Intermediate Specimens Research Articles

Experimental Investigation of a Novel CFRP-Steel Composite Tube-Confined Seawater-Sea Sand Concrete Intermediate Long Column

In order to fully utilize sea sand in offshore engineering, a novel carbon fiber-reinforced polymer (CFRP)-steel composite tube-confined seawater-sea sand concrete (FCTSSC) column structure has been developed. This study conducts experimental investigations on FCTSSC intermediate long columns for the first time. It investigates the failure modes and the impact of the external CFRP layers number on the axial compression performance. The results reveal that the FCTSSC intermediate long column specimens exhibit the failure modes of global buckling and localized steel tube bulging. After CFRP restriction, the ultimate load bearing capacity of the specimens increased from 12.51% to 20.87%. The ultimate load bearing capacity, its enhancement percentage, and peak lateral deformation are all positively correlated with the external CFRP layers number. Finally, a summary and assessment were conducted on the applicability and accuracy of the existing load bearing capacity models, providing a reference for subsequent research.

Axial compressive performance of CFRP-steel composite tube confined seawater sea-sand concrete intermediate slender columns

To alleviate the scarcity of river sand resources and fully utilize the advantages of Carbon Fiber Reinforced Polymer (CFRP), a new type of CFRP-steel composite tube was developed to confine seawater-sea sand concrete (FCTSSC) column structures. This study conducted experimental research on FCTSSC intermediate slender columns for the first time, analyzing their failure modes and working mechanisms. The investigation explored the effects of outer CFRP layers and slenderness ratios on the mechanical performance. The results indicate that the FCTSSC intermediate slender column specimens exhibited global buckling accompanied by local bulging of steel tubes as their failure mode. The load-displacement curves can be divided into strong confinement and weak confinement models. Specimens confined by CFRP exhibited a 12.51–31 % increase in ultimate bearing capacity. The ultimate bearing capacity and its enhancement rate were positively correlated with the outer CFRP layers and negatively correlated with the slenderness ratio. Peak lateral displacements were positively correlated with both parameters. Finally, the model for calculating the axial compression ultimate bearing capacity of FCTSSC intermediate slender columns was proposed, providing a reference for future practical applications in offshore engineering.

Shear‐Enhanced Electrical Conductivity of Synthetic Quartz‐Graphite Gouges: Implications for Electromagnetic Observations in Carbonaceous Shear Zones

AbstractGraphite is considered as a material that promotes fault weakening and electrical conductivity (σ) enhancement at fault zones. We studied how shear deformation may affect the evolution of friction and electrical conductivity of synthetic quartz (Qz)‐graphite (Gr) mixtures and, more importantly, whether the σ of the mixtures present visible changes at the beginning of the simulated fault slip. Long‐displacement friction experiments were performed on 1.2–2.3 mm‐thick gouge specimens of varied Gr volume fraction (XGr = 0–100 vol.%) under identical normal stress (2 or 5 MPa), slip rate (∼1.0 mm/s), and N2‐flushing conditions. The experimental results suggested that the σ of the specimens with ≥4.6 vol.% XGr abruptly increased under limited shear displacement. With continued shear, the steady‐state electrical conductivity (σss) increased by more than seven orders of magnitude when XGr > 3.4 vol.%, while the steady‐state frictional coefficient remained high (0.54–0.80) except for the specimens with XGr > 13.6 vol.%. The post‐mortem microstructures revealed that the high σss observed in the intermediate Gr content specimens (3.4–13.6 vol.%) is associated with an ad‐hoc fabric (graphite–cortex clasts) present in the principal slip zone. For high Gr content, excess Gr flakes fill the pores and help develop mechanically lubricated surfaces. We propose that low Gr content (i.e., as low as 3.4 vol.%) can cause high conductivity anomalies in natural shear zones. Overall, the findings suggest that the initiation of slips within carbonaceous shear zones can be detected by identifying unusual temporal signals using electromagnetic stations.

