Rotational Intervals Research Articles

Observer agreement of volar tilt of the wrist is influenced by forearm rotation

Dorsal/volar tilt is an important radiographic measurement commonly included in the treatment decision of distal radius fractures (DRFs). However, studies have shown that forearm positioning relative to rotation (i.e., supination and pronation) can affect the measured tilt value but with substantial interobserver variance. To examine whether interobserver agreement on radiographic tilt measurement is influenced by forearm rotation. We radiographed 21 cadaveric forearms at 5° rotational intervals between 15° supination and 15° pronation on lateral radiographs. A radiologist and a hand surgeon measured tilt in a blinded and randomized fashion. Bland-Altman analyses with bias and limits of agreement (LoA) were used to estimate interobserver agreement for forearms in all degrees of rotation, non-rotated forearms, supinated forearms, and pronated forearms. Interobserver agreement varied with forearm rotation. Bias (95% confidence interval [CI]; LoA) was -1.54° (95% CI: -2.53, -0.55; LoA: -13.46, 10.38) when measuring tilt on radiographs with all degrees of forearm rotation, and -1.48° (95% CI: -4.13, 1.17; LoA: -12.88, 9.92) when measuring tilt on true lateral 0° radiographs. When measuring on supinated and pronated radiographs, bias was -0.03° (95% CI: -1.35, 1.29; LoA: -8.34, 8.28) and -3.23° (95% CI: -5.41, -1.06; LoA: -16.90, 10.44), respectively. Interobserver agreement on tilt was similar when comparing measurements made on true lateral radiographs to those made on the group with all degrees of forearm rotation. However, interobserver agreement improved with supination and worsened with pronation.

Influence of brush seal hysteresis effect on the nonlinear characteristics of rotor system

The hysteresis effect of brush seal is a key factor affecting the sealing performance of the rotor system, so it is particularly important to study the nonlinear behaviors of the rotor-bearing-brush seal system under the hysteresis effect. First, the entire circle of bristle pack is classified according to the position angle and contact condition of single bristle, and the rotor support force, the interaction force between the bristles, the air pressure and the friction of back plate are considered. It is proposed to use the loss rate to calculate the uniform load of the back plate, according to the linear beam theory, the bending force model of bristle under different rotor eccentricity is established. Second, the hysteresis angle is proposed to represent the degree of hysteresis effect of the whole circle of bristle pack, and the seal force model under hysteresis effect is established. Third, considering the interaction of seal force and oil-film force, the dynamic model of Jeffcott rotor-bearing-brush seal system is established. The influence of hysteresis effect on the dynamic characteristics of rotor system is studied by using bifurcation diagram, axis orbit, Poincaré map, spectrum diagram and time history. It is found that the hysteresis effect has different degrees of influence on the nonlinear dynamic characteristics of the rotor system in different rotational velocity intervals. In addition, the influence of seal interference on the motion state of rotor system cannot be ignored.

Determination of the Critical Speed of a Cracked Shaft from Experimental Data.

In this work, a procedure to obtain an accurate value of the critical speed of a cracked shaft is presented. The method is based on the transversal displacements of the cracked section when the shaft is rotating at submultiples of the critical speed. The SERR (Strain Energy Ralease Rate) theory and the CCL (Crack Closure Line) approach are used to analyse the proposed methodology for considering the behaviour of the crack. In order to obtain the best information and to define the procedure, the orbits and the frequency spectra at different subcritical rotational speed intervals are analyzed by means of the Fast Fourier Transform. The comparison of the maximum values of the FFT peaks within the intervals allows the subcritical speed to be determined, along with the value of the critical speed. When verified, the proposed procedure is applied to shafts with the same geometry and material and with cracks of increasing depth. The results show that the critical speed diminishes with the severity of the crack, as expected. A comparison is made between the critical speed obtained using the vertical and the horizontal displacements, finding no remarkable differences, meaning that in practical applications only one sensor for one of the displacements (in the vertical or horizontal direction) is needed to determine the critical speed. This is one of the main contributions of the paper, as it means that the orbits of the shaft are not needed. Finally, after this study we can conclude that the best results are achieved when the critical speed is obtained using data displacement in only one direction within the intervals around 12 or 13 of the critical speed.

