Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti₃Al (α ₂) + disordered beta(β), while the Ti-21 Al-22Nb matrix contained three phases: α₂, ordered beta (β ₀), and ordered orthorhombic(O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products(i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in theα ₂ +β matrix composite were much more rapid than in theO +β ₀ +α ₂ matrix composite. Additionally, interfacial reaction in theα ₂ +β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in theO +β ₀+α ₂ matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α₂+β alloy in all of these mechanical behavioral areas, on both an absolute and a specific(i.e., density corrected) basis.     

Mechanical properties and 95 ° aging characteristics of zircon-reinforced Zn-4AI-3Cu alloy

A process for preparing zinc alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles in Zn-4Al-3Cu (ZAS) alloy melts and subsequently casting these melts in permanent molds. It was found that additions of zircon resulted in an increase in the sliding wear resistance and in the proportional limit in compression. The aging characteristics of the ZAS alloy have also been investigated by hardness tests, dilatometry technique, and transmission electron microscopy observations. There are two kinds of precipitates that occur during the aging process. The α-phase precipitates from the ŋ phase in the early stage of aging and the copper-rich ɛ-phase precipitates from the ŋ phase in the later stage of aging. Therefore, there are two peaks in the hardening curve caused by both a-phase and ŋ-phase precipitation. The a-phase precipitation induces the dimensional shrinkage, and the copper-rich ŋ phase precipitation results in dimensional expansion. Zircon particles existing in ZAS alloy reduce the maximum shrinkage from 353 × 10^-6 for the monolith to 167 × 10^-6 for the composite. Two groups of parallel a-phase plates had formed within the ŋ dendrite during aging at 95 °. The orientation relationship between the a phase and matrix was determined as [άcr1l01]_ŋ//[lάrc10]_a, (1120)ŋ/(lll)α.     

Nutrition screening: an essential assessment parameter

Nutrition plays a significant role in preventing the incidence and prevalence of disease and more importantly, promoting health. Nutrition screening is an important tool used by nurses and dietitians to identify and assess clients at risk for nutritional compromise.     

Tuberculosis among Filipino patients with systemic lupus erythematosus

A retrospective review of the clinical records of 54 patients with systemic lupus erythematosus (SLE) and documented tuberculosis (TB) infection seen at the University of Santo Tomas Hospital was accomplished. There were 53 women and one man, with a mean age of 32.2 +/- 10 years and a total of 57 TB occurrences. Pulmonary involvement was recorded in 42 (74%): upper lungfield in 25, mid to lower lungfield in 7, and miliary pattern or diffuse infiltrates in 10. TB arthritis was noted in 8, osteomyelitis in 4, and soft tissue abscesses in 4. Central nervous system involvement consisted of brain abscesses (tuberculomas) in two and meningitis in one. Two patients each had TB lymphadenitis, genitourinary TB, ileocecal TB, and TB peritonitis. Hepatobiliary and cutaneous TB occurred in one patient each. Eight of 10 patients with disseminated or miliary TB died primarily of respiratory failure; six of these eight patients also had some form of extrapulmonary involvement. Using the Wilcoxon rank-sum test, there were significant differences in the mean SLE Disease Activity Index (SLEDAI) and Severity of Disease Index (SDI) scores between those with limited TB (SLEDAI 24 +/- 7 SD; SDI 19 +/- 18 SD) versus those with extensive TB (SLEDAI 41 +/- 16 SD; SDI 36 +/- 21 SD), P < .05. There was no significant difference in the average daily prednisone dose (mg) between those with limited TB (25 +/- 17 SD) versus those with extensive TB (31 +/- 16 SD). The contributory role of tuberculous infection in the morbidity and mortality of patients with SLE must be emphasized, especially in areas endemic for TB.     

Threshold value of glucose screening tests in pregnancy: could it be standardized for every population?

We aimed to determine a threshold value that perfectly demarcates women at high risk for gestational diabetes mellitus (GDM) in the Turkish population. One thousand gravid women of 24 to 32 weeks of gestation were given 50 g, 1-hour glucose screening tests. A 100 g, 3-hour glucose tolerance test (GTT) was performed on all patients whose screening test plasma glucose value was 130 mg/dL or greater. The sensitivity and specificity of each screening test value was found, and the GDM rate of each value was calculated. Three-hundred-and-five patients were identified for GTT and 66 were shown to have GDM with two or more abnormal values in GTT. The incidence of GDM was found to be 6.6%. The maximum specificity and sensitivity were met at 140 mg/dL. However, this value underestimated 12% of patients with GDM, and the lowest value for a positive GTT appeared to be 134 mg/dL. We recommend a 135 mg/dL threshold for GTT since this threshold accurately diagnoses almost all women with GDM while eliminating unnecessary GTT.     

Using live theatre combined with role playing and discussion to examine what at-risk adolescents think about substance abuse, its consequences, and prevention

Live theater is used as a means of stimulating thought and discussion among adolescents on topics related to the effects of substance abuse in their lives. A thirty-minute professional and contemporary live musical play, Captain Clean, was performed at three Chicago high schools (grades 9-12). In general, students in these schools had been judged to be at risk for drug problems by school administrators and by the Illinois Criminal Justice Information Authority. Students' responses to issues highlighted in the play were examined through ethnographic procedures used during role playing and discussion immediately following the performance. In addition, written comments were collected from the students two weeks after viewing. The amount of interaction and level of student response indicate that live theater is an effective means for stimulating both thought and discussion pertaining to the effects of drugs in the lives of adolescents. In addition, analysis of the students' responses reveals: (1) an unmet need for individual counseling; (2) a pervasive ignorance of the legal consequences of drug use; (3) the importance of family as a source of information and support; and (4) an expressed concern for their own futures as well as those of their peers.     

Clostridium tertium bacteremia: 2 cases and review

Clostridium tertium bacteremia is unusual, seen most often with gastrointestinal disease and/or neutropenia. Two cases are described. The first was a 19-yr-old female with acute leukemia, who developed gastrointestinal symptoms and C. tertium bacteremia while neutropenic. The second was a 57-yr-old female with quiescent ulcerative colitis, who presented with fever, rigors and epigastric pain. Four organisms including C. tertium were isolated from blood cultures. This patient responded to broad spectrum antimicrobial therapy, whereas the first patient required the addition of specific agents to recover. C. tertium is aerotolerant and thus can be misidentified as a Bacillus or Corynebacterium spp. Our isolates had a distinctive Gram stain morphology, were catalase negative and failed to sporulate aerobically--this aided in the recognition of this significant Gram-positive bacillus.