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"Paradise, Thomas R"
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Defining tafoni
Cavernous rock decay processes represent a global phenomenon, ubiquitous to all environments, with the viewable-in-landscape form usually being the final descriptor (e.g. “alveoli”), sometimes alluding to the specific decay process (e.g. “pitting”), other times not (e.g. “honeycombing”). Yet, definitive terminology remains inconsistent, usually owing to variability in dimension, morphometry, distribution, and/or academic lineage. This lack of an established lexicon limits scientific collaboration and can generate scientific bias. With no official consensus on appropriate distinctions, researchers and scientists must either be familiar with all the possible terminology, or know the apparent distinction between “forms”—which can seem arbitrary and, even more frustrating, often differs from researcher to researcher, scientist to scientist. This article reviews the historical and contemporary progression of scientific inquiry into this decay—and, arguably, erosional—feature to identify lexical inconsistencies and promote a singular unifying term for future scholars. Ultimately, the authors support using “tafoni” (singular: “tafone”) as the non-scalar universal term—the form created by numerous processes involved in cavernous decay features—and strongly suggest researchers adopt the same vernacular in order to promote collaboration.
Journal Article
Defining tafoni
Cavernous rock decay processes represent a global phenomenon, ubiquitous to all environments, with the viewable-in-landscape form usually being the final descriptor (e.g. \"alveoli\"), sometimes alluding to the specific decay process (e.g. \"pitting\"), other times not (e.g. \"honeycombing\"). Yet, definitive terminology remains inconsistent, usually owing to variability in dimension, morphometry, distribution, and/or academic lineage. This lack of an established lexicon limits scientific collaboration and can generate scientific bias. With no official consensus on appropriate distinctions, researchers and scientists must either be familiar with all the possible terminology, or know the apparent distinction between \"forms\"--which can seem arbitrary and, even more frustrating, often differs from researcher to researcher, scientist to scientist. This article reviews the historical and contemporary progression of scientific inquiry into this decay--and, arguably, erosional--feature to identify lexical inconsistencies and promote a singular unifying term for future scholars. Ultimately, the authors support using \"tafoni\" (singular: \"tafone\") as the non-scalar universal term--the form created by numerous processes involved in cavernous decay features--and strongly suggest researchers adopt the same vernacular in order to promote collaboration.
Journal Article
Disparate Sandstone Weathering beneath Lichens, Red Mountain, Arizona
Though the ability of lichens to disaggregate and dissolve the substrate is understood, zones of disparate weathering mechanisms examined in this study were previously unobserved. On a steep (60°) northern (340°N) slope on Red Mountain, Arizona, a 5×5 m study plot was chosen for its maximum lichen coverage (33%) of the same lichen genus Xanthoparmelia in varying growth stages, on a sandstone substrate of consistent lithology. From twenty-two (22) representative lichen thalli, portions were removed to examine sub-thallic rhizine density, and others were resin-imbedded for optical, scanning and backscatter electron microscopy. In every sample, sandstone beneath and adjacent to the lichen thallus displayed disparate weathering mechanisms. Beneath the center of the lichen cortex, where rhizine density was observed to be the greatest, rhizine penetration disaggregated the sandstone clasts from the matrix, but little chemical dissolution was apparent. This study found physical weathering predominates beneath the lichen cortex, and chemical weathering predominates at the thallus fringe and beyond the thallus boundary. It was generally found that physical weathering decreased (disaggregation) and chemical weathering increased (dissolution) from the cortex center to the thallus edge. Toward the thallus fringe, minimal clast disaggregation was observed, and substrate dissolution was obvious.
Journal Article
Disparate sandstone weathering beneath lichens, red mountain, arizona
Though the ability of lichens to disaggregate and dissolve the substrate is understood, zones of disparate weathering mechanisms examined in this study were previously unobserved. On a steep (60°) northern (340°N) slope on Red Mountain, Arizona, a 5×5 m study plot was chosen for its maximum lichen coverage (33%) of the same lichen genus Xanthoparmelia in varying growth stages, on a sandstone substrate of consistent lithology. From twenty-two (22) representative lichen thalli, portions were removed to examine sub-thallic rhizine density, and others were resin-inbedded for optical, scanning and backscatter electron microscopy.
