Dynamic TCP acknowledgment in the LogP model

When messages, which are to be sent point-to-point in a network, become available at irregular intervals, a decision must be made each time a new message becomes available as to whether it should be sent immediately or if it is better to wait for more messages and send them all together. Because of physical properties of the networks, a certain minimum amount of time must elapse in between the transmission of two packets. Thus, whereas waiting delays the transmission of the current data, sending immediately may delay the transmission of the next data to become available even more. We propose a new quality measure and derive optimal deterministic and randomized algorithms for this on-line problem.     

Highly sensitive and interference-free determination of bismuth in environmental samples by electrothermal vaporization atomic fluorescence spectrometry after hydride trapping on iridium-coated tungsten coil

Bismuthine was on-line trapped on tungsten coil and subsequently electrothermally vaporized for the determination by atomic fluorescence spectrometry (AFS). Several noble metals, including Pd, Rh, Pt, and Ir, were explored as permanent chemical modifier for tungsten coil on-line trapping. Investigation showed that Ir gave the best performance, in which bismuthine was on-line trapped on Ir-coated tungsten coil at 560 °C, and then released at 1550 °C for subsequent transfer to AFS by a mixture of Ar and H₂. Under optimum instrumental conditions, the trapping efficiency was found to be 73 ± 3%. With 120 s (12 mL sample volume) trapping time, a limit of detection (LOD) of 4 ng L^− 1 was obtained, compared to conventional hydride generation AFS (0.09 μg L^− 1); the LOD can be lowered down to 1 ng L^− 1 by increasing the trapping time to 480 s. The LOD was found to be better or at least comparable to literature levels involving on-line trapping and some other sophisticated instrumental methods such as ICP-MS and GF-AAS. A comprehensive interference study involving conventional hydride-forming elements and some transition metals was carried out, and the result showed that the gas phase interference from other hydride-forming elements was largely reduced, thanks to the use of on-line tungsten coil trapping. Finally, the proposed method was applied to the determination of bismuth in several biological and environmental standard reference materials, and a t-test shows that the analytical results by the proposed method have no significant difference from the certified values at the confidence level of 95%.     

Mikroprozessor-Interface zur on-line Erfassung von Wägedaten

Zusammenfassung Als ergänzender Schritt für die Automatisierung der Flüssigkeitschromatographie wurde in unseren analytischen Laboratorien für Routinemessungen die automatische Erfassung von Wägedaten während der Probenvorbereitung eingeführt. Zu diesem Zweck wurde ein von einem Mikroprozessor gesteuertes Datenerfassungsgerät entwickelt, welches die Gewichtswerte von der Analysenwaage on-line in das Hewlett-Packard Lab-Data-System 3354 übermittelt. Das bedienungsfreundliche Konzept bringt eine wesentliche Arbeitserleichterung und schließt Fehlermöglichkeiten weitgehendst aus. Mit Geräten, welche seit über einem Jahr in Betrieb stehen konnten die Erwartungen voll erfüllt werden.

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Microprocessor-interface for the on-line aquisition of weight data

Summary With the on-line data aquisition of sample weights an additional step to the automation of liquid chromatography was introduced in our analytical laboratories. A new developed microprocessor controlled equipment connects a balance to the Hewlett-Packard Lab-Data-System 3354 and controls the on-line transfer of the weight data. The design is based on an easy application for users and gives essential reductions of workload and of error possibilities. Equipment are now in use with excellent results for over one year.

     

Kinetic Spectrophotometric Determination of Total Iron in Natural Water by Flow Injection Analysis Using On-Line Preconcentration

A new flow injection catalytic spectrophotometric method for on-line preconcentration and determination of total iron in natural water is described. The method is based on a combination of iron-catalyzed oxidation of diaminoditolyl by potassium bromate and the use of on-line preconcentration of iron onto 8-hydroxy-quinoline immobilized on silica gel. The corresponding calibration graph is linear over the range of 2.0–110ngmL^–1 for Fe(III) using a time-based technique for 5min preconcentration. The relative standard deviation of 11 measurements of 60ngmL^–1 Fe(III) was 0.67%. The method was applied to the determination of iron in natural water. The results obtained by the proposed method were compared with those obtained by ICP-AES. The t-test showed no significant differences between the two methods at a confidence level of 95%.     

Epoxidized soy bean oil migrating from the gaskets of lids into food packed in glass jars. Analysis by on-line liquid chromatography-gas chromatography

The migration of epoxidized soy bean oil (ESBO) from the gasket in the lids of glass jars into foods, particularly those rich in edible oil, often far exceeds the legal limit (60 mg/kg). ESBO was determined through a methyl ester isomer of diepoxy linoleic acid. Transesterification occurred directly in the homogenized food. From the extracted methyl esters, the diepoxy components were isolated by normal-phase LC and transferred on-line to gas chromatography with flame ionization detection using the on-column interface in the concurrent solvent evaporation mode. The method involves verification elements to ensure the reliability of the results for every sample analyzed. The detection limit is 2-5 mg/kg, depending on the food. Uncertainty of the procedure is below 10%.     

Automatic determination of phylloquinone in vegetables and fruits using on-line photochemical reduction and fluorescence detection via solid phase extraction and flow injection

A very simple, rapid and highly sensitive flow injection fluorimetric method was developed for the determination of phylloquinone. The assay was based on the on-line reduction of phylloquinone in dodecylsulfate micelles after irradiation with UV light. The micellar medium enhanced the fluorescence and stability of the reduced phylloquinone. Under optimum experimental conditions, the range of application of the technique was between 0.09 and 45.0 μg mL⁻¹ and the detection limit was 0.05 μg mL⁻¹. The sample throughput was 90 injections per hour. The reliability of the method for the routine analysis of phylloquinone in vegetables and fruits is demonstrated. Extractions were made with hexane, and an automated solid phase extraction system was used to purify the sample extracts prior to injection into the flow injection manifold.     

