bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the effects of wall adsorption of the visualization agent on baseline noise characteristics for indirect UV detection in capillary electrophoresis
Authors: Choy Tom M. H. , Huie Carmen W.
Published: September 2003

New insights into the effects of the wall adsorption of the visualization agent on baseline noise characteristics in indirect UV detection in capillary electrophoresis were provided. When compared to relatively small, hydrophilic cationic (1‐(4‐pyridyl)pyridinium chloride hydrochloride) or anionic chromophores (bromide and benzoate), the use of a UV‐absorbing long‐chain cationic surfactant (benzyldimethylhexadecylammonium chloride) as a probe (visualization agent) for studying baseline noise characteristics as a function of various experimental conditions, such as applied voltage, pH or buffer composition, was found to provide noise data that were very different under certain conditions. For cationic visualization agents that have a strong tendency of adsorbing onto the capillary surfaces due to electrostatic and/or hydrophobic interactions, it appeared that the interplay of both thermal as well as adsorption/desorption events occurring within the capillary is likely responsible for a fluctuation of the visualization agent concentration at the detector.
Use of poly(sodium oleyl‐L‐leucylvalinate) surfactant for the separation of chiral compounds in micellar electrokinetic chromatography
Authors: Mwongela Simon , Akbay Cevdet , Zhu Xiaofeng , Collins Sibrina , Warner Isiah M.
Published: September 2003

A chiral amino acid‐based monomeric and polymeric surfactant, sodium oleyl‐L‐leucylvalinate) (L‐SOLV) and poly(sodium oleyl‐L‐leucylvalinate) (poly‐L‐SOLV) were synthesized and used for chiral separations in micellar electrokinetic chromatography (MEKC). Poly‐L‐SOLV was used successfully in the separation of various enantiomers of neutral, acidic, and basic analytes such as 1,1'‐bi‐2‐napthol, 1,1'‐binaphthyl‐2,2'‐diamine, benzoin, hydrobenzoin, benzoin methylether, warfarin, and coumachlor obtaining well‐resolved peaks but with only partial separation of temazepam. In addition, the atropisomer 1,1'‐binaphthyl‐2, 2'‐dihydrogen phosphate was chosen to study the applicability of the polymeric surfactant over a wide range of parameters such as concentration, temperature, voltage, and pH. The most striking characteristic of this new surfactant is its high hydrophobicity. It is favorable to interactions with hydrophobic chiral analytes, and thus may provide better chiral recognition for the compounds.
Investigation of conditions allowing the synthesis of acrylamide‐based monolithic microcolumns for capillary electrochromatography and of factors determining the retention of aromatic compounds on these stationary phases
Authors: Hoegger Daniela , Freitag Ruth
Published: September 2003

The influence of the cross‐linker (concentration), the porogen (lyotrophic salt) and the solvent type as well as the type and concentration of up to three “functional”, i.e., interactive monomers on the morphology and the chromatographic properties of acrylamide‐based hydrophilic monoliths are investigated. High total monomer concentrations favored polymers with a rigid rather than gel‐like structure. High cross‐linker concentrations also favor the formation of a nodular structure. The addition of a lyotrophic salt favors the formation of small nodules especially at higher monomer concentration; the pore size of the polymer can also be modulated through the salt concentration. Suitable monoliths were further investigated as potential stationary phases for capillary electrochromatography (CEC). Depending on the type and concentration of the monomers, plate numbers between 50 000 and 100 000 were routinely obtained. The standard deviation of the run‐to‐run reproducibility was below 2% and that of the batch‐to‐batch reproducibility below 5%. A set of nine hydrophobic and polar aromatic compounds (all noncharged) was used to investigate the retention mechanism. Possible candidates for chromatographic interaction and retention in these monoliths are the hydrophobic polymer backbone itself and the alkyl, carbonyl, hydroxy, amino, amide, and charged groups introduced by the various functional monomers. Judging from our results, the carbonyl and the hydroxy functions, as well as the hydrophobic polymer backbone can be supposed to be the main sites of interaction. The charged but also the alkyl functions seem to be less important in this regard. The polymerization conditions and especially the composition of the reaction mixture have a strong influence on the behavior of the final column.
Determination of heterocyclic aromatic amines by capillary electrophoresis coupled to mass spectrometry using in‐line preconcentration
Authors: Sentellas Sònia , Moyano Encarnación , Puignou Lluís , Galceran M. Teresa
Published: September 2003

This paper shows the potentiality of capillary electrophoresis (CE) coupled to mass spectrometry (MS) for the analysis of heterocyclic aromatic amines obtaining good results in terms of sensitivity and precision. These compounds have a special interest since they can be carcinogenic for humans. The optimization of a CE‐MS method was performed and the best conditions were obtained using a 16 mM formic acid/ammonium formate solution at pH 4.5 with 60% methanol as running electrolyte. For CE‐MS coupling, a sheath liquid methanol/20 mM formic acid (75/25) solution at a flow rate of 3μL/min and hydrodynamic injection of methanol mixtures for 10 s were used. Detection limits ranging from 18 ng/g to 360 ng/g and precisions up to 1.4% and 12% for migration time and concentration, respectively, were obtained. In order to improve sensitivity, field‐amplified sample injection was applied as an in‐line preconcentration method. Methanol/5 mM formic acid (50/50) as a sample solvent, 3 s hydrodynamic injection (0.5 psi) of a methanol plug, and 25 s of electrokinetic injection (10 kV) of the sample were found to be the optimum conditions. Detection limits up to 25 times lower and similar precisions than those reported for hydrodynamic injection were obtained.
Role of the charge in continuous beds in the chiral separation of hydroxy acids by ligand‐exchange capillary electrochromatography
Authors: Lecnik Oliver , Gübitz Gerald , Schmid Martin G.
Published: September 2003

