Experimental and simulation studies on similitude design method for shock responses of beam-plate coupled structure

The similitude theory helps to understand the physical behaviors of large structures through scaled models. Several papers have studied the similitude of shock issues. However, the dynamic similitude for shock responses of coupled structures is rarely incorporated in open studies. In this paper, scaling laws are derived for the shock responses and spectra of coupled structures. In the presented scaling laws, the geometric distortion and energy loss are considered. The ability of the proposed scaling laws is demonstrated in the simulation and experimental cases. In both cases, the similitude prediction for the prototype's time-domain waveform and spectrum is conducted with the scaled model and scaling laws. The simulation and experimental cases indicate that the predicted shock responses and spectra agree well with those of the prototype, which verifies the proposed scaling laws for predicting shock responses.

Shock-induced energy localization and reaction growth considering chemical-inclusions effects for crystalline explosives

Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear.Herein shock-induced energy localization,overall physical responses,and reactions in a-1,3,5-trinitro-1,3,5-triazinane(a-RDX)crystal entrained various chemical inclusions were investigated by the multi-scale shock technique implemented in the reactive molecular dynamics method.Results indicated that energy localization and shock reaction were affected by the intrinsic factors within chemical inclusions,i.e.,phase states,chemical compositions,and concentrations.The atomic origin of chemical-inclusions effects on energy localization is dependent on the dynamics mechanism of interfacial molecules with free space volume,which includes homogeneous intermolecular compression,interfacial impact and shear,and void collapse and jet.As introducing various chemical inclusions,the initiation of those dynamics mechanisms triggers diverse decay rates of bulk RDX molecules and hereby impacts on growth speeds of final reactions.Adding chemical inclusions can reduce the effectiveness of the void during the shock impacting.Under the shockwave velocity of 9 km/s,the parent RDX decay rate in RDX entrained amorphous carbon decreases the most and is about one fourth of that in RDX with a vacuum void,and solid HMX and TATB inclusions are more reactive than amorphous carbon but less reactive than dry air or acetone inclusions.The lessdense shocking system denotes the greater increases in local temperature and stress,the faster energy liberation,and the earlier final reaction into equilibrium,revealing more pronounced responses to the present intense shockwave.The quantitative models associated with the relative system density(RD_(sys))were proposed for indicating energy-localization mechanisms and evaluating initiation safety in the shocked crystalline explosive.RD_(sys)is defined by the density ratio of defective RDX to perfect crystal after dynamics relaxation and reveals the global density characteristic in shocked systems filled with chemical inclusions.When RD_(sys)is below 0.9,local hydrodynamic jet initiated by void collapse dominates upon energy localization instead of interfacial impact.This study sheds light on novel insights for understanding the shock chemistry and physical-based atomic origin in crystalline explosives considering chemical-inclusions effects.

Numerical study on the shock responses of submunition drop on various mediums

The shock responses of submunition drop on various ground-mediums are modeled and investigated by numerical simulation in this paper. Submunition impacts on concrete surface, gravel ground or sand with various drop velocities, different drop angles and attack angles are calculated in a finite element program. The loads and dynamic responses of submunition are analyzed, curves of various drop velocities, drop angles and attack angles related to peak overload are calculated and law of interaction time on different ground mediums is obtained.

Vibration Response Characteristics against the Radial and Axial Shocks on Small Size Hard Disk Drive Spindle Supported by Oil Film Bearings

This paper describes the experimental study on shock response of FDB （fluid dynamic bearing） spindle for HDDs （hard disk drives）. The FDBs are widely used as rotating shaft support elements for HDD spindle motors. Recently, the opportunity for the HDD spindle motors exposed to external vibration has been increasing because the HDDs are used for various information related equipment such as mobile PCs （personal computers）, video cameras, car navigation systems and so on. Hence, the rotating shaft has a possibility to come in contact with the bearing by external shocks and it causes wear or seizure to the bearing surface. To avoid the problem, it is extremely important to know how the spindle moves against the large shock on HDDs experimentally. However, as far as the authors know, there are few experimental studies treating the shock response of HDD spindles. In this paper, firstly, we propose a new test rig and experimental method for shock response of FDB spindles. Then the shock tests against the radial and axial disturbance on FDB spindle for 2.5＂ HDD are conducted. Finally, the experimental results of shock response waveforms and maximum displacement of disk are shown.

