Hydride-Reduced Eu2SrFe2O6: A T-to-T' Conversion Enabling Fe2+ in Square-Planar Coordination.

Low-temperature reaction of A-site-ordered layered perovskite Eu2SrFe2O7 (T structure) with CaH2 induces a shift in the Eu2O2 slabs to form Eu2SrFe2O6 with a T' structure (I4/mmm space group) in which only the Fe cation is reduced. Contrary to the previously reported T' structures with Jahn-Teller-active d9 cations (Cu2+ and Ni+), stabilization of Eu2SrFe2O6 with the Fe2+ (d6) cation reflects the stability of the FeO4 square-planar unit. The stability of T'-type Eu2SrFe2O6 over a T-type polymorph is confirmed by density functional theory calculations, revealing the dz2 occupancy for the T' structure. Eu2SrFe2O6 has a bilayer magnetic framework with an Fe-O-Fe superexchange J∥ and an Fe-Fe direct exchange J⊥ (where J∥ > J⊥), which broadly explains the observed TN of 390-404 K. Interestingly, the magnetic moments of Eu2SrFe2O6 lie in the ab plane, in contrast to the structurally similar Sr3Fe2O4Cl2 having an out-of-plane spin alignment.

Particle size effect on the superconducting properties of YBa2Cu3O7-x particles.

YBCO samples with different microstructures were prepared after the thermal treatment of a precursor previously obtained by autocombustion. A drastic influence of the particle size on the magnetic behavior of the samples was observed. Thus, particles smaller than 110 nm do not exhibit superconducting properties and for those ranging around 200 nm the diamagnetic signal characteristic of the superconductivity at low temperature disappears in a large applied magnetic field. Particles larger than 300 nm do not exhibit the particle size effect. Accompanying such a phenomenon, an increase of the superconducting critical temperature is observed with the augmentation of the particle size, the lowest value being 18 K which corresponds to 110 nm particles.

Food preferences and Hg distribution in Chelonia mydas assessed by stable isotopes.

Mercury (Hg) is a highly toxic pollutant that poses in risk several marine animals, including green turtles (Chelonia mydas). Green turtles are globally endangered sea turtle species that occurs in Brazilian coastal waters as a number of life stage classes (i.e., foraging juveniles and nesting adults). We assessed total Hg concentrations and isotopic signatures ((13)C and (15)N) in muscle, kidney, liver and scute of juvenile green turtles and their food items from two foraging grounds with different urban and industrial development. We found similar food preferences in specimens from both areas but variable Hg levels in tissues reflecting the influence of local Hg backgrounds in food items. Some juvenile green turtles from the highly industrialized foraging ground presented liver Hg levels among the highest ever reported for this species. Our results suggest that juvenile foraging green turtles are exposed to Hg burdens from locally anthropogenic activities in coastal areas.

Core-level photoemission spectra of Mo0.3Cu0.7Sr2ErCu2Oy, a superconducting perovskite derivative. Unconventional structure-property relationships.

Detailed studies of the electronic states for Mo(0.3)Cu(0.7)Sr(2)ErCu(2)Oy samples with different oxygen contents are presented here. The influence of oxygenation on the electronic states for the Mo(0.3)Cu(0.7)Sr(2)ErCu(2)Oy system from the semiconducting to the superconducting state has been investigated by means of X-ray photoelectron spectroscopy (XPS). The XPS studies show that Mo is in a mixed Mo(V) and Mo(VI) oxidation state and Mo(V) is predominant over the Mo(VI) in the as-prepared (AP) sample. Yet annealing under an oxygen atmosphere enhances the Mo(VI) state. At the same time, a reduction in the copper species is observed. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E(S)-E(M)) and a lower intensity ratio (I(S)/I(M)) are found to correlate with higher values of the superconducting transition temperature (T(C)). Analysis of these spectra within the Configuration Interaction (CI) model suggests that higher values of TC are related to lower values of the O 2p-Cu 3d charge transfer energy. The change in the Sr 3d and O 1s core level spectra correlates with the oxygen insertion in the (Mo/Cu)O(1+δ) chain site, after oxygenation. The hole concentration (Ph) in the copper plane has been obtained using the room temperature thermoelectric power (TEP) value; this shows an increasing tendency with increasing T(C), after oxygenation. From these experimental results, one observes that T(C)increases with decreasing charge transfer energy. This is, indeed, opposite to the accepted views and occurs in parallel with the shortening of the apical copper-oxygen distance (Cu(2)-O(2)) and the increasing of the CuO(2) plane buckling angle.