This paper deals with the chiral separation of hydroxy acids using diallyl‐dimethylammonium chloride as a positive charge‐providing agent in the continuous bed. The chiral continuous bed was prepared by in situ copolymerization of monomers, including an L‐4‐hydroxyproline derivative as a chiral selector. This phase was applied to the chiral separation of hydroxy monocarboxylic acids and hydroxy dicarboxylic acids, respectively. The influence of both the selector concentration and the charge‐providing agent on retention and separation was investigated.
Capillary electrophoresis frontal analysis: Principles and applications for the study of drug‐plasma protein binding
Authors: Østergaard Jesper , Heegaard Niels H. H.
Published: September 2003

Capillary electrophoresis is a well‐established technique for the study of noncovalent interactions. Various approaches exist and capillary electrophoresis‐frontal analysis provides an interesting alternative to the migration shift affinity capillary electrophoresis methods and conventional methods. The present work reviews the principles on which the frontal analysis method is founded. Advantages and limitations of capillary electrophoresis frontal analysis in comparison with both conventional and other capillary electrophoresis based methods for quantification of binding interactions are discussed. Investigations utilizing capillary electrophoresis‐frontal analysis have focused on the interaction of drugs with plasma proteins. These studies, primarily addressing the binding of drugs to human serum albumin, α1‐acid glycoprotein, and lipoproteins are reviewed together with some recent developments in capillary electrophoresis‐frontal analysis methodology.
Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity
Authors: Lämmerhofer Michael , Tobler Ernst , Zarbl Elfriede , Lindner Wolfgang , Svec Frantisek , Fréchet Jean M. J.
Published: September 2003

A new chiral monomer derived from cinchona alkaloid, namely O‐9‐(tert‐butylcarbamoyl)‐11‐[2‐(methacryloyloxy)ethylthio]‐10,11‐dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2‐hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1‐dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O‐9‐[2‐(methacryloyloxy)ethylcarbamoyl]‐10,11‐dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross‐linking (10 wt% related to total monomers) and a pore diameter of about 1 μm in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C‐term contribution to peak broadening) and more homogeneous flow profile (smaller A‐term). Most importantly, as expected the new poly(1‐co‐HEMA‐co‐EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4‐co‐HEMA‐co‐EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine‐ and quinidine‐derived monomers. Fluorescence‐labeled 9‐fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7‐dimethylaminosulfonyl‐1,3,2‐benzoxadiazol‐4‐yl (DBD), carbazole‐9‐carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100 000 and 200 000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in‐line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency.
Multiple injection techniques for microfluidic sample handling
Authors: Fu Lung‐Ming , Yang Ruey‐Jen , Lee Gwo‐Bin , Pan Yu‐Jen
Published: September 2003

This paper presents an experimental and numerical investigation into electrokinetic focusing flow injection for bioanalytical applications on 1×N (i.e., 1 sample inlet port and N outlet ports) and M×N (i.e., M sample inlet ports and N outlet ports) microfluidic chips. A novel device is presented which integrates two important microfluidic phenomena, namely electrokinetic focusing and valveless flow switching within multiported microchannels. The study proposes a voltage control model which achieves electrokinetic focusing in a prefocusing sample injection system and which allows the volume of the sample to be controlled. Using the developed methods, the study shows how the sample may be prefocused electrokinetically into a narrow stream prior to being injected continuously into specified outlet ports. The microfluidic chips presented within this paper possess an exciting potential for use in a variety of techniques, including high‐throughput chemical analysis, cell fusion, fraction collection, fast sample mixing, and many other applications within the micrototalanalysis systems field.
A new micellar electrokinetic capillary chromatography method for separation of the components of the aminoglycoside antibiotics
Authors: Wienen Frank , Holzgrabe Ulrike
Published: September 2003

Aminoglycoside antibiotics are always a mixture of structurally related amino sugars, which do not have a chromophore or fluorophore. The aim of the study was to find one method for evaluation of the components and impurities of the antibiotics. Derivatization with o‐phthaldialdehyde and thioglycolic acid is found to be appropriate for all antibiotics. The components of gentamicin (GM), sisomicin, netilmicin, kanamycin, amikacin, and tobramycin were tried to separate by means of micellar electrokinetic chromatography. The background electrolyte was composed of sodium tetraborate (100 mM, pH 10.0), sodium deoxycholate (20 mM), and β‐cyclodextrin (15 mM). This method is valid for evaluation of GM, kanamycin, and tobramycin. It has to be improved for amikacin and netilmicin. In addition, 46 bulk samples of GM of different manufacturer or pharmaceutical companies were investigated. Many samples were found to contain many minor products and different amounts. Beside different patterns of the main compounds GM C1, GM C1a, GM C2a, and GM C2, many lots were found consisting of a substantial number of minor products. The appearance of a high number of minor products is always associated with the existence of sisomicin, which is not found in “pure” samples. However, almost all samples met the requirements of the European Pharmacopoeia (EP) and United States Pharmacopoeia (USP).
Microchip‐based capillary electrochromatography using packed beds
Authors: Jemere Abebaw B. , Oleschuk Richard D. , Harrison D. Jed
Published: September 2003

