A surface-mounted device assembly technique for small optics based on laser reflow soldering

The three-dimensional miniaturized optical surface-mounted device (TRIMO-SMD) is a new flexible and automated assembly technique for small optical components (maximum diameter for a lens is 2 mm) based on laser reflow soldering technique. This technology can be compared to the electronic SMD technique but applied to micro-optical devices. We present some recent developments of TRIMO-SMD in its application to industrial products.     

Square-wave voltammetric (SWV) determination of Captopril in reconstituted serum and pharmaceutical formulations

A simple, fast and sensitive square-wave voltammetric (SWV) method for the determination of trace amounts of Captopril in pharmaceutical formulation and reconstituted serum is reported. A three-electrode system containing the static mercury drop electrode (SMDE) working electrode, Pt auxiliary electrode and Ag/AgCl reference electrode was used throughout. Sodium sulfite was used as both supporting electrolyte and oxygen removing agent. No nitrogen purging is needed for oxygen removal from sample solution. Calibration graph showed good linearity in the concentration range of 0.5-50.0 μg mL⁻¹ of Captopril and regression coefficient of 0.9957 is obtained. R.S.D. for eight replicate measurements and LOD of the proposed method are 1.2% and 6.28 × 10⁻³ μg mL⁻¹, respectively. The effect of various parameters (equilibration time, scan increment, pulse height, drop size, frequency and sodium sulfite concentration) on the determination were investigated. The procedure was successfully applied to the determination of Captopril in pharmaceutical formulation and reconstituted serum.     

Catalytic Effect of Electric Fields on the Kemp Elimination Reactions with Neutral Bases

The effect of solvent reaction fields and oriented electric fields on the Kemp elimination reaction between methylamine or imidazole and 5-nitrobenzisoxazole has been theoretically studied. The Kemp reaction is the most widely used for the design of new enzymes. Our results, using the SMD continuous model for solvents, are in quite good agreement with the experimental fact that the rate of the analogous reaction with butylamine is one order of magnitude smaller in water than in acetonitrile. In the case of external electric fields, our results show that they can increase or decrease the energy barrier depending on the magnitude and orientation of the field. A duly oriented electric field may have a notable catalytic effect on the reaction. So, external electric fields and reaction fields due to the medium can contribute to the design of new enzymes. Several factors that must be taken into account to increase the catalytic effect are discussed.     

在轴向气流作用下液体轴对称抛撒二次破碎的实验研究

液体轴对称抛撒的实验研究是以云雾爆轰武器的研制为背景的。为了研究轴向气流作用下液体轴对称抛撒二次破碎所形成的雾化场特性,本文利用两台激波管并对之加以改造,成功地在实验室实现了轴向气流作用下液体的轴对称抛撒。为了研究其雾化场的远场特性,本文利用激光粒子测量仪获得了在不同实验工况和不同位置下的雾化场SMD分布曲线。实验数据表明,由于轴向气流速度的增加,液体破碎的Weber数得到了提高,导致二次破碎初期雾化场的SMD随之减小;随着抛撒驱动压力的提高,二次破碎初期雾化场的SMD也随之减小;在同一工况下,雾化场SMD随着测量位置与喷口距离的增加而变大。     

Beyond labels: A review of the application of quantum dots as integrated components of assays, bioprobes, and biosensors utilizing optical transduction

A comprehensive review of the development of assays, bioprobes, and biosensors using quantum dots (QDs) as integrated components is presented. In contrast to a QD that is selectively introduced as a label, an integrated QD is one that is present in a system throughout a bioanalysis, and simultaneously has a role in transduction and as a scaffold for biorecognition. Through a diverse array of coatings and bioconjugation strategies, it is possible to use QDs as a scaffold for biorecognition events. The modulation of QD luminescence provides the opportunity for the transduction of these events via fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), charge transfer quenching, and electrochemiluminescence (ECL). An overview of the basic concepts and principles underlying the use of QDs with each of these transduction methods is provided, along with many examples of their application in biological sensing. The latter include: the detection of small molecules using enzyme-linked methods, or using aptamers as affinity probes; the detection of proteins via immunoassays or aptamers; nucleic acid hybridization assays; and assays for protease or nuclease activity. Strategies for multiplexed detection are highlighted among these examples. Although the majority of developments to date have been in vitro, QD-based methods for ex vivo biological sensing are emerging. Some special attention is given to the development of solid-phase assays, which offer certain advantages over their solution-phase counterparts.     

