Advances in small lasers Hill, Martin T; Gather, Malte C
Nature photonics,
12/2014, Letnik:
8, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Small lasers have dimensions or modes sizes close to or smaller than the wavelength of emitted light. In recent years there has been significant progress towards reducing the size and improving the ...characteristics of these devices. This work has been led primarily by the innovative use of new materials and cavity designs. This Review summarizes some of the latest developments, particularly in metallic and plasmonic lasers, improvements in small dielectric lasers, and the emerging area of small bio-compatible or bio-derived lasers. We examine the different approaches employed to reduce size and how they result in significant differences in the final device, particularly between metal- and dielectric-cavity lasers. We also present potential applications for the various forms of small lasers, and indicate where further developments are required.
Abstract
A compact optical switch concept based on moving a negative-index media (NIM) load is extended here to include waveguides carrying transverse magnetic (TM) modes. Many current metamaterial ...NIM implementations work with TM waves. Simulations show that with a current metamaterial NIM implementation switching is possible for TM modes. The simulated switch structure is based on an optical waveguide coupler made by a commercial foundry process. The NIM load is realized above the waveguides in a post foundry micro-electro mechanical systems (MEMS) layer. Metal loads are also shown to be suitable for switching TM modes. However, only NIM loads can in theory permit simultaneous switching of both transverse electric and TM modes.
Progesterone is a steroid hormone traditionally linked with female fertility and pregnancy. In current reproductive medicine, progesterone and its analogues play crucial roles. While the discovery of ...its effects has a long history, over recent decades, various novel actions of this interesting steroid have been documented, of which its neuro- and immunoprotective activities are the most widely discussed. Discoveries of the novel biological activities of progesterone have also driven research and development in the field of progesterone analogues used in human medicine. Progestogen treatment has traditionally and predominately been used in maintaining pregnancy, the prevention of preterm labor, various gynecological pathologies, and in lowering the negative effects of menopause. However, there are also various other medical fields where progesterone and its analogues could find application in the future. The aim of this work is to show the mechanisms of action of progesterone and its metabolites, the physiological and pharmacological actions of progesterone and its synthetic analogues in human medicine, as well as the impacts of its production and use on the environment.
Background: Aquatic ecosystems in South Africa are prone to invasion by several invasive alien aquatic weeds, most notably, Eichhornia crassipes (Mart.) Solms-Laub. (Pontederiaceae) (water hyacinth); ...Pistia stratiotes L. (Araceae) (water lettuce); Salvinia molesta D.S. Mitch. (Salviniaceae) (salvinia); Myriophyllum aquaticum (Vell. Conc.) Verd. (parrot’s feather); and Azolla filiculoides Lam. (Azollaceae) (red water fern).Objective: We review the biological control programme on waterweeds in South Africa.Results: Our review shows significant reductions in the extent of invasions, and a return on biodiversity and socio-economic benefits through the use of this method. These studies provide justification for the control of widespread and emerging freshwater invasive alien aquatic weeds in South Africa.Conclusions: The long-term management of alien aquatic vegetation relies on the correct implementation of biological control for those species already in the country and the prevention of other species entering South Africa.
Metal–insulator–metal (MIM) waveguides are demonstrated which have electrically pumped semiconductor gain medium at their core. In particular electrical contacts are made well away from the optical ...mode and carriers are transported to the gain medium via semiconductor pathways a few tens of nanometers thick. Wet chemical etching is employed to form the gain medium cores, which can have widths on the order of 150 nanometers (nm). Total thickness of the layers between the metal sheets in the MIM structure is approximately 260 nm. Spectra obtained from devices with wider core widths operating at low temperatures and wavelengths near 1550 nm are examined. The nanowire like gain medium cores have an approximately rectangular cross section. Key process steps to form these waveguide structures with their electrically pumped cores are also described.
Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect ...herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score, full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In the European energy market, the community energy sector is earmarked to make a significant contribution to the transition from fossil fuels to sustainable sources. Based on the diffusion of ...innovation model, large-scale development of community energy requires that the concept and the success of existing energy communities be widely communicated to potential participants and that user confidence be developed over time. In this paper, we present the architecture, design, prototyping, and testing of a digital support platform, co-designed with EU-wide energy communities, to support this process. The platform has been designed to engage early-stage or ongoing groups to progress projects and to connect and share experiences with other communities. This “community of communities” creates the necessary communication channel defined in the Diffusion of Innovation model. A transactional architecture for such a platform is outlined with clear links to all community energy actors. Based on this architecture, a prototype one-stop-shop (OSS) implementation is presented. Feedback gathered and lessons learned from beta testing with a representative group of end-users are outlined. The OSS architecture shows potential as a communications channel to expand the community energy concept and as a monitoring tool to track the progress of the energy community sector.
The aim of this study was to test the effect of a plant-based dietary intervention on beta-cell function in overweight adults with no history of diabetes. Participants (
= 75) were randomized to ...follow a low-fat plant-based diet (
= 38) or to make no diet changes (
= 37) for 16 weeks. At baseline and 16 weeks, beta-cell function was quantified with a mathematical model. Using a standard meal test, insulin secretory rate was calculated by C-peptide deconvolution. The Homeostasis Model Assessment (HOMA-IR) index was used to assess insulin resistance while fasting. A marked increase in meal-stimulated insulin secretion was observed in the intervention group compared with controls (interaction between group and time, Gxt,
< 0.001). HOMA-IR index fell significantly (
< 0.001) in the intervention group (treatment effect -1.0 (95% CI, -1.2 to -0.8); Gxt,
= 0.004). Changes in HOMA-IR correlated positively with changes in body mass index (BMI) and visceral fat volume (
= 0.34;
= 0.009 and
= 0.42;
= 0.001, respectively). The latter remained significant after adjustment for changes in BMI (
= 0.41;
= 0.002). Changes in glucose-induced insulin secretion correlated negatively with BMI changes (
= -0.25;
= 0.04), but not with changes in visceral fat. Beta-cell function and insulin sensitivity were significantly improved through a low-fat plant-based diet in overweight adults.
Vitamin D is no longer considered an agent only affecting calcium phosphate metabolism. A number of studies over the past few years have demonstrated its role in immunomodulation and its influence on ...the development and functioning of the brain and nervous system. In the current epidemiological crisis caused by coronavirus disease 2019 (COVID-19), the immunoprotective role of vitamin D has been discussed by some authors regarding whether it contributes to protection against this serious disease or whether its use does not play a role. Non-standard approaches taken by laboratories in examining the serum levels of the vitamin D metabolite calcidiol have contributed to inconsistent results. We examined the serum of 60 volunteers in the spring and autumn of 2021 who declared whether they were taking vitamin D at the time of sampling. Furthermore, the tested participants noted whether they had experienced COVID-19. A newly developed liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was used to measure calcidiol levels. The analysis of variance (ANOVA) model of Statgraphics Centurion 18 statistical software from Statgraphics Technologies was used for calculations. The results of this study showed that those who took vitamin D suffered significantly less often from COVID-19 than those who did not take vitamin D.
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