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Abstract Background Bovine parvovirus (BPV) is an autonomous DNA virus with a smaller molecular size and subtle differences in its structural proteins, unlike other animal parvoviruses. More importantly, this virus has the potential to produce visible to silent economic catastrophes in the livestock business, despite receiving very little attention. Parvoviral virus-like particles (VLPs) as vaccines and as logistical platforms for vaccine deployment are well studied. However, no single experimental report on the role of VP1 in the assembly and stability of BPV-VLPs is available. Furthermore, the self-assembly, integrity and stability of the VLPs of recombinant BPV VP2 in comparison to VP1 VP2 Cap proteins using any expression method has not been studied previously. In this study, we experimentally evaluated the self-assembling ability with which BPV virus-like particles (VLPs) could be synthesized from a single structural protein (VP2) and by integrating both VP2 and VP1 amino acid sequences. Methods In silico and experimental cloning methods were carried out. His-tagged and without-His-tag VP2 and V1VP2-encoding amino acid sequences were cloned and inserted into pFastbacdual, and insect cell-generated recombinant protein was evaluated by SDS‒PAGE and western blot. Period of infectivity and expression level were determined by IFA. The integrity and stability of the BPV VLPs were evaluated by transmission electron microscopy. The secondary structure of the BPV VLPs from both VP2 and V1VP2 was analyzed by circular dichroism. Results Our findings show that VP2 alone was equally expressed and purified into detectable proteins, and the stability at different temperatures and pH values was not appreciably different between the two kinds of VLPs. Furthermore, BPV-VP2 VLPs were praised for their greater purity and integrity than BPV-VP1VP2 VLPs, as indicated by SDS‒PAGE. Therefore, our research demonstrates that the function of VP1 has no bearing on the stability or integrity of BPV-VLPs. Conclusions In summary, incredible physiochemically stable BPV VP2-derived VLPs have been found to be promising candidates for the development of multivalent vaccines and immunodiagnostic kits against enteric viruses and to carry heterogeneous epitopes for various economically important livestock diseases.

An experimental study of the intrinsic instabilities of H2/CO lean (φ = 0.4 to φ = 1.0) premixed flames at different hydrogen fractions ranging from 0% to 100% at elevated pressure and room temperature was performed in a constant volume vessel using a Schlieren system. The unstretched laminar burning velocities were compared with data from the previous literature and simulated results. The results indicate that excellent agreements are obtained. The cellular instabilities of syngas-air flames were discussed and critical flame radii were measured. When hydrogen fractions are above 50%, the flame tends to be more stable as the equivalence ratio increases; however, the instability increases for flames of lower hydrogen fractions. For the premixed syngas flame with hydrogen fractions greater than 50%, the decline in cellular instabilities induced by the increase in equivalence ratio can be attributed to a reduction of diffusive-thermal instabilities rather than increased hydrodynamic instabilities. For premixed syngas flames with hydrogen fractions lower than 50%, as the equivalence ratio increases, the cellular instabilities become more evident because the enhanced hydrodynamic instabilities become the dominant effect. For premixed syngas flames, the enhancement of cellular instabilities induced by the increase in hydrogen fraction is the result of both increasing diffusive-thermal and hydrodynamic instabilities.

Buoyant unstable behavior in initially spherical lean hydrogen-air premixed flames within a center-ignited combustion vessel have been studied experimentally under a wide range of pressures (including reduced, normal, and elevated pressures). The experimental observations show that the flame front of lean hydrogen-air premixed flames will not give rise to the phenomenon of cellular instability when the equivalence ratio has been reduced to a certain value, which is totally different from the traditional understanding of the instability characteristics of lean hydrogen premixed flames. Accompanied by the smoothened flame front, the propagation mode of lean hydrogen premixed flames transitions from initially spherical outwardly towards upwardly when the flames expand to certain sizes. To quantitatively investigate such buoyant instability behaviors, two parameters, “float rate (ψ)” and “critical flame radius (Rcr)”, have been proposed in the present article. The quantitative results demonstrate that the influences of initial pressure (Pint) on buoyant unstable behaviors are different. Based on the effects of variation of density difference and stretch rate on the flame front, the mechanism of such buoyant unstable behaviors has been explained by the competition between the stretch force and the results of gravity and buoyancy, and lean hydrogen premixed flames will display buoyant unstable behavior when the stretch effects on the flame front are weaker than the effects of gravity and buoyancy.

