Interface optical phonons in spheroidal dots: Raman selection rules

The contribution of interface phonons to the first order Raman scattering in nanocrystals with non spherical geometry is analyzed. Interface optical phonons in the spheroidal geometry are discussed and the corresponding Frohlich-like electron-phonon interaction is reported in the framework of the dielectric continuum approach. It is shown that the interface phonon modes are strongly dependent on the nanocrystal geometry, particularly on the ellipsoid's semi-axis ratio. The new Raman selection rules have revealed that solely interface phonon modes with even angular momentum are allowed to contribute to the first order phonon-assisted scattering of light. On this basis we are able to give an explanation for the observed low frequency shoulders present in the Raman cross-section of several II-VI semiconductor nanostructures.Comment: 8 pages, 2 figure

Electric field and exciton structure in CdSe nanocrystals

Quantum Stark effect in semiconductor nanocrystals is theoretically investigated, using the effective mass formalism within a $4\times 4$ Baldereschi-Lipari Hamiltonian model for the hole states. General expressions are reported for the hole eigenfunctions at zero electric field. Electron and hole single particle energies as functions of the electric field ($\mathbf{E}_{QD}$) are reported. Stark shift and binding energy of the excitonic levels are obtained by full diagonalization of the correlated electron-hole Hamiltonian in presence of the external field. Particularly, the structure of the lower excitonic states and their symmetry properties in CdSe nanocrystals are studied. It is found that the dependence of the exciton binding energy upon the applied field is strongly reduced for small quantum dot radius. Optical selection rules for absorption and luminescence are obtained. The electric-field induced quenching of the optical spectra as a function of $\mathbf{E}_{QD}$ is studied in terms of the exciton dipole matrix element. It is predicted that photoluminescence spectra present anomalous field dependence of the emission lines. These results agree in magnitude with experimental observation and with the main features of photoluminescence experiments in nanostructures.Comment: 9 pages, 7 figures, 1 tabl

Long-term effects of medical management on growth and weight in individuals with urea cycle disorders

Low protein diet and sodium or glycerol phenylbutyrate, two pillars of recommended long-term therapy of individuals with urea cycle disorders (UCDs), involve the risk of iatrogenic growth failure. Limited evidence-based studies hamper our knowledge on the long-term effects of the proposed medical management in individuals with UCDs. We studied the impact of medical management on growth and weight development in 307 individuals longitudinally followed by the Urea Cycle Disorders Consortium (UCDC) and the European registry and network for Intoxication type Metabolic Diseases (E-IMD). Intrauterine growth of all investigated UCDs and postnatal linear growth of asymptomatic individuals remained unaffected. Symptomatic individuals were at risk of progressive growth retardation independent from the underlying disease and the degree of natural protein restriction. Growth impairment was determined by disease severity and associated with reduced or borderline plasma branched-chain amino acid (BCAA) concentrations. Liver transplantation appeared to have a beneficial effect on growth. Weight development remained unaffected both in asymptomatic and symptomatic individuals. Progressive growth impairment depends on disease severity and plasma BCAA concentrations, but cannot be predicted by the amount of natural protein intake alone. Future clinical trials are necessary to evaluate whether supplementation with BCAAs might improve growth in UCDs

Cinética da secagem de clones de café (Coffea canephora Pierre) em terreiro de chão batido Kinetics of coffee berry clones drying (Coffea canephora Pierre) in ground pavement

Objetivou-se com o presente trabalho estudar a cinética da secagem de quatro clones de café da espécie Coffea canephora submetidos à secagem em terreiro de chão batido, bem como ajustar diferentes modelos matemáticos aos valores experimentais selecionando aquele que melhor representa o fenômeno em estudo. Foram utilizados frutos de café dos clones: Cpafro 194, Cpafro 193, Cpafro 167 e Cpafro180, colhidos com os teores de água iniciais de 1,20; 1,32; 1,51 e 1,46 (decimal base seca (b.s.)), respectivamente. A secagem prosseguiu em terreiro de chão batido até que o produto atingisse o teor de água de 0,137; 0,133; 0,142 e 0,140 (decimal b.s.) respectivamente para os clones Cpafro 194, Cpafro 193, Cpafro 167 e Cpafro 180. Aos dados experimentais foram ajustados dez modelos matemáticos citados na literatura específica e utilizados para representação do processo de secagem de produtos agrícolas. Baseando-se em parâmetros estatísticos, conclui-se que os modelos Verma, Dois Termos e Aproximação da Difusão foram adequados para representação da secagem dos quatro clones de café analisados, e além destes, para o clone Cpafro 167, os modelos Thompson, Page, Newton, Logarítmico, Henderson e Pabis e Exponencial de Dois Termos também se mostraram satisfatórios na descrição do fenômeno; já o tempo necessário para a secagem em terreiro de chão batido dos clones de café Cpafro 194, Cpafro 193, Cpafro 167 e Cpafro 180 foi de 189,5 h.<br>The objective of this work was to study the drying kinetics of four coffee berry clones Coffea canephora species dried in ground pavement and to fit different mathematical models to different experimental data selecting the one that best represents the phenomenon. Have been used coffee berry of clones: Cpafro 194, Cpafro 193, Cpafro 167 and Cpafro 180, harvested at moisture content of 1.20; 1.32; 1.51 e 1.46 (decimal d.b.), respectively. The drying continued in ground pavement until achieved the moisture content of 0.13 (decimal d.b.). Ten mathematical models cited in the literature were fitted to the experimental data in order to represent the drying process. Based on the statistical parameters it can be concluded that the Verma, Dois Termos and Aproximação da Difusão models represent well the drying of four coffee berry clones, and beyond these for the clone Cpafro 167, the Thompson, Page, Newton, Logarítmico, Henderson e Pabis and Exponencial de Dois Termos models also shown in satisfactory description of the phenomenon; the drying time in ground pavement of coffee berry clones Cpafro 194, Cpafro 193, Cpafro 167 and Cpafro 180, until the moisture content of 0.13 (decimal d.b.) was 189.5 hours

Correction to: SERENA: Particle Instrument Suite for Determining the Sun-Mercury Interaction from BepiColombo (Space Science Reviews, (2021), 217, 1, (11), 10.1007/s11214-020-00787-3)

The original online version of this article was revised because a number of authors had the wrong affiliation number next to their names. © 2021, Springer Nature B.V