Harmonic Fitting Research Articles

A SELF-SIMILAR EXPANSION MODEL FOR USE IN SOLAR WIND TRANSIENT PROPAGATION STUDIES

Since the advent of wide-angle imaging of the inner heliosphere, a plethora of techniques have been developed to investigate the three-dimensional structure and kinematics of solar wind transients, such as coronal mass ejections, from their signatures in single- and multi-spacecraft imaging observations. These techniques, which range from the highly complex and computationally intensive to methods based on simple curve fitting, all have their inherent advantages and limitations. In the analysis of single-spacecraft imaging observations, much use has been made of the fixed ϕ fitting (FPF) and harmonic mean fitting (HMF) techniques, in which the solar wind transient is considered to be a radially propagating point source (fixed ϕ, FP, model) and a radially expanding circle anchored at Sun centre (harmonic mean, HM, model), respectively. Initially, we compare the radial speeds and propagation directions derived from application of the FPF and HMF techniques to a large set of STEREO/Heliospheric Imager (HI) observations. As the geometries on which these two techniques are founded constitute extreme descriptions of solar wind transients in terms of their extent along the line of sight, we describe a single-spacecraft fitting technique based on a more generalized model for which the FP and HM geometries form the limiting cases. In addition to providing estimates of a transient's speed and propagation direction, the self-similar expansion fitting (SSEF) technique provides, in theory, the capability to estimate the transient's angular extent in the plane orthogonal to the field of view. Using the HI observations, and also by performing a Monte Carlo simulation, we assess the potential of the SSEF technique.

Speeds and Arrival Times of Solar Transients Approximated by Self-similar Expanding Circular Fronts

The NASA STEREO mission opened up the possibility to forecast the arrival times, speeds and directions of solar transients from outside the Sun-Earth line. In particular, we are interested in predicting potentially geo-effective Interplanetary Coronal Mass Ejections (ICMEs) from observations of density structures at large observation angles from the Sun (with the STEREO Heliospheric Imager instrument). We contribute to this endeavor by deriving analytical formulas concerning a geometric correction for the ICME speed and arrival time for the technique introduced by Davies et al. (2012, ApJ, in press) called Self-Similar Expansion Fitting (SSEF). This model assumes that a circle propagates outward, along a plane specified by a position angle (e.g. the ecliptic), with constant angular half width (lambda). This is an extension to earlier, more simple models: Fixed-Phi-Fitting (lambda = 0 degree) and Harmonic Mean Fitting (lambda = 90 degree). This approach has the advantage that it is possible to assess clearly, in contrast to previous models, if a particular location in the heliosphere, such as a planet or spacecraft, might be expected to be hit by the ICME front. Our correction formulas are especially significant for glancing hits, where small differences in the direction greatly influence the expected speeds (up to 100-200 km/s) and arrival times (up to two days later than the apex). For very wide ICMEs (2 lambda > 120 degree), the geometric correction becomes very similar to the one derived by M\"ostl et al. (2011, ApJ, 741, id. 34) for the Harmonic Mean model. These analytic expressions can also be used for empirical or analytical models to predict the 1 AU arrival time of an ICME by correcting for effects of hits by the flank rather than the apex, if the width and direction of the ICME in a plane are known and a circular geometry of the ICME front is assumed.

