Power Switching in Hybrid Coherent Couplers

We report on a theoretical and numerical investigation of the switching of power in new hybrid models of nonlinear coherent couplers consisting of optical slab waveguides with various orders of nonlinearity. The first model consists of two guides with second-order instead of the usual third-order susceptibilities as typified by the Jensen coupler. This second-order system is shown to have a power self-trapping transition at a critical power greater than the third-order susceptibility coupler. Next, we consider a mixed coupler composed of a second-order guide coupled to a third-order guide and show that, although it does not display a rigorous self-trapping transition, for a particular choice of parameters it does show a fairly abrupt trapping of power at a lower power than in the third-order coupler. By coupling this mixed nonlinear pair to a third, purely linear guide, the power trapping can be brought to even lower levels and in this way a satisfactory switching profile can be achieved at less than one sixth the input power needed in the Jensen coupler.Comment: Latex source,17 pages, 5 figure

The molecular aspects of biological development

Conference on molecular aspects of biological developmen

The A+B -> 0 annihilation reaction in a quenched random velocity field

Using field-theoretic renormalization group methods the long-time behaviour of the A+B -> 0 annihilation reaction with equal initial densities n_A(0) = n_B(0) = n_0 in a quenched random velocity field is studied. At every point (x, y) of a d-dimensional system the velocity v is parallel or antiparallel to the x-axis and depends on the coordinates perpendicular to the flow. Assuming that v(y) have zero mean and short-range correlations in the y-direction we show that the densities decay asymptotically as n(t) ~ A n_0^(1/2) t^(-(d+3)/8) for d<3. The universal amplitude A is calculated at first order in \epsilon = 3-d.Comment: 19 pages, LaTeX using IOP-macros, 5 eps-figures. It is shown that the amplitude of the density is universal, i.e. independent of the reaction rat

Methodology comparison for canopy structure parameters extraction from digital hemispherical photography in boreal forests

The retrieval of canopy architectural parameters using off-the-shelf digital cameras with fish-eye lens is investigated. The technique used takes advantage of the sensor’s linear response to light of these cameras to improve the estimation of gap fraction using: (1) the digital numbers of mixed sky-canopy pixels to estimate the within-pixel gap fraction; and (2) this process is done considering the variation in view zenith angle to take into account the sky radiance distribution and the canopy multiple scattering effects. The foliage element clumping index is retrieved over a wide range of view zenith angles using: (1) the accumulated gap size distribution theory developed for the TRAC by Chen and Cihlar (1995a); (2) the Lang and Xiang (1986) finite-length averaging method; and (3) a method combining the gap size distribution and the Lang and Xiang finite-length methods. Using data from Canadian and Russian boreal forests, comparisons of gap fraction, clumping index and plant area index measured with the tracing radiation and architecture of canopies (TRAC) and digital hemispherical photography are presented. Evaluation of the LAI estimated from digital hemispherical photography with allometric LAI of two boreal forest stands suggest that that the clumping index combined method may be more accurate

Extraction, Storage and Eruption of Multiple Isolated Magma Batches in the Paired Mamaku and Ohakuri Eruption, Taupo Volcanic Zone, New Zealand

The Taupo Volcanic Zone (TVZ) is well known for its extraordinary rate of rhyolitic magma generation and caldera-forming eruptions. Less is known about how large volumes of rhyolitic magma are extracted and stored prior to eruption, and the role tectonics might play in the process of melt extraction and control of caldera eruption(s). Here we present a new model for the extraction, storage and simultaneous eruption of the >245 km3 paired Mamaku and Ohakuri magmas sourced from calderas centred ∼30 km apart (the Rotorua and Ohakuri calderas, respectively) in the central TVZ. The Mamaku and Ohakuri ignimbrites share a similar bulk pumice composition and the same phenocryst assemblage; however, bulk-rock compositions suggest several poorly mixed magma types in each erupted volume, which are randomly distributed throughout the eruptive deposits. To refine models of the pre-eruptive geometry of the magmatic system and discuss a possible origin for triggering of each eruption, we present an expanded database of matrix glass and quartz-hosted melt inclusion compositions along with the existing bulk-rock and mineral compositions. Major and trace element compositions show that the region produced five different magma batches, extracted from the same source region, and a continuous intermediate mush zone beneath the Mamaku-Ohakuri region is suggested here. These magma batches were most probably juxtaposed but isolated from each other in the upper crust, and evolved separately until eruption. The observed geochemical differences between the batches are likely to be generated by different extraction conditions of the rhyolitic melt from a slightly heterogeneous mush. The lack of evidence for more mafic recharge prior to eruption (for example, there are no bright cathodoluminescence rims on quartz crystals) suggests that a magmatic input is unlikely to be an eruption trigger. However, tectonic activity could be an efficient way to trigger the eruption of isolated magma batches, with the evacuation of one magma batch causing a disturbance to the local stress field and activating regionally linked faults, which then lead to the eruption of additional magma batches and associated caldera subsidence. In addition, the extensional tectonic regime coupled with a high heat flux could be the controlling factor in the emplacement of some of the shallowest and most SiO2-rich magmas on Eart

