Syntheses and studies of acetylenic polymers

A series of new diiodo aryl compounds have been conveniently synthesized. Based on these diiodo compounds, a series of novel soluble polymers, poly(2,5-dialkoxy-1,4-phenyleneethynylene)s (PPE polymers) have been synthesized by using a palladium-catalyzed polymerization. These PPE polymers have been well characterized by routine methods. The molecular weights range from 8,000 to 40,000;The properties of these PPE polymers such as absorption, fluorescence, and conductivity have been studied. A PPE polymer with the butoxy side chain exhibits a weak electrical conductivity ([sigma] = 10[superscript]-3 S/cm) after doping with AsF[subscript]5. The absorption spectra of PPE polymers in THF solution at room temperature show an absorption maximum at [lambda] = 440 nm. However, the absorption spectra of PPE polymers in the film state at room temperature show an absorption maximum at [lambda] = 480 nm. PPE polymer-based light emitting diode (LED) devices have been prepared and studied. Greenish light from these LED devices can be observed;Furthermore, poly(ethynylene-p-arylene-ethynylene-silylene)s have been synthesized through the same palladium-catalyzed polymerization. These polymers have also been characterized by routine methods. The molecular weights of these polymers are between 6,000 and 82,000. Their absorption and fluorescence have been studied. Some of these polymers exhibit thermotropic liquid crystalline properties. In addition, the nonlinear optical properties of these polymers have been briefly examined;Poly(silylene-ethynylene) homopolymers as well as alternating copolymers have been synthesized through a novel palladium-catalyzed polymerization. The molecular weights of these polymers range from 56 x 10[superscript]3 to 5.3 x 10[superscript]3. The thermal stability of these polymers has also been investigated and the char yields range from 51% to 83%. One of these polymers exhibits thermotropic liquid crystalline properties

Tertiary Regulation of Cascaded Run-of-the-River Hydropower in the Islanded Renewable Power System Considering Multi-Timescale Dynamics

To enable power supply in rural areas and to exploit clean energy, fully renewable power systems consisting of cascaded run-of-the-river hydropower and volatile energies such as pv and wind are built around the world. In islanded operation mode, the primary and secondary frequency control, i.e., hydro governors and automatic generation control (AGC), ensure the frequency stability. However, due to limited water storage capacity of run-of-the-river hydropower and river dynamics constraints, without coordination between the cascaded plants, the traditional AGC with fixed participation factors cannot fully exploit the adjustability of cascaded hydropower. When imbalances between the volatile energy and load occur, load shedding can be inevitable. To address this issue, this paper proposes a coordinated tertiary control approach by jointly considering power system dynamics and the river dynamics that couples the cascaded hydropower plants. The timescales of the power system and river dynamics are very different. To unify the multi-timescale dynamics to establish a model predictive controller that coordinates the cascaded plants, the relation between AGC parameters and turbine discharge over a time interval is approximated by a data-based second-order polynomial surrogate model. The cascaded plants are coordinated by optimising AGC participation factors in a receding-horizon manner, and load shedding is minimised. Simulation of a real-life system shows a significant improvement in the proposed method in terms of reducing load shedding.Comment: Submitted to IET Renewable Power Generation; 11 page

Data-constrained Magnetohydrodynamic Simulation of an Intermediate Solar Filament Eruption

Solar eruptive activities could occur in weak magnetic field environments and over large spatial scales, especially relevant to eruptions involving intermediate or quiescent solar filaments. To handle the large scales, we implement and apply a flux rope embedding method using regularized Biot-Savart laws in the spherical coordinate system. Combined with a potential field source surface model and a magneto-frictional method, a nonlinear force-free field comprising a flux rope embedded in a potential field is constructed. Using the combined nonlinear force-free field as the initial condition, we then perform a zero-$\beta$ data-constrained magnetohydrodynamic (MHD) simulation for an M8.7 flare at 03:38 UT on 2012 January 23. The MHD model reproduces the eruption process, flare ribbon evolution (represented by the quasi-separatrix layer evolution) and kinematics of the flux rope. This approach could potentially model global-scale eruptions from weak field regions.Comment: 23 pages, 7 figures, accepted for publicaiton in Ap

Seroprevalence Study of Pertussis in Adults at Childbearing Age and Young Infants Reveals the Necessity of Booster Immunizations in Adults in China

