The use of holographic optics for heat flow control in wire-based laser cladding

Laser cladding with wire utilises a focussing lens to melt the surface of the substrate, into which the wire is fed to build up a clad track on the surface. Process reliablity issues in practice include; clad tracks with high levels of dilution, surface cracking and other defects. Key to this is wire reflectivity calculations. Here using Fresnel equations that relate angle of incidence to heat absorption, we are able to show a direct correlation between the applied heat profile of the laser beam and the absorption profile of the wire surface; this has been modelled using COMSOL multiphysics conduction simulations which showed that the heat profile of the applied laser beam has a direct effect on the size and shape of the resulting melt pool. Using computer generated Holographic Optical Elements (HOE), a novel form of optic that alters the heat profile of the laser beam to a user-specified 3d profile, a conventional 1.25 mm diameter Gaussian beam shape and a 1.25 mm square uniform ‘pedestal’ HOE-derived beam shape were tested and compared, using a 1 mm diameter AISI 316 stainless steel wire on a 0.8mm mild steel substrate. These results were also compared to an enlarged 3.5 mm diameter Gaussian beam, in order to evaluate different methods of altering the heat distribution applied to the wire. The HOE generated beam gave superior results, due to its shorter thermal cycle, which reduced the amount of heat going into the clad track and resulted in lower dilution

Laser processing of printed copper interconnects on polymer substrates

With the increasing demand for integration of electronics embedded within devices there has been a consequent increase in the requirement for the deposition of electrically conductive materials to form connecting tracks on or within non-traditional substrate materials, such as temperature sensitive polymers, that may also have non-planar surfaces. In this work, micron scale copper powder based materials were deposited onto acrylic and glass substrates and then selectively laser processed to form electrically conductive copper tracks. Before deposition, the copper powder was chemically treated to remove the surface oxide and subsequently protected with a self-assembled monolayer coating. The copper was then patterned onto the substrate either as a dry powder confined within pre-formed grooves, or was combined with a binder to be printed as a paste. A CO2 laser was then used to heat the copper powder in air, leading to tracks that showed good electrical conductivity. At low laser power levels, the tracks appeared largely unchanged from the original material, but showed measureable conductivity. With higher laser power levels the tracks showed evidence of partial melting of the surface layers and further reductions in resistivity, to values approximately 30 times those of bulk copper, were obtained

Laser additive manufacturing of embedded 3D circuit system and microstructure manipulation using Gaussian and holographic optical elements reconstructed beams

In Printed Circuit Board (PCB) manufacturing. making the conductive tracks 3D and embedding the electronic components in substrate can effectively reduce the circuit board volume, and improve the power delivery performance. Laser based additive manufacturing has been developed for many years but currently it is still used to create non-functional product. This PhD work will combine the two technologies together to generate a complete 3D embedded circuit system. hi addition. the laser beam will be reconstructed using Holographic Optical Elements (HOE) to control the microstructure of the product. [Continues.

Three dimensional printed electronic devices realised by selective laser melting of copper/high-density-polyethylene powder mixtures

A manufacturing process with the capability to integrate electronics into 3D structures is of great importance to the development of next-generation miniaturised devices. In this study, Selective Laser Melting (SLM) was used to process copper/high-density-polyethylene (HDPE) powder mixtures to build conductive tracks in a 3D circuit system. The effects of copper/HDPE volume ratio, laser input power and scanning speed on the resistivity of CO 2 laser processed tracks were investigated. The resistivity of the tracks decreased from 26.6 ± 0.6 × 10 −4 Ωcm to 1.9 ± 0.1 × 10 −4 Ωcm as the copper volume ratio increased from 30% to 60%. However, further increasing the copper ratio to 100% resulted in poor conductivity. The lowest resistivity was achieved with an input power of 20 W and scanning speed of 80 mm/s. Additionally, processing using single-track-scanning and raster-scanning programs was compared; the overall energy distribution on the surface was more uniform using a raster-scanning program, which further reduced the resistivity to 0.35 ± 0.04 × 10 −4 Ωcm. Based on the results, a 3D multi-layered circuit system was manufactured with the HDPE as the substrate/matrix material and copper/HDPE mixture as the conductive-track material. This circuit system was successfully manufactured, demonstrating the possibility of using SLM technology to manufacture dissimilar materials towards 3D electronic applications

HuR antagonizes the effect of an intronic pyrimidine-rich sequence in regulating WT1 +/−KTS isoforms

