bluuebunny/crossref_metadata_2025 huggingface dataset:
Low molecular weight protamine as an efficient and nontoxic gene carrier: in vitro study
Authors: Park Yoon Jeong , Liang Jun Feng , Ko Kyung Soo , Kim Sung Wan , Yang Victor C.
Published: July 2003

Background

The structural similarity between low molecular weight protamine (LMWP), prepared by enzymatic digestion of protamine, and HIV‐TAT protein transduction peptide suggested the feasibility of LMWP as an efficient carrier for delivering therapeutic genes while alleviating the cytotoxicity of currently employed gene carriers.

Methods

LMWP was prepared by enzymatic digestion of protamine with thermolysine. The prepared LMWP peptide and TAT peptide, as well as their complexes with plasmid DNA (pDNA), were examined for cellular uptake behaviors by using confocal microscopy and flow cytometry. The complexation of pDNA and LMWP was monitored by gel retardation test as well as size and zeta potential measurements, and was then further assessed by DNase I protection assay. The transfection efficiency of pDNA/LMWP was examined by varying the pDNA content and charge ratio in the complex, and then compared with that of pDNA/PEI. Cytotoxicity induced by pDNA/LMWP and pDNA/PEI was also examined.

Results

Prepared LMWP showed similar transcellular localization behavior and kinetics to those of TAT, and efficiently transferred the pDNA into nucleus and cytoplasm in a short time period. The size and zeta potential of the pDNA/LMWP complex were 120 nm and 30 mV, respectively, which were adequately suitable for cellular uptake. After forming the complex, LMWP appeared to effectively protect pDNA against DNase I attack. The pDNA/LMWP complex showed significantly enhanced gene transfer than both naked pDNA and the pDNA/PEI complex, while exhibiting a markedly reduced cytotoxicity than that of the pDNA/PEI complex.

Conclusions

The present study suggested that LMWP could be a useful and safe tool for enhancing delivery of bioactive molecules and therapeutic DNA products into cells when applied in gene therapy. Copyright © 2003 John Wiley & Sons, Ltd.
Gene therapy for HIV/AIDS: the potential for a new therapeutic regimen
Authors: Fanning Greg , Amado Rafael , Symonds Geoff
Published: July 2003

Human Immunodeficiency Virus (HIV) is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS). HIV/AIDS is a disease that, compared with the not so distant past, is now better held in check by current antiretroviral drugs. However, it remains a disease not solved. Highly active antiretroviral therapy (HAART) generally uses two non‐nucleoside and one nucleoside reverse transcriptase (RT) inhibitor or two non‐nucleoside RT and one protease inhibitor. HAART is far more effective than the mono‐ or duo‐therapy of the past, which used compounds like the nucleoside reverse transcriptase inhibitor AZT or two nucleoside reverse transcriptase inhibitors. However, even with the relatively potent drug cocktails that comprise HAART, there are the issues of (i) HIV escape mutants, (ii) an apparent need to take the drugs in an ongoing manner, and (iii) the drugs' side effects that are often severe. This review speaks to the potential addition to these potent regimens of another regimen, namely the genetic modification of target hematopoietic cells. Such a new treatment paradigm is conceptually attractive as it may yield the constant intracellular expression of an anti‐HIV gene that acts to inhibit HIV replication and pathogenicity. A body of preclinical work exists showing the inhibition of HIV replication and decreased HIV pathogenicity by anti‐HIV genetic agents. This preclinical work used hematopoietic cell lines and primary cells as the target tissue. More recently, several clinical trials have sought to test this concept in vivo. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular electrostatic potential as a factor of drug–receptor recognition
Authors: Dukhovich Felix S. , Darkhovskii Michael B.
Published: July 2003

When a drug molecule approaches a non‐specific acceptor both molecules are in electrostatic fields of equal sign which prevents drug–acceptor complex formation. At the same time, the drug–acceptor system does not achieve the thermodynamic global minimum. Otherwise, when a certain drug interacts with its specific receptor, mutual compensation of their molecular electrostatic potentials takes place. Then separate atoms and groups of the drug molecule can bind to the receptor. We show that the fundamental role of molecular electrostatic potential in the process of drug–receptor recognition consists in fast correction of errors. Copyright © 2003 John Wiley & Sons, Ltd.
Long‐range and short‐range mechanisms of hydrophobic attraction and hydrophilic repulsion in specific and aspecific interactions
Authors: van Oss Carel Jan
Published: July 2003

