Letteratura scientifica selezionata sul tema "In situ µ-analysis"

By reacting [{Cp‴Fe(CO)2}2(µ,η1:1-P4)] (1) with in situ generated phosphenium ions [Ph2P][A] ([A]− = [OTf]− = [O3SCF3]−, [PF6]−), a mixture of two main products of the composition [{Cp‴Fe(CO)2}2(µ,η1:1-P5(C6H5)2)][PF6] (2a and 3a) could be identified by extensive 31P NMR spectroscopic studies at 193 K. Compound 3a was also characterized by X-ray diffraction analysis, showing the rarely observed bicyclo[2.1.0]pentaphosphapentane unit. At room temperature, the novel compound [{Cp‴Fe}(µ,η4:1-P5Ph2){Cp‴(CO)2Fe}][PF6] (4) is formed by decarbonylation. Reacting 1 with in situ generated diphenyl arsenium ions gives short-lived intermediates at 193 K which disproportionate at room temperature into tetraphenyldiarsine and [{Cp‴Fe(CO)2}4(µ4,η1:1:1:1-P8)][OTf]2 (5) containing a tetracyclo[3.3.0.02,7.03,6]octaphosphaoctane ligand.

In the present work, polystyrene composites using wheat husk, rice husk and mustard husk as fillers are synthesized using in-situ polymerisation technique. Three different filler loading (5%, 10% and 15 %) and three different filler sizes (250-355 µ, 355-500 µ, 500-710 µ) were utilized for the studying the effect of these compositions on different mechanical properties of the synthesized composites. The results have shown that the filler size 250-355 µ and 5 % loading give the maximum values for tensile strength, flexural strength and hardness for all the three types of fillers. While in case of water absorptivity lower the size/loading, lesser would be the water absorbed. The SEM analysis is done to study the fractured surface of the specimen.

Ex situ conservation is an important complementary strategy for in situ to conserve endangered plant species. However, the limited areas designated for ex situ conservation such as in botanic gardens have become a great challenge for conservation practitioners and scientists attempting to optimally conserve the genetic diversity of targeted plant species. Our study aimed to assess genetic diversity and structure of wild seedlings of Vatica bantamensis, an endemic and critically endangered dipterocarp from Java (Indonesia). We also estimated genetic differentiation between the wild seedlings and existing ex situ collection and evaluated the genetic diversity preserved in the ex situ collection. Our analysis, using 730 single-nucleotide polymorphisms loci, showed that wild seedlings exhibited higher genetic diversity than the ex situ collection (nucleotide diversity, µ = 0.26 and 0.16, respectively). Significant genetic differentiation was also detected ( FST = 0.32) between wild seedlings and ex situ collection. Furthermore, we found high kinship within the ex situ collection suggesting low genetic diversity since the founding collection. We also detected three distinct genetic clusters from all samples combined (analysis of molecular variance, ϕ = 0.48, p < .001), with two clusters present in the wild seedlings that were not represented in the ex situ collection. We recommend that supplementary collections from the two newly identified genetic clusters in the wild seedlings should be incorporated to increase genetic diversity in the ex situ collection. Furthermore, our study demonstrated that understanding the population genetics of targeted endangered species provides better results for ex situ conservation strategies.

Precious corals belong to the family Coralliidae (Cnidaria, Octocorallia), and their axis, which consists of high magnesian calcium carbonate, has long been used in jewelry. With its low growth rate and long lifespan, precious coral is a representative taxon of the vulnerable marine ecosystem. Due to years of overfishing, coral fishery has become a controversial issue. To estimate the growth rate and clarify the uptake process of trace elements in relation to the growth of the carbonate axis, Japanese red coral (Corallium japonicum) was cultured at a depth of 135 m off Takeshima Island, Kagoshima, Japan for 98 months and analyzed by microscopic X-ray fluorescence/soft X-ray photoabsorption (µ-XRF/XAS) speciation mapping. The growth rate was estimated to be 0.37 mm/year in diameter, and 10–11 growth rings were observed in a cross section of the axis. This estimated growth-rate value is the first ever to be obtained from the in-situ culture of Japanese precious coral. The fluctuation in water temperature near the in-situ-culture site was recorded for part of the culture period and then compared with the changes in the growth ring and the distribution of trace elements in a cross section of the coral axis during the same period. When the water temperature was increasing, the growth ring was light in color, sulfur and phosphorus concentrations were low, and magnesium was high. Conversely, a dark band in the growth ring, high sulfur and phosphorus, and low magnesium concentrations were observed when the water temperature was decreasing. In a cross section of the coral axis, the distribution of sulfur and magnesium from the center to the surface corresponded, respectively, to dark and light bands in the annual growth ring. Sulfur concentration was high in the dark band and low in the light band, while magnesium was negatively correlated with sulfur.

