Early evolution of the vertebrate eye-fossil evidence

Evidence of detailed brain morphology is illustrated and described for 400-million-year-old fossil skulls and braincases of early vertebrates (placoderm fishes). Their significance is summarized in the context of the historical development of knowledge of vertebrate anatomy, both before and since the time of Charles Darwin. These ancient extinct fishes show a unique type of preservation of the cartilaginous braincase and demonstrate a combination of characters unknown in other vertebrate species, living or extinct. The structure of the oldest detailed fossil evidence for the vertebrate eye and brain indicates a legacy from an ancestral segmented animal, in which the braincase is still partly subdivided, and the arrangement of nerves and muscles controlling eye movement was intermediate between the living jawless and jawed vertebrate groups. With their unique structure, these placoderms fill a gap in vertebrate morphology and also in the vertebrate fossil record. Like many other vertebrate fossils elucidated since Darwin’s time, they are key examples of the transitional forms that he predicted, showing combinations of characters that have never been observed together in living species

Would use of the prerogative to denounce the ECHR "frustrate" the Human Rights Act? Lessons from Miller

Considers, in light of the ruling in R. (on the application of Miller) v Secretary of State for Exiting the European Union (SC), whether the royal prerogative could be invoked to withdraw the UK from the ECHR while the Human Rights Act 1998 remained in force. Reviews the facts of Miller, and evaluates the conflicting dependence and bifurcation arguments on whether the provisions of the 1998 Act could operate as free-standing measures

Boundary element method modelling of KEMAR for binaural rendering: Mesh production and validation

Head and torso simulators are used extensively within acoustic research, often in place of human subjects in time-consuming or repetitive experiments. Particularly common is the Knowles Electronics Manikin for Acoustic Research (KEMAR), which has the acoustic auditory properties of an average human head. As an alternative to physical acoustic measurements, the boundary element method (BEM) is widely used to calculate the propagation of sound using computational models of a scenario. Combining this technique with a compatible 3D surface mesh of KEMAR would allow for detailed binaural analysis of speaker distributions and decoder design - without the disadvantages associated with making physical measurements. This paper details the development and validation of a BEM-compatible mesh model of KEMAR, based on the original computer-aided design (CAD) file and valid up to 20 kHz. Use of the CAD file potentially allows a very close match to be achieved between the mesh and the physical manikin. The mesh is consistent with the original CAD description, both in terms of overall volume and of local topology, and the numerical requirements for BEM compatibility have been met. Computational limitations restrict usage of the mesh in its current state, so simulation accuracy cannot as yet be compared with acoustically measured HRTFs. Future work will address the production of meshes suitable for use in BEM with lower computational requirements, using the process validated in this wor

New findings in a 400 million-year-old Devonian placoderm shed light on jaw structure and function in basal gnathostomes

Arthodire placoderms have been proposed as the sister group of Chinese 'maxillate' placoderms plus all the more crownward gnathostomes. These basal groups provide key information for understanding the early evolution of jaws. Here, we test previous assumptions about placoderm jaw structure and function by using high-resolution computed tomography, digital dissection, and enlarged 3D printouts on a unique articulated 400 million-year-old buchanosteid arthrodire. The upper jaw has a double ethmoid and a palatobasal connection, but no otic connection; the dermal bone attachment for the quadrate is different to other placoderms. A separately ossified cartilage behind the mandibular joint is comparable to the interhyal of osteichthyans. Two articular facets on the braincase associated with the hyomandibular nerve foramen supported a possible epihyal element and a separate opercular cartilage. Reassembling and manipulating 3D printouts demonstrates the limits of jaw kenetics. The new evidence indicates unrecognized similarities in jaw structure between arthrodires and osteichthyans, and will help to clarify the sequence of character acquisition in the evolution of basal gnathostome groups. New details on the hyoid arch will help to reformulate characters that are key in the heated debate of placoderm monophyly or paraphyly

Asia-Gondwana connections indicated by Devonian fishes from Australia: palaeogeographic considerations

