bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performances of high numerical aperture water and oil immersion objective in deep‐tissue, multi‐photon microscopic imaging of excised human skin
Authors: Dong Chen‐Yuan , Yu Betty , Kaplan Peter D. , So Peter T.C. 
Published: December 2003

AbstractMulti‐photon fluorescence microscopy (MPFM) is a powerful technique for imaging scattering, biological specimens in depth. In addition to the sectioning effect generated by the point‐like excitation volume, the near‐infrared wavelengths used for multi‐photon excitation allow deeper penetration into optically turbid specimens. In physiological specimens, the optical properties such as the scattering coefficients and refractive indices are often heterogeneous. In these specimens, it is not clear which type of immersion objective can provide optimized images in‐depth. In particular, in‐depth dermatological imaging applications using MPFM requires such optimization to obtain qualitative and quantitative information from the skin specimens. In this work, we address this issue by comparing the performances of two common types of high numerical aperture (NA) objectives: water‐immersion and oil‐immersion. A high‐quality water‐immersion objective (Zeiss, 40× C‐Apochromat, NA 1.2) and a comparable oil‐immersion objective (Zeiss, 40× Fluar, NA 1.25) were used for in‐depth imaging of autofuorescent excised human skin and sulforhodamine B treated human skin specimens. Our results show that in the epidermal layers, the two types of immersion objectives perform comparably. However, in the dermis, multi‐photon imaging using the oil immersion objective results in stronger fluorescence detection. These observations are most likely due to the degraded point‐spread‐function (PSF) caused by refractive index mismatch between the epidermis and the dermis. Microsc. Res. Tech. 63:81–86, 2004. © 2003 Wiley‐Liss, Inc.
Qualitative assessment of rhizodeposits in non‐sterile soil by analytical pyrolysis
Authors: Kuzyakov Yakov , Leinweber Peter , Sapronov Dmitri , Eckhardt Kai‐Uwe 
Published: December 2003

AbstractEstimation of the amount of root exudates and simultaneous identification of their composition in non‐sterile soil is a challenging objective in rhizosphere research. We coupled 3 methods: (1) labeling of corn in 14CO2 atmosphere to separate root‐derived and soil‐derived organic substances in the rhizosphere, (2) a previously developed leaching method to collect rhizodeposits, and (3) pyrolysis field ionization mass spectrometry (Py‐FIMS) to investigate the molecular‐chemical composition of rhizodeposits. Eluted rhizodeposits accounted for 2.8 % (Loam) and 0.97 % (nutrient solution in quartz sand) of recovered 14C and showed clear differences in composition between the growth substrates. The 14CO2 evolved mostly by root respiration accounted for 3.5–4.0 % without significant differences according to growth substrate or diurnal dynamics. Principal component analysis of the Py‐FI mass spectra of leachates showed a clear diurnal dynamics of the amount and the composition of corn rhizodeposits collected during day‐time and night‐time. Differences originated mostly from signals assigned to carbohydrates, sterols, and peptides. This approach is recommended for forthcoming studies of rhizodeposition in different soil substrates, crops grown, and time‐series of exudate sampling.
Retention of dissolved organic matter by illitic soils and clay fractions: Influence of mineral phase properties
Authors: Kahle Maren , Kleber Markus , Jahn Reinhold 
Published: December 2003

AbstractThe dependency of the retention of dissolved organic carbon (DOC) on mineral phase properties in soils remains uncertain especially at neutral pH. To specifically elucidate the role of mineral surfaces and pedogenic oxides for DOC retention at pH 7, we sorbed DOC to bulk soil (illitic surface soils of a toposequence) and corresponding clay fraction (< 2 μm) samples after the removal of organic matter and after removal of organic matter and pedogenic oxides. The DOC retention was related to the content of dithionite‐extractable iron, specific surface area (SSA, BET‐N2 method) and cation exchange capacity (pH 7). The reversibility of DOC sorption was determined by a desorption experiment. All samples sorbed 20–40 % of the DOC added. The DOC sorption of the clay fractions explained the total sorption of the bulk soils. None of the mineral phase properties investigated was able to solely explain the DOC retention. A sorption of 9 to 24 μg DOC m–2 indicated that DOC interacted only with a fraction of the mineral surface, since loadings above 500 μg m–2 would be expected for a carbon monolayer. Under the experimental conditions used, the surface of the silicate clay minerals seemed to be more important for the DOC sorption than the surface of the iron oxides. The desorption experiment removed 11 to 31 % of the DOC sorbed. Most of the DOC was strongly sorbed.
Can ATP be measured in soils treated with industrial oily waste?
Authors: Wen Guang , Voroney R. Paul , McGonigle Terry P. , Inanaga Shinobu 
Published: December 2003

