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3.
J Hum Evol ; 158: 103048, 2021 09.
Artículo en Inglés | MEDLINE | ID: mdl-34340120

RESUMEN

Homo naledi fossils from the Rising Star cave system provide important insights into the diversity of hand morphology within the genus Homo. Notably, the pollical (thumb) metacarpal (Mc1) displays an unusual suite of characteristics including a median longitudinal crest, a narrow proximal base, and broad flaring intrinsic muscle flanges. The present study evaluates the affinities of H. naledi Mc1 morphology via 3D geometric morphometric analysis of shaft shape using a broader comparative sample (n = 337) of fossil hominins, recent humans, apes, and cercopithecoid monkeys than in prior work. Results confirm that the H. naledi Mc1 is distinctive from most other hominins in being narrow at the proximal end but surmounted by flaring muscle flanges distally. Only StW 418 (Australopithecus cf. africanus) is similar in these aspects of shape. The gracile proximal shaft is most similar to cercopithecoids, Pan, Pongo, Australopithecus afarensis, and Australopithecus sediba, suggesting that H. naledi retains the condition primitive for the genus Homo. In contrast, Neandertal Mc1s are characterized by wide proximal bases and shafts, pinched midshafts, and broad distal flanges, while those of recent humans generally have straight shafts, less robust muscle flanges, and wide proximal shafts/bases. Although uncertainties remain regarding character polarity, the morphology of the H. naledi thumb might be interpreted as a retained intermediate state in a transformation series between the overall gracility of the shaft and the robust shafts of later hominins. Such a model suggests that the addition of broad medial and lateral muscle flanges to a primitively slender shaft was the first modification in transforming the Mc1 into the overall more robust structure exhibited by other Homo taxa including Neandertals and recent Homo sapiens in whose shared lineage the bases and proximal shafts became expanded, possibly as an adaptation to the repeated recruitment of powerful intrinsic pollical muscles.


Asunto(s)
Fósiles , Hominidae/anatomía & histología , Huesos del Metacarpo/anatomía & histología , Animales , Evolución Biológica , Cuevas , Haplorrinos/anatomía & histología , Humanos , Hombre de Neandertal/anatomía & histología
4.
Res Pract Thromb Haemost ; 4(1): 154-160, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31989097

RESUMEN

INTRODUCTION: Previous research from the United Kingdom and Spain has identified several areas of unmet clinical and support need for cancer patients diagnosed with venous thromboembolism. It is not known whether such experiences are restricted to those countries health care systems and culture. We therefore evaluated patients' experience of cancer-associated thrombosis (CAT) within a Canadian setting. METHODS: Purposive sampling of patients with CAT attending a regional thrombosis clinic in Vancouver was undertaken. Semistructured interviews were audio recorded, transcribed, and coded using NVivo software. A deductive approach was taken by applying the framework matrix from the original study to these data on a case-by-case basis. RESULTS: Twenty patients (10 male, 10 female) aged 39 to 74 (mean, 63) representing a breadth of different cancers participated. Commonalities between the UK and Canadian patients included the traumatic nature of experiencing CAT, the need for information, and adaptive behaviors through ritualization. Two new themes were identified: (1) Patients with incidental pulmonary emboli (iPE) were usually telephoned about their thrombus with little support and suboptimal communication; and (2) cost implications of accessing low-molecular-weight heparin varied according to insurance cover. Patients were sometimes converted to warfarin for financial reasons. CONCLUSION: The distress associated with CAT is a common experience across different populations but may be ameliorated by early access to specialist services, information, and support. The current process for managing iPE could be improved with better communication and a dedicated clinical pathway. Funding issues may influence choice of anticoagulant.

5.
J Hum Evol ; 123: 84-95, 2018 10.
Artículo en Inglés | MEDLINE | ID: mdl-30057326

RESUMEN

The rate of change in primate mandibular symphyseal angles was modeled with particular aim of locating a rate-shift within the hominin clade. Prior work noted that the human symphyseal angle must have experienced a rapid rate of change in order to assume the modern human form, suggestive of the non-random work of natural selection. This study indicates that the rate of symphyseal evolution rose dramatically between Australopithecus anamensis and Australopithecus afarensis and continued throughout the diversification of the hominin clade. Noting the timing of this event, we speculate as to what ecological factors could have been at play in driving this rearrangement of the anterior mandible, contributing to the eventual appearance of the human chin.


