TLS Model Research Articles

Multi-Sensor Data Fusion for 3D Reconstruction of Complex Structures: A Case Study on a Real High Formwork Project

As the most comprehensive document types for the recording and display of real-world information regarding construction projects, 3D realistic models are capable of recording and displaying simultaneously textures and geometric shapes in the same 3D scene. However, at present, the documentation for much of construction infrastructure faces significant challenges. Based on TLS, GNSS/IMU, mature photogrammetry, a UAV platform, computer vision technologies, and AI algorithms, this study proposes a workflow for 3D modeling of complex structures with multiple-source data. A deep learning LoFTR network was used first for image matching, which can improve matching accuracy. Then, a NeuralRecon network was employed to generate a 3D point cloud with global consistency. GNSS information was used to reduce search space in image matching and produce an accurate transformation matrix between the image scene and the global reference system. In addition, to enhance the effectiveness and efficiency of the co-registration of the two-source point clouds, an RPM-net was used. The proposed workflow processed the 3D laser point cloud and UAV low-altitude multi-view image data to generate a complete, accurate, high-resolution, and detailed 3D model. Experimental validation on a real high formwork project was carried out, and the result indicates that the generated 3D model has satisfactory accuracy with a registration error value of 5 cm. Model comparison between the TLS, image-based, data fusion 1 (using the common method), and data fusion 2 (using the proposed method) models were conducted in terms of completeness, geometrical accuracy, texture appearance, and appeal to professionals. The results denote that the generated 3D model has similar accuracy to the TLS model yet also provides a complete model with a photorealistic appearance that most professionals chose as their favorite.

INTEGRATED 3D SURVEY FOR THE DOCUMENTATION AND VISUALIZATION OF A ROCK-CUT UNDERGROUND BUILT HERITAGE

Abstract. The research presented here is part of an on-going research focused on the 3D documentation of rock-cut Underground Built Heritage with a complex morphology and characterised by narrow spaces, the Hypogeum of Calaforno (province of Ragusa, Sicily). It is one of the most interesting prehistoric monuments in Sicily in terms of size and unique rock-cut architecture. Various digital techniques have been tested over the years on the site, to represent its spatiality, such as Laser Scanner and Structure from Motion. The proposed methodological approach for the knowledge and the documentation of this archaeological site is based on an interdisciplinary approach involving archaeological and engineering disciplines. This paper focuses on the use of expeditious techniques such as iMMS (indoor Mobile Mapping Systems) based on SLAM (Simultaneous Localization and Mapping) and on the comparison of different surveying equipment in order to verify data quality and accuracy, as well as the inherent advantages of using one technology over another in relation to the characteristics of the site. Through the global verification of TLS and SLAM model reliability, we maintain that such research can contribute to enriching the protocols surrounding the archaeological investigation of sites characterized by complex morphology, irregular surfaces, narrow spaces, specific chromatic features, scarce or total lack of lighting, and physical obstacles.

