Average Colony Size Research Articles

Improving mechanisms of lamellar microstructure and mechanical properties by Y and in-situ Y2O3: Modification of carbides particles and complete transformation of Ti2AlC particles

To reveal the modification mechanism of carbides particles by in-situ Y2O3, and then the improvement mechanisms for Ti42Al6Nb2.6C-xY alloys, the microstructures were observed by SEM, XRD and TEM, and the mechanical properties were examined. Results show that the flaky TiC transformed completely into Ti2AlC, and the morphology of Ti2AlC turned fine-needle shaped into short-rod shaped. The content of Ti2AlC with the aspect ratio of 1–5 increased from 24.2 to 81.4%, and the average aspect ratio decreased from 7.9 to 3.7 as Y increased from 0 to 0.08 at. %. The average lamellar colony size and lamellar spacing decreased from 24.054 to 17.500 μm and 0.531 to 0.304 μm, respectively. The growth of TiC phase was constrained by in-situ Y2O3, which alleviated agglomeration distribution of TiC and provided a fine TiC substrate for the nucleation of Ti2AlC. The interfacial interaction between in-situ Y2O3 and Ti2AlC restricted the longitudinal and transverse growth of Ti2AlC. The modified Ti2AlC and in-situ Y2O3 particles as nucleation sites for β grains were the basis for obtaining fine lamellar structure. For mechanical properties, the compressive strength increased from 1388 to 1781 MPa, the yield strength increased from 1265 to 1544 MPa, and the Vickers hardness increased from 495 to 609 HV. The refinement of lamellar colony by modified Ti2AlC and in-situ Y2O3, and the load strengthening of Ti2AlC particle contributed to the mechanical properties.

Tailoring lamellar orientation and tensile properties of TNM alloy via extrusion

The rectangular billet of TNM alloy with oriented lamellar microstructure was obtained by extrusion above its α transus temperature. The as-extruded TNM alloy exhibits a nearly lamellar microstructure with an average colony size of approximately 60 μm, and the proportion of lamellar colonies with an angle between the interface and the extrusion direction less than 30° exceeds 70 %. EBSD results show that strong basal texture of α phase with basal planes parallel to the extrusion direction was formed during the extrusion process in the (α+β) two-phase field. During the subsequent cooling process, the γ lamellae precipitates along the (0001) plane of α phase according to the Blackburn orientation relationship, allowing the lamellar structure to inherit the orientation of the parent phase. Tensile test results indicate that the strength and fracture elongation of the as-extruded TNM alloy along the extrusion direction (ED) increased simultaneously, which were 1100 MPa and 1.26 %, respectively. The hindrance effect of interfaces on dislocations and stacking faults in lamellar colonies parallel to the extrusion direction helps to improve strength, while the activation of the prismatic slip and pyramidal slip systems in the α2 lamellae is beneficial to the plasticity. This study shows that it is feasible to control the lamellar orientation and improve the mechanical properties of TNM alloy by extrusion above its α transus temperature.

Reef structure of the Florida Reef Tract for the period 2005–2020

Shallow-water coral reefs of the Florida Reef Tract compose the third largest reef in the world, but during the last several decades, scleractinian (stony) corals have suffered unprecedented declines from global and local stressors. A program to evaluate the effects of high-temperature bleaching events was initiated by The Nature Conservancy’s Florida Reef Resilience Program in 2005 and surveys have been completed across at least some portion of the entire region every year since. The program adopted a demographic (colony-based) assessment approach, which records colony species, size (height and maximum diameter), and estimated partial mortality (percent barren skeleton). Because reef structure is critical to ecosystem functioning and services, data from 2005 to 2020 were analyzed to describe the abundance, size, and morphological complexity of stony coral colonies forming the biogenic reef. Colony height, footprint, surface area, and volume summed for 6016 transects were used to describe reef structure and averages were used to characterize the components that contributed to the structure. Nearly 150,000 colonies representing 49 species were reported during this period and results demonstrated both spatial and temporal changes for the region and for geographic subregions. Some subregions showed increasing colony density, especially for three small, hemispheric species, and declining average colony size.

