Computational analysis of expression of human embryonic stem cell-associated signatures in tumors

<p>Abstract</p> <p>Background</p> <p>The cancer stem cell model has been proposed based on the linkage between human embryonic stem cells and human cancer cells. However, the evidences supporting the cancer stem cell model remain to be collected. In this study, we extensively examined the expression of human embryonic stem cell-associated signatures including core genes, transcription factors, pathways and microRNAs in various cancers using the computational biology approach.</p> <p>Results</p> <p>We used the class comparison analysis and survival analysis algorithms to identify differentially expressed genes and their associated transcription factors, pathways and microRNAs among normal vs. tumor or good prognosis vs. poor prognosis phenotypes classes based on numerous human cancer gene expression data. We found that most of the human embryonic stem cell- associated signatures were frequently identified in the analysis, suggesting a strong linkage between human embryonic stem cells and cancer cells.</p> <p>Conclusions</p> <p>The present study revealed the close linkage between the human embryonic stem cell associated gene expression profiles and cancer-associated gene expression profiles, and therefore offered an indirect support for the cancer stem cell theory. However, many interest issues remain to be addressed further.</p

Theoretical investigations on simultaneous operation of vapour compression refrigeration cycle and Stirling cycle in miniature Stirling cooler with two-component two-phase mixture

The cyclic analysis of Stirling cycle working with a single gaseous fluid is modified to suit two-component two-phase mixtures. When the results were examined carefully these showed that a substantial increase in cooling effect is obtained. In order to understand how the two-component two-phase working fluid functions in the Stirling cooler, some other processes, generally not coming into picture with a single gaseous fluid, are also considered to get good idea about the working of the cooler and then the estimates about the performance of the cooler are obtained. The processes include, simultaneous compression of gases with different ratios of C-p and C-v, the drop-wise condensation, isentropic expansion of liquid in presence of other gas, the entrainment process as observed in heat pipes, and saturation process as observed in air humidification process. The change in regenerator effectiveness due to condensation in the regenerator also has to be considered. How the above mentioned processes are affecting the system performance is discussed in detail. The analysis shows that the Stirling cycle and vapour compression cycle with isentropic expansion operate simultaneously. The criterion for selection of the gaseous carrier fluid and the condensable fluid, which undergoes phase change is established. For selection of carrier gas, helium and hydrogen are considered and for the condensable fluid, nitrogen, carbon mono-oxide, nitrogen-tri-fluoride and neon are compared. Using the above mentioned criterion, helium and nitrogen combination has been chosen for cold tip temperatures in liquid nitrogen temperature range. The paper discusses the analytical approach and the results indicate that the presence of vapour compression cycle with isentropic expansion, operating under a small difference between the condensation and evaporation temperatures, leads to high values of cooling effect and coefficient of performance (COP). It also shows that beyond a certain concentration, the cooling effect starts dropping and becomes zero at certain higher concentration. It can be mentioned that no changes in the hardware are necessary as the cooler can operate at pressures lower than normal working pressure and still provide large capacity with marginally higher power input. (.

Cyclic simulation of stirling cycle cryogenerator using two component two phase working fluid combinations

In this paper, cyclic simulation has been carried out for PLN-106, used for liquefaction of nitrogen with a capacity of 6- 6.5 dm 3 h(-1), with a single component working nuid and two component two phase working fluids. The results are compared with that for hydrogen and helium being considered as single component working fluids. The results are encouraging and need to be compared through experiments

Optimization of design parameters of 2-stage, split type, free displacer stirling cryocooler

A computer model for multistage Stirling cryocoolers has been developed. Following the validation by experimental results the model has been applied to optimise the design parameters of a two stage, split type, free displacer plastic Stirling cryocooler using gap regeneration. This paper presents the determination of optimum design parameters considering two important design options. The paper also shows the effect of variations of design parameters on the optimisation function. The design parameters are determined for compression volume of 50 cc and for stable temperatures at 1(st) and 2(nd) stage of expansion of 160 K and 77 K respectively

DEVELOPMENT OF A COMPUTER-MODEL FOR 3-STAGE, SPLIT TYPE, FREE DISPLACER STIRLING CRYOCOOLER

Development of a model for a multiple stage Stirling cycle cryocooler has been a topic of research for the last four to five years. The model can help to optimize the design parameters of the machine and to predict the performance of the machine under different operating conditions. In this paper, the authors have given a computer model for a three-stage, free displacer, split type Stirling cryocooler. The model so developed has been validated by experimental results

OPTIMIZATION OF DESIGN PARAMETERS OF STIRLING CYCLE MACHINE

The performance of a Stirling cryocooler is governed by six principal design parameters, namely speed, pressure limits, the temperature of the working fluid in the compression and expansion spaces, the ratio of the compression and expansion space swept volumes, the ratio of total dead volume and expansion space swept volume and the phase angle between the volume variations of the expansion space and compression space. For optimizing the performance of a cryocooler, its cyclic analysis should be considered along with a loss analysis. The present paper attempts to find out the optimum combination of these design parameters for machines PLN-106 and PLN-108s, for which design data are known. The objective functions of optimization can be based on COP maximization or any design constraints such as the total volume or space taken up by the machine, maximum pressure generation, etc. This paper first applies the optimization routine to the Philips machine and identifies the optimization function for which the machines are designed. The routine is then further extended to develop a generalized procedure for designing a cryocooler of any capacity. The procedure is applied to determine the different dimensions of machines with a liquid nitrogen producing capacity of 8 dm3 h-1. The design developed using this procedure is then compared with the actual existing design

Cyclic analysis and optimization of design parameters for Beta-configuration Stirling engine using rhombic drive

Design and development of Beta configuration Stirling engine is a complex combination of thermodynamic analysis and mechanical design of components. The present work uses the second order cyclic analysis for the thermodynamic investigations and includes the effect of the overlapping volume displaced by piston and displacer within cylinder. It determines the ideal heat input, ideal power output and related losses separately. This provides estimate of net heat input, net brake power and cooling duty. The sensitivity analysis of various design and operating parameters is carried out to decide the order in which these should be modified and includes heater tube assembly parameters; annular regenerator assembly parameters; and cooler assembly parameters, using univariate method. The optimization considers the combined effect of the net power output and the efficiency instead of a single Optimization Parameter. The present work thus presents the cyclic analysis and optimization of design parameters of a Beta configuration Stirling Engine of 1.5 kWe using rhombic drive. It was observed that the power output exceeds the requirement of 1.5 kWe. Instead of carrying out the optimization process all over again, the operating parameter p(mean) is adjusted to 24 bar to obtain the desired output of 1.5 kWe. (C) 2017 Elsevier Ltd. All rights reserved