scholarly journals Chlorodifluoromethane Hydrodechlorination on Carbon-Supported Pd-Pt Catalysts. Beneficial Effect of Catalyst Oxidation

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 525
Author(s):  
Monika Radlik ◽  
Wojciech Juszczyk ◽  
Wioletta Raróg-Pilecka ◽  
Magdalena Zybert ◽  
Zbigniew Karpiński
Keyword(s):  
Active Surface ◽  
Turnover Frequency ◽  
Palladium Surface ◽  
Order Of Magnitude ◽  
Carbon Burning ◽  
The Relationship ◽  
Magnitude Increase ◽  
Supported Pd ◽  
Palladium Platinum ◽  
Catalyst Oxidation

Previously tested 2 wt % palladium-platinum catalysts supported on Norit activated carbon preheated to 1600 °C have been reinvestigated in CHFCl2 hydrodechlorination. An additionally adopted catalyst oxidation at 350–400 °C produced nearly an order of magnitude increase in the turnover frequency of Pd/C, from 4.1 × 10−4 to 2.63 × 10−3 s−1. This increase is not caused by changes in metal dispersion or possible decontamination of the Pd surface from superficial carbon, but rather by unlocking the active surface, originally inaccessible in metal particles tightly packed in the pores of carbon. Burning carbon from the pore walls attached to the metal changes the pore structure, providing easier access for the reactants to the entire palladium surface. Calcination of Pt/C and Pd-Pt/C catalysts results in much smaller evolution of catalytic activity than that observed for Pd/C. This shapes the relationship between turnover frequency (TOF) and alloy composition, which now does not confirm the Pd-Pt synergy invoked in the previous work. The absence of this synergy is confirmed by gradual regular changes in product selectivity, from 70 to 80% towards CH2F2 for Pd/C to almost 60% towards CH4 for Pt/C. The use of even higher-preheated carbon (1800 °C), completely free of micropores, results in a Pd/C catalyst that does not need to be oxidized to achieve high activity and excellent selectivity to CH2F2 (>90%).

scholarly journals Hydrodechlorination of CHClF2 (HCFC-22) over Pd-Pt catalysts supported on thermally modified activated carbon. Beneficial effect of catalyst oxidation.

2021 ◽  
Author(s):  
Monika Radlik ◽  
Wojciech Juszczyk ◽  
Wioletta Raróg-Pilecka ◽  
Magdalena Zybert ◽  
Zbigniew Karpiński
Keyword(s):  
Alloy Composition ◽  
Active Surface ◽  
Metal Particles ◽  
Pt Catalysts ◽  
Modified Activated Carbon ◽  
Palladium Surface ◽  
Order Of Magnitude ◽  
Carbon Burning ◽  
Magnitude Increase ◽  
Catalyst Oxidation

Pd-Pt catalysts supported on carbon preheated to 1600°C have been reinvestigated in CHFCl2 hydrodechlorination. An additionally adopted catalyst oxidation at 350-400°C produced an order of magnitude increase in the catalytic activity of Pd/C. This increase is not caused by changes in metal dispersion or possible decontamination of the Pd surface from superficial carbon, but rather by unlocking the active surface, originally inaccessible in metal particles tightly packed in the pores of carbon. Burning carbon from the pore walls attached to the metal changes the pore structure, providing easier access for the reactants to the entire palladium surface. As upon calcination the performance of the rest of the Pd-Pt/C catalysts changes less than for Pd/C, the relation between the turnover frequency and alloy composition does not confirm the Pd-Pt synergy invoked in our previous work. The use of even higher-preheated carbon (1800°C), completely free of micropores, results in a Pd/C catalyst that does not need to be oxidized to achieve high activity and excellent selectivity up to CH2F2 (>90%).

