Structural determination of Bi-doped magnetite multifunctional nanoparticles for contrast imaging.

To determine with precision how Bi atoms are distributed in Bi-doped iron oxide nanoparticles their structural characterization has been carried out by X-ray absorption spectroscopy (XAS) recorded at the K edge of Fe and at the L3 edge of Bi. The inorganic nanoparticles are nominally hybrid structures integrating an iron oxide core and a bismuth oxide shell. Fe K-edge XAS indicates the formation of a structurally ordered, non-stoichiometric magnetite (Fe3-δO4) phase for all the nanoparticles. The XAS spectra show that, in the samples synthesized by precipitation in aqueous media and laser pyrolysis, the Bi atoms neither enter into the iron oxide spinel lattice nor form any other mixed Bi-Fe oxides. No modification of the local structure around the Fe atoms induced by the Bi atoms is observed at the Fe K edge. In addition, contrary to expectations, our results indicate that the Bi atoms do not form a well-defined Bi oxide structure. The XAS study at the Bi L3 edge indicates that the environment around Bi atoms is highly disordered and only a first oxygen coordination shell is observed. Indefinite [BiO6-x(OH)x] units (isolated or aggregated forming tiny amorphous clusters) bonded through hydroxyl bridges to the nanoparticle, rather than a well defined Bi2O3 shell, surround the nanoparticle. On the other hand, the XAS study indicates that, in the samples synthesized by thermal decomposition, the Bi atoms are embedded in a longer range ordered structure showing the first and second neighbors.

Interfacial magnetic coupling between Fe nanoparticles in Fe­Ag granular alloys.

The role of the interface in mediating interparticle magnetic interactions has been analysed in Fe50Ag50 and Fe55Ag45 granular thin films deposited by the pulsed laser deposition technique (PLD). These samples are composed of crystalline bcc Fe (2­4 nm) nanoparticles and fcc Ag (10­12 nm) nanoparticles, separated by an amorphous Fe50Ag50 interface, occupying around 20% of the sample volume, as determined by x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS), and high resolution transmission electron microscopy (HRTEM). Interfacial magnetic coupling between Fe nanoparticles is studied by dc magnetization and x-ray magnetic circular dichroism (XMCD) measurements at the Fe K and Ag L2,3 edges. This paper reveals that these thin films present two magnetic transitions, at low and high temperatures, which are strongly related to the magnetic state of the amorphous interface, which acts as a barrier for interparticle magnetic coupling.

Dimensionality-driven metal-insulator transition in spin-orbit-coupled IrO2.

A metal-insulator transition is observed in spin-orbit-coupled IrO2 thin films upon reduction of the film thickness. In the epitaxially grown samples, the critical thickness (t ∼ 1.5-2.2 nm) is found to depend on growth orientation (001), (100) or (110). Interestingly from the applied point of view, the insulating behavior is found even in polycrystalline ultrathin films. By analyzing the experimental electrical response with various theoretical models, we find good fits to the Efros-Shklovskii-VRH and the Arrhenius-type behaviors, which suggests an important role of electron correlations in determining the electrical properties of IrO2. Our magnetic measurements also point to a significant role of magnetic order. Altogether, our results would point to a mixed Slater- and Mott-type of insulator.

The DYX2 locus and neurochemical signaling genes contribute to speech sound disorder and related neurocognitive domains.

A major milestone of child development is the acquisition and use of speech and language. Communication disorders, including speech sound disorder (SSD), can impair a child's academic, social and behavioral development. Speech sound disorder is a complex, polygenic trait with a substantial genetic component. However, specific genes that contribute to SSD remain largely unknown. To identify associated genes, we assessed the association of the DYX2 dyslexia risk locus and markers in neurochemical signaling genes (e.g., nicotinic and dopaminergic) with SSD and related endophenotypes. We first performed separate primary associations in two independent samples - Cleveland SSD (210 affected and 257 unaffected individuals in 127 families) and Denver SSD (113 affected individuals and 106 unaffected individuals in 85 families) - and then combined results by meta-analysis. DYX2 markers, specifically those in the 3' untranslated region of DCDC2 (P = 1.43 × 10(-4) ), showed the strongest associations with phonological awareness. We also observed suggestive associations of dopaminergic-related genes ANKK1 (P = 1.02 × 10(-2) ) and DRD2 (P = 9.22 × 10(-3) ) and nicotinic-related genes CHRNA3 (P = 2.51 × 10(-3) ) and BDNF (P = 8.14 × 10(-3) ) with case-control status and articulation. Our results further implicate variation in putative regulatory regions in the DYX2 locus, particularly in DCDC2, influencing language and cognitive traits. The results also support previous studies implicating variation in dopaminergic and nicotinic neural signaling influencing human communication and cognitive development. Our findings expand the literature showing genetic factors (e.g., DYX2) contributing to multiple related, yet distinct neurocognitive domains (e.g., dyslexia, language impairment, and SSD). How these factors interactively yield different neurocognitive and language-related outcomes remains to be elucidated.