Subversion of cellular stress responses by poxviruses

Cellular stress responses are powerful mechanisms that prevent and cope with the accumulation of macromolecular damage in the cells and also boost host defenses against pathogens. Cells can initiate either protective or destructive stress responses depending, to a large extent, on the nature and duration of the stressing stimulus as well as the cell type. The productive replication of a virus within a given cell places inordinate stress on the metabolism machinery of the host and, to assure the continuity of its replication, many viruses have developed ways to modulate the cell stress responses. Poxviruses are among the viruses that have evolved a large number of strategies to manipulate host stress responses in order to control cell fate and enhance their replicative success. Remarkably, nearly every step of the stress responses that is mounted during infection can be targeted by virally encoded functions. The fine-tuned interactions between poxviruses and the host stress responses has aided virologists to understand specific aspects of viral replication; has helped cell biologists to evaluate the role of stress signaling in the uninfected cell; and has tipped immunologists on how these signals contribute to alert the cells against pathogen invasionand boost subsequent immune responses. This review discusses the diverse strategies that poxviruses use to subvert host cell stress responses.

Modal analysis and pulse response of mobile hard disk head actuator arm assembly

Head actuator arm assembly (HAA) is the most important mechanical component of a mobile hard disk drive (HDD) and its shock dynamic response is a principal index of vibration resistance. In this paper,a finite element (FE) model is firstly developed in ANSYS of 2.5 inch (1 inch=25.4 mm) mobile hard disk. This model includes actuator arm,voice coil motor (VCM) and pivot bearing. The various step modal of HAA is calculated by FE model. Then the actuator arm vibration behavior is simulated with LS-DYNA procedure. The influence of pulse waveform,pulse amplitude and pulse width on the shock response of the relative displacement of the head actuator arm assembly is studied.

SOME PROBLEMS ON JUMP CONDITIONS OF SHOCK WAVES IN 3-DIMENSIONAL SOLIDS

Based on the general conservation laws in continuum mechanics, the Eulerian and Lagrangian descriptions of the jump conditions of shock waves in 3-dimensional solids were presented respectively. The implication of the jump conditions and their relations between each other, particularly the relation between the mass conservation and the displacement continuity, were discussed. Meanwhile the shock wave response curves in 3- dimensional solids, i.e. the Hugoniot curves were analysed, which provide the foundation for studying the coupling effects of shock waves in 3-dimensional solids.

Zinc alleviates the heat stress of primary cultured hepatocytes of broiler embryos via enhancing the antioxidant ability and attenuating the heat shock responses

