Tetraphenolate niobium and tantalum complexes for the ring opening polymerization of ε-caprolactone

Reaction of the pro-ligand α,α,α′,α′-tetra(3,5-di-tert-butyl-2-hydroxyphenyl-p-)xylene-para-tetraphenol (p-L¹H₄) with two equivalents of [NbCl₅] in refluxing toluene afforded, after work-up, the complex {[NbCl₃(NCMe)]₂(μ-p-L¹)}·6MeCN (1·6MeCN). When the reaction was conducted in the presence of excess ethanol, the orange complex {[NbCl₂(OEt)(NCMe)]₂(μ-p-L¹)}·3½MeCN·0.614toluene (2·3½MeCN·0.614toluene) was formed. A similar reaction using [TaCl₅] afforded the yellow complex {[TaCl₂(OEt)(NCMe)]₂(μ-p-L¹)}·5MeCN (3·5MeCN). In the case of the meta pro-ligand, namely α,α,α′,α′tetra(3,5-di-tert-butyl-2-hydroxyphenyl-m-)xylene-meta-tetraphenol (m-L²H₄) only the use of [Nb(O)Cl₃(NCMe)₂] led to the isolation of crystalline material, namely the orange bis-chelate complex {[Nb(NCMe)Cl(m-L²H₂)₂]}·3½MeCN (4·3½MeCN) or {[Nb(NCMe)Cl(m-L²H₂)₂]}·5MeCN (4·5MeCN). The molecular structures of 1–4 and the tetraphenols L¹H₄ and m-L²H₄·2MeCN have been determined. Complexes 1–4 have been screened as pre-catalysts for the ring opening polymerization of ε-caprolactone, both with and without benzyl alcohol or solvent present, and at various temperatures; conversion rates were mostly excellent (>96%) with good control either at >100 °C over 20 h (in toluene) or 1 h (neat)

Surface constraints on the depth of the Atlantic meridional overturning circulation: Southern Ocean versus North Atlantic

Paleoclimate proxy evidence suggests that the Atlantic meridional overturning circulation (AMOC) was about 1000 m shallower at the Last Glacial Maximum (LGM) compared to the present. Yet it remains unresolved what caused this glacial shoaling of the AMOC, and many climate models instead simulate a deeper AMOC under LGM forcing. While some studies suggest that Southern Ocean surface buoyancy forcing controls the AMOC depth, others have suggested alternatively that North Atlantic surface forcing or interior diabatic mixing plays the dominant role. To investigate the key processes that set the AMOC depth, here we carry out a number of MITgcm ocean-only simulations with surface forcing fields specified from the simulation results of three coupled climate models that span much of the range of glacial AMOC depth changes in phase 3 of the Paleoclimate Model Intercomparison Project (PMIP3). We find that the MITgcm simulations successfully reproduce the changes in AMOC depth between glacial and modern conditions simulated in these three PMIP3 models. By varying the restoring time scale in the surface forcing, we show that the AMOC depth is more strongly constrained by the surface density field than the surface buoyancy flux field. Based on these results, we propose a mechanism by which the surface density fields in the high latitudes of both hemispheres are connected to the AMOC depth. We illustrate the mechanism using MITgcm simulations with idealized surface forcing perturbations as well as an idealized conceptual geometric model. These results suggest that the AMOC depth is largely determined by the surface density fields in both the North Atlantic and the Southern Ocean

The predictors to medication adherence among adults with diabetes in the United Arab Emirates.

BackgroundDiabetes is a chronic medical condition and adherence to medication in adults with diabetes is important. Identifying predictors to medication adherence in adults with diabetes would help identify vulnerable patients who are likely to benefit by improving their adherence levels.MethodsWe conducted a cross-sectional study at the Dubai Police Health Centre between February 2015 and November 2015. Questionnaires were used to collect socio-demographic, clinical and disease related variables and the primary measure of outcome was adherence levels as measured by the Morisky Medication Adherence Scale (MMAS-8©). Multivariate logistic regression was carried out to identify predictors to adherence.ResultsFour hundred and forty six patients were interviewed. Mean age 61 year +/- 11. 48.4 % were male. The mean time since diagnosis of diabetes was 3.2 years (Range 1-15 years). Two hundred and eighty eight (64.6 %) patients were considered non-adherent (MMAS-8© adherence score < 6) while 118 (26.5 %) had moderate adherence (MMAS-8© adherence score 6 = <8) and 40 (9.0 %) high adherence (MMAS-8© adherence scores <8) to their medication respectively. The strongest predictor for adherence as predicted by the multi-logistic regression model was the patient's level of education. A technical diploma certificate as compared to a primary school level of education was the strongest predictor of adherence (OR = 66.1 CI: 6.93 to 630.43); p < 0.001). The patient's age was also a predictor of adherence with older patients reporting higher levels of adherence (OR = 1.113 (CI: 1.045 to 1.185; p = 0.001 for every year increase in age). The duration of diabetes was also a predictor of adherence (OR = 1.830 (CI: 1.270 to 2.636; p = 0.001 for every year increase in the duration of diabetes). Other predictors to medication adherence include Insulin use, ethnicity and certain cultural behaviours.ConclusionA number of important predictors to medication adherence in diabetics were identified in this study. Such predictors could help develop policies for improving adherence in diabetics

Advantages of nonclassical pointer states in postselected weak measurements

We investigate, within the weak measurement theory, the advantages of non-classical pointer states over semi-classical ones for coherent, squeezed vacuum, and Schr\"{o}inger cat states. These states are utilized as pointer state for the system operator $\hat{A}$ with property $\hat{A}^{2}=\hat{I}$, where $\hat{I}$ represents the identity operator. We calculate the ratio between the signal-to-noise ratio (SNR) of non-postselected and postselected weak measurements. The latter is used to find the quantum Fisher information for the above pointer states. The average shifts for those pointer states with arbitrary interaction strength are investigated in detail. One key result is that we find the postselected weak measurement scheme for non-classical pointer states to be superior to semi-classical ones. This can improve the precision of measurement process.Comment: 8 pages, 5 figure

The Prediction of GDP by Aggregate Accounting Information. A Neural Network Model

Currently, accounting information plays a key role in the economic world and bridges the gap between macroeconomics and microeconomics. The existing literature corroborates that aggregate-level accounting earnings data encapsulates information regarding GDP growth. Nonetheless, accounting data derived from GDP components have not been given due consideration. Consequently, this research proposes an aggregate-level model grounded in the four components of the GDP income-based method, intending to assess the predictive power of aggregate-level accounting data concerning GDP. Furthermore, this paper scrutinizes the forecasting performance of a neural network model built upon the conventional linear regression framework. Finally, a comparison of the outcomes derived from both models is conducted. The findings reveal that both the present value model and the value-added model corroborate the notion that accounting information derived from the four components of the income-based GDP accounting framework encapsulates data pertinent to future GDP. Furthermore, the model demonstrates heightened sensitivity towards the performance of the subsequent second quarter's GDP. Among the variables, Depreciation and Income exhibit the most substantial impact, while Salaries exhibit the least impact. Concurrently, this research noted an improvement in the fitting performance of the neural network model as compared to that of the traditional linear model

Research on Factors Influencing the Quality of Talent Cultivation in Music Majors in Higher Education

This study aims to assess the current status of music professional talent cultivation quality in universities. It seeks to integrate factors influencing the quality of music talent cultivation, including the interplay between quality indicators, cultivation mechanisms, and autonomy. A theoretical model for the quality of music talent cultivation is proposed based on a sample of 1988 students from 16 undergraduate universities with music majors in Shaanxi Province. The study utilizes mathematical statistics and SPSS for data analysis, focusing on questionnaire reliability. Confirmatory factor analysis uses AMOS24.0 software, and model fit testing is performed against established indicators. The research findings reveal that the theoretical model aligns with the measured data, meeting fitting standards. Descriptive analysis and correlation testing show positive correlations between variables. Univariate analysis of variance based on majors, ages, and regions indicates significant differences. The study highlights the positive impact of understanding influencing factors on practical efforts to enhance the quality of music talent cultivation in universities. It recommends innovative reforms, such as expanding major choices, developing personalized curricula, and adopting tech-supported teaching methods. Strengthening management systems, effective supervision, and enhancing quality standards are emphasized for improving music education and talent cultivation, fostering overall progress and reform in this field

Diagnostic value of 18F-FDG PET in the assessment of myocardial viability in coronary artery disease: A comparative study with 99mTc SPECT and echocardiography

Objectives: To investigate the diagnostic value of 18F-FDG PET in the assessment of myocardial viability in patients with known coronary artery disease (CAD) when compared to 99mTc SPECT and echocardiography, with invasive coronary angiography as the gold standard.Methods: Thirty patients with diagnosed CAD met the selection criteria, with 10 of them (9 men; mean age 59.5 ± 10.5 years) undergoing all of these imaging procedures consisting of SPECT and PET, echocardiography and invasive angiography. Diagnostic sensitivity of these less invasive modalities for detection of myocardial viability was compared to invasive coronary angiography. Inter- and intra-observer agreement was assessed for diagnostic performance of SPECT and PET.Results: Of all patients with proven CAD, 50% had triple vessel disease. Diagnostic sensitivity of SPECT, PET and echocardiography was 90%, 100% and 80% at patient-based assessment, respectively. Excellent agreement was achieved between inter-observer and intra-observer agreement of the diagnostic value of SPECT and PET in myocardial viability (k=0.9).Conclusions: 18F-FDG PET has high diagnostic value in the assessment of myocardial viability in patients with known CAD when compared to SPECT and echocardiography. Further studies based on a large cohort with incorporation of 18F-FDG PET into patient management are warranted