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Rotation Angles (rotation + angle)
Selected AbstractsObject detection using straight line matching in ,-, spaceELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2010Taisei Okuzono Abstract The contours of many industrial parts contain straight lines and the positions of the lines are therefore useful information for object detection. This paper presents a matching technique for straight lines. The method consists of ,-matching, ,-matching, and pose estimation. Any lines in 2D space are represented with parameters , and , by the Hough transform. In order to find the corresponding lines in a model and a scene, the , and , values are evaluated in ,-matching and ,-matching. When an object is translated and rotated, the contour lines of the object are also transferred and the , values of the lines are merely shifted by the rotation angle in the ,-, space. Thus, the relative positions of the , values are invariant. In ,-matching, the corresponding lines of the model and the scene are selected so that the relative , values of the corresponding lines are nearly equal. In ,-matching, the corresponding lines are evaluated further by computing the deviations of their , values. Finally, the transfer parameters of the selected pairs are estimated in pose estimation. The experiments show that this technique is robust to rotation, occlusion, and scaling of the objects. We also discuss the computation time, in which the preprocess such as edge detection and the Hough transform takes much of the time. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(3): 34,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10176 [source] Statistical thermodynamics of internal rotation in a hindering potential of mean force obtained from computer simulationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2003Vladimir Hnizdo Abstract A method of statistical estimation is applied to the problem of one-dimensional internal rotation in a hindering potential of mean force. The hindering potential, which may have a completely general shape, is expanded in a Fourier series, the coefficients of which are estimated by fitting an appropriate statistical,mechanical distribution to the random variable of internal rotation angle. The function of reduced moment of inertia of an internal rotation is averaged over the thermodynamic ensemble of atomic configurations of the molecule obtained in stochastic simulations. When quantum effects are not important, an accurate estimate of the absolute internal rotation entropy of a molecule with a single rotatable bond is obtained. When there is more than one rotatable bond, the "marginal" statistical,mechanical properties corresponding to a given internal rotational degree of freedom are educed. The method is illustrated using Monte Carlo simulations of two public health relevant halocarbon molecules, each having a single internal-rotation degree of freedom, and a molecular dynamics simulation of an immunologically relevant polypeptide, in which several dihedral angles are analyzed. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1172,1183, 2003 [source] Effects of distal radius malunion on distal radioulnar joint mechanics,an in vivo studyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2007Joseph J. Crisco Abstract Patients with a malunited distal radius often have painful and limited forearm rotation, and may progress to arthritis of the distal radioulnar joint (DRUJ). The purpose of this study was to determine if DRUJ congruency and mechanics were altered in patients with malunited distal radius fractures. In nine subjects with unilateral malunions, interbone distances and dorsal and palmar radioulnar ligament lengths were computed from tomographic images of both forearms in multiple forearm positions using markerless bone registration (MBR) techniques. The significance of the changes were assessed using a generalized linear model, which controlled for forearm rotation angle (,60° to 60°). In the malunited forearm, compared to the contralateral uninjured arm, we found that ulnar joint space area significantly decreased by approximately 25%, the centroid of this area moved an average of 1.3 mm proximally, and the dorsal radioulnar ligament elongated. Despite our previous findings of insignificant changes in the pattern of radioulnar kinematics in patients with malunited fractures, we found significant changes in DRUJ joint area and ligament lengthening. These findings suggest that alterations in joint mechanics and soft tissues may play an important role in the dysfunction associated with these injuries. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:547,555, 2007 [source] Effects of rotation on measurement of lower limb alignment for knee osteotomyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2004Hideo Kawakami Abstract The purposes of this study were to clarify the effects of rotation on two-dimensional measurement of lower limb alignment for knee osteotomy using a three-dimensional method and to determine whether this 3-D simulation method could help with planning of knee osteotomy. We developed computer software to calculate femorotibial angle (FTA) and hip,knee,ankle angle (HKA) and simulate knee osteotomy from a CT-based 3-D bone model of the lower limb. Lower limb rotation on anteroposterior long-standing radiographs was measured by superimposing the 3-D bone models. Changes in alignment with limb rotation were calculated using the software. FTA after virtual closed-wedged osteotomy was measured for a hypothetical case of a rotation error of the osteotomy plane in reattaching the proximal cutting surface to the distal cutting surface. For 31 varus knees in 20 patients with medial compartment arthritis, the mean rotation angle, relative to the epicondylar axis, with variable limb position was 7.4 ± 3.9° of internal rotation (mean ± SD), ranging from 8° of external rotation to 14° of internal rotation; the mean changes in FTA and HKA were 3.5 ± 2.2° (range, 0.4,8.6) and 1.6 ± 1.3° (range, 0.2,4.9), respectively. The FTA "flexion angle" (lateral view alignment from neutral AP) and the absolute HKA "flexion angle" correlated with the change in FTA and HKA with limb rotation, respectively (FTA, R = 0.999; HKA, R = 0.993). The mean change in FTA after virtual closed-wedged osteotomy was 3.2° for internal and external 10° rotation errors in reattaching the osteotomy plane. Rotation may affect measurement of lower limb alignment for knee osteotomy, and 3-D methods are preferable for surgical planning. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] One-dimensional approximations of the eigenvalue problem of curved rodsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 12 2001Josip Tamba In this work we analyse the asymptotic behaviour of eigenvalues and eigenfunctions of the linearized elasticity eigenvalue problem of curved rod-like bodies with respect to the small thickness , of the rod. We show that the eigenfunctions and scaled eigenvalues converge, as , tends to zero, toward eigenpairs of the eigenvalue problem associated to the one-dimensional curved rod model which is posed on the middle curve of the rod. Because of the auxiliary function appearing in the model, describing the rotation angle of the cross-sections, the limit eigenvalue problem is non-classical. This problem is transformed into a classical eigenvalue problem with eigenfunctions being inextensible displacements, but the corresponding linear operator is not a differential operator. Copyright © 2001 John Wiley & Sons, Ltd. [source] Photoinduced Faraday rotation in the magnetic semiconductor CdCr2Se4PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2004L. L. Golik Abstract A growth of the excitonic peak in the absorption spectrum and an enhancement of the Faraday rotation band (approximately 50% of the linear effect value) were induced by intensive radiation of Nd3+ -laser (h, = 1.17 eV) in ferromagnetic phase of magnetic semiconductor CdCr2Se4. The photoinduced effects increased during a pumping pulse and also with growth of pump intensity. In studies of the non-linear Faraday rotation a change of the spectral band shape was observed along with the growth of the rotation angle. The observed effects can be explained by the screening of internal electric fields existing in CdCr2Se4 crystals by photoexcited charge carriers. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural comparisons between methylated and unmethylated nitrophenyl lophinesACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Diana Yanover The lophine derivative 2-(2-nitrophenyl)-4,5-diphenyl-1H -imidazole, C21H15N3O2, (I), crystallized from ethanol as a solvent-free crystal and from acetonitrile as the monosolvate, C21H15N3O2·C2H3N, (II). Crystallization of 2-(4-nitrophenyl)-4,5-diphenyl-1H -imidazole from methanol yielded the methanol monosolvate, C21H15N3O2·CH4O, (III). Three lophine derivatives of methylated imidazole, namely, 1-methyl-2-(2-nitrophenyl)-4,5-diphenyl-1H -imidazole methanol solvate, C22H17N3O2·CH4O, (IV), 1-methyl-2-(3-nitrophenyl)-4,5-diphenyl-1H -imidazole, C22H17N3O2, (V), and 1-methyl-2-(4-nitrophenyl)-4,5-diphenyl-1H -imidazole, C22H17N3O2, (VI), were recrystallized from methanol, acetonitrile and ethanol, respectively, but only (IV) produced a solvate. Compounds (III) and (IV) each crystallize with two independent molecules in the asymmetric unit. Five imidazole molecules in the six crystals differ in their molecular conformations by rotation of the aromatic rings with respect to the central imidazole ring. In the absence of a methyl group on the imidazole [compounds (I),(III)], the rotation angles are not strongly affected by the position of the nitro group [44.8,(2) and 