Angular Settings Research Articles

Elaboration on the hexagonal grid and spiral trace schemes for pole figure data collection

A practical description of the mathematics required to implement the hexagonal grid and spiral trace pole figure data collection schemes is presented. Applying the concepts of stereographic and equal area projections with geometry, spreadsheets were created to calculate the angular settings of the goniometer. Using the generated settings, the hexagonal grid and spiral trace schemes were programmed into the existing X-ray software and employed to collect data for a sample of aluminum foil. The resulting (111) pole figures were similar to those collected with the conventional 5°χ×5°ϕ grid. The hexagonal grid has been shown by others to reduce the number of data points and time needed to complete a pole figure, while providing equal area sampling. Although not optimized, the spiral method was also investigated as another alternative to the 5°χ×5°ϕ grid.

Focus on Photonics and Imaging

Focus on Photonics and Imaging

Alternating translocation of protein substrates from both ends of ClpXP protease.

In ClpXP protease complexes, hexameric rings of the ATP-dependent ClpX chaperone stack on one or both faces of the double-heptameric rings of ClpP. We used electron microscopy to record the initial binding of protein substrates to ClpXP and their accumulation inside proteolytically inactive ClpP. Proteins with N- or C-terminal recognition motifs bound to complexes at the distal surface of ClpX and, upon addition of ATP, were translocated to ClpP. With a partially translocated substrate, the non-translocated portion remained on the surface of ClpX, aligned with the central axis of the complex, confirming that translocation proceeds through the axial channel of ClpXP. Starting with substrate bound on both ends, most complexes translocated substrate from only one end, and rarely (<5%) from both ends. We propose that translocation from one side is favored for two reasons: initiation of translocation is infrequent, making the probability of simultaneous initiation low; and, further, the presence of protein within the cis side translocation channel or within ClpP generates an inhibitory signal blocking translocation from the trans side.

Rydberg Matter of K and N 2: angular dependence of the time-of-flight for neutral and ionized clusters formed in Coulomb explosions

Laser fragmentation via Coulomb explosions in a cloud of Rydberg Matter (RM) is shown to give an angular dependence of the time-of-flight (TOF) observations for neutral RM clusters. The RM cloud is formed by emission from a K doped FeO catalyst sample at 700–900 K and is formed of K ∗ atoms, or N 2 ∗ molecules after nitrogen gas adsorption in the emitter. Close to the surface normal of the emitter, relatively large clusters from high excitation states in the RM dominate, while at large angles (40–50°) smaller clusters and monomers with high kinetic energy release from lower excitation states are observed more frequently. N 2 RM usually gives smaller clusters and more monomers than K RM. The extension of the RM cloud in the apparatus is easily observed by the different TOFs for the various particles at different angular settings of the detector, and by direct shifting of the laser focus point. The TOF results show well defined Rydberg states and RM clusters with very low translational temperature, below 100 K even for the monomers.

The versatility of collimated plane grating monochromators

In the last few years monochromator development at the German synchrotron radiation facility BESSY II improved conventional monochromator designs, especially the SX700 design, considerably. It was possible to convert the high brilliance of undulator radiation at third generation synchrotron sources very successfully into outstanding monochromator performance in terms of high energy resolution, photon flux and focus size. New mechanical designs and precise control of the angular settings of optical elements resulted in very high monochromator stability and allowed even for an absolute energy calibration of monochromators. This report reviews the design principles of collimated plane grating monochromators and presents results obtained within the first two years of BESSY II operation.

A pair of clamps for a safe removing and repositioning of beta and gamma angular settings of Brown-Roberts-Wells stereotactic system during operation.