Asunto(s)
Evolución Biológica , Fósiles/anatomía & histología , Hominidae/anatomía & histología , Mandíbula/anatomía & histología , Animales , Humanos
6.
J Hum Evol ; 104: 124-135, 2017 03.
Artículo en Inglés | MEDLINE | ID: mdl-27836166

RESUMEN

The discovery of Homo naledi has expanded the range of phenotypic variation in Homo, leading to new questions surrounding the mosaic nature of morphological evolution. Though currently undated, its unique morphological pattern and possible phylogenetic relationships to other hominin taxa suggest a complex evolutionary scenario. Here, we perform geometric morphometric analyses on H. naledi cranial and mandibular remains to investigate its morphological relationship with species of Homo and Australopithecus. We use Generalized Procrustes analysis to place H. naledi within the pattern of known hominin skull diversity, distributions of Procrustes distances among individuals to compare H. naledi and Homo erectus, and neighbor joining trees to investigate the potential phenetic relationships between groups. Our goal is to address a set of hypotheses relating to the uniqueness of H. naledi, its affinity with H. erectus, and the age of the fossils based on skull morphology. Our results indicate that, cranially, H. naledi aligns with members of the genus Homo, with closest affiliations to H. erectus. The mandibular results are less clear; H. naledi closely associates with a number of taxa, including some australopiths. However, results also show that although H. naledi shares similarities with H. erectus, some distances from this taxon - especially small-brained members of this taxon - are extreme. The neighbor joining trees place H. naledi firmly within Homo. The trees based on cranial morphology again indicate a close relationship between H. naledi and H. erectus, whereas the mandibular tree places H. naledi closer to basal Homo, suggesting a deeper antiquity. Altogether, these results emphasize the unique combination of features (H. erectus-like cranium, less derived mandible) defining H. naledi. Our results also highlight the variability within Homo, calling for a greater focus on the cause of this variability, and emphasizing the importance of using the total morphological package for species diagnoses.


Asunto(s)
Fósiles/anatomía & histología , Hominidae/anatomía & histología , Mandíbula/anatomía & histología , Filogenia , Cráneo/anatomía & histología , Animales , Evolución Biológica , Sudáfrica
7.
J Hum Evol ; 104: 100-123, 2017 03.
Artículo en Inglés | MEDLINE | ID: mdl-27855982

RESUMEN

The species Homo naledi was recently named from specimens recovered from the Dinaledi Chamber of the Rising Star cave system in South Africa. This large skeletal sample lacks associated faunal material and currently does not have a known chronological context. In this paper, we present comprehensive descriptions and metric comparisons of the recovered cranial and mandibular material. We describe 41 elements attributed to Dinaledi Hominin (DH1-DH5) individuals and paratype U.W. 101-377, and 32 additional cranial fragments. The H. naledi material was compared to Plio-Pleistocene fossil hominins using qualitative and quantitative analyses including over 100 linear measurements and ratios. We find that the Dinaledi cranial sample represents an anatomically homogeneous population that expands the range of morphological variation attributable to the genus Homo. Despite a relatively small cranial capacity that is within the range of australopiths and a few specimens of early Homo, H. naledi shares cranial characters with species across the genus Homo, including Homo habilis, Homo rudolfensis, Homo erectus, and Middle Pleistocene Homo. These include aspects of cranial form, facial morphology, and mandibular anatomy. However, the skull of H. naledi is readily distinguishable from existing species of Homo in both qualitative and quantitative assessments. Since H. naledi is currently undated, we discuss the evolutionary implications of its cranial morphology in a range of chronological frameworks. Finally, we designate a sixth Dinaledi Hominin (DH6) individual based on a juvenile mandible.


Asunto(s)
Fósiles/anatomía & histología , Hominidae/anatomía & histología , Mandíbula/anatomía & histología , Cráneo/anatomía & histología , Animales , Evolución Biológica , Sudáfrica
8.
J Hum Evol ; 97: 17-26, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-27457542

