课程文献中心 更多>>

关键词： fetal alcohol syndrome   fetal growth   intervention   Placenta   sex-specific effects  

摘要： Background Fetal alcohol spectrum disorders (FASD) are preventable adverse outcomes consequent to prenatal alcohol exposure. Supplemental choline confers neuroprotection to the alcohol-exposed offspring, but its actions outside the brain are unclear. We previously reported that prenatal exposure of mice to 4.5 g/kg of alcohol decreased placental weight in females only, but decreased body weight and liver-to-body weight ratio and increased brain-to-body weight ratio in both sexes. Here we test the hypotheses that a lower alcohol dose will elicit similar outcomes, and that concurrent choline treatment will mitigate these outcomes. Methods Pregnant C57BL/6J mice were gavaged with alcohol (3 g/kg;Alc) or maltodextrin (MD) from embryonic day (E) 8.5-17.5. Some also received a subcutaneous injection of 100 mg/kg choline chloride (Alc + Cho, MD + Cho). Outcomes were evaluated on E17.5. Results Alc dams had lower gestational weight gain than MD;this was normalized by choline. In males, Alc decreased placental weight whereas choline increased placental efficiency, and Alc + Cho (vs. MD) tended to further reduce placental weight and increase efficiency. Despite no significant alcohol effects on these measures, choline increased fetal body weight but not brain weight, thus reducing brain-to-body weight ratio in both sexes. This ratio was also lower in the Alc + Cho (vs. MD) fetuses. Alc reduced liver weight and the liver-to-body weight ratio;choline did not improve these. Placental weight and efficiency correlated with litter size, whereas placental efficiency correlated with fetal morphometric measurements. Conclusions Choline prevents an alcohol-induced reduction in gestational weight gain and fetal body weight and corrects fetal brain sparing, consistent with clinical findings of improvements in alcohol-exposed children born to mothers receiving choline supplementation. Importantly, we show that choline enhances placental efficiency in the alcohol-exposed offspring but does

关键词： Oscillatory ordinary differential equations   Nested Picard Integrator   Uniformly accurate  

摘要： A uniformly second order accurate nested Picard iterative integrator (NPI) is proposed to solve a system of oscillatory ordinary equations involving a parameter 0 < epsilon <= 1. The solution of this system propagateswave with O(epsilon(2)) wavelength and O(epsilon(4))/O(epsilon(2)) amplitude for well-prepared/ill-prepared initial data. Based on the NPI and the exponential integrator, a uniformly accurate (w.r.t epsilon) second order numerical scheme with O(tau(2)) error has been developed. The method can be generalized to higher order. Numerical tests are presented to confirm our error estimates.

关键词： electrocorticography   epilepsy   glutamate transporters   glutaminase   glutamine synthetase   in vivo voltammetry   pentylenetetrazole  

摘要： Epilepsy is a neurological disorder resulting from abnormal neuronal firing in the brain. Glutamate transporters and the glutamate-glutamine cycle play crucial roles in the development of seizures. In the present study, the correlation of epilepsy with glutamate transporters and enzymes was investigated. Herein, male Wistar rats were randomly allocated into four groups (six animals/group);35 mg/kg pentylenetetrazole (PTZ) was used to induce a kindling model of epilepsy. Once the kindling model was established, animals were treated for 15 days with either valproic acid (VPA, 350 mg/kg) or ceftriaxone (CEF, 200 mg/kg) in addition to the control group receiving saline. After treatment, electrocorticography (ECoG) was performed to record the electrical activity of the cerebral cortex. The glutamate reuptake time (T-80) was also determined in situ using an in vivo voltammetry. The expression levels of glutamate transporters and enzymes in the M1 and CA3 areas of the brain were determined using a real-time polymerase chain reaction (RT-PCR). ECoG measurements showed that the mean spike number of the PTZ + VPA and PTZ + CEF groups was significantly lower (p < 0.05) than that of the PTZ group. Compared with the PTZ group, VPA or CEF treatment decreased the glutamate reuptake time (T-80). The expression levels of EAAC1, GLT-1, GLAST, glutamine synthetase (GS), and glutaminase were increased in the PTZ group. Treatment with VPA or CEF enhanced the expression levels of GLT-1, GLAST, EAAC1, and GS, whereas the glutaminase expression level was reduced. The current results suggest that VPA or CEF decreases seizure activity by increasing glutamate reuptake by upregulating GLT-1 and GLAST expression, implying a possible mechanism for treating epilepsy. Also, we have suggested a novel mechanism for the antiepileptic activity of VPA via decreasing glutaminase expression levels. To our knowledge, this is the first study to measure the glutamate reuptake time in situ during the seizure

