Design and analysis of refractive index sensors based on slotted photonic crystal nanobeam cavities with sidewall gratings.

We propose and numerically investigate a refractive index sensor based on a one-dimensional slotted photonic crystal nanobeam cavity with sidewall gratings for refractive index sensing in a gaseous environment. By using the three-dimensional finite-difference time-domain method, we demonstrate that our proposed sensor simultaneously possesses a high quality factor of $ 3.71 \times {10^6} $3.71×106 and a high sensitivity of 508 nm/RIU (refractive index unit) at the resonant wavelength near 1583 nm, yielding a detection limit as low as $ 1.97 \times {10^{ - 6}} $1.97×10-6 RIU. Moreover, the mode volume of the cavity's fundamental resonant mode is found to be as small as $ 0.022(\lambda /n)^3 $0.022(λ/n)3, resulting in a very compact effective sensing area. We finally study and assess the effect of fabrication disorder on the performances of our proposed sensor. We believe our proposed sensor will be a promising candidate for applications not only in multiplexed biochemical sensing and multielement mixture detection, but also in optical trapping of single biomolecules or nanoparticles.

Simulation study on active control of electromagnetically induced transparency analogue in coupled photonic crystal nanobeam cavity-waveguide systems integrated with graphene.

We proposed and numerically investigated a coupled photonic crystal nanobeam (PCN) cavity-waveguide system which is composed of a bus waveguide and two one-dimensional PCN cavities, acting as bright and dark mode cavities, to achieve a distinct electromagnetically induced transparency analogue (EIT-like) effect by changing the near-field coupling strength between two cavities. By further integrating with graphene on top of the dark mode cavity, the three-dimensional finite-difference time-domain simulation results show that the generated EIT-like transparency window can be actively tuned and a complete on-to-off modulation of the EIT-like effect is realized by electrically tuning the graphene's Fermi level without reoptimizing or refabricating the structure. Theoretical analysis based on the coupled mode theory is then conducted and the results are highly consistent with the numerical results. In addition, we demonstrated that the group delay of the system can also be actively modulated by changing the Fermi level of graphene, achieving a well-controlled slow light effect. Our proposed coupled PCN cavity-waveguide system, combining the merits of PCN cavity and graphene in a single device, may provide a new platform for applications in chip-integrated slow light devices, tunable switches, optical modulators and high-sensitive sensors.

Elevated serum cystatin C in severe OSA younger men without complications.

PURPOSE: Serum cystatin C is a promising new biomarker of glomerular filtration rate and cardiovascular events, but few studies focused on serum cystatin C levels in obstructive sleep apnea (OSA) patients. The aim of our study was to evaluate the association between serum cystatin C and OSA in younger men (≤40 years old of age) without complications. METHODS: We prospectively recruited consecutive participants without comorbidities who underwent polysomnography. Fasting blood samples were obtained from all subjects for biological profile measurements. Statistical analysis was used to evaluate the relationship between serum cystatin C and other parameters. RESULTS: The population consisted of 98 subjects (mean age = 32.5 years, mean body mass index = 27.93 kg/m(2)) that were divided according to polysomnographic finding into control group (n = 23), mild (n = 15), moderate (n = 24), and severe (n = 36) OSA group. Compared with the control group, patients with severe OSA were significantly heavier (body mass index, 29.69 ± 3.81 vs. 26.42 ± 3.10) and presented significantly higher levels of high sensitive C-reactive protein (hsCRP) (1.10 ± 0.28 vs. 0.88 ± 0.20 mg/l) and serum cystatin C (0.87 ± 0.12 vs. 0.74 ± 0.10 mg/l) (p < 0.05 for all comparisons). Cystatin C was correlated with Apnea Hypopnea Index (AHI), Oxygen Desaturation Index, hsCRP, creatinine, and estimated glomerular filtration rate (r = 0.319, 0.279, 0.321, 0.233, -0.241, p = 0.001, 0.005, 0.001, 0.021, 0.017, respectively). After adjustment for confounding factors, AHI was significantly and positively associated with serum cystatin C levels (ß = 0.284, p = 0.007). CONCLUSIONS: Our finding indicated that serum cystatin C was associated with the severity of OSA in younger men. Further study is needed to find out whether OSA patients with increased serum cystatin C levels are prone to subclinical cardiovascular and renal diseases.

