Hydroxyapatite biomaterial implanted in human periodontal defects: an histological and ultrastructural study

The purpose of the present work was to study the response of human periodontium to hydroxyapatite biomaterial particles (180-200 µm). The biomaterial was implanted in two infraosseous periodontal defects (two patients) after clearing of the granulation tissue. At two months post-surgery, biopsies were studied using light and electron microscopy. No sign of inflammation was observed, the biomaterial aggregates were surrounded either by typical fibroblasts or larger phagocytotic cells with phagocytosis vesicles containing biomaterial crystals. These intracellular crystals were noticeably smaller than the nonphagocytized ones. Some of the phagocytized crystals showed morphological signs of intracellular dissolution. The spaces between the crystals constitutive of the aggregates were filled with organic substance containing collagen fibers.Le présent travail a pour but d’étudier la réponse du parodonte humain à des particules d’hydroxyapatite de 180 à 200 µm. Le biomatériau a été implanté dans deux poches parodontales infraosseuses (deux patients) après élimination du tissu de granulation. Deux mois après l’intervention, des biopsies ont été étudiées en microscopie photonique et en microscopie électronique. Aucun signe d’inflammation n’a été décelé, les agrégats de biomatériau sont bordés soit de fibroblastes, soit de cellules phagocytaires, de taille plus importante, avec des vésicules de phagocytose renfermant des cristaux de biomatériau. Ces cristaux intracellulaires sont notablement plus petits que les cristaux non phagocytés. La morphologie de certains cristaux phagocytés traduit l’existence d’une dissolution intracellulaire. Les espaces entre les cristaux constitutifs des agrégats sont comblés par une substance organique contenant des fibres de collagène

Correction of profiles of in-situ chlorophyll fluorometry for the contribution of fluorescence originating from non-algal matter

In situ chlorophyll fluorometers have been widely employed for more than half a century, and to date, it still remains the most used instrument to estimate chlorophyll-a concentration in the field, especially for measurements onboard autonomous observation platforms, e.g., Bio-Argo floats and gliders. However, in deep waters (> 300 m) of some specific regions, e.g., subtropical gyres and the Black Sea, the chlorophyll fluorescence profiles frequently reveal “deep sea red fluorescence” features. In line with previous studies and through the analysis of a large data set (cruise transect in the South East Pacific and data acquired by 82 Bio- Argo floats), we show that the fluorescence signal measured by a humic-like DOM fluorometer is highly correlated to the “deep sea red fluorescence.” Both fluorescence signals are indeed linearly related in deep waters. To remove the contribution of non-algal organic matter from chlorophyll fluorescence profiles, we introduce a new correction. Rather that removing a constant value (generally the deepest chlorophyll a fluorescence value from the profile, i.e., so-called “deep-offset correction”), we propose a correction method which relies on DOM fluorometry and on its variation with depth. This new method is validated with chlorophyll concentration extracted from water samples and further applied on the Bio-Argo float data set. More generally, we discuss the potential of the proposed method to become a standard and routine procedure in quality-control and correction of chlorophyll a fluorescence originating from Bio-Argo network

Recommendations for obtaining unbiased chlorophyll estimates from in situ chlorophyll fluorometers: A global analysis of WET Labs ECO sensors

Chlorophyll fluorometers provide the largest in situ global data set for estimating phytoplankton biomass because of their ease of use, size, power consumption, and relatively low price. While in situ chlorophyll a (Chl) fluorescence is proxy for Chl a concentration, and hence phytoplankton biomass, there exist large natural variations in the relationship between in situ fluorescence and extracted Chl a concentration. Despite this large natural variability, we present here a global validation data set for the WET Labs Environmental Characterization Optics (ECO) series chlorophyll fluorometers that suggests a factor of 2 overestimation in the factory calibrated Chl a estimates for this specific manufacturer and series of sensors. We base these results on paired High Pressure Liquid Chromatography (HPLC) and in situ fluorescence match ups for which non-photochemically quenched fluorescence observations were removed. Additionally, we examined matches between the factory-calibrated in situ fluorescence and estimates of chlorophyll concentration determined from in situ radiometry, absorption line height, NASA’s standard ocean color algorithm as well as laboratory calibrations with phytoplankton monocultures spanning diverse species that support the factor of 2 bias. We therefore recommend the factor of 2 global bias correction be applied for the WET Labs ECO sensors, at the user level, to improve the global accuracy of chlorophyll concentration estimates and products derived from them. We recommend that other fluorometer makes and models should likewise undergo global analyses to identify potential bias in factory calibration