High-Throughput Gel Microbeads as Incubators for Bacterial Competition Study.

Bacteria primarily live in structured environments, such as colonies and biofilms, attached to surfaces or growing within soft tissues. They are engaged in local competitive and cooperative interactions impacting our health and well-being, for example, by affecting population-level drug resistance. Our knowledge of bacterial competition and cooperation within soft matrices is incomplete, partly because we lack high-throughput tools to quantitatively study their interactions. Here, we introduce a method to generate a large amount of agarose microbeads that mimic the natural culture conditions experienced by bacteria to co-encapsulate two strains of fluorescence-labeled Escherichia coli. Focusing specifically on low bacterial inoculum (1-100 cells/capsule), we demonstrate a study on the formation of colonies of both strains within these 3D scaffolds and follow their growth kinetics and interaction using fluorescence microscopy in highly replicated experiments. We confirmed that the average final colony size is inversely proportional to the inoculum size in this semi-solid environment as a result of limited available resources. Furthermore, the colony shape and fluorescence intensity per colony are distinctly different in monoculture and co-culture. The experimental observations in mono- and co-culture are compared with predictions from a simple growth model. We suggest that our high throughput and small footprint microbead system is an excellent platform for future investigation of competitive and cooperative interactions in bacterial communities under diverse conditions, including antibiotics stress.

Bestands- und Brutplatzerfassung von Mehlschwalben (Delichon urbicum, Linnaeus, 1758) und Rauchschwalben (Hirundo rustica, Linnaeus, 1758) im Südwesten und Westen Luxemburgs

Population size, distribution and nesting site characteristics of breeding house martins and barn swallows were investigated in the mixed rural and urban landscape of southwestern and western Luxembourg. House martins were mapped in 34 municipalities (670 km2) between 2013 and 2020 and barn swallows in 11 municipalities (228 km2) between 2017 and 2020, representing nearly a quarter and a tenth of the national surface, respectively. By means of one visit per season, nests as well as their occupation status were recorded in a comprehensive mapping effort comprising settlements as well as farmsteads. For the house martin, 4,109 nests were mapped, 1,025 of which were occupied and distributed over 368 colonies with an average number of 2.78 breeding pairs per colony and a population density of 1.62 breeding pairs per km2. Nearly one third of the recorded martin pairs were settled in artificial nests, underlining the effectiveness of this conservation measure. Barn swallow nests numbered 1,395, of which 655 housed breeding pairs, distributed over 107 sites with an average colony size of 6.12 breeding pairs and a population density of 2.89 breeding pairs per km2. Between-year occupancy rates as well as abundances varied strongly between different municipalities in the study area in both species. Generally low breeding densities reflect the unfavourable conservation status for both red-listed swallow species.

Microstructure and Mechanical Properties of a High-Strength Ti-4Al-2Fe-3Cu Alloy Fabricated by Sintering and Hot Extrusion

A Ti-4Al-2Fe-3Cu (wt pct) alloy containing only low-cost alloying elements was fabricated by vacuum sintering a blend of TiH2, Al, Fe, and Cu powders at 1200 °C for 1 hour followed by hot extrusion at the same temperature. The as-extruded alloy exhibited a microstructure consisting of mainly α/β lamellar colonies and Ti2Cu as a minor phase. The average colony size and lamella thickness were 118 and 12 µm, respectively, and Fe and Cu were predominantly distributed in the β lamellae. The as-extruded alloy had a high tensile yield strength (YS) and ultimate tensile strength (UTS) of 1248 and 1270 MPa, respectively, but a limited ductility (elongation to fracture: 2.3 pct). Annealing at 750 °C for 4 hour caused the average colony size and lamella thickness of the alloy to increase to 145 and 17 µm, respectively, and the volume fraction of the β phase decreased with the annealing. These microstructural changes resulted in a slight decrease of the YS and UTS to 1221 and 1253 MPa, but a clear increase of the ductility with the elongation to fracture reaching 4 pct. This work demonstrates that a combination of relatively low-temperature vacuum sintering, hot extrusion, and annealing can be effectively utilized to fabricate a low-cost Ti-4Al-2Fe-3Cu alloy with high strength and appreciable tensile ductility.

