLIPS by roll-to-roll coating of a fluorinated lubricant, and these surfaces have outstanding repellence to a variety of liquids. Furthermore, both SHS and SLIPS display antibiofouling properties when challenged with Escherichia coli K12 MG1655. The current article describes the transformation of artificial biomimetic structures from small, lab-scale coupons to low-cost, large area platforms. PMID:26423494

  1. Synthesis of biomimetic segmented polyurethanes as antifouling biomaterials.

    PubMed

    Francolini, I; Crisante, F; Martinelli, A; D'Ilario, L; Piozzi, A

    2012-02-01

    Controlling the non-specific adsorption of proteins, cells and bacteria onto biomaterial surfaces is of crucial importance for the development of medical devices with specific levels of performance. Among the strategies pursued to control the interactions between material surfaces and biological tissues, the immobilization of non-fouling polymers on biomaterial surfaces as well as the synthesis of the so-called biomimetic polymers are considered promising approaches to elicit specific cellular responses. In this study, in order to obtain materials able to prevent infectious and thrombotic complications related to the use of blood-contacting medical devices, heparin-mimetic segmented polyurethanes were synthesized and fully characterized. Specifically, sulfate or sulfamate groups, known to be responsible for the biological activity of heparin, were introduced into the side chain of a carboxylated polyurethane. Due to the introduction of these groups, the obtained polymers possessed a higher hard/soft phase segregation (lower glass transition temperatures) and a greater hydrophilicity than the pristine polymer. In addition, the synthesized polymers were able to significantly delay the activated partial thromboplastin time, this increased hemocompatibility being related both to polymer hydrophilicity and to the presence of the -SO3H groups. This last feature was also responsible for the ability of these biomimetic polymers to prevent the adhesion of a strain of Staphylococcus epidermidis. PMID:22051237

  2. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

    PubMed Central

    2011-01-01

    Summary The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera) leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab. PMID:21977417

  3. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity.

    PubMed

    Bhushan, Bharat

    2011-01-01

    The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera) leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab. PMID:21977417

  4. Towards Biomimetic Virtual Constraint Control of a Powered Prosthetic Leg

    PubMed Central

    Sensinger, Jonathon W.

    2014-01-01

    This brief presents a novel control strategy for a powered prosthetic ankle based on a biomimetic virtual constraint. We first derive a kinematic constraint for the “effective shape” of the human ankle-foot complex during locomotion. This shape characterizes ankle motion as a function of the Center of Pressure (COP)–the point on the foot sole where the resultant ground reaction force is imparted. Since the COP moves monotonically from heel to toe during steady walking, we adopt the COP as a mechanical representation of the gait cycle phase in an autonomous feedback controller. We show that our kinematic constraint can be enforced as a virtual constraint by an output linearizing controller that uses only feedback available to sensors onboard a prosthetic leg. Using simulations of a passive walking model with feet, we show that this novel controller exactly enforces the desired effective shape whereas a standard impedance (i.e., proportional-derivative) controller cannot. This work provides a single, biomimetic control law for the entire single-support period during robot-assisted locomotion. PMID:25552894

  5. Biomimetic optical system using polymer lenses with tunable focus

    NASA Astrophysics Data System (ADS)

    Liang, Dan; Xiang, Ke; Du, Jia-Wei; Yang, Jun-Nan; Wang, Xuan-Yin

    2014-10-01

    A biomimetic system using polymer lenses for the optical design and application is developed. The system mainly consisted of a bionic cornea lens, voice coil motor, compression ring, bionic crystalline lens, substrate, and CCD sensor. By controlling the current of the voice coil motor, we could change the motion of the compression ring to alter the curvature radius of the bionic crystalline lens, thus adjusting the focal length of the whole system. The integrated constructure of the optical system was presented, as well as the detailed description of the lens composition, material, and fabrication process. Images under different displacement loads were captured, the relationship among the curvature radius, observed back focal length, and predicted effective focal length was analyzed, and the spot diagram of the optical system was simulated using ZEMAX software. The focal length of the optical system ranged from 17.3 to 24.5 mm under a tiny displacement load from 0 to 0.14 mm. Besides, the images captured at different rotating angles presented almost identical patterns and the same image quality, which showed good robustness to the gravity. The biomimetic optical system is of interest to develop an integrated, low-cost, and stable imaging system.

  6. Rapid prototyping of biomimetic vascular phantoms for hyperspectral reflectance imaging.

    PubMed

    Ghassemi, Pejhman; Wang, Jianting; Melchiorri, Anthony J; Ramella-Roman, Jessica C; Mathews, Scott A; Coburn, James C; Sorg, Brian S; Chen, Yu; Pfefer, T Joshua

    2015-01-01

    The emerging technique of rapid prototyping with three-dimensional (3-D) printers provides a simple yet revolutionary method for fabricating objects with arbitrary geometry. The use of 3-D printing for generating morphologically biomimetic tissue phantoms based on medical images represents a potentially major advance over existing phantom approaches. Toward the goal of image-defined phantoms, we converted a segmented fundus image of the human retina into a matrix format and edited it to achieve a geometry suitable for printing. Phantoms with vessel-simulating channels were then printed using a photoreactive resin providing biologically relevant turbidity, as determined by spectrophotometry. The morphology of printed vessels was validated by x-ray microcomputed tomography. Channels were filled with hemoglobin (Hb) solutions undergoing desaturation, and phantoms were imaged with a near-infrared hyperspectral reflectance imaging system. Additionally, a phantom was printed incorporating two disjoint vascular networks at different depths, each filled with Hb solutions at different saturation levels. Light propagation effects noted during these measurements—including the influence of vessel density and depth on Hb concentration and saturation estimates, and the effect of wavelength on vessel visualization depth—were evaluated. Overall, our findings indicated that 3-D-printed biomimetic phantoms hold significant potential as realistic and practical tools for elucidating light–tissue interactions and characterizing biophotonic system performance. PMID:26662064

  7. Rapid prototyping of biomimetic vascular phantoms for hyperspectral reflectance imaging

    NASA Astrophysics Data System (ADS)

    Ghassemi, Pejhman; Wang, Jianting; Melchiorri, Anthony J.; Ramella-Roman, Jessica C.; Mathews, Scott A.; Coburn, James C.; Sorg, Brian S.; Chen, Yu; Joshua Pfefer, T.

    2015-12-01

    The emerging technique of rapid prototyping with three-dimensional (3-D) printers provides a simple yet revolutionary method for fabricating objects with arbitrary geometry. The use of 3-D printing for generating morphologically biomimetic tissue phantoms based on medical images represents a potentially major advance over existing phantom approaches. Toward the goal of image-defined phantoms, we converted a segmented fundus image of the human retina into a matrix format and edited it to achieve a geometry suitable for printing. Phantoms with vessel-simulating channels were then printed using a photoreactive resin providing biologically relevant turbidity, as determined by spectrophotometry. The morphology of printed vessels was validated by x-ray microcomputed tomography. Channels were filled with hemoglobin (Hb) solutions undergoing desaturation, and phantoms were imaged with a near-infrared hyperspectral reflectance imaging system. Additionally, a phantom was printed incorporating two disjoint vascular networks at different depths, each filled with Hb solutions at different saturation levels. Light propagation effects noted during these measurements-including the influence of vessel density and depth on Hb concentration and saturation estimates, and the effect of wavelength on vessel visualization depth-were evaluated. Overall, our findings indicated that 3-D-printed biomimetic phantoms hold significant potential as realistic and practical tools for elucidating light-tissue interactions and characterizing biophotonic system performance.

  8. Small-Scale Fabrication of Biomimetic Structures for Periodontal Regeneration

    PubMed Central

    Green, David W.; Lee, Jung-Seok; Jung, Han-Sung

    2016-01-01

    The periodontium is the supporting tissues for the tooth organ and is vulnerable to destruction, arising from overpopulating pathogenic bacteria and spirochaetes. The presence of microbes together with host responses can destroy large parts of the periodontium sometimes leading tooth loss. Permanent tissue replacements are made possible with tissue engineering techniques. However, existing periodontal biomaterials cannot promote proper tissue architectures, necessary tissue volumes within the periodontal pocket and a “water-tight” barrier, to become clinically acceptable. New kinds of small-scale engineered biomaterials, with increasing biological complexity are needed to guide proper biomimetic regeneration of periodontal tissues. So the ability to make compound structures with small modules, filled with tissue components, is a promising design strategy for simulating the anatomical complexity of the periodotium attachment complexes along the tooth root and the abutment with the tooth collar. Anatomical structures such as, intima, adventitia, and special compartments such as the epithelial cell rests of Malassez or a stellate reticulum niche need to be engineered from the start of regeneration to produce proper periodontium replacement. It is our contention that the positioning of tissue components at the origin is also necessary to promote self-organizing cell–cell connections, cell–matrix connections. This leads to accelerated, synchronized and well-formed tissue architectures and anatomies. This strategy is a highly effective preparation for tackling periodontitis, periodontium tissue resorption, and to ultimately prevent tooth loss. Furthermore, such biomimetic tissue replacements will tackle problems associated with dental implant support and perimimplantitis. PMID:26903872

  9. Biomimetic and synthetic interfaces to tune immune responses (Review)

    PubMed Central

    Garapaty, Anusha; Champion, Julie A.

    2015-01-01

    Organisms depend upon complex intercellular communication to initiate, maintain, or suppress immune responses during infection or disease. Communication occurs not only between different types of immune cells, but also between immune cells and nonimmune cells or pathogenic entities. It can occur directly at the cell–cell contact interface, or indirectly through secreted signals that bind cell surface molecules. Though secreted signals can be soluble, they can also be particulate in nature and direct communication at the cell–particle interface. Secreted extracellular vesicles are an example of native particulate communication, while viruses are examples of foreign particulates. Inspired by communication at natural immunological interfaces, biomimetic materials and designer molecules have been developed to mimic and direct the type of immune response. This review describes the ways in which native, biomimetic, and designer materials can mediate immune responses. Examples include extracellular vesicles, particles that mimic immune cells or pathogens, and hybrid designer molecules with multiple signaling functions, engineered to target and bind immune cell surface molecules. Interactions between these materials and immune cells are leading to increased understanding of natural immune communication and function, as well as development of immune therapeutics for the treatment of infection, cancer, and autoimmune disease. PMID:26178262

  10. An organic electronic biomimetic neuron enables auto-regulated neuromodulation.

    PubMed

    Simon, Daniel T; Larsson, Karin C; Nilsson, David; Burström, Gustav; Galter, Dagmar; Berggren, Magnus; Richter-Dahlfors, Agneta

    2015-09-15

    Current therapies for neurological disorders are based on traditional medication and electric stimulation. Here, we present an organic electronic biomimetic neuron, with the capacity to precisely intervene with the underlying malfunctioning signalling pathway using endogenous substances. The fundamental function of neurons, defined as chemical-to-electrical-to-chemical signal transduction, is achieved by connecting enzyme-based amperometric biosensors and organic electronic ion pumps. Selective biosensors transduce chemical signals into an electric current, which regulates electrophoretic delivery of chemical substances without necessitating liquid flow. Biosensors detected neurotransmitters in physiologically relevant ranges of 5-80 µM, showing linear response above 20 µm with approx. 0.1 nA/µM slope. When exceeding defined threshold concentrations, biosensor output signals, connected via custom hardware/software, activated local or distant neurotransmitter delivery from the organic electronic ion pump. Changes of 20 µM glutamate or acetylcholine triggered diffusive delivery of acetylcholine, which activated cells via receptor-mediated signalling. This was observed in real-time by single-cell ratiometric Ca(2+) imaging. The results demonstrate the potential of the organic electronic biomimetic neuron in therapies involving long-range neuronal signalling by mimicking the function of projection neurons. Alternatively, conversion of glutamate-induced descending neuromuscular signals into acetylcholine-mediated muscular activation signals may be obtained, applicable for bridging injured sites and active prosthetics. PMID:25932795

  11. Development of autonomous eating mechanism for biomimetic robots

    NASA Astrophysics Data System (ADS)

    Jeong, Kil-Woong; Cho, Ik-Jin; Lee, Yun-Jung

    2005-12-01

    Most of the recently developed robots are human friendly robots which imitate animals or humans such as entertainment robot, bio-mimetic robot and humanoid robot. Interest for these robots are being increased because the social trend is focused on health, welfare, and graying. Autonomous eating functionality is most unique and inherent behavior of pets and animals. Most of entertainment robots and pet robots make use of internal-type battery. Entertainment robots and pet robots with internal-type battery are not able to operate during charging the battery. Therefore, if a robot has an autonomous function for eating battery as its feeds, the robot is not only able to operate during recharging energy but also become more human friendly like pets. Here, a new autonomous eating mechanism was introduced for a biomimetic robot, called ELIRO-II(Eating LIzard RObot version 2). The ELIRO-II is able to find a food (a small battery), eat and evacuate by itself. This work describe sub-parts of the developed mechanism such as head-part, mouth-part, and stomach-part. In addition, control system of autonomous eating mechanism is described.

  12. Biomimetic surface modification of polyurethane with phospholipids grafted carbon nanotubes.

    PubMed

    Tan, Dongsheng; Liu, Liuxu; Li, Zhen; Fu, Qiang

    2015-08-01

    To improve blood compatibility of polyurethane (PU), phospholipids grafted carbon nanotubes (CNTs) were prepared through zwitterion-mediated cycloaddition reaction and amide condensation, and then were added to the PU as fillers via solution mixing to form biomimetic surface. The properties of phospholipids grafted CNTs (CNT-PC) were investigated by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance ((1) H NMR). The results indicated that the phospholipids were grafted onto CNTs in high efficiency, and the hydrophilicity and dispersibility of the modified CNTs were improved effectively. The structures and properties of composites containing CNT-PC were investigated by optical microscope, XPS, and water contact angles. The results indicated that phospholipids were enriched on the surface with addition of 0.1 wt % of CNT-PC, which significantly reduced protein adsorption and platelet adhesion. The method of carrying phospholipids on the nanofiller to modify polymers has provided a promising way of constructing biomimetic phospholipid membrane on the surface to improve blood compatibility. PMID:25630300

  13. Biomimetic Photonic Crystals based on Diatom Algae Frustules

    NASA Astrophysics Data System (ADS)

    Mishler, Jonathan; Alverson, Andrew; Herzog, Joseph

    2015-03-01

    Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal.