Neurogenesis of the hamster suprachiasmatic nucleus.

Neurogenesis of the hypothalamic suprachiasmatic nucleus (SCN) was described in the Syrian hamster (Mesocricetus auratus) using tritiated [3H]thymidine autoradiography. Pregnant hamsters were given single intraperitoneal injections of [3H]thymidine at different times during prenatal development, and labeled cells were analyzed in the offspring of 4-5 weeks of age. Cells of the hamster SCN became postmitotic (were 'born') over two and a half days from 10.5 to 13.0 days postfertilization (dpf) with a peak around 11.5 dpf, 4 days before birth. Two gradients in SCN neurogenesis were observed. Posterior cells were produced somewhat earlier than anterior cells and ventrolateral cells were produced before dorsomedial cells. An exception to the second gradient was a small population of ventrolateral cells produced near the end of SCN neurogenesis. The pattern of SCN neurogenesis in the hamster was similar to that described in the rat, including a predominant ventrolateral to dorsomedial gradient and the presence of ventral or ventrolateral cells produced relatively late, contrary to the predominant gradient.

A comparison of the cognitive deficits in reading disability and attention-deficit/hyperactivity disorder.

This study used a nonreferred sample of twins to contrast the performance of individuals with reading disability (RD; n = 93), attention-deficit/hyperactivity disorder (ADHD; n = 52), RD and ADHD (n = 48), and neither RD nor ADHD (n = 121) on measures of phoneme awareness (PA) and executive functioning (EF). Exploratory factor analysis of the EF measures yielded underlying factors of working memory, inhibition, and set shifting. Results revealed that ADHD was associated with inhibition deficits, whereas RD was associated with significant deficits on measures of PA and verbal working memory. The RD + ADHD group was most impaired on virtually all measures, providing evidence against the phenocopy hypothesis as an explanation for comorbidity between RD and ADHD.

Competing effects in the magnetic polarization of non-magnetic atoms.

The magnetic polarization of the Lu 5d states through the Ho(1-x)Lu(x)(Fe(1-y)Al(y))(2) series has been studied by means of x-ray magnetic circular dichroism. A combined study of the dichroic signals performed at the Fe K-, Ho L(2)- and Lu L(2,3)-edges gives a complete picture of the polarization scheme at the conduction band. The results show that in the presence of competing localized magnetic moments, µ(Fe)(3d) and µ(Ho)(4f), the dichroic signal at the Lu site is mainly due to the Fe atoms, the effect of the magnetic rare-earth being negligible. Estimation of the spin and orbital components of the Lu(5d) induced magnetic moment have been obtained by applying the magneto-optical sum rules derived for x-ray magnetic circular dichroism.

Magnetic disorder in diluted FexM100-x granular thin films (M=Au, Ag, Cu; x < 10 at.%).

Nanogranular thin films of Fe7Au93, Fe7Ag93 and Fe9Cu91 have been sputtered onto Si(100) substrates with the aim of studying the magnetic interactions. X-ray diffraction shows a major noble metal matrix with broad peaks stemming from (111) textured fcc-Au, Ag and Cu. The noble metal forms a nanogranular environment, as confirmed by transmission electron microscopy, with mean particle sizes below 10 nm. The high magnetoresistance (>6%) reveals the existence of Fe nanoparticles. X-ray absorption near edge spectroscopy confirms the presence of a bcc-Fe atom arrangement and some dissolved Fe atoms in the matrix, and XMCD shows the polarization of Au by the Fe nanoparticles. DC-magnetization displays a field-dependent irreversibility produced by the freezing of magnetic nanoparticles into a superspin-glass state. The hysteresis loops remain unsaturated at 5 K and 45 kOe. The coercivity displays a sharp temperature decrease towards a minimum below 50 K, levelling off at higher values, reaching Hc = 200 Oe at 300 K. Annealing of FeAu results in a double-peak zero field cooled magnetization and a slight decrease of the coercivity. The interpretation of the results supports the presence of Fe nanoparticles embedded in the major noble matrix, with some diluted Fe atoms/clusters.

