1,849 research outputs found
Digital image correlation approach to cracking and decohesion in a brittle coating/ductile substrate system
By using a digital image correlation technique, the full/local field strain in a brittle coating/ductile substrate system during tension has been successfully monitored. One of the most important experimental results indicates that the distribution of interfacial shear stress in the segmented coating is antisymmetric about the center, which clarifies several controversial assumptions introduced in theoretical models. Two key mechanical properties of thermal barrier coatings, fracture strength in coating and interfacial adhesion strength, were determined as 35.0 Β± 4.6 and 14.1 Β± 3.2 MPa, respectively, which are consistent with available experimental data
Extracellular secretion of Carocin S1 in Pectobacterium carotovorum subsp. carotovorum occurs via the type III secretion system integral to the bacterial flagellum
Background: Pectobacterium carotovorum subsp. carotovorum is a phytopathogenic enterobacterium responsible for soft rot, a disease characterized by extensive maceration of the affected plant tissue. This species also produces two or more antibacterial substances called bacteriocins, which enhance its competitiveness against related rival species. However, the secretion mechanism for low-molecular-weight bacteriocin is still unknown. Results: A mutant (flhC::Tn5) that did not secrete the low-molecular-weight bacteriocin (LMWB), Carocin S1, was generated by Tn5 insertional mutagenesis. Sequence analysis indicated that this insertion disrupted open reading frame 2 (ORF2) and ORF3 of this strain. Deletion and rescue experiments indicated that ORF2 and ORF3 were both required for extracellular LMWB secretion. The ORF2 and ORF3 sequences showed high homology with the flhD and flhC gene sequences of Pectobacterium carotovorum subsp. atroseptica, Serratia marcescens, Yersinia enterocolitica, and Escherichia coli, indicating that they likely encoded key regulatory components of the type III flagella secretion system. Conclusion: Thus, the extracellular export of Carocin S1 by Pectobacterium carotovorum subsp. carotovorum appears to utilize the type III secretion system integral to bacterial flagella
High current density induced damage mechanisms in electronic solder joints: a state-of-the-art review
High current density induced damages such as electromigration in the on-chip interconnection /metallization of Al or Cu has been the subject of intense study over the last 40 years. Recently, because of the increasing trend of miniaturization of the electronic packaging that encloses the chip, electromigration as well as other high current density induced damages are becoming a growing concern for off-chip interconnection where low melting point solder joints are commonly used. Before long, a huge number of publications have been explored on the electromigration issue of solder joints. However, a wide spectrum of findings might confuse electronic companies/designers. Thus, a review of the high current induced damages in solder joints is timely right this moment. We have selected 6 major phenomena to review in this paper. They are (i) electromigration (mass transfer due electron bombardment), (ii) thermomigration (mass transfer due to thermal gradient), (iii) enhanced intermetallic compound growth, (iv) enhanced current crowding, (v) enhanced under bump metallisation dissolution and (vi) high Joule heating and (vii) solder melting. the damage mechanisms under high current stressing in the tiny solder joint, mentioned in the review article, are significant roadblocks to further miniaturization of electronics. Without through understanding of these failure mechanisms by experiments coupled with mathematical modeling work, further miniaturization in electronics will be jeopardize
