Scalar time domain modeling and coupling of second harmonic generation process in GaAs discontinuous optical waveguide

We present in this work the scalar potential formulation of second harmonic generation process in chi((2)) nonlinear analysis. This approach is intrinsically well suited to the applications of the concept of circuit analysis and synthesis to nonlinear optical problems, and represents a novel alternative method in the analysis of nonlinear optical waveguide, by providing a good convergent numerical solution. The time domain modeling is applied to nonlinear GaAs asymmetrical waveguide with dielectric discontinuities in the hypothesis of quasi phase matching condition in order to evaluate the efficiency conversion of the second harmonic signal. The accuracy of the modeling is validated by the good agreement with the published experimental results. The effective dielectric constant method allows to extend the analysis also to 3D optical waveguides. (c) 2008 Optical Society of America

Novel Time-Domain Circuit Modelling of χ(2) Nonlinear Process in Periodic Optical Waveguide

In this work we present a new time domain modelling approach of χ (2) nonlinear processes in periodic slab waveguides and cavities. This method exploits the Hertzian Potential Modelling (HPM) to design discontinuous dielectric interfaces. It is based on a circuital approach which considers the time-domain nonlinear wave propagation in transmission lines coupled with voltage and current generators. These generators are placed directly on the interface nodes thus optimizing the numerical error of the temporal second derivatives at the dielectric boundaries, and providing an accurate characterization of the nonlinear processes in integrated optics

Design of nonlinear GaAs/AlGaAs second harmonic converters

Abstract In this work we present the design of a three-dimensional wavelength converter consisting of GaAs/AlGaAs nonlinear ridge waveguide with a quasi-phase-matched grating. A fundamental mode at λ FU = 1.55 μ m , and a copropagating second harmonic mode at λ SH = 0.775 μ m are considered. The second harmonic generation process in the χ ( 2 ) nonlinear waveguides is analysed by analytical and numerical approaches. The numerical approach is performed by the Hertzian potential formulation typically used for the modelling of χ ( 2 ) nonlinear processes. A good agreement between analytical and numerical results is observed

Design and modeling of χ(2) second harmonic amplification in circular photonic crystal

We analyze in this work the second harmonic amplification of χ(2) nonlinear process in membrane type GaAs circular photonic crystal. This unconventional kind of photonic crystal is well suited for the generation of whispering gallery modes due to the circular symmetric periodic pattern. The Gaussian beam of a fundamental pump signal at 1.55 μm defines a whispering gallery mode resonance and generates a second harmonic mode at 0.775 μm in the central missing hole micro-cavity. The periodic pattern and the micro-cavity are tailored and optimized in order to generate a second harmonic conversion efficiency of 50 %. We predict the resonances by an accurate 2D time domain model including χ(2) nonlinearity and also by a 3D Finite Element Method FEM. Moreover, by using a 3D membrane configuration, we predict a quality factor of the second harmonic mode of the order of 35000

A systematic review and meta-analysis of the effects of flavanol-containing tea, cocoa and apple products on body composition and blood lipids: exploring the factors responsible for variability in their efficacy

Several randomized controlled trials (RCTs) and meta-analyses support the benefits of flavanols on cardiometabolic health, but the factors affecting variability in the responses to these compounds have not been properly assessed. The objectives of this meta-analysis were to systematically collect the RCTs-based-evidence of the effects of flavanol-containing tea, cocoa and apple products on selected biomarkers of cardiometabolic risk and to explore the influence of various factors on the variability in the responses to the consumption of these products. A total of 120 RCTs were selected. Despite a high heterogeneity, the intake of the flavanol-containing products was associated using a random model with changes (reported as standardized difference in means (SDM)) in body mass index (−0.15, p < 0.001), waist circumference (−0.29, p < 0.001), total-cholesterol (−0.21, p < 0.001), LDL-cholesterol (−0.23, p < 0.001), and triacylglycerides (−0.11, p = 0.027), and with an increase of HDL-cholesterol (0.15, p = 0.005). Through subgroup analyses, we showed the influence of baseline-BMI, sex, source/form of administration, medication and country of investigation on some of the outcome measures and suggest that flavanols may be more effective in specific subgroups such as those with a BMI ≥ 25.0 kg/m2, non-medicated individuals or by specifically using tea products. This meta-analysis provides the first robust evidence of the effects induced by the consumption of flavanol-containing tea, cocoa and apple products on weight and lipid biomarkers and shows the influence of various factors that can affect their bioefficacy in humans. Of note, some of these effects are quantitatively comparable to those produced by drugs, life-style changes or other natural products. Further, RCTs in well-characterized populations are required to fully comprehend the factors affecting inter-individual responses to flavanol and thereby improve flavanols efficacy in the prevention of cardiometabolic disorders

