Nanosecond retinal structure changes in K-590 during the room-temperature bacteriorhodopsin photocycle: picosecond time-resolved coherent anti-stokes Raman spectroscopy.

PubMed

Weidlich, O; Ujj, L; Jäger, F; Atkinson, G H

1997-05-01

Time-resolved vibrational spectra are used to elucidate the structural changes in the retinal chromophore within the K-590 intermediate that precedes the formation of the L-550 intermediate in the room-temperature (RT) bacteriorhodopsin (BR) photocycle. Measured by picosecond time-resolved coherent anti-Stokes Raman scattering (PTR/CARS), these vibrational data are recorded within the 750 cm-1 to 1720 cm-1 spectral region and with time delays of 50-260 ns after the RT/BR photocycle is optically initiated by pulsed (< 3 ps, 1.75 nJ) excitation. Although K-590 remains structurally unchanged throughout the 50-ps to 1-ns time interval, distinct structural changes do appear over the 1-ns to 260-ns period. Specifically, comparisons of the 50-ps PTR/CARS spectra with those recorded with time delays of 1 ns to 260 ns reveal 1) three types of changes in the hydrogen-out-of-plane (HOOP) region: the appearance of a strong, new feature at 984 cm-1; intensity decreases for the bands at 957 cm-1, 952 cm-1, and 939 cm-1; and small changes intensity and/or frequency of bands at 855 cm-1 and 805 cm-1; and 2) two types of changes in the C-C stretching region: the intensity increase in the band at 1196 cm-1 and small intensity changes and/or frequency shifts for bands at 1300 cm-1 and 1362 cm-1. No changes are observed in the C = C stretching region, and no bands assignable to the Schiff base stretching mode (C = NH+) mode are found in any of the PTR/CARS spectra assignable to K-590. These PTR/CARS data are used, together with vibrational mode assignments derived from previous work, to characterize the retinal structural changes in K-590 as it evolves from its 3.5-ps formation (ps/K-590) through the nanosecond time regime (ns/K-590) that precedes the formation of L-550. The PTR/CARS data suggest that changes in the torsional modes near the C14-C15 = N bonds are directly associated with the appearance of ns/K-590, and perhaps with the KL intermediate proposed in earlier studies. These

Vibrational spectrum of the K-590 intermediate in the bacteriorhodopsin photocycle at room temperature: picosecond time-resolved resonance coherent anti-Raman spectroscopy

NASA Astrophysics Data System (ADS)

Ujj, L.; Jäger, F.; Popp, A.; Atkinson, G. H.

1996-12-01

The vibrational spectrum of the K-590 intermediate, thought to contribute significantly to the energy storage and transduction mechanism in the bacteriorhodopsin (BR) photocycle, is measured at room temperature using picosecond time-resolved resonance coherent anti-Stokes Raman scattering (PTR/CARS). The room-temperature BR photocycle is initiated by the 3 ps, 570 nm excitation of the ground-state species, BR-570, prepared in both H 2O and D 2O suspensions of BR. PTR/CARS data, recorded 50 ps after BR-570 excitation, at which time only BR-570 and K-590 are present, have an excellent S/N which provides a significantly more detailed view of the K-590 vibrational degrees of freedom than previously available. Two picosecond (6 ps FWHM) laser pulses, ω1 (633.4 nm) and ωS (675-700 nm), are used to record PTR/CARS data via electronic resonance enhancement in both BR-570 and K-590, each of which contains a distinct retinal structure (assigned as 13- rans, 15- anti, 13- cis, respectively). To obtain the vibrational spectrum of K-590 separately, the PTR/CARS spectra from the mixture of isomeric retinals is quantitatively analyzed in terms of third-order susceptibility ( η(3)) relationships. PTR/CARS spectra of K-590 recorded from both H 2O and D 2O suspensions of BR are compared with the analogous vibrational data obtained via spontaneous resonance Raman (RR) scattering at both low (77 K) and room temperature. Analyses of these vibrational spectra identify temperature-dependent effects and changes assignable to the substitution of deuterium at the Schiff-base nitrogen not previously reported.

Testing BR photocycle kinetics.

PubMed Central

Nagle, J F; Zimanyi, L; Lanyi, J K

1995-01-01

An improved K absorption spectrum in the visible is obtained from previous photocycle data for the D96N mutant of bacteriorhodopsin, and the previously obtained M absorption spectrum in the visible and the fraction cycling are confirmed at 25 degrees C. Data at lower temperatures are consistent with negligible temperature dependence in the spectra from 5 degrees C to 25 degrees C. Detailed analysis strongly indicates that there are two intermediates in addition to the first intermediate K and the last intermediate M. Assuming two of the intermediates have the same spectrum and using the L spectrum obtained previously, the best kinetic model with four intermediates that fits the time course of the intermediates is rather unusual, with two L's on a cul-de-sac. However, a previously proposed, more conventional model with five intermediates, including two L's with the same spectra and two M's with the same spectra, also fits the time course of the intermediates nearly as well. A new criterion that tests an individual proposed spectrum against data is also proposed. PMID:7787034

Bacteriorhodopsin Material and Film Fabrication Issues for Holographic Applications

NASA Technical Reports Server (NTRS)

Downie, John D.; Timucin, Dogan A.; Smithey, Daniel T.; Crew, Marshall; Rayfield, George W.; Lan, Sonie (Technical Monitor)

1998-01-01

We discuss issues associated with bacteriorhodopsin (BR) materials and films that affect optical performance in holographic applications. For the D85N variant, some critical parameters include degree of hydration and recording wavelength. The quantum efficiency of the molecular state transition is observed to be apparently dependent on the illumination wavelength. We explain this effect by modeling the photo-activity of the D85N variant as two competing photocycles between the 9-cis and 13-cis retinal configurations. We are able to determine the pure excited P-state absorbance spectrum from the ground state spectrum and mixed population spectra obtained by bleaching to steady-state conditions.

Unraveling the mechanism of proton translocation in the extracellular half-channel of bacteriorhodopsin.

PubMed

Ge, Xiaoxia; Gunner, M R

2016-05-01

Bacteriorhodopsin, a light activated protein that creates a proton gradient in halobacteria, has long served as a simple model of proton pumps. Within bacteriorhodopsin, several key sites undergo protonation changes during the photocycle, moving protons from the higher pH cytoplasm to the lower pH extracellular side. The mechanism underlying the long-range proton translocation between the central (the retinal Schiff base SB216, D85, and D212) and exit clusters (E194 and E204) remains elusive. To obtain a dynamic view of the key factors controlling proton translocation, a systematic study using molecular dynamics simulation was performed for eight bacteriorhodopsin models varying in retinal isomer and protonation states of the SB216, D85, D212, and E204. The side-chain orientation of R82 is determined primarily by the protonation states of the residues in the EC. The side-chain reorientation of R82 modulates the hydrogen-bond network and consequently possible pathways of proton transfer. Quantum mechanical intrinsic reaction coordinate calculations of proton-transfer in the methyl guanidinium-hydronium-hydroxide model system show that proton transfer via a guanidinium group requires an initial geometry permitting proton donation and acceptance by the same amine. In all the bacteriorhodopsin models, R82 can form proton wires with both the CC and the EC connected by the same amine. Alternatively, rare proton wires for proton transfer from the CC to the EC without involving R82 were found in an O' state where the proton on D85 is transferred to D212. © 2016 Wiley Periodicals, Inc.

The effect of charged lipids on bacteriorhodopsin membrane reconstitution and its photochemical activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Zhen; Bai Jing; Xu Yuhong

2008-07-11

Bacteriorhodopsin (BR) was reconstituted into artificial lipid membrane containing various charged lipid compositions. The proton pumping activity of BR under flash and continuous illumination, proton permeability across membrane, as well as the decay kinetics of the photocycle intermediate M{sub 412} were studied. The results showed that lipid charges would significantly affect the orientation of BR inserted into lipid membranes. In liposomes containing anionic lipids, BRs were more likely to take natural orientation as in living cells. In neutral or positively charged liposomes, most BRs were reversely assembled, assuming an inside out orientation. Moreover, the lipids charges also affect BR's Mmore » intermediate kinetics, especially the slow component in M intermediate decay. The half-life M{sub 412s} increased significantly in BRs in liposomes containing cationic lipids, while decreased in those in anionic liposomes.« less

Protein changes associated with reprotonation of the Schiff base in the photocycle of Asp96-->Asn bacteriorhodopsin. The MN intermediate with unprotonated Schiff base but N-like protein structure

NASA Technical Reports Server (NTRS)

Sasaki, J.; Shichida, Y.; Lanyi, J. K.; Maeda, A.

1992-01-01

The difference Fourier transform infrared spectrum for the N intermediate in the photoreaction of the light-adapted form of bacteriorhodopsin can be recorded at pH 10 at 274 K (Pfefferle, J.-M., Maeda, A., Sasaki, J., and Yoshizawa, T. (1991) Biochemistry 30, 6548-6556). Under these conditions, Asp96-->Asn bacteriorhodopsin gives a photoproduct which shows changes in protein structure similar to those observed in N of wild-type bacteriorhodopsin. However, decreased intensity of the chromophore bands and the single absorbance maximum at about 400 nm indicate that the Schiff base is unprotonated, as in the M intermediate. This photoproduct was named MN. At pH 7, where the supply of proton is not as restricted as at pH 10, Asp96-->Asn bacteriorhodopsin yields N with a protonated Schiff base. The Asn96 residue, which cannot deprotonate as Asp96 in wild-type bacteriorhodopsin, is perturbed upon formation of both MN at pH 10 and N at pH 7. We suggest that the reprotonation of the Schiff base is preceded by a large change in the protein structure including perturbation of the residue at position 96.

A spectroscopic investigation of the Schiff base reprotonation mechanism of bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Russell, Terence Stephen

This thesis reports time-resolved visible spectroscopy experiments performed on the light-driven proton pumping protein, bacteriorhodopsin (bR), and a number of artificially produced analogs. These analogs comprise a variety of single and double amino acid substitutions produced in several of the residues previously implicated in proton transport in bR. Also addressed are the results of resonance Raman and FTIR difference spectroscopy which provide information about the vibrational modes of the protein. The results from these experiments confirm aspects of both structural and functional models of bR based on previous electron diffraction and spectroscopic data. During a phase of the proton pumping photocycle in bR known as Schiff base reprotonation (also referred to as M intermediate decay), a proton is transferred over a 12 A distance from a proton donor residue (Asp-96) to the light-absorbing active site. The behavior of the M intermediate was monitored by time-resolved visible spectroscopy. In the single substitution known as D96N, the Asp-96 residue was replaced with a less efficient proton donor, asparagine. This mutant exhibited an M intermediate which decayed slowly in comparison to that of wild-type bR. However, this effect was reversed with the double substitution, T46D/D96N. This result indicates that the proton donor group can be moved to another nearby location and still yield a system functionally similar to the native protein. Replacement of the donor group with a histidine, His-96, resulted in a photocycle similar to D96N above pH 7. However, below this pH, the M intermediate is not detected. FTIR difference spectroscopy indicates that the protonation state of the substituted His-96 residue influences the structure of the active site of bR which suggests that a proton that is associated with His-96 may move towards the active site and thereby block M intermediate formation. Finally, the residue Thr-89 was replaced with an asparagine. This

Conformational flexibility of arginine-82 as source for the heterogeneous and pH-dependent kinetics of the primary proton transfer step in the bacteriorhodopsin photocycle: An electrostatic model

NASA Astrophysics Data System (ADS)

Scharnagl, Christina; Fischer, Sighart F.

1996-11-01

We use equilibrium thermodynamic concepts to relate protein conformational and protonation substates and their pH-dependent population to kinetic schemes for the rise of the M intermediate in the photocycle of bacteriorhodopsin. Conformational flexibility of arginine R82 is described by a two-state model. The analysis accounts for the electrostatic coupling between its orientation and hydrogen ion titration and presents a structural basis for the linkage between the protonation states of the primary proton acceptor, aspartate D85, and the extracellular release group, glutamate E204. We find that the charge state of D85 is a significant determinant for the orientation of R82. The molecular model predicts the following: the primary proton transfer to D85 can be described by a kinetic scheme with two heterogeneous substates. They control the event with different activation parameters due to the reorientation of R82 away from the chromophore binding site. Their population depends on the external pH and the proton exchange equilibrium between the membrane buried residues and the bulk aqueous solvent. Proton transfer in the physiologic pH range is strongly activated and followed by the reorientation of R82 which shifts the equilibrium toward complete transfer. In the alkaline pH region a different mechanism operates, which involves the increased population of a substate with already reoriented R82 as a consequence of the deprotonation of E204, leading to accelerated proton transfer. Assuming full proton exchange equilibrium with the bulk water on the millisecond time scale leads to an increased population of substates which are non-productive for proton transfer.

Reaction cycle and thermodynamics in bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1992-01-01

Light causes the all-trans to 13-cis isomerization of the retinal in bacteriorhodopsin; the thermal relaxation leading back to the initial state drives proton transport first via proton transfer between the retinal Schiff base and D85 and then between the Schiff base and D96. The reaction sequence and thermodynamics of this photocycle are described by measuring time-resolved absorption changes with a gated multichannel analyzer between 100 ns and 100 ms, at six temperatures between 5 degrees C and 30 degrees C. Analysis of the energetics of the chromophore reaction sequence is on the basis of a recently proposed model (Varo & Lanyi, Biochemistry 30, 5016-5022, 1991) which consists of a single cycle and many reversible reactions: BR -hv-->K<==>L<==>M1-->M2<==>N<==>O-->BR. The existence of the M1-->M2 reaction, which functions as the switch in the proton transfer, is confirmed by spectroscopic evidence. The calculated thermodynamic parameters indicate that the exchange of free energy between the protein and the protons is at the switch step. Further, a large entropy decrease at this reaction suggests a protein conformation change which will conserve delta G for driving the completion of the reaction cycle. The results provide insights to mechanism and energy coupling in this system, with possible relevance to the general question of how ion pumps function.

Photochemical and Thermal Stability of Green and Blue Proteorhodopsins: Implications for Protein-Based Bioelectronic Devices

PubMed Central

Ranaghan, Matthew J.; Shima, Sumie; Ramos, Lavosier; Poulin, Daniel S.; Whited, Gregg; Rajasekaran, Sanguthevar; Stuart, Jeffery A.; Albert, Arlene D.; Birge, Robert R.

2010-01-01

The photochemical and thermal stability of the detergent solubilized blue- and green-absorbing proteorhodpsins, BPR and GPR respectively, are investigated to determine viability of these proteins for photonic device applications. Photochemical stability is studied by using pulsed laser excitation and differential uv-vis spectroscopy to assign the photocyclicity. GPR, with a cyclicity of 7×104 photocycles protein−1, is 4–5 times more stable than BPR (9×103 photocycles protein−1), but is less stable than native bacteriorhodopsin (9×105 photocycles protein−1) or the 4-keto-bacteriorhodopsin analog (1×105 photocycles protein−1). The thermal stabilities are assigned by using differential scanning calorimetry and thermal bleaching experiments. Both proteorhodopsins display excellent thermal stability, with melting temperatures above 85°C, and remain photochemically stable up to 75°C. The biological relevance of our results is also discussed. The lower cyclicity of BPR is found to be adequate for the long-term biological function of the host organism at ocean depths of 50 m or more. PMID:20964279

Bacteriorhodopsin-based photo-electrochemical cell.

PubMed

Chu, Li-Kang; Yen, Chun-Wan; El-Sayed, Mostafa A

2010-10-15

A simple solution-based electrochemical cell has been constructed and successfully employed in the detection of the photoelectric response upon photoexcitation of bacteriorhodopsin (bR) without external bias. Commercially-available indium tin oxide (ITO) glasses served as the optical windows and electrodes. Small amounts of bR suspensions (∼100 μL) were utilized as the photovoltaic medium to generate the proton gradient between two half-cells separated by a molecular porous membrane. Continuous broadband visible light (λ>380 nm) and a short-pulse 532-nm laser were employed for the photoexcitation of bR. Upon the modulated cw broadband irradiation, an instantaneous rise and decay of the current was observed. Our observations of the pH-dependent photocurrent are consistent with previous reports in a bR thin film configuration, which also showed a polarity inversion at pH 5-6. This is due to the change of the priority of the proton release and proton uptake in the photocycle of bR. Studies on the ionic strength effect were also carried out at different KCl concentrations, which resulted in the acceleration of the rise and decay of the photoelectric response. This was accompanied by a decrease in the stationary photocurrent at higher KCl concentrations in the broadband excitation experiments. The solution-based electrochemical cell uses aqueous medium, which is required for the completion of the bR proton pumping function. Due to the generation of the stationary current, it is advantageous to convert solar energy into electricity without the need of film-based photovoltaic devices with external bias. Copyright © 2010 Elsevier B.V. All rights reserved.

Coordinating the Structural Rearrangements Associated with Unidirectional Proton Transfer in the Bacteriorhodopsin Photocycle Induced by Deprotonation of the Proton-Release Group: A Time-Resolved Difference FTIR Spectroscopic Study†

PubMed Central

Morgan, Joel E.; Vakkasoglu, Ahmet S.; Lanyi, Janos K.; Gennis, Robert B.; Maeda, Akio

2014-01-01

In the photocycle of bacteriorhodopsin at pH 7, proton release from the proton releasing group (PRG) to the extracellular medium occurs during formation of the M intermediate. This proton release is inhibited at acidic pH, below the pKa of the PRG, ∼6 in M, and instead occurs later in the cycle as the initial state is restored from the O intermediate. Here, structural changes related to deprotonation of the PRG have been investigated by time-resolved FTIR spectroscopy at 25°C. The vibrational features at 2100-1790 cm-1, 1730-1685 cm-1, 1661 cm-1, and 1130-1045 cm-1 have greater negative intensity in the pure M-minus-BR spectrum and even in the M-minus-BR spectrum, that is present earlier together with the L-minus-BR spectrum, at pH 7, than in the corresponding M-minus-BR spectra at pH 5 or pH 4. The D212N mutation abolishes the decreases in the intensities of the broad feature between 1730 and 1685 cm-1 and the band at 1661 cm-1. The 1730-1685 cm-1 feature may arise from transition dipole coupling of the backbone carbonyl groups of Glu204, Phe208, Asp212 and Lys216 interacting with Tyr57 and C15-H of the chromophore. The 1661 cm-1 band, which is insensitive to D2O substitution, may arise by interaction of the backbone carbonyl of Asp212 with C15-H. The 2100-1790 cm-1 feature with a trough at 1885 cm-1 could be due to a water cluster. Depletion of these bands upon deprotonation of the PRG is attributable to disruption of a coordinated structure, held in place by interactions of Asp212. Deprotonation of the PRG is accompanied also by disruption of the interaction of the water molecule near Arg82. The liberated Asp212 may stabilize the protonated state of Asp85, and thus confer uni-directionality to the transport. PMID:20232848

Incoherent manipulation of the photoactive yellow protein photocycle with dispersed pump-dump-probe spectroscopy.

PubMed

Larsen, Delmar S; van Stokkum, Ivo H M; Vengris, Mikas; van Der Horst, Michael A; de Weerd, Frank L; Hellingwerf, Klaas J; van Grondelle, Rienk

2004-09-01

Photoactive yellow protein is the protein responsible for initiating the "blue-light vision" of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This "incoherent" manipulation of the photocycle allows for the detailed spectroscopic investigation of the underlying photocycle dynamics and the construction of a fully self-consistent dynamical model. This model requires three kinetically distinct excited-state intermediates, two (ground-state) photocycle intermediates, I(0) and pR, and a ground-state intermediate through which the protein, after unsuccessful attempts at initiating the photocycle, returns to the equilibrium ground state. Also observed is a previously unknown two-photon ionization channel that generates a radical and an ejected electron into the protein environment. This second excitation pathway evolves simultaneously with the pathway containing the one-photon photocycle intermediates.

Incoherent Manipulation of the Photoactive Yellow Protein Photocycle with Dispersed Pump-Dump-Probe Spectroscopy

PubMed Central

Larsen, Delmar S.; van Stokkum, Ivo H. M.; Vengris, Mikas; van der Horst, Michael A.; de Weerd, Frank L.; Hellingwerf, Klaas J.; van Grondelle, Rienk

2004-01-01

Photoactive yellow protein is the protein responsible for initiating the “blue-light vision” of Halorhodospira halophila. The dynamical processes responsible for triggering the photoactive yellow protein photocycle have been disentangled with the use of a novel application of dispersed ultrafast pump-dump-probe spectroscopy, where the photocycle can be started and interrupted with appropriately tuned and timed laser pulses. This “incoherent” manipulation of the photocycle allows for the detailed spectroscopic investigation of the underlying photocycle dynamics and the construction of a fully self-consistent dynamical model. This model requires three kinetically distinct excited-state intermediates, two (ground-state) photocycle intermediates, I0 and pR, and a ground-state intermediate through which the protein, after unsuccessful attempts at initiating the photocycle, returns to the equilibrium ground state. Also observed is a previously unknown two-photon ionization channel that generates a radical and an ejected electron into the protein environment. This second excitation pathway evolves simultaneously with the pathway containing the one-photon photocycle intermediates. PMID:15345564

Effects of tyrosine-26 and tyrosine-64 nitration on the photoreactions of bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Scherrer, P.; Stoeckenius, W.

1985-01-01

The photoreactions of nitrated bacteriorhodopsin (bR) are examined. Flash-induced difference spectra of bR, bR with aminotyrosine in position 26 (bR-N26R) and bR with aminotyrosine in position 64 are analyzed. It is observed that changes in the actinic wavelength (from 520 to 500 or 580 nm) have no affect on the shape of the spectra and the formation and decay kinetics of the O and M intermediates. Nitration of tyrosine-64 decreases the chromophore absorbance, shifts the absorption maximum to 535 nm, and affects photocycle kinetics independent of the pK of its phenolic group. Light-dark adaptation spectra for bR are studied. The kinetics of the M and O intermediates in bR with nitrotyrosine in position 64 (bR-N64) and bR with aminotyrosine in position 64 and bR with nitrotyrosine in position 26 and bR-N26R are described and compared to bR; the pH dependence and M and O decay rates are considered. The deprotonation of bR-N64 during the photoreaction cycle and the effects of nitration on the activity of proton pumping are investigated.

Bacteriorhodopsin-based photochromic pigments for optical security applications

NASA Astrophysics Data System (ADS)

Hampp, Norbert A.; Fischer, Thorsten; Neebe, Martin

2002-04-01

Bacteriorhodopsin is a two-dimensional crystalline photochromic protein which is astonishingly stable towards chemical and thermal degradation. This is one of the reasons why this is one of the very few proteins which may be used as a biological pigment in printing inks. Variants of the naturally occurring bacteriorhodopsin have been developed which show a distinguished color change even with low light intensities and without the requirement of UV-light. Several pigments with different color changes are available right now. In addition to this visual detectable feature, the photochromism, the proteins amino acid sequence can be genetically altered in order to code and identify specific production lots. For advanced applications the data storage capability of bacteriorhodopsin will be useful. Write-once-read-many (WORM) recording of digital data is accomplished by laser excitation of printed bacteriorhodopsin inks. A density of 1 MBit per square inch is currently achieved. Several application examples for this biological molecule are described where low and high level features are used in combination. Bacteriorhodopsin-based inks are a new class of optical security pigments.

The photochemical cycle of bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lozier, R. H.; Niederberger, W.

1977-01-01

The reaction cycle of bacteriorhodopsin in the purple membrane isolated from Halobacterium halobium has been studied by optical absorption spectroscopy using low-temperature and flash kinetic techniques. After absorption of light, bacteriorhodopsin passes through at least five distinct intermediates. The temperature and pH dependence of the absorbance changes suggests that branch points and/or reversible steps exist in this cycle. Flash spectroscopy in the presence of a pH-indicating dye shows that the transient release of a proton accompanies the photoreaction cycle. The proton release occurs from the exterior and the uptake is on the cytoplasmic side of the membrane, as required by the function of bacteriorhodopsin as a light-driven proton pump. Proton translocating steps connecting release and uptake are indicated by deuterium isotope effects on the kinetics of the cycle. The rapid decay of a light-induced linear dichroism shows that a chromophore orientation change occurs during the reaction cycle.

Nonlinear Optical Image Processing with Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.; Deiss, Ron (Technical Monitor)

1994-01-01

The transmission properties of some bacteriorhodopsin film spatial light modulators are uniquely suited to allow nonlinear optical image processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude transmission feature of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. The bacteriorhodopsin film displays the logarithmic amplitude response for write beam intensities spanning a dynamic range greater than 2.0 orders of magnitude. We present experimental results demonstrating the principle and capability for several different image and noise situations, including deterministic noise and speckle. Using the bacteriorhodopsin film, we successfully filter out image noise from the transformed image that cannot be removed from the original image.

Reconstitution of Biological Molecular generators of electric current. Bacteriorhodopsin.

PubMed

Drachev, L A; Frolov, V N; Kaulen, A D; Liberman, E A; Ostroumov, S A; Plakunova, V G; Semenov, A Y; Skulachev, V P

1976-11-25

1. Photoinduced generation of electric current by bacteriorhodopsin, incorporated into the planar phospholipid membrane, has been directly measured with conventional electrometer techniques. 2. Two methods for bacteriorhodopsin incorporation have been developed: (a) formation of planar membrane from a mixture of decane solution of phospholipids and of the fraction of violet fragments of the Halobacterium halobium membrane (bacteriorhodopsin sheets), and (b) adhesion of bacteriorhodopsin-containing reconstituted spherical membranes (proteoliposomes) to the planar membrane in the presence of Ca2+ or some other cations. In both cases, illumination was found to induce electric current generation directed across the planar membrane, an effect which was measured by macroelectrodes immersed into electrolyte solutions on both sides of the membrane. 3. The maximal values of the transmembrane electric potential were of about 150 mV at a current of about 10(-11) A. The electromotive force measured by means of counterbalancing the photoeffect by an external battery, was found to reach the value of 300 mV. 4. The action spectrum of the photoeffect coincides with the bacteriorhodopsin absorption spectrum (maximum about 570 nm). 5. Both components of the electrochemical potential of H+ ions (electric potential and delta pH) across the planar membrane affect the bacteriorhodopsin photoelectric response in a fashion which could be expected if bacteriorhodopsin were a light-dependent electrogenic proton pump. 6. La3+ ions were shown to inhibit operation of those bacteriorhodopsin which pump out H+ ions from the La3+-containing compartment. 7. The photoeffect, mediated by proteoliposomes associated with thick planar membrane, is decreased by gramicidin A at concentrations which do not influence the planar membrane resistance in the light. On the contrary, a protonophorous uncoupler, trichlorocarbonylcyanidephenylhydrazone, decreases the photoeffect only if it is added at a

Optical Data Storage Capabilities of Bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Gary, Charles

1998-01-01

We present several measurements of the data storage capability of bacteriorhodopsin films to help establish the baseline performance of this material as a medium for holographic data storage. In particular, we examine the decrease in diffraction efficiency with the density of holograms stored at one location in the film, and we also analyze the recording schedule needed to produce a set of equal intensity holograms at a single location in the film. Using this information along with the assumptions about the performance of the optical system, we can estimate potential data storage densities in bacteriorhodopsin.

Photocycle dynamics of the E149A mutant of cryptochrome 3 from Arabidopsis thaliana.

PubMed

Zirak, P; Penzkofer, A; Moldt, J; Pokorny, R; Batschauer, A; Essen, L-O

2009-11-09

The E149A mutant of the cryDASH member cryptochrome 3 (cry3) from Arabidopsis thaliana was characterized in vitro by optical absorption and emission spectroscopic studies. The mutant protein non-covalently binds the chromophore flavin adenine dinucleotide (FAD). In contrast to the wild-type protein it does not bind N5,N10-methenyl-5,6,7,8-tetrahydrofolate (MTHF). Thus, the photo-dynamics caused by FAD is accessible without the intervening coupling with MTHF. In dark adapted cry3-E149A, FAD is present in the oxidized form (FAD(ox)), semiquinone form (FADH(.)), and anionic hydroquinone form (FAD(red)H(-)). Blue-light photo-excitation of previously unexposed cry3-E149A transfers FAD(ox) to the anionic semiquinone form (FAD()(-)) with a quantum efficiency of about 2% and a back recovery time of about 10s (photocycle I). Prolonged photo-excitation leads to an irreversible protein re-conformation with structure modification of the U-shaped FAD and enabling proton transfer. Thus, a change in the photocycle dynamics occurs with photo-conversion of FAD(ox) to FADH(.), FADH(.) to FAD(red)H(-), and thermal back equilibration in the dark (photocycle II). The photocycle dynamics of cry3-E149A is compared with the photocycle behaviour of wild-type cry3 and other photo-sensory cryptochromes.

Biological Significance of Photoreceptor Photocycle Length: VIVID Photocycle Governs the Dynamic VIVID-White Collar Complex Pool Mediating Photo-adaptation and Response to Changes in Light Intensity

PubMed Central

Dasgupta, Arko; Chen, Chen-Hui; Lee, ChangHwan; Gladfelter, Amy S.; Dunlap, Jay C.; Loros, Jennifer J.

2015-01-01

Most organisms on earth sense light through the use of chromophore-bearing photoreceptive proteins with distinct and characteristic photocycle lengths, yet the biological significance of this adduct decay length is neither understood nor has been tested. In the filamentous fungus Neurospora crassa VIVID (VVD) is a critical player in the process of photoadaptation, the attenuation of light-induced responses and the ability to maintain photosensitivity in response to changing light intensities. Detailed in vitro analysis of the photochemistry of the blue light sensing, FAD binding, LOV domain of VVD has revealed residues around the site of photo-adduct formation that influence the stability of the adduct state (light state), that is, altering the photocycle length. We have examined the biological significance of VVD photocycle length to photoadaptation and report that a double substitution mutant (vvdI74VI85V), previously shown to have a very fast light to dark state reversion in vitro, shows significantly reduced interaction with the White Collar Complex (WCC) resulting in a substantial photoadaptation defect. This reduced interaction impacts photoreceptor transcription factor WHITE COLLAR-1 (WC-1) protein stability when N. crassa is exposed to light: The fast-reverting mutant VVD is unable to form a dynamic VVD-WCC pool of the size required for photoadaptation as assayed both by attenuation of gene expression and the ability to respond to increasing light intensity. Additionally, transcription of the clock gene frequency (frq) is sensitive to changing light intensity in a wild-type strain but not in the fast photo-reversion mutant indicating that the establishment of this dynamic VVD-WCC pool is essential in general photobiology and circadian biology. Thus, VVD photocycle length appears sculpted to establish a VVD-WCC reservoir of sufficient size to sustain photoadaptation while maintaining sensitivity to changing light intensity. The great diversity in photocycle

Proline 54 trans-cis isomerization is responsible for the kinetic partitioning at the last-step photocycle of photoactive yellow protein

PubMed Central

Lee, Byoung-Chul; Hoff, Wouter D.

2008-01-01

Photoactive yellow protein (PYP), a blue-light photoreceptor for Ectothiorhodospira halophila, has provided a unique system for studying protein folding that is coupled with a photocycle. Upon receptor activation by blue light, PYP proceeds through a photocycle that includes a partially folded signaling state. The last-step photocycle is a thermal recovery reaction from the signaling state to the native state. Bi-exponential kinetics had been observed for the last-step photocycle; however, the slow phase of the bi-exponential kinetics has not been extensively studied. Here we analyzed both fast and slow phases of the last-step photocycle in PYP. From the analysis of the denaturant dependence of the fast and slow phases, we found that the last-step photocycle proceeds through parallel channels of the folding pathway. The burial of the solvent-accessible area was responsible for the transition state of the fast phase, while structural rearrangement from the compact state to the native state was responsible for the transition state of the slow phase. The photocycle of PYP was linked to the thermodynamic cycle that includes both unfolding and refolding of the fast- and slow-phase intermediates. In order to test the hypothesis of proline-limited folding for the slow phase, we constructed two proline mutants: P54A and P68A. We found that only a single phase of the last-step photocycle was observed in P54A. This suggests that there is a low energy barrier between trans to cis conformation in P54 in the light-induced state of PYP, and the resulting cis conformation of P54 generates a slow-phase kinetic trap during the photocycle-coupled folding pathway of PYP. PMID:18794212

Fourier Transform Infrared and Resonance Raman Spectroscopic Studies of Bacteriorhodopsin.

NASA Astrophysics Data System (ADS)

Earnest, Thomas Nixon

Fourier transform infrared and resonance Raman spectroscopy were used to investigate the structure and function of the light-activated, transmembrane proton pump, bacteriorhodopsin, from the purple membrane of Halobacterium halobium. Bacteriorhodopsin (bR) is a 27,000 dalton integral membrane protein consisting of 248 amino acids with a retinylidene chromophore. Absorption of a photon leads to the translocation of one or two protons from the inside of the cell to the outside. Resonance Raman spectroscopy allows for the study of the configuration of retinal in bR and its photointermediates by the selective enhancement of vibrational modes of the chromophore. This technique was used to determine that the chromophore is attached to lysine-216 in both the bR _{570} and the M _{412} intermediates. In bR with tyrosine-64 selectively nitrated or aminated, the chromophore appears to have the same configuration in that bR _{570} (all- trans) and M _{412} (13- cis) states as it does in unmodified bR. Polarized Fourier transform infrared spectroscopy (FTIR) permits the study of the direction of transition dipole moments arising from molecular vibrations of the protein and the retinal chromophore. The orientation of alpha helical and beta sheet components was determined for bR with the average helical tilt found to lie mostly parallel to the membrane normal. The beta sheet structures also exhibit an IR linear dichroism for the amide I and amide II bands which suggest that the peptide backbone is mostly perpendicular to the membrane plane although it is difficult to determine whether the bands originate from sheet or turn components. The orientation of secondary structure components of the C-1 (residues 72-248) and C-2 (residues 1-71) fragments were also investigated to determine the structure of these putative membrane protein folding intermediates. Polarized, low temperature FTIR -difference spectroscopy was then used to investigate the structure of bR as it undergoes

Optical Logarithmic Transformation of Speckle Images with Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.

1995-01-01

The application of logarithmic transformations to speckle images is sometimes desirable in converting the speckle noise distribution into an additive, constant-variance noise distribution. The optical transmission properties of some bacteriorhodopsin films are well suited to implement such a transformation optically in a parallel fashion. I present experimental results of the optical conversion of a speckle image into a transformed image with signal-independent noise statistics, using the real-time photochromic properties of bacteriorhodopsin. The original and transformed noise statistics are confirmed by histogram analysis.

Application of bacteriorhodopsin films in an adaptive-focusing schlieren system

NASA Astrophysics Data System (ADS)

Downie, John D.

1995-09-01

The photochromic property of bacteriorhodopsin films is exploited in the application of a focusing schlieren optical system for the visualization of optical phase information. By encoding an image on the film with light of one wavelength and reading out with a different wavelength, the readout beam can effectively see the photographic negative of the original image. The potential advantage of this system over previous focusing schlieren systems is that the updatable nature of the bacteriorhodopsin film allows system adaptation. I discuss two image encoding and readout techniques for the bacteriorhodopsin and use film transmission characteristics to choose the more appropriate method. I demonstrate the system principle with experimental results using argon-ion and He-Cd lasers as the two light sources of different wavelengths, and I discuss current limitations to implementation with a white-light source.

Application of Bacteriorhodopsin Films in an Adaptive-Focusing Schlieren System

NASA Technical Reports Server (NTRS)

Downie, John D.

1995-01-01

The photochromic property of bacteriorhodopsin films is exploited in the application of a focusing schlieren optical system for the visualization of optical phase information. By encoding an image on the film with light of one wavelength and reading out with a different wavelength, the readout beam can effectively see the photographic negative of the original image. The potential advantage of this system over previous focusing schlieren systems is that the updatable nature of the bacteriorhodopsin film allows system adaptation. I discuss two image encoding and readout techniques for the bacteriorhodopsin and use film transmission characteristics to choose the more appropriate method. I demonstrate the system principle with experimental results using argon-ion and He-Cd lasers as the two light sources of different wavelengths, and I discuss current limitations to implementation with a white-light source.

Photoisomerization in bacteriorhodopsin studied by FTIR, linear dichroism and photoselection experiments combined with quantum chemical theoretical analysis

NASA Astrophysics Data System (ADS)

Fahmy, K.; Siebert, F.; Großjean, M. F.; Tavan, P.

1989-12-01

Orientations of IR transition moments of the retinal chromophore of bacteriorhodopsin (BR) and of the apo-protein are investigated by FTIR linear dichroism and photoselection measurements. Low temperature difference spectra for the photoinduced transitions of BR to its photocycle intermediates K and L are evaluated using improved methods. Quantum chemical calculations of directions of IR and electronic transition moments of model chromophores are employed to analyze corresponding observations. The chromophore of light-adapted BR 568 is shown to exhibit small (15-30°) twists around the CC single bonds of retinals polyene chain but no large overall helicity (⩽15°). The average retinal plane is demonstrated to form an angle of 90±20° with the plane of the purple membrane. The C 9C 10 double bond of retinal is found approximately parallel to the plane of the membrane. Upon photoisomerization the orientation of the chromophore moiety from C 1 to C 13 is estimated to be largely conserved. The single bond twists of the chromophore in L are shown to be larger than those in BR 568. This result is in agreement with the previous prediction of increased single bond twists in L, which can cause a p K decrease of the chromophore and, thereby, enforce its deprotonation in the L→M transition [Schulten and Tavan, Nature, 272 (1978) 85].

Multiplexed Holographic Data Storage in Bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Mehrl, David J.; Krile, Thomas F.

1999-01-01

Biochrome photosensitive films in particular Bacteriorhodopsin exhibit features which make these materials an attractive recording medium for optical data storage and processing. Bacteriorhodopsin films find numerous applications in a wide range of optical data processing applications; however the short-term memory characteristics of BR limits their applications for holographic data storage. The life-time of the BR can be extended using cryogenic temperatures [1], although this method makes the system overly complicated and unstable. Longer life-times can be provided in one modification of BR - the "blue" membrane BR [2], however currently available films are characterized by both low diffraction efficiency and difficulties in providing photoreversible recording. In addition, as a dynamic recording material, the BR requires different wavelengths for recording and reconstructing of optical data in order to prevent the information erasure during its readout. This fact also put constraints on a BR-based Optical Memory, due to information loss in holographic memory systems employing the two-lambda technique for reading-writing thick multiplexed holograms.

The two photocycles of photoactive yellow protein from Rhodobacter sphaeroides.

PubMed

Haker, Andrea; Hendriks, Johnny; van Stokkum, Ivo H M; Heberle, Joachim; Hellingwerf, Klaas J; Crielaard, Wim; Gensch, Thomas

2003-03-07

The absorption spectrum of the photoactive yellow protein from Rhodobacter sphaeroides (R-PYP) shows two maxima, absorbing at 360 nm (R-PYP(360)) and 446 nm (R-PYP(446)), respectively. Both forms are photoactive and part of a temperature- and pH-dependent equilibrium (Haker, A., Hendriks, J., Gensch, T., Hellingwerf, K. J., and Crielaard, W. (2000) FEBS Lett. 486, 52-56). At 20 degrees C, for PYP characteristic, the 446-nm absorbance band displays a photocycle, in which the depletion of the 446-nm ground state absorption occurs in at least three phases, with time constants of <30 ns, 0.5 micros, and 17 micros. Intermediates with both blue- and red-shifted absorption maxima are transiently formed, before a blue-shifted intermediate (pB(360), lambda(max) = 360 nm) is established. The photocycle is completed with a monophasic recovery of the ground state with a time constant of 2.5 ms. At 7 degrees C these photocycle transitions are slowed down 2- to 3-fold. Upon excitation of R-PYP(360) with a UV-flash (330 +/- 50 nm) a species with a difference absorption maximum at approximately 435 nm is observed that returns to R-PYP(360) on a minute time scale. Recovery can be accelerated by a blue light flash (450 nm). R-PYP(360) and R-PYP(446) differ in their overall protein conformation, as well as in the isomerization and protonation state of the chromophore, as determined with the fluorescent polarity probe Nile Red and Fourier Transform Infrared spectroscopy, respectively.

Conformational Change of Bacteriorhodopsin Quantitatively Monitored by Microcantilever Sensors

PubMed Central

Braun, Thomas; Backmann, Natalija; Vögtli, Manuel; Bietsch, Alexander; Engel, Andreas; Lang, Hans-Peter; Gerber, Christoph; Hegner, Martin

2006-01-01

Bacteriorhodopsin proteoliposomes were used as a model system to explore the applicability of micromechanical cantilever arrays to detect conformational changes in membrane protein patches. The three main results of our study concern: 1), reliable functionalization of micromechanical cantilever arrays with proteoliposomes using ink jet spotting; 2), successful detection of the prosthetic retinal removal (bleaching) from the bacteriorhodopsin protein by measuring the induced nanomechanical surface stress change; and 3), the quantitative response thereof, which depends linearly on the amount of removed retinal. Our results show this technique to be a potential tool to measure membrane protein-based receptor-ligand interactions and conformational changes. PMID:16443650

Spontaneous stacking of purple membranes during immobilization with physical cross-linked poly(vinyl alcohol) hydrogel with retaining native-like functionality of bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Yokoyama, Yasunori; Tanaka, Hikaru; Yano, Shunsuke; Takahashi, Hiroshi; Kikukawa, Takashi; Sonoyama, Masashi; Takenaka, Koshi

2017-05-01

We previously discovered the correlation between light-induced chromophore color change of a photo-receptor membrane protein bacteriorhodopsin (bR) and its two-dimensional crystalline state in the membrane. To apply this phenomenon to a novel optical memory device, it is necessary that bR molecules are immobilized as maintaining their structure and functional properties. In this work, a poly(vinyl alcohol) (PVA) hydrogel with physical cross-linkages (hydrogen bonds between PVA chains) that resulted from repeated freezing-and-thawing (FT) cycles was used as an immobilization medium. To investigate the effects of physically cross-linked PVA gelation on the structure and function of bR in purple membranes (PMs), spectroscopic techniques were employed against PM/PVA immobilized samples prepared with different FT cycle numbers. Visible circular dichroism spectroscopy strongly suggested PM stacking during gelation. X-ray diffraction data also indicated the PM stacking as well as its native-like crystalline lattice even after gelation. Time-resolved absorption spectroscopy showed that bR photocycle behaviors in PM/PVA immobilized samples were almost identical to that in suspension. These results suggested that a physically cross-linked PVA hydrogel is appropriate for immobilizing membrane proteins in terms of maintaining their structure and functionality.

Protein folding thermodynamics applied to the photocycle of the photoactive yellow protein.

PubMed Central

Van Brederode, M E; Hoff, W D; Van Stokkum, I H; Groot, M L; Hellingwerf, K J

1996-01-01

Two complementary aspects of the thermodynamics of the photoactive yellow protein (PYP), a new type of photoreceptor that has been isolated from Ectothiorhodospira halophila, have been investigated. First, the thermal denaturation of PYP at pH 3.4 has been examined by global analysis of the temperature-induced changes in the UV-VIS absorbance spectrum of this chromophoric protein. Subsequently, a thermodynamic model for protein (un)folding processes, incorporating heat capacity changes, has been applied to these data. The second aspect of PYP that has been studied is the temperature dependence of its photocycle kinetics, which have been reported to display an unexplained deviation from normal Arrhenius behavior. We have extended these measurements in two solvents with different hydrophobicities and have analyzed the number of rate constants needed to describe these data. Here we show that the resulting temperature dependence of the rate constants can be quantitatively explained by the application of a thermodynamic model which assumes that heat capacity changes are associated with the two transitions in the photocycle of PYP. This result is the first example of an enzyme catalytic cycle being described by a thermodynamic model including heat capacity changes. It is proposed that a strong link exists between the processes occurring during the photocycle of PYP and protein (un)folding processes. This permits a thermodynamic analysis of the light-induced, physiologically relevant, conformational changes occurring in this photoreceptor protein. PMID:8804619

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9.

PubMed

Köhler, Thomas; Weber, Ingrid; Glaubitz, Clemens; Wachtveitl, Josef

2017-05-01

The retinal protein proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of proteorhodopsin, the pK a of the primary proton acceptor Asp-97 (pK a  ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in proteorhodopsin and bacteriorhodopsin. The pK a of proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms. © 2017 The American Society of Photobiology.

Structural events in the photocycle of green fluorescent protein.

PubMed

van Thor, Jasper J; Zanetti, Giulia; Ronayne, Kate L; Towrie, Michael

2005-08-25

Picosecond time-resolved mid-infrared absorption changes of the wild type green fluorescent protein from Aequorea victoria are reported on structural events during the photocycle. Concomitant with rapid H/D transfer following excitation of the neutral A state at 400 nm, a transient signal at 1721/1711 cm(-1) (H/D) developed belonging to protonated glutamate 222, which was definitively assigned using the E222D mutant from the altered proton-transfer kinetics to aspartate in addition to the altered band position and intensity in the spectra. A transient at 1697 cm(-1), assigned to a structural perturbation of glutamine 69, had a H/D kinetic isotope effect of >32, showing the conformational dynamics to be sensitive to the active site H/D vibrations. The kinetic data up to 2 ns after excitation in the 1250-1800 cm(-1) region in D2O provided 10 and 75 ps time constants for the excited-state deuteron transfer and the associated A1* - A1 and A2* - A2 difference spectra and showed the radiative intermediate I state vibrations and the transient accumulation of the long-lived ground-state intermediate I2. Assignments of chromophore modes for the A1, A2, and I2 ground states are proposed on the basis of published model compound studies (Esposito, A. P.; Schellenberg, P.; Parson, W. W.; Reid, P. J. J. Mol. Struct. 2001, 569, 25 and He, X.; Bell, A. F.; Tonge, P. J. J. Phys. Chem. B 2002, 106, 6056). Tentative assignments for the singlet-state intermediates A1*, A2*, and I* are discussed. An unexpected and unassigned band that may be a C=C chromophore vibration was observed in the ground state (1665 cm(-1)) as well as in all photocycle intermediates. Optical dumping of the transient I population was achieved using an additional 532 nm pulse and the directly obtained I2 - I* difference spectrum was highly similar to the I2 - I* photocycle spectrum. The pump-dump-probe spectrum differed from the pump-probe photocycle difference spectrum with respect to the intensity of the phenol

Systematic investigations on fused π-system compounds of seven benzene rings prepared by photocyclization of diphenanthrylethenes.

PubMed

Fujino, Shota; Yamaji, Minoru; Okamoto, Hideki; Mutai, Toshiki; Yoshikawa, Isao; Houjou, Hirohiko; Tani, Fumito

2017-06-14

We studied the photoproducts of 1-(n-phenanthryl)-2-(m-phenanthryl)ethenes (nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorption measurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing nEm by photocyclization of stilbene derivatives. We obtained four types of primary photoproducts (n@m) from the corresponding nEm. Two of them were found to have racemic molecular structures in the single crystal determined by X-ray crystallography. Besides the primary photoproducts, two types of secondary photoproducts (n@mPP) were isolated. Fluorescence quantum yields and lifetimes of the obtained photoproducts were determined in solution whereas the definite fluorescence quantum yields were obtained in the powder. Observation of the triplet-triplet absorption spectra in solution by laser photolysis techniques showed that intersystem crossing to the triplet state competes with the fluorescence process.

Monolithically integrated bacteriorhodopsin-GaAs/GaAlAs phototransceiver.

PubMed

Shin, Jonghyun; Bhattacharya, Pallab; Xu, Jian; Váró, György

2004-10-01

A monolithically integrated bacteriorhodopsin-semiconductor phototransceiver is demonstrated for the first time to the authors' knowledge. In this novel biophotonic optical interconnect, the input photoexcitation is detected by bacteriorhodopsin (bR) that has been selectively deposited onto the gate of a GaAs-based field-effect transistor. The photovoltage developed across the bR is converted by the transistor into an amplified photocurrent, which drives an integrated light-emitting diode with a Ga0.37Al0.63As active region. Advantage is taken of the high-input impedance of the field-effect transistor, which matches the high internal resistance of bR. The input and output wavelengths are 594 and 655 nm, respectively. The transient response of the optoelectronic circuit to modulated input light has also been studied.

Influence of the intrinsic membrane protein bacteriorhodopsin on gel-phase domain topology in two-component phase-separated bilayers.

PubMed Central

Schram, V; Thompson, T E

1997-01-01

We have investigated the effect of the intrinsic membrane protein bacteriorhodopsin of Halobacterium halobium on the lateral organization of the lipid phase structure in the coexistence region of an equimolar mixture of dimyristoylphos-phatidylcholine and distearoylphosphatidylcholine. The fluorescence recovery after photobleaching (FRAP) technique was used to monitor the diffusion of both a lipid analog (N-(7-nitrobenzoxa-2,3-diazol-4-yl)-dimyristoylphosphatidyle thanolamine, NBD-DMPE) and fluorescein-labeled bacteriorhodopsin (Fl-BR). In the presence of bacteriorhodopsin, the mobile fractions of the two fluorescent probes display a shift of the percolation threshold toward lower temperatures (larger gel-phase fractions), independent of the protein concentration, from 43 degrees C (without bacteriorhodopsin) to 39 degrees C and 41 degrees C for NBD-DMPE and Fl-BR, respectively. Moreover, in the presence of bacteriorhodopsin, the gel-phase domains are much less efficient in restricting the diffusion of both probes than they are in the absence of the protein in the two-phase coexistence region. Bacteriorhodopsin itself, however, obstructs diffusion of NBD-DMPE and Fl-BR to about the same extent in the fluid phase of the two-phase region as it does in the homogeneous fluid phase. These observations suggest that 1) the protein induces the formation of much larger and/or more centrosymmetrical gel-phase domains than those formed in its absence, and 2) bacteriorhodopsin partitions almost equally between the coexisting fluid and gel phases. Although the molecular mechanisms involved are not clear, this phenomenon is fully consistent with the effect of the transmembrane peptide pOmpA of Escherichia coli investigated by electron spin resonance in the same lipid system. PMID:9129824

Multiplexed Holographic Optical Data Storage In Thick Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.; Timucin, Dogan A.; Gary, Charles K.; Ozcan, Meric; Smithey, Daniel T.; Crew, Marshall

1998-01-01

The optical data storage capacity of photochromic bacteriorhodopsin films is investigated by means of theoretical calculations, numerical simulations, and experimental measurements on sequential recording of angularly multiplexed diffraction gratings inside a thick D85N BR film.

Nonlinear coherent optical image processing using logarithmic transmittance of bacteriorhodopsin films

NASA Astrophysics Data System (ADS)

Downie, John D.

1995-08-01

The transmission properties of some bacteriorhodopsin-film spatial light modulators are uniquely suited to allow nonlinear optical image-processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude-transmission characteristic of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. I present experimental results demonstrating the principle and the capability for several different image and noise situations, including deterministic noise and speckle. The bacteriorhodopsin film studied here displays the logarithmic transmission response for write intensities spanning a dynamic range greater than 2 orders of magnitude.

Nonlinear Coherent Optical Image Processing Using Logarithmic Transmittance of Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.

1995-01-01

The transmission properties of some bacteriorhodopsin-film spatial light modulators are uniquely suited to allow nonlinear optical image-processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude-transmission characteristic of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. I present experimental results demonstrating the principle and the capability for several different image and noise situations, including deterministic noise and speckle. The bacteriorhodopsin film studied here displays the logarithmic transmission response for write intensities spanning a dynamic range greater than 2 orders of magnitude.

Light-driven Na + pump from Gillisia limnaea: A high-affinity Na + binding site is formed transiently in the photocycle

DOE PAGES

Balashov, Sergei P.; Imasheva, Eleonora S.; Dioumaev, Andrei K.; ...

2014-11-06

A group of microbial retinal proteins most closely related to the proton pump xanthorhodopsin has a novel sequence motif and a novel function. Instead of, or in addition to, proton transport, they perform light-driven sodium ion transport, as reported for one representative of this group (KR2) from Krokinobacter. In this paper, we examine a similar protein, GLR from Gillisia limnaea, expressed in Escherichia coli, which shares some properties with KR2 but transports only Na +. The absorption spectrum of GLR is insensitive to Na + at concentrations of ≤3 M. However, very low concentrations of Na + cause profound differencesmore » in the decay and rise time of photocycle intermediates, consistent with a switch from a “Na +-independent” to a “Na +-dependent” photocycle (or photocycle branch) at ~60 μM Na +. The rates of photocycle steps in the latter, but not the former, are linearly dependent on Na + concentration. This suggests that a high-affinity Na + binding site is created transiently after photoexcitation, and entry of Na + from the bulk to this site redirects the course of events in the remainder of the cycle. A greater concentration of Na + is needed for switching the reaction path at lower pH. The data suggest therefore competition between H + and Na + to determine the two alternative pathways. The idea that a Na + binding site can be created at the Schiff base counterion is supported by the finding that upon perturbation of this region in the D251E mutant, Na + binds without photoexcitation. Furthermore, binding of Na+ to the mutant shifts the chromophore maximum to the red like that of H +, which occurs in the photocycle of the wild type.« less

Monitoring light-induced structural changes of Channelrhodopsin-2 by UV-visible and Fourier transform infrared spectroscopy.

PubMed

Ritter, Eglof; Stehfest, Katja; Berndt, Andre; Hegemann, Peter; Bartl, Franz J

2008-12-12

Channelrhodopsin-2 (ChR2) is a microbial type rhodopsin and a light-gated cation channel that controls phototaxis in Chlamydomonas. We expressed ChR2 in COS-cells, purified it, and subsequently investigated this unusual photoreceptor by flash photolysis and UV-visible and Fourier transform infrared difference spectroscopy. Several transient photoproducts of the wild type ChR2 were identified, and their kinetics and molecular properties were compared with those of the ChR2 mutant E90Q. Based on the spectroscopic data we developed a model of the photocycle comprising six distinguishable intermediates. This photocycle shows similarities to the photocycle of the ChR2-related Channelrhodopsin of Volvox but also displays significant differences. We show that molecular changes include retinal isomerization, changes in hydrogen bonding of carboxylic acids, and large alterations of the protein backbone structure. These alterations are stronger than those observed in the photocycle of other microbial rhodopsins like bacteriorhodopsin and are related to those occurring in animal rhodopsins. UV-visible and Fourier transform infrared difference spectroscopy revealed two late intermediates with different time constants of tau = 6 and 40 s that exist during the recovery of the dark state. The carboxylic side chain of Glu(90) is involved in the slow transition. The molecular changes during the ChR2 photocycle are discussed with respect to other members of the rhodopsin family.

Monitoring Light-induced Structural Changes of Channelrhodopsin-2 by UV-visible and Fourier Transform Infrared Spectroscopy*

PubMed Central

Ritter, Eglof; Stehfest, Katja; Berndt, Andre; Hegemann, Peter; Bartl, Franz J.

2008-01-01

Channelrhodopsin-2 (ChR2) is a microbial type rhodopsin and a light-gated cation channel that controls phototaxis in Chlamydomonas. We expressed ChR2 in COS-cells, purified it, and subsequently investigated this unusual photoreceptor by flash photolysis and UV-visible and Fourier transform infrared difference spectroscopy. Several transient photoproducts of the wild type ChR2 were identified, and their kinetics and molecular properties were compared with those of the ChR2 mutant E90Q. Based on the spectroscopic data we developed a model of the photocycle comprising six distinguishable intermediates. This photocycle shows similarities to the photocycle of the ChR2-related Channelrhodopsin of Volvox but also displays significant differences. We show that molecular changes include retinal isomerization, changes in hydrogen bonding of carboxylic acids, and large alterations of the protein backbone structure. These alterations are stronger than those observed in the photocycle of other microbial rhodopsins like bacteriorhodopsin and are related to those occurring in animal rhodopsins. UV-visible and Fourier transform infrared difference spectroscopy revealed two late intermediates with different time constants of τ = 6 and 40 s that exist during the recovery of the dark state. The carboxylic side chain of Glu90 is involved in the slow transition. The molecular changes during the ChR2 photocycle are discussed with respect to other members of the rhodopsin family. PMID:18927082

FTIR spectroscopic study on individual amino acid residues in the proton pumping process of bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Liu, Xiaomei

1998-05-01

My thesis project has concentrated on clarifying the role of individual amino acids such as tyrosine, arginine and threonine in the active proton transferring process of Bacteriorhodopsin(bR). BR is a protein found in the purple membrane of Halobacteria salinarium. The main function of bR is to transfer a proton from the interior side of the cell to the external medium upon illumination by visible light. BR belongs to a family of retinal- containing membrane proteins which includes rhodopsin, a visual receptor found in the eye, and sensory rhodopsin I, a light receptor for phototaxis found in H. salinarium. Complete understanding of the proton transferring mechanism of bR can help explain the energy transduction and active ion transport in biological systems. This information also provides insight into other members of the retinal-containing protein family. To study the behavior of a single amino acid in a protein which consists of 248 amino acids, I employed the Fourier transform infrared (FTIR) difference spectroscopy technique. This was combined with the recently developed genetic engineering method of site directed isotope labeling (SDIL). As complementary work, I also characterized the vibrational properties of individual amino acids in various environments. Because of the high resolution and sensitivity of FTIR difference spectroscopy, along with the ability of SDIL to detect structural changes at the single amino acid level, we are able to determine changes in the structure of specific amino acids at different steps in bR photocycle. My research results provide strong evidence for a proton pump model. This model predicts the participation of tyrosine 185 and one or more threonines in a hydrogen bonded chain which can transfer proton across the membrane. My data also suggest a more accurate model for the proton release step which involves arginine 82.

Cell-free expressed bacteriorhodopsin in different soluble membrane mimetics: biophysical properties and NMR accessibility.

PubMed

Etzkorn, Manuel; Raschle, Thomas; Hagn, Franz; Gelev, Vladimir; Rice, Amanda J; Walz, Thomas; Wagner, Gerhard

2013-03-05

Selecting a suitable membrane-mimicking environment is of fundamental importance for the investigation of membrane proteins. Nonconventional surfactants, such as amphipathic polymers (amphipols) and lipid bilayer nanodiscs, have been introduced as promising environments that may overcome intrinsic disadvantages of detergent micelle systems. However, structural insights into the effects of different environments on the embedded protein are limited. Here, we present a comparative study of the heptahelical membrane protein bacteriorhodopsin in detergent micelles, amphipols, and nanodiscs. Our results confirm that nonconventional environments can increase stability of functional bacteriorhodopsin, and demonstrate that well-folded heptahelical membrane proteins are, in principle, accessible by solution-NMR methods in amphipols and phospholipid nanodiscs. Our data distinguish regions of bacteriorhodopsin that mediate membrane/solvent contacts in the tested environments, whereas the protein's functional inner core remains almost unperturbed. The presented data allow comparing the investigated membrane mimetics in terms of NMR spectral quality and thermal stability required for structural studies. Copyright © 2013 Elsevier Ltd. All rights reserved.

New photocycle intermediates in the photoactive yellow protein from Ectothiorhodospira halophila: picosecond transient absorption spectroscopy.

PubMed

Ujj, L; Devanathan, S; Meyer, T E; Cusanovich, M A; Tollin, G; Atkinson, G H

1998-07-01

Previous studies have shown that the room temperature photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila involves at least two intermediate species: I1, which forms in <10 ns and decays with a 200-micros lifetime to I2, which itself subsequently returns to the ground state with a 140-ms time constant at pH 7 (Genick et al. 1997. Biochemistry. 36:8-14). Picosecond transient absorption spectroscopy has been used here to reveal a photophysical relaxation process (stimulated emission) and photochemical intermediates in the PYP photocycle that have not been reported previously. The first new intermediate (I0) exhibits maximum absorption at approximately 510 nm and appears in photocycle.

Measurement and global analysis of the absorbance changes in the photocycle of the photoactive yellow protein from Ectothiorhodospira halophila.

PubMed Central

Hoff, W D; van Stokkum, I H; van Ramesdonk, H J; van Brederode, M E; Brouwer, A M; Fitch, J C; Meyer, T E; van Grondelle, R; Hellingwerf, K J

1994-01-01

The photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila was examined by time-resolved difference absorption spectroscopy in the wavelength range of 300-600 nm. Both time-gated spectra and single wavelength traces were measured. Global analysis of the data established that in the time domain between 5 ns and 2 s only two intermediates are involved in the room temperature photocycle of PYP, as has been proposed before (Meyer T.E., E. Yakali, M. A. Cusanovich, and G. Tollin. 1987. Biochemistry. 26:418-423; Meyer, T. E., G. Tollin, T. P. Causgrove, P. Cheng, and R. E. Blankenship. 1991. Biophys. J. 59:988-991). The first, red-shifted intermediate decays biexponentially (60% with tau = 0.25 ms and 40% with tau = 1.2 ms) to a blue-shifted intermediate. The last step of the photocycle is the biexponential (93% with tau = 0.15 s and 7% with tau = 2.0 s) recovery to the ground state of the protein. Reconstruction of the absolute spectra of these photointermediates yielded absorbance maxima of about 465 and 355 nm for the red- and blue-shifted intermediate with an epsilon max at about 50% and 40% relative to the epsilon max of the ground state. The quantitative analysis of the photocycle in PYP described here paves the way to a detailed biophysical analysis of the processes occurring in this photoreceptor molecule. PMID:7819501

Substitution of amino acids Asp-85, Asp-212, and Arg-82 in bacteriorhodopsin affects the proton release phase of the pump and the pK of the Schiff base.

PubMed

Otto, H; Marti, T; Holz, M; Mogi, T; Stern, L J; Engel, F; Khorana, H G; Heyn, M P

1990-02-01

Photocycle and flash-induced proton release and uptake were investigated for bacteriorhodopsin mutants in which Asp-85 was replaced by Ala, Asn, or Glu; Asp-212 was replaced by Asn or Glu; Asp-115 was replaced by Ala, Asn, or Glu; Asp-96 was replaced by Ala, Asn, or Glu; and Arg-82 was replaced by Ala or Gln in dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate micelles at pH 7.3. In the Asp-85----Ala and Asp-85----Asn mutants, the absence of the charged carboxyl group leads to a blue chromophore at 600 and 595 nm, respectively, and lowers the pK of the Schiff base deprotonation to 8.2 and 7, respectively, suggesting a role for Asp-85 as counterion to the Schiff base. The early part of the photocycles of the Asp-85----Ala and Asp-85----Asn mutants is strongly perturbed; the formation of a weak M-like intermediate is slowed down about 100-fold over wild type. In both mutants, proton release is also slower but clearly precedes the rise of M. The amplitude of the early (less than 0.2 microseconds) reversed photovoltage component in the Asp-85----Asn mutant is very large, and the net charge displacement is close to zero, indicating proton release and uptake on the cytoplasmic side of the membrane. The data suggest an obligatory role for Asp-85 in the efficient deprotonation of the Schiff base and in the proton release phase, probably as proton acceptor. In the Asp-212----Asn mutant, the rise of the absorbance change at 410 nm is slowed down to 220 microsecond, its amplitude is small, and the release of protons is delayed to 1.9 ms. The absorbance changes at 650 nm indicate perturbations in the early time range with a slow K intermediate. Thus Asp-212 also participates in the early events of charge translocation and deprotonation of the Schiff base. In the Arg-82----Gln mutant, no net transient proton release was observed, whereas, in the Arg-82----Ala mutant, uptake and release were reversed. The pK shift of the purple

Optical Processing of Speckle Images with Bacteriorhodopsin for Pattern Recognition

NASA Technical Reports Server (NTRS)

Downie, John D.; Tucker, Deanne (Technical Monitor)

1994-01-01

Logarithmic processing of images with multiplicative noise characteristics can be utilized to transform the image into one with an additive noise distribution. This simplifies subsequent image processing steps for applications such as image restoration or correlation for pattern recognition. One particularly common form of multiplicative noise is speckle, for which the logarithmic operation not only produces additive noise, but also makes it of constant variance (signal-independent). We examine the optical transmission properties of some bacteriorhodopsin films here and find them well suited to implement such a pointwise logarithmic transformation optically in a parallel fashion. We present experimental results of the optical conversion of speckle images into transformed images with additive, signal-independent noise statistics using the real-time photochromic properties of bacteriorhodopsin. We provide an example of improved correlation performance in terms of correlation peak signal-to-noise for such a transformed speckle image.

Photonic switching based on the photoinduced birefringence in bacteriorhodopsin films

NASA Astrophysics Data System (ADS)

Huang, Yuhua; Wu, Shin-Tson; Zhao, Youyuan

2004-03-01

Photoinduced birefringence in bacteriorhodopsin films was investigated using pump-probe method and its application for photonic switching explored. A diode-pumped second-harmonic YAG laser was used as a pumping beam and a diode laser at λ=660 nm was used as a probing beam. The pump and probe beams overlap at the sample. Without the pumping beam, the probing light cannot transmit the analyzer to the detector. However, due to the photoinduced anisotropy, a portion of the probing light is detected when the pumping beam is present. Since λ=660 nm is far from the absorption peak (˜570 nm) of the ground state, the photoinduced birefringence predominates. Using the intensity-dependent photoinduced birefringence in a bacteriorhodopsin film, we have demonstrated a photonic switch with ˜1000:1 contrast ratio, ˜0.6 s rise time and ˜1.5 s decay time.

Development and Characterization of Titanium Dioxide Gel with Encapsulated Bacteriorhodopsin for Hydrogen Production.

PubMed

Johnson, Kaitlin E; Gakhar, Sukriti; Risbud, Subhash H; Longo, Marjorie L

2018-06-06

We study bacteriorhodopsin (BR) in its native purple membrane encapsulated within amorphous titanium dioxide, or titania, gels and in the presence of titania sol-particles to explore this system for hydrogen production. Förster resonance energy transfer between BR and titanium dioxide sol particles was used to conclude that there is nanometer-scale proximity of bacteriorhodopsin to the titanium dioxide. The detection of BR-titania sol aggregates by fluorescence anisotropy and particle sizing indicated the affinity amorphous titania has for BR without the use of additional cross-linkers. UV-Visible spectroscopy of BR-titania gels show that methanol addition did not denature BR at a 25 mM concentration presence as a sacrificial electron donor. Additionally, confinement of BR in the gels significantly limited protein denaturation at higher concentration of added methanol or ethanol. Subsequently, titania gels fabricated through the sol-gel process using a titanium ethoxide precursor, water and the addition of 25 mM methanol were used to encapsulate BR and a platinum reduction catalyst for the production of hydrogen gas under white light irradiation. The inclusion of 5 µM bacteriorhodopsin resulted in a hydrogen production rate of about 3.8 µmole hydrogen mL -1 hr -1 , an increase of 52% compared to gels containing no protein. Electron transfer and proton pumping by BR in close proximity to the titania gel surface are feasible explanations for the enhanced production of hydrogen without the need to crosslink BR to the titania gel. This work sets the stage for further developments of amorphous, rather than crystalline, titania-encapsulated bacteriorhodopsin for solar-driven hydrogen production through water-splitting.

