Non-Linear Electronic Effects in Cluster-Solid Interactions

A review will be given of the effects of non- additivity under impacts of clusters, observed only in a variety of electronic energy loss phenomena. They include electron emission, luminescence, projectile charge state formation, electron-hole pairs generation causing the surface barrier detector response and the high-energy part of the secondary ion emission under cluster impacts. The sublinear effects consist in decreasing the yields per one incident atom with increasing number of cluster constituents at the same velocity. The ratio of the yields R_n = Y_n/nY_1, being the measure of the effect, is less than 1 and usually decreases with increasing projectile velocity, and the number of atoms in the cluster n. The reduction is caused by the mechanism of sweeping - out - electrons, that removes some electrons from the cluster trek in binary collisions between the front running cluster atoms and the target atoms, leaving fewer available for the tailing ones

Utilidad del índice de Flint como predictor de complicaciones postoperatorias en trauma de colon. Hospital Central Universitario Dr. Antonio María Pineda

In order to determine the usefulness of the Flint Index as a predictor of postoperative complications in colon trauma in patients admitted to the Servicio de Cirugía General of the Hospital Universitario Dr. Antonio María Pineda, we conducted a cross-sectional descriptive study with 77 patients with an average age of 28.2 ± 10.8 years and predominance of male sex (98.7%). The most frequent mechanism of trauma was by single shot firearm (67.5%); the most affected segment was sigmoid colon (32.4%) and transverse (31.1%); 74% of patients had only one lesion in colon and the most common associated lesions were localized in small intestine (59.7%), liver (19.4%) and kidney (12.9%). According to the severity of trauma, perforation was found in 54.5% of cases, moderate contamination (42.8%), presence of associated lesions (85.7%), discrete hemodynamic situation (59.7%) and delay in treatment of less than 6 hours (45.4%). According to the Flint index, 51.9% of patients had a severity grade III, 40.2% grade II and 7.7% grade I. The treatment was surgical in 88.3% of cases and the most used surgical technique was primary raffia (55.8%), followed by resection/anastomosis (27.9%) and resection/colostomy (25%). In conclusion, the Flint scale is a predictive tool for postoperative complications in patients with colonic trauma.Con el objetivo de determinar la utilidad del índice de Flint como predictor de complicaciones postoperatorias en trauma de colon en pacientes que ingresaron al Servicio de Cirugía General del Hospital Central Universitario Dr. Antonio María Pineda, se realizó un estudio descriptivo transversal que incluyó 77 pacientes cuya edad promedio fue de 28,2 ± 10,8 años con predominio del sexo masculino (98,7%). Los resultados indican que el mecanismo de producción del trauma más frecuente fue por arma de fuego carga única (67,5%); el segmento más afectado fue colon sigmoide (32,4%) y transverso (31,1%); 74% de los pacientes presentaron una única lesión en colon y los órganos con lesiones asociadas más comunes fueron intestino delgado (59,7%), hígado (19,4%) y riñón (12,9%). Se encontró perforación en el 54,5% de los casos, contaminación moderada (42,8%), presencia de lesiones asociadas (85,7%), situación hemodinámica discreta (59,7%) y retardo en el tratamiento < 6 horas (45,4%). Según el índice de Flint, 51,9% de los pacientes mostraron una gravedad grado III, 40,2% grado II y 7,7% grado I. El tratamiento fue quirúrgico en 88,3% de los casos y la técnica quirúrgica más utilizada fue rafia primaria (55,8%), seguida de resección/anastomosis (27,9%) y resección/colostomía (25%). En conclusión, la escala de Flint es una herramienta de predicción para complicaciones postoperatorias en los pacientes con traumatismo de colon

Interaction of highly charged clusters with surface

The purpose of this paper is to draw attention to phenomena occurring on solid surfaces under impact of new kinds of projectiles—slow, very large and highly charged clusters produced in modern electrospray ionization sources. It is known that slow highly charged atomic ions, for instance Xe^(+44), approaching a non-metal surface cause sputtering, erosion and create craters and blisters via the mechanism of Coulomb explosion following a cascade Auger neutralization, emitting vast amounts of secondary electrons. The same mechanism should create analogous nano-features on a non-metal surface under impacts of clusters containing up to 10^8–10^9 molecules with a mass of up to 10^9–10^(10) amu and a diameter as large as 10^3 nm, their charge reaching several 10^3 e, albeit the charge-to-mass ratio would not exceed 10^(−7)–10^(−6) e amu^(−1). When accelerated using a voltage of up to 10^4 V, the clusters can acquire a kinetic energy of 10^4 keV, but a very slow velocity, less than 5×10^4 cm s^(−1), which corresponds to about 10^(−2) eV atom^(−1), well below the threshold of kinetic electron emission. The conditions are favorable for Auger neutralization-induced potential electron emission. The estimates, inevitably approximate in the absence of any experimental data, predict that the diameter of the craters could be around 10 nm, the number of sputtered atoms could be as large as 10^5 atoms per cluster and the yield of ejected electrons could reach up to several thousand electrons per cluster. These numbers show that both experimental studies of the phenomena and a search for their possible applications are worth performing

Interaction of highly charged clusters with surface

The purpose of this paper is to draw attention to phenomena occurring on solid surfaces under impact of new kinds of projectiles—slow, very large and highly charged clusters produced in modern electrospray ionization sources. It is known that slow highly charged atomic ions, for instance Xe+44, approaching a non-metal surface cause sputtering, erosion and create craters and blisters via the mechanism of Coulomb explosion following a cascade Auger neutralization, emitting vast amounts of secondary electrons. The same mechanism should create analogous nano-features on a non-metal surface under impacts of clusters containing up to 108–109 molecules with a mass of up to 109–1010 amu and a diameter as large as 103 nm, their charge reaching several 103 e, albeit the charge-to-mass ratio would not exceed 10−7–10−6 e amu−1. When accelerated using a voltage of up to 104 V, the clusters can acquire a kinetic energy of 104 keV, but a very slow velocity, less than 5×104 cm s−1, which corresponds to about 10−2 eV atom−1, well below the threshold of kinetic electron emission. The conditions are favorable for Auger neutralization-induced potential electron emission. The estimates, inevitably approximate in the absence of any experimental data, predict that the diameter of the craters could be around 10 nm, the number of sputtered atoms could be as large as 105 atoms per cluster and the yield of ejected electrons could reach up to several thousand electrons per cluster. These numbers show that both experimental studies of the phenomena and a search for their possible applications are worth performing.</jats:p