Zinc(Zn)has been shown to attenuate the adverse effects of heat stress on broilers,but the mechanisms involving this process remain unclear.We aimed to investigate possible protective mechanisms of Zn on primary cultured hepatocytes of broiler embryos subjected to heat stress.Three experiments were conducted.In Exp.1,hepatocytes were treated with 0,50,100,200,or 400μmol/L added Zn as inorganic Zn sulfate(iZn)for 12,24 or 48 h.In Exp.2,cells were exposed to 40℃(a normal temperature[NT])and 44℃(a high temperature[HT])for 1,2,4,6,or 8 h.In Exp.3,cells were preincubated with 0 or 50μmol/L Zn as iZn or organic Zn lysine chelate(oZn)for 8 h under NT,and then incubated with the same Zn treatments under NT or HT for 4 or 6 h.The biomarkers of antioxidative status and heat stress in cells were measured.The results in Exp.1 indicated that 50μmol/L Zn and 12 h incubation were the optimal conditions for increasing antioxidant ability of hepatocytes.In Exp.2,the 4 or 6 h incubation under HT was effective in inducing heat shock responses of hepatocytes.In Exp.3,HT elevated(P<0.01)malondialdehyde content and expressions of heat shock protein 70(HSP70)mRNA and protein,as well as HSP90 mRNA.However,Zn supplementation increased(P<0.05)copper zinc superoxide dismutase(CuZnSOD)activity and metallothionein mRNA expression,and effectively decreased(P<0.05)the ex-pressions of HSP70 mRNA and protein,as well as HSP90 mRNA.Furthermore,oZn was more effective(P<0.05)than iZn in enhancing CuZnSOD activity of hepatocytes under HT.It was concluded that Zn(especially oZn)could alleviate heat stress of broiler hepatocytes via enhancing their antioxidant ability and attenuating heat shock responses.

Shock response mitigation of a large-scale structure by modal energy redistribution facilitated by a strongly nonlinear absorber

A lightweight geometrically nonlinear attachment,the strongly nonlinear absorber(SNA),is adopted to suppress the shock response of a linear,large-scale nine-story structure.The role of the SNA is not only to dissipate but also to redistribute the shock energy among the modes of the structure.In this study,single-and two-degree-of-freedom(SDOF and Two-DOF)SNAs are investigated.The quantitative results for shock energy redistribution indicate that with strong geometric nonlinearity,one can achieve low-to-high frequency nonlinear targeted energy transfer in this structure.Specifically,the percentages of shock energy dissipated by higher structural modes for the cases of locked SNA,SDOF SNA,and Two-DOF SNA are 0.08%,0.43%,and 30.04%,respectively.The results indicate that the Two-DOF SNA is capable of rapidly scattering far more energy to much higher frequencies than the SDOF SNA,thereby more quickly reducing the shock response of the primary structure.The robustness of the performance of the SNAs is also studied for varying shock intensities,where the Two-DOF SNA is shown to be significantly more robust at scattering shock energy from low to high frequencies.Last,an effective damping measure is employed to verify and quantify the redistribution of the modal energies in the primary structure.The potential applications of this new passive shock mitigation method are discussed.

Induction of Antioxidant and Heat Shock Protein Responses During Torpor in the Gray Mouse Lemur, Microcebus murinus

A natural tolerance of various environmental stresses is typically supported by various cytoprotective mechanisms that protect macromolecules and promote extended viability. Among these are antioxidant defenses that help to limit damage from reactive oxygen species and chaperones that help to minimize protein misfolding or unfolding under stress conditions. To understand the molecular mechanisms that act to protect cells during primate torpor, the present study characterizes antioxidant and heat shock protein（HSP） responses in various organs of control（aroused）and torpid gray mouse lemurs, Microcebus murinus. Protein expression of HSP70 and HSP90 a was elevated to 1.26 and 1.49 fold, respectively, in brown adipose tissue during torpor as compared with control animals, whereas HSP60 in liver of torpid animals was 1.15 fold of that in control（P 〈 0.05）. Among antioxidant enzymes, protein levels of thioredoxin 1 were elevated to 2.19 fold in white adipose tissue during torpor, whereas Cu–Zn superoxide dismutase 1 levels rose to 1.1 fold in skeletal muscle（P 〈 0.05）. Additionally, total antioxidant capacity was increased to 1.6 fold in liver during torpor（P 〈 0.05）, while remaining unchanged in the five other tissues. Overall, our data suggest that antioxidant and HSP responses are modified in a tissue-specific manner during daily torpor in gray mouse lemurs. Furthermore, our data also show that cytoprotective strategies employed during primate torpor are distinct from the strategies in rodent hibernation as reported in previous studies.