Among the three different non‐covalent forces acting in aqueous media, i.e. Lifshitz–van der Waals (LW), Lewis acid–base (AB) and electrical double layer (EL) forces, the AB forces or electron–acceptor/electron–donor interactions are quantitatively by far the predominant ones. A subset of the AB forces acting in water causes the hydrophobic effect, which is the attraction caused by the hydrogen‐bonding (AB) free energy of cohesion between the water molecules which surround all apolar as well as polar molecules and particles when they are immersed in water. As the polar energy of cohesion among water molecules is an innate property of water, the hydrophobic attraction (due to the hydrophobic effect) is unavoidably always present in aqueous media and has a value of ΔGhydrophobic = −102 mJ/m2, at 20 °C, being equal to the AB free energy of cohesion between the water molecules at that temperature. The strong underlying hydrophobic attraction due to this effect can, however, be surmounted by very hydrophilic molecules and particles that attract water molecules more strongly than the free energy of attraction of these molecules or particles for one another, plus the hydrogen‐bonding free energy of cohesion between the water molecules, thus resulting in a net non‐electrical double layer repulsion. Each of the three non‐covalent forces, LW, AB or EL, any of which can be independently attractive or repulsive, decays, dependent on the circumstances, as a function of distance according to different rules. These rules, following an extended DLVO (XDLVO) approach, are given, as well as the measurement methods for the LW, AB and EL surface thermodynamic properties, determined at ‘contact’. The implications of the resulting hydrophobic attractive and hydrophilic repulsive free energies, as a function of distance, are discussed with respect to specific and aspecific interactions in biological systems. The discussion furnishes a description of the manner by which shorter‐range specific attractions can surmount the usually much stronger long‐range aspecific repulsion, and ends with examples of in vitro and in vivo effects of hydrophilization of biopolymers, particles or surfaces by linkage with polyethylene oxide (PEO; also called polyethylene glycol, PEG). Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of the pH‐dependencies of the association and dissociation kinetics of HIV‐1 protease inhibitors
Authors: Gossas Thomas , Danielson U. Helena
Published: July 2003

The kinetic constants for the interactions between HIV‐1 protease and a selection of inhibitors were determined at different pH‐values using a biosensor based interaction assay. Since this technique does not involve a substrate, it was possible to determine the pH‐dependencies of the association and dissociation rates of an inhibitor, without the complication of a pH‐dependent enzyme‐substrate/product equilibrium. The importance of these interactions was evaluated by correlating the free energy changes upon association and dissociation of inhibitors with the predicted change in electrostatic properties of the interacting groups as a result of altered pH. It was found that the kinetic parameters varied with pH in a unique manner for all inhibitors, demonstrating that the kinetic features were associated with the specific structure of each inhibitor. Association and dissociation had different pH‐profiles, indicating that the two processes proceeded by different pathways/mechanisms. The energy barrier for dissociation of the enzyme–indinavir complex increased with pH from 4.1 to 7.4, while it was generally reduced for the other inhibitors as the pH was increased from 5.1 to 7.4. The pH‐dependent interactions involved in the recognition/binding of inhibitors and in the stabilization of the complex were identified by analysing three‐dimensional structures of enzyme–inhibitor complexes. The interaction between the pyridine nitrogen of indinavir with Arg‐8 was hypothesized to be responsible for the unique pH‐dependency of indinavir. The analysis revealed features of interactions that are significant for understanding enzyme function and for optimization of new drug leads. It also highlighted the importance of environmental conditions on interactions. Copyright © 2003 John Wiley & Sons, Ltd.
Directional shape complementarity at the protein–DNA interface
Authors: Yeh Ching‐Sheng , Chen Fang‐Ming , Wang Jaw‐Yuan , Cheng Tian‐Lu , Hwang Ming‐Jing , Tzou Wen‐Shyong
Published: July 2003

Nature utilizes various styles of architecture for DNA‐binding proteins to recognize diverse DNA sequences, a process facilitated by a complementary surface between protein and DNA. However, the extent and ways this ‘shape complementarity’ occurs at the protein–DNA interface have yet to be characterized. Here, by analyzing a set of diverse protein–DNA complexes of known three‐dimensional structures, we investigated whether the normal vectors of a protein surface at the interface exhibited any relationship with DNA conformation. Generally, the normal vectors of a DNA‐contacting protein surface distinctly preferred certain angles, enabling them to align with certain axes characterizing the conformation of DNA. Thus, a new geometric property of DNA‐binding protein is demonstrated, i.e. the ‘shape complementarity’ of protein–DNA recognition clearly bears the property of ‘directionality’. Copyright © 2003 John Wiley & Sons, Ltd.
Solid supports for microarray immunoassays
Authors: Kusnezow Wlad , Hoheisel Jörg D.
Published: July 2003

Stimulated by the achievements of the first phase in genomics and the resulting need of assigning functions to the acquired sequence information, novel formats of immunoassays are being developed for high‐throughput multi‐analyte studies. In principle, they are similar in nature to the microarray assays already established at the level of nucleic acids. However, the biochemical diversity and the sheer number of proteins are such that an equivalent analysis is much more complex and thus difficult to accomplish. The wide range of protein concentration complicates matters further. Performing microarray immunoassays already represents a challenge at the level of preparing a working chip surface. Arrays have been produced on filter supports, in microtiter plate wells and on glass slides, the last two usually coated with one‐, two‐ or three‐dimensionally structured surface modifications. The usefulness and suitability of all these support media for the construction and application of antibody microarrays are reviewed in this manuscript in terms of the different kinds of immunoassay and the various detection procedures. Additionally, the employment of microarrays containing alternative sensor molecules is discussed in this context. The sensitivity of microspot immunoassays predicted by the current analyte theory is not yet a reality, indicating the extent of both the technology's potential and the size of the task still ahead. Copyright © 2003 John Wiley & Sons, Ltd.
Derivatization reaction of the mycotoxin moniliformin with 1,2‐diamino‐4,5‐dichlorobenzene: structure elucidation of an unexpected reaction product by liquid chromatography/tandem mass spectrometry and liquid chromatography/nuclear magnetic resonance spectroscopy
Authors: Zöllner Peter , Lienau Annette , Albert Klaus , Lindner Wolfgang
Published: July 2003