Behaviour of concrete-Filled steel tube having granulated blast furnace slag as fine aggregate in normal strength concrete after exposure to elevated temperature

The significant growth of steel production in India has led to a considerable increase in the production of granulated blast furnace slag (GBS). To resolve the environmental concerns associated with GBS production, it can be used as a substitute for natural fine aggregate in concrete within concrete-filled steel tube (CFST). However, literatures regarding the behaviour of GBS aggregate added concrete-filled steel tubular columns (GBSCFST) after exposure to fire is very limited. Hence the present research work aims to investigate fill the aforementioned research gap. A total 30 number of GBSCFST specimens having square, circular and rectangular shapes, including both intermediate and stub columns, are tested. GBS is used as fine aggregate for preparing infill concrete. All the specimens are heated to varying target temperatures of 200°C, 400°C, 600°C and 800°C with a temperature holding time of 2 h in a furnace. Afterwards, the specimens were left inside the furnace for cooling purposes. Axial compression load was applied to all the specimens by using a compression testing machine with a strain-controlled procedure. The reduction in the load carrying capacity ranged from 1.07% to 12.68% for stub specimens and 1.05% to 19.35% for intermediate specimens heated upto 600°C. However, the load carrying capacity experienced a significant reduction reaching a maximum percentage decrease of 24% and 34% when heated at 800°C. The primary failure shapes observed were local buckling and bulging in stub specimens and mid-height buckling in intermediate specimens.

Genetic and morphological assessment of Helichrysum Mill. from Tuscan Archipelago (Italy)

In the Mediterranean area, the species of the genus Helichrysum Mill. (Asteraceae) have very similar genetic traits despite they may show different morphological characteristics. A first genetic and morphological assessment on twelve populations of Helichrysum from Elba, Capraia and Giglio Islands, in the Tuscan Archipelago (Italy) was carried out. To determine their taxonomic identity, additional reference specimens belonging to the three Helichrysum species reported from the Tuscan Islands in the literature -H. italicum (Roth) G. Don subsp. italicum, H. litoreum Guss., and H. stoechas L.-, were also included in the assessments. Our results show that the Tuscan Archipelago populations have low levels of morphological and genetic variation. In particular, the variability was mainly observed at the intra-population level, as revealed by the coefficient of variation and AMOVA-Gst in the morphological and genetic analyses, respectively. Basing on our results, all examined populations from the Tuscan Archipelago seem fit in H. italicum subsp. italicum. However, we detect and discuss the existence of some intermediate specimens, mainly with H. litoreum, reflecting the complexity of Helichrysum’s taxonomy and highlighting the need for additional studies to fully understand the various patterns and the underlying evolutionary events that originated them.

Fire induced concrete spalling in combination with size effects

The size effect has its origin in fracture mechanics and describes the formation as well as propagation of cracks in brittle and solid materials in dependence of the specimen size. However, the size effect in concrete spalling describes the damage behaviour on a macroscopic scale for different sized specimens in case of fire. Concrete spalling is a very complex and yet not fully understood phenomenon. To reduce the effort of fire tests to analyse the spalling behaviour of concrete mixtures, this study investigates the susceptibility to spalling for six different concrete mixtures and three specimen sizes. The sizes were divided in full scale slabs (1.8 m × 1.2 m × 0.3 m), intermediate scale cuboids (0.6 m × 0.6 m × 0.3 m) and small scale cylinders (Ø0.15 m × 0.3 m). For this purpose, a novel test set-up was built to test six intermediate scale or twelve small scale specimens simultaneously to ensure a similar heating regime for every specimen. All specimens were fire exposed on one side and remained unrestrained. A size effect occurred for four of the six concrete mixtures. Compared to the full scale specimens the spalling was reduced significantly for all smaller specimen sizes. Additionally, spalling did not occur for the small scale specimens. The results show that the specimen size is an essential parameter to investigate the susceptibility to spalling of a concrete mixture. For future investigations the testing conditions must be adjusted for the intermediate scale specimens to recreate the conditions of the slabs.