<strong>Community Structure and Habitat of Coral Fish on Artificial Reef in Awang and Bumbang Bay, Lombok Island</strong>. Artificial reefs which were placed in Teluk Awang and Teluk Bumbang intended to restore habitat fish resources. This paper aims to evaluate the development of artificial reefs in both locations. The activities was conducted in June and December 2015. Data collection included fish and benthic communities, biological parameters (phytoplankton, zooplankton, meroplanton), physical parameters (temperature, salinity, conductivity, pH, turbidity, dissolved oxygen), and chemical parameters waters (nitrates and phosphates). Observation of fish community using SCUBA diving equipment, underwater sheets, stationery and GPS, then visual observations using a modified stationary visual census technique. Visual recorded also used for benthic communities. Water sampling taken on the surface and bottom at depths of 9 m and 11 m using water quality checker. Biological parameters were taken using 60 µ, 300 µ and plankton net sizes 700 µ. Nutrients were observed in the laboratory by taking water samples in situ. Laboratory tests were carried out for nutrients as well as plankton and meroplankton. Benthic communities were categorized into four life forms, namely live coral covered, dead coral, biota (algae and other biota) as well as the abiotic component. Habitat preferences identified through analysis of factors related to fish abundance by principal component analysis method. The results showed that on those artificial reefs in Awang and Bumbang Bay found as many as 8 - 16 species of coral fish belongs to 15 families, dominated by Apogonidae (Archamia fucata), Pomacentridae (Neopomacentrus cyanomos) and Phempherididae (Phempheris oulensis), ranges of the abundance 268 to1088 individual. The ecological index showed low to moderate type of diversity, the dominance index does not indicate the dominance of certain species and the evenness index indicated that the fish dispersal characteristic is quite flat. Fish habitat preference in Awang Bay supported by the presence of algae and other biota, nutrients, and salinity. While in Teluk Bumbang supported by the abundance of fito-zooplankton, dissolved oxygen, and turbidity

Purpose: The aim of this study was to report multimodal refractive imaging findings that may predict ectasia susceptibility on nonoperated eyes of patients who developed post-LASIK ectasia in the fellow eye. Study Design: This is a retrospective case series. Methods: The nonoperated fellow eyes of 5 patients who had unilateral LASIK with progressive ectasia underwent a comprehensive ophthalmologic evaluation and multimodal refractive imaging (MRI), including Pentacam HR and Corvis ST (Oculus; Wetzlar, Germany), along with segmental OCT (RTVue; Optovue, Inc, Fremont, CA). Different objective indices and parameters from the Pentacam, Corvis ST, and OCT were analyzed. Results: None of the 5 cases showed ectasia detection on the Pentacam TKC (topographic keratoconus classification), and inferior–superior (IS) asymmetry values were lower than 1.0 D in all 5 cases. Corneal thicknesses at the thinnest points measured with the Pentacam were 530, 466, 517, 488, and 511 µ, and with the OCT were 512, 460, 508, 480, and 495 µ, in cases 1to 5, respectively. The keratoconus risk scoring system based on OCT measurements demonstrated a high risk in 2 patients. The BAD-D (Belin-Ambrósio Enhanced Ectasia Deviation) was higher than 1.22 in all 5 cases and higher than 1.6 in 2 cases. Four cases had ARTmax (Ambrósio Relational Thickness to the meridian with maximal progression increase) lower than 390. The PRFI (Pentacam Random Forest Index) was equal or higher than 0.12 in all 5 cases, and enhanced posterior elevation, which is calculated using data from the standard elevation map, excluding a 3.5-mm area centered on the thinnest point, was abnormal in all 5 cases. The value of the current version of the tomographic biomechanical index (TBI V1), derived from artificial intelligence (AI) algorithms, which integrate Scheimpflug-based tomography and biomechanical data, was equal or higher than 0.29 in 3 cases. Conclusions: Signs of ectasia susceptibility were detected in all nonoperated eyes based on multimodal imaging. These findings support the clinical relevance of such analysis when screening for ectasia risk among candidates for refractive surgery.