中国东部亚热带地区树轮δ13C方位变化的谐波分析

PDF HTML阅读 XML下载 导出引用 引用提醒 中国东部亚热带地区树轮δ13C方位变化的谐波分析 DOI: 10.5846/stxb201109191378 作者: 作者单位: 临沂大学资源与环境研究院,临沂大学化学与化工学院,南京师范大学地理科学学院,南京师范大学地理科学学院,中国科学院南京地理与湖泊研究所湖泊沉积与环境开放实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(41072139); 山东省自然科学基金项目(Y2008E15); 临沂大学博士启动基金项目(BS07014) Analyzing the azimuth distribution of tree ring δ13C in subtropical regions of eastern China using the harmonic analysis Author: Affiliation: Research Institute of Resources and Environment, Linyi University,School of Chemistry,College of Geographical Science, Nanjing Normal University,College of Geographical Science, Nanjing Normal University,Lake Sediment and Environmental Opening Laboratory of Nanjing Geography and Limnology Institute, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对浙江天目山2株柳杉(Cryptomeria fortunei Hooibrenk ex Otto et Dietr,分别简称为CF-1,CF-3)及南京紫金山8株马尾松(Pinus massoniana Lamb.,分别简称为PM-1-PM-4,PM-7-PM-10)树轮δ13C平均值方位序列及2株柳杉树轮δ13C方位平均值年序列进行了谐波分析。分析结果及相关性检验表明,树轮δ13C值的方位变化有很强的谐波特征。第1次谐波与第2次谐波分量的方差贡献率占原序列总方差的百分比,除PM-8与PM-10低于70%外,其余均在70％以上,其中,CF-1与PM-9分别达到了93%和96.5％。第1次与第2次(或第3次)谐波的拟合序列与原序列的相关性极高,相关系数均在0.8以上,都通过了0.05的显著性检验,而且,两次谐波的拟合度均比较高,均在75％以上,拟合效果较好。分析结果表明,用2π与π(PM-1与PM-7为2π/3)两个主要谐波周期就可以较好地拟合各树轮δ13C序列的方位变化。初相位值的计算结果显示,第1、2次谐波的初相位值存在明显差异,这表明:不同树体2次谐波振幅的峰值出现的方位区域不同,即以2π及以π(PM-1与PM-7为2π/3)为周期的树轮δ13C方位变化的极大值并不出现在固定方位区。所以,两次谐波叠加的结果使树轮δ13C极值出现的方位区域更复杂。对天目山2株柳杉树轮δ13C各方位均值年序列的分析结果表明,2树轮δ13C极值均存在明显的年际漂移,其极大值出现频率较高的方位随树木生长坡向而发生转移。两树轮相比,多数年份其δ13C的主极大值出现的方位区基本发生45°的方位转移。而主、次极大值叠加的结果却使δ13C极值出现的方位基本发生90°的转移,这种极值转移的方向及转移度数与2株树所在坡向的变化和坡向变化度数正好相一致。 Abstract:The azimuth average sequence of δ13C in tree rings of two Cryptomeria fortunei Hooibrenk ex Otto et Dietr disks(named CF-1, CF-3,respectively) and eight Pinus massoniana Lamb disks(named PM-1-PM-4, PM-7-PM-10,respectively), as well as the average orientation annual series of δ13C in tree rings of Cryptomeria fortunei, were investigated using harmonic analysis. Data related to Cryptomeria fortunei and Pinus massoniana were collected from Tianmu Mountain, Zhejiang Province and Purple Mountain of Nanjing, Jiangsu Province, respectively. The analysis showed the azimuth variations of δ13C in tree-rings had very strong harmonic characteristics. The variance contribution of the first and second harmonic components as a percentage of the total variance of the original sequence were mostly above 70%, including CF-1 and PM-9 which reached 93% and 96.5%, respectively, the two exceptions were PM-8 and PM-10. The correlation coefficients were greater than 0.8 (P ＜ 0.05) between the first and the second (or the third) harmonic fitting sequence, and the original sequence. The two harmonic fitting sequences were relatively high, both above 75%, and exhibited a good fit to the data. The azimuth variations of δ13C in tree rings could be well explained by two harmonic cycles of 2 π and π (PM-1 and PM-7 were 2 π/3). The initial phase values of the first and the second harmonics had clear differences. This indicates that the doubling of the harmonic amplitude peak in different trees was present in different azimuth regions:the maximum of the azimuth variations of δ13C in tree rings with 2π and π harmonic cycles were in different regions. When the results of the two harmonic cycles were superimposed, the orientation of the maximum δ13C in tree rings became complex. Harmonic analysis of the average annual sequences of δ13C in different azimuths of C. fortunei showed that the extremes have obvious inter-annual drift. The azimuths of the δ13C maximum changed with slope of tree growth. In most years, the azimuth of the δ13C maximum transferred 45°, but when the main and secondary maximums were superimposed, it became 90°. The change in the direction and magnitude of the δ13C maximums are consistent with the slope changes in the growth of the two trees. 参考文献 相似文献 引证文献

Dynamic Consumption and Portfolio Decisions withEstimated Low Frequency Movements of Asset Returns

This article estimates and employs low frequency components of asset returns and uses dynamic programming to evaluate dynamic consumption and asset allocation decisions. The low frequency components are estimated through fast Fourier transform (FFT). After harmonic fits of actual U.S. time series data using FFT, dynamic programming is used to solve for dynamic consumption and asset allocation decisions. Furthermore, dynamic consumption and asset allocation decisions are explored for varying risk aversions and varying time horizons across investors. The welfare of investors as well as the fate of their wealth is also explored. We also spell out some rough practical guidelines for financial investments for the case of time-varying asset returns.

