Ph Group Research Articles

Control of Molecular Catalysts for Oxygen Reduction by Variation of pH and Functional Groups.

In the search for replacement of the platinum-based catalysts for fuel cells, MN4 molecular catalysts based on abundant transition metals play a crucial role in modeling and investigation of the influence of the environment near the active site in platinum-group metal-free (PGM-free) oxygen reduction reaction (ORR) catalysts. To understand how the ORR activity of molecular catalysts can be controlled by the active site structure through modification by the pH and substituent functional groups, the change of the ORR onset potential and the electron number in a broad pH range was examined for three different metallocorroles. Experiments revealed a switch between two different ORR mechanisms and a change from 2e- to 4e- pathway in the pH range of 3.5-6. This phenomenon was shown by density functional theory (DFT) calculations to be related to the protonation of the nitrogen atoms and carboxylic acid groups on the corroles indicated by the pKa values of the protonation sites in the vicinity of the ORR active sites. Control of the electron-withdrawing nature of these groups characterized by the pKa values could switch the ORR from the H+ to e- rate-determining step mechanisms and from 2e- to 4e- ORR pathways and also controlled the durability of the corrole catalysts. The results suggest that protonation of the nitrogen atoms plays a vital role in both the ORR activity and durability for these materials and that pKa of the N atoms at the active sites can be used as a descriptor for the design of high-performance, durable PGM-free catalysts.

Cross-linking induced thermo-responsive self-healing hydrogel with gel-sol–gel transition constructed on dynamic covalent bond

Based on the favorable biocompatibility, thermo-responsive hydrogels have attracted much attention. Therefore, more and more researchers have focused on the synthesis, characterizations and applications of thermo-responsive hydrogels.In this study, copolymer of P(N-hydroxymethyl acrylamide-co-diacetone acrylamide) P(NAM-co-DAA) with ketone groups were prepared to construct the thermo-responsive hydrogel through cross-linking induced thermo-response (CIT). The dihydrazide compounds were employed to cross-link the copolymer to make a self-healing hydrogel which containing ketone type reversible acylhydrazone bond. The resultant self-healing hydrogel has shown the excellent mechanical properties and chemical stabilities. At the same time, the hydrogel presented reversible gel-sol based on the pH value and group ratio. These thermo-responsive self-healing hydrogels also demonstrate wonderful biocompatibility, which extends its potential applications as biomaterials.

Combined pre- and post-capillary pulmonary hypertension: The clinical implications for patients with heart failure.

BackgroundThe prognostic implications of combined pre- and post-capillary pulmonary hypertension (Cpc-PH) in patients with pulmonary hypertension due to left heart disease (PH-LHD) remain controversial. The aim of this retrospective study was to evaluate the new PH-LHD criteria, recommended by the 6th World Symposium on Pulmonary Hypertension and to determine the prognostic value of Cpc-PH.MethodsA total of 701 patients with symptomatic heart failure who had undergone right-heart catheterization were divided into the following four groups: (i) Isolated post-capillary PH (Ipc-PH) group; mean pulmonary artery pressure (mPAP) >20 mmHg, pulmonary artery wedge pressure (PAWP) >15 mmHg, and pulmonary vascular resistance (PVR) <3 Wood units (WU) (ii) Cpc-PH group; mPAP >20 mmHg, PAWP >15 mmHg, and PVR ≥3 WU (iii) borderline-PH group; mPAP >20 mmHg and PAWP ≤15 mmHg (iv) non-PH group; mPAP ≤20 mmHg. Multivariate Cox hazard analysis was used to investigate whether Cpc-PH was associated with cardiac outcomes.ResultsThe study subjects were allocated into the Ipc-PH (n = 268), Cpc-PH (n = 54), borderline-PH (n = 112), or non-PH (n = 267) groups. The Cpc-PH group was associated significantly with adverse cardiac events even after adjustment for clinically relevant confounding factors for heart failure prognosis (vs. non-PH group: HR 2.98 [95% CI 1.81–4.90], P <0.001; vs. Ipc-PH group: HR: 1.92 [95% CI 1.19–3.08], P = 0.007).ConclusionsThe new definitions of PH-LHD stratified patients into 4 categories. Long-term clinical outcomes were significantly different between the four categories, with Cpc-PH having the worst cardiac outcomes.