Complex-valued Burgers and KdV-Burgers equations
Spatially periodic complex-valued solutions of the Burgers and KdV-Burgers
equations are studied in this paper. It is shown that for any sufficiently
large time T, there exists an explicit initial data such that its corresponding
solution of the Burgers equation blows up at T. In addition, the global
convergence and regularity of series solutions is established for initial data
satisfying mild conditions
A tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure
Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV=m ο¬eld strength can be achieved by using appropriate grating parameter
Real-Time Substructure Tests and Numerical Simulation of Mechanical Characteristics of Natural Rubber-Laminated Bearings
Natural rubber lamination is a kind of seismic isolation of bearings often used in civil engineering. The advantage of laminated bearings is large vertical stiffness and small lateral stiffness. In seismic regions, structural periods would be extended and the effect of seismic forces can be lowered using bearings. In previous tests, the static cyclic loading method was mainly used that failed to take account of the loading rate. The real-time substructure testing is proposed to simulate true seismic loads. This testing and test setup were first introduced, and the effect of the loading rate was studied. Then the effects of vertical pressure and peak acceleration of ground motion were studied. At last the test results were simulated by the finite element method, and an accurate method to calculate seismic responses of bridges with laminated bearings was proposed.ΠΠ°ΠΌΠΈΠ½ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΡΠΈΡΠΎΠ΄Π½ΡΠΌ ΠΊΠ°ΡΡΡΠΊΠΎΠΌ β ΠΎΠ΄ΠΈΠ½ ΠΈΠ· Π²ΠΈΠ΄ΠΎΠ² ΡΠ΅ΠΉΡΠΌΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΈΠ·ΠΎΠ»ΡΡΠΈΠΈ ΠΎΠΏΠΎΡ, ΡΠ°ΡΡΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅ΠΌΡΠΉ Π² Π³ΡΠ°ΠΆΠ΄Π°Π½ΡΠΊΠΎΠΌ ΡΡΡΠΎΠΈΡΠ΅Π»ΡΡΡΠ²Π΅. ΠΠ°ΠΌΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΡΠ΅ ΠΎΠΏΠΎΡΡ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·ΡΡΡΡΡ Π²ΡΡΠΎΠΊΠΎΠΉ Π²Π΅ΡΡΠΈΠΊΠ°Π»ΡΠ½ΠΎΠΉ ΠΆΠ΅ΡΡΠΊΠΎΡΡΡΡ ΠΈ Π½ΠΈΠ·ΠΊΠΎΠΉ ΠΏΠΎΠΏΠ΅ΡΠ΅ΡΠ½ΠΎΠΉ ΠΆΠ΅ΡΡΠΊΠΎΡΡΡΡ. Π ΡΠ΅ΠΉΡΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ΅Π³ΠΈΠΎΠ½Π°Ρ
ΡΡΠΎΠΊΠΈ ΡΡΡΠΎΠΈΡΠ΅Π»ΡΡΡΠ²Π° ΡΠ²Π΅Π»ΠΈΡΠΈΠ²Π°ΡΡΡΡ, Π° Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΡΠ΅ΠΉΡΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠΈΠ» ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΡΠΌΠ΅Π½ΡΡΠ΅Π½ΠΎ Π·Π° ΡΡΠ΅Ρ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΠΏΠΎΠ΄ΠΎΠ±Π½ΡΡ
ΠΎΠΏΠΎΡ. ΠΠΎ ΡΠΈΡ
ΠΏΠΎΡ ΠΎΡΠ½ΠΎΠ²ΠΎΠΉ Π΄Π»Ρ ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ ΡΠ»ΡΠΆΠΈΠ» ΡΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΌΠ΅ΡΠΎΠ΄ ΡΠΈΠΊΠ»ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π½Π°Π³ΡΡΠΆΠ΅Π½ΠΈΡ, Π½Π΅ ΠΏΠΎΠ·Π²ΠΎΠ»ΡΠ²ΡΠΈΠΉ ΡΡΠΈΡΡΠ²Π°ΡΡ Π΅Π³ΠΎ ΡΠΊΠΎΡΠΎΡΡΡ. ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ ΠΌΠ΅ΡΠΎΠ΄ ΠΈΡΠΏΡΡΠ°Π½ΠΈΡ Π² ΡΠ΅Π°Π»ΡΠ½ΡΡ
ΡΡΠ»ΠΎΠ²ΠΈΡΡ