The influence of calculation method on estimates of cerebral critical closing pressure

The critical closing pressure (CrCP) of cerebral circulation is normally estimated by extrapolation of instantaneous velocity–pressure curves. Different methods of estimation were analysed to assess their robustness and reproducibility in both static and dynamic applications. In ten healthy subjects (mean ± SD age 37.5 ± 9.2 years) continuous recordings of arterial blood pressure (BP, Finapres) and bilateral cerebral blood flow velocity (transcranial Doppler ultrasound, middle cerebral arteries) were obtained at rest. Each session consisted of three separate 5 min recordings. A total of four recording sessions for each subject took place over a 2 week period. A total of 117 recordings contained 34 014 cardiac cycles. For each cardiac cycle, CrCP and resistance-area product (RAP) were estimated using linear regression (LR), principal component analysis (PCA), first harmonic fitting (H1), 2-point systolic/diastolic values (2Ps) and 2-point mean/diastolic values (2Pm). LR and PCA were also applied using only the diastolic phase (LRd, PCAd). The mean values of CrCP and RAP for the entire 5 min recording (‘static’ condition) were not significantly different for LRd, PCAd, H1 and 2Pm, as opposed to the other methods. The same four methods provided the best results regarding the absence of negative values of CrCP and the coefficient of variation (CV) of the intra-subject standard error of the mean (SEM). On the other hand, ‘dynamic’ applications, such as the transfer function between mean BP and RAP (coherence and RAP step response) led to a different ranking of methods, but without significant differences in CV SEM coherence. For the CV of the RAP step response though, LRd and PCAd performed badly. These results suggest that H1 or 2Pm perform better than LR analysis and should be used for the estimation of CrCP and RAP for both static and dynamic applications.

Long-term monitoring of a marine geologic hydrocarbon source by a coastal air pollution station in Southern California

Hourly total hydrocarbon (THC) data, spanning 1990–2008 from a California air pollution station located near the Coal Oil Point (COP) seep field, were analyzed and clearly showed geologic CH 4 emissions as the dominant local source. Annual COP emissions are conservatively estimated as 0.015 Tg CH 4 year −1 and represent a natural and concentrated geologic methane source (24 m 3 m −2 day −1 gas flux at some active seeps, Clark et al., 2010). For a sense of the scale and potential importance to the regional Southern California methane budget, COP emits an amount equivalent to 8% of the estimated Los Angeles County anthropogenic emissions. Station THC measurements near COP showed a strong wind dependency with elevated levels closely correlated with a sonar-derived spatial distribution of seep field emissions. THC varied seasonally, with a maximum in January and minimum in July and a peak-to-peak amplitude of 0.24 ppm. The seasonal signal was more readily apparent midday ( R 2 = 0.69 harmonic fit), compared to nighttime and morning ( R 2 < 0.45). The bimodal diel THC pattern consisted of seasonally-modulated peaks in the morning and evening. THC temporal and spatial trends were consistent with both transport and source emission variations. Long-term, annual seep field emissions consistently decreased on a field-wide basis until the late 1990s, before increasing consistently, most likely as a function of underlying geologic processes. This study demonstrates the value of municipal air quality monitoring stations for insight into local greenhouse gas sources and highlights the non-negligible and variable contribution from marine geologic seepage.

