Ferromagnetic nanoparticles suspensions in twisted nematic
Cîrtoaje, Cristina; Petrescu, Emil; Stan, Cristina; Creangă, Dorina
2016-05-01
Ferromagnetic nanoparticles insertions in nematic liquid crystals (NLC) in twisted configuration are studied and a theoretical model is proposed to explain the results. Experimental observation revealed that nanoparticles tend to overcrowd in long strings parallel to the rubbing direction of the alignment substrate of the LC cell. Their behavior under external field was studied and their interaction with their nematic host is described using elastic continuum theory.
Charge retention of twisted nematic liquid-crystal displays
Yang, K. H.
1990-01-01
A simulated thin-film transistor (TFT) circuit has been built to drive the twisted nematic (TN) cell for the measurements of charge retention and the transmission versus peak voltage applied to the drain electrode of the simulated TFT using the gate pulse width as a parameter. The established rule that the transmission of the TN cell depends only on the rms voltage applied to the cell has been confirmed by calculating the rms voltage of the charge retention curves in correlation with the measured transmissions. The deviation of the decaying charge retention curves from the exponential behavior has been observed and can be qualitatively explained by a combination of the dielectric and transport properties of nematic liquid-crystal medium.
Institute of Scientific and Technical Information of China (English)
LI Baozhong; HE Tianbai; DING Mengxian
1997-01-01
The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin films were used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratios and enlarge viewing angles' was explained in this paper. A certain polyimide thin film was taken as an example to show compensation effect on NW-TN-LCD.
Report on twisted nematic and supertwisted nematic device characterization program
1995-01-01
In this study we measured the optical characteristics of normally white twisted nematic (NWTN) and super twisted nematic (STN ) cells. Though no dynamic computer model was available, the static observations were compared with computer simulated behavior. The measurements were taken as a function of both viewing angle and applied voltage and included in the static case not only luminance but also contrast ratio and chromaticity . We employed the computer model Twist Cell Optics, developed at Kent State in conjunction with this study, and whose optical modeling foundation, Iike the ViDEOS program, is the 4 x 4 matrix method of Berreman. In order to resolve discrepancies between the experimental and modeled data the optical parameters of the individual cell components, where not known, were determined using refractometry, profilometry, and various forms of ellipsometry. The resulting agreement between experiment and model is quite good due primarily to a better understanding of the structure and optics of dichroic sheet polarizers. A description of the model and test cells employed are given in section 2. Section 3 contains the experimental data gathered and section 4 gives examples of the fit between model and experiment. Also included with this report are a pair of papers which resulted from the research and which detail the polarizer properties and some of the cell characterization methods.
Driving Method by Digital Signal for Twisted Nematic Liquid Crystal Display%TN-LCD的数字信号驱动方法
Institute of Scientific and Technical Information of China (English)
包旭鹤; 曾晓洋
2008-01-01
提出了用数字信号取代多电平信号驱动TN-LCD的方法,利用数字信号相位差和占空比的不同,实现行(COMMON)和列(SEGMENT)信号电压差均方根值差异而达到显示图形的效果.文中首先构造了数字单行扫描模式,但其对显示对比度影响较大;进而借鉴了多路寻址液晶驱动的原理,构造出数字两行扫描模式改善了显示对比度;最后得到的数字两行扫描模式的TN-LCD驱动方法具有元静态功耗、驱动能力强、成本低、实现灵活等优点.低于16行LCD应用条件下其显示对比度已接近传统方法.通过FPGA和流片试验,结果证明此方法是可实现的.实际观察到的显示对比度和静态工作电流已达到预期目标.
Nematic twist cell: Strong chirality induced at the surfaces
Lin, Tzu-Chieh; Nemitz, Ian R.; Pendery, Joel S.; Schubert, Christopher P. J.; Lemieux, Robert P.; Rosenblatt, Charles
2013-04-01
A nematic twist cell having a thickness gradient was filled with a mixture containing a configurationally achiral liquid crystal (LC) and chiral dopant. A chiral-based linear electrooptic effect was observed on application of an ac electric field. This "electroclinic effect" varied monotonically with d, changing sign at d =d0 where the chiral dopant exactly compensated the imposed twist. The results indicate that a significant chiral electrooptic effect always exists near the surfaces of a twist cell containing molecules that can be conformationally deracemized. Additionally, this approach can be used to measure the helical twisting power (HTP) of a chiral dopant in a liquid crystal.
The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle
Mandle, Richard J.; Archbold, Craig T.; Sarju, Julia P.; Andrews, Jessica L.; Goodby, John W.
2016-11-01
We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D 1H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models.
Timofeev, Ivan V; Gunyakov, Vladimir A; Myslivets, Sergey A; Arkhipkin, Vasily G; Vetrov, Stepan Ya; Lee, Wei; Zyryanov, Victor Ya
2011-01-01
Defect modes are investigated in a band gap of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal (1D PC/TN). Their frequency shift and interference under applied voltage are studied both experimentally and theoretically. We deal with the case where the defect layer thickness is much larger than the wavelength (Mauguin condition). It is shown theoretically that the defect modes could have a complex structure with the elliptic polarization. Two series of polarized modes interact with each other and exhibit an avoided crossing phenomenon in the case of opposite parity.
Ma, Baiheng; Peng, Fei; Kang, Mingwu; Zhou, Jiawu
2014-11-01
Twisted-nematic liquid crystal displays (TN-LCD) are widely used in numerous research fields of optics working as spatial light modulators. Approaches to obtaining desired intensity or phase modulation by TN-LCD have been extensively studied based on the knowledge of TN-LCD's internal structure parameters, e.g., the orientation of LC molecules at the surfaces, the twist angle, the thickness of the LC layer, and the birefringence of the material. Generally TN-LCD placed between two linear polarizers (P) produces coupled intensity and phase modulation. To obtain the commonly used pure phase modulation, quarter wave plates (QWP) are often used in front of and/or behind the LCD. In this paper, we present a method to optimize the optical modulation properties of the TN-LCD to obtain pure phase modulation in the configuration of P-QWP-LCD-QWP-P each with proper orientation. Firstly an improved method for determining the Jones matrix of the TN-LCD without knowing its internal parameters is presented, which is based on the macroscopical Jones matrix descriptions for TN-LCD, linear polarizer and QWP. Only three sets of intensity measurements are needed for the complete determination of the TN-LCD's Jones matrix for a single wavelength. Then Jones matrix calculations are carried out to determine the orientations of the polarizers and QWPs for pure phase modulation response. In addition, we prove that the phase modulation depth (PMD) of the TN-LCD can be further increased provided that the mean intensity transmission is decreased to a lower level, which is very useful when the TN-LCD is used as a phase modulator and the ratio between the intensities of the desired diffracted order relative to the other diffracted orders is required higher. Experimental results coincide well with the optical modulation properties of the TN-LCD predicted by our determined Jones matrix. In contrast to the traditional method which requires knowledge of the TN-LCD's internal structure parameters
ON THE SATURATION BEHAVIOUR OF TWISTED NEMATIC LIQUID CRYSTAL CELLS WITH A NONZERO PRETILT ANGLE
Institute of Scientific and Technical Information of China (English)
ZHANG ZHI-DONG; YU HUI; LI LI
2001-01-01
Equations are obtained for the surface tilt angle and the twist angle of the director in a twisted nematic liquid crystal cell under a high magnetic field. Under a zero pretilt angle, the two equations reduce to those obtained by Sugimura et al.[2,3] This fact has also been demonstrated numerically. With finite field strength and nonzero pretilt angle, no saturation transition exists.
Robles-Hernández, Beatriz; Sebastián, Nerea; de la Fuente, M. Rosario; López, David O.; Diez-Berart, Sergio; Salud, Josep; Ros, M. Blanca; Dunmur, David A.; Luckhurst, Geoffrey R.; Timimi, Bakir A.
2015-12-01
The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and 2H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and 2H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. 2H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.
Breatherlike defects and their dynamics in the one-dimensional roll structure of twisted nematics
Energy Technology Data Exchange (ETDEWEB)
Skaldin, O. A.; Delev, V. A., E-mail: delev@anrb.ru; Shikhovtseva, E. S.; Lebedev, Yu. A.; Batyrshin, E. S. [Russian Academy of Sciences, Institute of Molecular and Crystal Physics, Ufa Research Center (Russian Federation)
2015-12-15
The dynamics of the nonsingular defects in the periodic structures of the rolls that appear in π/2-twisted nematic liquid crystals during electroconvection is studied experimentally and theoretically. The roll structures in twisted nematics are characterized by the presence of an axial component of the hydrodynamic flow velocity with opposite directions in neighboring rolls. The critical oscillation frequency of structural defects is quantitatively estimated using a nonlinear equation of motion for roll displacements. It is found that a pair of edge dislocations with topological charges of +1 and–1 nucleates and annihilates periodically during the oscillations of a defect with a nonsingular core. Oscillating defects with a zero topological charge is shown to correspond to the solution of the sine-Gordon equation in the form of standing breathers. Asymmetry is detected in the full oscillation cycle of a breather defect, and it is related to the twist symmetry of a twist nematic. This asymmetry is taken into account as effective anisotropic friction. The behavior of a breather on a trap, namely, a classical defect (dislocation), is investigated. Dislocation motion is shown to be anisotropic in the oscillation cycle: in one direction, a dislocation moves regularly; in the second phase, the transition into the initial state proceeds via the decay of the breather into a dipole pair of dislocations of opposite signs followed by their annihilation.
A Simple Method to Measure the Twist Elastic Constant of a Nematic Liquid Crystal
2015-01-01
as 180° super- twisted nematic (STN) cell. Next, we assume the helical twisting power ( HTP ) of chiral dopant is also unknown, same as K22. To solve...threshold voltages of these two 180° STN cells, both K22 and HTP can be obtained simultaneously. In the whole process, there is no need to measure...Equation (1), if we sub- stitute ϕ = π and pitch length P = 1/( HTP · c) (where c is chiral concentration), then the critical voltage can be rewritten
Liu, Yang; Lim, Young Jin; Kundu, Sudarshan; Lee, Seung Hee; Lee, Gi-Dong
2015-03-01
The application of a single-wall carbon-nanotube (SWCNT) and polyimide (PI) composite thin film on an indium tin-oxide (ITO) glass substrate, working as the command surface in a twisted nematic liquid crystal display (LCD), is described. SWCNTs were chopped and oxidized in a strong acid medium to make them more miscible in a polyimide solution. A film of this newly-developed PISWCNT composite was rubbed to determine the director direction for the LC molecules. The newlyfabricated command surface was examined using a laser beam profiler and atomic force microscopy. Sizes of shortened SWCNTs were characterized by using field-emission scanning electron microscopy (FE-SEM). Finally, small-sized test panels were fabricated from this composite-coated ITO glass, and their electro-optic performances were measured. Although the operating voltage to switch a cell was increased by around 41%, the switching speed was improved remarkably. The rise time of the test cells was found to be improved by around 10.12% and the decay time by around 29.77%. Thus, an overall improvement of around 16.12% in the total switching time was achieved. The change in the surface morphology of the newly-developed composite materials was found to be one of the factors responsible for the faster switching of the device. Detailed discussions are given in this report to explain the faster switching of the newly-developed twisted nematic liquid crystal display (TN-LCD). The device can be useful for practical applications.
Fang, Angbo
2008-12-08
Parallel to the highly successful Ericksen-Leslie hydrodynamic theory for the bulk behavior of nematic liquid crystals (NLCs), we derive a set of coupled hydrodynamic boundary conditions to describe the NLC dynamics near NLC-solid interfaces. In our boundary conditions, translational flux (flow slippage) and rotational flux (surface director relaxation) are coupled according to the Onsager variational principle of least energy dissipation. The application of our boundary conditions to the truly bistable π -twist NLC cell reveals a complete picture of the dynamic switching processes. It is found that the thus far overlooked translation-rotation dissipative coupling at solid surfaces can accelerate surface director relaxation and enhance the flow rate. This can be utilized to improve the performance of electro-optical nematic devices by lowering the required switching voltages and reducing the switching times. © 2008 The American Physical Society.
Institute of Scientific and Technical Information of China (English)
Hai Quan Zhang; An Lei Qin
2012-01-01
In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and 1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host (SLC- 1717).The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants.Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.
Novel cell parameter determination of a twisted-nematic liquid crystal display
Institute of Scientific and Technical Information of China (English)
Huang Xia; Jing Hai; Fu Guo-Zhu
2008-01-01
In this paper a novel method is proposed to determine the cell parameters including the twist angle, optic retardation and rubbing direction of twisted-nematic liquid crystal displays (TNLCD) by rotating the TNLCD. It is a single-wavelength method. Because using subtraction equation of transmittance as curve fitting equation, the influence of the light from environment and the absorption by polarizer, the sample of TNLCD and analyser on the transmittance is eliminated. Accurate results can also be obtained in imperfect darkness. By large numbers of experiments, we found that not only the experimental setup is quite simple and can be easily adopted to be carried out, but also the results are accurate.
Honma, Michinori; Takahashi, Koki; Yamaguchi, Rumiko; Nose, Toshiaki
2016-04-01
We investigated the micropattern-sensitive driving voltage properties of twisted nematic liquid crystal (LC) cells and found that the threshold voltage for inducing the Fréedericksz transition strongly depends on the micropatterned LC molecular orientation state. We discuss the effects of various cell parameters such as the period of the micropattern Λ, the LC layer thickness d, and the twist angle Φ on the threshold voltage. By a computer simulation of the LC molecular orientation, we found that the threshold voltage V th varies in response to the deformation factor Δ (= d 2/Λ2 + Φ2/π2) of the spatially distributed LC molecular orientation. We confirm that V\\text{th}2 is proportional to 1 - Δ from both theoretical and experimental standpoints.
Song, Dong Han; Kim, Ki-Han; Kim, Jung-Wook; Kim, Jae Chang; Yoon, Tae-Hoon
2011-06-01
We propose a twisted nematic liquid crystal device that can be operated in dynamic or memory mode, based on the information content to be displayed at that time. +90°-twisted and -90°-twisted states are used as two stable states for operation in the memory mode. A vertical electric field is applied to realize gray levels for operation in the dynamic mode. The proposed device has a memory retention time of over a month for the memory mode and a response time of 12 ms for the dynamic mode. Contrast ratios of over 500∶1 can be obtained in both the dynamic and memory modes.
Nematic Cells for Digital Light Deflection
Pishnyak, Oleg; Golovin, Andrii; Laventovich, Oleg; Kreminska, Liubov; Winker, Bruce; Pouch, John; Miranda, Felix
2008-01-01
Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction.
Rauzan, Brittany; Lee, Lay Min; Nuzzo, Ralph
2015-03-01
Vibrational spectroscopic studies of a surface induced, twisted alignment of the nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB) and its temperature-dependent electro-optical (EO) dynamics were studied near the crystalline-nematic and nematic-isotropic transition temperatures, and at a median temperature in the nematic phase. A 50 nm thick film of 5CB was confined in nanocavities defined by the dimensions of a gold interdigitated electrode array patterned on a unidirectionally polished ZnSe substrate. The film was assembled between two polished substrates bearing extended nanometer-scaled grooves that are oriented orthogonally to one another. The results show that with this anchoring scheme, the molecular director of the LC film undergoes a ninety-degree twist. Step-scan time resolved spectroscopy (TRS) measurements were made to determine the rate constants for the temperature-dependent EO dynamics of both the electric field-induced orientation and thermal relaxation processes of the LC film. The work rationalizes the impacts of organizational anisotropy and illustrates how it can be exploited as a design principle to effectively influence the electric field-induced dynamics of LC systems.
Tanaka, Shingo; Dhara, Surajit; Sadashiva, B K; Shimbo, Yoshio; Takanishi, Yoichi; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo
2008-04-01
We report an unusual electroconvection in the nematic phase of a bent-core liquid crystal. In a voltage-frequency diagram, two frequency regions exhibiting prewavy stripe patterns were found, as reported by Wiant We found that these stripes never show extinction dark when cells were rotated under crossed polarizers. Based on the color interchange in between neighboring stripes by the rotation of the cells or an analyzer, twisted molecular orientation is suggested; i.e., the directors are alternately twisted from the top to the bottom surfaces with a pretilt angle in adjacent stripes, which is an analogue of the twisted (splayed) structure observed in surface-stabilized ferroelectric liquid crystal cells. The transmittance spectra calculated using the 4x4 matrix method from the model structure are consistent with the experimental observation.
Cofré, Aaron; García-Martínez, Pascuala; Vargas, Asticio; Moreno, Ignacio
2017-01-01
In this work we propose the use of twisted-nematic liquid-crystal spatial light modulators (TN-LC-SLM) as a useful tool for training students in the manipulation of light beams with phase-only masks. In particular, we focus the work on the realization of phase-only gratings and phase-only spiral phases for the generation of vortex beams, beams carrying orbital angular momentum (OAM). Despite the extensive activity in this field, its experimental implementation for educational purposes is limited because it requires the use of very expensive high-resolution liquid-crystal on silicon (LCOS) SLMs. Here, we show that a low-cost experimental implementation can be done with older TNLC technology. However, these devices, intended for display applications, exhibit rather limited optical phase modulation properties in comparison with modern LCOS devices, such as a very low range of phase modulation and a general coupled intensity modulation. However, we show that a precise characterization of their retardance parameters permits their operation in useful modulation configurations. As examples, we include one continuous phase-only configuration useful for reproducing the optimal triplicator phase grating, and a binary π-phase modulation. We include experiments with the realization of different phase diffraction gratings, and their combination with spiral phase patterns and lens functions to generate a variety of vortex beams.
Parsouzi, Z; Welch, C; Ahmed, Z; Mehl, G H; Baldwin, A R; Gleeson, J T; Lavrentovich, O D; Allender, D W; Selinger, J V; Jakli, A; Sprunt, S
2016-01-01
The nematic twist-bend (TB) phase, exhibited by certain achiral thermotropic liquid crystalline (LC) dimers, features a nanometer-scale, heliconical rotation of the average molecular long axis (director) with equally probable left- and right-handed domains. On meso to macroscopic scales, the TB phase may be considered as a stack of equivalent slabs or "pseudo-layers", each one helical pitch in thickness. The long wavelength fluctuation modes should then be analogous to those of a smectic-A phase, and in particular the hydrodynamic mode combining "layer" compression and bending ought to be characterized by an effective layer compression elastic constant $B_{eff}$ and average director splay constant $K_1^{eff}$. The magnitude of $K_1^{eff}$ is expected to be similar to the splay constant of an ordinary nematic LC, but due to the absence of a true mass density wave, $B_{eff}$ could differ substantially from the typical value of $\\sim 10^6$ Pa in a conventional smectic-A. Here we report the results of a dynamic l...
de Coss Martinez, Romeo; Gonzalez Murguia, Jose Luis
2011-03-01
In this work we study the response of a Twisted Nematic Liquid Crystal Display (TN-LCD) by varying both the concentration and the polymer used for the microgroove. We compare the performance of two polymers: polyvinyl alcohol and soy lecithin. In particular, the light transmission for the ON/OFF states is evaluated. The polyvinyl alcohol is a polymer widely used in LCDs while lecithin soy is a natural polymer.
Microwave modulation characteristics of twisted liquid crystals with chiral dopant
Directory of Open Access Journals (Sweden)
Rui Yuan
2017-01-01
Full Text Available Adding a chiral dopant in twisted nematic (TN liquid crystal cell can stabilize the orientation of liquid crystal molecules, particularly in high TN (HTN or super TN (STN liquid crystal cells. The difference in pitches in liquid crystal is induced by the chiral dopant, and these different pitches affect the orientation of liquid crystal director under an external applied voltage and influence the characteristics of microwave modulation. To illustrate this point, the microwave phase shift per unit length (MPSL versus voltage is calculated on the basis of the elastic theory of liquid crystal and the finite-difference iterative method. Enhancing the pitch induced by the chiral dopant in liquid crystal increases the MPSLs, but the stability of the twisted structures is decreased. Thus, appropriate pitches of 100d, 4d, and 2d can be applied in TN, HTN, and STN cells with cell gap d to enhance the characteristics of microwave modulation and stabilize the structures in twisted cell. This method can improve the characteristics of liquid crystal microwave modulators such that the operating voltage and the size of such phase shifters can be decreased.
Design of a Super Twisted Nematic LCD Driver%一种STN LCD驱动芯片的设计研究
Institute of Scientific and Technical Information of China (English)
杨廉峰; 常昌远; 应征; 夏君; 周震; 吴金; 魏同立
2001-01-01
A super tw isted nematic （ STN） LCD driver is described in thepaper. The key modules including interface circuit， control circuit， driver circuit and power supply circuit are discuss ed in detail. And the Verilog Hardware Description Language （VHDL） is used t o verify the function of this LCD driver.%介绍了一种超扭曲向列（STN）LCD驱动芯片的总体设计方案，重点讨论分析了其关键模块——接口电路、控制电路和驱动电路以及电源电路的设计，并用Verilog硬件描述语言对所设计的驱动芯片的功能进行了仿真验证。
Zanchetta, Giuliano; Giavazzi, Fabio; Nakata, Michi; Buscaglia, Marco; Cerbino, Roberto; Clark, Noel A; Bellini, Tommaso
2010-10-12
Concentrated solutions of duplex-forming DNA oligomers organize into various mesophases among which is the nematic (N(∗)), which exhibits a macroscopic chiral helical precession of molecular orientation because of the chirality of the DNA molecule. Using a quantitative analysis of the transmission spectra in polarized optical microscopy, we have determined the handedness and pitch of this chiral nematic helix for a large number of sequences ranging from 8 to 20 bases. The B-DNA molecule exhibits a right-handed molecular double-helix structure that, for long molecules, always yields N(∗) phases with left-handed pitch in the μm range. We report here that ultrashort oligomeric duplexes show an extremely diverse behavior, with both left- and right-handed N(∗) helices and pitches ranging from macroscopic down to 0.3 μm. The behavior depends on the length and the sequence of the oligomers, and on the nature of the end-to-end interactions between helices. In particular, the N(∗) handedness strongly correlates with the oligomer length and concentration. Right-handed phases are found only for oligomers shorter than 14 base pairs, and for the sequences having the transition to the N(∗) phase at concentration larger than 620 mg/mL. Our findings indicate that in short DNA, the intermolecular double-helical interactions switch the preferred liquid crystal handedness when the columns of stacked duplexes are forced at high concentrations to separations comparable to the DNA double-helix pitch, a regime still to be theoretically described.
Piecek, W.; Jaroszewicz, L. R.; Miszczyk, E.; Raszewski, Z.; Mrukiewicz, M.; Perkowski, P.; Nowinowski-Kruszelnicki, E.; Zieliński, J.; Olifierczuk, M.; Kędzierski, J.; Sun, X. W.; Garbat, K.; Kowiorski, K.; Morawiak, P.; Mazur, R.; Tkaczyk, J.
2016-12-01
There exists a need in a quality and accuracy of a three-dimensional laser metrology operating in numerically controlled automatic machines. For this purpose, one sends three laser beams mutually perpendicular. These three beams of the wavelength λ = 0.6328 μm are generated by the same laser and are directed along three independent, orthogonal, mutually perpendicular, optical paths with a given light polarization plain. Using these beams, constituting the frame of coordinates, three independent laser rangefinders are able to determine spatial coordinates of a working tool or a workpiece. To form these optical pulses, a special refractive index matched Half-Wave Plate with nematic Liquid Crystal (LCHWP) was applied. The presented half-wave plate is based on a single Twisted Nematic (TN) cell (with the twist angle Φ = π/2) of a rather high cell gap d 15 μm filled with a newly developed High-Birefringence Nematic Liquid Crystal Mixture (HBLCM) of optical anisotropy as high as Δn 0.40 at λ = 0.6328 μm, where the Mauguin limit above 5.00 Δnd >> λ/2 = 0.32 is fulfilled.
CSIR Research Space (South Africa)
Forbes, A
2010-12-01
Full Text Available Research at the Mathematical Optics Group uses "twisted" light to study new quatum-based information security systems. In order to understand the structure of "twisted" light, it is useful to start with an ordinary light beam with zero twist, namely...
Static and dynamic properties of magnetic nanowires in nematic fluids (invited)
Lapointe, C.; Cappallo, N.; Reich, D. H.; Leheny, R. L.
2005-05-01
Microscopy experiments are employed to characterize the elastic interactions of magnetic nickel nanowires suspended in a nematic liquid crystal. The nematic imposes a torque on an isolated wire that increases linearly with the angle between the wire and the nematic director in a manner quantitatively consistent with predictions based on an analogy between the nematic elasticity and electrostatics. An extension of this analogy also explains a measured orientation-dependent repulsive force between a wire and a wall. The angular relaxation of a wire in response to the elastic torque displays a nonexponential time dependence from which effective viscosities for the fluid are determined. The behavior of a wire in a twisted nematic cell further demonstrates how spatial variations in the director can convert the torque to a controlled translational force that levitates a wire to a specified height.
Switching Shape of Nematic Elastomers
Urayama, Kenji
2012-02-01
Nematic elastomers (NEs) are a novel class of materials. NEs possess both the elastic properties of rubbers and the orientational properties of liquid crystals. The combination of these two properties makes the shape of NEs very sensitive to external stimuli. We focus on the thermally induced deformation of the NE films inherently possessing the two types of inhomogeneous director alignments, i.e., hybrid and twist alignments. In the NEs with hybrid alignments (HNEs), the director continuously changes by 90 degree from planar alignment to vertical alignment between the top and bottom surfaces. In the twist NEs, the director parallel to the surfaces smoothly rotates by 90 degree around the thickness axis, and the director at the mid-plane is parallel to the long or short axis of the film. In the HNEs and TNEs, the director change along the normal of the films causes the planes at different depth to respond differently to temperature variation, and the films are thus expected to change shape. We experimentally demonstrate that (i) depending on the width/thickness ratio, the TNE ribbons form the spiral ribbons or helicoids whose spiral or helical pitch markedly depends on temperature [1], and (ii) the HNE ribbons exhibit giant bending in response to temperature variation [2]. We theoretically interpret these experimental observations on the basis of the elastic models with the data of thermally induced uniaxial deformation of the corresponding NEs with globally planar alignment.[4pt] [1] Sawa, Ye, Urayama, Takigawa, Gimenez-Pinto, Selinger, R., Selinger, J., Proc. Natl. Acad. Sci., USA, 108, 6364 (2011).[0pt] [2] Sawa, Urayama, Takigawa, DeSimone, Teresi, Macromolecules, 43, 4362 (2010).
Modulated nematic structures induced by chirality and steric polarization
Longa, Lech; PajÄ k, Grzegorz
2016-04-01
What kind of one-dimensional modulated nematic structures (ODMNS) can form nonchiral and chiral bent-core and dimeric materials? Here, using the Landau-de Gennes theory of nematics, extended to account for molecular steric polarization, we study a possibility of formation of ODMNS, both in nonchiral and intrinsically chiral liquid crystalline materials. Besides nematic and cholesteric phases, we find four bulk ODMNS for nonchiral materials, two of which, to the best of our knowledge, have not been reported so far. These two structures are longitudinal (NLP) and transverse (NTP) periodic waves where the polarization field being periodic in one dimension stays parallel and perpendicular, respectively, to the wave vector. The other two phases are the twist-bend nematic phase (NTB) and the splay-bend nematic phase (NSB), but their fine structure appears more complex than that considered so far. The presence of molecular chirality converts nonchiral NTP and NSB into new NTB phases. Surprisingly, the nonchiral NLP phase can stay stable even in the presence of intrinsic chirality.
Dullin, Holger R
2015-01-01
A complete description of twisting somersaults is given using a reduction to a time-dependent Euler equation for non-rigid body dynamics. The central idea is that after reduction the twisting motion is apparent in a body frame, while the somersaulting (rotation about the fixed angular momentum vector in space) is recovered by a combination of dynamic and geometric phase. In the simplest "kick-model" the number of somersaults $m$ and the number of twists $n$ are obtained through a rational rotation number $W = m/n$ of a (rigid) Euler top. This rotation number is obtained by a slight modification of Montgomery's formula [9] for how much the rigid body has rotated. Using the full model with shape changes that take a realistic time we then derive the master twisting-somersault formula: An exact formula that relates the airborne time of the diver, the time spent in various stages of the dive, the numbers $m$ and $n$, the energy in the stages, and the angular momentum by extending a geometric phase formula due to C...
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and
Dickens, Charles
2005-01-01
Oliver Twist is one of Dickens's most popular novels, with many famous film, television and musical adaptations. It is a classic story of good against evil, packed with humour and pathos, drama and suspense, in which the orphaned Oliver is brought up in a harsh workhouse, and then taken in and explo
Nematic liquid crystals on sinusoidal channels: the zigzag instability
Silvestre, Nuno M.; Romero-Enrique, Jose M.; Telo da Gama, Margarida M.
2017-01-01
Substrates which are chemically or topographically patterned induce a variety of liquid crystal textures. The response of the liquid crystal to competing surface orientations, typical of patterned substrates, is determined by the anisotropy of the elastic constants and the interplay of the relevant lengths scales, such as the correlation length and the surface geometrical parameters. Transitions between different textures, usually with different symmetries, may occur under a wide range of conditions. We use the Landau-de Gennes free energy to investigate the texture of nematics in sinusoidal channels with parallel anchoring bounded by nematic-air interfaces that favour perpendicular (hometropic) anchoring. In micron size channels 5CB was observed to exhibit a non-trivial texture characterized by a disclination line, within the channel, which is broken into a zigzag pattern. Our calculations reveal that when the elastic anisotropy of the nematic does not favour twist distortions the defect is a straight disclination line that runs along the channel, which breaks into a zigzag pattern with a characteristic period, when the twist elastic constant becomes sufficiently small when compared to the splay and bend constants. The transition occurs through a twist instability that drives the defect line to rotate from its original position. The interplay between the energetically favourable twist distortions that induce the defect rotation and the liquid crystal anchoring at the surfaces leads to the zigzag pattern. We investigate in detail the dependence of the periodicity of the zigzag pattern on the geometrical parameters of the sinusoidal channels, which in line with the experimental results is found to be non-linear.
Institute of Scientific and Technical Information of China (English)
TU; Mei; HUANG; Yaoxiong
2004-01-01
The laser light scattering technique for non-invasive in situ simultaneous measurements on elastic constants and viscosity coefficients of nematic liquid crystals is introduced. By measuring the autocorrelation function of the scattered light from nematic liquid crystals at different scattering angles, the splay and twist elastic constants K11 and K22 are obtained from the amplitudes of the autocorrelation function, and the viscosity coefficients of (Splay and (Twist are determined using the viscoelastic ratios K11/( Splay and K22/(Twist from the relaxation parameters of the two modes.
Hermann, Keith; Pratumyot, Yaowalak; Polen, Shane; Hardin, Alex M; Dalkilic, Erdin; Dastan, Arif; Badjić, Jovica D
2015-02-23
A preparative procedure for obtaining a pair of twisted molecular baskets, each comprising a chiral framework with either right ((P)-1syn) or left ((M)-1syn) sense of twist and six ester groups at the rim has been developed and optimized. The racemic (P/M)-1syn can be obtained in three synthetic steps from accessible starting materials. The resolution of (P/M)-1syn is accomplished by its transesterification with (1R,2S,5R)-(-)-menthol in the presence of a Ti(IV) catalyst to give diastereomeric 8(P) and 8(M). It was found that dendritic-like cavitands 8(P) and 8(M), in CD2Cl2, undergo self-inclusion ((1)H NMR spectroscopy) with a menthol moiety occupying the cavity of each host. Importantly, the degree of inclusion of the menthol group was ((1)H NMR spectroscopy) found to be greater in the case of 8(P) than 8(M). Accordingly, it is suggested that different folding characteristic of 8(P) and 8(M) ought to affect the physicochemical characteristics of the hosts to permit their effective separation by column chromatography. The absolute configuration of 8(P)/8(M), encompassing right- and left-handed "cups", was determined with the exciton chirality method and also verified in silico (DFT: B3LYP/TZVP). Finally, the twisted baskets are strongly fluorescent due to three naphthalene chromophores, having a high fluorescence quantum yield within the rigid framework of 8(P)/8(M).
Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.
2017-01-01
Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter. PMID:28117325
Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.
2017-01-01
Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter.
Sensing and tuning microfiber chirality with nematic chirogyral effect
Čopar, Simon; Seč, David; Aguirre, Luis E.; Almeida, Pedro L.; Dazza, Mallory; Ravnik, Miha; Godinho, Maria H.; Pieranski, Pawel; Žumer, Slobodan
2016-03-01
Microfibers with their elongated shape and translation symmetry can act as important components in various soft materials, notably for their mechanics on the microscopic level. Here we demonstrate the mechanical response of a micro-object to imposed chirality, in this case, the tilt of disclination rings in an achiral nematic medium caused by the chiral surface anchoring on an immersed microfiber. This coupling between chirality and mechanical response, used to demonstrate sensing of chirality of electrospun cellulose microfibers, is revealed in the optical micrographs due to anisotropy in the elastic response of the host medium. We provide an analytical explanation of the chirogyral effect supported with numerical simulations and perform an experiment to test the effect of the cell confinement and fiber size. We controllably twist the microfibers and demonstrate the response of the nematic medium. More generally the demonstrated study provides means for experimental discrimination of surface properties and allows mechanical control over the shape of disclination rings.
Institute of Scientific and Technical Information of China (English)
余飞鸿; 王谦; 潘为民; 陈军; 郭海成
2000-01-01
反射式液晶显示器(RLCDs)具有亮度高、无视差等优点,并且结构简单,适合于现行的制造工艺和驱动方式.本文利用我们提出的参数空间法(偏振片角度、扭曲角及双折射率的函数)研究了适用于反射式液晶显示器,这种研究表明所有的反射式液晶显示模式都可以在这个参数空间里得以表述,如扭曲向列型的电控双折射模式(TN-ECB),混合场效应模式(HFE),混合向列型模式(MTN),以及自补偿向列型模式(SCTN).在此基础上我们提出几种新的反射模式,如反射向列型及反射超扭曲向列型(通过搜索参数空间得到),二者均适用于直视型和投影型显示方式.我们已制成反射向列型及反射超扭曲向列型样品,实验结果和理论设计符合一致.%Reflective liquid crystal display (RLCDs) are characterized by high brightnessand free from viewing parallax.It also costs less material to construct and is compatible with existing manufacturing and driving practices.A parameter space for RLCD as a function of polarizer angle,liquid crystal twist angle and birefringence is constructed and discussed in this paper.It is shown that all published RLCD modes can be depicted in this parameter space,including the twisted-nematic-electrically controlled birefringence (TN-ECB) modes,the hybrid field effect (HFE) mode,the mixed-mode TN (MTN),and the self-compensated TN (SCTN) mode.Additionally it is shown several new RLCD modes,including the reflective TN (RTN) and the reflective STN (RSTN) which can be obtained from searching the parameter space systematically.All RLCD modes are related by a variation of the 3 LCD parameters.The RTN and RSTN modes have applications to both directive view and projection display systems.Sample RTN and RSTN displays were fabricated.Experimental results show good agreement with the theoretical design.
Photoswitching of helical twisting power by chiral photochromic diarylethene dopants
Yamaguchi, Tadatsugu; Irie, Masahiro
2002-12-01
Two kinds of chiral diarylethene derivatives were synthesized and used as dopants for photoresponsive liquid crystals. Both derivatives underwent thermally irreversible and fatigue resistant photochromic reactions and exhibited reversible circular diochroism (CD) spectral changes. Large photostimulated pitch chances of chiral nematic K-15 liquid crystals were observed by the addition of the derivatives as dopants. The relation between the optical rotation and the twisting power force was discussed.
Seeing and Sculpting Nematic Liquid Crystal Textures with the Thom construction
Chen, Bryan; Alexander, Gareth
2012-02-01
Nematic liquid crystals are the foundation for modern display technology and also exhibit topological defects that can readily be seen under a microscope. Recently, experimentalists have been able to create and control several new families of interesting defect textures, including reconfigurably knotted defect lines around colloids (Ljubljana) and the ``toron,'' a pair of hedgehogs bound together with a ring of double-twist between them (CU Boulder). We apply the Thom construction from algebraic topology to visualize 3 dimensional molecular orientation fields as certain colored surfaces in the sample. These surfaces turn out to be a generalization to 3 dimensions of the dark brushes seen in Schlieren textures of two-dimensional samples of nematics. Manipulations of these surfaces correspond to deformations of the nematic orientation fields, giving a hands-on way to classify liquid crystal textures which is also easily computable from data and robust to noise.
Salamon, P; Eber, N; Seltmann, J; Lehmann, M; Gleeson, J T; Sprunt, S; Jákli, A
2012-06-01
The effect of director pretilt on the twist magnetic Fréedericksz transition of nematics was investigated in a planar cell. The director configuration was calculated as a function of magnetic inductance. The dielectric and optical response of the nematic liquid crystal was numerically modeled. A dielectric measurement method for determining the elastic constant K_{22} is presented. The influence of the conditions for the Mauguin effect is discussed. The theoretical predictions were confirmed by our experiments. Experimental data for all elastic constants of a bent-core nematic material are presented and discussed.
Institute of Scientific and Technical Information of China (English)
郭玉强; 王翼飞; 刘建龙; 王森; 马红梅; 孙玉宝
2016-01-01
In order to protect the LC and devices with high operating voltage,the thicker thickness of the alignment layer is used.When the thickness of the alignment layer can not be neglected,the in-creasing of the alignment layer’s thickness leads to the increasing of the operating voltage.The influ-ences of the thickness and dielectric constant of the alignment layer on LCD are researched in simula-tion and experiment based on twist nematic liquid crystal display (TN-LCD).The results show that the operating voltage can be reduced effectively when the dielectric constant of the alignment layer is larger than 20,a little effect of the various thickness on the operating voltage can be seen when the di-electric constant is larger than 500.The result has an important significance for reducing the operating voltage of liquid crystal device with high operating voltage.%在具有高驱动电压的液晶显示器中，为了对液晶器件起到保护作用，以采用增加取向层厚度的方法来解决某些显示器件由于驱动电压过高导致的问题。当取向层厚度不可忽略时，随着取向层厚度增加会导致器件驱动电压升高。本文利用扭曲向列相液晶显示器结构，通过模拟和实验分析了取向层厚度对 LCD 的影响以及不同介电常数的取向层对LCD 的影响。结果表明：当取向层的介电常数大于20时，能够有效降低 TN-LCD 驱动电压。当其介电常数大于500时，其厚度变化对驱动电压的影响变得很小。本文结果对降低高驱动电压液晶器件的驱动电压有重要的指导性意义。
McGinn, Christine K.; Laderman, Laura I.; Zimmermann, Natalie; Kitzerow, Heinz-S.; Collings, Peter J.
2013-12-01
Chromonic liquid crystals are formed by molecules that spontaneously assemble into anisotropic structures in water. The ordering unit is therefore a molecular assembly instead of a molecule as in thermotropic liquid crystals. Although it has been known for a long time that certain dyes, drugs, and nucleic acids form chromonic liquid crystals, only recently has enough knowledge been gained on how to control their alignment so that studies of their fundamental liquid crystal properties can be performed. In this article, a simple method for producing planar alignment of the nematic phase in chromonic liquid crystals is described, and this in turn is used to create twisted nematic structures of both achiral and chiral chromonic liquid crystals. The optics of 90-degree twist cells allows the anchoring strength to be measured in achiral systems, which for this alignment technique is quite weak, about 3×10-7 J/m2 for both disodium cromoglycate and Sunset Yellow FCF. The addition of a chiral amino acid to the system causes the chiral nematic phase to form, and similar optical measurements in 90-degree twist cells produce a measurement of the intrinsic pitch of the chiral nematic phase. From these measurements, the helical twisting power for L-alanine is found to be (1.1±0.4)×10-2 μm-1 wt%-1 for 15 wt% disodium cromoglycate.
Generalised twisted partition functions
Petkova, V B
2001-01-01
We consider the set of partition functions that result from the insertion of twist operators compatible with conformal invariance in a given 2D Conformal Field Theory (CFT). A consistency equation, which gives a classification of twists, is written and solved in particular cases. This generalises old results on twisted torus boundary conditions, gives a physical interpretation of Ocneanu's algebraic construction, and might offer a new route to the study of properties of CFT.
Casey, E. J.; Commadore, C. C.; Ingles, M. E.
1980-01-01
Long wire bundles twist into uniform spiral harnesses with help of simple apparatus. Wires pass through spacers and through hand-held tool with hole for each wire. Ends are attached to low speed bench motor. As motor turns, operator moves hand tool away forming smooth twists in wires between motor and tool. Technique produces harnesses that generate less radio-frequency interference than do irregularly twisted cables.
Twisted network programming essentials
Fettig, Abe
2005-01-01
Twisted Network Programming Essentials from O'Reilly is a task-oriented look at this new open source, Python-based technology. The book begins with recommendations for various plug-ins and add-ons to enhance the basic package as installed. It then details Twisted's collection simple network protocols, and helper utilities. The book also includes projects that let you try out the Twisted framework for yourself. For example, you'll find examples of using Twisted to build web services applications using the REST architecture, using XML-RPC, and using SOAP. Written for developers who want to s
Dynamic Soft Elasticity in Monodomain Nematic Elastomers
Hotta, A; Terentjev, E. M.
2002-01-01
We study the linear dynamic mechanical response of monodomain nematic liquid crystalline elastomers under shear in the geometry that allows the director rotation. The aspects of time-temperature superposition are discussed at some length and Master Curves are obtained between the glassy state and the nematic transition temperature Tni. However, the time-temperature superposition did not work through the clearing point Tni, due to change from the ``soft-elasticity'' nematic regime to the ordin...
Active nematic gels as active relaxing solids
Turzi, Stefano S
2017-01-01
I put forward a continuum theory for active nematic gels, defined as fluids or suspensions of orientable rodlike objects endowed with active dynamics, that is based on symmetry arguments and compatibility with thermodynamics. The starting point is our recent theory that models (passive) nematic liquid crystals as relaxing nematic elastomers. The interplay between viscoelastic response and active dynamics of the microscopic constituents is naturally taken into account. By contrast with standar...
Dynamical numerical model for nematic order reconstruction
Lombardo, G.; Ayeb, H.; Barberi, R.
2008-05-01
In highly frustrated calamitic nematic liquid crystals, a strong elastic distortion can be confined on a few nanometers. The classical elastic theory fails to describe such systems and a more complete description based on the tensor order parameter Q is required. A finite element method is used to implement the Q dynamics by a variational principle and it is shown that a uniaxial nematic configuration can evolve passing through transient biaxial states. This solution, which connects two competing uniaxial nematic textures, is known as “nematic order reconstruction.”
Singh, Gautam; Fu, Jinxin; Agra-Kooijman, Dena M.; Song, Jang-Kun; Vengatesan, M. R.; Srinivasarao, Mohan; Fisch, Michael R.; Kumar, Satyendra
2016-12-01
The temperature dependence of the orientational order parameters cos β ) > and cos β ) > in the nematic (N ) and twist-bend nematic (Ntb) phases of the liquid crystal dimer CB7CB have been measured using x-ray and polarized Raman scattering. The cos β ) > obtained from both techniques are the same, while cos β ) > , determined by Raman scattering is, as expected, systematically larger than its x-ray value. Both order parameters increase in the N phase with decreasing temperature, drop across the N -Ntb transition, and continue to decrease. In the Ntb phase, the x-ray value of cos β ) > eventually becomes negative, providing a direct and independent confirmation of a conical molecular orientational distribution. The heliconical tilt angle α, determined from orientational distribution functions in the Ntb phase, increases to ˜24∘ at ˜15 K below the transition. In the Ntb phase, α (T ) ∝(T*-T)λ , with λ =0.19 ±0.03 . The transition supercools by 1.7 K, consistent with its weakly first-order nature. The value of λ is close to 0.25 indicating close proximity to a tricritical point.
Overregularity in Oliver Twist
Institute of Scientific and Technical Information of China (English)
孔祥曼
2015-01-01
Oliver Twist is one of the earliest works of Charles Dickens. In this novel, the author uses many writing skills which impress the readers a lot. This paper gives a brief description of overregularity in Oliver Twist at the phonological and syntactical levels.
Modulational instability of nematic phase
Indian Academy of Sciences (India)
T Mithun; K Porsezian
2014-02-01
We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in = 2 spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic field triggers the modulational instability and demonstrate that irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability.
Brookside Mills, Knox County, TN
Brookside Mills, located in Knox County, TN, was a textile mill that was founded in 1885 and at its peak employed over 1,000 people. Its former uses included fabric weaving, dying, and sewing operations. It was at some point a department store, and during a portion of its history, coal was used as an energy source. Weaving operations continued in some form at the Brookside factory until 1969. In 1996 the buildings were demolished.
Mingoia, Marina; Morici, Eleonora; Tili, Emily; Giovanetti, Eleonora; Montanari, Maria Pia; Varaldo, Pietro E
2013-09-01
Tn5801, originally detected in Staphylococcus aureus Mu50, is a Tn916 family element in which a unique int gene (int5801) replaces the int and xis genes in Tn916 (int916 and xis916). Among 62 tet(M)-positive tetracycline-resistant Streptococcus agalactiae isolates, 43 harbored Tn916, whereas 19 harbored a Tn5801-like element (Tn5801.Sag, ∼20.6 kb). Tn5801.Sag was characterized (PCR mapping, partial sequencing, and chromosomal integration) and compared to other Tn5801-like elements. Similar to Tn5801 from S. aureus Mu50, tested in parallel, Tn5801.Sag was unable to undergo circularization and conjugal transfer.
Freed, Daniel S
2012-01-01
We show how general principles of symmetry in quantum mechanics lead to twisted notions of a group representation. This framework generalizes both the classical 3-fold way of real/complex/quaternionic representations as well as a corresponding 10-fold way which has appeared in condensed matter and nuclear physics. We establish a foundation for discussing continuous families of quantum systems. Having done so, topological phases of quantum systems can be defined as deformation classes of continuous families of gapped Hamiltonians. For free particles there is an additional algebraic structure on the deformation classes leading naturally to notions of twisted equivariant K-theory. In systems with a lattice of translational symmetries we show that there is a canonical twisting of the equivariant K-theory of the Brillouin torus. We give precise mathematical definitions of two invariants of the topological phases which have played an important role in the study of topological insulators. Twisted equivariant K-theor...
Institute of Scientific and Technical Information of China (English)
MATHAI; Varghese
2010-01-01
We review the Reidemeister, Ray-Singer’s analytic torsion and the Cheeger-Mller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsion of invariant forms are inverse to each other for any dimension.
