Cryogenic silicon Fabry-Perot resonator with Al0.92Ga0.08As/GaAs mirror coatings

The sensitivity and stability of today's most precise optical interferometers, like gravitational wave detectors and ultra-stable lasers, are fundamentally limited by thermodynamically induced length fluctuations of high-reflectivity mirror coatings. Among them, Brownian thermal noise related to internal friction is the dominant contribution and can be reduced by using coating materials with lower mechanical loss. Owing to their low mechanical losses, AlGaAs/GaAs crystalline mirror coatings are expected to reduce this limit set by conventional dielectric coatings as demonstrated from a room temperature measurement. However, due to the high noise contributions from other resonator constituents in previous study, accurate characterization of the noise of crystalline coatings has yet been possible. In this work, the first detailed study on the spatial and temporal noise properties of crystalline coatings at an unprecedented level of precision is presented. This was achieved by using these novel coatings in a cryogenic silicon Fabry-Perot resonator operating at a temperature of 124 K and at a wavelength of 1.5 µm. To observe the expected low fractional frequency instability of mod σ_y=1x10^-17 imposed significant challenges in suppressing technical noise contributions. With methods and experimental setups described in this work, technical noise contributions were suppressed to a level well below the predicted coating noise. Nevertheless, the measured frequency was significantly higher than the predicted thermal and the total technical noise, which indicates the existence of excess noise in crystalline coatings. To disentangle the different excess noise sources, a sophisticated interrogation scheme, which investigates spatiotemporal correlations between different cavity eigenmodes by stabilizing two independent lasers simultaneously on the resonator, was developed. With this interrogation scheme, noise mechanisms related to the large birefringence mode splitting in these coatings were discovered. Upon a step change of optical power, anticorrelated frequency transient responses between the two birefringence-induced polarization eigenmodes of the silicon resonator were measured. The frequency noise induced by power fluctuations from this photo-birefringent effect was reduced to a neglectable level by active stabilization of optical power. However, anticorrelated spontaneous frequency fluctuations between the two polarization eigenmodes were still observed, indicating intrinsic birefringence fluctuations. To cancel this dominant excess noise - birefringent noise - in the crystalline coating, a dual-frequency locking technique was developed to stabilize the laser to the average of both polarization eigenmodes. With this technique, the expected low Brownian thermal noise was verified, but at the same time, this revealed another novel global excess noise with a correlation length larger than the mode diameter of 1 mm. This excess noise currently limits the frequency stability of the new cryogenic silicon resonator at a level comparable to dielectric coatings. Due to its large correlation length, increasing the beam size will only marginally reduce the noise level. In future ultra-sensitive interferometers using similar coatings based on semiconductor materials, these novel noise contributions discovered in this thesis must be carefully considered

Nonlinear stability of prestressed stayed columns with multiple crossarm systems

Prestressed stayed steel columns are increasing in popularity in the construction industry. This type of structure possesses a considerably higher buckling resistance as compared to the conventional column without a commensurate increase in self-weight, owing to the extra stiffnesses provided by the system of crossarms and cable stays. Most of the previous literature focused on the buckling load of the stayed column while systematic studies on the post-buckling behaviour of the single-bay column have only been conducted more recently. Although the significance of the post-buckling behaviour of such structures has already been demonstrated, certain relevant topics have not been satisfactorily studied for the stayed columns with multiple crossarm systems, which potentially possess even higher buckling resistances as compared to the single crossarm cases. Therefore, the aim of the current thesis is to reveal the post-buckling behaviour of the prestressed stayed column with multiple crossarms along the length. A finite element model of a prestressed stayed column with multiple crossarms along the length is developed with the initial imperfections and the prestress taken into consideration. Interactive buckling is found to be the most dangerous case particularly when the critical buckling mode is anti-symmetric. It is found that the post-buckling behaviour is strongly linked to the actual geometric arrangement of the structure. Sensitivities to the levels of the prestress and the initial imperfections are also presented. The observations obtained from the FE model are first validated qualitatively by a simplified analytical model. The simplified model also reveals the process for how the pure buckling modes interact during the post-buckling stage. To compare with the results of the FE model quantitatively, a more sophisticated analytical model is subsequently developed. The total potential energy of the system is formulated in conjunction with the Rayleigh--Ritz method. The slackening of the stays is also successfully simulated. An identical observation, in that interactive buckling governs the post-buckling response when anti-symmetric buckling is critical, is obtained also. Excellent quantitative agreement is found between the results from the FE and the more sophisticated analytical model. Parametric studies on the geometric configurations where interactive buckling is most significant are also presented. Finally, a large number of separate cases with different structural geometries and levels of prestress are studied. The actual optimal prestress, which accounts for the load carrying capacity of the column and the required material resistances of different structural components, is determined for the triple-bay stayed column. This demonstrates that the nonlinear response of the stayed column system is practically important from a safety as well as an efficiency perspective.Open Acces

