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1.
BMC Med Inform Decis Mak ; 16: 75, 2016 06 24.
Article in English | MEDLINE | ID: mdl-27343060

ABSTRACT

BACKGROUND: The use of telemonitoring is a promising approach to optimizing outcomes in the treatment of heart failure (HF) for patients living in the community. HF telemonitoring interventions, however, have not been tested for use with individuals residing in disparity communities. METHODS: The current study describes the results of a community based participatory research approach to adapting a telemonitoring HF intervention so that it is acceptable and feasible for use with a lower-income, Black and Hispanic patient population. The study uses the ADAPT-ITT framework to engage key community stakeholders in the process of adapting the intervention in the context of two consecutive focus groups. In addition, data from a third focus group involving HF telemonitoring patient participants was also conducted. All three focus group discussions were audio recorded and professionally transcribed and lasted approximately two hours each. Structural coding was used to mark responses to topical questions in the interview guide. RESULTS: This is the first study to describe the formative process of a community-based participatory research study aimed at optimizing telehealth utilization among African-American and Latino patients from disparity communities. Two major themes emerged from qualitative analyses of the focus group data. The first theme that arose involved suggested changes to the equipment that would maximize usability. Subthemes identified included issues that reflect the patient populations targeted, such as Spanish translation, font size and medical jargon. The second theme that arose involved suggested changes to the RCT study structure in order to maximize participant engagement. Subthemes also identified issues that reflect concerns of the targeted patient populations, such as the provision of reassurances regarding identity protection to undocumented patients in implementing an intervention that utilizes a camera, and that their involvement in telehealth monitoring would not replace their clinic care, which for many disparity patients is their only connection to medical care. CONCLUSIONS: The adaptation, based on the analysis of the data from the three focus groups, resulted in an intervention that is acceptable and feasible for HF patients residing in disparity communities. TRIAL REGISTRATION: NCT02196922 ; ClinicalTrials.gov (US National Institutes of Health).


Subject(s)
Black or African American , Community-Based Participatory Research/methods , Heart Failure/diagnosis , Hispanic or Latino , Monitoring, Ambulatory/methods , Qualitative Research , Telemedicine/methods , Community-Based Participatory Research/standards , Healthcare Disparities , Heart Failure/therapy , Humans , Monitoring, Ambulatory/standards , Telemedicine/standards
2.
Persoonia ; 30: 1-10, 2013 Jun.
Article in English | MEDLINE | ID: mdl-24027344

ABSTRACT

Molecular clock data indicate that the first zygomycetous fungi occurred on Earth during the Precambrian, however, fossil evidence of these organisms has been slow to accumulate. In this paper, the fossil record of the zygomycetous fungi is compiled, with a focus on structurally preserved Carboniferous and Triassic fossils interpreted as zygosporangium-gametangia complexes and resembling those of modern Endogonales. Enigmatic microfossils from the Precambrian to Cenozoic that have variously been interpreted as, or compared to, zygomycetous fungi are also discussed. Among these, the spherical structures collectively termed 'sporocarps' are especially interesting because of their complex investments and abundance in certain Carboniferous and Triassic rocks. Circumstantial evidence suggests that at least some 'sporocarp' types represent mantled zygosporangia. Zygomycetous fungi probably were an important element in terrestrial paleoecosystems at least by the Carboniferous.