RESUMEN

Homo naledi is a recently discovered species of fossil hominin from South Africa. A considerable amount is already known about H. naledi but some important questions remain unanswered. Here we report a study that addressed two of them: "Where does H. naledi fit in the hominin evolutionary tree?" and "How old is it?" We used a large supermatrix of craniodental characters for both early and late hominin species and Bayesian phylogenetic techniques to carry out three analyses. First, we performed a dated Bayesian analysis to generate estimates of the evolutionary relationships of fossil hominins including H. naledi. Then we employed Bayes factor tests to compare the strength of support for hypotheses about the relationships of H. naledi suggested by the best-estimate trees. Lastly, we carried out a resampling analysis to assess the accuracy of the age estimate for H. naledi yielded by the dated Bayesian analysis. The analyses strongly supported the hypothesis that H. naledi forms a clade with the other Homo species and Australopithecus sediba. The analyses were more ambiguous regarding the position of H. naledi within the (Homo, Au. sediba) clade. A number of hypotheses were rejected, but several others were not. Based on the available craniodental data, Homo antecessor, Asian Homo erectus, Homo habilis, Homo floresiensis, Homo sapiens, and Au. sediba could all be the sister taxon of H. naledi. According to the dated Bayesian analysis, the most likely age for H. naledi is 912 ka. This age estimate was supported by the resampling analysis. Our findings have a number of implications. Most notably, they support the assignment of the new specimens to Homo, cast doubt on the claim that H. naledi is simply a variant of H. erectus, and suggest H. naledi is younger than has been previously proposed.


Asunto(s)
Fósiles/anatomía & histología , Hominidae/anatomía & histología , Hominidae/clasificación , Filogenia , Animales , Teorema de Bayes , Evolución Biológica
9.
Am J Phys Anthropol ; 161(2): 226-36, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27346254

RESUMEN

OBJECTIVES: The curve of Spee (COS) is a mesio-distally curved alignment of the canine through distal molar cusp tips in certain mammals including modern humans and some fossil hominins. In humans, the alignment varies from concave to flat, and previous studies have suggested that this difference reflects craniofacial morphology, including the degree of alveolar prognathism. However, the relationship between prognathism and concavity of the COS has not been tested in craniofacially variant populations. We tested the hypothesis that greater alveolar prognathism covaries with a flatter COS in African-American and European-American populations. We further examined this relationship in fossil Homo including Homo neanderthalensis and early anatomically modern Homo sapiens, which are expected to extend the amount of variation in the COS from the extant sample. METHODS AND MATERIALS: These hypotheses were tested using three-dimensional geometric morphometrics. Landmarks were recorded from the skulls of 166 African-Americans, 123 European-Americans, and 10 fossil hominin mandible casts. Landmarks were subjected to generalized Procrustes analysis, principal components analysis, and two-block partial least squares analysis. RESULTS: We documented covariation between the COS and alveolar prognathism such that relatively prognathic individuals have a flatter COS. Mandibular data from the fossil hominin taxa generally confirm and extend this correlation across a greater range of facial size and morphology in Homo. DISCUSSION: Our results suggest that the magnitude of the COS is related to a suite of features associated with alveolar prognathism in modern humans and across anthropoids. We also discuss the implications for spatial interactions between the dental arches.


Asunto(s)
Diente Canino/anatomía & histología , Hominidae/anatomía & histología , Mandíbula/anatomía & histología , Hombre de Neandertal/anatomía & histología , Animales , Antropología Física , Evolución Biológica , Fósiles , Humanos
11.
Elife ; 42015 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-26354291

RESUMEN

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.


Asunto(s)
Hominidae/anatomía & histología , Hominidae/clasificación , Animales , Antropometría , Humanos , Filogenia , Sudáfrica
12.
Rev Sci Instrum ; 85(2): 023701, 2014 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-24593365

RESUMEN

A novel sample mount design with integrated fiducial marks and software for assisting operators in easily and efficiently locating points of interest established in previous analytical sessions is described. The sample holder and software were evaluated with experiments to demonstrate the utility and ease of finding the same points of interest in two different microscopy instruments. Also, numerical analysis of expected errors in determining the same position with errors unbiased by a human operator was performed. Based on the results, issues related to acquiring reproducibility and best practices for using the sample mount and software were identified. Overall, the sample mount methodology allows data to be efficiently and easily collected on different instruments for the same sample location.

13.
Anxiety Stress Coping ; 27(1): 38-54, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-23799773

RESUMEN

Although single-session individual debriefing is contraindicated, the efficacy of group psychological debriefing remains unresolved. We conducted the first randomized controlled trial of critical incident stress debriefing (CISD) with emergency workers (67 volunteer fire-fighters) following shared exposure to an occupational potentially traumatic event (PTE). The goals of group CISD are to prevent post-traumatic stress and promote return to normal functioning following a PTE. To assess both goals we measured four outcomes, before and after the intervention: post-traumatic stress, psychological distress, quality of life, and alcohol use. Fire brigades were randomly assigned to one of three treatment conditions: (1) CISD, (2) Screening (i.e., no-treatment), or (3) stress management Education. Controlling for pre-intervention scores, CISD was associated with significantly less alcohol use post-intervention relative to Screening, and significantly greater post-intervention quality of life relative to Education. There were no significant effects on post-traumatic stress or psychological distress. Overall, CISD may benefit broader functioning following exposure to work-related PTEs. Future research should focus on individual, group, and organizational factors and processes that can promote recovery from operational stressors. Ultimately, an occupational health (rather than victim-based) approach will provide the best framework for understanding and combating potential threats to the health and well-being of workers at high risk for PTE exposure.


