Carbon-oxygen surface formation enhances secondary electron yield in Cu, Ag and Au.

First-principles calculations coupled with Monte Carlo simulations are used to probe the role of a surface CO monolayer formation on secondary electron emission (SEE) from Cu, Ag, and Au (110) materials. It is shown that formation of such a layer increases the secondary electron emission in all systems. Analysis of calculated total density of states (TDOS) in Cu, Ag, and Au, and partial density of states (PDOS) of C and O confirm the formation of a covalent type bonding between C and O atoms. It is shown that such a bond modifies the TDOS and extended it to lower energies, which is then responsible for an increase in the probability density of secondary electron generation. Furthermore, a reduction in inelastic mean free path is predicted for all systems. Our predicted results for the secondary electron yield (SEY) compare very favorably with experimental data in all three materials, and exhibit increases in SEY. This is seen to occur despite increases in the work function for Cu, Ag, and Au. The present analysis can be extended to other absorbates and gas atoms at the surface, and such analyses will be present elsewhere.

Epignatus con extensión intracraneana: autopsia, reporte de un caso, y revisión bibliográfica / Epignatus with intracranial extension: autopsy, case report, and literature review

Metodología y descripción: se reporta el caso de una paciente de 31 años de edad, primigesta, que consulta a las 20 semanas por hallazgo ecográfico de tumoración orofaríngea fetalAutopsia y resultados: se obtuvo un feto femenino de 950 grs con teratoma maduro de 10x6x5 cm que protruye a través de la boca. Discusión: en la actualidad, se aplica el término epignatus a cualquier teratoma de la cavidad orofaríngea sin especificar el sitio de origen. La pesquisa es por ecografía(3) pero es necesaria una resonancia obstétrica para descartar algunos diagnósticos diferenciales (meningo encefalocele, neuroblastoma, glioma nasal, teratoma cervical) y malformaciones en otras localizaciones que puedan asociarse(2). Pueden tener un crecimiento unidireccional o bidireccional. La mayoría de las publicaciones de epignatus con tumor intracraneano se limitan a reportes de casos. Conclusión: actualmente, el tratamiento quirúrgico agresivo del epignatus con extensión intracraneana no está recomendado. Creemos que correlacionando los estudios pre-natales con los hallazgos post-natales, se podría establecer una clasificación que determine la viabilidad fetal y los casos que serían candidatos a beneficiarse con un tratamiento quirúrgico.

Enfermedad de Graves en niños: presentación clínica y respuesta al tratamiento / Graves' disease in childs

Se incluyeron 14 niños entre 1991 y 2000 con enfermedad de Graves para evaluar la presentación clínica. En conclusión, la enfermedad de Graves se presenta con mayor frecuencia en las niñas y el propiltiouracilo se puede considerar como una medida terapéutica inicial adecuada

Effects of stimulus intensity and duration on posterior tibial nerve somatosensory-evoked potential patterns obtained under anesthesia.

STUDY DESIGN: This study analyzed systematic changes in stimulus intensity and duration on the latencies and amplitudes of somatosensory-evoked potential peaks obtained upon posterior tibial nerve stimulation of orthopedic patients under anesthesia. OBJECTIVES: To examine the effects of systematic stimulus changes on somatosensory-evoked potential patterns and to compare the sensitivity of different peaks. SUMMARY OF BACKGROUND DATA: Previous studies primarily examined the effects of either stimulus intensity or stimulus duration but not their interactions. METHODS: Nine orthopedic patients were tested using three stimulus intensities and three stimulus durations. Five peak latencies and four amplitudes were measured. Data consisted of frequency of peak occurrences under each condition and analyses of variances of peak latencies and amplitudes. RESULTS: Three latencies yielded stable findings (P40, N50, P60). Peak latencies under anesthesia were not affected by stimulus intensity or duration. Amplitudes, however, were affected differentially. P40-N50 increased with increases in stimulus intensity or stimulus duration, but no significant interaction effects were found. N50-P60 showed no significant changes associated with stimulus intensity or duration. CONCLUSION: Under combined isoflurane/nitrous oxide anesthesia, somatosensory-evoked potential patterns obtained upon stimulation of the posterior tibial nerves showed no significant changes in major peak latencies with changes in stimulus intensity or duration. However, changes in amplitude were found. Stimulus intensity-duration interaction effects were observed, described, and interpreted.

[Use of freeze-fracturing to observe the ultrastructure of Candida albicans with scanning electron microscopy]. / Uso de criofractura para observación de la ultraestructura en Candida albicans con microscopía electrónica de barrido.

