Simultaneous Solid Phase Fermentation and Saccharification of Cassava Fibrous Residue for Production of Ethanol

A total of 16.5% reducing sugars in the saccharified pulp of cassava fibrous residue are achieved with the use of 30% slurry. The yield of ethanol was highest and the amount of residual reducing sugars was lowest with the use of 2.5% acid. The increase in dose of glucoamylase leads to improved yields of ethanol without any lowering in the residual reducing sugars. The ethanol yield and productivity were better and the residual reducing sugars were lower in solid phase fermentation as compared to the fermentation of liquid hydrolysate obtained by hydraulic pressing of the saccharified pulp. The slightly lower yield of ethanol in large batch static fermentation probably due to poor mass transfer and limited contact of yeast cells as well as enzyme with their substrates could be effectively overcome by employing appropriate strategies.     

Atomistic and electrical simulations of a GaN-AlN-(4H)SiC heterostructure optically-triggered vertical power semiconductor device

In this paper, a comprehensive simulation study is conducted to investigate the switching characteristics, gain, and breakdown voltage of a GaN-AlN-(4H)SiC based optically-triggered (OT) heterostructure vertical power semiconductor device (PSD). It comprises a 1 nm AlN buffer layer between the GaN and SiC heterointerface to achieve a reasonable compromise between lattice mismatch and lower forward drop. The results are compared with an all-(4H)SiC OT PSD. The all-(4H)SiC homostructure PSD is based completely on SiC and has no buffer layer. Further, it has the same structure, dimensions, and doping densities as that of the GaN-AlN-(4H)SiC based heterostructure PSD. While there have been studies on GaN-AlN-SiC lateral heterostructures, their primary focus has been on lateral conduction in the GaN structure with a thick (typically >300 nm) AlN buffer layer residing on top of a SiC substrate. Such an approach will not be useful for our vertical PSD because of the thick AlN layer. As such, first, a scaled molecular dynamics simulation (MDS) is carried out in DMol³ emulating the GaN-AlN-(4H)SiC heterointerface pn junction of the vertical PSD (with 1 nm AlN buffer) to assess the possibility of vertical conduction and stability of the heterointerface by calculating the density of states (DOS) at the Fermi level and the potential energy, respectively. Subsequently, detailed electrical simulations of the GaN-AlN-(4H)SiC and all-(4H)SiC vertical PSDs are carried out in Silvaco to assess their switching performances, gain, on-state drop, and blocking capabilities. The overall results indicate that, the GaN-AlN-(4H)SiC vertical PSD provides superior switching performance and optical absorption compared to the all-(4H)SiC vertical PSD, while the latter provides better gain. The blocking capabilities and forward drops are found to be comparable for both the PSDs from a practical standpoint.     

Sketching asynchronous data streams over sliding windows

We study the problem of maintaining a sketch of recent elements of a data stream. Motivated by applications involving network data, we consider streams that are asynchronous, in which the observed order of data is not the same as the time order in which the data was generated. The notion of recent elements of a stream is modeled by the sliding timestamp window, which is the set of elements with timestamps that are close to the current time. We design algorithms for maintaining sketches of all elements within the sliding timestamp window that can give provably accurate estimates of two basic aggregates, the sum and the median, of a stream of numbers. The space taken by the sketches, the time needed for querying the sketch, and the time for inserting new elements into the sketch are all polylogarithmic with respect to the maximum window size. Our sketches can be easily combined in a lossless and compact way, making them useful for distributed computations over data streams. Previous works on sketching recent elements of a data stream have all considered the more restrictive scenario of synchronous streams, where the observed order of data is the same as the time order in which the data was generated. Our notion of recency of elements is more general than that studied in previous work, and thus our sketches are more robust to network delays and asynchrony. The work of the authors was supported in part through NSF grants CNS 0520102 and CNS 0520009. A preliminary version of this paper appeared in Proceedings of the ACM Symposium on Principles of Distributed Computing (PODC) 2006, pages 82–91. Work done while the third author was at Rensselaer Polytechnic Institute. Authors are listed in reverse alphabetical order.     

Robust vibration invariant SSHI rectifier circuit for piezoelectric device

Analog Integrated Circuits and Signal Processing - Rectifier is the most critical block of the power conditioning circuit designed for the Piezoelectric Energy Harvester (PZEH). Maintaining high...     

Production of bio-epoxide and bio-adhesive from non-edible oil

Epoxidation of Nahor oil was performed by H₂O₂ in the presence of acid catalyst at 50 °C. It was possible to obtain around 70% epoxide yield within 8 hrs of reaction. Amberlite IR 120H showed better epoxide yield compared to H₂SO₄ and Dowex 50 WX8. The performance of carboxylic acids was found to be in the order of formic acid>acetic acid>propanoic acid. The curing of epoxidized nahor oil involved using ethylenediamine (EDA) and diethylenetriamine (DETA). The adhesive property of the cured resins was tested and compared with commercially available glue. The force required to detach the cardboard joint was about 36.3 N for DETA-cured resin.     

Identifying frequent items in a network using gossip

We present algorithms for identifying frequently occurring items in a large distributed data set. Our algorithms use gossip as the underlying communication mechanism, and do not rely on any central control, nor on an underlying network structure, such as a spanning tree. Instead, nodes repeatedly select a random partner and exchange data with that partner. If this process continues for a (short) period of time, the desired results are computed, with probabilistic guarantees on the accuracy. Our algorithm for identifying frequent items is built by layering a novel small space “sketch” of data over a gossip-based data dissemination mechanism. We prove that the algorithm identifies the frequent items with high probability, and provides bounds on the time till convergence. To our knowledge, this is the first work on identifying frequent items using gossip.     