Evaluation of imazapic and flumioxazin carryover risk for Carinata (Brassica carinata) establishment

AbstractCarinata (Brassica carinata A. Braun) is a potential crop for biofuel production, but the risk of injury resulting from carryover of soil herbicides used in rotational crops is of concern. The present study evaluated the carryover risk of imazapic and flumioxazin for carinata. Label rates of imazapic (70 g ai ha−1) and flumioxazin (107 g ai ha−1) were applied 24, 18, 12, 6, and 3 mo before carinata planting (MBP). The same herbicides were applied preemergence right after carinata planting at 1X, 0.5X, 0.25X, 0.125X, 0.063X, and 0X the label rate. When either herbicide was applied earlier than 3 MBP, there was no difference in plant density compared with the nontreated control. Carinata damage was <25% when flumioxazin or imazapic was applied at least 6 MBP in Clayton, NC (sandy loam soil), while in Jackson Springs, NC (coarser-textured soil and higher precipitation), at least 12 MPB were needed to lower plant damage to <25%. Preemergence application of 0.063X each herbicide decreased plant density by 40%, with damage reaching >25%. Quantification of herbicide residues in both soils showed that imazapic moved deeper in the soil profile than flumioxazin. This was more evident in Jackson Springs, where 0.68, 3.52, and 7.77 ng of imazapic g−1 soil were detected (15- to 20-cm depth) when the herbicide was applied at 12, 6 and 3 MBP, respectively, while no flumioxazin residues were detected at the same soil depths and times. When residues were 7.78 and 6.90 ng herbicide g−1 soil in the top 10 cm of soil for imazapic and flumioxazin, respectively, carinata exhibited at least 25% damage. Rotational intervals to avoid imazapic and flumioxazin damage to carinata should be between 6 and 12 MBP depending on soil type and environmental conditions, with longer intervals for the former than the latter.

Multipole-moment effects in ion-molecule reactions at low temperatures: part I - ion-dipole enhancement of the rate coefficients of the He+ + NH3 and He+ + ND3 reactions at collisional energies Ecoll/kB near 0 K.

The energy dependence of the rates of the reactions between He+ and ammonia (NY3, Y = {H,D}), forming NY2+, Y and He as well as NY+, Y2 and He, and the corresponding product branching ratios have been measured at low collision energies Ecoll between 0 and kB·40 K using a recently developed merged-beam technique [Allmendinger et al., ChemPhysChem, 2016, 17, 3596]. To avoid heating of the ions by stray electric fields, the reactions are observed within the large orbit of a highly excited Rydberg electron. A beam of He Rydberg atoms was merged with a supersonic beam of ammonia using a curved surface-electrode Rydberg–Stark deflector, which is also used for adjusting the final velocity of the He Rydberg atoms, and thus the collision energy. A collision-energy resolution of about 200 mK was reached at the lowest Ecoll values. The reaction rate coefficients exhibit a sharp increase at collision energies below ∼kB·5 K and pronounced deviations from Langevin-capture behaviour. The experimental results are interpreted in terms of an adiabatic capture model describing the rotational-state-dependent orientation of the ammonia molecules by the electric field of the He+ atom. The model faithfully describes the experimental observations and enables the identification of three classes of |JKMp〉 rotational states of the ammonia molecules showing different low-energy capture behaviour: (A) high-field-seeking states with |KM| ≥ 1 correlating to the lower component of the umbrella-motion tunnelling doublet at low fields. These states undergo a negative linear Stark shift, which leads to strongly enhanced rate coefficients; (B) high-field-seeking states subject to a quadratic Stark shift at low fields and which exhibit only weak rate enhancements; and (C) low-field-seeking states with |KM| ≥ 1. These states exhibit a positive Stark shift at low fields, which completely suppresses the reactions at low collision energies. Marked differences in the low-energy reactivity of NH3 and ND3—the rate enhancements in ND3 are more pronounced than in NH3—are quantitatively explained by the model. They result from the reduced magnitudes of the tunnelling splitting and rotational intervals in ND3 and the different occupations of the rotational levels in the supersonic beam caused by the different nuclear-spin statistical weights. Thermal capture rate constants are derived from the model for the temperature range between 0 and 10 K relevant for astrochemistry. Comparison of the calculated thermal capture rate coefficients with the absolute reaction rates measured above 27 K by Marquette et al. (Chem. Phys. Lett., 1985, 122, 431) suggests that only 40% of the close collisions are reactive.

