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Sample records for modulate helical organ

  1. 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.

  2. 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

  3. 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

  4. Pediatric organ dose measurements in axial and helical multislice CT

    SciTech Connect

    McDermott, Alanna; White, R. Allen; Mc-Nitt-Gray, Mike; Angel, Erin; Cody, Dianna

    2009-05-15

    An anthropomorphic pediatric phantom (5-yr-old equivalent) was used to determine organ doses at specific surface and internal locations resulting from computed tomography (CT) scans. This phantom contains four different tissue-equivalent materials: Soft tissue, bone, brain, and lung. It was imaged on a 64-channel CT scanner with three head protocols (one contiguous axial scan and two helical scans [pitch=0.516 and 0.984]) and four chest protocols (one contiguous axial scan and three helical scans [pitch=0.516, 0.984, and 1.375]). Effective mA s [=(tube currentxrotation time)/pitch] was kept nearly constant at 200 effective mA s for head and 290 effective mA s for chest protocols. Dose measurements were acquired using thermoluminescent dosimeter powder in capsules placed at locations internal to the phantom and on the phantom surface. The organs of interest were the brain, both eyes, thyroid, sternum, both breasts, and both lungs. The organ dose measurements from helical scans were lower than for contiguous axial scans by 0% to 25% even after adjusting for equivalent effective mA s. There was no significant difference (p>0.05) in organ dose values between the 0.516 and 0.984 pitch values for both head and chest scans. The chest organ dose measurements obtained at a pitch of 1.375 were significantly higher than the dose values obtained at the other helical pitches used for chest scans (p<0.05). This difference was attributed to the automatic selection of the large focal spot due to a higher tube current value. These findings suggest that there may be a previously unsuspected radiation dose benefit associated with the use of helical scan mode during computed tomography scanning.

  5. Pediatric organ dose measurements in axial and helical multislice CT

    PubMed Central

    McDermott, Alanna; White, R. Allen; Mc-Nitt-Gray, Mike; Angel, Erin; Cody, Dianna

    2009-01-01

    An anthropomorphic pediatric phantom (5-yr-old equivalent) was used to determine organ doses at specific surface and internal locations resulting from computed tomography (CT) scans. This phantom contains four different tissue-equivalent materials: Soft tissue, bone, brain, and lung. It was imaged on a 64-channel CT scanner with three head protocols (one contiguous axial scan and two helical scans [pitch=0.516 and 0.984]) and four chest protocols (one contiguous axial scan and three helical scans [pitch=0.516, 0.984, and 1.375]). Effective mA s [=(tube current×rotation time)∕pitch] was kept nearly constant at 200 effective mA s for head and 290 effective mA s for chest protocols. Dose measurements were acquired using thermoluminescent dosimeter powder in capsules placed at locations internal to the phantom and on the phantom surface. The organs of interest were the brain, both eyes, thyroid, sternum, both breasts, and both lungs. The organ dose measurements from helical scans were lower than for contiguous axial scans by 0% to 25% even after adjusting for equivalent effective mA s. There was no significant difference (p>0.05) in organ dose values between the 0.516 and 0.984 pitch values for both head and chest scans. The chest organ dose measurements obtained at a pitch of 1.375 were significantly higher than the dose values obtained at the other helical pitches used for chest scans (p<0.05). This difference was attributed to the automatic selection of the large focal spot due to a higher tube current value. These findings suggest that there may be a previously unsuspected radiation dose benefit associated with the use of helical scan mode during computed tomography scanning. PMID:19544765

  6. Comparison of arc-modulated cone beam therapy and helical tomotherapy for three different types of cancer

    SciTech Connect

    Ulrich, Silke; Sterzing, Florian; Nill, Simeon; Schubert, Kai; Herfarth, Klaus K.; Debus, Juergen; Oelfke, Uwe

    2009-10-15

    Purpose: Arc-modulated cone beam therapy (AMCBT) is a fast treatment technique deliverable in a single rotation with a conventional C-arm shaped linac. In this planning study, the authors assess the dosimetric properties of single-arc therapy in comparison to helical tomotherapy for three different tumor types. Methods: Treatment plans for three patients with prostate carcinoma, three patients with anal cancer, and three patients with head and neck cancer were optimized for helical tomotherapy and AMCBT. The dosimetric comparison of the two techniques is based on physical quantities derived from dose-volume histograms. Results: For prostate cancer, the quality of dose distributions calculated for AMCBT was of equal quality as that generated for tomotherapy with the additional benefits of a faster delivery and a lower integral dose. For highly complex geometries, the plan quality achievable with helical tomotherapy could not be achieved with arc-modulated cone beam therapy. Conclusions: Rotation therapy with a conventional linac in a single arc is capable to deliver a high and homogeneous dose to the target and spare organs at risk. Advantages of this technique are a fast treatment time and a lower integral dose in comparison to helical tomotherapy. For highly complex cases, e.g., with several target regions, the dose shaping capabilities of AMCBT are inferior to those of tomotherapy. However, treatment plans for AMCBT were also clinically acceptable.

  7. Hierarchical Helical Order in the Twisted Growth of Plant Organs

    NASA Astrophysics Data System (ADS)

    Wada, Hirofumi

    2012-09-01

    The molecular and cellular basis of left-right asymmetry in plant morphogenesis is a fundamental issue in biology. A rapidly elongating root or hypocotyl of twisting mutants of Arabidopsis thaliana exhibits a helical growth with a handedness opposite to that of the underlying cortical microtubule arrays in epidermal cells. However, how such a hierarchical helical order emerges is currently unknown. We propose a model for investigating macroscopic chiral asymmetry in Arabidopsis mutants. Our elastic model suggests that the helical pattern observed is a direct consequence of the simultaneous presence of anisotropic growth and tilting of cortical microtubule arrays. We predict that the root helical pitch angle is a function of the microtubule helical angle and elastic moduli of the tissues. The proposed model is versatile and is potentially important for other biological systems ranging from protein fibrous structures to tree trunks.

  8. Alpha-turn mimetics: short peptide alpha-helices composed of cyclic metallopentapeptide modules.

    PubMed

    Kelso, Michael J; Beyer, Renée L; Hoang, Huy N; Lakdawala, Ami S; Snyder, James P; Oliver, Warren V; Robertson, Tom A; Appleton, Trevor G; Fairlie, David P

    2004-04-21

    Alpha-Helices are key structural components of proteins and important recognition motifs in biology. Short peptides (helical sequences are rarely helical away from their stabilizing protein environments. New techniques for stabilizing short peptide helices could be valuable for studying protein folding, modeling proteins, creating artificial proteins, and may aid the design of inhibitors or mimics of protein function. This study reports the facile incorporation of 3- and 4-alpha turns in 10-15 residue peptides through formation in situ of multiple cyclic metallopeptide modules [Pd(en)(H*XXXH*)](2+). The nonhelical peptides Ac-H*ELTH*H*VTDH*-NH(2) (1), Ac-H*ELTH*AVTDYH*ELTH*-NH(2) (2), and Ac-H*AAAH*HELTH*H*VTDH*-NH(2) (3) (H is histidine-methylated at imidazole-N3) react in N,N-dimethylformamide (DMF) or water with 2, 2, and 3 molar equivalents, respectively, of [Pd(en)(NO(3))(2)] to form exclusively [Pd(2)(en)(2)(Ac-H*ELTH*H*VTDH*-NH(2))](4+) (4), [Pd(2)(en)(2)(Ac-H*ELTH*AVTDYH*ELTH*-NH(2))](4+) (5), and [Pd(3)(en)(3)(Ac-H*AAAH*HELTH*H*VTDH*-NH(2))](6+) (6), characterized by mass spectrometry, 1D and 2D (1)H- and 1D (15)N-NMR spectroscopy. Despite the presence of multiple histidines and other possible metal-binding residues in these peptides, 2D (1)H NMR spectra reveal that Pd(en)(2+) is remarkably specific in coordinating to imidazole-N1 of only (i, i + 4) pairs of histidines (i.e., only those separated by three amino acids), resulting in 4-6 made up of cyclic metallopentapeptide modules ([Pd(en)(H*XXXH*)](2+))(n), n = 2, 2, 3, respectively, each cycle being a 22-membered ring. We have previously shown that a single metallopentapeptide can nucleate alpha-helicity (Kelso et al., Angew. Chem., Int. Ed. 2003, 42, 421-424.). We now demonstrate its use as an alpha-turn-mimicking module for the facile conversion of unstructured short peptides into helices of macrocycles and provide 1D and 2D NMR spectroscopic data, structure

  9. Comparison of Plan Quality Provided by Intensity-Modulated Arc Therapy and Helical Tomotherapy

    SciTech Connect

    Cao Daliang; Holmes, Timothy W.; Afghan, Muhammad K.N.; Shepard, David M.

    2007-09-01

    Purpose: Intensity-modulated arc therapy (IMAT) is an arc-based approach to intensity-modulated radiotherapy (IMRT) that can be delivered on a conventional linear accelerator using a conventional multileaf collimator. In a previous work, we demonstrated that our arc-sequencing algorithm can produce highly conformal IMAT plans. Through plan comparisons, we explored the ability of IMAT to serve as an alternative to helical tomotherapy. Methods and Materials: The IMAT plans were created for 10 patients previously treated with helical tomotherapy. Treatment plan comparisons, according to the target dose coverage and critical structure sparing, were performed to determine whether similar plan quality could be achieved using IMAT. Results: In 8 of 10 patient cases, IMAT was able to provide plan quality comparable to that of helical tomotherapy. In 2 of these 8 cases, the use of non-axial coplanar or non-coplanar arcs in IMAT planning led to significant improvements in normal tissue sparing. The remaining 2 cases posed particular dosimetric challenges. In 1 case, the target was immediately adjacent to a spinal cord that had received previous irradiation. The second case involved multiple target volumes and multiple prescription levels. Both IMAT and tomotherapy were able to produce clinically acceptable plans. Tomotherapy, however, provided a more uniform target dose and improved critical structure sparing. Conclusions: For most cases, IMAT can provide plan qualities comparable to that of helical tomotherapy. For some intracranial tumors, IMAT's ability to deliver non-coplanar arcs led to significant dosimetric improvements. Helical tomotherapy, however, can provide improved dosimetric results in the most complex cases.

  10. Intensity-Modulated Proton Therapy Versus Helical Tomotherapy in Nasopharynx Cancer: Planning Comparison and NTCP Evaluation

    SciTech Connect

    Widesott, Lamberto Pierelli, Alessio; Fiorino, Claudio; Dell'Oca, Italo; Broggi, Sara; Cattaneo, Giovanni Mauro; Di Muzio, Nadia; Fazio, Ferruccio; Calandrino, Riccardo; Schwarz, Marco

    2008-10-01

    Purpose: To compare intensity-modulated proton therapy (IMPT) and helical tomotherapy (HT) treatment plans for nasopharynx cancer using a simultaneous integrated boost approach. Methods and Materials: The data from 6 patients who had previously been treated with HT were used. A three-beam IMPT technique was optimized in the Hyperion treatment planning system, simulating a 'beam scanning' technique. HT was planned using the tomotherapy treatment planning system. Both techniques were optimized to simultaneously deliver 66 Gy in 30 fractions to planning target volume (PTV1; GTV and enlarged nodes) and 54 Gy to PTV2 subclinical, electively treated nodes. Normal tissue complication probability calculation was performed for the parotids and larynx. Results: Very similar PTVs coverage and homogeneity of the target dose distribution for IMPT and HT were found. The conformity index was significantly lower for protons than for photons (1.19 vs. 1.42, respectively). The mean dose to the ipsilateral and contralateral parotid glands decreased by 6.4 Gy and 5.6 Gy, respectively, with IMPT. The volume of mucosa and esophagus receiving {>=}20 Gy and {>=}30 Gy with IMPT was significantly lower than with HT. The average volume of larynx receiving {>=}50 Gy was significantly lower with HT, while for thyroid, it was comparable. The volume receiving {>=}30, {>=}20, and {>=}10 Gy in total body volume decreased with IMPT by 14.5%, 19.4%, and 23.1%, respectively. The normal tissue complication probability for the parotid glands was significantly lower with IMPT for all sets of parameters; however, we also estimated an almost full recovery of the contralateral parotid with HT. The normal tissue complication probability for the larynx was not significantly different between the two irradiation techniques. Conclusion: Excellent target coverage, homogeneity within the PTVs, and sparing of the organs at risk were reached with both modalities. IMPT allows for better sparing of most organs at

  11. Stereotactic Image-Guided Intensity Modulated Radiotherapy Using the HI-ART II Helical Tomotherapy System

    SciTech Connect

    Holmes, Timothy W. Hudes, Richard; Dziuba, Sylwester; Kazi, Abdul; Hall, Mark; Dawson, Dana

    2008-07-01

    The highly integrated adaptive radiation therapy (HI-ART II) helical tomotherapy unit is a new radiotherapy machine designed to achieve highly precise and accurate treatments at all body sites. The precision and accuracy of the HI-ART II is similar to that provided by stereotactic radiosurgery systems, hence the historical distinction between external beam radiotherapy and stereotactic procedures based on differing precision requirements is removed for this device. The objectives of this work are: (1) to describe stereotactic helical tomotherapy processes (SRS, SBRT); (2) to show that the precision and accuracy of the HI-ART meet the requirements defined for SRS and SBRT; and (3) to describe the clinical implementation of a stereotactic image-guided intensity modulated radiation therapy (IG-IMRT) system that incorporates optical motion management.

  12. Modulated helical metals at magnetic domain walls of pyrochlore iridium oxides

    NASA Astrophysics Data System (ADS)

    Yamaji, Youhei; Imada, Masatoshi

    2016-05-01

    Spontaneous symmetry breakings, metal-insulator transitions, and transport properties of magnetic-domain-wall states in pyrochlore iridium oxides are studied by employing a symmetry-adapted effective Hamiltonian with a slab perpendicular to the (111) direction of the pyrochlore structure. Emergent metallic domain wall, which has an unconventional topological nature with a controllable and mobile metallic layer, is shown to host Fermi surfaces with modulated helical spin textures resembling Rashba metals. The helical nature of the domain-wall Fermi surfaces is experimentally detectable by anomalous Hall conductivity, circular dichroism, and optical Hall conductivity under external magnetic fields. Possible applications of the domain-wall metals to spin-current generation and "half-metallic" conduction are also discussed.

  13. Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite

    NASA Astrophysics Data System (ADS)

    Johnson, R. D.; Khalyavin, D. D.; Manuel, P.; Bombardi, A.; Martin, C.; Chapon, L. C.; Radaelli, P. G.

    2016-05-01

    Through a combination of neutron diffraction and Landau theory we describe the spin ordering in the ground state of the quadruple perovskite manganite CaMn7O12 —a magnetic multiferroic supporting an incommensurate orbital density wave that onsets above the magnetic ordering temperature, TN 1=90 K. The multi-k magnetic structure in the ground state was found to be a nearly-constant-moment helix with modulated spin helicity, which oscillates in phase with the orbital occupancies on the Mn3 + sites via trilinear magneto-orbital coupling. Our phenomenological model also shows that, above TN 2=48 K, the primary magnetic order parameter is locked into the orbital wave by an admixture of helical and collinear spin density wave structures. Furthermore, our model naturally explains the lack of a sharp dielectric anomaly at TN 1 and the unusual temperature dependence of the electrical polarization.

  14. Helical Tomotherapy of Nasopharyngeal Carcinoma-Any Advantages Over Conventional Intensity-Modulated Radiotherapy?

    SciTech Connect

    Wu, W.C. Vincent Mui, Wing-lun A.; Fung, Wing-ki W.

    2010-07-01

    Helical tomotherapy uses different planning algorithm and dose delivery method from the linear accelerator (linac)-based intensity-modulated radiotherapy (IMRT). This study compared the dosimetric outcomes between the tomotherapy plans and conventional linac-based IMRT plans in the treatment of nasopharyngeal carcinoma (NPC). Fifteen stage II-III cancer (American Joint Committee on Cancer) NPC patients treated by tomotherapy were conveniently recruited. Apart from the tomotherapy plans, a 7-field 6-MV photon conventional IMRT plan was computed for each patient with the same CT dataset and reference from the dose constraints and target dose prescriptions of the tomotherapy plans using the XiO treatment planning system. Average values of the dose parameters including the conformity index (CI), homogeneity index (HI), maximum and minimum doses of the target volumes, and the maximum and mean doses of the organs at risk (OAR) were compared between the two treatment methods. Better dose coverage of the planning target volume (PTV) was demonstrated in the tomotherapy plans, in which the differences in the maximum and mean doses reached statistical significance (p < 0.05). Besides, the CI of the tomotherapy plans were significantly higher than the conventional linac-based plans for the nasopharynx PTV (NP-PTV) and neck lymphatics PTV (LN-PTV) (p = 0.017 and 0.010, respectively). The HI was significantly smaller in both NP-PTV and LN-PTV (p = 0.024 and < 0.001, respectively). Among the OAR, the brain stem and spinal cord doses in the tomotherapy plans were lower than that of the conventional IMRT plans. However, the doses to the other OAR did not show significant dosimetric differences. In the treatment of nasopharyngeal carcinoma, tomotherapy plans were superior to the 7-field conventional IMRT plans in PTV dose conformity and homogeneity and the sparing of the brain stem and spinal cord. However, no significant advantages were observed for the rest of the OAR.

  15. The Effect of Loops on the Structural Organization of α-Helical Membrane Proteins

    PubMed Central

    Tastan, Oznur; Klein-Seetharaman, Judith; Meirovitch, Hagai

    2009-01-01

    Loops connecting the transmembrane (TM) α-helices in membrane proteins are expected to affect the structural organization of the thereby connected helices and the helical bundles as a whole. This effect, which has been largely ignored previously, is studied here by analyzing the x-ray structures of 41 α-helical membrane proteins. First we define the loop flexibility ratio, R, and find that 53% of the loops are stretched, where a stretched loop constrains the distance between the two connected helices. The significance of this constraining effect is supported by experiments carried out with bacteriorhodopsin and rhodopsin, in which cutting or eliminating their (predominately stretched) loops has led to a decrease in protein stability, and for rhodopsin, in most cases, also to the destruction of the structure. We show that for nonstretched loops in the extramembranous regions, the fraction of hydrophobic residues is comparable to that for soluble proteins; furthermore (as is also the case for soluble proteins), the hydrophobic residues in these regions are preferentially buried. This is expected to lead to the compact structural organization of the loops, which is transferred to the TM helices, causing them to assemble. We argue that a soluble protein complexed with a membrane protein similarly promotes compactness; other properties of such complexes are also studied. We calculate complementary attractive interactions between helices, including hydrogen bonds and van der Waals interactions of sequential motifs, such as GXXXG. The relative and combined effects of all these factors on the association of the TM helices are discussed and protein structures with only a few of these factors are analyzed. Our study emphasizes the need for classifying membrane proteins into groups according to structural organization. This classification should be considered when procedures for structural analysis or prediction are developed and applied. Detailed analysis of each structure

  16. SmartArc-Based Volumetric Modulated Arc Therapy for Oropharyngeal Cancer: A Dosimetric Comparison With Both Intensity-Modulated Radiation Therapy and Helical Tomotherapy

    SciTech Connect

    Clemente, Stefania; Wu, BinBin; Sanguineti, Giuseppe; Fusco, Vincenzo; Ricchetti, Francesco; Wong, John; McNutt, Todd

    2011-07-15

    Purpose: To investigate the roles of volumetric modulated arc therapy with SmartArc (VMAT-S), intensity-modulated radiation therapy (IMRT), and helical tomotherapy (HT) for oropharyngeal cancer using a simultaneous integrated boost (SIB) approach. Methods and Materials: Eight patients treated with IMRT were selected at random. Plans were computed for both IMRT and VMAT-S (using Pinnacle TPS for an Elekta Infinity linac) along with HT. A three-dose level prescription was used to deliver 70 Gy, 63 Gy, and 58.1 Gy to regions of macroscopic, microscopic high-risk, and microscopic low-risk disease, respectively. All doses were given in 35 fractions. Comparisons were performed on dose-volume histogram data, monitor units per fraction (MU/fx), and delivery time. Results: VMAT-S target coverage was close to that achieved by IMRT, but inferior to HT. The conformity and homogeneity within the PTV were improved for HT over all strategies. Sparing of the organs at risk (OAR) was achieved with all modalities. VMAT-S (along with HT) shortened delivery time (mean, -38%) and reduced MU/fx (mean, -28%) compared with IMRT. Conclusion: VMAT-S represents an attractive solution because of the shorter delivery time and the lower number of MU/fx compared with IMRT. However, in this complex clinical setting, current VMAT-S does not appear to provide any distinct advantage compared with helical tomotherapy.

  17. Probing Conserved Helical Modules of Portal Complexes by Mass Spectrometry based Hydrogen/deuterium Exchange

    PubMed Central

    Kang, Sebyung; Poliakov, Anton; Sexton, Jennifer; Renfrow, Matthew B.; Prevelige, Peter E.

    2008-01-01

    The dsDNA bacteriophage P22 has a ring shaped dodecameric complex composed of the 84 kDa portal protein subunit which forms the central channel of the phage’s DNA packaging motor. The overall morphology of the P22 portal complex is similar to that of the portal complexes of Phi29, SPP1, T3, T7 phages and herpes simplex virus. Secondary structure prediction of P22 portal protein and its threading onto the crystal structure of the Phi29 portal complexes suggested that P22 portal protein complex shares conserved helical modules which were found in the dodecameric interfaces of the Phi29 portal complex. To identify the amino acids involved in inter-subunit contacts in the P22 portal ring complexes and validate the threading model, we performed comparative hydrogen/deuterium exchange analysis of monomeric and in vitro assembled portal proteins of P22 and the dodecameric Phi29 portal. Hydrogen/deuterium exchange experiments provided evidence of inter-subunit interactions in the P22 portal complex similar to those in the Phi29 portal which map to the regions predicted to be conserved helical modules. PMID:18621389

  18. Light-Directed Dynamic Chirality Inversion in Functional Self-Organized Helical Superstructures.

    PubMed

    Bisoyi, Hari Krishna; Li, Quan

    2016-02-24

    Helical superstructures are widely observed in nature, in synthetic polymers, and in supramolecular assemblies. Controlling the chirality (the handedness) of dynamic helical superstructures of molecular and macromolecular systems by external stimuli is a challenging task, but is of great fundamental significance with appealing morphology-dependent applications. Light-driven chirality inversion in self-organized helical superstructures (i.e. cholesteric, chiral nematic liquid crystals) is currently in the limelight because inversion of the handedness alters the chirality of the circularly polarized light that they selectively reflect, which has wide potential for application. Here we discuss the recent developments toward inversion of the handedness of cholesteric liquid crystals enabled by photoisomerizable chiral molecular switches or motors. Different classes of chiral photoresponsive dopants (guests) capable of conferring light-driven reversible chirality inversion of helical superstructures fabricated from different nematic hosts are discussed. Rational molecular designs of chiral molecular switches toward endowing handedness inversion to the induced helical superstructures of cholesteric liquid crystals are highlighted. This Review is concluded by throwing light on the challenges and opportunities in this emerging frontier, and it is expected to provide useful guidelines toward the development of self-organized soft materials with stimuli-directed chirality inversion capability and multifunctional host-guest systems. PMID:26764018

  19. Intensity-modulated radiation therapy (IMRT) dosimetry of the head and neck: A comparison of treatment plans using linear accelerator-based IMRT and helical tomotherapy

    SciTech Connect

    Sheng Ke . E-mail: ks2mc@virginia.edu; Molloy, Janelle A.; Read, Paul W.

    2006-07-01

    Purpose: To date, most intensity-modulated radiation therapy (IMRT) delivery has occurred using linear accelerators (linacs), although helical tomotherapy has become commercially available. To quantify the dosimetric difference, we compared linac-based and helical tomotherapy-based treatment plans for IMRT of the oropharynx. Methods and Materials: We compared the dosimetry findings of 10 patients who had oropharyngeal carcinoma. Five patients each had cancers in the base of the tongue and tonsil. Each plan was independently optimized using either the CORVUS planning system (Nomos Corporation, Sewickly, PA), commissioned for a Varian 2300 CD linear accelerator (Varian Medical Systems, Palo Alto, CA) with 1-cm multileaf collimator leaves, or helical tomotherapy. The resulting treatment plans were evaluated by comparing the dose-volume histograms, equivalent uniform dose (EUD), dose uniformity, and normal tissue complication probabilities. Results: Helical tomotherapy plans showed improvement of critical structure avoidance and target dose uniformity for all patients. The average equivalent uniform dose reduction for organs at risk (OARs) surrounding the base of tongue and the tonsil were 17.4% and 27.14% respectively. An 80% reduction in normal tissue complication probabilities for the parotid glands was observed in the tomotherapy plans relative to the linac-based plans. The standard deviation of the planning target volume dose was reduced by 71%. In our clinic, we use the combined dose-volume histograms for each class of plans as a reference goal for helical tomotherapy treatment planning optimization. Conclusions: Helical tomotherapy provides improved dose homogeneity and normal structure dose compared with linac-based IMRT in the treatment of oropharyngeal carcinoma resulting in a reduced risk for complications from focal hotspots within the planning target volume and for the adjacent parotid glands.

  20. Fast radiographic film calibration procedure for helical tomotherapy intensity modulated radiation therapy dose verification

    SciTech Connect

    Yan Yulong; Papanikolaou, Nikos; Weng Xuejun; Penagaricano, Jose; Ratanatharathorn, Vaneerat

    2005-06-15

    Film dosimetry offers an advantageous in-phantom planar dose verification tool in terms of spatial resolution and ease of handling for quality assurance (QA) of intensity modulated radiation therapy (IMRT) plans. A critical step in the success of such a technique is that the film calibration be appropriately conducted. This paper presents a fast and efficient film calibration method for a helical tomotherapy unit using a single sheet of film. Considering the unique un-flattened cone shaped profile from a helical tomotherapy beam, a custom leaf control file (sinogram) was created, to produce a valley shaped intensity pattern. There are eleven intensity steps in the valley pattern, representing varying dose values from 38 to 265 cGy. This dose range covers the most commonly prescribed doses in fractionated IMRT treatments. An ion chamber in a solid water phantom was used to measure the dose in each of the eleven steps. For daily film calibration the whole procedure, including film exposure, processing, digitization and analysis, can be completed within 15 min, making it practical to use this technique routinely. This method is applicable to film calibration on a helical tomotherapy unit and is particularly useful in IMRT planar dose verification due to its efficiency and reproducibility. In this work, we characterized the dose response of the KODAK EDR2 ready-pack film which was used to develop the step valley dose maps and the IMRT QA planar doses. A comparison between the step valley technique and multifilm based calibration showed that both calibration methods agreed with less than 0.4% deviation in the clinically useful dose ranges.

  1. Dynamic and Progressive Control of DNA Origami Conformation by Modulating DNA Helicity with Chemical Adducts.

    PubMed

    Chen, Haorong; Zhang, Hanyu; Pan, Jing; Cha, Tae-Gon; Li, Shiming; Andréasson, Joakim; Choi, Jong Hyun

    2016-05-24

    DNA origami has received enormous attention for its ability to program complex nanostructures with a few nanometer precision. Dynamic origami structures that change conformation in response to environmental cues or external signals hold great promises in sensing and actuation at the nanoscale. The reconfiguration mechanism of existing dynamic origami structures is mostly limited to single-stranded hinges and relies almost exclusively on DNA hybridization or strand displacement. Here, we show an alternative approach by demonstrating on-demand conformation changes with DNA-binding molecules, which intercalate between base pairs and unwind DNA double helices. The unwinding effect modulates the helicity mismatch in DNA origami, which significantly influences the internal stress and the global conformation of the origami structure. We demonstrate the switching of a polymerized origami nanoribbon between different twisting states and a well-constrained torsional deformation in a monomeric origami shaft. The structural transformation is shown to be reversible, and binding isotherms confirm the reconfiguration mechanism. This approach provides a rapid and reversible means to change DNA origami conformation, which can be used for dynamic and progressive control at the nanoscale. PMID:27057775

  2. A Porous Metal-Organic Framework with Helical Chain Building Units Exhibiting Facile Transition from Micro- to Meso-porosity

    SciTech Connect

    Park, Jinhee; Li, Jian-Rong; Carolina Sañudo, E.; Yuan, Daqiang; Zhou, Hong-Cai

    2012-01-01

    A metal–organic framework (MOF) with helical channels has been constructed by bridging helical chain secondary building units with 2,6-di-p-carboxyphenyl-4,4'-bipyridine ligands. The activated MOF shows permanent porosity and gas adsorption selectivity. Remarkably, the MOF exhibits a facile transition from micro- to meso-porosity.

  3. Dosimetric comparison of three-dimensional conformal radiotherapy, intensity modulated radiotherapy, and helical tomotherapy for lung stereotactic body radiotherapy.

    PubMed

    Kinhikar, Rajesh Ashok; Ghadi, Yogesh G; Sahoo, Priyadarshini; Laskar, Sarbani Ghosh; Deshpande, Deepak D; Shrivastava, Shyam K; Agarwal, Jaiprakash

    2015-01-01

    To compare the treatment plans generated with three-dimensional conformal radiation therapy (3DCRT), intensity modulated radiotherapy (IMRT), and helical tomotherapy (HT) for stereotactic body radiotherapy of lung, twenty patients with medically inoperable (early nonsmall cell lung cancer) were retrospectively reviewed for dosimetric evaluation of treatment delivery techniques (3DCRT, IMRT, and HT). A dose of 6 Gy per fraction in 8 fractions was prescribed to deliver 95% of the prescription dose to 95% volume of planning target volume (PTV). Plan quality was assessed using conformity index (CI) and homogeneity index (HI). Doses to critical organs were assessed. Mean CI with 3DCRT, IMRT, and HT was 1.19 (standard deviation [SD] 0.13), 1.18 (SD 0.11), and 1.08 (SD 0.04), respectively. Mean HI with 3DCRT, IMRT, and HT was 1.14 (SD 0.05), 1.08 (SD 0.02), and 1.07 (SD 0.04), respectively. Mean R50% values for 3DCRT, IMRT, and HT was 8.5 (SD 0.35), 7.04 (SD 0.45), and 5.43 (SD 0.29), respectively. D2cm was found superior with IMRT and HT. Significant sparing of critical organs can be achieved with highly conformal techniques (IMRT and HT) without compromising the PTV conformity and homogeneity. PMID:26865754

  4. Bis(haloBODIPYs) with Labile Helicity: Valuable Simple Organic Molecules That Enable Circularly Polarized Luminescence.

    PubMed

    Ray, César; Sánchez-Carnerero, Esther M; Moreno, Florencio; Maroto, Beatriz L; Agarrabeitia, Antonia R; Ortiz, María J; López-Arbeloa, Íñigo; Bañuelos, Jorge; Cohovi, Komlan D; Lunkley, Jamie L; Muller, Gilles; de la Moya, Santiago

    2016-06-20

    Simple organic molecules (SOM) based on bis(haloBODIPY) are shown to enable circularly polarized luminescence (CPL), giving rise to a new structural design for technologically valuable CPL-SOMs. The established design comprises together synthetic accessibility, labile helicity, possibility of reversing the handedness of the circularly polarized emission, and reactive functional groups, making it unique and attractive as advantageous platform for the development of smart CPL-SOMs. PMID:27123965

  5. Membrane Curvature Sensing by Amphipathic Helices Is Modulated by the Surrounding Protein Backbone

    PubMed Central

    Doucet, Christine M.; Esmery, Nina; de Saint-Jean, Maud; Antonny, Bruno

    2015-01-01

    Membrane curvature is involved in numerous biological pathways like vesicle trafficking, endocytosis or nuclear pore complex assembly. In addition to its topological role, membrane curvature is sensed by specific proteins, enabling the coordination of biological processes in space and time. Amongst membrane curvature sensors are the ALPS (Amphipathic Lipid Packing Sensors). ALPS motifs are short peptides with peculiar amphipathic properties. They are found in proteins targeted to distinct curved membranes, mostly in the early secretory pathway. For instance, the ALPS motif of the golgin GMAP210 binds trafficking vesicles, while the ALPS motif of Nup133 targets nuclear pores. It is not clear if, besides curvature sensitivity, ALPS motifs also provide target specificity, or if other domains in the surrounding protein backbone are involved. To elucidate this aspect, we studied the subcellular localization of ALPS motifs outside their natural protein context. The ALPS motifs of GMAP210 or Nup133 were grafted on artificial fluorescent probes. Importantly, ALPS motifs are held in different positions and these contrasting architectures were mimicked by the fluorescent probes. The resulting chimeras recapitulated the original proteins localization, indicating that ALPS motifs are sufficient to specifically localize proteins. Modulating the electrostatic or hydrophobic content of Nup133 ALPS motif modified its avidity for cellular membranes but did not change its organelle targeting properties. In contrast, the structure of the backbone surrounding the helix strongly influenced targeting. In particular, introducing an artificial coiled-coil between ALPS and the fluorescent protein increased membrane curvature sensitivity. This coiled-coil domain also provided membrane curvature sensitivity to the amphipathic helix of Sar1. The degree of curvature sensitivity within the coiled-coil context remains correlated to the natural curvature sensitivity of the helices. This suggests

  6. A Comparison of Helical Intensity-Modulated Radiotherapy, Intensity-Modulated Radiotherapy, and 3D-Conformal Radiation Therapy for Pancreatic Cancer

    SciTech Connect

    Poppe, Matthew M.; Narra, Venkat; Yue, Ning J.; Zhou Jinghao; Nelson, Carl; Jabbour, Salma K.

    2011-01-01

    We assessed dosimetric differences in pancreatic cancer radiotherapy via helical intensity-modulated radiotherapy (HIMRT), linac-based IMRT, and 3D-conformal radiation therapy (3D-CRT) with regard to successful plan acceptance and dose to critical organs. Dosimetric analysis was performed in 16 pancreatic cases that were planned to 54 Gy; both post-pancreaticoduodenectomy (n = 8) and unresected (n = 8) cases were compared. Without volume modification, plans met constraints 75% of the time with HIMRT and IMRT and 13% with 3D-CRT. There was no statistically significantly improvement with HIMRT over conventional IMRT in reducing liver V35, stomach V45, or bowel V45. HIMRT offers improved planning target volume (PTV) dose homogeneity compared with IMRT, averaging a lower maximum dose and higher volume receiving the prescription dose (D100). HIMRT showed an increased mean dose over IMRT to bowel and liver. Both HIMRT and IMRT offer a statistically significant improvement over 3D-CRT in lowering dose to liver, stomach, and bowel. The results were similar for both unresected and resected patients. In pancreatic cancer, HIMRT offers improved dose homogeneity over conventional IMRT and several significant benefits to 3D-CRT. Factors to consider before incorporating IMRT into pancreatic cancer therapy are respiratory motion, dose inhomogeneity, and mean dose.

  7. SmartArc-based volumetric modulated arc therapy for endometrial cancer: a dosimetric comparison with helical tomotherapy and intensity-modulated radiation therapy

    PubMed Central

    2013-01-01

    Background The purpose of the present study was to investigate the feasibility of using volumetric modulated arc therapy with SmartArc (VMAT-S) to achieve radiation delivery efficiency higher than that of intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) when treating endometrial cancer, while maintaining plan quality. Methods Nine patients with endometrial cancer were retrospectively studied. Three plans per patient were generated for VMAT-S, IMRT and HT. The dose distributions for the planning target volume (PTV), organs at risk (OARs) and normal tissue were compared. The monitor units (MUs) and treatment delivery time were also evaluated. Results The average homogeneity index was 1.06, 1.10 and 1.07 for the VMAT-S, IMRT and HT plans, respectively. The V40 for the rectum, bladder and pelvis bone decreased by 9.0%, 3.0% and 3.0%, respectively, in the VMAT-S plan relative to the IMRT plan. The target coverage and sparing of OARs were comparable between the VMAT-S and HT plans. The average MU was 823, 1105 and 8403 for VMAT-S, IMRT and HT, respectively; the average delivery time was 2.6, 8.6 and 9.5 minutes, respectively. Conclusions For endometrial cancer, the VMAT-S plan provided comparable quality with significantly shorter delivery time and fewer MUs than with the IMRT and HT plans. In addition, more homogeneous PTV coverage and superior sparing of OARs in the medium to high dose region were observed in the VMAT-S relative to the IMRT plan. PMID:24175929

  8. Juxta-terminal Helix Unwinding as a Stabilizing Factor to Modulate the Dynamics of Transmembrane Helices.

    PubMed

    Mortazavi, Armin; Rajagopalan, Venkatesan; Sparks, Kelsey A; Greathouse, Denise V; Koeppe, Roger E

    2016-03-15

    Transmembrane helices of integral membrane proteins often are flanked by interfacial aromatic residues that can serve as anchors to aid the stabilization of a tilted transmembrane orientation. Yet, physical factors that govern the orientation or dynamic averaging of individual transmembrane helices are not well understood and have not been adequately explained. Using solid-state (2) H NMR spectroscopy to examine lipid bilayer-incorporated model peptides of the GWALP23 (acetyl-GGALW(LA)6 LWLAGA-amide) family, we observed substantial unwinding at the terminals of several tilted helices spanning the membranes of DLPC, DMPC, or DOPC lipid bilayers. The fraying of helix ends might be vital for defining the dynamics and orientations of transmembrane helices in lipid bilayer membranes. PMID:26749271

  9. Helical Tomotherapy Versus Single-Arc Intensity-Modulated Arc Therapy: A Collaborative Dosimetric Comparison Between Two Institutions

    SciTech Connect

    Rong Yi; Tang, Grace; Welsh, James S.; Mohiuddin, Majid M.; Paliwal, Bhudatt; Yu, Cedric X.

    2011-09-01

    Purpose: Both helical tomotherapy (HT) and single-arc intensity-modulated arc therapy (IMAT) deliver radiation using rotational beams with multileaf collimators. We report a dual-institution study comparing dosimetric aspects of these two modalities. Methods and Materials: Eight patients each were selected from the University of Maryland (UMM) and the University of Wisconsin Cancer Center Riverview (UWR), for a total of 16 cases. Four cancer sites including brain, head and neck (HN), lung, and prostate were selected. Single-arc IMAT plans were generated at UMM using Varian RapidArc (RA), and HT plans were generated at UWR using Hi-Art II TomoTherapy. All 16 cases were planned based on the identical anatomic contours, prescriptions, and planning objectives. All plans were swapped for analysis at the same time after final approval. Dose indices for targets and critical organs were compared based on dose-volume histograms, the beam-on time, monitor units, and estimated leakage dose. After the disclosure of comparison results, replanning was done for both techniques to minimize diversity in optimization focus from different operators. Results: For the 16 cases compared, the average beam-on time was 1.4 minutes for RA and 4.8 minutes for HT plans. HT provided better target dose homogeneity (7.6% for RA and 4.2% for HT) with a lower maximum dose (110% for RA and 105% for HT). Dose conformation numbers were comparable, with RA being superior to HT (0.67 vs. 0.60). The doses to normal tissues using these two techniques were comparable, with HT showing lower doses for more critical structures. After planning comparison results were exchanged, both techniques demonstrated improvements in dose distributions or treatment delivery times. Conclusions: Both techniques created highly conformal plans that met or exceeded the planning goals. The delivery time and total monitor units were lower in RA than in HT plans, whereas HT provided higher target dose uniformity.

  10. Effects of geometric parameters on swimming of micro organisms with single helical flagellum in circular channels.

    PubMed

    Acemoglu, Alperen; Yesilyurt, Serhat

    2014-04-01

    We present a computational fluid dynamics (CFD) model for the swimming of micro organisms with a single helical flagellum in circular channels. The CFD model is developed to obtain numerical solutions of Stokes equations in three dimensions, validated with experiments reported in literature, and used to analyze the effects of geometric parameters, such as the helical radius, wavelength, radii of the channel and the tail and the tail length on forward and lateral swimming velocities, rotation rates, and the efficiency of the swimmer. Optimal shapes for the speed and the power efficiency are reported. Effects of Brownian motion and electrostatic interactions are excluded to emphasize the role of hydrodynamic forces on lateral velocities and rotations on the trajectory of swimmers. For thin flagella, as the channel radius decreases, forward velocity and the power efficiency of the swimmer decreases as well; however, for thick flagella, there is an optimal radius of the channel that maximizes the velocity and the efficiency depending on other geometric parameters. Lateral motion of the swimmer is suppressed as the channel is constricted below a critical radius, for which the magnitude of the lateral velocity reaches a maximum. Results contribute significantly to the understanding of the swimming of bacteria in micro channels and capillary tubes. PMID:24703315

  11. Helical Magnetic Self-Organization in the RFX-mod and MST devices

    NASA Astrophysics Data System (ADS)

    Franz, P.; Piovesan, P.; Spolaore, M.; Cappello, S.; Puiatti, M. E.; Chapman, B. E.; Sarff, J. S.; den Hartog, D. J.; Goetz, J. A.; McGarry, M. B.; Parke, E.; Reusch, J. A.; Stephens, H. D.; Yang, Y. M.

    2010-11-01

    Self-organization of the reversed field pinch with large helical structure (QSH regimes) is predominant as plasma current is increased. In RFX-mod, the persistence and strength of the QSH state increases markedly above 1 MA. An internal transport barrier appears, and plasma thermalization within the helical magnetic surfaces reflects improved confinement. The QSH regime is also obtained in MST plasmas, which operates with plasma current up to nearly 0.6 MA. We report here a statistical analysis of the tearing mode behavior in MST (e.g., amplitudes and QSH persistency) that reveals a trend with plasma current similar to that observed in RFX-Mod. This trend supports an expectation for universal behavior that depends on parameters such as the Lundquist number that vary with the plasma current. Analysis of the common database from the two devices should help reveal key physics for QSH onset and dynamics. Planned Thomson scattering measurements and transport analysis on MST will be important to compare with the confinement behavior established for RFX-Mod. Work supported by USDoE.

  12. Effects of Geometric Parameters on Swimming of Micro Organisms with Single Helical Flagellum in Circular Channels

    PubMed Central

    Acemoglu, Alperen; Yesilyurt, Serhat

    2014-01-01

    We present a computational fluid dynamics (CFD) model for the swimming of micro organisms with a single helical flagellum in circular channels. The CFD model is developed to obtain numerical solutions of Stokes equations in three dimensions, validated with experiments reported in literature, and used to analyze the effects of geometric parameters, such as the helical radius, wavelength, radii of the channel and the tail and the tail length on forward and lateral swimming velocities, rotation rates, and the efficiency of the swimmer. Optimal shapes for the speed and the power efficiency are reported. Effects of Brownian motion and electrostatic interactions are excluded to emphasize the role of hydrodynamic forces on lateral velocities and rotations on the trajectory of swimmers. For thin flagella, as the channel radius decreases, forward velocity and the power efficiency of the swimmer decreases as well; however, for thick flagella, there is an optimal radius of the channel that maximizes the velocity and the efficiency depending on other geometric parameters. Lateral motion of the swimmer is suppressed as the channel is constricted below a critical radius, for which the magnitude of the lateral velocity reaches a maximum. Results contribute significantly to the understanding of the swimming of bacteria in micro channels and capillary tubes. PMID:24703315

  13. Radiation dose for normal organs by helical tomotherapy for lung cancer.

    PubMed

    Tseng, Hsien-Chun; Liu, Wen-Shan; Tsai, Hsiao-Han; Chu, Hsin-Yi; Lin, Jye-Bin; Chen, Chien-Yi

    2015-08-01

    This study derived a simple equation of effective dose (E) versus normal organ of patients with varying body weights undergoing lung cancer treatment of helical tomotherapy (TOMO). Five tissue-equivalent and Rando phantoms were used to simulate lung cancer patients. This study then measured E and equivalent dose of organ or tissues (DT) using thermoluminescent dosimetry (TLD-100H). The TLD-100H was calibrated using TOMO 6MV photons, then inserted into phantom positions that closely corresponded with the position of the represented organs and tissues. Both E and DT were evaluated by ICRP 103. Peripheral doses varied markedly at positions close to the tumor center. The maximum statistical and total errors were 16.7-22.3%. This analytical result indicates that E of Rando and tissue-equivalent phantoms was in the ranged of 9.44±1.70 (10kg) to 4.58±0.83 (90kg)mSv/Gy. Notably, E decreased exponentially as phantom weight increased. Peripheral doses were also evaluated by TLD as a function of distance from the tumor center. Finally, experimental results are compared with those in literature. These findings will prove useful to patients, physicians, radiologists, and the public. PMID:25935507

  14. Molecular organization in striated domains induced by transmembrane alpha-helical peptides in dipalmitoyl phosphatidylcholine bilayers.

    PubMed

    Sparr, Emma; Ganchev, Dragomir N; Snel, Margot M E; Ridder, Anja N J A; Kroon-Batenburg, Loes M J; Chupin, Vladimir; Rijkers, Dirk T S; Killian, J Antoinette; de Kruijff, Ben

    2005-01-11

    Transmembrane (TM) alpha-helical peptides with neutral flanking residues such as tryptophan form highly ordered striated domains when incorporated in gel-state 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers and inspected by atomic force microscopy (AFM) (1). In this study, we analyze the molecular organization of these striated domains using AFM, photo-cross-linking, fluorescence spectroscopy, nuclear magnetic resonance (NMR), and X-ray diffraction techniques on different functionalized TM peptides. The results demonstrate that the striated domains consist of linear arrays of single TM peptides with a dominantly antiparallel organization in which the peptides interact with each other and with lipids. The peptide arrays are regularly spaced by +/-8.5 nm and are separated by somewhat perturbed gel-state lipids with hexagonally organized acyl chains, which have lost their tilt. This system provides an example of how domains of peptides and lipids can be formed in membranes as a result of a combination of specific peptide-peptide and peptide-lipid interactions. PMID:15628840

  15. On the performances of Intensity Modulated Protons, RapidArc and Helical Tomotherapy for selected paediatric cases

    PubMed Central

    Fogliata, Antonella; Yartsev, Slav; Nicolini, Giorgia; Clivio, Alessandro; Vanetti, Eugenio; Wyttenbach, Rolf; Bauman, Glenn; Cozzi, Luca

    2009-01-01

    Background To evaluate the performance of three different advanced treatment techniques on a group of complex paediatric cancer cases. Methods CT images and volumes of interest of five patients were used to design plans for Helical Tomotherapy (HT), RapidArc (RA) and Intensity Modulated Proton therapy (IMP). The tumour types were: extraosseous, intrathoracic Ewing Sarcoma; mediastinal Rhabdomyosarcoma; metastastis of base of skull with bone, para-nasal and left eye infiltration from Nephroblastoma of right kidney; metastatic Rhabdomyosarcoma of the anus; Wilm's tumour of the left kidney with multiple liver metastases. Cases were selected for their complexity regardless the treatment intent and stage. Prescribed doses ranged from 18 to 53.2 Gy, with four cases planned using a Simultaneous Integrated Boost strategy. Results were analysed in terms of dose distributions and dose volume histograms. Results For all patients, IMP plans lead to superior sparing of organs at risk and normal healthy tissue, where in particular the integral dose is halved with respect to photon techniques. In terms of conformity and of spillage of high doses outside targets (external index (EI)), all three techniques were comparable; CI90% ranged from 1.0 to 2.3 and EI from 0 to 5%. Concerning target homogeneity, IMP showed a variance (D5%–D95%) measured on the inner target volume (highest dose prescription) ranging from 5.9 to 13.3%, RA from 5.3 to 11.8%, and HT from 4.0 to 12.2%. The range of minimum significant dose to the same target was: (72.2%, 89.9%) for IMP, (86.7%, 94.1%) for RA, and (79.4%, 94.8%) for HT. Similarly, for maximum significant doses: (103.8%, 109.4%) for IMP, (103.2%, 107.4%) for RA, and (102.4%, 117.2%) for HT. Treatment times (beam-on time) ranged from 123 to 129 s for RA and from 146 to 387 s for HT. Conclusion Five complex pediatric cases were selected as representative examples to compare three advanced radiation delivery techniques. While differences were noted

  16. Assessing the Role of Volumetric Modulated Arc Therapy (VMAT) Relative to IMRT and Helical Tomotherapy in the Management of Localized, Locally Advanced, and Post-Operative Prostate Cancer

    SciTech Connect

    Davidson, Melanie T.M.; Blake, Samuel J.; Batchelar, Deidre L.; Cheung, Patrick; Mah, Katherine

    2011-08-01

    Purpose: To quantify differences in treatment delivery efficiency and dosimetry between step-and-shoot intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) for prostate treatment. Methods and Materials: Twenty-five prostate cancer patients were selected retrospectively for this planning study. Treatment plans were generated for: prostate alone (n = 5), prostate + seminal vesicles (n = 5), prostate + seminal vesicles + pelvic lymph nodes (n = 5), prostate bed (n = 5), and prostate bed + pelvic lymph nodes (n = 5). Target coverage, dose homogeneity, integral dose, monitor units (MU), and sparing of organs at risk (OAR) were compared across techniques. Time required to deliver each plan was measured. Results: The dosimetric quality of IMRT, VMAT, and HT plans were comparable for target coverage (planning target volume V95%, clinical target volume V100% all >98.7%) and sparing of organs at risk (OAR) for all treatment groups. Although HT resulted in a slightly higher integral dose and mean doses to the OAR, it yielded a lower maximum dose to all OAR examined. VMAT resulted in reductions in treatment times over IMRT (mean = 75%) and HT (mean = 70%). VMAT required 15-38% fewer monitor units than IMRT over all treatment volumes, with the reduction per fraction ranging from 100-423 MU from the smallest to largest volumes. Conclusions: VMAT improves efficiency of delivery for equivalent dosimetric quality as IMRT and HT across various prostate cancer treatment volumes in the intact and postoperative settings.

  17. Treatment of nasopharyngeal carcinoma using simultaneous modulated accelerated radiation therapy via helical tomotherapy: a phase II study

    PubMed Central

    Du, Lei; Zhang, Xin Xin; Feng, Lin Chun; Chen, Jing; Yang, Jun; Liu, Hai Xia; Xu, Shou Ping; Xie, Chuan Bin

    2016-01-01

    Abstract Background The aim of the study was to evaluate short-term safety and efficacy of simultaneous modulated accelerated radiation therapy (SMART) delivered via helical tomotherapy in patients with nasopharyngeal carcinoma (NPC). Methods Between August 2011 and September 2013, 132 newly diagnosed NPC patients were enrolled for a prospective phase II study. The prescription doses delivered to the gross tumor volume (pGTVnx) and positive lymph nodes (pGTVnd), the high risk planning target volume (PTV1), and the low risk planning target volume (PTV2), were 67.5 Gy (2.25 Gy/F), 60 Gy (2.0 Gy/F), and 54 Gy (1.8 Gy/F), in 30 fractions, respectively. Acute toxicities were evaluated according to the established RTOG/EORTC criteria. This group of patients was compared with the 190 patients in the retrospective P70 study, who were treated between September 2004 and August 2009 with helical tomotherapy, with a dose of 70-74 Gy/33F/6.5W delivered to pGTVnx and pGTVnd. Results The median follow-up was 23.7 (12–38) months. Acute radiation related side-effects were mainly problems graded as 1 or 2. Only a small number of patients suffered from grade 4 leucopenia (4.5%) or thrombocytopenia (2.3%). The local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), local-nodal relapse-free survival (LNRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were 96.7%, 95.5%, 92.2%, 92.7% and 93.2%, at 2 years, respectively, with no significant difference compared with the P70 study. Conclusions Smart delivered via the helical tomotherapy technique appears to be associated with an acceptable acute toxicity profile and favorable short-term outcomes for patients with NPC. Long-term toxicities and patient outcomes are under investigation. PMID:27247555

  18. ModuleOrganizer: detecting modules in families of transposable elements

    PubMed Central

    2010-01-01

    Background Most known eukaryotic genomes contain mobile copied elements called transposable elements. In some species, these elements account for the majority of the genome sequence. They have been subject to many mutations and other genomic events (copies, deletions, captures) during transposition. The identification of these transformations remains a difficult issue. The study of families of transposable elements is generally founded on a multiple alignment of their sequences, a critical step that is adapted to transposons containing mostly localized nucleotide mutations. Many transposons that have lost their protein-coding capacity have undergone more complex rearrangements, needing the development of more complex methods in order to characterize the architecture of sequence variations. Results In this study, we introduce the concept of a transposable element module, a flexible motif present in at least two sequences of a family of transposable elements and built on a succession of maximal repeats. The paper proposes an assembly method working on a set of exact maximal repeats of a set of sequences to create such modules. It results in a graphical view of sequences segmented into modules, a representation that allows a flexible analysis of the transformations that have occurred between them. We have chosen as a demonstration data set in depth analysis of the transposable element Foldback in Drosophila melanogaster. Comparison with multiple alignment methods shows that our method is more sensitive for highly variable sequences. The study of this family and the two other families AtREP21 and SIDER2 reveals new copies of very different sizes and various combinations of modules which show the potential of our method. Conclusions ModuleOrganizer is available on the Genouest bioinformatics center at http://moduleorganizer.genouest.org PMID:20860790

  19. A Water-Stable Metal-Organic Framework with a Double-Helical Structure for Fluorescent Sensing.

    PubMed

    Liu, Xiao-Jing; Zhang, Ying-Hui; Chang, Ze; Li, Ai-Lin; Tian, Dan; Yao, Zhao-Quan; Jia, Yan-Yuan; Bu, Xian-He

    2016-08-01

    Water instability is a crucial limiting factor in the practical application of most fluorescent metal-organic frameworks (MOFs). Here, by introducing a fascinating double-helical structure generated through dense stacking of organic ligands, a water-stable fluorescence MOF has been synthesized, namely, [Cd2(tib)2(bda)2]·(solvent)n (1) [tib =1,3,5-tris(1-imidazolyl) benzene; H2bda = 2,2'-biphenyl dicarboxylic acid]. This helical structure helps to enhance the stability of 1 against common organic solvents and water, even acid/base aqueous solutions with a pH value ranging from 3 to 11. Furthermore, this material can be a potential fluorescent sensor for ketones. PMID:27409244

  20. Organ and effective doses in newborn patients during helical multislice computed tomography examination

    NASA Astrophysics Data System (ADS)

    Staton, Robert J.; Lee, Choonik; Lee, Choonsik; Williams, Matt D.; Hintenlang, David E.; Arreola, Manuel M.; Williams, Jonathon L.; Bolch, Wesley E.