Oxygen-participated electrochemistry of new lithium-rich layered oxides Li3MRuO5 (M = Mn, Fe).

We describe the synthesis, crystal structure and lithium deinsertion-insertion electrochemistry of two new lithium-rich layered oxides, Li3MRuO5 (M = Mn, Fe), related to rock salt based Li2MnO3 and LiCoO2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m) where Li and (Li0.2Mn0.4Ru0.4) layers alternate along the c-axis, while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R3[combining macron]m) structure where Li and (Li0.2Fe0.4Ru0.4) layers are stacked alternately. Magnetic measurements indicate for Li3MnRuO5 the presence of Mn(3+) and low spin configuration for Ru(4+) where the itinerant electrons occupy a π*-band. The onset of a net maximum in the χ vs. T plot at 9.5 K and the negative value of the Weiss constant (θ) of -31.4 K indicate the presence of antiferromagnetic superexchange interactions according to different pathways. Lithium electrochemistry shows a similar behaviour for both oxides and related to the typical behaviour of Li-rich layered oxides where participation of oxide ions in the electrochemical processes is usually found. A long first charge process with capacities of 240 mA h g(-1) (2.3 Li per f.u.) and 144 mA h g(-1) (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. An initial sloping region (OCV to ca. 4.1 V) is followed by a long plateau (ca. 4.3 V). Further discharge-charge cycling points to partial reversibility (ca. 160 mA h g(-1) and 45 mA h g(-1) for Mn and Fe, respectively). Nevertheless, just after a few cycles, cell failure is observed. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn(3+) and Ru(4+) are partially oxidized to Mn(4+) and Ru(5+) in the sloping region at low voltage, while in the long plateau, O(2-) is also oxidized. Oxygen release likely occurs which may be the cause for failure of cells upon cycling. Interestingly, some other Li-rich layered oxides have been reported to cycle acceptably even with the participation of the O(2-) ligand in the reversible redox processes. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O(2-) (plateau) while Fe seems to retain its 3+ state.

Huperzia saururus Lam. Trevis. (Lycopodiaceae) facilitates ejaculation in spinal cord transected male rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Huperzia saururus (Lam.) Trevis. has an extensive ethnopharmacological use, mainly because of its aphrodisiac properties. The species is consumed as decoctions or infusions in traditional medicine. The purpose of the present research was to determine if Huperzia saururus is able to increase sexual potency by evaluating the ejaculatory response, in the presence of a decoction in spinal cord transected male rats. MATERIALS AND METHODS: The fictive ejaculation model to record the rhythmic contractions of the bulbospongiosus muscles that accompany ejaculation as an indicator of ejaculation occurrence was used. Sexually experienced male Wistar rats were used. The activation of the fictive ejaculation by the i.v. administration of a decoction was tested, as well as the effects of the oxytocinergic, cholinergic, adrenergic and nitrergic antagonism upon the pro-ejaculatory activity of Huperzia saururus. RESULTS: Decoction (3µg/animal) was able to activate the fictive ejaculation in spinal male rats, producing a statistically significant diminution on the latency of discharge parameter and a statistically significant augment for the number of discharges. Moreover, when sequential treatments using antagonists plus decoction were administered, the effects produced showed that prazosin prevent the pro-ejaculatory effect of the decoction and that the four antagonists assayed blocked the facilitatory effect of Huperzia saururus since the facilitation in the latency of response was prevented, and the number of discharges was reduced. Together these findings support the notion that the decoction exerts an aphrodisiac effect influencing the ejaculatory potency which is partially mediated by oxytocinergic, cholinergic, adrenergic and nitrergic spinal mechanisms. CONCLUSION: In agreement to the ethnopharmacological uses, Huperzia saururus decoction has aphrodisiac properties by influence on the ejaculatory potency.

