Interaction Effects on Number Fluctuations in a Bose-Einstein Condensate of Light

We investigate the effect of interactions on condensate-number fluctuations in Bose-Einstein condensates. For a contact interaction we variationally obtain the equilibrium probability distribution for the number of particles in the condensate. To facilitate comparison with experiment, we also calculate the zero-time delay autocorrelation function $g^{(2)}(0)$ for different strengths of the interaction. Finally, we focus on the case of a condensate of photons and discuss possible mechanisms for the interaction.Comment: 13 pages, version 3, 4 figure

Phase diffusion in a Bose-Einstein condensate of light

We study phase diffusion in a Bose-Einstein condensate of light in a dye-filled optical microcavity, i.e., the spreading of the probability distribution for the condensate phase. To observe this phenomenon, we propose an interference experiment between the condensed photons and an external laser. We determine the average interference patterns, considering quantum and thermal fluctuations as well as dissipative effects due to the dye. Moreover, we show that a representative outcome of individual measurements can be obtained from a stochastic equation for the global phase of the condensate

Theory for Bose-Einstein condensation of light in nano-fabricated semiconductor microcavities

We construct a theory for Bose-Einstein condensation of light in nano-fabricated semiconductor microcavities. We model the semiconductor by one conduction and one valence band which consist of electrons and holes that interact via a Coulomb interaction. Moreover, we incorporate screening effects by using a contact interaction with the scattering length for a Yukawa potential and describe in this manner the crossover from exciton gas to electron-hole plasma as we increase the excitation level of the semiconductor. We then show that the dynamics of the light in the microcavities is damped due to the coupling to the semiconductor. Furthermore, we demonstrate that on the electron-hole plasma side of the crossover, which is relevant for the Bose-Einstein condensation of light, this damping can be described by a single dimensionless damping parameter that depends on the external pumping. Hereafter, we propose to probe the superfluidity of light in these nano-fabricated semiconductor microcavities by making use of the differences in the response in the normal or superfluid phase to a sudden rotation of the trap. In particular, we determine frequencies and damping of the scissors modes that are excited in this manner. Moreover, we show that a distinct signature of the dynamical Casimir effect can be observed in the density-density correlations of the excited light fluid

De problematiek van de kasgrondteelten: Mogelijke oplossingen aangedragen door ondernemers met substraatbedden in het bijzonder

De kasgrond glastuinbouw ziet zich geconfronteerd met stijgende kosten en een afname van de hoeveelheid toegelaten gewasbeschermingsmiddelen. Het middelenpakket tegen schadelijke bodemschimmels en aaltjes wordt mogelijk verkleind (Spruit e.a. 2008). Op dit moment is grondstomen nog een optie, maar door de sterk toenemende energie- en arbeidskosten wordt grondstomen steeds duurder. In voorgaande gesprekken met ondernemers en betrokkenen blijkt dat een teeltsysteem dat relatief goedkoop, en gemakkelijk in de praktijk is in te passen, de voorkeur heeft. Doelstelling van dit project is daarom het in kaart brengen van problemen met mogelijke oplossingen ten aanzien van bodemproblematiek in kasgrondteelten

Soil suppressiveness of Meloidogyne, Verticillium and Pythium in diverse agricultural soils: possible mechanisms, and options for sustainable management

Grond uit veertien verschillende glastuinbedrijven is door middel van biotoetsen getest op ziektewerend vermogen tegen drie belangrijke pathogenen, namelijk Meloidogyne incognita, Pythium aphanidermatum and Verticillium dahliae

A modified passive-dynamic ankle-foot orthosis:can it prevent amputation and arthrodesis in patients with ankle-foot trauma?