  14. Biomimetics of fetal alveolar flow phenomena using microfluidics.

    PubMed

    Tenenbaum-Katan, Janna; Fishler, Rami; Rothen-Rutishauser, Barbara; Sznitman, Josué

    2015-01-01

    At the onset of life in utero, the respiratory system begins as a liquid-filled tubular organ and undergoes significant morphological changes during fetal development towards establishing a respiratory organ optimized for gas exchange. As airspace morphology evolves, respiratory alveolar flows have been hypothesized to exhibit evolving flow patterns. In the present study, we have investigated flow topologies during increasing phases of embryonic life within an anatomically inspired microfluidic device, reproducing real-scale features of fetal airways representative of three distinct phases of in utero gestation. Micro-particle image velocimetry measurements, supported by computational fluid dynamics simulations, reveal distinct respiratory alveolar flow patterns throughout different stages of fetal life. While attached, streamlined flows characterize the shallow structures of premature alveoli indicative of the onset of saccular stage, separated recirculating vortex flows become the signature of developed and extruded alveoli characteristic of the advanced stages of fetal development. To further mimic physiological aspects of the cellular environment of developing airways, our biomimetic devices integrate an alveolar epithelium using the A549 cell line, recreating a confluent monolayer that produces pulmonary surfactant. Overall, our in vitro biomimetic fetal airways model delivers a robust and reliable platform combining key features of alveolar morphology, flow patterns, and physiological aspects of fetal lungs developing in utero. PMID:25759753

  15. Biomimetic Acoustically-Responsive Vesicles for Theranostic Applications

    PubMed Central

    Hsieh, Chen-Chan; Kang, Shih-Tsung; Lin, Yee-Hsien; Ho, Yi-Ju; Wang, Chung-Hsin; Yeh, Chih-Kuang; Chang, Chien-Wen

    2015-01-01

    In recent years, biomimetic cell membrane-derived particles have emerged as a new class of drug delivery system with advantages of biocompatibility, ease of isolation and long circulation profile. Here we report the development and potential theranostic applications of a new biomimetic acoustically-responsive droplet system derived from mammalian red blood cell membrane (RBCM). We hypothesized that drug-loaded RBCM droplets (RBCMDs) would undergo a transition from liquid (droplets) to gas (bubbles) upon high intensity focused ultrasound (HIFU) insonation, resulting in on-demand drug release. The generated microbubbles could also serve as a contrast agent to enhance ultrasound imaging. As-synthesized RBCMDs exhibited uniform size, good dispersity and preservation of RBCM-associated proteins that prevented uptake by macrophages. Camptothecin (CPT), an anti-cancer drug, was successfully loaded in the RBCMDs with a loading efficiency of 2-3% and an encapsulation efficiency of 62-97%. A short (3 min) exposure to HIFU irradiation triggered release of CPT from the RBCMDs and the physical explosion of droplets damaged nearby cancer cells resulting in significant cell death. In addition, the acoustically vaporized RBCMDs significantly increased the ultrasound echo signal to 30 dB. Lastly, we demonstrated that RBCMDs could be acoustically vaporized in vivo in target tissues, and enhancing ultrasound imaging. Taken together, we have developed a new class of naturally derived RBCMDs which show great potential for future application in remotely triggered drug delivery and ultrasound imaging enhancement. PMID:26379791

  16. Small-Scale Fabrication of Biomimetic Structures for Periodontal Regeneration.

    PubMed

    Green, David W; Lee, Jung-Seok; Jung, Han-Sung

    2016-01-01

    The periodontium is the supporting tissues for the tooth organ and is vulnerable to destruction, arising from overpopulating pathogenic bacteria and spirochaetes. The presence of microbes together with host responses can destroy large parts of the periodontium sometimes leading tooth loss. Permanent tissue replacements are made possible with tissue engineering techniques. However, existing periodontal biomaterials cannot promote proper tissue architectures, necessary tissue volumes within the periodontal pocket and a "water-tight" barrier, to become clinically acceptable. New kinds of small-scale engineered biomaterials, with increasing biological complexity are needed to guide proper biomimetic regeneration of periodontal tissues. So the ability to make compound structures with small modules, filled with tissue components, is a promising design strategy for simulating the anatomical complexity of the periodotium attachment complexes along the tooth root and the abutment with the tooth collar. Anatomical structures such as, intima, adventitia, and special compartments such as the epithelial cell rests of Malassez or a stellate reticulum niche need to be engineered from the start of regeneration to produce proper periodontium replacement. It is our contention that the positioning of tissue components at the origin is also necessary to promote self-organizing cell-cell connections, cell-matrix connections. This leads to accelerated, synchronized and well-formed tissue architectures and anatomies. This strategy is a highly effective preparation for tackling periodontitis, periodontium tissue resorption, and to ultimately prevent tooth loss. Furthermore, such biomimetic tissue replacements will tackle problems associated with dental implant support and perimimplantitis. PMID:26903872

  17. Helical localized wave solutions of the scalar wave equation.

    PubMed

    Overfelt, P L

    2001-08-01

    A right-handed helical nonorthogonal coordinate system is used to determine helical localized wave solutions of the homogeneous scalar wave equation. Introducing the characteristic variables in the helical system, i.e., u = zeta - ct and v = zeta + ct, where zeta is the coordinate along the helical axis, we can use the bidirectional traveling plane wave representation and obtain sets of elementary bidirectional helical solutions to the wave equation. Not only are these sets bidirectional, i.e., based on a product of plane waves, but they may also be broken up into right-handed and left-handed solutions. The elementary helical solutions may in turn be used to create general superpositions, both Fourier and bidirectional, from which new solutions to the wave equation may be synthesized. These new solutions, based on the helical bidirectional superposition, are members of the class of localized waves. Examples of these new solutions are a helical fundamental Gaussian focus wave mode, a helical Bessel-Gauss pulse, and a helical acoustic directed energy pulse train. Some of these solutions have the interesting feature that their shape and localization properties depend not only on the wave number governing propagation along the longitudinal axis but also on the normalized helical pitch. PMID:11488494

  18. Stabilization of Helical Macromolecular Phases by Confined Bending

    NASA Astrophysics Data System (ADS)

    Williams, Matthew J.; Bachmann, Michael

    2015-07-01

    By means of extensive replica-exchange simulations of generic coarse-grained models for helical polymers, we systematically investigate the structural transitions into all possible helical phases for flexible and semiflexible elastic polymers with self-interaction under the influence of torsion barriers. The competing interactions lead to a variety of conformational phases including disordered helical arrangements, single helices, and ordered, tertiary helix bundles. Most remarkably, we find that a bending restraint entails a clear separation and stabilization of the helical phases. This aids in understanding why semiflexible polymers such as double-stranded DNA tend to form pronounced helical structures and proteins often exhibit an abundance of helical structures, such as helix bundles, within their tertiary structure.

  19. THE MAGNETIC ENERGY-HELICITY DIAGRAM OF SOLAR ACTIVE REGIONS

    SciTech Connect

    Tziotziou, Kostas; Georgoulis, Manolis K.; Raouafi, Nour-Eddine

    2012-11-01

    Using a recently proposed nonlinear force-free method designed for single-vector magnetograms of solar active regions, we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the free magnetic energy and the relative magnetic helicity in the studied regions. This correlation implies that magnetic helicity, in addition to free magnetic energy, may be an essential ingredient for major solar eruptions. Eruptive active regions appear well segregated from non-eruptive ones in both free energy and relative helicity with major (at least M-class) flares occurring in active regions with free energy and relative helicity exceeding 4 Multiplication-Sign 10{sup 31} erg and 2 Multiplication-Sign 10{sup 42} Mx{sup 2}, respectively. The helicity threshold agrees well with estimates of the helicity contents of typical coronal mass ejections.

  20. Study of proteolytic removal of Fab delta and Fe delta determinants of lymphocyte membrane IgD using a direct rosette assay.

    PubMed Central

    Calvert, J E; Ling, N R; Jefferis, R

    1981-01-01

    Proteolysis of lymphocyte surface membrane immunoglobulin (SIg) by trypsin, papain and pronase was investigated. Cleavage in the hinge region resulting in removal of Fab delta was distinguished from removal of the whole SIgD molecule using antisera specific for c delta l and Fc delta. Using the sensitive direct rosette assay SIgD determinants were detected after digestion under conditions previously thought to remove IgD from the membrane. By increasing digestion times is was shown that whilst papain and pronase remove the whole IgD molecule, Fc delta but not Fab delta determinants survive trypsin. The implications of the results for structural differences between membrane and serum IgD and for models of insertion of SIgD into the plasma membrane are discussed. PMID:6168571

  1. Guided wave helical ultrasonic tomography of pipes.

    PubMed

    Leonard, Kevin R; Hinders, Mark K

    2003-08-01

    Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT) that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call "cross borehole" tomography. In HUT, the Lamb-like guided waves travel the various helical criss-cross paths between two parallel circumferential transducer arrays instead of the planar criss-cross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. In this paper we demonstrate HUT via laboratory scans on steel pipe segments into which controlled thinnings have been introduced. PMID:12942959

  2. Algebraic Apect of Helicities in Hadron Physics

    NASA Astrophysics Data System (ADS)

    An, Murat; Ji, Chueng

    2015-04-01

    We examined the relation of polarization vectors and spinors of (1 , 0) ⊕(0 , 1) representation of Lorentz group in Clifford algebra Cl1 , 3 , their relation with standard algebra, and properties of these spinors. Cl1 , 3 consists of different grades:e.g. the first and the second grades represent (1 / 2 , 1 / 2) and (1 , 0) ⊕(0 , 1) representation of spin groups respectively with 4 and 6 components. However, these Clifford numbers are not the helicity eigenstates and thus we transform them into combinations of helicity eigenstates by expressing them as spherical harmonics. We relate the spin-one polarization vectors and (1 , 0) ⊕(0 , 1) spinors under one simple transformation with the spin operators. We also link our work with Winnberg's work of a superfield of a spinors of Clifford algebra by giving a physical meaning to Grassmann variables and discuss how Grassman algebra is linked with Clifford algebra.

  3. Guided wave helical ultrasonic tomography of pipes

    NASA Astrophysics Data System (ADS)

    Leonard, Kevin R.; Hinders, Mark K.

    2003-08-01

    Ultrasonic guided waves have been used for a wide variety of ultrasonic inspection techniques. We describe here a new variation called helical ultrasound tomography (HUT) that uses guided ultrasonic waves along with tomographic reconstruction algorithms that have been developed by seismologists for what they call ``cross borehole'' tomography. In HUT, the Lamb-like guided waves travel the various helical criss-cross paths between two parallel circumferential transducer arrays instead of the planar criss-cross seismic paths between two boreholes. Although the measurement itself is fairly complicated, the output of the tomographic reconstruction is a readily interpretable map of a quantity of interest such as pipe wall thickness. In this paper we demonstrate HUT via laboratory scans on steel pipe segments into which controlled thinnings have been introduced.

  4. Vacuum systems for the ILC helical undulator

    SciTech Connect

    Malyshev, O. B.; Scott, D. J.; Bailey, I. R.; Barber, D. P.; Baynham, E.; Bradshaw, T.; Brummitt, A.; Carr, S.; Clarke, J. A.; Cooke, P.; Dainton, J. B.; Ivanyushenkov, Y.; Malysheva, L. I.; Moortgat-Pick, G. A.; Rochford, J.; Department of Physics, University of Liverpool Oxford St. Liverpool L69 7ZE; Cockcroft Institute, Warrington WA4 4AD

    2007-07-15

    The International Linear Collider (ILC) positron source uses a helical undulator to generate polarized photons of {approx}10 MeV at the first harmonic. Unlike many undulators used in synchrotron radiation sources, the ILC helical undulator vacuum chamber will be bombarded by photons, generated by the undulator, with energies mostly below that of the first harmonic. Achieving the vacuum specification of {approx}100 nTorr in a narrow chamber of 4-6 mm inner diameter, with a long length of 100-200 m, makes the design of the vacuum system challenging. This article describes the vacuum specifications and calculations of the flux and energy of photons irradiating the undulator vacuum chamber and considers possible vacuum system design solutions for two cases: cryogenic and room temperature.

  5. Viscosity of Sheared Helical filament Suspensions

    NASA Astrophysics Data System (ADS)

    Sartucci, Matthew; Urbach, Jeff; Blair, Dan; Schwenger, Walter

    The viscosity of suspensions can be dramatically affected by high aspect ratio particles. Understanding these systems provides insight into key biological functions and can be manipulated for many technological applications. In this talk, the viscosity as a function of shear rate of suspensions of helical filaments is compared to that of suspensions of straight rod-like filaments. Our goal is to determine the impact of filament geometry on low volume fraction colloidal suspensions in order to identify strategies for altering viscosity with minimal volume fraction. In this research, the detached flagella of the bacteria Salmonella Typhimurium are used as a model system of helical filaments and compared to mutated straight flagella of the Salmonella. We compare rheological measurements of the suspension viscosity in response to shear flow and use a combination of the rheology and fluorescence microscopy to identify the microstructural changes responsible for the observed rheological response.

  6. Windmill artifact in multislice helical CT

    NASA Astrophysics Data System (ADS)

    Silver, Michael D.; Taguchi, Katsuyuki; Hein, Ilmar A.; Chiang, BeShan; Kazama, Masahiro; Mori, Issei

    2003-05-01

    Multi-slice helical CT-systems suffer from windmill artifacts: black/white patterns that spin off of features with high longitudinal gradients. The number of black/white pairs matches the number of slices (detector rows) in the multi-slive detector. The period of spin is the same as the helical pitch. We investigate the cause of the pattern by following the traces of selected voxels through the multi-slive detector array as a function of view position. This forms an "extracted sinogram" which represents the data used to reconstruct the specific voxel. Now we can determine the cause of the artifact by correlating the windmill streak in the image with the extracted data. The investigation shows that inadequate sampling along the longitudinal direction causes the artifact.

  7. Solar flares controlled by helicity conservation

    NASA Technical Reports Server (NTRS)

    Gliner, Erast B.; Osherovich, Vladimir A.

