White Band Research Articles

Novel antibacterial activity of Sargassum fusiforme extract against coral white band disease

BackgroundCoral diseases are one of the serious threats embroiling in the imbalance of the coral holobiont integrity through disruption of the complex symbiotic relationship between endobiotic alga, coral animal, and a group of microorganisms. Such diseases are usually associated with many bacterial pathogens inflicting gross lesions in corals which show resistance against antibiotics. Therefore, this has led scientists to draw more attention towards the curative compounds from natural resources like herbal plants and seaweeds as substitutes for chemical antimicrobial agents. This study aimed to evaluate the antibacterial activity of the crude extracts (n-hexane, ethyl acetate, and ethanol), alkaloids, and flavonoids from Sargassum fusiforme through Well Diffusion Assay against different isolated bacterial coral pathogens such as (Vibrio owensii, Empedobacter brevis, Providencia vermicola, and Brevibacterium linens) which cause white band disease to coral reef Porites lutea. This study was also validated by bacterial growth kinetics using optical density, dry weight, and plate count method for the isolated coral bacterial pathogens. ResultsThe results indicated that the crude extract with n-hexane and alkaloid extract showed prominent inhibiting activity against the tested bacterial pathogens compared to other extracts. ConclusionsHere we report S. fusiforme extracts as a novel antibacterial agent against four Porites lutea bacterial pathogens and further investigation is recommended against other coral pathogens. Overall, S. fusiforme extracts might be able to improve the health status of commercially important coral species.How to cite: Ahmed N, Mohamed HF, Xu C, et al. Novel antibacterial activity of Sargassum fusiforme extract against coral white band disease. Electron J Biotechnol 2022;57. https://doi.org/10.1016/j.ejbt.2022.03.002.

CORAL DISEASES IN NORTHEASTERN BRAZILIAN REEFS

In the last decade, corals from northeastern Brazil have experienced bleaching events linked to thermal anomalies, the consequences of which have been the appearance of disease outbreaks affecting different species. As a way to explain and monitoring diseases progression and other characteristics regarding the identification in the field for coral diseases, this article aimed to demonstrate the particularities that follows each diseases symptom. This study presents the results of an assessment of the presence of coral diseases on six coastal reefs in northeastern Brazil, including marine protected areas. After 300 hours of visual censuses, a total of 875 colonies were observed; of these, 114 colonies had some disease, representing 13.02% of the colonies analyzed. Five diseases/syndromes were recorded in four host coral species: white syndrome, white plague, red band, dark spots, and white band. This is the first record of white band on the Brazilian coast. The massive coral Siderastrea stellata showed colonies with all registered diseases, which arouses great concern for conservation of the Brazilian coast.

The taxonomic identity of the monocle bream Scolopsis vosmeri species complex (Perciformes: Nemipteridae), with comments on molecular phylogenetic relationships within the genus Scolopsis.

The monocle bream Scolopsis vosmeri species complex is revised. Three species in the complex are recognized: Scolopsis vosmeri (Bloch, 1792), widespread in the Indo-West Pacific, from the northern Indian Ocean (Pakistan, western India, Sri Lanka, Bay of Bengal, and the Andaman Sea, but not recorded from the Red Sea or Arabian Gulf, east African coast or Madagascar) to western Indonesia and Borneo; S. japonica (Bloch, 1793), restricted to the western Pacific Ocean from western Indonesia and north-western Australia east to the Philippines and north to southern Japan; and S. curite Cuvier, 1815, widespread from the western to the eastern Indian Ocean, including the Red Sea and Arabian Gulf. All three species are similar morphologically, and have been confused taxonomically, but phylogenetic analysis of the COI barcoding region shows they are evolutionarily divergent. The three species are redescribed in detail and characters found to distinguish them. Scolopsis vosmeri is easily distinguished from S. japonica and S. curite in having a white band along the side of the body; having a black spot on most body scales (versus greenish yellow spot in S. japonica and S. curite); in lacking a distinct black spot (sometimes a small and faint spot present) on the upper pectoral-fin base (versus small black wedge-shaped spot present in S. japonica and S. curite); caudal peduncle whitish in live individuals (versus caudal peduncle usually yellowish in S. japonica and S. curite); and pelvic and anal fins crimson to orange-red (versus yellow in S. japonica and S. curite). Scolopsis japonica and S. curite are indistinguishable by color pattern but differ in the degree of spination on the preopercular margin. Neotypes are designated for Scolopsis japonica and S. curite. Nomenclatural problems, including validity of the genus Scolopsis, are discussed. We regard Scolopsis curite Cuvier, 1815 as a valid binomial name and thus the type species of Scolopsis Cuvier, 1814 by subsequent monotypy.

