Search results

1 – 10 of over 32000
To view the access options for this content please click here
Book part
Publication date: 24 August 2005

Hideyuki Saya

Natural selection is the mechanism of evolution originally proposed by Charles Darwin. This process is driven by mutation and death. Therefore, “individual death” is a…

Abstract

Natural selection is the mechanism of evolution originally proposed by Charles Darwin. This process is driven by mutation and death. Therefore, “individual death” is a critical event for evolution of species. Analogous to the significance of individual death in species evolution, recent biological observations have revealed that “cell death” is an important event for maintenance of individuals and offspring. Cell death is caused not only by injuries and pathological conditions, but also by programed intracellular signals. This type of programed cell death is called “apoptosis.” Apoptosis signals are regulated in mitochondria, eukaryotic organelles of symbiotic origin, and play a critical role in survival of individuals by eliminating some cells.

Details

Taking Life and Death Seriously - Bioethics from Japan
Type: Book
ISBN: 978-0-76231-206-1

To view the access options for this content please click here
Article
Publication date: 24 October 2021

Anges Akim Aminou Moussavou, Ayokunle Oluwaseun Ayeleso, Marcos Adonis and Atanda Raji

This paper aims to develop a selective energy optimisation of the photovoltaic–thermal (PV/T) system performance. The PV cell inside the PV/T system could be periodically…

Abstract

Purpose

This paper aims to develop a selective energy optimisation of the photovoltaic–thermal (PV/T) system performance. The PV cell inside the PV/T system could be periodically manipulated to produce domestic hot water without applying an external power supply.

Design/methodology/approach

A numerical simulation model of the proposed PV/T model was developed in MATLAB/Simulink to analyse the selective energy optimisation of the model. The extrinsic cell resistance (Rse) is adjusted to control the ratio of thermal to the electrical energy, generated from the PV cell inside the PV/T system. Therefore, the internal heat of the PV cell inside the PV/T system is periodically used as a thermal element to produce electrical power and hot water.

Findings

The optimisation of PV/T energy shows that the electrical power efficiency can increase by 11.6% when Rse was 0 Ω, and the 200 L water tank temperature increased by 22ºC when Rse was 50 Ω.

Originality/value

This study showed that the use of the PV cell could be extended to domestic hot water and space heating, and not only for electricity.

Details

Journal of Engineering, Design and Technology , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1726-0531

Keywords

To view the access options for this content please click here
Article
Publication date: 9 July 2020

I. St. Doltsinis

The purpose of the present study is to explore the incomplete substitution of the simplex triangular finite element by either of two models: one evolving out as part of…

Abstract

Purpose

The purpose of the present study is to explore the incomplete substitution of the simplex triangular finite element by either of two models: one evolving out as part of the element flexibility, and the other as part of the element stiffness.

Design/methodology/approach

The elastic energy stored in each of the units under stress or strain decides on stiffer and weaker responses. The pertaining Rayleigh quotient in terms of the flexibility matrices allows bounding the distance of the spring cell models to the finite element in dependence of the triangle configuration.

Findings

Despite a superiority of the flexibility cell concept observed in computations, the study reveals constellations of shape and stressing of the triangle that favour the stiffness concept. The latter is seen to behave stiffer than its flexibility counterpart and produces results more distant to the finite element in most cases.

Research limitations/implications

The difference between the stiffness and the flexibility approach to spring cells is investigated for triangular elements in dependence of the geometrical configuration under specific conditions of stressing. This suffices to refute an exclusive superiority of the flexibility concept although largely true.

Practical implications

The results of the investigation appear useful in deciding between the spring cell models depending on the case of a spring lattice application.

Originality/value

The flexibility approach to the spring cell is not widely known yet. This cell model deserves a study on performance and comparison to the different, more common stiffness cell model.

Details

Engineering Computations, vol. 38 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

To view the access options for this content please click here
Article
Publication date: 29 September 2021

Fatemeh Aamazadeh, Jaleh Barar, Yalda Rahbar Saadat and Alireza Ostadrahimi

This study aimed to evaluate the cytotoxic/apoptotic effects of sweet apricot kernel ethanolic extract (SAEE) on human cancerous PANC-1 and 293/KDR normal cells.

Abstract

Purpose

This study aimed to evaluate the cytotoxic/apoptotic effects of sweet apricot kernel ethanolic extract (SAEE) on human cancerous PANC-1 and 293/KDR normal cells.

Design/methodology/approach

The extract was prepared by maceration, and its chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS). The biological effects of SAEE on PANC-1 and 293/KDR cells were investigated using MTT (3–(4, 5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide) assay, DAPI (4',6-diamidino-2-phenylindole) and AnnexinV/propidium iodide (PI) staining. The expression of pro- and anti-apoptotic genes was evaluated by real-time quantitative polymerase chain reaction (real-time q-PCR) analysis.