This paper presents the absorbance and fluorescence optical properties of various phytoplankton species, looking to achieve an accurate method to detect and identify a number of phytoplankton taxonomic groups. The methodology to select the excitation and detection wavelengths that results in superior identification of phytoplankton is reported. The macroscopic analyses and the implemented methodology are the base for designing a lab-on-a-chip device for a phytoplankton group identification, based on cell analysis with multi-wavelength lighting excitation, aiming for a cheap and portable platform. With such methodology in a lab-on-a-chip device, the analysis of the phytoplankton cells’ optical properties, e.g., fluorescence, diffraction, absorption and reflection, will be possible. This device will offer, in the future, a platform for continuous, autonomous and in situ underwater measurements, in opposition to the conventional methodology. A proof-of-concept device with LED light excitation at 450 nm and a detection photodiode at 680 nm was fabricated. This device was able to quantify the concentration of the phytoplankton chlorophyll a. A lock-in amplifier electronic circuit was developed and integrated in a portable and low-cost sensor, featuring continuous, autonomous and in situ underwater measurements. This device has a detection limit of 0.01 µ/L of chlorophyll a, in a range up to 300 µg/L, with a linear voltage output with chlorophyll concentration.

Purpose The purpose of this study is to increase the wear resistance of Mg alloy by adding hard ceramic particles to it. The inclusion of hard ceramic particles further strengthen the Mg alloy, resulting in higher wear resistance. Mg alloys containing Zn, rare earth and Zr exhibit high specific strength and excellent creep resistance, making them suitable for aerospace components such as aircraft gearboxes and generator housings. Design/methodology/approach In the present study, composites have been produced in situ by using RZ5 mg alloy as matrix and TiC as reinforcement by self-propagating high-temperature synthesis technique. The abrasive wear behavior of RZ5 Mg alloy matrix reinforced with TiC particulates has also been examined. The pin-on-disc apparatus has been used for the tests. The abrasive paper is used as a counter body, and the results are obtained by changing sliding distance and applied load. Findings A notable enhancement in the wear resistance and mechanical properties of tested composite has been observed as compared to the RZ5 Mg alloy as a matrix. There is a uniform increment in the change in weight loss of RZ5-TiC composite with increasing sliding distance and applied load, but it decreases with increasing TiC content. The coefficient of friction (µ) also decreases uniformly with an increase in the reinforcement of TiC, but it decreases with an increase in applied load and sliding distance. The investigation of the worn composite, which determines dominant wear mechanisms as abrasion and plowing grooves on tested samples, has been done using field emission scanning electron microscopy. Originality/value The current manuscript provides a detailed abrasive wear analysis of RZ5-TiC composite by using different wear parameters. Specifically, extensive experimental data have been provided for RZ5-TiC composite. The effects of parameters such as applied load, sliding distance and Wt.% of TiC on the weight loss and coefficient of friction of the composites have been analyzed and discussed thoroughly.

Abstract Swimming of micro-scale bodies is different from macro-scale counterparts due to low Reynolds number (Re) fluid-swimmer interaction. The Re is defined as the ratio of inertial force to viscous force and it can be expressed as, Re =ρ𝑣𝑙/µ, where ρ and µ are the density and viscosity of the fluid medium, v and l are the velocity and length of the swimmer. For microswimmers, due to the small length scale Re < 1, the inertial forces are negligible compared to viscous forces. Unlike the macroscale swimmers which exploit the inertial force for locomotion, microswimmers must use a different strategy to propel in low Re condition. These strategies are already available and used by microorganisms, which are perfect low Re swimmers, for example, Spermatozoon exploits their tail flexibility and anisotropic drag to swim, and E. coli bacteria use their helical tail to generate a non-reciprocal motion. By mimicking these microswimmers, researchers have developed many bioinspired microswimmers/microrobots having the potential to perform biomedical tasks like drug delivery, cell manipulation, in-situ sensing, and detoxification. Theoretical modeling and simulation of microswimmers are generally done by assuming that the microswimmer is in an infinite fluid medium, but the type of biomedical applications aimed are in confined environments with boundaries. Also, the environments are very complex, and it requires precise control and efficacy. In this paper, we present the modeling of flagellated magnetic microswimmer (inspired by Spermatozoon) in a microchannel using the finite element method. The dynamics were simulated by incorporating the complete hydrodynamic interactions (HI), that is intra-HI between the parts of the swimmer and inter-HI between the swimmer and the boundary walls of the channel. The parametric dependence analysis reveals that swimmer kinematics are dependent on the length and width of the tail, the head radius, width of the channel, and the actuation frequency of the driving magnetic field. These dependencies are explored to find a navigation control mechanism for the propulsion of microswimmer in a channel.

