Double Twist Research Articles

Double Twist and Shout: An Emergency Caused by Torsion of the Ovary and the Wandering Spleen

Double Twist and Shout: An Emergency Caused by Torsion of the Ovary and the Wandering Spleen

Influence of the twisting and nano fluids on performance of a triangular double tube heat exchanger

Abstract The hydraulic and thermals performance of flow in a double-tube heat exchanger with an inner twisted triangle tube of length L = 1 m has been studied numerically. Equations for energy, turbulence, and Navier–Stokes were used to model the fluid flow and heat transfer in a double-tube heat exchanger with an inner twisted triangle tube. The Reynolds number range was 5000–30,000 for nanofluid (water-Al2O3) as a working fluid under a turbulent flow regime. The considered configuration was examined by varying the volume concentration of nanofluid while keeping the twist ratio constant (Tr = 5). Different cases of volume concentration of nanofluid are triggered (0.05 %, 1 %, 2.5 %, and 4 %, respectively). The numerical outcomes of a double-twisted tube heat exchanger with an inner triangle-twisted tube are validated with the obtainable numerical data. The governing equations were solved with ANSYS Fluent 18.2. The findings reveal that the larger volume concentration of nanofluid (4 %) gives a greater Nusselt number and vice versa due to the increased thermal conductivity of the nanofluid in the double twist tube heat exchanger compared with a plain tube. However, the nanofluid Nusselt number grows with the rise of both the Reynolds number and volume concentration (Ø), and the best value of the Nusselt number is 210 when Reynolds number = 30,000 and Ø = 4 %. The effectiveness of the heat exchanger grows with an increase in the concentration of the nanofluid and a reduction in the torsion ratio compared to the normal tube. The effectiveness of the double-tube heat exchanger with an inner twist triangle tube increases to the highest value of 0.38 at Reynolds 30,000 and Ø = 4 %.

“A double twist” presentation – a case report of purulent cardiac tamponade following a rare complication of small-cell lung cancer radiotherapy

Background: Small cell lung cancer is an aggressive tumor with a poor prognosis that requires prompt treatment. While radiotherapy may enhance survival when superior vena cava syndrome is present, radiation therapy–induced pericardial disease can be a potential complication. Case Report: A 55-year-old man, who recently underwent radiotherapy for stage IV small-cell lung cancer complicated by superior vena cava syndrome, presented with chest pain and dyspnea. In the emergency room, he was dyspneic, hypotensive, and tachycardic. Pulmonary auscultation revealed the absence of lung sounds on the right. The initial electrocardiogram showed ST-segment elevation in lateral leads and in lead DII, with reciprocal changes in lead DIII. A bedside transthoracic echocardiogram revealed cardiac tamponade and emergent pericardiocentesis was performed, removing 500 ml of purulent fluid, resulting in an immediate clinical improvement. Thoracentesis was also performed, showing no empyema. Large spectrum empirical antibiotic therapy was started. Cultures from the pericardial fluid and peripheral blood grew multi-sensitive Streptococcus pneumoniae. Cytological analysis of the pericardial fluid was consistent with infection. The patient improved after 2 weeks of targeted antibiotic therapy and underwent the first cycle of chemotherapy. He was discharged with an early scheduled pulmonology appointment. Conclusions: Although the most common causes of pericardial effusion in lung cancer are malignant, non-malignant etiologies should also be considered. This patient had an infectious pericardial effusion most probably due to a pericardial-mediastinal mass fistula caused by radiotherapy. This was a diagnostic challenge, both in the emergency room as well in the inpatient setting.