45.5,(1)° in (I) and (II), respectively, and 15.7,(2) and 31.5,(1)° in the two molecules of (III)]. However, the rotation angle is strongly affected by the presence of a methyl group on the imidazole [compounds (IV),(VI)], and the position of the nitro group (ortho, meta or para) on a neighbouring benzene ring; values of the rotation angle range from 26.0,(1) [in (VI)] to 85.2,(1)° [in (IV)]. This group repulsion also affects the outer N,C,N bond angle. The packing of the molecules in (I), (II) and (III) is determined by hydrogen bonding. In (I) and (II), molecules form extended chains through N,H...N hydrogen bonds [with an N...N distance of 2.944,(5),Å in (I) and 2.920,(3),Å in (II)], while in (III) the chain is formed with a methanol solvent molecule as the mediator between two imidazole rings, with O...N distances of 2.788,(4),2.819,(4),Å. In the absence of the imidazole N,H H-atom donor, the packing of molecules (IV),(VI) is determined by weaker intermolecular interactions. The methanol solvent molecule in (IV) is hydrogen bonded to imidazole [O...N = 2.823,(4),Å] but has no effect on the packing of molecules in the unit cell. [source] The Importance of dQ/dt on the Flow Field in a Turbodynamic Pump With Pulsatile FlowARTIFICIAL ORGANS, Issue 9 2009Fangjun Shu Abstract Fluid dynamic analysis of turbodynamic blood pumps (TBPs) is often conducted under steady flow conditions. However, the preponderance of clinical applications for ventricular assistance involves unsteady, pulsatile flow,due to the residual contractility of the native heart. This study was undertaken to demonstrate the importance of pulsatility and the associated time derivative of the flow rate (dQ/dt) on hemodynamics within a clinical-scale TBP. This was accomplished by performing flow visualization studies on a transparent model of a centrifugal TBP interposed within a cardiovascular simulator with controllable heart rate and stroke volume. Particle image velocimetry triggered to both the rotation angle of the impeller and phase of the cardiac cycle was used to quantify the velocity field in the outlet volute and in between the impeller blades for 16 phases of the cardiac cycle. Comparison of the unsteady flow fields to corresponding steady conditions at the same (instantaneous) flow rates revealed marked differences. In particular, deceleration of flow was found to promote separation within the outlet diffuser, while acceleration served to stabilize the velocity field. The notable differences between the acceleration and deceleration phases illustrated the prominence of inertial fluid forces. These studies emphasize the importance of dQ/dt as an independent variable for thorough preclinical validation of TBPs intended for use as a ventricular assist device. [source] Einbindetiefen und Schnittgrößen bei gestützten Wänden mit beliebiger FußauflagerungBAUTECHNIK, Issue 9 2009Achim Hettler Univ.-Prof. Geotechnik; Bodenmechanik; Geotechnical Engineering; Soil Mechanics Abstract Dieser Beitrag beinhaltet die Ermittlung von Schnittgrößen und Einbindetiefen bei gestützten Wänden. Zunächst wird ein Modell der Fußauflagerung vorgestellt, das sowohl eine freie Auflagerung, eine Teil einspannung als auch eine volle Einspannung umfasst. Die erforderliche Einbindetiefe lässt sich durch Ansatz von Bemessungsgrößen wesentlich einfacher berechnen als am System mit charakteristischen Größen. Bei einer teilweisen Einspannung im Boden können durch Vorgabe eines Drehwinkels im theoretischen Auflagerpunkt die charakteristischen Bodenreaktionen eindeutig festgelegt werden. Für den Fall, dass nur ständige Einwirkungen auftreten, können charakteristische Größen und Bemessungsgrößen durch einen Faktor ineinander umgerechnet werden. Eine weitere Vereinfachung ergibt sich, wenn man, den Empfehlungen des Arbeitskreises "Baugruben" folgend, die veränderlichen Einwirkungen mit einem Erhöhungsfaktor vergrößert und wie für den Lastfall mit ständigen Einwirkungen behandelt. Embedment depths and sectional forces for propped walls with different foot supports. In the following contribution the calculation of the embedment depth and the sectional forces is treated for the case of propped walls. A model for the earth support at the foot of the wall is presented including a free, a partly fixed and a fixed earth support. The determination of the embedment depth at the system with design loads is essentially easier compared to a calculation with characteristic quantities. Assuming a value for the rotation angle at the theoretical foot point of the wall permits to calculate the magnitude of the characteristic soil reactions. In the case that only permanent actions react on the wall, characteristic and design quantities are related by a simple factor. According to the recommendations of excavations a further simplification is possible, if the transient actions are increased by a factor