<div><p>ABSTRACT</p><p>WT1 +KTS and -KTS isoforms only differ in three amino acids in protein sequence but show significant functional difference. The +/−KTS isoforms were generated by alternative usage of two adjacent 5′ splice sites at RNA level, however, how these two isoforms are regulated is still elusive. Here we report the identification of an intronic pyrimidine-rich sequence that is critical for the ratio of +/−KTS isoforms, deletion or partial replacement of the sequence led to full/significant shift to -KTS isoform. To identify trans-factors that can regulate +/−KTS isoforms via the binding to the element, we performed RNP assembly using in vitro transcribed RNA with or without the pyrimidine-rich sequence. Mass spectrometry analysis of purified RNPs showed that the element associated with many splicing factors. Co-transfection of these factors with WT1 reporter revealed that HuR promoted the production of -KTS isoform at the reporter level. RNA immuno-precipitation experiment indicated that HuR interacted with the pyrimidine-rich element in WT1 intron 9. We further presented evidence that transient or stable over-expression of HuR led to enhanced expression of endogenous -KTS isoform. Moreover, knockdown of HuR resulted in decreased expression of endogenous -KTS isoform in 293T, SW620, SNU-387 and AGS cell lines. Together, these data indicate that HuR binds to the pyrimidine-rich sequence and antagonize its effect in regulating WT1 +/−KTS isoforms.</p></div

Copper-Ion-Assisted Growth of Gold Nanorods in Seed-Mediated Growth: Significant Narrowing of Size Distribution via Tailoring Reactivity of Seeds

In the well-developed seed-mediated growth of gold nanorods (GNRs), adding the proper amount of Cu²⁺ ions in the growth solution leads to significant narrowing in the size distribution of the resultant GNRs, especially for those with shorter aspect ratios (corresponding longitudinal surface plasmon resonance (LSPR) peaks shorter than 750 nm). Cu²⁺ ions were found to be able to catalyze the oxidative etching of gold seeds by oxygen, thus mediating subsequent growth kinetics of the GNRs. At proper Cu²⁺ concentrations, the size distribution of the original seeds is greatly narrowed via oxidative etching. The etched seeds are highly reactive and grow quickly into desired GNRs with significantly improved size distribution. A similar mechanism can be employed to tune the end cap of the GNRs. Except for copper ions, no observable catalytic effect is observed from other cations presumably due to their lower affinity to oxygen. Considering the widespread use of seed-mediated growth in the morphology-controlled synthesis of noble metal nanostructures, the tailoring in seed reactivity we presented herein could be extended to other systems

Additional file 1: of Roles of astrocytic connexin-43, hemichannels, and gap junctions in oxygen-glucose deprivation/reperfusion injury induced neuroinflammation and the possible regulatory mechanisms of salvianolic acid B and carbenoxolone

Figure S1. Analysis of purity of primary cultured astrocytes or microglia. Primary glial cells were prepared, astrocytes and microglial cells were prepared and purified. (A1) Cells were stained with anti-CD11b-FITC antibody and detected with flow cytometry. The staining showed that < 0.1% of the cultured cells were microglia; (A2) Immunofluorescent staining revealed astrocytes stained with GFAP (green). Nuclei were stained with DAPI (blue). The GFAP staining showed that > 98% of the cultured cells were astrocytes. For microglial cells separated from the mix culture, both flow cytometry analysis and immunofluorescent staining showed that > 99% of the cultured cells were microglia in (B1-B2). Scale bar = 50 μm. Figure S2. MTT assay for cell viability of astrocytes undergone OGD/R injury. Primary astrocytes were prepared from newborn mice and subjected to OGD/R injury. (A) MTT assay to measure cell viability in astrocytes after treatment with SalB at 5 to 100 μg/mL concentrations. Con: control; (B) MTT assay to measure cell viability in astrocytes after treatment with CBX at 10 to 5000 μM concentrations. Con: control; (C) MTT assay to measure cell viability in astrocytes after treatment with CBX at 10 μM, SalB at 20 μg/mL, Gap19 at 100 μM, Gap26 at 100 μM; Also, Gap19, Gap26 or CBX pretreatment followed by SalB incubation and SalB pretreatment for 30 min followed by Gap19, Gap26 or CBX incubation with the above indicated concentrations; All error bars:±SEM. We evaluated the statistical significance with ANOVA and Duncan’s multiple comparisons test. *p < 0.05, **p < 0.01, and ***p < 0.001. Figure S3. Standard curve for ATP detection. ATP levels in conditioned medium were determined. The fluorescence levels from five serial ATP dilutions—0, 10, 30, 60, 100, 300, and 1000 nM are shown. Figure S4 (A-B) Western blotting were performed to evaluate the M2 marker arginase-1. Arginase-1 protein expression was decreased in the OGD/R group’s activated microglia, but SalB reversed this effect; (C-D) Arginase-1 expression was decreased in OGD/R-ACM-treated microglia while increased in microglia treated with OGD/R-SalB-ACM or OGD/R-CBX-ACM. We evaluated the statistical significance with ANOVA and Duncan’s multiple comparisons test. *p < 0.05, **p < 0.01, and ***p < 0.001. (PPTX 11400 kb