Overlooked for over a century: Ophioderma occultum sp. nov. (Echinodermata), a new species of brittle star from the Eastern Pacific

ABSTRACT We describe a new species of ophiodermatid brittle star from the Eastern Pacific: Ophioderma occultum sp. nov. This species has been mistakenly recorded since 1899 as a colour phase of one of its congeners, Ophioderma panamense. However, the integrative use of morphological and molecular data, and comparison with type material of other Eastern Pacific Ophioderma, led to its differentiation as a novel species. Ophioderma occultum sp. nov. is characterised by having radial shields and adoral shields covered with granules, dorsal arm plates divided typically into two pieces, and a particular colour pattern: a dark grey to brown body, and arms with subtle lighter transverse bands and parallel longitudinal white bands over some median and distal segments. Molecular information based on the mitochondrial genes cytochrome oxidase subunit I (COI) and 16S also supported the species’ validity, coinciding with the morphological observations. In particular, the molecular marker 16S had not been used before for species delimitation in this genus and was proven here to be resolutive. In contrast to most species of Ophioderma from the area, Ophioderma occultum sp. nov. shows a restricted distribution to the northern Mexican Pacific (Gulf of California and islas Revillagigedo). This new species is the 10th Ophioderma described from the Eastern Pacific and the 34th worldwide. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A5FFAC55-E5BE-42F6-8371-7B745911F157

Performance Comparison between Handover Decision Algorithms for Horizontal Handover in Long Term Evolution Networks

Comparative Analyses of Handover Decision Algorithms (HODA) for horizontal handovers in Long Term Evolution Network (LTE-A) in terms of Key Performance Indicators (KPIs) were conducted using system level simulation in MATLAB. The KPIs analyzed were the users’ throughput, spectral efficiency, cell –edge Spectral efficiency, handover success rate , call drop Rate, Cumulative Distribution Function (CDF) of Received Signal Reference Power (RSRP), Average RSRP over Primary Component Carrier (PCC) and Secondary Carrier (SCC) and interruption time. . From the results obtained, the algorithm based on spectrum aggregation of carriers from wireless communication spectrum and television white space band referred to as the proposed-TVWS algorithm showed remarkable performance improvements in all the chosen KPIs when compared with MIF and CONV except in handover success rate at UEs speeds less than 70 km/hr of which MIF-HODA algorithm seemed to perform better. Therefore, the proposed-TVWS has yielded baseline certainty in the increase of wireless network quality of service in addition to the seamless network connectivity for the mobile users.

First Report of Growth Rate Juvenile Tokay Gecko (Gekko gecko Linnaeus, 1758) during Twenty-four Weeks in Captive Breeding Facility

As a conservation strategies to reduce the wild harvest of tokay geckos, captive breeding becomes one of the solution to fulfill demand market. To achieve this goal, scientific data on biological information on the growth of tokay gecko in captive breeding facility is needed to support management conservation of tokay gecko. A total of seven individual juveniles tokay gecko consisting of four males and three females were observed during 24 weeks old. We feed the juvenile of tokay gecko with 10-15 crickets every three days. We collected the growth rate data by weekly measuring Snout-vent Length (SVL), head length (HL), head width (HW) and body weight. Newly hatched tokay gecko have an SVL of 48.08 mm (44.70-53.24 mm) and weight 2.40 gram (1.90- 2.70 gram). Juvenile at the age of one to three months have a special characteristic in having a black and white bands on the tail. This characteristic fades when entering the age of more than twelve weeks. Female individuals were recorded to have smaller hatching sizes than males, but have faster growth rate (p=0.9536). For 24 weeks, male and female individuals have SVL of 70.77 mm (64.35-76.74) and 73.02 mm (67.11-80.35), respectively. Sexual dimorphism in males and females show significant results in the HW/SVL ratio (p=0.02697). Further study on the observation of growth rate during life span are needed to describe whole process of growth stage tokay gecko which is very useful for captive breeding management of this species.

