Sequestration of Martian CO2 by mineral carbonation

Carbonation is the water-mediated replacement of silicate minerals, such as olivine, by carbonate, and is commonplace in the Earth’s crust. This reaction can remove significant quantities of CO2 from the atmosphere and store it over geological timescales. Here we present the first direct evidence for CO2 sequestration and storage on Mars by mineral carbonation. Electron beam imaging and analysis show that olivine and a plagioclase feldspar-rich mesostasis in the Lafayette meteorite have been replaced by carbonate. The susceptibility of olivine to replacement was enhanced by the presence of smectite veins along which CO2-rich fluids gained access to grain interiors. Lafayette was partially carbonated during the Amazonian, when liquid water was available intermittently and atmospheric CO2 concentrations were close to their present-day values. Earlier in Mars’ history, when the planet had a much thicker atmosphere and an active hydrosphere, carbonation is likely to have been an effective mechanism for sequestration of CO2

Blood cultures in ambulatory outpatients

BACKGROUND: Blood cultures are a gold standard specific test for diagnosing many infections. However, the low yield may limit their usefulness, particularly in low-risk populations. This study was conducted to assess the utility of blood cultures drawn from ambulatory outpatients. METHODS: Blood cultures drawn at community-based collection sites in the Calgary Health Region (population 1 million) in 2001 and 2002 were included in this study. These patients were analyzed by linkages to acute care health care databases for utilization of acute care facilities within 2 weeks of blood culture draw. RESULTS: 3102 sets of cultures were drawn from 1732 ambulatory outpatients (annual rate = 89.4 per 100,000 population). Significant isolates were identified from 73 (2.4%) sets of cultures from 51 patients, including Escherichia coli in 18 (35%) and seven (14%) each of Staphylococcus aureus and Streptococcus pneumoniae. Compared to patients with negative cultures, those with positive cultures were older (mean 49.6 vs. 40.1 years, p < 0.01), and more likely to subsequently receive care at a regional emergency department, outpatient antibiotic clinic, or hospital (35/51 vs. 296/1681, p < 0.0001). Of the 331 (19%) patients who received acute care treatment, those with positive cultures presented sooner after community culture draw (median 2 vs. 3 days, p < 0.01) and had longer median treatment duration (6 vs. 2 days, p < 0.01). CONCLUSION: Blood cultures drawn in outpatient settings are uncommonly positive, but may define patients for increased intensity of therapy. Strategies to reduce utilization without excluding patients with positive cultures need to be developed for this patient population

First Steps in Eukaryogenesis: Physical phenomena in the origin and evolution of chromosome structure

Our present understanding of the origin and evolution of chromosomes differs considerably from current understanding of the origin and evolution of the cell itself. Chromosome origins have been less prominent in research, as the emphasis has not shifted so far appreciably from the phenomenon of primeval nucleic acid encapsulation to that of the origin of gene organization, expression, and regulation. In this work we discuss some reasons why preliminary steps in this direction are being taken. We have been led to examine properties that have contributed to raise the ancestral prokaryotic programmes to a level where we can appreciate in eukaryotes a clear departure from earlier themes in the evolution of the cell from the last common ancestor. We shift our point of view from the evolution of cell morphology to the point of view of the genes. In particular, we focus attention on possible physical bases for the way transmission of information has evolved in eukaryotes, namely, the inactivation of whole chromosomes. The special case of the inactivation of the X chromosome in mammals is discussed, paying particular attention to the physical process of the spread of X inactivation in monotremes (platypus and echidna). When experimental data is unavailable some theoretical analysis is possible based on the idea that in certain cases collective phenomena in genetics, rather than chemical detail, are better correlates of complex chemical processes

Gynecologic oncology group trials of chemotherapy for metastatic and recurrent cervical cancer

Because only 16% of patients with metastatic cervical cancer are alive 5 years after diagnosis, the Gynecologic Oncology Group (GOG) has carefully designed and conducted many phase II studies to identify promising drugs. Cisplatin has emerged as the most active single agent with overall response rates of 19%. Recent phase III trials have documented response rates of 27% and 39% when cisplatin has been combined with either paclitaxel or topotecan, respectively. The comparison of cisplatin to cisplatin plus topotecan in GOG-179 has yielded the first study to show a statistically significant impact on the overall response rate, median progression-free survival, and median survival, with all outcome measures favoring the two-drug regimen. Despite these encouraging results, however, most of the responses are partial and of short duration. The need for novel combinations and the implementation of active biologic agents is implicit. The accumulated data in this disease setting, as evidenced by the experience of the GOG, are presented in this review

