Optimum Blend of Chitosan and Poly-(��-caprolactone) for Fabrication of Films for Food Packaging Applications

The present work deals with the preparation and characterization of the chitosan and poly-ε-caprolactone (PCL) solution-casted blended films in various proportions (chitosan–PCL ratio 90:10, 80:20, and 70:30). The films were casted and dried at 55 °C, which were characterized based on the mechanical, barrier, thermal, and microscopic properties. The film prepared from chitosan to PCL ratio 80:20 resulted in increase percentage elongation by 20.56% as compared to pure chitosan film. Fourier transform infrared spectrum indicated a shift in peak of absorption from 1743.9 to 1724.8 cm⁻¹ due to carbonyl group of PCL indicating the miscibility and interaction between the PCL and chitosan. Scanning electron microscopy revealed that PCL appeared as a co-continuous phase with chitosan for ratio 80:20, confirmed the interaction between chitosan and PCL. The above study indicated that the properties of chitosan films can be modified with the addition of PCL and may find its versatile use in food packaging.     

Acute corneal hydrops: a case report including confocal and histopathological considerations.

This is a case report of corneal hydrops associated with keratoconus with a review of current literature pertaining to diagnosis, histopathology, and treatment options. A 30-year-old African American male presented to the University Eye Institute with acute unilateral pain, redness, and visual impairment. His symptoms, clinical presentation and past diagnosis of keratoconus confirmed his condition to be acute corneal hydrops (CH). The condition was closely followed utilizing topical treatment including hyper-osmotic (Muro 128) and non-steroidal anti-inflammatory agents (Acular and Voltaren). After 4 months, the patient's condition resolved but subsequent corneal scarring resulted. Corneal ectasia in patients with keratoconus may progress into acute rupture of the posterior limiting lamina (PLL) and the endothelium, resulting in CH, which may manifest as an area of edematous and opacified cornea lasting up to 4 months in duration. Acute complications such as CH seldom occur. Histopathology and confocal microscopy can be used to help visualize and understand CH on a cellular level. After regeneration of the corneal structures, central scarring may limit visual acuity and necessitate a corneal transplant.     

Creep Design of Epoxy Bonded Anchor System

This article presents a systematic study on creep design of epoxy bonded anchor system. First, a theoretical model for prediction of long-term performance of an anchor system is suggested assuming epoxy layer following Maxwell visco-elastic behavior, which is then validated through an ABAQUS numerical model. A close match between the ABAQUS result and the theoretical model has been reached. Next, a general-purpose methodology for estimating creep capacity of an adhesive bonded anchor system is suggested following AC58 and two creep capacity equations are reached for Model Dry Epoxy and Model Wet Epoxy bonded anchor systems. The derived creep capacity is then used to re-examine the Boston D Tunnel anchor design and a safe design is reached through the suggested method considering the anchor system's long-term creep performance. Last, the ABAQUS model is extended to include the effect of curing temperatures, which shows significant influences of curing temperature on the capacity of an epoxy bonded anchor system.     

Three‐dimensional hydrogel encapsulated embryonic stem and carcinoma cells as culture platforms for cytotoxicity studies

The utility of alginate hydrogels for three‐dimensional (3‐D) culture of mouse embryonic stem cells (mESCs) and future development of 3‐D stem cell culture‐based in vitro screens of toxicity is described. Using alginate hydrogels of various stiffness, we first evaluated the impact of substrate modulus on mESC viability, proliferation, as well as expression of pluripotency and germ‐layer markers and observed that low concentration alginate hydrogels (0.5% and 1% alginate) were most suitable for long‐term culture of mESCs. These results were not unique to mESCs; long‐term viability and proliferation of mouse embryonic carcinoma cells (mECCs) was also best supported by similar conditions. Finally, we determined cytotoxic responses of alginate encapsulated cells to commercially available chemicals and interestingly observed similar responses for mESCs and mECCs, thereby suggesting that mECCs can predict stem cell responses to chemicals. These studies will facilitate future design of optimal stem cell‐based platforms of organ‐specific and developmental toxicity. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3180–3184, 2015     

Two timescale convergent Q-learning for sleep-scheduling in wireless sensor networks

