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The evolution of nuclear spin state populations is investigated for the case of a 13C2-labeled triyne in solution, for which the near-equivalent coupled pairs of 13C nuclei experience cross-correlated relaxation mechanisms. Inversion-recovery experiments reveal different recovery curves for the main peak amplitudes, especially when the conversion of population imbalances to observable coherences is induced by a radio frequency pulse with a small flip angle. Measurements are performed over a range of magnetic fields by using a sample shuttle apparatus. In some cases, the time constant TS for decay of nuclear singlet order is more than 100 times larger than the time constant T1 for the equilibration of longitudinal magnetization. The results are interpreted by a theoretical model incorporating cross-correlated relaxation mechanisms, anisotropic rotational diffusion, and an external random magnetic field. A Lindbladian formalism is used to describe the dissipative dynamics of the spin system in an environment of finite temperature. Good agreement is achieved between theory and experiment. [ABSTRACT FROM AUTHOR]

Around the world, groundwater supply is critical for vital needs such as drinking and irrigation. This work investigates groundwater in the carbonate aquifer of the Middle Miocene in the east El Minia area, Egypt. In this regard, thirty-two groundwater samples were collected. The water samples were analyzed for Ca2+, Mg2+, Na+, K+, Cl−, SO42−, NO3−, CO2−, HCO3−, Fe, Mn, Cd, As, Cr, Cu, and Pb. Groundwater has been evaluated using two methods, which are water quality index (WQI) and health risk assessment (HRA). The predominant groundwater is soft water, and the samples range in salinity from fresh to slightly salty. The groundwater mostly falls into the alkaline water type. All the groundwater samples under study are deemed low quality for human consumption due to water contamination. Fe, Mn, Cd, Cu, and Pb have high HQnc values, which can result in non-carcinogenic health issues in adults, while Mn, Cu, and Pb can give rise to non-carcinogenic health issues in children.

The presence of permanent hardness ions (sulfate and chloride) in drinkable water in large amounts causes many problems, either health effects like bad taste, color, and odor of water or technical effects like the formation of stains and scales in house vessels and pipelines. This paper presented an applicable concept for using a newly prepared composite composed of modified local clay and locally extracted chitosan as a second-stage filter after pressure sand filters in the conventional iron and manganese removal plant to remove sulfate and chloride from raw drinkable groundwater. The morphology and structure of the raw samples and the modified clay/chitosan (MCCh) composite were explored by using different techniques. Also, this study deals with the experimental batch and column studies to examine the prepared composite ability to remove permanent hardness ions. The adsorption capacity of MCCh for sulfate and chloride ions was investigated under various conditions, e.g., temperature, pH, contact time, various initial concentrations, and adsorbent dosage. Results indicated that the MCCh composite exhibited a good adsorption capacity (3.2 mg/g) for permanent hardness ions at optimized conditions, a pH range of 3–6.5, and 60 min contact time. Regeneration experiments were performed for the MCCh composite for 6 cycles. The % of sulfate and chloride ions removal reached about 92% at a powerful acidic solution and about 70% at a neutral pH for really applied raw groundwater.

Abstract Background Minimally invasive cardiac surgery (MICS) has steadily become more and more popular. MICS is less invasive and has a faster return to normality after surgery. Patients who had MICS continue to exercise more frequently than those who had the conventional median sternotomy surgery. It is generally established that physical activity lowers mortality and the risk of cardiac disease. The purpose of the study: is to evaluate and compare physical activity levels in MICS and conventional surgery. Result The level of preoperative physical activity did not significantly differ between the two groups. However, the MICS group significantly exceeded the conventional group in terms of postoperative progress, amount of physical activity, and 6-minute walking test. Also, Visual Analog Scale (VAS) score was significantly less. Conclusion Minimally invasive cardiac surgery has a higher margin of benefit, and speedy recovery to normality, which is accompanied by a lower VAS score and increased physical activity in comparison to conventional surgery.

