Bright Metal Research Articles

SURFACE QUALITY AND CORROSION RESISTANCE OF 316L STAINLESS STEEL ELECTROPOLISHED USING PHOSPHORIC – SULFURIC ACIDS

Electropolishing is an electrochemical surface finishing technique. It is commonly applied to equipment that requires a gleaming finish. This surface property is frequently required in 316L stainless steel (SS) medical implants. Electropolishing removes a thin layer from the metal's surface through electrochemical processes. This results in a very clean, smooth, and bright metal surface. The process parameters, such as electrolyte solution, electrical current, and electropolishing time, influence surface roughness and glossiness. The dissolution of metallic ions during the process may also affect the corrosion resistance of the treated material in addition to producing a shiny surface. This study investigated the surface glossiness, surface roughness, and corrosion of electropolished 316L SS. Electropolishing experiments on 316 SS were carried out using various H3PO4 (50%) and H2SO4 (32%) electrolyte solution compositions. The influences of electrolyte solution composition, electric current, and electropolishing time were studied. The results showed that increasing the H2SO4 content of the mixture and electropolishing the 316L SS for a longer period of time improved the surface roughness and glossiness. Under 10 Amp electric currents, the best surface glossiness was discovered. A corrosion test revealed that the electropolishing produced a Cr and Ni-rich layer that improved the corrosion resistance of the samples.

Study on structural parameters of cup-type axial magnetic contacts on gap magnetic field and arc characteristics

The axial magnetic field (AMF) plays a crucial role in maintaining the diffusion of vacuum arcs within contact gaps, making it a key component in vacuum breaking systems. To enhance contact surface utilization, a novel vacuum cup-type AMF contact was designed, featuring a stronger axial magnetic field at the edge and weaker at the centre. Through Ansys Maxwell 3D simulations, the designed contact increased the effective utilization area by 18 %. Experimental analysis demonstrated that, compared to traditional contacts, the designed contact exhibited lower arc voltage and significant arc diffusion. Ablation of the designed contact was more concentrated at the edge, with scanning electron microscope (SEM) images revealing four microscopic morphologies: overlapping craters, bright metal droplets, various-sized flakes, and fine particles. Energy dispersive spectrum (EDS) analysis provided insights into the cathode surface's elemental composition and droplet growth. Additionally, the study explored the influence of different slotting parameters on vacuum arc characteristics, including contact plate configurations, cup bottom slotting, and cup wall tilt, focusing on the arc initiation stage, arc voltage rise, and arc shape transition.

DNA Nanoribbon-Assisted Intracellular Biosynthesis of Fluorescent Gold Nanoclusters for Cancer Cell Imaging.

Metal nanoclusters (NCs) have emerged as a promising class of fluorescent probes for cellular imaging due to their high resistance to photobleaching and low toxicity. Nevertheless, their widespread use in clinical diagnosis is limited by their unstable intracellular fluorescence. In this study, we develop an intracellularly biosynthesized fluorescent probe, DNA nanoribbon-gold NCs (DNR/AuNCs), for long-term cellular tracking. Our results show that DNR/AuNCs exhibit a 4-fold enhancement of intracellular fluorescence intensity compared to free AuNCs. We also investigated the mechanism underlying the fluorescence enhancement of AuNCs by DNRs. Our findings suggest that the higher synthesis efficiency and stability of AuNCs in the lysosome may contribute to their fluorescence enhancement, which enables long-term (up to 15 days) fluorescence imaging of cancer cells (enhancement of ∼60 times compared to free AuNCs). Furthermore, we observe similar results with other metal NCs, confirming the generality of the DNR-assisted biosynthesis approach for preparing highly bright and stable fluorescent metal NCs for cancer cell imaging.

Carbene-stabilized enantiopure heterometallic clusters featuring EQE of 20.8% in circularly-polarized OLED

Bright and efficient chiral coinage metal clusters show promise for use in emerging circularly polarized light-emitting materials and diodes. To date, highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with enantiopure metal clusters have not been reported. Herein, through rational design of a multidentate chiral N-heterocyclic carbene (NHC) ligand and a modular building strategy, we synthesize a series of enantiopure Au(I)-Cu(I) clusters with exceptional stability. Modulation of the ligands stabilize the chiral excited states of clusters to allow thermally activated delayed fluorescence, resulting in the highest orange-red photoluminescence quantum yields over 93.0% in the solid state, which is accompanied by circularly polarized luminescence. Based on the solution process, a prototypical orange-red CP-OLED with a considerably high external quantum efficiency of 20.8% is prepared. These results demonstrate the extensive designability of chiral NHC ligands to stabilize polymetallic clusters for high performance in chiroptical applications.

