Microbe-Assisted Nanocomposite Anodes for Aqueous Li-Ion Batteries.

With the rapid increase in the use of lithium-ion batteries (LIBs), the development of safe LIBs has become an important social issue. Replacing flammable organic liquid electrolytes in current LIBs with water can be an alternative route to resolve this safety concern. The water-in-salt (WIS) electrolytes received great attention as next-generation electrolytes due to their large electrochemical stability window. However, their high cathodic limit remains as a challenge, impeding the use of low-potential anodes. Here, we report the first biodirected synthesis of carbonaceous layers on anodes to use them as interlayers that prevent a direct contact of water molecules to anode particles. High-aspect ratio microbes are utilized as precursors of carbonaceous layers on TiO2 nanoparticles (m-TiO2) to enhance the conductivity and to reduce the electrolysis of WIS electrolytes. We selected the cylindrical shape of microbes that offers geometric diversity, providing us a toolkit to investigate the effect of microbe length in forming the network in binary composites and their impacts on the battery performance with WIS electrolytes. Using microbes with varying aspect ratios, the optimal microbe size to maximize the battery performance is determined. The effects of storage time on microbe size are also studied. Compared to uncoated TiO2 anodes, m-TiO2 exhibited 49% higher capacity at the 40th cycle and enhanced the cycle life close to anodes made with a conventional carbon precursor while using an 11% less amount of carbon. We performed density functional theory calculations to unravel the underlying mechanism of the performance improvement using microbe-derived carbon layers. Computational results show that high amounts of pyridinic nitrogen present in the peptide bonds in microbes are expected to slow down the water diffusion. Our findings provide key insights into the design of an interlayer for WIS anodes and open an avenue to fabricate energy storage materials using biomaterials.

Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions.

The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

Using risk for advanced proximal colonic neoplasia to tailor endoscopic screening for colorectal cancer.

BACKGROUND: Colonoscopic screening for colorectal cancer has been suggested because sigmoidoscopy misses nearly half of persons with advanced proximal neoplasia. OBJECTIVE: To create a clinical index to stratify risk for advanced proximal neoplasia and to identify a subgroup with very low risk in which screening sigmoidoscopy alone might suffice. DESIGN: Cross-sectional study. SETTING: A company-based program of screening colonoscopy for colorectal cancer. PATIENTS: Consecutive persons 50 years of age or older undergoing first-time screening colonoscopy between September 1995 and June 2001. MEASUREMENTS: A clinical index with 3 variables was created from information on the first 1994 persons. Points were assigned to categories of age, sex, and distal findings. Risk for advanced proximal neoplasia (defined as an adenoma 1 cm or larger or one with villous histology, severe dysplasia, or cancer) was measured for each score. The index was tested on the next 1031 persons from the same screening program. RESULTS: Of 1994 persons, 67 (3.4%) had advanced proximal neoplasia. A low-risk subgroup comprising 37% of the cohort had scores of 0 or 1 and a risk of 0.68% (95% CI, 0.22% to 1.57%). Among the validation group of 1031 persons, risk for advanced proximal neoplasia in the low-risk subgroup (comprising 47% of the cohort) was 0.4% (upper confidence limit of 1.49%). Application of this index detected 92% of persons with advanced proximal neoplasms and, if applied following screening sigmoidoscopy, could reduce the need for colonoscopy by 40%. The marginal benefit of colonoscopy among low-risk persons was small: To detect 7 additional persons with advanced proximal neoplasia, 1217 additional colonoscopies would be required. CONCLUSIONS: This clinical index stratifies the risk for advanced proximal neoplasia and identifies a subgroup at very low risk. If it is validated in other cohorts or groups, the index could be used to tailor endoscopic screening for colorectal cancer.

Results of screening colonoscopy among persons 40 to 49 years of age.

BACKGROUND: The prevalence of colorectal lesions in persons 40 to 49 years of age, as identified on colonoscopy, has not been determined. METHODS: We reviewed the procedure and pathology reports for 906 consecutive persons 40 to 49 years of age who voluntarily participated in an employer-based screening-colonoscopy program. The histologic features of lesions that were identified and removed on endoscopy were categorized according to those of the most advanced lesion removed proximally (up to the junction of the splenic flexure and the descending colon) and the most advanced lesion removed distally. An advanced lesion was defined as an adenoma at least 1 cm in diameter, a polyp with villous histologic features or severe dysplasia, or a cancer. RESULTS: Among those who underwent colonoscopic screening, 78.9 percent had no detected lesions, 10.0 percent had hyperplastic polyps, 8.7 percent had tubular adenomas, and 3.5 percent had advanced neoplasms, none of which were cancerous (95 percent confidence interval for cancer, 0 to 0.4 percent). Eighteen of 33 advanced neoplasms (55 percent) were located distally and were potentially within reach of a sigmoidoscope. If these results are applicable to the general population, at least 250 persons, and perhaps 1000 or more, would need to be screened to detect one cancer in this age group. CONCLUSIONS: Colonoscopic detection of colorectal cancer is uncommon in asymptomatic persons 40 to 49 years of age. The noncancerous lesions are equally distributed proximally and distally. The low yield of screening colonoscopy in this age group is consistent with current recommendations about the age at which to begin screening in persons at average risk.