B2 Clusters Research Articles

Short-Range Order in Gallium Solid Solutions in α-Iron

Short-range order in soft magnetic FeGa alloys containing from 3 to 25 at % Ga was studied using nuclear gamma resonance (Mössbauer) spectroscopy. The Mössbauer spectra were analyzed via fitting with subspectra corresponding to different configurations of the neighborhoods of the Fe atoms with Ga in the first and second coordination shells. It has been shown that in samples of alloys containing from 3 to 17 at % gallium, the short-range order is almost independent of the heat treatment conditions (quenching from a paramagnetic state or exposure in a ferromagnetic state) and is characterized by the presence of pairs of Ga atoms in the position of the second neighbors (B2-type clusters). At a Ga content of 17 to 21 at %, the portion of B2 clusters turns out to be significantly higher after quenching than after annealing, which correlates with the observed effect of heat treatment on the magnitude of magnetostriction. As the Ga concentration (21–25 at %) further increases, the observed features in the distribution of Ga atoms indicate the appearance and growth of D03 phase regions.

Automobile Workshop Management Skills Improvement Needs of Auto-Mechanic for Effective Maintenance of Motor Vehicles in Delta State

This paper investigated automobile workshop management skills improvement needs of auto-mechanic for effective maintenance of motor vehicles in Delta State. Two research questions guided the study and two null hypotheses were formulated. Descriptive survey research design was used in this study. The study involved 120 mechanics from 28 automotive workshops in six main cities in Delta State, including managers, supervisors, and technicians. A validated structured questionnaire was created, divided into two parts, A and B, with each part consisting of 25 pieces. The questionnaire was divided into A1, B1, and B2 clusters. A 5-point answer scale was used for both categories, and the instrument had a Cronbach Alpha reliability coefficient of 0.77. Data was analyzed using weighted mean and improvement needed index (INI) for both ‘Needed’ and ‘Performance’ sets. The independent samples t-test was used to test hypotheses at a 0.05 level of significance. The finding revealed that auto mechanics need to enhance their motivational skills in automobile workshop management for effective maintenance. These skills include awarding performance-based bonuses or salary increases, fostering non-judgmental discussions with fellow mechanics, learning from mistakes instead of punishing mistakes, and recognizing unique talents among team members. More so, it was found out that auto mechanics need to enhance four safety precautionary skills for effective vehicle maintenance. Based on the findings, it was recommended amongst others that Government and members of society should equip all the training institutions with modern tools, machines and equipment and qualified personnel for effective teaching and learning.

Covert dissemination of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae: emergence of low virulence phenotype strains.

This study aimed to explore the epidemic, clinical characteristics, and molecular and virulence attributes of Klebsiella pneumoniae serotype K54 (K54-Kp). A retrospective study was conducted on 328 strains of Klebsiella pneumoniae screened in a Chinese hospital from January 2016 to December 2019. The virulence genes and antibiotic resistance genes (ARGs) were detected by PCR, and a drug sensitivity test was adopted to detect drug resistance. Multilocus sequence typing (MLST) and PFGE were performed to determine the clonal correlation between isolates. Biofilm formation assay, serum complement-mediated killing, and Galleria mellonella infection were used to characterize the virulence potential. Our results showed that thirty strains of K54-Kp were screened from 328 strains of bacteria, with an annual detection rate of 2.29%. K54-Kp had a high resistance rate to antibiotics commonly used in the clinic, and patients with hepatobiliary diseases were prone to K54-Kp infection. MLST typing showed 10 sequence typing, mainly ST29 (11/30), which concentrated in the B2 cluster. K54-Kp primarily carried virulence genes of aerobactin, silS, allS, wcaG, wabG, and mrkD, among which the terW gene was closely related to ST29 (p<0.05). The strains infected by the bloodstream had strong biofilm formation ability (p<0.05). Most strains were sensitive to serum. Still, the virulence of pLVPK-like virulence plasmid in ST29-K54 Klebsiella pneumoniae was lower than that of ST11 type and NTUH-K2044 in the Galleria mellonella model. Therefore, these findings supply a foundation to roundly comprehend K54-Kp, and clinicians should strengthen supervision and attention.

