Development of a Test Facility and Preliminary Testing of Flow Boiling Heat Transfer of R410a Refrigerant with Al2o3 Nanolubricants

In vapor compression cycles, a small portion of the oil circulates with the refrigerant throughout the system components, while most of the oil stays in the compressors. In heat exchangers, the lubricant in excess penalizes the heat transfer and increases the pressure losses: both effects are highly undesired but yet unavoidable. Nanoparticles dispersed in the excess lubricant are expected to provide enhancements in heat transfer. While solubility and miscibility of refrigerants in polyolesters (POE) lubricant are well established knowledge, there is a lack of information regarding if and how nanoparticles dispersed in the lubricant affect these properties. This thesis presents experimental data of solubility of two types of Al2O3 nanolubricants with refrigerant R-410A. The nanoparticles were dispersed in POE lubricant by using different surfactants and dispersion methods. The nanolubricants appeared to have slightly lower solubility than that of R-410A but actually the solid nanoparticles did not really interfere with the POE oil solubility characteristics. A test facility and experimental methodology was developed for the investigation of heat transfer coefficient and pressure drop. The pressure drop of the refrigerant lubricant mixtures during flow boiling depended on the mass flux of the refrigerant. Greater augmentation was seen in the pressure drop results with decreasing mass flow rate. Pure refrigerant R410A showed the lowest pressure drop, addition of nanolubricants to the refrigerant showed a slightly higher pressure drop and POE-refrigerant mixture showed the highest pressure drop in the tests conducted. Enhancement or degradation in heat transfer coefficient during flow boiling depended on the nanoparticle concentration in the lubricant as well as the lubricant concentration in refrigerant. R410A showed the highest heat transfer coefficient for all conditions tested. For a concentration of 1% nanolubricant in refrigerant, the heat transfer coefficient showed more enhancement with increase in nanoparticle concentration compared to POE refrigerant mixtures. For a concentration of 3% nanolubricant in refrigerant mixtures there was little to no enhancement for tests conducted.Mechanical & Aerospace Engineerin

Thermodynamic and Heat Transfer Properties of Al2O3 Nanolubricants

In vapor compression cycles, a small portion of the oil circulates with the refrigerant throughout the system components, while most of the oil stays in the compressors. In heat exchangers, the lubricant in excess penalizes the heat transfer and increases the pressure losses: both effects are highly undesired but yet unavoidable. Nanoparticles dispersed in the excess lubricant are expected to provide enhancements in heat transfer. While solubility and miscibility of refrigerants in polyolesters (POE) lubricant are well established knowledge there is a lack of information regarding if and how nanoparticles dispersed in the lubricant affect these two properties. This paper presents experimental data of solubility and miscibility of three types of Al2O3 nanolubricants with refrigerant R410A. The nanoparticles were dispersed in POE lubricant by using different surfactants and dispersion methods and the nanolubricants showed lower refrigerant R410A solubility than that of POE oil. High viscosity suspensions are expected to stabilize the nanoparticles and avoid clustering. This aspect was verified in the present paper for the Al2O3 nanolubricants and long term stability and the degree of agglomeration, when present, were measured. The data identified optimum combinations of surfactants to achieve stable and uniform nanolubricant dispersions for several months. Surfactants affected slightly the thermal conductivity, specific heat, viscosity, and solubility properties of the nanolubricants. The specific heats of the nanolubricants were lower than that of POE oil at temperatures from 0 to 20°C while they were similar at 40°C. Thermal conductivity ranged from 1.1 times higher at 5°C to 1.4 times higher at 40°C than that of POE lubricant. The viscosity was about 2.6 times higher at 5°C while it was similar to that of POE lubricant at 40°C. The thermal and transport properties data for three nanolubricants provided in this paper advance the basic understanding of nanoparticles interaction with R410A refrigerant and POE lubricant mixtures

Isobolographic analysis of the hypnotic interaction between propofol and thiopental