The Brown-Roberts-Wells arc system is a non-target-centered design, i.e., without an independent approach angle. The approach angle of this system strictly depends on precalculated values (entry and target point). Therefore, some components of the system used sometimes prevent a direct insight into the operation field. Once the entry point has been set, the arc system normally has to be taken off to permit an unimpeded approach to the burr hole. To facilitate rotation and return to the primary beta and gamma angular settings during stereotactic craniotomy and other surgery, a pair of clamps was designed for the BRW arc system. These clamps help the approach to the entry point in such a way that some components of the arc (e.g., the guide block holder) are removed from the surgical field, thus giving wide visual access for the stereotactic approach. Consequently, it is no longer necessary to remove the entire arc system, resulting in an increased operation safety and shorter operation times.

Calibrated single-plunge bipolar electrode array for mapping myocardial vector fields in three dimensions during high-voltage transthoracic defibrillation.

Mapping of the myocardial scalar electric potential during defibrillation is normally performed with unipolar electrodes connected to voltage dividers and a global potential reference. Unfortunately, vector potential gradients that are calculated from these data tend to exhibit a high sensitivity to measurement errors. This paper presents a calibrated single-plunge bipolar electrode array (EA) that avoids the error sensitivity of unipolar electrodes. The EA is triaxial, uses a local potential reference, and simultaneously measures all three components of the myocardial electric field vector. An electrode spacing of approximately 500 microm allows the EA to be direct-coupled to high-input-impedance, isolated, differential amplifiers and eliminates the need for voltage dividers. Calibration is performed with an electrolytic tank in which an accurately measured, uniform electric field is produced. For each EA, unique calibration matrices are determined which transform potential difference readings from the EA to orthogonal components of the electric field vector. Elements of the matrices are evaluated by least squares multiple regression analysis of data recorded during rotation of the electric field. The design of the electrolytic tank and electrode holder allows the electric field vector to be rotated globally with respect to the electrode axes. The calibration technique corrects for both field perturbation by the plunge electrode body and deviations from orthogonality of the electrode axes. A unique feature of this technique is that it eliminates the need for mechanical measurement of the electrode spacing. During calibration, only angular settings and voltages are recorded. For this study, ten EAs were calibrated and their root-mean-square (rms) errors evaluated. The mean of the vector magnitude rms errors over the set of ten EAs was 0.40% and the standard deviation 0.07%. Calibrated EAs were also tested for multisite mapping in four dogs during high-voltage transthoracic shocks.

Crystal Structure of 2(3H)-Benzoxazolone-3-propionitrile

crystal structure of benzoxazolone having propionitrile. To 500 ml of water were added 0.25 mol of 2-benzoxazolone, 0.3 mol of triethylamine, and 0.3 mol of acrylonitrile. The mixture was heated at 50 – 60 C for 6 h and then stirred at room temperature for 18 h. At the end of this time, the solid material precipitated was filtered, washed with water to become neutral to turnusol paper, dried and crystallized from methanol (mp. 120 C). The cell dimensions were determined from the angular settings of 25 reflections obtained from an Enraf-Nonius CAD-4 diffractometer. The space group P21/n was determined from the systematic absences. Intensity data were collected in the range 2.2<θ<74.3 with variable-speed ω/2θ scans using graphitemonochromated Cu Kα radiation. Three standard reflections were monitored at intervals of 120 min. Data were corrected for an intensity variation of 2%. The crystal and experimental data are listed in Table 1. The crystal structure was solved by a direct method using SHELXS-97,1 and was refined by a fullmatrix least-squares method using SHELXL-972 with anisotropic temperature factors for non-H atoms. The hydrogen atoms were located geometrically. The final coordinates and equivalent thermal parameters for non-hydrogen atoms are given in Table 2; selected bond distances and angles are given in Table 3. The molecular structure of the title compound (Fig. 1) is shown in Fig. 2. The bond lengths and angles are in good agreement with the literature.3,4 All atoms, 1361 ANALYTICAL SCIENCES DECEMBER 2000, VOL. 16 2000 © The Japan Society for Analytical Chemistry

Coactivation of the ankle musculature during maximal isokinetic dorsiflexion at different angular velocities.

