The main feature of polymeric materials is the hierarchy of bonds between molecular groups. This feature is explicitly taken into account in a model of photothermal laser ablation of polymers derived in the present work. According to this model the reason for laser ablation is a photothermal bond-breaking reaction within the bulk of material originated from laser heating. In order to address the movement of the interface between gaseous and condensed phases, we change the Stefan-like boundary condition considered previously for the Frenkel–Wilson one. In the latter case the activation energy for elimination of a short enough polymer chain from the surface is proportional to the sum of the energies of weak bonds connecting this chain with the surface. We compare predictions of this model with the previously derived Stefan-like bulk model and with the surface photothermal evaporation model with respect to kinetics and dynamics of laser ablation by both nanosecond and subpicosecond pulses, including ablation by two subpicosecond pulses. This consideration suggests experimental evidence that allows one to distinguish between surface and bulk photothermal ablation mechanisms. The parameters used in numerical calculation correspond to the KrF excimer laser ablation of polyimide. The results of the theoretical modeling are compared with the existing data on kinetics of nanosecond laser ablation as well as with findings of time-resolved UV subpicosecond laser ablation experiments.

In this study, we describe the putative mechanosensory neurons, which are involved in the control of avoidance behavior of the terrestrial snail Helix lucorum. These neurons, which were termed pleural ventrolateral (PlVL) neurons, mediated part of the withdrawal response of the animal via activation of the withdrawal interneurons. Between 15 and 30 pleural mechanosensory neurons were located on the ventrolateral side of each pleural ganglion. Intracellular injection of neurobiotin revealed that all PlVL neurons sent their axons into the skin nerves. The PlVL neurons had no spontaneous spike activity or fast synaptic potentials. In the reduced "CNS-foot" preparations, mechanical stimulation of the skin covering the dorsal surface of the foot elicited spikes in the PlVL neurons without any noticeable prepotential activity. Mechanical stimulus-induced action potentials in these cells persisted in the presence of high-Mg(2+)/zero-Ca(2+) saline. Each neuron had oval-shaped receptive field 5-20 mm in length located on the dorsal surface of the foot. Partial overlapping of the receptive fields of different neurons was observed. Intracellular stimulation of the PlVL neurons produced excitatory inputs to the parietal and pleural withdrawal interneurons, which are known to control avoidance behavior. The excitatory postsynaptic potentials (EPSPs) in the withdrawal interneurons were induced in 1:1 ratio to the PlVL neuron spikes, and spike-EPSP latency was short and highly stable. These EPSPs also persisted in the high-Mg(2+)/high-Ca(2+) saline, suggesting monosynaptic connections. All these data suggest that PlVL cells were the primary mechanosensory neurons.

Coordination between different motor centers is essential for the orderly production of all complex behaviors, in both vertebrates and invertebrates. The current study revealed that rhythmic activities of two feeding structures of the pteropod mollusk Clione limacina, radula and hooks, which are used to extract the prey from its shell, are highly coordinated in a phase-dependent manner. Hook protraction always coincided with radula retraction, while hook retraction coincided with radula protraction. Thus hooks and radula were always moving in the opposite phases, taking turns grabbing and pulling the prey tissue out of the shell. Identified buccal ganglia motor neurons controlling radula and hooks protraction and retraction were rhythmically active in the same phase-dependent manner. Hook protractor motor neurons were active in the same phase with radula retractor motor neurons, while hook retractor motor neurons burst in phase with radula protractor motor neurons. One of the main mechanisms underlying the phase-locked coordination was electrical coupling between hook protractor and radula retractor motor neurons. In addition, reciprocal inhibitory synaptic connections were found between hook protractor and radula protractor motor neurons. These electrical and inhibitory synaptic connections ensure that rhythmically active hooks and radula controlling motor neurons are coordinated in the specific phase-dependent manner described above. The possible existence of a single multifunctional central pattern generator for both radula and hook motor centers is discussed.

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