Zhongchao Tan

Subcritical hydrothermal liquefaction of cattle manure to bio-oil: effects of conversion parameters on bio-oil yield and characterization of bio-oil.

In this study, cattle manure was converted to bio-oil by subcritical hydrothermal liquefaction in the presence of NaOH. The effects of conversion temperature, process gas, initial conversion pressure, residence time and mass ratio of cattle manure to water on the bio-oil yield were studied. The bio-oil was characterized in terms of elemental composition, higher heating value, ultraviolet-visible (UV/Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Results showed that the bio-oil yield depended on the conversion temperature and the process gas. Higher initial conversion pressure, longer residence time and larger mass ratio of cattle manure to water, however, had negative impacts on the bio-oil yield. The higher heating value of bio-oil was 35.53MJ/kg on average. The major non-polar components of bio-oil were toluene, ethyl benzene and xylene, which are components of crude oil, gasoline and diesel.

Thalamus provides layer 4 of primary visual cortex with orientation- and direction-tuned inputs

Understanding the functions of a brain region requires knowing the neural representations of its myriad inputs, local neurons and outputs. Primary visual cortex (V1) has long been thought to compute visual orientation from untuned thalamic inputs, but very few thalamic inputs have been measured in any mammal. We determined the response properties of ∼28,000 thalamic boutons and ∼4,000 cortical neurons in layers 1–5 of awake mouse V1. Using adaptive optics that allows accurate measurement of bouton activity deep in cortex, we found that around half of the boutons in the main thalamorecipient L4 carried orientation-tuned information and that their orientation and direction biases were also dominant in the L4 neuron population, suggesting that these neurons may inherit their selectivity from tuned thalamic inputs. Cortical neurons in all layers exhibited sharper tuning than thalamic boutons and a greater diversity of preferred orientations. Our results provide data-rich constraints for refining mechanistic models of cortical computation.

Multiplexed aberration measurement for deep tissue imaging in vivo.

We describe an adaptive optics method that modulates the intensity or phase of light rays at multiple pupil segments in parallel to determine the sample-induced aberration. Applicable to fluorescent protein–labeled structures of arbitrary complexity, it allowed us to obtain diffraction-limited resolution in various samples in vivo. For the strongly scattering mouse brain, a single aberration correction improved structural and functional imaging of fine neuronal processes over a large imaging volume.

Alkaline hydrothermal conversion of cellulose to bio-oil: Influence of alkalinity on reaction pathway change

The effects of alkalinity on alkaline hydrothermal conversion (alkaline-HTC) of cellulose to bio-oil were investigated in this study. The results showed that the initial alkalinity greatly influenced the reaction pathways. Under initial strong alkaline conditions with final pH greater than 7, alkaline-HTC only followed the alkaline pathway. However, under initial weak alkaline conditions with final pH of less than 7, acidic as well as alkaline pathways were involved. The main mechanism behind this change of reaction pathways under weak alkaline conditions was that carboxylic acids were first formed from cellulose via the alkaline pathway and then neutralized/acidified the alkaline solutions. Once the pH of the alkaline solutions decreased to less than 7, the acidic instead of the alkaline reaction pathway occurred. This change of the reaction pathways with initial alkalinity partly explained the inconsistent results in the literature of alkaline-HTC bio-oil compositions and yields.

SPRAY, IGNITION, AND COMBUSTION MODELING OF BIODIESEL FUELS FOR INVESTIGATING NOX EMISSIONS

The objective of this research was to develop a detailed numerical spray atomization, ignition, and combustion model for direct-injection diesel engines using KIVA3V code that could be applied to biodiesel fuels for investigating NOx emissions. Several modified or recalibrated submodels were incorporated into KIVA3V, including a KH-RT spray breakup model, a Shell ignition model, and a single-step kinetic combustion model. This modified model was applied to a John Deere 4045T direct-injection diesel engine fueled by a soybean methyl ester, a yellow grease methyl ester, and No. 2 diesel fuel. The output of the model was in close agreement with the experimental measurements of cylinder pressure and heat release rate from this engine. It was predicted from the modeling results that the two biodiesel fuels had shorter ignition delay and higher overall cylinder temperatures than diesel fuel. The in-cylinder spray analysis indicated that the soybean methyl ester had slightly longer penetration than diesel fuel, but the yellow grease methyl ester had shorter penetration than diesel fuel. Fewer particle numbers were predicted for the two biodiesel fuels. Both soybean methyl ester and yellow grease methyl ester had more widespread high-temperature distribution areas than diesel fuel, which could account for the increases in NOx emissions typically measured for biodiesel fuels.