    1995-01-01

    The energy release in a class of solar flares is studied on the assumption that during burst events in highly conducting plasma the magnetic helicity of plasma is approximately conserved. The available energy release under a solar flare controlled by the helicity conservation is shown to be defined by the magnetic structure of the associated prominence. The approach throws light on some solar flare enigmas: the role of the associated prominence. The approach throws light on some solar flare enigmas: the role of the associated prominences; the discontinuation of the reconnection of magnetic lines long before the complete reconnection of participated fields occurs; the existence of quiet prominences which, in spite of their usual optical appearance, do not initiate any flare events; the small energy release under a solar flare in comparison with the stockpile of magnetic energy in surrounding fields. The predicted scale of the energy release is in a fair agreement with observations.

  8. On the energy density of helical proteins.

    PubMed

    Barros, Manuel; Ferrández, Angel

    2014-12-01

    We solve the problem of determining the energy actions whose moduli space of extremals contains the class of Lancret helices with a prescribed slope. We first see that the energy density should be linear both in the total bending and in the total twisting, such that the ratio between the weights of them is the prescribed slope. This will give an affirmative answer to the conjecture stated in Barros and Ferrández (J Math Phys 50:103529, 2009). Then, we normalize to get the best choice for the helical energy. It allows us to show that the energy, for instance of a protein chain, does not depend on the slope and is invariant under homotopic changes of the cross section which determines the cylinder where the helix is lying. In particular, the energy of a helix is not arbitrary, but it is given as natural multiples of some basic quantity of energy. PMID:24390481

  9. A Helical Magnet Design for RHIC^*.

    NASA Astrophysics Data System (ADS)

    Willen, E.; Gupta, R.; Kelly, E.; Muratore, J.

    1997-05-01

    Helical dipole magnets are required in a project for the Relativistic Heavy Ion Collider (RHIC) to control and preserve the beam polarization in order to allow the collision of polarized proton beams. The project requires superconducting magnets with a 100 mm coil aperture and a 4 Tesla field in which the field rotates 360 degrees over a distance of 2.4 meters. A design restraint is that the magnets operate at relatively low current (less than 500 amperes) in order to minimize the heat load from the current leads. A magnet has been developed that uses a small diameter superconducting cable wound into helical grooves machined into a thick-walled aluminum cylinder. The design and test results of this prototype magnet will be described. ^*Work supported by the U.S. Department of Energy.

  10. Broadband optical isolator based on helical metamaterials.

    PubMed

    Cao, Hu; Yang, ZhenYu; Zhao, Ming; Wu, Lin; Zhang, Peng

    2015-05-01

    Based on helical metamaterials, a new broadband optical isolator with a triple-helix structure is proposed in this paper. The right-handed circularly polarized light can transmit through the isolator with its polarization unchanged. The reverse propagating light, which is caused by the reflection of the latter optical devices, is converted into left-handed circularly polarized light that is suppressed by the proposed isolator because of absorption. Our design has some unprecedented advantages such as broad frequency ranges and a compact structure; moreover, neither polarizers nor adscititious magnetic fields are required. Properties of the isolator are investigated using the finite-difference time-domain method, and this phenomenon is studied by the mechanism of helical antenna theory. PMID:26366900

  11. Helical relativistic electron beam Vlasov equilibria

    NASA Astrophysics Data System (ADS)

    Lai, H. M.

    1980-08-01

    Three existing helical relativistic electron beam models are discussed and compared. Both Yoshikawa's and Lawson's models are shown to be derivable from appropriate Vlasov equilibria. A new helical Vlasov equilibrium with energy spread is presented and studied. Unlike Auer's axial current model in which the allowance of an energy spread limits the total current in the relativistic beam case, the present model, with the addition of an azimuthal current, permits solutions with arbitrarily large current. On the other hand, like the model studied by Kan and Lai, the present model leads to nonhollowed-out beam solutions in which, the larger the beam current, the more force-free is the magnetic field configuration.

  12. Helicity of a toroidal vortex with swirl

    NASA Astrophysics Data System (ADS)

    Bannikova, E. Yu.; Kontorovich, V. M.; Poslavsky, S. A.

    2016-04-01

    Based on the solutions of the Bragg-Hawthorne equation, we discuss the helicity of a thin toroidal vortex in the presence of swirl, orbital motion along the torus directrix. The relation between the helicity and circulations along the small and large linked circumferences (the torus directrix and generatrix) is shown to depend on the azimuthal velocity distribution in the core of the swirling ring vortex. In the case of nonuniform swirl, this relation differs from the well-known Moffat relation, viz., twice the product of such circulations multiplied by the number of linkages. The results can find applications in investigating the vortices in planetary atmospheres and the motions in the vicinity of active galactic nuclei.

  13. Coherent electron transport in a helical nanotube

    NASA Astrophysics Data System (ADS)

    Liang, Guo-Hua; Wang, Yong-Long; Du, Long; Jiang, Hua; Kang, Guang-Zhen; Zong, Hong-Shi

    2016-09-01

    The quantum dynamics of carriers bound to helical tube surfaces is investigated in a thin-layer quantization scheme. By numerically solving the open-boundary Schrödinger equation in curvilinear coordinates, geometric effect on the coherent transmission spectra is analysed in the case of single propagating mode as well as multimode. It is shown that, the coiling endows the helical nanotube with different transport properties from a bent cylindrical surface. Fano resonance appears as a purely geometric effect in the conductance, the corresponding energy of quasibound state is obviously influenced by the torsion and length of the nanotube. We also find new plateaus in the conductance. The transport of double-degenerate mode in this geometry is reminiscent of the Zeeman coupling between the magnetic field and spin angular momentum in quasi-one-dimensional structure.

  14. Helical Muon Beam Cooling Channel Engineering Design

    SciTech Connect

    Kashikhin, V.S.; Lopes, M.L.; Romanov, G.V.; Tartaglia, M.A.; Yonehara, K.; Yu, M.; Zlobin, A.V.; Flanagan, G.; Johnson, R.P.; Kazakevich, G.M.; Marhauser, F.; /MUONS Inc., Batavia

    2012-05-01

    The Helical Cooling Channel (HCC), a novel technique for six-dimensional (6D) ionization cooling of muon beams, has shown considerable promise based on analytic and simulation studies. However, the implementation of this revolutionary method of muon cooling requires new techniques for the integration of hydrogen-pressurized, high-power RF cavities into the low-temperature superconducting magnets of the HCC. We present the progress toward a conceptual design for the integration of 805 MHz RF cavities into a 10 T Nb{sub 3}Sn based HCC test section. We include discussions on the pressure and thermal barriers needed within the cryostat to maintain operation of the magnet at 4.2 K while operating the RF and energy absorber at a higher temperature. Additionally, we include progress on the Nb{sub 3}Sn helical solenoid design.

  15. A PIP1 Aquaporin Contributes to Hydrostatic Pressure-Induced Water Transport in Both the Root and Rosette of Arabidopsis1[C][W

    PubMed Central

    Postaire, Olivier; Tournaire-Roux, Colette; Grondin, Alexandre; Boursiac, Yann; Morillon, Raphaël; Schäffner, Anton R.; Maurel, Christophe

    2010-01-01

    Aquaporins are channel proteins that facilitate the transport of water across plant cell membranes. In this work, we used a combination of pharmacological and reverse genetic approaches to investigate the overall significance of aquaporins for tissue water conductivity in Arabidopsis (Arabidopsis thaliana). We addressed the function in roots and leaves of AtPIP1;2, one of the most abundantly expressed isoforms of the plasma membrane intrinsic protein family. At variance with the water transport phenotype previously described in AtPIP2;2 knockout mutants, disruption of AtPIP1;2 reduced by 20% to 30% the root hydrostatic hydraulic conductivity but did not modify osmotic root water transport. These results document qualitatively distinct functions of different PIP isoforms in root water uptake. The hydraulic conductivity of excised rosettes (Kros) was measured by a novel pressure chamber technique. Exposure of Arabidopsis plants to darkness increased Kros by up to 90%. Mercury and azide, two aquaporin inhibitors with distinct modes of action, were able to induce similar inhibition of Kros by approximately 13% and approximately 25% in rosettes from plants grown in the light or under prolonged (11–18 h) darkness, respectively. Prolonged darkness enhanced the transcript abundance of several PIP genes, including AtPIP1;2. Mutant analysis showed that, under prolonged darkness conditions, AtPIP1;2 can contribute to up to approximately 20% of Kros and to the osmotic water permeability of isolated mesophyll protoplasts. Therefore, AtPIP1;2 can account for a significant portion of aquaporin-mediated leaf water transport. The overall work shows that AtPIP1;2 represents a key component of whole-plant hydraulics. PMID:20034965

  16. Development of a rapid, sensitive TaqMan real-time RT-PCR assay for the detection of Rose rosette virus using multiple gene targets.

    PubMed

    Babu, Binoy; Jeyaprakash, Ayyamperumal; Jones, Debra; Schubert, Timothy S; Baker, Carlye; Washburn, Brian K; Miller, Steven H; Poduch, Kristina; Knox, Gary W; Ochoa-Corona, Francisco M; Paret, Mathews L

    2016-09-01

    Rose rosette virus (RRV), belonging to the genus Emaravirus, is a highly destructive pathogen that causes rose rosette disease. The disease is a major concern for the rose industry in the U.S. due to the lack of highly sensitive methods for early detection of RRV. This is critical, as early identification of the infected plants and eradication is necessary in minimizing the risks associated with the spread of the disease. A highly reliable, specific and sensitive detection assay is thus required to test and confirm the presence of RRV in suspected plant samples. In this study a TaqMan real-time reverse transcription-polymerase chain reaction (RT-PCR) assay was developed for the detection of RRV from infected roses, utilizing multiple gene targets. Four pairs of primers and probes; two of them (RRV_2-1 and RRV_2-2) based on the consensus sequences of the glycoprotein gene (RNA2) and the other two (RRV_3-2 and RRV_3-5) based on the nucleocapsid gene (RNA3) were designed. The specificity of the primers and probes was evaluated against other representative viruses infecting roses, belonging to the genera Alfamovirus, Cucumovirus, Ilarvirus, Nepovirus, Tobamovirus, and Tospovirus and one Emaravirus (Wheat mosaic virus). Dilution assays using the in vitro transcripts (spiked with total RNA from healthy plants, and non-spiked) showed that all the primers and probes are highly sensitive in consistently detecting RRV with a detection limit of 1 fg. Testing of the infected plants over a period of time (three times in monthly intervals) indicated high reproducibility, with the primer/probe RRV_3-5 showing 100% positive detection, while RRV_2-1, RRV_2-2 and RRV_3-2 showed 90% positive detection. The developed real-time RT-PCR assay is reliable, highly sensitive, and can be easily used in diagnostic laboratories for testing and confirmation of RRV. PMID:27210549

  17. Helical Tomotherapy for Parotid Gland Tumors

    SciTech Connect

    Lee, Tae Kyu; Rosen, Isaac I.; Gibbons, John P.; Fields, Robert S.; Hogstrom, Kenneth R.

    2008-03-01

    Purpose: To investigate helical tomotherapy (HT) intensity-modulated radiotherapy (IMRT) as a postoperative treatment for parotid gland tumors. Methods and Materials: Helical tomotherapy plans were developed for 4 patients previously treated with segmental multileaf collimator (SMLC) IMRT. A primary planning target volume (PTV64) and two secondary PTVs (PTV60, PTV54) were defined. The clinical goals from the SMLC plans were applied as closely as possible to the HT planning. The SMLC plans included bolus, whereas HT plans did not. Results: In general, the HT plans showed better target coverage and target dose homogeneity. The minimum doses to the desired coverage volume were greater, on average, in the HT plans for all the targets. Minimum PTV doses were larger, on average, in the HT plans by 4.6 Gy (p = 0.03), 4.8 Gy (p = 0.06), and 4.9 Gy (p = 0.06) for PTV64, PTV60, and PTV54, respectively. Maximum PTV doses were smaller, on average, by 2.9 Gy (p = 0.23), 3.2 Gy (p = 0.02), and 3.6 Gy (p = 0.03) for PTV64, PTV60, and PTV54, respectively. Average dose homogeneity index was statistically smaller in the HT plans, and conformity index was larger for PTV64 in 3 patients. Tumor control probabilities were higher for 3 of the 4 patients. Sparing of normal structures was comparable for the two techniques. There were no significant differences between the normal tissue complication probabilities for the HT and SMLC plans. Conclusions: Helical tomotherapy treatment plans were comparable to or slightly better than SMLC plans. Helical tomotherapy is an effective alternative to SMLC IMRT for treatment of parotid tumors.

  18. Sawtooth oscillations about helical current channels

    NASA Technical Reports Server (NTRS)

    Theobald, M. L.; Montgomery, David; Doolen, G. D.; Dahlburg, J. P.

    1989-01-01

    An existing pseudospectral code for solving the three-dimensional equations of reduced magnetohydrodynamics is extended by adding a temperature equation. Resistivities and thermal conductivities are given their (isotropic) Braginskii temperature dependences, and are advanced self-consistently. Realistic-looking sawtooth oscillations are observed at modest Lundquist and Reynolds numbers. However, the oscillations are excited upon, and relax back to, a helical (rather than an axisymmetric) current channel.

  19. Bacteria that glide with helical tracks

    PubMed Central

    Nan, Beiyan; McBride, Mark J.; Chen, Jing; Zusman, David R.; Oster, George

    2014-01-01

    Many bacteria glide smoothly on surfaces, but with no discernable propulsive organelles on their surface. Recent experiments with Myxococcus xanthus and Flavobacterium johnsoniae show that both distantly related bacterial species glide utilizing proteins that move in helical tracks, albeit with significantly different motility mechanisms. Both species utilize proton motive force for movement. However, the motors that power gliding in M. xanthus have been identified, while the F. johnsoniae motors remain to be discovered. PMID:24556443

  20. Field of a helical Siberian Snake

    SciTech Connect

    Luccio, A.

