Lower Devonian Zosterophyllum-like plants from central Victoria, Australia, and their significance

Three specimens belonging to Zosterophyllaceae are described. Two of these possess bilateral symmetry and are the first to be described with this arrangement from the Lower Devonian of Victoria. One of these specimens is similar to Zosterophyllum fertile, and the other cf. Zosterophyllum sp. A. is unusual in possessing vascularised long stalks. The third specimen described cf. Zosterophyllum sp. B. from Ghin Ghin Road, near Yea possesses a small spike and has sporangia that appear vertically elliptical and similar to some South China taxa. All the specimens are significantly different to previous zosterophyll taxa described from Victoria.

Spikelets in pyramidal neurons: generating mechanisms, distinguishing properties, and functional implications

Spikelets are small spike-like depolarizations that are found in somatic recordings of many neuron types. Spikelets have been assigned important functions, ranging from neuronal synchronization to the regulation of synaptic plasticity, which are specific to the particular mechanism of spikelet generation. As spikelets reflect spiking activity in neuronal compartments that are electrotonically distinct from the soma, four modes of spikelet generation can be envisaged: (1) dendritic spikes or (2) axonal action potentials occurring in a single cell as well as action potentials transmitted via (3) gap junctions or (4) ephaptic coupling in pairs of neurons. In one of the best studied neuron type, cortical pyramidal neurons, the origins and functions of spikelets are still unresolved; all four potential mechanisms have been proposed, but the experimental evidence remains ambiguous. Here we attempt to reconcile the scattered experimental findings in a coherent theoretical framework. We review in detail the various mechanisms that can give rise to spikelets. For each mechanism, we present the biophysical underpinnings as well as the resulting properties of spikelets and compare these predictions to experimental data from pyramidal neurons. We also discuss the functional implications of each mechanism. On the example of pyramidal neurons, we illustrate that several independent spikelet-generating mechanisms fulfilling vastly different functions might be operating in a single cell.

Two new species of treefrog (Pelodrydidae: Litoria) from southern New Guinea elucidated by DNA barcoding

New Guinea is home to the world’s most diverse insular frog biota, but only a small number of taxa have been included in genetically informed assessments of species diversity. Here we describe two new species of New Guinea treefrog in the genus Litoria that were first flagged during assessments of genetic diversity (DNA barcoding) and are currently only known from the holotypes. Litoria pterodactyla sp. nov. is a large green species in the Litoria graminea species complex from hill forests in Western Province, Papua New Guinea and is the third member of this group known from south of the Central Cordillera. Litoria vivissimia sp. nov. is a small, spike-nosed species from mid-montane forests on the Central Cordillera. It is morphologically very similar to Litoria pronimia, but occurs nearly 1000 m higher than any known locality for that species. More extensive genetically informed assessment of diversity in New Guinea frogs seems certain to reveal many more as-yet-unrecognised taxa in complexes of morphologically similar species.

Venous Thromboprophylaxis With Neuromuscular Stimulation: Is It Calf Muscle Pumping or Just Twitches and Jerks?

The common peroneal nerve stimulator (CPNS) is a UK–approved device for reducing venous thromboembolism risk. It resembles a wrist watch and is placed over the common peroneal nerve to fire at 1 electrical impulse/sec. The aim was to quantify the claim that it drives the venous muscle pump and imitates walking. Twelve healthy volunteers performed 10 tip-toe maneuvers and 10 ankle dorsiflexions to imitate walking movements. The reductions in calf volume were recorded using air plethysmography (APG). The common peroneal nerve was stimulated for over 10 seconds at each of the 7 increasing electrical impulse settings, and the volume reductions were measured for comparison. The results are expressed as median (interquartile range) absolute (mL), and percentage reduction in calf volume. Tip-toe and dorsiflexion pumping maneuvers were not significantly different: 59 (33.6-96.1), 81.9% vs 51.4 (34-68.5), 59.7%, respectively ( P = .53). However, they both outperformed the CPNS: 10.8 (7.3-18), 13.2% at P = .002 and P = .002, respectively. Qualitatively, the CPNS registered on the tracings as a small spike (muscle twitch) at low settings, with larger amplitudes (ankle jerk) at higher settings. The CPNS activity spikes were discrete, lasting a median (range) of 0.24 (0.16- .3) seconds. The claim that the CPNS empties veins by pumping is supported statistically. However, the amount is small versus the tip-toe and dorsiflexion maneuvers. Furthermore, the CPNS has a short activity profile on the APG trace. Innovations that produce sustained contraction and involve the posterior calf compartments may improve pumping.