A novel method to detect unlabeled inorganic nanoparticles and submicron particles in tissue by sedimentation field-flow fractionation

A novel methodology to detect unlabeled inorganic nanoparticles was experimentally demonstrated using a mixture of nano-sized (70 nm) and submicron (250 nm) silicon dioxide particles added to mammalian tissue. The size and concentration of environmentally relevant inorganic particles in a tissue sample can be determined by a procedure consisting of matrix digestion, particle recovery by centrifugation, size separation by sedimentation field-flow fractionation (SdFFF), and detection by light scattering

Gaps in the Hepatitis C Continuum of Care among Sex Workers in Vancouver, British Columbia: Implications for Voluntary Hepatitis C Virus Testing, Treatment and Care

BACKGROUND: Hepatitis C virus (HCV) eradication leads to reduced morbidity, mortality and transmission. Despite the disproportionate burden of HCV among sex workers, data regarding the HCV care continuum in this population remain negligible. METHODS: Using baseline data from an ongoing cohort of women sex workers in Vancouver (An Evaluation of Sex Workers’ Health Access, January 2010 to August 2013), the authors assessed HCV prevalence and engagement in the HCV care continuum within the past year. Multivariable logistic regression analyses were used to evaluate associations with recent (ie, in the past year) HCV testing. RESULTS: Among 705 sex workers, 302 (42.8%) were HCV seropositive. Of these, 22.5% were previously unaware of their HCV status, 41.7% had accessed HCV-related care, 13.9% were offered treatment and only 1.0% received treatment. Among 552 HCV-seronegative sex workers, only one-half (52.9%) reported a recent HCV test. In multivariable analysis, women who self-identified as a sexual/gender minority (adjusted OR [aOR] 1.89 [95% CI 1.11 to 3.24]), resided in the inner city drug use epicentre (aOR 3.19 [95%CI 1.78 to 5.73]) and used injection (aOR 2.00 [95% CI 1.19 to 3.34]) or noninjection drugs (aOR 1.95 [95% CI 1.00 to 3.78]) had increased odds of undergoing a recent HCV test, while immigrant participants (aOR 0.24 [95% CI 0.12 to 0.48]) had decreased odds. CONCLUSIONS: Despite a high burden of HCV among sex workers, large gaps in the HCV care continuum remain. Particularly concerning are the low access to HCV testing, with one-fifth of women living with HCV being previously unaware of their status, and the exceptionally low prevalence of HCV treatment. There is a critical need for further research to better understand and address barriers to engage in the HCV continuum for sex workers

A ‘near‐life experience’: lived experiences of spirituality from the perspective of people who have been subject to inpatient psychiatric care

Aims: To describe lived experiences of spirituality from the perspective of people who have been subject to inpatient psychiatric care and to interpret these experiences from an understanding of health as dialectical. Methods: After approval from a regional ethical board,eleven participants were recruited from two organisations for people with mental health problems. Participants were asked to narrate about spiritual experiences and occasions where such experiences had come close. The transcribed interviews were analysed by means of a phenomenological hermeneutical approach. Findings: A structural analysis of the text resulted in three themes; perceiving the presence of something extra mundane, making sense of reality and struggling for acceptance. The comprehensive understanding highlights spiritual experiences as going beyond religion, even though religious experiences appear as part of it. These experiences can indeed be a resource contributing to experiences of hope, connectedness, meaning and coherence in life. However, they can also give rise to doubt, anxiety and feelings of loneliness and hopelessness. Rather than understanding spiritual experiences as being either ‘good’ or ‘bad’, we could approach spirituality as something that is always present in alternate and inter-related forms. Metaphorically, this could be understood as a ‘near-life experience’, summarising participants’experiences related to their struggle with issues related to suffering and health which are simultaneously present. Conclusions: If psychiatric nurses could approach this complexity and, without being judgemental, explore seemingly positive and negative experiences of spirituality as dialectically related to each other, rather than viewing them as either resources or problems, this could contribute to insiderness care and hopefully also support people who struggle with these experiences to seek help when needed