Reduction of Metal Artifacts Caused by Titanium Peduncular Screws in the Spine by Means of Monoenergetic Images and the Metal Artifact Reduction Software in Dual-Energy Computed Tomography.

Objectives:To evaluate the reduction of metal artifacts in patients with titanium peduncular screws in the spine using (1) conventional images (CI), (2) virtual monoenergetic reconstructions (VMRs), and (3) VMR + Metal Artifact Reduction Software (VMR + MARS), with dual-energy computed tomography (DECT).Materials and Methods:Twenty-four patients with titanium peduncular screws in the spine were studied using a 64-channel DECT. During the postprocessing phase, the CI, the VMRs from 100 to 140 keV, and the VMR at 140 keV + MARS were synthesized. All the images were considered, and a quantitative evaluation was performed measuring the attenuation values (in terms of Hounsfield Units) with region of interest, in correspondence with the most hyperdense and hypodense artifacts. All the values were then compared. A qualitative evaluation, in terms of image quality and extent of artifacts, was also performed by two radiologists.Results:In quantitative terms, the 140 keV + MARS reconstruction was able to significantly reduce both bright and dark metal artifacts, compared to CI and to VMRs. The VMR was capable of significantly reducing both dark and bright artifacts, compared to CI. In qualitative terms, the VMR at 140 keV proved to be the best, compared to CI and VMR + MARS images.Conclusions:The VMR + MARS image reduces metal artifacts from titanium peduncular screws more than VMRs alone and CI. Furthermore, the VMR can decrease metal artifacts from a quantitative and a qualitative point of view. Combining information from VMRs and VMR + MARS images could be the best way to solve the issue of metal artifacts on computed tomography images.

Building Materials for Cities and Climate Change – a Material Catalogue with Recommendations

High urban density with heat accumulating materials and sealed surfaces can cause heat stress and reduced nocturnal cooling in summer. Appropriate building materials may contribute to the mitigation of this effect. The research project evaluates building materials for façades and outer surfaces (ground) on the resulting urban microclimate and on factors like glare, acoustics and embedded energy. The present publication focuses on the impact on the microclimate. The analysis comprises the simulation of forty-seven data sets in a microclimatic model with ENVI-met. The results show that during daytime the PET for the whole neighborhood ranges between 30.1 and 36.4 °C. Choosing a bright instead of a dark color can lower the PET between 0.2 and 1.0 K. Dark colored metal sheets may cause turbulences which lead to a reduction of the PET between 2.0 and 3.8 K (compared to a bright metal sheet). However, this effect may not be reproducible under varying boundary conditions. During night-time, the resulting span of ambient temperatures between the materials reaches 21.4 to 22.0 °C (level 1.7 m). The temperature difference between the materials at the level of 10.7 m (for night ventilation) is found to be approx. 0.3 K and can be considered irrelevant.

PEDOT: PSS doped with cesium chloride for highly efficient and bright metal halide perovskite light-emitting diodes

PEDOT: PSS doped with cesium chloride for highly efficient and bright metal halide perovskite light-emitting diodes

Facile and low-cost green synthesis of eco-friendly chitosan-silver nanocomposite as novel and promising corrosion inhibitor for mild steel in chilled water circuits

