210 research outputs found
Analysis of spatial emission structures in vertical-cavity surface-emitting lasers with feedback of a volume Bragg grating
We investigate the spatial and spectral properties of broad-area
vertical-cavity surface-emitting lasers (VCSEL) with frequency-selective
feedback by a volume Bragg grating (VBG). We demonstrate wavelength locking
similar to the case of edge-emitters but the spatial mode selection is
different from the latter. On-axis spatial solitons obtained at threshold give
way to off-axis extended lasing states beyond threshold. The investigations
focus on a self-imaging external cavity. It is analyzed how deviations from the
self-imaging condition affect the pattern formation and a certain robustness of
the phenomena is demonstrated
Frequency and phase locking of laser cavity solitons
Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyse experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators
Live performance, carcass quality, and economic assessment of over 100kg slaughtered pigs
Design, rationale, and analysis plan for the Stand Up for Health trial in contact centres:a stepped wedge feasibility study
Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector
We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope
150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a
complete background model for this isotope, including a measurement of the two-neutrino double-β decay
half-life of T2ν
1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents
the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays
in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay
mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the standard model. The observed lower limit, assuming light
Majorana neutrino exchange mediates the decay, is T0ν
1=2 > 2.0 × 1022 y at the 90% C.L., corresponding to
an upper limit on the effective neutrino mass of hmνi < 1.6–5.3 eV
The role of dietary fibre in pig production, with a particular emphasis on reproduction
Abstract Fibres from a variety of sources are a common constituent of pig feeds. They provide a means to utilise locally-produced plant materials which are often a by-product of the food or drink industry. The value of a high fibre diet in terms of producing satiety has long been recognised. However the addition of fibre can reduce feed intake, which is clearly detrimental during stages of the production cycle when nutrient needs are high, for example in growing piglets and during lactation. More recently, fibre has been found to promote novel benefits to pig production systems, particularly given the reduction in antimicrobial use world-wide, concern for the welfare of animals fed a restricted diet and the need to ensure that such systems are more environmentally friendly. For example, inclusion of dietary fibre can alter the gut microbiota in ways that could reduce the need for antibiotics, while controlled addition of certain fibre types may reduce nitrogen losses into the environment and so reduce the environmental cost of pig production. Of particular potential value is the opportunity to use crude fibre concentrates as ‘functional’ feed additives to improve young pig growth and welfare. Perhaps the greatest opportunity for the use of high fibre diets is to improve the reproductive efficiency of pigs. Increased dietary fibre before mating improves oocyte maturation, prenatal survival and litter size; providing a consumer-acceptable means of increasing the amount of saleable meat produced per sow. The mechanisms responsible for these beneficial effects remain to be elucidated. However, changes in plasma and follicular fluid concentrations of key hormones and metabolites, as well as effects of the hypothalamic satiety centre on gonadotrophin secretion and epigenetic effects are strong candidates
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