Findings

The SAEE showed the selective growth inhibitory activity against PANC-1 cells with an IC50 (the 50% inhibitory concentration) value of about 1 mg/mL at 72 h. Further investigations by DAPI staining and flow cytometry revealed nucleus fragmentation and elevation of apoptotic cells, respectively. Also, a significant decrease in B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated x protein (Bax) ratio (0.41, p = 0.001) and the up-regulation of caspase-3 expression (1.5 fold, p = 0.002) indicated the induction of apoptosis in PANC-1 cells but not in 293/KDR non-cancerous cells. These results suggest that SAEE could induce apoptosis in cancer cells via a mitochondrial dependent pathway. Furthermore, GC-MS analysis showed that the SAEE is rich in γ-sitosterol and γ-tocopherol. Overall, the findings suggest that because of the selective impacts of SAEE on PANC-1 cells, it can be considered as a supportive care in adjuvant therapy for pancreatic cancer. However, the potent anticancer effects of main components of SAEE and its clinical value as an antitumor drug should be further investigated.

Research limitations/implications

Considerable limitations of this study were that the related mechanisms of selective impacts of SAEE on cancerous and normal cells and potent cytotoxic/apoptotic effects of γ-sitosterol and γ-tocopherol as major components of SAEE were not investigated.

Originality/value

Recently, a growing interest has been dedicated to plant-based natural products. Sweet apricot kernel exerts a number of pharmacological activities; however, the anticancer effect, related mechanisms and its active compounds were rarely investigated. In this study, the authors aimed to evaluate the cytotoxic/apoptotic effects of SAEE on human cancerous PANC-1 and 293/KDR normal cells.

Details

Nutrition & Food Science , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0034-6659

Keywords

To view the access options for this content please click here
Article
Publication date: 31 July 2009

Zhi‐Yuan Cui, Joong‐Ho Choi, Yeong‐Seuk Kim, Shi‐Ho Kim and Nam‐Soo Kim

The purpose of this paper is to describe the application of low‐glitch current cell in a digital to analog converter (DAC) to reduce the clock‐feedthrough effect and…

Abstract

Purpose

The purpose of this paper is to describe the application of low‐glitch current cell in a digital to analog converter (DAC) to reduce the clock‐feedthrough effect and achieve a low power consumption.

Design/methodology/approach

A low‐glitch current switch cell is applied in a ten‐bit two‐stage DAC which is composed of a unary cell matrix for six most significant bits and a binary weighted array for four least significant bits (LSBs). The current cell is composed of four transistors to neutralize the clock‐feedthrough effect and it enables DAC to operate in good linearity and low power consumption. The prototype DAC is being implemented in a 0.35μm complementary metal‐oxide semiconductor process. The reduction in glitch energy and power consumption has been realized by preliminary experiment and simulation.

Findings

Compared to conventional current cell, more than 15 per cent reduction of glitch energy has been obtained in this work. The DAC is estimated that differential nonlinearity is within 0.1 LSB and the maximum power consumption is 68 mW at the sampling frequency of 100 MHz.

Originality/value

Comparison with other conventional work indicates that the current cell proposed in this paper shows much better performance in terms of switching spike and glitch, which may come from the extra dummy transistor in cell and reduce the clock‐feedthrough effect.

Details

Microelectronics International, vol. 26 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 1994

C.Y. Chan, A.H. Redford and N.N. Ekere

Rework is an integral part of printed circuit board assembly (PCBA) manufacturing. However, the state‐of‐the‐art for PCBA rework still relies on operator activity and is…

Abstract

Rework is an integral part of printed circuit board assembly (PCBA) manufacturing. However, the state‐of‐the‐art for PCBA rework still relies on operator activity and is therefore semi‐automatic. As a result, the quality of rework depends very much on the skill of the operator. When developing an automatic PCBA rework cell, the cell controller is an essential part which organises and controls the overall rework operation. This paper describes the software modelling of the cell controller for the PCBA rework cell which has been implemented for reworking through‐hole and surface mounted components. The software model is based on hybrid representations and rule‐based control.

Details

Soldering & Surface Mount Technology, vol. 6 no. 3
Type: Research Article
ISSN: 0954-0911

To view the access options for this content please click here
Article
Publication date: 8 January 2018

William Webb

Small cells, or microcells, are often seen as a way to substantially enhance the capacity of cellular networks. Previous assumptions have been that by deploying a dense…

Abstract

Purpose

Small cells, or microcells, are often seen as a way to substantially enhance the capacity of cellular networks. Previous assumptions have been that by deploying a dense layer of small cells within a macrocell, capacity can be improved by an order of magnitude or more. However, there are complexities such as the need to share frequencies between macrocell and small cells, varying patterns of users, the balance between indoor and outdoor subscribers and the different options available within 4G for balancing loading. The purpose of this study is to understand the impact these real-world constraints have on the capacity enhancements that small cells can provide.