3.
Geobiology ; 10(6): 479-95, 2012 Nov.
Article in English | MEDLINE | ID: mdl-22845834

ABSTRACT

Forests are expected to expand into northern polar latitudes in the next century. However, the impact of forests at high latitudes on climate and terrestrial biogeochemical cycling is poorly understood because such forests cannot be studied in the modern. This study presents forestry and geochemical analyses of three in situ fossil forests from Late Permian strata of Antarctica, which grew at polar latitudes. Stem size measurements and stump spacing measurements indicate significant differences in forest density and canopy structure that are related to the local depositional setting. For forests closest to fluvial systems, tree density appears to decrease as the forests mature, which is the opposite trend of self-thinning observed in modern forests. We speculate that a combination of tree mortality and high disturbance created low-density mature forests without understory vegetation near Late Permian river systems. Stable carbon isotopes measured from permineralized wood in these forests demonstrate two important points: (i) recently developed techniques of high-resolution carbon isotope studies of wood and mummified wood can be applied to permineralized wood, for which much of the original organic matter has been lost and (ii) that the fossil trees maintained a deciduous habit at polar latitudes during the Late Permian. The combination of paleobotanical, sedimentologic, and paleoforestry techniques provides an unrivaled examination of the function of polar forests in deep time; and the carbon isotope geochemistry supplements this work with subannual records of carbon fixation that allows for the quantitative analysis of deciduous versus evergreen habits and environmental parameters, for example, relative humidity.


Subject(s)
Botany/methods , Fossils , Soil/chemistry , Trees , Antarctic Regions , Carbon Isotopes/analysis
4.
Leukemia ; 26(4): 633-43, 2012 Apr.
Article in English | MEDLINE | ID: mdl-22005783

ABSTRACT

Chronic graft-versus-host disease (cGVHD) remains a major cause of non-relapse morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Currently there are no accepted measures of cGVHD activity to aid in clinical management and disease staging. We analyzed clinical markers of inflammation in the sera of patients with established cGVHD and correlated those with definitions of disease activity. In all, 189 adults with cGVHD (33% moderate and 66% severe according to National Institutes of Health (NIH) global scoring) were consecutively enrolled onto a cross-sectional prospective cGVHD natural history study. At the time of evaluation, 80% were receiving systemic immunosuppression and failed a median of four prior systemic therapies (PST) for their cGVHD. Lower albumin (P<0.0001), higher C-reactive protein (P = 0.043), higher platelets (P = 0.030) and higher number of PST (P<0.0001) were associated with active disease defined as clinician's intention to intensify or alter systemic therapy due to the lack of response. Higher platelet count (P = 0.021) and higher number of PST (P<0.0001) were associated with more severe diseased defined by NIH global score. This study identified common laboratory indicators of inflammation that can serve as markers of cGVHD activity and severity.


Subject(s)
C-Reactive Protein/analysis , Graft vs Host Disease/diagnosis , Adolescent , Adult , Aged , Biomarkers , Chronic Disease , Complement C3/analysis , Cross-Sectional Studies , Cytokines/blood , Female , Graft vs Host Disease/blood , Humans , Immunosuppression Therapy , Male , Middle Aged , Proportional Hazards Models , Prospective Studies
5.
Neuropeptides ; 42(4): 423-34, 2008 Aug.
Article in English | MEDLINE | ID: mdl-18533255

ABSTRACT

Pituitary adenylyl cyclase activating polypeptide, 38 amino acids (PACAP38) is a brain-gut peptide with diverse physiological functions and is neuroprotective in several models of neurological disease. In this study, we show that systemic administration of PACAP38, which is transported across the blood-brain barrier, greatly reduces the neurotoxicity of methamphetamine (METH). Mice treated with PACAP38 exhibited an attenuation of striatal dopamine loss after METH exposure as well as greatly reduced markers of oxidative stress. PACAP38 treatment also prevented striatal neuroinflammation after METH administration as measured by overexpression of glial fibrillary acidic protein (GFAP), an indicator of astrogliosis, and glucose transporter 5 (GLUT5), a marker of microgliosis. In PACAP38 treated mice, the observed protective effects were not due to an altered thermal response to METH. Since the mice were not challenged with METH until 28 days after PACAP38 treatment, this suggests the neuroprotective effects are mediated by regulation of gene expression. At the time of METH administration, PACAP38 treated animals exhibited a preferential increase in the expression and function of the vesicular monoamine transporter (VMAT2). Genetic reduction of VMAT2 has been shown to increase the neurotoxicity of METH, thus we propose that the increased expression of VMAT2 may underlie the protective actions of PACAP38 against METH. The ability of PACAP38 to increase VMAT2 expression suggests that PACAP38 signaling pathways may constitute a novel therapeutic approach to treat and prevent disorders of dopamine storage.


