1,555 research outputs found
Characterization and corrosion properties of electroformed AuCu+B4C
No full textThe electroforming technique is widely employed in jewellery and electronics to produce Au alloys.
The addition of B4C to the electrodeposited AuCu may improve the mechanical properties of the layers. In this paper the microstructure and corrosion resistance properties of AuCu and codeposited AuCu/B4C from cyanide free baths are presented.
The composite samples were obtained by dispersing micrometric B4C, at diffreent concentrations, in the deposition bath.
The microstructure, volume fractions and corrosion properties of samples with different B4C concentration codeposits have been investigated and compared to those belonging to AuCulayers. The addition of B4C slightly increases the hardness of the electroformed and induces a moderate decrease of corrosion resistance
Corrosion Behaviour of a Superduplex Stainless Steel in Chloride Aqueous Solution
No full textSuper duplex stainless steels (SDSS) have been widely used as structural materials for chemical plants (especially in those engaged in phosphoric acid production), in the hydrometallurgy industries, and as materials for offshore applications due to their excellent corrosion resistance in chloride environments, compared with other commercial types of ferritic stainless steels. These alloys also possess superior weld-ability and better mechanical properties than austenitic stainless steels. However, due to their two-phase structure, the nature of which is very dependent on their composition and thermal history, the behavior of SDSS regarding localized corrosion appears difficult to predict, especially in chloride environments. To improve their final properties, the effect of the partition of the alloying elements between the two phases, and the composition and microstructure of each phase are the key to understanding the localized corrosion phenomena of SDSS. This paper concerns the effects of the SDSS microstructure and heat treatment on the SDSS corrosion resistance in aqueous solutions, containing different amounts of NaCl at room temperature
A SW Ka-Band linearizer structure with minimum surface electric field for the compact light XLS project
No full textThere is a strong demand for accelerating structures able to achieve higher gradients and more compact dimensions for the next generation of linear accelerators for research, industrial and medical applications. In the framework of the Compact Light XLS project, an ultra-high gradient higher harmonic RF accelerating structure is needed for the linearization of the longitudinal phase space. In order to determine the maximum sustainable gradients in normal conducting RF powered particle beam accelerators with extremely low probability of RF breakdown, investigations are in progress for using short accelerating structures in the Ka-band regime. We here report an electromagnetic design of a compact linearizer standing wave (SW) accelerating structure. The cavity has a length of about 8 cm and operates on the π-mode at 35.982 GHz, which is the third harmonic with respect to the Linac frequency (11.994 GHz). The accelerating gradient is 100 MV/m and the cavity geometry is optimized in order to minimize the surface peak electric field
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Research with variola virus after smallpox eradication: Development of a mouse model for variola virus infection
No full textIn this issue of PLOS Pathogens, Hutson and coworkers at the Centers for Disease Control
and Prevention (CDC) in Atlanta, USA describe a study with infectious variola virus that was
approved by the World Health Organization (WHO) Advisory Committee on Variola Virus
Research (ACVVR)
Surface hardening od Ti-6Al-4V alloy using combined electroless Ni-B plating and diffusion treatments
No full textThe electroless plating process allows the production of a nickel-boron coating on the surface of a Ti-6Al-4V alloy, by immersion in a nickel chloride aqueous solution using dimethylamine borane (DMAB) as a reducing agent. A series of diffusion treatments was carried out at temperatures ranging from 400 to 900°C in order to achieve deep case hardening. The characterisation of both the electroless coating and the diffusion treated alloy was performed using XRD, SEM, EDS, and glow discharge optical spectrometry (GDOS). Microhardness and compositional profiles were carried out in order to reveal the hardening effect and the nickel and boron penetration. The results showed that a significant improvement in the hardness can be achieved by choosing the correct treatment parameters. Surface hardnesses up to 850 HV and a depth of hardening larger than 500 μm were achieved at 900°C in an inert atmosphere
A novel exact analytical expression for the magnetic field of a solenoid
No full textIn this paper we present the analytical calculations to derive the magnetic field of a solenoid by solving exactly a fractional integral with the use of a novel method. Starting from the Biot-Savart law, we consider a coil of negligible thickness with a stationary electric current. We derive the expressions of the on- and off-axes magnetic field components. The results have been compared to some simplified and known analytical formulae as well as to a commercial numerical code showing a good agreement
Phylogeographical and evolutionary history of variola major virus; a question of timescales?
No full textAim of this study was to reconstruct the phylogeography of variola virus (VARV) in the XX century, using 47 VARV whole genome sequences available in public databases, through two different methods for ancestral character reconstruction: a frequently used Bayesian framework and a fast maximum-likelihood (ML) based method. The substitution rate of the whole VARV genome was estimated to be between 6.7×10-6 and 1.1×10-5 substitutions/site/year. Both ML and Bayesian methods gave similar trees topology, showing two distinct monophyletic groups: one (known as P1) including the great part of variola major and the second (P2) including West African and American (variola minor) isolates and close evolutionary rate estimations, between 6.73×10-6 and 1.1×10-5 for the whole genome. The phylogeographical reconstruction of P1 suggested that the common ancestor of the variola major circulating in the Old World between the 1940s and the 1970s most probably originated in the Far East in the first decades of the XX century, and then spread to Indian subcontinent in the 1920s. India represented a center of further spread of VARV to eastern Africa in the 1940s and to the Middle East in the 1960s. The phylogeographic scenario obtained by the maximum-likelihood based method was congruent with that obtained by Bayesian framework, but the analysis was faster indicating the usefulness of this method in the analyses of large viral genomes. Our results may help to explain the controversial reconstructions of the history of VARV obtained using long or short timescale for calibration
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