bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antecedents of two‐photon excitation laser scanning microscopy
Authors: Masters Barry R. , So Peter T.C. 
Published: December 2003

AbstractIn 1931, Maria Göppert‐Mayer published her doctoral dissertation on the theory of two‐photon quantum transitions (two‐photon absorption and emission) in atoms. This report describes and analyzes the theoretical and experimental work on nonlinear optics, in particular two‐photon excitation processes, that occurred between 1931 and the experimental implementation of two‐photon excitation microscopy by the group of Webb in 1990. In addition to Maria Göppert‐Mayer's theoretical work, the invention of the laser has a key role in the development of two‐photon microscopy. Nonlinear effects were previously observed in different frequency domains (low‐frequency electric and magnetic fields and magnetization), but the high electric field strength afforded by lasers was necessary to demonstrate many nonlinear effects in the optical frequency range. In 1978, the first high‐resolution nonlinear microscope with depth resolution was described by the Oxford group. Sheppard and Kompfner published a study in Applied Optics describing microscopic imaging based on second‐harmonic generation. In their report, they further proposed that other nonlinear optical effects, such as two‐photon fluorescence, could also be applied. However, the developments in the field of nonlinear optical stalled due to a lack of a suitable laser source. This obstacle was removed with the advent of femtosecond lasers in the 1980s. In 1990, the seminal study of Denk, Strickler, and Webb on two‐photon laser scanning fluorescence microscopy was published in Science. Their paper clearly demonstrated the capability of two‐photon excitation microscopy for biology, and it served to convince a wide audience of scientists of the potential capability of the technique. Microsc. Res. Tech. 63:3–11, 2004. © 2003 Wiley‐Liss, Inc.
Novel diode‐pumped infrared tunable laser system for multi‐photon microscopy
Authors: Deguil Nelly , Mottay Eric , Salin Francois , Legros Philippe , Choquet Daniel 
Published: December 2003

AbstractWe report on a novel laser source, emitting high energy (20 nanoJoule) femtosecond pulses, in a broad spectrum (250 nm). This source is easily tuned from 950 to 1200 nm, without any laser adjustment, and delivers sub‐300 femtosecond pulses with a 10‐nm spectral width. Microsc. Res. Tech. 63:23–26, 2004. © 2003 Wiley‐Liss, Inc.
Ultracompact autocorrelator for multiphoton microscopy
Authors: Quercioli F. , Ghirelli A. , Tiribilli B. , Vassalli M. 
Published: December 2003

AbstractPulse temporal characterization is a fundamental task when operating a Ti:Sapphire ultrafast laser system for multiphoton microscopy applications. In the present report, an ultracompact autocorrelator setup and a simple procedure is reported to perform pulse width measurements at the focal plane of the microscope objective without the need of any further instrumentation, aside from a few optical elements, since the confocal microscope, detection, data acquisition, processing, and displaying capabilities are used. Microsc. Res. Tech. 63:27–33, 2004. © 2003 Wiley‐Liss, Inc.
Fluorescence lifetime imaging by time‐correlated single‐photon counting
Authors: Becker W. , Bergmann A. , Hink M.A. , König K. , Benndorf K. , Biskup C. 
Published: December 2003

AbstractWe present a time‐correlated single photon counting (TCPSC) technique that allows time‐resolved multi‐wavelength imaging in conjunction with a laser scanning microscope and a pulsed excitation source. The technique is based on a four‐dimensional histogramming process that records the photon density over the time of the fluorescence decay, the x‐y coordinates of the scanning area, and the wavelength. The histogramming process avoids any time gating or wavelength scanning and, therefore, yields a near‐perfect counting efficiency. The time resolution is limited only by the transit time spread of the detector. The technique can be used with almost any confocal or two‐photon laser scanning microscope and works at any scanning rate. We demonstrate the application to samples stained with several dyes and to CFP‐YFP FRET. Microsc. Res. Tech. 63:58–66, 2004. © 2003 Wiley‐Liss, Inc.
Probing microscopic diffusion by 2‐photon flash photolysis: Measurement of isotropic and anisotropic diffusion in lens fiber cells
Authors: Cannell M.B. , Jacobs M.D. , Donaldson P.J. , Soeller C. 
Published: December 2003