New promising samples of silver nanoparticles: (SNPs)-chitosan (CT) nanocomposite (NC) abbreviated as (SNPs-CTNC) have been synthesized and characterized using the novel green chemistry approach. All the synthesized formulations showed innovative corrosion inhibition for the mild steel samples in the cooling water system. The experimental conditions for the green synthesis of eco-friendly silver nanoparticles (SNPs) using chitosan (CT) biopolymer as both reducing and protecting coating agent for SNPs have been optimized. The synthesis route presented herein was performed by the reduction of silver nitrate (AgNO3) by CT in an autoclave reactor vessel under 1 bar applied pressure at the reaction temperature of 120 °C and various contact time (2, 4, 8, and 16 h) between (AgNO3) and chitosan (CT). The four prepared samples of SNPs-CT NC have been abbreviated in terms of the reaction or the contact time as (2 h, 4 h, 8 h, and 16 h). The four SNPs-CT NC samples were characterized using: UV–Visible spectroscopy; Fourier transform infrared (FTIR); X-ray diffraction (XRD) and transmission electron microscopy (TEM). The SNPs coated by chitosan biopolymer showed good antimicrobial activity, and have extremely fine particle size approaching that of the quantum dots nanoparticles. The particle size distribution of all the prepared nanocomposite samples lies around the nanometer scale range of 3–6 nm. The corrosion rate of the standard corrosion coupons of mild steel in the industrial chilled water in the absence and the presence of different concentrations of SNPs-CTNC samples were measured by the gravimetric method as well as the electrochemical impedance spectroscopy (EIS) and DC-potentiodynamic polarization techniques. The inhibition efficiency (%IE) of SNPs-CTNC achieved up to 97–98% at the concentration of 150 ppm SNPs-CTNC of all the prepared samples (from chemical gravimetric weight loss results). The inhibition efficiency (%IE) of the best performance SNPs-CTNC sample (8 h) showed inhibition efficiency above 80% at 100 ppm (as evident by the further electrochemical techniques: impedance and potentiodynamic polarization results). Both the inhibition efficiency and the antimicrobial activity of SNPs-CT NC samples remained unchanged on aging for twelve months storage where: The percent inhibition efficiency of all SNPs-CTNC samples remain above the percentage of 93% on aging for this relatively long storage time period, the sample 2 h showed the most constant inhibition efficiency (97.6% for the fresh prepared sample and 97.5% for the twelve months aged sample). In addition, the scanning electron (SEM) micrographs have been showed that: A clean and bright metal surface was maintained after the exposure to the chilled water in the presence of SNPs-CTNC along the immersion time of one year. The nanocomposite samples acted by spontaneous physisorption on the metal surface as indicated by the negative value of ΔG°adsorption (equals −18.002 kJ·mol−1). The adsorption data represented in the surface coverage (θ) were found to be linearly fitted well to Langmuir adsorption isotherm with positive and relatively large value of the binding equilibrium constant (K) (43.6) that represented the strong attraction forces between the adsorbed nanocomposite particles and the metal surface. The mode of the adsorption of these nanocomposite particles on the metal surface has been interpreted in terms of the electrostatic interaction between the negatively charged colloidal SNPs and the positively the charged metal surface.

Use of Laser Markers for Supplementary Marking of Steel Billets

This paper discusses whether laser technology holds promise for use in marking steel billets in a continuous-production environment. A laser-marking experiment was performed on “dull metal” and “bright metal,” which have different oxidation layers. The experiment was performed on rolled-shape samples produced using a wide variety of carbon steels and differing scale produced by using different cooling rates during heat treatment (in water, or in a furnace). A QR code or bar code was applied to the heat-treated samples using laser markers where the laser exposure and laser power used for application of the code were varied. The experimental results revealed significant technical difficulties preventing use of this technology with “dull metal” (application of the code to areas coated with scale causes the corresponding areas to change color — gray instead of bronze resulting in the code being impossible to read using standard equipment). Delamination of the oxide coating on the billet will lead to loss of code, and make the code impossible to subsequently read. Successful laser marking of “dull metal” requires initial preparation of the surface for marking in order to remove scale inclusions, so that the code will have uniform color and contrast. A clean surface requires less time to laser mark and lower laser-marker power because of the high contrast between the code and the surface. The code remained intact and readable after long storage (on the order of 9 months) under standard conditions.