Veering and merging analysis of nonlinear resonance frequencies of an assembly bladed disk system

This paper presents an investigation of the eigenvalues of veering and merging phenomena of a bladed disk system with contact features (an assembly bladed disk system). Of particular interest are the vibrational characteristics at rotational speed intervals at which the eigenvalue loci exhibit veering and merging phenomena. Furthermore, the current work attempts to investigate the interactions between the disk-dominated and blade-dominated families of modes in an assembly bladed disk system. In this regard, a representative model of an assembly bladed disk system is proposed, implementing an improved Euler-Bernoulli beam to model the rotating blade. The coupled equations of the bladed disk system are discretized using the modal functions which satisfy the eigenvalue problem. The change in modal properties of a blisk system with rotational speed is initially depicted to provide a reference for the analysis of a nonlinear system. Thereafter, the modal spectrum of the assembly bladed disk system is computed and analyzed by a frequency-domain method. Numerical analysis reveals that coupling interaction induces a series of eigenvalue veering and merging phenomena and that the modal frequencies at low rotational speeds are significantly affected by the nonlinearity of contact features. In particular, corresponding analysis of the mechanisms of these phenomena is presented. Furthermore, the present work also investigates the sensitivity of a low rotational speed interval and merging phenomena to several parameters.

Pasture productivity and quality of Urochloa brizantha cultivar Marandu evaluated at two grazing intervals and their impact on milk production

The present study aimed to evaluate two rotational stocking intervals (GI) over three consecutive grazing periods on forage productivity, crude protein and neutral detergent fibre of Urochloa brizantha cv. Marandu pastures, and the subsequent impact on milk production. Grazing treatments were (1) fixed rest period at 30 days (30-FG) and (2) grazing interval when canopy was intercepting 95% photosynthetically active radiation (95-LI). Eighteen multiparous Holstein × Zebu cows (548 ± 61.0 kg bodyweight, BW) and 70 ± 18.1 days in milk were used. Experiment lasted for 99 days (i.e. 33 days per period). Nine cows with similar milk production and BW were randomly allocated to each GI treatment balanced on milk production and BW. The adjustment of carrying capacity per paddock was made aiming to achieve a post-grazing residual height of 20 cm. For this, additional dry Holstein × Zebu cows (averaging 550 kg BW) were added and removed from the paddocks according put-and-take technique. Data were statistically analysed considering field sites as block (n = 2), GI (30-FG vs 95-LI), periods (three consecutive) and interaction GI × periods. Interactions occurred between GI and periods for pre- and post-grazing height (P ≤ 0.05). Greater pre-grazing height was observed for 30-FG (P < 0.01), but post-grazing height was greater (P < 0.01) for 30-FG only in the third period. GI for treatment 30-FG was ~6 days longer (P = 0.01) than that for 95-LIand light interception was greater (2%) for 30-FG. Total forage, stem and dead material mass per area were greater (P < 0.01) for 30-FG than 95-LI. However, stocking rate was 11.3% greater (P = 0.02) for 95-LI than 30-FG. In the pre-grazing period, 95-LI had greater (P < 0.01) proportion of leaves and a greater leaf : stem ratio, whereas neutral detergent fibre concentration tended to be lower (P = 0.08) and crude protein concentration greater (P < 0.01) in 95-LI than in 30-FG. Daily milk productivity per area and its components were 16–28% greater (P < 0.01) for 95-LI than for 30-FD. These results suggest that GI of Marandu grass determined by light interception at 95% (95-LI) enabled the reduction of GI, improved forage nutritive value and increased milk productivity compared with a fixed 30 days (30-FG) of rest.

Sensitivity to electron-to-proton mass ratio variation from 12C2H2 rovibrational transitions to v1 + v3 and v1 + v2 + v4 + v5 interacting levels

Calculations of the sensitivity to a variation of the electron-to-proton mass ratio μ for 12C2H2 transitions of the v1+v3 and v1+v2+v4+v5 bands in the spectral region at 1.5μm are presented. They account for the Fermi and l-type rotation and vibration resonances of the excited states. The frequency splittings between near resonant transitions, arising from a cancellation of effective rotational intervals with frequency shifts associated to the vibrational band origin, the anharmonicity and the rotation-vibration interactions, have sensitivity coefficients to a variation of μ of both signs in the range of 10–103. The measurements of temporal drifts of frequency splittings against the Cs frequency standard have the potential to better constrain a variation of μ comparing to that of other fundamental constants. The systematic frequency shifts for frequency splittings are discussed for experimental setups based on intracavity saturated absorption spectroscopy and the constraint of a measurement of a fractional variation of μ is projected at 10−10 level.

