Journal articles: 'False chirality'

1

Vavilin, Maxim, and Ivan Fernandez-Corbaton. "Multidimensional measures of electromagnetic chirality and their conformal invariance." New Journal of Physics 24, no. 3 (March 1, 2022): 033022. http://dx.doi.org/10.1088/1367-2630/ac57e8.

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Abstract Proper assignment of left- and right-handed labels to general chiral objects is known to be a theoretically unfeasible problem. Attempts to utilize a pseudoscalar function to distinguish enantiomers face two unavoidable difficulties: false chiral zeros and unhanded chiral states. In here, we demonstrate how both of these problems can be solved in the context of light–matter interactions. First, we introduce a two-dimensional quantity called complex electromagnetic chirality that solves the problem of false chiral zeros. Next, we define an infinite-dimensional pseudovector called chirality signature that completely quantifies the multidimensional nature of electromagnetic chirality, does not have false global chiral zeros, and allows to continuously distinguish any pair of enantiomers because it does not produce unhanded chiral states. We prove that the introduced measures are invariant under the largest group of symmetries of Maxwell’s equations—the conformal group. The complete, continuous, and conformally invariant quantification of electromagnetic chirality provided by the chirality signature distinguishes it as a particularly suitable tool for the study of chirality and its applications.

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Barron, Laurence D. "Cosmic Chirality both True and False." Chirality 24, no. 12 (August 28, 2012): 957–58. http://dx.doi.org/10.1002/chir.22106.

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Barron, L. D. "True and false chirality and parity violation." Chemical Physics Letters 123, no. 5 (January 1986): 423–27. http://dx.doi.org/10.1016/0009-2614(86)80035-5.

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Barron, Laurence David. "True and false chirality and absolute enantioselection." Rendiconti Lincei 24, no. 3 (February 12, 2013): 179–89. http://dx.doi.org/10.1007/s12210-013-0224-6.

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Barron, L. D. "True and false chirality and absolute asymmetric synthesis." Journal of the American Chemical Society 108, no. 18 (September 1986): 5539–42. http://dx.doi.org/10.1021/ja00278a029.

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Barron, Laurence D. "False Chirality, Absolute Enantioselection and CP Violation: Pierre Curie’s Legacy." Magnetochemistry 6, no. 1 (January 15, 2020): 5. http://dx.doi.org/10.3390/magnetochemistry6010005.

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The 1884 suggestion of Pierre Curie (1859–1906) that the type of dissymmetry shown by collinear electric and magnetic fields may induce an enantiomeric excess, in a chemical reaction that would otherwise produce a racemic mixture, is explored in the context of fundamental symmetry arguments. Curie’s arrangement exhibits false chirality (time-noninvariant enantiomorphism), and so it may not induce absolute enantioselection (ae) in a process that has reached thermodynamic equilibrium, since it does not lift the degeneracy of chiral enantiomers. However, it may do so in far-from-equilibrium processes via a breakdown in microscopic reversibility analogous to that observed in elementary particle processes under the influence of CP violation, the associated force possessing false chirality with respect to CP enantiomorphism. In contrast, an influence like circularly polarized light exhibiting true chirality (time-invariant enantiomorphism) lifts the degeneracy of enantiomers, and so may induce ae in all circumstances. Although to date, ae has not been observed under the influence of Curie’s arrangement of collinear electric and magnetic fields, it is argued that two different experiments have now demonstrated ae under a falsely chiral influence in systems far from equilibrium, namely in a spinning sample under a gravitational field, and in the separation of enantiomers at a ferromagnetic surface.

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Barron, L. D. "False chirality, CP violation and the breakdown of microscopic reversibility in chiral molecular and elementary particle processes." Journal of Biological Physics 20, no. 1-4 (1995): 235–39. http://dx.doi.org/10.1007/bf00700441.

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Krabacher, Rachel, Steve Kim, Yen Ngo, Joseph Slocik, Christina Harsch, and Rajesh Naik. "Identification of Chiral-Specific Carbon Nanotube Binding Peptides Using a Modified Biopanning Method." Chemosensors 9, no. 9 (September 1, 2021): 245. http://dx.doi.org/10.3390/chemosensors9090245.

