Primary Contact Zone Research Articles

Nano lubricants in machining and tribology applications: A state of the art review on challenges and future trend

Nanofluids are a unique class of fluids generally prepared by adding nanosized particles to different types of base fluids, such as water, oil, etc. When nanoparticles are added to the base fluids, their thermophysical parameters like viscosity, heat transfer characteristics, and thermal conductivity are improved and provide good results. For this reason, the demand for fluids enriched with nanoparticles has considerably increased in the manufacturing sector. This comprehensive state-of-the-art review covers nanolubricants' role in friction reduction, wear resistance, and machining efficiency applications. Initially, the lubricants and their properties are revealed in the introduction section. Then, the different types of nanoparticles, their basic structure, and their different applications in machining and tribology are portrayed in different sections. In addition, it provides a comprehensive analysis of the difficulties related to nanofluids and their utilization in machining and tribology. Ultimately, this evaluation provides final comments on the latest advancements in both the academic and industrial sectors, as well as a strategy for future expansion. The results indicated that the fluids loaded with nanoparticles had a beneficial effect in lowering friction and temperature at the primary contact zone.

The novel expression of clonality following whole-genome multiplication compensates for reduced fertility in natural autopolyploids.

Exploring the fitness consequences of whole-genome multiplication (WGM) is essential for understanding the establishment of autopolyploids in diploid parental populations, but suitable model systems are rare. We examined the impact of WGM on reproductive traits in three major cytotypes (2x, 3x, 4x) of Pilosella rhodopea, a species with recurrent formation of neo-autopolyploids in mixed-ploidy populations. We found that diploids had normal female sporogenesis and gametogenesis, high fertility, and produced predominantly euploid seed progeny. By contrast, autopolyploids had highly disturbed developmental programs that resulted in significantly lower seed set and a high frequency of aneuploid progeny. All cytotypes, but particularly triploids, produced gametes of varying ploidy, including unreduced ones, that participated in frequent intercytotype mating. Noteworthy, the reduced investment in sexual reproduction in autopolyploids was compensated by increased production of axillary rosettes and the novel expression of two clonal traits: adventitious rosettes on roots (root-sprouting), and aposporous initial cells in ovules which, however, do not result in functional apomixis. The combination of increased vegetative clonal growth in autopolyploids and frequent intercytotype mating are key mechanisms involved in the formation and maintenance of the largest diploid-autopolyploid primary contact zone ever recorded in angiosperms.

Disentangling the components of triploid block and its fitness consequences in natural diploid-tetraploid contact zones of Arabidopsisarenosa.

Hybrid seed inviability (HSI) is an important mechanism of reproductive isolation and speciation. HSI varies in strength among populations of diploid species but it remains to be tested whether similar processes affect natural variation in HSI within ploidy-variable species (triploid block). Here we used extensive endosperm, seed and F1 -hybrid phenotyping to explore HSI variation within a diploid-autotetraploid species. By leveraging 12 population pairs from three ploidy contact zones, we tested for the effect of interploidy crossing direction (parent of origin), ploidy divergence and spatial arrangement in shaping reproductive barriers in a naturally relevant context. We detected strong parent-of-origin effects on endosperm development, F1 germination and survival, which was also reflected in the rates of triploid formation in the field. Endosperm cellularization failure was least severe and F1 -hybrid performance was slightly better in the primary contact zone, with genetically closest diploid and tetraploid lineages. We demonstrated overall strong parent-of-origin effects on HSI in a ploidy variable species, which translate to fitness effects and contribute to interploidy reproductive isolation in a natural context. Subtle intraspecific variation in these traits suggests the fitness consequences of HSI are predominantly a constitutive property of the species regardless of the evolutionary background of its populations.