Comparative proteomic and transcriptomic analysis reveals high pH-induced expression signatures of Chinese shrimp Fenneropenaeus chinensis.

pH has a great impact on the distribution, growth, behavior, and physiology in many aquatic animals. The comparison of proteomics between normal and high pH stress samples was successfully achieved using iTRAQ proteomic analysis to screen key response proteins and pathways. After high pH stress, 124 upregulated and 41 downregulated proteins were identified. The higher expression levels of proteins like citrate synthase, glutathione S-transferase, glutathione peroxidase, and cytochrome c oxidase are associated with oxidative stress and mitochondrial dysfunction. The upregulation of glucose-regulated protein 78 indicated that the endoplasmic reticulum stress is induced by high pH stress. There were significant upregulation expressions of V-type H+-ATPase, Na+, K+-ATPase, 14-3-3 protein, as well as ATP-binding cassette transmembrane transporters after high pH exposure, which indicating their important roles in response to high pH stress. The abundance of proteins involved in protein glycosylation, oxidative pentose phosphate pathway, protein export, and glutathione metabolism were found enriched in high pH group than in control group. Quantitative proteomic profiling and integrated analysis with transcriptomic data provide new insights into the mechanisms underlying the molecular response to high pH stress in Fenneropenaeus chinensis.

Iridium-Catalyzed Direct Amidation of Imidazoles at the C-2 Position with Isocyanates in the Presence of Hydrosilanes Leading to Imidazole-2-Carboxamides

AbstractRegioselective coupling reaction of N-substituted imidazoles with isocyanates in the presence of a stoichiometric amount of hydrosilanes catalyzed by Ir4(CO)12 to give imidazole-2-carboxamides is reported. Imidazoles bearing an (O-silyl)carboximidate group at the 2-position appear to be initially formed in the reaction; these are then hydrolyzed to the final products in situ. The addition of the hydrosilane was essential for the catalytic reaction to proceed. Substituents on the imidazole ring had no effect on the reaction, except for certain bulky substituents such as t Bu and Ph groups at the 4-position. Triazoles such as 4-methyl-4H-1,2,4-triazole and 1-methyl-1H-1,2,4-triazole were also applicable to this C–H amidation, and the latter reaction proceeded regioselectively at the carbon atom between the sp3 and sp2 nitrogen atoms of the ring, and not between the two sp2 nitrogen atoms.

Post-expiry stability of freeze-dried plasma under field conditions - Can shelf life be extended?

This prospective study evaluated the effect of routine, uncontrolled, Israeli field storage conditions on the safety and efficacy of Lyo-Plas N Freeze-Dried Plasma (FDP) at the end of the manufacturer's shelf life, and up to 24 months post expiry. Clotting factors V, VIII and XI, proteins S, C, fibrinogen, PTT, ATIII, VWF, and INR as well as TEG, DDM, residual moisture, pH, and sterility of FDP returned from field units after uncontrolled storage were evaluated. Parameters measured at the end of manufacturer shelf life, as well as 6, 12, 18, and 24 months after expiry, were compared to those of freshly supplied FDP doses. Changes were found when comparing freshly supplied FDP to all field-stored groups in INR, PT, PTT, pH, fibrinogen, and factor VIII. A significant change was also seen in Factor XI in the 12, 18, and 24 months post-expiry samples, Factor V and R in the 24 months post-expiry samples, MA in the 12, 24 months post-expiry group, and Protein C in the 18 months post-expiry group. An increase in the residual moisture from 0.90% in freshly supplied FDP to 1.35% in 24 months post-expiry FDP.; all p < .05. No growth was found in sterility analysis. Despite uncontrolled field storage conditions, the findings demonstrate that the safety and efficacy of FDP units, stored in uncontrolled conditions are only slightly affected, even beyond their expiration date. This information allows consideration of possibly extending the shelf life.