关键词： Crack growth   Fracture   Peridynamics   Peridynmaic differential operators (PDOs)   Nonlocal differential operators (NDOs)  

摘要： In recent years, two types of nonlocal differential operators and their theories and formulations have been proposed and used in numerical modeling and computations, particularly simulations of material and structural failures, such as fracture and crack propagations in solids. Since the differences of these nonlocal operators are subtle, and they often cause confusion and misunderstandings. The first type of nonlocal differential operators is derived from the Taylor series expansion of nonlocal interpolation, e.g., Bergel and Li (Comput Mech 58(2):351-370, 2016), Madenci et al. (Comput Methods Appl Mech Eng 304:408-451, 2016) and Ren et al. (Comput Methods Appl Mech Eng 358:112621, 2020). The second type of nonlocal operators is based on the nonlocal operator theory in peridynamic theory, which is a class of antisymmetric nonlocal operators stemming from the nonlocal balance laws, e.g., Gunzburger and Lehoucq (Multiscale Model Simul 8(5):1581-1598, 2010) and Du et al. (SIAM Rev 54(4):667-696, 2012;Math Models Methods Appl Sci 23(03):493-540, 2013a). In this work, a comparative study is conducted for evaluating the computational performances of these two types of nonlocal differential operators. It is found that the first type of nonlocal differential operators can yield convergent results in both uniform and non-uniform particle distributions. In contrast, the second type of nonlocal differential operators can only converge in uniform particle distributions. Specifically, we have evaluated the performance of the two types of nonlocal differential operators in three crack propagation simulation examples. The results show that the second type of nonlocal differential operators is more suitable to deal with complex crack branching patterns than the first type of nonlocal differential operators, and the simulation results obtained by using the second type of nonlocal differential operators have better agreement with experimental observations. For modelings of simple cr

关键词： Sensitivity   Frequency estimation   Optimization   Memetics   Harmonic analysis   Particle swarm optimization   Cutoff frequency   Adaptive periodic-disturbance observer (APDOB)   differential evolutionary (DE) algorithm   Levy flight   periodic disturbance   memetic algorithm  

摘要： Periodic disturbances occur during repetitive operations, and compensation for the periodic disturbances is an important issue to realize precise machine works because the periodic disturbances deteriorate the control precision. In addition, the periodic disturbance becomes a frequency-varying periodic disturbance when the periodicity of the operations changes, which makes the compensation difficult. To eliminate the frequency-varying periodic disturbance, an adaptive periodic-disturbance observer (APDOB) was proposed. However, the APDOB has a problem that the design of the APDOB is complicated with six design parameters. This article proposes a differential evolutionary algorithm with local search that optimizes the six design parameters of the APDOB for the optimal frequency-varying periodic disturbance compensation. The proposed method based on a memetic algorithm framework can explore globally using the differential evolutionary algorithm and explore locally using the local search including the Levy flight. Moreover, the proposed method can reduce the number of the design parameters.

关键词： High-Q   Quadrature voltage-controlled oscillator (QVCO)   Phase noise   Complementary metal-oxide semiconductor (CMOS)   Symmetric differential inductor  

摘要： Phase noise performance and current consumption of radio frequency (RF) voltage controlled oscillator (VCO) are largely dependent on the Quality (Q) factor of inductor-capacitor (LC) tank. Because the Q-factor of the LC tank is determined by an on-chip differential inductor, we designed, analyzed, and modeled the differential inductor using the high-frequency structure simulator software (HFSS), we could estimate the Q-factor and inductance of the differential symmetric inductor, to enhance the differential Q-factor, reduce current consumption and save silicon area. To verify its use in RF applications, we designed a 5 GHz differential LC-QVCO. Because accurate quadrature local oscillator (LO) signal is a key element in modern wireless transceivers, especially for direct conversion transceivers which are proliferating in a wide range of RF communication systems. Quadrature LO can be obtained by letting VCO oscillate at double the desired frequency and dividing its output. The higher oscillation frequency and frequency division circuitry, however, results in increased power consumption. Quadrature LO can also be obtained by feeding the differential outputs of the VCO oscillating at the desired frequency to a polyphase filter which is usually implemented as an RC network. This scheme results in substantial power consumption as well due to the LO buffers required to compensate for the loss of the passive filter. The third method of quadrature LO generation is QVCO where two symmetric LC-tank VCOs are coupled to each other. To obtain a smaller chip area and higher Q-factor, herein we designed a high-performance symmetric differential inductor for IEEE 802.11a and used it to design a quadrature voltage-controlled oscillator (QVCO). Using the high-frequency structure simulator software (HFSS), we could estimate the Q-factor and inductance of the differential symmetric inductor. Using a 0.13-mu m CMOS process, the proposed differential inductor was designed with a width of