Integration of a packed column onto a microchip for performance of capillary electrochromatography (CEC) is described. The quartz device incorporated a cross‐injector, and a double weir trapping design for formation of 1, 2 and 5 mm long CEC columns. Three fluorescent dyes were baseline‐resolved with plate numbers of 330 (330 000 plates/m; height equivalent to a theoretical plate, H = 3.0 μm) for BODIPY 493/503, 360 (360 000 plates/m; H = 2.8 μm) for rhodamine 123 and 244 (244 000 plates/m; H = 4.1 μm) for acridine orange (AO) with 500 V applied on a 1 mm long column. The 2 mm column yielded ∼1.8 times more theoretical plates than did the 1 mm column, when operated at the same flow rate. Van Deemter plots were obtained for the three column lengths, showing increased plate height for the 5 mm length. A 2 mm column gave peak height and area relative standard deviation (RSD) values of 2.5 and 3.3%, respectively, as averages for the three dyes (n = 15). The RSD for the dye retention times was 1% (n = 6) over one day, and 3% (n = 30) over five days. Indirect fluorescence detection of thiourea and of amino acids was possible using a neutral indicator dye (BODIPY 493/503), with a detection limit of 10 μM for amino acids.
Bilayered phospholipid micelles and capillary electrophoresis: A new additive for electrokinetic chromatography
Authors: Holland Lisa A. , Leigh Alyison M.
Published: September 2003

Phospholipid micelles and bilayered micelles (bicelles) were investigated as a new media for electrokinetic chromatography. The benefit to using these additives for micellar electrokinetic chromatography (MEKC) is the potential of a simple bilayer membrane model operated with fast analysis time, and low sample injection volumes. The system is used to separate peptides/protein and is tested with a series of beta‐blockers. The results suggest that bicelle electrokinetic chromatography provides selectivity and holds potential as an alternative approach to modeling membrane phenomenon.
Large‐volume sample stacking combined with separation by 2‐hydroxypropyl‐β‐cyclodextrin for analysis of isoxyzolylpenicillins by capillary electrophoresis
Authors: Zhu Zhiwei , Zhang Lifeng , Marimuthu Arun , Yang Zhaoguang
Published: September 2003

A simple, quick and sensitive capillary electrophoretic technique has been developed for the pharmaceutical analysis of isoxazolylpenicillins (oxacillin, cloxacillin and dicloxacillin) at trace levels for the first time. This method comprises large‐volume sample stacking using the electroosmotic flow (EOF) pump (LVSEP), separation using 2‐hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as selective complex‐forming background electrolyte additive, and direct UV detection. A complete resolution was achieved in the optimal background electrolyte containing 5.2 mM HP‐β‐CD. LVSEP was successfully applied in their determinations to improve the sensitivity, where the EOF in the buffer zone was suppressed by using an acidic buffer with pH 3.6. The detection limits of the current technique were found to be 2.0 μg/L for each of the isoxazolylpenicillins based on the signal‐to‐noise ratio of 3. The curves of peak response versus concentration were linear from 5.0 to 400.0 μg/L with regression coefficients of 0.9982, 0.9986 and 0.9976, respectively. The interaction of isoxazolylpenicillins with HP‐β‐CD was discussed. The association constants for complexes of HP‐β‐CD with isoxazolylpenicillins were determined by electrophoretic method. The obtained association constants were 27.3, 34.9, and 48.5 M−1, respectively, being proportional to their hydrophobic properties and steric hindrances. A simple and easy‐manipulative sample preparation method was developed and validated by analyzing commercially available milk samples. It was found that with current sample preparation process and instrumentation system, 0.1 mL of milk sample is enough for the analysis of isoxazolylpenicillins to meet European Union (EU) guideline of 30 μg/kg.
Effect of multivalent ions on electroosmotic flow in micro‐ and nanochannels
Authors: Zheng Zhi , Hansford Derek J. , Conlisk Albert T.
Published: September 2003

In this work, the effect of multivalent ions on electroosmotic flow is investigated for multiple electrolyte components. The cases studied include incorporating Ca2+ and HPO42‐ and other monovalent ions, such as K+ and H2PO4‐, into an aqueous NaCl solution. The governing equations are derived and solved numerically. The boundary conditions for the governing equations are obtained from the electrochemical equilibrium requirements. In comparison with monovalent ions, the results show that in micro‐ and nanochannels having fixed surface charges, multivalent counterions, even in very small amounts, reduce electroosmotic flow significantly, while the multivalent co‐ions have little effect on the electroosmotic flow. Due to the enhanced ion‐wall interactions multivalent counterions compose the majority of ions in the electric double layer (EDL), causing a decrease of net charge at the surface.
Complexation trends and binding constants between dextrin oligomers and small molecules as measured through affinity capillary electrophoresis
Authors: Hoffmann Julia , Mechref Yehia , Cassely Aaron , Novotny Milos V.
Published: September 2003