Subject(s)
Dopamine Agents/toxicity , Methamphetamine/toxicity , Pituitary Adenylate Cyclase-Activating Polypeptide/metabolism , Vesicular Monoamine Transport Proteins/metabolism , Animals , Biomarkers/metabolism , Body Temperature , Dopamine/metabolism , Inflammation/metabolism , Male , Mice , Mice, Inbred C57BL , Oxidative Stress , Pituitary Adenylate Cyclase-Activating Polypeptide/administration & dosage
6.
Science ; 308(5724): 1017-20, 2005 May 13.
Article in English | MEDLINE | ID: mdl-15890881

ABSTRACT

The fossil record of fungi and lichens is scarce. Here we report the discovery of lichen-like fossils, involving filamentous hyphae closely associated with coccoidal cyanobacteria or algae, preserved in marine phosphorite of the Doushantuo Formation (between 551 and 635 million years old) at Weng'an, South China. These fossils indicate that fungi developed symbiotic partnerships with photoautotrophs before the evolution of vascular plants.


Subject(s)
Cyanobacteria/isolation & purification , Fossils , Fungi/isolation & purification , Lichens/isolation & purification , Symbiosis , China , Cyanobacteria/physiology , Fungi/cytology , Fungi/physiology , Hyphae/cytology , Lichens/physiology
7.
Mycologia ; 97(1): 269-85, 2005.
Article in English | MEDLINE | ID: mdl-16389979

ABSTRACT

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1-5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.


Subject(s)
Ascomycota , Fossils , Plants/microbiology , Polymorphism, Genetic , Ascomycota/classification , Ascomycota/genetics , Ascomycota/isolation & purification , Ascomycota/ultrastructure , History, Ancient , Spores, Fungal/physiology , Spores, Fungal/ultrastructure
8.
Occup Environ Med ; 59(10): 664-70, 2002 Oct.
Article in English | MEDLINE | ID: mdl-12356925

ABSTRACT

In order to identify functional status measures for epidemiological studies among workers with mild to moderate disorders of the neck and upper extremity, a literature search was conducted for the years 1966 to 2001. Inclusion criteria were: (1) relevance to neck and upper extremity; (2) assessment among workers; and (3) relevance to mild to moderate disorders. Of 13 instruments reviewed, six measures were tested among workers. The three best measures, depending on the purpose of research, included the standardised Nordic Musculoskeletal Questionnaire, the Upper Extremity Questionnaire, and the Neck and Upper Limb Instrument. Development of a functional protocol is regarded as a realistic enhancement for research of neck and upper extremity disorders in the workplace. For research and clinical practice, measures of functional status, sensitive enough to measure the subtle conditions in mild to moderate disorders, may provide prognostic information about the risk of developing musculoskeletal disorders in apparently healthy patients. Appropriate use of functional status questionnaires is imperative for a meaningful portrayal of health.


Subject(s)
Disability Evaluation , Health Status Indicators , Musculoskeletal Diseases/diagnosis , Occupational Diseases/diagnosis , Humans , Neck/physiopathology , Reproducibility of Results , Upper Extremity/physiopathology
9.
Rev Palaeobot Palynol ; 115(3-4): 107-117, 2001 Jun.
Article in English | MEDLINE | ID: mdl-11440765

ABSTRACT

Anatomically preserved ovules are described from silicified peat of Late Permian age collected from Skaar Ridge in the central Transantarctic Mountains, Antarctica. The small ovules are significant in possessing fleshy apical appendages and a funnel-shaped micropylar extension formed by the sarcotestal layer of the integument, by which they differ from all other Permian ovules described to date. The apical modifications may have functioned in pollination and/or seed dispersal. Similarity with the apical organization of earlier Paleozoic ovules is shown to be superficial, since the analogous structures are developmentally derived from different tissues. Although the ovules occur in rocks in which glossopterids are the only gymnosperms represented, there is insufficient evidence to assign them to a taxonomic group. These ovules are of particular importance because there are so few anatomically preserved gymnosperm reproductive structures known from the Permian and thus provide new data on the diversity of late Paleozoic gymnosperms.

