965 research outputs found
Formation, electrochemical and radical scavenging properties of novel ruthenium compounds with N, X-donor (X = O, N) heterocyclic chelators
Herein, we communicate the formation of novel ruthenium compounds with N, X-donor (X = O, N) heterocyclic-
derived ligands. A paramagnetic ruthenium(IV) complex, [RuCl(pho)(bzca)(PPh3)](1) (pho = 2-
aminophenolate; bzca = 2-carboxylate-1H-benzimidazole) was isolated from the reaction of the
ruthenium(II) precursor, trans-[RuCl2(PPh3)3] and 2-((1H-benzimidazole)methylamino)phenol (Hbzap).
The 1:1 molar reaction between the same metal precursor and N-(benzoxazole)-2-hydroxybenzamide
(H2bhb) led to the formation of cis-Cl, trans-P-[RuIII(Hbhb)Cl2(PPh3)2](2). The dinuclear ruthenium
compounds, (l-Htba,Cl)2[RuIICl(PPh3)]2(3) (Htba = N-(thiophene)methyl-benzoxazole-2-amine) and
(l-Cl)2[RuIIICl(Hchpr)(PPh3)]2(4) (H2chpr = 2-amino-3-((tetrahydro-2H-pyran-4-ylimino)methyl)-4Hchromen-
4-one) were formed from the equimolar ratio coordination reactions between trans-
[RuCl2(PPh3)3] and the respective free-ligands, Htba and H2chpr. These metal complexes were
characterized via IR-, NMR- and UV–Vis spectroscopy, molar conductivity measurements and structural
elucidations were confirmed by single crystal X-ray analysis. The X-ray studies revealed that all the
metallic compounds exhibited octahedral geometries and that the Hbzap free ligand has undergone a
unique molecular transformation to afford the pho and bzca bidentate chelators in 1. The electrochemical
properties of the respective metal complexes were investigated by voltammetric analysis. The cyclic
voltammograms (CVs) of 1–3 showed one redox couple while within the CV of the dinuclear compound
4, two redox couples were observed. The ligands and their metal complexes were also subjected to DPPH
radical scavenging studies. The IC50 values showed that all the metallic compounds have higher radical
scavenging activities than their corresponding free-ligands and the natural antioxidant, Vitamin C
Ruthenium complexes with lumazine derivatives: structural, electrochemical, computational and radical scavenging studies
In this research study, the formation and characterization
of new ruthenium(II) and (III) complexes encompassing
multidentate ligands derived from 6-acetyl-1,3,
7-trimethyllumazine (almz) are reported. The 1:1 molar coordination
reactions of trans-[RuCl2(PPh3)3] with N-1-[1,3,
7-trimethyllumazine]benzohydride (bzlmz) and 6-(N-methyloxime)-
1,3,7-trimethyllumazine (ohlmz) formed a diamagnetic
ruthenium(II) complex, cis-[RuCl2(bzlmz)(PPh3)] (1),
and paramagnetic complex, cis-[RuIIICl2(olmz)(PPh3)] (2)
[Holmz = 6-(N-hydroxy-N0-methylamino)-1,3,7-trimethyllumazine],
respectively. These ruthenium complexes were
characterized via physico-chemical and spectroscopic
methods. Structural elucidations of the metal complexes
were confirmed using single crystal X-ray analysis. The
redox properties of the metal complexes were investigated
via cyclic voltammetry. Electron spin resonance spectroscopy
confirmed the presence of a paramagnetic metal
centre in 2. The radical scavenging activities of the metal
complexes were explored towards the DPPH and NO radicals.
Quantum calculations at the density functional theory
level provided insight into the interpretation of the IR and
UV–Vis experimental spectra of 1
Coordination of di- and triimine ligands at ruthenium(II) and ruthenium(III) centers: structural, electrochemical and radical scavenging studies
Herein, we explore the coordination of di- and triimine chelators at
ruthenium(II) and ruthenium(III) centers. The reactions of 2,6-bis-((4-
tetrahydropyranimino)methyl)pyridine (thppy), N1,N2-bis((3-chromone)
methylene)benzene-1,2-diamine (chb), and tris-((1H-pyrrol-2-ylmethylene)
ethane)amine (H3pym) with trans-[RuIICl2(PPh3)3] afforded the diamagnetic
ruthenium(II) complex cis-[RuCl2(thppy)(PPh3)] (1) and the paramagnetic
complexes [mer-Ru2(μ-chb)Cl6(PPh3)2] (2), and [Ru(pym)] (3), respectively.