Quantitative aspects of a previously reported pre‐equilibration affinity/capillary electrophoretic methodology (Hong, M., et al., Anal. Chem. 1998, 70, 3590–3597) were studied using fluorescently labeled oligosaccharides and analgesic drugs. Frontal analysis capillary electrophoresis (FA‐CE) was investigated for these interaction systems. In order to fulfill certain FA requirements, the analysis conditions of the sugar‐drug combinations had to be adjusted individually. Only after the establishment of these conditions, acceptable binding data (association constants) could be obtained. The constants are in the range of weak hydrogen bonding and are comparable to the constants that were independently obtained through 1H nuclear magnetic resonance (NMR) spectroscopy.
Validation of capillary electrophoresis – mass spectrometry methods for the analysis of a pharmaceutical formulation
Authors: Geiser Laurent , Rudaz Serge , Veuthey Jean‐Luc
Published: September 2003

The coupling of capillary electrophoresis (CE) to mass spectrometry (MS) with an electrospray ionization (ESI) technique is generally performed for qualitative applications, and only few quantitative results have been reported. This paper investigates the validation of a CE‐ESI‐MS method for the analysis of a pharmaceutical formulation containing lidocaine. Some important ESI criteria are discussed including sheath‐liquid composition, nebulizing gas pressure and position of the CE capillary outlet. After optimization of these parameters, an intermediate precision of about 5% was achieved. The latter, as well as efficiency and resolution, were compared to those achieved with UV detection. Besides, a multiple injection procedure was developed to reduce analysis time per sample and was successfully applied to both UV and MS detectors. The validation results achieved by multiple injections were identical to those obtained with classical injection, but afforded a gain of time by a factor of 2.5.
Capillary electrophoresis – electrospray ionization – mass spectrometry for the characterization of natural organic matter: An evaluation with free flow electrophoresis‐off‐line flow injection electrospray ionization‐mass spectrometry
Authors: Schmitt‐Kopplin Philippe , Kettrup Antonius
Published: September 2003

The separation of Suwannee River natural organic matter (NOM) with capillary zone electrophoresis hyphenated to electrospray ionization‐mass spectrometry (CZE‐ESI‐MS) is presented. The obtained electropherograms and signal distributions are comparable to the mobility distributions obtained with more classical UV detection. A direct comparison of the results was possible with free‐flow electrophoresis (FFE), which allows an upscaling of the CZE method and the analysis of the collected fractions in an off‐line modus with flow‐injection electrospray ionization‐mass spectrometry (FI‐ESI‐MS). The changes of the m/z distributions with mobility are very similar with both methods and show a decrease of the m/z with increasing electrophoretic mobility in the humic hump at alkaline pH; superimposed on this hump a low‐molecular‐weight fraction migrates at lower mobility. The analysis of benzene carboxylic acids, glycerrhycic acid as well as oligomers of polystyrene sulfonic acid and polyacrylic acid additionally illustrates possible fragmentation, formation of adducts and multiplicity of the charges of the molecules prior to MS detection. These hardly controllable difficulties add a challenge to the interpretation of the obtained m/z distributions of NOM in terms of charge and mass distributions of molecules present in the NOM mixture.
Analysis of N‐acyl‐L‐homoserine lactones produced by Burkholderia cepacia with partial filling micellar electrokinetic chromatography – electrospray ionization‐ion trap mass spectrometry
Authors: Frommberger Moritz , Schmitt‐Kopplin Philippe , Menzinger Franz , Albrecht Valerie , Schmid Michael , Eberl Leo , Hartmann Anton , Kettrup Antonius
Published: September 2003

A method for the analysis of N‐acyl‐L‐homoserine lactones (AHLs) with micellar electrokinetic chromatography coupled to electrospray ionization‐ion trap mass spectrometry, combining the flexibility of capillary electrophoresis with the unmatched structural information provided by mass spectrometry is presented. Different surfactants were evaluated, with sodium dodecyl sulfate (SDS) yielding the best results considering sensitivity and flexibility. We examined the interaction of AHLs with the SDS micelles at different analysis conditions and applied the optimized method to the analysis of a real bacterial sample. Two AHLs from Burkholderia cepacia colonizing the rhizosphere of traditional Indian rice cultivars could be unambiguously determined in an ethyl acetate extract with high resolution flexibility.
Recent developments in capillary electrokinetic chromatography with replaceable charged pseudostationary phases or additives
Authors: Perič Iván , Kenndler Ernst
Published: September 2003

Although electrochromatography in packed beds or monolithic columns has gained enormous interest, techniques based on charged pseudostationary phases like micelles are of high practical importance in electrically driven separation science. However, nonmicellar alternatives, e.g., using charged soluble polymers or smaller additives are still attractive, as they allow high concentrations of organic solvents, and their application is not limited by the critical micellar concentration. This review discusses the developments in the field of electrokinetic chromatography with these additives in the last three years, covering ionic polymeric pseudostationary phases, dendrimers and so‐called micelle polymers, but also small molecules which implement separation selectivity due to their specific interaction with the analytes.
Mother–child and metapelet–child touch behavior with three‐year‐old kibbutz children in two contexts
Authors: Landau Rivka , Shusel Ronit , Eshel Yohanan , Ben‐Aaron Miriam
Published: September 2003