Spread of Trichomonas gallinae in species of birds in balad district with the effect of infection on histological picture

Trichomoniasis in birds is one of the most common types of infection that affects birds worldwide, and it is caused by Trichomonas gallinae. This study was carried out to examine and determine the presence of T. gallinae in Columba livia, Streptopelia turtur, and Gallus gallus domesticus microscopic examination (direct smear and Giemsa stained). The study was conducted in Balad district in Salah al-Din Governorate, north of Baghdad, Iraq, from October 2021 to March 2022. The results showed the microscopic examination that the incidence of T. gallinae average was 19.17%, distributed between 14.16% for C. livia, while S. turtur constituted 14.0%, and the rate of G. gallus domesticus was 27.92%, but there were no significant differences at P> 0.05 among these bird species. The gender of birds showed that there were no differences between a male and a female of each type. In males of the two types of pigeons (C. livia, and S. turtur) and Gallus gallus domesticus, the rates of infection were (16.10, 15.05, and 5.75 %), while in female types of C. livia, S. turtur, and Gallus gallus domesticus, the rates of infection were (12.17, 12.28, and 31.11%), respectively. The incidence of T.gallinae is distributed for the most studied months, as it showed the highest infection rate for pigeons in January at 20% for C. livia, and 32% for S. turtur, and while January to February had 33% as the highest rate of infection in G.gallus domesticus, although there were no significant differences (P>0.05) among studied birds. The histological changes of infected organs for all species as well as for healthy birds, as the parasite was located in the upper part of the gastrointestinal tract, which was tongue, pharynx, vesicle, and gizzard. Granular lesions and infiltration of lymphoid and inflammatory cells were found, as well as degeneration in a number of gland-forming cells. The mucous in the affected areas as a result of parasite penetration into the tissue, congestion of blood vessels and appearance of granulation tissue in the upper part of healthy alimentary canal was compared with that of C. livia, S. turtur and Gallus gallus domesticus of Balad distract. In pharynx, the infiltration of large numbers of white blood cells, scattered and nodular form, and the sloughing of surface cells, and presence of strands of sloughed keratin appeared in pharynx cavity, and in vesicle tissue, and in gizzard, the histological sections showed the presence of parasite in muscle layer surrounded by a white transparent band, the infiltration of a large number of white blood cells appeared, and degeneration of epithelial cells at the bases of epithelial cells appeared in mucous folds.

Status of benthic cover in Carbin Reef, Sagay Marine Reserve, Western Visayas, the Philippines

This study determined the status of Carbin Reef benthic cover, Sagay Marine Reserve, Negros Occidental. The underwater benthic assessment was conducted on March 2019 by laying eight 50-meter transect lines at the depths of 6 meters (crest) and 12 meters (slope). Photo-quadrat method was used in obtaining still benthic images for every 1-m across eight 50-meter transect lines. A total of 400 still images were acquired and analyzed using Coral Point Count with Excel Extension (CPCe). The sedimentation rate was also determined by deploying sediment collectors. Results showed that Carbin Reef is characterized by 26.09% live coral cover and 43.25% abiotic structure such as rocks, sand, and coral rubbles. Fifty-five (55) coral species belonging to thirty-three (33) genera were identified, dominated by Porites, Fungia, and Goniastrea. Throughout the area, Porites lobata was the most dominant coral species. The overall hard coral cover seemed to have decreased since 2014. Further analysis showed the prevalence of bleached corals and diseases such as white syndrome, and white band disease. Similarly, two signs of compromised health including sediment damage and competition overgrowth were also present. The sedimentation rate per day was below the maximum tolerable levels by most corals during dry season. Overall, this study presents the first extensive study of coral diversity in Carbin Reef–characterized by a moderately diverse area and considered as a moderately stressed habitat.