Despite the importance of rhodium complexes in catalysis, and the favorable 100% natural abundance of the spin-1/2 103Rh nucleus, there are few reports of 103Rh nuclear magnetic resonance (NMR) parameters in the literature. In part, this is the consequence of the very low gyromagnetic ratio of 103Rh and its dismal NMR sensitivity. In a previous paper [Harbor-Collins et al., J. Chem. Phys. 159, 104 307 (2023)], we demonstrated an NMR methodology for 1H-enhanced 103Rh NMR and demonstrated an application to the 103Rh NMR of the dirhodium formate paddlewheel complex. In this paper, we employ selective 18O labeling to break the magnetic equivalence of the 103Rh spin pair of dirhodium formate. This allows the estimation of the 103Rh–103Rh spin–spin coupling and provides access to the 103Rh singlet state. We present the first measurement of a 18O-induced 103Rh secondary isotope shift as well as the first instance of singlet order generated in a 103Rh spin pair. The field-dependence of 103Rh singlet relaxation is measured by field-cycling NMR experiments. [ABSTRACT FROM AUTHOR]

The nuclear magnetic resonance (NMR) spectroscopy of spin-1/2 nuclei with low gyromagnetic ratio is challenging due to the low NMR signal strength. Methodology for the rapid acquisition of 103Rh NMR parameters is demonstrated for the case of the rhodium formate "paddlewheel" complex R h 2 (H C O 2 ) 4 . A scheme is described for enhancing the 103Rh signal strength by polarization transfer from 1H nuclei, which also greatly reduces the interference from ringing artifacts, a common hurdle for the direct observation of low-γ nuclei. The 103Rh relaxation time constants T1 and T2 are measured within 20 min by using 1H-detected experiments. The field dependence of the 103Rh T1 is measured. The high-field relaxation is dominated by the chemical shift anisotropy mechanism. The 103Rh shielding anisotropy is found to be very large: |Δσ| = 9900 ± 540 ppm. This estimate is compared with density functional theory calculations. [ABSTRACT FROM AUTHOR]

The increasing interest in axially chiral biaryl moieties, which are prevalent in chiral ligands, organocatalysts, and bioactive molecules, has raised the need for developing novel efficient synthetic methods for these types of molecules. In addition to the currently available methods, such as kinetic resolution, desymmetrization and enantio‐ and diastereo‐selective biaryl coupling, we herein report a lipase‐catalyzed dynamic kinetic resolution (DKR) of racemic 2‐hydroxybiaryls through enantioselective O‐acylation. This method features the production of enantiomerically enriched atropisomers (89 %–98 % ee) in 91 %–99 % yields from eleven racemates. Notably, the DKR proceeds without any racemization catalyst since in situ‐racemization was achieved by easy rotation about the biaryl axis of the substrates. The enzymatic O‐acylation then furnished conformationally stable biaryl‐containing esters, in which the increased steric bulkiness of the O‐acyl moiety suppresses the rotation, i. e., racemization, under the reaction conditions of 35–50 °C. This experimental study was accompanied by a computational determination of the rotational barrier of substrates and products. The choice of suitable substrates with a significant difference in their rotational barrier compared to that of their products turned out to be the key to an efficient implementation of this method. [ABSTRACT FROM AUTHOR]

Organic halogen compounds are cornerstones of applied chemical sciences. Halogen substitution is a smart molecular design strategy adopted to influence reactivity, membrane permeability and receptor interaction. Chiral bioreceptors may restrict the stereochemical requirements in the halo‐ligand design. Straightforward (but expensive) catalyzed stereospecific halogenation has been reported. Historically, PCl5 served access to uncatalyzed stereoselective chlorination although the stereochemical outcomes were influenced by steric parameters. Nonetheless, stereochemical investigation of PCl5 reaction mechanism with carbamoyl (RCONHX) compounds has never been addressed. Herein, we provide the first comprehensive stereochemical mechanistic explanation outlining halogenation of carbamoyl compounds with PCl5; the key regioselectivity‐limiting nitrilimine intermediate (8‐Z.HCl); how substitution pattern influences regioselectivity; why oxadiazole byproduct (P1) is encountered; stereo‐electronic factors influencing the hydrazonoyl chloride (P2) production; and discovery of two stereoselectivity‐limiting parallel mechanisms (stepwise and concerted) of elimination of HCl and POCl3. DFT calculations, synthetic methodology optimization, X‐ray evidence and experimental reaction kinetics study evidence all supported the suggested mechanism proposal (Scheme 2). Finally, we provide mechanism‐inspired future recommendations for directing the reaction stereoselectivity toward elusive and stereochemically inaccessible (E)‐bis‐hydrazonoyl chlorides along with potentially pivotal applications of both (E/Z)‐stereoisomers especially in medicinal chemistry and protein modification. [ABSTRACT FROM AUTHOR]

