Influence of parameters on flame expansion in a high-speed flow : experimental and numerical study

Flameholder-stabilized flames are conventional and also commonly used in propulsion and various power generation fields to maintain combustion process. The characteristics of flame expansion were obtained with various blockage ratios, which were observed to be highly sensitive to inlet conditions such as temperatures and velocities. Experiments and simulations combined methodology was performed; also the approach adopted on image processing was calculated automatically through a program written in MATLAB. It was found that the change of flame expansion angle indicated increasing fuel supply could contribute to the growth of flame expansion angle in lean premixed combustion. Besides, the influence of inlet velocity on flame expansion angle varies with different blockage ratios, i.e. under a small blockage ratio (BR ¼ 0.1), flame expansion angle declined with the increase of velocity; however, under a larger blockage ratio (BR ¼ 0.2 or 0.3), flame expansion angle increased firstly and then decreased with the increasing velocity. Likewise, flame expansion angle increased firstly and then decreased with the increasing temperature under BR ¼ 0.2/0.3. In addition, flame expansion angle was almost the same for BR ¼ 0.2 and BR ¼ 0.3 at a higher temperature (900 K), and both of which were bigger than BR ¼ 0.1. Overall, BR ¼ 0.2 is the best for increasing flame expansion angle and reducing total pressure loss. The influence of velocity and temperature on flame expansion angle found from this research are vital for engineering practice and for developing a further image processing method to measure flame boundary

Perfect codes in 2-valent Cayley digraphs on abelian groups

For a digraph $\Gamma$, a subset $C$ of $V(\Gamma)$ is a perfect code if $C$ is a dominating set such that every vertex of $\Gamma$ is dominated by exactly one vertex in $C$. In this paper, we classify strongly connected 2-valent Cayley digraphs on abelian groups admitting a perfect code, and determine completely all perfect codes of such digraphs

Molecular basis for heat desensitization of TRPV1 ion channels.

The transient receptor potential vanilloid 1 (TRPV1) ion channel is a prototypical molecular sensor for noxious heat in mammals. Its role in sustained heat response remains poorly understood, because rapid heat-induced desensitization (Dh) follows tightly heat-induced activation (Ah). To understand the physiological role and structural basis of Dh, we carried out a comparative study of TRPV1 channels in mouse (mV1) and those in platypus (pV1), which naturally lacks Dh. Here we show that a temperature-sensitive interaction between the N- and C-terminal domains of mV1 but not pV1 drives a conformational rearrangement in the pore leading to Dh. We further show that knock-in mice expressing pV1 sensed heat normally but suffered scald damages in a hot environment. Our findings suggest that Dh evolved late during evolution as a protective mechanism and a delicate balance between Ah and Dh is crucial for mammals to sense and respond to noxious heat

Microwave Photonic Imaging Radar with a Millimeter-level Resolution

Microwave photonic radars enable fast or even real-time high-resolution imaging thanks to its broad bandwidth. Nevertheless, the frequency range of the radars usually overlaps with other existed radio-frequency (RF) applications, and only a centimeter-level imaging resolution has been reported, making them insufficient for civilian applications. Here, we propose a microwave photonic imaging radar with a millimeter-level resolution by introducing a frequency-stepped chirp signal based on an optical frequency shifting loop. As compared with the conventional linear-frequency modulated (LFM) signal, the frequency-stepped chirp signal can bring the system excellent capability of anti-interference. In an experiment, a frequency-stepped chirp signal with a total bandwidth of 18.2 GHz (16.9 to 35.1 GHz) is generated. Postprocessing the radar echo, radar imaging with a two-dimensional imaging resolution of ~8.5 mm$\times$~8.3 mm is achieved. An auto-regressive algorithm is used to reconstruct the disturbed signal when a frequency interference exists, and the high-resolution imaging is sustained

Integrated metabolomics and metagenomics analysis of plasma and urine identified microbial metabolites associated with coronary heart disease

Coronary heart disease (CHD) is top risk factor for health in modern society, causing high mortality rate each year. However, there is no reliable way for early diagnosis and prevention of CHD so far. So study the mechanism of CHD and development of novel biomarkers is urgently needed. In this study, metabolomics and metagenomics technology are applied to discover new biomarkers from plasma and urine of 59 CHD patients and 43 healthy controls and trace their origin. We identify GlcNAc-6-P which has good diagnostic capability and can be used as potential biomarkers for CHD, together with mannitol and 15 plasma cholines. These identified metabolites show significant correlations with clinical biochemical indexes. Meanwhile, GlcNAc-6-P and mannitol are potential metabolites originated from intestinal microbiota. Association analysis on species and function levels between intestinal microbes and metabolites suggest a close correlation between Clostridium sp. HGF2 and GlcNAc-6-P, Clostridium sp. HGF2, Streptococcus sp. M143, Streptococcus sp. M334 and mannitol. These suggest the metabolic abnormality is significant and gut microbiota dysbiosis happens in CHD patients

The DNA Recognition Motif of GapR Has an Intrinsic DNA Binding Preference towards AT-rich DNA

The nucleoid-associated protein GapR found in Caulobacter crescentus is crucial for DNA replication, transcription, and cell division. Associated with overtwisted DNA in front of replication forks and the 3′ end of highly-expressed genes, GapR can stimulate gyrase and topo IV to relax (+) supercoils, thus facilitating the movement of the replication and transcription machines. GapR forms a dimer-of-dimers structure in solution that can exist in either an open or a closed conformation. It initially binds DNA through the open conformation and then undergoes structural rearrangement to form a closed tetramer, with DNA wrapped in the central channel. Here, we show that the DNA binding domain of GapR (residues 1–72, GapRΔC17) exists as a dimer in solution and adopts the same fold as the two dimer units in the full-length tetrameric protein. It binds DNA at the minor groove and reads the spatial distribution of DNA phosphate groups through a lysine/arginine network, with a preference towards AT-rich overtwisted DNA. These findings indicate that the dimer unit of GapR has an intrinsic DNA binding preference. Thus, at the initial binding step, the open tetramer of GapR with two relatively independent dimer units can be more efficiently recruited to overtwisted regions

characterizationofthermalshockcracksinceramicbars

Experimental analysis of the cracking in the ceramics subsequent to water quenching have been conducted to clarify the uncertainties of cracking in the ceramics when subjected to thermal shock. The results here indicate that at the critical point of quench temperature, the crack density and the depth reached the minimum and the maximum limits, respectively. On increase of the quench temperature, the crack density increased rapidly before reaching its saturation point, while the crack depth initially decreased rapidly and then increased gradually before reaching its saturation point

An experimental study on heat transfer performance of a pulsating heat pipe radiator for CPU heat dissipation

To meet the requirement of electronic heat dissipation with high heat flux, a kind of heat dissipation device using pulsating heat pipe (PHP) for CPU heat dissipation was put forward. The heat transfer performance and surface temperature distribution of the radiator are analyzed by analyzing the wall temperature distribution and the distribution of the evaporator and condenser of the PHP. The experimental results show that the change of wind speed has obvious influence on the operation of the PHP radiator. The surface temperature distribution of the PHP radiator is very uniform, which is especially beneficial for CPU cooling. The heat transfer performance of the PHP is better, and the minimum average thermal resistance is 0.19 k/W. In addition, there is no drying phenomenon when the temperature reaches about 120 °C, which indicates that the pulsating heat pipe has a very high heat transfer limit

The urban-rural disparities and factors associated with the utilization of public health services among diabetes patients in China

Abstract Background Basic public health services for diabetes play an essential role in controlling glycemia in patients with diabetes. This study was conducted to understand the urban-rural disparities in the utilization of basic public health services for people with diabetes and the factors influencing them. Methods The data were obtained from the 2018 China Health and Retirement Longitudinal Study (CHARLS) with 2976 diabetes patients. Chi-square tests were used to examine the disparities in the utilization of diabetes physical examination and health education between urban and rural areas. Logistic regression was performed to explore the factors associated with the utilization of diabetes public health services. Results Among all participants, 8.4% used diabetes physical examination in the past year, and 28.4% used diabetes health education services. A significant association with age (OR = 0.64, 95% CI:0.49–0.85; P < 0.05) was found between patients’ use of health education services. Compared with diabetes patients living in an urban area, diabetes patients living in a rural area used less diabetes health education. (χ2= 92.39, P < 0.05). Patients’ self-reported health status (OR = 2.04, CI:1.24–3.35; P < 0.05) and the use of glucose control (OR = 9.33, CI:6.61–13.16; P < 0.05) were significantly positively associated with the utilization of diabetes physical examination. Patients with higher education levels were more likely to use various kinds of health education services than their peers with lower education levels (OR = 1.64, CI:1.21–2.22; P < 0.05). Conclusion Overall, urban-rural disparities in the utilization of public health services existed. Vulnerable with diabetes, such as those in rural areas, are less available to use diabetes public health services. Providing convenient health service infrastructure facilitates the utilization of basic public health services for diabetes in older patients with diabetes, especially in rural areas