An Investigation of the Cling of Thin Polymeric Films

The results of an investigation into the mechanisms and debonding energy associated with the cling between thin polymeric films and various substrates are presented in this paper. The thermodynamic work of adhesion as well as electrostatic attraction apparently play significant roles in the cling of a film to a substrate. Peel tests are conducted and strain energy release rates are determined which show different debonding energies for the various film-substrate combinations.     

Activation of the K-ras oncogene in colorectal neoplasms is associated with decreased apoptosis

BACKGROUND: Recent in vitro data indicate that the oncogenic effects of activated ras genes may be mediated, at least in part, through inhibition of apoptotic cell death. To examine this proposition in vivo, the relationship between mutations of the K-ras gene and the frequency of apoptosis was studied in a series of 69 sporadic colorectal neoplasms (11 adenomas and 58 carcinomas). METHODS: Mutations in codon 12 of K-ras were determined by a single tube, enriched polymerase chain reaction. Apoptotic cells in tumor sections were identified by in situ end-labeling of fragmented DNA, whereas levels of bcl-2 and p53 proteins were determined by immunohistochemistry. RESULTS: Tumors with mutant K-ras had a significantly lower apoptotic index than those with the wild-type allele (P < 0.05). They were also more likely to exhibit positive bcl-2 staining (P < 0.05). Adenomas showed significantly greater bcl-2 positivity than carcinomas (89% and 51%, respectively; P < 0.05). The frequency of apoptosis in these tumors was not related to either bcl-2 positivity or p53 status. CONCLUSIONS: These findings suggest that activation of K-ras in colorectal carcinoma may inhibit apoptosis and thus favor tumor progression. Alternatively, this association may reflect an accumulation of K-ras mutations in cells in which normal apoptotic pathways have been impaired.     

Water Affinity to Epitaxial Graphene: The Impact of Layer Thickness

The sensitivity to water vapour of one‐, two‐, and three‐layer epitaxial graphene (1, 2, and 3LG) is examined in this study. It is unambiguously shown that graphene's response to water, as measured by changes in work function and carrier density, is dependent on its thickness, with 1LG being the most sensitive to water adsorption and environmental concentration changes. This is furthermore substantiated by surface adhesion measurements, which bring evidence that 1LG is less hydrophobic than 2LG. Yet, surprisingly, it is found that other contaminants commonly present in ambient air have a greater impact on graphene response than water vapor alone. This study indicates that graphene sensor design and calibration to minimize or discriminate the effect of the ambient, in which it is intended to operate, are necessary to insure the desired sensitivity and reliability of sensors. The present work will aid in developing models for realistic graphene sensors and establishing protocols for molecular sensor design and development.     

Reducing residential fuel consumption through cost-effective interseasonal energy transfer

Energy savings obtainable through effective interseasonal energy transfer are explored by means of a detailed dynamic computer simulation. The mechanism of interseasonal energy transfer is the solar assisted Annual Cycle Energy System (ACES). The operational concept of the ACES is discussed and the modeling methodology used in evaluating the system is presented. Annual energy consumption and associated costs are investigated for the Full, Minimum and Cost Optimized ACES in a variety of U.S. climates. The energy and economic effectiveness of the ACES is evaluated by comparing the ACES to four conventional heating and cooling systems. Results show that the ACES can be three to four times more energy efficient than the conventional systems investigated in this study. Under prototype equipment cost constraints, the residential ACES are not, in general, cost competitive with the conventional systems. However, with realistic projections on the cost of mature components, the residential ACES are far superior to the conventional systems.     

Theoretical analysis of the dynamic interactions of vapor compression heat pumps

A detailed mathematical model of vapor compression heat pumps is described. Model derivations of the various heat pump components are given. The component models include the condenser, evaporator, accumulator, expansion device, and compressor. Details of the modeling techniques are presented, as is the solution methodology. Preliminary simulation results are also illustrated. The model developed predicts the spatial values of temperature and enthalpy as functions of time for the two heat exchangers. The temperatures and enthalpies in the accumulator, compressor and expansion device are modeled in lumped-parameter fashion. Pressure responses are determined by using continuity satisfying models for both the condenser and evaporator. The discussion of the solution methodology describes the combined implicit/explicit integration formulation that is used to solve the governing equations. The summary provides a list of future work anticipated in the area of dynamic heat pump modeling.     