Synthesis and characterization of site selective photo-crosslinkable glycidyl methacrylate functionalized gelatin-based 3D hydrogel scaffold for liver tissue engineering

The presented work outlined the development of a new biocompatible hydrogel material that has potential applications in soft tissue engineering. As a proof of concept, human hepatocytes were used to demonstrate the suitability of this material in providing conducive environment for cellular growth and functional development. Herein, a detailed synthesis of novel gelatin derivatives - photo-crosslinkable glycidyl methacrylate (GMA) functionalized gelatins (Gelatin-GMA), and preparation of three-dimensional (3D) hydrogel scaffolds for the encapsulated Huh-7.5 cells is reported. The Gelatin-GMA biopolymers were synthesized at two different pH values of 3.5 (acidic) and 10.5 (basic) where two different photo-crosslinkable polymers were formed utilizing –COOH & –OH groups in acidic pH, and –NH2 & –OH groups in basic pH. The hydrogels were prepared using an initiator (Irgacure I2959) in the presence of UV light. The Gelatin-GMA biopolymers were characterized using spectroscopic studies which confirmed the successful preparation of the polymer derivatives. Rheological measurement was carried out to characterize the mechanical properties and derive the mesh sizes of the 3D hydrogels. Subsequently, detailed in vitro hepatocyte compatibility and functionality studies were performed in the 3D cell seeded hydrogel platform. The 3D hydrogel design with larger mesh sizes utilizes the advantage of the excellent diffusion properties of porous platform, and enhanced cell-growth was observed, which in turn elicited favorable Huh-7.5 response. The hydrogels led to improved cellular functions such as differentiation, viability and proliferation. Overall, it showed that the Gelatin-GMA based hydrogels presented better results compared to control sample (GelMA) because of the higher mesh sizes in Gelatin-GMA based hydrogels. Additionally, the functional group studies of the two Gelatin-GMA samples revealed that the cell functionalities are almost unaffected even after the tripeptide - Arg-Gly-Asp (RGD) in Gelatin-GMA synthesized at pH 3.5 is no longer completely available.

The predictive value of minute ventilation versus carbon dioxide production in pulmonary hypertension associated with left heart disease.

BackgroundThe aim of the present study was to investigate the role of key cardiopulmonary exercise testing (CPET) parameters in the identification of pre-capillary components in patients with pulmonary hypertension associated with left heart disease (PH-LHD), and to evaluate their correlations with hemodynamic parameters.MethodsNinety patients with PH-LHD underwent right-heart catheterization, echocardiography, and CPET. The differences in related indexes between a combined post- and pre-capillary PH (Cpc-PH) group (n=47) and an isolated post-capillary PH (Ipc-PH) group (n=43) were compared. Correlation analysis was performed. Logistic regression and receiver operator characteristic (ROC) analyses were performed to assess the ability of CPET variables to distinguish patients with Cpc-PH from those with Ipc-PH.ResultsThe hemodynamics, hyperventilation and right ventricular function of Cpc-pH group were worse than those of Ipc-pH group. The parameters related to minute ventilation versus carbon dioxide production (VE/VCO2) played a significant role in the differentiation of Cpc-PH and Ipc-PH, and had a moderate positive correlation with pulmonary vascular resistance (PVR). Univariate and multivariate logistic analyses showed that lowest percentage of VE/VCO2 in predicted value (VE/VCO2%pred) was the single best predictor of Cpc-PH, and the area under ROC curve also confirmed that lowest VE/VCO2%pred (≥137%) could serve as a novel diagnostic marker for Cpc-PH. On the basis of this lowest VE/VCO2%pred threshold, patients were divided into two groups. Most hemodynamic parameters were worse in patients with a lowest VE/VCO2%pred ≥137%.ConclusionsVE/VCO2-related parameters are powerful prognosticators for the presence of pre-capillary components in patients with PH-LHD, especially lowest VE/VCO2%pred.