Ruxolitinib Rescues Mice from Lethal Interferon Beta Toxicity and TLS

Introduction. Oncolytic Vesicular Stomatitis Virus expressing human interferon beta and the sodium iodide symporter reporter gene (VSV-hIFNβ-NIS) is in Phase 1 clinical testing for systemic administration in patients with relapsed multiple myeloma, acute myeloid leukemia and T cell lymphoma (NCT03017820). Local production of interferon β enhances virotherapy by activating the immune system, and restricts viral replication in normal cells by activating IFN induced antiviral responses. Thus, the virus propagates efficiently in IFN non-responsive cancer cells but is constrained in IFN responsive cells. Cancer cells that are defective in their viral sensing and IFN response pathways are exquisitely sensitive to VSV-IFNβ-NIS oncolysis, cumulating in tumor lysis syndrome and IFNβ induced toxicity in the MPC-11 mouse plasmacytoma model. Here, we evaluated the feasibility of using ruxolitinib, a clinically approved Jak1/2 inhibitor, to rescue mice from virotherapy induced TLS and IFNβ toxicity.Methods. To characterize IFNβ toxicity in the absence of TLS , varying levels of mIFNβ were achieved in the blood of mice by intramuscular injection of an AAV1 vector encoding mIFNβ. For the virotherapy-associated TLS and IFNβ toxicity model, Balb/c mice with subcutaneous MPC-11 murine plasmacytoma were given one intravenous administration of VSV-mIFNβ-NIS. To determine whether the Jak/STAT inhibitor ruxolitonib could impact IFNβ toxicity, mice were treated with ruxolitinib (2 mg/dose by oral gavage) given twice a day for 10 days. All mice were monitored for adverse clinical signs andtumor size. Plasma IFNβ levels, CBC and comprehensive clinical chemistry panels were analyzed at necropsy.Results. There was a dose dependent increase in plasma IFNβ levels with increasing doses of AAV1-mIFNβ given intramuscularly to mice. Adverse clinical signs were seen in mice given high doses of AAV1-mIFNβ. There was a good correlation between IFNβ and AST or ALT levels. High circulating levels of IFNβ resulted in elevation in transaminases, thrombocytopenia, anemia and lymphopenia. IFN receptor defective mice were completely resistant to these toxic effects even with blood levels of >80,000 pg/ml IFNβ. Nontumor bearing Balb/c mice were shown to tolerate high IV doses of VSV-mIFNβ-NIS with transient lymphopenia and transaminases. In Balb/c mice with IFN nonresponsive MPC-11 tumors that support robust viral replication, VSV-mIFNβ-NIS therapy was highly effective for tumor control, but resulted in TLS and IFNβ toxicity, requiring early euthanasia of mice. Mice given VSV and a neutralizing anti-IFNR antibody did not show any adverse clinical signs due to IFNβ toxicity but control of tumor growth was significantly impaired in comparison to virus treatment alone. In contrast combination treatment of mice VSV and ruxolitinib resulted in reversal of lethal IFNβ toxicity without loss of effective tumor control.Conclusions. Our data demonstrate that ruxolitinib reverses the toxicity of IFNβ seen following highly efficacious VSV-IFNβ-NIS virotherapy in the MPC-11 plasmacytoma model. Clinical evaluation of this promising combination is warranted. [Display omitted] DisclosuresPeng:Vyriad: Equity Ownership; Imanis Life Sciences: Employment, Equity Ownership. Russell:Vyriad: Equity Ownership; Imanis Life Sciences: Equity Ownership.

Application of a proposed TLS model in a Lean Productive System

The current market, becoming more rigid, forces companies to search continuously for innovation and improvement of their processes and products as a way to keep competitive and gain strategic advantages. Due to the global economic crisis, more and more companies try an approach through new management methodologies that allow better performances in terms of earning, profit and cost reduction. The present article proposes an integrated TOC (Theory of Constraints), Lean and Six-Sigma (TLS) model, with the objective of improving continuously a productive system, although it shows flexibility to be applied in other kinds of systems. The model synergistically integrate the best practices found in existing TOC, Lean and Six-Sigma models. The proposed model derivatives mainly from Eliyahu Goldratt’s TOC model of the “5 focus steps” and TLS model “Ultimate Improvement Cycle”, developed by Bob Sproull. The proposed TLS model was tested on an important Portuguese Manufacture. The implementation of a first continuous improvement cycle was completed and a second cycle began. The main results obtained by the implementation of the TLS model were extremely satisfactory.

PRELIMINARY TESTS OF A NEW LOW-COST PHOTOGRAMMETRIC SYSTEM

Abstract. This paper presents preliminary tests of a new low-cost photogrammetric system for 4D modelling of large scale areas for civil engineering applications. The system consists of five stand-alone units. Each of the units is composed of a Raspberry Pi 2 Model B (RPi2B) single board computer connected to a PiCamera Module V2 (8 MP) and is powered by a 10 W solar panel. The acquisition of the images is performed automatically using Python scripts and the OpenCV library. Images are recorded at different times during the day and automatically uploaded onto a FTP server from where they can be accessed for processing. Preliminary tests and outcomes of the system are discussed in detail. The focus is on the performance assessment of the low-cost sensor and the quality evaluation of the digital surface models generated by the low-cost photogrammetric systems in the field under real test conditions. Two different test cases were set up in order to calibrate the low-cost photogrammetric system and to assess its performance. First comparisons with a TLS model show a good agreement.