The objectives of this study were to determine the differences in the level of coactivation among the ankle agonist and antagonist muscles during maximal isokinetic dorsiflexion and to determine whether velocity alters the activation levels. Raw surface electromyograms (EMG) were recorded from six muscle sites--two over the agonist tibialis anterior (upper and lower sites) and four over the antagonist (lateral and medial gastrocnemius, plus lateral and medial soleus) muscles--in ten healthy subjects (two males and eight females) as they performed maximal dorsiflexor efforts against an isokinetic dynamometer at each of three angular velocity settings (30, 90 and 150 degrees/s). The root-mean-square amplitude (RMS) was calculated over a 35 degree angular displacement for each EMG recording, then was normalized (RMS(Nji)) to the amplitude measured during maximal voluntary isometric contractions (MVIC) of the dorsifexors and plantarflexors (i.e. RMS(MVICj)). A two-factor repeated-measures analysis of variance (ANOVA) tested the muscle site by velocity interaction and the main effects of muscle site and velocity separately. The raw EMG signals were then full-wave rectified and low-pass filtered (6 Hz) and ensemble average curves of the sample were calculated, for each muscle site, at each velocity. The ANOVA revealed a statistically significant muscle-by-velocity interaction (P < 0.05). The RMS(Nji) values for the two tibialis anterior sites were not significantly different from each other for any of the three velocity settings, nor for the two gastrocnemius muscles at 30 degrees/s velocity. All other between-muscle comparisons were statistically significant (P < 0.05). The RMS(Nji) means were 28, 23, 59, 52, 98 and 98% MVIC for the lateral and medial gastrocnemius, the lateral and medial sites on the soleus, and for the upper and lower sites on the tibialis anterior, respectively. The RMS(Nji) from the lower site on the tibialis anterior yielded the only statistically significant difference (P < 0.05) among velocities; at this site, the RMS(Nji) at 150 degrees/s was higher than at the other two velocities. The ensemble-average curves revealed that not all muscle sites are activated to a consistent level throughout the entire movement. The interaction between agonist and antagonist activation during isokinetic dorsiflexion has implications for interpreting the results of isokinetic dynamometry for strength assessment and for understanding the neuromuscular control strategies used in this exercise modality.

Alignment system for crossed parabolic x-ray mirrors

We describe the implementation of a crossed graded parabolic x-ray mirror system that is suitable for incorporation into both conventional and high resolution x-ray diffraction systems. A novel optical alignment system has been devised that permits independent adjustment of the positions and the angular settings of the mirrors. This alignment system is simple and inexpensive to construct, yet is mechanically stable and easy to use. The crossed mirror system has been successfully introduced into both protein crystallography and high resolution x-ray diffraction systems.

Npfinal-state interaction in the reaction2H(p→,pp)natEp→=19 MeV

We investigated the ${}^{2}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{p},pp)n$ breakup reaction by measuring an angular distribution of the cross section and analyzing power in the $\mathrm{np}$ final-state interaction (FSI) at ${E}_{\stackrel{\ensuremath{\rightarrow}}{p}}=19\mathrm{MeV}$ as a function of the $\mathrm{np}$ production angle. Kinematically complete measurements at 12 angular settings of detectors have been done. The observables around the exact FSI point were compared with predictions of four modern $\mathrm{NN}$ potentials, calculated for ${}^{2}\mathrm{H}(n,np)n,$ i.e., without inclusion of the Coulomb interaction. The resulting good overall agreement between the data and theory indicates the smallness of three-nucleon force (3NF) effects as well as the insignificance of the Coulomb force for this particular configuration and energy. This conclusion is supported by results of three-nucleon (3N) Faddeev calculations performed with 2\ensuremath{\pi}-exchange Tucson-Melbourne 3NF with cutoff parameter adjusted individually for each $\mathrm{NN}$ interaction to fit the experimental triton binding.

