Comparison of Nonlinear Phase Noise and Intrachannel Four-Wave-Mixing for RZ-DPSK Signals in Dispersive Transmission Systems

Self-phase modulation induced nonlinear phase noise is reduced with the increase of fiber dispersion but intrachannel four-wave-mixing (IFWM) is increased with dispersion. Both degrading DPSK signals, the standard deviation of nonlinear phase noise induced differential phase is about three times that from IFWM even in highly dispersive transmission systems.Comment: 3 pages, 2 figure

The effects of foraging behaviour on food-web structure and dynamics

A food web summarises the foraging relationships among creatures within a community. Therefore, to understand how food-web structural and dynamical properties emerge, it is essential to clarify how foraging behaviour (as the underpinning driver) shapes the properties at the level of the whole food web. In this thesis, we examine the influence of several behavioural aspects of foraging on food webs, as well as the mechanisms that cause these influences. In Chapter 2, by conducting food-web dynamical modelling that is constrained by species’ metabolism (following Metabolic Theory of Ecology, MTE), we bring to light how the foraging strategy and dimensionality interact with food-web structures to determine species coexistence in food webs. In Chapter 3, by further introducing Optimal Foraging Theory (OFT) as a diet choice mechanism, we explore the food-web structural and dynamical consequences when species are able to adjust their diet depending on resource abundances. We show that incorporating OFT indeed significantly affect both the structure and the dynamics of food webs, while the impacts can be varied and dependent on parameters that control the properties of both the community and its species’ behaviour. We then proceed in Chapter 4, by modelling using the same MTEOFT framework, to investigate the emergent food-web structure under conditions where species cannot fully comply with OFT but rather are constrained by the predation risk they undertake. We develop a new model that describes consumers’ diet choice under this predation-risk effect, and find that we can capture better the empirical food-web structure than can the classical OFT model without predation-risk considerations. By showing how foraging strategy and dimensionality, adaptive diet choice, and predation risk-driven response scale up their effect to determine food-web properties, overall, the findings of this thesis shed light on how food-web properties emerge from organismal foraging behaviour. Also, the present thesis lays a firm quantitative foundation for future work in food-web ecology.Open Acces

Simultaneous Amplitude and Phase Measurement for Periodic Optical Signals Using Time-Resolved Optical Filtering

Time-resolved optical filtering (TROF) measures the spectrogram or sonogram by a fast photodiode followed a tunable narrowband optical filter. For periodic signal and to match the sonogram, numerical TROF algorithm is used to find the original complex electric field or equivalently both the amplitude and phase. For phase-modulated optical signals, the TROF algorithm is initiated using the craters and ridges of the sonogram.Comment: 10 pages, 5 figure

On the effect of dispersion on nonlinear phase noise

The variance of nonlinear phase noise is analyzed by including the effect of intrachannel cross-phase modulation (IXPM)-induced nonlinear phase noise. Consistent with Ho and Wang [1] but in contrary to the conclusion of both Kumar [2] and Green et al. [3], the variance of nonlinear phase noise does not decrease much with the increase of chromatic dispersion. The results are consistent with a careful reexamination of both Kumar [2] and Green et al. [3].Comment: 3 pages, 1 figure, submitted to Optics Letter

Mechanistic insights on riverine meta‐ecosystems: Network shape drives spatial biodiversity and trophic structures

Rivers exhibit hierarchical spatial structures of habitat and physical attributes, providing directed pathways for biological population and community dynamics and thus shaping the meta‐ecosystems therein. While the River Continuum Concept has generalized the spatial patterns of abiotic and biotic components along rivers, a mechanistic understanding of how river networks' shape may constrain the attributes of riverine meta‐ecosystems remains lacking. Here, we address this gap with an in silico study. We integrate the Optimal Channel Network concept (and the well‐established scaling of river geomorphological and hydrological attributes) with a meta‐ecosystem model (with trait‐based food‐web dynamics and spatial dynamics of species and inorganic resources) to explore how distinct river network shapes (elongated vs. compact) may drive the spatial patterns of biodiversity and community trophic structure. We analyse metrics of biomass distribution, trophic structure and composition of locally realized food webs and show that elongated and compact networks foster very different upstream‐downstream biological patterns, and even more contrasting patterns are often observed between the long and short paths of elongated networks. Overall, we observe a transition from prevailing detritus‐based to nutrient‐based trophic channels moving downstream, leading to peaks in alpha diversity at intermediate river size, where both channels are more balanced. Higher spatial heterogeneity in community composition and lower biomass levels are observed in elongated than in compact networks, driven by higher variability in nutrient input loads and higher water volumes, respectively. Together, our findings associate river shapes to the emergent riverine meta‐ecosystems properties and help reveal the underpinning physical attributes‐driven mechanisms