Development of an on-line automated sample clean-up method and liquid chromatography–tandem mass spectrometry analysis: application in an in vitro proteolytic assay

Fluorescence detection has been a method of choice in industry for screening assays, including identification of enzyme inhibitors, owing to its high-throughput capabilities, excellent reproducibility, and sensitivity. Occasionally, inhibitors are identified that challenge the fluorescence assay limit, necessitating the development of more sensitive detection methods to assess these compounds. For data mining purposes, however, original assay conditions may be required. A direct method transfer to highly sensitive and specific LC-MS-based methods has not always been possible due to the presence of MS-incompatible neutral detergents and non-volatile salts in the assay matrix. Utilizing an in vitro proteolytic screening assay for the serine protease hepatitis C virus (HCV) nonstructural (NS) 3 protease as a test case, we report the development of an automated sample clean-up procedure implemented on-line with liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis to complement fluorescence detection. Ion exchange and peptide microtraps were employed to remove MS-incompatible assay matrix components. Three protease inhibitors were used to validate the MS/MS method. Comparable potencies were achieved for these compounds when assessed by fluorescence and MS/MS detection. Furthermore, four-fold less enzyme could be utilized when employing the MS/MS method compared to fluorescence detection. The longer analysis time, however, resulted in reduced sample capacity. The potency of our designed HCV NS3 protease inhibitors are thus routinely evaluated using a continuous fluorescence-based assay. Only pertinent inhibitors approaching the fluorescence assay sensitivity limit are subsequently analyzed further by LC-MS/MS. This methodology allows us to maintain a database and to compare results independent of the detection method. Despite the relatively slow sample turnaround time of this LC-MS approach, the versatility of the automated on-line clean-up procedure and sample analysis can be applied to assays containing reagents which were historically considered to be MS incompatible.     

Development of an on-line immobilized-enzyme reversed-phase HPLC method for protein digestion and peptide separation

This paper describes use of a novel glass bead-based immobilized-enzyme micro column for simple and swift on-line protein digestion then peptide separation by reversed-phase HPLC. The inexpensive and easily made immobilized-enzyme micro column was prepared from aminopropyl controlled-pore glass that was reacted first with glutaraldehyde then with trypsin in the presence of phosphate buffer. Tryptic digestion of bovine serum albumin (BSA) was achieved simply by passing pretreated protein solution through the laboratory made immobilized-trypsin column; the tryptic fragments were then separated by reversed-phase HPLC. The peptide separation was found to be identical to separation of a sample which had undergone conventional enzymatic protein digestion in solution. Digestion of BSA by the immobilized-trypsin column decreased with increasing flow rate of the solution through the column, and 1.0 μL min⁻¹ was found to be the optimum flow rate for on-line protein digestion with our system. It was also found that the sample required pretreatment with urea before injection, because of a change in the properties of the protein in the presence of urea, and the immobilized-trypsin column lost its function in the presence of acetonitrile. This on-line proteomics system enables simple and rapid protein digestion and was successfully applied to partially micro two-dimensional (2D) chromatographic separation of proteins.     

Study on intelligent monitoring methodology based on the mathematical model of heat transfer for blast furnace stave

In order to monitor the thermal status of a blast furnace stave, an intelligent simulation technique is developed. The intelligent simulation model is built using a combined model based on the mathematical model of heat transfer and the technique of artificial intelligence. The intelligent simulation model of blast furnace cast steel stave is based on correction factor of parameters obtained by training the samples of test data of the cast steel cooling stave. Simulating currently existing blast furnace stave situation which is only a monitoring point on the stave and the velocity and temperature of cooling water are difficult to real-time be detected, the experimental verification of the model is done. The results show that the data of intelligent simulation model is nearly consistent with that of experiment. The model of high accuracy can on-line predict the thermal status of blast furnace stave.     

PMOXA/PAA Brushes toward on-Line Preconcentration for BSA in Capillary Electrophoresis

In this work, a binary-mixed-brushes-coated (BBC) capillary with switchable protein adsorption/desorption properties was developed and applied for on-line preconcentration of proteins. Firstly, amine-terminated poly(2-methyl-2-oxazoline) (PMOXA-NH₂) and thiolterminated poly(acrylic acid) (PAA-SH) were synthesized by using cationic ring-opening polymerization (CROP) and reversible addition fragmentation chain transfer (RAFT) polymerization, respectively. Then, the BBC capillary based on poly(2-methyl-2-oxazoline) (PMOXA) and poly(acrylic acid) (PAA) was prepared by sequentially grafting of PMOXA-NH₂ and PAA-SH onto fused-silica capillary inner surface through poly(dopamine) (PDA) as an anchor. The obtained PMOXA/PAA coating formed on the capillary or capillary's raw material was characterized in terms of the thickness, surface chemical composition by using scanning electron microscope (SEM) and X-ray photoelectron spectrum (XPS). The switchable protein adsorption/desorption performance of the BBC capillary was investigated by using fluorescence microscope under di erent solutions with certain pH and ionic strength(I). The results showed that bovine serum albumin (BSA) could be adsorbed on BBC capillary at pH=5.0 (I=10^-5 mol/L), and then the adsorbed BSA could be released at pH=9.0 (I=0.1 mol/L). This switchable protein adsorption/desorption property of coated capillary was then used to preconcentrate proteins on-line for increasing the detection sensitivity of BSA in capillary electrophoresis (CE). With this method, a sensitivity enhancement factor (SEF) more than 5000 for BSA detection was obtained.