In this work, a kinetics‐integrated CFD model based on coupling computational fluid dynamics (CFD) and biokinetic was developed to guide the industrial scale‐up for fermentation of docosahexaenoic ...acid (DHA). Two‐substrate biokinetic equations for a 5 L bioreactor with oxygen and nitrogen source as limiting substrates were established, which were further coupled with CFD to simulate the biomass growth and lipid accumulation as well as flow field environment in the fermentation process. The coupled CFD‐biokinetic model can accurately reflect the changes of each relevant variable in the 50 L bioreactor under different operating conditions. The optimal working conditions of a 35 m3 bioreactor were predicted by this model and have secured the one‐step scale‐up of DHA fermentation, resulting in a biomass, lipid concentration, and DHA content in lipids of 99.2 g/L, 55.7 g/L, and 52.5%, respectively. This study thus provides an effective strategy for rapid industrial scale‐up of DHA production.
Polysaccharides are important active ingredients in Ophiocordyceps gracilis with many physiological functions. It can be obtained from the submerged fermentation by the anamorph (Paraisaria dubia) of ...Ophiocordyceps gracilis. However, it was found that the mycelial pellets of Paraisaria dubia were dense and increased in volume in the process of fermentation, and the center of the pellets was autolysis due to the lack of nutrient delivery, which extremely reduced the yield of polysaccharides. Therefore, it is necessary to excavate a fermentation strategy based on morphological regulation for Paraisaria dubia to promote polysaccharides accumulation.
In this study, we developed a method for enhancing polysaccharides production by Paraisaria dubia using microparticle enhanced technology, talc microparticle as morphological inducer, and investigated the enhancement mechanisms by transcriptomics. The optimal size and dose of talc were found to be 2000 mesh and 15 g/L, which resulted in a high polysaccharides yield. It was found that the efficient synthesis of polysaccharides requires an appropriate mycelial morphology through morphological analysis of mycelial pellets. And, the polysaccharides synthesis was found to mainly rely on the ABC transporter-dependent pathway revealed by transcriptomics. This method was also showed excellent robustness in 5-L bioreactor, the maximum yields of intracellular polysaccharide and exopolysaccharides were 83.23 ± 1.4 and 518.50 ± 4.1 mg/L, respectively. And, the fermented polysaccharides were stable and showed excellent biological activity.
This study provides a feasible strategy for the efficient preparation of cordyceps polysaccharides via submerged fermentation with talc microparticles, which may also be applicable to similar macrofungi.
Mapping neural circuits is critical for understanding the structure and function of the nervous system. Engineered viruses are a valuable tool for tracing neural circuits. However, current tracers do ...not fully meet the needs for this approach because of various drawbacks, such as toxicity and characteristics that are difficult to modify. Therefore, there is an urgent need to develop a new tracer with low toxicity and that allows for long-term studies. In this study, we constructed an engineered Sindbis virus (SINV) expressing enhanced green fluorescent protein (EGFP) reporter gene (SINV-EGFP) and found that it had no significant difference in biological characterization compared with the wild-type Sindbis virus in BHK-21 cells and neurons in vitro. We injected the virus into the visual circuit of mouse brain and found that the virus infected neurons in the local injected site and anterogradely spread in the neural circuits. Although the efficiency of transmission was limited, the findings demonstrate that SINV can be used as a new anterograde tracer to map neural circuits in mouse brain and that it spreads exclusively in the anterograde direction. Further, use of SINV in mouse brain research will provide longer time windows for circuit tracing than is possible with herpes simplex virus and vesicular stomatitis virus tracers.
Abstract
This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) telescope. The development of key low ...noise microwave parts of coupling low noise amplifier (Coupling-LNA) and conical quad-ridge orthogonal mode transducers (OMT) and reasonable system integration achieve outstanding performance of receiver. It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver. Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. Its return loss is more than 18 dB, and output 1 dB compression power is +5 dBm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver’s system noise temperature is below 9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.
Abstract
This paper presents an ultra-wide bandwidth (UWB) low-frequency radio astronomical cryogenic receiver for the Five-hundred-meter Aperture Spherical radio Telescope (FAST). It covers 6.6:1 ...bandwidth from 0.5 to 3.3 GHz. The receiver consists of a Quad-Ridged Flared Horn (QRFH), a cryogenic microwave unit, an optical transceiver and a warm microwave and frequency mixing unit. A QRFH with a concentric-loaded dielectric spear is developed: the average return losses are larger than 20 dB; the average ports polarization isolation is 43.87 dB; the average dish efficiency is higher than 65%. Many UWB cryogenic low loss components are developed for the fabrication of a cryogenic microwave unit. The average noise temperature lower than 14.2 K and 22.5 K are achieved as referred to the input ports of cryogenic Dewar and the output of horn, respectively. Compared to other similar advanced UWB receivers, such as Parkes 0.7–4.2 GHz (6:1 bandwidth) receiver and FAST 0.27–1.62 GHz (6:1 bandwidth) receiver, wider relative bandwidth of the proposed receiver is achieved and it is a new attempt to expand the bandwidth of UWB low-frequency receiver.