AbstractSoil samples were collected from a field with a long‐term (10 yr) oily wastewater application history, containing 70 mg g–1 of oil and grease and an accumulation of heavy metals, and also from a short‐term (1 yr) wastewater application involving different rates of waste, tillage, and nitrogen (N) fertilization. Prior to ATP extraction, the soils were incubated at 22 °C and a water potential of –60 kPa for 21 d and 2 d for the long‐ and short‐term trials, respectively. The light emitted from the bioluminescence reaction was partly quenched in the extract of steam‐sterilized long‐term waste‐treated soil, and curvilinearly responded to the addition of ATP at concentrations higher than 4 ng ATP per assay in contrast to the linear response from the pure extractant and the extract of control soil. Calibration curves developed from the extracts of steam‐sterilized soils were used for calculating ATP in that given soil. ATP determined in the long‐term treated soil was as high as 3201 ng (g soil)–1. Still, residual oil to ATP concentration ratio was about an order of magnitude higher in the long‐ than in the short‐term waste‐treated soil, reflecting the accumulation of recalcitrant material. In the short‐term treated soils, ATP ranged from 355 to 760 ng (g soil)–1 and responded to the rate of waste application, tillage, and fertilization. The use of ATP measurement has potential for assessing land management effects and developing tillage and fertilization recommendations for enhanced biodegradation of the oil waste.
Minirhizotron quantification of soybean root growth as affected by reduced A horizon in soil
Authors: Yang John , Hammer R. David , Blanchar Robert W. 
Published: December 2003

AbstractShallow soil A horizon (topsoil) caused by soil erosion and soil movement from cultivation is known to reduce soil and crop productivity. The reduction may be related to limitation of root growth. A field study was conducted to investigate the effects of topsoil thickness on distributions of root density and growth. Soybeans [Glycine max (L.) Merr.] were grown on plots of Mexico silt loam (fine, montmorillonitic, mesic Mollic Endoaqualfs) with topsoil thicknesses of 0, 12.5, 25.0, and 37.5 cm above the Bt horizons. Root density was measured 60 and 90 days after planting using a minirhizotron video‐camera system. Root density was significantly reduced as topsoil thickness decreased from 37.5 to 0 cm. Mean density and net change of the density across profile between 30 and 60 days of growth had a linear function of topsoil thickness. The reduction and lower activity induced by shallow topsoil were attributed to detrimental properties in the Bt horizons. Root distribution pattern and rooting depth were not significantly affected by topsoil thickness. The roots appeared to be accumulated on the upper layers of the Bt horizons. Roots growing in thicker topsoil were more active than roots growing without topsoil. High soil moisture content during the growing season may mitigate the detrimental effects of shallow topsoil, inhibit root penetration, and enhance root activity.
Enzyme activities in semiarid soils under conservation reserve program, native rangeland, and cropland
Authors: Acosta‐Martínez Veronica , Klose Susanne , Zobeck Ted M. 
Published: December 2003