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Peptides can recognize and selectively bind to a wide variety of materials dependent on both their surface properties and the environment. Biopanning with phage or cell peptide display libraries can identify material-specific binding peptides. However, the limitations with sequence diversity of traditional bacteriophage (phage) display libraries and loss of unique phage clones during the amplification cycles results in a smaller pool of peptide sequences identified. False positive sequences tend to emerge during the biopanning process due to highly proliferating, yet nonspecific, phages. In order to overcome this limitation of traditional biopanning methodology, a modified method using high-throughput next generation sequencing (HTS) was tested to select for unique peptides specific to two types of single wall carbon nanotube (SWNTs) sources with varying diameter distribution and chirality. Here, the process, analysis, and characterization of peptide sequences identified using the modified method is further described and compared to a peptide identified in literature using the traditional method. Selected sequences from this study were incorporated in a SWNT dispersion experiment to probe their selectivity to the nanotube diameter. We show that NHTS can uncover unique binding sequences that might have otherwise been lost during the traditional biopanning method.

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BROWER, RICHARD C., YUE SHEN, and CHUNG-I. TAN. "CHIRALLY EXTENDED QUANTUM CHROMODYNAMICS." International Journal of Modern Physics C 06, no. 05 (October 1995): 725–42. http://dx.doi.org/10.1142/s0129183195000599.

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We propose an extended Quantum Chromodynamics (XQCD) Lagrangian in which the fermions are coupled to elementary scalar fields through a Yukawa coupling which preserves chiral invariance. Our principle motivation is to find a new lattice formulation for QCD which avoids the source of critical slowing down usually encountered as the bare quark mass is tuned to the chiral limit. The phase diagram and the weak coupling limit for XQCD are studied. They suggest a conjecture that the continuum limit of XQCD is the same as the continuum limit of conventional lattice formulation of QCD. As examples of such universality, we present the large N solutions of two prototype models for XQCD, in which the mass of the spurious pion and sigma resonance go to infinity with the cut-off. Even if the universality conjecture turns out to be false, we believe that XQCD will still be useful as a low energy effective action for QCD phenomenology on the lattice. Numerical simulations are recommended to further investigate the possible benefits of XQCD in extracting QCD predictions.

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Sun, Chao, Xueyan Zhang, Yuyu Xie, Yunlong Zhou, and Xiaoqing Gao. "True and False Chirality in Chiral Magnetic Nanoparticles." Journal of Physical Chemistry Letters, April 24, 2024, 4679–85. http://dx.doi.org/10.1021/acs.jpclett.4c01016.

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Ishito, Kyosuke, Huiling Mao, Yusuke Kousaka, Yoshihiko Togawa, Satoshi Iwasaki, Tiantian Zhang, Shuichi Murakami, Jun-ichiro Kishine, and Takuya Satoh. "Truly chiral phonons in α-HgS." Nature Physics, October 31, 2022. http://dx.doi.org/10.1038/s41567-022-01790-x.

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AbstractChirality is a manifestation of the asymmetry inherent in nature. It has been defined as the symmetry breaking of the parity of static objects, and the definition was extended to dynamic motion such that true and false chiralities were distinguished. Recently, rotating, yet not propagating, atomic motions were predicted and observed in two-dimensional materials, and they were referred to as ‘chiral phonons’. A natural development would be the discovery of truly chiral phonons that propagate while rotating in three-dimensional materials. Here we used circularly polarized Raman scattering and first-principles calculations to identify truly chiral phonons in chiral bulk crystals. This approach enabled us to determine the chirality of a crystal in a non-contact and non-destructive manner. In addition, we demonstrated that the law of the conservation of pseudo-angular momentum holds between circularly polarized photons and chiral phonons. These findings are expected to help develop ways for transferring the pseudo-angular momentum from photons to electron spins via propagating chiral phonons in opto-phononic-spintronic devices.

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Bondesson, Johan, Ga-Young Suh, Michael D. Dake, Jason T. Lee, and Christopher P. Cheng. "Cardiac Pulsatile Helical Deformation of the Thoracic Aorta Before and After Thoracic Endovascular Aortic Repair of Type B Dissections." Journal of Endovascular Therapy, June 10, 2023, 152660282311795. http://dx.doi.org/10.1177/15266028231179592.

