Analysis and revamping of heat exchanger networks for crude oil refineries using temperature driving force graphical technique

Clean Technologies and Environmental Policy - The refining industry is an energy-intensive industry; most of the energy is consumed in heating and cooling requirements. Revamping or retrofitting of...     

Exploring the Role of Genetic Variability and Lifestyle in Oxidative Stress Response for Healthy Aging and Longevity

Oxidative stress is both the cause and consequence of impaired functional homeostasis characterizing human aging. The worsening efficiency of stress response with age represents a health risk and leads to the onset and accrual of major age-related diseases. In contrast, centenarians seem to have evolved conservative stress response mechanisms, probably derived from a combination of a diet rich in natural antioxidants, an active lifestyle and a favorable genetic background, particularly rich in genetic variants able to counteract the stress overload at the level of both nuclear and mitochondrial DNA. The integration of these factors could allow centenarians to maintain moderate levels of free radicals that exert beneficial signaling and modulator effects on cellular metabolism. Considering the hot debate on the efficacy of antioxidant supplementation in promoting healthy aging, in this review we gathered the existing information regarding genetic variability and lifestyle factors which potentially modulate the stress response at old age. Evidence reported here suggests that the integration of lifestyle factors (moderate physical activity and healthy nutrition) and genetic background could shift the balance in favor of the antioxidant cellular machinery by activating appropriate defense mechanisms in response to exceeding external and internal stress levels, and thus possibly achieving the prospect of living a longer life.     

The effect of ferrous ions,calcium ions and citric acid on absorption of ciprofloxacin across caco-2 cells: practical and structural approach

Objective: To study the potential influence of selected metal ions on absorption (and hence oral bioavailability of ciprofloxacin (Cipro) in presence and absence of a competing ligand.

Significance: The presence of metal ions together with Cipro results in complexes exhibiting a decreased bioavailability. Attempts were made to better understand the mechanism of decreased Cipro bioavailability in the presence of metals such as calcium and ferrous ions, and a small-sized ligand citric acid (CitA).

Methods: Effect of complex size or other potential factors was studied using diffusion through synthetic membrane, permeation studies across Caco-2 cells and capillary electrophoresis. A molecular dynamics (MD) simulation study was conducted to find the arrangement and the nature of the interactions between Cipro molecules and ferrous ions.

Results: Cipro was shown to form complexes with metals and CitA. The presence of CitA improved permeation of Cipro through the synthetic membrane but this was not as obvious in case of Caco-2 cells. Capillary electrophoresis suggested the existence of large molecular aggregates of Cipro: metal complexes. MD simulations offered clear evidence of large size aggregates in line with the experimental findings. CitA alone significantly improved permeation of Cipro through Caco-2 cells.

Conclusions: The size of the formed complexes, rather than the decrease in the solubility of formed complexes, plays a significant role in permeation (absorption) of Cipro. CitA might ameliorate the effect of co-administered metal ions on the bioavailability of Cipro.     

Ti3SiC2-Cu composites by mechanical milling and spark plasma sintering: Possible microstructure formation scenarios

We present several possible microstructure development scenarios in Ti₃SiC₂-Cu composites during mechanical milling and Spark Plasma Sintering (SPS). We have studied the effect of in situ consolidation during milling of Ti₃SiC₂ and Cu powders and melting of the Cu matrix during the SPS on the hardness and electrical conductivity of the sintered materials. Under low-energy milling, (3–5) vol.%Ti₃SiC₂-Cu composite particles of platelet morphology formed, which could be easily SPS-ed to 92–95% relative density. Under high-energy milling, millimeter-scale (3–5) vol.%Ti₃SiC₂-Cu granules formed as a result of in situ consolidation and presented a challenge to be sintered into a bulk fully dense sample; the corresponding SPS-ed compacts demonstrated a finer-grained Cu matrix and more significant levels of hardening compared to composites of the same composition processed by low-energy milling. The 3 vol.% Ti₃SiC₂-Cu in situ consolidated and Spark Plasma Sintered granules showed an extremely high hardness of 227 HV. High electrical conductivity of the Ti₃SiC₂-Cu composites sintered from the granules was an indication of efficient sintering of the granules to each other. Partial melting of the Cu matrix, if induced during the SPS, compromised the phase stability and uniformity of the microstructure of the Ti₃SiC₂-Cu composites and thus it is not to be suggested as a pathway to enhanced densification in this system.     

Synthesis of light weight recron fiber-reinforced sodium silicate based silica aerogel blankets at an ambient pressure for thermal protection

Journal of Porous Materials - In this work, for the sake of improving the performance of homogeneous and flexible silica aerogel blankets in practical applications, lightweight recron fibers were...     