Two databases derived from BGC-Argo float measurements for marine biogeochemical and bio-optical applications

Since 2012, an array of 105 Biogeochemical-Argo (BGC-Argo) floats has been deployed across the world’s oceans to assist in filling observational gaps that are required for characterizing open-ocean environments. Profiles of biogeochemical (chlorophyll and dissolved organic matter) and optical (single-wavelength particulate optical backscattering, downward irradiance at three wavelengths, and photosynthetically available radiation) variables are collected in the upper 1000m every 1 to 10 days. The database of 9837 vertical profiles collected up to January 2016 is presented and its spatial and temporal coverage is discussed. Each variable is quality controlled with specifically developed procedures and its time series is quality-assessed to identify issues related to biofouling and/or instrument drift. A second database of 5748 profile-derived products within the first optical depth (i.e., the layer of interest for satellite remote sensing) is also presented and its spatiotemporal distribution discussed. This database, devoted to field and remote ocean color applications, includes diffuse attenuation coefficients for downward irradiance at three narrow wavebands and one broad waveband (photosynthetically available radiation), calibrated chlorophyll and fluorescent dissolved organic matter concentrations, and single wavelength particulate optical backscattering. To demonstrate the applicability of these databases, data within the first optical depth are compared with previously established bio-optical models and used to validate remotely derived bio-optical products. The quality-controlled databases are publicly available from the SEANOE (SEA scieNtific Open data Edition) publisher at https://doi.org/10.17882/49388 and https://doi.org/10.17882/47142 for vertical profiles and products within the first optical depth, respectively

Indicators of phosphorus status in soils: significance and relevance for crop soils in southern Belgium. A review

Introduction. Phosphorus (P) is an essential element for plant growth. Therefore, it is essential to accurately evaluate its content in the soil. This requires reliable indicators of soil P status. Literature. This paper reviews literature regarding the indicators of P status in soils. Many indicators can be found, including single extractions (soluble, available, or total P), which are the most common indicators used worldwide. Over time, increasingly complex P indicators have been developed as sequential extractions which characterize the various forms of P, degree of P saturation, diffusive gradients in thin films, biological extractions, isotopic methods, or more complex models. To make a choice among them, different criteria should be applied, including relevance, cost and time, ease of interpretation, and, most importantly, the objective of the analysis. It is also necessary to analyze the appropriateness to soil and climate. Firstly, this paper describes the various types of indicators present in the literature, and proposes a classification system. Secondly, all cited indicators are evaluated and compared. Finally, the P indicators met in Wallonia, southern Belgium are discussed. Conclusions. Each P indicator presents advantages and disadvantages. This review highlights the importance of careful consideration of indicator choice, and the establishment of interpretation thresholds