Energy scaling of the "heartbeat" pulse width of GRS 1915+105, IGR J17091-3624, and MXB 1730-335 from Rossi-XTE observations

We investigate some key aspects of the "heartbeat" variability consisting of series of bursts with a slow rise and a fast decay, thus far detected only in GRS 1915+105, IGR J17091-3624, and MXB 1730-335. A previous analysis based on BeppoSAX data of GRS 1915+105 revealed a hard-X delay (HXD), that is a lag of the burst rise at higher energies with respect to lower ones; this leads to narrower pulse widths, w, at higher energies. We here use some light curves of Rossi-XTE observations of GRS 1915+105 for a deeper analysis of this effect and search for its presence in those extracted from some IGR J17091-3624 and MXB 1730-335 observations performed with the same satellite. Our results show that, at variance with GRS 1915+105, no HXD is evident in the light curves of MXB 1730-335 and only a marginal HXD may be argued for IGR J17091-3624. For GRS 1915+105 we find a decreasing trend of the pulse width with energy following a power law w = A ⋅ E ˆ (-s) with an index s ≈ 0.8. Furthermore, we confirm the increase of the HXD with the recurrence time T_rec of the bursts in each series that was already found in previous works using BeppoSAX data. Based on a spectral analysis of these three sources we conclude that the differences highlighted in the properties of the "heartbeat" variability are probably related to the different accreting compact object and the eventual presence of a corona in these binary interacting systems

Evaluation of Ki-67 expression in feline non-ocular melanocytic tumours

Fifty tumours located in skin (n = 33) and mucosae (n = 17) were included. Forty-eight percent and 95% of amelanotic tumours (n = 21) stained positive for Melan A and S100, respectively. Most achromic tumours were mucosal (P  5, Ki-67 > 20% and lack of treatment administration. On multivariable analysis, only tumour histotype and treatment retained prognostic significance. Conclusions Although the majority of feline NOMs behave aggressively, Ki-67 index, together with other parameters, may contribute to prognostic assessment. Prospective studies on homogeneous populations are warranted to identify reliable threshold values for this marker

Serological markers and risk factors for hepatitis B and C viruses in patients infected with human immunodeficiency virus

Both hepatitis B and hepatitis C viruses (HBV and HCV) infection are common in HIV-infected individuals as a result of shared risk factors for acquisition. A serological study for HBV and HCV was performed in 251 HIV-positive individuals from Medellín, Colombia. A qualitative RT-PCR for HCV was done in 90 patients with CD4+ T-cell count < 150 per mm³. Serological markers for HBV infection were present in 97 (38.6%) patients. Thirty six of them (37.1%) had isolated anti-HBc. A multivariate analysis indicated that the following risk factors were significantly associated with the presence of these markers: age (OR = 1.05, 95% CI: 1.01-1.08), pediculosis pubis (OR = 1.83, 95% CI: 1.01-3.33), men who have sex with men and women (OR = 3.23, 95% CI: 1.46-7.13) and men who have sex only with men (OR = 3.73, 95% CI: 1.58-8.78). The same analysis restricted to women showed syphilis as the only significant risk factor. Thus, HBV infection was considerably associated with high risk sexual behavior. HCV was present in only two (0.8%) of HIV patients. Both of them were positive by RT-PCR and anti-HCV. This low frequency of HIV/HCV coinfection was probably due to the uncommon intravenous drug abuse in this population. The frequent finding of isolated anti-HBc warrants molecular approaches to rule out the presence of cryptic HBV infection.La infección por los virus de la hepatitis B y hepatitis C (VHB y VHC) es frecuente en individuos infectados por el VIH como resultado de compartir factores de riesgo para su contagio. Se realizó un estudio serológico para el VHB y VHC en 251 individuos VIH positivos de la ciudad de Medellín, Colombia. En 90 pacientes con un recuento de linfocitos T < 150 células por mm³ se hizo una PCR-RT cualitativa para el VHC. Se encontraron marcadores serológicos para la infección por el VHB en 97 (38.6%) pacientes. Treinta y seis de 97 (37.1%) tuvieron un anti-HBc aislado. El análisis multivariado indicó que los factores de riesgo significativos asociados a la presencia de estos marcadores fueron: edad (OR = 1.05, 95% IC: 1.01-1.08), pediculosis púbica (OR = 1.83, 95% IC: 1.01-3.33), hombres que tienen sexo con hombres y mujeres (OR = 3.23, 95% IC: 1.46-7.13) y hombres que tienen sexo solo con hombres (OR = 3.73, 95% IC: 1.58-8.78). El mismo análisis restringido a mujeres mostró que la sífilis fue el único factor de riesgo significativo. Por lo tanto, la infección por el VHB fue considerablemente asociada a conductas sexuales de alto riesgo. El VHC se presentó en solo 2 (0.8%) de los pacientes VIH. Ambos pacientes fueron positivos por la PCR-RT y los anti-VHC. La baja frecuencia de la coinfección VIH/VHC fue probablemente debido al bajo uso de drogas intravenosas en esta población. El hallazgo frecuente de anti-HBc como marcador aislado asegura estudios moleculares para descartar la presencia de infección críptica por el VHB