AbstractTwo‐photon excited flash photolysis (TPEFP) was used to photorelease caged fluorescein in test solutions and inside fiber cells of the eye lens. Accurate alignment between the focus of the IR beam and the probe beam from the confocal microscope was achieved with an accessory focussing lens and computer models of diffusion were fit to experimental data to extract apparent diffusion coefficients. Inside a fiber cell, the diffusion coefficient for fluorescein was 4 × 10−7 cm2/s at 21°C, a value an order of magnitude lower than observed in free solution. Fluorescence also diffused between fiber cells via gap junctions. In the periphery, diffusion between cells occurred mainly in a radial direction while deep in the lens the diffusion between cells appeared more isotropic. Diffusion between cells was slower than inside cells and corresponded to less than ∼1% of the area between cells being available for diffusion. This value is in good agreement with that expected from measurements of gap junction structure and packing density if a 1–1.5‐nm aqueous gap junction pore is nearly always open. Microsc. Res. Tech. 63:50–57, 2004. © 2003 Wiley‐Liss, Inc.
Practical limits of resolution in confocal and non‐linear microscopy
Authors: Cox Guy , Sheppard Colin J.R. 
Published: December 2003

AbstractCalculated and measured resolution figures are presented for confocal microscopes with different pinhole sizes and for nonlinear (2‐photon and second harmonic) microscopes. A modest degree of super‐resolution is predicted for a confocal microscope but in practice this is not achievable and confocal fluorescence gives little resolution improvement over widefield. However, practical non‐linear microscopes do approach their theoretical resolution and therefore show no resolution disadvantage relative to confocal microscopes in spite of the longer excitation wavelength. Microsc. Res. Tech. 63:18–22, 2004. © 2003 Wiley‐Liss, Inc.
Notes on theory and experimental conditions behind two‐photon excitation microscopy
Authors: Esposito Alessandro , Federici Federico , Usai Cesare , Cannone Fabio , Chirico Giuseppe , Collini Maddalena , Diaspro Alberto 
Published: December 2003

AbstractThis report deals with the fundamental quantum physics behind two‐photon excitation also providing a link to the experimental consequences exploited in microscopy. The optical sectioning effect is demonstrated as well as the distribution of excitation and of fluorescence emission. Microsc. Res. Tech. 63:12–17, 2004. © 2003 Wiley‐Liss, Inc.
Live cell ultraviolet microscopy: A comparison between two‐ and three‐photon excitation
Authors: Balaji J. , Desai R. , Maiti S. 
Published: December 2003

AbstractWe compare conventional infrared laser based three‐photon excitation with a visible laser based two‐photon excitation scheme for imaging the ultraviolet fluorophore serotonin in solution and in live cells. To obtain a signal level of 1,000 photons per second per mM serotonin solution, we need a back aperture power of 5 mW at 550 nm (for two‐photon excitation) and 33 mW at 740 nm (for three‐photon excitation). The detectivity of serotonin (defined as the concentration of serotonin that yields a signal equivalent to three times the standard deviation of the signal obtained from the buffer alone) is 12 μM for two‐photon, and 220 μM for three‐photon excitation. Surprisingly, for live cell imaging of vesicular serotonin in serotonergic cells, three‐photon excitation appears to provide better image contrast than two‐photon excitation. The origin of this is traced to the concentration‐dependent shift of the serotonin emission spectrum. Microsc. Res. Tech. 63:67–71, 2004. © 2003 Wiley‐Liss, Inc.
Manganese availability and microbial populations in the rhizosphere of wheat genotypes differing in tolerance to Mn deficiency
Authors: Marschner Petra , Fu Qinglin , Rengel Zed 
Published: December 2003

