Enhanced Thermal Shock Resistance of Ceramics through Biomimetically Inspired Nanofins

We propose here a new method to make ceramics insensitive to thermal shock up to their melting temperature. In this method the surface of ceramics was biomimetically roughened into nanofinned surface that creates a thin air layer enveloping the surface of the ceramics during quenching. This air layer increases the heat transfer resistance of the surface of the ceramics by about 10 000 times so that the strong thermal gradient and stresses produced by the steep temperature difference in thermal shock did not occur both on the actual surface and in the interior of the ceramics. This method effectively extends the applications of existing ceramics in the extreme thermal environments.

Direct Numerical Simulation of Shock/Turbulent Boundary Layer Interaction in a Supersonic Compression Ramp

A direct numerical simulation of the shock/turbulent boundary layer interaction flow in a supersonic 24-degree compression ramp is conducted with the free stream Mach number 2.9. The blow-and-suction disturbance in the upstream wall boundary is used to trigger the transition. Both the mean wall pressure and the velocity profiles agree with those of the experimental data, which validates the simulation. The turbulent kinetic energy budget in the separation region is analyzed. Results show that the turbulent production term increases fast in the separation region, while the turbulent dissipation term reaches its peak in the near-wall region. The turbulent transport term contributes to the balance of the turbulent conduction and turbulent dissipation. Based on the analysis of instantaneous pressure in the downstream region of the mean shock and that in the separation bubble, the authors suggest that the low frequency oscillation of the shock is not caused by the upstream turbulent disturbance, but rather the instability of separation bubble.

Effects of Magnetohydrodynamic Interaction-Zone Position on Shock-Wave/Boundary-Layer Interaction

A third-order weighted essentially nonoscillatory and non-free-parameter difference scheme magnetohydrodynamic solver has been established to investigate the mechanisms of magnetohydrodynamics controlling separation induced by an oblique shock wave impinging on a flat plate. The effects of magnetohydrodynamic interaction-zone location on the separation point, reattachment point, separation-bubble size, and boundary-layer velocity profiles are analyzed. The results show that there exists a best location for the magnetohydrodynamic zone to be applied, where the separation point is delayed the farthest, and the separation bubble is decreased up to about 50% in size compared to the case without magnetohydrodynamic control, which demonstrated the promising of magnetohydrodynamics suppressing the separation induced by shock-wave/boundary-layer interactions.

A New High Order Accurate Shock Capture Method with Wave Booster

A new kind of shock capturing method is developed. Before applying the high order accurate traditional scheme which is called as base scheme in this paper the fluid parameters are preconditioned in order to control the group velocity. The newly constructed scheme is high order accurate, simple, has high resolution of the shock, and less computer time consumed.

Parallel Fully-Implicit Computation of Magnetohydrodynamics Acceleration Experiments

A three-dimensional MHD solver is described in the paper. The solver simulates reacting flows with nonequilibrium between translational-rotational, vibrational and electron translational modes. The conservation equations are discretized with implicit time marching and the second-order modified Steger-Warming scheme, and the resulted linear system is solved iteratively with Newton-Krylov-Schwarz method that is implemented by PETS,: package. The results of convergence tests arc plotted, which show good scalability and convergence around twice faster when compared with the DPLR method. Then five test runs are conducted simulating the experiments done at the NASA Ames MHD channel, and the calculated pressures, temperatures, electrical conductivity, back EMF, load factors and flow accelerations are shown to agree with the experimental data. Our computation shows that the electrical conductivity distribution is not uniform in the powered section of the MHD channel, and that it is important to include Joule heating in order to calculate the correct conductivity and the MHD acceleration.

Early Embryonic Exposure to Polychlorinated Biphenyls Disrupts Heat-Shock Protein 70 Cognate Expression in Zebrafish