TESTING THE LOW-COST RPAS POTENTIAL IN 3D CULTURAL HERITAGE RECONSTRUCTION

Abstract. In order to analyze the potential as well as the limitations of low-cost RPAS photogrammetric systems for architectural cultural heritage reconstruction, some tests were performed by a small RPAS equipped with an ultralight camera. The tests were carried out in a site of remarkable historical interest. A great amount of images were taken with camera’s optical axis in vertical and oblique position. Images were processed by the commercial software PhotoScan of Agisoft and numerous models were realized, each of them was compared with an accurate TLS model used as a reference. The test, despite some problems found, has provided good results in terms of accuracy (average error <2cm) and reliability.

Temperature Variation of Ultralow Frequency Modes and Mean Square Displacements in Solid Lasamide (Diuretic Drug) Studied by 35Cl-NQR, X-ray and DFT/QTAIM

The application of combined (35)Cl-NQR/X-ray/DFT/QTAIM methods to study the temperature variation of anisotropic displacement parameters and ultralow frequency modes of anharmonic torsional vibrations in the solid state is illustrated on the example of 2,4-dichloro-5-sulfamolybenzoic acid (lasamide, DSBA) which is a diuretic and an intermediate in the synthesis of furosemide and thus its common impurity. The crystallographic structure of lasamide is solved by X-ray diffraction and refined to a final R-factor of 3.06% at room temperature. Lasamide is found to crystallize in the triclinic space group P-1, with two equivalent molecules in the unit cell a = 7.5984(3) Å, b = 8.3158(3) Å, c = 8.6892(3) Å; α = 81.212(3)°, β = 73.799(3)°, γ = 67.599(3)°. Its molecules form symmetric dimers linked by two short and linear intermolecular hydrogen bonds O-H···O (O-H···O = 2.648 Å and ∠OHO = 171.5°), which are further linked by weaker and longer intermolecular hydrogen bonds N-H···O (N-H···O = 2.965 Å and ∠NHO = 166.4°). Two (35)Cl-NQR resonance frequencies, 36.899 and 37.129 MHz, revealed at room temperature are assigned to chlorine sites at the ortho and para positions, relative to the carboxyl functional group, respectively. The difference in C-Cl(1) and C-Cl(2) bond lengths only slightly affects the value of (35)Cl-NQR frequencies, which results mainly from chemical inequivalence of chlorine atoms but also involvement in different intermolecular interactions pattern. The smooth decrease in both (35)Cl-NQR frequencies with increasing temperature in the range of 77-300 K testifies to the averaging of EFG tensor at each chlorine site due to anharmonic torsional vibrations. Lasamide is thermally stable; no temperature-induced release of chlorine or decomposition of this compound is detected. The temperature dependence of ultralow frequency modes of anharmonic small-angle internal torsional vibrations averaging EFG tensor and mean square angle displacements at both chlorine sites is derived from the (35)Cl-NQR temperature dependence. The frequencies of torsional vibrations higher for the para site than the ortho site are in good agreement with those obtained from thermal parameters obtained from X-ray studies. The mean square angle displacements are in good agreement with those estimated from X-ray data with the use of the TLS model. The detailed DFT/QTAIM analysis suggests that the interplay between different hydrogen bonds in adjacent molecules forming dimers is responsible for the differences in flexibility of the carboxyl and sulphonamide substituents as well as both C-Cl(1) and C-Cl(2) bonds. Three ultralow wavenumber modes of internal vibrations in Raman and IR spectra obtained at the B3LYP/6-311++G(d,p) level close to those obtained within the TLS model suggest that internal and external modes of vibrations are not well separated.

PDB_REDO: constructive validation, more than just looking for errors.