Effects of the number of simulation iterations and meshing accuracy in monte-carlo random finite-difference analysis

Monte-Carlo random finite-difference analysis (MCRFDA) can incorporate the spatial variability of soil properties into the analysis of geotechnical structures. However, two factors, namely, the fineness of the generated elements (reflected by the number of elements, Ne) and the number of MC simulation iterations, NMC, considerably affect the computational efficiency of this method, creating a barrier to its broad use in real-world engineering problems. Hence, an MCRFDA model of a circular underground cavern is developed in this study. The convergent deformation of the cavern is analyzed while considering the spatial variability distribution of the elastic modulus. Moreover, the effects of NMC and Ne on random FD calculations are investigated. The results show the following. An NMC greater than 500 is desirable for the FD analysis of a conventional structure. For a specific structure, Ne does not have a significant impact on the mean of the simulated values but appreciably affects the standard deviation (SD) of the simulated values, where reducing Ne increases the SD of the simulated values

PPGAN: Privacy-preserving Generative Adversarial Network

Generative Adversarial Network (GAN) and its variants serve as a perfect representation of the data generation model, providing researchers with a large amount of high-quality generated data. They illustrate a promising direction for research with limited data availability. When GAN learns the semantic-rich data distribution from a dataset, the density of the generated distribution tends to concentrate on the training data. Due to the gradient parameters of the deep neural network contain the data distribution of the training samples, they can easily remember the training samples. When GAN is applied to private or sensitive data, for instance, patient medical records, as private information may be leakage. To address this issue, we propose a Privacy-preserving Generative Adversarial Network (PPGAN) model, in which we achieve differential privacy in GANs by adding well-designed noise to the gradient during the model learning procedure. Besides, we introduced the Moments Accountant strategy in the PPGAN training process to improve the stability and compatibility of the model by controlling privacy loss. We also give a mathematical proof of the differential privacy discriminator. Through extensive case studies of the benchmark datasets, we demonstrate that PPGAN can generate high-quality synthetic data while retaining the required data available under a reasonable privacy budget.Comment: This paper was accepted by IEEE ICPADS 2019 Workshop. This paper contains 10 pages, 3 figure

Evaluating diabetes and hypertension disease causality using mouse phenotypes

<p>Abstract</p> <p>Background</p> <p>Genome-wide association studies (GWAS) have found hundreds of single nucleotide polymorphisms (SNPs) associated with common diseases. However, it is largely unknown what genes linked with the SNPs actually implicate disease causality. A definitive proof for disease causality can be demonstration of disease-like phenotypes through genetic perturbation of the genes or alleles, which is obviously a daunting task for complex diseases where only mammalian models can be used.</p> <p>Results</p> <p>Here we tapped the rich resource of mouse phenotype data and developed a method to quantify the probability that a gene perturbation causes the phenotypes of a disease. Using type II diabetes (T2D) and hypertension (HT) as study cases, we found that the genes, when perturbed, having high probability to cause T2D and HT phenotypes tend to be hubs in the interactome networks and are enriched for signaling pathways regulating metabolism but not metabolic pathways, even though the genes in these metabolic pathways are often the most significantly changed in expression levels in these diseases.</p> <p>Conclusions</p> <p>Compared to human genetic disease-based predictions, our mouse phenotype based predictors greatly increased the coverage while keeping a similarly high specificity. The disease phenotype probabilities given by our approach can be used to evaluate the likelihood of disease causality of disease-associated genes and genes surrounding disease-associated SNPs.</p

Evaluation of oral Lanzhou lamb rotavirus vaccine via passive transfusion with CD4+/CD8+ T lymphocytes