Ion-molecule reactions between ionized nitrile oxides and neutral nitrite

International audienceThe ion-molecule reactions of ionized nitrite oxide, R-C=N+-O-., with several neutral nitrites have been studied using both tandem mass spectrometric techniques and ab initio molecular orbital calculations. Ionized oxygen atom transfer as well as a formal substitution of nitric oxide by the neutral reagent in the radical cation were the main processes. Whereas the former reaction yields the corresponding ionized nitrite oxide, the second process gives an even electron species tentatively ascribed, following high-kinetic energy collisional activation experiments, to an aromatic azirinyl cation. All the experimental data point to a two-step reaction sequence where the primarily formed intermediate ions competitively dissociate by the loss of nitrite or of nitric oxide respectively giving nitrite oxide ions and azirinyl ions. From a theoretical point of view, the mechanism of the simplest reaction HCNO.+ + HCN --> cyclo-HCCHN+ + NO. has been explored at the MP2/6-31G(d) level of theory. The most favorable reaction profile involves the formation of a C-N bond between the positively charged carbon atom of HCNO.+ and the nitrogen atom of cyanhydric acid giving an HCNO.+/HCN intermediate which isomerizes into an ionized nitrosoazirine before losing NO.

Crop residue management in arable cropping systems under a temperate climate. Part 2: Soil physical properties and crop production. A review

Introduction. Residues of previous crops provide a valuable amount of organic matter that can be used either to restore soil fertility or for external use. A better understanding of the impact of crop residue management on the soil-water-plant system is needed in order to manage agricultural land sustainably. This review focuses on soil physical aspects related to crop residue management, and specifically on the link between soil structure and hydraulic properties and its impact on crop production. Literature. Conservation practices, including crop residue retention and non-conventional tillage, can enhance soil health by improving aggregate stability. In this case, water infiltration is facilitated, resulting in an increase in plant water availability. Conservation practices, however, do not systematically lead to higher water availability for the plant. The influence of crop residue management on crop production is still unclear; in some cases, crop production is enhanced by residue retention, but in others crop residues can reduce crop yield. Conclusions. In this review we discuss the diverse and contrasting effects of crop residue management on soil physical properties and crop production under a temperate climate. The review highlights the importance of environmental factors such as soil type and local climatic conditions, highlighting the need to perform field studies on crop residue management and relate them to specific pedo-climatic contexts

Characterization of cyanogen N-oxide radical cation (NCCNO center dot+) in the gas phase by tandem mass spectrometry methodologies and ab initio calculations

On-line coupling of flash-vacuum pyrolysis and mass spectrometry has been applied to 3,4-dicyano-1,2,5-oxadiazole-2-oxide [1] (dicyanofuroxan). In agreement with previous work, it is found that 1 is almost quantitatively pyrolyzed in a 500-600 degrees C temperature range. Using collisional activation, the main pyrolysis products are identified as cyanogen N-oxide [2] and cyanogen (NC-CN). Dicyanoethyne (NCC=CCN) and carbon dioxide are also detected as minor products. The fragmentations observed in the CA spectrum of the [C2N2O](.+) ions (m/z 68) are in keeping with the proposed NCCNO connectivity and in good agreement with theoretical predictions. A peak of low intensity at m/z 40 (loss of CO) however suggests a partial contribution of isomeric cyano isocyanate ions, 3(.+). It is found that an homogeneous beam of cyanogen N-oxide ions is only obtained by dissociative ionization of 3,4-dicyano-1,2,5-oxadiazole [4] which loses intensively NCCN after ionization. Neutralization-reionization experiments confirm the stability of neutral cyanogen N-oxide in the gas phase. Calculated stability of the NCCNO neutral and the fragmentation energies of the NCCNO.+ radical cations (at the G2(MP2,SVP) level) are in good accord with the CA/NR experiments. Contrasting with the analogous cyanogen N-sulfide and N-selenide ions, cyanogen N-oxide ions do not exhibit significant ion-molecule reactions with various neutral targets (nitric oxide and pyridine). This unusual chemical behaviour is attributed to the stronger NO bond (higher double-bond character of the NO linkage) and the energetics (thermodynamics) of the oxygen transfer reactions

A new example of internal oxidation of remote groups in organic nitroaromatic ions

Intramolecular redox reactions occurring in ionized benzotriazoles and triazolopyridines bearing o-nitroaryl substituents on nitrogen produce ionized fulven-6-one and azafulven-6-ones