The complexes were characterized by IR, NMR, and UV–vis spectroscopy
and molar conductivity measurements. The structures were confirmed by
single crystal X-ray diffraction studies. The redox properties of the metal
complexes were probed via cyclic- and squarewave voltammetry. Finally, the
radical scavenging capabilities of the metal complexes towards the NO and
2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radicals were investigate
Student Misconceptions about Plants – A First Step in Building a Teaching Resource
Plants are ubiquitous and found in virtually every ecosystem on Earth, but their biology is often poorly understood, and inaccurate ideas about how plants grow and function abound. Many articles have been published documenting student misconceptions about photosynthesis and respiration, but there are substantially fewer on such topics as plant cell structure and growth; plant genetics, evolution, and classification; plant physiology (beyond energy relations); and plant ecology. The available studies of misconceptions held on those topics show that many are formed at a very young age and persist throughout all educational levels. Our goal is to begin building a central resource of plant biology misconceptions that addresses these underrepresented topics, and here we provide a table of published misconceptions organized by topic. For greater utility, we report the age group(s) in which the misconceptions were found and then map them to the ASPB – BSA Core Concepts and Learning Objectives in Plant Biology for Undergraduates, developed jointly by the American Society of Plant Biologists and the Botanical Society of America
Ruthenium complexes with Schiff base ligands containing benz(othiazole/imidazole) moieties: Structural, electron spin resonance and electrochemistry studies
Novel ruthenium(II/III) complexes of Schiff bases containing benzimidazole (bz) or benzothiazole (bs)
moieties were isolated: the diamagnetic ruthenium complex, cis-[RuIICl2(bzpy)(PPh3)2] (1) was formed
from the 1:1 M reaction between N-((pyridine-2-yl)methylene)-1H-benzimidazole (bzpy) and metal precursor,
trans-[RuCl2(PPh3)3]. The same metal precursor, when reacted with the benzimidazole-derived
Schiff bases [N-(2-hydroxybenzylidene)-benzothiazole (Hbsp) and N-(2-hydroxybenzylidene)-benzimidazole
(Hbzp)], afforded the paramagnetic ruthenium(III) complexes [RuCl(bsp)2(PPh3)] (2) and
trans-[RuCl(bzp)(PPh3)2] (3), respectively. These metal complexes were characterized via IR, mass and
UV–Vis spectroscopy, elemental analysis, single crystal XRD analysis as well as conductivity measurements.
Their redox properties were probed by voltammetry and accompanying UV–Vis spectroelectrochemistry
experiments. Structural features of complex 1 were further investigated by multinuclear (1H
and 31P) NMR spectroscopy
CheXpert: A Large Chest Radiograph Dataset with Uncertainty Labels and Expert Comparison
Large, labeled datasets have driven deep learning methods to achieve
expert-level performance on a variety of medical imaging tasks. We present
CheXpert, a large dataset that contains 224,316 chest radiographs of 65,240
patients. We design a labeler to automatically detect the presence of 14
observations in radiology reports, capturing uncertainties inherent in
radiograph interpretation. We investigate different approaches to using the
uncertainty labels for training convolutional neural networks that output the
probability of these observations given the available frontal and lateral
radiographs. On a validation set of 200 chest radiographic studies which were
manually annotated by 3 board-certified radiologists, we find that different
uncertainty approaches are useful for different pathologies. We then evaluate
our best model on a test set composed of 500 chest radiographic studies
annotated by a consensus of 5 board-certified radiologists, and compare the
performance of our model to that of 3 additional radiologists in the detection
of 5 selected pathologies. On Cardiomegaly, Edema, and Pleural Effusion, the
model ROC and PR curves lie above all 3 radiologist operating points. We
release the dataset to the public as a standard benchmark to evaluate
performance of chest radiograph interpretation models.