Inadequate energy management leads to more emission exposure, which causes climate change, severe environmental contamination, and human health risks. Therefore, the World Health Organisation (WHO) monitors universal efforts to prevent emissions and encourages governments to develop industries to transform the green economy. During the current study, the energy and cost variation was observed through three years (2020, 2021, and 2022) at a surface water plant in southern Egypt. Consistent with applying operation strategies that met convenient standard operating procedures (SOPs) during 2021 and 2022. Energy consumption was reduced by 13% to 17%, and the cost decreased by 5% to 12% for 2021 and 2022, respectively. These energy and financial savings should be considered as an influence of the water safety plans (WSPs). Detrended correspondence analysis (DCA) was utilised to identify the mechanism of energy consumption and its impact on the cost during the study period. The finding proves that the energy and cost rise is related to increased water demand during the summer months, periodic/emergency maintenance, and comprehensive cleaning activities. WSPs were applied to control biological oxygen demand (BOD), chemical oxygen demand (COD), and oil and grease (O & G) that show increasing values than Egyptian law. [ABSTRACT FROM AUTHOR]

The primary goal of this study is to analyze the hydrogeochemical properties and assess the groundwater quality for drinking, domestic, and irrigation purposes in West El Minia, Egypt. Major components were determined in 49 groundwater samples to evaluate water quality in the study area. Principal component analysis (PCA), hierarchical cluster analysis (HCA), geostatistics, and spatial mapping were used to identify the chemical components and processes that influence groundwater quality and highlight areas of health risks. According to the TDS values, about 22% of the groundwater samples are suitable for drinking. Due to the elevated values of hardness in the examined water, none of the water samples are suitable for use in a household. The majority of groundwater samples are acceptable for irrigation based on the sodium adsorption ratio (SAR), residual sodium carbonate (RSC), Kelley ratio (KR), magnesium hazard (MH), and permeability index, and some can be adequately treated. The study indicated that different groundwater characteristics (such as TDS, Na+, K+, HCO3−, Cl−, and SO42−) do not comply with WHO requirements in some regions, which may pose a threat to human health.

Globally, groundwater is a valuable natural resource that may be relied upon for irrigation and drinking needs. The main purpose of this study is to investigate the groundwater geochemistry in the West of El Qusiya, Assuit, Egypt. Groundwater suitability for irrigation has been estimated with some methods, for instance, electrical conductivity (EC), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), Killey ratio (KR), magnesium hazard (MH), permeability index (PI), Piper trilinear diagram, and USSL diagram. The Piper diagram shows that the sodium and potassium (Na+K) kind dominates the water chemistry, followed by the mixed type. The principal coordinate analysis (PCoA), cluster analysis (CA), principal component analysis (PCA), and Pearson correlation matrix analysis (PCMA) statistical methods reveal that the physicochemical parameters of water collected from the Eocene and Pleistocene aquifers are produced from mixed origins. The geogenic origin reflects the lithologic impact of aquifers matrix and water interactions, in addition to anthropogenic sources caused by infiltration of secondary salts initiated due to fertilizers and agriculture water. These factors are the controller for groundwater’s ionic (Na+, Ca2+, Mg2+, K+, Cl−, SO42−, and HCO3−) variation in the area studied. Based on SAR, KR, and PI results, groundwater is acceptable for irrigation. Consistent with RSC, MH, and Na% results, approximately 50% of the groundwater samples are unsuitable for irrigation use.

Signal Amplification By Reversible Exchange (SABRE) can provide strong signal enhancement (SE) to an array of molecules through reversible exchange of parahydrogen (pH2) derived hydrides and a suitable substrate coordinated to a transition metal. Among the substrates that can be used as a probe for hyperpolarised NMR and MRI, pyruvate has gained much attention. SABRE can hyperpolarise pyruvate in a low cost, fast, and reversible fashion that does not involve technologically demanding equipment. Most SABRE polarization studies have been done using methanol-d4 as a solvent, which is not suitable for in vivo application. The main goal of this work was to obtain hyperpolarized pyruvate in a solvent other than methanol which may open the door to further purification steps and enable a method to polarize pyruvate in water in future. This work demonstrates hyperpolarization of the [2-13C]pyruvate as well as [1-13C]pyruvate by SABRE in an acetone/water solvent system at room temperature as an alternative to methanol, which is commonly used. NMR signals are detected using a 1.1 T benchtop NMR spectrometer. In this work we have primarily focused on the study of [2-13C]pyruvate and investigated the effect of catalyst concentration, DMSO presence and water vs. acetone solvent concentration on the signal enhancement. The relaxation times for [2-13C]-pyruvate solutions are reported in the hope of informing the development of future purification methods. [ABSTRACT FROM AUTHOR]