and are treated as in the case of permanent situations. [source] Design and application of layered composites with the prescribed magnetic permeabilityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2010Jae Seok Choi Abstract This research aims to design the microstructure with the prescribed magnetic permeability and proposes a design method to control the magnetic flux flow using layered microstructures. In the optimization problem for the microstructure design, the objective function is set up to minimize the difference between the homogenized magnetic permeability during the design process and the prescribed permeability based on the so-called inverse homogenization method. Based on the microstructure design result, a microstructure composed of layered materials is proposed for the purpose of the efficient magnetic flux control. In addition, its analytical calculation is added to confirm the feasibility of the optimized results. The layered composite of a very thin ferromagnetic material is expected to guide the magnetic flux and the performance of the magnetic system can be improved by turning the microstructures appropriately. Optimal rotation angles of microstructures are determined using the homogenization design method. The proposed design method is applied to an example to confirm its feasibility. Copyright © 2009 John Wiley & Sons, Ltd. [source] Moiré Pattern Formation on Porous Alumina Arrays Using Nanoimprint Lithography,ADVANCED MATERIALS, Issue 18 2003J. Choi Porous alumina arrays with various Moiré patterns (see Figure) are prepared by two-step nanoindentation with different rotation angles and subsequent anodization. The patterns on the porous alumina array are in good agreement with the theory of Moiré patterns in terms of the rotation angles. In addition, replicas of photoresist polymer with the Moiré pattern are successfully prepared. [source] Conformational analysis: A new approach by means of chemometricsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 2 2002Aline Thaís Bruni Abstract In conformational analysis, the systematic search method completely maps the space but suffers from the combinatorial explosion problem because the number of conformations increases exponentially with the number of free rotation angles. This study introduces a new methodology of conformational analysis that controls the combinatorial explosion. It is based on a dimensional reduction of the system through the use of principal component analysis. The results are exactly the same as those obtained for the complete search but, in this case, the number of conformations increases only quadratically with the number of free rotation angles. The method is applied to a series of three drugs: omeprazole, pantoprazole, lansoprazole,benzimidazoles that suppress gastric-acid secretion by means of H+, K+ -ATPase enzyme inhibition. © 2002 Wiley Periodicals, Inc. J Comput Chem 23: 222,236, 2002 [source] Three-dimensional knee joint kinematics during golf swing and stationary cycling after total knee arthroplastyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 12 2008Satoshi Hamai Abstract The expectation of returning to sports activities after total knee arthroplasty (TKA) has become more important to patients than ever. To our knowledge, no studies have been published evaluating the three-dimensional knee joint kinematics during sports activity after TKA. Continuous X-ray images of the golf swing and stationary cycling were taken using a large flat panel detector for four and eight post-arthroplasty knees, respectively. The implant flexion and axial rotation angles were determined using a radiographic-based, image-matching technique. Both the golf swing from the set-up position to the top of the backswing, and the stationary cycling from the top position of the crank to the bottom position of the crank, produced progressive axial rotational motions (p,=,0.73). However, the golf swing from the top of the backswing to the end of the follow-through produced significantly larger magnitudes of rotational motions in comparison to stationary cycling (p,<,0.01). Excessive internal,external rotations generated from the top of the backswing to the end of the follow-through could contribute to accelerated polyethylene wear. However, gradual rotational movements were consistently demonstrated during the stationary cycling. Therefore, stationary cycling is recommended rather than playing golf for patients following a TKA who wish to remain physically active. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2004Andrea Pucci Abstract Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed. Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles ,. [source] 16×16 Mirror type optical switch with integrated fiber alignment and steady switching stateMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Qinghua H. Chen Abstract This paper reports a micro electro mechanical system (MEMS) 16×16 free space optical switch based on high-reflectivity mirrors. The mirror monolithically integrated with the fiber grooves can enlarge its rotation angles up to 90°, and keep this as a steady state to steer the optical signal. The reflectivity of the mirror is measured to be 93.1 , 96.3%. The smallest fiber-mirror-fiber insertion loss is 2.1 dB by utilizing optiFocusTM collimating lensed fibers. Moreover, only about ±0.01 dB oscillating amplitude of insertion loss is provoked after the device is tested for 15 min for 5 , 90 Hz in the vertical vibration amplitude of 3 mm. In addition, excellent antifatigue performance of the mirror, which can endure more than 109 cycles of actuation, has been proven. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3012,3016, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23879 [source] Coupling matrix of a 10th -order dual-mode asymmetric canonical filterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2003Juseop Lee Abstract This paper deals with a simple method to extract the coupling matrix of a 10th -order dual-mode asymmetric canonical filter. The coupling matrix of an asymmetric canonical filter is obtained by applying a plane rotation technique to the coupling matrix of a symmetric canonical filter. This paper gives a list of pivots and rotation angles to obtain the coupling matrix of an asymmetric canonical-structure filter. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 64,68, 2003 [source] Anatomical information is needed in ultrasound imaging of muscle to avoid potentially substantial errors in measurement of muscle geometryMUSCLE AND NERVE, Issue 5 2009Menno R. Bénard MSc Abstract This study validates two-dimensional (2D) ultrasound measurements of muscle geometry of the human medial gastrocnemius (GM) and investigates effects of probe orientation on errors in these measurements. Ultrasound scans of GM muscle belly were made both on human cadavers (n = 4) and on subjects in vivo (n = 5). For half of the cadavers, ultrasound scans obtained according to commonly applied criteria of probe orientation deviated 15° from the true fascicle plane. This resulted in errors of fascicle length and fascicle angle up to 14% and 23%, respectively. Fascicle-like structures were detectable over a wide range of probe tilt and rotation angles, but they did not always represent true fascicles. Errors of measurement were either linear or quadratic functions of tilt angle. Similar results were found in vivo. Therefore, we conclude that similar errors are likely to occur for in vivo measurements. For all cadavers, at the distal end of GM, the true fascicle plane was shown to be perpendicular to the distal aponeurosis. Using transverse images of GM to detect the curvature of the deep aponeurosis at the distal end of the muscle belly is a simple strategy to help identify the fascicle plane. For subsequent longitudinal imaging, probe alignment within this plane will help minimize measurement errors of fascicle length, fascicle angle, and muscle thickness. Muscle Nerve, 2009 [source] Optimal designs for calibration of orientationsTHE CANADIAN JOURNAL OF STATISTICS, Issue 3 2007Hwashin H. Shin Abstract This paper concerns designed experiments involving observations of orientations following the models of Prentice (1989) and Rivest &Chang (2006). The authors state minimal conditions on the designs for consistent least squares estimation of the matrix parameters in these models. The conditions are expressed in terms of the axes and rotation angles of the design orientations. The authors show that designs satisfying U1 + , + Un = 0 are optimal in the sense of minimizing the estimation error average angular distance. The authors give constructions of optimal n -point designs when n , 4 and they compare the performance of several designs through approximations and simulation. Plans d'expérience optimaux pour la calibration d'orientations Cet article concerne la planification d'expériences dans le cadre des modèles de Prentice (1989) et de Rivest &Chang (2006) pour des mesures d'orientation. Les auteurs donnent des conditions minimales qu'un plan expérimental doit respecter pour que l'estimation des moindres carrés des paramètres matriciels de ces modèles soit convergente. Ces conditions s'expriment en fonction des axes et des angles des matrices de rotation du plan. Les auteurs montrent que les plans tels que U1 + , + Un = 0 sont optimaux au sens oú la distance angulaire moyenne des erreurs d'estimation est minimisée. Ils précisent la forme des plans optimaux à n , 4 points et comparent la performance de divers plans au moyen d'approximations et de simulations. [source] Structural comparisons between methylated and unmethylated nitrophenyl lophinesACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009Diana Yanover The lophine