Improvement by heating of the electronic conductivity of cobalt spinel phases, electrochemically synthesized in various electrolytes

The nature of the alkaline electrolyte (based on KOH, NaOH, LiOH), in which Co₃O₄ spinel type phases are synthesized by electrooxidation of CoO, is shown to play a key role on the composition, the structure and the electronic conductivity of the materials. In the materials, prepared in pure LiOH electrolyte or in mixed ternary electrolyte (KOH, NaOH, LiOH), Co⁴⁺ ions are present in the octahedral framework, which entails electronic delocalization in the cobalt T_2g band and a high conductivity. The structure of the sample, synthesized in KOH, is on the opposite closer to that of ideal Co₃O₄, with only Co³⁺ in the octahedral sublattice, which leads to a semi-conducting behavior. Whatever the initial material, a thermal treatment induces an increase of the Co⁴⁺/Co³⁺ ratio in the octahedral network, resulting in a significant increase of the electronic conductivity.     

Low frequency vocalizations attributed to sei whales (Balaenoptera borealis)

Low frequency (<100 Hz) downsweep vocalizations were repeatedly recorded from ocean gliders east of Cape Cod, MA in May 2005. To identify the species responsible for this call, arrays of acoustic recorders were deployed in this same area during 2006 and 2007. 70 h of collocated visual observations at the center of each array were used to compare the localized occurrence of this call to the occurrence of three baleen whale species: right, humpback, and sei whales. The low frequency call was significantly associated only with the occurrence of sei whales. On average, the call swept from 82 to 34 Hz over 1.4 s and was most often produced as a single call, although pairs and (more rarely) triplets were occasionally detected. Individual calls comprising the pairs were localized to within tens of meters of one another and were more similar to one another than to contemporaneous calls by other whales, suggesting that paired calls may be produced by the same animal. A synthetic kernel was developed to facilitate automatic detection of this call using spectrogram-correlation methods. The optimal kernel missed 14% of calls, and of all the calls that were automatically detected, 15% were false positives.     

Sounds produced by Norwegian killer whales, Orcinus orca, during capture

To date very little is still known about the acoustic behavior of Norwegian killer whales, in particular that of individual whales. In this study a unique opportunity was presented to document the sounds produced by five captured killer whales in the Vestfjord area, northern Norway. Individuals produced 14 discrete and 7 compound calls. Two call types were used both by individuals 16178 and 23365 suggesting that they may belong to the same pod. Comparisons with calls documented in Strager (1993) showed that none of the call types used by the captured individuals were present. The lack of these calls in the available literature suggests that call variability within individuals is likely to be large. This short note adds to our knowledge of the vocal repertoire of this population and demonstrates the need for further studies to provide behavioural context to these sounds.     

Local Observation of Field Polarity Dependent Flux Pinning by Magnetic Dipoles

A scanning Hall probe microscope is used to study flux pinning in a thin superconducting Pb film covering a square array of single-domain Co dots with in-plane magnetization. We show that single flux quanta of opposite sign thread the superconducting film below T(c) at the opposite poles of these dipoles. Depending on the polarity of the applied field, flux lines are attracted to a specific pole of the dipoles, due to the direct interaction with the vortexlike structures induced by the local stray field.     

Acute Ultraviolet Radiation Perturbs Epithelialization but not the Biomechanical Strength of Full‐thickness Cutaneous Wounds

We hypothesized that priming of the skin with ultraviolet radiation (UVR) before being injured would enhance wound healing. Four groups, each comprising 20 immunocompetent hairless mice, were exposed to simulated solar irradiation in escalating UVR doses; 0 standard erythema dose (SED) = control, 1 SED, 3 SED and 5 SED. Twenty‐four hours after UV irradiation, inflammation was quantified by skin reflectance (erythema) and myeloperoxidase (MPO) tissue levels, and two 6 mm full‐thickness excisional wounds and one 3 cm incisional wound were inflicted. Epidermal hyperplasia was assessed by quantitative histology. Five days after wounding, wound coverage by neoepithelium and wound width of the excisional wounds was quantified in hematoxylin–eosin sections, and breaking strength was measured in strips from incisional wounds. Erythema (P < 0.001), MPO levels (P < 0.0005) and epidermal cell layers (P < 0.001) increased dose‐dependently by UV exposure of dorsal skin. In the excisional wounds, epithelial coverage decreased (P = 0.024) by increasing the UVR dose, whereas there was no significant difference (P = 0.765) in wound MPO levels. Neither wound width (P = 0.850) nor breaking strength (P = 0.320) differed among the groups. Solar‐simulated UVR 24 h before wounding impaired epithelialization but was not detrimental for surgical incisional wound healing.     

