This paper characterizes novel “star” defects in GaN films grown with metal–organic vapor phase deposition (MOVPE) on GaN substrates with electron channeling contrast imaging (ECCI) and high-resolution electron backscatter diffraction (HREBSD). These defects are hundreds of microns in size and tend to aggregate threading dislocations at their centers. They are the intersection of six nearly ideal low-angle tilt boundaries composed of $\langle a\rangle$-type pyramidal edge dislocations, each on a unique slip system.

Traditional ambulatory rhythm monitoring in children can have limitations, including cumbersome leads and limited monitoring duration. The ZioTM patch ambulatory monitor is a small, adhesive, single-channel rhythm monitor that can be worn up to 2 weeks. In this study, we present a retrospective cross-sectional analysis of the ZioTM monitor’s impact in clinical practice. Patients aged 0–18 years were included in the study. A total of 373 studies were reviewed in 332 patients. In all, 28.4% had structural heart disease, and 16.9% had a prior surgical, catheterisation, or electrophysiology procedure. The most common indication for monitoring was tachypalpitations (41%); 93.5% of these patients had their symptoms captured during the study window. The median duration of monitoring was 5 days. Overall, 5.1% of ZioTM monitoring identified arrhythmias requiring new intervention or increased medical management; 4.0% identified arrhythmias requiring increased clinical surveillance. The remainder had either normal-variant rhythm or minor rhythm findings requiring no change in management. For patients with tachypalpitations and no structural heart disease, 13.2% had pathological arrhythmias, but 72.9% had normal-variant rhythm during symptoms, allowing discharge from cardiology care. Notably, for patients with findings requiring intervention or increased surveillance, 56% had findings first identified beyond 24 hours, and only 62% were patient-triggered findings. Seven studies (1.9%) were associated with complications or patient intolerance. The ZioTM is a well-tolerated device that may improve what traditional Holter and event monitoring would detect in paediatric cardiology patients. This study shows a positive clinical impact on the management of patients within a paediatric cardiology practice.

The endolithic life habit has evolved several times in the Bivalvia, e.g., in the superfamilies Modiolopsoidea (family Modiolopsidae), Mytiloidea (family Mytilidae, subfamily Lithophaginae), Arcoidea (family Arcidae), Cardioidea (family Tridacnidae), Veneroidea (family Petricolidae), Gastrochaenoidea, Myoidea (family Myidae), Hiatelloidea, and Pholadoidea (families Pholadidae and Teredinidae) (Otter, 1937; Yonge, 1963; Cox, 1969; Carter, 1978; Kleemann, 1980). The oldest known definite bivalve borings are Ordovician slotlike depressions in stromatoporoids, made by the facultative nestler/borer modiolopsid Corallidomus Whitfield, 1893 [1895] (Pojeta and Palmer, 1976; Wilson and Palmer, 1988). Pojeta and Palmer (1976) and Morton (1990) cited Corallidomus as the ancestor of the Lithophaginae. However, lithophaginids more likely evolved from modiolinid mytilids, which in turn evolved from modiolopsids (Fang and Morris, 1997; Fang, 1998; Carter et al., 2000). Lithophaga-like shells are known from the Carboniferous and Permian, but these Upper Paleozoic examples are not known to have been endolithic (Kleemann, 1983, 1990, table 2). Wilson and Palmer (1998) attributed certain borings without associated shells in Upper Carboniferous limestone cobbles to lithophaginids because the borings are widest near their anterior end and they lack a constricted neck. However, if, as Wilson and Palmer suggested, these borings are not posteriorly truncated, then their openings are relatively much wider than typical lithophaginid borings. One boring illustrated by Wilson and Palmer (1998, fig. 4) has an irregular anterior cross-sectional shape that is unlike lithophaginid and gastrochaenid borings. This irregularity recalls the Early Ordovician ichnospecies Gastrochaenolites oelandicus Ekdale and Bromley, 2001, which is similarly vase-shaped. Ekdale and Bromley (2001) noted that the latter boring predates known endolithic bivalves, so they attributed it to an unknown invertebrate.