Rhythmic motor patterns accompanying ejaculation in spinal cord-transected male rats.

A spinal pattern generator controls the ejaculatory response. Activation of this spinal generator elicits rhythmic motor patterns of the striated musculature that surrounds the genital tract that contributes to the expulsion of seminal secretions. In the present study, we elicited ejaculation in spinal cord-transected male rats by mechanically stimulating the urethra and registered rhythmic motor patterns in the cremasteric, iliopsoas and pubococcygeus muscles. The rhythmic motor activity recorded in these muscles was compared with that elicited in the bulbospongiosus muscles; the results revealed similarities in the motor parameters among all the muscles. Data of this study, showing the occurrence of rhythmic motor behaviour in the cremasteric, iliopsoas and pubococcygeus muscles during ejaculation, suggest that these muscles might be under the control of the spinal generator for ejaculation.

Spin glass to superconducting phase transformation by oxidation of a molybdo-cuprate: Mo0.3Cu0.7Sr2TmCu2Oy.

A detailed study of the structure and properties for the as-prepared and oxygen annealed Mo0.3Cu0.7Sr2TmCu2Oy material is reported. The Cu/Mo cationic distribution is established using a combination of x-ray/neutron powder diffraction refinement. The chemical substitution of the Mo ions for the Cu ions in the CuYSr2Cu2O(7-δ) structure is found to occur in both of the copper sites for the as-prepared sample. Interestingly, no trace of Mo substitution in the copper plane site is found to occur after oxygenation. The as-prepared Mo0.3Cu0.7Sr2TmCu2Oy material is found to be a spin glass (SG) system and explained on the basis of the cluster-by-cluster freezing model. On the other hand, the oxygen annealed material is superconducting (SC) (T(SC,onset) = 31 K). A peak has been observed in the critical current density plot and can be explained on the basis of field induced pins. The influence of oxygen annealing in the structure and properties of this material are presented and discussed. This seems to be the first case of a SG-SC transformation following an oxidation reaction in cuprates.

Driving Curie temperature towards room temperature in the half-metallic ferromagnet K2Cr8O16 by soft redox chemistry.

The half-metallic ferromagnet K(2)Cr(8)O(16) with the hollandite structure has been chemically modified using soft chemistry methods to increase the average oxidation state of chromium. The synthesis of the parent material has been performed under high pressure/high temperature conditions. Following this, different redox reactions have been carried out on K(2)Cr(8)O(16). Oxidation to obtain potassium-de-inserted derivatives, K(2-x)Cr(8)O(16) (0 ≤x≤ 1), has been investigated with electrochemical methods, while the synthesis of sizeable amounts was achieved chemically by using nitrosonium tetrafluoroborate as a highly oxidizing agent. The maximum amount of extracted K ions corresponds to x = 0.8. Upon oxidation the hollandite structure is maintained and the products keep high crystallinity. The de-insertion of potassium changes the Cr(3+)/Cr(4+) ratio, and therefore the magnetic properties. Interestingly, the Curie temperature increases from ca. 175 K to 250 K, getting therefore closer to room temperature.

Accumulation trends of petroleum hydrocarbons in commercial shellfish from the Galician coast (NW Spain) affected by the Prestige oil spill.