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that have documented neurological effects in children exposed in utero. To better define neuronally linked molecular targets during early development, zebrafish embryos were exposed to Aroclor 1254, a mixture of PCB congeners that are common environmental contaminants. Microarray analysis of the zebrafish genome revealed consistent significant changes in 38 genes. Of these genes, 55% (21) are neuronally related. One gene that showed a consistent 50% reduction in expression in PCB-treated embryos was heat-shock protein 70 cognate (Hsc70). The reduction in Hsc70 expression was confirmed by real-time polymerase chain reaction (PCR), revealing a consistent 30% reduction in expression in PCB-treated embryos. Early embryonic exposure to PCBs also induced structural changes in the ventro-rostral cluster as detected by immunocytochemistry. In addition, there was a significant reduction in dorso-rostral neurite outgrowth emanating from the RoL1 cell cluster following PCB exposure. The serotonergic neurons in the developing diencephalon showed a 34% reduction in fluorescence when labeled with a serotonin antibody following PCB exposure, corresponding to a reduction in serotonin concentration in the neurons. The total size of the labeled neurons was not significantly different between treated and control embryos, indicating that the development of the neurons was not affected, only the production of serotonin within the neurons. The structural and biochemical changes in the developing central nervous system following early embryonic exposure to Aroclor 1254 may lead to alterations in the function of the affected regions.

Thermal-shock resistance of LnMgAl(11)O(19) (Ln = La, Nd, Sm, Gd) with magnetoplumbite structure

Lanthanide hexaaluminates including LaMgAl11O19, NdMgAl11O19, SmMgAl11O19 and GdMgAl11O19 were synthesized via Sol-Gel method. Due to the anisotropic crystal growth, these oxides crystallize in the form of platelets and the platelet thickness increases with the decrease of rare-earth ionic radius. It was observed that the thermal-shock resistances of LaMgAl11O19, NdMgAl11O19 and SmMgAl11O19 oxides were superior to 8YSZ as proved by water quenching tests. In addition, the thinner the platelet. the more interstices are retained in the sintered specimen, and the better thermal-shock resistance the oxide has. Based on SEM images, it can be seen that the SmMgAl11O19 sample exhibits a mixture of the intergranular and transgranular fracture after thermal cycling failure.

Single-walled carbon nanotubes binding to human telomeric i-motif DNA: significant acceleration of S1 nuclease cleavage rate

Single-walled carbon nanotubes (SWNTs) binding to human telomeric i-motif DNA can significantly accelerate S1 nuclease cleavage rate by increasing the enzyme turnover number.

Cloning of cytoplasmic heat shock protein 90 (FcHSP90) from Fenneropenaeus chinensis and its expression response to heat shock and hypoxia

Heat shock protein 90 (HSP90) works as a multi-functional chaperone and is involved in the regulation of many essential cellular pathways. In this study, we have identified a full-length complementary DNA (cDNA) of HSP90 (FcHSP90) from Chinese shrimp Fenneropenaeus chinensis. FcHSP90 full-length cDNA comprised 2,552 bp, including a 2,181-bp open reading frame encoding 726 amino acids. Both homology analyses using alignment with previously identified HSP90 and a phylogeny tree indicated that FcHSP90 was a cytoplasmic HSP90. Real-time reverse transcription polymerase chain reaction analysis revealed that FcHSP90 was ubiquitously expressed in all the examined tissues but with highest levels in ovary of F. chinensis. FcHSP90 mRNA levels were sensitively induced by heat shock (from 25A degrees C to 35A degrees C) and reached the maximum at 6 h during heat shock treatment. Under hypoxia conditions, FcHSP90 mRNA levels, in both hemocytes and gill, were induced at 2 h and depressed at 8 h during hypoxia stress. The assessment of FcHSP90 mRNA levels under heat shock and hypoxia stresses indicated that the transcription of FcHSP90 was very sensitive to heat shock and hypoxia, so we deduced that FcHSP90 might play very important roles for shrimp to cope with environmental stress.

Cloning, sequencing and expression analysis of cDNA encoding a constitutive heat shock protein 70 (HSC70) in Fenneropenaeus chinensis

The cDNA encoding hsc70 of Chinese shrimp Fenneropenaeus chinensis was cloned from hepatopancreas by RT-PCR based on its EST sequence. The full length cDNA of 2090 bp contained an open reading frame of 1956 nucleotides and partial 5'- and 3'-untranslated region(5'- and 3'-UTR). PCR amplification and sequencing analysis showed the existence of introns in the region of 1-547 bp, but they did not exist in the region of 548-2090 bp of hsc70 cDNA. When the deduced 652 amino acid sequence of HSC70 was compared with the members of HSP70 family from other organisms, the results showed 85.9% similarity with HSC71 from Oncorhynchus mykiss and HSC70 from Homo sapiens. It also exhibited 85.8% similarity with HSP70 from Mus musculu and 85.4% with HSC70 from Manduca sexta. Expression analysis showed that hsc70 mRNA was espressed constitutively in hepatopancreas, muscle, eyestalks, haemocytes, heart, ovary, intestine and gills in Fenneropenaeus chinensis. No difference could be detected on hsc70 mRNA level in muscle between heat-shocked and control animals.