Antagonism of NMDA receptors as a potential treatment for Down syndrome: a pilot randomized controlled trial.

Down syndrome (DS) is the most common genetic cause of intellectual disability. The N-methyl-D-aspartate (NMDA) receptor uncompetitive antagonist, memantine hydrochloride (memantine), has been shown to improve learning/memory and rescue one form of hippocampus synaptic plasticity dysfunction in the best-studied mouse model of DS available, the Ts65Dn mouse. Given the status of memantine as a treatment for Alzheimer's disease (AD) approved by the Food and Drug Administration, the preclinical evidence of potential efficacy in Ts65Dn mice, and the favorable safety profile of memantine, we designed a study to investigate whether the findings in the mouse model could be translated to individuals with DS. In this pilot, proof-of-principle study we hypothesized that memantine therapy would improve test scores of young adults with DS on measures of episodic and spatial memory, which are generally considered to be hippocampus dependent. Accordingly, in this randomized, double-blind, placebo-controlled trial, we compared the effect of 16-week treatment with either memantine or placebo on cognitive and adaptive functions of 40 young adults with DS using a carefully selected set of neuropsychological outcome measures. Safety and tolerability were also monitored. Although no significant differences were observed between the memantine and placebo groups on the two primary outcome measures, we found a significant improvement in the memantine group in one of the secondary measures associated with the primary hypothesis. Only infrequent and mild adverse events were noted.

The access and processing of familiar idioms by brain-damaged and normally aging adults.

Idiom interpretation tasks are routinely used in the clinical evaluation of adults with brain damage, and idiom processing has received increasing attention in the psycholinguistic literature. Clinical evidence suggests that adults with unilateral right-hemisphere damage (RHD) are insensitive to nonliteral meanings conveyed by idiomatic expressions and other figurative forms. However, this portrayal is derived from their terminal responses to tasks that reflect multiple aspects of mental operations (off-line measures), obscuring the source of poor performance. This study used an on-line word-monitoring task to assess RHD, left-hemisphere-damaged, and normally aging adults' implicit knowledge of familiar idiomatic expressions. Brain-damaged subjects performed similarly to normal controls on this task, even though the clinical subjects fared poorly by comparison on an off-line idiom definition measure. These results suggest that adults with unilateral brain damage can activate and retrieve familiar idiomatic forms, and that their idiom-interpretation deficits most likely reflect impairment at some later stage of information processing. Further, error analysis of idiom-definition performance did not support the customary characterization of RHD adults as excessively literal responders. The paper discusses clinical implications of the nature and use of idiom interpretation tasks.

Chemical defense: bestowal of a nuptial alkaloidal garment by a male moth on its mate.

Males of the moth Cosmosoma myrodora (Arctiidae) acquire pyrrolizidine alkaloid by feeding on the excrescent fluids of certain plants (for instance, Eupatorium capillifolium). They incorporate the alkaloid systemically and as a result are protected against spiders. The males have a pair of abdominal pouches, densely packed with fine cuticular filaments, which in alkaloid-fed males are alkaloid laden. The males discharge the filaments on the female in bursts during courtship, embellishing her with alkaloid as a result. The topical investiture protects the female against spiders. Alkaloid-free filaments, from alkaloid-deprived males, convey no such protection. The males also transmit alkaloid to the female by seminal infusion. The systemic alkaloid thus received, which itself may contribute to the female's defense against spiders, is bestowed in part by the female on the eggs. Although paternal contribution to egg defense had previously been demonstrated for several arctiid moths, protective nuptial festooning of a female by its mate, such as is practiced by C. myrodora, appears to be without parallel among insects.

[Isolation and identification of Vibrio genus microorganisms in the Quibu River]. / Aislamiento e identificación de microorganismos del género Vibrio en las aguas del río Quibú.

The Quibú River sewages were studied during 9 weeks, in order to isolate and characterize Vibrio genus microorganisms. Twenty Moore's hyssops were placed 2 or 3 times a week on the banks of the river, where each of them was kept in a passive capture stay for 24 hours. In all the hyssops placed, Vibrio cholerae non-01 were isolated.

[Aeromonas hydrophila. Infection in Xenopus laevis]. / Aeromonas hydrophila. Infección en Xenopus laevis.