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Purpose: Type B aortic dissections propagate with either achiral (nonspiraling) or right-handed chiral (spiraling) morphology, have mobile dissection flaps, and are often treated with thoracic endovascular aortic repair (TEVAR). We aim to quantify cardiac-induced helical deformation of the true lumen of type B aortic dissections before and after TEVAR. Material and Methods: Retrospective cardiac-gated computed tomography (CT) images before and after TEVAR of type B aortic dissections were used to construct systolic and diastolic 3-dimensional (3D) surface models, including true lumen, whole lumen (true+false lumens), and branch vessels. This was followed by extraction of true lumen helicity (helical angle, twist, and radius) and cross-sectional (area, circumference, and minor/major diameter ratio) metrics. Deformations between systole and diastole were quantified, and deformations between pre- and post-TEVAR were compared. Results: Eleven TEVAR patients (59.9±4.6 years) were included in this study. Pre-TEVAR, there were no significant cardiac-induced deformations of helical metrics; however, post-TEVAR, significant deformation was observed for the true lumen proximal angular position. Pre-TEVAR, cardiac-induced deformations of all cross-sectional metrics were significant; however, only area and circumference deformations remained significant post-TEVAR. There were no significant differences of pulsatile deformation from pre- to post-TEVAR. Variance of proximal angular position and cross-sectional circumference deformation decreased after TEVAR. Conclusion: Pre-TEVAR, type B aortic dissections did not exhibit significant helical cardiac-induced deformation, indicating that the true and false lumens move in unison (do not move with respect to each other). Post-TEVAR, true lumens exhibited significant cardiac-induced deformation of proximal angular position, suggesting that exclusion of the false lumen leads to greater rotational deformations of the true lumen and lack of true lumen major/minor deformation post-TEVAR means that the endograft promotes static circularity. Population variance of deformations is muted after TEVAR, and dissection acuity influences pulsatile deformation while pre-TEVAR chirality does not. Clinical Impact Description of thoracic aortic dissection helical morphology and dynamics, and understanding the impact of thoracic endovascular aortic repair (TEVAR) on dissection helicity, are important for improving endovascular treatment. These findings provide nuance to the complex shape and motion of the true and false lumens, enabling clinicians to better stratify dissection disease. The impact of TEVAR on dissection helicity provides a description of how treatment alters morphology and motion, and may provide clues for treatment durability. Finally, the helical component to endograft deformation is important to form comprehensive boundary conditions for testing and developing new endovascular devices.

13

Portillo, Abiud E., Umang Dhaubhadel, Ondrej Horacek, Y.-S. Sung, and Daniel W. Armstrong. "Investigating chirality in quorum sensing by analysis of Burkholderia cepacia and Vibrio fischeri with comprehensive chiral LC-MS/MS and GC-MS/MS methods." FEMS Microbiology Letters, February 10, 2023. http://dx.doi.org/10.1093/femsle/fnad011.

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Abstract N-Acyl homoserine lactones (N-HLs) are signaling molecules used by Gram-negative bacteria in a phenomenon called quorum sensing (QS). Bacteria will detect N-HLs as a way of monitoring their population which, upon reaching a critical level, will express a specific phenotype. An example is the expression of bioluminescence by Vibrio fischeri. A limited number of studies have considered the chirality of these molecules nor used highly sensitive detection methods. Here, the production of D,L-N-HLs are monitored for V. fischeri, B. cepacia, P. fluorescens and P. putida, using highly sensitive tandem mass spectrometry analysis. Novel N-HLs are reported for both V. fischeri and B. cepacia including a plethora of previously unknown D-N-HLs, including the first D-N-HLs containing oxo and hydroxy functionalities. Anomalously, N-HLs were not detected in any cultures of P. fluorescens and P. putida, which are species that previously were reported to produce N-HLs. However, it is apparent that differences in the reported occurrence and levels of N-HLs can result from: different strains of bacteria, b) different growth media and environmental conditions and c) sometimes false positive results from detection methodologies. Time studies of V. fischeri suggest the possibility that separate synthetic and elimination pathways exist between D- and L-N-HLs. Possible biological processes that could be the source of D-N-HL production are considered.