Studies on processing of layered oxide-bonded porous sic ceramic filter materials

Oxide-bonded porous SiC ceramic filter supports were prepared using SiC powder (d₅₀ = 212 µm), Al₂O₃, and clay as bond forming additives and graphite as pore former following reaction bonding of powder compacts at 1400°C in air. Reaction bonding characteristics, phase composition, porosity, pore size, mechanical strength, and microstructure of porous SiC ceramic supports were investigated. Mullite bond phase formation kinetics was studied following the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model using non-isothermal differential thermal analysis (DTA) data. Compared to porous SiC ceramic filter supports having no needle-like mullite bond phase, materials processed by the mullite bonding technique exhibited higher average strength (22.1%) and elastic modulus (5.4%) at a similar porosity level of ~38%, with upper and lower bounds of their strength, modulus, and porosity being 39.1 MPa, 40.2 GPa, and 36.3% and 34.2 MPa, 31.3 GPa, and 33.0%, respectively. Spray coating method was applied for preparation of oxidation-bonded SiC filtration layer having thickness of ~150 µm and pore size of ~5–20 µm over the porous SiC support compacts using aqueous slurry made of fine SiC powder (d₅₀ = 15 µm) followed by sintering. The layered ceramics thus prepared are potential materials for gas filter applications.     

Kinetics of epoxidation of jatropha oil with peroxyacetic and peroxyformic acid catalysed by acidic ion exchange resin

The kinetics of epoxidation of jatropha oil by peroxyacetic/peroxyformic acid, formed in situ by the reaction of aqueous hydrogen peroxide and acetic/formic acid, in the presence of an acidic ion exchange resin as catalyst in or without toluene, was studied. The presence of an inert solvent in the reaction mixture appeared to stabilise the epoxidation product and minimise the side reaction such as the opening of the oxirane ring. The effect of several reaction parameters such as stirring speed, hydrogen peroxide-to-ethylenic unsaturation molar ratio, acetic/formic acid-to-ethylenic unsaturation molar ratio, temperature, and catalyst loading on the epoxidation rate as well as on the oxirane ring stability and iodine value of the epoxidised jatropha oil were examined. The multiphase process consists of a consecutive reaction, acidic ion exchange resin catalysed peroxyacid formation followed by epoxidation. The catalytic reaction of peroxyacetic/peroxyformic acid formation was found to be characterised by adsorption of only acetic (or formic) acid and peroxyacetic/peroxyformic acid on the active catalyst sites, and the irreversible surface reaction was the overall rate determining step. The proposed kinetic model takes into consideration two side reactions, namely, epoxy ring opening involving the formation of hydroxy acetate and hydroxyl groups and the reaction of the peroxyacid and epoxy group. The kinetic and adsorption constants of the rate equations were estimated by the best fit using nonlinear regression method. Good agreement between experimental and predicted data validated the proposed kinetic model. From the estimated kinetic constants, the apparent activation energy for epoxidation reaction was found to be 53.6 kJ/mol. This value compares well with those reported by other investigators for the same reaction over similar catalysts.     

HCV-hepatocellular carcinoma: new findings and hope for effective treatment

We present here a comprehensive review of the current literature plus our own findings about in vivo and in vitro analysis of hepatitis C virus (HCV) infection, viral pathogenesis, mechanisms of interferon action, interferon resistance, and development of new therapeutics. Chronic HCV infection is a major risk factor for the development of human hepatocellular carcinoma. Standard therapy for chronic HCV infection is the combination of interferon alpha and ribavirin. A significant number of chronic HCV patients who cannot get rid of the virus infection by interferon therapy experience long-term inflammation of the liver and scarring of liver tissue. Patients who develop cirrhosis usually have increased risk of developing liver cancer. The molecular details of why some patients do not respond to standard interferon therapy are not known. Availability of HCV cell culture model has increased our understanding on the antiviral action of interferon alpha and mechanisms of interferon resistance. Interferons alpha, beta, and gamma each inhibit replication of HCV, and the antiviral action of interferon is targeted to the highly conserved 5'UTR used by the virus to translate protein by internal ribosome entry site mechanism. Studies from different laboratories including ours suggest that HCV replication in selected clones of cells can escape interferon action. Both viral and host factors appear to be involved in the mechanisms of interferon resistance against HCV. Since interferon therapy is not effective in all chronic hepatitis C patients, alternative therapeutic strategies are needed to treat chronic hepatitis C patients not responding to interferon therapy. We also reviewed the recent development of new alternative therapeutic strategies for chronic hepatitis C, which may be available in clinical use within the next decade. There is hope that these new agents along with interferon will prevent the occurrence of hepatocellular carcinoma due to chronic persistent hepatitis C virus infection. This review is not inclusive of all important scientific publications due to space limitation.     

Handover and new call blocking performance with dynamic single‐channel assignment in linear cellular arrays

We consider dynamic assignment of a single channel in a linear cellular array, and derive closed‐form expressions for the blocking probability of handover calls and new calls in terms of the array size and traffic load assuming a Markov traffic model. Handover and new call blocking performance in the limit of large arrays and extreme traffic loads is also determined. This revised version was published online in August 2006 with corrections to the Cover Date.