Solid-state transformations during diffusion bonding of copper to iron

Solid-state bonding between dissimilar metals, produced at elevated temperatures with the application of a bonding pressure, causes structural changes in the microstructure of the zones nearest to the bond interface. These metallurgical transformations, produced by interdiffusion in the vicinity of the bond, decide the final properties of the joint. In the present paper, such diffusional transformations have been investigated for diffusion-bonded joints of Armco iron and copper with different oxygen contents (ETPC and OFLPC). The formation of iron oxide (wustite) has been observed in the ETPC-Armco iron joints. This oxide did not appear in OFLPC-Armco iron diffusion-bonded joints. This suggests that iron oxide forms by reaction of iron with oxygen dissolved in the ETPC base metal. The formation of copper particles in the iron base matrix, near the bond interface, has been observed. This may be due to two different processes: the solid-state precipitation of copper into iron and the eutectoid reaction (γ →ε +α) at bonding temperatures above 900° C.     

The structure of toluene-doped counterflow gaseous diffusion flames

The structure of gaseous counterflow diffusion flames perturbed with the addition of hundreds of ppm of prevaporized toluene is studied in two distinct flame environments: a blue methane flame stabilized on the fuel side of the gas stagnation plane and an incipiently sooting ethylene flame stabilized on the oxidizer side. The goal is to provide a well-defined testbed in terms of temperature–time history, major species and part of the radical pool, for the examination of reference fuels that are critical components of practical fuel blends. Gas samples are extracted from the flame with fused silica microprobes for subsequent GC/MS analysis and thermocouples and thin filament pyrometry are used to characterize the temperature field. Profiles of critical toluene pyrolysis products and stable soot precursors are compared with computational models using two semi-detailed chemical mechanisms. Results show that in the methane flame some oxygen containing radicals like O and OH are contributing early on to the toluene destruction path. In the incipiently sooting ethylene flame, the primary attack is from H alone. This finding confirms the different challenges that such flames pose to the validation of a chemical kinetic mechanism. The onset of toluene decay in these flames begins at relatively modest temperatures, on the order of 800 K. This reactivity is captured reasonably well by both chemical mechanisms in the methane flame, in the absence of reactants larger than C2, but not so in the ethylene flame, in the presence of a richer, more complex mixture. The aromatic ring opening mechanisms are not adequately modeled in either case. This discrepancy has implications for the modeling of practically relevant fuel blends with both aliphatic and aromatic compounds. The dominant species larger than toluene in the doped methane flame is ethylbenzene, which at least one of the mechanisms reproduces quite well. The largest measured species in the incipiently sooting flame is indene, whose concentration increase due to toluene addition is properly captured by one of the models. The experimental dataset reported here may help identifying future improvements to chemical kinetic mechanisms and complement other reactor datasets lacking the coupling of kinetics and transport of flame environments.     

Asking questions on handwritten document collections

International Journal on Document Analysis and Recognition (IJDAR) - This work addresses the problem of Question Answering (QA) on handwritten document collections. Unlike typical QA and Visual...     

Robotic Locomotion and Piezo1 Activity Controlled with Novel Liquid Marble-based Soft Actuators

A novel soft actuator is designed, fabricated, and optimized for applied use in soft robotics and biomedical applications. The soft actuator is powered by the expansion and contraction of a graphene-containing and encased liquid marble using the photothermal effect. Unfortunately, conventional liquid marbles are found to be too fragile and prone to cracking and failure for such applications. After experimentation, it is possible to remedy this problem by synthesizing liquid marbles encased with polymeric shells–polymerized in situ–for added mechanical strength and robustness. These marbles are shown to have intrinsic photothermal activity. They are then situated in bimorph-type soft actuators where one side of the actuator has a dramatically different Young's modulus than the other, leading to directional actuation which is successfully demonstrated in multistep walking soft robots. The soft actuators are shown to successfully activate the mechanosensitive Piezo protein in a transfected human cell line with high effectiveness and no toxicity. Overall, the liquid marble-powered soft actuators described here represent a new soft actuation methodology and a novel tool for mechanobiological studies, such as stem cell fate and organoid differentiation.     

