Active management of multi-service networks.

Future multiservice networks will be extremely large and complex. Novel management solutions will be required to keep the management costs reasonable. Active networking enables management to be delegated to network users as a large set of independent small scale management systems. A novel architecture for an active network based management solution for multiservice networking is presented

Ordered and chaotic vortex streets behind circular cylinders at low Reynolds numbers

We report some experiments undertaken to investigate the origin of ordered and chaotic laminar vortex streets behind circular cylinders at low Reynolds numbers. We made simultaneous measurements of near wake longitudinal velocity and cylinder lateral vibration amplitude spectra for cylinder Reynolds numbers in the range from 40 to 160. For a non-vibrating cylinder the velocity energy spectra contained only a single peak, at the Strouhal frequency. When the cylinder was observed to vibrate in response to forcing by the vortex wake, additional dominant spectral peaks appeared in the resulting ‘ordered’ velocity spectra. Cylinder vibrations too small to be noticed with the naked eye or from audible Aeolian tones produced a coupled wake-cylinder response with dramatic effects in hot-wire and cylinder vibration detector signals. The velocity spectra associated with these coupled motions had dominant peaks at the Strouhal frequency fs, at a frequency fc proportional to the fundamental cylinder vibration frequency, and at sum and difference combinations of multiples of fs and fc. In windows of chaos the velocity spectra were broadened by switching between different competing coupling modes. The velocity spectra were very sensitive to the nature of the boundary conditions at the ends of the cylinder. Our measurements strongly suggest that the very similar regions of ‘order’ and ‘chaos’ observed by Sreenivasan and interpreted by him as transition through quasi-periodic states in the sense of the Ruelle, Takens, and Newhouse theory were also due to aeroelastic coupling of the vortex wake with cylinder vibration modes

Hydrodynamic stability of swimming in ostraciid fishes: role of the carapace in the smooth trunkfish Lactophrys triqueter (Teleostei: Ostraciidae)

The hydrodynamic bases for the stability of locomotory motions in fishes are poorly understood, even for those fishes, such as the rigid-bodied smooth trunkfish Lactophrys triqueter, that exhibit unusually small amplitude recoil movements during rectilinear swimming. We have studied the role played by the bony carapace of the smooth trunkfish in generating trimming forces that self-correct for instabilities. The flow patterns, forces and moments on and around anatomically exact, smooth trunkfish models positioned at both pitching and yawing angles of attack were investigated using three methods: digital particle image velocimetry (DPIV), pressure distribution measurements, and force balance measurements. Models positioned at various pitching angles of attack within a flow tunnel produced well-developed counter-rotating vortices along the ventro-lateral keels. The vortices developed first at the anterior edges of the ventro-lateral keels, grew posteriorly along the carapace, and reached maximum circulation at the posterior edge of the carapace. The vortical flow increased in strength as pitching angles of attack deviated from 0°, and was located above the keels at positive angles of attack and below them at negative angles of attack. Variation of yawing angles of attack resulted in prominent dorsal and ventral vortices developing at far-field locations of the carapace; far-field vortices intensified posteriorly and as angles of attack deviated from 0°. Pressure distribution results were consistent with the DPIV findings, with areas of low pressure correlating well with regions of attached, concentrated vorticity. Lift coefficients of boxfish models were similar to lift coefficients of delta wings, devices that also generate lift through vortex generation. Furthermore, nose-down and nose-up pitching moments about the center of mass were detected at positive and negative pitching angles of attack, respectively. The three complementary experimental approaches all indicate that the carapace of the smooth trunkfish effectively generates self-correcting forces for pitching and yawing motions — a characteristic that is advantageous for the highly variable velocity fields experienced by trunkfish in their complex aquatic environment. All important morphological features of the carapace contribute to producing the hydrodynamic stability of swimming trajectories in this species

Flow Patterns Around the Carapaces of Rigid-bodied, Multi-propulsor Boxfishes (Teleostei: Ostraciidae)

Boxfishes (Teleostei: Ostraciidae) are rigid-body, multi-propulsor swimmers that exhibit unusually small amplitude recoil movements during rectilinear locomotion. Mechanisms producing the smooth swimming trajectories of these fishes are unknown, however. Therefore, we have studied the roles the bony carapaces of these fishes play in generating this dynamic stability. Features of the carapaces of four morphologically distinct species of boxfishes were measured, and anatomically-exact stereolithographic models of the boxfishes were constructed. Flow patterns around each model were investigated using three methods: 1) digital particle image velocimetry (DPIV), 2) pressure distribution measurements, and 3) force balance measurements. Significant differences in both cross-sectional and longitudinal carapace morphology were detected among the four species. However, results from the three interrelated approaches indicate that flow patterns around the various carapaces are remarkably similar. DPIV results revealed that the keels of all boxfishes generate strong longitudinal vortices that vary in strength and position with angle of attack. In areas where attached, concentrated vorticity was detected using DPIV, low pressure also was detected at the carapace surface using pressure sensors. Predictions of the effects of both observed vortical flow patterns and pressure distributions on the carapace were consistent with actual forces and moments measured using the force balance. Most notably, the three complementary experimental approaches consistently indicate that the ventral keels of all boxfishes, and in some species the dorsal keels as well, effectively generate self-correcting forces for pitching motions—a characteristic that is advantageous for the highly variable velocity fields in which these fishes reside