AbstractThere is limited knowledge of biochemical processes in low carbon content soils of semiarid regions under different land use and management. This study investigated several enzyme activities of C, N, P, and S transformations in semiarid soils with different clay (10–21 %) and sand (59–85 %) contents that were under conservation reserve program (CRP), native rangeland (NR), and cropland (CL) under sunflowers (Eriophyllum ambiguum (Gray)), continuous cotton (Gossypium hirsutum L.), or in rotations with wheat (Triticum aestivum L.) or sorghum (Sorghum bicolor L.) in West Texas, USA. Soils under CRP and NR showed higher total C and N contents than cultivated soils under continuous cotton, but soil pH (6.7–8.4) was not affected by the management or land use studied. The activities of β‐glucosidase, β‐glucosaminidase, arylamidase, acid and alkaline phosphatase, phosphodiesterase, and arylsulfatase (mg product (kg soil)–1 h–1) were lower in CL under continuous cotton compared to cotton in rotation with other crops, CRP, and NR. The enzyme activities were also lower when compared to soils from other regions. Linear regression analyses indicated positive correlations between enzyme activities and total C (r values up to 0.96, P < 0.01). There was a positive relationship between enzyme activities and total N, but soil pH showed the opposite trend. Enzyme activities were significantly intercorrelated with r values up to 0.98 (P < 0.001). The specific enzyme activities (mg product (g organic C)–1) were lower in continuous cotton in comparison to the uncultivated soils (i.e., NR and CRP) reflecting differences in organic matter quantity and quality due to cultivation. Among the enzymes studied, the specific activities of β‐glucosidase and arylamidase showed a more pronounced decrease with increasing soil depth. In general, soils under CRP or wheat‐cotton rotations revealed higher enzyme activities than soils under the common agricultural practice for these regions, i.e., continuous cotton under conventional tillage.
Suitability of the ESS laboratory method to determine the equilibrium soil solution composition of agricultural soils, and suggestions for simplification of the experimental procedure
Authors: Matschonat Gunda , Ingwersen Joachim , Streck Thilo 
Published: December 2003

AbstractThe proper selection of the background electrolyte is of special importance studying element availability and mobility in the laboratory. The determination of the background solution composition can be done with the equilibrium soil solution method ESS (Matschonat and Vogt, 1997). The ESS method is a procedure to find out a salt solution of major cations and anions that does not undergo changes in its composition when brought into contact with a specific soil sample. This composition is experimentally approximated in an iterative procedure until certain quality criteria are fulfilled. We tested if the ESS method, which was developed for forest soils, can successfully be applied also to agricultural soils. The solution composition was confirmed by an independent method. We used samples of a glasshouse and an arable loess soil. Because the ESS method is relatively time and work consuming, we tested modifications which should simplify the procedure: the use of dried and frozen samples instead of field fresh soil, an approximation according to the solution's electric conductivity only, and the modeling of cation exchange to omit iteration steps. The ESS method caused slight overestimation (10–25 %) in cation concentrations, but in general, these were well met. Individual anion concentrations, however, were not buffered in this soil and could not unequivocally be determined. We recommend to adjust the anion concentrations in the ESS procedure according to their proportions in an initial water extract. As ion concentrations are functions of the soil : solution ratio, any method based on addition of water to the soil, like the so‐called soil saturation extract (Germany: Bodensättigungsextrakt), runs a risk to seriously underestimate ion concentrations at field conditions. The ESS method may therefore be especially well suited for soils with a low water content. The use of frozen soil gave good results and the omission of iteration steps by cation exchange modeling was promising and will be explored with the aim to operationalize it in forthcoming work.
Improved separation and quantitative determination of hydrocarbon types in gas oil by normal phase high‐performance TLC with UV and fluorescence scanning densitometry
Authors: Matt Muriel , Galvez Eva M. , Cebolla Vicente L. , Membrado Luis , Bacaud Robert , Pessayre Stephanie 
Published: December 2003

AbstractImproved methods for separation and quantitative determination of hydrocarbon types from gas oil have been developed, which were based on high‐performance thin‐layer chromatography with ultraviolet and fluorescence scanning densitometry using horizontal elution. One of the methods allows the separation, detection, and determination of alkanes and naphthenes to be carried out, using berberine‐impregnated silica gel HPTLC plates, elution with n‐hexane, and berberine‐induced fluorescence detection at 365 nm. Another developed method allows total aromatics to be determined using silica gel HPTLC plates by elution with n‐hexane and acetone, and UV detection. In turn, PACs over three aromatic rings can be determined on either silica gel or caffeine‐impregnated silica gel HPTLC plates, elution with n‐hexane, and selective detection using native fluorescence at 365 nm. Concentrations lower than 5 wt% can be determined using this technique. In addition, a technique for an efficient, baseline‐resolved separation of a gas oil according to the number of aromatics rings (mono + di‐, tri‐, and polyaromatic compounds with more than three rings) is presented here. This technique involves a multistep elution on a mixed (silica gel and caffeine‐impregnated silica gel HPTLC plate) using a counter‐elution device, and UV detection.
Quantitative extraction of sulfonamides in meats by supercritical methanol‐modified carbon dioxide: A foray into real‐world sampling
Authors: Arancibia Verónica , Valderrama Mauricio , Rodriguez Pía , Hurtado Francisco , Segura Rodrigo 
Published: December 2003