The derivatization reaction of the mycotoxin moniliformin with 1,2‐diamino‐4,5‐dichlorobenzene was previously introduced to improve distinctly the sensitivity of an assay applying high‐performance liquid chromatography prior to fluorescence detection. In the course of the implementation of this derivatization approach into a liquid chromatographic/mass spectrometric method, an unexpected derivatization product has now been discovered by mass spectrometry. In order to elucidate its structure, detailed investigations with liquid chromatography/tandem mass spectrometry and liquid chromatography coupled on‐line with NMR spectroscopy were performed. These studies give evidence for a heterocyclic structure that has been formed by the loss of one water and one carbon monoxide molecule. A reasonable mechanism for this derivatization reaction is proposed. Copyright © 2003 John Wiley & Sons, Ltd.
Internal residue loss produced by rearrangement of a novel cationic glycosphingolipid, glyceroplasmalopsychosine, in collision‐induced dissociation
Authors: Tadano‐Aritomi Keiko , Hikita Toshiyuki , Kubota Masayuki , Kasama Takeshi , Toma Kazunori , Hakomori Sen‐itiroh , Ishizuka Ineo
Published: July 2003

A novel plasmal conjugate of galactosylsphingosine (psychosine), Gro1(3)‐O‐plasmal‐O‐6Galβ‐sphingosine (glyceroplasmalopsychosine), was analyzed by electrospray ionization and liquid secondary ion mass spectrometry with low‐ or high‐energy collision‐induced dissociation (CID). In the product ion spectra of the [M + H]+ ions, [M + H − glycerol]+ ions arising from the loss of a glycerol were predominant. Unexpectedly, CID of the [M + H − glycerol]+ ion produced an outstanding ion, [(M + H − glycerol) − Hex]+, which required the loss of the galactose from inside the molecule. This ion was greatly reduced in the spectra of N,N‐dimethyl derivatives, indicating that the [(M + H − glycerol) − Hex]+ ion is formed from an intramolecular rearrangement with migration of the plasmal residue to the free amino group of sphingosine. It would be expected that the rearrangement occurs simultaneously with the elimination of glycerol or a rearranged [M + H]+ ion leads to the elimination of glycerol, to form a Schiff base‐type [M + H − glycerol]+ ion, from which the terminal galactose could be removed by the normal mechanism of glycosidic cleavage. On the other hand, the [M + Na − glycerol]+ ion derived from the sodiated molecule did not produce an ion corresponding to the rearrangement reaction, possibly owing to a higher stability of the sodiated ions against conformational changes. Copyright © 2003 John Wiley & Sons, Ltd.
Studies on the non‐covalent complexes between oleanolic acid and cyclodextrins using electrospray ionization tandem mass spectrometry
Authors: Guo Mingquan , Zhang Suoqing , Song Fengrui , Wang Daowu , Liu Zhiqiang , Liu Shuying
Published: July 2003

Non‐covalent inclusion complexes formed between an anti‐inflammatory drug, oleanolic acid (OA), and α‐, β‐ and γ‐cyclodextrins (CDs) were investigated by means of solubility studies and electrospray ionization tandem mass spectrometry (ESI‐MSn). The order of calculated association constants (K1 : 1) of complexes between OA and different CDs in solution is in good agreement with the order of their relative peak intensities and the relative CID energies of the complexes under the same ESI‐MSn conditions. These results indicate a direct correlation between the behaviors of solution‐ and gas‐phase complexes. ESI‐MS can thus be used to evaluate solution‐phase non‐covalent complexes successfully. The experimental results show that the most stable 1 : 1 inclusion complexes between three CDs and OA can be formed, but 2 : 1 CD–OA complexes can be formed with β‐ and γ‐CDs. Multi‐component complexes of α‐CD–OA–β‐CD (1 : 1 : 1), α‐CD–OA–γ‐CD (1 : 1 : 1) and β‐CD–OA–γ‐CD (1 : 1 : 1) were found in equimolar CD mixtures with excess OA. The formation of 2 : 1 and multi‐component 1 : 1 : 1 non‐covalent CD–OA complexes indicates that β‐ and γ‐CD are able to form sandwich‐type inclusion non‐covalent complexes with OA. The above results can be partly supported by the relative sizes of OA and CD cavities by molecular modeling calculations. All the complexes allow the detection of gaseous deprotonated CD–OA complexes in the negative ion mode at high abundances. The relative stabilities of the CDs–OA inclusion complexes in the gas phase can be evaluated from the relative CID energies in the ion trap (α‐CD–OA < β‐CD–OA < γ‐CD–OA) in the negative ion mode. Copyright © 2003 John Wiley & Sons, Ltd.
A sensitive and selective liquid chromatographic/electrospray ionization tandem mass spectrometric assay for the simultaneous quantification of α‐,β‐arteether and its metabolite dihydroartemisinin in plasma, useful for pharmacokinetic studies
Authors: Sabarinath S. , Rajanikanth M. , Madhusudanan K. P. , Gupta R. C.
Published: July 2003

