Light-assisted domain engineering, waveguide fabrication and microstructuring of lithium niobate

The thesis is focussing on the interaction of lithium niobate with UV and ultrafast laser radiation to achieve 1) ferroelectric domain inversion, 2) waveguide fabrication, and 3) surface microstructuring. Preferential ferroelectric domain inversion has been demonstrated by 'latent light-assisted poling' and 'inhibition of poling' using ultrafast laser irradiation at 400 nm and CW highly absorbed UV radiation (305..244 nm) respectively. The characteristics of the resultant domains have been experimentally investigated as a function of the fabrication conditions and a theoretical model have been proposed to explain the experimental observations. UV radiation in the 305 nm to 244 nm range have been used for the fabrication of optical waveguides in lithium niobate. The waveguiding characteristics and electro-optic response of the UV written optical channel waveguides have been investigated experimentally. Inhibition of poling and post processing has been used for the fabrication of ridge waveguide structures with enhanced refractive index change. Finally, a method for the fabrication of ultra-smooth lithium niobate single crystal photonic microstructures has been proposed. The method is based on surface tension reshaping of surface microstructures which are produced by preferential poling and subsequent etching. Whispering gallery mode resonators have been fabricated and characterised here

Depth resolution of Piezoresponse force microscopy

Given that a ferroelectric domain is generally a three dimensional entity, the determination of its area as well as its depth is mandatory for full characterization. Piezoresponse force microscopy (PFM) is known for its ability to map the lateral dimensions of ferroelectric domains with high accuracy. However, no depth profile information has been readily available so far. Here, we have used ferroelectric domains of known depth profile to determine the dependence of the PFM response on the depth of the domain, and thus effectively the depth resolution of PFM detection

A framework for orchestrating secure and dynamic access of IoT services in multi-cloud environments

IoT devices have complex requirements but their limitations in terms of storage, network, computing, data analytics, scalability and big data management require it to be used it with a technology like cloud computing. IoT backend with cloud computing can present new ways to offer services that are massively scalable, can be dynamically configured, and delivered on demand with largescale infrastructure resources. However, a single cloud infrastructure might be unable to deal with the increasing demand of cloud services in which hundreds of users might be accessing cloud resources, leading to a big data problem and the need for efficient frameworks to handle a large number of user requests for IoT services. These challenges require new functional elements and provisioning schemes. To this end, we propose the usage of multi-clouds with IoT which can optimize the user requirements by allowing them to choose best IoT services from many services hosted in various cloud platforms and provide them with more infrastructure and platform resources to meet their requirements. This paper presents a novel framework for dynamic and secure IoT services access across multi-clouds using cloud on-demand model. To facilitate multi-cloud collaboration, novel protocols are designed and implemented on cloud platforms. The various stages involved in the framework for allowing users access to IoT services in multi-clouds are service matchmaking (i.e. to choose the best service matching user requirements), authentication (i.e. a lightweight mechanism to authenticate users at runtime before granting them service access), and SLA management (including SLA negotiation, enforcement and monitoring). SLA management offers benefits like negotiating required service parameters, enforcing mechanisms to ensure that service execution in the external cloud is according to the agreed SLAs and monitoring to verify that the cloud provider complies with those SLAs. The detailed system design to establish secure multi-cloud collaboration has been presented. Moreover, the designed protocols are empirically implemented on two different clouds including OpenStack and Amazon AWS. Experiments indicate that proposed system is scalable, authentication protocols result only in a limited overhead compared to standard authentication protocols, and any SLA violation by a cloud provider could be recorded and reported back to the user.N/

Advances in the Relationships Between Cow’s Milk Protein Allergy and Gut Microbiota in Infants

Cow’s milk protein allergy (CMPA) is an immune response to cow’s milk proteins, which is one of the most common food allergies in infants and young children. It is estimated that 2–3% of infants and young children have CMPA. The diet, gut microbiota, and their interactions are believed to be involved in the alterations of mucosal immune tolerance, which might lead to the development of CMPA and other food allergies. In this review, the potential molecular mechanisms of CMPA, including omics technologies used for analyzing microbiota, impacts of early microbial exposures on CMPA development, and microbiota–host interactions, are summarized. The probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and other modulation strategies for gut microbiota and the potential application of microbiota-based design of diets for the CMPA treatment are also discussed. This review not only summarizes the current studies about the interactions of CMPA with gut microbiota but also gives insights into the possible CMPA treatment strategies by modulating gut microbiota, which might help in improving the life quality of CMPA patients in the future

A signature of five 7-methylguanosine-related genes is a prognostic marker for lung squamous cell carcinoma.

