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Abstract Background Acute and critical neurological diseases are often accompanied with elevated intracranial pressure (ICP), leading to insufficient cerebral perfusion, which may cause severe secondary lesion. Existing ICP monitoring techniques often fail to effectively meet the demand for real-time noninvasive ICP monitoring and warning. This study aimed to explore the use of electrical impedance tomography (EIT) to provide real-time early warning of elevated ICP by observing cerebral perfusion. Methods An intracranial hypertension model was prepared by injecting autologous un-anticoagulated blood into the brain parenchyma of twelve Landrace swine. Invasive ICP monitoring was used as a control method, and a high-precision EIT system was used to acquire and analyze the changing patterns of cerebral perfusion EIT image parameters with respect to ICP. Four EIT parameters related to cerebral perfusion were extracted from the images, and their potential application in detecting ICP elevation was analyzed. Results When ICP increased, all EIT perfusion parameters decreased significantly (P 22 mmHg), the correlation between EIT perfusion parameters and ICP was more significant (P

Background: Acute and critical neurological diseases are often accompanied with elevated intracranial pressure (ICP), leading to insufficient cerebral perfusion, which may cause severe secondary lesion. Existing ICP monitoring techniques often fail to effectively meet the demand for real-time noninvasive ICP monitoring and warning. This study aimed to explore the use of electrical impedance tomography (EIT) to provide real-time early warning of elevated ICP by observing cerebral perfusion. Methods: An intracranial hypertension model was prepared by injecting autologous un-anticoagulated blood into the brain parenchyma of twelve Landrace swine. Invasive ICP monitoring was used as a control method, and a high-precision EIT system was used to acquire and analyze the changing patterns of cerebral perfusion EIT image parameters with respect to ICP. Four EIT parameters related to cerebral perfusion were extracted from the images, and their potential application in detecting ICP elevation was analyzed. Results: When ICP increased, all EIT perfusion parameters decreased significantly (P < 0.05). When the subjects were in a state of intracranial hypertension (ICP > 22 mmHg), the correlation between EIT perfusion parameters and ICP was more significant (P < 0.01), with correlation coefficients ranging from −0.72 to −0.83. We tested the objects when they were in baseline ICP and in ICP of 15–40 mmHg. Under both circumstances, ROC curve analysis showed that the comprehensive model of perfusion parameters based on the random forest algorithm had a sensitivity and specificity of more than 90% and an area under the curve (AUC) of more than 0.9 for detecting ICP increments of both 5 and 10 mmHg. Conclusion: This study demonstrates the feasibility of using perfusion EIT to detect ICP increases in real time, which may provide a new method for real-time non-invasive monitoring of patients with increased ICP. [ABSTRACT FROM AUTHOR]

Metal additive manufacturing (MAM) technology has experienced rapid development in recent years. As both equipment and materials progress towards increased maturity and commercialization, material metallurgy technology based on high energy sources has become a key factor influencing the future development of MAM. The calculation of phase diagrams (CALPHAD) is an essential method and tool for constructing multi-component phase diagrams by employing experimental phase diagrams and Gibbs free energy models of simple systems. By combining with the element mobility data and non-equilibrium phase transition model, it has been widely used in the analysis of traditional metal materials. The development of CALPHAD application technology for MAM is focused on the compositional design of printable materials, the reduction of metallurgical imperfections, and the control of microstructural attributes. This endeavor carries considerable theoretical and practical significance. This paper summarizes the important achievements of CALPHAD in additive manufacturing (AM) technology in recent years, including material design, process parameter optimization, microstructure evolution simulation, and properties prediction. Finally, the limitations of applying CALPHAD technology to MAM technology are discussed, along with prospective research directions. [ABSTRACT FROM AUTHOR]