Non-Lambertian photometric stereo vision algorithm based on a multi-scale convolution deep learning architecture

As a form of fine 3D measurement technology, photometric stereo vision is widely used in 3D reconstruction, defect detection, biomedicine, and other fields, but the traditional reflection model has limited ability to reflect the real physical properties of materials and is not suitable for non-Lambertian surfaces with nonlinear light reflection characteristics such as bright metal, greatly limiting broader application of the technology. This paper proposes a photometric stereo vision algorithm based on a multi-scale convolution deep learning architecture that implements high precision reconstruction of a nontransparent material surface under arbitrary illumination conditions. The algorithm implements a multi-scale convolution structure in the deep network. The small-scale convolution kernel strengthens the expression of photometric physics that gives the model superior detail prediction performance. The large-scale convolution kernel encourages deep networks to take advantage of neighborhood features and enhances the ability of models to overcome shadows and distinguish multiple materials. To further address the problem of arbitrary illumination conditions, the algorithm employs a multi-resolution polar coordinate division method for the illumination vector space that integrates the input image information and fully utilizes the multi-scale convolution. It is experimentally demonstrated that the multi-scale convolution deep learning architecture effectively integrates the advantages of both photometric stereo and deep learning and greatly improves the adaptability to non-Lambertian surfaces while retaining the ability to perform fine reconstruction. It provides powerful support for a wide range of applications in photometric technology.

A combined X-ray, optical, and radio view of the merging galaxy cluster MACS J0417.5–1154

We present a comprehensive multi-wavelength analysis of the merging galaxy cluster MACS~J0417.5-1154 at a redshift of $z=0.44$, using available images red obtained with \chandra\ in X-ray, {\it Subaru}, {\it Hubble Space Telescope} (HST) in optical, {\it Giant Metrewave Radio Telescope} (GMRT) in radio and {\it Bolocam} at 2.1~mm wavelength. This is an example of a complex merging galaxy cluster also hosting a steep-spectrum Mpc scale radio halo. The mass distribution obtained by weak lensing reconstruction shows that MACS~J0417.5-1154 belongs to the dissociative class of mergers, where one of its substructures has had its gas content detached after the pericentric passage. We find the main cluster mass $M_{200}~=~11.5^{+3.0}_{-3.5} \times 10^{14}\ M_\odot$ and the smaller second (sub)cluster mass to be $M_{200}~=~1.96^{+1.60}_{-0.95} \times 10^{14}\ M_\odot$, leading to a large total mass of $M_{200}~=~13.8^{+2.6}_{-2.8} \times 10^{14}\ M_\odot$. The overall structure, surface brightness profile, temperature and metal abundance of the intra-cluster medium (ICM) all point towards the presence of a cold front and merger induced gas-sloshing motion near the core. We detect a surface brightness edge to the south$-$east direction at a projected distance of $\sim$45 arcsec ($\sim$255\,kpc) from the centre of this cluster. The X-ray spectral analysis across the inner and outer edge allows us to confirm the detected edge as a cold front. The GMRT 235\,MHz observation shows a comet$-$like extended sychrotron radio halo emission trailing behind the cold front. The peak of the Sunyaev-Zel'dovich decrement is found displaced from the centre of X-ray emission, which is interpreted as consequence of the merger dynamics.

Corrosion products and microstructure of copper alloy coins from the Byzantine-period Ma'agan Mikhael B shipwreck, Israel

Seven coins, covered with black concretion coating, found in the Byzantine-period Ma'agan Mikhael B shipwreck, were examined in this study. Metallurgical methods comprising visual testing, XRF, multi-focal light microscopy, SEM-EDS analysis and Raman spectroscopy, were used to determine the corrosion products and microstructure of the coins. The analysis results show that the coins were made of copper-lead alloy with a heterogeneous microstructure of bright and dark metal areas. The external surfaces of the coins were mostly composed of oxides and corrosion product compounds rich in Cu, Pb and Sn, while the external dark concretion coating was rich in Si, S, Ca and C compounds. Gradual variation of the composition and structure of the oxides and concretion coating layers was observed.