The distinct transcriptome of virulence-associated phylogenetic group B2 Escherichia coli.

Escherichia coli strains of phylogenetic group B2 are often associated with urinary tract infections (UTIs) and several other diseases. Recent genomic and transcriptomic analyses have not suggested or identified specific genes required for virulence, but have instead suggested multiple virulence strategies and complex host-pathogen interactions. Previous analyses have not compared core gene expression between phylogenetic groups or between pathogens and nonpathogens within phylogenetic groups. We compared the core gene expression of 35 strains from three phylogenetic groups that included both pathogens and nonpathogens after growth in a medium that allowed comparable growth of both types of strains. K-means clustering suggested a B2 cluster with 17 group B2 strains and two group A strains; an AD cluster with six group A strains, five group D strains and one B2 strain; and four outliers which included the highly studied model uropathogenic E. coli strains UTI89 and CFT073. Half of the core genes were differentially expressed between B2 and AD cluster strains, including transcripts of genes for all aspects of macromolecular synthesis-replication, transcription, translation, and peptidoglycan synthesis-energy metabolism, and environmental-sensing transcriptional regulators. Notably, core gene expression between nonpathogenic and uropathogenic transcriptomes within phylogenetic groups did not differ. If differences between pathogens and nonpathogens exist, then the differences do not require transcriptional reprogramming. In summary, B2 cluster strains have a distinct transcription pattern that involves hundreds of genes. We propose that this transcription pattern is one factor that contributes to virulence. IMPORTANCE Escherichia coli is a diverse species and an opportunistic pathogen that is associated with various diseases, such as urinary tract infections. When examined, phylogenetic group B2 strains are more often associated with these diseases, but the specific properties that contribute to their virulence are not known. From a comparative transcriptomic analysis, we found that group B2 strains grown in a nutrient-rich medium had a distinct transcription pattern, which is the first evidence that core gene expression differs between phylogenetic groups. Understanding the consequences of group B2 transcription pattern will provide important information on basic E. coli biology, the basis for E. coli virulence, and possibly for developing therapies for a majority of urinary tract infections and other group B2-associated diseases.

Metal‐Rich Metallaboranes: Synthesis, Structure, and Bonding of Heteronuclear Trimetallic Clusters containing (μ3‐BH) Ligand

AbstractBuilding upon our earlier results on the chemistry of nido‐1,2‐[(Cp*RuH)2B3H7] (Cp*=ɳ5‐C5Me5) (nido‐1) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido‐1 with [Mn2(CO)10] led to the isolation of a trimetallic [(Cp*Ru)2{Mn(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (2) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2, a similar reaction was carried out with [Re2(CO)10] that yielded the trimetallic [(Cp*Ru)2{Re(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (3) cluster having a triply bridging borylene unit. Along with 3, a trimetallic square pyramid cluster [(Cp*Ru)2{Re(CO)3}(μ‐H)2(μ‐CO)(μ3,ɳ2‐B2H5)] (4), and heterotrimetallic hydride clusters [{Cp*Ru(CO)2}‐{Re(CO)4}2(μ‐H)] (5) and [{Cp*Ru(CO)}{Re(CO)4}2(μ‐H)3] (6) were isolated. Cluster 4 is a unique example of a M2M′B2 cluster having diboron capped Ru2Re‐triangle. The hydride clusters 5 and 6 have triangular RuRe2 frameworks with one and three μ‐Hs respectively. All the clusters have been characterized by using mass spectrometry, 1H, 11B{1H}, 13C{1H} NMR and IR spectroscopies analyses and the structures of clusters 2–6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal‐rich clusters, DFT calculations have been performed.