The modern Kaoping transient fan offshore SW Taiwan: Morphotectonics and development

Using bathymetry and seismic reflection profiles, this study examined and determined the transient nature of the Kaoping Fan located in the topographically complex slope offshore southwest Taiwan. Kaoping Fan is located west of the lower reach of the Kaoping Canyon at the lower Kaoping Slope, ranging from 2,200 to 3,000 m water depth, and has a relatively small areal extent restricted in the topographic lows confined by structural highs due to mud diapiric uplifting and thrust faulting. Kaoping Fan shows an asymmetrical triangular fan-shaped bathymetric feature elongated in an NW-SE direction but with a strong skew toward the east. The fan deposits consist of three main seismic facies: layered high-amplitude reflections in the upper section and stratified, parallel to sub-parallel low-amplitude reflections with variable continuity and channel fill facies in the lower section. In the absence of ground-truthing from core data, the seismic patterns suggest that the Kaoping Fan recorded the onset of channelized and over-bank deposits in the lower part and layered turbidite facies in the upper part subsequently. The development of the Kaoping Fan can be divided into three stages in terms of canyon activities and fan-feeding processes. Initially, Kaoping Fan was mainly fed by a point sediment source at the apex of the fan. Secondly, Kaoping Fan was maintained as a slope fan, mainly fed laterally by over-spilled sediments from the canyon. Finally, the Kaoping Canyon completely passes through the Kaoping Fan and supplies over-spilled sediments laterally, forming a transient fan with canyon incision and sediment by-passing. The accumulation of sediments and the growth of Kaoping Fan are primarily controlled by inherited complex paleo-topography and the evolution of Kaoping Canyon. The sediment delivery system of Kaoping Fan is characterized by lateral supply of over-spilling sediment flows and sediments bypassing to and beyond the base of slope. The Kaoping Fan together with the ponded Fangliao Fan in the topographically complex Kaoping Slope can be used as a type model for evaluating the topographic effects on the development of submarine fans on complex slopes in general

Coupled biological and hydrological processes shape spatial food-web structures in riverine metacommunities

IntroductionUnderstanding how species are distributed in space and how they interact with each other is central for scientific and conservation purposes. Species' distributions and interactions result from a complex interplay of local trophic dynamics, dispersal processes, resource availability, and abiotic factors governed by the landscape matrix, which also determines the spatial connectivity for organisms' dispersal and resource fluxes. River networks not only exhibit universal spatial structures, but their dendritic landscape structure is tightly linked to species and metacommunity processes therein.MethodsHere, using a mechanistic model of spatially connected food webs integrating both essential biological and hydrological aspects, we investigate how food-web properties vary in space, and how these patterns are influenced by key model parameters. We then contrast our predictions with a suite of null models, where different aspects (such as spatial structure or trophic interactions) of the spatial food-web model are alternatively relaxed.ResultsWe find that species richness is highest in areas where local nutrient load is maximal (lowland headwaters, according to our default assumption). Overall, species richness is positively associated with link density, modularity and omnivory, and negatively related to connectance, nestedness, and niche overlap. However, for metrics such as connectance and omnivory, stochasticity of trophic interactions is a much stronger predictor than spatial variables such as distance to outlet and drainage area. Remarkably, relationships between species richness and food-web metrics do not generally hold in null models, and are hence the outcome of coupled biological and physical (i.e., hydrological) processes characteristic to river networks.DiscussionOur model generates realistic patterns of species richness and food-web properties, shows that no universal food-web patterns emerge as a result of the riverine landscape structure, and paves the way for future applications aimed at disentangling metacommunity dynamics in river networks