Mathai, Varghese
2009-01-01
We review the Reidemeister and Ray-Singer's analytic torsions and the Cheeger-M"uller theorem. We describe the analytic torsion of the de Rham complex twisted by a flux form introduced by the current authors and recall its properties. We define a new twisted analytic torsion for the complex of invariant differential forms on the total space of a principal circle bundle twisted by an invariant flux form. We show that when the dimension is even, such a torsion is invariant under certain deformation of the metric and the flux form. Under T-duality which exchanges the topology of the bundle and the flux form and the radius of the circular fiber with its inverse, the twisted torsions are inverse to each other for any dimensions.
Elastic properties of the nematic phase in hard ellipsoids of short aspect ratio
Heymans, S.; Schilling, T.
2017-08-01
We present a Monte Carlo simulation study of suspensions of hard ellipsoids of revolution. Based on the spatial fluctuations of the orientational order, we have computed the Frank elastic constants for prolate and oblate ellipsoids and compared them to the affine transformation model. The affine transformation model predicts the right order of magnitude of the twist and bend constant but not of the splay constant. In addition, we report the observation of a stable nematic phase at an aspect ratio as low as 2.5.
Twisted radio waves and twisted thermodynamics.
Kish, Laszlo B; Nevels, Robert D
2013-01-01
We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta 'twisted wave' mode, to the far field in free space is therefore not possible.
Possible surface nematic order in iron pnictides
Song, Kok Wee; Koshelev, Alexei
Nematic fluctuations play important role in the physics of the iron-based superconductors. Indications for weak precursor nematic transition has been found in the compound BaAs2-xPxFe2 [1 ]. However, high-resolution specific-heat measurements did not reveal any bulk transition [2 ]. To resolve this controversy, we consider the possibility of the surface nematic transition preceding the bulk transition. We consider the simplest model of two interacting quasi-two-dimensional electronic bands and explore the free-surface effects on the nematic order. We found that three-dimensional effects suppress the bulk nematic order and therefore this order is enhanced near the surface. [1 ]Kasahara, S., et al. ''Electronic nematicity above the structural and superconducting transition in Ba(As1-xPxFe)2.'' Nature 486.7403 (2012): 382-385. [2 ]Luo, X., et al. ''Antiferromagnetic and nematic phase transitions in Ba(As1-xPxFe)2 studied by ac microcalorimetry and SQUID magnetometry.'' Physical Review B 91.9 (2015): 094512. This work was supported by the Center for Emergent Superconductivity, an Energy FrontierResearch Center funded by the US DOE, Office of Science, under Award No. DEAC0298CH1088.
Dispersive shock waves in nematic liquid crystals
Smyth, Noel F.
2016-10-01
The propagation of coherent light with an initial step intensity profile in a nematic liquid crystal is studied using modulation theory. The propagation of light in a nematic liquid crystal is governed by a coupled system consisting of a nonlinear Schrödinger equation for the light beam and an elliptic equation for the medium response. In general, the intensity step breaks up into a dispersive shock wave, or undular bore, and an expansion fan. In the experimental parameter regime for which the nematic response is highly nonlocal, this nematic bore is found to differ substantially from the standard defocusing nonlinear Schrödinger equation structure due to the effect of the nonlocality of the nematic medium. It is found that the undular bore is of Korteweg-de Vries equation-type, consisting of bright waves, rather than of nonlinear Schrödinger equation-type, consisting of dark waves. In addition, ahead of this Korteweg-de Vries bore there can be a uniform wavetrain with a short front which brings the solution down to the initial level ahead. It is found that this uniform wavetrain does not exist if the initial jump is below a critical value. Analytical solutions for the various parts of the nematic bore are found, with emphasis on the role of the nonlocality of the nematic medium in shaping this structure. Excellent agreement between full numerical solutions of the governing nematicon equations and these analytical solutions is found.
Electro-osmosis in nematic liquid crystals
Tovkach, O. M.; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg; Walkington, Noel J.
2016-07-01
We derive a mathematical model of a nematic electrolyte based on a variational formulation of nematodynamics. We verify the model by comparing its predictions to the results of the experiments on the substrate-controlled liquid-crystal-enabled electrokinetics. In the experiments, a nematic liquid crystal confined to a thin planar cell with surface-patterned anchoring conditions exhibits electro-osmotic flows along the "guiding rails" imposed by the spatially varying director. Extending our previous work, we consider a general setup which incorporates dielectric anisotropy of the liquid-crystalline matrix and the full set of nematic viscosities.
Tennessee Comptroller of the Treasury (TN COMP)
Social Security Administration — The Tennessee Comptroller of the Treasury (TN COMP) uses SSA's assistance in administering the Tennessee Property Tax Rebate Program. SSA provides assistance through...
Twisted derivations of Hopf algebras
Davydov, Alexei
2012-01-01
In the paper we introduce the notion of twisted derivation of a bialgebra. Twisted derivations appear as infinitesimal symmetries of the category of representations. More precisely they are infinitesimal versions of twisted automorphisms of bialgebras. Twisted derivations naturally form a Lie algebra (the tangent algebra of the group of twisted automorphisms). Moreover this Lie algebra fits into a crossed module (tangent to the crossed module of twisted automorphisms). Here we calculate this crossed module for universal enveloping algebras and for the Sweedler's Hopf algebra.
Spontaneous thermal expansion of nematic elastomers
Tajbakhsh, A. R.; Terentjev, E.M.
2001-01-01
We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from isotropic phase. At higher concentration of main chains their behaviour dominates th...
KEGG DRUG / Acutect (TN) [KEGG DRUG
Lifescience Database Archive (English)
Full Text Available DRUG: D06027 Entry D06027Drug Name Technetium Tc 99m apcitide (USP); Acutect (TN) F... 1 838085 1 848586 1 857781 1 868182 1 878280 1 888687 1 898288 2 908689 2 918390 1 929091 2 939092 1 949495 2 KEGG DRUG / Acutect (TN) ...
DEFF Research Database (Denmark)
Yiu, Man Lung; Jensen, Christian Søndergaard; Xuegang, Huang
2008-01-01
-based matching generally fall short in offering practical query accuracy guarantees. Our proposed framework, called SpaceTwist, rectifies these shortcomings for k nearest neighbor (kNN) queries. Starting with a location different from the user's actual location, nearest neighbors are retrieved incrementally...
Reweighting twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2015-01-01
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, $\\theta$. As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of $\\theta=\\pi/2$ in a volume $16\\times 8^3$, and we observe a syst...
Wang, Zuoqin
2007-01-01
The "twisted Mellin transform" is a slightly modified version of the usual classical Mellin transform on $L^2(\\mathbb R)$. In this short note we investigate some of its basic properties. From the point of views of combinatorics one of its most important interesting properties is that it intertwines the differential operator, $df/dx$, with its finite difference analogue, $\
Reversal of helicoidal twist handedness near point defects of confined chiral liquid crystals
Ackerman, Paul J.; Smalyukh, Ivan I.
2016-05-01
Handedness of the director twist in cholesteric liquid crystals is commonly assumed to be the same throughout the medium, determined solely by the chirality of constituent molecules or chiral additives, albeit distortions of the ground-state helicoidal configuration often arise due to the effects of confinement and external fields. We directly probe the twist directionality of liquid crystal director structures through experimental three-dimensional imaging and numerical minimization of the elastic free energy and show that spatially localized regions of handedness opposite to that of the chiral liquid crystal ground state can arise in the proximity of twisted-soliton-bound topological point defects. In chiral nematic liquid crystal confined to a film that has a thickness less than the cholesteric pitch and perpendicular surface boundary conditions, twisted solitonic structures embedded in a uniform unwound far-field background with chirality-matched handedness locally relieve confinement-imposed frustration and tend to be accompanied by point defects and smaller geometry-required, energetically costly regions of opposite twist handedness. We also describe a spatially localized structure, dubbed a "twistion," in which a twisted solitonic three-dimensional director configuration is accompanied by four point defects. We discuss how our findings may impinge on the stability of localized particlelike director field configurations in chiral and nonchiral liquid crystals.
Yu, Meina; Zhou, Xiaochen; Jiang, Jinghua; Yang, Huai; Yang, Deng-Ke
2016-05-11
Chiral nematic liquid crystals possess a self-assembled helical structure and exhibit unique selective reflection in visible and infrared light regions. Their optical properties can be electrically tuned. The tuning involves the unwinding and restoring of the helical structure. We carried out an experimental study on the mechanism of the restoration of the helical structure. We constructed chiral nematic liquid crystals with variable elastic constants by doping bent-dimers and studied their impact on the restoration. With matched twist and bend elastic constants, the helical structure can be restored dramatically fast from the field-induced homeotropic state. Furthermore, defects can be eliminated to produce a perfect planar state which exhibits high selective reflection.
Colloidal spirals in nematic liquid crystals.
Senyuk, Bohdan; Pandey, Manoj B; Liu, Qingkun; Tasinkevych, Mykola; Smalyukh, Ivan I
2015-12-07
One of the central experimental efforts in nematic colloids research aims to explore how the interplay between the geometry of particles along with the accompanying nematic director deformations and defects around them can provide a means of guiding particle self-assembly and controlling the structure of particle-induced defects. In this work, we design, fabricate, and disperse low-symmetry colloidal particles with shapes of spirals, double spirals, and triple spirals in a nematic fluid. These spiral-shaped particles, which are controlled by varying their surface functionalization to provide tangential or perpendicular boundary conditions of the nematic molecular alignment, are found inducing director distortions and defect configurations with non-chiral or chiral symmetry. Colloidal particles also exhibit both stable and metastable multiple orientational states in the nematic host, with a large number of director configurations featuring both singular and solitonic nonsingular topological defects accompanying them, which can result in unusual forms of colloidal self-assembly. Our findings directly demonstrate how the symmetry of particle-generated director configurations can be further lowered, or not, as compared to the low point group symmetry of solid micro-inclusions, depending on the nature of induced defects while satisfying topological constraints. We show that achiral colloidal particles can cause chiral symmetry breaking of elastic distortions, which is driven by complex three-dimensional winding of induced topological line defects and solitons.
Cui, Xiaoyan; Rohl, Andrew L; Shtukenberg, Alexander; Kahr, Bart
2013-03-06
Banded spherulites of aspirin have been crystallized from the melt in the presence of salicylic acid either generated from aspirin decomposition or added deliberately (2.6-35.9 mol %). Scanning electron microscopy, X-ray diffraction analysis, and optical polarimetry show that the spherulites are composed of helicoidal crystallites twisted along the growth directions. Mueller matrix imaging reveals radial oscillations in not only linear birefringence, but also circular birefringence, whose origin is explained through slight (∼1.3°) but systematic splaying of individual lamellae in the film. Strain associated with the replacement of aspirin molecules by salicylic acid molecules in the crystal structure is computed to be large enough to work as the driving force for the twisting of crystallites.
EnviroAtlas - Memphis, TN - Block Groups
U.S. Environmental Protection Agency — This EnviroAtlas dataset is the base layer for the Memphis, TN EnviroAtlas community. The block groups are from the US Census Bureau and are included/excluded based...
Directory of Open Access Journals (Sweden)
Daijiro Fukuda
2004-01-01
Full Text Available Using diagrammatic pictures of tensor contractions, we consider a Hopf algebra (Aop⊗ℛλA** twisted by an element ℛλ∈A*⊗Aop corresponding to a Hopf algebra morphism λ:A→A. We show that this Hopf algebra is quasitriangular with the universal R-matrix coming from ℛλ when λ2=idA, generalizing the quantum double construction which corresponds to the case λ=idA.
Vranish, John M. (Inventor)
1996-01-01
A planetary gear system includes a sun gear coupled to an annular ring gear through a plurality of twist-planet gears, a speeder gear, and a ground structure having an internal ring gear. Each planet gear includes a solid gear having a first half portion in the form of a spur gear which includes vertical gear teeth and a second half portion in the form of a spur gear which includes helical gear teeth that are offset from the vertical gear teeth and which contact helical gear teeth on the speeder gear and helical gear teeth on the outer ring gear. One half of the twist planet gears are preloaded downward, while the other half are preloaded upwards, each one alternating with the other so that each one twists in a motion opposite to its neighbor when rotated until each planet gear seats against the sun gear, the outer ring gear, the speeder gear, and the inner ring gear. The resulting configuration is an improved stiff anti-backlash gear system.
Janus Nematic Colloids with Designable Valence
Directory of Open Access Journals (Sweden)
Simon Čopar
2014-05-01
Full Text Available Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale.
Theory of solvation in polar nematics
Kapko, V; Kapko, Vitaly; Matyushov, Dmitry V.
2005-01-01
We develop a linear response theory of solvation of ionic and dipolar solutes in anisotropic, axially symmetric polar solvents. The theory is applied to solvation in polar nematic liquid crystals. The formal theory constructs the solvation response function from projections of the solvent dipolar susceptibility on rotational invariants. These projections are obtained from Monte Carlo simulations of a fluid of dipolar spherocylinders which can exist both in the isotropic and nematic phase. Based on the properties of the solvent susceptibility from simulations and the formal solution, we have obtained a formula for the solvation free energy which incorporates experimentally available properties of nematics and the length of correlation between the dipoles in the liquid crystal. Illustrative calculations are presented for the Stokes shift and Stokes shift correlation function of coumarin-153 in 4-n-pentyl-4'-cyanobiphenyl (5CB) and 4,4-n-heptyl-cyanopiphenyl (7CB) solvents as a function of temperature in both th...
Transverse vibration of nematic elastomer Timoshenko beams
Zhao, Dong; Liu, Ying; Liu, Chuang
2017-01-01
Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.
Dynamic structure of active nematic shells
Zhang, Rui; Zhou, Ye; Rahimi, Mohammad; de Pablo, Juan J.
2016-11-01
When a thin film of active, nematic microtubules and kinesin motor clusters is confined on the surface of a vesicle, four +1/2 topological defects oscillate in a periodic manner between tetrahedral and planar arrangements. Here a theoretical description of nematics, coupled to the relevant hydrodynamic equations, is presented here to explain the dynamics of active nematic shells. In extensile microtubule systems, the defects repel each other due to elasticity, and their collective motion leads to closed trajectories along the edges of a cube. That motion is accompanied by oscillations of their velocities, and the emergence and annihilation of vortices. When the activity increases, the system enters a chaotic regime. In contrast, for contractile systems, which are representative of some bacterial suspensions, a hitherto unknown static structure is predicted, where pairs of defects attract each other and flows arise spontaneously.
Phase separation and disorder in doped nematic elastomers
Köpf, M. H.
2013-10-01
We formulate and analyse a model describing the combined effect of mechanical deformation, dynamics of the nematic order parameter, and concentration inhomogeneities in an elastomeric mixture of a mesogenic and an isotropic component. The uniform nematic state may exhibit a long-wave instability corresponding to nematic-isotropic demixing. Numerical simulations starting from either a perfectly ordered nematic state or a quenched isotropic state show that coupling between the mesogen concentration and the nematic order parameter influences the shape and orientation of the domains formed during the demixing process. © EDP Sciences/ Società Italiana di Fisica/ Springer-Verlag 2013.
Direct and inverted nematic dispersions for soft matter photonics.
Muševič, I; Skarabot, M; Humar, M
2011-07-20
General properties and recent developments in the field of nematic colloids and emulsions are discussed. The origin and nature of pair colloidal interactions in the nematic colloids are explained and an overview of the stable colloidal 2D crystalline structures and superstructures discovered so far is given. The nature and role of topological defects in the nematic colloids is discussed, with an emphasis on recently discovered entangled colloidal structures. Applications of inverted nematic emulsions and binding force mechanisms in nematic colloids for soft matter photonic devices are discussed.
The Gravitational Field of a Twisted Skyrmion
Hadi, Miftachul; Husein, Andri
2015-01-01
We study nonlinear sigma model, especially Skyrme model without twist and Skyrme model with twist: twisted Skyrme model. Twist term, $mkz$, is indicated in vortex solution. We are interested to construct a space-time containing a string with Lagrangian plus a twist. To add gravity, we replace $\\eta^{\\mu\
Properties of twisted ferromagnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-02-01
The full set of equations for twisted ferromagnetic filaments is derived. The linear stability analysis of twisted ferromagnetic filament is carried out. Two different types of the buckling instability are found - monotonous and oscillatory. The first in the limit of large twist leads to the shape of filament reminding pearls on the string, the second to spontaneous rotation of the filament, which may constitute the working of chiral microengine.
Zhou, Shuang; Neupane, Krishna; Nastishin, Yuriy A; Baldwin, Alan R; Shiyanovskii, Sergij V; Lavrentovich, Oleg D; Sprunt, Samuel
2014-09-14
Using dynamic light scattering, we study orientational fluctuation modes in the nematic phase of a self-assembled lyotropic chromonic liquid crystal (LCLC) disodium cromoglycate and measure the Frank elastic moduli and viscosity coefficients. The elastic moduli of splay (K1) and bend (K3) are in the order of 10 pN while the twist modulus (K2) is an order of magnitude smaller. The splay constant K1 and the ratio K1/K3 both increase substantially as the temperature T decreases, which we attribute to the elongation of the chromonic aggregates at lower temperatures. The bend viscosity is comparable to that of thermotropic liquid crystals, while the splay and twist viscosities are several orders of magnitude larger. The temperature dependence of bend viscosity is weak. The splay and twist viscosities change exponentially with the temperature. In addition to the director modes, the fluctuation spectrum reveals an additional mode that is attributed to diffusion of structural defects in the column-like aggregates.
Spin nematic and orthogonal nematic states in S=1 non-Heisenberg magnet
Energy Technology Data Exchange (ETDEWEB)
Fridman, Yu.A., E-mail: frid@tnu.crimea.edu [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Kosmachev, O.A. [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Klevets, Ph.N. [V.I. Vernadsky Taurida national university, Academician Vernadsky ave., 4, 95007 Simferopol (Ukraine); Institut fuer Physik, Universitaet Augsburg, Universitaetsstrasse 1, 86159 Augsburg (Germany)
2013-01-15
Phases of S=1 non-Heisenberg magnet at various relationships between the exchange integrals are studied in the mean-field limit at zero temperature. It is shown that four phases can be realized in the system under consideration: the ferromagnetic, antiferromagnetic, nematic, and the orthogonal nematic states. The phase diagram is constructed. It is shown that the phase transitions between the ferromagnetic phase and the orthogonal nematic phase and between the antiferromagnetic phase and the orthogonal nematic phase are the degenerated first-order transitions. For the first time the spectra of elementary excitations in all phases are obtained within the mean-field limit. - Highlights: Black-Right-Pointing-Pointer We investigated phases of S=1 non-Heisenberg magnet. Black-Right-Pointing-Pointer Found four phases: ferromagnetic, antiferromagnetic, nematic, and orthogonal nematic. Black-Right-Pointing-Pointer The phase diagram is determined. Black-Right-Pointing-Pointer The spectra of elementary excitations are obtained in all phases for the first time.
Energy Technology Data Exchange (ETDEWEB)
Shindler, A. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-07-15
I review the theoretical foundations, properties as well as the simulation results obtained so far of a variant of the Wilson lattice QCD formulation: Wilson twisted mass lattice QCD. Emphasis is put on the discretization errors and on the effects of these discretization errors on the phase structure for Wilson-like fermions in the chiral limit. The possibility to use in lattice simulations different lattice actions for sea and valence quarks to ease the renormalization patterns of phenomenologically relevant local operators, is also discussed. (orig.)
Hydrodynamic correlation functions in nematic liquid crystals
Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.
1976-01-01
The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t
High-Genus nematic liquid crystal droplets
Jayalakshmi, V.; Ekapop, P.; Fernandez-Nieves, Alberto
2017-05-01
We will discuss the defect structures that originate in nematic droplets with two or more handles. In these cases, the topology of the bounding surface requires the presence of defects. Our experiments elucidate where do these defects locate and how many of them populated the ground state of the system.
Hydrodynamic correlation functions in nematic liquid crystals
Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.
1976-01-01
The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t
The development of chiral nematic mesoporous materials.
Kelly, Joel A; Giese, Michael; Shopsowitz, Kevin E; Hamad, Wadood Y; MacLachlan, Mark J
2014-04-15
Cellulose nanocrystals (CNCs) are obtained from the sulfuric acid-catalyzed hydrolysis of bulk cellulose. The nanocrystals have diameters of ~5-15 nm and lengths of ~100-300 nm (depending on the cellulose source and hydrolysis conditions). This lightweight material has mostly been investigated to reinforce composites and polymers because it has remarkable strength that rivals carbon nanotubes. But CNCs have an additional, less explored property: they organize into a chiral nematic (historically referred to as cholesteric) liquid crystal in water. When dried into a thin solid film, the CNCs retain the helicoidal chiral nematic order and assemble into a layered structure where the CNCs have aligned orientation within each layer, and their orientation rotates through the stack with a characteristic pitch (repeating distance). The cholesteric ordering can act as a 1-D photonic structure, selectively reflecting circularly polarized light that has a wavelength nearly matching the pitch. During CNC self-assembly, it is possible to add sol-gel precursors, such as Si(OMe)4, that undergo hydrolysis and condensation as the solvent evaporates, leading to a chiral nematic silica/CNC composite material. Calcination of the material in air destroys the cellulose template, leaving a high surface area mesoporous silica film that has pore diameters of ~3-10 nm. Importantly, the silica is brilliantly iridescent because the pores in its interior replicate the chiral nematic structure. These films may be useful as optical filters, reflectors, and membranes. In this Account, we describe our recent research into mesoporous films with chiral nematic order. Taking advantage of the chiral nematic order and nanoscale of the CNC templates, new functional materials can be prepared. For example, heating the silica/CNC composites under an inert atmosphere followed by removal of the silica leaves highly ordered, mesoporous carbon films that can be used as supercapacitor electrodes. The composition
[Transpon Tn5 mutagenesis in Citrobacter].
Wang, A Q; Yin, P; Chen, X Z
1990-04-01
When E. coli 1830/PJB4JI mating with four Citrobacter strains all were Kanamycin resistant, but a majority of KanrGens transconjugants were obtained from C-3-1. Among 3000 KanrGens 21 were auxotrophs, these are Lys-(1), Ura-(1), Arg-(2), Iso-(2), His-(2), Met-(1), Phe-(1), Tyr-(1), Ser-(1), Thr-(1), Leu-(3), Pro-(1), Ade-(3), Lac-(1), PJB4JI plasmid DNA were detected in parent strain E. coli 1830, but not in auxotrophs strains which carrying Tn5 induced mutations. Twenty auxotrophs chromosome DNA were hybridized with Tn5 DNA labeled with 32P respectively, all auxotrophs has positive reaction. Therefore, we concluded from genetic and physical data that auxotrophs resulted from Tn5 transposition from PJB4JI into C-3-1 chromosome.
Twisting formula of epsilon factors
Indian Academy of Sciences (India)
SAZZAD ALI BISWAS
2017-09-01
For characters of a non-Archimedean local field we have explicit formula for epsilon factors. But in general, we do not have any generalized twisting formula of epsilon factors. In this paper, we give a generalized twisting formula of epsilon factorsvia local Jacobi sums.
Twisted supergravity and its quantization
Costello, Kevin
2016-01-01
Twisted supergravity is supergravity in a background where the bosonic ghost field takes a non-zero value. This is the supergravity counterpart of the familiar concept of twisting supersymmetric field theories. In this paper, we give conjectural descriptions of type IIA and IIB supergravity in $10$ dimensions. Our conjectural descriptions are in terms of the closed-string field theories associated to certain topological string theories, and we conjecture that these topological string theories are twists of the physical string theories. For type IIB, the results of arXiv:1505.6703 show that our candidate twisted supergravity theory admits a unique quantization in perturbation theory. This is despite the fact that the theories, like the original physical theories, are non-renormalizable. Although we do not prove our conjectures, we amass considerable evidence. We find that our candidates for the twisted supergravity theories contain the residual supersymmetry one would expect. We also prove (using heavily a res...
Twisted bialgebroids versus bialgebroids from a Drinfeld twist
Borowiec, Andrzej; Pachoł, Anna
2017-02-01
Bialgebroids (respectively Hopf algebroids) are bialgebras (Hopf algebras) over noncommutative rings. Drinfeld twist techniques are particularly useful in the (deformation) quantization of Lie algebras as well as the underlying module algebras (=quantum spaces). A smash product construction combines both of them into the new algebra which, in fact, does not depend on the twist. However, we can turn it into a bialgebroid in a twist-dependent way. Alternatively, one can use Drinfeld twist techniques in a category of bialgebroids. We show that both the techniques indicated in the title—the twisting of a bialgebroid or constructing a bialgebroid from the twisted bialgebra—give rise to the same result in the case of a normalized cocycle twist. This can be useful for the better description of a quantum deformed phase space. We argue that within this bialgebroid framework one can justify the use of deformed coordinates (i.e. spacetime noncommutativity), which are frequently postulated in order to explain quantum gravity effects.
Two-state model for nematic liquid crystals made of bent-core molecules
Madhusudana, N. V.
2017-08-01
Nematic (N ) liquid crystals made of bent-core molecules exhibit unusual physical properties such as an intermediate phase between the N and isotropic (I ) phases, a very weak N I transition as inferred from magnetic birefringence measurements in a low field, which is apparently incompatible with a large shift in the N I transition temperature (Tn i) measured under a high field. Using our conformational studies on the aromatic cores, we propose that only conformers which are more straightened than those in the ground state (GS) form clusters with a few layers, which persist even in the isotropic phase, as inferred from x-ray and rheological experiments. We present a Landau-de Gennes theory of the medium, including an orientational coupling between the clusters and the GS molecules, which accounts for all the unusual properties. The intermediate phase to isotropic transition is predicted to exhibit critical behavior at a very low magnetic field of <1 kG .
The mechanism of long-range exciton diffusion in a nematically organized porphyrin layer.
Huijser, Annemarie; Savenije, Tom J; Meskers, Stefan C J; Vermeulen, Martien J W; Siebbeles, Laurens D A
2008-09-17
The exciton diffusion length in a nematically organized meso-tetra(4-n-butylphenyl)porphyrin (TnBuPP) layer was found to exceed 40 nm at a temperature of 90 K and to be equal to 22 +/- 3 nm at 300 K. The exciton diffusion coefficient decreases from > or = 3.1 x 10(-6) m(2)/s at 90 K to (2.5 +/- 0.5) x 10(-7) m(2)/s at 300 K. This thermal deactivation is attributed to exciton motion via a band mechanism. The motion of an exciton is not limited by polaronic effects; that is, the deformation of the atomic lattice around the exciton. The absence of polaronic self-trapping implies that the exciton diffusion coefficient can be enhanced by improvement of structural order and rigidity of the material.
Threshold property of a nematic liquid crystal cell with two grating surface substrates
Institute of Scientific and Technical Information of China (English)
Ye Wen-Jiang; Xing Hong-Yu; Yang Guo-Chen; Yuan Meng-Yao
2009-01-01
A grating surface can drive the liquid crystal molecules to orientate along the direction parallel or vertical to the projected plane of the grating surface. The nematic liquid crystal (NLC) cell manufactured with two pre-treated grating surface substrates may realize the vertical display, parallel display and twist display. In this paper, the threshold property of this NLC cell is investigated systematically. With the Frank elastic theory and the equivalent anchoring energy formula of grating surface substrate, the analytic expressions of the threshold voltage related to three displays are obtained, which are dependent on their geometrical parameters such as amplitude δ and pitch λ of the grating surface substrate. For a certain anchoring strength, the threshold voltage increases or decreases with the increase of the value δ/λ of the different displays.
78 FR 48762 - Tennessee Disaster #TN-00076
2013-08-09
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77 FR 51100 - Tennessee Disaster #TN-00068
2012-08-23
... From the Federal Register Online via the Government Publishing Office SMALL BUSINESS ADMINISTRATION Tennessee Disaster TN-00068 AGENCY: U.S. Small Business Administration. ACTION: Notice. SUMMARY... INFORMATION CONTACT: A. Escobar, Office of Disaster Assistance, U.S. Small Business Administration, 409...
Simple mucin-type Tn and sialosyl-Tn carbohydrate antigens in salivary gland carcinomas
DEFF Research Database (Denmark)
Therkildsen, M H; Mandel, U; Christensen, M
1993-01-01
BACKGROUND: Neoplastic transformation is associated frequently with changes in the glycosylation process. Simple mucin-type glycosylation in cancer cells has been found to be characterized by incomplete synthesis with precursor accumulation, leading to the exposure of the structures Tn and sialosyl...... adenoma, when the malignant component was an adenocarcinoma. In contrast, acinic cell carcinomas and adenoid cystic carcinomas expressed only minimal amounts of Tn and sialosyl-Tn, and the staining was seen only in relation to the luminal membrane and mucin of a few glandular structures. CONCLUSIONS...
Buckling transition of nematic gels in confined geometry
Meng, Guangnan; Meyer, Robert B.
2009-01-01
A spontaneous buckling transition in thin layers of monodomain nematic liquid crystalline gel was observed by polarized light microscopy. The coupling between the orientational ordering of liquid crystalline solvent and the translational ordering of crosslinked polymer backbones inside the nematic gel contributes to such buckling transition. As the nematic mesogens become more ordered when the gel is cooled down from a higher gelation temperature, the polymeric backbones tend to elongate alon...
Nematic order by elastic interactions and cellular rigidity sensing
Friedrich, B. M.; Safran, S. A.
2011-01-01
We predict spontaneous nematic order in an ensemble of active force generators with elastic interactions as a minimal model for early nematic alignment of short stress fibers in non-motile, adhered cells. Mean-field theory is formally equivalent to Maier-Saupe theory for a nematic liquid. However, the elastic interactions are long-ranged (and thus depend on cell shape and matrix elasticity) and originate in cell activity. Depending on the density of force generators, we find two regimes of cellular rigidity sensing for which orientational, nematic order of stress fibers depends on matrix rigidity either in a step-like manner or with a maximum at an optimal rigidity.
Photonic crystals, light manipulation, and imaging in complex nematic structures
Ravnik, Miha; Å timulak, Mitja; Mur, Urban; Čančula, Miha; Čopar, Simon; Žumer, Slobodan
2016-03-01
Three selected approaches for manipulation of light by complex nematic colloidal and non-colloidal structures are presented using different own custom developed theoretical and modelling approaches. Photonic crystals bands of distorted cholesteric liquid crystal helix and of nematic colloidal opals are presented, also revealing distinct photonic modes and density of states. Light propagation along half-integer nematic disclinations is shown with changes in the light polarization of various winding numbers. As third, simulated light transmission polarization micrographs of nematic torons are shown, offering a new insight into the complex structure characterization. Finally, this work is a contribution towards using complex soft matter in optics and photonics for advanced light manipulation.
Phenomenological Theory of Isotropic-Genesis Nematic Elastomers
Lu, Bing-Sui; Ye, Fangfu; Xing, Xiangjun; Goldbart, Paul M.
2012-06-01
We consider the impact of the elastomer network on the nematic structure and fluctuations in isotropic-genesis nematic elastomers, via a phenomenological model that underscores the role of network compliance. The model contains a network-mediated nonlocal interaction as well as a new kind of random field that reflects the memory of the nematic order present at network formation and also encodes local anisotropy due to localized nematogenic polymers. This model enables us to predict regimes of short-ranged oscillatory spatial correlations (thermal and glassy) in the nematic alignment.
Thermal diode made by nematic liquid crystal
Energy Technology Data Exchange (ETDEWEB)
Melo, Djair, E-mail: djfmelo@gmail.com [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Fernandes, Ivna [Instituto de Física, Universidade Federal de Alagoas, Av. Lourival Melo Mota, s/n, 57072-900 Maceió, AL (Brazil); Moraes, Fernando [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa, PB (Brazil); Departamento de Física, Universidade Federal Rural de Pernambuco, 52171-900 Recife, PE (Brazil); Fumeron, Sébastien [Institut Jean Lamour, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre les Nancy (France); Pereira, Erms [Escola Politécnica de Pernambuco, Universidade de Pernambuco, Rua Benfíca, 455, Madalena, 50720-001 Recife, PE (Brazil)
2016-09-07
This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed. - Highlights: • An escaped radial disclination as a thermal diode made by a nematic liquid crystal. • Rectifying effects comparable to those caused by carbon and boron nitride nanotubes. • Thermal rectification increasing with radius and decreasing with height of the tube. • Asymmetric BCs cause rectification from the spatial asymmetry produced by the escape. • Symmetric BCs provide rectifications smaller than those yields by asymmetric BCs.
Light-controllable linear dichroism in nematics.
Petriashvili, Gia; Hamdi, Ridha; De Santo, Maria Penelope; Gary, Ramla; Barberi, Riccardo
2015-10-01
We report a method to obtain a light-controllable dichroism. The main effect is achieved using spiropyran-doped (SP-doped) nematic liquid crystal mixtures. SP molecules exhibit a high solubility in the liquid crystal host, which can vary between 1% and 4% in weight, without destroying the liquid crystalline phase. Due to their elongated shape, SP molecules are oriented along the nematic liquid crystal director. The obtained linear dichroism was measured to be 1.08 with a dichroic ratio of 7.12. Further, a two-direction linear dichroism was obtained by adding a dichroic dye to the mixture. The angle between the two dichroic axes was found to be 11°. Two-direction linear dichroism is also light controllable and can be switched back to one-direction dichroism.
Nematic films at chemically structured surfaces
Silvestre, N. M.; Telo da Gama, M. M.; Tasinkevych, M.
2017-02-01
We investigate theoretically the morphology of a thin nematic film adsorbed at flat substrate patterned by stripes with alternating aligning properties, normal and tangential respectively. We construct a simple ‘exactly-solvable’ effective interfacial model where the liquid crystal distortions are accounted for via an effective interface potential. We find that chemically patterned substrates can strongly deform the nematic-air interface. The amplitude of this substrate-induced undulations increases with decreasing average film thickness and with increasing surface pattern pitch. We find a regime where the interfacial deformation may be described in terms of a material-independent universal scaling function. Surprisingly, the predictions of the effective interfacial model agree semi-quantitatively with the results of the numerical solution of a full model based on the Landau-de Gennes theory coupled to a square-gradient phase field free energy functional for a two phase system.
Molecular engineering of discotic nematic liquid crystals
Indian Academy of Sciences (India)
Sandeep Kumar
2003-08-01
Connecting two columnar phase forming discotic mesogens via a short rigid spacer leads to the formation of a -conjugated discotic dimer showing discotic nematic (D) phase. Attaching branched-alkyl chains directly to the core in hexaalkynylbenzene resulted in the stabilisation of D phase at ambient temperature. Pentalkynylbenzene derivatives possessing a combination of normal-and branched-alkoxy chains display a very broad D phase which is stable well below and above the room temperature.
On Some Elastic Instabilities in Biaxial Nematics
Sukumaran, Sreejith; G. Ranganath
1997-01-01
Within the framework of the continuum elastic theory of biaxial nematic liquid crystals, we have addressed ourselves to the structure, stability and energetics of some singular and non–singular topological defects, and certain director configurations. We find that certain non–singular hybrid disclinations could be energetically favourable relative to certain half–strength disclinations. The interaction between singular hybrids depends strongly on the biaxial elastic anisotropy. We suggest pos...
Stacking Nematic Elastomers for Artificial Muscle Applications
2006-04-01
amputees nd variable impendence ankle-foot orthoses for patients suffering from drop oot, a gait pathology caused by stroke, cerebral palsy , and multiple...by de Gennes [8]. In particular, niqueness of nematic LCEs stems from the fact that they exhibit eversible macroscopic and anisotropic contraction as...Irgacure-369 (Ciba pecialty Chemicals) were heated above TNI and filled into a lass cell on a temperature-controlled hot stage. Glass cells ere composed
Electrically controlled dispersion in a nematic cell
Energy Technology Data Exchange (ETDEWEB)
Mendoza, Carlos I. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-360, 04510 Mexico, D.F. (Mexico)]. E-mail: cmendoza@iim.unam.mx; Olivares, J.A. [Centro de Investigacion en Polimeros, COMEX, Blvd. M. Avila Camacho 138, PH1 y 2, Lomas de Chapultepec 11560, Mexico, D.F. (Mexico); Reyes, J.A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 20-364, 01000 Mexico, D.F. (Mexico)
2007-01-01
In this work, we show theoretically how the trajectories of a propagating optical beam traveling in a planar-homeotropic hybrid nematic crystal cell depend on the wavelength of the optical beam. We apply a uniform electric field perpendicular to the cell to modify these trajectories. The influence of both, the electric field intensity and the refraction index dependence on the wavelength, give rise to an electrically tuned dispersion that may be useful for practical applications.
Post-Tanner spreading of nematic droplets
Energy Technology Data Exchange (ETDEWEB)
Mechkov, S; Oshanin, G [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 5 (France); Cazabat, A M, E-mail: mechkov@lptmc.jussieu.f, E-mail: anne-marie.cazabat@lps.ens.f, E-mail: oshanin@lptmc.jussieu.f [Laboratoire de Physique Statistique, Ecole Normale Superieure, 75252 Paris Cedex 5 (France)
2009-11-18
The quasistationary spreading of a circular liquid drop on a solid substrate typically obeys the so-called Tanner law, with the instantaneous base radius R(t) growing with time as Rapproxt{sup 1/10}-an effect of the dominant role of capillary forces for a small-sized droplet. However, for droplets of nematic liquid crystals, a faster spreading law sets in at long times, so that Rapproxt{sup a}lpha with alpha significantly larger than the Tanner exponent 1/10. In the framework of the thin film model (or lubrication approximation), we describe this 'acceleration' as a transition to a qualitatively different spreading regime driven by a strong substrate-liquid interaction specific to nematics (antagonistic anchoring at the interfaces). The numerical solution of the thin film equation agrees well with the available experimental data for nematics, even though the non-Newtonian rheology has yet to be taken into account. Thus we complement the theory of spreading with a post-Tanner stage, noting that the spreading process can be expected to cross over from the usual capillarity-dominated stage to a regime where the whole reservoir becomes a diffusive film in the sense of Derjaguin.
Semantic Deviation in Oliver Twist
Institute of Scientific and Technical Information of China (English)
康艺凡
2016-01-01
Dickens, with his adeptness with language, applies semantic deviation skillfully in his realistic novel Oliver Twist. However, most studies and comments home and abroad on it mainly focus on such aspects as humanity, society, and characters. Therefore, this thesis will take a stylistic approach to Oliver Twist from the perspective of semantic deviation, which is achieved by the use of irony, hyperbole, and pun and analyze how the application of the technique makes the novel attractive.
Speziale, Simone
2013-01-01
We define and investigate a quantisation of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrisation of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with space-like faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalims are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, abelian geometric picture. It can be described by an Euclidean singular structure on the 2-dimensional space-like surface defined by a foliation of space-time by null hypersurfaces. This geometric structure is na...
Elastic interactions and manipulation of wire-shaped inclusions in nematic liquid crystals
Lapointe, Clayton P.
Anisotropic particles suspended in a nematic liquid crystal disturb the alignment of the liquid crystal molecules and experience small forces and torques mediated by the elasticity of the fluid. These elastic interactions depend upon the orientation of the particle relative to the alignment of the liquid crystal as well as the nature of the molecular-scale alignment at the surface of the particle. In this thesis, I present the results of video microscopy studies on elastic interactions on ferromagnetic nanowires suspended in the nematic liquid crystal 4-pentyl-4-cyanobiphenyl (5CB). In the first part, I describe measurements that characterize the orientation-dependent elastic torque on a nanowire with longitudinal anchoring in uniformly aligned 5CB, its temperature dependence, as well as the elastic repulsion of a nanowire from a flat wall. These measurements were found to be quantitatively consistent with theoretical predictions based on the elastic properties of 5CB. In the second part of this thesis, I demonstrate that distorting the liquid crystal from a state of uniform alignment results in converting the elastic torque on a nanowire into an orientation-dependant translational force that can be utilized to reversibly manipulate the positions of isolated nanowires as well as to assemble suspensions of them into pre-designed arrays on a substrate. First, I describe measurements of an orientation-dependent levitating force on a nanowire in a twisted nematic cell. This force can be used to position nanowires to pre-determined heights above the bottom substrate by controlling their orientation with an external magnetic field. I then describe a series of experiments in which in a liquid crystal cell with a pattern of micron-scale stripe domains was used to drive nanowires held at a fixed orientation with external magnetic fields selectively into the middle of the stripe domains. In the last part of this thesis, I discuss video microscopy experiments to probe the
Modulated liquid-crystal phases induced by polarity: Twist-bend, splay-bend, and blue phases
Selinger, Jonathan; Shamid, Shaikh; Allender, David
2014-03-01
Nematic liquid crystals exhibit flexoelectric couplings between polar order and gradients in the director field. When the couplings become strong enough, the uniform nematic phase can become unstable to the formation of a modulated polar phase. The question is then: What is the structure of the modulated polar phase? Classic work by Meyer and further studies by Dozov predicted two possible structures, known as twist-bend and splay-bend. One of these predictions, the twist-bend phase, has recently been identified in experiments on bent-core liquid crystals. Here, we investigate modulated polar phases through a combination of Landau theory and lattice simulations. We find a range of possibilities, including the twist-bend and splay-bend phases as well as polar blue phases, with 2D or 3D modulations of the director field and the polar order. We compare these polar blue phases with chiral blue phases, and discuss opportunities for observing them experimentally. Supported by NSF DMR-1106014.
Isotropic-to-nematic nucleation in suspensions of colloidal rods
Cuetos, A.; van Roij, R.H.H.G.; Dijkstra, M.
2008-01-01
Using computer simulations, we study the isotropic-to-nematic nucleation in a fluid of colloidal hard rods as well as in a mixture of colloidal rods and non-adsorbing polymer. In order to follow the transformation of the system from the isotropic to the nematic phase, we use a new cluster criterion
Fractional Brownian motion of director fluctuations in nematic ordering
DEFF Research Database (Denmark)
Zhang, Z.; Mouritsen, Ole G.; Otnes, K.
1993-01-01
to determine the Hurst exponent H. Theory and experiment are in good agreement. A value of H congruent-to 1 was found for the nematic phase, characterizing fractional Brownian motion, whereas H congruent-to 0.5, reflecting ordinary Brownian motion, applies in the isotropic phase. Field-induced crossover from...... fractional to ordinary Brownian motion was observed in the nematic phase....
76 FR 1512 - Amendment of Class E Airspace; Savannah, TN
2011-01-11
... Instrument Approach Procedures (SIAPs) have been developed for Savannah-Hardin County Airport. This action... SIAPs developed at Savannah-Hardin County Airport, Savannah, TN. Airspace reconfiguration is necessary... Savannah, TN Savannah-Hardin County Airport, TN (Lat. 35 10'13'' N., long. 88 13'00'' W.) That...
Negative ion photoelectron spectroscopy of 2,2'-bithiophene cluster anions, (2T)n- (n = 1 100)
Mitsui, M.; Matsumoto, Y.; Ando, N.; Nakajima, A.
2005-07-01
Cluster anions of 2,2'-bithiophene, (2T){n}-, were produced up to n ˜ 500 in the gas-phase. The energetics of the excess electron in the (2T){n}- clusters with n =1{-}100 were explored by negative ion photoelectron spectroscopy. When the vertical detachment energies (VDEs) obtained from the photoelectron spectra were analyzed by a plot against n-1/3, it has been revealed that the excess electron trapping level thus extrapolated is located at ˜ 0.8 eV below the conduction band minimum (i.e. LUMO) of the 2T thin film. The large slope of the VDEs vs. n-1/3 plot suggests that the neutral 2T molecules surrounding the anion core take non-planar twisted conformations with permanent dipole moments, resulting in the exceedingly deep trapping of the excess electron in the 2T cluster anions.
Holographic RG flows with nematic IR phases
Cremonini, Sera; Rong, Junchen; Sun, Kai
2014-01-01
We construct zero-temperature geometries that interpolate between a Lifshitz fixed point in the UV and an IR phase that breaks spatial rotations but preserves translations. We work with a simple holographic model describing two massive gauge fields coupled to gravity and a neutral scalar. Our construction can be used to describe RG flows in non-relativistic, strongly coupled quantum systems with nematic order in the IR. In particular, when the dynamical critical exponent of the UV fixed point is z=2 and the IR scaling exponents are chosen appropriately, our model realizes holographically the scaling properties of the bosonic modes of the quadratic band crossing model.
Thermal diode made by nematic liquid crystal
Melo, Djair; Fernandes, Ivna; Moraes, Fernando; Fumeron, Sébastien; Pereira, Erms
2016-09-01
This work investigates how a thermal diode can be designed from a nematic liquid crystal confined inside a cylindrical capillary. In the case of homeotropic anchoring, a defect structure called escaped radial disclination arises. The asymmetry of such structure causes thermal rectification rates up to 3.5% at room temperature, comparable to thermal diodes made from carbon nanotubes. Sensitivity of the system with respect to the heat power supply, the geometry of the capillary tube and the molecular anchoring angle is also discussed.
Carbon Nanoparticles in Nematic Liquid Crystals
Institute of Scientific and Technical Information of China (English)
S.Eren San; Mustafa Okutan; O(g)uz K(o)ysal; Yusuf Yer-li
2008-01-01
Fullerene G60,C70,single-walled and multi-walled carbon nanotubes and graphene sheets are doped to nematic liquid crystal(LC)host in the same percentage.Planar samples of these mixtures are prepared and our measurements constitute an optimization basis for possible applications.Fullerene balls are found to be the best compatible material for optical aims and reorientation of LC molecules,while the carbon nanotubes experience some reorientation possibility in LC media and graphene layers are good barriers to preserve reorientation.
Organization of tn2610 containing two transposition modules.
Takaya, Akiko; Watanabe, Masato; Yamamoto, Tomoko
2006-04-01
Transposon Tn2610, found in a conjugative plasmid from an Escherichia coli isolate recovered at a hospital in Chiba, Japan, in 1975, was completely sequenced. Tn2610 is 23,883 bp long and is bracketed by two transposition modules, a Tn1721-like module and a Tn21-derived module, which correspond, respectively, to the long inverted repeats IRa and IRb previously described for this transposon. Although both tnpA genes are intact, only that in the Tn21-derived module (IRb) functions in the transposition, while that in the Tn1721-derived module (IRa) cannot recognize the 38-bp imperfect repeat at the end of the IRb element. Both tnpR and res are present in IRa, while the tnpR gene of IRb is interrupted by the insertion of an IS26 insertion element. The intervening region, between the res site of the Tn1721 module and IS26, carries multiple integron-associated resistance genes within a Tn21 backbone, including a region identical to that found in the genome of Salmonella enterica serovar Typhimurium DT104. These findings suggest that Tn2610 originated from Tn1721 and Tn21, with extensive recombination events with other elements which have resulted in a complex mosaic structure.
Polarization twist in perovskite ferrielectrics.
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-02
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of 'polarization twist', which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Fluctuational shift of nematic-isotropic phase transition temperature
Kats, E. I.