Accurate and highly complete synchrotron protein crystal Laue diffraction data using the ESRF CCD and the Daresbury Laue software

Developments in electronic area detectors such as CCDs and image plates have transformed the capability of the synchrotron Laue protein crystallography technique compared with film. The rapid readout of CCDs makes practical the use of rather fine angular interval settings of the crystal between each Laue exposure and a large overall angle coverage. The use of the ESRF CCD (image intensifier type) presented here in the Laue data collection on ESRF ID09 (the `Laue beamline') from a single crystal of the 34 kDa wild-type hydroxymethylbilane synthase (HMBS), space group P21212 a = 88.06, b = 75.73, c = 50.35 A, yielded 47 Laue exposures in 2.5° angle intervals from a single crystal. The data processed by the Daresbury Laue software is highly complete (∞–2dmin = 77.5%; 2dmin–dmin= 91.7%) to 2.3 A with high redundancy (11.2). Comparison with calculated structure factors and careful analysis of the Laue geometry shows that between ∞ and 5dmin better completeness still should be possible, which can ideally be realized from CCD detector dynamic range hardware improvements and/or software algorithms to integrate saturated spot profiles. Prospects for Laue diffraction data collection using yet faster detectors such as the `pixel detector' to study irreversible catalytic structural processes in a crystal, the most challenging of all time-resolved experiments, are bright.

Strangeness production in high density baryon matter

Strangeness production in heavy ion collisions, when compared with proton-proton collisions, is potentially a sensitive probe for collective energy deposition and therefore for reaction mechanisms in general. It may therefore provide insight into possible quark-gluon plasma formation in dense nuclear matter. To establish an understanding of the observed yields, a systematic study of high density baryon matter at different beam energies is essential. This might also reveal possible discontinuities in the energy dependence of the reaction mechanism. We present preliminary results for kaon production in Au + Au collisions at beam kinetic energies of 6, 8, and 10.7 GeV/u obtained by the E917 experiment at the AGS (BNL). These measurements complement those carried out by the E866 Collaboration at 2, 4, and 10.7 GeV/u with a significantly enlarged data sample. In both experiments a large range of rapidities was covered by taking data at different angular settings of the magnetic spectrometer.

Deviation of the Subjective Vertical in Long-standing Unilateral Vestibular Loss

We evaluated changes in the subjectively perceived gravitational vertical as an index of imbalance in the function of the right and left otolith organs. In addition to normal subjects (n =25), we measured patients with a longstanding (mean 4.5 year ± 3.2 SD; range 0.5-11.5 years) unilateral vestibular loss after surgery for acoustic neuroma (n = 32), patients with partial unilateral vestibular loss (n = 7) and patients with bilateral vestibular hyporeflexia (n = 8). Normal subjects could accurately align a vertical luminous bar to the gravitational vertical in an otherwise completely dark room (mean setting –0.14° ± 1.11 SD). Patients with leftsided (complete; n = 13) or rightsided (complete; n = 19 and partial; n = 7) unilateral vestibular loss made mean angular settings at 2.55° ± 1.57 (SD) leftward and 2.22° (±1.96 SD) rightward, respectively. These means differed highly significantly from the normal mean (p < 0.00001). In the time interval investigated (0.5-11.5 years) the magnitude of the tilt angle showed no correlation with the time elapsed since the operation. The mean setting by patients with clinically bilateral vestibular loss (– 1.17° ± 1.96 SD; n = 8) did not significantly differ from the control group. The systematic tilts of the subjective vertical in patients with a unilateral vestibular impairment were correlated with their imbalance in canal-ocular reflexes, as reflected by drift during head-oscillation at 2 Hz (r2 = 0.44) and asymmetries in VOR-gain for head-steps (r2 = 0.48-0.67). These correlations were largely determined by the signs of the asymmetries; correlation between the absolute values of the VOR gain asymmetries and subjective vertical angles proved to be virtually absent. We conclude that the setting of the subjective vertical is a very sensitive tool in detecting a left-right imbalance in otolith function, and that small but significant deviations towards the defective side may persist for many years (probably permanently) after unilateral lesions of the labyrinth or the vestibular nerve.