Effect of changes in the soil calcium-to-magnesium ratio by calcium application on soybeans, Glycine max (L.) Merr., growth

ABSTRACT There have been few studies in Japan on the effects of the application of lime materials, especially in regard to the soil calcium-to-magnesium ratio (Ca:Mg). The aim of this study was to explore the effects of changes in the soil Ca:Mg on soybean growth via pot and field tests over two growing seasons: 2018–2019. The field tests were conducted in two different fields, one in each year, and the soil for the pot tests in both years was collected from the respective fields used in the field tests. In the pot test from 2018 to 2019, we adjusted the soil Ca:Mg ratio and soil pH using Ca(OH)2 and CaSO4, with three conditions: control (pH = 5.2, Ca:Mg = 1.3), CaMg (pH = 5.0, Ca:Mg = 2.6), and CaMg + pH (pH = 5.7, Ca:Mg = 2.4). Moreover, we added two further conditions for the pot test in 2019: CaCO3 (pH = 5.9, Ca:Mg = 1.8) and dolomite groups (pH = 6.4, Ca:Mg = 1.3). In the field test, we adjusted only the soil Ca:Mg ratio using phosphogypsum and had two conditions: control (pH = 5.0, Ca:Mg = 1.1) and gypsum (pH = 4.7, Ca:Mg = 1.9). In both tests, the application of Ca except for dolomite contributed to the increase in the concentration and uptake of Ca both in the whole plants and some parts of the soybean plants. Likewise, application of Ca except for dolomite contributed to a significant increase in the total number of pods. The weight of seeds and the total dry weight in the CaMg + pH and CaCO3 groups and in the gypsum plot were significantly higher than were those in each control group. Thus, the study suggests that the Ca:Mg ratio in soils with a low Ca:Mg ratio may limit soybean growth to a greater extent than does the soil pH. However, the effect of the interaction between the soil Ca:Mg ratio and soil pH on dry-matter production of soybeans was different between the pot and field tests, and further studies were needed to clarify the discrepancy.

Stimuli-responsive polymersomes of poly [2-(dimethylamino) ethyl methacrylate]-b-polystyrene

Amphiphilic diblock copolymers may assemble in aqueous solutions to form vesicles delimited by a polymeric double layer, also known as polymersomes, considered a more robust option to liposomes. Diblock copolymers may respond to pH, temperature, and other conditions. Because of such properties, polymersomes are currently being studied as drug delivery systems or as nanoreactors. pH-responsive polymersomes are potentially crucial because unusual pH gradients are present in cells under several physiological and pathological conditions. We synthesized two diblock copolymers of poly [2-(dimethylamino) ethyl methacrylate]-block-polystyrene (PDMAEMA-b-PS) via RAFT. We both developed new materials and better-understood polymersomes' properties with pH and temperature-responsive groups with these polymers. GPC, 1H-NMR, and FTIR characterized copolymers. The ionization equilibrium of the PDMAEMA amino groups on the polymersomes was analyzed by potentiometric titration and Zeta potential measurements. The hydrodynamic radius of the polymersomes in different pH and temperatures was analyzed by DLS. Entrapment of an electron paramagnetic resonance probe indicated the presence of a hydrophilic inner core. Negative staining transmission electron microscopy showed spherical aggregates and confirmed the diameter around 80 nm. These polymersomes with dual stimulus–response (i.e., pH and temperature) may be a platform for gene delivery and nanoreactors.

Regional shape, global function and mechanics in right ventricular volume and pressure overload conditions: a three-dimensional echocardiography study

Our aim was to assess the regional right ventricular (RV) shape changes in pressure and volume overload conditions and their relations with RV function and mechanics. The end-diastolic and end-systolic RV endocardial surfaces were analyzed with three-dimensional echocardiography (3DE) in 33 patients with RV volume overload (rToF), 31 patients with RV pressure overload (PH), and 60 controls. The mean curvature of the RV inflow (RVIT) and outflow (RVOT) tracts, RV apex and body (both divided into free wall (FW) and septum) were measured. Zero curvature defined a flat surface, whereas positive or negative curvature indicated convexity or concavity, respectively. The longitudinal and radial RV wall motions were also obtained. rToF and PH patients had flatter FW (body and apex) and RVIT, more convex interventricular septum (body and apex) and RVOT than controls. rToF demonstrated a less bulging interventricular septum at end-systole than PH patients, resulting in a more convex shape of the RVFW (r = − 0.701, p < 0.0001), and worse RV longitudinal contraction (r = − 0.397, p = 0.02). PH patients showed flatter RVFW apex at end-systole compared to rToF (p < 0.01). In both groups, a flatter RVFW apex was associated with worse radial RV contraction (r = 0.362 in rToF, r = 0.482 in PH at end-diastole, and r = 0.555 in rToF, r = 0.379 in PH at end-systole, respectively). In PH group, the impairment of radial contraction was also related to flatter RVIT (r = 0.407) and more convex RVOT (r = − 0.525) at end-systole (p < 0.05). In conclusion, different loading conditions are associated to specific RV curvature changes, that are related to longitudinal and radial RV dysfunction.