2017-02-01
In this work we discuss a macroscopic counterpart to the microscopic mechanism of the straightening dimer mesogens conformations, proposed recently by S.M. Saliti, M.G.Tamba, S.N. Sprunt, C.Welch, G.H.Mehl, A. Jakli, J.T. Gleeson (Phys. Rev. Lett. 116, 217801 (2016)) to explain their experimental observation of the unprecedentedly large shift of the nematic-isotropic transition temperature. Our interpretation is based on singular longitudinal fluctuations of the nematic order parameter. Since these fluctuations are governed by the Goldstone director fluctuations they exist only in the nematic state. External magnetic field suppresses the singular longitudinal fluctuations of the order parameter (similarly as it is the case for the transverse director fluctuations, although with a different scaling over the magnetic field). The reduction of the fluctuations changes the equilibrium value of the modulus of the order parameter in the nematic state. Therefore it leads to additional (with respect to the mean field contribution) fluctuational shift of the nematic-isotropic transition temperature. Our mechanism works for any nematic liquid crystals, however the magnitude of the fluctuational shift increases with decrease of the Frank elastic moduli. Since some of these moduli supposed to be anomalously small for so-called bent-core or dimer nematic liquid crystals, just these liquid crystals are promising candidates for the observation of the predicted fluctuational shift of the phase transition temperature.
Relevance of saddle-splay elasticity in complex nematic geometries.
Kos, Žiga; Ravnik, Miha
2016-01-28
We demonstrate the relevance of saddle-splay elasticity in nematic liquid crystalline fluids in the context of complex surface anchoring conditions and the complex geometrical confinement. Specifically, nematic cells with patterns of surface anchoring and colloidal knots are shown as examples where saddle-splay free energy contribution can have a notable role which originates from nonhomogeneous surface anchoring and the varying surface curvature. Patterned nematic cells are shown to exhibit various (meta)stable configurations of nematic field, with relative (meta)stability depending on the saddle-splay. We show that for high enough values of saddle-splay elastic constant K24 a previously unstable conformation can be stabilised, more generally indicating that the saddle-splay can reverse or change the (meta)stability of various nematic structures affecting their phase diagrams. Furthermore, we investigate saddle-splay elasticity in the geometry of highly curved boundaries - the colloidal particle knots in nematic - where the local curvature of the particles induces complex spatial variations of the saddle-splay contributions. Finally, a nematic order parameter tensor based saddle-splay invariant is shown, which allows for the direct calculation of saddle-splay free energy from the Q-tensor, a possibility very relevant for multiple mesoscopic modelling approaches, such as Landau-de Gennes free energy modelling.
Intertwined nematic orders in a frustrated ferromagnet
Iqbal, Yasir; Ghosh, Pratyay; Narayanan, Rajesh; Kumar, Brijesh; Reuther, Johannes; Thomale, Ronny
2016-12-01
We investigate the quantum phases of the frustrated spin-1/2 J1-J2-J3 Heisenberg model on the square lattice with ferromagnetic J1 and antiferromagnetic J2 and J3 interactions. Using the pseudofermion functional renormalization group technique, we find an intermediate paramagnetic phase located between classically ordered ferromagnetic, stripy antiferromagnetic, and incommensurate spiral phases. We observe that quantum fluctuations lead to significant shifts of the spiral pitch angles compared to the classical limit. By computing the response of the system with respect to various spin rotation and lattice symmetry-breaking perturbations, we identify a complex interplay between different nematic spin states in the paramagnetic phase. While retaining time-reversal invariance, these phases either break spin-rotation symmetry, lattice-rotation symmetry, or a combination of both. We therefore propose the J1-J2-J3 Heisenberg model on the square lattice as a paradigmatic example where different intimately connected types of nematic orders emerge in the same model.
Field-driven dynamics of nematic microcapillaries
Khayyatzadeh, Pouya; Fu, Fred; Abukhdeir, Nasser Mohieddin
2015-12-01
Polymer-dispersed liquid-crystal (PDLC) composites long have been a focus of study for their unique electro-optical properties which have resulted in various applications such as switchable (transparent or translucent) windows. These composites are manufactured using desirable "bottom-up" techniques, such as phase separation of a liquid-crystal-polymer mixture, which enable production of PDLC films at very large scales. LC domains within PDLCs are typically spheroidal, as opposed to rectangular for an LCD panel, and thus exhibit substantially different behavior in the presence of an external field. The fundamental difference between spheroidal and rectangular nematic domains is that the former results in the presence of nanoscale orientational defects in LC order while the latter does not. Progress in the development and optimization of PDLC electro-optical properties has progressed at a relatively slow pace due to this increased complexity. In this work, continuum simulations are performed in order to capture the complex formation and electric field-driven switching dynamics of approximations of PDLC domains. Using a simplified elliptic cylinder (microcapillary) geometry as an approximation of spheroidal PDLC domains, the effects of geometry (aspect ratio), surface anchoring, and external field strength are studied through the use of the Landau-de Gennes model of the nematic LC phase.
DEFF Research Database (Denmark)
de Vries, Lisbeth Elvira; Christensen, H.; Skov, R. L.;
2009-01-01
sequenced and compared with tet(M) deposited in GenBank. Based on phylogenetic analysis isolates were screened for Tn916- and Tn5801-like xis/int genes, and transposons were confirmed by linking PCR. spa typing was performed and selected isolates were used as donors in a filter mating experiment. Forty...
Challenges in Antibody Development against Tn and Sialyl-Tn Antigens
Loureiro, Liliana R.; Carrascal, Mylène A.; Barbas, Ana; Ramalho, José S.; Novo, Carlos; Delannoy, Philippe; Videira, Paula A.
2015-01-01
The carbohydrate antigens Tn and sialyl-Tn (STn) are expressed in most carcinomas and usually absent in healthy tissues. These antigens have been correlated with cancer progression and poor prognosis, and associated with immunosuppressive microenvironment. Presently they are used in clinical trials as therapeutic vaccination, but with limited success due to their low immunogenicity. Alternatively, anti-Tn and/or STn antibodies may be used to harness the immune system against tumor cells. Whilst the development of antibodies against these antigens had a boost two decades ago for diagnostic use, so far no such antibody entered into clinical trials. Possible limitations are the low specificity and efficiency of existing antibodies and that novel antibodies are still necessary. The vast array of methodologies available today will allow rapid antibody development and novel formats. Following the advent of hybridoma technology, the immortalization of human B cells became a methodology to obtain human monoclonal antibodies with better specificity. Advances in molecular biology including phage display technology for high throughput screening, transgenic mice and more recently molecularly engineered antibodies enhanced the field of antibody production. The development of novel antibodies against Tn and STn taking advantage of innovative technologies and engineering techniques may result in innovative therapeutic antibodies for cancer treatment. PMID:26270678
Drinfel'd basis of twisted Yangians
Belliard, Samuel
2014-01-01
We present a quantization of a Lie bi-ideal structure for twisted half-loop algebras of finite dimensional simple complex Lie algebras. We obtain Drinfel'd basis formalism and algebra closure relations of twisted Yangians for all symmetric pairs of simple Lie algebras and for simple twisted even half-loop Lie algebras. We also give an explicit form of twisted Yangians in Drinfel'd basis for the sl3 Lie algebra.
Topological Insulators and Nematic Phases from Spontaneous Symmetry Breaking in
Energy Technology Data Exchange (ETDEWEB)
Sun, K.
2010-05-26
We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At the non-interacting level, we show that a QBCP exists and is topologically stable for a Berry flux {-+}2{pi}, if the point symmetry group has either fourfold or sixfold rotational symmetries. This putative topologically stable free-fermion QBCP is marginally unstable to arbitrarily weak shortrange repulsive interactions. We consider both spinless and spin-1/2 fermions. Four possible ordered states result: a quantum anomalous Hall phase, a quantum spin Hall phase, a nematic phase, and a nematic-spin-nematic phase.
Towards the biaxial nematic phase via specific intermolecular interactions
Omnes, L
2001-01-01
The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase
Properly twisted groups and their algebras
Bales, John W
2011-01-01
A twist property is developed which imparts certain properties on the twisted group algebra. These include an involution * satisfying (xy)*=y*x* and an inner product satisfying = and =. Examples of twisted group algebras having this property are the Cayley-Dickson algebras and Clifford algebras.
"Oliver Twist": A Teacher's Guide.
Cashion, Carol; Fischer, Diana
This teacher's guide for public television's 3-part adaptation of Charles Dickens's "Oliver Twist" provides information that will help enrich students' viewing of the series, whether or not they read the novel. The guide includes a wide range of discussion and activity ideas; there is also a series Web site and a list of Web resources.…
Helically twisted photonic crystal fibres.
Russell, P St J; Beravat, R; Wong, G K L
2017-02-28
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic 'space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of 'numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Authors.
Helically twisted photonic crystal fibres
Russell, P. St. J.; Beravat, R.; Wong, G. K. L.
2017-02-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic `space', cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of `numerical experiments' based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue 'Optical orbital angular momentum'.
Helically twisted photonic crystal fibres
Beravat, R.; Wong, G. K. L.
2017-01-01
Recent theoretical and experimental work on helically twisted photonic crystal fibres (PCFs) is reviewed. Helical Bloch theory is introduced, including a new formalism based on the tight-binding approximation. It is used to explore and explain a variety of unusual effects that appear in a range of different twisted PCFs, including fibres with a single core and fibres with N cores arranged in a ring around the fibre axis. We discuss a new kind of birefringence that causes the propagation constants of left- and right-spinning optical vortices to be non-degenerate for the same order of orbital angular momentum (OAM). Topological effects, arising from the twisted periodic ‘space’, cause light to spiral around the fibre axis, with fascinating consequences, including the appearance of dips in the transmission spectrum and low loss guidance in coreless PCF. Discussing twisted fibres with a single off-axis core, we report that optical activity in a PCF is opposite in sign to that seen in a step-index fibre. Fabrication techniques are briefly described and emerging applications reviewed. The analytical results of helical Bloch theory are verified by an extensive series of ‘numerical experiments’ based on finite-element solutions of Maxwell's equations in a helicoidal frame. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069771
Cui, Lin-ying; Liu, Fei
2008-01-01
Spider dragline silk is an intriguing biomaterial of practical use, and it has long been suggested to be a liquid crystalline material. We model the dragline silk as nematics by using continuum liquid crystal theory. The overall stress-strain curve and the yield point can be evaluated quantitatively and agree with experiment data well. Additionally, our model can account for the drop of stress in wet spider dragline, i.e. in supercontracted dragline silk.
Impact of Nanoparticles on Nematic Ordering in Square Wells
Directory of Open Access Journals (Sweden)
M. Slavinec
2015-01-01
Full Text Available Nematic liquid crystalline structures within square wells are studied numerically using both Lebwohl-Lasher lattice semimicroscopic and the Landau-de Gennes mesoscopic approach. At lateral boundary wall strong planar anchoring is enforced. The cell thickness h along the z Cartesian coordinate is assumed to be smaller than the characteristic square well size R. Using semimicroscopic modelling we restrict to effectively two-dimensional systems which we study in terms of the tensor nematic order parameter. We consider impact of appropriate nanoparticles (NPs on nematic configuration for cases where R becomes comparable to the biaxial order parameter correlation length. In this case a star-like order reconstruction biaxial profile could be formed in absence of NPs. We demonstrate existence of a rich variety of different nematic structures, including topological defects, which are enabled by presence of appropriate NPs.
Defect driven shapes in nematic droplets: analogies with cell division
Leoni, Marco; Bowick, Mark J; Marchetti, M Cristina
2016-01-01
Building on the striking similarity between the structure of the spindle during mitosis in living cells and nematic textures in confined liquid crystals, we use a continuum model of two-dimensional nematic liquid crystal droplets, to examine the physical aspects of cell division. The model investigates the interplay between bulk elasticity of the microtubule assembly, described as a nematic liquid crystal, and surface elasticity of the cell cortex, modelled as a bounding flexible membrane, in controlling cell shape and division. The centrosomes at the spindle poles correspond to the cores of the topological defects required to accommodate nematic order in a closed geometry. We map out the progression of both healthy bipolar and faulty multi-polar division as a function of an effective parameter that incorporates active processes and controls centrosome separation. A robust prediction, independent of energetic considerations, is that the transition from a single cell to daughters cells occurs at critical value...
Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface
Directory of Open Access Journals (Sweden)
Vasily F. Shabanov
2013-08-01
Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.
Adsorption phenomena and anchoring energy in nematic liquid crystals
Barbero, Giovanni
2005-01-01
Despite the large quantity of phenomenological information concerning the bulk properties of nematic phase liquid crystals, little is understood about the origin of the surface energy, particularly the surface, interfacial, and anchoring properties of liquid crystals that affect the performance of liquid crystal devices. Self-contained and unique, Adsorption Phenomena and Anchoring Energy in Nematic Liquid Crystals provides an account of new and established results spanning three decades of research into the problems of anchoring energy and adsorption phenomena in liquid crystals.The book contains a detailed discussion of the origin and possible sources of anchoring energy in nematic liquid crystals, emphasizing the dielectric contribution to the anchoring energy in particular. Beginning with fundamental surface and anchoring properties of liquid crystals and the definition of the nematic phase, the authors explain how selective ion adsorption, dielectric energy density, thickness dependence, and bias voltage...
Colloidal interactions in two-dimensional nematic emulsions
Indian Academy of Sciences (India)
N M Silvestre; P Patrício; M M Telo Da Gama
2005-06-01
We review theoretical and experimental work on colloidal interactions in two-dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions between colloids and fluid (deformable) interfaces and the shape of fluid colloids in smectic-C films.
Sheng, C; Chen, Q; Norwood, R A; Wang, J; Thomas, J; Peyghambarian, N
2011-10-20
We have examined pure nematic liquid crystal (LC), 4'-pentyl-4-biphenylcarbonitrile (5-CB), with a 90° twisted alignment within a cell made of two cross-polarized absorptive plastic polarizers, and investigated the nonlinear transmission properties using cw (532 nm) lasers. We observed optically self-activated polarization switching with a factor of three lower switching power than a dye-doped LC cell with similar linear transmittance using glass substrates. We also studied the dynamics of the switching processes and observed millisecond switching time. These studies have demonstrated a simpler but more efficient way for fabricating broadband, low switching power, millisecond time scale switching, and optical limiting devices. © 2011 Optical Society of America
Surface-plasmon-polariton wave propagation guided by a metal slab in a sculptured nematic thin film
Faryad, Muhammad
2010-01-01
Surface-plasmon-polariton~(SPP) wave propagation guided by a metal slab in a periodically nonhomogeneous sculptured nematic thin film~(SNTF) was studied theoretically. The morphologically significant planes of the SNTF on both sides of the metal slab could either be aligned or twisted with respect to each other. The canonical boundary-value problem was formulated, solved for SPP-wave propagation, and examined to determine the effect of slab thickness on the multiplicity and the spatial profiles of SPP waves. Decrease in slab thickness was found to result in more intense coupling of two metal/SNTF interfaces. But when the metal slab becomes thicker, the coupling between the two interfaces reduces and SPP waves localize to one of the two interfaces. The greater the coupling between the two metal/SNTF interfaces, the smaller is the phase speed.
Blinov, Lev M.; Barberi, Riccardo; Kozlovsky, Mikhail V.; Lazarev, Vladimir V.; de Santo, Maria P.
Spin coated films of a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains are optically isotropic in their twisted smectic-like glassy state. In contact with a nematic liquid crystal (5CB, E7, MBBA) they provide a degenerate planar orientation. When irradiated by unpolarized UV light, they orient the same nematics homeotropically. Treated with linearly polarized UV light they orient nematics homogeneously with the director along the electric vector of the exciting light. After a combined irradiation first with unpolarized UV light and then with linearly polarized visible light, the films again provide a homogeneous liquid crystal orientation, this time with the director perpendicular to the visible light electric vector. The phenomena observed are related to the light induced optical anisotropy. Two main processes are responsible for the anisotropy (1) a UV light depletion of trans-isomers of the azobenzene chromophores from the chosen direction and (2) a reorientation of the chromophores by polarized visible light.
Liang, Shuhua; Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio
2015-09-01
The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic in-plane quenched disorder strength and dilution by means of computational techniques applied to a three-orbital (x z ,y z ,x y ) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. In this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly, our Monte Carlo simulations reveal that the fast reduction with doping of the Néel TN and the structural TS transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled in our model by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi surface produced by electron doping affect only slightly both critical temperatures. Our results also suggest that the specific material-dependent phase diagrams experimentally observed could be explained as a consequence of the variation in disorder profiles introduced by the different dopants. Our findings are also compatible with neutron scattering and scanning tunneling microscopy, unveiling a patchy network of locally magnetically ordered clusters with anisotropic shapes, even though the quenched disorder is locally isotropic. This study reveals a remarkable and unexpected degree of complexity in pnictides: the fragile tendency to nematicity intrinsic of translational invariant electronic systems needs to be supplemented by quenched disorder and dilution to stabilize the robust nematic phase experimentally found in electron-doped 122 compounds.
Wu, A M; Shen, F; Herp, A; Song, S C; Wu, J H
1995-02-27
Fraction A of the armadillo submandibular glycoprotein (ASG-A) is one of the simplest glycoproteins among mammalian salivary mucins. The carbohydrate side chains of this mucous glycoprotein have one-third of the NeuAc alpha 2-->6GalNAc (sialyl-Tn) sequence and two thirds of Tn (GalNAc alpha-->Ser/Thr) residues. Those of the desialylated product (ASG-Tn) are almost exclusively unsubstituted GalNAc residues (Tn determinant). When the binding properties of these glycoproteins were tested by a precipitin assay with Gal, GalNAc and GlcNAc specific lectins, it was found that ASG-Tn reacted strongly with all of the Tn-active lectins and completely precipitated Vicia villosa (VVL both B4 and mixture of A and B), Maclura pomifera (MPA), and Artocarpus integrifolia (jacalin) lectins. However, it precipitated poorly or negligibly with Ricinus communis (RCA1); Dolichos biflorus (DBA); Viscum album, ML-I; Arachis hypogaea (PNA), and Triticum vulgaris (WGA). The reactivity of ASG-A (sialyl-Tn) was as active as that of ASG-Tn with MPA and less or slightly less active than that of ASG-Tn with VVL-A+B, VVL-B4, HPA, WFA, and jacalin, as one-third of its Tn was sialylated. These findings indicate that ASG-A and its desialylated product (ASG-Tn) are highly useful reagents for the differentiation of Tn, T (Gal beta 1-->3GalNAc), A (GalNAc alpha 1-->3Gal) or Gal specific lectins and monoclonal antibodies against such epitopes.
Renormalization constants for 2-twist operators in twisted mass QCD
Alexandrou, C; Korzec, T; Panagopoulos, H; Stylianou, F
2010-01-01
Perturbative and non-perturbative results on the renormalization constants of the fermion field and the twist-2 fermion bilinears are presented with emphasis on the non-perturbative evaluation of the one-derivative twist-2 vector and axial vector operators. Non-perturbative results are obtained using the twisted mass Wilson fermion formulation employing two degenerate dynamical quarks and the tree-level Symanzik improved gluon action. The simulations have been performed for pion masses in the range of about 450-260 MeV and at three values of the lattice spacing $a$ corresponding to $\\beta=3.9, 4.05, 4.20$. Subtraction of ${\\cal O}(a^2)$ terms is carried out by performing the perturbative evaluation of these operators at 1-loop and up to ${\\cal O}(a^2)$. The renormalization conditions are defined in the RI$'$-MOM scheme, for both perturbative and non-perturbative results. The renormalization factors, obtained for different values of the renormalization scale, are evolved perturbatively to a reference scale set...
Oh, Jiyoung; Gleeson, Helen F.; Dierking, Ingo
2017-02-01
The application of an electric field to microspheres suspended in a liquid crystal causes particle translation in a plane perpendicular to the applied field direction. Depending on applied electric field amplitude and frequency, a wealth of different motion modes may be observed above a threshold, which can lead to linear, circular, or random particle trajectories. We present the stability diagram for these different translational modes of particles suspended in the isotropic and the chiral nematic phase of a liquid crystal and investigate the angular velocity, circular diameter, and linear velocity as a function of electric field amplitude and frequency. In the isotropic phase a narrow field amplitude-frequency regime is observed to exhibit circular particle motion whose angular velocity increases with applied electric field amplitude but is independent of applied frequency. The diameter of the circular trajectory decreases with field amplitude as well as frequency. In the cholesteric phase linear as well as circular particle motion is observed. The former exhibits an increasing velocity with field amplitude, while decreasing with frequency. For the latter, the angular velocity exhibits an increase with field amplitude and frequency. The rotational sense of the particles on a circular trajectory in the chiral nematic phase is independent of the helicity of the liquid crystalline structure, as is demonstrated by employing a cholesteric twist inversion compound.
Kalinovskii, I. O.; Mastshenko, V. I.; Vinokur, R. A.; Boiko, Natalia I.; Shibaev, Peter V.; Shibaev, Valery P.
1998-01-01
The synthetic pathways of preparation of new optically active 1,1-binaphthyl (BN) derivatives containing various radicals including mesogenic ones were suggested and realized. No mesophase was found, but having atropisomeric chirality origin the novel substances proved to be effective chiral dopants inducing the highly twisted supramolecular structure both in low molecular mass and in polymer liquid crystals (LC). The helical twisting power (HTP) in two different standard nematic mixtures and in the copolymers based on the nematogenic methoxy-phenyl benzoate acrylic monomer was investigated. The systematic growth of the HTP in the low molecular mass nematics was found when the longer or mesogenic radicals were attached to the binaphthyl core. In the LC-copolymers the HTP of the BN-monomer and mesophase stability were analyzed depending on temperature and the molar fraction of the BN-fragments. The observed HTP value was found to be about thrice as much as those reported for the cholesterol and binaphthyl chiral monomers.
Functional Characterization of Tn4401, a Tn3-Based Transposon Involved in blaKPC Gene Mobilization
G Cuzon; Naas, T; Nordmann, P
2011-01-01
The carbapenemase gene blaKPC, which is rapidly spreading worldwide, is located on a Tn3-based transposon, Tn4401. In a transposition-conjugation assay, Tn4401 was able to mobilize blaKPC-2 gene at a frequency of 4.4 × 10−6/recipient cell. A 5-bp target site duplication was evidenced upon each insertion without target site specificity. This study demonstrated that Tn4401 is an active transposon capable of mobilizing blaKPC genes at high frequency.
The twist box domain is required for Twist1-induced prostate cancer metastasis.
Gajula, Rajendra P; Chettiar, Sivarajan T; Williams, Russell D; Thiyagarajan, Saravanan; Kato, Yoshinori; Aziz, Khaled; Wang, Ruoqi; Gandhi, Nishant; Wild, Aaron T; Vesuna, Farhad; Ma, Jinfang; Salih, Tarek; Cades, Jessica; Fertig, Elana; Biswal, Shyam; Burns, Timothy F; Chung, Christine H; Rudin, Charles M; Herman, Joseph M; Hales, Russell K; Raman, Venu; An, Steven S; Tran, Phuoc T
2013-11-01
Twist1, a basic helix-loop-helix transcription factor, plays a key role during development and is a master regulator of the epithelial-mesenchymal transition (EMT) that promotes cancer metastasis. Structure-function relationships of Twist1 to cancer-related phenotypes are underappreciated, so we studied the requirement of the conserved Twist box domain for metastatic phenotypes in prostate cancer. Evidence suggests that Twist1 is overexpressed in clinical specimens and correlated with aggressive/metastatic disease. Therefore, we examined a transactivation mutant, Twist1-F191G, in prostate cancer cells using in vitro assays, which mimic various stages of metastasis. Twist1 overexpression led to elevated cytoskeletal stiffness and cell traction forces at the migratory edge of cells based on biophysical single-cell measurements. Twist1 conferred additional cellular properties associated with cancer cell metastasis including increased migration, invasion, anoikis resistance, and anchorage-independent growth. The Twist box mutant was defective for these Twist1 phenotypes in vitro. Importantly, we observed a high frequency of Twist1-induced metastatic lung tumors and extrathoracic metastases in vivo using the experimental lung metastasis assay. The Twist box was required for prostate cancer cells to colonize metastatic lung lesions and extrathoracic metastases. Comparative genomic profiling revealed transcriptional programs directed by the Twist box that were associated with cancer progression, such as Hoxa9. Mechanistically, Twist1 bound to the Hoxa9 promoter and positively regulated Hoxa9 expression in prostate cancer cells. Finally, Hoxa9 was important for Twist1-induced cellular phenotypes associated with metastasis. These data suggest that the Twist box domain is required for Twist1 transcriptional programs and prostate cancer metastasis. Targeting the Twist box domain of Twist1 may effectively limit prostate cancer metastatic potential. ©2013 AACR.
"Twisted" black holes are unphysical
Gray, Finnian; Schuster, Sebastian; Visser, Matt
2016-01-01
So-called "twisted" black holes have recently been proposed by Zhang (1609.09721 [gr-qc]), and further considered by Chen and Jing (1610.00886 [gr-qc]), and more recently by Ong (1610.05757 [gr-qc]). While these spacetimes are certainly Ricci-flat, and so mathematically satisfy the vacuum Einstein equations, they are also merely minor variants on Taub--NUT spacetimes. Consequently they exhibit several unphysical features that make them quite unreasonable as realistic astrophysical objects. Specifically, these "twisted" black holes are not (globally) asymptotically flat. Furthermore, they contain closed timelike curves that are not hidden behind any event horizon --- the most obvious of these closed timelike curves are small azimuthal circles around the rotation axis, but the effect is more general. The entire region outside the horizon is infested with closed timelike curves.
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-01-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms. PMID:27586824
Polarization twist in perovskite ferrielectrics
Kitanaka, Yuuki; Hirano, Kiyotaka; Ogino, Motohiro; Noguchi, Yuji; Miyayama, Masaru; Moriyoshi, Chikako; Kuroiwa, Yoshihiro
2016-09-01
Because the functions of polar materials are governed primarily by their polarization response to external stimuli, the majority of studies have focused on controlling polar lattice distortions. In some perovskite oxides, polar distortions coexist with nonpolar tilts and rotations of oxygen octahedra. The interplay between nonpolar and polar instabilities appears to play a crucial role, raising the question of how to design materials by exploiting their coupling. Here, we introduce the concept of ‘polarization twist’, which offers enhanced control over piezoelectric responses in polar materials. Our experimental and theoretical studies provide direct evidence that a ferrielectric perovskite exhibits a large piezoelectric response because of extended polar distortion, accompanied by nonpolar octahedral rotations, as if twisted polarization relaxes under electric fields. The concept underlying the polarization twist opens new possibilities for developing alternative materials in bulk and thin-film forms.
Energy Technology Data Exchange (ETDEWEB)
Sicard, D.; Verdier, A. [COGEMA Logistics (AREVA Group) (France); Monsigny, P.A. [NOK/KKL (Switzerland)
2004-07-01
The LEIBSTADT (KKL) nuclear power plant in Switzerland has opted to ship spent fuel to a central facility called ZWILAG for interim storage. In the mid-nineties, COGEMA LOGISTICS was contracted by KKL for the supply of the TN trademark a52L and TN trademark 97L transport and storage casks for BWR fuel types. In 2003, KKL also ordered from COGEMA LOGISTICS the supply of six TNae24 BHL transport and storage casks. This paper shows how all the three cask designs have responded to the KKL needs to ship and store BWR spent fuel. In addition, it highlights the already significant operational feedback of the TN trademark 52L and TN trademark 97L casks by the KKL and ZWILAG operators.
Twisted Chern-Simons supergravity
Energy Technology Data Exchange (ETDEWEB)
Castellani, L. [Dipartimento di Scienze e Innovazione Tecnologica, Univ. del Piemonte Orientale, Alessandria (Italy); INFN Gruppo collegato di Alessandria (Italy)
2014-09-11
We present a noncommutative version of D = 5 Chern-Simons supergravity, where noncommutativity is encoded in a *-product associated to an abelian Drinfeld twist. The theory is invariant under diffeomorphisms, and under the *-gauge supergroup SU(2,2 vertical stroke 4), including Lorentz and N = 4 local supersymmetries. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Counting Polyominoes on Twisted Cylinders
Barequet, Gill; Moffie, Micha; Ribó, Ares; Rote, Günter
2005-01-01
International audience; We improve the lower bounds on Klarner's constant, which describes the exponential growth rate of the number of polyominoes (connected subsets of grid squares) with a given number of squares. We achieve this by analyzing polyominoes on a different surface, a so-called $\\textit{twisted cylinder}$ by the transfer matrix method. A bijective representation of the "states'' of partial solutions is crucial for allowing a compact representation of the successive iteration vec...
New twist on artificial muscles
Haines, Carter S.; Li, Na; Spinks, Geoffrey M.; Aliev, Ali E.; Di, Jiangtao; Baughman, Ray H.
2016-01-01
Lightweight artificial muscle fibers that can match the large tensile stroke of natural muscles have been elusive. In particular, low stroke, limited cycle life, and inefficient energy conversion have combined with high cost and hysteretic performance to restrict practical use. In recent years, a new class of artificial muscles, based on highly twisted fibers, has emerged that can deliver more than 2,000 J/kg of specific work during muscle contraction, compared with just 40 J/kg for natural muscle. Thermally actuated muscles made from ordinary polymer fibers can deliver long-life, hysteresis-free tensile strokes of more than 30% and torsional actuation capable of spinning a paddle at speeds of more than 100,000 rpm. In this perspective, we explore the mechanisms and potential applications of present twisted fiber muscles and the future opportunities and challenges for developing twisted muscles having improved cycle rates, efficiencies, and functionality. We also demonstrate artificial muscle sewing threads and textiles and coiled structures that exhibit nearly unlimited actuation strokes. In addition to robotics and prosthetics, future applications include smart textiles that change breathability in response to temperature and moisture and window shutters that automatically open and close to conserve energy. PMID:27671626
The Role of Sialyl-Tn in Cancer
Directory of Open Access Journals (Sweden)
Jennifer Munkley
2016-02-01
Full Text Available Activation of an aberrant glycosylation pathway in cancer cells can lead to expression of the onco-foetal sialyl-Tn (sTn antigen. STn is a truncated O-glycan containing a sialic acid α-2,6 linked to GalNAc α-O-Ser/Thr and is linked with an adverse outcome and poor prognosis in cancer patients. The biosynthesis of the sTn antigen has been linked to the expression of the sialytransferase ST6GalNAc1, and also to mutations in and loss of heterozygosity of the COSMC gene. sTn neo- or over-expression occurs in many types of epithelial cancer including gastric, colon, breast, lung, oesophageal, prostate and endometrial cancer. sTn is believed to be carried by a variety of glycoproteins and may influence protein function and be involved in tumour development. This review discusses how the role of sTn in cancer development and tumour cell invasiveness might be organ specific and occur through different mechanisms depending on each cancer type or subtype. As the sTn-antigen is expressed early in carcinogenesis targeting sTn in cancer may enable the targeting of tumours from the earliest stage.
A review of the TN theory and its cousins
Tachikawa, Yuji
2015-11-01
The T_N theory is a four-dimensional N = 2 superconformal field theory that has played a central role in the analysis of supersymmetric dualities in the last few years. The aim of this review is to collect known properties of the T_N theory and its cousins in one place as a quick reference.
Simple mucins (T, sialosyl-T, Tn and sialosyl-Tn) are not diagnostic for malignant breast lesions
DEFF Research Database (Denmark)
Reed, W; Bryne, M; Clausen, H
1994-01-01
Immunohistochemical study of the distribution of carbohydrate core-structures on O-linked glycoproteins (T, sialosyl-T, Tn and sialosyl-Tn) was performed using specific monoclonal antibodies on 148 primary breast lesions, including 10 normal breast tissues, 16 benign lesions and 122 invasive carc...
Simple mucins (T, sialosyl-T, Tn and sialosyl-Tn) are not diagnostic for malignant breast lesions
DEFF Research Database (Denmark)
Reed, W; Bryne, M; Clausen, H
1994-01-01
positive for T antigen, 82% for s-T antigen, 66% for Tn antigen and 22% for s-Tn antigen. The staining pattern was nearly identical for carcinomas with and without lymph node metastases. In conclusion, immunostaining for simple mucins does not permit a clear distinction between benign and malignant breast...
Noncommutative principal bundles through twist deformation
Aschieri, Paolo; Pagani, Chiara; Schenkel, Alexander
2016-01-01
We construct noncommutative principal bundles deforming principal bundles with a Drinfeld twist (2-cocycle). If the twist is associated with the structure group then we have a deformation of the fibers. If the twist is associated with the automorphism group of the principal bundle, then we obtain noncommutative deformations of the base space as well. Combining the two twist deformations we obtain noncommutative principal bundles with both noncommutative fibers and base space. More in general, the natural isomorphisms proving the equivalence of a closed monoidal category of modules and its twist related one are used to obtain new Hopf-Galois extensions as twists of Hopf-Galois extensions. A sheaf approach is also considered, and examples presented.
The Twist Limit for Bipolar Active Regions
Moore, Ron; Falconer, David; Gary, Allen
2008-01-01
We present new evidence that further supports the standard idea that active regions are emerged magnetic-flux-rope omega loops. When the axial magnetic twist of a cylindrical flux rope exceeds a critical amount, the flux rope becomes unstable to kinking, and the excess axial twist is converted into writhe twist by the kinking. This suggests that, if active regions are emerged omega loops, then (1) no active region should have magnetic twist much above the limit set by kinking, (2) active regions having twist near the limit should often arise from kinked omega loops, and (3) since active regions having large delta sunspots are outstandingly twisted, these arise from kinked omega loops and should have twist near the limit for kinking. From each of 36 vector magnetograms of bipolar active regions, we have measured (1) the total flux of the vertical field above 100 G, (2) the area covered by this flux, and (3) the net electric current that arches over the polarity inversion line. These three quantities yield an estimate of the axial magnetic twist in a simple model cylindrical flux rope that corresponds to the top of the active region s hypothetical omega loop prior to emergence. In all 36 cases, the estimated twist is below the critical limit for kinking. The 11 most twisted active regions (1) have estimated twist within a factor of approx.3 of the limit, and (2) include all of our 6 active regions having large delta sunspots. Thus, our observed twist limit for bipolar active regions is in good accord with active regions being emerged omega loops.
Fine structure of point defects and soliton decay in nematic liquid crystals
Penzenstadler, E.; Trebin, H. -R.
1989-01-01
On the basis of Landau-de Gennes-theory it is demonstrated that point defects in nematic liquid crystals may have a biaxial nonsingular core. From this result a critical diameter is derived for linear topological solitons in nematics. Solitons of smaller diameter can relax to the uniform nematic state without energy barrier via an intermediate biaxial phase.
DVCS amplitude with kinematical twist-3 terms
Radyushkin, A V
2000-01-01
We compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude we include the operators of twist-3 which appear as total derivatives of twist-2 operators. Our results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. We find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.
Macroscopic Behavior of Nematics with D2d Symmetry
Pleiner, Harald; Brand, Helmut R.
2010-03-01
We discuss the symmetry properties and the macroscopic behavior of a nematic liquid crystal phase with D2d symmetry. Such a phase is a prime candidate for nematic phases made from banana-shaped molecules where the usual quadrupolar order coexists with octupolar (tetrahedratic) order. The resulting nematic phase is non-polar. While this phase could resemble the classic D∞h nematic in the polarizing microscope, it has many static as well as reversible and irreversible properties unknown to non-polar nematics without octupolar order. In particular, there is a linear gradient term in the free energy that selects parity leading to ambidextrously helical ground states when the molecules are achiral. In addition, there are static and irreversible coupling terms of a type only met otherwise in macroscopically chiral liquid crystals, e.g. the ambidextrous analogues of Lehmann-type effects known from cholesteric liquid crystals. Finally, we discuss certain nonlinear aspects of the dynamics related to the non-commutativity of three-dimensional finite rotations as well as other structural nonlinear hydrodynamic effects.
Stability of Disclinations in Nematic Liquid Crystals
Institute of Scientific and Technical Information of China (English)
WANG Yu-Sheng; YANG Guo-Hong; TIAN Li-Jun; DUAN Yi-Shi
2006-01-01
In the light of φ-mapping method and topological current theory, the stability of disclinations around a spherical particle in nematic liquid crystals is studied. We consider two different defect structures around a spherical particle: disclination ring and point defect at the north or south pole of the particle. We calculate the free energy of these different defects in the elastic theory. It is pointed out that the total Frank free energy density can be divided into two parts. One is the distorted energy density of director field around the disclinations. The other is the free energy density of disclinations themselves, which is shown to be concentrated at the defect and to be topologically quantized in the unit of (k -k24)π/2. It is shown that in the presence of saddle-splay elasticity a dipole (radial and hyperbolic hedgehog) configuration that accompanies a particle with strong homeotropic anchoring takes the structure of a small disclination ring, not a point defect.
Twisted conjugacy in braid groups
González-Meneses, Juan
2011-01-01
In this note we solve the twisted conjugacy problem for braid groups, i.e. we propose an algorithm which, given two braids $u,v\\in B_n$ and an automorphism $\\phi \\in Aut (B_n)$, decides whether $v=(\\phi (x))^{-1}ux$ for some $x\\in B_n$. As a corollary, we deduce that each group of the form $B_n \\rtimes H$, a semidirect product of the braid group $B_n$ by a torsion-free hyperbolic group $H$, has solvable conjugacy problem.
DEFF Research Database (Denmark)
de Vries, Lisbeth Elvira; Christensen, H.; Skov, R. L.
2009-01-01
To analyse the sequence diversity of the tetracycline resistance gene tet(M) in Staphylococcus aureus from humans and animals and to determine mobile elements associated with tet(M) in S. aureus. In total, 205 tetracycline-resistant isolates were screened for tet(M) by PCR. tet(M) genes were...... sequenced and compared with tet(M) deposited in GenBank. Based on phylogenetic analysis isolates were screened for Tn916- and Tn5801-like xis/int genes, and transposons were confirmed by linking PCR. spa typing was performed and selected isolates were used as donors in a filter mating experiment. Forty......-one isolates (21.3%, 60.7%, 2.6% and 4.4% of the human, pig, poultry and cattle isolates, respectively) were tet(M) positive. tet(M) was located on Tn5801-like and Tn916-like transposons in humans and on a specific Tn916-like element in animals. Human isolates were of different spa types (t034, t008, t037, t...
Dielectrophoretic manipulation of the mixture of isotropic and nematic liquid
Kim, Soo-Dong; Lee, Bomi; Kang, Shin-Woong; Song, Jang-Kun
2015-08-01
In various applications involving liquid crystals, the manipulation of the nanoscale molecular assembly and microscale director alignment is highly useful. Here we show that a nematic-isotropic mixture, a unique bi-liquid system, has potential for the fabrication of microstructures having an ordered phase within a disordered phase, or vice versa. The volume expansion and shrinkage, migration, splitting, mergence and elongation of one phase within the other are easily accomplished via thermal treatment and dielectrophoretic manipulation. This is particularly achievable when one phase is suspended in the middle. In that case, a highly biased ordered-phase preference of surfaces, that is, the nematic-philic nature of a polyimide layer and the nematic-phobic nature of a self-assembled monolayer of chlorosilane derivatives, is used. Further, by combining this approach with photopolymerization, the patterned microstructure is solidified as a patterned polymer film having both isotropic and anisotropic molecular arrangements simultaneously, or as a template with a morphological variation.
Flow of a viscous nematic fluid around a sphere
Gómez-González, Manuel
2013-01-01
We analyze the creeping flow generated by a spherical particle moving through a viscous fluid with nematic directional order, in which momentum diffusivity is anisotropic and which opposes resistance to bending. Specifically, we provide closed-form analytical expressions for the response function, i.e. the equivalent to Stokes's drag formula for nematic fluids. Particular attention is given to the rotationally pseudo-isotropic condition defined by zero resistance to bending, and to the strain pseudo-isotropic condition defined by isotropic momentum diffusivity. We find the former to be consistent with the rheology of biopolymer networks and the latter to be closer to the rheology of nematic liquid crystals. These "pure" anisotropic conditions are used to benchmark existing particle tracking microrheology methods that provide effective directional viscosities by applying Stokes's drag law separately in different directions. We find that the effective viscosity approach is phenomenologically justified in rotati...
Nematic Ordering of Rigid Rods in a Gravitational Field
Baulin, V A; Baulin, Vladimir A.; Khokhlov, Alexei R.
1999-01-01
The isotropic-to-nematic transition in an athermal solution of long rigid rods subject to a gravitational (or centrifugal) field is theoretically considered in the Onsager approximation. The new feature emerging in the presence of gravity is a concentration gradient which coupled with the nematic ordering. For rodlike molecules this effect becomes noticeable at centrifugal acceleration g ~ 10^3--10^4 m/s^2, while for biological rodlike objects, such as tobacco mosaic virus, TMV, the effect is important even for normal gravitational acceleration conditions. Rods are concentrated near the bottom of the vessel which sometimes leads to gravity induced nematic ordering. The concentration range corresponding to phase separation increases with increasing g. In the region of phase separation the local rod concentration, as well as the order parameter, follow a step function with height.
Quenched disorder and spin-glass correlations in XY nematics
Energy Technology Data Exchange (ETDEWEB)
Petridis, L; Terentjev, E M [Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE (United Kingdom)
2006-08-04
We present a theoretical study of the equilibrium ordering in a 3D XY nematic system with quenched random disorder. Within this model, treated with the replica trick and Gaussian variational method, the correlation length is obtained as a function of the local nematic order parameter Q and the effective disorder strength {gamma}. These results, {xi} {approx} Q{sup 2}e{sup 1/Q{sup 2}} and {xi} {approx} (1/{gamma}) e{sup -{gamma}}, clarify what happens in the limiting cases of diminishing Q and {gamma}, that is near a phase transition of a pure system. In particular, it is found that quenched disorder is irrelevant as Q {yields} 0 and hence does not change the character of the continuous XY nematic-isotropic phase transition. We discuss how these results compare with experiments and simulations.
Nematic ordering dynamics of an antiferromagnetic spin-1 condensate
Symes, L. M.; Blakie, P. B.
2017-07-01
We consider the formation of order in a quasi-two-dimensional antiferromagnetic spin-1 condensate quenched from an easy-axis to an easy-plane nematic phase. We define the relevant order parameter to quantify the spin-nematic degrees of freedom and study the evolution of the spin-nematic and superfluid order during the coarsening dynamics using numerical simulations. We observe dynamical scaling in the late-time dynamics, with both types of order extending across the system with a diffusive growth law. We identify half-quantum vortices as the relevant topological defects of the ordering dynamics and demonstrate that the growth of both types of order is determined by the mutual annihilation of these vortices.
STRUCTURE FORMATION OF COLLOIDS IN NEMATIC LIQUID CRYSTALS
Directory of Open Access Journals (Sweden)
B.I.Lev
2003-01-01
Full Text Available We investigated the behaviour of colloidal particles suspended in nematic liquid crystals. These colloidal particles interact through elastic deformation of the nematic director field which can result in nontrivial collective behavior, leading to the formation of spatially modulated structures. In this paper, the formation of lattice structures is described both by computer simulations and by analytical theory. Effective interactions of the pairs of spherical macroparticles suspended in nematic liquid crystals have been suggested by many authors. Using these pairwise interactions, spatial structures are obtained by means of dynamic simulations. We have suggested a number of possible structures, which may be formed in multi-macroparticle systems. Regions of temperatures and concentrations are determined in which such a structure might appear.
Electroosmotically enabled Electrorheological Effects in a Planar Nematic Crystal Flow
Dhar, Jayabrata; Chakraborty, Suman
2016-01-01
Study of electrokinetics of nematic liquid crystals (LCs) with dissolved impurities hold utmost importance in understanding director distribution characteristics and modified flow rheology. However, no concrete theory for the non-uniform potential and ionic species distribution, due to an induced electrical double layer (EDL) at the LC-substrate interface, derived from fundamental principles have been put forward in this regard. In this work, we have developed coupled governing equations from fundamental free energy considerations for the potential distribution and the director configuration of the nematic LC within the induced electrical double layer which is generated due to certain physico-chemical interactions at the LC-substrate interface. With these considerations, an electroosmotically-enabled nematodynamics for a particular LC, namely, MBBA, with strong planar anchoring at the boundaries is studied. We obtained multiple solution for director configuration, which is an integral characteristics of nemat...
Ketov, Sergei V.; Lechtenfeld, Olaf; Parkes, Andrew J.
1995-03-01
The most general homogeneous monodromy conditions in N=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)⊗openZ2. For classes which generate a discrete subgroup Γ, the corresponding target space backgrounds openC1,1/Γ include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for Γ=open1 (untwisted) and Γ=openZ2 (in the manner of Mathur and Mukhi), as well as for Γ being a parabolic element of U(1,1). In particular, the 16 openZ2-twisted sectors of the N=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of ``spacetime'' supersymmetry, with the number of supersymmetries being dependent on global ``spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless ``spacetime'' fermions.
Symmetry fractionalization and twist defects
Tarantino, Nicolas; Lindner, Netanel H.; Fidkowski, Lukasz
2016-03-01
Topological order in two-dimensions can be described in terms of deconfined quasiparticle excitations—anyons—and their braiding statistics. However, it has recently been realized that this data does not completely describe the situation in the presence of an unbroken global symmetry. In this case, there can be multiple distinct quantum phases with the same anyons and statistics, but with different patterns of symmetry fractionalization—termed symmetry enriched topological order. When the global symmetry group G, which we take to be discrete, does not change topological superselection sectors—i.e. does not change one type of anyon into a different type of anyon—one can imagine a local version of the action of G around each anyon. This leads to projective representations and a group cohomology description of symmetry fractionalization, with the second cohomology group {H}2(G,{{ A }}{{abelian}}) being the relevant group. In this paper, we treat the general case of a symmetry group G possibly permuting anyon types. We show that despite the lack of a local action of G, one can still make sense of a so-called twisted group cohomology description of symmetry fractionalization, and show how this data is encoded in the associativity of fusion rules of the extrinsic ‘twist’ defects of the symmetry. Furthermore, building on work of Hermele (2014 Phys. Rev. B 90 184418), we construct a wide class of exactly-solvable models which exhibit this twisted symmetry fractionalization, and connect them to our formal framework.
Multiple Twisted -Euler Numbers and Polynomials Associated with -Adic -Integrals
Directory of Open Access Journals (Sweden)
Jang Lee-Chae
2008-01-01
Full Text Available By using -adic -integrals on , we define multiple twisted -Euler numbers and polynomials. We also find Witt's type formula for multiple twisted -Euler numbers and discuss some characterizations of multiple twisted -Euler Zeta functions. In particular, we construct multiple twisted Barnes' type -Euler polynomials and multiple twisted Barnes' type -Euler Zeta functions. Finally, we define multiple twisted Dirichlet's type -Euler numbers and polynomials, and give Witt's type formula for them.
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Large N reduction on a twisted torus
González-Arroyo, A; Neuberger, H
2005-01-01
We consider SU(N) lattice gauge theory at infinite N defined on a torus with a CP invariant twist. Massless fermions are incorporated in an elegant way, while keeping them quenched. We present some numerical results which suggest that twisting can make numerical simulations of planar QCD more efficient.
