Mn(III)-porphyrin catalysts for the cycloaddition of CO2 with epoxides at atmospheric pressure: effects of Lewis acidity and ligand structure

2021 ◽  
Author(s):  
Bruno Noschang Cabral ◽  
Jorge Luiz Sônego Milani ◽  
Alexandre Moreira Meireles ◽  
Dayse Carvalho da Silva Martins ◽  
Stephany Larissa da Silva Ribeiro ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Effects ◽  
Lewis Acidity ◽  
Ligand Structure ◽  
Structural Aspects ◽  
Electron Withdrawing Substituents

A series of eight Mn(III)-porphyrin (MnP) complexes with electron-withdrawing substituents at the meso and/or β-pyrrole positions of the macrocycle were designed to uncover electronic and structural aspects of MnP catalytic...

scholarly journals Analysis of long-term observations of the groundwater level In an aseismic region

2019 ◽  
pp. 47-67
Author(s):  
A. A. Lyubushin ◽  
O. S. Kazantseva ◽  
A. B. Manukin
Keyword(s):  
Time Series ◽  
Groundwater Level ◽  
Atmospheric Pressure ◽  
Active Regions ◽  
Sampling Interval ◽  
Pressure Effects ◽  
Adaptive Compensation ◽  
Groundwater Level Fluctuations ◽  
And Cluster Analysis

The results of the analysis of continuous precise time series of atmospheric pressure and groundwater level fluctuations in a well drilled to a depth of 400 m in the territory of Moscow are presented. The observations are remarkable in terms of their duration of more than 22 years (from February 2, 1993 to April 4, 2015) and by the sampling interval of 10 min. These long observations are suitable for exploring the stationarity of the properties of hydrogeological time series in a seismically quiet region, which is important from the methodological standpoint for interpreting the similar observations in seismically active regions aimed at earthquake prediction. Factor and cluster analysis applied to the sequence of multivariate vectors ofthe statistical properties of groundwater level time series in the successive 10-day windows after adaptive compensation for atmospheric pressure effects distinguish five different statistically significant states of the time series with the transitions between them. An attempt to geophysically interpret the revealed states is made. Two significant periods – 46 and 275 days – are established by spectral analysis of the sequence of the transitions times between the clusters.

Wavelet filter analysis of local atmospheric pressure effects on gravity variations

2005 ◽  
Vol 79 (8) ◽  
pp. 447-459 ◽  
Author(s):  
X.-G Hu ◽  
L.-T Liu ◽  
J. Hinderer ◽  
H.-P Sun
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Effects ◽  
Wavelet Filter ◽  
Gravity Variations ◽  
Filter Analysis

Experimental and Modeling Study of Atmospheric Pressure Effects on Ignition of Pine Wood at Different Altitudes

2010 ◽  
Vol 24 (1) ◽  
pp. 609-615 ◽  
Author(s):  
Jiakun Dai ◽  
Lizhong Yang ◽  
Xiaodong Zhou ◽  
Yafei Wang ◽  
Yupeng Zhou ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Pressure Effects ◽  
Pine Wood ◽  
Different Altitudes ◽  
Modeling Study

Atmospheric Pressure Effects on Glucose Monitoring Devices

Diabetes Care ◽  
1995 ◽  
Vol 18 (3) ◽  
pp. 423-424 ◽  
Author(s):  
E. H. Piepmeier ◽  
C. Hammett-Stabler ◽  
M. E. Price ◽  
G. B. Kemper ◽  
M. G. Davis
Keyword(s):  
Atmospheric Pressure ◽  
Glucose Monitoring ◽  
Pressure Effects ◽  
Monitoring Devices

Use of Partial Molar Volumes of Model Compounds in the Interpretation of High-Pressure Effects on Proteins

1996 ◽  
Author(s):  
Kenneth E. Prehoda ◽  
John L. Markley
Keyword(s):  
Volume Change ◽  
Atmospheric Pressure ◽  
Protein Unfolding ◽  
Partial Molar Volumes ◽  
Bulk Water ◽  
Pressure Effects ◽  
Molar Volumes ◽  
Positive Term ◽  
Full Characterization ◽  
The Difference