    2006-10-01

    In this study, two computational phantoms of the newborn patient were used to assess individual organ doses and effective doses delivered during head, chest, abdomen, pelvis, and torso examinations using the Siemens SOMATOM Sensation 16 helical multi-slice computed tomography (MSCT) scanner. The stylized phantom used to model the patient anatomy was the revised ORNL newborn phantom by Han et al (2006 Health Phys.90 337). The tomographic phantom used in the study was that developed by Nipper et al (2002 Phys. Med. Biol. 47 3143) as recently revised by Staton et al (2006 Med. Phys. 33 3283). The stylized model was implemented within the MCNP5 radiation transport code, while the tomographic phantom was incorporated within the EGSnrc code. In both codes, the x-ray source was modelled as a fan beam originating from the focal spot at a fan angle of 52° and a focal-spot-to-axis distance of 57 cm. The helical path of the source was explicitly modelled based on variations in collimator setting (12 mm or 24 mm), detector pitch and scan length. Tube potentials of 80, 100 and 120 kVp were considered in this study. Beam profile data were acquired using radiological film measurements on a 16 cm PMMA phantom, which yielded effective beam widths of 14.7 mm and 26.8 mm for collimator settings of 12 mm and 24 mm, respectively. Values of absolute organ absorbed dose were determined via the use of normalization factors defined as the ratio of the CTDI100 measured in-phantom and that determined by Monte Carlo simulation of the PMMA phantom and ion chamber. Across various technique factors, effective dose differences between the stylized and tomographic phantoms ranged from +2% to +9% for head exams, -4% to -2% for chest exams, +8% to +24% for abdominal exams, -16% to -12% for pelvic exams and -7% to 0% for chest-abdomen-pelvis (CAP) exams. In many cases, however, relatively close agreement in effective dose was accomplished at the expense of compensating errors in individual organ

  1. Organ and effective doses in pediatric patients undergoing helical multislice computed tomography examination

    SciTech Connect

    Lee, Choonik; Lee, Choonsik; Staton, Robert J.; Hintenlang, David E.; Arreola, Manuel M.; Williams, Jonathon L.; Bolch, Wesley E.

    2007-05-15

    As multidetector computed tomography (CT) serves as an increasingly frequent diagnostic modality, radiation risks to patients became a greater concern, especially for children due to their inherently higher radiosensitivity to stochastic radiation damage. Current dose evaluation protocols include the computed tomography dose index (CTDI) or point detector measurements using anthropomorphic phantoms that do not sufficiently provide accurate information of the organ-averaged absorbed dose and corresponding effective dose to pediatric patients. In this study, organ and effective doses to pediatric patients under helical multislice computed tomography (MSCT) examinations were evaluated using an extensive series of anthropomorphic computational phantoms and Monte Carlo radiation transport simulations. Ten pediatric phantoms, five stylized (equation-based) ORNL phantoms (newborn, 1-year, 5-year, 10-year, and 15-year) and five tomographic (voxel-based) UF phantoms (9-month male, 4-year female, 8-year female, 11-year male, and 14-year male) were implemented into MCNPX for simulation, where a source subroutine was written to explicitly simulate the helical motion of the CT x-ray source and the fan beam angle and collimator width. Ionization chamber measurements were performed and used to normalize the Monte Carlo simulation results. On average, for the same tube current setting, a tube potential of 100 kVp resulted in effective doses that were 105% higher than seen at 80 kVp, and 210% higher at 120 kVp regardless of phantom type. Overall, the ORNL phantom series was shown to yield values of effective dose that were reasonably consistent with those of the gender-specific UF phantom series for CT examinations of the head, pelvis, and torso. However, the ORNL phantoms consistently overestimated values of the effective dose as seen in the UF phantom for MSCT scans of the chest, and underestimated values of the effective dose for abdominal CT scans. These discrepancies increased

  2. SU-E-T-371: Validation of Organ Doses Delivered During Craniospinal Irradiation with Helical Tomotherapy

    SciTech Connect

    Perez-Andujar, A; Chen, J; Garcia, A; Haas-Kogan, D

    2014-06-01

    Purpose: New techniques have been developed to deliver more conformal treatments to the craniospinal axis. One concern, however, is the widespread low dose delivered and implications for possible late effects. The purpose of this work is for the first time to validate the organ doses calculated by the treatment planning system (TPS), including out-of-field doses for a pediatric craniospinal treatment (CSI). Methods: A CSI plan prescribed to 23.4 Gy and a posterior fossa boost plan to 30.6 Gy (total dose 54.0 Gy) was developed for a pediatric anthropomorphic phantom representing a 13 yearold- child. For the CSI plan, the planning target volumes (PTV) consisted of the brain and spinal cord with 2 mm and 5 mm expansions, respectively. Organs at risk (OAR) were contoured and included in the plan optimization. The plans were delivered on a helical tomotherapy unit. Thermoluminescent dosimeters (TLDs) were used to measure the dose at 54 positions within the PTV and OARs. Results: For the CSI treatment, the mean percent difference between TPS dose calculations and measurements was 5% for the PTV and 10% for the OARs. For the boost, the average was 3% for the PTV. The percent difference for the OARs, which lie outside the field and received a small fraction of the prescription dose, varied from 15% to 200%. However in terms of absolute dose, the average difference between measurement and TPS per treatment Gy was 2 cGy/Gy and 3 mGy/Gy for the CSI and boost plans, respectively. Conclusion: There was good agreement between doses calculated by the TPS and measurements for the CSI treatment. Higher percent differences were observed for out-of-field doses in the boost plan, but absolute dose differences were very small compared to the prescription dose. These findings can help in the estimation of late effects after radiotherapy for pediatric patients.

  3. Radiobiologic comparison of helical tomotherapy, intensity modulated radiotherapy, and conformal radiotherapy in treating lung cancer accounting for secondary malignancy risks

    SciTech Connect

    Komisopoulos, Georgios; Mavroidis, Panayiotis; Rodriguez, Salvador; Stathakis, Sotirios; Papanikolaou, Nikos; Nikiforidis, Georgios C.; Sakellaropoulos, Georgios C.

    2014-01-01

    The aim of the present study is to examine the importance of using measures to predict the risk of inducing secondary malignancies in association with the clinical effectiveness of treatment plans in terms of tumor control and normal tissue complication probabilities. This is achieved by using radiobiologic parameters and measures, which may provide a closer association between clinical outcome and treatment delivery. Overall, 4 patients having been treated for lung cancer were examined. For each of them, 3 treatment plans were developed based on the helical tomotherapy (HT), multileaf collimator-based intensity modulated radiation therapy (IMRT), and 3-dimensional conformal radiation therapy (CRT) modalities. The different plans were evaluated using the complication-free tumor control probability (p{sub +}), the overall probability of injury (p{sub I}), the overall probability of control/benefit (p{sub B}), and the biologically effective uniform dose (D{sup ¯¯}). These radiobiologic measures were used to develop dose-response curves (p-D{sup ¯¯} diagram), which can help to evaluate different treatment plans when used in conjunction with standard dosimetric criteria. The risks for secondary malignancies in the heart and the contralateral lung were calculated for the 3 radiation modalities based on the corresponding dose-volume histograms (DVHs) of each patient. Regarding the overall evaluation of the different radiation modalities based on the p{sub +} index, the average values of the HT, IMRT, and CRT are 67.3%, 61.2%, and 68.2%, respectively. The corresponding average values of p{sub B} are 75.6%, 70.5%, and 71.0%, respectively, whereas the average values of p{sub I} are 8.3%, 9.3%, and 2.8%, respectively. Among the organs at risk (OARs), lungs show the highest probabilities for complications, which are 7.1%, 8.0%, and 1.3% for the HT, IMRT, and CRT modalities, respectively. Similarly, the biologically effective prescription doses (D{sub B}{sup ¯¯}) for the

  4. De novo designed library of linear helical peptides: an exploratory tool in the discovery of protein-protein interaction modulators.

    PubMed

    Bonache, M Ángeles; Balsera, Beatriz; López-Méndez, Blanca; Millet, Oscar; Brancaccio, Diego; Gómez-Monterrey, Isabel; Carotenuto, Alfonso; Pavone, Luigi M; Reille-Seroussi, Marie; Gagey-Eilstein, Nathalie; Vidal, Michel; de la Torre-Martinez, Roberto; Fernández-Carvajal, Asia; Ferrer-Montiel, Antonio; García-López, M Teresa; Martín-Martínez, Mercedes; de Vega, M Jesús Pérez; González-Muñiz, Rosario

    2014-05-12

    Protein-protein interactions (PPIs) have emerged as important targets for pharmaceutical intervention because of their essential role in numerous physiological and pathological processes, but screening efforts using small-molecules have led to very low hit rates. Linear peptides could represent a quick and effective approach to discover initial PPI hits, particularly if they have inherent ability to adopt specific peptide secondary structures. Here, we address this hypothesis through a linear helical peptide library, composed of four sublibraries, which was designed by theoretical predictions of helicity (Agadir software). The 13-mer peptides of this collection fixes either a combination of three aromatic or two aromatic and one aliphatic residues on one face of the helix (Ac-SSEEX(5)ARNX(9)AAX(12)N-NH2), since these are structural features quite common at PPIs interfaces. The 81 designed peptides were conveniently synthesized by parallel solid-phase methodologies, and the tendency of some representative library components to adopt the intended secondary structure was corroborated through CD and NMR experiments. As proof of concept in the search for PPI modulators, the usefulness of this library was verified on the widely studied p53-MDM2 interaction and on the communication between VEGF and its receptor Flt-1, two PPIs for which a hydrophobic α-helix is essential for the interaction. We have demonstrated here that, in both cases, selected peptides from the library, containing the right hydrophobic sequence of the hot-spot in one of the protein partners, are able to interact with the complementary protein. Moreover, we have discover some new, quite potent inhibitors of the VEGF-Flt-1 interaction, just by replacing one of the aromatic residues of the initial F(5)Y(9)Y(12) peptide by W, in agreement with previous results on related antiangiogenic peptides. Finally, the HTS evaluation of the full collection on thermoTRPs has led to a few antagonists of TRPV1 and TRPA

  5. Self-organization of helically forced MHD flow in confined cylindrical geometries

    NASA Astrophysics Data System (ADS)

    Roberts, Malcolm; Leroy, Matthieu; Morales, Jorge; Bos, Wouter; Schneider, Kai

    2014-12-01

    The dynamics of a magnetically forced conducting fluid in confined geometries is studied. A pseudospectral method with volume penalisation is used to solve the resistive magnetohydrodynamic equations. A helical magnetic field is imposed via boundary conditions, which generates a response in the velocity field for large enough magnitudes. Different helical structures are observed in the flow depending on the magnitude and direction of the forcing and the cross-sectional geometry of the fluid domain. A computational technique for finding a solenoidal vector field which can be used in complex geometries is also proposed.

  6. N-terminal segments modulate the α-helical propensities of the intrinsically disordered basic regions of bZIP proteins.

    PubMed

    Das, Rahul K; Crick, Scott L; Pappu, Rohit V

    2012-02-17

    Basic region leucine zippers (bZIPs) are modular transcription factors that play key roles in eukaryotic gene regulation. The basic regions of bZIPs (bZIP-bRs) are necessary and sufficient for DNA binding and specificity. Bioinformatic predictions and spectroscopic studies suggest that unbound monomeric bZIP-bRs are uniformly disordered as isolated domains. Here, we test this assumption through a comparative characterization of conformational ensembles for 15 different bZIP-bRs using a combination of atomistic simulations and circular dichroism measurements. We find that bZIP-bRs have quantifiable preferences for α-helical conformations in their unbound monomeric forms. This helicity varies from one bZIP-bR to another despite a significant sequence similarity of the DNA binding motifs (DBMs). Our analysis reveals that intramolecular interactions between DBMs and eight-residue segments directly N-terminal to DBMs are the primary modulators of bZIP-bR helicities. We test the accuracy of this inference by designing chimeras of bZIP-bRs to have either increased or decreased overall helicities. Our results yield quantitative insights regarding the relationship between sequence and the degree of intrinsic disorder within bZIP-bRs, and might have general implications for other intrinsically disordered proteins. Understanding how natural sequence variations lead to modulation of disorder is likely to be important for understanding the evolution of specificity in molecular recognition through intrinsically disordered regions (IDRs). PMID:22226835

  7. The thermodynamics of the self-assembly of covalently linked oligomeric naphthalenediimides into helical organic nanotubes.

    PubMed

    Tambara, Koujiro; Olsen, John-Carl; Hansen, David E; Pantoş, G Dan

    2014-01-28

    The mechanism and thermodynamic functions of the self-assembly of a family of covalently linked oligomeric naphthalenediimides (NDIs) were investigated through variable-temperature NMR and CD studies. The NDIs were shown to self-assemble into helical supramolecular nanotubes via an isodesmic polymerisation mechanism, and regardless of the oligomer length a surprising entropy-enthalpy compensation was observed. PMID:24287562

  8. Assessment of Extended-Field Radiotherapy for Stage IIIC Endometrial Cancer Using Three-Dimensional Conformal Radiotherapy, Intensity-Modulated Radiotherapy, and Helical Tomotherapy

    SciTech Connect

    Lian Jidong Mackenzie, Marc; Joseph, Kurian; Pervez, Nadeem; Dundas, George; Urtasun, Raul; Pearcey, Robert

    2008-03-01

    Purpose: To perform a dosimetric comparison of three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and helical tomotherapy (HT) plans for pelvic and para-aortic RT in postoperative endometrial cancer patients; and to evaluate the integral dose (ID) received by critical structures within the radiation fields. Methods and Materials: We selected 10 patients with Stage IIIC endometrial cancer. For each patient, three plans were created with 3D-CRT, IMRT, and HT. The IMRT and HT plans were both optimized to keep the mean dose to the planning target volume (PTV) the same as that with 3D-CRT. The dosimetry and ID for the critical structures were compared. A paired two-tailed Student t test was used for data analysis. Results: Compared with the 3D-CRT plans, the IMRT plans resulted in lower IDs in the organs at risk (OARs), ranging from -3.49% to -17.59%. The HT plans showed a similar result except that the ID for the bowel increased 0.27%. The IMRT and HT plans both increased the IDs to normal tissue (see and text for definition), pelvic bone, and spine (range, 3.31-19.7%). The IMRT and HT dosimetry showed superior PTV coverage and better OAR sparing than the 3D-CRT dosimetry. Compared directly with IMRT, HT showed similar PTV coverage, lower Ids, and a decreased dose to most OARs. Conclusion: Intensity-modulated RT and HT appear to achieve excellent PTV coverage and better sparing of OARs, but at the expense of increased IDs to normal tissue and skeleton. HT allows for additional improvement in dosimetry and sparing of most OARs.

  9. Homochiral 3D metal-organic frameworks from chiral 1D rods: 6-way helical packing.

    PubMed

    Shin, Sung Min; Moon, Dohyun; Jeong, Kyung Seok; Kim, Jaheon; Thallapally, Praveen K; Jeong, Nakcheol

    2011-09-01

    The chiral 3D MOFs resulted from the packing of chiral 1D SBBs were studied. It was demonstrated that the final packing pattern is sensitively dependent on the dimension of SBBs. In addition, we were able to identify a new plywood-like network from ligand 2H(2) exhibiting an unprecedented six-way chiral helical packing motif, which extends the list of invariant rod packings. PMID:21773637

  10. Superiority of helical tomotherapy on liver sparing and dose escalation in hepatocellular carcinoma: a comparison study of three-dimensional conformal radiotherapy and intensity-modulated radiotherapy

    PubMed Central

    Zhao, Qianqian; Wang, Renben; Zhu, Jian; Jin, Linzhi; Zhu, Kunli; Xu, Xiaoqing; Feng, Rui; Jiang, Shumei; Qi, Zhonghua; Yin, Yong

    2016-01-01

    Background and purpose To compare the difference of liver sparing and dose escalation between three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), and helical tomotherapy (HT) for hepatocellular carcinoma. Patients and methods Sixteen unresectable HCC patients were enrolled in this study. First, some evaluation factors of 3DCRT, IMRT, and HT plans were calculated with prescription dose at 50 Gy/25 fractions. Then, the doses were increased using HT or IMRT independently until either the plans reached 70 Gy or any normal tissue reached the dose limit according to quantitative analysis of normal tissue effects in the clinic criteria. Results The conformal index of 3DCRT was lower than that of IMRT (P<0.001) or HT (P<0.001), and the homogeneity index of 3DCRT was higher than that of IMRT (P<0.001) or HT (P<0.001). HT took the longest treatment time (P<0.001). For V50% (fraction of normal liver treated to at least 50% of the isocenter dose) of the normal liver, there was a significant difference: 3DCRT > IMRT > HT (P<0.001). HT had a lower Dmean (mean dose) and V20 (Vn, the percentage of organ volume receiving ≥n Gy) of liver compared with 3DCRT (P=0.005 and P=0.005, respectively) or IMRT (P=0.508 and P=0.007, respectively). Dmean of nontarget normal liver and V30 of liver were higher for 3DCRT than IMRT (P=0.005 and P=0.005, respectively) or HT (P=0.005 and P=0.005, respectively). Seven patients in IMRT (43.75%) and nine patients in HT (56.25%) reached the isodose 70 Gy, meeting the dose limit of the organs at risk. Conclusion HT may provide significantly better liver sparing and allow more patients to achieve higher prescription dose in HCC radiotherapy. PMID:27445485

  11. Dosimetric Evaluation of Intensity-Modulated Radiotherapy, Volumetric Modulated Arc Therapy, and Helical Tomotherapy for Hippocampal-Avoidance Whole Brain Radiotherapy

    PubMed Central

    Rong, Yi; Evans, Josh; Xu-Welliver, Meng; Pickett, Cadron; Jia, Guang; Chen, Quan; Zuo, Li

    2015-01-01

    Background Whole brain radiotherapy (WBRT) is a vital tool in radiation oncology and beyond, but it can result in adverse health effects such as neurocognitive decline. Hippocampal Avoidance WBRT (HA-WBRT) is a strategy that aims to mitigate the neuro-cognitive side effects of whole brain radiotherapy treatment by sparing the hippocampi while delivering the prescribed dose to the rest of the brain. Several competing modalities capable of delivering HA-WBRT, include: Philips Pinnacle step-and-shoot intensity modulated radiotherapy (IMRT), Varian RapidArc volumetric modulated arc therapy (RapidArc), and helical TomoTherapy (TomoTherapy). Methods In this study we compared these methods using 10 patient datasets. Anonymized planning CT (computerized tomography) scans and contour data based on fused MRI images were collected. Three independent planners generated treatment plans for the patients using three modalities, respectively. All treatment plans met the RTOG 0933 criteria for HA-WBRT treatment. Results In dosimetric comparisons between the three modalities, TomoTherapy has a significantly superior homogeneity index of 0.15 ± 0.03 compared to the other two modalities (0.28 ± .04, p < .005 for IMRT and 0.22 ± 0.03, p < .005 for RapidArc). RapidArc has the fastest average delivery time of 2.5 min compared to the other modalities (15 min for IMRT and 18 min for TomoTherapy). Conclusion TomoTherapy is considered to be the preferred modality for HA-WBRT due to its superior dose distribution. When TomoTherapy is not available or treatment time is a concern, RapidArc can provide sufficient dose distribution meeting RTOG criteria and efficient treatment delivery. PMID:25894615

  12. A synergistic effect between cholesterol and tryptophan-flanked transmembrane helices modulates membrane curvature.

    PubMed

    van Duyl, Bianca Y; Meeldijk, Hans; Verkleij, Arie J; Rijkers, Dirk T S; Chupin, Vladimir; de Kruijff, Ben; Killian, J Antoinette

    2005-03-22

    The aim of this study was to gain insight into the structural consequences of hydrophobic mismatch for membrane proteins in lipid bilayers that contain cholesterol. For this purpose, tryptophan-flanked peptides, designed to mimic transmembrane segments of membrane proteins, were incorporated in model membranes of unsaturated phosphatidylcholine bilayers of varying thickness and containing varying amounts of cholesterol. Analysis of the lipid organization by (31)P NMR and cryo-TEM demonstrated the formation of an isotropic phase, most likely representing a cubic phase, which occurred exclusively in mixtures containing lipids with relatively long acyl chains. Formation of this phase was inhibited by incorporation of lysophosphatidylcholine. These results indicate that the isotropic phase is formed as a consequence of negative hydrophobic mismatch and that its formation is related to a negative membrane curvature. When either peptide or cholesterol was omitted from the mixture, isotropic-phase formation did not occur, not even when the concentrations of these compounds were significantly increased. This suggests that formation of the isotropic phase is the result of a synergistic effect between the peptides and cholesterol. Interestingly, isotropic-phase formation was not observed when the tryptophans in the peptide were replaced by either lysines or histidines. We propose a model for the mechanism of this synergistic effect, in which its dependence on the flanking residues is explained by preferential interactions between cholesterol and tryptophan residues. PMID:15766283

  13. Helical Tomotherapy Versus Conventional Intensity-Modulated Radiation Therapy for Primary Chemoradiation in Cervical Cancer Patients: An Intraindividual Comparison

    SciTech Connect

    Marnitz, Simone; Lukarski, Dusko; Koehler, Christhardt; Wlodarczyk, Waldemar; Ebert, Andreas; Budach, Volker; Schneider, Achim; Stromberger, Carmen

    2011-10-01

    Purpose: To compare intensity-modulated radiotherapy (IMRT) delivered by helical tomotherapy (HT) with conventional IMRT for primary chemoradiation in cervical cancer patients. Methods and Materials: Twenty cervical cancer patients undergoing primary chemoradiation received radiation with HT; 10 patients underwent pelvic irradiation (PEL) and 10 extended-field irradiation (EXT). For treatment planning, the simultaneously integrated boost (SIB) concept was applied. Tumor, pelvic, with or without para-aortic lymph nodes were defined as planning target volume A (PTV-A) with a prescribed dose of 1.8/50.4 Gy (28 fractions). The SIB dose for the parametrium (PTV-B), was 2.12/59.36 Gy. The lower target constraints were 95% of the prescribed dose in 95% of the target volume, and the upper dose constraint was 107%. The irradiated small-bowel volumes were kept as low as possible. For every HT plan, a conventional IMRT plan was calculated and compared with regard to dose-volume histogram, conformity index and conformity number, and homogeneity index. Results: Both techniques allowed excellent target volume coverage and sufficient SB sparing. Conformity index and conformity number results for both PTV-A and PTV-B, homogeneity index for PTV-B, and SB sparing for V45, V50, Dmax, and D1% were significantly better with HT. SB sparing was significantly better for conventional IMRT at low doses (V10). Conclusions: Both HT and conventional IMRT provide optimal treatment of cervical cancer patients. The HT technique was significantly favored with regard to target conformity, homogeneity, and SB sparing. Randomized trials are needed to assess the oncological outcome, toxicity, and clinical relevance of these differences.

  14. Form and Function: An Organic Chemistry Module. Teacher's Guide.

    ERIC Educational Resources Information Center

    Jarvis, Bruce; Mazzocchi, Paul; Hearle, Robert

    This teacher's guide is designed to provide science teachers with the necessary guidance and suggestions for teaching organic chemistry. In this book, the diverse field of organic chemistry modules is introduced. The material in this book can be integrated with the other modules in a sequence that helps students to see that chemistry is a unified…

  15. 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.

  16. Co-assembly of Zn(SPh){sub 2} and organic linkers into helical and zig-zag polymer chains

    SciTech Connect

    Liu Yi; Yu Lingmin; Loo, Say Chye Joachim; Blair, Richard G.; Zhang Qichun

    2012-07-15

    Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (EG=ethylene glycol) (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized under solvothermal conditions at 150 Degree-Sign C or room temperature by the co-assembly of Zn(SPh){sub 2} and organic linkers such as 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPyTA) and 1,3-bis(trans-4-pyridylvinyl)benzene (BPyVB). X-ray crystallography study reveals that both polymers 1 and 2 crystallize in space group P2{sub 1}/c of the monoclinic system. The solid-state UV-vis absorption spectra show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. - Graphical abstract: Two novel one-dimensional coordination polymers, single helicate [Zn(SPh){sub 2}(TPyTA)(EG)]{sub n} (1) and zig-zag structure [Zn(SPh){sub 2}(BPyVB)]{sub n} (2), were synthesized. Solid-state UV-vis absorptions show that 1 and 2 have maxium absorption onsets at 400 nm and 420 nm, respectively. TGA analysis indicates that 1 and 2 are stable up to 110 Degree-Sign C and 210 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Two novel one-dimensional coordination polymers have been synthesized. Black-Right-Pointing-Pointer TPyTA results in helical structures in 1 while BPyVB leads to zig-zag chains in 2. Black-Right-Pointing-Pointer Solid-state UV-vis absorption spectra and TGA analysis of the title polymers were studied.

  17. Construction of Covalent Organic Nanotubes by Light-Induced Cross-Linking of Diacetylene-Based Helical Polymers.

    PubMed

    Maeda, Kaho; Hong, Liu; Nishihara, Taishi; Nakanishi, Yusuke; Miyauchi, Yuhei; Kitaura, Ryo; Ousaka, Naoki; Yashima, Eiji; Ito, Hideto; Itami, Kenichiro

    2016-08-31

    Organic nanotubes (ONTs) are tubular nanostructures composed of small molecules or macromolecules that have found various applications including ion sensor/channels, gas absorption, and photovoltaics. While most ONTs are constructed by self-assembly processes based on weak noncovalent interactions, this unique property gives rise to the inherent instability of their tubular structures. Herein, we report a simple "helix-to-tube" strategy to construct robust, covalent ONTs from easily accessible poly(m-phenylene diethynylene)s (poly-PDEs) possessing chiral amide side chains that can adopt a helical conformation through hydrogen-bonding interactions. The helically folded poly-PDEs subsequently undergo light-induced cross-linking at longitudinally aligned 1,3-butadiyne moieties across the whole helix to form covalent tubes (ONTs) both in solution and solid phases. The structures of poly-PDEs and covalent ONTs were characterized by spectroscopic analyses, diffraction analysis, and microscopic analyses. We envisage that this simple yet powerful "helix-to-tube" strategy will generate a range of ONT-based materials by introducing functional moieties into a monomer. PMID:27486790

  18. An In-tether Chiral Center Modulates the Helicity, Cell Permeability, and Target Binding Affinity of a Peptide.

    PubMed

    Hu, Kuan; Geng, Hao; Zhang, Qingzhou; Liu, Qisong; Xie, Mingsheng; Sun, Chengjie; Li, Wenjun; Lin, Huacan; Jiang, Fan; Wang, Tao; Wu, Yun-Dong; Li, Zigang

    2016-07-01

    The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X-ray diffraction analysis suggests that the absolute configuration of the in-tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation. PMID:27167181

  19. Hippocampal-Sparing Whole-Brain Radiotherapy: A 'How-To' Technique Using Helical Tomotherapy and Linear Accelerator-Based Intensity-Modulated Radiotherapy

    SciTech Connect

    Gondi, Vinai; Tolakanahalli, Ranjini; Mehta, Minesh P.; Tewatia, Dinesh; Rowley, Howard; Kuo, John S.; Khuntia, Deepak; Tome, Wolfgang A.

    2010-11-15

    Purpose: Sparing the hippocampus during cranial irradiation poses important technical challenges with respect to contouring and treatment planning. Herein we report our preliminary experience with whole-brain radiotherapy using hippocampal sparing for patients with brain metastases. Methods and Materials: Five anonymous patients previously treated with whole-brain radiotherapy with hippocampal sparing were reviewed. The hippocampus was contoured, and hippocampal avoidance regions were created using a 5-mm volumetric expansion around the hippocampus. Helical tomotherapy and linear accelerator (LINAC)-based intensity-modulated radiotherapy (IMRT) treatment plans were generated for a prescription dose of 30 Gy in 10 fractions. Results: On average, the hippocampal avoidance volume was 3.3 cm{sup 3}, occupying 2.1% of the whole-brain planned target volume. Helical tomotherapy spared the hippocampus, with a median dose of 5.5 Gy and maximum dose of 12.8 Gy. LINAC-based IMRT spared the hippocampus, with a median dose of 7.8 Gy and maximum dose of 15.3 Gy. On a per-fraction basis, mean dose to the hippocampus (normalized to 2-Gy fractions) was reduced by 87% to 0.49 Gy{sub 2} using helical tomotherapy and by 81% to 0.73 Gy{sub 2} using LINAC-based IMRT. Target coverage and homogeneity was acceptable with both IMRT modalities, with differences largely attributed to more rapid dose fall-off with helical tomotherapy. Conclusion: Modern IMRT techniques allow for sparing of the hippocampus with acceptable target coverage and homogeneity. Based on compelling preclinical evidence, a Phase II cooperative group trial has been developed to test the postulated neurocognitive benefit.

  20. Technology for the Organic Chemist: Three Exploratory Modules

    ERIC Educational Resources Information Center

    Esteb, John J.; McNulty, LuAnne M.; Magers, John; Morgan, Paul; Wilson, Anne M.

    2010-01-01

    The ability to use computer-based technology is an essential skill set for students majoring in chemistry. This exercise details the introduction of appropriate uses for this technology in the organic chemistry series. The incorporation of chemically appropriate online resources (module 1), scientific databases (module 2), and the use of a…

  1. Module organization and variance in protein-protein interaction networks

    PubMed Central

    Lin, Chun-Yu; Lee, Tsai-Ling; Chiu, Yi-Yuan; Lin, Yi-Wei; Lo, Yu-Shu; Lin, Chih-Ta; Yang, Jinn-Moon

    2015-01-01

    A module is a group of closely related proteins that act in concert to perform specific biological functions through protein–protein interactions (PPIs) that occur in time and space. However, the underlying module organization and variance remain unclear. In this study, we collected module templates to infer respective module families, including 58,041 homologous modules in 1,678 species, and PPI families using searches of complete genomic database. We then derived PPI evolution scores and interface evolution scores to describe the module elements, including core and ring components. Functions of core components were highly correlated with those of essential genes. In comparison with ring components, core proteins/PPIs were conserved across multiple species. Subsequently, protein/module variance of PPI networks confirmed that core components form dynamic network hubs and play key roles in various biological functions. Based on the analyses of gene essentiality, module variance, and gene co-expression, we summarize the observations of module organization and variance as follows: 1) a module consists of core and ring components; 2) core components perform major biological functions and collaborate with ring components to execute certain functions in some cases; 3) core components are more conserved and essential during organizational changes in different biological states or conditions. PMID:25797237

  2. Information Identification and Organization. Student Study Guide. Module II: Organization and Acquisition of Information and Materials.

    ERIC Educational Resources Information Center

    Bolvin, Boyd M.; West, Sharon

    This second module in a three module program examines the types of materials and services that are available in a community information center or library and the tools or sources for obtaining them. The module covers: ways in which books and other materials are arranged and organized; descriptions of library catalogs and the basic information…

  3. Helicenes as All-in-One Organic Materials for Application in OLEDs: Synthesis and Diverse Applications of Carbo- and Aza[5]helical Diamines.

    PubMed

    Jhulki, Samik; Mishra, Abhaya Kumar; Chow, Tahsin J; Moorthy, Jarugu Narasimha

    2016-06-27

    A set of eight helical diamines were designed and synthesized to demonstrate their relevance as all-in-one materials for multifarious applications in organic light-emitting diodes (OLEDs), that is, as hole-transporting materials (HTMs), EMs, bifunctional hole transporting + emissive materials, and host materials. Azahelical diamines function very well as HTMs. Indeed, with high Tg values (127-214 °C), they are superior alternatives to popular N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB). All the helical diamines exhibit emissive properties when employed in nondoped as well as doped devices, the performance characteristics being superior in the latter. One of the carbohelical diamines (CHTPA) serves the dual function of hole transport as well as emission in simple double-layer devices; the efficiencies observed were better by quite some margin than those of other emissive helicenes reported. The twisting endows helical diamines with significantly high triplet energies such that they also function as host materials for red and green phosphors, that is, [Ir(btp)2 acac] (btp=2-(2'-benzothienyl)pyridine; acac=acetylacetonate) and [Ir(ppy)3 ] (ppy=2-phenylpyridine), respectively. The results of device fabrications demonstrate how helicity/ helical scaffold may be diligently exploited to create molecular systems for maneuvering diverse applications in OLEDs. PMID:27244223

  4. 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...

  5. Submolecular-Scale Imaging of α-Helices and C-Terminal Domains of Tubulins by Frequency Modulation Atomic Force Microscopy in Liquid

    PubMed Central

    Asakawa, Hitoshi; Ikegami, Koji; Setou, Mitsutoshi; Watanabe, Naoki; Tsukada, Masaru; Fukuma, Takeshi

    2011-01-01

    In this study, we directly imaged subnanometer-scale structures of tubulins by performing frequency modulation atomic force microscopy (FM-AFM) in liquid. Individual α-helices at the surface of a tubulin protofilament were imaged as periodic corrugations with a spacing of 0.53 nm, which corresponds to the common pitch of an α-helix backbone (0.54 nm). The identification of individual α-helices allowed us to determine the orientation of the deposited tubulin protofilament. As a result, C-terminal domains of tubulins were identified as protrusions with a height of 0.4 nm from the surface of the tubulin. The imaging mechanism for the observed subnanometer-scale contrasts is discussed in relation to the possible structures of the C-terminal domains. Because the C-terminal domains are chemically modified to regulate the interactions between tubulins and other biomolecules (e.g., motor proteins and microtubule-associated proteins), detailed structural information on individual C-terminal domains is valuable for understanding such regulation mechanisms. The results obtained in this study demonstrate that FM-AFM is capable of visualizing the structural variation of tubulins with subnanometer resolution. This is an important first step toward using FM-AFM to analyze the functions of tubulins. PMID:21889465

  6. A Dual Modulated Homochiral Helical Nanofilament Phase with Local Columnar Ordering Formed by Bent Core Liquid Crystals: Effects of Molecular Chirality.

    PubMed

    Li, Lin; Salamonczyk, Miroslaw; Jákli, Antal; Hegmann, Torsten

    2016-08-01

    Helical nanofilament (HNF) phases form as a result of an intralayer mismatch between top and bottom molecular halves in bent-core liquid crystals (BC-LCs) that is relieved by local saddle-splay geometry. HNFs are immensely attractive for photovoltaic and chiral separation applications and as templates for the chiral spatial assembly of guest molecules. Here, the synthesis and characterization of two unichiral BC-LCs and one racemic mixture with tris-biphenyl-diester cores featuring chiral (R,R) and (S,S) or racemic 2-octyloxy aliphatic side chains are presented. In comparison to the achiral compound with linear side chains forming an intralayer modulated HNF phase (HNFmod ), synchrotron small angle X-ray diffraction indicates that the unichiral derivatives form a dual modulated HNF phase with intra- as well as interlayer modulations (HNFmod2 ) suggesting a columnar local structure of the nanofilaments. Transmission electron microscopy and circular dichroism spectropolarimetry confirm that the unichiral materials exclusively form homochiral HNFs with a twist sense-matching secondary twist. A contact preparation provides the first example of two identical chiral liquid crystal phases only differing in their handedness that do not mix and form an achiral liquid crystal phase with an entirely different structure in the contact zone. PMID:27334846

  7. Fast, simple, and informative patient-specific dose verification method for intensity modulated total marrow irradiation with helical tomotherapy

    PubMed Central

    2014-01-01

    Background Patient-specific dose verification for treatment planning in helical tomotherapy is routinely performed using a homogeneous virtual water cylindrical phantom of 30 cm diameter and 18 cm length (Cheese phantom). Because of this small length, treatment with total marrow irradiation (TMI) requires multiple deliveries of the dose verification procedures to cover a wide range of the target volumes, which significantly prolongs the dose verification process. We propose a fast, simple, and informative patient-specific dose verification method which reduce dose verification time for TMI with helical tomotherapy. Methods We constructed a two-step solid water slab phantom (length 110 cm, height 8 cm, and two-step width of 30 cm and 15 cm), termed the Whole Body Phantom (WB phantom). Three ionization chambers and three EDR-2 films can be inserted to cover extended field TMI treatment delivery. Three TMI treatment plans were conducted with a TomoTherapy HiArt Planning Station and verified using the WB phantom with ion chambers and films. Three regions simulating the head and neck, thorax, and pelvis were covered in a single treatment delivery. The results were compared to those with the cheese phantom supplied by Accuray, Inc. following three treatment deliveries to cover the body from head to pelvis. Results Use of the WB phantom provided point doses or dose distributions from head and neck to femur in a single treatment delivery of TMI. Patient-specific dose verification with the WB phantom was 62% faster than with the cheese phantom. The average pass rate in gamma analysis with the criteria of a 3-mm distance-to-agreement and 3% dose differences was 94% ± 2% for the three TMI treatment plans. The differences in pass rates between the WB and cheese phantoms at the upper thorax to abdomen regions were within 2%. The calculated dose agreed with the measured dose within 3% for all points in all five cases in both the WB and cheese phantoms. Conclusions Our

  8. A Series of Lanthanide Metal-Organic Frameworks with Interesting Adjustable Photoluminescence Constructed by Helical Chains.

    PubMed

    Liu, Ying; Zhang, Yu; Hu, Gong Hao; Zhou, Shuai; Fan, Ruiqing; Yang, Yulin; Xu, Yan

    2015-07-13

    Based on the isonicotinic acid (HIN=pyridine-4-carboxylic acid), seven lanthanide metal-organic frameworks (MOFs) with the formula [Ln(IN)2 L] (Ln=Eu (1), Tb (2), Er (3), Dy (4), Ho (5), Gd (6), La (7), L=OCH2 CH2 OH) have been synthesized by mixing Ln2 O3 with HIN under solvothermal conditions, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy, and fluorescence spectroscopy. Crystal structural analysis shows that compounds 1-6 are isostructural, crystallize in a chiral space group P21 21 21 , whereas compound 7 crystallizes in space group C2/c. Nevertheless, they all consist of new intertwined chains. Simultaneously, on the basis of the above-mentioned compounds, we have realized a rational design strategy to form the doped Ln MOFs [(Eux Tb1-x )(IN)2 L] (x=0.35 (8), x=0.19 (9), x=0.06 (10)) by utilizing Tb(III) as the second "rare-earth metal". Interestingly, the photoluminescence of [(Eux Tb1-x )(IN)2 L] are not only adjustable by the ratios of Eu/Tb, but also temperature or excitation wavelength. PMID:26042654

  9. 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

  10. 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.

  11. High-speed and low-power silicon-organic hybrid modulators for advanced modulation formats

    NASA Astrophysics Data System (ADS)

    Lauermann, M.; Wolf, S.; Palmer, R.; Koeber, S.; Schindler, P. C.; Wahlbrink, T.; Bolten, J.; Giesecke, A. L.; Koenigsmann, M.; Kohler, M.; Malsam, D.; Elder, D. L.; Dalton, L. R.; Leuthold, J.; Freude, W.; Koos, C.

    2015-05-01

    We demonstrate silicon-organic hybrid (SOH) modulators for generating advanced modulation formats at high data rates and with low energy consumption. SOH integration combines slot waveguides on conventional silicon-on-insulator substrates with highly efficient electro-optic materials. With this approach we generate 16QAM signals at symbol rates of 28 GBd and 40 GBd leading to gross data rates (net data rates) of up to 160 Gbit/s (133 Gbit/s) for a single polarization. This is the highest value achieved by a silicon-based modulator up to now. With a maximum symbol rate of 28 GBd, low drive voltages of only 0.6 Vpp are sufficient and result in a record-low energy consumption of only 19 fJ/bit. This is the lowest energy consumption that has so far been reported for a 16QAM modulator at 28 GBd.

  12. Re-irradiation of unresectable recurrent head and neck cancer: using Helical Tomotherapy as image-guided intensity-modulated radiotherapy

    PubMed Central

    Jeong, Songmi; Yoo, Eun Jung; Kim, Ji Yoon; Han, Chi Wha; Kim, Ki Jun

    2013-01-01

    Purpose Re-irradiation (re-RT) is considered a treatment option for inoperable locoregionally recurrent head and neck cancer (HNC) after prior radiotherapy. We evaluated the efficacy and safety of re-RT using Helical Tomotherapy as image-guided intensity-modulated radiotherapy in recurrent HNC. Materials and Methods Patients diagnosed with recurrent HNC and received re-RT were retrospectively reviewed. Primary endpoint was overall survival (OS) and secondary endpoints were locoregional control and toxicities. Results The median follow-up period of total 9 patients was 18.7 months (range, 4.1 to 76 months) and that of 3 alive patients was 49 months (range, 47 to 76 months). Median dose of first radiotherapy and re-RT was 64.8 and 47.5 Gy10. Median cumulative dose of the two courses of radiotherapy was 116.3 Gy10 (range, 91.8 to 128.9 Gy10) while the median interval between the two courses of radiation was 25 months (range, 4 to 137 months). The response rate after re-RT of the evaluated 8 patients was 75% (complete response, 4; partial response, 2). Median locoregional relapse-free survival after re-RT was 11.9 months (range, 3.4 to 75.1 months) and 5 patients eventually presented with treatment failure (in-field failure, 2; in- and out-field failure, 2; out-field failure, 1). Median OS of the 8 patients was 20.3 months (range, 4.1 to 75.1 months). One- and two-year OS rates were 62.5% and 50%, respectively. Grade 3 leucopenia developed in one patient as acute toxicity, and grade 2 osteonecrosis and trismus as chronic toxicity in another patient. Conclusion Re-RT using Helical Tomotherapy for previously irradiated patients with unresectable locoregionally recurrent HNC may be a feasible treatment option with long-term survival and acceptable toxicities. PMID:24501708

  13. Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen.

    PubMed

    Terajima, Masahiko; Taga, Yuki; Chen, Yulong; Cabral, Wayne A; Hou-Fu, Guo; Srisawasdi, Sirivimol; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Kurie, Jonathan M; Marini, Joan C; Yamauchi, Mitsuo

    2016-04-29

    Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1-3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation. PMID:26934917

  14. Dose to organs at risk in the upper abdomen in patients treated with extended fields by helical tomotherapy: a dosimetric and clinical preliminary study

    PubMed Central

    2013-01-01

    Background The aim of this work was to determine the technical feasibility and safety of extended-field radiotherapy (EF), performed by Helical TomoTherapy, in patients with positive pelvic and/or para-aortic nodes. Dosimetric data were collected and acute and sub-acute toxicities of the upper abdominal organs at risk (OAR) were evaluated. Methods Twenty-nine patients suitable for EF irradiation for local disease and/or nodal disease in the pelvic or para-aortic area were treated. The prescription dose was 50.4/54 Gy (1.7-1.8 Gy/fraction) for prophylactic lymph nodes (N-) and 60–70.5 Gy (2–2.35 Gy/fraction) for clinically evident gross disease (N+). Modulation factor (MF), pitch and field width (FW) were chosen to optimize dose distribution and treatment duration. Dose values of PTVs and OAR were analysed. The length of the treatment field, the N + and N- volumes, and treatment duration were reported. To evaluate the safety of treatment, haematological, hepatic, renal and pancreatic functions were assessed before, during and after treatment. The median follow-up time was 17.6 months (range: 6–22 months). Results The treatment was well tolerated and all patients but one completed treatment without interruption. Four of the 29 patients experienced G3 haematological acute toxicity (13.8%), but no patient experienced sub-acute grade G3 toxicity. Ten patients experienced G1 and three G2 acute gastrointestinal toxicity (nausea). No sub-acute gastrointestinal or renal toxicity was observed. Only one (3.7%) patient had a persistent slight increase of pancreatic enzymes and two (7.4%) patients a slight increase of hepatic enzymes six months after radiotherapy (G1 toxicity). Conclusions With our treatment design and dose regimen, we found that EF treatment by TomoTherapy could be safely and effectively delivered with minimal acute and sub-acute toxicities in the upper abdomen area. PMID:24160769

  15. 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.

  16. Inhomogeneous nuclear spin polarization induced by helicity-modulated optical excitation of fluorine-bound electron spins in ZnSe

    NASA Astrophysics Data System (ADS)

    Heisterkamp, F.; Greilich, A.; Zhukov, E. A.; Kirstein, E.; Kazimierczuk, T.; Korenev, V. L.; Yugova, I. A.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.

    2015-12-01

    Optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer is studied by time-resolved Kerr rotation using resonant excitation of donor-bound excitons. Excitation with helicity-modulated laser pulses results in a transverse nuclear spin polarization, which is detected as a change of the Larmor precession frequency of the donor-bound electron spins. The frequency shift in dependence on the transverse magnetic field exhibits a pronounced dispersion-like shape with resonances at the fields of nuclear magnetic resonance of the constituent zinc and selenium isotopes. It is studied as a function of external parameters, particularly of constant and radio frequency external magnetic fields. The width of the resonance and its shape indicate a strong spatial inhomogeneity of the nuclear spin polarization in the vicinity of a fluorine donor. A mechanism of optically induced nuclear spin polarization is suggested based on the concept of resonant nuclear spin cooling driven by the inhomogeneous Knight field of the donor-bound electron.

  17. The Structure and Organization within the Membrane of the Helices Composing the Pore-Forming Domain of Bacillus thuringiensis δ -Endotoxin are Consistent with an ``Umbrella-Like'' Structure of the Pore

    NASA Astrophysics Data System (ADS)

    Gazit, Ehud; La Rocca, Paolo; Sansom, Mark S. P.; Shai, Yechiel

    1998-10-01

    The aim of this study was to elucidate the mechanism of membrane insertion and the structural organization of pores formed by Bacillus thuringiensis δ -endotoxin. We determined the relative affinities for membranes of peptides corresponding to the seven helices that compose the toxin pore-forming domain, their modes of membrane interaction, their structures within membranes, and their orientations relative to the membrane normal. In addition, we used resonance energy transfer measurements of all possible combinatorial pairs of membrane-bound helices to map the network of interactions between helices in their membrane-bound state. The interaction of the helices with the bilayer membrane was also probed by a Monte Carlo simulation protocol to determine lowest-energy orientations. Our results are consistent with a situation in which helices α 4 and α 5 insert into the membrane as a helical hairpin in an antiparallel manner, while the other helices lie on the membrane surface like the ribs of an umbrella (the ``umbrella model''). Our results also support the suggestion that α 7 may serve as a binding sensor to initiate the structural rearrangement of the pore-forming domain.

  18. A 3D chiral metal-organic framework based on left-handed helices containing 3-amino-1 H-1,2,4-triazole ligand

    SciTech Connect

    Liu, Bing; Yang, Tian-Yi; Feng, Hui-Jun; Zhang, Zong-Hui; Xu, Ling

    2015-10-15

    A chiral metal-organic framework, [Cu(atr)(OH)]·0.5H{sub 2}O·0.5en (1) (Hatr=3-amino-1 H-1,2,4-triazole, en=ethylenediamine), was constructed via diffusion reaction of the achiral Hatr ligand and CuSO{sub 4} as starting materials. Compound 1 crystallizes in the chiral space group P3{sub 2}21 and features a porous metal-organic framework with 44.1% solvent-accessible volume fabricated by left-handed helices with a pitch height of l{sub p}=10.442 Å. Six helices gather around in a cycle forming a large honeycomb channel with a 6.58 Å inner diameter. Cu(II) center and atr{sup ‒} ligand regarded as 3-connected nodes, compound 1 can be simplified to a 3-c uninodal (4.12{sup 2}) (qtz-h) topological network. A gradual decreasing in the magnetic moment depending on temperature decreasing indicates an antiferromagnetic interaction in 1. The powder XRD confirms the bulk sample is a single crystal pure phase, and the thermogravimetric analysis shows the thermal stability of 1 is up to ca. 240 °C. - Highlights: • The present 3D chiral MOF is built from achiral Hatr ligand. • Six left-handed helices gather into a honeycomb channel in chiral sp P3{sub 2}21. • Compound 1 shows a 3-c uninodal (4.12{sup 2}) or qtz-h topological network. • Compound 1 indicates an antiferromagnetic interaction.

  19. Dosimetric study and in-vivo dose verification for conformal avoidance treatment of anal adenocarcinoma using helical tomotherapy

    SciTech Connect

    Han Chunhui . E-mail: chan@coh.org; Chen Yijen; Liu An; Schultheiss, Timothy E.; Wong, Jeffrey Y.C.

    2007-04-01

    This study evaluated the efficacy of using helical tomotherapy for conformal avoidance treatment of anal adenocarcinoma. We retrospectively generated step-and-shoot intensity-modulated radiotherapy (sIMRT) plans and helical tomotherapy plans for two anal cancer patients, one male and one female, who were treated by the sIMRT technique. Dose parameters for the planning target volume (PTV) and the organs-at-risk (OARs) were compared between the sIMRT and the helical tomotherapy plans. The helical tomotherapy plans showed better dose homogeneity in the PTV, better dose conformity around the PTV, and, therefore, better sparing of nearby OARs compared with the sIMRT plans. In-vivo skin dose measurements were performed during conformal avoidance helical tomotherapy treatment of an anal cancer patient to verify adequate delivery of skin dose and sparing of OARs.

  20. Ligand Symmetry Modulation for Designing Mixed-Ligand Metal-Organic Frameworks: Gas Sorption and Luminescence Sensing Properties.

    PubMed

    Chen, Di-Ming; Tian, Jia-Yue; Liu, Chun-Sen

    2016-09-01

    Herein, we report the synthesis of a new mixed-linker Zn(II)-based metal-organic framework (MOF), {[Zn2(atz)2(bpydb)](DMA)8}n (1) (atz = deprotonated 3-amino-1,2,4-triazole, bpydb = deprotonated 4,4'-(4,4'-bipyridine-2,6-diyl) dibenzoic acid, DMA = N,N-dimethylacetamide), through symmetry modulation of a triazole ligand. The desymmetrized triazole linkers not only bond to the Zn(II) ions to result in a new helical Zn-triazolate chain building unit but also lead to the formation of a highly porous framework (N2 uptake: 617 cm(3)/g; BET surface area: 2393 m(2)/g) with 1D helical channels. The adsorption properties of desolved 1 were investigated by H2, C2H2, CO2, and CH4 sorption experiments, which showed that 1 exhibited high uptake capacity for H2 at 77 K and C2H2 around room temperature. More importantly, the high C2H2 uptake capacity but low binding energy makes this MOF a promising candidate for effective C2H2 capture from C2H2/CO2 and C2H2/CH4 mixed gases with low regenerative energy cost. In addition, 1 shows potential application for the luminescence sensing of small aromatic molecules picric acid (PA) and p-xylene (PX). PMID:27494087

  1. Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

    SciTech Connect

    Ciaccio, G. Spizzo, G.; Schmitz, O. Frerichs, H.; Abdullaev, S. S.; Evans, T. E.; White, R. B.

    2015-10-15

    The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted by simulations with the Hamiltonian guiding center code ORBIT. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for these effects. An analytical model for the plasma potential is implemented in the code ORBIT, and analyses of ion and electron radial diffusion show that both ion- and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggest that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

  2. Measurement of organic/polymer material by phase modulation ellipsometry

    NASA Astrophysics Data System (ADS)

    Ji, Yong; Teboul, Eric; Kramer, Alan R.

    2004-06-01

    Due to they can be tailored to provide a wide range of physical properties and their easiness of processing and fabrication, polymeric materials have found widespread use in the manufacture of microwave, electronics, photonics and bio-tech systems. This paper presents the basic principle of phase modulation spectroscopic ellipsometer (PMSE) and its advantages over other ellipsometry in measuring polymer film. Used for thin film measurements ultra-thin dielectric, meal film and organic film, the PMSE technique is now used over a wide spectral range from the vacuum ultraviolet to the mid infrared. Film thickness ranging from Angstrom up to 50um can be measured by PMSE. Applications of PMSE on measurement and characterization of polymer/organic material are given in the paper.

  3. A two-fold interpenetrating 3D metal-organic framework material constructed from helical chains linked via 4,4'-H{sub 2}bpz fragments

    SciTech Connect

    Xie Yiming; Zhao Zhenguo; Wu Xiaoyuan; Zhang Qisheng; Chen Lijuan; Wang Fei; Chen Shanci; Lu Canzhong

    2008-12-15

    A 3-connected dia-f-type metal-organic framework compound {l_brace}[Ag(L){sub 3/2}H{sub 2}PO{sub 4}]{r_brace}{sub n} (1) has been synthesized by self-assembly of 4,4'-H{sub 2}bpz (L=4,4'-H{sub 2}bpz=3,3',5,5'-tetramethyl-4,4'-bipyrazole) and Ag{sub 4}P{sub 2}O{sub 7} under hydrothermal conditions. It crystallizes in the tetragonal space group I4{sub 1}/acd with a=21.406(4) A, b=21.406(4) A, c=36.298(8) A, Z=32. X-ray single-crystal diffraction reveals that 1 has a three-dimensional framework with an unprecedented alternate left- and right-handed helices structure, featuring a non-uniform two-fold interpenetrated (4.14{sup 2}) net. Photoluminescent investigation reveals that the title compound displays interesting emissions in a wide region, which shows that the title compound may be a good potential candidate as a photoelectric material. - Graphical abstract: A 3-connected dia-f-type metal-organic framework compound [Ag(4,4'-bpz){sub 3/2}H{sub 2}PO{sub 4}] shows unprecedented alternating left- and right-handed helices structure, featuring a non-uniform two-fold interpenetrated (4.14{sup 2}) net.

  4. Metal-Organic Nanotube with Helical and Propeller-Chiral Motifs Composed of a C10-Symmetric Double-Decker Nanoring.

    PubMed

    Yamagishi, Hiroshi; Fukino, Takahiro; Hashizume, Daisuke; Mori, Tadashi; Inoue, Yoshihisa; Hikima, Takaaki; Takata, Masaki; Aida, Takuzo

    2015-06-24

    Coassembly of an achiral ferrocene-cored tetratopic pyridyl ligand (FcL) with AgBF4 in CH2Cl2/MeCN (7:3 v/v) containing chiral Bu4N(+) (+)- or (-)-menthylsulfate (MS*(-)) results in the formation of an "optically active" metal-organic nanotube (FcNT) composed of a C10-symmetric double-decker nanoring featuring 10 FcL units and 20 Ag(+) ions. The circular dichroism spectrum of FcNT along with its 2D X-ray diffraction (2D XRD) pattern indicates that the constituent metal-organic nanorings in FcNT stack one-handed helically on top of each other. A crystal structure of the dimeric double-decker model complex (Ag2(FcL')2) from a ditopic ferrocene ligand (FcL') and AgBF4 allowed for confirming the binding of MS*(-) onto the Ag(+) center of the complex. The results of detailed spectroscopic studies indicate that in its double-decker aromatic arrays, FcNT possibly possesses propeller-chiral twists in addition to the helically chiral structure, where the former is considerably more dynamic than the latter. Notably, both chiral structural motifs responded nonlinearly to an enantiomeric excess of MS*(-) (majority rule) though with no stereochemical influence on one another. PMID:26053066

  5. A 3D chiral metal-organic framework based on left-handed helices containing 3-amino-1 H-1,2,4-triazole ligand

    NASA Astrophysics Data System (ADS)

    Liu, Bing; Yang, Tian-Yi; Feng, Hui-Jun; Zhang, Zong-Hui; Xu, Ling

    2015-10-01

    A chiral metal-organic framework, [Cu(atr)(OH)]·0.5H2O·0.5en (1) (Hatr=3-amino-1 H-1,2,4-triazole, en=ethylenediamine), was constructed via diffusion reaction of the achiral Hatr ligand and CuSO4 as starting materials. Compound 1 crystallizes in the chiral space group P3221 and features a porous metal-organic framework with 44.1% solvent-accessible volume fabricated by left-handed helices with a pitch height of lp=10.442 Å. Six helices gather around in a cycle forming a large honeycomb channel with a 6.58 Å inner diameter. Cu(II) center and atr‒ ligand regarded as 3-connected nodes, compound 1 can be simplified to a 3-c uninodal {4.122} (qtz-h) topological network. A gradual decreasing in the magnetic moment depending on temperature decreasing indicates an antiferromagnetic interaction in 1. The powder XRD confirms the bulk sample is a single crystal pure phase, and the thermogravimetric analysis shows the thermal stability of 1 is up to ca. 240 °C.