The frequency and function of self‐touch and of touching another was studied among 32 three‐year‐old kibbutz children, their mothers, and their metaplot [caretakers; singular: metapelet] in two contexts: coconstruction of a narrative with Duplo toys, and coconstruction of a narrative with an emotion‐evoking picture book without text. Self‐touch, mainly fidgeting, was more frequent for children during the task with the picture book and more frequent for adults during the task with the Duplo toys. Mothers and children touched each other more often than metaplot and children. Adults' touches of the children were perceived as either expressions of affection or as acts of grooming and were task‐related. The children's touching of the adults was mainly task‐related. It appears that self‐touch is for children and adults alike a mode of self‐regulation of mild stress and that touching the other has a wide range of functions, especially in intimate relationships. ©2003 Michigan Association for Infant Mental Health.
Fits and starts: A mother–infant case‐study involving intergenerational violent trauma and pseudoseizures across three generations
Authors: Schechter Daniel S. , Kaminer Tammy , Grienenberger John F. , Amat Jose
Published: September 2003

This case‐study presents in detail the clinical assessment of a 29‐year‐old mother and her daughter who first presented to infant mental health specialists at age 16 months, with a hospital record suggesting the presence of a dyadic disturbance since age eight months. Data from psychiatric and neurological assessments, as well as observational measures of child and mother, are reviewed with attention to issues of disturbed attachment, intergenerational trauma, and cultural factors for this innercity Latino dyad. Severe maternal affect dysregulation in the wake of chronic, early‐onset violent‐trauma exposure manifested as psychogenic seizures, referred to in the mother's native Spanish as “ataques de nervios,” the latter, an idiom of distress, commonly associated with childhood trauma and dissociation. We explore the mechanisms by which the mothers' reexperiencing of violent traumatic experience, together with physiologic hyperarousal and associated negative affects, are communicated to the very young child and the clinician‐observer via action and language from moment to moment during the assessment process. The article concludes with a discussion of diagnostic and treatment implications by Drs. Marshall, Gaensbauer, and Zeanah. ©2003 Michigan Association for Infant Mental Health.
Mother–infant behavioral interactions in teenage and adult mothers during the first six months postpartum: Relations with infant development
Authors: Pomerleau Andrée , Scuccimarri Connie , Malcuit Gérard
Published: September 2003

The purpose of this study was to compare adolescent mothers' (high‐risk group), at‐risk adult mothers' (moderate‐risk group), and no‐risk adult mothers' (low‐risk group) behavioral interactions at one and six months postpartum, and to examine the relationships between maternal behaviors and infant developmental scores on the Bayley scales. Results indicated that high‐risk teenage mothers and moderate‐risk adult mothers vocalized less and had lower contingency rating scores compared to low‐risk adult mothers. Also, infants in the high‐risk and moderate‐risk groups obtained lower mental scores at six months compared to the low‐risk group. Moderate stability across time was found for maternal vocalizations and infant scores on the mental scale. Maternal vocalizations and behavioral contingency rating scores at one month were associated with infants' six‐month performance on the Bayley scales. Specific intervention strategies were discussed with the aim of targeting and improving early maternal behavioral patterns in at‐risk groups. ©2003 Michigan Association for Infant Mental Health.
Packing paths in digraphs
Authors: Brewster Richard C. , Hell Pavol , Pantel Sarah H. , Rizzi Romeo , Yeo Anders
Published: September 2003

Let ${\cal G}$ be a fixed set of digraphs. Given a digraph H, a ${\cal G}$‐packing in H is a collection ${\cal P}$ of vertex disjoint subgraphs of H, each isomorphic to a member of ${\cal G}$. A ${\cal G}$‐packing ${\cal P}$ is maximum if the number of vertices belonging to members of ${\cal P}$ is maximum, over all ${\cal G}$‐packings. The analogous problem for undirected graphs has been extensively studied in the literature. The purpose of this paper is to initiate the study of digraph packing problems. We focus on the case when ${\cal G}$ is a family of directed paths. We show that unless ${\cal G}$ is (essentially) either $\{ \vec {P}_1 \}$, or $\{ \vec {P}_1, \vec {P}_2 \}$, the G‐packing problem is NP‐complete. When ${\cal G} = \{ \vec {P}_1 \}$, the ${\cal G}$‐packing problem is simply the matching problem. We treat in detail the one remaining case, ${\cal G} = \{ \vec {P}_1, \vec {P}_2 \}$. We give in this case a polynomial algorithm for the packing problem. We also give the following positive results: a Berge type augmenting configuration theorem, a min‐max characterization, and a reduction to bipartite matching. These results apply also to packings by the family ${\cal G}$ consisting of all directed paths and cycles. We also explore weighted variants of the problem and include a polyhedral analysis. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 81–94, 2003
Circular chromatic number of subgraphs
Authors: Hajiabolhassan Hossein , Zhu Xuding
Published: September 2003