Introduction: Giving two intravenous anaesthetic agents simultaneously generally results in an additive effect. The aim of this study was to investigate the interaction between propofol and thiopental when given to patients who have had sedative premedication. Methods: Fifty patients were admitted into the study. All patients received oral midazolam 3.75 mg and intravenous fentanyl 100 mg before induction of anaesthesia. Twenty patients received an infusion of either propofol or thiopental while 30 patients received an infusion of an admixture of both drugs. Isobolographic analysis was used to determine the interaction between the two drugs. Results: The interaction between propofol and thiopental was additive. The average dose at loss of the eyelash reflex for propofol and thiopental was 0.71 mg kg-1 and 1.54 mg kg-1 respectively. Premedication decreased the induction dose by 38.2%. Conclusion: Propofol and thiopental interact in an additive fashion when given at induction of anaesthesia

Correlates of physical activity level among hemodialysis patients in Selangor, Malaysia.

INTRODUCTION: There is mounting evidence demonstrating the importance of adequate physical activity to promote better well-being among hemodialysis patients. Available data pertaining to the levels of physical activity and its determinants among hemodialysis patients is, however, scarce in Malaysia. The objectives of this study are hence to determine the levels of physical activity and it associated factors among hemodialysis patients. METHODOLOGY: A total of 70 subjects were recruited from three dialysis centres in Selangor. A face-to-face interview was conducted to obtain socio-demographic data and subjects' knowledge on dietary sources. Medical history, biochemical parameters and weight status were obtained from medical records. Physical activity level (PAL) was assessed using the Global Physical Activity Questionnaire (GPAQ). RESULTS: A total of 81.4% and 18.6% of the respondents had low and moderate PALs, respectively. Thus, none of the respondents had high PAL. Serum creatinine, education level, personal income and knowledge score on potassium-related medical complications were factors found to correlate significantly with PAL. Multiple linear regression analysis showed that higher PAL was predicted by a lower knowledge score on dietary sodium source, higher education and higher serum creatinine. CONCLUSION: Despite consistent documentation of the potential positive impact of physical exercise on hemodialysis outcomes, the level of physical activity remains low among these patients. It is hoped that these findings can add to the existing body of knowledge and serve as a supporting document for the formulation of appropriate interventions to improve the status of physical activity among hemodialysis patients in Malaysia

Effect of Nanoparticles Aspect Ratio on the Two Phase Flow Boiling Heat Transfer Coefficient and Pressure Drop of Refrigerant and Nanolubricants Mixtures in a 9.5 mm Micro-fin Tube.

In vapor compression cycles of air conditioning and refrigeration systems, a small amount of the compressor lubricating oil is carried with the refrigerant and it circulates in the system components. In the heat exchangers, oil is a contaminant and it decreases the heat transfer rate and increases the pressure losses: both are unavoidable challenges. Nanolubricants, that is, nanoparticles dispersed in the non-volatile component of a refrigerant and oil mixture and working as thermal energy transport vectors within the mixture, have the potential to overcome these challenges in a cost-neutral manner for both new and retrofitting applications. This papers documents the effects of the nanoparticles thermal conductivity and aspect ratio on the two-phase flow heat transfer coefficients and pressure drop of nanolubricants by experimentally studying two types of nanolubricants. The first type used spherical Alumina (γ-Al2O3) nanoparticles with 40 nm nominal particle diameter. The second type used ZnO nanoparticles with 20 to 40 nm nominal particle diameter and with an elongated hexagonal wurtzite shape. The experimental results indicated that the thermal conductivity of the nanolubricants increased linearly with the added amount of nanoparticles in POE oil, and γ-Al2O3 and ZnO based nanolubricants had similar thermal conductivity if the nanoparticle concentration was 10 wt. % and 20 wt. %. However, even when diluted in the liquid phase of the refrigerant R410A and POE oil mixture, these two types of nanoparticles provided heat transfer performance that were measurably different from each other during two phase flow boiling inside an horizontal 9.5 mm micro-fin evaporator tube. Depending on the mass flux, oil concentration, and heat flux, nanolubricants provided either an enhancement or a degradation of the heat transfer coefficients. These results supported the hypothesis that thermal conductivity of the nanolubricants was not the main property responsible for the heat transfer coefficient intensification during flow boiling. The experimental results also suggested that the magnitude of the enhancements of the two phase flow boiling heat transfer coefficient due to the nanoparticles dispersed in the POE oil were depended on the mass flux and shear rates within the liquid phase of the mixture. Interesting, even when high heat transfer coefficients were observed for the nanolubricants, the effect of the nanoparticles on the two phase flow pressure drop of the mixture was negligible.

