Rheological behaviour of processed avocado pulp emulsions

Shear rate vs. shear stress data were obtained on avocado pulp in water emulsions using a concentric cylinder rheometer and fitted to a power law model. Dilution, as volume fraction of water, had a pronounced effect on the apparent viscosity of the pulp emulsions and the Richardson equation, (η_R= exp.( a φ) for the emulsion viscosity fitted the data well. A mean slope coefficient, a , of 4.57 can be used as a first approximation. Enzymatic treatment (40°C, 1 h), is slightly more effective than thermal treatment (65°C, 1 h), in reducing the initial apparent viscosity of the pulp-water emulsions     

Securing DSR against wormhole attacks in multirate ad hoc networks

A wormhole attack is one of the hardest problems to detect whereas it can be easily implanted in any type of wireless ad hoc network. A wormhole attack can easily be launched by the attacker without having knowledge of the network or compromising any legitimate nodes. Most existing solutions either require special hardware devices or make strong assumptions in order to detect wormhole attacks which limit the usability of these solutions. In this paper, we present a security enhancement to dynamic source routing (DSR) protocol against wormhole attacks for ad hoc networks which relies on calculation of round trip time (RTT). Our protocol secures DSR against a wormhole attack in ad hoc networks for multirate transmissions. We also consider the processing and queuing delays of each participating node in the calculation of RTTs between neighbors which to date has not been addressed in the existing literature. This work provides two test cases that show that not taking multirate transmission into consideration results in miss identifying a wormhole attack.     

Novel method to transform ZnO nanorods into interlaced tattered nanosheets by changing the target inclination angle

ZnO nanoparticles were synthesized by liquid-phase pulse laser ablation of a Zn foil target immersed in deionized water. Nanosecond Q-switched Nd:YAG laser pulses of 532 nm were applied to the Zn foil target at a perpendicular and inclined (θ = 45°) angles. X-ray diffraction analysis revealed that both cases feature a ZnO nanostructure with a hexagonal wurtzite structure and that the particle size increases with the inclined target angle. Field emission scanning electron microscopy results of a colloidal drop cast on a glass substrate showed the ZnO has a nanorod structure in the case of a perpendicular target angle and an interlaced tattered nanosheet structure in the case of an inclined target angle. Photoluminescence spectra showed emission peaks in the UV, violet, blue, and green spectral regions, which correspond to excitonic and various defects resulting in an enhancement of emissions at inclined target angle.     

An Integrated Experimental and Computational System for the Thermal Characterization of Complex Three-Dimensional Submicron Electronic Devices

This work presents the creation of a coupled analysis engine and experimental system capable of fully characterizing the thermal behavior of complex, 3D, active, submicron, electronic devices. First, the surface temperature field of an activated device is non-invasively measured with submicron spatial resolution. Next, the thermal conductivity of each thin-film layer composing the device is measured and a numerical model is built using these values. The measured temperature distribution map is then used as input for an ultra-fast inverse computational solution to fully characterize the thermal behavior of the complex 3D device. By bringing together measurement and computation, it becomes possible for the first time to non-invasively extract the 3D thermal behavior of nanoscale embedded features that cannot otherwise be accessed. The power of the method was demonstrated by verifying that it can extract details of interest of a representative MOSFET device.     

Minimizing broadcast latency and redundancy in asynchronous wireless sensor networks

Asynchronous duty cycle Medium Access Control (MAC) protocols do not require global synchronization because nodes determine their wake-up schedule independently. As a result, these MACs have superior performance to those that employ synchronous duty-cycles in terms of energy expenditure, and advantageously, they are simple to implement. A key limitation is that they do not support efficient broadcast. A node needs to transmit a broadcast packet multiple times via unicast because only a subset of its neighbors may be awake at any given point in time. To address this problem, this paper proposes a centralized and distributed asynchronous broadcast algorithm that achieves minimal broadcast latency and redundancy. In addition, it uses a novel asynchronous MAC protocol that ensures all neighbors of a broadcasting node are awake to receive a broadcast. The performance of our algorithms is evaluated under different network configurations. We show via extensive simulation studies that our algorithms have near optimal network performance in terms of broadcast latency. In particular, compared to OTAB, the best broadcast scheduling algorithm to date, the broadcast latency and transmission times achieved by our designs are 1/5 and 1/2 that of OTAB, respectively.     

Vancomycin penetration into biofilm covering infected prostheses and effect on bacteria

To evaluate the adequacy of penetration of antibiotics into biofilm, a novel in vitro model for prosthesis-related infection was developed. Sterile stainless steel orthopedic nuts were incubated with slime-producing Staphylococcus epidermidis. Biofilm-covered nuts were exposed to varying concentrations of vancomycin; then biofilms were harvested. Vancomycin levels in biofilm, as measured by fluorescent polarization immunoassay, far exceeded the MIC and MBC of vancomycin for the organism. Bacterial growth in biofilm was inversely related to vancomycin concentration in biofilm, but even extremely high drug concentrations did not eradicate bacteria embedded in biofilm. The MICs and MBCs for bacteria recovered from biofilm did not differ from those for incubating organisms. Thus, failure of glycopeptide antibiotics to cure prosthesis-related infection is not due to poor penetration of drugs into biofilm but likely due to diminished antimicrobial effect on bacteria in the biofilm environment.     

In vivo efficacy of antimicrobial-coated fabric from prosthetic heart valve sewing rings

Escherichia coli tRNA(Val) with pyrimidine substitutions for the universally conserved 3'-terminal adenine can be readily aminoacylated. It cannot, however, transfer valine into polypeptides. Conversely, despite being a poor substrate for valyl-tRNA synthetase, tRNA(Val) with a 3'-terminal guanine is active in in vitro polypeptide synthesis. To better understand the function of the 3'-CCA sequence of tRNA in protein synthesis, the effects of systematically varying all three bases on formation of the Val-tRNA(Val):EF-Tu:GTP ternary complex were investigated. Substitutions at C74 and C75 have no significant effect, but replacing A76 with pyrimidines decreases the affinity of valyl-tRNA(Val) for EF-Tu:GTP, thus explaining the inability of these tRNA(Val) variants to function in polypeptide synthesis. Valyl-tRNA(Val) terminating in 3'-guanine is readily recognized by EF-TU:GTP. Dissociation constants of the EF-Tu:GTP ternary complexes with valine tRNAs having nucleotide substitutions at the 3' end increase in the order adenine < guanine < uracil; EF-Tu has very little affinity for tRNA terminating in 3' cytosine. Similar observations were made in studies of the interaction of 3' end mutants of E. coli tRNA(Ala) and tRNA(Phe) with EF-Tu:GTP. These results indicate that EF-Tu:GTP preferentially recognizes purines and discriminates against pyrimidines, especially cytosine, at the 3' end of aminoacyl-tRNAs.     

Transient thermo-reflectance measurements of the thermal conductivity and interface resistance of metallized natural and isotopically-pure silicon

The transient thermoreflectance method has been used to measure the thermal conductivity of natural silicon and isotopically-pure silicon-28 layers that are epitaxially grown on natural silicon substrates. The measurements were performed at room temperature for both a low level (10¹⁶) and a higher level (2×10¹⁹) of Boron doping of the epitaxial layers. The results indicate a gain of approximately 55% in the thermal conductivity of Si²⁸ as compared to that of natural Si, at both low and higher levels of doping, and a loss of approximately 19% for both types of silicon due to the higher level of doping.