Developments of the PDB_REDO procedure that combine re-refinement and rebuilding within a unique decision-making framework to improve structures in the PDB are presented. PDB_REDO uses a variety of existing and custom-built software modules to choose an optimal refinement protocol (e.g. anisotropic, isotropic or overall B-factor refinement, TLS model) and to optimize the geometry versus data-refinement weights. Next, it proceeds to rebuild side chains and peptide planes before a final optimization round. PDB_REDO works fully automatically without the need for intervention by a crystallographic expert. The pipeline was tested on 12 000 PDB entries and the great majority of the test cases improved both in terms of crystallographic criteria such as R(free) and in terms of widely accepted geometric validation criteria. It is concluded that PDB_REDO is useful to update the otherwise `static' structures in the PDB to modern crystallographic standards. The publically available PDB_REDO database provides better model statistics and contributes to better refinement and validation targets.

Structure of an orthorhombic form of xylanase II fromTrichoderma reeseiand analysis of thermal displacement

An orthorhombic crystal of xylanase II from Trichoderma reesei was grown in the presence of sodium iodide. Crystal structures at atomic resolution were determined at 100 and 293 K. Protein molecules were aligned along a crystallographic twofold screw axis, forming a helically extended polymer-like chain mediated by an iodide ion. The iodide ion connected main-chain peptide groups between two adjacent molecules by an N-H...I-...H-N hydrogen-bond bridge, thus contributing to regulation of the molecular arrangement and suppression of the rigid-body motion in the crystal with high diffraction quality. The structure at 293 K showed considerable thermal motion in the loop regions connecting the beta-strands that form the active-site cleft. TLS model analysis of the thermal motion and a comparison between this structure and that at 100 K suggest that the fluctuation of these loop regions is attributable to the hinge-like movement of the beta-strands.

Structural phase transition of monoclinic crystals of hen egg-white lysozyme

Two monoclinic crystals (space group P2(1)) of hen egg-white lysozyme, a type I crystal grown at room temperature in a D2O solution with pD 4.5 containing 2%(w/v) sodium nitrate and a type II crystal grown at 313 K in a 10%(w/v) sodium chloride solution with pH 7.6, were each transformed into another monoclinic crystal with the same space group by dehydration-induced phase transition. Changes in X-ray diffraction were recorded to monitor the progress of the crystal transformation, which started with the appearance of diffuse streaks. In both crystals, the intensity of h + l odd reflections gradually weakened and finally disappeared on completion of the transformation. X-ray diffraction in the intermediate state indicated the presence of lattices of both the native and transformed crystals. In the native type I crystal, two alternate conformations were observed in the main chain of the region Gly71-Asn74. One conformer bound a sodium ion which was replaced with a water molecule in the other conformer. In the transformed crystal, the sodium ion was removed and the main-chain conformation of this region was converted to that of the water-bound form. The transformed crystal diffracted to a higher resolution than the native crystal, while the peak width of the diffraction spots increased. Analysis of the thermal motion of protein molecules using the TLS model has shown that the enhancement of the diffraction power in the transformed crystal is mainly ascribable to the suppression of rigid-body motion owing to an increase in intermolecular contacts as a result of the loss of bulk solvent.

A neutron diffraction study of xylitol: derivation of mean square internal vibrations for H atoms from a rigid-body description.

A neutron diffraction study of xylitol (C(5)O(5)H(12)) is presented. The nuclear anisotropic displacement parameters have been analysed showing that the carbon-oxygen skeleton conforms to a rigid-body (TLS) description. Applying this TLS model to the xylitol H atoms allows characterization of the internal molecular displacements of the H nuclei, assuming that the observed H nuclear mean-square displacements are a sum of the internal displacements and rigid-body displacements. These internal molecular displacements are very similar for chemically equivalent H atoms and in good agreement with the values obtained by other methods. In all cases the smallest eigenvector of the residual mean-square displacement tensor is almost parallel to the X-H bond. The use of ab initio calculations to obtain the internal vibrations in xylitol is discouraging. Another 12 structures extracted from the literature which have been investigated by neutron diffraction were subjected to a similar analysis. The results for the nine compounds investigated at low temperature conform to the results from xylitol and provide estimates of the internal vibrations of H atoms in a range of chemical environments.