Chaos in Shear Flows

Almost 25 years ago Lorenz published his seminal study on the existence of a strange attractor in the phase space of a severely truncated model system arising from the hydrodynamical equations describing two-dimensional convection. Nearly a century ago Poincare published his famous treatise Les Methodes Noovelles de la Mecaniaue Celeste (1892) in which the possible complexity of behavior in nonintegrable, conservative systems was first envisioned. Both these works address an age old puzzle: How do apparently stochastic outputs arise from an entirely deterministic system subject to non-stochastic inputs

sy680 is a novel allele of pkd-2

A new allele of pkd-2 was isolated in a behavioral genetic screen for male mating defects, and found to result in a substitution of Arginine for Glycine in the equivalent of human PKD2 alanine 615. The C. elegans ortholog of polcystin-2 is encoded by pkd-2 (Barr et al., 2001). From an EMS screen of a plg-1; him-5 strain for male mating defective mutants and a secondary behavioral screen for defects in discrete steps of male mating behavior, namely response to contact to hermaphrodites and vulval location (described in Schindelman et al., 2006), we identified a new allele of pkd-2 based on mapping and complementation. sy680 fails to complement pkd-2(sy606) for defects in response to contact with hermaphrodite and vulval location. Here we report the sequence of this allele. PCR amplification and sequencing of pkd-2 exons indicated that there was a c-->t transition in the transcribed DNA strand (g-->a in the pkd-2 sense strand; Figure 1A). This change leads to an altered codon, a Glycine to Arginine substitution the PKD-2 protein. This position corresponds to A615 of the human protein (Figure 1B)

A new mutation with a polycystin phenotypic spectrum in Caenorhabditis elegans

lov-1 and pkd-2, which encode the C. elegans orthologs of human polycystin-1 and -2, are necessary for three particular aspects of male mating behavior. In a screen for male mating defective mutants with similar spectrum of mating defects, we identified a mutation that apparently defines a new locus, lov-3. We isolated the sy682 mutation in an ethyl-methane sulphonate (EMS)-screen of Caenorhabditis elegans strain PS1395 [genotype: plg-1(e2001d); him-5(e1490)] for mutant males that do not mate efficiently and hence do not form plugs on hermaphrodites (Liu et al, 2017). sy682 is defective in the males’ response to contact with hermaphrodite and in vulval location (Table 1). The vulval location defect is failing to stop at the vulva. These two phenotypes are associated with lov-1 (Barr, 1999) and pkd-2 loss-of-function mutations (Barr et al. 2001; Whittaker et al., 2017). sy682 maps to the X chromosome and thus is distinct from lov-1 and pkd-2, so it defines a likely new locus, lov-3

Caenorhabditis elegans Gα_q Regulates Egg-Laying Behavior via a PLCβ-Independent and Serotonin-Dependent Signaling Pathway and Likely Functions Both in the Nervous System and in Muscle

egl-30 encodes the single C. elegans ortholog of vertebrate Gα_q family members. We analyzed the expression pattern of EGL-30 and found that it is broadly expressed, with highest expression in the nervous system and in pharyngeal muscle. We isolated dominant, gain-of-function alleles of egl-30 as intragenic revertants of an egl-30reduction-of-function mutation. Using these gain-of-function mutants and existing reduction-of-function mutants, we examined the site and mode of action of EGL-30. On the basis of pharmacological analysis, it has been determined that egl-30 functions both in the nervous system and in the vulval muscles for egg-laying behavior. Genetic epistasis over mutations that eliminate detectable levels of serotonin reveals that egl-30requires serotonin to regulate egg laying. Furthermore, pharmacological response assays strongly suggest that EGL-30 may directly couple to a serotonin receptor to mediate egg laying. We also examined genetic interactions with mutations in the gene that encodes the single C. elegans homolog of PLCβ and mutations in genes that encode signaling molecules downstream of PLCβ. We conclude that PLCβ functions in parallel with egl-30 with respect to egg laying or is not the major effector of EGL-30. In contrast, PLCβ-mediated signaling is likely downstream of EGL-30 with respect to pharyngeal-pumping behavior. Our data indicate that there are multiple signaling pathways downstream of EGL-30 and that different pathways could predominate with respect to the regulation of different behaviors

Extrasynaptic acetylcholine signaling through a muscarinic receptor regulates cell migration

Acetylcholine (ACh) promotes various cell migrations in vitro, but there are few investigations into this nonsynaptic role of ACh signaling in vivo. Here we investigate the function of a muscarinic receptor on an epithelial cell migration in Caenorhabditis elegans. We show that the migratory gonad leader cell, the linker cell (LC), uses an M1/M3/M5-like muscarinic ACh receptor GAR-3 to receive extrasynaptic ACh signaling from cholinergic neurons for its migration. Either the loss of the GAR-3 receptor in the LC or the inhibition of ACh release from cholinergic neurons resulted in migratory path defects. The overactivation of the GAR-3 muscarinic receptor caused the LC to reverse its orientation through its downstream effectors Gαq/egl-30, PLCβ/egl-8, and TRIO/unc-73. This reversal response only occurred in the fourth larval stage, which corresponds to the developmental time when the GAR-3::yellow fluorescent protein receptor in the membrane relocalizes from a uniform to an asymmetric distribution. These findings suggest a role for the GAR-3 muscarinic receptor in determining the direction of LC migration