Coupled biological and hydrological processes shape spatial food-web structures in riverine metacommunities

IntroductionUnderstanding how species are distributed in space and how they interact with each other is central for scientific and conservation purposes. Species' distributions and interactions result from a complex interplay of local trophic dynamics, dispersal processes, resource availability, and abiotic factors governed by the landscape matrix, which also determines the spatial connectivity for organisms' dispersal and resource fluxes. River networks not only exhibit universal spatial structures, but their dendritic landscape structure is tightly linked to species and metacommunity processes therein.MethodsHere, using a mechanistic model of spatially connected food webs integrating both essential biological and hydrological aspects, we investigate how food-web properties vary in space, and how these patterns are influenced by key model parameters. We then contrast our predictions with a suite of null models, where different aspects (such as spatial structure or trophic interactions) of the spatial food-web model are alternatively relaxed.ResultsWe find that species richness is highest in areas where local nutrient load is maximal (lowland headwaters, according to our default assumption). Overall, species richness is positively associated with link density, modularity and omnivory, and negatively related to connectance, nestedness, and niche overlap. However, for metrics such as connectance and omnivory, stochasticity of trophic interactions is a much stronger predictor than spatial variables such as distance to outlet and drainage area. Remarkably, relationships between species richness and food-web metrics do not generally hold in null models, and are hence the outcome of coupled biological and physical (i.e., hydrological) processes characteristic to river networks.DiscussionOur model generates realistic patterns of species richness and food-web properties, shows that no universal food-web patterns emerge as a result of the riverine landscape structure, and paves the way for future applications aimed at disentangling metacommunity dynamics in river networks

Phase and Amplitude Responses of Narrow-Band Optical Filter Measured by Microwave Network Analyzer

The phase and amplitude responses of a narrow-band optical filter are measured simultaneously using a microwave network analyzer. The measurement is based on an interferometric arrangement to split light into two paths and then combine them. In one of the two paths, a Mach-Zehnder modulator generates two tones without carrier and the narrow-band optical filter just passes through one of the tones. The temperature and environmental variations are removed by separated phase and amplitude averaging. The amplitude and phase responses of the optical filter are measured to the resolution and accuracy of the network analyzer

Overweight and Obesity-related Metabolic Disorders in Hospital Employees

BackgroundObesity is associated with metabolic disorders and cardiovascular diseases. This study investigated the relationship between overweight and obese status and the incidence of type 2 diabetes, hypertension, hyperlipidemia and hyperuricemia.MethodsThis prospective cohort study comprised 1749 hospital employees who received baseline health check-ups in 1993. Data from the 1027 participants (832 women, 195 men; mean age, 36 ± 7 years) who repeated check-ups in 2003 were used in the analysis. Relative risks (RRs) for development of metabolic disorders during follow-up associated with different body mass index (BMI) categories at baseline as defined by Asia-Pacific recommendations and the Department of Health in Taiwan were calculated after adjustment for covariates.ResultsThe prevalence of overweight and obesity at baseline check-up were 17.6% and 14.5%, respectively. Obese subjects with baseline BMI ≥ 25 kg/m2 had a significant multivariate-adjusted RR of 2.7 for hypertension, 14.8 for type 2 diabetes, 3.2 for hypertriglyceridemia, and 2.8 for hyperuricemia, compared to subjects with baseline BMI < 23.0 kg/m2. RR for diabetes was higher in women than in men, but RR for hypertriglyceridemia was higher in men. The risks of hypertension and hyperuricemia significantly increased for subjects with baseline BMI ≥ 23 kg/m2, while RRs for type 2 diabetes increased significantly for baseline BMI ≥ 24 kg/m2 and hypertriglyceridemia increased for baseline BMI ≥ 25 kg/m2. The risks attributable to obesity (baseline BMI ≥ 25 kg/m2) were 23.0% for hypertension, 70.8% for diabetes, 27.9% for hypertriglyceridemia, and 24.1% for hyperuricemia.ConclusionThis study revealed that a high prevalence of overweight and obesity was associated with significantly increased risk of development of type 2 diabetes, hypertension, hypertriglyceridemia and hyperuricemia in hospital employees, suggesting the need for programs to improve weight management