The two parallel photocycles of the Chlamydomonas sensory photoreceptor histidine kinase rhodopsin 1.

PubMed

Luck, Meike; Hegemann, Peter

2017-10-01

Histidine kinase rhodopsins (HKRs) belong to a class of unexplored sensory photoreceptors that share a similar modular architecture. The light sensing rhodopsin domain is covalently linked to signal-transducing modules and in some cases to a C-terminal guanylyl-cyclase effector. In spite of their wide distribution in unicellular organisms, very little is known about their physiological role and mechanistic functioning. We investigated the photochemical properties of the recombinant rhodopsin-fragment of Cr-HKR1 originating from Chlamydomonas reinhardtii. Our spectroscopic studies revealed an unusual thermal stability of the photoproducts with the deprotonated retinal Schiff base (RSB). Upon UV-irradiation these Rh-UV states with maximal absorbance in the UVA-region (Rh-UV) photochemically convert to stable blue light absorbing rhodopsin (Rh-Bl) with protonated chromophore. The heterogeneity of the sample is based on two parallel photocycles with the chromophore in C 15 =N-syn- or -anti-configuration. This report represents an attempt to decipher the underlying reaction schemes and interconversions of the two coexisting photocycles. Copyright © 2017 Elsevier GmbH. All rights reserved.

White Light Schlieren Optics Using Bacteriorhodopsin as an Adaptive Image Grid

NASA Technical Reports Server (NTRS)

Peale, Robert; Ruffin, Boh; Donahue, Jeff; Barrett, Carolyn

1996-01-01

A Schlieren apparatus using a bacteriorhodopsin film as an adaptive image grid with white light illumination is demonstrated for the first time. The time dependent spectral properties of the film are characterized. Potential applications include a single-ended Schlieren system for leak detection.

Separation of photoactive conformers based on hindered diarylethenes: efficient modulation in photocyclization quantum yields.

PubMed

Li, Wenlong; Jiao, Changhong; Li, Xin; Xie, Yongshu; Nakatani, Keitaro; Tian, He; Zhu, Weihong

2014-04-25

Endowing both solvent independency and excellent thermal bistability, the benzobis(thiadiazole)-bridged diarylethene system provides an efficient approach to realize extremely high photocyclization quantum yields (Φo-c , up to 90.6 %) by both separating completely pure anti-parallel conformer and suppressing intramolecular charge transfer (ICT). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Crystal structure of Escherichia coli-expressed Haloarcula marismortui bacteriorhodopsin I in the trimeric form.

PubMed

Shevchenko, Vitaly; Gushchin, Ivan; Polovinkin, Vitaly; Round, Ekaterina; Borshchevskiy, Valentin; Utrobin, Petr; Popov, Alexander; Balandin, Taras; Büldt, Georg; Gordeliy, Valentin

2014-01-01

Bacteriorhodopsins are a large family of seven-helical transmembrane proteins that function as light-driven proton pumps. Here, we present the crystal structure of a new member of the family, Haloarcula marismortui bacteriorhodopsin I (HmBRI) D94N mutant, at the resolution of 2.5 Å. While the HmBRI retinal-binding pocket and proton donor site are similar to those of other archaeal proton pumps, its proton release region is extended and contains additional water molecules. The protein's fold is reinforced by three novel inter-helical hydrogen bonds, two of which result from double substitutions relative to Halobacterium salinarum bacteriorhodopsin and other similar proteins. Despite the expression in Escherichia coli and consequent absence of native lipids, the protein assembles as a trimer in crystals. The unique extended loop between the helices D and E of HmBRI makes contacts with the adjacent protomer and appears to stabilize the interface. Many lipidic hydrophobic tail groups are discernible in the membrane region, and their positions are similar to those of archaeal isoprenoid lipids in the crystals of other proton pumps, isolated from native or native-like sources. All these features might explain the HmBRI properties and establish the protein as a novel model for the microbial rhodopsin proton pumping studies.

Bacteriorhodopsin as an electronic conduction medium for biomolecular electronics.

PubMed

Jin, Yongdong; Honig, Tal; Ron, Izhar; Friedman, Noga; Sheves, Mordechai; Cahen, David

2008-11-01

Interfacing functional proteins with solid supports for device applications is a promising route to possible applications in bio-electronics, -sensors, and -optics. Various possible applications of bacteriorhodopsin (bR) have been explored and reviewed since the discovery of bR. This tutorial review discusses bR as a medium for biomolecular optoelectronics, emphasizing ways in which it can be interfaced, especially as a thin film, solid-state current-carrying electronic element.

Spectroscopic studies of bacteriorhodopsin fragments dissolved in organic solution.

PubMed Central

Torres, J; Padrós, E

1995-01-01

Fourier transform infrared and UV fourth-derivative spectroscopies were used to study the secondary structure of bacteriorhodopsin and its chymotryptic and one of the sodium borohydride fragments dissolved in chloroform-methanol (1:1, v/v), 0.1 M LiClO4. The C1 fragment (helices C, D, E, F, and G) showed an alpha-helical content of about 53%, whereas C2 (helices A and B) had about 60%, and B2 (helices F and G) about 65% alpha-helix. The infrared main band indicated differences in alpha-helical properties between these fragments. These techniques were also used to obtain information on the interactions among helices. According to the results obtained from the hydrogen/deuterium exchange kinetics, about 40% of the amide protons of C2 are particularly protected against exchange, whereas for the C1 fragment this process is unexpectedly fast. UV fourth-derivative spectra of these samples were used to obtain information about the environment of Trp side chains. The results showed that the Trp residues of C2 are more shielded from the solvent than those of C1 or B2. The results of this work indicate that the specific interactions existing between the transmembrane segments induce different types of helical conformations in native bacteriorhodopsin. PMID:7612847

Conversion of light-energy into molecular strain in the photocycle of the photoactive yellow protein.

PubMed

Gamiz-Hernandez, Ana P; Kaila, Ville R I

2016-01-28

The Photoactive Yellow Protein (PYP) is a light-driven photoreceptor, responsible for the phototaxis of halophilic bacteria. Recently, a new short-lived intermediate (pR0) was characterized in the PYP photocycle using combined time-resolved X-ray crystallography and density functional theory calculations. The pR0 species was identified as a highly contorted cis-intermediate, which is stabilized by hydrogen bonds with protein residues. Here we show by hybrid quantum mechanics/classical mechanics (QM/MM) molecular dynamics simulations, and first-principles calculations of optical properties, that the optical shifts in the early steps of the PYP photocycle originate from the conversion of light energy into molecular strain, stored in the pR0 state, and its relaxation in subsequent reaction steps. Our calculations quantitatively reproduce experimental data, which enables us to identify molecular origins of the optical shifts. Our combined approach suggests that the short-lived pR0 intermediate stores ∼1/3 of the photon energy as molecular strain, thus providing the thermodynamic driving force for later conformational changes in the protein.

Determination of retinal chromophore structure in bacteriorhodopsin with resonance Raman spectroscopy.

PubMed

Smith, S O; Lugtenburg, J; Mathies, R A

1985-01-01

The analysis of the vibrational spectrum of the retinal chromophore in bacteriorhodopsin with isotopic derivatives provides a powerful "structural dictionary" for the translation of vibrational frequencies and intensities into structural information. Of importance for the proton-pumping mechanism is the unambiguous determination of the configuration about the C13=C14 and C=N bonds, and the protonation state of the Schiff base nitrogen. Vibrational studies have shown that in light-adapted BR568 the Schiff base nitrogen is protonated and both the C13=C14 and C=N bonds are in a trans geometry. The formation of K625 involves the photochemical isomerization about only the C13=C14 bond which displaces the Schiff base proton into a different protein environment. Subsequent Schiff base deprotonation produces the M412 intermediate. Thermal reisomerization of the C13=C14 bond and reprotonation of the Schiff base occur in the M412------O640 transition, resetting the proton-pumping mechanism. The vibrational spectra can also be used to examine the conformation about the C--C single bonds. The frequency of the C14--C15 stretching vibration in BR568, K625, L550 and O640 argues that the C14--C15 conformation in these intermediates is s-trans. Conformational distortions of the chromophore have been identified in K625 and O640 through the observation of intense hydrogen out-of-plane wagging vibrations in the Raman spectra (see Fig. 2). These two intermediates are the direct products of chromophore isomerization. Thus it appears that following isomerization in a tight protein binding pocket, the chromophore cannot easily relax to a planar geometry. The analogous observation of intense hydrogen out-of-plane modes in the primary photoproduct in vision (Eyring et al., 1982) suggests that this may be a general phenomenon in protein-bound isomerizations. Future resonance Raman studies should provide even more details on how bacterio-opsin and retinal act in concert to produce an

Molecular dynamics of bacteriorhodopsin.

PubMed

Lupo, J A; Pachter, R

1997-02-01

A model of bacteriorhodopsin (bR), with a retinal chromophore attached, has been derived for a molecular dynamics simulation. A method for determining atomic coordinates of several ill-defined strands was developed using a structure prediction algorithm based on a sequential Kalman filter technique. The completed structure was minimized using the GROMOS force field. The structure was then heated to 293 K and run for 500 ps at constant temperature. A comparison with the energy-minimized structure showed a slow increase in the all-atom RMS deviation over the first 200 ps, leveling off to approximately 2.4 A relative to the starting structure. The final structure yielded a backbone-atom RMS deviation from the crystallographic structure of 2.8 A. The residue neighbors of the chromophore atoms were followed as a function of time. The set of persistent near-residue neighbors supports the theory that differences in pKa values control access to the Schiff base proton, rather than formation of a counterion complex.

Ozil IP torsional mode versus combined torsional/longitudinal microcoaxial phacoemulsification.

PubMed

Helvacioglu, Firat; Tunc, Zeki; Yeter, Celal; Oguzhan, Hasan; Sencan, Sadik

2012-01-01

To compare the safety and efficacy of microcoaxial phacoemulsification surgeries performed with the Ozil Intelligent Phaco (IP) torsional mode and combined torsional/longitudinal ultrasound (US) mode using the Infiniti Vision System (Alcon Laboratories). In this prospective randomized comparative study, 60 eyes were assigned to 2.2-mm microcoaxial phacoemulsification using the Ozil IP torsional mode (group 1) or combined torsional/longitudinal US mode (group 2). The primary outcome measures were US time (UST), cumulative dissipated energy (CDE), longitudinal and torsional ultrasound amplitudes, mean operation time, mean volume of balanced salt solution (BSS) used, and surgical complications. Both groups included 30 eyes. Mean UST, CDE, and longitudinal and torsional ultrasound amplitudes in group 1 were 1 minute 15±34.33 seconds, 8.74±5.64, 0.43±0.74, and 25.56±8.56, respectively, and these parameters in group 2 were 1 minute 40±51.44 seconds, 9.28±5.99, 3.64±1.55, and 3.71±1.34, respectively. UST and longitudinal amplitudes were found to be significantly low in group 1 (p<0.001, p<0.001), whereas torsional amplitude was found to be significantly high in this group (p=0.001). Mean volumes of BSS used in groups 1 and 2 were 63.30±18.00 cc and 84.50±28.65 cc, respectively (p=0.001). The Ozil IP torsional mode may provide more effective lens removal than the combined torsional/longitudinal US mode with a lower UST and volume of BSS used.

Determination of Membrane Protein Structure by Rotational Resonance NMR: Bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Creuzet, F.; McDermott, A.; Gebhard, R.; van der Hoef, K.; Spijker-Assink, M. B.; Herzfeld, J.; Lugtenburg, J.; Levitt, M. H.; Griffin, R. G.

1991-02-01

Rotationally resonant magnetization exchange, a new nuclear magnetic resonance (NMR) technique for measuring internuclear distances between like spins in solids, was used to determine the distance between the C-8 and C-18 carbons of retinal in two model compounds and in the membrane protein bacteriorhodopsin. Magnetization transfer between inequivalent spins with an isotropic shift separation, δ, is driven by magic angle spinning at a speed ω_r that matches the rotational resonance condition δ = nω_r, where n is a small integer. The distances measured in this way for both the 6-s-cis- and 6-s-trans-retinoic acid model compounds agreed well with crystallographically known distances. In bacteriorhodopsin the exchange trajectory between C-8 and C-18 was in good agreement with the internuclear distance for a 6-s-trans configuration [4.2 angstroms (overset{circ}{mathrm A})] and inconsistent with that for a 6-s-cis configuration (3.1 overset{circ}{mathrm A}). The results illustrate that rotational resonance can be used for structural studies in membrane proteins and in other situations where diffraction and solution NMR techniques yield limited information.

Light as an Energy Source in Continuous Cultures of Bacteriorhodopsin-Containing Halobacteria

PubMed Central

Rodriguez-Valera, F.; Nieto, J. J.; Ruiz-Berraquero, F.

1983-01-01

The role of light as an energy source for slightly aereated cultures of halobacteria was studied, using continuous cultures with low nutrient concentrations and a low oxygen supply. A series of experiments were carried out with non-illuminated and differently illuminated cultures and with different oxygen transfer rates. Under low oxygen availability, light proved to be a decisively important energy source that allowed the populations to reach higher growth rates and much higher population densities. Oxygen influenced the growth over only a minimal level, below which neither the illuminated nor the dark cultures were affected by the oxygen transfer rate. From these results, it appears that the bacteriorhodopsin-mediated energy supply could have a very important role for the ecology of halobacteria in their microaerophilic habitats. In the illuminated cultures, cells that originated purple colonies on plates appeared. These cells, which could be bacteriorhodopsin-constitutive mutants, are now being studied. PMID:16346250

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1994-05-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)

1995-01-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Astrophysics Data System (ADS)

Alhorn, Dean C.; Polites, Michael E.

1995-08-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Variable stiffness torsion springs

NASA Technical Reports Server (NTRS)

Alhorn, Dean C. (Inventor); Polites, Michael E. (Inventor)

1994-01-01

In a torsion spring the spring action is a result of the relationships between the torque applied in twisting the spring, the angle through which the torsion spring twists, and the modulus of elasticity of the spring material in shear. Torsion springs employed industrially have been strips, rods, or bars, generally termed shafts, capabable of being flexed by twisting their axes. They rely on the variations in shearing forces to furnish an internal restoring torque. In the torsion springs herein the restoring torque is external and therefore independent of the shearing modulus of elasticity of the torsion spring shaft. Also provided herein is a variable stiffness torsion spring. This torsion spring can be so adjusted as to have a given spring constant. Such variable stiffness torsion springs are extremely useful in gimballed payloads such as sensors, telescopes, and electronic devices on such platforms as a space shuttle or a space station.

Evidence of multipolar response of Bacteriorhodopsin by noncollinear second harmonic generation.

PubMed

Bovino, F A; Larciprete, M C; Sibilia, C; Váró, G; Gergely, C

2012-06-18

Noncollinear second harmonic generation from a Bacteriorhodopsin (BR) oriented multilayer film was systematically investigated by varying the polarization state of both fundamental beams. Both experimental results and theoretical simulations, show that the resulting polarization mapping is an useful tool to put in evidence the optical chirality of the investigated film as well as the corresponding multipolar contributions to the nonlinear.

Time-resolved resonance Raman spectroscopy of intermediates of bacteriorhodopsin: The bK(590) intermediate.

PubMed

Terner, J; Hsieh, C L; Burns, A R; El-Sayed, M A

1979-07-01

We have combined microbeam and flow techniques with computer subtraction methods to obtain the resonance Raman spectrum of the short lived batho-intermediate (bK(590)) of bacteriorhodopsin. Comparison of the spectra obtained in (1)H(2)O and (2)H(2)O, as well as the fact that the bK(590) intermediate shows large optical red shifts, suggests that the Schiff base linkage of this intermediate is protonated. The fingerprint region of the spectrum of bK(590), sensitive to the isomeric configuration of the retinal chromophore, does not resemble the corresponding region of the parent bR(570) form. The resonance Raman spectrum of bK(590) as well as the spectra of all of the other main intermediates in the photoreaction cycle of bacteriorhodopsin are discussed and compared with resonance Raman spectra of published model compounds.

Voltage Dependence of Proton Pumping by Bacteriorhodopsin Mutants with Altered Lifetime of the M Intermediate

PubMed Central

Geibel, Sven; Lörinczi, Èva; Bamberg, Ernst; Friedrich, Thomas

2013-01-01

The light-driven proton pump bacteriorhodopsin (BR) from Halobacterium salinarum is tightly regulated by the [H+] gradient and transmembrane potential. BR exhibits optoelectric properties, since spectral changes during the photocycle are kinetically controlled by voltage, which predestines BR for optical storage or processing devices. BR mutants with prolonged lifetime of the blue-shifted M intermediate would be advantageous, but the optoelectric properties of such mutants are still elusive. Using expression in Xenopus oocytes and two-electrode voltage-clamping, we analyzed photocurrents of BR mutants with kinetically destabilized (F171C, F219L) or stabilized (D96N, D96G) M intermediate in response to green light (to probe H+ pumping) and blue laser flashes (to probe accumulation/decay of M). These mutants have divergent M lifetimes. As for BR-WT, this strictly correlates with the voltage dependence of H+ pumping. BR-F171C and BR-F219L showed photocurrents similar to BR-WT. Yet, BR-F171C showed a weaker voltage dependence of proton pumping. For both mutants, blue laser flashes applied during and after green-light illumination showed reduced M accumulation and shorter M lifetime. In contrast, BR-D96G and BR-D96N exhibited small photocurrents, with nonlinear current-voltage curves, which increased strongly in the presence of azide. Blue laser flashes showed heavy M accumulation and prolonged M lifetime, which accounts for the strongly reduced H+ pumping rate. Hyperpolarizing potentials augmented these effects. The combination of M-stabilizing and -destabilizing mutations in BR-D96G/F171C/F219L (BR-tri) shows that disruption of the primary proton donor Asp-96 is fatal for BR as a proton pump. Mechanistically, M destabilizing mutations cannot compensate for the disruption of Asp-96. Accordingly, BR-tri and BR-D96G photocurrents were similar. However, BR-tri showed negative blue laser flash-induced currents even without actinic green light, indicating that Schiff base

[Penile torsion. Case report].

PubMed

Arch Canas, Albert; Gutiérfz del Pozo, Rafael

2006-01-01

To report the clinical characteristics and therapeutic options of penile torsion. We report the case of a male with asymptomatic penile torsion as an incidental finding after consultation for other reasons. The patient was treated conservatively because it was not an important aesthetic trouble and it was asymptomatic. Penile torsion is rare. Surgical treatment is reserved for very important degrees of torsion, symptomatic patients or, when patient feels discomfort with the aesthetic alteration.

A Native Threonine Coordinates Ordered Water to Tune Light-Oxygen-Voltage (LOV) Domain Photocycle Kinetics and Osmotic Stress Signaling in Trichoderma reesei ENVOY.

PubMed

Lokhandwala, Jameela; Silverman Y de la Vega, Rafael I; Hopkins, Hilary C; Britton, Collin W; Rodriguez-Iglesias, Aroa; Bogomolni, Roberto; Schmoll, Monika; Zoltowski, Brian D

2016-07-08

Light-oxygen-voltage (LOV) domain-containing proteins function as small light-activated modules capable of imparting blue light control of biological processes. Their small modular nature has made them model proteins for allosteric signal transduction and optogenetic devices. Despite intense research, key aspects of their signal transduction mechanisms and photochemistry remain poorly understood. In particular, ordered water has been identified as a possible key mediator of photocycle kinetics, despite the lack of ordered water in the LOV active site. Herein, we use recent crystal structures of a fungal LOV protein ENVOY to interrogate the role of Thr(101) in recruiting water to the flavin active site where it can function as an intrinsic base to accelerate photocycle kinetics. Kinetic and molecular dynamic simulations confirm a role in solvent recruitment to the active site and identify structural changes that correlate with solvent recruitment. In vivo analysis of T101I indicates a direct role of the Thr(101) position in mediating adaptation to osmotic stress, thereby verifying biological relevance of ordered water in LOV signaling. The combined studies identify position 101 as a mediator of both allostery and photocycle catalysis that can impact organism physiology. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Improved free-energy landscape reconstruction of bacteriorhodopsin highlights local variations in unfolding energy.

PubMed

Heenan, Patrick R; Yu, Hao; Siewny, Matthew G W; Perkins, Thomas T

2018-03-28

Precisely quantifying the energetics that drive the folding of membrane proteins into a lipid bilayer remains challenging. More than 15 years ago, atomic force microscopy (AFM) emerged as a powerful tool to mechanically extract individual membrane proteins from a lipid bilayer. Concurrently, fluctuation theorems, such as the Jarzynski equality, were applied to deduce equilibrium free energies (ΔG 0 ) from non-equilibrium single-molecule force spectroscopy records. The combination of these two advances in single-molecule studies deduced the free-energy of the model membrane protein bacteriorhodopsin in its native lipid bilayer. To elucidate this free-energy landscape at a higher resolution, we applied two recent developments. First, as an input to the reconstruction, we used force-extension curves acquired with a 100-fold higher time resolution and 10-fold higher force precision than traditional AFM studies of membrane proteins. Next, by using an inverse Weierstrass transform and the Jarzynski equality, we removed the free energy associated with the force probe and determined the molecular free-energy landscape of the molecule under study, bacteriorhodopsin. The resulting landscape yielded an average unfolding free energy per amino acid (aa) of 1.0 ± 0.1 kcal/mol, in agreement with past single-molecule studies. Moreover, on a smaller spatial scale, this high-resolution landscape also agreed with an equilibrium measurement of a particular three-aa transition in bacteriorhodopsin that yielded 2.7 kcal/mol/aa, an unexpectedly high value. Hence, while average unfolding ΔG 0 per aa is a useful metric, the derived high-resolution landscape details significant local variation from the mean. More generally, we demonstrated that, as anticipated, the inverse Weierstrass transform is an efficient means to reconstruct free-energy landscapes from AFM data.

Improved free-energy landscape reconstruction of bacteriorhodopsin highlights local variations in unfolding energy

NASA Astrophysics Data System (ADS)

Heenan, Patrick R.; Yu, Hao; Siewny, Matthew G. W.; Perkins, Thomas T.

2018-03-01

Precisely quantifying the energetics that drive the folding of membrane proteins into a lipid bilayer remains challenging. More than 15 years ago, atomic force microscopy (AFM) emerged as a powerful tool to mechanically extract individual membrane proteins from a lipid bilayer. Concurrently, fluctuation theorems, such as the Jarzynski equality, were applied to deduce equilibrium free energies (ΔG0) from non-equilibrium single-molecule force spectroscopy records. The combination of these two advances in single-molecule studies deduced the free-energy of the model membrane protein bacteriorhodopsin in its native lipid bilayer. To elucidate this free-energy landscape at a higher resolution, we applied two recent developments. First, as an input to the reconstruction, we used force-extension curves acquired with a 100-fold higher time resolution and 10-fold higher force precision than traditional AFM studies of membrane proteins. Next, by using an inverse Weierstrass transform and the Jarzynski equality, we removed the free energy associated with the force probe and determined the molecular free-energy landscape of the molecule under study, bacteriorhodopsin. The resulting landscape yielded an average unfolding free energy per amino acid (aa) of 1.0 ± 0.1 kcal/mol, in agreement with past single-molecule studies. Moreover, on a smaller spatial scale, this high-resolution landscape also agreed with an equilibrium measurement of a particular three-aa transition in bacteriorhodopsin that yielded 2.7 kcal/mol/aa, an unexpectedly high value. Hence, while average unfolding ΔG0 per aa is a useful metric, the derived high-resolution landscape details significant local variation from the mean. More generally, we demonstrated that, as anticipated, the inverse Weierstrass transform is an efficient means to reconstruct free-energy landscapes from AFM data.

Direct Measurement of the Photoelectric Response Time of Bacteriorhodopsin via Electro-Optic Sampling

PubMed Central

Xu, J.; Stickrath, A. B.; Bhattacharya, P.; Nees, J.; Váró, G.; Hillebrecht, J. R.; Ren, L.; Birge, R. R.

2003-01-01

The photovoltaic signal associated with the primary photochemical event in an oriented bacteriorhodopsin film is measured by directly probing the electric field in the bacteriorhodopsin film using an ultrafast electro-optic sampling technique. The inherent response time is limited only by the laser pulse width of 500 fs, and permits a measurement of the photovoltage with a bandwidth of better than 350 GHz. All previous published studies have been carried out with bandwidths of 50 GHz or lower. We observe a charge buildup with an exponential formation time of 1.68 ± 0.05 ps and an initial decay time of 31.7 ps. Deconvolution with a 500-fs Gaussian excitation pulse reduces the exponential formation time to 1.61 ± 0.04 ps. The photovoltaic signal continues to rise for 4.5 ps after excitation, and the voltage profile corresponds well with the population dynamics of the K state. The origin of the fast photovoltage is assigned to the partial isomerization of the chromophore and the coupled motion of the Arg-82 residue during the primary event. PMID:12885657

Constraining torsion with Gravity Probe B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao Yi; Guth, Alan H.; Cabi, Serkan

2007-11-15

It is well-entrenched folklore that all torsion gravity theories predict observationally negligible torsion in the solar system, since torsion (if it exists) couples only to the intrinsic spin of elementary particles, not to rotational angular momentum. We argue that this assumption has a logical loophole which can and should be tested experimentally, and consider nonstandard torsion theories in which torsion can be generated by macroscopic rotating objects. In the spirit of action=reaction, if a rotating mass like a planet can generate torsion, then a gyroscope would be expected to feel torsion. An experiment with a gyroscope (without nuclear spin) suchmore » as Gravity Probe B (GPB) can test theories where this is the case. Using symmetry arguments, we show that to lowest order, any torsion field around a uniformly rotating spherical mass is determined by seven dimensionless parameters. These parameters effectively generalize the parametrized post-Newtonian formalism and provide a concrete framework for further testing Einstein's general theory of relativity (GR). We construct a parametrized Lagrangian that includes both standard torsion-free GR and Hayashi-Shirafuji maximal torsion gravity as special cases. We demonstrate that classic solar system tests rule out the latter and constrain two observable parameters. We show that Gravity Probe B is an ideal experiment for further constraining nonstandard torsion theories, and work out the most general torsion-induced precession of its gyroscope in terms of our torsion parameters.« less

Enhanced photocurrent in engineered bacteriorhodopsin monolayer.

PubMed

Patil, Amol V; Premaruban, Thenhuan; Berthoumieu, Olivia; Watts, Anthony; Davis, Jason J

2012-01-12

The integration of the transmembrane protein bacteriorhodopsin (BR) with man-made electrode surfaces has attracted a great deal of interest for some two decades or more and holds significant promise from the perspective of derived photoresponse or energy capture interfaces. Here we demonstrate that a novel and strategically engineered cysteine site (M163C) can be used to intimately and effectively couple delipidated BR to supporting metallic electrode surfaces. By virtue of the combined effects of the greater surface molecular density afforded by delipidation, and the vicinity of the electrostatic changes associated with proton pumping to the transducing metallic continuum, the resulting films generate a considerably greater photocurrent density on wavelength-selective illumination than previously achievable with monolayers of BR. Given the uniquely photoresponsive, wavelength-selective, and photostable characteristics of this protein, the work has implications for utilization in solar energy capture and photodetector devices.

Forster Resonance Energy Transfer Between Core/Shell Quantum Dots and Bacteriorhodopsin

DTIC Science & Technology

2012-01-01

through 1 -ethyl- 3 -( 3 - dimethylaminopropyl ) carbodiimide hydrochloride (EDC) linker techniques. An amide linkage between the carboxyl- QD and bR amino...Förster Resonance Energy Transfer between Core/Shell QuantumDots and Bacteriorhodopsin Mark H. Griep, 1 , 2, 3 Eric M.Winder,2, 4 Donald R. Lueking,2, 4...failing to comply with a collection of information if it does not display a currently valid OMB control number. 1 . REPORT DATE 2012 2. REPORT TYPE 3

Catalytical Photocyclization of Arylamines with a-Olefins in the Synthesis of 2-Alkylquinoline

ERIC Educational Resources Information Center

Makhmutov, Aynur; Usmanov, Salavat; Mustafin, Ahat

2016-01-01

The article deals with the results of investigation of the process of catalytical photocyclization of aniline and aniline hydrochloride with a-olefins (hexene-1, heptene-1 and octene-1). The following compounds of d- and f-metals are tested as probable catalysts: CuSO4•5H2O, EuCl3•6H2O, PrCl3•6H2O, TbCl3•6H2O, La2O3, MnO2, NiSO4•6H2O, NiCl2•6H2O,…

Formation of M-Like Intermediates in Proteorhodopsin in Alkali Solutions (pH ≥ ∼8.5) Where the Proton Release Occurs First in Contrast to the Sequence at Lower pH.

PubMed

Tamogami, Jun; Sato, Keitaro; Kurokawa, Sukuna; Yamada, Takumi; Nara, Toshifumi; Demura, Makoto; Miyauchi, Seiji; Kikukawa, Takashi; Muneyuki, Eiro; Kamo, Naoki

2016-02-23

Proteorhodopsin (PR) is an outward light-driven proton pump observed in marine eubacteria. Despite many structural and functional similarities to bacteriorhodopsin (BR) in archaea, which also acts as an outward proton pump, the mechanism of the photoinduced proton release and uptake is different between two H(+)-pumps. In this study, we investigated the pH dependence of the photocycle and proton transfer in PR reconstituted with the phospholipid membrane under alkaline conditions. Under these conditions, as the medium pH increased, a blue-shifted photoproduct (defined as Ma), which is different from M, with a pKa of ca. 9.2 was produced. The sequence of the photoinduced proton uptake and release during the photocycle was inverted with the increase in pH. A pKa value of ca. 9.5 was estimated for this inversion and was in good agreement with the pKa value of the formation of Ma (∼ 9.2). In addition, we measured the photoelectric current generated by PRs attached to a thin polymer film at varying pH. Interestingly, increases in the medium pH evoked bidirectional photocurrents, which may imply a possible reversal of the direction of the proton movement at alkaline pH. On the basis of these findings, a putative photocycle and proton transfer scheme in PR under alkaline pH conditions was proposed.

Newton-Cartan gravity and torsion

NASA Astrophysics Data System (ADS)

Bergshoeff, Eric; Chatzistavrakidis, Athanasios; Romano, Luca; Rosseel, Jan

2017-10-01

We compare the gauging of the Bargmann algebra, for the case of arbitrary torsion, with the result that one obtains from a null-reduction of General Relativity. Whereas the two procedures lead to the same result for Newton-Cartan geometry with arbitrary torsion, the null-reduction of the Einstein equations necessarily leads to Newton-Cartan gravity with zero torsion. We show, for three space-time dimensions, how Newton-Cartan gravity with arbitrary torsion can be obtained by starting from a Schrödinger field theory with dynamical exponent z = 2 for a complex compensating scalar and next coupling this field theory to a z = 2 Schrödinger geometry with arbitrary torsion. The latter theory can be obtained from either a gauging of the Schrödinger algebra, for arbitrary torsion, or from a null-reduction of conformal gravity.

Efficient production and purification of functional bacteriorhodopsin with a wheat-germ cell-free system and a combination of Fos-choline and CHAPS detergents.

PubMed

Genji, Takahisa; Nozawa, Akira; Tozawa, Yuzuru

2010-10-01

Cell-free translation is one potential approach to the production of functional transmembrane proteins. We have now examined various detergents as supplements to a wheat-germ cell-free system in order to optimize the production and subsequent purification of a functional model transmembrane protein, bacteriorhodopsin. We found that Fos-choline and CHAPS detergents counteracted each other's inhibitory effects on cell-free translation activity and thereby allowed the efficient production and subsequent purification of functional bacteriorhodopsin in high yield. Copyright © 2010 Elsevier Inc. All rights reserved.

A three-dimensional movie of structural changes in bacteriorhodopsin.

PubMed

Nango, Eriko; Royant, Antoine; Kubo, Minoru; Nakane, Takanori; Wickstrand, Cecilia; Kimura, Tetsunari; Tanaka, Tomoyuki; Tono, Kensuke; Song, Changyong; Tanaka, Rie; Arima, Toshi; Yamashita, Ayumi; Kobayashi, Jun; Hosaka, Toshiaki; Mizohata, Eiichi; Nogly, Przemyslaw; Sugahara, Michihiro; Nam, Daewoong; Nomura, Takashi; Shimamura, Tatsuro; Im, Dohyun; Fujiwara, Takaaki; Yamanaka, Yasuaki; Jeon, Byeonghyun; Nishizawa, Tomohiro; Oda, Kazumasa; Fukuda, Masahiro; Andersson, Rebecka; Båth, Petra; Dods, Robert; Davidsson, Jan; Matsuoka, Shigeru; Kawatake, Satoshi; Murata, Michio; Nureki, Osamu; Owada, Shigeki; Kameshima, Takashi; Hatsui, Takaki; Joti, Yasumasa; Schertler, Gebhard; Yabashi, Makina; Bondar, Ana-Nicoleta; Standfuss, Jörg; Neutze, Richard; Iwata, So

2016-12-23

Bacteriorhodopsin (bR) is a light-driven proton pump and a model membrane transport protein. We used time-resolved serial femtosecond crystallography at an x-ray free electron laser to visualize conformational changes in bR from nanoseconds to milliseconds following photoactivation. An initially twisted retinal chromophore displaces a conserved tryptophan residue of transmembrane helix F on the cytoplasmic side of the protein while dislodging a key water molecule on the extracellular side. The resulting cascade of structural changes throughout the protein shows how motions are choreographed as bR transports protons uphill against a transmembrane concentration gradient. Copyright © 2016, American Association for the Advancement of Science.

The Effects of Torsional Preloading on the Torsional Resistance of Nickel-titanium Instruments.

PubMed

Oh, Seung-Hei; Ha, Jung-Hong; Kwak, Sang Won; Ahn, Shin Wook; Lee, WooCheol; Kim, Hyeon-Cheol

2017-01-01

This study evaluated the effect of torsional preloading on the torsional resistance of nickel-titanium (NiTi) endodontic instruments. WaveOne Primary (Dentsply Maillefer, Ballaigues, Switzerland) and ProTaper Universal F2 (Dentsply Maillefer) files were used. The ultimate torsional strength until fracture was determined for each instrument. In the phase 1 experiment, the ProTaper and WaveOne files were loaded to have a maximum load from 2.0 up to 2.7 or 2.8 Ncm, respectively. In the phase 2 experiment, the number of repetitions of preloading for each file was increased from 50 to 200, whereas the preloading torque was fixed at 2.4 Ncm. Using torsionally preloaded specimens from phase 1 and 2, the torsional resistances were calculated to determine the ultimate strength, distortion angle, and toughness. The results were analyzed using 1-way analysis of variance and Duncan post hoc comparison. The fracture surfaces and longitudinal aspect of 5 specimens per group were examined under a scanning electron microscope. All preloaded groups showed significantly higher ultimate strength than the unpreloaded groups (P < .05). There was no significant difference among all groups for distortion angle and toughness. Although WaveOne had no significant difference between the repetition groups for ultimate strength, fracture angle, and toughness, ProTaper had a higher distortion angle and toughness in the 50-repetition group compared with the other repetition groups (P < .05). Scanning electron microscopic examinations of the fractured surface showed typical features of torsional fracture. Torsional preloading within the ultimate values could enhance the torsional strength of NiTi instruments. The total energy until fracture was maintained constantly, regardless of the alloy type. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Torsion and buckling of open sections

NASA Technical Reports Server (NTRS)

Wagner, H; Pretschner, W

1936-01-01

Following an abstract of the well-known theory of torsion in compression, the writers give directions for the practical calculation of the values of C(sub BT) (resistance to flexure and torsion) and i(sub SP(exp 2)), which determine the torsion. The second part treats the experiments in support of the theory of torsion of plain and flanged angle sections.

Hydrogen exchange mass spectrometry of bacteriorhodopsin reveals light-induced changes in the structural dynamics of a biomolecular machine.

PubMed

Pan, Yan; Brown, Leonid; Konermann, Lars

2011-12-21

Many proteins act as molecular machines that are fuelled by a nonthermal energy source. Examples include transmembrane pumps and stator-rotor complexes. These systems undergo cyclic motions (CMs) that are being driven along a well-defined conformational trajectory. Superimposed on these CMs are thermal fluctuations (TFs) that are coupled to stochastic motions of the solvent. Here we explore whether the TFs of a molecular machine are affected by the occurrence of CMs. Bacteriorhodopsin (BR) is a light-driven proton pump that serves as a model system in this study. The function of BR is based on a photocycle that involves trans/cis isomerization of a retinal chromophore, as well as motions of transmembrane helices. Hydrogen/deuterium exchange (HDX) mass spectrometry was used to monitor the TFs of BR, focusing on the monomeric form of the protein. Comparative HDX studies were conducted under illumination and in the dark. The HDX kinetics of BR are dramatically accelerated in the presence of light. The isotope exchange rates and the number of backbone amides involved in EX2 opening transitions increase roughly 2-fold upon illumination. In contrast, light/dark control experiments on retinal-free protein produced no discernible differences. It can be concluded that the extent of TFs in BR strongly depends on photon-driven CMs. The light-induced differences in HDX behavior are ascribed to protein destabilization. Specifically, the thermodynamic stability of the dark-adapted protein is estimated to be 5.5 kJ mol(-1) under the conditions of our work. This value represents the free energy difference between the folded state F and a significantly unfolded conformer U. Illumination reduces the stability of F by 2.2 kJ mol(-1). Mechanical agitation caused by isomerization of the chromophore is transferred to the surrounding protein scaffold, and subsequently, the energy dissipates into the solvent. Light-induced retinal motions therefore act analogously to an internal heat

Resonance Raman spectra of bacteriorhodopsin's primary photoproduct: evidence for a distorted 13-cis retinal chromophore.

PubMed Central

Braiman, M; Mathies, R

1982-01-01

We have obtained the resonance Raman spectrum of bacteriorhodopsin's primary photoproduct K with a novel low-temperature spinning sample technique. Purple membrane at 77 K is illuminated with spatially separated actinic (pump) and probe laser beams. The 514-nm pump beam produces a photostationary steady-state mixture of bacteriorhodopsin and K. This mixture is then rotated through the red (676 nm) probe beam, which selectively enhances the Raman scattering from K. The essential advantage of our successive pump-and-probe technique is that it prevents the fluorescence excited by the pump beam from masking the red probe Raman scattering. K exhibits strong Raman lines at 1516, 1294, 1194, 1012, 957, and 811 cm-1. The effects of C15 deuteration on K's fingerprint lines correlate well with those seen in 13-cis model compounds, indicating that K has a 13-cis chromophore. However, the presence of unusually strong "low-wavenumber" lines at 811 and 957 cm-1, attributable to hydrogen out-of-plane wags, indicates that the protein holds the chromophore in a distorted conformation after trans leads to cis isomerization. PMID:6281770

Isolated penile torsion in newborns.

PubMed

Eroglu, Egemen; Gundogdu, Gokhan

2015-01-01

We reported on the incidence of isolated penile torsion among our healthy children and our approach to this anomaly. Between 2011 and 2014, newborn babies with penile torsion were classified according to the angle of torsion. Surgical correction (penile degloving and reattachment for moderate cases and dorsal dartos flap technique in case of resistance) after 6 months was advised to the babies with rotations more than 45°. Among 1000 newborn babies, 200 isolated penile torsions were found, and among these, 43 had torsions more than 45°, and 4 of these had angles greater than 90°. The mean angle of the rotations was found 30.45° (median: 20°). In total, 8 children with 60° torsions were previously circumcised. Surgery was performed on 19 patients, with a mean patient age of 12 ± 2 months. Of these 19, 13 babies were corrected with degloving and reattachment. This technique was not enough on the remaining 6 patients; therefore, derotational dorsal dartos flap was added to correct the torsion. After a mean of 15.6 ± 9.8 months, residual penile rotation, less than 15°, was found only in 2 children. The incidence of isolated penile torsion is 20% in newborns. However, rotation more than 45° angles are seen in 4.3% of male babies. Correction is not necessary in mild degrees, and penile degloving with reattachment is enough in most cases. If the initial correction is insufficient, dorsal dartos flap rotation is easy and effective. Prior circumcision neither disturbs the operative procedure nor affects the outcomes.

Development of a simple computerized torsion test to quantify subjective ocular torsion.

PubMed

Kim, Y D; Yang, H K; Hwang, J-M

2017-11-01

PurposeThe double Maddox-rod test (DMRT) and Lancaster red-green test (LRGT) are the most widely used tests worldwide to assess subjective ocular torsion. However, these tests require equipment and the quantified results of ocular torsion are only provided in rough values. Here we developed a novel computerized torsion test (CTT) for individual assessment of subjective ocular torsion and validated the reliability and accuracy of the test compared with those of the DMRT and LRGT.MethodsA total of 30 patients with cyclovertical strabismus and 30 controls were recruited. The CTT was designed using Microsoft Office PowerPoint. Subjects wore red-green filter spectacles and viewed gradually tilted red and cyan lines on an LCD monitor and pressed the keyboard to go through the slides, until both lines seemed parallel. All subjects underwent the CTT, DMRT, and LRGT. Intraclass correlation coefficients and Bland-Altman plots were analyzed to assess the acceptability of the CTT compared with that of the DMRT.ResultsBoth the DMRT and CTT showed no significant test-retest differences in the strabismus and control groups. The DMRT and CTT results demonstrated an acceptable agreement. The reliability of the CTT was better than that of the DMRT. The LRGT showed low sensitivity for the detection of ocular torsion compared with the DMRT (40.0%) and CTT (39.1%).ConclusionOur results suggest that the assessment of subjective ocular torsion using the CTT based on PowerPoint software is simple, reproducible, and accurate and can be applied in clinical practice.

Inter-study reproducibility of left ventricular torsion and torsion rate quantification using MR myocardial feature tracking.

PubMed

Kowallick, Johannes T; Morton, Geraint; Lamata, Pablo; Jogiya, Roy; Kutty, Shelby; Lotz, Joachim; Hasenfuß, Gerd; Nagel, Eike; Chiribiri, Amedeo; Schuster, Andreas

2016-01-01

To determine the inter-study reproducibility of MR feature tracking (MR-FT) derived left ventricular (LV) torsion and torsion rates for a combined assessment of systolic and diastolic myocardial function. Steady-state free precession (SSFP) cine LV short-axis stacks were acquired at 9:00 (Exam A), 9:30 (Exam B), and 14:00 (Exam C) in 16 healthy volunteers at 3 Tesla. SSFP images were analyzed offline using MR-FT to assess rotational displacement in apical and basal slices. Global peak torsion, peak systolic and peak diastolic torsion rates were calculated using different definitions ("twist", "normalized twist" and "circumferential-longitudinal (CL) shear angle"). Exam A and B were compared to assess the inter-study reproducibility. Morning and afternoon scans were compared to address possible diurnal variation. The different methods showed good inter-study reproducibility for global peak torsion (intraclass correlation coefficient [ICC]: 0.90-0.92; coefficient of variation [CoV]: 19.0-20.3%) and global peak systolic torsion rate (ICC: 0.82-0.84; CoV: 25.9-29.0%). Conversely, global peak diastolic torsion rate showed little inter-study reproducibility (ICC: 0.34-0.47; CoV: 40.8-45.5%). Global peak torsion as determined by the CL shear angle showed the best inter-study reproducibility (ICC: 0.90;CoV: 19.0%). MR-FT results were not measurably affected by diurnal variation between morning and afternoon scans (CL shear angle: 4.8 ± 1.4°, 4.8 ± 1.5°, and 4.1 ± 1.6° for Exam A, B, and C, respectively; P = 0.21). MR-FT based derivation of myocardial peak torsion and peak systolic torsion rate has high inter-study reproducibility as opposed to peak diastolic torsion rate. The CL shear angle was the most reproducible parameter independently of cardiac anatomy and may develop into a robust tool to quantify cardiac rotational mechanics in longitudinal MR-FT patient studies. © 2015 Wiley Periodicals, Inc.

Bacteriorhodopsin films for optical signal processing and data storage

NASA Technical Reports Server (NTRS)

Walkup, John F. (Principal Investigator); Mehrl, David J. (Principal Investigator)

1996-01-01

This report summarizes the research results obtained on NASA Ames Grant NAG 2-878 entitled 'Investigations of Bacteriorhodopsin Films for Optical Signal Processing and Data Storage.' Specifically we performed research, at Texas Tech University, on applications of Bacteriorhodopisin film to both (1) dynamic spatial filtering and (2) holographic data storage. In addition, measurements of the noise properties of an acousto-optical matrix-vestor multiplier built for NASA Ames by Photonic Systems Inc. were performed at NASA Ames' Photonics Laboratory. This research resulted in two papers presented at major optical data processing conferences and a journal paper which is to appear in APPLIED OPTICS. A new proposal for additional BR research has recently been submitted to NASA Ames Research Center.

Torsional Tribological Behavior and Torsional Friction Model of Polytetrafluoroethylene against 1045 Steel

PubMed Central

Wang, Shibo; Niu, Chengchao

2016-01-01

In this work, the plane-on-plane torsional fretting tribological behavior of polytetrafluoroethylene (PTFE) was studied. A model of a rigid, flat-ended punch acting on an elastic half-space was built according to the experimental conditions. The results indicate that the shape of T–θ curves was influenced by both the torsional angle and the normal load. The torsion friction torque and wear rate of PTFE exponentially decreased when the torsion angle rose. The torsional torque increased from 0.025 N·m under a normal load of 43 N to 0.082 N·m under a normal load of 123 N. With sequentially increasing normal load, the value of torque was maintained. With rising normal load, the wear mass loss of PTFE disks was increased and the wear rate was decreased. Good agreement was found with the calculated torque according to the model and the experimental torque except for that under a normal load of 163 N. The difference under a normal load of 163 N was caused by the coefficient of friction. Usually the coefficient of friction of a polymer decreases with increasing normal load, whereas a constant coefficient of friction was applied in the model. PMID:26799324

Directed evolution of bacteriorhodopsin for applications in bioelectronics

PubMed Central

Wagner, Nicole L.; Greco, Jordan A.; Ranaghan, Matthew J.; Birge, Robert R.

2013-01-01

In nature, biological systems gradually evolve through complex, algorithmic processes involving mutation and differential selection. Evolution has optimized biological macromolecules for a variety of functions to provide a comparative advantage. However, nature does not optimize molecules for use in human-made devices, as it would gain no survival advantage in such cooperation. Recent advancements in genetic engineering, most notably directed evolution, have allowed for the stepwise manipulation of the properties of living organisms, promoting the expansion of protein-based devices in nanotechnology. In this review, we highlight the use of directed evolution to optimize photoactive proteins, with an emphasis on bacteriorhodopsin (BR), for device applications. BR, a highly stable light-activated proton pump, has shown great promise in three-dimensional optical memories, real-time holographic processors and artificial retinas. PMID:23676894

Millitesla magnetic field effects on the photocycle of an animal cryptochrome

NASA Astrophysics Data System (ADS)

Sheppard, Dean M. W.; Li, Jing; Henbest, Kevin B.; Neil, Simon R. T.; Maeda, Kiminori; Storey, Jonathan; Schleicher, Erik; Biskup, Till; Rodriguez, Ryan; Weber, Stefan; Hore, P. J.; Timmel, Christiane R.; MacKenzie, Stuart R.

2017-02-01

Drosophila have been used as model organisms to explore both the biophysical mechanisms of animal magnetoreception and the possibility that weak, low-frequency anthropogenic electromagnetic fields may have biological consequences. In both cases, the presumed receptor is cryptochrome, a protein thought to be responsible for magnetic compass sensing in migratory birds and a variety of magnetic behavioural responses in insects. Here, we demonstrate that photo-induced electron transfer reactions in Drosophila melanogaster cryptochrome are indeed influenced by magnetic fields of a few millitesla. The form of the protein containing flavin and tryptophan radicals shows kinetics that differ markedly from those of closely related members of the cryptochrome-photolyase family. These differences and the magnetic sensitivity of Drosophila cryptochrome are interpreted in terms of the radical pair mechanism and a photocycle involving the recently discovered fourth tryptophan electron donor.

Pathways of proton transfer in the light-driven pump bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1993-01-01

The mechanism of proton transport in the light-driven pump bacteriorhodopsin is beginning to be understood. Light causes the all-trans to 13-cis isomerization of the retinal chromophore. This sets off a sequential and directed series of transient decreases in the pKa's of a) the retinal Schiff base, b) an extracellular proton release complex which includes asp-85, and c) a cytoplasmic proton uptake complex which includes asp-96. The timing of these pKa changes during the photoreaction cycle causes sequential proton transfers which result in the net movement of a proton across the protein, from the cytoplasmic to the extracellular surface.

Intermittent Ovarian Torsion in Pregnancy

PubMed Central

Young, Randall; Cork, Kelly

2017-01-01

Ovarian torsion during pregnancy is a fairly uncommon complication with a high patient morbidity and fetal mortality if not immediately treated. Ovarian torsion should be considered a clinical diagnosis, and a high level of clinical suspicion is needed by the practitioner to ensure that this diagnosis is not missed. We present an unusual case of intermittent ovarian torsion discussing both the presentation and the operative and post-operative management. PMID:29849404

Low-power bacteriorhodopsin-silicon n-channel metal-oxide field-effect transistor photoreceiver.

PubMed

Shin, Jonghyun; Bhattacharya, Pallab; Yuan, Hao-Chih; Ma, Zhenqiang; Váró, György

2007-03-01

A bacteriorhodopsin (bR)-silicon n-channel metal-oxide field-effect transistor (NMOSFET) monolithically integrated photoreceiver is demonstrated. The bR film is selectively formed on an external gate electrode of the transistor by electrophoretic deposition. A modified biasing circuit is incorporated, which helps to match the resistance of the bR film to the input impedance of the NMOSFET and to shift the operating point of the transistor to coincide with the maximum gain. The photoreceiver exhibits a responsivity of 4.7 mA/W.

Progress toward an explicit mechanistic model for the light-driven pump, bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1999-01-01

Recent crystallographic information about the structure of bacteriorhodopsin and some of its photointermediates, together with a large amount of spectroscopic and mutational data, suggest a mechanistic model for how this protein couples light energy to the translocation of protons across the membrane. Now nearing completion, this detailed molecular model will describe the nature of the steric and electrostatic conflicts at the photoisomerized retinal, as well as the means by which it induces proton transfers in the two half-channels leading to the two membrane surfaces, thereby causing unidirectional, uphill transport.

Critical current degradation behaviour of GdBCO CC tapes in pure torsion and combined tension-torsion modes

NASA Astrophysics Data System (ADS)

Gorospe, Alking; Bautista, Zhierwinjay; Shin, Hyung-Seop

2016-10-01

Coated conductor (CC) tapes utilized in high-current-density superconducting cables are commonly subjected to different loading modes, primarily torsion and tension especially in the case of twisted stacked-tape cable. Torsion load can occur due to twisting along the length or when winding the CC tapes around a former, while tension load can occur due to pre-tension when coiled and as a hoop stress when the coil is energized. In this study, electromechanical properties of single CC tapes under torsion load were investigated using a new test apparatus. The results could provide basic information for cable designers to fully characterize stacked cables. Copper-electroplated and brass-laminated CC tapes fabricated with different deposition techniques were subjected to pure torsion and combined tension-torsion loading. The critical current, I c degradation behaviours of CC tapes under torsional deformation were examined. Also, the effect of further external lamination on the I c degradation behaviour of the CC tapes under such loading conditions was investigated. In the case of the combined tension-torsion test, short samples were subjected to twist pitches of 200 mm and 100 mm. Critical parameters including reversible axial stress and strain in such twist pitch conditions were also investigated.

[The adnexal torsion in children].

PubMed

Khemakhem, Rachid; Barhoumi, Amel; Matoussi, Nadia; Hidouri, Saida; Ghorbel, Sofiane; Nouira, Faouzi; Jlidi, Said; Ben Becheur, Saida; Chaouachi, Béji

2008-05-01

Adnexal torsion is the most frequent gynaecological emergency in children. It requires an early diagnosis and an urgent surgical treatment. to study the clinical, paraclinical and therapeutic aspect of adnexal torsion in paediatric population. This is a retrospective review of nine girls with the diagnosis of ovarian torsion observed over a 7 years period (January 1999 to December 2005). The average age is 9 years (extreme 6 to 13 years). This pathology was located in 5 cases on the right side and in 3 cases on the left side; a case of bilateral torsion of poly-cystic ovary was encountered in a girl with down syndrome. Clinical presentation is made in all the cases by abdominal pains and vomiting. The disorders of the transit and the urinary signs are associated in 3 and 2 cases respectively, the clinical examination objectified a pelvic defense in all the cases and an abdominal mass in 2 cases. Pelvic ultra-sonography was made in 6 observations and give the diagnosis of torsion of the ovary in 4 cases, whereas it was doubtful in the 2 remaining cases when an ovarian mass was observed. In the 3 remaining cases, this examination was not performed since one the diagnosis of acute appendicitis was retained and the patient operated in emergency. All the children of our series were operated; in 1/3 of the cases we found a necrosis of the ovary. 4 cases out of 9 present a torsion on pathologic ovary (cyst, dysplasia), whereas in the 5 remaining cases, we noted a torsion on healthy ovary. 4 young girls have undergoes a annexectomy, of which one was bilateral. The evolution was favorable in all the cases. Adnexal torsion is a surgical emergency that need an early diagnosis and management to preserve ovarian function in girls and Doppler sonography every must be done every time there is a pelvic pain without fever in girls

Structural changes due to the deprotonation of the proton release group in the M-photointermediate of bacteriorhodopsin as revealed by time-resolved FTIR spectroscopy.

PubMed

Morgan, Joel E; Vakkasoglu, Ahmet S; Lugtenburg, Johan; Gennis, Robert B; Maeda, Akio

2008-11-04

One of the steps in the proton pumping cycle of bacteriorhodopsin (BR) is the release of a proton from the proton-release group (PRG) on the extracellular side of the Schiff base. This proton release takes place shortly after deprotonation of the Schiff base (L-to-M transition) and results in an increase in the pKa of Asp85, which is a crucial mechanistic step for one-way proton transfer for the entire photocycle. Deprotonation of the PRG can also be brought about without photoactivation, by raising the pH of the enzyme (pKa of PRG; approximately 9). Thus, comparison of the FTIR difference spectrum for formation of the M intermediate (M minus initial unphotolyzed BR state) at pH 7 to the corresponding spectrum generated at pH 10 may reveal structural changes specifically associated with deprotonation of the PRG. Vibrational bands of BR that change upon M formation are distributed across a broad region between 2120 and 1685 cm(-1). This broad band is made up of two parts. The band above 1780 cm(-1), which is insensitive to C15-deuteration of the retinal, may be due to a proton delocalized in the PRG. The band between 1725 and 1685 cm(-1), on the lower frequency side of the broad band, is sensitive to C15-deuteration. This band may arise from transition dipole coupling of the vibrations of backbone carbonyl groups in helix G with the side chain of Tyr57 and with the C15H of the Schiff base. In M, these broad bands are abolished, and the 3657 cm(-1) band, which is due to the disruption of the hydrogen bonding of a water molecule, probably with Arg82, appears. Loss of the interaction of the backbone carbonyl groups in helix G with Tyr57 and the Schiff base, and separation of Tyr57 from Arg82, may be causes of these spectral changes, leading to the stabilization of the protonated Asp85 in M.

Torsional ultrasound mode versus combined torsional and conventional ultrasound mode phacoemulsification for eyes with hard cataract.

PubMed

Fakhry, Mohamed A; El Shazly, Malak I

2011-01-01

To compare torsional versus combined torsional and conventional ultrasound modes in hard cataract surgery regarding ultrasound energy and time and effect on corneal endothelium. Kasr El Aini hospital, Cairo University, and International Eye Hospital, Cairo, Egypt. Ninety-eight eyes of 63 patients were enrolled in this prospective comparative randomized masked clinical study. All eyes had nuclear cataracts of grades III and IV using the Lens Opacities Classification System III (LOCS III). Two groups were included, each having an equal number of eyes (49). The treatment for group A was combined torsional and conventional US mode phacoemulsification, and for group B torsional US mode phacoemulsification only. Pre- and post-operative assessments included best corrected visual acuity (BCVA), intraocular pressure (IOP), slit-lamp evaluation, and fundoscopic evaluation. Endothelial cell density (ECD) and central corneal thickness (CCT) were measured preoperatively, 1 day, 7 days, and 1 month postoperatively. All eyes were operated on using the Alcon Infiniti System (Alcon, Fort Worth, TX) with the quick chop technique. All eyes were implanted with AcrySof SA60AT (Alcon) intraocular lens (IOL). The main phaco outcome parameters included the mean ultrasound time (UST), the mean cumulative dissipated energy (CDE), and the percent of average torsional amplitude in position 3 (%TUSiP3). Improvement in BCVA was statistically significant in both groups (P < 0.001). Comparing UST and CDE for both groups revealed results favoring the pure torsional group (P = 0.002 and P < 0.001 for UST; P = 0.058 and P = 0.009 for CDE). As for %TUSiP3, readings were higher for the pure torsional group (P = 0.03 and P = 0.01). All changes of CCT, and ECD over time were found statistically significant using one-way ANOVA testing (P < 0.001). Both modes are safe in hard cataract surgery, however the pure torsional mode showed less US energy used.

Tibiotalar torsion: bioengineering paradigm.

PubMed

Michele, A A; Nielsen, P M

1976-10-01

1. Medial tibiotalar torsion is the most common disorder peculiar to mankind. 2. The pathogonomic findings are (a) an axial medially rotated and adducted distal third of the shaft of the tibia, (b) the plafond of the tibia with its mortise containing the "track-bound" talus, which is deflected strongly toward the tibial side, (c) an exaggerated midtarsal equinus, (d) ostensible restriction of dorsiflexion of the hindfoot against the tibia, (e) mild separation of the distal tibiofibular articulation, and (f) forward displacement of the gravitational axis to the naviculocunei-form joint. 3. Faulty leg crossing in utero resulting in an abnormal pelvofemoral-tibial design is discussed and its important consequences in the vulnerable 40 per cent of the population are emphasized. 4. The kinesiomechanics of the leg, ankle and foot is reviewed. 5. The radiographic parameters of medial tibiotalar torsion are presented, as well as the multiple facets of the clinical examination. 6. Methods of treatment depending on age and severity of the disorder are recommended. Surgery, detortional casts, and corrective footwear are discussed. Shoes presently available are inadequate for tibiotalar torsion and therefore engineering principles must be applied in the design and construction of all footwear, including sneakers and sportswear. This can be done only if the pathological biomechanics of this group of disorders is recognized. Biplane proximal tibial osteotomy is recommended in refractory cases, especially when tibiotalar torsion is demonstrated. 7. After 30 years of experience, the author finds that results with these patients have been uniformly good to excellent, depending on age and mode of treatment. 8. In medial tibiotalar torsion, the consequent adaptive changes are readily observed, but rarely are they recognized as the inevitable sequelae of medial tibiotalar torsion. 9. Adaptive compensating disorders are identified and their mechanism described. 10. The management of

Picosecond molecular motions in bacteriorhodopsin from neutron scattering.

PubMed Central

Fitter, J; Lechner, R E; Dencher, N A

1997-01-01

The characteristics of internal molecular motions of bacteriorhodopsin in the purple membrane have been studied by quasielastic incoherent neutron scattering. Because of the quasihomogeneous distribution of hydrogen atoms in biological molecules, this technique enables one to study a wide variety of intramolecular motions, especially those occurring in the picosecond to nanosecond time scale. We performed measurements at different energy resolutions with samples at various hydration levels within a temperature range of 10-300 K. The analysis of the data revealed a dynamical transition at temperatures Td between 180 K and 220 K for all motions resolved at time scales ranging from 0.1 to a few hundred picoseconds. Whereas below Td the motions are purely vibrational, they are predominantly diffusive above Td, characterized by an enormously broad distribution of correlation times. The variation of the hydration level, on the other hand, mainly affects motions slower than a few picoseconds. PMID:9336208

Inverse problems for torsional modes.

USGS Publications Warehouse

Willis, C.

1984-01-01

Considers a spherically symmetric, non-rotating Earth consisting of an isotropic, perfect elastic material where the density and the S-wave velocity may have one or two discontinuities in the upper mantle. Shows that given the velocity throughout the mantle and the crust and given the density in the lower mantle, then the freqencies of the torsional oscillations of one angular order (one torsional spectrum), determine the density in the upper mantle and in the crust uniquely. If the velocity is known only in the lower mantle, then the frequencies of the torsional oscillations of two angular orders uniquely determine both the density and the velocity in the upper mantle and in the crust. In particular, the position and size of the discontinuities in the density and velocity are uniquely determined by two torsional spectra.-Author

Optically probing torsional superelasticity in spider silks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Bhupesh; Thakur, Ashish; Panda, Biswajit

2013-11-11

We investigate torsion mechanics of various spider silks using a sensitive optical technique. We find that spider silks are torsionally superelastic in that they can reversibly withstand great torsion strains of over 10{sup 2−3} rotations per cm before failure. Among various silks from a spider, we find the failure twist-strain is greatest in the sticky capture silk followed by dragline and egg-case silk. Our in situ laser-diffraction measurements reveal that torsional strains on the silks induce a nano-scale transverse compression in its diameter that is linear and reversible. These unique torsional properties of the silks could find applications in silk-basedmore » materials and devices.« less

Investigation of the torsional stiffness of flexible disc coupling

NASA Astrophysics Data System (ADS)

Buryy, A.; Simonovsky, V.; Obolonik, V.

2017-08-01

Calculation of flexible coupling torsional stiffness is required when analyzing the torsional vibrations of the reciprocating machinery train. While having the lowest torsional stiffness of all the elements of the train, flexible coupling has a significant influence on the natural frequencies of torsional vibration. However, considering structural complexity of coupling, precise definition of its torsional stiffness is quite a difficult task. The paper presents a method for calculating the torsional stiffness of flexible disc coupling based on the study of its finite element model response under the action of torque. The analysis of the basic parameters that quantitatively and qualitatively affect the coupling torsional stiffness has been also provided. The results of the calculation as well as model adequacy, sufficient for practical application, have been confirmed at the experimental measurement of flexible disc coupling torsional stiffness. The obtained elastic characteristics (dependences of applied torque and torsional stiffness versus twist angle) are nonlinear in the initial stage of loading. This feature should be taken into account when creating reliable mathematical models of torsional vibrations of reciprocating machinery trains containing flexible disc couplings.

Torsional Optomechanics of a Levitated Nonspherical Nanoparticle

NASA Astrophysics Data System (ADS)

Hoang, Thai M.; Ma, Yue; Ahn, Jonghoon; Bang, Jaehoon; Robicheaux, F.; Yin, Zhang-Qi; Li, Tongcang

2016-09-01

An optically levitated nanoparticle in vacuum is a paradigm optomechanical system for sensing and studying macroscopic quantum mechanics. While its center-of-mass motion has been investigated intensively, its torsional vibration has only been studied theoretically in limited cases. Here we report the first experimental observation of the torsional vibration of an optically levitated nonspherical nanoparticle in vacuum. We achieve this by utilizing the coupling between the spin angular momentum of photons and the torsional vibration of a nonspherical nanoparticle whose polarizability is a tensor. The torsional vibration frequency can be 1 order of magnitude higher than its center-of-mass motion frequency, which is promising for ground state cooling. We propose a simple yet novel scheme to achieve ground state cooling of its torsional vibration with a linearly polarized Gaussian cavity mode. A levitated nonspherical nanoparticle in vacuum will also be an ultrasensitive nanoscale torsion balance with a torque detection sensitivity on the order of 10-29 N m /√{Hz } under realistic conditions.

Methamphetamine use can mimic testicular torsion.

PubMed

Doherty, Michael H; Gerscovich, Eugenio O; Corwin, Michael T; Wilkendorf, Stephen R

2013-09-01

We report the case of a patient presenting with the classic clinical appearance of testicular torsion. Ultrasound showed testicular ischemia supporting the clinical diagnosis, but the lack of visualization of spermatic cord torsion was of concern. An attempt of clinical detorsion was considered unsuccessful and the patient was explored. No torsion was found. On postoperative review of the patient's medical history, we found methamphetamine use, with a positive urine test at the time of his emergent consultation for the scrotal pain episode. The use of amphetamines has been previously reported as the cause of ischemia of multiple organs, but we could not find previous reports of involvement of the testis mimicking torsion. Copyright © 2013 Wiley Periodicals, Inc.

Torsional ultrasound mode versus combined torsional and conventional ultrasound mode phacoemulsification for eyes with hard cataract

PubMed Central

Fakhry, Mohamed A; Shazly, Malak I El

2011-01-01

Purpose To compare torsional versus combined torsional and conventional ultrasound modes in hard cataract surgery regarding ultrasound energy and time and effect on corneal endothelium. Settings Kasr El Aini hospital, Cairo University, and International Eye Hospital, Cairo, Egypt. Methodology Ninety-eight eyes of 63 patients were enrolled in this prospective comparative randomized masked clinical study. All eyes had nuclear cataracts of grades III and IV using the Lens Opacities Classification System III (LOCS III). Two groups were included, each having an equal number of eyes (49). The treatment for group A was combined torsional and conventional US mode phacoemulsification, and for group B torsional US mode phacoemulsification only. Pre- and post-operative assessments included best corrected visual acuity (BCVA), intraocular pressure (IOP), slit-lamp evaluation, and fundoscopic evaluation. Endothelial cell density (ECD) and central corneal thickness (CCT) were measured preoperatively, 1 day, 7 days, and 1 month postoperatively. All eyes were operated on using the Alcon Infiniti System (Alcon, Fort Worth, TX) with the quick chop technique. All eyes were implanted with AcrySof SA60AT (Alcon) intraocular lens (IOL). The main phaco outcome parameters included the mean ultrasound time (UST), the mean cumulative dissipated energy (CDE), and the percent of average torsional amplitude in position 3 (%TUSiP3). Results Improvement in BCVA was statistically significant in both groups (P < 0.001). Comparing UST and CDE for both groups revealed results favoring the pure torsional group (P = 0.002 and P < 0.001 for UST; P = 0.058 and P = 0.009 for CDE). As for %TUSiP3, readings were higher for the pure torsional group (P = 0.03 and P = 0.01). All changes of CCT, and ECD over time were found statistically significant using one-way ANOVA testing (P < 0.001). Conclusion Both modes are safe in hard cataract surgery, however the pure torsional mode showed less US energy used. PMID

External torsion in a proximal tibia and internal torsion in a distal tibia occur independently in varus osteoarthritic knees compared to healthy knees.