The Influence of Homogenization on the Elemental Distribution and Properties of Cu-10Ni-1Fe-1Mn Alloy Ingot

A set of Cu-10Ni-1Fe-1Mn alloys were prepared. Electromagnetic casting, DC casting ingot organization, properties and composition distribution of the alloy were studied using Optical Microscope (OM), Scanning Electron Microscopy (SEM), Energy spectrum analysis (EDS), Xray diffraction (XRD), Brinell Hardness Test, and electrochemical tests. The results suggested that homogenization of the Cu-10Ni-1Fe-1Mn alloy changed its properties and distribution of composition. The results also suggest that electromagnetic casting can refine casting organization, homogenize the composition of the alloy, and the casting mechanical performance is superior compared to those of DC casting. However, the composition between Dendritic branch and Dendrites was still not homogeneous. After 1 h of homogenization treatment at 950°C, the ingot composition distribution became more homogeneous, and its stiffness decreased. The tube prepared by squeezing the homogenized ingot, was soaked in 3.5% NaCl solution for 240 h, after which the tube blank surface remained a bright metal luster and XRD analysis indicated that a Cu2O protective film of high density covered the surface of the tube. The homogenization treatment significantly improved the corrosion resistant properties of the alloy tubes.

New Artificial Interphase with Li-Ion Pathway between Li Metal and Electrolytes for Secure Lithium Metal Anodes

While Li-ion batteries were firstly studied with Li metal as anodes due to its high theoretical specific capacity (3860 mA h g-1) and lowest negative electrochemical potential (-3.040 V vs SHE), commercial Li-ion batteries since 1992 consisted of graphite as an anode because of critical safety issues. However, for several decades, many strategies have been developed to surmount difficulties like problems of dendrite growth using modifications of electrolytes with additives, a change of lithium metal morphology, and an introduction of chemical/physical coating layers on Li metal. Herein, we report a simple approach to improve the electrochemical performance of Li metal anodes in Li-ion batteries with commercial carbonate-based electrolytes by utilizing a high Li-ion conductor, Li2TiO3, on Li metal anodes. Monoclinic Li2TiO3 is electrochemically inert in a wide voltage range with excellent structural stability in a liquid electrolyte. In addition, it structurally has a 3D path for Li-ion diffusions, leading to more uniform Li-ion flux. Li2TiO3 nanoparticles with a size of sub-100 nm were synthesized via a sol-gel method, and then the resulting particles were mixed with carbon as a conducting material and PVDF-HFP as a binder. A bright Li metal surface was covered with gray Li2TiO3 films in Figure 1a. From various Li plating and striping tests with pristine and modified Li metal as working electrodes, the modified Li metal exhibited outstanding electrochemical performances such as stable coulombic efficiency over 100th cycles at 1 mA/cm2 as shown in Figure 1c. Moreover, the modified Li metal was applied for practical lithium-ion batteries as a counter electrode to confirm the protective effects with LMO as a working electrode at a room temperature (25 oC) and high temperature (60 oC). Figure 1

(Invited) Characterisation of Metal Deposition and Metal Dissolution Processes in Deep Eutectic Solvents Using Electrochemical, Gravimetric and Neutron Scattering Methods