High-resolution spectroscopy of [formula omitted] using Rydberg-series extrapolation and Zeeman-decelerated supersonic beams of metastable He2

Recently, high-resolution spectroscopy of slow beams of metastable helium molecules He2∗ generated by multistage Zeeman deceleration was used in combination with Rydberg-series extrapolation techniques to obtain the lowest rotational interval in the molecular helium ion at a precision of 18MHz (Jansen et al., 2015), limited by the temporal width of the Fourier-transform-limited laser pulses used to record the spectra. We present here an extension of these measurements in which we have (1) measured higher rotational intervals of He2+, (2) replaced the pulsed UV laser by a cw UV laser and improved the resolution of the spectra by a factor of more than five, and (3) studied MJ redistribution processes in regions of low magnetic fields of the Zeeman decelerator and shown how these processes can be exploited to assign transitions originating from specific spin–rotational levels (N″,J″) of He2∗.

Sensitivity to proton-to-electron mass ratio variation from pairs of isotopic lithium hydride rotational and rovibrational transitions

Calculations of the sensitivities of rotational and rovibrational transitions of isotopic lithium hydride in the electronic ground state to a variation of the proton-to-electron mass ratio constant are presented. A highly enhanced sensitivity coefficient is observed for the splitting of near resonant transitions arising from a cancellation between rotational intervals and frequency shifts associated respectively to the isotope effect, to the anharmonicity and to the rotation-vibration interaction. It ranges from 73 748.47(1) to −21 672(137) for the transitions with low to intermediate rotational quantum numbers in the lowest vibrational energy levels. The splittings of rotational transitions of 7LiD in the vibrational level v = 0 and 6LiD in the vibrational level v = 2 have a sensitivity coefficient of ∼−3 for J up to 29 and that of 6LiH R(0) and 7LiH R(1) rovibrational transitions in the v = 0 − >1 band has a sensitivity coefficient of −585. The approach allowed comparison of frequency intervals between rotational lines with ammonia inversion lines detected in the microwave spectra of B0218 + 367 quasar to put constraints to a variation of the proton-to-electron mass ratio.

Morfogênese de gramíneas nativas do Rio Grande do Sul (Brasil) submetidas a pastoreio rotativo durante primavera e verão

O trabalho objetivou determinar a influência de intervalos de pastoreio rotativo sobre a morfogênese de cinco gramíneas nativas da região central do Rio Grande do Sul (RS), agrupadas segundo uma tipologia funcional, nas estações de primavera e verão. Foram avaliadas taxa de aparecimento, elongação e senescência foliares (TAF/TEF/TSF), filocrono e duração de vida e de elongação foliares (DVF/DEF) em Axonopus affinis, Aristida laevis, Andropogon lateralis, Paspalum notatum e Paspalum plicatulum, sob dois intervalos de pastoreio rotativo, definidos por somas térmicas (°C), 375 e 750 graus-dia, na primavera 2010 e verão 2010/2011. Não houve diferença significativa entre intervalos de pastoreio, mas houve entre espécies e entre estações. Paspalum notatum se destacou por apresentar adaptações bem marcadas ao pastejo. Axonopus affinis e P. notatum foram as espécies com maiores TAF e menores DVF, já A. lateralis apresentou características morfogênicas que contradizem a literatura. Quanto às estações, primavera se caracterizou como a estação de crescimento, e verão, como o início do florescimento. Pastejo afeta a morfogênese de forrageiras, no entanto, os intervalos de pastoreio usados não têm efeito sobre o desenvolvimento das espécies e a influência estacional é marcante no desenvolvimento dessas gramíneas.