PubMed

Mochizuki, Tomoharu; Tanifuji, Osamu; Koga, Yoshio; Hata, Ryosuke; Mori, Takahiro; Nishino, Katsutoshi; Sato, Takashi; Kobayashi, Koichi; Omori, Go; Sakamoto, Makoto; Tanabe, Yuji; Endo, Naoto

2017-05-01

The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees. In total, 61 limbs in 58 healthy subjects (age: 54 ± 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 ± 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis. The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p < 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group. The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees. Level Ⅲ. Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

Computational insights into the photocyclization of diclofenac in solution: effects of halogen and hydrogen bonding.

PubMed

Bani-Yaseen, Abdulilah Dawoud

2016-08-21

The effects of noncovalent interactions, namely halogen and hydrogen bonding, on the photochemical conversion of the photosensitizing drug diclofenac (DCF) in solution were investigated computationally. Both explicit and implicit solvent effects were qualitatively and quantitatively assessed employing the DFT/6-31+G(d) and SQM(PM7) levels of theory. Full geometry optimizations were performed in solution for the reactant DCF, hypothesized radical-based intermediates, and the main product at both levels of theories. Notably, in good agreement with previous experimental results concerning the intermolecular halogen bonding of DCF, the SQM(PM7) method revealed different values for d(ClO, Å) and ∠(C-ClO, °) for the two chlorine-substituents of DCF, with values of 2.63 Å/162° and 3.13 Å/142° for the trans and cis orientations, respectively. Employing the DFT/6-31+G(d) method with implicit solvent effects was not conclusive; however, explicit solvent effects confirmed the key contribution of hydrogen and halogen bonding in stabilizing/destabilizing the reactant and hypothesized intermediates. Interestingly, the obtained results revealed that a protic solvent such as water can increase the rate of photocyclization of DCF not only through hydrogen bonding effects, but also through halogen bonding. Furthermore, the atomic charges of atoms majorly involved in the photocyclization of DCF were calculated using different methods, namely Mulliken, Hirshfeld, and natural bond orbital (NBO). The obtained results revealed that in all cases there is a notable nonequivalency in the noncovalent intermolecular interactions of the two chlorine substituents of DCF and the radical intermediates with the solvent, which in turn may account for the discrepancy of their reactivity in different media. These computational results provide insight into the importance of halogen and hydrogen bonding throughout the progression of the photochemical conversion of DCF in solution.

Torsion balances with fibres of zero length

NASA Astrophysics Data System (ADS)

Speake, Clive C.; Collins, Christopher J.

2018-04-01

Torsion balances have good immunity to tilt and low rotational stiffness. However precise control of the position of the suspended torsion 'bob' is difficult in the presence of ground vibrations and tilt and this is a limiting factor in applications where Casimir forces or putative non-Newtonian short-range forces are being measured. We describe how the desirable characteristics of torsion balances can be reproduced in a rigid body that is suspended using applied forces rather than a torsion fibre. The suspension system can then provide a more precise control of the degrees of freedom of the suspended body. We apply these ideas to a superconducting levitated torsion balance, developed by the authors, and a generic electrostatic suspension. We present results of preliminary experiments that provide support for our analyses.

Association of Torsion With Testicular Cancer: A Retrospective Study.

PubMed

Uguz, Sami; Yilmaz, Sercan; Guragac, Ali; Topuz, Bahadır; Aydur, Emin

2016-02-01

Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported with the association of torsion in surgical specimens, and the published data remain scant on the association of torsion with testicular tumors. By retrospective medical record review, we identified 32 patients who had been diagnosed with testicular torsion, 20 of whom had undergone orchiectomy. Of these 20 patients, 2 were diagnosed with a malignancy. Our study, the largest case series to date, has shown an association between testicular torsion and testicular cancer of 6.4%. Testicular torsion is a medical emergency that usually requires surgical exploration. However, testicular malignancy has been anecdotally reported in association with torsion in surgical specimens. However, the published data remain scant on the association between torsion and the presence of testicular tumors. The present retrospective study explored the association between torsion and testicular cancer in patients with testicular torsion undergoing orchiectomy during scrotal exploration. A medical record review was performed of patients who had had a diagnosis of testicular torsion from January 2003 to February 2015. The clinicopathologic characteristics of the patients were recorded. A total of 32 patients were identified. Their mean age was 21.1 years (range, 7-39 years). All the patients had unilateral testicular torsion, which affected the left side in 17 and the right side in 15. Manual detorsion was successful in 6 patients, and 26 patients underwent emergency surgery with testicular detorsion (6 fixation surgery and 20 orchiectomy). The type of incision was scrotal in 6, inguinal in 10, and unspecified in 4. Pathologic examination of the orchiectomy specimens showed malignancy in 2 cases (seminoma and malign mixed germ cell tumor). To the best of our knowledge, the present single-center case series is the largest case series to date of

Green proteorhodopsin reconstituted into nanoscale phospholipid bilayers (nanodiscs) as photoactive monomers.

PubMed

Ranaghan, Matthew J; Schwall, Christine T; Alder, Nathan N; Birge, Robert R

2011-11-16

Over 4000 putative proteorhodopsins (PRs) have been identified throughout the oceans and seas of the Earth. The first of these eubacterial rhodopsins was discovered in 2000 and has expanded the family of microbial proton pumps to all three domains of life. With photophysical properties similar to those of bacteriorhodopsin, an archaeal proton pump, PRs are also generating interest for their potential use in various photonic applications. We perform here the first reconstitution of the minimal photoactive PR structure into nanoscale phospholipid bilayers (nanodiscs) to better understand how protein-protein and protein-lipid interactions influence the photophysical properties of PR. Spectral (steady-state and time-resolved UV-visible spectroscopy) and physical (size-exclusion chromatography and electron microscopy) characterization of these complexes confirms the preparation of a photoactive PR monomer within nanodiscs. Specifically, when embedded within a nanodisc, monomeric PR exhibits a titratable pK(a) (6.5-7.1) and photocycle lifetime (∼100-200 ms) that are comparable to the detergent-solubilized protein. These ndPRs also produce a photoactive blue-shifted absorbance, centered at 377 or 416 nm, that indicates that protein-protein interactions from a PR oligomer are required for a fast photocycle. Moreover, we demonstrate how these model membrane systems allow modulation of the PR photocycle by variation of the discoidal diameter (i.e., 10 or 12 nm), bilayer thickness (i.e., 23 or 26.5 Å), and degree of saturation of the lipid acyl chain. Nanodiscs also offer a highly stable environment of relevance to potential device applications.

Linking Regions between Helices in Bacteriorhodopsin Revealed

PubMed Central

Agard, David A.; Stroud, Robert M.

1982-01-01

Three-dimensional electron-microscopic structural analysis requires the combination of many different tilted views of the same specimen. The relative difficulty of tilting the sample to high angles >60° without introducing severe distortion due to different focal distances across the specimen entails that the observable range of electron diffraction data is often limited to this range of angles. Thus, it is generally not possible to observe the diffraction maxima that lie within the conical region of reciprocal space around the direction perpendicular to the electron microscope grid. The absence of data in this region leads to a predictable distortion in the object, and for ±60° tilting makes the resolution essentially twice as bad in the direction perpendicular to the grid as it is for the in-plane image. Constrained density map modification and refinement methods can significantly reduce these effects. A method has been developed, tested on model cases, and applied to the electron-microscopic structure determination of bacteriorhodopsin in order to visualize the location of linking regions between helices. Electron-microscopic structural analysis of bacteriorhodopsin (Henderson and Unwin. 1975 Nature [Lond.] 257:28-32.) showed that the molecule consists of seven rods of density each nearly spanning the lipid bilayer. Owing to the distortion introduced by the missing conical region of reciprocal space data, no density was visible for the polypeptide segments linking the α-helices. Density in the refined maps indicates the location of at least five of the extrahelical segments of the polypeptide. The total number of possible ways of interconnecting the helices is reduced from 7! (5,040) to the five most consistent possibilities without recourse to other considerations. In addition, the density for the helical regions is more uniform and cylindrical throughout their length, and the length of the helices increases from 35 to 45 Å, close to the membrane thickness

Some Properties and Uses of Torsional Overlap Integrals

NASA Astrophysics Data System (ADS)

Mekhtiev, Mirza A.; Hougen, Jon T.

1998-01-01

The first diagonalization step in a rho-axis-method treatment of methyl-top internal rotation problems involves finding eigenvalues and eigenvectors of a torsional Hamiltonian, which depends on the rotational projection quantum numberKas a parameter. Traditionally the torsional quantum numbervt= 0, 1, 2···is assigned to eigenfunctions of givenKin order of increasing energy. In this paper we propose an alternative labeling scheme, using the torsional quantum numbervT, which is based on properties of theK-dependent torsional overlap integrals . In particular, the quantum numbervTis assigned in such a way that torsional wavefunctions |vT,K> vary as slowly as possible whenKchanges by unity. Roughly speaking,vT=vtfor torsional levels below the barrier, whereasvTis more closely related to the free-rotor quantum number for levels above the barrier. Because of the latter fact, we believevTwill in general be a physically more meaningful torsional quantum number for levels above the barrier. The usefulness of overlap integrals for qualitative prediction of torsion-rotation band intensities and for rationalizing the magnitudes of perturbations involving some excitation of the small-amplitude vibrations in an internal rotor problem is also discussed.

Monolithically integrated bacteriorhodopsin/semiconductor opto-electronic integrated circuit for a bio-photoreceiver.

PubMed

Xu, J; Bhattacharya, P; Váró, G

2004-03-15

The light-sensitive protein, bacteriorhodopsin (BR), is monolithically integrated with an InP-based amplifier circuit to realize a novel opto-electronic integrated circuit (OEIC) which performs as a high-speed photoreceiver. The circuit is realized by epitaxial growth of the field-effect transistors, currently used semiconductor device and circuit fabrication techniques, and selective area BR electro-deposition. The integrated photoreceiver has a responsivity of 175 V/W and linear photoresponse, with a dynamic range of 16 dB, with 594 nm photoexcitation. The dynamics of the photochemical cycle of BR has also been modeled and a proposed equivalent circuit simulates the measured BR photoresponse with good agreement.

Testicular torsion

MedlinePlus

... Nelson Textbook of Pediatrics . 20th ed. Philadelphia, PA: Elsevier; 2016:chap 545. Ferri FF. Testicular torsion. In: ... FF, ed. Ferri's Clinical Advisor 2018 . Philadelphia, PA: Elsevier; 2017:1255-1255. Kryger JV. Acute and chronic ...

Torsional Carbon Nanotube Artificial Muscles

NASA Astrophysics Data System (ADS)

Foroughi, Javad; Spinks, Geoffrey M.; Wallace, Gordon G.; Oh, Jiyoung; Kozlov, Mikhail E.; Fang, Shaoli; Mirfakhrai, Tissaphern; Madden, John D. W.; Shin, Min Kyoon; Kim, Seon Jeong; Baughman, Ray H.

2011-10-01

Rotary motors of conventional design can be rather complex and are therefore difficult to miniaturize; previous carbon nanotube artificial muscles provide contraction and bending, but not rotation. We show that an electrolyte-filled twist-spun carbon nanotube yarn, much thinner than a human hair, functions as a torsional artificial muscle in a simple three-electrode electrochemical system, providing a reversible 15,000° rotation and 590 revolutions per minute. A hydrostatic actuation mechanism, as seen in muscular hydrostats in nature, explains the simultaneous occurrence of lengthwise contraction and torsional rotation during the yarn volume increase caused by electrochemical double-layer charge injection. The use of a torsional yarn muscle as a mixer for a fluidic chip is demonstrated.

Torsion Profiling of Proteins Using Magnetic Particles

PubMed Central

van Reenen, A.; Gutiérrez-Mejía, F.; van IJzendoorn, L.J.; Prins, M.W.J.

2013-01-01

We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 103 and 5 × 103 pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships. PMID:23473490

Attentional Modulation of Eye Torsion Responses

NASA Technical Reports Server (NTRS)

Stevenson, Scott B.; Mahadevan, Madhumitha S.; Mulligan, Jeffrey B.

2016-01-01

Eye movements generally have both reflexive and voluntary aspects, but torsional eye movements are usually thought of as a reflexive response to image rotation around the line of sight (torsional OKN) or to head roll (torsional VOR). In this study we asked whether torsional responses could be modulated by attention in a case where two stimuli rotated independently, and whether attention would influence the latency of responses. The display consisted of rear-projected radial "pinwheel" gratings, with an inner annulus segment extending from the center to 22 degrees eccentricity, and an outer annulus segment extending from 22 degrees out to 45 degrees eccentricity. The two segments rotated around the center in independent random walks, stepping randomly 4 degrees clockwise or counterclockwise at 60 Hz. Subjects were asked to attend to one or the other while keeping fixation steady at the center of the display. To encourage attention on one or the other segment of the display, subjects were asked to move a joystick in synchrony with the back and forth rotations of one part of the image while ignoring the other. Eye torsion was recorded with the scleral search coil technique, sampled at 500 Hz. All four subjects showed roughly 50% stronger torsion responses to the attended compared to unattended segments. Latency varied from 100 to 150 msec across subjects and was unchanged by attention. These findings suggest that attention can influence eye movement responses that are not typically under voluntary control.

Torsional oscillations of magnetized relativistic stars

NASA Astrophysics Data System (ADS)

Messios, Neophytos; Papadopoulos, Demetrios B.; Stergioulas, Nikolaos

2001-12-01

Strong magnetic fields in relativistic stars can be a cause of crust fracturing, resulting in the excitation of global torsional oscillations. Such oscillations could become observable in gravitational waves or in high-energy radiation, thus becoming a tool for probing the equation of state of relativistic stars. As the eigenfrequency of torsional oscillation modes is affected by the presence of a strong magnetic field, we study torsional modes in magnetized relativistic stars. We derive the linearized perturbation equations that govern torsional oscillations coupled to the oscillations of a magnetic field, when variations in the metric are neglected (Cowling approximation). The oscillations are described by a single two-dimensional wave equation, which can be solved as a boundary-value problem to obtain eigenfrequencies. We find that, in the non-magnetized case, typical oscillation periods of the fundamental l=2 torsional modes can be nearly a factor of 2 larger for relativistic stars than previously computed in the Newtonian limit. For magnetized stars, we show that the influence of the magnetic field is highly dependent on the assumed magnetic field configuration, and simple estimates obtained previously in the literature cannot be used for identifying normal modes observationally.

Ovarian torsion in a three-year-old girl.

PubMed

Ochsner, Todd Justin; Roos, Joel A; Johnson, Andrew S; Henderson, Janet L

2010-05-01

Ovarian torsion is the fifth most encountered gynecological emergency requiring surgery. Representing only 2.7% of surgical emergencies, it is an entity that is worth being familiar with in the emergency department (ED). Untreated ovarian torsion may result in loss of ovarian function, tissue necrosis, and death from thromboembolism or sepsis. Presenting with vague symptoms and abdominal pain, diagnosing ovarian torsion can be difficult, especially in children. The objective of this article is to present a case of pediatric ovarian torsion and to review its epidemiology, diagnosis, and treatment. A 3-year-old girl presented to the ED with vomiting, fever, anorexia, and abdominal pain. Initially diagnosed with appendicitis by physical examination and computed tomography scan, this patient was taken to the operating room for surgical exploration. The patient was subsequently found to have ovarian torsion, which was treated appropriately. Although a rare phenomenon, this case serves to increase awareness of the clinical presentation of ovarian torsion in the pediatric patient. Abdominal pain in the female child represents a challenging differential diagnosis, for which a physician must consider ovarian torsion. Copyright (c) 2010. Published by Elsevier Inc.

Multifunctional optical security features based on bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Hampp, Norbert A.; Neebe, Martin; Juchem, Thorsten; Wolperdinger, Markus; Geiger, Markus; Schmuck, Arno

2004-06-01

Bacteriorhodopsin (BR), a photochromic retinal protein, has been developed into a new materials platform for applications in anti-counterfeiting. The combination of three different properties of the material on its molecular level, a light-inducible color change, photochemical data storage and traceability of the protein due to molecular marker sequences make this protein a promising material for security applications. The crystalline structure of the biopigment combines these properties with high stability. As BR is a biological material specialized knowledge for modification, cost- effective production and suitable processing of the material is required. Photochromic BR-based inks have been developed for screen printing, pad printing and ink jet printing. These prints show a high photochromic sensitivity towards variation of illumination. For this reason it is not possible to reproduce the dynamic color by photocopying. In addition to such visual inspection the printed symbols offer the possibility for digital write-once-read-many (WORM) data storage. Photochemical recording is accomplished by a two-photon process. Recording densities in a range from 106 bit/cm2 to 108 bit/cm2 have been achieved. Data structures are stored in a polarization sensitive mode which allows an easy and efficient data encryption.

Modeling Current-Voltage Charateristics of Proteorhodopsin and Bacteriorhodopsin: Towards an Optoelectronics Based on Proteins.

PubMed

Alfinito, Eleonora; Reggiani, Lino

2016-10-01

Current-voltage characteristics of metal-protein-metal structures made of proteorhodopsin and bacteriorhodopsin are modeled by using a percolation-like approach. Starting from the tertiary structure pertaining to the single protein, an analogous resistance network is created. Charge transfer inside the network is described as a sequential tunneling mechanism and the current is calculated for each value of the given voltage. The theory is validated with available experiments, in dark and light. The role of the tertiary structure of the single protein and of the mechanisms responsible for the photo-activity is discussed.

Torsion of partial cleft of ear lobule.

PubMed

Kumaraswamy, M; Waiker, Veena P

2014-02-01

Torsion is a well-known phenomenon involving organs with long mesentery. Torsion in the ear lobule is rare. Ear lobule is very well vascularized. In cases of partial cleft ear lobule, there is a small segment of lobule inferior to the cleft which is vascularized through the pedicles on either side of the cleft. A lady aged 89 years presented with discoloration of the ear lobule. She was diagnosed as having gangrene of the central part of lobule. The segment of the lobule had undergone more than 360° torsion. She underwent debridement of gangrenous part and lobuloplasty. In our case laxity of the stretched lobule caused the torsion of the segment followed by gangrene. This rare complication indicates the need for correction of the cleft lobule not only for esthetic purpose, but also for the prevention of torsion. Copyright © 2013 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

Production of functional bacteriorhodopsin by an Escherichia coli cell-free protein synthesis system supplemented with steroid detergent and lipid.

PubMed

Shimono, Kazumi; Goto, Mie; Kikukawa, Takashi; Miyauchi, Seiji; Shirouzu, Mikako; Kamo, Naoki; Yokoyama, Shigeyuki

2009-10-01

Cell-free expression has become a highly promising tool for the efficient production of membrane proteins. In this study, we used a dialysis-based Escherichia coli cell-free system for the production of a membrane protein actively integrated into liposomes. The membrane protein was the light-driven proton pump bacteriorhodopsin, consisting of seven transmembrane alpha-helices. The cell-free expression system in the dialysis mode was supplemented with a combination of a detergent and a natural lipid, phosphatidylcholine from egg yolk, in only the reaction mixture. By examining a variety of detergents, we found that the combination of a steroid detergent (digitonin, cholate, or CHAPS) and egg phosphatidylcholine yielded a large amount (0.3-0.7 mg/mL reaction mixture) of the fully functional bacteriorhodopsin. We also analyzed the process of functional expression in our system. The synthesized polypeptide was well protected from aggregation by the detergent-lipid mixed micelles and/or lipid disks, and was integrated into liposomes upon detergent removal by dialysis. This approach might be useful for the high yield production of functional membrane proteins.

Peculiar torsion dynamical response of spider dragline silk

NASA Astrophysics Data System (ADS)

Liu, Dabiao; Yu, Longteng; He, Yuming; Peng, Kai; Liu, Jie; Guan, Juan; Dunstan, D. J.

2017-07-01

The torsional properties of spider dragline silks from Nephila edulis and Nephila pilipes spiders are investigated by using a torsion pendulum technique. A permanent torsional deformation is observed after even small torsional strain. This behaviour is quite different from that of the other materials tested here, i.e., carbon fiber, thin metallic wires, Kevlar fiber, and human hair. The spider dragline thus displays a strong energy dissipation upon the initial excitation (around 75% for small strains and more for a larger strain), which correspondingly reduces the amplitude of subsequent oscillations around the new equilibrium position. The variation of torsional stiffness in relaxation dynamics of spider draglines for different excitations is also determined. The experimental result is interpreted in the light of the hierarchical structure of dragline silk.

Protonation states and pH titration in the photocycle of photoactive yellow protein.

PubMed

Demchuk, E; Genick, U K; Woo, T T; Getzoff, E D; Bashford, D

2000-02-08

Photoactive yellow protein (PYP) undergoes a light-driven cycle of color and protonation states that is part of a mechanism of bacterial phototaxis. This article concerns functionally important protonation states of PYP and the interactions that stabilize them, and changes in the protonation state during the photocycle. In particular, the chromophore pK(a) is known to be shifted down so that the chromophore is negatively charged in the ground state (dark state) even though it is buried in the protein, while nearby Glu46 has an unusually high pK(a). The photocycle involves changes of one or both of these protonation states. Calculations of pK(a) values and protonation states using a semi-macroscopic electrostatic model are presented for the wild-type and three mutants, in both the ground state and the bleached (I(2)) intermediate state. Calculations allowing multiple H-bonding arrangements around the chromophore also have been carried out. In addition, ground-state pK(a) values of the chromophore have been measured by UV-visible spectroscopy for the wild-type and the same three mutants. Because of the unusual protonation states and strong electrostatic interactions, PYP represents a severe test of the ability of theoretical models to yield correct calculations of electrostatic interactions in proteins. Good agreement between experiment and theory can be obtained for the ground state provided the protein interior is assumed to have a relatively low dielectric constant, but only partial agreement between theory and experiment is obtained for the bleached state. We also present a reinterpretation of previously published data on the pH-dependence of the recovery of the ground state from the bleached state. The new analysis implies a pK(a) value of 6.37 for Glu46 in the bleached state, which is consistent with other available experimental data, including data that only became available after this analysis. The new analysis suggests that signal transduction is modulated

Can Gravity Probe B usefully constrain torsion gravity theories?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flanagan, Eanna E.; Rosenthal, Eran

2007-06-15

In most theories of gravity involving torsion, the source for torsion is the intrinsic spin of matter. Since the spins of fermions are normally randomly oriented in macroscopic bodies, the amount of torsion generated by macroscopic bodies is normally negligible. However, in a recent paper, Mao et al. (arXiv:gr-qc/0608121) point out that there is a class of theories, including the Hayashi-Shirafuji (1979) theory, in which the angular momentum of macroscopic spinning bodies generates a significant amount of torsion. They further argue that, by the principle of action equals reaction, one would expect the angular momentum of test bodies to couplemore » to a background torsion field, and therefore the precession of the Gravity Probe B gyroscopes should be affected in these theories by the torsion generated by the Earth. We show that in fact the principle of action equals reaction does not apply to these theories, essentially because the torsion is not an independent dynamical degree of freedom. We examine in detail a generalization of the Hayashi-Shirafuji theory suggested by Mao et al. called Einstein-Hayashi-Shirafuji theory. There are a variety of different versions of this theory, depending on the precise form of the coupling to matter chosen for the torsion. We show that, for any coupling to matter that is compatible with the spin transport equation postulated by Mao et al., the theory has either ghosts or an ill-posed initial-value formulation. These theoretical problems can be avoided by specializing the parameters of the theory and in addition choosing the standard minimal coupling to matter of the torsion tensor. This yields a consistent theory, but one in which the action equals reaction principle is violated, and in which the angular momentum of the gyroscopes does not couple to the Earth's torsion field. Thus, the Einstein-Hayashi-Shirafuji theory does not predict a detectable torsion signal for Gravity Probe B. There may be other torsion theories which

Multiplexed Holographic Data Storage in Bacteriorhodopsin

NASA Technical Reports Server (NTRS)

Mehrl, David J.; Krile, Thomas F.

1997-01-01

High density optical data storage, driven by the information revolution, remains at the forefront of current research areas. Much of the current research has focused on photorefractive materials (SBN and LiNbO3) and polymers, despite various problems with expense, durability, response time and retention periods. Photon echo techniques, though promising, are questionable due to the need for cryogenic conditions. Bacteriorhodopsin (BR) films are an attractive alternative recording medium. Great strides have been made in refining BR, and materials with storage lifetimes as long as 100 days have recently become available. The ability to deposit this robust polycrystalline material as high quality optical films suggests the use of BR as a recording medium for commercial optical disks. Our own recent research has demonstrated the suitability of BR films for real time spatial filtering and holography. We propose to fully investigate the feasibility of performing holographic mass data storage in BR. Important aspects of the problem to be investigated include various data multiplexing techniques (e.g. angle- amplitude- and phase-encoded multiplexing, and in particular shift-multiplexing), multilayer recording techniques, SLM selection and data readout using crossed polarizers for noise rejection. Systems evaluations of storage parameters, including access times, memory refresh constraints, erasure, signal-to-noise ratios and bit error rates, will be included in our investigations.

Systems Issues Pertaining to Holographic Optical Data Storage in Thick Bacteriorhodopsin Films

NASA Technical Reports Server (NTRS)

Downie, John D.; Timucin, Dogan A.; Gary, Charles K.; Oezcan, Meric; Smithey, Daniel T.; Crew, Marshall; Lau, Sonie (Technical Monitor)

1998-01-01

The optical data storage capacity and raw bit-error-rate achievable with thick photochromic bacteriorhodopsin (BR) films are investigated for sequential recording and read- out of angularly- and shift-multiplexed digital holograms inside a thick blue-membrane D85N BR film. We address the determination of an exposure schedule that produces equal diffraction efficiencies among each of the multiplexed holograms. This exposure schedule is determined by numerical simulations of the holographic recording process within the BR material, and maximizes the total grating strength. We also experimentally measure the shift selectivity and compare the results to theoretical predictions. Finally, we evaluate the bit-error-rate of a single hologram, and of multiple holograms stored within the film.

Testicular torsion repair

MedlinePlus

... and fertility. Patient Instructions Surgical wound care - open Images Male reproductive anatomy Testicular torsion repair - series References Elder JS. Disorders and anomalies of the scrotal contents. In: ...

Torsion limits from t t macr production at the LHC

NASA Astrophysics Data System (ADS)

de Almeida, F. M. L.; de Andrade, F. R.; do Vale, M. A. B.; Nepomuceno, A. A.

2018-04-01

Torsion models constitute a well-known class of extended quantum gravity models. In this work, one investigates the phenomenological consequences of a torsion field interacting with top quarks at the LHC. A torsion field could appear as a new heavy state characterized by its mass and couplings to fermions. This new state would form a resonance decaying into a top antitop pair. The latest ATLAS t t ¯ production results from LHC 13 TeV data are used to set limits on torsion parameters. The integrated luminosity needed to observe torsion resonance at the next LHC upgrades are also evaluated, considering different values for the torsion mass and its couplings to Standard Model fermions. Finally, prospects for torsion exclusion at the future LHC phases II and III are obtained using fast detector simulations.

Torsional ARC Effectively Expands the Visual Field in Hemianopia

PubMed Central

Satgunam, PremNandhini; Peli, Eli

2012-01-01

Purpose Exotropia in congenital homonymous hemianopia has been reported to provide field expansion that is more useful when accompanied with harmonios anomalous retinal correspondence (HARC). Torsional strabismus with HARC provides a similar functional advantage. In a subject with hemianopia demonstrating a field expansion consistent with torsion we documented torsional strabismus and torsional HARC. Methods Monocular visual fields under binocular fixation conditions were plotted using a custom dichoptic visual field perimeter (DVF). The DVF was also modified to measure perceived visual directions under dissociated and associated conditions across the central 50° diameter field. The field expansion and retinal correspondence of a subject with torsional strabismus (along with exotropia and right hypertropia) with congenital homonymous hemianopia was compared to that of another exotropic subject with acquired homonymous hemianopia without torsion and to a control subject with minimal phoria. Torsional rotations of the eyes were calculated from fundus photographs and perimetry. Results Torsional ARC documented in the subject with congenital homonymous hemianopia provided a functional binocular field expansion up to 18°. Normal retinal correspondence was mapped for the full 50° visual field in the control subject and for the seeing field of the acquired homonymous hemianopia subject, limiting the functional field expansion benefit. Conclusions Torsional strabismus with ARC, when occurring with homonymous hemianopia provides useful field expansion in the lower and upper fields. Dichoptic perimetry permits documentation of ocular alignment (lateral, vertical and torsional) and perceived visual direction under binocular and monocular viewing conditions. Evaluating patients with congenital or early strabismus for HARC is useful when considering surgical correction, particularly in the presence of congenital homonymous hemianopia. PMID:22885782

Torsional actuator motor using solid freeform fabricated PZT ceramics

NASA Astrophysics Data System (ADS)

Kim, Chulho; Wu, Carl C. M.; Bender, Barry

2004-07-01

A torsional actuator has been developed at NRL utilizing the high piezoelectric shear coefficient, d15. This torsional actuator uses an even number of alternately poled segments of electroactive PZT. Under an applied electric field, the torsional actuator produces large angular displacement and a high torque. The solid freeform fabrication technique of the laminated object manufacturing (LOM) is used for rapid prototyping of torsional actuator with potential cost and time saving. First step to demonstrate the feasibility of the LOM technique for the torsional actuator device fabrication is to make near net shape segments. We report a prototype PZT torsional actuator using LOM prepared PZT-5A segments. Fabrication processes and test results are described. The torsional actuator PZT-5A tube has dimensions of 13 cm long, 2.54 cm OD and 1.9 cm ID. Although the piezoelectric strain is small, it may be converted into large displacement via accumulation of the small single cycle displacements over many cycles using AC driving voltage such as with a rotary 'inchworm' actuator or an ultrasonic rotary motor. A working prototype of a full-cycle motor driven by the piezoelectric torsional actuator has been achieved. The rotational speed is 1,200 rpm under 200 V/cm field at the resonant frequency of 4.5 kHz.

Static vacuum solutions on curved space-times with torsion

NASA Astrophysics Data System (ADS)

Shabani, Hamid; Ziaie, Amir Hadi

2018-06-01

The Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity naturally extends Einstein’s general relativity (GR) to include intrinsic angular momentum (spin) of matter. The main feature of this theory consists of an algebraic relation between space-time torsion and spin of matter, which indeed deprives the torsion of its dynamical content. The Lagrangian of ECKS gravity is proportional to the Ricci curvature scalar constructed out of a general affine connection so that owing to the influence of matter energy-momentum and spin, curvature and torsion are produced and interact only through the space-time metric. In the absence of spin, the space-time torsion vanishes and the theory reduces to GR. It is however possible to have torsion propagation in vacuum by resorting to a model endowed with a nonminimal coupling between curvature and torsion. In the present work we try to investigate possible effects of the higher order terms that can be constructed from space-time curvature and torsion, as the two basic constituents of Riemann-Cartan geometry. We consider Lagrangians that include fourth-order scalar invariants from curvature and torsion and then investigate the resulting field equations. The solutions that we find show that there could exist, even in vacuum, nontrivial static space-times that admit both black holes and naked singularities.

Incidence and predictive factors of isolated neonatal penile glanular torsion.

PubMed

Sarkis, Pierrot E; Sadasivam, Muthurajan

2007-12-01

To determine the incidence of isolated neonatal penile glanular torsion, describe the basic characteristics, and explore the relationship between foreskin and glans torsion. A prospective survey was conducted of all male newborns admitted to nursery after delivery, or neonates less than 3 months presenting for circumcision. Cases with associated genital malformations were excluded. The incidence of isolated neonatal penile torsion was 27% (95% CI: 22.2%-31.84%), to the left in 99% of cases. In 3.5% of cases, the penis had an angle <10 degrees, and 9.5% >20 degrees. Using Spearman's correlational coefficient, deviation of penile raphe from the midline at the foreskin tip had a better correlation with glans torsion than deviation of raphe at the coronal sulcus (0.727 vs 0.570; both significant at p<0.01). Isolated neonatal penile torsion is more common than reported. The median raphe of the penis may be normal and mask unexpected glans torsion. Median raphe torsion at foreskin tip can be used as a predictor for glans torsion. Clinical significance and relation to adult penile torsion are beyond the scope of the study.

An Axial-Torsional, Thermomechanical Fatigue Testing Technique

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

1995-01-01

A technique for conducting strain-controlled, thermomechanical, axial-torsional fatigue tests on thin-walled tubular specimens was developed. Three waveforms of loading, namely, the axial strain waveform, the engineering shear strain waveform, and the temperature waveform were required in these tests. The phasing relationships between the mechanical strain waveforms and the temperature and axial strain waveforms were used to define a set of four axial-torsional, thermomechanical fatigue (AT-TMF) tests. Real-time test control (3 channels) and data acquisition (a minimum of 7 channels) were performed with a software program written in C language and executed on a personal computer. The AT-TMF testing technique was used to investigate the axial-torsional thermomechanical fatigue behavior of a cobalt-base superalloy, Haynes 188. The maximum and minimum temperatures selected for the AT-TMF tests were 760 and 316 C, respectively. Details of the testing system, calibration of the dynamic temperature profile of the thin-walled tubular specimen, thermal strain compensation technique, and test control and data acquisition schemes, are reported. The isothermal, axial, torsional, and in- and out-of-phase axial-torsional fatigue behaviors of Haynes 188 at 316 and 760 C were characterized in previous investigations. The cyclic deformation and fatigue behaviors of Haynes 188 in AT-TMF tests are compared to the previously reported isothermal axial-torsional behavior of this superalloy at the maximum and minimum temperatures.

Torsional Splitting in the Degenerate Vibrational States of (70)Ge(2)H(6): Rotation-Torsion Analysis of the nu(7) and nu(9) Fundamentals.

PubMed

Lattanzi; di Lauro C; Bürger; Mkadmi

2000-09-01

The rotational and torsional structure of the nu(7) and nu(9) degenerate fundamentals of (70)Ge(2)H(6) has been analyzed under high resolution. The torsional structure of both v(7) = 1 and v(9) = 1 states can be fitted by a simple one-parameter formula. The x,y-Coriolis interaction with the parallel nu(5) fundamental was accounted for in the analysis of nu(7). A strong perturbation of the J structure of the E(3s) torsional component of the KDeltaK = -2 subbranches of nu(9) can be explained by the resonance with an E(3s) excited level of the pure torsional manifold. The perturber is centered at 361.58 cm(-1), very close to the value estimated with a barrier height of 285 cm(-1). This confirms that the fundamental torsional wavenumber is close to 103 cm(-1), in good agreement with the "ab initio" prediction. The torsional splittings of all the infrared active degenerate fundamentals, nu(7), nu(8), and nu(9), follow the trend predicted by theory, and have been fitted by exploratory calculations accounting only for the torsional Coriolis-coupling mechanism of all degenerate vibrational fundamentals in several torsional states. This confirms that torsional Coriolis coupling is the dominant mechanism responsible for the decrease of the torsional splitting in the degenerate vibrational states. A higher value of the barrier had to be used for the nu(9) mode. Copyright 2000 Academic Press.

Hydroxyl free radical production during torsional phacoemulsification.

PubMed

Aust, Steven D; Hebdon, Thomas; Humbert, Jordan; Dimalanta, Ramon

2010-12-01

To quantitate free radical generation during phacoemulsification using an ultrasonic phacoemulsification device that includes a torsional mode and evaluate tip designs specific to the torsional mode. Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. Experimental study. Experiments were performed using the Infiniti Vision System and OZil handpiece. Hydroxyl radical concentrations in the aspirated irrigation solution during torsional phacoemulsification were quantitated as nanomolar malondialdehyde (nM MDA) and determined spectrophotometrically using the deoxyribose assay. The mean free radical production during phacoemulsification with torsional modality at 100% amplitude was 30.1 nM MDA ± 5.1 (SD) using a 0.9 mm 45-degree Kelman tapered ABS tip. With other tip designs intended for use with the torsional modality, free radical production was further reduced when fitted with the 0.9 mm 45-degree Kelman mini-flared ABS tip (13.2 ± 5.6 nM MDA) or the 0.9 mm 45-degree OZil-12 mini-flared ABS tip (14.3 ± 6.7 nM MDA). Although the measurements resulting from the use of the latter 2 tips were not statistically significantly different (P ≈ .25), they were different from those of the tapered tip (P<.0001). The MDA concentration in the aspirated irrigation solution using the torsional modality was approximately one half that reported for the handpiece's longitudinal modality in a previous study using the same bent-tip design (Kelman tapered, P<.0001). The level of MDA was further reduced approximately one half with torsional-specific tips. Copyright © 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richter, H.T.; Brown, L.S.; Lanyi, J.K.

Because asp-85 is the acceptor of the retinal Schiff base proton during light-driven proton transport by bacteriorhodopsin, modulation of its pK{sub a} in the photocycle is to be expected. The complex titration of asp-85 in the unphotolyzed protein was suggested to reflect the dependence of this residue on the protonation state of another, unidentified group. from the pH dependencies of the rate constant for the thermal equilibration of retinal isomeric states (dark adaptation) and the deprotonation kinetics of the Schiff base during the photocycle in the E204Q and E204D mutants, we identify the residue as glu-204. The nature of itsmore » interaction with our recent finding that glu-204 is the origin of the proton released to the extracellular surface upon protonation of asp-85 during that transport. We propose, therefore, that the following series of events occur in the photocycle. Protonation of asp-85 in the proton equilibrium with the Schiff base of the photoisomerized retinal results in the dissociation of glu-204 and proton release to the extracellular surface upon protonation of asp-85 during the transport. We propose, therefore, that the following series of events occur in the photocycle. Protonation of asp-85 in the proton equilibrium with the Schiff base shifts toward complete proton transfer. This constitutes the first phase of the reprotonation switch because it excludes asp-85 as a donor in the reprotonation of the Schiff base that follows. The sequential structural changes of the protein that ensue, detected earlier by diffraction, are suggested to facilitate the change of the access of the Schiff base toward the cytoplasmic side at the second phase of the switch, and the lowering the pK{sub a} of asp-96, so as to make it a proton donor, as the third phase. 77 refs., 6 figs.« less

Hydrostatic self-aligning axial/torsional mechanism

DOEpatents

O'Connor, Daniel G.; Gerth, Howard L.

1990-01-01

The present invention is directed to a self-aligning axial/torsional loading mechanism for testing the strength of brittle materials which are sensitive to bending moments. Disposed inside said self-aligning loading mechanism is a frictionless hydrostatic ball joint with a flexure ring to accommodate torsional loads through said ball joint.

The role of proline residues in the dynamics of transmembrane helices: the case of bacteriorhodopsin.

PubMed

Perálvarez-Marín, Alex; Bourdelande, José-Luis; Querol, Enric; Padrós, Esteve

2006-01-01

Proline residues in transmembrane helices have been found to have important roles in the functioning of membrane proteins. Moreover, Pro residues occur with high frequency in transmembrane alpha-helices, as compared to alpha-helices for soluble proteins. Here, we report several properties of the bacteriorhodopsin mutants P50A (helix B), P91A (helix C) and P186A (helix F). Compared to wild type, strongly perturbed behaviour has been found for these mutants. In the resting state, increased hydroxylamine accessibility and altered Asp-85 pKa and light-dark adaptation were observed. On light activation, hydroxylamine accessibility was increased and proton transport activity, M formation kinetics and FTIR difference spectra of M and N intermediates showed clear distortions. On the basis of these alterations and the near identity of the crystalline structures of mutants with that of wild type, we conclude that the transmembrane proline residues of bacteriorhodopsin fulfil a dynamic role in both the resting and the light-activated states. Our results are consistent with the notion that mutation of Pro to Ala allows the helix to increase its flexibility towards the direction originally hindered by the steric clash between the ring Cgamma and the carbonyl O of the i-4 residue, at the same time decreasing the mobility towards the opposite direction. Due to their properties, transmembrane Pro residues may serve as transmission elements of conformational changes during the transport process. We propose that these concepts can be extended to other transmembrane proteins.

Heat production: Longitudinal versus torsional phacoemulsification.

PubMed

Han, Young Keun; Miller, Kevin M

2009-10-01

To compare the heat production of longitudinal versus torsional phacoemulsification under strict laboratory test conditions. Department of Ophthalmology, David Geffen School of Medicine at UCLA, and Jules Stein Eye Institute, Los Angeles, California, USA. Two Infiniti phacoemulsification handpieces were inserted into silicone test chambers filled with a balanced salt solution and imaged serially using a thermal camera. Incision compression was simulated by suspending 25.3 g weights from the silicone chambers. To simulate occlusion of the phacoemulsification tip, the aspiration line was clamped. Peak temperatures were measured 0, 10, 30, 60, and 120 seconds after the commencement of continuous ultrasound power. The 2 handpieces, operating exclusively in longitudinal or torsional modes, were compared 3 ways: (1) using the same power displayed on the instrument console, (2) using identical stroke lengths, and (3) using the same applied energy, a product of stroke length and frequency. For all 3 comparisons, torsional phacoemulsification resulted in lower temperatures at each time point. At the same displayed power setting, the scenario most familiar to cataract surgeons, longitudinal phacoemulsification elevated temperatures up to 41.5 degrees C more than torsional phacoemulsification. Torsional phacoemulsification generated less heat than longitudinal phacoemulsification in all 3 comparison tests. Lower operating temperatures indicate lower heat generation within the same volume of fluid, and this may provide additional thermal protection during cataract surgery.

Nonminimal couplings, gravitational waves, and torsion in Horndeski's theory

NASA Astrophysics Data System (ADS)

Barrientos, José; Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Medina, Perla; Narbona, Daniela; Rodríguez, Eduardo; Valdivia, Omar

2017-10-01

The Horndeski Lagrangian brings together all possible interactions between gravity and a scalar field that yield second-order field equations in four-dimensional spacetime. As originally proposed, it only addresses phenomenology without torsion, which is a non-Riemannian feature of geometry. Since torsion can potentially affect interesting phenomena such as gravitational waves and early universe inflation, in this paper we allow torsion to exist and propagate within the Horndeski framework. To achieve this goal, we cast the Horndeski Lagrangian in Cartan's first-order formalism and introduce wave operators designed to act covariantly on p -form fields that carry Lorentz indices. We find that nonminimal couplings and second-order derivatives of the scalar field in the Lagrangian are indeed generic sources of torsion. Metric perturbations couple to the background torsion, and new torsional modes appear. These may be detected via gravitational waves but not through Yang-Mills gauge bosons.

Retinal isomerization in bacteriorhodopsin captured by a femtosecond x-ray laser.

PubMed

Nogly, Przemyslaw; Weinert, Tobias; James, Daniel; Carbajo, Sergio; Ozerov, Dmitry; Furrer, Antonia; Gashi, Dardan; Borin, Veniamin; Skopintsev, Petr; Jaeger, Kathrin; Nass, Karol; Båth, Petra; Bosman, Robert; Koglin, Jason; Seaberg, Matthew; Lane, Thomas; Kekilli, Demet; Brünle, Steffen; Tanaka, Tomoyuki; Wu, Wenting; Milne, Christopher; White, Thomas; Barty, Anton; Weierstall, Uwe; Panneels, Valerie; Nango, Eriko; Iwata, So; Hunter, Mark; Schapiro, Igor; Schertler, Gebhard; Neutze, Richard; Standfuss, Jörg

2018-06-14

Ultrafast isomerization of retinal is the primary step in photoresponsive biological functions including vision in humans and ion-transport across bacterial membranes. We studied the sub-picosecond structural dynamics of retinal isomerization in the light-driven proton pump bacteriorhodopsin using an x-ray laser. A series of structural snapshots with near-atomic spatial and temporal resolution in the femtosecond regime show how the excited all- trans retinal samples conformational states within the protein binding pocket prior to passing through a twisted geometry and emerging in the 13 -cis conformation. Our findings suggest ultrafast collective motions of aspartic acid residues and functional water molecules in the proximity of the retinal Schiff base as a key ingredient for this stereo-selective and efficient photochemical reaction. Copyright © 2018, American Association for the Advancement of Science.

Torsional vibration measurements on rotating shaft system using laser doppler vibrometer

NASA Astrophysics Data System (ADS)

Xiang, Ling; Yang, Shixi; Gan, Chunbiao

2012-11-01

In this work, a laser torsional vibrameter was used to measure the torsion vibration of a rotating shaft system under electrical network impact. Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) are non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. Furthermore, a highly complex shafting system is analyzed by a modified Riccati torsional transfer matrix. The system is modeled as a chain consisting of an elastic spring with concentrated mass points, and the multi-segments lumped mass model is established for this shafting system. By the modified Riccati torsional transfer matrix method, an accumulated calculation is effectively eliminated to obtain the natural frequencies. The electrical network impacts can activize the torsional vibration of shaft system, and the activized torsion vibration frequencies contained the natural frequencies of shaft system. The torsional vibrations of the shaft system were measured under electrical network impacts in laser Doppler torsional vibrometer. By comparisons, the natural frequencies by measurement were consistent with the values by calculation. The results verify the instrument is robust, user friendly and can be calibrated in situ. The laser torsional vibrometer represents a significant step forward in rotating machinery diagnostics.

Refractive index of dark-adapted bacteriorhodopsin and tris(hydroxymethyl)aminomethane buffer between 390 and 880 nm.

PubMed

Heiner, Zsuzsanna; Osvay, Károly

2009-08-10

The refractivity of wild-type bacteriorhodopsin (bR(WT)) suspended in tris(hydroxymethyl)aminomethane (TRIS) buffer has been measured in the spectral range of 390-840 nm by the method of angle of minimal deviation with the use of a hollow glass prism. The refractive indices of pure bR(WT) as well as of TRIS buffer have been determined from the concentration dependent refraction values. Sellmeier-type dispersion equations have been fitted for both the TRIS buffer and pure bR(WT).

Design and analysis of a torsion braid pendulum displacement transducer

NASA Technical Reports Server (NTRS)

Rind, E.; Bryant, E. L.

1981-01-01

The dynamic properties at various temperatures of braids impregnated with polymer can be measured by using the braid as the suspension of a torsion pendulum. This report describes the electronic and mechanical design of a torsional braid pendulum displacement transducer which is an advance in the state of the art. The transducer uses a unique optical design consisting of refracting quartz windows used in conjunction with a differential photocell to produce a null signal. The release mechanism for initiating free torsional oscillation of the pendulum has also been improved. Analysis of the precision and accuracy of the transducer indicated that the maximum relative error in measuring torsional amplitude was approximately 0. A serious problem inherent in all instruments which use a torsional suspension was analyzed: misalignment of the physical and torsional axes of the torsional member which results in modulation of the amplitude of the free oscillation.

Seismic cross-coupling noise in torsion pendulums

NASA Astrophysics Data System (ADS)

Shimoda, Tomofumi; Aritomi, Naoki; Shoda, Ayaka; Michimura, Yuta; Ando, Masaki

2018-05-01

Detection of low-frequency gravitational waves around 0.1 Hz is one of the important targets for future gravitational wave observation. One of the main sources of the expected signals is gravitational waves from binary intermediate-mass black hole coalescences which is proposed as one of the formation scenarios of supermassive black holes. By using a torsion pendulum, which can have a resonance frequency of a few millihertz, such signals can be measured on the ground since its rotational motion can act as a free mass down to 0.01 Hz. However, sensitivity of a realistic torsion pendulum will suffer from torsional displacement noise introduced from translational ground motion in the main frequency band of interest. Such noise is called seismic cross-coupling noise, and there has been little research on it. In this paper, systematic investigation is performed to identify routes of cross-coupling transfer for standard torsion pendulums. Based on the results, this paper also proposes reduction schemes of cross-coupling noise, and they were demonstrated experimentally in agreement with theory. This result establishes a basic way to reduce seismic noise in torsion pendulums for the most significant coupling routes.

Torsional vibration of aircraft engines

NASA Technical Reports Server (NTRS)

Lurenbaum, Karl

1932-01-01

Exhaustive torsional-vibration investigations are required to determine the reliability of aircraft engines. A general outline of the methods used for such investigations and of the theoretical and mechanical means now available for this purpose is given, illustrated by example. True vibration diagrams are usually obtained from vibration measurements on the completed engine. Two devices for this purpose and supplementing each other, the D.V.L. torsiograph and the D.V.L. torsion recorder, are described in this report.

MSTor version 2013: A new version of the computer code for the multi-structural torsional anharmonicity, now with a coupled torsional potential

NASA Astrophysics Data System (ADS)

Zheng, Jingjing; Meana-Pañeda, Rubén; Truhlar, Donald G.

2013-08-01

We present an improved version of the MSTor program package, which calculates partition functions and thermodynamic functions of complex molecules involving multiple torsions; the method is based on either a coupled torsional potential or an uncoupled torsional potential. The program can also carry out calculations in the multiple-structure local harmonic approximation. The program package also includes seven utility codes that can be used as stand-alone programs to calculate reduced moment of inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes for torsional subdomains defined by Voronoi tessellation of the conformational subspace, to generate template input files for the MSTor calculation and Voronoi calculation, and to calculate one-dimensional torsional partition functions using the torsional eigenvalue summation method. Restrictions: There is no limit on the number of torsions that can be included in either the Voronoi calculation or the full MS-T calculation. In practice, the range of problems that can be addressed with the present method consists of all multitorsional problems for which one can afford to calculate all the conformational structures and their frequencies. Unusual features: The method can be applied to transition states as well as stable molecules. The program package also includes the hull program for the calculation of Voronoi volumes, the symmetry program for determining point group symmetry of a molecule, and seven utility codes that can be used as stand-alone programs to calculate reduced moment-of-inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes of the torsional subdomains defined by Voronoi tessellation of the conformational subspace, to generate template input files, and to calculate one-dimensional torsional

Non-minimally coupled scalar field cosmology with torsion

NASA Astrophysics Data System (ADS)

Cid, Antonella; Izaurieta, Fernando; Leon, Genly; Medina, Perla; Narbona, Daniela

2018-04-01

In this work we present a generalized Brans-Dicke lagrangian including a non-minimally coupled Gauss-Bonnet term without imposing the vanishing torsion condition. In the resulting field equations, the torsion is closely related to the dynamics of the scalar field, i.e., if non-minimally coupled terms are present in the theory, then the torsion must be present. For the studied lagrangian we analyze the cosmological consequences of an effective torsional fluid and we show that this fluid can be responsible for the current acceleration of the universe. Finally, we perform a detailed dynamical system analysis to describe the qualitative features of the model, we find that accelerated stages are a generic feature of this scenario.

Comparison of torsional and longitudinal modes using phacoemulsification parameters.

PubMed

Rekas, Marek; Montés-Micó, Robert; Krix-Jachym, Karolina; Kluś, Adam; Stankiewicz, Andrzej; Ferrer-Blasco, Teresa

2009-10-01

To compare phacoemulsification parameters of torsional and longitudinal ultrasound modes. Ophthalmology Department, Military Health Service Institute, Warsaw, Poland. This prospective study evaluated eyes 1, 7, and 30 days after phacoemulsification with an Infiniti Vision System using the torsional or longitudinal ultrasound (US) mode. Cataract classification was according to the Lens Opacities Classification System II. Nucleus fragmentation was by the phaco-chop and quick-chop methods. Primary outcome measures were phaco time, mean phaco power, mean torsional amplitude, and aspiration time. Total energy, defined as cumulative dissipated energy (CDE) x aspiration time, and the effective coefficient, defined as aspiration time/phaco time, were also calculated. Four hundred eyes were evaluated. The CDE was statistically significantly lower in the torsional mode for nucleus grades I, II, and III (P<.001) but not for grade IV (P>.05). Aspiration time was statistically significantly shorter in the torsional mode than in the longitudinal mode for nucleus grades III and IV (P<.05). Total energy was significantly lower in the torsional mode for all nucleus densities (P<.05). The effective coefficient was significantly lower in the longitudinal mode except for nucleus grade I (P<.05). Torsional phacoemulsification was more effective than longitudinal phacoemulsification in the amount of applied fluid and the quantity of US energy expended. With the torsional method, it was possible to maintain a constant ratio of amount of fluid flow to quantity of US energy used, regardless of nucleus density.

The Torsional Spectrum of Doubly Deuterated Methanol CHD_2OH

NASA Astrophysics Data System (ADS)

Ndao, M.; Coudert, L. H.; Kwabia Tchana, F.; Barros, J.; Margulès, L.; Manceron, Laurent; Roy, P.

2014-06-01

Although the torsional spectrum of several isotopic species of methanol with a symmetrical CH_3 or CD_3 was analyzed some time ago, it is recently, and only for the monodeuterated species CH_2DOH, that such an analysis was extended to the case of an asymmetrical methyl group. In this talk, based on a Fourier transform high-resolution spectrum recorded in the 20 to 670 wn region, the first analysis of the torsional spectrum of doubly deuterated methanol CHD_2OH will be presented. The Q branch of many torsional subbands could be observed and their assignment was initiated using a theoretical torsion-rotation spectrum computed with an approach accounting for the torsion-rotation Coriolis coupling and for the dependence of the generalized inertia tensor on the angle of internal rotation. 46 torsional subbands were thus assigned. For 28 of them, their rotational structure could be assigned and fitted using an effective Hamiltonian expressed as a J(J+1) expansion; and for 2 of them microwave transitions within the lower torsional level could also be included in the analysis. In several cases these analysis revealed that the torsional levels are strongly perturbed. In the talk, the torsional parameters retrieved in the analysis of the torsional subband centers will be discussed. The results of the analysis of the rotational structure of the torsional subbands will be presented and we will also try to understand the nature of the perturbations. At last, preliminary results about the analysis of the microwave spectrum will be presented. El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. 135 (2011) 194309 Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spectrosc. 256 (2009) 204 Quade, Liu, Mukhopadhyay, and Su, J. Mol. Spectrosc. 192 (1998) 378 Pearson, Yu, and Drouin, J. Mol. Spectrosc. 280 (2012) 119

Neutrino Oscillation in a Space-Time with Torsion

NASA Astrophysics Data System (ADS)

Alimohammadi, M.; Shariati, A.

Using Einstein-Cartan-Dirac theory, we study the effect of torsion on neutrino oscillation. We see that torsion cannot induce neutrino oscillation, but affects it whenever oscillation exists for other reasons. We show that the torsion effect on neutrino oscillation is as important as the neutrino mass effect, whenever the ratio of neutrino number density to neutrino energy is ~ 1069 cm-3/eV, or the number density of the matter is ~ 1069cm-3.

Torsion in gauge theory

NASA Astrophysics Data System (ADS)

Nieh, H. T.

2018-02-01

The potential conflict between torsion and gauge symmetry in the Riemann-Cartan curved spacetime was noted by Kibble in his 1961 pioneering paper and has since been discussed by many authors. Kibble suggested that, to preserve gauge symmetry, one should forgo the covariant derivative in favor of the ordinary derivative in the definition of the field strength Fμ ν for massless gauge theories, while for massive vector fields, covariant derivatives should be adopted. This view was further emphasized by Hehl et al. in their influential 1976 review paper. We address the question of whether this deviation from normal procedure by forgoing covariant derivatives in curved spacetime with torsion could give rise to inconsistencies in the theory, such as the quantum renormalizability of a realistic interacting theory. We demonstrate in this paper the one-loop renormalizability of a realistic gauge theory of gauge bosons interacting with Dirac spinors, such as the SU(3) chromodynamics, for the case of a curved Riemann-Cartan spacetime with totally antisymmetric torsion. This affirmative confirmation is one step toward providing justification for the assertion that the flat-space definition of the gauge-field strength should be adopted as the proper definition.

Pseudotopological quasilocal energy of torsion gravity

NASA Astrophysics Data System (ADS)

Ko, Sheng-Lan; Lin, Feng-Li; Ning, Bo

2017-08-01

Torsion gravity is a natural extension to Einstein gravity in the presence of fermion matter sources. In this paper we adopt Wald's covariant method of calculating the Noether charge to construct the quasilocal energy of the Einstein-Cartan-fermion system, and find that its explicit expression is formally independent of the coupling constant between the torsion and axial current. This seemingly topological nature is unexpected and is reminiscent of the quantum Hall effect and topological insulators. However, a coupling dependence does arise when evaluating it on shell, and thus the situation is pseudotopological. Based on the expression for the quasilocal energy, we evaluate it for a particular solution on the entanglement wedge and find agreement with the holographic relative entropy obtained before. This shows the equivalence of these two quantities in the Einstein-Cartan-fermion system. Moreover, the quasilocal energy in this case is not always positive definite, and thus it provides an example of a swampland in torsion gravity. Based on the covariant Noether charge, we also derive the nonzero fermion effect on the Komar angular momentum. The implications of our results for future tests of torsion gravity in gravitational-wave astronomy are also discussed.

The vibrationally adiabatic torsional potential energy surface of trans-stilbene

NASA Astrophysics Data System (ADS)

Chowdary, Praveen D.; Martinez, Todd J.; Gruebele, Martin

2007-05-01

The effect of vibrational Zero Point Energy (ZPE) on the torsional barriers of trans-stilbene is studied in the adiabatic approximation. The two torsional modes corresponding to phenyl rotation are explicitly separated, and the remaining modes are treated as normal coordinates. ZPE reduces the adiabatic barrier along the in-phase torsion from 198 to 13 cm -1. A one-dimensional adiabatic potential for the anti-phase torsion, including the ZPE of the in-phase torsion, reduces the adiabatic barrier from 260 to 58 cm -1. Comparison with recent electronic structure benchmark calculations suggests that vibrational corrections play a significant role in trans-stilbene's experimentally observed planar structure.

Torsion sensing based on patterned piezoelectric beams

NASA Astrophysics Data System (ADS)

Cha, Youngsu; You, Hangil

2018-03-01

In this study, we investigated the sensing characteristics of piezoelectric beams under torsional loads. We used partially patterned piezoelectric beams to sense torsion. In particular, the piezoelectric patches are located symmetrically with respect to the line of the shear center of the beam. The patterned piezoelectric beam is modeled as a slender beam, and its electrical responses are obtained by piezoelectric electromechanical equations. To validate the modeling framework, experiments are performed using a setup that forces pure torsional deformation. Three different geometric configurations of the patterned piezoelectric layer are used for the experiments. The frequency and amplitude of the forced torsional load are systematically varied in order to study the behavior of the piezoelectric sensor. Experimental results demonstrate that two voltage outputs of the piezoelectric beam are approximately out of phase with identical amplitude. Moreover, the length of the piezoelectric layers has a significant influence on the sensing properties. Our theoretical predictions using the model support the experimental findings.

Web flexibility and I-beam torsional oscillation

NASA Astrophysics Data System (ADS)

Stephen, N. G.; Wang, P. J.

1986-08-01

Two recent theories on torsional oscillation of general doubly-symmetric non-circular cross-section beams incorporate a second order effect, that of in-plane shear deformation involving a change in cross-sectional shape, and are found to give excellent agreement with exact results for an elliptical section rod. For "technical" torsional oscillation theories of I-section beams this in-plane shear has previously been considered within the flanges only; in the present work the greater effect of shear distortion of the web is included, having previously been considered only in static analysis. The theory predicts three modes of wave propagation, one of which is essentially torsional in character; a second mode may be identified with predominatly flange bending according to the second branch of Timoshenko beam theory whilst a new mode involves individual flange torsion with asymmetric web deformation, and has the lowest phase velocity except at the longest wavelength. An alternative symmetric web deformation is also considered.

Aeroelastic considerations for torsionally soft rotors

NASA Technical Reports Server (NTRS)

Mantay, W. R.; Yeager, W. T., Jr.

1985-01-01

A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades.

An analysis of 3D solvation structure in biomolecules: application to coiled coil serine and bacteriorhodopsin.

PubMed

Hirano, Kenji; Yokogawa, Daisuke; Sato, Hirofumi; Sakaki, Shigeyoshi

2010-06-17

Three-dimensional (3D) solvation structure around coiled coil serine (Coil-Ser) and inner 3D hydration structure in bacteriorhodopsin (bR) were studied using a recently developed method named multicenter molecular Ornstein-Zernike equation (MC-MOZ) theory. In addition, a procedure for analyzing the 3D solvent distribution was proposed. The method enables us to calculate the coordination number of solvent water as well as the strength of hydrogen bonding between the water molecule and the protein. The results for Coil-Ser and bR showed very good agreement with the experimental observations.

Muscular Basis of Whisker Torsion in Mice and Rats.

PubMed

Haidarliu, Sebastian; Bagdasarian, Knarik; Shinde, Namrata; Ahissar, Ehud

2017-09-01

Whisking mammals move their whiskers in the rostrocaudal and dorsoventral directions with simultaneous rolling about their long axes (torsion). Whereas muscular control of the first two types of whisker movement was already established, the anatomic muscular substrate of the whisker torsion remains unclear. Specifically, it was not clear whether torsion is induced by asymmetrical operation of known muscles or by other largely unknown muscles. Here, we report that mystacial pads of newborn and adult rats and mice contain oblique intrinsic muscles (OMs) that connect diagonally adjacent vibrissa follicles. Each of the OMs is supplied by a cluster of motor end plates. In rows A and B, OMs connect the ventral part of the rostral follicle with the dorsal part of the caudal follicle. In rows C-E, in contrast, OMs connect the dorsal part of the rostral follicle to the ventral part of the caudal follicle. This inverse architecture is consistent with previous behavioral observations [Knutsen et al.: Neuron 59 (2008) 35-42]. In newborn mice, torsion occurred in irregular single twitches. In adult anesthetized rats, microelectrode mediated electrical stimulation of an individual OM that is coupled with two adjacent whiskers was sufficient to induce a unidirectional torsion of both whiskers. Torsional movement was associated with protracting movement, indicating that in the vibrissal system, like in the ocular system, torsional movement is mechanically coupled to horizontal and vertical movements. This study shows that torsional whisker rotation is mediated by specific OMs whose morphology and attachment sites determine rotation direction and mechanical coupling, and motor innervation determines rotation dynamics. Anat Rec, 300:1643-1653, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Direct torsional actuation of microcantilevers using magnetic excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gosvami, Nitya Nand; Nalam, Prathima C.; Tam, Qizhan

2014-09-01

Torsional mode dynamic force microscopy can be used for a wide range of studies including mapping lateral contact stiffness, torsional frequency or amplitude modulation imaging, and dynamic friction measurements of various materials. Piezo-actuation of the cantilever is commonly used, but it introduces spurious resonances, limiting the frequency range that can be sampled, and rendering the technique particularly difficult to apply in liquid medium where the cantilever oscillations are significantly damped. Here, we demonstrate a method that enables direct torsional actuation of cantilevers with high uniformity over wide frequency ranges by attaching a micrometer-scale magnetic bead on the back side ofmore » the cantilever. We show that when beads are magnetized along the width of the cantilever, efficient torsional actuation of the cantilevers can be achieved using a magnetic field produced from a solenoid placed underneath the sample. We demonstrate the capability of this technique by imaging atomic steps on graphite surfaces in tapping mode near the first torsional resonance of the cantilever in dodecane. The technique is also applied to map the variations in the lateral contact stiffness on the surface of graphite and polydiacetylene monolayers.« less

Control of retinal isomerization in bacteriorhodopsin in the high-intensity regime

PubMed Central

Florean, Andrei C.; Cardoza, David; White, James L.; Lanyi, J. K.; Sension, Roseanne J.; Bucksbaum, Philip H.

2009-01-01

A learning algorithm was used to manipulate optical pulse shapes and optimize retinal isomerization in bacteriorhodopsin, for excitation levels up to 1.8 × 1016 photons per square centimeter. Below 1/3 the maximum excitation level, the yield was not sensitive to pulse shape. Above this level the learning algorithm found that a Fourier-transform-limited (TL) pulse maximized the 13-cis population. For this optimal pulse the yield increases linearly with intensity well beyond the saturation of the first excited state. To understand these results we performed systematic searches varying the chirp and energy of the pump pulses while monitoring the isomerization yield. The results are interpreted including the influence of 1-photon and multiphoton transitions. The population dynamics in each intermediate conformation and the final branching ratio between the all-trans and 13-cis isomers are modified by changes in the pulse energy and duration. PMID:19564608

Mechanical origins of rightward torsion in early chick brain development

NASA Astrophysics Data System (ADS)

Chen, Zi; Guo, Qiaohang; Dai, Eric; Taber, Larry

2015-03-01

During early development, the neural tube of the chick embryo undergoes a combination of progressive ventral bending and rightward torsion. This torsional deformation is one of the major organ-level left-right asymmetry events in development. Previous studies suggested that bending is mainly due to differential growth, however, the mechanism for torsion remains poorly understood. Since the heart almost always loops rightwards that the brain twists, researchers have speculated that heart looping affects the direction of brain torsion. However, direct evidence is lacking, 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. Moreover, the asymmetry of the looping heart gives rise to the chirality of the twisted brain. A computational model and a 3D printed physical model are employed to help interpret these findings. Our work clarifies the mechanical origins of brain torsion and the associated left-right asymmetry, and further reveals that the asymmetric development in one organ can induce the asymmetry of another developing organ through mechanics, reminiscent of D'Arcy Thompson's view of biological form as ``diagram of forces''. Z.C. is supported by the Society in Science - Branco Weiss fellowship, administered by ETH Zurich. L.A.T acknowledges the support from NIH Grants R01 GM075200 and R01 NS070918.

Cyclic Axial-Torsional Deformation Behavior of a Cobalt-Base Superalloy

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

The cyclic, high-temperature deformation behavior of a wrought cobalt-base super-alloy, Haynes 188, is investigated under combined axial and torsional loads. This is accomplished through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue database has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gage section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. The fatigue behavior of Haynes 188 at 760 C under axial, torsional, and combined axial-torsional loads and the monotonic and cyclic deformation behaviors under axial and torsional loads have been previously reported. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress ,versus engineering shear strain, axial strain versus engineering shear strain. and axial stress versus shear stress spaces are presented for cyclic in-phase and out-of-phase axial-torsional tests. For in-phase tests, three different values of the proportionality constant lambda (the ratio of engineering shear strain amplitude to axial strain amplitude, are examined, viz. 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 degrees with lambda equals 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress-strain and the maximum shear stress-maximum engineering shear strain (Tresca) curves. Comparisons are also made between the hardening behaviors of cyclic axial, torsional, and combined in-phase (lambda = 1.73 and phi = 0) and out-of-phase (lambda = 1.73 and phi = 90') axial-torsional fatigue tests. These comparisons

Determination of the Glass-Transition Temperature of GRPS and CFRPS Using a Torsion Pendulum in Regimes of Freely Damped Vibrations and Quasi-Stastic Torsion of Specimens

NASA Astrophysics Data System (ADS)

Startsev, V. O.; Lebedev, M. P.; Molokov, M. V.