Prevalence and abundance of 9 periodontal pathogens in the saliva of periodontally healthy adults and patients undergoing supportive periodontal therapy.

PurposeThis study aimed to examine the prevalence and abundance of 9 representative periodontal pathogens in the saliva samples of periodontally healthy subjects (PH) and patients with periodontitis who underwent supportive periodontal therapy (SPT). The age-specific distribution of these pathogens in periodontally healthy individuals was also analyzed.MethodsOne hundred subjects (aged >35 years) were recruited (50 each in the PH and SPT groups) between August 2016 and April 2019. The prevalence and abundance of periodontal pathogens in the PH group were compared with those in periodontally healthy young subjects (94 subjects; aged <35 years), who were included in our previous study. DNA copy numbers of Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), Treponema denticola (Td), Prevotella intermedia (Pi), Fusobacterium nucleatum (Fn), Campylobacter rectus (Cr), Peptostreptococcus anaerobius (Pa), and Eikenella corrodens (Ec) were analyzed using real-time polymerase chain reaction.ResultsThe detection frequencies of all pathogens, except Aa, were high in the PH and SPT groups. The ranking order of pathogen DNA copy numbers was similar in both groups. In both groups, Fn had the highest abundance, Aa had the lowest abundance. Additionally, Td was significantly more abundant in men than in women in both groups (P<0.05). Compared with the PH group, the SPT group exhibited significantly lower total bacteria and Fn abundance and higher Pg abundance (P<0.05). The age-specific pathogen distribution analysis revealed a significantly low Aa abundance and high Tf and Cr abundance in the PH group.ConclusionsThe clinical parameters and microbial profiles were similar between the SPT and PH groups. However, patients with periodontitis require supportive care to prevent recurrence. As the abundance of some bacteria varied with age, future studies must elucidate the correlation between age-related physiological changes and periodontal bacterial composition.

A new amido-phosphane as ligand for copper and silver complexes. Synthesis, characterization and catalytic application for azide-alkyne cycloaddition in glycerol.

The new sterically hindered amido-phosphane 1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane-3,7-diylbis(phenylmethanone), DBPTA (1), has been obtained via an open-cage double N-acylation of 1,3,5-triaza-7-phosphadamantane (PTA) using benzoic anhydride. DBPTA is the only acyl derivative of PTA that contains an aromatic appendage. Due to the bulky nature of the benzoyl C(O)Ph groups, they exhibit mutual anti configuration as confirmed by solution NMR and single crystal X-ray diffraction. Compound 1 is readily soluble in common polar organic and green solvents, making it a very versatile ligand that could be used in a variety of reaction systems. To assess the coordination characteristics of the new phosphane, seven copper complexes of formulas [Cu(DBPTA)4]BF4 (2), [CuX(DBPTA)3] {X = Br (3) and I (4)}, [Cu(μ-X)(DBPTA)2]2 {X = Br (5) and I (6)}, [Cu(bpy)(DBPTA)2]Y {Y = BF4 (7) and BPh4 (8)} {bpy = 2,2'-bipyridine}, and three silver complexes with formulas [Ag(DBPTA)4]NO3 (9), [Ag(Tpm*)(DBPTA)]NO3 (10) and [Ag(Tpms)(DBPTA)] (11) {Tpm* = tris(3,5-dimethyl-1-pyrazolyl)methane, Tpms = tris(pyrazol-1-yl)methanesulfonate} have been synthesised. Compounds 1-11 were characterized by elemental analyses and electrospray ionization mass spectrometry (ESI-MS), as well as by FT-IR and NMR (1H, 13C, 31P, COSY and HSQC) spectroscopic techniques. The catalytic activity of the complexes has been investigated for 1,3-dipolar azide-alkyne cycloaddition reaction using glycerol as a reaction medium to afford 1,4-disubstituted-1,2,3-triazoles. Complex 7 was found to be the most efficient catalyst, affording triazoles in yields up to 97% after 18 h under standard bench experimental conditions (at 23 °C, aerobic conditions and in the absence of any additional bases) and up to 98% after 15 minutes under microwave irradiation (125 °C, 30 W). The catalysis proceeds with a broad substrate scope according to "Click" rules providing a significant contribution to "Green Chemistry".

