High-Current Field Emission from an Atomic Quantum Wire

Linear chains of carbon atoms have been proposed as the electron emitting structures of open tip carbon nanotubes subject to an electric field. To better understand the implications of the results of Smalley and collaborators, the electromagnetic response of linear carbon chains to both static and dynamics fields have been studied, making use of ab-initio methods. It is found that the associated emission currents, plotted as a function of the bias potential, follow Fowler-Nordheim intensity-voltage curves typical of the field emission of metallic tips. Under standard bias conditions, linear carbon chains of one nanometer of length are expected to deliver currents of the order of one microampere. These systems behave, furthermore, as conducting needles in photoabsorption processes. Linear carbon chains are thus likely to constitute the ultimate atomic-scale realization of metallic wires.Comment: 10 pages, 4 figures, RevTe

Supercontinuum generation from 1.35 to 1.7 mu m by nanosecond pumping near the second zero-dispersion wavelength of a microstructured fiber

International audienceWe experimentally study a new regime for supercontinuum (SC) generation in the nanosecond pulsed regime using a nucrostructured optical fiber with two zero-dispersion wavelengths (ZDWs). Pumping at 1535 nm around the second ZDW yields a nearly flat SC over 1350-1700 nm. The interplay between the effects of modulation instability and stimulated Raman scattering are described through simple phase-matching relations

Influence of Age on Perception of Midwives and Their Performance in Objective Structured Clincial Examination (Osce) in Nigeria

Objective structured clinical examination (OSCE) is a means of assessing clinical competence based on objective testing through direct observation. OSCE, as a method of evaluation, was introduced in 1990 by the Nursing & Midwifery council of Nigeria (N&MCN). The aim of this quantitative study is to ascertain if age has any influence on midwives’ perception of OSCE and their performance in the examination. Ex-post facto design was adopted for this study. That is because the independent variable was studied in retrospect in order to establish possible relationship with the dependent variables. We were concerned with ascertaining and establishing the status quo and facts at the time of the research and used such facts to analyze data, interpret and extrapolate and also draw inferences. Eight institutions of midwifery education in Akwa Ibom and Cross River states of Nigeria were used for this study. 502 out of 532 midwives who graduated from the institutions between 2004 to 2006 participated in the study. Two validated instruments were used for data collection namely: OSCE stake holder’s questionnaire and achievement test on OSCE. The reliability index for perception stood at (r) 0.60 while the index performance stood at (r) 0.66.Data were analyzed using linear regression analysis and one way analysis of variance. Findings show that older midwives had significant higher perception of OSCE than the younger midwives. Conclusion: age has significant influence on midwives’ perception of OSCE but perception has no influence on their performance in OSCE

Formalism for Multiphoton Plasmon Excitation in Jellium Clusters

We present a new formalism for the description of multiphoton plasmon excitation processes in jellium clusters. By using our method, we demonstrate that, in addition to dipole plasmon excitations, the multipole plasmons (quadrupole, octupole, etc) can be excited in a cluster by multiphoton absorption processes, which results in a significant difference between plasmon resonance profiles in the cross sections for multiphoton as compared to single-photon absorption. We calculate the cross sections for multiphoton absorption and analyse the balance between the surface and volume plasmon contributions to multipole plasmons.Comment: 29 pages, 1 figur

Complete experimental characterization of stimulated Brillouin scattering in photonic crystal fiber

International audienceWe provide a complete experimental characterization of stimulated Brillouin scattering in a 160 m long solid-core photonic crystal fiber, including threshold and spectrum measurements as well as positionresolved mapping of the Brillouin frequency shift. In particular, a three-fold increase of the Brillouin threshold power is observed, in excellent agree-ment with the spectrally-broadened Brillouin gain spectrum. Distributed measurements additionally reveal that the rise of the Brillouin threshold results from the broadband nature of the gain spectrum all along the fiber and is strongly influenced by strain. Our experiments confirm that these unique fibers can be exploited for the passive control or the suppression of Brillouin scattering

Photoionization of the fullerene ion C60+

Photoionization cross section of the fullerene ion C60+ has been calculated within a single-electron approximation and also by using a consistent many-body theory accounting for many-electron correlations.Comment: 8 pages, 3 figure

Effect of COVID-19 lockdown on reproductive activity in Rivers state

Background: Reproductive activity is an important biological process that always take place between married and unmarried couples across the globe. The study was carried out to evaluate the effect of COVID-19 on reproductive activity during and post-lockdown in Rivers state. The aim of the study was to evaluate the effect of COVID-19 on reproductive activity during and post-lockdown in Rivers state.Methods: A well-structured questionnaire containing demographics and effect of COVID-19 on reproductive activity were administered to participants. Each participant had one questionnaire to fill appropriately and independently after instructions were given to them by the researchers.Results: The study revealed that 57.58% (57/99) of the participants were between the ages 16-20, 58.82% (60/102) were single and 99.03% (102/103) of the participants (women) have unprotected sexual intercourse during COVID-19 lockdown. 99.03% (102/103) the participants engaged in unprotected sex because the pharmacist’s stores were closed. The study also shows that 43.69% (103) have the urge for sex due to inactivity and 76.60% (102) of the participants got pregnant and 96.25% (77/80) of the pregnancy were not planned. 51.29% (41/80) of the participants aborted the pregnancy and 92.68% (38/41) 0f the women who got pregnant did not attend antenatal clinic.Conclusions: A total number of 103 respondents participated in the research. 76.6% of the population got pregnant during the lockdown for different reasons and most of the participants were singles and did not plan for the pregnancy.

C60_{60} in intense femtosecond laser pulses: nonlinear dipole response and ionization

We study the interaction of strong femtosecond laser pulses with the C$_{60}$ molecule employing time-dependent density functional theory with the ionic background treated in a jellium approximation. The laser intensities considered are below the threshold of strong fragmentation but too high for perturbative treatments such as linear response. The nonlinear response of the model to excitations by short pulses of frequencies up to 45eV is presented and analyzed with the help of Kohn-Sham orbital resolved dipole spectra. In femtosecond laser pulses of 800nm wavelength ionization is found to occur multiphoton-like rather than via excitation of a ``giant'' resonance.Comment: 14 pages, including 1 table, 5 figure

Application of time-dependent density functional theory to optical activity

As part of a general study of the time-dependent local density approximation (TDLDA), we here report calculations of optical activity of chiral molecules. The theory automatically satisfies sum rules and the Kramers-Kronig relation between circular dichroism and optical rotatory power. We find that the theory describes the measured circular dichroism of the lowest states in methyloxirane with an accuracy of about a factor of two. In the chiral fullerene C_76 the TDLDA provides a consistent description of the optical absorption spectrum, the circular dichroism spectrum, and the optical rotatory power, except for an overall shift of the theoretical spectrum.Comment: 17 pages and 13 PostScript figure