STM-electroluminescence from clustered C3N4 nanodomains synthesized via green chemistry process.

A Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and synchrotron X-ray diffraction study on clustered C3N4 nanoparticles (nanoflakes) is conducted on green-chemistry synthesized samples obtained from chitosan through high power sonication. Morphological aspects and the electronic characteristics are investigated. The observed bandgap of the nanoflakes reveals the presence of different phases in the material. Combining STM morphology, STS spectra and X-ray diffraction (XRD) results one finds that the most abundant phase is graphitic C3N4. A high density of defects is inferred from the XRD measurements. Additionally, STM-electroluminescence (STMEL) is detected in C3N4 nanoflakes deposited on a gold substrate. The tunneling current creates photons that are three times more energetic than the tunneling electrons of the STM sample. We ponder about the two most probable models to explain the observed photon emission energy: either a nonlinear optical phenomenon or a localized state emission.

Characterization of the Dynamics of Photoluminescence Degradation in Aqueous CdTe/CdS Core-Shell Quantum Dots.

We investigate the effects of the excitation power on the photoluminescence spectra of aqueous CdTe/CdS core-shell quantum dots. We have focused our efforts on nanoparticles that are drop-cast on a silicon nitride substrate and dried out. Under such conditions, the emission intensity of these nanocrystals decreases exponentially and the emission center wavelength shifts with the time under laser excitation, displaying a behavior that depends on the excitation power. In the low-power regime a blueshift occurs, which we attribute to photo-oxidation of the quantum dot core. The blueshift can be suppressed by performing the measurements in a nitrogen atmosphere. Under high-power excitation the nanoparticles thermally expand and aggregate, and a transition to a redshift regime is then observed in the photoluminescence spectra. No spectral changes are observed for nanocrystals dispersed in the solvent. Our results show a procedure that can be used to determine the optimal conditions for the use of a given set of colloidal quantum dots as light emitters for photonic crystal optical cavities.

Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats.

Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)2 quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl2 aerosol (since Cd(2+) was present as impurity), 6h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl2 were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd(2+) ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation.

Status of cis and trans fatty acids in Brazilian adolescent mothers and their newborns.

STUDY OBJECTIVE: The objective was to quantify cis and trans fatty acids in maternal plasma and infant cord plasma from adolescent mothers. DESIGN: From 80 adolescent healthy mothers, we sampled postpartum maternal blood and umbilical cord blood at birth. Trans fatty acids (tFAs), linoleic (18:2), and arachidonic (AA, 20:4) acids of the n-6 family, and α-linolenic (18:3), eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids of the n-3 family were analyzed by gas-liquid chromatography. Results were expressed as a percentage of total fatty acids. RESULTS: Linoleic fatty acid was present in greater proportions in the maternal plasma than in that of the umbilical cord, whereas AA was present in greater proportions in the total lipids of umbilical cord blood. Docosahexaenoic acid was the long-chain polyunsaturated fatty acid of the n-3 family that was predominant in both maternal and umbilical cord plasma. The tFAs in the maternal plasma had a negative correlation with oleic acid and linoleic acid. Linolenic acid had a positive correlation with cephalic perimeter upon birth. A tendency for a negative correlation between trans isomers and gestational age at birth (P = .05) was observed. CONCLUSIONS: Long-chain polyunsaturated fatty acids, which are important to fetal growth and development, were found in greater quantities in the cord blood of newborns of adolescents than in the maternal blood, indicating a priority of transfer of AA and docosahexaenoic fatty acids to the fetus. Despite the lower levels of tFAs found in maternal blood, we verified potential risk for premature birth.

Short term inhalation toxicity of a liquid aerosol of CdS/Cd(OH)2 core shell quantum dots in male Wistar rats.

Colloidal quantum dots (QD) show great promise as fluorescent markers. The QD used in this study were obtained in aqueous medium rather than the widely used colloidal QD. Both methodologies used for the production of QD are associated with the presence of heavy metals such as cadmium (Cd). Here we investigate the short-term inhalation toxicity of water-soluble core-shell CdS/Cd(OH)2 QD. Male Wistar rats were head-nose exposed for 6 h/day on 5 days at the technically maximum concentration (0.52 mg Cd/m³). Histological examination was performed directly after the last exposure. Additional rats were used for Cd organ burden determinations. Clinical parameters in blood, bronchoalveolar lavage fluid and lung tissue were determined 3 days after the last exposure. To analyze the reversibility or progression of effects, the examinations were performed again after a recovery period of 3 weeks. The results of the study indicate that CdS/Cd(OH)2 QD caused local neutrophil inflammation in the lungs that partially regressed after the 3-week recovery period. There was no evidence that QD were translocated to the central nervous system nor that a systemic acute phase response occurred.

Envenomation caused by Latrodectus geometricus in São Paulo state, Brazil: a case report

Widow spiders (Latrodectus spp.), also known as "black widows", have a worldwide distribution and can cause latrodectism. To the best of our knowledge, in Brazil, only one case of Latrodectus geometricus (Koch, 1841) envenomation in a human has been reported. The aim of the present report is to describe a spider bite caused by Latrodectus geometricus in a patient who lives in Paranapanema, São Paulo state, Brazil.(AU)

A crianca hospitalizada: refexoes de equipe. / Hospitalized child: reflexions of the health team

Este trabalho foi escrito a partir das reflexoes de um grupo que se reunia semanalmente para discutir aspectos relativos a internacao de seus pacientes, sendo um primeiro esforco de sistematizacao e supondo dois momentos: o questionamento de aspectos que consideramos muito pregnantes em nossas relacoes com a crianca hospitalizada e seus familiares e o aprofundamento destas questoes a partir de uma compreensao teorica. Procuramos, assim, identificar em aspectos particulares os denominadores comuns do trabalho de uma equipe de saude, detectando vivencias e sentimentos que nao se prenderiam as especificidades desta equipe, mas que seriam quase determinados pelo lidar com a crianca hospitalizada

O impacto emocional da hospitalizacao da crianca. / Emotional impact in child hospitalization

Neste trabalho, refletimos sobre a situacao de hospitalizacao da crianca. Admitimos que esta e uma experiencia estressante, mas que pode ser amenizada pelo favorecimento de certas condicoes, como presenca de familiares, contato com outras criancas, disponibilidade afetiva da equipe, informacao etc. Analisamos problemas como recusa a medicacao ou dificuldade em permitir a realizacao de exames dolorosos e assinalamos a maior sensibilizacao da crianca com doenca cronica ou terminal.Observamos que as criancas costumam expressar suas duvidas e angustias por vias indiretas, ou mesmo por perguntas a alguem da equipe, sendo fundamental estar atento a comunicacao da crianca hospitalizada

A hospitalizacao da crianca: a visao do familiar. / Children hospitalization: the familiar view

Neste trabalho, procuramos pensar a questao da hospitalizacao da crianca pelo lado do familiar, dando especial atencao a maneira como a familia vive este problema.Utilizamos material diretamente expresso pelos familiares ou observacoes realizadas em nosso contato quotidiano, podendo concluir que, em geral, os familiares desejam acompanhar suas criancas, excetuando-se situacoes onde existam graves impedimentos objetivos e (ou) emocionais. Observamos, tambem, que o esclarecimento a familia desempenha importante papel na relacao equipe-familiar, embora, muitas vezes, a familia possa negar uma informacao grave, necessitando de um tempo emocional para elaborar o que foi comunicado. Finalmente, e importante observar que processos emocionais foram desencadeados pela situacao de hospitalizacao, atualizando os antigos conflitos