Short-range order and its impacts on the BCC MoNbTaW multi-principal element alloy by the machine-learning potential

We utilize a machine-learning force field, trained by a neural network (NN) with bispectrum coefficients as descriptors, to investigate the chemical short-range order (SRO) influences on the BCC MoNbTaW alloy strengthening mechanism. The NN interatomic potential offers a transferable force field that exhibits accuracy comparable to density functional theory. This innovative NN potential is employed to examine the SRO effects on various aspects such as elasticity, vibrational modes, plasticity, and strength in the MoNbTaW multi-principal element alloy (MPEA). The findings reveal a significant attraction between Mo-Ta pairs, resulting in the formation of locally ordered B2 clusters. These clusters can be adjusted via temperature and enhanced by Nb content. The presence of SRO leads to an increase in high-frequency phonon modes and introduces additional lattice friction to dislocation motion. This approach facilitates efficient compositional screening, paving the way for computational-guided materials design of novel MPEAs with enhanced performance. Furthermore, it opens up avenues for tuning the mechanical properties through optimization of the processing parameters.

Determination of natural distribution areas and some agro-morphological characteristics with sexual dimorphism of wild asparagus (Asparagus officinalis L.) in Iğdır plain-Turkey

Globally, interest in wild plants has been on the rise in recent years. The potential of wild plants to be used in breeding for sustainable agriculture and people's preference for consumption attract research attentions. The study was aimed to investigate the natural distribution of Asparagus officinalis L. taxon, along the Iğdır plain, one of the largest micro-climate regions of Turkey and consumed by the people of the region. The research was also motivated to evaluate wild Asparagus species using some agro-morphological characteristics, including sexual dimorphism, for a two years study period. It has been identified that asparagus spreads along the Aras river forming the border of Armenia at altitudes of 800–1076 m in the region and most densely populated in Karakoyunlu district. The result of the present investigation revealed a wide range of variations for agro-morphological characteristics like days to fruit ripening (76–91 day), edible spear length (168.21–315.34 mm), diameter (6.30–10.86 mm), fresh weight (5.27–19.52 g), dry weight (0.38–1.55 g), number of spear (8–26 plant−1), number of fruit (61–2467 spear−1), fruit weight (8.0–258.3 g spear−1), male plant length (1116.9–2.163.7 mm), female plant length (1219.4–2110.2 mm), male pedicle length (3.72–4.17 mm) and female pedicle length (3.21–3.54 mm) were observed, which can be useful for breeding purposes. Cluster constellation analysis was conducted to investigate the genetic diversity of 31 asparagus genotypes. According to the agro-morphological properties, asparagus were divided into 2 main groups and 4 sub-groups (A; A1, A2 and B; B1, B2). Aralık district samples were mostly collected in the B1, Karakoyunlu district in the B2, Tuzluca district in the Al and A2, and Iğdır district mostly in the B2 cluster. As a result, Karakoyunlu were found superior with the highest asparagus density and edible spear yield as compared to other districts. In order protect the habitat of wild asparagus from excessive consumption and losses due to climate changes and land use, seeds should be collected from these areas to be used for cultivation and breeding purposes. In addition, it is advisable to keep seeds in gene banks for sustainable agriculture and protection of genetic diversity.

Tribologically induced amorphization in the subsurface of aged Ni-rich TiNi alloy during dry sliding

The microstructure modification due to friction energy transformation in near-surface zone is crucial to the tribological performance of materials. To study the surface and subsurface response of materials exhibiting stress-induced martensitic transformation to repeated sliding, we have investigated the quite novel microstructure changes induced during the dry sliding of an aged Ti-51.5 at.% Ni alloy against the GCr15 spheres. In the process of reciprocating sliding, the B2 austenite primarily transforms into amorphous phase in the worn subsurface area. Remarkably, B2 clusters of nanocrystals below 10 nm are randomly embedded in the amorphous ribbon in the topmost region whereas the medium-range-ordered debris in the order of 3–5 nm are retained in the deeper layer. More importantly, it can be found that large number of nanocrystalline phase and amorphous structure coexist in the strip at a depth about 2.5 μm. Additionally, XRD patterns of the worn tracks show the appearance of B19’, being different from the B2 in the original microstructure. The martensitic transformation therefore plays a crucial role in accommodating associated plastic deformation for the formation of an amorphous layer. The distinctive elementary mechanisms identified here will be essential for the future modeling of the tribologically deformed layer of the alloys.