Asunto(s)
Intervención en la Crisis (Psiquiatría) , Socorristas/psicología , Bomberos/psicología , Acontecimientos que Cambian la Vida , Enfermedades Profesionales/terapia , Psicoterapia de Grupo , Trastornos por Estrés Postraumático/terapia , Adaptación Psicológica , Adulto , Consumo de Bebidas Alcohólicas/psicología , Australia , Medicina Basada en la Evidencia , Femenino , Estudios de Seguimiento , Procesos de Grupo , Humanos , Masculino , Tamizaje Masivo/psicología , Persona de Mediana Edad , Enfermedades Profesionales/diagnóstico , Enfermedades Profesionales/psicología , Trastornos por Estrés Postraumático/diagnóstico , Trastornos por Estrés Postraumático/psicología , Encuestas y Cuestionarios
14.
Crit Care Med ; 41(8): 2002-7, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23863231

RESUMEN

OBJECTIVES: To assess the feasibility and reliability of systematic evaluations of analgesia, sedation level, and delirium features in the neurologically critically ill and to determine whether delirium features are linked to clinical outcomes in this population. DESIGN: Multicentered prospective observational study. SETTING: Neurological, Neurosurgical, Neurosciences or Surgical Trauma ICUs from three hospitals (two in Canada and one in the United States). PATIENTS: A convenience sample of adult NICU or neurologic, neurosurgical, neurosciences, or surgical trauma ICU patients admitted for greater than 12 hours from November 2011 to April 2012. INTERVENTIONS: Systematic assessments were simultaneously and independently performed by a neurologist, intensivists, or trauma surgeon, and a nurse in three multispecialty ICUs. Pain was evaluated with the numeric rating scale or behavioral pain scale. Sedation was assessed using the Richmond Agitation-Sedation Scale. Patients with Richmond Agitation-Sedation Scale greater than or equal to -4 were screened for features of delirium with the Intensive Care Delirium Screening Checklist. Intraclass correlation coefficient was used to evaluate inter-rater reliability between the nurse and the physician for pain and sedation scales, and the kappa coefficient was calculated for concordance of the Intensive Care Delirium Screening Checklist items. MEASUREMENTS AND MAIN RESULTS: 151 patients had 439 assessments. Pain and sedation were always assessable with excellent inter-rater reliability (numeric rating scale intraclass correlation coefficient, 0.92; behavior pain scale intraclass correlation coefficient, 0.83; and Richmond Agitation-Sedation Scale intraclass correlation coefficient, 0.92). Patients were sufficiently alert for delirium screening 3/4 of the time; Intensive Care Delirium Screening Checklist items had good concordance (kappa coefficients between 0.58 and 0.91 for the eight Intensive Care Delirium Screening Checklist items). Nonevaluable items were most often orientation, hallucinations, and speech or mood content. Furthermore, each additional Intensive Care Delirium Screening Checklist item present in proportion to the total evaluable Intensive Care Delirium Screening Checklist score was associated with a 10% increase in ICU length of stay. CONCLUSIONS: Pain and sedation can be systematically assessed in the neurologically critically ill; the majority can also be screened for delirium features with excellent inter-rater reliability. Increased proportion of Intensive Care Delirium Screening Checklist items is associated with worse outcomes.


Asunto(s)
Sedación Consciente , Cuidados Críticos/normas , Enfermedad Crítica , Delirio/diagnóstico , Dimensión del Dolor/métodos , Agitación Psicomotora , Estudios de Factibilidad , Femenino , Humanos , Unidades de Cuidados Intensivos , Tiempo de Internación , Masculino , Persona de Mediana Edad , Pautas de la Práctica en Medicina/estadística & datos numéricos , Estudios Prospectivos , Reproducibilidad de los Resultados , Encuestas y Cuestionarios
15.
Appl Opt ; 51(7): B155-64, 2012 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-22410914

RESUMEN

Automated interpretation of laser-induced breakdown spectroscopy (LIBS) data is necessary due to the plethora of spectra that can be acquired in a relatively short time. However, traditional chemometric and artificial neural network methods that have been employed are not always transparent to a skilled user. A fuzzy logic approach to data interpretation has now been adapted to LIBS spectral interpretation. Fuzzy logic inference rules were developed using methodology that includes data mining methods and operator expertise to differentiate between various copper-containing and stainless steel alloys as well as unknowns. Results using the fuzzy logic inference engine indicate a high degree of confidence in spectral assignment.