Acrobeloides varius sp. n. (Rhabditida: Cephalobidae) from South Korea

A new Acrobeloides is described and illustrated from samples collected in rice farmland in South Korea. Acrobeloides varius sp. n. exhibits morphological characters of other acrobeloids, including a corpus with elongate spindle-like swelling and lateral incisures that extend to the tail end region. However, this new species is distinguished from other acrobeloids by having lateral incisures that change in number from one to five, three low rounded labial probolae, and a conical pointed tail end with a small spike-shaped mucron. In this study, a detailed morphological comparison of Acrobeloides species is provided, along with new molecular sequence data from the D2-D3 regions of LSU, SSU and partial mtDNA cox1 region from the new species, which can be used as molecular barcode sequences.

Compressor Leading Edge Spikes: A New Performance Criterion

Compressor blades often have a small “spike” in the surface pressure distribution at the leading edge. This may result from blade erosion, manufacture defects, or compromises made in the original design process. This paper investigates the effect of these spikes on profile loss, and presents a criterion to ensure they are not detrimental to compressor performance. In the first part of the paper, two geometries of leading edge are tested. One has a small spike, typical of those found on modern compressors; the other has no spike, characteristic of an idealized leading edge. Testing was undertaken on the stator of a single-stage low speed compressor. The time resolved boundary layer was measured using a hot-wire microtraversing system. It is shown that the presence of the small spike changes the time resolved transition process on the suction surface, but that this results in no net increase in loss. In the second part of the paper, spike height is systematically changed using a range of leading edge geometries. It is shown that below a critical spike height, the profile loss is constant. If the critical spike height is exceeded, the leading edge separates and profile loss rises by 30%. Finally, a criterion is developed, based on the total diffusion across the spike. Three different leading edge design philosophies are investigated. It is shown that if the spike diffusion factor is kept below 0.1 over the blade’s incidence range, performance is unaffected by leading edge geometry.

Compressor Leading Edge Spikes: A New Performance Criterion

Compressor blades often have a small ‘spike’ in the surface pressure distribution at the leading edge. This may result from blade erosion, manufacture defects or compromises made in the original design process. This paper investigates the effect of these spikes on profile loss and presents a criterion to ensure they are not detrimental to compressor performance. In the first part of the paper two geometries of leading edge are tested. One has a small spike, typical of those found on modern compressors; the other has no spike, characteristic of an idealized leading edge. Testing was undertaken on the stator of a single-stage low speed compressor. The time-resolved boundary layer was measured using a hot-wire micro traversing system. It is shown that the presence of the small spike changes the time resolved transition process on the suction surface, but that this results in no net increase in loss. In the second part of the paper, spike height is systematically changed using a range of leading edge geometries. It is shown that below a critical spike height the profile loss is constant. If the critical spike height is exceeded, the leading edge separates and profile loss rises by 30%. Finally a criterion is developed, based on the total diffusion across the spike. Three different leading edge design philosophies are investigated. It is shown that if the spike diffusion factor is kept below 0.1 over the blade’s incidence range, performance is unaffected by leading edge geometry.

Alteration in uterine contractility in mares with experimentally induced placentitis

An experimental model of ascending placentitis was developed in the mare to characterize the uterine myoelectrical pattern in late gestation and determine how ascending placentitis altered this pattern. In experiment 1, myometrial electrical activity was analyzed during the early morning, late morning and evening hours in four mares in the last 15 days of gestation to identify patterns of activity. In experiment 2, nine mares received intra-cervical inoculations ofStreptococcus equisubspecieszooepidemicus. Myoelectrical activity in the early morning and evening hours in these mares was compared with four control mares. In experiment 1, the number of spike burst clusters >30 s was greater in the evening than in the late morning hours (P< 0.04). Spike burst activity (number × duration) of mares in experiment 1 was similar during day and night recordings until the last 6 days of gestation when it gradually increased each evening until parturition (P< 0.05). In experiment 2, control mares experienced a gradual increase in the number of small spike burst clusters in the last 6 days (P= 0.008) and an increase in large and small spike burst clusters in the evening hours in the last 4 days of gestation (P= 0.03). Mares with experimentally induced placentitis never exhibited a rise in spike burst clusters but had an increase in the mean duration and activity index of large spike burst clusters in the 4 days before parturition (P< 0.04). In conclusion, control mares had a progressive, reversible rise in myoelectrical activity at night in the week preceding parturition. This was not observed in mares with experimentally induced placentitis. They exhibited an increase in the intensity and duration of large spike burst clusters possibly in response to local inflammation.