Atomic resolution structure of prokaryotic phospholipase A2: analysis of internal motion and implication for a catalytic mechanism.

We have found a secreted phospholipase A(2) (PLA(2), EC 3.1.1.4) from Streptomyces violaceoruber A-2688, which is the first PLA(2) identified in prokaryote, and determined its tertiary structure by NMR and X-ray analyses. In this study, we collected the X-ray diffraction data of the bacterial PLA(2) at room temperature (297 K) using conventional MoK(alpha) radiation and refined the structure at a 1.05 A resolution. The atomic resolution analysis led us to introduce disordered conformations and hydrogen atoms into a full anisotropic model. The molecular motion, which is expressed as the sum of rigid-body motion and internal motion of protein, is roughly estimated as the thermal motion when the X-ray diffraction data are collected at room temperature. In this study, we applied a TLS (rigid-body motion in terms of translation, libration, and screw motions) model to analyze the rigid-body motion of the bacterial PLA(2) and calculated the internal motion by subtracting the estimate of the rigid-body motion from the observed anisotropic temperature factor. We also subjected the TLS model to estimate the internal motion of the bovine pancreatic PLA(2) using the anisotropic temperature factor deposited in the Protein Data Bank. Both results indicate that the localization of regions exhibiting larger internal motion in the bacterial PLA(2) is almost the same as that in the bovine pancreatic PLA(2), suggesting that although the tertiary structure of the bacterial PLA(2) is strikingly different from that of the bovine pancreatic PLA(2), the internal motion, which is associated with the calcium(II) ion-binding, phospholipid-binding, and allosteric interfacial activation, is commonly observed in both PLA(2)s.

Ethanol Glass Dynamics: Logarithmic Line Broadening and Optically Induced Dephasing

The TLS model has been quite successful in the description of the anomalous low-temperature properties of glasses. It also predicts that these properties are time dependent, which has indeed been shown to be the case. 5,6 This effect has been attributed to the existence of a broad distribution of rates in the glass at which the tunneling processes occur. The optical properties of a chromophore dissolved in a glass are dependent on dynamical processes in the direct vicinity of the chromophore. Therefore, these optical properties will also be time dependent. A number of optical techniques have been employed to explore the dynamics of the chromophores on different time scales and thus probe the distribution of rates of tunneling processes. Most notably hole burning, photon echo, and singlemolecule spectroscopy have been employed to probe glass dynamics on a range of time scales spanning up to 18 orders of magnitude. This allows for the investigation of the particular nature of the TLS’s. These so-called optical line-narrowing experiments provide a pivotal test for the adequacy of the TLS model in describing glass dynamics. However, the interpretation of chromophore dynamics in amorphous solids is frustrated by qualitative and quantitative discrepancies between the results rendered by different techniques. Thus, although separate results are in qualitative agreement with the TLS model, the quantitative discrepancies between results rendered by different techniques indicated the need for further refinement of the TLS model. Notwithstanding these problems, the concept of low-energy excitations being accountable for the properties of amorphous solids is well accepted. At the same time it is clear that the interpretation of experimental results has to be done with great caution. Indeed the optical dynamical properties can be influenced by various inconspicuous parameters in the experiments. Examples are the cooling history of the sample, the particular subset of chromophores selected in an experiment, 7,8 and also, as was recently pointed out, 9,10 laser fluence. In this paper we revisit the effect of laser fluence on the observed optical dynamics and confirm earlier conclusions regarding its importance in optical dephasing experiments. We further show that optically induced spectral diffusion, an effect unrelated to laser fluence, is of significant importance to the interpretation of all optical line-narrowing techniques. This finding points at the inadequacy of the currently used weakcoupling chromophore-TLS model for a complete description of glass dynamics.

