Cooperative data collection in ad hoc networks

This paper studies the problem of data gathering in multi-hop wireless ad hoc networks. In this scenario, a set of wireless devices constantly sample their surroundings and initiate report messages addressed to the base station. The messages are forwarded in a multi-hop fashion, where the wireless devices act both as senders and relays. We consider data gathering without aggregation, i.e. the nodes are required to forward all the messages initiated by other nodes (in addition to their own) to the base station. This is in contrast to the well studied problem of data gathering with aggregation, which is significantly simpler. As some nodes experience a larger load of forward requests, these nodes will have their battery charges depleted much faster than the other nodes—which can rapidly break the connectivity of the network. We focus on maximizing the network lifetime through efficient balancing of the consumed transmission energy. We show that the problem is NP-hard for two network types and develop various approximation schemes. Our results are validated through extensive simulations.     

Impaired Functional Connectivity Underlies Fragile X Syndrome

Fragile X syndrome (FXS), the most common form of inherited intellectual disability, is caused by a developmentally regulated silencing of the FMR1 gene, but its effect on human neuronal network development and function is not fully understood. Here, we isolated isogenic human embryonic stem cell (hESC) subclones—one with a full FX mutation and one that is free of the mutation (control) but shares the same genetic background—differentiated them into induced neurons (iNs) by forced expression of NEUROG-1, and compared the functional properties of the derived neuronal networks. High-throughput image analysis demonstrates that FX-iNs have significantly smaller cell bodies and reduced arborizations than the control. Both FX- and control-neurons can discharge repetitive action potentials, and FX neuronal networks are also able to generate spontaneous excitatory synaptic currents with slight differences from the control, demonstrating that iNs generate more mature neuronal networks than the previously used protocols. MEA analysis demonstrated that FX networks are hyperexcitable with significantly higher spontaneous burst-firing activity compared to the control. Most importantly, cross-correlation analysis enabled quantification of network connectivity to demonstrate that the FX neuronal networks are significantly less synchronous than the control, which can explain the origin of the development of intellectual dysfunction associated with FXS.     

Stokes flow due to infinite arrays of stokeslets in three dimensions

Infinite periodic arrays of stokeslets in three dimensions are summed up by obtaining various rapidly converging infinite series. The three cases treated here are: 1. Identical stokeslets distributed at constant intervals on a line parallel to a plate, 2. An array of identical stokeslets distributed on a two-dimensional periodic lattice on a plane parallel to a plate, 3. The same array, but parallel to and in between two plates. Computational results are shown and comparisons with previously averaged expressions are made.     

Simulations of three-dimensional ciliary beats and cilia interactions

A new set of equations describing the time evolution of torsion and curvature for an inextensible curve is developed. Combined with our recently developed Slender Body Theory approach to such problems, these equations were applied to simulate three-dimensional ciliary beats, while allowing for cilia interactions. The computer animation technique, which was originally designed to display two-dimensional beats, has been enhanced to accommodate the new three-dimensional results.     

Target oriented network intelligence collection: effective exploration of social networks

World Wide Web - Target Oriented Network Intelligence Collection (TONIC) is a crawling process whose goal is to find social network profiles that contain information about a given target. Such...     

Mechanical Alloying and Spark Plasma Sintering of Higher Manganese Silicides for Thermoelectric Applications

The present challenges in the energy crisis require finding new ways to reduce consumption of fossil fuels. Thermoelectrics can help reduce fuel consumption by producing electricity from waste heat. The higher manganese silicides (HMS) have shown promise in this field as inexpensive, nontoxic, and highly stable p-type thermoelectric materials. One of the production techniques for HMS is mechanical alloying by ball milling. In this research the effect of the ball-milling duration and speed on the phases produced was studied. Mn and Si powders were milled at speeds of 200 RPM to 800 RPM for 1 h to 7 h. X-ray diffraction (XRD) results of the samples prepared using mechanical alloying show deterioration into the MnSi phase. The sample that underwent 5 h of milling at 800 RPM showed the greatest amount of HMS phase and was subsequently spark plasma sintered. The sample showed insufficient thermoelectric properties (ZT ≈ 0.1 at 450°C), compared with either solid-state reaction samples showing ZT ≈ 0.4 or cast samples showing ZT ≈ 0.63 at 450°C. The reduced ZT values of the mechanically alloyed and spark-plasma-sintered samples were attributed to the high relative amount of MnSi phase. The correlation between the relative amount of MnSi and the transport properties is described in detail.     

Evidence of zeta protein kinase C involvement in polymorphonuclear neutrophil integrin-dependent adhesion and chemotaxis

Classical chemoattractants and chemokines trigger integrin-dependent adhesion of blood leukocytes to vascular endothelium and also direct subsequent extravasation and migration into tissues. In studies of human polymorphonuclear neutrophil responses to formyl peptides and to interleukin 8, we show evidence of involvement of the atypical zeta protein kinase C in the signaling pathway leading to chemoattractant-triggered actin assembly, integrin-dependent adhesion, and chemotaxis. Selective inhibitors of classical and novel protein kinase C isozymes do not prevent chemoattractant-induced neutrophil adhesion and chemotaxis. In contrast, chelerythrine chloride and synthetic myristoylated peptides with sequences based on the endogenous zeta protein kinase C pseudosubstrate region block agonist-induced adhesion to fibrinogen, chemotaxis and F-actin accumulation. Biochemical analysis shows that chemoattractants trigger rapid translocation of zeta protein kinase C to the plasma membrane accompanied by rapid but transient increase of the kinase activity. Moreover, pretreatment with C3 transferase, a specific inhibitor of Rho small GTPases, blocks zeta but not alpha protein kinase C plasma membrane translocation. Synthetic peptides from zeta protein kinase C also inhibit phorbol ester-induced integrin-dependent adhesion but not NADPH-oxidase activation, and C3 transferase pretreatment blocks phorbol ester-triggered translocation of zeta but not alpha protein kinase C. These data suggest the involvement of zeta protein kinase C in chemoattractant-induced leukocyte integrin-dependent adhesion and chemotaxis. Moreover, they highlight a potential link between atypical protein kinase C isozymes and Rho signaling pathways leading to integrin-activation.     

Scaling-up of process for production of antibiotic of Myxococcus xanthus TA

A process for the production of Myxococcus xanthus TA (M. xanthus TA) antibiotic was scaled-up to bench and pilot plant scales. The process includes the following steps: (a) propagation of M. xanthus TA in cultures of up to 750 litres. After 4 days of growth the maximum antibiotic yield achieved was 24 units/ml supernatant, and the highest titres were obtained at a low oxygen absorption rate of 0.2; (b) processing of the clarified culture supernatant. Two methods were successfully piloted: the chloroform extraction method and the kaolin adsorption method. Both methods were followed by elution with 20% methanol in chloroform. The recoveries of antibiotic activity were 90% and 85% respectively by the two methods. The process described could be used for the large-scale preparation of the novel antibiotic of M. xanthus TA.