Asunto(s)
Lógica Difusa , Rayos Láser , Procesamiento de Señales Asistido por Computador , Análisis Espectral/métodos , Algoritmos , Cobre/análisis , Minería de Datos , Redes Neurales de la Computación , Acero Inoxidable/análisis
16.
Appl Opt ; 51(7): B165-70, 2012 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-22410915

RESUMEN

A Fabry-Perot etalon was coupled to a Czerny-Turner spectrometer to acquire high-resolution measurements in laser-induced breakdown spectroscopy (LIBS). The spectrometer was built using an inexpensive etalon coupled to a standard 0.5 m imaging spectrometer. The Hg emission doublet at 313.2 nm was used to evaluate instrument performance because it has a splitting of 29 pm. The 313.2 nm doublet was chosen due to the similar splitting seen in isotope splitting from uranium at 424.437 nm, which is 25 pm. The Hg doublet was easily resolved from a continuous-source Hg lamp with a 2 s acquisition. The doublet was also resolved in LIBS spectra of cinnabar (HgS) from the accumulation of 600 laser shots at rate of 10 Hz, or 1 min, under a helium atmosphere. In addition to the observed splitting of the 313.2 nm Hg doublet, the FWHM of the 313.1844 nm line from the doublet is reported at varying helium atmospheric pressures. The high performance, low cost, and compact footprint make this system highly competitive with 2 m double-pass Czerny-Turner spectrometers.

17.
Int Arch Allergy Immunol ; 157(3): 259-68, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22042170

RESUMEN

BACKGROUND: Allergic conjunctivitis is characterized by itchy, watery and swollen eyes which occur in response to exposure to seasonal or environmental allergens. The early phase reaction of allergic conjunctivitis is primarily mediated by mast cell degranulation while the late phase reaction is driven by Th2 cells and eosinophils. Prostaglandin D(2) (PGD(2)), released from mast cells, is present in allergic conjunctival tears and may elicit classical allergic responses via interaction with the high-affinity DP2 receptor (chemoattractant receptor-homologous molecule expressed on Th2 cells, CRTh2). Furthermore, antagonism of this receptor is well known to inhibit eosinophil chemotaxis, basophil activation and Th2 cytokine production. PGD(2), therefore, may be involved in both early and late phase reactions in response to allergen challenge. METHODS: Thus, we explored whether our novel and selective DP2 antagonist AM156 would be efficacious in animal models of allergic conjunctivitis. Furthermore, as respiratory syncytial virus (RSV) has been implicated in the pathogenesis of allergic conjunctivitis, we examined the effects of DP2 antagonism in a murine model of RSV ocular infection. RESULTS: Utilizing a guinea pig ovalbumin model and a murine ragweed model we demonstrated that AM156 reduces redness, discharge and swelling in response to allergen challenge. These effects were equal to or greater than those of current clinical treatment options for allergic conjunctivitis including topical corticosteroids and a dual-mechanism antihistamine and decongestant. AM156 significantly reduced RSV-induced ocular inflammation and IL-4 production. CONCLUSION: These results suggest that a topical DP2 antagonist such as AM156 may represent a novel therapeutic for allergic conjunctivitis.


Asunto(s)
Antialérgicos/uso terapéutico , Bencilaminas/uso terapéutico , Conjuntivitis Alérgica/tratamiento farmacológico , Conjuntivitis Viral/tratamiento farmacológico , Receptores Inmunológicos/antagonistas & inhibidores , Receptores de Prostaglandina/antagonistas & inhibidores , Infecciones por Virus Sincitial Respiratorio/tratamiento farmacológico , Administración Tópica , Alérgenos/inmunología , Ambrosia/inmunología , Animales , Conjuntivitis Alérgica/inmunología , Conjuntivitis Alérgica/metabolismo , Conjuntivitis Viral/inmunología , Conjuntivitis Viral/metabolismo , Modelos Animales de Enfermedad , Femenino , Cobayas , Interleucina-4/inmunología , Interleucina-4/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Ovalbúmina/inmunología , Receptores Inmunológicos/inmunología , Receptores de Prostaglandina/inmunología , Infecciones por Virus Sincitial Respiratorio/inmunología , Infecciones por Virus Sincitial Respiratorio/metabolismo
18.
Bioorg Med Chem Lett ; 21(21): 6608-12, 2011 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-21958540