This paper describes the design, construction, and performance of the wideband orthomode transducers (OMTs) for the L- (1.2-1.8 GHz), the S- (2-3 GHz) and the P- (0.56-1.12 GHz) band receiver systems ...of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These OMTs operate at the cryogenic temperature of 70K to reduce their thermal noise contribution to the receiver chains. The development on the FAST L- and S-band quad-ridged waveguide (QRWG) OMTs is carried out based on the theoretical mode analysis. In view of the miniaturization of FAST cryogenic receiver system at P-band, a novel wideband compact bowtie dipole OMT is designed with an octave bandwidth as well as a length of only quarter wavelength. The proposed L-, S- and P-band OMTs are designed and optimized by using Ansys High Frequency Structure Simulator (HFSS), and then manufactured, tested at room temperature. Measurement of FAST cryogenic receiver system noise is also performed with the L-, S- and P-band OMTs installed. The measured results fully comply with the design specifications.
This paper reports on the time and frequency standard system for the Five-hundred meter Aperture Spherical radio Telescope (FAST), including the system design, stability measurements and pulsar ...timing observations. The stability and drift rate of the frequency standard are calculated using 1-year monitoring data. The UTC-NIM Disciplined Oscillator (NIMDO) system improves the system time accuracy and stability to the level of 5 ns. Pulsar timing observations were carried out for several months. The weighted RMS of timing residuals reaches the level of less than 3.0 μs.
This study aims to develop a fermentation method instead of fruiting body extraction for Cordyceps polysaccharide (CP). The fermentation characteristics of P. dubia at different pH were inspected. ...The mechanism of microcycle conidiation of P. dubia was activated under pH 9.0 and produced yeast-like spores. A pH-shift strategy was raised based on the analysis of fermentation kinetics parameters. And, yeast-like spores were used as fermentation seeds to increase culture density. To further improve efficiency, a fed-batch fermentation with a pH-shift strategy was executed, CP production reached 13.54 g/L, with the productivity of 0.42 g/(L d), and the specific rate of CP to biomass was increased to 0.27, which improved by 47.6 %, 64.3 % and 97.1 % respectively, compared with fermentation without process controls. And, CP from fermented and extracted had the same monosaccharide composition except for differences in molecular weight. This study provides a feasible strategy for the efficient preparation of CP through spores fermentation.
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•Microcycle conidiation of P. dubia was activated at pH 9.0 and produced spores.•A spores fermentation method was first introduced to the production of CP.•The stage kinetic characteristics of CP fermentation by P. dubia were proposed.•A maximum CP yield of 13.54 g/L was gained in fed-batch with pH-shift strategy.
Dementia is increasing dramatically and imposes a huge burden on society. To date, there is a lack of data on the health status of patients with dementia in China. In an attempt to investigate the ...comorbidity burden of dementia patients in China at the national level, we enrolled 2,938 patients with Alzheimer’s disease(AD), vascular dementia(Va D), or other types of dementia, who were admitted to tertiary hospitals in seven regions of China from January2003 to December 2012. The Charlson Comorbidity Index(CCI) was used to evaluate the comorbidity burden of the patients with dementia. Among these patients, 53.4% had AD, 26.3% had Va D, and 20.3% had other types of dementia. The CCI was 3.0 ± 1.9 for all patients,3.4 ± 1.8 for those with Va D, and 3.0 ± 2.1 for those with AD. The CCI increased with age in all patients, andthe length of hospital stay and daily expenses rose with age and CCI. Males had a higher CCI and a longer stay than females. Moreover, patients admitted in the last 5 years of the study had a higher CCI than those admitted in the first 5 years. We found that the comorbidity burden of patients with dementia is heavy. These findings provide a better understanding of the overall health status of dementia patients, and help to increase the awareness of clinicians and policy-makers to improve medical care for patients.
This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for FAST telescope. The development of key low noise microwave parts of Coupling-LNA and conical quad-ridge OMT and ...reasonable system integration achieve outstanding performance of receiver.It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver.Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. And its return loss is more than 18 dB, and output 1 dB compression power is +5 dBm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver's system noise temperature is below 9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.
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