Stress effects in twisted highly birefringent fibers
Wolinski, Tomasz R.
1994-03-01
Hydrostatic pressure and uniaxial longitudinal strain effects in twisted highly birefringent optical fibers have been investigated from the point of the Marcuse mode-coupling theory. The problem is analyzed in terms of local normal modes of the ideal fiber and in the limit of weak twist, where large linear birefringence dominates over twist effect, and therefore twist coupling between local modes is not effective. The authors present the results of birefringence measurements in highly birefringent bow-tie fibers influenced simultaneously by hydrostatic pressure up to 100 MPa and twisting the result for highly birefringent elliptical-core fibers influenced by uniaxial longitudinal strain up to 4000 (mu) (epsilon) and twisting effect. The birefringence measurement method is based on twist-induced effects and has been successfully applied in a stress environment. The experiment was conducted with a specially designed stress generating device that makes it possible to simultaneously generate various mechanical perturbations such as hydrostatic and radial pressure, axial strain and twist, allowing study of their influence on mode propagation in optical fibers. A comparison with theoretical results as well as with pervious experimental data on stress influence on the beat length parameter in highly birefringent fibers is also provided.
Decay constants from twisted mass QCD
Dimopoulos, P; Michael, C; Simula, S; Urbach, C
2008-01-01
We present results for chiral extrapolations of the mass and decay constants of the rho meson. The data sets used are the nf=2 unquenched gauge configurations generated with twisted mass fermions by the European Twisted Mass Collaboration. We describe a calculation of three decay constants in charmonium and explain why they are required.
Twisting theory for weak Hopf algebras
Institute of Scientific and Technical Information of China (English)
CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong
2008-01-01
The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).
Colloidal interactions and transport in nematic liquid crystals.
Tatarkova, S A; Burnham, D R; Kirby, A K; Love, G D; Terentjev, E M
2007-04-13
We describe a new nematic liquid-crystal colloid system which is characterized by both charge stabilization of the particles and an interaction force. We estimate the effective charge of the particles by electrophoretic measurements and find that in such systems the director anchoring energy W is very low and the particles have little director distortion around them. The interaction force is created by producing a radial distribution of the nematic order parameter around a locally isotropic region created by ir laser heating. We theoretically describe this as being due to the induced flexoelectric polarization, the quadrupolar symmetry of which provides the required long-range force acting on charged particles.
STATISTICAL MODELS FOR SEMI-RIGID NEMATIC POLYMERS
Institute of Scientific and Technical Information of China (English)
WANG Xinjiu
1995-01-01
Semi-rigid liquid crystal polymer is a class of liquid crystal polymers different from long rigid rod liquid crystal polymer to which the well-known Onsager and Flory theories are applied. In this paper, three statistical models for the semi-rigid nematic polymer were addressed. They are the elastically jointed rod model, worm-like chain model, and non-homogeneous chain model.The nematic-isotropic transition temperature was examined. The pseudo-second transition temperature is expressed analytically. Comparisons with the experiments were made and the agreements were found.
Cluster Monte Carlo simulations of the nematic-isotropic transition
Priezjev, N. V.; Pelcovits, Robert A.
2001-06-01
We report the results of simulations of the three-dimensional Lebwohl-Lasher model of the nematic-isotropic transition using a single cluster Monte Carlo algorithm. The algorithm, first introduced by Kunz and Zumbach to study two-dimensional nematics, is a modification of the Wolff algorithm for spin systems, and greatly reduces critical slowing down. We calculate the free energy in the neighborhood of the transition for systems up to linear size 70. We find a double well structure with a barrier that grows with increasing system size. We thus obtain an upper estimate of the value of the transition temperature in the thermodynamic limit.
A faster switching regime for zenithal bistable nematic displays
Energy Technology Data Exchange (ETDEWEB)
Rudin, J
1997-12-01
A simpler and faster switching regime for Zenithal Bistable Nematic displays is reported. A cell, based on homeotropic alignment of nematic liquid crystal over a continuous blazed monograting on one surface, can be switched using bipolar pulses an order of magnitude faster than monopolar pulses of the same voltage. We propose that this regime relies on simple dielectric coupling to drive the cell into a higher energy state with a long pulse time, and the relaxation into a lower energy state after the creation of surface defects from a shorter applied pulse. Although flexoelectric effects are observed, they do not form the basis of state selection as was proposed for the monopolar pulses
Kato, J; Miyake, A; Kato, Junji; Kawamoto, Noboru; Miyake, Akiko
2005-01-01
We propose N=4 twisted superspace formalism in four dimensions by introducing Dirac-Kahler twist. In addition to the BRST charge as a scalar counter part of twisted supercharge we find vector and tensor twisted supercharges. By introducing twisted chiral superfield we explicitly construct off-shell twisted N=4 SUSY invariant action. We can propose variety of supergauge invariant actions by introducing twisted vector superfield. We may, however, need to find further constraints to identify twisted N=4 super Yang-Mills action. We propose a superconnection formalism of twisted superspace where constraints play a crucial role. It turns out that N=4 superalgebra of Dirac-Kahler twist can be decomposed into N=2 sectors. We can then construct twisted N=2 super Yang-Mills actions by the superconnection formalism of twisted superspace in two and four dimensions.
Transposon Tn5 specifies streptomycin resistance in Rhizobium spp.
1984-01-01
Transposon Tn5 conferred streptomycin resistance on different strains of Rhizobium meliloti, Rhizobium leguminosarum, and Rhizobium trifolii but not on Escherichia coli. A gene (str) specifying this phenotype has been identified and localized on the physical and genetic map of Tn5. It is transcribed from the promoter of neo, the gene that encodes neomycin phosphotransferase. The str gene is downstream from neo in a single transcriptional unit, as revealed by molecular cloning of different seg...
Host-dependent transposon Tn5-mediated streptomycin resistance.
1984-01-01
Transposon Tn5 encodes streptomycin resistance in addition to kanamycin-neomycin resistance. This resistance was not detectable in Escherichia coli but was efficiently expressed in Rhizobium meliloti and certain other strains. By analysis of cloned Tn5 restriction endonuclease fragments, the streptomycin resistance (str) gene was located in the right-hand side of the central region as the transposon is conventionally drawn. Transcription of str appeared to originate at pL, the promoter for th...
Nematic quantum critical point without magnetism in FeSe1-xSx superconductors
Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada
2016-07-01
In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near ≈0.17, the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.
Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.
Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada
2016-07-19
In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.
Hidden Beauty in Twisted Viking Neck Rings
Olsen, Kasper
2010-01-01
Many hoards found in Ireland, Scotland, Orkney Islands, and Scandinavia demonstrate the vikings ability to fabricate beautiful arm and neck rings of twisted silver and gold rods. Characteristic for such rings is the uniform appearance of the twisted pattern along the length of the arm ring, as well as from one arm ring to another, also when found at distant geographical locations. How can the appearance of the twisted wires be so perfectly repetitive? We demonstrate that the answer is that the vikings utilized a self-forming motif: The pattern arises from a twisting of the wires to a maximally rotated configuration. That is why the twist patterns in these arm and neck rings are beautiful, repetitive, and universal.
Twisted spacetime in Einstein gravity
Zhang, Hongsheng
2016-01-01
We find a vacuum stationary twisted solution in four-dimensional Einstein gravity. Its frame dragging angular velocities are antisymmetric with respect to the equatorial plane. It possesses a symmetry of joint inversion of time and parity with respect to the equatorial plane. Its Arnowitt-Deser-Misner (ADM) mass and angular momentum are zero. It is curved but regular all over the manifold. Its Komar mass and Komar angular momentum are also zero. Its infinite red-shift surface coincides with its event horizon, since the event horizon does not rotate. Furthermore we extend this solution to the massive case, and find some similar properties. This solution is a stationary axisymmetric solution, but not Kerr. It explicitly proves that pure Einstein gravity permits different rotational mode other than Kerr. Our results demonstrate that the Einstein theory may have much more rich structures than what we ever imagine.
Twisting cracks in Bouligand structures.
Suksangpanya, Nobphadon; Yaraghi, Nicholas A; Kisailus, David; Zavattieri, Pablo
2017-06-10
The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of natural and biomimetic Bouligand structures. One particular species that utilizes the Bouligand structure to achieve outstanding mechanical performance is the smashing Mantis Shrimp, Odontodactylus Scyllarus (or stomatopod). The mantis shrimp generates high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region [16] that consists of a Bouligand structure. This region is capable of developing a significant amount of nested twisting microcracks without exhibiting catastrophic failure. The development and propagation of these microcracks are a source of energy dissipation and stress relaxation that ultimately contributes to the remarkable damage tolerance properties of the dactyl club. We develop a theoretical model to provide additional insights into the local stress intensity factors at the crack front of twisting cracks formed within the Bouligand structure. Our results reveal that changes in the local fracture mode at the crack front leads to a reduction of the local strain energy release rate, hence, increasing the necessary applied energy release rate to propagate the crack, which is quantified by the local toughening factor. Ancillary 3D simulations of the asymptotic crack front field were carried out using a J-integral to validate the theoretical values of the energy release rate and the local stress intensity factors. Copyright © 2017 Elsevier Ltd. All rights reserved.
Transient Splitting of Conoscopic Isogyres of a Uniaxial Nematic
Kim, Young-Ki; Senuk, Bohdan; Tortora, Luana; Sprunt, Samuel; Lehmann, Matthias; Lavrentovich, Oleg D.
2012-02-01
The phase identification is often based on conoscopic observations of homeotropic cells: A uniaxial nematic produces a pattern with crossed isogyres, while the biaxial nematic shows a split of isogyres. We demonstrate that the splitting of isogyres occurs even when the material remains in the uniaxial nematic phase. In particular, in the bent core material J35, splitting of isogyres is caused by change of the temperature. The effect is transient and the isogyres return to a uniaxial (crossed) configuration after a certain time that depends on sample thickness, temperature, and rate of temperature change; the time varies from a few seconds to tens of hours. The transient splitting is caused by the temperature-induced material flow that triggers a (uniaxial) director tilt in the cell. The flows and the director tilt are demonstrated by the CARS microscopy and fluorescent confocal polarizing microscopy (FCPM). This transient effect is general and can be observed even in E7 and 5CB. The effect should be considered in textural identifications of potential biaxial nematic materials.
DYNAMICS OF STRONGLY TWISTED RELATIVISTIC MAGNETOSPHERES
Energy Technology Data Exchange (ETDEWEB)
Parfrey, Kyle [Astronomy Department, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Beloborodov, Andrei M.; Hui, Lam, E-mail: parfrey@astro.princeton.edu [Physics Department and Columbia Astrophysics Laboratory, Columbia University, 538 West 120th Street, New York, NY 10027 (United States)
2013-09-10
Magnetar magnetospheres are believed to be strongly twisted due to shearing of the stellar crust by internal magnetic stresses. We present time-dependent axisymmetric simulations showing in detail the evolution of relativistic force-free magnetospheres subjected to slow twisting through large angles. When the twist amplitude is small, the magnetosphere moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the magnetosphere becomes tearing-mode unstable to forming a resistive current sheet, initiating large-scale magnetic reconnection in which a significant fraction of the magnetic free energy can be dissipated. This ''critical'' twist angle is insensitive to the resistive length scale. Rapid shearing temporarily stabilizes the magnetosphere beyond the critical angle, allowing the magnetosphere of a rapidly differentially rotating star to store and dissipate more free energy. In addition to these effects, shearing the surface of a rotating star increases the spindown torque applied to the star. If shearing is much slower than rotation, the resulting spikes in spindown rate can occur on timescales anywhere from the long twisting timescale to the stellar spin period or shorter, depending both on the stellar shear distribution and the existing distribution of magnetospheric twists. A model in which energy is stored in the magnetosphere and released by a magnetospheric instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.
Novel Properties of Twisted-Photon Absorption
Afanasev, Andrei; Mukherjee, Asmita
2014-01-01
We discuss novel features of twisted-photon absorption both by atoms and by micro-particles. First, we extend the treatment of atomic photoexcitation by twisted photons to include atomic recoil, derive generalized quantum selection rules and consider phenomena of forbidden atomic transitions. Second, we analyze the radiation pressure from twisted-photon beams on micro- and nano-sized particles and observe that for particular conditions the pressure is negative in a small area near the beam axis. A central part of the beam therefore acts as a "tractor beam".
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-07-01
In noncommutative geometry, the spectral triple of a manifold does not generate bosonic fields, for fluctuations of the Dirac operator vanish. A Connes-Moscovici twist forces the commutative algebra to be multiplied by matrices. Keeping the space of spinors untouched, twisted-fluctuations then yield perturbations of the spin connection. Applied to the spectral triple of the Standard Model, a similar twist yields the scalar field needed to stabilize the vacuum and to make the computation of the Higgs mass compatible with its experimental value.
Twist1 Is Essential for Tooth Morphogenesis and Odontoblast Differentiation.
Meng, Tian; Huang, Yanyu; Wang, Suzhen; Zhang, Hua; Dechow, Paul C; Wang, Xiaofang; Qin, Chunlin; Shi, Bing; D'Souza, Rena N; Lu, Yongbo
2015-12-04
Twist1 is a basic helix-loop-helix-containing transcription factor that is expressed in the dental mesenchyme during the early stages of tooth development. To better delineate its roles in tooth development, we generated Twist1 conditional knockout embryos (Twist2(Cre) (/+);Twist1(fl/fl)) by breeding Twist1 floxed mice (Twist1(fl/fl)) with Twist2-Cre recombinase knockin mice (Twist2(Cre) (/+)). The Twist2(Cre) (/+);Twist1(fl/fl) embryos formed smaller tooth germs and abnormal cusps during early tooth morphogenesis. Molecular and histological analyses showed that the developing molars of the Twist2(Cre) (/+);Twist1(fl/fl) embryos had reduced cell proliferation and expression of fibroblast growth factors 3, 4, 9, and 10 and FGF receptors 1 and 2 in the dental epithelium and mesenchyme. In addition, 3-week-old renal capsular transplants of embryonic day 18.5 Twist2(Cre) (/+);Twist1(fl/fl) molars showed malformed crowns and cusps with defective crown dentin and enamel. Immunohistochemical analyses revealed that the implanted mutant molars had defects in odontoblast differentiation and delayed ameloblast differentiation. Furthermore, in vitro ChIP assays demonstrated that Twist1 was able to bind to a specific region of the Fgf10 promoter. In conclusion, our findings suggest that Twist1 plays crucial roles in regulating tooth development and that it may exert its functions through the FGF signaling pathway. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.
Topological hypermultiplet on N=2 twisted superspace in four dimensions
Kato, J; Kato, Junji; Miyake, Akiko
2005-01-01
We propose a N=2 twisted superspace formalism with a central charge in four dimensions by introducing a Dirac-K\\"ahler twist. Using this formalism, we construct a twisted hypermultiplet action and find an explicit form of fermionic scalar, vector and tensor transformations. We construct a off-shell Donaldson-Witten theory coupled to the twisted hypermultiplet. We show that this action possesses N=4 twisted supersymmetry at on-shell level. It turns out that four-dimensional Dirac-K\\"ahler twist is equivalent to the Marcus's twist.
Transmission properties of cryogenic twisted pair filters
Energy Technology Data Exchange (ETDEWEB)
Song, Woon; Rehman, Mushtaq; Chong, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Ryu, Sangwan [Chonnam National University, Gwangju (Korea, Republic of)
2010-12-15
We fabricated a cryogenic low pass filter that consists of twisted pairs of manganin wires wrapped in copper tape and measured its transmission characteristics at frequencies up to 18 GHz. The dependence of the microwave transmission characteristics on the filter length was studied, which showed that a filter of length 1.0 m had a 70-dB attenuation at 1 GHz. We also studied the dependence of common- and differential-mode transmission on the number of twists per unit length and found that the number of twists per unit length affects differential-mode transmission but not common-mode transmission. Because the shielded twisted pair filter is more compact than a conventional copper powder filter, it can solve the space and thermal load issues when many cables are required for precision electronic transport experiments at low temperatures.
Mutations in the human TWIST gene.
Gripp, K W; Zackai, E H; Stolle, C A
2000-01-01
Saethre-Chotzen syndrome is a relatively common craniosynostosis disorder with autosomal dominant inheritance. Mutations in the TWIST gene have been identified in patients with Saethre-Chotzen syndrome. The TWIST gene product is a transcription factor with DNA binding and helix-loop-helix domains. Numerous missense and nonsense mutations cluster in the functional domains, without any apparent mutational hot spot. Two novel point mutations and one novel polymorphism are included in this review. Large deletions including the TWIST gene have been identified in some patients with learning disabilities or mental retardation, which are not typically part of the Saethre-Chotzen syndrome. Comprehensive studies in patients with the clinical diagnosis of Saethre-Chotzen syndrome have demonstrated a TWIST gene abnormality in about 80%, up to 37% of which may be large deletions [Johnson et al., 1998]. The gene deletions and numerous nonsense mutations are suggestive of haploinsufficiency as the disease-causing mechanism. No genotype phenotype correlation was apparent.
Observation of subluminal twisted light in vacuum
Bouchard, Frédéric; Mand, Harjaspreet; Boyd, Robert W; Karimi, Ebrahim
2015-01-01
Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over the speed of light in such media, no experimental demonstration of altered light speeds has hitherto been achieved in vacuum for ``twisted'' optical beams. We show that ``twisted'' light pulses exhibit subluminal velocities in vacuum, being slowed by 0.1\\% relative to c. This work does not challenge relativity theory, but experimentally supports a body of theoretical work on the counterintuitive vacuum group velocities of twisted pulses. These results are particularly important given recent interest in applications of twisted light to quantum information, communication and quantum key distribution.
Twisted Vector Bundles on Pointed Nodal Curves
Indian Academy of Sciences (India)
Ivan Kausz
2005-05-01
Motivated by the quest for a good compactification of the moduli space of -bundles on a nodal curve we establish a striking relationship between Abramovich’s and Vistoli’s twisted bundles and Gieseker vector bundles.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper,we construct an orbifold quantum cohomology twisted by a flat gerbe. Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtous, Pavel; Frolov, Valeri P; Kolar, Ivan
2015-01-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by `unspinning' the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of deformed and/or twisted sphere, with the deformation and twist characterized by the `Euclidean NUT' parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Gerbes and twisted orbifold quantum cohomology
Institute of Scientific and Technical Information of China (English)
PAN JianZhong; RUAN YongBin; YIN XiaoQin
2008-01-01
In this paper, we construct an orbifold quantum cohomology twisted by a flat gerbe.Then we compute these invariants in the case of a smooth manifold and a discrete torsion on a global quotient orbifold.
Deformed and twisted black holes with NUTs
Krtouš, Pavel; Kubizňák, David; Frolov, Valeri P.; Kolář, Ivan
2016-06-01
We construct a new class of vacuum black hole solutions whose geometry is deformed and twisted by the presence of NUT charges. The solutions are obtained by ‘unspinning’ the general Kerr-NUT-(A)dS spacetimes, effectively switching off some of their rotation parameters. The resulting geometry has a structure of warped space with the Kerr-like Lorentzian part warped to a Euclidean metric of a deformed and/or twisted sphere, with the deformation and twist characterized by the ‘Euclidean NUT’ parameters. In the absence of NUTs, the solution reduces to a well known Kerr-(A)dS black hole with several rotations switched off. New geometries inherit the original symmetry of the Kerr-NUT-(A)dS family, namely, they possess the full Killing tower of hidden and explicit symmetries. As expected, for vanishing NUT, twist, and deformation parameters, the symmetry is further enlarged.
Genomic pathways modulated by Twist in breast cancer
Vesuna, Farhad; Bergman, Yehudit; Raman, Venu
2017-01-01
Background The basic helix-loop-helix transcription factor TWIST1 (Twist) is involved in embryonic cell lineage determination and mesodermal differentiation. There is evidence to indicate that Twist expression plays a role in breast tumor formation and metastasis, but the role of Twist in dysregulating pathways that drive the metastatic cascade is unclear. Moreover, many of the genes and pathways dysregulated by Twist in cell lines and mouse models have not been validated against data obtaine...
DDalphaAMG for Twisted Mass Fermions
Bacchio, Simone; Finkenrath, Jacob; Frommer, Andreas; Kahl, Karsten; Rottmann, Matthias
2016-01-01
We present the Adaptive Aggregation-based Domain Decomposition Multigrid method extended to the twisted mass fermion discretization action. We show comparisons of results as a function of tuning the parameters that enter the twisted mass version of the DDalphaAMG library (https://github.com/sbacchio/DDalphaAMG). Moreover, we linked the DDalphaAMG library to the tmLQCD software package and give details on the performance of the multigrid solver during HMC simulations at the physical point.
Twisted Covariant Noncommutative Self-dual Gravity
Estrada-Jimenez, S; Obregón, O; Ramírez, C
2008-01-01
A twisted covariant formulation of noncommutative self-dual gravity is presented. The recent formulation introduced by J. Wess and coworkers for constructing twisted Yang-Mills fields is used. It is shown that the noncommutative torsion is solved at any order of the $\\theta$-expansion in terms of the tetrad and the extra fields of the theory. In the process the first order expansion in $\\theta$ for the Pleba\\'nski action is explicitly obtained.
OAM mode converter in twisted fibers
DEFF Research Database (Denmark)
Usuga Castaneda, Mario A.; Beltran-Mejia, Felipe; Cordeiro, Cristiano
2014-01-01
We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA.......We analyze the case of an OAM mode converter based on a twisted fiber, through finite element simulations where we exploit an equivalence between geometric and material transformations. The obtained converter has potential applications in MDM. © 2014 OSA....
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this type of twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets.
On Supermultiplet Twisting and Spin-Statistics
Hubsch, Tristan
2012-01-01
Twisting of off-shell supermultiplets in models with 1+1-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if non-trivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all...
The gradient flow in a twisted box
Energy Technology Data Exchange (ETDEWEB)
Ramos, Alberto [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2013-08-15
We study the perturbative behavior of the gradient flow in a twisted box. We apply this information to define a running coupling using the energy density of the flow field. We study the step-scaling function and the size of cutoff effects in SU(2) pure gauge theory. We conclude that the twisted gradient flow running coupling scheme is a valid strategy for step-scaling purposes due to the relatively mild cutoff effects and high precision.
Twisted Boundary Conditions in Lattice Simulations
Sachrajda, Christopher T C
2004-01-01
By imposing twisted boundary conditions on quark fields it is possible to access components of momenta other than integer multiples of 2pi/L on a lattice with spatial volume L^3. We use Chiral Perturbation Theory to study finite-volume effects with twisted boundary conditions for quantities without final-state interactions, such as meson masses, decay constants and semileptonic form factors, and confirm that they remain exponentially small with the volume. We show that this is also the case for "partially twisted" boundary conditions, in which (some of) the valence quarks satisfy twisted boundary conditions but the sea quarks satisfy periodic boundary conditions. This observation implies that it is not necessary to generate new gluon configurations for every choice of the twist angle, making the method much more practicable. For K->pipi decays we show that the breaking of isospin symmetry by the twisted boundary conditions implies that the amplitudes cannot be determined in general (on this point we disagree ...
2013-02-05
... Administration 14 CFR Part 71 Amendment of Class D and E Airspace; Tri-Cities, TN; Revocation of Class E Airspace; Tri-City, TN AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This action amends Class D and Class E airspace and removes Class E airspace in the Tri-Cities, TN, area, to...
Elastic Properties of Nematic Liquid Crystals Formed by Living and Migrating Cells
Kemkemer, R; Kaufmann, D; Gruler, H; Kemkemer, Ralf; Kling, Dieter; Kaufmann, Dieter; Gruler, Hans
1998-01-01
In culture migrating and interacting amoeboid cells can form nematic liquid crystal phases. A polar nematic liquid crystal is formed if the interaction has a polar symmetry. One type of white blood cells (granulocytes) form clusters where the cells are oriented towards the center. The core of such an orientational defect (disclination) is either a granulocyte forced to be in an isotropic state or another cell type like a monocyte. An apolar nematic liquid crystal is formed if the interaction has an apolar symmetry. Different cell types like human melanocytes (=pigment cells of the skin), human fibroblasts (=connective tissue cells), human osteoblasts (=bone cells), human adipocytes (= fat cells) etc., form an apolar nematic liquid crystal. The orientational elastic energy is derived and the orientational defects (disclination) of nematic liquid crystals are investigated. The existence of half-numbered disclinations show that the nematic phase has an apolar symmetry. The density- and order parameter dependence...
Nematic fluctuations balancing the zoo of phases in half-filled quantum Hall systems
Mesaros, Andrej; Lawler, Michael J.; Kim, Eun-Ah
2017-03-01
Half-filled Landau levels form a zoo of strongly correlated phases. These include non-Fermi-liquids (NFLs), fractional quantum Hall (FQH) states, nematic phases, and FQH nematic phases. This diversity begs the following question: what keeps the balance between the seemingly unrelated phases? The answer is elusive because the Halperin-Lee-Read description that offers a natural departure point is inherently strongly coupled. However, the observed nematic phases suggest that nematic fluctuations play an important role. To study this possibility, we apply a recently formulated controlled double-expansion approach in large-N composite fermion flavors and small ɛ nonanalytic bosonic action to the case with both gauge and nematic boson fluctuations. In the vicinity of a nematic quantum critical line, we find that depending on the amount of screening of the gauge- and nematic-mediated interactions controlled by ɛ 's, the renormalization-group flow points to all four mentioned correlated phases. When pairing preempts the nematic phase, NFL behavior is possible at temperatures above the pairing transition. We conclude by discussing measurements at low tilt angles, which could reveal the stabilization of the FQH phase by nematic fluctuations.
Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria
Nishiguchi, Daiki; Chaté, Hugues; Sano, Masaki
2016-01-01
We study the collective dynamics of long, filamentous, non-tumbling bacteria swimming in a very thin fluid layer. The strong confinement induces nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. We show that this homogeneous but fluctuating phase, observed on the largest experimentally-accessible scale of millimeters, exhibits the same properties as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and non-trivial giant number fluctuations
Long-range nematic order and anomalous fluctuations in suspensions of swimming filamentous bacteria
Nishiguchi, Daiki; Nagai, Ken H.; Chaté, Hugues; Sano, Masaki
2017-02-01
We study the collective dynamics of elongated swimmers in a very thin fluid layer by devising long filamentous nontumbling bacteria. The strong confinement induces weak nematic alignment upon collision, which, for large enough density of cells, gives rise to global nematic order. This homogeneous but fluctuating phase, observed on the largest experimentally accessible scale of millimeters, exhibits the properties predicted by standard models for flocking, such as the Vicsek-style model of polar particles with nematic alignment: true long-range nematic order and nontrivial giant number fluctuations.
Elamu Pärnus Lõuna tn 2A / Jaak Huimerind
Huimerind, Jaak, 1957-
2014-01-01
Nõukogude aeg oli oma vaesus hea konservaator ja muinsuskaitsja. Kuidas käis eestiaegsete ehitiste käsi uue iseseisvusaja algul. Olev Siinmaa kaks kõige väärtuslikumat villat säilisid aastatuhande alguseni. Elamu Lõuna tn 2 restaureerimisest
Studies on Nematic Liquid Crystal Using Spin Wave Theory
Institute of Scientific and Technical Information of China (English)
LIUJian-Jun; LIUXiao-Jing; SHENMan; YANGGuo-Chen
2004-01-01
A spin wave theory is proposed to study nematic liquid crystals. Since the orientation of the molecular long axis and the angular momentum of the molecule rotating around its long axis have the same direction, operators can be introduced to research the nematic liquid crystal. By transforming the intermolecular interaction potential,the Hamiltonian of the system has the same form as that of the ferromagnetic substance. The relation of the order parameters to the reduced temperature can be obtained. It is in good agreement with the experimental results in the low temperature region. In the high temperature region close to the transition point, by using the Hamiltonian, the transition point can be obtained, which is near to the Maier-Saupe's result.
Droplet Breakup of the Nematic Liquid Crystal MBBA
Nachman, Benjamin
2012-01-01
Droplet breakup is a well studied phenomena in Newtonian fluids. One property of this behavior is that, independent of initial conditions, the minimum radius exhibits power law scaling with the time left to breakup tau. Because they have additional structure and shear dependent viscosity, liquid crystals pose an interesting complication to such studies. Here, we investigate the breakup of a synthetic nematic liquid crystal known as MBBA. We determine the phase of the solution by using a cross polarizer setup in situ with the liquid bridge breakup apparatus. Consistent with previous studies of scaling behavior in viscous-inertial fluid breakup, when MBBA is in the isotropic phase, the minimum radius decreases as tau^{1.03 \\pm 0.04}. In the nematic phase however, we observe very different thinning behavior. Our measurements of the thinning profile are consistent with two interpretations. In the first interpretation, the breakup is universal and consists of two different regimes. The first regime is characterize...
Spatially modulated structures in nematic colloids: Statistical thermodynamics and kinetics.
Kleshchonok, A V; Reshetnyak, V Yu; Tatarenko, V A
2011-03-01
We examine the spatial distribution of rigid-sphere-like particles in a nematic host. Using a continuum model we analyse the conditions necessary for the appearance of a modulated lamellar structure. There is a long-range effective interaction between the particles, which can lead to the formation of superstructures. In general, this interaction includes several contributions: van der Waals-type direct interaction and indirect interaction via the director field distortions. The latter depends on the temperature of the sample, the coupling energy between a colloidal particle and a nematic host, and the particle concentration. This effective interaction controls the spatial structure and the kinetic properties of the system. We obtained the analytical expression for the temperature when the system loses the stability with respect to the modulated structure formation. Typical contours of the diffuse light scattering are presented.
Relativistic Lagrangian model of a nematic liquid crystal
Obukhov, Yuri N; Rubilar, Guillermo F
2012-01-01
We develop a relativistic variational model for a nematic liquid crystal interacting with the electromagnetic field. The constitutive relation for an anisotropic uniaxial diamagnetic and dielectric medium is analyzed. We discuss light wave propagation in this moving uniaxial medium, for which the corresponding optical metrics are identified explicitly. A Lagrangian for the coupled system of a nematic liquid crystal and the electromagnetic field is constructed. We derive a complete set of equations of motion for the system. The canonical energy-momentum and spin tensors are systematically obtained. We compare our results with those within the non-relativistic models. As an application of our general formalism, we discuss the so-called Abraham-Minkowski controversy on the momentum of light in a medium.
Ordering Quantum Dot Clusters via Nematic Liquid Crystal Defects
Rodarte, Andrea; Pandolfi, R.; Hirst, L. S.; Ghosh, S.
2012-11-01
Nematic liquid crystal (LC) materials can be used to create ordered clusters of CdSe/ZnS core/shell quantum dots (QDs) from a homogeneous isotropic dispersion. At the phase transition, the ordered domains of nematic LC expel the majority of dispersed QDs into the isotropic domains. The final LC phase produces a series of QD clusters that are situated at the defect points of the liquid crystal texture. Lower concentrations of QDs are organized in a network throughout the LC matrix that originates from the LC phase transition. Inside the QD clusters the inter-particle distance enables efficient energy transfer from high energy dots to lower energy dots. Because the QD clusters form at defect sites, the location of the clusters can be preselected by seeding the LC cell with defect nucleation points.
An In Vitro Nematic Model for Proliferating Cell Cultures
Pai, Sunil; Green, Morgaine; Cordeiro, Christine; Cabral, Elise; Chen, Bertha; Baer, Thomas
2016-01-01
Confluent populations of elongated cells give rise to ordered patterns seen in nematic phase liquid crystals. We correlate cell elongation and intercellular distance with intercellular alignment using an amorphous spin glass model. We compare in vitro time-lapse imaging with Monte Carlo simulation results by framing a novel hard ellipses model in terms of Boltzmann statistics. Furthermore, we find a statistically distinct alignment energy at quasi-steady state among fibroblasts, smooth muscle cells, and pluripotent cell populations when cultured in vitro. These findings have important implications in both non-invasive clinical screening of the stem cell differentiation process and in relating shape parameters to coupling in active crystal systems such as nematic cell monolayers.
Transitions through critical temperatures in nematic liquid crystals
Majumdar, Apala
2013-08-06
We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.
Hybrid graphene nematic liquid crystal light scattering device
Qasim, M. M.; Khan, A. A.; Kostanyan, A.; Kidambi, P. R.; Cabrero-Vilatela, A.; Braeuninger-Weimer, P.; Gardiner, D. J.; Hofmann, S.; Wilkinson, T. D.
2015-08-01
A hybrid graphene nematic liquid crystal (LC) light scattering device is presented. This device exploits the inherent poly-crystallinity of chemical vapour deposited (CVD) graphene films to induce directional anchoring and formation of LC multi-domains. This thereby enables efficient light scattering without the need for crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (crossed polarisers or separate alignment layers/additives. The hybrid LC device exhibits switching thresholds at very low electric fields (< 1 V μm-1) and repeatable, hysteresis free characteristics. This exploitation of LC alignment effects on CVD graphene films enables a new generation of highly efficient nematic LC scattering displays as well as many other possible applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04094a
Probing the shear viscosity of an active nematic film
Guillamat, Pau; Ignés-Mullol, Jordi; Shankar, Suraj; Marchetti, M. Cristina; Sagués, Francesc
2016-12-01
In vitro reconstituted active systems, such as the adenosine triphosphate (ATP)-driven microtubule bundle suspension developed by the Dogic group [T. Sanchez, D. T. Chen, S. J. DeCamp, M. Heymann, and Z. Dogic, Nature (London) 491, 431 (2012), 10.1038/nature11591], provide a fertile testing ground for elucidating the phenomenology of active liquid crystalline states. Controlling such novel phases of matter crucially depends on our knowledge of their material and physical properties. In this Rapid Communication, we show that the shear viscosity of an active nematic film can be probed by varying its hydrodynamic coupling to a bounding oil layer. Using the motion of disclinations as intrinsic tracers of the flow field and a hydrodynamic model, we obtain an estimate for the shear viscosity of the nematic film. Knowing this now provides us with an additional handle for robust and precision tunable control of the emergent dynamics of active fluids.
Soft tissue twisting injuries of the knee
Energy Technology Data Exchange (ETDEWEB)
Magee, T.; Shapiro, M. [Neuroimaging Inst., Melbourne, FL (United States)
2001-08-01
Twisting injuries occur as a result of differential motion of different tissue types in injuries with some rotational force. These injuries are well described in brain injuries but, to our knowledge, have not been described in the musculoskeletal literature. We correlated the clinical examination and MR findings of 20 patients with twisting injuries of the soft tissues around the knee. Design and patients: We prospectively followed the clinical courses of 20 patients with knee injuries who had clinical histories and MR findings to suggest twisting injuries of the subcutaneous tissues. Patients with associated internal derangement of the knee (i.e., meniscal tears, ligamentous or bone injuries) were excluded from this study. MR findings to suggest twisting injuries included linear areas of abnormal dark signal on T1-weighted sequences and abnormal bright signal on T2-weighted or short tau inversion recovery (STIR) sequences and/or signal to suggest hemorrhage within the subcutaneous tissues. These MR criteria were adapted from those established for indirect musculotendinous junction injuries. Results: All 20 patients presented with considerable pain that suggested internal derangement on physical examination by the referring orthopedic surgeons. All presented with injuries associated with rotational force. The patients were placed on a course of protected weight-bearing of the affected extremity for 4 weeks. All patients had pain relief by clinical examination after this period of protected weight-bearing. Twisting injuries of the soft tissues can result in considerable pain that can be confused with internal derangement of the knee on physical examination. Soft tissue twisting injuries need to be recognized on MR examinations as they may be the cause of the patient's pain despite no MR evidence of internal derangement of the knee. The demonstration of soft tissue twisting injuries in a patient with severe knee pain but no documented internal derangement on MR
Modelling Ferroelectric Nanoparticles in Nematic Liquid Crystals (FERNANO)
2015-02-26
DIPARTIMENTO DI CHIMICA FISICA ED INORGANICA VIALE DEL RISORGIMENTO 4 BOLOGNA, 40136 ITALY EOARD GRANT #FA8655-11-1-3046 Report...AND ADDRESS(ES) DIPARTIMENTO DI CHIMICA FISICA ED INORGANICA VIALE DEL RISORGIMENTO 4 BOLOGNA, 40136 ITALY 8. PERFORMING ORGANIZATION... Molecular Dynamics simulations, nematic liquid crystal, nematogen (5CB), tetragonal BaTiO3, tetragonal crystal 16. SECURITY CLASSIFICATION OF: 17
Thermo optical study of nematic liquid crystal doped with ferrofluid
Jessy P., J.; Shalini, M.; Patel, Nainesh; Sarawade, Pradip; Radha, S.
2017-05-01
Liquid crystal composite materials with tunable physical properties are of great scientific interest because of optoelectronic and biomedical applications. We report our study of modified optical properties of 5CB Nematic Liquid Crystal (NLC) by doping with ferrofluid at low concentrations of 0.1% by the investigation of thermo optic behaviour. The observed sensitivity of optical response in ferrofluid doped NLC is expected to pave way for several thermo-optic applications.
Three dielectric constants and orientation order parameters in nematic mesophases
Yoon, Hyung Guen; Jeong, Seung Yeon; Kumar, Satyendra; Park, Min Sang; Park, Jung Ok; Srinivasarao, M.; Shin, Sung Tae
2011-03-01
Temperature dependence of the three components ɛ1 , ɛ2 , and ɛ3 of dielectric constant and orientation order parameters in the nematic phase of mesogens with rod, banana, and zero-order dendritic shape were measured using the in-plane and vertical switching geometries, and micro-Raman technique. Results on the well-known uniaxial (Nu) nematogens, E7 and 5CB, revealed two components ɛ1 = ~ɛ| | and ɛ2 = ~ɛ3 = ~ɛ⊥ , as expected. The three dielectric constants were different for two azo substituted (A131 and A103) and an oxadiazole based (ODBP-Ph-C12) bent core mesogens, and a Ge core tetrapode. In some cases, two of the components became the same indicating a loss of biaxiality at temperatures coinciding with the previously reported Nu to biaxial nematic transition. This interpretation is substantiated by micro-Raman measurements of the uniaxial and biaxial nematic order parameters. Supported by the US Department of Energy, Basic Energy Sciences grant ER46572 and by Samsung Electronics Corporation.
Photorefractivity in polymer-stabilized nematic liquid crystals
Energy Technology Data Exchange (ETDEWEB)
Wiederrecht, G.P. [Argonne National Lab., IL (United States). Chemistry Div.; Wasielewski, M.R. [Argonne National Lab., IL (United States). Chemistry Div.]|[Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry
1998-07-01
Polymer-stabilized liquid crystals, consisting of low concentrations of a polymeric electron acceptor, are shown to exhibit significantly enhanced photorefractive properties. The charge generation and transport properties of these composite systems are strongly modified from nematic liquid crystals doped with electron donors and acceptors. The new composites are produced by polymerizing a small quantity of a 1,4:5,8-naphthalenediimide electron acceptor functionalized with an acrylate group in an aligned nematic liquid crystal. Photopolymerization creates an anisotropic gel-like medium in which the liquid crystal is free to reorient in the presence of a space charge field, while maintaining charge trapping sites in the polymerized regions of the material. The presence of these trapping sites results in the observation of longer lived, higher resolution holographic gratings in the polymer-stabilized liquid crystals than observed in nematic liquid crystals alone. These gratings display Bragg regime diffraction. Asymmetric beam coupling, photo-conductivity, and four-wave mixing experiments are performed to characterize the photophysics of these novel materials.
Anisotropic Elastic Properties of Muscle-like Nematic Elastomers
Ratna, Banahalii; Thomseniii, Donald L.; Shenoy, Devanand; Srinivasan, Amritha; Keller, Patrick
2001-03-01
De Gennes suggested in 1997 that the liquid crystal elastomers are an excellent framework to mimic muscular action. We have prepared anisotropic freestanding films of nematic elastomers from laterally attached side-chain polymers that show muscle-like mechanical properties. The orientational order of the liquid crystal side groups imposes a conformational anisotropy in the polymer backbone. When the order parameter drops at the nematic-isotropic phase transition, there is a concomitant loss of order in the backbone which results in a contraction of the film in the direction of the director orientation. Dynamic mechanical data along directions parallel and perpendicular to the optic axis, show anisotropic stress-strain behavior. The film exhibits soft elasticity when strained in the perpendicular direction when the liquid crystal mesogens reorient without appreciable stress build up. Thermostrictive studies in the parallel direction show 40constriction at the nematic-isotropic phase transition. Isometric studies show that the elastic energy stored is purely entropic in origin and the elastomer acts like a spring with unusually large spring constant at the NI transition. The maximum stress measured is 300kPa. A strain rate of 5s-1 is estimated from shear relaxation studies.
Topological Nematic States and Non-Abelian Lattice Dislocations
Directory of Open Access Journals (Sweden)
Maissam Barkeshli
2012-08-01
Full Text Available An exciting new prospect in condensed matter physics is the possibility of realizing fractional quantum Hall states in simple lattice models without a large external magnetic field. A fundamental question is whether qualitatively new states can be realized on the lattice as compared with ordinary fractional quantum Hall states. Here we propose new symmetry-enriched topological states, topological nematic states, which are a dramatic consequence of the interplay between the lattice translational symmetry and topological properties of these fractional Chern insulators. The topological nematic states are realized in a partially filled flat band with a Chern number N, which can be mapped to an N-layer quantum Hall system on a regular lattice. However, in the topological nematic states the lattice dislocations can act as wormholes connecting the different layers and effectively change the topology of the space. Consequently, lattice dislocations become defects with a nontrivial quantum dimension, even when the fractional quantum Hall state being realized is, by itself, Abelian. Our proposal leads to the possibility of realizing the physics of topologically ordered states on high-genus surfaces in the lab even though the sample has only the disk geometry.
Transparent nematic phase in a liquid-crystal-based microemulsion.
Yamamoto, J; Tanaka, H
2001-01-18
Complex fluids are usually produced by mixing together several distinct components, the interactions between which can give rise to unusual optical and rheological properties of the system as a whole. For example, the properties of microemulsions (composed of water, oil and surfactants) are determined by the microscopic structural organization of the fluid that occurs owing to phase separation of the component elements. Here we investigate the effect of introducing an additional organizing factor into such a fluid system, by replacing the oil component of a conventional water-in-oil microemulsion with an intrinsically anisotropic fluid--a nematic liquid crystal. As with the conventional case, the fluid phase-separates into an emulsion of water microdroplets (stabilized by the surfactant as inverse micelles) dispersed in the 'oil' phase. But the properties are further influenced by a significant directional coupling between the liquid-crystal molecules and the surfactant tails that emerge (essentially radially) from the micelles. The result is a modified bulk-liquid crystal that is an ordered nematic at the mesoscopic level, but which does not exhibit the strong light scattering generally associated with bulk nematic order: the bulk material here is essentially isotropic and thus transparent.
Noncommutative geometry in string and twisted Hopf algebra of diffeomorphism
Watamura, Satoshi
2011-09-01
We discuss the Hopf algebra structure in string theory and present the twist quantization as a unified formulation of the world sheet quantization of the string and the symmetry of the target spacetime. Applying it to the case with a nonzero B-field background, we explain a method to decompose the twist into two successive twists. There are two different possibilities of decomposition: The first is a natural decomposition from the viewpoint of the twist quantization, leading to a new type of twisted Poincaré symmetry. The second decomposition reveals the relation of our formulation to the twisted Poincaré symmetry on the Moyal type noncommutative space.
Twisted electron-acoustic waves in plasmas
Aman-ur-Rehman, Ali, S.; Khan, S. A.; Shahzad, K.
2016-08-01
In the paraxial limit, a twisted electron-acoustic (EA) wave is studied in a collisionless unmagnetized plasma, whose constituents are the dynamical cold electrons and Boltzmannian hot electrons in the background of static positive ions. The analytical and numerical solutions of the plasma kinetic equation suggest that EA waves with finite amount of orbital angular momentum exhibit a twist in its behavior. The twisted wave particle resonance is also taken into consideration that has been appeared through the effective wave number qeff accounting for Laguerre-Gaussian mode profiles attributed to helical phase structures. Consequently, the dispersion relation and the damping rate of the EA waves are significantly modified with the twisted parameter η, and for η → ∞, the results coincide with the straight propagating plane EA waves. Numerically, new features of twisted EA waves are identified by considering various regimes of wavelength and the results might be useful for transport and trapping of plasma particles in a two-electron component plasma.
Exotic twisted equivariant cohomology of loop spaces,twisted Bismut-Chern character and T-duality
Han, Fei
2014-01-01
We define completed periodic {\\em exotic twisted $\\mathbb{T}$-equivariant cohomology} for loop spaces of smooth manifolds. We then show that the twisted Bismut-Chern character, defined on the twisted K-theory of the smooth manifold, twisted by a gerbe with connection, takes values in the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology of the loop space of the smooth manifold. We establish a localisation theorem for the completed periodic exotic twisted $\\mathbb{T}$-equivariant cohomology for loop spaces and apply it to establish T-duality in a background flux in type II String Theory from a loop space perspective.
Unraveling cellulose microfibrils: a twisted tale.
Hadden, Jodi A; French, Alfred D; Woods, Robert J
2013-10-01
Molecular dynamics (MD) simulations of cellulose microfibrils are pertinent to the paper, textile, and biofuels industries for their unique capacity to characterize dynamic behavior and atomic-level interactions with solvent molecules and cellulase enzymes. While high-resolution crystallographic data have established a solid basis for computational analysis of cellulose, previous work has demonstrated a tendency for modeled microfibrils to diverge from the linear experimental structure and adopt a twisted conformation. Here, we investigate the dependence of this twisting behavior on computational approximations and establish the theoretical basis for its occurrence. We examine the role of solvent, the effect of nonbonded force field parameters [partial charges and van der Waals (vdW) contributions], and the use of explicitly modeled oxygen lone pairs in both the solute and solvent. Findings suggest that microfibril twisting is favored by vdW interactions, and counteracted by both intrachain hydrogen bonds and solvent effects at the microfibril surface.
Analysis of gun barrel rifling twist
Sun, Jia; Chen, Guangsong; Qian, Linfang; Liu, Taisu
2017-05-01
Aiming at the problem of gun barrel rifling twist, the constraint relation between rifling and projectile is investigated. The constraint model of rifling and projectile is established and the geometric relation between the twist and the motion of projectile is analyzed. Based on the constraint model, according to the rotating band that is fired, the stress and the motion law of the rotating band in bore are analyzed. The effects to rotating band (double rotating band or wide driving band) caused by different rifling (rib rifling, increasing rifling and combined rifling) are also investigated. The model is demonstrated by several examples. The results of numerical examples and the constraint mode show that the uncertainty factors will be brought in the increasing rifling and combined rifling during the projectile move in the bore. According to the amplitude and the strength of the twist acting on rotating band, the steady property of rotational motion of the projectile, the rib rifling is a better choose.