The 12C(e, e′p) and 12C(e, e′pp) reactions in the Δ-resonance region

Abstract Coincidence cross sections for the 12 C(e, e′pp) and 12 C(e, e′p) reactions have been measured in the Δ-resonance region. The 12 C(e, e′pp) reaction has been measured at three different angular settings of the proton detectors to investigate the angular correlation between the emitted protons. The data, which have a low statistical accuracy, are compared with a calculation based on the direct-knockout mechanism, which includes one- and two-body currents. NN-correlations are accounted for via a correlation function, Δ-excitation via a two-body current and final-state interactions of the emitted protons via an optical potential. The 12 C(e, e′p) data, taken at large proton-emission angles, cover the region of high missing-energy values (145–275 MeV). The data are compared to results of a calculation taking into account meson exchange, intermediate Δ-excitation and pion production. This comparison shows that there is ample evidence for processes leading to multi-nucleon knockout.

Redetermination of the structure of guanine hydrochloride monohydrate

Redetermination of the structure of guanine hydrochloride monohydrate

Computer Assisted Stereotactic Biopsy and Volumetric Resection of Pediatric Brain Tumors

Like adults, children may undergo stereotactic CT, MRI, and digital angiography with their heads fixed in an imaging compatible head holder. Tumor volumes are digitized from stereotactic CT and MRI slice images. The tumor volume can then be sliced perpendicular to the surgical view line, which is the surgical approach expressed in terms of angular settings on the stereotactic instrument. These sliced images are displayed on a computer monitor in the operating room and are used to guide the surgery and help the surgeon identify the plane between tumor and surrounding brain tissue.

ChemInform Abstract: Structure of Decamethylferrocenium Tribromide

Fe{Cs(CH3)5}2)Br3, Mr=5658, ortho- rhombic, Cmcm, a = 15.162(5), b = 12.358 (5), c = 11-936 (5) A, V = 2236.4 A 3, Z = 4, Dx = 1.681 Mg m -a, A(Mo Ka) = 0.71069 A, /z = 5.985 mm-', F(000) = 1124, room temperature, final R = 0.040, wR = 0-044 for 856 reflections with I_ 2tr(/) and 86 variables. The solid is comprised of layers of alternating cations and anions, no signifi- cant interactions between the layers are observed. Introduction. Although a large number of ferrocene derivatives have been characterized by X-ray studies, only comparatively few compounds containing the ferrocenium ion have been investigated. Among these are ferrocenium triiodide (Bernstein & Herbstein, 1968), ferrocenium tetrachloroferrate (Paulus & Sch~ifer, 1978), 1,1'-dimethylferrocenium triiodide (Bats, de Boer & Bright, 1971) and a series of charge-transfer complexes containing the deca- methylferrocenium ion and spacious anions such as tetracyanoethenide (TCNE) and pentacyano- propenide (PCNP), which interact with the ferro- cenium moieties and give rise to interesting physical properties, for example, metamagnetism (Miller, Calabrese, Rommelmann, Chittipeddi, Zhang, Reiff & Epstein, 1987, and literature cited therein). Whereas the unsubstituted ferrocenium cations are mostly disordered, so that exact structural informa- tion on the cations cannot be obtained, substituted (e.g. decamethylferrocenium) cations do not seem to exhibit disorder. With this in view we have determined the crystal structure of the decamethyl- ferrocenium cation with a simple counterion, the Br3 anion. Experimental. The title compound was prepared by reaction of decamethylferrocene with Br2 in CC14 and recrystallized from methanol. Dark-green crystal plates, dimensions of crystal used for measurement 0.5 x 0.2 × 0-05 mm. Enraf-Nonius CAD-4 diffrac- tometer, graphite-crystal monochromator, Mo Ka radiation, unit-cell parameters determined from the angular settings of 25 reflections with 0.0 ___ 0 ___ 15 °. Intensity data for 1033 unique reflections up to 0 = 25 ° in the range O<_h_< 18, O_<k_< 14, 0<_l<_14 measured, using the oy-20-scan technique with a scan angle of 1.00 ° and a variable scan rate with a maxi- mum scan time of 60 s per reflection. Three check reflections measured at intervals of 200 reflections showed no significant intensity variation during the period of measurement. The data set was corrected for Lorentz and polarization effects, a Gaussian absorption correction procedure (Frenz, 1981) was used (Tmi, = 055, Tma x = 098). Systematic absences (hklwith h+k=2n+l; hOlwith h and l=2n+l;