Electrolytic coatings of metals such as nickel, chromium, zinc, silver and gold are commonly applied as decorative and/or functional coatings. Some of the functional benefits which metal coatings provide are corrosion resistance, wear resistance, electrocatalysis and use in magnetic applications. A range of strategic manufacturing industries are dependent on such electrolytic coatings including electronics, aerospace, automotive and energy. The vast majority of electrolytic coatings are plated from aqueous solutions but stringent health and safety legislation governing transport, use and disposal of feedstock chemicals has driven the challenge for innovation in electrolyte technology that facilitates coatings from less toxic materials and in a manner that is more efficient and more consistent with environmental and process sustainability. We have been motivated by this challenge and have developed a range of novel solvent systems for deposition of metal coatings as alternatives to existing process (e.g. Ni, Zn, Cu, Ag, Ag) as well as novel electrolytes for deposition of reactive metals such as Al. These electrolytes have become known as Deep Eutectic Solvents and have shown utility and promise in a range of metal finishing processes. [1] Whilst the thermodynamics, kinetics, metal ion speciation and growth processes of electrolytic coatings from aqueous solutions have been studied for more than one hundred years, little is currently known about these fundamental aspects of electrochemical deposition from DES media. [2] Here we describe our studies into the electrochemical characterisation of a range of metals in DES electrolytes. In particular, we will focus on aspects of growth and dissolution processes and how these effect the morphology and composition of metal films. We will describe the characterisation of thin metal films in DES media using a range of time resolved techniques including cyclic voltammetry, chronopotentiometry, chronoampertometry, gravimetry (QCM), neutron reflectometry (NR) and surface metrology. The use of in-situ electrochemical NR methods is novel and we will present new data on the growth and dissolution of single metal and bi-layer metals films. The Figure shows time resolved NR data for the electrochemical dissolution of a Cu/Ag bi-layer on a Au substrate. We will also present complimentary data on the characterisation of the same systems using so-called Simultaneous Thickness Electrochemical Potential (STEP) chronopotentiometric methods. We will consider the effect of small-molecule additives on surface morphology and finish (roughness) of electrolytic coatings. [3] Organic and inorganic additives are often added to electroplating solutions to improve surface finish, reduce roughness and promote uniform surface morphology of the coatings. Such additives are usually small molecules and often referred to as brighteners or levellers. However, there have been limited investigations into the effect of such additives on electrodeposition from ionic liquids (ILs) and deep eutectic solvents (DESs). Here we will describe the effect of four additives on electrolytic plating of exemplar metals, nickel and zinc, from an ethyleneglycol based DES; these are nicotinic acid (NA), methylnicotinate (MN), 5,5-dimethyl- hydantoin (DMH) and boric acid (BA). The additives show limited influence on the bulk speciation but have significant influence on the electrochemical behaviour of metal deposition. Small concentrations (ca. 15 mM) of NA and MN show inhibition of metal ion reduction whereas high concentrations of DMH and BA are required for a modest difference in behaviour from the additive free system. NA and MN also show that they significantly alter the nucleation and growth mechanism when compared to the additive free system and those with DMH and BA. Each of the additive systems had the effect of producing brighter and flatter bulk electrodeposits and with increased coating hardness. “Deep Eutectic Solvents (DESs) and their Applications”, Emma L. Smith, Karl S. Ryder and Andrew P. Abbott, Chem. Rev., 2014, 114, 11060.“EXAFS Study into the Speciation of Metal Salts Dissolved in Ionic Liquids and Deep Eutectic Solvents”, Jennifer M. Hartley, Chung-Man Ip, Gregory C.H. Forrest, Kuldip Singh, Stephen J. Gurman, Karl S. Ryder, Andrew P. Abbott and Gero Frisch, Inorg. Chem., 2014, 53(12), 6280.“Bright Metal Coatings from Sustainable Electrolytes: The Effect of Molecular Additives on Electrodeposition of Nickel from a Deep Eutectic Solvent”, Andrew P. Abbott, Andrew Ballantyne, Robert C. Harris, Jamil A. Juma and Karl S. Ryder, Phys. Chem. Chem. Phys., 2017, 19. 3219. Figure 1

Bright metal coatings from sustainable electrolytes: the effect of molecular additives on electrodeposition of nickel from a deep eutectic solvent.

Organic and inorganic additives are often added to nickel electroplating solutions to improve surface finish, reduce roughness and promote uniform surface morphology of the coatings. Such additives are usually small molecules and often referred to as brighteners or levellers. However, there have been limited investigations into the effect of such additives on electrodeposition from ionic liquids (ILs) and deep eutectic solvents (DESs). Here we study the effect of four additives on electrolytic nickel plating from an ethyleneglycol based DES; these are nicotinic acid (NA), methylnicotinate (MN), 5,5-dimethylhydantoin (DMH) and boric acid (BA). The additives show limited influence on the bulk Ni(ii) speciation but have significant influence on the electrochemical behaviour of Ni deposition. Small concentrations (ca. 15 mM) of NA and MN show inhibition of Ni(ii) reduction whereas high concentrations of DMH and BA are required for a modest difference in behaviour from the additive free system. NA and MN also show that they significantly alter the nucleation and growth mechanism when compared to the additive free system and those with DMH and BA. Each of the additive systems had the effect of producing brighter and flatter bulk electrodeposits with increased coating hardness but XRD shows that NA and MN direct crystal growth to the [111] orientation whereas DMH and BA direct crystal growth to the [220] orientation.