Aliphatic and aromatic hydrocarbons were determined in three species of commercial shellfish, namely razor shells (Ensis arcuatus and Ensis siliqua), goose barnacle (Pollicipes cornucopia) and sea urchin (Paracentrotus lividus), living in different habitats and exhibiting different feeding behaviors. The samples were collected monthly, from January 2003 to October 2004, in three stations of the Galicia coast (NW Spain), following the Prestige oil spill, with the aim of assessing their response to the spill and, therefore, their suitability for monitoring purposes. The aliphatic fractions were mostly dominated by biogenic hydrocarbons, reflecting the diet composition of the organisms and their low metabolic capacity. The presence of oil was assessed by the determination of chemical markers. The analysis of the aromatic fractions revealed the occurrence of 3-6 ring parent and alkylated PAHs, consistent with a mixed petrogenic-pyrolytic origin, with the common feature of the predominance of chrysene in all samples collected after the spill. However, the distributions exhibited both temporal and interspecies variations. The PAH concentrations (Sigma13) increased significantly after the spill and decreased 6-7 months later close to background levels for the region. One year after the accident, the median values were: 58 microg/kg for razor shells, 26 microg/kg for barnacles, and 25 microg/kg for sea urchins. The temporal evolution of the PAH concentrations along the survey period was used to estimate loss rates for bioavailable PAHs in barnacles and sea urchins after the spill. Half-life values were in the order of 30 and 60 d, respectively. The results of the study demonstrate that barnacles can be suitable species for oil spill monitoring.

Polycyclic aromatic hydrocarbon composition of sediments in the Ría de Vigo (NW Spain).

Individual parent polycyclic aromatic hydrocarbons (PAHs) were identified and quantified in samples of recent sediments at 32 stations in the Ria de Vigo (NW Spain) and its adjacent shelf by high-performance liquid chromatography and a fluorescence detector. This area suffers the pressure of nearly 500,000 inhabitants and includes a number of important marine organisms. The total concentration for the sum of the 13 PAHs quantified were in the range 28-3203 ng/g. The highest concentrations were found near the city of Vigo, where marinas and dockyards as well as highways with a high traffic flow are established. Low PAH concentrations were determined in the outermost part of the estuary, far from the anthropogenic influence. PAH isomers concentration ratios were assessed, indicating that the main source of these compounds in the whole area is pyrolysis. When compared with the EACs, threshold effect level, and probable effect level values, only the samples from the inner part of the ría can occasionally present adverse biological effects due to the PAH concentrations.

Kinematic assessment of paediatric forefoot varus.

Forefoot varus is a static deformity not easy to assess clinically. If left uncorrected, it is thought to affect both the posture of the patient and the kinematics of their lower limbs, and even the spine. Three-dimensional gait assessment could help to confirm forefoot varus diagnosis and provide objective evidence of the functional adaptive mechanisms postulated in the literature. The recently available Oxford Foot Model was used, simultaneously with a conventional lower limb model, to compare the kinematics of 10 forefoot varus children (aged 8-13) and 11 healthy controls (aged 7-13) during gait. Data acquisition was performed using a six-camera motion capture system, with a total of 27 reflective markers. A patient-by-patient comparison with the controls suggested several compensation patterns, although statistically significant differences were found only for the mean values of hip adduction/abduction during load response and midstance and hip flexion/extension during pre-swing. A multivariate statistical technique was used to determine which of the measured variables better separated both groups. The best discriminant model presented here includes hip adduction/abduction during load response, hindfoot/tibia inversion/eversion during pre-swing, hindfoot/tibia dorsiflexion/plantar flexion during load response and arch height during midstance, providing a rate of correct classification of 81%. The results could not fully confirm the kinematic relationships suggested in the literature. The small degree of forefoot varus deformity present in the patient group could have prevented other variables from becoming discriminant. A larger patient sample would help determine the possible different compensatory patterns to different degrees of forefoot varus.

Fishes of the family Ipnopidae (Teleostei: Aulopiformes) collected on the Brazilian continental slope between 11 degrees and 23 degrees S.

A collection of fishes from the Brazilian continental slope between 11 degrees and 23 degrees S obtained through trawling revealed nine species of Ipnopidae. Bathypterois bigelowi and Bathytyphlops marionae represent first records from the south-western Atlantic Ocean and Bathypterois grallator is reported off Brazil for the first time. Four species have their distribution extended in Brazilian waters: Bathypterois phenax, Bathypterois quadrifilis, Bathypterois viridensis and Ipnops murrayi. An identification key of Ipnopidae species from the south-western Atlantic Ocean is included.

