1,022 research outputs found
6-(4-Fluorophenyl)-8-phenyl-2,3-dihydro-4H-imidazo[5,1-b][1,3]thiazin-4-one: an unusual [6-5] fused-ring system
The title compound, CââHââFNâOS, is the first structural example of a [6-5] fused ring incorporating the 2,3-dihydro-4H-imidazo[5,1-b][1,3]thiazin-4-one molecular scaffold. The six-membered 2,3-dihydro-1,3-thiazin-4-one ring adopts an envelope conformation, with the S-CHâ C atom displaced by 0.761 (2) Ă
from the five-atom plane (all within 0.05 Ă
of the mean plane). The imidazole ring is planar. The phenyl ring is twisted from coplanarity with the imidazole ring by 23.84 (5)° and the 4-fluorophenyl ring is twisted by 53.36 (6)°, due to a close C(aryl)-H...O=C contact with the thiazin-4-one carbonyl O atom. The primary intermolecular interaction involves a CHâ group with the F atom [C...F = 3.256 (2) Ă
and C-H...F = 137°]
Internal and External Induced Circular Dichroism in Cyclodextrin Complexes: A Study of the Complexes of α-Cyclodextrin with (R)-3-Methylcyclopentanone and Cyclopentanone
The circular dichroism (CD) of (R)-3-methylcyclopentanone
1 in the presence of a-cyclodextrin (aCx) in -water has been
measured. The formation constant (K\u27 = 24 mol-1 litre) of al-l
complex, specific CD (do = +1.74) of 1 in water solution, and
specific CD of this complex in water (t1c\u27 = +1.4,5)have been
calculated. Similarly, the induced CD (ICD) of cyclopentanone
2 in the presence of aCx in water has been measured. The formation
constant (K = 25 mol-1 litre) of a 1-1 complex and the
specific CD (t1c\u27 = -0.034)of this complex have been calculated.
A model is presented for the interpretation of the lCD data.
Various theoretical possibi1ities are discussed. A comparison with
X-Ray and low-temperature neutron-diffraction data for the
(2-aCx) complex is attempted. It seems reasonable to conclude
that there is only a weak chiral discrimination in this complex in
water solution at room temperature
Soil Geographical Database of Eurasia and the Mediterranean: Instructions Guide for Elaboration at Scale 1:1,000,000
Abstract not availableJRC.H-Institute for environment and sustainability (Ispra
Probing material nonlinearity at various depths by time reversal mirrors
International audienceIn this letter, the time reversal mirror is used to focus elastic energy at a prescribed location and to analyze the amplitude dependence of the focus signal, thus providing the nonlinearity of the medium. By varying the frequency content of the focused waveforms, the technique can be used to probe the surface, by penetrating to a depth defined by the wavelength of the focused waves. The validity of this concept is shown in the presence of gradual and distributed damage in concrete by comparing actual results with a reference nonlinear measurement and X ray tomography images
Fertilité des sols: conclusions du rapport sur l'état des sols de France
Les sols constituent une ressource naturelle non renouvelable. Leurs usages et leur devenir reprĂ©sentent un enjeu collectif majeur, tant pour les activitĂ©s agricoles ou sylvicoles que pour la prĂ©servation de la qualitĂ© de notre environnement. AprĂšs dix ans de travaux, le Groupement dâIntĂ©rĂȘt Scientifique sur les sols, le Gis Sol, a dressĂ© le premier bilan scientifiquement quantifiĂ© de lâĂ©tat des sols de France mĂ©tropolitaine et dâOutre-mer dans un rapport sur lâĂ©tat des sols de France publiĂ© en 2011. Ce rapport relĂšve des points positifs mais Ă©galement un certain nombre de prĂ©occupations du point de vue de la fertilitĂ©. Les sols agricoles ne prĂ©sentent pas dâĂ©volution mesurable de leur aciditĂ©, ce quiindique une bonne gestion du pH Ă lâĂ©chelle nationale. Le rapport fait en revanche Ă©tat de teneurs en phosphore relativement faibles pour de nombreux sols, et Ă lâinverse de situations dâexcĂ©dents trĂšs prĂ©occupantes en raison de son impact sur la qualitĂ© des eaux et lâeutrophisation des milieux. Il pose ainsi la question de la durabilitĂ© Ă long terme du systĂšme agricole actuel et celle dâune meilleure valorisation des effluents dâĂ©levage. Dâassez nombreuses situations pourraient Ă©galement ĂȘtre susceptibles de provoquer des carences en oligo-Ă©lĂ©ments pour des cultures exigeantes. Enfin, une inquiĂ©tude majeure concerne la progression de lâartificialisation des sols, qui sâest accĂ©lĂ©rĂ©e durant la derniĂšre dĂ©cennie et occasionne des pertes importantes de sols agricoles.Soils are a non-renewable, natural resource. Their uses and their future represent, therefore, a collective issue for agricultural and forestry production, as well as for the preservation of our environment. After ten years of work, the âGroupement dâintĂ©rĂȘt scientifique sur les solsâ, the Gis Sol (Soils Scientific Interest Group) has presented the first appraisal of soil quality in mainland France and its overseas territories in a report on the state of the soils in France published in 2011. This appraisal shows evidence for positive points but also highlights some concerns regarding soil fertility. Agricultural soils do not show a measurable change in their acidity, thus indicating an efficient management of pH at a national level. On the other hand, the report shows relatively low phosphorus levels for numerous soils, and inversely situations of structural excess which remain very worrying due to its impact on water quality and on the eutrophication of the environments. It also raises the questionsof the long-term sustainability of current cultivation systems and of a better treatment of effluents from livestock farming. Numerous situations also seem to be incompatible, for certain oligo-elements, with demanding cultures. At last, a major concern is the development of soil sealing, which has accelerated over the last decade and is responsible for the loss of large areas of agricultural soils
Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record
Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132âČSâ78°04.847âČW) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328âČSâ78°09.175âČW) is a glacially formed lake with an inflow and outflow in high Andean PĂĄramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes
Exploring the effects of extended interval dosing of natalizumab and drug concentrations on brain atrophy in multiple sclerosis
BACKGROUND: Extended interval dosing (EID) of natalizumab treatment is increasingly used in multiple sclerosis. Besides the clear anti-inflammatory effect, natalizumab is considered to have neuroprotective properties as well. OBJECTIVES: This study aimed to study the longitudinal effects of EID compared to standard interval dosing (SID) and natalizumab drug concentrations on brain atrophy. METHODS: Patients receiving EID or SID of natalizumab with a minimum radiological follow-up of 2 years were included. Changes in brain atrophy measures over time were derived from clinical routine 3D-Fluid Attenuated Inversion Recovery (FLAIR)-weighted magnetic resonance imaging (MRI) scans using SynthSeg. RESULTS: We found no differences between EID (n = 32) and SID (n = 50) for whole brain (-0.21% vs -0.16%, p = 0.42), ventricular (1.84% vs 1.13%, p = 0.24), and thalamic (-0.32% vs -0.32%, p = 0.97) annualized volume change over a median follow-up of 3.2 years. No associations between natalizumab drug concentration and brain atrophy rate were found. CONCLUSION: We found no clear evidence that EID compared to SID or lower natalizumab drug concentrations have a negative impact on the development of brain atrophy over time
Stratigraphy and chronology of a 15ka sequence of multi-sourced silicic tephras in a montane peat bog, eastern North Island, New Zealand.
We document the stratigraphy, composition, and chronology of a succession of 16 distal, silicic tephra layers interbedded with lateglacial and Holocene peats and muds up to c. 15 000 radiocarbon years (c. 18 000 calendar years) old at a montane site (Kaipo Bog) in eastern North Island, New Zealand. Aged from 665 +/- 15 to 14 700 +/- 95 14C yr BP, the tephras are derived from six volcanic centres in North Island, three of which are rhyolitic (Okataina, Taupo, Maroa), one peralkaline (Tuhua), and two andesitic (Tongariro, Egmont). Correlations are based on multiple criteria: field properties and stratigraphic interrelationships, ferromagnesian silicate mineral assemblages, glass-shard major element composition (from electron microprobe analysis), and radiocarbon dating. We extend the known distribution of tephras in eastern North Island and provide compositional data that add to their potential usefulness as isochronous markers. The chronostratigraphic framework established for the Kaipo sequence, based on both site-specific and independently derived tephra-based radiocarbon ages, provides the basis for fine-resolution paleoenvironmental studies at a climatically sensitive terrestrial site from the mid latitudes of the Southern Hemisphere. Tephras identified as especially useful paleoenvironmental markers include Rerewhakaaitu and Waiohau (lateglacial), Konini (lateglacial-early Holocene), Tuhua (middle Holocene), and Taupo and Kaharoa (late Holocene)
Mesophotic depth biogenic accumulations (âbiogenic moundsâ) offshore the Maltese Islands, Central Mediterranean Sea
The mesophotic domain is a poorly explored part of the oceans, notably in the Mediterranean Sea. Benthic communities in these depths are not well documented and as such are under higher risk from anthropogenic impacts. Hard substrate habitats in this depth window are not common and are a key ecotope. The Malta Plateau in the central Mediterranean, which is characterized by low sedimentation rates, offers a potentially unexplored domain for these features. Bathymetric and backscatter data offshore of the eastern coast of the island of Malta were used to identify > 1,700 small structures in mesophotic depths. These structures were verified to be biogenic mounds by dives. The mounds extend from several meters to tens of meters in diameter and occur in two main depth windows â40 to 83 meters below present sea level (mbpsl) and 83â120 mbpslâeach formed probably in a different stage during the last glacial cycle. The mounds are composed of interlocking bioconstruction by encrusting organisms and are colonized by sponges and various cold water corals (most of which are protected; e.g., Madrepora oculata). This unique and important habitat is currently under grave threat by human activity, most immediately by trawling and anchoring activity
Optimal estimation of qubit states with continuous time measurements
We propose an adaptive, two steps strategy, for the estimation of mixed qubit
states. We show that the strategy is optimal in a local minimax sense for the
trace norm distance as well as other locally quadratic figures of merit. Local
minimax optimality means that given identical qubits, there exists no
estimator which can perform better than the proposed estimator on a
neighborhood of size of an arbitrary state. In particular, it is
asymptotically Bayesian optimal for a large class of prior distributions.
We present a physical implementation of the optimal estimation strategy based
on continuous time measurements in a field that couples with the qubits.
The crucial ingredient of the result is the concept of local asymptotic
normality (or LAN) for qubits. This means that, for large , the statistical
model described by identically prepared qubits is locally equivalent to a
model with only a classical Gaussian distribution and a Gaussian state of a
quantum harmonic oscillator.
The term `local' refers to a shrinking neighborhood around a fixed state
. An essential result is that the neighborhood radius can be chosen
arbitrarily close to . This allows us to use a two steps procedure by
which we first localize the state within a smaller neighborhood of radius
, and then use LAN to perform optimal estimation.Comment: 32 pages, 3 figures, to appear in Commun. Math. Phy
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