    1995-02-01

    To preserve the spin polarization of a beam of high energy protons in a circular accelerator, magnets with periodic magnetic field, called Siberian Snakes are being used. Recently, it was proposed to build Siberian Snakes with superconducting helical dipoles. In a helical, or twisted dipole, the magnetic field is perpendicular to the axis of the helix and rotates around it as one proceeds along the magnet. In an engineering study of a 4 Tesla helical snake, the coil geometry is derived, by twisting, from the geometry of a cosine superconducting dipole. While waiting for magnetic measurement data on such a prototype, an analytical expression for the field of the helice is important, to calculate the particle trajectories and the spin precession in the helix. This model will also allow to determine the optical characteristics of the snake, as an insertion in the lattice of the accelerator. In particular, one can calculate the integrated multipoles through the magnet and the equivalent transfer matrix. An expression for the field in the helix body, i.e., excluding the fringe field was given in a classical paper. An alternate expression can be found by elaborating on the treatment of the field of a transverse wiggler obtained under the rather general conditions that the variables are separable. This expression exactly satisfies Maxwell`s div and curl equations for a stationary field, {del} {center_dot} B = 0, {del} x B = 0. This approach is useful in that it will allow one to use much of the work already done on the problem of inserting wigglers and undulators in the lattice of a circular accelerator.

  1. Noncontrast helical CT for ureteral stones.

    PubMed

    Boridy, I C; Nikolaidis, P; Kawashima, A; Sandler, C M; Goldman, S M

    1998-01-01

    Noncontrast helical computed tomography (CT) has recently been found to be superior to excretory urography (IVU) in the evaluation of patients with suspected ureterolithiasis. Noncontrast helical CT does not require the use of intravenous contrast material with its associated cost and risk of adverse reactions and can be completed within 5 min, in most cases. Noncontrast CT often detects extraurinary pathology responsible for the patient's symptoms. CT is also more sensitive than IVU in detecting the calculus, regardless of its size, location, and chemical composition. However, confidently differentiating ureteral calculi from phleboliths along the course of the ureter may, at times, be difficult. The "tissue-rim" sign, a rim of soft tissue attenuation around the suspicious calcification, is helpful in making this distinction. Noncontrast CT does not provide physiological information about renal function and the degree of obstruction. A pilot study has suggested a proportional relationship between the extent of perinephric edema and the degree of obstruction. The cost of the examination and the radiation dose delivered to the patient may be higher with CT. Despite these limitations, noncontrast helical CT has quickly become the imaging study of choice in evaluating patients with acute flank pain. PMID:9542010

  2. The infrared dichroism of transmembrane helical polypeptides.

    PubMed Central

    Axelsen, P H; Kaufman, B K; McElhaney, R N; Lewis, R N

    1995-01-01

    Polarized attenuated total internal reflectance techniques were applied to study the infrared dichroism of the amide I transition moment in two membrane-bound peptides that are known to form oriented transmembrane helices: gramicidin A in a supported phospholipid monolayer and Ac-Lys2-Leu24-Lys2-amide (L24) in oriented multibilayers. These studies were performed to test the ability of these techniques to determine the orientation of these peptides, to verify the value of optical parameters used to calculate electric field strengths, to examine the common assumptions regarding the amide I transition moment orientation, and to ascertain the effect of surface imperfections on molecular disorder. The two peptides exhibit marked differences in the shape and frequency of their amide I absorption bands. Yet both peptides are highly ordered and oriented with their helical axes perpendicular to the membrane surface. In the alpha-helix formed by L24, there is evidence for a mode with type E1 symmetry contributing to amide I, and the amide I transition moment must be more closely aligned with the peptide C=O (< 34 degrees) than earlier studies have suggested. These results indicate that long-standing assumptions about the orientation of amide I in a peptide require some revision, but that in general, infrared spectroscopy yields reliable information about the orientation of membrane-bound helical peptides. Images FIGURE 1 PMID:8599683

  3. Total scalp irradiation using helical tomotherapy

    SciTech Connect

    Orton, Nigel . E-mail: nporton@facstaff.wisc.edu; Jaradat, Hazim; Welsh, James; Tome, Wolfgang

    2005-09-30

    Homogeneous irradiation of the scalp poses technical and dosimetric challenges due to the extensive, superficial, curved treatment volume. Conventional treatments on a linear accelerator use multiple matched electron fields or a combination of electron and photon fields. Problems with these techniques include dose heterogeneity in the target due to varying source-to-skin distance (SSD) and angle of beam incidence, significant dose to the brain, and the potential for overdose or underdose at match lines between the fields. Linac-based intensity-modulated radiation therapy (IMRT) plans have similar problems. This work presents treatment plans for total scalp irradiation on a helical tomotherapy machine. Helical tomotherapy is well-suited for scalp irradiation because it has the ability to deliver beamlets that are tangential to the scalp at all points. Helical tomotherapy also avoids problems associated with field matching and use of more than one modality. Tomotherapy treatment plans were generated and are compared to plans for treatment of the same patient on a linac. The resulting tomotherapy plans show more homogeneous target dose and improved critical structure dose when compared to state-of-the-art linac techniques. Target equivalent uniform dose (EUD) for the best tomotherapy plan was slightly higher than for the linac plan, while the volume of brain tissue receiving over 30 Gy was reduced by two thirds. Furthermore, the tomotherapy plan can be more reliably delivered than linac treatments, because the patient is aligned prior to each treatment based on megavoltage computed tomography (MVCT)

  4. Bifurcated helical core equilibrium states in tokamaks

    NASA Astrophysics Data System (ADS)

    Cooper, W. A.; Chapman, I. T.; Schmitz, O.; Turnbull, A. D.; Tobias, B. J.; Lazarus, E. A.; Turco, F.; Lanctot, M. J.; Evans, T. E.; Graves, J. P.; Brunetti, D.; Pfefferlé, D.; Reimerdes, H.; Sauter, O.; Halpern, F. D.; Tran, T. M.; Coda, S.; Duval, B. P.; Labit, B.; Pochelon, A.; Turnyanskiy, M. R.; Lao, L.; Luce, T. C.; Buttery, R.; Ferron, J. R.; Hollmann, E. M.; Petty, C. C.; van Zeeland, M.; Fenstermacher, M. E.; Hanson, J. M.; Lütjens, H.

    2013-07-01

    Tokamaks with weak to moderate reversed central shear in which the minimum inverse rotational transform (safety factor) qmin is in the neighbourhood of unity can trigger bifurcated magnetohydrodynamic equilibrium states, one of which is similar to a saturated ideal internal kink mode. Peaked prescribed pressure profiles reproduce the ‘snake’ structures observed in many tokamaks which has led to a novel explanation of the snake as a bifurcated equilibrium state. Snake equilibrium structures are computed in simulations of the tokamak à configuration variable (TCV), DIII-D and mega amp spherical torus (MAST) tokamaks. The internal helical deformations only weakly modulate the plasma-vacuum interface which is more sensitive to ripple and resonant magnetic perturbations. On the other hand, the external perturbations do not alter the helical core deformation in a significant manner. The confinement of fast particles in MAST simulations deteriorate with the amplitude of the helical core distortion. These three-dimensional bifurcated solutions constitute a paradigm shift that motivates the applications of tools developed for stellarator research in tokamak physics investigations.

  5. Mechanical resonances of helically coiled carbon nanowires.

    PubMed

    Saini, D; Behlow, H; Podila, R; Dickel, D; Pillai, B; Skove, M J; Serkiz, S M; Rao, A M

    2014-01-01

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f₂/f₁ was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers. PMID:24986377

  6. Manipulation of wavefront using helical metamaterials.

    PubMed

    Yang, Zhenyu; Wang, Zhaokun; Tao, Huan; Zhao, Ming

    2016-08-01

    Helical metamaterials, a kind of 3-dimensional structure, has relatively strong coupling effect among the helical nano-wires. Therefore, it is expected to be a good candidate for generating phase shift and controlling wavefront with high efficiency. In this paper, using the finite-difference time-domain (FDTD) method, we studied the phase shift properties in the helical metamaterials. It is found that the phase shift occurs for both transmitted and reflected light waves. And the maximum of reflection coefficients can reach over 60%. In addition, the phase shift (φ) is dispersionless in the range of 600 nm to 860 nm, that is, it is only dominated by the initial angle (θ) of the helix. The relationship between them is φ = ± 2θ. Using Jones calculus we give a further explanation for these properties. Finally, by arranging the helixes in an array with a constant phase gradient, the phenomenon of anomalous refraction was also observed in a broad wavelength range. PMID:27505790

  7. Buckling transition in long α-helices

    SciTech Connect

    Palenčár, Peter; Bleha, Tomáš

    2014-11-07

    The treatment of bending and buckling of stiff biopolymer filaments by the popular worm-like chain model does not provide adequate understanding of these processes at the microscopic level. Thus, we have used the atomistic molecular-dynamic simulations and the Amber03 force field to examine the compression buckling of α-helix (AH) filaments at room temperature. It was found that the buckling instability occurs in AHs at the critical force f{sub c} in the range of tens of pN depending on the AH length. The decrease of the force f{sub c} with the contour length follows the prediction of the classic thin rod theory. At the force f{sub c} the helical filament undergoes the swift and irreversible transition from the smoothly bent structure to the buckled one. A sharp kink in the AH contour arises at the transition, accompanied by the disruption of the hydrogen bonds in its vicinity. The kink defect brings in an effective softening of the AH molecule at buckling. Nonbonded interactions between helical branches drive the rearrangement of a kinked AH into the ultimate buckled structure of a compact helical hairpin described earlier in the literature.

  8. Helical antimicrobial polypeptides with radial amphiphilicity

    PubMed Central

    Xiong, Menghua; Lee, Michelle W.; Mansbach, Rachael A.; Song, Ziyuan; Bao, Yan; Peek, Richard M.; Yao, Catherine; Chen, Lin-Feng; Ferguson, Andrew L.; Wong, Gerard C. L.; Cheng, Jianjun

    2015-01-01

    α-Helical antimicrobial peptides (AMPs) generally have facially amphiphilic structures that may lead to undesired peptide interactions with blood proteins and self-aggregation due to exposed hydrophobic surfaces. Here we report the design of a class of cationic, helical homo-polypeptide antimicrobials with a hydrophobic internal helical core and a charged exterior shell, possessing unprecedented radial amphiphilicity. The radially amphiphilic structure enables the polypeptide to bind effectively to the negatively charged bacterial surface and exhibit high antimicrobial activity against both gram-positive and gram-negative bacteria. Moreover, the shielding of the hydrophobic core by the charged exterior shell decreases nonspecific interactions with eukaryotic cells, as evidenced by low hemolytic activity, and protects the polypeptide backbone from proteolytic degradation. The radially amphiphilic polypeptides can also be used as effective adjuvants, allowing improved permeation of commercial antibiotics in bacteria and enhanced antimicrobial activity by one to two orders of magnitude. Designing AMPs bearing this unprecedented, unique radially amphiphilic structure represents an alternative direction of AMP development; radially amphiphilic polypeptides may become a general platform for developing AMPs to treat drug-resistant bacteria. PMID:26460016

  9. Nuclear design of Helical Cruciform Fuel rods

    SciTech Connect

    Shirvan, K.; Kazimi, M. S.

    2012-07-01

    In order to increase the power density of current and new light water reactor designs, the Helical Cruciform Fuel (HCF) rods are proposed. The HCF rods are equivalent to a cylindrical rod, with the fuel in a cruciform shaped, twisted axially. The HCF rods increase the surface area to volume ratio and inter-subchannel mixing behavior due to their cruciform and helical shapes, respectively. In a previous study, the HCF rods have shown the potential to up-rate existing PWRs by 50% and BWRs by 25%. However, HCF rods do display different neutronics modeling and performance. The cruciform cross section of HCF rods creates radially asymmetric heat generation and temperature distribution. The nominal HCF rod's beginning of life reactivity is reduced, compared to a cylindrical rod with the same fuel volume, by 500 pcm, due to increase in absorption in cladding. The rotation of these rods accounts for reactivity changes, which depends on the H/HM ratio of the pin cell. The HCF geometry shows large sensitivities to U{sup 235} or gadolinium enrichments compared to a cylindrical geometry. In addition, the gadolinium-containing HCF rods show a stronger effect on neighboring HCF rods than in case of cylindrical rods, depending on the orientation of the HCF rods. The helical geometry of the rods introduces axial shadowing of about 600 pcm, not seen in typical cylindrical rods. (authors)

  10. Mechanical Resonances of Helically Coiled Carbon Nanowires

    NASA Astrophysics Data System (ADS)

    Saini, D.; Behlow, H.; Podila, R.; Dickel, D.; Pillai, B.; Skove, M. J.; Serkiz, S. M.; Rao, A. M.

    2014-07-01

    Despite their wide spread applications, the mechanical behavior of helically coiled structures has evaded an accurate understanding at any length scale (nano to macro) mainly due to their geometrical complexity. The advent of helically coiled micro/nanoscale structures in nano-robotics, nano-inductors, and impact protection coatings has necessitated the development of new methodologies for determining their shear and tensile properties. Accordingly, we developed a synergistic protocol which (i) integrates analytical, numerical (i.e., finite element using COMSOL®) and experimental (harmonic detection of resonance; HDR) methods to obtain an empirically validated closed form expression for the shear modulus and resonance frequency of a singly clamped helically coiled carbon nanowire (HCNW), and (ii) circumvents the need for solving 12th order differential equations. From the experimental standpoint, a visual detection of resonances (using in situ scanning electron microscopy) combined with HDR revealed intriguing non-planar resonance modes at much lower driving forces relative to those needed for linear carbon nanotube cantilevers. Interestingly, despite the presence of mechanical and geometrical nonlinearities in the HCNW resonance behavior the ratio of the first two transverse modes f2/f1 was found to be similar to the ratio predicted by the Euler-Bernoulli theorem for linear cantilevers.

  11. A biomimetic jellyfish robot based on ionic polymer metal composite actuators

    NASA Astrophysics Data System (ADS)

    Yeom, Sung-Weon; Oh, Il-Kwon

    2009-08-01

    A biomimetic jellyfish robot based on ionic polymer metal composite actuators was fabricated and activated to mimic real locomotive behavior with pulse and recovery processes. To imitate the curved shape of the jellyfish, a thermal treatment was applied to obtain a permanent initial deformation of a hemispherical form. The bio-inspired input signal was generated for mimicking real locomotion of the jellyfish. The vertical floating displacement and the thrust force of the biomimetic jellyfish robot under various input signals were measured and compared. The present results show that the bio-inspired electrical input signal with pulse-recovery process generates much higher floating velocity of the biomimetic jellyfish robot in comparison with pure sinusoidal excitations. The curved shape of the IPMC actuator through thermal treatments can be successfully applied to mimic the real biomimetic robots with smooth curves.