[Effects of long term nasal continuous positive airway pressure on the blood pressure of patients with obstructive sleep apnea hypopnea syndrome].

OBJECTIVE: To analyze the effects of long term nasal continuous positive airway pressure on the blood pressure of patients with OSAHS. METHODS: From April 1997 to October 2008, 2898 patients from the First Affiliated Hospital of Fujian Medical University who complained snore during sleeping were studied. Nine hundred eighty cases were diagnosed as OSAHS with hypertension, and these patients were randomly divided into 2 groups: one group was treated with antihypertensive drugs and nasal continuous positive airway pressure (nCPAP), while the other group only received antihypertensive drugs. The polysomnography (PSG) was recorded during sleeping and the blood pressure was remeasured after 6 months or more. All patients were followed up for 5 years to observe the long-term effects of nCPAP or drugs. RESULTS: Systolic and diastolic blood pressure in the nCPAP group significantly decreased after 6 months [(125 ± 16) mm Hg (1 mm Hg = 0.133 kPa) vs (136 ± 19) mm Hg, (83 ± 10) mm Hg vs (95 ± 15) mm Hg, P < 0.05], and the decreasing extent of blood pressure in nCPAP group was more notable than antihypertensive drug group [decreasing extent of systolic blood pressure:(10 ± 11) mm Hg vs (4 ± 11) mm Hg; decreasing extent of diastolic blood pressure: (11 ± 7) mm Hg vs (6 ± 7) mm Hg; P < 0.05]. The total effective rate in nCPAP group was significantly higher than that in antihypertensive drug group (90% vs 38%, P < 0.01). One hundred and eighty three cases in nCPAP group and 157 cases in antihypertensive drug group completed the 5-year follow-up and the blood pressure was controlled within the normal range. Some patients could gradually reduce or stop the use of antihypertensive drugs and the blood pressure didn't appear to rebound. The number of antihypertensive drugs in the nCPAP group was significantly fewer as compared to the antihypertensive drugs group after 2, 3, 4 and 5 years' follow-up. CONCLUSIONS: nCPAP is a safe and effective treatment for high blood pressure in patients with OSAHS.

Effect of size disorder on the optical transport in chains of coupled microspherical resonators.

We investigate statistical properties of collective optical excitations in disordered chains of microspheres using transfer-matrix method based on nearest-neighbors approximation. Radiative losses together with transmission and reflection coefficients of optical excitations are studied numerically. We found that for the macroscopically long chain, the transmission coefficient demonstrates properties typical for a one dimensional strongly localized system: log-normal distribution with parameters obeying standard scaling relation. At the same time, we show that the distribution function of the radiative losses behaves very differently from other lossy optical systems. We also studied statistical properties of the optical transport in short chains of resonators and demonstrated that even small disorder results in significant drop of transmission coefficient acompanied by strong enhancement of the radiative losses.

[The role of polymorphonuclear cells in lung ischemia-reperfusion injury in a canine model of pulmonary thromboembolism].