A nanohybrid material termed graphene oxide/metal-organic framework-74/Fe3O4/polytyramine (GO/MOF-74/Fe3O4­/PTy) was fabricated and applied in magnetic dispersive micro-solid phase extraction (MD-µ-SPE) coupled with high performance liquid chromatography (HPLC) for simultaneous determination of fluoroquinolones compounds including, ofloxacin, ciprofloxacin, lomefloxacin, enrofloxacin and sperfloxacin in egg samples. The GO/MOF-74/Fe3O4/PTy nanocomposite was fabricated through an in situ synthesis of MOF-74 in the presence of magnetic GO and followed with an oxidative polymerization of tyramine using horsedish peroxide (HRP) enzyme. The modifier agents improved the merits of the nanoporous sorbent. Extraction protocols based on GO/MOF nanocomposites have various benefit such as, the high stability, the tunable porosity, the fast mast transfer and reasonable enrichment factor. The fabricated material was characterized via energy dispersive x-ray analysis (EDX), the scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and the x-ray diffraction (XRD). The calibration curves revealed linearity (0.992 ≤ r2 ≤ 0.997) in the ranges of 1.0-475.0, 0.5-350.0, 0.5-350.0, 0.5-375.0 and 1.5-300.0 ng mL-1 with limit of detections (LODs, S/N=3) of 0.3, 0.1, 0.2, 0.1 and 0.4 ng mL-1 for ofloxacin, ciprofloxacin, lomefloxacin, enrofloxacin and sperfloxacin, respectively. The intra-assay (≤7.7%, n = 9) and inter-assay (≤7.0%, n = 9) precisions along with accuracy less than 9.0% were obtained.