In China, the vaccination strategy against pertussis is started from 3 months of age, with no booster dose used after the booster given at two years. Despite a high vaccination coverage, pertussis has been increasingly reported since the last decade. This study evaluates the prevalence of serum anti-pertussis toxin (PT) IgG antibodies in adults at childbearing age and infants before the age of primary immunization in Beijing, China. A total of 1175 serum samples randomly selected from individuals who attended an annual health examination at the Sixth Medical Center of the PLA General Hospital, Beijing, in 2019, was included. The geometric mean concentration (GMC) and median concentration of anti-PT IgG antibodies among adults aged 20-39 years were 3.81 IU/mL and 3.24 IU/mL, and the corresponding concentrations were 1.72 IU/mL and 1.43 IU/mL among infants under 3 months of age. The seroprevalence of PT IgG antibodies >= 40 IU/mL in adults and infants was 2.0% (15/735) and 1.1% (5/440). In total, 65.99% (485/735) of adults and 83.41% (367/440) of infants had non-detectable pertussis-specific antibodies (<5 IU/mL). Our results showed that the majority of adults at a reproductive age and young infants are vulnerable to pertussis, suggesting that booster vaccinations in adults should be considered in this country

Serum cytokine profile of pediatric patients with laboratory confirmed pneumococcal meningitis

Background: Streptococcus pneumoniae infection is a leading cause of bacterial meningitis in children with severe sequelae. Cytokines are important molecules in regulating of host inflammatory and antiinflammatory responses. So far, the cytokine profile of bacterial meningitis caused by single pathogen has been rarely reported. The aim of this study was to explore serum cytokine profile in pediatric patients with pneumococcal meningitis (PM) and its clinical relevance which could be considered as a valuable tool for differential diagnosis of PM.Methods: During 2015 & ndash;2018, 95 children with laboratory-confirmed PM were included. Of them, 63 had serum samples at admission. Ten cytokines including TNF-a, IL-12p40, IL-17A, IL-1(3, IFN-eta, GM-CSF, IL-10, CXCL-1, IL-8 and IL-13 were measured by multiplex immunoassay in sera of 63 PM patients and 55 age-matched healthy controls (HCs). Level of serum cytokines was compared with different clinical features of patients.Results: Significantly higher level of IL-10 was observed in patients than HCs (median, 2.19 vs. 1.92 pg/mL, p = 0.017). Significantly lower levels of serum IL-12p40, IL-17A and IL-1 beta were observed in patients than HCs (median, 0.68 vs. 10.12 pg/mL, p Conclusions: Our results suggested that there might be significant changes in serum pro-inflammatory and anti-inflammatory cytokines in PM children and that the determination of these cytokines may have limited value for evaluation of clinical outcome of pediatric PM.(c) 2021 The Author(s). Published by Elsevier Ltd on behalf of King Saud Bin Abdulaziz University for Health Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).</div

Seroprevalence of Pertussis in Adults at Childbearing Age Pre- and Post- COVID-19 in Beijing, China

The number of reported pertussis cases has significantly decreased during the coronavirus disease 2019 (COVID-19) pandemic under the influence of strict public health measures in many countries including China. This study evaluated the prevalence of serum anti-pertussis toxin (anti-PT) IgG antibodies in adults at childbearing age pre- and post- COVID-19 in Beijing, China. Altogether, 2021 serum samples collected from individuals aged 20 to 39 years who attended an annual health examination at the Sixth Medical Center of PLA General Hospital, Beijing, in 2018--2020 were measured by ELISA. The median concentration of anti-PT IgG antibodies among participants in 2020 (2.96 IU/mL) was significantly lower than that in 2018 (3.27 IU/mL) (p = 0.011) and in 2019 (3.24 IU/mL) (p = 0.014). The percentage of participants with anti-PT IgG antibodies higher than 40 IU/mL (indicating a pertussis infection within the past few years) was 1.79% (9/503) in 2018, 2.04% (15/735) in 2019 and 1.66% (13/783) in 2020, respectively. The corresponding numbers of the non-detectable (<5 IU/mL) rate of anti-PT IgG antibodies were 66.60%, 65.99% and 70.24%. Our results showed that there was a significant difference between true and reported incidence rates even during the COVID-19 pandemic. The proportion of adults at childbearing age without pertussis-specific antibodies is high, suggesting that booster vaccinations in adults should be considered in this country