  6. Laminar circuit organization and response modulation in mouse visual cortex

    PubMed Central

    Olivas, Nicholas D.; Quintanar-Zilinskas, Victor; Nenadic, Zoran; Xu, Xiangmin

    2012-01-01

    The mouse has become an increasingly important animal model for visual system studies, but few studies have investigated local functional circuit organization of mouse visual cortex. Here we used our newly developed mapping technique combining laser scanning photostimulation (LSPS) with fast voltage-sensitive dye (VSD) imaging to examine the spatial organization and temporal dynamics of laminar circuit responses in living slice preparations of mouse primary visual cortex (V1). During experiments, LSPS using caged glutamate provided spatially restricted neuronal activation in a specific cortical layer, and evoked responses from the stimulated layer to its functionally connected regions were detected by VSD imaging. In this study, we first provided a detailed analysis of spatiotemporal activation patterns at specific V1 laminar locations and measured local circuit connectivity. Then we examined the role of cortical inhibition in the propagation of evoked cortical responses by comparing circuit activity patterns in control and in the presence of GABAa receptor antagonists. We found that GABAergic inhibition was critical in restricting layer-specific excitatory activity spread and maintaining topographical projections. In addition, we investigated how AMPA and NMDA receptors influenced cortical responses and found that blocking AMPA receptors abolished interlaminar functional projections, and the NMDA receptor activity was important in controlling visual cortical circuit excitability and modulating activity propagation. The NMDA receptor antagonist reduced neuronal population activity in time-dependent and laminar-specific manners. Finally, we used the quantitative information derived from the mapping experiments and presented computational modeling analysis of V1 circuit organization. Taken together, the present study has provided important new information about mouse V1 circuit organization and response modulation. PMID:23060751

  7. Band gap modulation of functionalized metal-organic frameworks.

    PubMed

    Musho, Terence; Li, Jiangtan; Wu, Nianqiang

    2014-11-21

    Metal-organic frameworks (MOFs) have been envisioned as alternatives to planar metallic catalysts for solar-to-fuel conversion. This is a direct result of their porous structure and the ability to tailor their optical absorption properties. This study investigates the band gap modulation of Zr-UiO-66 MOFs from both the computational and experimental points of view for three linker designs that include benzenedicarboxylate (BDC), BDC-NO2, and BDC-NH2. Emphasis in this study was aimed at understanding the influence of the bonding between the aromatic ring and the functional group. A ground state density functional theory (DFT) calculation was carried out to investigate the projected density of states and the origins of the modulation. A time-dependent density functional theory (TDDFT) calculation of the hydrogen terminated linkers confirmed the modulation and accounted for the electron charge transfer providing comparable optical band gap predictions to experimental results. Computational results confirmed the hybridization of the carbon-nitrogen bond in conjunction with the donor state resulting from the NH2 functionalization. The NO2 functionalization resulted in an acceptor configuration with marginal modification to the valence band maximum. The largest modulation was BDC-NH2 with a band gap of 2.75 eV, followed by BDC-NO2 with a band gap of 2.93 eV and BDC with a band gap of 3.76 eV. The electron effective mass was predicted from the band structure to be 8.9 me for all MOF designs. PMID:25269595

  8. Determination of W boson helicity fractions in top quark decays in p anti-p collisions at CDF Run II and production of endcap modules for the ATLAS Silicon Tracker

    SciTech Connect

    Moed, Shulamit; /Geneva U.

    2007-01-01

    The thesis presented here includes two parts. The first part discusses the production of endcap modules for the ATLAS SemiConductor Tracker at the University of Geneva. The ATLAS experiment is one of the two multi-purpose experiments being built at the LHC at CERN. The University of Geneva invested extensive efforts to create an excellent and efficient module production site, in which 655 endcap outer modules were constructed. The complexity and extreme requirements for 10 years of LHC operation with a high resolution, high efficiency, low noise tracking system resulted in an extremely careful, time consuming production and quality assurance of every single module. At design luminosity about 1000 particles will pass through the tracking system each 25 ns. In addition to requiring fast tracking techniques, the high particle flux causes significant radiation damage. Therefore, modules have to be constructed within tight and accurate mechanical and electrical specification. A description of the ATLAS experiment and the ATLAS Semiconductor tracker is presented, followed by a detailed overview of the module production at the University of Geneva. My personal contribution to the endcap module production at the University of Geneva was taking part, together with other physicists, in selecting components to be assembled to a module, including hybrid reception tests, measuring the I-V curve of the sensors and the modules at different stages of the production, thermal cycling the modules and performing electrical readout tests as an initial quality assurance of the modules before they were shipped to CERN. An elaborated description of all of these activities is given in this thesis. At the beginning of the production period the author developed a statistics package which enabled us to monitor the rate and quality of the module production. This package was then used widely by the ATLAS SCT institutes that built endcap modules of any type, and kept being improved and updated

  9. Formation of functional super-helical assemblies by constrained single heptad repeat

    PubMed Central

    Mondal, Sudipta; Adler-Abramovich, Lihi; Lampel, Ayala; Bram, Yaron; Lipstman, Sophia; Gazit, Ehud

    2015-01-01

    Inspired by the key role of super-helical motifs in molecular self-organization, several tandem heptad repeat peptides were used as building blocks to form well-ordered supramolecular nano-assemblies. However, the need for stable helical structures limits the length of the smallest described units to three heptad repeats. Here we describe the first-ever self-assembling single heptad repeat module, based on the ability of the non-coded α-aminoisobutyric acid to stabilize very short peptides in helical conformation. A conformationally constrained peptide comprised of aromatic, but not aliphatic, residues, at the first and fourth positions formed helical fibrillar assemblies. Single crystal X-ray analysis of the peptide demonstrates super-helical packing in which phenylalanine residues formed an ‘aromatic zipper' arrangement at the molecular interface. The modification of the minimal building block with positively charged residues results in tight DNA binding ascribed to the combined factors of helicity, hydrophobicity and charge. The design of these peptides defines a new direction for assembly of super-helical nanostructures by minimal molecular elements. PMID:26468599

  10. Organic anion transporting polypeptide 1B transporters modulate hydroxyurea pharmacokinetics

    PubMed Central

    Lancaster, Cynthia S.; Finkelstein, David; Ware, Russell E.; Sparreboom, Alex

    2013-01-01

    Hydroxyurea is currently the only FDA-approved drug that ameliorates the pathophysiology of sickle cell anemia. Unfortunately, substantial interpatient variability in the pharmacokinetics (PK) of hydroxyurea may result in variation of the drug's efficacy. However, little is known about mechanisms that modulate hydroxyurea PK. Recent in vitro studies identifying hydroxyurea as a substrate for organic anion transporting polypeptide (OATP1B) transporters prompted the current investigation assessing the role of OATP1B transporters in modulating hydroxyurea PK. Using wild-type and Oatp1b knockout (Oatp1b−/−) mice, hydroxyurea PK was analyzed in vivo by measuring [14C]hydroxyurea distribution in plasma, kidney, liver, urine, or the exhaled 14CO2 metabolite. Plasma levels were significantly reduced by 20% in Oatp1b−/− mice compared with wild-type (area under the curve of 38.64 or 48.45 μg·h−1·ml−1, respectively) after oral administration, whereas no difference was observed between groups following intravenous administration. Accumulation in the kidney was significantly decreased by twofold in Oatp1b−/− mice (356.9 vs. 748.1 pmol/g), which correlated with a significant decrease in urinary excretion. Hydroxyurea accumulation in the liver was also decreased (136.6 vs. 107.3 pmol/g in wild-type or Oatp1b−/− mice, respectively) correlating with a decrease in exhaled 14CO2. These findings illustrate that deficiency of Oatp1b transporters alters the absorption, distribution, and elimination of hydroxyurea thus providing the first in vivo evidence that cell membrane transporters may play a significant role in modulating hydroxyurea PK. Future studies to investigate other transporters and their role in hydroxyurea disposition are warranted for understanding the sources of variation in hydroxyurea's PK. PMID:23986199

  11. Self-organized plasmonic metasurfaces for all-optical modulation

    NASA Astrophysics Data System (ADS)

    Della Valle, G.; Polli, D.; Biagioni, P.; Martella, C.; Giordano, M. C.; Finazzi, M.; Longhi, S.; Duò, L.; Cerullo, G.; Buatier de Mongeot, F.

    2015-06-01

    We experimentally demonstrate a self-organized metasurface with a polarization dependent transmittance that can be dynamically controlled by optical means. The configuration consists of tightly packed plasmonic nanowires with a large dispersion of width and height produced by the defocused ion-beam sputtering of a thin gold film supported on a silica glass. Our results are quantitatively interpreted according to a theoretical model based on the thermomodulational nonlinearity of gold and a finite-element numerical analysis of the absorption and scattering cross-sections of the nanowires. We found that the polarization sensitivity of the metasurface can be strongly enhanced by pumping with ultrashort laser pulses, leading to potential applications in ultrafast all-optical modulation and switching of light.

  12. A series connection architecture for large-area organic photovoltaic modules with a 7.5% module efficiency

    NASA Astrophysics Data System (ADS)

    Hong, Soonil; Kang, Hongkyu; Kim, Geunjin; Lee, Seongyu; Kim, Seok; Lee, Jong-Hoon; Lee, Jinho; Yi, Minjin; Kim, Junghwan; Back, Hyungcheol; Kim, Jae-Ryoung; Lee, Kwanghee

    2016-01-01

    The fabrication of organic photovoltaic modules via printing techniques has been the greatest challenge for their commercial manufacture. Current module architecture, which is based on a monolithic geometry consisting of serially interconnecting stripe-patterned subcells with finite widths, requires highly sophisticated patterning processes that significantly increase the complexity of printing production lines and cause serious reductions in module efficiency due to so-called aperture loss in series connection regions. Herein we demonstrate an innovative module structure that can simultaneously reduce both patterning processes and aperture loss. By using a charge recombination feature that occurs at contacts between electron- and hole-transport layers, we devise a series connection method that facilitates module fabrication without patterning the charge transport layers. With the successive deposition of component layers using slot-die and doctor-blade printing techniques, we achieve a high module efficiency reaching 7.5% with area of 4.15 cm2.

  13. A series connection architecture for large-area organic photovoltaic modules with a 7.5% module efficiency.

    PubMed

    Hong, Soonil; Kang, Hongkyu; Kim, Geunjin; Lee, Seongyu; Kim, Seok; Lee, Jong-Hoon; Lee, Jinho; Yi, Minjin; Kim, Junghwan; Back, Hyungcheol; Kim, Jae-Ryoung; Lee, Kwanghee

    2016-01-01

    The fabrication of organic photovoltaic modules via printing techniques has been the greatest challenge for their commercial manufacture. Current module architecture, which is based on a monolithic geometry consisting of serially interconnecting stripe-patterned subcells with finite widths, requires highly sophisticated patterning processes that significantly increase the complexity of printing production lines and cause serious reductions in module efficiency due to so-called aperture loss in series connection regions. Herein we demonstrate an innovative module structure that can simultaneously reduce both patterning processes and aperture loss. By using a charge recombination feature that occurs at contacts between electron- and hole-transport layers, we devise a series connection method that facilitates module fabrication without patterning the charge transport layers. With the successive deposition of component layers using slot-die and doctor-blade printing techniques, we achieve a high module efficiency reaching 7.5% with area of 4.15 cm(2). PMID:26728507

  14. Reducing radiation dose to selected organs by selecting the tube start angle in MDCT helical scans: A Monte Carlo based study

    SciTech Connect

    Zhang Di; Zankl, Maria; DeMarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; McNitt-Gray, Michael F.

    2009-12-15

    Purpose: Previous work has demonstrated that there are significant dose variations with a sinusoidal pattern on the peripheral of a CTDI 32 cm phantom or on the surface of an anthropomorphic phantom when helical CT scanning is performed, resulting in the creation of ''hot'' spots or ''cold'' spots. The purpose of this work was to perform preliminary investigations into the feasibility of exploiting these variations to reduce dose to selected radiosensitive organs solely by varying the tube start angle in CT scans. Methods: Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, and eye lenses) resulting from MDCT scans were estimated using Monte Carlo simulation methods on voxelized patient models, including GSF's Baby, Child, and Irene. Dose to fetus was also estimated using four pregnant female models based on CT images of the pregnant patients. Whole-body scans were simulated using 120 kVp, 300 mAs, both 28.8 and 40 mm nominal collimations, and pitch values of 1.5, 1.0, and 0.75 under a wide range of start angles (0 deg. - 340 deg. in 20 deg. increments). The relationship between tube start angle and organ dose was examined for each organ, and the potential dose reduction was calculated. Results: Some organs exhibit a strong dose variation, depending on the tube start angle. For small peripheral organs (e.g., the eye lenses of the Baby phantom at pitch 1.5 with 40 mm collimation), the minimum dose can be 41% lower than the maximum dose, depending on the tube start angle. In general, larger dose reductions occur for smaller peripheral organs in smaller patients when wider collimation is used. Pitch 1.5 and pitch 0.75 have different mechanisms of dose reduction. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x-ray tube is posterior to the patient when it passes the longitudinal location of the organ. For pitch 0.75 scans, the dose is lowest when the tube start angle is such that the x

  15. Reducing radiation dose to selected organs by selecting the tube start angle in MDCT helical scans: A Monte Carlo based study

    PubMed Central

    Zhang, Di; Zankl, Maria; DeMarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; McNitt-Gray, Michael F.

    2009-01-01

    Purpose: Previous work has demonstrated that there are significant dose variations with a sinusoidal pattern on the peripheral of a CTDI 32 cm phantom or on the surface of an anthropomorphic phantom when helical CT scanning is performed, resulting in the creation of “hot” spots or “cold” spots. The purpose of this work was to perform preliminary investigations into the feasibility of exploiting these variations to reduce dose to selected radiosensitive organs solely by varying the tube start angle in CT scans. Methods: Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, and eye lenses) resulting from MDCT scans were estimated using Monte Carlo simulation methods on voxelized patient models, including GSF’s Baby, Child, and Irene. Dose to fetus was also estimated using four pregnant female models based on CT images of the pregnant patients. Whole-body scans were simulated using 120 kVp, 300 mAs, both 28.8 and 40 mm nominal collimations, and pitch values of 1.5, 1.0, and 0.75 under a wide range of start angles (0°–340° in 20° increments). The relationship between tube start angle and organ dose was examined for each organ, and the potential dose reduction was calculated. Results: Some organs exhibit a strong dose variation, depending on the tube start angle. For small peripheral organs (e.g., the eye lenses of the Baby phantom at pitch 1.5 with 40 mm collimation), the minimum dose can be 41% lower than the maximum dose, depending on the tube start angle. In general, larger dose reductions occur for smaller peripheral organs in smaller patients when wider collimation is used. Pitch 1.5 and pitch 0.75 have different mechanisms of dose reduction. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x-ray tube is posterior to the patient when it passes the longitudinal location of the organ. For pitch 0.75 scans, the dose is lowest when the tube start angle is such that the x

  16. SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator

    SciTech Connect

    Anderson, J; Bernard, D; Liao, Y; Templeton, A; Turian, J; Chu, J

    2014-06-01

    Purpose: Craniospinal irradiation (CSI) of systemic disease requires a high level of beam intensity modulation to reduce dose to bone marrow and other critical structures. Current helical delivery machines can take 30 minutes or more of beam-on time to complete these treatments. This pilot study aims to test the feasibility of performing helical treatments with a conventional linear accelerator using longitudinal couch travel during multiple gantry revolutions. Methods: The VMAT optimization package of the Eclipse 10.0 treatment planning system was used to optimize pseudo-helical CSI plans of 5 clinical patient scans. Each gantry revolution was divided into three 120° arcs with each isocenter shifted longitudinally. Treatments requiring more than the maximum 10 arcs used multiple plans with each plan after the first being optimized including the dose of the others (Figure 1). The beam pitch was varied between 0.2 and 0.9 (couch speed 5- 20cm/revolution and field width of 22cm) and dose-volume histograms of critical organs were compared to tomotherapy plans. Results: Viable pseudo-helical plans were achieved using Eclipse. Decreasing the pitch from 0.9 to 0.2 lowered the maximum lens dose by 40%, the mean bone marrow dose by 2.1% and the maximum esophagus dose by 17.5%. (Figure 2). Linac-based helical plans showed dose results comparable to tomotherapy delivery for both target coverage and critical organ sparing, with the D50 of bone marrow and esophagus respectively 12% and 31% lower in the helical linear accelerator plan (Figure 3). Total mean beam-on time for the linear accelerator plan was 8.3 minutes, 54% faster than the tomotherapy average for the same plans. Conclusions: This pilot study has demonstrated the feasibility of planning pseudo-helical treatments for CSI targets using a conventional linac and dynamic couch movement, and supports the ongoing development of true helical optimization and delivery.

  17. Carrier modulation layer-enhanced organic light-emitting diodes.

    PubMed

    Jou, Jwo-Huei; Kumar, Sudhir; Singh, Meenu; Chen, Yi-Hong; Chen, Chung-Chia; Lee, Meng-Ting

    2015-01-01

    Organic light-emitting diode (OLED)-based display products have already emerged in the market and their efficiencies and lifetimes are sound at the comparatively low required luminance. To realize OLED for lighting application sooner, higher light quality and better power efficiency at elevated luminance are still demanded. This review reveals the advantages of incorporating a nano-scale carrier modulation layer (CML), also known as a spacer, carrier-regulating layer, or interlayer, among other terms, to tune the chromaticity and color temperature as well as to markedly improve the device efficiency and color rendering index (CRI) for numerous OLED devices. The functions of the CML can be enhanced as multiple layers and blend structures are employed. At proper thickness, the employment of CML enables the device to balance the distribution of carriers in the two emissive zones and achieve high device efficiencies and long operational lifetime while maintaining very high CRI. Moreover, we have also reviewed the effect of using CML on the most significant characteristics of OLEDs, namely: efficiency, luminance, life-time, CRI, SRI, chromaticity, and the color temperature, and see how the thickness tuning and selection of proper CML are crucial to effectively control the OLED device performance. PMID:26193252

  18. Land Application of Wastes: An Educational Program. Organic Matter - Module 17, Objectives, and Script.

    ERIC Educational Resources Information Center

    Clarkson, W. W.; And Others

    This module sketches out the impact of sewage organic matter on soils. For convenience, that organic matter is separated into the readily decomposable compounds and the more resistant material (volatile suspended solids, refractory organics, and sludges). The fates of those organics are reviewed along with loading rates and recommended soil…

  19. Flow-modulated targeted signal enhancement for volatile organic compounds.

    PubMed

    Hayward, Taylor; Gras, Ronda; Luong, Jim

    2016-06-01

    Comprehensive two-dimensional gas chromatography is a technique that is becoming more widespread within the analytical community, especially in the separation of complex mixtures. Modulation in comprehensive two-dimensional gas chromatography can be achieved by manipulating temperature or flow and offers many advantages such as increased separation power, but one underutilized advantage is increased detectability due to the reduction of peak width from the use of a modulator. A flow modulator was used to selectively target analytes for increased detectability with a standard flame ionization detector operated at 100 Hz, without the need for cryogens or advanced modulation software. By the collection of the entire peak volume followed by peak transfer rather than further separation, an increase of 12 times in peak height and detectability was realized for the analytes tested using an internal loop modulator configuration. An external loop flow modulator configuration allowed for more volatile analytes (with k < 5), and demonstrated an analyte detectability enhancement factor of at least 6. The collection loop size can be readily increased with an external loop configuration to accommodate for these naturally broader peaks. This novel flow modulated targeted signal enhancement approach was applied to industrially significant analyses like the analysis of methanol in a hydrocarbon streams. Methanol was detected at 7 ppb with a conventional flame ionization detector and without the need for pre-concentration. PMID:27120133

  20. Poly(isophthalic acid)(ethylene oxide) as a Macromolecular Modulator for Metal-Organic Polyhedra.

    PubMed

    Chen, Teng-Hao; Wang, Le; Trueblood, Jonathan V; Grassian, Vicki H; Cohen, Seth M

    2016-08-01

    A new strategy was developed by using a polymer ligand, poly(isophthalic acid)(ethylene oxide), to modulate the growth of metal-organic polyhedra (MOP) crystals. This macromolecular modulator can effectively control the crystal habit of several different Cu24L24 (L = isophthalic acid derivatives) MOPs. The polymer also directed the formation of MOP structures under reaction conditions that only produce metal-organic frameworks in the absence of modulator. Moreover, the polymer also enabled the deposition of MOP crystals on glass surfaces. This macromolecular modulator strategy provides an innovative approach to control the morphology and assembly of MOP particles. PMID:27400759

  1. Assessment of Organ Motion in Postoperative Endometrial and Cervical Cancer Patients Treated With Intensity-Modulated Radiation Therapy

    SciTech Connect

    Harris, Eleanor E.R.; Latifi, Kujtim; Rusthoven, Chad; Javedan, Ken; Forster, Kenneth

    2011-11-15

    Purpose: Intensity-modulated radiation therapy (IMRT) may be useful to reduce toxicity in gynecologic cancer patients requiring postoperative pelvic irradiation. This study was undertaken to quantify vaginal wall organ motion during the course of postoperative pelvic irradiation using pelvic IMRT. Methods and Materials: Twenty-two consecutive patients treated with postoperative pelvic IMRT on helical tomotherapy had fiducial markers placed at the vaginal apex prior to simulation then daily megavoltage computed tomography (CT) scans for positioning. The daily positions of the fiducials were registered and measured in reference to the initial CT scan to quantify the degree of vaginal wall organ motion during the entire course of therapy. Results: The total motion of the fiducials center of mass (COM) was a median of 5.8 mm (range, 0.6-20.2 mm), and 95% of all COM positions fell within 15.7 mm of their original position. Directional margins of 3.1 mm along the right-left axis, 9.5 mm along the superoinferior axis, and of 12.1 mm along the anteroposterior axis encompassed the vaginal fiducials in 95% of treatments. Mean organ deformation for all patients was 3.9 mm, (range, 0-27.5 mm; standard deviation, 3.1 mm), with significant distortions of greater than 10 mm in 17% of secondary image sets. Conclusions: These data suggest a planning target volume margin of 16 mm will account for maximal organ motion in the majority of gynecologic patients undergoing postoperative pelvic IMRT, and it may be possible to incorporate directional motion into the planning target volume margin.

  2. 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.

  3. Comparison of the dosimetries of 3-dimensions Radiotherapy (3D-RT) with linear accelerator and intensity modulated radiotherapy (IMRT) with helical tomotherapy in children irradiated for neuroblastoma

    PubMed Central

    2012-01-01

    Background Intensity modulated radiotherapy is an efficient radiotherapy technique to increase dose in target volumes and decrease irradiation dose in organs at risk. This last objective is mainly relevant in children. However, previous results suggested that IMRT could increase low dose, factor of risk for secondary radiation induced cancer. This study was performed to compare dose distributions with 3D-radiotherapy (3D-RT) and IMRT with tomotherapy (HT) in children with neuroblastoma. Seven children with neuroblastoma were irradiated. Treatment plans were calculated for 3D-RT, and for HT. For the volume of interest, the PTV-V95% and conformity index were calculated. Dose constraints of all the organs at risk and integral dose were compared. Results The conformity index was statistically better for HT than for 3D-RT. PTV-V95% constraint was reached in 6 cases with HT compared to 2 cases with 3D-RT. For the ipsilateral kidney of the tumor, the V12 Gy constraint was reached for 3 patients with both methods. The values were lower with HT than with 3D-RT in two cases and higher in one case. The threshold was not reached for one patient with either technique, but the value was lower with HT than with 3D-RT. For the contralateral kidney of the tumors, the V12 Gy constraint was reached for all patients with both methods. The values were lower with HT than with 3D-RT in 5 of 7 children, equal in one patient and higher in one patient. The organ-at-risk volumes receiving low doses were significantly lower with 3D-RT but larger for the highest doses, compared to those irradiated with HT. The integral doses were not different. Conclusions IMRT with HT allows a better conformity treatment, a more frequently acceptable PTV-V95% than 3D-RT and, concomitantly, a better shielding of the kidneys. The integral doses are comparable between both techniques but consideration of differences in dose distribution between the two techniques, for the organs at risk, has to be taken in

  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. Highly efficient terahertz wave modulators by photo-excitation of organics/silicon bilayers

    SciTech Connect

    Yoo, Hyung Keun; Kang, Chul; Hwang, In-Wook; Yoon, Youngwoon; Lee, Kiejin; Kee, Chul-Sik; Lee, Joong Wook

    2014-07-07

    Using hybrid bilayer systems comprising a molecular organic semiconductor and silicon, we achieve optically controllable active terahertz (THz) modulators that exhibit extremely high modulation efficiencies. A modulation efficiency of 98% is achieved from thermally annealed C{sub 60}/silicon bilayers, due to the rapid photo-induced electron transfer from the excited states of the silicon onto the C{sub 60} layer. Furthermore, we demonstrate the broadband modulation of THz waves. The cut-off condition of the system that is determined by the formation of efficient charge separation by the photo-excitation is highly variable, changing the system from insulating to metallic. The phenomenon enables an extremely high modulation bandwidth and rates of electromagnetic waves of interest. The realization of near-perfect modulation efficiency in THz frequencies opens up the possibilities of utilizing active modulators for THz spectroscopy and communications.

  6. 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.

  7. High-efficiency THz modulator based on phthalocyanine-compound organic films

    SciTech Connect

    He, Ting; Zhang, Bo E-mail: sjl-phy@cnu.edu.cn; Shen, Jingling E-mail: sjl-phy@cnu.edu.cn; Zang, Mengdi; Chen, Tianji; Hu, Yufeng; Hou, Yanbing

    2015-02-02

    We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl{sub 2}Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface.

  8. High-efficiency THz modulator based on phthalocyanine-compound organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Shen, Jingling; Zang, Mengdi; Chen, Tianji; Hu, Yufeng; Hou, Yanbing

    2015-02-01

    We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl2Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface.

  9. 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

  10. 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.

  11. COMODO: an adaptive coclustering strategy to identify conserved coexpression modules between organisms.

    PubMed

    Zarrineh, Peyman; Fierro, Ana C; Sánchez-Rodríguez, Aminael; De Moor, Bart; Engelen, Kristof; Marchal, Kathleen

    2011-04-01

    Increasingly large-scale expression compendia for different species are becoming available. By exploiting the modularity of the coexpression network, these compendia can be used to identify biological processes for which the expression behavior is conserved over different species. However, comparing module networks across species is not trivial. The definition of a biologically meaningful module is not a fixed one and changing the distance threshold that defines the degree of coexpression gives rise to different modules. As a result when comparing modules across species, many different partially overlapping conserved module pairs across species exist and deciding which pair is most relevant is hard. Therefore, we developed a method referred to as conserved modules across organisms (COMODO) that uses an objective selection criterium to identify conserved expression modules between two species. The method uses as input microarray data and a gene homology map and provides as output pairs of conserved modules and searches for the pair of modules for which the number of sharing homologs is statistically most significant relative to the size of the linked modules. To demonstrate its principle, we applied COMODO to study coexpression conservation between the two well-studied bacteria Escherichia coli and Bacillus subtilis. COMODO is available at: http://homes.esat.kuleuven.be/∼kmarchal/Supplementary_Information_Zarrineh_2010/comodo/index.html. PMID:21149270

  12. 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

  13. 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…

  14. RM-SORN: a reward-modulated self-organizing recurrent neural network.

    PubMed

    Aswolinskiy, Witali; Pipa, Gordon

    2015-01-01

    Neural plasticity plays an important role in learning and memory. Reward-modulation of plasticity offers an explanation for the ability of the brain to adapt its neural activity to achieve a rewarded goal. Here, we define a neural network model that learns through the interaction of Intrinsic Plasticity (IP) and reward-modulated Spike-Timing-Dependent Plasticity (STDP). IP enables the network to explore possible output sequences and STDP, modulated by reward, reinforces the creation of the rewarded output sequences. The model is tested on tasks for prediction, recall, non-linear computation, pattern recognition, and sequence generation. It achieves performance comparable to networks trained with supervised learning, while using simple, biologically motivated plasticity rules, and rewarding strategies. The results confirm the importance of investigating the interaction of several plasticity rules in the context of reward-modulated learning and whether reward-modulated self-organization can explain the amazing capabilities of the brain. PMID:25852533

  15. RM-SORN: a reward-modulated self-organizing recurrent neural network

    PubMed Central

    Aswolinskiy, Witali; Pipa, Gordon

    2015-01-01

    Neural plasticity plays an important role in learning and memory. Reward-modulation of plasticity offers an explanation for the ability of the brain to adapt its neural activity to achieve a rewarded goal. Here, we define a neural network model that learns through the interaction of Intrinsic Plasticity (IP) and reward-modulated Spike-Timing-Dependent Plasticity (STDP). IP enables the network to explore possible output sequences and STDP, modulated by reward, reinforces the creation of the rewarded output sequences. The model is tested on tasks for prediction, recall, non-linear computation, pattern recognition, and sequence generation. It achieves performance comparable to networks trained with supervised learning, while using simple, biologically motivated plasticity rules, and rewarding strategies. The results confirm the importance of investigating the interaction of several plasticity rules in the context of reward-modulated learning and whether reward-modulated self-organization can explain the amazing capabilities of the brain. PMID:25852533

  16. Hypofractionated helical intensity-modulated radiotherapy of the prostate bed after prostatectomy with or without the pelvic lymph nodes - the PRIAMOS trial

    PubMed Central

    2012-01-01

    Background While evidence on safety and efficacy of primary hypofractionated radiotherapy in prostate cancer is accumulating, data on postoperative hypofractionated treatment of the prostate bed and of the pelvic lymph nodes is still scarce. This phase II trial was initiated to investigate safety and feasibility of hypofractionated treatment of the prostate bed alone or with the pelvic lymph nodes. Methods/design A total of 80 prostate cancer patients with the indication for adjuvant radiotherapy will be enrolled, where 40 patients with a low risk of lymph node involvement (arm 1) and another 40 patients with a high risk of lymph node involvement (arm 2) will each receive 54 Gy in 18 fractions to the prostate bed. Arm 2 will be given 45 Gy to the pelvic lymph nodes additionally. Helical Tomotherapy and daily image guidance will be used. Discussion This trial was initiated to substantiate data on hypofractionated treatment of the prostate bed and generate first data on adjuvant hypofractionated radiotherapy of the pelvic lymph nodes. Trial registration ClinicalTrials.gov; NCT01620710 PMID:23114055

  17. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-04-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; turning on organic-inorganic interactions only when the water content associated with organic compounds is significant; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 29.7 with ±15% deviation from benchmark results. These speedup methods are applicable to other SOA modules that are based on partitioning theories.

  18. Electro-Optic Modulator Based on Organic Planar Waveguide Integrated with Prism Coupler

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S.

    2002-01-01

    The objectives of the project, as they were formulated in the proposal, are the following: (1) Design and development of novel electro-optic modulator using single crystalline film of highly efficient electro-optic organic material integrated with prism coupler; (2) Experimental characterization of the figures-of-merit of the modulator. It is expected to perform with an extinction ratio of 10 dB at a driving signal of 5 V; (3) Conclusions on feasibility of the modulator as an element of data communication systems of future generations. The accomplishments of the project are the following: (1) The design of the electro-optic modulator based on a single crystalline film of organic material NPP has been explored; (2) The evaluation of the figures-of-merit of the electro-optic modulator has been performed; (3) Based on the results of characterization of the figures-of-merit, the conclusion was made that the modulator based on a thin film of NPP is feasible and has a great potential of being used in optic communication with a modulation bandwidth of up to 100 GHz and a driving voltage of the order of 3 to 5 V.

  19. Toward engineering functional organ modules by additive manufacturing.

    PubMed

    Marga, Francoise; Jakab, Karoly; Khatiwala, Chirag; Shepherd, Benjamin; Dorfman, Scott; Hubbard, Bradley; Colbert, Stephen; Gabor, Forgacs

    2012-06-01

    Tissue engineering is emerging as a possible alternative to methods aimed at alleviating the growing demand for replacement tissues and organs. A major pillar of most tissue engineering approaches is the scaffold, a biocompatible network of synthetic or natural polymers, which serves as an extracellular matrix mimic for cells. When the scaffold is seeded with cells it is supposed to provide the appropriate biomechanical and biochemical conditions for cell proliferation and eventual tissue formation. Numerous approaches have been used to fabricate scaffolds with ever-growing complexity. Recently, novel approaches have been pursued that do not rely on artificial scaffolds. The most promising ones utilize matrices of decellularized organs or methods based on multicellular self-assembly, such as sheet-based and bioprinting-based technologies. We briefly overview some of the scaffold-free approaches and detail one that employs biological self-assembly and bioprinting. We describe the technology and its specific applications to engineer vascular and nerve grafts. PMID:22406433

  20. Organic-based electro-optic modulators for microwave photonic applications

    NASA Astrophysics Data System (ADS)

    Eng, David

    As cutting-edge microwave photonic systems with higher complexity and stringent device requirement are being developed, the demand higher performance modulators with lower drive voltages and higher bandwidth is beginning to overtake the physical limitations of existing modulators based in LiNbO3. To address this growing demand, groundbreaking work in the field of organic electro-optic materials has been achieved over the past 10--15 years that has resulted in materials with electro-optic coefficients up to 10 times that of LiNbO3 and with demonstrated response times into the THz regime. This dissertation details work towards developing low drive-voltage, high bandwidth organic-based electro-optic modulators to support next generation microwave photonic systems. Initial efforts were focused on designing an organic electro-optic material based low frequency phase modulator and developing a fabrication procedure that successfully integrates the material without compromising its electro optic activity. Additionally a procedure for inducing the high electro-optic activity in the waveguide core through a process known as 'poling' was developed. The phase modulators were then characterized to confirm the expected high electro-optic activity and correspondingly low drive voltages. To transition from low frequency modulation to broadband operation it was necessary to gather some dielectric information of the waveguide materials for RF design. Because traditional RF dielectric constant measurements assume thick substrates on the order of 100s of microns, a modified microstrip ring resonator technique was developed to measure the dielectric constant of thin, polymer waveguide films on the order of 10 mum out to 110 GHz. A high frequency traveling wave microstrip modulator was then designed and optimized for operation up to 50 GHz, and efforts were turned towards RF packaging of the microstrip modulators for practical utilization and integration. To feed the RF signals a

  1. Prospective optimization of CT under tube current modulation: I. organ dose

    NASA Astrophysics Data System (ADS)

    Tian, Xiaoyu; Li, Xiang; Segars, W. Paul; Frush, Donald; Samei, Ehsan

    2014-03-01

    In an environment in which computed tomography (CT) has become an indispensable diagnostic tool employed with great frequency, dose concerns at the population level have become a subject of public attention. In that regard, optimizing radiation dose has become a core problem to the CT community. As a fundamental step to optimize radiation dose, it is crucial to effectively quantify radiation dose for a given CT exam. Such dose estimates need to be patient-specific to reflect individual radiation burden. It further needs to be prospective so that the scanning parameters can be dynamically adjusted before the scan is performed. The purpose of this study was to prospectively estimate organ dose in abdominopelvic CT exams under tube current modulation (TCM). CTDIvol-normalized-organ dose coefficients ( hfixed ) for fixed tube current were first estimated using a validated Monte Carlo simulation program and 58 computational phantoms. To account for the effect of TCM scheme, a weighted CTDIvol was computed for each organ based on the tube current modulation profile. The organ dose was predicted by multiplying the weighted CTDIvol with the organ dose coefficients ( hfixed ). To quantify prediction accuracy, each predicted organ dose was compared with organ dose simulated from Monte Carlo program with TCM profile explicitly modeled. The predicted organ dose showed good agreement with simulated organ dose across all organs and modulation strengths. For an average CTDIvol of a CT exam of 10 mGy, the absolute median error across all organs were 0.64 mGy (-0.21 and 0.97 for 25th and 75th percentiles, respectively). The percentage differences (normalized by CTDIvol of the exam) were within 15%. This study developed a quantitative model to predict organ dose under clinical abdominopelvic scans. Such information may aid in the optimization of CT protocols.

  2. A computationally-efficient secondary organic aerosol module for three-dimensional air quality models

    NASA Astrophysics Data System (ADS)

    Liu, P.; Zhang, Y.

    2008-07-01

    Accurately simulating secondary organic aerosols (SOA) in three-dimensional (3-D) air quality models is challenging due to the complexity of the physics and chemistry involved and the high computational demand required. A computationally-efficient yet accurate SOA module is necessary in 3-D applications for long-term simulations and real-time air quality forecasting. A coupled gas and aerosol box model (i.e., 0-D CMAQ-MADRID 2) is used to optimize relevant processes in order to develop such a SOA module. Solving the partitioning equations for condensable volatile organic compounds (VOCs) and calculating their activity coefficients in the multicomponent mixtures are identified to be the most computationally-expensive processes. The two processes can be speeded up by relaxing the error tolerance levels and reducing the maximum number of iterations of the numerical solver for the partitioning equations for organic species; conditionally activating organic-inorganic interactions; and parameterizing the calculation of activity coefficients for organic mixtures in the hydrophilic module. The optimal speed-up method can reduce the total CPU cost by up to a factor of 31.4 from benchmark under the rural conditions with 2 ppb isoprene and by factors of 10 71 under various test conditions with 2 10 ppb isoprene and >40% relative humidity while maintaining ±15% deviation. These speed-up methods are applicable to other SOA modules that are based on partitioning theories.

  3. Organ dose conversion coefficients for tube current modulated CT protocols for an adult population

    NASA Astrophysics Data System (ADS)

    Fu, Wanyi; Tian, Xiaoyu; Sahbaee, Pooyan; Zhang, Yakun; Segars, William Paul; Samei, Ehsan

    2016-03-01

    In computed tomography (CT), patient-specific organ dose can be estimated using pre-calculated organ dose conversion coefficients (organ dose normalized by CTDIvol, h factor) database, taking into account patient size and scan coverage. The conversion coefficients have been previously estimated for routine body protocol classes, grouped by scan coverage, across an adult population for fixed tube current modulated CT. The coefficients, however, do not include the widely utilized tube current (mA) modulation scheme, which significantly impacts organ dose. This study aims to extend the h factors and the corresponding dose length product (DLP) to create effective dose conversion coefficients (k factor) database incorporating various tube current modulation strengths. Fifty-eight extended cardiac-torso (XCAT) phantoms were included in this study representing population anatomy variation in clinical practice. Four mA profiles, representing weak to strong mA dependency on body attenuation, were generated for each phantom and protocol class. A validated Monte Carlo program was used to simulate the organ dose. The organ dose and effective dose was further normalized by CTDIvol and DLP to derive the h factors and k factors, respectively. The h factors and k factors were summarized in an exponential regression model as a function of body size. Such a population-based mathematical model can provide a comprehensive organ dose estimation given body size and CTDIvol. The model was integrated into an iPhone app XCATdose version 2, enhancing the 1st version based upon fixed tube current modulation. With the organ dose calculator, physicists, physicians, and patients can conveniently estimate organ dose.

  4. Cell Type-Specific Modulation of Respiratory Chain Supercomplex Organization.

    PubMed

    Sun, Dayan; Li, Bin; Qiu, Ruyi; Fang, Hezhi; Lyu, Jianxin

    2016-01-01

    Respiratory chain complexes are organized into large supercomplexes among which supercomplex In + IIIn + IVn is the only one that can directly transfer electrons from NADH to oxygen. Recently, it was reported that the formation of supercomplex In + IIIn + IVn in mice largely depends on their genetic background. However, in this study, we showed that the composition of supercomplex In + IIIn + IVn is well conserved in various mouse and human cell lines. Strikingly, we found that a minimal supercomplex In + IIIn, termed "lowest supercomplex" (LSC) in this study because of its migration at the lowest position close to complex V dimers in blue native polyacrylamide gel electrophoresis, was associated with complex IV to form a supercomplex In + IIIn + IVn in some, but not all of the human and mouse cells. In addition, we observed that the 3697G>A mutation in mitochondrial-encoded NADH dehydrogenase 1 (ND1) in one patient with Leigh's disease specifically affected the assembly of supercomplex In + IIIn + IVn containing LSC, leading to decreased cellular respiration and ATP generation. In conclusion, we showed the existence of LSC In + IIIn + IVn and impairment of this supercomplex causes disease. PMID:27338358

  5. Cell Type-Specific Modulation of Respiratory Chain Supercomplex Organization

    PubMed Central

    Sun, Dayan; Li, Bin; Qiu, Ruyi; Fang, Hezhi; Lyu, Jianxin

    2016-01-01

    Respiratory chain complexes are organized into large supercomplexes among which supercomplex In + IIIn + IVn is the only one that can directly transfer electrons from NADH to oxygen. Recently, it was reported that the formation of supercomplex In + IIIn + IVn in mice largely depends on their genetic background. However, in this study, we showed that the composition of supercomplex In + IIIn + IVn is well conserved in various mouse and human cell lines. Strikingly, we found that a minimal supercomplex In + IIIn, termed “lowest supercomplex” (LSC) in this study because of its migration at the lowest position close to complex V dimers in blue native polyacrylamide gel electrophoresis, was associated with complex IV to form a supercomplex In + IIIn + IVn in some, but not all of the human and mouse cells. In addition, we observed that the 3697G>A mutation in mitochondrial-encoded NADH dehydrogenase 1 (ND1) in one patient with Leigh’s disease specifically affected the assembly of supercomplex In + IIIn + IVn containing LSC, leading to decreased cellular respiration and ATP generation. In conclusion, we showed the existence of LSC In + IIIn + IVn and impairment of this supercomplex causes disease. PMID:27338358

  6. Feasibility and efficacy of helical intensity-modulated radiotherapy for stage III non-small cell lung cancer in comparison with conventionally fractionated 3D-CRT

    PubMed Central

    He, Jian; Huang, Yan; Chen, Yixing; Shi, Shiming; Ye, Luxi; Hu, Yong; Zhang, Jianying

    2016-01-01

    Background The standard treatment for stage III non-small-cell lung cancer (NSCLC) is still 60 Gy in conventional fractions combined with concurrent chemotherapy; however, the resulting local controls are disappointing. The aim of this study was to compare and assess the feasibility and efficacy of hypofractionated chemoradiotherapy using helical tomotherapy (HT) with conventional fractionation as opposed to using three-dimensional conformal radiotherapy (3D-CRT) for stage III NSCLC. Methods Sixty-nine patients with stage III (AJCC 7th edition) NSCLC who underwent definitive radiation treatment at our institution between July 2011 and November 2013 were reviewed and analyzed retrospectively. A dose of 60 Gy in 20 fractions was delivered in the HT group (n=34), whereas 60 Gy in 30 fractions in the 3D-CRT group (n=35). Primary endpoints were toxicity, overall response rate, overall survival (OS) and progression-free survival (PFS). Results The median follow-up period was 26.4 months. V20 (P=0.005), V30 (P=0.001), V40 (P=0.004), mean lung dose (P=0.000) and max dose of spinal cord (P=0.005) were significantly lower in the HT group than in the 3D-CRT group. There was no significant difference in the incidences of acute radiation pneumonitis (RP) ≥ grade 2 between the two groups, whereas the incidences of acute radiation esophagitis ≥ grade 2 were significantly lower in the HT group than in the 3D-CRT group (P=0.027). Two-year overall response rate was significantly higher in the HT group than in the 3D-CRT group (P=0.015). One- and 2-year OS rates were significantly higher in the HT group (95.0% and 68.7%, respectively) than in the 3D-CRT group (85.5% and 47.6%, respectively; P=0.0236). One- and 2-year PFS rates were significantly higher in the HT group (57.8% and 26.3%, respectively) than in the 3D-CRT group (32.7% and 11.4%, respectively; P=0.0351). Univariate analysis indicated that performance status (PS), T stage and radiotherapy technique were significant

  7. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Wang, Guo-cui; Zang, Meng-di; Hou, Yan-bing; Shen, Jing-ling

    2016-02-01

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator.

  8. Modulation by Amino Acids: Toward Superior Control in the Synthesis of Zirconium Metal-Organic Frameworks.

    PubMed

    Gutov, Oleksii V; Molina, Sonia; Escudero-Adán, Eduardo C; Shafir, Alexandr

    2016-09-12

    The synthesis of zirconium metal-organic frameworks (Zr MOFs) modulated by various amino acids, including l-proline, glycine, and l-phenylalanine, is shown to be a straightforward approach toward functional-group incorporation and particle-size control. High yields in Zr-MOF synthesis are achieved by employing 5 equivalents of the modulator at 120 °C. At lower temperatures, the method provides a series of Zr MOFs with increased particle size, including many suitable for single-crystal X-ray diffraction studies. Furthermore, amino acid modulators can be incorporated at defect sites in Zr MOFs with an amino acid/ligand ratio of up to 1:1, depending on the ligand structure and reaction conditions. The MOFs obtained through amino acid modulation exhibit an improved CO2 -capture capacity relative to nonfunctionalized materials. PMID:27482849

  9. 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.

  10. Prospective estimation of organ dose in CT under tube current modulation

    SciTech Connect

    Tian, Xiaoyu; Li, Xiang; Segars, W. Paul; Frush, Donald P.; Samei, Ehsan

    2015-04-15

    Purpose: Computed tomography (CT) has been widely used worldwide as a tool for medical diagnosis and imaging. However, despite its significant clinical benefits, CT radiation dose at the population level has become a subject of public attention and concern. In this light, optimizing radiation dose has become a core responsibility for the CT community. As a fundamental step to manage and optimize dose, it may be beneficial to have accurate and prospective knowledge about the radiation dose for an individual patient. In this study, the authors developed a framework to prospectively estimate organ dose for chest and abdominopelvic CT exams under tube current modulation (TCM). Methods: The organ dose is mainly dependent on two key factors: patient anatomy and irradiation field. A prediction process was developed to accurately model both factors. To model the anatomical diversity and complexity in the patient population, the authors used a previously developed library of computational phantoms with broad distributions of sizes, ages, and genders. A selected clinical patient, represented by a computational phantom in the study, was optimally matched with another computational phantom in the library to obtain a representation of the patient’s anatomy. To model the irradiation field, a previously validated Monte Carlo program was used to model CT scanner systems. The tube current profiles were modeled using a ray-tracing program as previously reported that theoretically emulated the variability of modulation profiles from major CT machine manufacturers Li et al., [Phys. Med. Biol. 59, 4525–4548 (2014)]. The prediction of organ dose was achieved using the following process: (1) CTDI{sub vol}-normalized-organ dose coefficients (h{sub organ}) for fixed tube current were first estimated as the prediction basis for the computational phantoms; (2) each computation phantom, regarded as a clinical patient, was optimally matched with one computational phantom in the library; (3

  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. Final Technical Report - Recovery Act: Organic Coatings as Encapsulants for Low Cost, High Performance PV Modules

    SciTech Connect

    Stuart Hellring; Jiping Shao; James Poole

    2011-12-05

    The objective of this project was to evaluate the feasibility of utilizing PPG's commercial organic coatings systems as efficient, modernized encapsulants for low cost, high performance, thin film photovoltaic modules. Our hypothesis was that the combination of an anticorrosive coating with a more traditional barrier topcoat would mitigate many electrochemical processes that are now responsible for the significant portion of photovoltaic (PV) failures, thereby nullifying the extremely high moisture barrier requirements of currently used encapsulation technology. Nine commercially available metal primer coatings and six commercially available top coatings were selected for screening. Twenty-one different primer/top coat combinations were evaluated. The primer coatings were shown to be the major contributor to corrosion inhibition, adhesion, and barrier properties. Two primer coatings and one top coating were downselected for testing on specially-fabricated test modules. The coated test modules passed initial current leakage and insulation testing. Damp Heat testing of control modules showed visible corrosion to the bus bar metal, whereas the coated modules showed none. One of the primer/top coat combinations retained solar power performance after Damp Heat testing despite showing some delamination at the EVA/solar cell interface. Thermal Cycling and Humidity Freeze testing resulted in only one test module retaining its power performance. Failure modes depended on the particular primer/top coating combination used. Overall, this study demonstrated that a relatively thin primer/top coating has the potential to replace the potting film and backsheet in crystalline silicon-based photovoltaic modules. Positive signals were received from commercially available coatings developed for applications having performance requirements different from those required for photovoltaic modules. It is likely that future work to redesign and customize these coatings would result in a

  13. Convolution-based estimation of organ dose in tube current modulated CT

    NASA Astrophysics Data System (ADS)

    Tian, Xiaoyu; Segars, W. Paul; Dixon, Robert L.; Samei, Ehsan

    2016-05-01

    Estimating organ dose for clinical patients requires accurate modeling of the patient anatomy and the dose field of the CT exam. The modeling of patient anatomy can be achieved using a library of representative computational phantoms (Samei et al 2014 Pediatr. Radiol. 44 460–7). The modeling of the dose field can be challenging for CT exams performed with a tube current modulation (TCM) technique. The purpose of this work was to effectively model the dose field for TCM exams using a convolution-based method. A framework was further proposed for prospective and retrospective organ dose estimation in clinical practice. The study included 60 adult patients (age range: 18–70 years, weight range: 60–180 kg). Patient-specific computational phantoms were generated based on patient CT image datasets. A previously validated Monte Carlo simulation program was used to model a clinical CT scanner (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). A practical strategy was developed to achieve real-time organ dose estimation for a given clinical patient. CTDIvol-normalized organ dose coefficients ({{h}\\text{Organ}} ) under constant tube current were estimated and modeled as a function of patient size. Each clinical patient in the library was optimally matched to another computational phantom to obtain a representation of organ location/distribution. The patient organ distribution was convolved with a dose distribution profile to generate {{≤ft(\\text{CTD}{{\\text{I}}\\text{vol}}\\right)}\\text{organ, \\text{convolution}}} values that quantified the regional dose field for each organ. The organ dose was estimated by multiplying {{≤ft(\\text{CTD}{{\\text{I}}\\text{vol}}\\right)}\\text{organ, \\text{convolution}}} with the organ dose coefficients ({{h}\\text{Organ}} ). To validate the accuracy of this dose estimation technique, the organ dose of the original clinical patient was estimated using Monte Carlo program with TCM profiles explicitly modeled

  14. Manifestation of helicity in one-dimensional iodobismuthate.

    PubMed

    Pandey, Souvik; Andrews, Alex P; Venugopal, Ajay

    2016-06-01

    We report here, the first example of an inorganic-organic hybrid material incorporating a helical iodobismuthate [BiI4]∞ templated by 2,6-diisopropylanilinium cations. The realisation of the helical iodobismuthate opens up the possibility of a wide range of physical properties among hybrid materials. PMID:27163408

  15. Mode-selective vibrational modulation of charge transport in organic electronic devices

    NASA Astrophysics Data System (ADS)

    Bakulin, Artem A.; Lovrincic, Robert; Yu, Xi; Selig, Oleg; Bakker, Huib J.; Rezus, Yves L. A.; Nayak, Pabitra K.; Fonari, Alexandr; Coropceanu, Veaceslav; Brédas, Jean-Luc; Cahen, David

    2015-08-01

    The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500-1,700 cm-1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron-phonon coupling and charge dynamics in (bio)molecular materials.

  16. Prospective estimation of organ dose in CT under tube current modulation

    PubMed Central

    Tian, Xiaoyu; Li, Xiang; Segars, W. Paul; Frush, Donald P.

    2015-01-01

    Purpose: Computed tomography (CT) has been widely used worldwide as a tool for medical diagnosis and imaging. However, despite its significant clinical benefits, CT radiation dose at the population level has become a subject of public attention and concern. In this light, optimizing radiation dose has become a core responsibility for the CT community. As a fundamental step to manage and optimize dose, it may be beneficial to have accurate and prospective knowledge about the radiation dose for an individual patient. In this study, the authors developed a framework to prospectively estimate organ dose for chest and abdominopelvic CT exams under tube current modulation (TCM). Methods: The organ dose is mainly dependent on two key factors: patient anatomy and irradiation field. A prediction process was developed to accurately model both factors. To model the anatomical diversity and complexity in the patient population, the authors used a previously developed library of computational phantoms with broad distributions of sizes, ages, and genders. A selected clinical patient, represented by a computational phantom in the study, was optimally matched with another computational phantom in the library to obtain a representation of the patient’s anatomy. To model the irradiation field, a previously validated Monte Carlo program was used to model CT scanner systems. The tube current profiles were modeled using a ray-tracing program as previously reported that theoretically emulated the variability of modulation profiles from major CT machine manufacturers Li et al., [Phys. Med. Biol. 59, 4525–4548 (2014)]. The prediction of organ dose was achieved using the following process: (1) CTDIvol-normalized-organ dose coefficients (horgan) for fixed tube current were first estimated as the prediction basis for the computational phantoms; (2) each computation phantom, regarded as a clinical patient, was optimally matched with one computational phantom in the library; (3) to account

  17. The Dosimetric Effect of Intrafraction Prostate Motion on Step-and-Shoot Intensity-Modulated Radiation Therapy Plans: Magnitude, Correlation With Motion Parameters, and Comparison With Helical Tomotherapy Plans

    SciTech Connect

    Langen, Katja M.; Chauhan, Bhavin; Siebers, Jeffrey V.; Moore, Joseph; Kupelian, Patrick A.