Le comportement des halogènes (F, Cl, Br et I) dans les systèmes magmatiques est loin d'être clairement compris. La communauté scientifique n'a qu'une connaissance fragmentaire des processus qui influencent le comportement de ces éléments pendant le stockage et l'ascension des magmas. Les études récentes du comportement des halogènes lourds comme le brome et l'iode se sont principalement concentrées sur les magmas liés à la subduction, dans le contexte du cycle géochimique des halogènes depuis la subduction jusqu'à l'atmosphère. Les études antérieures sur la solubilité des halogènes (à saturation en saumure) ont montré que les liquides calco-alcalins felsiques, fortement polymérisés, présentent une solubilité des halogènes (à l'exception du F) plus faible que les liquides felsiques riches en alcalins. En outre, les magmas riches en alcalins peuvent produire des éruptions de grand volume (par exemple, le système du rift est-africain), ce qui peut conduire à une émission massive d'halogènes dans l'atmosphère. Les émissions d'halogènes dans l'atmosphère sont donc potentiellement sous-estimées dans ces contextes, en raison d'un manque de compréhension détaillée du comportement des halogènes (et notamment du brome et de l'iode) pendant le dégazage magmatique. Dans ce contexte, l'objectif de cette thèse est de contraindre expérimentalement le partage des halogènes entre la phase fluide magmatique et le liquide silicaté dans les systèmes alcalins felsiques et de conduire une étude préliminaire de l'abondance des halogènes (notamment du brome et de l'iode) dans les verres alcalins naturels mafiques à felsiques provenant de différents contextes géodynamiques. Nous avons réalisé des expériences HP-HT (800 -1100 °C ; 10-200 MPa ; NNO-0.6 - NNO+3.4) en utilisant quatre compositions de liquide silicaté de teneur en SiO2 et de rapport molaire [(Na₂O+K₂O)/Al₂O₃] variables (phonolite, comendite, pantellerite et un analogue synthétique de la composition phonolitique). Nos résultats montrent que la composition du liquide a un impact important sur le partage des halogènes entre le fluide et le liquide silicaté. Le Dhalogens (avec Dhalogens = concentration de l'halogène dans la phase fluide/concentration de l'halogène dans le liquide silicaté) augmente avec la teneur en SiO₂ et diminue avec l'alcalinité des liquides, en accord avec les données de solubilité. Nous avons effectué une étude systématique de l'influence de la température et de la pression sur le partage des halogènes entre le fluide et le liquide silicaté et les résultats montrent que la température a un effet plus prononcé sur le partage que la pression. L'influence des conditions redox a également été étudiée et les résultats montrent que le D_I diminue avec la diminution de la fO2, tandis que DBr et le DCl montrent un effet inverse. Nous présentons la première détermination des abondances en halogènes lourds (Br et I) dans des verres felsiques riches en alcalins, avec des concentrations de l'ordre de ~10 ppm de Br et jusqu'à ~1 ppm de I dans les rhyolites riches en alcalins. Les concentrations en iode de ces verres sont au moins un ordre de grandeur plus élevées que les concentrations déterminées par l'analyse roche totale des produits volcaniques calco-alcalins publiées par ailleurs, mettant en exergue la nécessité de quantifier davantage les halogènes lourds dans les magmas afin de mieux évaluer les émissions atmosphériques d'halogènes et leur impact sur l'environnement
The behavior of halogens (F, Cl, Br and I) in magmatic systems is far from being clearly understood. The scientific community has only a fragmentary understanding of the processes that influence the behaviour of these elements during magma storage and ascent to the surface. Recent studies of heavy halogens (Br and I) behaviour have focused mainly on subduction-related magmas, in the context of the geochemical cycle of the halogens from subduction to the atmosphere. Previous studies of halogens solubility (at brine saturation) have shown that felsic, highly-polymerized calc-alkaline melts have lower halogens (except F) solubility than felsic alkali-rich melts. In addition, alkali-rich melts can produce large volume eruptions (e.g., East Africa Rift System), leading to potential massive release of halogens into the atmosphere. Emissions of halogens to the atmosphere are therefore likely to be underestimated, due to the lack of detailed understanding of the behavior of halogens (and in particular bromine and iodine) during magmatic degassing. In this work, we have addressed this gap by experimentally constraining fluid/melt halogen partitioning in felsic alkali-rich systems, with a focus on Br and I, and by a preliminary study of halogens abundances in natural mafic to felsic alkali-rich glasses from different geodynamic contexts. We performed HP-HT experiments (800°-1100 °C; 10 -200 MPa; NNO-0.6 -NNO+3.4) using four melt compositions, with variable SiO2 contents and [(Na₂O+K₂O)/Al₂O₃] molar ratios (natural phonolite, comendite and pantellerite and a synthetic analogue of phonolitic composition). Our results show that melt composition has a strong effect on the partitioning of halogens between fluid and melt. Dhalogens (with Dhalogens = halogen concentration in the fluid phase / halogen concentration in the silicate melt) increases with SiO₂ content and decreases with melt alkalinity, in agreement with the solubility data. We have carried out a systematic investigation of the influence of temperature and pressure on the fluid-melt partitioning of halogens and the results show that temperature has a more pronounced effect on partitioning than pressure. The effect of the redox conditions on halogens fluid/melt partitioning was also explored and the results indicate that DI decreases with decreasing fO₂, whereas DBr and DCl show the opposite effect. We present the first determination of heavy halogens (Br and I) abundances in felsic alkali-rich glasses, with concentrations in the order of ~10 ppm of Br and up to ~1 ppm of I in alkali-rich rhyolites. Iodine concentrations for these melts are at least an order of magnitude higher than concentrations determined by bulk rock analysis of calc-alkaline volcanic rocks in previous studies, highlighting the need for further quantification of heavy halogens in magmas to better assess their atmospheric emission and impact

Abstract The classification of the imperative as a MOOD, correlative with subj., opt., and indicat., is obviously an analysis faute de mieux. But no straightforward alternative analysis suggests itself. Since the imperative is a kind of future, it is perhaps reminiscent of opt. and subj., moods; but probably it has most in common FUNCTIONALLY with the desiderative (457). The main differences are the roles: in the desiderative, desire is ascribed at will to any person, who is also the one to undertake the action, whereas in imperatives the desire for a (future) action is only on the part of the speaker, and the action itself is always on the part of someone else: ‘I want you to build a fire’ is not a possible expression via the IE desiderative. What sets the IE imperatives most sharply apart from the moods (and the desiderative also) is morphology: they have no special stem marker, in­ stead having special person-markers. In the 2pl. active there is no difference in form between the imperative and indicative endings (and in fact most of the special endings are lost in L). Of course, the expression of desire for a future action on the part of a speaker can be couched in a variety of ways, some of them using actual mood paradigms, as in the hortatory forms familiar from the classical languages, or else the sentence complement structure of NE let’s, or else syntactic particles (as in G µ ), and circumlocutions for various purposes, differing according to such variables as politeness, intimacy, and so on (Why don’t we sit down or How about sitting down or Perhaps you would like to sit down, and so on).