Increasing the structural complexity of chromium(IV) oxides by high-pressure and high-temperature reactions of CrO2.

This work presents an overview of a series of increasingly complex oxides synthesized from CrO 2, under high-pressure and high-temperature conditions, having Cr (4+) in octahedral coordination. Although the emphasis is on the structure and microstructure of the compounds as obtained from X-ray diffraction and transmission electron microscopy and diffraction, attention is also given to their interesting electronic and magnetic properties. The study is complemented with an electron energy loss spectroscopic analysis of the different phases. These are the cubic perovskite SrCrO 3, the orthorhombic perovskite CaCrO 3, the solid solution Sr 1-xCa xCrO 3, the Ruddlesden-Popper-type Sr 3Cr 2O 7, the family CrSr 2RECu 2O 8 (RE = rare earth), a compositionally modulated perovskite "PbCrO 3", and the misfit layer oxide SrO 2[CrO 2] 1.85.

Impact of discards of beam trawl fishing on the nematode community from the Tagus estuary (Portugal).

The impact of dead discards, originating from beam trawl fishing on the nematode community from the Tagus estuary was investigated in terms of vertical distribution of the dominant nematode groups. Sediment cores were collected from a mud-flat from the Tagus estuary. Crangoncrangon (Linnaeus, 1758) carcasses were added to the surface of the cores, simulating the settling of dead discards on the sediment. The vertical distribution of the dominant nematode groups was determined up to 4cm deep at four different moments in time post deposition (0, 2, 4 and 6h) and compared to control cores. The C.crangon addition to the sediment led to the formation of black spots and therefore oxygen depleted areas at the sediment surface. The Chromadora/Ptycholaimellus group, normally dominant at the surface layer, migrated downwards due to their high sensibility to toxic conditions. Sabatieria presented the opposite trend and became the dominant group at the surface layer. Since Sabatieria is tolerant to oxygen stressed conditions and high sulphide concentrations, we suggest that it migrated opportunistically towards an unoccupied niche. Daptonema, Metachromadora and Terschellingia did not show any vertical migration, reflecting their tolerance to anoxic and high sulphidic conditions. Our study showed that an accumulation of dead discards at the sediment surface might therefore alter the nematode community vertical distribution. This effect is apparently closely related to toxic conditions in the sediment, induced by the deposition of C.crangon at the sediment surface. These alterations might be temporal and reflect an adaptation of the nematode community to dynamic intertidal environments.

Ahead of the lanthanide contraction; pressure and ionic size in the synthesis of MSr2RECu2O8 (RE = Rare Earth, M = Ru, Cr, Ir): a Gaussian relation.

We have been working for sometime on the synthesis at high pressure (P < or = 12.5 Gpa) and high temperature (T < or = 1400 K) of new materials of the type MSr2RECu2O8 (RE = Rare Earth), which formally derive from YBCO (i.e., CuBa2YCu2O7) by replacing the [Cu-O4] squares in the basal plane of the structure by [M-O6] octahedra (M = Ru, Cr or Ir). The adequate formation of these cuprates, as majority phases, can only be performed in a particular and relatively narrow window of P and T, outside which they cannot be obtained pure or even obtained at all. These "optimum conditions" bear a remarkable Gaussian correlation with the rare earth ion size, the rare earth cation being at the center of the unit cell in the YBCO setting, and they do not follow the classic lanthanide contraction so often observed in the chemistry of those elements. Instead, interelectronic repulsion seems to play a major role in fixing the synthesis conditions. Moreover, the position of the Gaussian tip in the pressure-ionic radii space is also dependent on the transition metal that sits in the octahedron, in a way that seems related to the thermodynamic stability of their simpler oxides.

Cell proliferation associated with actions of the substance P/NK-1 receptor complex in keratocystic odontogenic tumours.

