Influence of low-molecular-weight and macromolecular organic additives on the morphology of calcium carbonate

1993 ◽  
Vol 89 (15) ◽  
pp. 2891 ◽  
Author(s):  
Jon M. Didymus ◽  
Peter Oliver ◽  
Stephen Mann ◽  
Arthur L. DeVries ◽  
Peter V. Hauschka ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Calcium Carbonate ◽  
Low Molecular Weight ◽  
Organic Additives

scholarly journals Experimental and Theoretical Studies of Carboxylic Polymers with Low Molecular Weight as Inhibitors for Calcium Carbonate Scale

Crystals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 406 ◽  
Author(s):  
Yuwei Zuo ◽  
Wenzhong Yang ◽  
Kegui Zhang ◽  
Yun Chen ◽  
Xiaoshuang Yin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Calcium Carbonate ◽  
Normal Growth ◽  
Dynamics Simulation ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
Crystal Surfaces ◽  
Molecular Weight Range ◽  
Scale Inhibition ◽  
Diffraction Patterns

Poly acrylic acid (PAA) and polyepoxysuccinic acid (PESA) were investigated as scale inhibitors. The static experiments certified that PAA was superior to PESA for the inhibition of calcium carbonate in the low molecular weight range. The X-ray diffraction patterns suggest that the effect of PAA on the calcite (1 0 4) and (1 1 0) crystal plane was more obvious. Scanning electron microscopy was used to study the surface morphology of the depositions, which indicated that the addition of scale inhibitors could disturb the normal growth of CaCO3 scale. The transmittance ratio of ferric oxide demonstrated that PAA had a better dispersion performance than PESA. The molecular dynamics simulation and quantum calculation were selected to theoretically explore the mechanism and structure of scale inhibitors, indicating that the interaction of PAA with (1 0 4) and (1 1 0) calcite crystal surfaces was stronger than PESA. In addition, the results indicated that the PAA with negative charge more easily adsorbed free Ca2+ in the aqueous phase. Based on these observations, PAA exhibited better scale inhibition and dispersion effects than PESA in the case of low molecular weight.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment

Venous thromboembolism in a general hospital. An update with low molecular weight heparin prophylaxis

VASA ◽  
2007 ◽  
Vol 36 (1) ◽  
pp. 17-22
Author(s):  
Schulz ◽  
Kesselring ◽  
Seeberger ◽  
Andresen
Keyword(s):  
Molecular Weight ◽  
Pulmonary Embolism ◽  
Venous Thromboembolism ◽  
Low Molecular Weight ◽  
Trauma Patients ◽  
Vte Prophylaxis ◽  
Vein Thrombosis ◽  
Patients At Risk ◽  
Hospital Stays ◽  
Event Rates

Background: Patients admitted to hospital for surgery or acute medical illnesses have a high risk for venous thromboembolism (VTE). Today’s widespread use of low molecular weight heparins (LMWH) for VTE prophylaxis is supposed to have reduced VTE rates substantially. However, data concerning the overall effectiveness of LMWH prophylaxis is sparse. Patients and methods: We prospectively studied all patients with symptomatic and objectively confirmed VTE seen in our hospital over a three year period. Event rates in different wards were analysed and compared. VTE prophylaxis with Enoxaparin was given to all patients at risk during their hospital stay. Results: A total of 50 464 inpatients were treated during the study period. 461 examinations were carried out for symptoms suggestive of VTE and yielded 89 positive results in 85 patients. Seventy eight patients were found to have deep vein thrombosis, 7 had pulmonary embolism, and 4 had both deep venous thrombosis and pulmonary embolism. The overall in hospital VTE event rate was 0.17%. The rate decreased during the study period from 0.22 in year one to 0,16 in year two and 0.13 % in year three. It ranged highest in neurologic and trauma patients (0.32%) and lowest (0.08%) in gynecology-obstetrics. Conclusions: With a simple and strictly applied regimen of prophylaxis with LMWH the overall rate of symptomatic VTE was very low in our hospitalized patients. Beside LMWH prophylaxis, shortening hospital stays and substantial improvements in surgical and anasthesia techniques achieved during the last decades probably play an essential role in decreasing VTE rates.

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