Aeromonas hydrophila caused severe disease in a group of 50 Xenopus leavis three weeks after being transferred from their laboratory conditions. The first clinical signs observed were marked pallor, petechiae, lethargy, anorexia, and edema. The duration of the disease was about 48 days, during which 4 animals acquired the disease and 10 died. The study of the bacteriology of the skin and skeletal muscles showed at necropsy subcutaneous edema, hemorrhage, and ascitis. Aeromonas hydrophila was isolated in 14 of the 50 animals studied.

[CAMP factor for the differentiation among Aeromonas species]. / Factor CAMP para la diferenciación en especies de Aeromonas.

The CAMP factor technique, described by Natale Figura as a presumptive method for the differentiation of the species hydrophila, sobria and caviae, was applied to 80 Aeromonas strains isolated from children under 5 years with acute diarrheic disease. The typical phenomenon was seen in aerobiosis and anaerobiosis conditions in 10 strains, which were classified as Aeromonas hydrophila. In aerobiosis conditions/alone, it was observed in 20 strains, which were identified as Aeromonas sobria. It was not observed in either of the incubation conditions above mentioned in 50 of the remaining strains, which were identified as Aeromonas caviae. The advantages of applying this new technique is emphasized.

[Identification of gram negative, facultative anaerobic, oxidase positive bacilli]. / Identificación de bacilos gramnegativos, anaerobios facultativos, oxidasas positivos.

We identified 100 strains of Gram-negative, oxidase-positive bacilli, facultative anaerobes, isolated from different human pathological products by conventional biochemical methods. From the total number of strains studied, 1 corresponded to genus Vibrio, 66 to genus Aeromonas, and 33 to genus Plesiomonas. It is of the utmost importance to conduct surveillance studies of these microorganisms in order to investigate their circulation in Cuba.

[Septicemia due to Shigella. A case report and review of the literature]. / Septicemia por Shigella. Presentación de un caso y revisión de la literatura.

Knowing that the isolation of Shigella in blood is considered as an unusual medical event, a case of an infant deceased from septicemia by Shigella sonnei is presented here. This is the first case of the kind reported in Pinar del Río province. A review of the literature is included.

[Application of the Moore swab method to the isolation of Aeromonas spp. from residual waters]. / Aplicación del método del hisopo de Moore en el aislamiento de Aeromonas spp. en aguas residuales.

The Moore swab technique was applied in waste water from three different areas of the "Pedro Kouri" Institute of Tropical Medicine, with the view to isolate organisms of the genus Aeromonas. Swabs were placed once a week, in the wards of Medicine, Screening, and Diagnostic Laboratory. Of 13 swabs placed in the Medicine ward, 8 were positive. Of 15 swabs placed in Diagnostic Laboratory, 8 were positive, and of 18 placed in the screening ward, 12 were positive. Of a total 46 swabs, 28 disclosed organisms of the genus Aeromonas.

[The identification of Aeromonas species isolated in Cuba]. / Identificación en especies de Aeromonas aisladas en Cuba.

100 Aeromonas strains, isolated from children under 5 years with acute diarrheal diseases from various health centers of the country, were studied from January to July, 1990. Using the Janda-modified Popoff's and Veron's model, 63% of the strains were identified in species through primary tests, and 100% of the other 37% were identified in Aeromonas sobria, Aeromonas hydrophila, and Aeromonas caviae, using also supplementary tests.

[The infectious etiology of acute diarrheal diseases in the Republic of Cuba, 1991]. / Etiología infecciosa de las enfermedades diarreicas agudas en la República de Cuba, 1991.

This study was carried out in 1991 to learn the behavior of enteropathogenic agents causing acute diarrheal diseases in Cuba. 30 children, admitted in hospitals or seen in outpatient services for acute diarrheal diseases, were selected in each province taking into account that they had not received antibiotic or chemotherapy treatments in the previous 72 hours. Feces samples were taken from all patients for virological, bacteriological, and parasitological studies, and results were sent to the Pedro Kourí Institute of Tropical Medicine. Data were processed in DBASE III. Higher positivity indices were attained in the winter months. The causative agents most frequently found were: rotavirus (8.2%); Entamoeba histolytica (6.1%); and Salmonella (4.2%). Escherichia coli, Campylobacter, Shigella and rotavirus showed higher indices in winter. Shigella flexneri and Shigella sonnei predominated. Salmonella serogroups D, B, and C, and enteropathogenic Escherichia coli 0119 and 026 subsets were the most frequently found.