Identification of the pathway of α-oxidation of cerebronic acid in peroxisomes

Cerebronic acid (2-hydroxytetracosanoic acid), an α-hydroxy very long-chain fatty acid (VLCFA) and a component of cerebrosides and sulfatides, is unique to nervous tissues. Studies were carried out to identify the pathway and the subcellular site involved in the oxidation of cerebronic acid. The results from these studies revealed that cerebronic acid was catabolized by α-oxidation to CO₂ and tricosanoic acid (23:0). Studies with subcellular fractions indicated that cerebronic acid was α-oxidized in fractions having particulate bound catalase and enzyme systems for the β-oxidation of VLCFA (e.g., lignoceric acid), suggesting peroxisomes as the subcellular organelle responsible for α-oxidation of cerebronic acid. Etomoxir, an inhibitor of mitochondrial fatty acid oxidation, had no effect on cerebronic acid α-oxidation. Further, cerebronic acid oxidation was found to be dependent on the presence of NAD⁺ but not FAD, NADPH, ATP, Mg²⁺, or CoASH. Intraorganellar localization studies indicated that the enzyme system for the α-oxidation of cerebronic acid was associated with the peroxisomal limiting membranes. Studies on cultured fibroblasts from normal subjects and patients with peroxisomal disorders indicated an impairment of α-oxidation of cerebronic acid in cell lines that lack peroxisomes [e.g., Zellweger syndrome (ZS)]. On the other hand, α-oxidation of cerebronic acid was found to be normal in cell lines from X-linked adrenoleukodystrophy, adult Refsum disease, and rhizomelic chondrodysplasia punctata. Our results clearly demonstrate that α-oxidation of α-hydroxy VLCFA (cerebronic acid) is a peroxisomal function and that this oxidation is impaired in ZS. Furthermore, this α-oxidation enzyme system is distinct from the one for the α-oxidation of β-carbon branched-chain fatty acids (e.g., phytanic acid).     

Operability and control in process intensification and modular design: Challenges and opportunities

In this article, the importance of considering operability and control criteria in the analysis and design of intensified and modular processes is discussed. We first analyze the impact on operability of key factors including: (i) degrees of freedom, (ii) process constraints, (iii) numbering up vs. scaling up, and (iv) dynamic/periodic operation. Comparative examples are presented to showcase the pros and cons in intensified/modular systems vs. their conventional counterparts from operability and control aspects. Then we look into metrics and tools to address these challenges such as: (i) flexibility analysis, (ii) operability-based design, and (iii) advanced model-based control. Considering different conceptual design stages as synthesis intensification, steady-state design, and dynamic operational optimization, we highlight the need to incorporate different levels of operability considerations. Future research opportunities and perspectives are also identified, particularly emphasizing the importance of a holistic strategy for integrated design, operability, and control of intensified and modular process systems.     

Temporal persistence and stability of surface soil moisture in a semi-arid watershed

Satellite soil moisture products, such as those from Advanced Microwave Scanning Radiometer (AMSR), require diverse landscapes for validation. Semi-arid landscapes present a particular challenge to satellite remote sensing validation using traditional techniques because of the high spatial variability and potentially rapid rates of temporal change in moisture conditions. In this study, temporal stability analysis and spatial sampling techniques are used to investigate the representativeness of ground observations at satellite scale soil moisture in a semi-arid watershed for a long study period (March 1, 2002 to September 13, 2005). The watershed utilized, the Walnut Gulch Experimental Watershed, has a dense network of 19 soil moisture sensors, distributed over a 150 km² study region. In conjunction with this monitoring network, intensive gravimetric soil moisture sampling conducted as part of the Soil Moisture Experiment in 2004 (SMEX04), contributed to the calibration of the network for large-scale estimation during the North American Monsoon System (NAMS). The sensor network is shown to be an excellent estimator of the watershed average with an accuracy of approximately 0.01 m³/m³ soil moisture. However, temporal stability analysis indicated that while much of the network is stable, the soil moisture spatial pattern, as represented by mean relative difference, is not replicated by the network mean relative difference pattern. Rather, the network is composed of statistical samples. Geophysical aspects of the watershed, including topography and soil type are also examined for their influence on the soil moisture variability and stability. Soil type, as characterized by bulk density, clay and sand content, was responsible for nearly 50% of the temporal stability. Topographic effects were less important in defining representativeness and stability.     

Aircraft based soil moisture retrievals under mixed vegetation and topographic conditions

An unresolved issue in global soil moisture retrieval using passive microwave sensors is the spatial integration of heterogeneous landscape features to the nominal 50 km footprint observed by most low frequency satellite systems. One of the objectives of the Soil Moisture Experiments 2004 (SMEX04) was to address some aspects of this problem, specifically variability introduced by vegetation, topography and convective precipitation. Other goals included supporting the development of soil moisture data sets that would contribute to understanding the role of the land surface in the concurrent North American Monsoon System. SMEX04 was conducted over two regions: Arizona — semi-arid climate with sparse vegetation and moderate topography, and Sonora (Mexico) — moderate vegetation with strong topographic gradients. The Polarimetric Scanning Radiometer (PSR/CX) was flown on a Naval Research Lab P-3B aircraft as part of SMEX04 (10 dates of coverage over Arizona and 11 over Sonora). Radio Frequency Interference (RFI) was observed in both PSR and satellite-based (AMSR-E) observations at 6.92 GHz over Arizona, but no detectable RFI was observed over the Sonora domain. The PSR estimated soil moisture was in agreement with the ground-based estimates of soil moisture over both domains. The estimated error over the Sonora domain (SEE = 0.021 cm³/cm³) was higher than over the Arizona domain (SEE = 0.014 cm³/cm³). These results show the possibility of estimating soil moisture in areas of moderate and heterogeneous vegetation and high topographic variability.     