  12. Bioinspired Design of Ultrathin 2D Bimetallic Metal-Organic-Framework Nanosheets Used as Biomimetic Enzymes.

    PubMed

    Wang, Yixian; Zhao, Meiting; Ping, Jianfeng; Chen, Bo; Cao, Xiehong; Huang, Ying; Tan, Chaoliang; Ma, Qinglang; Wu, Shixin; Yu, Yifu; Lu, Qipeng; Chen, Junze; Zhao, Wei; Ying, Yibin; Zhang, Hua

    2016-06-01

    With the bioinspired design of organic ligands and metallic nodes, novel ultrathin 2D bimetallic metal-organic-framework nanosheets are successfully synthesized, which can serve as advanced 2D biomimetic nanomaterials to mimic heme proteins. PMID:27008574

  13. Evolution of field line helicity during magnetic reconnection

    SciTech Connect

    Russell, A. J. B. Hornig, G.; Wilmot-Smith, A. L.; Yeates, A. R.

    2015-03-15

    We investigate the evolution of field line helicity for magnetic fields that connect two boundaries without null points, with emphasis on localized finite-B magnetic reconnection. Total (relative) magnetic helicity is already recognized as an important topological constraint on magnetohydrodynamic processes. Field line helicity offers further advantages because it preserves all topological information and can distinguish between different magnetic fields with the same total helicity. Magnetic reconnection changes field connectivity and field line helicity reflects these changes; the goal of this paper is to characterize that evolution. We start by deriving the evolution equation for field line helicity and examining its terms, also obtaining a simplified form for cases where dynamics are localized within the domain. The main result, which we support using kinematic examples, is that during localized reconnection in a complex magnetic field, the evolution of field line helicity is dominated by a work-like term that is evaluated at the field line endpoints, namely, the scalar product of the generalized field line velocity and the vector potential. Furthermore, the flux integral of this term over certain areas is very small compared to the integral of the unsigned quantity, which indicates that changes of field line helicity happen in a well-organized pairwise manner. It follows that reconnection is very efficient at redistributing helicity in complex magnetic fields despite having little effect on the total helicity.

  14. Cryo-EM Structure Determination Using Segmented Helical Image Reconstruction.

    PubMed

    Fromm, S A; Sachse, C

    2016-01-01

    Treating helices as single-particle-like segments followed by helical image reconstruction has become the method of choice for high-resolution structure determination of well-ordered helical viruses as well as flexible filaments. In this review, we will illustrate how the combination of latest hardware developments with optimized image processing routines have led to a series of near-atomic resolution structures of helical assemblies. Originally, the treatment of helices as a sequence of segments followed by Fourier-Bessel reconstruction revealed the potential to determine near-atomic resolution structures from helical specimens. In the meantime, real-space image processing of helices in a stack of single particles was developed and enabled the structure determination of specimens that resisted classical Fourier helical reconstruction and also facilitated high-resolution structure determination. Despite the progress in real-space analysis, the combination of Fourier and real-space processing is still commonly used to better estimate the symmetry parameters as the imposition of the correct helical symmetry is essential for high-resolution structure determination. Recent hardware advancement by the introduction of direct electron detectors has significantly enhanced the image quality and together with improved image processing procedures has made segmented helical reconstruction a very productive cryo-EM structure determination method. PMID:27572732

  15. Faraday signature of magnetic helicity from reduced depolarization

    SciTech Connect

    Brandenburg, Axel; Stepanov, Rodion

    2014-05-10

    Using one-dimensional models, we show that a helical magnetic field with an appropriate sign of helicity can compensate the Faraday depolarization resulting from the superposition of Faraday-rotated polarization planes from a spatially extended source. For radio emission from a helical magnetic field, the polarization as a function of the square of the wavelength becomes asymmetric with respect to zero. Mathematically speaking, the resulting emission occurs then either at observable or at unobservable (imaginary) wavelengths. We demonstrate that rotation measure (RM) synthesis allows for the reconstruction of the underlying Faraday dispersion function in the former case, but not in the latter. The presence of positive magnetic helicity can thus be detected by observing positive RM in highly polarized regions in the sky and negative RM in weakly polarized regions. Conversely, negative magnetic helicity can be detected by observing negative RM in highly polarized regions and positive RM in weakly polarized regions. The simultaneous presence of two magnetic constituents with opposite signs of helicity is shown to possess signatures that can be quantified through polarization peaks at specific wavelengths and the gradient of the phase of the Faraday dispersion function. Similar polarization peaks can tentatively also be identified for the bi-helical magnetic fields that are generated self-consistently by a dynamo from helically forced turbulence, even though the magnetic energy spectrum is then continuous. Finally, we discuss the possibility of detecting magnetic fields with helical and non-helical properties in external galaxies using the Square Kilometre Array.

  16. Biomimetic and microbial approaches to solar fuel generation.

    PubMed

    Magnuson, Ann; Anderlund, Magnus; Johansson, Olof; Lindblad, Peter; Lomoth, Reiner; Polivka, Tomas; Ott, Sascha; Stensjö, Karin; Styring, Stenbjörn; Sundström, Villy; Hammarström, Leif

    2009-12-21

    Photosynthesis is performed by a multitude of organisms, but in nearly all cases, it is variations on a common theme: absorption of light followed by energy transfer to a reaction center where charge separation takes place. This initial form of chemical energy is stabilized by the biosynthesis of carbohydrates. To produce these energy-rich products, a substrate is needed that feeds in reductive equivalents. When photosynthetic microorganisms learned to use water as a substrate some 2 billion years ago, a fundamental barrier against unlimited use of solar energy was overcome. The possibility of solar energy use has inspired researchers to construct artificial photosynthetic systems that show analogy to parts of the intricate molecular machinery of photosynthesis. Recent years have seen a reorientation of efforts toward creating integrated light-to-fuel systems that can use solar energy for direct synthesis of energy-rich compounds, so-called solar fuels. Sustainable production of solar fuels is a long awaited development that promises extensive solar energy use combined with long-term storage. The stoichiometry of water splitting into molecular oxygen, protons, and electrons is deceptively simple; achieving it by chemical catalysis has proven remarkably difficult. The reaction center Photosystem II couples light-induced charge separation to an efficient molecular water-splitting catalyst, a Mn(4)Ca complex, and is thus an important template for biomimetic chemistry. In our aims to design biomimetic manganese complexes for light-driven water oxidation, we link photosensitizers and charge-separation motifs to potential catalysts in supramolecular assemblies. In photosynthesis, production of carbohydrates demands the delivery of multiple reducing equivalents to CO(2). In contrast, the two-electron reduction of protons to molecular hydrogen is much less demanding. Virtually all microorganisms have enzymes called hydrogenases that convert protons to hydrogen, many of

  17. From natural to bioassisted and biomimetic artificial water channel systems.

    PubMed

    Barboiu, Mihail; Gilles, Arnaud

    2013-12-17

    Within biological systems, natural channels and pores transport metabolites across the cell membranes. Researchers have explored artificial ion-channel architectures as potential mimics of natural ionic conduction. All these synthetic systems have produced an impressive collection of alternative artificial ion-channels. Amazingly, researchers have made far less progress in the area of synthetic water channels. The development of synthetic biomimetic water channels and pores could contribute to a better understanding of the natural function of protein channels and could offer new strategies to generate highly selective, advanced water purification systems. Despite the imaginative work by synthetic chemists to produce sophisticated architectures that confine water clusters, most synthetic water channels have used natural proteins channels as the selectivity components, embedded in the diverse arrays of bioassisted artificial systems. These systems combine natural proteins that present high water conductance states under natural conditions with artificial lipidic or polymeric matrixes. Experimental results have demonstrated that natural biomolecules can be used as bioassisted building blocks for the construction of highly selective water transport through artificial membranes. A next step to further the potential of these systems was the design and construction of simpler compounds that maintain the high conduction activity obtained with natural compounds leading to fully synthetic artificial biomimetic systems. Such studies aim to use constitutional selective artificial superstructures for water/proton transport to select functions similar to the natural structures. Moving to simpler water channel systems offers a chance to better understand mechanistic and structural behaviors and to uncover novel interactive water-channels that might parallel those in biomolecular systems. This Account discusses the incipient development of the first artificial water channels

  18. New Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence

    NASA Astrophysics Data System (ADS)

    Banerjee, Supratik; Galtier, Sebastien

    2016-04-01

    Hall magnetohydrodynamics is a mono-fluid plasma model appropriate for probing Final{some of the} physical processes (other than pure kinetic effects) at length scales smaller than the scales of standard MHD. In sub-ionic space plasma turbulence (e.g. the solar wind) this fluid model has been proved to be useful. Three-dimensional incompressible Hall magnetohydrodynamics (MHD) possesses three inviscid invariants which are the total energy, the magnetic helicity and the generalized helicity. In this presentation, we would like to discuss new exact relations for helicities (magnetic helicities and generalized helicities) which are derived for homogeneous stationary (not necessarily isotropic) Hall MHD turbulence (and also for its inertialess electron MHD limit) in the asymptotic limit of large Reynolds numbers. The universal laws are written only in terms of mixed second-order structure functions, i.e. the scalar product of two different increments and are written simply as ηM = di < δ ( {b} × {j}) \\cdot δ {b} >, with ηM the average magnetic helicity flux rate, {b} the magnetic field, {j} the current and ± ηG = < δ ( {v} × {Ω} ) \\cdot δ {Ω} > , with ηM the average generalized helicity flux rate, {v} the fluid velocity and {Ω} = {b} + dI {ω} being the generalized helicity where ω is simply the fluid vorticity ( = nabla × {v}). It provides, therefore, a direct measurement of the dissipation rates for the corresponding helicities even in case of an anisotropic plasma turbulence. This study shows that the generalized helicity cascade is strongly linked to the left polarized fluctuations while the magnetic helicity cascade is linked to the right polarized fluctuations. The newly derived relations also show that like energy, a non-zero helicity flux can only be associated to a departure of Beltrami flow state. {Reference} S. Banerjee & S. Galtier, {Chiral Exact Relations for Helicities in Hall Magnetohydrodynamic Turbulence} (submitted).

  19. SMART Observation of Magnetic Helicity in Solar Filaments

    NASA Astrophysics Data System (ADS)

    Hagino, M.; Kitai, R.; Shibata, K.

    2006-08-01

    We examined the magnetic helicity of solar filaments from their structure in the chromosphere and corona. The H-alpha telescope of the Solar Magnetic Activity Research Telescope (SMART) observed 239 intermediate filaments from 2005 July 1 to 2006 May 15. The intermediate filament usually locates between two active regions. Using these images, we identified the filament spine and its barbs, and determined the chromospheric filament helicity from the mean angle between each barbs and a spine. We found that 71% (78 of 110) of intermediate filaments in the northern hemisphere are negative helicity and 67% (87 of 129) of filaments in the southern hemisphere are positive, which agreed with the well-known hemispheric tendency of the magnetic helicity. Additionally, we studied the coronal helicity of intermediate filaments. The coronal filament helicity is defined as the crossing angle of threads formed a filament. The helicity pattern of coronal filaments obtained with EIT/SOHO 171A also shows the helicity hemispheric tendency. Namely, 65% (71 of 110) of coronal filaments in the northern hemisphere exhibit negative helicity and the 65% (84 of 129) of filaments in the southern hemisphere show negative helicity. These data were observed in the same day with the SMART H-alpha data. Moreover, we found 12 filament eruptions in our data. The 7 of 12 filaments show the clear opposite sign of the hemispheric tendency of the magnetic helicity. The helicity seems to be change during temporal evolution. This results suggest that filament instability may be driven by the opposite sign helicity injection from the foot point of the barb.

  20. Design and demonstration of a biomimetic wing section using lightweight piezoceramic composite actuator (LIPCA)

    NASA Astrophysics Data System (ADS)

    Lim, Sahng M.; Lee, Sangki; Park, Hoon C.; Yoon, Kwang J.; Goo, Nam Seo

    2003-08-01

    Biomimetic wing sections actuated by piezoceramics actuator LIPCA have been designed and their actuation displacements estimated by using the thermal analogy and MSC/NASTRAN based on the linear elasticity. The wing sections are fabricated as the design and tested for evaluation. Measured actuation displacements were larger than the estimated values mainly due to the material non-linearity of the PZT wafer. The biomimetic wing sections can be used for control surfaces of small scale UAVs.

