Energy, Exergy, and Environmental (3E) Analysis of Hydrocarbons as Low GWP Alternatives to R134a in Vapor Compression Refrigeration Configurations

The phase-down of hydrofluorocarbons and substitution with low global warming potential values are consequences of the awareness about the environmental impacts of greenhouse gases. This theoretical study evaluated the energy and exergy performances and the environmental impact of three vapor compression system configurations operating with the hydrocarbons R290, R600a, and R1270 as alternatives to R134a. The refrigeration cycle configurations investigated in this study include a single-stage cycle, a cycle equipped with an internal heat exchanger, and a two-stage cycle with vapor injection. According to the results, the alternative hydrocarbon refrigerants could provide comparable system performance to R134a. The analysis results also revealed that using an internal heat exchanger or a flash tank vapor injection could improve the system’s efficiency while decreasing the heating capacity. The most efficient configuration was the two-stage refrigeration cycle with vapor injection, as revealed by the exergy analysis. The environmental impact analysis indicated that the utilization of environmentally-friendly refrigerants and improving the refrigeration system’s efficiency could mitigate equivalent CO2 emissions significantly. The utilization of hydrocarbons reduced the carbon footprint by 50%, while a 1% to 8% reduction could be achieved using the internal heat exchanger and flash tank vapor injection

Numerical Experimental Investigation of Solidification Thickness around Cylindrical Surfaces for HVAC Cold Storage Systems

Thermal Ice Storage System (TISS) is an innovative way of storing night-time off-peak energy for daytime peak USAge. In many locations, demand for electrical power peaks during summer time. Air-conditioning equipment are the main reason accounting for as much as half of the power demand during the hot mid-day hours when electricity is most expensive. Since utilities have spare electrical generating capacity at night, electricity generated during this ldquo;off-peakrdquo; is much less expensive. In this research a numerical model for Latent Heat Storage (LHS) cylindrical tank has been obtained from a numerical package, ANSYS software ver. 15, and compared to an experimental data gathered from similar tank. The data showed good agreement with the experimental data with an error of 9%. The numerical model can be used to estimate ice thickness and tank geometries for any future work

مقاصد الكتابة في القرآن الكريم = The purposes of writing in the Holy Qur’an

يعد موضوع الكتابة من الموضوعات المهمة في القرآن الكريم؛ لتعلقها بالاجتهاد العقلي، ورغم كثرة الآيات التي تتحدث عن الكتابة إلا أن الحديث عن مقاصد الكتابة في القرآن الكريم يشكل تحديا ا للباحثين، وجاءت هذه الدراسة لبيان مقاصد الكتابة ومتعلقاتها في القرآن الكريم، وتكمن أهم ي ة البحث في اهتمام القرآن الكريم بالكتابة لأنها إحدى وسائل توثيق لكثير من القضايا، كالعقود المالية، والعلاقات الاجتماعية والسياسية، حيث ذكرت الكتابة بصفة صريحة في القرآن الكريم في حوالي مائتين وثمانين موضعاا، كما أ نها كانت وسيلة راقية في عهد الن بي ﷺ، خاطب بها الملوك والزعماء، ومن خلالها تم توثيق القرآن الكريم والسنة النبوية. واعتمد البحث المنهج الاستقرائي، من خلال جمع الآيات القرآنية التي تحدثت عن مقاصد الكتابة في القرآن الكريم، وذلك بالرجوع إلى برامج البحث في القرآن الكريم وكتب التفسير القديمة والحديثة، كما اعتمد المنهج التحليلي، وذلك بتفسير الآيات وتحليلها وتصنيفها ،واستنباط مقاصد الكتابة في القرآن الكر يم، ويب ين البحث أ ن من مقاصد الكتابة إثبات الحقوق المالية وبخاصة الديون من خلال كتابتها، وكذلك حفظ النسب وحقوق الزوجين من خلال توثيق عقود الزواج. ****************************************************************************** The topic of inscribing in the Holy Qur’an is one of the important topics at, because it is related to mental endeavor, and despite the many verses that speak about inscribing, talking about the objectives of inscribing in the Holy Qur'an is a challenge for researchers. This study illustrates the objectives of inscribing and its derivatives in the Holy Qur’an. The importance of this research lies in the interest of the Holy Qur’an in the subject of inscribing because it is one of the means through which many issues are documented, such as financial contracts, social and political relations, where inscribing is mentioned explicitly in the Holy Qur’an in about two hundred and eighty places. In addition, as it was a stylish means during the era of the Prophet Muhammad (Pace be upon him), who used it for addressing kings and leaders, and it was used for documentation of the Holy Qur’an and Sunnah. This research adopted the inductive methodology, by collecting Qur’anic verses that talked about the objectives of inscribing in the Holy Qur’an, by referring to search programs in the Holy Qur’an, and by referring to Tafsir books. The analytical methodology was also adopted in this research, by interpreting, analyzing, and categorizing verses, and deriving the objectives and semantics of inscribing in the Holy Qur’an. The research concludes with the objectives of inscribing in the Holy Quran such as to prove financial rights, especially debts, by writing a receipt, and another objective is to preserve the lineages and rights of spouses through the documentation of marriage contracts