A sensitive, selective, specific and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric assay method was developed and validated for the simultaneous quantitation of α‐,β‐arteether (α‐,β‐AE) and its metabolite α‐dihydroartemisinin (DHA) in monkey plasma using the propyl ether analogue of β‐arteether (PE) as an internal standard. The method involves a simple two‐step liquid–liquid extraction with hexane. The analytes were chromatographed on a C18 reversed‐phase chromatographic column by isocratic elution with methanol–ammonium acetate buffer (pH 4) (92 : 8, v/v) and analysed by mass spectrometry in the multiple reaction monitoring mode. The chromatographic run time was 7 min and the weighted (1/x2) calibration curves were linear over the range 0.78–200 ng ml−1. The method was validated in terms of accuracy, precision, absolute recovery, freeze–thaw stability, bench‐top stability and re‐injection reproducibility. The limit of detection and lower limit of quantification in monkey plasma were 0.39 and 0.78 ng ml−1 respectively for all the analytes. The intra‐ and inter‐batch precision and accuracy were found to be well within acceptable limits (<15%). All three analytes were stable even after three freeze–thaw cycles (deviation < 15%). The average absolute recoveries of α‐,β‐AE, DHA and PE, used as an internal standard, from spiked plasma samples were 85.85 ± 6.56, 70.10 ± 7.06, 54.37 ± 3.39 and 93.90 ± 6.9%, respectively. The assay method described here could be applied to study the pharmacokinetics of α‐,β‐AE and DHA in rhesus monkeys. Copyright © 2003 John Wiley & Sons, Ltd.
High‐sensitivity quantitation of cabergoline and pergolide using a triple‐quadrupole mass spectrometer with enhanced mass‐resolution capabilities
Authors: Hughes Nicola , Winnik Witold , Dunyach Jean‐Jacques , Amad Ma'an , Splendore Maurizio , Paul Gary
Published: July 2003

Quantitative analysis of pharmaceuticals with low systemic plasma levels requires the utmost in sensitivity and selectivity from the analytical method used. A recently introduced triple‐quadrupole mass spectrometer with unique enhanced mass‐resolution capability was evaluated in the analysis of two such drugs, cabergoline and pergolide, in plasma. Liquid chromatographic/electrospray ionization selected reaction monitoring determination of cabergoline in plasma at unit mass‐resolution demonstrated improved sensitivity (50 fg on‐column), coupled with suitable accuracy and precision over a broad linear dynamic range covering five orders of magnitude (50 fg to 5 ng on‐column). Liquid chromatographic/atmospheric pressure chemical ionization selective reaction monitoring determination of pergolide in plasma also attained a high level of sensitivity (500 fg on‐column) at unit mass‐resolution, with accuracy and precision values well within pharmaceutical industry standards. Again, a linear dynamic range covering five orders of magnitude (500 fg to 50 ng on‐column) was achieved for the assay. Utility of the enhanced mass‐resolution feature of the triple‐quadrupole mass spectrometer in the determination of pergolide resulted in an improvement in analyte sensitivity (250 fg on‐column) and linear dynamic range (250 fg to 50 ng on‐column). Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of alkylacyl, alk‐1‐enylacyl and lyso subclasses of glycerophosphocholine by tandem quadrupole mass spectrometry with electrospray ionization
Authors: Hsu Fong‐Fu , Turk John , Thukkani Arun K. , Messner Maria C. , Wildsmith Kristin R. , Ford David A.
Published: July 2003

Positive ion tandem quadrupole mass spectrometric methods for structural characterization of the subclasses of sn‐glycero‐3‐phosphocholine (PC), including alkylacyl‐ and alk‐1‐enylacylphosphocholine and lysophosphatidylcholine (LPC), are described. Following collisionally activated dissociation, the [M + Li]+ ions generated by electrospray ionization yield abundant informative fragment ions that permit structural determination, and distinction of regioisomers among lysophosphatidylcholine can be easily achieved. In contrast, structurally informative ions arising from [M + H]+ or [M + Na]+ ions are less prominent. The most abundant ion observed in the product‐ion spectra of the [M + Li]+ ions of plasmenyl‐ and plasmanyl‐PC and of LPC arises from loss of N(CH3)3 ([M + Li − 59]+). This feature permits their distinction from a product‐ion spectrum arising from a diacylphosphatidylcholine, in which the [M + Li − 183]+ ion reflecting loss of phosphocholine is the most prominent. Examples for identification of various subclasses of PC in biological extracts by tandem mass spectrometry applying various constant neutral loss scannings are also shown. Copyright © 2003 John Wiley & Sons, Ltd.
Mass spectrometric methods for the analysis of chlorinated and nitrated isoflavonoids: a novel class of biological metabolites
Authors: Prasain Jeevan K. , Patel Rakesh , Kirk Marion , Wilson Landon , Botting Nigel , Darley‐Usmar Victor M. , Barnes Stephen
Published: July 2003

