Two-pump parametric amplification in the presence of fiber dispersion fluctuations: a comparative study

Fiber optical parametric amplifiers (FOPAs) operating based on four-wave mixing (FWM) are versatile devices with increasing applications in optical communication systems. In this paper, the effects of dispersion fluctu�ations on the performance of bandwidth, ripple, parametric gain, and saturation power of a two-pump FOPA based on four-wave and six-wave models are studied and compared. Coupled-amplitude equations representing the non-degenerate FWM process in optical fiber are solved numerically to compute the parametric gain over the communication wavelengths. The behaviors of the performance parameters are critically analyzed and compared with different types of fluctuation strengths (or amplitudes) specified by the combinations of correlation length (Lc) and fluctuation amplitude (σ). Based on the results, it was found that the flat gain bandwidth for the four-wave model remains unchanged and is insensitive to the strengths of fluctuations. The gain ripples, however, get higher as the fluctuation strengths increase. On the other hand, the flat gain bandwidths of the six-wave model are hardly identified due to the tremendous and continuous ripples within the pump wavelengths. In addition, the minimum parametric gain values for both four-wave and six-wave models reduce as the fluctuation strengths increase. Also, the lowest value of parametric gain leads to the highest saturation power and vice versa. The dispersion fluctuations affect the FWM process’s efficiency and deteriorate the overall amplifier performance, particularly for the six-wave model. The numerical analysis obtained via the six-wave model is especially useful since this model closely matches with practical circumstances

A consumer ethnocentrism model of foreign grocery retail store patronage in Beijing : do extrinsic cues and shopping orientation matter?

The most widely used marketing concept to explain consumers' reluctance to patronise foreign retail stores and to purchase imported products is consumer ethnocentrism (CET). To date, however, research has mostly concentrated on the antecedents and consequences of CET, whilst little is known about variables that may offset the impact of CET. This study represents the first step in addressing this gap by examining shopping orientation, specifically utilitarian value, as a moderator of the relationship between CET and the consumers' willingness to shop in foreign grocery retail stores (WTS). Other important research gaps addressed in this study are context specific (i.e., consumers and grocery retailers in China), which includes an investigation of the impact of country-of-origin cue, store brand cue, CET and shopping orientation on WTS, the causal relationships between CET, WTS and customer loyalty (i.e., attitudinal and behavioural loyalty) as well as between shopping orientation and customer loyalty, and the robustness of the CETSCALE (i.e., CET measurement instrument) in relation to socially desirable response bias. Building on an extensive literature review, a consumer ethnocentrism model of foreign grocery retail store patronage was conceptualised and examined for its theoretical applicability in Beijing via an initial qualitative study. The conclusive quantitative phase was store-intercept surveys conducted in four Beijing hypermarkets owned by two established domestic and foreign grocery retailers in China; this achieved a total sample of 500 questionnaires. Rigorous statistical assessment of the collected questionnaires was undertaken, where the raw data was verified for data entry accuracy, missing values in the raw datasets were resolved via the multiple imputation method, and the multiple imputed datasets were assessed for outliers and non-normality. The conceptual model was then tested using Structural Equation Modelling (SEM). Based on conventional SEM procedures, the main results revealed that utilitarian value was a significant moderator of the relationship between CET and WTS, whilst the country-of- origin cue and store brand cue returned non-significant effects. In addition, store origin was a significant moderator of the relationship between WTS and loyalty intention towards foreign grocery retailers, i. e., this relationship was positively related for Beijing consumers who shop in foreign grocery stores but non-significant for those who shop in domestic grocery stores. The findings, theoretical and managerial implications, limitations and directions for future research are discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Simulation of Internal Undular Bores Propagating over a Slowly Varying Region

Internal undular bores have been observed in many parts of the world. Studies have shown that many marine structures face danger and risk of destruction caused by internal undular bores due to the amount of energy it carries. This paper looks at the transformation of internal undular bore in two-layer fluid flow under the influence of variable topography. Thus, the surface of the bottom is considered to be slowly varying. The appropriate mathematical model is the variable-coefficient extended Korteweg-de Vries equation. We are particularly interested in looking at the transformation of KdV-type and table-top undular bore over the variable topography region. The governing equation is solved numerically using the method of lines, where the spatial derivatives are first discretised using finite difference approximation so that the partial differential equation becomes a system of ordinary differential equations which is then solved by 4th order Runge-Kutta method. Our numerical results show that the evolution of internal undular bore over different types of varying depths regions leads to a number of adiabatic and non-adiabatic effects. When the depth decreases slowly, a solitary wavetrain is observed at the front of the transformed internal undular bore. On the other hand, when the depth increases slowly, we observe the generation of step-like wave and weakly nonlinear trailing wavetrain, the occurrence of multi-phase behaviour, the generation of transformed undular bore of negative polarity and diminishing transformed undular bore depending on the nature of the topography after the variable topography

Instantons of M(atrix) Theory in PP-Wave Background

M(atrix) theory in PP-wave background possesses a discrete set of classical vacua, all of which preserves 16 supersymmetry and interpretable as collection of giant gravitons. We find Euclidean instanton solutions that interpolate between them, and analyze their properties. Supersymmetry prevents direct mixing between different vacua but still allows effect of instanton to show up in higher order effective interactions, such as analog of v^4 interaction of flat space effective theory. An explicit construction of zero modes is performed, and Goldstone zero modes, bosonic and fermionic, are identified. We further generalize this to massive M(atrix) theory that includes fundamental hypermultiplets, corresponding to insertion of longitudinal fivebranes in the background. After a brief comparison to their counterpart in AdS\times S, we close with a summary.Comment: 25 pages, LaTeX, references added, section 5 update

Mechanical And Thermal Properties Of Hydroxyapatite Filled Poly(Methyl Methacrylate) Composites.

Poly(methyl methacrylate) (PMMA) filled with hydroxyapatite (HA) filler has been widely used in biomaterial application. Acrylic denture base material was prepared from PMMA filled with HA

Functional conservation of a forebrain enhancer from the elephant shark (Callorhinchus milii) in zebrafish and mice

Background: The phylogenetic position of the elephant shark (Callorhinchus milii ) is particularly relevant to study the evolution of genes and gene regulation in vertebrates. Here we examine the evolution of Dlx homeobox gene regulation during vertebrate embryonic development with a particular focus on the forebrain. We first identified the elephant shark sequence orthologous to the URE2 cis -regulatory element of the mouse Dlx1/Dlx2 locus (herein named CmURE2). We then conducted a comparative study of the sequence and enhancer activity of CmURE2 with that of orthologous regulatory sequences from zebrafish and mouse. Results: The CmURE2 sequence shows a high percentage of identity with its mouse and zebrafish counterparts but is overall more similar to mouse URE2 (MmURE2) than to zebrafish URE2 (DrURE2). In transgenic zebrafish and mouse embryos, CmURE2 displayed enhancer activity in the forebrain that overlapped with that of DrURE2 and MmURE2. However, we detected notable differences in the activity of the three sequences in the diencephalon. Outside of the forebrain, CmURE2 shows enhancer activity in areas such as the pharyngeal arches and dorsal root ganglia where its' counterparts are also active. Conclusions: Our transgenic assays show that part of the URE2 enhancer activity is conserved throughout jawed vertebrates but also that new characteristics have evolved in the different groups. Our study demonstrates that the elephant shark is a useful outgroup to study the evolution of regulatory mechanisms in vertebrates and to address how changes in the sequence of cis -regulatory elements translate into changes in their regulatory activity

Genetics of diabetic kidney disease: A follow-up study in the Arab population of the United Arab Emirates

Background: Two genome-wide association studies in European and Japanese populations reported on new loci for diabetic kidney disease (DKD), including FTO. In this study, we have replicated these investigations on a cohort of 410 Type 2 diabetes mellitus (T2DM) patients of Arab origin from the United Arab Emirates (UAE). Methods and Results: The cohort included 145 diabetic patients diagnosed with DKD and 265 diabetics free of the disease. In general, we were able to confirm the association between the FTO locus and DKD, as reported in the Japanese population. Specifically, there were significant associations with two single nucleotide polymorphisms (SNPs), namely rs1421086 (p =.013, OR = 1.52 depending on allele G, 95% CI: 1.09–2.11) and rs17817449 (p =.0088, OR = 1.55 depending on allele C, 95% CI: 1.12–2.14) of the FTO locus. Both SNPs were in linkage disequilibrium with rs56094641, also as reported in the Japanese population. While the alleles of both SNPs, which increase the risk of DKD, were associated with higher Body Mass Index (BMI), their associations with DKD were independent of the BMI effects. Conclusions: This study confirms that FTO is a multiethnic locus for DKD which is independent from any influence of BMI and/or obesity

Clinical and genetic associations of renal function and diabetic kidney disease in the United Arab Emirates: A cross-sectional study

OBJECTIVES: Within the Emirati population, risk factors and genetic predisposition to diabetic kidney disease (DKD) have not yet been investigated. The aim of this research was to determine potential clinical, laboratory and reported genetic loci as risk factors for DKD. RESEARCH DESIGN AND METHODS: Four hundred and ninety unrelated Emirati nationals with type 2 diabetes mellitus (T2DM) were recruited with and without DKD, and clinical and laboratory data were obtained. Following adjustments for possible confounders, a logistic regression model was developed to test the associations of 63 single nucleotide polymorphisms (SNPs) in 43 genetic loci with DKD (145 patients with DKD and 265 without DKD). Linear regression models, adjusted for age and gender, were then used to study the genetic associations of five renal function traits, including 83 SNPs with albumin-to-creatinine ratio, 92 SNPs with vitamin D (25-OH cholecalciferol), 288 SNPs with estimated glomerular filtration rate (eGFR), 363 SNPs with serum creatinine and 73 SNPs with blood urea. RESULTS: Patients with DKD, as compared with those without the disease, were mostly men (52%vs38% for controls), older (67vs59 years) and had significant rates of hypertension and dyslipidaemia. Furthermore, patients with DKD had T2DM for a longer duration of time (16vs10 years), which in an additive manner was the single factor that significantly contributed to the development of DKD (p=0.02, OR=3.12, 95% CI 1.21 to 8.02). Among the replicated associations of the genetic loci with different renal function traits, the most notable included CONCLUSIONS: Associations were found between several genetic loci and risk markers for DKD, which may influence kidney function traits and DKD in a population of Arab ancestry