珊瑚礁生态系统病毒研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 珊瑚礁生态系统病毒研究进展 DOI: 10.5846/stxb202005021086 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重大项目（42090041）；国家自然科学基金重点项目（42030502）；广西南海珊瑚礁研究重点实验室自主基金项目（GXLSCRSCS2021103） A review of recent researches on viruses in coral reef ecosystem Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:病毒对珊瑚礁生态系统中的生物进化、生物地球化学循环、珊瑚疾病等方面具有重要的生态影响。随着珊瑚礁的全球性退化，病毒在珊瑚礁生态系统中的功能与危害日益显现。综述了珊瑚礁生态系统中病毒的研究现状与进展，包括：（1）珊瑚礁病毒的多样性与分布特征（水体、宿主、核心病毒组）；（2）珊瑚礁病毒的生态功能（感染方式、促进生物进化、生物地球化学循环）；（3）珊瑚礁病毒对全球气候变化的响应（热压力、珊瑚疾病）。总体而言，珊瑚礁生态系统具有极高的病毒多样性，所发现的60个科占已知所有病毒科数量的58%。珊瑚的核心病毒组主要由双链DNA病毒、单链DNA病毒、单链逆转录病毒所组成，珊瑚黏液层对病毒具有富集作用。"Piggyback-the-Winner"（依附-胜利）是病毒在珊瑚礁中主要的生物动力学模式，其可通过水平基因迁移的方式促进礁区生物进化。病毒可通过裂解细菌与浮游藻类的途径参与珊瑚礁的生物地球化学循环，尤其是碳循环与氮循环过程。此外，病毒还具有介导珊瑚热白化与直接引发珊瑚疾病的能力，这会影响珊瑚礁生态系统应对气候变化的适应性与恢复力。基于国际上的研究进展综述，结合南海珊瑚礁生态现状提出以下研究方向，以期促进我国珊瑚礁病毒学的发展：（1）开展南海珊瑚礁中病毒多样性的识别及其时-空分布特征研究；（2）探索病毒对南海珊瑚热白化、珊瑚疾病的介导作用及其与气候变化的关系；（3）揭示病毒对南海珊瑚礁生物地球化学循环的贡献。 Abstract:Viruses have an important ecological impact on the biological evolution, biogeochemical cycle, and coral diseases in coral reef ecosystems. With the global degradation of coral reefs, the functions and hazards of viruses in coral reef regions have become increasingly prominent. In this article, recent researches on viruses in coral reef ecosystems were reviewed, which included:(1) The diversity and distribution characteristics of viruses in coral reef ecosystem (sea water, host and core coral virome); (2) Ecological function of viruses in coral reef ecosystem (infection pattern, promoting biological evolution, and biogeochemical cycle); (3) Viruses response to global climate change in coral reef ecosystem (thermal stress and coral diseases). Accordingly, coral reef ecosystems have an extremely high viral richness and diversity. About 60 virus families are reported in coral reef ecosystems around the world, which account for 58% of all known viral families. Also, the core coral virome is manly composed of double-stranded DNA virus (dsDNA virus), single-stranded DNA virus (ssDNA virus) and retrovirus. The viruses in coral surface mucus layer are more abundant and diverse, due to enrichment with viruses from around environment in coral reef ecosystem. "Piggyback-the-Winner" is the main biodynamic mode of viruses in coral reefs, which indicates that viruses can promote the evolution of organisms by horizontal gene transduction in reef regions. In addition, viruses can participate in the carbon and nitrogen cycles of coral reefs by lysing bacteria and planktonic algae, respectively, which plays an important role in biogeochemical cycles of coral reef ecosystem. It's worth noting that viruses have ability to mediate coral thermal bleaching, which has closely associations with Phycodnaviridae and Herpesviridae. Moreover, viruses can also lead to coral diseases (e.g., white plague, white band disease and yellow blotch), which can affect the adaptability and resilience of coral reefs to global climate change. Herein, based on a systematic review of international research progress and current ecological status of coral reefs in the South China Sea, this article proposes the following research directions, in order to promote the development of coral reef virology:(1) The diversity and spatial-temporal distribution characteristics of viruses in coral reefs from the South China Sea; (2) The mediation effect of viruses on coral thermal bleaching and diseases in the South China Sea, and their relationship with intensified global climate change; (3) The contribution of viruses in biogeochemical cycles (e.g., carbon and nitrogen cycles) of coral reef ecosystems in the South China Sea. 参考文献 相似文献 引证文献

Distribution, abundance, and health indicators of the critically endangered coral species Acropora cervicornis in Los Roques National Park, 2014