10.
Rev Palaeobot Palynol ; 114(3-4): 209-222, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11389915

ABSTRACT

Cuticles of Mariopteris occidentalis are described from the Desmoinesian (Middle Pennsylvanian) of Oklahoma (USA). This species, like other mariopteroids, had a vine- to liana-like growth habit and climbed with specialized climber hooks. However, M. occidentalis is different from other mariopteroids in having small recurved hooks on the abaxial surfaces of the pinna axes. The diagnosis for M. occidentalis White 1899 is emended based on additional macroscopical observations and data on the epidermal anatomy; a lectotype is designated. M. occidentalis is compared with Pseudomariopteris cordato-ovata from the Stephanian and Autunian of Europe and North America, a taxon which is considered very similar and may be related. Although the two taxa indeed display similarities, significant evidence for a closer relationship could not be found. Finally, some features, e.g. marginal water pits and the stomatal structure, are considered with regard to their palaeoautecological significance where they are interpreted as adaptations to special physiological requirements of a vine- to liana-like life form.

11.
Am J Bot ; 88(5): 767-76, 2001 May.
Article in English | MEDLINE | ID: mdl-11353702

ABSTRACT

The growth habit of the Late Carboniferous-Early Permian pteridosperm Pseudomariopteris busquetii is reconstructed based on compression material from the upper Stephanian of the Blanzy-Montceau and Commentry Basins (Massif Central, France), and the upper Rotliegend of the Saar-Nahe Basin (Nahe Group, N 4, Rheinland Pfalz, Germany). Pseudomariopteris busquetii was a medium-sized, vine- to liana-like plant with slender stems to which small bipartite fronds were attached. What is most interesting is that the species used at least two different strategies to both anchor and support the plant body. Most specimens possess specialized climber hooks developed from apical extensions of the pinna axes, indicating that the fronds were used to attach the plant. A few specimens suggest that the stem may also have had some capacity for attachment. In the absence of suitable supports, however, P. busquetii was apparently able to grow in dense stands or thickets in which the individual plants supported each other.

12.
Med Decis Making ; 21(2): 122-32, 2001.
Article in English | MEDLINE | ID: mdl-11310945

ABSTRACT

OBJECTIVE: The objective of this study was to determine rheumatoid arthritis (RA) patients' preferences for validated health state scenarios depicting glucocorticoid adverse events, predictors of these preferences, and psychometric properties of different preference techniques in this population. METHODS: Preferences were elicited by rating scale and time trade-off methods. Time trade-offs included trading current health for either time spent alive in an adverse health state for chronic conditions (time trade-off) or time spent in a sleeplike state for acute conditions (sleep trade-off). RESULTS: A total of 107 subjects with long-standing RA participated in the preference interviews. Mean preference values (rating scale/trade-off) were lowest for serious fracture adverse events, including hip fracture requiring a nursing home stay (0.55+/-0.22/0.76+/-0.36) and vertebral fracture with chronic pain (0.59+/-0.23/0.67+/-0.35), and highest for cataracts (0.84 + 0.17/0.96 0.09) and wrist fracture (0.82+/-0.18/0.81+/-0.29). Rating scales had a stronger correlation (r= 0.88) with physician ranking of scenarios than trade-off methods (r = 0.31). All methods were feasible and demonstrated good reliability, while rating scale method showed better construct validity than trade-off techniques. CONCLUSION: Relative to their current health, RA patients assigned low preference values to many glucocorticoid adverse events, particularly those associated with chronic fracture outcomes. Results varied with the preference measure used, indicating that methodological attributes of preference determinations must be considered in clinical decision making.