Design/methodology/approach

This paper describes a model that simulates the impact of small cell deployments in macrocells in a typical 4G network.

Findings

It shows that, in some cases, small cells can actually reduce capacity, while in the best case, maximum capacity gains are less than 100 per cent.

Originality/value

It shows that, in some cases, small cells can actually reduce capacity contrary to perceived wisdom.

Details

Digital Policy, Regulation and Governance, vol. 20 no. 1
Type: Research Article
ISSN: 2398-5038

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 2018

Boyang Qu, Peng Zhang, Jianmin Luo, Shie Yang and Yongsheng Chen

The purpose of this paper is to investigate a light-trapping structure based on Ag nanograting for amorphous silicon (a-Si) thin-film solar cell. Silver nanopillar arrays…

Abstract

Purpose

The purpose of this paper is to investigate a light-trapping structure based on Ag nanograting for amorphous silicon (a-Si) thin-film solar cell. Silver nanopillar arrays on indium tin oxide layer of the a-Si thin-film solar cells were designed.

Design/methodology/approach

The effects of the geometrical parameters such as nanopillar radius (R) and array period (P) were investigated by using the finite element simulation.

Findings

The optimization results show that the absorption of the solar cell with Ag nanopillar structure and anti-reflection film is enhanced up to 29.5 per cent under AM1.5 illumination in the 300- to 800-nm wavelength range compared with the reference cell. Furthermore, physical mechanisms of absorption enhancement at different wavelength range are discussed according to the electrical field amplitude distributions in the solar cells.

Research limitations/implications

The research is still in progress. Further studies mainly focus on the performance of solar cells with different nanograting materials.

Practical implications

This study provides a feasible method for light-trapping structure based on Ag nanograting for a-Si thin-film solar cell.

Originality/value

This study is promising for the design of a-Si thin-film solar cells with enhanced performance.

Details

Microelectronics International, vol. 35 no. 4
Type: Research Article
ISSN: 1356-5362

Keywords

To view the access options for this content please click here
Article
Publication date: 1 July 1995

D.J. Stockton and R.J. Lindley

Functional plant layouts are normally adopted in organizations thatmanufacture large varieties of components in low annual volumes.Attempts to improve the efficiency of…

Downloads
3148

Abstract

Functional plant layouts are normally adopted in organizations that manufacture large varieties of components in low annual volumes. Attempts to improve the efficiency of these layouts have normally focused on the identification and implication of group technology cells which process a limited range of parts using flow process principles. Cell layouts provide the condition for kanban control procedures to operate, hence the benefits of just‐in‐time can be achieved in batch processing environments. However, in high variety/low volume (HV/LV) environments there is often insufficient commonality between part types to justify the formation of cells. Describes an alternative plant layout procedure (process sequence cell layout) currently being developed that allocates equipment to cells according to their position in the process routes of components. Uses a case study to illustrate how such a layout may be identified for an organization that has a typical high variety/low volume environment. Discusses the problems that need to be overcome if such systems are to be implemented and offers a description of how integrated MRP II/kanban control mechanisms can be used to control production.

Details

International Journal of Operations & Production Management, vol. 15 no. 7
Type: Research Article
ISSN: 0144-3577

Keywords

To view the access options for this content please click here
Article
Publication date: 3 April 2007

Elena Carcadea, H. Ene, D.B. Ingham, R. Lazar, L. Ma, M. Pourkashanian and I. Stefanescu

This paper aims to present a three‐dimensional computational fluid dynamics (CFD) model that simulates the fluid flow, species transport and electric current flow in PEM…

Downloads
3984

Abstract

Purpose

This paper aims to present a three‐dimensional computational fluid dynamics (CFD) model that simulates the fluid flow, species transport and electric current flow in PEM fuel cells.

Design/methodology/approach

The model makes use of a general‐purpose CFD software as a basic tool incorporating fuel cell specific submodels for multi‐component species transport, electrochemical kinetics, water management and electric phase potential analysis in order to simulate various processes that occur in a PEM fuel cell.

Findings

Three dimensional results for the flow field, species transport, including waster formations, and electric current distributions are presented for two test flow configurations in the PEM fuel cell. For the two cases presented, reasonable predictions have been obtained, and this provides an insight into the effect of the flow designs to the operation of the fuel cell.

Research limitations/implications

It is appreciated that the CFD modeling of fuel cells is, in general, still facing significant challenges due to the limited understanding of the complex physical and chemical processes existing within the fuel cell. The model is now under further development to improve its capabilities and undergoing further validations.

Practical implications

The model simulations can provide detailed information on some of the key fluid dynamics, physical and chemical/electro‐chemical processes that exist in fuel cells which are crucial for fuel cell design and optimization.

Originality/value

The model can be used to understand the operation of the fuel cell and provide and alternative to experimental investigations in order to improve the performance of the fuel cell.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 17 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

1 – 10 of over 32000