The effects of coral assemblage shift on reef functions in Akumal, Mexico

Caribbean coral reefs have suffered shifts in their coral assemblages, driven by local and global stressors. These shifts have affected reef functions, ecosystem processes, and services essential to human well-being. Akumal Reef, located in the northern Mexican Caribbean, generates valuable ecosystem services, mainly linked to tourism, that depend on the persistence of the reef’s physical functionality. In this study, decadal changes in coral assemblages and their effects on functional traits decline were investigated. Coral species cover was systematically monitored at 14 sites along Akumal Reef in 2001, 2010, and 2019. These data were translated to functional traits allowing the classification of coral species into life-history strategies (competitive, stress-tolerant, and more opportunistic ‘weedy’ species). Our results indicate a significant decline in stress-tolerant species cover (mostly from the genusOrbicella)in Akumal Reef between 2001 and 2010 and between 2010 and 2019, with no significant changes in coral cover of other life-history strategies. The significant shifts away from stress-tolerant species during the time studied in Akumal Reef influenced the deterioration of functional traits related to reef physical functionality, such as calcification, rugosity, average maximum colony size, and reef functional index. Currently, Akumal reef sites are dominated by non-framework-building weedy coral species and are mostly below the 10% hard cover estimated threshold for positive reef accretion in the Caribbean. Therefore, management strategies in Akumal Reef should be integrative and oriented towards reducing local stressors while actively restoring the functional structure of coral reefs and maintaining their environmental services.

Microstructures and mechanical properties of high strength Ti-XAl-2Fe-3Cu alloys fabricated by powder compact extrusion

Ti-XAl-2Fe-3Cu (X = 2.7, 4 wt%) alloys with a high tensile yield strength of up to 1150 MPa were synthesized using powder compact extrusion from blended TiH2 and elemental powders. The microstructures and mechanical properties of the extruded rods without and with a homogenization heat treatment at 1000 °C for 1 h followed by furnace cooling were investigated. It was found that the Al content and heat treatment had significant effects on the microstructures and mechanical properties. With increasing the Al content from 2.7 to 4 wt%, the average lamellar colony size and lamellar thickness of the as-extruded Ti-XAl-2Fe-3Cu alloy decreased from 442.4 to 224.1 µm and 6.7–5.2 µm respectively. The heat treatment increased the lamellar thickness as well as the level of partitioning of Fe and Cu between α and β phases. As a result of the microstructural changes, increasing Al from 2.7 to 4 wt% caused a slight increase in the strength of Ti-XAl-2Fe-3Cu alloys without changing the ductility, while the heat treatment slightly reduced the strength of the alloys, but clearly increased their tensile ductility. The correlation between microstructures and mechanical properties is discussed.

Humic acid inhibits colony formation of the cyanobacterium Microcystis at high level of iron

Colony formation is a key process for the occurrence of Microcystis blooms. In order to inhibit colony formation of Microcystis at high level of iron using humic acid, unicellular Microcystis aeruginosa was cultivated in laboratory treated with varying concentrations of iron and humic acid. Our results showed that the extracellular polysaccharides (EPS) content and average colony size increased from 0.57 pg cells−1 and 4.0 μm to 0.93 pg cells−1 and 26.1 μm, respectively, while iron concentration increased from 0.68 mg L−1 to 6.8 mg L−1, suggesting that high level of iron stimulated EPS secretion and induced unicellular Microcystis to form colonies. Transcriptome analysis showed that two genes described as glycosyltransferases (BH695-2217 and BH695-3696) were significantly up-regulated while EPS content increased with increasing iron concentration indicating that iron may regulate the expression of genes involved in polysaccharide synthesis. When treated with 10 mg C L−1 humic acid at high level of iron, the EPS content and average colony size decreased by 35.5% and 56.3%, respectively, revealing that humic acid inhibited EPS secretion under high level of iron condition, and ultimately inhibited colony formation of Microcystis. Our results suggested that humic acid could be used as an agentia inhibiting large colony formation of Microcystis and thereby reducing the occurrence of Microcystis blooms.