The specimens of Gastrochaena cuneiformis Spengler, 1783, with Spengler-written labels at the Zoologisk Museum, Copenhagen, did not come from Spengler's type locality in the Nicobar Islands, and may instead be syntypes of Chemnitz's (1788) West Indies “Pholas hians”. the identity of Gastrochaena cuneiformis as a senior synonym of Gastrochaena gigantea (Deshayes, 1830) is established on the basis of Spengler's original descriptions and illustrations, and by examination of specimens from the type locality. A neotype for G. cuneiformis is designated and illustrated, and its genus is revised to exclude Rocellaria Blainville, 1829, and Lamychaena Freneix in Freneix and Roman, 1979. Gastrochaena Spengler, 1783 is the most plesiomorphic of these three genera, as shown by its simple boring, short siphons, and diffuse, poorly differentiated anterior pedal muscles. Rocellaria evolved from a close common ancestor with Gastrochaena, and is characterized by a ventral shift and fusion of the posteroventral pallial sinus with the posteroventral pallial band, low, irregular posterior commarginal lamellae, and well defined anterior pedal retractor muscles generally supported by myophores. Lamychaena evolved from Rocellaria during the Oligocene, extending its ctenidia far posterior into the siphonal part of the boring, and, in some species, uniting its anterior pedal retractor and protractor muscles as they approach the byssus apparatus.

Modern pinnoideans, or “pen shells,” are shallowly to deeply endobyssate, equivalved, edentulous, ham-shaped bivalves with a single, slightly submerged, opisthodetic ligament. Malacologists have generally regarded pinnids as closely related to the pterioid superfamily Pterioidea, especially its Paleozoic family Pterineidae (e.g., Zittel, 1927, p. 446; Thiele, 1935, p. 803; Pojeta, 1978; Waller, 1978). As early as 1890, Jackson suggested that pinnids evolved from the Silurian-Permian pterineid Leptodesma Hall, 1883. More recently, Pojeta (1978, p. 239) speculated that they evolved from the pterineid Pteronitella Billings, 1874 (a Silurian genus similar to Leptodesma) through the morphologically intermediate Devonian Palaeopinna Hall, 1883. The hinge and ligament of Palaeopinna remain unknown, so its family-level placement is uncertain (Newell and LaRocque, 1969, p. N301). However, Leptodesma and Pteronitella have hinge teeth, inequivalved shells, and a duplivincular ligament similar to other pterineids (Newell and LaRocque, 1969, p. N299–N301; Pojeta, 1978, p. 239; Pojeta and Runnegar, 1985, fig. 16D; Carter, 1990a, p. 205; 1990b, p. 334).

McRoberts (1992, figs. 4.13, 4.14, 6.8) illustrated the shell microstructure of late Triassic Gryphaea (Gryphaea) arcuataeformis Kiparisova, 1936, and Gryphaea (Gryphaea) nevadensis McRoberts, 1992. McRoberts (1992, p. 33) described the left valve of G. arcuataeformis as showing “neomorphosed calcite with multiple laminae of ?prismatic structure perpendicular to [the] outer shell surface ….” He described the left valve of G. nevadensis as consisting of two distinct layers of neomorphosed calcite:“…an outer layer with ?prismatic structure occasionally with bands of dark material (?micritic matrix), and a much thinner inner layer with ?cross-foliated structure ….” Subsequent study has shown these microstructural diagnoses to be inaccurate. They are revised as follows.

