Numerical study of using different Organic Rankine cycle working fluids for engine coolant energy recovery

Engine waste heat recovery technology especially Organic Rankine cycle (ORC) has been widely studied in order to achieve higher overall thermal efficiency, reduce the engine emissions and improve the fuel economy. The coolant energy occupies around 30% of the fuel energy can be used as the heat source for ORC system. This paper studies thermal status of the engine heated components when using different ORC working fluids as engine coolant to avoid the heat loos using heat exchanger to transfer coolant to the ORC fluid. A Solid-Liquid Conjugated Heat Transfer (SLCHT) calculation method is developed to calculate the heat transfer inside the engine, which can solve the temperature field of both solid zone and fluid zone. The simulation results have been validated by the experimental data from a 6-cylinder medium duty diesel engine, when water is the coolant in the system. The simulation model is then used to predict the temperature profile using different ORC working fluids and investigate the influence of different ORC working fluids on the cooling effects of the engine heated parts. The maximum temperature of the heated components has been selected as the evaluation parameters. The results reveals that applying selected ORC working fluids in engine as coolant is not practical under the designed conditions, which will make the engine overheated. Further investigation showed that increasing mass flow rate of the coolant can decrease the thermal status of the heated components but still cannot meet the cooling demands even under 200% of the original mass flow rate. The variations of the coolant outlet temperature and exergy were also analysed

Comparison study of trilateral Rankine cycle, organic flash cycle and basic organic Rankine cycle for low grade heat recovery

Organic Rankine Cycle (ORC) has been widely used for the recovery of low-grade heat into power such as solar energy and industrial waste heat. The overall thermal efficiency of ORC is affected by large exergy destruction in the evaporator due to the temperature mismatching between the heat source and working fluid. Trilateral Cycle (TLC) and Organic Flash Cycle (OFC) have been recognized as potential solutions because of their better performance on temperature matching between the heat source and working fluid at the evaporator. In this study, thermodynamic models of above three cycles are established in MATLAB/REFPROP. Results indicate that TLC obtains the largest net power output, thermal efficiency and exergy efficiency of 13.6 kW, 14.8% and 40.8% respectively at the evaporation temperature of 152℃, which is 37% higher than that of BORC (9.9 kW) and 58% higher than that of OFC (8.6 kW). BORC is more suitable under the conditions low evaporation temperature is relatively low due to the achieved maximum net power output, thermal efficiency and exergy efficiency. OFC has the minimum net power output, thermal efficiency and exergy efficiency under all the conditions of evaporation temperature compared to TLC and BORC. As for the UA value, TLC has the largest one ranging from 7.9 kW/℃ to 8.8 kW/℃ under all conditions while OFC gains the minimum UA value at low evaporation temperature and BORC gains the minimum UA value at high evaporation temperature

Single-shot time-gated fluorescence lifetime imaging using three-frame images

Qualitative and quantitative measurements of complex flows demand for fast single-shot fluorescence lifetime imaging (FLI) technology with high precision. A method, single-shot time-gated fluorescence lifetime imaging using three-frame images (TFI-TGFLI), is presented. To our knowledge, it is the first work to combine a three-gate rapid lifetime determination (RLD) scheme and a four-channel framing camera to achieve this goal. Different from previously proposed two-gate RLD schemes, TFI-TGFLI can provide a wider lifetime range 0.6 ~ 13ns with reasonable precision. The performances of the proposed approach have been examined by both Monte-Carlo simulations and toluene seeded gas mixing jet diagnosis experiments. The measured average lifetimes of the whole excited areas agree well with the results obtained by the streak camera, and they are 7.6ns (N2 = 7L/min; O2 < 0.1L/min) and 2.6ns (N2 = 19L/min; O2 = 1L/min) with the standard deviations of 1.7ns and 0.8ns among the lifetime image pixels, respectively. The concentration distributions of the quenchers and fluorescent species were further analyzed, and they are consistent with the experimental settings

Smad7 enables STAT3 activation and promotes pluripotency independent of TGF-β signaling

TGF-β and related growth factors critically regulate cell potency and functions. Smad7 is induced by TGF-βs and inhibits the physiological functions of TGF-β signaling. This study describes an unexpected finding that Smad7 promotes self-renewal of embryonic stem cells (ESCs) in a manner independent of its inhibition on TGF-β signaling. Instead, Smad7 acts to induce activation of transcription factor signal transducers and activators of transcription 3 (STAT3) in ESCs. Smad7 activates STAT3 through its direct binding to the cytokine receptor upstream of STAT3 activation. In agreement with the role of STAT3 in maintaining ESC pluripotency, Smad7 promotes ESC self-renewal and induced pluripotent stem cell reprogramming. This finding illustrates a regulatory mechanism for Smad7 in maintaining pluripotency, and likely in cancer and inflammation

Retaining mTeSR1 Medium during Hepatic Differentiation Facilitates Hepatocyte-Like Cell Survival by Decreasing Apoptosis