Optimization of triploid induction by heat shock in Chinese shrimp Fenneropenaeus chinensis

Chromosome manipulation for commercially valuable marine animals plays an important role in aquaculture. The special reproductive characteristics of shrimp make it difficult to control fertilization and synchronize egg development, so research on chromosome manipulation in shrimp has proceeded very slowly. In the present study, triploid shrimp Fenneropenaeus chinensis were induced by heat shocks and the optimal-inducing condition was screened at different spawning temperatures. Level of triploid induction for each treatment was evaluated by flow cytometry at nauplius stage. The highest level of triploid induction reached to more than 90%. Starting time for each treatment was very crucial for triploid induction in shrimp. One optimal treatment condition for triploid induction was heat shock (29-32 degreesC), starting at 18-20 min for duration of 10 min. These conditions varied depending on the temperature at spawning. Triploid level at embryo stage and nauplius stage was not different, suggesting the same hatching rate between diploids and triploids. Heat shock is a very effective way to induce triploids in this species, and can be easily used on large scale without any harmful effect on the environment as compared with chemical treatment. (C) 2003 Elsevier Science B.V. All rights reserved.

cDNA cloning and mRNA expression of heat shock protein 90 gene in the haemocytes of Zhikong scallop Chlamys farreri

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. The full-length cDNA of Zhikong scallop Chlamysfarreri HSP90 (designated CfHSP90) was cloned by EST and rapid RACE techniques. It was of 2710 bp, including an open reading frame (ORF) of 2181 bp encoding a polypeptide of 726 amino acids with all the five HSP90 family signatures. BLAST analysis revealed that the CfHSP90 gene shared high similarity with other known HSP90 genes. Fluorescent real-time quantitative RT-PCR was used to examine the expression pattern of CfHSP90 mRNA in haemocytes of scallops exposed to Cd2+, Pb2+ and Cu2+ for 10 and 20 days, respectively. All the three heavy metals could induce CfHSP90 expression. There was a clear dose-dependent expression pattern of CfHSP90 after heavy metals exposure for 10 days or 20 days. Different concentrations of the same metal resulted in different effects on CfHSP90 expression. The results indicated that CfHSP90 responded to various heavy metal stresses with a dose-dependent expression pattern as well as exposure time effect, and could be used as a molecular biomarker in a heavy metal polluted environment. (c) 2007 Elsevier Inc. All rights reserved.

Molecular cloning, characterization and expression of heat shock protein 90 gene in the haemocytes of bay scallop Argopecten irradians

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that plays key roles in the folding, maintenance of structural integrity and regulation of a subset of cytosolic proteins. In the present study, the cDNA of Argopecten irradians HSP90 (designated AiHSP90) was cloned by the combination of homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of AiHSP90 was of 2669 bp, including an open reading frame (ORF) of 2175 bp encoding a polypeptide of 724 amino acids with predicted molecular weight of 83.08 kDa and theoretical isoelectric point of 4.81. BLAST analysis revealed that AiHSP90 shared high similarity with other known HSP90s, and the five conserved amino acid blocks defined as HSP90 protein family signatures were also identified in AiHSP90, which indicated that AiHSP90 should be a cytosolic member of the HSP90 family. Fluorescent real-time quantitative PCR was employed to examine the expression pattern of AiHSP90 mRNA in haemocytes of scallops challenged by Gram-negative bacteria Vibrio anguillarum and Gram-positive bacteria Micrococcus luteus. In both bacterial challenged groups, the relative expression level of AiHSP90 transcript was up-regulated and reached maximal. level at 9 h after injection, and then dropped progressively to the original level at about 48 h post challenge. The results indicated that AiHSP90 was potentially involved in the immune responses against bacteria challenge in scallop A. irradian. (c) 2007 Elsevier Ltd. All rights reserved.