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T > TC) and ferromagnetic (T < TC) state. In the first case, the structural state was fixed by quenching from the annealing temperature into water; in the second case, the structural state was obtained by slow cooling. The structural studies of the single-crystal samples were conducted on a four-circle X-ray diffractometer at room temperature. From the X-ray diffraction data, it follows that the alloy, independently on the heat treatment, contains B2 clusters, i.e., locally ordered regions with the CsCl-type structure observed in alloys of iron with silicon (to 10 at % Si) and aluminum (7 at % Al) before. In addition to the B2‑clusters, regions with the D03 short-range order are observed in the quenched sample; the sizes of these regions significantly increases after annealing in the ferromagnetic state, i.e., a long-range order forms. The relation of the fine structural changes in the alloy due to various heat treatments with its magnetoelastic and magnetostriction properties is discussed.

Simultaneous enhancement of strength and plasticity by nano B2 clusters and nano-γ phase in a low carbon low alloy steel

Nano B2 FeCu ordered clusters and multiphase microstructure consisting of intercritical ferrite, tempered martensite and nano-γ phase (reverted austenite) were obtained by two-step heat treatment involving intercritical annealing and intercritical tempering. The experimental steel with nano Cu precipitates and nano-γ phase exhibited high strength and high ductility combination. The yield strength and total elongation of the experimental steel increased from 758 MPa and 16.8% to 984 MPa and 29.5% after the second step intercritical tempering for 5 min. High resolution transmission electron microscopy (HRTEM) and three-dimensional atom probe (3DAP) studies provided evidence to support that high density of nano B2 FeCu ordered clusters contributed to high strength. First principle calculations suggested that the feasibility of B2 FeCu nano-ordered clusters, and the stability of B2 structure is related to the coherent stress field at the interface between clusters and the BCC-Fe matrix. The average size of B2 FeCu nano-ordered clusters was 4 nm with a lattice constant of 0.2893 nm and an orientation relationship of (1 1 0)B2//(1 1 0)α and [0 0 1]B2//[0 0 1]α. 9R Cu without twinned structure was discovered at different tempering times. The proportion of Cu in Cu precipitates varied from 24.4 at% to 61.2 at% with change in crystal structure and increase in the size of precipitates. The significant increase in yield strength is discussed in terms of ordered domain strengthening, modulus strengthening and lattice misfit strengthening mechanisms. Bright field TEM image and selected area electron diffraction (SAED) pattern discovered and proved that spindle nano-γ phase was present at phase boundary between tempered martensite and intercritical ferrite. The size of them were among 242–375 nm in length and 52–80 nm in width. The two needle tip ends of nano-γ phase were just at phase boundaries, indicating the preferred growth direction. (1 −1 1)γ plane of nano-γ phase was parallel to (1 −1 0)α plane of the adjacent tempered martensite. The effect of nano-γ phase on enhancing the plasticity was revealed by instantaneous work hardening index curve.

Severe plastic deformation driven nanostructure and phase evolution in a Al0.5CoCrFeMnNi dual phase high entropy alloy

The effect of severe plastic deformation on microstructure and phase evolution was investigated in a dual phase Al0.5CoCrFeMnNi high entropy alloy (HEA). For this purpose, the as-cast HEA was subjected to initial thermo-mechanical processing by warm-rolling and annealing. The annealed dual phase alloy showed FCC and B2 phases. The B2 phase was enriched with Ni and Al, while the converse held good for the FCC phase. These annealed HEA specimens were severely deformed by high pressure torsion (HPT) up to five complete rotations (R). The severely deformed HEA revealed nanostructured FCC grains containing nano-twinned regions and coarser B2 phase. The nanostructure formation in the softer FCC phase was attributed to greater strain partitioning and propensity for the formation of nano-twins. Although with increasing rotations, the hardness difference between the edge and centre region was reduced, the 5R HPT processed specimens showed inhomogeneity featured by intermittent hardness spikes. Upon annealing, recrystallized dual phase microstructure was confirmed in the 5R HPT processed specimen. Microstructural differences between centre and edge regions were revealed by way of large B2 clusters (5 μm-10 μm) at the centre region. Remarkably, annealing resulted in the formation of a (Fe,Cr) rich σ-phase. The formation of σ-phase resulted in much greater hardness inhomogeneity in the annealed material as compared to the 5R HPT processed material.