Blind analysis results of the TWIST experiment
Hillairet, A; Bueno, J F; Davydov, Y I; Depommier, P; Faszer, W; Fujiwara, M C; Gagliardi, C A; Gaponenko, A; Grossheim, A; Gill, D R; Gumplinger, P; Hasinoff, M D; Henderson, R S; Hu, J; Koetke, D D; MacDonald, R P; Marshall, G M; Mathie, E W; Mischke, R E; Olchanski, K; Olin, A; Openshaw, R; Poutissou, J -M; Poutissou, R; Selivanov, V; Sheffer, G; Shin, B; Stanislaus, T D S; Tacik, R; Tribble, R E
2010-01-01
The TRIUMF Weak Interaction Symmetry Test (TWIST) experiment was designed to test the standard model at high precision in the purely leptonic decay of polarized muons. A general four-fermion interaction model is used to describe the muon decay. TWIST measures three of the four muon decay parameters of this model, $\\rho$, $\\delta$ and $P_{\\mu}^{\\pi} \\xi$, from the shape of the momentum-angle spectrum. The results of this model independent approach are compared to the standard model predictions and used to constrain new physics. Our collaboration has finalized the blind analysis of the final experimental data taken in 2006 and 2007. This analysis mostly reached our goal of a precision of an order of magnitude improvement over the pre-TWIST measurements.
Helicoids, wrinkles, and loops in twisted ribbons.
Chopin, Julien; Kudrolli, Arshad
2013-10-25
We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales.
Dynamical Twisted Mass Fermions with Light Quarks
Boucaud, P; Farchioni, F; Frezzotti, R; Giménez, V; Herdoiza, G; Jansen, K; Lubicz, V; Martinelli, G; McNeile, C; Michael, C; Montvay, I; Palao, D; Papinutto, Mauro; Pickavance, J; Rossi, G C; Scorzato, L; Shindler, A; Simula, S; Urbach, C; Wenger, U; Boucaud, Ph.
2007-01-01
We present results of dynamical simulations with 2 flavours of degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses from 300 to 550 MeV. The simulations are performed at one value of the lattice spacing a \\lesssim 0.1 fm. In order to have O(a) improvement and aiming at small residual cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, \\bar{l}_3 and \\bar{l}_4 are evaluated with small statistical errors.
Matrix theory compactifications on twisted tori
Chatzistavrakidis, Athanasios
2012-01-01
We study compactifications of Matrix theory on twisted tori and non-commutative versions of them. As a first step, we review the construction of multidimensional twisted tori realized as nilmanifolds based on certain nilpotent Lie algebras. Subsequently, matrix compactifications on tori are revisited and the previously known results are supplemented with a background of a non-commutative torus with non-constant non-commutativity and an underlying non-associative structure on its phase space. Next we turn our attention to 3- and 6-dimensional twisted tori and we describe consistent backgrounds of Matrix theory on them by stating and solving the conditions which describe the corresponding compactification. Both commutative and non-commutative solutions are found in all cases. Finally, we comment on the correspondence among the obtained solutions and flux compactifications of 11-dimensional supergravity, as well as on relations among themselves, such as Seiberg-Witten maps and T-duality.
On reweighting for twisted boundary conditions
Bussone, Andrea; Hansen, Martin; Pica, Claudio
2016-01-01
We consider the possibility of using reweighting techniques in order to correct for the breaking of unitarity when twisted boundary conditions are imposed on valence fermions in simulations of lattice gauge theories. We start by studying the properties of reweighting factors and their variances at tree-level. That leads us to the introduction of a factorization for the fermionic reweighting determinant. In the numerical, stochastic, implementation of the method, we find that the effect of reweighting is negligible in the case of large volumes but it is sizeable when the volumes are small and the twisting angles are large. More importantly, we find that for un-improved Wilson fermions, and in small volumes, the dependence of the critical quark mass on the twisting angle is quite pronounced and results in large violations of the continuum dispersion relation.
Wu, A M; Shen, F; Herp, A; Wu, J H
1994-04-01
Hamster submaxillary glycoprotein (HSM), one of the simplest glycoproteins among mammalian salivary mucins, is composed of approximately equivalent amounts of protein, hexosamine and sialic acid. The Thr and Ser residues in the protein core account for more than half of all of the amino acid residues, while Lys, Glu, Pro and Ala are the major components of the remaining portion of amino acids. The carbohydrate side chains of this mucous glycoprotein have mainly the NeuAc-GalNAc-(sialyl-Tn) sequence (HSM), and those of the desialylated product (HSM-Tn) are almost exclusively unsubstituted GalNAc residues (Tn determinants). The binding properties of sialyl-Tn (HSM) and asialo-HSM (HSM-Tn) glycoproteins were tested by precipitin assay with Gal, GalNAc and GlcNAc specific lectins. The HSM-Tn completely precipitated Vicia villosa (VVL both B4 and mixture of A and B), Maclura pomifera (MPL), and Artocarpus integrifolia (Jacalin) lectins; less than 2 micrograms of HSM-Tn were required for precipitating 50% of 5.0-6.3 micrograms lectin nitrogen added. HSM-Tn also reacted well with Helix pomatia lectin (HPL), Wistaria floribunda lectin (WFL) and Abrus precatorius agglutinin (APA) and precipitated in each case over 81% of the lectin nitrogen added. The reactivity of HSM-Tn with other lectins (Ricinus communis, RCA1; Dolichol biflorus, DBL; Viscum album, ML-I; Arachis hypogaea, PNA, and Triticum vulgaris, WGA) was weak or negligible. The activity of sialyl-Tn (HSM) was more restricted; HSM reacted well with Jacalin, moderately with MPL and VVL-B4, but was inactive or only weakly with the other lectins used. These findings indicate that HSM and its desialylated product (HSM-Tn) are highly useful reagents for the differentiation of Tn and T/Gal specific lectins and for anti-T, Tn and Af monoclonal antibodies.
Local index formula and twisted spectral triples
Moscovici, Henri
2009-01-01
We prove a local index formula for a class of twisted spectral triples of type III modeled on the transverse geometry of conformal foliations with locally constant transverse conformal factor. Compared with the earlier proof of the untwisted case, the novel aspect resides in the fact that the twisted analogues of the JLO entire cocycle and of its retraction are no longer cocycles in their respective Connes bicomplexes. We show however that the passage to the infinite temperature limit, respectively the integration along the full temperature range against the Haar measure of the positive half-line, has the remarkable effect of curing in both cases the deviations from the cocycle identity.
On Supermultiplet Twisting and Spin-Statistics
Hübsch, T.
2013-10-01
Twisting of off-shell supermultiplets in models with (1+1)-dimensional spacetime has been discovered in 1984, and was shown to be a generic feature of off-shell representations in worldline supersymmetry two decades later. It is shown herein that in all supersymmetric models with spacetime of four or more dimensions, this off-shell supermultiplet twisting, if nontrivial, necessarily maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature is shown to be ubiquitous in all fully off-shell supersymmetric models with (BV/BRST-treated) constraints.
Multi-twist optical Mobius strips
Freund, Isaac
2009-01-01
Circularly polarized Gauss-Laguerre GL(0,0) and GL(0,1) laser beams that cross at their waists at a small angle are shown to generate a quasi-paraxial field that contains an axial line of circular polarization, a C line, surrounded by polarization ellipses whose major and minor axes generate multi-twist Mobius strips with twist numbers that increase with distance from the C point. These Mobius strips are interpreted in terms of Berry's phase for parallel transport of the ellipse axes around the C point.
Effects Of Twist On Ceramic Threads
Sawko, Paul M.; Tran, Huy Kim
1989-01-01
Report describes study of effects of yarn twist and other manufacturing parameters on strength of ceramic sewing threads. Three types of thread considered; silica, aluminoborosilicate (ABS) with 14 percent boria, and ABS with 2 percent boria. For silica thread, best twist found 300 turns per meter. Produced highest break strength at temperatures up to about 540 degree C. Overall strengths of both ABS threads higher than silica thread. Threads used to stitch insulating blankets for reusable spacraft; must resist high temperatures and high aerodynamic loads of reentry into atmosphere of Earth.
Spectral flows and twisted topological theories
Gato-Rivera, Beatriz; Gato-Rivera, Beatriz; Rosado, Jose Ignacio
1995-01-01
We analyze the action of the spectral flows on N=2 twisted topological theories. We show that they provide a useful mapping between the two twisted topological theories associated to a given N=2 superconformal theory. This mapping can also be viewed as a topological algebra automorphism. In particular null vectors are mapped into null vectors, considerably simplifying their computation. We give the level 2 results. Finally we discuss the spectral flow mapping in the case of the DDK and KM realizations of the topological algebra.
Mathematical Studies and Simulations of Nematic Liquid Crystal Polymers and Nanocomposites
2010-01-01
been spun into high strength fibers and then manufactured into special airbags that cushioned the successful landing of NASA’s highly publicized...shaped, boomerang-shaped or banana shaped.76 Recall that in a nematic phase the molecules tend to align along the director n. A biax- ial nematic phase
Nguyen, Thanh-Dinh; Hamad, Wadood Y; MacLachlan, Mark J
2013-12-14
We have discovered that the self-assembly of cellulose nanocrystals (CNCs) into chiral nematic phases varies significantly with the substrate and evaporation rate. These variables allow the reflectance peak of iridescent chiral nematic films of CNCs and mesoporous silica templated from CNCs to be tuned over a wide range of wavelengths.
Mass-deformed $T_N$ as a linear quiver
Hayashi, Hirotaka; Yonekura, Kazuya
2014-01-01
The $T_N$ theory is a non-Lagrangian theory with SU(N) flavor symmetry. We argue that when mass terms are given so that two of SU(N)'s are both broken to SU(N-1) x U(1), it becomes $T_{N-1}$ theory coupled to an SU(N-1) vector multiplet together with N fundamentals. This implies that when two of SU(N)'s are both broken to U(1)$^{N-1}$, the theory becomes a linear quiver. We perform various checks of this statement, by using the 5d partition function, the structure of the coupling constants, the Higgs branch, and the Seiberg-Witten curve. We also study the case with more general punctures.
A non-commuting twist in the partition function
Govindarajan, Suresh
2012-01-01
We compute a twisted index for an orbifold theory when the twist generating group does not commute with the orbifold group. The twisted index requires the theory to be defined on moduli spaces that are compatible with the twist. This is carried out for CHL models at special points in the moduli space where they admit dihedral symmetries. The commutator subgroup of the dihedral groups are cyclic groups that are used to construct the CHL orbifolds. The residual reflection symmetry is chosen to act as a `twist' on the partition function. The reflection symmetries do not commute with the orbifolding group and hence we refer to this as a non-commuting twist. We count the degeneracy of half-BPS states using the twisted partition function and find that the contribution comes mainly from the untwisted sector. We show that the generating function for these twisted BPS states are related to the Mathieu group M_{24}.
Thermodynamic evidence for nematic superconductivity in CuxBi2Se3
Yonezawa, Shingo; Tajiri, Kengo; Nakata, Suguru; Nagai, Yuki; Wang, Zhiwei; Segawa, Kouji; Ando, Yoichi; Maeno, Yoshiteru
2016-10-01
In condensed matter physics, spontaneous symmetry breaking has been a key concept, and discoveries of new types of broken symmetries have greatly increased our understanding of matter. Recently, electronic nematicity, novel spontaneous rotational-symmetry breaking leading to an emergence of a special direction in electron liquids, has been attracting significant attention. Here, we show bulk thermodynamic evidence for nematic superconductivity, in which the nematicity emerges in the superconducting gap amplitude, in CuxBi2Se3. Based on high-resolution calorimetry of single-crystalline samples under accurate two-axis control of the magnetic field direction, we discovered clear two-fold symmetry in the specific heat and in the upper critical field despite the trigonal symmetry of the lattice. Nematic superconductivity for this material should possess a unique topological nature associated with odd parity. Thus, our findings establish a new class of spontaneously symmetry-broken states of matter--namely, odd-parity nematic superconductivity.
Institute of Scientific and Technical Information of China (English)
李晶晶
2011-01-01
记者:李教授,您好!目前,TnPM(全面规范化生产维护,Total Normalized Productive Maintenance)的推进工作在全国不断深入,您认为其主要原因是什么?李葆文:中国已经从一个落后的农业国逐渐过渡到制造业大国,高速、精密、自动化的设备越来越多,设备资产密集、技术密集型企业也越来越多,管理创新的诉求也日益强烈.TnPM是一个助力制造业人机系统管理的良好平台,全国TnPM大会恰恰为广大企业的设备管理者搭建了这样一个平台.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-11-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
On Twisting Real Spectral Triples by Algebra Automorphisms
Landi, Giovanni; Martinetti, Pierre
2016-08-01
We systematically investigate ways to twist a real spectral triple via an algebra automorphism and in particular, we naturally define a twisted partner for any real graded spectral triple. Among other things, we investigate consequences of the twisting on the fluctuations of the metric and possible applications to the spectral approach to the Standard Model of particle physics.
78 FR 43971 - Amendment of Class E Airspace; Tri-Cities, TN
2013-07-23
... Federal Aviation Administration 14 CFR Part 71 Amendment of Class E Airspace; Tri-Cities, TN AGENCY... airspace for the Tri-Cities, TN area, by correcting the regulatory text of the Class E surface airspace at Tri-Cities Regional Airport, Tri-Cities, TN. Exclusionary language was omitted in the final rule...
Twisting singular solutions of Bethe's equations
Nepomechie, Rafael I
2014-01-01
The Bethe equations for the periodic XXX and XXZ spin chains admit singular solutions, for which the corresponding eigenvalues and eigenvectors are ill-defined. We use a twist regularization to derive conditions for such singular solutions to be physical, in which case they correspond to genuine eigenvalues and eigenvectors of the Hamiltonian.
Disconnected Loops with Twisted Mass Lattice QCD
Wilcox, W; Morgan, R; Lewis, R; Wilcox, Walter; Darnell, Dean; Morgan, Ron; Lewis, Randy
2005-01-01
We give a general introduction and discussion of the issues involved in using the twisted mass formulation of lattice fermions in the context of disconnected loop calculations, including a short orientation on the present experimental situation for nucleon strange quark form factors. A prototype calculation of the disconnected part of the nucleon scalar form factor is described.
Phase diagram of twisted mass lattice QCD
Sharpe, Stephen R.; Wu, Jackson M.
2004-11-01
We use the effective chiral Lagrangian to analyze the phase diagram of two-flavor twisted mass lattice QCD as a function of the normal and twisted masses, generalizing previous work for the untwisted theory. We first determine the chiral Lagrangian including discretization effects up to next-to-leading order (NLO) in a combined expansion in which m2π/(4πfπ)2˜aΛ (a being the lattice spacing, and Λ=ΛQCD). We then focus on the region where m2π/(4πfπ)2˜(aΛ)2, in which case competition between leading and NLO terms can lead to phase transitions. As for untwisted Wilson fermions, we find two possible phase diagrams, depending on the sign of a coefficient in the chiral Lagrangian. For one sign, there is an Aoki phase for pure Wilson fermions, with flavor and parity broken, but this is washed out into a crossover if the twisted mass is nonvanishing. For the other sign, there is a first order transition for pure Wilson fermions, and we find that this transition extends into the twisted mass plane, ending with two symmetrical second order points at which the mass of the neutral pion vanishes. We provide graphs of the condensate and pion masses for both scenarios, and note a simple mathematical relation between them. These results may be of importance to numerical simulations.
Gluon polarization and higher twist effects
Leader, Elliot; Stamenov, Dimiter
2008-01-01
We examine the influence of the recent CLAS and COMPASS experiments on our understanding of higher twist (HT) effects and the gluon polarization, and show how EIC could discriminate between negative and positive gluon polarizations. We comment on the issue of HT and the recent DSSV analysis.
Twisted Ribbons: Theory, Experiment and Applications
Chopin, Julien; Davidovitch, Benjamin; Silva, Flavio A.; Toledo Filho, Romildo D.; Kudrolli, Arshad
2014-03-01
We investigate, experimentally and theoretically, the buckling and wrinkling instabilities of a pre-stretched ribbon upon twisting and propose strategies for the fabrication of structured yarns. Our experiment consists in a thin elastic sheet in the form of a ribbon which is initially stretched by a fixed load and then subjected to a twist by rotating the ends through a prescribed angle. We show that a wide variety of shapes and instabilities can be obtained by simply varying the applied twist and tension. The observed structures which include helicoids with and without longitudinal and transverse wrinkles, and spontaneous creases, can be organized in a phase diagram with the tension and twist angle as control parameters [J. Chopin and A. Kudrolli, PRL (2013)]. Using a far-from-threshold analysis and a slender body approximation, we provide a comprehensive understanding of the longitudinal and transverse instabilities and show that several regimes emerge depending on subtle combinations of loading and geometrical parameters. Further, we show that the wrinkling instabilities can be manipulated to fabricate structured yarns which may be used to encapsulate amorphous materials or serve as efficient reinforcements for cement-based composites. COPPETEC / CNPq - Science Without Border Program
HOMOCLINIC TWIST BIFURCATIONS WITH Z(2) SYMMETRY
ARONSON, DG; VANGILS, SA; KRUPA, M
1994-01-01
We analyze bifurcations occurring in the vicinity of a homoclinic twist point for a generic two-parameter family of Z2 equivariant ODEs in four dimensions. The results are compared with numerical results for a system of two coupled Josephson junctions with pure capacitive load.
Redefining B twisted topological sigma models
Jonghe, F. de; Termonia, P.; Troost, W.; Vandoren, S.
2007-01-01
The recently proposed procedure to perform the topological B-twist in rigid N = 2 models is applied to the case of the o model on a Kähler manifold. This leads to an alternative description of Witten’s topological o model, which allows for a proper BRST interpretation and ghost number assignement. W
Generalized Weyl modules for twisted current algebras
Makedonskyi, I. A.; Feigin, E. B.
2017-08-01
We introduce the notion of generalized Weyl modules for twisted current algebras. We study their representation-theoretic and combinatorial properties and also their connection with nonsymmetric Macdonald polynomials. As an application, we compute the dimension of the classical Weyl modules in the remaining unknown case.
Analysis of Cohesion inOliver Twist
Institute of Scientific and Technical Information of China (English)
程文文
2016-01-01
Cohesion is an important concept in the study of stylistics. This thesis aims to study the applications of cohesion in the Charles Dicken’ world-famous novelOliver Twist, including both the grammatical and lexical cohesive devices in the work.
Energy Release in Driven Twisted Coronal Loops
Bareford, M. R.; Gordovskyy, M.; Browning, P. K.; Hood, A. W.
2016-01-01
We investigate magnetic reconnection in twisted magnetic fluxtubes, representing coronal loops. The main goal is to establish the influence of the field geometry and various thermodynamic effects on the stability of twisted fluxtubes and on the size and distribution of heated regions. In particular, we aim to investigate to what extent the earlier idealised models, based on the initially cylindrically symmetric fluxtubes, are different from more realistic models, including the large-scale curvature, atmospheric stratification, thermal conduction and other effects. In addition, we compare the roles of Ohmic heating and shock heating in energy conversion during magnetic reconnection in twisted loops. The models with straight fluxtubes show similar distribution of heated plasma during the reconnection: it initially forms a helical shape, which subsequently becomes very fragmented. The heating in these models is rather uniformly distributed along fluxtubes. At the same time, the hot plasma regions in curved loops are asymmetric and concentrated close to the loop tops. Large-scale curvature has a destabilising influence: less twist is needed for instability. Footpoint convergence normally delays the instability slightly, although in some cases, converging fluxtubes can be less stable. Finally, introducing a stratified atmosphere gives rise to decaying wave propagation, which has a destabilising effect.
Nematic antiferromagnetic states in bulk FeSe
Liu, Kai; Lu, Zhong-Yi; Xiang, Tao
2016-05-01
The existence of nematic order, which breaks the lattice rotational symmetry with nonequivalent a and b axes in iron-based superconductors, is a well-established experimental fact. An antiferromagnetic (AFM) transition is accompanying this order, observed in nearly all parent compounds, except bulk FeSe. The absence of the AFM order in FeSe casts doubt on the magnetic mechanism of iron-based superconductivity, since the nematic order is believed to be driven by the same interaction that is responsible for the superconducting pairing in these materials. Here we show, through systematic first-principles electronic structure calculations, that the ground state of FeSe is in fact strongly AFM correlated but without developing a magnetic long-range order. Actually, there are a series of staggered n -mer AFM states with corresponding energies below that of the single stripe AFM state, which is the ground state for the parent compounds of most iron-based superconductors. Here, the staggered n -mer (n any integer >1 ) means a set of n adjacent parallel spins on a line along the b axis with antiparallel spins between n -mers along both a and b axes. Moreover, different n -mers can antiparallelly mix with each other to coexist. Among all the states, we find that the lowest energy states formed by the staggered dimer, staggered trimer, and their random antiparallel aligned spin states along the b axis are quasidegenerate. The thermal average of these states does not show any magnetic long-range order, but it does possess a hidden one-dimensional AFM order along the a axis, which can be detected by elastic neutron scattering measurements. Our finding gives a natural account for the absence of long-range magnetic order and suggests that the nematicity is driven predominantly by spin fluctuations even in bulk FeSe, providing a unified description on the phase diagram of iron-based superconductors.
Effective Field Theory of Fractional Quantized Hall Nematics
Energy Technology Data Exchange (ETDEWEB)
Mulligan, Michael; /MIT, LNS; Nayak, Chetan; /Station Q, UCSB; Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC
2012-06-06
We present a Landau-Ginzburg theory for a fractional quantized Hall nematic state and the transition to it from an isotropic fractional quantum Hall state. This justifies Lifshitz-Chern-Simons theory - which is shown to be its dual - on a more microscopic basis and enables us to compute a ground state wave function in the symmetry-broken phase. In such a state of matter, the Hall resistance remains quantized while the longitudinal DC resistivity due to thermally-excited quasiparticles is anisotropic. We interpret recent experiments at Landau level filling factor {nu} = 7/3 in terms of our theory.
Analysis of Nematic Liquid Crystals with Disclination Lines
Bauman, P; Phillips, D
2011-01-01
We investigate the structure of nematic liquid crystal thin films described by the Landau--de Gennes tensor-valued order parameter with Dirichlet boundary conditions of nonzero degree. We prove that as the elasticity constant goes to zero a limiting uniaxial texture forms with disclination lines corresponding to a finite number of defects, all of degree 1/2 or all of degree -1/2. We also state a result on the limiting behavior of minimizers of the Chern-Simons-Higgs model without magnetic field that follows from a similar proof.
Biaxial nematic liquid crystals theory, simulation and experiment
Luckhurst, Geoffrey R
2015-01-01
Liquid Crystals are a state of matter that have properties between those of conventional liquid and those of a solid crystal. Thermotropic liquid crystals react to changes in temperature or, in some cases, pressure. The reaction of lyotropic liquid crystals, which are used in the manufacture of soaps and detergents, depends on the type of solvent they are mixed with. Since the accidental discovery of the chiral nematic (ordered) phase in 1888 many liquid crystal phases have been found, sometimes by chance and sometimes by design. The existence of one such phase was predicted by Freiser in 197
Characterization of a chiral nematic mesoporous organosilica using NMR
Manning, Alan; Shopsowitz, Kevin; Giese, Michael; MacLachlan, Mark; Dong, Ronald; Michal, Carl
2012-10-01
Using templation with nanocrystalline cellulose, a mesoporous organosilica film with a chiral nematic pore structure has recently been developed. [1] We have used a variety of Nuclear Magnetic Resonance (NMR) techniques to characterize the pore structure. The pore size distribution has been found by analyzing the freezing point depression of absorbed water via NMR cryoporometry. The effective longitudinal and transverse pore diameters for diffusing water were investigated with Pulsed-Field Gradient (PFG) NMR and compared to a 1-D connected-pore model. Preliminary data on testing imposed chiral ordering in absorbed liquid crystals is also presented. [4pt] [1] K.E. Shopsowitz et al. JACS 134(2), 867 (2012)
Theory of nonlocal soliton interaction in nematic liquid crystals
DEFF Research Database (Denmark)
Rasmussen, Per Dalgaard; Bang, Ole; Krolikowski, Wieslaw
2005-01-01
We investigate interactions between spatial nonlocal bright solitons in nematic liquid crystals using an analytical “effective particle” approach as well as direct numerical simulations. The model predicts attraction of out-of-phase solitons and the existence of their stable bound state....... This nontrivial property is solely due to the nonlocal nature of the nonlinear response of the liquid crystals. We further predict and verify numerically the critical outwards angle and degree of nonlocality which determine the transition between attraction and repulsion of out-of-phase solitons....
Equilibrium configurations of nematic liquid crystals on a torus.
Segatti, Antonio; Snarski, Michael; Veneroni, Marco
2014-07-01
The topology and the geometry of a surface play a fundamental role in determining the equilibrium configurations of thin films of liquid crystals. We propose here a theoretical analysis of a recently introduced surface Frank energy, in the case of two-dimensional nematic liquid crystals coating a toroidal particle. Our aim is to show how a different modeling of the effect of extrinsic curvature acts as a selection principle among equilibria of the classical energy and how new configurations emerge. In particular, our analysis predicts the existence of stable equilibria with complex windings.
Band structures in the nematic elastomers phononic crystals
Yang, Shuai; Liu, Ying; Liang, Tianshu
2017-02-01
As one kind of new intelligent materials, nematic elastomers (NEs) represent an exciting physical system that combines the local orientational symmetry breaking and the entropic rubber elasticity, producing a number of unique physical phenomena. In this paper, the potential application of NEs in the band tuning is explored. The band structures in two kinds of NE phononic crystals (PCs) are investigated. Through changing NE intrinsic parameters, the influence of the porosity, director rotation and relaxation on the band structures in NE PCs are analyzed. This work is a meaningful try for application of NEs in acoustic field and proposes a new intelligent strategy in band turning.
Modulation instability and solitons in two-color nematic crystals
Horikis, Theodoros P
2016-01-01
The conditions under which stable evolution of two nonlinear interacting waves are derived within the context of nematic crystals. Two cases are considered: plane waves and solitons. In the first case, the modulation instability analysis reveals that while the nonlocal term suppresses the growth rates, substantially, the coupled system exhibits significantly higher growth rates than its scalar counterpart. In the soliton case, the necessary conditions are derived that lead the solitons to exhibit stable, undistorted evolution, suppressing any breathing behavior and radiation, leading to soliton mutual guiding.
Higher Twist Distribution Amplitudes of the Nucleon in QCD
Braun, V M; Mahnke, N; Stein, E
2000-01-01
We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A complete set of distribution amplitudes is constructed, which satisfies equations of motion and constraints that follow from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules.
Shear-stress-controlled dynamics of nematic complex fluids.
Klapp, Sabine H L; Hess, Siegfried
2010-05-01
Based on a mesoscopic theory we investigate the nonequilibrium dynamics of a sheared nematic liquid, with the control parameter being the shear stress σ xy (rather than the usual shear rate, γ). To this end we supplement the equations of motion for the orientational order parameters by an equation for γ, which then becomes time dependent. Shearing the system from an isotropic state, the stress-controlled flow properties turn out to be essentially identical to those at fixed γ. Pronounced differences occur when the equilibrium state is nematic. Here, shearing at controlled γ yields several nonequilibrium transitions between different dynamic states, including chaotic regimes. The corresponding stress-controlled system has only one transition from a regular periodic into a stationary (shear-aligned) state. The position of this transition in the σ xy-γ plane turns out to be tunable by the delay time entering our control scheme for σ xy. Moreover, a sudden change in the control method can stabilize the chaotic states appearing at fixed γ.
Nematic-like stable glasses without equilibrium liquid crystal phases.
Gómez, Jaritza; Gujral, Ankit; Huang, Chengbin; Bishop, Camille; Yu, Lian; Ediger, M D
2017-02-07
We report the thermal and structural properties of glasses of posaconazole, a rod-like molecule, prepared using physical vapor deposition (PVD). PVD glasses of posaconazole can show substantial molecular orientation depending upon the choice of substrate temperature, Tsubstrate, during deposition. Ellipsometry and IR measurements indicate that glasses prepared at Tsubstrate very near the glass transition temperature (Tg) are highly ordered. For these posaconazole glasses, the orientation order parameter is similar to that observed in macroscopically aligned nematic liquid crystals, indicating that the molecules are mostly parallel to one another and perpendicular to the interface. To our knowledge, these are the most anisotropic glasses ever prepared by PVD from a molecule that does not form equilibrium liquid crystal phases. These results are consistent with a previously proposed mechanism in which molecular orientation in PVD glasses is inherited from the orientation present at the free surface of the equilibrium liquid. This mechanism suggests that molecular orientation at the surface of the equilibrium liquid of posaconazole is nematic-like. Posaconazole glasses can show very high kinetic stability; the isothermal transformation of a 400 nm glass into the supercooled liquid occurs via a propagating front that originates at the free surface and requires ∼10(5) times the structural relaxation time of the liquid (τα). We also studied the kinetic stability of PVD glasses of itraconazole, which is a structurally similar molecule with equilibrium liquid crystal phases. While itraconazole glasses can be even more anisotropic than posaconazole glasses, they exhibit lower kinetic stability.
Nematic phase formation in suspensions of carbon nanotubes
Zakri, Cecile; Poulin, Philippe
This chapter describes the chemical composition, phase behavior and structure of recently investigated carbon nanotube (CNT) based liquid crystals. Because nanotubes are long and thin rigid cylinders, their phase behavior shares several similarities with many other systems such as rigid polymers and rod-like particle suspensions. CNT liquid crystals are achieved in highly concentrated suspensions comprised of raw or chemically functionalized particles. But extreme aspect ratio, rigidity, high sensitivity to interactions, optical properties and structural features of CNTs make their liquid crystalline phases unique in several ways. In particular, the chapter discusses the importance of the CNT waviness on the phase ordering and the role of excess surfactant or biomolecules used to stabilize the CNTs. The unique resonant Raman scattering of CNT allows original and accurate measurements of order parameters at a micron-scale. Highly oriented nematic tactoids could even be characterized by polarized Raman microscopy. From a more applied point of view, nematic ordering is shown to be a route towards the processing of new materials such as anisotropic conductive films and high strength fibers made of oriented carbon nanotubes. Examples of functional materials and nanocomposites achieved from CNT liquid crystals are given.
Points or vectors? The polar structure of disclinations in active and passive nematics
Giomi, Luca; Vromans, Arthur
Topological defects play a pivotal role in the physics of liquid crystals and represent one of the most prominent and well studied aspects of mesophases. While in two-dimensional nematics, disclinations are traditionally treated as point-like objects, recent experimental studies on active nematics have suggested that half-strength disclinations might in fact posses a polar structure. In this talk I will provide a precise definition of polarity for half-strength nematic disclinations, introduce a simple and robust method to calculate this quantity from experimental and numerical data and investigate how the orientational properties of active and passive half-strength disclinations affect their dynamics.
Superconductivity and non-Fermi liquid behavior near a nematic quantum critical point
Lederer, Samuel; Schattner, Yoni; Berg, Erez; Kivelson, Steven A.
2017-05-01
Using determinantal quantum Monte Carlo, we compute the properties of a lattice model with spin mn>1mn>mn>2mn>12 itinerant electrons tuned through a quantum phase transition to an Ising nematic phase. The nematic fluctuations induce superconductivity with a broad dome in the superconducting TcTc enclosing the nematic quantum critical point. For temperatures above TcTc, we see strikingly non-Fermi liquid behavior, including a “nodal-antinodal dichotomy” reminiscent of that seen in several transition metal oxides. In addition, the critical fluctuations have a strong effect on the low-frequency optical conductivity, resulting in behavior consistent with “bad metal” phenomenology.
A molecular dynamics study of ferroelectric nanoparticles immersed in a nematic liquid crystal.
Pereira, M S S; Canabarro, A A; de Oliveira, I N; Lyra, M L; Mirantsev, L V
2010-01-01
A large number of interesting phenomena related to the insertion of colloidal particles in liquid crystals (LC) have recently been reported. Here, we investigate effects caused by the addition of spherically shaped ferroelectric nanoparticles to a nematic liquid crystal. Using molecular dynamics (MD) simulations, the density of LC molecules, the orientational order parameter, and the polar and azimuthal angle profiles are calculated as functions of the distance to the center of the immersed nanoparticle for different temperatures of the system. We observe that the assembly of ferroelectric nanoparticles enhances the nematic order in the LC medium changing many properties of its host above the nematic-isotropic transition temperature T (*) (NI) .
Nematic order by elastic interactions and rigidity sensing of living cells
Friedrich, Benjamin M
2010-01-01
We predict spontaneous nematic order in an ensemble of active force generators with elastic interactions as a minimal model for early cytoskeletal self-polarization. Mean-field theory is formally equivalent to Maier-Saupe theory for a nematic liquid. However, the elastic interactions are long-ranged (and thus depend on cell shape and matrix elasticity) and originate in cell activity. Depending on the density of force generators, we find two regimes of cellular rigidity sensing for which nematic order depends on matrix rigidity either in a step-like manner or with a maximum at an optimal rigidity.
Concurrence of bulk and surface order reconstruction to the relaxation of frustrated nematics
Amoddeo, Antonino
2016-08-01
Applying appropriate electric pulses to a nematic liquid crystal confined between plates, the bulk order reconstruction can occur, a mechanism allowing the switching between topologically different nematic textures without any director rotation. Using a moving mesh finite element method we describe the order tensor dynamics for a nematic inside an asymmetric n-cell, putting in evidence as textural distortions induced by strong asymmetries can be relaxed via both bulk and surface order reconstruction, occurring close to a confining plate with different time duration.
General relativistic neutron stars with twisted magnetosphere
Pili, A G; Del Zanna, L
2014-01-01
Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.
Twisted black hole is Taub-NUT
Ong, Yen Chin
2017-01-01
Recently a purportedly novel solution of the vacuum Einstein field equations was discovered: it supposedly describes an asymptotically flat twisted black hole in 4-dimensions whose exterior spacetime rotates in a peculiar manner—the frame dragging in the northern hemisphere is opposite from that of the southern hemisphere, which results in a globally vanishing angular momentum. Furthermore it was shown that the spacetime has no curvature singularity. We show that the geometry of this black hole spacetime is nevertheless not free of pathological features. In particular, it harbors a rather drastic conical singularity along the axis of rotation. In addition, there exist closed timelike curves due to the fact that the constant r and constant t surfaces are not globally Riemannian. In fact, none of these are that surprising since the solution is just the Taub-NUT geometry. As such, despite the original claim that the twisted black hole might have observational consequences, it cannot be.
Twisted mass QCD at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Ilgenfritz, E.M.; Mueller-Preussker, M.; Petschlies, M. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Jansen, K. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Lombardo, M.P. [Istituto Nazionale di Fisica Nucleare, LNF, Frascati (Italy); Philipsen, O.; Zeidlewicz, L. [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Sternbeck, A. [Adelaide Univ. (Australia). CSSM School of Chemistry and Physics
2007-10-15
We discuss the use of Wilson fermions with twisted mass for simulations of QCD thermodynamics. As a prerequisite for a future analysis of the finite-temperature transition making use of automatic {partial_derivative} (a) improvement, we investigate the phase structure in the space spanned by the hopping parameter {kappa}, the coupling {beta}, and the twisted mass parameter {mu}. We present results for N{sub f}=2 degenerate quarks on a 16{sup 3} x 8 lattice, for which we investigate the possibility of an Aoki phase existing at strong coupling and vanishing {mu}, as well as of a thermal phase transition at moderate gauge couplings and non-vanishing {mu}. (orig.)
Magnetic Field Twisting by Intergranular Downdrafts
Taroyan, Youra; Williams, Thomas
2016-10-01
The interaction of an intergranular downdraft with an embedded vertical magnetic field is examined. It is demonstrated that the downdraft may couple to small magnetic twists leading to an instability. The descending plasma exponentially amplifies the magnetic twists when it decelerates with depth due to increasing density. Most efficient amplification is found in the vicinity of the level, where the kinetic energy density of the downdraft reaches equipartition with the magnetic energy density. Continual extraction of energy from the decelerating plasma and growth in the total azimuthal energy occurs as a consequence of the wave-flow coupling along the downdraft. The presented mechanism may drive vortices and torsional motions that have been detected between granules and in simulations of magnetoconvection.
Factorising the 3D Topologically Twisted Index
Cabo-Bizet, Alejandro
2016-01-01
In this work, path integral representations of the 3D topologically twisted index were studied. First, the index can be "factorised" into a couple of "blocks". The "blocks" being the partition functions of a type A semi-topological twisting of 3D N = 2 SYM placed on $\\mathbb{S}_2\\times (0, \\pi)$ and $\\mathbb{S}_2 \\times (\\pi, 2 \\pi)$ respectively. Second, as the path integral of the aforementioned theory over $\\mathbb{S}_2$ times $\\mathbb{S}_1$ with a point excluded. In this way we recover the sum over fluxes from integration over the real path and without sacrificing positive definiteness of the bosonic part of the localising action. We also reproduce the integration over the complex contour by using the localising term with positive definite bosonic part.
Tinkertoys for the Twisted D-Series
Chacaltana, Oscar; Trimm, Anderson
2013-01-01
We study 4D N=2 superconformal field theories that arise from the compactification of 6D N=(2,0) theories of type D_N on a Riemann surface, in the presence of punctures twisted by a Z_2 outer automorphism. Unlike the untwisted case, the family of SCFTs is in general parametrized, not by M_{g,n}, but by a branched cover thereof. The classification of these SCFTs is carried out explicitly in the case of the D_4 theory, in terms of three-punctured spheres and cylinders, and we provide tables of properties of twisted punctures for the D_5 and D_6 theories. We find realizations of Spin(8) and Spin(7) gauge theories with matter in all combinations of vector and spinor representations with vanishing beta-function, as well as Sp(3) gauge theories with matter in the 3-index traceless antisymmetric representation.
Valve-aided twisted Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Jaya Rajkumar, M.; Saha, U.K.
2006-05-15
Accessories, such as end plates, deflecting plates, shielding and guide vanes, may increase the power of a Savonius rotor, but make the system structurally complex. In such cases, the rotor can develop a relatively large torque at small rotational speeds and is cheap to build, however it harnesses only a small fraction of the incident wind energy. Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades. Such methods have been studied experimentally with a twisted-blade Thus improving a Savonius rotor's energy capture. This new concept has been named as the 'Valve-Aided Twisted Savonius'rotor. Tests were conducted in a low-speed wind tunnel to evaluate performance. This mechanism is found to be independent of flow direction, and shows potential for large machines. [Author].
Energy Technology Data Exchange (ETDEWEB)
Chono, S.; Tsuji, T. (Fukui University, Fukui (Japan). Faculty of Engineering); Denn, M. (University of California, Barkeley, CA (United States))
1994-06-25
The nematic liquid crystal is liquid crystal having the simplest structure of molecular arrangement. Though its molecules are oriented in a fixed direction, its gravity is, similarly to that of the isotropic fluid, located at random. After having described the Leslie-Ericksen continuum (L-E) theory utilizable as a structural equation of nematic crystal, the present paper explained how a planar 4:1 contraction flow was numerically analyzed with the L-E theory for a wide range of Ericksen numbers. Further, the velocity field and orientation field were analyzed as well. The transversely isotropic fluid (TIF) was also studied about its stream line and orientation angle distribution of liquid crystal, and stream line of Newtonian fluid. Around a convex part in the liquid crystal flow, generated is its comparatively large secondary flow, which is made slightly smaller by an increase in Ericksen number. The secondary flow of TIF is small and resembles the Newtonian fluid flow in configuration. It is also the case with the main flow of TIF. 20 refs., 8 figs., 1 tab.
Overlap fermions on a twisted mass sea
Bär, O; Schäefer, S; Scorzato, L; Shindler, A
2006-01-01
We present first results of a mixed action project. We analyze gauge configurations generated with two flavors of dynamical twisted mass fermions. Neuberger's overlap Dirac operator is used for the valence sector. The various choices in the setup of the simulation are discussed. We employ chiral perturbation theory to describe the effects of using different actions in the sea and valence sector at non-zero lattice spacing.
Disconnected diagrams with twisted-mass fermions
Abdel-Rehim, Abdou; Constantinou, Martha; Finkenrath, Jacob; Hadjiyiannakou, Kyriakos; Jansen, Karl; Kallidonis, Christos; Koutsou, Giannis; Avilés-Casco, Alejandro Vaquero
2016-01-01
The latest results from the Twisted-Mass collaboration on disconnected diagrams at the physical value of the pion mass are presented. In particular, we focus on the sigma terms, the axial charges and the momentum fraction, all of them for the nucleon. A detailed error analysis for each observable follows, showing the strengths and weaknesses of the one-end trick. Alternatives are discussed.
DNA Packaging in Bacteriophage: Is Twist Important?
Spakowitz, Andrew James; Wang, Zhen-Gang
2005-01-01
We study the packaging of DNA into a bacteriophage capsid using computer simulation, specifically focusing on the potential impact of twist on the final packaged conformation. We perform two dynamic simulations of packaging a polymer chain into a spherical confinement: one where the chain end is rotated as it is fed, and one where the chain is fed without end rotation. The final packaged conformation exhibits distinct differences in these two cases: the packaged conformation from feeding with...
On rectangular HOMFLY for twist knots
Kononov, Ya
2016-01-01
As a new step in the study of rectangularly-colored knot polynomials, we reformulate the prescription of arXiv:1606.06015 for twist knots in the double-column representations $R=[rr]$ in terms of skew Schur polynomials. These, however, are mysteriously shifted from the standard topological locus, what makes further generalization to arbitrary $R=[r^s]$ not quite straightforward.
Twisted Radiation by Electrons in Spiral Motion
Katoh, M; Mirian, N S; Konomi, T; Taira, Y; Kaneyasu, T; Hosaka, M; Yamamoto, N; Mochihashi, A; Takashima, Y; Kuroda, K; Miyamoto, A; Miyamoto, K; Sasaki, S
2016-01-01
We theoretically show that a single free electron in circular/spiral motion radiates an electromagnetic wave possessing helical phase structure and carrying orbital angular momentum. We experimentally demonstrate it by double-slit diffraction on radiation from relativistic electrons in spiral motion. We show that twisted photons should be created naturally by cyclotron/synchrotron radiations or Compton scatterings in various situations in astrophysics. We propose promising laboratory vortex photon sources in various wavelengths ranging from radio wave to gamma-rays.
Twisted spectral geometry for the standard model
Martinetti, Pierre
2015-01-01
The Higgs field is a connection one-form as the other bosonic fields, provided one describes space no more as a manifold M but as a slightly non-commutative generalization of it. This is well encoded within the theory of spectral triples: all the bosonic fields of the standard model - including the Higgs - are obtained on the same footing, as fluctuations of a generalized Dirac operator by a matrix-value algebra of functions on M. In the commutative case, fluctuations of the usual free Dirac operator by the complex-value algebra A of smooth functions on M vanish, and so do not generate any bosonic field. We show that imposing a twist in the sense of Connes-Moscovici forces to double the algebra A, but does not require to modify the space of spinors on which it acts. This opens the way to twisted fluctuations of the free Dirac operator, that yield a perturbation of the spin connection. Applied to the standard model, a similar twist yields in addition the extra scalar field needed to stabilize the electroweak v...
Design optimization for active twist rotor blades
Mok, Ji Won
This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to
Directory of Open Access Journals (Sweden)
A Avazpour
2014-12-01
Full Text Available Density functional approach was used to study the isotropic- nematic (I-N transition and calculate the values of freezing parameters of the Gay- Berne liquid crystal model. New direct and pair correlation functions of a molecular fluid with Gay- Berne pair potential were used. These new functions were used in density functional theory as input to calculate the isotropic- nematic transition densities for elongation at various reduced temperatures. It was observed that the isotropic- nematic transition densities increase as the temperature increases. It was found that the new direct correlation function is suitable to study the isotropic- nematic transition of Gay- Berne liquids. Comparison to other works showed qualitative agreement
Pleiner, Harald; Brand, Helmut R
2014-02-01
We discuss the symmetry properties as well as the dynamic behavior of various non-polar nematic liquid crystal phases with tetrahedral order. We concentrate on systems that show biaxial nematic order coexisting with octupolar (tetrahedral) order. Non-polar examples are phases with D2 and S4 symmetries, which can be characterized as biaxial nematics lacking inversion symmetry. It is this combination that allows for new features in the statics and dynamics of these phases. The D2-symmetric phase is chiral, even for achiral molecules, and shows ambidextrous chirality in all three preferred directions. The achiral S4-symmetric phase allows for ambidextrous helicity, similar to the higher-symmetric D2d-symmetric phase. Such phases are candidates for nematic phases made from banana-shaped molecules.
Expression of Twist Gene in Primary Liver Cancer
Institute of Scientific and Technical Information of China (English)
XU Jing; CHEN Xiaoping
2007-01-01
In order to investigate the possibility of overexpression of Twist in primary liver cancer (PLC), the Twist expression was detected by using immunohistochemical analysis and RT-PCR assay in 45 patients with PLC. Control tissues were obtained from 9 patients with liver hemangioma. It was found that in 36 (80.0%) out of 45 PLC patients, cancerous regions showed positive cytoplasm and nucleus staining for Twist with a diffuse pattern. In noncancerous adjacent areas and control liver tissues, the expression of Twist was 57.8% and 22.2% respectively. The results of RT-PCR assay re- vealed that the expression of Twist was stronger in the cancerous tissues than that in the noncancer- ous adjacent tissues. It was suggested that the expression of Twist was up-regulated in PLC, which play an important role in the progression of PLC.
Chromonic nematic phase and scalar order parameter of indanthrone derivative with ionic additives
Boiko O.P.; Vasyuta R.M.; Semenyshyn O.M.; Nastishin Yu.A.; Nazarenko V.G.
2008-01-01
We investigate influence of different ionic additives on the phase behaviour and scalar order parameter of lyotropic chromonic nematic liquid crystals formed by the molecules representing derivatives of indanthrone. KI, (NH4)2SO4 and NaCl salts increase biphasic nematic region on the temperature-concentration phase diagram, whereas the scalar orientational order parameter is hardly sensitive to their presence. We suggest that these changes are attributed to increase in the ag-gregate length a...
Magnetic-Field-Induced Weak Order in Nematic Liquid Crystals Formed by Biaxial Molecules
Institute of Scientific and Technical Information of China (English)
ZHANG Zhi-Dong; ZHANG De-Xian; SUN Yu-Bao
2000-01-01
Nematic liquid crystal system of interacting biaxial particles via dispersion forces is studied. The molecular orienting potential form in a magnetic field is given for the first time. Weakly ordered isotropic phase is treated in the two-particle cluster approximation. Taking account of the molecular biaxiality, it is found that the ratio of the lowest supercooling temperature T* to the nematic-isotropic phase transition temperature TC approaches the observed value, and the validity of the mean field theory is clarified.