Exploring molecular sieve capabilities of activated carbon fibers to reduce the impact of NOM preloading on trichloroethylene adsorption

Adsorption of trichloroethylene (TCE) by two activated carbon fibers (ACFs) and two granular activated carbons (GACs) preloaded with hydrophobic and transphilic fractions of natural organic matter (NOM) was examined. ACF10, the most microporous activated carbon used in this study, had over 90% of its pore volume in pores smaller than 10 A. It also had the highest volume in pores 5-8 A, which is the optimum pore size region for TCE adsorption, among the four activated carbons. Adsorption of NOM fractions by ACF10 was, in general, negligible. Therefore, ACF10, functioning as a molecular sieve during preloading, exhibited the least NOM uptake for each fraction, and subsequently the highest TCE adsorption. The other three sorbents had wider pore size distributions, including high volumes in pores larger than 10 A, where NOM molecules can adsorb. As a result, they showed a higher degree of uptake for all NOM fractions, and subsequently lower adsorption capacities for TCE, as compared to ACF10. The results obtained in this study showed that understanding the interplay between the optimum pore size region for the adsorption of target synthetic organic contaminant (SOC) and the pore size region for the adsorption of NOM molecules is important for controlling NOM-SOC competitions. Experiments with different NOM fractions indicated that the degree of NOM loading is important in terms of preloading effects; however the waythatthe carbon pores are filled and loaded by different NOM fractions can be different and may create an additional negative impact on TCE adsorption.     

Heat tolerance of Salmonella enterica serovars Agona, Enteritidis, and Typhimurium in peanut butter

Recent large foodborne outbreaks caused by Salmonella enterica serovars have been associated with consumption of foods with high fat content and reduced water activity, even though their ingredients usually undergo pasteurization. The present study was focused on the heat tolerance of Salmonella enterica serovars Agona, Enteritidis, and Typhimurium in peanut butter. The Salmonella serovars in the peanut butter were resistant to heat, and even at a temperature as high as 90 degrees C only 3.2-log reduction in CFU was observed. The obtained thermal inactivation curves were upwardly concave, indicating rapid death at the beginning (10 min) followed by lower death rates and an asymptotic tail. The curves fitted the nonlinear Weibull model with beta parameters < 1, indicating that the remaining cells have a lower probability of dying. beta at 70 degrees C (0.40 +/- 0.04) was significantly lower than beta at 80 degrees C (0.73 +/- 0.19) and 90 degrees C (0.69 +/- 0.17). Very little decrease in the viable population (less than 2-log decrease) was noted in cultures that were exposed to a second thermal treatment. Peanut butter is a highly concentrated colloidal suspension of lipid and water in a peanut meal phase. We hypothesized that differences in the local environments of the bacteria, with respect to fat content or water activity, explained the observed distribution and high portion of surviving cells (0.1%, independent of the initial cell number). These results demonstrate that thermal treatments are inadequate to consistently destroy Salmonella in highly contaminated peanut butter and that the pasteurization process cannot be improved significantly by longer treatment or higher temperatures.     

Effect of subsidence on recharge at abandoned coal mines generating acidic drainage: The Majestic Mine, Athens County, Ohio

This paper addresses the relationship between the geology, hydrology, and transient variations in discharge and water chemistry of acidic water discharged by an abandoned underground coal mine: the Majestic Mine in Athens County, Ohio, a partially-flooded, downdip, drift mine. The Middle Kittanning (No. 6) Coal (Allegheny Series, Pennsylvanian System) was mined room-and-pillar until 1921. Loss of support from mine collapse has created large vertical subsidence fractures along the naturally occurring joints within the brittle sandstone overburden. The mine discharge hydrograph, temperature, and pH of the mine discharge indicate that the hydrology of the Majestic Mine can be explained in terms of pseudokarst hydrology. During rainfall events, water is preferentially recharged through the subsidence features. Increased pressure from the mine inflow is transmitted through the flooded workings, causing a rapid increase in discharge, and forcing older mine water out of the mine. A stream draining an overlying watershed is captured by one of the subsidence features, contributing 60 to 80% of the mine water outflow. During the summer, recharge to the mine is negligible because potential evapotranspiration is higher than precipitation. During late summer and fall months, when the mine pool is at its lowest elevation, atmospheric oxygen penetrates back into the mine workings, enhancing the oxidation reactions. During the increased discharge of the spring months, washing of the reaction products from the mine walls produces the highest metals concentrations and chemical loads. *** DIRECT SUPPORT *** A03BX002 00004