Sensors and observers in distributed parameter systems

Luenberger observer theory is extended to distributed parameter systems. This extension is based on the consideration of sensors. For systems with infinite dimensional state spaces, it is possible to construct the state vector asymptotically (or a part of the state vector) by a ‘good’ choice of sensors. We show that the link between detectability and sensor structure may be of some interest in the construction of observers.     

Aggregation convergecast scheduling in wireless sensor networks

We consider the problem of scheduling in wireless sensor networks for the purposes of aggregation convergecast. We observe that existing schemes adopt essentially a two phase approach, consisting of, first, a tree construction and, second, a scheduling phase. Following a similar approach, we propose two new improvements, one to each of the two phases. Starting with a new lower bound on the schedule length, we make use of it in the tree construction phase. The tree construction phase consists of solutions to instances of bipartite graph semi-matchings. The scheduling phase is a weight-based priority scheme that obeys dependency (tree) and interference constraints. Our extensive experiments show that, overall, our proposed solution not only outperforms all previously proposed solutions in terms of schedule length, but it also significantly extends the network’s lifetime.     

Hybrid nanocomposites for mid-range ballistic protection

This paper focuses on ballistic tests of a new class of composite materials, i.e. hybrid nanocomposites. The two hybrid nanocomposites studied are fiber glass/epoxy/nanoclay and fiber glass/epoxy/nanographite. The fiber glass used is a plain weave 200 g/m², while the nanoclay is an organically modified montmorillonite ceramic (Nanomer I30E). The expandable graphite used to generate the graphene nanosheets was from Graftech (grade 160-80N). Ballistic tests were performed considering two types of ammunition, i.e. 38 caliber and 9 mm full metal jacketed. The results showed that for a 38 revolver projectile a 5 mm thick nanocomposite with additional 5 mm nanoclay layer was able to absorb the energy efficiently. A 9 mm projectile, with speed of 380 m/s, was stopped by a two plates (5 mm each) arrangement with elastic deformation of the second plate less than 18 mm. The energies during the ballistic tests ranged from 316 to 576 J.     

Plasma ignition threshold disparity between silver nanoparticle-based target and bulk silver target at different laser wavelengths

Plasma ignition threshold of nanoparticle-based and bulk silver targets was measured in air. The plasma was initiated by a Nd:YAG laser at wavelengths of 355, 532, and 1064 nm. The plasma ignition was monitored utilizing the prominent Ag I line at 546.5 nm. Lower ignition thresholds of the nanoparticle-based silver target were estimated at 0.4?±?0.02, 0.34?±?0.04, and 0.27?±?0.035 J cm~(-2) coupled with the different laser wavelengths, respectively. In contrast, the bulk silver target plasma exhibited an order of magnitude higher ignition threshold. A three orders of magnitude enhanced emission intensity from the nano-based target over the bulk target was achieved at lower levels of laser irradiation. A reduction of the thermal diffusion length of the nanosilver was assumed in order to theoretically predict this reduction in the plasma threshold. In addition, the effect of self-reversal on the resonance lines was taken into consideration.     

Methylmercury Causes Neurodegeneration and Downregulation of Myelin Basic Protein in the Spinal Cord of Offspring Rats after Maternal Exposure

Methylmercury (MeHg) is one of the most dangerous toxic pollutants spread throughout the earth. Chronic MeHg intoxication by contaminated food ingestion is the most common threat to human health, including impairment to the developing fetus. The present study aims at investigating the effects of maternal exposure to MeHg during gestation and lactation on the spinal cord of offspring. Pregnant rats received oral doses of MeHg (40 μg/kg/day) over a period of 42 days (21 gestation and 21 lactation). Control animals received the vehicle only. Total mercury concentration was measured in blood samples from offspring collected at the 41st postnatal day. Counting of motor neurons and immunoreactivity for myelin basic protein (MBP) were assessed in the spinal cords in both control and MeHg-intoxicated animals. Our results showed that MeHg promoted an increase in blood Hg levels. In addition, it caused a reduction in the number of spinal cord motor neurons as well as decreased MBP immunoreactivity in the cervical, thoracic and lumbar segments. Our present findings suggest that MeHg intoxication during rat pregnancy and lactation is associated with a pattern of motor neuron degeneration and downregulation of myelin basic protein in different segments of a developing spinal cord. Further studies are needed to establish the effect of MeHg intoxication in both young and adult rats.     

Interconnection between the solidification and precipitation hardening processes of an AlSiCu alloy

Horizontal directional solidification and precipitation hardening experiments were performed with the Al5.5Si3Cu alloy. Solidification thermal and microstructural parameters such as growth and cooling rates (V_L and T_R, respectively) and the secondary dendrite arm spacing (λ₂) were determined experimentally. As-solidified samples were selected and submitted to the T6-heat treatment (T6-HT). The T6-HT was carried out considering two solution times: 8 and 5?h at 490?±?2°C, followed by quenching in warm water (60?±?2°C), aging for 5?h at 155?±?2°C and air-cooling. Higher HV values were observed for the solution time of 5 h. As highlights of this work, the influence of the processing parameters (V_L, T_R and λ₂) on the distribution, morphology and size of the eutectic Si particles has been investigated.     

Liposomes as Proteinase Carriers for the Accelerated Ripening of Saint-Paulin Type Cheese

The possibility of accelerated cheese ripening through addition of liposome entrapped proteinase to milk was investigated. Both enzyme encapsulation rate in liposomes and their retention in cheese were evaluated with multilamellar vesicles (MLV) and reverse-phase evaporation vesicles (REV). Using REV in Saint-Paulin type curd, no nitrogen loss was observed to the whey due to the added enzymes in liposomes. In cheese, REV produced a more progressive proteolysis during ripening than MLV did. REV addition did not lead to texture defects. Bitterness development, a critical defect in enzyme added cheese, could be delayed and minimized using REV.     

Endothelin receptors mediating vasoconstriction in rat pressurized small arteries

The effects of endothelin-1 (ET-1), a nonselective ETA and ETB receptor agonist, and sarafotoxin S6c, a selective ETB agonist, were investigated in the presence and absence of BQ123 and BQ788, ETA- and ETB-selective antagonists, respectively, in rat mesenteric small arteries, using a perfusion pressurized arteriograph in which segments of vessels were cannulated and exposed to constant pressure and flow. ET-1 (10(-13)-10(-7) M) induced vasoconstriction in both intact and endothelium-denuded arteries in a concentration-dependent manner. BQ123 (10(-7) and 10(-6) M) inhibited the effect of ET-1, displacing the concentration-response curve to the right in a concentration-dependent manner. The effect of ET-1 was not significantly affected by BQ788 (10(-7) and 10(-6) M), a selective antagonist of ETB receptors. Sarafotoxin S6c (10(-11)-10(-7) M) also induced a slight concentration-dependent vasoconstriction. The effect of sarafotoxin S6c (10(-8) M) was inhibited by the ETB-selective antagonist BQ788 (10(-7) M), but was not significantly changed by BQ123 (10(-7) M). Vasoconstriction induced by sarafotoxin S6c (10(-8) M) in a single bolus concentration was significantly greater than the contraction induced by the same concentration as part of a cumulative concentration-response curve, indicating desensitization or downregulation of ETB receptors during the latter. Repeated application of single concentrations of sarafotoxin S6c (10(-8) M) caused progressively smaller contraction of arteries. These results show the existence of both ETA and ETB vasoconstrictor receptors located on smooth muscle of small arteries. They also show that ETB receptors induce a smaller constrictor effect, and rapidly undergo desensitization after sustained or repeated activation.