Predicting the optimal rotation length of Teak plantations using a simulation model

The traditional problem in Forest Economics has been mainly dealt with the estimation of optimalrotation length for sustainable management. However, given the limitation of the availability of timeseries data on growth and management in forest plantations in Sri Lanka, such estimations are notfeasible. Against this background, this study attempted to develop a simulation model and predictrotational interval of teak plantation under different management conditions.A field survey was conducted to identify the plantation related parameters in the Kurunegala District.Meantime, a simulation model was developed with Microsoft Visual Basic and Microsoft Excel usingthe equations specified in the Teak Management Plan (1997) to supplement the field data. The pastdata obtained from the Forest Department was used to parameterize the model. Using the age andthe height of a plantation at a particular time, the model was capable of predicting the plantationrelated parameters such as dbh and timber volume over the time.According to the values predicted by the simulation model, four different categories were identifiedbased on the site index, which represents the level of growth of a stand. Rotational interval wasestimated using the Faustman rotational model at different discount rates. Thereby it was estimatedthat the rotational intervals for the four categories at discount rates 10%, 15% and 20% as 19, 17 and15 years respectively. The internal rate of return obtained through the simulation was above themarket rate of 12%. Though the model yielded shorter rotational intervals than the present fieldvalues, the approach could be used in future with more reliable field data.

Phase-resolved spectroscopic study of the isolated neutron star RBS 1223 (1RXS J130848.6+212708)

The data from all observations of RBS 1223 (1RXS J130848.6+212708) conducted by XMM-Newton EPIC pn with the same instrumental setup in 2003-2007 were combined to form spin-phase resolved spectra. A number of complex models of neutron stars with strongly magnetized ($B_{pole} 10^{13}-10^{14}$ G) surface, with temperature and magnetic field distributions around magnetic poles, and partially ionized hydrogen thin atmosphere above it have been implemented into the X-ray spectral fitting package XSPEC for simultaneous fitting of phase-resolved spectra. A Markov-Chain-Monte-Carlo (MCMC) approach is also applied to verify results of fitting and estimating in multi parameter models. The spectra in different rotational phase intervals and light curves in different energy bands with high S/N ratio show a high complexity. The spectra can be parameterized with a Gaussian absorption line superimposed on a blackbody spectrum, while the light curves with double-humped shape show strong dependence of pulsed fraction upon the energy band (13%-42%), which indicates that radiation emerges from at least two emitting areas. A model with condensed iron surface and partially ionized hydrogen thin atmosphere above it allows us to fit simultaneously the observed general spectral shape and the broad absorption feature observed at 0.3 keV in different spin phases of RBS 1223. It allowed to constrain some physical properties of X-ray emitting areas, i.e. the temperatures ($T_{p1} ~ 105$ eV, $T_{p2} ~ 99$ eV), magnetic field strengths ($B_{p1}= B_{p2} ~ 8.6x10^{13}$G) at the poles, and their distributions parameters ($a_{1} 0.61, a_{2} 0.29$, indicating an absence of strong toroidal magnetic field component). In addition, it puts some constraints on the geometry of the emerging X-ray emission and gravitational redshift ($z=0.16^{+0.03}_{-0.01}$) of RBS 1223.

Acoustic Signatures of Three Marine Arthropods, Squilla mantis (Linnaeus, 1758), Homarus americanus (H. Milne Edwards, 1837), and Nephrops norvegicus (Linnaeus, 1758) (Arthropoda, Malacostraca)

AbstractThe acoustic signatures of three marine crustaceans, Squilla mantis (Linnaeus, 1758), Homarus americanus (H. Milne Edwards, 1837), and Nephrops norvegicus (Linnaeus 1758) (Arthropoda, Malacostraca), were experimentally determined in measurements using the calibration tank at the NATO Undersea Research Center, La Spezia, Italy. The specimens were insonified at 45° rotational intervals with a sound source emitting pings from 30 to 120 kHz. For all three species, the value of the nondimensional parameter ka (where k is the acoustic wave number and a is the characteristic dimension of the object) was >5. The absorption spectra, defined as the frequencies at which the intensity of the reflected sound was less than 5% of the incident intensity, were determined. These spectra changed with the changing aspects and were unique for each animal in this study. Two of the species were in the same infraorder, Astacidea. Our results contribute to the development of an acoustic identification system for surveys of marine animals.