  1. Guest-Induced Arylamide Polymer Helicity: Twist-Sense Bias and Solvent-Dependent Helicity Inversion.

    PubMed

    Zhang, Peng; Zhang, Liang; Wang, Ze-Kun; Zhang, Yun-Chang; Guo, Rong; Wang, Hui; Zhang, Dan-Wei; Li, Zhan-Ting

    2016-06-01

    A benzene/naphthalene alternately incorporated amide polymer was synthesized and characterized. (1) H NMR spectroscopy, fluorescence, and circular dichroism (CD) experiments indicated that, in chloroform, the polymer could be induced by the chiral l-aspartic acid dianion or one of its derivatives to form a helical tubular conformation with twist-sense bias. CD titration studies showed that the l-aspartic acid dianion (8 equiv.) could lead to a maximum Cotton effect. It was also revealed that the twist-sense bias obeyed the majority rule, and 70 % enantiomeric excess could realize the maximum helicity bias. Adding acetonitrile to the solution of chloroform caused inversion of the guest-induced helicity bias of the polymer. PMID:27027979

  2. Helical muon beam cooling channel engineering design

    SciTech Connect

    Johnson, Rolland

    2015-08-07

    The Helical Cooling Channel (HCC) achieves effective ionization cooling of the six-dimensional (6d) phase space of a muon beam by means of a series of 21st century inventions. In the HCC, hydrogen-pressurized RF cavities enable high RF gradients in strong external magnetic fields. The theory of the HCC, which requires a magnetic field with solenoid, helical dipole, and helical quadrupole components, demonstrates that dispersion in the gaseous hydrogen energy absorber provides effective emittance exchange to enable longitudinal ionization cooling. The 10-year development of a practical implementation of a muon-beam cooling device has involved a series of technical innovations and experiments that imply that an HCC of less than 300 m length can cool the 6d emittance of a muon beam by six orders of magnitude. We describe the design and construction plans for a prototype HCC module based on oxygen-doped hydrogen-pressurized RF cavities that are loaded with dielectric, fed by magnetrons, and operate in a superconducting helical solenoid magnet. The first phase of this project saw the development of a conceptual design for the integration of 805 MHz RF cavities into a 10 T Nb3Sn based HS test section. Two very novel ideas are required to realize the design. The first idea is the use of dielectric inserts in the RF cavities to make them smaller for a given frequency so that the cavities and associated plumbing easily fit inside the magnet cryostat. Calculations indicate that heat loads will be tolerable, while RF breakdown of the dielectric inserts will be suppressed by the pressurized hydrogen gas. The second new idea is the use of a multi-layer Nb3Sn helical solenoid. The technology demonstrations for the two aforementioned key components of a 10T, 805 MHz HCC were begun in this project. The work load in the Fermilab Technical Division made it difficult to test a multi-layer Nb3Sn solenoid as originally planned. Instead, a complementary project was approved by the DOE

  3. Friction and wear behaviors of compacted graphite iron with different biomimetic units fabricated by laser cladding

    NASA Astrophysics Data System (ADS)

    Sun, Na; Shan, Hongyu; Zhou, Hong; Chen, Darong; Li, Xiaoyan; Xia, Wen; Ren, Luquan

    2012-07-01

    Mimicking the biological characters on the cuticles of pangolin scales, biomimetic units were fabricated on the surfaces of compacted graphite cast iron (CGI) with different unit materials using laser cladding process. The influences of various unit materials including TiC, WC, B4C and Al2O3 powders on the friction and wear behaviors of CGI were investigated. The wear resistance mechanism of biomimetic specimens was discussed. The results indicated that the wear resistance of biomimetic specimens cladding TiC was the best; the specimens cladding WC or B4C were in the middle; and the specimens cladding Al2O3 was the worst. The sequence of friction coefficient values of biomimetic specimens cladding different ceramic powders from high to low was B4C, TiC, WC and Al2O3. The wear mechanism of untreated specimen was mainly adhesion wear, abrasive wear as well as the oxidation wear, whereas the adhesive wear and abrasive wear was the main wear mechanism of the regions of substrate in biomimetic specimens and slight adhesion, abrasive wear and fatigue wear on the regions of biomimetic units.

  4. Biomimetic microchannels of planar reactors for optimized photocatalytic efficiency of water purification.

    PubMed

    Liao, Wuxia; Wang, Ning; Wang, Taisheng; Xu, Jia; Han, Xudong; Liu, Zhenyu; Zhang, Xuming; Yu, Weixing

    2016-01-01

    This paper reports a biomimetic design of microchannels in the planar reactors with the aim to optimize the photocatalytic efficiency of water purification. Inspired from biology, a bifurcated microchannel has been designed based on the Murray's law to connect to the reaction chamber for photocatalytic reaction. The microchannels are designed to have a constant depth of 50 μm but variable aspect ratios ranging from 0.015 to 0.125. To prove its effectiveness for photocatalytic water purification, the biomimetic planar reactors have been tested and compared with the non-biomimetic ones, showing an improvement of the degradation efficiency by 68%. By employing the finite element method, the flow process of the designed microchannel reactors has been simulated and analyzed. It is found that the biomimetic design owns a larger flow velocity fluctuation than that of the non-biomimetic one, which in turn results in a faster photocatalytic reaction speed. Such a biomimetic design paves the way for the design of more efficient planar reactors and may also find applications in other microfluidic systems that involve the use of microchannels. PMID:26958102

  5. Resistive Interchange Modes Destabilized by Helically Trapped Energetic Ions in a Helical Plasma

    NASA Astrophysics Data System (ADS)

    Du, X. D.; Toi, K.; Osakabe, M.; Ohdachi, S.; Ido, T.; Tanaka, K.; Yokoyama, M.; Yoshinuma, M.; Ogawa, K.; Watanabe, K. Y.; Isobe, M.; Nagaoka, K.; Ozaki, T.; Sakakibara, S.; Seki, R.; Shimizu, A.; Suzuki, Y.; Tsuchiya, H.

    2015-04-01

    A new bursting m =1 /n =1 instability (m ,n : poloidal and toroidal mode numbers) with rapid frequency chirping down has been observed for the first time in a helical plasma with intense perpendicular neutral beam injection. This is destabilized in the plasma peripheral region by resonant interaction between helically trapped energetic ions and the resistive interchange mode. A large radial electric field is induced near the edge due to enhanced radial transport of the trapped energetic ions by the mode, and leads to clear change in toroidal plasma flow, suppression of microturbulence, and triggering an improvement of bulk plasma confinement.

  6. Lipid oxidation induces structural changes in biomimetic membranes.

    PubMed

    Weber, Georges; Charitat, Thierry; Baptista, Maurício S; Uchoa, Adjaci F; Pavani, Christiane; Junqueira, Helena C; Guo, Yachong; Baulin, Vladimir A; Itri, Rosangela; Marques, Carlos M; Schroder, André P

    2014-06-28

    Oxidation can intimately influence and structurally compromise the levels of biological self-assembly embodied by intracellular and plasma membranes. Lipid peroxidation, a natural metabolic outcome of life with oxygen under light, is also a salient oxidation reaction in photomedicine treatments. However, the effect of peroxidation on the fate of lipid membranes remains elusive. Here we use a new photosensitizer that anchors and disperses in the membrane to achieve spatial control of the oxidizing species. We find, surprisingly, that the integrity of unsaturated unilamellar vesicles is preserved even for fully oxidized membranes. Membrane survival allows for the quantification of the transformations of the peroxidized bilayers, providing key physical and chemical information to understand the effect of lipid oxidation on protein insertion and on other mechanisms of cell function. We anticipate that spatially controlled oxidation will emerge as a new powerful strategy for tuning and evaluating lipid membranes in biomimetic media under oxidative stress. PMID:24871383

  7. Enzymatically active biomimetic micropropellers for the penetration of mucin gels

    PubMed Central

    Walker, Debora; Käsdorf, Benjamin T.; Jeong, Hyeon-Ho; Lieleg, Oliver; Fischer, Peer

    2015-01-01

    In the body, mucus provides an important defense mechanism by limiting the penetration of pathogens. It is therefore also a major obstacle for the efficient delivery of particle-based drug carriers. The acidic stomach lining in particular is difficult to overcome because mucin glycoproteins form viscoelastic gels under acidic conditions. The bacterium Helicobacter pylori has developed a strategy to overcome the mucus barrier by producing the enzyme urease, which locally raises the pH and consequently liquefies the mucus. This allows the bacteria to swim through mucus and to reach the epithelial surface. We present an artificial system of reactive magnetic micropropellers that mimic this strategy to move through gastric mucin gels by making use of surface-immobilized urease. The results demonstrate the validity of this biomimetic approach to penetrate biological gels, and show that externally propelled microstructures can actively and reversibly manipulate the physical state of their surroundings, suggesting that such particles could potentially penetrate native mucus. PMID:26824056

  8. A biomimetic nanosponge that absorbs pore-forming toxins

    NASA Astrophysics Data System (ADS)

    Hu, Che-Ming J.; Fang, Ronnie H.; Copp, Jonathan; Luk, Brian T.; Zhang, Liangfang

    2013-05-01

    Detoxification treatments such as toxin-targeted anti-virulence therapy offer ways to cleanse the body of virulence factors that are caused by bacterial infections, venomous injuries and biological weaponry. Because existing detoxification platforms such as antisera, monoclonal antibodies, small-molecule inhibitors and molecularly imprinted polymers act by targeting the molecular structures of toxins, customized treatments are required for different diseases. Here, we show a biomimetic toxin nanosponge that functions as a toxin decoy in vivo. The nanosponge, which consists of a polymeric nanoparticle core surrounded by red blood cell membranes, absorbs membrane-damaging toxins and diverts them away from their cellular targets. In a mouse model, the nanosponges markedly reduce the toxicity of staphylococcal alpha-haemolysin (α-toxin) and thus improve the survival rate of toxin-challenged mice. This biologically inspired toxin nanosponge presents a detoxification treatment that can potentially treat a variety of injuries and diseases caused by pore-forming toxins.

  9. Biomimetic Nanotubes Based on Cyclodextrins for Ion-Channel Applications.

    PubMed

    Mamad-Hemouch, Hajar; Ramoul, Hassen; Abou Taha, Mohammad; Bacri, Laurent; Huin, Cécile; Przybylski, Cédric; Oukhaled, Abdelghani; Thiébot, Bénédicte; Patriarche, Gilles; Jarroux, Nathalie; Pelta, Juan

    2015-11-11

    Biomimetic membrane channels offer a great potential for fundamental studies and applications. Here, we report the fabrication and characterization of short cyclodextrin nanotubes, their insertion into membranes, and cytotoxicity assay. Mass spectrometry and high-resolution transmission electron microscopy were used to confirm the synthesis pathway leading to the formation of short nanotubes and to describe their structural parameters in terms of length, diameter, and number of cyclodextrins. Our results show the control of the number of cyclodextrins threaded on the polyrotaxane leading to nanotube synthesis. Structural parameters obtained by electron microscopy are consistent with the distribution of the number of cyclodextrins evaluated by mass spectrometry from the initial polymer distribution. An electrophysiological study at single molecule level demonstrates the ion channel formation into lipid bilayers, and the energy penalty for the entry of ions into the confined nanotube. In the presence of nanotubes, the cell physiology is not altered. PMID:26471761

  10. Biomimetic tissues on a chip for drug discovery

    PubMed Central

    Ghaemmaghami, Amir M.; Hancock, Matthew J.; Harrington, Helen; Kaji, Hirokazu; Khademhosseini, Ali

    2011-01-01

    Teaser Recent advances in tissue engineering have enabled the development of microscale biomimetic ‘organ on a chip’ tissue models which have the potential to make an important impact on the various stages of drug discovery and toxicity testing. Developing biologically relevant models of human tissues and organs is an important enabling step for disease modeling and drug discovery. Recent advances in tissue engineering, biomaterials and microfluidics have led to the development of microscale functional units of such models also referred to as ‘organs on a chip’. In this review, we provide an overview of key enabling technologies and highlight the wealth of recent work regarding on-chip tissue models. In addition, we discuss the current challenges and future directions of organ-on-chip development. PMID:22094245

  11. Tissue Engineering of Articular Cartilage with Biomimetic Zones

    PubMed Central

    Klein, Travis J.; Malda, Jos; Sah, Robert L.

    2009-01-01

    Articular cartilage damage is a persistent and increasing problem with the aging population, and treatments to achieve biological repair or restoration remain a challenge. Cartilage tissue engineering approaches have been investigated for over 20 years, but have yet to achieve the consistency and effectiveness for widespread clinical use. One of the potential reasons for this is that the engineered tissues do not have or establish the normal zonal organization of cells and extracellular matrix that appears critical for normal tissue function. A number of approaches are being taken currently to engineer tissue that more closely mimics the organization of native articular cartilage. This review focuses on the zonal organization of native articular cartilage, strategies being used to develop such organization, the reorganization that occurs after culture or implantation, and future prospects for the tissue engineering of articular cartilage with biomimetic zones. PMID:19203206

  12. Biomimetic spiroid winglets for lift and drag control

    NASA Astrophysics Data System (ADS)

    Guerrero, Joel E.; Maestro, Dario; Bottaro, Alessandro

    2012-01-01

    In aeronautical engineering, drag reduction constitutes a challenge and there is room for improvement and innovative developments. The drag breakdown of a typical transport aircraft shows that the lift-induced drag can amount to as much as 40% of the total drag at cruise conditions and 80-90% of the total drag in take-off configuration. One way of reducing lift-induced drag is by using wingtip devices. By applying biomimetic abstraction of the principle behind a bird's wingtip feathers, we study spiroid wingtips, which look like an extended blended wingtip that bends upward by 360 degrees to form a large rigid ribbon. The numerical investigation of such a wingtip device is described and preliminary indications of its aerodynamic performance are provided.

  13. Crustacean-derived biomimetic components and nanostructured composites.

    PubMed

    Grunenfelder, Lessa Kay; Herrera, Steven; Kisailus, David

    2014-08-27

    Over millions of years, the crustacean exoskeleton has evolved into a rigid, tough, and complex cuticle that is used for structural support, mobility, protection of vital organs, and defense against predation. The crustacean cuticle is characterized by a hierarchically arranged chitin fiber scaffold, mineralized predominately by calcium carbonate and/or calcium phosphate. The structural organization of the mineral and organic within the cuticle occurs over multiple length scales, resulting in a strong and tough biological composite. Here, the ultrastructural details observed in three species of crustacean are reviewed: the American lobster (Homarus americanus), the edible crab (Cancer pagurus), and the peacock mantis shrimp (Odontodactylus scyllarus). The Review concludes with a discussion of recent advances in the development of biomimetics with controlled organic scaffolding, mineralization, and the construction of nanoscale composites, inspired by the organization and formation of the crustacean cuticle. PMID:24833136

  14. CPG Network Optimization for a Biomimetic Robotic Fish via PSO.

    PubMed

    Yu, Junzhi; Wu, Zhengxing; Wang, Ming; Tan, Min

    2016-09-01

    In this brief, we investigate the parameter optimization issue of a central pattern generator (CPG) network governed forward and backward swimming for a fully untethered, multijoint biomimetic robotic fish. Considering that the CPG parameters are tightly linked to the propulsive performance of the robotic fish, we propose a method for determination of relatively optimized control parameters. Within the framework of evolutionary computation, we use a combination of dynamic model and particle swarm optimization (PSO) algorithm to seek the CPG characteristic parameters for an enhanced performance. The PSO-based optimization scheme is validated with extensive experiments conducted on the actual robotic fish. Noticeably, the optimized results are shown to be superior to previously reported forward and backward swimming speeds. PMID:26259223

  15. Electroactive polymers (EAP) as an enabling tool in biomimetics

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, Yoseph

    2007-04-01

    Nature is filled with highly effective biological mechanisms that were refined thru evolution over millions of years offering an incredible model for inspiring human innovation. Humans have always made efforts to imitate nature's inventions. Advances in technology led to capabilities that allow adapting nature innovation beyond simply copying and the pool of possibilities in materials, structures, methods, processes and systems is enormous. Electroactive polymers (EAP) are increasingly being recognized as an important enabling technology for making biologically inspired capabilities. Using them as artificial muscles they are being considered for use a wide range of fields including medical, commercial, entertainment and many others. This paper reviews the up to date role that EAP is playing in advancing biomimetics and the field outlook.