Ab Initio Conformational Analysis of 3,7-Diacetyl-3,7-Diazabicyclo[3.3.1]Nonanes

Introduction: The importance of the conformational behavior comprehension for proper prediction of properties for a certain compound or for a class of compounds is indisputable. For 3,7-diacylbispidines (3,7-diacyl-3,7-diazabicyclo[3.3.1]nonanes), only “double chair” (CC) conformers were prior found experimentally in the condensed phase, which differ only in the acyl groups relative orientation, “parallel,” pa or “antiparallel,” ap. However, 2 other conformer families, “boat-chair,” BC and “double twist,” TT, are known for other bicyclo[3.3.1]nonane derivatives. Features of these conformers would be useful for the accurate prediction of properties and activities of the compounds. Methods: Second-order perturbation theory ab initio techniques (MP2) in the triple-zeta correlation-consistent orbital basis set cc-pVTZ was employed to optimize the electronic energy for structures, to characterize the optimized structures as potential energy surface minima by energy hessian eigenvalue calculations and to calculate zero-point energy corrections for the minima using the “rigid rotor-harmonic oscillator” approximation to model the molecular ensemble thermodynamics. Additionally, the computational chemical thermodynamics benefits much from the concept of the molecular strain and its energy assessed successfully through the bond separation energy formalism. We combine both approaches in our investigation to find and consistently characterize the conformers previously unknown for the compounds under the studies. Results: Six possible conformers were found for the investigated 3,7-diacetyl-3,7-diazabicyclo[3.3.1]nonanes 1-4, formed by combining the skeletal conformation changes with the internal rotation of acyl substituents. The conformational behavior is quite similar for all investigated molecules. In all cases, the CC conformation is optimal for the bicyclic skeleton and ap orientation prevails over pa for 2 acetyl groups. This prevalence is 4-5 kcal mol−1 in CC and less than 1 kcal mol−1 in other skeletal forms, making rotation of 2 acyl groups in BC and TT almost independent. Concerning the skeletal conformations, the common energy sequence CC < BC < TT is found. While the relative BC energy is 6-7 kcal mol−1 over the optimal CC structure, TT forms are all strained by more than 12 kcal mol−1. Conclusions: For the first time, both BC and TT conformers of 3,7-diacetylbispidines were characterized by their strain and conformation energies together with known less strained CC forms. On the basis of our calculations, the relative energies of BC conformers are expected to be close to those of the CC acetyl amide bond rotamers found previously in experiment, therefore, their exclusion from the conformational behavior would look unjustified. On the contrary, TT conformers are found to be much more strained enough to be neglected in the conformational ensemble modeling.

Inderdigitation, double twist, and topological defects in a system of hard lollipops

ABSTRACT Using hard particle Monte Carlo simulations, we studied a three-dimensional system consisting of identical, lollipop-like particles. Each lollipop was built of five identical, tangent balls placed along a line and one larger ball at one side of the particle and modelled the RM734 molecule, for which ferroelectric and splay nematics were recently discovered in the experiment. Although our model did not recreate these phases, we observed inherently polar type A and C interdigitated smectics. Moreover, an intriguing, isotropic phase consisting of double-twisted clusters joined by planar defects was formed for a moderate packing fraction and ball diameter ratio.

The ‘Double Twist’ Technique: A Novel Approach to Secure Sternal Closure and Prevent Dehiscence in Obese Patients After Cardiac Surgery

Sternal wound dehiscence after cardiac surgery, particularly in people with obesity, is a devastating complication. We present a ‘double twist’ technique for sternal closure, which firmly stabilizes the sternal halves without additional risk of wound complications.

Generalized torsion elements in the fundamental groups of 3-manifolds obtained by 0-surgeries along some double twist knots

We consider the 3-manifold obtained by the 0-surgery along a double twist knot. We construct a candidate for a generalized torsion element in the fundamental group of the surgered manifold, and see that there exists the cases where the candidate is actually a generalized torsion element. For a proof, we use the JSJ-decomposition of the surgered manifold. We also prove that the fundamental group of the 3-manifold obtained by 0-surgery along a double twist knot is bi-orderable if and only if it admits no generalized torsion elements. We also list some examples of the surgered manifolds whose fundamental groups admit generalized torsion elements.