    2012-12-01

    Purpose: To determine the daily and cumulative dosimetric effects of intrafraction prostate motion on step-and-shoot (SNS) intensity-modulated radiation therapy (IMRT) plans, to evaluate the correlation of dosimetric effect with motion-based metrics, and to compare on a fraction-by-fraction basis the dosimetric effect induced in SNS and helical tomotherapy plans. Methods and Materials: Intrafraction prostate motion data from 486 fractions and 15 patients were available. A motion-encoded dose calculation technique was used to determine the variation of the clinical target volume (CTV) D{sub 95%} values with respect to the static plan for SNS plans. The motion data were analyzed separately, and the correlation coefficients between various motion-based metrics and the dosimetric effect were determined. The dosimetric impact was compared with that incurred during another IMRT technique to assess correlation across different delivery techniques. Results: The mean ({+-}1 standard deviation [SD]) change in D{sub 95%} in the CTV over all 486 fractions was 0.2 {+-} 0.5%. After the delivery of five and 12 fractions, the mean ({+-}1 SD) changes over the 15 patients in CTV D{sub 95%} were 0.0 {+-} 0.2% and 0.1 {+-} 0.2%, respectively. The correlation coefficients between the CTV D{sub 95%} changes and the evaluated motion metrics were, in general, poor and ranged from r = -0.2 to r = -0.39. Dosimetric effects introduced by identical motion in SNS and helical tomotherapy IMRT techniques were poorly correlated with a correlation coefficient of r = 0.32 for the CTV. Conclusions: The dosimetric impact of intrafraction prostate motion on the CTV is, in general, small. In only 4% of all fractions did the dosimetric consequence exceed 1% in the CTV. As expected, the cumulative effect was further reduced with fractionation. The poor correlations between the calculated motion parameters and the subsequent dosimetric effect implies that motion-based thresholds are of limited value in

  18. From Highly Crystalline to Outer Surface-Functionalized Covalent Organic Frameworks—A Modulation Approach

    PubMed Central

    2015-01-01

    Crystallinity and porosity are of central importance for many properties of covalent organic frameworks (COFs), including adsorption, diffusion, and electronic transport. We have developed a new method for strongly enhancing both aspects through the introduction of a modulating agent in the synthesis. This modulator competes with one of the building blocks during the solvothermal COF growth, resulting in highly crystalline frameworks with greatly increased domain sizes reaching several hundreds of nanometers. The obtained materials feature fully accessible pores with an internal surface area of over 2000 m2 g–1. Compositional analysis via NMR spectroscopy revealed that the COF-5 structure can form over a wide range of boronic acid-to-catechol ratios, thus producing frameworks with compositions ranging from highly boronic acid-deficient to networks with catechol voids. Visualization of an −SH-functionalized modulating agent via iridium staining revealed that the COF domains are terminated by the modulator. Using functionalized modulators, this synthetic approach thus also provides a new and facile method for the external surface functionalization of COF domains, providing accessible sites for post-synthetic modification reactions. We demonstrate the feasibility of this concept by covalently attaching fluorescent dyes and hydrophilic polymers to the COF surface. We anticipate that the realization of highly crystalline COFs with the option of additional surface functionality will render the modulation concept beneficial for a range of applications, including gas separations, catalysis, and optoelectronics. PMID:26694214

  19. From Highly Crystalline to Outer Surface-Functionalized Covalent Organic Frameworks--A Modulation Approach.

    PubMed

    Calik, Mona; Sick, Torben; Dogru, Mirjam; Döblinger, Markus; Datz, Stefan; Budde, Harald; Hartschuh, Achim; Auras, Florian; Bein, Thomas

    2016-02-01

    Crystallinity and porosity are of central importance for many properties of covalent organic frameworks (COFs), including adsorption, diffusion, and electronic transport. We have developed a new method for strongly enhancing both aspects through the introduction of a modulating agent in the synthesis. This modulator competes with one of the building blocks during the solvothermal COF growth, resulting in highly crystalline frameworks with greatly increased domain sizes reaching several hundreds of nanometers. The obtained materials feature fully accessible pores with an internal surface area of over 2000 m(2) g(-1). Compositional analysis via NMR spectroscopy revealed that the COF-5 structure can form over a wide range of boronic acid-to-catechol ratios, thus producing frameworks with compositions ranging from highly boronic acid-deficient to networks with catechol voids. Visualization of an -SH-functionalized modulating agent via iridium staining revealed that the COF domains are terminated by the modulator. Using functionalized modulators, this synthetic approach thus also provides a new and facile method for the external surface functionalization of COF domains, providing accessible sites for post-synthetic modification reactions. We demonstrate the feasibility of this concept by covalently attaching fluorescent dyes and hydrophilic polymers to the COF surface. We anticipate that the realization of highly crystalline COFs with the option of additional surface functionality will render the modulation concept beneficial for a range of applications, including gas separations, catalysis, and optoelectronics. PMID:26694214

  20. Significance of bending restraints for the stability of helical polymer conformations

    NASA Astrophysics Data System (ADS)

    Williams, Matthew J.; Bachmann, Michael

    2016-06-01

    We performed parallel-tempering Monte Carlo simulations to investigate the formation and stability of helical tertiary structures for flexible and semiflexible polymers, employing a generic coarse-grained model. Structural conformations exhibit helical order with tertiary ordering into single helices, multiple helical segments organized into bundles, and disorganized helical arrangements. For both bending-restrained semiflexible and bending-unrestrained flexible helical polymers, the stability of the structural phases is discussed systematically by means of hyperphase diagrams parametrized by suitable order parameters, temperature, and torsion strength. This exploration lends insight into the restricted flexibility of biological polymers such as double-stranded DNA and proteins.

  1. 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

  2. Minimizing a tricky situation in breast irradiation with helical tomotherapy.

    PubMed

    Franco, Pierfrancesco; Zeverino, Michele; Migliaccio, Fernanda; Torielli, Paolo; Angelini, Veronica; Sciacero, Piera; Girelli, Giuseppe; Cante, Domenico; Arrichiello, Cecilia; Casanova Borca, Valeria; Numico, Gianmauro; La Porta, Maria Rosa; Tofani, Santi; Ricardi, Umberto

    2014-01-01

    We report on a patient with breast cancer undergoing adjuvant intensity-modulated whole breast and lymph node irradiation with static angle tomotherapy (TomoDirect), who experienced a traumatic ipsilateral humeral fracture and was able to continue radiotherapy with helical tomotherapy and daily dosimetric monitoring by means of the Planned Adaptive module. PMID:24852873

  3. Convolution-based estimation of organ dose in tube current modulated CT.

    PubMed

    Tian, Xiaoyu; Segars, W Paul; Dixon, Robert L; Samei, Ehsan

    2016-05-21

    Estimating organ dose for clinical patients requires accurate modeling of the patient anatomy and the dose field of the CT exam. The modeling of patient anatomy can be achieved using a library of representative computational phantoms (Samei et al 2014 Pediatr. Radiol. 44 460-7). The modeling of the dose field can be challenging for CT exams performed with a tube current modulation (TCM) technique. The purpose of this work was to effectively model the dose field for TCM exams using a convolution-based method. A framework was further proposed for prospective and retrospective organ dose estimation in clinical practice. The study included 60 adult patients (age range: 18-70 years, weight range: 60-180 kg). Patient-specific computational phantoms were generated based on patient CT image datasets. A previously validated Monte Carlo simulation program was used to model a clinical CT scanner (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). A practical strategy was developed to achieve real-time organ dose estimation for a given clinical patient. CTDIvol-normalized organ dose coefficients ([Formula: see text]) under constant tube current were estimated and modeled as a function of patient size. Each clinical patient in the library was optimally matched to another computational phantom to obtain a representation of organ location/distribution. The patient organ distribution was convolved with a dose distribution profile to generate [Formula: see text] values that quantified the regional dose field for each organ. The organ dose was estimated by multiplying [Formula: see text] with the organ dose coefficients ([Formula: see text]). To validate the accuracy of this dose estimation technique, the organ dose of the original clinical patient was estimated using Monte Carlo program with TCM profiles explicitly modeled. The discrepancy between the estimated organ dose and dose simulated using TCM Monte Carlo program was quantified. We further compared the

  4. 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.

  5. 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.

  6. 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.

  7. Josephson junction through a disordered topological insulator with helical magnetization

    NASA Astrophysics Data System (ADS)

    Zyuzin, Alexander; Alidoust, Mohammad; Loss, Daniel

    2016-06-01

    We study supercurrent and proximity vortices in a Josephson junction made of disordered surface states of a three-dimensional topological insulator with a proximity induced in-plane helical magnetization. In a regime where the rotation period of helical magnetization is larger than the junction width, we find supercurrent 0 -π crossovers as a function of junction thickness, magnetization strength, and parameters inherent to the helical modulation and surface states. The supercurrent reversals are associated with proximity induced vortices, nucleated along the junction width, where the number of vortices and their locations can be manipulated by means of the superconducting phase difference and the parameters mentioned above.

  8. Organ Function as a Modulator of Organ Formation: Lessons from Zebrafish.

    PubMed

    Collins, Michelle M; Stainier, Didier Y R

    2016-01-01

    Organogenesis requires an intricate balance between cell differentiation and tissue growth to generate a complex and fully functional organ. However, organogenesis is not solely driven by genetic inputs, as the development of several organ systems requires their own functionality. This theme is particularly evident in the developing heart as progression of cardiac development is accompanied by increased and altered hemodynamic forces. In the absence or disruption of these forces, heart development is abnormal, suggesting that the heart must sense these changes and respond appropriately. Here, we discuss concepts of how embryonic heart function contributes to heart development using lessons learned mostly from studies in zebrafish. PMID:26969993

  9. Flexible organic tandem solar modules: a story of up-scaling

    NASA Astrophysics Data System (ADS)

    Spyropoulos, George D.; Kubis, Peter; Li, Ning; Lucera, Luca; Salvador, Michael; Baran, Derya; Machui, Florian; Ameri, Tayebeh; Voigt, Monika M.; Brabec, Christoph J.

    2014-10-01

    The competition in the field of solar energy between Organic Photovoltaics (OPVs) and several Inorganic Photovoltaic technologies is continuously increasing to reach the ultimate purpose of energy supply from inexpensive and easily manufactured solar cell units. Solution-processed printing techniques on flexible substrates attach a tremendous opportunity to the OPVs for the accomplishment of low-cost and large area applications. Furthermore, tandem architectures came to boost up even more OPVs by increasing the photon-harvesting properties of the device. In this work, we demonstrate the road of realizing flexible organic tandem solar modules constructed by a fully roll-to-roll compatible processing. The modules exhibit an efficiency of 5.4% with geometrical fill factors beyond 80% and minimized interconnection-resistance losses. The processing involves low temperature (<70 °C), coating methods compatible with slot die coating and high speed and precision laser patterning.

  10. Analysis of peripheral doses for base of tongue treatment by linear accelerator and helical TomoTherapy IMRT.

    PubMed

    Bennett, Brian Richard; Lamba, Michael A S; Elson, Howard R

    2010-01-01

    The purpose of this study was to compare the peripheral doses to various organs from a typical head and neck intensity-modulated radiation therapy (IMRT) treatment delivered by linear accelerator (linac) and helical TomoTherapy. Multiple human CT data sets were used to segment critical structures and organs at risk, fused and adjusted to an anthropomorphic phantom. Eighteen contours were designated for thermoluminescent dosimeter (TLD) placement. Following the RTOG IMRT Protocol 0522, treatment of the primary tumor and involved nodes (PTV70) and subclinical disease sites (PTV56) was planned utilizing IMRT to 70Gy and 56 Gy. Clinically acceptable treatment plans were produced for linac and TomoTherapy treatments. TLDs were placed and each treatment plan was delivered to the anthropomorphic phantom four times. Within 2.5 cm (one helical TomoTherapy field width) superior and inferior to the field edges, normal tissue doses were on average 45% lower using linear accelerator. Beyond 2.5 cm, the helical TomoTherapy normal tissue dose was an average of 52% lower. The majority of points proved to be statistically different using the Student's t-test with p > 0.05. Using one method of calculation, probability of a secondary malignancy was 5.88% for the linear accelerator and 4.08% for helical TomoTherapy. Helical TomoTherapy delivers more dose than a linac immediately above and below the treatment field, contributing to the higher peripheral doses adjacent to the field. At distances beyond one field width (where leakage is dominant), helical TomoTherapy doses are lower than linear accelerator doses. PMID:20717081

  11. Encouraging Early Clinical Outcomes With Helical Tomotherapy-Based Image-Guided Intensity-Modulated Radiation Therapy for Residual, Recurrent, and/or Progressive Benign/Low-Grade Intracranial Tumors: A Comprehensive Evaluation

    SciTech Connect

    Gupta, Tejpal

    2012-02-01

    Purpose: To report early clinical outcomes of helical tomotherapy (HT)-based image-guided intensity-modulated radiation therapy (IMRT) in brain tumors of varying shape, size, and location. Materials and Methods: Patients with residual, recurrent, and/or progressive low-grade intracranial and skull-base tumors were treated on a prospective protocol of HT-based IMRT and followed clinicoradiologically. Standardized metrics were used for plan evaluation and outcome analysis. Results: Twenty-seven patients with 30 lesions were treated to a median radiotherapy dose of 54 Gy in 30 fractions. All HT plans resulted in excellent target volume coverage with steep dose-gradients. The mean (standard deviation) dose homogeneity index and conformity index was 0.07 (0.05) and 0.71 (0.08) respectively. At first response assessment, 20 of 30 lesions were stable, whereas 9 showed partial regression. One patient with a recurrent clival chordoma though neurologically stable showed imaging-defined progression, whereas another patient with stable disease on serial imaging had sustained neurologic worsening. With a median follow-up of 19 months (interquartile range, 11-26 months), the 2-year clinicoradiological progression-free survival and overall survival was 93.3% and 100% respectively. Conclusions: Careful selection of radiotherapy technique is warranted for benign/low-grade brain tumors to achieve durable local control with minimum long-term morbidity. Large or complex-shaped tumors benefit most from IMRT. Our early clinical experience of HT-based IMRT for brain tumors has been encouraging.

  12. Helical Tomotherapy vs. Intensity-Modulated Proton Therapy for Whole Pelvis Irradiation in High-Risk Prostate Cancer Patients: Dosimetric, Normal Tissue Complication Probability, and Generalized Equivalent Uniform Dose Analysis

    SciTech Connect

    Widesott, Lamberto; Pierelli, Alessio; Fiorino, Claudio; Lomax, Antony J.; Amichetti, Maurizio; Cozzarini, Cesare; Soukup, Martin; Schneider, Ralf; Hug, Eugen; Di Muzio, Nadia; Calandrino, Riccardo; Schwarz, Marco

    2011-08-01

    Purpose: To compare intensity-modulated proton therapy (IMPT) and helical tomotherapy (HT) treatment plans for high-risk prostate cancer (HRPCa) patients. Methods and Materials: The plans of 8 patients with HRPCa treated with HT were compared with IMPT plans with two quasilateral fields set up (-100{sup o}; 100{sup o}) and optimized with the Hyperion treatment planning system. Both techniques were optimized to simultaneously deliver 74.2 Gy/Gy relative biologic effectiveness (RBE) in 28 fractions on planning target volumes (PTVs)3-4 (P + proximal seminal vesicles), 65.5 Gy/Gy(RBE) on PTV2 (distal seminal vesicles and rectum/prostate overlapping), and 51.8 Gy/Gy(RBE) to PTV1 (pelvic lymph nodes). Normal tissue calculation probability (NTCP) calculations were performed for the rectum, and generalized equivalent uniform dose (gEUD) was estimated for the bowel cavity, penile bulb and bladder. Results: A slightly better PTV coverage and homogeneity of target dose distribution with IMPT was found: the percentage of PTV volume receiving {>=}95% of the prescribed dose (V{sub 95%}) was on average >97% in HT and >99% in IMPT. The conformity indexes were significantly lower for protons than for photons, and there was a statistically significant reduction of the IMPT dosimetric parameters, up to 50 Gy/Gy(RBE) for the rectum and bowel and 60 Gy/Gy(RBE) for the bladder. The NTCP values for the rectum were higher in HT for all the sets of parameters, but the gain was small and in only a few cases statistically significant. Conclusions: Comparable PTV coverage was observed. Based on NTCP calculation, IMPT is expected to allow a small reduction in rectal toxicity, and a significant dosimetric gain with IMPT, both in medium-dose and in low-dose range in all OARs, was observed.

  13. Patterns of morphological integration in marine modular organisms: supra-module organization in branching octocoral colonies.

    PubMed Central

    Sánchez, Juan Armando; Lasker, Howard R

    2003-01-01

    Despite the relative simplicity of their modular growth, marine invertebrates such as arborescent gorgonian octocorals (Octocorallia: Cnidaria) generate complex colonial forms. Colony form in these taxa is a consequence of modular (polyp) replication, and if there is a tight integration among modular and supramodular traits (e.g. polyp aperture, inter-polyp spacing, branch thickness, internode and branch length), then changes at the module level may lead to changes in colony architecture. Alternatively, different groups of traits may evolve semi-independently (or conditionally independent). To examine the patterns of integration among morphological traits in Caribbean octocorals, we compared five morphological traits across 21 species, correcting for the effects of phylogenetic relationships among the taxa. Graphical modelling and phylogenetic independence contrasts among the five morphological characters indicate two groups of integrated traits based on whether they were polyp- or colony-level traits. Although all characters exhibited bivariate associations, multivariate analyses (partial correlation coefficients) showed the strongest integration among the colony-level characters (internode distance and branch length). It is a quantitative demonstration that branching characters within the octocorals studied are independent of characters of the polyps. Despite the universally recognized modularity of octocorals at the level of polyps, branching during colony development may represent an emergent level of integration and modularity. PMID:14561292

  14. 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.

  15. Antenna-coupled silicon-organic hybrid integrated photonic crystal modulator for broadband electromagnetic wave detection

    NASA Astrophysics Data System (ADS)

    Zhang, Xingyu; Hosseini, Amir; Subbaraman, Harish; Wang, Shiyi; Zhan, Qiwen; Luo, Jingdong; Jen, Alex K.; Chung, Chi-jui; Yan, Hai; Pan, Zeyu; Nelson, Robert L.; Lee, Charles Y.; Chen, Ray T.

    2015-03-01

    The detection and measurement of electromagnetic fields have attracted significant amounts of attention in recent years. Traditional electronic electromagnetic field sensors use large active conductive probes which perturb the field to be measured and also make the devices bulky. In order to address these problems, integrated photonic electromagnetic field sensors have been developed, in which an optical signal is modulated by an RF signal collected by a miniaturized antenna. In this work, we design, fabricate and characterize a compact, broadband and highly sensitive integrated photonic electromagnetic field sensor based on a silicon-organic hybrid modulator driven by a bowtie antenna. The large electro-optic (EO) coefficient of organic polymer, the slow-light effects in the silicon slot photonic crystal waveguide (PCW), and the broadband field enhancement provided by the bowtie antenna, are all combined to enhance the interaction of microwaves and optical waves, enabling a high EO modulation efficiency and thus a high sensitivity. The modulator is experimentally demonstrated with a record-high effective in-device EO modulation efficiency of r33=1230pm/V. Modulation response up to 40GHz is measured, with a 3-dB bandwidth of 11GHz. The slot PCW has an interaction length of 300μm, and the bowtie antenna has an area smaller than 1cm2. The bowtie antenna in the device is experimentally demonstrated to have a broadband characteristics with a central resonance frequency of 10GHz, as well as a large beam width which enables the detection of electromagnetic waves from a large range of incident angles. The sensor is experimentally demonstrated with a minimum detectable electromagnetic power density of 8.4mW/m2 at 8.4GHz, corresponding to a minimum detectable electric field of 2.5V/m and an ultra-high sensitivity of 0.000027V/m Hz-1/2 ever demonstrated. To the best of our knowledge, this is the first silicon-organic hybrid device and also the first PCW device used for the

  16. Hierarchically arranged helical fibre actuators driven by solvents and vapours

    NASA Astrophysics Data System (ADS)

    Chen, Peining; Xu, Yifan; He, Sisi; Sun, Xuemei; Pan, Shaowu; Deng, Jue; Chen, Daoyong; Peng, Huisheng

    2015-12-01

    Mechanical responsiveness in many plants is produced by helical organizations of cellulose microfibrils. However, simple mimicry of these naturally occurring helical structures does not produce artificial materials with the desired tunable actuations. Here, we show that actuating fibres that respond to solvent and vapour stimuli can be created through the hierarchical and helical assembly of aligned carbon nanotubes. Primary fibres consisting of helical assemblies of multiwalled carbon nanotubes are twisted together to form the helical actuating fibres. The nanoscale gaps between the nanotubes and micrometre-scale gaps among the primary fibres contribute to the rapid response and large actuation stroke of the actuating fibres. The compact coils allow the actuating fibre to rotate reversibly. We show that these fibres, which are lightweight, flexible and strong, are suitable for a variety of applications such as energy-harvesting generators, deformable sensing springs and smart textiles.

  17. Hierarchically arranged helical fibre actuators driven by solvents and vapours.

    PubMed

    Chen, Peining; Xu, Yifan; He, Sisi; Sun, Xuemei; Pan, Shaowu; Deng, Jue; Chen, Daoyong; Peng, Huisheng

    2015-12-01

    Mechanical responsiveness in many plants is produced by helical organizations of cellulose microfibrils. However, simple mimicry of these naturally occurring helical structures does not produce artificial materials with the desired tunable actuations. Here, we show that actuating fibres that respond to solvent and vapour stimuli can be created through the hierarchical and helical assembly of aligned carbon nanotubes. Primary fibres consisting of helical assemblies of multiwalled carbon nanotubes are twisted together to form the helical actuating fibres. The nanoscale gaps between the nanotubes and micrometre-scale gaps among the primary fibres contribute to the rapid response and large actuation stroke of the actuating fibres. The compact coils allow the actuating fibre to rotate reversibly. We show that these fibres, which are lightweight, flexible and strong, are suitable for a variety of applications such as energy-harvesting generators, deformable sensing springs and smart textiles. PMID:26367106

  18. CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

    SciTech Connect

    Komm, Rudolf; Gosain, Sanjay

    2015-01-01

    We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%, respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign.

  19. A Research Module for the Organic Chemistry Laboratory: Multistep Synthesis of a Fluorous Dye Molecule.

    PubMed

    Slade, Michael C; Raker, Jeffrey R; Kobilka, Brandon; Pohl, Nicola L B

    2014-01-14

    A multi-session research-like module has been developed for use in the undergraduate organic teaching laboratory curriculum. Students are tasked with planning and executing the synthesis of a novel fluorous dye molecule and using it to explore a fluorous affinity chromatography separation technique, which is the first implementation of this technique in a teaching laboratory. Key elements of the project include gradually introducing students to the use of the chemical literature to facilitate their searching, as well as deliberate constraints designed to force them to think critically about reaction design and optimization in organic chemistry. The project also introduces students to some advanced laboratory practices such as Schlenk techniques, degassing of reaction mixtures, affinity chromatography, and microwave-assisted chemistry. This provides students a teaching laboratory experience that closely mirrors authentic synthetic organic chemistry practice in laboratories throughout the world. PMID:24501431

  20. Image-guided total marrow and total lymphatic irradiation using helical tomotherapy

    SciTech Connect

    Schultheiss, Timothy E. . E-mail: Schultheiss@coh.org; Wong, Jeffrey; Liu, An; Olivera, Gustavo; Somlo, George

    2007-03-15

    Purpose: To develop a treatment technique to spare normal tissue and allow dose escalation in total body irradiation (TBI). We have developed intensity-modulated radiotherapy techniques for the total marrow irradiation (TMI), total lymphatic irradiation, or total bone marrow plus lymphatic irradiation using helical tomotherapy. Methods and Materials: For TBI, we typically use 12 Gy in 10 fractions delivered at an extended source-to-surface distance (SSD). Using helical tomotherapy, it is possible to deliver equally effective doses to the bone marrow and lymphatics while sparing normal organs to a significant degree. In the TMI patients, whole body skeletal bone, including the ribs and sternum, comprise the treatment target. In the total lymphatic irradiation, the target is expanded to include the spleen and major lymph node areas. Sanctuary sites for disease (brain and testes) are included when clinically indicated. Spared organs include the lungs, esophagus, parotid glands, eyes, oral cavity, liver, kidneys, stomach, small and large intestine, bladder, and ovaries. Results: With TBI, all normal organs received the TBI dose; with TMI, total lymphatic irradiation, and total bone marrow plus lymphatic irradiation, the visceral organs are spared. For the first 6 patients treated with TMI, the median dose to organs at risk averaged 51% lower than would be achieved with TBI. By putting greater weight on the avoidance of specific organs, greater sparing was possible. Conclusion: Sparing of normal tissues and dose escalation is possible using helical tomotherapy. Late effects such as radiation pneumonitis, veno-occlusive disease, cataracts, neurocognitive effects, and the development of second tumors should be diminished in severity and frequency according to the dose reduction realized for the organs at risk.

  1. 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

  2. Vitamin D Treatment Modulates Organic Dust-Induced Cellular and Airway Inflammatory Consequences

    PubMed Central

    Golden, Gregory A.; Wyatt, Todd A.; Romberger, Debra J.; Reiff, Daniel; McCaskill, Michael; Bauer, Christopher; Gleason, Angela M.; Poole, Jill A.

    2014-01-01

    Exposure to organic dusts elicits airway inflammatory diseases. Vitamin D recently has been associated with various airway inflammatory diseases, but its role in agricultural organic dust exposures is unknown. This study investigated whether vitamin D reduces organic dust-induced inflammatory outcomes in cell culture and animal models. Organic dust extracts obtained from swine confinement facilities induced neutrophil chemokine production (human IL-8, murine CXCL1/CXCL2). Neutrophil chemokine induction was reduced in human blood monocytes, human bronchial epithelial cells and murine lung slices pretreated with 1,25-(OH)2D3. Intranasal inhalation of organic dust extract induced neutrophil influx and CXCL1/CXCL2 release also was decreased in mice fed a relatively high vitamin D diet as compared to mice fed a low vitamin D diet. These findings were associated with reduced tracheal epithelial cell PKCα and PKCε activity and whole lung TLR2 and TLR4 gene expression. Collectively, vitamin D plays a role in modulating organic dust-induced airway inflammatory outcomes. PMID:23281135

  3. Mediastinal irradiation in a patient affected by lung carcinoma after heart transplantation: Helical tomotherapy versus three dimensional conformal radiotherapy

    PubMed Central

    Iorio, Vincenzo; Cammarota, Fabrizio; Toledo, Diego; Senese, Rossana; Francomacaro, Ferdinando; Muto, Matteo; Muto, Paolo

    2016-01-01

    Abstract Patients who have undergone solid organ transplants are known to have an increased risk of neoplasia compared with the general population. We report our experience using mediastinal irradiation with helical tomotherapy versus three‐dimensional conformal radiation therapy to treat a patient with lung carcinoma 15 years after heart transplantation. Our dosimetric evaluation showed no particular difference between the techniques, with the exception of some organs. Mediastinal irradiation after heart transplantation is feasible and should be considered after evaluation of the risk. Conformal radiotherapy or intensity‐modulated radiotherapy appears to be the appropriate treatment in heart‐transplanted oncologic patients. PMID:27148425

  4. Mediastinal irradiation in a patient affected by lung carcinoma after heart transplantation: Helical tomotherapy versus three dimensional conformal radiotherapy.

    PubMed

    Giugliano, Francesca M; Iorio, Vincenzo; Cammarota, Fabrizio; Toledo, Diego; Senese, Rossana; Francomacaro, Ferdinando; Muto, Matteo; Muto, Paolo

    2016-04-26

    Patients who have undergone solid organ transplants are known to have an increased risk of neoplasia compared with the general population. We report our experience using mediastinal irradiation with helical tomotherapy versus three-dimensional conformal radiation therapy to treat a patient with lung carcinoma 15 years after heart transplantation. Our dosimetric evaluation showed no particular difference between the techniques, with the exception of some organs. Mediastinal irradiation after heart transplantation is feasible and should be considered after evaluation of the risk. Conformal radiotherapy or intensity-modulated radiotherapy appears to be the appropriate treatment in heart-transplanted oncologic patients. PMID:27148425

  5. Mode-selective vibrational modulation of charge transport in organic electronic devices

    PubMed Central

    Bakulin, Artem A.; Lovrincic, Robert; Yu, Xi; Selig, Oleg; Bakker, Huib J.; Rezus, Yves L. A.; Nayak, Pabitra K.; Fonari, Alexandr; Coropceanu, Veaceslav; Brédas, Jean-Luc; Cahen, David

    2015-01-01

    The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500–1,700 cm−1 region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron–phonon coupling and charge dynamics in (bio)molecular materials. PMID:26246039

  6. Mode-selective vibrational modulation of charge transport in organic electronic devices.

    PubMed

    Bakulin, Artem A; Lovrincic, Robert; Yu, Xi; Selig, Oleg; Bakker, Huib J; Rezus, Yves L A; Nayak, Pabitra K; Fonari, Alexandr; Coropceanu, Veaceslav; Brédas, Jean-Luc; Cahen, David

    2015-01-01

    The soft character of organic materials leads to strong coupling between molecular, nuclear and electronic dynamics. This coupling opens the way to influence charge transport in organic electronic devices by exciting molecular vibrational motions. However, despite encouraging theoretical predictions, experimental realization of such approach has remained elusive. Here we demonstrate experimentally that photoconductivity in a model organic optoelectronic device can be modulated by the selective excitation of molecular vibrations. Using an ultrafast infrared laser source to create a coherent superposition of vibrational motions in a pentacene/C60 photoresistor, we observe that excitation of certain modes in the 1,500-1,700 cm(-1) region leads to photocurrent enhancement. Excited vibrations affect predominantly trapped carriers. The effect depends on the nature of the vibration and its mode-specific character can be well described by the vibrational modulation of intermolecular electronic couplings. This presents a new tool for studying electron-phonon coupling and charge dynamics in (bio)molecular materials. PMID:26246039

  7. 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.

  8. Modulation of volatile organic compound formation in the Mycodiesel-producing endophyte Hypoxylon sp. CI-4.

    PubMed

    Ul-Hassan, Syed Riyaz; Strobel, Gary A; Booth, Eric; Knighton, Berk; Floerchinger, Cody; Sears, Joe

    2012-02-01

    An endophytic Hypoxylon sp. (strain CI-4) producing a wide spectrum of volatile organic compounds (VOCs), including 1,8-cineole, 1-methyl-1,4-cyclohexadiene and cyclohexane, 1,2,4-tris(methylene), was selected as a candidate for the modulation of VOC production. This was done in order to learn if the production of these and other VOCs can be affected by using agents that may modulate the epigenetics of the fungus. Many of the VOCs made by this organism are of interest because of their high energy densities and thus the potential they might have as Mycodiesel fuels. Strain CI-4 was exposed to the epigenetic modulators suberoylanilide hydroxamic acid (SAHA, a histone deacetylase) and 5-azacytidine (AZA, a DNA methyltransferase inhibitor). After these treatments the organism displayed striking cultural changes, including variations in pigmentation, growth rates and odour, in addition to significant differences in the bioactivities of the VOCs. The resulting variants were designated CI4-B, CI4-AZA and CI4-SAHA. GC/MS analyses of the VOCs produced by the variants showed considerable variation, with the emergence of several compounds not previously observed in the wild-type, particularly an array of tentatively identified terpenes such as α-thujene, sabinene, γ-terpinene, α-terpinolene and β-selinene, in addition to several primary and secondary alkanes, alkenes, organic acids and derivatives of benzene. Proton transfer reaction mass spectroscopic analyses showed a marked increase in the ratio of ethanol (mass 47) to the total mass of all other ionizable VOCs, from ~0.6 in the untreated strain CI-4 to ~0.8 in CI-4 grown in the presence of AZA. Strain CI4-B was created by exposure of the fungus to 100 µM SAHA; upon removal of the epigenetic modulator from the culture medium, it did not revert to the wild-type phenotype. Results of this study have implications for understanding why there may be a wide range of VOCs found in various isolates of this fungus in nature

  9. Chemically Stable Covalent Organic Framework (COF)-Polybenzimidazole Hybrid Membranes: Enhanced Gas Separation through Pore Modulation.

    PubMed

    Biswal, Bishnu P; Chaudhari, Harshal D; Banerjee, Rahul; Kharul, Ulhas K

    2016-03-24

    Highly flexible, TpPa-1@PBI-BuI and TpBD@PBI-BuI hybrid membranes based on chemically stable covalent organic frameworks (COFs) could be obtained with the polymer. The loading obtained was substantially higher (50 %) than generally observed with MOFs. These hybrid membranes show an exciting enhancement in permeability (about sevenfold) with appreciable separation factors for CO2/N2 and CO2/CH4. Further, we found that with COF pore modulation, the gas permeability can be systematically enhanced. PMID:26865381

  10. Extraordinary Separation of Acetylene-Containing Mixtures with Microporous Metal-Organic Frameworks with Open O Donor Sites and Tunable Robustness through Control of the Helical Chain Secondary Building Units.

    PubMed

    Yao, Zizhu; Zhang, Zhangjing; Liu, Lizhen; Li, Ziyin; Zhou, Wei; Zhao, Yunfeng; Han, Yu; Chen, Banglin; Krishna, Rajamani; Xiang, Shengchang

    2016-04-11

    Acetylene separation is a very important but challenging industrial separation task. Here, through the solvothermal reaction of CuI and 5-triazole isophthalic acid in different solvents, two metal-organic frameworks (MOFs, FJU-21 and FJU-22) with open O donor sites and controllable robustness have been obtained for acetylene separation. They contain the same paddle-wheel {Cu2 (COO2 )4 } nodes and metal-ligand connection modes, but with different helical chains as secondary building units (SBUs), leading to different structural robustness for the MOFs. FJU-21 and FJU-22 are the first examples in which the MOFs' robustness is controlled by adjusting the helical chain SBUs. Good robustness gives the activated FJU-22 a, which has higher surface area and gas uptakes than the flexible FJU-21 a. Importantly, FJU-22 a shows extraordinary separation of acetylene mixtures under ambient conditions. The separation capacity of FJU-22 a for 50:50 C2 H2 /CO2 mixtures is about twice that of the high-capacity HOF-3, and its actual separation selectivity for C2 H2 /C2 H4 mixtures containing 1 % acetylene is the highest among reported porous materials. Based on first-principles calculations, the extraordinary separation performance of C2 H2 for FJU-22 a was attributed to hydrogen-bonding interactions between the C2 H2 molecules with the open O donors on the wall, which provide better recognition ability for C2 H2 than other functional sites, including open metal sites and amino groups. PMID:26934040

  11. 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

  12. Assessment of an organ-based tube current modulation in thoracic computed tomography.

    PubMed

    Matsubara, Kosuke; Sugai, Mai; Toyoda, Asami; Koshida, Haruka; Sakuta, Keita; Takata, Tadanori; Koshida, Kichiro; Iida, Hiroji; Matsui, Osamu

    2012-01-01

    Recently, specific computed tomography (CT) scanners have been equipped with organ-based tube current modulation (TCM) technology. It is possible that organ-based TCM will replace the conventional dose-reduction technique of reducing the effective milliampere-second. The aim of this study was to determine if organ-based TCM could reduce radiation exposure to the breasts without compromising the image uniformity and beam hardening effect in thoracic CT examinations. Breast and skin radiation doses and the absorbed radiation dose distribution within a single section were measured with an anthropomorphic phantom and radiophotoluminescent glass dosimeters using four approaches to thoracic CT (reference, organ-based TCM, copper shielding, and the combination of the above two techniques, hereafter referred to as the combination technique). The CT value and noise level were measured using the same calibration phantom. Organ-based TCM and copper shielding reduced radiation doses to the breast by 23.7% and 21.8%, respectively. However, the CT value increased, especially in the anterior region, using copper shielding. In contrast, the CT value and noise level barely increased using organ-based TCM. The combination technique reduced the radiation dose to the breast by 38.2%, but greatly increased the absorbed radiation dose from the central to the posterior regions. Moreover, the CT value increased in the anterior region and the noise level increased by more than 10% in the entire region. Therefore, organ-based TCM can reduce radiation doses to breasts with only small increases in noise levels, making it preferable for specific groups of patients, such as children and young women. PMID:22402390

  13. A common rejection module (CRM) for acute rejection across multiple organs identifies novel therapeutics for organ transplantation

    PubMed Central

    Khatri, Purvesh; Roedder, Silke; Kimura, Naoyuki; De Vusser, Katrien; Morgan, Alexander A.; Gong, Yongquan; Fischbein, Michael P.; Robbins, Robert C.; Naesens, Maarten

    2013-01-01

    Using meta-analysis of eight independent transplant datasets (236 graft biopsy samples) from four organs, we identified a common rejection module (CRM) consisting of 11 genes that were significantly overexpressed in acute rejection (AR) across all transplanted organs. The CRM genes could diagnose AR with high specificity and sensitivity in three additional independent cohorts (794 samples). In another two independent cohorts (151 renal transplant biopsies), the CRM genes correlated with the extent of graft injury and predicted future injury to a graft using protocol biopsies. Inferred drug mechanisms from the literature suggested that two FDA-approved drugs (atorvastatin and dasatinib), approved for nontransplant indications, could regulate specific CRM genes and reduce the number of graft-infiltrating cells during AR. We treated mice with HLA-mismatched mouse cardiac transplant with atorvastatin and dasatinib and showed reduction of the CRM genes, significant reduction of graft-infiltrating cells, and extended graft survival. We further validated the beneficial effect of atorvastatin on graft survival by retrospective analysis of electronic medical records of a single-center cohort of 2,515 renal transplant patients followed for up to 22 yr. In conclusion, we identified a CRM in transplantation that provides new opportunities for diagnosis, drug repositioning, and rational drug design. PMID:24127489

  14. 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

  15. 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.

  16. 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)

  17. 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.

  18. 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

  19. 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.

  20. Differentially organized top-down modulation of prepulse inhibition of startle.

    PubMed

    Du, Yi; Wu, Xihong; Li, Liang

    2011-09-21

    Prepulse inhibition (PPI) of startle is the suppression of the startle reflex when a weaker sensory stimulus (the prepulse) shortly precedes the startling stimulus. PPI can be attentionally enhanced in both humans and laboratory animals. This study investigated whether the following three forebrain structures, which are critical for initial cortical processing of auditory signals, auditory fear conditioning/memories, and spatial attention, respectively, play a role in the top-down modulation of PPI in rats: the primary auditory cortex (A1), lateral nucleus of the amygdala (LA), and posterior parietal cortex (PPC). The results show that, under the noise-masking condition, PPI was enhanced by fear conditioning of the prepulse in a prepulse-specific manner, and the conditioning-induced PPI enhancement was further increased by perceptual separation between the conditioned prepulse and the noise masker. Reversibly blocking glutamate receptors in the A1 with 2 mm kynurenic acid eliminated both the conditioning-induced and perceptual separation-induced PPI enhancements. Blocking the LA eliminated the conditioning-induced but not the perceptual separation-induced PPI enhancement, and blocking the PPC specifically eliminated the perceptual separation-induced PPI enhancement. The two types of PPI enhancements were also eliminated by the extinction manipulation. Thus, the top-down modulation of PPI is differentially organized and depends on operations of various forebrain structures. Due to the fine-tuned modulation by higher-order cognitive processes, functions of PPI can be more flexible to complex environments. The top-down enhancements of PPI in rats are also useful for modeling some mental disorders, such as schizophrenia, attention deficit/hyperactivity disorder, and posttraumatic stress disorder. PMID:21940455

  1. 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.

  2. C. elegans ADAMTS ADT-2 regulates body size by modulating TGFβ signaling and cuticle collagen organization

    PubMed Central

    Fernando, Thilini; Flibotte, Stephane; Xiong, Sheng; Yin, Jianghua; Yzeiraj, Edlira; Moerman, Donald G.; Meléndez, Alicia; Savage-Dunn, Cathy

    2011-01-01

    Organismal growth and body size are influenced by both genetic and environmental factors. We have utilized the strong molecular genetic techniques available in the nematode C. elegans to identify genetic determinants of body size. In C. elegans, DBL-1, a member of the conserved family of secreted growth factors known as the Transforming Growth Factor β superfamily, is known to play a major role in growth control. The mechanisms by which other determinants of body size function, however, is less well understood. To identify additional genes involved in body size regulation, a genetic screen for small mutants was previously performed. One of the genes identified in that screen was sma-21. We now demonstrate that sma-21 encodes ADT-2, a member of the ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs) family of secreted metalloproteases. ADAMTS proteins are believed to remodel the extracellular matrix and may modulate the activity of extracellular signals. Genetic interactions suggest that ADT-2 acts in parallel with or in multiple size regulatory pathways. We demonstrate that ADT-2 is required for normal levels of expression of a DBL-1-responsive transcriptional reporter. We further demonstrate that adt-2 regulatory sequences drive expression in glial-like and vulval cells, and that ADT-2 activity is required for normal cuticle collagen fibril organization. We therefore propose that ADT-2 regulates body size both by modulating TGFβ signaling activity and by maintaining normal cuticle structure. PMID:21256840

  3. The feasibility of a regional CTDIvol to estimate organ dose from tube current modulated CT exams

    PubMed Central

    Khatonabadi, Maryam; Kim, Hyun J.; Lu, Peiyun; McMillan, Kyle L.; Cagnon, Chris H.; DeMarco, John J.; McNitt-Gray, Michael F.

    2013-01-01

    Purpose: In AAPM Task Group 204, the size-specific dose estimate (SSDE) was developed by providing size adjustment factors which are applied to the Computed Tomography (CT) standardized dose metric, CTDIvol. However, that work focused on fixed tube current scans and did not specifically address tube current modulation (TCM) scans, which are currently the majority of clinical scans performed. The purpose of this study was to extend the SSDE concept to account for TCM by investigating the feasibility of using anatomic and organ specific regions of scanner output to improve accuracy of dose estimates. Methods: Thirty-nine adult abdomen/pelvis and 32 chest scans from clinically indicated CT exams acquired on a multidetector CT using TCM were obtained with Institutional Review Board approval for generating voxelized models. Along with image data, raw projection data were obtained to extract TCM functions for use in Monte Carlo simulations. Patient size was calculated using the effective diameter described in TG 204. In addition, the scanner-reported CTDIvol (CTDIvol,global) was obtained for each patient, which is based on the average tube current across the entire scan. For the abdomen/pelvis scans, liver, spleen, and kidneys were manually segmented from the patient datasets; for the chest scans, lungs and for female models only, glandular breast tissue were segmented. For each patient organ doses were estimated using Monte Carlo Methods. To investigate the utility of regional measures of scanner output, regional and organ anatomic boundaries were identified from image data and used to calculate regional and organ-specific average tube current values. From these regional and organ-specific averages, CTDIvol values, referred to as regional and organ-specific CTDIvol, were calculated for each patient. Using an approach similar to TG 204, all CTDIvol values were used to normalize simulated organ doses; and the ability of each normalized dose to correlate with patient size

  4. Efficient terahertz-wave generation and its ultrafast optical modulation in charge ordered organic ferroelectrics

    SciTech Connect

    Itoh, Hirotake Iwai, Shinichiro; Itoh, Keisuke; Goto, Kazuki; Yamamoto, Kaoru; Yakushi, Kyuya

    2014-04-28

    Efficient terahertz (THz) wave generation in strongly correlated organic compounds α-(ET){sub 2}I{sub 3} and α′-(ET){sub 2}IBr{sub 2} (ET:bis(ethylenedithio)-tetrathiafulvalene) was demonstrated. The spontaneous polarization induced by charge ordering or electronic ferroelectricity was revealed to trigger the THz-wave generation via optical rectification; the estimated 2nd-order nonlinear optical susceptibility for α-(ET){sub 2}I{sub 3} is over 70 times larger than that for prototypical THz-source ZnTe. Ultrafast (<1 ps) and sensitive (∼40%) photoresponse of the THz wave was observed for α-(ET){sub 2}I{sub 3}, which is attributable to photoinduced quenching of the polarization accompanied by insulator(ferroelectric)-to-metal transition. Modulation of the THz wave was observed for α′-(ET){sub 2}IBr{sub 2} upon the poling procedure, indicating the alignment of polar domains.

  5. 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.

  6. 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.

  7. High temporal resolution for multislice helical computed tomography.

    PubMed

    Taguchi, K; Anno, H

    2000-05-01

    Multislice helical computed tomography (CT) substantially reduces scanning time. However, the temporal resolution of individual images is still insufficient for imaging rapidly moving organs such as the heart and adjacent pulmonary vessels. It may, in some cases, be worse than with current single-slice helical CT. The purpose of this study is to describe a novel image reconstruction algorithm to improve temporal resolution in multislice helical CT, and to evaluate its performance against existing algorithms. The proposed image reconstruction algorithm uses helical interpolation followed by data weighting based on the acquisition time. The temporal resolution, the longitudinal (z-axis) spatial resolution, the image noise, and the in-plane image artifacts created by a moving phantom were compared with those from the basic multislice helical reconstruction (helical filter interpolation, HFI) algorithm and the basic single-slice helical reconstruction algorithm (180 degrees linear interpolation, 180LI) using computer simulations. Computer simulation results were verified with CT examinations of the heart and lung vasculature using a 0.5 second multislice scanner. The temporal resolution of HFI algorithm varies from 0.28 and 0.86 s, depending on helical pitch. The proposed method improves the resolution to a constant value of 0.29 s, independent of pitch, allowing moving objects to be imaged with reduced blurring or motion artifacts. The spatial (z) resolution was slightly worse than with the HFI algorithm; the image noise was worse than with the HFI algorithm but was comparable to axial (step-and-shoot) CT. The proposed method provided sharp images of the moving objects, portraying the anatomy accurately. The proposed algorithm for multislice helical CT allowed us to obtain CT images with high temporal resolution. It may improve the image quality of clinical cardiac, lung, and vascular CT imaging. PMID:10841388

  8. Development of an Organic Rankine-Cycle power module for a small community solar thermal power experiment

    NASA Technical Reports Server (NTRS)

    Kiceniuk, T.

    1985-01-01

    An organic Rankine-cycle (ORC) power module was developed for use in a multimodule solar power plant to be built and operated in a small community. Many successful components and subsystems, including the reciever, power conversion subsystem, energy transport subsystem, and control subsystem, were tested. Tests were performed on a complete power module using a test bed concentrator in place of the proposed concentrator. All major single-module program functional objectives were met and the multimodule operation presented no apparent problems. The hermetically sealed, self-contained, ORC power conversion unit subsequently successfully completed a 300-hour endurance run with no evidence of wear or operating problems.

  9. Variation in the helical structure of native collagen.

    PubMed

    Orgel, Joseph P R O; Persikov, Anton V; Antipova, Olga

    2014-01-01

    The structure of collagen has been a matter of curiosity, investigation, and debate for the better part of a century. There has been a particularly productive period recently, during which much progress has been made in better describing all aspects of collagen structure. However, there remain some questions regarding its helical symmetry and its persistence within the triple-helix. Previous considerations of this symmetry have sometimes confused the picture by not fully recognizing that collagen structure is a highly complex and large hierarchical entity, and this affects and is effected by the super-coiled molecules that make it. Nevertheless, the symmetry question is not trite, but of some significance as it relates to extracellular matrix organization and cellular integration. The correlation between helical structure in the context of the molecular packing arrangement determines which parts of the amino acid sequence of the collagen fibril are buried or accessible to the extracellular matrix or the cell. In this study, we concentrate primarily on the triple-helical structure of fibrillar collagens I and II, the two most predominant types. By comparing X-ray diffraction data collected from type I and type II containing tissues, we point to evidence for a range of triple-helical symmetries being extant in the molecules native environment. The possible significance of helical instability, local helix dissociation and molecular packing of the triple-helices is discussed in the context of collagen's supramolecular organization, all of which must affect the symmetry of the collagen triple-helix. PMID:24586843

  10. 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.

  11. Dosimetric comparison of helical tomothearpy and linac-based IMRT in whole abdomen radiotherapy

    NASA Astrophysics Data System (ADS)

    Kang, Young-nam; Kim, Dae-Hyun; Jang, Hong Seok; Song, Jin Ho; Choi, Byung Ock; Cho, Seok Goo; Jung, Ji-Young; Kay, Chul Seung

    2012-10-01

    Recent advances in radiotherapy techniques have allowed a significant improvement in the therapeutic ratio of whole abdominal irradiation (WAI) through linear-accelerator (Linac) based intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT). IMRT has been shown to reduce the dose to organs at risk (OAR) while adequately treating the tumor volume. HT operates by adjusting 51 beam directions, couch speed, pitch and shapes of a binary multileaf collimator (MLC), with the purpose of clinically increasing the befit to the patient. We incorporated helical tomotherapy as a new modality for WAI for the treatment of non-Hodgkin's lymphoma patients whose disease involved the intestine and the mesenteric lymph nodes. Excellent tumor coverage with effective sparing of normal organ sparings, and homogeneous dose distribution could be achieved. This study dosimetrically compared HT and linac-based IMRT by using several indices, including the conformity index (CI) and the homogeneity index (HI) for the planning target volume (PTV), as well as the, max dose and the mean dose and the quality index (QI) for five organs at risk (OARs). The HI and the CI were used to compare the quality of target coverage while the QI was used compare the dosimetric performans for OAR systems. The target coverages between the two systems were similar, but the most QIs were lower than 1, what means that HT is batter at sparing OARs than IMRT. Tomotherapy enabled excellent target coverage, effective sparing of normal tissues, and homogeneous dose distribution without severe acute toxicity.

  12. Light Modulates the Biosynthesis and Organization of Cyanobacterial Carbon Fixation Machinery through Photosynthetic Electron Flow.

    PubMed

    Sun, Yaqi; Casella, Selene; Fang, Yi; Huang, Fang; Faulkner, Matthew; Barrett, Steve; Liu, Lu-Ning

    2016-05-01

    Cyanobacteria have evolved effective adaptive mechanisms to improve photosynthesis and CO2 fixation. The central CO2-fixing machinery is the carboxysome, which is composed of an icosahedral proteinaceous shell encapsulating the key carbon fixation enzyme, Rubisco, in the interior. Controlled biosynthesis and ordered organization of carboxysomes are vital to the CO2-fixing activity of cyanobacterial cells. However, little is known about how carboxysome biosynthesis and spatial positioning are physiologically regulated to adjust to dynamic changes in the environment. Here, we used fluorescence tagging and live-cell confocal fluorescence imaging to explore the biosynthesis and subcellular localization of β-carboxysomes within a model cyanobacterium, Synechococcus elongatus PCC7942, in response to light variation. We demonstrated that β-carboxysome biosynthesis is accelerated in response to increasing light intensity, thereby enhancing the carbon fixation activity of the cell. Inhibition of photosynthetic electron flow impairs the accumulation of carboxysomes, indicating a close coordination between β-carboxysome biogenesis and photosynthetic electron transport. Likewise, the spatial organization of carboxysomes in the cell correlates with the redox state of photosynthetic electron transport chain. This study provides essential knowledge for us to modulate the β-carboxysome biosynthesis and function in cyanobacteria. In translational terms, the knowledge is instrumental for design and synthetic engineering of functional carboxysomes into higher plants to improve photosynthesis performance and CO2 fixation. PMID:26956667

  13. Fabry-Perot Interferometer-Based Electrooptic Modulator using LiNbO3 and Organic Thin Films

    NASA Technical Reports Server (NTRS)

    Banks, C.; Frazier, D.; Penn, B.; Abdeldayem, H.; Sharma, A.; Yelleswarapu, C.; Leyderman, Alexander; Correa, Margarita; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    We report the study of a Fabry-Perot electro-optical modulator using thin crystalline film NPP, and Crystalline LiNbO3. We are able to observe 14, and 60 percent degree of modulation. Measurements were carried using a standard lock-in amplifier with a silicon detector. The proposal to design a Fabry-Perot electro-optic modulator with an intracavity electro-optically active organic material was based on the initial results using poled polymer thin films. The main feature of the proposed device is the observation that in traditional electrooptic modulators like a Packets cell, it requires few kilovolts of driving voltage to cause a 3 dB modulation even in high figure-of-merit electrooptic materials like LiNbO3. The driving voltage for the modulator can be reduced to as low as 10 volts by introducing the electrooptic material inside die resonant cavity of a Fabry-Perot modulator. This is because the transmission of the Fabry-Perot cavity varies nonlinearly with the change of refractive index or phase of light due to applied electric field.

  14. 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.

  15. 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

  16. 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

  17. Design principles for Bernal spirals and helices with tunable pitch

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    Using the framework of potential energy landscape theory, we describe two in silico designs for self-assembling helical colloidal superstructures based upon dipolar dumbbells and Janus-type building blocks, respectively. Helical superstructures with controllable pitch length are obtained using external magnetic field driven assembly of asymmetric dumbbells involving screened electrostatic as well as magnetic dipolar interactions. The pitch of the helix is tuned by modulating the Debye screening length over an experimentally accessible range. The second design is based on building blocks composed of rigidly linked spheres with short-range anisotropic interactions, which are predicted to self-assemble into Bernal spirals. These spirals are quite flexible, and longer helices undergo rearrangements via cooperative, hinge-like moves, in agreement with experiment.Using the framework of potential energy landscape theory, we describe two in silico designs for self-assembling helical colloidal superstructures based upon dipolar dumbbells and Janus-type building blocks, respectively. Helical superstructures with controllable pitch length are obtained using external magnetic field driven assembly of asymmetric dumbbells involving screened electrostatic as well as magnetic dipolar interactions. The pitch of the helix is tuned by modulating the Debye screening length over an experimentally accessible range. The second design is based on building blocks composed of rigidly linked spheres with short-range anisotropic interactions, which are predicted to self-assemble into Bernal spirals. These spirals are quite flexible, and longer helices undergo rearrangements via cooperative, hinge-like moves, in agreement with experiment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00324a

  18. Organization of the polarization splay modulated smectic liquid crystal phase by topographic confinement

    PubMed Central

    Ki Yoon, Dong; Deb, Rajdeep; Chen, Dong; Körblova, Eva; Shao, Renfan; Ishikawa, Ken; Rao, Nandiraju V. S.; Walba, David M.; Smalyukh, Ivan I.; Clark, Noel A.

    2010-01-01

    Recently, the topographic patterning of surfaces by lithography and nanoimprinting has emerged as a new and powerful tool for producing single structural domains of liquid crystals and other soft materials. Here the use of surface topography is extended to the organization of liquid crystals of bent-core molecules, soft materials that, on the one hand, exhibit a rich, exciting, and intensely studied array of novel phases, but that, on the other hand, have proved very difficult to align. Among the most notorious in this regard are the polarization splay modulated (B7) phases, in which the symmetry-required preference for ferroelectric polarization to be locally bouquet-like or “splayed” is expressed. Filling space with splay of a single sign requires defects and in the B7 splay is accommodated in the form of periodic splay stripes spaced by defects and coupled to smectic layer undulations. Upon cooling from the isotropic phase this structure grows via a first order transition in the form of an exotic array of twisted filaments and focal conic defects that are influenced very little by classic alignment methods. By contrast, growth under conditions of confinement in rectangular topographic channels is found to produce completely new growth morphology, generating highly ordered periodic layering patterns. The resulting macroscopic order will be of great use in further exploration of the physical properties of bent-core phases and offers a route for application of difficult-to-align soft materials as are encountered in organic electronic and optical applications. PMID:21098307

  19. Shaping organs by a wingless-int/Notch/nonmuscle myosin module which orients feather bud elongation.

    PubMed

    Li, Ang; Chen, Meng; Jiang, Ting-Xin; Wu, Ping; Nie, Qing; Widelitz, Randall; Chuong, Cheng-Ming

    2013-04-16

    How organs are shaped to specific forms is a fundamental issue in developmental biology. To address this question, we used the repetitive, periodic pattern of feather morphogenesis on chicken skin as a model. Avian feathers within a single tract extend from dome-shaped primordia to thin conical structures with a common axis of orientation. From a systems biology perspective, the process is precise and robust. Using tissue transplantation assays, we demonstrate that a "zone of polarizing activity," localized in the posterior feather bud, is necessary and sufficient to mediate the directional elongation. This region contains a spatially well-defined nuclear β-catenin zone, which is induced by wingless-int (Wnt)7a protein diffusing in from posterior bud epithelium. Misexpressing nuclear β-catenin randomizes feather polarity. This dermal nuclear β-catenin zone, surrounded by Notch1 positive dermal cells, induces Jagged1. Inhibition of Notch signaling disrupts the spatial configuration of the nuclear β-catenin zone and leads to randomized feather polarity. Mathematical modeling predicts that lateral inhibition, mediated by Notch signaling, functions to reduce Wnt7a gradient variations and fluctuations to form the sharp boundary observed for the dermal β-catenin zone. This zone is also enriched for nonmuscle myosin IIB. Suppressing nonmuscle myosin IIB disrupts directional cell rearrangements and abolishes feather bud elongation. These data suggest that a unique molecular module involving chemical-mechanical coupling converts a pliable chemical gradient to a precise domain, ready for subsequent mechanical action, thus defining the position, boundary, and duration of localized morphogenetic activity that molds the shape of growing organs. PMID:23576731

  20. Shaping organs by a wingless-int/Notch/nonmuscle myosin module which orients feather bud elongation

    PubMed Central

    Li, Ang; Chen, Meng; Jiang, Ting-Xin; Wu, Ping; Nie, Qing; Widelitz, Randall; Chuong, Cheng-Ming

    2013-01-01

    How organs are shaped to specific forms is a fundamental issue in developmental biology. To address this question, we used the repetitive, periodic pattern of feather morphogenesis on chicken skin as a model. Avian feathers within a single tract extend from dome-shaped primordia to thin conical structures with a common axis of orientation. From a systems biology perspective, the process is precise and robust. Using tissue transplantation assays, we demonstrate that a “zone of polarizing activity,” localized in the posterior feather bud, is necessary and sufficient to mediate the directional elongation. This region contains a spatially well-defined nuclear β-catenin zone, which is induced by wingless-int (Wnt)7a protein diffusing in from posterior bud epithelium. Misexpressing nuclear β-catenin randomizes feather polarity. This dermal nuclear β-catenin zone, surrounded by Notch1 positive dermal cells, induces Jagged1. Inhibition of Notch signaling disrupts the spatial configuration of the nuclear β-catenin zone and leads to randomized feather polarity. Mathematical modeling predicts that lateral inhibition, mediated by Notch signaling, functions to reduce Wnt7a gradient variations and fluctuations to form the sharp boundary observed for the dermal β-catenin zone. This zone is also enriched for nonmuscle myosin IIB. Suppressing nonmuscle myosin IIB disrupts directional cell rearrangements and abolishes feather bud elongation. These data suggest that a unique molecular module involving chemical–mechanical coupling converts a pliable chemical gradient to a precise domain, ready for subsequent mechanical action, thus defining the position, boundary, and duration of localized morphogenetic activity that molds the shape of growing organs. PMID:23576731

  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. The silicatein propeptide acts as inhibitor/modulator of self-organization during spicule axial filament formation.