Subject(s)
Arthritis, Rheumatoid/drug therapy , Fractures, Bone/psychology , Glucocorticoids/adverse effects , Patient Satisfaction , Quality of Life , Adult , Aged , Arthritis, Rheumatoid/complications , Arthritis, Rheumatoid/prevention & control , Female , Glucocorticoids/therapeutic use , Humans , Logistic Models , Male , Middle Aged , Psychometrics , Surveys and Questionnaires
13.
Am J Bot ; 88(9): 1558-67, 2001 Sep.
Article in English | MEDLINE | ID: mdl-21669688

ABSTRACT

Modern cladistic analyses support earlier suggestions that the Hymenophyllaceae (the "filmy ferns") are basal filicaleans. However, the fossil record of the family is ambiguous. A new fossil fern, Hopetedia praetermissa gen. et sp. nov., from the Upper Triassic Pekin Formation of North Carolina (USA), is described and interpreted as the oldest unequivocal representative of the Hymenophyllaceae based primarily on general frond morphology, indirect evidence for a filmy (membranaceous) habit, and soral position and morphology. Particularly compelling as evidence for the hymenophyllaceous affinity of H. praetermissa is the funneliform structure of the indusium (involucre), which is similar to that found primarilly in the extant Trichomanes (sensu lato) clade. However, the receptacle in H. praetermissa is relatively short and, thus, more like most representatives of the Hymenophyllum (sensu lato) clade. The Triassic age of this fossil is consistent with the basal or near basal position of the Hymenophyllaceae in all recent phylogenetic analyses of the filicalean ferns. Hopetedia preatermissa is evaluated in relationship to several previous reports of fossil Hymenophyllaceae.

14.
Am J Bot ; 87(6): 757-68, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10860906

ABSTRACT

A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.

15.
Am J Bot ; 86(8): 1200-6, 1999 Aug.
Article in English | MEDLINE | ID: mdl-10449400

ABSTRACT

Megaspore and microspore massulae of Paleoazolla patagonica gen. et sp. nov. are described from the Upper Cretaceous of La Colonia Formation, Chubut Province, Argentina. The new fern possesses megaspore complexes with three to four glochidiate floats attached directly to the megaspore; a columella-like structure appears to be absent. The megaspore wall consists of a two-layered exine that is smooth to irregularly perforate, a two-layered perine with a spongy, densely packed endoperine, and a loosely organized exoperine. Infrafilosum hairs cover the exoperine. Microspore massulae are irregular in size and shape and bear multibarbed glochidia that generally have anchor-shaped tips. A comparison with other azollaceous and salviniaceous genera, particularly Azolla, is provided, together with a discussion of some evolutionary trends within the family.

16.
Nature ; 399(6737): 648, 1999 Jun 17.
Article in English | MEDLINE | ID: mdl-10385115

Subject(s)
Ascomycota , Fossils , Scotland
17.
Endocrinol Metab Clin North Am ; 26(1): 67-87, 1997 Mar.
Article in English | MEDLINE | ID: mdl-9074853

ABSTRACT

This article provides a review of methods for conducting cost-effectiveness, cost-utility, and cost-benefit studies. Economic evaluations of interventions designed to improve outcomes of patients with diabetes and osteoporosis are reviewed, and key issues for future research are discussed. The role of cost-effectiveness analysis in reimbursement decision making at the public and private levels is explored.


Subject(s)
Endocrinology/economics , Cost-Benefit Analysis , Costs and Cost Analysis , Diabetes Mellitus/economics , Diabetes Mellitus/therapy , Diabetic Nephropathies/economics , Diabetic Nephropathies/therapy , Diabetic Retinopathy/economics , Diabetic Retinopathy/therapy , Endocrine System Diseases/economics , Endocrine System Diseases/therapy , Humans , Osteoporosis/economics , Osteoporosis/therapy
18.
Drugs ; 54 Suppl 3: 51-7; discussion 57-8, 1997.
Article in English | MEDLINE | ID: mdl-9360852