Anaerobic culture on growth efficient bi-layered culture plate in a modified candle jar using a rapid and slow combustion system

Success for maximum isolation of anaerobes depends on maintaining critically low oxygen levels throughout and growth in a reduced medium with exclusion of inhibitory substances. Hence a dual system was used equipped with candle combustion for instant exhaustion of major part of oxygen from a sealed jar, along with acidified steel wool for residual oxygen purging. For inhibitory substances removal, test anaerobes were grown on anaerobic medium layered on buffer charcoal agar bed. After 48 hours incubation average colony sizes were compared with that of growths in conventional Gas-Pak system. Better growths were noted in the innovative system.

Rapid Population Decline of the Pillar Coral Dendrogyra cylindrus Along the Florida Reef Tract

Coral reefs worldwide are in a state of decline, but the population status and impacts of stressors for rare species are generally not well documented using broad-scale monitoring protocols. We fate-tracked all known colonies of the pillar coral, Dendrogyra cylindrus, on the Florida Reef Tract (FRT) from 2013 to 2020 to assess population condition and trend, and to document the relative impacts of chronic and acute stressors. Large average colony size, an absence of juveniles, and large geographic distances between genotypes suggest that the Florida D. cylindrus population has been reproductively extinct for decades. During the study period, low-intensity chronic stressors were balanced by regrowth, while back-to-back years of coral bleaching and thermally-exacerbated disease led to declines that the subsequent recovery rates suggest would require 11 uninterrupted years to overcome. The most recent stressor on Florida’s D. cylindrus population is “stony coral tissue loss disease” (SCTLD). Following the appearance of the disease in Florida in 2014, unrecoverable losses occurred within the D. cylindrus population as tissue, colonies, and whole genotypes suffered complete mortality. Losses of 94% of coral tissue, 93% of colonies, and 86% of genotypes between 2014 and the end of 2020 have led to functional extinction of D. cylindrus on the FRT.

Microstructure and microhardness of Ti-48Al alloy prepared by rapid solidification

To improve the microstructure and microhardness, Ti-48Al (at.%) alloy was rapidly solidified by melt spinning under different cooling rates. The microstructure and microhardness of rapidly solidified Ti-48Al alloy were systematically investigated. Results show that the average lamellar colony size of the alloy reduces from 60.6 µm to 11 µm as the cooling rate increases from 2.3×105 to 5.1×105 K·s−1, caused by the increase of nucleation rate at a higher cooling rate. At the high cooling rate of (4.3–5.1)×105 K·s−1, the ± phase is the primary phase, and a few metastable α phases are reserved, which then transform into α2 phase and subsequently lead to the formation of α2 equiaxed grain. The lamellar spacing also decreases with the increase of cooling rate. The relationship between lamellar spacing (d) and cooling rate (v) is d=33.6v−1.34. The microhardness increases with the increase of cooling rate because the refined lamellar spacing and grain size can improve the microhardness.

Prematurity negatively affects regenerative properties of human amniotic epithelial cells in the context of lung repair.

There is a growing appreciation of the role of lung stem/progenitor cells in the development and perpetuation of chronic lung disease including idiopathic pulmonary fibrosis. Human amniotic epithelial cells (hAECs) were previously shown to improve lung architecture in bleomycin-induced lung injury, with the further suggestion that hAECs obtained from term pregnancies possessed superior anti-fibrotic properties compared with their preterm counterparts. In the present study, we aimed to elucidate the differential effects of hAECs from term and preterm pregnancies on lung stem/progenitor cells involved in the repair. Here we showed that term hAECs were better able to activate bronchioalveolar stem cells (BASCs) and type 2 alveolar epithelial cells (AT2s) compared with preterm hAECs following bleomycin challenge. Further, we observed that term hAECs restored TGIF1 and TGFβ2 expression levels, while increasing c-MYC expression despite an absence of significant changes to Wnt/β-catenin signaling. In vitro, term hAECs increased the average size and numbers of BASC and AT2 colonies. The gene expression levels of Wnt ligands were higher in term hAECs, and the expression levels of BMP4, CCND1 and CDC42 were only increased in the BASC and AT2 organoids co-cultured with hAECs from term pregnancies but not preterm pregnancies. In conclusion, term hAECs were more efficient at activating the BASC niche compared with preterm hAECs. The impact of gestational age and/or complications leading to preterm delivery should be considered when applying hAECs and other gestational tissue-derived stem and stem-like cells therapeutically.