Knowing your limits: estimating range boundaries and co‐occurrence zones for two competing plethodontid salamanders

AbstractUnderstanding threats to species persistence requires knowledge of where species currently occur. We explore methods for estimating two important facets of species distributions, namely where the range limit occurs and how species interactions structure distributions. Accurate understanding of range limits is crucial for predicting range dynamics and shifts in response to interspecific interactions and climate change. Additionally, species interactions are increasingly recognized as an important but not well‐understood predictor of range shifts. Our objective was to predict range limits and contact zones for two plethodontid salamanders, the highly range‐restricted Shenandoah salamander (Plethodon shenandoah) and the wide‐ranging red‐backed salamander (Plethodon cinereus). Using detection/non‐detection data, we assess four methodological decisions when estimating species’ distributions: (1) accounting for imperfect detection, (2) covariates to predict species occurrences, (3) accounting for species interactions, and (4) the inclusion of spatial autocorrelation. We found that Shenandoah salamander and red‐backed salamander co‐occurrence would have been underestimated and the range edge misidentified had we not accounted for incomplete detection. Covariates related to habitat were not sufficient to explain species’ range boundaries. Models that included spatial autocorrelation (i.e., a conditional autoregressive random effect) performed better than models that included just species interactions (i.e., detection and occurrence were conditional on the other species being present) and models that included both spatial autocorrelation and species interactions. Further, we found that the breadth of primary contact zones was typically 60–170 m, which is greater on average than previous estimates. In addition, we frequently observed secondary, disjunct contact zones along the range boundary. Understanding the extent to which species co‐occur and how the range boundaries are shaped is crucial to conservation efforts. Our work indicates that accounting for detection is crucial for accurately characterizing range edges and that spatial models may be especially effective in modeling distributions at the boundary.

Researches Regarding the Influence of Technological Parameters on the Alloying Efficiency in Powder Injection Process

The injection of the powdered materials into molten melts is a common practice in the metallurgical technology of steel refining and alloying. During process development, within the metal bath is formed a mixed three-phase with different structures depending on the parameters of the hydrodynamic injection. The “plume zone” represents a domain inside of the molten metal in which takes place the forming, coalescence and disintegration of the gas bubbles, that penetrate into the molten metal together with the powdered material. The “plume zone” is the primary contact zone between the powdered particles and the molten metal. Inside of contact zone is take place the chemical reactions between the reactive material and the metal bath components. The “plume zone” size, shape and structure are functions of the hydrodynamic parameters of the injection process, the most important being the injection speed. The size of this parameter leads at the appearance of a multitude of possible structures types of the metal bath. These structures dictate the metallurgical process efficiency in defining the steelmaking process and refining of metal bath. In the present paper are investigated and discussed the “plume zone” structures formed during injection with graphite particle of a molten steel bath and the metallurgical results obtained experimentally under the influence of the injection velocity.

Improved Stress Shielding of a Coated Cemented Hip Stem by Functionally Graded Materials

Abstract Surfaces are the primary contact zones between a biomaterial and its host organism. Surface treatment or coating provides a means to fulfill demanding structural and mechanical requirements of the prostheses. As well as, a number of studies have been performed on functionally graded materials (FGM) and their suitability for use as the biomaterial of choice in various prostheses. This study investigates the effect of utilizing the two concepts of FGM and coating, in designing new hip stem material. The results of this study concluded that the optimal FGM cemented stem is consisting of titanium at the upper stem layers graded to collagen at lower stem layers. The optimal functionally graded stem coated with collagen reduced the stress shielding by 51% compared to homogenous titanium stem coated with collagen. However, this optimal graded stem coated with hydroxyapatite showed a reduction of stress shielding by 57% compared to homogenous titanium stem coated with hydroxyapatite.

Nonadaptive processes governing early stages of polyploid evolution: Insights from a primary contact zone of relict serpentine Knautia arvensis (Caprifoliaceae).