Shock Characteristics and Protective Design of Equipment During Spacecraft Docking Process

The shock loads generated by spacecraft during docking can cause functional failure and structural damage to aerospace electronic equipment and even lead to catastrophic flight accidents.There is currently a lack of systematic and comprehensive research on the shock environment of spacecraft electronic equipment due to the diversity and complexity of the shock environment.In this paper,the validity of the finite element model is verified based on the sinusoidal vibration experiment results of the spacecraft reentry capsule.The method of shock dynamic response analysis is used to obtain the shock environment of electronic equipment under different shock loads.The shock response spectrum is used to describe the shock environment of aerospace electronic equipment.The results show that the resonance frequency error between the sinusoidal vibration experiment and the model is less than 4.06%.When the docking relative speed of the reentry capsule is 2 m/s,the shock response spectrum values of one of the equipment are 30 m^(2)/s,0.67 m/s,and 0.059 m,respectively.The wire rope spring on the mating surface can provide vibration isolation and shock resistance.An increase in spring damping coefficient results in a decrease in the amplitude and time of the vibration generated.An increase in spring stiffness reduces the input of shock load within a certain range.These research results can provide guidance for the design and evaluation of shock environmental adaptability of aerospace electronic equipment.

Increased expression of heat shock protein 70 and heat shock factor 1 in chronic dermal ulcer tissues treated with laser-aided therapy

Background Chronic dermal ulcers are also referred to as refractory ulcers. This study was conducted to elucidate the therapeutic effect of laser on chronic dermal ulcers and the induced expression of heat shock factor 1 （HSF1） and heat shock protein 70 （HSP70） in wound tissues. Methods Sixty patients with 84 chronic dermal ulcers were randomly divided into traditional therapy and laser therapy groups. Laser treatment was performed in addition to traditional therapy in the laser therapy group. The treatment efficacy was evaluated after three weeks. Five tissue sections of healing wounds were randomly collected along with five normal skin sections as controls. HSP70-positive cells from HSP70 immunohistochemical staining were counted and the gray scale of positive cells was measured for statistical analysis. Reverse transcription-polymerase chain reaction （RT-PCR） and Western blotting were performed to determine the mRNA and protein expressions of HSF1 and HSP70. Results The cure rate of the wounds and the total efficacy in the laser therapy group were significantly higher than those in the traditional therapy group （P 〈0.05, P 〈0.01, respectively）. Immunohistochemical staining revealed that the HSP70-positive cell count was significantly higher in laser therapy group than those in the traditional therapy group and controls （P 〈0.01）, and the gray scale of the cell signal was obviously lower than traditional therapy group and controls （P 〈0.05）. By contrast, the traditional therapy group and the control group were not significantly different. The RNA levels of HSF1 and HSP70 were higher in the laser therapy group by RT-PCR, but very low in normal skin and the traditional therapy group. The analysis on the gray scale of the Western blot bands indicated that the expression of HSF1 and HSP70 in the laser therapy group was significantly higher than in the traditional therapy group and the control group （P 〈0.01）, and the expression in the traditional therapy group was also higher than in the control group （P 〈0.05）. Conclusion Laser-aided therapy of chronic dermal ulcers plays a facilitating role in healing due to the mechanism of laser-activated endogenous heat shock protection in cells in wound surfaces.

Characterization of three transcripts encoding small heat shock proteins expressed in the codling moth, Cydia pomonella （Lepidoptera： Tortricidae）