AbstractPlant genotypes differ in their capacity to grow in soils with low manganese (Mn) availability. The physiological mechanisms underlying differential tolerance to Mn deficiency are poorly understood. To study the relationship between Mn content in soil, plant genotypes, and rhizosphere microorganisms in differential Mn efficiency, two wheat (Triticum aestivum L.) cultivars, RAC891 (tolerant to Mn deficiency) and Yanac (sensitive), were grown in a Mn‐deficient soil to which 5, 10, 20 or 40 mg Mn kg–1 were added. The shoot dry matter of both cultivars increased with increasing Mn addition to the soil. At all soil Mn fertilizer levels, the tolerant RAC891 had a greater shoot dry matter and a higher total shoot Mn uptake than the sensitive Yanac. The concentration of DTPA‐extractable Mn in the rhizosphere soil of RAC891 at Mn20 and Mn40 was slightly lower than in the rhizosphere of Yanac. The population density of culturable microorganisms in the rhizosphere soil was low (log 6.8–6.9 cfu (g soil)–1) in both cultivars and neither Mn oxidation nor reduction were observed in vitro. To assess the non‐culturable fraction of the soil microbial community, the ribosomal intergenetic spacer region of the bacterial DNA in the rhizosphere soil was amplified (RISA) and separated in agarose gels. The RISA banding patterns of the bacterial rhizosphere communities changed markedly with increasing soil Mn level, but there were no differences between the wheat cultivars. The bacterial community structure in the rhizosphere was significantly correlated with the concentration of DPTA‐extractable Mn in the rhizosphere, fertilizer Mn level, shoot dry matter, and total shoot Mn uptake. The results obtained by RISA indicate that differential tolerance to Mn deficiency in wheat may not be related to changes in the composition of the bacterial community in the rhizosphere.
Effect of nitrogen supply on leaf traits related to photosynthesis during grain filling in two maize genotypes with different N efficiency
Authors: Paponov Iwan A. , Engels Christof 
Published: December 2003

AbstractIn the present study, plant traits related to the photosynthetic capacity at the whole plant level were compared during grain filling in two maize genotypes with different nitrogen (N) efficiency. The plants were grown in a greenhouse in large root containers and supplied either with suboptimal or optimal rates of N fertilizer. Suboptimal N supply reduced total plant biomass at maturity (47 days (d) after flowering) by 29 % for the efficient genotype and by 36 % for the inefficient genotype. Suboptimal N supply reduced leaf growth of both genotypes. The reduction of leaf area was less severe in the N‐efficient genotype, despite of lower N content in the leaves. This indicates lower sensitivity of leaf growth towards internal N limitation in the efficient genotype. At low N supply, the green leaf area per plant gradually decreased after flowering in both genotypes, because of loss of chlorophyll during leaf senescence. The rate of net photosynthesis per unit leaf area (A) was reduced at low in comparison with high N supply. The ratio of A/leaf N content or leaf chlorophyll content was higher in the efficient genotype, indicating more efficient utilization of internal N for photosynthesis. At the end of grain filling, low N supply led to enhanced intercelluar CO2 concentrations (Ci) in the leaves, indicating limitation of CO2 assimilation by carboxylation rather than by stomatal resistance. The N deficiency‐induced increase of Ci was less pronounced in the efficient genotype. Furthermore, higher photosynthetic rate of the efficient genotype at suboptimal N supply was associated with lower contents of reducing sugars and sucrose in the leaves, whereas starch content was higher than in the inefficient genotype. The ability to avoid excessive sugar accumulation in the leaves under N deficiency might be related to higher photosynthetic N efficiency.
Relative Agronomic Effectiveness of phosphate rocks and P adsorption characteristics of an Oxic Rhodustalf in Eastern India
Authors: Ghosal Prabir K. , Chakraborty Trishit , Bhattacharya Buddhadeb , Bagchi Dipak K. 
Published: December 2003