OBJECTIVE: To explore the effects of polymorphonuclear cells (PMN) on lung ischemia-reperfusion (I/R) injury in a canine model of pulmonary thromboembolism. METHODS: Fifteen dogs were divided into three groups: a sham group (n = 5), an ischemia group (n = 5) and a reperfusion group (n = 5). PMN in the whole blood were isolated with density gradient centrifugation. Apoptosis rates of the PMN was measured through flow cytometer after the cells were labeled by Annexin V-FITC before embolectomy and at 2, 4, 6 h after the operation. The myeloperoxidase (MPO) concentrations in lung homogenates were measured by ELISA. Alveolar PMN in the reperfusion lobar were observed by optical microscopy. The lung ultrastructure was studied by transmission electron microscopy. RESULTS: Alveolar PMN infiltration and the concentrations of MPO in the reperfusion group were significantly higher than those in the ischemia group (PMN (31 +/- 11) vs (8 +/- 4)/ten high power fields, MPO (11.7 +/- 1.6) vs (9.1 +/- 0.5) microg/L, P < 0.05). In the reperfusion group, abundant inflammatory cell infiltration was observed, predominantly with PMN in the alveoli. Apoptosis rates of the blood PMN at 6 h after reperfusion were much lower than before reperfusion (3.0 +/- 2.5)% vs (7.4 +/- 4.5)%, P < 0.05). At 4 and 6 h after operation, the PMN apoptosis rates in the reperfusion group were significantly lower than the ischemia group (4 h: (4.8 +/- 2.6)% vs (9.3 +/- 2.0)%, 6 h: (3.0 +/- 2.5)% vs (8.0 +/- 1.6)%, P < 0.05). PMN attaching firmly to the alveolar septum were observed by electron microscope. CONCLUSION: PMN with enhanced activities and decreased apoptosis rate, are involved in the cellular mechanisms of the lung I/R injury in this model of pulmonary thromboembolism.

[Effects of different durations of thromboembolism on blood gases, hemodynamics, pulmonary arteriography and thrombo-pathology in a canine model with selective embolization of pulmonary lobar arteries].

OBJECTIVE: To investigate the effects of different durations of thromboembolism on blood gases, hemodynamic parameters, pulmonary arteriography and thrombo-pathology in an animal model mimicking chronic pulmonary thromboembolism (PTE). METHODS: Sixteen dogs were embolized with five thrombi developed by autologous blood into the left lower pulmonary artery (n = 15) and the right lower pulmonary artery (n = 1, used to confirm the available method of selective embolization). The 15 dogs were divided into three groups: sham group (n = 5), one-week group (n = 5) and two-week group (n = 5) according to the different durations of embolization. Swan-Ganz catheter was used to guide a plastic duct, through which the thrombi were injected selectively into the left or right lower pulmonary artery by X-ray fluoroscopy. Local pulmonary arteriography of lower pulmonary arteries was taken. Blood pressure (BP), and blood gases were measured. Central venous pressure (CVP), mean pulmonary arterial pressure (MPAP), pulmonary arteriole wedge pressure (PAWP), and cardiac output (CO) were recorded, and pulmonary vascular resistance (PVR) was calculated. Each dog underwent muscular injection with tranexamic acid for one or two weeks to prevent thrombolysis. The lower lung lobe was dissected to confirm the thromboembolism after one or two weeks. The lung sections were stained with phosphotungstic acid hematoxylin (PTAH) to observe thromboemboli with optical microscopy. RESULTS: In the PTE group, PaO(2)/FiO(2), MPAP and PVR changed significantly as compared to baseline values (P < 0.05) after one hour of embolization, with MPAP increasing from (15 +/- 3) mm Hg to (21 +/- 4) mm Hg, PVR increasing from (178 +/- 114) mm Hg.s/L to (404 +/- 260) mm Hg.s/L, and PaO(2)/FiO(2) decreasing from (508 +/- 58) mm Hg to (395 +/- 100) mm Hg; these parameters returned to the baseline values one or two weeks later. After embolization, pulmonary arteriography demonstrated lower lobar artery cut-off perfusion defects. One week later, pulmonary arteriography demonstrated irregularities and stiffness of the arterial wall, enlarged proximal part of lower pulmonary artery and cut-off perfusion defects. Poor filling at embolus site was evident after embolization for two weeks. In the 1-week PTE group, organized tissue covered with the blue-purple fibrin nest was observed in the thrombus with PTAH stain. In the two-week group, the well organized thrombi were partially recanalized and surrounded and invaded by hyperplastic tissues from pulmonary artery wall. CONCLUSIONS: A canine model mimicking chronic PTE can be established by the use of fibrinolytic inhibitor tranexamic acid. Different manifestations on pulmonary arteriography and varied degree of organization of thrombi are evident at different times after embolization.