Operational modes of solar heating and cooling systems

This paper emphasizes factors associated with the subsystems that are required to extract heat from solar collectors, store this heat, and deliver it to the loads upon demand. While minimum use of auxiliary energy is the general objective, it must be sought with due regard to safety, convenience and cost. Subsystem alterations that improve energy efficiency typically come at added cost in terms of installation and maintenance. In some cases, the advantages of a specified component or arrangement of components are immediately evident. In other cases, such options are less decisive and will require longer periods of comparative operation to arrive at accurate assessments. The Colorado State University Solar House I allows for such comparative operation in several experimental modes. These selected modes of operation provide for different methods of solar heat transfer and employ different arrangements of system components and control functions. The principles underlying these modes as well as results of these studies are presented. In addition, the methods of operation found necessary for efficient and reliable performance are discussed. While this evaluation is an ongoing process, the initial “start up” and “break in” periods have been experienced and serve as a basis for several recommendations concerning subsystem components and component arrangements.     

Preliminary performance of CSU Solar House I heating and cooling system

The NSF/CSU Solar House I solar heating and cooling system became operational on 1 July 1974. During the first months of operation the emphasis was placed on adjustment, “tuning”, and fault correction in the solar collection and the solar/fuel/cooling subsystems. Following this initial check out period, analysis and testing of the system utilizing a full year of data was begun. This paper discusses the preliminary performance of the heating and cooling system.

During the period 1 August 1974–31 January 1975, approximately 40 per cent of the cooling load was provided by solar energy. Solar heating over the same period of time provided 86 per cent of the space heating load and 68 per cent of the domestic hot water heating load. These percentages represent a total solar contribution of 33,996 MJ delivered to load (8061 MJ to the cooling unit; 20,687 MJ to heating; 5248 MJ to hot water). Natural gas accounted for 22,442 MJ, total. In addition, preliminary analysis has provided several significant results associated with the operating characteristics of the solar system and the individual components.     

Dielectric and piezoelectric properties in the lead-free system Na0.5K0.5NbO3-BiScO3-LiTaO3

Phase relations, dielectric and piezoelectric properties are reported for the ternary system 98%[(1 - x) (Na(0.5)K(0.5)NbO(3))-x(LiTaO(3))]-2%[BiScO(3)] for compositions x ≤ 10 mol% LiTaO(3). The phase content at room-temperature changed from mixed phase, monoclinic + tetragonal, for unmodified 98%(Na(0.5)K(0.5)NbO(3))-2%(BiScO(3)), to tetragonal phase for compositions >2 mol% LiTaO(3). Curie peaks at 360 to 370°C were observed for all compositions, but peaks became diffuse at x ≥ 3 mol%, and two dielectric peaks, at 370 and 470°C, were observed for 5 mol% LiTaO(3). Phase segregation, and finite size affects associated with the core-shell structure, account for the occurrence of two dielectric peaks in 5 mol% LiTaO(3), and diffuse dielectric behavior. The value of d(33) piezoelectric charge coefficient increased from ~160 pC/N for 0 mol% LiTaO(3) to 205 to 214 pC/N for 1 to 2 mol% LiTaO3 solid solutions, before falling sharply at 3 mol% LiTaO(3). TEM-EDX analysis revealed core-shell grain structures with segregation of Bi, Sc, and Ta in the outer ~100-nm shell of the 5 mol% LT sample.     

Long-term (18 years) performance of a residential solar heating system

The long-term performance of a residential solar heating system has been determined for a system which has been operating continuously since 1957 with no maintenance. This residential solar heating system is the Colorado Solar House located in Denver, Colorado, designed and operated by George O. G. Löf.The performance of this system was determined during the 1959–1960 heating season, and the results were publised. The performance of this system was redetermined during the 1974–1975 heating season so that changes in performance occurring over a period of 15 yr could be determined.The collector is an Overlapped-Glass Plate Solar-Air Heater. The system is completely automatic with provision for water heating in addition to space heating. Solar heat is stored in a rock bed of primarily granitic rock approximately 1.3–2.5 cm in diameter.The ratio of useful collected solar heat divided by the total solar radiation on the collector dropped to 71.8 per cent of its original value in 15 yr. For both seasons, the useful collected solar heat was correlated with the ratio of degree days per month divided by the total solar radiation on the collector. For the same value of this ratio, less useful collected solar heat was delivered during the latter season.Additional work that will be published at a later date includes the detailed performance of the hot water heating system.     

Evidence for the need of a cheap simple solar radiation recorder

The recording of solar radiation data in eight tropical countries is surveyed. The author urges the development of an inexpensive solar radiation recorder with an accuracy of plus or minus five percent which would provide reliable data for engineers and agriculturalists.