Electrospray ionization combined with tandem mass spectrometry was applied to a study of some representative chlorinated and nitrated isoflavones—potential metabolites of isoflavones in inflammatory cells. Upon collision‐induced dissociation of deprotonated [M − H]− ions of these compounds, a number of structurally characteristic product ions were produced. The product ion analysis of 3′‐ and 8‐chlorodaidzein in the tandom mass spectra led to ready differentiation of these isomers. 3‐Nitro derivatives of both genistein and daidzein have product ions due to the losses of HNO2 and two OH groups. Chlorinated derivatives of isoflavones were detected in cell‐based experiments and their structures were proposed by comparing the tandem mass spectra of their product ions with those of standards. This work provides a suitable analytical basis to aid the characterization of chlorinated and nitrated metabolites in studies in vivo and in vitro. Copyright © 2003 John Wiley & Sons, Ltd.
Two‐laser infrared and ultraviolet matrix‐assisted laser desorption/ionization
Authors: Little Mark W. , Kim Jae‐Kuk , Murray Kermit K.
Published: July 2003

Matrix‐assisted laser desorption/ionization (MALDI) was performed using two pulsed lasers with wavelengths in the IR and UV regions. A 10.6 µm pulsed CO2 laser was used to irradiate a MALDI target, followed after an adjustable delay by a 337 nm pulsed nitrogen laser. The sample consisted of a 2,5‐dihydroxybenzoic acid matrix and bovine insulin guest molecule. The pulse energy for both of the lasers was adjusted so that the ion of interest, either the matrix or guest ion, was not produced by either of the lasers alone. The delay time for maximum ion yield occurs at 1 µs for matrix and guest ions and the signal decayed to zero in ∼400 µs. A mechanism is presented for enhanced UV MALDI ion yield following the IR laser pulse based on transient heating. Copyright © 2003 John Wiley & Sons, Ltd.
Direct tissue analysis using matrix‐assisted laser desorption/ionization mass spectrometry: practical aspects of sample preparation
Authors: Schwartz Sarah A. , Reyzer Michelle L. , Caprioli Richard M.
Published: July 2003

Practical guidelines for the preparation of tissue sections for direct analysis by matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry are presented. Techniques for proper sample handling including tissue storage, sectioning and mounting are described. Emphasis is placed on optimizing matrix parameters such as the type of matrix molecule used, matrix concentration, and solvent composition. Several different techniques for matrix application are illustrated. Optimal instrument parameters and the necessity for advanced data analysis approaches with regards to direct tissue analysis are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Printed dual‐band U‐slotted monopole antenna for WLAN access point
Authors: Su Saou‐Wen , Cheng Yuan‐Tung , Wong Kin‐Lu
Published: August 2003

A novel printed U‐slotted monopole antenna suitable for application in 2.4/5.2‐GHz dual‐band wireless local area network (WLAN) access points is presented. The monopole antenna without the U‐shaped slot has a lower or fundamental resonant mode for the 2.4‐GHz WLAN band. When a U‐shaped slot is embedded, an additional smaller monopole is formed, which generates an upper resonant mode for the 5.2‐GHz WLAN band. Experimental results of a constructed prototype are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 436–438, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11083
Novel probe‐feeding architectures for stacked microstrip patch antennas
Authors: Kona Keerti S. , Rahmat‐Samii Yahya
Published: August 2003

Dual‐band stacked microstrip patch antennas are a popular choice for wireless and other vehicular communication applications. They are also being considered for use in feed arrays for reflector antennas. In this paper, novel center‐feeding schemes to achieve the desired dual‐band response will be presented. Also, novel side‐feeding schemes for a potential application in arrays have been investigated. L‐band frequencies were chosen to test the concept. For the stacked patch configuration, the primary objective was to get the antenna to resonate at two frequencies—1.575 GHz for the upper patch and 1.228 GHz for the lower patch—with a shared aperture and two independent excitations. Return‐loss, isolation, and pattern measurements for several antenna prototypes are presented. The measured results are compared with the simulation results from an FDTD code developed at UCLA. Extension of the concept for dual‐polarization and array configurations has been explored. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 467–475, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11092
Characteristics of Gaussian pulses transmitting in the G.652 fiber with FBG dispersion compensation
Authors: Pei Li , Jian Shuisheng , Yan Fengping , Li Tangjun , Ning Tigang
Published: August 2003

The compression characteristics of a Gaussian pulse with varied chirp and pulse width are obtained by theoretical analysis and experiments. The compensation effects are diverse, even with the same chirped optical fiber Bragg grating (FBG) dispersion compensator, and the optimal dispersion compensation length is related to the position of the FBG. At present, in most of transmission systems, the signal from the lasers are Gaussian pulses, thus an analysis of its broader characteristics, before and after it is reflected from the FBG, will be significant. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 480–484, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11095
Numerical and experimental investigation of the strength of corrugated board packages
Authors: Biancolini M. E. , Brutti C.
Published: July 2003

The buckling behaviour of corrugated paper packages was studied by means of an experimental and theoretical analysis. Mechanical behaviour of paperboard was first evaluated experimentally, then a local geometry FEM model, able to reproduce with a very good accuracy buckling loads obtained experimentally in the standard edge compression test, was developed. In order to investigate the buckling of a complete package, a finite element ‘corrugated board’ was introduced by means of a dedicated homogenization procedure. The FEM model of the package, assembled with this new element, can accurately predict the experimental data of incipient buckling observed during the standard box compression test, despite the few degrees of freedom and the minimal computational effort. Copyright © 2003 John Wiley & Sons, Ltd.
The control of dissolved oxygen content in probiotic yoghurts by alternative packaging materials
Authors: Miller Craig W. , Nguyen Minh H. , Rooney Michael , Kailasapathy Kaila
Published: July 2003

