34,256 research outputs found
Radial distribution functions of water: Models vs experiments
No full textWe study the temperature behavior of the first four peaks of the oxygen-oxygen radial distribution function of water, simulated by the TIP4P/2005, MB-pol, TIP5P, and SPC/E models and compare to experimental X-ray diffraction data, including a new measurement which extends down to 235 K [H. Pathak et al., J. Chem. Phys. 150, 224506 (2019)]. We find the overall best agreement using the MB-pol and TIP4P/2005 models. We observe, upon cooling, a minimum in the position of the second shell simulated with TIP4P/2005 and SPC/E potentials, located close to the temperature of maximum density. We also calculated the two-body entropy and the contributions coming from the first, second, and outer shells to this quantity. We show that, even if the main contribution comes from the first shell, the contribution of the second shell can become important at low temperature. While real water appears to be less ordered at short distance than obtained by any of the potentials, the different water potentials show more or less order compared to the experiments depending on the considered length-scale
Fixed and coincidence points of hybrid mappings
No full textsummary:The purpose of this note is to provide a substantial improvement and appreciable generalizations of recent results of Beg and Azam; Pathak, Kang and Cho; Shiau, Tan and Wong; Singh and Mishra
Modelling the quantitative evaluation of soil nutrient supply, nutrient use efficiency, and fertilizer requirements of wheat in India
No full textWheat yields in many parts of India are stagnant. The main reason for this is conventional blanket fertilizer recommendation, lower fertilizer use efficiency, and imbalanced use of fertilizers. Estimation of fertilizer requirements based on quantitative approaches can assist in improving wheat yields and increasing nutrient use efficiency. We used the QUEFTS (QUantitative Evaluation of Fertility of Tropical Soils) model for estimation of nitrogen (N), phosphorus (P), and potassium (K) requirements and fertilizer recommendations for a target yield of wheat. The model considers the interactions of N, P, and K, and climate adjusted potential yield of the region. Published data from several field experiments dealing with N, P, and K conducted during the years 1970 to 1998 across wheat-growing environments of India, covering a wide range of soil and climatic conditions, were used to reflect the environmental variability. The relationships between indigenous N, P, and K supply and soil organic carbon, Olsen P, and ammonium acetate-extractable K, respectively, were established. The required N, P, and K accumulation in the plant for 1 tonne grain yield was 23.1, 3.5, and 28.5 kg, respectively, suggesting an average NPK ratio in the plant dry matter of about 6.6:1:8.1. The constants for minimum and maximum accumulation (kg grain kg-1) of N (27 and 60), P (162 and 390), and K (20 and 59) were derived as the standard model parameters in QUEFTS for fertilizer recommendation for irrigated wheat in the tropical and subtropical regions of India. Relationships of apparent recovery efficiencies of fertilizer N, P, and K with levels of their application were also determined. The observed yields of wheat with different amounts of these nutrients were in good agreement with the values predicted by the model, indicating that the model can be used for fertilizer recommendations
Sleep apnea and cardiac arrhythmia: a timely wake-up call!
No full textRajeev K. Pathak, Rajiv Mahajan, Dennis H. Lau, Prashanthan Sander
Prevention and regressive effect of weight-loss and risk factor modification on atrial fibrillation: the reverse-AF study - authors' reply
No full textAbstract not availableMelissa E. Middeldorp, Rajeev K. Pathak, Dennis H. Lau and Prashanthan Sander
Efficient Hybrid discrete Fourier transform-moment method for fast analysis of large rectangular arrays
No full textA novel approach combining the moment method (MOM) and the discrete Fourier
transfomi DFT) is developed for the fast analysis of electromagnetic (EM) radiation/scattering
from electrically large, finite, planar rectangular arrays. In particular, the unknown array
distribution to be solved is represented in terms of the DFT within the MOM for a given array
excitation. The proposed DFT-MOM approach for large arrays has the advantage that it can
overcome the inefficiency of the conventional MOM approach by drastically reducing the number
of unknowns. The latter is possible because only a relatively few DFT terms are significant in ths
DFT-MOM. A useful criterion to select significant DFT terms is described. Numerical results are
presented to indicate the efficiency and accuracy of the DFT-MOM analysis for determining the
array distribution and the radiation pattern of large rectangular arrays with uniform excitation. It is
found that the efficiency and accuracy of the DFT-MOM increases dramatically with an increase in
array size. Furthermore, the DFT representation employed within the MOM can provide an
asymptotic closed form solution for both the near and far fields of the array, which can be
described in the ray format of the uniform geometrical theory of diffraction (UTD)
Metastable Innershell Molecular State (MIMS) IV: Heteronucleus K-shell MIMS with H+ and He+
No full textAbstractThe model of MIMS (Metastable Innershell Molecular State) has been applied to interpreting the Kα X-ray satellite data of target atoms in H+ and He+ ion impact on Al, Ca and Ti targets. The binding energies of the heteronucleus H-K-MIMS (K-shell MIMS formed with H and a target atom) and He-K-MIMS have been obtained. The binding energy trend of the H-K-MIMS shows a Z2 dependency similar to that of the homonucleus K-MIMS, while that of the He-K-MIMS shows a transitional behavior from the former to the latter. These behaviors were interpreted with the Z-expansion theory of heteronucleus molecules
Catheter ablation of atrial fibrillation in patients with concomitant left ventricular impairment: a systematic review of efficacy and effect on ejection fraction
No full textAbstract not availableAnand N. Ganesan, Savvy Nandal, Jakob Lüker, Rajeev K. Pathak, Rajiv Mahajan, Darragh Twomey, Dennis H. Lau, Prashanthan Sander
X-ray Scattering and O-O Pair-Distribution Functions of Amorphous Ices
No full textThe structure factor and oxygen-oxygen pair-distribution functions of amorphous ices at liquid nitrogen temperature (T = 77 K) have been derived from wide-angle X-ray scattering (WAXS) up to interatomic distances of r = 23 Å, where local structure differences between the amorphous ices can be seen for the entire range. The distances to the first coordination shell for low-, high-, and very-high-density amorphous ice (LDA, HDA, VHDA) were determined to be 2.75, 2.78, and 2.80 Å, respectively, with high accuracy due to measurements up to a large momentum transfer of 23 Å-1. Similarities in pair-distribution functions between LDA and supercooled water at 254.1 K, HDA and liquid water at 365.9 K, and VHDA and high-pressure liquid water were found up to around 8 Å, but beyond that at longer distances, the similarities were lost. In addition, the structure of the high-density amorphous ices was compared to high-pressure crystalline ices IV, IX, and XII, and conclusions were drawn about the local ordering
Methods for Efficiently Computing the MoM Impedance Matrix for APEx Type Basis Functions
No full textAlternative methods for efficiently computing the elements of the impedance matrix arising in the method-of-moments (MoM) based asymptotic phasefront extraction (APEx) method are presented. In APEx, the number of unknowns can be drastically reduced by making use of the phasefront characteristics of the local currents at smooth parts of the scatterer obtained at a lower frequency. At the high frequency of interest, the scaled basis functions are in the form of linearly phased constant amplitude currents or traveling waves (TWs) defined on supports that are significantly larger than the ones for the conventional MoM. The standard way of computing the mutual coupling impedance between these TW basis/test functions requires a 4-fold numerical surface integration on the supports (or patches) that typically are a few wavelengths long over a single dimension. Specifically, three different methods are investigated to efficiently and accurately compute the mutual coupling impedance. The advantages and disadvantages as well as the range of applicability of each method are discussed. Accuracy and CPU time comparisons are provide
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