FRONT FLIP HALF TWIST

2017 ◽  
Vol 105 (2) ◽  
pp. 12-12 ◽  
Author(s):  
Clive James
Keyword(s):  
Half Twist

ON POWERS OF HALF-TWISTS IN M(0, 2n)

2017 ◽  
Vol 60 (2) ◽  
pp. 333-338 ◽  
Author(s):  
GREGOR MASBAUM
Keyword(s):  
Mapping Class Group ◽  
Class Group ◽  
Normal Closure ◽  
Mapping Class ◽  
Infinite Index ◽  
Skein Theory ◽  
Half Twist

AbstractWe use elementary skein theory to prove a version of a result of Stylianakis (Stylianakis, The normal closure of a power of a half-twist has infinite index in the mapping class group of a punctured sphere, arXiv:1511.02912) who showed that under mild restrictions on m and n, the normal closure of the mth power of a half-twist has infinite index in the mapping class group of a sphere with 2n punctures.

Effect of Ability on Twisting Techniques in Forward Somersaults on the Trampoline

1995 ◽  
Vol 11 (3) ◽  
pp. 267-287 ◽  
Author(s):  
Ross H. Sanders
Keyword(s):  
Dimensional Analysis ◽  
Twist Angle ◽  
Three Dimensional ◽  
Frame Of Reference ◽  
Flexion Angle ◽  
Lateral Flexion ◽  
Analysis Techniques ◽  
Half Twist

This study was designed to investigate the effect of ability on technique in the forward somersault with half twist (Barani) and the forward somersault with one and one half twists (Rudi) on the trampoline. Eleven trampolinists ranging in ability from elite (national representative) to early intermediate (regional representative) were analyzed using three-dimensional analysis techniques. Cumulative twist angle, rate of twist, angle of tilt of the twist axis, chest rotation, hip angle, and hip lateral flexion angle were measured. Characteristics of the arm actions were also assessed using an internal frame of reference. To generate twist in the Baranis, trampolinists tilted the axis between 5° and 14°; the amount of tilt was inversely related to ability (p < .05). In the Rudis, subjects tilted the axis between 15° and 23° using more asymmetrical arm actions and larger and more rapid hip extensions, hip lateral flexions, and chest rotations than in the Baranis. The timing and magnitude of the actions differed among the subjects and were related to ability.

scholarly journals The normal closure of a power of a half-twist has infinite index in the mapping class group of a punctured sphere

2019 ◽  
Vol 11 (02) ◽  
pp. 273-292
Author(s):  
Charalampos Stylianakis
Keyword(s):  
Free Group ◽  
Braid Group ◽  
Mapping Class Group ◽  
Abelian Subgroup ◽  
Infinite Order ◽  
Class Group ◽  
Normal Closure ◽  
Mapping Class ◽  
Infinite Index ◽  
Half Twist

In this paper we show that the normal closure of the [Formula: see text]th power of a half-twist has infinite index in the mapping class group of a punctured sphere if [Formula: see text] is at least five. Furthermore, in some cases we prove that the quotient of the mapping class group of the punctured sphere by the normal closure of a power of a half-twist contains a free abelian subgroup. As a corollary we prove that the quotient of the hyperelliptic mapping class group of a surface of genus at least two by the normal closure of the [Formula: see text]th power of a Dehn twist has infinite order, and for some integers [Formula: see text] the quotient contains a free group. As a second corollary we recover a result of Coxeter: the normal closure of the [Formula: see text]th power of a half-twist in the braid group of at least four strands has infinite index. Our method is to reformulate the Jones representation of the mapping class group of a punctured sphere, using the action of Hecke algebras on [Formula: see text]-graphs, as introduced by Kazhdan–Lusztig.

scholarly journals Dominant ferromagnetism in the spin-1/2 half-twist ladder 334 compounds, Ba3Cu3In4O12and Ba3Cu3Sc4O12

2012 ◽  
Vol 24 (16) ◽  
pp. 166001 ◽  
Author(s):  
S E Dutton ◽  
M Kumar ◽  
Z G Soos ◽  
C L Broholm ◽  
R J Cava
Keyword(s):  
Half Twist

scholarly journals PALINDROMES AND ORDERINGS IN ARTIN GROUPS

2010 ◽  
Vol 19 (02) ◽  
pp. 145-162 ◽  
Author(s):  
FLORIAN DELOUP
Keyword(s):  
Finite Type ◽  
Braid Group ◽  
Type A ◽  
Reverse Order ◽  
Artin Groups ◽  
Left Order ◽  
Group B ◽  
Half Twist

The braid group Bn, endowed with Artin's presentation, admits two distinguished involutions. One is the anti-automorphism rev : Bn →Bn, [Formula: see text], defined by reading braids in the reverse order (from right to left instead of left to right). Another one is the conjugation τ : x ↦ Δ-1xΔ by the generalized half-twist (Garside element). More generally, the involution rev is defined for all Artin groups (equipped with Artin's presentation) and the involution τ is defined for all Artin groups of finite type. A palindrome is an element invariant under rev. We study palindromes and palindromes invariant under τ in Artin groups of finite type. Our main results are the injectivity of the map [Formula: see text] in all finite-type Artin groups, the existence of a left-order compatible with rev for Artin groups of type A, B, D, and the existence of a decomposition for general palindromes. The uniqueness of the latter decomposition requires that the Artin groups carry a left-order.