Probiotic bacteria, added to yoghurt to impart health benefits, require a low‐oxygen environment for maximum viability. The aim of this experiment was to produce yoghurt with minimal oxygen content using packaging systems. Three packaging systems were evaluated for the effect they exert on the dissolved oxygen content of two types of yoghurt. High‐impact polystyrene (the Australian yoghurt industry's material of choice) was compared with new oxygen‐barrier material and an oxygen‐scavenging active packaging system. Stirred‐type and set‐type yoghurts were observed in each packaging material for dissolved oxygen content, over a normal shelf‐life for yoghurt. Oxygen‐barrier packaging combined with an oxygen‐scavenging material was found to be the most effective system, particularly when used with set‐type yoghurt. Set‐type yoghurt was found to be more conducive to oxygen reduction using packaging methods. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of temperature on the cushioning properties of some foamed plastic materials
Authors: Marcondes Jorge , Hatton Kayo , Graham Jennifer , Schueneman Herb
Published: July 2003

Foamed plastics are used to cushion products to protect them from shock and vibration. Design data is in most cases derived from laboratory tests, performed under standard conditions. However, during distribution, most shock and vibration events occur under conditions different from those under which the materials were evaluated. Two commonly used foams in packaging, expanded polyethylene and expanded polystyrene, were used to investigate how changes in temperature affect the performance properties of these materials. The materials were tested for shock and vibration under four different temperatures (−17°C, 3°C, 23°C and 43°C). The results show that the properties of expanded polystyrene were the least influenced and those of expanded polyethylene were the most influenced by changes in temperature. Copyright © 2003 John Wiley & Sons, Ltd.
Simple models for evaluating effects of small leaks on the gas barrier properties of food packages
Authors: Chung Donghwan , Papadakis Spyridon E. , Yam Kit L.
Published: July 2003

A detailed theoretical analysis and calculations were made for providing a simple and explicit means to evaluate the effects of small leaks on the barrier properties of food packages. Small leaks, such as pinholes and channel leaks, were approximated as cylindrical pores with diameters of 50–300 μm. The first part of the current study proposes a simple mathematical model based on Fick's law of diffusion, which accounts for both the gas leakage across small leaks and the gas permeation across package walls. The model uses an effective permeability that depends on leak dimensions, type of diffusing gas, type of packaging material and gas conditions around the leak ends. In the second part of the study, three practical cases are presented to illustrate the application of the proposed model in examining the significance of leaks. These demonstrate in a simple and explicit manner that for LDPE packages: (a) leaks affect the oxygen transfer more than the water vapour transfer; (b) leak effects are more significant at lower storage temperatures; and (c) that for high gas barrier packages, the effect of leaks is very important and should not be neglected. The model can be also used to arrive at conclusions about the significance of leaks in other packaging situations (e.g. other than LDPE packaging materials) and to correct the shelf‐life estimation of gas‐ and water vapour‐sensitive foods for errors from package leaks. Copyright © 2003 John Wiley & Sons, Ltd.
History of FDA good laboratory practices
Authors: Baldeshwiler Anne M.
Published: July 2003

The United States Food and Drug Administration (FDA) requires nonclinical studies of new drugs, food additives and chemicals to predict their safety and potential efficacy in humans. The significance of the information gained from these studies requires that they be conducted according to sound scientific principles and with strict attention to quality assurance and quality control. Human health and safety are dependent upon the decisions made from these studies. The discovery of the lack of companies' adherence to these principles led to the development of the good laboratory practice (GLP) regulations, the driving force behind the quality of nonclinical laboratory studies. As the 25th anniversary of the publication of the regulations approaches, a description of the events leading to the proposal of the GLP regulations provides understanding about their significance and the importance of their use in assuring the quality and integrity of nonclinical safety data. Copyright © 2003 John Wiley & Sons, Ltd.
Clinical quality assurance: Auditing phase II trials
Authors: Winchell Terry
Published: July 2003

Clinical quality assurance (CQA) auditing of Phase II trials may help eliminate potential problems before they occur by providing valuable quality input before pivotal Phase III trials are undertaken. CQA auditing of Phase II trials can affect critical elements of design regarding Phase III protocols, and may be extremely useful in the early evaluation of vendors prior to investing in Phase III research. Copyright © 2003 John Wiley & Sons, Ltd.
Raising the quality of publications: Now we have GPP!
Authors: Wager Elizabeth
Published: July 2003

Until recently, few guidelines were available to assist companies in publishing their clinical trials and, compared to other phases of research, the quality of publications and the processes by which publications are developed have not received much scrutiny. However, guidelines on Good Publication Practice (GPP) for pharmaceutical companies have just been published. These aim to raise the quality of publications and to encourage ethical and responsible publication practices. The GPP guidelines were designed to be used alongside existing guidelines such as those from the International Committee of Medical Journal Editors (ICMJE) and the CONSORT statement. These, and other documents relevant to preparing publications, are reviewed and recommendations for ways in which companies might improve the quality of their publications are proposed. Copyright © 2003 John Wiley & Sons, Ltd.
The quality profession and its role in the world
Authors: Dedhia Navin S.
Published: July 2003

The concept of quality evolved from inspection, measurement, and testing, which had been in practice for many, many years. Long ago, an artist or a sculptor took pride in his work and as a result always tried to excel in what was created. Mass production systems brought the concept of inspection by someone other than the craftsman in the first half of the 20th century. Application of statistical control came later as a result of World War production methods. Quality as a profession and the managerial process associated in the quality function was introduced during the second‐half of the 20th century, and has evolved since then.