Structure of decamethylferrocenium tribromide

Fe{Cs(CH3)5}2)Br3, Mr=5658, ortho- rhombic, Cmcm, a = 15.162(5), b = 12.358 (5), c = 11-936 (5) A, V = 2236.4 A 3, Z = 4, Dx = 1.681 Mg m -a, A(Mo Ka) = 0.71069 A, /z = 5.985 mm-', F(000) = 1124, room temperature, final R = 0.040, wR = 0-044 for 856 reflections with I_ 2tr(/) and 86 variables. The solid is comprised of layers of alternating cations and anions, no signifi- cant interactions between the layers are observed. Introduction. Although a large number of ferrocene derivatives have been characterized by X-ray studies, only comparatively few compounds containing the ferrocenium ion have been investigated. Among these are ferrocenium triiodide (Bernstein & Herbstein, 1968), ferrocenium tetrachloroferrate (Paulus & Sch~ifer, 1978), 1,1'-dimethylferrocenium triiodide (Bats, de Boer & Bright, 1971) and a series of charge-transfer complexes containing the deca- methylferrocenium ion and spacious anions such as tetracyanoethenide (TCNE) and pentacyano- propenide (PCNP), which interact with the ferro- cenium moieties and give rise to interesting physical properties, for example, metamagnetism (Miller, Calabrese, Rommelmann, Chittipeddi, Zhang, Reiff & Epstein, 1987, and literature cited therein). Whereas the unsubstituted ferrocenium cations are mostly disordered, so that exact structural informa- tion on the cations cannot be obtained, substituted (e.g. decamethylferrocenium) cations do not seem to exhibit disorder. With this in view we have determined the crystal structure of the decamethyl- ferrocenium cation with a simple counterion, the Br3 anion. Experimental. The title compound was prepared by reaction of decamethylferrocene with Br2 in CC14 and recrystallized from methanol. Dark-green crystal plates, dimensions of crystal used for measurement 0.5 x 0.2 × 0-05 mm. Enraf-Nonius CAD-4 diffrac- tometer, graphite-crystal monochromator, Mo Ka radiation, unit-cell parameters determined from the angular settings of 25 reflections with 0.0 ___ 0 ___ 15 °. Intensity data for 1033 unique reflections up to 0 = 25 ° in the range O<_h_< 18, O_<k_< 14, 0<_l<_14 measured, using the oy-20-scan technique with a scan angle of 1.00 ° and a variable scan rate with a maxi- mum scan time of 60 s per reflection. Three check reflections measured at intervals of 200 reflections showed no significant intensity variation during the period of measurement. The data set was corrected for Lorentz and polarization effects, a Gaussian absorption correction procedure (Frenz, 1981) was used (Tmi, = 055, Tma x = 098). Systematic absences (hklwith h+k=2n+l; hOlwith h and l=2n+l;

Angular-resolved ion-beam sputtering apparatus for large-area deposition

A new apparatus to utilize the directional nature of ion-beam sputter deposition is presented. Employment of an angular setting slit together with translational substrate scanning enables large-area deposition, keeping the angular settings unchanged. The merits of this apparatus were demonstrated step by step on a typical example: CdTe obliquely deposited films known for the anomolous photovoltaic effect.