Morphological Reanalysis of the Pedicularis sudetica Complex of Arctic North America: Character Trimming with Occam’s Razor

Abstract— Pedicularis sudetica can be a difficult complex to identify and classify using herbarium specimens. Colors fade, rendering corolla patterns indistinct. Especially problematic is the presence of spots on the lobes of the lower lip and color patterns of the galea. Spots are either clearly visible or so faded that only a few spots are visible on one or two flowers in the inflorescence. Galeas are either unequivocally bicolored, solid, or indistinctly diffuse. Other characters have been inconsistently applied by taxonomists and/or are difficult to discern. All these factors combined only serve to confound taxon identity and classification, and members of the complex have been classified as species, subspecies, or even varieties by different taxonomists. Multiple correspondence analysis (MCA) of qualitative traits and principal component analysis (PCA) of quantitative traits were employed to explore the character and taxonomic structure of the group. MCA revealed that only three characters are necessary to classify the four taxa of the complex. No taxon structure was evident with PCA. Abundance of intermediate specimens over a broad geographic range indicates hybridization is extensive among members of the complex and suggests that a subspecific classification of the group is appropriate.

Rapid Electrochemical-Based PCR-Less Microbial Quantification and Antimicrobial Susceptibility Profiling Directly From Blood and Urine With Unknown Microbial Load or Species.

Novel molecular platforms are available for identifying (ID) the causative agents of microbial infections and generating antimicrobial susceptibility testing (AST) profiles, which can inform the suitable course of treatment. Many methods claim to perform AST in minutes or hours, often ignoring the need for time-consuming steps such as enrichment cultures and isolation of pure cultures. In clinical microbiology laboratories, an infectious microbial must first be cultured (overnight to days) and identified at the species level, followed by a subsequent AST with an additional turnaround time of 12–48 h due to the need for regrowth of the organism in the absence and presence of relevant antibiotics. Here, we present an electrochemical-based direct-from-specimen ID/AST method for reporting directly from unprocessed urine and blood in hours. In a limit of detection study of 0.5-ml whole blood samples for point-of-care and pediatric applications, 16.7% (4/24) of samples contrived at 2 CFU/ml and 100% (24/24) of samples contrived at 6 CFU/ml were reported positive in 6.5 h, indicating a limit of detection of 6 CFU/ml. In a separate direct-from-specimen AST study, the categorical susceptibility was reported correctly for blinded susceptible, intermediate, resistant, and polymicrobial contrived specimens in 4 h.

Species Delimitation and Conservation in Taxonomically Challenging Lineages: The Case of Two Clades of Capurodendron (Sapotaceae) in Madagascar.

Capurodendron is the largest endemic genus of plants from Madagascar, with around 76% of its species threatened by deforestation and illegal logging. However, some species are not well circumscribed and many of them remain undescribed, impeding a confident evaluation of their conservation status. Here we focus on taxa delimitation and conservation of two species complexes within Capurodendron: the Arid and Western complexes, each containing undescribed morphologies as well as intermediate specimens alongside well-delimited taxa. To solve these taxonomic issues, we studied 381 specimens morphologically and selected 85 of them to obtain intergenic, intronic, and exonic protein-coding sequences of 794 nuclear genes and 227 microsatellite loci. These data were used to test species limits and putative hybrid patterns using different approaches such as phylogenies, PCA, structure analyses, heterozygosity level, FST, and ABBA-BABA tests. The potential distributions were furthermore estimated for each inferred species. The results show that the Capurodendron Western Complex contains three well-delimited species, C. oblongifolium, C. perrieri, and C. pervillei, the first two hybridizing sporadically with the last and producing morphologies similar to, but genetically distinct from C. pervillei. The Arid Complex shows a more intricate situation, as it contains three species morphologically well-delimited but genetically intermixed. Capurodendron mikeorum nom. prov. is shown to be an undescribed species with a restricted distribution, while C. androyense and C. mandrarense have wider and mostly sympatric distributions. Each of the latter two species contains two major genetic pools, one showing interspecific admixture in areas where both taxa coexist, and the other being less admixed and comprising allopatric populations having fewer contacts with the other species. Only two specimens out of 172 showed clear genetic and morphological signals of recent hybridization, while all the others were morphologically well-delimited, independent of their degree of genetic admixture. Hybridization between Capurodendron androyense and C. microphyllum, the sister species of the Arid Complex, was additionally detected in areas where both species coexist, producing intermediate morphologies. Among the two complexes, species are well-defined morphologically with the exception of seven specimens (1.8%) displaying intermediate patterns and genetic signals compatible with a F1 hybridization. A provisional conservation assessment for each species is provided.