Urban effects on the diurnal temperature cycle in Phoenix, Arizona

Empirical estimations of urban effects on the diurnal temperature cycle were carried out for Phoenix, Arizona, through a framework capable of estimating the mean urban effect on air temperature. The analysis of pre-urban and urban differences in hourly temperature data at Sky Harbor International Airport during dry tropical conditions in June and January revealed a significant urban influence. Minimum temperature was most influenced by urbanization with the mean minimum temperature during the urban period exceeding that of the pre-urban period by 4.4°C (2.4°C) in June (January). A significant urban heat sink in January maximum temperatures was evident as the mean maximum temperature during the pre-urban period exceeded that of the urban period by 1.5°C. The greater thermal inertia due to urban growth around the airport and the growth of the airport itself has also had an effect on nocturnal cooling rates. Pre-urban January minimum temperatures typically occurred between 06:00 and 07:00 local standard time (LST) in the pre-urban period and between 07:00 and 08:00 LST in the urban period. Similarly, in June, the minimum temperature occurred on average around 05:00 LST during the pre-urban period and between 05:00 and 06:00 LST during the urban period. This apparent decrease in cooling rates was modeled well by the first harmonic fit to the average hourly temperature data.

The Perceptual Salience of Symmetrical and Asymmetrical Sections of a Line

A vertical line segment intersecting a horizontal one at different crossing points generates line sections. Visual perception of such line sections was investigated here in two experiments. In both experiments participants were most accurate and precise when they had to reproduce symmetrical sections. Interestingly, the different asymmetrical sections of a line were not equivalent in terms of participants' performance: constant errors changed as a function of sections and the error curve was nicely interpolated by the composition of two harmonics of the line length. In consistence with the harmonic fitting of the data, we propose that the perceptual salience of specific asymmetrical sections is a byproduct of the automatic triggering of a line midpoint identification process. Being perceptually tuned to symmetry warps our visual representation of the line, which results in systematic misperceptions. The way of bringing present and past experimental findings into a unitary whole is proposed.

Reverse convection potential saturation during northward IMF under various driving conditions

We report the results of an investigation of the reverse convection potentials in the dayside high‐latitude ionosphere during periods of steady northward interplanetary magnetic field (IMF). While it has been demonstrated that the reverse convection potentials exhibit saturation behavior, an investigation into how the saturated reverse convection cells respond to various driving conditions has not yet been performed. We use the OMNI database from 1998 to 2007 to search for events in solar wind data propagated to the bow shock when the IMF is northward and when various driving parameters are stable for more than 40 min. We then use bin‐averaged SuperDARN Doppler radar velocity data to apply a spherical harmonic fit to calculate the average potential pattern for various driving conditions. Results show that the saturated reverse convection potential during northward IMF is substantially lower than during southward IMF (as expected), but the strength of the saturation electric field at a particular location is comparable during northward IMF to what it is during southward IMF. Seasonal dependence and dependence on the Alfvènic Mach number and solar wind β are also investigated. It appears that the reverse convection potential demonstrates the opposite of what is expected for seasonal dependence, and that the Alfvènic Mach number is not the fundamental driver of its saturation.

Satellite observation of Brazil Current inshore thermal front in the SW South Atlantic: Space/time variability and sea surface temperatures

A data set of 199 sea surface temperature maps derived from the Advanced Very High Resolution Radiometer for the period 2000–2002 was processed to derive the position of the surface inshore thermal front of the Brazil Current (BCIF) in the SE Brazilian coastal and oceanic area. After the derivation of the position of the BC front for each image, the ensemble of digital frontal vectors was processed using the algorithm of frontal density (FD). For each 5′×5′ cell in the domain the calculated FD provided an index expressing the presence and persistence of the front in the area or the probability of finding the front in the region. In the paper we present the results of the FD analysis to get a better view of the space and time variability of the BC front in the region. The highest values of FD were in general observed close to or at the shelf break zone (between 200 and 1000 m isobaths). From 20°S to 23°S there is a tendency of BCIF to be positioned over the outer shelf, inshore of the 200 m isobaths. SE of Cape Sao Tome and S of Cape Frio it was observed a bimodal spatial distribution of highest FD caused by the presence of two semi-permanent frontal eddies. After moving offshore near Cape Frio, the BCIF tends to return to the shelf break zone south of 24°S probably due to a potential vorticity conservation mechanism. The position of the highest FD values calculated for different seasons confirms previous studies in that BCIF is closer to the coast during the summer and furthest offshore in the winter. Statistical analysis of the SST data gave for the BCIF an average SST gradient of 0.31°C km −1 with a standard deviation of 0.15°C km −1. A mean frontal width of 6 km was inferred from the average SST gradient and typical temperatures near the front at both sides, at outer shelf and in the BC itself. A Weibull probability density function can be fitted to describe the BCIF SST gradients with scale factor c=0.3460°C km −1 and shape factor k=2.1737. The BCIF SST gradient showed a seasonal variability with the smallest gradients in summer (~0.24 °C km −1) and the highest in autumn (~0.33 °C km −1). Using a three harmonic Fourier fit for the SST field near the BCIF, at the outer shelf and at interior of BC, it was possible to derive an analytical model for the time variability of the SST gradient of BCIF.