Middle Palaeozoic vertebrate fossil occurrences are summarised for Australia, with reference to faunal connections between Asia and East Gondwana, as first indicated by fish distributions of Lower Devonian fossil sites. Major endemic groups discussed are pituriaspid (Australian) and galeaspid (Asian) agnathans, wuttagoonaspids (Australian) and antarctaspid (Antarctic, Australian, Asian) arthrodires, yunnanolepid and sinolepid antiarchs (South China, Indochina terrane, Australia), and early tetrapodomorphs (South China, Australia). More widespread groups that lived in shallow marine environments (lungfishes, buchanosteid arthrodires, antiarch Bothriolepis) also show species groups shared between South China and East Gondwana. Exchange of continental facies fishes (e.g. tristichopterid tetrapodomorphs) may have been interrupted by marine transgression in the Frasnian, but were restored in the late Famennian with the appearance of Grenfellaspis in eastern Australia, the only sinolepid antiarch known from outside Asia. The hypothesis of Gondwana dispersion and Asian accretion, to explain the collage of geological terranes forming modern east and southeast Asia, implies increasing dissimilarity with increasing age, but the Siluro-Devonian early vertebrate evidence is inconsistent with this. Previous cladistic analysis of Asian terranes predicted galeaspid agnathans on the Indochina terrane, and their subsequent discovery at Ly Hoa, Vietnam, confirms that Indochina and South China had come together across the Song Ma suture by Middle Devonian timeResearch was supported by funding to JL under the Strategic Priority Research Program, Chinese Academy of Sciences (Grant No. XDB26000000), and the National Natural Science Foundation of China (41472016). Australian funding was under Australian Research Council Discovery grants DP1092870 and DP140104161. JL was also supported by a Director’s strategic postdoctoral fellowship in the ANU Research School of Physics (2016) and the 2018 Marcelja fellowship of the ANU Department of Applied Mathematics

New Information on Culmacanthus (Acanthodii: Diplacanthiformes) from the ?Early–Middle Devonian of Southeastern Australia

A new articulated acanthodian from the Devonian Bunga Beds on the south coast of New South Wales is assigned to Culmacanthus sp., and reveals that this diplacanthiform has smooth dental plates on the occlusal surfaces of the lower jaws. Within the Acanthodii, this type of element was first identified in “Gladiobranchus” probaton from the earliest Devonian MOTH locality, Northwest Territories, Canada, and has now also been identified in “Euthacanthus” curtus (Lochkovian, Lower Old Red Sandstone, Scotland) and Diplacanthus spp. (Givetian, Scotland and Frasnian, Canada). The dental plates in Culmacanthus have the same morphology as those of “Gladiobranchus” probaton and “Euthacanthus” curtus. Reexamination of type specimens of Culmacanthus shows that its pectoral fin spines do not have long insertions, and the purported lack of prepectoral, admedian and prepelvic fin spines could be due to loss of the elements before burial rather than morphological absence

Kinetics of slow release of nitrogen fertiliser from multi-layered nanofibrous structures

Fertilisers are essential in modern agriculture to enhance plant growth, crop production and product quality. Recent research has focused on the development of delivery systems designed to prolong fertiliser release. This study introduces a new technology to encapsulate and release molecules of fertilisers by using multi-layered electrospun nanofibre as a carrier. Single-layer poly L-lactic acid (PLLA) nanofibres loaded with urea were fabricated using electrospinning. Triple-layer nanofibrous structures were produced by electrospinning polyhydroxybutyrate (PHB) nanofibres as external layers with PLLA nanofibres impregnated with urea fertiliser as the middle layer. Scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometry (FTIR) were employed to characterize the morphology of electrospun nanofibres. Urea release dynamic was analysed using a total nitrogen instrument (TNM-1). The results indicated that triple-layered urea-impregnated nanofibrous structures led to lower initial rate of nitrogen release and slower release rate of cumulative nitrogen which extended for more than three months. It is concluded that triple-layer nanofibrous structures have the potential for slow release delivery of fertilisers

Micromirror total internal reflection microscopy for high-performance single particle tracking at interfaces

Single particle tracking has found broad applications in the life and physical sciences, enabling the observation and characterisation of nano- and microscopic motion. Fluorescence-based approaches are ideally suited for high-background environments, such as tracking lipids or proteins in or on cells, due to superior background rejection. Scattering-based detection is preferable when localisation precision and imaging speed are paramount due to the in principle infinite photon budget. Here, we show that micromirror-based total internal reflection dark field microscopy enables background suppression previously only reported for interferometric scattering microscopy, resulting in nm localisation precision at 6 $\mu$s exposure time for 20 nm gold nanoparticles with a 25 x 25 $\mu$m$^{2}$ field of view. We demonstrate the capabilities of our implementation by characterizing sub-nm deterministic flows of 20 nm gold nanoparticles at liquid-liquid interfaces. Our results approach the optimal combination of background suppression, localisation precision and temporal resolution achievable with pure scattering-based imaging and tracking of nanoparticles at regular interfaces.Comment: 27 pages, 4 figure