Conditioned adaptive barrier-based double integral super twisting SMC for trajectory tracking of a quadcopter and hardware in loop using IGWO algorithm

Researchers working in the field of unmanned aerial vehicles are observing rapid developments in the field, such as the use of quadrotors to grasp, manipulate, and transport objects. These advancements are made possible through sophisticated control systems, new types of actuation and sensing technologies, and a greater understanding of the aerodynamic effects and gyroscopic moment generated by the rotating blades of the quadrotor involved. Therefore, this research work proposes four novel optimized control laws, i.e., conditioned adaptive barrier-based double integral super twisting sliding mode controller (CABDIST-SMC), BF double integral SMC (BF-DISMC), BF integral SMC, and barrier function-based SMC control laws, for attitude, heading, position, and altitude trajectory tracking of the quadcopter. The non-linear model of the quadcopter is developed using the Lagrange formalism in MATLAB ODE-45 environment, including the gyroscopic moments and aerodynamic effects, and a Lyapunov stability analysis is performed to ensure the asymptotic stability of the system. A 3D-helical complex trajectory is employed to analyze the performance and consistency of the proposed optimized controllers. For performance comparison, the proposed four variants of the SMC are compared with three traditional control strategies, i.e., backstepping SMC, optimized adaptive SMC via particle swarm optimization algorithm, and improved adaptive SMC. These traditional control strategies have also been developed and tested in MATLAB-Simulink. All the controllers are optimized using the improved grey wolf optimization algorithm, and to determine the best control law, six performance indexes, i.e., mean absolute percentage error (MAPE), root mean square error (RMSE), integral square error (ISE), integral absolute error (IAE), integral time absolute error (ITAE), and integral time square error (ITSE) are used. A hardware-in-loop (HIL) test is also performed to validate the performance of the designed novel control law. The C2000 Delfino MCU F28379D launchpad is used for performing the HIL validation test. The simulated results showed that the performance of optimized CABDIST-SMC surpassed all other control laws for altitude, heading, position, and attitude trajectory tracking. It has achieved MAPE of 0.02%, RMSE of 3.9912e−5, ISE of 3.1859e−8, IAE of 7.9823e−4, ITAE of 0.0080, and ITSE of 3.1849e−7 in case of yaw angle control. The proposed control laws have successfully passed the HIL validation test, and real-time implementation of the proposed control laws indicates no significant variations compared to the simulated results.

On the nonorientable 4-genus of double twist knots

We investigate the nonorientable 4-genus [Formula: see text] of a special family of 2-bridge knots, the double twist knots [Formula: see text]. Because the nonorientable 4-genus is bounded by the nonorientable 3-genus, it is known that [Formula: see text]. By using explicit constructions to obtain upper bounds on [Formula: see text] and known obstructions derived from Donaldson’s diagonalization theorem to obtain lower bounds on [Formula: see text], we produce infinite subfamilies of [Formula: see text] where [Formula: see text] and [Formula: see text], respectively. However, there remain infinitely many double twist knots where our work only shows that [Formula: see text] lies in one of the sets [Formula: see text], or [Formula: see text]. We tabulate our results for all [Formula: see text] with [Formula: see text] and [Formula: see text] up to 50. We also provide an infinite number of examples which answer a conjecture of Murakami and Yasuhara.

Significant acceleration of E-Z photoisomerization induced by molecular planarity breaking

E-Z photoisomerization constitutes the footstone of photosensitive proteins, molecular photoswitches and sunscreens and is believed to be controlled by photoinduced intramolecular charge transfer. In this work, we have made methylation on isomerizable alkene bond of plant sunscreen sinapate esters to break the coplanarity between phenol ring and CC double bond in ground state. Femtosecond transient absorption spectroscopy combined with time-dependent density functional theory calculations determine that this molecular planarity breaking triggers an immediate excited-state CC double bond twisting and thus accelerates the isomerization by more than one order of magnitude. These results highlight the role of molecular geometry on isomerization dynamics.