The widely used vertical bipolar inter-company (VBIC) model for bipolar junction transistor-heterjunction bipolar transistors (HBTs) was modified to incorporate high-current effects. The modified VBIC model keeps all features of the original model and adds new features such as mobile carrier modulation of the base-collector capacitance, high-current Kirk effects, high-current reverse emitter-base injection, and current dependence of the reverse transit time in HBTs. The new model accurately fits the dc I-V characteristics, the bias-dependent transit-time, and S-parameters at active and quasi-saturation region biases. It is shown that the new formulation accurately models the strong current dependence of [f.sub.t] and [G.sub.max] over a wide range of biases. It also predicts very well the power performance in class-AB operation and at the loading for maximum power-added efficiency and maximum output power. The model also shows good fitting of two-tone linearity characteristics when simulated with the same fundamental and harmonic load conditions as in the measurements. Index Terms--Heterojunction bipolar transistor (HBT), high current, semiconductor device modeling, vertical bipolar inter-company (VBIC).

Optimum loading for a power enhancement-mode pseudomorphic high electron-mobility transistor (E-pHEMT) is determined by a systematic harmonic load-pull simulation. The simulation uses a modified Angelov-Parker model that can accurately predict dc, small-signal RF, and power performance of the devices. The optimum second harmonic loading for a 2-mm device is found to be open circuit and the optimum third harmonic is at the third quadrant, which is about 1 [angle] 210[degrees]. The measured versus modeled results show very good agreement and, therefore, verify the model. The simulation predicts that as high as 80% poweradded efficiency can be achieved for E-pHEMT under optimum source and load termination with harmonic tuning.

Using novel characterization techniques, output gain, and phase jumps (with respect to input frequency or input level) of multistage monolithic-microwave integrated-circuit power amplifiers were correlated with heterojunction field-effect transistor (HFET) drain-current kinks and negative gate resistances. Both physical and phenomenological models were used to explain the correlation through hole-trapping and self-biasing mechanisms. A remedy involving bias-stabilization diodes was experimentally verified. Other possible remedies are also discussed. The present conclusion can be extended to other metal-semiconductor field-effect transistor and HFET amplifiers with similar gain/phase jump problems. Index Terms - Charge - carrier processes, electric breakdown, gain control, heterojunction, MESFET's, microwave power amplifiers, MMIC's, phase control.

A comprehensive large-signal model of a GaAs MESFET is presented to account for charge conservation and effects of dispersion and self-heating. An improved set of capacitance and charge equations, along with an enhanced Triquint Own model (TOM)-like drain current model, is used for consistent small- and large-signal simulations. Charge conservation is satisfied by deriving the capacitance part of the model from charge equations. Transconductance and output conductance dispersion is modeled by combination of a feedback network and a subcircuit, which describes the self-heating effect. An improved description of the near-pinchoff characteristics, high-voltage breakdown, and gain compression at high-current region in the TOM is introduced. The new model accurately predicts the I-V, CV, bias-dependent S-parameter, waveform, power, and linearity characteristics of the MESFET.

A large-signal heterojunction bipolar transistor (HBT) model has been developed which includes self-heating, collector transit-time, and RF-breakdown effects. The model has a compact form which is based on a compromise between accuracy and utility. As such, the model can be readily extracted and verified with the aid of RF waveform measurements. Using the model in simulations, it was found that RF breakdown was dependent on base biasing and loading conditions. Therefore, with proper circuit design, the maximum output power of the HBT can significantly exceed the limit of open-base breakdown voltage.

Bioreactor is the key equipment of microbial metabolic reactions. The heat transfer of bioreactor is very important to cell growth, reproduction and metabolism. However, there are few reports on heat transfer in bioreactor so far. Here, a new type of plate-fin heat exchanger with high efficiency is introduced for replacing the traditional heat transfer mode of bioreactor, and coe!ficients of heat transfer of the plate-fin heat exchanger and the tubular heat exchangers under different conditions of no ventilation, ventilation, viscosity, stirring speeds and ventilations are compared. Results show that coe!ficients of heat transfer of the plate-fin heat exchanger can reach 5-6 times of that of the tubular heat exchanger, and coe!ficient of heat transfer of the two kinds of heat exchangers in the case of ventilation is 2-3 times of that in the case of no ventilation. Results indicate that the introduction of a new type of high-eeficiency heat exchanger in bioreactor can not only save energy and reduce consumption, but also benefit the development of fermentation industry. At the same time, this study can provide reference for the application of the plate-fin heat exchanger in bioreactor. [ABSTRACT FROM AUTHOR]