ANN Modeling to Analyze the R404A Replacement with the Low GWP Alternative R449A in an Indirect Supermarket Refrigeration System

Artificial neural networks (ANNs) have been considered for assessing the potential of low GWP refrigerants in experimental setups. In this study, the capability of using R449A as a lower GWP replacement of R404A in different temperature levels of a supermarket refrigeration system is investigated through an ANN model trained using field measurements as input. The supermarket refrigeration was composed of two indirect expansion circuits operated at low and medium temperatures and external subcooling. The results predicted that R449A provides, on average, a higher 10% and 5% COP than R404A at low and medium temperatures, respectively. Moreover, the cooling capacity was almost similar with both refrigerants in both circuits. This study also revealed that the ANN model could be employed to accurately predict the energy performance of a commercial refrigeration system and provide a reasonable judgment about the capability of the alternative refrigerant to be retrofitted in the system. This is very important, especially when the measurement data comes from field measurements, in which values are obtained under variable operating conditions. Finally, the ANN results were used to compare the carbon footprint for both refrigerants. It was confirmed that this refrigerant replacement could reduce the emissions of supermarket refrigeration systems

In Vitro Evaluation of Leakage at Implant-Abutment Connection of Three Implant Systems Having the Same Prosthetic Interface Using Rhodamine B

Objectives. Hollow space between implant and abutment may act as reservoir for commensal and/or pathogenic bacteria representing a potential source of tissue inflammation. Microbial colonization of the interfacial gap may ultimately lead to infection and bone resorption. Using Rhodamine B, a sensitive fluorescent tracer dye, we aim in this study to investigate leakage at implant-abutment connection of three implant systems having the same prosthetic interface. Materials and Methods. Twenty-one implants (seven Astra Tech, seven Euroteknika, and seven Dentium) with the same prosthetic interface were connected to their original abutments, according to the manufacturers’ recommendation. After determination of the inner volume of each implant systems, the kinetic quantification of leakage was evaluated for each group using Rhodamine B (10−2 M). For each group, spectrophotometric analysis was performed to detect leakage with a fluorescence spectrophotometer at 1 h (T0) and 48 h (T1) of incubation time at room temperature. Results. Astra Tech had the highest inner volume (6.8 μL), compared to Dentium (4 μL) and Euroteknika (2.9 μL). At T0 and T1, respectively, the leakage volume and percentage of each system were as follows: Astra Tech 0.043 μL or 1.48% (SD 0.0022), 0.08 μL or 5.56% (SD 0.0074), Euroteknika 0.09 μL or 6.93% (SD 0.0913), 0.21 μL or 20.55% (SD 0.0035), and Dentium 0.07 μL or 4.6% (SD 0.0029), 0.12 μL or 10.47% (SD 0.0072). Conclusion. The tested internal conical implant-abutment connections appear to be unable to prevent leakage. In average, Astra Tech implants showed the highest inner volume and the least leakage

