Numerical computation of natural convection in an isosceles triangular cavity with a partially active base and filled with a Cu–water nanofluid

This paper discusses the results of a study related to natural convection cooling of a heat source located on the bottom wall of an inclined isosceles triangular enclosure filled with a Cu water-nanofluid. The right and left walls of the enclosure are both maintained cold at constant equal temperatures, while the remaining parts of the bottom wall are insulated. The study has been carried out for a Rayleigh number in the range 10⁴ ≤ Ra ≤ 10⁶, for a heat source length in the range 0.2 ≤ ε ≤0.8, for a solid volume fraction in the range 0 ≤ ?≤0.06 and for an inclination angle in the range 0° ≤ δ≤45°. Results are presented in the form of streamline contours, isotherms, maximum temperature at the heat source surface and average Nusselt number. It is noticed that the addition of Cu nanoparticles enhances the heat transfer rate and therefore cooling effectiveness for all values of Rayleigh number, especially at low values of Ra. The effect of the inclination angle becomes more noticeable as one increases the value of Ra. For high Rayleigh numbers, a critical value for the inclination angle of δ = 15° is found for which the heat source maximum temperature is highest.     

Effect of Pregnancy on the Speaking Voice

The study aims to investigate the vocal symptoms and acoustic changes in pregnant women pre- and postpartum in comparison to the controls. A total of 25 pregnant women who presented for delivery were enrolled in this study. Twenty-one nonpregnant women were matched as controls. Vocal symptoms such as hoarseness, vocal fatigue, and aphonia were assessed. Acoustic analysis included fundamental frequency (F₀), habitual pitch, relative average perturbation (RAP), shimmer, noise-to-harmony ratio (NHR), and maximum phonation time (MPT). There were no significant differences in the incidence of vocal symptoms in pregnant women versus controls. However, vocal fatigue was more prevalent in the pregnant group. With respect to the acoustic parameters, there was a significant decrease in the MPT at term. The rest of the variables were comparable. Postpartum, the MPT significantly increased and there was an increase in F₀ and a significant decrease in the voice turbulence index (VTI). Pregnant women have more vocal fatigue and a reduction in MPT compared to the controls. Immediately after delivery, there is a significant increase in MPT.     

The impact of constant effort harvesting on the dynamics of a discrete‐time contest competition model

In this paper, we study a general discrete‐time model representing the dynamics of a contest competition species with constant effort exploitation. In particular, we consider the difference equation x _{n +1}=x _n f (x _{n ?k} )?h x _n where h >0, k ∈{0,1}, and the density dependent function f satisfies certain conditions that are typical of a contest competition. The harvesting parameter h is considered as the main parameter, and its effect on the general dynamics of the model is investigated. In the absence of delay in the recruitment (k =0), we show the effect of h on the stability, the maximum sustainable yield, the persistence of solutions, and how the intraspecific competition change from contest to scramble competition. When the delay in recruitment is 1 (k =1), we show that a Neimark‐Sacker bifurcation occurs, and the obtained invariant curve is supercritical. Furthermore, we give a characterization of the persistent set.     

Synthesis and properties of a new copper(II)-hafnium phosphate Cu0.5Hf2(PO4)3

Phosphates of general formula M_0.5Hf₂(PO₄)₃ with M=Cd²⁺, Ca²⁺, Sr²⁺ and Cu²⁺ were prepared by coprecipitation and characterized by several physical techniques. The compounds containing Cd²⁺, Ca²⁺, Sr²⁺ belong to the Nasicon-type structure, whereas Cu_0.5Hf₂(PO₄)₃ exhibited substantially different DRX patterns. Combined temperature programmed reduction (TPR) and temperature-programmed oxidation (TPO) showed that the copper in Cu_0.5Hf₂(PO₄)₃ was distributed between two energetically different sites in proportions respectively equal to 40 and 60%. Electron Paramagnetic Resonance (EPR) investigations confirmed the TPR/TPO results and revealed that the two sites hosting the Cu²⁺ ions are of orthorhombic symmetry. Moreover, the Cu²⁺ ions might be reduced by hydrogen to Cu⁺. These results were also supported by the UV–visible studies that showed the disappearance, under reducing conditions, of the band corresponding to crystal field transitions of Cu²⁺ ions and the emergence of a new peak attributed to the transitions between (3d)¹⁰ and (3d)⁹(4s)¹ Cu⁺ levels. At the same time, IR spectroscopy confirmed that protons entered the open lattice framework of the material and gave rise to a new protonated phase containing monovalent copper Cu_0.5^IH_0.5Hf₂(PO₄)₃. This redox process was proven to be reversible without any subsequent change in the network of the phosphate.     

