Dyson-Schwinger Equations and Coulomb Gauge Yang-Mills Theory

Coulomb gauge Yang-Mills theory is considered within the first order formalism. It is shown that the action is invariant under both the standard BRS transform and an additional component. The Ward-Takahashi identity arising from this non-standard transform is shown to be automatically satisfied by the equations of motion.Comment: 3 pages, talk given at Quark Confinement and the Hadron Spectrum VII (2-7 Sep, 2006), Ponta Delgada, Azore

The ghost propagator in Coulomb gauge

We present results for a numerical study of the ghost propagator in Coulomb gauge whereby lattice results for the spatial gluon propagator are used as input to solving the ghost Dyson-Schwinger equation. We show that in order to solve completely, the ghost equation must be supplemented by a boundary condition (the value of the inverse ghost propagator dressing function at zero momentum) which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to low momenta until `forced' to freeze out in the infrared to the value of the boundary condition. The boundary condition can be interpreted in terms of the Gribov gauge-fixing ambiguity; we also demonstrate that this is not connected to the renormalization. Further, the connection to the temporal gluon propagator and the infrared slavery picture of confinement is discussed.Comment: 3 pages, 2 figures, talk presented at "Quark Confinement and the Hadron Spectrum IX", Madrid, August 30-September 3, 2010, to appear in the proceeding

Thermosensitivity of the lobster, Homarus americanus, as determined by cardiac assay

It is generally accepted that crustaceans detect, and respond to, changes in water temperature, yet few studies have directly addressed their thermosensitivity. In this investigation a cardiac assay was used as an indicator that lobsters (Homarus americanus) sensed a change in temperature. The typical cardiac response of lobsters to a 1-min application of a thermal stimulus, either warmer (n = 19) or colder (n = 17) than the holding temperature of 15 degrees C, consisted of a short bradycardia (39.5 +/- 8.0 s) followed by a prolonged tachycardia (188.2 +/- 10.7 s). Lobsters exposed to a range of rates of temperature change (0.7, 1.4, 2.6, 5.0 degrees C/min) responded in a dose-dependent manner, with fewer lobsters responding at slower rates of temperature change. The location of temperature receptors could not be determined, but lesioning of the cardioregulatory nerves eliminated the cardiac response. Although the absolute detection threshold is not known, it is conservatively estimated that lobsters can detect temperature changes of greater than 1 degree C, and probably as small as 0.15 degrees C. A comparison of winter and summer lobsters, both held at 15 degrees C for more than 4 weeks, revealed that although their responses to temperature changes were similar, winter lobsters (n = 18) had a significantly lower baseline heart rate (34.8 +/- 4.4 bpm) and a shorter duration cardiac response (174 s) than summer lobsters (n = 18; 49.9 +/- 5.0 bpm, and 320 s respectively). This suggests that some temperature-independent seasonal modulation of cardiac activity may be occurring

The Ability of Horseshoe Crabs (Limulus polyphemus) To Detect Changes in Temperature

Previous studies have suggested that horseshoe crabs prefer warm water, suggesting that they may be able to detect changes in water temperature. The overall goal of this study was to test this hypothesis. Our specific objectives were to: 1) find out if horseshoe crabs can detect temperature changes; 2) determine the magnitude of temperature change they can detect, and; 3) determine whether their temperature receptors are located internally or externally. Animals were placed in a light-tight chamber that received a constant flow of cooled seawater. Their heart rates were continuously recorded and a change in heart rate following the addition of warmer water was used as an indicator that they sensed the change in temperature. The results showed that 50% of horseshoe crabs responded to a temperature change of 1°C, while 100% responded to a temperature change of 2.6°C. Over half of the horseshoe crabs also responded to a rate of temperature change of less than 1.5°C. Both of these results indicate that horseshoe crabs can, indeed, sense temperature changes. Also, the horseshoe crabs typically showed a response before their internal temperature changed, indicating that their temperature receptors are most likely located externally

An Investigation of Philadelphia's Youth Aid Panel: A Community-Based Diversion Program for First-Time Youthful Offenders