  16. Aquaporin-Based Biomimetic Polymeric Membranes: Approaches and Challenges

    PubMed Central

    Habel, Joachim; Hansen, Michael; Kynde, Søren; Larsen, Nanna; Midtgaard, Søren Roi; Jensen, Grethe Vestergaard; Bomholt, Julie; Ogbonna, Anayo; Almdal, Kristoffer; Schulz, Alexander; Hélix-Nielsen, Claus

    2015-01-01

    In recent years, aquaporin biomimetic membranes (ABMs) for water separation have gained considerable interest. Although the first ABMs are commercially available, there are still many challenges associated with further ABM development. Here, we discuss the interplay of the main components of ABMs: aquaporin proteins (AQPs), block copolymers for AQP reconstitution, and polymer-based supporting structures. First, we briefly cover challenges and review recent developments in understanding the interplay between AQP and block copolymers. Second, we review some experimental characterization methods for investigating AQP incorporation including freeze-fracture transmission electron microscopy, fluorescence correlation spectroscopy, stopped-flow light scattering, and small-angle X-ray scattering. Third, we focus on recent efforts in embedding reconstituted AQPs in membrane designs that are based on conventional thin film interfacial polymerization techniques. Finally, we describe some new developments in interfacial polymerization using polyhedral oligomeric silsesquioxane cages for increasing the physical and chemical durability of thin film composite membranes. PMID:26264033

  17. Plasmonic nanoparticles tuned thermal sensitive photonic polymer for biomimetic chameleon

    NASA Astrophysics Data System (ADS)

    Yan, Yang; Liu, Lin; Cai, Zihe; Xu, Jiwen; Xu, Zhou; Zhang, Di; Hu, Xiaobin

    2016-08-01

    Among many thermo-photochromic materials, the color-changing behavior caused by temperature and light is usually lack of a full color response. And the study on visible light-stimuli chromic response is rarely reported. Here, we proposed a strategy to design a thermo-photochromic chameleon biomimetic material consisting of photonic poly(N-isopropylacrylamide-co-methacrylic acid) copolymer and plasmonic nanoparticles which has a vivid color change triggered by temperature and light like chameleons. We make use of the plasmonic nanoparticles like gold nanoparticles and silver nanoparticles to increase the sensitivity of the responsive behavior and control the lower critical solution temperature of the thermosensitive films by tuning the polymer chain conformation transition. Finally, it is possible that this film would have colorimetric responses to the entire VIS spectrum by the addition of different plasmonic nanoparticles to tune the plasmonic excitation wavelength. As a result, this method provides a potential use in new biosensors, military and many other aspects.

  18. Superhydrophobic and superhydrophilic plant surfaces: an inspiration for biomimetic materials.

    PubMed

    Koch, Kerstin; Barthlott, Wilhelm

    2009-04-28

    The diversity of plant surface structures, evolved over 460 million years, has led to a large variety of highly adapted functional structures. The plant cuticle provides structural and chemical modifications for surface wetting, ranging from superhydrophilic to superhydrophobic. In this paper, the structural basics of superhydrophobic and superhydrophilic plant surfaces and their biological functions are introduced. Wetting in plants is influenced by the sculptures of the cells and by the fine structure of the surfaces, such as folding of the cuticle, or by epicuticular waxes. Hierarchical structures in plant surfaces are shown and further types of plant surface structuring leading to superhydrophobicity and superhydrophilicity are presented. The existing and potential uses of superhydrophobic and superhydrophilic surfaces for self-cleaning, drag reduction during moving in water, capillary liquid transport and other biomimetic materials are shown. PMID:19324720

  19. A biomimetic accelerometer inspired by the cricket's clavate hair

    PubMed Central

    Droogendijk, H.; de Boer, M. J.; Sanders, R. G. P.; Krijnen, G. J. M.

    2014-01-01

    Crickets use so-called clavate hairs to sense (gravitational) acceleration to obtain information on their orientation. Inspired by this clavate hair system, a one-axis biomimetic accelerometer has been developed and fabricated using surface micromachining and SU-8 lithography. An analytical model is presented for the design of the accelerometer, and guidelines are derived to reduce responsivity due to flow-induced contributions to the accelerometer's output. Measurements show that this microelectromechanical systems (MEMS) hair-based accelerometer has a resonance frequency of 320 Hz, a detection threshold of 0.10 ms−2 and a dynamic range of more than 35 dB. The accelerometer exhibits a clear directional response to external accelerations and a low responsivity to airflow. Further, the accelerometer's physical limits with respect to noise levels are addressed and the possibility for short-term adaptation of the sensor to the environment is discussed. PMID:24920115

  20. Aquaporin-Based Biomimetic Polymeric Membranes: Approaches and Challenges.

    PubMed

    Habel, Joachim; Hansen, Michael; Kynde, Søren; Larsen, Nanna; Midtgaard, Søren Roi; Jensen, Grethe Vestergaard; Bomholt, Julie; Ogbonna, Anayo; Almdal, Kristoffer; Schulz, Alexander; Hélix-Nielsen, Claus

    2015-01-01

    In recent years, aquaporin biomimetic membranes (ABMs) for water separation have gained considerable interest. Although the first ABMs are commercially available, there are still many challenges associated with further ABM development. Here, we discuss the interplay of the main components of ABMs: aquaporin proteins (AQPs), block copolymers for AQP reconstitution, and polymer-based supporting structures. First, we briefly cover challenges and review recent developments in understanding the interplay between AQP and block copolymers. Second, we review some experimental characterization methods for investigating AQP incorporation including freeze-fracture transmission electron microscopy, fluorescence correlation spectroscopy, stopped-flow light scattering, and small-angle X-ray scattering. Third, we focus on recent efforts in embedding reconstituted AQPs in membrane designs that are based on conventional thin film interfacial polymerization techniques. Finally, we describe some new developments in interfacial polymerization using polyhedral oligomeric silsesquioxane cages for increasing the physical and chemical durability of thin film composite membranes. PMID:26264033

  1. Locomotion Performance of Biomimetic Fish-like Swimming Devices

    NASA Astrophysics Data System (ADS)

    Epps, Brenden P.; Valdivia Y Alvarado, Pablo; Techet, Alexandra H.

    2007-11-01

    The swimming performance of a biomimetic, fish-like swimming device, designed to exploit the natural dynamics of its compliant body to achieve locomotion, is studied experimentally. A theoretical model combines beam-bending stress analysis and unsteady hydrodynamic forcing with known material properties of the robot to reveal desired geometry distributions and actuation modes. Swimming kinematics and corresponding performance of the device are also predicted and tested for a carangiform prototype device in a quiescent tank of water. Experimental swimming tests show good agreement with the simplified theoretical models. The hydrodynamic characteristics of the wake behind the device are investigated using time-resolved particle imaging velocimetry (PIV) over a range of tail beat frequencies, from 1 to 4 Hz, to asses vortical wake patterns and hydrodynamic forces. PIV data are compared to theoretical model predictions. Reynolds numbers for the swimming device are between 2500 and 8500 based on body length.

  2. Efficient Enzyme-Free Biomimetic Sensors for Natural Phenol Detection.

    PubMed

    Ferreira Garcia, Luane; Ribeiro Souza, Aparecido; Sanz Lobón, Germán; Dos Santos, Wallans Torres Pio; Alecrim, Morgana Fernandes; Fontes Santiago, Mariângela; de Sotomayor, Rafael Luque Álvarez; de Souza Gil, Eric

    2016-01-01

    The development of sensors and biosensors based on copper enzymes and/or copper oxides for phenol sensing is disclosed in this work. The electrochemical properties were studied by cyclic and differential pulse voltammetry using standard solutions of potassium ferrocyanide, phosphate/acetate buffers and representative natural phenols in a wide pH range (3.0 to 9.0). Among the natural phenols herein investigated, the highest sensitivity was observed for rutin, a powerful antioxidant widespread in functional foods and ubiquitous in the plant kingdom. The calibration curve for rutin performed at optimum pH (7.0) was linear in a broad concentration range, 1 to 120 µM (r = 0.99), showing detection limits of 0.4 µM. The optimized biomimetic sensor was also applied in total phenol determination in natural samples, exhibiting higher stability and sensitivity as well as distinct selectivity for antioxidant compounds. PMID:27529208

  3. Bacteriorhodopsin-based bipolar photosensor for biomimetic sensing

    NASA Astrophysics Data System (ADS)

    Kasai, Katsuyuki; Haruyama, Yoshihiro; Yamada, Toshiki; Akiba, Makoto; Tominari, Yukihiro; Kaji, Takahiro; Terui, Toshifumi; Peper, Ferdinand; Tanaka, Shukichi; Katagiri, Yoshitada; Kikuchi, Hiroshi; Okada-Shudo, Yoshiko; Otomo, Akira

    2013-10-01

    Bacteriorhodopsin (bR) is a promising biomaterial for several applications. Optical excitation of bR at an electrode-electrolyte interface generates differential photocurrents while an incident light is turned on and off. This unique functional response is similar to that seen in retinal neurons. The bR-based bipolar photosensor consists of the bR dip-coated thin films patterned on two ITO plates and the electrolyte solution. This bipolar photocell will function as a biomimetic photoreceptor cell. The bipolar structure, due to the photocurrent being generated in alignment with the cathodic direction, makes the excitatory and inhibitory regions possible. This scheme shows our bipolar cell can act as a basic unit of edge detection and forms the artificial visual receptive field.

  4. A biomimetic tongue by photoluminescent metal-organic frameworks.

    PubMed

    Lee, Tu; Lin Lee, Hung; Hsun Tsai, Meng; Cheng, Shao-Liang; Lee, Sheng-Wei; Hu, Jung-Chih; Chen, Lien-Tai

    2013-05-15

    The taste sensing capabilities of a "biomimetic tongue" based on the photoluminescence (PL) responses of metal-organic frameworks (MOFs), [In(OH)(bdc)]n (bdc=1,4-benzenedicarboxylate), [Tb(btc)]n (MOF-76, btc=benzene-1,3,5-tricarboxylate), and [Ca3(btc)2(DMF)2(H2O)2]·3H2O are proven on aqueous solutions of five basic tastants: sucrose (sweet), caffeine (bitter), citric acid (sour), sodium chloride (salty) and monosodium glutamate (umami). For [In(OH)(bdc)]n, the tastant interacts stereochemically with poly(acrylic acid) (PAA) and alters its conformations. The frequency and magnitude of chelation between COO(-) pendant groups of PAA and In(3+) nodes of [In(OH)(bdc)]n framework influence the corresponding PL reponses. For MOF-76, the tastant interacts with incorporated water in MOF-76 through hydrogen bonding. The limitation of O-H bond stretching of water results in the enhancement of the PL intensity. For [Ca3(BTC)2(DMF)2(H2O)2]·3H2O, it is added as a third MOF component to increase the precision on taste discrimination. The significance of MOF-based "biomimetic tongue" includes: (1) PAA on [In(OH)(bdc)]n mimics the taste receptor cells (TRCs) for their structural flexibility, (2) the Weber-Fechner law of human sensing that sensation is proportional to the logarithm of the stimulus intensity is observed between the PL emission response of MOF-76 and the concentration of tastant, (3) the strength of taste is quantified by the τ scale and the PL emission intensity of MOF-76, which are dependent on the logarithmic tastant concentration, (4) the tastant is identified by the shape of the 3D principal component analysis contour map (i.e., pattern recognition method), and (5) the fabrication of [In(OH)(bdc)]n/PAA film by brushing is illustrated. PMID:23277340

  5. Nanocrystal-based biomimetic system for quantitative flow cytometry

    NASA Astrophysics Data System (ADS)

    Yim, Peter; Dobrovolskaia, Marina; Kang, HyeongGon; Clarke, Matthew; Patri, Anil K.; Hwang, Jeeseong

    2007-02-01

    Flow cytometry has been instrumental in rapid analysis of single cells since the 1970s. One of the common approaches is the immunofluorescence study involving labeling of cells with antibodies conjugated to organic fluorophores. More recently, as the application of flow cytometry extended from simple cell detection to single-cell proteomic analysis, the need of determining the actual number of antigens in a single cell has driven the flow cytomery technique towards a quantitative methodology. However, organic fluorophores are challenging to use as probes for quantitative detection due to the lack of photostability and of quantitative fluorescence standards. National Institute of Standards and Technologies (NIST) provides a set of fluorescein isothiocyanate (FITC) labeled beads, RM 8640, which is the only nationally recognized fluorescent particle standard. On the other hand, optical characteristics of semiconductor nanocrystals or quantum dots or QDs are superior to traditional dye molecules for the use as tags for biological and chemical fluorescent sensors and detectors. Compelling advantages of QDs include long photostability, broad spectral coverage, easy excitation, and suitability for multiplexed sensing. Recently, novel surface coatings have been developed to render QDs water soluble and bio-conjugation ready, leading to their use as fluorescent tags and sensors for a variety of biological applications including immunolabeling of cells. Here, we describe our approach of using fluorescent semiconductor QDs as a novel tool for quantitative flow cytometry detection. Our strategy involves the development of immuno-labeled QD-conjugated silica beads as "biomimetic cells." In addition to flow cytometry, the QD-conjugated silica beads were characterized by fluorescence microscopy to quantitate the number of QDs attached to a single silica bead. Our approach enables flow cytometry analysis to be highly sensitive, quantitative, and encompass a wide dynamic range of