AbstractThe Relative Agronomic Effectiveness (RAE) of rock phosphates as compared to water soluble Triple Super Phosphate was measured on direct, residual, and cumulative application of the P fertilizers in a field experiment with rice on an Oxic‐Rhodustalf in the eastern plateau region of India. The fertilizers were Morocco Rock Phosphate (MORP), Mussoorie Rock Phosphate (MRP), Partially Acidulated Rock Phosphate (PARP), and Triple Super Phosphate (TSP). The RAE of the rock phosphates were lower for direct application (54–80 %) and cumulative application (70–93 %) of P but roughly equal or larger for the residual effect (92–142 %) as compared to TSP. The P adsorption characteristic of the experimental soil conformed to the linear relationship of both Freundlich and Langmuir isotherm equation. The adsorption data when plotted according to Langmuir equation deviated from a single linear relationship at higher concentration (10 μg ml–1), thereby giving two adsorption maximum values ( 68.49 μg g–1 and 256.41 μg g–1) and binding energies ( 2.86 ml μg–1 and 0.089 ml μg–1) for the soil. Two populations of P adsorption site with widely different affinity for P probably existed in the soil.
Effects of parent material and land use on soil erodibility
Authors: Özdemir Nutullah , Aşkin Tayfun 
Published: December 2003

AbstractThe objective of the present investigation was to find out the effect of different parent materials and land use on soil erodibility. Four types of parent materials such as andesite, basalt, alluvial, and gypsum, and three land use types such as grass, clover, and maize, all wide spread in Erzurum Province in Turkey, were tested. Aggregate stability and soil erodibility factors were determined. The susceptibility of soils against erosion decreased in the order of parent materials basalt > andesite > alluvial > gypsum. Likewise, the susceptibility of land use can be sorted as follows: grass > clover > maize.
Field efficiency of biofertilizers on the growth of okra (Abelmoschus esculentus [(L.) Moench])
Authors: Nuruzzaman M. , Ashrafuzzaman M. , Zahurul Islam M. , Rafiqul Islam M. 
Published: December 2003

AbstractAn experiment was carried out at the Farm of the Department of Crop Botany, Bangladesh Agricultural University, Mymensingh from March to July, 2001 to investigate the effect of biofertilizers on morpho‐physiological characters of okra. The experiment was laid out in a randomized complete block design with four replications. There were nine treatments such as T0 (control), T1 (Azotobacter biofertilizer), T2 (Azospirillum. biofertilizer), T3 (Azotobacter + Azospirillum. biofertilizers), T4 (Azotobacter + Cowdung 5 t ha–1), T5 (Azospirillum + 5 t ha–1 cowdung), T6 (Azotobacter + Azospirillum + 5 t ha–1 cowdung), T7 (5 t ha–1 cowdung), and T8 (60 % N). The experimental results revealed significant variations among the treatments in respect of morphological characters, e.g. plant height, number of leaves per plant, stem base diameter, tap root length, and physiological characters like root dry weight, leaf area index, and crop growth rate. Number of leaves per plant, stem base diameter, root length, root dry weight, leaf area index, and crop growth rate were larger in T4, T5, T6, and T8 than the others. In all the parameters, T8 gave the similar result with biofertilizers in combination with cowdung treatments, and T7 was identical with T0 (control). These experimental results revealed that morpho‐physiological characters of okra could be modified by the application of biofertilizer + cowdung. However, biofertilizers + cowdung treatments were comparable to T8 (60 % N) in this study. This suggests that T4 or T6 or T5 were more benificial in environmentally friendly okra cultivation and may be used as an alternative of inorganic N by saving cost of production and sustaining productivity.
Decomposition of leguminous crop residues in a ‘jhum’ cultivation system in Arunachal Pradesh, India
Authors: Arunachalam Kusum , Singh Narendra Deo , Arunachalam Ayyanadar 
Published: December 2003