AbstractLanzhou Lamb derived Rotavirus (RV) Vaccine (namely LLR) for children is only used in China. Since there were no reports on evaluation of LLR, even the data of phase IV clinical trial, we proceed the evaluation of LLR through focusing on T-cell to investigate whether LLR could induce the potential function involving in protection as a vaccine. Four groups of nude mice were transfused with CD4+/CD8+ T-cells isolated from LLR-immunized (primed) and LLR-unimmunized (naïve) mice via intraperitonea (i.p.) respectively. Consequently, the adoption mice were challenged with mice-origin wild rotavirus EDIM (Epizootic Diarrhea of Infant Mice) by intragastric administration. Series of fecal/serum samples were collected and viral shedding, then serum IgA/IgG and secreted IgA were assayed. Compared to the mice transfused with T lymphocytes from naïve mice, the nude mice transfused with CD4+ T lymphocytes from primed mice induce fecal and serum IgA increasing more rapidly, and have a shorter duration of virus shedding too. Whereas, no significant difference in virus clearance was found between the mice transfused with CD8+ T lymphocytes isolated from primed and naïve mice. Therefore, we cleared the distinct roles of transfused CD4+/CD8+ T lymphocytes for rotavirus clearance in nude mice, that the viral clearance conducted by CD4+ T lymphocytes. Meanwhile, it has ability to help induction of LLR specific immunogenicity. Comparing with the transfusion of cell from primed and naïve mice, LLR can induce CD4+ T lymphocytes memory which is a potential index to reflect the immunogenicity and protection, while CD8+ T lymphocytes remove rotavirus by CTL with little memory ability

Effect of Preparation Technologies on Properties of Reactive Powder Concrete with Nano-zirconia

Reactive powder concrete filled with 3% content of nano-zirconia (NZ) are fabricated to investigate&nbsp;the effect of preparation technologies on the mechanical strength. The preparation technologies involve internal&nbsp;(NZ is added in RPC and replaced cement )/external mixing(NZ is added in RPC but not replaced cement),&nbsp;ultrasonic time, high mixing speed, saturated lime water/high temperature curing media(curing in water at 90℃).&nbsp;The influencing mechanisms of processing method are revealed through X-ray powder diffraction (XRD) and&nbsp;thermogravimetry (TG) analysis, scanning electron microscope observation. Experiment results showed that&nbsp;high mixing speed and high temperature curing media can improve the mechanical strength obviously. The&nbsp;compressive strength of NZ filled reactive powder concrete with high mixing speed increase 49.9%. The&nbsp;compressive strength, flexural strength and splitting strength of reactive powder concrete with NZ under high&nbsp;temperature curing media increase 35%, 15% and 17% respectively compared with control concrete

Irisin Lowers Blood Pressure by Improvement of Endothelial Dysfunction via AMPK‐Akt‐eNOS‐NO Pathway in the Spontaneously Hypertensive Rat

Background Exercise is a major nonpharmacological treatment for hypertension, but its underlying mechanisms are still not completely elucidated. Irisin, a polypeptide containing 112 amino acids, which is secreted mainly by skeletal muscle cells during exercise, exerts a protective role in metabolic diseases, such as diabetes mellitus and obesity. Because of the close relationship between irisin and metabolic diseases, we hypothesized that irisin may play a role in the regulation of blood pressure. Methods and Results Blood pressures of male Wistar‐Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) were monitored through the carotid artery. Our study found that acute intravenous injection of irisin reduced blood pressure in SHRs, but not WKY rats. Irisin, by itself, had no direct vasorelaxing effect in phenylephrine‐preconstricted mesenteric arteries from SHRs. However, irisin augmented the acetylcholine‐induced vasorelaxation in mesenteric arteries from SHRs that could be reversed by Nω‐nitro‐L‐arginine‐methyl ester (L‐NAME;100 μmol/L), indicating a role of nitric oxide (NO) in this action. Indeed, irisin increased NO production and phosphorylation of endothelial nirtic oxide synthase (eNOS) in endothelial cells. 5′‐AMP‐activated protein kinase (AMPK) was involved in the vasorelaxing effect of irisin because compound C (20 μmol/L), an AMPKinhibitor, blocked the irisin‐mediated increase in phosphorylation of eNOS and protein kinase B (Akt) in endothelial cells and vasodilation in mesenteric arteries. Conclusions We conclude that acute administration of irisin lowers blood pressure of SHRs by amelioration of endothelial dysfunction of the mesenteric artery through the AMPK‐Akt‐eNOS‐NO signaling pathway