The atomization process of swirling sprays in gas turbine engines has been investigated using a LES-VOF model. With fine grid resolution, the ligament and droplet formation processes are captured in detail. The spray structure of fully developed sprays and the flow field are observed firstly. A central recirculation zone is generated inside the hollow cone section due to the entrainment of air by the liquid sheet and strong turbulent structures promote the breakup of ligaments. At the exit of injector nozzle, surface instability occurs due to disturbance factors. Axial and transverse mode instabilities produce a net-like structure ligament zone. Finally, the generation mechanism of the droplet is analyzed. It is found that the breakup mechanism of ligaments is located at the Raleigh capillary region. Axial symmetry oscillation occurs due to the surface tension force and the capillary waves pinch off from the neck of the ligaments. Secondary breakup and coalescence occur at the “droplet zone,” resulting in a wider distribution curve at the downstream area.

In the present investigation the explosion characteristics of 30% H2/70% CH4-blended fuels have been experimentally studied in different turbulent environments. Some important indicators about the explosion characteristics, including maximum explosion pressure (pmax), explosion duration (tc), maximum rate of pressure rise ((dp/dt)max), deflagration index (KG), and fast burn period (tb) have been studied. Furthermore, the influences of turbulent intensity associated with the equivalence ratio on explosion characteristics have been compressively analysed. The results indicated that, with the increase of turbulent intensity (u’rms), the value of pmax will be correspondingly raised while the equivalent ratio (φ) corresponding to the peak value of pmax gradually changes from stoichiometric to 1.2. Based upon the value of pmax in laminar condition, the growth extent of pmax monotonically rises to u’rms, but under a same u’rms the growth extent of pmax first declines and then rises with the increase of φ in the rage of 0.6 to 1.2. Under a laminar environment, the peak value of (dp/dt)max is attained at φ = 1.0; although such a conclusion is maintained in the studied range of turbulent intensity, the difference on the value of (dp/dt)max between φ = 1.0 and φ = 1.2 is obviously reduced with the increase of u’rms. Meanwhile, from the variation of KG, it could be found that turbulence can raise the hazardous potential of disaster. With the increase of u’rms, both the values of tc and tb reduce, the quota of tb in the explosion performs a similar regulation, but the detailed variation extent is also controlled by u’rms.

Compared with hydrazine propellant, energetic ammonium dinitramide (ADN)-based liquid monopropellant has the advantages of high specific impulse, nontoxic, pollution-free, and easy storage. Moreover, ADN-based space engine has been applied in orbit, indicating a good application prospect. However, due to the use of a catalyst and catalyst preheating, it is impossible to realize the long life time of a thruster and the cold start of an engine in emergency. In this study, a new resistive ignition method was used to ignite ADN-based liquid propellant without a catalyst, and the electric ignition characteristics of ADN-based liquid propellant in nitrous oxide environment were studied. The results show that the resistive ignition method could be used to ignite ADN-based liquid propellant in nitrous oxide environment. The increase in voltage affected the decrease of ignition delay time, but slightly affected the combustion duration. With the increase in ambient pressure, the ignition duration of droplet gradually decreased. Voltage and ambient pressure slightly affected the energy consumption in nitrous oxide environment. Moreover, because the ignition delay time was much longer than the combustion duration, the ignition energy accounted for a high proportion of the energy consumed in the entire reaction process. [ABSTRACT FROM AUTHOR]