    PubMed

    Müller, Werner E G; Schröder, Heinz C; Muth, Sandra; Gietzen, Sabine; Korzhev, Michael; Grebenjuk, Vlad A; Wiens, Matthias; Schloßmacher, Ute; Wang, Xiaohong

    2013-04-01

    Silicateins are crucial enzymes that are involved in formation of the inorganic biosilica scaffold of the spicular skeleton of siliceous sponges. We show that silicatein acquires its structure-guiding and enzymatically active state by processing of silicatein from pro-silicatein to the mature enzyme. A recombinant propeptide (PROP) of silicatein from the siliceous demosponge Suberites domuncula was prepared, and antibodies were raised against the peptide. In sponge tissue, these antibodies reacted with both surface structures and the central region of the spicules. Using phage display expression, spicule-binding 12-mer peptides were identified that are rich in histidine residues. In the predicted tertiary structure of PROP, these histidine residues are only present in the α-helical region. The recombinant PROP was found to inhibit self-assembly of silicatein molecules. By light scattering, it was shown that, in the presence of 4 m urea, the recombinant silicatein is obtained in the mono/oligomeric form with a hydrodynamic radius of 4 nm, while lower urea concentrations promote self-aggregation and assembly of the protein. Finally, it is shown that the enzymatic activity of silicatein is abolished by PROP in silicatein samples that predominantly contain mono- or oligomeric silicatein particles, but the enzyme is not affected if present in the filamentous aggregated form. It is concluded that the functions of silicatein, acting as a structural template for its biosilica product and as an enzyme, are modulated and controlled by its propeptide. PMID:23398942

  3. Highly efficient low color temperature organic LED using blend carrier modulation layer

    NASA Astrophysics Data System (ADS)

    Hsieh, Yao-Ching; Chen, Szu-Hao; Shen, Shih-Ming; Wang, Ching-Chiun; Chen, Chien-Chih; Jou, Jwo-Huei

    2012-10-01

    Color temperature (CT) of light has great effect on human physiology and psychology, and low CT light, minimizing melatonin suppression and decreasing the risk of breast, colorectal, and prostate cancer. We demonstrates the incorporation of a blend carrier modulation interlayer (CML) between emissive layers to improve the device performance of low CT organic light emitting diodes, which exhibits an external quantum efficiency of 22.7% and 36 lm W-1 (54 cd A-1) with 1880 K at 100 cd m-2, or 20.8% and 29 lm W-1 (50 cd A-1) with 1940 K at 1000 cd m-2. The result shows a CT much lower than that of incandescent bulbs, which is 2500 K with 15 lmW-1 efficiency, and even as low as that of candles, which is 2000 K with 0.1 lmW-1. The high efficiency of the proposed device may be attributed to its CML, which helps effectively distribute the entering carriers into the available recombination zones.

  4. Activation of Aurora-A is essential for neuronal migration via modulation of microtubule organization.

    PubMed

    Takitoh, Takako; Kumamoto, Kanako; Wang, Chen-Chi; Sato, Makoto; Toba, Shiori; Wynshaw-Boris, Anthony; Hirotsune, Shinji

    2012-08-01

    Neuronal migration is a critical feature to ensure proper location and wiring of neurons during cortical development. Postmitotic neurons migrate from the ventricular zone into the cortical plate to establish neuronal lamina in an "inside-out" gradient of maturation. Here, we report that the mitotic kinase Aurora-A is critical for the regulation of microtubule organization during neuronal migration via an Aurora-A-NDEL1 pathway in the mouse. Suppression of Aurora-A activity by inhibitors or siRNA resulted in severe impairment of neuronal migration of granular neurons. In addition, in utero injection of the Aurora-A kinase-dead mutant provoked defective migration of cortical neurons. Furthermore, we demonstrated that suppression of Aurora-A impaired microtubule modulation in migrating neurons. Interestingly, suppression of CDK5 by an inhibitor or siRNA reduced Aurora-A activity and NDEL1 phosphorylation by Aurora-A, which led to defective neuronal migration. We found that CDK5RAP2 is a key molecule that mediates functional interaction and is essential for centrosomal targeting of Aurora-A. Our observations demonstrated novel and surprising cross talk between Aurora-A and CDK5 during neuronal migration. PMID:22875938

  5. Constraints on Sensitivity to Auditory Modulation in the Perceptual Organization of Speech

    PubMed Central

    Remez, Robert E.; Thomas, Emily F.; Wycoff, Andrea M.; Giglio, Rebecca E.; Crank, Aislinn T.; Cheimets, Chloe B.; Koinis, Stavroula M.

    2015-01-01

    Background The perception of speech requires the integration of sensory details from a rapidly fading trace of a time-varying spectrum. This effortful cognitive function has been difficult to assess. New tests measuring intelligibility of sine-wave replicas of speech provided an assay of this critical function in normal hearing young adults. Method Four time-varying sinusoids replicated the frequency and amplitude variation of the natural resonances of spoken sentences. The temporal tolerance of perceptual integration of speech was measured by determining the effect on intelligibility of desynchronizing a single sine-wave component in each sentence. This method was applied in tests in which the sentences were temporally compressed or expanded over a 40% range. Results Desynchrony was harmful to perceptual integration over a narrow temporal range, indicating that modulation sensitivity is keyed to a rate of 20 Hz. No effect of variation in speech rate was observed on the intelligibility measure, whether rate was accelerated or decelerated relative to the natural rate. Conclusion Performance measures of desynchrony tolerance did not vary when speech rate was accelerated or decelerated, revealing constraints on integration that are arguably primitive, sensory, auditory, and fixed. Because these are not adaptable, they limit the potential for perceptual learning in this aspect of perceptual organization. Implications for describing the elderly listener are noted. PMID:26683038

  6. 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

  7. A fixed-jaw method to protect critical organs during intensity-modulated radiotherapy

    SciTech Connect

    Chen, Jiayun; Chen, Xinyuan; Huang, Manni; Dai, Jianrong

    2014-01-01

    Intensity-modulated radiotherapy (IMRT) plays an important role in cancer radiotherapy. For some patients being treated with IMRT, the extremely low tolerances of critical organs (such as lens, ovaries, and testicles) cannot be met during treatment planning. The aim of this article is to introduce a new planning method to overcome that problem. In current planning practice, jaw positions are automatically set to cover all target volumes by the planning system (e.g., Pinnacle{sup 3} system). Because of such settings, critical organs may be fully blocked by the multileaf collimator (MLC), but they still sit in the field that is shaped by collimator jaws. These critical organs receive doses from the transmission and leakage of MLC leaves. We manually fixed jaw positions to block them to further reduce such doses. This method has been used for different treatment sites in our clinic, and it was thoroughly evaluated in patients with radical hysterectomy plus ovarian transposition after surgery. For each patient, 2 treatment plans were designed with the same optimization parameters: the original plan with automatically chosen jaw positions (called O-plan) and the plan with fixed-jaw positions (named F-plan). In the F-plan, the jaws were manually fixed to block the ovaries. For target coverage, the mean conformity index (CI) of the F-plan (1.28 ± 0.02) was remarkably lower than that of the O-plan (1.53 ± 0.09) (p < 0.05). The F-plan and the O-plan performed similarly in target dose homogeneity. Meanwhile, for the critical organ sparing, the mean dose of both ovaries were much lower in the F-plan than that in the O-plan (p < 0.05). The V{sub 20}, V{sub 30}, and V{sub 40} of bladder were also lower in the F-plan (93.57 ± 1.98, 73.99 ± 5.76, and 42.33 ± 3.7, respectively) than those in the O-plan (97.98 ± 1.11, 85.07 ± 4.04, and 49.71 ± 3.63, respectively) (p < 0.05). The maximum dose to the spinal cord planning organ at risk (OAR) volume (PRV) in the O-plan (3940

  8. Dose as a Function of Lung Volume and Planned Treatment Volume in Helical Tomotherapy Intensity-Modulated Radiation Therapy-Based Stereotactic Body Radiation Therapy for Small Lung Tumors

    SciTech Connect

    Baisden, Joseph M.; Romney, Davis A.; Reish, Andrew G.; Cai Jing; Sheng Ke; Jones, David R.; Benedict, Stanley H.; Read, Paul W.; Larner, James M. . E-mail: JML2P@virginia.edu

    2007-07-15

    Purpose: To evaluate the limitations of Hi-Art Helical Tomotherapy (Middleton, WI) stereotactic body radiotherapy (SBRT) for lung lesions, and to provide an initial report on patients treated with this method. Stereotactic body radiotherapy was shown to be an effective, well-tolerated treatment for early-stage, non-small-cell lung carcinoma (NSCLC). The Radiation Therapy Oncology Group (RTOG) 0236 protocol is currently evaluating three-dimensional conformal SBRT that delivers 60 Gy in three fractions. Methods and Materials: Inverse treatment planning for hypothetical lung gross tumor volumes (GTV) and planned treatment volume (PTV) expansions were performed. We tested the hypothesis that the maximum acceptable dose (MAD) to be delivered to the lesion by SBRT could be predicted by PTV and lung volume. Dose constraints on normal tissue were as designated by the RTOG protocol. Inverse planning was performed to find the maximum tolerated SBRT dose up to 60 Gy. Results: Regression analysis of the data obtained indicated a linear relationship between MAD, PTV, and lung volume. This generated two equations which may be useful predictive tools. Seven patients with Stage I and II NSCLC treated at University of Virginia with this method tolerated the treatment extremely well, and suffered no greater than grade I toxicity, with no evidence of disease recurrence in follow-up from 2-20 months. Conclusions: Helical tomotherapy SBRT for lung lesions is well-tolerated. In addition, the likely MAD for patients considered for this type of treatment can be predicted by PTV and lung volume.

  9. Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility.

    PubMed

    Cai, Yunsong; Guo, Zhiqian; Chen, Jianmei; Li, Wenlong; Zhong, Liubiao; Gao, Ya; Jiang, Lin; Chi, Lifeng; Tian, He; Zhu, Wei-Hong

    2016-02-24

    Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA. PMID:26709946

  10. GABAergic modulation of serotonin release in the rat subfornical organ area.

    PubMed

    Takahashi, Makoto; Nomura, Masahiko; Tanaka, Junichi

    2016-09-01

    The present study was carried out to examine whether γ-aminobutyric acid (GABA) receptor mechanisms are involved in the release of serotonin (5-hydroxytryptamine, 5-HT) in the subfornical organ (SFO) using intracerebral microdialysis techniques. Perfusion with the GABA receptor antagonists as well as agonists was performed in the region of the SFO through a microdialysis probe and extracellular concentrations of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) were measured in freely moving rats. Perfusion with the GABAA receptor antagonist bicuculline (10 and 50μM), but not the GABAB receptor antagonist phaclofen (10 and 50μM), increased dialysate 5-HT and 5-HIAA concentrations in the SFO area, suggesting that the GABAergic system may tonically inhibit the 5-HT release in the SFO area through GABAA receptors. Higher perfusion with the GABAA receptor agonist muscimol (50μM) or the GABAB receptor agonist baclofen (250μM) decreased extracellular levels of 5-HT and 5-HIAA in the SFO area. Nonhypotensive hypovolemia induced by subcutaneous injection of polyethylene glycol (PEG, 30%, 5ml) significantly enhanced the 5-HT and 5-HIAA concentrations in the SFO area. The enhanced 5-HT and 5-HIAA levels elicited the PEG treatment were reduced by perfusion with muscimol (10μM), but not by baclofen (50μM). These results show the involvement of both GABAA and GABAB receptors in the modulation of the 5-HT release in the SFO area, and imply that the GABAA receptor mechanism may be importance for the serotonergic regulatory system of body fluid balance. PMID:27453060

  11. 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.

  12. 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.

  13. 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.

  14. Temporary organ displacement coupled with image-guided, intensity-modulated radiotherapy for paraspinal tumors

    PubMed Central

    2013-01-01

    Background To investigate the feasibility and dosimetric improvements of a novel technique to temporarily displace critical structures in the pelvis and abdomen from tumor during high-dose radiotherapy. Methods Between 2010 and 2012, 11 patients received high-dose image-guided intensity-modulated radiotherapy with temporary organ displacement (TOD) at our institution. In all cases, imaging revealed tumor abutting critical structures. An all-purpose drainage catheter was introduced between the gross tumor volume (GTV) and critical organs at risk (OAR) and infused with normal saline (NS) containing 5-10% iohexol. Radiation planning was performed with the displaced OARs and positional reproducibility was confirmed with cone-beam CT (CBCT). Patients were treated within 36 hours of catheter placement. Radiation plans were re-optimized using pre-TOD OARs to the same prescription and dosimetrically compared with post-TOD plans. A two-tailed permutation test was performed on each dosimetric measure. Results The bowel/rectum was displaced in six patients and kidney in four patients. One patient was excluded due to poor visualization of the OAR; thus 10 patients were analyzed. A mean of 229 ml (range, 80–1000) of NS 5-10% iohexol infusion resulted in OAR mean displacement of 17.5 mm (range, 7–32). The median dose prescribed was 2400 cGy in one fraction (range, 2100–3000 in 3 fractions). The mean GTV Dmin and PTV Dmin pre- and post-bowel TOD IG-IMRT dosimetry significantly increased from 1473 cGy to 2086 cGy (p=0.015) and 714 cGy to 1214 cGy (p=0.021), respectively. TOD increased mean PTV D95 by 27.14% of prescription (p=0.014) while the PTV D05 decreased by 9.2% (p=0.011). TOD of the bowel resulted in a 39% decrease in mean bowel Dmax (p=0.008) confirmed by CBCT. TOD of the kidney significantly decreased mean kidney dose and Dmax by 25% (0.022). Conclusions TOD was well tolerated, reproducible, and facilitated dose escalation to previously radioresistant tumors

  15. Information Identification and Organization. Student Study Guide. Module III: Information Types and Sources.

    ERIC Educational Resources Information Center

    Bolvin, Boyd M.; Dupras, Rheba

    This third module, in a three module program, begins with a discussion of basic reference sources such as dictionaries, encyclopedias, almanacs, atlases, and periodical indexes. It then describes the uses of special Alaska resources such as Alaska Almanac, Alaska Blue Book, Milepost, Education Directory, AULS (Alaska Union List of Serials), and…

  16. Winding light beams along elliptical helical trajectories

    NASA Astrophysics Data System (ADS)

    Wen, Yuanhui; Chen, Yujie; Zhang, Yanfeng; Chen, Hui; Yu, Siyuan

    2016-07-01

    Conventional caustic methods in real or Fourier space produced accelerating optical beams only with convex trajectories. We developed a superposition caustic method capable of winding light beams along nonconvex trajectories. We ascertain this method by constructing a one-dimensional (1D) accelerating beam moving along a sinusoidal trajectory, and subsequently extending to two-dimensional (2D) accelerating beams along arbitrarily elliptical helical trajectories. We experimentally implemented the method with a compact and robust integrated optics approach by fabricating micro-optical structures on quartz glass plates to perform the spatial phase and amplitude modulation to the incident light, generating beam trajectories highly consistent with prediction. The theoretical and implementation methods can in principle be extended to the construction of accelerating beams with a wide variety of nonconvex trajectories, thereby opening up a route of manipulating light beams for fundamental research and practical applications.

  17. 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.

  18. 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.

  19. Test results of an organic Rankine-cycle power module for a small community solar thermal power experiment

    NASA Technical Reports Server (NTRS)

    Clark, T. B.

    1985-01-01

    The organic Rankine-cycle (ORC) power conversion assembly was tested. Qualification testing of the electrical transport subsystem was also completed. Test objectives were to verify compatibility of all system elements with emphasis on control of the power conversion assembly, to evaluate the performance and efficiency of the components, and to validate operating procedures. After 34 hours of power generation under a wide range of conditions, the net module efficiency exceeded 18% after accounting for all parasitic losses.

  20. 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.

  1. 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

  2. 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.

  3. Intra-helical salt-bridge and helix destabilizing residues within the same helical turn: Role of functionally important loop E half-helix in channel regulation of major intrinsic proteins.

    PubMed

    Verma, Ravi Kumar; Prabh, Neel Duti; Sankararamakrishnan, Ramasubbu

    2015-06-01

    The superfamily of major intrinsic proteins (MIPs) includes aquaporin (AQP) and aquaglyceroporin (AQGP) and it is involved in the transport of water and neutral solutes across the membrane. Diverse MIP sequences adopt a unique hour-glass fold with six transmembrane helices (TM1 to TM6) and two half-helices (LB and LE). Loop E contains one of the two conserved NPA motifs and contributes two residues to the aromatic/arginine selectivity filter. Function and regulation of majority of MIP channels are not yet characterized. We have analyzed the loop E region of 1468 MIP sequences and their structural models from six different organism groups. They can be phylogenetically clustered into AQGPs, AQPs, plant MIPs and other MIPs. The LE half-helix in all AQGPs contains an intra-helical salt-bridge and helix-breaking residues Gly/Pro within the same helical turn. All non-AQGPs lack this salt-bridge but have the helix destabilizing Gly and/or Pro in the same positions. However, the segment connecting LE half-helix and TM6 is longer by 10-15 residues in AQGPs compared to all non-AQGPs. We speculate that this longer loop in AQGPs and the LE half-helix of non-AQGPs will be relatively more flexible and this could be functionally important. Molecular dynamics simulations on glycerol-specific GlpF, water-transporting AQP1, its mutant and a fungal AQP channel confirm these predictions. Thus two distinct regions of loop E, one in AQGPs and the other in non-AQGPs, seem to be capable of modulating the transport. These regions can also act in conjunction with other extracellular residues/segments to regulate MIP channel transport. PMID:25797519

  4. Self-assembly of magnetite nanocubes into helical superstructures.

    PubMed

    Singh, Gurvinder; Chan, Henry; Baskin, Artem; Gelman, Elijah; Repnin, Nikita; Král, Petr; Klajn, Rafal

    2014-09-01

    Organizing inorganic nanocrystals into complex architectures is challenging and typically relies on preexisting templates, such as properly folded DNA or polypeptide chains. We found that under carefully controlled conditions, cubic nanocrystals of magnetite self-assemble into arrays of helical superstructures in a template-free manner with >99% yield. Computer simulations revealed that the formation of helices is determined by the interplay of van der Waals and magnetic dipole-dipole interactions, Zeeman coupling, and entropic forces and can be attributed to spontaneous formation of chiral nanocube clusters. Neighboring helices within their densely packed ensembles tended to adopt the same handedness in order to maximize packing, thus revealing a novel mechanism of symmetry breaking and chirality amplification. PMID:25061133

  5. Low Cost, Light Weight SOlar Modules Based on Organic Photovoltaic Technology

    SciTech Connect

    Russell Gaudiana; David GInley; Robert Birkmeyer

    2009-09-20

    Objectives - In order to produce solar modules for rooftop applications the performance and the lifetime must be improved to 5% - 7% and >10 year life. Task 1 Stability - (1) Flexible modules are stable to 1000 hrs at 65 C/85%RH, (2) Flexible modules in glass are stable to >2000 hrs at 85 C/85%RH (no decrease in performance); (3) Adhesive + filler helps stabilize modules; and (4) Solution coatable barriers exhibit good WVTR; work in-progress. Task 2 Performance: n-type charge carriers - (1) N-type polymers could not be synthesized; and (2) More than 30 fullerene derivatives synthesized and tested, Several deep LUMO derivatives accept charge from deep LUMO polymers, higher voltage observed, Improvement in cell efficiency not observed, morphology problem. Task 3 Performance: grid electrode - (1) Exceeded flatness and roughness goals; (2) Exceeds sheet resistance goals; (3) Achieved %T goals; and (4) Performance equivalent to ITO - 2% Efficiency ( av.); work in-progress.

  6. 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.

  7. Structural Basis by Which Alternative Splicing Modulates the Organizer Activity of FGF8 in the Brain

    SciTech Connect

    Olsen,S.; Li, J.; Eliseenkova, A.; Ibrahimi, O.; Lao, Z.; Zhang, F.; Linhardt, R.; Joyner, A.; Mohammadi, M.

    2006-01-01

    Two of the four human FGF8 splice isoforms, FGF8a and FGF8b, are expressed in the mid-hindbrain region during development. Although the only difference between these isoforms is the presence of an additional 11 amino acids at the N terminus of FGF8b, these isoforms possess remarkably different abilities to pattern the midbrain and anterior hindbrain. To reveal the structural basis by which alternative splicing modulates the organizing activity of FGF8, we solved the crystal structure of FGF8b in complex with the 'c' splice isoform of FGF receptor 2 (FGFR2c). Using surface plasmon resonance (SPR), we also characterized the receptor-binding specificity of FGF8a and FGF8b, the 'b' isoform of FGF17 (FGF17b), and FGF18. The FGF8b-FGFR2c structure shows that alternative splicing permits a single additional contact between phenylalanine 32 (F32) of FGF8b and a hydrophobic groove within Ig domain 3 of the receptor that is also present in FGFR1c, FGFR3c, and FGFR4. Consistent with the structure, mutation of F32 to alanine reduces the affinity of FGF8b toward all these receptors to levels characteristic of FGF8a. More importantly, analysis of the mid-hindbrain patterning ability of the FGF8b{sup F32A} mutant in chick embryos and murine midbrain explants shows that this mutation functionally converts FGF8b to FGF8a. Moreover, our data suggest that the intermediate receptor-binding affinities of FGF17b and FGF18, relative to FGF8a and FGF8b, also account for the distinct patterning abilities of these two ligands. We also show that the mode of FGF8 receptor-binding specificity is distinct from that of other FGFs and provide the first biochemical evidence for a physiological FGF8b-FGFR1c interaction during mid-hindbrain development. Consistent with the indispensable role of FGF8 in embryonic development, we show that the FGF8 mode of receptor binding appeared as early as in nematodes and has been preserved throughout evolution.

  8. Functional tetrametallic linker modules for coordination polymers and metal-organic frameworks.

    PubMed

    Johansson, Frank B; Bond, Andrew D; McKenzie, Christine J

    2007-03-19

    The new biphenol-based tetranucleating ligand, 2,2',6,6'-tetrakis(N,N-bis(2-pyridylmethyl)aminomethyl)-4,4'-biphenolate, dbpbp2-, comprises two linearly disposed phenolato-hinged dinucleating heptadentate units, each of which offer one O and three N donors to a total of four metal ions. The ligand has been isolated as the zinc chloride complex [Zn4(dbpbp)Cl4]2+, and the ZnII ions have been completely or partially substituted by CuII, FeIII, CoII, and CoIII in metathesis reactions. Similarly, the chloride ligands of [Zn4(dbpbp)Cl4]2+ have been exchanged for solvent molecules (acetonitrile and/or water) and bridging carboxylate ligands. The resulting complexes have been characterized by single-crystal X-ray diffraction, ESI mass spectrometry (ESI-MS), cyclic voltammetry (CV), and EPR spectroscopy. The structures containing [M4(dbpbp)Cl4]2+ with M = ZnII or CuII exhibit 2-D polymeric honeycomb sheets in which intermolecular M...Cl interactions bridge between adjacent [M4(dbpbp)Cl4]2+ cations. Two mixed-metal tetrabenzoate complexes [M4(dbpbp)(O2CC6H5)4]2+/3+ have also been prepared, namely a stoichiometric CuII2ZnII2 complex and a nonstoichiometric FeIII/ZnII system. In the latter case, ESI-MS identifies FeZn3, Fe2Zn2, and Zn4 species, and X-ray crystallography suggests an average composition of Fe0.8Zn3.2. Preparation of a CoII4 complex by metathesis was considerably more difficult than preparation of [Cu4(dbpbp)Cl4]2+, requiring both a large excess of the cobalt source and the presence of auxiliary benzoate. In the presence of 2 equiv of benzoate per starting [Zn4(dbpbp)Cl4]2+ unit and excess CoII, dioxygen binds as peroxide at each end of the molecule to give the CoIII4 complex [Co4(dbpbp)(O2)2(O2CC6H5)2]4+. This latter complex, together with new tetra- and hexametallic benzenedicarboxylato- and benzenetricarboxylato-bridged complexes of dinuclear [Co2(O2)(bpbp)]3+ units (bpbp- = 2,6-bis(N,N-bis-(2-pyridylmethyl)aminomethyl)-4-tert-butyl-phenolate), is a module for

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Tetraspanin CD82 regulates bone marrow homing of acute myeloid leukemia by modulating the molecular organization of N-cadherin.

    PubMed

    Marjon, K D; Termini, C M; Karlen, K L; Saito-Reis, C; Soria, C E; Lidke, K A; Gillette, J M

    2016-08-01

    Communication between acute myeloid leukemia (AML) and the bone marrow microenvironment is known to control disease progression. Therefore, regulation of AML cell trafficking and adhesion to the bone marrow is of significant interest. In this study, we demonstrate that differential expression of the membrane scaffold CD82 modulates the bone marrow homing of AML cells. By combining mutational analysis and super-resolution imaging, we identify membrane protein clustering by CD82 as a regulator of AML cell adhesion and bone marrow homing. Cluster analysis of super-resolution data indicates that N-linked glycosylation and palmitoylation of CD82 are both critical modifications that control the microdomain organization of CD82 as well as the nanoscale clustering of associated adhesion protein, N-cadherin. We demonstrate that the inhibition of CD82 glycosylation increases the molecular packing of N-cadherin and promotes the bone marrow homing of AML cells. In contrast, we find that the inhibition of CD82 palmitoylation disrupts the formation and organization of N-cadherin clusters and significantly diminishes bone marrow trafficking of AML. Taken together, these data establish a mechanism where the membrane organization of CD82, through specific posttranslational modifications, regulates N-cadherin clustering and membrane density, which impacts the in vivo trafficking of AML cells. As such, these observations provide an alternative model for targeting AML where modulation of protein organization within the membrane may be an effective treatment therapy to disrupt the bone marrow homing potential of AML cells. PMID:26592446

  15. Tetraspanin CD82 regulates bone marrow homing of acute myeloid leukemia by modulating the molecular organization of N-cadherin

    PubMed Central

    Marjon, Kristopher D.; Termini, Christina M.; Karlen, Karin L.; Saito-Reis, Chelsea; Soria, Cesar E.; Lidke, Keith A.; Gillette, Jennifer M.

    2016-01-01

    Communication between acute myeloid leukemia (AML) and the bone marrow microenvironment is known to control disease progression. Therefore, regulation of AML cell trafficking and adhesion to the bone marrow is of significant interest. In this study, we demonstrate that differential expression of the membrane scaffold CD82 modulates the bone marrow homing of AML cells. By combining mutational analysis and super-resolution imaging, we identify membrane protein clustering by CD82 as a regulator of AML cell adhesion and bone marrow homing. Cluster analysis of super-resolution data indicates that N-linked glycosylation and palmitoylation of CD82 are both critical modifications that control the microdomain organization of CD82 as well as the nanoscale clustering of associated adhesion protein, N-cadherin. We demonstrate that inhibition of CD82 glycosylation increases the molecular packing of N-cadherin and promotes the bone marrow homing of AML cells. In contrast, we find that inhibition of CD82 palmitoylation disrupts the formation and organization of N-cadherin clusters and significantly diminishes bone marrow trafficking of AML. Taken together, these data establish a mechanism where the membrane organization of CD82, through specific post-translational modifications, regulates N-cadherin clustering and membrane density, which impacts the in vivo trafficking of AML cells. As such, these observations provide an alternative model for targeting AML where modulation of protein organization within the membrane may be an effective treatment therapy to disrupt the bone marrow homing potential of AML cells. PMID:26592446

  16. Standard and Nonstandard Craniospinal Radiotherapy Using Helical TomoTherapy

    SciTech Connect

    Parker, William; Brodeur, Marylene; Roberge, David; Freeman, Carolyn

    2010-07-01

    Purpose: To show the advantages of planning and delivering craniospinal radiotherapy with helical TomoTherapy (TomoTherapy Inc., Madison, WI) by presenting 4 cases treated at our institution. Methods and Materials: We first present a standard case of craniospinal irradiation in a patient with recurrent myxopapillary ependymoma (MPE) and follow this with 2 cases requiring differential dosing to multiple target volumes. One of these, a patient with recurrent medulloblastoma, required a lower dose to be delivered to the posterior fossa because the patient had been previously irradiated to the full dose, and the other required concurrent boosts to leptomeningeal metastases as part of his treatment for newly diagnosed MPE. The final case presented is a patient with pronounced scoliosis who required spinal irradiation for recurrent MPE. Results: The four cases presented were planned and treated successfully with Helical Tomotherapy. Conclusions: Helical TomoTherapy delivers continuous arc-based intensity-modulated radiotherapy that gives high conformality and excellent dose homogeneity for the target volumes. Increased healthy tissue sparing is achieved at higher doses albeit at the expense of larger volumes of tissue receiving lower doses. Helical TomoTherapy allows for differential dosing of multiple targets, resulting in very elegant dose distributions. Daily megavoltage computed tomography imaging allows for precision of patient positioning, permitting a reduction in planning margins and increased healthy tissue sparing in comparison with standard techniques.

  17. Monte Carlo simulation of helical tomotherapy with PENELOPE

    NASA Astrophysics Data System (ADS)

    Sterpin, E.; Salvat, F.; Cravens, R.; Ruchala, K.; Olivera, G. H.; Vynckier, S.

    2008-04-01

    Helical tomotherapy (HT) delivers intensity-modulated radiation therapy (IMRT) using the simultaneous movement of the couch, the gantry and the binary multileaf collimator (MLC), a procedure that differs from conventional dynamic or step-and-shoot IMRT. A Monte Carlo (MC) simulation of HT in the helical mode therefore requires a new approach. Using validated phase-space files (PSFs) obtained through the MC simulation of the static mode with PENELOPE, an analytical model of the binary MLC, called the 'transfer function' (TF), was first devised to perform the transport of particles through the MLC much faster than time-consuming MC simulation and with no significant loss of accuracy. Second, a new tool, called TomoPen, was designed to simulate the helical mode by rotating and translating the initial coordinates and directions of the particles in the PSF according to the instantaneous position of the machine, transporting the particles through the MLC (in the instantaneous configuration defined by the sinogram), and computing the dose distribution in the CT structure using PENELOPE. Good agreement with measurements and with the treatment planning system of tomotherapy was obtained, with deviations generally well within 2%/1 mm, for the simulation of the helical mode for two commissioning procedures and a clinical plan calculated and measured in homogeneous conditions.

  18. The Strip-Hippo Pathway Regulates Synaptic Terminal Formation by Modulating Actin Organization at the Drosophila Neuromuscular Synapses.

    PubMed

    Sakuma, Chisako; Saito, Yoshie; Umehara, Tomoki; Kamimura, Keisuke; Maeda, Nobuaki; Mosca, Timothy J; Miura, Masayuki; Chihara, Takahiro

    2016-08-30

    Synapse formation requires the precise coordination of axon elongation, cytoskeletal stability, and diverse modes of cell signaling. The underlying mechanisms of this interplay, however, remain unclear. Here, we demonstrate that Strip, a component of the striatin-interacting phosphatase and kinase (STRIPAK) complex that regulates these processes, is required to ensure the proper development of synaptic boutons at the Drosophila neuromuscular junction. In doing so, Strip negatively regulates the activity of the Hippo (Hpo) pathway, an evolutionarily conserved regulator of organ size whose role in synapse formation is currently unappreciated. Strip functions genetically with Enabled, an actin assembly/elongation factor and the presumptive downstream target of Hpo signaling, to modulate local actin organization at synaptic termini. This regulation occurs independently of the transcriptional co-activator Yorkie, the canonical downstream target of the Hpo pathway. Our study identifies a previously unanticipated role of the Strip-Hippo pathway in synaptic development, linking cell signaling to actin organization. PMID:27545887

  19. Measurement-guided volumetric dose reconstruction for helical tomotherapy.

    PubMed

    Stambaugh, Cassandra; Nelms, Benjamin; Wolf, Theresa; Mueller, Richard; Geurts, Mark; Opp, Daniel; Moros, Eduardo; Zhang, Geoffrey; Feygelman, Vladimir

    2015-01-01

    It was previously demonstrated that dose delivered by a conventional linear accelerator using IMRT or VMAT can be reconstructed - on patient or phantom datasets - using helical diode array measurements and a technique called planned dose perturbation (PDP). This allows meaningful and intuitive analysis of the agreement between the planned and delivered dose, including direct comparison of the dose-volume histograms. While conceptually similar to modulated arc techniques, helical tomotherapy introduces significant challenges to the PDP formalism, arising primarily from TomoTherapy delivery dynamics. The temporal characteristics of the delivery are of the same order or shorter than the dosimeter's update interval (50 ms). Additionally, the prevalence of often small and complex segments, particularly with the 1 cm Y jaw setting, lead to challenges related to detector spacing. Here, we present and test a novel method of tomotherapy-PDP (TPDP) designed to meet these challenges. One of the novel techniques introduced for TPDP is organization of the subbeams into larger subunits called sectors, which assures more robust synchronization of the measurement and delivery dynamics. Another important change is the optional application of a correction based on ion chamber (IC) measurements in the phantom. The TPDP method was validated by direct comparisons to the IC and an independent, biplanar diode array dosimeter previously evaluated for tomotherapy delivery quality assurance. Nineteen plans with varying complexity were analyzed for the 2.5 cm tomotherapy jaw setting and 18 for the 1 cm opening. The dose differences between the TPDP and IC were 1.0% ± 1.1% and 1.1% ± 1.1%, for 2.5 and 1.0 cm jaw plans, respectively. Gamma analysis agreement rates between TPDP and the independent array were: 99.1%± 1.8% (using 3% global normalization/3 mm criteria) and 93.4% ± 7.1% (using 2% global/2 mm) for the 2.5 cm jaw plans; for 1 cm plans, they were 95.2% ± 6.7% (3% G/3) and 83.8%

  20. Mechanism of optical terahertz-transmission modulation in an organic/inorganic semiconductor interface and its application to active metamaterials.

    PubMed

    Matsui, Tatsunosuke; Takagi, Ryosuke; Takano, Keisuke; Hangyo, Masanori

    2013-11-15

    Terahertz (THz) transmission modulation through copper phthalocyanine (CuPc)-coated Si under various laser light irradiation conditions was investigated using THz time-domain spectroscopy. The charge carrier transfer from Si to CuPc is crucial for photo-induced metallization, and the thickness of the CuPc layer is a critical parameter for achieving high charge carrier density for metallization. Transmission through a split-ring resonator array metamaterial, fabricated on CuPc-coated Si, can be efficiently modulated by laser light irradiation. Our findings may open the way for various types of metamaterials using organic conjugated materials that are suitable for easy device fabrication using printing technologies. PMID:24322092

  1. DEMONSTRATION OF PILOT-SCALE PERVAPORATION SYSTEMS FOR VOLATILE ORGANIC COMPOUND REMOVAL FROM A SURFACTANT ENHANCED AQUIFER REMEDIATION FLUID. II. HOLLOW FIBER MEMBRANE MODULES

    EPA Science Inventory

    Pilot-scale demonstration of pervaporation-based removal of volatile organic compounds from a surfactant enhanced aquifer remediation (SEAR) fluid has been conducted at USEPA's Test & Evaluation Facility using hollow fiber membrane modules. The membranes consisted of microporous...

  2. Architecture of the Mediator head module.

    PubMed

    Imasaki, Tsuyoshi; Calero, Guillermo; Cai, Gang; Tsai, Kuang-Lei; Yamada, Kentaro; Cardelli, Francesco; Erdjument-Bromage, Hediye; Tempst, Paul; Berger, Imre; Kornberg, Guy Lorch; Asturias, Francisco J; Kornberg, Roger D; Takagi, Yuichiro

    2011-07-14

    Mediator is a key regulator of eukaryotic transcription, connecting activators and repressors bound to regulatory DNA elements with RNA polymerase II (Pol II). In the yeast Saccharomyces cerevisiae, Mediator comprises 25 subunits with a total mass of more than one megadalton (refs 5, 6) and is organized into three modules, called head, middle/arm and tail. Our understanding of Mediator assembly and its role in regulating transcription has been impeded so far by limited structural information. Here we report the crystal structure of the essential Mediator head module (seven subunits, with a mass of 223 kilodaltons) at a resolution of 4.3 ångströms. Our structure reveals three distinct domains, with the integrity of the complex centred on a bundle of ten helices from five different head subunits. An intricate pattern of interactions within this helical bundle ensures the stable assembly of the head subunits and provides the binding sites for general transcription factors and Pol II. Our structural and functional data suggest that the head module juxtaposes transcription factor IIH and the carboxy-terminal domain of the largest subunit of Pol II, thereby facilitating phosphorylation of the carboxy-terminal domain of Pol II. Our results reveal architectural principles underlying the role of Mediator in the regulation of gene expression. PMID:21725323

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Micromechanical Models of Helical Superstructures in Ligament and Tendon Fibers Predict Large Poisson’s Ratios

    PubMed Central

    Reese, Shawn P.; Maas, Steve A.; Weiss, Jeffrey A.

    2010-01-01

    Experimental measurements of the Poisson’s ratio in tendon and ligament tissue greatly exceed the isotropic limit of 0.5. This is indicative of volume loss during tensile loading. The microstructural origin of the large Poisson’s ratios is unknown. It was hypothesized that a helical organization of fibrils within a fiber would result in a large Poisson’s ratio in ligaments and tendons, and that this helical organization would be compatible with the crimped nature of these tissues, thus modeling their classic nonlinear stress strain behavior. Micromechanical finite element models were constructed to represent crimped fibers with a super helical organization, composed of fibrils embedded within a matrix material. A homogenization procedure was performed to determine both the effective Poisson’s ratio and the Poisson function. The results showed that helical fibril organization within a crimped fiber was capable of simultaneously predicting large Poisson’s ratios and the nonlinear stress strain behavior seen experimentally. Parametric studies revealed that the predicted Poisson’s ratio was strongly dependent on the helical pitch, crimp angle and the material coefficients. The results indicated that, for physiologically relevant parameters, the models were capable of predicting the large Poisson’s ratios seen experimentally. It was concluded that helical organization within a crimped fiber can produce both the characteristic nonlinear stress strain behavior and large Poisson’s ratios, while fiber crimp alone could only account for the nonlinear stress-strain behavior. PMID:20181336

  11. 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.

  12. Modules for Introducing Organometallic Reactions: A Bridge between Organic and Inorganic Chemistry

    ERIC Educational Resources Information Center

    Schaller, Chris P.; Graham, Kate J.; Johnson, Brian J.

    2015-01-01

    Transition metal organometallic reactions have become increasingly important in the synthesis of organic molecules. A new approach has been developed to introduce organometallic chemistry, along with organic and inorganic chemistry, at the foundational level. This change highlights applications of organometallic chemistry that have dramatically…

  13. Neurocardiovascular instability may modulate end-organ damage: A review of this hypothesis investigating the eye and manifestations of NCVI.

    PubMed

    Ní Bhuachalla, Bláithín; McGarrigle, Christine A; Kenny, Rose Anne

    2015-11-01

    Neurocardiovascular instability (NCVI) represents age-related changes in blood pressure and heart rate behaviour. It has been associated with increased leukoaraiosis in the brain and also conditions which are likely to be are related to cerebral end-organ damage, such as stroke and falls. The eye is a 'window' into the brain and cardiovascular (CV) system, changes in retinal microvasculature being independently predictive of cardiovascular events. The eye is highly vascular, having two circulatory systems and as such the ideal target end-organ to investigate NCVI and early end-organ damage. The retinal and choroidal circulations of the eye would be vulnerable to NCVI if ocular vasoregulation becomes impaired with age, particularly given the high metabolic activity of the retina. The choroid is predominantly extrinsically regulated by the autonomic nervous system. In patients with NCVI, autonomic dysfunction is more common and thus impairment of the tightly regulated ocular microcirculation may indeed be compromised. We review the evidence for the hypothesis that NCVI may modulate end-organ cardiovascular pathology and that the eye is the ideal target organ to monitor this. PMID:26272606

  14. 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.

  15. Intermolecular electronic coupling in organic molecular thin films measured by temperature modulation spectroscopy

    SciTech Connect

    Yadav, Abhishek; Jin, Y; Chan, P. K. L.; Shtein, Max; Pipe, Kevin P.

    2010-01-01

    Temperature modulation spectroscopy is used to obtain the temperature dependences of oscillator strength, exciton transition energy, and line width for a copper phthalocyanine thin film. With increasing temperature, the oscillator strength exhibits a pronounced decrease for charge transfer (CT) excitons, making this technique suitable for differentiating exciton types. From the measured magnitude and temperature dependence of the CT oscillator strength, we obtain estimates for the intermolecular electronic coupling and its exponential decay coefficient.

  16. A growth factor-induced, spatially organizing cytoskeletal module enables rapid and persistent fibroblast migration

    PubMed Central

    Martin, Katrin; Vilela, Marco; Jeon, Noo Li; Danuser, Gaudenz; Pertz, Olivier

    2015-01-01

    Summary Directional migration requires robust front/back polarity. We find that fibroblasts treated with platelet-derived growth factor (PDGF) and pre-polarized by plating on a fibronectin line substrate, exhibit persistent migration for hours. This does not occur in the absence of PDGF, or on uniformly-coated fibronectin substrates. Persistent migration arises from establishment of two functional modules at cell front and back. At the front, formation of a zone containing podosome-like structures (PLS), dynamically correlates with low RhoA and myosin activity, and absence of a contractile lamella. At the back, myosin contractility specifically controls tail retraction with minimal crosstalk to the front module. The PLS zone is maintained in a dynamic steady state that preserves size and position relative to the cell front, allowing for long term coordination of front and back modules. We propose that front/back uncoupling achieved by the PLS zone is crucial for persistent migration in absence of directional cues. PMID:25268172

  17. Synthesis of Hydrogen-Bond Surrogate α-helices as Inhibitors of Protein-Protein Interactions

    PubMed Central

    Miller, Stephen E.; Thomson, Paul F.; Arora, Paramjit S.

    2014-01-01

    The α-helix is a prevalent secondary structure in proteins and critical in mediating protein-protein interactions (PPIs). Peptide mimetics that adopt stable helices have become powerful tools for the modulation of PPIs in vitro and in vivo. Hydrogen-bond surrogate (HBS) α-helices utilize a covalent bond in place of an N-terminal i to i+4 hydrogen bond and have been used to target and disrupt PPIs that become dysregulated in disease states. These compounds have improved conformational stability and cellular uptake as compared to their linear peptide counterparts. The protocol presented here describes current methodology for the synthesis of HBS α-helical mimetics. The solid phase synthesis of HBS helices involves solid phase peptide synthesis with three key steps involving incorporation of N-allyl functionality within the backbone of the peptide, coupling of a secondary amine, and a ring-closing metathesis step. PMID:24903885

  18. Stabilization of Collagen-Model, Triple-Helical Peptides for In Vitro and In Vivo Applications

    PubMed Central

    Bhowmick, Manishabrata; Fields, Gregg B.

    2014-01-01

    The triple-helical structure of collagen has been accurately reproduced in numerous chemical and recombinant model systems. Triple-helical peptides and proteins have found application for dissecting collagen-stabilizing forces, isolating receptor- and protein-binding sites in collagen, mechanistic examination of collagenolytic proteases, and development of novel biomaterials. Introduction of native-like sequences into triple-helical constructs can reduce the thermal stability of the triple-helix to below that of the physiological environment. In turn, incorporation of nonnative amino acids and/or templates can enhance triple-helix stability. We presently describe approaches by which triple-helical structure can be modulated for use under physiological or near-physiological conditions. PMID:24014440

  19. cMonkey2: Automated, systematic, integrated detection of co-regulated gene modules for any organism

    PubMed Central

    Reiss, David J.; Plaisier, Christopher L.; Wu, Wei-Ju; Baliga, Nitin S.

    2015-01-01

    The cMonkey integrated biclustering algorithm identifies conditionally co-regulated modules of genes (biclusters). cMonkey integrates various orthogonal pieces of information which support evidence of gene co-regulation, and optimizes biclusters to be supported simultaneously by one or more of these prior constraints. The algorithm served as the cornerstone for constructing the first global, predictive Environmental Gene Regulatory Influence Network (EGRIN) model for a free-living cell, and has now been applied to many more organisms. However, due to its computational inefficiencies, long run-time and complexity of various input data types, cMonkey was not readily usable by the wider community. To address these primary concerns, we have significantly updated the cMonkey algorithm and refactored its implementation, improving its usability and extendibility. These improvements provide a fully functioning and user-friendly platform for building co-regulated gene modules and the tools necessary for their exploration and interpretation. We show, via three separate analyses of data for E. coli, M. tuberculosis and H. sapiens, that the updated algorithm and inclusion of novel scoring functions for new data types (e.g. ChIP-seq and transcription factor over-expression [TFOE]) improve discovery of biologically informative co-regulated modules. The complete cMonkey2 software package, including source code, is available at https://github.com/baliga-lab/cmonkey2. PMID:25873626

  20. cMonkey2: Automated, systematic, integrated detection of co-regulated gene modules for any organism.

    PubMed

    Reiss, David J; Plaisier, Christopher L; Wu, Wei-Ju; Baliga, Nitin S

    2015-07-27

    The cMonkey integrated biclustering algorithm identifies conditionally co-regulated modules of genes (biclusters). cMonkey integrates various orthogonal pieces of information which support evidence of gene co-regulation, and optimizes biclusters to be supported simultaneously by one or more of these prior constraints. The algorithm served as the cornerstone for constructing the first global, predictive Environmental Gene Regulatory Influence Network (EGRIN) model for a free-living cell, and has now been applied to many more organisms. However, due to its computational inefficiencies, long run-time and complexity of various input data types, cMonkey was not readily usable by the wider community. To address these primary concerns, we have significantly updated the cMonkey algorithm and refactored its implementation, improving its usability and extendibility. These improvements provide a fully functioning and user-friendly platform for building co-regulated gene modules and the tools necessary for their exploration and interpretation. We show, via three separate analyses of data for E. coli, M. tuberculosis and H. sapiens, that the updated algorithm and inclusion of novel scoring functions for new data types (e.g. ChIP-seq and transcription factor over-expression [TFOE]) improve discovery of biologically informative co-regulated modules. The complete cMonkey2 software package, including source code, is available at https://github.com/baliga-lab/cmonkey2. PMID:25873626

  1. 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

  2. Insights into the Hendra virus NTAIL-XD complex: Evidence for a parallel organization of the helical MoRE at the XD surface stabilized by a combination of hydrophobic and polar interactions.

    PubMed

    Erales, Jenny; Beltrandi, Matilde; Roche, Jennifer; Maté, Maria; Longhi, Sonia

    2015-08-01

    The Hendra virus is a member of the Henipavirus genus within the Paramyxoviridae family. The nucleoprotein, which consists of a structured core and of a C-terminal intrinsically disordered domain (N(TAIL)), encapsidates the viral genome within a helical nucleocapsid. N(TAIL) partly protrudes from the surface of the nucleocapsid being thus capable of interacting with the C-terminal X domain (XD) of the viral phosphoprotein. Interaction with XD implies a molecular recognition element (MoRE) that is located within N(TAIL) residues 470-490, and that undergoes α-helical folding. The MoRE has been proposed to be embedded in the hydrophobic groove delimited by helices α2 and α3 of XD, although experimental data could not discriminate between a parallel and an antiparallel orientation of the MoRE. Previous studies also showed that if the binding interface is enriched in hydrophobic residues, charged residues located close to the interface might play a role in complex formation. Here, we targeted for site directed mutagenesis two acidic and two basic residues within XD and N(TAIL). ITC studies showed that electrostatics plays a crucial role in complex formation and pointed a parallel orientation of the MoRE as more likely. Further support for a parallel orientation was afforded by SAXS studies that made use of two chimeric constructs in which XD and the MoRE were covalently linked to each other. Altogether, these studies unveiled the multiparametric nature of the interactions established within this complex and contribute to shed light onto the molecular features of protein interfaces involving intrinsically disordered regions. PMID:25960280

  3. From plasma crystals and helical structures towards inorganic living matter

    NASA Astrophysics Data System (ADS)

    Tsytovich, V. N.; Morfill, G. E.; Fortov, V. E.; Gusein-Zade, N. G.; Klumov, B. A.; Vladimirov, S. V.

    2007-08-01

    Complex plasmas may naturally self-organize themselves into stable interacting helical structures that exhibit features normally attributed to organic living matter. The self-organization is based on non-trivial physical mechanisms of plasma interactions involving over-screening of plasma polarization. As a result, each helical string composed of solid microparticles is topologically and dynamically controlled by plasma fluxes leading to particle charging and over-screening, the latter providing attraction even among helical strings of the same charge sign. These interacting complex structures exhibit thermodynamic and evolutionary features thought to be peculiar only to living matter such as bifurcations that serve as 'memory marks', self-duplication, metabolic rates in a thermodynamically open system, and non-Hamiltonian dynamics. We examine the salient features of this new complex 'state of soft matter' in light of the autonomy, evolution, progenity and autopoiesis principles used to define life. It is concluded that complex self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter that may exist in space provided certain conditions allow them to evolve naturally.

  4. Remarkable improvement in microwave absorption by cloaking a micro-scaled tetrapod hollow with helical carbon nanofibers.

    PubMed

    Jian, Xian; Chen, Xiangnan; Zhou, Zuowan; Li, Gang; Jiang, Man; Xu, Xiaoling; Lu, Jun; Li, Qiming; Wang, Yong; Gou, Jihua; Hui, David

    2015-02-01

    Helical nanofibers are prepared through in situ growth on the surface of a tetrapod-shaped ZnO whisker (T-ZnO), by employing a precursor decomposition method then adding substrate. After heat treatment at 900 °C under argon, this new composite material, named helical nanofiber-T-ZnO, undergoes a significant change in morphology and structure. The T-ZnO transforms from a solid tetrapod ZnO to a micro-scaled tetrapod hollow carbon film by reduction of the organic fiber at 900 °C. Besides, helical carbon nanofibers, generated from the carbonization of helical nanofibers, maintain the helical morphology. Interestingly, HCNFs with the T-hollow exhibit remarkable improvement in electromagnetic wave loss compared with the pure helical nanofibers. The enhanced loss ability may arise from the efficient dielectric friction, interface effect in the complex nanostructures and the micro-scaled tetrapod-hollow structure. PMID:25510199

  5. Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode

    PubMed Central

    Lee, Jiyoul; van Breemen, Albert J. J. M.; Khikhlovskyi, Vsevolod; Kemerink, Martijn; Janssen, Rene A. J.; Gelinck, Gerwin H.

    2016-01-01

    We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit. PMID:27080264

  6. Pulse-modulated multilevel data storage in an organic ferroelectric resistive memory diode

    NASA Astrophysics Data System (ADS)

    Lee, Jiyoul; van Breemen, Albert J. J. M.; Khikhlovskyi, Vsevolod; Kemerink, Martijn; Janssen, Rene A. J.; Gelinck, Gerwin H.

    2016-04-01

    We demonstrate multilevel data storage in organic ferroelectric resistive memory diodes consisting of a phase-separated blend of P(VDF-TrFE) and a semiconducting polymer. The dynamic behaviour of the organic ferroelectric memory diode can be described in terms of the inhomogeneous field mechanism (IFM) model where the ferroelectric components are regarded as an assembly of randomly distributed regions with independent polarisation kinetics governed by a time-dependent local field. This allows us to write and non-destructively read stable multilevel polarisation states in the organic memory diode using controlled programming pulses. The resulting 2-bit data storage per memory element doubles the storage density of the organic ferroelectric resistive memory diode without increasing its technological complexity, thus reducing the cost per bit.

  7. Modulation of superoxide dismutase (SOD) isozymes by organ development and high long-term salinity in the halophyte Cakile maritima.