Background/Aims: Hepatocyte-like cells derived from human pluripotent stem cells could be an important cell source for hepatocyte transplantation. The present study investigated the effect of retaining mTeSR1 medium during hepatic differentiation on hepatocyte-like cells in vitro. Methods: Human embryonic stem cell line H1 were treated with activin A and bone morphogenetic protein 4 (BMP4) for definitive endoderm (DE) cell induction and subsequently treated with BMP2 and fibroblast growth factor 4 (FGF4) for early hepatic cell induction. Hepatocyte growth factor (HGF) and fibroblast growth factor (KGF) were added for early hepatic cell expansion and then mixed with oncostatin-M for maturation. During DE induction, 0%, 25%, 50% and 75% concentrations of mTeSR1 medium were separately added for early hepatic induction and expansion. For optimization, the expression levels of SRY-related HMG-box 17 (SOX17) and forkhead box A2 (FOXA2) at day 4, alpha fetoprotein (AFP) and hepatocyte nuclear factor 4α (HNF4α) at day 15, and albumin (ALB) at day 25 were quantified in differentiated cells by qRT-PCR. The ALB-positive cell proportion was measured by flow cytometry. Functional tests including ALB secretion and indocyanine green (ICG) angiography uptake and release by ELISA, urea production by urea assay kit, and glycogen storage ability by periodic acid Schif reaction (PAS) staining were performed in the differentiated cells. The induced pluripotent stem (iPS) cells were used to examine whether the optimized method was suitable for differentiating iPS cells. DE and hepatic markers were detected by immunostaining, and functional testing was performed as described above. Flow cytometry with an Annexin V-FITC apoptosis detection kit and fluorescence microscopy with Hoechst 33258 were used to analyze apoptosis in differentiated cells derived from H1 cells. Results: All differentiated cells with retention of 0%, 25%, 50% and 75% mTeSR1 expressed SOX17, FOXA2, AFP, HNF4α, and ALB, while higher expression levels were observed in differentiated cells in the 0% and 25% groups. The flow cytometry results showed that the proportion of ALB-positive differentiated cells derived from H1 cells was higher in the 25% mTeSR1 group than in other groups. However, no significant difference in ALB secretion, urea production, ICG uptake and release and glycogen storage ability was detected between the 25% and 0% groups. The iPS cells could differentiate into hepatocyte-like cells with 25% mTeSR1 retention. The apoptosis ratio of differentiated cells was lower in the 25% mTeSR1 group than in the 0% mTeSR1 group. Conclusion: Retaining 25% mTeSR1 medium during hepatic differentiation has been proposed to increase the percentage of ALB-positive cells and cell survival by decreasing cell apoptosis

Methicillin-resistant Staphylococcus aureus, Hawaii, 2000–2002

Annual trends showed a significant increase in the proportion of MRSA among adult but not among pediatric patients

Ppm1b negatively regulates necroptosis through dephosphorylating ​Rip3

该研究论文发现蛋白磷酸酶Ppm1b 通过去磷酸化RIP3负调控程序性细胞坏死（necroptosis），阐明了RIP3磷酸化状态的精确调控对于细胞和机体在生理和病理状态下的存活至关重要。The auto-phosphorylation of murine ​receptor-interacting protein 3 (​Rip3) on Thr 231 and Ser 232 in the necrosome is required to trigger necroptosis. However, how ​Rip3 phosphorylation is regulated is still largely unknown. Here we identified ​protein phosphatase 1B (​Ppm1b) as a ​Rip3 phosphatase and found that ​Ppm1b restricts necroptosis in two settings: spontaneous necroptosis caused by ​Rip3 auto-phosphorylation in resting cells, and ​tumour necrosis factor-α (​TNF)-induced necroptosis in cultured cells. We revealed that ​Ppm1b selectively suppresses necroptosis through the dephosphorylation of ​Rip3, which then prevents the recruitment of ​mixed lineage kinase domain-like protein (​Mlkl) to the necrosome. We further showed that ​Ppm1b deficiency (​Ppm1bd/d) in mice enhanced ​TNF-induced death in a ​Rip3-dependent manner, and the role of ​Ppm1b in inhibiting necroptosis was evidenced by elevated ​Rip3 phosphorylation and tissue damage in the caecum of ​TNF-treated ​Ppm1bd/d mice. These data indicate that ​Ppm1b negatively regulates necroptosis through dephosphorylating ​Rip3 in vitro and in vivo

Interaction of transient fast flows with biological cells in microfluidic confinement

This thesis deals with the interaction of biological cells with transient fast flows mainly from bubbles in microfluidic confinement. These interactions can be utilized to stretch and porate cell membranes toward a label-free biomarker for human diseases, and drug or gene delivery, respectively. The rapid expansion and collapse of a single laser-induced cavitation bubble generate a strong shear flow, which is mainly located within the boundary layer close to the bubble. This leads to impulsive stretching of red blood cells with large strains while larger spherical cancer cells have to be stretched by an extension flow with inertial focusing. The deformability of cancer cells is found to correlate with their invasive potential. Besides, the fast jetting flow from shock wave/cavitation bubble-gas bubble interaction is exploited for localized cell membrane poration. We also study this kind of fast jetting flow in detail with different geometrical arrangements of the gas bubbles and some novel phenomena are observed.DOCTOR OF PHILOSOPHY (SPMS

Yield strength of human Erythrocyte membranes to impulsive stretching

Deformability while remaining viable is an important mechanical property of cells. Red blood cells (RBCs) deform considerably while flowing through small capillaries. The RBC membrane can withstand a finite strain, beyond which it ruptures. The classical yield areal strain of 2-4% for RBCs is generally accepted for a quasi-static strain. It has been noted previously that this threshold strain may be much larger with shorter exposure duration. Here we employ an impulse-like forcing to quantify this yield strain of RBC membranes. In the experiments, RBCs are stretched within tens of microseconds by a strong shear flow generated from a laser-induced cavitation bubble. The deformation of the cells in the strongly confined geometry is captured with a high-speed camera and viability is successively monitored with fluorescence microscopy. We find that the probability of cell survival is strongly dependent on the maximum strain. Above a critical areal strain of ~40%, permanent membrane damage is observed for 50% of the cells. Interestingly, many of the cells do not rupture immediately and exhibit ghosting, but slowly obtain a round shape before they burst. This observation is explained with structural membrane damage leading to subnanometer-sized pores. The cells finally lyse from the colloidal osmotic pressure imbalance