Sequence variation in the small-subunit rRNA gene of Plasmodium malariae and prevalence of isolates with the variant sequence in Sichuan, China

By two PCR-based diagnostic methods, Plasmodium malariae infections have been rediscovered at two foci in the Sichuan province of China, a region where no cases of P. malariae have been officially reported for the last 2 decades. In addition, a variant form of P. malariae which has a deletion of 19 bp and seven substitutions of base pairs in the target sequence of the small-subunit (SSU) rRNA gene was detected with high frequency. Alignment analysis of Plasmodium sp. SSU rRNA gene sequences revealed that the 5' region of the variant sequence is identical to that of P. vivax or P. knowlesi and its 3' region is identical to that of P. malariae. The same sequence variations were also found in P. malariae isolates collected along the Thai-Myanmar border, suggesting a wide distribution of this variant form from southern China to Southeast Asia.     

Sequence, structure, and chromosomal mapping of the mouse Lgals6 gene, encoding galectin-6

In the accompanying paper (Gitt, M. A., Colnot, C., Poirier, F., and Barondes, S. H., and Leffler, H. (1998) J. Biol. Chem. 273, 2954-2960), we reported that mouse gastrointestinal tract specifically expresses two closely related galectins, galectins-4 and -6, each with two carbohydrate recognition domains in the same peptide. Here, we report the isolation, characterization, and chromosomal mapping of the complete mouse Lgals6 gene, which encodes galectin-6, and of a fragment of a distinct gene, Lgals4, which encodes galectin-4. The coding sequence of galectin-6 is specified by eight exons. The upstream region contains two putative promoters. Both Lgals6 and the closely related Lgals4 are clustered together about 3.2 centimorgans proximal to the apoE gene on mouse chromosome 7. The syntenic human region is 19q13.1-13.3.     

Characterization and structure of the mitochondrial small rRNA gene of the entomopathogenic fungus Beauveria bassiana

HCV infection and interferon-alpha (IFN-alpha) therapy have been associated with autoimmunity. To assess whether chronic liver disease (CLD) due to HCV infection or its treatment with IFN-alpha cause autoimmune manifestations, the prevalence of tissue autoantibodies in 51 children with chronic HCV infection and 84 with other CLD was analysed by standard techniques. Sixty-five percent of patients with chronic HCV infection, 66% with chronic hepatitis B infection and 60% with Wilson's disease were positive for at least one autoantibody. In the 51 subjects with chronic HCV infection (29 treated with IFN-alpha, 22 untreated), tested on 165 occasions over a median of 9 months (range 5-42 months), autoantibodies to nuclei (ANA), smooth muscle (SMA), gastric parietal cell (GPC) and/or liver kidney microsomal type 1 (LKM-1) were similarly prevalent in treated and untreated patients (90% versus 68%, P = 0.12). Positivity for SMA was present in 67%, GPC in 32%, ANA in 10%, LKM-1 in 8% of cases. Treatment with IFN-alpha had to be suspended due to transaminase elevation in one SMA-positive, one ANA-positive but in three of four LKM-1-positive patients. Our results show that: (i) autoantibodies are common in viral-induced hepatitis and Wilson's disease; (ii) positivity for SMA, GPC, ANA is part of the natural course of chronic HCV infection, their prevalence being unaffected by IFN-alpha; and (iii) IFN-alpha should be used cautiously in the treatment of LKM-1/HCV-positive patients.     

Strain characterization and classification of oxyphotobacteria in clone cultures on the basis of 16S rRNA sequences from the variable regions V6, V7, and V8

A major problem in development of a polyphasic taxonomy is that the identification of oxyphotobacterial strains (cyanobacteria and prochlorophytes) in culture collections may be incorrect. We have therefore developed a diagnostic system using the DNA sequence polymorphism in the 16S rRNA regions V6 to V8 for individual strain characterization and identification. PCR primers amplifying V6 to V8 from oxyphotobacteria in unialgal cultures were constructed. Direct solid-phase or cyclic sequencing was used to determine the sequences from the amplified DNA. This survey includes 10 strains of Nostoc/Anabaena/Aphanizomenon (Nostoc category), 5 strains of Microcystis (Microcystis category), and 4 strains of Planktothrix (Planktothrix category). Fifteen additional strains of cyanobacteria and two strains of prochlorophytes were included such that the major phyletic groups were represented. One of the strains, Phormidium sp. NIVA-CYA 203, contained an 11-nucleotide insertion with no homology to other known 16S rRNA sequences. Based on parsimony and neighbor-joining trees, the phyletic relationships of the strains were investigated. Thirteen major branches were found, with Pseudanabaena limnetica NIVA-CYA 276/6 as the most divergent strain. The strain categories Nostoc, Planktothrix, and Microcystis were all monophyletic. The sequence polymorphism within Nostoc was higher than that in Planktothrix and Microcystis. Based on the sequence and phyletic information, group-specific PCR primers for the categories Nostoc, Planktothrix, and Microcystis were constructed. For the strains included in this work, the amplifications were specific for the relevant groups. By combination of magnetic solid-phase DNA isolation and group-specific PCR amplifications, an accurate method for characterization, classification and identification of oxyphotobacterial clone cultures has been developed.     

Surface residual stresses,surface topography and the fatigue behavior of Ti-6AI-4V

Fatigue tests have been conducted on Ti-6Al-4V from 293 to 589 K to determine the influence of surface residual stresses and surface topography on low and high cycle fatigue properties. Four types of machined surfaces as well as shot peened surfaces were included in the investigation. It was found that surface residual stresses play a key role in controlling the development of microcracks and, therefore, overall fatigue lives at both room and elevated temperature. X-ray measurement of the stability of surface residual stresses under thermal activation and/or cyclic loading demonstrated that, for the conditions studied, cyclic loading was primarily responsible for residual stress decay. In addition, the magnitude of the decay was dependent on the relationship between the sign of the residual stress and the sign of the imposed mean strain. Finally, it was demonstrated that the sharpness of machining grooves is more important than their depth in controlling fatigue resistance. The work was performed when all authors were affiliated with Pratt and Whitney Aircraft, Middletown, Connecticut.     

Modelling the Competitive Growth of Primary,Allotriomorphic, and Secondary Alpha in Ti-6Al-4V

Metallurgical and Materials Transactions A - The competitive formation of allotriomorphic α along the prior β grain boundaries, secondary α-phase and the growth of globular primary...     

Phylogenetic relationships inferred from the sequence and secondary structure of ITS1 rRNA in Albinaria and putative Isabellaria species (Gastropoda, Pulmonata, Clausiliidae)

It has been suggested that liking for the taste, flavour and aroma of, for example, coffee and tea is acquired through the process of classical conditioning, involving association of these orosensory cues with the psychopharmacological consequences of caffeine ingestion. Accordingly, this study investigated caffeine reinforcement by assessing changes in preference for a novel drink consumed with or without caffeine. Particular care was taken to use "ecologically valid" procedures; that is, overnight caffeine abstinence followed by a cup-of-coffee equivalent dose of caffeine (70 mg) at breakfast. Caffeine had no significant effects on drink preference or mood in subjects with habitually low intakes of caffeine. In contrast, moderate users of caffeine developed a relative dislike for the drink lacking caffeine and showed somewhat lowered mood following overnight caffeine abstinence (e.g., less lively, clearheaded and cheerful), which was significantly improved by caffeine. These together with other recent results strongly suggest that, in everyday life, caffeine reinforcement can occur as the result of the alleviation by caffeine of the adverse effects of overnight caffeine abstinence (negative reinforcement). They also demonstrate the utility of this flavour-conditioning procedure, which could be applied in the wider investigation of the reinforcing properties of drugs.     

Immunochemical study on mannans of genus Candida. I. Structural investigation of antigenic factors 1, 4, 5, 6, 8, 9, 11, 13, 13b and 34

Since the late 1960s, we have been conducting a series of immunochemical studies on the mannans of the genus Candida with emphasis on the structural determination of antigenic factors composing of the antigenic formula of medically relevant Candida species proposed by Tsuchiya and his colleagues. This review is a chronological account of the structural studies on 10 antigenic factors conducted by two groups of workers: Fukazawa, the senior student of Tsuchiya, and Suzuki.     

Linear friction welding of Ti-6Al-4V: Processing,microstructure, and mechanical-property inter-relationships

The linear friction welding behavior of Ti-6Al-4V was investigated using varying processing conditions of frequency (15 to 70 Hz), amplitude (1 to 3 mm), pressure (50 to 90 MPa), and axial shortening (1 to 2 mm). Examination of linear friction welded Ti-6Al-4V using microscopic techniques indicated that the process requires certain critical conditions at the interface and its adjacent region to be reached for producing joints without structural defects along the weld centerline, such as voids or oxide inclusions. Characterization of the weldments included analysis of the microstructural features of the weld and thermomechanically affected zones (TMAZs) in relation to the parent material. It was observed that in the weld region, exposure to supertransus temperatures (>995 °C) combined with hot-deformation working and rapid cooling after joining produced recrystallization of the beta grain structure that had a Widmanstätten alpha-beta transformation microstructure. In the TMAZ, the bimodal microstructure of the parent material was deformed and the presence of elongated alpha grains with broken beta-phase particles was established. Through examination of the mechanical properties, using microhardness and tensile testing, the integrity of the joints was determined in order to assess the impact of the various processing parameters and to define the optimum welding conditions.     

An analysis of the flow stress of a two-phase alloy system,Ti-6Al-4V

An analysis of the tensile deformation behavior of a two-phase body-centered cubic (bcc)-hexagonal close-packed (hcp) alloy, Ti-6Al-4V, has been made. This has shown that the temperature dependence of the flow stress, the logarithm of the effective stress, and the strain-rate sensitivities can be described by simple analytical equations if the thermally activated strain-rate equation contains the Yokobori activation enthalpyH=H ^o ln (σ*₀/σ*), whereH ^o is a constant,σ* the effective stress, andσ*₀ its 0 K value. The flow stress-temperature plateau region (500 to 600 K) also can be rationalized analytically in terms of oxygen dynamic strain aging in the alpha phase     

Distinguishing the influence of aluminium and vanadium additions on microstructural evolution and densification behaviour during the sintering of ti6Al,ti4V and ti6al4v

In this work, the influence of pure Al (Ti6Al) and V (Ti4?V) powder additions on the sintering behaviour of a coarse CP-Ti powder compact was investigated. Pure Al melts and spreads to form intermetallic layers at the CP-Ti surface, causing swelling and prevention of sintering and shrinkage below 1050°C. Ti4?V compacts do not swell and begin to sinter at 990°C. The sinter rate for both Ti4?V and Ti6Al are similar at 1200°C and higher than the CP-Ti compact alone. Aluminium melting distributes this element better than the dispersed V particles, leading to more rapid homogenisation. When both pure Al and V are present (Ti6Al4?V), the sintering rate at 1200°C is similar to that of Ti6Al and Ti4?V. However, swelling is increased and homogenisation is slower, resulting in a reduced sintering aid effect compared to Ti6Al and Ti4?V.     

Opposing and Driving Forces Associated with the Dynamic Transformation of Ti-6Al-4V

The opposing and driving forces associated with dynamic transformation in Ti-6Al-4V are evaluated. It is shown that the stored energy is less than the opposing forces inhibiting transformation and insufficient to initiate the phenomenon. By contrast, the driving force derived from the net softening is greater than the opposing force and is responsible for initiating the reaction. This approach indicates that deformation reduces the transus temperature and leads to the formation of a thermodynamically metastable state.     

An analysis of the low temperature,low and high strain-rate deformation of Ti−6Al−4V

The deformation behavior of Ti−6Al−4V at temperatures between 76 and 495 K, strain rates between 0.001 and 3000 s⁻¹, and compressive strains to 0.3 has been investigated. Measurements of yield stress as a function of test temperature, strain rate, and prestrain history are analyzed according to the model proposed by Kocks and Mecking. The mechanical threshold stress (flow stress at 0 K) is used as an internal state variable, and the contributions to the mechanical threshold stress from the various strengthening mechanisms present in this alloy are analyzed. Transmission electron microscopy (TEM) is used to correlate deformation substructure evolution with the constitutive behavior. The deformation substructure of Ti-6-4 is observed to consist of planar slip in the α grains at quasistatic strain rates. At high strain rates, deformation twinning is observed in addition to planar slip. Increasing the temperature to 495 K is seen to alter the deformation mode to more random slip; the effect of this on the proposed deformation model is discussed.     

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

The effects of postweld heat treatment (PWHT) on 3.2-mm- and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.     

Effect of Yttrium on the Fatigue Behavior of Investment-Cast and Wrought Ti-6Al-4V

The effect of yttrium (Y)-containing particles on the microstructure and fatigue behavior of investment-cast and hot isostatically pressed (HIP) Ti-6Al-4V has been investigated. Elemental Y was added to the Ti-6Al-4V melt to obtain a concentration of 200 ppm Y, which is 4 times the amount allowed by current industrial specifications. The observed particles were between 100 nm and 1 μm in diameter, were widely dispersed, and did not agglomerate. High-cycle fatigue tests were conducted and an extensive fractography study revealed that the effect of the particles was negligible compared to the large colony size, and therefore slip length, in the cast material. The fatigue lives were consistent with those in the literature for tests conducted on specimens containing standard concentrations of Y. A section of the casting was extruded to refine the grain size in order to study the effects of the particles on a microstructure with shorter slip lengths. The results of the fractography study on these specimens were not as straightforward. A fine particle was observed at the crack-initiation site of one of the specimens of extruded material and shallow depressions on the size scale of the particles were present in other samples. However, no evidence of Y was detected by energy-dispersive spectroscopy (EDS) and the fatigue lives were on the high end of the scatter band typically encountered in wrought and annealed Ti-6Al-4V.     

The Origin of Microstructural Diversity,Texture, and Mechanical Properties in Electron Beam Melted Ti-6Al-4V

An additive layer manufacture (ALM) technique, electron beam melting, has been used for the production of simple geometries, from prealloyed Ti-6Al-4V powder. Microstructure, texture, and mechanical properties achieved under standard operating conditions have been investigated. Three transitional regions are observed with a change in microstructural formation dependent on the thermal mass of deposited material. Prior β-phase reconstruction, from room temperature α-phase electron backscatter diffraction (EBSD) data, reveals a strong texture perpendicular to the build axis. Variation of build temperature within the processing window of 898 K to 973 K (625 °C to 700 °C) is seen to have a significant effect on the properties and microstructure of both as-deposited and hot isostatically pressed (HIP) samples.