2018-03-01

A method to measure the glass-transition temperature of polymers and polymeric matrices of composite materials with the help of an inverse torsion pendulum over a wide range of temperatures is considered combining the method of free torsional vibrations and a quasi-static torsion of specimens. The glass-transition temperature Tg of a KMKS-1-80. T10 fiberglass, on increasing the frequency of freely damped torsional vibrations from 0.7 to 9.6 Hz, was found to increase from 132 to 140°C. The value of Tg of these specimens, determined by measuring the work of their torsion through a small fixed angle was 128.6°C ± 0.8°C. It is shown that the use of a torsion pendulum allows one to determine the glass-transition temperature of polymeric or polymer matrices of PCMs in dynamic and quasi-static deformation regimes of specimens.

Direct observation of methyl rotor and vib-rotor states of S0 toluene: a revised torsional barrier due to torsion-vibration coupling.

PubMed

Gascooke, Jason R; Virgo, Edwina A; Lawrance, Warren D

2015-01-14

We report a two dimensional, laser induced fluorescence study of the lowest 345 cm(-1) region of S0 toluene. Methyl rotor levels of 00 up to m = 6 and of 201 up to m = 4 are observed. The rotor levels of 00 and 201 have quite different energy spacings that are well fit by a model that includes strong torsion-vibration coupling between them. The model requires that the rotor barrier height be revised from -4.84 cm(-1) (methyl hydrogens in a staggered conformation) to +1.57 cm(-1) (eclipsed conformation). However, the 3a2″ state lies below the 3a1″ state as expected for a staggered conformation due to energy shifts associated with the torsion-vibration coupling. It is shown that the rotor wave-functions exhibit little localization at the torsional energy minima. The variation in the m = 0 wavefunction probability distribution with torsional angle is shown to be very similar for the previously accepted negative V6 value and the torsion-vibration coupling model as this coupling shifts the phase of the wavefunction by 30° compared with its phase for V6 alone. The presence of a strong Δυ = ± 1 torsion-vibration coupling involving the lowest frequency vibrational mode provides a potential pathway for rapid intramolecular vibrational energy redistribution at higher energies.

Torsional osteotomies of the tibia in patellofemoral dysbalance.

PubMed

Dickschas, Jörg; Tassika, Aliki; Lutter, Christoph; Harrer, Jörg; Strecker, Wolf

2017-02-01

Anterior knee pain or patellofemoral instability is common symptom of patellofemoral dysbalance or maltracking. Tibial torsional deformities can be the reason of this pathology. After appropriate diagnostic investigation, the treatment of choice is a torsional osteotomy. This study addresses the diagnostic investigation, treatment, and the outcome of torsional osteotomies of the tibia. Does this treatment result in patellofemoral stability and provide pain relief? Forty-nine tibial torsional osteotomies were included. The major symptoms were patellofemoral instability in 19 cases and anterior knee pain in 42 cases. In addition to clinical and radiographic analysis, a torsional angle CT scan was performed pre-operatively. A visual analog scale (VAS), the Japanese Knee Society score, the Tegner activity score, and the Lysholm score were assessed pre-operatively and at the 42-month follow-up. Mean tibial external torsion was 47.4° (SD 5.41; range 37°-66°; standard value 34°). Surgical treatment consisted of an acute supratuberositary tibial internal torsional osteotomy (mean 10.8°; SD 3.01°; range 5°-18°). At the follow-up investigation, the Tegner activity score was increased 0.4 points (p value 0.014) from 3.9 (SD 1.33; range 2-7) to 4.3 (SD 1.25; range 0-7). The Lysholm score increased 26 points (SD 16.32; p value 0.001) from 66 (SD 14.94; range 32-94) to 92 (SD 9.29; range 70-100) and the Japanese Knee Society score increased 18 points (SD 14.70; p value 0.001) from 72 (SD 13.72, range 49-100) to 90 (SD 9.85, range 60-100). VAS was reduced 3.4 points (SD 2.89; p value 0.001) from 5.7 (SD 2.78; range 0-10) to 2.3 (SD 1.83; range 0-7). As regards patellofemoral instability, no redislocation occurred in the follow-up period. The results of this study show that in cases of tibial maltorsion, a torsional osteotomy can lead to patellofemoral stability and pain relief, and should be considered as a treatment option. The improved clinical scores in the present

Humeral torsion revisited: a functional and ontogenetic model for populational variation.

PubMed

Cowgill, Libby W

2007-12-01

Anthropological interest in humeral torsion has a long history, and several functional explanations for observed variation in the orientation of the humeral head have been proposed. Recent clinical studies have revived this topic by linking patterns of humeral torsion to habitual activities such as overhand throwing. However, the precise functional implications and ontogenetic history of humeral torsion remain unclear. This study examines the ontogeny of humeral torsion in a large sample of primarily immature remains from six different skeletal collections (n = 407). The results of this research confirm that humeral torsion displays consistent developmental variation within all populations of growing children; neonates display relatively posteriorly oriented humeral heads, and the level of torsion declines steadily into adulthood. As in adults, variation in the angle of humeral torsion in immature individuals varies by population, and these differences arise early in development. However, when examined in the context of the developing muscles of the shoulder complex, it becomes apparent that variation in the angle of humeral torsion is not necessarily related to specific habitual activities. Variability in this feature is more likely caused by a generalized functional imbalance between muscles of medial and lateral rotation that can be produced by a wide variety of upper limb activity patterns during growth. (c) 2007 Wiley-Liss, Inc.

Should Torsion Balance Technique Continue to be Taught to Pharmacy Students?

PubMed

Bilger, Rhonda; Chereson, Rasma; Salama, Noha Nabil

2017-06-01

Objective. To determine the types of balances used in compounding pharmacies: torsion or digital. Methods. A survey was mailed to the pharmacist-in-charge at 698 pharmacies, representing 47% of the pharmacies in Missouri as of July 2013. The pharmacies were randomly selected and stratified by region into eight regions to ensure a representative sample. Information was gathered regarding the type and use of balances and pharmacists' perspectives on the need to teach torsion balance technique to pharmacy students. Results. The response rate for the survey was 53.3%. Out of the total responses received, those pharmacies having a torsion balance, digital balance or both were 46.8%, 27.4% and 11.8%, respectively. About 68.3% of respondents compound prescriptions. The study showed that 52% of compounding pharmacies use torsion balances in their practice. Of those with a balance in their pharmacy, 65.6% favored continuation of torsion balance instruction. Conclusions. Digital balances have become increasingly popular and have replaced torsion balances in some pharmacies, especially those that compound a significant number of prescriptions. The results of this study indicate that torsion balances remain integral to compounding practice. Therefore, students should continue being taught torsion balance technique at the college.

Should Torsion Balance Technique Continue to be Taught to Pharmacy Students?

PubMed Central

Bilger, Rhonda; Chereson, Rasma

2017-01-01

Objective. To determine the types of balances used in compounding pharmacies: torsion or digital. Methods. A survey was mailed to the pharmacist-in-charge at 698 pharmacies, representing 47% of the pharmacies in Missouri as of July 2013. The pharmacies were randomly selected and stratified by region into eight regions to ensure a representative sample. Information was gathered regarding the type and use of balances and pharmacists’ perspectives on the need to teach torsion balance technique to pharmacy students. Results. The response rate for the survey was 53.3%. Out of the total responses received, those pharmacies having a torsion balance, digital balance or both were 46.8%, 27.4% and 11.8%, respectively. About 68.3% of respondents compound prescriptions. The study showed that 52% of compounding pharmacies use torsion balances in their practice. Of those with a balance in their pharmacy, 65.6% favored continuation of torsion balance instruction. Conclusions. Digital balances have become increasingly popular and have replaced torsion balances in some pharmacies, especially those that compound a significant number of prescriptions. The results of this study indicate that torsion balances remain integral to compounding practice. Therefore, students should continue being taught torsion balance technique at the college. PMID:28720913

Complete body-neck torsion of the gallbladder: a case report.

PubMed

Pu, Ta-Wei; Fu, Chun-Yu; Lu, Huai-En; Cheng, Wei-Tung

2014-10-14

Gallbladder torsion is a rare, acute abdominal disease. It was first reported by Wendell in 1898. Since then, only 500 cases have been reported. Gallbladder torsion occurs in all age groups, although it usually appears in the latter stages of life. The occurrence ratio between women and men is 3:1. Most cases are diagnosed during surgery. The main treatment is surgical detorsion and cholecystectomy. Despite progress in radiologic imaging diagnosis, it is not easy to obtain a precise preoperative diagnosis of gallbladder torsion. In previous reports, only 9.8% of all gallbladder torsion cases were diagnosed preoperatively. We present a case of acute body-neck gallbladder torsion in an elderly man, and we review the radiologic findings of magnetic resonance imaging, computed tomography, and ultrasonography. The radiologic findings in the present case were helpful in obtaining a preoperative diagnosis of gallbladder torsion. The diagnosis was confirmed by T2-weighted magnetic resonance images, which showed an intra-gallbladder segment located between the body and neck of the gallbladder, with a notable crease within this segment.

Experimental investigation of cyclic thermomechanical deformation in torsion

NASA Technical Reports Server (NTRS)

Ellis, John R.; Castelli, Michael G.; Bakis, Charles E.

1992-01-01

An investigation of thermomechanical testing and deformation behavior of tubular specimens under torsional loading is described. Experimental issues concerning test accuracy and control specific to thermomechanical loadings under a torsional regime are discussed. A series of shear strain-controlled tests involving the nickel-base superalloy Hastelloy X were performed with various temperature excursions and compared to similar thermomechanical uniaxial tests. The concept and use of second invariants of the deviatoric stress and strain tensors as a means of comparing uniaxial and torsional specimens is also briefly presented and discussed in light of previous thermomechanical tests conducted under uniaxial conditions.

Leiomyomatosis peritonealis disseminata presenting as omental torsion.

PubMed

Tan, Chjoong Howe Alvin; Ho, Bernard Chi Shern; Shelat, Vishalkumar; Tan, Cher Heng

2012-04-01

Leiomyomatosis peritonealis disseminata is usually asymptomatic or mimics widespread malignancy; acute presentation is rare. We describe a patient with right iliac fossa and lower abdominal pain. Two masses were detected via computed tomography, but at surgery, one of these implanted leiomyomas had undergone acute omental torsion. This case illustrates a rare complication of omental leiomyoma torsion clinically mimicking acute appendicitis.

Chiral dynamos and magnetogenesis induced by torsionful Maxwell-Chern Simons electrodynamics

NASA Astrophysics Data System (ADS)

de Andrade, L. C. Garcia

2018-03-01

Recently chiral anomalous currents have been investigated by Boyarsky et al. and Brandenburg et al. with respect to applications to the early universe. In this paper we show that these magnetic field anomalies, which can give rise to dynamo magnetic field amplification can also be linked to spacetime torsion through the use of a chemical potential and Maxwell electrodynamics with torsion firstly proposed by de Sabbata and Gasperini. When the axial torsion is constant this electrodynamics acquires the form of a Maxwell-Chern-Simmons (MCS) equations where the chiral current appears naturally and the zero component of torsion plays the role of a chemical potential, while the other components play the role of anisotropic conductivity. The chiral dynamo equation in torsionful spacetime is derived here from MSC electrodynamics. Here we have used a recently derived a torsion LV bound of T0˜ {10^{-26}} GeV and the constraint that this chiral magnetic field is a seed for galactic dynamo. This estimate is weaker than the one obtained from the chiral battery seed of ˜ {10^{30}} G without making use of Cartan torsion. The torsion obtained here was derived at 500 pc coherence scale. When a chiral MF is forced to seed a galactic dynamo one obtains a yet weaker MF, of the order of B˜ {10^{12}} G, which is the value of a MF at nucleosynthesis. By the use of chiral dynamo equations from parity-violating torsion one obtains a seed field of B˜ {10^{27}} G, which is a much stronger MF closer to the one obtained by making use of chiral batteries. Chiral vortical currents in non-Riemannian spacetimes derived in Riemannian spaces previously by Flaschi and Fukushima are extended to include minimal coupling with torsion. The present universe yields B˜ {10^{-24}} G, still sufficient to seed galactic dynamos.

The Rotation-Torsion Spectrum of CH_2DOH

NASA Astrophysics Data System (ADS)

Hilali, A. El; Coudert, L. H.; Margulès, L.; Motiyenko, R.; Klee, S.

2010-06-01

Due to the asymmetry of the CH_2D group, the internal rotation problem in the partially deuterated species of methanol CH_2DOH is a complicated one as, unlike in the normal species CH_3OH, the inertia tensor depends on the angle of internal rotation. The CH_2DOH species also displays a dense far infrared torsional spectrum difficult to assign. Recently 38 torsional subbands of CH_2DOH have been identified, but for most of them there is neither an assignment nor an analysis of their rotational structure. In this paper an analysis of the rotation-torsion spectrum of CH_2DOH will be presented. The rotational structure of 23 torsional subbands have been assigned. These subbands are Δ v_t &ge 1 perpendicular subbands with a value of v'_t up to 10b and values of K' and K'' ranging from 0 to 9. For all subbands, the Q-branch was assigned, for 3 subbands, the R- and P-branches could also be found. The results of the rotational analysis with an expansion in J(J+1) of the new subbands and of already observed ones will be presented. When available, microwave lines within the lower torsional level, recorded in this work or already measured, were added to the data set. A theoretical approach aimed at calculating the rotation-torsion energy levels has also been developed. It is based on an expansion in terms of rotation-torsion operators with C_s symmetry and accounts for the dependence of the inertia tensor on the angle of internal rotation. This approach will be used to carry out a preliminary global analyses of the wavenumbers and of the frequencies. Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spec. 256 (2009) 204. Quade, Liu, Mukhopadhyay, and Su, J. Mol. Spec. 192 (1998) 378; Mukhopadhyay, J. Mol. Struct. 695-696 (2004) 357. Liu and Quade, J. Mol. Spec. 146 (1991) 252 Mukhopadhyay et al., J. Chem. Phys. 116 (2002) 3710.

Torsion-rotation intensities in methanol

NASA Astrophysics Data System (ADS)

Pearson, John

Methanol exists in numerous kinds of astronomical objects featuring a wide range of local conditions. The light nature of the molecule coupled with the internal rotation of the methyl group with respect to the hydroxyl group results in a rich, strong spectrum that spans the entire far-infrared region. As a result, any modest size observational window will have a number of strong methanol transitions. This has made it the gas of choice for testing THz receivers and to extract the local physical conditions from observations covering small frequency windows. The latter has caused methanol to be dubbed the Swiss army knife of astrophysics. Methanol has been increasingly used in this capacity and will be used even more for subsequent investigations into the Herschel archive, and with SOFIA and ALMA. Interpreting physical conditions on the basis of a few methanol lines requires that the molecular data, line positions, intensities, and collision rates, be complete, consistent and accurate to a much higher level than previously required for astrophysics. The need for highly reliable data is even more critical for modeling the two classes of widespread maser action and many examples of optical pumping through the torsional bands. Observation of the torsional bands in the infrared will be a unique opportunity to directly connect JWST observations with those of Herschel, SOFIA, and ALMA. The theory for the intensities of torsion-rotation transitions in a molecule featuring a single internally rotating methyl group is well developed after 70 years of research. However, other than a recent very preliminary and not completely satisfactory investigation of a few CH3OH torsional bands, this theory has never been experimentally tested for any C3V internal rotor. More alarming is a set of recent intensity calibrated microwave measurements that showed deviations relative to calculations of up to 50% in some ground state rotational transitions commonly used by astronomers to extract

Engineering a Robust Photovoltaic Device with Quantum Dots and Bacteriorhodopsin

PubMed Central

2015-01-01

We present a route toward a radical improvement in solar cell efficiency using resonant energy transfer and sensitization of semiconductor metal oxides with a light-harvesting quantum dot (QD)/bacteriorhodopsin (bR) layer designed by protein engineering. The specific aims of our approach are (1) controlled engineering of highly ordered bR/QD complexes; (2) replacement of the liquid electrolyte by a thin layer of gold; (3) highly oriented deposition of bR/QD complexes on a gold layer; and (4) use of the Forster resonance energy transfer coupling between bR and QDs to achieve an efficient absorbing layer for dye-sensitized solar cells. This proposed approach is based on the unique optical characteristics of QDs, on the photovoltaic properties of bR, and on state-of-the-art nanobioengineering technologies. It permits spatial and optical coupling together with control of hybrid material components on the bionanoscale. This method paves the way to the development of the solid-state photovoltaic device with the efficiency increased to practical levels. PMID:25383133

Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequencing Effects

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

2000-01-01

Cumulative fatigue behavior of a wrought cobalt-base superalloy, Haynes 188 was investigated at 538 C under various single-step sequences of axial and torsional loading conditions. Initially, fully-reversed, axial and torsional fatigue tests were conducted under strain control at 538 C on thin-walled tubular specimens to establish baseline fatigue life relationships. Subsequently, four sequences (axial/axial, torsional/torsional, axial/torsional, and torsional/axial) of two load-level fatigue tests were conducted to characterize both the load-order (high/low) and load-type sequencing effects. For the two load-level tests, summations of life fractions and the remaining fatigue lives at the second load-level were computed by the Miner's Linear Damage Rule (LDR) and a nonlinear Damage Curve Approach (DCA). In general, for all four cases predictions by LDR were unconservative. Predictions by the DCA were within a factor of two of the experimentally observed fatigue lives for a majority of the cumulative axial and torsional fatigue tests.

Planar torsion spring

NASA Technical Reports Server (NTRS)

Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)

2012-01-01

A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.

Torsion Bounds from CP Violation α2-DYNAMO in Axion-Photon Cosmic Plasma

NASA Astrophysics Data System (ADS)

Garcia de Andrade, L. C.

Years ago Mohanty and Sarkar [Phys. Lett. B 433, 424 (1998)] have placed bounds on torsion mass from K meson physics. In this paper, associating torsion to axions a la Campanelli et al. [Phys. Rev. D 72, 123001 (2005)], it is shown that it is possible to place limits on spacetime torsion by considering an efficient α2-dynamo CP violation term. Therefore instead of Kostelecky et al. [Phys. Rev. Lett. 100, 111102 (2008)] torsion bounds from Lorentz violation, here torsion bounds are obtained from CP violation through dynamo magnetic field amplification. It is also shown that oscillating photon-axion frequency peak is reduced to 10-7 Hz due to torsion mass (or Planck mass when torsion does not propagate) contribution to the photon-axion-torsion action. Though torsion does not couple to electromagnetic fields at classical level, it does at the quantum level. Recently, Garcia de Andrade [Phys. Lett. B 468, 28 (2011)] has shown that the photon sector of Lorentz violation (LV) Lagrangian leads to linear nonstandard Maxwell equations where the magnetic field decays slower giving rise to a seed for galactic dynamos. Torsion constraints of the order of K0≈10-42 GeV can be obtained which are more stringent than the value obtained by Kostelecky et al. A lower bound for the existence of galactic dynamos is obtained for torsion as K0≈10-37 GeV.

Standardized education and parental awareness are lacking for testicular torsion.

PubMed

Friedman, Ariella A; Ahmed, Haris; Gitlin, Jordan S; Palmer, Lane S

2016-06-01

Testicular torsion leads to orchiectomy in 30-50% of cases, which may cause psychological upset and parental guilt over a potentially avertable outcome. Presentation delay is an important modifiable cause of orchiectomy; yet, families are not routinely educated about torsion or its urgency. The present study assessed parental knowledge regarding acute scrotal pain. An anonymous survey was distributed to parents in Urology and ENT offices, asking about their children's gender and scrotal pain history, urgency of response to a child's acute scrotal pain, and familiarity with testicular torsion. Surveys of 479 urology and 59 ENT parents were analyzed. The results between the two were not statistically different. Among the urology parents, 34% had heard of testicular twisting/torsion, most commonly through friends, relatives or knowing someone with torsion (35%); only 17% were informed by pediatricians (Summary Figure). Parents presenting for a child's scrotal pain were significantly more likely to have heard of torsion (69%) than those presenting for other reasons (30%, OR 5.24, P < 0.0001). Only 13% of parents of boys had spoken with their children about torsion. Roughly three quarters of them would seek emergent medical attention - by day (75%) or night (82%) - for acute scrotal pain. However, urgency was no more likely among those who knew about torsion. This was the first study to assess parental knowledge of the emergent nature of acute scrotal pain in a non-urgent setting, and most closely approximating their level of knowledge at the time of pain onset. It also assessed parents' hypothetical responses to the scenario, which was markedly different than documented presentation times, highlighting a potential area for improvement in presentation times. Potential limitations included lack of respondent demographic data, potential sampling bias of a population with greater healthcare knowledge or involvement, and assessment of parents only. Parental knowledge of

Deep learning methods for protein torsion angle prediction.

PubMed

Li, Haiou; Hou, Jie; Adhikari, Badri; Lyu, Qiang; Cheng, Jianlin

2017-09-18

Deep learning is one of the most powerful machine learning methods that has achieved the state-of-the-art performance in many domains. Since deep learning was introduced to the field of bioinformatics in 2012, it has achieved success in a number of areas such as protein residue-residue contact prediction, secondary structure prediction, and fold recognition. In this work, we developed deep learning methods to improve the prediction of torsion (dihedral) angles of proteins. We design four different deep learning architectures to predict protein torsion angles. The architectures including deep neural network (DNN) and deep restricted Boltzmann machine (DRBN), deep recurrent neural network (DRNN) and deep recurrent restricted Boltzmann machine (DReRBM) since the protein torsion angle prediction is a sequence related problem. In addition to existing protein features, two new features (predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments) are used as input to each of the four deep learning architectures to predict phi and psi angles of protein backbone. The mean absolute error (MAE) of phi and psi angles predicted by DRNN, DReRBM, DRBM and DNN is about 20-21° and 29-30° on an independent dataset. The MAE of phi angle is comparable to the existing methods, but the MAE of psi angle is 29°, 2° lower than the existing methods. On the latest CASP12 targets, our methods also achieved the performance better than or comparable to a state-of-the art method. Our experiment demonstrates that deep learning is a valuable method for predicting protein torsion angles. The deep recurrent network architecture performs slightly better than deep feed-forward architecture, and the predicted residue contact number and the error distribution of torsion angles extracted from sequence fragments are useful features for improving prediction accuracy.

Frequency-dependent solvent friction and torsional damping in liquid 1,2-difluoroethane

NASA Astrophysics Data System (ADS)

MacPhail, Richard A.; Monroe, Frances C.

1991-04-01

We have used Raman spectroscopy to study the torsional dynamics, rotational dynamics, and conformational solvation energy of liquid 1,2-difluoroethane. From the Raman intensities, we obtain Δ H(g-t) = -2.4±0.1 kcal/mol, indicating strong dipolar solvation of the gauche conformer. We analyze the Raman linewidths of the CCF bending bands to obtain the zero-frequency torsional damping coefficient or well friction for the gauche conformer, and from the linewidth of the torsion band we obtain the friction evaluated at the torsional frequency. The zero-frequency well friction shows deviations from hydrodynamic behavior reminiscent of those observed for barrier friction, whereas the high-frequency friction is considerably smaller in magnitude and independent of temperature and viscosity. The zero-frequency torsional friction correlates linearly with the rotational friction. It is argued that the small amplitude of the torsional fluctuations emphasizes the short distance, or high wavevector components of the solvent friction. Dielectric friction apparently does not contribute to the torsional friction at the observed frequencies.

Nonlinear Evolution of Short-wavelength Torsional Alfvén Waves

NASA Astrophysics Data System (ADS)

Shestov, S. V.; Nakariakov, V. M.; Ulyanov, A. S.; Reva, A. A.; Kuzin, S. V.

2017-05-01

We analyze nonlinear evolution of torsional Alfvén waves in a straight magnetic flux tube filled in with a low-β plasma, and surrounded with a plasma of lower density. Such magnetic tubes model, in particular, a segment of a coronal loop or a polar plume. The wavelength is taken comparable to the tube radius. We perform a numerical simulation of the wave propagation using ideal magnetohydrodynamics. We find that a torsional wave nonlinearly induces three kinds of compressive flows: the parallel flow at the Alfvén speed, which constitutes a bulk plasma motion along the magnetic field, the tube wave, and also transverse flows in the radial direction, associated with sausage fast magnetoacoustic modes. In addition, the nonlinear torsional wave steepens and its propagation speed increases. The latter effect leads to the progressive distortion of the torsional wave front, I.e., nonlinear phase mixing. Because of the intrinsic non-uniformity of the torsional wave amplitude across the tube radius, the nonlinear effects are more pronounced in regions with higher wave amplitudes. They are always absent at the axes of the flux tube. In the case of a linear radial profile of the wave amplitude, the nonlinear effects are localized in an annulus region near the tube boundary. Thus, the parallel compressive flows driven by torsional Alfvén waves in the solar and stellar coronae, are essentially non-uniform in the perpendicular direction. The presence of additional sinks for the wave energy reduces the efficiency of the nonlinear parallel cascade in torsional Alfvén waves.

Analysis of the Rotation-Torsion Spectrum of CH_2DOH Within the e_0, e_1, and o_1 Torsional Levels

NASA Astrophysics Data System (ADS)

Coudert, L. H.; Pearson, John C.; Yu, Shanshan; Margules, L.; Motiyenko, R. A.; Klee, S.

2013-06-01

Since the first assignments of Quade and coworkers, a more satisfactory understanding of the spectrum of CH_2DOH has now been achieved. Thanks to a multidimensional potential energy surface and to a new theoretical approach accounting for the internal rotation of a partially deuterated methyl group, 76 torsional subbands could be identified in the microwave and FIR domains. 8356 rotation and rotation-torsion transitions were also assigned for the three lowest lying torsional levels, e_0, e_1, and o_1, in the microwave and terahertz domains and were analyzed with empirical models. In this paper, a new approach aimed at accounting for the rotation-torsion energy levels of CH_2DOH will be presented. It is based on the exact expression of the generalized 4× 4 inertia tensor of the molecule and accounts for the C_s symmetry of the partially deuterated methyl group, for the dependence of the rotational constants on the angle of internal rotation, and for the rotation-torsion Coriolis coupling. This approach will be used to analyze high-resolution data involving the three lowest lying torsional levels, up to k=11. In addition to the microwave data reported recently,^d new transitions recorded in the terahertz domain at JPL will be analyzed. The results of the analysis will be presented in the paper and the parameters determined in the analysis will be discussed. Quade and Suenram, J. Chem. Phys. {73} (1980) 1127; and Su and Quade, J. Mol. Spec. {134} (1989) 290. Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spec. {256} (2009) 204. El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. {135} (2011) 194309. Pearson, Yu, and Drouin, J. Mol. Spec. {280} (2012) 119. Quade and Lin, J. Chem. Phys. {38} (1963) 540.

Aeroelastic considerations for torsionally soft rotors

NASA Technical Reports Server (NTRS)

Mantay, W. R.; Yeager, W. T., Jr.

1986-01-01

A research study was initiated to systematically determine the impact of selected blade tip geometric parameters on conformable rotor performance and loads characteristics. The model articulated rotors included baseline and torsionally soft blades with interchangeable tips. Seven blade tip designs were evaluated on the baseline rotor and six tip designs were tested on the torsionally soft blades. The designs incorporated a systemmatic variation in geometric parameters including sweep, taper, and anhedral. The rotors were evaluated in the NASA Langley Transonic Dynamics Tunnel at several advance ratios, lift and propulsive force values, and tip Mach numbers. A track sensitivity study was also conducted at several advance ratios for both rotors. Based on the test results, tip parameter variations generated significant rotor performance and loads differences for both baseline and torsionally soft blades. Azimuthal variation of elastic twist generated by variations in the tip parameters strongly correlated with rotor performance and loads, but the magnitude of advancing blade elastic twist did not. In addition, fixed system vibratory loads and rotor track for potential conformable rotor candidates appears very sensitive to parametric rotor changes.

Mannitol has a protective effect on testicular torsion: An experimental rat model.

PubMed

Kurt, Omer; Yazici, Cenk Murat; Erboga, Mustafa; Turan, Cuneyt; Bozdemir, Yeliz; Akbas, Alpaslan; Turker, Polat; Aktas, Cevat; Aydin, Murat; Yesildag, Ebru

2016-06-01

Testicular torsion is an emergency condition that causes testicular injury. Any treatment opportunity reducing the destructive effect of testicular torsion is important for the future life of patients. In this experimental study we investigated the protective effect of mannitol on ischemia-reperfusion (I/R) injury in a rat testes torsion model. In total, 32 male Sprague Dawley rats were included. Four experimental groups included eight rats each. Group A was a sham group in which the right testis was brought out through a scrotal incision and then replaced in the scrotum without torsion. In Group B, the right testis was torsioned, by rotating 720° clockwise and fixed to the scrotum with no treatment. In Group C, the same testicular torsion process was performed with saline infusion just after testicular torsion. In group D, mannitol infusion was used just after testicular torsion. Testicles were detorsioned after 3 h and left inside for more than 2 h before orchiectomy. Histopathological, immunohistochemical, and biochemical analyses were performed. Testicular architecture was disturbed significantly in the torsion groups without mannitol infusion. However, testicular tissue structure was significantly better in the mannitol-treated group, demonstrating a protective effect. Similar findings were also shown for the proliferating cell nuclear antigen (PCNA) index and antioxidant activity; both were higher in the mannitol group than in the no-treatment and saline groups (p < 0.01). The apoptotic index was also significantly lower in the mannitol-treated group compared with the no treatment and saline groups (p < 0.01). The seminiferous tubule structure in testicular torsion without mannitol treatment was significantly disturbed, whereas the structural disruption was considerably less in the mannitol group. Mannitol treatment also decreased reactive oxygen radical levels significantly and was able to decrease apoptosis. These results were consistent with other

Torsion effect on fully developed flow in a helical pipe

NASA Technical Reports Server (NTRS)

Kao, Hsiao C.

1987-01-01

Two techniques, a series expansion method of perturbed Poiseuille flow valid for low Dean numbers and a solution of the complete Navier-Stokes equation applicable to intermediate Dean values, are used to investigate the torsion effect on the fully developed laminar flow in a helical pipe of constant circular cross section. For the secondary flow patterns, the results show that the presence of torsion can produce a significant effect if the ratio of the curvature to the torsion is of order unity. The secondary flow is distorted in these cases. It is noted that the torsion effect is, however, usually small, and that the secondary flow has the usual pattern of a pair of counter-rotating vortices of nearly equal strength.

Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures.

PubMed

Sheng, Jun; Gandhi, Dheeraj; Gullapalli, Rao; Simard, J Marc; Desai, Jaydev P

2017-02-01

This paper presents the design, modeling, and control of a meso-scale torsion actuator based on shape memory alloy (SMA) for image-guided surgical procedures. Developing a miniature torsion actuator is challenging, but it opens the possibility of significantly enhancing the robot agility and maneuverability. The proposed torsion actuator is bi-directionally actuated by a pair of antagonistic SMA torsion springs through alternate Joule heating and natural cooling. The torsion actuator is integrated into a surgical robot prototype to demonstrate its working performance in the humid environment under C-Arm CT image guidance.

Development of a Meso-Scale SMA-Based Torsion Actuator for Image-Guided Procedures

PubMed Central

Sheng, Jun; Gandhi, Dheeraj; Gullapalli, Rao; Simard, J. Marc; Desai, Jaydev P.

2016-01-01

This paper presents the design, modeling, and control of a meso-scale torsion actuator based on shape memory alloy (SMA) for image-guided surgical procedures. Developing a miniature torsion actuator is challenging, but it opens the possibility of significantly enhancing the robot agility and maneuverability. The proposed torsion actuator is bi-directionally actuated by a pair of antagonistic SMA torsion springs through alternate Joule heating and natural cooling. The torsion actuator is integrated into a surgical robot prototype to demonstrate its working performance in the humid environment under C-Arm CT image guidance. PMID:28210189

Gastric dilatation-volvulus after splenic torsion in two dogs.

PubMed

Millis, D L; Nemzek, J; Riggs, C; Walshaw, R

1995-08-01

Two dogs developed gastric dilatation-volvulus 2 and 17 months, respectively, after splenectomy for treatment of splenic torsion. Splenic displacement and torsion may stretch the gastric ligaments, allowing increased mobility of the stomach. After splenectomy, an anatomic void may be created in the cranioventral part of the abdomen, contributing to the mobility of the stomach. Veterinarians treating dogs with isolated splenic torsion may wish to consider prophylactic gastropexy at splenectomy, to reduce the chance of future gastric dilatation-volvulus. Prophylactic gastropexy should be done only if the dog's hemodynamic status is stable enough to allow for performance of the additional surgery.

Improving the sensitivity of a torsion pendulum by using an optical spring method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Qinglan; Yeh Hsienchi; Zhou Zebing

We present a scheme aiming at improving the sensitivity of a torsion pendulum by means of radiation-pressure-induced optical spring. Two partial-reflective mirrors are installed on the opposite sides of a torsion pendulum, and one high-reflective mirror is mounted at the end of the torsion beam so that two identical Fabry-Perot cavities can be formed and aligned in series. Due to the antisymmetric radiation pressures acting on the opposite sides of the torsion beam, a negative restoring coefficient can be generated within a certain dynamic range, such that both the resultant torsional rigidity and the resonant frequency of the torsion pendulummore » are reduced, and the minimum detectable response torque in high-frequency region can be reduced accordingly.« less

[Torsion of wandering spleen in a teenager: about a case].

PubMed

Dème, Hamidou; Akpo, Léra Géraud; Fall, Seynabou; Badji, Nfally; Ka, Ibrahima; Guèye, Mohamadou Lamine; Touré, Mouhamed Hamine; Niang, El Hadj

2016-01-01

Wandering or migrating spleen is a rare anomaly which is usually described in children. Complications, which include pedicle torsion, are common and can be life-threatening. We report the case of a 17 year-old patient with a long past medical history of epigastric pain suffering from wandering spleen with chronic torsion of the pedicle. The clinical picture was marked by spontaneously painful epigastric mass, evolved over the past 48 hours. Abdominal ultrasound objectified heterogeneous hypertrophied ectopic spleen in epigastric position and a subcapsular hematoma. Doppler showed a torsion of splenic pedicle which was untwisted 2 turns and a small blood stream on the splenic artery. Abdominal CT scan with contrast injection showed a lack of parenchymal enhancement of large epigastric ectopic spleen and a subcapsular hematoma. The diagnosis of wandering spleen with chronic torsion of the pedicle complicated by necrosis and subcapsular hematoma was confirmed. The patient underwent splenectomy. The postoperative course was uneventful. We here discuss the contribution of ultrasound and CT scan in the diagnosis of wandering spleen with chronic torsion of the pedicle.

Local metrics admitting a principal Killing-Yano tensor with torsion

NASA Astrophysics Data System (ADS)

Houri, Tsuyoshi; Kubizňák, David; Warnick, Claude M.; Yasui, Yukinori

2012-08-01

In this paper we initiate a classification of local metrics admitting the principal Killing-Yano tensor with a skew-symmetric torsion. It is demonstrated that in such spacetimes rank-2 Killing tensors occur naturally and mutually commute. We reduce the classification problem to that of solving a set of partial differential equations, and we present some solutions to these PDEs. In even dimensions, three types of local metrics are obtained: one of them naturally generalizes the torsion-less case while the others occur only when the torsion is present. In odd dimensions, we obtain more varieties of local metrics. The explicit metrics constructed in this paper are not the most general possible admitting the required symmetry; nevertheless, it is demonstrated that they cover a wide variety of solutions of various supergravities, such as the Kerr-Sen black holes of (un-)gauged Abelian heterotic supergravity, the Chong-Cvetic-Lü-Pope black hole solution of five-dimensional minimal supergravity or the Kähler with torsion manifolds. The relation between generalized Killing-Yano tensors and various torsion Killing spinors is also discussed.

A tension-torsional fatigue testing apparatus for micro-scale components.

PubMed

Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

2016-01-01

Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results.

A tension-torsional fatigue testing apparatus for micro-scale components

NASA Astrophysics Data System (ADS)

Fu, Sichao; Wang, Lei; Chen, Gang; Yu, Dunji; Chen, Xu

2016-01-01

Mechanical characterization of micro-scale components under complex loading conditions is a great challenge. To meet such a challenge, a microtension-torsional fatigue testing apparatus is developed in this study that specializes in the evaluation of multiaxial fatigue behavior of thin stent wires. The actuation and measurement in two controlled directions are incorporated in the tensile and torsional load frames, respectively, and a thrust air bearing is applied for the coupling of the two frames. The axial deformation of specimens measured by a grating sensor built in the linear motor and by a non-contact displacement detect system is compared and corrected. The accuracy of the torque measurement is proved by torsion tests on thin wires of 316L stainless steel in nominal diameters of 100 μm. Multistep torsion test, multiaxial ratcheting test, and a fully strain controlled multiaxial cyclic test are performed on 100 μm and 200 μm-diameter 316L wires using this apparatus. The capability of the equipment in tension-torsional cyclic tests for micro-scale specimens is demonstrated by the experimental results.

Torsional Stability of Aluminum Alloy Seamless Tubing

NASA Technical Reports Server (NTRS)

Moore, R L; Paul, D A

1939-01-01

Torsion tests were made on 51ST aluminum-alloy seamless tubes having diameter-to-thickness ratios of from 77 to 139 and length-to-diameter ratios of from 1 to 60. The torsional strengths developed in the tubes which failed elastically (all tubes having lengths greater than 2 to 6 times the diameter) were in most cases within 10 percent of the value indicated by the theories of Donnel, Timoshenko, and Sturm, assuming a condition of simply supported ends.

Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11.

PubMed

Brack, T L; Delaney, J K; Atkinson, G H; Albeck, A; Sheves, M; Ottolenghi, M

1993-08-01

The picosecond molecular dynamics in an artificial bacteriorhodopsin (BR) pigment containing a structurally modified all-trans retinal chromphore with a six-membered ring bridging the C11=C12-C13 positions (BR6.11) are measured by picosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. Time-dependent intensity and spectral changes in absorption in the 570-650-nm region are monitored for delays as long as 5 ns after the 7-ps, 573-nm excitation of BR6.11. Two intermediates, J6.11 and K6.11/1, both with enhanced absorption to the red (> 600 nm) of the BR6.11 spectrum are observed within approximately 50 ps. The J6.11 intermediate decays with a time constant of 12 +/- 3 ps to form K6.11/1. The K6.11/1 intermediate decays with an approximately 100-ps time constant to form a third intermediate, K6.11/2, which is observed through diminished 650-nm absorption (relative to that of K6.11/1). No other transient absorption changes are found during the remainder of the initial 5-ns period of the BR6.11 photoreaction. Fluorescence in the 650-900-nm region is observed from BR6.11, K6.11/1, and K6.11/2, but no emission assignable to J6.11 is found. The BR6.11 fluroescence spectrum has a approximately 725-nm maximum which is blue-shifted by approximately 15 nm relative to that of native BR-570 and is 4.2 +/- 1.5 times larger in intensity (same sample optical density). No differences in the profile of the fluorescence spectra of BR6.11 and the intermediates K6.11/1 and K6.11/2 are observed. Following ground-state depletion of the BR6.11 population, the time-resolved fluroescence intensity monitored at 725 nm increases with two time constants, 12 +/- 3 and approximately 100 ps, both of which correlate well with changes in the picosecond transient absorption data. The resonance Raman spectrum of ground-state BR6.11, measured with low-energy, 560-nm excitation, is significantly different from the spectrum of native BR-570, thus confirming that the

Nonlinear Hysteretic Torsional Waves

NASA Astrophysics Data System (ADS)

Cabaret, J.; Béquin, P.; Theocharis, G.; Andreev, V.; Gusev, V. E.; Tournat, V.

2015-07-01

We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters.

Torsion of the fallopian tube--a late complication of sterilisation.

PubMed

Sivanesaratnam, V

1986-02-01

Torsion of an intact fallopian tube, unaccompanied by torsion of the ipsilateral ovary, was noted as a complication of bilateral tubal occlusion by the Pomeroy method in a 45-year old Indian woman. The sterilization was performed 5 years previously, at the time of Cesarean section delivery. The patient presented with a history of pain in the right iliac fossa. Laparotomy showed that the distal segment of the right fallopian tube was twisted 3 times on the distal mesosalpinx and appeared tense and gangrenous. The right ovary was normal and a 2 cm gap was noted between the proximal and distal segments of the tube. As a rare complication of the Pomeroy method, the gap in the tube can allow the distal mesosalpinx to act as a pedicle, and with a long mesosalpinx, the fimbriated segment of the tube lies free and may swing and twist to produce torsion. The occurrence of torsion is further promoted by a vascular disturbance leading to venous congestion, edema, and increased weight of the free fimbrial end of the tube. In those patients with a history of sterilization, torsion of the fallopian tube should be considered in the differential diagnosis of acute lower abdominal pain. Torsion of the fallopian tube has also been reported following other methods of tubal occlusion, including cautery and clips.

Decreased left ventricular torsion in patients with isolated mitral stenosis.

PubMed

Kirilmaz, B; Asgun, F; Saygi, S; Ercan, E

2015-02-01

Left ventricular (LV) torsion is a sensitive indicator of myocardial contractility and cardiac structure, and has recently been recognized as a sensitive indicator of cardiac performance. The aim of our study was to assess the effect of isolated mitral stenosis on LV torsion. We enrolled 19 patients with isolated mitral stenosis and 19 age- and gender-matched healthy subjects in the study. All patients had a normal sinus rhythm. All study subjects underwent two-dimensional echocardiography. Basal and apical LV rotations and LV torsion were evaluated using speckle-tracking echocardiography. Demographic characteristics, basic echocardiographic measures of LV ejection fraction, LV wall thickness, and LV mass index were similar between the two groups. The degrees of LV torsion (11.3 ± 4.7, 15.4 ± 4.9°, p=0.014) and LV basal rotation (- 3.7 ± 1.9, - 6.5 ± 2.1°, p< 0.001) were significantly decreased in the mitral stenosis group. There was a moderate positive correlation between mitral valve area and LV torsion (r=0.531, p=0.019). We showed significant reductions in LV torsion and LV basal rotation in patients with mitral valve stenosis. Structural and anatomical changes occurring during the progression of mitral stenosis may be responsible for these impaired movements.

Investigations on Torsion of the Two-Chords Single Laced Members

NASA Astrophysics Data System (ADS)

Lorkowski, Paweł; Gosowski, Bronisław

2017-06-01

The paper presents experimental and numerical studies to determine the equivalent second moment of area of the uniform torsion of the two-chord steel single laced members. The members are used as poles of railway traction network gates, and steel columns of framed buildings as well. The stiffness of uniform torsion of this kind of columns allows to the determine the critical loads of the spatial stability. The experimental studies have been realized on a single - span members with rotation arrested at their ends, loaded by a torque applied at the mid-span. The relationship between angle of rotation of the considered cross-section and the torque has been determined. Appropriate numerical model was created in the ABAQUS program, based on the finite element method. A very good compatibility has been observed between experimental and numerical studies. The equivalent second moment of area of the uniform torsion for analysed members has been determined by comparing the experimental and analytical results to those obtained from differential equation of non-uniform torsion, based on Vlasov's theory. Additionally, the parametric analyses of similar members subjected to the uniform torsion, for the richer range of cross-sections have been carried out by the means of SOFiSTiK program. The purpose of the latter was determining parametrical formulas for calculation of the second moment of area of uniform torsion.

Nonlinear Evolution of Short-wavelength Torsional Alfvén Waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shestov, S. V.; Nakariakov, V. M.; Ulyanov, A. S.

2017-05-10

We analyze nonlinear evolution of torsional Alfvén waves in a straight magnetic flux tube filled in with a low- β plasma, and surrounded with a plasma of lower density. Such magnetic tubes model, in particular, a segment of a coronal loop or a polar plume. The wavelength is taken comparable to the tube radius. We perform a numerical simulation of the wave propagation using ideal magnetohydrodynamics. We find that a torsional wave nonlinearly induces three kinds of compressive flows: the parallel flow at the Alfvén speed, which constitutes a bulk plasma motion along the magnetic field, the tube wave, andmore » also transverse flows in the radial direction, associated with sausage fast magnetoacoustic modes. In addition, the nonlinear torsional wave steepens and its propagation speed increases. The latter effect leads to the progressive distortion of the torsional wave front, i.e., nonlinear phase mixing. Because of the intrinsic non-uniformity of the torsional wave amplitude across the tube radius, the nonlinear effects are more pronounced in regions with higher wave amplitudes. They are always absent at the axes of the flux tube. In the case of a linear radial profile of the wave amplitude, the nonlinear effects are localized in an annulus region near the tube boundary. Thus, the parallel compressive flows driven by torsional Alfvén waves in the solar and stellar coronae, are essentially non-uniform in the perpendicular direction. The presence of additional sinks for the wave energy reduces the efficiency of the nonlinear parallel cascade in torsional Alfvén waves.« less

Torsional Dynamics of Steerable Needles: Modeling and Fluoroscopic Guidance

PubMed Central

Swensen, John P.; Lin, MingDe; Okamura, Allison M.; Cowan, Noah J.

2017-01-01

Needle insertions underlie a diversity of medical interventions. Steerable needles provide a means by which to enhance existing needle-based interventions and facilitate new ones. Tip-steerable needles follow a curved path and can be steered by twisting the needle base during insertion, but this twisting excites torsional dynamics that introduce a discrepancy between the base and tip twist angles. Here, we model the torsional dynamics of a flexible rod—such as a tip-steerable needle—during subsurface insertion and develop a new controller based on the model. The torsional model incorporates time-varying mode shapes to capture the changing boundary conditions inherent during insertion. Numerical simulations and physical experiments using two distinct setups—stereo camera feedback in semi-transparent artificial tissue and feedback control with real-time X-ray imaging in optically opaque artificial tissue— demonstrate the need to account for torsional dynamics in control of the needle tip. PMID:24860026

[The functional sport shoe parameter "torsion" within running shoe research--a literature review].

PubMed

Michel, F I; Kälin, X; Metzger, A; Westphal, K; Schweizer, F; Campe, S; Segesser, B

2009-12-01

Within the sport shoe area torsion is described as the twisting and decoupling of the rear-, mid- and forefoot along the longitudinal axis of the foot. Studies have shown that running shoes restrict the torsion of the foot and thus they increase the pronation of the foot. Based on the findings, it is recommended to design running shoes, which allow the natural freedom of movement of the foot. The market introduction of the first torsion concept through adidas(R) took place in 1989. Independently of the first market introduction, only one epidemiological study was conducted in the running shoe area. The study should investigate the occurrence of Achilles tendon problems of the athletes running in the new "adidas Torsion(R) shoes". However, further studies quantifying the optimal region of torsionability concerning the reduction of injury incidence are still missing. Newer studies reveal that the criterion torsion only plays a secondary roll regarding the buying decision. Moreover, athletes are not able to perceive torsionability as a discrete functional parameter. It is to register, that several workgroups are dealing intensively with the detailed analysis of the foot movement based on kinematic multi-segment-models. However, scientific as well as popular scientific contributions display that the original idea of the torsion concept is still not completely understood. Hence, the "inverse" characteristic is postulated. The present literature review leads to the deduction that the functional characteristics of the torsion concept are not fully implemented within the running shoe area. This implies the necessity of scientific studies, which investigate the relevance of a functional torsion concept regarding injury prevention based on basic and applied research. Besides, biomechanical studies should analyse systematically the mechanism and the effects of torsion relevant technologies and systems.

Cross-axis adaptation of torsional components in the yaw-axis vestibulo-ocular reflex

NASA Technical Reports Server (NTRS)

Trillenberg, P.; Shelhamer, M.; Roberts, D. C.; Zee, D. S.

2003-01-01

The three pairs of semicircular canals within the labyrinth are not perfectly aligned with the pulling directions of the six extraocular muscles. Therefore, for a given head movement, the vestibulo-ocular reflex (VOR) depends upon central neural mechanisms that couple the canals to the muscles with the appropriate functional gains in order to generate a response that rotates the eye the correct amount and around the correct axis. A consequence of these neural connections is a cross-axis adaptive capability, which can be stimulated experimentally when head rotation is around one axis and visual motion about another. From this visual-vestibular conflict the brain infers that the slow-phase eye movement is rotating around the wrong axis. We explored the capability of human cross-axis adaptation, using a short-term training paradigm, to determine if torsional eye movements could be elicited by yaw (horizontal) head rotation (where torsion is normally inappropriate). We applied yaw sinusoidal head rotation (+/-10 degrees, 0.33 Hz) and measured eye movement responses in the dark, and before and after adaptation. The adaptation paradigm lasted 45-60 min, and consisted of the identical head motion, coupled with a moving visual scene that required one of several types of eye movements: (1) torsion alone (-Roll); (2) horizontal/torsional, head right/CW torsion (Yaw-Roll); (3) horizontal/torsional, head right/CCW torsion (Yaw+Roll); (4) horizontal, vertical, torsional combined (Yaw+Pitch-Roll); and (5) horizontal and vertical together (Yaw+Pitch). The largest and most significant changes in torsional amplitude occurred in the Yaw-Roll and Yaw+Roll conditions. We conclude that short-term, cross-axis adaptation of torsion is possible but constrained by the complexity of the adaptation task: smaller torsional components are produced if more than one cross-coupling component is required. In contrast, vertical cross-axis components can be easily trained to occur with yaw head

Ovarian torsion in children: management and outcomes.

PubMed

Geimanaite, Lina; Trainavicius, Kestutis

2013-09-01

The purpose of this study is to evaluate the clinical symptoms, diagnosis, management, and outcomes in children with ovarian torsion. The charts of 50 patients with 53 cases of ovarian torsion treated between January 1989 and March 2012 were reviewed retrospectively. Long term follow up was available for 20 girls who had their ovaries left in the abdominal cavity after detorsion. In 22 cases ovaries were removed, and in 31 cases the torsion was relieved and the ovaries left in the abdominal cavity. Twenty-five of the salvaged ovaries were black-bluish and 10 bluish in color. Since 2005, after a change in preferred treatment, all ovaries treated by detorsion were left in the abdominal cavity. The long term results were observed clinically and by ultrasound in 20 girls. Multifollicular ovaries were found in 17 girls. One girl had a normal size paucifollicular ovary, a one-year-old girl had a normal size ovary with microfollicles, and one girl had no ovarian material detectable by ultrasound. Long term analysis of the treatment of ovarian torsion revealed that ovaries treated by detorsion and left in the abdominal cavity preserved their normal anatomy and function. Conservative surgical treatment proved to be safe. None of the girls had thromboembolism or peritonitis, and no malignant tumors were found in the operated ovaries. Copyright © 2013 Elsevier Inc. All rights reserved.

An Assessment of Cumulative Axial and Torsional Fatigue in a Cobalt-Base Superalloy

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

2010-01-01

Cumulative fatigue under axial and torsional loading conditions can include both load-order (higMow and low/high) as well as load-type sequence (axial/torsional and torsional/axial) effects. Previously reported experimental studies on a cobalt-base superalloy, Haynes 188 at 538 C, addressed these effects. These studies characterized the cumulative axial and torsional fatigue behavior under high amplitude followed by low amplitude (Kalluri, S. and Bonacuse, P. J., "Cumulative Axial and Torsional Fatigue: An Investigation of Load-Type Sequance Effects," in Multiaxial Fatigue and Deformation: Testing and Prediction, ASTM STP 1387, S. Kalluri, and P. J. Bonacuse, Eds., American Society for Testing and Materials, West Conshohocken, PA, 2000, pp. 281-301) and low amplitude followed by high amplitude (Bonacuse, P. and Kalluri, S. "Sequenced Axial and Torsional Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading," Biaxial/Multiaxial Fatigue and Fracture, ESIS Publication 31, A. Carpinteri, M. De Freitas, and A. Spagnoli, Eds., Elsevier, New York, 2003, pp. 165-182) conditions. In both studies, experiments with the following four load-type sequences were performed: (a) axial/axial, (b) torsional/torsional, (c) axial/torsional, and (d) torsional/axial. In this paper, the cumulative axial and torsional fatigue data generated in the two previous studies are combined to generate a comprehensive cumulative fatigue database on both the load-order and load-type sequence effects. This comprehensive database is used to examine applicability of the Palmgren-langer-Miner linear damage rule and a nonlinear damage curve approach for Haynes 188 subjected to the load-order and load-type sequencing described above. Summations of life fractions from the experiments are compared to the predictions from both the linear and nonlinear cumulative fatigue damage approaches. The significance of load-order versus load-type sequence effects for axial and torsional loading conditions

Torsional Properties of TiNi Shape Memory Alloy Tape for Rotary Actuator

NASA Astrophysics Data System (ADS)

Takeda, K.; Tobushi, H.; Mitsui, K.; Nishimura, Y.; Miyamoto, K.

2012-12-01

In order to develop novel shape memory actuators, the torsional deformation of a shape memory alloy (SMA) tape and the actuator models driven by the tape were investigated. The results obtained can be summarized as follows. In the SMA tape subjected to torsion, the martensitic transformation appears along both edges of the tape due to elongation of these elements and grows to the central part. The fatigue life in both the pulsating torsion and alternating torsion is expressed by the unified relationship of the dissipated work in each cycle. Based on an opening and closing door model and a solar-powered active blind model, the two-way rotary driving actuator with a small and simple mechanism can be developed by using torsion of the SMA tape.

Development of Torsional and Linear Piezoelectrically Driven Motors

NASA Technical Reports Server (NTRS)

Duong, Khanh; Newton, David; Garcia, Ephrahim

1996-01-01

The development of rotary and linear inchworm-motors using piezoelectric actuators is presented. The motors' design has the advantage of a macro and micro stepper motor with high load and speed. The torsional design is capable of fast angular positioning with micro level accuracy. Additionally, the rotary motor, as designed, can be used as a clutch/brake mechanism. Constructed prototype motors of both types along with their characteristics are presented. The torsional motor consists of a torsional section that provides angular displacement and torque, and two alternating clamping sections which provide the holding force. The motor relies on the principal piezoelectric coupling coefficient (d33) with no torsional elements, increasing its torque capability. The linear motor consists of a longitudinal vibrator that provides displacement and load, and two alternating clamping sections which provide the holding force. This design eliminates bending moment, tension and shear applied to the actuator elements, increase its load capability and life. Innovative flexure designs have been introduced for both motor types. Critical issues that affect the design and performance of the motors are explored and discussed. Experiments are performed demonstrating the motor prototypes based on the aforementioned design considerations.

Optical monitoring of testicular torsion using a miniaturized near infrared spectroscopy sensor

NASA Astrophysics Data System (ADS)

Shadgan, Babak; Kajbafzadeh, Majid; Nigro, Mark; Kajbafzadeh, A. M.; Macnab, Andrew

2017-02-01

Background: Testicular torsion is an acute urological emergency occurring in children and adolescents. Accurate and fast diagnosis is important as the resulting ischemia can destroy the testis. Currently, Doppler ultrasound is the preferred diagnostic method. Ultrasound is not readily available in all centers which may delay surgical treatment. In this study, a rat model was used to examine the feasibility and sensitivity of using spatially-resolved near infrared spectroscopy (SR-NIRS) with a custom-made miniaturized optical sensor probe to detect and study changes in testicular hemodynamics and oxygenation during three degrees of induced testicular torsion, and after detorsion. Methods: Eight anesthetized rats (16 testes) were studied using SR-NIRS with the miniaturized optical probe applied directly onto the surface of the surgically exposed testis during 360, 720 and 1080 degrees of torsion followed by detorsion. Oxygenated, deoxygenated and total hemoglobin and TOI% were studied pre-and post-manipulations. Results: NIRS monitoring reflected acute testicular ischemia and hypoxia on induction of torsion, and tissue reperfusionreoxygenation after detorsion. Testicular torsion at 720 degrees induced the maximum observed degree of hypoxic changes. In all cases, rhythmic changes were observed in the NIRS signals before inducing torsion; these disappeared after applying 360 degrees of torsion and did not reappear after detorsion. Conclusion: This animal study indicates that SR-NIRS monitoring of the testes using a directly applied miniature sensor is a feasible and sensitive method to detect testicular ischemia and hypoxia immediately after torsion occurs, and testicular reperfusion upon detorsion. This study offers the potential for a SR-NIRS system with a miniaturized sensor to be explored further as a rapid, noninvasive, optical method for detecting testicular torsion in children.

Determining Angle of Humeral Torsion Using Image Software Technique.

PubMed

Patil, Sachin; Sethi, Madhu; Vasudeva, Neelam

2016-10-01

Several researches have been done on the measurement of angles of humeral torsion in different parts of the world. Previously described methods were more complicated, not much accurate, cumbersome or required sophisticated instruments. The present study was conducted with the aim to determine the angles of humeral torsion with a newer simple technique using digital images and image tool software. A total of 250 dry normal adult human humeri were obtained from the bone bank of Department of Anatomy. The length and mid-shaft circumference of each bone was measured with the help of measuring tape. The angle of humeral torsion was measured directly from the digital images by the image analysis using Image Tool 3.0 software program. The data was analysed statistically with SPSS version 17 using unpaired t-test and Spearman's rank order correlation coefficient. The mean angle of torsion was 64.57°±7.56°. On the right side it was 66.84°±9.69°, whereas, on the left side it was found to be 63.31±9.50°. The mean humeral length was 31.6 cm on right side and 30.33 cm on left side. Mid shaft circumference was 5.79 on right side and 5.63 cm on left side. No statistical differences were seen in angles between right and left humeri (p>0.001). From our study, it was concluded that circumference of shaft is inversely proportional to angle of humeral torsion. The length and side of humerus has no relation with the humeral torsion. With advancement of digital technology, it is better to use new image softwares for anatomical studies.

Effects of torsion on the thermal conductivity of multi-layer graphene

NASA Astrophysics Data System (ADS)

Si, Chao; Lu, Gui; Cao, Bing-Yang; Wang, Xiao-Dong; Fan, Zhen; Feng, Zhi-Hai

2017-05-01

This work employs the equilibrium molecular dynamics method to study the effects of torsion on the thermal conductivity of multi-layer graphene. Thermal conductivities of twisted 10-layer 433.91 × 99.68 Å2 graphene with torsion angles of 0°, 11.25°, 22.5°, 33.75°, 45°, 67.5°, 90°, 112.5°, and 135° are calculated. The corresponding radial distribution functions and nearest atomic distances are calculated to reveal the effects of torsion on lattice structures. The spectral energy density (SED) method is utilized to analyze the phonon transport properties. It is very interesting that the thermal conductivity of multi-layer graphene decreases slightly at first and then increases with the increasing torsion angle, and the valley is located at θG = 22.5° with the lowest thermal conductivity of 4692.40 W m-1 K-1. The torsion effect can be considered as a combination of the compression effect and the dislocation effect. Further SED analysis confirms that the effect of dislocation on thermal conductivities can be negligible, while the compression effect decreases the phonon lifetimes of flexural out-of-plane acoustic (ZA) branches and increases the ZA group velocities and the phonon specific heat. The decrease becomes dominated when the torsion angle is small, whereas the increase becomes more and more dominated when the torsion angle becomes larger, which are responsible for the reported variation of thermal conductivities.

Decreased Left Ventricular Torsion and Untwisting in Children with Dilated Cardiomyopathy

PubMed Central

Jin, Seon Mi; Bae, Eun Jung; Choi, Jung Yun; Yun, Yong Soo

2007-01-01

The purpose of this study was to analyze left ventricular (LV) torsion and untwisting, and to evaluate the correlation between torsion and other components of LV contraction in children with dilated cardiomyopathy (DCM). Segmental and global rotation, rotational rate (Vrot) were measured at three levels of LV using the two-dimensional (2D) speckle tracking imaging (STI) method in 10 DCM patients (range 0.6-15 yr, median 6.5 yr, 3 females) and 17 age- and sex-matched normal controls. Global torsion was decreased in DCM (peak global torsion; 10.9±4.6° vs. 0.3±2.1°, p<0.001). Loss of LV torsion occurred mainly by the diminution of counterclockwise apical rotation and was augmented by somewhat less reduction in clockwise basal rotation. In DCM, the normal counterclockwise apical rotation was not observed, and the apical rotation about the central axis was clockwise or slightly counterclockwise (peak apical rotation; 5.9±4.1° vs. -0.9±3.1°, p<0.001). Systolic counterclockwise Vrot and early diastolic clockwise Vrot at the apical level were decreased or abolished. In DCM, decreased systolic torsion and loss of early diastolic recoil contribute to LV systolic and diastolic dysfunction. The STI method may facilitate the serial evaluation of the LV torsional behavior in clinical settings and give new biomechanical concepts for better management of patients with DCM. PMID:17728501

Color-coded duplex sonography for diagnosis of testicular torsion.

PubMed

Zoeller, G; Ringert, R H

1991-11-01

By color-coded duplex sonography moving structures are visualized as red or blue colors within a normal gray-scale B-mode ultrasound image. Thus, blood flow even within small vessels can be visualized clearly. Color-coded duplex sonographic examination was performed in 11 patients who presented with scrotal pain. This method proved to be reliable to differentiate between testicular torsion and testicular inflammation. By clearly demonstrating a lack of intratesticular blood flow in testicular torsion, while avoiding flow in scrotal skin vessels being misinterpreted as intratesticular blood flow, this method significantly decreases the number of patients in whom surgical evaluation is necessary to exclude testicular torsion.

5D Lovelock gravity: New exact solutions with torsion

NASA Astrophysics Data System (ADS)

Cvetković, B.; Simić, D.

2016-10-01

Five-dimensional Lovelock gravity is investigated in the first order formalism. A new class of exact solutions is constructed: the Bañados, Teitelboim, Zanelli black rings with and without torsion. We show that our solution with torsion exists in a different sector of the Lovelock gravity, as compared to the Lovelock Chern-Simons sector or the one investigated by Canfora et al. The conserved charges of the solutions are found using Nester's formula, and the results are confirmed by the canonical method. We show that the theory linearized around the background with torsion possesses two additional degrees of freedom with respect to general relativity.

Torsional anharmonicity in the conformational thermodynamics of flexible molecules

NASA Astrophysics Data System (ADS)

Miller, Thomas F., III; Clary, David C.

We present an algorithm for calculating the conformational thermodynamics of large, flexible molecules that combines ab initio electronic structure theory calculations with a torsional path integral Monte Carlo (TPIMC) simulation. The new algorithm overcomes the previous limitations of the TPIMC method by including the thermodynamic contributions of non-torsional vibrational modes and by affordably incorporating the ab initio calculation of conformer electronic energies, and it improves the conventional ab initio treatment of conformational thermodynamics by accounting for the anharmonicity of the torsional modes. Using previously published ab initio results and new TPIMC calculations, we apply the algorithm to the conformers of the adrenaline molecule.

Thermal characterization of phacoemulsification probes operated in axial and torsional modes.

PubMed

Zacharias, Jaime

2015-01-01

To analyze temperature increases and identify potential sources of heat generated when sleeved and sleeveless phacoemulsification probes were operated in axial and torsional modes using the Infiniti Vision System with the Ozil torsional handpiece. Phacodynamics Laboratory, Pasteur Ophthalmic Clinic, Santiago, Chile. Experimental study. Two computer-controlled thermal transfer systems were developed to evaluate the contribution of internal metal stress and tip-to-sleeve friction on heat generation during phacoemulsification using axial and torsional ultrasound modalities. Both systems incorporated infrared thermal imaging and used a black-body film to accurately capture temperature measurements. Axial mode was consistently associated with greater temperature increases than torsional mode whether tips were operated with or without sleeves. In tests involving bare tips, axial mode and torsional mode peaked at 51.7°C and 34.2°C, respectively. In an example using sleeved tips in which a 30.0 g load was applied for 1 second, temperatures for axial mode reached 45°C and for torsional mode, 38°C. Friction between the sleeved probe and the incisional wall contributed more significantly to the temperature increase than internal metal stress regardless of the mode used. In all experiments, the temperature increase observed with axial mode was greater than that observed with torsional mode, even when conditions such as power or amplitude and flow rate were varied. Tip-to-sleeve friction was a more dominant source of phaco probe heating than internal metal stress. The temperature increase due to internal metal stress was greater with axial mode than with torsional mode. Dr. Zacharias received research funding from Alcon Laboratories, Inc., to conduct this study. He has no financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Instability of ocular torsion in zero gravity - Possible implications for space motion sickness

NASA Technical Reports Server (NTRS)

Diamond, Shirley G.; Markham, Charles H.; Money, Ken E.

1990-01-01

It is proposed that study of the eye torsion reflex and its behavior under novel gravitational states may possibly provide the basis for a long-sought test to predict space motion sickness (SMS). Measures of eye torsion such as ocular counterrolling and spontaneous eye torsion, were examined during hypo- and hypergravity in parabolic flight on the NASA KC-135 aircraft. Ten subjects, including two astronauts, one who had experienced SMS and one who had not, were ranked according to scores of torsional inability at 0 G and divided into two equal groups of high and low susceptibility to SMS. At 1.8 G the groups were significantly different in both the instability measure and the measure of torsional ability. No differences were detected in eye torsion in either 0 G or 1.8 G and none of the tests were significantly different in 1 G. Results suggest that tests of eye torsion on the KC-135 might differentiate those who would experience SMS from those who would not, although it is noted that this is not yet proven.

Extended Reissner-Nordström solutions sourced by dynamical torsion

NASA Astrophysics Data System (ADS)

Cembranos, Jose A. R.; Valcarcel, Jorge Gigante

2018-04-01

We find a new exact vacuum solution in the framework of the Poincaré Gauge field theory with massive torsion. In this model, torsion operates as an independent field and introduces corrections to the vacuum structure present in General Relativity. The new static and spherically symmetric configuration shows a Reissner-Nordström-like geometry characterized by a spin charge. It extends the known massless torsion solution to the massive case. The corresponding Reissner-Nordström-de Sitter solution is also compatible with a cosmological constant and additional U (1) gauge fields.

Damping system for torsion modes of mirror isolation filters in TAMA300

NASA Astrophysics Data System (ADS)

Arase, Y.; Takahashi, R.; Arai, K.; Tatsumi, D.; Fukushima, M.; Yamazaki, T.; Fujimoto, Masa-Katsu; Agatsuma, K.; Nakagawa, N.