关键词： Bacillus licheniformis   Multicellularity of bacteria   Colonial dynamics   Exopolysaccharides   Heavy metal-resistant bacteria  

摘要： Bacillus licheniformis is a multi-metal tolerant bacteria, isolated from the paddy rhizospheric soil sample. Upon the multiple metal toxicity, B. licheniformis altered their phenotypic/morphogenesis. Here we examined the effects of cadmium (Cd2+), chromium (Cr2+), and mercury (Hg2+) on the morphogenesis of B. licheniformis in comparison to control. We found that the ability of bacteria to grow effectively in presence of cadmium and chromium comes at a cost of acquiring cell density-driven mobility and reformation of filamentous to donut shape respectively. In particular, when bacteria grown on mercury it showed the bacteriostatic strategy to resist mercury. Furthermore, the findings suggest a large variation in the production of exo-polysaccharides (EPS) and suggest the possible role of EPS in gaining resistance to cadmium and chromium. Together this study identifies previously unknown characteristics of B. licheniformis to participate in bioremediation and provides the first evidence on positive effects of bacterial morphogenesis and the involvement of EPS in bacteria to resisting metal toxicity.

关键词： Conformable fractional stochastic   integrodifferential equations   Approximate controllability   Null controllability   Rosenblatt process  

摘要： In this work, we consider a class of conformable fractional stochastic differential equations driven by Rosenblatt process. By employing stochastic analysis, fractional calculus and fixed point theorem, we investigate the approximate controllability and null controllability results for the considered problems. Finally, two examples are introduced to explain the obtained results. (C) 2021 Elsevier B.V. All rights reserved.

关键词： differential microstrip sensor   urine sensor   complex permittivity   open-stub resonator  

摘要： A microstrip highly sensitive differential sensor for complex permittivity characterization of urine samples was designed, fabricated and tested. The sensing area contains two pairs of open-stub resonators, and the working frequency of the unloaded sensor is 1.25 GHz. The sensor is easily implemented on an affordable substrate FR-4 Epoxy with a thickness of 1.6 mm. A Teflon beaker is mounted on the sensor without affecting the measurements. Numerically, liquid mixtures of water and urine at different percentages were introduced to the proposed sensor to evaluate the frequency variation. The percentage of water content in the mixture varied from 0% (100% urine) to 100% (0% urine) with a step of 3.226%, thus giving 32 data groups of the simulated results. Experimentally, the mixtures of: 0% urine (100% water), 20% urine (80% water), 33% urine (66% water), 50% urine (50% water), 66% urine (33% water), and 100% urine (0% water) were considered for validation. The complex permittivity of the considered samples was evaluated using a nonlinear least square curve fitting in MATLAB in order to realize a sensing sensitivity of about 3%.

关键词： Distributed order fractional differential equations   Caputo fractional derivative   The second kind Chebyshev wavelets   Operational vector   Error bound  

摘要： The main aim of this research study is to present a new and efficient numerical method based on the second kind Chebyshev wavelets for solving the general form of distributed order fractional differential equations in the time domain with the Caputo fractional derivatives. For the first time, based on the second kind Chebyshev wavelets, an exact formula for the operational vector of the Riemann-Liouville fractional integral operator is derived by using the unit step function and Laplace transform method. Applying this operational vector via the collocation method in our approach provides an approximate solution by converting the problem under consideration into a system of algebraic equations which can be solved by the Newton method. Discussion on the error bound and convergence analysis for the proposed method is presented. Finally, five test problems are considered to confirm the reliability and effectiveness of the proposed method.