This paper proves that every (n + )‐chromatic graph contains a subgraph H with $\chi _c (H) = n$. This provides an easy method for constructing sparse graphs G with $\chi_c (G) = \chi ( G) = n$. It is also proved that for any ε > 0, for any fraction k/d > 2, there exists an integer g such that if G has girth at least g and $\chi _c (G) = k/d$ then for every vertex v of G, $\chi _c (G-{v})> k/d - \varepsilon $. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 95–105, 2003
Circular chromatic number and Mycielski construction
Authors: Hajiabolhassan Hossein , Zhu Xuding
Published: September 2003

This paper gives a sufficient condition for a graph G to have its circular chromatic number equal to its chromatic number. By using this result, we prove that for any integer t ≥ 1, there exists an integer n such that for all $k \ge n, \chi _c (M^t(K_k))\,= \chi(M^t(K_k))$. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 106–115, 2003
Minimally (k, k)‐edge‐connected graphs
Authors: Hennayake Kamal , Lai Hong‐Jian , Li Deying , Mao Jingzhong
Published: September 2003

For an integer l > 1, the l‐edge‐connectivity of a connected graph with at least l vertices is the smallest number of edges whose removal results in a graph with l components. A connected graph G is (k, l)‐edge‐connected if the l‐edge‐connectivity of G is at least k. In this paper, we present a structural characterization of minimally (k, k)‐edge‐connected graphs. As a result, former characterizations of minimally (2, 2)‐edge‐connected graphs in [J of Graph Theory 3 (1979), 15–22] are extended. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 116–131, 2003
Graphs embedded in the plane with a bounded number of accumulation points
Authors: Bonnington C. Paul , Richter R. Bruce
Published: September 2003

Halin's Theorem characterizes those infinite connected graphs that have an embedding in the plane with no accumulation points, by exhibiting the list of excluded subgraphs. We generalize this by obtaining a similar characterization of which infinite connected graphs have an embedding in the plane (and other surfaces) with at most k accumulation points. Thomassen [7] provided a different characterization of those infinite connected graphs that have an embedding in the plane with no accumulation points as those for which the ℤ2‐vector space generated by the cycles has a basis for which every edge is in at most two members. Adopting the definition that the cycle space is the set of all edge‐sets of subgraphs in which every vertex has even degree (and allowing restricted infinite sums), we prove a general analogue of Thomassens's result, obtaining a cycle space characterization of a graph having an embedding in the sphere with k accumulation points. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 132–147, 2003
Upper total domination in claw‐free graphs
Authors: Favaron Odile , Henning Michael A.
Published: September 2003

A set S of vertices in a graph G is a total dominating set of G if every vertex of G is adjacent to some vertex in S (other than itself). The maximum cardinality of a minimal total dominating set of G is the upper total domination number of G, denoted by Γt(G). We establish bounds on Γt(G) for claw‐free graphs G in terms of the number n of vertices and the minimum degree δ of G. We show that $\Gamma _t(G) \le 2(n+1)/3$ if $\delta \in \{ 1,2\}, \Gamma _t(G) \le 4n/(\delta + 3)$ if $\delta \in \{ 3,4\}$, and $\Gamma _t(G) \le n/2$ if δ ≥ 5. The extremal graphs are characterized. © 2003 Wiley Periodicals, Inc. J Graph Theory 44: 148–158, 2003
Adsorption and translocation of sulfur in some tropical acid soils
Authors: Biswas Hrittick , Rattan R.K. , Datta S.P. , Singh A.K.
Published: September 2003

In view of growing concern about sulfur (S) deficiency, we attempted to study the effect of soil characteristics on the adsorption and translocation of S in soils. Laboratory experiments were conducted with five surface soils collected from three regions in the state of Orissa (Eastern India). In an adsorption study, all the soils were equilibrated with graded doses of potassium sulfate (K2SO4). Freundlich adsorption isotherms provided good fit to S adsorption data. Free Fe2O3 and Al2O3 in the soils were primarily responsible for retaining added S in soils. Further, studies on the movement of sulfate‐S in 30‐cm plexiglass columns, where radio‐labeled S along with water (5 cm) was applied as gypsum and K2SO4, showed that K2SO4‐S migrated deeper than gypsum‐S. Sulfur moved deeper in case of initially water‐saturated soils than in initially air‐dry soils.
Effect of the nitrification inhibitor nitrapyrin on the fate of nitrogen applied to a soil incubated under laboratory conditions
Authors: Kaleem Abbasi M. , Shah Zahir , Adams W.A.
Published: September 2003

The aim of this study was to examine the effect of the nitrification inhibitor nitrapyrin on the fate and recovery of fertilizer nitrogen (N) and on N mineralization from soil organic sources. Intact soil cores were collected from a grassland field. Diammonium phosphate (DAP) and urea were applied as N sources. Cores were equilibrated at –5 kPa matric potential and incubated at 20 °C for 42 to 56 days. Changes in NH4+‐N, accumulation of NO3–‐N, apparent recovery of applied N, and emission of N2O (acetylene was used to block N2O reductase) were examined during the study. A significant increase in NH4+‐N released through mineralization was recorded when nitrapyrin was added to the control soil without N fertilizer application. In the soils to which N was added either as urea or DAP, 50–90 % of the applied N disappeared from the NH4+‐N pool. Some of this N (8–16 %) accumulated as NO3–‐N, while a small proportion of N (1 %) escaped as N2O. Addition of nitrapyrin resulted in a decrease and delay of NH4+‐N disappearance, accumulation of much lower soil NO3–‐N contents, a substantial reduction in N2O emissions, and a 30–40 % increase in the apparent recovery of added N. The study indicates that N recovery can be increased by using the nitrification inhibitor nitrapyrin in grassland soils at moisture condition close to field capacity.
Importance of iron use‐efficiency of nodules in common bean (Phaseolus vulgaris L.) for iron deficiency chlorosis resistance
Authors: Krouma Abdelmajid , Abdelly Chedly
Published: September 2003