14

Mersch, Johannes, Nicholas S. Witham, Florian Solzbacher, and Gerald Gerlach. "Continuous textile manufacturing method for twisted coiled polymer artificial muscles." Textile Research Journal, July 25, 2023. http://dx.doi.org/10.1177/00405175231181095.

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Twisted, coiled polymer actuators (TCPAs) are a promising type of fiber-based actuators with high energy density, low material costs, and good recyclability; however, current manufacturing methods limit the length and stability of TCPAs, hampering their potential for large-scale textile applications. To overcome this limitation, we propose a textile manufacturing method based on the false-twisting principle, allowing for continuous and rapid production of highly twisted monofilaments. Additionally, this process enables the plying of two or more twisted monofilaments together, as well as the integration of wires for heating and sensing purposes. The resulting twist-stable plies can then be mandrel-coiled and annealed to create a new class of TCPAs with three superimposed levels of helicity, in contrast to the usual two levels. In this study, we investigate the impact of the additional helix level and various factors, including twist density, annealing temperature, cooling speed, and chirality, on the contractility of these TCPAs. Furthermore, due to the twist-stability of the plied yarns, they can be processed on standard textile machines, enabling the manufacture of TCPAs with multiple active yarns that can form contracting artificial muscles using a circular braiding machine. Our key findings reveal that the twisted monofilament coils can contract up to 60%, and higher twist density leads to improved performance for monofilament TCPAs. Notably, this phenomenon is not observed in plied-yarn TCPAs, where varying levels of twist on the monofilament and yarn helix level result in enhanced contractile performance. Overall, this work presents a novel textile manufacturing method for producing twist-stable TCPAs with good contractile performance, providing insights into the design and fabrication of advanced fiber-based actuators for potential applications in large-scale textiles, robotics, and biomedical devices.

15

Eich, Andreas, Andrzej Grzechnik, Yixi Su, Bachir Ouladdiaf, Denis Sheptyakov, Thomas Wolf, Vaclav Petricek, Hend Shahed, and Karen Friese. "Incommensurate magnetic structure of CrAs at low temperatures and high pressures." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 79, no. 6 (October 12, 2023). http://dx.doi.org/10.1107/s205252062300817x.

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The magnetic structure of chromium arsenide CrAs is studied with neutron powder diffraction at ambient pressure in the temperature range 1.5–300 K as well as with neutron single-crystal diffraction at 2 K and 0.12 GPa. The material undergoes an anti-isostructural phase transition at T N = 267 K and atmospheric conditions, in which both orthorhombic phases have the same space-group symmetry (Pnma, Z = 4) but different distortions of the parent hexagonal structure of the NiAs type (P63/mmc, Z = 2). The magnetic structure below T N is incommensurate with the propagation vector k = (0, 0, k c). At ambient pressure, the component k c decreases from k c = 0.3807 (7) at 260 K to k c = 0.3531 (6) at 50 K. Below this temperature, it is basically constant. With increasing pressure at 2 K, k c is also constant within standard uncertainties [k c = 0.353 (2)]. For the analysis of the magnetic structure, a group-theoretical approach based on the space group of the nuclear structure and its subgroups is used. To avoid falling into false minima in the refinements, a random search for magnetic moments in the models is implemented. In the literature, the magnetic structure has been determined on the basis of powder diffraction data as a double helix propagating along the c axis. Although this double-helical model leads to satisfactory agreement factors for our powder data, it does not reproduce the intensities of the magnetic satellite reflections measured on single-crystal data in a satisfactory way and can therefore be discarded. Instead, several other models are found that lead to better agreement. Each of them is spiral-like with directional components in all three directions and with no spin-density wave character that would cause a non-constant magnetic moment. In all these models, the ordering of the spins is neither a pure helix nor a pure cycloid. Instead, the unit vectors of the spin rotation planes make an angle α, 0° < α < 90°, with respect to the c* direction. The model in superspace group P21.1′(α0γ)0s yields the best agreement factors in the refinements of the neutron single-crystal and powder diffraction data. This model is unique as it is the only one in which all the magnetic moments rotate with the same chirality.

Journal articles on the topic 'False chirality'

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