Spectral diffusion in PMMA on a long time scale at 4.2 K. Nonlogarithmic hole broadening and absence of aging effect

Spectral diffusion (SD) in PMMA doped with H 2-TPP is investigated at 4.2 K on a time scale of 3– 10 6 s via optical hole burning. Two contradictory results – within the framework of the TLS model – are obtained. The first one is the absence of aging effects which puts the upper limit for the TLS relaxation times to tens of minutes. The second one is an intensive superlogarithmic SD on the whole time scale of the experiment, which evidences the presence of very slow relaxations, independent of the sample history on a time scale of up to 2 months. The presented results provide clear evidence of a deviation of SD behavior from the TLS model predictions at moderately low temperatures. The concept of structural relaxations is applied for a qualitative interpretation of the experimental data.

Photon echoes in doped organic amorphous systems over a wide (0.35–50 K) temperature range

Optical photon echo measurements on seven doped organic amorphous systems (resorufin (Res) in D- and D 6-ethanol (EtOD and EtOD 6), tetra-tert-butylterrylene (TBT) in polyisobutylene and in polymethylmetacrylate (PMMA), zinc-tetraphenylporphine (ZnTPP) in EtOD and EtOD 6 and in PMMA) have been performed in a wide temperature range (0.35–50 K). This wide temperature interval (more than two decades) permits to clearly separate for the first time the two different contributions to the line width (optical dephasing): low-temperature broadening which follows a power law, and high-temperature broadening which demonstrates an exponential-like behavior. The values of the exponent α obtained at low temperatures in the cases of TBT and ZnTPP in PMMA matrix show some marked discrepancy with theoretical predictions, which can be attributed to a failure of the standard TLS model for a treatment of these systems or to an inaccuracy of the PMMA parameters calculated in literature. A comparison of the high-temperature part of the line broadening of different dye molecules (ZnTPP and Res), embedded in the same matrices (EtOD and EtOD 6) shows that the optical dephasing is determined by two contributions – the dynamics of matrix itself and the dynamics which is related to the doped molecules.

Long-time scale spectral diffusion in PMMA: Beyond the TLS model?

Spectral diffusion (SD) in PMMA doped with H 2-TPP is investigated at 4.2 K on a time scale of 3 ÷ 10 6 s via optical hole burning. Two contradictory (in frames of the TLS model) results are obtained. The first is the absence of aging effects which put the upper limit for the TLS relaxation times to tens of minutes. The second is an intensive superlogarithmic SD on the whole time scale of the experiment, which evidences the presence of very slow relaxations, independent of the sample history on the time scale of up to 2 months. The presented results provide the clear evidence of the deviation of SD behavior from the TLS model predictions at moderately low temperatures. The concept of structural relaxations is applied for a qualitative interpretation of the experimental data.

Crystallographic evaluation of internal motion of human α-lactalbumin refined by full-matrix least-squares method

The low temperature form of human α-lactalbumin (HAL) was crystallized from a 2H2O solution and its structure was refined to the R value of 0.119 at 1.15 Å resolution by the full-matrix least-squares method. Average estimated standard deviations of atomic parameters for non-hydrogen atoms were 0.038 Å for coordinates and 0.044 Å2 for anisotropic temperature factors (Uij). The magnitude of equivalent isotropic temperature factors (Ueqv) was highly correlated with the distance from the molecular centroid and fitted to a quadratic equation as a function of atomic coordinates. The atomic thermal motion was rather isotropic in the core region and the anisotropy increased towards the molecular surface. The statistical analysis revealed the out-of-plane motion of main-chain oxygen atoms, indicating that peptide groups are in rotational vibration around a Cα⋯Cα axis. The TLS model, which describes the rigid-body motion in terms of translation, libration, and screw motions, was adopted for the evaluation of the molecular motion and the TLS parameters were determined by the least-squares fit to Uij. The reproduced Ueqvcal from the TLS parameters was in fair agreement with observed Ueqv, but differences were found in regions of residues, 5–22, 44–48, 70–75, and 121–123, where Ueqv was larger than Ueqvcal because of large local motions. To evaluate the internal motion of HAL, the contribution of the rigid-body motion was determined to be 42.4 % of Ueqv in magnitude, which was the highest estimation to satisfy the condition that the Uijint tensors of the internal motion have positive eigen values. The internal motion represented with atomic thermal ellipsoids clearly showed local motions different from those observed in chicken-type lysozymes which have a backbone structure very similar to HAL. The result indicates that the internal motion is closely related to biological function of proteins.