    PubMed

    Houmani, Hayet; Rodríguez-Ruiz, Marta; Palma, José M; Abdelly, Chedly; Corpas, Francisco J

    2016-05-01

    Superoxide dismutase (SOD) activity catalyzes the disproportionation of superoxide radicals into hydrogen peroxide and oxygen. This enzyme is considered to be a first line of defense for controlling the production of reactive oxygen species (ROS). In this study, the number and type of SOD isozymes were identified in the principal organs (roots, stems, leaves, flowers, and seeds) of Cakile maritima. We also analyzed the way in which the activity of these SOD isozymes is modulated during development and under high long-term salinity (400 mM NaCl) stress conditions. The data indicate that this plant contains a total of ten SOD isozymes: two Mn-SODs, one Fe-SOD, and seven CuZn-SODs, with the Fe-SOD being the most prominent isozyme in the different organs analyzed. Moreover, the modulation of SOD isozymes, particularly CuZn-SODs, was only detected during development and under severe salinity stress conditions. These data suggest that, in C. maritima, the occurrence of these CuZn-SODs in roots and leaves plays an adaptive role since this CuZn-SOD isozyme might replace the diminished Fe-SOD activity under salinity stress to overcome this adverse environmental condition. PMID:26159565

  8. Mechanics of helical mesostructures from polymer-nanoparticle hybrids

    NASA Astrophysics Data System (ADS)

    Pham, Jonathan; Lawrence, Jimmy; Grason, Gregory; Emrick, Todd; Crosby, Alfred

    2015-03-01

    We describe the fabrication and mechanics of polymer and nanoparticle (NP)-based high-aspect ratio mesostructures, which we refer to as ribbons, with nm-scale cross-sections and up to cm-scale lengths. When placed into a fluid like water, interfacial tension associated with the ribbons' intrinsic geometric asymmetry balances the elastic cost of bending, turning ribbons into helices with tunable preferred curvature. This universal, elastocapillary-based mechanism enables the reversible formation of helices from a variety of polymer and NP compositions, as demonstrated with specific examples of poly(methyl methacrylate), CdSe quantum dots, and gold NPs with polystyrene-azide or undecene ligands. Using custom-designed characterization methods, we quantitatively show that helices are highly stretchable with force-displacement relationships described by a nonlinear spring of finite extensibility. At small strains, these helices generate nN forces, affording mesostructures with a stiffness similar to single polymer chains (ca. 10-6 N/m), and when fully stretched, they display properties similar to synthetic polymer nanofibers. These mesostructures offer a novel platform for engineering tunable materials with a broad range of mechanical properties and organic or inorganic functionality.

  9. Biologically inspired, sophisticated motions from helically assembled, conducting fibers.

    PubMed

    Chen, Peining; Xu, Yifan; He, Sisi; Sun, Xuemei; Guo, Wenhan; Zhang, Zhitao; Qiu, Longbin; Li, Jianfeng; Chen, Daoyong; Peng, Huisheng

    2015-02-11

    A hierarchically helical organization of carbon nanotubes into macroscopic fibers enables sophistication while controlling three-dimensional electromechanical actuations, e.g., an artificial swing and tail. The actuation generates a stress of more than 260 times that of a typical natural skeletal muscle and an accelerated velocity of more than 10 times that of a cheetah at low electric currents with high reversibility, good stability, and availability to various media. PMID:25446835

  10. Designing artificial photosynthetic devices using hybrid organic-inorganic modules based on polyoxometalates.

    PubMed

    Symes, Mark D; Cogdell, Richard J; Cronin, Leroy

    2013-08-13

    Artificial photosynthesis aims at capturing solar energy and using it to produce storable fuels. However, while there is reason to be optimistic that such approaches can deliver higher energy conversion efficiencies than natural photosynthetic systems, many serious challenges remain to be addressed. Perhaps chief among these is the issue of device stability. Almost all approaches to artificial photosynthesis employ easily oxidized organic molecules as light harvesters or in catalytic centres, frequently in solution with highly oxidizing species. The 'elephant in the room' in this regard is that oxidation of these organic moieties is likely to occur at least as rapidly as oxidation of water, meaning that current device performance is severely curtailed. Herein, we discuss one possible solution to this problem: using self-assembling organic-polyoxometalate hybrid structures to produce compartments inside which the individual component reactions of photosynthesis can occur without such a high incidence of deleterious side reactions. PMID:23816903

  11. Differential responses of sugar, organic acids and anthocyanins to source-sink modulation in Cabernet Sauvignon and Sangiovese grapevines

    PubMed Central

    Bobeica, Natalia; Poni, Stefano; Hilbert, Ghislaine; Renaud, Christel; Gomès, Eric; Delrot, Serge; Dai, Zhanwu

    2015-01-01

    Grape berry composition mainly consists of primary and secondary metabolites. Both are sensitive to environment and viticultural management. As a consequence, climate change can affect berry composition and modify wine quality and typicity. Leaf removal techniques can impact berry composition by modulating the source-to-sink balance and, in turn, may mitigate some undesired effects due to climate change. The present study investigated the balance between technological maturity parameters such as sugars and organic acids, and phenolic maturity parameters such as anthocyanins in response to source-sink modulation. Sugar, organic acid, and anthocyanin profiles were compared under two contrasting carbon supply levels in berries of cv. Cabernet Sauvignon and Sangiovese collected at 9 and 14 developmental stages respectively. In addition, whole-canopy net carbon exchange rate was monitored for Sangiovese vines and a mathematic model was used to calculate the balance between carbon fixation and berry sugar accumulation. Carbon limitation affected neither berry size nor the concentration of organic acids at harvest. However, it significantly reduced the accumulation of sugars and total anthocyanins in both cultivars. Most interestingly, carbon limitation decreased total anthocyanin concentration by 84.3% as compared to the non source-limited control, whereas it decreased sugar concentration only by 27.1%. This suggests that carbon limitation led to a strong imbalance between sugars and anthocyanins. Moreover, carbon limitation affected anthocyanin profiles in a cultivar dependent manner. Mathematical analysis of carbon-balance indicated that berries used a higher proportion of fixed carbon for sugar accumulation under carbon limitation (76.9%) than under carbon sufficiency (48%). Thus, under carbon limitation, the grape berry can manage the metabolic fate of carbon in such a way that sugar accumulation is maintained at the expense of secondary metabolites. PMID:26074942

  12. Effects of Organic Molecules with Different Structures and Absorption Bandwidth on Modulating Photoresponse of MoS2 Photodetector.

    PubMed

    Huang, Yanmin; Zheng, Wei; Qiu, Yunfeng; Hu, PingAn

    2016-09-01

    Organic dye molecules possessing modulated optical absorption bandwidth and molecular structures can be utilized as sensitizing species for the enhancement of photodetector performance of semiconductor via photoinduced charge transfer mechanism. MoS2 photodetector were modified by drop-casting of methyl orange (MO), rhodamine 6G (R6G), and methylene blue (MB) with different molecular structures and extinction coefficients, and enhanced photodetector performance in terms of photocurrent, photoresponsity, photodetectivity, and external quantum efficiency were obtained after modification of MO, R6G, and MB, respectively. Furthermore, dyes showed different modulating abilities for photodetector performance after combination with MoS2, mainly due to the variation of molecular structures and optical absorption bandwidth. Among tested dyes, deposition of MB onto monolayer MoS2 grown by CVD resulted in photocurrent ∼20 times as high as pristine MoS2 due to favorable photoinduced charge transfer of photoexcited electrons from flat MB molecules to the MoS2 layer. Meanwhile, the corresponding photoresponsivity, photodetectivity, and an external quantum efficiency are 9.09 A W(1-), 2.2 × 10(11) Jones, 1729% at 610 nm, respectively. Photoinduced electron-transfer measurements of the pristine MoS2 and dye-modified MoS2 indicated the n-doping effect of dye molecules on the MoS2. Additionally, surface-enhanced Raman measurements also confirmed the direct correlation with charge transfer between organic dyes and MoS2 taking into account the chemically enhanced Raman scattering mechanism. Present work provides a new clue for the manipulation of high-performance of two-dimensional layered semiconductor-based photodetector via the combination of organic dyes. PMID:27530058

  13. Self-Assembled Silica Nanostructures: Simultaneous Discrimination of Handedness, Pitch and Diameter of Helical Silica Nanotubes.

    PubMed

    Oh, C Y; Kim, D Y; Jin, S M; Kim, T K; Kim, J P; Jeong, E D; Hyun, M H; Sim, E K; Lee, Y C; Jin, J S

    2016-02-01

    The left- and right-handed helical silica nanostructures were obtained with the aid of organic templates, the formation of the nanostructures might follow a co-operation self-assembly mechanism. The chirality of the organogel self-assemblies was successfully transcribed in to the silica. The helical pitch and pore size of the silica nanotubes sensitively depended on the optical purity of the neutral gelator in the reaction mixtures. PMID:27433714

  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. The xanthophyll cycle pigments, violaxanthin and zeaxanthin, modulate molecular organization of the photosynthetic antenna complex LHCII.

    PubMed

    Janik, Ewa; Bednarska, Joanna; Zubik, Monika; Sowinski, Karol; Luchowski, Rafal; Grudzinski, Wojciech; Matosiuk, Dariusz; Gruszecki, Wieslaw I

    2016-02-15

    The effect of violaxanthin and zeaxanthin, two main carotenoids of the xanthophyll cycle, on molecular organization of LHCII, the principal photosynthetic antenna complex of plants, was studied in a model system based on lipid-protein membranes, by means of analysis of 77 K chlorophyll a fluorescence and "native" electrophoresis. Violaxanthin was found to promote trimeric organization of LHCII, contrary to zeaxanthin which was found to destabilize trimeric structures. Moreover, violaxanthin was found to induce decomposition of oligomeric LHCII structures formed in the lipid phase and characterized by the fluorescence emission band at 715 nm. Both pigments promoted formation of two-component supramolecular structures of LHCII and xanthophylls. The violaxanthin-stabilized structures were composed mostly of LHCII trimers while, the zeaxanthin-stabilized supramolecular structures of LHCII showed more complex organization which depended periodically on the xanthophyll content. The effect of the xanthophyll cycle pigments on molecular organization of LHCII was analyzed based on the results of molecular modeling and discussed in terms of a physiological meaning of this mechanism. Supramolecular structures of LHCII stabilized by violaxanthin, prevent uncontrolled oligomerization of LHCII, potentially leading to excitation quenching, therefore can be considered as structures protecting the photosynthetic apparatus against energy loses at low light intensities. PMID:26773208

  19. Marine Organisms in the Classroom. Project CAPE [Teaching Module] SC1.

    ERIC Educational Resources Information Center

    Hampton, Carolyn H.; Weston, Toni

    Nine lessons which involve the use of marine organisms in the classroom are presented in this seventh-grade biology unit. The unit offers instructors alternative ways of meeting common life science goals. It is not meant to be an extra curriculum added to the normal course load, but was developed to consolidate a group of activities designed for…

  20. Volatile Organic Compounds Identified in Post-Flight Air Analysis of the Multipurpose Logistics Module from International Space Station

    NASA Astrophysics Data System (ADS)

    Peterson, B.; Wheeler, R.

    Bioregenerative systems involve storing and processing waste along with atmospheric management. The MPLM, Multipurpose Logistics Module, is a reusable logistics carrier and primary delivery system used to resupply the International Space Station (ISS) and return Station cargo that requires a pressurized environment. The cylindrical module is approximately 6.4 meters long, 4.6 meters in diameter, and weighs almost 4,082kg. The module provides storage and additional workspace for up to two astronauts when docked to the ISS. It can carry up to 9,072 kg of supplies, science experiments, spare parts and other logistical components for ISS. There is concern for a potentially hazardous condition caused by contamination of the atmosphere in the MPLM upon return from orbit. This would be largely due to unforeseen spills or container leakage. This has led to the need for special care in handling the returned module prior to processing the module for its next flight. Prior to opening the MPLM, atmospheric samples are analyzed for trace volatile organic compounds, VOC's. It is noted that our analyses also reflect the atmosphere in the ISS on that day of closure. With the re turn of STS-108, 12th ISS Flight (UF1), the analysis showed 24 PPM of methane. This corresponds to the high levels on space station during a time period when the air filtration system was shut off. Chemical characterization of atmospheres on the ISS and MPLM provide useful information for concerns with plant growth experiments on ISS. Work with closed plant growth chambers show potential for VOC's to accumulate to toxic levels for plants. The ethylene levels for 4 MPLM analyses over the course on one year were measured at, 0.070, 0.017, 0.012 and 0.007 PPM. Phytochemical such as ethylene are detected with natural plant physiological events such as flowering and as a result of plant damage or from decaying food. A build up of VOC's may contribute to phytotoxic effects for the plant growth experiments or

  1. Cell-cell contact modulation of myosin organization in the early mouse embryo.

    PubMed

    Sobel, J S

    1983-11-01

    Preimplantation mouse embryos are characterized by a polarized distribution of cortical myosin (J. S. Sobel (1983). Dev. Biol. 95, 227-231.). Myosin was present in the peripheral regions of the blastomers and was not detectable in regions of cell contact. Disaggregation of the embryos yielded blastomeres which had a continuous layer of cortical myosin. Development of new contact relations in aggregates, between daughter cells of divided blastomeres, and in chimaeras resulted in renewed polarization of cortical myosin. The results indicate that continuous cell contact interaction modulates the distribution of myosin throughout the preimplantation stages of development. The loss of detectable myosin from regions of cell contact was correlated with development of cell contacts that remained stable after Triton X-100 extraction. PMID:6617992

  2. A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 3: Development of a secondary organic aerosol module

    NASA Astrophysics Data System (ADS)

    Utembe, S. R.; Watson, L. A.; Shallcross, D. E.; Jenkin, M. E.

    A Photochemical Trajectory Model (PTM), containing the Master Chemical Mechanism version 3.1 (MCM v3.1) coupled with an optimised representation of gas-aerosol absorptive partitioning of 365 oxygenated product species, has been used to simulate mass concentrations of secondary organic aerosol (SOA) for the conditions of the TORCH-2003 campaign in the south-east UK in late July and August 2003. A comprehensive reference dataset of 50 case study arrival events (and 4750 associated hourly air mass history events) has been compiled, which considers the base case conditions and scenarios in which emissions of anthropogenic pollution have been reduced by factors of up to 100. The relative contributions of SOA derived from anthropogenic and biogenic precursors are presented for the range of conditions, and the composition of these simulated components is discussed in terms of average molecular formulae, atomic ratios (H/C, O/C and N/C) and organic aerosol mass to organic carbon mass ratios (OM/OC), which are compared to reported measurements. The MCM v3.1 dataset has been used as a reference benchmark for development and optimisation of a reduced (14 species) SOA module for use with version 2 the Common Representative Intermediates mechanism (CRI v2), described in the first of two preceding companion papers [Jenkin, M.E., Watson, L.A., Utembe, S.R., Shallcross, D.E., 2008a. A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 1: gas phase mechanism development. Atmospheric Environment, 42, pp. 7185-7195. doi:10.1016/j.atmosenv.2008.07.028.]. The resultant version of the PTM containing CRI v2 and the reduced SOA module has been used to simulate the entire TORCH-2003 campaign at hourly resolution, and the contributions of SOA derived from anthropogenic and biogenic precursors are presented and discussed. The reduced SOA module is also shown to be compatible with the most reduced CRI variant (CRI v2-R5), described in the second of two preceding

  3. Binding of copper(II) ions to the polyproline II helices of PEVK modules of the giant elastic protein titin as revealed by ESI-MS, CD, and NMR.

    PubMed

    Ma, Kan; Wang, Kuan

    2003-10-01

    Titin, a family of giant elastic proteins, constitutes an elastic sarcomere matrix in striated muscle. In the I-band region of the sarcomere, the titin PEVK segment acts as a molecular spring to generate elasticity as well as sites of adhesion with parallel thin filaments. Previously, we reported that PEVK consists of tandem repeats of 28 residue modules and that the "polyproline II-coil" motif is the fundamental conformational motif of the PEVK module. In order to characterize the factors that may affect and alter the PPII-coil conformational motifs, we have initiated a systematic study of the interaction with divalent cations (Cu2+, Ca2+, Zn2+, and Ni2+) and a conformational profile of PEVK peptides (a representative 28-mer peptide PR: PEPPKEVVPEKKAPVAPPKKPEVPPVKV and its subfragments PR1: kvPEPPKEVVPE, PR2: VPEKKAPVAPPK, PR3: KPEVPPVKV). UV-Vis absorption difference spectra and CD spectra showed that Cu2+ bound to PR1 with high affinity (20 microM), while its binding to PR2 and PR3 as well as the binding of other cations to all four peptides were of lower affinity (>100 microM). Conformational studies by CD revealed that Cu2+ binding to PR1 resulted in a polyproline II to turn transition up to a 1:2 PR1/Cu2+ ratio and a coil to turn transition at higher Cu2+ concentration. ESI-MS provided the stoichiometry of PEVK peptide-Cu2+ complexes at both low and high ion strength, confirming the specific high affinity binding of Cu2+ to PR1 and PR. Furthermore, NMR and ESI-MS/MS fragmentation analysis elucidated the binding sites of the PEVK peptide-Cu2+ complexes at (-2)KVPE2, 8VPE10, 13APV15, and 22EVP24. A potential application of Cu2+ binding in peptide sequencing by mass spectrometry was also revealed. We conclude that Cu2+ binds and bends PEVK peptides to a beta-turn-like structure at specific sites. The specific targeting of Cu2+ towards PPII is likely to be of significant value in elucidating the roles of PPII in titin elasticity as well as in interactions of

  4. Mycobacterium bovis, BCG, modulation of murine antibody responses: influence of dose and degree of aggregation of live or dead organisms.

    PubMed

    Brown, C A; Brown, I N

    1982-04-01

    Mycobacteria have the ability to enhance or depress immune responses. This paper describes experiments designed to investigate the parameters determining the direction of modulation. It has been shown previously that 10(8) liver Mycobacterium bovis BCG depress the ability of mouse spleen cells to produce a primary antibody response in vitro to SRBC 2-3 weeks after i.v. injection, whereas the same number of dead organisms enhance this response. Using the same growth medium for the BCG (Glaxo glycerol-free medium), we now find that decreasing the BCG dose to mice from 10(8) to 10 (6) liver organisms results in enhanced responses and increasing the dose to more than 10(8) dead organisms results in depressed responses. It thus appears that bacterial load is the important factor determining whether depression or enhancement of the primary antibody response will occur, rather than the viability of the organisms per se. However, when the BCG was grown in Middlebrook 7H9 broth, doses as high as 4 X 10(9) dead BCG/mouse failed to depress although depressed responses were found if sufficient live organisms (7 X 10(8)) were injected. In view of the known growth characteristics of BCG in these 2 bacteriological media, it is suggested that the degree of aggregation of the injected suspension may also be of importance in determining whether or not depression will occur. A comparison of the effects of BCG injected untreated or after dispersion of bacterial aggregates supports this idea. Some degree of splenomegaly was always found in mice with depressed splenic responses but a large spleen did not necessarily yield cell suspensions with depressed responses. PMID:7041944

  5. Pulsatile driving of the helical flow pump.

    PubMed

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

    2013-01-01

    The helical flow pump (HFP) is newly developed blood pomp for total artificial heart (TAH). HFP can work with lower rotational speed than axial and centrifugal blood pump. It can be seen reasonable feature to generate pulsatile flow because high response performance can be realized. In this article, pulsatility of HFP was evaluated using mock circulation loop. Pulsatile flow was generated by modulating the rotational speed in various amplitude and heart rate. In the experiment, relationship between Pump flow, pump head, rotational speed amplitude, heart rate and power consumption is evaluated. As the result, complete pulsatile flow with mean flow rate of 5 L/min and mean pressure head of 100 mmHg can be obtained at ± 500 rpm with mean rotational speed of 1378 to 1398 rpm in hart rate from 60 to 120. Flow profiles which are non-pulsatile, quasi-pulsatile or complete flow can be adjusted arbitrarily. Therefore, HFP has excellent pulsatility and control flexibility of flow profile. PMID:24110290

  6. SU-E-I-37: Eye Lens Dose Reduction From CT Scan Using Organ Based Tube Current Modulation

    SciTech Connect

    Liu, H; Liu, T; Xu, X; Wu, J; Zhuo, W

    2015-06-15

    Purpose: To investigate the eye lens dose reduction by CT scan with organ based tube current modulation (OBTCM) using GPU Monte Carlo code ARCHER-CT. Methods: 36 X-ray sources and bowtie filters were placed around the patient head with the projection angle interval of 10° for one rotation of CT scan, each projection was simulated respectively. The voxel eye models with high resolution(0.1mm*0.1mm*0.1mm) were used in the simulation and different tube voltage including 80kVp, 100kVp, 120kVp and 140kVp were taken into consideration. Results: The radiation doses to the eye lens increased with the tube voltage raised from 80kVp to 140kVp, and the dose results from 0° (AP) direction are much higher than those from 180° (PA) direction for all the 4 different tube voltage investigated. This 360° projection dose characteristic enables organ based TCM, which can reduce the eye lens dose by more than 55%. Conclusion: As the eye lens belongs to superficial tissues, its radiation dose to external exposure like CT is direction sensitive, and this characteristic feature makes organ based TCM to be an effective way to reduce the eye lens dose, so more clinical use of this technique were recommended. National Nature Science Foundation of China(No.11475047)

  7. Organic trace mineral supplementation enhances local and systemic innate immune responses and modulates oxidative stress in broiler chickens.

    PubMed

    Echeverry, H; Yitbarek, A; Munyaka, P; Alizadeh, M; Cleaver, A; Camelo-Jaimes, G; Wang, P; O, K; Rodriguez-Lecompte, J C

    2016-03-01

    The effect of organic trace mineral supplementation on performance, intestinal morphology, immune organ weights (bursa of Fabricius and spleen), expression of innate immune response related genes, blood heterophils/lymphocytes ratio, chemical metabolic panel, natural antibodies (IgG), and oxidative stress of broiler chickens was studied. A total of 1,080 day-old male broilers were assigned to 1 of 3 dietary treatments, which included basal diet with Monensin (control), control diet supplemented with bacitracin methylene disalicylate (BMD), and BMD diet supplemented with organic trace minerals (OTM). No difference in feed conversion ratio was observed among treatments; ileum histomorphological analysis showed a lower crypt depth, higher villi height/crypt depth ratio, and lower villi width in the OTM treatment compared to control. Furthermore, OTM treatment resulted in higher uric acid and lower plasma malondehaldehyde (MDA), indicating lower oxidative stress. Gene expression analysis showed that OTM treatment resulted in up-regulations of TLR2 bin the ileum, and TLR2b, TLR4, and IL-12p35 in the bursa of Fabricius, and down-regulation of TLR2b and TLR4 in the cecal tonsils. In the spleen, OTM treatment resulted in up-regulation of IL-10. In conclusion, OTM supplementation to broiler diets may have beneficial effects on intestinal development, immune system status, and survival by improving ileum histomorphological parameters, modulation of Toll-like receptors and anti-inflammatory cytokines, and decreasing level of MDA, which in conjunction could enhance health status. PMID:26740133

  8. Resistive switching and voltage induced modulation of tunneling magnetoresistance in nanosized perpendicular organic spin valves

    NASA Astrophysics Data System (ADS)

    Göckeritz, Robert; Homonnay, Nico; Müller, Alexander; Fuhrmann, Bodo; Schmidt, Georg

    2016-04-01

    Nanoscale multifunctional perpendicular organic spin valves have been fabricated. The devices based on an La0.7Sr0.3MnO3/Alq3/Co trilayer show resistive switching of up to 4-5 orders of magnitude and magnetoresistance as high as -70% the latter even changing sign when voltage pulses are applied. This combination of phenomena is typically observed in multiferroic tunnel junctions where it is attributed to magnetoelectric coupling between a ferromagnet and a ferroelectric material. Modeling indicates that here the switching originates from a modification of the La0.7Sr0.3MnO3 surface. This modification influences the tunneling of charge carriers and thus both the electrical resistance and the tunneling magnetoresistance which occurs at pinholes in the organic layer.

  9. Electronic Structure Modulation of Metal–Organic Frameworks for Hybrid Devices

    PubMed Central

    2014-01-01

    The study of metal–organic frameworks has largely been motivated by their structural and chemical diversity; however, these materials also possess rich physics, including optical, electronic, and magnetic activity. If these materials are to be employed in devices, it is necessary to develop an understanding of their solid-state behavior. We report an approach to calculate the effect of strain on the band structure of porous frameworks. The origin of the bidirectional absolute deformation potentials can be described from perturbations of the organic and inorganic building blocks. The unified approach allows us to propose several uses for hybrid materials, beyond their traditionally posited applications, including gas sensing, photoelectrochemistry, and as hybrid transistors. PMID:25436990

  10. Auxin response factors mediate Arabidopsis organ asymmetry via modulation of KANADI activity.

    PubMed

    Pekker, Irena; Alvarez, John Paul; Eshed, Yuval

    2005-11-01

    Members of the KANADI gene family in Arabidopsis thaliana regulate abaxial identity and laminar growth of lateral organs. Promoter APETALA3-mediated ectopic expression of KANADI restricts petal expansion and was used in a genetic screen for factors involved in KANADI-mediated signaling. Through this screen, mutations in ETTIN (ETT; also known as Auxin Response Factor3 [ARF3]) were isolated as second site suppressors and found to ameliorate ectopic KANADI activity throughout the plant as well. Mutant phenotypes of ett are restricted to flowers; however, double mutants with a closely related gene ARF4 exhibit transformation of abaxial tissues into adaxial ones in all aerial parts, resembling mutations in KANADI. Accordingly, the common RNA expression domain of both ARFs was found to be on the abaxial side of all lateral organs. Truncated, negatively acting gene products of strong ett alleles map to an ARF-specific, N-terminal domain of ETT. Such gene products strongly enhance abaxial tissue loss only when ARF activities are compromised. As KANADI is not required for either ETT or ARF4 transcription, and their overexpression cannot rescue kanadi mutants, cooperative activity is implied. ARF proteins are pivotal in mediating auxin responses; thus, we present a model linking transient local auxin gradients and gradual partitioning of lateral organs along the abaxial/adaxial axis. PMID:16199616

  11. Dietary Omega-3 Fatty Acids Modulate Large-Scale Systems Organization in the Rhesus Macaque Brain

    PubMed Central

    Kroenke, Christopher D.; Neuringer, Martha; Fair, Damien A.

    2014-01-01

    Omega-3 fatty acids are essential for healthy brain and retinal development and have been implicated in a variety of neurodevelopmental disorders. This study used resting-state functional connectivity MRI to define the large-scale organization of the rhesus macaque brain and changes associated with differences in lifetime ω-3 fatty acid intake. Monkeys fed docosahexaenoic acid, the long-chain ω-3 fatty acid abundant in neural membranes, had cortical modular organization resembling the healthy human brain. In contrast, those with low levels of dietary ω-3 fatty acids had decreased functional connectivity within the early visual pathway and throughout higher-order associational cortex and showed impairment of distributed cortical networks. Our findings illustrate the similarity in modular cortical organization between the healthy human and macaque brain and support the notion that ω-3 fatty acids play a crucial role in developing and/or maintaining distributed, large-scale brain systems, including those essential for normal cognitive function. PMID:24501348

  12. 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.

  13. 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.

  14. The feasibility of a regional CTDI{sub vol} to estimate organ dose from tube current modulated CT exams

    SciTech Connect

    Khatonabadi, Maryam; Kim, Hyun J.; Lu, Peiyun; McMillan, Kyle L.; Cagnon, Chris H.; McNitt-Gray, Michael F.; DeMarco, John J.

    2013-05-15

    Purpose: In AAPM Task Group 204, the size-specific dose estimate (SSDE) was developed by providing size adjustment factors which are applied to the Computed Tomography (CT) standardized dose metric, CTDI{sub vol}. However, that work focused on fixed tube current scans and did not specifically address tube current modulation (TCM) scans, which are currently the majority of clinical scans performed. The purpose of this study was to extend the SSDE concept to account for TCM by investigating the feasibility of using anatomic and organ specific regions of scanner output to improve accuracy of dose estimates. Methods: Thirty-nine adult abdomen/pelvis and 32 chest scans from clinically indicated CT exams acquired on a multidetector CT using TCM were obtained with Institutional Review Board approval for generating voxelized models. Along with image data, raw projection data were obtained to extract TCM functions for use in Monte Carlo simulations. Patient size was calculated using the effective diameter described in TG 204. In addition, the scanner-reported CTDI{sub vol} (CTDI{sub vol,global}) was obtained for each patient, which is based on the average tube current across the entire scan. For the abdomen/pelvis scans, liver, spleen, and kidneys were manually segmented from the patient datasets; for the chest scans, lungs and for female models only, glandular breast tissue were segmented. For each patient organ doses were estimated using Monte Carlo Methods. To investigate the utility of regional measures of scanner output, regional and organ anatomic boundaries were identified from image data and used to calculate regional and organ-specific average tube current values. From these regional and organ-specific averages, CTDI{sub vol} values, referred to as regional and organ-specific CTDI{sub vol}, were calculated for each patient. Using an approach similar to TG 204, all CTDI{sub vol} values were used to normalize simulated organ doses; and the ability of each normalized

  15. Regulation of responsiveness of phosphorescence toward dissolved oxygen concentration by modulating polymer contents in organic-inorganic hybrid materials.

    PubMed

    Okada, Hiroshi; Tanaka, Kazuo; Chujo, Yoshiki

    2014-06-15

    Platinum(II) octaethylporphyrin (PtOEP)-loaded organic-inorganic hybrids were obtained via the microwave-assisted sol-gel condensation with methyltrimethoxysilane and poly(vinylpyrrolidone). From transparent and homogeneous hybrid films, the strong phosphorescence from PtOEP was observed. Next, the resulting hybrids were immersed in the aqueous buffer, and the emission intensity was monitored by changing the dissolved oxygen level in the buffer. When the hybrid with relatively-higher amount of the silica element, the strong phosphorescence was observed even under the aerobic conditions. In contrast, the emission from the hybrids with lower amounts of the silica element was quenched under the hypoxic conditions. This is, to the best of our knowledge, the first example to demonstrate that the responsiveness of the phosphorescence intensity of PtOEP in hybrid films to the dissolved oxygen concentration in water can be modulated by changing the percentage of the contents in the material. PMID:24794749

  16. Generation of 64 GBd 4ASK signals using a silicon-organic hybrid modulator at 80°C.

    PubMed

    Lauermann, M; Wolf, S; Hartmann, W; Palmer, R; Kutuvantavida, Y; Zwickel, H; Bielik, A; Altenhain, L; Lutz, J; Schmid, R; Wahlbrink, T; Bolten, J; Giesecke, A L; Freude, W; Koos, C

    2016-05-01

    We demonstrate a silicon-organic hybrid (SOH) Mach-Zehnder modulator (MZM) generating four-level amplitude shift keying (4ASK) signals at symbol rates of up to 64 GBd both at room temperature and at an elevated temperature of 80°C. The measured line rate of 128 Gbit/s corresponds to the highest value demonstrated for silicon-based MZM so far. We report bit error ratios of 10-10 (64 GBd BPSK), 10-5 (36 GBd 4ASK), and 4 × 10-3 (64 GBd 4ASK) at room temperature. At 80 °C, the respective bit error ratios are 10-10, 10-4, and 1.3 × 10-2. The high-temperature experiments were performed in regular oxygen-rich ambient atmosphere. PMID:27137555

  17. Cortical organization of inhibition-related functions and modulation by psychopathology

    PubMed Central

    Warren, Stacie L.; Crocker, Laura D.; Spielberg, Jeffery M.; Engels, Anna S.; Banich, Marie T.; Sutton, Bradley P.; Miller, Gregory A.; Heller, Wendy

    2013-01-01

    Individual differences in inhibition-related functions have been implicated as risk factors for a broad range of psychopathology, including anxiety and depression. Delineating neural mechanisms of distinct inhibition-related functions may clarify their role in the development and maintenance of psychopathology. The present study tested the hypothesis that activity in common and distinct brain regions would be associated with an ecologically sensitive, self-report measure of inhibition and a laboratory performance measure of prepotent response inhibition. Results indicated that sub-regions of DLPFC distinguished measures of inhibition, whereas left inferior frontal gyrus and bilateral inferior parietal cortex were associated with both types of inhibition. Additionally, co-occurring anxiety and depression modulated neural activity in select brain regions associated with response inhibition. Results imply that specific combinations of anxiety and depression dimensions are associated with failure to implement top-down attentional control as reflected in inefficient recruitment of posterior DLPFC and increased activation in regions associated with threat (MTG) and worry (BA10). Present findings elucidate possible neural mechanisms of interference that could help explain executive control deficits in psychopathology. PMID:23781192

  18. Increasing the size of an aromatic helical foldamer cavity by strand intercalation.

    PubMed

    Singleton, Michael L; Pirotte, Geert; Kauffmann, Brice; Ferrand, Yann; Huc, Ivan

    2014-11-24

    The postsynthetic modulation of capsules based on helical aromatic oligoamide foldamers would be a powerful approach for controlling their receptor properties without altering the initial monomer sequences. With the goal of developing a method to increase the size of a cavity within a helix, a single-helical foldamer capsule was synthesized with a wide-diameter central segment that was designed to intercalate with a second shorter helical strand. Despite the formation of stable double-helical homodimers (K(dim)>10(7) M(-1)) by the shorter strand, when it was mixed with the single-helical capsule sequence, a cross-hybridized double helix was formed with K(a)>10(5) M(-1). This strategy makes it possible to direct the formation of double-helical heterodimers. On the basis of solution- and solid-state structural data, this intercalation resulted in an increase in the central-cavity size to give a new interior volume of approximately 150 Å(3). PMID:25284711

  19. Spatial modulation spectroscopy for imaging and quantitative analysis of single dye-doped organic nanoparticles inside cells

    NASA Astrophysics Data System (ADS)

    Devadas, Mary Sajini; Devkota, Tuphan; Guha, Samit; Shaw, Scott K.; Smith, Bradley D.; Hartland, Gregory V.

    2015-05-01

    Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer.Imaging of non-fluorescent nanoparticles in complex biological environments, such as the cell cytosol, is a challenging problem. For metal nanoparticles, Rayleigh scattering methods can be used, but for organic nanoparticles, such as dye-doped polymer beads or lipid nanoparticles, light scattering does not provide good contrast. In this paper, spatial modulation spectroscopy (SMS) is used to image single organic nanoparticles doped with non-fluorescent, near-IR croconaine dye. SMS is a quantitative imaging technique that yields the absolute extinction cross-section of the nanoparticles, which can be used to determine the number of dye molecules per particle. SMS images were recorded for particles within EMT-6 breast cancer cells. The measurements allowed mapping of the nanoparticle location and the amount of dye in a single cell. The results demonstrate how SMS can facilitate efforts to optimize dye-doped nanoparticles for effective photothermal therapy of cancer. Electronic supplementary information (ESI

  20. Living organisms influence on environmental conditions: pH modulation by amphibian embryos versus aluminum toxicity.

    PubMed

    Herkovits, Jorge; Castañaga, Luis Alberto; D'Eramo, José Luis; Jourani, Victoria Platonova

    2015-11-01

    The LC10, 50 and 90/24h of aluminum for Rhinella arenarum embryos at complete operculum stage were 0.55, 0.75 and 1mgAl(3+)/L respectively. Those values did not change significantly by expanding the exposure period till 168h. The aluminum toxicity was evaluated in different pH conditions by means of a citrate buffer resulting for instance, 1mgAl(3+)/L at pH 4, 4.1, 5 and 6 in 100%, 70%, 35% and 0% of lethality respectively. As an outstanding feature, the embryos changed the pH of the maintaining media both in the case of Al(3+) or citrate buffer treatments toward neutral. 10 embryos in 40mL of AMPHITOX solution were able to increase the pH from 4.2 to 7.05, a fact related with a metabolic shift resulting in an increase in nitrogen loss as ammonia. Our study point out the natural selection of the most resistant amphibian embryos both for pH or aluminum as well as the capacity of living organisms (as a population) to alter their chemical environment toward optimal conditions for their survival. As these facts occur at early life stages, it expand the concept that living organisms at ontogenic stages are biomarker of environmental signatures of the evolutionary process (Herkovits, 2006) to a global Onto-Evo concept which imply also the feedback mechanisms from living organisms to shape environmental conditions in a way that benefits them. PMID:26126231

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. The nuclear lamina regulates germline stem cell niche organization via modulation of EGFR signaling

    PubMed Central

    Chen, Haiyang; Chen, Xin; Zheng, Yixian

    2013-01-01

    Summary Stem cell-niche interactions have been studied extensively with regard to cell polarity and extracellular signaling. Less is known about the way in which signals and polarity cues integrate with intracellular structures to ensure appropriate niche organization and function. Here we report that nuclear lamins function in the cyst stem cells (CySCs) of Drosophila testis to control the interaction of CySCs with the hub. This interaction is important for regulation of CySC differentiation and organization of the niche that supports the germline stem cells (GSCs). Lamin promotes nuclear retention of phosphorylated ERK in the CySC lineage by regulating the distribution of specific nucleoporins within the nuclear pores. Lamin-regulated nuclear EGFR signaling in the CySC lineage is essential for proliferation and differentiation of the GSCs and the transient amplifying germ cells. Thus, we have uncovered a role for the nuclear lamina in integration of EGF signaling to regulate stem cell niche function. PMID:23827710

  6. A non-classical view of the modulation of mineral precipitation by organic additives

    NASA Astrophysics Data System (ADS)

    Ruiz-Agudo, Encarnacion; Ruiz-Agudo, Cristina; Burgos-Cara, Alejandro; Putnis, Christine; Rodriguez-Navarro, Carlos; Putnis, Andrew

    2016-04-01

    Questions persist on the mechanisms of crystallization of sparingly soluble minerals such as calcium carbonate, calcium oxalate or barium sulphate. Compared to CaCO3, the mechanisms of nucleation and growth in the CaC2O4-H2O or BaSO4-H2O systems have received less attention. These phases are important due to their relevance as biominerals and/or unwanted mineral deposits in technological applications. Growing evidence suggests that sparingly soluble salts form by non-classical nucleation and growth pathways, where pre-nucleation ion associates and amorphous (solid or liquid) precursor phase(s) play a critical role (e.g. Rodríguez-Navarro et al. (2015), Ruiz-Agudo et al. (2015)). Indeed the identification of pre-nucleation species in these systems and their strong interactions with organic compounds (Verch et al. 2011) raises the possibility that the control of organics on biomineralization may begin even earlier than previously thought. A sound knowledge of the physical mechanisms by which acidic macromolecules affect nucleation and early growth may offer general insights concerning the molecular control of biomineralization, as well as being critical for improving strategies to control unwanted mineral deposition or for the synthesis of biomimetic materials. Here we present investigations on the initial stages of the precipitation of these relevant minerals in organic-free solutions to identify the precipitation pathway and to look for any potential precursor phase(s) to the final, crystalline polymorph. As well, we explore the effects that several acidic organic compounds have on the different precipitation stages identified. We find that organic additives such as citric acid, polyacrilic acid or a commercial copolymer of maleic acid/allyl sulfonic acid with phosphonate groups can be active at modifying pre-nucleation stages (destabilizing of pre-nucleation species or hampering the aggregation and growth of pre-nucleation associates) and subsequently strongly

  7. Developmental programming: postnatal estradiol modulation of prenatally organized reproductive neuroendocrine function in sheep.

    PubMed

    Puttabyatappa, Muraly; Cardoso, Rodolfo C; Herkimer, Carol; Veiga-Lopez, Almudena; Padmanabhan, Vasantha

    2016-08-01

    Gestational testosterone (TS) excess, acting via both the androgenic and estrogenic pathways, advances puberty and disrupts the neuroendocrine estradiol (E2) feedback and periovulatory hormonal dynamics in female sheep. These prenatally programmed defects may be subject to postnatal modifications by continued organizational and/or activational effects of steroids. This study investigated (1) the organizational contribution of prenatal estrogen excess and (2) the impact of postnatal exposure to E2 in modulating the effects of prenatal androgen excess (TS and dihydrotestosterone (DHT)) on puberty, neuroendocrine feedback mechanisms, and periovulatory hormonal dynamics in sheep. Pregnant Suffolk sheep were treated with TS, DHT, E2, or E2 plus DHT (ED) from days 30 to 90 of gestation. A subset of the control (C), TS, and DHT female offspring received a constant-release E2 implant postnatally. Findings revealed that (1) prenatal E2-treatment failed to reproduce the neuroendocrine disruptions predicted to be programmed by the estrogenic pathway and (2) prenatal E2D-treatment did not adequately replicate the reproductive neuroendocrine defects induced by prenatal TS excess. More importantly, continuous postnatal E2-treatment, while delaying the onset of puberty and reducing the inhibitory effects of E2 on tonic luteinizing hormone (LH) release, failed to amplify the E2-positive feedback and periovulatory defects induced by prenatal TS-treatment. Our results indicate that disruptions in E2-positive feedback mechanisms and periovulatory gonadotropin secretion induced by prenatal TS-treatment are programmed predominantly during the prenatal life with postnatal exposure to E2 excess not contributing further to these disruptions. PMID:27222598

  8. Amyloid β peptide stimulates platelet activation through RhoA-dependent modulation of actomyosin organization.

    PubMed

    Sonkar, Vijay K; Kulkarni, Paresh P; Dash, Debabrata

    2014-04-01

    Platelets contribute to 95% of circulating amyloid precursor protein in the body and have widely been employed as a "peripheral" model of neurons in Alzheimer's disease. We sought to analyze the effects of amyloid β (Aβ) on platelets and to understand the underlying molecular mechanism. The Aβ active fragment containing amino acid sequence 25-35 (Aβ(25-35); 10-20 μM) was found to induce strong aggregation of human platelets, granule release, and integrin activation, similar to that elicited by physiological agonists. Platelets exposed to Aβ(25-35) retracted fibrin clot and displayed augmented adhesion to collagen under arterial shear, reflective of a switch to prothrombotic phenotype. Exposure of platelets to Aβ peptide (20 μM) resulted in a 4.2- and 2.3-fold increase in phosphorylation of myosin light chain (MLC) and MLC phosphatase, respectively, which was reversed by Y27632, an inhibitor of Rho-associated coiled-coil protein kinase (ROCK). Aβ(25-35)-induced platelet aggregation and clot retraction were also significantly attenuated by Y27632. Consistent with these findings, Aβ(25-35) elicited a significant rise in the level of RhoA-GTP in platelets. Platelets pretreated with reverse-sequenced Aβ fragment (Aβ(35-25)) and untreated resting platelets served as controls. We conclude that Aβ induces cellular activation through RhoA-dependent modulation of actomyosin, and hence, RhoA could be a potential therapeutic target in Alzheimer's disease and cerebral amyloid angiopathy. PMID:24421399

  9. Parkin Modulates Endosomal Organization and Function of the Endo-Lysosomal Pathway.

    PubMed

    Song, Pingping; Trajkovic, Katarina; Tsunemi, Taiji; Krainc, Dimitri

    2016-02-24

    Mutations in PARK2 (parkin), which encodes Parkin protein, an E3 ubiquitin ligase, are associated with autosomal recessive early-onset Parkinson's disease (PD). While several studies implicated Parkin in the regulation of mitophagy and proteasomal degradation, the precise mechanism leading to neurodegeneration upon Parkin loss of function remains incompletely understood. In this study, we found that Parkin modulates the endocytic pathway through the regulation of endosomal structure and function. We showed that loss of Parkin function led to decreased endosomal tubulation and membrane association of vesicle protein sorting 35 (VPS35) and sorting nexin 1 (SNX1), as well as decreased mannose 6 phosphate receptor (M6PR), suggesting the impairment of retromer pathway in Parkin-deficient cells. We also found increased formation of intraluminal vesicles coupled with enhanced release of exosomes in the presence of mutant Parkin. To elucidate the molecular mechanism of these alterations in the endocytic pathway in Parkin-deficient cells, we found that Parkin regulates the levels and activity of Rab7 by promoting its ubiquitination on lysine 38 residue. Both endogenous Rab7 in Parkin-deficient cells and overexpressed K38 R-Rab7 mutant displayed decreased effector binding and membrane association. Furthermore, overexpression of K38R-Rab7 in HEK293 cells phenocopied the increased secretion of exosomes observed in Parkin-deficient cells, suggesting that Rab7 deregulation may be at least partially responsible for the endocytic phenotype observed in Parkin-deficient cells. These findings establish a role for Parkin in regulating the endo-lysosomal pathway and retromer function and raise the possibility that alterations in these pathways contribute to the development of pathology in Parkin-linked Parkinson's disease. PMID:26911690

  10. Comparing step-and-shoot IMRT with dynamic helical tomotherapy IMRT plans for head-and-neck cancer

    SciTech Connect

    Vulpen, Marco van . E-mail: M.vanVulpen@azu.nl; Field, Colin; Raaijmakers, Cornelis P.J.; Parliament, Matthew B.; Terhaard, Chris H.J.; MacKenzie, Marc A.; Scrimger, Rufus; Lagendijk, Jan J.W.; Fallone, B. Gino

    2005-08-01

    Purpose: The goal of this planning study was to compare step-and-shoot intensity-modulated radiotherapy (IMRT) plans with helical dynamic IMRT plans for oropharynx patients on the basis of dose distribution. Methods and Materials: Five patients with oropharynx cancer had been previously treated by step-and-shoot IMRT at University Medical Centre Utrecht, The Netherlands, applying five fields and approximately 60-90 segments. Inverse planning was carried out using Plato, version 2.6.2. For each patient, an inverse IMRT plan was also made using Tomotherapy Hi-Art System, version 2.0, and using the same targets and optimization goals. Statistical analysis was performed by a paired t test. Results: All tomotherapy plans compared favorably with the step-and-shoot plans regarding sparing of the organs at risk and keeping an equivalent target dose homogeneity. Tomotherapy plans in particular realized sharper dose gradients compared with the step-and-shoot plans. The mean dose to all parotid glands (n = 10) decreased on average 6.5 Gy (range, -4 to 14; p = 0.002). The theoretical reduction in normal tissue complication probabilities in favor of the tomotherapy plans depended on the parotid normal tissue complication probability model used (range, -3% to 32%). Conclusion: Helical tomotherapy IMRT plans realized sharper dose gradients compared with the clinically applied step-and shoot plans. They are expected to be able to reduce the parotid normal tissue complication probability further, keeping a similar target dose homogeneity.

  11. Attenuation-based size metric for estimating organ dose to patients undergoing tube current modulated CT exams

    SciTech Connect

    Bostani, Maryam McMillan, Kyle; Lu, Peiyun; Kim, Hyun J.; Cagnon, Chris H.; McNitt-Gray, Michael F.; DeMarco, John J.

    2015-02-15

    Purpose: Task Group 204 introduced effective diameter (ED) as the patient size metric used to correlate size-specific-dose-estimates. However, this size metric fails to account for patient attenuation properties and has been suggested to be replaced by an attenuation-based size metric, water equivalent diameter (D{sub W}). The purpose of this study is to investigate different size metrics, effective diameter, and water equivalent diameter, in combination with regional descriptions of scanner output to establish the most appropriate size metric to be used as a predictor for organ dose in tube current modulated CT exams. Methods: 101 thoracic and 82 abdomen/pelvis scans from clinically indicated CT exams were collected retrospectively from a multidetector row CT (Sensation 64, Siemens Healthcare) with Institutional Review Board approval to generate voxelized patient models. Fully irradiated organs (lung and breasts in thoracic scans and liver, kidneys, and spleen in abdominal scans) were segmented and used as tally regions in Monte Carlo simulations for reporting organ dose. Along with image data, raw projection data were collected to obtain tube current information for simulating tube current modulation scans using Monte Carlo methods. Additionally, previously described patient size metrics [ED, D{sub W}, and approximated water equivalent diameter (D{sub Wa})] were calculated for each patient and reported in three different ways: a single value averaged over the entire scan, a single value averaged over the region of interest, and a single value from a location in the middle of the scan volume. Organ doses were normalized by an appropriate mAs weighted CTDI{sub vol} to reflect regional variation of tube current. Linear regression analysis was used to evaluate the correlations between normalized organ doses and each size metric. Results: For the abdominal organs, the correlations between normalized organ dose and size metric were overall slightly higher for all three

  12. Metal-Organic Frameworks Modulated by Doping Er(3+) for Up-Conversion Luminescence.

    PubMed

    Zhang, Xindan; Li, Bin; Ma, Heping; Zhang, Liming; Zhao, Haifeng

    2016-07-13

    Here we present metal-organic frameworks prepared by a one-step synthesis method, possessing both architectural properties of MOF building and up-conversion luminescence of rare earth Er(3+) (hereafter denoted as Up-MOFs). Up-MOFs have characteristic up-conversion emissions at 520, 540, and 651 nm under the excitation of 980 nm owing to the multiple photon absorption. The up-conversion mechanism of these Up-MOFs has been discussed, and it can be attributed to the excited state absorption process. The design and synthesis of Up-MOF materials possessing near-infrared region excitation and up-conversion luminescence are fully expected to be candidates for the advancement of applications in bioimaging, sensors, optoelectronics, and energy conversion/storage devices. PMID:27315339

  13. Modulation of sialic acid levels among some organs during insulin resistance or hyperglycemic states.

    PubMed

    Ibrahim, Mohammed Auwal; Abdulkadir, Aisha; Onojah, Alice; Sani, Lawal; Adamu, Auwal; Abdullahi, Hadiza

    2016-01-01

    Previous studies have suggested a possible connection between insulin resistance and chronic hyperglycemia with membrane sialic acid content. In this study, the effects of high (20% ad libitum) fructose and glucose feeding on the sialic acid levels of some organs were investigated in rats. The blood glucose levels of the high fructose- and glucose-fed rats were consistently and significantly (P < 0.05) higher than the normal control throughout the experiment. Free serum sialic acid and total hepatic sialic acid levels were elevated in the high fructose- and glucose-fed rats compared to normal control, but only the data for the high glucose-fed group were significantly (P < 0.05) different from the normal control. Conversely, a significant (P < 0.05) decrease in the pancreatic sialic acid level was observed in high glucose-fed group compared to normal control. Also, the high fructose-fed rats had lower, but insignificant (P > 0.05), pancreatic sialic acid level than the normal control. On the other hand, high fructose and glucose feeding did not significantly (P > 0.05) affect the sialic acid levels of the skeletal muscle and heart, though a tendency to increase the sialic acid level was evident in the heart. In the kidney, the sialic acid level was significantly (P < 0.05) increased in both high fructose- and glucose-fed groups. It was concluded that the liver and kidney tend to stimulate sialic acid synthesis, while the pancreas downregulate sialic acids synthesis and/or promote sialic acid release from glycoconjugates. Also, these organs may contribute to high-serum sialic acid level observed during diabetes. PMID:26468092

  14. Combining and Correlating DC, Modulated, and Transient Measurement Techniques to Disentangle and Quantify Key Physical Properties for Organic Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Gundlach, David

    2015-03-01

    Organic thin film electronics offer the potential to significantly impact how humans interface with their surroundings and society in general. Substantial contributions over the past two decades in this highly multidisciplinary area of research have led to significant improvements in discrete device performance and several impressive advanced technology demonstrations. However, fundamental understanding and quantification of the physical properties and processes that govern device operation remains limited compared to conventional semiconductors, such as silicon. In this presentation I will discuss our recent development and application of combined and correlated optical-electrical measurement methods to obtain a more nuanced understanding and quantification of the critical properties and fundamental processes relevant to device operation. In particular, I will discuss the use of steady state and pulsed light techniques combined with modulated and DC electrical measurements tailored to the specific operating regimes and device structures of organic diodes (solar cells and light emitters) and transistors to provide greater understanding of charge injection, transport, lifetime, density, and recombination kinetics.

  15. miR-8 modulates cytoskeletal regulators to influence cell survival and epithelial organization in Drosophila wings.

    PubMed

    Bolin, Kelsey; Rachmaninoff, Nicholas; Moncada, Kea; Pula, Katharine; Kennell, Jennifer; Buttitta, Laura

    2016-04-01

    The miR-200 microRNA family plays important tumor suppressive roles. The sole Drosophila miR-200 ortholog, miR-8 plays conserved roles in Wingless, Notch and Insulin signaling - pathways linked to tumorigenesis, yet homozygous null animals are viable and often appear morphologically normal. We observed that wing tissues mosaic for miR-8 levels by genetic loss or gain of function exhibited patterns of cell death consistent with a role for miR-8 in modulating cell survival in vivo. Here we show that miR-8 levels impact several actin cytoskeletal regulators that can affect cell survival and epithelial organization. We show that loss of miR-8 can confer resistance to apoptosis independent of an epithelial to mesenchymal transition while the persistence of cells expressing high levels of miR-8 in the wing epithelium leads to increased JNK signaling, aberrant expression of extracellular matrix remodeling proteins and disruption of proper wing epithelial organization. Altogether our results suggest that very low as well as very high levels of miR-8 can contribute to hallmarks associated with cancer, suggesting approaches to increase miR-200 microRNAs in cancer treatment should be moderate. PMID:26902111

  16. Light Modulates the Biosynthesis and Organization of Cyanobacterial Carbon Fixation Machinery through Photosynthetic Electron Flow1[OPEN

    PubMed Central

    Sun, Yaqi; Casella, Selene

    2016-01-01

    Cyanobacteria have evolved effective adaptive mechanisms to improve photosynthesis and CO2 fixation. The central CO2-fixing machinery is the carboxysome, which is composed of an icosahedral proteinaceous shell encapsulating the key carbon fixation enzyme, Rubisco, in the interior. Controlled biosynthesis and ordered organization of carboxysomes are vital to the CO2-fixing activity of cyanobacterial cells. However, little is known about how carboxysome biosynthesis and spatial positioning are physiologically regulated to adjust to dynamic changes in the environment. Here, we used fluorescence tagging and live-cell confocal fluorescence imaging to explore the biosynthesis and subcellular localization of β-carboxysomes within a model cyanobacterium, Synechococcus elongatus PCC7942, in response to light variation. We demonstrated that β-carboxysome biosynthesis is accelerated in response to increasing light intensity, thereby enhancing the carbon fixation activity of the cell. Inhibition of photosynthetic electron flow impairs the accumulation of carboxysomes, indicating a close coordination between β-carboxysome biogenesis and photosynthetic electron transport. Likewise, the spatial organization of carboxysomes in the cell correlates with the redox state of photosynthetic electron transport chain. This study provides essential knowledge for us to modulate the β-carboxysome biosynthesis and function in cyanobacteria. In translational terms, the knowledge is instrumental for design and synthetic engineering of functional carboxysomes into higher plants to improve photosynthesis performance and CO2 fixation. PMID:26956667

  17. Nano-clustering of ligands on surrogate antigen presenting cells modulates T cell membrane adhesion and organization.

    PubMed

    Dillard, Pierre; Pi, Fuwei; Lellouch, Annemarie C; Limozin, Laurent; Sengupta, Kheya

    2016-03-14

    We investigate the adhesion and molecular organization of the plasma membrane of T lymphocytes interacting with a surrogate antigen presenting cell comprising glass supported ordered arrays of antibody (α-CD3) nano-dots dispersed in a non-adhesive matrix of polyethylene glycol (PEG). The local membrane adhesion and topography, as well as the distribution of the T cell receptors (TCRs) and the kinase ZAP-70, are influenced by dot-geometry, whereas the cell spreading area is determined by the overall average density of the ligands rather than specific characteristics of the dots. TCR clusters are recruited preferentially to the nano-dots and the TCR cluster size distribution has a weak dot-size dependence. On the patterns, the clusters are larger, more numerous, and more enriched in TCRs, as compared to the homogeneously distributed ligands at comparable concentrations. These observations support the idea that non-ligated TCRs residing in the non-adhered parts of the proximal membrane are able to diffuse and enrich the existing clusters at the ligand dots. However, long distance transport is impaired and cluster centralization in the form of a central supramolecular cluster (cSMAC) is not observed. Time-lapse imaging of early cell-surface contacts indicates that the ZAP-70 microclusters are directly recruited to the site of the antibody dots and this process is concomitant with membrane adhesion. These results together point to a complex interplay of adhesion, molecular organization and activation in response to spatially modulated stimulation. PMID:26887857

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation.