Influence of Microstructure on the Mechanical Properties of a Pearlitic Steel

The effect of austenite grain size on microstructure and mechanical properties was studied for a pearlitic steel. The best combination of ultimate tensile strength (UTS) and percent reduction in area (pct RA) was obtained when the material was austenitized at 950 °C, and the corresponding austenite grain size, before the start of cooling, was approximately 71 μm. Pearlite lamella spacing and colony size were minimum for these samples. Both UTS and pct RA were found to maintain a kind of power law-type relationship with microstructural aspects such as pearlite lamella spacing and colony size. The experimental data suggest that further enhancement of the strength of prestressed concrete (PC) wire rod (beyond 1200 MPa) would require a fine pearlitic microstructure in which pearlite lamella spacing would be below 0.05 μm and average colony size would be below 4 μm.

Glucocorticoids Induce the Maintenance and Expansion of an Immature CFU-E Erythroid Progenitor Population in Humans

Glucocorticoids are widely used to increase red cell production in a number of hematological disorders including Diamond Blackfan anemia (DBA). Despite their clinical effectiveness we do not fully understand the mechanistic basis for the regulation of human erythropoiesis by glucocorticoids. To improve the clinical management of these patients, we studied the mechanisms of dexamethasone (Dex) on human erythroid progenitors. We employed an erythroid culture system to differentiate primary human CD34+ cells isolated from patients with DBA and healthy controls as well as cord blood samples. We found that Dex increases the proliferation of CD34+ cells derived from peripheral blood but surprisingly not of CD34+ cells from cord blood. Furthermore, by mass spectrometry proteomic analysis, we found that Dex specifically altered the induction of several targets unique to peripheral blood including the transcription factor and cell cycle regulator NR4A1. When examining the cell populations expanded with Dex treatment by immunophenotyping, we detected a specific expansion of CFU-Es. Dex increased the average size of CFU-E colonies in methylcellulose colony forming assays in the presence of Epo alone, suggesting that CFU-Es are the most Dex responsive progenitor in humans. In support of this hypothesis, reticulocyte counts from patients with DBA treated with prednisone were found to increase approximately one week after treatment, consistent with the time course of differentiation of CFU-E to reticulocytes in bone marrow. In order to further resolve the progenitor target of steroid responsive progenitor we developed a new gating scheme that allows for increased resolution of BFU-E and CFU-E subpopulations by monitoring surface expression of CD71 and CD105. Using this system, we found that Dex treatment led to the maintenance of a novel immature transitional progenitor population in peripheral blood-derived cells that we term immature CFU-E. In methylcellulose colony forming assays, these peripheral blood-derived immature CFU-E treated with Dex produced larger colonies than the untreated controls and mature CFU-E. The expansion and proliferation of Dex treated immature CFU-Es derived from peripheral blood was associated with a decreased percentage of cells in the S phase of the cell cycle. No change was noted for either Dex treated BFU-E from peripheral blood or for BFU-E or CFU-E from cord blood. Importantly, Dex responsive peripheral blood-derived CFU-Es divided at a faster rate than untreated CFU-Es, revealing a dissociation in the link between differentiation and proliferation. Mechanistically, we found that Dex treated peripheral blood CFU-E exhibited increased expression of the negative cell cycle regulator p57Kip2. Moreover, this protein was also found to be dysregulated in CD34+ cells from transfusion-dependent patients with DBA, wherein p57Kip2 expression was not significantly altered following Dex treatment, indicating a role for p57Kip2 in the erythroid progenitor defects seen in these patients. To further evaluate the role of p57Kip2 in the Dex dependent alteration in CFU-E proliferation, peripheral blood-derived CD34+ cells were transduced with p57Kip2-specific shRNA lentiviral constructs. shRNA knockdown of p57Kip2 abrogated the effects of Dex on growth and induced a premature EPO-mediated differentiation. In summary, our findings provide new insights into functional heterogeneity of human erythroid progenitors and reveal mechanistic insights into the action of Dex in normal and disordered erythropoiesis. Disclosures Vlachos: Novartis: Other: Steering committee member.