An overview of analytical methodologies for the determination of antibiotics in environmental waters

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.     

Polydisperse effects in jet spray flames

A laminar jet polydisperse spray diffusion flame is analysed mathematically for the first time using an extension of classical similarity solutions for gaseous jet flames. The analysis enables a comparison to be drawn between conditions for flame stability or flame blow-out for purely gaseous flames and for spray flames. It is found that, in contrast to the Schmidt number criteria relevant to gas flames, droplet size and initial spray polydispersity play a critical role in determining potential flame scenarios. Some qualitative agreement for lift-off height is found when comparing predictions of the theory and sparse independent experimental evidence from the literature.     

Manipulation of biomolecules: A molecular dynamics study

With the rapid progression of bionanorobotics, manipulation of nano-scale biosamples is becoming increasingly attractive for different biological purposes. Nevertheless, the interaction between a robotic probe and a biological sample is poorly understood and the conditions for appropriate handling is not well-known. Here, we use the molecular dynamics (MD) simulation method to investigate the manipulation process when a nanoprobe tries to move a biosample on a substrate. For this purpose, we have used Ubiquitin (UBQ) as the biomolecule, a single-walled carbon nanotube (SWCNT) as the manipulation probe, and a double-layered graphene sheets as the substrate. A series of simulations were conducted to study the effects of different conditions on the success of the manipulation process. These conditions include the tip diameter, the vertical gap between the tip and substrate, and the initial orientation of the protein. Also we have studied two strategies for the manipulation of the protein by a nano-scale probe that we have named pushing and pulling. Interaction force between carbon nanotube (CNT) tips and the biomolecule, the root-mean-square deviation (RMSD), and the radius of gyration of the protein are monitored for different conditions. We found that larger tip diameters, smaller gaps between tip and substrate, and a pulling strategy increase the chance of a successful manipulation.     

Application and New Developments in Fluorescence Spectroscopic Techniques in Studying Individual Molecules

Abstract

Techniques based on fluorescence have played a variety of roles in chemistry, physics, spectroscopy, medicine, nanotechnology, and biotechnology due to their high selectivity, sensitivity, simplicity, and fastness in spectroscopic and imaging measurements. While detecting fluorescence from individual molecules by fluorescence‐based techniques, poor signal, limited lifespan of fluorophores, trade‐off between time resolution, and the level of detail of information were few major concerns. Ultrasensitive detectors permit the combination of the high time resolution of single photon counting devices with the large field of view and spectral resolution allowed by two‐dimensional detectors. Photobleaching and on‐off blinking of fluorophores can be improved dramatically by chemical modifications or changing the reagents. New ways of controlling local fields such as optic, electric, magnetic, chemical, or biochemical environments take advantage of the noninvasiveness and high temporal and spatial resolution of single‐molecule fluorescence (SMF) to get a direct feedback of events at the nanometer scale in various domains of research. Some of the applications and new developments in fluorescence spectroscopic techniques in detecting, investigating, and/or manipulating individual molecules have been discussed.     

Characteristic enhancement of white LED lamp using low temperature co-fired ceramic-chip on board package

In this paper, we propose low temperature co-fired ceramic-chip on board (LTCC-COB) package with improved thermal characteristics; no insulation layer exists between the LED chip and metal base. In actual measurement as well as in thermal simulation, the proposed LED lamp structure showed excellent thermal properties, compared with surface mound device-printed circuit board (SMD-PCB) package LED lamp. The optical output power, thermal distribution, current-voltage (I-V) and electroluminescence (EL) were measured and compared to analyze the characteristics of LTCC-COB package LED lamp with SMD-PCB package LED lamp. EL peak intensity of LTCC-COB package LED lamp is 1.75 times better than that of SDM-PCB package LED lamp. The thermal resistance between packing area and air was found to be 7.3 K/W and 7.9 K/W for LTCC-COB package and SMD-PCB package respectively. The proposed LTCC-COB packaged LED lamp is not only suitable for high power LED package due to its low thermal resistance but also a promising solution for illumination modules.