Long-term photometric monitoring with the Mercator telescope

Gamma Doradus stars are excellent targets for asteroseismology since the gravity modes present in these stars probe the deep stellar interiors. Mode identification will improve the knowledge of these stars considerably. A selected group of Gamma Doradus stars and some candidates were observed with the Mercator telescope to find and/or confirm the periodicities in the light variations and to derive reliable amplitude ratios in different pass bands. A frequency analysis was performed on all new data obtained in the Geneva photometric system. In order to have more reliable and accurate frequencies, the new data were combined with similar data from the literature and with Hipparcos observations. A set of frequencies that minimized the the residuals in a harmonic fit was searched for while allowing means and amplitudes to vary from one observation set to another. Frequencies and amplitudes in the photometric passbands of the Geneva system are given for 21 Gamma Doradus stars. We report the discovery of HD 74504 as a newly found Gamma Doradus star. Our study provides the first extensive multicolour database for the understanding of gravity modes in F-type stars.

Seasonal variation of nocturnal temperatures between 1 and 105 km altitude at 54° N observed by lidar

Abstract. Temperature soundings are performed by lidar at the mid-latitude station of Kühlungsborn (Germany, 54° N, 12° E). The profiles cover the complete range from the lower troposphere (~1 km) to the lower thermosphere (~105 km) by simultaneous and co-located operation of a Rayleigh-Mie-Raman lidar and a potassium resonance lidar. Observations have been done during 266 nights between June 2002 and July 2007, each of 3–15 h length. This large and unique data set provides comprehensive information on the altitudinal and seasonal variation of temperatures from the troposphere to the lower thermosphere. The remaining day-to-day-variability is strongly reduced by harmonic fits at constant altitude levels and a representative data set is achieved. This data set reveals a two-level mesopause structure with an altitude of about 86–87 km (~144 K) in summer and ~102 km (~170 K) during the rest of the year. The average stratopause altitude is ~48 km throughout the whole year, with temperatures varying between 258 and 276 K. From the fit parameters amplitudes and phases of annual, semi-annual, and quarter-annual variations are derived. The amplitude of the annual component is largest with amplitudes of up to 30 K in 85 km, while the quarter-annual variation is smallest and less than 3 K at all altitudes. The lidar data set is compared with ECMWF temperatures below about 70 km altitude and reference data from the NRLMSISE-00 model above. Apart from the temperature soundings the aerosol backscatter ratio is measured between 20 and 35 km. The seasonal variation of these values is presented here for the first time.

Reverse convection potential saturation during northward IMF

We report the results of an investigation of the reverse convection potentials in the day side high latitude ionosphere during periods of steady northward interplanetary magnetic field (IMF). While it has been shown that the polar cap potential in the ionosphere exhibits non‐linear saturation behavior when the IMF becomes increasingly southward, it has yet to be shown whether the high latitude reverse convection cells in response to increasingly northward IMF exhibit similar behavior. We use solar wind data from the ACE satellite from 1998 to 2005 to search for events in the solar wind when the IMF is northward and the interplanetary electric field is stable for more than 40 minutes. We then use bin‐averaged SuperDARN convection data and apply a spherical harmonic fit to calculate the average potential pattern for each northward IMF bin. Results show that the reverse convection cells do, in fact, exhibit non‐linear saturation behavior. The saturation potential is approximately 20 kV and is achieved when the electric coupling function reaches between 18 and 30 kV/RE.