Cardiovascular Events According To Maternal Or Paternal Heritability Of Genetic Mutation In Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic autosomal disease, characterized by high levels of cholesterol since birth, that leads to a very high cardiovascular (CV) risk. In patients with the heterozygous FH (HeFH), in case of a maternal transmission, fetus is exposed to high maternal cholesterol levels during pregnancy. Based on the Developmental Origins of Health and Disease concept, our objective was to study the effect of heritability of genetic FH mutation on the occurrence of CV events in adults with HeFH. We included 138 HeHF patients with a genetic diagnosis and a clear familial history of hypercholesterolemia among 513 patients included in the Marseille's REFERCHOL register. Occurrence of CV events were compared by maternal (MH group, 64 patients) or paternal (PH group, 74 patients) heritability. The logistic regression method was used to determine the predictors of CV events. At inclusion, parameters were comparable between groups except more hypertension (25% vs. 9.4%, P = 0.01), more treatment by anti-PCSK9 (20.3 vs. 5.4%, P = 0.008) and less familial early CV events (28.6 vs. 51.4%, P = 0.007) in the MH group. Regarding CV events, 35.9% of MH patients and 27% of PH patients had a CV event ( P = 0.26). Predictive factors of CV event were sex ( P = 0.0004), age at start of statins ( P = 0.0003), maximal LDL-c ( P = 0.009) and Lp(a) ( P = 0.007). On multivariate analysis, heritability was not statistically associated with CV risk (PH risk vs. MH risk: OR = 0.34, P = 0.076). Sex, age at start of statins and Lp(a) were still associated with CV events occurrence (OR = 0.3, P = 0.044 for female; OR = 1.08, P = 0.001 for a later start of statins; OR = 6.98, P = 0.0096 for Lp(a)). Heritability has no significant effect on the occurrence of CV event during adulthood although paternal heritability seems to be protective. We are recruiting all HeFH patients from French FH register to improve the power of the study and confirm the observed trend.

The content of active materials in miswak (Salvadora persica): An Analytical study using Fourier-transform infrared spectroscopy and ultraviolet–visible spectrophotometer

Aim: The trend of cleaning teeth with miswak amidst the modern technological developments can be found in the majority of large countries. Many advantages of miswak increase its trade throughout the world, causing it to be easily obtainable on the market. However, until now, there have not been many studies that explain the active substances in miswak sold on the market. This study aims to analyze the content of active substances from various types of miswaks, which are sold freely on the market. Materials and Methods: A total of five miswaks from Saudi Arabia and Pakistan were taken as the study sample. The miswak was divided into three types of samples: powder, extract, and evaporated extract samples. All miswaks were extracted using maceration method. The chemical content was tested using Fourier-transform infrared (FTIR) spectroscopy and an ultraviolet–visible (UV–Vis) spectrophotometer. The research results were analyzed using Origin software. Results: FTIR test of the miswak powder showed that miswak B had a dominant phosphoric acid (PH) group and pH ester with a wave range of 2425-2325 cm‒1. The FTIR test of the miswak extract showed phosphorus atoms at wavenumber 867.96 cm‒1 with PO groups and 430.01 cm‒1 with the P-Cl group in the compound. UV–Vis test of the miswak extract showed that miswak B and miswak E had higher absorbance values than other miswaks. The UV–Vis test of the evaporated miswak extract resulted in the breakdown of molecular bonds in miswak E after going through the evaporation process, causing more than one wave peak to be produced. The FTIR test of the evaporated miswak extract showed that miswak R had a strong bond between molecules. Hence, the PH group is not broken during the evaporation process. Conclusion: Miswaks which are sold freely in the market contain an active substance in the form of phosphoric acid which consists of phosphorus atoms which are beneficial to human teeth and bones.