Explicit formulae for Chern-Simons invariants of the hyperbolic J(2n,-2m) knot orbifolds

We calculate the Chern-Simons invariants of the hyperbolic double twist knot orbifolds using the Schläfli formula for the generalized Chern-Simons function on the family of cone-manifold structures of double twist knots.

Tuning of optical properties and phase behavior of Nanomaterial-stabilized blue phase liquid crystals

HypothesisNanoparticles of various shapes and sizes can affect the optical properties and blue phase (BP) stabilization of BP liquid crystals (BPLCs). This is because nanoparticles, which are more compatible with the LC host, can be dispersed in both the double twist cylinder (DTC) and disclination defects in BPLCs. ExperimentsThis study presents the first systematic study of the use of CdSe nanoparticles having various sizes and shapes (spheres, tetrapods and nanoplatelets) to stabilize BPLCs. Unlike previous studies using commercial nanoparticles (NPs), we custom-synthesized NPs with the same core and nearly identical long chain hydrocarbon ligand materials. Two LC hosts were used to investigate the NP effect on BPLCs. FindingsThe size and shape of nanomaterials greatly influence the interaction with LCs, and the dispersion of NPs in the LC medium affects the position of the BP reflection band and the stabilization of BPs. Spherical NPs were found to be more compatible with the LC medium than tetrapod shape and platelet shape NPs, resulting in a wider temperature range of BP and a redshift of the reflection band of BP. In addition, the inclusion of spherical NPs tuned the optical properties of BPLCs to a significant extent, whereas BPLCs with nanoplatelets displayed a limited influence on the optical properties and temperature window of BPs due to poor compatibility with LC hosts. The tunable optical behavior of BPLC as a function of the type and concentration of NPs has not been reported.

EVALUATION OF CARBON FIBRE REINFORCED POLYMERS USING FUZZY TOPSIS MCDM METHOD

Carbon Fiber Reinforced Polymer (CFRP) is Repair of reinforced concrete structures and both are used for reinforcement One of the composite materials. Polymer reinforced with carbon fibres an advanced non-metal made of resin compound, which is of high strength, Weight loss, itching and excessive fatigue It has many excellent performances like resistance. Carbon fiber reinforced polymer (CFRP) is the best specific machine has properties, so these products High such as automobile and aerospace sectors widely used in technical industries. Dimensional or assembly related requirements CFRP composites to complement Machining is often necessary. The approach is based on the Fuzzy TOPSIS technique (Fuzzy Technique for Order Preference by Similarity to Ideal Solution) this analysis using the Alternative Value Conventional twist drill, Double point angle twist drill, Brad & spur drill, Dagger drill, Core drill and Cutting force, Cutting torque, Tool wear, Cutting temperature is Evaluation parameters value Core drill is got the first rank whereas is the Dagger drill is having the lowest rank.

Spontaneous Twisting of Achiral Hard Rod Nematics.

Since Onsager's seminal work, hard rods have been taken as a prototype of nematic liquid crystals, characterized by uniaxial order and a uniform director field as a ground state. Here, using Onsager theory to calculate the free energy in the presence of arbitrary deformations, we find that hard rod nematics have an intrinsic tendency to twist around their ordering axis (double twist), driven by a mechanism in which the orientational fluctuations of particles play a key role. The anisotropic hard core potential used here is arguably the simplest form of interaction able to originate spontaneous breaking of mirror symmetry in a 3D fluid. Our results are discussed in relation to the recent discovery of a double twisted ground state in cylindrically confined lyotropic chromonic liquid crystals.

Precursor skyrmion states near the ordering temperatures of chiral magnets.