Acropora cervicornis is one of the most important coral species in shallow reefs of the Caribbean as it provides habitat and structural complexity to several species of invertebrates and fish. However, the distribution range of A. cervicornis has shrunk and collapsed considerably during the last five decades, due to a combination of factors including the increase of disease prevalence, storm frequency, and anthropogenic threats. Despite being classed as “Critically Endangered” in the IUCN Red List, information regarding its population status and condition across large Caribbean coralline areas is limited. Herein we conducted the first Marine Protected Area (MPA) scale survey for this species at the Los Roques archipelago, which included visual census across 127 sites to determine the abundance, spatial distribution, habitat type (i.e., leeward, windward), and patch morphology of A. cervicornis (i.e., continuous, dispersed, scatter, isolated). We selected 11 sites, where this species was predicted and reported to be ubiquitous, to determine live A. cervicornis cover, its recent and old mortality cover, and white band disease prevalence as proxies for coral health. For this, four 25-m long photomosaics were analysed at each site. We found Acropora cervicornis in only 29% of the surveyed sites; indicating that this species currently has a narrow and very restricted distribution in Los Roques and suggesting that either this species is rare or has declined over the past decades within the MPA. Dispersed and scattered patches prevailed upon continuous patches, which only occurred in two of the surveyed sites. Moreover, these patches were located near the largest human population settlements, and inside the low protection zones of the MPA where fishing and touristic activities are permitted. The photomosaic survey showed that more than 75% A. cervicornis patches showed an average live cover above 27%, low prevalence of white band disease (<7%), and low macroalgal abundance (<10%); suggesting that Los Roques still holds healthy populations. Our results indicate that the persistence of this species urgently requires re-evaluating current MPA zoning, especially following recent evidence of overfishing and inadequate law enforcement. This study provides a baseline of A. cervicornis populations in Los Roques and Southern Caribbean that can be later used for local population management and conservation.

Determinative Structural Features Identified With Probe-based Confocal Endomicroscopy for the Accurate Diagnosis of Gallbladder Malignancy.

Probe-based confocal laser endomicroscopy (pCLE) can visualize microscopic structures at high resolution but has not yet yielded definitive diagnostic features of gallbladder malignancy, as opposed to benign changes. A total of 73 patients had their gallbladder evaluated with pCLE performed on resected benign and malignant gallbladder surgical specimens, which were sprayed with fluorescein. Malignant and benign features of pCLE findings were identified on the basis of Miami and Paris Classifications. Standard histopathological diagnoses and individual patient pCLE findings of gallbladder lesions were correlated. Of the 73 consecutive patients that had their gallbladder evaluated ex vivo with pCLE, 11 were identified with gallbladder malignancy. pCLE identified features of gallbladders examined ex vivo, including the presence of thick dark bands and dark clumps, which together correlated with histopathologically-determined biliary malignancy at 100% sensitivity. Thick white bands and visualized epithelium, also identified with pCLE, together correlated with histopathologically-determined malignancy at 100% specificity. pCLE can be used for real-time differentiation of cancerous/non-cancerous regions in the gallbladder using the diagnostic criteria identified in the present study.

Effect of structure and phase content on wear resistance of the economical alloyed metastable and secondary hardening steels of Cr-Mn-Ti system

Despite a large number of studies in the field of assessing the causes of the formation of hot and cold cracks during surfacing of wear-resistant alloys, today the issues of working out the use of economically alloyed wear-resistant materials and the technique of their surfacing remain relevant. Goal: The purpose of this work is to study the effect of the structure and phase composition on the wear resistance of economically alloyed metastable and secondary hardening steels of the Cr-Mn-Ti system, as well as with additional alloying with Mo, B, V. Mechanized surfacing was carried out with flux cored wires AN-22 and AN-20 with the supply of a de-energized additive to the head of the weld pool, which reduces the content of sulfur and phosphorus, the specific consumption of electricity and increases the assimilation of alloying elements and the relative mass of the flux. Cladding by manual arc welding was carried out with coated electrodes with the addition of a depleted CaF2-coated flux-cored wire filler. When surfacing with a de-energized additive, the ratio of the filler to the main electrode, the relative mass was determined by β = m1 / m2 (m1, m2 are the mass of the filler and the electrode rod, respectively). Submerged arc surfacing was carried out in the following modes: IN = 300 ... 350 A, UD = 26 ... 30 V, q = 6 ... 10 kJ / cm, with manual surfacing - IN = 180 ... 220 A, UD = 25 ... Results: The studies carried out confirm the possibility of the formation of a “white band” both in alloys with a high concentration of austenitizing elements (Mn, C, Ni) and when alloying carbide-forming elements with a relatively low affinity for carbon (V, Mo). The indicators of resistance to cracking (КС, j-integral, δС), and, consequently, resistance to wear of secondary hardening steels are higher than those of metastable and tool steels.