    PubMed

    Petriello, Michael C; Newsome, Bradley J; Dziubla, Thomas D; Hilt, J Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

    2014-09-01

    Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associated with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body's vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. PMID:24530186

  3. Organic electronics for precise delivery of neurotransmitters to modulate mammalian sensory function

    NASA Astrophysics Data System (ADS)

    Simon, Daniel T.; Kurup, Sindhulakshmi; Larsson, Karin C.; Hori, Ryusuke; Tybrandt, Klas; Goiny, Michel; Jager, Edwin W. H.; Berggren, Magnus; Canlon, Barbara; Richter-Dahlfors, Agneta

    2009-09-01

    Significant advances have been made in the understanding of the pathophysiology, molecular targets and therapies for the treatment of a variety of nervous-system disorders. Particular therapies involve electrical sensing and stimulation of neural activity, and significant effort has therefore been devoted to the refinement of neural electrodes. However, direct electrical interfacing suffers from some inherent problems, such as the inability to discriminate amongst cell types. Thus, there is a need for novel devices to specifically interface nerve cells. Here, we demonstrate an organic electronic device capable of precisely delivering neurotransmitters in vitro and in vivo. In converting electronic addressing into delivery of neurotransmitters, the device mimics the nerve synapse. Using the peripheral auditory system, we show that out of a diverse population of cells, the device can selectively stimulate nerve cells responding to a specific neurotransmitter. This is achieved by precise electronic control of electrophoretic migration through a polymer film. This mechanism provides several sought-after features for regulation of cell signalling: exact dosage determination through electrochemical relationships, minimally disruptive delivery due to lack of fluid flow, and on-off switching. This technology has great potential as a therapeutic platform and could help accelerate the development of therapeutic strategies for nervous-system disorders.

  4. Modulation of persistent organic pollutant toxicity through nutritional intervention: emerging opportunities in biomedicine and environmental remediation

    PubMed Central

    Petriello, Michael C.; Newsome, Bradley J.; Dziubla, Thomas D.; Hilt, J. Zach; Bhattacharyya, Dibakar; Hennig, Bernhard

    2014-01-01

    Environmental pollution is increasing worldwide, and there is evidence that exposure to halogenated persistent organic pollutants (POPs) such as polychlorinated biphenyls can contribute to the pathology of inflammatory diseases such as atherosclerosis, diabetes, and cancer. Pollutant removal from contaminated sites and subsequent pollutant degradation are critical for reducing the long-term health risks associated with exposure. However, complete remediation of a toxicant from the environment is very difficult and cost-prohibitive. Furthermore, remediation technologies often result in the generation of secondary toxicants. Considering these circumstances, environmentally-friendly and sustainable remediation technologies and biomedical solutions to reduce vulnerability to environmental chemical insults need to be explored to reduce the overall health risks associate with exposure to environmental pollutants. We propose that positive lifestyle changes such as healthful nutrition and consumption of diets rich in fruits and vegetables or bioactive nutrients with antioxidant and/or anti-inflammatory properties will reduce the body’s vulnerability to environmental stressors and thus reduce toxicant-mediated disease pathologies. Interestingly, emerging evidence now implicates the incorporation of bioactive nutrients, such as plant-derived polyphenols, in technologies focused on the capture, sensing and remediation of halogenated POPs. We propose that human nutritional intervention in concert with the use of natural polyphenol sensing and remediation platforms may provide a sensible means to develop primary and long-term prevention strategies of diseases associated with many environmental toxic insults including halogenated POPs. PMID:24530186

  5. Monte Carlo calculation of helical tomotherapy dose delivery

    SciTech Connect

    Zhao Yingli; Mackenzie, M.; Kirkby, C.; Fallone, B. G.

    2008-08-15

    Helical tomotherapy delivers intensity modulated radiation therapy using a binary multileaf collimator (MLC) to modulate a fan beam of radiation. This delivery occurs while the linac gantry and treatment couch are both in constant motion, so the beam describes, from a patient/phantom perspective, a spiral or helix of dose. The planning system models this continuous delivery as a large number (51) of discrete gantry positions per rotation, and given the small jaw/fan width setting typically used (1 or 2.5 cm) and the number of overlapping rotations used to cover the target (pitch often <0.5), the treatment planning system (TPS) potentially employs a very large number of static beam directions and leaf opening configurations to model the modulated fields. All dose calculations performed by the system employ a convolution/superposition model. In this work the authors perform a full Monte Carlo (MC) dose calculation of tomotherapy deliveries to phantom computed tomography (CT) data sets to verify the TPS calculations. All MC calculations are performed with the EGSnrc-based MC simulation codes, BEAMnrc and DOSXYZnrc. Simulations are performed by taking the sinogram (leaf opening versus time) of the treatment plan and decomposing it into 51 different projections per rotation, as does the TPS, each of which is segmented further into multiple MLC opening configurations, each with different weights that correspond to leaf opening times. Then the projection is simulated by the summing of all of the opening configurations, and the overall rotational treatment is simulated by the summing of all of the projection simulations. Commissioning of the source model was verified by comparing measured and simulated values for the percent depth dose and beam profiles shapes for various jaw settings. The accuracy of the MLC leaf width and tongue and groove spacing were verified by comparing measured and simulated values for the MLC leakage and a picket fence pattern. The validated source

  6. A protein kinase associated with paired helical filaments in Alzheimer disease.

    PubMed Central

    Vincent, I J; Davies, P

    1992-01-01

    We have identified a protein kinase in immunoaffinity-purified preparations of paired helical filaments from brain tissue of individuals with Alzheimer disease. The kinase phosphorylates the filament proteins in vitro in a manner independent of second messenger regulation or of modulation by heparin and polyamines. Physiological concentrations of hemin, an oxidized heme porphyrin, inhibit the kinase and abolish Alz-50 immunoreactivity of the proteins. Since paired helical filaments are composed of hyperphosphorylated proteins, association of a protein kinase with the filaments provides a mechanism for abnormal processing of the proteins in disease. Images PMID:1557394

  7. A method to dynamically balance intensity modulated radiotherapy dose between organs-at-risk

    SciTech Connect

    Das, Shiva K.

    2009-05-15

    The IMRT treatment planning process typically follows a path that is based on the manner in which the planner interactively adjusts the target and organ-at-risk (OAR) constraints and priorities. The time-intensive nature of this process restricts the planner from fully understanding the dose trade-off between structures, making it unlikely that the resulting plan fully exploits the extent to which dose can be redistributed between anatomical structures. Multiobjective Pareto optimization has been used in the past to enable the planner to more thoroughly explore alternatives in dose trade-off by combining pre-generated Pareto optimal solutions in real time, thereby potentially tailoring a plan more exactly to requirements. However, generating the Pareto optimal solutions can be nonintuitive and computationally time intensive. The author presents an intuitive and fast non-Pareto approach for generating optimization sequences (prior to planning), which can then be rapidly combined by the planner in real time to yield a satisfactory plan. Each optimization sequence incrementally reduces dose to one OAR at a time, starting from the optimization solution where dose to all OARs are reduced with equal priority, until user-specified target coverage limits are violated. The sequences are computationally efficient to generate, since the optimization at each position along a sequence is initiated from the end result of the previous position in the sequence. The pre-generated optimization sequences require no user interaction. In real time, a planner can more or less instantaneously visualize a treatment plan by combining the dose distributions corresponding to user-selected positions along each of the optimization sequences (target coverage is intrinsically maintained in the combination). Interactively varying the selected positions along each of the sequences enables the planner to rapidly understand the nature of dose trade-off between structures and, thereby, arrive at a

  8. Organic Cation Transporters Modulate the Uptake and Cytotoxicity of Picoplatin, a Third-Generation Platinum Analogue

    PubMed Central

    More, Swati S.; Li, Shuanglian; Yee, Sook Wah; Chen, Ligong; Xu, Zhidong; Jablons, David M.; Giacomini, Kathleen M.

    2012-01-01

    Picoplatin, a third-generation platinum agent, is efficacious against lung cancers that are otherwise resistant or become refractory during platinum treatment. This effort was aimed at the determination of the influence of organic cation transporters 1, 2, and 3 (OCT1, OCT2, and OCT3) and their genetic variants on cellular uptake of picoplatin and on the individual components of the ensuing cytotoxicity such as DNA adduct formation. The effect of OCT1 on picoplatin pharmacokinetics and antitumor efficacy was determined using OCT knockout mice and HEK293 xenografts stably expressing OCT1. The uptake and DNA adduct formation of picoplatin were found to be significantly enhanced by the expression of the OCTs. Expression of OCT1 and OCT2, but not OCT3, significantly enhanced picoplatin cytotoxicity, which was reduced in the presence of an OCT inhibitor. Common reduced functional variants of OCT1 and OCT2 led to reduction in uptake and DNA adduct formation of picoplatin in comparison with the reference OCT1 and OCT2. Pharmacokinetic parameters of picoplatin in Oct1−/− and Oct1+/+ mice were not significantly different, suggesting that the transporters do not influence the disposition of the drug. In contrast, the volume of OCT1-expressing xenografts in mice was significantly reduced by picoplatin treatment, suggesting that OCT1 may enhance the antitumor efficacy of picoplatin. These studies provide a basis for follow-up clinical studies that would seek to examine the relationship between the anticancer efficacy of picoplatin and expression levels of OCTs and their genetic variants in tumors. PMID:20371711

  9. Estimation of breast dose saving potential using a breast positioning technique for organ-based tube current modulated CT

    NASA Astrophysics Data System (ADS)

    Fu, Wanyi; Tian, Xiaoyu; Sturgeon, Gregory; Agasthya, Greeshma; Segars, William Paul; Goodsitt, Mitchell M.; Kazerooni, Ella A.; Samei, Ehsan

    2016-04-01

    In thoracic CT, organ-based tube current modulation (OTCM) reduces breast dose by lowering the tube current in the 120° anterior dose reduction zone of patients. However, in practice the breasts usually expand to an angle larger than the dose reduction zone. This work aims to simulate a breast positioning technique (BPT) to constrain the breast tissue to within the dose reduction zone for OTCM and to evaluate the corresponding potential reduction in breast dose. Thirteen female anthropomorphic computational phantoms were studied (age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modeled in the supine position with and without application of the BPT. Attenuation-based tube current (ATCM, reference mA) was generated by a ray-tracing program, taking into account the patient attenuation change in the longitudinal and angular plane (CAREDose4D, Siemens Healthcare). OTCM was generated by reducing the mA to 20% between +/- 60° anterior of the patient and increasing the mA in the remaining projections correspondingly (X-CARE, Siemens Healthcare) to maintain the mean tube current. Breast tissue dose was estimated using a validated Monte Carlo program for a commercial scanner (SOMATOM Definition Flash, Siemens Healthcare). Compared to standard tube current modulation, breast dose was significantly reduced using OTCM by 19.8+/-4.7%. With the BPT, breast dose was reduced by an additional 20.4+/-6.5% to 37.1+/-6.9%, using the same CTDIvol. BPT was more effective for phantoms simulating women with larger breasts with the average breast dose reduction of 30.2%, 39.2%, and 49.2% from OTCMBP to ATCM, using the same CTDIvol for phantoms with 0.5, 1.5, and 2.5 kg breasts, respectively. This study shows that a specially designed BPT improves the effectiveness of OTCM.

  10. 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.

  11. Parotid Gland Sparing With Helical Tomotherapy in Head-and-Neck Cancer

    SciTech Connect

    Voordeckers, Mia; Farrag, Ashraf; Everaert, Hendrik; Tournel, Koen; Storme, Guy; Verellen, Dirk; De Ridder, Mark

    2012-10-01

    Purpose: This study evaluated the ability of helical tomotherapy to spare the function of the parotid glands in patients with head-and-neck cancer by analyzing dose-volume histograms, salivary gland scintigraphy, and quality of life assessment. Methods and Materials: Data from 76 consecutive patients treated with helical tomotherapy (Hi-Art Tomotherapy) at University Hospital Brussel were analyzed. During planning, priority was given to planning target volume (PTV) coverage: {>=}95% of the dose must be delivered to {>=}95% of the PTV. Elective nodal regions received 54 Gy (1.8 Gy/fraction). A dose of 70.5 Gy (2.35 Gy/fraction) was prescribed to the primary tumor and pathologic lymph nodes (simultaneous integrated boost scheme). Objective scoring of salivary excretion was performed by salivary gland scintigraphy. Subjective scoring of salivary gland function was evaluated by the European Organization for Research and Treatment of Cancer quality of life questionnaires Quality of Life Questionnaire-C30 (QLQ-C30) and Quality of Life Questionnaire-Head and Neck 35 (H and N35). Results: Analysis of dose-volume histograms (DVHs) showed excellent coverage of the PTV. The volume of PTV receiving 95% of the prescribed dose (V95%) was 99.4 (range, 96.3-99.9). DVH analysis of parotid gland showed a median value of the mean parotid dose of 32.1 Gy (range, 17.5-70.3 Gy). The median parotid volume receiving a dose <26 Gy was 51.2%. Quality of life evaluation demonstrated an initial deterioration of almost all scales and items in QLQ-C30 and QLQ-H and N35. Most items improved in time, and some reached baseline values 18 months after treatment. Conclusion: DVH analysis, scintigraphic evaluation of parotid function, and quality of life assessment of our patient group showed that helical tomotherapy makes it possible to preserve parotid gland function without compromising disease control. We recommend mean parotid doses of <34 Gy and doses <26 Gy to a maximum 47% of the parotid

  12. 320-Row wide volume CT significantly reduces density heterogeneity observed in the descending aorta: comparisons with 64-row helical CT.

    PubMed

    Yamashiro, Tsuneo; Miyara, Tetsuhiro; Honda, Osamu; Kamiya, Ayano; Tanaka, Yuko; Murayama, Sadayuki

    2014-01-01

    The aim of this study was to compare density heterogeneity on wide volume (WV) scans with that on helical CT scans. 22 subjects underwent chest CT using 320-WV and 64-helical modes. Density heterogeneity of the descending aorta was evaluated quantitatively and qualitatively. At qualitative assessment, the heterogeneity was judged to be smaller on WV scans than on helical scans (p<0.0001). Mean changes in aortic density between two contiguous slices were 1.64 HU (3.40%) on WV scans and 2.29 HU (5.19%) on helical scans (p<0.0001). CT density of thoracic organs is more homogeneous and reliable on WV scans than on helical scans. PMID:24210879

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Strategies for Online Organ Motion Correction for Intensity-Modulated Radiotherapy of Prostate Cancer: Prostate, Rectum, and Bladder Dose Effects

    SciTech Connect

    Rijkhorst, Erik-Jan; Lakeman, Annemarie; Nijkamp, Jasper; Bois, Josien de; Herk, Marcel van; Lebesque, Joos V.; Sonke, Jan-Jakob

    2009-11-15

    Purpose: To quantify and evaluate the accumulated prostate, rectum, and bladder dose for several strategies including rotational organ motion correction for intensity-modulated radiotherapy (IMRT) of prostate cancer using realistic organ motion data. Methods and Materials: Repeat computed tomography (CT) scans of 19 prostate patients were used. Per patient, two IMRT plans with different uniform margins were created. To quantify prostate and seminal vesicle motion, repeat CT clinical target volumes (CTVs) were matched onto the planning CTV using deformable registration. Four different strategies, from online setup to full motion correction, were simulated. Rotations were corrected for using gantry and collimator angle adjustments. Prostate, rectum, and bladder doses were accumulated for each patient, plan, and strategy. Minimum CTV dose (D{sub min}), rectum equivalent uniform dose (EUD, n = 0.13), and bladder surface receiving >=78 Gy (S78), were calculated. Results: With online CTV translation correction, a 7-mm margin was sufficient (i.e., D{sub min} >= 95% of the prescribed dose for all patients). A 4-mm margin required additional rotational correction. Margin reduction lowered the rectum EUD(n = 0.13) by approx2.6 Gy, and the bladder S78 by approx1.9%. Conclusions: With online correction of both translations and rotations, a 4-mm margin was sufficient for 15 of 19 patients, whereas the remaining four patients had an underdosed CTV volume <1%. Margin reduction combined with online corrections resulted in a similar or lower dose to the rectum and bladder. The more advanced the correction strategy, the better the planned and accumulated dose agreed.

  19. Microscopic hole-transfer efficiency in organic thin-film transistors studied with charge-modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Miyata, Kiyoshi; Tanaka, Shunsuke; Ishino, Yuuta; Watanabe, Kazuya; Uemura, Takafumi; Takeya, Jun; Sugimoto, Toshiki; Matsumoto, Yoshiyasu

    2015-05-01

    While the microscopic transfer properties of carriers are of primary importance for carrier transport of organic semiconductors, the mesoscopic features including the morphologies of grains and the structure of grain boundaries limit the overall carrier transport particularly in polycrystalline organic thin films. Thus the conventional evaluation methods of carrier mobility that rely on macroscopic properties such as I -V curves of devices are not capable to determine carrier transfer probability at the molecular level. Here, we present a method for evaluating the relative strengths of transfer integrals using charge-modulation spectroscopy on thin-film transistors of dinaphtho[2 ,3 -b :2',3'-f ]thieno[3 ,2 -b ]thiophene (DNTT) and its alkylated derivatives (Cn-DNTT, n =8 , 10, and 12). The band edges of absorption spectra of holes at around 1.9 eV show bathochromic shifts with increasing length of alkyl chains introduced at both ends of a DNTT chromophore. Applying a two-dimensional model with Holstein-type Hamiltonians to electronic transitions of holes, we have been able to simulate the features of the absorption band edges observed. The simulations indicate that the bathochromic shifts are due to an increase in the transfer integrals of holes with increasing length of alkyl chains. Thus this analysis confirmed that the subtle changes in the mutual orientations between adjacent DNTT chromophores induced by alkyl chains enhance the microscopic hole transfer rate. Although this fastener effect has been suggested by hole mobility measurements by I -V curves, the spectral analysis in this study gives clear evidence of this effect at the molecular level.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Modulated Hydrothermal Synthesis of UiO-66(Hf)-Type Metal-Organic Frameworks for Optimal Carbon Dioxide Separation.

    PubMed

    Hu, Zhigang; Nalaparaju, Anjaiah; Peng, Yongwu; Jiang, Jianwen; Zhao, Dan

    2016-02-01

    Recently, there has been growing interest in hafnium (Hf) metal-organic frameworks (MOFs). These MOFs may perform better as gas adsorbents than zirconium (Zr) MOFs due to the presence of Brønsted acid sites with high affinity toward adsorbates, together with the outstanding chemical and hydrothermal stabilities similar to their Zr analogues. However, Hf-MOFs have been rarely reported due to the lack of effective synthetic methods. We herein report a modulated hydrothermal synthesis of UiO-66(Hf)-type MOFs. Among these MOFs, UiO-66(Hf)-(OH)2 possesses a very high CO2 gravimetric uptake of 1.81 mmol g(-1) at 0.15 bar and 298 K, which is 400% higher than that of UiO-66(Hf) (0.36 mmol g(-1)). It also exhibits a record-high volumetric CO2 uptake of 167 v/v at 1 bar and 298 K. Ideal adsorbed solution theory calculations showed a CO2/N2 (molar ratio 15:85) selectivity of 93 and CO2/H2 (molar ratio 30:70) selectivity above 1700. Breakthrough simulations also confirmed its optimal CO2 separation attribute. Our results have demonstrated for the first time the strong potential of Hf-MOFs for advanced adsorbents for high-performance CO2-related separations. PMID:26751503

  6. Magnetically modulated electroluminescence from hybrid organic/inorganic light-emitting diodes based on electron donor-acceptor exciplex blends

    NASA Astrophysics Data System (ADS)

    Pang, Zhiyong; Baniya, Sangita; Zhang, Chuang; Sun, Dali; Vardeny, Z. Valy

    2016-03-01

    We report room temperature magnetically modulated electroluminescence from a hybrid organic/inorganic light-emitting diode (h-OLED), in which an inorganic magnetic tunnel junction (MTJ) with large room temperature magnetoresistance is coupled to an N,N,N ',N '-Tetrakis(4-methoxyphenyl)benzidine (MeO-TPD): tris-[3-(3-pyridyl)mesityl]borane (3TPYMB) [D-A] based OLED that shows thermally activated delayed luminescence. The exciplex-based OLED provides two spin-mixing channels: upper energy channel of polaron pairs and lower energy channel of exciplexes. In operation, the large resistance mismatch between the MTJ and OLED components is suppressed due to the non-linear I-V characteristic of the OLED. This leads to enhanced giant magneto-electroluminescence (MEL) at room temperature. We measured MEL of ~ 75% at ambient conditions. Supported by SAMSUNG Global Research Outreach (GRO) program, and also by the NSF-Material Science & Engineering Center (MRSEC) program at the University of Utah (DMR-1121252).

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Total marrow irradiation using Helical TomoTherapy

    NASA Astrophysics Data System (ADS)

    Garcia-Fernandez, Lourdes Maria

    Clinical dose response data of human tumours are limited or restricted to a radiation dose range determined by the level of toxicity to the normal tissues. This is the case for the most common disseminated plasma cell neoplasm, multiple myeloma, where the maximum dose deliverable to the entire bony skeleton using a standard total body irradiation (TBI) technique is limited to about 12 Gy. This study is part of scientific background of a phase I/II dose escalation clinical trial for multiple myeloma using image-guided intensity modulated radiotherapy (IG-IMRT) to deliver high dose to the entire volume of bone marrow with Helical TomoTherapy (HT). This relatively new technology can deliver highly conformal dose distributions to complex target shapes while reducing the dose to critical normal tissues. In this study tools for comparing and predicting the effectiveness of different approaches to total marrow irradiation (TMI) using HT were provided. The expected dose response for plasma cell neoplasms was computed and a radiobiological evaluation of different treatment cohorts in a dose escalating study was performed. Normal tissue complication probability (NTCP) and tumour control probability (TCP) models were applied to an actual TMI treatment plan for a patient and the implications of using different longitudinal field widths were assessed. The optimum dose was ˜39 Gy for which a predicted tumour control of 95% (+/-3%) was obtained, with a predicted 3% (0, 8%) occurrence of radiation pneumonitis. Tissue sparing was seen by using smaller field widths only in the organs of the head. This suggests it would be beneficial to use the small fields in the head only since using small fields for the whole treatment would lead to long treatment times. In TMI it may be necessary to junction two longitudinally adjacent treatment volumes to form a contiguous planning target volume PTV. For instance, this is the case when a different SUP-INF spatial resolution is required or when

  13. 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

  14. 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.

  15. 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.

  16. TRAJELIX: a computational tool for the geometric characterization of protein helices during molecular dynamics simulations.

    PubMed

    Mezei, Mihaly; Filizola, Marta

    2006-02-01

    We have developed a computer program with the necessary mathematical formalism for the geometric characterization of distorted conformations of alpha-helices proteins, such as those that can potentially be sampled during typical molecular dynamics simulations. This formalism has been incorporated into TRAJELIX, a new module within the SIMULAID framework (http://inka.mssm.edu/~mezei/simulaid/) that is capable of monitoring distortions of alpha-helices in terms of their displacement, global and local tilting, rotation around their axes, compression/extension, winding/unwinding, and bending. Accurate evaluation of these global and local structural properties of the helix can help study possible intramolecular and intermolecular changes in the helix packing of alpha-helical membrane proteins, as shown here in an application to the interacting helical domains of rhodopsin dimers. Quantification of the dynamic structural behavior of alpha-helical membrane proteins is critical for our understanding of signal transduction, and may enable structure-based design of more specific and efficient drugs. PMID:16783601

  17. 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.

  18. Electric field-induced transport modulation in VO2 FETs with high-k oxide/organic parylene-C hybrid gate dielectric

    NASA Astrophysics Data System (ADS)

    Wei, Tingting; Kanki, Teruo; Fujiwara, Kohei; Chikanari, Masashi; Tanaka, Hidekazu

    2016-02-01

    We report on the observation of reversible and immediate resistance switching by high-k oxide Ta2O5/organic parylene-C hybrid dielectric-gated VO2 thin films. Resistance change ratios at various temperatures in the insulating regime were demonstrated to occur in the vicinity of phase transition temperature. We also found an asymmetric hole-electron carrier modulation related to the suppression of phase transition temperature. The results in this research provide a possibility for clarifying the origin of metal-insulator transition in VO2 through the electrostatic field-induced transport modulation.

  19. Quasi-single helicity spectra in the Madison Symmetric Torus

    NASA Astrophysics Data System (ADS)

    Marrelli, L.; Martin, P.; Spizzo, G.; Franz, P.; Chapman, B. E.; Craig, D.; Sarff, J. S.; Biewer, T. M.; Prager, S. C.; Reardon, J. C.

    2002-07-01

    Evidence of a self-organized collapse towards a narrow spectrum of magnetic instabilities in the Madison Symmetric Torus [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] reversed field pinch device is presented. In this collapsed state, dubbed quasi-single helicity (QSH), the spectrum of magnetic modes condenses spontaneously to one dominant mode more completely than ever before observed. The amplitudes of all but the largest of the m=1 modes decrease in QSH states. New results about thermal features of QSH spectra and the identification of global control parameters for their onset are also discussed.

  20. 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.

  1. 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.

  2. Poster — Thur Eve — 35: The impact of intensity- and energy-modulated photon radiotherapy (XMRT) optimization on a variety of organ geometries

    SciTech Connect

    McGeachy, P.; Villarreal-Barajas, J. E.; Khan, R.; Zinchenko, Y.

    2014-08-15

    We previously reported on a novel, modulated in both energy and intensity; photon radiotherapy (XMRT) optimization technique. The purpose of this investigation was to test this XMRT optimization against conventional intensity modulated radiotherapy (IMRT) optimization on four different organ test geometries. All geometries mimicked clinically relevant scenarios. Both IMRT and XMRT were based on a linear programming approach where the objective function was the mean dose to healthy organs and organ-specific linear dose-point constraints were used. For IMRT, the beam energy was fixed to 6 MV while XMRT optimized in terms of both 6 and 18 MV beams. All plans consisted of a seven beam coplanar arrangement. All organ geometries were contoured on a 25cm diameter cylindrical water phantom in open source radiotherapy research software known as CERR. Solutions for both IMRT and XMRT were obtained for each geometry using a numerical solver Gurobi. Analyzing the quality of the solutions was done by comparing dose distributions and dose volume histograms calculated using CERR. For all four geometries, IMRT and XMRT solutions were comparable in terms of target coverage. For two of the geometries, IMRT provided an advantage in terms of reduced dose to the healthy structures. XMRT showed improved dose reduction to healthy organs for one geometry and a comparable dose distribution to IMRT for the remaining geometry. The inability to exploit the benefits of using multiple energies may be attributed to limited water phantom diameter and having the majority of the organs in close proximity to the transverse axis.

  3. Solid-state Marx based two-switch voltage modulator for the On-Line Isotope Mass Separator accelerator at the European Organization for Nuclear Research.

    PubMed

    Redondo, L M; Silva, J Fernando; Canacsinh, H; Ferrão, N; Mendes, C; Soares, R; Schipper, J; Fowler, A

    2010-07-01

    A new circuit topology is proposed to replace the actual pulse transformer and thyratron based resonant modulator that supplies the 60 kV target potential for the ion acceleration of the On-Line Isotope Mass Separator accelerator, the stability of which is critical for the mass resolution downstream separator, at the European Organization for Nuclear Research. The improved modulator uses two solid-state switches working together, each one based on the Marx generator concept, operating as series and parallel switches, reducing the stress on the series stacked semiconductors, and also as auxiliary pulse generator in order to fulfill the target requirements. Preliminary results of a 10 kV prototype, using 1200 V insulated gate bipolar transistors and capacitors in the solid-state Marx circuits, ten stages each, with an electrical equivalent circuit of the target, are presented, demonstrating both the improved voltage stability and pulse flexibility potential wanted for this new modulator. PMID:20687749

  4. Solid-state Marx based two-switch voltage modulator for the On-Line Isotope Mass Separator accelerator at the European Organization for Nuclear Research

    NASA Astrophysics Data System (ADS)

    Redondo, L. M.; Silva, J. Fernando; Canacsinh, H.; Ferrão, N.; Mendes, C.; Soares, R.; Schipper, J.; Fowler, A.

    2010-07-01

    A new circuit topology is proposed to replace the actual pulse transformer and thyratron based resonant modulator that supplies the 60 kV target potential for the ion acceleration of the On-Line Isotope Mass Separator accelerator, the stability of which is critical for the mass resolution downstream separator, at the European Organization for Nuclear Research. The improved modulator uses two solid-state switches working together, each one based on the Marx generator concept, operating as series and parallel switches, reducing the stress on the series stacked semiconductors, and also as auxiliary pulse generator in order to fulfill the target requirements. Preliminary results of a 10 kV prototype, using 1200 V insulated gate bipolar transistors and capacitors in the solid-state Marx circuits, ten stages each, with an electrical equivalent circuit of the target, are presented, demonstrating both the improved voltage stability and pulse flexibility potential wanted for this new modulator.

  5. Solid-state Marx based two-switch voltage modulator for the On-Line Isotope Mass Separator accelerator at the European Organization for Nuclear Research

    SciTech Connect

    Redondo, L. M.; Canacsinh, H.; Ferrao, N.; Mendes, C.; Silva, J. Fernando; Soares, R.; Schipper, J.; Fowler, A.

    2010-07-15

    A new circuit topology is proposed to replace the actual pulse transformer and thyratron based resonant modulator that supplies the 60 kV target potential for the ion acceleration of the On-Line Isotope Mass Separator accelerator, the stability of which is critical for the mass resolution downstream separator, at the European Organization for Nuclear Research. The improved modulator uses two solid-state switches working together, each one based on the Marx generator concept, operating as series and parallel switches, reducing the stress on the series stacked semiconductors, and also as auxiliary pulse generator in order to fulfill the target requirements. Preliminary results of a 10 kV prototype, using 1200 V insulated gate bipolar transistors and capacitors in the solid-state Marx circuits, ten stages each, with an electrical equivalent circuit of the target, are presented, demonstrating both the improved voltage stability and pulse flexibility potential wanted for this new modulator.

  6. Analyzing the effectiveness of flare dispensing programs against pulse width modulation seekers using self-organizing maps

    NASA Astrophysics Data System (ADS)

    Şahingil, Mehmet C.; Aslan, Murat Š.

    2013-10-01

    Infrared guided missile seekers utilizing pulse width modulation in target tracking is one of the threats against air platforms. To be able to achieve a "soft-kill" protection of own platform against these type of threats, one needs to examine carefully the seeker operating principle with its special electronic counter-counter measure (ECCM) capability. One of the cost-effective ways of soft kill protection is to use flare decoys in accordance with an optimized dispensing program. Such an optimization requires a good understanding of the threat seeker, capabilities of the air platform and engagement scenario information between them. Modeling and simulation is very powerful tool to achieve a valuable insight and understand the underlying phenomenology. A careful interpretation of simulation results is crucial to infer valuable conclusions from the data. In such an interpretation there are lots of factors (features) which affect the results. Therefore, powerful statistical tools and pattern recognition algorithms are of special interest in the analysis. In this paper, we show how self-organizing maps (SOMs), which is one of those powerful tools, can be used in analyzing the effectiveness of various flare dispensing programs against a PWM seeker. We perform several Monte Carlo runs for a typical engagement scenario in a MATLAB-based simulation environment. In each run, we randomly change the flare dispending program and obtain corresponding class: "successful" or "unsuccessful", depending on whether the corresponding flare dispensing program deceives the seeker or not, respectively. Then, in the analysis phase, we use SOMs to interpret and visualize the results.

  7. Increasing O-GlcNAcylation Level on Organ Culture of Soleus Modulates the Calcium Activation Parameters of Muscle Fibers

    PubMed Central

    Cieniewski-Bernard, Caroline; Montel, Valerie; Berthoin, Serge; Bastide, Bruno

    2012-01-01

    O-N-acetylglucosaminylation is a reversible post-translational modification which presents a dynamic and highly regulated interplay with phosphorylation. New insights suggest that O-GlcNAcylation might be involved in striated muscle physiology, in particular in contractile properties such as the calcium activation parameters. By the inhibition of O-GlcNAcase, we investigated the effect of the increase of soleus O-GlcNAcylation level on the contractile properties by establishing T/pCa relationships. We increased the O-GlcNAcylation level on soleus biopsies performing an organ culture of soleus treated or not with PUGNAc or Thiamet-G, two O-GlcNAcase inhibitors. The enhancement of O-GlcNAcylation pattern was associated with an increase of calcium affinity on slow soleus skinned fibers. Analysis of the glycoproteins pattern showed that this effect is solely due to O-GlcNAcylation of proteins extracted from skinned biopsies. We also characterized the O-GlcNAcylated contractile proteins using a proteomic approach, and identified among others troponin T and I as being O-GlcNAc modified. We quantified the variation of O-GlcNAc level on all these identified proteins, and showed that several regulatory contractile proteins, predominantly fast isoforms, presented a drastic increase in their O-GlcNAc level. Since the only slow isoform of contractile protein presenting an increase of O-GlcNAc level was MLC2, the effect of enhanced O-GlcNAcylation pattern on calcium activation parameters could involve the O-GlcNAcylation of sMLC2, without excluding that an unidentified O-GlcNAc proteins, such as TnC, could be potentially involved in this mechanism. All these data strongly linked O-GlcNAcylation to the modulation of contractile activity of skeletal muscle. PMID:23110217

  8. Intensity Modulated Proton Therapy for Craniospinal Irradiation: Organ-at-Risk Exposure and a Low-Gradient Junctioning Technique

    SciTech Connect

    Stoker, Joshua B.; Grant, Jonathan; Zhu, X. Ronald; Pidikiti, Rajesh; Mahajan, Anita; Grosshans, David R.

    2014-11-01

    Purpose: To compare field junction robustness and sparing of organs at risk (OARs) during craniospinal irradiation (CSI) using intensity modulated proton therapy (IMPT) to conventional passively scattered proton therapy (PSPT). Methods and Materials: Ten patients, 5 adult and 5 pediatric patients, previously treated with PSPT-based CSI were selected for comparison. Anterior oblique cranial fields, using a superior couch rotation, and posterior spinal fields were used for IMPT planning. To facilitate low-gradient field junctioning along the spine, the inverse-planning IMPT technique was divided into 3 stages. Dose indices describing target coverage and normal tissue dose, in silico error modeling, and film dosimetry were used to assess plan quality. Results: Field junction robustness along the spine was improved using the staged IMPT planning technique, reducing the worst case impact of a 4-mm setup error from 25% in PSPT to <5% of prescription dose. This was verified by film dosimetry for clinical delivery. Exclusive of thyroid dose in adult patients, IMPT plans demonstrated sparing of organs at risk as good or better than PSPT. Coverage of the cribriform plate for pediatric (V95% [percentage of volume of the target receiving at least 95% of the prescribed dose]; 87 ± 11 vs 92 ± 7) and adult (V95%; 94 ± 7 vs 100 ± 1) patients and the clinical target in pediatric (V95%; 98 ± 2 vs 100 ± 1) and adult (V95%; 100 ± 1 vs 100 ± 1) patients for PSPT and IMPT plans, respectively, were comparable or improved. For adult patients, IMPT target dose inhomogeneity was increased, as determined by heterogeneity index (HI) and inhomogeneity coefficient (IC). IMPT lowered maximum spinal cord dose, improved spinal dose homogeneity, and reduced exposure to other OARs. Conclusions: IMPT has the potential to improve CSI plan quality and the homogeneity of intrafractional dose at match lines. The IMPT approach developed may also simplify treatments and reduce

  9. Helical Tomotherapy in Children and Adolescents: Dosimetric Comparisons, Opportunities and Issues

    PubMed Central

    Mascarin, Maurizio; Giugliano, Francesca Maria; Coassin, Elisa; Drigo, Annalisa; Chiovati, Paola; Dassie, Andrea; Franchin, Giovanni; Minatel, Emilio; Trovò, Mauro Gaetano

    2011-01-01

    Helical Tomotherapy (HT) is a highly conformal image-guided radiation technique, introduced into clinical routine in 2006 at the Centro di Riferimento Oncologico Aviano (Italy). With this new technology, intensity-modulated radiotherapy (IMRT) is delivered using a helicoidal method. Here we present our dosimetric experiences using HT in 100 children, adolescents and young adults treated from May 2006 to February 2011. The median age of the patients was 13 years (range 1–24). The most common treated site was the central nervous system (50; of these, 24 were craniospinal irradiations), followed by thorax (22), head and neck (10), abdomen and pelvis (11), and limbs (7). The use of HT was calculated in accordance to the target dose conformation, the target size and shape, the dose to critical organs adjacent to the target, simultaneous treatment of multiple targets, and re-irradiation. HT has demonstrated to improve target volume dose homogeneity and the sparing of critical structures, when compared to 3D Linac-based radiotherapy (RT). In standard cases this technique represented a comparable alternative to IMRT delivered with conventional linear accelerator. In certain cases (e.g., craniospinal and pleural treatments) only HT generated adequate treatment plans with good target volume coverage. However, the gain in target conformality should be balanced with the spread of low-doses to distant areas. This remains an open issue for the potential risk of secondary malignancies (SMNs) and longer follow-up is mandatory. PMID:24213120

  10. Evaluation of modulators and electron-capture detectors for comprehensive two-dimensional GC of halogenated organic compounds.

    PubMed

    Kristenson, E Maria; Korytár, Peter; Danielsson, Conny; Kallio, Minna; Brandt, Menno; Mäkelä, Jani; Vreuls, René J J; Beens, Jan; Brinkman, Udo A Th

    2003-11-26

    Different cryogenic and a heated GC x GC modulator(s) were evaluated and compared for the analysis of high-boiling halogenated compounds. The cryogenic modulators investigated were: (i) the longitudinally modulated cryogenic system; (ii) the liquid-nitrogen-cooled jet modulator (KT2001); (iii) a dual-jet CO2 modulator (made in-house); (iv) a semi-rotating cryogenic modulator (made in-house) and (v) a CO2 loop modulator (KT2003); the heated modulator was the slotted heater system (sweeper). Each modulator was optimised with respect to analyte peak widths at half height in the second-dimension. n-Alkanes, chlorinated alkanes, polychlorinated biphenyls (PCBs) and fluorinated polycyclic aromatic hydrocarbons (F-PAHs) were used as test analytes. The flow rate of the coolant was found to be an important parameter, i.e. the flow rate of the gaseous nitrogen in the KT2001, and of the liquid CO2 in the other cryogenic modulators. For the slotted heater the stroke velocity and pause time were important parameters. This modulator had a limited application range in terms of temperature due to a necessary 100 degrees C difference between sweeper and oven temperature. All cryogenic modulators were found to be suitable for the GC x GC analysis of high-boiling compounds, but the CO2 modulators are to be preferred to the KT2001 due to a wider application range and slightly narrower peaks. As regards the performance of three commercially available electron-capture detectors (ECDs), the aim was to obtain narrow peak widths in GC x GC, i.e. to avoid band broadening caused by the cell volume. The most important parameters were the flow rate of the make-up gas and the detector temperature which both should be as high as possible. Comparison of analyte peak widths obtained with ECD mode and flame ionisation detection (FID) showed that all ECDs exhibited band broadening compared to the FID. The narrowest peaks were obtained with the Agilent micro-ECD, which has a cell volume of only 150

  11. 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.

  12. 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

  13. Development of a European Organization for Research and Treatment of Cancer Module to Assess the Quality of Life of Patients With Proctitis After Pelvic Radiotherapy for Malignancy

    SciTech Connect

    Spry, Nigel; Halkett, Georgia Aoun, Samar; Spry, Jane; Yeoh, Eric

    2008-10-01

    Purpose: To describe the development of a proctitis-specific quality-of-life module to supplement the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30). Methods and Materials: The module was developed according to EORTC guidelines, which consisted of an extensive literature review to identify previously described issues and interviews conducted with seven health professionals and 10 patients to rationalize the item list for construction into a provisional module. The module developed was then pretested with 28 patients and five health professionals. Results: The final module contains 21-items that are suitable to obtain information about the patients' quality of life after high-dose pelvic irradiation. The questionnaire has now been translated into four languages and commenced field testing in late 2007. Conclusions: The EORTC QLQ-C30, supplemented by EORTC QLQ-PRT21, will enable health professionals to more accurately monitor the side effects that patients experience after pelvic irradiation.

  14. A Spring-Like Behavior of Chiral Block Copolymer with Helical Nanostructure Driven by Crystallization

    SciTech Connect

    Chiang, W.; Ho, R; Thomas, E; Burger, C; Hsiao, B

    2009-01-01

    The crystallization of helical nanostructure resulting from the self-assembly of a chiral diblock copolymer, poly(styrene)-b-poly(L-lactide) (PS-PLLA), is studied. Various crystalline PS-PLLA nanostructures are obtained by controlling the crystallization temperature of PLLA (T{sub c,PLLA}), at which crystalline helices and crystalline cylinders occur while T{sub c,PLLA} < T{sub g,PS} (the glass transition temperature of PS) and T{sub c,PLLA} T{sub g,PS}, respectively. As evidenced by selected-area electron diffraction and two-dimensional X-ray diffraction results, the PLLA crystallites under confinement reveal a unique anisotropic character regardless of the crystallization temperature. On the basis of observed uniaxial scattering results the PLLA crystallites grown within the microdomains are identified as crystals with preferential growth directions either along the [100] or along the [110]-axes of the PLLA crystalline unit cell, at which the molecular chains and the growth direction are normal and parallel to the central axes of helices, respectively. The formation of this exclusive crystalline growth is attributed to the spatial confinement effect for crystallization. While T{sub c,PLLA} < T{sub g,PS}, owing to the directed crystallization by helical confinement, the preferential crystalline growth leads to the crystallization following a helical track with growth direction parallel to the central axes of helices through a twisting mechanism. Consequently, winding crystals with specific crystallographic orientation within the helical microdomains can be found. By contrast, while T{sub c,PLLA} {ge} T{sub g,PS}, the preferential growth may modulate the curvature of microdomains by shifting the molecular chains to access the fast path for crystalline growth due to the increase in chain mobility. As a result, a spring-like behavior of the helical nanostructure can be driven by crystallization so as to dictate the transformation of helices, resulting in crystalline

  15. Bistable N-H···N hydrogen bonds for reversibly modulating the dynamic motion in an organic co-crystal.

    PubMed

    Ji, Chengmin; Li, Shenhui; Deng, Feng; Liu, Sijie; Asghar, Muhammad Adnan; Sun, Zhihua; Hong, Maochun; Luo, Junhua

    2016-04-28

    Bistable N-H···N hydrogen bonds between rotors and stators enable delicate modulation of dynamic molecular motion by slowing down the fast rotation in a N-H···N hydrogen-bonded organic co-crystal of 1,2-diazabicyclo(2.2.2)octane bis(thiourea), which has been elucidated by the combination of variable-temperature (VT) X-ray structure analyses and VT solid-state nuclear magnetic resonance techniques. PMID:27063634

  16. 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.

  17. Helical bunching and symmetry lowering inducing multiferroicity in Fe langasites

    NASA Astrophysics Data System (ADS)

    Chaix, L.; Ballou, R.; Cano, A.; Petit, S.; de Brion, S.; Ollivier, J.; Regnault, L.-P.; Ressouche, E.; Constable, E.; Colin, C. V.; Zorko, A.; Scagnoli, V.; Balay, J.; Lejay, P.; Simonet, V.

    2016-06-01

    The chiral Fe-based langasites represent model systems of triangle-based frustrated magnets with a strong potential for multiferroicity. We report neutron-scattering measurements for the multichiral Ba3M Fe3Si2O14 (M =Nb ,Ta ) langasites revealing new important features of the magnetic order of these systems: the bunching of the helical modulation along the c axis and the in-plane distortion of the 120∘ Fe-spin arrangement. We discuss these subtle features in terms of the microscopic spin Hamiltonian and provide the link to the magnetically induced electric polarization observed in these systems. Thus, our findings put the multiferroicity of this attractive family of materials on solid ground.

  18. 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.

  19. 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).

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. Toward high-resolution computational design of helical membrane protein structure and function

    PubMed Central

    Barth, Patrick; Senes, Alessandro

    2016-01-01

    The computational design of α-helical membrane proteins is still in its infancy but has made important progress. De novo design has produced stable, specific and active minimalistic oligomeric systems. Computational re-engineering can improve stability and modulate the function of natural membrane proteins. Currently, the major hurdle for the field is not computational, but the experimental characterization of the designs. The emergence of new structural methods for membrane proteins will accelerate progress PMID:27273630

  6. Multifrequency channel microwave reflectometer with frequency hopping operation for density fluctuation measurements in Large Helical Device

    SciTech Connect

    Tokuzawa, T.; Kawahata, K.; Ejiri, A.

    2010-10-15

    In order to measure the internal structure of density fluctuations using a microwave reflectometer, the broadband frequency tunable system, which has the ability of fast and stable hopping operation, has been improved in the Large Helical Device. Simultaneous multipoint measurement is the key issue of this development. For accurate phase measurement, the system utilizes a single sideband modulation technique. Currently, a dual channel heterodyne frequency hopping reflectometer system has been constructed and applied to the Alfven eigenmode measurements.

  7. 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.

  8. Organizations.

    ERIC Educational Resources Information Center

    Aviation/Space, 1980

    1980-01-01

    This is a list of aerospace organizations and other groups that provides educators with assistance and information in specific areas. Both government and nongovernment organizations are included. (Author/SA)

  9. Intensity Modulated Radiation Therapy for Retroperitoneal Sarcoma: A Case for Dose Escalation and Organ at Risk Toxicity Reduction

    PubMed Central

    Koshy, Mary; Lawson, Joshua D.; Staley, Charles A.; Esiashvili, Natia; Howell, Rebecca; Ghavidel, Shahram; Davis, Lawrence W.

    2003-01-01

    Purpose: Radiation therapy for retroperitoneal sarcoma remains challenging because of proximity to surrounding organs at risk (OAR). We report the use of intensity modulated radiation therapy (IMRT) in the treatment of retroperitoneal sarcomas to minimize dose to OAR while concurrently optimizing tumor dose coverage. Patients and methods: From January 2000 to October 2002, 10 patients (average age 56 years) with retroperitoneal sarcoma and one with inguinal sarcoma were treated with radiation at Emory University. Prescription dose to the planning treatment volume (PTV) was commonly 50.4 at 1.8 Gy/fraction. CT simulation was used in each patient, three patients were treated with 3D-conformal treatment (3D-CRT), and the remaining eight received multi-leaf collimator-based (MLC) IMRT. IMRT treatment fields ranged from eight to 11 and average volume treated was 3498 cc. Optimal 3D-CRT plans were generated and compared with IMRT with respect to tumor coverage and OAR dose toxicity. Dose volume histograms were compared for both the 3D-CRT and IMRT plans. Results: Mean dose to small bowel decreased from 36 Gy with 3D-CRT to 27 Gy using IMRT, and tumor coverage (V95) increased from 95.3% with 3D-CRT to 98.6% using IMRT. Maximum and minimum doses delivered to the PTV were significantly increased by 6 and 22%, respectively (P = 0.011, P = 0.055). Volume of small bowel receiving > 30Gy was significantly decreased from 63.5 to 43.1% with IMRT compared with conventional treatment (P = 0.043). Seven patients developed grade 2 nausea, three developed grade 2 diarrhea, one had grade 2 skin toxicity, and one patient developed grade 3 liver toxicity (RTOG toxicity scale). No other delayed toxicities related to radiation were observed. At a median follow-up of 58 weeks, there were no local recurrences and only one patient developed disease progression with distant metastasis in the liver. Conclusions: IMRT for retroperitoneal sarcoma allowed enhanced tumor coverage and better sparing

  10. 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.

  11. A database for estimating organ dose for coronary angiography and brain perfusion CT scans for arbitrary spectra and angular tube current modulation

    SciTech Connect

    Rupcich, Franco; Badal, Andreu; Kyprianou, Iacovos; Schmidt, Taly Gilat

    2012-09-15

    Purpose: The purpose of this study was to develop a database for estimating organ dose in a voxelized patient model for coronary angiography and brain perfusion CT acquisitions with any spectra and angular tube current modulation setting. The database enables organ dose estimation for existing and novel acquisition techniques without requiring Monte Carlo simulations. Methods: The study simulated transport of monoenergetic photons between 5 and 150 keV for 1000 projections over 360 Degree-Sign through anthropomorphic voxelized female chest and head (0 Degree-Sign and 30 Degree-Sign tilt) phantoms and standard head and body CTDI dosimetry cylinders. The simulations resulted in tables of normalized dose deposition for several radiosensitive organs quantifying the organ dose per emitted photon for each incident photon energy and projection angle for coronary angiography and brain perfusion acquisitions. The values in a table can be multiplied by an incident spectrum and number of photons at each projection angle and then summed across all energies and angles to estimate total organ dose. Scanner-specific organ dose may be approximated by normalizing the database-estimated organ dose by the database-estimated CTDI{sub vol} and multiplying by a physical CTDI{sub vol} measurement. Two examples are provided demonstrating how to use the tables to estimate relative organ dose. In the first, the change in breast and lung dose during coronary angiography CT scans is calculated for reduced kVp, angular tube current modulation, and partial angle scanning protocols relative to a reference protocol. In the second example, the change in dose to the eye lens is calculated for a brain perfusion CT acquisition in which the gantry is tilted 30 Degree-Sign relative to a nontilted scan. Results: Our database provides tables of normalized dose deposition for several radiosensitive organs irradiated during coronary angiography and brain perfusion CT scans. Validation results indicate

  12. Respiratory motion effects on whole breast helical tomotherapy

    SciTech Connect

    Moeckly, Steven R.; Lamba, Michael; Elson, Howard R.

    2008-04-15

    The effects of intrafraction respiratory motion on nonhelical intensity-modulated radiotherapy have been well addressed in the literature, both theoretically and experimentally. However, the consequences of respiratory motion on helical tomotherapy, for patient-specific treatment plans, are less well known. Parameters specific to this treatment modality such as pitch, gantry speed, and degree of modulation may play prominent roles in radiation delivery with respect to intrafraction respiratory motion. This phantom-based study specifically addressed the effects of intrafraction respiratory motion on whole breast helical tomotherapy. A device capable of driving an acrylic phantom with reproducible, one-dimensional, anterior-posterior motion resembling a sinusoid of 4.6 mm crest-trough amplitude was developed. A plan to irradiate the corner of an acrylic phantom using parameters typical of a whole breast helical tomotherapy technique was developed using the TomoTherapy Hi-Art-II System registered . The treatment was delivered to the phantom, with Kodak EDR2 film in the axial plane, for each of the following conditions: (i) phantom at 270 deg. initial sinusoidal phase and 12 cycles/min motion, (ii) phantom at 270 deg. initial sinusoidal phase and 18 cycles/min motion, and (iii)-(v) phantom at 18 cycles/min motion with 0 deg., 90 deg., and 180 deg. initial sinusoidal phases. A measure of technique reproducibility was also performed for several irradiations with the phantom static at 270 deg. initial sinusoidal phase. Films were processed using a Kodak MIN-R mammography film processor, scanned with a Vidar NXR-16 Dosimetry Pro scanner and analyzed with RIT113 v.4.2 software. Films were compared to a reference film irradiated under the conditions of no motion and 270 deg. sinusoidal phase. For all comparisons, 5% dose difference threshold, 3% dose difference and 2 mm distance-to-agreement gamma analysis, and isodose plots were generated. The results of this study show a

  13. A field theory approach to the evolution of canonical helicity and energy

    NASA Astrophysics Data System (ADS)

    You, S.

    2016-07-01

    A redefinition of the Lagrangian of a multi-particle system in fields reformulates the single-particle, kinetic, and fluid equations governing fluid and plasma dynamics as a single set of generalized Maxwell's equations and Ohm's law for canonical force-fields. The Lagrangian includes new terms representing the coupling between the motion of particle distributions, between distributions and electromagnetic fields, with relativistic contributions. The formulation shows that the concepts of self-organization and canonical helicity transport are applicable across single-particle, kinetic, and fluid regimes, at classical and relativistic scales. The theory gives the basis for comparing canonical helicity change to energy change in general systems. For example, in a fixed, isolated system subject to non-conservative forces, a species' canonical helicity changes less than total energy only if gradients in density or distribution function are shallow.

  14. Lipid packing drives the segregation of transmembrane helices into disordered lipid domains in model membranes

    PubMed Central

    Schäfer, Lars V.; de Jong, Djurre H.; Holt, Andrea; Rzepiela, Andrzej J.; de Vries, Alex H.; Poolman, Bert; Killian, J. Antoinette; Marrink, Siewert J.

    2011-01-01

    Cell membranes are comprised of multicomponent lipid and protein mixtures that exhibit a complex partitioning behavior. Regions of structural and compositional heterogeneity play a major role in the sorting and self-assembly of proteins, and their clustering into higher-order oligomers. Here, we use computer simulations and optical microscopy to study the sorting of transmembrane helices into the liquid-disordered domains of phase-separated model membranes, irrespective of peptide–lipid hydrophobic mismatch. Free energy calculations show that the enthalpic contribution due to the packing of the lipids drives the lateral sorting of the helices. Hydrophobic mismatch regulates the clustering into either small dynamic or large static aggregates. These results reveal important molecular driving forces for the lateral organization and self-assembly of transmembrane helices in heterogeneous model membranes, with implications for the formation of functional protein complexes in real cells. PMID:21205902

  15. Histone Octamer Helical Tubes Suggest that an Internucleosomal Four-Helix Bundle Stabilizes the Chromatin Fiber

    PubMed Central

    Frouws, Timothy D.; Patterton, Hugh-G.; Sewell, Bryan T.

    2009-01-01

    Abstract A major question in chromatin involves the exact organization of nucleosomes within the 30-nm chromatin fiber and its structural determinants of assembly. Here we investigate the structure of histone octamer helical tubes via the method of iterative helical real-space reconstruction. Accurate placement of the x-ray structure of the histone octamer within the reconstructed density yields a pseudoatomic model for the entire helix, and allows precise identification of molecular interactions between neighboring octamers. One such interaction that would not be obscured by DNA in the nucleosome consists of a twofold symmetric four-helix bundle formed between pairs of H2B-α3 and H2B-αC helices of neighboring octamers. We believe that this interface can act as an internucleosomal four-helix bundle within the context of the chromatin fiber. The potential relevance of this interface in the folding of the 30-nm chromatin fiber is discussed. PMID:19383479

  16. Helically Assembled Pyrene Arrays on an RNA Duplex That Exhibit Circularly Polarized Luminescence with Excimer Formation.