In noncentrosymmetric magnets, chiral Dzyaloshinskii-Moriya interactions (DMI) provide a distinctive mechanism for the stabilization of localized skyrmion states in two and three dimensions with a fixed sense of rotation. Near the ordering transition, the skyrmion strings develop attractive skyrmion-skyrmion interactions and ultimately become confined in extended clusters or textures [A. O. Leonov and U. K. Rößler, Nanomaterials, 2023, 13, 891], which is a consequence of the coupling between the magnitude and the angular part of the order parameter. Multi-skyrmionic states built from isolated skyrmions (IS) can form multiple modulated magnetic phases that may underlie the exotic magnetic phenomena of "partial order" or the field-driven "A-phase" observed in MnSi and other cubic helimagnets. Based on the standard phenomenological Dzyaloshinskii model, we obtain numerically exact solutions for skyrmion lattices (SkL), formulate their basic properties, and elucidate physical mechanisms of their formation and stability. Our detailed numerical studies show that the bound skyrmion states arise as hexagonal lattices of ±π-skyrmions (with the magnetization in the center along or opposite to the magnetic field) or square staggered lattices of π/2-skyrmions, which contain defect lines with zero modulus value and thus may form thermodynamically stable states only near the ordering temperature. In the simplest case of a two-dimensional (2D) skyrmionic texture, the structure is homogeneous in the third dimension (3D). The skyrmions preserve an ideal axisymmetric "double twist" core in condensed phases, while continuation into a space-filling texture is frustrated. The evolution of skyrmion lattices in an increasing magnetic field leads to a succession of phase transitions of first or second kind between diverse textures and finally ends due to the formation of isolated skyrmion-filaments with fixed radius and shape embedded in a homogeneously magnetized matrix. In the framework of the phenomenological model including only isotropic interactions (exchange, Zeeman, and DM energy contributions), the considered skyrmion lattices are only metastable states as the competing conical one-dimensional spiral forms the equilibrium state. But due to the weak couplings between skyrmions, secondary effects like anisotropies can stabilize skyrmionic textures as compared to simple helices. Also the topological nature of skyrmion condensates makes the magnetization processes in chiral magnets history-dependent and hysteretic.

Explicit demonstration of geometric frustration in chiral liquid crystals.

Many solid materials and liquid crystals exhibit geometric frustration, meaning that they have an ideal local structure that cannot fill up space. For that reason, the global phase must be a compromise between the ideal local structure and geometric constraints. As an explicit example of geometric frustration, we consider a chiral liquid crystal confined in a long cylinder with free boundaries. When the radius of the tube is sufficiently small, the director field forms a double-twist configuration, which is the ideal local structure. However, when the radius becomes larger (compared with the natural twist of the liquid crystal), the double-twist structure cannot fill space, and hence the director field must transform into some other chiral structure that can fill space. This space-filling structure may be either (1) a cholesteric phase with single twist, or (2) a set of double-twist regions separated by a disclination, which can be regarded as the beginning of a blue phase. We investigate these structures using theory and simulations, and show how the relative free energies depend on the system size, the natural twist, and the disclination energy. As another example, we also study a cholesteric liquid crystal confined between two infinite parallel plates with free boundaries.

Curvature and confinement effects on chiral liquid crystal morphologies.

Chiral liquid crystals (ChLCs) exhibit an inherent twist that originates at the molecular scale and can extend over multiple length scales when unconstrained. Under confinement, the twist is thwarted, leading to formation of defects in the molecular order that offer distinct optical responses and opportunities for colloidal driven assembly. Past studies have explored spheroidal confinement down to the nanoscopic regime, where curved boundaries produce surface defects to accommodate topological constraints and restrict the propagation of cuboidal defect networks. Similarly, strict confinement in channels and shells has been shown to give rise to escaped configurations and skyrmions. However, little is known about the role of extrinsic curvature in the development of cholesteric textures and Blue Phases (BP). In this paper, we examine the palette of morphologies that arises when ChLCs are confined in toroidal and cylindrical cavities. The equilibrium morphologies are obtained following an annealing strategy of a Landau-de Gennes free energy functional. Three dimensionless groups are identified to build phase diagrams: the natural twist, the ratio of elastic energies, and the circumscription of a BP cell. Curvature is shown to introduce helical features that are first observed as a Double Twist, and progress to Chiral Ribbons and, ultimately, Helical BP and BP. Chiral ribbons are examined as useful candidates for driven assembly given their tunability and robustness.