The transfer of liquid hydrocarbons into water is accompanied by a large decrease in volume at 25 °C and atmospheric pressure, with typical values for ΔV°tr of — 2.0 ml mol methylene−1. Considering the large amount of apolar surface that is exposed when a globular protein unfolds, the hydrocarbon transfer results imply that the change in volume accompanying the unfolding process (ΔV°obs) should be highly negative under these conditions. However, experimental data on the pressure denaturation of proteins typically yield relatively small values of ΔV°obs at atmospheric pressure and 25 °C. We analyze this apparent inconsistency in terms of a simple thermodynamic dissection of the partial molar volume. This approach allows the volume effects that result from solute-solvent interactions to be determined from experimental partial molar volumes. The use of absolute quantities (partial molar volumes) circumvents assumptions associated with the use of results from transfer experiments. An important finding is that hydration of apolar species is less dense than bulk water. This discovery leads to the conclusion that the contribution to ΔV°obs for protein unfolding from the hydration of apolar surfaces is highly positive, contrary to predictions based on transfer data. Further, hydration of polar surfaces makes a positive contribution to ΔV°obs. The large, positive term from the differential hydration of the folded and unfolded states is compensated by the difference in free volume of the protein in the two states. This finding provides a new framework for interpreting pressure effects on macromolecules. The full characterization of a macromolecular system requires knowledge of the effect of pressure on the system. The thermodynamic information obtained from using pressure as a perturbation is a volume change for the particular reaction being studied. The observed volume change, ΔV°obs, for protein unfolding may provide insight into the mechanisms that determine the three-dimensional structure of the folded state. Pressure denaturation experiments have been demonstrated for a number of proteins, including ribonuclease A (Gill & Glogovsky, 1965; Brandts et al., 1970), chymotrypsinogen (Hawley, 1971), metmyoglobin (Zipp & Kauzmann, 1973), and, more recently, lysozyme (Samarasinghe et al., 1992) and staphylococcal nuclease (Royer et al., 1993).

scholarly journals THE ATMOSPHERIC PRESSURE EFFECT ON MUON DATA NORMALIZATION BY SPECTRAL ANALYSIS STUDIES

2013 ◽  
Vol 31 (3) ◽  
pp. 507 ◽  
Author(s):  
Nivaor Rodolfo Rigozo ◽  
Adriano Petry
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Atmospheric Pressure ◽  
Amplitude Spectrum ◽  
Cosmic Ray ◽  
Pressure Effects ◽  
Pressure Amplitude ◽  
Analysis Method ◽  
Amplitude Spectra ◽  
Spectral Analysis Method

ABSTRACT. This paper presents a study of the atmospheric pressure effects on ground cosmic ray muon time series, using the iterative regression spectral analysis method. Along the study, it was observed that the 34 periods present in the atmospheric pressure amplitude spectrum are present in the muon data amplitude spectra as well. It was concluded that the normalization of muon data is only efficient for periods shorter than nine days, in order to eliminate the atmospheric effects.Keywords: cosmic rays, time series, spectral analysis. RESUMO. Este artigo apresenta um estudo dos efeitos da pressão atmosférica nas series temporais de raios cósmicos, usando a metodologia da análise espectral pela iteração regressiva. Foi observado um total de 34 periodicidades presentes no espectro de amplitude da pressão atmosférica que também estão presentes no espectro de amplitude dos dados de muons. Conclui-se que a padronização dos dados de muons para eliminar os efeitos da pressão atmosférica é eficiente somente para períodos abaixo de 9 diasPalavras-chave: raios cósmicos, série temporal, análise espectral.

Pressure Effects on the Interactions of the Sarcoplasmic Reticulum Calcium Transport Enzyme with Calcium and Dinitrophenyl Phosphate

1988 ◽  
Vol 43 (11-12) ◽  
pp. 929-937 ◽  
Author(s):  
Wilhelm Hasselbach
Keyword(s):  
Pressure Dependence ◽  
Atmospheric Pressure ◽  
Calcium Binding ◽  
Calcium Transport ◽  
Activation Volume ◽  
Atp Hydrolysis ◽  
Pressure Effects ◽  
Volume Changes ◽  
Calcium Dependent ◽  
Nitrophenyl Phosphate

Abstract The effect of hydrostatic pressure on the calcium-dependent hydrolysis of dinitrophenyl phosphate by the sarcoplasmic calcium transport enzyme has been studied. The magnesium dinitrophenyl phosphate complex is the true substrate of the enzyme (K - 7000 M-1) by which it is hydrolyzed at 20 °C with a turnover rate of 4 s-1 . Activation by calcium ions occurs between 0.1 and 1 μM as observed for ATP hydrolysis. The activation volume of the enzyme saturated with both ligands exhibits pronounced pressure-dependence, rising from 25 ml/mol at atmospheric pressure to 80 ml/mol at 100 MPa. The apparent binding volumes for magnesium dinitrophenyl phosphate and calcium are likewise pressure-dependent. The volume changes connected with the binding of magnesium dinitrophenyl phosphate is quite small approaching zero at 100 MPa. The apparent binding volume for calcium greatly increases with pressure from 35 ml/mol at atmospheric pressure to 150 ml/mol at 70 MPa. A nearly constant binding volume of approximately 40 ml/mol results if the effect of pressure on the respective rate constants that contribute to the apparent binding constant, is taken into account. The pressure-dependence of enzyme activity at subsaturating calcium concentrations yields an activation volume of 250 ml/mol related to the rate of calcium binding indicating the occurrence of a transient large volume expansion of the enzyme complex. The volume changes observed for the calcium-dependent interaction of the enzyme with magnesium dinitrophenyl phosphate well agree with that found for magnesium p-nitrophenyl phosphate (W. Hasselbach and L. Stephan, Z. Naturforsch. 42c, 641-652 (1987)) indicating that the found volume changes are intrinsic properties of the transport enzyme, independent of the respective energy donor.

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