RESUMEN

Biphenylacetic acid (5) was identified through a library screen as an inhibitor of the prostaglandin D(2) receptor DP2 (CRTH2). Optimization for potency and pharmacokinetic properties led to a series of selective CRTH2 antagonists. Compounds demonstrated potency in a human DP2 binding assay and a human whole blood eosinophil shape change assay, as well as good oral bioavailability in rat and dog, and efficacy in a mouse model of allergic rhinitis following oral dosing.


Asunto(s)
Modelos Animales de Enfermedad , Descubrimiento de Drogas , Fenilacetatos/farmacología , Receptores Inmunológicos/antagonistas & inhibidores , Receptores de Prostaglandina/antagonistas & inhibidores , Rinitis Alérgica Perenne/tratamiento farmacológico , Animales , Disponibilidad Biológica , Perros , Ratones , Fenilacetatos/química , Fenilacetatos/farmacocinética , Fenilacetatos/uso terapéutico , Ratas
19.
Anal Chim Acta ; 697(1-2): 38-47, 2011 Jul 04.
Artículo en Inglés | MEDLINE | ID: mdl-21641417

RESUMEN

Recovery of chemical contaminants from fixed surfaces for analysis can be challenging, particularly if it is not possible to acquire a solid sample to be taken to the laboratory. A simple device is described that collects semi-volatile organic compounds from fixed surfaces by creating an enclosed volume over the surface, then generating a modest vacuum. A solid-phase microextraction (SPME) fiber is then inserted into the evacuated volume where it functions to sorb volatilized organic contaminants. The device is based on a syringe modified with a seal that is used to create the vacuum, with a perforable plunger through which the SPME fiber is inserted. The reduced pressure speeds partitioning of the semi-volatile compounds into the gas phase and reduces the boundary layer around the SPME fiber, which enables a fraction of the volatilized organics to partition into the SPME fiber. After sample collection, the SPME fiber is analyzed using conventional gas chromatography/mass spectrometry. The methodology has been used to collect organophosphorus compounds from glass surfaces, to provide a simple test for the functionality of the devices. Thirty minute sampling times (ΔT(vac)) resulted in fractional recovery efficiencies that ranged from 10(-3) to >10(-2), and in absolute terms, collection of low nanograms was demonstrated. Fractional recovery values were positively correlated to the vapor pressure of the compounds being sampled. Fractional recovery also increased with increasing ΔT(vac) and displayed a roughly logarithmic profile, indicating that an operational equilibrium is being approached. Fractional recovery decreased with increasing time between exposure and sampling; however, recordable quantities of the phosphonates could be collected three weeks after exposure.

20.
Anal Bioanal Chem ; 400(10): 3217-27, 2011 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-21553217

RESUMEN

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been shown to enhance LIBS spectra. Several researchers have reported significant increases in signal-to-noise and/or spectral intensity compared to single-pulse (SP) LIBS. In addition to DP-LIBS, atmospheric conditions can also increase sensitivity. Thus, in this study, a collinear DP-LIBS scheme was used along with manipulation of the atmospheric conditions. The DP-LIBS scheme consisted of an initial 45-mJ pulse at 1,064-nm fired into a sample contained in a controlled atmospheric/vacuum chamber. A second analytical 45-mJ pulse at 1,064-nm was then fired 0 to 200 µs after and along the same path of the first pulse. Ar, He, and air at pressures ranging from atmospheric pressure to 1 Torr are introduced during DP-LIBS and SP-LIBS experiments. For a brass sample, significant increases in the spectral intensities of Cu and Zn lines were observed in DP-LIBS under Ar compared to DP-LIBS in air. It was also found that Cu and Zn lines acquired with SP-LIBS in Ar are nearly as intense as DP-LIBS in air. While collinear DP-LIBS is effective for increasing the sensitivity for some reduced atmospheres (i.e., Ar and air at 630 to 100 Torr and He at 300 Torr), the enhanced spectral intensity ultimately dropped off as the pressure was reduced below 10 Torr for all atmospheric compositions in the experimental arrangement used in this study. At all pressures of air and Ar, the plasma temperature remained rather constant with increased inter-pulse delays; however, the plasma temperature was more variable for different He gas pressures and inter-pulse delays.

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