Anchoring-Induced Texture & Shear Banding of Nematic Polymers in Shear Cells
2007-10-01
varying orientation tensor ellipsoid at several locations between the plates. The Doi- Hess kinetic theory is developed to study the dynamics of LCP...profile is evident in one of the snapshots, a phenomenon seen by Sebastian Heidenreich in related studies and in full kinetic flow-nematic simulations of...kinetic phase diagram for nematic polymers, Rheol. Acta., 43 (2004), 17–37. [20] M.G. Forest, Q. Wang and R. Zhou, The flow-phase diagram of Doi- Hess
Caldarelli, Stefano; Catalano, Donata; Di Bari, Lorenzo; Lumetti, Marco; Ciofalo, Maurizio; Alberto Veracini, Carlo
1994-07-01
The dipolar couplings observed by NMR spectroscopy of solutes in nematic solvents (LX-NMR) are used to build up the maximum entropy (ME) probability distribution function of the variables describing the orientational and internal motion of the molecule. The ME conformational distributions of 2,2'- and 3,3'-dithiophene and 2,2':5',2″-terthiophene (α-terthienyl)thus obtained are compared with the results of previous studies. The 2,2'- and 3,3'-dithiophene molecules exhibit equilibria among cisoid and transoid forms; the probability maxima correspond to planar and twisted conformers for 2,2'- or 3,3'-dithiophene, respectively, 2,2':5',2″-Terthiophene has two internal degrees of freedom; the ME approach indicates that the trans, trans and cis, trans planar conformations are the most probable. The correlation between the two intramolecular rotations is also discussed.
Advection of nematic liquid crystals by chaotic flow
O'Naraigh, Lennon
2016-01-01
Consideration is given to the effects of inhomogeneous shear flow (both regular and chaotic) on nematic liquid crystals in a planar two-dimensional geometry. The Landau-de Gennes equation coupled to an externally-prescribed flow field is the basis for the study: this is solved numerically in a periodic spatial domain. The focus is on a limiting case where the advection is passive, such that variations in the liquid-crystal properties do not feed back into the equation of motion for the uid velocity. The numerical simulations demonstrate that the coarsening of the liquid-crystal domains is arrested by the ow. The nature of the arrest is different depending on whether the flow is regular or chaotic. For the specific case where tumbling is important, the flow has a strong effect on the the liquid-crystal morphology: this provides a mechanism for controlling the shape of the liquid-crystal domains.
Vector nematicons: Coupled spatial solitons in nematic liquid crystals
Horikis, Theodoros P.; Frantzeskakis, Dimitrios J.
2016-11-01
Families of soliton pairs, namely vector solitons, are found within the context of a coupled nonlocal nonlinear Schrödinger system of equations, as appropriate for modeling beam propagation in nematic liquid crystals. In the focusing case, bright soliton pairs have been found to exist provided their amplitudes satisfy a specific condition. In our analytical approach, focused on the defocusing regime, we rely on a multiscale expansion methods, which reveals the existence of dark-dark and antidark-antidark solitons, obeying an effective Korteweg-de Vries equation, as well as dark-bright solitons, obeying an effective Mel'nikov system. These pairs are discriminated by the sign of a constant that links all physical parameters of the system to the amplitude of the stable continuous wave solutions, and, much like the focusing case, the solitons' amplitudes are linked, leading to mutual guiding.
Asymmetric dynamic phase holographic grating in nematic liquid crystal
Ren, Chang-Yu; Shi, Hong-Xin; Ai, Yan-Bao; Yin, Xiang-Bao; Wang, Feng; Ding, Hong-Wei
2016-09-01
A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect. Project supported by the Science and Technology Programs of the Educational Committee of Heilongjiang Province, China (Grant No. 12541730) and the National Natural Science Foundation of China (Grant No. 61405057).
Oscillatory motion of sheared nanorods beyond the nematic phase.
Strehober, David A; Engel, Harald; Klapp, Sabine H L
2013-07-01
We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial orientational order parameter. We investigate these equations via a systematic bifurcation analysis based on a numerical continuation technique, focusing on spatially homogeneous states. Exploring a wide range of parameters we find, unexpectedly, that states with oscillatory motion can exist even under conditions where the equilibrium system is isotropic. These oscillatory states are characterized by a wagging motion of the paranematic director, and they occur if the tumbling parameter is sufficiently small. We also present full nonequilibrium phase diagrams in the plane spanned by the concentration and the shear rate.
Programming complex shapes in thin nematic elastomer and glass sheets
Plucinsky, Paul; Lemm, Marius; Bhattacharya, Kaushik
2016-07-01
Nematic elastomers and glasses are solids that display spontaneous distortion under external stimuli. Recent advances in the synthesis of sheets with controlled heterogeneities have enabled their actuation into nontrivial shapes with unprecedented energy density. Thus, these have emerged as powerful candidates for soft actuators. To further this potential, we introduce the key metric constraint which governs shape-changing actuation in these sheets. We then highlight the richness of shapes amenable to this constraint through two broad classes of examples which we term nonisometric origami and lifted surfaces. Finally, we comment on the derivation of the metric constraint, which arises from energy minimization in the interplay of stretching, bending, and heterogeneity in these sheets.
Hidden topological constellations and polyvalent charges in chiral nematic droplets
Posnjak, Gregor; Čopar, Simon; Muševič, Igor
2017-02-01
Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=-2, -3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules.
Light and phospholipid driven structural transitions in nematic microdroplets
Energy Technology Data Exchange (ETDEWEB)
Dubtsov, A. V., E-mail: alexanderdubtsov@gmail.com; Pasechnik, S. V.; Shmeliova, D. V. [Moscow State University of Instrument Engineering and Computer Science, Stromynka 20, Moscow 107996 (Russian Federation); Kralj, Samo [Condensed Matter Physics Department, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); FNM, University of Maribor, Koroska 160, 2000 Maribor (Slovenia)
2014-10-13
We studied the UV-irradiation and phospholipid driven bipolar-radial structural transitions within azoxybenzene nematic liquid crystal (LC) droplets dispersed in water. It was found that the UV-irradiation induced trans-cis isomerisation of LC molecules could enable structural transitions into radial-type configurations at a critical UV-irradiation time t{sub c}. In particular, we show that under appropriate conditions, a value of t{sub c} could sensitively fingerprint the concentration of phospholipid molecules present in LC-water dispersions. This demonstrated proof-of-principle mechanism could be exploited for development of sensitive detectors for specific nanoparticles (NPs), where value of t{sub c} reveals concentration of NPs.
Nematic Equilibria on a Two-Dimensional Annulus
Lewis, A. H.
2017-01-16
We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.
Fluctuation-induced interactions in nematics with disordered anchoring energy
Karimi Pour Haddadan, Fahimeh; Naji, Ali; Shirzadiani, Nafiseh; Podgornik, Rudolf
2014-12-01
We examine fluctuation-induced (pseudo-Casimir) interactions in nematic liquid-crystalline films confined between two surfaces, where one of the surfaces imposes a strong homeotropic anchoring (ensuring a uniform mean director profile), while the other one is assumed to be a chemically disordered substrate exhibiting an annealed distribution of anchoring energies. We employ a saddle-point approximation to evaluate the free energy of interaction mediated between the two surfaces and investigate how the interaction force is influenced by the presence of disordered surface anchoring energy. It is shown that the disorder results in a renormalization of the effective surface anchoring parameter in a way that it leads to quantitative and qualitative changes (including a change of sign at intermediate inter-surface separations) in the pseudo-Casimir interaction force when compared with the interaction force in the absence of disorder.
Elastic interactions between topological defects in chiral nematic shells
Darmon, Alexandre; Dauchot, Olivier; Lopez-Leon, Teresa; Benzaquen, Michael
2016-12-01
We present a self-consistent and robust theoretical model to investigate elastic interactions between topological defects in liquid crystal shells. Accounting for the nonconcentric nature of the shell in a simple manner, we are able to successfully and accurately explain and predict the positions of the defects, most relevant in the context of colloidal self-assembly. We calibrate and test our model on existing experimental data and extend it to all observed defects configurations in chiral nematic shells. We perform experiments to check further and confirm the validity of the present model. Moreover, we are able to obtain quantitative estimates of the energies of +1 or +3 /2 disclination lines in cholesterics, whose intricate nature was only reported recently [A. Darmon, et al. Proc. Natl. Acad. Sci. USA 113, 9469 (2016), 10.1073/pnas.1525059113].
Impact of diffusion limited aggregates of impurities on nematic ordering
Harkai, S.; Ambrožič, M.; Kralj, S.
2017-02-01
We study the impact of random bond-type disorder on two-dimensional (2D) orientational ordering of nematic liquid crystal (LC) configurations. The lattice Lebwohl-Lasher pseudospin model is used to model orientational ordering perturbed by frozen-in rod-like impurities of concentration p exhibiting the isotropic orientational probability distribution. The impurities are either (i) randomly spatially distributed or (ii) form diffusion limited aggregation (DLA)-type patterns characterized by the fractal dimensions df, where we consider cases df ∼ 1.7 and df ∼ 1.9. The degree of orientational ordering is quantified in terms of the orientational pair correlation function G(r) . Simulations reveal that the DLA pattern imposed disorder has a significantly weaker impact for a given concentration of impurities. Furthermore, if samples are quenched from the isotropic LC phase, then the fractal dimension is relatively strongly imprinted on quantitative characteristics of G(r) .
Orientational defects near colloidal particles in a nematic liquid crystal.
Feng, James J; Zhou, Chixing
2004-01-01
We study the interaction between a surface-anchoring colloidal particle and a liquid-crystalline host, and in particular the formation of orientational defects near the particle. A mean-field theory based on the nonlocal Marrucci-Greco nematic potential is used to represent molecular interactions in an inhomogeneous orientational field. An evolution equation for the molecular configuration tensor is solved numerically whose steady state minimizes the total free energy of the system. With strong homeotropic anchoring on the particle surface, three types of solutions may appear depending on initial conditions and particle size: Saturn rings, satellite point defects, and polar rings. The Saturn ring remains stable on micrometer-sized particles, contrary to previous calculations but consistent with experiments. A phase diagram is constructed for the three regimes. Based on the free energy, the most stable state is the Saturn ring for smaller particles and the satellite defect for larger ones.
Oscillatory motion of sheared nanorods beyond the nematic phase
Strehober, David A.; Engel, Harald; Klapp, Sabine H. L.
2013-07-01
We study the role of the control parameter triggering nematic order (temperature or concentration) on the dynamical behavior of a system of nanorods under shear. Our study is based on a set of mesoscopic equations of motion for the components of the tensorial orientational order parameter. We investigate these equations via a systematic bifurcation analysis based on a numerical continuation technique, focusing on spatially homogeneous states. Exploring a wide range of parameters we find, unexpectedly, that states with oscillatory motion can exist even under conditions where the equilibrium system is isotropic. These oscillatory states are characterized by a wagging motion of the paranematic director, and they occur if the tumbling parameter is sufficiently small. We also present full nonequilibrium phase diagrams in the plane spanned by the concentration and the shear rate.
Theory of nine elastic constants of biaxial nematics
Institute of Scientific and Technical Information of China (English)
Liu Hong
2008-01-01
In this paper, a rotational invariant of interaction energy between two biaxial-shaped molecules is assumed and in the mean field approximation, nine elastic constants for simple distortion patterns in biaxial nematica are derived in terms of the thermal averagewhere D(l)mn is the Wigner rotation matrix.In the lowest order terms, the elastic constants depend on coefficients г,г',λ, order parameters Q0=Q0+Q2vj'j''j(r12) and probability function fk'k'' k (r12), where r12 is the distance between two molecules, andλis proportional to temperature. Q0 and Q2 are parameters related to multiple moments of molecules. Comparing these results with those obtained from Landau-de Gennes theory, we have obtained relationships between coefficients, order parameters used in both theories. In the special case of uniaxial nematics, both results are reduced to a degenerate case where K11=K33.
Hidden topological constellations and polyvalent charges in chiral nematic droplets
Posnjak, Gregor; Čopar, Simon; Muševič, Igor
2017-01-01
Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=−2, −3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules. PMID:28220770
Theory of Electron Nematic Order in LaOFeAs
Energy Technology Data Exchange (ETDEWEB)
Fang, Chen
2010-04-06
We study a spin S quantum Heisenberg model on the Fe lattice of the rare-earth oxypnictide superconductors. Using both large S and large N methods, we show that this model exhibits a sequence of two phase transitions: from a high temperature symmetric phase to a narrow region of intermediate 'nematic' phase, and then to a low temperature spin ordered phase. Identifying phases by their broken symmetries, these phases correspond precisely to the sequence of structural (tetragonal to monoclinic) and magnetic transitions that have been recently revealed in neutron scattering studies of LaOFeAs. The structural transition can thus be identified with the existence of incipient ('fluctuating') magnetic order.
Tamba, Maria-Gabriela; Yu, Chih Hao; Tang, Bai Jia; Welch, Christopher; Kohlmeier, Alexandra; Schubert, Christopher P; Mehl, Georg H
2014-04-30
The construction of liquid crystal compositions consisting of the dimeric liquid crystal, CB_C9_CB (cyanobiphenyl dimer = 1'',9''-bis(4-cyanobiphenyl-4'-yl)nonane), and the range of nematic systems is explored. The materials include a laterally functionalized monomer, which was used to construct a phase diagram with CB_C9_CB, as well as one laterally linked dimer liquid crystal material and two liquid crystal gold nanoparticle (LC-Au-NPs) systems. For the Au-NP-LCs, the NP diameters were varied between ~3.3 nm and 10 nm. Stable mixtures that exhibit a nematic-nematic phase transition are reported and were investigated by POM (polarizing optical microscopy), DSC (differential scanning calorimetry) and X-ray diffraction studies.
Twisted exponential sums of polynomials in one variable
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The twisted T-adic exponential sums associated to a polynomial in one variable are studied.An explicit arithmetic polygon in terms of the highest two exponents of the polynomial is proved to be a lower bound of the Newton polygon of the C-function of the twisted T-adic exponential sums.This bound gives lower bounds for the Newton polygon of the L-function of twisted p-power order exponential sums.
Negative Regulatory Role of TWIST1 on SNAIL Gene Expression.
Forghanifard, Mohammad Mahdi; Ardalan Khales, Sima; Farshchian, Moein; Rad, Abolfazl; Homayouni-Tabrizi, Masoud; Abbaszadegan, Mohammad Reza
2017-01-01
Epithelial-mesenchymal transition (EMT) is crucial for specific morphogenetic movements during embryonic development as well as pathological processes of tumor cell invasion and metastasis. TWIST and SNAIL play vital roles in both developmental and pathological EMT. Our aim in this study was to investigate the functional correlation between TWIST1 and SNAIL in human ESCC cell line (KYSE-30). The packaging cell line GP293T was cotransfected with either control retroviral pruf-IRES-GFP plasmid or pruf-IRES-GFP-hTWIST1 and pGP plasmid. The KYSE-30 ESCC cells were transduced with produced viral particles and examined with inverted fluorescence microscope. DNA was extracted from transduced KYSE-30 cells and analyzed for copy number of integrated retroviral sequences in the target cell genome. The concentration of retroviral particles was determined by Real-time PCR. After RNA extraction and cDNA synthesis, the mRNA expression of TWIST1 and SNAIL was assessed by comparative real-time PCR amplification. Ectopic expression of TWIST1 in KYSE-30, dramatically reduces SNAIL expression. Retroviral transduction enforced TWIST1 overexpression in GFP-hTWIST1 nearly 9 folds in comparison with GFP control cells, and interestingly, this TWIST1 enforced expression caused a - 7 fold decrease of SNAIL mRNA expression in GFP-hTWIST1 compared to GFP control cells. Inverse correlation of TWIST1 and SNAIL mRNA levels may introduce novel molecular gene expression pathway controlling EMT process during ESCC aggressiveness and tumorigenesis. Consequently, these data extend the spectrum of biological activities of TWIST1 and propose that therapeutic repression of TWIST1 may be an effective strategy to inhibit cancer cell invasion and metastasis.
Induced smectic phases in phase diagrams of binary nematic liquid crystal mixtures.
Huang, Tsang-Min; McCreary, Kathleen; Garg, Shila; Kyu, Thein
2011-03-28
To elucidate induced smectic A and smectic B phases in binary nematic liquid crystal mixtures, a generalized thermodynamic model has been developed in the framework of a combined Flory-Huggins free energy for isotropic mixing, Maier-Saupe free energy for orientational ordering, McMillan free energy for smectic ordering, Chandrasekhar-Clark free energy for hexagonal ordering, and phase field free energy for crystal solidification. Although nematic constituents have no smectic phase, the complexation between these constituent liquid crystal molecules in their mixture resulted in a more stable ordered phase such as smectic A or B phases. Various phase transitions of crystal-smectic, smectic-nematic, and nematic-isotropic phases have been determined by minimizing the above combined free energies with respect to each order parameter of these mesophases. By changing the strengths of anisotropic interaction and hexagonal interaction parameters, the present model captures the induced smectic A or smectic B phases of the binary nematic mixtures. Of particular importance is the fact that the calculated phase diagrams show remarkable agreement with the experimental phase diagrams of binary nematic liquid crystal mixtures involving induced smectic A or induced smectic B phase.
Occurrence of Tn4371-related mobile elements and sequences in (chloro)biphenyl-degrading bacteria.
Springael, D; Ryngaert, A; Merlin, C; Toussaint, A; Mergeay, M
2001-01-01
Tn4371, a 55-kb transposable element involved in the degradation and biphenyl or 4-chlorobiphenyl identified in Ralstonia eutropha A5, displays a modular structure including a phage-like integrase gene (int), a Pseudomonas-like (chloro)biphenyl catabolic gene cluster (bph), and RP4- and Ti-plasmid-like transfer genes (trb) (C. Merlin, D. Springael, and A. Toussaint, Plasmid 41:40-54, 1999). Southern blot hybridization was used to examine the presence of different regions of Tn4371 in a collection of (chloro)biphenyl-degrading bacteria originating from different habitats and belonging to different bacterial genera. Tn4371-related sequences were never detected on endogenous plasmids. Although the gene probes containing only bph sequences hybridized to genomic DNA from most strains tested, a limited selection of strains, all beta-proteobacteria, displayed hybridization patterns similar to the Tn4371 bph cluster. Homology between Tn4371 and DNA of two of those strains, originating from the same area as strain A5, extended outside the catabolic genes and covered the putative transfer region of Tn4371. On the other hand, none of the (chloro)biphenyl degraders hybridized with the outer left part of Tn4371 containing the int gene. The bph catabolic determinant of the two strains displaying homology to the Tn4371 transfer genes and a third strain isolated from the A5 area could be mobilized to a R. eutropha recipient, after insertion into an endogenous or introduced IncP1 plasmid. The mobilized DNA of those strains included all Tn4371 homologous sequences previously identified in their genome. Our observations show that the bph genes present on Tn4371 are highly conserved between different (chloro)biphenyl-degrading hosts, isolated globally but belonging mainly to the beta-proteobacteria. On the other hand, Tn4371-related mobile elements carrying bph genes are apparently only found in isolates from the environment that provided the Tn4371-bearing isolate A5.
A twist tale of cancer metastasis and tumor angiogenesis.
Tseng, Jen-Chieh; Chen, Hsiao-Fan; Wu, Kou-Juey
2015-11-01
Twist1 is an evolutionally conserved transcription factor. Originally identified in Drosophila as a key regulator for mesoderm development, it was later implicated in many human diseases, including Saethre-Chotzen syndrome and cancer. Twist1's involvement in cancer has been well recognized. Driven by hypoxia-induced factor-1 (HIF-1), Twist1 has been considered as a proto-oncogene and its overexpression has been observed in a wide variety of human cancers. High expression level of Twist1 is closely related to tumor aggressiveness and metastatic potential. In cancer cells, Twist1 has been shown to function as a key regulator of epithelial-mesenchymal transition (EMT), a critical process for metastasis initiation. Twist1 has also been implicated in maintaining cancer stemness for self-renewal and chemoresistance. This review first summarizes the roles of Twist1 in embryo development and Saethre-Chotzen syndrome followed by a discussion of Twist1's critical functions in cancer. In particular, the review focuses on the recent discovery of Twist1's capability to promote endothelial transdifferentiation of cancer cells beyond EMT.
Twist1 activity thresholds define multiple functions in limb development
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson; Costantini, Frank; Behringer, Richard R.; Laufer, Ed
2010-01-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1−/− embryos die at midgestation. However, studies on early limb buds found that Twist1−/− mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional...
Optical Möbius strips and twisted ribbon cloaks.
Freund, Isaac
2014-02-15
Optical Möbius strips that surround points of circular polarization, C points, in a generic three-dimensional optical field are cloaked by lines of twisted ribbons attached to the C points. When cloaking occurs, the observable signed twist index that counts the number of half-twists (one or three), and also measures the handedness (right or left), of a generic Möbius strip is determined by the twisted ribbon cloaks. Although some cloaks can be detached, they can never all be removed.
Twisted rudder for reducing fuel-oil consumption
Directory of Open Access Journals (Sweden)
Kim Jung-Hun
2014-09-01
Full Text Available Three twisted rudders fit for large container ships have been developed; 1 the Z-twisted rudder that is an asymmetry type taking into consideration incoming flow angles of the propeller slipstream, 2 the ZB-twisted rudder with a rudder bulb added onto the Z-twisted rudder, and 3 the ZB-F twisted rudder with a rudder fin attached to the ZB-twisted rudder. The twisted rudders have been designed computationally with the hydrodynamic characteristics in a self-propulsion condition in mind. The governing equation is the Navier-Stokes equations in an unsteady turbulent flow. The turbulence model applied is the Reynolds stress. The calculation was carried out in towing and self-propulsion conditions. The sliding mesh technique was employed to simulate the flow around the propeller. The speed performances of the ship with the twisted rudders were verified through model tests in a towing tank. The twisted versions showed greater performance driven by increased hull efficiency from less thrust deduction fraction and more effective wake fraction and decreased propeller rotating speed
Finite-dimensional representations of twisted hyper loop algebras
Bianchi, Angelo
2012-01-01
We investigate the category of finite-dimensional representations of twisted hyper loop algebras, i.e., the hyperalgebras associated to twisted loop algebras over finite-dimensional simple Lie algebras. The main results are the classification of the irreducible modules, the definition of the universal highest-weight modules, called the Weyl modules, and, under a certain mild restriction on the characteristic of the ground field, a proof that the simple modules and the Weyl modules for the twisted hyper loop algebras are isomorphic to appropriate simple and Weyl modules for the non-twisted hyper loop algebras, respectively, via restriction of the action.
Modelling of Nonthermal Microwave Emission From Twisted Magnetic Loops
Sharykin, I N
2016-01-01
Microwave gyrosynchrotron radio emission generated by nonthermal electrons in twisted magnetic loops is modelled using the recently developed simulation tool GX Simulator. We consider isotropic and anisotropic pitch-angle distributions. The main scope of the work is to understand impact of the magnetic field twisted topology on resulted radio emission maps. We have found that nonthermal electrons inside twisted magnetic loops produce gyrosynchrotron radio emission with peculiar polarization distribution. The polarization sign inversion line is inclined relatively to the axis of the loop. Radio emission source is more compact in the case of less twisted loop, considering anisotropic pitch-angle distribution of nonthermal electrons.
Twist decomposition of proton structure from BFKL and BK amplitudes
Motyka, Leszek
2014-01-01
An analysis of twist composition of Balitsky-Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit the BK evolution of color dipole -- proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models.
Nonlinear pressure dependence of TN in almost multiferroic EuTiO3
Guguchia, Z.; Caslin, K.; Kremer, R. K.; Keller, H.; Shengelaya, A.; Maisuradze, A.; Bettis, J. L., Jr.; Köhler, J.; Bussmann-Holder, A.; Whangbo, M.-H.
2013-09-01
The antiferromagnetic (AFM) phase transition temperature TN of EuTiO3 has been studied as a function of pressure p. The data reveal a nonlinear dependence of TN on p with TN increasing with increasing pressure. The exchange interactions exhibit an analogous dependence on p as TN (if the absolute value of the nearest neighbor interaction is considered) and there is evidence that the AFM transition is robust with increasing pressure. The corresponding Weiss temperature ΘW remains anomalous since it always exhibits positive values. The data are analyzed within the Bloch power law model and provide excellent agreement with experiment.
Equilibrium shapes of twisted magnetic filaments
Energy Technology Data Exchange (ETDEWEB)
Belovs, Mihails; Cirulis, Teodors; Cebers, Andrejs [University of Latvia, Zellu 8, LV-1002 (Latvia)], E-mail: aceb@tesla.sal.lv
2009-06-12
It is shown that ferromagnetic filaments with free and unclamped ends undergo buckling instabilities under the action of twist. Solutions of nonlinear equations describing the buckled shapes are found, and it is shown that the transition to the buckled shape is subcritical if the magnetization is parallel to the field and supercritical when the magnetization of the straight filament is opposite to the external field. Solutions with the localized curvature distribution are found in the case of long filaments. The class of solutions corresponding to helices is described, and the behavior of coiled ferromagnetic and superparamagnetic filaments is compared.
Non-destructive identification of twisted light.
Li, Pengyun; Wang, Bo; Song, Xinbing; Zhang, Xiangdong
2016-04-01
The non-destructive identification of the orbital angular momentum (OAM) is essential to various applications in the optical information processing. Here, we propose and demonstrate experimentally an efficient method to identify non-destructively the OAM by using a modified Mach-Zehnder interferometer. Our schemes are applicable not only to the case with integer charges, but also to optical vortices with noninteger charges. Our Letter presents the first experimental demonstration of the non-destructive identification of twisted light with integer or noninteger topological charges, which has potential applications in the OAM-based data transmission for optical communications.
Instanton corrections to twist-two operators
Alday, Luis F
2016-01-01
We present the calculation of the leading instanton contribution to the scaling dimensions of twist-two operators with arbitrary spin and to their structure constants in the OPE of two half-BPS operators in $\\mathcal N=4$ SYM. For spin-two operators we verify that, in agreement with $\\mathcal N=4$ superconformal Ward identities, the obtained expressions coincide with those for the Konishi operator. For operators with high spin we find that the leading instanton correction vanishes. This arises as the result of a rather involved calculation and requires a better understanding.
Berry phase transition in twisted bilayer graphene
Rode, Johannes C.; Smirnov, Dmitri; Schmidt, Hennrik; Haug, Rolf J.
2016-09-01
The electronic dispersion of a graphene bilayer is highly dependent on rotational mismatch between layers and can be further manipulated by electrical gating. This allows for an unprecedented control over electronic properties and opens up the possibility of flexible band structure engineering. Here we present novel magnetotransport data in a twisted bilayer, crossing the energetic border between decoupled monolayers and coupled bilayer. In addition a transition in Berry phase between π and 2π is observed at intermediate magnetic fields. Analysis of Fermi velocities and gate induced charge carrier densities suggests an important role of strong layer asymmetry for the observed phenomena.
Quantum mass correction for the twisted kink
Pawellek, Michael
2008-01-01
We present an analytic result for the 1-loop quantum mass correction in semiclassical quantization for the twisted \\phi^4 kink on S^1 without explicit knowledge of the fluctuation spectrum. For this purpose we use the contour integral representation of the spectral zeta function. By solving the Bethe ansatz equations for the n=2 Lame equation we obtain an analytic expression for the corresponding spectral discriminant. We discuss the renormalization issues of this model. An energetically preferred size for the compact space is finally obtained.
Needleless electrospinning with twisted wire spinneret.
Holopainen, Jani; Penttinen, Toni; Santala, Eero; Ritala, Mikko
2015-01-16
A needleless electrospinning setup named 'Needleless Twisted Wire Electrospinning' was developed. The polymer solution is electrospun from the surface of a twisted wire set to a high voltage and collected on a cylindrical collector around the wire. Multiple Taylor cones are simultaneously self-formed on the downward flowing solution. The system is robust and simple with no moving parts aside from the syringe pump used to transport the solution to the top of the wire. The structure and process parameters of the setup and the results on the preparation of polyvinyl pyrrolidone (PVP), hydroxyapatite (HA) and bioglass fibers with the setup are presented. PVP fiber sheets with areas of 40 × 120 cm(2) and masses up to 1.15 g were prepared. High production rates of 5.23 g h(-1) and 1.40 g h(-1) were achieved for PVP and HA respectively. The major limiting factor of the setup is drying of the polymer solution on the wire during the electrospinning process which will eventually force to interrupt the process for cleaning of the wire. Possible solutions to this problem and other ways to develop the setup are discussed. The presented system provides a simple way to increase the production rate and area of fiber sheet as compared with the conventional needle electrospinning.
Holographic generation of highly twisted electron beams
Grillo, Vincenzo; Mafakheri, Erfan; Frabboni, Stefano; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wavefront corresponding to the electron's wavefunction forms a helical structure with a number of twists given by the \\emph{angular speed}. Beams with a high number of twists are of particular interest because they carry a high magnetic moment about the propagation axis. Among several different techniques, electron holography seems to be a promising approach to shape a \\emph{conventional} electron beam into a helical form with large values of angular momentum. Here, we propose and manufacture a nano-fabricated phase hologram for generating a beam of this kind with an orbital angular momentum up to 200$\\hbar$. Based on a novel technique the value of orbital angular momentum of the generated beam are measured, then compared with simulations. Our work, apart from the technological achievements, may lead to a way of generating electron beams with a high quanta of magnetic momen...
Twisting the [ital N]=2 string
Energy Technology Data Exchange (ETDEWEB)
Ketov, S.V.; Lechtenfeld, O. (Institut fuer Theoretische Physik, Universitaet Hannover, Appelstrasse 2, 30167 Hannover (Germany)); Parkes, A.J. (Department of Artificial Intelligence, 80 South Bridge, Edinburgh EH1 9HN (United Kingdom))
1995-03-15
The most general homogeneous monodromy conditions in [ital N]=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)[direct product][ital openZ][sub 2]. For classes which generate a discrete subgroup [Gamma], the corresponding target space backgrounds [ital openC][sup 1,1]/[Gamma] include half spaces, complex orbifolds, and tori. We propose a generalization of the intercept formula to matrix-valued twists, but find massless physical states only for [Gamma]=[ital open]1 (untwisted) and [Gamma]=[ital openZ][sub 2] (in the manner of Mathur and Mukhi), as well as for [Gamma] being a parabolic element of U(1,1). In particular, the 16 [ital openZ][sub 2]-twisted sectors of the [ital N]=2 string are investigated, and the corresponding ground states are identified via bosonization and BRST cohomology. We find enough room for an extended multiplet of spacetime'' supersymmetry, with the number of supersymmetries being dependent on global spacetime'' topology. However, world-sheet locality for the chiral vertex operators does not permit interactions among all massless spacetime'' fermions.
Twisting Fluorescence through Extrinsic Chiral Antennas.
Yan, Chen; Wang, Xiaolong; Raziman, T V; Martin, Olivier J F
2017-03-22
Plasmonic antennas and planar structures have been undergoing intensive developments in order to control the scattering and absorption of light. One specific class, extrinsic chiral surfaces, that does not possess 2-fold rotational symmetry exhibits strong asymmetric transmission for different circular polarizations under obliquely incident illumination. In this work, we show that the design of those surfaces can be optimized with complex multipolar resonances in order to twist the fluorescence emission from nearby molecules. While this emission is usually dipolar and linearly polarized, the interaction with these resonances twists it into a multipolar radiation pattern with opposite helicity in different directions. The proposed structure maximizes this effect and provides control over the polarization of light. Splitting of left- and right-handed circularly polarized light is experimentally obtained in the backward direction. These results highlight the intricate interplay between the near-field absorption and the far-field scattering of a plasmonic nanostructure and are further used for modifying the emission of incoherent quantum sources. Our finding can potentially lead to the development of polarization- and angle-resolved ultracompact optical devices.
Twisted Alexander polynomials of hyperbolic knots
Dunfield, Nathan M; Jackson, Nicholas
2011-01-01
We study a twisted Alexander polynomial naturally associated to a hyperbolic knot in an integer homology 3-sphere via a lift of the holonomy representation to SL(2, C). It is an unambiguous symmetric Laurent polynomial whose coefficients lie in the trace field of the knot. It contains information about genus, fibering, and chirality, and moreover is powerful enough to sometimes detect mutation. We calculated this invariant numerically for all 313,209 hyperbolic knots in S^3 with at most 15 crossings, and found that in all cases it gave a sharp bound on the genus of the knot and determined both fibering and chirality. We also study how such twisted Alexander polynomials vary as one moves around in an irreducible component X_0 of the SL(2, C)-character variety of the knot group. We show how to understand all of these polynomials at once in terms of a polynomial whose coefficients lie in the function field of X_0. We use this to help explain some of the patterns observed for knots in S^3, and explore a potential...
Twisted geometries, twistors and conformal transformations
Långvik, Miklos
2016-01-01
The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a time-like direction singled out. The isomorphism depends on the Immirzi parameter, and reduces to the identity when the parameter goes to infinity. Using this twistorial representation we study the action of the conformal group SU(2,2) on the classical phase space of loop quantum gravity, described by twisted geometry. The generators of translations and conformal boosts do not preserve the geometric structure, whereas the dilatation generator does. It corresponds to a 1-parameter family of embeddings of T*SL(2,C) in twistor space, and its action preserves the intrinsic geometry while changing the extrinsic one - that is the boosts among polyhedra. We discuss the implication of this action from a dynamical point of view, and compare it with a discretisation of the dilatation generator of the continuum phase space, given by the Lie derivative of the group character. At leading order in the continuu...
How the embryonic brain tube twists
Chen, Zi; Guo, Qiaohang; Forsch, Nickolas; Taber, Larry
2014-03-01
During early development, the tubular brain of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This deformation is one of the major organ-level symmetry-breaking events in development. Available evidence suggests that bending is caused by differential growth, but the mechanism for torsion remains poorly understood. Since the heart almost always loops in the same direction that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is virtually nonexistent, nor is the mechanical origin of such torsion understood. In our study, experimental perturbations show that the bending and torsional deformations in the brain are coupled and that the vitelline membrane applies an external load necessary for torsion to occur. In addition, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model is used to interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''.
Structure of twisted and buckled bilayer graphene
Jain, Sandeep K.; Juričić, Vladimir; Barkema, Gerard T.
2017-03-01
We study the atomic structure of twisted bilayer graphene, with very small mismatch angles (θ ∼ {0.28}0), a topic of intense recent interest. We use simulations, in which we combine a recently presented semi-empirical potential for single-layer graphene, with a new term for out-of-plane deformations, (Jain et al 2015 J. Phys. Chem. C 119 9646) and an often-used interlayer potential (Kolmogorov et al 2005 Phys. Rev. B 71 235415). This combination of potentials is computationally cheap but accurate and precise at the same time, allowing us to study very large samples, which is necessary to reach very small mismatch angles in periodic samples. By performing large scale atomistic simulations, we show that the vortices appearing in the Moiré pattern in the twisted bilayer graphene samples converge to a constant size in the thermodynamic limit. Furthermore, the well known sinusoidal behavior of energy no longer persists once the misorientation angle becomes very small (θ \\lt {1}0). We also show that there is a significant buckling after the relaxation in the samples, with the buckling height proportional to the system size. These structural properties have direct consequences on the electronic and optical properties of bilayer graphene.
Compression induced phase transition of nematic brush: A mean-field theory study
Energy Technology Data Exchange (ETDEWEB)
Tang, Jiuzhou [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Xinghua, E-mail: zhangxh@bjtu.edu.cn [School of Science, Beijing Jiaotong University, Beijing 100044 (China); Yan, Dadong, E-mail: yandd@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China)
2015-11-28
Responsive behavior of polymer brush to the external compression is one of the most important characters for its application. For the flexible polymer brush, in the case of low grafting density, which is widely studied by the Gaussian chain model based theory, the compression leads to a uniform deformation of the chain. However, in the case of high grafting density, the brush becomes anisotropic and the nematic phase will be formed. The normal compression tends to destroy the nematic order, which leads to a complex responsive behaviors. Under weak compression, chains in the nematic brush are buckled, and the bending energy and Onsager interaction give rise to the elasticity. Under deep compression, the responsive behaviors of the nematic polymer brush depend on the chain rigidity. For the compressed rigid polymer brush, the chains incline to re-orientate randomly to maximize the orientational entropy and its nematic order is destroyed. For the compressed flexible polymer brush, the chains incline to fold back to keep the nematic order. A buckling-folding transition takes place during the compressing process. For the compressed semiflexible brush, the chains are collectively tilted to a certain direction, which leads to the breaking of the rotational symmetry in the lateral plane. These responsive behaviors of nematic brush relate to the properties of highly frustrated worm-like chain, which is hard to be studied by the traditional self-consistent field theory due to the difficulty to solve the modified diffusion equation. To overcome this difficulty, a single chain in mean-field theory incorporating Monte Carlo simulation and mean-field theory for the worm-like chain model is developed in present work. This method shows high performance for entire region of chain rigidity in the confined condition.
Cellularity of diagram algebras as twisted semigroup algebras
Wilcox, Stewart
2010-01-01
The Temperley-Lieb and Brauer algebras and their cyclotomic analogues, as well as the partition algebra, are all examples of twisted semigroup algebras. We prove a general theorem about the cellularity of twisted semigroup algebras of regular semigroups. This theorem, which generalises a recent result of East about semigroup algebras of inverse semigroups, allows us to easily reproduce the cellularity of these algebras.
Behaviour at infinity of solutions of twisted convolution equations
Energy Technology Data Exchange (ETDEWEB)
Volchkov, Valerii V; Volchkov, Vitaly V [Donetsk National University, Donetsk (Ukraine)
2012-02-28
We obtain a precise characterization of the minimal rate of growth at infinity of non-trivial solutions of twisted convolution equations in unbounded domains of C{sup n}. As an application, we obtain definitive versions of the two-radii theorem for twisted spherical means.
On the commutator length of a Dehn twist
Szepietowski, Blazej
2010-01-01
We show that on a nonorientable surface of genus at least 7 any power of a Dehn twist is equal to a single commutator in the mapping class group and the same is true, under additional assumptions, for the twist subgroup, and also for the extended mapping class group of an orientable surface of genus at least 3.
Quadratic Twists of Rigid Calabi–Yau Threefolds Over
DEFF Research Database (Denmark)
Gouvêa, Fernando Q.; Kiming, Ian; Yui, Noriko
2013-01-01
We consider rigid Calabi–Yau threefolds defined over Q and the question of whether they admit quadratic twists. We give a precise geometric definition of the notion of a quadratic twists in this setting. Every rigid Calabi–Yau threefold over Q is modular so there is attached to it a certain newfo...
Design optimization of a twist compliant mechanism with nonlinear stiffness
Tummala, Y.; Frecker, M. I.; Wissa, A. A.; Hubbard, J. E., Jr.
2014-10-01
A contact-aided compliant mechanism called a twist compliant mechanism (TCM) is presented in this paper. This mechanism has nonlinear stiffness when it is twisted in both directions along its axis. The inner core of the mechanism is primarily responsible for its flexibility in one twisting direction. The contact surfaces of the cross-members and compliant sectors are primarily responsible for its high stiffness in the opposite direction. A desired twist angle in a given direction can be achieved by tailoring the stiffness of a TCM. The stiffness of a compliant twist mechanism can be tailored by varying thickness of its cross-members, thickness of the core and thickness of its sectors. A multi-objective optimization problem with three objective functions is proposed in this paper, and used to design an optimal TCM with desired twist angle. The objective functions are to minimize the mass and maximum von-Mises stress observed, while minimizing or maximizing the twist angles under specific loading conditions. The multi-objective optimization problem proposed in this paper is solved for an ornithopter flight research platform as a case study, with the goal of using the TCM to achieve passive twisting of the wing during upstroke, while keeping the wing fully extended and rigid during the downstroke. Prototype TCMs have been fabricated using 3D printing and tested. Testing results are also presented in this paper.
Twisted tubular photobioreactor fluid dynamics evaluation for energy consumption minimization
Gómez-Pérez, C.A.; Espinosa Oviedo, J.J.; Montenegro Ruiz, L.C.; Boxtel, van A.J.B.
2017-01-01
This paper discusses a new tubular PhotoBioReactor (PBR) called twisted tubular PBR. The geometry of a twisted tubular PBR induces swirl mixing to guarantee good exposure of microalgae to Light-Dark (LD) cycles and to the nutrients and dissolved CO 2 . The paper analyses the energy uptake for fluid
Resonances and higher twist in polarized lepton-nucleon scattering
Edelmann, J; Kaiser, N; Weise, W
2000-01-01
We present a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g_1. For each of these moments, it is found that there exists a characteristic Q^2 region in which (perturbative) higher twist corrections coexist with (non-perturbative) resonance contribution of comparable magnitude.
Mini-Tn7 transposons for site-specific tagging of bacteria with fluorescent proteins
DEFF Research Database (Denmark)
Lambertsen, L.; Sternberg, Claus; Molin, Søren
2004-01-01
The mini-Tn7 transposon system is a convenient tool for site-specific tagging of bacteria in which the tagging DNA is inserted at a unique and neutral chromosomal site. We have expanded the panel of mini-Tn7 delivery plasmids expressing different fluorescent proteins (stable and unstable) from th...
76 FR 35909 - Temporary Concession Contract for Big South Fork National Recreation Area, TN/KY
2011-06-20
... National Recreation Area, TN/KY. SUMMARY: Pursuant to 36 CFR 51.24, public notice is hereby given that the...] Temporary Concession Contract for Big South Fork National Recreation Area, TN/KY AGENCY: National Park... visitor services within Big South Fork National Recreation Area, Tennessee and Kentucky, for a term not...
ST6GalNAc-I controls expression of sialyl-Tn antigen in gastrointestinal tissues
DEFF Research Database (Denmark)
Marcos, Nuno T; Bennett, Eric P; Gomes, Joana
2011-01-01
found that ST6GalNAc-I is weakly expressed in normal gastric mucosa, but over-expressed in intestinal metaplasia, co-localized with sialyl-Tn. In gastric carcinomas ST6GalNAc-I was also associated with sialyl-Tn, but with heterogeneous staining and partial co-localization. Our results showed ST6Gal...
Base flipping in tn10 transposition: an active flip and capture mechanism.
Directory of Open Access Journals (Sweden)
Julien Bischerour
Full Text Available The bacterial Tn5 and Tn10 transposases have a single active site that cuts both strands of DNA at their respective transposon ends. This is achieved using a hairpin intermediate that requires the DNA to change conformation during the reaction. In Tn5 these changes are controlled in part by a flipped nucleoside that is stacked on a tryptophan residue in a hydrophobic pocket of the transposase. Here we have investigated the base flipping mechanism in Tn10 transposition. As in Tn5 transposition, we find that base flipping takes place after the first nick and is required for efficient hairpin formation and resolution. Experiments with an abasic substrate show that the role of base flipping in hairpin formation is to remove the base from the DNA helix. Specific interactions between the flipped base and the stacking tryptophan residue are required for hairpin resolution later in the reaction. We show that base flipping in Tn10 transposition is not a passive reaction in which a spontaneously flipped base is captured and retained by the protein. Rather, it is driven in part by a methionine probe residue that helps to force the flipped base from the base stack. Overall, it appears that base flipping in Tn10 transposition is similar to that in Tn5 transposition.
75 FR 52364 - Notice of Intent To Repatriate Cultural Items: Memphis Pink Palace Museum, Memphis, TN
2010-08-25
... Cultural Items: Memphis Pink Palace Museum, Memphis, TN AGENCY: National Park Service, Interior. ACTION... Memphis Pink Palace Museum, Memphis, TN, that meet the definition of unassociated funerary objects under... objects from the site. Officials of the Memphis Pink Palace Museum have determined that, pursuant to 25...
75 FR 52367 - Notice of Inventory Completion: Memphis Pink Palace Museum, Memphis, TN
2010-08-25
... Completion: Memphis Pink Palace Museum, Memphis, TN AGENCY: National Park Service, Interior. ACTION: Notice... Memphis Pink Palace Museum, Memphis, TN. The human remains were removed from Crittenden, Cross, Poinsett... made by Memphis Pink Palace Museum professional staff and consultants in consultation...
75 FR 65584 - Proposed Amendment of Class E Airspace; Savannah, TN
2010-10-26
... Savannah-Hardin County Airport. This action would enhance the safety and airspace management of Instrument... surface to support new SIAPs developed at Savannah-Hardin County Airport, Savannah, TN. Airspace... at Savannah-Hardin County Airport, Savannah, TN. Lists of Subjects in 14 CFR Part 71...
Twisted Fock representations of noncommutative Kähler manifolds
Sako, Akifumi; Umetsu, Hiroshi
2016-09-01
We introduce twisted Fock representations of noncommutative Kähler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by applying creation operators to a vacuum state. "Twisted" means that creation operators are not Hermitian conjugate of annihilation operators in this representation. In deformation quantization of Kähler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the Kähler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative Kähler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative Kähler manifolds concretely.
Landau damping of Langmuir twisted waves with kappa distributed electrons
Energy Technology Data Exchange (ETDEWEB)
Arshad, Kashif, E-mail: kashif.arshad.butt@gmail.com; Aman-ur-Rehman [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Mahmood, Shahzad [Pakistan Institute of Engineering and Applied Sciences, P. O. Nilore, Islamabad 45650 (Pakistan); Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad 44000 (Pakistan)
2015-11-15
The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].
Analysis list: Twist1 [Chip-atlas[Archive
Lifescience Database Archive (English)
Full Text Available Twist1 Embryo,Neural + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Tw...ist1.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Twist1.5.tsv http://dbarchive.biosciencedbc....jp/kyushu-u/mm9/target/Twist1.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Twist1.Embryo.tsv,http://dbarchive.bioscien...cedbc.jp/kyushu-u/mm9/colo/Twist1.Neural.tsv http://dbarchive.bioscience...dbc.jp/kyushu-u/mm9/colo/Embryo.gml,http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Neural.gml ...
Twisted Fock Representations of Noncommutative K\\"ahler Manifolds
Sako, Akifumi
2016-01-01
We introduce twisted Fock representations of noncommutative K\\"ahler manifolds and give their explicit expressions. The twisted Fock representation is a representation of the Heisenberg like algebra whose states are constructed by acting creation operators on a vacuum state. "Twisted" means that creation operators are not hermitian conjugate of annihilation operators in this representation. In deformation quantization of K\\"ahler manifolds with separation of variables formulated by Karabegov, local complex coordinates and partial derivatives of the K\\"ahler potential with respect to coordinates satisfy the commutation relations between the creation and annihilation operators. Based on these relations, we construct the twisted Fock representation of noncommutative K\\"ahler manifolds and give a dictionary to translate between the twisted Fock representations and functions on noncommutative K\\"ahler manifolds concretely.