Automated supervised classification of variable stars

Context: The fast classification of new variable stars is an important step in making them available for further research. Selection of science targets from large databases is much more efficient if they have been classified first. Defining the classes in terms of physical parameters is also important to get an unbiased statistical view on the variability mechanisms and the borders of instability strips. Aims: Our goal is twofold: provide an overview of the stellar variability classes that are presently known, in terms of some relevant stellar parameters; use the class descriptions obtained as the basis for an automated ``supervised classification'' of large databases. Such automated classification will compare and assign new objects to a set of pre-defined variability training classes. Methods: For every variability class, a literature search was performed to find as many well-known member stars as possible, or a considerable subset if too many were present. Next, we searched on-line and private databases for their light curves in the visible band and performed period analysis and harmonic fitting. The derived light curve parameters are used to describe the classes and define the training classifiers. Results: We compared the performance of different classifiers in terms of percentage of correct identification, of confusion among classes and of computation time. We describe how well the classes can be separated using the proposed set of parameters and how future improvements can be made, based on new large databases such as the light curves to be assembled by the CoRoT and Kepler space missions. Conclusions: The derived classifiers' performances are so good in terms of success rate and computational speed that we will evaluate them in practice from the application of our methodology to a large subset of variable stars in the OGLE database and from comparison of the results with published OGLE variable star classifications based on human intervention. These results will be published in a subsequent paper. The documented classification software codes as well as the light curves and the set of classification parameters for the definition stars, are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/475/1159

The variability of 558 nm OI nightglow intensity measured over Adelaide, Australia

The intensity of the OI 558 nm nightglow emission from heights near 97 km has been routinely measured since 1995 at Buckland Park (34.9°S, 138.6°E) near Adelaide, Australia. The intensity exhibits spring and autumn enhancements, bright nights and clear seasonal and inter-annual periodicities. Like many other mid-latitude observations, the autumn enhancement is greater than the spring enhancement. A Lomb periodogram analysis of the intensity indicates the presence of annual, semi-annual, and quasi-biennial oscillations. The annual and semi-annual oscillations have about equal intensity at this latitude, with amplitudes of between 17(±5)% and 14(±5)% of the mean intensity, respectively. This is consistent with Adelaide being a transitional latitude between a dominant semi-annual oscillation observed at low latitudes and the dominant annual oscillation observed at mid-latitudes. The annual oscillation is observed to peak in summer while the semi-annual oscillation takes maximum values near equinox. The quasi-biennial oscillation has a smaller amplitude at about 5(±1)% of the mean intensity and takes a maximum value near the autumnal equinox. There is evidence of a solar cycle dependence of the intensity, with nightglow intensity tracking the solar cycle. A harmonic fit to this period yields an amplitude of about 20(±15)% of the mean intensity, but naturally, this result needs to be treated with some caution, as there is only about one period present.

LATTICE EQUILIBRIUM THEORY AND SIZE EFFECTS FOR BOSONS IN A BOUNDED HARMONIC POTENTIAL

Effects of finite spatial size of boson assemblies in traps are studied in a self-consistent lattice theory by modeling the trap as a bounded harmonic potential of size R0. The thermodynamic quantities exhibit scaling and crossover from ideal gas behaviour at small (R0/a0) to that appropriate to an unbounded harmonic potential at large (R0/a0) with a crossover parameter [Formula: see text], a0 being the harmonic oscillator length, and τ denoting the dimensionless thermal energy. The numerical results obtained earlier by computing the energy levels of the bounded harmonic oscillator fit the general structure predicted by the theory very well. For a1&gt;10, the spatial size effects are negligible but for a1&lt;10 they become appreciable and experimentally measurable in suitably designed traps. At low temperatures the self consistent cell size is found to be about 2.5a0 implying that the condensate is essentially a single coherent state contained in the central cell.

A unique method by which to quantitate synchrony with equilibrium radionuclide angiography