The development of the techniques of sample preparation for the observation of ultrastructure with scanning electron microscopy (SEM) include, among others, the method O-D-O reported by Tanaka and Naguro in 1981, based on the initial fixing of the specimen (eukaryotic tissue) in 1% OsO4; treatment with dimethyl sulphoxide (DMSO) as a cryoprotectant, followed by cryofracture, removal of cytoplasmatic matrix by psot-fixing with 1% OsO4 and a further conductive stain. In this paper we report the application of the method O-D-O in a culture of Candida albicans modifying the pre-fixing carried out overnight and excepting the osmic maceration, in order to observe the cell ultrastructure of this eukaryotic microorganism with SEM at a normal resolution. Through the tridimensional images obtained, in which we can observe the fracture of Candida albicans without cytoplasmatic matrix but with details of a normal and deformed cell wall, as well as cells conserving their cytoplasmatic matrix where globose and filamentous structures become evident and suggest a pattern of organization and cells with a very clear character of what we believe is the nuclear zone of the microorganism, we night conclude that our method is suitable for eukaryotic unicellular organisms in order to observe the cell ultrastructure with SEM at normal resolution and show images comparable with those reported with SEM at high resolution, contributing to the development of the ultrastructural cytology, traditionally restricted to the transmission electron microscopy (TEM). These findings reveal an additional aid which will allow to obtain a clearer aspect of the complex cell structure of unicellular organisms.

Somatosensory evoked potential peak latencies and amplitudes in contralateral and ipsilateral hemispheres in normal and severely traumatized brain-injured subjects.

The purpose of this study was to compare in normal and traumatic brain injury (TBI) subjects long latency cortical brain-evoked potential patterns obtained upon stimulation of the median nerves. Quantitative data were analysed involving nine peak latencies and eight amplitudes obtained simultaneously contralaterally and ipsilaterally. Left-right hemispheric differences were also analysed. The following was found: TBI latencies were significantly longer for five of nine peaks (N30, P40, N60, P185, P285). TBI amplitudes were significantly smaller for two of eight amplitudes (P185-N240 and N240-P285). A significant contralateral-ipsilateral latency difference occurred only at P40 where latencies in the contralateral hemisphere are shorter for both normals and TBIs. Significant contralateral-ipsilateral amplitude differences occurred in the four early amplitudes (N30-P40, P40-N60, N60-P105, P105-N140) with amplitudes being smaller on the ipsilateral side. A differential effect, however, was found for amplitudes N30-P40 and P40-N60 where the difference is significantly larger in the contralateral hemisphere for normals but not for TBIs. This suggests that contralateral-ipsilateral amplitude difference can be a marker of extent and severity of injury and may also be helpful in localizing site of injury, particularly interhemispheric or corpus callosal injury. The differential latency and amplitude responses for later peaks occurring in the P300 region suggest sensitivity to detecting impairments in pre-cognitive and early cognitive activities.

Effects of stimulus intensity on posterior tibial nerve somatosensory evoked potentials.

Relationships between stimulus intensity and peak latencies and amplitudes in posterior tibial nerve somatosensory evoked potential patterns were evaluated in ten healthy subjects. Eight intermediate latency peaks between 30 and 125 milliseconds (ms) after stimulus onset and seven amplitudes were analyzed. In general, there was a decrease in latency with each increase in stimulus intensity over a five step intensity range between 5 and 19 milliamps (mA) for most peaks. Similarly, increases in amplitudes generally occurred with increases in stimulus intensity for most peaks. Later peaks N105 and P115 as well as amplitudes P90-N105 and N105-P115 were least sensitive to stimulus intensity changes. The greatest changes in peak latency and amplitude occurred as stimulus intensity was increased from 7 to 11 mA. Beyond 11 mA relatively little change was observed in either peak latencies or amplitudes. Under anesthesia, by contrast, there was no stimulus intensity-peak latency interaction and beyond 11 mA there were decreases in amplitudes. Possible reasons for these findings are discussed.

Effects of anesthesia and stimulus intensity on posterior tibial nerve somatosensory evoked potentials.

Under anesthesia peak latencies occurring up to 75 milliseconds after stimulus onset upon somatosensory evoked potential testing of the somatosensory evoked potential testing of the posterior tibial nerve were not affected by stimulus intensity (between 5 and 19 ma) or by length of time under isoflurane and nitrous oxide up to over 2 hours. When pre- and postoperative tests on patients who were not under anesthesia were compared with results under anesthesia, no significant latency differences were found in relation to stimulus intensity for peaks N30, P40 and N50. For peaks P60 and N75, however, significantly increased latencies were seen during anesthesia, more pronounced and consistent for N75. Amplitudes, however, were affected by both stimulus intensity and anesthesia duration. A curvilinear relationship was found during early anesthesia. Maximum amplitudes were found at 7 or 11 ma stimulus intensity levels, depending upon which peak was analyzed, with lesser amplitudes occurring at both lower and higher stimulus intensity levels. Stimulus intensity and anesthesia interacted such that maximum amplitude occurred, in general, at 11 ma after short duration anesthesia (6') and at 7 ma after long duration anesthesia (125'). Under long duration anesthesia amplitudes were significantly diminished, mostly at the 11 ma intensity level. At 15 and 19 ma intensity levels peak amplitudes remained relatively constant regardless of anesthesia duration and therefore are the intensities to use to monitor changes during prolonged surgeries. When preoperative during prolonged surgeries. When preoperative and postoperative tests were compared to tests under anesthesia, there was a decrease in amplitude under anesthesia, greater for long than short duration anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

[Early stress tests following an uncomplicated myocardial infarct: a comparison between symptom-limited and submaximal tests]. / Las pruebas de esfuerzo tempranas postinfarto miocárdico no complicado: comparación entre limitadas por síntomas y submaximas.