The presence of heavy metals in drinking water or wastewater poses a serious threat to the ecosystem. Hence, the present study focused on synthesizing SnCaAl2O3 core-shell nanoparticles (C.N.P.s) in the α-Alumina phase by thermal annealing a stacked structure sandwiched between two Al2O3 layers at low temperatures. The obtained structure showed Sn N.P. floating gate with an Al2O3 dielectric stacked tunneling barrier to remove the excess of these heavy metals from polluted water. To characterize the prepared composites, X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM) were used. The synthesized SnCaAl2O3 C.N.P.s composite was examined to utilize it as an adsorbent for removing Zn, Cd, and Pb divalent cations. The removal efficiency was studied by various parameters such as adsorbent dose, pH, contact time, metal concentrations, temperature, and coexisting ions. The experimental results were tested via Langmuir and Freundlich isotherm models. The obtained results were convenient to the Freundlich isotherm model. Moreover, the adsorption thermodynamic behavior of Zn+2, Cd+2, and Pb+2 on the synthesized composite was examined, and the process is endothermic and spontaneous under experimental conditions. The results illustrated that the adsorption efficiency of the SnCaAl2O3 core-shell nanoparticles (C.N.P.s) ranged from 88% to about 100% for all cations.

Background Cardioplegia is responsible for myocardial protection during open heart surgery. Cardioplegia was first presented as an agent for hypothermic hyperkalemic arrest. Blood was then introduced as a vehicle to convey potassium to the heart. Custodiol Histidine-Tryptophan- ketoglutarate (HTK) solution is safe and used as a single dose, which can last for up to 3 h. The comparison of the clinical outcomes of this particular solution with warm blood cardioplegia in coronary artery bypass graft (CABG) with poor left ventricular (LV) function has received little attention. Objective To compare the clinical outcomes of custodiol solution with warm blood cardioplegia in CABG with poor LV function. Patients and methods This single-center randomized prospective study was carried out from January 2017 till January 2018, at National Heart Institute of Egypt. Overall, 50 patients with poor LV function undergoing isolated CABG were divided randomly according to type of myocardial protection during revascularization into two groups: group A included 25 patients who received warm blood cardioplegia, and group B included 25 patients who received custodiol cardioplegia. Data from each group were collected and compared with each other. Results Baseline demographic and intraoperative data showed no significant difference between the two groups. The need for intra-aortic balloon pump was similar in both groups. The need for inotropic support, length of mechanical ventilation, and ICU stay was statistically nonsignificant between the two groups. Postoperative arrhythmia was significantly higher in custodiol group [nine (34.62%)] compared with warm blood group [two (8%)] (P = 0.021). Overall mortality shows a statistically nonsignificant difference. Improvement in left ventricular ejection fraction after surgical revascularization was observed among both groups. Conclusion Both custodiol cardioplegia and warm blood cardioplegia offer a satisfactory method for myocardial protection in low ejection fraction ischemic heart disease, with increased incidence of postoperative arrhythmia in custodiol cardioplegia.

The population imbalance between nuclear singlet states and triplet states of strongly coupled spin-1/2 pairs, also known as nuclear singlet order, is well protected against several common relaxation mechanisms. We study the nuclear singlet relaxation of 13C pairs in aqueous solutions of 1,2-13C2 squarate over a range of pH values. The 13C singlet order is accessed by introducing 18O nuclei in order to break the chemical equivalence. The squarate dianion is in chemical equilibrium with hydrogen-squarate (SqH−) and squaric acid (SqH2) characterized by the dissociation constants pK1 = 1.5 and pK2 = 3.4. Surprisingly, we observe a striking increase in the singlet decay time constants TS when the pH of the solution exceeds ∼10, which is far above the acid–base equilibrium points. We derive general rate expressions for chemical-exchange-induced nuclear singlet relaxation and provide a qualitative explanation of the TS behavior of the squarate dianion. We identify a kinetic contribution to the singlet relaxation rate constant, which explicitly depends on kinetic rate constants. Qualitative agreement is achieved between the theory and the experimental data. This study shows that infrequent chemical events may have a strong effect on the relaxation of nuclear singlet order. [ABSTRACT FROM AUTHOR]