Relationship Study and Primary Application between Gas Permeability and Crack State on Bridge Joint Concrete

2021 ◽  
Vol 1018 ◽  
pp. 153-161
Author(s):  
Guo Rong Zhang ◽  
Xiao Dong Wang ◽  
Jian Kun Han ◽  
Yi Xuan Han
Keyword(s):  
Crack Width ◽  
Gas Permeability ◽  
Field Tests ◽  
Initial State ◽  
Order Of Magnitude ◽  
Structural Levels ◽  
The Relationship ◽  
Curve Equation ◽  
Magnitude Increase ◽  
Compaction Performance

For evaluating the crack state on solid bridge joint on site, the relationship between gas permeability and crack width of joint concrete is studied both on material and structural levels in this article. In laboratory tests, gas permeability tests on concrete samples with macrocrack are performed, the relationship between the relative gas permeability rate k/k0 and the relative variation of crack width ac is established combining with regression analysis, the fitting curve equation is . when ac increases by 1.125×10-2 mm, the gas permeability increases about 10 times compared with the initial state. In field tests, “pulse tests” are performed on bridge joint based on 3 embedded pulse probes to measure the evolution of gas permeability during bridge operation. The results show, firstly, the gas permeability of joint concrete are in the order of 10-16~10-19 m2, which indicates a good compaction performance; Secondly, an order of magnitude increase of gas permeability of one probe in different ages, or the fact that the gas permeability at one position in solid joint is obviously larger than the other positions, these phenomena indicate the existence of original defects, or the possibility of macrocrack appearance from microcracks, and the crack width increases by about 0.01 mm.

Pound Wise and Penny Foolish? Weight Loss and The Dynamics of Health Care Spending

2011 ◽  
Vol 14 (2) ◽  
Author(s):  
Thomas G Koch
Keyword(s):  
Weight Loss ◽  
Cost Savings ◽  
Cost Effective ◽  
Economic Consequences ◽  
Health Care Spending ◽  
Order Of Magnitude ◽  
Dynamic Measures ◽  
The Cost ◽  
The Impact ◽  
The Relationship

Current estimates of obesity costs ignore the impact of future weight loss and gain, and may either over or underestimate economic consequences of weight loss. In light of this, I construct static and dynamic measures of medical costs associated with body mass index (BMI), to be balanced against the cost of one-time interventions. This study finds that ignoring the implications of weight loss and gain over time overstates the medical-cost savings of such interventions by an order of magnitude. When the relationship between spending and age is allowed to vary, weight-loss attempts appear to be cost-effective starting and ending with middle age. Some interventions recently proven to decrease weight may also be cost-effective.

scholarly journals Hydraulic transmissivity inferred from ice-sheet relaxation following Greenland supraglacial lake drainages

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ching-Yao Lai ◽  
Laura A. Stevens ◽  
Danielle L. Chase ◽  
Timothy T. Creyts ◽  
Mark D. Behn ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Ice Sheet ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Field Observations ◽  
Surface Uplift ◽  
Drainage Networks ◽  
Order Of Magnitude ◽  
Lake Drainage ◽  
Magnitude Increase

AbstractSurface meltwater reaching the base of the Greenland Ice Sheet transits through drainage networks, modulating the flow of the ice sheet. Dye and gas-tracing studies conducted in the western margin sector of the ice sheet have directly observed drainage efficiency to evolve seasonally along the drainage pathway. However, the local evolution of drainage systems further inland, where ice thicknesses exceed 1000 m, remains largely unknown. Here, we infer drainage system transmissivity based on surface uplift relaxation following rapid lake drainage events. Combining field observations of five lake drainage events with a mathematical model and laboratory experiments, we show that the surface uplift decreases exponentially with time, as the water in the blister formed beneath the drained lake permeates through the subglacial drainage system. This deflation obeys a universal relaxation law with a timescale that reveals hydraulic transmissivity and indicates a two-order-of-magnitude increase in subglacial transmissivity (from 0.8 ± 0.3 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 to 215 ± 90.2 $${\rm{m}}{{\rm{m}}}^{3}$$ m m 3 ) as the melt season progresses, suggesting significant changes in basal hydrology beneath the lakes driven by seasonal meltwater input.