Malayan Tapir Behaviour, Habitat Use And Density In Belum, Perak.

Listed as endangered under the IUCN Red List of Threatened Species, the ecological knowledge for the Malayan tapir is still severely lacking; not only for Peninsular Malaysia, but also for the Southeast Asia region. Estimated to be between 1,500 to 1,700 individuals left in the country, the Malayan tapir is now threatened mainly by habitat loss, and fragmentation. In recent years, there has been an increase in tapir road-kills due to the direct impact of road fragmentation. Large-scale natural forest conversion has likely caused tapirs to venture out into human dominated areas. In an effort to conserve Malayan tapirs, this thesis therefore seeks to better understand the population ecology of tapir by investigating its activity pattern, factors that influence its habitat preference, assessing its population status and Relative Abundance Index (RAI) within RBSP, a primary forest and TFR, a selectively logged forest. The Malayan tapir’s activity pattern was found to be predominantly nocturnal; 1900 hrs to 0659 hrs (83.20%). Activity pattern of the Malayan tapir is not significantly different with predominantly diurnal activity of human in the landscape (P>0.05, Mann-Whitney) with kernel density estimate of 0.16 (CI: 0.10-0.22) in TFR and 0.12 (CI: 0.07-0.17) in RBSP. Spatial avoidance towards human habitation was observed from the habitat use analysis, where the Malayan tapir was found to prefer forested areas which are away from the human settlements and at high elevation in the RBSP and TFR landscape

The impact of topical mupirocin on peritoneal dialysis infection rates in Singapore general hospital.

Background. Peritonitis and exit-site infections (ESI) are major causes of technique failure and morbidity in peritoneal dialysis (PD) patients. Topical mupirocin on the exit-site has been shown to reduce such complications and prolong life in PD. Since the year 2000, such an approach has been adopted for our new incident PD population. We now report the results of this new protocol. We also studied the effect of co-morbidity on peritonitis occurrence. Methods. A total of 740 incident PD patients were studied. Patients were divided into two groups based on year of entry into PD (Group 1 from January 1998–December 1999 without topical mupirocin and Group 2 from January 2000–March 2004 with topical mupirocin). Variables studied included gender, age, diabetic status, ischaemic heart disease, peripheral vascular disease, cerebrovascular disease and serum albumin. Results. Topical mupirocin at the exit-site has led to a significant reduction in peritonitis rate (0.443 vs 0.339 episodes/patient-year; P<0.0005) and ESI (0.168 vs 0.156 episodes/patient-year; P<0.005) attributed primarily to the significant reduction in Staphylococcus aureus infections. There was an unexpected finding of lower Pseudomonas aeruginosa peritonitis in the mupirocin group (P<0.005). Stepwise multiple logistic regression analysis revealed that only mupirocin application and serum albumin were significant predictors of peritonitis. Conclusions. Our study, although limited by its retrospective nature, demonstrated that topical mupirocin was associated with a significant reduction in ESI and peritonitis with unexpected findings of lower Pseudomonas peritonitis. Serum albumin prior to the initiation of PD was a strong predictor of subsequent peritonitis. Mupirocin, with its low toxicity, ease of application and demonstrable beneficial effect in reducing ESI and peritonitis is now used on all incident PD patients

