Concave Butterfly-Shaped Organometallic Hydrocarbons?

A metamorphosis of the tetraethynyl precursor 1 through double Cu-catalyzed ring closure leads to the corresponding butterfly-shaped cyclobutadiene complexes 2 in high yield (94 %). Single-crystal X-ray diffraction shows that the large organic ligand is distinctly nonplanar with a concave topology. Cp=cyclopentadiene.

LIBS using dual- and ultra-short laser pulses.

Pre-ablation dual-pulse LIBS enhancement data for copper, brass and steel using ns laser excitation are reported. Although large enhancements are observed for all samples, the magnitude of the enhancement is matrix dependent. Whereas all of the dual-pulse studies used ns laser excitation we see interesting effects when using ps and fs laser excitation for single-pulse LIBS.

Conjugated organometallic polymers containing Vollhardt's cyclobutadiene complex: aggregation and morphologies.

Organometallic polymers were prepared by acyclic diyne metathesis (ADIMET) or by Pd-catalyzed coupling of 1,3-diethynylcyclobutadiene(cyclopentadienyl)cobalt with a suitably substituted diiodobenzene. The polymers obtained by Heck coupling show a degree of polymerization (Pn) of 20-60. The monomers for ADIMET were made by the Pd-catalyzed coupling of [1,3-bis(trimethylsilylethynyl)-2,4-bis(trimethylsilyl)cyclobutadiene](cyclopentadienyl)cobalt to 1-bromo-2,5-dialkyl-4-propynylbenzenes in the presence of KOH in yields of 40-48%.

Assets-oriented community assessment.

Determining how to promote community health requires that community health workers first assess where the community stands. The authors maintain that Healthy Communities initiatives are better served by assets-oriented assessment methods than by standard "problem-focused" or "needs-based" approaches. An assets orientation allows community members to identify, support, and mobilize existing community resources to create a shared vision of change, and encourages greater creativity when community members do address problems and obstacles.

Cancer and pregnancy: a health care dilemma.

When cancer occurs during pregnancy, a conflict exists between the family's hopes and dreams for the future and the reality of the diagnosis of a potentially terminal illness. The nurse has a pivotal role in the assessment and management of the pregnant oncologic patient's physical and emotional health. The perinatal nurse must assure that the care experienced by the family balances the reality of a potentially life-threatening illness with the joy that accompanies the birth of a baby.

A governing relationship for repetitive muscular contraction.

During repetitive contractions, muscular work has been shown to exhibit complex relationships with muscle strain length, cycle frequency, and muscle shortening velocity. Those complex relationships make it difficult to predict muscular performance for any specific set of movement parameters. We hypothesized that the relationship of impulse with cyclic velocity (the product of shortening velocity and cycle frequency) would be independent of strain length and that impulse-cyclic velocity relationships for maximal cycling would be similar to those of in situ muscle performing repetitive contraction.

Comparison between supercritical carbon dioxide extraction and aqueous surfactant washing of an oily machining waste.

Mathematical models are developed to compare aqueous surfactant washing to supercritical carbon dioxide (SCCO2) extraction. These two cleaning processes are potentially competitive technologies which can be used to remove oily contaminants from a solid waste. In both processes, the cleaning efficiency for a batch of waste is evaluated by quantifying the residual oil content in the treated sample.

Diastolic effects of chronic digitalization in systolic heart failure.

Background: The efficacy of short-term digitalization on exercise tolerance may, in part, reflect enhanced diastolic performance. However, cardiac glycosides can impair ventricular relaxation from cytosolic Ca++ overload. To detect any time-dependent adverse effect, we assessed the diastolic function after long-term use of digitalis in patients with mild to moderate systolic left ventricular failure.

Outlier detection in multivariate analytical chemical data.

The unreliability of multivariate outlier detection techniques such as Mahalanobis distance and hat matrix leverage has been known in the statistical community for well over a decade. However, only within the past few years has a serious effort been made to introduce robust methods for the detection of multivariate outliers into the chemical literature. Techniques such as the minimum volume ellipsoid (MVE), multivariate trimming (MVT), and M-estimators (e.

Changes in the forward and reverse metabolism of aromatizable androgens during the development of large ovarian cysts in the pregnant rat.

Twice-daily treatments with subovulatory doses of hCG result in the development of large ovarian cysts that possess the capacity to produce preovulatory amounts of estradiol (E2) in the presence of exogenous substrate (Biol Reprod 1991; 45:34-42). To determine the effects of prolonged stimulation by subovulatory doses of LH-like activity on the ability of ovarian follicles to produce aromatizable androgens and their metabolites and on the capacity of similar follicles to metabolize exogenous androstenedione (A4) and testosterone, pregnant rats were treated with either 0 (control), 1, or 3 IU hCG twice daily for 9 days, beginning on Day 13 of pregnancy. The largest follicles or cysts in the ovaries of these animals on Days 15, 17, 19, and 22 were incubated for 4 h in the presence of 1) medium alone, 2) 1 mM cAMP, 3) 800 ng/ml A4 with or without cAMP, or 4) 800 ng/ml testosterone with or without cAMP.

Use of partially mismatched related donors extends access to allogeneic marrow transplant.

Most patients requiring allogeneic bone marrow transplant (allo-BMT) do not have an HLA-matched sibling donor. A phenotypically matched unrelated donor graft has been made available for approximately 50% of Caucasians and less than 10% of ethnic and racial minorities in need. However, almost all patients have a readily available partially mismatched related donor (PMRD).

Time use and change in academic achievement: A longitudinal follow-up.

As a follow-up of the research of Smith in 1990, academic achievement results from two years later are added to the data for 1208 of the 1584 seventh and ninth graders for whom Smith studied relationships between achievement and time use. Growth in academic achievement over two years, like contemporaneous achievement, is not positively related to time spent on homework or with parents at the beginning of the period. The other findings are also in general accord with the results of the previous study, although the associations are somewhat weaker and less consistent.

Exercise Intensity Reproduction: Children versus Adults.

Seventeen children, ages 8-14 years, were compared to an adult group ( = 19) in their ability to execute prescriptive exercise using the Borg 6-20 rating of perceived exertion (RPE) scale. Subjects cycled at a controlled pace (setting resistance) for 2 minutes or traveled one lap of a 400-meter track at four RPE levels: 7, 10, 13, and 16. Results indicated that for pace-controlled cycling, children were similar to adults, reproducing four incremental intensities.

Time and academic achievement.

In questionnaire and achievement-test data from 1584 seventh- and ninth-grade students, relationships between academic achievement and amounts of time devoted to various uses related to school, family, peers, and the mass media are examined, with relevant demographic factors controlled. Multiple regression analyses support hypotheses of (a) a negative relationship among ninth graders between achievement and time spent listening to radio and records, (c) an interaction between parental occupation and time spent watching television, with trends toward positive association between achievement and TV time when occupational status is low and negative association when it is high, and (d) a positive relationship between reading and overall achievement and time spent on leisure reading. Hypotheses of positive relationships between achievement and time spent on homework in this age range and mere time spent with the parent receive no support.