AbstractOptimizing operational parameters and obtaining the highest possible recovery are two of the major objectives to be attained when any extraction process is performed on a real sample in which the true analyte concentration is unknown. Sulfadiazine (SDZ), sulfamerazine (SMR), and sulfamethazine (SMZ) were extracted from real samples of chicken liver, beef liver, and pig kidney, using methanol‐modified supercritical CO2. The optimum extraction parameters were found to be 17.237 MPa and 160°C for two of the three analytes; SMZ, on the other hand, was completely extracted at 120°C. Under these conditions of high temperature, high amounts of modifier (3.0 mL of methanol in a 10‐mL extraction vessel) and low pressure, all three sulfonamides (SAs) were shown to be quantitatively extracted from spiked samples from domestic animals which had not been given sulfonamides. Under the same conditions, meat samples of commercial origin were analyzed. These results were compared with those obtained by conventional extraction methods. Almost all the meat samples contained sulfa drug residue levels far exceeding the current tolerance levels allowed for most sulfonamides. Eighteen of thirty samples contained at least one of the three sulfonamides, and seven of these samples contained from 1.1 to 4.2 mg kg–1 of SMZ. The SAs were quantified by HPLC with UV absorbance and amperometric detection.
Chromatographic characterization of high‐boiling petroleum fractions
Authors: Sharma Brajendra K. , Sarowha Sukh Lal S. , Bhagat Shib D. 
Published: December 2003

AbstractDetailed investigation of solvent‐separated fractions of petroleum vacuum residues is necessary for understanding the separation mechanism using different solvents and to prepare better feedstocks for secondary conversion processes. The efficiency of different solvents to remove polars and insolubles from vacuum residues (of two Indian crude oils) has been studied. The solvents used were n‐heptane, n‐hexane, and n‐pentane (non‐polar) and ethyl acetate (polar). Soluble fractions were characterized for hydrocarbon group type analysis using high performance liquid chromatography (HPLC), average molecular weights using size exclusion chromatography (SEC), and boiling point distribution using high temperature gas chromatography (HTGC). Method development for HPLC analysis involved the study of parameters such as columns, solvent polarity, detectors, model compounds study, calibration, flow, and solvent gradient programming. The study demonstrated that ultimate soluble fractions have the least content of polar structures of the kind which can cause problems, during cracking and are least prone to cracking. The HPLC, SEC, and simulated distillation (SIMDIS) methods developed and standardized are simple, accurate, and suitable for the rapid assay needed for quick compositional surveys.
Performance of an aqueous two‐phase‐based countercurrent chromatographic system for horseradish peroxidase purification
Authors: Magri María L. , Cabrera Rosa B. , Miranda María V. , Fernández‐Lahore Héctor M. , Cascone Osvaldo 
Published: December 2003

AbstractCountercurrent chromatography (CCC) purification of horseradish peroxidase (HRP) from Armoracia rusticana root extracts was achieved by employing polymer‐phosphate aqueous two‐phase systems (ATPS). By using preparative columns at 1000 rpm, a 25–30% retention of the top phase of an ATPS composed of 10% w/w PEG 1540 and 14.8% w/w phosphate – with added 2 mol/kg sodium chloride – was obtained. The retention level was stable during the standard separation running time (4 h). Horseradish root extract samples were injected into the system (10–25 mL; 200–250 U/mL peroxidase; 2.0–4.0 mg/mL total protein). Retention of HRP in the CCC “column” during the chromatographic run was attained in the selected ATPS, where the partition coefficient K for the enzyme was ≥ 8. Replacement of the mobile phase with a fresh one but in the absence of added salt brought about product elution. Recovery of HRP in this fraction accounts for ≥ 45% of the total activity loaded, with a purification factor of 6. Enzyme activity was also found in the pass‐through fraction and in the remaining liquid (stationary) phase, a fact that should be ascribed to the existence of multiple peroxidase isoforms. SDS‐PAGE of the active fraction showed a protein band at 44 kDa, compatible with the presence of HRP. Thus, the optimised CCC system allowed the separation of HRP directly from a complex biological material. These results open up the possibility of achieving protein separation with CCC/ATPS and of scaling‐up processes in industrial separators.
HPTLC analysis of Withaferine A from an herbal extract and polyherbal formulations
Authors: Mahadevan N. , Rahul P. Kasar , Subburaju T. , Suresh B. 
Published: December 2003