1-Benzoyl-3-[4-(3-benzoyl­thio­ureido)phen­yl]thio­urea

The mol­ecule of the title compound, C22H18N4O2S2, lies across a crystallographic inversion centre. The mol­ecule adopts a syn–anti configuration with respect to the positions of the carbonyl groups and terminal phenyl rings relative to the thione S atom across the C—N bond. There are two intra­molecular N—H⋯O and C—H⋯S hydrogen bonds within each molecule, resulting in the formation of four six-membered S(6) rings. The central and terminal rings make a dihedral angle of 13.55 (15)°. In the crystal, mol­ecules are linked by inter­molecular C—H⋯S hydrogen bonds, forming R 2 2(14) rings and resulting in zigzag chains

Poor sleep quality, depression and social support are determinants of serum phosphate level among hemodialysis patients in Malaysia

Despite optimal control of serum phosphate level being imperative to avoid undesirable health outcomes, hyperphosphataemia is a highly prevalent mineral abnormality among the dialysis population. This study aimed to determine factors associated with hyperphosphatemia among hemodialysis patients in Malaysia. Multiple linear regression analysis was used to ascertain the possible factors that influence serum phosphate levels. A total of 217 hemodialysis patients were recruited. Hyperphosphatemia was prevalent. Only approximately 25% of the patients were aware that optimal control of hyperphosphatemia requires the combined effort of phosphate binder medication therapy, dietary restriction, and dialysis prescription. The presence of diabetes mellitus may affect serum phosphate levels, complicating dietary phosphorus management. Patients who were less depressive portrayed higher serum phosphate levels, implying intentional non-compliance. Better compliance on phosphate binder, longer sleep duration, and higher social support was associated with a lower level of serum phosphate. Despite sleep disturbance being one of the most prevalent and intense symptom burdens identified by hemodialysis patients, relatively few studies have addressed this issue. It is time to formulate sleep therapeutic interventions besides the encouragement of strong social support, hoping which many clinical outcomes including hyperphosphatemia can be better controlled among hemodialysis patients

Asian venous thromboembolism guidelines: updated recommendations for the prevention of venous thromboembolism

The Asian venous thromboembolism (VTE) prophylaxis guidelines were first published in 2012. Since its first edition, the Asian Venous Thrombosis Forum (AVTF) working group have updated the Asian VTE epidemiology and reviewed issues that were not addressed in the previous guidelines. The authors noted that the rising incidence of VTE across Asia may be attributable to aging population, dietary changes, and increasing incidence of obesity and diabetes. The new additions in the guideline include role of thrombophilia in VTE, bleeding risk in Asians, individual risk assessment, updates in the prevention of VTE in medically ill, bariatric surgery, cancer, orthopedic and trauma patients. The influence of primary thrombophilia in perioperative VTE is still unclear. The secondary risk factors, however, are similar between Asians and Caucasians. The group found no evidence of increased risk of bleeding while using pharmacological agents, including the use of novel anti-coagulants. At present, Caprini risk assessment model is widely used for individual risk assessment. Further validation of this model is needed in Asia. In medically ill patients, pharmacological agents are preferred if there is no bleeding risk. Intermittent pneumatic compression device (IPC) is recommended in patients with bleeding risk but we do not recommend using graduated compressive stockings. In bariatric patients, data on VTE is lacking in Asia. We recommend following current international guidelines. A high index of suspicion should be maintained during postbariatric surgery to detect and promptly treat portomesenteric venous thrombosis. Different cancer types have different thrombotic risks and the types of surgery influence to a large extent the overall VTE risk. Cancer patients should receive further risk assessment. In patients with higher thrombotic risk, either due to predisposing risk or concomitant surgery, low molecular weight heparin is indicated. Different countries appear to have different incidence of VTE following trauma and major orthopedic surgery. We recommend mechanical prophylaxis using IPC as the main method and additional pharmacological prophylaxis if the thrombotic risk is high. As for obstetric practice, we propose adherence to the UK Greentop guideline that is widely accepted and utilized across Asia. To improve VTE thromboprophylaxis implementation in the region, we propose that there should be better health education, establishment of hospital-based guidelines and multidisciplinary collaboration