Efficacy of Clopidogrel and Clinical Outcome When Clopidogrel Is Coadministered With Atorvastatin and Lansoprazole: A Prospective, Randomized, Controlled Trial.

This prospective, randomized, nonblind, controlled trial evaluated the effects of clopidogrel on platelet function upon coadministration with atorvastatin and lansoprazole.One hundred four adult patients with non-ST-segment elevated acute coronary syndrome (NSTE-ACS) who underwent percutaneous coronary intervention (PCI) with drug-eluting stent implantation were included. All patients were treated with standard dual antiplatelet therapy (DAPT) plus rosuvastatin 10 mg daily after the operation. On the sixth day after PCI, patients were randomly divided into 4 groups, Group A: DAPT + atorvastatin 20 mg daily (a change from rosuvastatin to atorvastatin) + lansoprazole 30 mg daily, Group B: DAPT + atorvastatin 20 mg daily (a change from rosuvastatin to atorvastatin), Group C: DAPT + lansoprazole 30 mg daily (continuing to take rosuvastatin), Group D is the control group. Additional drugs were used according to the situation of patients. Platelet function and concentrations of platelet activation markers (granular membrane protein 140 (P-selectin), thromboxane B2 (TXB2), and human soluble cluster of differentiation 40 ligand (sCD40L)) were assessed before randomization and at 15- and 30-day follow-up visits. All patients were maintained on treatment for 6 months and observed for bleeding and ischemic events.A total of 104 patients were enrolled, 27 patients in group A, 26 patients in Group B/C, 25 patients in Group D separately, and all the patients were analyzed. There were no differences in platelet function and the levels of platelet activation markers (P-selectin, TXB2, and sCD40L) among or within the 4 groups at the 3 time points of interest (P > 0.05). In the subsequent 6 months, no significant bleeding events occurred, and 12 patients experienced ischemic events, these results were also not significantly different among the groups (P > 0.05).In patients diagnosed with NSTE-ACS who have had drug-eluting stent implantation, simultaneously administering clopidogrel, atorvastatin, and lansoprazole did not decrease the antiplatelet efficacy of clopidogrel or increase adverse event frequency over 6 months.

Ab Initio Search for Global Minimum Structures of Pure and Boron Doped Silver Clusters.

The global minimum structures of pure and boron doped silver clusters up to 16 atoms are determined through ab initio calculations and unbiased structure searching methods. The structural and electronic properties of neutral, anionic, and cationic Ag(n)B (n ≤ 15) and Ag(n)B2 (n ≤ 14) clusters are much distinct from those of the corresponding pure silver. Considering that Ag and B possess one and three valence electrons, respectively, both the single and the double boron-atom doped silver clusters with even number of valence electrons are more stable than those with odd number of electrons, a feature also observed in the pure silver clusters. We demonstrate that the species with a valence count of 8 and 14 appear to be magic numbers with enhanced stability irrespective of component or the charged state. A new putative global minimum structure of Ag13(-) cluster, with high symmetry of C(2v), is unexpectedly observed as the ground state, which is lower in energy than the previous suggested bilayer structure.

Structure of α-FeSi alloys with 8 and 10 at % silicon

The atomic structure of single-crystal samples of Fe1 − xSix (x = 0.08, 0.10) alloys has been investigated using X-ray diffraction. It has been shown that the body-centered cubic (BCC) lattice of these alloys contain clusters with local ordering of the B2 type, which are characteristic of alloys with depleted composition (x = 0.05−0.06). The Fe3Si phase with the D03 structure has been revealed at silicon concentrations x = 0.08 and 0.10. The volume fraction of Fe3Si-phase regions increases both with an increase in the silicon concentration in the Fe1 − xSix alloy and during annealing of the samples with this silicon concentration at a temperature of 450°C. Based on the results obtained, it has been concluded that the anisotropic distribution of the B2 clusters, which arises as a result of thermomagnetic or thermomechanical treatment, is responsible for the induction and stability of the uniaxial magnetic anisotropy in the Fe1 − xSix (x = 0.05−0.10) alloys.