P-Alkynyl functionalized benzazaphospholes as transmetalating agents.

Exposure of 10π-electron benzazaphosphole 1 to HCl, followed by nucleophilic substitution with the Grignard reagent BrMgCCPh afforded alkynyl functionalized 3 featuring an exocyclic -C[triple bond, length as m-dash]C-Ph group with an elongated P-C bond (1.7932(19) Å). Stoichiometric experiments revealed that treatment of trans-Pd(PEt3)2(Ar)(i) (Ar = p-Me (C) or p-F (D)) with 3 generated trans-Pd(PEt3)2(Ar)(CCPh) (Ar = p-Me (E) or p-F (F)), 5, which is the result of ligand exchange between P-I byproduct 4 and C/D, and the reductively eliminated product (Ar-C[triple bond, length as m-dash]C-Ph). Cyclic voltammetry studies showed and independent investigations confirmed 4 is also susceptible to redox processes including bimetallic oxidative addition to Pd(0) to give Pd(i) dimer 6-Pd2-(P(t-Bu)3)2 and reduction to diphosphine 7. During catalysis, we hypothesized that this unwanted reactivity could be circumvented by employing a source of fluoride as an additive. This was demonstrated by conducting a Sonogashira-type reaction between 1-iodotoluene and 3 in the presence of 10 mol% Na2PdCl4, 20 mol% P(t-Bu)Cy2, and 5 equiv. of tetramethylammonium fluoride (TMAF), resulting in turnover and the isolation of Ph-C[triple bond, length as m-dash]C-(o-Tol) as the major product.

The pH and Bismuth Oxide Particle Size can Affect Diametral Tensile Strength of Mineral Trioxide Aggregate.

Objective:The aim of the present study was to evaluate the effect of different pHs (4.4, 5.4, 6.4, 7.4, 8.4, and 9.4) and three different particle sizes of bismuth oxide on diametral tensile strength (DTS) of white Mineral Trioxide Aggregate (WMTA).Methods:Thirty cylindrical moulds were divided into six groups of five; WMTA was mixed, placed inside the moulds, and wrapped in pieces of gauze soaked in synthetic tissue fluid (STF) with pH values of either 4.4, 5.4, 6.4, 7.4, 8.4, 9.4. For bismuth oxide, eighteen similar molds were divided into three groups of six (n=6). Then bismuth oxide with three particle sizes, including fine (120 nm), medium (200 nm), and coarse (10 μm), were provided and added to the Portland cement, which did not have any bismuth oxide to create WMTA. Then WMTA was mixed, placed inside cylindrical molds. After incubation at 95% humidity for 48 hours, samples were subjected to DTS testing by an Instron Universal testing machine with a crosshead speed of 1 mm/min. Then, one sample from each group was subjected to scanning electron microscope (SEM) analysis. Data were analysed by ANOVA and Tukey tests (α=0.05).Results:The comparison of DTS in pH groups were: 8.4>7.4>9.4>6.4>5.4>4.4 (P<0.05); and in bismuth oxide groups were: fine particles > medium particles > coarse particles (P<0.05). Acidic pH, negatively affected the distribution of Ca2+ and Si4+ ions, while bismuth oxide with fine particles enhanced it.Conclusion:Acidic pH can decline the DTS of MTA significantly. However, reducing the particle size of bismuth oxide can increase the DTS of MTA significantly.

Nuclearity expansion in Pd clusters triggered by the migration of a phenyl group in cyclooligosilanes.