Morphological and physiological characterization of nitrogen fixing rhizobia isolated from country bean (Lablaba perpureus) of Narail, Bangladesh

Nitrogen is one of the important constituents of the plants. It is fixed in legume plants from the atmosphere by the association of beneficial gram negative soil bacteria named rhizobia. This study aimed to distinguish the morpho-physiological characteristics of naturally growing rhizobia having higher environmental and external stress tolerance. Twenty-two isolates were isolated from country bean root nodules and characterized based on different tests. The isolates varied from one another with level of parameters of the treatments. Most of them exhibited cream color colonies and some isolates evolved white and pink colonies. The average colony size of the isolates was ranged between 0.83 to 2.83 mm after one day and 1.33 to 5.00 mm after two days. Among them, 17 isolates were alkali producers, three isolates were acid producer and only two isolates produced neutral mucous. All the isolates showed complete resistance at pH 5.0 to 10.0, 2% NaCl, 10 to 42oC temperature, and 0.1 mM of heavy metallic salt MnCl2, FeCl3 and PbCl3. Nevertheless, most of the isolates also tolerated pH 4.0; 3 to 7% NaCl; 47oC temperature; 0.1 mM CuSO4. On the other hand, a few numbers of the isolates resisted 100 µg/ml and 200 µg/ml ampicillin, kanamycin and tetracycline antibiotics. Therefore, exploration of country bean rhizobia for their environmental stress tolerance capacity might be a core study for the production of cost-effective bio-fertilizer to boost up country bean yield.

Comparison of algal harvest and hydrogen peroxide treatment in mitigating cyanobacterial blooms via an in situ mesocosm experiment

The use of short-term, fast-acting curative treatments to rapidly suppress the proliferation of upcoming cyanobacterial blooms without negative side effects on overall water quality is important for environmental regulatory agencies. A 15-day in situ mesocosm experiment was conducted to evaluate the effects of algal harvest at different intensities and the effect of hydrogen peroxide on the mitigation of cyanobacterial blooms, subsequent algal growth and phytoplankton community structure. The results indicate that filtration through a 30-μm-pore-size net could remove most of the Microcystis colonies, leading to a decline in algal biomass. However, algal harvest at 30% and 60% intensities tended to promote cyanobacterial growth under nutrient-replete conditions, and the mitigation effect only lasted a few days, since cyanobacteria biomass exhibited no significant difference between the control and those two treatments on Day 6. When the algal harvest intensity was 90%, the cyanobacterial biomass remained at a relatively low level for 15 days. The average Microcystis colony size rapidly returned to the initial level after an initial decline across all the algal harvest intensities, indicating that algal harvest should be repeatedly performed within a short time period to mitigate Microcystis blooms. Furthermore, removing Microcystis colonies by filtration led to increased diversity in the phytoplankton community, as the proportion of non-Microcystis cyanobacteria increased with harvest intensity. This result might pose a challenge for cyanobacterial bloom control over the long term if filamentous cyanobacteria become dominant. The 10.0 mg L−1 H2O2 treatment selectively suppressed cyanobacteria throughout the experimental period, leading to succession from a cyanobacteria-dominated to a Chlorophyta-dominated community after Day 9. Overall, using hydrogen peroxide is more effective than algal harvesting as a one-time quick curative measure.