The dataset is freely available at
https://stanfordmlgroup.github.io/competitions/chexpert .Comment: Published in AAAI 201
Thermal design and characterization of a modular integrated liquid cooled 1200 V-35 A SiC MOSFET bi-directional switch
The aim of this work is the thermal design of a modular direct liquid cooled package for 1200 V–35 A SiC power MOSFETs, in order to take full advantage of the high power density and high frequency performance of these devices, in the development of a modular integrated solution for power converters. An accurate electro-thermal fluid dynamic model is set up and validated by thermal characterization on a prototype; numerical models have been used to study the internal temperature distribution and to propose further optimization
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Refractory Hypertension: Determination of Prevalence, Risk Factors and Comorbidities in a Large, Population-Based Cohort
Refractory hypertension is an extreme phenotype of antihypertensive treatment failure. Participants in the REasons for Geographic And Racial Differences in Stroke (REGARDS) Study, a large (n=30 239), population-based cohort were evaluated to determine the prevalence of refractory hypertension and associated cardiovascular risk factors and comorbidities. Refractory hypertension was defined as uncontrolled blood pressure (systolic/diastolic, ≥140/90 mm Hg) on ≥5 antihypertensive drug classes. Participants with resistant hypertension (systolic/diastolic, ≥140/90 mm Hg on ≥3 or <140/90 mm Hg on ≥4 antihypertensive classes) and all participants treated for hypertension served as comparator groups. Of 14 809 REGARDS participants receiving antihypertensive treatment, 78 (0.5%) had refractory hypertension. The prevalence of refractory hypertension was 3.6% among participants with resistant hypertension (n=2144) and 41.7% among participants on ≥5 antihypertensive drug classes. Among all participants with hypertension, black race, male sex, living in the stroke belt or buckle, higher body mass index, lower heart rate, reduced estimated glomerular filtration rate, albuminuria, diabetes mellitus, and history of stroke and coronary heart disease were associated with refractory hypertension. Compared with resistant hypertension, prevalence ratios for refractory hypertension were increased for blacks (3.00; 95% confidence interval, 1.68–5.37) and those with albuminuria (2.22; 95% confidence interval, 1.40–3.52) and diabetes mellitus (2.09; 95% confidence interval, 1.32–3.31). The median 10-year Framingham risk for coronary heart disease and stroke was higher among participants with refractory hypertension when compared with those with either comparator group. These data indicate that although resistant hypertension is relatively common among treated patients with hypertension, true antihypertensive treatment failure is rare
Apparent treatment-resistant hypertension and risk for stroke, coronary heart disease, and all-cause mortality
Apparent treatment-resistant hypertension (aTRH) is defined as uncontrolled hypertension despite the use of three or more antihypertensive medication classes or controlled hypertension while treated with four or more antihypertensive medication classes. We evaluated the association of aTRH with incident stroke, coronary heart disease (CHD), and all-cause mortality. Participants from the population-based REasons for Geographic And Racial Differences in Stroke (REGARDS) Study treated for hypertension with aTRH (n = 2043) and without aTRH (n = 12,479) were included. aTRH was further categorized as controlled aTRH (≥4 medication classes and controlled hypertension) and uncontrolled aTRH (≥3 medication classes and uncontrolled hypertension). Over a median of 5.9, 4.4, and 6.0 years of follow-up, the multivariable adjusted hazard ratio for stroke, CHD, and all-cause mortality associated with aTRH versus no aTRH was 1.25 (0.94–1.65), 1.69 (1.27–2.24), and 1.29 (1.14–1.46), respectively. Compared with controlled aTRH, uncontrolled aTRH was associated with CHD (hazard ratio, 2.33; 95% confidence interval, 1.21–4.48), but not stroke or mortality. Comparing controlled aTRH with no aTRH, risk of stroke, CHD, and all-cause mortality was not elevated. aTRH was associated with an increased risk for coronary heart disease and all-cause mortality
Success Factors of European Syndromic Surveillance Systems: A Worked Example of Applying Qualitative Comparative Analysis
Introduction: Syndromic surveillance aims at augmenting traditional public health surveillance with timely information. To gain a head start, it mainly analyses existing data such as from web searches or patient records. Despite the setup of many syndromic surveillance systems, there is still much doubt about the benefit of the approach. There are diverse interactions between performance indicators such as timeliness and various system characteristics. This makes the performance assessment of syndromic surveillance systems a complex endeavour. We assessed if the comparison of several syndromic surveillance systems through Qualitative Comparative Analysis helps to evaluate performance and identify key success factors.
Materials and Methods: We compiled case-based, mixed data on performance and characteristics of 19 syndromic surveillance systems in Europe from scientific and grey literature and from site visits. We identified success factors by applying crisp-set Qualitative Comparative Analysis. We focused on two main areas of syndromic surveillance application: seasonal influenza surveillance and situational awareness during different types of potentially health threatening events.
Results: We found that syndromic surveillance systems might detect the onset or peak of seasonal influenza earlier if they analyse non-clinical data sources. Timely situational awareness during different types of events is supported by an automated syndromic surveillance system capable of analysing multiple syndromes. To our surprise, the analysis of multiple data sources was no key success factor for situational awareness.
Conclusions: We suggest to consider these key success factors when designing or further developing syndromic surveillance systems. Qualitative Comparative Analysis helped interpreting complex, mixed data on small-N cases and resulted in concrete and practically relevant findings
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