Activation of Oxygen-Mediating Pathway Using Copper Ions: Fine-Tuning of Growth Kinetics in Gold Nanorod Overgrowth

Growth kinetics plays an important role in the shape control of nanocrystals (NCs). Herein, we presented a unique way to fine-tune the growth kinetics via oxidative etching activated by copper ions. For the overgrowth of gold nanorods (Au NRs), competitive adsorption of dissolved oxygen on rod surface was found to slow down the overgrowth rate. Copper ions were able to remove the adsorbed oxygen species from the Au surface via oxidative etching, thus exposing more reaction sites for Au deposition. In this way, copper ions facilitated the overgrowth process. Furthermore, Cu²⁺ rather than Cu⁺ acted as the catalyst for the oxidative etching. Comparative study with Ag⁺ indicated that Cu²⁺ cannot regulate NC shapes via an underpotential deposition mechanism. In contrast, Ag⁺ led to the formation of Au tetrahexahedra (THH) and a slight decrease of the growth rate at similar growth conditions. Combining the distinct roles of the two ions enabled elongated THH to be produced. Copper ions activating the O₂ pathway suggested that dissolved oxygen has a strong affinity for the Au surface. Moreover, the results of NC-sensitized singlet oxygen (¹O₂) indicated that the absorbed oxygen species on the surface of Au NCs bounded with low-index facets mainly existed in the form of molecular O₂

Plasmon Enhancement Effect in Au Gold Nanorods@Cu₂O Core–Shell Nanostructures and Their Use in Probing Defect States

Au@Cu₂O core–shell nanostructures are fabricated to have a plasmon enhancement effect using Au nanorods (Au NRs) as a plasmon-tailorable core. By varying the concentration of Au NRs, we can tune the shell thickness in the range of 10–25 nm. The shell is composed of Cu₂O nanocrystallites. Because of the thin shells, the extinction spectra at wavelength >500 nm are dominated by the Au core. However, the large dielectric constant of the shell causes an obvious red shift of the surface plasmon resonance (SPR) band of the Au nanorod. Besides, transverse octupolar SPR appears as a result of the anisotropy of the core and the high dielectric constant of the shell. The anisotropic geometry of the Au NR is found to support the octupolar resonances at smaller sizes than for their spherical counterpart. Theoretical simulations indicate that the transverse SPR bands are divided into two resonances, which are dipolar- and octupolar-dominant, respectively. The Cu₂O shell degrades via a defect-mediated oxidative pathway, which is aggravated upon longitudinal SPR excitation. The SPR-mediated local field enhancement and resonance energy transfer are found to enhance the excitation of the defect states in the shell, thus providing a simple yet selective probing strategy for defect states

Enhanced Ultraviolet Random Lasing from Au/MgO/ZnO Heterostructure by Introducing p‑Cu₂O Hole-Injection Layer

Ultraviolet light-emitting devices (LEDs) were fabricated on the basis of Au/MgO/ZnO metal/insulator/semiconductor (MIS) heterostructures. By introducing a thermally oxidized p-type Cu₂O hole-injection layer into this MIS structure, enhanced ultraviolet electroluminescence (EL) and random lasing with reduced threshold injection current are achieved. The enhancement mechanism is attributed to effective hole transfer from p-Cu₂O to i-MgO under forward bias, which increases the initial carrier concentration of MgO dielectric layer and further promotes “impact-ionization” effect induced carrier generation and injection. The current study proposes a new and effective route to improve the EL performance of MIS junction LEDs via introducing extrinsic hole suppliers