On the performance analysis of Savonius rotor with twisted blades
Energy Technology Data Exchange (ETDEWEB)
Saha, U.K.; Rajkumar, M. Jaya [Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati-781 039 (India)
2006-09-15
The present investigation is aimed at exploring the feasibility of twisted bladed Savonius rotor for power generation. The twisted blade in a three-bladed rotor system has been tested in a low speed wind tunnel, and its performance has been compared with conventional semicircular blades (with twist angle of 0{sup o}). Performance analysis has been made on the basis of starting characteristics, static torque and rotational speed. Experimental evidence shows the potential of the twisted bladed rotor in terms of smooth running, higher efficiency and self-starting capability as compared to that of the conventional bladed rotor. Further experiments have been conducted in the same setup to optimize the twist angle. (author)
Alpha Heating and TN Burn in NIF Experiments
Cheng, Baolian; Kwan, Thomas; Wang, Yi-Ming; Merrill, Frank; Cerjan, Charlie; Batha, Steven
2015-11-01
Sustainable TN burn requires alpha-particle energy deposition in the hot fuel. Recently, we developed an analytic model to estimate the neutron yield generated by the alpha-particle energy deposited in the hot spot, in terms of the measured total neutron yield, the adiabat of the cold fuel and the peak implosion kinetic energy of the pusher. Our alpha heating model has been applied to a number of inertial confinement fusion capsule experiments performed at the National Ignition Facility (NIF). Our model predictions are consistent with the post-shot calibrated code simulations and experimental data. We have also studied the uncertainty and sensitivities of alpha heating on various physics parameters, such as the adiabat of cold fuel, total neutron yield and peak implosion velocity. Our analysis demonstrates that the alpha particle heating was appreciable in only high-foot experiments. Based on our work, we will discuss paths and parameters to reach ignition at NIF (LA-UR-15-25507). This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.
Twist1 activity thresholds define multiple functions in limb development.
Krawchuk, Dayana; Weiner, Shoshana J; Chen, You-Tzung; Lu, Benson C; Costantini, Frank; Behringer, Richard R; Laufer, Ed
2010-11-01
The basic helix-loop-helix transcription factor Twist1 is essential for normal limb development. Twist1(-/-) embryos die at midgestation. However, studies on early limb buds found that Twist1(-/-) mutant limb mesenchyme has an impaired response to FGF signaling from the apical ectodermal ridge, which disrupts the feedback loop between the mesenchyme and AER, and reduces and shifts anteriorly Shh expression in the zone of polarizing activity. We have combined Twist1 null, hypomorph and conditional alleles to generate a Twist1 allelic series that survives to birth. As Twist1 activity is reduced, limb skeletal defects progress from preaxial polydactyly to girdle reduction combined with hypoplasia, aplasia or mirror symmetry of all limb segments. With reduced Twist1 activity there is striking and progressive upregulation of ectopic Shh expression in the anterior of the limb, combined with an anterior shift in the posterior Shh domain, which is expressed at normal intensity, and loss of the posterior AER. Consequently limb outgrowth is initially impaired, before an ectopic anterior Shh domain expands the AER, promoting additional growth and repatterning. Reducing the dosage of FGF targets of the Etv gene family, which are known repressors of Shh expression in anterior limb mesenchyme, strongly enhances the anterior skeletal phenotype. Conversely this and other phenotypes are suppressed by reducing the dosage of the Twist1 antagonist Hand2. Our data support a model whereby multiple Twist1 activity thresholds contribute to early limb bud patterning, and suggest how particular combinations of skeletal defects result from differing amounts of Twist1 activity.
Aeromechanical Evaluation of Smart-Twisting Active Rotor
Lim, Joon W.; Boyd, D. Douglas, Jr.; Hoffman, Frauke; van der Wall, Berend G.; Kim, Do-Hyung; Jung, Sung N.; You, Young H.; Tanabe, Yasutada; Bailly, Joelle; Lienard, Caroline; Delrieux, Yves
2014-01-01
An investigation of Smart-Twisting Active Rotor (STAR) was made to assess potential benefits of the current active twist rotor concept for performance improvement, vibration reduction, and noise alleviation. The STAR rotor is a 40% Mach-scaled, Bo105 rotor with an articulated flap-lag hinge at 3.5%R and no pre-cone. The 0-5 per rev active twist harmonic inputs were applied for various flight conditions including hover, descent, moderate to high speed level flights, and slowed rotor high advance ratio. For the analysis, the STAR partners used multiple codes including CAMRAD II, S4, HOST, rFlow3D, elsA, and their associated software. At the high thrust level in hover, the 0 per rev active twist with 80% amplitude increased figure of merit (FM) by 0.01-0.02 relative to the baseline. In descent, the largest BVI noise reduction was on the order of 2 to 5 dB at the 3 per rev active twist. In the high speed case (mu = 0.35), the 2 per rev actuation was found to be the most effective in achieving a power reduction as well as a vibration reduction. At the 2 per rev active twist, total power was reduced by 0.65% at the 60 deg active twist phase, and vibration was reduced by 47.6% at the 45 deg active twist phase. The use of the 2 per rev active twist appears effective for vibration reduction. In the high advance ratio case (mu = 0.70), the 0 per rev actuation appeared to have negligible impact on performance improvement. In summary, computational simulations successfully demonstrated that the current active twist concept provided a significant reduction of the maximum BVI noise in descent, a significant reduction of the vibration in the high speed case, a small improvement on rotor performance in hover, and a negligible impact on rotor performance in forward flight.
DEFF Research Database (Denmark)
Brorson, Michael; Galsbøl, Frode; Simonsen, Kim
1998-01-01
for the preparation of [Rh(tn)3]Cl3 in quantitative yield from Rh(thtp)3Cl3 is also given. The complexes were characterized by 1H and 13C NMR and by UV/VIS spectroscopy. The conformation of the six-membered chelate rings of [Ir(tn)3]3+ in the solid state was determined by single-crystal X-ray diffraction of [Ir(tn)3......] [Co(CN)6] x 5H2O. The three chelate rings all adopt the energetically favoured chair conformation; however, the overall idealized symmetry is C1. A comparative ligand field analysis, based on Gaussian resolution of the solution UV/VIS spectra for a number of homoleptic [M(N6)]3+ (M=CoIII, RhIII, Ir...
DEFF Research Database (Denmark)
Brorson, Michael; Galsbøl, Frode; Simonsen, Kim;
1998-01-01
for the preparation of [Rh(tn)3]Cl3 in quantitative yield from Rh(thtp)3Cl3 is also given. The complexes were characterized by 1H and 13C NMR and by UV/VIS spectroscopy. The conformation of the six-membered chelate rings of [Ir(tn)3]3+ in the solid state was determined by single-crystal X-ray diffraction of [Ir(tn)3......] [Co(CN)6] x 5H2O. The three chelate rings all adopt the energetically favoured chair conformation; however, the overall idealized symmetry is C1. A comparative ligand field analysis, based on Gaussian resolution of the solution UV/VIS spectra for a number of homoleptic [M(N6)]3+ (M=CoIII, RhIII, Ir...
Do twisted laser beams evoke nuclear hyperpolarization?
Schmidt, A. B.; Andrews, D. L.; Rohrbach, A.; Gohn-Kreuz, C.; Shatokhin, V. N.; Kiselev, V. G.; Hennig, J.; von Elverfeldt, D.; Hövener, J.-B.
2016-07-01
The hyperpolarization of nuclear spins promises great advances in chemical analysis and medical diagnosis by substantially increasing the sensitivity of nuclear magnetic resonance (NMR). Current methods to produce a hyperpolarized sample, however, are arduous, time-consuming or costly and require elaborate equipment. Recently, a much simpler approach was introduced that holds the potential, if harnessed appropriately, to revolutionize the production of hyperpolarized spins. It was reported that high levels of hyperpolarization in nuclear spins can be created by irradiation with a laser beam carrying orbital angular momentum (twisted light). Aside from these initial reports however, no further experimental verification has been presented. In addition, this effect has so far evaded a critical theoretical examination. In this contribution, we present the first independent attempt to reproduce the effect. We exposed a sample of immersion oil or a fluorocarbon liquid that was placed within a low-field NMR spectrometer to Laguerre-Gaussian and Bessel laser beams at a wavelength of 514.5 nm and various topological charges. We acquired 1H and 19F NMR free induction decay data, either during or alternating with the irradiation that was parallel to B0. We observed an irregular increase in NMR signal in experiments where the sample was exposed to beams with higher values of the topological charge. However, at no time did the effect reach statistical significance of 95%. Given the measured sensitivity of our setup, we estimate that a possible effect did not exceed a hyperpolarization (at 5 mT) of 0.14-6%, depending on the assumed hyperpolarized volume. It should be noted though, that there were some differences between our setup and the previous implementation of the experiment, which may have inhibited the full incidence of this effect. To approach a theoretical description of this effect, we considered the interaction of an electron with a plane wave, which is known to be
Variation of TN in the Water of the Shanchong River%山冲河河道水体中 TN 的迁移变化分析
Institute of Scientific and Technical Information of China (English)
秦洁; 朱春蓉; 吴献花; 张晶晶
2015-01-01
The Shanchong River is one of the main rivers into the Fuxianhu Lake.The TN concentration of its water-course on the northern coast of the Fuxian Lake was monitored during the period from October 2012 to October 2013.The results showed that the concentration of TN was at a high level and the water quality of the river fell into Class V of stand-ards.The main pollution source was the rural agricultural non-point sources in the drainage basin.The concentration of TN varied with different water periods:it is at a low level in dry water period,increased in normal season,and at a higher level in raining season.%山冲河是抚仙湖的主要入湖河流之一。从对山冲河河道水体中 TN 浓度监测的结果看，其水体中的 TN 浓度较高，整体达到劣 V 类水质标准，而主要的污染源则来自流域内的农村农业面源污染。此外，山冲河不同水期的总氮浓度也有不同的变化，呈现出枯水期 TN 浓度低，平水期次之，丰水期 TN 浓度较高的特点。
Vitrified chiral-nematic liquid crystalline films for selective reflection and circular polarization
Energy Technology Data Exchange (ETDEWEB)
Katsis, D.; Chen, P.H.M.; Mastrangelo, J.C.; Chen, S.H. [Univ. of Rochester, NY (United States); Blanton, T.N. [Eastman Kodak Co., Rochester, NY (United States)
1999-06-01
Nematic and left-handed chiral-nematic liquid crystals comprising methoxybiphenylbenzoate and (S)-(-)-1-phenylethylamine pendants to a cyclohexane core were synthesized and characterized. Although pristine samples were found to be polycrystalline, thermal quenching following heating to and annealing at elevated temperatures permitted the molecular orders characteristic of liquid crystalline mesomorphism to be frozen in the glassy state. Left at room temperature for 6 months, the vitrified liquid crystalline films showed no evidence of recrystallization. An orientational order parameter of 0.65 was determined with linear dichroism of a vitrified nematic film doped with Exalite 428 at a mole fraction of 0.0025. Birefringence dispersion of a blank vitrified nematic film was determined using a phase-difference method complemented by Abbe refractometry. A series of vitrified chiral-nematic films were prepared to demonstrate selective reflection and circular polarization with a spectral region tunable from blue to the infrared region by varying the chemical composition. The experimentally measured circular polarization spectra were found to agree with the Good-Karali theory in which all four system parameters were determined a priori: optical birefringence, average refractive index, selective reflection wavelength, and film thickness.
Wrinkling of a thin film on a nematic liquid-crystal elastomer
Soni, Harsh; Pelcovits, Robert A.; Powers, Thomas R.
2016-07-01
Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)], 10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.
Quantum control of spin-nematic squeezing in a dipolar spin-1 condensate
Huang, Yixiao; Xiong, Heng-Na; Yang, Yang; Hu, Zheng-Da; Xi, Zhengjun
2017-01-01
Versatile controllability of interactions and magnetic field in ultracold atomic gases ha now reached an era where spin mixing dynamics and spin-nematic squeezing can be studied. Recent experiments have realized spin-nematic squeezed vacuum and dynamic stabilization following a quench through a quantum phase transition. Here we propose a scheme for storage of maximal spin-nematic squeezing, with its squeezing angle maintained in a fixed direction, in a dipolar spin-1 condensate by applying a microwave pulse at a time that maximal squeezing occurs. The dynamic stabilization of the system is achieved by manipulating the external periodic microwave pulses. The stability diagram for the range of pulse periods and phase shifts that stabilize the dynamics is numerical simulated and agrees with a stability analysis. Moreover, the stability range coincides well with the spin-nematic vacuum squeezed region which indicates that the spin-nematic squeezed vacuum will never disappear as long as the spin dynamics are stabilized. PMID:28233786
Orbital-dependent Fermi surface shrinking as a fingerprint of nematicity in FeSe
Fanfarillo, Laura; Mansart, Joseph; Toulemonde, Pierre; Cercellier, Hervé; Le Fèvre, Patrick; Bertran, François; Valenzuela, Belen; Benfatto, Lara; Brouet, Véronique
2016-10-01
A large anisotropy in the electronic properties across a structural transition in several correlated systems has been identified as the key manifestation of electronic nematic order, breaking rotational symmetry. In this context, FeSe is attracting tremendous interest, since electronic nematicity develops over a wide range of temperatures, allowing accurate experimental investigation. Here we combine angle-resolved photoemission spectroscopy and theoretical calculations based on a realistic multiorbital model to unveil the microscopic mechanism responsible for the evolution of the electronic structure of FeSe across the nematic transition. We show that the self-energy corrections due to the exchange of spin fluctuations between hole and electron pockets are responsible for an orbital-dependent shrinking of the Fermi surface that affects mainly the x z /y z parts of the Fermi surface. This result is consistent with our experimental observation of the Fermi surface in the high-temperature tetragonal phase, which includes the x y electron sheet that was not clearly resolved before. In the low-temperature nematic phase, we experimentally confirm the appearance of a large (˜50 meV) x z /y z splitting. It can be well reproduced in our model by assuming a moderate splitting between spin fluctuations along the x and y crystallographic directions. Our mechanism shows how the full entanglement between orbital and spin degrees of freedom can make a spin-driven nematic transition equivalent to an effective orbital order.
Wrinkling of a thin film on a nematic liquid-crystal elastomer.
Soni, Harsh; Pelcovits, Robert A; Powers, Thomas R
2016-07-01
Wrinkles commonly develop in a thin film deposited on a soft elastomer substrate when the film is subject to compression. Motivated by recent experiments [Agrawal et al., Soft Matter 8, 7138 (2012)]1744-683X10.1039/c2sm25734c that show how wrinkle morphology can be controlled by using a nematic elastomer substrate, we develop the theory of small-amplitude wrinkles of an isotropic film atop a nematic elastomer. The directors of the nematic elastomer are initially uniform. For uniaxial compression of the film along the direction perpendicular to the elastomer directors, the system behaves as a compressed film on an isotropic substrate. When the uniaxial compression is along the direction of nematic order, we find that the soft elasticity characteristic of liquid-crystal elastomers leads to a critical stress for wrinkling which is very small compared to the case of an isotropic substrate. We also determine the wavelength of the wrinkles at the critical stress and show how the critical stress and wavelength depend on substrate depth and the anisotropy of the polymer chains in the nematic elastomer.
Twist-joints and double twist-joints in RNA structure.
Boutorine, Yury I; Steinberg, Sergey V
2012-12-01
Analysis of available RNA crystal structures has allowed us to identify a new family of RNA arrangements that we call double twist-joints, or DTJs. Each DTJ is composed of a double helix that contains two bulges incorporated into different strands and separated from each other by 2 or 3 bp. At each bulge, the double helix is over-twisted, while the unpaired nucleotides of both bulges form a complex network of stacking and hydrogen-bonding with nucleotides of helical regions. In total, we identified 14 DTJ cases, which can be combined in three groups based on common structural characteristics. One DTJ is found in a functional center of the ribosome, another DTJ mediates binding of the pre-tRNA to the RNase P, and two more DTJs form the sensing domains in the glycine riboswitch.
2006-03-01
COUETTE & POISEUILLE FLOWS OF NEMATIC POLYMERS IN VISCOUS SOLVENTS: MORPHOLOGY IN MOLECULAR ORIENTATION, STRESS & FLOW Hong Zhou...viscoelastic stresses, and flow feedback. Pre- vious studies in plane Couette & Poiseuille flow (with the exception of [7]) have focused on the coupling between...with Plane Couette & Poiseuille Flows of Nematic Polymers in Viscous Solvents: Morphology in Molecular Orientation, Stress & Flow 5a. CONTRACT
Isotropic-nematic phase equilibria of hard-sphere chain fluids—Pure components and binary mixtures
Oyarzun, B.; Van Westen, T.; Vlugt, T.J.H.
2015-01-01
The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are
Straining soft colloids in aqueous nematic liquid crystals
Mushenheim, Peter C.; Pendery, Joel S.; Weibel, Douglas B.; Spagnolie, Saverio E.; Abbott, Nicholas L.
2016-05-01
Liquid crystals (LCs), because of their long-range molecular ordering, are anisotropic, elastic fluids. Herein, we report that elastic stresses imparted by nematic LCs can dynamically shape soft colloids and tune their physical properties. Specifically, we use giant unilamellar vesicles (GUVs) as soft colloids and explore the interplay of mechanical strain when the GUVs are confined within aqueous chromonic LC phases. Accompanying thermal quenching from isotropic to LC phases, we observe the elasticity of the LC phases to transform initially spherical GUVs (diameters of 2-50 µm) into two distinct populations of GUVs with spindle-like shapes and aspect ratios as large as 10. Large GUVs are strained to a small extent (R/r minor radii, respectively), consistent with an LC elasticity-induced expansion of lipid membrane surface area of up to 3% and conservation of the internal GUV volume. Small GUVs, in contrast, form highly elongated spindles (1.54 materials and suggest previously unidentified designs of LC-based responsive and reconfigurable materials.
Fine structure of defects in radial nematic droplets
Mkaddem; Gartland
2000-11-01
We investigate the structure of defects in nematic liquid crystals confined in spherical droplets and subject to radial strong anchoring. Equilibrium configurations of the order-parameter tensor field in a Landau-de Gennes free energy are numerically modeled using a finite-element package. Within the class of axially symmetric fields, we find three distinct solutions: the familiar radial hedgehog, the small ring (or loop) disclination predicted by Penzenstadler and Trebin, and a solution that consists of a short disclination line segment along the rotational symmetry axis terminating in isotropic end points. Phase and bifurcation diagrams are constructed to illustrate how the three competing configurations are related. They confirm that the transition from the hedgehog to the ring structure is first order. The third configuration is metastable (in our symmetry class) and forms an alternate solution branch bifurcating off the radial hedgehog branch at the temperature below which the hedgehog ceases to be metastable. Dependence on temperature, droplet size, and elastic constants is investigated, and comparisons with other studies are made.
Nucleation type instabilities in partially wetting nanoscale nematic liquid films
Lam, Michael; Cummings, Linda; Kondic, Lou
2016-11-01
Nucleation type instabilities are studied in nematic liquid crystal (NLC) films with thicknesses less than a micrometer. Within the framework of the long wave approximation, a 4th order nonlinear partial differential equation is proposed for the free surface height. Unlike simple fluids, NLC molecules have a dipole moment which induces an elastic response due to deformation in the bulk of the fluid. The model includes the balance between the bulk elasticity energy and the anchoring (boundary) energy at the substrate and free surface, and van der Waals' intermolecular forces, by means of a structural disjoining pressure. In this presentation, we focus on two-dimensional flow and present simulation results for a flat film with a localized perturbation. We are interested in the morphology of the dewetted film as a function of the initial film thickness. We will show that there exists a range of film thicknesses within the linearly unstable flat film regime where stability analysis does not explain the morphology of the dewetted film. Marginal stability criterion (MSC) is used to derive an analytical expression for the velocity at which a perturbation propagates into the unstable flat film. Finally, we discuss the degree to which MSC can be used to explain the observed morphology.
Novais, Ângela; Baquero, Fernando; Machado, Elisabete; Cantón, Rafael; Peixe, Luísa; Coque, Teresa M.
2010-01-01
TEM-24 remains one of the most widespread TEM-type extended-spectrum β-lactamases (ESBLs) among Enterobacteriaceae. To analyze the reasons influencing its spread and persistence, a multilevel population genetics study was carried out on 28 representative TEM-24 producers from Belgium, France, Portugal, and Spain (13 Enterobacter aerogenes isolates, 6 Escherichia coli isolates, 6 Klebsiella pneumoniae isolates, 2 Proteus mirabilis isolates, and 1 Klebsiella oxytoca isolate, from 1998 to 2004). Clonal relatedness (XbaI pulsed-field gel electrophoresis [PFGE] and E. coli phylogroups) and antibiotic susceptibility were determined by standard procedures. Plasmid analysis included determination of the incompatibility group (by PCR, hybridization, and/or sequencing) and comparison of restriction fragment length polymorphism (RFLP) patterns. Characterization of genetic elements conferring antibiotic resistance included integrons (classes 1, 2, and 3) and transposons (Tn3, Tn21, and Tn402). Similar PFGE patterns were identified among E. aerogenes, K. pneumoniae, and P. mirabilis isolates, while E. coli strains were diverse (phylogenetic groups A, B2, and D). Highly related 180-kb IncA/C2 plasmids conferring resistance to kanamycin, tobramycin, chloramphenicol, trimethoprim, and sulfonamides were identified. Each plasmid contained defective In0-Tn402 (dfrA1-aadA1, aacA4, or aacA4-aacC1-orfE-aadA2-cmlA1) and In4-Tn402 (aacA4 or dfrA1-aadA1) variants. These integrons were located within Tn21, Tn1696, or hybrids of these transposons, with IS5075 interrupting their IRtnp and IRmer. In all cases, blaTEM-24 was part of an IS5075-ΔTn1 transposon within tnp1696, mimicking other genetic elements containing blaTEM-2 and blaTEM-3 variants. The international dissemination of TEM-24 is fuelled by an IncA/C2 plasmid acquired by different enterobacterial clones which seem to evolve by gaining diverse genetic elements. This work highlights the risks of a confluence between highly
Directory of Open Access Journals (Sweden)
Anneliese Müller
Full Text Available Controlling the food-borne pathogen Listeria (L. monocytogenes is of great importance from a food safety perspective, and thus for human health. The consequences of failures in this regard have been exemplified by recent large listeriosis outbreaks in the USA and Europe. It is thus particularly notable that tolerance to quaternary ammonium compounds such as benzalkonium chloride (BC has been observed in many L. monocytogenes strains. However, the molecular determinants and mechanisms of BC tolerance of L. monocytogenes are still largely unknown. Here we describe Tn6188, a novel transposon in L. monocytogenes conferring tolerance to BC. Tn6188 is related to Tn554 from Staphylococcus (S. aureus and other Tn554-like transposons such as Tn558, Tn559 and Tn5406 found in various Firmicutes. Tn6188 comprises 5117 bp, is integrated chromosomally within the radC gene and consists of three transposase genes (tnpABC as well as genes encoding a putative transcriptional regulator and QacH, a small multidrug resistance protein family (SMR transporter putatively associated with export of BC that shows high amino acid identity to Smr/QacC from S. aureus and to EmrE from Escherichia coli. We screened 91 L. monocytogenes strains for the presence of Tn6188 by PCR and found Tn6188 in 10 of the analyzed strains. These isolates were from food and food processing environments and predominantly from serovar 1/2a. L. monocytogenes strains harboring Tn6188 had significantly higher BC minimum inhibitory concentrations (MICs (28.5 ± 4.7 mg/l than strains without Tn6188 (14 ± 3.2 mg/l. Using quantitative reverse transcriptase PCR we could show a significant increase in qacH expression in the presence of BC. QacH deletion mutants were generated in two L. monocytogenes strains and growth analysis revealed that ΔqacH strains had lower BC MICs than wildtype strains. In conclusion, our results provide evidence that Tn6188 is responsible for BC tolerance in various L
Müller, Anneliese; Rychli, Kathrin; Muhterem-Uyar, Meryem; Zaiser, Andreas; Stessl, Beatrix; Guinane, Caitriona M; Cotter, Paul D; Wagner, Martin; Schmitz-Esser, Stephan
2013-01-01
Controlling the food-borne pathogen Listeria (L.) monocytogenes is of great importance from a food safety perspective, and thus for human health. The consequences of failures in this regard have been exemplified by recent large listeriosis outbreaks in the USA and Europe. It is thus particularly notable that tolerance to quaternary ammonium compounds such as benzalkonium chloride (BC) has been observed in many L. monocytogenes strains. However, the molecular determinants and mechanisms of BC tolerance of L. monocytogenes are still largely unknown. Here we describe Tn6188, a novel transposon in L. monocytogenes conferring tolerance to BC. Tn6188 is related to Tn554 from Staphylococcus (S.) aureus and other Tn554-like transposons such as Tn558, Tn559 and Tn5406 found in various Firmicutes. Tn6188 comprises 5117 bp, is integrated chromosomally within the radC gene and consists of three transposase genes (tnpABC) as well as genes encoding a putative transcriptional regulator and QacH, a small multidrug resistance protein family (SMR) transporter putatively associated with export of BC that shows high amino acid identity to Smr/QacC from S. aureus and to EmrE from Escherichia coli. We screened 91 L. monocytogenes strains for the presence of Tn6188 by PCR and found Tn6188 in 10 of the analyzed strains. These isolates were from food and food processing environments and predominantly from serovar 1/2a. L. monocytogenes strains harboring Tn6188 had significantly higher BC minimum inhibitory concentrations (MICs) (28.5 ± 4.7 mg/l) than strains without Tn6188 (14 ± 3.2 mg/l). Using quantitative reverse transcriptase PCR we could show a significant increase in qacH expression in the presence of BC. QacH deletion mutants were generated in two L. monocytogenes strains and growth analysis revealed that ΔqacH strains had lower BC MICs than wildtype strains. In conclusion, our results provide evidence that Tn6188 is responsible for BC tolerance in various L. monocytogenes
Optical Twist Induced by Plasmonic Resonance
Chen, Jun; Wang, Neng; Cui, Liyong; Li, Xiao; Lin, Zhifang; Ng, Jack
2016-06-01
Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster.
Twisted Light Transmission over 143 kilometers
Krenn, Mario; Fink, Matthias; Fickler, Robert; Ursin, Rupert; Malik, Mehul; Zeilinger, Anton
2016-01-01
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, while free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here we show the transmission of orbital angular momentum modes of light over a distance of 143 kilometers between two Canary Islands, which is 50 times greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order, and decode the transmitted message with an error rate of 8.33%....
Twisted Polynomials and Forgery Attacks on GCM
DEFF Research Database (Denmark)
Abdelraheem, Mohamed Ahmed A. M. A.; Beelen, Peter; Bogdanov, Andrey;
2015-01-01
nonce misuse resistance, such as POET. The algebraic structure of polynomial hashing has given rise to security concerns: At CRYPTO 2008, Handschuh and Preneel describe key recovery attacks, and at FSE 2013, Procter and Cid provide a comprehensive framework for forgery attacks. Both approaches rely...... heavily on the ability to construct forgery polynomials having disjoint sets of roots, with many roots (“weak keys”) each. Constructing such polynomials beyond naïve approaches is crucial for these attacks, but still an open problem. In this paper, we comprehensively address this issue. We propose to use...... in an improved key recovery algorithm. As cryptanalytic applications of our twisted polynomials, we develop the first universal forgery attacks on GCM in the weak-key model that do not require nonce reuse. Moreover, we present universal weak-key forgeries for the nonce-misuse resistant AE scheme POET, which...
Obregón, O; Ryan, M P; Obregon, Octavio; Quevedo, Hernando; Ryan, Michael P.
2004-01-01
We construct a family of time and angular dependent, regular S-brane solutions which corresponds to a simple analytical continuation of the Zipoy-Voorhees 4-dimensional vacuum spacetime. The solutions are asymptotically flat and turn out to be free of singularities without requiring a twist in space. They can be considered as the simplest non-singular generalization of the singular S0-brane solution. We analyze the properties of a representative of this family of solutions and show that it resembles to some extent the asymptotic properties of the regular Kerr S-brane. The R-symmetry corresponds, however, to the general Lorentzian symmetry. Several generalizations of this regular solution are derived which include a charged S-brane and an additional dilatonic field.
A Solvable Twisted One-Plaquette Model
Billó, M.; D'Adda, A.
We solve a hot twisted Eguchi-Kawai model with only timelike plaquettes in the deconfined phase, by computing the quadratic quantum fluctuations around the classical vacuum. The solution of the model has some novel features: the eigenvalues of the timelike link variable are separated in L bunches, if L is the number of links of the original lattice in the time direction, and each bunch obeys a Wigner semicircular distribution of eigenvalues. This solution becomes unstable at a critical value of the coupling constant, where it is argued that a condensation of classical solutions takes place. This can be inferred by comparison with the heat-kernel model in the Hamiltonian limit, and the related Douglas-Kazakov phase transition in QCD2. As a byproduct of our solution, we can reproduce the dependence of the coupling constant from the parameter describing the asymmetry of the lattice, and compare it to previous results by Karsch.
Twisted and Nontwisted Bifurcations Induced by Diffusion
Lin, X B
1996-01-01
We discuss a diffusively perturbed predator-prey system. Freedman and Wolkowicz showed that the corresponding ODE can have a periodic solution that bifurcates from a homoclinic loop. When the diffusion coefficients are large, this solution represents a stable, spatially homogeneous time-periodic solution of the PDE. We show that when the diffusion coefficients become small, the spatially homogeneous periodic solution becomes unstable and bifurcates into spatially nonhomogeneous periodic solutions. The nature of the bifurcation is determined by the twistedness of an equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients decrease. In the nontwisted case two spatially nonhomogeneous simple periodic solutions of equal period are generated, while in the twisted case a unique spatially nonhomogeneous double periodic solution is generated through period-doubling. Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic bifurcations; periodic solutions.
Energy release in driven twisted coronal loops
Bareford, M R; Browning, P K; Hood, A W
2015-01-01
In the present study we investigate magnetic reconnection in twisted magnetic fluxtubes with different initial configurations. In all considered cases, energy release is triggered by the ideal kink instability, which is itself the result of applying footpoint rotation to an initially potential field. The main goal of this work is to establish the influence of the field topology and various thermodynamic effects on the energy release process. Specifically, we investigate convergence of the magnetic field at the loop footpoints, atmospheric stratification, as well as thermal conduction. In all cases, the application of vortical driving at the footpoints of an initally potential field leads to an internal kink instability. With the exception of the curved loop with high footpoint convergence, the global geometry of the loop change little during the simulation. Footpoint convergence, curvature and atmospheric structure clearly influences the rapidity with which a loop achieves instability as well as the size of t...
Twisted accretion discs: Pt. 5; Viscous evolution
Energy Technology Data Exchange (ETDEWEB)
Kumar, S. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (Germany, F.R.). Inst. fuer Astrophysik)
1990-08-15
The time-dependence of accretion discs with orbits tilted out of the symmetry plane is studied. The effects of mass inflow modulation, and tilt variation at the disc outer edge, are examined for both circumbinary discs and for discs around compact objects. The appendices extend the numerical work to some analytic examples of tilt diffusion and external forcing effects. It is also shown that the disc must not be treated as a rigid tilted object if global angular momentum is to be conserved. These results are relevant to the problem of long-term periodicities of the light curves in Her X1 and {epsilon} Aur, the S-type symmetry of radio jets, warped gas discs in galaxies and polar rings in Neptune. Twisted discs may also arise in star-forming regions. (author).
Optical twists in phase and amplitude
DEFF Research Database (Denmark)
Daria, Vincent R.; Palima, Darwin; Glückstad, Jesper
2011-01-01
beams, the far field projection of the twisted optical beam maintains a high photon concentration even at higher values of topological charge. Optical twisters have therefore profound applications to fundamental studies of light and atoms such as in quantum entanglement of the OAM, toroidal traps......Light beams with helical phase profile correspond to photons having orbital angular momentum (OAM). A Laguerre-Gaussian (LG) beam is an example where its helical phase sets a phase-singularity at the optical axis and forms a ring-shaped transverse amplitude profile. Here, we describe a unique beam...... where both phase and amplitude express a helical profile as the beam propagates in free space. Such a beam can be accurately referred to as an optical twister. We characterize optical twisters and demonstrate their capacity to induce spiral motion on particles trapped along the twisters’ path. Unlike LG...
Twisted Black Hole Is Taub-NUT
Ong, Yen Chin
2016-01-01
Recently a purportedly novel solution of the vacuum Einstein field equations was discovered: it supposedly describes an asymptotically flat twisted black hole in 4-dimensions whose exterior spacetime rotates in a peculiar manner -- the frame dragging in the northern hemisphere is opposite from that of the southern hemisphere, which results in a globally vanishing angular momentum. Furthermore it was shown that the spacetime has no curvature singularity. We show that the geometry of this black hole spacetime is nevertheless not free of pathological features. In particular, it harbors a rather drastic conical singularity along the axis of rotation. In addition, there exist closed timelike curves due to the fact that the constant r and constant t surfaces are not globally Riemannian. In fact, none of these are that surprising since the solution is just the Taub-NUT geometry.
Unusual presentation of twisted ovarian cyst
Directory of Open Access Journals (Sweden)
Vineet V Mishra
2016-01-01
Full Text Available Ovarian torsion (also termed as adnexal torsion refers to partial or complete rotation of the ovary and a portion of fallopian tube along its supplying vascular pedicle. It occurs commonly in reproductive age group; more on the right side (60% and often presents with acute lower abdominal pain lasting for few hours and up to 24 h, accounting for 2.7% of acute gynecological conditions. It is one of the devastating conditions, hampering blood supply of ovary which may lead to total necrosis of ovarian tissue and complications, if not diagnosed and managed in time. Hence, we present a case on a twisted ovarian cyst in postmenopausal woman with unusual symptomatology leading to delayed diagnosis and loss of an ovary.
Twisted boundary states in c=1 coset conformal field theories
Ishikawa, H; Ishikawa, Hiroshi; Yamaguchi, Atsushi
2003-01-01
We study the mutual consistency of twisted boundary conditions in the coset conformal field theory G/H. We calculate the overlap of the twisted boundary states of G/H with the untwisted ones, and show that the twisted boundary states are consistently defined in the diagonal modular invariant. The overlap of the twisted boundary states is expressed by the branching functions of a twisted affine Lie algebra. As a check of our argument, we study the diagonal coset theory so(2n)_1 \\oplus so(2n)_1/so(2n)_2, which is equivalent with the orbifold S^1/\\Z_2. We construct the boundary states twisted by the automorphisms of the unextended Dynkin diagram of so(2n), and show their mutual consistency by identifying their counterpart in the orbifold. For the triality of so(8), the twisted states of the coset theory correspond to neither the Neumann nor the Dirichlet boundary states of the orbifold and yield the conformal boundary states that preserve only the Virasoro algebra.
Heat Transfers Enhancement with Different Square Jagged Twisted Tapes
Directory of Open Access Journals (Sweden)
Mr. A.V.Gawandare
2014-03-01
Full Text Available The present experimental work are carried out with copper twisted tape inserts 3mm with 5.2,4.2 and 3.2 twists respectively. The inserts when placed in the path of the flow of the fluid, create a high degree of turbulence resulting in an increase in the heat transfer rate and the pressure drop. The work includes the determination of friction factor and heat transfer coefficient for various twisted wire inserts with varying twists and different materials. The Reynolds number is varied from 5000 to 16000. Correlations for Nusselt number and friction factor are developed for the twisted wire inserts from the obtained results. The results of varying twists in square jagged tape with different pitches have been compared with the values for the smooth tube. The 3mm thick with 3.2 twists copper insert shows increase in Nusselt number values by 76% however there is increase in friction factor by only 19.5% as compared to the smooth tube values.
ST6GalNAc-I controls expression of sialyl-Tn antigen in gastrointestinal tissues
DEFF Research Database (Denmark)
Marcos, Nuno T; Bennett, Eric Paul; Gomes, Joana;
2011-01-01
Sialyl-Tn is a simple mucin-type carbohydrate antigen aberrantly expressed in gastrointestinal adenocarcinomas and in the precursor lesion intestinal metaplasia. Sialyl-Tn tumour expression is an independent indicator of poor prognosis. We have previously shown in vitro that ST6GalNAc-I and ST6GalNAc......-II sialyltransferases can synthesize sialyl-Tn. The aim of the present study was to establish whether ST6GalNAc-I is the major enzyme responsible for the expression of sialyl-Tn. We used a model of CHO-ldlD cells producing only MUC1-Tn glycoform and showed that ST6GalNAc-I is the key-enzyme leading to sialyl......-Tn biosynthesis. We developed novel monoclonal antibodies specific for ST6GalNAc-I and evaluated its expression in gastrointestinal tissues. ST6GalNAc-I was detected in normal colon mucosa co-localized with O-acetylated sialyl-Tn. Expression was largely unaltered in colorectal adenocarcinomas. In contrast, we...
The elusive thermotropic biaxial nematic phase in rigid bent-core molecules
Indian Academy of Sciences (India)
Bharat R Acharya; Andrew Primak; Theo J Dingemans; Edward T Samulski; Satyendra Kumar
2003-08-01
The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to ﬁnd it in various systems resulted in mis-identiﬁcations. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(-hydroxyphenyl)-1,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D2h, in which the overall long axes of the molecules are oriented parallel to each other to deﬁne the major axis of the biaxial phase. The apex of the bent-cores deﬁnes the minor axis of this phase along which the planes containing the bent-cores of neighboring molecules are oriented parallel to each other.
Kelly, Joel A; Shopsowitz, Kevin E; Ahn, Jun Myun; Hamad, Wadood Y; MacLachlan, Mark J
2012-12-18
Chiral nematic mesoporous materials decorated with metal nanoparticles have been prepared using the templated self-assembly of nanocrystalline cellulose (NCC). By adding small quantities of ionic compounds to aqueous dispersions of NCC and tetramethoxysilane (TMOS), the helical pitch of the chiral nematic structure could be manipulated in a manner complementary to the ratio of NCC/TMOS previously demonstrated by our group. We have studied the transformation of these ion-loaded composites into high surface area mesoporous silica and carbon films decorated with metal nanoparticles through calcination and carbonization, respectively. This general and straightforward approach to prepare chiral nematic metal nanoparticle assemblies may be useful in a variety of applications, particularly for their chiral optical properties.
Elastic anisotropy effects on the electrical responses of a thin sample of nematic liquid crystal
Gomes, O. A.; Yednak, C. A. R.; Ribeiro de Almeida, R. R.; Teixeira-Souza, R. T.; Evangelista, L. R.
2017-03-01
The electrical responses of a nematic liquid crystal cell are investigated by means of the elastic continuum theory. The nematic medium is considered as a parallel circuit of a resistance and a capacitance and the electric current profile across the sample is determined as a function of the elastic constants. In the reorientation process of the nematic director, the resistance and capacitance of the sample are determined by taking into account the elastic anisotropy. A nonmonotonic profile for the current is observed in which a minimum value of the current may be used to estimate the elastic constants values. This scenario suggests a theoretical method to determine the values of the bulk elastic constants in a single planar aligned cell just by changing the direction of applied electrical field and measuring the resulting electrical current.
Pseudo-Casimir forces in nematics with disorders in the bulk
Karimi Pour Haddadan, Fahimeh
2016-10-01
A nematic liquid-crystalline slab is considered in which some rod-like particles are randomly distributed. The particles are locally elongated either homeotropic or planar with respect to the confining substrates of the cell. We consider thermal fluctuations of a nematic director which is aligned perpendicular to the confining substrates due to strong homeotropic anchoring at the substrates. The resulting fluctuation-induced force across the cell is analyzed for an annealed disorder in the anchoring of the nematic director at the dispersed mesoscopic particles. Within the saddle-point approximation to free energy of the system, the effect of the disorder is renormalization of the strength of the mean anchoring which is assumed to be homeotropic. By increasing the variance of the disorder, the modes become less massive and deviations from the mean behavior become larger, so that the disorder-free universal long-range attraction, due to the soft modes, is approached.
Molecular field theory for nematic liquid crystal film with finite layers
Institute of Scientific and Technical Information of China (English)
Zhang Zhi-Dong; Li Jing; Wei Huai-Peng
2005-01-01
The nematic liquid crystal film composed of n molecular layers is studied based upon a spatially anisotropic pair potential, which reproduces approximately the elastic free energy density. On condition that the system has perfect nematic order, as in the Lebwohl-Lasher model, the director in the film is isotropic. The effect of the temperature is investigated by means of molecular field theory. Some new results are obtained. Firstly, symmetry breaking takes place when taking account of the temperature, and the state with the director along the normal of the film has the lowest free energy. Secondly, the N-I phase transition temperature increases as an effect of finite sizes instead of decreasing as in the Lebwohl-Lasher model. Thirdly, the nematic order is induced in the layers near the surface in the isotropic phase.
Alberucci, Alessandro; Laudyn, Urszula A.; Piccardi, Armando; Kwasny, Michał; Klus, Bartlomiej; Karpierz, Mirosław A.; Assanto, Gaetano
2017-07-01
We investigate nonlinear optical propagation of continuous-wave (CW) beams in bulk nematic liquid crystals. We thoroughly analyze the competing roles of reorientational and thermal nonlinearity with reference to self-focusing/defocusing and, eventually, the formation of nonlinear diffraction-free wavepackets, the so-called spatial optical solitons. To this extent we refer to dye-doped nematic liquid crystals in planar cells excited by a single CW beam in the highly nonlocal limit. To adjust the relative weight between the two nonlinear responses, we employ two distinct wavelengths, inside and outside the absorption band of the dye, respectively. Different concentrations of the dye are considered in order to enhance the thermal effect. The theoretical analysis is complemented by numerical simulations in the highly nonlocal approximation based on a semi-analytic approach. Theoretical results are finally compared to experimental results in the Nematic Liquid Crystals (NLC) 4-trans-4'-n-hexylcyclohexylisothiocyanatobenzene (6CHBT) doped with Sudan Blue dye.
Sun, Tong; Fu, Junjiang; Shen, Tao; Lin, Xia; Liao, Lan; Feng, Xin-Hua; Xu, Jianming
2016-05-27
Twist1 is a basic helix-loop-helix transcription factor that strongly promotes epithelial-to-mesenchymal transition, migration, invasion, and metastasis of cancer cells. The MAPK-phosphorylated Twist1 on its serine 68 (Ser(P)(68)-Twist1) has a significantly enhanced stability and function to drive cancer cell invasion and metastasis. However, the phosphatase that dephosphorylates Ser(P)(68)-Twist1 and destabilizes Twist1 has not been identified and characterized. In this study, we screened a serine/threonine phosphatase cDNA expression library in HEK293T cells with ectopically coexpressed Twist1. We found that the small C-terminal domain phosphatase 1 (SCP1) specifically dephosphorylates Ser(P)(68)-Twist1 in both cell-free reactions and living cells. SCP1 uses its amino acid residues 43-63 to interact with the N terminus of Twist1. Increased SCP1 expression in cells decreased Ser(P)(68)-Twist1 and total Twist1 proteins, whereas knockdown of SCP1 increased Ser(P)(68)-Twist1 and total Twist1 proteins. Furthermore, the levels of SCP1 are negatively correlated with Twist1 protein levels in several cancer cell lines. SCP1-dephosphorylated Twist1 undergoes fast degradation via the ubiquitin-proteasome pathway. Importantly, an increase in SCP1 expression in breast cancer cells with either endogenous or ectopically expressed Twist1 largely inhibits the Twist1-induced epithelial-to-mesenchymal transition phenotype and the migration and invasion capabilities of these cells. These results indicate that SCP1 is the phosphatase that counterregulates the MAPK-mediated phosphorylation of Ser(68)-Twist1. Thus, an increase in SCP1 expression and activity may be a useful strategy for eliminating the detrimental roles of Twist1 in cancer cells.
Prediction of Microcystis Blooms Based on TN:TP Ratio and Lake Origin
Directory of Open Access Journals (Sweden)
Yoshimasa Amano
2008-01-01
Full Text Available We evaluated the relationship between TN:TP ratio and Microcystis growth via a database that includes worldwide lakes based on four types of lake origin (dammed, tectonic, coastal, and volcanic lakes. We used microcosm and mesocosm for the nutrient elution tests with lake water and four kinds of sediment (nontreated, MgO sprinkling treated, dissolved air flotation [DAF] treated, and combined treated sediment in order to control TN:TP ratio and to suppress Microcystis growth. Microcystis growth was related to TN:TP ratio, with the maximum value at an optimum TN:TP ratio and the minimum values when the TN:TP ratios reached to 0 or ∞. The kurtosis of the distribution curve varied with the type of lake origin; the lowest kurtosis was found in dammed lakes, while the highest was found in volcanic lakes. The lake trophic state could affect the change in the kurtosis, providing much lower kurtosis at eutrophic lakes (dammed lakes than that at oligotrophic lakes (volcanic lakes. The relationship between TN:TP ratio and Microcystis growth could be explained by the nutrient elution tests under controlled TN:TP ratios through the various sediment treatments. A significant suppression of Microcystis growth of 70% could be achieved when the TN:TP ratios exceeded 21. Lake origin could be regarded as an index including morphological and geographical factors, and controlling the trophic state in lakes. The origin rather than trophic state for lakes could be considered as an important factor of TN:TP influences on Microcystis growth.
Tri-bimaximal mixing from twisted Friedberg-Lee symmetry
Energy Technology Data Exchange (ETDEWEB)
Araki, Takeshi [National Tsing Hua University, Department of Physics, Hsinchu (China); Takahashi, Ryo [Osaka University, Department of Physics, Graduate School of Science, Osaka (Japan)
2009-10-15
We investigate the Friedberg-Lee (FL) symmetry and its promotion to include the {mu}-{tau} symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation of the FL symmetry. The second one is based on the S{sub 3} permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each scheme are also presented. (orig.)
Tri-bimaximal mixing from twisted Friedberg-Lee symmetry
Araki, Takeshi; Takahashi, Ryo
2009-10-01
We investigate the Friedberg-Lee (FL) symmetry and its promotion to include the μ- τ symmetry, and call this the twisted FL symmetry. Based on the twisted FL symmetry, two possible schemes are presented toward the realistic neutrino mass spectrum and the tri-bimaximal mixing. In the first scheme, we suggest the semi-uniform translation of the FL symmetry. The second one is based on the S 3 permutation family symmetry. The breaking terms, which are twisted FL symmetric, are introduced. Some viable models in each scheme are also presented.
Assembly and Folding of Twisted Baskets in Organic Solvents.