ABSTRACT

The economic consequences of the approximately 500,000 strokes that occur each year in the US are staggering. The direct cost of providing care for stroke victims in 1993 has been estimated to be $US17 billion, with an additional $US13 billion in indirect costs attributable to lost earnings due to stroke-related mortality and morbidity. Estimates of the cost of stroke over a patient's lifetime vary according to age at first stroke and type of stroke. In 1990, these estimates ranged from $US91,000 for ischaemic stroke, $US124,000 for intracerebral haemorrhage, and $US228,000 for subarachnoid haemorrhage. Factors driving the economics of stroke include the epidemiology of stroke, treatment patterns and settings, and social and behavioural factors. Evaluating the economic consequences of alternative interventions designed to prevent strokes or improve stroke outcomes involves a weighing of incremental costs and effectiveness. Previous efforts have focused primarily on measuring costs, with a recent shift to trying to measure patient preferences for stroke outcomes.


Subject(s)
Cerebrovascular Disorders/economics , Cost of Illness , Cerebrovascular Disorders/prevention & control , Cost-Benefit Analysis , Female , Health Care Costs/statistics & numerical data , Hospital Charges/statistics & numerical data , Humans , Male , Prescription Fees , United States
19.
Stroke ; 27(9): 1459-66, 1996 Sep.
Article in English | MEDLINE | ID: mdl-8784113

ABSTRACT

BACKGROUND AND PURPOSE: Stroke imposes a substantial economic burden on individuals and society. This study estimates the lifetime direct and indirect costs associated with the three major types of stroke: subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH), and ischemic stroke (ISC). METHODS: We developed a model of the lifetime cost of incident strokes occurring in 1990. An epidemiological model of stroke incidence, survival, and recurrence was developed based on a review of the literature. Data on direct cost of treating stroke were obtained from Medicare claims data, the 1987 National Medical Expenditure Survey (NMES), and insurance claims data representing a group of large, self-insured employers. Indirect costs (the value of foregone market and nonmarket production) associated with premature morbidity and mortality were estimated based on data from the US Bureau of Economic Analysis and the 1987 NMES. RESULTS: The lifetime cost per person of first strokes occurring in 1990 is estimated to be $228,030 for SAH, $123,565 for ICH, $90,981 for ISC, and $103,576 averaged across all stroke sub-types. Indirect costs accounted for 58.0% of lifetime costs. Aggregate lifetime cost associated with an estimated 392,344 first strokes in 1990 was $40.6 billion: $5.6 billion for SAH, $6.0 billion for ICH, and $29.0 billion for ISC. Acute-care costs incurred in the 2 years following a first stroke accounted for 45.0%, long-term ambulatory care accounted for 35.0%, and nursing home costs accounted for 17.5% of aggregate lifetime costs of stroke. CONCLUSIONS: The lifetime cost of stroke varies considerably by type of stroke and entails considerable costs beyond the first 2 years after a stroke.


Subject(s)
Cerebrovascular Disorders/therapy , Health Care Costs , Adolescent , Adult , Aged , Aged, 80 and over , Cerebrovascular Disorders/economics , Cerebrovascular Disorders/epidemiology , Child , Child, Preschool , Epidemiologic Methods , Female , Humans , Infant , Infant, Newborn , Male , Middle Aged , Sensitivity and Specificity , United States/epidemiology
20.
Appl Opt ; 35(12): 2069-82, 1996 Apr 20.
Article in English | MEDLINE | ID: mdl-21085336

ABSTRACT

We emphasize two points: (l) the properties and mechanisms of very low-fluence ablation of copper surfaces and (2) the sensitivity and selectivity of resonant laser ablation (RLA). We present results for ablation of bulk copper and copper thin films; spot-size effects; the effects of surface-sample preparation and beam polarization; and an accurate measurement of material removal rates, typically ≤ 10(-3) Å at 35 mJ/cm(2). Velocity distributions were Maxwellian, with peak velocities ≈ 1-2 × 10(5) cm/s. In addition, we discuss the production of diffractionlike surface features, and the probable participation of nonthermal desorption mechanisms. RLA is shown to be a sensitive and useful diagnostic for studies of low-fluence laser-material interactions.

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