The expression of substance P (SP) and its NK-1 receptor (NK-1R) in keratocystic odontogenic tumours (KOTs) was studied to determine whether the intrinsic growth potential of these lesions is related to a cell proliferation stimulus mediated by the SP/NK-1R complex. A total of 65 tissue samples of solitary non-recurrent KOTs, solitary recurrent KOTs, KOTs associated with nevoid basal cell carcinoma syndrome (NBCCS) and KOTs with chondroid wall were studied by immunohistochemistry, using anti-SP, anti-NK-1R and anti-Ki-67 monoclonal antibodies. Expression of these markers was analysed in infiltrating lymphocytes, in fibrous capsule, and in membrane, cytoplasm and nucleus of epithelial cells. SP expression in infiltrating lymphocytes was significantly associated with SP in fibrous capsule and epithelial cells. KOTs associated with NBCCS showed a significantly higher SP expression in all tissues and cell compartments compared with other KOT types. Finally, SP expression in epithelial cells was associated with positive Ki-67 expression in dysplastic epithelium. This first published report on SP and NK-1R expressions in KOTs demonstrates that actions of the SP/NK-1R complex may constitute a mechanism to stimulate epithelial cell proliferation in KOT. This pathway may be of special relevance in the multiple KOTs associated with NBCCS.

Bupropion in atopic dermatitis.

Bupropion is an antidepressive drug whose main mechanism of action seems to be the inhibition of noradrenaline and dopamine recapture. We present a clinical case of a 50-year-old person with severe atopic dermatitis (A.D.) and without psychiatric symptoms associated, who was casually treated with bupropion with very good results. The mechanisms of action are not yet known, given the diversity of the implied physiopathology mechanisms: genetic, immunological, inflammatory, etc. The use of bupropion in serious and resistant cases to other treatments could constitute a pertinent therapeutic alternative.

Spatial and temporal trends of petroleum hydrocarbons in wild mussels from the Galician coast (NW Spain) affected by the Prestige oil spill.

Polycyclic aromatic hydrocarbons (PAHs) were determined in tissues of wild mussels (Mytilus galloprovincialis) from the Galicia coast (NW Spain) in order to assess the extent of the environmental impact caused by the Prestige oil spill (November 13, 2002). Three sampling campaigns were carried out in February, June and November 2003 at 24 stations along the Galicia coast, from La Guardia (Pontevedra) to Ribadeo (Lugo). The spatial distribution of PAHs found in the first sampling period, clearly revealed the central area (Costa da Morte) as the most affected by the oil spill. In these stations, concentrations up to 7780 microg/kg dw of the sum of 13 parent PAHs were found 2-3 months after the spill. Molecular parameters within the aliphatic and aromatic fractions confirmed the presence of the Prestige oil in these samples. The levels markedly decreased at most of the stations in the second sampling and recovered to levels found before the spill in November 2003, 1 year after the accident (29-279 microg/kg dw, av. 133+/-83 microg/kg dw). However, a certain increase was observed in some sites which could be related to the remobilization of oil residues from still unclean intertidal spots or sediments due to the winter marine weather conditions.

Characterization of Bordetella bronchiseptica strains using phenotypic and genotypic markers.

Thirty-five strains of Bordetella bronchiseptica, recovered primarily from pigs, rabbits, dogs, cats and humans, were characterized by phenotypic and genotypic markers. Biochemical typing only showed variation in the ability to reduce nitrate to nitrite. OMP profiles from virulent strains showed variations in the region of 85-95kDa, which lead us to describe five OMP-types alpha, beta, gamma, delta and epsilon. Genotypic markers included the presence of IS1001, and polymorphisms in the flagellin gene (flaA) and pertussis toxin (PT) promoter region. The IS1001 was detected in 16 isolates (2 from humans and 10 from pigs) but was absent in rabbit isolates. The restriction profiles of the flaA gene allowed us to differentiate the strains into types A-C. The PT types were characterized by an RFLP assay and could be typed through patterns III-V. There was no apparent association between the flaA or PT types and the origin of the isolates. Eleven groups of isolates were identified on the basis of specific combinations of the analyzed markers. The combination of phenotypic and genotypic tests used could be useful in characterizing isolates and differentiating between certain clonal types of B. bronchiseptica.