• Premise of the study: Contact zones between polyploids and their diploid progenitors may provide important insights into the mechanisms of sympatric speciation and local adaptation. However, most published studies investigated secondary contact zones where the effects of genome duplication can be confounded by previous independent evolution of currently sympatric cytotypes. We compared genetically close diploid and autotetraploid serpentine cytotypes of Knautia arvensis (Caprifoliaceae) in a primary contact zone and evaluated the role of adaptive and nonadaptive processes for cytotype coexistence.• Methods: DNA flow cytometry was used to determine ploidy distribution at various spatial scales (from across the entire contact zone to microgeographic). Habitat preferences of diploids and polyploids were assessed by comparing vegetation composition of nearby ploidy-uniform sites and by recording plant species immediately surrounding both cytotypes in mixed-ploidy plots.• Key results: Tetraploids considerably outnumbered their diploid progenitors in the contact zone. Both cytotypes were segregated at all investigated spatial scales. This pattern was not driven by ecological shifts, because both diploids and tetraploids inhabited sites with nearly identical vegetation cover. Certain interploidy niche differentiation was indicated only at the smallest spatial scale; ecologically nonadaptive processes were most likely responsible for this difference.• Conclusions: We conclude that a shift in ecological preferences (i.e., the adaptive scenario) is not necessary for the establishment and evolutionary success of autopolyploid derivatives in primary contact zones. Spatial segregation that would support ploidy coexistence can also be achieved by ecologically nonadaptive processes, including the founder effect, limited dispersal ability, intense clonal growth, and triploid block.

Labrish and Mooncakes: The Meeting of Vernaculars in the Work of Easton Lee

This essay contributes to ongoing debates about cultural and national identity and belonging in Jamaica by taking up the primary trope of the “shop” as the sole site of black and Chinese interaction. Through analyzing the fiction and poetry of Easton Lee, the essay considers how Lee’s poetry and fiction resituate the primary contact zone of the shop from an urban space to the rural outpost, where the meeting of black and Chinese was also a meeting of “patois” and “pidgin.” Lee’s work challenges representations of Chinese shopkeepers as parasitic, casting them instead as integral parts of the communities they serve, thus intervening in the way that the “shop,” and by extension Jamaican Chinese history, has been written.

Use of multiple markers demonstrates a cryptic western refugium and postglacial colonisation routes of Atlantic salmon (Salmo salar L.) in northwest Europe

Glacial and postglacial processes are known to be important determinants of contemporary population structuring for many species. In Europe, refugia in the Italian, Balkan and Iberian peninsulas are believed to be the main sources of species colonising northern Europe after the glacial retreat; however, there is increasing evidence of small, cryptic refugia existing north of these for many cold-tolerant species. This study examined the glacial history of Atlantic salmon in western Europe using two independent classes of molecular markers, microsatellites (nuclear) and mitochondrial DNA variation. Alongside the well-documented refuge in the Iberian Peninsula, evidence for a cryptic refuge in northwest France is also presented. Critically, methods utilised to estimate divergence times between the refugia indicated that salmon in these two regions had diverged a long time before the last glacial maximum; coalescence analysis (as implemented in the program IMa2) estimated divergence times at around 60 000 years before present. Through the examination of haplotype frequencies, previously glaciated areas of northwest Europe, that is, Britain and Ireland, appear to have been colonised from salmon expanding out of both refugia, with the southwest of England being the primary contact zone and exhibiting the highest genetic diversity.

Allozyme Variation in Diploid, Polyploid and Mixed-Ploidy Populations of the Pilosella alpicola Group (Asteraceae): Relation to Morphology, Origin of Polyploids and Breeding System