Several studies suggest that the Fabaceae‐Rhizobium symbiosis is particularly sensitive to iron (Fe) deficiency with respect to NO3–‐dependent plants. The aim of this study, which is part of a screening program for common bean tolerance to Fe deficiency, was to study genotypical differences in Fe requirement and Fe use‐efficiency of common bean cultivars depending on symbiotic nitrogen fixation (SNF). Results show that ARA14 produces more whole plant dry matter and particularly more nodule biomass than Coco blanc. ARA14 is characterized by a high capacity of nitrogen fixation and a better Fe use‐efficiency for the growth and the function of the nodules.
Boron toxicity in kiwifruit plants (Actinidia deliciosa), treated with nitrate, ammonium, and a mixture of both
Authors: Sotiropoulos Thomas E. , Therios Ioannis N. , Dimassi Kortessa N.
Published: September 2003

The objective of this research was to study the effects of nitrogen (N) forms (NO3–, 2.6 mM; NH4+, 2.6 mM; NO3–, 1 mM + NH4+, 1.6 mM) on the growth and mineral composition of kiwifruit plants exposed to three boron (B) levels (0.025, 0.1, 0.3 mM). The kiwifruit plants were grown in a 1:1 sand : perlite mixture and irrigated daily with nutrient solutions. Shoot height, mean shoot dry weight, the number of leaves, mean leaf dry weight, and N concentration of NH4‐treated plants were significantly higher compared to the NO3– treatment at all B levels. The concentration of 0.3 mM B significantly reduced shoot height for all N treatments. Boron toxicity symptoms appeared 14 days after starting the experiment, when plants were treated with 0.1 and/or 0.3 mM B. The nitrate supply reduced the B concentration of roots, but B levels of different leaf parts were hardly affected by the N form. Furthermore, the NH4‐N form significantly reduced the Mg concentration of the leaves.
Seasonal soil nitrogen dynamics in rice‐wheat cropping systems of Nepal
Authors: Pande K.R. , Becker M.
Published: September 2003

The rice‐wheat annual double cropping system occupies some 0.5 million ha in the Himalayan foothills of Nepal. Alternating soil drying and wetting cycles characterize the 6–10 weeks long dry‐to‐wet season transition period (DWT) after wheat harvesting and before wetland rice transplanting. Mineral fertilizer use in the predominant smallholder agriculture is low and crops rely largely on native soil N for their nutrition. Changes in soil aeration status during DWT are likely to stimulate soil N losses. The effect of management options that avoid the nitrate build‐up in soils during DWT by N immobilization in plant or microbial biomass was studied under controlled conditions in a greenhouse (2001/2002) and validated under field conditions in Nepal in 2002. In potted soil in the greenhouse, the gradual increase in soil moisture resulted in a nitrate N peak of 20 mg (kg soil)–1 that rapidly declined as soil moisture levels exceeded 40 % water‐filled pore space (equiv. 75 % field capacity). Similarly, the maximum soil nitrate build‐up of 40 kg N ha–1 under field conditions was followed by its near complete disappearance with soil moisture levels exceeding 46 % water‐filled pore space at the onset of the monsoon rains. Incorporation of wheat straw and/or N uptake by green manure crops reduced nitrate accumulation in the soil to < 5 mg N kg–1 in pots and < 30 kg N ha–1 in the field (temporary N immobilization), thus reducing the risk for N losses to occur. This “saved” N benefited the subsequent crop of lowland rice with increases in N accumulation from 130 mg pot–1 (bare soil) to 185 mg pot–1 (green manure plus wheat straw) and corresponding grain yield increases from 1.7 Mg ha–1 to 3.6 Mg ha–1 in the field. While benefits from improved soil N management on lowland rice are obvious, possible carry‐over effects on wheat and the feasibility of proposed options at the farm level require further studies.
Presubmergence and green manure affect the transformations of nitrogen‐15‐labeled urea under lowland soil conditions
Authors: Thind H.S. , Rowell D.L.
Published: September 2003

The effect of presubmergence and green manuring on various processes involved in [15N]‐urea transformations were studied in a growth chamber after [15N]‐urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH3 volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH4+‐N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH3 volatilization losses. Although green manure did not affect the KCl extractable NH4+‐N from applied fertilizer, it maintained higher NH4+‐N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9 % (T1), 23.9 % (T2), and 36.4 % (T3) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N.
Detection of non‐equilibrium contaminant release in soil columns: Delineation of experimental conditions by numerical simulations
Authors: Wehrer Markus , Totsche Kai Uwe
Published: September 2003