Pratumyot, Yaowalak; Chen, Shigui; Hu, Lei; Polen, Shane M; Hadad, Christopher M; Badjić, Jovica D
2016-09-02
A synthetic method for obtaining enantiopure and twisted baskets of type (P)-3 is described. These chiral cavitands were found to fold quinoline gates, at the rim of their twisted platform, in acetonitrile and give molecular capsules that assemble into large unilamellar vesicles. In a less polar dichloromethane, however, cup-shaped (P)-3 packed into vesicles but with the quinoline gates in an unfolded orientation. The ability of twisted baskets to form functional nanostructured materials could be of interest for building stereoselective sensors and catalysts.
TWIST1 promotes invasion through mesenchymal change in human glioblastoma
Directory of Open Access Journals (Sweden)
Wakimoto Hiroaki
2010-07-01
Full Text Available Abstract Background Tumor cell invasion into adjacent normal brain is a mesenchymal feature of GBM and a major factor contributing to their dismal outcomes. Therefore, better understandings of mechanisms that promote mesenchymal change in GBM are of great clinical importance to address invasion. We previously showed that the bHLH transcription factor TWIST1 which orchestrates carcinoma metastasis through an epithelial mesenchymal transition (EMT is upregulated in GBM and promotes invasion of the SF767 GBM cell line in vitro. Results To further define TWIST1 functions in GBM we tested the impact of TWIST1 over-expression on invasion in vivo and its impact on gene expression. We found that TWIST1 significantly increased SNB19 and T98G cell line invasion in orthotopic xenotransplants and increased expression of genes in functional categories associated with adhesion, extracellular matrix proteins, cell motility and locomotion, cell migration and actin cytoskeleton organization. Consistent with this TWIST1 reduced cell aggregation, promoted actin cytoskeletal re-organization and enhanced migration and adhesion to fibronectin substrates. Individual genes upregulated by TWIST1 known to promote EMT and/or GBM invasion included SNAI2, MMP2, HGF, FAP and FN1. Distinct from carcinoma EMT, TWIST1 did not generate an E- to N-cadherin "switch" in GBM cell lines. The clinical relevance of putative TWIST target genes SNAI2 and fibroblast activation protein alpha (FAP identified in vitro was confirmed by their highly correlated expression with TWIST1 in 39 human tumors. The potential therapeutic importance of inhibiting TWIST1 was also shown through a decrease in cell invasion in vitro and growth of GBM stem cells. Conclusions Together these studies demonstrated that TWIST1 enhances GBM invasion in concert with mesenchymal change not involving the canonical cadherin switch of carcinoma EMT. Given the recent recognition that mesenchymal change in GBMs is
Topological duality twist and brane instantons in F-theory
Energy Technology Data Exchange (ETDEWEB)
Martucci, Luca [Dipartimento di Fisica ed Astronomia “Galileo Galilei”, Università di Padova andINFN - Sezione di Padova,Via Marzolo 8, I-35131 Padova (Italy)
2014-06-30
A variant of the topological twist, involving SL(2,ℤ) dualities and hence named topological duality twist, is introduced and explicitly applied to describe a U(1) N=4 super Yang-Mills theory on a Kähler space with holomorphically space-dependent coupling. Three-dimensional duality walls and two-dimensional chiral theories naturally enter the formulation of the duality twisted theory. Appropriately generalized, this theory is relevant for the study of Euclidean D3-brane instantons in F-theory compactifications. Some of its properties and implications are discussed.
Twist Neutrality and the Diameter of the Nucleosome Core Particle
DEFF Research Database (Denmark)
Bohr, Jakob; Olsen, Kasper
2012-01-01
The diameter of the nucleosome core particle is the same for all the eukaryotes. Here we discuss the possibility that this selectiveness is consistent with a propensity for twist neutrality, in particular, for the double helical DNA to stay rotationally neutral when strained. Reorganization of DNA...... cannot be done without some level of temporal tensile stress, and as a consequence chiral molecules, such as helices, will twist under strain. The requirement that the nucleosome, constituting the nucleosome core particle and linker DNA, has a vanishing strain-twist coupling leads to a requirement...
Differential forms and {kappa}-Minkowski spacetime from extended twist
Energy Technology Data Exchange (ETDEWEB)
Juric, Tajron; Meljanac, Stjepan [Rudjer Boskovic Institute, Zagreb (Croatia); Strajn, Rina [Jacobs University Bremen, Bremen (Germany)
2013-07-15
We analyze bicovariant differential calculus on {kappa}-Minkowski spacetime. It is shown that corresponding Lorentz generators and noncommutative coordinates compatible with bicovariant calculus cannot be realized in terms of commutative coordinates and momenta. Furthermore, {kappa}-Minkowski space and NC forms are constructed by twist related to a bicrossproduct basis. It is pointed out that the consistency condition is not satisfied. We present the construction of {kappa}-deformed coordinates and forms (super-Heisenberg algebra) using extended twist. It is compatible with bicovariant differential calculus with {kappa}-deformed igl(4)-Hopf algebra. The extended twist leading to {kappa}-Poincare-Hopf algebra is also discussed. (orig.)
基于推进TnPM体系的问题探讨%Discussion into Advancing the TnPM System
Institute of Scientific and Technical Information of China (English)
齐梦飞
2014-01-01
为完善全面规范化生产维护(Total normalized Productive Maintenance,TnPM)体系的推进,结合中国石化广州石化公用工程部在实践TnPM体系过程中的案例,在对存在的问题整合分析、按质归类基础上,进行体系的理念宣贯、体系建设与推进要领3个方面的探讨,以期真正体现推进TnPM体系的最优价值.
Induction of the Tn10 Precise Excision in E. coli Cells after Accelerated Heavy Ions Irradiation
Zhuravel, D V
2003-01-01
The influence of the irradiation of different kinds on the indication of the structural mutations in the bacteria Escherichia coli is considered. The regularities of the Tn10 precise excision after accelerated ^{4}He and ^{12}C ions irradiations with different linear energy transfer (LET) were investigated. Dose dependences of the survival and relative frequency of the Tn10 precise excision were obtained. It was shown, that the relative frequency of the Tn10 precise excision is the exponential function from the irradiation dose. Relative biological efficiency (RBE), and relative genetic efficiency (RGE) were calculated, and were treated as the function of the LET.
2007-01-01
6ErN) (1 + s0 − 2s20 −B1 Er)ErD 2 , C1 = B3 − 2C3 sinh(Er 1/2D) 2 sinh(Er1/2F ) . This result for Poiseuille flow is qualitatively similar to Couette ...nematic flows ,” Physical Review A 34 (4), 3393-3404 (1986). [3] Cui, Z., Forest, M.G., Wang, Q., and Zhou, H., “On weak plane Couette and Poiseuille ...Zhou, H. and Forest, M. G., “Anchoring distortions coupled with plane Couette & Poiseuille flows of nematic polymers in viscous solvents: morphology
Physical Properties of Nematic Decylammonium Chloride/ammonium Chloride/water Systems.
Stefanov, Michael Edwin
This study reports new measurements of some physical properties (i.e., density and diamagnetic susceptibility) and also measurements on the curvature elasticity and flow properties of the amphiphilic nematic system of decylammonium chloride (DACl), ammonium chloride (NH(,4)Cl) and water. The mixtures exhibit a lamellar-smectic (neat soap) phase, a nematic lamellar (N(,L)) phase, and an isotropic micellar region. The densities were determined to an accuracy of 10('-4) by weighing an immersed calibrated bulb. The density does not show a discontinuous change at the nematic-isotropic transition and is estimated to be less than 0.01%. There is also only a small difference in the expansion coefficients between the nematic and isotropic regions. The diamagnetic susceptibilities were determined using the Gouy method with the error of the measurement on the order of 10('-4). The anisotropy in the diamagnetic susceptibility varies in the nematic range from 2 x 10(' -9) near T(,N(--->)I) to 5 x 10('-9) near T(,S(--->)N). The elasticity coefficients were measured by deforming a surface-aligned film by a magnetic field. An effective viscosity coefficient was calculated using the Leslie-Erickson hydrodynamic theory in the limit of small distortions. For the mixtures studied, the ratio of K(,11)/K(,33) is 0.9 near the N(--->)I transition. The ratio of (gamma)(,1)('*)/K(,33) varies from 7.74 x 10('6) s/cm('2) at 40.4(DEGREES)C to a maximum of 9.26 x 10('6) s/cm('2) at 33.5(DEGREES)C and then decreases to a value of 8.60 x 10('6) s/cm('2) at 30.0(DEGREES)C. Absolute values of K(,11), K(,33) and (gamma)(,1)('*) are derived by combining these results for (chi)(,a) with previously reported results for K(,11)/(chi)(,a), K(,33)/(chi)(,a), and (gamma)(,1)('*)/(chi)(,a). The absolute value of K(,11) varies from 1 x 10('-7) dynes at the N(--->)I transition to (TURN)5 x 10('-7) dynes at the neat soap-nematic transition. K(,33) varies accordingly from 2 x 10('-7) to the highest measured
Lattice Boltzmann Simulation of 3D Nematic Liquid Crystal near Phase Transition
Institute of Scientific and Technical Information of China (English)
ZHANG Jun; TAO Rui-Bao
2002-01-01
Phase transition between nematic and isotropic liquid crystal is a very weak first order phase transition.We avoid to use the normal Landau-de Gennes's free energy that reduces a strong first order transition, and set up adata base of free energy calculated by means of Tao-Sheng Lin's extended molecular field theory that can explain theexperiments of the equilibrium properties of nematic liquid crystal very well. Then we use the free energy method oflattice Boltzmann developed by Oxford group to study the phase decomposition, pattern formation in the flow of theliquid crystal near transition temperature.
Global well-posedness of the 2D nonhomogeneous incompressible nematic liquid crystal flows
Liu, Qiao; Liu, Shengquan; Tan, Wenke; Zhong, Xin
2016-12-01
This paper concerns the Cauchy problem of the two-dimensional (2D) nonhomogeneous incompressible nematic liquid crystal flows on the whole space R2 with vacuum as far field density. It is proved that the 2D nonhomogeneous incompressible nematic liquid crystal flows admit a unique global strong solution provided that the initial data density and the gradient of orientation decay not too slow at infinity, and the initial orientation satisfies a geometric condition (see (1.3)). In particular, the initial data can be arbitrarily large and the initial density may contain vacuum states and even have compact support. Furthermore, the large time behavior of the solution is also obtained.
Dhakal, Subas; Solis, Francisco J.; Olvera de la Cruz, Monica
2012-07-01
Recent experiments have shown that defect conformations in spherical nematic liquid crystals can be controlled through variations of temperature, shell thickness, and other environmental parameters. These modifications can be understood as a result of the induced changes in the effective elastic constants of the system. To characterize the relation between defect conformations and elastic anisotropy, we carry out Monte Carlo simulations of a nematic on a spherical surface. As the anisotropy is increased, the defects flow from a tetrahedral arrangement to two coalescing pairs and then to a great circle configuration. We also analyze this flow using a variational method based on harmonic configurations.
Pardaev, Shokir A; Williams, J C; Twieg, R J; Jakli, A; Gleeson, J T; Ellman, B; Sprunt, S
2015-03-01
Angle-resolved, second-harmonic-light scattering (SHLS) measurements are reported for three different classes of thermotropic nematic liquid crystals (NLCs): polar and nonpolar rodlike compounds and a bent-core compound. Results revealing well-defined scattering peaks are interpreted in terms of the electric polarization induced by distortions of the nematic orientational field ("flexopolarity") associated with inversion wall defects, nonsingular disclinations, analogous to Neel walls in ferromagnets, that often exhibit a closed loop morphology in NLCs. Analysis of the SHLS patterns based on this model provides a "proof-of-concept" for a potentially useful method to probe the flexopolar properties of NLCs.
Fluctuations and topological transitions of quantum Hall stripes: Nematics as anisotropic hexatics
Ettouhami, A. M.; Doiron, C. B.; Côté, R.
2007-10-01
We study fluctuations and topological melting transitions of quantum Hall stripes near half filling of intermediate Landau levels. Taking the stripe state to be an anisotropic Wigner crystal (AWC) allows us to identify the quantum Hall nematic state conjectured in previous studies of the two-dimensional (2D) electron gas as an anisotropic hexatic. The transition temperature from the AWC to the quantum Hall nematic state is explicitly calculated, and a tentative phase diagram for the 2D electron gas near half filling is suggested.
Chen, Yu-Jen; Lin, Yu-Sung; Jiang, I-Min; Tsai, Ming-Shan
2008-03-17
This study investigates the optical nonlinearity of beam propagation in homogeneously aligned nematic liquid crystal (NLC) cells at a temperature close to the nematic-isotropic temperature (TNI). The undulate propagation mode with convergent and divergent loops appearing alternately is reported and the thermally enhanced optical reorientation nonlinearity at the focus is described. The optically induced phase transition exists along the pump beam direction. With the application of the conscopic technique, the arrangements of LC at the focus are proposed in this study. Results of this study demonstrate that the evolution of the LC configuration was affected by the pump beam based on the analysis of conoscopic patterns.
Fiber-to-fiber nonlinear coupling via a nematic liquid crystal
Nyushkov, B. N.; Trashkeev, S. I.; Ivanenko, A. V.; Kolker, D. B.; Purtov, P. A.
2017-01-01
Nonlinear optical coupling between two single-mode fibers terminated coaxially in a nematic liquid crystal (NLC) was explored for the first time. Light-induced reorientation of nematic molecules can result in the stable self-collimation of light transmitted through the gap between fibers. Thus, high coupling efficiency can be achieved despite large fiber spacing. We demonstrated a coupling efficiency of up to ∼0.7, achieved with spacing equal to four diffraction lengths. This feature opens up possibilities for the development of novel in-line fiber-optic elements based on NLCs. For instance, a polarization controller was proposed and considered.
A Simple Free Energy for the Isotropic-Nematic Phase Transition of Rods
Directory of Open Access Journals (Sweden)
Remco Tuinier
2016-01-01
Full Text Available A free energy expression is proposed that describes the isotropic-nematic binodal concentrations of hard rods. A simple analytical form for this free energy was yet only available using a Gaussian trial function for the orientation distribution function (ODF, leading, however, to a significant deviation of the predicted binodals. The new free energy proposed here is based upon a rationalized correction to the orientational and packing entropies when using the Gaussian ODF. In combination with Parsons-Lee theory or scaled particle theory, it enables describing the isotropic-nematic phase coexistence concentrations of rods accurately using the simple Gaussian ODF for a wide range of aspect ratios.
Testing mixed action approaches to meson spectroscopy with twisted mass sea quarks
Berlin, Joshua; Wagner, Marc
2013-01-01
We explore and compare three mixed action setups with Wilson twisted mass sea quarks and different valence quark actions: (1) Wilson twisted mass, (2) Wilson twisted mass + clover and (3) Wilson + clover. Our main goal is to reduce lattice discretization errors in mesonic spectral quantities, in particular to reduce twisted mass parity and isospin breaking.
Directory of Open Access Journals (Sweden)
Laurent Jacqueroud
2016-05-01
Full Text Available The TWIST1 embryonic transcription factor displays biphasic functions during the course of carcinogenesis. It facilitates the escape of cells from oncogene-induced fail-safe programs (senescence, apoptosis and their consequent neoplastic transformation. Additionally, it promotes the epithelial-to-mesenchymal transition and the initiation of the metastatic spread of cancer cells. Interestingly, cancer cells recurrently remain dependent on TWIST1 for their survival and/or proliferation, making TWIST1 their Achilles’ heel. TWIST1 has been reported to form either homodimeric or heterodimeric complexes mainly in association with the E bHLH class I proteins. These complexes display distinct, sometimes even antagonistic, functions during development and unequal prometastatic functions in prostate cancer cells. Using a tethered dimer strategy, we successively assessed the ability of TWIST1 dimers to cooperate with an activated version of RAS in human mammary epithelial cell transformation, to provide mice with the ability to spontaneously develop breast tumors, and lastly to maintain a senescence program at a latent state in several breast cancer cell lines. We demonstrate that the TWIST1-E12 complex, unlike the homodimer, is an oncogenic form of TWIST1 in mammary epithelial cells and that efficient binding of both partners is a prerequisite for its activity. The detection of the heterodimer in human premalignant lesions by a proximity ligation assay, at a stage preceding the initiation of the metastatic cascade, is coherent with such an oncogenic function. TWIST1-E protein heterodimeric complexes may thus constitute the main active forms of TWIST1 with regard to senescence inhibition over the time course of breast tumorigenesis.
Asymmetric electrooptic response in a nematic liquid crystal
Energy Technology Data Exchange (ETDEWEB)
Dascalu, Constanta [Politechnica University of Bucharest, Bucharest (Romania)
2001-06-01
An asymmetric electrooptic response in nematic liquid crystal (LC) has been obtained. The liquid crystal hybrid cell was made by using a standard configuration. One of the ITO (Indium Tin Oxide) electrodes was covered with a surfactant, which induces a homeotropic alignment. The second of the indium tin oxide electrodes was covered by a thin layer of photopolymer, which was previously mixed with an acid, which favours a process of release of protons. Such cations are responsible of electrochemical process in the LC leading to an asymmetric electrooptic response, which depend on the polarity of the applied electric field. This fact is due to an internal field, which change the effective voltage thresholds for the reorientation of the liquid crystal. During the anodic polarization, the optical switching is inhibited because the effective field decreases below the threshold value. On contrary for the opposite polarization the effective field is enough to determine a homeotropic alignment. [Spanish] Se ha obtenido una respuesta electro-optica asimetrica en cristales liquidos neumaticos. La celula hibrida de cristal liquido fue construida utilizando una configuracion estandar. Uno de los electrodos ITO fue cubierto con una pelicula delgada de material organico para inducir una alineacion homeotropa. El otro electrodo ITO fue cubierto con una pelicula delgada de fotopolimero anteriormente mezclada con un acido para favorecer la emision de protones. Estos cationes son responsables del proceso electroquimico en LC, conduciendo a una respuesta electro-optica asimetrica que depende de la polaridad del campo electrico aplicado. Este efecto es originado por un campo interno que cambia el umbral efectivo del voltaje para la reorientacion del cristal liquido. Durante la polarizacion anodica, la conmutacion optica se inhibe debido a que el campo efectivo disminuye abajo del valor del umbral. Por el contrario, para la polarizacion opuesta el campo efectivo es suficiente para
Shadow casted by a twisted and rotating black hole
Chen, Songbai
2016-01-01
Zhang have obtained recently a twisted rotating black hole metric, which is a vacuum solution in four-dimensional Einstein gravity. This black hole solution has a rotation parameter, but without the total angular moment. Here, we have investigated the shadow casted by a twisted rotating black hole. Our results show that the shape of the shadow of the twisted rotating black hole is a standard round disk and does not depend on the inclination angle of the observer. It means that although the twisted rotating black hole has a rotation parameter, its shadow possesses the same behaviors as the common static black hole rather than the usual Kerr-like black holes. Moreover, we find that the marginally circular orbit radius of photon is independent of the direction of photon around the black hole. The value of the marginally circular orbit radius of photon and the size of shadow increase monotonously with the rotation parameter.
Cayley-Dickson and Clifford Algebras as Twisted Group Algebras
Bales, John W
2011-01-01
The effect of some properties of twisted groups on the associated algebras, particularly Cayley-Dickson and Clifford algebras. It is conjectured that the Hilbert space of square-summable sequences is a Cayley-Dickson algebra.
Determination of Elastic Twist in Horizontal Axis Wind Turbines (HAWTs)
Energy Technology Data Exchange (ETDEWEB)
Stoddard, F.; Nelson, V.; Starcher, K.; Andrews, B.
2006-06-01
This report presents the results of a project at the Alternative Energy Institute (AEI) which measured and calculated the elastic twist of three representative composite horizontal-axis blades: Carter 300, Gougeon ESI 54, and UTRC 8 kW.
Quarks with Twisted Boundary Conditions in the Epsilon Regime
Energy Technology Data Exchange (ETDEWEB)
Thomas Mehen; Brian C. Tiburzi
2005-05-01
We study the effects of twisted boundary conditions on the quark fields in the epsilon regime of chiral perturbation theory. We consider the SU(2){sub L} x SU(2){sub R} chiral theory with non-degenerate quarks and the SU(3){sub L} x SU(3){sub R} chiral theory with massless up and down quarks and massive strange quarks. The partition function and condensate are derived for each theory. Because flavor-neutral Goldstone bosons are unaffected by twisted boundary conditions chiral symmetry is still restored in finite volumes. The dependence of the condensate on the twisting parameters can be used to extract the pion decay constant from simulations in the epsilon regime. The relative contribution to the partition function from sectors of different topological charge is numerically insensitive to twisted boundary conditions.
Spectrum of a duality-twisted Ising quantum chain
Grimm, U
2002-01-01
The Ising quantum chain with a peculiar twisted boundary condition is considered. This boundary condition, first introduced in the framework of the spin-1/2 XXZ Heisenberg quantum chain, is related to the duality transformation, which becomes a symmetry of the model at the critical point. Thus, at the critical point, the Ising quantum chain with the duality-twisted boundary is translationally invariant, similar as in the case of the usual periodic or antiperiodic boundary conditions. The complete energy spectrum of the Ising quantum chain is calculated analytically for finite systems, and the conformal properties of the scaling limit are investigated. This provides an explicit example of a conformal twisted boundary condition and a corresponding generalised twisted partition function.
The Kostant partition functions for twisted Kac-Moody algebras
Directory of Open Access Journals (Sweden)
Ranabir Chakrabarti
2000-01-01
Full Text Available Employing the method of generating functions and making use of some infinite product identities like Euler, Jacobi's triple product and pentagon identities we derive recursion relations for Kostant's partition functions for the twisted Kac-Moody algebras.
Polanski lavastas filmi "Oliver Twist" oma lastele / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm "Oliver Twist" Charles Dickensi romaani ainetel esilinastus Prahas, kus toimusid ka filmivõtted. Tšehhi, Suurbritannia, Prantsusmaa ja Itaalia koostöös valminud filmi lavastas Roman Polanski
Õnnetu saatusega Oliver Twist Polanski meelevallas / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm Charles Dickensi romaani järgi "Oliver Twist" : stsenarist Ronald Harwood : režissöör Roman Polanski : nimiosas Barney Clark, Fagin - Ben Kingsley : Suurbritannia - Tšehhi - Prantsusmaa - Itaalia 2005
Polarisation of microwave emission from reconnecting twisted coronal loops
Gordovskyy, Mykola; Kontar, Eduard
2016-01-01
Magnetic reconnection and particle acceleration due to the kink instability in twisted coronal loops can be a viable scenario for confined solar flares. Detailed investigation of this phenomenon requires reliable methods for observational detection of magnetic twist in solar flares, which may not be possible solely through extreme UV and soft X-ray thermal emission. The gradient of microwave polarisation across flaring loops can serve as one of the detection criteria. The aim of this study is to investigate the effect of magnetic twist in flaring coronal loops on the polarisation of gyro-synchrotron microwave emission, and determine whether microwave emission polarisation could provide a means for observational detection. We use time-dependent magnetohydrodynamic and test-particle models, developed using LARE3D and GCA codes to investigate twisted coronal loops relaxing following the kink-instability, and calculate synthetic microwave emission maps (I and V Stokes components) using GX simulator. It is found t...
Twistted ξ-(α,β expansive mappings in metric spaces
Directory of Open Access Journals (Sweden)
Poonam Nagpal
2016-04-01
Full Text Available In this paper, we introduce a pair of twisted ζ-(α,β expansive mappings in metric spaces and prove fixed point theorems for these mappings. Some examples are also provided to support our main results.
Polanski lavastas filmi "Oliver Twist" oma lastele / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm "Oliver Twist" Charles Dickensi romaani ainetel esilinastus Prahas, kus toimusid ka filmivõtted. Tšehhi, Suurbritannia, Prantsusmaa ja Itaalia koostöös valminud filmi lavastas Roman Polanski
Õnnetu saatusega Oliver Twist Polanski meelevallas / Andres Laasik
Laasik, Andres, 1960-2016
2005-01-01
Mängufilm Charles Dickensi romaani järgi "Oliver Twist" : stsenarist Ronald Harwood : režissöör Roman Polanski : nimiosas Barney Clark, Fagin - Ben Kingsley : Suurbritannia - Tšehhi - Prantsusmaa - Itaalia 2005
Radiative Capture of Twisted Electrons by Bare Ions
Matula, Oliver; Serbo, Valeriy G; Surzhykov, Andrey; Fritzsche, Stephan
2014-01-01
Recent advances in the production of twisted electron beams with a subnanometer spot size offer unique opportunities to explore the role of orbital angular momentum (OAM) in basic atomic processes. In the present work, we address one of these processes: radiative recombination of twisted electrons with bare ions. Based on the density matrix formalism and the non-relativistic Schr\\"odinger theory, analytical expressions are derived for the angular distribution and the linear polarization of photons emitted due to the capture of twisted electrons into the ground state of (hydrogen-like) ions. We show that these angular and polarization distributions are sensitive to both, the transverse momentum and the topological charge of the electron beam. To observe in particular the value of this charge, we propose an experiment that makes use of the coherent superposition of two twisted beams.
A Stylistic Analysis of Register Theory in Oliver Twist
Institute of Scientific and Technical Information of China (English)
刘鑫
2015-01-01
Stylistic analysis refers to the linguistic approach to literature.Stylistics will mainly focus on the register theory,taking Charles Dickens' masterpiece Oliver Twist as a good example to demonstrate how the register theory is embodied in the work.
The Kostant partition functions for twisted Kac-Moody algebras
Ranabir Chakrabarti; Santhanam, Thalanayar S.
2000-01-01
Employing the method of generating functions and making use of some infinite product identities like Euler, Jacobi's triple product and pentagon identities we derive recursion relations for Kostant's partition functions for the twisted Kac-Moody algebras.
Applying Twisted Boundary Conditions for Few-body Nuclear Systems
Körber, Christopher
2015-01-01
We describe and implement twisted boundary conditions for the deuteron and triton systems within finite-volumes using the nuclear lattice EFT formalism. We investigate the finite-volume dependence of these systems with different twists angles. We demonstrate how various finite-volume information can be used to improve calculations of binding energies in such a framework. Our results suggests that with appropriate twisting of boundaries, infinite-volume binding energies can be reliably extracted from calculations using modest volume sizes with cubic length $L\\approx8-14$ fm. Of particular importance is our derivation and numerical verification of three-body analogue of `i-periodic' twist angles that eliminate the leading order finite-volume effects to the three-body binding energy.
Double twist helical nanofilaments in bent-core liquid crystals
Zhang, Cuiyu; Diorio, Nicholas; Lavrentovich, Oleg D.; Jakli, Antal
2014-03-01
Cryo-TEM observations on 40-150 nm films of four bent-core liquid crystal materials in their helical nanofilament (HNF) phase show that the filaments get deformed near the substrate, and the subsequent arrays of nanofilaments are not parallel, but twisted with respect to each other. The effect can explain the mysterious properties of the HNF materials, such as structural color and ambidextrous optical activity. The observed double twist structure was not expected in the previous models of this phase. Being principally different from the packing of molecules in the twist grain boundary (TGB) and blue (BP) phases, the double-twist structure of HNF expands the rich word of nanostructured organic materials. This work was financially supported by NSF DMR-0964765 and DMR 1104850. The cryo-TEM facility was supported by the Ohio Research Scholars Program. We are grateful for Prof. G. Heppke and Dr. D. Lotsch for providing the PnOPIMB materials for us.
A Stylistic Analysis of Register Theory in Oliver Twist
Institute of Scientific and Technical Information of China (English)
刘鑫
2015-01-01
Stylistic analysis refers to the linguistic approach to literature.Stylistics will mainly focus on the register theory,taking Charles Dickens’ masterpiece Oliver Twist as a good example to demonstrate how the register theory is embodied in the work.
Representations of Knot Groups and Twisted Alexander Polynomials
Institute of Scientific and Technical Information of China (English)
Xiao Song LIN
2001-01-01
We present a twisted version of the Alexander polynomial associated with a matrix representation of the knot group. Examples of two knots with the same Alexander module but differenttwisted Alexander polynomials are given.
EnviroAtlas - Memphis, TN - One Meter Resolution Urban Land Cover Data (2012)
U.S. Environmental Protection Agency — The Memphis, TN EnviroAtlas One Meter-scale Urban Land Cover (MULC) dataset comprises 2,733 km2 around the city of Memphis, surrounding towns, and rural areas. These...
EnviroAtlas -- Memphis, TN (2012) -- One Meter Resolution Urban Land Cover Data
U.S. Environmental Protection Agency — The Memphis, TN EnviroAtlas One Meter-scale Urban Land Cover (MULC) dataset comprises 2,733 km2 around the city of Memphis, surrounding towns, and rural areas. These...
EnviroAtlas - Memphis, TN - One Meter Resolution Urban Land Cover Data (2012) Web Service
U.S. Environmental Protection Agency — This EnviroAtlas web service supports research and online mapping activities related to EnviroAtlas (https://www.epa.gov/enviroatlas ). The Memphis, TN EnviroAtlas...
EnviroAtlas - Memphis, TN - Meter-Scale Urban Land Cover (MULC) Data (2012)
U.S. Environmental Protection Agency — The Memphis, TN EnviroAtlas One Meter-scale Urban Land Cover (MULC) dataset comprises 2,733 km2 around the city of Memphis, surrounding towns, and rural areas. These...
EnviroAtlas -- Memphis, TN (2012) -- One Meter Resolution Urban Land Cover Data Web Service
U.S. Environmental Protection Agency — This EnviroAtlas web service supports research and online mapping activities related to EnviroAtlas (https://www.epa.gov/enviroatlas ). The Memphis, TN EnviroAtlas...
The Algebra of Formal Twisted Pseudodifferential Symbols and a Noncommutative Residue
Zadeh, Farzad Fathi; Khalkhali, Masoud
2010-10-01
Motivated by Connes-Moscovici’s notion of a twisted spectral triple, we define an algebra of formal twisted pseudodifferential symbols with respect to a twisting of the base algebra. We extend the Adler-Manin trace and the logarithmic cocycle on the algebra of pseudodifferential symbols to our twisted setting. We also give a general method to construct twisted pseudodifferential symbols on crossed product algebras.
A super-twisted Dirac operator and Novikov inequalities
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A super-twisted Dirac operator is constructed and deformed suitably.Following Shubin's approach to Novikov inequalities associated to the deformed de Rham-Hodge operator,we give a formula for the index of the super-twisted Dirac operator,and Novikov type inequalities for the deformed operator.In particular,we obtain a purely analytic proof of the Hopf index theorem for general vector bundles.
A super-twisted Dirac operator and Novikov inequalities
Institute of Scientific and Technical Information of China (English)
冯惠涛; 郭恩力
2000-01-01
A s黳er-twisted Dirac operator is constructed and deformed suitably. Following Shubin’s approach to Novikov inequalities associated to the deformed de Rham-Hodge operator, we give a for-mula for the index of the super-twisted Dirac operator, and Novikov type inequalities for the deformed operator, In particular, we obtain a purely analytic proof of the Hopf index theorem for general vector bundles.
Geometry of Quantum Group Twists, Multidimensional Jackson Calculus and Regularization
Demichev, A. P.
1995-01-01
We show that R-matricies of all simple quantum groups have the properties which permit to present quantum group twists as transitions to other coordinate frames on quantum spaces. This implies physical equivalence of field theories invariant with respect to q-groups (considered as q-deformed space-time groups of transformations) connected with each other by the twists. Taking into account this freedom we study quantum spaces of the special type: with commuting coordinates but with q-deformed ...
Dehn twists and free subgroups of symplectic mapping class groups
Keating, Ailsa
2012-01-01
Given two Lagrangian spheres in an exact symplectic manifold, we find conditions under which the Dehn twists about them generate a free non-abelian subgroup of the symplectic mapping class group. This extends a result of Ishida for Riemann surfaces. The proof generalises the categorical version of Seidel's long exact sequence to arbitrary powers of a fixed Dehn twist. We also show that the Milnor fibre of any isolated degenerate hypersurface singularity contains such pairs of spheres.
Topological Twisted Sigma Model with H-flux Revisited
Energy Technology Data Exchange (ETDEWEB)
Chuang, Wu-yen
2006-08-18
In this paper we revisit the topological twisted sigma model with H-flux. We explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian geometry. we show that the resulting action consists of a BRST exact term and pullback terms, which only depend on one of the two generalized complex structures and the B-field. We then discuss the topological feature of the model.
Blade tip vortex measurements on actively twisted rotor blades
Bauknecht, André; Ewers, Benjamin; Schneider, Oliver; Raffel, Markus
2017-05-01
Active rotor control concepts, such as active twist actuation, have the potential to effectively reduce the noise and vibrations of helicopter rotors. The present study focuses on the experimental investigation of active twist for the reduction of blade-vortex interaction (BVI) effects on a model rotor. Results of a large-scale smart-twisting active rotor test under hover conditions are described. This test investigated the effects of individual blade twist control on the blade tip vortices. The rotor blades were actuated with peak torsion amplitudes of up to 2° and harmonic frequencies of 1-5/rev with different phase angles. Time-resolved stereoscopic particle image velocimetry was carried out to study the effects of active twist on the strength and trajectories of the tip vortices between ψ _ {v}= 3.6° and 45.7° of vortex age. The analysis of the vortex trajectories revealed that the 1/rev active twist actuation mainly caused a vertical deflection of the blade tip and the corresponding vortex trajectories of up to 1.3% of the rotor radius R above and -1%R below the unactuated condition. An actuation with frequencies of 2 and 3/rev significantly affected the shapes of the vortex trajectories and caused negative vertical displacements of the vortices relative to the unactuated case of up to 2%R within the first 35° of wake age. The 2 and 3/rev actuation also had the most significant effects on the vortex strength and altered the initial peak swirl velocity by up to -34 and +31% relative to the unactuated value. The present aerodynamic investigation reveals a high control authority of the active twist actuation on the strength and trajectories of the trailing blade tip vortices. The magnitude of the evoked changes indicates that the active twist actuation constitutes an effective measure for the mitigation of BVI-induced noise on helicopters.
Twisted Bundle on Noncommutative Space and U(1) Instanton
Ho, P M
2000-01-01
We study the notion of twisted bundles on noncommutative space. Due to theexistence of projective operators in the algebra of functions on thenoncommutative space, there are twisted bundles with non-constant dimension.The U(1) instanton solution of Nekrasov and Schwarz is such an example. As amathematical motivation for not excluding such bundles, we find gaugetransformations by which a bundle with constant dimension can be equivalent toa bundle with non-constant dimension.
The Levels and Distribution of TN, TP and TOC in the South China Sea
Wang, H.; Han, D.
2012-04-01
The marine biogeochemistries of carbon, nitrogen and phosphorous have come under increased scrutiny because of their close involvement in climate change and coastal eutrophication. The South China Sea is unique in that located in a subtropical zone, and therefore represents an important regime for biogeochemical studies. However, to our knowledge, few data are available for total nitrogen (TN), total phosphorous (TP) and total organic carbon (TOC) in South Sea, China. The present study aims to contribute to the knowledge of their status through investigating the level and distribution of TN, TP and TOC in South China Sea. A total of 108 seawater samples of 11 sites in south sea, china were collected during August 29- September 4, 2006. An automated and simultaneous method for determination of TN and TOC was applied to all seawater samples. The combined system allowed simultaneous determination for TOC and TN in the same sample using a single injection and provided low detection limits and excellent linear ranges for both TOC and TN. The risk of contamination has been remarkably reduced due to the minimal sample manipulation and automated analyses. And quantitative analyses of TP in seawater were accomplished by a typical chemical method. Concentration ranges of TN and TP were 0.06-0.67, and 0.003-0.071 mg/L, respectively, as well as that of TOC were 0.23-2.51mg/L. The values of TN and TP showed that the status of nutrition is relatively better in south china sea than other marine areas. Moreover, the upright change trend of TN concentration level as well as TP and TOC according to the experimental results at the total 11 sites are simultaneity studied. The concentration of TN initial increases with the increasing of the depth, later the value becomes almost constant. In contrast, the concentration of TOC reduces with the increasing of the depth, later the value becomes almost unchangeable. Compared with the trend of TN and TOC, that of TP appears relatively stable
Directory of Open Access Journals (Sweden)
Joaquim Julio Vicente
1990-01-01
Full Text Available São reunidas neste trabalho todas as espécies de nematóides parasitas de anfíbios encontradas no Brasil, com dados suficientes para a sua identificação especifica. Na primeira parte que é o catálogo dos nematóides parasitos de anfíbios, são relacionadas nove superfamilias, quatorze famílias, vinte e quatro gêneros e sessenta e três espécies, sendo que destas, são dadas figuras e medidas. Na segunda parte que é o catálogo dos anfíbios hospedeiros, todos pertencentes à ordem Anura, são referidas seis famílias e cinqüenta e cinco espécies de anfíbios, estas com os nematóides respectivos. A identificação dos nematóides é auxiliada por chaves de determinação das superfamílias, famílias e gêneros, sendo a identificação específica feita através de quadros de medidas e figuras.A survey of nematode species parasitizing Brazilian amphibians is presented, with data enough to provide their specific identification. The first section refers to the catalogation of the species, related to 9 superfamilies, 14 families, 24 genera and 63 species that are figurated and included in measurement tables. The second section is concerned to the catalogue of host amphibians of the order Anura, with 6 families, and 55 species and their respective parasite nematodes. The identification of these helminths is achieved by means of keys to the superfamilies, families and genera. Specific determination is induced through the figures and tables as above mentioned.
Transposition of Tn5096 from a temperature-sensitive transducible plasmid in Streptomyces spp.
McHenney, M A; Baltz, R H
1991-09-01
Transposon Tn5096 was inserted into a derivative of the temperature-sensitive plasmid pMT660 containing the bacteriophage FP43 pac site. The resulting plasmid, pRHB126, was transduced by FP43 into several Streptomyces species. Tn5096 transposed from pRHB126 into different sites in the genomes of Streptomyces ambofaciens, Streptomyces cinnamonensis, Streptomyces coelicolor A3(2), Streptomyces fradiae, Streptomyces griseofuscus, and Streptomyces thermotolerans.
Internal size variations in Tn1546-like elements due to the presence of IS1216V
DEFF Research Database (Denmark)
Jensen, Lars Bogø
1998-01-01
In this study, internal size variations in the VanA gene cluster Tn1546, encoding resistance to glycopeptides, is described. Studies of previously uncharacterized size variations of an internal region, encoding the vanX and vanY genes of Tn1546, revealed that these variations were due to the pres......-essential for vancomycin resistance. (C) 1998 Federation of European Microbiological Societies....
Transposition of Tn5096 from a temperature-sensitive transducible plasmid in Streptomyces spp.
McHenney, M A; Baltz, R H
1991-01-01
Transposon Tn5096 was inserted into a derivative of the temperature-sensitive plasmid pMT660 containing the bacteriophage FP43 pac site. The resulting plasmid, pRHB126, was transduced by FP43 into several Streptomyces species. Tn5096 transposed from pRHB126 into different sites in the genomes of Streptomyces ambofaciens, Streptomyces cinnamonensis, Streptomyces coelicolor A3(2), Streptomyces fradiae, Streptomyces griseofuscus, and Streptomyces thermotolerans.
Twist decomposition of Drell-Yan structure functions: phenomenological implications
Brzemiński, Dawid; Motyka, Leszek; Sadzikowski, Mariusz; Stebel, Tomasz
2017-01-01
The forward Drell-Yan process in pp scattering at the LHC at √{S} = 14 TeV is considered. We analyze the Drell-Yan structure functions assuming the dominance of a Compton-like emission of a virtual photon from a fast quark scattering off the small x gluons. The color dipole framework is applied to perform quantitatively the twist decomposition of all the Drell-Yan structure functions. Two models of the color dipole scattering are applied: the Golec-Biernat-Wüsthoff model and the dipole cross section obtained from the Balitsky-Fadin-Kuraev-Lipatov evolution equation. The two models have essentially different higher twist content and the gluon transverse momentum distribution and lead to different significant effects beyond the collinear leading twist description. It is found that the gluon transverse momentum effects are significant in the Drell-Yan structure functions for all Drell-Yan pair masses M, and the higher twist effects become important for M ≲ 10GeV. It is found that the structure function W TT related to the A 2 angular coefficient and the Lam-Tung observable A 0 - A 2 are particularly sensitive to the gluon k T effects and to the higher twist effects. A procedure is suggested how to disentangle the higher twist effects from the gluon transverse momentum effects.
Twist-induced Magnetosphere Reconfiguration for Intermittent Pulsars
Huang, Lei; Tong, Hao
2016-01-01
We propose that the magnetosphere reconfiguration induced by magnetic twists in the closed field line region can account for the mode-switching of intermittent pulsars. We carefully investigate the properties of axisymmetric force-free pulsar magnetospheres with magnetic twists in closed field line region around the polar caps. The magnetosphere with twisted closed lines leads to enhanced spin-down rates. The enhancement in spin-down rate depends on the size of region with twisted closed lines. Typically, it is increased by a factor of $\\sim2$, which is consistent with the intermittent pulsars' spin down behavior during the `off' and `on' states. We find there is a threshold of maximal twist angle $\\Delta\\phi_{\\rm thres}\\sim1$. The magnetosphere is stable only if the closed line twist angle is less than $\\Delta\\phi_{\\rm thres}$. Beyond this value, the magnetosphere becomes unstable and gets untwisted. The spin-down rate would reduce to its off-state value. The quasi-periodicity in spin-down rate change can be...
Universal corner entanglement from twist operators
Bueno, Pablo; Witczak-Krempa, William
2015-01-01
The entanglement entropy in three-dimensional conformal field theories (CFTs) receives a logarithmic contribution characterized by a regulator-independent function $a(\\theta)$ when the entangling surface contains a sharp corner with opening angle $\\theta$. In the limit of a smooth surface ($\\theta\\rightarrow\\pi$), this corner contribution vanishes as $a(\\theta)=\\sigma\\,(\\theta-\\pi)^2$. In arXiv:1505.04804, we provided evidence for the conjecture that for any $d=3$ CFT, this corner coefficient $\\sigma$ is determined by $C_T$, the coefficient appearing in the two-point function of the stress tensor. Here, we argue that this is a particular instance of a much more general relation connecting the analogous corner coefficient $\\sigma_n$ appearing in the $n$th R\\'enyi entropy and the scaling dimension $h_n$ of the corresponding twist operator. In particular, we find the simple relation $h_n/\\sigma_n=(n-1)\\pi$. We show how it reduces to our previous result as $n\\rightarrow 1$, and explicitly check its validity for f...
DNA packaging in bacteriophage: is twist important?
Spakowitz, Andrew James; Wang, Zhen-Gang
2005-06-01
We study the packaging of DNA into a bacteriophage capsid using computer simulation, specifically focusing on the potential impact of twist on the final packaged conformation. We perform two dynamic simulations of packaging a polymer chain into a spherical confinement: one where the chain end is rotated as it is fed, and one where the chain is fed without end rotation. The final packaged conformation exhibits distinct differences in these two cases: the packaged conformation from feeding with rotation exhibits a spool-like character that is consistent with experimental and previous theoretical work, whereas feeding without rotation results in a folded conformation inconsistent with a spool conformation. The chain segment density shows a layered structure, which is more pronounced for packaging with rotation. However, in both cases, the conformation is marked by frequent jumps of the polymer chain from layer to layer, potentially influencing the ability to disentangle during subsequent ejection. Ejection simulations with and without Brownian forces show that Brownian forces are necessary to achieve complete ejection of the polymer chain in the absence of external forces.
Twisted light transmission over 143 km
Krenn, Mario; Handsteiner, Johannes; Fink, Matthias; Fickler, Robert; Ursin, Rupert; Malik, Mehul; Zeilinger, Anton
2016-11-01
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, whereas free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here, we show the transmission of orbital angular momentum modes of light over a distance of 143 km between two Canary Islands, which is 50× greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order and decode the transmitted message with an error rate of 8.33%. Using our data, we estimate that the distribution of orbital angular momentum entanglement over more than 100 km of free space is feasible. Moreover, the quality of our free-space link can be further improved by the use of state-of-the-art adaptive optics systems.
Roots of Dehn twists about separating curves
Rajeevsarathy, Kashyap
2011-01-01
Let $C$ be a curve in a closed orientable surface $F$ of genus $g \\geq 2$ that separates $F$ into subsurfaces $\\widetilde {F_i}$ of genera $g_i$, for $i = 1,2$. We study the set of roots in $\\Mod(F)$ of the Dehn twist $t_C$ about $C$. All roots arise from pairs of $C_{n_i}$-actions on the $\\widetilde{F_i}$, where $n=\\lcm(n_1,n_2)$ is the degree of the root, that satisfy a certain compatibility condition. The $C_{n_i}$ actions are of a kind that we call nestled actions, and we classify them using tuples that we call data sets. The compatibility condition can be expressed by a simple formula, allowing a classification of all roots of $t_C$ by compatible pairs of data sets. We use these data set pairs to classify all roots for $g = 2$ and $g = 3$. We show that there is always a root of degree at least $2g^2+2g$, while $n \\leq 4g^2+2g$. We also give some additional applications.
Baryon masses with dynamical twisted mass fermions
Alexandrou, C; Koutsou, G; Baron, R; Guichon, P; Brinet, M; Carbonell, J; Drach, V; Liu, Z; Pène, O; Urbach, C
2007-01-01
We present results on the mass of the nucleon and the $\\Delta$ using two dynamical degenerate twisted mass quarks. The evaluation is performed at four quark masses corresponding to a pion mass in the range of 690-300 MeV on lattices of size 2.1 fm and 2.7 fm. We check for cutoff effects by evaluating these baryon masses on lattices of spatial size 2.1 fm with lattice spacings $a(\\beta=3.9)=0.0855(6)$ fm and $a(\\beta=4.05)=0.0666(6)$ fm, determined from the pion sector and find them to be within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. The nucleon mass at the physical point provides a determination of the lattice spacing. Using heavy baryon chiral perturbation theory at ${\\cal O}(p^3)$ we find $a(\\beta=3.9)=0.0879(12)$ fm, with a systematic error due to the chiral extrapolation estimated to be about the same as the statistical error. This value of the lattice spacing is in good agreement with the value determined from the pion se...
Dark Matter in a twisted bottle
Arbey, Alexandre; Deandrea, Aldo; Kubik, Bogna
2013-01-01
The real projective plane is a compact, non-orientable orbifold of Euler characteristic 1 without boundaries, which can be described as a twisted Klein bottle. We shortly review the motivations for choosing such a geometry among all possible two-dimensional orbifolds, while the main part of the study will be devoted to dark matter study and limits in Universal Extra Dimensional (UED) models based on this peculiar geometry. In the following we consider such a UED construction based on the direct product of the real projective plane with the standard four-dimensional Minkowski space-time and discuss its relevance as a model of a weakly interacting Dark Matter candidate. One important difference with other typical UED models is the origin of the symmetry leading to the stability of the dark matter particle. This symmetry in our case is a remnant of the six-dimensional Minkowski space-time symmetry partially broken by the compactification. Another important difference is the very small mass splitting between the ...