AbstractWithania somnifera has been used in Ayurvedic medicine for treatment of depression and inflammation, and as an aphrodisiac. It contains many phytochemicals such as Withaferine A, withanine, anahygrine, tropine, and withanolides. Of these, withaferine A is considered to be the most active compound. Withaferine A was estimated in herbal extract and polyherbal formulations by high performance thin layer chromatography (HPTLC). As there is no official HPTLC protocol for quantitation of the above phytochemicals, an attempt was made to quantify withaferine A in herbal extract and polyherbal formulations produced from Withania somnifera. Precoated silica gel G (aluminium backed) plates were used as stationary phase and toluene:ethyl acetate: formic acid (50 : 15 : 5) was used as mobile phase. Detection and quantification were performed by densitometry at λ 213 nm. The linear range was 1 μg to 3 μg. This HPTLC method was found to be reproducible, accurate, and precise.
Methacrylate monolithic columns for capillary liquid chromatography polymerized using ammonium peroxodisulfate as initiator
Authors: Holdšvendová Petra , Coufal Pavel , Suchánková Jana , Tesařová Eva , Bosáková Zuzana 
Published: December 2003

AbstractFour methacrylate ester‐based monolithic columns for capillary liquid chromatography (CLC) were prepared by radical polymerization with ammonium peroxodisulfate (3 columns) and by thermal initiation (1 column). The polymerization mixture consisted of butyl methacrylate (BMA) and ethylene glycol dimethacrylate (EDMA), propan‐1‐ol, butane‐1,4‐diol, water, and ammonium peroxodisulfate as initiator. It was necessary to add N,N,N′,N ′‐tetramethylethylenediamine (TEMED) to the polymerization mixture to activate the reaction. The amount of initiator and activator was optimized to attain quantitative polymerization. The reproducibility of three columns prepared at ambient temperature was studied. The most efficient column with HETP of 29 μm for uracil was compared to the monolithic column prepared by thermal initiation with α,α′‐azobisisobutyronitrile (AIBN). The efficiencies of all the test columns were characterized by van Deemter curves. Their total porosities were calculated from the retention time of uracil. Walters indices of hydrophobicity (HI) were calculated from the retention factors of anthracene and benzene. The columns prepared by both methods are comparable in their selectivities and efficiencies. They show the same characteristics because their total porosities and Walters indices of hydrophobicity are consistent. However, the preparation of monoliths using ammonium peroxodisulfate was less demanding, because polymerization was possible at ambient temperature.
Effect of analyte lipophilicity on the resolution of α‐ and β‐amino acids on liquid chromatographic ligand exchange chiral stationary phases
Authors: Hyun Myung Ho , Whangbo Sung Hee , Cho Yoon Jae 
Published: December 2003

AbstractSeparation of the two enantiomers of racemic α‐ and β‐amino acids on two ligand exchange chiral stationary phases (CSPs) prepared previously by covalently bonding sodium N‐((S)‐1‐hydroxymethy‐3‐methylbutyl)‐N‐undecylaminoacetate or sodium N‐((R)‐2‐hydroxy‐1‐phenylethyl)‐N‐undecylaminoacetate on silica gel was studied with variation of the organic modifier (methanol) concentration in the aqueous mobile phase. In particular, the variation of retention factors with changing organic modifier concentration in the aqueous mobile phase was found to be strongly dependent on both the analyte lipophilicity and the stationary phase lipophilicity. In general, the retention factors of relatively lipophilic analytes on relatively lipophilic CSPs tend to increase with increasing organic modifier concentration in the aqueous mobile phases while those of less lipophilic or hydrophilic analytes tend to increase. However, only highly lipophilic analytes show decreasing retention factors with increasing organic modifier concentration in the aqueous mobile phase on less lipophilic CSPs. The contrasting retention behaviors on the two CSPs were rationalized by the balance of the two competing interactions, viz. hydrophilic interaction of analytes with polar aqueous mobile phase and the lipophilic interaction of analytes with the stationary phase.