Negative body size-dependent resource allocation underlies conspicuous sexual ornaments in a territorial damselfly.

Sexual ornaments, signalling individual quality to choosy females or rival males, often show steeper body size scaling compared with non-sexually selected traits. Theory posits such steeper body size scaling is the result of differential resource allocation, reflecting trade-offs between different components of fitness. Yet, the process of resource allocation towards body size-dependent sexual ornaments has been rarely understood empirically. Using the Neotropical territorial damselfly Megaloprepus caerulatus, whose males and females carry wax-based, sex-specific white wing bands and white wing tips respectively, we investigated nutrition sensitivity and body size scaling of both traits by manipulating larval food availability and directly quantified both the fat allocated to wing ornaments and the fat reserve from which allocations are made. Both colour traits exhibited sensitivity to food availability during larval development and steeper body size scaling compared with control traits. Although the absolute amount of fat invested in developing the colour ornaments increased with body size, the proportion of total fat allocated to the ornaments decreased with body size, making exaggerated ornaments less affordable for smaller individuals. Our data demonstrate that measuring the proportion of resource pool from which an individual's ornaments are derived (i.e. its affordability) is essential for understanding the maintenance of honesty of sexual signals.

Review: Death and Rebirth in a Southern City: Richmond’s Historic Cemeteries, by Ryan K. Smith

Review: <i>Death and Rebirth in a Southern City: Richmond’s Historic Cemeteries</i>, by Ryan K. Smith

A new semifossorial snake of the genus Arrhyton (Squamata: Dipsadidae) from eastern Cuba, with taxonomic comments on other species.

The genus Arrhyton is endemic to Cuba, with eight currently known species. A new species, Arrhyton albicollum sp. nov., is described from the karst areas of Gibara, Holgun Province. The new species is closely related to A. redimitum, another eastern species, according to morphology and molecular phylogeny. It differs from all other species of the genus by having a conspicuous, white nuchal band, a contrasting black pattern on the head, a gray-colored body with faint stripes, and a high number of ventral and subcaudal scales. Additional comments on other species include new locality records and information on morphology and relationships.

Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au-Ag Systems: Utility and Implications for Mineral Exploration.

Raman spectroscopy of fine-grained hydrothermal alteration minerals, and phyllosilicates in particular, presents certain challenges. However, given the increasingly widespread recognition of field portable visible–near infrared–shortwave infrared (Vis-NIR-SWIR) spectroscopy as a valuable tool in the mineral exploration industry, Raman microspectroscopy has promise as an approach for developing detailed complementary information on hydrothermal alteration phases in ore-forming systems. Here we present exemplar high-quality Raman and Vis-NIR-SWIR spectra of four key hydrothermal alteration minerals (pyrophyllite, white mica, chlorite, and alunite) that are common in precious metal epithermal systems, from deposits on the island of Newfoundland, Canada. The results reported here demonstrate that Raman microspectroscopy can accurately characterize pyrophyllite, white mica, chlorite, and alunite and provide details on their compositional variation at the microscale. In particular, spectral differences in the 1000–1150 cm−1 white mica Raman band allows the distinction between low-Tschermak phases (muscovite, paragonite) and phases with higher degrees of Tschermak substitution (phengitic white mica composition). The peak position of the main chlorite Raman band shifts between 683 cm−1 for Mg-rich chlorite and 665 cm−1 for Fe-rich chlorite and can be therefore used for semiquantitative estimation of the Fe2+ content in chlorite. Furthermore, while Vis-NIR-SWIR macrospectroscopy allows the rapid identification of the overall composition of the most abundant hydrothermal alteration mineral in a given sample, Raman microspectroscopy provides an in-depth spectral and chemical characterization of individual mineral grains, preserving the spatial and paragenetic context of each mineral and allowing for the distinction of chemical variation between (and within) different mineral grains. This is particularly useful in the case of alunite, white mica, and chlorite, minerals with extensive solid solution, where microscale characterization can provide information on the alteration zonation useful for mineral exploration and provide insight into mineral deposit genesis.