derivative 2-(2-nitrophenyl)-4,5-diphenyl-1H -imidazole, C21H15N3O2, (I), crystallized from ethanol as a solvent-free crystal and from acetonitrile as the monosolvate, C21H15N3O2·C2H3N, (II). Crystallization of 2-(4-nitrophenyl)-4,5-diphenyl-1H -imidazole from methanol yielded the methanol monosolvate, C21H15N3O2·CH4O, (III). Three lophine derivatives of methylated imidazole, namely, 1-methyl-2-(2-nitrophenyl)-4,5-diphenyl-1H -imidazole methanol solvate, C22H17N3O2·CH4O, (IV), 1-methyl-2-(3-nitrophenyl)-4,5-diphenyl-1H -imidazole, C22H17N3O2, (V), and 1-methyl-2-(4-nitrophenyl)-4,5-diphenyl-1H -imidazole, C22H17N3O2, (VI), were recrystallized from methanol, acetonitrile and ethanol, respectively, but only (IV) produced a solvate. Compounds (III) and (IV) each crystallize with two independent molecules in the asymmetric unit. Five imidazole molecules in the six crystals differ in their molecular conformations by rotation of the aromatic rings with respect to the central imidazole ring. In the absence of a methyl group on the imidazole [compounds (I),(III)], the rotation angles are not strongly affected by the position of the nitro group [44.8,(2) and 45.5,(1)° in (I) and (II), respectively, and 15.7,(2) and 31.5,(1)° in the two molecules of (III)]. However, the rotation angle is strongly affected by the presence of a methyl group on the imidazole [compounds (IV),(VI)], and the position of the nitro group (ortho, meta or para) on a neighbouring benzene ring; values of the rotation angle range from 26.0,(1) [in (VI)] to 85.2,(1)° [in (IV)]. This group repulsion also affects the outer N,C,N bond angle. The packing of the molecules in (I), (II) and (III) is determined by hydrogen bonding. In (I) and (II), molecules form extended chains through N,H...N hydrogen bonds [with an N...N distance of 2.944,(5),Å in (I) and 2.920,(3),Å in (II)], while in (III) the chain is formed with a methanol solvent molecule as the mediator between two imidazole rings, with O...N distances of 2.788,(4),2.819,(4),Å. In the absence of the imidazole N,H H-atom donor, the packing of molecules (IV),(VI) is determined by weaker intermolecular interactions. The methanol solvent molecule in (IV) is hydrogen bonded to imidazole [O...N = 2.823,(4),Å] but has no effect on the packing of molecules in the unit cell. [source] Cluster analysis for phasing with molecular replacement: a feasibility studyACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2009Andreas Buehler Molecular replacement can fail to find a solution, namely a unique orientation and position of a search model, even when many search models are tested under various conditions. Simultaneous use of the results of these searches may help in the solution of such difficult structures. A closeness between the peaks of several calculated rotation functions may identify the model orientation. The largest and most compact cluster of such peaks usually corresponds to models which are oriented similarly to the molecule under study. A search for the optimal translation may be more problematic and both individual translation functions and straightforward cluster analysis in the space of geometric parameters such as rotation angles and translation vectors may give no result. An improvement may be obtained by performing cluster analysis of the peaks of several translation functions in phase-set space. In this case, the Fourier maps computed using the observed structure-factor magnitudes and the phases calculated from differently positioned models are compared. Again, as a rule, the largest and the most compact cluster corresponds to the correct solution. The result of the updated procedure is no longer a single search model but an averaged Fourier map. [source] Cloning, crystallization and preliminary X-ray studies of XC2981 from Xanthomonas campestris, a putative CutA1 protein involved in copper-ion homeostasisACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2006Chien-Hung Lin Divalent metal ions play key roles in all living organisms, serving as cofactors for many proteins involved in a variety of electron-transfer activities. However, copper ions are highly toxic when an excessive amount is accumulated in a cell. CutA1 is a protein found in all kingdoms of life that is believed to participate in copper-ion tolerance in Escherichia coli, although its specific function remains unknown. Several crystal structures of multimeric CutA1 with different rotation angles and degrees of interaction between trimer interfaces have been reported. Here, the cloning, expression, crystallization and preliminary X-ray analysis of XC2981, a possible CutA1 protein present in the plant pathogen Xanthomonas campestris, are reported. The XC2981 crystals diffracted to a resolution of 2.6,Å. They are cubic and belong to space group I23, with unit-cell parameters a = b = c = 130.73,Å. [source] | ||||||||||||||||||||||