Hydrothermal Conversion of Cellulose to 5-Hydroxymethyl Furfural

5-hydroxymethyl furfural (HMF) is an important biomass-derived material for alkane bio-oil production. HMF is currently produced from edible glucose and fructose. Until recently, some researchers successfully applied ionic liquids to convert cellulose, a type of inedible biomass, to HMF. However, ionic liquids usually are toxic and/or require sophisticated skills to prepare. It would be more cost-effective if water can be employed as the reaction media. This paper studied hydrothermal conversion of cellulose to HMF under acidic, neutral and alkaline conditions. The results showed that, at 275–320°C and the reaction residence time of 0–30 min, the order of HMF yields followed the order of acidic, neutral and alkaline conditions. In terms of HMF purity, the order changed to neutral, acidic and alkaline conditions. Moreover, high temperatures (>300°C) and long reaction residence time had negative effects on the HMF yields in acidic and neutral solutions, mostly because of the promoted decomposition and the polymerization of HMF to levulinic acid and char, respectively. Therefore, the conditions of acidic aqueous solutions, medium range temperatures and short reaction residence time were recommended for hydrothermal conversion of cellulose to HMF. On the other hand, this study revealed that cellulose can also be converted to HMF under alkaline conditions. With the carboxylic acids produced from cellulose under alkaline conditions, the initial alkaline hydrothermal condition can gradually become acidic.

How Particle Resuspension from Inner Surfaces of Ventilation Ducts Affects Indoor Air Quality—A Modeling Analysis

Dust particles deposited on the inner surfaces of the ventilation ducts can be resuspended by passing airflow. A physical-science-based model is developed to understand how particle resuspension affects the indoor air quality. This integrated model takes into consideration particle mass balance models for straight ventilation duct, duct bend, ventilation room, and air filter. The straight duct and room models have been validated using experimental data. With the integrated model, we find that in-duct resuspension of particles could lead to significant increase in exposure to airborne particles for indoor occupants. It is also found that indoor particle exposure is a linear function of dust mass loading. Greater ventilation rate, which means higher air speed above the dust particles, would lead to greater exposure ratio, while fresh air ratio has little influence. Possible control methods are discussed as well.

A Particle Resuspension Model in Ventilation Ducts

A turbulent burst model is used and evaluated for particle resuspension in ventilation ducts in this study. The model is a prolongation of the turbulent burst model developed by Cleaver and Yates with an approach to the critical jump-start air velocity for particle resuspension. This critical jump-start air velocity is introduced to estimate the fraction of particles resuspended under the turbulent burst. The model results were compared with experimental data that is available in literature. Both the model results and experiments show that resuspension rate increased with the increase of particle diameter and air speed in ducts. However, the model results did not show a significant decay of particle resuspension rate over time, which was shown in the experiments. Limitations of the model are discussed to explain the discrepancy between the model and the experimental results. Copyright 2012 American Association for Aerosol Research

Neuronal Representation of Ultraviolet Visual Stimuli in Mouse Primary Visual Cortex

The mouse has become an important model for understanding the neural basis of visual perception. Although it has long been known that mouse lens transmits ultraviolet (UV) light and mouse opsins have absorption in the UV band, little is known about how UV visual information is processed in the mouse brain. Using a custom UV stimulation system and in vivo calcium imaging, we characterized the feature selectivity of layer 2/3 neurons in mouse primary visual cortex (V1). In adult mice, a comparable percentage of the neuronal population responds to UV and visible stimuli, with similar pattern selectivity and receptive field properties. In young mice, the orientation selectivity for UV stimuli increased steadily during development, but not direction selectivity. Our results suggest that, by expanding the spectral window through which the mouse can acquire visual information, UV sensitivity provides an important component for mouse vision.

On the kinetics of the absorption of nitric oxide into ammoniacal cobalt(II) solutions.

Experiments were conducted using a custom double-stirred tank reactor to determine the rate constants of reactions between nitric oxide (NO) and both pentaaminecobalt(II) and hexaaminecobalt(II) at temperatures of 298.2 and 303.2 K and pH levels between 8.50 and 9.87 under atmospheric pressure. The NO concentration of simulated flue gas stream ranged from 400 to 1400 ppmv. Ammoniacal cobalt(II) solutions were prepared by adding aqueous ammonia into a cobalt(II) nitrate solution in the presence of concentrated ammonium nitrate. The reaction rate constants were calculated with an enhancement factor for gas absorption associated with parallel chemical reactions. The results showed that the reaction between NO and pentaaminecobalt(II) was first order with respect to both the NO and the pentaamminecobalt(II) ion. Similarly, the reaction between NO and hexaamminecobalt(II) was first order with respect to both the NO and the hexaamminecobalt(II) ion. The forward reaction rate constants of these two reactions were 6.43 × 10(6) and 1.00 × 10(7) L · mol(-1) · s(-1) at 298.2 K, respectively, and increased to 7.57 × 10(6) and 1.12 × 10(7) L · mol(-1) · s(-1) at 303.2 K, respectively. Ammoniacal cobalt(II) solutions also have the potential to simultaneously remove CO2, SO2, and NOx from postcombustion flue gas.