Introduction High-energy lower extremity trauma (HELET) may cause severe damage within the foot-ankle complex. Occasionally, arthrodesis or amputation are the only remaining options to increase activity levels. The modified passive dynamic ankle-foot orthosis (PDAFO) may prove to be a nonsurgical alternative. This study evaluated the effect of a modified PDAFO with a 6-week training program on pain and performance in patients after HELET. Materials and methods A retrospective cohort study was conducted on seventeen patients who considered an arthrodesis or an amputation after HELET. In an attempt to avoid surgery, the modified PDAFO with a 6-week training program was provided. Pain scores was measured with the Numeric Rating Scale and administered at the start of testing, immediately after the two performance tests and at the end of the day of testing. Performance was evaluated with the 6-min walk test (6MWT) and the Comprehensive high-level activity mobility predictor (CHAMP). Results A significant pain reduction was achieved after the treatment procedure. At the start of the test days (p = 0.002), after the 6MWT (p = 0.001), after the CHAMP (p < 0.001) and at the end of the day (p < 0.001). In addition, a significant improvement on performance was observed in the 6MWT (p < 0.001) and the CHAMP (p = 0.01). None of the patients considered a surgical intervention anymore. Conclusions Patients after HELET show a decrease in pain and an improvement in performance after a 6-week training program with modified PD-AFO. The results suggest that the modified PDAFO is an effective alternative for a surgical approach

Siren songs or path to salvation? Interpreting the visions of web technology at a UK regional newspaper in crisis, 2006-11

A 5-year case study of an established regional newspaper in Britain investigates journalists about their perceptions of convergence in digital technologies. This research is the first ethnographic longitudinal case study of a UK regional newspaper. Although conforming to some trends observed in the wider field of scholarship, the analysis adds to skepticism about any linear or directional views of innovation and adoption: the Northern Echo newspaper journalists were observed to have revised their opinions of optimum Web practices, and sometimes radically reversed policies. Technology is seen in the period as a fluid, amorphous entity. Central corporate authority appeared to diminish in the period as part of a wider reduction in formalism. Questioning functionalist notions of the market, the study suggests cause and effect models of change are often subverted by contradictory perceptions of particular actions. Meanwhile, during technological evolution, the ‘professional imagination’ can be understood as strongly reflecting the parent print culture and its routines, despite pioneering a new convergence partnership with an independent television company

Handbook for Composting and Compost Use in Organic Horticulture

Compost, as a product of recycling processes, can be a very appropriate input material for organic farming, provided the composting process is well-managed, the input materials are free of contaminants, and the resulting product is applied according to the system’s ecological needs. Compost is a very important input material for organic greenhouse production. Organic greenhouse production may vary in the level of intensity, but it is generally a system with high turnover rates of organic matter, high inputs of both nutrients and energy, and high production levels. Compost is used as an important source of organic matter and nutrients in greenhouse horticulture, and is an important component of growing media for nurseries. Compost plays an important role in building a resilient farming system, by providing both the energy sources and the nutrients to sustain soil biodiversity

Loss of Ep-CAM (CO17-1A) expression predicts survival in patients with gastric cancer

Preoperative staging of gastric cancer is difficult and not optimal. The TNM stage is an important prognostic factor, but it can only be assessed reliably after surgery. Therefore, there is need for additional, reliable prognostic factors that can be determined preoperatively in order to select patients who might benefit from (neo) adjuvant treatment. Expression of immunohistochemical markers was demonstrated to be associated with tumour progression and metastasis. The expression of p53, CD44 (splice variants v5, v6 and v9), E-cadherin, Ep-CAM (CO17-1A antigen) and c-erB2/neu were investigated in tumour tissues of 300 patients from the Dutch Gastric Cancer Trial, investigating the value of extended lymphadenectomy compared to that of limited lymphadenectomy). The expression of tumour markers was analysed with respect to patient survival. Patients without loss of Ep-CAM-expression of tumour cells (19%) had a significantly better 10-year survival (P<0.0001) compared to patients with any loss: 42% (s.e.=7%) vs 22% (s.e.=3%). Patients with CD44v6 (VFF18) expression in more than 25% of the tumour cells (69% of the patients) also had a significantly better survival (P=0.01) compared to patients with expression in less than 25% of the tumour cells: 10 year survival rate of 29% (s.e.=3%) vs 19% (s.e.=4%). The prognostic value of both markers was stronger in stages I and II, and independent of the TNM stage. Ep-CAM and CD44v6-expression provides prognostic information additional to the TNM stage. Loss of Ep-CAM-expression identifies aggressive tumours especially in patients with stage I and II disease. This information may be helpful in selecting patients suitable for surgery or for additional treatment pre- or postoperatively