Flow boiling of R245fa in vertical small metallic tubes

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University LondonThe research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.Thomas Gerald Gray charitable trus

A late injection combustion strategy using a novel ramped combustion system

Traffic related NOx and particle emission remain a significant concern particularly in the urban environment. Electrification offers a medium to long term solution, but there remains a need to significantly reduce internal combustion engine emissions in the short and medium term, and potentially in the long term for long range inter city transportation. Late injection low temperature combustion (LTC) has the potential to achieve ultra-low emissions levels in a compression ignition engine by increasing the lean pre-mixed burn fraction. However, significant quantities of diluent are normally required to achieve the required delay in ignition and pre-mixing to achieve LTC. This results in high boost requirements, increased pumping work and the complexity of the air handling system and potentially adversely impacting fuel economy. In this paper, results from a single cylinder light duty research engine are presented using a novel ramped combustion chamber focused at mid to high engine loads. The ramped combustion chamber improves mixing and enables more retarded injection timings than those possible on conventional bowl designs. This combustion strategy has enabled LTC conditions to be achieved at lower dilution rates, typically 20-30% at loads up to 15bar IMEP. CFD analysis of the air-fuel interaction indicates the ramped bowl effectively deflects fuel away from the squish region enabling very late injection timings. One dimensional analysis of the engine system was used to investigate the potential of late exhaust valve opening in improving work recovery, resulting in improved fuel consumption over the baseline LTC valve timing

HealthMpowerment.org: Building Community Through a Mobile-Optimized, Online Health Promotion Intervention

Both young Black men who have sex with men as well as young Black transgender women (YBMSM/TW) continue to experience a significant increase in HIV incidence. HealthMpowerment.org (HMP) is a mobile phone-optimized, online intervention for both YBMSM/TW to build community and facilitate supportive relationships

Putting Prevention in Their Pockets: Developing Mobile Phone-Based HIV Interventions for Black Men Who Have Sex with Men

Young black men who have sex with men (MSM) bear a disproportionate burden of HIV. Rapid expansion of mobile technologies, including smartphone applications (apps), provides a unique opportunity for outreach and tailored health messaging. We collected electronic daily journals and conducted surveys and focus groups with 22 black MSM (age 18–30) at three sites in North Carolina to inform the development of a mobile phone-based intervention. Qualitative data was analyzed thematically using NVivo. Half of the sample earned under $11,000 annually. All participants owned smartphones and had unlimited texting and many had unlimited data plans. Phones were integral to participants' lives and were a primary means of Internet access. Communication was primarily through text messaging and Internet (on-line chatting, social networking sites) rather than calls. Apps were used daily for entertainment, information, productivity, and social networking. Half of participants used their phones to find sex partners; over half used phones to find health information. For an HIV-related app, participants requested user-friendly content about test site locators, sexually transmitted diseases, symptom evaluation, drug and alcohol risk, safe sex, sexuality and relationships, gay-friendly health providers, and connection to other gay/HIV-positive men. For young black MSM in this qualitative study, mobile technologies were a widely used, acceptable means for HIV intervention. Future research is needed to measure patterns and preferences of mobile technology use among broader samples

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival