The fabrication of an eccentric three-core fiber and its application as a twist sensor

The fabrication and application for twist sensing of an eccentric three-core fiber were demonstrated. The fiber was made by stack-and-draw technique, in which silica rods and core canes were put in a tube and drawn on a fiber drawing tower. Three cores formed a Mach-Zehnder interferometer, where the lights transmitted in the three cores interfered with each other, resulted in the formation of envelopes on spectrum. Because two of the cores were off axis, phase differences among the cores varied with twist due to different stretches on each core, which caused shift of the spectral envelopes of the interference signal. Wide range twist measurement can be realized with relatively high sensitivity by tracking lower dips of the envelopes. Experimental results revealed that the dips shift quadratically with twist angle, which means that the sensitivity increases with twist. The compensation of temperature influence was also implemented by inscribing a Bragg grating on one of the cores with femtosecond laser. Because the fiber can be mass-produced, it is suitable for twist sensing in practical application for its low cost

β2-Adrenergic receptor promoter haplotype influences the severity of acute viral respiratory tract infection during infancy: a prospective cohort study.

BACKGROUND: Despite the significant interest in β2-Adrenergic receptor (ADRB2) polymorphisms related to asthma, whether ADRB2 genetic variants are similarly associated with acute respiratory tract infections have not been studied. We hypothesized that genetic variants in ADRB2 associated with a response to asthma therapy during an asthma exacerbation were also associated with severity of acute respiratory tract infections. METHODS: To test this hypothesis, we genotyped 5 common polymorphisms in the promoter region and coding block of the ADRB2 gene (loci -2387, -2274, -1343, +46, and +79) from 374 Caucasian and African American term infants who were enrolled at the time of acute respiratory illness over four respiratory viral seasons. Severity of respiratory tract infections was measured using a bronchiolitis severity score (BSS; range = 0-12, clinically significant difference = 0.5) with a higher score indicating more severe disease. We assigned the promoter, coding and combined promoter and coding haplotypes to the unphased genotype data. The associations between each of these five single-nucleotide polymorphisms (SNPs) as well as the haplotypes and infant BSS were analyzed using nonparametric univariate analysis and multivariable proportional odds model separately in Caucasians and African Americans. RESULTS: There was no significant association between infant BSS and each of the SNPs in both Caucasians and African Americans. However, promoter haplotype CCA was associated with a decreased BSS in African Americans in a dose dependent manner. The median (interquartile range) BSS of infants with no copies of the CCA haplotype, one copy, and two copies of the CCA haplotype were 5.5 (2.0, 8.0), 4.0 (1.0, 7.5), and 3.0 (1.0, 4.0), respectively. This dose dependent relationship persisted after adjusting for infant age, gender, daycare exposure, secondhand smoke exposure, prior history of breastfeeding, siblings at home, and enrollment season (adjusted odds ratio: 0.59, 95 % confidence interval: 0.36, 0.98). There was no similar protective relationship of haplotype CCA on severity of respiratory tract infections identified in Caucasians. CONCLUSIONS: ADRB2 genotype may be predictive of severity of acute respiratory tract infections in African Americans, and potentially identify a subset of infants who may respond to beta-agonist therapy

Electrically Tuning Characteristics of LC Selectively Infiltrated PCF Sagnac Interferometer

A photonic crystal fiber was selectively infiltrated only two of the air holes near the core with liquid crystal. The selective infiltration caused geometric asymmetry and created high birefringence. Because of the geometric asymmetry, the response to varying electric field is concerned with electric field direction. A Sagnac interferometer was set to investigate the electric tuning characteristics of the selectively infiltrated photonic crystal fiber. The effective refractive-indices of the fiber varies with electric field due to reorientation of liquid crystal molecules. The highest sensitivity was 1.12 nm/V (504 nm/kV/mm) with tuning range of 7 nm when electric field direction was parallel to the connecting line of infiltrated holes. The response time of the selectively infiltrated photonic crystal fiber was studied. The device can be utilized as voltage sensors, electro-optical modulators and filters

Electrically Sensing Characteristics of the Sagnac Interferometer Embedded With a Liquid Crystal-Infiltrated Photonic Crystal Fiber

The electrically sensing characteristics of a liquid-crystal (LC)-infiltrated polarization-maintaining photonic crystal fiber (PCF) have been studied. The small holes on the end face of the fiber collapse and two large holes remain open by controlling discharging-time, -current, and -position of a fiber splicer, then LC is selectively infiltrated into the two large holes, which can not only save LC but also make the welding between the LC-infiltrated polarization-maintaining PCF and single-mode fiber much easier. A new method to weld the two fibers is proposed by filling and volatilizing ethanol to make LC a few millimeters away from the end face which can improve the sensing system stability and prevent the discharge of a fiber splicer from destroying LC molecules. A Sagnac interferometer is set up by embedding the LC-infiltrated polarization-maintaining PCF in a fiber loop and then its electroresponse characteristics are studied. The refractive-index distribution of the LC-infiltrated polarization-maintaining PCF varies with electric voltage due to the variable index of LC, which makes it possible to detect voltage. Three voltage ranges are discussed by the different dips and the sensitivity is improved with voltage increasing. The high sensitivity is up to 3.49 nm/V with the tuning range of 7 nm as voltage changes from 149.67 to 151.61 V. The Sagnac interferometer embedded with an LC-infiltrated polarization-maintaining PCF can be utilized as a voltage sensor, electro-optical modulator, or filter

Cascaded Sagnac loops embedded with two polarization maintaining photonic crystal fibers for highly-sensitive strain measurement

A strain sensor based on cascaded Sagnac loops with two PMPCFs has been experimentally demonstrated. Air holes distributed on the cross section of PMPCF go through the whole fiber which make the special fiber more sensitive to ambient force compared with conventional optical fiber. The lengths of the two PMPCFs are close, but not the same, to form envelopes on the total output spectrum and then obtain high resolution to the detected parameter by Vernier effect. The influences of the difference in length of the two PMPCFS on spectral envelopes are discussed. As the length of the PMPCF in reference loop increases, free spectrum range of the cascaded Sagnac loops (or envelope period) and magnification decrease. The sensitivities of this strain sensor are calculated by tracking upper- and lower-envelope. Results reveal that its average sensitivity is up to 45.15 pm/με and the corresponding resolution is 0.44 με as strain varies from 0 to 2000 με. Compared with a single Sagnac loop, the sensitivity magnification is about 28.94. The sensing characteristics of a conventional PMF are studied to compare with the PMPCF. Moreover, reversibility has also been proved to possess low error rate. In short, the fiber strain sensor possesses high sensitivity and great reversibility

Personalized Infant Risk Prediction for Severe Respiratory Syncytial Virus Lower Respiratory Tract Infection Requiring Intensive Care Unit Admission

BACKGROUND: Currently, there are no available tools to identify infants at the highest risk of significant morbidity and mortality from respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) who would benefit most from RSV prevention products. The objective was to develop and internally validate a personalized risk prediction tool for use among all newborns that uses readily available birth/postnatal data to predict RSV LRTI requiring intensive care unit (ICU) admission. METHODS: We conducted a population-based birth cohort study of infants born from 1995 to 2007, insured by the Tennessee Medicaid Program, and who did not receive RSV immunoprophylaxis during the first year of life. The primary outcome was severe RSV LRTI requiring ICU admission during the first year of life. We built a multivariable logistic regression model including demographic and clinical variables available at or shortly after birth to predict the primary outcome. RESULTS: In a population-based sample of 429 365 infants, 713 (0.2%) had severe RSV LRTI requiring ICU admission. The median age of admission was 66 days (interquartile range, 37-120). Our tool, including 19 variables, demonstrated good predictive accuracy (area under the curve, 0.78; 95% confidence interval, 0.77-0.80) and identified infants who did not qualify for palivizumab, based on American Academy of Pediatrics guidelines, but had higher predicted risk levels than infants who qualified (27% of noneligible infants with >0.16% predicted probabilities [lower quartile for eligible infants]). CONCLUSIONS: We developed a personalized tool that identified infants at increased risk for severe RSV LRTI requiring ICU admission, expected to benefit most from immunoprophylaxis

Informing randomized clinical trials of respiratory syncytial virus vaccination during pregnancy to prevent recurrent childhood wheezing::a sample size analysis

Background: Early RSV illness is associated with wheeze-associated disorders in childhood. Candidate respiratory syncytial virus (RSV) vaccines may prevent acute RSV illness in infants. We investigated the feasibility of maternal RSV vaccine trials to demonstrate reductions in recurrent childhood wheezing in general paediatric populations. Methods: We calculated vaccine trial effect sizes that depended on vaccine efficacy, allocation ratio, rate of early severe RSV illness, risk of recurrent wheezing at age 3, and increased risk of RSV infection on recurrent wheezing. Model inputs came from systematic reviews and meta-analyses. For each combination of inputs, we estimated the sample size required to detect the effect of vaccination on recurrent wheezing. Results: There were 81 scenarios with 1:1 allocation ratio. Risk ratios between vaccination and recurrent wheezing ranged from 0.9 to 1.0 for 70% of the scenarios. Among the 57 more plausible scenarios, the lowest sample size required to detect significant reductions in recurrent wheezing was 6196 mother-infant pairs per trial arm; however, 75% and 47% of plausible scenarios required >31,060 and >100,000 mother-infant pairs per trial arm, respectively. Studies with asthma endpoints at age 5 will likely need to be larger. Discussion: Clinical efficacy trials of candidate maternal RSV vaccines undertaken for licensure are unlikely to demonstrate an effect on recurrent wheezing illness due to the large sample sizes likely needed to demonstrate a significant effect. Further efforts are needed to plan for alternative study designs to estimate the impact of maternal RSV vaccine programs on recurrent childhood wheezing in general populations

Reactive Oxygen Species Released from Hypoxic Hepatocytes Regulates MMP-2 Expression in Hepatic Stellate Cells

Hypoxia is a common environmental stress factor and is associated with fibrogenesis. Matrix metalloproteinase-2 (MMP-2), produced by hepatic stellate cells (HSCs), plays an important role in liver fibrogenesis. However, inconsistent results have been reported on the impact of hypoxia on MMP-2 expression and activity in HSCs. We speculated that cell–cell interaction is involved in the regulation of MMP-2 expression and activity at low oxygen level in vivo. Therefore, in this report we investigated the mechanism by which hypoxic hepatocytes regulates MMP-2 expression in HSCs. Our results showed that the conditioned medium from hypoxia-treated rat hepatocytes strongly induced the expression of MMP-2 mRNA and protein in rat HSC-T6 cells. Reduced glutathione neutralized ROS released from hypoxic hepatocytes, leading to reduced MMP-2 expression in HSC-T6 cells. In addition, phospho-IκB-α protein level was increased in HSC-T6 cells treated with hypoxia conditioned medium, and NF-κB signaling inhibitor inhibited MMP-2 expression in HSC-T6 cells. Taken together, our data suggest that ROS is an important factor released by hypoxic hepatocytes to regulate MMP-2 expression in HSCs, and NF-κB signaling is crucially involved in ROS-induced MMP-2 expression in HSCs. Our findings suggest that strategies aimed at antagonizing the generation of ROS in hypoxic hepatocytes and inhibiting NF-κB signaling in HSCs may represent novel therapeutic options for liver fibrosis

β2-Adrenergic receptor promoter haplotype influences the severity of acute viral respiratory tract infection during infancy: a prospective cohort study

Abstract Background Despite the significant interest in β2-Adrenergic receptor (ADRB2) polymorphisms related to asthma, whether ADRB2 genetic variants are similarly associated with acute respiratory tract infections have not been studied. We hypothesized that genetic variants in ADRB2 associated with a response to asthma therapy during an asthma exacerbation were also associated with severity of acute respiratory tract infections. Methods To test this hypothesis, we genotyped 5 common polymorphisms in the promoter region and coding block of the ADRB2 gene (loci -2387, -2274, -1343, +46, and +79) from 374 Caucasian and African American term infants who were enrolled at the time of acute respiratory illness over four respiratory viral seasons. Severity of respiratory tract infections was measured using a bronchiolitis severity score (BSS; range = 0-12, clinically significant difference = 0.5) with a higher score indicating more severe disease. We assigned the promoter, coding and combined promoter and coding haplotypes to the unphased genotype data. The associations between each of these five single-nucleotide polymorphisms (SNPs) as well as the haplotypes and infant BSS were analyzed using nonparametric univariate analysis and multivariable proportional odds model separately in Caucasians and African Americans. Results There was no significant association between infant BSS and each of the SNPs in both Caucasians and African Americans. However, promoter haplotype CCA was associated with a decreased BSS in African Americans in a dose dependent manner. The median (interquartile range) BSS of infants with no copies of the CCA haplotype, one copy, and two copies of the CCA haplotype were 5.5 (2.0, 8.0), 4.0 (1.0, 7.5), and 3.0 (1.0, 4.0), respectively. This dose dependent relationship persisted after adjusting for infant age, gender, daycare exposure, secondhand smoke exposure, prior history of breastfeeding, siblings at home, and enrollment season (adjusted odds ratio: 0.59, 95 % confidence interval: 0.36, 0.98). There was no similar protective relationship of haplotype CCA on severity of respiratory tract infections identified in Caucasians. Conclusions ADRB2 genotype may be predictive of severity of acute respiratory tract infections in African Americans, and potentially identify a subset of infants who may respond to beta-agonist therapy

Assessing the strength of evidence for a causal effect of respiratory syncytial virus lower respiratory tract infections on subsequent wheezing illness: a systematic review and meta-analysis

BACKGROUND: Although a positive association has been established, it is unclear whether lower respiratory tract infections (LRTIs) with respiratory syncytial virus (RSV) cause chronic wheezing illnesses. If RSV-LRTI were causal, we would expect RSV-LRTI prevention to reduce the incidence of chronic wheezing illnesses in addition to reducing acute disease. We aimed to evaluate the strength of evidence for a causal effect of RSV-LRTI on subsequent chronic wheezing illness to inform public health expectations for RSV vaccines. METHODS: We did a systematic review and meta-analysis of observational studies evaluating the association between RSV-LRTI and subsequent wheezing illness (exposure studies) and studies evaluating the association between RSV immunoprophylaxis and subsequent wheezing illness (immunoprophylaxis studies). Exposure studies were included if the exposure group members had an LRTI with laboratory-confirmed RSV and if the exposure ascertainment period began before 2 years of age and ended before 5 years of age. We required a wash-out period of more than 30 days between the index RSV-LRTI and the outcome measurement to allow for resolution of the acute illness. Comparisons between RSV-LRTI and non-RSV-LRTI were not included. Immunoprophylaxis studies were included if they measured the association with subsequent wheezing illness relative to a control group, either in a randomised controlled trial (RCT) or an observational design. For the immunoprophylaxis drugs in question, we required evidence of efficacy in targeting RSV-LRTI from at least one RCT to ensure biological plausibility. All variations of wheezing illness were combined into a single outcome that refers broadly to asthma or any other respiratory illness with wheezing symptoms. Ovid MEDLINE and Embase databases were searched from inception up to Aug 28, 2018. We evaluated whether data from exposure studies could provide evidence against the most viable non-causal theory that RSV-LRTI is a marker of respiratory illness susceptibility rather than a causal factor. Additionally, we tested whether RSV immunoprophylaxis reduces the odds of subsequent wheezing illnesses. We used a random-effects modelling framework and, to accommodate studies providing multiple correlated estimates, robust variance estimation meta-regressions. Meta-regression coefficients (b) quantify differences between exposure and comparator groups on the loge odds ratio (loge OR) scale. FINDINGS: From 14 235 records we identified 57 eligible articles that described 42 studies and provided 153 effect estimates. 35 studies estimated the direct effect of RSV-LRTI on wheezing illnesses (exposure studies) and eight evaluated the effect of RSV immunoprophylaxis (immunoprophylaxis studies). Exposure studies that adjusted for genetic influences yielded a smaller mean adjusted OR estimate (aOR+ 2·45, 95% CI 1·23-4·88) compared with those that did not (4·17, 2·36-7·37), a significant difference (b 0·53, 95% CI 0·04-1·02). Infants who were not protected with RSV immunoprophylaxis tended to have higher odds of subsequent wheezing illness, as we would expect if RSV-LRTI were causal, but the effect was not significant (OR+ 1·21, 95% CI 0·73-1·99). There was generally a high threat of confounding bias in the observational studies. Additionally, in both the observational studies and immunoprophylaxis RCTs, there was high risk of bias due to missing outcome data. INTERPRETATION: Our findings, limited to exposure and immunoprophylaxis studies, do not support basing policy decisions on an assumption that prevention of RSV-LRTI will reduce recurrent chronic wheezing illnesses. FUNDING: Bill & Melinda Gates Foundation