Cardiac resynchronization therapy (CRT) improves symptoms and the survival rate in patients with advanced heart failure by improving synchrony. However, CRT is not always successful, is costly, and is applied without individualization. There is no specific measure of synchrony. The goal of this study was to analyze new quantitative parameters of synchrony and compare them with established measures. Equilibrium radionuclide angiography, phase angle (Ø), and amplitude quantitate regional contraction timing and magnitude and are the basis for new synchrony (S) and entropy (E) parameters. S is the vector sum of all amplitudes based on the angular distribution of Ø divided by the scalar sum of the length of all vectors. Complete S equals 1, and its absence equals 0. E measures the disorder in the region of interest, is 1 with random contraction and 0 with full synchrony, and differentiates among differing contraction patterns. Left ventricular S and E were measured in 22 normal equilibrium radionuclide angiography studies, where regions of interest were drawn from the left ventricle, left atrium, and background to analyze model ventricles with normal wall motion (N), ventricles with aneurysm (An), ventricles with severe diffuse dysfunction (Diff), and ventricles with severe regional dysfunction (Reg). The new S and E parameters were highly reproducible and well differentiated among N, An, Diff, and Reg, which were not separated by SD Ø (SD of ventricular phase), which has gained popularity as a measure of synchrony. Unique scintigraphic parameters for the evaluation of ventricular synchrony were derived, and their added value was determine compared with established measures. Indications for pacemaker therapy now include the treatment of severe congestive heart failure (CHF). Atrial triggered biventricular pacemakers reduce CHF symptoms and prolong life in patients with cardiomyopathy, severe CHF, left ventricular (LV) ejection fraction (EF) lower than 35%, and QRS greater than 120 milliseconds. Such pacing, or cardiac resynchronization therapy (CRT), seeks to reduce the heterogeneity and increase the synchrony of ventricular activation, conduction, and contraction. CRT has improved hemodynamics, increased exercise tolerance, reduced symptoms and the need for hospitalization, reversed ventricular remodeling, and reduced the all-cause mortality rate in CHF. However, CRT is costly, fails to improve symptoms or activity level in more than 30% of patients, and is applied blindly without individualization or consideration of lead placement sight. A variety of echocardiographic methods have sought to measure synchrony and its serial changes with CRT. A recent study presented evidence of the poor reproducibility of several widely applied echocardiographic measurements by which to determine ventricular synchrony. Magnetic resonance imaging has excellent resolution of regional wall motion and has been applied to assess ventricular synchrony and its response to pacing therapy. However, these methods are complex and are not well established or widely available, and magnetic resonance imaging has not been widely applied after pacing. An accurate and reproducible method is needed by which to objectively measure regional ventricular synchrony. Phase image analysis, a functional method based on the first Fourier harmonic fit of the gated blood pool time versus radioactivity curve, generates the parameters of amplitude (A), which parallels the extent of regional ventricular contraction or stroke volume, and phase angle (Ø), which represents the timing of regional contraction. It was applied early with demonstrated reproducibility to show the linkage between electrical and mechanical dyssynchrony and to characterize the contraction pattern in heart failure and its alteration with CRT. The SD of ventricular Ø, applied as a marker of synchrony, has been shown to demonstrate the beneficial effects of biventricular pacing, and its strong prognostic value has been shown in patients with congestive cardiomyopathy and CHF, superior to LVEF. The SD Ø may not be optimal for synchrony evaluation. We sought improved, more sensitive parameters to better differentiate synchrony among the spectrum of possible patterns of dyssynergy. We derived, initially evaluated, and here present new synchrony (S) and entropy (E) parameters, based on the phase method, to quantitate regional and global ventricular synchrony and applied them in simulation and clinical protocols.

Online LIB problems: Heuristics for Bin Covering and lower bounds for Bin Packing

We consider the NP Hard problems of online Bin Covering and Packing while requiring that larger (or longer, in the one dimensional case) items be placed at the bottom of the bins, below smaller (or shorter) items — we call such a version, the LIB version of problems. Bin sizes can be uniform or variable. We look at computational studies for both the Best Fit and Harmonic Fit algorithms for uniform sized bin covering. The Best Fit heuristic for this version of the problem is introduced here. The approximation ratios obtained were well within the theoretical upper bounds. For variable sized bin covering, a more thorough analysis revealed definite trends in the maximum and average approximation ratios. Finally, we prove that for online LIB bin packing with uniform size bins, no heuristic can guarantee an approximation ratio better than 1.76 under the online model considered.

Analysis of Diurnal Patterns in Winter Precipitation across the Conterminous United States

Abstract Hourly winter (November–March) precipitation data were assembled for nearly 5000 stations in the conterminous United States over the period 1948–98. Despite a potential observation bias in the 24th hour, a general tendency for winter precipitation events was found to occur more frequently near sunrise than for any other time of the day. Based on the standardized amplitude of the first harmonic wave, the pattern is most pronounced in Texas and in an area surrounding Colorado and Wyoming. The pattern also appears significant in the southeastern United States and in northern California based on the variance explained by the first harmonic fit. It is suggested that the diurnal patterns seen in the conterminous United States are related to increased relative humidity values occurring near sunrise and increased wind speeds in the warm sector of cyclonic storms.