Lack of assortative mating might explain reduced phenotypic differentiation where two grasshopper species meet.

Hybridization is an evolutionary process with wide‐ranging potential outcomes, from providing populations with important genetic variation for adaptation to being a substantial fitness cost leading to extinction. Here, we focussed on putative hybridization between two morphologically distinct species of New Zealand grasshopper. We collected Phaulacridium marginale and Phaulacridium otagoense specimens from a region where mitochondrial introgression had been detected and where their habitat has been modified by introduced mammals eating the natural vegetation and by the colonization of many non‐native plant species. In contrast to observations in the 1970s, our sampling of wild pairs of grasshoppers in copula provided no evidence of assortative mating with respect to species. Geometric morphometrics on pronotum shape of individuals from areas of sympatry detected phenotypically intermediate specimens (putative hybrids), and the distribution of phenotypes in most areas of sympatry was found to be unimodal. These results suggest that hybridization associated with anthropogenic habitat changes has led to these closely related species forming a hybrid swarm, with random mating. Without evidence of hybrid disadvantage, we suggest a novel hybrid lineage might eventually result from the merging of these two species.

Genetic Introgression and Morphological Variation in Naked-Back Bats (Chiroptera: Mormoopidae: Pteronotus Species) along Their Contact Zone in Central America

Two sibling bare-backed bat species (Pteronotus fulvus and P. gymnonotus) have been traditionally differentiated by their size. However, intermediate specimens between the two species have been found in sympatric populations along southern Mexico and it has been suggested that they may be the outcome of a hybridization process between the two species. We used one mitochondrial (COI), three nuclear markers (PRKCL, STAT5A and RAG2) and 13 microsatellites to explore the evolutionary relationships between these two species and elucidate whether the intermediate morphotypes correspond to hybrid individuals. These markers have been analyzed in sympatric and allopatric populations of the two species plus the closely related species Pteronotus davyi. We confirmed the species-level differentiation of the three lineages (P. fulvus, P. davyi and P. gymnonotus), but the phylogenetic hypotheses suggested by the nuclear and mitochondrial markers were discordant. We confirm that the discordance between markers is due to genetic introgression through the mitochondrial capture of P. fulvus in P. gymnonotus populations. Such introgression was found in all P. gymnonotus specimens across its sympatric distribution range (Mexico to Costa Rica) and is related to expansion/retraction species distribution pulses associated with changes in forest distribution during the Quaternary climate cycles. Microsatellite analyses showed contemporary genetic contact between the two sympatric species and 3.0% of the samples studied were identified as hybrids. In conclusion, we found a historical and asymmetric genetic introgression (through mitochondrial capture) of P. fulvus into P. gymnonotus in Mexico and Central America and a limited contemporary gene exchange between the two species. However, no relationship was found between hybridization and the intermediate-sized specimens from southern Mexico, which might likely result from a clinal variation with latitude. These results confirm the need for caution when using forearm size to identify these species in the field and when differentiating them in the laboratory based on mitochondrial DNA alone.

Seismic design of RC moment-resisting frames with concrete block infill walls considering local infill-frame interactions

Concrete block infill walls, due to their high strength and stiffness, can significantly influence the seismic behavior of the frames. The infill walls can increase the overall lateral frame strength and can also induce local failures in the surrounding frames. In general, if local failure can be avoided, the presence of the infill walls can provide additional reserved strength that can be beneficial to the frames. For this reason, a new RC frame with infill walls could be designed as a bare frame without considering the increase in strength, but measures must be taken to prevent local failures due to the infill wall-frame interaction. However, this infill wall-frame interaction is very complex, and clear design strategies to prevent local failures are not normally given in design codes. For this reason, two full-scale intermediate RC moment-resisting frame specimens with infill concrete block walls were tested under a horizontal cyclic load to study the infill wall-frame interaction. Finite element analysis was carried out to evaluate the response particularly on the infill-frame interactions. Based on the results, a design strategy to eliminate local failure in the surrounding frame is suggested. The proposed method is based on local plastic mechanism analysis of the column considering the variation in the column shear demand and column shear capacity at different states of the response as the frame deforms. The shear demand depends on the magnitude and direction of the bearing force from the infill wall. The column is considered as a captive or slender column depending on the restraint from the infill wall, thereby affecting the shear capacity of the column. The proposed approach can be readily applied without radically changing common design practices and design codes.