The formal justice system currently does not have the resources to effectively deal with nonviolent first-time offending youth, oftentimes leaving them with little punishment aside from a criminal record. This report offers a close examination of Philadelphia's Youth Aid Panels (YAP), which seeks to provide alternative sentencing for this high-risk population through the collaboration of volunteer community members, victims, parent(s)/guardian and a law enforcement official. YAP offers victims a better sense of restitution while also providing the youth with the real opportunity to reintegrate into society without a record. Our initial exploratory evaluation shows promising results, and we offer a several recommendations to strengthen YAP programs

Central pattern generator for swimming in Melibe

The nudibranch mollusc Melibe leonina swims by bending from side to side. We have identified a network of neurons that appears to constitute the central pattern generator (CPG) for this locomotor behavior, one of only a few such networks to be described in cellular detail. The network consists of two pairs of interneurons, termed `swim interneuron 1\u27 (sint1) and `swim interneuron 2\u27 (sint2), arranged around a plane of bilateral symmetry. Interneurons on one side of the brain, which includes the paired cerebral, pleural and pedal ganglia, coordinate bending movements toward the same side and communicate via non-rectifying electrical synapses. Interneurons on opposite sides of the brain coordinate antagonistic movements and communicate over mutually inhibitory synaptic pathways. Several criteria were used to identify members of the swim CPG, the most important being the ability to shift the phase of swimming behavior in a quantitative fashion by briefly altering the firing pattern of an individual neuron. Strong depolarization of any of the interneurons produces an ipsilateral swimming movement during which the several components of the motor act occur in sequence. Strong hyperpolarization causes swimming to stop and leaves the animal contracted to the opposite side for the duration of the hyperpolarization. The four swim interneurons make appropriate synaptic connections with motoneurons, exciting synergists and inhibiting antagonists. Finally, these are the only neurons that were found to have this set of properties in spite of concerted efforts to sample widely in the Melibe CNS. This led us to conclude that these four cells constitute the CPG for swimming. While sint1 and sint2 work together during swimming, they play different roles in the generation of other behaviors. Sint1 is normally silent when the animal is crawling on a surface but it depolarizes and begins to fire in strong bursts once the foot is dislodged and the animal begins to swim. Sint2 also fires in bursts during swimming, but it is not silent in non-swimming animals. Instead activity in sint2 is correlated with turning movements as the animal crawls on a surface. This suggests that the Melibe motor system is organized in a hierarchy and that the alternating movements characteristic of swimming emerge when activity in sint1 and sint2 is bound together

Second messenger systems underlying amine and peptide actions on cardiac muscle in the horseshoe crab, Limulus polyphemus

The biochemical mechanisms by which octopamine, catecholamines and the peptide proctolin exert their actions on Limulus cardiac muscle were investigated. Amines produced long-lasting increases in the amplitude of contractions evoked by electrical stimulation. At 10(−5) mol l-1, the apparent order of potency for amine-induced increases in evoked contraction amplitude was dopamine approximately equal to octopamine greater than norepinephrine approximately equal to epinephrine. At this dose, amines produced long-lasting increases in the levels of cyclic AMP (octopamine greater than dopamine approximately equal to norepinephrine approximately equal to epinephrine), but not of cyclic GMP, in Limulus cardiac muscle. Like the amines, the adenylate cyclase activator forskolin enhanced cardiac muscle contractility and increased levels of cyclic AMP, but not of cyclic GMP. The phosphodiesterase inhibitor IBMX produced a transient increase in cardiac muscle contractility, but typically produced long-lasting negative inotropy. This agent increased levels of both cyclic AMP and cyclic GMP in Limulus cardiac muscle. Proctolin and the protein kinase C activator phorbol dB increased the contraction amplitude of the intact heart and the electrically stimulated myocardium. These compounds, as well as dopamine, elicited sustained contractures and rhythmic contractions when applied to deganglionated Limulus cardiac muscle rings. Unlike the amines, proctolin and phorbol dB did not increase cardiac muscle cyclic AMP levels. These results suggest that several second-messenger systems may be utilized by amines and peptides to produce excitatory actions on cardiac muscle fibers of the Limulus heart. Cyclic AMP appears to be an important second messenger underlying the effects of amines to enhance cardiac muscle contractility. Pharmacological data suggest that proctolin may alter cardiac muscle contractility and excitability by a mechanism which involves the phosphatidylinositol pathway. Dopamine, unlike the other amines, produces a number of proctolin-like effects and may activate both the cyclic AMP and the phosphatidylinositol systems in Limulus cardiac muscle