Comment on “Enhanced upper stratospheric ozone: Sign of recovery or solar cycle effect?” by W. Steinbrecht et al.

[01] Steinbrecht et al. [2004] (hereinafter referred to as S4) have discussed the trend in upper stratospheric ozone at 35–45-km altitude determined from their lidar measurements at Hohenpeissenberg (47.8 N, 11.0 E) from 1987 to 2003. They question the conclusion of Newchurch et al. [2003] (hereinafter referred to as N3) that after approximately 1997 the downward trend of upper stratospheric ozone at 35–45-km altitude has diminished significantly. They argue instead that recent ozone changes are associated with the recent solar maximum (i.e., the solar cycle effect on ozone). In this comment we question their procedure for identifying the solar cycle effect. Moreover, we argue that the solar cycle effect was appropriately accounted for in the N3 analysis, and we buttress our argument by demonstrating that the more extensive data set used by N3 shows that the trend in upper stratospheric ozone has diminished significantly since 1997 and that this is evidence of the first stage of ozone recovery. [2] In the following text, unless specifically indicated otherwise, we will be comparing and contrasting here, as Steinbrecht et al. [2004] did, the Hohenpeissenberg analysis at 35–45-km altitude against the Stratospheric Aerosol and Gas Experiment (SAGE)-Halogen Occultation Experiment (HALOE) analysis at 35–45-km altitude and 30 –50 N. We do note that the single-station lidar record is remarkably representative of the longer global SAGE and HALOE records during the time period of coincidence (1987– 2003). Newchurch et al. [2003] used the 10.7-cm solar radio flux (F10.7cm flux) as a proxy for the temporal variability of the effect of the solar cycle on upper stratospheric ozone. S4, on the other hand, inferred the effect of the solar cycle using a multiple linear regression approach based on a combination of 10-, 13-, 67-, and 135-month periodicities derived from 193 months of ozone lidar data. In each case, the amplitude of the solar cycle effect was obtained by fitting the F10.7cm flux (N3) or the harmonics (S4) to the ozone observations, resulting in a peak-to-peak solar effect of approximately 3% given by N3 and 7% given by S4. It should be noted that S4 commented that when they repeated their calculations using the F10.7cm flux as the proxy instead of using harmonics they obtained a solar cycle effect in the differential absorption lidar (DIAL) observations virtually the same as the result that N3 obtained from SAGE. Therefore S4’s use of harmonics as the proxy for representing the solar cycle effect and the longer period of data used by N3 (1979–2003) are the two major factors producing the different conclusions obtained by N3 and S4. [3] The F10.7cm flux or the Mg II line emission constitute the standard procedures used by both modelers and analysts for representing the solar cycle effect because both parameters are proxies for variations in the ultraviolet flux that cause ozone change [e.g.,McCormack and Hood, 1996; Lee and Smith, 2003]. We also favor the solar flux proxy approach because it is physically based. Nevertheless, in order to provide a relatively direct comparison between the N3 and the S4 results we have calculated the best fit harmonics for the SAGE data over the lidar period from 1987 to 2003 (after having first removed a small mean difference between the two sets of measurements and a quasi-biennial oscillation (QBO), i.e., following the same initial steps used by both N3 and S4). This optimal harmonic fitting procedure results in 127and 63-month components over the full SAGE/solar backscatter ultraviolet instrument (SBUV) period from 1979 to 2003; 140and 70-month components from the SAGE data over the shorter lidar period 1987–2003; and 135and 67-month components from the lidar data fitted by S4. Figure 1 shows a comparison of these solar cycle fits: SAGE/SBUV full period, 127and 63-month components, dashed black trace; SAGE optimal fit over the lidar period, 1987–2003, 140and 70-month components, dotted red trace; and SAGE 1987–2003 fit with the S4 lidar-fitted components of 135 and 67 months, solid black trace. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D14305, doi:10.1029/2004JD004826, 2004