Prototyping an ionization source for non-engineers

Novel mass spectrometry (MS) based analytical platforms have enabled scientists to detect and quantify molecules within biological and environmental samples more accurately. Novel MS instrumentation starts as a prototype and, after years of development, can become a commercial product to be used by the larger MS community. Without the initial prototype, many MS-based instruments today would not be produced. Additionally, biotechnology companies are the main drivers for research, development, and production of novel instruments, but the tools for prototyping instrumentation have never been more accessible. Here, we present a tutorial on prototyping instrumentation through the case study of developing the Next Generation IR-MALDESI source to show that an engineering degree is not required to design and construct a prototype instrument with modern hardware and software. We discuss the prototyping process, the necessary skills required for efficient prototyping, and information about common hardware and software used within initial prototypes.     

Assembly and performance of a 6.4 T cryogen‐free dynamic nuclear polarization system

We report on the assembly and performance evaluation of a 180‐GHz/6.4 T dynamic nuclear polarization (DNP) system based on a cryogen‐free superconducting magnet. The DNP system utilizes a variable‐field superconducting magnet that can be ramped up to 9 T and equipped with cryocoolers that can cool the sample space with the DNP assembly down to 1.8 K via the Joule–Thomson effect. A homebuilt DNP probe insert with top‐tuned nuclear magnetic resonance coil and microwave port was incorporated into the sample space in which the effective sample temperature is approximately 1.9 K when a 180‐GHz microwave source is on during DNP operation. ¹³C DNP of [1‐¹³C] acetate samples doped with trityl OX063 and 4‐oxo‐TEMPO in this system have resulted in solid‐state ¹³C polarization levels of 58 ± 3% and 18 ± 2%, respectively. The relatively high ¹³C polarization levels achieved in this work have demonstrated that the use of a cryogen‐free superconducting magnet for ¹³C DNP is feasible and in fact, relatively efficient—a major leap to offset the high cost of liquid helium consumption in DNP experiments.     

MicroRNA快速检测系统的设计

为了实现MicroRNA的快速检测,设计了一种便携式MicroRNA快速检测仪.基于等温滚环扩增技术,采用光电检测方法,检测标志物受激发出的荧光光强,建立特征荧光分析检测系统.通过改变激发光强度、MicroRNA试剂浓度等参量,验证了该仪器可测量的MicroRNA的浓度范围为0.01~0.1μmol,可检测出的最低检出限为7个拷贝数,MicroRNA浓度与荧光信号强度之间为线性关系(R2=0.999 1).     

Field measured pre-stress concrete losses versus design code estimates

In Florida, pre-stressed concrete bridges with a hybrid structural configuration, consisting of simply supported girders and continuous deck units providing composite action, are prevalent. In this study, an actual bridge with this configuration is instrumented with embedded vibrating wire strain gages during construction. The axial strain data are utilized to determine the time-dependent pre-stress loss variation and distribution in the pre-tensioned concrete girders used for the bridge. In this paper, however, we discuss the bridge instrumentation and monitoring technique used, and the deduced pre-stress losses obtained from field-measured strains up to 150 days, before placement of the composite slab. A comparison of the measured loss with the estimates of the Precast/Prestressed Concrete Institute (PCI) and the American Association of State Highway and Transportation Officials (AASHTO) indicates that the field-measured pre-stress loss is non-uniform across the girder depth, opposed to a uniform distribution implicitly assumed in most codes. The measured pre-stress variation is used in computing the concrete stress distribution in the girder at different depths within the given cross-section. When compared to the concrete stress from using the PCI and AASHTO suggested losses, the stress distribution resulting fron using the field-measured loss is found to be non-linear, and in most cases higher.     

A new method for manufacture of thin film heat flux gauges

The manufacture of thin film gauges for measuring transient temperatures and heat fluxes is described. A new method of using ceramic substrates (ZrO₂) with two sintered platinum wires is described. Examples of static and dynamic calibrations are given. Sample measurements in a shock tunnel are presented. The gauges show good mechanical strength and sensitivity.This article was processed using Springer- Verlag T_EX Shock Waves macro package 1990.     

An impedance method for the measurement of liquid hold-up in two-phase flow

A liquid hold-up gauge based on the measurement of the electrical impedance has been developed for application in gas-liquid pipe flow. The gauge consists of two ring electrodes mounted flush to the pipe wall. The impedance (capacitance or conductance) seen by the electrodes depends on the distance between them and on the liquid hold-up. For distances above three tube diameters, the impedance is independent of the flow configuration for all separated flow patterns and, with good approximation, also for intermittent flows. Moreover, capacitance or conductance are linearly related to the liquid hold-up. The impedance under bubble flow conditions closely follows the theoretical predictions due to Maxwell. Also for the other flow configurations (annular, stratified, intermittent) the results of static and/or dynamic calibration agree closely with theoretical models.     

Low-cost set-up for Fourier-transform infrared spectroscopy in diamond anvil cell from 4000 to 400 cm−1

An experimental set-up for Fourier-transform infrared (FTIR) studies at high pressure in the mid-IR region (400–4000 cm^?1) is constructed using a compact TEO-400 FTIR interferometer module and an external microscopic optical bench with cassegrain focusing objectives. Cassegrain-type reflective objectives act as an excellent beam condenser that facilitates the interfacing between FTIR spectrometer and diamond anvil cell. This set-up is capable of recording transmission and reflection infrared spectra at high pressure. Preliminary results are reported both in the reflection (pressure dependence of polar phonons in CuWO₄) and transmission configuration (polarized light absorption of polar phonons across the wurtzite-to-rocksalt transition in ZnO).     

Technical Development of Raman Spectroscopy: From Instrumental to Advanced Combined Technologies

Abstract

Raman-based techniques have developed into excellent analytical tools in various research fields, primarily due to their noninvasive sampling capability, minimal sample preparation, and short analysis time. Major improvements in lasers, spectrometers, detectors, and holographic optical components have made Raman spectroscopy an effective tool for analyzing natural and synthetic materials. This article presents a short introduction to Raman spectroscopy and several recently related advances, including, Fourier transform (FT) Raman spectroscopy, micro-Raman spectroscopy, Raman sensing, and stand-off Raman spectroscopy techniques. Other topics discussed in this article are the importance of its combination with laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF).     

A lattice of magneto-optical and magnetic traps for cold atoms

We describe basic periodic trapping configurations for ultracold atoms above surfaces. The approach is based on a simple wire grid and can be scaled to provide large arrays of periodically arranged magnetic or magneto-optical traps. The unit cells of the trap lattices are based on crossed wire segments. By alternating the current directions in the wires of the grid it can be distinguished between 3 basic lattice configurations. As a first demonstration, we used macroscopic wires in a 2 layer configuration to realize the unit cells of the lattices. With this experimental setup, we observe two of the basic unit cells and an array of 2×2 magneto optical traps. Received 29 August 2002 / Received in final form 12 December 2002 Published online 18 February 2003     

Managing the Complexity of Human/Machine Interactions in Computerized Learning Environments: Guiding Students’ Command Process through Instrumental Orchestrations

After an introduction which addresses some basic questions, this article is organized around three points: (1) The theoretical framework of the so-called “instrumental approach” which has been a theme in the last two CAME symposia; (2) A consideration of two processes (instrumentalization and instrumentation) which interact in the instrumental genesis; and (3) The introduction of the idea of instrumental orchestration as a way of allowing the teacher to assist the student’s instrumental genesis.This article originates from a lecture given at the Third CAME (Computer Algebra in Mathematics Education) Symposium (Reims, June 2003).