To compare the diagnostic and prognostic usefulness of symptom-limited versus load-limited submaximal stress testing, 76 patients, during the first week post acute non-complicated myocardial infarction, were submitted to a symptom-limited Naughton-modified protocol stress test. At 2 METs, 3 METs and maximal effort levels, the tests were classified as positive or negative following the currently used criteria. After a mean follow-up of 15 months, the symptom-limited protocol showed the best sensitivity (95%), specificity (78%), positive (64%) and negative (98%) predictive value, and also the highest risk ratio (27.4) for prediction of subsequent coronary events (2p less than 0.01 vs 2 METs, 3 METs and 2D-Echocardiogram results). Forward stepped multiple correlation analysis indicated independent prognostic value for the results of the symptom-limited stress test (R2: .52 p less than 0.01) and for the location of the myocardial infarction (R2: .05 p less than 0.05) only. In addition, the discriminant prognostic power of the symptom-limited protocol was significant after the fourth month of follow-up (2p less than 0.05 vs submaximal tests and 2D-Echo). Therefore, we recommend the performance of a symptom-limited stress test during the first week post acute non-complicated myocardial infarction, provided that all coronary active medication has been withheld 24 hours before the test.

[Cardiac myxoma, diagnostic methods and curative surgery. Report of 5 cases]. / Mixoma cardiaco, metodos diagnósticos y cirugía curativa. Informe de 5 casos.

We report five patients with Myxomas of the left atrium studied by catheterization and/or Echocardiography between november 1976 and october 1978. Four patients were operated immediately with extracorporeal circulation which confirmed the diagnosis. The last patient died before surgical intervention due to a severe hepatorenal syndrome and extensive pulmonary infection. Another patient died postoperatively on the second day due to irreversible pulmonary hypertensión. The remaining three patients are asymptomatic (average 28 months after surgery). Reviewing the diagnostic methods, particularly the Echocardiogram, we found that it is a good diagnostic tool, making catheterization with the risks of myxomatous embolization unnecessary. Furthermore, the Echo facilitates simple and economic observation for the detection of relapses. Finally, broad and careful surgical management most be emphasized in order to avoid transoperative emboli, tumoral dissemination, and latent relapses, mediated by the greater use of filters and a broad resection of the implantation pedicule.

[Elective permanent exteriorization of cardiac pacemakers]. / Exteriorezacion permanente electiva de marcapasos cardíacos.

Three clinical cases are reported in which the authors decided for the permanent exteriorization of a cardiac pacemaker. The decision was based in that many previous surgical procedures had been performed and the possibilities of new approaches were exhausted or that the soft tissues were not in a satisfactory condition to support a new pacemaker. Considerations are made of the indications of this procedure, of the absence of previous reports in the literature, and the possibilities of long term follow-up morbidity. Emphasis is made in the necessity of thoroughly explaining the patients and their relatives of the risks involved, and not to overindicate the procedure if other possibilities have not been exhausted.

Exteriorizacion permanente electiva de marcapasos cardiacos. / Elective permanent exteriorization of cardiac pacemakers

Se informan tres casos clinicos en los cuales se opto por la exteriorizacion permanente del generador de un marcapaso cardiaco, considerando que se habian hecho demasiados procedimientos quirurgicos, que se habian agotado las posibilidades de nuevas vias de abordaje, o que no existian tejidos blandos satisfactorios para soportar una nueva bolsa para el generador. Se presentan consideraciones respecto a las indicaciones del procedimiento, a la ausencia de precedentes informados en la literatura y a las posibilidades de morbilidad a largo plazo que dicho procedimiento implica, haciendo enfasis en la necesidad de presentarlo adecuadamente al paciente y sus familiares y en no sobreindicar el recurso si no se han agotado otras posibilidades de resolver el problema

[Is closed mitral commissurotomy still indicated? Patient selection and postoperative problems. Analysis of 221 cases]. / Aún está indicada la comisurotomía mitral cerrada? Selección de pacientes y problemas transoperatorios. Análisis de 221 casos.

Indications, findings, complications, and immediate results in 221 patients in whom a closed mitral commissurotomy was practiced are presented. Emphasis is placed on the rigidity of the clinical criteria to select these patients with the object of diminishing to a minimum the accidents or problems and unexpected findings. The results are considered satisfactory and comparable to those reported in other great centers. Finally we considered that the results obtained with this criteria for selection were very satisfactory, with reduction of the immediate mortality to 0% in comparison with others reported, and maintaining an index of complications which we consider minimum in its clinical repercussion to the patient and less than in other series.