Phase Transformation and Fine Fully Lamellar (FFL) Structure Formation in a High Nb‐Containing Beta‐Gamma TiAl Alloy

TiAl intermetallics with fine fully lamellar (FFL) microstructure exhibit great potential application in high‐performance combustion engines. In this paper, the phase transformation sequence of a high Nb‐containing beta‐gamma TiAl alloy is obtained by using metallographic method. The results indicate that the single α‐phase field of Ti‐43Al‐8Nb‐0.2W‐0.2B alloy is inexistent or extremely narrow, which is caused by slight W element possibly. The temperatures of γ‐solvus and β‐transus are in the range of 1225–1230 °C and 1400–1410 °C, respectively. Based on the phase transformation temperatures, an improved multi‐step heat treatment of homogenizing in single β‐phase field followed by slightly higher than γ‐solvus is designed to obtain a FFL microstructure. The average lamellar colony size of the optimal microstructure is about 80 µm and the volume fraction of B2 phase is about 1%. Further analyses indicate that the elements redistribution and the secondary particles pinning effect are the mainly mechanisms of transforming to FFL microstructure.

Trends in tricolored blackbird colony size: 2008 through 2017

ABSTRACTTricolored blackbird (Agelaius tricolor) is a colonial breeder, largely restricted to grasslands, wetlands, and agricultural areas of California, USA. Tricolored blackbird abundance declined considerably during the twentieth century. Recent trends have been less clear, however, hindering efforts to evaluate the conservation needs of the species. We assessed trends in tricolored blackbird colony size using 2008, 2011, 2014, and 2017 Triennial Tricolored Blackbird Statewide Survey, a community‐science effort involving hundreds of volunteer observers. After accounting for variation in observer characteristics and survey effort, we found a clear, statistically significant decrease in average colony size of approximately 5% per year, which translated to a decrease in average colony size of approximately 40% between 2008 and 2017. This decrease in colony size matches the overall decline in abundance reported in another recent study and reinforces the conclusion that tricolored blackbird is in need of protection and recovery efforts. © 2019 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Formation of Ti2AlN and TiB and its effect on mechanical properties of Ti46Al4Nb1Mo alloy by adding BN particles

The synergistic effects of B and N on the microstructure evolution, mechanical properties and fracture behavior of Ti46Al4Nb1Mo alloy were investigated by adding BN particles. Ti46Al4Nb1Mo-xB-xN (x = 0, 0.4%, 0.8%, 1.2%, 1.6%, atomic percent, hereafter in at.%) alloys were prepared by vacuum arc melting. Compared with Ti46Al4Nb1Mo alloy, B2 phase disappeared and curvy TiB phase appeared at the interdendritic region in the Ti46Al4Nb1Mo-0.4B-0.4 N alloy. When 0.8% B and 0.8% N were added, Ti2AlN particles appeared in α2/γ lamellar colonies, tiny TiB particles and a few curvy TiB phases formed both at lamellar boundaries and lamellar colonies. With further increasing B and N content, the volume fraction of Ti2AlN and tiny TiB phases increased, and some long TiB phases appeared in the Ti46Al4Nb1Mo-1.6B-1.6 N alloy. Ti2AlN and TiB phases formed by the reaction between Ti46Al4Nb1Mo alloy and BN particles. The different formation mechanism between Ti2AlN and TiB was related to the different solid solubility of B and N in the Ti46Al4Nb1Mo alloy and solute redistribution during solidification process. When the content of B and N increased from 0 to 1.2%, the average lamellar colony size decreased from 358.4 μm to 48.7 μm, which resulted from synergistic effect of Ti2AlN and TiB. Compression results showed that the strength was improved from 1961 MPa to 2493 MPa without decreasing compressive strain. The fracture morphology showed inter-granular and inter-lamellar fracture mode in the Ti46Al4Nb1Mo alloy, while the fracture morphology showed trans-lamellar mode in the reinforced composites. The second phase strengthening of Ti2AlN and TiB, grain boundary strengthening by refined α2/γ lamellae, and elimination of B2 phase contributed to the improvement of strength.