Constraining gas motions in the Centaurus cluster using X-ray surface brightness fluctuations and metal diffusion

We compare two different methods of constraining the characteristic velocity and spatial scales of gas motions in the X-ray bright, nearby Centaurus cluster, using new deep (760ks) Chandra observations. The power spectrum of excess surface brightness fluctuations in the 0.5-6.0 keV band in a sector to the west is measured and compared to theoretical expectations for Kolmogorov index fluctuations. The observed power spectrum is flatter than these expectations, and the surface brightness fluctuations are around the 8 percent level on length scales of 2 kpc. We convert the 2D power spectrum of fluctuations into a 3D power spectrum using the method of Churazov et al., and then convert this into constraints on the one-component velocity of the gas motions as a function of their length scale. We find one-component velocities in the range 100-150 km/s on spatial scales of 4-10 kpc. An independent constraint on the characteristic velocity and length scales of the gas motions is then found by considering the diffusion coefficient needed to explain the distribution of metals in the Centaurus cluster, combined with the need to balance the rate of gas cooling with the rate of heat dissipated by the gas motions. We find that these two methods of constraining the velocity and length scales of the gas motions are in good agreement.

On-Board CBCT Imaging Using 2.5 MV Beam on a Radiation Therapy Linac for Metal Artifact Reduction

Purpose/Objective(s): Highly attenuating metallic objects such as dental fillings, hip/shoulder prosthesis, fiducial markers, cause severe streaking artifacts in on-board kV CBCT imaging and can lead to errors in imageguided patient setup. The purpose of this work is to reduce metal artifact in on-board CBCT imaging using new 2.5 MV beam available on a radiation therapy Linac. Materials/Methods: A head phantom with a copper bar inserted in the center was scanned with the 2.5 MV beam. With a full gantry rotation, 68 projection views were collected for a total of 20 MU. For comparison, a CBCT scan was also performed using the on-board kV imaging system. The peak voltage for kV scanning was 100 kVp. Due to the sparse projections of MV scanning, we performed iterative image reconstruction on both kV and MV data respectively. Several representative regions of interest were selected for evaluation of metal artifacts and contrast. Results: The mean CT numbers of the bright and dark metal artifacts in kV CBCT are 9000HU and -3000HU. In comparison, there are no bright metal artifacts and the mean CT number of dark metal artifacts is reduced to -460HU in MV CBCT. The mean CT numbers of the bone and metal are 1000HU, 5000HU for kV, and 380HU, 3600HU for MV. The mean CT numbers for three low contrast regions are -800HU, -600HU, -400HU for kV, and -460HU,-300HU, -100HU for MV. Conclusions: Using the new 2.5 MV beam for on-board CBCT imaging, we have significantly reduced metal artifacts compared with kV imaging, although with a decrease in soft-tissue contrast. Combining kV and MV imaging may lead to improved soft-tissue contrast with negligible metal artifact. Author Disclosure: Q. Xu: None. R. Li: None. Y. Yang: None. L. Xing: None.

The role of metals in cooling gas behind shock fronts in the atmospheres of cool stars

The influence of various chemical elements on radiative cooling of the gas flowing from a viscous jump is investigated in a model with a stationary shock in the atmosphere of a cool star. A closed system of equations is written for the thermal energy per heavy particle, the electron temperature, and the relative concentrations of elements in all ionization states. In addition to hydrogen and helium, atomic, singly ionized, and doubly ionized carbon, nitrogen, oxygen, sodium, magnesium, aluminum, silicon, sulfur, potassium, calcium, and iron are included, assuming they have their normal cosmic abundances. The high optical depth in Lyman-series lines leads to a return of the thermal energy to electrons via secondary collisions. As a result, the contribution of hydrogen to the cooling rate falls to the level of the contribution of metals, mainly carbon, magnesium, and iron. Thus, such shock models are able to explain the presence of bright metal lines in the spectra of cool and solar-type stars.

Problem Analysis of Conoprobe in Gear Measurement Application

Conoprobe is used for non-contact measurement utilizing conoscopic holography technology, which has characteristics of high measurement precision and large measuring angle range. However, the conoprobe performs inaccurate and instable in gear measurement applications. To verify its accuracy, an experiment setup is built using high performance coordinate measuring machine (CMM) to measure surfaces of gaugeblocks that have similar material as gear workpieces. Compared the collected data from the CMM with the conoprobe values, those problems mentioned above are validated. In this study it can be stated that measuring accuracy of conoprobe drops dramatically when measuring bright metal surfaces, and even its measuring error could be more than dozens of microns when the measurement is in large angle, therefore it is completely not fit for precision measurement applications.