Full-matrix least-squares refinement of lysozymes and analysis of anisotropic thermal motion.

Crystal structures of turkey egg lysozyme (TEL) and human lysozyme (HL) were refined by full-matrix least-squares method using anisotropic temperature factors. The refinement converged at the conventional R-values of 0.104 (TEL) and 0.115 (HL) for reflections with Fo > 0 to the resolution of 1.12 A and 1.15 A, respectively. The estimated r.m.s. coordinate errors for protein atoms were 0.031 A (TEL) and 0.034 A (HL). The introduction of anisotropic temperature factors markedly reduced the R-value but did not significantly affect the main chain coordinates. The degree of anisotropy of atomic thermal motion has strong positive correlation with the square of distance from the molecular centroid. The ratio of the radial component of thermal ellipsoid to the r.m.s. magnitude of three principal components has negative correlation with the distance from the molecular centroid, suggesting the domination of libration rather than breathing motion. The TLS model was applied to elucidate the characteristics of the rigid-body motion. The TLS tensors were determined by the least-squares fit to observed temperature factors. The profile of the magnitude of reproduced temperature factors by the TLS method well fitted to that of observed B(eqv). However, considerable disagreement was observed in the shape and orientation of thermal ellipsoid for atoms with large temperature factors, indicating the large contribution of local motion. The upper estimate of the external motion, 67% (TEL) and 61% (HL) of B(eqv), was deduced from the plot of the magnitude of TLS tensors determined for main chain atoms which were grouped into shells according to the distance from the center of libration. In the external motion, the translational portion is predominant and the contribution of libration and screw motion is relatively small. The internal motion, estimated by subtracting the upper estimate of the external motion from the observed temperature factor, is very similar between TEL and HL in spite of the difference in 54 of 130 amino acid residues and in crystal packing, being suggested to reflect the intrinsic internal motion of chicken-type lysozymes.

Optical investigation of electric-field-induced relaxations in amorphous solids at low temperatures

The influence of external electric fields on low-temperature relaxations in polymer glasses has been discovered and investigated in the temperature regime of 50–700 mK. An external field pulse, applied to polymer samples, creates nonequilibrium populations in the ensemble of specific local low-energy excitations (TLS). This manifests itself in a reversible nonequilibrium contribution to spectral diffusion (SD), which was monitored via the method of spectral hole burning. The temperature dependence of the electric-field-induced SD as well as the dependence on both field strength and pulse duration are investigated and quantitatively interpreted in the framework of an extended TLS model. The average value of the static electric dipole moment of TLS is measured for two polymers: PMMA and PS. The agreement of our experimental data with the model calculations is very good.

Rigid-Body Disorder Models for the High-Temperature Phase of Ferrocene

Ferrocene, [Fe(C5H5)2], which crystallizes at room temperature in space group P21/a with Z = 2, is described in many textbooks as having D 5d symmetry. Previous work has shown, however, that the librational amplitude associated with motion about the fivefold axis does not decrease with temperature and that the crystals are probably disordered. Ferrocene molecules in triclinic crystals grown below 169 K have approximate D 5 symmetry and an almost eclipsed conformation; the low- and high-temperature phases may be related by an order–disorder transition, during which the number of independent atoms changes by a factor of 4. The structure of the high-temperature phase has been reinvestigated with rigid-body refinements of the neutron diffraction data collected at 173 and 298 K by Takusagawa & Koetzle [Acta Cryst. (1979), B35, 1074–1081]. The C5H5 ring was treated as a rigid group of C 5 symmetry; C—C and C—H distances were allowed to vary, as was the displacement of the H atoms from the C5 plane. The rigid-body motion of the C5H5 ligand was described by the TLS model. All the rigid-body disorder models fit better than conventional independent-atom models. A disorder model that includes three sites for each C5H5 ring is the best of the models that were investigated, which indicates that the structure of the high-temperature phase cannot be described by the superposition of the two independent ferrocene molecules in the low-temperature phase. The phase transition between the high- and low-temperature phases is not a simple order–disorder transition.