Analysis of optical properties of strained semiconductor quantum dots for electromagnetically induced transparency

Using multiband k*p theory we study the size and geometry dependence on the slow light properties of conical semiconductor quantum dots. We find the V-type scheme for electromagnetically induced transparency (EIT) to be most favorable, and identify an optimal height and size for efficient EIT operation. In case of the ladder scheme, the existence of additional dipole allowed intraband transitions along with an almost equidistant energy level spacing adds additional decay pathways, which significantly impairs the EIT effect. We further study the influence of strain and band mixing comparing four different k*p band structure models. In addition to the separation of the heavy and light holes due to the biaxial strain component, we observe a general reduction in the transition strengths due to energy crossings in the valence bands caused by strain and band mixing effects. We furthermore find a non-trivial quantum dot size dependence of the dipole moments directly related to the biaxial strain component. Due to the separation of the heavy and light holes the optical transition strengths between the lower conduction and upper most valence-band states computed using one-band model and eight-band model show general qualitative agreement, with exceptions relevant for EIT operation.Comment: 9 pages, 12 figure

Temperature dependence of acoustic vibrations of CdSe and CdSe–CdS core–shell nanocrystals measured by low-frequency Raman spectroscopy

We measure the temperature dependence of breathing-mode acoustic vibrations of semiconductor nanocrystals using low-frequency Raman spectroscopy. In CdSe core-only nanocrystals, the lowest-energy l = 0 mode red-shifts with increasing temperature by ∼5% between 77–300 K. Changes to the interatomic bond distances in the inorganic crystal lattice, with corresponding changes to the bulk modulus and density of the material, contribute to the observed energy shift but do not fully explain its magnitude across all nanocrystal sizes. Invariance of the Raman linewidth over the same temperature range suggests that the acoustic breathing mode is inhomogeneously broadened. The acoustic phonons of CdSe/CdS core–shell composite nanocrystals display similar qualitative behavior. However, for large core–shell nanocrystals, we observe a higher-order Raman peak at approximately twice the energy of the l = 0 mode, which we identify as a higher spherical harmonic—the n = 2, l = 0 eigenmode—rather than a two-phonon scattering event.Eni-MIT Solar Frontiers CenterEni S.p.A

Introduction : The Period Products (Free Provision) (Scotland) Act 2021 in the context of menstrual politics and history

The research for this Special Collection volume was funded by a Royal Society of Edinburgh’s Arts and Humanities Research Network Award (64992).In January 2021, Scotland became the first country in the world to make universal access to free period products a legal right, an initiative which attracted extraordinary international attention. This introduction outlines what is indeed new and ground-breaking about this law from the perspective of the history of menstruation, and what merely continues traditional and widespread conceptions, policies and practices surrounding menstruation. On the basis of an analysis of the parliamentary debates of the Act, we show that it gained broad political support by satisfying a combination of ten different political agendas: (1) promoting gender equality for women, while also (2) acknowledging broader gender diversity; (3) taking practical steps to alleviate one high-profile aspect of poverty at a relatively low overall cost to the state, while also (4) stimulating the production of menstrual products; (5) tackling menstrual stigma; (6) improving access to education; (7) working with grassroots campaigners; (8) improving public health; and (9) accommodating sustainability concerns; as well as (10) the desire to pass world-leading legislation in itself. In each case, we explore the extent to which the political aim is typical of, or departs from, wider trajectories in the history and politics of menstruation, and, where pertinent, trajectories in Scottish political history. The ten agendas in their international context provide kaleidoscopic insight into the current state of menstrual politics and history in Scotland and beyond. This introduction also situates this Special Collection as a whole in relation to the field of Critical Menstruation Studies and provides background information about the legislative process and key terminology in Scottish politics and in the history of menstruation.Publisher PDFPeer reviewe

Effect of Chronic Treatment with Diuretics on Mouse Liver: A Morphological and Microanalytical Investigation

In an attempt to produce an animal model for the disease cystic fibrosis (CF), mice were treated chronically with the diuretics amiloride and furosemide, in order to cause chronic inhibition of transepithelial ion transport. Experiments were carried out on adult mice (2 months treatment); in addition, pregnant mice were treated with diuretics, and tissue from offspring 2 and 7 days post partum was investigated. Since biliary cirrhosis is a common occurrence in CF, hepatocytes in the treated mice were investigated by X-ray microanalysis and by light and electron microscopy. Treatment with amiloride caused a significant decrease in cellular Na concentration in adult animals and in in utero treated mice 2 days after birth. The decrease in Na was parallelled by a decrease in Cl, but K levels were not affected. Furosemide caused a slight increase of cellular Na concentrations, especially in animals aged 7 days. In the adult animals, both amiloride and furosemide caused a significant decrease of the cellular Na and Cl levels. No signs of cirrhosis could be observed. Inconsistent changes in the accumulation of lipid droplets in hepatocytes of adult animals treated with amiloride were observed by electron microscopy. It can be concluded that chronic treatment with diuretics, even though it causes some, possibly pathological, changes of the liver, is only of very limited value for generating an animal model to study liver disease in CF

Modal properties of photonic crystal cavities and applications to lasers

Photonic crystal cavities enable strong light–matter interactions, with numerous applica-tions, such as ultra-small and energy-efficient semiconductor lasers, enhanced nonlinearities and single-photon sources. This paper reviews the properties of the modes of photonic crystal cavities, with a special focus on line-defect cavities. In particular, it is shown how the fundamental resonant mode in line-defect cavities gradually turns from Fabry–Perot-like to distributed-feedback-like with increasing cavity size. This peculiar behavior is directly traced back to the properties of the guided Bloch modes. Photonic crystal cavities based on Fano interference are also covered. This type of cavity is realized through coupling of a line-defect waveguide with an adjacent nanocavity, with applications to Fano lasers and optical switches. Finally, emerging cavities for extreme dielectric confinement are covered. These cavities promise extremely strong light–matter interactions by realizing deep sub-wavelength mode size while keeping a high quality factor

Internett i naturfagundervisningen

Kommentar til artikkelen “Udfordringer og muligheder i netbaseret undervisning”, MONA 2011 (1

Spatial Structure in Length at Age of Cod in the Barents Sea

Cod "Gadus morhua" population in the Barents Sea was found to be spatially structured with regard to length-at-age. Results were based on data collected doing research surveys in the Barents Sea between 1982 and 1997. The identified spatial structure was most pronounced for age groups 2 to 4 years and decreased for the older age groups with higher potential for migration. A positive linear correlation between mean length-at-age and mean geographical temperature was established for age groups 2 to 4 years. This correlation was shown to be strongest when based on mean temperatures during 3-year periods ending with the year of capture. The spatial structure in length-at-age was shown to follow the temperature gradient of the Barents Sea. A large part of the observed area effects could be explained by temperature variation between areas. Evidence is also presented which indicates that the predictability and sensitivity of the dependence of length-at-age on temperature increases under extreme environmental conditions, i.e. in the northern and eastern areas of the Barents Sea