Genotyping of Bacillus anthracis Isolated from Croatia and Bosnia and Herzegovina

Anthrax is a serious disease caused by Bacillus anthracis. Humans can become infected by handling products from infected animals, by breathing spores and rarely by eating undercooked meat from infected animals. The genome of B. anthracis is highly monomorphic and thus shows very low DNA sequence variation. We analysed the molecular characteristics of 12 B. anthracis isolates from outbreaks in Croatia and Bosnia and Herzegovina, which have occurred during the past 10 years along with two vaccine strains. Genotyping system based on variable-number tandem repeat analysis at six loci revealed that six isolates belong to genotype from the A1.a cluster whilst six isolates relate to the B2 cluster, compared to 89 previously described genotypes. The distribution of two evolutionarily distant clusters suggests an introduction of B. anthracis to this area in at least two separate events.

Kinetics of large B clusters in crystalline and preamorphized silicon

We present an extended model for B clustering in crystalline or in preamorphized Si and with validity under conditions below and above the equilibrium solid solubility limit of B in Si. This model includes boron-interstitial clusters (BICs) with BnIm configurations—complexes with n B atoms and m Si interstitials—larger (n &amp;gt; 4), and eventually more stable, than those included in previous models. In crystalline Si, the formation and dissolution pathways into large BICs configurations require high B concentration and depend on the flux of Si interstitials. In the presence of high Si interstitial flux, large BICs with a relatively large number of interstitials (m ≥ n) are formed, dissolving under relatively low thermal budgets. On the contrary, for low Si interstitial flux large BICs with few interstitials (m ≪ n) can form, which are more stable than small BICs, and whose complete dissolution requires very intense thermal budgets. We have also investigated the kinetics of large BICs in preamorphized Si, both experimentally and theoretically. B was implanted at a high-dose into preamorphized Si, and the B precipitation was studied by transmission electron microscopy and by sheet resistance and Hall measurement techniques. A simplified model for B clustering and redistribution in amorphous Si is proposed, including the experimental value for the B diffusivity in amorphous Si and the energetics of BICs. Our model suggests that B2, B3I, B4I and B4I2 clusters are the most energetically favored configurations, with relative abundance depending on B concentration. After recrystallization, thermal anneals up to 1100 °C evidence that BICs evolve under very low flux of Si interstitials under the particular experimental conditions considered. Simulations indicate that for very high B concentrations and low Si interstitial flux a significant fraction of the initial small BICs evolves into larger and very stable BIC configurations that survive even after intense thermal budgets, as confirmed by energy filtered transmission electron microscopy analyses. The correlation between simulations and Hall measurements on these samples suggest that hole mobility is significantly degraded by the presence of a high concentration of BICs.

Multi-Locus Sequence Typing of Enteroaggregative Escherichia coli Isolates from Nigerian Children Uncovers Multiple Lineages

BackgroundEnteroaggregative Escherichia coli (EAEC) are defined by their stacked-brick adherence pattern to human epithelial cells. There is no all-encompassing genetic marker for EAEC. The category is commonly implicated in diarrhea but research is hampered by perplexing heterogeneity.Methodology/Principal FindingsTo identify key EAEC lineages, we applied multilocus sequence typing to 126 E. coli isolates from a Nigerian case-control study that showed aggregative adherence in the HEp-2 adherence assay, and 24 other EAEC strains from diverse locations. EAEC largely belonged to the A, B1 and D phylogenetic groups and only 7 (4.6%) isolates were in the B2 cluster. As many as 96 sequence types (STs) were identified but 60 (40%) of the EAEC strains belong to or are double locus variants of STs 10, 31, and 394. The remainder did not belong to predominant complexes. The most common ST complex, with predicted ancestor ST10, included 32 (21.3%) of the isolates. Significant age-related distribution suggests that weaned children in Nigeria are at risk for diarrhea from of ST10-complex EAEC. Phylogenetic group D EAEC strains, predominantly from ST31- and ST394 complexes, represented 38 (25.3%) of all isolates, include genome-sequenced strain 042, and possessed conserved chromosomal loci.Conclusions/SignificanceWe have developed a molecular phylogenetic framework, which demonstrates that although grouped by a shared phenotype, the category of ‘EAEC’ encompasses multiple pathogenic lineages. Principal among isolates from Nigeria were ST10-complex EAEC that were associated with diarrhea in children over one year and ECOR D strains that share horizontally acquired loci.