Morphological and chemical evidence of Teucrium x rohlenae K.Malý (Lamiaceae), a new hybrid in Croatia

Several natural hybrids of Teucrium montanum L. and T. polium L. have been described in certain parts of the area where these two species are sympatric. A new population with intermediate individuals that share morphological characteristics of both T. montanum and T. polium has been found in Croatia (Bisko near Trilj), and most likely represents a hybridogenous taxon. The aim of this study is to compare the morpho-anatomical and phytochemical characteristics of the two parental species and their putative hybrid, as well as to determine the most important distinguishing characters between these three groups. In order to describe the variability and significance of morpho-anatomical and phytochemical differentiation of the analysed groups several multivariate statistical analysis were conducted (PCA, CDA, DFA, UPGMA-clustering). All analyses confirm the separation of two species, T. polium and T. montanum, and reveal the intermediate position of the putative hybrid. In this way, data on morphological and anatomical analysis together with data on the composition of the essential oils support the assumption of the hybridogenous origin of the intermediate individuals. Based on descriptions and original indication of parental species of previously described hybrids T. × castrense Verg., T. × bogoutdinovae Melinkov and T. × rohlenae K.Malý, we found that the intermediate specimens collected in Croatia perfectly correspond to T. × rohlenae, a hybridogenous taxon discovered by Rohlena in the vicinity of Kotor in Montenegro, and thus prove the presence of a new natural hybrid in the flora of Croatia.

Evidence of hybridization between Galatella villosa and G. linosyris, and a taxonomic reappraisal of the hybrid G. ×subvillosa

At the westernmost distribution of the steppe herbaceous plant, Galatella villosa, in Hungary, Serbia and Ukraine, we recently observed intermediate specimens between this species and its close relative, G. linosyris. We were able to demonstrate the hybrid origin of these individuals by sequencing the biparentally inherited nuclear ribosomal internal transcribed spacer (nrITS) region and checking additive polymorphism in the hybrids. In addition, examination of the maternally inherited plastid regions (trnH-psbA and trnL-trnF intergenic spacers) revealed that G. villosa is likely to be the maternal parent in the Hungarian and Ukrainian populations and G. linosyris in the Serbian population. The intermediate forms produced only sterile seeds. The alleged hybrid between the above two species has already been described as G. ×subvillosa based on a very brief diagnosis. Still, the analysis of the morphological characters using linear discriminant analyses clearly separated the holotype of G. ×subvillosa from individuals of G. linosyris × G. villosa. The latter appeared to be morphologically intermediate between populations of G. villosa and G. linosyris. Contrary to the originally stated hybrid origin of the type plants of G. ×subvillosa, morphological evidence indicates the involvement of G. divaricata not G. linosyris. The hybrid G. linosyris × G. villosa is thus described here, as a new nothospecies G. ×feketegaborii. This study highlights the power of easily available molecular phylogenetic tools for demonstrating the hybrid origin of plants and illustrates how additive polymorphism can be distinguished from other types of intraindividual polymorphism in nuclear DNA sequences.

Microstructure and mechanical properties of laser powder bed-fused IN625 alloy

This study focuses on linking the mechanical properties of laser powder bed fusion-processed IN625 alloy, more specifically its propensity for elevated temperature ductility loss, to the microstructure of this alloy resulted from different post-processing heat treatments.Firstly, it is shown that delta phase precipitates formed during stress relief annealing at 870 °C are not responsible for the elevated temperature ductility loss, since their dissolution after intermediate-temperature annealing at 980 °C did not allow improving the alloy ductility. Secondly, it is shown that carbide precipitates contained in the solution-treated alloy (1120 °C) are not responsible for this ductility loss either, since increasing their content during subsequent aging of the solution-treated alloy did not significantly affect the alloy ductility at elevated temperature.Finally, it is demonstrated that deformation of the solution-treated alloy at elevated temperatures is accompanied by dynamic strain aging, while deformation of the stress-relieved and intermediate temperature-annealed specimens is accompanied by dynamic recrystallization. Thus, it seems that at elevated temperatures, there is competition between the dynamic strain aging and dynamic recrystallization processes, with the former decreasing, and the latter increasing the alloy ductility.

