Unattended Manner Research Articles

Ultra-fast quantitation of saquinavir in human plasma by matrix-assisted laser desorption/ionization and selected reaction monitoring mode detection

We present herein an ultra-fast quantitative assay for the quantitation of saquinavir in human plasma, without prior chromatographic separation, with matrix-assisted laser desorption/ionization using the selected reaction monitoring quantitation mode (MALDI-SRM/MS). The method was found to be linear from 5 to 10,000 ng/ml using pentadeuterated saquinavir (SQV-d5) as an internal standard, and from 5 to 1000 ng/ml using reserpine as internal standard (IS). Accuracy and precision were in the range of 101–108%, 3.9–11% with SQV-d5 and in the range 93–108%, 3.5–15% with reserpine. Plasma samples (250 μl) were extracted with a mixture of ethyl acetate/hexane. MALDI spotting of the extract was automated using electrodeposition and the dried droplet method using α-cyano-4-hydroxycinnamic acid (CHCA) as matrix. A 96 spots MALDI plate was prepared within 20 min in a fully unattended manner. Each sample was spotted four times and quantitation was based on the average of their analyte/IS area ratio. Samples were analyzed on a triple quadrupole linear ion trap (QqQ LIT) equipped with a high repetition laser source (1000 Hz). The analysis time of one sample was approximately 6 s, therefore 96 samples could be analyzed in less than 10 min. With liquid–liquid extraction sample preparation no significant matrix effects were observed. Moreover, the assay showed sufficient selectivity for samples to be analyzed at the lower limit of quantification (LLOQ) in the presence of other antiretroviral drugs, without prior chromatographic steps. In parallel, to assess the selectivity of the assay with real samples, a liquid chromatography (LC)–SRM/MS method was developed and a cross validation with clinical samples was successfully performed.

Redundancy Analysis and a Distributed Self-Organization Protocol for Fault-Tolerant Wireless Sensor Networks

Sensor nodes in a distributed sensor network can fail due to a variety of reasons, e.g., harsh environmental conditions, sabotage, battery failure, and component wear-out. Since many wireless sensor networks are intended to operate in an unattended manner after deployment, failing nodes cannot be replaced or repaired during field operation. Therefore, by designing the network to be fault-tolerant, we can ensure that a wireless sensor network can perform its surveillance and tracking tasks even when some nodes in the network fail. In this paper, we describe a fault-tolerant self-organization scheme that designates a set of backup nodes to replace failed nodes and maintain a backbone for coverage and communication. The proposed scheme does not require a centralized server for monitoring node failures and for designating backup nodes to replace failed nodes. It operates in a fully distributed manner and it requires only localized communication. This scheme has been implemented on top of an energy-efficient self-organization technique for sensor networks. The proposed fault-tolerance-node selection procedure can tolerate a large number of node failures using only localized communication, without losing either sensing coverage or communication connectivity.

Modeling of NMR processing, toward efficient unattended processing of NMR experiments

Many alternative processing techniques have recently been proposed in the literature. Most of these techniques rely on specific acquisition protocols as well as on specific data processing techniques, the need for an efficient versatile and expandable NMR processing tool would be a particularly timely addition to the modern NMR spectroscopy laboratory. The work presented here consists in a modeling of the various possible NMR data processing approaches. This modeling presents a common working frame for most of the modern acquisition/processing protocols. Two different data modeling approaches are presented, strong modeling and weak modeling, depending whether the system under study or the measurement is modeled. The emphasis is placed on the weak modeling approach. This modeling is implemented in a computer program developed in python and called NPK standing (standing for NMR Processing Kernel), organized in four logical layers (i) mathematical kernel; (ii) elementary actions; (iii) processing phases; (iv) processing strategies. This organisation, along with default values for most processing parameters allows the use of the program in an unattended manner, producing close to optimal spectra. Examples are shown for 1D and 2D processing, and liquid and solid NMR spectroscopy. NPK is available from the site: http://abcis.cbs.cnrs.fr/NPK.

An automated measurement system for characterization of RF and gradient coil parameters.

A fully automated laboratory-based measurement system for characterization of coil system parameters is presented. This method uses an inexpensive personal computer (PC)-controlled stepper motor positioning system in conjunction with a network/spectrum analyzer and an analog-to-digital converter (A/D) board that allows high resolution data acquisition in an unattended manner. A graphical interface was created for complete control of stepper motor movement, measurement, and data acquisition. The system is capable of performing a wide range of measurements that can, either individually or combined, characterize radiofrequency (RF) and gradient coils used in MRI. Measurement methods, theory, and results for conductor and shield current distributions, mutual impedance, and magnetic fields are given. Comparisons with theoretical calculations are included to validate the accuracy and utility of the system.

Modification of a Microprocessor-Controlled Autosampler for LC to Accept Other Injection Valves

Autosampling devices for liquid chromatography have become popular for safe and accurate sample introduction in an unattended manner. A modern autosampler was modified to allow for greater sampling flexibility and more precise, accurate injections. The modification is described using simple electronic circuitry.