Influence of Natural Inshore and Offshore Thermal Regimes on Egg Development and Time of Hatch in American lobsters, Homarus americanus

Some egg-bearing (ovigerous) American lobsters (Homarus americanus) make seasonal inshore-to-offshore movements, subjecting their eggs to different thermal regimes than those of eggs carried by lobsters that do not make these movements. Our goal was to determine if differences in thermal regimes influence the rate of egg development and the subsequent time of hatch. We subjected ovigerous lobsters to typical inshore or offshore water temperatures from September to August in the laboratory (n = 8 inshore and 8 offshore, each year) and in the field (n = 8 each, inshore and offshore), over 2 successive years. Although the rate of egg development did not differ significantly between treatments in the fall (P ∼ 0.570), eggs exposed to inshore thermal regimes developed faster in the spring (P \u3c 0.001). “Inshore” eggs hatched about 30 days earlier (mean = 26 June) than “offshore” eggs (mean = 27 July), and their time of development from the onset of eyespot to hatch was significantly shorter (inshore = 287 ± 11 days vs. offshore: 311.5 ± 7.5 days, P = 0.034). Associated growing degree-days (GDD) did not differ significantly between inshore and offshore thermal treatments (P = 0.061). However, eggs retained by lobsters exposed to offshore thermal regimes accumulated more GDD in the winter than did eggs carried by inshore lobsters, while eggs exposed to inshore temperatures acquired them more rapidly in the spring. Results suggest that seasonal movements of ovigerous lobsters influence the time and location of hatching, and thus the transport and recruitment of larvae to coastal and offshore locations

Mechanisms underlying the production of carapace vibrations and associated waterborne sounds in the American lobster, Homarus americanus

American lobsters produce carapace vibrations, which also lead to waterborne acoustic signals, by simultaneously contracting the antagonistic remotor and promotor muscles located at the base of the second antenna. These vibrations have a mean frequency of 183.1 Hz (range 87–261 Hz), range in duration from 68 to 1720 ms (mean 277.1 ms) and lead to waterborne sounds of similar frequencies. Lobsters most often produce these signals using only one pair of muscles at a time and alternate between the muscles of the left and right antennae when making a series of vibrations. Occasionally, they vibrate their carapace by simultaneously contracting both sets of muscles. While the remotor muscle is required for producing carapace vibrations, the promotor appears to play a secondary role. Electrical stimulation of the remotor, but not the promotor, results in the production of vibrations, while lesions of the remotor, but not promotor, eliminate the ability of lobsters to vibrate their carapace. Lobsters of all sizes and both sexes produce these signals when startled, grasped or threatened. However, at this time, the behavioral significance of vibration and/or sound production by American lobsters is not known

Size at Maturity of Female American Lobsters from an Estuarine and Coastal Population

The size at which female lobsters reach sexual maturity was determined for two populations that inhabit waters along the coast of New Hampshire. One group was captured in the Great Bay estuary, where water temperatures in the summer typically average between 17 C and 20 C. The other gorup of lobsters resided in coastal waters, near the Isles of Shoals, where the water temperature was much colder during the summer (11-15 C). Maturity was assessed using criteria that included the following: ovarian classification; abdominal width/carapce length (CL) ratio; and the size frequency distribution of berried females. All the techniques yielded similar results and consistently demonstrated that female lobsters in the estuary matured at a smaller size than those in colder coastal waters. The smallest mature females from Great Bay were 72 mm in CL, with 50% reaching sexual maturity by 83 mm CL and all becoming mature by 89 mm CL. The difference in the proportion of mature lobsters in the estuarine versus coastal populations was much greater in the smaler size classes than in the larger size claases, suggesting a mixing of the two populations, most likely due to females from Great Bay migrating into coastal waters