Reusable pouch development for long term space missions: A 3D ohmic model for verification of sterilization efficacy

One of the challenges of food system development during a long term space mission is the need for reheating of food, processing and stabilization of waste products, including food and biological waste. We have previously reported on the development of a pouch with electrodes, which permits reheating and sterilization of its internal contents, and the development of a two-dimensional heat transfer model for design optimization. However, a fully three-dimensional model is necessary for ensuring that thermal processes result in sterility of all parts of the product, particularly edge regions. The ohmic heating of tomato soup in a pouch was simulated using computational fluid dynamics (CFD) codes with user defined functions (UDFs) for electric field equations. In general, good agreement was observed between model and experiment, excepting a zone at the edge, where the model tended to underpredict temperature. The 3D model permitted identification of the potential cold spots over the entire pouch, which was not obvious using our previous 2D model. In particular, the bottom corners of the pouch were found to be a zone of low current density, and showed a temperature of only 53.3 °C even when the peak pouch temperature was 139 °C. The 3D model is a useful tool to optimize electrode configurations, and to assure adequate sterilization processes.     

A Scalable and High Capacity All-Optical Packet Switch: Design,Analysis, and Control

In this paper, a modular and scalable all-optical packet switch (AOPS) is proposed. The range of its capacity can be easily scaled from gigabit per second to multi-terabits per second. Due to its broadcast-and-select property, the proposed AOPS is capable of performing a multicast function. By taking the advantage of wavelength division multiplexing (WDM), this architecture can provide the best network performance using a limited number of optical fiber delay lines as buffers. To perform the header replacement function, a novel all-optical header replacement unit (HRU) is introduced to be integrated with the switching function. The proposed HRU is shared by all the inputs which provides cost advantages. In addition, we present a generic control scheme for the proposed AOPS. To implement the function of the AOPS, two possible approaches, based on the design of wavelength conversion pools (WCPs), are presented and their cascadability performances are compared. Our simulations show that the proposed AOPS with an arrayed waveguide grating (AWG) based WCP provides better cascadability performance than the one with a star coupler based WCP. We conclude that, based on the status of current optical and electronic technologies, the proposed architecture is feasible to be implemented, and can be a good candidate for future packet switching solutions.     

Reactivation and growth of non-culturable indicator bacteria in anaerobically digested biosolids after centrifuge dewatering

Recent literature has reported that high concentrations of indicator bacteria such as fecal coliforms (FCs) were measured in anaerobically digested sludges immediately after dewatering even though low concentrations were measured prior to dewatering. This research hypothesized that the indicator bacteria can enter a non-culturable state during digestion, and are reactivated during centrifuge dewatering. Reactivation is defined as restoration of culturability. To examine this hypothesis, a quantitative polymerase chain reaction (qPCR) method was developed to enumerate Escherichia coli, a member of the FC group, during different phases of digestion and dewatering. For thermophilic digestion, the density of E. coli measured by qPCR could be five orders of magnitude greater than the density measured by standard culturing methods (SCMs), which is indicative of non-culturable bacteria. For mesophilic digestion, qPCR enumerated up to about one order of magnitude more E. coli than the SCMs. After centrifuge dewatering, the non-culturable organisms could be reactivated such that they are enumerated by SCMs, and the conditions in the cake allowed rapid growth of FCs and E. coli during cake storage.     

Preparation of thermal resistant gas barrier chitosan nanobiocomposites

Nanobiocomposites of chitosan/clay were prepared by solution method using CuSO₄/glycine chelate complex as the catalyst with variable percentage of clay loading. The chemical interaction of chitosan and clay was studied by Fourier transform infrared spectroscopy. The structure of chitosan and clay nanobiocomposites was investigated by X‐ray diffraction and high resolution transmission electron microscopy. From thermogravimetric analysis, it was found that chitosan/clay nanobiocomposites were more thermally stable as compared to pure chitosan. A substantial reduction in oxygen permeability was obtained from the gas permeameter with increase in clay concentrations by which the synthesized nanocomposites materials may be used for packaging applications. POLYM. COMPOS., 35:2324–2328, 2014. © 2014 Society of Plastics Engineers     

Synthesis and characterization of iron oxide nanoparticles by solvothermal method

In the present work iron oxide nanoparticles have been synthesized by alkaline solvo thermal method using anhydrous ferric chloride, sodium hydroxide, polyethylene glycol and cetyl trimethyl ammonium bromide and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray Spectroscopy (EDX) and Thermal Gravimetric Analysis (TGA). XRD indicated that the product is a mixture of different phases of iron oxide viz. gamma-Fe₂O₃ (maghemite, tetragonal), Fe₂O₃ (maghemite, cubic), Fe₃O₄ (magnetite, cubic) and ?-Fe₂O₃(epsilon iron oxide). FESEM studies indicated that size of the particles is observed in the range of about 19.8 nm to 48 nm. EDX spectral analysis reveals the presence of carbon, oxygen, iron in the synthesized nanoparticles. The FTIR spectra indicated absorption bands due to O-H stretching, C-O bending, N-H stretching and bending, C-H stretching and Fe-O stretching vibrations. TGA curve represented weight loss of around 3.0446 % in the sample at temperature of about 180°C due to the elimination of the water molecules absorbed by the nanoparticles from the atmosphere.     