In every sample, sandstone beneath and adjacent to the lichen thallus displayed disparate weathering mechanisms. Beneath the center of the lichen cortex, where rhizine density was observed to be the greatest, rhizine penetration disaggregated the sand-stone clasts from the matrix, but little chemical dissolution was apparent. This study found physical weathering predominates beneath the lichen cortex, and chemical weathering predominates at the thallus fringe and beyond the thallus boundary. It was generally found that physical weathering decreased (disaggregation) and chemical weathering increased (dissolution) from the cortex center to the thallus edge. Toward the thallus fringe, minimal clast disaggregation was observed, and substrate dissolution was obvious.
Journal Article
Shortened Antimicrobial Treatment for Acute Otitis Media in Young Children
In children 6 to 23 months of age with otitis media, 5 days of antibiotic therapy was associated with less-favorable outcomes than standard 10-day treatment. The shorter course did not result in a lower rate of adverse events or of emergence of antimicrobial resistance.
Next to the common cold, acute otitis media is the most frequently diagnosed illness in children in the United States
1
and the most commonly cited indication for antimicrobial treatment.
2
Concerns about the possible encouragement of antimicrobial resistance have led to recommendations by some clinicians that antimicrobial agents be withheld in large subgroups of children with acute otitis media, unless symptoms persist or worsen.
3
However, two trials lend support for routine antimicrobial treatment in young children, because affected participants younger than 3 years of age who received antimicrobial treatment for 7 or 10 days had more favorable outcomes than those who . . .
Journal Article
Synthesis and reactivity of the stable silylene N,N'-di-tert-butyl-1,3-diaza-2-sila-2-ylidene
The synthesis and several reactions of the stable silylene
1
(N,N'-di-tert-butyl-1,3-diaza-2-sila-2-ylidene) are reported. Overreduction of
1
with alkali metals results in the formation of a dimeric dianion, which can be trapped with a proton source to give the dihydride derivative
9
. In the solid state or in concentrated solutions,
1
undergoes a reversible conversion into the novel tetrameric disilene,
10
.
1
reacts with ethanol, phenol, and water via insertion into the OH bond, and with iodomethane by insertion into the CI bond. A reaction of
1
with the diene 2,3-dimethyl-1,3-butadiene affords the silacyclopentene,
15
. This reaction is markedly different from the one found for the unsaturated analog of the silylene,
2
, which catalyzes the conversion of this diene into a highly cross-linked polymer.Key words: silylene, carbene analog, disilene, divalent compounds, N-heterocycles.
Journal Article
Safety and Toxicity of Nonoxynol-9 Gel As a Rectal Microbicide
Background and Objectives: Methods of HIV and STD prevention, which can be controlled by the receptive partner, are a high priority for research and development. Studies on the safety of Nonoxynol-9 (N-9) on the vaginal mucosa have yielded conflicting results. No Phase I study has evaluated the effect of N-9 on the rectal mucosa. Goals: To assess the safety of 52.5 mg of N-9 in a 1.5-g gel when applied one to four applicators per day to the rectum and penis. Study Design: The study included 25 HIV-negative and 10 HIV-positive, monogamous gay male couples in which each partner was exclusively insertive or receptive while using N-9 gel. Each participant served as his own control during placebo gel use compared to during N-9 gel use. Receptive partners underwent anoscopic examination after 1 week of placebo use and after 2, 5, and 6 weeks of N-9 gel use, with rectal biopsies obtained after 1 week of placebo use and after 5 and 6 weeks of N-9 gel use. Insertive partners had safety monitoring after 1 week of placebo use and after 2, 5, and 6 weeks of N-9. Results: No rectal ulcers were detected; superficial rectal erosions were noted in two HIV-negative participants. Abnormal or slightly abnormal histologie abnormalities of rectal biopsies were detected in 31 (89%) receptive participants after N-9 gel use compared to 24 (69%) participants after 1 week of placebo gel use. Meatal ulcération, not caused by herpes simplex virus, was detected in one HIV-negative participant. Conclusion: Low-dose N-9 gel was not associated with macroscopic rectal and penile epithelial disruption or inflammation, but histologie abnormalities were commonly observed during N-9 gel as well as during placebo gel use.
Journal Article
Opportunistic intracellular bacteria and immunity
Opportunistic, intracellular bacterial infections are at the forefront of research because of the challenges they present to immunocompromised patients. In this volume, the pathogenesis and immune reaction of these intracellular infections is featured, as are the most typical problems related to antimicrobial chemotherapy, and current approaches to their solution. Individual chapters set the pace for research on pathogenic and immune reactions to such infections as, mycobacterium tuberculosis, legionella pneumophila, chlamydia trachomatis and brucella.
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