Soil moisture estimates from TRMM Microwave Imager observations over the Southern United States

The lack of continuous soil moisture fields at large spatial scales, based on observations, has hampered hydrologists from understanding its role in weather and climate. The most readily available observations from which a surface wetness state could be derived is the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) observations at 10.65 GHz. This paper describes the first attempt to map daily soil moisture from space over an extended period of time. Methods to adjust for diurnal changes associated with this temporal variability and how to mosaic these orbits are presented. The algorithm for deriving soil moisture and temperature from TMI observations is based on a physical model of microwave emission from a layered soil-vegetation-atmosphere medium. An iterative, least-squares minimization method, which uses dual polarization observations at 10.65 GHz, is employed in the retrieval algorithm. Soil moisture estimates were compared with ground measurements over the U.S. Southern Great Plains (SGP) in Oklahoma and the Little River Watershed, Georgia. The soil moisture experiment in Oklahoma was conducted in July 1999 and Little River in June 2000. During both the experiments, the region was dry at the onset of the experiment, and experienced moderate rainfall during the course of the experiment. The regions experienced a quick dry-down before the end of the experiment. The estimated soil moisture compared well with the ground observations for these experiments (standard error of 2.5%). The TMI-estimated soil moisture during 6-22 July over Southern U.S. was analyzed and found to be consistent with the observed meteorological conditions.     

Sequential mixing as effective method in the reduction of percolation threshold of multiwall carbon nanotube in poly(methyl methacrylate)/high‐density poly(ethylene)/MWCNT nanocomposites

This work demonstrates sequential heating protocol to be an effective method in the reduction of percolation threshold of multiwall carbon nanotube (MWCNT) in (70/30 w/w) poly(methyl methacrylate) (PMMA)/high‐density poly(ethylene) (HDPE)/MWCNT nanocomposites. Here, the percolation threshold (P_c) value was reduced to 0.08 wt % of MWCNT, which is the lowest among the ever reported values of P_c for the PMMA system. Moreover, a co‐continuous morphology of the minor HDPE phase was evident throughout the major PMMA phase in a highly asymmetric composition (70/30 w/w) of the blend constituents. The AC conductivity as well as the dielectric permittivity values were increased with increase in loading of MWCNT in the nanocomposites. The detailed analysis of electrical and morphological properties is discussed in depth in the article. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40235.     

Reduction of percolation threshold of multiwall carbon nanotube (MWCNT) in polystyrene (PS)/low‐density polyethylene (LDPE)/MWCNT nanocomposites: An eco‐friendly approach

In this article, we introduce an eco‐friendly approach to achieve electrical conductivity at sufficiently lower loading of MWCNT in the PS/LDPE/MWCNT nanocomposites through judicious control of temperature during melt blending. The percolation threshold was achieved at 0.21 wt% of MWCNT following this method, which is lower, compared to the result obtained from direct mixing as well as the previously reported data. The morphological analysis revealed a co‐continuous structure of the (70/30, PS/LDPE)/MWCNT nanocomposites in such a high asymmetric composition of blend constituents, which facilitates in the lowering of percolation threshold through selective dispersion of MWCNT in the minor LDPE phase. The electron conduction in the nanocomposites has well been explained in terms of tunneling mechanism, supporting thin coating of polymer over individual CNTs. The morphological, electric and dielectric properties have been well explained in this article. POLYM. COMPOS., 36:1574–1583, 2015. © 2014 Society of Plastics Engineers     

Remote Sensing and GIS Based Approach for Identification of Artificial Recharge Sites

The main aim of this paper is to demonstrate the capabilities of Remote Sensing (RS) and Geographic Information System (GIS) techniques for the demarcation of suitable sites for artificial recharge of groundwater aquifers, in the Loni watershed, located in Unnao and Raebareli districts, Uttar Pradesh, India. In this study, the SCS-CN model, groundwater depth data and morphological parameters (bifurcation ratio, elongation ratio, drainage density, ruggedness number, relief ratio, and circulatory ratio) have been used to delineate the recharge sites for undertaking water conservation measures. Augmentation of water resource is proposed in the watershed by constructing runoff storage structures, like check dam, percolation tank and nala bund. The site suitability for these water harvesting structures is determined by considering spatially varying parameters, like runoff potential, slope, groundwater fluctuation data and morphometric information of the watershed. GIS has been used as an effective tool to store, analyse and integrate spatial and attribute information pertaining to runoff, slope, drainage, groundwater fluctuation and morphometric characteristics for such studies.