2008-07-01

The seismic attenuation system (SAS) in TAMA300 consists of a three-legged inverted pendulum and mirror isolation filters in order to provide a high level of seismic isolation. However, the mirror isolation filters have torsion modes with long decay time which disturb the interferometer operation for about half an hour if they get excited. In order to damp the torsion modes of the filters, we constructed a digital damping system using reflective photosensors with a large linear range. This system was installed to all of four SASs. By damping of the target torsion modes, the effective quality factors of the torsion modes are reduced to less than 10 or to unmeasurable level. This system is expected to reduce the inoperative period by the torsion mode excitation, and thus will contribute to improve the duty time of the gravitational wave detector.

Energy harvesting from torsions of patterned piezoelectrics

NASA Astrophysics Data System (ADS)

Cha, Youngsu; You, Hangil

2018-03-01

In this paper, we investigate the feasibility of energy harvesting from the torsions using a piezoelectric beam. The piezoelectric beam is partially patterned and is tested in an experimental setup to force pure torsional deformation. In particular, the beam consists of two identical piezoelectric parts attached on one side of a supporting substrate. We propose a model for the energy harvesting system through the equations for a slender composite beam with the physical properties and the electromechanical coupling equations of the piezoelectric material. The theoretical predictions are validated by the comparison with the experimental results.

Bacteriorhodopsin as a chemical and biological sensor

NASA Astrophysics Data System (ADS)

Heeg, Bauke; Needleman, Richard; Khizhnyak, Anatoliy; L'Esperance, Drew M.; Scott, Eddie; Markov, Vladimir B.; Trolinger, James D.

2003-08-01

Bacteriorhodopsin (bR) is a small protein containing the chromophore retinal, and resides in the membrane of the Halobacterium salinarium. When the retinal absorbs a photon, a cycle of structural changes is triggered resulting in a cross-membrane proton transfer, which is used to generate energy for the organism. Many studies have been conducted to elucidate the dynamical structure - optical property relations, and the overall mechanism of photo-induced proton transport in bR is now well understood. On the other hand, site selective mutagenesis allows engineering of the original ("wild-type") bR, such that the protein can be made sensitive to specific chemicals or biological structures that consequently induce changes in the proton-transport. As such, bR provides a unique molecular platform onto which various functional elements can be built: peptide receptors for molecular recognition of pathogens (e.g. viruses, cancer cells, spores, bacteria, bio-toxins), fluorescent tags (using the inherent optical transduction mechanism of bR), and chemical anchors for capturing target cells. In particular, the stability of bR in extreme environments (pH range of 1 - 11, temperatures up to 110 °C) allows for optical detection under a large range of environmental conditions. In this paper we present and discuss experimental data of several bR mutants and their potential as chemical and biological sensors. In particular, the optical changes associated with metal ligand binding are discussed for two mutants, 170C and 169C/96N, as well as the optical changes associated with streptavidin-coated beads bound to bR with strep II tags inserted in the E/F loop.

Raman spectra of gases. XVI - Torsional transitions in ethanol and ethanethiol

NASA Technical Reports Server (NTRS)

Durig, J. R.; Bucy, W. E.; Wurrey, C. J.; Carreira, L. A.

1975-01-01

The Raman spectra of gaseous ethanol and ethanethiol have been investigated. Thiol torsional fundamentals for the gauche conformer of EtSH and EtSD have been observed and the asymmetric potential function for this vibration has been calculated. Methyl torsional transitions and overtones have also been observed for both of these molecules. Barriers to internal rotation for the methyl top are calculated to be 3.77 and 3.84 kcal/mol for the EtSH and EtSD compounds, respectively. Hydroxyl torsional fundamentals were observed at 207 and 170 per cm in the EtOH and EtOD spectra, respectively. Overtones of the methyl torsion in both molecules yield a barrier to internal rotation of 3.62 kcal/mol for the gauche conformer.

Rat disc torsional mechanics: effect of lumbar and caudal levels and axial compression load.

PubMed

Espinoza Orías, Alejandro A; Malhotra, Neil R; Elliott, Dawn M

2009-03-01

Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior to evaluate changes after model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Cadaveric biomechanical study. Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. The apparent torsional modulus was higher in the lumbar region than in the caudal region: 0.081+/-0.026 (MPa/degrees, mean+/-SD) for lumbar axially loaded; 0.066+/-0.028 for caudal axially loaded; 0.091+/-0.033 for lumbar in pure torsion; and 0.056+/-0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/degrees. Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics.

[Correlation analysis on the disorders of patella-femoral joint and torsional deformity of tibia].

PubMed

Sun, Zhen-Jie; Yuan, Yi; Liu, Rui-Bo

2015-03-01

To reveal the possible mechanism involved in patella-femoral degenerative arthritis (PFDA) in- duced by torsion-deformity of tibia via analyzing the relationship between torsion-deformity of the tibia in patients with PFDA and the disorder of patella-femoral joint under the static and dynamic conditions. From October 2009 to October 2010, 50 patients (86 knees, 24 knees of male patients and 62 knees of female patients) with PFDA were classified as disease group and 16 people (23 knees, 7 knees of males and 16 knees of females) in the control group. The follow indexes were measured: the torsion-angle of tibia on CT scanning imagings, the patella-femoral congruence angle and lateral patella-femoral angle under static and dynamic conditions when the knee bent at 30 degrees of flexion. Based on the measurement results, the relationship between the torsion-deformity of tibias and the disorders of patella-femoral joints in patients with PFDA were analyzed. Finally,the patients were divided into three groups including large torsion-angle group, small torsion-angle group and normal group according to the size of torsion-angle, in order to analyze the relationship between torsion-deformity and disorders of patella-femoral joint, especially under the dynamic conditions. Compared with patients without PFDA, the ones with PFDA had bigger torsion-angle (30.30 ± 7.11)° of tibia, larger patella-femoral congruence angle (13.20 ± 3.94)° and smaller lateral patella-femoral angle (12.30 ± 3.04)°. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had statistical differences respectively in both too-big torsion-angle group and too-small torsion-angle group. The congruence angle and lateral patella-femoral angle under static and dynamic conditions had no statistical differences in normal torsion-angle group. Torsion-deformity of tibia is the main reason for disorder of patella-femoral joint in the patients with PFDA. Torsion-deformity of

Ionic polymer-metal composite torsional sensor: physics-based modeling and experimental validation

NASA Astrophysics Data System (ADS)

Aidi Sharif, Montassar; Lei, Hong; Khalid Al-Rubaiai, Mohammed; Tan, Xiaobo

2018-07-01

Ionic polymer-metal composites (IPMCs) have intrinsic sensing and actuation properties. Typical IPMC sensors are in the shape of beams and only respond to stimuli acting along beam-bending directions. Rod or tube-shaped IPMCs have been explored as omnidirectional bending actuators or sensors. In this paper, physics-based modeling is studied for a tubular IPMC sensor under pure torsional stimulus. The Poisson–Nernst–Planck model is used to describe the fundamental physics within the IPMC, where it is hypothesized that the anion concentration is coupled to the sum of shear strains induced by the torsional stimulus. Finite element simulation is conducted to solve for the torsional sensing response, where some of the key parameters are identified based on experimental measurements using an artificial neural network. Additional experimental results suggest that the proposed model is able to capture the torsional sensing dynamics for different amplitudes and rates of the torsional stimulus.

The Integration of Bacteriorhodopsin Proteins with Semiconductor Heterostructure Devices

NASA Astrophysics Data System (ADS)

Xu, Jian

2008-03-01

Bioelectronics has emerged as one of the most rapidly developing fields among the active frontiers of interdisciplinary research. A major thrust in this field is aimed at the coupling of the technologically-unmatched performance of biological systems, such as neural and sensing functions, with the well developed technology of microelectronics and optoelectronics. To this end we have studied the integration of a suitably engineered protein, bacteriorhodopsin (BR), with semiconductor optoelectronic devices and circuits. Successful integration will potentially lead to ultrasensitive sensors with polarization selectivity and built-in preprocessing capabilities that will be useful for high speed tracking, motion and edge detection, biological detection, and artificial vision systems. In this presentation we will summarize our progresses in this area, which include fundamental studies on the transient dynamics of photo-induced charge shift in BR and the coupling mechanism at protein-semiconductor interface for effective immobilizing and selectively integrating light sensitive proteins with microelectronic devices and circuits, and the device engineering of BR-transistor-integrated optical sensors as well as their applications in phototransceiver circuits. Work done in collaboration with Pallab Bhattacharya, Jonghyun Shin, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI; Robert R. Birge, Department of Chemistry, University of Connecticut, Storrs, CT 06269; and György V'ar'o, Institute of Biophysics, Biological Research Center of the Hungarian Academy of Science, H-6701 Szeged, Hungary.

Isolated torsion of fallopian tube during pregnancy; report of two cases.

PubMed

Yalcin, O T; Hassa, H; Zeytinoglu, S; Isiksoy, S

1997-08-01

Isolated torsion of fallopian tube is very uncommon during pregnancy. Predisposing factors for torsion are hydrosalpinx, prior tubal operation, pelvic congestion, ovarian and paraovarian masses and trauma. Although the most important clinical symptom is abdominal pain in lower quadrants, the diagnosis is usually established during the operation performed for acute abdomen and salpingectomy is almost always necessary. Two cases of torsion of fallopian tube during pregnancy, one with hydrosalpinx, the other with paratubal cyst are presented and symptoms and predisposing factors are discussed.

TT-Cut Torsional Quartz Crystal Resonators of Free-Free Bar-Type

NASA Astrophysics Data System (ADS)

Kawashima, Hirofumi; Nakazato, Mitsuhiro

1994-05-01

This paper describes a TT-cut torsional quartz crystal resonator of free-free bar type. An object of this paper is to clarify the frequency temperature behavior, series resistance and a quality factor for TT-cut torsional quartz crystal resonators of free-free bar-type. The analysis results are then compared with the measured data. The principal results indicate that the calculated values of frequency temperature behavior for resonators of free-free bar-type agree comparatively well with the measured ones. Similar to the torsional resonators of tuning fork-type, a torsional quartz crystal resonator of free-free bar-type is also found to have an absolute value of the second order temperature coefficient β smaller than half a value of that for a flexural mode quartz crystal resonator.

Nature of the ``yield tooth'' under torsion in plastic-deformed whiskers

NASA Astrophysics Data System (ADS)

Bataronov, I. L.; Belikov, A. M.; Drozhzhin, A. I.; Roshchupkin, A. M.

1987-07-01

The plastic torsion of whiskers with high Peierls barriers has been studied. As the samples for the studies we chose p-type germanium whiskers with <111> growth axis. The diameter of the whisker was (5 60)·10-6 m and the gauge length was (1 4)·10-3 m. The whiskers were dislocation-free in the initial state. Within the framework of the continuum model developed by us for the plastic deformation of whiskers under torsion, we analyze the anomalies of the torsional stress-strain diagram under different testing conditions and with preliminary deformation. The “flow tooth” during the torsion of a whisker is attributable to the nonuniform distribution of dislocations over the cross section of the whisker and high barriers to the dislocation motion.

The Spectrum of Torsional Oscillations of the Moon

NASA Astrophysics Data System (ADS)

Gudkova, T. V.; Zharkov, V. N.

2000-11-01

The diagnostic potentialities of the torsional oscillations for probing the structure of the interiors of the Moon are investigated. Models with no core, a liquid core, and a solid core are considered. The profiles of compressional and shear wave velocities V_P and V_S for the lunar interior estimated by Bills and Ferrari (1977), Goins et al. (1981), and Nakamura (1983) from the Apollo lunar seismic network are used. For all these models, the periods of torsional oscillations for n = 2-100 and four overtones have been calculated. The derivatives of the dimensionless eigenfrequency with respect to the dimensionless shear modulus and density are calculated and tabulated for use. These data can be used to determine corrections to the model density and shear modulus distributions due to their small change. The damping of torsional oscillations is studied. Several trial radial distributions of the dissipative function Q are considered.

Magnesium: does it reduce ischemia/reperfusion injury in an adnexal torsion rat model?

PubMed Central

Celik Kavak, Ebru; Gulcu Bulmus, Funda; Bulmus, Ozgur; Kavak, Salih Burcin; Kocaman, Nevin

2018-01-01

Aim The aim of the present study was to assess the protective effects of magnesium sulfate (MgSO4) on ischemia/reperfusion (I/R) induced ovarian damage in a rat ovarian torsion model. Methods Forty-two female Sprague Dawley rats were included in the study. They were divided into six groups as Group 1, sham; Group 2, bilateral ovarian torsion; Group 3, bilateral ovarian torsion–detorsion; Group 4, MgSO4–sham; Group 5, MgSO4–bilateral ovarian torsion; Group 6, bilateral ovarian torsion–MgSO4–detorsion. Both torsion and detorsion periods lasted 3 hours. In Groups 4, 5 and 6, MgSO4 (600 mg/kg) was administered by intraperitoneal route 30 minutes before sham operation, torsion and detorsion, respectively. At the end of the study period, both ovaries were removed. One of the ovaries was used for histopathological analyses and the other for biochemical analyses. Results In the torsion–detorsion group, all the histopathological scores were higher compared to the sham and torsion only group (p<0.05). Administration of MgSO4 only caused significant decrease in the inflammatory cell scores of the torsion–detorsion group (p<0.05). MgSO4, whether given before torsion or before detorsion, suppressed malondialdehyde levels when compared to the untreated groups (p<0.01 and p<0.001, respectively). Glutathione peroxidase activities were significantly higher in the MgSO4 applied torsion and detorsion groups than Groups 2 and 3 (p<0.05, for both). Administration of MgSO4 also caused an increase in glutathione levels in the torsion and detorsion groups compared to the torsion only and detorsion only groups (p<0.05, for both). Also, total oxidant status levels decreased in the MgSO4 applied torsion and detorsion groups compared to the untreated corresponding ones (p<0.01 and p<0.001, respectively). MgSO4 significantly decreased the Oxidative Stress Index levels in the torsion–detorsion group compared to Group 2 (p<0.001). Conclusion Histopathological and biochemical

Human ocular torsion during parabolic flights: an analysis with scleral search coil

NASA Technical Reports Server (NTRS)

Cheung, B. S.; Money, K.; Howard, I.; Kirienko, N.; Johnson, W.; Lackner, J.; Dizio, P.; Evanoff, J.

1992-01-01

Rotation of the eyes about the visual axis is known as ocular torsion. A lateral inclination (a "roll") of the head induces ocular torsion in the opposite direction, a response known as ocular counterrolling. For six subjects, we recorded the static (head still) and dynamic (head in oscillatory roll motion) ocular torsion in normal 1 g condition and also during the microgravity and hypergravity periods of parabolic flight, using the electromagnetic scleral search coil technique. With the head still, the direction and magnitude of torsion that occurred in response to microgravity and hypergravity differed substantially from one individual to another, but there was a significant difference in torsional magnitude between the microgravity and hypergravity periods, for all static head positions including the upright position. Under normal 1 g conditions, counterrolling compensated for about 16% of (voluntary) static head roll, while dynamic counterroll was much larger, up to 36% of head roll at 0.55 Hz. With increasing frequency of head oscillation between 0.33 Hz and 0.55 Hz, the gain of counterrolling increased and there was no change in the phase relationship. The gain of dynamic counterroll (in response to voluntary head rolling) was not significantly less in hypogravity, suggesting that on the ground at these frequencies the contribution of gravity and gravity receptors to this reflex is redundant: this reflex is probably driven by the semicircular canals. In some subjects, the torsional displacement in microgravity is accompanied by micro-torsional oscillatory motion.

Rat Disc Torsional Mechanics: Effect of Lumbar and Caudal Levels and Axial Compression Load

PubMed Central

Elliott, Dawn M; Espinoza Orías, Alejandro A; Malhotra, Neil R

2009-01-01

Background Context Rat models with altered loading are used to study disc degeneration and mechano-transduction. Given the prominent role of mechanics in disc function and degeneration, it is critical to measure mechanical behavior in order to evaluate changes following model interventions. Axial compression mechanics of the rat disc are representative of the human disc when normalized by geometry, and differences between the lumbar and caudal disc have been quantified in axial compression. No study has quantified rat disc torsional mechanics. Purpose Compare the torsional mechanical behavior of rat lumbar and caudal discs, determine the contribution of combined axial load on torsional mechanics, and compare the torsional properties of rat discs to human lumbar discs. Study Design Cadaveric biomechanical study. Methods Cyclic torsion without compressive load followed by cyclic torsion with a fixed compressive load was applied to rat lumbar and caudal disc levels. Results The apparent torsional modulus was higher in the lumbar region than in the caudal region,: 0.081±0.026 (MPa/°, Mean±SD) for lumbar axially loaded; 0.066±0.028 caudal axially loaded; 0.091±0.033 for lumbar in pure torsion; and 0.056±0.035 for caudal in pure torsion. These values were similar to human disc properties reported in the literature ranging from 0.024 to 0.21 MPa/°. Conclusions Use of the caudal disc as a model may be appropriate if the mechanical focus is within the linear region of the loading regime. These results provide support for use of this animal model in basic science studies with respect to torsional mechanics. PMID:18495544

Faraday Rotation and Primordial Magnetic Fields Constraints on Ultraviolet Lorentz Violation with Spacetime Torsion

NASA Astrophysics Data System (ADS)

de Andrade, L. C. Garcia

Recently Kahniashvili et al.9 presented a unified treatment for ultraviolet Lorentz violation (LV) testing through electromagnetic wave propagation in magnetized plasmas, based on dispersion and rotation measured data. Based on the fact discovered recently by Kostelecky et al., 3 that LV may place constraints on spacetime torsion, in this paper it is shown that on the limit of very low frequency torsion waves, it is possible to constraint torsion from Faraday rotation and CMB on a similar fashion as Minkowski spacetime plus torsion. Here, the Maxwells modified equations are obtained by a perturbative method introduced by de Sabbata and Gasperini [Introduction to Gravitation (World Scientific, 1980)]. Torsion is constraint to QCMB≈10-18 GeV which is not so stringent as the 10-31 GeV obtained by Kostelecky et al. However, Gamma-Ray Bursts (GRBs) may lead to the more string value obtained by Kostelecky et al.Another interesting constraint on torsion is shown to be placed by galactic dynamo seed magnetic fields. For torsion effects be compatible with the galactic dynamo seeds, one obtains a torsion constraint of 10-33 GeV which is two orders of magnitude more stringent that the above Kostelecky et al. limit.

The effect of neck torsion on postural stability in subjects with persistent whiplash.

PubMed

Yu, Li-Ju; Stokell, Raina; Treleaven, Julia

2011-08-01

Dysfunction of cervical receptors in neck disorders has been shown to lead to disturbances in postural stability. The neck torsion manoeuvre used in the smooth pursuit neck torsion (SPNT) test is thought to be a specific measure of neck afferent dysfunction on eye movement in those with neck pain. This study aimed to determine whether neck torsion could change balance responses in those with persistent whiplash-associated disorders (WADs). Twenty subjects with persistent WAD and 20 healthy controls aged between 18 and 50 years stood on a computerised force plate with eyes closed in comfortable stance under 5 conditions: neutral head, head turned to left and right and neck torsion to left and right. Root mean square (rms) amplitude of sway was measured in the anterior-posterior (AP) and medial-lateral (ML) directions. The whiplash group had significantly greater rms amplitude in the AP direction following neck torsion compared to the control group (p < 0.03). The results show that the neck torsion manoeuvre may lead to greater postural deficits in individuals with persistent WAD and provides further evidence of neck torsion to identify abnormal cervical afferent input, as an underlying cause of balance disturbances in WAD. Further research is warranted. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Ovarian torsion: diagnostic features on CT and MRI with pathologic correlation.

PubMed

Duigenan, Shauna; Oliva, Esther; Lee, Susanna I

2012-02-01

The CT and MRI features of ovarian torsion are illustrated with gross pathologic correlation. Ovarian enlargement with or without an underlying mass is the finding most frequently associated with torsion, but it is nonspecific. A twisted pedicle, although not often detected on imaging, is pathognomonic when seen. Subacute ovarian hemorrhage and abnormal enhancement is usually seen, and both features show characteristic patterns on CT and MRI. Ipsilateral uterine deviation can also be seen. Diagnostic pitfalls that may mimic ovarian torsion and observations for discriminating them are discussed.

Angle of torsion of the femur and its correlates.

PubMed

Prasad, R; Vettivel, S; Isaac, B; Jeyaseelan, L; Chandi, G

1996-01-01

Unpaired femora (171), devoid of gross pathology and grouped by gender (94 male and 77 female) and side (88 left and 83 right), were used to measure the angle of femoral torsion and the maximum femur length and to score the degree of prominency of the superior cervical tubercle, intertrochanteric line, quadrate tubercle, linea aspera, and adductor tubercle. The angle of torsion ranged from -9 to +35 degrees with a mean of +12.3 degrees. The means were not significantly different either by gender or side. The angle correlated negatively with superior cervical tubercle, intertrochanteric line, and adductor tubercle (P < 0.001), positively with quadrate tubercle (P < 0.001) but not with linea aspera, neck-shaft angle, or length of femur. Bony prominences were significantly more apparent in males. There was no significant association between prominency and side. The torsion seems to be brought about by muscular activity and capsular and ligamentous strain at the hip. This study suggests to clinicians the possibility of correction of torsion defects in certain hip diseases of growing children by suitable alteration in posture of the lower extremity.

Rapid pH change due to bacteriorhodopsin measured with a tin-oxide electrode.

PubMed Central

Robertson, B; Lukashev, E P

1995-01-01

The photocurrent transient generated by bacteriorhodopsin (bR) on a tin-oxide electrode is due to pH change and not to charge displacement as previously assumed. Films of either randomly oriented or highly oriented purple membranes were deposited on transparent electrodes made of tin-oxide-coated glass. The membranes contained either wild-type or D96N-mutant bR. When excited with yellow light through the glass, the bR pumps protons across the membrane. The result is a rapid local pH change as well as a charge displacement. Experiments with these films show that it is the pH change rather than the displacement that produces the current transient. The calibration for the transient pH measurement is given. The sensitivity of a tin-oxide electrode to a transient pH change is very much larger than its sensitivity to a steady-state pH change. PMID:7787036

Torsion Tests of 24S-T Aluminum-alloy Noncircular Bar and Tubing

NASA Technical Reports Server (NTRS)

Moore, R L; Paul, D A

1943-01-01

Tests of 24S-T aluminum alloy have been made to determine the yield and ultimate strengths in torsion of noncircular bar and tubing. An approximate basis for predicting these torsional strength characteristics has been indicated. The results show that the torsional stiffness and maximum shearing stresses within the elastic range may be computed quite closely by means of existing formulas based on mathematical analysis and the membrane analogy.

Chromophore dynamics in the PYP photocycle from femtosecond stimulated Raman spectroscopy.

PubMed

Creelman, Mark; Kumauchi, Masato; Hoff, Wouter D; Mathies, Richard A

2014-01-23

Femtosecond stimulated Raman spectroscopy (FSRS) is used to examine the structural dynamics of the para-hydroxycinnamic acid (HCA) chromophore during the first 300 ps of the photoactive yellow protein (PYP) photocycle, as the system transitions from its vertically excited state to the early ground state cis intermediate, I0. A downshift in both the C7═C8 and C1═O stretches upon photoexcitation reveals that the chromophore has shifted to an increasingly quinonic form in the excited state, indicating a charge shift from the phenolate moiety toward the C9═O carbonyl, which continues to increase for 170 fs. In addition, there is a downshift in the C9═O carbonyl out-of-plane vibration on an 800 fs time scale as PYP transitions from its excited state to I0, indicating that weakening of the hydrogen bond with Cys69 and out-of-plane rotation of the C9═O carbonyl are key steps leading to photoproduct formation. HOOP intensity increases on a 3 ps time scale during the formation of I0, signifying distortion about the C7═C8 bond. Once on the I0 surface, the C7═C8 and C1═O stretches blue shift, indicating recovery of charge to the phenolate, while persistent intensity in the HOOP and carbonyl out-of-plane modes reveal HCA to be a cissoid structure with significant distortion about the C7═C8 bond and of C9═O out of the molecular plane.

Large scale magnetic fields from torsion modes and massive photon inflation

NASA Astrophysics Data System (ADS)

Garcia de Andrade, L. C.

2017-10-01

Previously, Barrow and Tsagas (2008 Phys. Rev. D 77 107302) showed that a slower decay of magnetic fields are present in open Friedmann universes, with traditional Maxwell equations. In their paper magnetic fields of the order of B˜ 10-33~G , which are far below the value required to seed galactic dynamos, were obtained. In this paper, galactic dynamo seeds of the order of B˜ 10-23~G are obtained from massive electrodynamics in an Einstein-Cartan-Proca expanding universe of de Sitter type. Slow decay of magnetic fields in photon-torsion coupling in quantum electrodynamics (Garcia de Andrade 2011 Phys. Lett. B 468 28) have been recently shown by the author Garcia de Andrade (2012 Phys. Lett. B 711 143) to also not be able to seed galactic dynamos. Torsion modes are constrained by the field equations. Spacetime torsion is shown to be explicitly responsible for the slow decay of a cosmic magnetic field. In the absence of massive photon torsion coupling the magnetic field decay is of the order B˜ t-\\frac{3{2}} , when torsion turns on B˜ t-1.2 . The pure massive-photon-torsion contribution amplifies the magnetic field by B_torsion˜ t0.1 which characterizes an extremely slow magnetic dynamo action due to purely torsion gravitational effects. Recently Barrow, Tsagas and Yamamoto (2012 Phys. Rev. D 86 023535) have obtained superadiabatic amplification of B-fields in Friedmann open cosmology which lies within {10-20~G} and 10-12~G which falls very comfortably within the limits to seed galactic dynamos. The are other simple solutions where a B-field decays as B˜ a-1 , a relatively weak photon-torsion coupling approximation. These solutions are obtained for de Sitter and Friedmann metrics. Numerical values as displayed in this new version of the paper specifically for GUT phases of inflation with and without massive photons; without photons we obtain the well known value of GR which is B_GUT˜ 1048~G while for the values with massive photons one obtains B_GUT/γ˜ 10

Torsional Angle Driver (TorAD) System for HyperChem/Excel

NASA Astrophysics Data System (ADS)

Starkey, Ronald

1999-02-01

The torsional angle driver system for HyperChem/Excel is a package of several Excel spreadsheets and macro programs to be used with HyperChem to obtain and plot information, such as total energy, for the conformations that result from a 360° rotation about a torsional angle system in a molecule. The TorAD system also includes several HyperChem scripts to facilitate its use. TorAD was developed for use in the undergraduate organic chemistry laboratory. The results obtained with TorAD could be obtained manually with HyperChem, but it would take considerable time and would not be instructive to the students. Use of the TorAD system allows students to spend their time on the more important aspect of conformation analysisinterpretation of results. The Excel spreadsheet/macro programs in TorAD include:

· Tor_xl_a and tor_xl obtain and plot the total energy at 5° torsional-angle intervals. The calculation method, the torsional-angle restraint, and the structure to be used at each angle can be set by the user. The advanced version, tor_xl_a, which requires HyperChem 4.5 or later, also allows torsional-angle structures to be saved for later recall as individual structures or, using a HyperChem script, in a movie format. It also provides a rapid scan of the 360° rotation where only single-point calculations, rather than geometry optimizations, are performed. The tor_xl system will perform routine tasks in a manner suitable for most instructional settings. · Tor_Comp performs molecular mechanics optimizations at 5° intervals and obtains and plots four energy parameters (total, torsional, nonbonded, and bond [bend plus stretch] energy) as a function of torsional angle. The calculation method and the restraint can be specified. · TorDipol produces a plot of the total energy and the calculated dipole moment at 5° steps of the torsional angle. The default calculation is the semi-empirical AM

Development of a method for measuring femoral torsion using real-time ultrasound.

PubMed

Hafiz, Eliza; Hiller, Claire E; Nicholson, Leslie L; Nightingale, E Jean; Clarke, Jillian L; Grimaldi, Alison; Eisenhuth, John P; Refshauge, Kathryn M

2014-07-01

Excessive femoral torsion has been associated with various musculoskeletal and neurological problems. To explore this relationship, it is essential to be able to measure femoral torsion in the clinic accurately. Computerized tomography (CT) and magnetic resonance imaging (MRI) are thought to provide the most accurate measurements but CT involves significant radiation exposure and MRI is expensive. The aim of this study was to design a method for measuring femoral torsion in the clinic, and to determine the reliability of this method. Details of design process, including construction of a jig, the protocol developed and the reliability of the method are presented. The protocol developed used ultrasound to image a ridge on the greater trochanter, and a customized jig placed on the femoral condyles as reference points. An inclinometer attached to the customized jig allowed quantification of the degree of femoral torsion. Measurements taken with this protocol had excellent intra- and inter-rater reliability (ICC2,1 = 0.98 and 0.97, respectively). This method of measuring femoral torsion also permitted measurement of femoral torsion with a high degree of accuracy. This method is applicable to the research setting and, with minor adjustments, will be applicable to the clinical setting.

Studies of torsional properties of DNA and nucleosomes using angular optical trapping

NASA Astrophysics Data System (ADS)

Sheinin, Maxim Y.

DNA in vivo is subjected to torsional stress due to the action of molecular motors and other DNA-binding proteins. Several decades of research have uncovered the fascinating diversity of DNA transformations under torsion and the important role they play in the regulation of vital cellular processes such as transcription and replication. Recent studies have also suggested that torsion can influence the structure and stability of nucleosomes---basic building blocks of the eukaryotic genome. However, our understanding of the impact of torsion is far from being complete due to significant experimental challenges. In this work we have used a powerful single-molecule experimental technique, angular optical trapping, to address several long-standing issues in the field of DNA and nucleosome mechanics. First, we utilized the high resolution and direct torque measuring capability of the angular optical trapping to precisely measure DNA twist-stretch coupling. Second, we characterized DNA melting under tension and torsion. We found that torsionally underwound DNA forms a left-handed structure, significantly more flexible compared to the regular B-DNA. Finally, we performed the first comprehensive investigation of the single nucleosome behavior under torque and force. Importantly, we discovered that positive torque causes significant dimer loss, which can have implications for transcription through chromatin.

Torsion as a dark matter candidate from the Higgs portal

NASA Astrophysics Data System (ADS)

Belyaev, Alexander S.; Thomas, Marc C.; Shapiro, Ilya L.

2017-05-01

Torsion is a metric-independent component of gravitation, which may provide a more general geometry than the one taking place within general relativity. On the other hand, torsion could lead to interesting phenomenology in both particle physics and cosmology. In the present work it is shown that a torsion field interacting with the SM Higgs doublet and having a negligible coupling to standard model (SM) fermions is protected from decaying by a Z2 symmetry, and therefore becomes a promising dark matter (DM) candidate. This model provides a good motivation for Higgs portal vector DM scenario. We evaluate the DM relic density and explore direct DM detection and collider constraints on this model to understand its consistency with experimental data and establish the most up-to-date limits on its parameter space. We have found in the model when the Higgs boson is only partly responsible for the generation of torsion mass, there is a region of parameter space where torsion contributes 100% to the DM budget of the Universe. Furthermore, we present the first results on the potential of the LHC to probe the parameter space of minimal scenario with Higgs portal vector DM using mono-jet searches and have found that LHC at high luminosity will be sensitive to the substantial part of model parameter space which cannot be probed by other experiments.

Use of optical coherence topography for objective assessment of fundus torsion.

PubMed

Sophocleous, Sophocles

2017-02-23

Objective assessment of fundus torsion is currently performed with indirect ophthalmoscopy or fundus photography. Using the infrared image of the macular scan of the optical coherence tomography one can assess the presence and amount of fundus torsion. In addition, the line scan through the fovea can be used as a reference to confirm the position of the foveal pit in relation to the optic nerve head. Two cases are used to demonstrate how to assess fundus torsion with the use of the optical coherence tomography. 2017 BMJ Publishing Group Ltd.

Protective effect of sildenafil citrate on contralateral testis injury after unilateral testicular torsion/detorsion.

PubMed

Yíldíz, Hamit; Durmus, Ali Said; Simşek, Halil; Yaman, Mine

2011-01-01

This study was designed to investigate prevention of contralateral testicular injury with sildenafil citrate after unilateral testicular torsion/detorsion. Thirty-seven adult male rats were divided into four groups: sham operated (group 1, n = 7), torsion/detorsion + saline (group 2, n = 10), torsion/detorsion + 0.7 mg of sildenafil citrate (group 3, n = 10) and torsion/detorsion + 1.4 mg of sildenafil citrate (group 4, n = 10). Unilateral testicular torsion was created by rotating the right testis 720º in a clockwise direction for 2 h in other groups, except for group 1, which was served as sham group. After torsion (2 h) and detorsion (2 h) periods, rats were killed. The level of reduced glutathion (GSH) (p < 0.05) and the activities of catalase (p < 0.01) and glutathione peroxidase (p < 0.05) in the contralateral testis from group 2 were significantly lower and nitric oxide (NO) (p < 0.05) level in the contralateral testis were significantly higher than those of group 1. Administration of low-dose sildenafil citrate (group 3) prevented the increases in malondialdehyde and NO levels and decreases in glutathione peroxidase activities and GSH values induced by testicular torsion. However, administration of high-dose sildenafil citrate (group 4) had no effect on these testicular parameters (p > 0.05). Histopathological changes were detected in groups 2, 3 and 4. These results suggest that biochemically and histologically torsion/detorsion injury occurs in the contralateral testis following 2-h torsion and 2-h detorsion and that administration of low-dose sildenafil citrate before detorsion prevents ischemia/reperfusion cellular damage in testicular tissue.

Torsion effect of swing frame on the measurement of horizontal two-plane balancing machine

NASA Astrophysics Data System (ADS)

Wang, Qiuxiao; Wang, Dequan; He, Bin; Jiang, Pan; Wu, Zhaofu; Fu, Xiaoyan

2017-03-01

In this paper, the vibration model of swing frame of two-plane balancing machine is established to calculate the vibration center position of swing frame first. The torsional stiffness formula of spring plate twisting around the vibration center is then deduced by using superposition principle. Finally, the dynamic balancing experiments prove the irrationality of A-B-C algorithm which ignores the torsion effect, and show that the torsional stiffness deduced by experiments is consistent with the torsional stiffness calculated by theory. The experimental datas show the influence of the torsion effect of swing frame on the separation ratio of sided balancing machines, which reveals the sources of measurement error and assesses the application scope of A-B-C algorithm.

Effects of {10-12} Twins on Dynamic Torsional Properties of Extruded AZ31 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Lee, Jong Un; Song, Seok Weon; Kim, Yongjin; Kim, Sang-Hoon; Kim, Ye Jin; Park, Sung Hyuk

2018-03-01

Effects of initial twins on dynamic torsional properties of extruded AZ31 alloy were investigated by introducing {10-12} twins into it through precompression to 3 and 6% strains along the extrusion direction and performing torsional testing at a strain rate of 1.4 × 103 s-1 using a torsional Kolsky bar system. The as-extruded sample without twins showed higher dynamic torsional properties than the precompressed samples with many initial twins; the maximum shear strength and fracture shear strain decreased with increasing amount of initial twins. In the as-extruded sample, twinning occurred vigorously throughout the gage section of the tubular specimen during high-strain-rate torsional tests, resulting in heavily deformed morphology, many macrocracks, and rough fractured surfaces. The increased amount of initial twins suppressed the twinning behavior and localized the applied torsional deformation; this resulted in an almost unchanged sample shape, no secondary cracks, and a flat fracture plane, thereby deteriorating the dynamic torsional properties of the extruded alloy.

Mechanisms responsible for the photocurrent in bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Alfinito, Eleonora; Reggiani, Lino

2015-03-01

Recently, there has been growing interest in the electrical properties of bacteriorhodopsin (bR), a protein belonging to the transmembrane protein family. Several experiments pointed out the role of green light in enhancing the current flow in nanolayers of bR, thus confirming potential applications of this protein in the field of optoelectronics. By contrast, the mechanisms underlying the charge transfer and the associated photocurrent are still far from being understood at a microscopic level. To take into account the structure-dependent nature of the current, in a previous set of papers we suggested a mechanism of sequential tunneling among neighboring amino acids. As a matter of fact, when irradiated with green light, bR undergoes a conformational change at a molecular level. Thus, the role played by the protein tertiary-structure in modeling the charge transfer cannot be neglected. The aim of this paper is to go beyond previous models, in the framework of a new branch of electronics we call proteotronics, which exploits the ability of using proteins as reliable, well-understood materials for the development of novel bioelectronic devices. In particular, the present approach assumes that the conformational change is not the unique transformation the protein undergoes when irradiated by light. Instead, the light can also promote an increase of the protein state free energy that, in turn, should modify its internal degree of connectivity. This phenomenon is here described by the change of the value of an interaction radius associated with the physical interactions among amino acids. The implemented model enables us to achieve a better agreement between theory and experiments in the region of a low applied bias by preserving the level of agreement at high values of applied bias. Furthermore, results provide new insights on the mechanisms responsible for bR photoresponse.

The accuracy of serum interleukin-6 and tumour necrosis factor as markers for ovarian torsion.

PubMed

Cohen, S B; Wattiez, A; Stockheim, D; Seidman, D S; Lidor, A L; Mashiach, S; Goldenberg, M

2001-10-01

The aim of this study was to investigate a possible role for interleukin-6 (IL-6) and tumour necrosis factor (TNF-alpha) as pre-operative markers for the diagnosis of ovarian torsion. Twenty consecutive patients admitted to the gynaecological emergency room with suspected clinical diagnosis of ovarian torsion were prospectively assigned to the study. Blood samples were drawn pre-operatively and examined for serum concentrations of IL-6 and TNF-alpha. Surgeons were blinded to laboratory results prior to laparoscopy. The pre-operative diagnosis of ovarian torsion was confirmed during an urgent diagnostic laparoscopy in 8 (40%) patients. The surgical diagnosis among the remaining 12 patients was a large ovarian cyst not in torsion. In six out of eight (75.0%) patients with ovarian torsion serum IL-6 concentrations were elevated. None of the 12 patients without torsion had elevated serum IL-6 concentrations. This difference was statistically significant (P < 0.001). There was no significant difference in the proportion of women with elevated serum TNF-alpha concentrations, two of eight (25.0%) patients with torsion and four of 12 (33.3%) control cases. Elevated serum IL-6 concentrations, but not serum TNF-alpha concentrations, were significantly associated with the occurrence of ovarian torsion. In patients with vague clinical signs of ovarian torsion, serum IL-6 might help to distinguish which patients should undergo diagnostic laparoscopy.

Electrophysiological examination and high frequency ultrasonography for diagnosis of radial nerve torsion and compression

PubMed Central

Shi, Miao; Qi, Hengtao; Ding, Hongyu; Chen, Feng; Xin, Zhaoqin; Zhao, Qinghua; Guan, Shibing; Shi, Hao

2018-01-01

Abstract This study aims to evaluate the value of electrophysiological examination and high frequency ultrasonography in the differential diagnosis of radial nerve torsion and radial nerve compression. Patients with radial nerve torsion (n = 14) and radial nerve compression (n = 14) were enrolled. The results of neurophysiological and high frequency ultrasonography were compared. Electrophysiological examination and high-frequency ultrasonography had a high diagnostic rate for both diseases with consistent results. Of the 28 patients, 23 were positive for electrophysiological examination, showing decreased amplitude and decreased conduction velocity of radial nerve; however, electrophysiological examination cannot distinguish torsion from compression. A total of 27 cases showed positive in ultrasound examinations among all 28 cases. On ultrasound images, the nerve was thinned at torsion site whereas thickened at the distal ends of torsion. The diameter and cross-sectional area of torsion or compression determined the nerve damage, and ultrasound could locate the nerve injury site and measure the length of the nerve. Electrophysiological examination and high-frequency ultrasonography can diagnose radial neuropathy, with electrophysiological examination reflecting the neurological function, and high-frequency ultrasound differentiating nerve torsion from compression. PMID:29480857

Nanosecond step-scan FT-infrared absorption spectroscopy in photochemistry and catalysis

NASA Astrophysics Data System (ADS)

Frei, H.

1998-06-01

Time-resolved step-scan FT-IR absorption spectroscopy has been expanded to a resolution of 20 nanosecond. Following a description of the experimental set-up, applications in four research areas are presented. In the first project, we discuss a reversible isomerization, namely the bacteriorhodopsin photocycle. Main results are the discovery of 2 processes with distinct kinetics on the nanosecond time scale not detected by previous spectroscopic techniques, and observation of an instantaneous response of the protein environment to chromophore dynamics within the nanosecond laser pulse duration. In a second project, alkane C-H bond activation by a transition metal complex in room temperature solution is investigated and the first measurement of the formation of a C-H insertion product reported (alkyl hydride). Then, a nanosecond study of a pericyclic reaction, the ring-opening of cyclohexadiene, is discussed. The fourth example describes the first observation of a transient molecule in a zeolite matrix, a triplet excited quinone, by time-resolved infrared spectroscopy.

Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

DOE PAGES

Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; ...

2016-08-22

Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within themore » crystal lattice is confirmed by time-resolved visible absorption spectroscopy. Furthermore, this study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.« less

Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

PubMed Central

Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; Coe, Jesse; Bean, Richard; Zhao, Yun; Båth, Petra; Dods, Robert; Harimoorthy, Rajiv; Beyerlein, Kenneth R.; Rheinberger, Jan; James, Daniel; DePonte, Daniel; Li, Chufeng; Sala, Leonardo; Williams, Garth J.; Hunter, Mark S.; Koglin, Jason E.; Berntsen, Peter; Nango, Eriko; Iwata, So; Chapman, Henry N.; Fromme, Petra; Frank, Matthias; Abela, Rafael; Boutet, Sébastien; Barty, Anton; White, Thomas A.; Weierstall, Uwe; Spence, John; Neutze, Richard; Schertler, Gebhard; Standfuss, Jörg

2016-01-01

Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. This study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX. PMID:27545823

Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett

Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within themore » crystal lattice is confirmed by time-resolved visible absorption spectroscopy. Furthermore, this study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.« less

Feasibility of using near-infrared spectroscopy to diagnose testicular torsion: an experimental study in sheep.

PubMed

Capraro, Geoffrey A; Mader, Timothy J; Coughlin, Bret F; Lovewell, Carolanne; St Louis, Myron R L; Tirabassi, Michael; Wadie, George; Smithline, Howard A

2007-04-01

To assess whether near-infrared spectroscopy can detect testicular hypoxia in a sheep model of testicular torsion within 6 hours of experimental torsion. This was a randomized, controlled, nonblinded study. Trans-scrotal, near-infrared, spectroscopy-derived testicular tissue saturation of oxygen values were obtained from the posterior hemiscrota of 6 anesthetized sheep at baseline and every 15 minutes for 6 hours after either experimental-side, 720-degree, unilateral, medial testicular torsion and orchidopexy or control-side sham procedure with orchidopexy and then for 75 minutes after reduction of torsion and pexy. Color Doppler ultrasonography was performed every 30 minutes to confirm loss of vascular flow on the experimental side, return of flow after torsion reduction, and preserved flow on the control side. Near infrared spectroscopy detected a prompt, sustained reduction in testicular tissue saturation of oxygen after experimental torsion. Further, it documented a rapid return of these values to pretorsion levels after reduction of torsion. Experimental-side testicular tissue saturation of oxygen fell from a median value of 59% (interquartile range [IQR] 57% to 69%) at baseline to 14% (IQR 11% to 29%) at 2.5 hours of torsion, and postreduction values were approximately 70%. Control-side testicular tissue saturation of oxygen values increased from a median value of 67% (IQR 59% to 68%) at baseline to 77% (IQR 77% to 94%) at 2.5 hours and remained at approximately 80% for the entire protocol. The difference in median testicular tissue saturation of oxygen between experimental and control sides, using the Friedman test, was found to be significant (P=.017). This study demonstrates the feasibility, in a sheep model, of using near-infrared spectroscopy for the noninvasive diagnosis of testicular torsion and for quantification of reperfusion after torsion reduction. The applicability of these findings, from an animal model using complete torsion, to the clinical

Elastic torsional buckling of thin-walled composite cylinders

NASA Technical Reports Server (NTRS)

Marlowe, D. E.; Sushinsky, G. F.; Dexter, H. B.

1974-01-01

The elastic torsional buckling strength has been determined experimentally for thin-walled cylinders fabricated with glass/epoxy, boron/epoxy, and graphite/epoxy composite materials and composite-reinforced aluminum and titanium. Cylinders have been tested with several unidirectional-ply orientations and several cross-ply layups. Specimens were designed with diameter-to-thickness ratios of approximately 150 and 300 and in two lengths of 10 in. and 20 in. The results of these tests were compared with the buckling strengths predicted by the torsional buckling analysis of Chao.

Some general aspects of torsional sensitivity and the GG-effect

NASA Astrophysics Data System (ADS)

Yu, C.-H.; Schäfer, L.; Ramek, M.; Miller, D. M.; Teppen, B. J.

1999-08-01

The geometries of 28 compounds of type X-C1-C2-C3-Y, with X,Y=CH 3, F, Cl, OH, NH 2, COH, and COOH, were fully optimized by ab initio HF/4-21G calculations at 30° grid points in their respective φ(X-C1-C2-C3), ψ(C1-C2-C3-Y)-torsional spaces. The results make it possible to construct parameter surfaces and their gradients in φ, ψ-space. The magnitude of the gradient, |∇ P|=[( ∂P/ ∂φ) 2+( ∂P/ ∂ψ) 2] 1/2, of a structural parameter P (a bond length, bond angle, or non-bonded distance) in φ, ψ-torsional space is a measure of torsional sensitivity (TS); i.e. a measure of the extent to which bond lengths, bond angles, and non-bonded distances change at a point in φ, ψ-space with backbone torsional angles. It is found that TS is not constant throughout the conformational space of a molecule, but varies in a characteristic way. It seems that, regardless of the nature of X or Y, extended forms are typically in regions of low TS; puckered conformations, of high TS. Conformations with two sequential gauche torsional angles (GG sequences) are characterized by high TS of 1,5-non-bonded distances concomitant with relatively low TS of other internal coordinates. This property of GG sequences is the source of a stabilizing and cooperative energy increment that is not afforded by other torsional sequences, such as trans- trans or trans- gauche. A structural data base, consisting of thousands of HF/4-21G structures of X-C-C-Y and X-C-C-C-Y systems has been assembled and is available on a CD.

A 55-Year-Old Man with Right Testicular Pain: Too Old for Torsion?

PubMed

Tang, Yu Ho; Yeung, Victor Hip Wo; Chu, Peggy Sau Kwan; Man, Chi Wai

2017-02-01

Testicular torsion is predominantly a disease of adolescence, but age itself should not be an exclusion criterion for the diagnosis. A lack of suspicion for testicular torsion in older patients may result in a missed or delayed diagnosis which jeopardizes the chance of testicular salvage. In this article, we report a case of testicular torsion in a 55-year-old Chinese man.

Structural evolution of nanoscale metallic glasses during high-pressure torsion: A molecular dynamics analysis

NASA Astrophysics Data System (ADS)

Feng, S. D.; Jiao, W.; Jing, Q.; Qi, L.; Pan, S. P.; Li, G.; Ma, M. Z.; Wang, W. H.; Liu, R. P.

2016-11-01

Structural evolution in nanoscale Cu50Zr50 metallic glasses during high-pressure torsion is investigated using molecular dynamics simulations. Results show that the strong cooperation of shear transformations can be realized by high-pressure torsion in nanoscale Cu50Zr50 metallic glasses at room temperature. It is further shown that high-pressure torsion could prompt atoms to possess lower five-fold symmetries and higher potential energies, making them more likely to participate in shear transformations. Meanwhile, a higher torsion period leads to a greater degree of forced cooperative flow. And the pronounced forced cooperative flow at room temperature under high-pressure torsion permits the study of the shear transformation, its activation and characteristics, and its relationship to the deformations behaviors. This research not only provides an important platform for probing the atomic-level understanding of the fundamental mechanisms of high-pressure torsion in metallic glasses, but also leads to higher stresses and homogeneous flow near lower temperatures which is impossible previously.

Ultrasonographic identification of nerve pathology in neuralgic amyotrophy: Enlargement, constriction, fascicular entwinement, and torsion.

PubMed

Arányi, Zsuzsanna; Csillik, Anita; Dévay, Katalin; Rosero, Maja; Barsi, Péter; Böhm, Josef; Schelle, Thomas

2015-10-01

The aim of this study was to characterize the ultrasonographic findings on nerves in neuralgic amyotrophy. Fourteen patients with neuralgic amyotrophy were examined using high-resolution ultrasound. Four types of abnormalities were found: (1) focal or diffuse nerve/fascicle enlargement (57%); (2) incomplete nerve constriction (36%); (3) complete nerve constriction with torsion (50%; hourglass-like appearance); and (4) fascicular entwinement (28%). Torsions were confirmed intraoperatively and were seen on the radial nerve in 85% of patients. A significant correlation was found between no spontaneous recovery of nerve function and constriction/torsion/fascicular entwinement (P = 0.007). Ultrasonographic nerve pathology in neuralgic amyotrophy varies in order of severity from nerve enlargement to constriction to nerve torsion, with treatment ranging from conservative to surgical. We postulate that the constriction caused by inflammation is the precursor of torsion and that development of nerve torsion is facilitated by the rotational movements of limbs. © 2015 Wiley Periodicals, Inc.

Flap-Lag-Torsion Stability in Forward Flight

NASA Technical Reports Server (NTRS)

Panda, B.; Chopra, I.

1985-01-01

An aeroelastic stability of three-degree flap-lag-torsion blade in forward flight is examined. Quasisteady aerodynamics with a dynamic inflow model is used. The nonlinear time dependent periodic blade response is calculated using an iterative procedure based on Floquet theory. The periodic perturbation equations are solved for stability using Floquet transition matrix theory as well as constant coefficient approximation in the fixed reference frame. Results are presented for both stiff-inplane and soft-inplane blade configurations. The effects of several parameters on blade stability are examined, including structural coupling, pitch-flap and pitch-lag coupling, torsion stiffness, steady inflow distribution, dynamic inflow, blade response solution and constant coefficient approximation.

Torsional Rigidity of Single Actin Filaments and Actin-Actin Bond Breaking Force under Torsion Measured Directly by in vitro Micromanipulation

NASA Astrophysics Data System (ADS)

Tsuda, Yuri; Yasutake, Hironori; Ishijima, Akihiko; Yanagida, Toshio

1996-11-01

Knowledge of the elastic properties of actin filaments is crucial for considering its role in muscle contraction, cellular motile events, and formation of cell shape. The stiffness of actin filaments in the directions of stretching and bending has been determined. In this study, we have directly determined the torsional rigidity and breaking force of single actin filaments by measuring the rotational Brownian motion and tensile strength using optical tweezers and microneedles, respectively. Rotational angular fluctuations of filaments supplied the torsional rigidity as (8.0 ± 1.2) × 10-26 Nm2. This value is similar to that deduced from the longitudinal rigidity, assuming the actin filament to be a homogeneous rod. The breaking force of the actin-actin bond was measured while twisting a filament through various angles using microneedles. The breaking force decreased greatly under twist, e.g., from 600-320 pN when filaments were turned through 90 degrees, independent of the rotational direction. Our results indicate that an actin filament exhibits comparable flexibility in the rotational and longitudinal directions, but breaks more easily under torsional load.

Intraoperative performance and postoperative outcome comparison of longitudinal, torsional, and transversal phacoemulsification machines.

PubMed

Christakis, Panos G; Braga-Mele, Rosa M

2012-02-01

To compare the intraoperative performance and postoperative outcomes of 3 phacoemulsification machines that use different modes. Kensington Eye Institute, Toronto, Ontario, Canada. Comparative case series. This chart and video review comprised consecutive eligible patients who had phacoemulsification by the same surgeon using a Whitestar Signature Ellips-FX (transversal), Infiniti-Ozil-IP (torsional), or Stellaris (longitudinal) machine. The review included 98 patients. Baseline characteristics in the groups were similar; the mean nuclear sclerosis grade was 2.0 ± 0.8. There were no significant intraoperative complications. The torsional machine averaged less phacoemulsification needle time (83 ± 33 seconds) than the transversal (99 ± 40 seconds; P=.21) or longitudinal (110 ± 45 seconds; P=.02) machines; the difference was accentuated in cases with high-grade nuclear sclerosis. The torsional machine had less chatter and better followability than the transversal or longitudinal machines (P<.001). The torsional and longitudinal machines had better anterior chamber stability than the transversal machine (P<.001). Postoperatively, the torsional machine yielded less central corneal edema than the transversal (P<.001) and longitudinal (P=.04) machines, corresponding to a smaller increase in mean corneal thickness (torsional 5%, transversal 10%, longitudinal 12%; P=.04). Also, the torsional machine had better 1-day postoperative visual acuities (P<.001). All 3 phacoemulsification machines were effective with no significant intraoperative complications. The torsional machine outperformed the transversal and longitudinal machines, with a lower mean needle time, less chatter, and improved followability. This corresponded to less corneal edema 1 day postoperatively and better visual acuity. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Cyclic axial-torsional deformation behavior of a cobalt-base superalloy

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1992-01-01

Multiaxial loading, especially at elevated temperature, can cause the inelastic response of a material to differ significantly from that predicted by simple flow rules, i.e., von Mises or Tresca. To quantify some of these differences, the cyclic high-temperature, deformation behavior of a wrought cobalt-based superalloy, Haynes 188, is investigated under combined axial and torsional loads. Haynes 188 is currently used in many aerospace gas turbine and rocket engine applications, e.g., the combustor liner for the T800 turboshaft engine for the RAH-66 Comanche helicopter and the liquid oxygen posts in the main injector of the space shuttle main engine. The deformation behavior of this material is assessed through the examination of hysteresis loops generated from a biaxial fatigue test program. A high-temperature axial, torsional, and combined axial-torsional fatigue data base has been generated on Haynes 188 at 760 C. Cyclic loading tests have been conducted on uniform gauge section tubular specimens in a servohydraulic axial-torsional test rig. Test control and data acquisition were accomplished with a minicomputer. In this paper, the cyclic hardening characteristics and typical hysteresis loops in the axial stress versus axial strain, shear stress versus engineering shear strain, axial strain versus engineering shear strain, and axial stress versus shear stress spaces are presented for cyclic, in-phase and out-of-phase, axial torsional tests. For in-phase tests three different values of the proportionality constant, lambda (ratio of engineering shear strain amplitude to axial strain amplitude), are examined, viz., 0.86, 1.73, and 3.46. In the out-of-phase tests, three different values of the phase angle, phi (between the axial and engineering shear strain waveforms), are studied, viz., 30, 60, and 90 deg with lambda = 1.73. The cyclic hardening behaviors of all the tests conducted on Haynes 188 at 760 C are evaluated using the von Mises equivalent stress

Torsional actuation with extension-torsion composite coupling and a magnetostrictive actuator

NASA Astrophysics Data System (ADS)

Bothwell, Christopher M.; Chandra, Ramesh; Chopra, Inderjit

1995-04-01

An analytical-experimental study of using magnetostrictive actuators in conjunction with an extension-torsion coupled composite tube to actuate a rotor blade trailing-edge flap to actively control helicopter vibration is presented. Thin walled beam analysis based on Vlasov theory was used to predict the induced twist and extension in a composite tube with magnetostrictive actuation. The study achieved good correlation between theory and experiment. The Kevlar-epoxy systems showed good correlation between measured and predicted twist values.

The exploration of the lunar interior using torsional oscillations

NASA Astrophysics Data System (ADS)

Gudkova, T. V.; Zharkov, V. N.

2002-08-01

The diagnostic capabilities of the torsional oscillations for probing the structure of the interiors of the Moon are investigated. Models with no core, a liquid core, and a solid core are considered. The profiles of compressional and shear wave velocities, VP and VS, for the lunar interior estimated by Bills and Ferrari (J. Geophys. Res. 82 (1977) 1306), Goins et al. (J. Geophys. Res. 86 (1981b) 5061) and Nakamura (J. Geophys. Res. 8 (1983) 677) from the Apollo lunar seismic network are used. For all these models the periods of torsional oscillations for fundamental modes ℓ=2-100 and four overtones have been calculated. The derivatives of the dimensionless eigenfrequency with respect to the dimensionless shear modulus and density are calculated and tabulated for use. These data can be used for the determination of corrections to the model density and shear modulus distributions due to their small change. The damping of torsional oscillations is also studied. Several trial distributions of the dissipative function Q as a function of radius are considered. It is shown, that the torsional modes with ℓ⩾7, n=0 can be recorded. These modes provide information on the external layers down to about 500 km depth.

Efficient minimization of multipole electrostatic potentials in torsion space

PubMed Central

Bodmer, Nicholas K.

2018-01-01

The development of models of macromolecular electrostatics capable of delivering improved fidelity to quantum mechanical calculations is an active field of research in computational chemistry. Most molecular force field development takes place in the context of models with full Cartesian coordinate degrees of freedom. Nevertheless, a number of macromolecular modeling programs use a reduced set of conformational variables limited to rotatable bonds. Efficient algorithms for minimizing the energies of macromolecular systems with torsional degrees of freedom have been developed with the assumption that all atom-atom interaction potentials are isotropic. We describe novel modifications to address the anisotropy of higher order multipole terms while retaining the efficiency of these approaches. In addition, we present a treatment for obtaining derivatives of atom-centered tensors with respect to torsional degrees of freedom. We apply these results to enable minimization of the Amoeba multipole electrostatics potential in a system with torsional degrees of freedom, and validate the correctness of the gradients by comparison to finite difference approximations. In the interest of enabling a complete model of electrostatics with implicit treatment of solvent-mediated effects, we also derive expressions for the derivative of solvent accessible surface area with respect to torsional degrees of freedom. PMID:29641557

Isolated torsion of fallopian tube in a post-menopausal patient: a case report.

PubMed

Ozgun, Mahmut Tuncay; Batukan, Cem; Turkyilmaz, Cagdas; Serin, Ibrahim Serdar

2007-07-20

Isolated fallopian tube torsion after menopause is a rare condition. Here we report the second case of isolated fallopian tube torsion in a post-menopausal woman. A 55-year-old post-menopausal woman presented with right lower abdominal pain. Sonography depicted a simple cystic mass adjacent to the right uterine border. Laparatomy revealed torsion of the right fallopian tube together with a paraovarian cyst. Total abdominal hysterectomy and bilateral salpingo-oophorectomy was performed. Histopathological examination revealed a simple paraovarian cyst with severe congestion, necrosis and hemorrhage. Tubal torsion should be considered in the differential diagnosis of acute lower abdominal pain, even in post-menopausal women.

Existence of Torsional Solitons in a Beam Model of Suspension Bridge

NASA Astrophysics Data System (ADS)

Benci, Vieri; Fortunato, Donato; Gazzola, Filippo

2017-11-01

This paper studies the existence of solitons, namely stable solitary waves, in an idealized suspension bridge. The bridge is modeled as an unbounded degenerate plate, that is, a central beam with cross sections, and displays two degrees of freedom: the vertical displacement of the beam and the torsional angles of the cross sections. Under fairly general assumptions, we prove the existence of solitons. Under the additional assumption of large tension in the sustaining cables, we prove that these solitons have a nontrivial torsional component. This appears relevant for security since several suspension bridges collapsed due to torsional oscillations.

A data acquisition and control program for axial-torsional fatigue testing

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Bonacuse, Peter J.

1989-01-01

A computer program was developed for data acquisition and control of axial-torsional fatigue experiments. The multitasked, interrupt-driven program was written in Pascal and Assembly. This program is capable of dual-channel control and six-channel data acquisition. It can be utilized to perform inphase and out-of-phase axial-torsional isothermal fatigue or deformation experiments. The program was successfully used to conduct inphase axial-torsional fatigue experiments on 304 stainless steel at room temperature and on Hastelloy X at 800 C. The details of the software and some of the results generated to date are presented.

Modeling of multi-rotor torsional vibrations in rotating machinery using substructuring

NASA Technical Reports Server (NTRS)

Soares, Fola R.

1986-01-01

The application of FEM modeling techniques to the analysis of torsional vibrations in complex rotating systems is described and demonstrated, summarizing results reported by Soares (1985). A substructuring approach is used for determination of torsional natural frequencies and resonant-mode shapes, steady-state frequency-sweep analysis, identification of dynamically unstable speed ranges, and characterization of transient linear and nonlinear systems. Results for several sample problems are presented in diagrams, graphs, and tables. STORV, a computer code based on this approach, is in use as a preliminary design tool for drive-train torsional analysis in the High Altitude Wind Tunnel at NASA Lewis.

Elevated temperature axial and torsional fatigue behavior of Haynes 188

NASA Astrophysics Data System (ADS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1992-06-01

The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

Elevated temperature axial and torsional fatigue behavior of Haynes 188

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1992-01-01

The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

Elevated temperature axial and torsional fatigue behavior of Haynes 188

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

1995-01-01

The results are reported for high-temperature axial and torsional low-cycle fatigue experiments performed at 760 C in air on thin-walled tubular specimens of Haynes 188, a wrought cobalt-based superalloy. Data are also presented for mean coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. This data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME Boiler and Pressure Code), Manson-Halford, modified multiaxiality factor (proposed in this paper), modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The modified multiaxiality factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

Free torsional vibrations of tapered cantilever I-beams

NASA Astrophysics Data System (ADS)

Rao, C. Kameswara; Mirza, S.

1988-08-01

Torsional vibration characteristics of linearly tapered cantilever I-beams have been studied by using the Galerkin finite element method. A third degree polynomial is assumed for the angle of twist. The analysis presented is valid for long beams and includes the effect of warping. The individual as well as combined effects of linear tapers in the width of the flanges and the depth of the web on the torsional vibration of cantilever I-beams are investigated. Numerical results generated for various values of taper ratios are presented in graphical form.

Singularity-free spinors in gravity with propagating torsion

NASA Astrophysics Data System (ADS)

Fabbri, Luca

2017-12-01

We consider the most general renormalizable theory of propagating torsion in Einstein gravity for the Dirac matter distribution and we demonstrate that in this case, torsion is a massive axial-vector field whose coupling to the spinor gives rise to conditions in terms of which gravitational singularities are not bound to form; we discuss how our results improve those that are presented in the existing literature, and that no further improvement can be achieved unless one is ready to re-evaluate some considerations on the renormalizability of the theory.

Surface Abrasive Torsion for Improved Mechanical Properties and Microstructure

NASA Astrophysics Data System (ADS)

Moon, Ji Hyun; Baek, Seung Mi; Lee, Seok Gyu; Yoon, Jae Ik; Lee, Sunghak; Kim, Hyoung Seop

2018-05-01

A novel process of discrete surface abrasion during simple torsion (ST), named "surface abrasive torsion (SAT)," is proposed to overcome the limitation of ST, i.e., insufficient strain for severe plastic deformation (SPD) due to cracks initiated on the surface, by removing the roughened surface region. The effect of SAT on delayed crack initiation was explained using finite element simulations. Larger shear deformation applicable to the specimen in SAT than ST was demonstrated experimentally.

Research on torsional vibration modelling and control of printing cylinder based on particle swarm optimization

NASA Astrophysics Data System (ADS)

Wang, Y. M.; Xu, W. C.; Wu, S. Q.; Chai, C. W.; Liu, X.; Wang, S. H.

2018-03-01

The torsional oscillation is the dominant vibration form for the impression cylinder of printing machine (printing cylinder for short), directly restricting the printing speed up and reducing the quality of the prints. In order to reduce torsional vibration, the active control method for the printing cylinder is obtained. Taking the excitation force and moment from the cylinder gap and gripper teeth open & closing cam mechanism as variable parameters, authors establish the dynamic mathematical model of torsional vibration for the printing cylinder. The torsional active control method is based on Particle Swarm Optimization(PSO) algorithm to optimize input parameters for the serve motor. Furthermore, the input torque of the printing cylinder is optimized, and then compared with the numerical simulation results. The conclusions are that torsional vibration active control based on PSO is an availability method to the torsional vibration of printing cylinder.

Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane.

PubMed

Shishkov, A V; Ksenofontov, A L; Bogacheva, E N; Kordyukova, L V; Badun, G A; Alekseevsky, A V; Tsetlin, V I; Baratova, L A

2002-05-15

The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

Contribution of facet joints, axial compression, and composition to human lumbar disc torsion mechanics.

PubMed

Bezci, Semih E; Eleswarapu, Ananth; Klineberg, Eric O; O'Connell, Grace D

2018-02-12

Stresses applied to the spinal column are distributed between the intervertebral disc and facet joints. Structural and compositional changes alter stress distributions within the disc and between the disc and facet joints. These changes influence the mechanical properties of the disc joint, including its stiffness, range of motion, and energy absorption under quasi-static and dynamic loads. There have been few studies evaluating the role of facet joints in torsion. Furthermore, the relationship between biochemical composition and torsion mechanics is not well understood. Therefore, the first objective of this study was to investigate the role of facet joints in torsion mechanics of healthy and degenerated human lumbar discs under a wide range of compressive preloads. To achieve this, each disc was tested under four different compressive preloads (300-1200 N) with and without facet joints. The second objective was to develop a quantitative structure-function relationship between tissue composition and torsion mechanics. Facet joints have a significant contribution to disc torsional stiffness (∼60%) and viscoelasticity, regardless of the magnitude of axial compression. The findings from this study demonstrate that annulus fibrosus GAG content plays an important role in disc torsion mechanics. A decrease in GAG content with degeneration reduced torsion mechanics by more than an order of magnitude, while collagen content did not significantly influence disc torsion mechanics. The biochemical-mechanical and compression-torsion relationships reported in this study allow for better comparison between studies that use discs of varying levels of degeneration or testing protocols and provide important design criteria for biological repair strategies. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Killing-Yano equations with torsion, worldline actions and G-structures

NASA Astrophysics Data System (ADS)

Papadopoulos, G.

2012-06-01

We determine the geometry of the target spaces of supersymmetric non-relativistic particles with torsion and magnetic couplings, and with symmetries generated by the fundamental forms of G-structures for G = U(n), SU(n), Sp(n), Sp(n) · Sp(1), G2 and Spin(7). We find that the Killing-Yano equation, which arises as a condition for the invariance of the worldline action, does not always determine the torsion coupling uniquely in terms of the metric and fundamental forms. We show that there are several connections with skew-symmetric torsion for G = U(n), SU(n) and G2 that solve the invariance conditions. We describe all these compatible connections for each of the G-structures and explain the geometric nature of the couplings.

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments.

