Performance Comparison of Air-source Heat Pumps Using Economizer Vapor Injection and Internal Heat Exchanger in Cold Regions

Air-source heat pump (ASHP) has been widely used for residential heating and domestic hot water due to its energy saving and environmental protection as well as its high efficiency. However, with ambient temperature decreasing, the heating performance of conventional ASHP degrades rapidly which restricts its application in cold regions. In order to improve the heating performance of ASHP, this paper not only analyzes two ASHP cycles using economizer vapor injection (EVI) and internal heat exchanger (IHX) theoretically and experimentally, but also compares the heating performance of both cycles with a conventional cycle. The results showed that both EVI cycle and IHX cycle have better potential for application in low ambient temperature environments. The further study indicated that the heating capacity and power consumption of EVI cycle were higher than those of IHX cycle at the same ambient temperature while the COP of EVI cycle was lower than that of ASHP with IHX due to the different refrigerant mass flow. In addition, using EVI could reduce the discharge temperature significantly while using IHX increased the discharge temperature in comparison to the conventional ASHP. Furthermore, ambient temperature range from -15°C to -10°C can be chosen as the switch range of the two cycles to satisfy the heating performance and economy simultaneously.

Performance Comparison of Air-source Heat Pumps Using Economizer Vapor Injection and Internal Heat Exchanger in Cold Regions

Air-source heat pump (ASHP) has been widely used for residential heating and domestic hot water due to its energy saving and environmental protection as well as its high efficiency. However, with ambient temperature decreasing, the heating performance of conventional ASHP degrades rapidly which restricts its application in cold regions. In order to improve the heating performance of ASHP, this paper not only analyzes two ASHP cycles using economizer vapor injection (EVI) and internal heat exchanger (IHX) theoretically and experimentally, but also compares the heating performance of both cycles with a conventional cycle. The results showed that both EVI cycle and IHX cycle have better potential for application in low ambient temperature environments. The further study indicated that the heating capacity and power consumption of EVI cycle were higher than those of IHX cycle at the same ambient temperature while the COP of EVI cycle was lower than that of ASHP with IHX due to the different refrigerant mass flow. In addition, using EVI could reduce the discharge temperature significantly while using IHX increased the discharge temperature in comparison to the conventional ASHP. Furthermore, ambient temperature range from -15°C to -10°C can be chosen as the switch range of the two cycles to satisfy the heating performance and economy simultaneously.

Induction of oxidative stress and related transcriptional effects of perfluorononanoic acid using an in vivo assessment

Perfluorononanoic acid (PFNA) is an organic pollutant ubiquitous in the environment. However, the potential toxicity of PFNA remains largely unknown in teleost fish. This study defined the oxidative stress and related transcriptional effects of PFNA at various concentrations on zebrafish larvae. Activities of superoxide dismutase were induced in PFNA-treated groups but attenuated with exposure to higher concentration. Catalase activity and lipid peroxidation were significantly inhibited or increased at the highest concentration, respectively. To test the apoptotic pathway, several genes related to cell apoptosis were examined using real-time PCR. The expression of p53, apoptosis-inducing factor (AIF) and c-Jun NH (2)-terminal kinase (JNK) was partially increased, while Bcl-2, an anti-apoptotic gene, was reduced, with no significant effects on Bax and caspase-3 during the exposure period. The effect of PFNA on lipid beta-oxidation system was investigated by examining the activity of peroxisome fatty acyl-COA oxidase (ACOX) and the expression of peroxisome proliferating activating receptors (PPARs). ACOX activity was moderately elevated with marginal significance and was not a significant consequence of PPAR alpha and PPAR gamma expression. The overall results suggest that turbulence of oxidative stress and apoptotic pathway is involved in PFNA-induced toxicity in zebrafish larvae, and the gene expression patterns are able to reveal some potential mechanisms of developmental toxicity. Crown Copyright (C) 2013 Published by Elsevier Inc. All rights reserved.Perfluorononanoic acid (PFNA) is an organic pollutant ubiquitous in the environment. However, the potential toxicity of PFNA remains largely unknown in teleost fish. This study defined the oxidative stress and related transcriptional effects of PFNA at various concentrations on zebrafish larvae. Activities of superoxide dismutase were induced in PFNA-treated groups but attenuated with exposure to higher concentration. Catalase activity and lipid peroxidation were significantly inhibited or increased at the highest concentration, respectively. To test the apoptotic pathway, several genes related to cell apoptosis were examined using real-time PCR. The expression of p53, apoptosis-inducing factor (AIF) and c-Jun NH (2)-terminal kinase (JNK) was partially increased, while Bcl-2, an anti-apoptotic gene, was reduced, with no significant effects on Bax and caspase-3 during the exposure period. The effect of PFNA on lipid beta-oxidation system was investigated by examining the activity of peroxisome fatty acyl-COA oxidase (ACOX) and the expression of peroxisome proliferating activating receptors (PPARs). ACOX activity was moderately elevated with marginal significance and was not a significant consequence of PPAR alpha and PPAR gamma expression. The overall results suggest that turbulence of oxidative stress and apoptotic pathway is involved in PFNA-induced toxicity in zebrafish larvae, and the gene expression patterns are able to reveal some potential mechanisms of developmental toxicity. Crown Copyright (C) 2013 Published by Elsevier Inc. All rights reserved