The subunit structure of human macrophage migration inhibitory factor: evidence for a trimer

The subunit structure of human macrophage migration inhibitoryfactor (MIF) has been studied by preliminary X-ray analysisof wild-type and selenomethionine-MIF and dynamic light scattering.Crystal form I of MIF belongs to space group P2₁2₁2₁ and isgrown from 2 M ammonium sulfate at pH 8.5. A native data sethas been collected to 2.4 Å resolution. Self-rotationstudies and V_m values indicate that three molecules per asymmetricunit are present A data set to 2.8 Å resolution has beencollected for crystal form II, which belongs to space groupP3¹21 or P3²21 and grows from 2 M ammonium sulfate, 2% polyethyleneglycol (average molecular mass 400), 0.1 M HEPES, pH 7.5. Three,four, five or six monomers in the asymmetric unit are consistentwith V_m values for this crystal form. Analysis of crystal formII containing selenomethionine-MIF indicates nine selenium sitesare present per asymmetric unit. Dynamic light scattering ofMIF suggests that the major form of the protein in solutionis a trimer. The results of these studies are in contrast toprevious reports indicating that MIF is a monomer or dimer.The subunit arrangement of MIF is similar to that of tumor necrosisfactor and suggests that signal transduction might require trimerizationof receptor subunits.     

A cubic B-spline quasi-interpolation algorithm to capture the pattern formation of coupled reaction-diffusion models

Diffusion plays a significant role in complex pattern formulations occurred in biological and chemical reactions. In this work, the authors study the effect of diffusion in coupled reaction-diffusion systems named the Gray-Scott model for complex pattern formation with the help of cubic B-spline quasi-interpolation (CBSQI) method and capture various formates of these patterns. The idea of Kronecker product is used first time with CBSQI method for 2D problems. Linear stability analysis of the reaction-diffusion system as well as stability of the proposed method is studied. Four test problems are considered to check the accuracy and efficiency of the method and found the stable patterns.

     

Linearly tapered meander line cross dipole circularly polarized antenna for UHF RFID tag applications

In this article, a circularly polarized antenna for ultra‐high frequency radio frequency identification (RFID) tag is presented. The circular polarization is realized by two orthogonal, unequal length linearly tapered meander line cross dipoles. The meander structure with capacitive tip loading is used for size miniaturization of the antenna. A modified T‐match network is employed to feed the cross dipole structure. The measured 10‐dB return loss bandwidth of the cross dipole antenna is 17 MHz (908‐923 MHz) and the corresponding 3‐dB axial ratio bandwidth is 6 MHz (912‐918 MHz). The overall size of the proposed antenna is 0.17λ₀ × 0.17λ₀ at 915 MHz. The maximum read range between the reader and the tag with the proposed antenna is 4.7 m larger than the analogous linearly polarized tag antenna due to the reduction in polarization loss between the tag and reader antennas. Thus, a maximum read range of 15.66 m with the gain of 1.28 dBic is achieved at 915 MHz.     

Removal of 17α‐ethinylestradiol,salicylic acid,trimethoprim, carbamazepine and nonylphenol through biological carbon and nitrogen removal processes

This study investigated five different trace organic contaminants (TOrCs) (one hormone: 17α‐ethinylestradiol (EE2), two pharmaceuticals: salicylic acid (SA) and trimethoprim (TMP), one analgesic drug: carbamazepine (CBZ), and one surfactant metabolite: nonylphenol (NP)) removal efficiency at a full‐scale Advanced Wastewater Treatment Plant (AWTP). The AWTP achieved average EE2, SA and NP removal over 80% at the biological carbon removal stages. The results also showed a 66% removal of TMP at the nitrogen removal stages. CBZ was recalcitrant throughout the plant, due to its high solubility and low distribution coefficient between wastewater and sludge. Batch experiments were conducted on active and inactive secondary, nitrification and denitrification sludge by adding TOrCs to understand the removal mechanism through sorption and biodegradation. Sorption was the dominant mechanism to remove EE2, SA and NP in secondary treatment processes. In nitrification and denitrification processes, higher percentage of TOrCs removal through biodegradation were observed compared to removal through sorption.     

Compositional and structural analysis of RF magnetron sputtered La3+-modified PZT thin films

In the present work, we report the preparation of lanthanum-modified lead zirconate titanate (PLZT) thin films in pure perovskite phase by RF magnetron sputtering. For this purpose, a 3-in. diameter target of PLZT (8/60/40) was prepared by conventional solid-state reaction route. The chemical composition of PLZT target was determined using gravimetric analysis followed by UV–vis and flame atomic absorption spectrometry. Various deposition parameters such as target-to-substrate spacing, deposition temperature, post-deposition annealing temperature and time have been optimized to obtain PLZT films in pure perovskite phase. The films prepared in pure argon at 100 W RF power without external substrate heating exhibited pure perovskite phase after rapid thermal annealing (RTA) as confirmed by X-ray diffraction (XRD). Compositional analysis of the PLZT film was performed by secondary ion mass spectroscopy (SIMS) using PLZT target as standard sample. Depth profile of the film shows very good stoichiometric uniformity of all elements of PLZT.