The Pilosella alpicola group includes four species (P. alpicola s.str., P. ullepitschii, P. rhodopea and P. serbica) with allopatric distributions (Alps, Balkans, Carpathians) and contrasting cytotype patterns (diploid, diploid-polyploid and polyploid species). Whereas diploid taxa (P. ullepitschii and P. serbica) reproduce sexually, the mode of reproduction of polyploid cytotypes reflects their origin: autopolyploids of P. rhodopea reproduce sexually, while allopolyploid cytotypes of P. alpicola s.str. apomictically. We used allozymes to elucidate overall genetic variation within the group and to test their utility for taxon discrimination, assessment of polyploid origin and possible correlations with breeding systems. Variation of five allozyme systems encoded by eight polymorphic loci and 29 alleles was studied in 20 populations and 298 plants representing all taxa. Allozymes were proved to be only of limited usefulness for the taxonomic classification within the P. alpicola group. The Western Carpathian populations of P. ullepitschii formed the only genetically well-differentiated group. The same allele suite shared by all cytotypes of P. rhodopea and presence of both balanced and unbalanced heterozygotes in tetraploids was consistent with autopolyploid origins of polyploids and provided further evidence for a primary contact zone. An isolated relic population of P. rhodopea from the Southern Carpathians exhibited lowered values of genetic diversity when compared to the core area. Pronounced fixed heterozygosity was found in P. alpicola s.str., supporting its allopolyploid origin. In accordance with assumptions, genotypic variability was significantly higher in sexually reproducing diploid and diploid-polyploid taxa than in apomictic P. alpicola s.str.

Phylogeography of the rare myrmecophagous butterfly Acrodipsas cuprea (Lepidoptera : Lycaenidae) from pinned museum specimens

Acrodipsas cuprea is the only polymorphic species in an uncommon myrmecophagous radiation within the Lycaenidae in Australia. A small cryptic butterfly, it is found almost exclusively on hilltop sites in eastern Australia where several geographically localised morphotypes are recognised. This study used mitochondrial DNA sequences extracted from museum specimens to reveal whether A. cuprea morphotypes evolved in isolation, such that intermediate populations resulted from secondary contact, or whether the distribution of morphotypes was maintained solely by selection across a primary contact zone. Genetic data were also used to assess the species' dispersal ability and to explain the historical processes resulting in its extant distribution. Analysis of molecular variance found that 81% of genetic variation was distributed among colour morphs, suggesting that different wing colours had evolved in isolation. Mixed haplotypes and morphotypes in a zone separating the otherwise discrete morphological populations, particularly along the Great Dividing Range in south-east Queensland, suggests a more recent secondary admixture. Isolation by distance detected by nested clade analysis and pairwise comparisons confirmed the limited dispersal ability of A. cuprea, which was more evident in the southern part of its range. Genetic relationships among haplotypes suggest that the species originated in the drier inland areas of central Queensland, before expanding to the coast and south to Victoria.

Headlamps and passive safety

Headlamps play a key role in the passive safety of motor vehicles — especially when it comes to accidents involving pedestrians. In almost 70% of all pedestrian accidents, the primary contact zone is in the corner areas of the vehicle front end. For this reason, the EU is expected to make a decision soon about further legislation on the subject of pedestrian protection. Against this background, Hella is working closely with the Institut fur Kraftfahrwesen in Aachen in order to optimise headlamp design with regard to energy absorption and deformation behaviour in the event of a crash.

Layer Silicates from Serpentinite-Pegmatite Contact (Wiry, Lower Silesia, Poland)

AbstractHighly tectonized contact between serpentinite and younger pegmatite in the magnesite mine of Wiry contains various layer silicates. Vermiculite, chlorite, smectite, and interstratified mica-vermiculite were recognized by means of routine XRD examination. Two three component interstratifications of mica-vermiculite-chlorite and chlorite-swelling chlorite-smectite were identified by a combined procedure of deconvolution of the XRD patterns and simulation of XRD tracings. A mineral with large diffraction maxima, displaying “chlorite intergrade” characteristics, appeared to be a mixture of chlorite, mixed layer chlorite-smectite, and vermiculite. Polytypes of phyllosilicates were determined by the X-ray transmission method. Due to the heritage of parent mineral polytype structure by transitional products of alteration, two distinct sequences of layer silicates were observed: one formed from trioctahedral mica (vermiculite, mixed layer mica-vermiculite); and one evolved from chlorite (e.g., mixed layer chlorite-swelling chloritesmectite). A tentative scheme of the primary contact zone structure, not obscured by subsequent brittle tectonics either by transformation of layer silicates, is proposed.