A new species of Homonota (Squamata: Gekkota: Phyllodactylidae) from Paraguay

The 12 recognized species of the genus Homonota are geographically restricted to central and southern South America in Argentina, Brazil, Uruguay, Bolivia, and Paraguay. The phylogenetic relationships within the genus are well known where three groups are identified, each of them containing four species: the whitii group (Homonota darwinii, H. williamsii, H. whitii, and H. andicola), the borellii group (H. borellii, H. taragui, H. rupicola, and H. uruguayensis) and the horrida group (H. horrida, H. underwoodi, H. septentrionalis, and H. marthae). During fieldwork in Paraguay, we found a specimen of Homonota with unique morphological and geographical traits. Thus, we performed a comparative morphological analysis against specimens housed in different Paraguayan collections. Additionally, we performed a DNA analysis of our specimen to assess its relationships within the genus. Results suggest that this specimen represents a new species of the Homonota horrida group based on molecular and morphological evidence. The new species is characterized by a robust body, 10 longitudinal rows of strongly keeled scales separated by one or two granular scales, square-shaped mental scales, small postmental scales, one or two rows of rectangular scales in the upper eye scales, rostral scale divided, edge of auditory meatus serrated posteriorly, and black and brown background coloration with one white vertebral line and seven white transverse bands. The new species is restricted to Paraguarí Department, characterized by herbaceous grasslands with rocky outcrops.

Strength Variation of Augen Gneiss in the Point Load Test under Different Loading Direction and Temperature

The anisotropic nature of rock strength varies with the degrees of an anisotropic plane. The study on strength index which are effect by anisotropic plane with different loading angle, the role of grain size of mineral and thermal behaviour in the point load index test. The rock material with the heterogeneous mineral of the dark and white bands of mineral with a different grain size that increases the foliation degree and reduced the strength value depends on grain size and their bounding. In Augen Gneiss the strength index depends on the anisotropy plane of the sample with loading direction, thermal variation, and fracturing pattern are controlled by the grain size of the mineral. The microcrack developed with temperature increases and the crack initiated with grain boundaries, and further developed intercrystalline crack with temperature increases. There is no significant difference in density up to 300° c when the natural moisture content is less.

Investigation of microstructural and mechanical properties of AA1050-AZ91D dissimilar friction stir welding

Joining of aluminium and magnesium alloys frequently pose significant challenges to the extent where joining may seem impossible, due to differences in the physical, metallurgical, and chemical properties of the materials. Friction stir welding is a solid-state welding technique which uses a non-consumable tool to join metals. This study examines the dissimilar friction stir welding of 3 mm thick AA1050 and AZ91D alloy sheets. Successful defect-free joints were achieved at rotational speeds of 400 rpm and 600 rpm, and a constant traverse speed of 50 mm/min. The metallurgical investigations used to characterize the microstructure of the welds are optical microscopy (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The microstructures of the samples show distinct morphology attributed to their different rotational speeds. However, Al3Mg2 intermetallics (IMCs) phase was detected in the white bands present in both weld samples. The IMCs were formed through solid-state diffusion. The mechanical properties characterizations includes the microhardness profiles and tensile testing. The variation in the rotational speeds do not have a significant effect on the microhardness distribution of the weld samples. The tensile strength of the dissimilar weld improved substantially with the presence of an interpenetration feature (IPF).

Development of white etching bands under accelerated rolling contact fatigue

Bearing steel under severe loading condition undergoes substantial subsurface microstructural alterations known as Dark etching regions and white etching bands. White etching bands (WEBs) develop after hundreds of millions of stress cycles in bearing components and have been reported for several decades but the formation mechanism of white bands is not fully elucidated. Current research presents a systematic rolling contact fatigue (RCF) testing in a rotary tribometer under accelerated conditions, where rolling cycles are simulated in a 4-ball test configuration. The post RCF investigations have been carried out to understand the formation mechanism of WEBs in a ball-on-ball point contact load. WEBs have been characterised with the help of nanoindentation and Energy-dispersive X-ray spectroscopy analysis. The quantitative analysis of WEBs growth with subsurface stress field has revealed that the unique orientations of white bands are governed by the plane of maximum relative normal stress along the contact track. Moreover, the accelerated growth and reversal of WEBs sequence at elevated temperature have revealed that the WEBs formation is dependent on temperature/load combination. The observed growth of lenticular carbides in current research is also compared with dislocation gliding model and the role of carbon diffusion within WEBs is highlighted.