TWIST MOVES AND VASSILIEV INVARIANTS

2004 ◽  
Vol 13 (06) ◽  
pp. 719-735
Author(s):  
MYEONG-JU JEONG ◽  
EUN-JIN KIM ◽  
CHAN-YOUNG PARK
Keyword(s):  
Vassiliev Invariants ◽  
Conway Polynomial ◽  
Vassiliev Invariant ◽  
Oriented Parallel ◽  
Half Twist

The transforms of two oriented parallel strands to a k-half twist of two strands are called tk-move and [Formula: see text]-move respectively depending on the orientations of the two strands. In this paper we give criterions to detect whether a knot K can be transformed to a knot K' by t2k-moves and [Formula: see text]-moves respectively and if so, we give some results on how many moves are needed in these transformations respectively, by using some Vassiliev invariants. Moreover we give a relation between the Δ-move and the t2k-move by considering the coefficient of z2 in the Conway polynomial of a knot, which is a Vassiliev invariant of degree 2.

scholarly journals An assembling procedure for DNA bipyramids with minimum component strands

2021 ◽  
Vol 87 (01) ◽  
pp. 179-192
Author(s):  
Tao Deng ◽  
Mengge Huang ◽  
Jingyi Zhang
Keyword(s):  
Drug Delivery ◽  
Dna Molecules ◽  
Design And Synthesis ◽  
Multiple Component ◽  
Half Twist

DNA cages are ideally suited to make nanostructures which serve as containers for drug delivery. Using fewer strands to assemble DNA cages is of importance to the design of DNA molecules with multiple component strands. In this study, we propose a rational assembling procedure to design and analyze DNA bipyramids with minimum strands. The results show that the odd-half twist has a major impact on assembling strands required to construct DNA cages and this method could offer a search of DNA bipyramids with minimum component strands faster. This research provides new insights into design and synthesis for DNA bipyramid-like cages from mathematical perspective.

scholarly journals Simplicial volume of links from link diagrams

2017 ◽  
Vol 166 (1) ◽  
pp. 75-81 ◽  
Author(s):  
OLIVER DASBACH ◽  
ANASTASIIA TSVIETKOVA
Keyword(s):  
Upper Bound ◽  
Link Diagram ◽  
Simplicial Volume ◽  
Link Diagrams ◽  
Hyperbolic Volume ◽  
Link Complements ◽  
Link Complement ◽  
Half Twist

AbstractThe hyperbolic volume of a link complement is known to be unchanged when a half-twist is added to a link diagram, and a suitable 3-punctured sphere is present in the complement. We generalise this to the simplicial volume of link complements by analysing the corresponding toroidal decompositions. We then use it to prove a refined upper bound for the volume in terms of twists of various lengths for links.

Heat Transfer and Pressure Drop Studies in a Circular Tube Fitted with Straight Half-Twist Inserts

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
V Siva Rama Krishna ◽  
Govardhan Pathipakka ◽  
Palani Sivashanmugam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Cfd Simulation ◽  
Circular Tube ◽  
Heat Transfer Augmentation ◽  
Appreciable Increase ◽  
Plain Tube ◽  
The Heat Transfer Coefficient ◽  
Half Twist

Experimental investigation of heat transfer characteristics of circular tube fitted with straight half twist insert has been presented. The heat transfer coefficient increases with Reynolds number and decreases with spacer distance for both the single direction and left-right twist inserts. Also, there is no appreciable increase in heat transfer enhancement in straight half twist insert with 2-inch spacer distance. Experiments were carried out in turbulent flow using straight half twist insert with 4-inch spacer and similar trend of increasing Nusselt number with Reynolds number was observed. CFD simulation for the heat transfer augmentation in the plain tube and the tube fitted with half twist inserts has also been explained using Fluent version 6.3.26. The data obtained by simulation are matching with the experimental value with the discrepancy of less than ±10% for the plain tube and the tube fitted with straight-half twist inserts for Nusselt number and friction factor.

Sign in / Sign up

Export Citation Format

Share Document