Biomechanical principles in diarthroses and synarthroses. IV: the mechanics of lumbar vertebrae. A pilot study

Theoretical considerations help define the requirements for an apparatus that is to localize the instantaneous helical axes (IHA) of axial rotations of lumbar segments. Since the range of axial rotation of an L3/4 segment is in only approximately +/- 1.5 degrees the rotational angle intervals have to be smaller than 0.3 degree with an resolution less than 0.03 degree in order to be able to determine the loci of the IHAs. For the first time in vitro measurements are presented that satisfy this requirement. The data prove that the guidance by the artt. zygapophysiales critically influence the possible positions of the IHA. Comparatively, ligaments and intervertebral disk play a marginally role. During axial torques Tz the IHAs lie dorsal to the intervertebral disk and migrate from one joint to the other depending on axial rotation (length of migration: approximately 3-4 cm). The IHAs lie almost parallel to the axial torque vector. When the joints are removed the IHA is stationary and almost perpendicular to the intervertebral disk and intersects the disk's central region. The screw inclination (pitch) of the instantaneous screw movement is proportional to the rotational angle. Therefore, depending on the direction of rotation, one obtains left or right handed screw movements. This means: axial torsional load leads to an increase in thickness of the intervertebral disk. During preloads that produces extensions the fixed centrodes (paths of axis migration) of intact segments are dorsally beaten out, whereas during flexional loads they are ventrally beaten out. Then, the IHAs migrate through the canalis vertebralis. By the concept "dimeric link chain" the different shapes of the fixed centrode are traced back to the morphology of curvature of the articulating surfaces. The measurements suggest the hypothesis that the distinct nonlinearity of the load displacement curves (s-shape of alpha = alpha (Tz) funktion is an affection of IHA migration. Comparatively, the influence of ligaments can be neglected. The measurements suggest the hypothesis that the hysteresis of the load displacement curves (neutral zone) is an artefact that does not appear in vivo. Altogether, the experiments prove that the loci of the IHAs are determined by the interplay of preload, structure of the applied force system and morphology of curvature of the articulating surfaces. By that the possibility is clinically given to calculate the multitude of possible movements as function of muscle activity when in the individual the shape and the position of the articulating surfaces are measured in vivo (by NMR-methods e.g.). A physically based classification of pathological cases seems to be possible.

Spectroscopic study of the 14NH radical in vibrationally excited levels of the X3Σ− state by far infrared laser magnetic resonance

Rotational transitions of vibrationally excited NH (ν = 1 and 2) in the ground X3Σ− electronic state have been detected by far-infrared laser magnetic resonance. The first four rotational intervals were investigated (N = 1 − 0, 2 − 1, 3 − 2, and 4 − 3) with a total of 17 far-infrared laser lines ranging in wavelength from 81.1 to 373.6 µm. For some rotational intervals, transitions between all components of the Zeeman manifolds were observed. An effective Hamiltonian was used to model the experimental measurements. The magnetic hyperfine parameters have been determined for the first time for the ν = 2 level and have been significantly improved for the ν = 1 level. In addition, the rotational, centrifugal distortion, spin-spin, spin-rotation, and Zeeman parameters have all been experimentally determined for the ν = 1 and 2 levels of NH.

Rotation length, canola variety and herbicide resistance system affect weed populations and yield

A 4-year study was initiated in 1997 to provide canola producers with information on the consequences of various rotational intervals with the use of new disease and herbicide-resistant canola varieties. The study was conducted at three locations in Alberta, Canada (Ellerslie, Strathmore, and Warburg). At each location, four canola rotations were established: continuous canola, and canola seeded in 1 of 2, 3, or 4 years. Canola varieties included the conventional varieties ‘AC Excel’ and ‘Quantum’, the glyphosate-resistant variety ‘Quest’, imidazolinone-resistant ‘45A71’, and a glufosinate-resistant hybrid, ‘Invigor 2153’. In the fourth year of the study, when canola was grown in all treatments, weed densities, weed species diversity, and evenness were determined preseeding and before and after in-crop herbicide application. Canola yield was greatest in the northern ecoregions of the Boreal Transition (Warburg) and Aspen Parkland (Ellerslie), and lowest in the Moist Mixed Grassland ecoregion (Strathmore). Weed populations increased and population diversity decreased and became less even where rotations were less diverse; in continuous canola and in the 1-in-4–year rotation. As expected, weed densities increased in poorly competitive, conventional canola varieties compared to herbicide-resistant varieties sprayed with their broader-spectrum herbicides. Where weed densities were high, variety/herbicide system became a critical factor affecting crop yield. Under these conditions, the herbicide-resistant varieties ‘Quest’ and ‘Invigor 2153’ typically outyielded the conventional varieties of ‘AC Excel’ and ‘Quantum’. Canola yield was highest when grown in a 1-in-3– or a 1-in-4–year rotation, although the 1-in-3–year rotation generally had lower weed densities, and allowed high-value canola to be grown more frequently in rotation.