  6. Thermal gelation and tissue adhesion of biomimetic hydrogels

    PubMed Central

    Burke, Sean A; Ritter-Jones, Marsha; Lee, Bruce P; Messersmith, Phillip B

    2008-01-01

    Marine and freshwater mussels are notorious foulers of natural and manmade surfaces, secreting specialized protein adhesives for rapid and durable attachment to wet substrates. Given the strong and water-resistant nature of mussel adhesive proteins, significant potential exists for mimicking their adhesive characteristics in bioinspired synthetic polymer materials. An important component of these proteins is L-3,4-dihydroxylphenylalanine (DOPA), an amino acid believed to contribute to mussel glue solidification through oxidation and crosslinking reactions. Synthetic polymers containing DOPA residues have previously been shown to crosslink into hydrogels upon the introduction of oxidizing reagents. Here we introduce a strategy for stimuli responsive gel formation of mussel adhesive protein mimetic polymers. Lipid vesicles with a bilayer melting transition of 37 °C were designed from a mixture of dipalmitoyl and dimyristoyl phosphatidylcholines and exploited for the release of a sequestered oxidizing reagent upon heating from ambient to physiologic temperature. Colorimetric studies indicated that sodium-periodate-loaded liposomes released their cargo at the phase transition temperature, and when used in conjunction with a DOPA-functionalized poly(ethylene glycol) polymer gave rise to rapid solidification of a crosslinked polymer hydrogel. The tissue adhesive properties of this biomimetic system were determined by in situ thermal gelation of liposome/polymer hydrogel between two porcine dermal tissue surfaces. Bond strength measurements showed that the bond formed by the adhesive hydrogel (mean = 35.1 kPa, SD = 12.5 kPa, n = 11) was several times stronger than a fibrin glue control tested under the same conditions. The results suggest a possible use of this biomimetic strategy for repair of soft tissues. PMID:18458476

  7. Biomimetics on seed dispersal: survey and insights for space exploration.

    PubMed

    Pandolfi, Camilla; Izzo, Dario

    2013-06-01

    Seeds provide the vital genetic link and dispersal agent between successive generations of plants. Without seed dispersal as a means of reproduction, many plants would quickly die out. Because plants lack any sort of mobility and remain in the same spot for their entire lives, they rely on seed dispersal to transport their offspring throughout the environment. This can be accomplished either collectively or individually; in any case as seeds ultimately abdicate their movement, they are at the mercy of environmental factors. Thus, seed dispersal strategies are characterized by robustness, adaptability, intelligence (both behavioral and morphological), and mass and energy efficiency (including the ability to utilize environmental sources of energy available): all qualities that advanced engineering systems aim at in general, and in particular those that need to enable complex endeavors such as space exploration. Plants evolved and adapted their strategy according to their environment, and taken together, they enclose many desirable characteristics that a space mission needs to have. Understanding in detail how plants control the development of seeds, fabricate structural components for their dispersal, build molecular machineries to keep seeds dormant up to the right moment and monitor the environment to release them at the right time could provide several solutions impacting current space mission design practices. It can lead to miniaturization, higher integration and packing efficiency, energy efficiency and higher autonomy and robustness. Consequently, there would appear to be good reasons for considering biomimetic solutions from plant kingdom when designing space missions, especially to other celestial bodies, where solid and liquid surfaces, atmosphere, etc constitute and are obviously parallel with the terrestrial environment where plants evolved. In this paper, we review the current state of biomimetics on seed dispersal to improve space mission design. PMID

  8. Multicompartmentalized polymeric systems: towards biomimetic cellular structure and function.

    PubMed

    Marguet, Maïté; Bonduelle, Colin; Lecommandoux, Sébastien

    2013-01-21

    The cell is certainly one of the most complex and exciting systems in Nature that scientists are still trying to fully understand. Such a challenge pushes material scientists to seek to reproduce its perfection by building biomimetic materials with high-added value and previously unmatched properties. Thanks to their versatility, their robustness and the current state of polymer chemistry science, we believe polymer-based materials to constitute or represent ideal candidates when addressing the challenge of biomimicry, which defines the focus of this review. The first step consists in mimicking the structure of the cell: its inner compartments, the organelles, with a multicompartmentalized structure, and the rest, i.e. the cytoplasm minus the organelles (mainly cytoskeleton/cytosol) with gels or particular solutions (highly concentrated for example) in one compartment, and finally the combination of both. Achieving this first structural step enables us to considerably widen the gap of possibilities in drug delivery systems. Another powerful property of the cell lies in its metabolic function. The second step is therefore to achieve enzymatic reactions in a compartment, as occurs in the organelles, in a highly controlled, selective and efficient manner. We classify the most exciting polymersome nanoreactors reported in our opinion into two different subsections, depending on their very final concept or purpose of design. We also highlight in a thorough table the experimental sections crucial to such work. Finally, after achieving control over these prerequisites, scientists are able to combine them and push the frontiers of biomimicry further: from cell structure mimics towards a controlled biofunctionality. Such a biomimetic approach in material design and the future research it will stimulate, are believed to bring considerable enrichments to the fields of drug delivery, (bio)sensors, (bio)catalysis and (bio)technology. PMID:23073077

  9. Biomimetic shark skin: design, fabrication and hydrodynamic function.

    PubMed

    Wen, Li; Weaver, James C; Lauder, George V

    2014-05-15

    Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species. PMID:24829323

  10. Helical growth in plant organs: mechanisms and significance.

    PubMed

    Smyth, David R

    2016-09-15

    Many plants show some form of helical growth, such as the circular searching movements of growing stems and other organs (circumnutation), tendril coiling, leaf and bud reversal (resupination), petal arrangement (contortion) and leaf blade twisting. Recent genetic findings have revealed that such helical growth may be associated with helical arrays of cortical microtubules and of overlying cellulose microfibrils. An alternative mechanism of coiling that is based on differential contraction within a bilayer has also recently been identified and underlies at least some of these growth patterns. Here, I provide an overview of the genes and cellular processes that underlie helical patterning. I also discuss the diversity of helical growth patterns in plants, highlighting their potential adaptive significance and comparing them with helical growth patterns in animals. PMID:27624832

  11. A Half Century of Magnetic Helicity in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Bieber, J. W.

    2015-12-01

    Using NASA's "OMNI" dataset, this work presents observations of the net magnetic helicity and the normalized helicity spectrum at 1 AU over the period 1965 - 2014. Past studies (1,2) reported that the helicity at large scales has a definite dominant sign organized with respect to the heliospheric current sheet, with negative helicities occurring north of the current sheet, and positive helicities south. The present study confirms this pattern and extends it by more than two solar cycles and past the most recent solar maximum. Particle scattering by turbulence with finite magnetic helicity is one of only two known particle transport mechanisms that are sensitive to particle charge sign and magnetic field polarity. Implications to cosmic ray transport will be discussed. References: (1) Bieber, Evenson, and Matthaeus, Geophys. Res. Lett. , Vol 14, p 864, 1987. (2) Smith and Bieber, Proc. 23rd Internat. Cosmic Ray Conf. (Calgary), Vol 3, p 493, 1993.

  12. Non-Kolmogorov cascade of helicity-driven turbulence

    NASA Astrophysics Data System (ADS)

    Kessar, Mouloud; Plunian, Franck; Stepanov, Rodion; Balarac, Guillaume

    2015-09-01

    We solve the Navier-Stokes equations with two simultaneous forcings. One forcing is applied at a given large scale and it injects energy. The other forcing is applied at all scales belonging to the inertial range and it injects helicity. In this way we can vary the degree of turbulence helicity from nonhelical to maximally helical. We find that increasing the rate of helicity injection does not change the energy flux. On the other hand, the level of total energy is strongly increased and the energy spectrum gets steeper. The energy spectrum spans from a Kolmogorov scaling law k-5 /3 for a nonhelical turbulence, to a non-Kolmogorov scaling law k-7 /3 for a maximally helical turbulence. In the latter case we find that the characteristic time of the turbulence is not the turnover time but a time based on the helicity injection rate. We also analyze the results in terms of helical modes decomposition. For a maximally helical turbulence one type of helical mode is found to be much more energetic than the other one, by several orders of magnitude. The energy cascade of the most energetic type of helical mode results from the sum of two fluxes. One flux is negative and can be understood in terms of a decimated model. This negative flux, however, is not sufficient to lead an inverse energy cascade. Indeed, the other flux involving the least energetic type of helical mode is positive and the largest. The least energetic type of helical mode is then essential and cannot be neglected.

  13. Decay of magnetic helicity producing polarized Alfven waves

    SciTech Connect

    Yoshida, Z.; Mahajan, S.M.

    1994-02-01

    When a super-Alfvenic electron beam propagates along an ambient magnetic field, the left-hand circularly polarized Alfven wave is Cherenkov-emitted (two stream instability). This instability results in a spontaneous conversion of the background plasma helicity to the wave helicity. The background helicity induces a frequency (energy) shift in the eigenmodes, which changes the critical velocity for Cherenkov emission, and it becomes possible for a sub-Alfvenic electron beam to excite a nonsingular Alfven mode.

  14. Helicity conservation under quantum reconnection of vortex rings.

    PubMed

    Zuccher, Simone; Ricca, Renzo L

    2015-12-01

    Here we show that under quantum reconnection, simulated by using the three-dimensional Gross-Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that the total length of the vortex system reaches a maximum at the reconnection time, while both writhe helicity and twist helicity remain separately unchanged throughout the process. Self-helicity is computed by two independent methods, and topological information is based on the extraction and analysis of geometric quantities such as writhe, total torsion, and intrinsic twist of the reconnecting vortex rings. PMID:26764622

  15. Spontaneous formation of organic helical architectures through dynamic covalent chemistry.

    PubMed

    Li, Wenfang; Dong, Zeyuan; Zhu, Junyan; Luo, Quan; Liu, Junqiu

    2014-12-01

    The spontaneous formation of organic helical structures, accompanied with an amplification of chirality, by dynamic covalent bonds between achiral and chiral building blocks is reported. PMID:25325888

  16. Large-scale flow generation by inhomogeneous helicity

    NASA Astrophysics Data System (ADS)

    Yokoi, N.; Brandenburg, A.

    2016-03-01

    The effect of kinetic helicity (velocity-vorticity correlation) on turbulent momentum transport is investigated. The turbulent kinetic helicity (pseudoscalar) enters the Reynolds stress (mirror-symmetric tensor) expression in the form of a helicity gradient as the coupling coefficient for the mean vorticity and/or the angular velocity (axial vector), which suggests the possibility of mean-flow generation in the presence of inhomogeneous helicity. This inhomogeneous helicity effect, which was previously confirmed at the level of a turbulence- or closure-model simulation, is examined with the aid of direct numerical simulations of rotating turbulence with nonuniform helicity sustained by an external forcing. The numerical simulations show that the spatial distribution of the Reynolds stress is in agreement with the helicity-related term coupled with the angular velocity, and that a large-scale flow is generated in the direction of angular velocity. Such a large-scale flow is not induced in the case of homogeneous turbulent helicity. This result confirms the validity of the inhomogeneous helicity effect in large-scale flow generation and suggests that a vortex dynamo is possible even in incompressible turbulence where there is no baroclinicity effect.

  17. Applying of helicity in an analysis of a severe sandstorm

    NASA Astrophysics Data System (ADS)

    Tao, Jian-hong; Wang, Jin-song; Feng, Jian-ying; Chang, Yue; Liu, Xiao-li

    2005-08-01

    The helicity of a severe sandstorm happened in Northwest China was analyzed by using global reanalysis grid data of NCEP/NCAR for 4 times a day. As an important physical parameter in analyzing and predicting severe convective weather, the helicity also has good indication in the forecasting of sandstorm. The distribution of helicity over the sandstorm area was negative at higher levels and positive at lower levels. There was definite relationship between the evolvement of helicity's negative value at higher levels and the occurrence of sandstorm.

  18. Helical Magnetic Fields from Sphaleron Decay and Baryogenesis

    SciTech Connect

    Copi, Craig J.; Ferrer, Francesc; Vachaspati, Tanmay; Achucarro, Ana

    2008-10-24

    Many models of baryogenesis rely on anomalous particle physics processes to give baryon number violation. By numerically evolving the electroweak equations on a lattice, we show that baryogenesis in these models creates helical cosmic magnetic fields, though the helicity created is smaller than earlier analytical estimates. After a transitory period, electroweak dynamics is found to conserve the Chern-Simons number and the total electromagnetic helicity. We argue that baryogenesis could lead to magnetic fields of nano-Gauss strength today on astrophysical length scales. In addition to being astrophysically relevant, such helical magnetic fields can provide an independent probe of baryogenesis and CP violation in particle physics.

  19. Potential vorticity and helicity in a moist atmosphere

    NASA Astrophysics Data System (ADS)

    Kurgansky, Michael

    2013-04-01

    The helicity balance equation and Ertel's theorem on potential vorticity are applied for an analysis of helical flows of moist unsaturated air and for clarifying the conditions of spontaneous amplification (generation) of helicity due to the atmospheric baroclinicity. Critical comparison is made with the case of dry atmosphere. Spontaneous amplification of helicity owing to the latent heating is also addressed and possible generalization of the proposed methodology onto the case of precipitating atmosphere is highlighted, aiming inter alia at the problem of origination of tornadoes and waterspouts.

  20. Helical structure of Bordetella pertussis fimbriae.

    PubMed Central

    Steven, A C; Bisher, M E; Trus, B L; Thomas, D; Zhang, J M; Cowell, J L

    1986-01-01

    The helical structures of Bordetella pertussis fimbriae of serotypes 2 and 6 were determined by optical diffraction analysis of electron micrographs of negatively stained paracrystalline bundles of purified fimbriae. The fimbrial structure is based on an axial repeat of 13 nm that contains five repeating units in two complete turns of a single-start helix. This structure was confirmed by direct measurements of mass per unit length for individual fimbriae performed by dark-field scanning transmission electron microscopy of unstained specimens. These data further established that the helically repeating unit is a monomer of fimbrial protein (Mr congruent to 22,000 for type 2 and Mr congruent to 21,500 for type 6). Radial density profiles calculated from the scanning transmission electron micrographs showed that the fimbria has peak density at its center, i.e., no axial channel, consistent with the results of conventional negative-staining electron microscopy. The radial profile gives an outermost diameter of approximately 7.5 nm, although the peripheral density is, on average, diffuse, allowing sufficient intercalation between adjacent fimbriae to give a center-to-center spacing of approximately 5.5 nm in the paracrystals. Despite serological and biochemical differences between type 2 and type 6 fimbriae, the packing arrangements of their fimbrial subunits are identical. From this observation, we infer that the respective subunits may have in common conserved regions whose packing dictates the helical geometry of the fimbria. It is plausible that a similar mechanism may underlie the phenomenon of phase variations in other systems of bacterial fimbriae. Images PMID:2875062