In this paper, we consider an intrusion detection application for Wireless Sensor Networks. We study the problem of scheduling the sleep times of the individual sensors, where the objective is to maximize the network lifetime while keeping the tracking error to a minimum. We formulate this problem as a partially-observable Markov decision process (POMDP) with continuous state-action spaces, in a manner similar to Fuemmeler and Veeravalli (IEEE Trans Signal Process 56(5), 2091–2101, 2008). However, unlike their formulation, we consider infinite horizon discounted and average cost objectives as performance criteria. For each criterion, we propose a convergent on-policy Q-learning algorithm that operates on two timescales, while employing function approximation. Feature-based representations and function approximation is necessary to handle the curse of dimensionality associated with the underlying POMDP. Our proposed algorithm incorporates a policy gradient update using a one-simulation simultaneous perturbation stochastic approximation estimate on the faster timescale, while the Q-value parameter (arising from a linear function approximation architecture for the Q-values) is updated in an on-policy temporal difference algorithm-like fashion on the slower timescale. The feature selection scheme employed in each of our algorithms manages the energy and tracking components in a manner that assists the search for the optimal sleep-scheduling policy. For the sake of comparison, in both discounted and average settings, we also develop a function approximation analogue of the Q-learning algorithm. This algorithm, unlike the two-timescale variant, does not possess theoretical convergence guarantees. Finally, we also adapt our algorithms to include a stochastic iterative estimation scheme for the intruder’s mobility model and this is useful in settings where the latter is not known. Our simulation results on a synthetic 2-dimensional network setting suggest that our algorithms result in better tracking accuracy at the cost of only a few additional sensors, in comparison to a recent prior work.     

Representation of spatial frequency and orientation in the visual cortex

Knowledge of the response of the primary visual cortex to the various spatial frequencies and orientations in the visual scene should help us understand the principles by which the brain recognizes patterns. Current information about the cortical layout of spatial frequency response is still incomplete because of difficulties in recording and interpreting adequate data. Here, we report results from a study of the cat primary visual cortex in which we employed a new image-analysis method that allows improved separation of signal from noise and that we used to examine the neurooptical response of the primary visual cortex to drifting sine gratings over a range of orientations and spatial frequencies. We found that (i) the optical responses to all orientations and spatial frequencies were well approximated by weighted sums of only two pairs of basis pictures, one pair for orientation and a different pair for spatial frequency; (ii) the weightings of the two pictures in each pair were approximately in quadrature (1/4 cycle apart); and (iii) our spatial frequency data revealed a cortical map that continuously assigns different optimal spatial frequency responses to different cortical locations over the entire spatial frequency range.     

Approach for uncertainty analysis and error evaluation of four-axis co-ordinate measuring machines

In the present investigation, a new form of space frame for error evaluation and uncertainty analysis of four-axis co-ordinate measuring machines (CMMs) is proposed and applied. The novel space frame comprises a ball plate that incorporates seven high accuracy spheres. The volumetric error data obtained when a CMM measures the space frame, in different angular locations, can be used to verify whether a CMM maintains the manufacturer specifications. The experimental results have demonstrated that this space frame provides a practical and cost effective mechanical artifact to assessing the volumetric performance of four-axis CMMs. The developed technique can be applied for verification, periodic re-verification and acceptance test of any type of four-axis CMMs.     

MARS: Link-layer rate selection for multicast transmissions in wireless mesh networks

IEEE 802.11 devices dynamically choose among different modulation schemes and bit-rates for frame transmissions. This rate adaptation, however, is restricted only to unicast frames. Multicast (and broadcast) frames are constrained to use a fixed low bit-rate modulation, resulting in low throughput for multicast streams. Availability of high bandwidth and efficient use of the medium is crucial to support multimedia multicast streaming applications such as IPTV, especially in multihop mesh networks. To address this problem, we propose a rate adaptation algorithm for multicast transmissions in these networks. The proposed algorithm, MARS, is distributed in nature, and relies on local network measurements to select a transmission bit-rate for a given multicast group. The algorithm also facilitates the joint use of bit-rate selection and link-layer mechanisms such as acknowledgements and retransmissions to improve reliability of high throughput multicast streams. Based on implementation and evaluation on a testbed, the algorithm provides up to 600% gain in throughput compared to traditional 802.11 networks in some scenarios. Additionally, the algorithm can support multicast streams while consuming a small fraction (20%) of the resources compared to the basic 802.11 operation.     

Microstructural and Mechanical Properties Investigation of TiC Reinforced Hardface Alloy Deposited on Mild Steel Substrate

Wear is one of the major problems faced in industry that reduces the life of industrial components and increases the operating costs. Therefore, hardfacing is widely employed by engineers to minimize components’ wear, in which single or multiple layers of hard material that mainly consists of carbides deposited on the base metal. However, these carbide-based materials suffer from solidification cracking due to lack of ductility. In this study, titanium carbide (TiC) reinforced alloy steel deposited using self-shielded flux cored arc welding technique. The microstructure and phase analysis in the hardfaced deposit by scanning electron microscope, energy dispersive x-ray and X-ray diffractometer revealed that the microstructure consists of finely distributed TiC within matrix of martensite and some retained austenite. Microhardness test and pin-on-disk wear test had shown that the clad deposit posses better hardness and wear resistance. Retained austenite formation and TiC precipitation were discussed in detail and correlated with the mechanical properties.