Codling moth is a major pest of apples and pears worldwide. Increasing knowledge of how this insect responds to environmental stress will improve field and postharvest control measures used against it. The small heat shock proteins （sHsps） play a maj or role in cellular responses to environmental stressors. A degenerate oligonucleotide primer, designed against the conserved α-crystallin domain, was used in 3＇ rapid amplification of complementary DNA （cDNA） ends reactions to amplify transcripts encoding sHsps expressed in the codling moth cell line, Cp169, subjected to heat shock. Three full-length cDNAs were cloned from Cp169 cells that contained open reading frames encoding sHsps. The cDNA for CpHsp 19.8 was 795 bp encoding 177 amino acids. The cDNA for CpHsp 19.9 was 749 bp encoding 175 amino acids. The cDNA for CpHsp22.2 was 737 bp encoding 192 amino acids. Analysis of the protein sequences of the three CpHsps indicated the presence of 83 amino acids with homology to the α-crystallin domain. For each of the CpHsps, the α-crystallin domain was surrounded by divergent N- and C-terminal regions, consistent with the conserved structural features of sHsps. Real-time polymerase chain reaction, used to determine the expression patterns of each of the sHsps in different developmental stages of codling moth revealed the presence of transcripts in all stages tested. Consistent with characteristics of other sHsps, expression of CpHsp transcripts were greatly enhanced when insects were subjected to heat shock. The results of this research can be used as a guide to study the roles of sHsps in codling moth control using various post-harvest treatments.

Ribosome Profiling Reveals Genome-wide Cellular Translational Regulation upon Heat Stress in Escherichia coli

Heat shock response is a classical stress-induced regulatory system in bacteria, character- ized by extensive transcriptional reprogramming. To compare the impact of heat stress on the tran- scriptome and translatome in Escherich＆ coli, we conducted ribosome profiling in parallel with RNA-Seq to investigate the alterations in transcription and translation efficiency when E. coli cells were exposed to a mild heat stress （from 30 ~C to 45 ~C）. While general changes in ribosome foot- prints correlate with the changes of mRNA transcripts upon heat stress, a number of genes show differential changes at the transcription and translation levels. Translation efficiency of a few genes that are related to environment stimulus response is up-regulated, and in contrast, some genes func- tioning in mRNA translation and amino acid biosynthesis are down-regulated at the translation level in response to heat stress. Moreover, our ribosome occupancy data suggest that in generalribosomes accumulate remarkably in the starting regions of ORFs upon heat stress. This study pro- vides additional insights into bacterial gene expression in response to heat stress, and suggests the presence of stress-induced but yet-to-be characterized cellular regulatory mechanisms of gene expression at translation level.

Influence of multiple structural parameters on buffer performance of a thin-walled circular tube based on the coupling modeling technique

Pyrotechnic devices are widely used in the aerospace and defense industries.However,these devices generate high-frequency and high-amplitude shock responses during their use,compromising safe operation of the system.In this paper,the application of a thin-walled circular tube as the energy absorber in pyrotechnic devices is investigated.To accurately predict the shock load and the buffer performance of the thin-walled circular tube,a coupled model connecting the energetic material combustion and finite element simulation is established.The validity of the coupled model is verified by comparing with experiments.Then,the collapse mechanism of the thin-walled circular tube is studied,and the influence of multiple structural parameters on its buffer performance is analyzed.The results show that the thin-walled circular tube effectively reduces the shock overload.The maximum shock overload reduced from 572612g to 11204g in the studied case.The structural parameters of the thin-walled circular tube mainly affect the deformation process and the maximum shock overload.The order of importance of structural parameters to the maximum shock overload is determined,among which the wall thickness has the most significant effect.

Exercise Training for the Elderly:Inflammaging and the Central Role for HSP70

Inflammation is a common feature of aging tissues,being involved in most,if not all,age-related diseases.The origin of a low-grade inflammation state in aging(inflammaging)is multifactorial and may involve changes in body composition,immunosenescence,autophagy,microbiota modification and loss of proteostasis.The heat shock response pathway(HSR,and HSP70 expression)plays an important role as a mechanism of resolution of inflammation and proteostasis control.In this review,we sought to discuss the mechanisms that may lead to inflammaging,and the importance of the HSP70 in this process.Besides,we also discuss how physical exercise,particularly resistance training,can improve the HSR and the inflammatory balance of elderly people.