Progressive loss of CD3 expression after HTLV-I infection results from chromatin remodeling affecting all the CD3 genes and persists despite early viral genes silencing

BACKGROUND: HTLV-I infected CD4+ T-cells lines usually progress towards a CD3- or CD3low phenotype. In this paper, we studied expression, kinetics, chromatin remodeling of the CD3 gene at different time-points post HTLV-I infection. RESULTS: The onset of this phenomenon coincided with a decrease of CD3gamma followed by the subsequent progressive reduction in CD3delta, then CD3epsilon and CD3zeta mRNA. Transient transfection experiments showed that the CD3gamma promoter was still active in CD3- HTLV-I infected cells demonstrating that adequate amounts of the required transcription factors were available. We next looked at whether epigenetic mechanisms could be responsible for this progressive decrease in CD3 expression using DNase I hypersensitivity (DHS) experiments examining the CD3gamma and CD3delta promoters and the CD3delta enhancer. In uninfected and cells immediately post-infection all three DHS sites were open, then the CD3gamma promoter became non accessible, and this was followed by a sequential closure of all the DHS sites corresponding to all three transcriptional control regions. Furthermore, a continuous decrease of in vivo bound transcription initiation factors to the CD3gamma promoter was observed after silencing of the viral genome. Coincidently, cells with a lower expression of CD3 grew more rapidly. CONCLUSION: We conclude that HTLV-I infection initiates a process leading to a complete loss of CD3 membrane expression by an epigenetic mechanism which continues along time, despite an early silencing of the viral genome. Whether CD3 progressive loss is an epiphenomenon or a causal event in the process of eventual malignant transformation remains to be investigated.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

VALPROIC ACID INDUCES APOPTOSIS AND INCREASES CXCR7 EXPRESSION IN EPITHELIAL OVARIAN CANCER CELL LINE SKOV-3.

Background: The chemokine receptor, CXCR7 is described to play a biologically relevant role in tumor growth and spread. Recently, it was reported that CXCR7 overexpression is associated with an unfavorable prognosis and metastatis of epithelial ovarian cancer (EOC). Aware that, several reports indicated that Histone deacetylases (HDACs) regulate the expression and activity of many proteins involved in both cancer initiation and progression, the aim of this work, was to study the effect of the HDAC inhibitor valproic acid (VPA) on the expression of CXCR7 as well as its impact on survival function in the epithelial ovarian cell line (SKOV-3). Methods: cells were cultured with varying concentrations of VPA (1, 2, 3, 4, 5 and 10 mM) for different durations (0, 12 h, 24 h and 48 h). Cell survival was assessed by Neutral red assay and by colony counting which being stained with crystal violet. CXCR7 expression was determined at mRNA level using quantitative real-time PCR (qRT-PCR) or at the protein level using western blotting. Results: VPA reduces cell survival of SKOV-3 cancer cells. The inhibition effect of VPA was dose and time-dependent. Exposure to VPA at concentrations above 2 mM at 24 h resulted in an increase expression of CXCR7 at both the mRNA and protein levels . Conclusion: These observations provide, for the first time, a better insight into the epigenetic mechanisms involved in regulating CXCR7 expression in EOC and will open new avenues for evaluating drugs that specifically stimulate the apoptosis of EOC with minimal unwanted side effect

Exposure of Endothelial Cells to Physiological Levels of Myeloperoxidase-Modified LDL Delays Pericellular Fibrinolysis

Blood fluidity is maintained by a delicate balance between coagulation and fibrinolysis. The endothelial cell surface is a key player in this equilibrium and cell surface disruptions can upset the balance. We investigated the role of pericellular myeloperoxidase oxidized LDLs (Mox-LDLs) in this balance.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe