Three-dimensional simulation of detonation initiation and propagation in supersonic combustible mixtures

Detonation initiation and propagation in supersonic combustible mixtures using a hot jet have been investigated in three-dimensional numerical simulations with the detailed reaction model on Tianhe-2 system. Results indicate that the side walls can help realize the triple lines collisions and triple lines reflections, which play an important role in the detonation initiation. There should exists a critical width between the front and back sides of the three-dimensional channel for the successful initiation, which is totally different from that of two-dimensional cases. When the width exceeds the critical value, there will be not the effective reflections of the bow shock surface on the side walls, hence resulting in the failure of detonation initiation. For the detonation propagation, none of the standard detonation modes(rectangular mode, diagonal mode and spinning mode) is observed in the three-dimensional case. The initiated detonation is actually in an overdriven state because of the presence of the hot jet in the supersonic flow field, thus resulting in more complex detonation fronts than that in the CJ detonation. Because of both directions of three-dimensional detonation development than that of the two-dimensional case where the transverse waves propagation and the collisions of triple points can be realized only in one direction, the detonation fronts in three-dimensional simulation shows significantly larger irregularities and variations

Recent Advances in the Application of Microfluidic Technology in Food Science

Microfluidics, an emerging interdisciplinary technology, shows great potential in food research due to its precise fluid control in microchannels. Compared with conventional methods, it offers advantages such as higher throughput, faster speed, cheaper cost, and more convenient, and outperforms in detecting foodborne pathogens, pesticide/veterinary residues and allergens and in preparing emulsions. Microfluidic technology mainly includes continuous flow microfluidics (CMF), droplet microfluidics (DMF), and spinning microfluidics (SMF), among which CMF and DMF are applied most extensively. This article summarizes the latest advances in the application of CMF for food safety testing, composition analysis and smart packaging, and the application of DMF for targeted enzyme/strain screening and emulsion preparation for the encapsulation and delivery of bioactives. While some technologies are still in the laboratory stage, ongoing interdisciplinary innovations will enhance food safety, quality control and nutrition, thus driving transformative solutions for the food industry

Effects of Vacuum and Shaking on Flavor Substances of Longnan White Tea

In this study, ultra-high performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UPLC-TQ-MS/MS) and full 2D gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS) were used to analyze the phenolic compounds, amino acids, purine alkaloids, and volatile constituents in Longnan white tea, and multivariate statistical analyses such as principal component analysis (PCA), were used to systematically evaluate the effects of vacuum combined with shaking on the biochemical and volatile constituents of Longnan white tea. The results showed that the combined treatment significantly increased the content of γ-aminobutyric acid in white tea to 1.54 mg/g, but decreased the contents of phenolics, catechins and caffeine differently, the large decrease being in epigallocatechin gallate (EGCG). Compared with the control group, vacuum treatment alone and followed by shaking decreased the EGCG content by 54.95% and 75.40%, respectively. Sensory evaluation showed that the three tea samples prepared by different processing methods each had their own aroma and taste characteristics. Compared with the control and vacuum treatment groups, white tea prepared by vacuum plus shaking showed a stronger and purer aroma with sweet and fruity notes as well as a slight floral note, and tasted sweet and mellow. Further analysis showed that vacuum treatment increased the number of volatile components, and compared with single vacuum treatment, the combined treatment increased the content of alcohols such as nerolidol, and decreased the content of unpleasant odors such as difurfuryldisulfide. Combining the results of odor activity value (OAV) and aroma character impact (ACI), we found that (E)-3,7-dimethyl-2,6-octadienal, nerolidol, and isoamyl aldehyde were the key aroma components in white tea prepared by sequential vacuum and shaking treatment, contributing to its obvious fruity aroma. Furthermore, this tea had a weaker irritating odor and tasted softer compared with that obtained from single vacuum treatment. This study provides technical support for the development of γ-aminobutyric acid-rich white tea with high aroma quality, which will promote the high-value development and utilization of Longnan white tea

Numerical simulation of detonation initiation and propagation in supersonic combustible mixtures with non-uniform species

Adaptive high-resolution simulations of gaseous detonation using a hot jet initiation were conducted in supersonic combustible mixtures with spatially non-uniform species. The two-dimensional Euler equations were used as the governing equations in combination with a detailed hydrogen-oxygen reaction model. Three different groups of mixtures, which represent various degrees of chemical reactivity, were investigated. The results show that when the mixtures generally have a high degree of chemical reactivity, detonation initiation can eventually be realized successfully by Mach reflection as well as the DDT mechanism, independent of the spatial distribution of the mixture in the channel. A recurring four-stage sequence of detonation initiation, detonation attenuation, initiation failure and detonation reinitiation can be identified. When the mixtures generally have an intermediate degree of chemical reactivity, detonation combustion can be fully realized in the channel, where different degrees of overdrive are found in the upper lower half. After the shutdown of the hot jet, the overdriven detonation attenuates gradually and eventually a slightly overdriven detonation and a slightly underdriven detonation are generated, which can be regarded as a new stable state of propagation. However, whether a detonation can be initiated successfully is determined by the spatial mixture distribution. In mixtures with low degree of chemical reactivity, detonation initiation can generally not be realized. In this case, successful realization of detonation initiation should be realizable by using of a stronger hot jet

A general-purpose signal processing algorithm for biological profiles using only first-order derivative information

Abstract Background Automatic signal-feature extraction algorithms are crucial for profile processing in bioinformatics. Both baseline drift and noise seriously affect the position and peak area of signals. An efficient algorithm named the derivative passing accumulation (DPA) method for simultaneous baseline correction and signal extraction is presented in this article. It is an efficient method using only the first-order derivatives which are obtained through taking the simple differences. Results We developed a new signal feature extracting procedure. The vector representing the discrete first-order derivative was divided into negative and positive parts and then accumulated to build a signal descriptor. The signals and background fluctuations are easily separated according to this descriptor via thresholding. In addition, the signal peaks are simultaneously located by checking the corresponding intervals in the descriptor. Therefore, the eternal issues of parsing the 1-dimensional output of detectors in biological instruments are solved together. Thereby, the baseline is corrected, and the signal peaks are extracted. Conclusions We have introduced a new method for signal peak picking, where baseline computation and peak identification are performed jointly. The testing results of both authentic and artificially synthesized data illustrate that the new method is powerful, and it could be a better choice for practical processing. </jats:sec

Potential conformational heterogeneity of p53 bound to S100B(ββ)

Citation: McDowell, C., Chen, J., & Chen, J. (2013). Potential conformational heterogeneity of p53 bound to S100B(ββ). Journal of Molecular Biology, 425(6), 999- 1010.The negative regulatory domain (NRD) of the p53 tumor suppressor is intrinsically disordered. It contains several post-translational modification (PTM) sites that are important for regulation of p53 activity. Calcium-dependent binding of dimeric S100B(ββ) to p53-NRD blocks access to these PTM sites and disrupts the p53 tetramer to inhibit p53 activation. Previous NMR structural studies have suggested that p53-NRD folds into a stable helix upon binding to S100B(ββ). Intriguingly, despite the well-converged and stably folded nature of the NMR structure ensemble, experimentally resolved intermolecular NOEs are extremely weak; most have 5−6 Å upper bounds, and mainly involve the C-terminal segment of p53-NRD. Such a systematic lack of strong intermolecular NOEs could suggest that the p53/S100B(ββ) interface is more dynamic than currently believed. Indeed, extensive atomistic simulations in explicit solvent (with 1.0 μs total effective sampling) revealed large heterogeneity in the S100B(ββ)-bound conformation of p53-NRD. Helix unwinding at the C-terminus allows key hydrophobic residues (Leu383 and Phe385) to make more extensive intermolecular contacts, whereas the highly helical N-terminus displays substantial flexibility in packing with S100B(ββ). Importantly, the predicted heterogeneous ensemble as a whole is highly consistent with experimental intermolecular NOEs, although many conformational sub-states coexist and individual sub-states satisfy only subsets of the NOE restraints. Furthermore, the simulated ensemble provides similar shielding of key PTM sites to support p53 inhibition. This study not only provides new insights into the structural basis of the p53/S100B(ββ) recognition, but also highlights the importance of recognizing dynamic complexes in structural studies of IDP interactions

Adaptive mesh refinement based simulations of three-dimensional detonation combustion in supersonic combustible mixtures with a detailed reaction model

Detonation combustion initiated with a hot jet in supersonic H2-O2-Ar mixtures are investigated by large-scale three-dimensional (3D) simulations in Tianhe-2 computing system with adaptive mesh refinement method. The reactive Euler equations are utilized as the governing equations with a detailed reaction model where the molar ratio of the combustible mixture is 2:1:7 under the condition of pressure 10kPa and temperature 298K. Results show that the Mach stem surface which is formed after the shock surface reflection on the upper wall is actually a local overdriven detonation. The side walls in 3D simulations can play an important role in detonation initiation in supersonic combustible mixtures, because they can help realize triple lines collisions and reflections during the initiation process. The width of the channel has an important influence on the strength of side-wall reflections, and under certain condition there might exist a critical width between the front and back sides of the channel for the successful initiation. Both the two-dimensional (2D) and the 3D detonations are overdriven and have a constant but different overdrive after their complete initiations. Although the overdrive degree of the 3D detonation is smaller than that of the 2D case, more complex and irregular detonation fronts can be observed in the 3D case compared with the 2D detonation, which is likely because of the propagation of transverse waves and collisions of triple lines in multi-directions in 3D detonations. After the hot jet is shut down, the newly formed 2D Chapman-Jouguet (CJ) detonation has almost the same characteristic parameters with the corresponding 3D case, indicating that the 2D instabilities can be perfectly preserved in 3D simulations. However, the slapping wave reflections on the side walls in the 3D detonation result in the second oscillation along with the main one, which presents stronger instabilities compared with the 2D case. The inherent stronger 3D instabilities is also verified through the quantitative comparison between the 2D and 3D cases where the 3D result always shows stronger fluctuations than the 2D case

Dissecting the regulation and function of ATP at the single-cell level.

Regulation of cellular ATP level is critical for diverse biological processes and may be defective in diseases such as cancer and mitochondrial disorders. While mitochondria play critical roles in ATP level regulation, we still lack a systematic and quantitative picture of how individual mitochondrial-related genes contribute to cellular ATP level and how dysregulated ATP levels may affect downstream cellular processes. Advances in genetically encoded ATP biosensors have provided new opportunities for addressing these issues. ATP biosensors allow researchers to quantify the changes of ATP levels in real time at the single-cell level and characterize corresponding effects at the cellular, tissue, and organismal level. Along this direction, several recent single-cell studies using ATP biosensors, including the work by Mendelsohn and colleagues, have started to uncover the principles for how genetic and nongenetic parameters may modulate ATP levels to affect cellular functions and human health

MOESM1 of A general-purpose signal processing algorithm for biological profiles using only first-order derivative information

Additional file 1. Testing data of the mass spectroscopy, infrared spectroscopy and energy curve of audio