Detection of Methanobrevibacter smithii in vaginal samples collected from women diagnosed with bacterial vaginosis.

Vaginosis is a dysbiotic condition of the vaginal cavity that has deleterious effects during pregnancy. The role of methanogens in this disease is unknown since current methods of investigation are not appropriate for the search of methanogens. We prospectively investigated the presence of methanogens in vaginal specimens collected from 33 women thereafter diagnosed with bacterial vaginosis and 92 women thereafter diagnosed without bacterial vaginosis (control group) by direct microscopic examination and fluorescent in situ hybridization, PCR-sequencing, and real-time PCR and isolation and culture. These investigations found only one methanogen, Methanobrevibacter smithii, exclusively in 97% bacterial vaginosis specimens and in two intermediate microbiota specimens. M. smithii was detected microscopically in 2/20 specimens analyzed, by PCR-based observations in 34/125 specimens with 99% sequence similarity with the reference 16S rRNA and mcrA gene sequences and was cultured in 9/40 specimens. These data suggest that the detection of M. smithii could be used as a biomarker for the laboratory diagnosis of bacterial vaginosis.

Revision of the taxonomic status of Rhodanthidium sticticum ordonezi (Dusmet, 1915), an anthidiine bee endemic to Morocco (Apoidea: Anthidiini)

Rhodanthidium ordonezi (Dusmet, 1815) is recognized here as a valid species endemic to central and southern Morocco. It has previously been regarded as a subspecies of R. sticticum (Fabricius). The two taxa are in allopatry throughout most of their respective ranges, but probably cooccur in the Middle Atlas Mountains. They are clearly distinguished by their coloration and some aspects of their color patterns. Structural differences are minor, but a multivariate discriminant function analysis of 11 morphometric traits has showed that these are sufficient to assign 82.7% of all specimens correctly. While R. ordonezi has a restricted range in central and southern Morocco (extending over approximately 500 km), R. sticticum is widely distributed in the Mediterranean basin with a range extending over approximately 2500 km from east to west. The distribution areas of these two species are contiguous in the same ecozone of the Middle Atlas mountain range, but sympatric occurrence or a transition zone where intermediate specimens occur is not known.

Abstract 4003: Comprehensive genomic profiling of Merkel cell carcinoma samples reveals bimodal distribution of tumor mutational burden and two mutually exclusive candidate mechanisms of malignant transformation