Heptanuclear palladium clusters with six palladium atoms in a planar arrangement were obtained from the reaction of [Pd(CNtBu)2]3 with Ph-substituted cyclotetrasilane or cyclopentasilane via the migration of a phenyl group. The molecular structures of these clusters as well as those of two possible intermediates were determined by single-crystal X-ray diffraction analyses.

The association of prepartum urine pH, plasma total calcium concentration at calving and postpartum diseases in Holstein dairy cattle

The use of anionic salts to prevent milk fever in dairy cattle has been an effective nutritional strategy; however, the degree of acidification that determines the most acceptable productive responses and well-being of the cow is still a controversial topic. The objective of this study was to assess urine pH in prepartum Holstein cows fed anionic diets and determine its association with plasma total Ca, Mg, P, β-hydroxyl-butyrate (BHB) concentrations at parturition and the occurrence of peripartum disorders. This investigation consisted of 2 studies. Study 1 was conducted on a grazing dairy. Between February and May 2019, 60 prepartum multiparous cows were tested for urine pH and plasma metabolite concentration at parturition. Total Ca, P, Mg and BHB at day 1 in milk (DIM) were assessed and statistically analyzed by ANOVA (models for polynomial regression). Study 2 was conducted on a drylot dairy farm. Between July 2018 and January 2019, 203 cows were evaluated for urine pH and followed-up for 30 DIM to obtain the incidence of dystocia, stillbirths, milk fever, retained fetal membranes, metritis, clinical mastitis and ketosis. Cows were categorized based on their last urine pH as group 1: pH > 7.0 (n = 135); group 2: pH between 6.0 and 7.0 (n = 46) and group 3: pH < 6.0 (n = 22). A logistic regression model for each health event was conducted considering urine pH group as the main effect. Urine sample was collected at 2.71 ± 2.84 days before parturition. In study 1, there was a quadratic effect of urine pH on total Ca. Total Ca concentration was higher between urine pH 6.0 and 7.0, while decreasing below pH 6.0 and above pH 7.0. There was a trend (P = 0.11) for a quadratic effect of urine pH on the concentration of plasma BHB at parturition. β-Hydroxyl-butyrate was lower approximately between urine pH 6.5 and 7.5. In study 2, the odds for a stillborn in cows with urine pH < 6.0 was 2.39 (95% CI = 1.06–5.40) times the odds for a stillborn in cows with urine pH ≥ 7.0. There was no association between urine pH and the other diseases. In conclusion, cows with prepartum urine pH < 6.0 and >7.0 had lower concentration of plasma total Ca and tended to have a higher concentration of BHB. Cows with urine pH < 6.0 had a higher incidence of stillbirths than cows with urine pH > 7.0.

Isospecific Polymerization of Methyl Methacrylate by Intramolecular Rare‐Earth Metal Based Lewis Pairs†

A series of cationic rare‐earth aryloxide complexes, i.e., [LREOAr']+[B(C6F5)4]– (L = CH3C(NAr)CHC(CH3)(NCH(R)CH2PPh2); RE = Y, Lu; Ar' =2,6‐tBu2‐C6H3, 2,6‐(PhCMe2)2‐4‐Me‐C6H2; Ar = 2,6‐iPr2‐C6H3, 2,6‐(Ph2CH)2‐4‐iPr‐C6H2; R = H, CH3, iPr, Ph), were prepared and applied to the Lewis pair polymerization of methyl methacrylate (MMA). The stereoregularity of the resulting PMMA was significantly affected by the R substituent on the pendant arm of the tridentate NNP ligand, and was found to increase with increase in the steric hindrance of R. When using a Ph group as R, the Y complex produced a highly isotactic polymer with an mm value of 95% and a Tg of 54.6 oC. In contrast, the steric hindrance of the Ar and Ar' groups had no effect on the tacticity of the resulting polymer, presumably because these two substituents were situated such that they pointed outward from the cyclic intermediates. Kinetics studies demonstrated that the polymerization was a first‐order process with regard to the monomer concentration prior to catalyst deactivation. End group analysis indicated that the polymerization was accompanied by two possibly competing chain‐termination side reactions that proceeded via intramolecular backbiting cyclization.