ΡΠΊΡΠΏΠ»ΡΠ°ΡΠ°ΡΠΈΠΈ, ΠΌΠΎΠ΄Π΅Π»ΠΈΡΡΡΡΠΈΠΉ ΠΈΡΡΠΈΠ½Π½ΡΠ΅ ΡΠ΅ΠΉΡΠΌΠΈΡΠ΅ΡΠΊΠΈΠ΅ Π½Π°Π³ΡΡΠ·ΠΊΠΈ. ΠΠ½Π΅Π΄ΡΠ΅Π½Ρ ΠΌΠ΅ΡΠΎΠ΄ ΠΈΡΠΏΡΡΠ°Π½ΠΈΠΉ ΠΈ ΠΈΡΠΏΡΡΠ°ΡΠ΅Π»ΡΠ½Π°Ρ ΡΡΡΠ°Π½ΠΎΠ²ΠΊΠ°, ΠΈΠ·ΡΡΠ΅Π½ΠΎ Π²Π»ΠΈΡΠ½ΠΈΠ΅ ΡΠΊΠΎΡΠΎΡΡΠΈ Π½Π°Π³ΡΡΠΆΠ΅Π½ΠΈΡ, Π²Π΅ΡΡΠΈΠΊΠ°Π»ΡΠ½ΠΎΠ³ΠΎ Π΄Π°Π²Π»Π΅Π½ΠΈΡ ΠΈ ΠΏΠΈΠΊΠΎΠ²ΠΎΠ³ΠΎ ΡΡΠΊΠΎΡΠ΅Π½ΠΈΡ Π΄Π²ΠΈΠΆΠ΅Π½ΠΈΡ Π³ΡΡΠ½ΡΠ°. ΠΡΠΏΠΎΠ»Π½Π΅Π½ΠΎ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠΎΠ² ΠΈΡΠΏΡΡΠ°Π½ΠΈΡ Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΌΠ΅ΡΠΎΠ΄Π° ΠΊΠΎΠ½Π΅ΡΠ½ΡΡ
ΡΠ»Π΅ΠΌΠ΅Π½ΡΠΎΠ². ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ ΡΠΎΡΠ½ΡΠΉ ΠΌΠ΅ΡΠΎΠ΄ ΡΠ°ΡΡΠ΅ΡΠ° ΡΠ΅ΠΉΡΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊ ΠΌΠΎΡΡΠΎΠ² Ρ ΠΎΠΏΠΎΡΠ°ΠΌΠΈ, Π»Π°ΠΌΠΈΠ½ΠΈΡΠΎΠ²Π°Π½Π½ΡΠΌΠΈ ΠΏΡΠΈΡΠΎΠ΄Π½ΡΠΌ ΠΊΠ°ΡΡΡΠΊΠΎΠΌ
Microstructures and properties of new Sn-Ag-Cu lead-free solder reinforced with Ni-coated graphene nanosheets
Β© 2015 Elsevier B.V. All rights reserved. This paper deals with microstructures and properties of SAC305 lead-free solder reinforced with graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS). These Ni-coated GNS nanosheets were synthesized by an in-situ chemical reduction method. After morphological and chemical characterization, Ni-GNS were successfully integrated into SAC305 lead-free solder alloy with different weight fractions (0, 0.05, 0.1 and 0.2 wt.%) through a powder metallurgy route. The obtained composite solders were then studied extensively with regard to their microstructures, wettability, thermal, electrical and mechanical properties. After addition of Ni-GNSs, cauliflower-like (Cu,Ni)6 Sn5 intermetallic compounds (IMCs) were formed at the interface between composite solder joint and copper substrate. Additionally, blocky Ni-Sn-Cu IMC/GNS hybrids were also observed homogenously distributed in the composite solder matrices. Composite solder alloys incorporating Ni-decorated GNSs nanosheets showed slightly reduced electrical resistivity compared to the unreinforced SAC305 solder alloy. With an increase in the amount of Ni-GNS, the composite solders showed an improvement in wettability with an insignificant change in their melting temperature. Mechanical tests demonstrated that addition of 0.2 wt.% Ni-GNS would result in 19.7% and 16.9% improvements in microhardness and shear strength, respectively, in comparison to the unreinforced solders. Finally, the added Ni-GNS reinforcements in the solder matrix were assessed with energy-dispersive X-ray spectroscopy, scanning electron microscopy and Raman spectroscopy
A Non-coding RNA of Insect HzNV-1 Virus Establishes Latent Viral Infection through MicroRNA
Heliothis zea nudivirus-1 (HzNV-1) is an insect virus previously known as Hz-1 baculovirus. One of its major early genes, hhi1, is responsible for the establishment of productive viral infection; another gene, pag1, which expresses a non-coding RNA, is the only viral transcript detectable during viral latency. Here we showed that this non-coding RNA was further processed into at least two distinct miRNAs, which targeted and degraded hhi1 transcript. This is a result strikingly similar to a recent report that herpes simplex virus produces tightly-regulated latent specific miRNAs to silence its own key early transcripts. Nevertheless, proof for the establishment of viral latency by miRNA is still lacking. We further showed that HzNV-1 latency could be directly induced by pag1-derived miRNAs in cells infected with a pag1-deleted, latency-deficient virus. This result suggests the existence of a novel mechanism, where miRNAs can be functional for the establishment of viral latency
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