Abstract Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer. Etiologic risk factors include long-term UV exposure, Merkel cell polyomavirus (MCV) infection, age, and immunosuppression. Large-scale investigations of MCC are hindered by its rarity and comprehensive understanding of this disease is currently lacking. In a study of 275 patients, representing the largest sequenced cohort of MCC samples to date, we sought to characterize the genomic landscape of MCC as well as identify whether causality could be attributed to MCV infection, UV exposure, or a synergistic effect between the two. Comprehensive genomic profiling of 395 cancer-related genes, including evaluation of tumor mutational burden (TMB) and mutational signatures, was performed on MCC tumors from 275 patients. The TMB of MCC exhibited a stark bimodal distribution between TMB high (≥20 mutations/mb) and TMB low (<6 mutations/mb) specimens with only 22 specimens having an intermediate TMB. Overall, 101/275 (37%) of MCC samples were TMB high (median 53.1 mutations/mb) with the majority carrying short variant mutations in TP53, RB1, or NOTCH1. Analysis of mutational signatures found that 94/101 (93%) of TMB high samples exhibited signs of UV damage. No signatures indicative of APOBEC activity or of intrinsic DNA repair defects such as microsatellite instability were observed in the TMB high group. In contrast, 152/275 (55%) of MCC specimens were TMB low (median 1.2 mutations/mb) with 39% of these samples having no known or likely genomic driver. We hypothesized that the primary driver in the TMB low group was MCV integration and examined MCV infection through de novo assembly of non-human sequencing reads in all specimens of the MCC cohort. We found 99/152 (65%) of TMB low specimens to be positive for MCV integration as opposed to 0/101 (0%) of TMB high specimens, which was a statistically significant difference (P = 2.20e-31, Fisher's exact test). Overall, 3 of the 22 TMB intermediate specimens were MCV-positive. In a large cohort of 275 patient samples, we have described two genomically distinct subsets of MCC: a TMB high group defined by UV damage with mutations in well-known tumor suppressors and a TMB low group defined by MCV integration. We propose that MCV integration is the dominant driver in the TMB low cohort. Indeed, most MCV sequences that we observed appear to be derived from the large or small T antigens, two established viral oncogenes. These results are suggestive of two distinct etiologies of MCC that appear to be mutually exclusive, namely UV exposure vs. MCV integration. These etiologies may have significant impact on targeted and immuno-therapy options for MCC patients. Citation Format: Meagan Montesion, Ethan S. Sokol, Todd C. Knepper, Andrew S. Brohl, Garrett M. Frampton, Phil J. Stephens, James A. DeCaprio, Kenneth Y. Tsai, Lee A. Albacker. Comprehensive genomic profiling of Merkel cell carcinoma samples reveals bimodal distribution of tumor mutational burden and two mutually exclusive candidate mechanisms of malignant transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4003.

Phylogeography of the House Bunting complex: discordance between species limits and genetic markers

Emberiza striolata has traditionally been viewed as a single polytypic species, but recent taxonomic reviews of its morphology, vocalizations and genetic data have led to the recommendation that two species be recognized within this complex, the House Bunting Emberiza sahari in the west, and the Striolated Bunting Emberiza striolata (including the subspecies Emberiza striolata saturiator and Emberiza striolata ‘jebelmarrae’) in the east of the range. However, reportedly intermediate birds have been described from northern Darfur, Sudan, and the Ennedi Massif, northeast Chad, bringing the two-species hypothesis into question. Here, we attempt a more comprehensive geographic sampling of all taxa of E. sahari and E. striolata, and we report the results of an examination of purported intermediate specimens, as well as the re-examination of the long type series of the controversial taxon Emberiza striolata ‘jebelmarrae’ described from western Sudan. Our results confirm a marked east–west divergence in the House Bunting complex based on two mitochondrial DNA (mtDNA) markers, but surprisingly reveal that samples of E. striolata ‘jebelmarrae’ cluster with the western clade, whereas their morphology is clearly allied with that of other populations in the eastern clade. However, our analysis suggests that all of the specimens believed to be intermediate in morphology can be categorically placed with other examples of the western clade (E. sahari). At present, it is impossible to definitively explain the phylogenetic position of E. striolata ‘jebelmarrae’, but we hypothesize that the paraphyly in mtDNA is the result of introgression during the initial phase of secondary contact, and does not impinge on the decision to recognize two species. Complex spatio-temporal population patterns caused by late Pleistocene climate changes might have led to multiple secondary contact events between the eastern and western clades.

Chemistry of Hydrolysis of FeCl3 in the Presence of Phosphate to Form Hematite Nanotubes and Nanorings

Through investigation of the intermediate specimens during the hydrolysis of FeCl3 in the presence of phosphate using mass spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, and inductively coupled plasma optical emission spectrometry, the formation mechanisms of α-Fe2O3 nanotubes and nanorings were revealed. At early stages, the precursor molecules polymerized and aggregated into large disordered particles, from which β-FeOOH nanorods grew up. When the NaH2PO4 concentration was low (e.g., 1 mM in a solution of 23 mM FeCl3), the β-FeOOH nanorods were relatively stable and underwent side-by-side aggregation into spindle-like particles. Phase transformation into self-orientated α-Fe2O3 nanocrystallites then took place on the surface of these spindle particles, followed by Ostwald ripening, to form a single-crystalline shell. The ends and the core of the spindle particles were dissolved, forming α-Fe2O3 nanotu...