PubMed

Pedullà, E; Lo Savio, F; Boninelli, S; Plotino, G; Grande, N M; Rapisarda, E; La Rosa, G

2015-11-01

To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel-titanium (NiTi), M-Wire or CM-Wire. Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two-way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two-way analyses of variance. Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M-wire and CM-wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading. © 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Research on torsional friction behavior and fluid load support of PVA/HA composite hydrogel.

PubMed

Chen, Kai; Zhang, Dekun; Yang, Xuehui; Cui, Xiaotong; Zhang, Xin; Wang, Qingliang

2016-09-01

Hydrogels have been extensively studied for use as synthetic articular cartilage. This study aimed to investigate (1) the torsional friction contact state and the transformation mechanism of PVA/HA composite hydrogel against CoCrMo femoral head and (2) effects of load and torsional angle on torsional friction behavior. The finite element method was used to study fluid load support of PVA/HA composite hydrogel. Results show fluid loss increases gradually of PVA/HA composite hydrogel with torsional friction time, leading to fluid load support decreases. The contact state changes from full slip state to stick-slip mixed state. As the load increases, friction coefficient and adhesion zone increase gradually. As the torsional angle increases, friction coefficient and slip trend of the contact interface increase, resulting in the increase of the slip zone and the reduction of the adhesion zone. Fluid loss increases of PVA/HA composite hydrogel as the load and the torsional angle increase, which causes the decrease of fluid load support and the increase of friction coefficient. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pancreatic torsion in a dog

PubMed Central

Brabson, Tamera L.; Maki, Lynn C.; Newell, Susan M.; Ralphs, S. Christopher

2015-01-01

A 6-month-old male intact Cane Corso mastiff dog was presented for a recent history of vomiting, abdominal pain, and lethargy. A diagnosis of pancreatic torsion was made during abdominal exploratory surgery and was confirmed with histopathology. The dog underwent partial pancreatectomy and recovered with no complications. PMID:25969579

Torsional strength of computer-aided design/computer-aided manufacturing-fabricated esthetic orthodontic brackets.

PubMed

Alrejaye, Najla; Pober, Richard; Giordano Ii, Russell

2017-01-01

To fabricate orthodontic brackets from esthetic materials and determine their fracture resistance during archwire torsion. Computer-aided design/computer-aided manufacturing technology (Cerec inLab, Sirona) was used to mill brackets with a 0.018 × 0.025-inch slot. Materials used were Paradigm MZ100 and Lava Ultimate resin composite (3M ESPE), Mark II feldspathic porcelain (Vita Zahnfabrik), and In-Ceram YZ zirconia (Vita Zahnfabrik). Ten brackets of each material were subjected to torque by a 0.018 × 0.025-inch stainless steel archwire (G&H) using a specially designed apparatus. The average moments and degrees of torsion necessary to fracture the brackets were determined and compared with those of commercially available alumina brackets, Mystique MB (Dentsply GAC). The YZ brackets were statistically significantly stronger than any other tested material in their resistance to torsion (P < .05). The mean torques at failure ranged from 3467 g.mm for Mark II to 11,902 g.mm for YZ. The mean torsion angles at failure ranged from 15.3° to 40.9°. Zirconia had the highest torsional strength among the tested esthetic brackets. Resistance of MZ100 and Lava Ultimate composite resin brackets to archwire torsion was comparable to commercially available alumina ceramic brackets.

Diagnosis of neonatal ovarian torsion: Emphasis on prenatal and postnatal sonographic findings.

PubMed

Kim, Hyun Su; Yoo, So-Young; Cha, Min Jae; Kim, Ji Hye; Jeon, Tae Yeon; Kim, Wee Kyoung

2016-06-01

Our aim was to retrospectively review the imaging findings of patients with neonatal ovarian torsion, emphasizing prenatal and postnatal sonographic findings. Eleven patients who had had neonatal ovarian torsion diagnosed surgically (n = 9) or clinicoradiologically (n = 2) were enrolled. Prenatal and postnatal sonographic features, including sequential postnatal change, were reviewed. Clinical and pathologic features were also investigated. All patients except one had a fetal ovarian cyst (mean, 5.3 cm) detected on third-trimester sonography, either simple (n = 6) or complex (n = 4). In all 11 patients, initial postnatal sonography had revealed a complex cyst (mean, 4.7 cm) with intracystic clot or debris, the double-wall sign, a fluid-fluid level, and multiple septation. None of the patients had had symptoms or signs related to the ovarian torsion. Follow-up sonography in seven patients had revealed increased echogenicity of the cyst wall with frequent calcification and a decrease in size of the cyst. In two patients, the interval of the change in cyst position was noted, and autoamputation of the torsed ovary had been surgically confirmed. Serous cystadenoma had been identified in one patient. Neonatal ovarian torsion most commonly manifests as an asymptomatic complex cyst on sonography due to torsion of a fetal ovarian cyst. Serial monitoring of a fetal ovarian cyst for its resolution or changes in its appearance is mandatory for making an early diagnosis of torsion. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:290-297, 2016. © 2016 Wiley Periodicals, Inc.

Torsion of the Vermiform Appendix: A Case Report and Review of Literature

PubMed Central

Hassan, Wan Amir Wan; Tay, Yeng Kwang; Ghadiri, Marjan

2018-01-01

Patient: Male, 30 Final Diagnosis: Torsion of appendix Symptoms: Abdominal pain • anorexia • nausea Medication: — Clinical Procedure: Laparoscopic appendicectomy Specialty: Surgery Objective: Rare disease Background: Torsion of the vermiform appendix is a rare condition that presents with symptoms analogous to those of common acute appendicitis; therefore, it is often diagnosed during surgery. It was first described by Payne et al. in 1918. Since then, there has been wide recognition of a primary and a secondary form of the condition, affecting both the pediatric and adult populations. We present a case of an adult patient and conducted a literature review in the adult demographic. Case Report: We report the case of a 30-year-old man who presented with clinically acute appendicitis. Laparoscopically, we diagnosed a torsion of the vermiform appendix secondary to a mucocele process. Histology confirmed a low-grade mucinous cystoadenoma, with a hemorrhagic necrosis of the wall, in keeping with torsion. Conclusions: Torsion of the vermiform appendix is a rare condition that presents similar to acute appendicitis, and therefore is often diagnosed intraoperatively. Since first described, 33 cases in adults were identified in the English literature, and recognition of a primary or secondary form has emerged. Preoperative radiological imaging is rarely useful in diagnosis. To the best of our knowledge, this is the eighth reported case in the English literature of a torsion of the vermiform appendix secondary to a mucinous cystoadenoma. PMID:29588439

Effects of axial compression and rotation angle on torsional mechanical properties of bovine caudal discs.

PubMed

Bezci, Semih E; Klineberg, Eric O; O'Connell, Grace D

2018-01-01

The intervertebral disc is a complex joint that acts to support and transfer large multidirectional loads, including combinations of compression, tension, bending, and torsion. Direct comparison of disc torsion mechanics across studies has been difficult, due to differences in loading protocols. In particular, the lack of information on the combined effect of multiple parameters, including axial compressive preload and rotation angle, makes it difficult to discern whether disc torsion mechanics are sensitive to the variables used in the test protocol. Thus, the objective of this study was to evaluate compression-torsion mechanical behavior of healthy discs under a wide range of rotation angles. Bovine caudal discs were tested under a range of compressive preloads (150, 300, 600, and 900N) and rotation angles (± 1, 2, 3, 4, or 5°) applied at a rate of 0.5°/s. Torque-rotation data were used to characterize shape changes in the hysteresis loop and to calculate disc torsion mechanics. Torsional mechanical properties were described using multivariate regression models. The rate of change in torsional mechanical properties with compression depended on the maximum rotation angle applied, indicating a strong interaction between compressive stress and maximum rotation angle. The regression models reported here can be used to predict disc torsion mechanics under axial compression for a given disc geometry, compressive preload, and rotation angle. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of test particle acceleration in torsional spine and fan reconnection regimes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosseinpour, M., E-mail: hosseinpour@tabrizu.ac.ir; Mehdizade, M.; Mohammadi, M. A.

2014-10-15

Magnetic reconnection is a common phenomenon taking place in astrophysical and space plasmas, especially in solar flares which are rich sources of highly energetic particles. Torsional spine and fan reconnections are important mechanisms proposed for steady-state three-dimensional null-point reconnection. By using the magnetic and electric fields for these regimes, we numerically investigate the features of test particle acceleration in both regimes with input parameters for the solar corona. By comparison, torsional spine reconnection is found to be more efficient than torsional fan reconnection in an acceleration of a proton to a high kinetic energy. A proton can gain as highmore » as 100 MeV of relativistic kinetic energy within only a few milliseconds. Moreover, in torsional spine reconnection, an accelerated particle can escape either along the spine axis or on the fan plane depending on its injection position. However, in torsional fan reconnection, the particle is only allowed to accelerate along the spine axis. In addition, in both regimes, the particle's trajectory and final kinetic energy depend on the injection position but adopting either spatially uniform or non-uniform localized plasma resistivity does not much influence the features of trajectory.« less

Effective Torsion and Spring Constants in a Hybrid Translational-Rotational Oscillator

ERIC Educational Resources Information Center

Nakhoda, Zein; Taylor, Ken

2011-01-01

A torsion oscillator is a vibrating system that experiences a restoring torque given by [tau] = -[kappa][theta] when it experiences a rotational displacement [theta] from its equilibrium position. The torsion constant [kappa] (kappa) is analogous to the spring constant "k" for the traditional translational oscillator (for which the restoring force…

Global geometric torsion estimation in adolescent idiopathic scoliosis.

PubMed

Kadoury, Samuel; Shen, Jesse; Parent, Stefan

2014-04-01

Several attempts have been made to measure geometrical torsion in adolescent idiopathic scoliosis (AIS) and quantify the three-dimensional (3D) deformation of the spine. However, these approaches are sensitive to imprecisions in the 3D modeling of the anatomy and can only capture the effect locally at the vertebrae, ignoring the global effect at the regional level and thus have never been widely used to follow the progression of a deformity. The goal of this work was to evaluate the relevance of a novel geometric torsion descriptor based on a parametric modeling of the spinal curve as a 3D index of scoliosis. First, an image-based approach anchored on prior statistical distributions is used to reconstruct the spine in 3D from biplanar X-rays. Geometric torsion measuring the twisting effect of the spine is then estimated using a technique that approximates local arc-lengths with parametric curve fitting centered at the neutral vertebra in different spinal regions. We first evaluated the method with simulated experiments, demonstrating the method's robustness toward added noise and reconstruction inaccuracies. A pilot study involving 65 scoliotic patients exhibiting different types of deformities was also conducted. Results show the method is able to discriminate between different types of deformation based on this novel 3D index evaluated in the main thoracic and thoracolumbar/lumbar regions. This demonstrates that geometric torsion modeled by parametric spinal curve fitting is a robust tool that can be used to quantify the 3D deformation of AIS and possibly exploited as an index to classify the 3D shape.

The g - 2 muon anomaly in di-muon production with the torsion in LHC

NASA Astrophysics Data System (ADS)

Syromyatnikov, A. G.

2016-06-01

It was considered within the framework of the conformal gauge gravitational theory CGTG coupling of the standard model fermions to the axial torsion and preliminary discusses the impact of extra dimensions, in particular, in a five-dimensional space-time with Randall-Sundrum metric, where the fifth dimension is compactified on an S1/Z 2 orbifold, which as it turns out is conformally to the fifth dimension flat Euclidean space with permanent trace of torsion, with a compactification radius R in terms of the radius of a CGTG gravitational screening, through torsion in a process Z → μ+μ- and LHC data. In general, have come to the correct set of the conformal calibration curvature the Faddeev-Popov diagram technique type, that follows directly from dynamics. This leads to the effect of restrictions on neutral spin currents of gauge fields by helicity and the Regge’s form theory. The diagrams reveals the fact of opening of the fine spacetime structure in a process pp → γ/Z/T → μ+μ- with a center-of-mass energy of 14TeV, indicated by dotted lines and texture columns, as a result of p-p collision on 1.3 ṡ 10-18cm scales from geometric shell gauge bosons of the SM continued by the heavy axial torsion resonance, and even by emerging from the inside into the outside of the ultra-light (freely-frozen in muon’s spin) axial torsion. We then evaluate the contribution of the torsion to the muon anomaly to derive new constraints on the torsion parameters. It was obtained that on the πN scattering through the exchange of axial torsion accounting, the nucleon anomalous magnetic moment in the eikonal phase leads to additive additives which is responsible for the spin-flip in the scattering process, the scattering amplitude is classical and characterized by a strong the torsion coupling ηT≅1. So the scattering of particles, occurs as on the Coulomb center with the charge fT This is the base model which is the g-2 muon anomaly. The muon anomaly contribution due to

Torsional Oscillations in a Global Solar Dynamo

NASA Astrophysics Data System (ADS)

Beaudoin, P.; Charbonneau, P.; Racine, E.; Smolarkiewicz, P. K.

2013-02-01

We characterize and analyze rotational torsional oscillations developing in a large-eddy magnetohydrodynamical simulation of solar convection (Ghizaru, Charbonneau, and Smolarkiewicz, Astrophys. J. Lett. 715, L133, 2010; Racine et al., Astrophys. J. 735, 46, 2011) producing an axisymmetric, large-scale, magnetic field undergoing periodic polarity reversals. Motivated by the many solar-like features exhibited by these oscillations, we carry out an analysis of the large-scale zonal dynamics. We demonstrate that simulated torsional oscillations are not driven primarily by the periodically varying large-scale magnetic torque, as one might have expected, but rather via the magnetic modulation of angular-momentum transport by the large-scale meridional flow. This result is confirmed by a straightforward energy analysis. We also detect a fairly sharp transition in rotational dynamics taking place as one moves from the base of the convecting layers to the base of the thin tachocline-like shear layer formed in the stably stratified fluid layers immediately below. We conclude by discussing the implications of our analyses with regard to the mechanism of amplitude saturation in the global dynamo operating in the simulation, and speculate on the possible precursor value of torsional oscillations for the forecast of solar-cycle characteristics.

Lung lobe torsion in dogs: 22 cases (1981-1999).

PubMed

Neath, P J; Brockman, D J; King, L G

2000-10-01

To identify breed disposition, postoperative complications, and outcome in dogs with lung lobe torsion. Retrospective study. 22 client-owned dogs. Information on signalment; history; clinical findings; results of clinicopathologic testing, diagnostic imaging, and pleural fluid analysis; surgical treatment; intra- and postoperative complications; histologic findings; and outcome were obtained from medical records. All 22 dogs had pleural effusion; dyspnea was the most common reason for examination. Fifteen dogs were large deep-chested breeds; 5 were toy breeds. Afghan Hounds were overrepresented, compared with the hospital population. One dog was euthanatized without treatment; the remaining dogs underwent exploratory thoracotomy and lung lobectomy. Eleven dogs recovered from surgery without complications, but 3 of these later died of thoracic disease. Four dogs survived to discharge but had clinically important complications within 2 months, including chylothorax, mediastinal mesothelioma, gastric dilatation, and a second lung lobe torsion. Six dogs died or were euthanatized within 2 weeks after surgery because of acute respiratory distress syndrome, pneumonia, septic shock, pneumothorax, or chylothorax. Chylothorax was diagnosed in 8 of the 22 dogs, including 4 Afghan Hounds. Results suggest that lung lobe torsion is rare in dogs and develops most frequently in large deep-chested dogs, particularly Afghan Hounds. Other predisposing causes were not identified, but an association with chylothorax was evident, especially in Afghan Hounds. Prognosis for dogs with lung lobe torsion was fair to guarded.

Dynamic torsional misalignment of eyes during laser in-situ keratomileusis.

PubMed

Shajari, Mehdi; Bühren, Jens; Kohnen, Thomas

2016-05-01

To determine the amount and characteristics of dynamic torsional misalignment of eyes during excimer ablation in laser in-situ keratomileusis (LASIK). Retrospective trial for evaluation of dynamic intraoperative torsional misalignment of 179 eyes that underwent LASIK for correction of myopia and/or astigmatism. Patients were treated with the Keracor 217z excimer laser implementing 25 Hz dynamic eye tracker ACE 100 (both Technolas Perfect Vision, Munich, Germany). From dynamic torsional misalignments, temporal power spectra were obtained by Fourier analysis up to a frequency of 12.5 Hz and an amplitude of ±15° from initial torsional status (limited by the tracking system). The f90, f95, and f99 criteria were defined as the frequency below which 90 %, 95 %, and 99 % of misalignments occur. A Wilcoxon rank sum test was performed to detect differences of f90, f95, and f99 in groups' gender, age, and eye (if both eyes underwent surgery at same day). Multiple regression analysis (MRA) was performed to evaluate possible preoperative predictors of f90, f95, and f99. Fourier analysis showed a dominance of high-frequency, low-power dynamic torsional misalignment. Mean f95 threshold of rotational movements was 4.89±2.12 Hz (median 4.54, ranging from 0.44 to 9.23 Hz). Wilcoxon rank sum test showed no differences in f90, f95, and f99 between groups' gender, age, and eye. MRA revealed age, gender, and optical zone as preoperative predictors on intraoperative f90, f95, and f99. Dynamic intraoperative torsional misalignments of eyes undergoing LASIK are dominated by low-frequency (slow), high-power (large) movements, with 95 % being slower than 4.89Hz regarding the spectrum analyzed (0-12.5Hz, ±15°). Movements can be predicted preoperatively by eye treated, patients' gender, and age in pre-LASIK diagnostics.

Singularities and n-dimensional black holes in torsion theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cembranos, J.A.R.; Valcarcel, J. Gigante; Torralba, F.J. Maldonado, E-mail: cembra@fis.ucm.es, E-mail: jorgegigante@ucm.es, E-mail: fmaldo01@ucm.es

2017-04-01

In this work we have studied the singular behaviour of gravitational theories with non symmetric connections. For this purpose we introduce a new criteria for the appearance of singularities based on the existence of black/white hole regions of arbitrary codimension defined inside a spacetime of arbitrary dimension. We discuss this prescription by increasing the complexity of the particular torsion theory under study. In this sense, we start with Teleparallel Gravity, then we analyse Einstein-Cartan theory, and finally dynamical torsion models.

Ruptured ectopic pregnancy with contralateral adnexal torsion after spontaneous conception.

PubMed

DiLuigi, Andrea J; Maier, Donald B; Benadiva, Claudio A

2008-11-01

To describe a case of ruptured ectopic pregnancy and contralateral adnexal torsion after spontaneous conception. Case report. Tertiary university medical center. A 23-year-old multiparous female with severe bilateral pelvic pain and a positive pregnancy test. Operative laparoscopy with detorsion of left adnexa, drainage of left ovarian hemorrhagic corpus luteum cyst, right salpingectomy, and dilation and curettage. Laparoscopy revealed a 5 cm hemorrhagic corpus luteum cyst of the left ovary, torsion of the left ovary and fallopian tube, and a ruptured right ampullary ectopic pregnancy. Normal perfusion of left ovary and fallopian tube after detorsion, resolution of left ovarian hemorrhagic corpus luteum cyst, patent left fallopian tube with chromopertubation, and successful removal of ectopic pregnancy. This is a unique case of adnexal torsion and contralateral ectopic pregnancy occurring after spontaneous conception.

Functional and evolutionary relationships between bacteriorhodopsin and halorhodopsin in the archaebacterium, halobacterium halobium

NASA Technical Reports Server (NTRS)

Lanyi, J. K.

1986-01-01

The archaebacteria occupy a unique place in phylogenetic trees constructed from analyses of sequences from key informational macromolecules, and their study continues to yield interesting ideas on the early evolution and divergence of biological forms. It is now known that the halobacteria among these species contain various retinal-proteins, resembling eukaryotic rhodopsins, but with different functions. Two of these pigments, located in the cytoplasmic membranes of the bacteria, are bacteriorhodopsin (a light-driven proton pump) and halorhodopsin (a light-driven chloride pump). Comparison of these systems is expected to reveal structure/function relationships in these simple (primitive?) energy transducing membrane components and evolutionary relationships which had produced the structural features which allow the divergent functions. Findings indicate that very different primary structures are needed for these proteins to accomplish their different functions. Indeed, analysis of partial amino acid sequences from halo-opsin shows already that few if any long segments exist which are homologous to bacterio-opsin. Either these proteins diverged a very long time ago to allow for the observed differences, or the evolutionary clock in the halobacteria runs faster than usual.

Time-resolved absorbance changes induced by fast acidification of bacteriorhodopsin in vesicle systems.

PubMed Central

Druckmann, S; Ottolenghi, M; Korenstein, R

1985-01-01

The direction of the accessibility to protons of the binding site in bacteriorhodopsin is of primary importance in elucidating the proton-pump mechanism. The problem is approached via the pH-dependent equilibrium bR560 in equilibrium bR605 in vesicles with preferentially oriented purple membranes. Fast acidification (stopped-flow) experiments with inside-out, monomeric, bR vesicles were carried out with and without a buffer enclosed in the vesicle interior. The results, showing a buffer-induced delay in the formation of bR605, indicate that the binding site is accessible to protons from the inside of the vesicles. We arrive at this conclusion also by working with inside-out trimeric vesicles in the presence and in the absence of H+ (and K+) ionophores. The results suggest that in Halobacterium halobium, the binding site and thus the retinal Schiff base are exposed to the outside of the cell. This conclusion is consistent with a pumping mechanism based on a light-induced pK change. PMID:3978185

Intravitreal Phacoemulsification Using Torsional Handpiece for Retained Lens Fragments

PubMed Central

Kumar, Vinod; Takkar, Brijesh

2016-01-01

Purpose: To evaluate the results of intravitreal phacoemulsification with torsional hand piece in eyes with posteriorly dislocated lens fragments. Methods: In this prospective, interventional case series, 15 eyes with retained lens fragments following phacoemulsification were included. All patients underwent standard three-port pars plana vitrectomy and intravitreal phacoemulsification using sleeveless, torsional hand piece (OZiL™, Alcon's Infiniti Vision System). Patients were followed up for a minimum of six months to evaluate the visual outcomes and complications. Results: The preoperative best-corrected visual acuity (BCVA) ranged from light perception to 0.3. No complications such as thermal burns of the scleral wound, retinal damage due to flying lens fragments, or difficult lens aspiration occurred during intravitreal phacoemulsification. Mean post-operative BCVA at the final follow-up was 0.5. Two eyes developed cystoid macular edema, which was managed medically. No retinal detachment was noted. Conclusion: Intravitreal phacoemulsification using torsional hand piece is a safe and effective alternative to conventional longitudinal phacofragmentation. PMID:27621783

Intravitreal Phacoemulsification Using Torsional Handpiece for Retained Lens Fragments.

PubMed

Kumar, Vinod; Takkar, Brijesh

2016-01-01

To evaluate the results of intravitreal phacoemulsification with torsional hand piece in eyes with posteriorly dislocated lens fragments. In this prospective, interventional case series, 15 eyes with retained lens fragments following phacoemulsification were included. All patients underwent standard three-port pars plana vitrectomy and intravitreal phacoemulsification using sleeveless, torsional hand piece (OZiL™, Alcon's Infiniti Vision System). Patients were followed up for a minimum of six months to evaluate the visual outcomes and complications. The preoperative best-corrected visual acuity (BCVA) ranged from light perception to 0.3. No complications such as thermal burns of the scleral wound, retinal damage due to flying lens fragments, or difficult lens aspiration occurred during intravitreal phacoemulsification. Mean post-operative BCVA at the final follow-up was 0.5. Two eyes developed cystoid macular edema, which was managed medically. No retinal detachment was noted. Intravitreal phacoemulsification using torsional hand piece is a safe and effective alternative to conventional longitudinal phacofragmentation.

Sequence-dependent response of DNA to torsional stress: a potential biological regulation mechanism.

PubMed

Reymer, Anna; Zakrzewska, Krystyna; Lavery, Richard

2018-02-28

Torsional restraints on DNA change in time and space during the life of the cell and are an integral part of processes such as gene expression, DNA repair and packaging. The mechanical behavior of DNA under torsional stress has been studied on a mesoscopic scale, but little is known concerning its response at the level of individual base pairs and the effects of base pair composition. To answer this question, we have developed a geometrical restraint that can accurately control the total twist of a DNA segment during all-atom molecular dynamics simulations. By applying this restraint to four different DNA oligomers, we are able to show that DNA responds to both under- and overtwisting in a very heterogeneous manner. Certain base pair steps, in specific sequence environments, are able to absorb most of the torsional stress, leaving other steps close to their relaxed conformation. This heterogeneity also affects the local torsional modulus of DNA. These findings suggest that modifying torsional stress on DNA could act as a modulator for protein binding via the heterogeneous changes in local DNA structure.

Sequence-dependent response of DNA to torsional stress: a potential biological regulation mechanism

PubMed Central

Reymer, Anna; Zakrzewska, Krystyna; Lavery, Richard

2018-01-01

Abstract Torsional restraints on DNA change in time and space during the life of the cell and are an integral part of processes such as gene expression, DNA repair and packaging. The mechanical behavior of DNA under torsional stress has been studied on a mesoscopic scale, but little is known concerning its response at the level of individual base pairs and the effects of base pair composition. To answer this question, we have developed a geometrical restraint that can accurately control the total twist of a DNA segment during all-atom molecular dynamics simulations. By applying this restraint to four different DNA oligomers, we are able to show that DNA responds to both under- and overtwisting in a very heterogeneous manner. Certain base pair steps, in specific sequence environments, are able to absorb most of the torsional stress, leaving other steps close to their relaxed conformation. This heterogeneity also affects the local torsional modulus of DNA. These findings suggest that modifying torsional stress on DNA could act as a modulator for protein binding via the heterogeneous changes in local DNA structure. PMID:29267977

Assessment of radial torsion using computed tomography in dogs with and without antebrachial limb deformity.

PubMed

Kroner, Kevin; Cooley, Katie; Hoey, Seamus; Hetzel, Scott J; Bleedorn, Jason A

2017-01-01

To evaluate the reliability of radial torsion assessment in dogs using computed tomography (CT). Cadaveric and retrospective observational clinical study. Thoracic limbs (n = 40) from bilateral normal cadaveric canine specimens (10 pairs) and unilateral antebrachial angular limb deformity (ALD) dogs (10 uniapical and 10 biapical deformities). Limbs were evaluated using CT. Frontal, sagittal, and axial plane (torsion) values were obtained using published guidelines and compared between groups and limbs. Radial torsion reliability was assessed among 3 observers using intraclass correlation coefficients (ICC). The mean (±SD) radial torsion of normal dogs was 3.6° ± 6.4° and contained a significant right to left limb variation of 2.6°. Mean radial torsion in uniapical ALD limbs (3.6° ± 18.7°) was not significantly different from biapical ALD limbs (8.9° ± 17.9°). There was a wide range of torsion values in normal and ALD limbs. The interobserver reliability was excellent (ICC > 0.8) for normal dogs, good (0.73) for uniapical, and excellent (0.89) for biapical ALD limbs. The intraobserver reliability was excellent (>0.8) for all groups. There was a small side-to-side variation of radial torsion in normal dogs. With directed training, torsion assessment using CT is reliable in dogs with and without antebrachial bone deformity. © 2016 The American College of Veterinary Surgeons.

Distributed torsion sensor based on cascaded coaxial cable Fabry-Perot interferometers

NASA Astrophysics Data System (ADS)

Cheng, Baokai; Zhu, Wenge; Hua, Liwei; Liu, Jie; Li, Yurong; Nygaard, Runar; Xiao, Hai

2016-07-01

Cascaded coaxial cable Fabry-Perot interferometers (FPI) are studied and demonstrated for distributed torsion measurement. Multiple weak reflectors are implemented on a coaxial cable so that any two consecutive reflectors can form a Fabry-Perot cavity. By fixing the cable sensor in a helical form on a shaft, the distributed torsion of the shaft can be measured by the cascaded Fabry-Perot cavities. A test on a single section shows that the sensor has a linear response with a sensitivity of 1.834 MHz (rad/m)-1 in the range of twisted rate from 0 to 8.726 rad m-1. The distributed torsion sensing capability is useful in drilling process monitoring, structure health monitoring and machine failure detection.

Torsional Vibration in the National Wind Technology Center’s 2.5-Megawatt Dynamometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sethuraman, Latha; Keller, Jonathan; Wallen, Robb

2016-08-31

This report documents the torsional drivetrain dynamics of the NWTC's 2.5-megawatt dynamometer as identified experimentally and as calculated using lumped parameter models using known inertia and stiffness parameters. The report is presented in two parts beginning with the identification of the primary torsional modes followed by the investigation of approaches to damp the torsional vibrations. The key mechanical parameters for the lumped parameter models and justification for the element grouping used in the derivation of the torsional modes are presented. The sensitivities of the torsional modes to different test article properties are discussed. The oscillations observed from the low-speed andmore » generator torque measurements were used to identify the extent of damping inherently achieved through active and passive compensation techniques. A simplified Simulink model of the dynamometer test article integrating the electro-mechanical power conversion and control features was established to emulate the torque behavior that was observed during testing. The torque response in the high-speed, low-speed, and generator shafts were tested and validated against experimental measurements involving step changes in load with the dynamometer operating under speed-regulation mode. The Simulink model serves as a ready reference to identify the torque sensitivities to various system parameters and to explore opportunities to improve torsional damping under different conditions.« less

Relative blood volume measurements by magnetic resonance imaging facilitate detection of testicular torsion.

PubMed

Cheng, H C; Khan, M A; Bogdanov, A; Kwong, K; Weissleder, R

1997-12-01

The authors determine the utility of relative blood volume measurements (rBV) using a blood pool marker for magnetic resonance imaging (MRI) in detection of early testicular torsion. Testicular torsion was induced in rats by counterclockwise 720 degrees rotation and fixation of the testis in the scrotum. MPEG-PL-DTPA-Gd enhanced MRI (30 mumol Gd/kg bolus injection) was performed 1 hour after torsion at 1.5 T using fat-suppressed three-dimensional fast spoiled gradient-recalled sequence for relative blood volume measurement and three-dimensional time-of-flight sequence for MR angiography (MRA). The rBV of the torqued testes was significantly lower (13.3% +/- 13.5%) than that of testes with sham operation (97.7% +/- 5.3%; P < 0.05). Rats with testicular torsion showed larger regions of ischemia than did animals with sham operation (63.4% +/- 13.0% versus 4.0% +/- 2.8% of all pixels in testis; P < 0.01). The MRA of testicular torsion showed engorgement of the distal testicular vein as a sign of venous compression or total disappearance of the testicular vein, indicating arterial insufficiency. The authors conclude that MPEG-PL-DTPA-Gd can be used to obtain functional (rBV), morphologic (tunica enhancement), and angiographic (venous engorgement, arterial compromise) findings that should improve the diagnosis of testicular torsion in the acute setting.

Comparison of endothelial changes and power settings between torsional and longitudinal phacoemulsification.

PubMed

Reuschel, Anna; Bogatsch, Holger; Barth, Thomas; Wiedemann, Renate

2010-11-01

To compare the intraoperative and postoperative outcomes of conventional longitudinal phacoemulsification and torsional phacoemulsification. Department of Ophthalmology, University of Leipzig, Germany. Randomized single-center clinical trial. Eyes with senile cataract were randomized to have phacoemulsification using the Infiniti Vision System and the torsional mode (OZil) or conventional longitudinal mode. Primary outcomes were corrected distance visual acuity (CDVA) and central endothelial cell density (ECD), calculated according to the Conference on Harmonisation-E9 Guidelines in which missing values were substituted by the median in each group (primary analysis) and the loss was then calculated using actual data (secondary analysis). Secondary outcomes were ultrasound (US) time, cumulative dissipated energy (CDE), and percentage total equivalent power in position 3. Postoperative follow-up was at 3 months. The mean preoperative CDVA was 0.41 logMAR in the torsional group and 0.38 logMAR in the longitudinal group, improving to 0.07 logMAR postoperatively in both groups. The mean ECD loss was 7.2% ± 4.6% in the torsional group (72 patients) and 7.1% ± 4.4% in the longitudinal group (76 patients), with no statistically significant differences in the primary analysis (P = .342) or secondary analysis (P = .906). The mean US time, CDE, and percentage total equivalent power in position 3 were statistically significantly lower in the torsional group (98 patients) than in the longitudinal group (94 patients) (P<.001). The torsional mode was as safe as the longitudinal mode in phacoemulsification for age-related cataract. Copyright © 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Electronic transport in torsional strained Weyl semimetals

NASA Astrophysics Data System (ADS)

Soto-Garrido, Rodrigo; Muñoz, Enrique

2018-05-01

In a recent paper (Muñoz and Soto-Garrido 2017 J. Phys.: Condens. Matter 29 445302) we have studied the effects of mechanical strain and magnetic field on the electronic transport properties in graphene. In this article we extended our work to Weyl semimetals (WSM). We show that although the WSM are 3D materials, most of the analysis done for graphene (2D material) can be carried out. In particular, we studied the electronic transport through a cylindrical region submitted to torsional strain and external magnetic field. We provide exact analytical expressions for the scattering cross section and the transmitted electronic current. In addition, we show the node-polarization effect on the current and propose a recipe to measure the torsion angle from transmission experiments.

FIR Synchrotron Spectroscopy of High Torsional Levels of CD_3OH: the Tau of Methanol

NASA Astrophysics Data System (ADS)

Lees, Ronald M.; Xu, Li-Hong; Billinghurst, Brant E.

2015-06-01

Sub-bands involving high torsional levels of the CD_3OH isotopologue of methanol have been analyzed in Fourier transform spectra recorded at the Far-Infrared beamline of the Canadian Light Source synchrotron in Saskatoon. Energy term values for A and E torsional species of the third excited torsional state, v_t = 3, are now almost complete up to rotational levels K = 15, and thirteen substates have so far been identified for v_t = 4. The spectra show interesting close groupings of high-v_t sub-bands related by Dennison's torsional symmetry label τ, rather than A and E, that can be understood in terms of a simple and universal free-rotor "spectral predictor" chart. Transitions between states on the same free rotor curve have torsional overlap matrix elements close to unity, so give rise to strong sub-bands providing radiative routes for rapid population transfer through the high torsional manifold. Where the energy curves for the v_t = 3 and 4 ground-state torsional levels pass through the excited vibrational states, strong resonances can occur and a number of anharmonic and Coriolis interactions have been detected through perturbations to the spectra and appearance of forbidden transitions due to strong mixing and intensity borrowing.

Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review.

PubMed

Budinski, Vedran; Donlagic, Denis

2017-02-23

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.Invited Paper.

The incidence of isolated penile torsion in North India: A study of 5,018 male neonates.

PubMed

Bhat, Amilal; Bhat, Mahakshit; Kumar, Vinay; Goyal, Suresh; Bhat, Akshita; Patni, Madhu

2017-10-01

Congenital penile torsion is a three-dimensional deformity with helical rotation of the distal corporal bodies with the penile crurae remaining fixed to the pubic rami. The first case of congenital penile torsion (hypospadias) was described in 1857. Isolated penile torsion is an under-reported anomaly. The reported incidence of isolated penile torsion is 1.7-27% and severe torsion is 0.7%. There are no studies available from Indian subcontinent on the incidence of isolated penile torque. The objective of this study was to determine the overall incidence of isolated penile torque in a north Indian population. A prospective study of deliveries of male children was conducted at our institute between April 2014 and June 2015. Penile torsion was measured using a small protractor either by the deviation of the median raphae or the direction of the meatus. Data were collected on the incidence of congenital isolated penile torsion, including the degree and direction (left or right) of torsion. Torsion was classified as mild (<450), moderate (450-900), and severe (>900). Statistical analysis was done using the chi-square test with variables of age and parity of the mother and weight of the child. There were 99 cases of isolated penile torque among 5018 male neonates assessed for penile torque. The incidence of isolated penile torque was 19.7 per 1000 births. The degree of torsion varied from 30 to 110° (average 51.46°). Seventy-nine percent (79%) of them had left side and 21% had right side torque (4:1). The degree of torsion was mild in 30%, with 20% having left side torque and 10% having right side torque (2:1). A moderate degree of torsion was seen in 69%: 84% of them had left torque and only 16% had right sided torque (5:1). Only one patient had severe left torque. The incidence of isolated congenital penile torsion was highest in the maternal age group of >30 years followed by the 26-30-year age group, and was lowest in 21-25 year age group. In multiparous women, the

Photochemical cycle of bacteriorhodopsin studied by resonance Raman spectroscopy.

PubMed

Stockburger, M; Klusmann, W; Gattermann, H; Massig, G; Peters, R

1979-10-30

Individual species of the photochemical cycle of bacteriorhodopsin, a retinal-protein complex of Halobacteria, were studied in aqueous suspensions of the "purple membrane" at room temperature by resonance Raman (RR) spectroscopy with flow systems. Two pronounced deuterium shifts were found in the RR spectra of the all-trans complex BR-570 in H2O-D2O suspensions. The first is ascribed to C=NH+ (C=ND+) stretching vibrations of the protonated Schiff base which links retinal to opsin. The second is assigned tentatively to an "X-H" ("X-D") bending mode, where "X" is an atom which carries an exchangeable proton. A RR spectrum of the 13-cis-retinal complex "BR-548" could be deduced from spectra of the dark-adapted purple membrane. The RR spectrum of the M-412 intermediate was monitored in a double-beam pump-probe experiment. The main vibrational features of the intermediate M' in the reaction M-412 in equilibrium hv M' leads to delta BR-570 could be deduced from a photostationary mixture of M-412 and M'. Difference procedures were applied to obtain RR spectra of the L-550 intermediate and of two new long-lived species, R1'-590 and R2-550. From kinetic data it is suggested that T1'-590 links the proton-translocating cycle to the "13-cis" cycle of BR-548. The protonation and isomeric states of the different species are discussed in light of the new spectroscopic and kinetic data. It is found that conformational changes during the photochemical cycle play an important role.

Impact of DNA twist accumulation on progressive helical wrapping of torsionally constrained DNA.

PubMed

Li, Wei; Wang, Peng-Ye; Yan, Jie; Li, Ming

2012-11-21

DNA wrapping is an important mechanism for chromosomal DNA packaging in cells and viruses. Previous studies of DNA wrapping have been performed mostly on torsionally unconstrained DNA, while in vivo DNA is often under torsional constraint. In this study, we extend a previously proposed theoretical model for wrapping of torsionally unconstrained DNA to a new model including the contribution of DNA twist energy, which influences DNA wrapping drastically. In particular, due to accumulation of twist energy during DNA wrapping, it predicts a finite amount of DNA that can be wrapped on a helical spool. The predictions of the new model are tested by single-molecule study of DNA wrapping under torsional constraint using magnetic tweezers. The theoretical predictions and the experimental results are consistent with each other and their implications are discussed.

Inhomogeneity in the excited-state torsional disorder of a conjugated macrocycle.

PubMed

Yang, Jaesung; Ham, Sujin; Kim, Tae-Woo; Park, Kyu Hyung; Nakao, Kazumi; Shimizu, Hideyuki; Iyoda, Masahiko; Kim, Dongho

2015-03-12

The photophysics of conjugated polymers has generally been explained based on the interactions between the component conjugated chromophores in a tangled chain. However, conjugated chromophores are entities with static and dynamic structural disorder, which directly affects the conjugated polymer photophysics. Here we demonstrate the impact of chain structure torsional disorder on the spectral characteristics for a macrocyclic oligothiophene 1, which is obscured in conventional linear conjugated chromophores by diverse structural disorders such as those in chromophore size and shape. We used simultaneous multiple fluorescence parameter measurement for a single molecule and quantum-mechanical calculations to show that within the fixed conjugation length across the entire ring an inhomogeneity from torsional disorder in the structure of 1 plays a crucial role in causing its energetic disorder, which affords the spectral broadening of ∼220 meV. The torsional disorder in 1 fluctuated on the time scale of hundreds of milliseconds, typically accompanied by spectral drifts on the order of ∼10 meV. The fluctuations could generate torsional defects and change the electronic structure of 1 associated with the ring symmetry. These findings disclose the fundamental nature of conjugated chromophore that is the most elementary spectroscopic unit in conjugated polymers and suggest the importance of engineering structural disorder to optimize polymer-based device photophysics. Additionally, we combined defocused wide-field fluorescence microscopy and linear dichroism obtained from the simultaneous measurements to show that 1 emits polarized light with a changing polarization direction based on the torsional disorder fluctuations.

A measurement of G with a cryogenic torsion pendulum.

PubMed

Newman, Riley; Bantel, Michael; Berg, Eric; Cross, William

2014-10-13

A measurement of Newton's gravitational constant G has been made with a cryogenic torsion pendulum operating below 4 K in a dynamic mode in which G is determined from the change in torsional period when a field source mass is moved between two orientations. The source mass was a pair of copper rings that produced an extremely uniform gravitational field gradient, whereas the pendulum was a thin fused silica plate, a combination that minimized the measurement's sensitivity to error in pendulum placement. The measurement was made using an as-drawn CuBe torsion fibre, a heat-treated CuBe fibre, and an as-drawn Al5056 fibre. The pendulum operated with a set of different large torsional amplitudes. The three fibres yielded high Q-values: 82 000, 120 000 and 164 000, minimizing experimental bias from fibre anelasticity. G-values found with the three fibres are, respectively: {6.67435(10),6.67408(15),6.67455(13)}×10(-11) m(3) kg(-1) s(-2), with corresponding uncertainties 14, 22 and 20 ppm. Relative to the CODATA2010 G-value, these are higher by 77, 37 and 107 ppm, respectively. The unweighted average of the three G-values, with the unweighted average of their uncertainties, is 6.67433(13)×10(-11) m(3) kg(-1) s(-2) (19 ppm). © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Nonsingular, big-bounce cosmology from spinor-torsion coupling

NASA Astrophysics Data System (ADS)

Popławski, Nikodem

2012-05-01

The Einstein-Cartan-Sciama-Kibble theory of gravity removes the constraint of general relativity that the affine connection be symmetric by regarding its antisymmetric part, the torsion tensor, as a dynamical variable. The minimal coupling between the torsion tensor and Dirac spinors generates a spin-spin interaction which is significant in fermionic matter at extremely high densities. We show that such an interaction averts the unphysical big-bang singularity, replacing it with a cusp-like bounce at a finite minimum scale factor, before which the Universe was contracting. This scenario also explains why the present Universe at largest scales appears spatially flat, homogeneous and isotropic.

Torsional Rigidity of Positively and Negatively Supercoiled DNA

NASA Astrophysics Data System (ADS)

Selvin, Paul R.; Cook, David N.; Pon, Ning G.; Bauer, William R.; Klein, Melvin P.; Hearst, John E.

1992-01-01

Time-correlated single-photon counting of intercalated ethidium bromide was used to measure the torsion constants of positively supercoiled, relaxed, and negatively supercoiled pBR322 DNA, which range in superhelix density from +0.042 to -0.123. DNA behaves as coupled, nonlinear torsional pendulums under superhelical stress, and the anharmonic term in the Hamiltonian is approximately 15 percent for root-mean-square fluctuations in twist at room temperature. At the level of secondary structure, positively supercoiled DNA is significantly more flexible than negatively supercoiled DNA. These results exclude certain models that account for differential binding affinity of proteins to positively and negatively supercoiled DNA.

Vertical bending strength and torsional rigidity analysis of formula student car chassis

NASA Astrophysics Data System (ADS)

Hazimi, Hashfi; Ubaidillah, Setiyawan, Adi Eka Putra; Ramdhani, Hanief Cahya; Saputra, Murnanda Zaesy; Imaduddin, Fitrian

2018-02-01

Formula Society of Automotive Engineers (FSAE) is a competition for students to construct formula student car. One of an essential part of a formula student car is its chassis. Chassis is an internal vehicle frame which holds all another part of the vehicle and secures the driver. The team have to design their chassis and tests their design to achieve the best chassis that fulfill the regulation. This paper contains chassis design from Bengawan FSAE Team and some FEA tests to find out the Tensile Strength, Torsional Rigidity, and Von Misses Stress of Formula SAE car. Torsional rigidity was found by applying the static torsional test. The results from torsional rigidity test are a maximum deformation of 9.9512 mm with 1.7064 safety factor, and 35.935 MPa maximum Von Misses Stress. Moreover, then the result of the vertical bending strength test is 8.1214 mm max deformation with safety factor 4.2717, and 29.226 MPa maximum Von Misses Stress.

Characterization and photochemistry of 13-desmethyl bacteriorhodopsin.

PubMed

Gillespie, Nathan B; Ren, Lei; Ramos, Lavoisier; Daniell, Heather; Dews, Deborah; Utzat, Karissa A; Stuart, Jeffrey A; Buck, Charles H; Birge, Robert R

2005-08-25

The photochemistry of the 13-desmethyl (DM) analogue of bacteriorhodopsin (BR) is examined by using spectroscopy, molecular orbital theory, and chromophore extraction followed by conformational analysis. The removal of the 13-methyl group permits the direct photochemical formation of a thermally stable, photochemically reversible state, P1(DM) (lambda(max) = 525 nm), which can be generated efficiently by exciting the resting state, bR(DM) with yellow or red light (lambda > 590 nm). Chromophore extraction analysis reveals that the retinal configuration in P1(DM) is 9-cis, identical to that of the retinal configuration in the native BR P1 state. Fourier transform infrared and Raman experiments on P1(DM) indicate an anti configuration around the C15=N bond, as would be expected of an O-state photoproduct. However, low-temperature spectroscopy and ambient, time-resolved studies indicate that the P1(DM) state forms primarily via thermal relaxation from the L(D)(DM) state. Theoretical studies on the BR binding site show that 13-dm retinal is capable of isomerizing into a 9-cis configuration with minimal steric hindrance from surrounding residues, in contrast to the native chromophore in which surrounding residues significantly obstruct the corresponding motion. Analysis of the photokinetic experiments indicates that the Arrhenius activation energy of the bR(DM) --> P1(DM) transition in 13-dm-BR is less than 0.6 kcal/mol (vs 22 +/-5 kcal/mol measured for the bR --> P (P1 and P2) reaction in 85:15 glycerol:water suspensions of wild type). Consequently, the P1(DM) state in 13-dm-BR can form directly from all-trans, 15-anti intermediates (bR(DM) and O(DM)) or all-trans, 15-syn (K(D)(DM)/L(D)(DM)) intermediates. This study demonstrates that the 13-methyl group, and its interactions with nearby binding site residues, is primarily responsible for channeling one-photon photochemical and thermal reactions and is limited to the all-trans and 13-cis species interconversions in the

Torsional stability of interference screws derived from bovine bone - a biomechanical study

PubMed Central

2010-01-01

Background In the present biomechanical study, the torsional stability of different interference screws, made of bovine bone, was tested. Interference screws derived from bovine bone are a possible biological alternative to conventional metallic or bioabsorbable polymer interference screws. Methods In the first part of the study we compared the torsional stability of self-made 8 mm Interference screws (BC) and a commercial 8 mm interference screw (Tutofix®). Furthermore, we compared the torsional strength of BC screws with different diameters. For screwing in, a hexagon head and an octagon head were tested. Maximum breaking torques in polymethyl methacrylate resin were recorded by means of an electronic torque screw driver. In the second part of the study the tibial part of a bone-patellar tendon-bone graft was fixed in porcine test specimens using an 8 mm BC screw and the maximum insertion torques were recorded. Each interference screw type was tested 5 times. Results There was no statistically significant difference between the different 8 mm interference screws (p = 0.121). Pairwise comparisons did not reveal statistically significant differences, either. It was demonstrated for the BC screws, that a larger screw diameter significantly leads to higher torsional stability (p = 9.779 × 10-5). Pairwise comparisons showed a significantly lower torsional stability for the 7 mm BC screw than for the 8 mm BC screw (p = 0.0079) and the 9 mm BC screw (p = 0.0079). Statistically significant differences between the 8 mm and the 9 mm BC screw could not be found (p = 0.15). During screwing into the tibial graft channel of the porcine specimens, insertion torques between 0.5 Nm and 3.2 Nm were recorded. In one case the hexagon head of a BC screw broke off during the last turn. Conclusions The BC screws show comparable torsional stability to Tutofix® interference screws. As expected the torsional strength of the screws increases significantly with the diameter. The safety

Torsional Restraint Problem of Steel Cold-Formed Beams Restrained By Planar Members

NASA Astrophysics Data System (ADS)

Balázs, Ivan; Melcher, Jindřich; Pešek, Ondřej

2017-10-01

The effect of continuous or discrete lateral and torsional restraints of metal thinwalled members along their spans can positively influence their buckling resistance and thus contribute to more economical structural design. The prevention of displacement and rotation of the cross-section results in stabilization of the member. The restraints can practically be provided e.g. by planar members of cladding supported by metal members (purlins, girts). The rate of stabilization of a member can be quantified using values of shear and rotational stiffness provided by the adjacent planar members. While the lateral restraint effected by certain shear stiffness can be often considered as sufficient, the complete torsional restraint can be safely considered in some practical cases only. Otherwise the values of the appropriate rotational stiffness provided by adjacent planar members may not be satisfactory to ensure full torsional restraint and only incomplete restraint is available. Its verification should be performed using theoretical and experimental analyses. The paper focuses on problem of steel thin-walled coldformed beams stabilized by planar members and investigates the effect of the magnitude of the rotational stiffness provided by the planar members on the resistance of the steel members. Cold-formed steel beams supporting planar members of cladding are considered. Full lateral restraint and incomplete torsional restraint are assumed. Numerical analyses performed using a finite element method software indicate considerable influence of the torsional restraint on the buckling resistance of a steel thin-walled member. Utilization of the torsional restraint in the frame of sizing of a stabilized beam can result in more efficient structural design. The paper quantifies this effect for some selected cases and summarizes results of numerical analysis.

Application of a boundary element method to the study of dynamical torsion of beams

NASA Technical Reports Server (NTRS)

Czekajski, C.; Laroze, S.; Gay, D.

1982-01-01

During dynamic torsion of beam elements, consideration of nonuniform warping effects involves a more general technical formulation then that of Saint-Venant. Nonclassical torsion constants appear in addition to the well known torsional rigidity. The adaptation of the boundary integral element method to the calculation of these constants for general section shapes is described. The suitability of the formulation is investigated with some examples of thick as well as thin walled cross sections.

Torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis).

PubMed

Kerrigan, Shannon M; Kapatkin, Amy S; Garcia, Tanya C; Robinson, Duane A; Guzman, David Sanchez-Migallon; Stover, Susan M

2018-04-01

OBJECTIVE To describe the torsional and axial compressive properties of tibiotarsal bones of red-tailed hawks (Buteo jamaicensis). SAMPLE 16 cadaveric tibiotarsal bones from 8 red-tailed hawks. PROCEDURES 1 tibiotarsal bone from each bird was randomly assigned to be tested in torsion, and the contralateral bone was tested in axial compression. Intact bones were monotonically loaded in either torsion (n = 8) or axial compression (8) to failure. Mechanical variables were derived from load-deformation curves. Fracture configurations were described. Effects of sex, limb side, and bone dimensions on mechanical properties were assessed with a mixed-model ANOVA. Correlations between equivalent torsional and compressive properties were determined. RESULTS Limb side and bone dimensions were not associated with any mechanical property. During compression tests, mean ultimate cumulative energy and postyield energy for female bones were significantly greater than those for male bones. All 8 bones developed a spiral diaphyseal fracture and a metaphyseal fissure or fracture during torsional tests. During compression tests, all bones developed a crushed metaphysis and a fissure or comminuted fracture of the diaphysis. Positive correlations were apparent between most yield and ultimate torsional and compressive properties. CONCLUSIONS AND CLINICAL RELEVANCE The torsional and axial compressive properties of tibiotarsal bones described in this study can be used as a reference for investigations into fixation methods for tibiotarsal fractures in red-tailed hawks. Although the comminuted and spiral diaphyseal fractures induced in this study were consistent with those observed in clinical practice, the metaphyseal disruption observed was not and warrants further research.

Development of a Meso-Scale Fiberoptic Rotation Sensor for a Torsion Actuator.

PubMed

Sheng, Jun; Desai, Jaydev P

2018-01-01

This paper presents the development of a meso-scale fiberoptic rotation sensor for a shape memory alloy (SMA) torsion actuator for neurosurgical applications. Within the sensor, a rotary head with a reflecting surface is capable of modulating the light intensity collected by optical fibers when the rotary head is coupled to the torsion actuator. The mechanism of light intensity modulation is modeled, followed by experimental model verification. Meanwhile, working performances for different rotary head designs, optical fibers, and fabrication materials are compared. After the calibration of the fiberoptic rotation sensor, the sensor is capable of precisely measuring rotary motion and controlling the SMA torsion actuator with feedback control.

Torsion sensing setup based on a Mach-Zehnder interferometer with photonics crystal fiber

NASA Astrophysics Data System (ADS)

Pacheco-Chacon, Eliana I.; Gallegos-Arellano, E.; Sierra-Hernandez, Juan M.; Rojas-Laguna, Roberto; Estudillo-Ayala, Julian M.; Hernandez, Emmanuel; Jauregui-Vazquez, D.; Hernandez-Garcia, J. C.

2017-02-01

A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.

Low temperature IR spectroscopic study of torsional vibrations of taurine

NASA Astrophysics Data System (ADS)

Bajaj, Naini; Bhatt, Himal; Vishwakarma, S. R.; Thomas, Susy; Murli, C.; Deo, M. N.

2018-04-01

The hydrogen bonding network in amino acids can give information about the structural stability under varying thermodynamic conditions such as temperature and pressure. We have carried out low temperature IR spectroscopic studies on Taurine, an amino acid with various bio-chemical applications in physiology and synthesis, in order to observe the behaviour of torsional modes, i.e. τ(CSH) and τ(NH3), which are very sensitive to the hydrogen bonding interactions. It was observed that the CSH torsional mode showed splitting at low temperature of nearly 250 K and the bandwidth shows linear temperature dependence, which can be attributed to anharmonicity. Another torsional mode, τ(NH3) showed no splitting, but the bandwidth has non-linear temperature dependence. This can be due to orientational changes at low temperature. These observations are strong evidences for a hydrogen bond reorientation induced phase transition at 250 K.

Transient Fourier holography with bacteriorhodopsin films for breast cancer diagnostics

NASA Astrophysics Data System (ADS)

Rao, Devulapalli; Kothapalli, Sri-Rajasekar; Wu, Pengfei; Yelleswarapu, Chandra

X-ray mammography is the current gold standard for breast cancer screening. Microcalcifications and other features which are helpful to the radiologist for early diagnostics are often buried in the noise generated by the surrounding dense tissue. So image processing techniques are required to enhance these important features to improve the sensitivity of detection. An innovative technique is demonstrated for recording a hologram of the mammogram. It is recorded on a thin polymer film of Bacteriorhodopsin (bR) as photo induced isomerization grating containing the interference pattern between the object beam containing the Fourier spatial frequency components of the mammogram and a reference beam. The hologram contains all the enhanced features of the mammogram. A significant innovation of the technique is that the enhanced components in the processed image can be viewed by the radiologist in time scale. A technician can record the movie and when the radiologist looks at the movie at his convenience, freezing the frame as and when desired, he would see the microcalcifications as the brightest and last long in time. He would also observe lesions with intensity decreasing as their size increases. The same bR film can be used repeatedly for recording holograms with different mammograms. The technique is versatile and a different frequency band can be chosen to be optimized by changing the reference beam intensity. The experimental arrangement can be used for mammograms in screen film or digital format.

University of Florida Torsion Pendulum for Testing Key LISA Technology

NASA Astrophysics Data System (ADS)

Apple, Stephen; Chilton, Andrew; Olatunde, Taiwo Janet; Hillsberry, Daniel; Parry, Samantha; Ciani, Giacomo; Wass, Peter; Mueller, Guido; Conklin, John

2018-01-01

This presentation will describe the design and performance of a new torsion pendulum at the University of Florida used for testing inertial sensors and associated technologies for use in space – based gravitational wave observatories and geodesy missions. In particular this new torsion pendulum facility is testing inertial sensors and associated technology for the upcoming LISA (laser interferometer space antenna) space-based gravitational wave observatory mission. The torsion pendulum apparatus is comprised of a suspended cross bar assembly that has LISA test mass mockups at each of its ends. Two of the test mass mockups are enclosed by capacitive sensors which provide actuation and position sensing. The entire assembly is housed in a vacuum chamber. The pendulum cross-bar converts rotational motion of the test masses about the suspension fiber axis into translational motion. The 22 cm cross bar arm length along with the extremely small torsional spring constant of the suspension fiber results in a near free fall condition in the translational degree-of-freedom orthogonal to both the member and the suspension fiber. The test masses are electrically isolated from the pendulum assembly and their charge is controlled via photoemission using fiber coupled UV LEDS. Position of the test masses is measured using both capacitive and interferometric readout. The broadband sensitivity of the capacitive readout and laser interferometer readout is 30 nm/√Hz and 0.5 nm/√Hz respectively. The performance of the pendulum measured in equivalent acceleration noise acting on a LISA test mass is approximately 3 × 10-13 ms-2/√Hz at 2 mHz. This presentation will also discuss the design and fabrication of a flight-like gravitational reference sensor that will soon be integrated into the torsion pendulum facility. This flight-like GRS will allow for noise performance measurements in a more LISA-like configuration.

Twisted ultrathin silicon nanowires: A possible torsion electromechanical nanodevice

NASA Astrophysics Data System (ADS)

Garcia, J. C.; Justo, J. F.

2014-11-01

Nanowires have been considered for a number of applications in nanometrology. In such a context, we have explored the possibility of using ultrathin twisted nanowires as torsion nanobalances to probe forces and torques at molecular level with high precision, a nanoscale system analogous to the Coulomb's torsion balance electrometer. In order to achieve this goal, we performed a first-principles investigation on the structural and electronic properties of twisted silicon nanowires, in their pristine and hydrogenated forms. The results indicated that wires with pentagonal and hexagonal cross-sections are the thinnest stable silicon nanostructures. Additionally, all wires followed a Hooke's law behavior for small twisting deformations. Hydrogenation leads to spontaneous twisting, but with angular spring constants considerably smaller than the ones for the respective pristine forms. We observed considerable changes on the nanowire electronic properties upon twisting, which allows to envision the possibility of correlating the torsional angular deformation with the nanowire electronic transport. This could ultimately allow a direct access to measurements on interatomic forces at molecular level.

Torsional, Vibrational and Vibration-Torsional Levels in the S_{1} and Ground Cationic D_{0}^{+} States of Para-Fluorotoluene

NASA Astrophysics Data System (ADS)

Gardner, Adrian M.; Tuttle, William Duncan; Whalley, Laura E.; Claydon, Andrew; Carter, Joseph H.; Wright, Timothy G.

2017-06-01

The S_{1} electronic state and ground state of the cation of para-fluorotoluene (pFT) have been investigated using resonance-enhanced multiphoton ionization (REMPI) spectroscopy and zero-kinetic-energy (ZEKE) spectroscopy. Here we focus on the low wavenumber region where a number of "pure" torsional, fundamental vibrational and vibration-torsional levels are expected; assignments of observed transitions are discussed, which are compared to results of published work on toluene (methylbenzene) from the Lawrance group. The similarity in the activity observed in the excitation spectrum of the two molecules is striking. A. M. Gardner, W. D. Tuttle, L. Whalley, A. Claydon, J. H. Carter and T. G. Wright, J. Chem. Phys., 145, 124307 (2016). J. R. Gascooke, E. A. Virgo, and W. D. Lawrance J. Chem. Phys., 143, 044313 (2015).

Torsion of a nongravid uterus with a large ovarian cyst: usefulness of contrast MR image.

PubMed

Matsumoto, Hiroki; Ohta, Tsuyoshi; Nakahara, Kenji; Kojimahara, Takanobu; Kurachi, Hirohisa

2007-01-01

Torsion of a nongravid uterus is extremely rare. Most cases of uterine torsion occur during pregnancy. Here we report a case of nongravid uterus torsion with a large adnexal mass. A 73-year-old woman presented at the emergency room with acute abdominal pain. A preoperative diagnosis of torsion of an ovarian cyst was made and laparotomy was performed. The left ovary was twisted 360 degrees in a clockwise rotation, and the uterine corpus had also undergone a 360 degrees rotation. Total abdominal hysterectomy and bilateral salpingo-oophorectomy were carried out. Although a preoperative diagnosis of uterine torsion was not possible, it is noteworthy that in the contrast-enhanced magnetic resonance images the uterine cervix was intensely enhanced, while the uterine corpus was not. This is the first report to show the magnetic resonance imaging findings of a twisted uterus. Copyright (c) 2007 S. Karger AG, Basel.

Weakly dynamic dark energy via metric-scalar couplings with torsion

NASA Astrophysics Data System (ADS)

Sur, Sourav; Singh Bhatia, Arshdeep

2017-07-01

We study the dynamical aspects of dark energy in the context of a non-minimally coupled scalar field with curvature and torsion. Whereas the scalar field acts as the source of the trace mode of torsion, a suitable constraint on the torsion pseudo-trace provides a mass term for the scalar field in the effective action. In the equivalent scalar-tensor framework, we find explicit cosmological solutions representing dark energy in both Einstein and Jordan frames. We demand the dynamical evolution of the dark energy to be weak enough, so that the present-day values of the cosmological parameters could be estimated keeping them within the confidence limits set for the standard LCDM model from recent observations. For such estimates, we examine the variations of the effective matter density and the dark energy equation of state parameters over different redshift ranges. In spite of being weakly dynamic, the dark energy component differs significantly from the cosmological constant, both in characteristics and features, for e.g. it interacts with the cosmological (dust) fluid in the Einstein frame, and crosses the phantom barrier in the Jordan frame. We also obtain the upper bounds on the torsion mode parameters and the lower bound on the effective Brans-Dicke parameter. The latter turns out to be fairly large, and in agreement with the local gravity constraints, which therefore come in support of our analysis.

Toward laboratory torsional spine magnetic reconnection

NASA Astrophysics Data System (ADS)

Chesny, David L.; Orange, N. Brice; Oluseyi, Hakeem M.; Valletta, David R.

2017-12-01

Magnetic reconnection is a fundamental energy conversion mechanism in nature. Major attempts to study this process in controlled settings on Earth have largely been limited to reproducing approximately two-dimensional (2-D) reconnection dynamics. Other experiments describing reconnection near three-dimensional null points are non-driven, and do not induce any of the 3-D modes of spine fan, torsional fan or torsional spine reconnection. In order to study these important 3-D modes observed in astrophysical plasmas (e.g. the solar atmosphere), laboratory set-ups must be designed to induce driven reconnection about an isolated magnetic null point. As such, we consider the limited range of fundamental resistive magnetohydrodynamic (MHD) and kinetic parameters of dynamic laboratory plasmas that are necessary to induce the torsional spine reconnection (TSR) mode characterized by a driven rotational slippage of field lines - a feature that has yet to be achieved in operational laboratory magnetic reconnection experiments. Leveraging existing reconnection models, we show that within a 3$ apparatus, TSR can be achieved in dense plasma regimes ( 24~\\text{m}-3$ ) in magnetic fields of -1~\\text{T}$ . We find that MHD and kinetic parameters predict reconnection in thin current sheets on time scales of . While these plasma regimes may not explicitly replicate the plasma parameters of observed astrophysical phenomena, studying the dynamics of the TSR mode within achievable set-ups signifies an important step in understanding the fundamentals of driven 3-D magnetic reconnection and the self-organization of current sheets. Explicit control of this reconnection mode may have implications for understanding particle acceleration in astrophysical environments, and may even have practical applications to fields such as spacecraft propulsion.

Integrability conditions for Killing-Yano tensors and maximally symmetric spaces in the presence of torsion

NASA Astrophysics Data System (ADS)

Batista, Carlos

2015-04-01

The integrability conditions for the existence of Killing-Yano tensors or, equivalently, covariantly closed conformal Killing-Yano tensors, in the presence of torsion are worked out. As an application, all metrics and torsions compatible with the existence of a Killing-Yano tensor of order n -1 are obtained. Finally, the issue of defining a maximally symmetric space with respect to connections with torsion is addressed.

Torsional vibration of a pipe pile in transversely isotropic saturated soil

NASA Astrophysics Data System (ADS)

Zheng, Changjie; Hua, Jianmin; Ding, Xuanming

2016-09-01

This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot's poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.

Clinical and imaging features in lung torsion and description of a novel imaging sign.

PubMed

Hammer, Mark M; Madan, Rachna

2018-04-01

We set out to identify the clinical and imaging features seen in lung torsion, a rare but emergent diagnosis leading to vascular compromise of a lobe or entire lung. We retrospectively identified 10 patients with torsion who underwent chest CT. We evaluated each case for the presence of bronchial obstruction and abnormal fissure orientation. In seven patients who underwent contrast-enhanced CTs, we assessed for the presence of the antler sign, a novel sign seen on axial images demonstrating abnormal curvature of the artery and branches originating on one side. Five patients had right middle lobe (RML) torsion after right upper lobectomy, and the remaining occurred following thoracentesis, aortic surgery, or spontaneously. Chest CTs demonstrated bronchial obstruction in eight cases and presence of abnormal fissure orientation in four patients. The antler sign was present in three patients with whole-lung torsion and one patient with lobar torsion; vascular swirling was seen on 3-D images in all seven patients with contrast-enhanced CTs. Lung parenchymal imaging findings in lung torsion may be non-specific. Identification of the antler sign on contrast-enhanced chest CT, in combination with other signs such as bronchial obstruction and abnormal fissure orientation, indicates rotation of the bronchovascular pedicle. The presence of this sign should prompt further evaluation with 3-dimensional reconstructions.

[Prelabour uterine torsion complicated by partial abruption and fetal death].

PubMed

Agar, N; Canis, M; Accoceberry, M; Bourdel, N; Lafaye, A-L; Gallot, D

2014-06-01

Uterine torsion is a rare obstetrical complication whose diagnosis remains challenging. We report a case of 180 degrees dextrogyre torsion at 36(+5) weeks of gestation complicated by partial abruption and in utero fetal death. Emergency cesarean section was performed through an unintentional posterior hysterotomy. Literature reports a few similar cases. Vertical hysterotomy should be advised in this context avoiding incision on lateral sides associated with increased risk of vascular or ureteral injury. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Development of a torsion balance for adhesion measurements

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa; Maeda, Chikayoshi; Masuo, Ryuichi

1988-01-01

A new torsion balance for study of adhesion in ceramics is discussed. A torsion wire and a linear variable differential transformer are used to monitor load and to measure pull-off force (adhesion force). The investigation suggests that this torsion balance is valuable in studying the interfacial properties of ceramics in controlled environments such as in ultrahigh vacuum. The pull-off forces measured in dry, moist, and saturated nitrogen atmosphere demonstrate that the adhesion of silicon nitride contacts remains low at humidities below 80 percent but rises rapidly above that. The adhesion at saturation is 10 times or more greater than that below 80 percent relative humidity. The adhesion in a saturated atmosphere arises primarily from the surface tension effects of a thin film of water adsorbed on the surface. The surface tension of the water film was 58 x 10 to the minus 5 to 65 x 10 to the minus 5 power. The accepted value for water is 72.7 x 10 to the minus 5 power N/cm. Adhesion characteristics of silicon nitride in contact with metals, like the friction characteristics of silicon carbide to metal contacts, can be related to the relative chemical activity of metals in ultrahigh vacuum. The more active the metal, the higher the adhesion.