Excited Fluorophores Enhance the Opening of Vesicles at Electrode Surfaces in Vesicle Electrochemical Cytometry

Electrochemical cytometry is a method developed recently to determine the content of an individual cell vesicle. The mechanism of vesicle rupture at the electrode surface involves the formation of a pore at the interface between a vesicle and the electrode through electroporation, which leads to the release and oxidation of the vesicle's chemical cargo. We have manipulated the membrane properties using excited fluorophores conjugated to lipids, which appears to make the membrane more susceptible to electroporation. We propose that by having excited fluorophores in close contact with the membrane, membrane lipids (and perhaps proteins) are oxidized upon production of reactive oxygen species, which then leads to changes in membrane properties and the formation of water defects. This is supported by experiments in which the fluorophores were placed on the lipid tail instead of the headgroup, which leads to a more rapid onset of vesicle opening. Additionally, application of DMSO to the vesicles, which increases the membrane area per lipid, and decreasing the membrane thickness result in the same enhancement in vesicle opening, which confirms the mechanism of vesicle opening with excited fluorophores in the membrane. Light‐induced manipulation of membrane vesicle pore opening might be an attractive means of controlling cell activity and exocytosis. Additionally, our data confirm that in experiments in which cells or vesicle membranes are labeled for fluorescence monitoring, the properties of the excited membrane change substantially.     

Blue shifting hydrogen bonding in the complexes of chlorofluoro haloforms with acetone-d(6) and oxirane-d(4)

Mixtures of haloforms of the type HCClnF3-n (n = 0-3) with oxirane-d4 and acetone-d6 have been studied in liquid krypton, using infrared spectroscopy. Analysis of the spectra shows that a small fraction of the monomers is transformed into 1:1 complexes in which the haloform C-H bond is hydrogen bonded to the oxygen atom of the base. For all complexes, the haloform CH stretch is blue shifted, with the shift increasing from chloroform to fluoroform, while the ratio of the infrared intensities of the C-H stretching bands of complexed and free C-H bonds changes from a value well over 50 for the chloroform to a value near 0.1 for the fluoroform complexes. These observations have been corroborated by ab initio calculations using CP-corrected gradient techniques.     

Multi-residue liquid chromatography/tandem mass spectrometric analysis of beta-agonists in urine using molecular imprinted polymers

Ion suppression, a matrix effect that affects quantitative mass spectrometry, is one of the main problems encountered in liquid chromatography/tandem mass spectrometry. Two different clean-up steps for the multi-residue analysis of beta-agonists in urine were evaluated with respect to minimisation of ion suppression, namely, a mixed-phase solid phase extraction (SPE) column, i.e., clean screen Dau (CSD), and a molecular imprinted polymer (MIP) SPE column. Ion suppression experiments revealed that CSD sample clean-up can lead to false negative results for some beta-agonists, and that clean-up using MIP columns is more selective for beta-agonists than the use of CSD columns.     

LC-MS/MS in the elucidation of an isomer of the recreational drug methylenedioxy ethylamphetamine: methylenedioxy dimethylamphetamine

This paper describes the surplus value of a quadrupole-orthogonal acceleration TOF mass spectrometer, coupled to a liquid chromatographic separation system, for the unequivocal identification and structural elucidation of an unknown compound in the field of designer drugs. In a patient sample set (blood, tissues, vitreous humor, etc.), analyzed with a dedicated liquid chromatographic-fluorescence detection method for the determination of methylenedioxy amphetamine, methylenedioxy methamphetamine, and methylenedioxy ethylamphetamine (MDEA), a "strange" inexplicable peak appeared at a retention time not corresponding to any of our reference materials. Based on the identical excitation and emission wavelengths in detection, and a retention behavior comparable to MDEA, it was assumed that this unknown compound was an isomer of the recreational drug MDEA. With a simple and straightforward methodological crossover between LC fluorescence detection and LC-MS/MS, additional information for structural elucidation was easily obtained. Chromatographic separation was achieved on a Hypersil BDS C18 column (fluorescence detection part) and on a Hypersil BDS phenyl column (mass spectrometric detection part). MS showed that the unknown compound's molecular mass was identical to that of MDEA, and, in addition, its fragmentation pattern too proved quite similar to that of MDEA. A thorough literature overview and study of the fragmentation pattern by means of the MS/MS spectrum led to an evidence-based hypothesis of 3,4-methylenedioxy N,N-dimethylamphetamine (MDDM) being the unknown compound. To confirm this hypothesis, MDDM was synthesized and its presence in our biological sample was finally demonstrated by co-injection with alternatively synthesized MDDM and MDEA. This application shows the synergism between LC and MS in the elucidation of unknown compounds, nevertheless emphasizing the essence of chromatographic separation when dealing with isomers.