scholarly journals Review of the soft-X-ray laser research at CEL-V

1991 ◽  
Vol 9 (2) ◽  
pp. 493-499
Author(s):  
D. Naccache ◽  
J-L. Bourgade ◽  
P. Combis ◽  
C. J. Keane ◽  
J-P. Le Breton ◽  
...  
Keyword(s):  
Atomic Number ◽  
Collisional Excitation ◽  
X Ray ◽  
Order Of Magnitude ◽  
Laser Experiments ◽  
Magnitude Increase

We present some significant results of collisional excitation X-ray laser experiments in plasmas produced by a laser. We studied the amplification in Ne- and Ni-like ions by varying both the nature and the thickness of targets, the irradiation, and the wavelength of the driving laser. Some potentially interesting scalings as a function of the atomic number of the lasing element are demonstrated in the Ne-like system. An order-of-magnitude increase in gain in the Ni-like experiments was determined.

scholarly journals Excessive Pressure in Multichambered Cuffs Used for Sequential Compression Therapy

2002 ◽  
Vol 82 (10) ◽  
pp. 1000-1008 ◽  
Author(s):  
Patrick Segers ◽  
Jean-Paul Belgrado ◽  
Andre Leduc ◽  
Olivier Leduc ◽  
Pascal Verdonck
Keyword(s):  
Time Course ◽  
Compression Therapy ◽  
Lymphatic Drainage ◽  
Chamber Pressure ◽  
Excessive Pressure ◽  
Ellipsoidal Model ◽  
Order Of Magnitude ◽  
Pneumatic Compression Devices ◽  
Target Pressure ◽  
The Relationship

Abstract Background and Purpose. Pneumatic compression devices, used as part of the therapeutic strategy for lymphatic drainage, often have cuffs with multiple chambers that are inflated sequentially. The purpose of this study was to investigate (1) the relationship between cuff chamber pressure (Pchamber) and the pressure on the cuff-skin interface (Pinterface) and (2) the mechanical interaction of cuff chambers and consequences for device control. Subjects and Methods. In this study, we used 3 cylindrical (60-, 80-, and 100-mm-diameter) model limbs and 1 ellipsoidal model of the arm to test a commercially available pressure controller using “target pressures,” indicated by the controller, of 30, 60, 80, and 100 mm Hg. We studied the time course of Pchamber and Pinterface during the inflation sequence and the effect of local curvature on Pinterface. Results. Our data indicated that, overall, Pinterface is of the same order of magnitude as Pchamber. There was some effect of model diameter and shape, with the smaller curvatures yielding the highest Pinterface. Cuff chamber interaction led to Pchamber and Pinterface values in the most distal (first inflated) chamber that were up to 80% higher than the target pressure. For the 80-mm cylindrical model, for instance, pressure in this chamber reached 54, 98, 121, and 141 mm Hg, respectively, instead of the 30, 60, 80, and 100 mm Hg indicated by the controller. Discussion and Conclusion. The discrepancy between the target pressure, indicated by the controller, and the pressure measured inside the cuff chambers undermines the therapeutic control and efficacy of the pneumatic compression devices. Because the measured pressures were far beyond the pressure level indicated by the controller, it is recommended that pneumatic compression devices be used at much lower target pressures (<30 mm Hg) than those applied in clinical practice.

