Equation-of-State Parameters for Poly(Dimethylsiloxane)

1973 ◽  
Vol 46 (2) ◽  
pp. 331-337 ◽  
Author(s):  
Hsiang Shih ◽  
P. J. Flory
Keyword(s):  
Molecular Weight ◽  
Pressure Coefficient ◽  
Thermal Expansivity ◽  
Low Molecular Weight ◽  
Characteristic Parameters ◽  
Thermal Pressure ◽  
Cohesive Energy Density ◽  
Intermolecular Energy ◽  
Temperature Ranges ◽  
Characteristic Pressure

Abstract The thermal expansivity α=V−1(∂V/∂T)p and thermal pressure coefficient γ=(∂p/∂T)v for poly(dimethylsiloxane) (PDMS), mol wt ≈ 105, have been determined accurately over the temperature ranges 20–207 and 24–161°, respectively. Characteristic parameters ν*, T*, and p* calculated from these results are compared with those for other polymers and for low molecular weight liquids. For PDMS, α is much larger and γ much smaller than for any other polymer. The characteristic pressure p* appears to be a more reliable index of the intermolecular energy than the cohesive energy density for this purpose. It is approximately the same for a polymer as for corresponding low molecular weight liquids. For PDMS and HMDS (hexamethyldisiloxane) p* assumes exceptionally low values of 341 and 358 J cm−3, respectively, which are duplicated only by the fluorocarbons (p* ≈ 360 J cm−3).

Determination of the Equation of State of Polyisobutylene

1969 ◽  
Vol 42 (5) ◽  
pp. 1409-1411
Author(s):  
B. E. Eichinger ◽  
P. J. Flory
Keyword(s):  
Thermal Expansion ◽  
Equation Of State ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Pressure Coefficient ◽  
Experimental Results ◽  
Characteristic Parameters ◽  
Thermal Pressure

Abstract The density, thermal expansion coefficient, and thermal pressure coefficient for polyisobutylene of mol wt 40,000 have been accurately determined from 0 to 150°. Results are compared with the reduced equation of state employed in the theory of solutions. The characteristic parameters v*, T*, and p* required for the treatment of polyisobutylene solutions are obtained from the experimental results.

The Thermal Pressure and Energy–Volume Coefficients of Dimethyl Sulfoxide – Water Mixtures

1971 ◽  
Vol 49 (4) ◽  
pp. 611-617 ◽  
Author(s):  
Digby D. Macdonald ◽  
J. B. Hyne
Keyword(s):  
Pressure Coefficient ◽  
Liquid System ◽  
Effect Of Temperature ◽  
Thermal Pressure ◽  
Binary Liquid ◽  
Cohesive Energy Density ◽  
Isothermal Expansion ◽  
Volume Coefficient ◽  
Pass Through ◽  
The Relationship

Thermal pressure and energy–volume coefficients are reported for several DMSO–water mixtures over the temperature range 13–55 °C. The energy–volume coefficient at 25 °C is found to pass through a maximum at 0.3–0.4 mole fraction DMSO and this observation is rationalized in terms of maximization of intercomponent interactions. The relationship between the energy–volume coefficient and the cohesive energy density of the binary liquid system is examined. The temperature dependence of the thermal pressure coefficient is discussed in terms of the effect of temperature on the susceptibility of the entropy of DMSO–water mixtures to isothermal expansion.

The assessment of the cohesive energy density between low molecular weight liquids and polymers

1977 ◽  
Vol 19 (5) ◽  
pp. 1159-1169 ◽  
Author(s):  
A.A. Askadskii ◽  
L.K. Kolmakova ◽  
A.A. Tager ◽  
G.L. Slonimskii ◽  
V.V. Korshak
Keyword(s):  
Molecular Weight ◽  
Energy Density ◽  
Cohesive Energy ◽  
Low Molecular Weight ◽  
Cohesive Energy Density

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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