Degradation of haloaromatic compounds

An ever increasing number of halogenated organic compounds has been produced by industry in the last few decades. These compounds are employed as biocides, for synthetic polymers, as solvents, and as synthetic intermediates. Production figures are often incomplete, and total production has frequently to be extrapolated from estimates for individual countries. Compounds of this type as a rule are highly persistent against biodegradation and belong, as "recalcitrant" chemicals, to the class of so-called xenobiotics. This term is used to characterise chemical substances which have no or limited structural analogy to natural compounds for which degradation pathways have evolved over billions of years. Xenobiotics frequently have some common features. e.g. high octanol/water partitioning coefficients and low water solubility which makes for a high accumulation ratio in the biosphere (bioaccumulation potential). Recalcitrant compounds therefore are found accumulated in mammals, especially in fat tissue, animal milk supplies and also in human milk. Highly sophisticated analytical techniques have been developed for the detection of organochlorines at the trace and ultratrace level

Origin and Evolution of Defective Interfering RNAs of Tomato Bushy Stunt Virus

Viruses with defective genomes have been identified in association with virtually every major family of viruses and have been widely utilized as tools for investigating virus functions in animal cell culture systems (Perrault, 1981). It is generally thought that defective interfering viruses (DIs) arise through deletion, rearrangement, or recombination of a competent viral genome. DIs tack the ability for independent existence relying on their parental helper viruses to supply factors required for replication, maturation, and/or encapsidation (Huang and Baltimore, 1977). The interference attributed to DIs is thought to result from competition with the helper virus for factors required in trans for replication and/or encapsidation (Schlesinger, 1988). It is these features that have made DIs very useful tools for mapping viral signals required for replication and packaging (e.g. Levis, et aI., 1986). The DIs associated with animal viruses have usually been detected after serial passage of virus at high multiplicities of infection (m.o.i.) in cell cultures. It has also been noted that maintenance in continuous passage results in fluctuations of helper and DI which reflect the relative abilities of each to interfere or support the other (Huang, 1988). DIs have also been detected in natural virus infections and, although there is some debate, may function in vivo to modulate virus diseases and allow more persistent infections (Huang, 1988). The majority of plant viruses have positive-sense, single-stranded RNA genomes. Additional RNA components capable of modulating symptoms have most commonly been associated with either satellite viruses or satellite RNAs. Satellite viruses differ from satellite RNAs by encoding their own capsid proteins, whereas satellite RNAs are encapsidated by their specific helper virus. Satellite RNAs are relatively common among plant viruses, having been found in association with at least 24 members in six virus groups (Francki, 1985). Unlike DIs, satellite RNAs in general share little sequence similarity with their specific heJper virus . The one exception is the chimeric satellite RNA-C of turnip crinkle virus (Simon, 1988). Satellite viruses and satellite RNAs have been shown to both intensify as well as attenuate symptoms normally expressed by their specific virus helpers (Kaper, and Collmer, 1988, Simon, 1988). In contrast to the many reports of satellites, few authentic DIs have been identified among plant viruses. These accounts include the presence of DI -Iike particles associated with the negative-stranded plant rhabdoviruses (Adam et al., 1983; Ishmail and Milner, 1988) and the bunyavirus-like tomato spotted wilt virus (Verkleij and Peters, 1983). DI-Iike RNA components have also been reported for wound tumor virus, a plant reovirus (Nuss, 1988). Among the positive, single-stranded RNA plant viruses, authentic DIs have been identified for only two viruses: tomato bushy stunt virus (TBSV) (Hillman et aI., 1987; Morris et al., 1989); and turnip crinkle virus (TCV)(Li et al., 1989). TBSV and TCV are members of two closely related groups of plant viruses, the tombusviruses and the carmoviruses respectively (see Martelli et al., 1988 and Morris et al., 1988 for reviews). Both viruses are good model systems for studying small RNA virus and DI RNA molecular biology because each has been well-defined biologically and detailed structural studies have been performed on both viruses. In addition, the genome of each virus has been cloned, entirely sequenced, and engineered to produce infectious RNA transcripts in vitro (Carrington et al., 1989; Heaton, et aI., 1989; Hearne, et al., 1990). The reader is referred to these papers for details on the genomic organizations of these two viruses. The features of the TBSV genome organization important in understanding the origins of associated DI RNAs are summarized in Figure 5. In this paper we will focus on the derivation, molecular characterization, and evolution of TBSV -associated DIs. We will also discuss the possibilities for using plant virus DIs as a general method for controlling virus diseases