    PubMed

    Nakamura, Mitsunobu; Suzuki, Junpei; Ota, Fuyuki; Takada, Tadao; Akagi, Kazuo; Yamana, Kazushige

    2016-06-27

    Circularly polarized luminescence (CPL) was observed in pyrene zipper arrays helically arranged on an RNA duplex. Hybridization of complementary RNA strands having multiple (two to five) 2'-O-pyrenylmethyl modified nucleosides affords an RNA duplex with normal thermal stability. The pyrene fluorophores are assembled like a zipper in a well-defined helical manner along the axis of RNA duplex, which, upon 350 nm UV illumination, resulted in CPL emission with pyrene excimer formation. CPL (glum ) levels observed for the pyrene arrays in dilute aqueous solution were +2×10(-2) -+3.5×10(-2) , which are comparable with |glum | for chiral organic molecules and related systems. The positive CPL signals are consistent with a right-handed helical structure. Temperature dependence on CPL emission indicates that the stable rigid RNA structure is responsible for the strong CPL signals. The single pyrene-modified RNA duplex did not show any CPL signal. PMID:27150679

  17. Assessment of organ dose reduction and secondary cancer risk associated with the use of proton beam therapy and intensity modulated radiation therapy in treatment of neuroblastomas

    PubMed Central

    2013-01-01

    Background To compare proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) with conformal radiation therapy (CRT) in terms of their organ doses and ability to cause secondary cancer in normal organs. Methods Five patients (median age, 4 years; range, 2–11 years) who underwent PBT for retroperitoneal neuroblastoma were selected for treatment planning simulation. Four patients had stage 4 tumors and one had stage 2A tumor, according to the International Neuroblastoma Staging System. Two patients received 36 Gy, two received 21.6 Gy, and one received 41.4 Gy of radiation. The volume structures of these patients were used for simulations of CRT and IMRT treatment. Dose–volume analyses of liver, stomach, colon, small intestine, pancreas, and bone were performed for the simulations. Secondary cancer risks in these organs were calculated using the organ equivalent dose (OED) model, which took into account the rates of cell killing, repopulation, and the neutron dose from the treatment machine. Results In all evaluated organs, the mean dose in PBT was 20–80% of that in CRT. IMRT also showed lower mean doses than CRT for two organs (20% and 65%), but higher mean doses for the other four organs (110–120%). The risk of secondary cancer in PBT was 24–83% of that in CRT for five organs, but 121% of that in CRT for pancreas. The risk of secondary cancer in IMRT was equal to or higher than CRT for four organs (range 100–124%). Conclusion Low radiation doses in normal organs are more frequently observed in PBT than in IMRT. Assessments of secondary cancer risk showed that PBT reduces the risk of secondary cancer in most organs, whereas IMRT is associated with a higher risk than CRT. PMID:24180282

  18. Temperature and Light modulate the trans-delta3-hexadecenoic acid content of phosphatidylglycerol: light-harvesting complex II organization and non-photochemical quenching.

    PubMed

    Gray, Gordon R; Ivanov, Alexander G; Król, Marianna; Williams, John P; Kahn, Mobashoher U; Myscich, Elizabeth G; Huner, Norman P A

    2005-08-01

    The interaction of light and temperature in the modulation of the trans-delta3-hexadecenoic acid (trans-16:1) content of phosphatidylglycerol (PG) in winter rye (Secale cereale L.) was assessed and related to the organization of light-harvesting complex II (LHCII). Increasing the growth irradiance from 50 to 800 micromol m(-2) s(-1) at 20 degrees C resulted in a 1.8-fold increase in the trans-16:1 content in PG which favoured a greater preponderance of oligomeric LHCII, measured in vitro as the ratio of oligomer : monomer. Similar irradiance-dependent increases were observed during growth at 5 degrees C; however, 1.4-fold lower trans-16:1 contents and lower LHCII oligomer : monomer ratios were observed compared with growth at 20 degrees C and the same irradiance. These trends were also observed under natural field conditions. Thus, the accumulation of trans-16:1, as well as the organization of LHCII are modulated by both growth irradiance and growth temperature in an independent but additive manner. We also examined how changes in the supramolecular organization of LHCII affected the capacity for non-photochemical quenching (q(N)) and photoprotection via antenna quenching (q(O)). While q(O) was positively correlated with q(N), there was no correlation with either LHCII organization or xanthophyll cycle activity under the steady-state growth conditions examined. PMID:15946983

  19. Caulobacter crescentus exploits its helical cell body to swim efficiently

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Mendoza, Marcos; Valenzuela, Joanna

    2015-11-01

    How an organism gets its shape remains an open question of fundamental science. In this study, we measure the 3D shape of a bacterium, Caulobacter crescentus, using a computational graphic technique for free-swimming microorganisms to analyze thousands of image frames of the same individual bacterium. Rather than having a crescent shape, the cell body of the organism is found to be twisted with a helical pitch angle around 45 degrees. Moreover, the detailed size and geometry of the cell body, matches the optimized cell body obtained by the slender body theory for swimming at fixed power. This result sheds new light on the shape evolution of microorganisms, and suggests that C. crescentus has adapted to its natural habitat of fresh-water lakes and streams, lacking nutrients.

  20. Distinct repressing modules on the distal region of the SBP2 promoter contribute to its vascular tissue-specific expression in different vegetative organs.

    PubMed

    Freitas, Rejane L; Carvalho, Claudine M; Fietto, Luciano G; Loureiro, Marcelo E; Almeida, Andrea M; Fontes, Elizabeth P B

    2007-11-01

    The Glycine max sucrose binding protein (GmSBP2) promoter directs vascular tissue-specific expression of reporter genes in transgenic tobacco. Here we showed that an SBP2-GFP fusion protein under the control of the GmSBP2 promoter accumulates in the vascular tissues of vegetative organs, which is consistent with the proposed involvement of SBP in sucrose transport-dependent physiological processes. Through gain-of-function experiments we confirmed that the tissue-specific determinants of the SBP2 promoter reside in the distal cis-regulatory domain A, CRD-A (position -2000 to -700) that is organized into a modular configuration to suppress promoter activity in tissues other than vascular tissues. The four analyzed CRD-A sub-modules, designates Frag II (-1785/-1508), Frag III (-1507/-1237), Frag IV (-1236/-971) and Frag V (-970/-700), act independently to alter the constitutive pattern of -92pSBP2-mediated GUS expression in different organs. Frag V fused to -92pSBP2-GUS restored the tissue-specific pattern of the full-length promoter in the shoot apex, but not in other organs. Likewise, Frag IV confined GUS expression to the vascular bundle of leaves, whereas Frag II mediated vascular specific expression in roots. Strong stem expression-repressing elements were located at positions -1485 to -1212, as Frag III limited GUS expression to the inner phloem. We have also mapped a procambium silencer to the consensus sequence CAGTTnCaAccACATTcCT which is located in both distal and proximal upstream modules. Fusion of either repressing element-containing module to the constitutive -92pSBP2 promoter suppresses GUS expression in the elongation zone of roots. Together our results demonstrate the unusual aspect of distal sequences negatively controlling tissue-specificity of a plant promoter. PMID:17710554

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Efficient optical terahertz-transmission modulation in solution-processable organic semiconductor thin films on silicon substrate

    NASA Astrophysics Data System (ADS)

    Matsui, Tatsunosuke; Mori, Hiroki; Inose, Yuto; Kuromiya, Shota; Takano, Keisuke; Nakajima, Makoto; Hangyo, Masanori

    2016-03-01

    Terahertz (THz)-transmission modulation through the Si substrate coated with four π-conjugated materials under various laser light irradiation conditions was investigated using THz time-domain spectroscopy. Two of the π-conjugated low molecules, the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), and two of the π-conjugated polymer materials, poly[5-(2-ethylhexyloxy)-2-methoxycyanoterephthalyliden] (MEH-CN-PPV) and poly(benzimidazobenzophenanthroline) (BBL), were investigated. Among these materials, PCBM and TIPS-pentacene showed higher modulation efficiencies and it was also shown that thermal annealing is quite effective in obtaining THz modulation efficiencies higher than those previously reported for copper phthalocyanine. Utilizing these solution-processable π-conjugated materials, various types of THz materials and devices could be fabricated by printing technologies. Our findings may open the way to fabricating various types of THz active devices.

  14. 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.

  15. 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.

  16. Quality assurance of the multileaf collimator with helical tomotherapy: Design and implementation

    SciTech Connect

    Sarkar, Vikren; Lin Lan; Shi Chengyu; Papanikolaou, Niko

    2007-07-15

    Quality assurance (QA) of the multileaf collimator (MLC) is a critical step for the delivery of intensity modulated radiation therapy treatment plan. While QA procedures for motor-driven MLC have been published extensively, those for binary MLCs such as the one used for helical tomotherapy have not been presented in the literature, as this is still a fairly new technology. In this study, seven test patterns for the MLC QA of a helical tomotherapy unit have been designed and implemented. The seven test patterns check the MLC alignment, MLC leakage, MLC timing and MLC leaf position error in detail. Those patterns can be easily implemented in any center with a helical tomotherapy unit as part of the routine QA. The QA procedures can be performed using existing QA resources such as solid water phantom and EDR2 film. A software toolkit called ''Tomo MLC QA'' has been developed to assist in generating the QA procedures and analyzing the results. Our results showed that the helical tomotherapy MLC is very robust, exhibiting interleaf leakage of 0.53%{+-}0.09%. Several issues with the MLC have been found and discussed. The QA results also illustrate the utilization and usefulness of the proposed QA procedures.

  17. 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.

  18. Organics.

    ERIC Educational Resources Information Center

    Chian, Edward S. K.; DeWalle, Foppe B.

    1978-01-01

    Presents water analysis literature for 1978. This review is concerned with organics, and it covers: (1) detergents and surfactants; (2) aliphatic and aromatic hydrocarbons; (3) pesticides and chlorinated hydrocarbons; and (4) naturally occurring organics. A list of 208 references is also presented. (HM)

  19. Organizers.

    ERIC Educational Resources Information Center

    Callison, Daniel

    2000-01-01

    Focuses on "organizers," tools or techniques that provide identification and classification along with possible relationships or connections among ideas, concepts, and issues. Discusses David Ausubel's research and ideas concerning advance organizers; the implications of Ausubel's theory to curriculum and teaching; "webbing," a specific…

  20. Magnetic and luminescent binuclear double-stranded helicates.

    PubMed

    Cucos, Paula; Tuna, Floriana; Sorace, Lorenzo; Matei, Iulia; Maxim, Catalin; Shova, Sergiu; Gheorghe, Ruxandra; Caneschi, Andrea; Hillebrand, Mihaela; Andruh, Marius

    2014-07-21

    Three new binuclear helicates, [M2L2]·3DMF (M = Co(II), 1, Zn(II), 3) and [Cu2L2]·DMF·0.4H2O (2), have been assembled using the helicand H2L that results from the 2:1 condensation reaction between o-vanillin and 4,4'-diaminodiphenyl ether. The metal ions within the binuclear helicates are tetracoordinated with a distorted tetrahedral geometry. Direct current magnetic characterization and EPR spectroscopy of the Co(II) derivative point to an easy axis type anisotropy for both Co(II) centers, with a separation of at least 55 K between the two doublets. Dynamic susceptibility measurements evidence slow relaxation of the magnetization in an applied dc field. Since the distance between the cobalt ions is quite large (11.59 Å), this is attributed in a first instance to the intrinsic properties of each Co(II) center (single-ion magnet behavior). However, the temperature dependence of the relaxation rate and the absence of slow dynamics in the Zn(II)-doped sample suggest that neither the simple Orbach mechanism nor Raman or direct processes can account for the relaxation, and collective phenomena have to be invoked for the observed behavior. Finally, due to the rigidization of the two organic ligands upon coordination, the pure zinc derivative exhibits fluorescence emission in solution, which was analyzed in terms of fluorescence quantum yields and lifetimes. PMID:24998701

  1. Crystallographic insight-guided nanoarchitectonics and conductivity modulation of an n-type organic semiconductor through peptide conjugation.

    PubMed

    Pandeeswar, M; Khare, Harshavardhan; Ramakumar, Suryanarayanarao; Govindaraju, T

    2015-05-14

    Crystallographic insight-guided nanoarchitectonics of peptide-conjugated naphthalene diimide (NDI) is described. In a bio-inspired approach, non-proteinogenic α-amino isobutyric acid (Aib)- and alanine (Ala)-derived peptides orchestrated the 1D achiral and 2D chiral molecular ordering of NDI, respectively, which resulted in modulation of nanoscale morphology, chiroptical and conductivity properties. PMID:25876756

  2. 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

  3. Effect of sinusoidal modulated currents and acute hypoxia on corticosterone content and activity of certain dehydrogenases in tissues of different rat organs during hypokinesia

    NASA Technical Reports Server (NTRS)

    Melik-Aslanova, L. L.; Frenkel, I. D.

    1980-01-01

    The state of hypokinesia in rats was reproduced by keeping them for 30 days in special box cages that restricted their mobility in all directions. Results show the resistance to acute hypoxic hypoxia is increased. This is linked to the considerable rise in the reduced level of corticosterone in different organs and the succinate dehydrogenase activity in the liver and brain. The letter indicated the primary oxidation of succinate, which has great importance in the adaptation of the oxidative metabolism to acute oxygen insufficiency. The use of sinusoidal modulated currents in the period of hypokinesia promotes normalization of the indices for resistance of the rats to acute hypoxia.

  4. 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

  5. Three-dimensional control of the helical axis of a chiral nematic liquid crystal by light

    NASA Astrophysics Data System (ADS)

    Zheng, Zhi-Gang; Li, Yannian; Bisoyi, Hari Krishna; Wang, Ling; Bunning, Timothy J.; Li, Quan

    2016-03-01

    Chiral nematic liquid crystals—otherwise referred to as cholesteric liquid crystals (CLCs)—are self-organized helical superstructures that find practical application in, for example, thermography, reflective displays, tuneable colour filters and mirrorless lasing. Dynamic, remote and three-dimensional control over the helical axis of CLCs is desirable, but challenging. For example, the orientation of the helical axis relative to the substrate can be changed from perpendicular to parallel by applying an alternating-current electric field, by changing the anchoring conditions of the substrate, or by altering the topography of the substrate’s surface; separately, in-plane rotation of the helical axis parallel to the substrate can be driven by a direct-current field. Here we report three-dimensional manipulation of the helical axis of a CLC, together with inversion of its handedness, achieved solely with a light stimulus. We use this technique to carry out light-activated, wide-area, reversible two-dimensional beam steering—previously accomplished using complex integrated systems and optical phased arrays. During the three-dimensional manipulation by light, the helical axis undergoes, in sequence, a reversible transition from perpendicular to parallel, followed by in-plane rotation on the substrate surface. Such reversible manipulation depends on experimental parameters such as cell thickness, surface anchoring condition, and pitch length. Because there is no thermal relaxation, the system can be driven either forwards or backwards from any light-activated intermediate state. We also describe reversible photocontrol between a two-dimensional diffraction state, a one-dimensional diffraction state and a diffraction ‘off’ state in a bilayer cell.

  6. Three-dimensional control of the helical axis of a chiral nematic liquid crystal by light.

    PubMed

    Zheng, Zhi-gang; Li, Yannian; Bisoyi, Hari Krishna; Wang, Ling; Bunning, Timothy J; Li, Quan

    2016-03-17

    Chiral nematic liquid crystals--otherwise referred to as cholesteric liquid crystals (CLCs)--are self-organized helical superstructures that find practical application in, for example, thermography, reflective displays, tuneable colour filters and mirrorless lasing. Dynamic, remote and three-dimensional control over the helical axis of CLCs is desirable, but challenging. For example, the orientation of the helical axis relative to the substrate can be changed from perpendicular to parallel by applying an alternating-current electric field, by changing the anchoring conditions of the substrate, or by altering the topography of the substrate's surface; separately, in-plane rotation of the helical axis parallel to the substrate can be driven by a direct-current field. Here we report three-dimensional manipulation of the helical axis of a CLC, together with inversion of its handedness, achieved solely with a light stimulus. We use this technique to carry out light-activated, wide-area, reversible two-dimensional beam steering--previously accomplished using complex integrated systems and optical phased arrays. During the three-dimensional manipulation by light, the helical axis undergoes, in sequence, a reversible transition from perpendicular to parallel, followed by in-plane rotation on the substrate surface. Such reversible manipulation depends on experimental parameters such as cell thickness, surface anchoring condition, and pitch length. Because there is no thermal relaxation, the system can be driven either forwards or backwards from any light-activated intermediate state. We also describe reversible photocontrol between a two-dimensional diffraction state, a one-dimensional diffraction state and a diffraction 'off' state in a bilayer cell. PMID:26950601

  7. 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.

  8. 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.

  9. Optical gating with organic building blocks. A quantitative model for the fluorescence modulation of photochromic perylene bisimide dithienylcyclopentene triads

    PubMed Central

    Pärs, Martti; Gradmann, Michael; Gräf, Katja; Bauer, Peter; Thelakkat, Mukundan; Köhler, Jürgen

    2014-01-01

    We investigated the capability of molecular triads, consisting of two strong fluorophores that were covalently linked to a photochromic molecule, for optical gating. Therefore we monitored the fluorescence intensity of the fluorophores as a function of the isomeric state of the photoswitch. From the analysis of our data we develop a kinetic model that allows us to predict quantitatively the degree of the fluorescence modulation as a function of the mutual intensities of the lasers that are used to induce the fluorescence and the switching of the photochromic unit. We find that the achievable contrast for the modulation of the fluorescence depends mainly on the intensity ratio of the two light beams and appears to be very robust against absolute changes of these intensities. The latter result provides valuable information for the development of all-optical circuits which would require to handle different signal strengths for the input and output levels. PMID:24614963

  10. Optical gating with organic building blocks. A quantitative model for the fluorescence modulation of photochromic perylene bisimide dithienylcyclopentene triads

    NASA Astrophysics Data System (ADS)

    Pärs, Martti; Gradmann, Michael; Gräf, Katja; Bauer, Peter; Thelakkat, Mukundan; Köhler, Jürgen

    2014-03-01

    We investigated the capability of molecular triads, consisting of two strong fluorophores that were covalently linked to a photochromic molecule, for optical gating. Therefore we monitored the fluorescence intensity of the fluorophores as a function of the isomeric state of the photoswitch. From the analysis of our data we develop a kinetic model that allows us to predict quantitatively the degree of the fluorescence modulation as a function of the mutual intensities of the lasers that are used to induce the fluorescence and the switching of the photochromic unit. We find that the achievable contrast for the modulation of the fluorescence depends mainly on the intensity ratio of the two light beams and appears to be very robust against absolute changes of these intensities. The latter result provides valuable information for the development of all-optical circuits which would require to handle different signal strengths for the input and output levels.

  11. Mechanism of helix induction in poly(4-carboxyphenyl isocyanide) with chiral amines and memory of the macromolecular helicity and its helical structures.

    PubMed

    Hase, Yoko; Nagai, Kanji; Iida, Hiroki; Maeda, Katsuhiro; Ochi, Noriaki; Sawabe, Kyoichi; Sakajiri, Koichi; Okoshi, Kento; Yashima, Eiji

    2009-08-01

    An optically inactive poly(4-carboxyphenyl isocyanide) (poly-1-H) changed its structure into the prevailing, one-handed helical structure upon complexation with optically active amines in dimethylsulfoxide (DMSO) and water, and the complexes show a characteristic induced circular dichroism in the polymer backbone region. Moreover, the macromolecular helicity induced in water and aqueous organic solutions containing more than 50 vol % water could be "memorized" even after complete removal of the chiral amines (h-poly-1b-H), while that induced in DMSO and DMSO-water mixtures containing less than 30 vol % water could not maintain the optical activity after removal of the chiral amines (poly-1a-H). We now report fully detailed studies of the helix induction mechanism with chiral amines and the memory of the macromolecular helicity in water and a DMSO-water mixture by various spectroscopic measurements, theoretical calculations, and persistence length measurements together with X-ray diffraction (XRD) measurements. From the spectroscopic results, such as circular dichroism (CD), absorption, IR, vibrational CD, and NMR of poly-1a-H, h-poly-1b-H, and original poly-1-H, we concluded that the specific configurational isomerization around the C horizontal lineN double bonds occurs during the helicity induction process in each solvent. In order to obtain the structural information, XRD measurements were done on the uniaxially oriented films of the corresponding methyl esters (poly-1-Me, poly-1a-Me, and h-poly-1b-Me) prepared from their liquid crystalline polymer solutions. On the basis of the XRD analyses, the most plausible helical structure of poly-1a-Me was proposed to be a 9-unit/5-turn helix with two monomer units as a repeating unit, and that of h-poly-1b-Me was proposed to be a 10-unit/3-turn helix consisting of one repeating monomer unit. The density functional theory calculations of poly(phenyl isocyanide), a model polymer of h-poly-1b-Me, afforded a 7-unit/2-turn

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. A versatile, non genetically modified organism (GMO)-based strategy for controlling low-producer mutants in Bordetella pertussis cultures using antigenic modulation.

    PubMed

    Goffin, Philippe; Slock, Thomas; Smessaert, Vincent; De Rop, Philippe; Dehottay, Philippe

    2015-08-01

    The uncontrolled presence of non-producer mutants negatively affects bioprocesses. In Bordetella pertussis cultures, avirulent mutants emerge spontaneously and accumulate. We characterized the dynamics of accumulation using high-throughput growth assays and competition experiments between virulent and avirulent (bvg(-) ) isolates. A fitness advantage of bvg(-) cells was identified as the main driver for bvg(-) accumulation under conditions of high virulence factor production. Conversely, under conditions that reduce their expression (antigenic modulation), bvg(-) takeover could be avoided. A control strategy was derived, which consists in applying modulating conditions whenever virulence factor production is not required. It has a wide range of applications, from routine laboratory operations to vaccine manufacturing, where pertussis toxin yields were increased 1.4-fold by performing early pre-culture steps in modulating conditions. Because it only requires subtle modifications of the culture medium and does not involve genetic modifications, this strategy is applicable to any B. pertussis isolate, and should facilitate regulatory acceptance of process changes for vaccine production. Strategies based on the same concept, could be derived for other industrially relevant micro-organisms. This study illustrates how a sound scientific understanding of physiological principles can be turned into a practical application for the bioprocess industry, in alignment with Quality by Design principles. PMID:26014907

  7. 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.

  8. 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

  9. 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.

  10. Potential in vivo roles of nucleic acid triple-helices

    PubMed Central

    Buske, Fabian A

    2011-01-01

    The ability of double-stranded DNA to form a triple-helical structure by hydrogen bonding with a third strand is well established, but the biological functions of these structures remain largely unknown. There is considerable albeit circumstantial evidence for the existence of nucleic triplexes in vivo and their potential participation in a variety of biological processes including chromatin organization, DNA repair, transcriptional regulation and RNA processing has been investigated in a number of studies to date. There is also a range of possible mechanisms to regulate triplex formation through differential expression of triplex-forming RNAs, alteration of chromatin accessibility, sequence unwinding and nucleotide modifications. With the advent of next generation sequencing technology combined with targeted approaches to isolate triplexes, it is now possible to survey triplex formation with respect to their genomic context, abundance and dynamical changes during differentiation and development, which may open up new vistas in understanding genome biology and gene regulation. PMID:21525785

  11. Viral and bacterial septicaemic infections modulate the expression of PACAP splicing variants and VIP/PACAP receptors in brown trout immune organs.

    PubMed

    Gorgoglione, Bartolomeo; Carpio, Yamila; Secombes, Christopher J; Taylor, Nick G H; Lugo, Juana María; Estrada, Mario Pablo

    2015-12-01

    Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and PACAP-Related Peptide (PRP) are structurally similar peptides encoded in the same transcripts. Their transcription has been detected not only in the brain but also in a wide range of peripheral tissues, even including organs of the immune system. PACAP exerts pleiotropic activities through G-protein coupled membrane receptors: the PACAP-specific PAC-1 and the VPAC-1 and VPAC-2 receptors that exhibit similar affinities for the Vasoactive Intestinal Peptide (VIP) and PACAP. Recent findings added PACAP and its receptors to the growing list of mediators that allow cross-talk between the nervous, endocrine and immune systems in fish. In this study the expression of genes encoding for PACAP and PRP, as well as VIP/PACAP receptors was studied in laboratory-reared brown trout (Salmo trutta) after septicaemic infections. Respectively Viral Haemorrhagic Septicaemia Virus (VHSV-Ia) or the Gram-negative bacterium Yersinia ruckeri (ser. O1 - biot. 2) were used in infection challenges. Kidney and spleen, the teleost main lymphopoietic organs, were sampled during the first two weeks post-infection. RT-qPCR analysis assessed specific pathogens burden and gene expression levels. PACAP and PRP transcription in each organ was positively correlated to the respective pathogen burden, assessed targeting the VHSV-glycoprotein or Y. ruckeri 16S rRNA. Results showed as the transcription of PACAP splicing variants and VIP/PACAP receptors is modulated in these organs during an acute viral and bacterial septicaemic infections in brown trout. These gene expression results provide clues as to how the PACAP system is modulated in fish, confirming an involvement during active immune responses elicited by both viral and bacterial aetiological agents. However, further experimental evidence is still required to fully elucidate and characterize the role of PACAP and PRP for an efficient immune response against pathogens. PMID:26481517

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

  17. 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

  18. 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)

  19. 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.

  20. Permanent polarization and charge distribution in organic light-emitting diodes (OLEDs): Insights from near-infrared charge-modulation spectroscopy of an operating OLED

    SciTech Connect

    Marchetti, Alfred P.; Haskins, Terri L.; Young, Ralph H.; Rothberg, Lewis J.

    2014-03-21

    Vapor-deposited Alq{sub 3} layers typically possess a strong permanent electrical polarization, whereas NPB layers do not. (Alq{sub 3} is tris(8-quinolinolato)aluminum(III); NPB is 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl.) The cause is a net orientation of the Alq{sub 3} molecules with their large dipole moments. Here we report on consequences for an organic light-emitting diode (OLED) with an NPB hole-transport layer and Alq{sub 3} electron-transport layer. The discontinuous polarization at the NPB|Alq{sub 3} interface has the same effect as a sheet of immobile negative charge there. It is more than compensated by a large concentration of injected holes (NPB{sup +}) when the OLED is running. We discuss the implications and consequences for the quantum efficiency and the drive voltage of this OLED and others. We also speculate on possible consequences of permanent polarization in organic photovoltaic devices. The concentration of NPB{sup +} was measured by charge-modulation spectroscopy (CMS) in the near infrared, where the NPB{sup +} has a strong absorption band, supplemented by differential-capacitance and current-voltage measurements. Unlike CMS in the visible, this method avoids complications from modulation of the electroluminescence and electroabsorption.

  1. Intracellular segment between transmembrane helices S0 and S1 of BK channel α subunit contains two amphipathic helices connected by a flexible loop

    SciTech Connect

    Shi, Pan; Li, Dong; Lai, Chaohua; Zhang, Longhua; Tian, Changlin

    2013-08-02

    Highlights: •The loop between S0 and S1 of BK channel was overexpressed and purified in DPC. •NMR studies indicated BK-IS1 contained two helices connected by a flexible loop. •Mg{sup 2+} titration of BK-IS1 indicated two possible binding sites of divalent ions. -- Abstract: The BK channel, a tetrameric potassium channel with very high conductance, has a central role in numerous physiological functions. The BK channel can be activated by intracellular Ca{sup 2+} and Mg{sup 2+}, as well as by membrane depolarization. Unlike other tetrameric potassium channels, the BK channel has seven transmembrane helices (S0–S6) including an extra helix S0. The intracellular segment between S0 and S1 (BK-IS1) is essential to BK channel functions and Asp99 in BK-IS1 is reported to be responsible for Mg{sup 2+} coordination. In this study, BK-IS1 (44–113) was over-expressed using a bacterial system and purified in the presence of detergent micelles for multidimensional heteronuclear nuclear magnetic resonance (NMR) structural studies. Backbone resonance assignment and secondary structure analysis showed that BK-IS1 contains two amphipathic helices connected by a 36-residue loop. Amide {sup 1}H–{sup 15}N heteronuclear NOE analysis indicated that the loop is very flexible, while the two amphipathic helices are possibly stabilized through interaction with the membrane. A solution NMR-based titration assay of BK-IS1 was performed with various concentrations of Mg{sup 2+}. Two residues (Thr45 and Leu46) with chemical shift changes were observed but no, or very minor, chemical shift difference was observed for Asp99, indicating a possible site for binding divalent ions or other modulation partners.

  2. Roll-to-roll printed silver nanowires for increased stability of flexible ITO-free organic solar cell modules

    NASA Astrophysics Data System (ADS)

    Dos Reis Benatto, Gisele A.; Roth, Bérenger; Corazza, Michael; Søndergaard, Roar R.; Gevorgyan, Suren A.; Jørgensen, Mikkel; Krebs, Frederik C.

    2015-12-01

    We report the use of roll-to-roll printed silver nanowire networks as front electrodes for fully roll-to-roll processed flexible indium-tin-oxide (ITO) free OPV modules. We prepared devices with two types of back electrodes, a simple PEDOT:PSS back electrode and a PEDOT:PSS back electrode with a printed silver grid in order to simultaneously explore the influence of the back electrode structure on the operational stability of the modules that did not include any UV-protection. We subjected the devices to stability testing under a number of protocols recommended by the international summit on OPV stability (ISOS). We explored accelerated ISOS-D-2, ISOS-D-3, ISOS-L-2, ISOS-L-3, ISOS-O-1 and ISOS-O-2 testing protocols and compared the performance to previous reports employing the same testing protocols on devices with PEDOT:PSS instead of the silver nanowires in the front electrode. We find significantly increased operational stability across all ISOS testing protocols over the course of the study and conclude that replacement of PEDOT:PSS in the front electrode with silver nanowires increase operational stability by up to 1000%. The duration of the tests were in the range of 140-360 days. The comparison of front and back electrode stability in this study shows that the modules with silver nanowire front electrodes together with a composite back electrode comprising PEDOT:PSS and a silver grid present the best operational stability.

  3. 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

  4. 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.

  5. 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).

  6. 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.

  7. Understanding the Role of Amphipathic Helices in N-BAR Domain Driven Membrane Remodeling

    PubMed Central

    Cui, Haosheng; Mim, Carsten; Vázquez, Francisco X.; Lyman, Edward; Unger, Vinzenz M.; Voth, Gregory A.

    2013-01-01

    Endophilin N-BAR (N-terminal helix and Bin/amphiphysin/Rvs) domain tubulates and vesiculates lipid membranes in vitro via its crescent-shaped dimer and four amphipathic helices that penetrate into membranes as wedges. Like F-BAR domains, endophilin N-BAR also forms a scaffold on membrane tubes. Unlike F-BARs, endophilin N-BARs have N-terminal H0 amphipathic helices that are proposed to interact with other N-BARs in oligomer lattices. Recent cryo-electron microscopy reconstructions shed light on the organization of the N-BAR lattice coats on a nanometer scale. However, because of the resolution of the reconstructions, the precise positioning of the amphipathic helices is still ambiguous. In this work, we applied a coarse-grained model to study various membrane remodeling scenarios induced by endophilin N-BARs. We found that H0 helices of N-BARs prefer to align in an antiparallel manner at two ends of the protein to form a stable lattice. The deletion of H0 helices causes disruption of the lattice. In addition, we analyzed the persistence lengths of the protein-coated tubes and found that the stiffness of endophilin N-BAR-coated tubules qualitatively agrees with previous experimental work studying N-BAR-coated tubules. Large-scale simulations on membrane liposomes revealed a systematic relation between H0 helix density and local membrane curvature fluctuations. The data also suggest that the H0 helix is required for BARs to form organized structures on the liposome, further illustrating its important function. PMID:23442862

  8. 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

  9. 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

  10. 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.

  11. Optochemical organization in a spatially modulated incandescent field: a single-step route to black and bright polymer lattices.

    PubMed

    Kasala, Kailash; Saravanamuttu, Kalaichelvi

    2013-01-29

    We report that incandescent beams patterned with amplitude depressions (dips) suffer instability in a photopolymerizable system and organize into lattices of black and bright self-trapped beams propagating respectively, through self-induced black and bright waveguides. Such optochemically organized lattices emerge when beams embedded with a hexagonal or square array of dips initiate free-radical polymerization and corresponding changes in refractive index (Δn) along their propagation paths. Under these nonlinear conditions, the dips evolve into a hexagonal or square lattice of black beams, while their bright interstitial regions become unstable and divide spontaneously into multiple filaments of light. These filaments have a characteristic diameter (d(f)) and organize into a variety of geometries, which are determined by the shape and dimensions of the bright interstices. At interstitial widths > 2d(f), filaments are randomly positioned in space, whereas at widths < 2d(f), the interstices are occupied by a single file of filaments encircling each dark channel. When the interstitial width ≈ d(f), the filaments organize into lattices with long-range hexagonal or square symmetry. By employing anisotropic interstices such as rectangles, filamentation can be selectively elicited along the long axis, leading to a lattice of filament doublets. This work demonstrates the versatility and significant potential of optochemical organization to generate complex, optically functional polymer lattices, which cannot be constructed through conventional lithography or self-assembly. Specifically, the study introduces a new generation of waveguide lattices, in which light propagation is co-operatively managed by black and bright waveguides; the former suppress local light propagation and, in this way, enhance light confinement and guidance in proximal bright waveguides. PMID:23252718

  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. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Helical currents in metallic Rashba strips

    NASA Astrophysics Data System (ADS)

    Hamad, Ignacio J.; Gazza, Claudio J.; Riera, José A.

    2016-05-01

    We study the texture of helical currents in metallic planar strips in the presence of Rashba spin-orbit coupling (RSOC) on the lattice at zero temperature. In the noninteracting case and in the absence of external electromagnetic sources, we determine, by exact numerical diagonalization of the single-particle Hamiltonian, the distribution across the strip section of these Rashba helical currents (RHC) as well as their sign oscillation, as a function of the RSOC strength, strip width, electron filling, and strip boundary conditions. Then, we study the effects of charge currents introduced into the system by an Aharonov-Bohm flux for the case of rings or by a voltage bias in the case of open strips. The former setup is studied by variational Monte Carlo, and the latter by the time-dependent density-matrix renormalization-group technique. Particularly for strips formed by two, three, and four coupled chains, we show how these RHC vary in the presence of such induced charge current, and how their differences between spin-up and spin-down electron currents on each chain help to explain the distribution across the strip of charge currents, both of the spin-conserving and the spin-flipping types. We also predict the appearance of polarized charge currents on each chain. Finally, we show that these Rashba helical currents and their derived features remain in the presence of an on-site Hubbard repulsion as long as the system remains metallic, at quarter filling, and even at half filling where a Mott-Hubbard metal-insulator transition occurs for large Hubbard repulsion.

  1. Optically pure, water-stable metallo-helical ‘flexicate’ assemblies with antibiotic activity

    NASA Astrophysics Data System (ADS)

    Howson, Suzanne E.; Bolhuis, Albert; Brabec, Viktor; Clarkson, Guy J.; Malina, Jaroslav; Rodger, Alison; Scott, Peter

    2012-01-01

    The helicates—chiral assemblies of two or more metal atoms linked by short or relatively rigid multidentate organic ligands—may be regarded as non-peptide mimetics of α-helices because they are of comparable size and have shown some relevant biological activity. Unfortunately, these beautiful helical compounds have remained difficult to use in the medicinal arena because they contain mixtures of isomers, cannot be optimized for specific purposes, are insoluble, or are too difficult to synthesize. Instead, we have now prepared thermodynamically stable single enantiomers of monometallic units connected by organic linkers. Our highly adaptable self-assembly approach enables the rapid preparation of ranges of water-stable, helicate-like compounds with high stereochemical purity. One such iron(II) ‘flexicate’ system exhibits specific interactions with DNA, promising antimicrobial activity against a Gram-positive bacterium (methicillin-resistant Staphylococcus aureus, MRSA252), but also, unusually, a Gram-negative bacterium (Escherichia coli, MC4100), as well as low toxicity towards a non-mammalian model organism (Caenorhabditis elegans).

  2. α-Peptide-Oligourea Chimeras: Stabilization of Short α-Helices by Non-Peptide Helical Foldamers.

    PubMed

    Fremaux, Juliette; Mauran, Laura; Pulka-Ziach, Karolina; Kauffmann, Brice; Odaert, Benoit; Guichard, Gilles

    2015-08-17

    Short α-peptides with less than 10 residues generally display a low propensity to nucleate stable helical conformations. While various strategies to stabilize peptide helices have been previously reported, the ability of non-peptide helical foldamers to stabilize α-helices when fused to short α-peptide segments has not been investigated. Towards this end, structural investigations into a series of chimeric oligomers obtained by joining aliphatic oligoureas to the C- or N-termini of α-peptides are described. All chimeras were found to be fully helical, with as few as 2 (or 3) urea units sufficient to propagate an α-helical conformation in the fused peptide segment. The remarkable compatibility of α-peptides with oligoureas described here, along with the simplicity of the approach, highlights the potential of interfacing natural and non-peptide backbones as a means to further control the behavior of α-peptides. PMID:26136402

  3. Dynamic Jaws and Dynamic Couch in Helical Tomotherapy

    SciTech Connect

    Sterzing, Florian; Uhl, Matthias; Hauswald, Henrik; Schubert, Kai; Sroka-Perez, Gabriele; Chen Yu; Lu Weiguo; Mackie, Rock; Debus, Juergen; Herfarth, Klaus; Oliveira, Gustavo

    2010-03-15

    Purpose: To investigate the next generation of helical tomotherapy delivery with dynamic jaw and dynamic couch movements. Methods and Materials: The new technique of dynamic jaw and dynamic couch movements is described, and a comparative planning study is performed. Ten nasopharyngeal cancer patients with skull base infiltration were chosen for this comparison of longitudinal dose profiles using regular tomotherapy delivery, running-start-stop treatment, and dynamic jaw and dynamic couch delivery. A multifocal simultaneous integrated boost concept was used (70.4Gy to the primary tumor and involved lymph nodes; 57.4Gy to the bilateral cervical lymphatic drainage pathways, 32 fractions). Target coverage, conformity, homogeneity, sparing of organs at risk, integral dose, and radiation delivery time were evaluated. Results: Mean parotid dose for all different deliveries was between 24.8 and 26.1Gy, without significant differences. The mean integral dose was lowered by 6.3% by using the dynamic technique, in comparison with a 2.5-cm-field width for regular delivery and 16.7% with 5-cm-field width for regular delivery. Dynamic jaw and couch movements reduced the calculated radiation time by 66% of the time required with regular 2.5-cm-field width delivery (199 sec vs. 595 sec, p < 0.001). Conclusions: The current delivery mode of helical tomotherapy produces dose distributions with conformal avoidance of parotid glands, brain stem, and spinal cord. The new technology with dynamic jaw and couch movements improves the plan quality by reducing the dose penumbra and thereby reducing the integral dose. In addition, radiation time is reduced by 66% of the regular delivery time.

  4. Triangular Helical Column for Centrifugal Countercurrent Chromatography.

    PubMed

    Ito, Yoichiro; Yu, Henry

    2009-01-01

    Effective column space and stationary phase retention have been improved by changing the configuration of the helical column originally used for toroidal coil countercurrent chromatography. The use of an equilateral triangular core for the helix column doubles effective column space and retains the stationary phase over 40% of the total column capacity without increasing the column pressure. The present results suggest that the stationary phase retention and the peak resolution will be further improved using new column designs fabricated by a new technology called "laser sintering for rapid prototyping." PMID:20046940

  5. Spin transport in helical biological systems

    SciTech Connect

    Díaz, Elena; Gutierrez, Rafael

    2014-08-20

    Motivated by the recent experimental demonstration of spin selective effects in monolayers of double-stranded DNA oligomers, our work presents a minimal model to describe electron transmission through helical fields. Our model highlight that the lack of inversion symmetry due to the chirality of the potential is a key factor which will lead to a high spin-polarization (SP). We also study the stability of the SP against fluctuations of the electronic structure induced by static disorder affecting the on-site energies. In the energy regions where the spin-filtering occurs, our results remain stable against moderate disorders although the SP is slightly reduced.

  6. Spinor helicity structures in higher spin theories

    NASA Astrophysics Data System (ADS)

    Ananth, Sudarshan

    2012-11-01

    It is shown that the coefficient of the cubic interaction vertex, in higher spin Lagrangians, has a very simple form when written in terms of spinor helicity products. The result for a higher-spin field, of spin λ, is equal to the corresponding Yang-Mills coefficient raised to the power λ. Among other things, this suggests perturbative ties, similar to the KLT relations, between higher spin theories and pure Yang-Mills. This result is obtained in four-dimensional flat spacetime.

  7. Landau theory for helical nematic phases

    NASA Astrophysics Data System (ADS)

    Kats, E. I.; Lebedev, V. V.

    2014-09-01

    We propose Landau phenomenology for the phase transition from the conventional nematic into the conical helical orientationally non-uniform structure recently identified in liquid crystals formed by "banana"-shaped molecules. The mean field predictions are mostly in agreement with experimental data. Based on the analogy with de Gennes model, we argue that fluctuations of the order parameter turn the transition to the first order phase transition rather than continuous one predicted by the mean-field theory. This conclusion is in agreement with experimental observations. We discuss the new Goldstone mode to be observed in the low-temperature phase.

  8. Conceptual Design for Superconducting Planar Helical Undulator

    NASA Astrophysics Data System (ADS)

    Sasaki, Shigemi

    2004-05-01

    A preliminary consideration was made on a short-period superconducting planar helical undulator (SCHU) for circularly polarized radiation. The SCHU consists of coils and iron poles/yokes. There is no magnetic structure in the horizontal plane of the electron orbit. The SCHU would provide the large horizontal aperture needed to allow injection into the storage ring. The expected field strength is at least 30% larger than that by an APPLE-type permanent-magnet device with the same gap and the same period.

  9. Helicon wave excitation with helical antennas

    SciTech Connect

    Light, M.; Chen, F.F.

    1995-04-01

    Components of the wave magnetic field in a helicon discharge have been measured with a single-turn, coaxial magnetic probe. Left- and right-handed helical antennas, as well as plane-polarized antennas, were used; and the results were compared with the field patterns computed for a nonuniform plasma. The results show that the right-hand circularly polarized mode is preferentially excited with all antennas, even those designed to excite the left-hand mode. For right-hand excitation, the radial amplitude profiles are in excellent agreement with computations. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Helical Disruptions in Small Loops of DNA

    NASA Astrophysics Data System (ADS)

    Zoli, Marco

    2015-01-01

    The thermodynamical stability of DNA minicircles is investigated by means of path integral techniques. Hydrogen bonds between base pairs on complementary strands can be broken by thermal fluctuations and temporary fluctuational openings along the double helix are essential to biological functions such as transcription and replication of the genetic information. Helix unwinding and bubble formation patterns are computed in circular sequences with variable radius in order to analyze the interplay between molecule size and appearance of helical disruptions. The latter are found in minicircles with < 100 base pairs and appear as a strategy to soften the stress due to the bending and torsion of the helix.

  11. Analysis of leaf development in fugu mutants of Arabidopsis reveals three compensation modes that modulate cell expansion in determinate organs.

    PubMed

    Ferjani, Ali; Horiguchi, Gorou; Yano, Satoshi; Tsukaya, Hirokazu

    2007-06-01

    In multicellular organisms, the coordination of cell proliferation and expansion is fundamental for proper organogenesis, yet the molecular mechanisms involved in this coordination are largely unexplored. In plant leaves, the existence of this coordination is suggested by compensation, in which a decrease in cell number triggers an increase in mature cell size. To elucidate the mechanisms of compensation, we isolated five new Arabidopsis (Arabidopsis thaliana) mutants (fugu1-fugu5) that exhibit compensation. These mutants were characterized together with angustifolia3 (an3), erecta (er), and a KIP-RELATED PROTEIN2 (KRP2) overexpressor, which were previously reported to exhibit compensation. Time-course analyses of leaf development revealed that enhanced cell expansion in fugu2-1, fugu5-1, an3-4, and er-102 mutants is induced postmitotically, indicating that cell enlargement is not caused by the uncoupling of cell division from cell growth. In each of the mutants, either the rate or duration of cell expansion was selectively enhanced. In contrast, we found that enhanced cell expansion in KRP2 overexpressor occurs during cell proliferation. We further demonstrated that enhanced cell expansion occurs in cotyledons with dynamics similar to that in leaves. In contrast, cell expansion was not enhanced in roots even though they exhibit decreased cell numbers. Thus, compensation was confirmed to occur preferentially in determinate organs. Flow cytometric analyses revealed that increases in ploidy level are not always required to trigger compensation, suggesting that compensation is only partially mediated by ploidy-dependent processes. Our results suggest that compensation reflects an organ-wide coordination of cell proliferation and expansion in determinate organs, and involves at least three different expansion pathways. PMID:17468216

  12. Electronic transport in single-helical protein molecules: Effects of multiple charge conduction pathways and helical symmetry

    NASA Astrophysics Data System (ADS)

    Kundu, Sourav; Karmakar, S. N.

    2016-07-01

    We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of environmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA.

  13. Predictive Mechanistic Model for the Electrical Impedance and Intensity-Modulated Photocurrent and Photovoltage Spectroscopic Responses of an Organic Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Set, Ying Ting; Birgersson, Erik; Luther, Joachim

    2016-05-01

    We develop a predictive and mechanistic model for the intensity-modulated photocurrent spectroscopic (IMPS), intensity-modulated photovoltage spectroscopic (IMVS), and electrical impedance spectroscopic (EIS) responses of organic bulk heterojunction (BHJ) solar cells. Unlike the dominant analytical framework—equivalent circuit analysis—the model uses physical parameters that directly reflect the device's fundamental electronic mechanisms, eliminating the ambiguity associated with interpreting phenomenological parameters. Formulated in the frequency domain, the model is a computationally efficient tool for extracting parameters from the measured spectra. With a set of physical parameters representing a device, we predict the device's spectra (a) in techniques employing different methods of perturbing a device and (b) at different bias voltages and illumination intensities. The predicted spectra show good agreement with the measured ones. By quantifying the device's internal electric field and charge carrier concentration and relating them to the spectra, we determine that the IMPS responses at the short-circuit condition and the IMVS responses at the open-circuit condition directly reflect the charge carrier extraction and recombination, respectively. Furthermore, the EIS response indicates the device's recombination time scale at different bias voltages.

  14. Abscisic Acid and LATERAL ROOT ORGAN DEFECTIVE/NUMEROUS INFECTIONS AND POLYPHENOLICS Modulate Root Elongation via Reactive Oxygen Species in Medicago truncatula1[W][OPEN

    PubMed Central

    Zhang, Chang; Bousquet, Amanda; Harris, Jeanne M.

    2014-01-01

    Abscisic acid (ABA) modulates root growth in plants grown under normal and stress conditions and can rescue the root growth defects of the Medicago truncatula lateral root-organ defective (latd) mutant. Here, we demonstrate that reactive oxygen species (ROS) function downstream of ABA in the regulation of root growth by controlling cell elongation. We also show that the MtLATD/NUMEROUS INFECTIONS AND POLYPHENOLICS (NIP) nitrate transporter is required for ROS homeostasis and cell elongation in roots and that this balance is perturbed in latd mutants, leading to an excess of superoxide and hydrogen peroxide and a corresponding decrease in cell elongation. We found that expression of the superoxide-generating NADPH oxidase genes, MtRbohA and MtRbohC (for respiratory burst oxidase homologs), is increased in latd roots and that inhibition of NADPH oxidase activity pharmacologically can both reduce latd root ROS levels and increase cell length, implicating NADPH oxidase function in latd root growth defects. Finally, we demonstrate that ABA treatment alleviates ectopic ROS accumulation in latd roots, restores MtRbohC expression to wild-type levels, and promotes an increase in cell length. Reducing the expression of MtRbohC using RNA interference leads to increased root elongation in both wild-type and latd roots. These results reveal a mechanism by which the MtLATD/NIP nitrate transporter and ABA modulate root elongation via superoxide generation by the MtRbohC NADPH oxidase. PMID:25192698

  15. Modulation of a Molecular π-Electron System in a Purely Organic Conductor that Shows Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism.

    PubMed

    Ueda, Akira; Hatakeyama, Akari; Enomoto, Masaya; Kumai, Reiji; Murakami, Youichi; Mori, Hatsumi

    2015-10-12

    New important aspects of the hydrogen-bond (H-bond)-dynamics-based switching of electrical conductivity and magnetism in an H-bonded, purely organic conductor crystal have been discovered by modulating its tetrathiafulvalene (TTF)-based molecular π-electron system by means of partial sulfur/selenium substitution. The prepared selenium analogue also showed a similar type of phase transition, induced by H-bonded deuterium transfer followed by electron transfer between the H-bonded TTF skeletons, and the resulting switching of the physical properties; however, subtle but critical differences due to sulfur/selenium substitution were detected in the electronic structure, phase transition nature, and switching function. A molecular-level discussion based on the crystal structures shows that this chemical modification of the TTF skeleton influences not only its own π-electronic structure and π-π interactions within the conducting layer, but also the H-bond dynamics between the TTF π skeletons in the neighboring layers, which enables modulation of the interplay between the H-bond and π electrons to cause such differences. PMID:26311352

  16. Modul.LES: a multi-compartment, multi-organism aquatic life support system as experimental platform for research in ∆g

    NASA Astrophysics Data System (ADS)

    Hilbig, Reinhard; Anken, Ralf; Grimm, Dennis

    In view of space exploration and long-term satellite missions, a new generation of multi-modular, multi-organism bioregenerative life support system with different experimental units (Modul.LES) is planned, and subunits are under construction. Modul.LES will be managed via telemetry and remote control and therefore is a fully automated experimental platform for different kinds of investigations. After several forerunner projects like AquaCells (2005), C.E.B.A.S. (1998, 2003) or Aquahab (OHB-System AG the Oreochromis Mossambicus Eu-glena Gracilis Aquatic Habitat (OmegaHab) was successfully flown in 2007 in course of the FOTON-M3 Mission. It was a 3 chamber controlled life support system (CLSS), compris-ing a bioreactor with the green algae Euglena gracilis, a fish chamber with larval cichlid fish Oreochromis mossambicus and a filter chamber with biodegrading bacteria. The sensory super-vision of housekeeping management was registered and controlled by telemetry. Additionally, all scientific data and videos of the organisms aboard were stored and sequentially transmitted to relay stations. Based on the effective performance of OmegaHab, this system was chosen for a reflight on Bion-M1 in 2012. As Bion-M1 is a long term mission (appr. 4 weeks), this CLSS (OmegaHab-XP) has to be redesigned and refurbished with enhanced performance. The number of chambers has been increased from 3 to 4: an algae bioreactor, a fish tank for adult and larval fish (hatchery inserted), a nutrition chamber with higher plants and crustaceans and a filter chamber. The OmegaHab-XP is a full automated system with an extended satellite downlink for video monitoring and housekeeping data acquisition, but no uplink for remote control. OmegaHab-XP provides numerous physical and chemical parameters which will be monitored regarding the state of the biological processes and thus enables the automated con-trol aboard. Besides the two basic parameters oxygen content and temperature, products of the

  17. Image quality and age-specific dose estimation in head and chest CT examinations with organ-based tube-current modulation.

    PubMed

    Yamauchi-Kawaura, C; Yamauchi, M; Imai, K; Ikeda, M; Aoyama, T

    2013-12-01

    The purpose of this study was to investigate the effects of an organ-based tube-current modulation (OBTCM) system on image quality and age-specific dose in head and chest CT examinations. Image noise, contrast-to-noise ratio (CNR) and image entropy were assessed using statistical and entropy analyses. Radiation doses for newborn, 6-y-old child and adult phantoms were measured with in-phantom dosimetry systems. The quality of CT images obtained with OBTCM was not different from that obtained without OBTCM. In head CT scans, the eye lens dose decreased by 20-33 % using OBTCM. In chest CT scans, breast dose decreased by 5-32 % using OBTCM. Posterior skin dose, however, increased by 11-20 % using OBTCM in head and chest CT scans. The reduction of effective dose using OBTCM was negligibly small. Detailed image quality and dose information provided in this study can be effectively used for OBTCM application. PMID:23734058

  18. Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits

    SciTech Connect

    Marsh, R. M.; Silosky, M.

    2015-04-15

    Purpose: The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. Methods: This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position the dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. Results: (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R{sup 2} = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o’clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and

  19. Transient Influx of Nickel in Root Mitochondria Modulates Organic Acid and Reactive Oxygen Species Production in Nickel Hyperaccumulator Alyssum murale*

    PubMed Central

    Agrawal, Bhavana; Czymmek, Kirk J.; Sparks, Donald L.; Bais, Harsh P.

    2013-01-01

    Mitochondria are important targets of metal toxicity and are also vital for maintaining metal homeostasis. Here, we examined the potential role of mitochondria in homeostasis of nickel in the roots of nickel hyperaccumulator plant Alyssum murale. We evaluated the biochemical basis of nickel tolerance by comparing the role of mitochondria in closely related nickel hyperaccumulator A. murale and non-accumulator Alyssum montanum. Evidence is presented for the rapid and transient influx of nickel in root mitochondria of nickel hyperaccumulator A. murale. In an early response to nickel treatment, substantial nickel influx was observed in mitochondria prior to sequestration in vacuoles in the roots of hyperaccumulator A. murale compared with non-accumulator A. montanum. In addition, the mitochondrial Krebs cycle was modulated to increase synthesis of malic acid and citric acid involvement in nickel hyperaccumulation. Furthermore, malic acid, which is reported to form a complex with nickel in hyperaccumulators, was also found to reduce the reactive oxygen species generation induced by nickel. We propose that the interaction of nickel with mitochondria is imperative in the early steps of nickel uptake in nickel hyperaccumulator plants. Initial uptake of nickel in roots results in biochemical responses in the root mitochondria indicating its vital role in homeostasis of nickel ions in hyperaccumulation. PMID:23322782

  20. SU-E-P-51: Dosimetric Comparison to Organs at Risk Sparing Using Volumetric-Modulated Arc Therapy Versus Intensity-Modulated Radiotherapy in Postoperative Radiotherapy of Left-Sided Breast Cancer

    SciTech Connect

    Qiao, L; Deng, G; Xie, J; Cheng, J; Liang, N; Zhang, J; Zhang, J; Luo, H

    2015-06-15

    Purpose: To compare the dosimetric characteristics of volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for left-sided breast cancer patients with modified radical mastectomy. Methods: Twenty-four left-sided breast cancer patients treated with modified radical mastectomy were selected in this study. The planning target volume (PTV) was generated by using 7-mm uniform expansion of the clinical target volume (CTV) in all direction except the skin surface. The organs at risk (OARs) included heart, left lung, right lung, and right breast. Dose volume histograms (DVHs) were utilized to evaluate the dose distribution in PTV and OARs. Results: Both VMAT and IMRT plans met the requirement of PTV coverage. VMAT was superior to IMRT in terms of conformity, with a statistically significant difference (p=0.024). Mean doses, V5 and V10 of heart and both lungs in VMAT plans were significantly decreased compared to IMRT plans (P<0.05), but in terms of heart volume irradiated by high doses (V30 and V45), no significant differences were observed (P>0.05). For right breast, VMAT showed the reduction of V5 in comparison with IMRT (P<0.05). Additionally, the mean number of monitor units (MU) and treatment time in VMAT (357.21, 3.62 min) were significantly less than those in IMRT (1132.85, 8.74 min). Conclusion: VMAT showed similar PTV coverage and significant advantage in OARs sparing compared with IMRT, especially in terms of decreased volumes irradiated by low doses, while significantly reducing the treatment time and MU number.