The shell microstructure of Carboniferous and Triassic permophorids; Triassic and Recent carditids; Devonian, Carboniferous, and Triassic crassatelloideans; and Jurassic through Recent cardioideans is examined in a phylogenetic context, using separate microstructural and morphologic data sets, as well as a combined data set. The microstructural and morphologic data sets are significantly incongruent, but the combined data set suggests that modiomorphoideans (modiomorphids and permophorids) are basal to crassatelloideans; crassatelloideans are basal to carditids (including Septocardia), and carditids are basal to cardiids. On the other hand, the possibility of direct permophorid ancestry for the carditid-cardiid clade cannot be excluded, as suggested by the retention of permophorid-like matted (transitional nacreous-porcelaneous) structure in some early carditids and cardiids. In the absence of stratigraphic data and other evidence for phylogenetic relationships, shell microstructure offers limited potential for assessing subfamily-level phylogenetic relationships within the Cardioidea. This is because of microstructural convergences reflecting biomechanical adaptations for fracture control and abrasion resistance, and possibly also selection for metabolic economy of secretion in tropical, oligotrophic habitats. General evolutionary trends in cardiid shell microstructure are nevertheless apparent: Cretaceous cardiids completely replaced an ancestral laminar, matted structure in their inner shell layer with non-laminar porcelaneous structures; evolved better defined CL structure, stronger reflection of the shell margins, and increased thickness or secondary loss of the ancestral prismatic outer shell layer; and, in Protocardia (Pachycardium) stantoni, added inductural deposition. Some Cenozoic cardiids then evolved wider first-order crossed lamellae, non-denticular composite prisms, composite fibrous prisms, ontogenetic submergence of a juvenile non-denticular composite prismatic outer shell layer into the CL middle shell layer, or ontogenetic submergence of the inner part of a juvenile fibrous prismatic outer shell layer into the CL middle shell layer.

The shell microstructure of Hemidonax donaciformis is unusual for a cardioidean, and suggests closer affinities with the superfamily Tellinoidea than with the superfamily Cardioidea.

Extensive inductural deposits in Protocardia (Pachycardium) stantoni raise the possibility that photosymbiosis evolved among some Mesozoic members of the Protocardiinae, thereby increasing the likelihood that this feature has evolved several times independently in the Cardiidae.

Cemented, calcareous periostracal granules or spines are known to occur in modiolopsoideans, mytiloideans, modiomorphids, permophorids, trigonioids, astartids, cardiids, myoids, pholadomyoids, and septibranchoids. Consequently, the presence of these structures is not necessarily indicative of close anomalodesmatan affinities.

Ecphora is one of the most easily recognized gastropod genera in late Oligocene, Miocene, and Pliocene marine formations in the southeastern United States. Its generally large size, strong spiral ribs, and brown, calcitic exterior are much prized by fossil collectors. However, despite speculations by Petuch (1988), its evolutionary origins have remained obscure. The present shell microstructural and mineralogical evidence suggests that the earliest ecphoras were entirely aragonitic and that the thick calcitic outer layer of the later Miocene and Pliocene species originated as a thin calcitic crust on the crests of the ribs of a latest Oligocene or earliest Miocene species.

The most important factor controlling the timing of Phanerozoic mineralogical evolution in the Bivalvia appears to be thermal potentiation of calcite deposition in colder marine and estuarine environments. Cold temperature has promoted mineralogical evolution in the Bivalvia by kinetically facilitating (potentiating) initially weak biological controls for calcite, thereby exposing their genetic basis to natural selection. Calcite has evolved in bivalve shells for a variety of selective advantages, including resistance to dissolution; resistance to chemical boring by algae and gastropods; reduced shell density in swimming and soft-bottom reclining species; enhanced flexibility in simple prismatic shell layers; and fracture localization and economy of secretion in association with certain foliated structures.

Endogenous calcite in bivalve shells varies from biologically induced to weakly and strongly biologically controlled. Biologically controlled calcite generally first appears in bivalve shells as an impersistent component of the outer shell layer, only later, in some groups, expanding to include the entire outer and then part or all of the middle and inner shell layers. The initial stages of mineralogical evolution are shown by certain modern Mytilidae, Veneridae and Petricolidae. In the latter two families, the calcite occurs as conellae in the outer part of the outer shell layer. Calcitic conellae in the inner shell layer of Pliocene Mercenaria are not barnacle plates, as previously indicated, but endogenous calcite comparable in origin to other venerid conellae. Their occurrence in Mercenaria may reflect thermal potentiation of weak biological controls for calcite, as well as local detachment of the secretory mantle epithelium near the pallial and adductor musculature.