Amorphous Alloy: Promising Precursor to Form Nanoflowerpot

Nanoporous copper is fabricated by dealloying the amorphous Ti2Cu alloy in 0.03 M HF electrolyte. The pore and ligament sizes of the nanoporous copper can be readily tailored by controlling the dealloying time. The as-prepared nanoporous copper provides fine and uniform nanoflowerpots to grow highly dispersed Au nanoflowers. The blooming Au nanoflowers in the nanoporous copper flowerpots exhibit both high catalytic activity and stability towards the oxidation of glucose, indicating that the amorphous alloys are ideal precursors to form nanoflowerpot which can grow functional nanoflowers

Enzyme-Free Electrochemical Glucose Sensors Prepared by Dealloying Pd-Ni-P Metallic Glasses

We report the formation of enzyme-free electrochemical glucose sensors by electrochemical dealloying palladium-containing Pd-Ni-P metallic glasses. When metallic glasses with different Pd contents are used as the dealloying precursor alloys, palladium-based nanoporous metals with different ligament and pore sizes can be obtained. The chemical compositions of the nanoporous metals also vary according to the different precursor compositions. All the as-obtained nanoporous metals exhibit electrochemical catalytic activity towards the oxidation of d-glucose, indicating that the nanoporous metals prepared by dealloying the Pd-Ni-P metallic glasses are promising materials for enzyme-free electrochemical glucose sensor

The Mitochondrial Deoxyguanosine Kinase is Required for Cancer Cell Stemness in Lung Adenocarcinoma

The mitochondrial deoxynucleotide triphosphate (dNTP) is maintained by the mitochondrial deoxynucleoside salvage pathway and dedicated for the mtDNA homeostasis, and the mitochondrial deoxyguanosine kinase (DGUOK) is a rate-limiting enzyme in this pathway. Here, we investigated the role of the DGUOK in the self-renewal of lung cancer stem-like cells (CSC). Our data support that DGUOK overexpression strongly correlates with cancer progression and patient survival. The depletion of DGUOK robustly inhibited lung adenocarcinoma tumor growth, metastasis, and CSC self-renewal. Mechanistically, DGUOK is required for the biogenesis of respiratory complex I and mitochondrial OXPHOS, which in turn regulates CSC self-renewal through AMPK-YAP1 signaling. The restoration of mitochondrial OXPHOS in DGUOK KO lung cancer cells using NDI1 was able to prevent AMPK-mediated phosphorylation of YAP and to rescue CSC stemness. Genetic targeting of DGUOK using doxycycline-inducible CRISPR/Cas9 was able to markedly induce tumor regression. Our findings reveal a novel role for mitochondrial dNTP metabolism in lung cancer tumor growth and progression, and implicate that the mitochondrial deoxynucleotide salvage pathway could be potentially targeted to prevent CSC-mediated therapy resistance and metastatic recurrence