Fatty acids (FAs) are one of the important factors that can influence cell growth and membrane composition. The aim of this study was to investigate the influence of supplementing MLM+ growth medium with C18 free fatty acids (C18-FFAs), including stearic (C18:0), oleic (C18:1), linoleic (C18:2), and linolenic (C18:3) acid, on the growth of Lactobacillus plantarum CICC21001 by forming ion pairs with lysine to increase the solubility of FAs in liquid medium. The utilization of C18-FFAs was further confirmed by GC-FID. The investigation of cell properties, including cell surface hydrophobicity and zeta potential, was carried out for the modified L. plantarum and control group (non-supplementation). Furthermore, cell survival was measured in real time under heat (at 55 and 62 °C for 5 min), acid (pH 2.2), and bile salt stress. Our results indicated that the action of L. plantarum was modulated by assimilating C18-FFAs. This study suggested that C18-FFAs altered the life cycles and physiochemical properties of L. plantarum, which provided a guideline for probiotics production and their medical application. [ABSTRACT FROM AUTHOR]

Fatty acids, composed of an amphiphilic carbon chain and a carboxyl group, are a simple class of anion surfactants when they are protonated in the presence of an alkali. They can form ion-pairing amphiphile molecules and self-assemble into different nanostructures, which can be widely applied. However, the phase transition of these nanostructures can be easily triggered by external conditions, such as pH, temperature, the addition of salts and so on. In this work, medium-chain fatty acids (MCFAs) containing 8–12 carbons were chosen as the objects for self-assembly with organic amino counter-ions, l-arginine. We investigated the effects of chain length, pH, temperature and solvent on the phase transition based on diagrams, which could be determined by freeze fracture transmission electron microscopy (FF-TEM) and polarizing microscopy observations (PMO) combined with rheological properties. The results showed that rich phase behavior was observed in the octanoic acid (C8:0) system. However, it was insensitive to changes in pH because of the lower hydrophobicity. In contrast, for decanoic acid (C10:0) and lauric acid (C12:0) systems, phase transition from the L1 phase (micelles) to the Lα phase (vesicles) was observed and they showed stimulus-response to the change of pH. At the same time, lauric acid was sensitive to temperature, which was ascribed to the higher Krafft point. Besides, when the solvent was replaced by glycerin, phase transitions occurred from vesicles to micelles in these three systems. We hope that this phase transition observed in the MCFA system will provide a good insight into drug delivery, material science, and other related areas. [ABSTRACT FROM AUTHOR]

BACKGROUND: Escherichia coli AFP111, a facultative anaerobic strain, shows a very lowcell growth and succinic acid production rate in minimal medium during exclusively anaerobic fermentation. Therefore, atmospheric and room temperature plasma (ARTP) and adaptive laboratory evolution (ALE) strategies were adopted to improve cell growth and succinic acid production under anaerobic conditions. RESULTS: A mutant, BER208, was obtained by ARTP and ALE used successively. When cultured in a 3 L stirred bioreactor, the specific growth rate of BER208was increased 3.12-fold comparedwith AFP111. Also, it consumed 40 g L-1 glucose and produced 27.9 g L-1 succinic acid with a glucose utilization rate of 0.54 g L-1 h-1 and succinic acid productivity of 0.38 g L-1 h-1,whichwere 3.7-fold and 2.5-fold higher than those of the original strain. Further investigation showed that the activities of glucokinase and phosphoenolpyruvate carboxykinase (PCK)were increased 3.3-fold and 16-fold in the mutant comparedwith the original strain. CONCLUSION: The combinedstrategyofARTPandALEwas aneffective approach to obtainmutants with improved performance. [ABSTRACT FROM AUTHOR]