The lower River Bend Formation at the Martin Marietta New Bern quarry in Craven County, North Carolina, contains a diverse and abundant moldic molluscan fauna. This fauna, reconstructed by latex casts, suggests a Vicksburgian or a post-Vicksburgian, pre-Chickasawhayan age for the New Bern exposure. Forty-one molluscan species and subspecies are presently identified from the lower River Bend Formation, 11 of which are new: Turritella caelatura alani, Turritella neusensis, Galeodaria britti, Phalium newbernensis, Cymatium planinodum, Oocorys vadosus, Ecphora wheeleri, Lyria concinna, Scaphella saintjeani, Turricula (Orthosurcula) aequa, and Lucina (Stewartia) micraulax. This fauna is virtually identical at the generic level and similar at the species level to the Vicksburgian faunas of the Gulf Coastal Plain. About 37 percent of the New Bern species also occur in the Vicksburgian of Mississippi, although many of these species reach considerably larger sizes at New Bern. Apparent evolutionary transitions between previously known Vicksburgian and Chickasawhayan mollusks suggest a time of deposition intermediate between these two Oligocene stages.

Moderately high molluscan diversity, the abundance of characteristically warm-water genera, and associated carbonate-rich sediments suggest that the lower River Bend Formation represents a subtropical, open-marine, predominantly carbonate environment immediately seaward of a nearshore lagoonal or barrier island complex.

The lower River Bend Formation at New Bern differs faunally, climatically, and sedimentologically from the upper River Bend Formation in quarry exposures near Belgrade, North Carolina. The upper River Bend Formation contains a lower diversity molluscan fauna with marked dominance diversity and few warm-water taxa. It represents a slightly cooler nearshore, open-marine environment in a transitional siliciclastic-carbonate sedimentary regime. The considerable taxonomic and sedimentologic differences between the lower and upper parts of the River Bend Formation corroborate microfossil evidence suggesting that they represent temporally distinct depositional cycles.

The Late Carboniferous bransoniid conocardioidean Apotocardium lanterna (Branson, 1965) had an entirely aragonitic shell with a finely prismatic outer shell layer, a predominantly crossed lamellar to complex crossed lamellar middle shell layer, and an “inner” shell layer of finely textured porcelaneous and/or matted structure. This “inner” layer is probably homologous with the inner part of the middle shell layer and the inner layer sensu stricto of bivalved molluscs. Shell morphological and microstructural convergences between conocardioids and living heart cockles suggest that at least some conocardioids may have farmed algal endosymbionts in their posterior mantle margins. This symbiosis may have helped conocardioids compete with the biomechanically more efficient bivalves during the latter part of the Paleozoic.

New shell microstructure data for the Triassic pectinid Pleuronectites reinforce shell morphological data suggesting that its family Pectinidae was derived from the superfamily Aviculopectinoidea and not from the Pernopectinidae-Entolioidesidae-Entoliidae clade. This would make the superfamily Pectinoidea, as defined by recent authors, polyphyletic. This would also imply that alivincular-alate ligaments evolved independently in the Pernopectinidae-Entolioidesidae-Entolidae and Pectinidae clades.

The authors study the influence of domestic political dissent and violence on incumbent dictators and their regimes. They argue that elite with an interest in preserving the regime hold dictators accountable when there is a significant increase in terrorism. To pinpoint the accountability of dictators to elite who are strongly invested in the current regime, the authors make a novel theoretical distinction between reshuffling coups that change the leader but leave the regime intact and regime-change coups that completely change the set of elites atop the regime. Using a new data set that distinguishes between these two coup types, the authors provide robust evidence that terrorism is a consistent predictor of reshuffling coups, whereas forms of dissent that require broader public participation and support, such as protests and insurgencies, are associated with regime-change coup attempts. This article is the first to show that incumbent dictators are held accountable for terrorist campaigns that occur on their watch.