Enhanced effect of temporal variation of the fine-structure constant in diatomic molecules

We show that the relative effect of variation of the fine-structure constant in microwave transitions between very close and narrow rotational-hyperfine levels may be enhanced 2--3 orders of magnitude in diatomic molecules with unpaired electrons like LaS, LaO, LuS, LuO, YbF, and similar molecular ions. The enhancement is result of cancellation between the hyperfine and rotational intervals.

Three-dimensional echocardiographic acquisition at 8 degree rotational intervals allows rapid volume rendered reconstruction of atrial septal defects with adequate morphological and accurate quantitative assessment Youssef F. M. Nosir, Anita Dall'Agata; Ron T van Domburg, Ad JJC Bogers and Jos RTC Roelandt. Heartcenter, Erasmus University, Rotterdam, The Netherlands, Cardiology Department, Al-Azhar University, Cairo, Egypt

Three-dimensional echocardiographic acquisition at 8 degree rotational intervals allows rapid volume rendered reconstruction of atrial septal defects with adequate morphological and accurate quantitative assessment Youssef F. M. Nosir, Anita Dall'Agata; Ron T van Domburg, Ad JJC Bogers and Jos RTC Roelandt. Heartcenter, Erasmus University, Rotterdam, The Netherlands, Cardiology Department, Al-Azhar University, Cairo, Egypt

Optimal Rotational Interval for 3-Dimensional Echocardiography Data Acquisition for Rapid and Accurate Measurement of Left Ventricular Function

Background: Prolonged 3-dimensional echocardiography (3DE) acquisition time currently limits its routine use for calculating left ventricular volume (LVV) and ejection fraction (EF). Our goal was to reduce the acquisition time by defining the largest rotational acquisition interval that still allows 3DE reconstruction for accurate and reproducible LVV and EF calculation. Methods: Twenty-one subjects underwent magnetic resonance imaging and precordial 3DE with 2° acquisition intervals. Images were processed to result in data sets containing images at 2°, 4°, 8°, 16°, 32°, and 64° intervals by excluding images in between. With use of the paraplane feature, 8 equidistant short-axis slices were generated from each data set. The suitability of these short-axis slices for manual endocardial tracing was scored visually by 4 independent experienced observers. The LVV and EF were calculated by using Simpson’s rule from 3DE data sets with 2°, 8°, and 16° intervals, and the results were compared with values obtained from magnetic resonance imaging. The probability of 3DE to detect LVV and EF differences was calculated. Results: All patients were in sinus rhythm with a mean heart rate of 72 bpm (SD ± 12). The LV short-axis images obtained with 16° rotational scanning intervals allowed LV endocardial tracing in all subjects. Good correlation, close limits of agreement, and nonsignificant differences were found between values of LVV and EF calculated with 3DE at 2°, 8°, and 16° rotational intervals and those obtained with magnetic resonance imaging. At steps of 16°, 3DE had excellent correlation (r = 98, 99, and 99), close limits of agreement (±38, ±28.6, and ±4.8), and nonsignificant differences (P =.5,.8, and.2) with values obtained from magnetic resonance imaging for calculating end-diastolic LVV, end-systolic LVV, and EF, respectively. Three-dimensional echocardiography with use of 16° rotational intervals could detect 15-mL differences in end-diastolic volume with a probability of 95%, 11-mL differences in end-systolic volume with a probability of 92%, and 0.02 differences in EF with a probability of 95%. Conclusions: The 3DE data sets reconstructed with images selected at 16° intervals from data sets obtained at 2° precordial rotational acquisition intervals allowed the generation of LV short-axis images with adequate quality for endocardial border tracing. Therefore precordial acquisition at 16° intervals would be sufficient for the reconstruction of 3DE data sets for LV function measurement. This would reduce the acquisition time while maintaining enough accuracy for clinical decision making and would thus make 3DE more practical as a routine method. (J Am Soc Echocardiogr 2000;13: 715-22.)