No other profession has seen as many changes as the quality profession. The quality profession grew from simple control, to engineering, to systems engineering. Quality control activities were predominant in the 1940s, 1950s, and 1960s. The 1970s were an era of quality engineering and the 1990s saw quality systems as an emerging field. Like medicine, accounting, and engineering, quality has achieved status as a recognized profession. Published in 2003 by John Wiley & Sons, Ltd.
Standard operating procedures for clinical research personnel‐‐Part 17
Authors: Bohaychuk Wendy , Ball Graham
Published: July 2003

This is the 17th in a series of articles containing proposals for wording and content of Standard Operating Procedures (SOPs) for clinical research activities conducted by sponsors and Contract Research Organisations (CROs). The procedures include those required by the International Conference on Harmonisation (ICH), the Food and Drug Administration (FDA), many other guidelines and regulations, and 'best practice' observed by the authors. The model forms require modification for actual use. In this article, SOPs are presented for management of study medications/devices: initial request for study medications/devices (SOP 501); labelling and packaging of study medications/devices (SOP 502) and shipment of study medications/devices to study sites (SOP 503). (The full text of all 101 SOPs is available from the authors.) Copyright © 2003 John Wiley & Sons, Ltd.
Steering a course for risk assessment: The impact of new draft guidance, 21 CFR part 11, scope and application, on the electronic records; electronic signatures rule
Authors: Kuniholm George G.
Published: July 2003

As a result of some re‐organization in the US Food and Drug Administration (FDA) and the introduction of the CGMP risk‐based approach, 21 CFR Part 11 is being revisited. The FDA has decided to re‐evaluate Part 11 and during the re‐evaluation, the FDA issued guidance on how Part 11 will be interpreted. The proposed guidance defines the FDA's approach to the scope and application of Part 11. The draft guidance has substantial regulatory impact by withdrawing previous Part 11 draft guidance as well as the Compliance Policy Guide 71523.17.

The scope of Part 11 is defined to be records required by predicate rules kept electronically in lieu of paper records or relied upon for regulated activities, as well as records submitted to the agency, and electronic signatures. Emphasis is given to following predicate rule requirements.

In applying Part 11, the FDA will exercise enforcement discretion in the areas of audit trail requirements, validation, copying electronic records, electronic record maintenance, and legacy systems. Emphasis is given to creating and following documented Risk Assessment practice.

This article examines the change in FDA focus and highlights key points in the draft guidance. Further, this article provides practical advice for industry, provides an overview on comments (industry feedback) submitted to the Agency on the guidance, and provides an interpretation of the likely direction for future Part 11 regulation. Copyright © 2003 John Wiley & Sons, Ltd.
What's New?
Authors: Bohaychuk Wendy , Broughton Steve
Published: July 2003

The What's New? section in the Quality Assurance Journal aims to draw attention to items of importance to QA professionals. There is usually a three‐month interval between final submission of manuscripts and distribution of the journal. For this issue, the entries in the What's New? Section arise from the period of 01 March 2003 to 31 May 2003. If you feel that there is any other new information that should be brought to the attention of readers, please let us know by e‐mailing wbohaychuk@aol.com Copyright © 2003 John Wiley & Sons, Ltd.
Dynamics of TCP over BoD satellite networks
Authors: Sooriyabandara Mahesh , Fairhurst Gorry
Published: July 2003

Bandwidth‐on‐Demand (BoD) mechanisms are used by most next generation satellite systems to efficiently share a limited radio spectrum among a large number of users. BoD design needs to consider a range of engineering issues: the anticipated number of users, interactions with other subsystems, and the contradictory design goals of optimising system utilization and delay/capacity offered to the network traffic. A BoD system may provide a range of quality of service classes to support different user classes and allow optimisation of allocation efficiency. Each class may have different delay and delay variation characteristics. The performance achieved by a TCP flow using such a BoD satellite network is highly dependent on the delay and the variation of the delay experienced by TCP. This paper describes the BoD mechanisms, and their expected impact on TCP behaviour. This discussion is supplemented by simulation results using an implementation of TCP combined with a model of some simple satellite BoD access schemes to characterize the performance and efficiency of BoD algorithms. Copyright © 2003 John Wiley & Sons, Ltd.
QoS‐oriented traffic management in multimedia satellite systems
Authors: Courville Nicolas
Published: July 2003

The next generation of satellite systems will likely use some on‐board switching techniques enabling the direct transmission of data from any up‐link spot‐beam to any down‐link spot‐beam. If the switch used in the payload of the system is an ATM‐based shared buffer switch, some losses and delays can occur. Fortunately, these drawbacks can be fought thanks to some buffer management policies (HSPO, SMXQ, EPD) that either ensure low delay or low loss ratio.