Optical diagnosis of testicular torsion: feasibility and methodology

NASA Astrophysics Data System (ADS)

Shadgan, Babak; Macnab, Andrew; Stothers, Lynn; Kajbafzadeh, A. M.

2014-03-01

Background: Torsion of the testis compromises blood flow through the spermatic cord; testicular ischemia results which if not diagnosed promptly and corrected surgically irrevocably damages the testis. Current diagnostic modalities aimed at rationalizing surgical exploration by demonstrating interruption of spermatic cord blood flow or testicular ischemia have limited applicability. Near infrared spectroscopy (NIRS) offers a non-invasive optical method for detection of ischemia; continuous wave and frequency domain devices have been used experimentally; no device customized for clinical use has been designed. Methods: A miniature spatially resolved NIRS device with light emitting diode light source was applied over the right and left spermatic cord and the difference in oxygen saturation between the two sides measured. Results: In a 14-month old boy with a history of unilateral testicular pain color Doppler ultrasonography was equivocal but the NIRS-derived tissue oxygen saturation index (TSI) was significantly reduced on the left side. Confirmation of torsion of the left testicle was made surgically. Conclusions: Spatially resolved NIRS monitoring of spermatic cord oxygen saturation is feasible in children, adding to prior studies of testicular oxygen saturation in adults. Customized device design and further clinical trials would enhance the applicability of NIRS as a diagnostic entity for torsion.

Highly Accurate Beam Torsion Solutions Using the p-Version Finite Element Method

NASA Technical Reports Server (NTRS)

Smith, James P.

1996-01-01

A new treatment of the classical beam torsion boundary value problem is applied. Using the p-version finite element method with shape functions based on Legendre polynomials, torsion solutions for generic cross-sections comprised of isotropic materials are developed. Element shape functions for quadrilateral and triangular elements are discussed, and numerical examples are provided.

Radiographic findings and clinical factors in dogs with surgically confirmed or presumed colonic torsion.

PubMed

Gremillion, Christine L; Savage, Mason; Cohen, Eli B

2018-05-01

Colonic torsion is a life-threatening condition in dogs and radiographic findings for this condition have not been well described. The purpose of this retrospective case series was to describe radiographic findings and clinical signs in a group of dogs with colonic torsion. Inclusion criteria were dogs presenting during the period of 2006 and 2016, and that had abdominal radiography and a surgically confirmed or presumed diagnosis of colonic torsion. For each dog, clinical data were recorded from medical records and imaging findings were recorded from retrieved plain radiographs and positive contrast radiographs in which barium enema was performed. Fourteen dogs met inclusion criteria. Of these, nine dogs had colonic torsion confirmed at surgery, with five dogs having surgical confirmation of colonic congestion or mesenteric torsion. Radiographic findings included segmental distention of the colon (14/14), focal narrowing of the colon (11/14), displacement of cecum (11/14), displacement of descending colon (14/14), and mild to no small intestinal distention (14/14). In cases where barium enema was performed, focal narrowing of the colon and longitudinal striations that course in a helical pattern were identified, termed the "torsion sign." Vomiting was the most common clinical sign observed (12/14), followed by abdominal pain in a small majority of cases (8/14). Severe abdominal pain and hypovolemic shock were uncommon in the patients reported (3/14). Colonic torsion should be considered as a differential diagnosis for dogs with radiographic segmental colonic distention with displacement of the descending colon and cecum. Barium enema is recommended for more definitive diagnosis. © 2018 American College of Veterinary Radiology.

Influence of DNA sequence on the structure of minicircles under torsional stress

PubMed Central

Wang, Qian; Irobalieva, Rossitza N.; Chiu, Wah; Schmid, Michael F.; Fogg, Jonathan M.; Zechiedrich, Lynn

2017-01-01

Abstract The sequence dependence of the conformational distribution of DNA under various levels of torsional stress is an important unsolved problem. Combining theory and coarse-grained simulations shows that the DNA sequence and a structural correlation due to topology constraints of a circle are the main factors that dictate the 3D structure of a 336 bp DNA minicircle under torsional stress. We found that DNA minicircle topoisomers can have multiple bend locations under high torsional stress and that the positions of these sharp bends are determined by the sequence, and by a positive mechanical correlation along the sequence. We showed that simulations and theory are able to provide sequence-specific information about individual DNA minicircles observed by cryo-electron tomography (cryo-ET). We provided a sequence-specific cryo-ET tomogram fitting of DNA minicircles, registering the sequence within the geometric features. Our results indicate that the conformational distribution of minicircles under torsional stress can be designed, which has important implications for using minicircle DNA for gene therapy. PMID:28609782

Perception of tilt and ocular torsion of vestibular patients during eccentric rotation.

PubMed

Clément, Gilles; Deguine, Olivier

2010-01-04

Four patients following unilateral vestibular loss and four patients complaining of otolith-dependent vertigo were tested during eccentric yaw rotation generating 1 x g centripetal acceleration directed along the interaural axis. Perception of body tilt in roll and in pitch was recorded in darkness using a somatosensory plate that the subjects maintained parallel to the perceived horizon. Ocular torsion was recorded by a video camera. Unilateral vestibular-defective patients underestimated the magnitude of the roll tilt and had a smaller torsion when the centrifugal force was towards the operated ear compared to the intact ear and healthy subjects. Patients with otolithic-dependent vertigo overestimated the magnitude of roll tilt in both directions of eccentric rotation relative to healthy subjects, and their ocular torsion was smaller than in healthy subjects. Eccentric rotation is a promising tool for the evaluation of vestibular dysfunction in patients. Eye torsion and perception of tilt during this stimulation are objective and subjective measurements, which could be used to determine alterations in spatial processing in the CNS.

Spacetime thermodynamics in the presence of torsion

NASA Astrophysics Data System (ADS)

Dey, Ramit; Liberati, Stefano; Pranzetti, Daniele

2017-12-01

It was shown by Jacobson in 1995 that the Einstein equation can be derived as a local constitutive equation for an equilibrium spacetime thermodynamics. With the aim to understand if such thermodynamical description is an intrinsic property of gravitation, many attempts have been made so far to generalize this treatment to a broader class of gravitational theories. Here we consider the case of the Einstein-Cartan theory as a prototype of theories with nonpropagating torsion. In doing so, we study the properties of Killing horizons in the presence of torsion, establish the notion of local causal horizon in Riemann-Cartan spacetimes, and derive the generalized Raychaudhuri equation for these kinds of geometries. Then, starting with the entropy that can be associated to these local causal horizons, we derive the Einstein-Cartan equation by implementing the Clausius equation. We outline two ways of proceeding with the derivation depending on whether we take torsion as a geometric field or as a matter field. In both cases we need to add internal entropy production terms to the Clausius equation as the shear and twist cannot be taken to be 0 a priori for our setup. This fact implies the necessity of a nonequilibrium thermodynamics treatment for the local causal horizon. Furthermore, it implies that a nonzero twist at the horizon in general contributes to the Hartle-Hawking tidal heating for black holes with possible implications for future observations.

A cost-effective, accurate machine for testing the torsional strength of sheep long bones.

PubMed

Jämsä, T; Jalovaara, P

1996-07-01

A cost-effective torsional testing machine for sheep long bones was constructed. The machine was fabricated on a disused standard turning lathe. The angular speed used was 6.5 degrees/s. A precision amplifier using modern low-noise, low-drift operational amplifiers was developed. The maximum torsional load was 250 Nm, the sensitivity 0.5 Nm and the total machine inaccuracy less than 1.0%. The standard error of torsional testing was 3.0% when seven pairs of intact sheep tibiae were tested.

Molecular dynamics simulation on the elastoplastic properties of copper nanowire under torsion

NASA Astrophysics Data System (ADS)

Yang, Yong; Li, Ying; Yang, Zailin; Zhang, Guowei; Wang, Xizhi; Liu, Jin

2018-02-01

Influences of different factors on the torsion properties of single crystal copper nanowire are studied by molecular dynamics method. The length, torsional rate, and temperature of the nanowire are discussed at the elastic-plastic critical point. According to the average potential energy curve and shear stress curve, the elastic-plastic critical angle is determined. Also, the dislocation at elastoplastic critical points is analyzed. The simulation results show that the single crystal copper nanowire can be strengthened by lengthening the model, decreasing the torsional rate, and lowering the temperature. Moreover, atoms move violently and dislocation is more likely to occur with a higher temperature. This work mainly describes the mechanical behavior of the model under different states.

Review of gastric torsion in eight guinea pigs (Cavia porcellus).

PubMed

Nógrádi, Anna Linda; Cope, Iain; Balogh, Márton; Gál, János

2017-12-01

The authors present eight cases of gastric dilatation and volvulus (GDV) in guinea pigs from the Department and Clinic of Exotic Animal and Wildlife Medicine, University of Veterinary Medicine, Budapest, Hungary between 2012 and 2016. Seven animals were operated on and two survived. Gastric torsion has been noted in many mammalian species. Gastric volvulus has a high morbidity and high mortality rate with a guarded to poor prognosis in all of these species. How GDV develops is still not widely understood. Postmortem examinations, in both our cases and previously reported cases, have failed to reveal the exact causes of the gastric torsions. The aetiology of gastric torsion in guinea pigs is probably multifactorial. Feeding fewer meals per day, eating rapidly, decreased food particle size, exercise, stress after a meal, competition, age, and an aggressive or fearful temperament, are all likely and potential risk factors for GDV development in a similar fashion to dogs. Sex, breeding, dental diseases, anatomical abnormalities, pain and pregnancy may also be contributing factors.

Fiber-Optic Sensors for Measurements of Torsion, Twist and Rotation: A Review †

PubMed Central

Budinski, Vedran; Donlagic, Denis

2017-01-01

Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation. PMID:28241510

Biaxial (Tension-Torsion) Testing of an Oxide/Oxide Ceramic Matrix Composite

DTIC Science & Technology

2013-03-01

estimation algorithms and constants . . . . . . . . . . . . . 61 4.27 Biaxial (tension-torsion) load spreadsheet with independent axial load and torsion...through the composite and provides the main load - bearing capability. The interaction of the two (or more) phases takes place in the interface. The...transfer loads between fibers[15]. The fiber-to-fiber load transfer mechanism provided by the matrix plays a major role in the load - bearing properties of the

A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

NASA Astrophysics Data System (ADS)

Keivani, M.; Abadian, N.; Koochi, A.; Mokhtari, J.; Abadyan, M.

2016-10-01

It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners.

Proposal for quantum many-body simulation and torsional matter-wave interferometry with a levitated nanodiamond

NASA Astrophysics Data System (ADS)

Ma, Yue; Hoang, Thai M.; Gong, Ming; Li, Tongcang; Yin, Zhang-qi

2017-08-01

Hybrid spin-mechanical systems have great potential in sensing, macroscopic quantum mechanics, and quantum information science. In order to induce strong coupling between an electron spin and the center-of-mass motion of a mechanical oscillator, a large magnetic gradient usually is required, which is difficult to achieve. Here we show that strong coupling between the electron spin of a nitrogen-vacancy (NV) center and the torsional vibration of an optically levitated nanodiamond can be achieved in a uniform magnetic field. Thanks to the uniform magnetic field, multiple spins can strongly couple to the torsional vibration at the same time. We propose utilizing this coupling mechanism to realize the Lipkin-Meshkov-Glick (LMG) model by an ensemble of NV centers in a levitated nanodiamond. The quantum phase transition in the LMG model and finite number effects can be observed with this system. We also propose generating torsional superposition states and realizing torsional matter-wave interferometry with spin-torsional coupling.

Theory of pure rotational transitions in doubly degenerate torsional states of ethane

NASA Technical Reports Server (NTRS)

Rosenberg, A.; Susskind, J.

1979-01-01

It is shown that pure rotational transitions in doubly degenerate torsional states of C2H6 (with selection rules Delta K = 0, plus or minus 1) are made allowed by Coriolis interaction between torsion and dipole-allowed vibrations. Expressions are presented for integrated intensities from which strengths of lines in the millimeter region can be calculated.

Enhanced Photocurrent Generation from Bacteriorhodopsin Photocells Using Grating-Structured Transparent Conductive Oxide Electrodes.

PubMed

Kaji, Takahiro; Kasai, Katsuyuki; Haruyama, Yoshihiro; Yamada, Toshiki; Inoue, Shin-Ichiro; Tominari, Yukihiro; Ueda, Rieko; Terui, Toshifumi; Tanaka, Shukichi; Otomo, Akira

2016-04-01

We fabricated a grating-structured electrode made of indium-doped zinc oxide (IZO) with a high refractive index (approximately 2) for a bacteriorhodopsin (bR) photocell. We investigated the photocurrent characteristics of the bR photocell and demonstrated that the photocurrent values from the bR/IZO electrode with the grating structure with a grating period of 340 nm were more than 3.5-4 times larger than those without the grating structure. The photocurrent enhancement was attributed to the resonance effect due to light coupling to the grating structure as well as the scattering effect based on the experimental results and analysis using the photonic band structure determined using finite-difference time-domain (FDTD) simulations. The refractive index of the bR film in electrolyte solution (1.40) used in the FDTD simulations was estimated by analyzing the extinction peak wavelength of 20-nm gold colloids in the bR film. Our results indicate that the grating- or photonic-crystal-structured transparent conductive oxide (TCO) electrodes can increase the light use efficiency of various bR devices such as artificial photosynthetic devices, solar cells, and light-sensing devices.

All-optical switching based on optical fibre long period gratings modified bacteriorhodopsin

NASA Astrophysics Data System (ADS)

Korposh, S.; James, S.; Partridge, M.; Sichka, M.; Tatam, R.

2018-05-01

All-optical switching using an optical fibre long-period gating (LPG) modified with bacteriorhodopsin (bR) is demonstrated. The switching process is based on the photo-induced RI change of bR, which in turn changes the phase matching conditions of the mode coupling by the LPG, leading to modulation of the propagating light. The effect was studied with an LPG immersed into a bR solution and with LPGs coated with the bR films, deposited onto the LPGs using the layer-by-layer electrostatic self-assembly (LbL) method. The dependence of the all-optical switching efficiency upon the concentration of the bR solution and on the grating period of the LPG was also studied. In addition, an in-fibre Mach-Zehnder interferometer (MZI) composed of a cascaded LPG pair separated by 30 mm and modified with bR was used to enhance the wavelength range of all-optical switching. The switching wavelength is determined by the grating period of the LPG. Switching efficiencies of 16% and 35% were observed when an LPG and an MZI were immersed into bR solutions, respectively. The switching time for devices coated with bR-films was within 1 s, 10 times faster than that observed for devices immersed into bR solution.

Sporadic adult onset primary torsion dystonia is a genetic disorder by the temporal discrimination test.

PubMed

Kimmich, Okka; Bradley, David; Whelan, Robert; Mulrooney, Nicola; Reilly, Richard B; Hutchinson, Siobhan; O'Riordan, Sean; Hutchinson, Michael

2011-09-01

Adult-onset primary torsion dystonia is an autosomal dominant disorder with markedly reduced penetrance; patients with sporadic adult-onset primary torsion dystonia are much more prevalent than familial. The temporal discrimination threshold is the shortest time interval at which two stimuli are detected to be asynchronous and has been shown to be abnormal in adult-onset primary torsion dystonia. The aim was to determine the frequency of abnormal temporal discrimination thresholds in patients with sporadic adult-onset primary torsion dystonia and their first-degree relatives. We hypothesized that abnormal temporal discrimination thresholds in first relatives would be compatible with an autosomal dominant endophenotype. Temporal discrimination thresholds were examined in 61 control subjects (39 subjects <50 years of age; 22 subjects >50 years of age), 32 patients with sporadic adult-onset primary torsion dystonia (cervical dystonia n = 30, spasmodic dysphonia n = 1 and Meige's syndrome n = 1) and 73 unaffected first-degree relatives (36 siblings, 36 offspring and one parent) using visual and tactile stimuli. Z-scores were calculated for all subjects; a Z > 2.5 was considered abnormal. Abnormal temporal discrimination thresholds were found in 1/61 (2%) control subjects, 27/32 (84%) patients with adult-onset primary torsion dystonia and 32/73 (44%) unaffected relatives [siblings (20/36; 56%), offspring (11/36; 31%) and one parent]. When two or more relatives were tested in any one family, 22 of 24 families had at least one first-degree relative with an abnormal temporal discrimination threshold. The frequency of abnormal temporal discrimination thresholds in first-degree relatives of patients with sporadic adult-onset primary torsion dystonia is compatible with an autosomal dominant disorder and supports the hypothesis that apparently sporadic adult-onset primary torsion dystonia is genetic in origin.

Investigations on bending-torsional vibrations of rotor during rotor-stator rub using Lagrange multiplier method

NASA Astrophysics Data System (ADS)

Mokhtar, Md Asjad; Kamalakar Darpe, Ashish; Gupta, Kshitij

2017-08-01

The ever-increasing need of highly efficient rotating machinery causes reduction in the clearance between rotating and non-rotating parts and increase in the chances of interaction between these parts. The rotor-stator contact, known as rub, has always been recognized as one of the potential causes of rotor system malfunctions and a source of secondary failures. It is one of few causes that influence both lateral and torsional vibrations. In this paper, the rotor stator interaction phenomenon is investigated in the finite element framework using Lagrange multiplier based contact mechanics approach. The stator is modelled as a beam that can respond to axial penetration and lateral friction force during the contact with the rotor. It ensures dynamic stator contact boundary and more realistic contact conditions in contrast to most of the earlier approaches. The rotor bending-torsional mode coupling during contact is considered and the vibration response in bending and torsion are analysed. The effect of parameters such as clearance, friction coefficient and stator stiffness are studied at various operating speeds and it has been found that certain parameter values generate peculiar rub related features. Presence of sub-harmonics in the lateral vibration frequency spectra are prominently observed when the rotor operates near the integer multiple of its lateral critical speed. The spectrum cascade of torsional vibration shows the presence of bending critical speed along with the larger amplitudes of frequencies close to torsional natural frequency of the rotor. When m × 1/n X frequency component of rotational frequency comes closer to the torsional natural frequency, stronger torsional vibration amplitude is noticed in the spectrum cascade. The combined information from the stator vibration and rotor lateral-torsional vibration spectral features is proposed for robust rub identification.

Torsional, Vibrational and Vibration-Torsional Levels in the S_{1} and Ground Cationic D_{0}^{+} States of Para-Xylene

NASA Astrophysics Data System (ADS)

Gardner, Adrian M.; Tuttle, William Duncan; Groner, Peter; Wright, Timothy G.

2017-06-01

Insight gained from examining the "pure" torsional, vibrational and vibration-torsional (vibtor) levels of the single rotor molecules: toluene (methylbenzene) and para-fluorotoluene (pFT), is applied to the double rotor para-xylene (p-dimethylbenzene) molecule . Resonance-enhanced multiphoton ionization (REMPI) spectroscopy and zero-kinetic-energy (ZEKE) spectroscopy are employed in order to investigate the S_{1} and ground cationic states of para-xylene. Observed transitions are assigned in the full molecular symmetry group (G_{72}) for the first time. J. R. Gascooke, E. A. Virgo, and W. D. Lawrance, J. Chem. Phys., 143, 044313 (2015). A. M. Gardner, W. D. Tuttle, L. Whalley, A. Claydon, J. H. Carter and T. G. Wright, J. Chem. Phys., 145, 124307 (2016). A. M. Gardner, W. D. Tuttle, P. Groner and T. G. Wright, J. Chem. Phys., (2017, in press).

Measurement of ventricular torsion by two-dimensional ultrasound speckle tracking imaging.

PubMed

Notomi, Yuichi; Lysyansky, Peter; Setser, Randolph M; Shiota, Takahiro; Popović, Zoran B; Martin-Miklovic, Maureen G; Weaver, Joan A; Oryszak, Stephanie J; Greenberg, Neil L; White, Richard D; Thomas, James D

2005-06-21

We sought to examine the accuracy/consistency of a novel ultrasound speckle tracking imaging (STI) method for left ventricular torsion (LVtor) measurement in comparison with tagged magnetic resonance imaging (MRI) (a time-domain method similar to STI) and Doppler tissue imaging (DTI) (a velocity-based approach). Left ventricular torsion from helically oriented myofibers is a key parameter of cardiac performance but is difficult to measure. Ultrasound STI is potentially suitable for measurement of angular motion because of its angle-independence. We acquired basal and apical short-axis left ventricular (LV) images in 15 patients to estimate LVtor by STI and compare it with tagged MRI and DTI. Left ventricular torsion was defined as the net difference of LV rotation at the basal and apical planes. For the STI analysis, we used high-frame (104 +/- 12 frames/s) second harmonic two-dimensional images. Data on 13 of 15 patients were usable for STI analysis, and LVtor profile estimated by STI strongly correlated with those by tagged MRI (y = 0.95x + 0.19, r = 0.93, p < 0.0001, analyzed by repeated-measures regression models). The STI torsional velocity profile also correlated well with that by the DTI method (y = 0.79x + 2.4, r = 0.76, p < 0.0001, by repeated-measures regression models) with acceptable bias. The STI estimation of LVtor is concordant with those analyzed by tagged MRI (data derived from tissue displacement) and also showed good agreement with those by DTI (data derived from tissue velocity). Ultrasound STI is a promising new method to assess LV torsional deformation and may make the assessment more available in clinical and research cardiology.

Anomaly formulas for the complex-valued analytic torsion on compact bordisms

PubMed Central

Maldonado Molina, Osmar

2013-01-01

We extend the complex-valued analytic torsion, introduced by Burghelea and Haller on closed manifolds, to compact Riemannian bordisms. We do so by considering a flat complex vector bundle over a compact Riemannian manifold, endowed with a fiberwise nondegenerate symmetric bilinear form. The Riemmanian metric and the bilinear form are used to define non-selfadjoint Laplacians acting on vector-valued smooth forms under absolute and relative boundary conditions. In order to define the complex-valued analytic torsion in this situation, we study spectral properties of these generalized Laplacians. Then, as main results, we obtain so-called anomaly formulas for this torsion. Our reasoning takes into account that the coefficients in the heat trace asymptotic expansion associated to the boundary value problem under consideration, are locally computable. The anomaly formulas for the complex-valued Ray–Singer torsion are derived first by using the corresponding ones for the Ray–Singer metric, obtained by Brüning and Ma on manifolds with boundary, and then an argument of analytic continuation. In odd dimensions, our anomaly formulas are in accord with the corresponding results of Su, without requiring the variations of the Riemannian metric and bilinear structures to be supported in the interior of the manifold. PMID:27087744

Design of a nonlinear torsional vibration absorber

NASA Astrophysics Data System (ADS)

Tahir, Ammaar Bin

Tuned mass dampers (TMD) utilizing linear spring mechanisms to mitigate destructive vibrations are commonly used in practice. A TMD is usually tuned for a specific resonant frequency or an operating frequency of a system. Recently, nonlinear vibration absorbers attracted attention of researchers due to some potential advantages they possess over the TMDs. The nonlinear vibration absorber, or the nonlinear energy sink (NES), has an advantage of being effective over a broad range of excitation frequencies, which makes it more suitable for systems with several resonant frequencies, or for a system with varying excitation frequency. Vibration dissipation mechanism in an NES is passive and ensures that there is no energy backflow to the primary system. In this study, an experimental setup of a rotational system has been designed for validation of the concept of nonlinear torsional vibration absorber with geometrically induced cubic stiffness nonlinearity. Dimensions of the primary system have been optimized so as to get the first natural frequency of the system to be fairly low. This was done in order to excite the dynamic system for torsional vibration response by the available motor. Experiments have been performed to obtain the modal parameters of the system. Based on the obtained modal parameters, the design optimization of the nonlinear torsional vibration absorber was carried out using an equivalent 2-DOF modal model. The optimality criterion was chosen to be maximization of energy dissipation in the nonlinear absorber attached to the equivalent 2-DOF system. The optimized design parameters of the nonlinear absorber were tested on the original 5-DOF system numerically. A comparison was made between the performance of linear and nonlinear absorbers using the numerical models. The comparison showed the superiority of the nonlinear absorber over its linear counterpart for the given set of primary system parameters as the vibration energy dissipation in the former is

Generalized Hodge dual for torsion in teleparallel gravity

NASA Astrophysics Data System (ADS)

Huang, Peng; Yuan, Fang-Fang

2016-07-01

For teleparallel gravity in four dimensions, Lucas and Pereira have shown that its action can be constructed via a generalized Hodge dual for torsion tensor. In this paper, we demonstrate that a direct generalization of this approach to other dimensions fails due to the fact that no generalized Hodge dual operator could be given in general dimensions. Furthermore, if one enforces the definition of a generalized Hodge dual to be consistent with the action of teleparallel gravity in general dimensions, the basic identity for any sensible Hodge dual would require an ad hoc definition for the second Hodge dual operation which is totally unexpected. Therefore, we conclude that at least for the torsion tensor, the observation of Lucas and Pereira only applies to four dimensions.

Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol

NASA Astrophysics Data System (ADS)

Belov, S. P.; Golubiatnikov, G. Yu.; Lapinov, A. V.; Ilyushin, V. V.; Alekseev, E. A.; Mescheryakov, A. A.; Hougen, J. T.; Xu, Li-Hong

2016-07-01

This paper presents an explanation based on torsionally mediated proton-spin-overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = - 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e., to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric "torsionally mediated spin-rotation operators" by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e±niα. The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A1 and A2 states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected.

Transverse vs torsional ultrasound: prospective randomized contralaterally controlled study comparing two phacoemulsification-system handpieces

PubMed Central

Assil, Kerry K; Harris, Lindsay; Cecka, Jeannie

2015-01-01

Purpose To compare surgical efficiency and multiple early clinical outcome variables in eyes undergoing phacoemulsification using either transversal or torsional ultrasound systems. Setting Assil Eye Institute, Beverly Hills, CA, USA. Design Prospective, randomized, clinician-masked, contralaterally controlled single-center evaluation. Patients and methods Patients seeking cataract removal in both eyes with implantation of multifocal intraocular lenses were randomly assigned to one of two treatment rooms for phacoemulsification with either a transverse ultrasound system or torsional handpiece system. The contralateral eye was treated at a later date with the alternate device. A total of 54 eyes of 27 patients having similar degrees of cataract, astigmatism, and visual potential were included. All operative data were collected for analysis, and patients were followed for 3 months after surgery. Results Similar visual acuity was reported at all postoperative visits between the two groups. Mean phacoemulsification time and total power required were both significantly lower with the transverse system than with the torsional technique (P<0.05 for both). Similarly, mean total balanced salt solution used was significantly less with the transverse system vs torsional (P<0.05). Postoperative safety demonstrated significantly lower endothelial cell loss at 1 day and 1 month (P<0.05) with transverse vs torsional. Macular swelling was less at 1 week, 1 month, and 3 months with transverse vs torsional, although the difference did not achieve significance (P=0.1) at any single time point. Clinically detectable corneal edema was reported less frequently at all postoperative time points with the transverse system. Conclusion The transverse ultrasound system was found to be possibly associated with less balanced salt-solution use, less phacoemulsification time, and less power required than the torsional phaco system. Postoperative data suggested that improved phaco efficiency may

Transverse vs torsional ultrasound: prospective randomized contralaterally controlled study comparing two phacoemulsification-system handpieces.

PubMed

Assil, Kerry K; Harris, Lindsay; Cecka, Jeannie

2015-01-01

To compare surgical efficiency and multiple early clinical outcome variables in eyes undergoing phacoemulsification using either transversal or torsional ultrasound systems. Assil Eye Institute, Beverly Hills, CA, USA. Prospective, randomized, clinician-masked, contralaterally controlled single-center evaluation. Patients seeking cataract removal in both eyes with implantation of multifocal intraocular lenses were randomly assigned to one of two treatment rooms for phacoemulsification with either a transverse ultrasound system or torsional handpiece system. The contralateral eye was treated at a later date with the alternate device. A total of 54 eyes of 27 patients having similar degrees of cataract, astigmatism, and visual potential were included. All operative data were collected for analysis, and patients were followed for 3 months after surgery. Similar visual acuity was reported at all postoperative visits between the two groups. Mean phacoemulsification time and total power required were both significantly lower with the transverse system than with the torsional technique (P<0.05 for both). Similarly, mean total balanced salt solution used was significantly less with the transverse system vs torsional (P<0.05). Postoperative safety demonstrated significantly lower endothelial cell loss at 1 day and 1 month (P<0.05) with transverse vs torsional. Macular swelling was less at 1 week, 1 month, and 3 months with transverse vs torsional, although the difference did not achieve significance (P=0.1) at any single time point. Clinically detectable corneal edema was reported less frequently at all postoperative time points with the transverse system. The transverse ultrasound system was found to be possibly associated with less balanced salt-solution use, less phacoemulsification time, and less power required than the torsional phaco system. Postoperative data suggested that improved phaco efficiency may translate to a better overall safety profile for the patient.

Modeling and testing miniature torsion specimens for SiC joining development studies for fusion

DOE PAGES

Henager, Jr., C. H.; Nguyen, Ba N.; Kurtz, Richard J.; ...

2015-08-05

The international fusion community has designed a miniature torsion specimen for neutron irradiation studies of joined SiC and SiC/SiC composite materials. For this research, miniature torsion joints based on this specimen design were fabricated using displacement reactions between Si and TiC to produce Ti 3SiC 2 + SiC joints with SiC and tested in torsion-shear prior to and after neutron irradiation. However, many miniature torsion specimens fail out-of-plane within the SiC specimen body, which makes it problematic to assign a shear strength value to the joints and makes it difficult to compare unirradiated and irradiated strengths to determine irradiation effects.more » Finite element elastic damage and elastic–plastic damage models of miniature torsion joints are developed that indicate shear fracture is more likely to occur within the body of the joined sample and cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The model results are compared and discussed with regard to unirradiated and irradiated test data for a variety of joint materials. The unirradiated data includes Ti 3SiC 2 + SiC/CVD-SiC joints with tailored joint moduli, and includes steel/epoxy and CVD-SiC/epoxy joints. Finally, the implications for joint data based on this sample design are discussed.« less

Weakly dynamic dark energy via metric-scalar couplings with torsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sur, Sourav; Bhatia, Arshdeep Singh, E-mail: sourav.sur@gmail.com, E-mail: arshdeepsb@gmail.com

We study the dynamical aspects of dark energy in the context of a non-minimally coupled scalar field with curvature and torsion. Whereas the scalar field acts as the source of the trace mode of torsion, a suitable constraint on the torsion pseudo-trace provides a mass term for the scalar field in the effective action. In the equivalent scalar-tensor framework, we find explicit cosmological solutions representing dark energy in both Einstein and Jordan frames. We demand the dynamical evolution of the dark energy to be weak enough, so that the present-day values of the cosmological parameters could be estimated keeping themmore » within the confidence limits set for the standard LCDM model from recent observations. For such estimates, we examine the variations of the effective matter density and the dark energy equation of state parameters over different redshift ranges. In spite of being weakly dynamic, the dark energy component differs significantly from the cosmological constant, both in characteristics and features, for e.g. it interacts with the cosmological (dust) fluid in the Einstein frame, and crosses the phantom barrier in the Jordan frame. We also obtain the upper bounds on the torsion mode parameters and the lower bound on the effective Brans-Dicke parameter. The latter turns out to be fairly large, and in agreement with the local gravity constraints, which therefore come in support of our analysis.« less

Determining optimal torsional ultrasound power for cataract surgery with automatic longitudinal pulses at maximum vacuum ex vivo.

PubMed

Ronquillo, Cecinio C; Zaugg, Brian; Stagg, Brian; Kirk, Kevin R; Gupta, Isha; Barlow, William R; Pettey, Jeff H; Olson, Randall J

2014-12-01

To determine the optimal longitudinal power settings for Infiniti OZil Intelligent Phaco (IP) at varying torsional amplitude settings; and to test the hypothesis that increasing longitudinal power is more important at lower torsional amplitudes to achieve efficient phacoemulsification. Laboratory investigation. setting: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. procedure: Individual porcine nuclei were fixed in formalin, then cut into 2.0 mm cubes. Lens cube phacoemulsification was done using OZil IP at 60%, 80%, and 100% torsional amplitude with 0%, 10%, 20%, 30%, 50%, 75%, or 100% longitudinal power. All experiments were done using a 20 gauge 0.9 mm bent reverse bevel phaco tip at constant vacuum (550 mm Hg), aspiration rate (40 mL/min), and bottle height (50 cm). main outcome measure: Complete lens particle phacoemulsification (efficiency). Linear regression analysis showed a significant increase in efficiency with increasing longitudinal power at 60% torsional amplitude (R(2) = 0.7269, P = .01) and 80% torsional amplitude (R(2) = 0.6995, P = .02) but not at 100% amplitude (R(2) = 0.3053, P = .2). Baseline comparison of 60% or 80% vs 100% torsional amplitude without longitudinal power showed increased efficiency at 100% (P = .0004). Increasing longitudinal power to 20% abolished the efficiency difference between 80% vs 100% amplitudes. In contrast, 75% longitudinal power abolished the efficiency difference between 60% vs 100% torsional amplitudes. Results suggest that longitudinal power becomes more critical at increasing phacoemulsification efficiencies at torsional amplitudes less than 100%. Increasing longitudinal power does not further increase efficiency at maximal torsional amplitudes. Copyright © 2014 Elsevier Inc. All rights reserved.

Quantitative characterization of the (D2O)3 torsional manifold by terahertz laser spectroscopy and theoretical analysis

NASA Astrophysics Data System (ADS)

Viant, Mark R.; Brown, Mac G.; Cruzan, Jeff D.; Saykally, Richard J.; Geleijns, Michel; van der Avoird, Ad

1999-03-01

We report the measurement of two new perpendicular (D2O)3 torsional bands by terahertz laser vibration-rotation-tunneling (VRT) spectroscopy of a planar pulsed supersonic expansion. The first (28.0 cm-1) band corresponds to the k=±2l←0 transition, and is the lowest frequency vibrational spectrum observed for a water cluster. The second (81.8 cm-1) band originates in the first excited torsional state, and has been assigned as k=3u←±1l. An effective three-dimensional Hamiltonian is derived to describe the rotational structure of each torsional state. Degenerate torsional levels with k=±1 and k=±2 exhibit a Coriolis splitting linear in K implying the presence of vibrational angular momentum, and a second-order splitting from off-diagonal coupling between degenerate sublevels with +|k| and -|k|. With this effective Hamiltonian we fit a total of 554 rovibrational transitions in five different bands connecting the lowest nine torsional states, with a rms residual of 1.36 MHz. The data set comprises the two new VRT bands together with the 41.1 cm-1 parallel band, the 89.6 cm-1 parallel band, and the 98.1 cm-1 perpendicular band. This analysis provides a comprehensive characterization of the torsional energy levels in (D2O)3 up to 100 cm-1 above the zero-point energy, and confirms the torsional assignments for all five (D2O)3 VRT bands observed to date. Moreover, it vindicates the adiabatic separation of the trimer torsional and hydrogen bond stretch/bend vibrational modes which underlies the torsional model.

Cosmological magnetic fields as string dynamo seeds and axion fields in torsioned spacetime

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Andrade, L.C. Garcia, E-mail: garcia@dft.if.uerj.br

2014-08-01

In this paper two examples of the generation cosmological magnetic fields (CMF) are given. The first is the string dynamo seed cosmological magnetic field estimated as B{sub seed}∼10{sup -24} Gauss from a static spin polarised cylinder in Einstein-Cartan-Maxwell spacetime. The string dynamo seeds from a static spin polarised cylinder is given by B∼σ{sup 2}R{sup 2} where σ is the spin-torsion density while R is the string radius. The B-field value above is able to seed galactic dynamo. In the BBN the magnetic fields around 10{sup 12} Gauss give rise to a string radius as small as 10{sup 17}l{sub P} where l{sub P}more » is the Planck length. The second is the CMF from axionic torsion field which is given by B{sub seed}∼10{sup -27} Gauss which is stronger than the primordial magnetic field B{sub BICEP2}∼10{sup -30} Gauss from the BICEP2 recent experiment on primordial gravitational waves and cosmological inflation to axionic torsion. The interaction Lagrangean between axionic torsion scalar φ and magnetic fields used in this last example is given by f{sup 2}(φ)F{sub μν}F{sup μν}. A similar lagrangean has been used by K. Bamba et al. [JCAP 10 (2012) 058] so generate magnetic fields without dynamo action. Since axionic torsion can be associated with axionic domain walls both examples discussed here could be consider as topological defects examples of the generation of primordial magnetic fields in universes endowed with spacetime torsion.« less

Success of torsional correction surgery after failed surgeries for patellofemoral pain and instability.

PubMed

Stevens, Peter M; Gililland, Jeremy M; Anderson, Lucas A; Mickelson, Jennifer B; Nielson, Jenifer; Klatt, Joshua W

2014-04-01

Torsional deformities of the femur and/or tibia often go unrecognized in adolescents and adults who present with anterior knee pain, and patellar maltracking or instability. While open and arthroscopic surgical techniques have evolved to address these problems, unrecognized torsion may compromise the outcomes of these procedures. We collected a group of 16 consecutive patients (23 knees), with mean age of 17, who had undergone knee surgery before torsion was recognized and subsequently treated by means of rotational osteotomy of the tibia and/or femur. By follow-up questionnaire, we sought to determine the role of rotational correction at mean 59-month follow-up. We reasoned that, by correcting torsional alignment, we might be able to optimize long-term outcomes and avert repeated knee surgery. Knee pain was significantly improved after torsional treatment (mean 8.6 pre-op vs. 3.3 post-op, p < 0.001), while 70 % of patients did have some continued knee pain postoperatively. Only 43 % of patients had continued patellar instability, and 57 % could trust their knee after surgery. Activity level remained the same or increased in 78 % of patients after torsional treatment. Excluding planned rod removal, subsequent knee surgery for continued anterior knee pain was undertaken on only 3 knees in 2 patients. We believe that malrotation of the lower limb not only raises the propensity for anterior knee symptoms, but is also a under-recognized etiology in the failure of surgeries for anterior knee pain and patellar instability. Addressing rotational abnormalities in the index surgery yields better clinical outcomes than osteotomies performed after other prior knee surgeries.

Torsional vibration signal analysis as a diagnostic tool for planetary gear fault detection

NASA Astrophysics Data System (ADS)

Xue, Song; Howard, Ian

2018-02-01

This paper aims to investigate the effectiveness of using the torsional vibration signal as a diagnostic tool for planetary gearbox faults detection. The traditional approach for condition monitoring of the planetary gear uses a stationary transducer mounted on the ring gear casing to measure all the vibration data when the planet gears pass by with the rotation of the carrier arm. However, the time variant vibration transfer paths between the stationary transducer and the rotating planet gear modulate the resultant vibration spectra and make it complex. Torsional vibration signals are theoretically free from this modulation effect and therefore, it is expected to be much easier and more effective to diagnose planetary gear faults using the fault diagnostic information extracted from the torsional vibration. In this paper, a 20 degree of freedom planetary gear lumped-parameter model was developed to obtain the gear dynamic response. In the model, the gear mesh stiffness variations are the main internal vibration generation mechanism and the finite element models were developed for calculation of the sun-planet and ring-planet gear mesh stiffnesses. Gear faults on different components were created in the finite element models to calculate the resultant gear mesh stiffnesses, which were incorporated into the planetary gear model later on to obtain the faulted vibration signal. Some advanced signal processing techniques were utilized to analyses the fault diagnostic results from the torsional vibration. It was found that the planetary gear torsional vibration not only successfully detected the gear fault, but also had the potential to indicate the location of the gear fault. As a result, the planetary gear torsional vibration can be considered an effective alternative approach for planetary gear condition monitoring.

On the torsional loading of elastoplastic spheres in contact

NASA Astrophysics Data System (ADS)

Nadimi, Sadegh; Fonseca, Joana

2017-06-01

The mechanical interaction between two bodies involves normal loading in combination with tangential, torsional and rotational loading. This paper focuses on the torsional loading of two spherical bodies which leads to twisting moment. The theoretical approach for calculating twisting moment between two spherical bodies has been proposed by Lubkin [1]. Due to the complexity of the solution, this has been simplified by Deresiewicz for discrete element modelling [2]. Here, the application of a simplified model for elastoplastic spheres is verified using computational modelling. The single grain interaction is simulated in a combined finite discrete element domain. In this domain a grain can deform using a finite element formulation and can interact with other objects based on discrete element principles. For an elastoplastic model, the contact area is larger in comparison with the elastic model, under a given normal force. Therefore, the plastic twisting moment is stiffer. The results presented here are important for describing any granular system involving torsional loading of elastoplastic grains. In particular, recent research on the behaviour of soil has clearly shown the importance of plasticity on grain interaction and rearrangement.

Influence of Torsion Effect on the Mechanical Characteristics of Reinforced Concrete Column

NASA Astrophysics Data System (ADS)

Wang, Debin; Fan, Guoxi

2017-11-01

The purpose of this paper is to study the effect of torsional effect and loading rate on the flexural capacity of RC members. Based on the fiber model of finite element software ABAQUS, a model has been established with the consideration of the strain rate sensitivity of steel and concrete. The model is used to reflect the influence of the rotational component of ground motion by applying the initial angular displacement. The mechanical properties of RC columns under monotonic loads are simulated. The simulation results show that there has been a decrease in the carrying capacity and initial stiffness of RC columns for high initial torsion angle. With the increase of initial torsion angle, the influence of loading rate on RC columns gradually increases.

Influence of torsional-lateral coupling on stability behavior of geared rotor systems

NASA Technical Reports Server (NTRS)

Schwibinger, P.; Nordmann, R.

1987-01-01

In high-performance turbomachinery trouble often arises because of unstable nonsynchronous lateral vibrations. The instabilities are mostly caused by oil-film bearings, clearance excitation, internal damping, annular pressure seals in pumps, or labyrinth seals in turbocompressors. In recent times the coupling between torsional and lateral vibrations has been considered as an additional influence. This coupling is of practical importance in geared rotor systems. The literature describes some field problems in geared drive trains where unstable lateral vibrations occurred together with torsional oscillations. This paper studies the influence of the torsional-lateral coupling on the stability behavior of a simple geared system supported by oil-film bearings. The coupling effect is investigated by parameter studies and a sensitivity analysis for the uncoupled and coupled systems.

Torsional Oscillations of the Earths's Core

NASA Technical Reports Server (NTRS)

Hide, Raymond; Boggs, Dale H.; Dickey, Jean O.

1997-01-01

Torsional oscillations of the Earth's liquid metallic outer core are investigated by diving the core into twenty imaginary e1qui-volume annuli coaxial with the axis of ratation of the Earth and determining temproal fluctuations in the axial component of angular memonetum of each annulus under the assumption of iso-rotation on cylindrical surfaces.

Coated Fused Silica Fibers for Enhanced Sensitivity Torsion Pendulum

NASA Technical Reports Server (NTRS)

Numata, Kenji; Horowitz, Jordan; Camp, Jordan

2007-01-01

In order to investigate the fundamental thermal noise limit of a torsion pendulum using a fused silica fiber, we systematically measured and modeled the mechanical losses of thin fused silica fibers coated by electrically conductive thin metal films. Our results indicate that it is possible to achieve a thermal noise limit for coated silica lower by a factor between 3 and 9, depending on the silica diameter, compared to the best tungsten fibers available. This will allow a corresponding increase in sensitivity of torsion pendula used for weak force measurements, including the gravitational constant measurement and ground-based force noise testing for the Laser Interferometer Space Antenna (LISA) mission.

Axial and Torsional Load-Type Sequencing in Cumulative Fatigue: Low Amplitude Followed by High Amplitude Loading

NASA Technical Reports Server (NTRS)

Bonacuse, Peter J.; Kalluri, Sreeramesh

2001-01-01

The experiments described herein were performed to determine whether damage imposed by axial loading interacts with damage imposed by torsional loading. This paper is a follow on to a study that investigated effects of load-type sequencing on the cumulative fatigue behavior of a cobalt base superalloy, Haynes 188 at 538 C Both the current and the previous study were used to test the applicability of cumulative fatigue damage models to conditions where damage is imposed by different loading modes. In the previous study, axial and torsional two load level cumulative fatigue experiments were conducted, in varied combinations, with the low-cycle fatigue (high amplitude loading) applied first. In present study, the high-cycle fatigue (low amplitude loading) is applied initially. As in the previous study, four sequences (axial/axial, torsion/torsion, axial/torsion, and torsion/axial) of two load level cumulative fatigue experiments were performed. The amount of fatigue damage contributed by each of the imposed loads was estimated by both the Palmgren-Miner linear damage rule (LDR) and the non-linear damage curve approach (DCA). Life predictions for the various cumulative loading combinations are compared with experimental results.

Diagnostic evaluation of ovarian torsion: An analysis of pediatric patients using the Nationwide Emergency Department Sample.

PubMed

Rialon, Kristy L; Wolf, Steven; Routh, Jonathan C; Adibe, Obinna O

2017-04-01

Ultrasonography (US) is the diagnostic modality of choice during work-up for ovarian torsion, although computed tomography (CT) may be used. We examined the utilization of CT in girls with ovarian torsion, and determined which patients are most likely to undergo this study. The Nationwide Emergency Department Sample dataset was searched for patients <18 years who presented with ovarian torsion from 2006 to 2012. Hospitals were categorized by the volume of pediatric patients seen. A total of 1279 patients were identified. Seven hundred twelve (56%) were seen at adult hospitals, 154 (12%) at pediatric privileged, and 413 (32%) at pediatric hospitals. Patients cared for in a pediatric or pediatric privileged hospital had more US alone performed to diagnose ovarian torsion (p < 0.01). Girls seen at pediatric hospitals are more likely to undergo US for work-up of ovarian torsion. Copyright © 2016 Elsevier Inc. All rights reserved.

Rotational Energies in Various Torsional Levels of CH_2DOH

NASA Astrophysics Data System (ADS)

Coudert, L. H.; Hilali, A. El; Margulès, L.; Motiyenko, R. A.; Klee, S.

2012-06-01

Using an approach accounting for the hindered internal rotation of a monodeuterated methyl group, an analysis of the torsional spectrum of the monodeuterated species of methanol CH_2DOH has been carried out recently and led to the assignment of 76 torsional subbands in its microwave, FIR, and IR spectra. Although this approach also allowed us to account for subband centers, the rotational structure of the torsional subbands is not well understood yet. In this paper, we will deal with the rotational energies of CH_2DOH. Analyses of the rotational structure of the available subbands^b have been performed using the polynomial-type expansion introduced in the case of the normal species of methanol. For each subband, FIR or IR transitions and a-type microwave lines, within the lower torsional level, were fitted. The frequencies of the latters were taken from previous investigations or from new measurements carried out from 50 to 950 GHz with the submillimeterwave solid state spectrometer in Lille. Subbands involving lower levels with v_t=0 and K ≥ 3 could be satisfactorily analyzed. For levels characterized by lower K-values, the expansion fails. In the case of the K=1, v_t=1 level, the frequencies of a-type microwave transitions involving the lower member of the K-type doublet cannot be well reproduced. For K=0 levels with v_t=1 and 2, a large number of terms is needed in the expansion. We will try to understand why the rotational energies of these levels cannot be reproduced. The results of the analyses will be compared to those obtained with a global approach based on the rotation-torsion Hamiltonian of the molecule. [2] El Hilali, Coudert, Konov, and Klee, J. Chem. Phys. 135 (2011) 194309. [3] Ioli, Moruzzi, Riminucci, Strumia, Moraes, Winnewisser, and Winnewisser, J. Mol. Spec. 171 (1995) 130. [4] Quade and Suenram, J. Chem. Phys. 73 (1980) 1127; and Su and Quade, J. Mol. Spec. 134 (1989) 290. [5] Lauvergnat, Coudert, Klee, and Smirnov, J. Mol. Spec. 256 (2009

Results from Investigations of Torsional Vibration in Turbine Set Shaft Systems

NASA Astrophysics Data System (ADS)

Taradai, D. V.; Deomidova, Yu. A.; Zile, A. Z.; Tomashevskii, S. B.

2018-01-01

The article generalizes the results obtained from investigations of torsional vibration in the shaft system of the T-175/210-12.8 turbine set installed at the Omsk CHPP-5 combined heat and power plant. Three different experimental methods were used to determine the lowest natural frequencies of torsional vibration excited in the shaft system when the barring gear is switched into operation, when the generator is synchronized with the grid, and in response to unsteady disturbances caused by the grid and by the turbine control and steam admission system. It is pointed out that the experimental values of the lowest natural frequencies (to the fourth one inclusively) determined using three different methods were found to be almost completely identical with one another, even though the shaft system was stopped in the experiments carried out according to one method and the shaft system rotated at the nominal speed in those carried out according to two other methods. The need to further develop the experimental methods for determining the highest natural frequencies is substantiated. The values of decrements for the first, third, and fourth natural torsional vibration modes are obtained. A conclusion is drawn from a comparison between the calculated and experimental data on the shaft system's static twisting about the need to improve the mathematical models for calculating torsional vibration. The measurement procedure is described, and the specific features pertinent to the way in which torsional vibration manifests itself as a function of time and turbine set operating mode under the conditions of its long-term operation are considered. The fundamental measurement errors are analyzed, and their influence on the validity of measured parameters is evaluated. With an insignificant level of free and forced torsional vibrations set up under the normal conditions of turbine set and grid operation, it becomes possible to exclude this phenomenon from the list of main factors

Measuring Femoral Torsion In Vivo Using Freehand 3-D Ultrasound Imaging.

PubMed

Passmore, Elyse; Pandy, Marcus G; Graham, H Kerr; Sangeux, Morgan

2016-02-01

Despite variation in bone geometry, muscle and joint function is often investigated using generic musculoskeletal models. Patient-specific bone geometry can be obtained from computerised tomography, which involves ionising radiation, or magnetic resonance imaging (MRI), which is costly and time consuming. Freehand 3-D ultrasound provides an alternative to obtain bony geometry. The purpose of this study was to determine the accuracy and repeatability of 3-D ultrasound in measuring femoral torsion. Measurements of femoral torsion were performed on 10 healthy adults using MRI and 3-D ultrasound. Measurements of femoral torsion from 3-D ultrasound were, on average, smaller than those from MRI (mean difference = 1.8°; 95% confidence interval: -3.9°, 7.5°). MRI and 3-D ultrasound had Bland and Altman repeatability coefficients of 3.1° and 3.7°, respectively. Accurate measurements of femoral torsion were obtained with 3-D ultrasound offering the potential to acquire patient-specific bone geometry for musculoskeletal modelling. Three-dimensional ultrasound is non-invasive and relatively inexpensive and can be integrated into gait analysis. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Plant-based torsional actuator with memory

Treesearch

Nayomi Plaza; Samuel L. Zelinka; Don S. Stone; Joseph E. Jakes

2013-01-01

A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg􀀀1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-...

Harvesting electrical energy from torsional thermal actuation driven by natural convection.

PubMed

Kim, Shi Hyeong; Sim, Hyeon Jun; Hyeon, Jae Sang; Suh, Dongseok; Spinks, Geoffrey M; Baughman, Ray H; Kim, Seon Jeong

2018-06-07

The development of practical, cost-effective systems for the conversion of low-grade waste heat to electrical energy is an important area of renewable energy research. We here demonstrate a thermal energy harvester that is driven by the small temperature fluctuations provided by natural convection. This harvester uses coiled yarn artificial muscles, comprising well-aligned shape memory polyurethane (SMPU) microfibers, to convert thermal energy to torsional mechanical energy, which is then electromagnetically converted to electrical energy. Temperature fluctuations in a yarn muscle, having a maximum hot-to-cold temperature difference of about 13 °C, were used to spin a magnetic rotor to a peak torsional rotation speed of 3,000 rpm. The electromagnetic energy generator converted the torsional energy to electrical energy, thereby producing an oscillating output voltage of up to 0.81 V and peak power of 4 W/kg, based on SMPU mass.

Adnexal Torsion in Postmenopausal Women: Clinical Presentation and Risk of Ovarian Malignancy.

PubMed

Cohen, Aviad; Solomon, Neta; Almog, Benny; Cohen, Yoni; Tsafrir, Ziv; Rimon, Eli; Levin, Ishai

2017-01-01

To investigate the clinical presentation, operative outcome, and incidence of malignancy in postmenopausal women who were diagnosed with adnexal torsion. Retrospective cohort study (Canadian Task Force classification II-2). Tertiary university-affiliated hospital. Postmenopausal women diagnosed with adnexal torsion between 1995 and 2014 (study group) were reviewed and compared with 220 premenopausal patients diagnosed with adnexal torsion during the same time period. Demographic data, clinical signs and symptoms, and intra- and postoperative characteristics were compared between the 2 groups. During the study period 44 postmenopausal women were diagnosed with adnexal torsion. Continuous dull pain was the most common presenting symptom in the postmenopausal group (57%), whereas acute-onset sharp pain was the predominant symptom in the premenopausal group (86%). The time interval from admission to surgery was significantly longer in the postmenopausal group (24 vs 6 hours, p < .001). Laparoscopic surgery was performed in 84.5% of the cases in the premenopausal group, whereas it was carried out in only 50% of cases in the postmenopausal group (p < .001). Four women in the postmenopausal group were diagnosed with malignancy, whereas only 1 case of malignancy was found in the premenopausal group (9% vs .4%, respectively; p = .003). Adnexal torsion in postmenopausal women is an uncommon event with a unique presentation. Because ovarian malignancy is not an uncommon finding in this group of patients, preparation for more extensive surgery should be contemplated. Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.

Comparison of animal discs used in disc research to human lumbar disc: torsion mechanics and collagen content.

PubMed

Showalter, Brent L; Beckstein, Jesse C; Martin, John T; Beattie, Elizabeth E; Espinoza Orías, Alejandro A; Schaer, Thomas P; Vresilovic, Edward J; Elliott, Dawn M

2012-07-01

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc. To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

Comparison of Animal Discs Used in Disc Research to Human Lumbar Disc: Torsion Mechanics and Collagen Content

PubMed Central

Showalter, Brent L.; Beckstein, Jesse C.; Martin, John T.; Beattie, Elizabeth E.; Orías, Alejandro A. Espinoza; Schaer, Thomas P.; Vresilovic, Edward J.; Elliott, Dawn M.

2012-01-01

Study Design Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these to the human disc. Objective To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content. Summary of Background Data There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content. Methods Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar, and cow, rat, and mouse caudal. Collagen content was measured and normalized by dry weight for the same discs except the rat and mouse. Collagen fiber stretch in torsion was calculated using an analytical model. Results Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics. Conclusion Disc torsion mechanics are comparable to human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented is useful for selecting and interpreting results for animal models of the disc. Structural composition of the disc, such as initial fiber angle, may explain the differences that were noted between species after geometric normalization. PMID:22333953

Practical methods for including torsional anharmonicity in thermochemical calculations on complex molecules: the internal-coordinate multi-structural approximation.

PubMed

Zheng, Jingjing; Yu, Tao; Papajak, Ewa; Alecu, I M; Mielke, Steven L; Truhlar, Donald G

2011-06-21

Many methods for correcting harmonic partition functions for the presence of torsional motions employ some form of one-dimensional torsional treatment to replace the harmonic contribution of a specific normal mode. However, torsions are often strongly coupled to other degrees of freedom, especially other torsions and low-frequency bending motions, and this coupling can make assigning torsions to specific normal modes problematic. Here, we present a new class of methods, called multi-structural (MS) methods, that circumvents the need for such assignments by instead adjusting the harmonic results by torsional correction factors that are determined using internal coordinates. We present three versions of the MS method: (i) MS-AS based on including all structures (AS), i.e., all conformers generated by internal rotations; (ii) MS-ASCB based on all structures augmented with explicit conformational barrier (CB) information, i.e., including explicit calculations of all barrier heights for internal-rotation barriers between the conformers; and (iii) MS-RS based on including all conformers generated from a reference structure (RS) by independent torsions. In the MS-AS scheme, one has two options for obtaining the local periodicity parameters, one based on consideration of the nearly separable limit and one based on strongly coupled torsions. The latter involves assigning the local periodicities on the basis of Voronoi volumes. The methods are illustrated with calculations for ethanol, 1-butanol, and 1-pentyl radical as well as two one-dimensional torsional potentials. The MS-AS method is particularly interesting because it does not require any information about conformational barriers or about the paths that connect the various structures.

Comparison of torsional and microburst longitudinal phacoemulsification: a prospective, randomized, masked clinical trial.

PubMed

Vasavada, Abhay R; Raj, Shetal M; Patel, Udayan; Vasavada, Vaishali; Vasavada, Viraj

2010-01-01

To compare intraoperative performance and postoperative outcome of three phacoemulsification technologies in patients undergoing microcoaxial phacoemulsification through 2.2-mm corneal incisions. The prospective, randomized, single-masked study included 360 eyes randomly assigned to torsional (Infiniti Vision System; Alcon Laboratories, Fort Worth, TX), microburst with longitudinal (Infiniti), or microburst with longitudinal (Legacy Everest, Alcon Laboratories) ultrasound. Assessments included surgical clock time, fluid volume, and intraoperative complications, central corneal thickness on day 1 and months 1 and 3 postoperatively, and endothelial cell density at 3 months postoperatively. Comparisons among groups were conducted. Torsional ultrasound required significantly less surgical clock time and fluid volume than the other groups. There were no intraoperative complications. Change in central corneal thickness and endothelial cell loss was significantly lower in the torsional ultrasound group at all postoperative visits (P < .001, Kruskal-Wallis test) compared to microburst longitudinal ultrasound modalities. Torsional ultrasound demonstrated quantitatively superior intraoperative performance and showed less increase in corneal thickness and less endothelial cell loss compared to microburst longitudinal ultrasound. Copyright 2010, SLACK Incorporated.

Electrically, chemically, and photonically powered torsional and tensile actuation of hybrid carbon nanotube yarn muscles.

PubMed

Lima, Márcio D; Li, Na; Jung de Andrade, Mônica; Fang, Shaoli; Oh, Jiyoung; Spinks, Geoffrey M; Kozlov, Mikhail E; Haines, Carter S; Suh, Dongseok; Foroughi, Javad; Kim, Seon Jeong; Chen, Yongsheng; Ware, Taylor; Shin, Min Kyoon; Machado, Leonardo D; Fonseca, Alexandre F; Madden, John D W; Voit, Walter E; Galvão, Douglas S; Baughman, Ray H

2012-11-16

Artificial muscles are of practical interest, but few types have been commercially exploited. Typical problems include slow response, low strain and force generation, short cycle life, use of electrolytes, and low energy efficiency. We have designed guest-filled, twist-spun carbon nanotube yarns as electrolyte-free muscles that provide fast, high-force, large-stroke torsional and tensile actuation. More than a million torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. Electrical, chemical, or photonic excitation of hybrid yarns changes guest dimensions and generates torsional rotation and contraction of the yarn host. Demonstrations include torsional motors, contractile muscles, and sensors that capture the energy of the sensing process to mechanically actuate.

Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles

NASA Astrophysics Data System (ADS)

Lima, Márcio D.; Li, Na; Jung de Andrade, Mônica; Fang, Shaoli; Oh, Jiyoung; Spinks, Geoffrey M.; Kozlov, Mikhail E.; Haines, Carter S.; Suh, Dongseok; Foroughi, Javad; Kim, Seon Jeong; Chen, Yongsheng; Ware, Taylor; Shin, Min Kyoon; Machado, Leonardo D.; Fonseca, Alexandre F.; Madden, John D. W.; Voit, Walter E.; Galvão, Douglas S.; Baughman, Ray H.

2012-11-01

Artificial muscles are of practical interest, but few types have been commercially exploited. Typical problems include slow response, low strain and force generation, short cycle life, use of electrolytes, and low energy efficiency. We have designed guest-filled, twist-spun carbon nanotube yarns as electrolyte-free muscles that provide fast, high-force, large-stroke torsional and tensile actuation. More than a million torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. Electrical, chemical, or photonic excitation of hybrid yarns changes guest dimensions and generates torsional rotation and contraction of the yarn host. Demonstrations include torsional motors, contractile muscles, and sensors that capture the energy of the sensing process to mechanically actuate.

Using a respiratory navigator significantly reduces variability when quantifying left ventricular torsion with cardiovascular magnetic resonance.

PubMed

Hamlet, Sean M; Haggerty, Christopher M; Suever, Jonathan D; Wehner, Gregory J; Andres, Kristin N; Powell, David K; Charnigo, Richard J; Fornwalt, Brandon K

2017-03-01

Left ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion. We assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure and then enforce variability in end-expiratory position between all LV basal and apical acquisitions. From these data, we quantified the inter-test variability of torsion in the absence and presence of enforced end-expiratory position variability, which established an upper bound for the expected torsion variability. For the second experiment (in 20 new, healthy volunteers), 10 pairs of cine DENSE basal and apical images were each acquired from consecutive breath-holds and consecutive navigator-gated scans (with a single acceptance position). Inter-test variability of torsion was compared between the breath-hold and navigator-gated scans to quantify the variability due to natural breath-hold variation. To demonstrate the importance of these variability reductions, we quantified the reduction in sample size required to detect a clinically meaningful change in LV torsion with the use of a respiratory navigator. The mean torsion was 3.4 ± 0.2°/cm. From the first experiment, enforced variability in end-expiratory position translated to considerable variability in measured torsion (0.56 ± 0.34°/cm), whereas inter-test variability with consistent end-expiratory position was 57% lower (0.24 ± 0.16°/cm, p < 0.001). From the second experiment, natural

The bacteriorhodopsin model membrane system as a prototype molecular computing element.

PubMed

Hong, F T

1986-01-01

The quest for more sophisticated integrated circuits to overcome the limitation of currently available silicon integrated circuits has led to the proposal of using biological molecules as computational elements by computer scientists and engineers. While the theoretical aspect of this possibility has been pursued by computer scientists, the research and development of experimental prototypes have not been pursued with an equal intensity. In this survey, we make an attempt to examine model membrane systems that incorporate the protein pigment bacteriorhodopsin which is found in Halobacterium halobium. This system was chosen for several reasons. The pigment/membrane system is sufficiently simple and stable for rigorous quantitative study, yet at the same time sufficiently complex in molecular structure to permit alteration of this structure in an attempt to manipulate the photosignal. Several methods of forming the pigment/membrane assembly are described and the potential application to biochip design is discussed. Experimental data using these membranes and measured by a tunable voltage clamp method are presented along with a theoretical analysis based on the Gouy-Chapman diffuse double layer theory to illustrate the usefulness of this approach. It is shown that detailed layouts of the pigment/membrane assembly as well as external loading conditions can modify the time course of the photosignal in a predictable manner. Some problems that may arise in the actual implementation and manufacturing, as well as the use of existing technology in protein chemistry, immunology, and recombinant DNA technology are discussed.

A black hole with torsion in 5D Lovelock gravity

NASA Astrophysics Data System (ADS)

Cvetković, B.; Simić, D.

2018-03-01

We analyze static spherically symmetric solutions of five dimensional (5D) Lovelock gravity in the first order formulation. In the Riemannian sector, when torsion vanishes, the Boulware–Deser black hole represents a unique static spherically symmetric black hole solution for the generic choice of the Lagrangian parameters. We show that a special choice of the Lagrangian parameters, different from the Lovelock Chern–Simons gravity, leads to the existence of a static black hole solution with torsion, the metric of which is asymptotically anti-de Sitter (AdS). We calculate the conserved charges and thermodynamical quantities of this black hole solution.

The Design and Performance Evaluation of Hydroformed Tubular Torsion Beam Axle

NASA Astrophysics Data System (ADS)

Kim, Jaehyun; Oh, Jinho; Choi, Hanho

2010-06-01

Suspensions for vehicles are structural devices used for suspending a vehicle body and absorbing shocks from the road. Thus, the suspensions must be designed such that they can attenuate shocks from a road and make passengers feel comfortable despite the shocks, and improve steering stability, determined by the ground contact force of tires during running of vehicles. Another important factor to be considered while designing suspensions is that the suspensions must maintain desired stiffness and desired durability despite the repeated application of shocks from roads thereto. The present relates, in general, to a tubular torsion beam for rear suspensions of vehicles and a manufacturing method thereof and, more particularly, to the provision of tubular torsion beams having excellent roll stiffness and excellent roll strength, produced through hydroforming. The hydroforming technology has a lot of benefit which is shape accuracy, good durability caused by compressive pressure, and good forming quality. In this study, the performance evaluation of the hydroformed tubular torsion beam axle is evaluated.

Practical Methods for Including Torsional Anharmonicity in Thermochemical Calculations on Complex Molecules: The Internal-Coordinate Multi-Structural Approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, J.; Yu, T.; Papajak, E.

2011-01-01

Many methods for correcting harmonic partition functions for the presence of torsional motions employ some form of one-dimensional torsional treatment to replace the harmonic contribution of a specific normal mode. However, torsions are often strongly coupled to other degrees of freedom, especially other torsions and low-frequency bending motions, and this coupling can make assigning torsions to specific normal modes problematic. Here, we present a new class of methods, called multi-structural (MS) methods, that circumvents the need for such assignments by instead adjusting the harmonic results by torsional correction factors that are determined using internal coordinates. We present three versions ofmore » the MS method: (i) MS-AS based on including all structures (AS), i.e., all conformers generated by internal rotations; (ii) MS-ASCB based on all structures augmented with explicit conformational barrier (CB) information, i.e., including explicit calculations of all barrier heights for internal-rotation barriers between the conformers; and (iii) MS-RS based on including all conformers generated from a reference structure (RS) by independent torsions. In the MS-AS scheme, one has two options for obtaining the local periodicity parameters, one based on consideration of the nearly separable limit and one based on strongly coupled torsions. The latter involves assigning the local periodicities on the basis of Voronoi volumes. The methods are illustrated with calculations for ethanol, 1-butanol, and 1-pentyl radical as well as two one-dimensional torsional potentials. The MS-AS method is particularly interesting because it does not require any information about conformational barriers or about the paths that connect the various structures.« less

Seismic performance of square RC bridge columns under combined loading including torsion with low shear.

