Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.     

Bipolar Electrochemiluminescence Imaging: A Way to Investigate the Passivation of Silicon Surfaces

This work depicts the original combination of electrochemiluminescence (ECL) and bipolar electrochemistry (BPE) to map in real-time the oxidation of silicon in microchannels. We fabricated model silicon-PDMS microfluidic chips, optionally containing a restriction, and monitored the evolution of the surface reactivity using ECL. BPE was used to remotely promote ECL at the silicon surface inside microfluidic channels. The effects of the fluidic design, the applied potential and the resistance of the channel (controlled by the fluidic configuration) on the silicon polarization and oxide formation were investigated. A potential difference down to 6 V was sufficient to induce ECL, which is two orders of magnitude less than in classical BPE configurations. Increasing the resistance of the channel led to an increase in the current passing through the silicon and boosted the intensity of ECL signals. Finally, the possibility of achieving electrochemical reactions at predetermined locations on the microfluidic chip was investigated using a patterning of the silicon oxide surface by etched micrometric squares. This ECL imaging approach opens exciting perspectives for the precise understanding and implementation of electrochemical functionalization on passivating materials. In addition, it may help the development and the design of fully integrated microfluidic biochips paving the way for development of original bioanalytical applications.     

Supramolecular Luminescent Lanthanide Dimers for Fluoride Sequestering and Sensing

Lanthanide complexes (Ln=Eu, Tb, and Yb) that are based on a C₂‐symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/Vis absorption, luminescence, and NMR spectroscopy and high‐resolution mass spectrometry. The X‐ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the Eu? F? Eu bridging motive, π stacking interactions, and a four‐component hydrogen‐bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nM .     

The versatility of pentalene coordination to transition metals: a density functional theory investigation

DFT calculations with full geometry optimization have been carried out on a series of real and hypothetical compounds of the type [CpM(C8H6)], [(CO)3M(C8H6)], [M(C8H6)2], [(CpM)2(C8H6)], [[(CO)3M]2(C8H6)], and [M2(C8H6)2] (M = transition metal). The bonding in all the currently known compounds is rationalized, as well as in the (so far) hypothetical stable complexes. Depending on the electron count and the nature of the metal(s), eta2 (predicted), eta3, eta5, eta8, or intermediate coordination modes can be adopted. In the case of the mononuclear species, the most favored closed-shell electron counts are 18 and 16 metal valence electrons (MVE). In the case of the dinuclear species, an electron count of 34 MVEs is most favored. However, other electron counts can be stabilized, especially in the case of dinuclear complexes. Coordinated pentalene should most often be considered as formally being a dianion, but sometimes as a neutral ligand. In the former case it can behave as an aromatic species made of two equivalent fused rings, as a C5 aromatic ring connected to an allylic anion, or even as two allylic anions bridged by a C7=C8 double bond. In the latter case, it can behave as a bond-alternating cyclic polyene or as a C5 aromatic ring connected to an allylic cation.     

Large-scale ultrasonic cleaning system: Design of a multi-transducer device for boat cleaning (20kHz)

The present study is part of a global project which consists in the development of an automatic cleaning station for immersed boats (cockle, ninepin, etc.) in a self-service mode, associating an innovative ultrasonic device for cleaning with a specific water treatment. The originality of the process is that cleaning is performed by three transducers operating simultaneously at low frequency and moving along the surface, thanks to programmable logic controllers, and that it includes a suction to collect the dirt removed. Therefore, the time required for boat maintenance is shortened, ensuring high quality cleaning without the need for dry docks and avoiding additional pollution in the harbor areas. One of the key points was the evaluation of washing efficiency, as it is really hard to give a quantitative estimation of the dirt removed. To obtain the first design laws, feasibility tests have been carried out on dirty cockle samples and on real boat hulls with a laboratory ultrasonic device. The influence of a large number of parameters was tested such as transducer-probe distance, displacement speed and transmitted power. The obtained data allowed us to design an optimized cleaning device combining high efficiency and speed.     

Performance studies of a full-length prototype for the CASTOR forward calorimeter at the CMS experiment

The Time-Of-Flight detector (TOF) of the ALICE experiment at the CERN LHC is based on Multi-gap Resistive Plate Chambers (MRPCs). The TOF detector consists of 152928 readout channels covering a total area of 141 m². In this paper the results of the calibration with cosmic-ray data collected during 2009 are presented.     

Vortex lattice of a Bose-Einstein condensate as a photonic band gap material

Photonic crystal behavior of a rotating Bose-Einstein condensate with a triangular vortex lattice is reviewed and a scheme for getting much wider band gaps is proposed. It is shown that photonic band gaps can be widened an order of magnitude more by using a Raman scheme of index enhancement, in comparison to previously considered upper level microwave scheme.