Real‐time (voice or MPEG video streams) and non‐real‐time applications (file transfer, email, web browsing using TCP/IP protocols) should be carried over these satellite systems with different quality of service (QoS) requirements. Different combinations of buffer management policies are presented to guaranty the QoS required by the user. Especially, special emphasis is put on the way to transmit efficiently layer 3 messages (IP datagrams) within a mix of traffic in order to avoid some high layer retransmission techniques (provided in TCP for instance) wasting both time and bandwidth. Copyright © 2003 John Wiley & Sons, Ltd.
A gateway architecture for IP satellite networks with dynamic resource management and DiffServ QoS provision
Authors: Ronga L. S. , Pecorella T. , Del Re E. , Fantacci R.
Published: July 2003

IP satellite networks are gaining a considerable interest mainly due to their ability to deliver high bandwidth services to nation‐wide areas. However some difficulties still exist to implement IP‐based transport mechanisms on geostationary satellite networks (i.e. TCP‐based protocols are affected by the large delay‐bandwidth product). The satellite network architecture presented in this paper is designed to provide a complete QoS support for IP traffic based on the DS paradigm, while minimizing the waste of the valuable satellite resource. The proposed technique operates on two time scales: a short‐term reaction compensates fast traffic variations by an appropriate scheduling while a medium term resource allocation mechanism reduces the wasted bandwidth. Copyright © 2003 John Wiley & Sons, Ltd.
An IP‐based satellite communication system architecture for interactive multimedia services
Authors: Iuoras Nicolae , Le‐Ngoc Tho , Ashour Mohamed , Elshabrawy Tallal
Published: July 2003

The paper presents an IP‐based broadband satellite access (BSA) network architecture for interactive multimedia services with an emphasis on the return link (upstream direction). Dynamic capacity allocation (DCA) strategies based on the Combined Free and Demand Assignment Multiple Access (CFDAMA) scheme to support the Digital Video Broadcasting‐Return Channel via Satellite (DVB‐RCS) standard and Differentiated Services (DiffServ) architecture in order to achieve short delay and different QoS requirements are proposed. DCA scheduling algorithms and multiple‐queue user terminal structures are presented. Simulation results on the traffic performance for various traffic loads, types and conditions confirm the effectiveness of the proposed structures. Copyright © 2003 John Wiley & Sons, Ltd.
A predictive demand assignment multiple access protocol for Internet access over broadband satellite networks
Authors: Jiang Zhifeng , C. M. Leung Victor
Published: July 2003

Medium access control (MAC) protocol is responsible for wireless resource management, which is crucial to satellite communication. To enhance the performance of broadband satellite networks, the application characteristics should be considered in the design of the MAC protocol. With the rapid expansion of Internet applications and the attractiveness of high speed Internet access via broadband satellite networks, it becomes an attractive objective to take into account the self‐similar nature of Internet traffic in MAC protocol designs. This paper presents a novel predictive demand assignment multiple access (PRDAMA) protocol for packet communications over broadband satellite networks. PRDAMA allocates free bandwidth resources by estimating the positive varying trend of the Internet traffic to facilitate prediction of the bandwidth requirements of the earth stations. Simulation results demonstrate that PRDAMA achieves a lower average delay and delay jitter compared with other DAMA protocols under highly bursty traffic due to its accurate traffic trend prediction. With less bursty traffic, PRDAMA still performs better than the other DAMA protocols under a heavy traffic load. Copyright © 2003 John Wiley & Sons, Ltd.
Static and dynamic resource allocation in a multiservice satellite network with fading
Authors: Celandroni Nedo , Davoli Franco , Ferro Erina
Published: July 2003

A control architecture for resource allocation in satellite networks is proposed, along with the specification of performance indexes and control strategies. The latter, besides being based on information on traffic statistics and network status, rely upon some knowledge of the fading conditions over the satellite network channels. The resource allocation problem consists of the assignment, by a master station, of a total available bandwidth among traffic earth stations in the presence of different traffic types. Traffic stations are assumed to measure continuously their signal fade level, but this information may either be used only locally or also communicated to the master station. According to the information made available on‐line to the master station on the level of the fading attenuation of the traffic stations, the assignment can be made static, based on the a priori knowledge of long‐term fading statistics, or dynamic, based on the updated measurements. In any case, the decisions can be adapted to slowly time‐varying traffic characteristics. At each earth station, two basic traffic types are assumed to be present, namely guaranteed bandwidth, real time, synchronous data (stream traffic) and best‐effort traffic (datagram traffic). Numerical results are provided for a specific architecture in the dynamic case, in a real environment, based on the Italsat satellite national coverage payload characteristics. Copyright © 2003 John Wiley & Sons, Ltd.
Networking issues in IP multicast over satellite
Authors: Sun Z. , Howarth M.P. , Cruickshank H. , Iyengar S. , Claverotte L.
Published: July 2003

This paper describes the issues that arise when using satellites for IP multicast, with the emphasis on multicast protocols and how their implementation depends on the satellite communications platform. Various link layer standards such as DVB‐S, DVB‐RCS and ATM can be used in satellites with on‐board processing, and applied to meet user and network requirements for IP multicast. The paper provides an overview of the networking issues and their interactions. Specifically, we show how multicast networking protocols have to be modified to take into account the satellite link characteristics: these protocols include IGMP, multicast routing protocols and reliable multicast protocols. We also discuss how security systems support IP multicast. Copyright © 2003 John Wiley & Sons, Ltd.