Background: N7-methylguanosine (m7G) is an important posttranscriptional modification affecting mRNA and tRNA functions and stability. The genes regulating the m7G process have been previously found involved in the carcinogenesis process. We aimed to analyze the role of m7G-related genes as potential prognostic markers for lung squamous cell carcinoma (LSCC). Methods: Twenty-nine m7G-related genes were selected for the analysis in the LSCC cohort of the Cancer Genome Atlas (TCGA). Univariate, multivariate, and Kaplan-Meier analyses were used to evaluate the predictive value of risk model developed with m7G signature for overall survival (OS). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of differentially expressed genes (DEGs) were performed for high- and low-risk LSCC groups. Results: We identified 17 differentially expressed m7G methylation-related genes in LSCC versus normal tissues. The expression of five m7G-related genes (EIF3D, LSM1, NCBP2, NUDT10, and NUDT11) was identified as an independent prognostic marker for OS in LSCC patients. A risk model with these five m7G-related genes predicted 2-, and 3-year survival rates of 0.623 and 0.626, respectively. The risk score significantly correlated with OS: LSCC patients with a higher risk score had shorter OS (P\u3c0.01) and it was associated with lower immune response (P\u3c0.01). Conclusions: We developed a novel m7G-related gene signature that can be of great utility to predict the prognosis for patients with LSCC. Keywords: Non-small cell lung cancer (NSCLC); N7-methylguanosine (m7G); The Cancer Genome Atlas (TCGA); prognosis; biomarke

Antiviral Ability of Kalanchoe gracilis Leaf Extract against Enterovirus 71 and Coxsackievirus A16

Pandemic infection or reemergence of Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) occurs in tropical and subtropical regions, being associated with hand-foot-and-mouth disease, herpangina, aseptic meningitis, brain stem encephalitis, pulmonary edema, and paralysis. However, effective therapeutic drugs against EV71 and CVA16 are rare. Kalanchoe gracilis (L.) DC is used for the treatment of injuries, pain, and inflammation. This study investigated antiviral effects of K. gracilis leaf extract on EV71 and CVA16 replications. HPLC analysis with a C-18 reverse phase column showed fingerprint profiles of K. gracilis leaf extract had 15 chromatographic peaks. UV/vis absorption spectra revealed peaks 5, 12, and 15 as ferulic acid, quercetin, and kaempferol, respectively. K. gracilis leaf extract showed little cytotoxicity, but exhibited concentration-dependent antiviral activities including cytopathic effect, plaque, and virus yield reductions. K. gracilis leaf extract was shown to be more potent in antiviral activity than ferulic acid, quercetin, and kaempferol, significantly inhibiting in vitro replication of EV71 (IC50 = 35.88 μg/mL) and CVA16 (IC50 = 42.91 μg/mL). Moreover, K. gracilis leaf extract is a safe antienteroviral agent with the inactivation of viral 2A protease and reduction of IL-6 and RANTES expressions

18F-Labeled GRPR Agonists and Antagonists: A Comparative Study in Prostate Cancer Imaging

Radiolabeled bombesin analogs are promising probes for cancer imaging of gastrin-releasing peptide receptor (GRPR). In this study, we developed 18F-labeled GRPR agonists and antagonists for positron emission tomography (PET) imaging of prostate cancer. GRPR antagonists ATBBN (D-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHCH2CH3) and MATBBN (Gly-Gly-Gly-Arg-Asp-Asn-D-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHCH2CH3), and agonists AGBBN (Gln-Trp-Ala-Val-Gly-His-Leu-MetNH2) and MAGBBN (Gly-Gly-Gly-Arg-Asp-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-MetNH2) were radiolabeled with 18F via 4-nitrophenyl 2-18F-fluoropropionate. The in vitro receptor binding, cell uptake, and efflux properties of the radiotracers were studied on PC-3 cells. An in vivo PET study was performed on mice bearing PC-3 tumors. Direct 18F-labeling of known GRPR antagonist ATBBN and agonist AGBBN did not result in good tumor targeting or appropriate pharmacokinetics. Modification was made by introducing a highly hydrophilic linker Gly-Gly-Gly-Arg-Asp-Asn. Higher receptor binding affinity, much higher cell uptake and slower washout were observed for the agonist 18F-FP-MAGBBN over the antagonist 18F-FP-MATBBN. Both tracers showed good tumor/background contrast, with the agonist 18F-FP-MAGBBN having significantly higher tumor uptake than the antagonist 18F-FP-MATBBN (P < 0.01). In conclusion, Gly-Gly-Gly-Arg-Asp-Asn linker significantly improved the pharmacokinetics of the otherwise hydrophobic BBN radiotracers. 18F-labeled BBN peptide agonists may be the probes of choice for prostate cancer imaging due to their relatively high tumor uptake and retention as compared with the antagonist counterparts