Critical current density and microstructure variations in YBa2Cu3O7−x + BaSnO3 films with different concentrations of BaSnO3

2008 ◽  
Vol 23 (12) ◽  
pp. 3363-3369 ◽  
Author(s):  
C.V. Varanasi ◽  
J. Burke ◽  
L. Brunke ◽  
H. Wang ◽  
J.H. Lee ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Gradual Increase ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
High Fields ◽  
Magnitude Increase

Previous work on YBa2Cu3O7−x (YBCO) + BaSnO3 (BSO) films with a single composition showed significant critical current density (Jc) improvements at higher fields but lowered Jc in low fields. A detailed study on BSO concentrations provided here demonstrates that significant Jc enhancement can occur even up to 20 mol% BSO inclusion, where typical particulate inclusions in these concentrations degrade the YBCO performance. YBCO + BSO films were processed on (100) LaAlO3 substrates using premixed targets of YBa2Cu3O7-x (YBCO) with additions of 2, 4, 10, and 20 mol% BSO. The critical transition temperature Tc of the films remained high (>87 K), even with large amounts (20 mol%) of BSO. YBCO + BSO films showed a gradual increase in Jc at high fields as the amount of BSO was increased. More than an order of magnitude increase in Jc was measured in YBCO + BSO samples as compared to regular YBCO at 4 T. YBCO + 10 mol% BSO films showed overall improvement at all the field ranges while YBCO + 20 mol% BSO was better only at high fields. Transmission electron microscopy revealed the presence of ∼7–8-nm-diameter BSO nanocolumns, the density of which increased with increasing BSO content correlating well with the observed improvements in Jc.

scholarly journals Large-area printing of ferroelectric surface and super-domains for efficient solar water splitting

2020 ◽  
Author(s):  
Yu Tian ◽  
Yaqing Wei ◽  
Minghui Pei ◽  
Rongrong Cao ◽  
Zhenao Gu ◽  
...  
Keyword(s):  
Water Splitting ◽  
Electric Fields ◽  
Electronic Structures ◽  
Active Sites ◽  
Large Area ◽  
Solar Water Splitting ◽  
High Efficient ◽  
Catalytic Sites ◽  
Order Of Magnitude ◽  
Magnitude Increase

Abstract Surface electronic structures of the photoelectrodes determine the activity and efficiency of the photoelectrochemical water splitting, but the controls of their surface structures and interfacial chemical reactions remain challenging. Here, we use ferroelectric BiFeO3 as a model system to demonstrate an efficient and controllable water splitting reaction by large-area constructing the hydroxyls-bonded surface. The up-shift of band edge positions at this surface enables and enhances the interfacial holes and electrons transfer through the hydroxyl-active-sites, leading to simultaneously enhanced oxygen and hydrogen evolutions. Furthermore, printing of ferroelectric super-domains with microscale checkboard up/down electric fields separates the distribution of reduction/oxidation catalytic sites, enhancing the charge separation and giving rise to an order of magnitude increase of the photocurrent. This large-area printable ferroelectric surface and super-domains offer an alternative platform for controllable and high-efficient photocatalysis.

scholarly journals Optbayesexpt: Sequential Bayesian Experiment Design for Adaptive Measurements

2021 ◽  
Vol 126 ◽  
Author(s):  
Robert D. McMichael ◽  
Sean M. Blakley ◽  
Sergey Dushenko
Keyword(s):  
Lower Cost ◽  
Adaptive Algorithms ◽  
Efficient Estimation ◽  
Function Parameter ◽  
Model Function ◽  
Measurement Results ◽  
Adaptive Measurements ◽  
Order Of Magnitude ◽  
Magnitude Increase ◽  
Python Package

Optbayesexpt is a public domain, open-source python package that provides adaptive algorithms for efficient estimation/measurement of parameters in a model function. Parameter estimation is the type of measurement one would conventionally tackle with a sequence of data acquisition steps followed by fitting. The software is designed to provide data-based control of experiments, effectively learning from incoming measurement results and using that information to select future measurement settings live and online as measurements progress. The settings are chosen to have the best chances of improving the measurement results. With these methods optbayesexpt is designed to increase the efficiency of a sequence of measurements, yielding better results and/or lower cost. In a recent experiment, optbayesexpt yielded an order of magnitude increase in speed for measurement of a few narrow peaks in a broad spectral range.

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