Performance Increases in Pair Skating and Ice Dance at International Championships and Olympic Games.

In pair skating and ice dance, performance seems to have increased at international competitions, which is potentially associated with changes in athlete age. We hypothesized increasing age, numbers of total points and more complex jumps of the best elite couples at international championships in recent years. Corresponding data were assessed via the results databases of the European and World Championships, as well as the Winter Olympics since 2005. Linear regression statistics were conducted, and significance was assessed via one-way ANOVAs. There were no significant changes in age. Increases in total points were found in both disciplines (World and European Championships both p < 0.001 for both disciplines, Olympics pair skating p = 0.003, ice dance n/a). Significant increases were found in the number of double and triple twist jumps at the European Championships (Double p = 0.046, triple p = 0.041), but not at the World Championships or the Olympics. At the World Championships, single solo jumps decreased (p = 0.031) in favor of triple jumps, which increased (p = 0.020), without a similar effect at the European Championships or Olympics. In conclusion, increases in total points and more complex jumps were observed at international championships without associated changes in age. Attention should be given to possible changes in the incidence of acute and overuse injuries following this development.

Cholesteric Shells: Two-Dimensional Blue Fog and Finite Quasicrystals.

We study the phase behavior of a quasi-two-dimensional cholesteric liquid crystal shell. We characterize the topological phases arising close to the isotropic-cholesteric transition and show that they differ in a fundamental way from those observed on a flat geometry. For spherical shells, we discover two types of quasi-two-dimensional topological phases: finite quasicrystals and amorphous structures, both made up of mixtures of polygonal tessellations of half-skyrmions. These structures generically emerge instead of regular double twist lattices because of geometric frustration, which disallows a regular hexagonal tiling of curved space. For toroidal shells, the variations in the local curvature of the surface stabilizes heterogeneous phases where cholesteric patterns coexist with hexagonal lattices of half-skyrmions. Quasicrystals and amorphous and heterogeneous structures could be sought experimentally by self-assembling cholesteric shells on the surface of emulsion droplets.

The Ontological Turn in Anthropology and Technological Change in the Indigenous Collective

For the conceptions of animism developed in the contemporary anthropology technological changes taking place in the indigenous collectives that consist of both human and non-human essences seem to be a blind spot. Anthropologists don’t notice any consequences of their visits and are tending to idealize the societies they study as “cold societies” (Claude Lévi-Strauss). If the technologies are entering the indigenous worlds they are easily absorbed by the traditional cosmologies. This article analyzes some of the theoretical models of the ontological turn in anthropology in order to understand its capacity to explain an indigenous collective in which the irreversible technological changes are taking place. By taking as a starting point a discussion between Philippe Descola and Eduardo Viveiros de Castro are defined the personalist conceptions of animism in which the communication with non humans beings and essences are built around a basic ontological premise about the existence of person and identity. In this kind of personalist models the collectives are considered as hermetic worlds in which the technologies cannot penetrate and even if they did, they left unnoticed (neither by indigenes nor by anthropologists). This anthropological blindness cannot be eliminated neither by application Descola’s concept of multiplicity of tabulations, nor by Viveiros de Castro’s principle of double twist. The attempt to correct the supposed rigidity of these theoretical models was made by Morten Axel Pedersen and Eduardo Kohn. Although, despite the assumption of existence of unstable identities and variable ontological status of beings and essences they don’t reject the ontological personalism. The conceptual solution is supposed to be found in the relationalist ontologies of Nurit Bird-David and Elizabeth Povinelli that accentuate the changing relations between actors instead of the concept of person. Those flexible and situational variations can abolish the principle person and identity by changing the relations with the non-human beings. In this sense, they could be more sensible to the (post) colonial technological changes in the indigenous collectives.