Reactive intermediates from DMDO oxidation of ynamides. Trapping of a de novo chiral push-pull carbene via cyclopropanation

The reaction profile of DMDO oxidations of ynamides is described. This work illustrates the first examples of highly diastereoselective intramolecular cyclopropanations of a push-pull carbene derived from alkyne oxidation. In addition, the ynamide oxidation provides facile access to ketoimides and reveals mechanistic insights into the chemistry of electronically biased oxirenes.     

Thermal decomposition of lanthanide(III) complexes of bis-(salicylaldehyde)-1,3-propylenediimine Schiff base ligand

The thermal decomposition of lanthanide complexes, with a general formula: [LnL(NO₃)₂](NO₃), where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, and Er; and L = bis-(salicyladehyde)-1,3-propylenediimine Schiff base ligand, was studied by thermogravimetric (TG) and derivative thermogravimetric (DTG) techniques. The TG and DTG data indicated that all complexes are thermostable up to 398 K. The thermal decomposition of all Ln(III) complexes was a two-stage process and the final residues were Ln₂O₃ (Ln = La, Nd, Sm, Gd, Dy, Er), Tb₄O₇, and Pr₆ O₁₁. The activation energies of thermal decomposition of the complexes were calculated from analysis of the TG-DTG curves using the Kissinger, Friedman, and Flynn-Well-Ozawa methods.     

Practical tests for randomized complete block designs

A class of affine-invariant test statistics, including a sign test and a related family of signed-rank tests, is proposed for randomized complete block designs with one observation per treatment. This class is obtained by using the transformation-retransformation approach of Chakraborty, Chaudhuri and Oja along with a directional transformation due to Tyler. Under the minimal assumption of directional symmetry of the underlying distribution, the null asymptotic distribution of the sign test statistic is shown to be chi-square with p-1 degrees of freedom. The same null distribution is also proved for the family of signed-rank statistics under the assumption of symmetry of the underlying distribution. The Pitman asymptotic relative efficiencies of the tests, relative to Hotelling-Hsu's T² are established. Several score functions are discussed including a simple linear score function and the optimal normal score function. The test based on the linear score function is compared to the other members of this family and other statistics in the literature through efficiency calculations and Monte Carlo simulations. This statistic has an excellent performance over a wide range of distributions and for small as well as large dimensions.     

The centroid of the zeroes of a polynomial via certain Laguerre-type operators

In this paper, we present several properties of the centroid of the zeroes of a polynomial. As an illustration, we apply these results to the d-orthogonal polynomials. Finally, we provide the relationship between different centroids of a general monic polynomial and its image under a certain Laguerre–type operator.     

Assessing Adherence to Antihypertensive Medication by Means of Dose-Dependent Reference Plasma Concentration Ranges and Ultra-High Performance Liquid Chromatography-Ion Trap Mass Spectrometry Analysis

Poor adherence to antihypertensive drug therapy is a well-recognized problem and can be assessed by mass spectrometry-based analyses of body fluids. However, contrary statements exist whether drug quantification in blood or qualitative screening in urine is more suitable. The present pilot study aimed to further elucidate the power of blood plasma drug concentrations for adherence monitoring by developing and validating a quantification procedure for nine antihypertensive drugs (amlodipine, bisoprolol, candesartan, canrenone, carvedilol, metoprolol, olmesartan, torasemide, and valsartan) in blood plasma using liquid–liquid extraction and an ultra-high-performance liquid chromatography-ion trap mass spectrometry analysis. The procedure should then be used for an adherence assessment and compared with the results of an established qualitative urine screening. Selectivity, carryover, matrix effect, accuracy, precision, dilution integrity, and stability were successfully validated, except for amlodipine. The applicability was demonstrated by analyzing 19 plasma samples containing 28 antihypertensive drugs and comparing the measured concentrations with calculated dose-dependent reference plasma concentration ranges. The interpretation of plasma concentrations was found to be more sophisticated and time-consuming than that of urine screening results, and adherence could not be assessed in two cases (10%) due to measured plasma concentrations below the lower limit of quantification. However, 14 out of 19 subjects were classified as adherent (75%) and three as nonadherent (15%), in contrast to 19 (100%) that were claimed to be adherent based on the results of the qualitative urine screening. Nevertheless, further data is needed to estimate whether plasma quantification is superior in terms of assessing adherence to antihypertensive medication.