DOT National Transportation Integrated Search

2009-12-01

During earthquake excitations, reinforced concrete bridge columns can be subjected to a combination of axial load, shear force, : flexural moments, and torsional moments. The torsional moment can be much more significant in columns of bridges that ar...

No. 341-Diagnosis and Management of Adnexal Torsion in Children, Adolescents, and Adults.

PubMed

Kives, Sari; Gascon, Suzy; Dubuc, Élise; Van Eyk, Nancy

2017-02-01

To review the evidence and provide recommendations on the diagnosis and management of adnexal torsion in children, adolescents, and women. Elements evaluated include the risk factors, diagnostic accuracy, management options, and outcomes of adnexal torsion. Published literature was retrieved through searches of MEDLINE, Embase, CINAHL, and the Cochrane Library using appropriate controlled vocabulary and key words ("adnexal torsion," "ovarian torsion"). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and new material incorporated in the guideline to December 2014. Grey (unpublished) literature was identified through searching the websites of health technology assessment and related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The evidence obtained was reviewed and evaluated by the Canadian Paediatric and Adolescent Gynaecology and Obstetrics Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) under the leadership of the principal authors. Recommendations were made according to guidelines developed by the Canadian Task Force on the Periodic Health Examination. Guideline implementation should assist the practitioner in developing an optimal approach to the diagnosis and management of adnexal torsion while minimizing harm and improving patient outcomes. These guidelines have been reviewed and approved by the Gynaecology Committee of the SOGC and approved by the council of the SOGC. The Society of Obstetricians and Gynaecologists of Canada SUMMARY STATEMENTS: RECOMMENDATIONS. Copyright © 2017. Published by Elsevier Inc.

Torsionally mediated spin-rotation hyperfine splittings at moderate to high J values in methanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belov, S. P.; Golubiatnikov, G. Yu.; Lapinov, A. V.

2016-07-14

This paper presents an explanation based on torsionally mediated proton-spin–overall-rotation interaction for the observation of doublet hyperfine splittings in some Lamb-dip sub-millimeter-wave transitions between ground-state torsion-rotation states of E symmetry in methanol. These unexpected doublet splittings, some as large as 70 kHz, were observed for rotational quantum numbers in the range of J = 13 to 34, and K = − 2 to +3. Because they increase nearly linearly with J for a given branch, we confined our search for an explanation to hyperfine operators containing one nuclear-spin angular momentum factor I and one overall-rotation angular momentum factor J (i.e.,more » to spin-rotation operators) and ignored both spin-spin and spin-torsion operators, since they contain no rotational angular momentum operator. Furthermore, since traditional spin-rotation operators did not seem capable of explaining the observed splittings, we constructed totally symmetric “torsionally mediated spin-rotation operators” by multiplying the E-species spin-rotation operator by an E-species torsional-coordinate factor of the form e{sup ±niα}. The resulting operator is capable of connecting the two components of a degenerate torsion-rotation E state. This has the effect of turning the hyperfine splitting pattern upside down for some nuclear-spin states, which leads to bottom-to-top and top-to-bottom hyperfine selection rules for some transitions, and thus to an explanation for the unexpectedly large observed hyperfine splittings. The constructed operator cannot contribute to hyperfine splittings in the A-species manifold because its matrix elements within the set of torsion-rotation A{sub 1} and A{sub 2} states are all zero. The theory developed here fits the observed large doublet splittings to a root-mean-square residual of less than 1 kHz and predicts unresolvable splittings for a number of transitions in which no doublet splitting was detected.« less

The fracture strength by a torsion test at the implant-abutment interface.

PubMed

Watanabe, Fumihiko; Hiroyasu, Kazuhiko; Ueda, Kazuhiko

2015-12-01

Fractured connections between implants and implant abutments or abutment screws are frequently encountered in a clinical setting. The purpose of this study was to investigate fracture strength using a torsion test at the interface between the implant and the abutment. Thirty screw-type implant with diameters of 3.3, 3.8, 4.3, 5.0, and 6.0 mm were submitted to a torsion test. Implants of each size were connected to abutments with abutment screws tightened to 20 N · cm. Mechanical stress was applied with a rotational speed of 3.6 °/min until fracture occurred, and maximum torque (fracture torque) and torsional yield strength were measured. The mean values were calculated and then compared using Tukey's test. The abutments were then removed, and the implant-abutment interfaces were examined using a scanning electron microscope (SEM). No significant differences in mean fracture torque were found among 3.3, 3.8, and 4.3 mm-diameter implants, but significant differences were found between these sizes and 5.0 and 6.0 mm-diameter implants (p < 0.01). Concerning mean torsional yield strength, significant differences were found between 3.3, 3.8, and 4.3 mm-diameter and 5.0 and 6.0 mm-diameter implants (p < 0.01). Observations under the SEM showed that all the projections of the abutment corresponding to the internal notches of the implant body had been destroyed. Smaller diameter implants demonstrated lower fracture torque and torsional yield strength than implants with larger diameters. In internal tube-in-tube connections, three abutment projections corresponding to rotation-prevention notches were destroyed in each implant.

On the relationship between tibia torsional deformation and regional muscle contractions in habitual human exercises in vivo.

PubMed

Yang, Peng-Fei; Kriechbaumer, Andreas; Albracht, Kirsten; Sanno, Maximilian; Ganse, Bergita; Koy, Timmo; Shang, Peng; Brüggemann, Gert-Peter; Müller, Lars Peter; Rittweger, Jörn

2015-02-05

The mechanical relationship between bone and muscle has been long recognized. However, it still remains unclear how muscles exactly load on bone. In this study, utilizing an optical segment tracking technique, the in vivo tibia loading regimes in terms of tibia segment deformation in humans were investigated during walking, forefoot and rear foot stair ascent and running and isometric plantar flexion. Results suggested that the proximal tibia primarily bends to the posterior aspect and twists to the external aspect with respect to the distal tibia. During walking, peak posterior bending and peak torsion occurred in the first half (22%) and second half (76%) of the stance phase, respectively. During stair ascent, two noticeable peaks of torsion were found with forefoot strike (38% and 82% of stance phase), but only one peak of torsion was found with rear foot strike (78% of stance phase). The torsional deformation angle during both stair ascent and running was larger with forefoot strike than rear foot strike. During isometric plantar flexion, the tibia deformation regimes were characterized more by torsion (maximum 1.35°) than bending (maximum 0.52°). To conclude, bending and torsion predominated the tibia loading regimes during the investigated activities. Tibia torsional deformation is closely related to calf muscle contractions, which further confirm the notion of the muscle-bone mechanical link and shift the focus from loading magnitude to loading regimes in bone mechanobiology. It thus is speculated that torsion is another, yet under-rated factor, besides the compression and tension, to drive long bone mechano-adaptation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Shape sensing for torsionally compliant concentric-tube robots

NASA Astrophysics Data System (ADS)

Xu, Ran; Yurkewich, Aaron; Patel, Rajni V.

2016-03-01

Concentric-tube robots (CTR) consist of a series of pre-curved flexible tubes that make up the robot structure and provide the high dexterity required for performing surgical tasks in constrained environments. This special design introduces new challenges in shape sensing as large twisting is experienced by the torsionally compliant structure. In the literature, fiber Bragg grating (FBG) sensors are attached to needle-sized continuum robots for curvature sensing, but they are limited to obtaining bending curvatures since a straight sensor layout is utilized. For a CTR, in addition to bending curvatures, the torsion along the robots shaft should be determined to calculate the shape and pose of the robot accurately. To solve this problem, in our earlier work, we proposed embedding FBG sensors in a helical pattern into the tube wall. The strain readings are converted to bending curvatures and torsion by a strain-curvature model. In this paper, a modified strain-curvature model is proposed that can be used in conjunction with standard shape reconstruction algorithms for shape and pose calculation. This sensing technology is evaluated for its accuracy and resolution using three FBG sensors with 1 mm sensing segments that are bonded into the helical grooves of a pre-curved Nitinol tube. The results show that this sensorized robot can obtain accurate measurements: resolutions of 0.02 rad/m with a 100 Hz sampling rate. Further, the repeatability of the obtained measurements during loading and unloading conditions are presented and analyzed.

Self-Assembly of 3D DNA Crystals Containing a Torsionally Stressed Component

DOE PAGES

Hernandez, Carina; Birktoft, Jens J.; Ohayon, Yoel P.; ...

2017-10-05

There is an increasing appreciation for structural diversity of DNA that is of interest to both DNA nanotechnology and basic biology. Here, we have explored how DNA responds to torsional stress by building on a previously reported two-turn DNA tensegrity triangle and demonstrating that we could introduce an extra nucleotide pair (np) into the original sequence without affecting assembly and crystallization. The extra np imposes a significant torsional stress, which is accommodated by global changes throughout the B-DNA duplex and the DNA lattice. Furthermore, the work reveals a near-atomic structure of naked DNA under a torsional stress of approximately 14%,more » and thus provides an example of DNA distortions that occur without a requirement for either an external energy source or the free energy available from protein or drug binding.« less

Self-Assembly of 3D DNA Crystals Containing a Torsionally Stressed Component

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez, Carina; Birktoft, Jens J.; Ohayon, Yoel P.

There is an increasing appreciation for structural diversity of DNA that is of interest to both DNA nanotechnology and basic biology. Here, we have explored how DNA responds to torsional stress by building on a previously reported two-turn DNA tensegrity triangle and demonstrating that we could introduce an extra nucleotide pair (np) into the original sequence without affecting assembly and crystallization. The extra np imposes a significant torsional stress, which is accommodated by global changes throughout the B-DNA duplex and the DNA lattice. Furthermore, the work reveals a near-atomic structure of naked DNA under a torsional stress of approximately 14%,more » and thus provides an example of DNA distortions that occur without a requirement for either an external energy source or the free energy available from protein or drug binding.« less

Self-Assembly of 3D DNA Crystals Containing a Torsionally Stressed Component.

PubMed

Hernandez, Carina; Birktoft, Jens J; Ohayon, Yoel P; Chandrasekaran, Arun Richard; Abdallah, Hatem; Sha, Ruojie; Stojanoff, Vivian; Mao, Chengde; Seeman, Nadrian C

2017-11-16

There is an increasing appreciation for structural diversity of DNA that is of interest to both DNA nanotechnology and basic biology. Here, we have explored how DNA responds to torsional stress by building on a previously reported two-turn DNA tensegrity triangle and demonstrating that we could introduce an extra nucleotide pair (np) into the original sequence without affecting assembly and crystallization. The extra np imposes a significant torsional stress, which is accommodated by global changes throughout the B-DNA duplex and the DNA lattice. The work reveals a near-atomic structure of naked DNA under a torsional stress of approximately 14%, and thus provides an example of DNA distortions that occur without a requirement for either an external energy source or the free energy available from protein or drug binding. Copyright © 2017 Elsevier Ltd. All rights reserved.

Charge displacement in bacteriorhodopsin during the forward and reverse bR-K phototransition.

PubMed Central

Groma, G I; Hebling, J; Ludwig, C; Kuhl, J

1995-01-01

Dried oriented purple membrane samples of Halobacterium salinarium were excited by 150 fs laser pulses of 620 nm with a 7 kHz repetition rate. An unusual complex picosecond electric response signal consisting of a positive and a negative peak was detected by a sampling oscilloscope. The ratio of the two peaks was changed by 1) reducing the repetition rate, 2) varying the intensity of the excitation beam, and 3) applying background illumination by light of 647 nm or 511 nm. All of these features can be explained by the simultaneous excitation of the bacteriorhodopsin ground form and the K intermediate. The latter was populated by the (quasi)continuous excitation attributable to its prolonged lifetime in a dehydrated state. Least-square analysis resulted in a 5 ps upper and 2.5 ps lower limit for the time constant of the charge displacement process, corresponding to the forward reaction. That is in good agreement with the formation time of K. The charge separation driven by the reverse phototransition was faster, having a time constant of a 3.5 ps upper limit. The difference in the rates indicates the existence of different routes for the forward and the reverse photoreactions. PMID:8580349

Exact solutions in 3D gravity with torsion

NASA Astrophysics Data System (ADS)

González, P. A.; Vásquez, Yerko

2011-08-01

We study the three-dimensional gravity with torsion given by the Mielke-Baekler (MB) model coupled to gravitational Chern-Simons term, and that possess electric charge described by Maxwell-Chern-Simons electrodynamics. We find and discuss this theory's charged black holes solutions and uncharged solutions. We find that for vanishing torsion our solutions by means of a coordinate transformation can be written as three-dimensional Chern-Simons black holes. We also discuss a special case of this theory, Topologically Massive Gravity (TMG) at chiral point, and we show that the logarithmic solution of TMG is also a solution of the MB model at a fixed point in the space of parameters. Furthermore, we show that our solutions generalize Gödel type solutions in a particular case. Also, we recover BTZ black hole in Riemann-Cartan spacetime for vanishing charge.

Bending and Torsion Load Alleviator With Automatic Reset

NASA Technical Reports Server (NTRS)

delaFuente, Horacio M. (Inventor); Eubanks, Michael C. (Inventor); Dao, Anthony X. (Inventor)

1996-01-01

A force transmitting load alleviator apparatus and method are provided for rotatably and pivotally driving a member to be protected against overload torsional and bending (moment) forces. The load alleviator includes at least one bias spring to resiliently bias cam followers and cam surfaces together and to maintain them in locked engagement unless a predetermined load is exceeded whereupon a center housing is pivotal or rotational with respect to a crown assembly. This pivotal and rotational movement results in frictional dissipation of the overload force by an energy dissipator. The energy dissipator can be provided to dissipate substantially more energy from the overload force than from the bias force that automatically resets the center housing and crown assembly to the normally fixed centered alignment. The torsional and bending (moment) overload levels can designed independently of each other.

Ghrelin and NUCB2/Nesfatin-1 expression in unilateral testicular torsion-induced rats with and without N-acetylcysteine.

PubMed

Sarac, M; Bakal, U; Tartar, T; Kuloglu, T; Yardim, M; Artas, G; Aydin, S; Kazez, A

2017-08-15

Testicular torsion (TT) is a common urological problem in the field of pediatric surgery. The degree and duration of torsion determines the degree of testicular damage; however, its effects on the expression of octanoylated ghrelin and nucleobindin 2 (NUCB2) /nesfatin-1 synthetized from testicular tissue remain unclear. We explored the effects of experimentally induced unilateral TT on serum and contralateral testicular tissue ghrelin and NUCB2/nesfatin-1 levels, and determined whether N-acetyl cysteine (NAS) treatment had any effects on their expression. A total of 42 Wistar Albino strain rats were divided into 7 groups: Group (G) I control, GII sham, GIII 12-hour torsion, GIV 12-hour torsion + detorsion + 100 mg/kg NAS, GV 24-hour torsion, GVI 24-hour torsion + detorsion + 100 mg/kg NAS, and GVII 100 mg/kg NAS. Octanoylated ghrelin and NUCB2/nesfatin-1 concentrations were evaluated in serum using the ELISA method and in testicular tissue with immunohistochemical methods. Immunoreactivity of octanoylated ghrelin significantly increased in GI compared to GIII, GV, and GVI (p<0.05). NUCB2/nesfatin-1 immunoreactivity increased in GV and GVIII relative to GI (p<0.05). In the 12-hour torsion group, a significant decrease in octanoylated ghrelin levels with NAS treatment was observed; however, in the 24-hour torsion group, a significant decrease was not observed. In the 12-hour torsion + NAS treatment group, a significant change was not observed in NUCB2/nesfatin-1 expression. Following 24-hour torsion, an increase in NUCB2/nesfatin-1 levels was observed, and NAS treatment did not reverse this increase. It was determined that increases in the expression of octanoylated ghrelin and NUCB2/nesfatin-1, the latter of which was a result of TT, reflect damage in this tissue. Importantly, NAS treatment could prevent this damage. Thus, there may be a clinical application for the combined use of NAS and octanoylated ghrelin in preventing TT-related infertility.

Wing Torsional Stiffness Tests of the Active Aeroelastic Wing F/A-18 Airplane

NASA Technical Reports Server (NTRS)

Lokos, William A.; Olney, Candida D.; Crawford, Natalie D.; Stauf, Rick; Reichenbach, Eric Y.

2002-01-01

The left wing of the Active Aeroelastic Wing (AAW) F/A-18 airplane has been ground-load-tested to quantify its torsional stiffness. The test has been performed at the NASA Dryden Flight Research Center in November 1996, and again in April 2001 after a wing skin modification was performed. The primary objectives of these tests were to characterize the wing behavior before the first flight, and provide a before-and-after measurement of the torsional stiffness. Two streamwise load couples have been applied. The wing skin modification is shown to have more torsional flexibility than the original configuration has. Additionally, structural hysteresis is shown to be reduced by the skin modification. Data comparisons show good repeatability between the tests.

Appearance of singularities of optical fields under torsion of crystals containing threefold symmetry axes.

PubMed

Skab, Ihor; Vasylkiv, Yurij; Zapeka, Bohdan; Savaryn, Viktoriya; Vlokh, Rostyslav

2011-07-01

We present an analysis of the effect of torsion stresses on the spatial distribution of optical birefringence in crystals of different point symmetry groups. The symmetry requirements needed so that the optical beam carries dislocations of the phase front are evaluated for the case when the crystals are twisted and the beam closely corresponds to a plane wave. It is shown that the torsion stresses can produce screw-edge, pure screw, or pure edge dislocations of the phase front in the crystals belonging to cubic and trigonal systems. The conditions for appearance of canonical and noncanonical vortices in the conditions of crystal torsion are analyzed. © 2011 Optical Society of America

Congenital or torsion-induced absence of Fallopian tubes. Two case reports.

PubMed

Paternoster, D M; Costantini, W; Uglietti, A; Vasile, C; Bocconi, L

1998-05-01

Unilateral absence of a uterine tube is an extremely rare finding, for which there are two possible etiopathogenic causes: in some cases it is due to haemorrhage filling of the cavity and its reabsorption as a result of asymptomatic torsion of the uterine tube during adult life, in pediatric age or even during intrauterine life; alternatively, the absence may be congenital, associated with developmental alterations of the mesonephric and paramesonephric ducts. The article presents two cases of fallopian tube absence: a congenital monolateral absence and a tubal torsion during pregnancy. The symptomatology of the torsion of the fallopian tube in pregnancy can be milder than in the classic description with peritoneal reaction and severe clinical alteration. The main risk factors for tubal torsion are: adhesions and inflammatory processes, ovarian cysts, usually of dermoid type, menstrual period, pregnancy, abnormal long mesosalpinx and/or mesovarium, pelvic congestion induced by constipation and disturbed venous blood flow from the adnexa. A congenital defect of the mesonephric duct is followed by a homolateral defect of the paramesonephric duct. The resulting anomaly is characterized by the absence of the uterine tube, uterus-tube angle, kidney and ureter. Partial or total unilateral defects of a paramesonephric duct are more common than aplasia of both ducts. Some authors have suggested that an inadequate blood supply during the descent into the pelvis of the caudal part of the paramesonephric duct might feasibly lead to incomplete tube development.

Premotor neurons encode torsional eye velocity during smooth-pursuit eye movements

NASA Technical Reports Server (NTRS)

Angelaki, Dora E.; Dickman, J. David

2003-01-01

Responses to horizontal and vertical ocular pursuit and head and body rotation in multiple planes were recorded in eye movement-sensitive neurons in the rostral vestibular nuclei (VN) of two rhesus monkeys. When tested during pursuit through primary eye position, the majority of the cells preferred either horizontal or vertical target motion. During pursuit of targets that moved horizontally at different vertical eccentricities or vertically at different horizontal eccentricities, eye angular velocity has been shown to include a torsional component the amplitude of which is proportional to half the gaze angle ("half-angle rule" of Listing's law). Approximately half of the neurons, the majority of which were characterized as "vertical" during pursuit through primary position, exhibited significant changes in their response gain and/or phase as a function of gaze eccentricity during pursuit, as if they were also sensitive to torsional eye velocity. Multiple linear regression analysis revealed a significant contribution of torsional eye movement sensitivity to the responsiveness of the cells. These findings suggest that many VN neurons encode three-dimensional angular velocity, rather than the two-dimensional derivative of eye position, during smooth-pursuit eye movements. Although no clear clustering of pursuit preferred-direction vectors along the semicircular canal axes was observed, the sensitivity of VN neurons to torsional eye movements might reflect a preservation of similar premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.

Low Activation Joining of SiC/SiC Composites for Fusion Applications: Modeling Miniature Torsion Tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henager, Charles H.; Nguyen, Ba Nghiep; Kurtz, Richard J.

2014-06-30

The use of SiC and SiC-composites in fission or fusion environments appears to require joining methods for assembling systems. The international fusion community has designed miniature torsion specimens for joint testing and for irradiation in HFIR. Therefore, miniature torsion joints were fabricated using displacement reactions between Si and TiC to produce Ti3SiC2 + SiC joints with CVD-SiC that were tested in shear prior to and after HFIR irradiation. However, these torsion specimens fail out-of-plane, which causes difficulties in determining a shear strength for the joints or for comparing unirradiated and irradiated joints. A finite element damage model has been developedmore » that indicates fracture is likely to occur within the joined pieces to cause out-of-plane failures for miniature torsion specimens when a certain modulus and strength ratio between the joint material and the joined material exists. The implications for torsion shear joint data based on this sample design are discussed.« less

Tensile and Torsional Structural Properties of the Native Scapholunate Ligament.

PubMed

Pang, Eric Quan; Douglass, Nathan; Behn, Anthony; Winterton, Matthew; Rainbow, Michael J; Kamal, Robin N

2018-02-17

The ideal material for reconstruction of the scapholunate interosseous ligament (SLIL) should replicate the mechanical properties of the native SLIL to recreate normal kinematics and prevent posttraumatic arthritis. The purpose of our study was to evaluate the cyclic torsional and tensile properties of the native SLIL and load to failure tensile properties of the dorsal SLIL. The SLIL bone complex was resected from 10 fresh-frozen cadavers. The scaphoid and lunate were secured in polymethylmethacrylate and mounted on a test machine that incorporated an x-y stage and universal joint, which permitted translations perpendicular to the rotation/pull axis as well as nonaxial angulations. After a 1 N preload, specimens underwent cyclic torsional testing (±0.45 N m flexion/extension at 0.5 Hz) and tensile testing (1-50 N at 1 Hz) for 500 cycles. Lastly, the dorsal 10 mm of the SLIL was isolated and displaced at 10 mm/min until failure. During intact SLIL cyclic torsional testing, the neutral zone was 29.7° ± 6.6° and the range of rotation 46.6° ± 7.1°. Stiffness in flexion and extension were 0.11 ± 0.02 and 0.12 ± 0.02 N m/deg, respectively. During cyclic tensile testing, the engagement length was 0.2 ± 0.1 mm, the mean stiffness was 276 ± 67 N/mm, and the range of displacement was 0.4 ± 0.1 mm. The dorsal SLIL displayed a 0.3 ± 0.2 mm engagement length, 240 ± 65 N/mm stiffness, peak load of 270 ± 91 N, and displacement at peak load of 1.8 ± 0.3 mm. We report the torsional properties of the SLIL. Our novel test setup allows for free rotation and translation, which reduces out-of-plane force application. This may explain our observation of greater dorsal SLIL load to failure than previous reports. By matching the natural ligament with respect to its tensile and torsional properties, we believe that reconstructions will better restore the natural kinematics of the wrist and lead to improved outcomes. Future clinical studies should aim to investigate this

Diesel engine torsional vibration control coupling with speed control system

NASA Astrophysics Data System (ADS)

Guo, Yibin; Li, Wanyou; Yu, Shuwen; Han, Xiao; Yuan, Yunbo; Wang, Zhipeng; Ma, Xiuzhen

2017-09-01

The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well.

Observation and control of coherent torsional dynamics in a quinquethiophene molecule.

PubMed

Cirmi, Giovanni; Brida, Daniele; Gambetta, Alessio; Piacenza, Manuel; Della Sala, Fabio; Favaretto, Laura; Cerullo, Giulio; Lanzani, Guglielmo

2010-07-28

By applying femtosecond pump-probe spectroscopy to a substituted quinquethiophene molecule in solution, we observe in the time domain the coherent torsional dynamics that drives planarization of the excited state. Our interpretation is based on numerical modeling of the ground and excited state potential energy surfaces and simulation of wavepacket dynamics, which reveals two symmetric excited state deactivation pathways per oscillation period. We use the acquired knowledge on torsional dynamics to coherently control the excited state population with a pump-dump scheme, exploiting the non-stationary Franck-Condon overlap between ground and excited states.

Electrothermally-Actuated Micromirrors with Bimorph Actuators--Bending-Type and Torsion-Type.

PubMed

Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che

2015-06-22

Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively.

Electrothermally-Actuated Micromirrors with Bimorph Actuators—Bending-Type and Torsion-Type

PubMed Central

Tsai, Cheng-Hua; Tsai, Chun-Wei; Chang, Hsu-Tang; Liu, Shih-Hsiang; Tsai, Jui-Che

2015-01-01

Three different electrothermally-actuated MEMS micromirrors with Cr/Au-Si bimorph actuators are proposed. The devices are fabricated with the SOIMUMPs process developed by MEMSCAP, Inc. (Durham, NC, USA). A silicon-on-insulator MEMS process has been employed for the fabrication of these micromirrors. Electrothermal actuation has achieved a large angular movement in the micromirrors. Application of an external electric current 0.04 A to the bending-type, restricted-torsion-type, and free-torsion-type mirrors achieved rotation angles of 1.69°, 3.28°, and 3.64°, respectively. PMID:26110409

Reverse left ventricular remodeling after acute myocardial infarction: the prognostic impact of left ventricular global torsion.

PubMed

Spinelli, Letizia; Morisco, Carmine; Assante di Panzillo, Emiliano; Izzo, Raffaele; Trimarco, Bruno

2013-04-01

Reverse left ventricular (LV) remodeling (>10 % reduction in LV end-systolic volume) may occur in patients recovering for acute ST-elevation myocardial infarction (STEMI), undergoing percutaneous revascularization of infarct-related coronary artery (PCI). To detect whether LV global torsion obtained by two-dimensional speckle-tracking echocardiography was predictive of reverse LV remodeling, 75 patients with first anterior wall STEMI were studied before (T1) and after PCI (T2) and at 6-month follow-up. Two-year clinical follow-up was also accomplished. LV volumes and both LV sphericity index and conic index were obtained by three-dimensional echocardiography. Reverse remodeling was observed in 25 patients (33 %). By multivariate analysis, independent predictors of reverse LV remodeling were: LV conic index, T2 LV torsion and Δ torsion (difference between T2 and T1 LV torsion expressed as percentage of this latter). According to receiver operating characteristic analysis, 1.34°/cm for T2 LV torsion (sensitivity 88 % and specificity 80 %) and 54 % for Δ torsion (sensitivity 92 % and specificity 82 %) were the optimal cutoff values in predicting reverse LV remodeling. In up to 24 month follow-up, 4 non-fatal re-infarction, 7 hospitalization for heart failure and 4 cardiac deaths occurred. By multivariate Cox analysis, the best variable significantly associated with event-free survival rate was reverse LV remodeling with a hazard ratio = 9.9 (95 % confidence interval, 7.9-31.4, p < 0.01). In conclusion, reverse LV remodeling occurring after anterior wall STEMI is associated with favorable long-term outcome. The improvement of global LV torsion following coronary artery revascularization is the major predictor of reverse LV remodeling.

Fluid dynamics, cavitation, and tip-to-tissue interaction of longitudinal and torsional ultrasound modes during phacoemulsification.

PubMed

Zacharias, Jaime; Ohl, Claus-Dieter

2013-04-01

To describe the fluidic events that occur in a test chamber during phacoemulsification with longitudinal and torsional ultrasound (US) modalities. Pasteur Ophthalmic Clinic Phacodynamics Laboratory, Santiago, Chile, and Nanyang Technological University, Singapore. Experimental study. Ultra-high-speed videos of a phacoemulsifying tip were recorded while the tip operated in longitudinal and torsional US modalities using variable US power. Two high-speed video cameras were used to record videos up to 625,000 frames per second. A high-intensity spotlight source was used for illumination to engage shadowgraphy techniques. Particle image velocimetry was used to evaluate fluidic patterns while a hyperbaric environmental system allowed the evaluation of cavitation effects. Tip-to-tissue interaction at high speed was evaluated using human cataract fragments. Particle imaging velocimetry showed the following flow patterns for longitudinal and torsional modes at high US powers: forward-directed streaming with longitudinal mode and backward-directed streaming with torsional mode. The ultrasound power threshold for the appearance of cavitation was 60% for longitudinal mode and 80% for torsional mode. Cavitation was suppressed with pressure of 1.0 bar for longitudinal mode and 0.3 bar for torsional mode. Generation of previously unseen stable gaseous microbubbles was noted. Tip-to-tissue interaction analysis showed the presence of cavitation bubbles close to the site of fragmentation with no apparent effect on cutting. High-speed imaging and particle image velocimetry yielded a better understanding and differentiated the fluidic pattern behavior between longitudinal and torsional US during phacoemulsification. These recordings also showed more detailed aspects of cavitation that clarified its role in lens material cutting for both modalities. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Left ventricular torsional mechanics and myocardial iron load in beta-thalassaemia major: a potential role of titin degradation.

PubMed

Chen, Mei-Pian; Li, Shu-Na; Lam, Wendy W M; Ho, Yuen-Chi; Ha, Shau-Yin; Chan, Godfrey C F; Cheung, Yiu-Fai

2014-04-12

Iron may damage sarcomeric proteins through oxidative stress. We explored the left ventricular (LV) torsional mechanics in patients with beta-thalassaemia major and its relationship to myocardial iron load. Using HL-1 cell and B6D2F1 mouse models, we further determined the impact of iron load on proteolysis of the giant sarcomeric protein titin. In 44 thalassaemia patients aged 25 ± 7 years and 38 healthy subjects, LV torsion and twisting velocities were determined at rest using speckle tracking echocardiography. Changes in LV torsional parameters during submaximal exercise testing were further assessed in 32 patients and 17 controls. Compared with controls, patients had significantly reduced LV apical rotation, torsion, systolic twisting velocity, and diastolic untwisting velocity. T2* cardiac magnetic resonance findings correlated with resting diastolic untwisting velocity. The increments from baseline and resultant LV torsion and systolic and diastolic untwisting velocities during exercise were significantly lower in patients than controls. Significant correlations existed between LV systolic torsion and diastolic untwisting velocities in patients and controls, both at rest and during exercise. In HL-1 cells and ventricular myocardium of B6D2F1 mice overloaded with iron, the titin-stained pattern of sarcomeric structure became disrupted. Gel electrophoresis of iron-overloaded mouse myocardial tissue further showed significant decrease in the amount of titin isoforms and increase in titin degradation products. Resting and dynamic LV torsional mechanics is impaired in patients with beta-thalassaemia major. Cell and animal models suggest a potential role of titin degradation in iron overload-induced alteration of LV torsional mechanics.

Torsion, infarction, and rupture of a nongravid uterus: a complication of a large ovarian cyst.

PubMed

Yap, Felix Y; Radin, Randall; Tchelepi, Hisham

2016-12-01

Torsion of a nongravid uterus is rare, as most cases of uterine torsion occur during pregnancy. We report a case of a large ovarian cyst causing uterine torsion, infarction, and rupture. A 57-year-old woman presented with acute-onset abdominal pain and increasing abdominal girth over the past year. Contrast-enhanced computed tomography (CT) demonstrated axial rotation and swirling of the uterus and the mesenteric fat, leading to a preoperative diagnosis of uterine torsion. Laparotomy confirmed that the uterine corpus had undergone a 180-degree axial rotation, and further revealed uterine wall infarction and rupture into the endometrium as well as partial decapitation of the uterus from the cervix. The swirled appearance of the uterus, radiologically similar to the "whirlpool sign" seen in bowel volvulus, is an important CT finding to recognize, especially in view of the risk of irreversible ischemic complications this uncommon entity may inflict on the uterus.

Wavelength regulation in bacteriorhodopsin and halorhodopsin: A Pariser-Parr-Pople multireference double excitation configuration interaction study of retinal dyes

NASA Astrophysics Data System (ADS)

Grossjean, Michael F.; Tavan, Paul

1988-04-01

A Pariser-Parr-Pople (PPP) Hamiltonian is employed to study many-electron excitations in protonated and unprotonated retinal Schiff bases. Excited states are described by a multireference double excitation configuration interaction expansion (MRD-CI) and a simplified perturbational treatment. The effects of electron correlation on the spectra of retinal dyes are analyzed and compared with experimental data. It is shown that the spectra of retinal Schiff bases are much more sensitive to the effects of protonation and charge environment than previously assumed. Based on an analysis of observations the computational results demonstrate that varying counterion distance is the essential mechanism of wavelength regulation in the retinal proteins bacteriohodopsin (BR) and halorhodopsin (HR). Spectral properties of intermediates of the photocycles of BR and HR are predicted and it is shown that available spectroscopic data are compatible with a 13,14-cis model of these cycles. Independent evidence is provided that the quantum yield of photoisomerization in BR is 0.6.

The Comparison between Torsional and Conventional Mode Phacoemulsification in Moderate and Hard Cataracts

PubMed Central

Kim, Dong-Hyun; Wee, Won-Ryang; Lee, Jin-Hak

2010-01-01

Purpose To compare the intraoperative performances and postoperative outcomes of cataract surgery performed with longitudinal phacoemulsification and torsional phacoemulsification in moderate and hard cataracts. Methods Of 85 patients who had senile cataracts, 102 eyes were operated on using the Infiniti Vision System. Preoperative examinations (slit lamp examination, mean central corneal thickness, and central endothelial cell counts) were performed for each patient. Cataracts were subdivided into moderate and hard, according to the Lens Opacities Classification System III grading of nucleus opalescence (NO). Eyes in each cataract group were randomly assigned to conventional and torsional phaco-mode. Intraoperative parameters, including ultrasound time (UST), cumulative dissipated energy (CDE), and the balanced salt solution plus (BSSP) volume utilized were evaluated. Best corrected visual acuity (BCVA) was checked on postoperative day 30; mean central corneal thickness and central endothelial cell counts were investigated on postoperative days 7 and 30. Results Preoperative BCVA and mean grading of NO showed no difference in both groups. Preoperative endothelial cell count and central corneal thickness also showed no significant difference in both groups. In the moderate cataract group, the CDE, UST, and BSSP volume were significantly lower in the torsional mode than the longitudinal mode, but they did not show any difference in the hard cataract group. Torsional group showed less endothelial cell loss and central corneal thickening at postoperative day seven in moderate cataracts but showed no significant differences, as compared with the longitudinal group, by postoperative day 30. Conclusions Torsional phacoemulsification showed superior efficiency for moderate cataracts, as compared with longitudinal phacoemulsification, in the early postoperative stage. PMID:21165231

The comparison between torsional and conventional mode phacoemulsification in moderate and hard cataracts.

PubMed

Kim, Dong-Hyun; Wee, Won-Ryang; Lee, Jin-Hak; Kim, Mee-Kum

2010-12-01

To compare the intraoperative performances and postoperative outcomes of cataract surgery performed with longitudinal phacoemulsification and torsional phacoemulsification in moderate and hard cataracts. Of 85 patients who had senile cataracts, 102 eyes were operated on using the Infiniti Vision System. Preoperative examinations (slit lamp examination, mean central corneal thickness, and central endothelial cell counts) were performed for each patient. Cataracts were subdivided into moderate and hard, according to the Lens Opacities Classification System III grading of nucleus opalescence (NO). Eyes in each cataract group were randomly assigned to conventional and torsional phaco-mode. Intraoperative parameters, including ultrasound time (UST), cumulative dissipated energy (CDE), and the balanced salt solution plus (BSSP) volume utilized were evaluated. Best corrected visual acuity (BCVA) was checked on postoperative day 30; mean central corneal thickness and central endothelial cell counts were investigated on postoperative days 7 and 30. Preoperative BCVA and mean grading of NO showed no difference in both groups. Preoperative endothelial cell count and central corneal thickness also showed no significant difference in both groups. In the moderate cataract group, the CDE, UST, and BSSP volume were significantly lower in the torsional mode than the longitudinal mode, but they did not show any difference in the hard cataract group. Torsional group showed less endothelial cell loss and central corneal thickening at postoperative day seven in moderate cataracts but showed no significant differences, as compared with the longitudinal group, by postoperative day 30. Torsional phacoemulsification showed superior efficiency for moderate cataracts, as compared with longitudinal phacoemulsification, in the early postoperative stage.

Type II string theory on Calabi-Yau manifolds with torsion and non-Abelian discrete gauge symmetries

DOE PAGES

Braun, Volker; Cvetič, Mirjam; Donagi, Ron; ...

2017-07-26

Here, we provide the first explicit example of Type IIB string theory compactication on a globally defined Calabi-Yau threefold with torsion which results in a fourdimensional effective theory with a non-Abelian discrete gauge symmetry. Our example is based on a particular Calabi-Yau manifold, the quotient of a product of three elliptic curves by a fixed point free action of Z 2 X Z 2. Its cohomology contains torsion classes in various degrees. The main technical novelty is in determining the multiplicative structure of the (torsion part of) the cohomology ring, and in particular showing that the cup product of secondmore » cohomology torsion elements goes non-trivially to the fourth cohomology. This specifies a non-Abelian, Heisenberg-type discrete symmetry group of the four-dimensional theory.« less

Type II string theory on Calabi-Yau manifolds with torsion and non-Abelian discrete gauge symmetries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braun, Volker; Cvetič, Mirjam; Donagi, Ron

Here, we provide the first explicit example of Type IIB string theory compactication on a globally defined Calabi-Yau threefold with torsion which results in a fourdimensional effective theory with a non-Abelian discrete gauge symmetry. Our example is based on a particular Calabi-Yau manifold, the quotient of a product of three elliptic curves by a fixed point free action of Z 2 X Z 2. Its cohomology contains torsion classes in various degrees. The main technical novelty is in determining the multiplicative structure of the (torsion part of) the cohomology ring, and in particular showing that the cup product of secondmore » cohomology torsion elements goes non-trivially to the fourth cohomology. This specifies a non-Abelian, Heisenberg-type discrete symmetry group of the four-dimensional theory.« less

THE MICROWAVE SPECTROSCOPY OF METHYL FORMATE IN THE SECOND TORSIONAL EXCITED STATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Kaori; Takamura, Kazunori; Sakai, Yusuke

2013-03-01

The cis-methyl formate molecule is a well known molecule found in interstellar space. Recently, rotational lines of methyl formate in the first CH{sub 3} torsional excited state were observed in Orion KL and W51e2. It is quite natural to observe methyl formate in even higher vibrational states considering the temperature estimated in Orion KL and W51e2. Maeda et al. reported results on the laboratory spectroscopy of methyl formate including the spectral analysis in its second CH{sub 3} torsional state. Their assignments were limited to a series of a-type R-branch lines and low K{sub a} b-type R-branch transitions, and many assignedmore » lines are excluded in the least-squares analysis. In the present study, we extended the line assignments of both the A- and E-species transitions in the second CH{sub 3} torsional state especially in the frequency region below the 120 GHz region. By combining the present assignments and those made by Maeda et al., 1951 transitions in total for the second CH{sub 3} torsional state, 1096 A-species transitions up to J = 39, and K{sub a} = 15 and 855 E-species transitions up to J = 35 and K{sub a} = 13, were least-squares analyzed by using the pseudo-principal-axis-method Hamiltonian with 42 parameters consisting of rotational, centrifugal distortion, and internal rotational constants in the second CH{sub 3} torsional state. In addition, 1012 transitions out of 1096 A-species transitions could also be least-squares analyzed by using Watson's A-reduced Hamiltonian with 43 parameters, which can serve to calculate the energy levels of the A-species lines of molecules with the CH{sub 3} internal rotation conveniently.« less

The Millimeter-Wave Spectrum of Methacrolein. Torsion-Rotation Effects in the Excited States

NASA Astrophysics Data System (ADS)

Zakharenko, Olena; Motiyenko, R. A.; Aviles Moreno, Juan-Ramon; Huet, T. R.

2015-06-01

Last year we reported the analysis of the rotational spectrum of s-trans conformer of methacrolein CH2=C(CH3)CHO in the ground vibrational state. In this talk we report the study of its low lying excited vibrational states. The study is based on room-temperature absorption spectra of methacrolein recorded in the frequency range 150 - 465 GHz using the spectrometer in Lille. The new results include assignment of the first excited torsional state (131 cm-1), and the joint analysis of the vt = 0 and vt = 1 states, that allowed us to improve the model in the frame of Rho-Axis-Method (RAM) Hamiltonian and to remove some strong correlations between parameters. Also we assigned the first excited vibrational state of the skeletal torsion mode (170 cm-1). The inverse sequence of A and E tunneling substates as well as anomalous A-E splittings observed for the rotational lines of vsk = 1 state clearly indicate a coupling between methyl torsion and skeletal torsion. However we were able to fit within experimental accuracy the rotational lines of vsk = 1 state using the RAM Hamiltonian. Because of the inversion of the A and E tunneling substates the rotational lines of the vsk = 1 states were assumed to belong to a virtual first excited torsional state. Finally, we assigned several low-Ka rotational transitions of the excited vibrational states above 200 cm-1 but their analysis is complicated by different rotation-vibration interactions. In particular there is an evidence of the Fermi-type resonance between the second excited torsional state and the first excited state of the in-plane skeletal bending mode (265 cm-1). Support from the French Laboratoire d'Excellence CaPPA (Chemical and Physical Properties of the Atmosphere) through contract ANR-10-LABX-0005 of the Programme d'Investissements d'Avenir is acknowledged. Zakharenko O. et al., 69th ISMS, 2014, TI01

A coupled two-dimensional main chain torsional potential for protein dynamics: generation and implementation.

PubMed

Li, Yongxiu; Gao, Ya; Zhang, Xuqiang; Wang, Xingyu; Mou, Lirong; Duan, Lili; He, Xiao; Mei, Ye; Zhang, John Z H

2013-09-01

Main chain torsions of alanine dipeptide are parameterized into coupled 2-dimensional Fourier expansions based on quantum mechanical (QM) calculations at M06 2X/aug-cc-pvtz//HF/6-31G** level. Solvation effect is considered by employing polarizable continuum model. Utilization of the M06 2X functional leads to precise potential energy surface that is comparable to or even better than MP2 level, but with much less computational demand. Parameterization of the 2D expansions is against the full main chain torsion space instead of just a few low energy conformations. This procedure is similar to that for the development of AMBER03 force field, except unique weighting factor was assigned to all the grid points. To avoid inconsistency between quantum mechanical calculations and molecular modeling, the model peptide is further optimized at molecular mechanics level with main chain dihedral angles fixed before the calculation of the conformational energy on molecular mechanical level at each grid point, during which generalized Born model is employed. Difference in solvation models at quantum mechanics and molecular mechanics levels makes this parameterization procedure less straightforward. All force field parameters other than main chain torsions are taken from existing AMBER force field. With this new main chain torsion terms, we have studied the main chain dihedral distributions of ALA dipeptide and pentapeptide in aqueous solution. The results demonstrate that 2D main chain torsion is effective in delineating the energy variation associated with rotations along main chain dihedrals. This work is an implication for the necessity of more accurate description of main chain torsions in the future development of ab initio force field and it also raises a challenge to the development of quantum mechanical methods, especially the quantum mechanical solvation models.

Effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy

NASA Astrophysics Data System (ADS)

Wu, Wenqian; Guo, Lin; Liu, Bin; Ni, Song; Liu, Yong; Song, Min

2017-12-01

The effects of torsional deformation on the microstructures and mechanical properties of a CoCrFeNiMo0.15 high-entropy alloy have been investigated. The torsional deformation generates a gradient microstructure distribution due to the gradient torsional strain. Both dislocation activity and deformation twinning dominated the torsional deformation process. With increasing the torsional equivalent strain, the microstructural evolution can be described as follows: (1) formation of pile-up dislocations parallel to the trace of {1 1 1}-type slip planes; (2) formation of Taylor lattices; (3) formation of highly dense dislocation walls; (3) formation of microbands and deformation twins. The extremely high deformation strain (strained to fracture) results in the activation of wavy slip. The tensile strength is very sensitive to the torsional deformation, and increases significantly with increasing the torsional angle.

Two methods for damping torsional vibrations in DFIG-based wind generators using power converters

NASA Astrophysics Data System (ADS)

Zhao, Zuyi; Lu, Yupu; Xie, Da; Yu, Songtao; Wu, Wangping

2017-01-01

This paper proposes novel damping control algorithms by using static synchronous compensator (STATCOM) and energy storage system (ESS) to damp torsional vibrations in doubly fed induction generator (DFIG) based wind turbine systems. It first analyses the operating characteristics of STATCOM and ESS for regulating power variations to increase grid voltage stability. Then, new control strategies for STATCOM and ESS are introduced to damp the vibrations. It is followed by illustration of their effectiveness to damp the drive train torsional vibrations of wind turbines, which can be caused by grid disturbances, such as voltage sags and frequency fluctuations. Results suggest that STATCOM is a promising technology to mitigate the torsional vibrations caused by grid voltage sags. By contrast, the ESS connected to the point of common coupling (PCC) of wind turbine systems shows even obvious advantages because of its capability of absorbing/releasing both active and reactive power. It can thus be concluded that STATCOM is useful for stabilizing power system voltage fluctuations, and ESS is more effective both in regulating PCC voltage fluctuations and damping torsional vibrations caused by grid voltage frequency fluctuations.

LISA technology development using the UF precision torsion pendulum

NASA Astrophysics Data System (ADS)

Apple, Stephen; Chilton, Andrew; Olatunde, Taiwo; Ciani, Giacomo; Mueller, Guido; Conklin, John

2015-04-01

LISA will directly observe low-frequency gravitational waves emitted by sources ranging from super-massive black hole mergers to compact galactic binaries. A laser interferometer will measure picometer changes in the distances between free falling test masses separated by millions of kilometers. A test mass and its associated sensing, actuation, charge control and caging subsystems are referred to as a gravitational reference sensor (GRS). The demanding acceleration noise requirement for the LISA GRS has motivated a rigorous testing campaign in Europe and a dedicated technology mission, LISA Pathfinder, scheduled for launch in the fall of 2015. At the University of Florida we are developing a nearly thermally noise limited torsion pendulum for testing GRS technology enhancements that may improve the performance and/or reduce the cost of the LISA GRS. This experimental facility is based on the design of a similar facility at the University of Trento, and consists of a vacuum enclosed torsion pendulum that suspends mock-ups of the LISA test masses, surrounded by electrode housings. Some of the technologies that will be demonstrated by this facility include a novel TM charge control scheme based on ultraviolet LEDs, an all-optical TM position and attitude sensor, and drift mode operation. This presentation will describe the design of the torsion pendulum facility, its current acceleration noise performance, and the status of the GRS technologies under development.

[Axial torsion and gangrene of Meckel's diverticulum: case report].

PubMed

2015-01-01

Meckel's diverticulum (MD) is the most prevalent congenital anomaly of small intestine. It develops due to the incomplete obliteration of omphalomesenterict duct which normally undergoes obliteration during the seventh week of gestation. In the majority of cases MD is asymptomatic but it may cause various complications, such as bleeding, intestinal obstruction and inflammation. Cases of umbilical sinuses, fistulas and neoplasms related with MD have been reported, but extremely rare gangrene due to its axial torsion, especially in children, as is the case of our patients. An 11-year-old boy admitted to hospital due to 24 hours epigastric pain, vomiting and malaise. After a complete physical examination, and appropriate pre-surgical laboratory and radiographic tests, surgical exploration was performed with a midline abdominal incision. On 60th cm proximal to the ileocecal valve we found a long and in a narrow based ganrenous MD with axial torsion and fibrotic cord extending from the tip of MD to the ileal mesentery. Surrounding ileum had normal appearance. A demarcation and subsequent resection of MD and the surrounding ileum was performed with end-to-end ileal anastomosis. Postoperative recovery was successful and the patient was discharged after six days. Axial torsion of MD is presented with non-specific abdominal symptoms and difficult preoperative diagnosis. The choice of diagnosis and therapy is surgical exploration and resection of MD.

Lateral-Torsional Buckling Instability Caused by Individuals Walking on Wood Composite I-Joists

NASA Astrophysics Data System (ADS)

Villasenor Aguilar, Jose Maria

Recent research has shown that a significant number of the falls from elevation occur when laborers are working on unfinished structures. Workers walking on wood I-joists on roofs and floors are prone to fall hazards. Wood I-joists have been replacing dimension lumber for many floor systems and a substantial number of roof systems in light-frame construction. Wood I-joists are designed to resist axial stresses on the flanges and shear stresses on the web while minimizing material used. However, wood I-joists have poor resistance to applied lateral and torsional loads and are susceptible to lateral-torsional buckling instability. Workers walking on unbraced or partially braced wood I-joists can induce axial and lateral forces as well as twist. Experimental testing demonstrated that workers cause lateral-torsional buckling instability in wood I-joists. However, no research was found related to the lateral-torsional buckling instability induced by individuals walking on the wood I-joists. Furthermore, no research was found considering the effects of the supported end conditions and partial bracing in the lateral-torsional buckling instability of wood I-joists. The goal of this research was to derive mathematical models to predict the dynamic lateral-torsional buckling instability of wood composite I-joists loaded by individuals walking considering different supported end conditions and bracing system configurations. The dynamic lateral-torsional buckling instability was analyzed by linearly combining the static lateral-torsional buckling instability with the lateral bending motion of the wood Ijoists. Mathematical models were derived to calculate the static critical loads for the simply supported end condition and four wood I-joist hanger supported end conditions. Additionally, mathematical models were derived to calculate the dynamic maximum lateral displacements and positions of the individual walking on the wood Ijoists for the same five different supported end

Tuned dynamics stabilizes an idealized regenerative axial-torsional model of rotary drilling

NASA Astrophysics Data System (ADS)

Gupta, Sunit K.; Wahi, Pankaj

2018-01-01

We present an exact stability analysis of a dynamical system idealizing rotary drilling. This system comprises lumped parameter axial-torsional modes of the drill-string coupled via the cutting forces and torques. The kinematics of cutting is modeled through a functional description of the cut surface which evolves as per a partial differential equation (PDE). Linearization of this model is straightforward as opposed to the traditional state-dependent delay (SDDE) model and both the approaches result in the same characteristic equation. A systematic study on the key system parameters influencing the stability characteristics reveals that torsional damping is very critical and stable drilling is, in general, not possible in its absence. The stable regime increases as the natural frequency of the axial mode approaches that of the torsional mode and a 1:1 internal resonance leads to a significant improvement in the system stability. Hence, from a practical point of view, a drill-string with 1:1 internal resonance is desirable to avoid vibrations during rotary drilling. For the non-resonant case, axial damping reduces the stable range of operating parameters while for the resonant case, an optimum value of axial damping (equal to the torsional damping) results in the largest stable regime. Interestingly, the resonant (tuned) system has a significant parameter regime corresponding to stable operation even in the absence of damping.

Total curvature and total torsion of knotted random polygons in confinement

NASA Astrophysics Data System (ADS)

Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

2018-04-01

Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

Torsional vibration characteristic study of the grid-connected DFIG wind turbine

NASA Astrophysics Data System (ADS)

Yu, Songtao; Xie, Da; Wu, Wangping; Gu, Chenghong; Li, Furong

2017-01-01

This paper studies the torsional vibration characteristics of the grid-connected doubly-fed induction generator (DFIG) wind turbine by small signal analysis method. Firstly a detailed small-signal stability union model of the grid-connected DFIG wind turbine is developed, including the mechanical system and electrical system. To study the dynamic characteristic of the blade, gearbox, low speed and high speed shafts, a three mass shaft model for the mechanical system is adopted. At the same time, small signal models of DFIG, the voltage source converter (VSC) and the transmission line of the electrical system are developed respectively. Then, through calculating the eigenvalues of the state matrix A and the corresponding participation factors, the modal analysis is conducted in the shaft torsional vibration issues. And the impact of the system parameters including the series compensation capacitor, the flat-wave reactor, the PI parameters, especially the speed controller of generator rotor on shaft torsional vibration are discussed. The results show that the speed controller strengthens association between the mechanical system and the electrical system, and also produces a low-frequency oscillation mode.

Analytical and finite element simulation of a three-bar torsion spring

NASA Astrophysics Data System (ADS)

Rădoi, M.; Cicone, T.

2016-08-01

The present study is dedicated to the innovative 3-bar torsion spring used as suspension solution for the first time at Lunokhod-1, the first autonomous vehicle sent for the exploration of the Moon in the early 70-ies by the former USSR. The paper describes a simple analytical model for calculation of spring static characteristics, taking into account both torsion and bending effects. Closed form solutions of this model allows quick and elegant parametric analysis. A comparison with a single torsion bar with the same stiffness reveal an increase of the maximum stress with more than 50%. A 3D finite element (FE) simulation is proposed to evaluate the accuracy of the analytical model. The model was meshed in an automated pattern (sweep for hubs and tetrahedrons for bars) with mesh morphing. Very close results between analytical and numerical solutions have been found, concluding that the analytical model is accurate. The 3-D finite element simulation was used to evaluate the effects of design details like fillet radius of the bars or contact stresses in the hex hub.

Effect of Torsion on the Friction Factor of Helical Pipe Flow

NASA Astrophysics Data System (ADS)

Kumer Datta, Anup; Yanase, Shinichiro; Hayamizu, Yasutaka; Kouchi, Toshinori; Nagata, Yasunori; Yamamoto, Kyoji

2017-06-01

Three-dimensional direct numerical simulations of a viscous incompressible fluid flow through a helical pipe with a circular cross section were conducted for three Reynolds numbers, Re (= 80, 300, and 1000), and two nondimensional curvatures, δ (= 0.1 and 0.05), over a wide range of torsion parameters, β (= nondimensional torsion/√{2δ } ), from 0.02 to 2.8. Well-developed axially invariant regions were obtained where the friction factors were calculated, in good agreement with the experimental data obtained by Yamamoto et al. [https://doi.org/10.1016/0169-5983(95)00022-6, Fluid Dyn. Res. 16, 237 (1995)]. It was found that the friction factor sharply increases as β increases from zero, then decreases after taking a maximum, and finally slowly approaches that of a straight pipe when β tends to infinity. It is interesting that a peak of the friction factor exists in the region 0.2 ≤ β ≤ 0.3 for all the Reynolds numbers and curvatures studied in the present paper, which manifests the importance of the torsion parameter in helical pipe flow.

Torsion of Meckel's Diverticulum in a Child

PubMed Central

Nose, Satoko; Okuyama, Hiroomi; Sasaki, Takashi; Nishimura, Mika

2013-01-01

Meckel's diverticulum (MD) is a common congenital anomaly of the gastrointestinal tract, the majority of cases of which are clinically silent. Patients with asymptomatic MD can unexpectedly develop acute abdominal pain. Making a diagnosis of MD is often difficult due to the lack of specific symptoms caused by this condition. Diagnostic laparotomy can be useful for making an accurate and prompt diagnosis of complicated MD. We herein describe a pediatric case of torsion of a MD in whom we performed laparoscopic-assisted emergency surgery. The patient was an 11-year-old male who developed sudden severe right lower abdominal pain. Clinical and laboratory findings were suggestive of appendicitis, however computed tomography scans showed a large cystic mass in the pelvis. Exploratory laparoscopy led to a diagnosis of torsion of a MD, and wedge resection of the gangrenous MD was performed through an umbilical port incision. The patient's postoperative course was uneventful. We conclude that diagnostic laparoscopy followed by laparoscopy-assisted Meckel's diverticulectomy via an umbilical incision is useful in the treatment of acute abdomen caused by MD. PMID:23466748

Improving Tensile and Compressive Properties of an Extruded AZ91 Rod by the Combined Use of Torsion Deformation and Aging Treatment

PubMed Central

Song, Bo; Wang, Chunpeng; Guo, Ning; Pan, Hucheng; Xin, Renlong

2017-01-01

In this study, AZ91 magnesium alloy rods were used to investigate the effects of torsion deformation on microstructure and subsequent aging behavior. Extruded AZ91 rod has a uniform microstructure and typical fiber texture. Torsion deformation can generate a gradient microstructure on the cross-section of the rod. After torsion, from the center to the edge in the cross-section of the rod, both stored dislocations and area fraction of {10-12} twins gradually increase, and the basal pole of the texture tends to rotate in the ED direction. Direct aging usually generates coarse discontinuous precipitates and fine continuous precipitates simultaneously. Both twin structures and dislocations via torsion deformation can be effective microstructures for the nucleation of continuous precipitates during subsequent aging. Thus, aging after torsion can promote continuous precipitation and generate gradient precipitation characteristics. Both aging treatment and torsion deformation can reduce yield asymmetry, and torsion deformation enhances the aging hardening effect by promoting continuous precipitation. Therefore, combined use of torsion deformation and aging treatment can effectively enhance the yield strength and almost eliminate the yield asymmetry of the present extruded AZ91 rod. Finally, the relevant mechanisms are discussed. PMID:28772638

Thermal study of longitudinal and torsional ultrasound phacoemulsification: tracking the temperature of the corneal surface, incision, and handpiece.

PubMed

Jun, Bokkwan; Berdahl, John P; Kim, Terry

2010-05-01

To evaluate the change and difference in the corneal surface, incision, and handpiece temperatures during longitudinal and torsional ultrasound (US) phacoemulsification with standard incisions (2.75 mm) and microincisions (2.20 mm) and the thermal effect on wounds. Department of Ophthalmology, Duke University, Durham, North Carolina, USA. In this prospective study, human cadaver eyes had simulated phacoemulsification. Group 1 had a 2.75 mm incision with 100% longitudinal US; Group 2, a 2.20 mm incision with 100% longitudinal US; Group 3, a 2.75 mm incision with 100% torsional US; and Group 4, a 2.20 mm incision with 100% torsional US. During phacoemulsification, the corneal incision was evaluated by surgical microscopy and scanning electron microscopy (SEM) and images of the corneal surface, incision, and handpiece were captured with an infrared camera. Twelve eyes (3 each group) were evaluated. The maximum incision temperature was higher in the longitudinal groups than in the torsional groups. With the same US modality, the maximum microincision temperature was higher than the maximum standard incision temperature. After application of full power for 40 seconds, wound burn was observed in all eyes in the longitudinal groups and no eyes in the torsional groups. On SEM, there was more extensive loss of Descemet membrane in the longitudinal groups than in the torsional groups. Incision temperature was influenced by US modality and was significantly lower with torsional US than with longitudinal US. Using torsional US with smaller incisions may decrease the risk for wound burn in eyes with denser cataracts. (c) 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

TANGLE: Two-Level Support Vector Regression Approach for Protein Backbone Torsion Angle Prediction from Primary Sequences

PubMed Central

Song, Jiangning; Tan, Hao; Wang, Mingjun; Webb, Geoffrey I.; Akutsu, Tatsuya

2012-01-01

Protein backbone torsion angles (Phi) and (Psi) involve two rotation angles rotating around the Cα-N bond (Phi) and the Cα-C bond (Psi). Due to the planarity of the linked rigid peptide bonds, these two angles can essentially determine the backbone geometry of proteins. Accordingly, the accurate prediction of protein backbone torsion angle from sequence information can assist the prediction of protein structures. In this study, we develop a new approach called TANGLE (Torsion ANGLE predictor) to predict the protein backbone torsion angles from amino acid sequences. TANGLE uses a two-level support vector regression approach to perform real-value torsion angle prediction using a variety of features derived from amino acid sequences, including the evolutionary profiles in the form of position-specific scoring matrices, predicted secondary structure, solvent accessibility and natively disordered region as well as other global sequence features. When evaluated based on a large benchmark dataset of 1,526 non-homologous proteins, the mean absolute errors (MAEs) of the Phi and Psi angle prediction are 27.8° and 44.6°, respectively, which are 1% and 3% respectively lower than that using one of the state-of-the-art prediction tools ANGLOR. Moreover, the prediction of TANGLE is significantly better than a random predictor that was built on the amino acid-specific basis, with the p-value<1.46e-147 and 7.97e-150, respectively by the Wilcoxon signed rank test. As a complementary approach to the current torsion angle prediction algorithms, TANGLE should prove useful in predicting protein structural properties and assisting protein fold recognition by applying the predicted torsion angles as useful restraints. TANGLE is freely accessible at http://sunflower.kuicr.kyoto-u.ac.jp/~sjn/TANGLE/. PMID:22319565

Predisposing factors for colonic torsion/volvulus in dogs: a retrospective study of six cases (1992-2010).

PubMed

Gagnon, Dominique; Brisson, Brigitte

2013-01-01

The purposes of this retrospective study were to review cases of colonic torsion/volvulus between July 1992 and August 2010 and to determine if any predisposing factors exist for the development of this condition. Six dogs were diagnosed with colonic torsion/volvulus during the study period. Four dogs had a history of previous gastric dilation-volvulus (GDV) with prophylactic gastropexy. Three of six dogs diagnosed with colonic torsion/volvulus had large intestinal entrapment and strangulation around the gastropexy site at the time of surgery. The history, clinical signs, physical examination, and radiologic findings were not specific for colonic torsion/volvulus in any dog. Early exploratory laparotomy was indicated to confirm the diagnosis and perform surgical correction of the affected bowel segments. Three of five dogs that underwent surgery had a left abdominal wall colopexy performed. All five dogs that underwent surgery in this study survived postoperatively. One patient was euthanized without surgical intervention. Results suggest that colonic torsion/volvulus should be considered in any large-breed dog with nonspecific gastrointestinal clinical signs and a history of previous gastropexy. Early recognition and prompt treatment of this condition may result in a good outcome.

Femoral Shaft Torsion in Injured and Uninjured Ballet Dancers and Its Association with Other Hip Measures: A Cross-sectional Study.

PubMed

Hafiz, Eliza; Hiller, Claire E; Nicholson, Leslie L; Nightingale, Elizabeth J; Grimaldi, Alison; Refshauge, Kathryn M

2016-03-01

Low range femoral torsion, termed "lateral shaft torsion," has been associated with greater range of hip external rotation and turnout in dancers. It is also hypothesized that achieving greater turnout at the hip minimizes torsion at the knee, shank, ankle, and foot, and consequently reduces incidence of lower limb injuries. The primary aims of this study were to investigate: 1. differences in range of femoral shaft torsion between dancers with and without lower limb injuries; and 2. the relationship between femoral shaft torsion, hip external rotation range, and turnout. A secondary aim was to examine the relationship between femoral shaft torsion and other hip measures: hip strength, lower limb joint hypermobility, hip stability, and foot progression angle, as explanatory variables. Demographic, dance, and injury data were collected, along with physical measures of femoral shaft torsion, hip rotation range of motion, and turnout. Hip strength, control, lower limb hypermobility, and foot progression angle were also measured. Eighty female dancers, 50 with lower limb injury (20.7 ± 4.8 years of age) and 30 without lower limb injury (17.8 ± 4.1 years of age), participated in the study. There was no difference in range of femoral shaft torsion between the groups (p = 0.941). Femoral shaft torsion was weakly correlated with range of hip external rotation (r = -0.034, p = 0.384) and turnout (r = -0.066, p = 0.558). Injured dancers had a significantly longer training history than non-injured dancers (p = 0.001). It was concluded that femoral shaft torsion does not appear to be associated with the overall incidence of lower limb injury in dancers or to be a primary factor influencing extent of turnout in this population.

Effect of dexmedetomidine on testicular torsion/detorsion damage in rats.

PubMed

Hanci, Volkan; Erol, Bülent; Bektaş, Sibel; Mungan, Görkem; Yurtlu, Serhan; Tokgöz, Hüsnü; Can, Murat; Ozkoçak Turan, Işil

2010-01-01

We assessed the antioxidant activity of dexmedetomidine (DEX) during an ischemic period in a rat model of testicular torsion/detorsion (T/DT) by using biochemical and histopathological methods. Wistar Albino male rats weighing 250-300 g were divided into three groups: sham (group S, n = 7); torsion/detorsion (group T/DT, n = 7), and DEX treatment (group DEX, n = 7). In the T/DT group, right testes were rotated 720 degrees for 1 h. Group S served for normal basal values. Rats in group T/DT were operated to make T/DT, this group served as a control group. Group DEX received intraperitoneal DEX 10 microg . kg(-1) after the 30-min torsion period. For measurement of total antioxidant enzyme activities and malondialdehyde (MDA) levels, testes of 7 animals in each group were excised after 4 h of reperfusion. Germ cell apoptosis was evaluated using the apoptosis protease-activating factor 1 (APAF-1) antibody in all groups and also on the expressions of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) were assessed within the bilateral testes. Mean MDA levels in group T/DT were significantly higher than in groups S and DEX (p < 0.05). There were also significant decreases in mean total antioxidant activities in group T/DT when compared to groups S and DEX (p < 0.05). These values were significantly higher in group DEX than group T/DT. Germ cell apoptosis, eNOS and iNOS levels were significantly higher in group T/DT when compared to groups S and DEX (p < 0.05). DEX treatment has potential biochemical and histopathological benefits by preventing ischemia/reperfusion-related cellular damage in an experimental testicular torsion model. Preference of DEX for anesthesia during the detorsion procedure may attenuate ischemia-reperfusion injury. Copyright 2010 S. Karger AG, Basel.

Direct observation of vibrational energy dispersal via methyl torsions.

PubMed

Gardner, Adrian M; Tuttle, William D; Whalley, Laura E; Wright, Timothy G

2018-02-28

Explicit evidence for the role of methyl rotor levels in promoting energy dispersal is reported. A set of coupled zero-order vibration/vibration-torsion (vibtor) levels in the S 1 state of para -fluorotoluene ( p FT) are investigated. Two-dimensional laser-induced fluorescence (2D-LIF) and two-dimensional zero-kinetic-energy (2D-ZEKE) spectra are reported, and the assignment of the main features in both sets of spectra reveals that the methyl torsion is instrumental in providing a route for coupling between vibrational levels of different symmetry classes. We find that there is very localized, and selective, dissipation of energy via doorway states, and that, in addition to an increase in the density of states, a critical role of the methyl group is a relaxation of symmetry constraints compared to direct vibrational coupling.

Acoustic Emission Monitoring of Multicell Reinforced Concrete Box Girders Subjected to Torsion

PubMed Central

Bagherifaez, Marya; Behnia, Arash; Majeed, Abeer Aqeel; Hwa Kian, Chai

2014-01-01

Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis. PMID:25180203

Micromechanical torsional digital-to-analog converter for open-loop angular positioning applications