AbstractDecomposition of leaves, stems, and roots of two leguminous plants, french bean and pea, was studied in a ‘jhum’ cultivation (shifting agriculture) system in north‐eastern India in litter bag experiments. The dynamics of decomposition varied between the crop residues and species studied. All the three studied types of residues of french bean and the leaves and roots of pea showed polynomial decomposition model with three distinct phases: an initial slow decomposition phase (1), followed by a faster decomposition rate (2) and again by a slow decomposition phase (3). However, the stems of pea plants showed an exponential increase in the decomposition rate during field incubation. Initial N, lignin, and lignin : N ratio were determined in crop residues. In general, roots decomposed slowly as compared to the leaves and stems due to greater lignin content. Soil microbial activity as determined by CO2evolution was significantly correlated with the decomposition rates. Over all, the decay constants reveal that these fast decomposing leguminous crop residues can be properly managed for soil nutrient management in the low input shifting agricultural fields in the hills.
”The principles of rational agriculture” by Albrecht Daniel Thaer (1752–1828). An approach to the sustainability of cropping systems at the beginning of the 19th century
Authors: Feller Christian L. , Thuriès Laurent J.‐M. , Manlay Raphaël J. , Robin Paul , Frossard Emmanuel 
Published: December 2003

AbstractThe identification of quantitative fertility indicators for evaluating the sustainability of cropping and farming systems has become a major issue. This question has been extensively studied by the German agronomist Albrecht Daniel Thaer at the beginning of the 19h century. In this paper Thaer's work is set in its historical background, from the end of the 16th century (Palissy, 1580) to the middle of the 19th century (Liebig, 1840). Then the paper focuses on Thaer's quantitative and complex fertility scale (expressed in “fertility degrees”), which was based on soil properties, on the requirement of nutrients by plants, and on the cropping system (including crop rotation). Thaer expressed soil fertility and economic results as a function of rye production in “scheffel of rye per journal” (ca. 200 kg per hectare). He also proposed a scale to describe the intrinsic fertility of soil. Thaer used this approach to assess the effect of major German cropping systems on soil fertility. He applied it to eight theoretical systems and nine existing systems in a true modeling approach. Thaer completed the fertility evaluation for the nine existing systems with a detailed economical analysis commenting the limits and potentialities of each system. Thaer's approach was used with success during half a century as it combined numerous empirical findings on soils and fertilization with organic substances in a sophisticated model. Unfortunately and despite effective practical applications, the scientific foundations of Thaer's “Humus Theory” proved definitively false as soon as 1840 when Sprengel and Liebig published on mineral nutrition of plants. Thaer's work deserves to be rediscovered since it approaches the modern issue of the sustainability of cropping and farming systems.
Nitrogen biomarkers and their fate in soil
Authors: Amelung Wulf 
Published: December 2003

AbstractMore than 90 % of the nitrogen (N) in soils can be organically bound, but the mechanisms and rates by which it is cycled have eluded researchers. The objective of this research was to contribute to a better understanding of the origin and transformation of soil organic N (SON) by using amino sugars and the enantiomers of amino acids as markers for microbial residues and/or aging processes. Studied samples presented here comprised (1) soil transects across different climates, (2) arable soils with different duration of cropping, and (3) radiocarbon‐dated soil profiles. The results suggested that increased microbial alteration of SON temporarily results in a sequestration of N in microbial residues, which are mineralized at later stages of SON decomposition. Microorganisms increasingly sequestered N within intact cell wall residues as frost periods shortened. At a mean annual temperature above 12–15 °C, these residues were mineralized, probably due to limitations in additional substrates. Breaking the grassland for cropping caused rapid SON losses. Microbial residues were decomposed in preference to total N, this effect being enhanced at higher temperatures. Hence, climate and cultivation interactively affected SON dynamics. Nevertheless, not all SON was available to soil microorganisms. In soil profiles, L‐aspartic acid and L‐lysine slowly converted into their D‐form, for lysine even at a similar rate in soils of different microbial activity. Formation of D‐aspartate with time was, therefore, induced by microorganisms while that of D‐lysine was not. The racemization of the two amino acids indicates that SON not available to microorganisms ages biotically and abiotically. In native soils, the latter is conserved for centuries, despite N deficiency frequently occurring in living terrestrial environments. Climate was not found to affect the fate of old protein constituents in surface soil. When native grassland was broken for cropping, however, old SON constituents had become available to microorganisms and were degraded.