DNA-encoding to improve performance and allow parallel evaluation of the binding characteristics of multiple antibodies in a surface-bound immunoassay format

High affinity capture agents against protein targets are essential components for immunoassays, regardless of specific analysis format. Here, we describe the use of DNA-encoded antibodies for rapidly screening the kinetic and equilibrium binding properties of twelve commercial antibodies in a parallel analysis format using a multiplexed array of microring optical resonators. We show that DNA-encoding offers advantages in terms of antigen binding capacity, compared to covalently tethered antibodies; we also demonstrate that this linkage modality facilitates the rapid self-assembly of multiplexed arrays on account of complementarity between the DNA sequences on the antibodies and sensor array, respectively. Furthermore, DNA-encoded antibodies also allow for sensor array regeneration and reprogramming, as chaotropic agents can be used to disrupt the DNA-DNA duplexes that link the capture agents to the sensor without harming the underlying DNA on the surface, which can subsequently be reloaded with antibodies either targeting the same or different antigens.     

A unified approach to the surgical exposure of pancreatic and duodenal injuries

OBJECTIVE: It is necessary to have thorough knowledge of the survival of extreme low birth weight infants (ELBWI) in order to make it easier for obstetricians, neonatologists and the family to make a decision. PATIENTS AND METHODS: A revision of the 100 ELBWI in our service between 1988 and 1995, considering live births, those deceased in the same birthing room and those followed until their discharge from the hospital, was performed. The differences between the periods before and after the introduction of pulmonary surfactant in 1992 were analyzed. RESULTS: The total survival was 37% for those with a birth weight superior to 750 g or 26 weeks gestation. There were 44.2% males and 28.9% females. The total survival improved from 26.1% during 1988-1991 to 46.3% during the period of 1992-1995. During this period (1992-1995), the newborns weighing more than 750 g had a survival rate of 72.4% and for those of 26 weeks gestation it was 73.3%. Those born at 28 weeks gestation and those with 25 weeks of gestation and weighing more than 750 g, the total survival was 63% and the survival rate in the last four years was 75.9%. CONCLUSIONS: The mortality of the ELBWI descends in similar proportion to the remainder fo the ELBWI. In order to predict the prognosis, it would be necessary to carry out a correct ultrasound estimation of the gestational age and weight. It is necessary to offer a mother in the process of childbirth with a fetus of 28 weeks gestation or with 25 weeks gestation and a fetus with an ultrasound weight greater than 750 g, intrapartum fetal monitoring and to finish by Cesarean section in case of acute fetal distress, as well as intense and immediate neonatal attention as indicated by the index of survival reached in the group mentioned during the later years.     

GOX-functionalized nanodiamond films for electrochemical biosensor

The importance of nanodiamond in biological and technological applications has been recognized recently, and applied in drug delivery, biochip, sensors and biosensors. Under this investigation, nanodiamond (ND) and nitrogen doped nanodiamond (NND) were deposited on n-type silicon films, and later functionalized with enzyme Glucose oxidase (GOX). The GOX functionalized doped and undoped ND films were characterized using combination of several techniques; i.e. FTIR spectroscopy, Raman spectroscopy, atomic force microscopy (AFM) and electrochemical techniques. ND/GOX and NND/GOX thin films on n-type silicon have been found to provide sensitive glucose sensor. GOX has been chosen as a model enzyme system to functionalize with ND at molecular level to understand the glucose biosensor.     

Diffusion bonding of an aluminium-lithium alloy (AA8090) using aluminium-copper alloy interlayers

Diffusion bonds have been produced between sheets of an Al-Li-Cu-Mg-Zr alloy using aluminium-4% copper vapour deposited metallic interlayers. Microstructural changes occurred both in the parent alloy and in the bond interface after diffusion bonding cycles and post-bonding heat treatments were analysed. Different metallographic techniques (light microscopy, scanning and transmission electron microscopy) have been used. Diffusion bonding trials were carried out using the same alloy (AA8090), both in non-superplastic (T6) and superplastic conditions. Differences in their behaviours in relation to diffusion bonding were observed.     

Smart dynamic wavelength equalizer based on an integrated planaroptical circuit for use in the 1550-nm region

A microprocessor-controlled dynamic wavelength equalizer is presented. Th subsystem is based on an integrated optical circuit made in silica and covers a large portion of the usable region of the electromagnetic spectrum for optical fiber transmission (1530-1565 nm). The chip is connected in a software-controlled feedback loop, and with its dynamic range of ~7 dB for each channel, the system is capable of flattening the spectral response of an erbium-doped fiber amplifier to within 0.35-dB peak-to-peak. Insertion loss equals ~8 dB