Robust and reliable laboratory methods are required to assess the rate of release of pollutants from contaminated materials. A widely used approach to determine release parameters are soil column experiments. Release rates are thereby obtained by the analysis of the concentration time profile measured at the column outlet, the so called breakthrough curve. Insufficient experimental information as a consequence of simple experimental designs, however, results in the non‐unique identification of the release processes. This is due to the equifinality, i.e., different processes result in the same breakthrough behavior. We analyzed column outflow experiments for their suitability for the identification of non‐equilibrium conditions by means of numerical simulations. Results show that non‐equilibrium conditions can be detected only in a small range of release time scale to transport time scale. Most frequently, non‐equilibrium remains undetected due to unmatched experimental conditions. Flow interruptions and modulation of the flow velocity are an important means to allow for better detection of possible non‐equilibrium release processes. The efficiency of flow interruptions sensitively depends on the experimental conditions, such as point of time and duration of the interruption and the imposed flow velocity. Column experiments are a suitable experimental tool to investigate non‐equilibrium. However, the course of the experiment has to be designed very carefully.
An Andosol from Eastern Saxony, Germany
Authors: Kleber Markus , Zikeli Sabine , Kastler Michael , Jahn Reinhold
Published: September 2003

We tested whether a ‘Lockerbraunerde’ from the heights of the Zittauer Gebirge in Eastern Saxony exhibited andic properties and classified it according to the rules of the World Reference Base for Soil Resources (WRB, 1998). To achieve this, we characterized a selected soil by means of routine soil analysis; selective dissolution procedures; X‐ray diffraction (XRD); X‐ray fluorescence (XRF), and Transmission Electron Microscopy (TEM). We used field criteria (Thixotropy; NaF‐field test) to obtain a map of the spatial distribution of soils with potential andic properties. We found that the soil fulfilled all requirements to be classified as an Andosol. The composition of the colloidal phases was exactly intermediate between sil‐andic and alu‐andic. At the same time, the soil had a spodic horizon [determined through the depth function of the Alo+½Feo criterion]. As there was no indication of vertical translocation of metal‐organic complexes, but sufficient evidence to suggest the downward movement of mobile Al/Si‐phases, we maintain to classify the soil as an Endoskeleti‐Umbric Andosol and propose the existence of a pedogenetic pathway intermediate between Podsolisation and Andosolization. We conclude that the spodic horizon in the WRB is not well defined because of the dominance of the Alo+½Feo criterion over morphological evidence. We further suggest the German soil taxonomy to be modified to better represent soils containing short range order minerals.
The potential for soil phosphorus tests to predict phosphorus losses in overland flow
Authors: Quinton John N. , Strauss Peter , Miller Nicola , Azazoglu Erol , Yli‐Halla Markku , Uusitalo Risto
Published: September 2003

Soil phosphorus tests offer a potentially powerful tool for land managers trying to predict the areas which will contribute diffuse losses of phosphorus (P) to surface water bodies through the overland flow vector – but do they work? We address this question at a range of scales, from patch (< 1 m2), through plot (several m2) to small watershed (several hectares). Our hypothesis is that as we increase the scale, and therefore the complexity of the system, soil P tests will predict P concentrations and losses associated with overland flow less well, and that this is partly due to a shift from dissolved P losses to P losses associated with eroded soil material.

At the patch scale soil P tests were used to predict the P concentration and load from 24 European soils exposed to simulated rainfall under controlled conditions in the laboratory. Results showed that soil P tests were generally good predictors of reactive P <0.45 μm, but did less well at predicting total P > 0.45 μm. By combining the soil P test with measured sediment concentrations predictions of total P concentrations improved. Outdoor rainfall simulation experiments on bare soil plots (10 m2) revealed the overwhelming influence of particle bound P losses compared with P losses in the water phase. Soil P tests, which relate primarily to the dissolved P fractions in soil, were not able to predict total P losses, but were related to reactive P < 0.45 μm losses. At the watershed scale soil P tests were able to predict reactive P < 0.45 μm losses, but with considerable uncertainty.

We conclude that soil P tests, in combination with sediment concentration provide a useful means of assessing the mobilization of P in overland flow, but should not be expected to provide watershed scale predictions of the movement of P into overland flow.
Microbiological and enzymatic properties of soil deposits originating from wind erosion
Authors: Sonnleitner Renate , Schinner Franz
Published: September 2003

A characterization of deposits originating from wind erosion of agriculturally managed soils in eastern Austria with the main soil types Chernozems and Allochthonous Calcaric Fluvisols was conducted using measurements of microbial counts, soil respiration, soil microbial biomass, and several enzyme activities. The deposits were rich in organic matter, silt‐ and clay‐sized mineral particles, and had high water‐holding and cation exchange capacities. Microbial counts, biomass, and enzyme activities of the deposits covered ranges frequently reported for agriculturally managed soils. Metabolic quotients indicated reduced energetic efficiences of deposit associated microbial communities. Microorganisms might suffer from stress imposed by habitat destruction, drifting, and unfavorable physical conditions in the deposits. Shifts in microbial communities or properties of organic materials in the deposits might also result in high metabolic quotients. It will be the subject of further study to clarify causal relationships.