Association between Mediterranean lifestyle and perception of well-being and distress in a sample population of university Italian students. Supplemental material

We investigated the extent to which adherence to the Mediterranean diet (MD) in combination with Mediterranean lifestyle factors influenced students’ perceptions of subjective well-being (SWB) and distress. 939 undergraduates completed a survey to assess sociodemographic and lifestyle characteristics, including adherence to the MD, depression, anxiety, stress, and SWB. Data were analysed with correlation, logistic, and multiple linear regression models. Higher adherence to MD correlated with better SWB. Fruit, red meat, sweet and caffeinated beverages contributed significantly. However, it was the combination of adherence to MD with other factors, including quality of social relationships, income, smoking, sleep, and physical activity that better predicted SWB. Our results confirm the positive influence of MD on SWB. However, they also suggest the need to consider perceptions of well-being by a more holistic approach that considers physical and social factors simultaneously to improve the development of more effective educational and motivational programmesMaterials and Methods: Study Design and Ethics Sample population description Statistical methods Table 1. Participants’ sociodemographic characteristics, lifestyle habits, and health status Table 2. Participants’ dietary preferences and eating habits. Table 3. Distribution of additional food and drink preferences of the students sample population with regards to the MD adherence classification Table 4: Correlations between sociodemographic factors, health status and lifestyle with adherence to MD Table 5. Multiple linear regression model to assess the relationship between stress, anxiety, depression, Mediterranean diet adherence, sociodemographic and lifestyle factors Table 6. Correlations between food choices and SWBPeer reviewe

Assessment of Subjective Well-Being in a Cohort of University Students and Staff Members: Association with Physical Activity and Outdoor Leisure Time during the COVID-19 Pandemic

Time spent outdoors and physical activity (PA) promote mental health. To confirm this relationship in the aftermath of COVID-19 lockdowns, we explored individual levels of anxiety, depression, stress and subjective well-being (SWB) in a cohort of academic students and staff members and tested their association with sport practice, PA at leisure time and time spent outdoors. Our cross-sectional study collected data during the COVID-19 outbreak (April–May 2021) on 939 students and on 238 employees, who completed an online survey on sociodemographic and lifestyle features, depression, anxiety, stress, and SWB. Results showed that the students exhibited higher levels of anxiety, depression, and stress, and lower levels of SWB (p < 0.001 for all domains) compared to the staff members. Correlation analysis confirmed that PA and time spent in nature were associated to high mental health scores among staff and, more consistently, among students. Finally, mediation analyses indicated that the time spent in nature, social relationships, and levels of energy play a mediator role in the relationship between sport practice and SWB. Our evidence reinforces the protective role of time spent in nature in improving mental health, and provides support for policymakers to make appropriate choices for a better management of COVID-19 pandemic consequencesP.P. was funded by Life Quality Research Centre—UIDP/04748/2020, a program financially supported by FCT—Fundação para a Ciência e Tecnolo-gia/Ministério da Educação e Ciência.Peer reviewe