Epidemiological Characteristics of Salmonella enterica Serovar Typhimurium from Healthy Pigs in Japan

We characterized 53 Salmonella enterica ser. Typhimurium strains recovered from healthy pigs during 1998-1999 (n=12) and 2004-2005 (n=41) as to their carriage of DT104 spacer region, class 1 and 2 integrons, virulence genes (spvC, rck, and pefA), and XbaI- and BlnI-Pulsed-Field Gel Electrophoresis (PFGE) profiles. No DT104 strain was detected in 1998-1999, whereas 65.9% (27/41) of the strains in 2004-2005 were DT104 showing resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracycline, and cephaloridine (R-type ACSSuT+). Class 1 intergron-associated genes, aadA2 (1.0-kbp amplicon) and pse1 (1.2-kbp amplicon), were found in all the DT104 strains (27/27). One strain showing resistance to streptomycin, sulfonamides, tetracyclin, and trimethoprim (R-type SsuTTm) harbored another class 1 integron-associated gene (dhfrXII-orfF- aadA2) on 1.9-kbp amplicon. Virulence gene spvC was found in 92.5% (49/53) and rck and pefA were found in 88.7% (47/53) of the strains, whereas spvC, rck, and pefA were found in all the DT104 strains. Ser. Typhimurium strains were categorized into four clusters (X1, X2, X3, and X4a/X4b) by XbaI-PFGE, or into nine clusters (B1, B2, B3a/B3b, B4, B5, B6, B7, B8, B9a/B9b) by BlnI-PFGE analyses. DT104 strains were restricted into X2, or into B2, B3a/B3b, and B6 clusters, indicating that our multidrug-resistant DT104 strains from healthy pigs might have derived from at least three independent clones, with the most widespread clone being the cluster B6 strains isolated in Kanto, Tokai, Chugoku, and Kyushu regions.

Characterization and the mechanism of formation of the ternary compoundMgNi2.5B2 inNi-doped MgB2 bulk

(MgB2)1−xNix bulksamples (x = 0.0, 0.04 and 0.06) were synthesized using a differential thermal analysis apparatus at750 °C. Bymeans of scanning electron microscopy and transmission electron microscopy, the secondary phaseMgNi2.5B2 is found for thefirst time in MgB2 samples, as a concentration of clusters. According to the magnetization measurements, the low doping levelof Ni (x<0.04) was observed to have small influence on the grain connectivity, and thus a highJc was maintained at low field. Because of the large grain size ofMgNi2.5B2 concentratedwithin the MgB2 grains, the Jc values at high field all show a significant decrease in the Ni-doped samples. On the basis ofthe analysis of the superconducting properties, the process of formation of theMgNi2.5B2 clusters is discussed in terms of a mechanism of precipitation from grain boundaries toMgB2 intra-grains as the sintering temperature increases.

X-ray diffraction studies of specific features in the atomic structure of Fe-Si alloys in the α area of the phase diagram

The atomic structure of Fe-Si alloys with a silicon concentration of 5–8 at % (α-area of the phase diagram) was studied using X-ray diffraction. The effect of quenching after annealing at a disordering temperature of 850°C on the structural state of the alloys was elucidated. It is shown that the quenched samples are characterized by a short-range ordering; namely, there is a local B2-type order at a concentration of 5–6 at % Si and, in addition, DO3-phase clusters are formed at 8 at % Si. The atomic structure of B2 clusters and their nearest surroundings is established.