Carboniferous atomodesmids (Mollusca: Bivalvia) from central Patagonia, Argentina Gonzalez, Carlos Roberto; Waterhouse, J. B. A group of bivalves from the Carboniferous rocks of central Patagonia show some resemblances with the Permian family Atomodesmidae. These specimens are known from fragmentary material; some may be in the early stages of the atomodesmids, and kolymiids, and are provisionally assigned to that genus. Four distinct forms are revised; they are Atomodesma amleri n. sp., Aphanaia? sp. indet., Aphanaia precursa n. sp., and Kolymia? sp. indet.

Evaluación de fungicidas curasemillas en garbanzo en Tucumán, R. Argentina de Lisi, Vicente; Gonzalez, Victoria Anahí; Reznikov, Sebastian; Stagnetto, Pablo; Ploper, Leonardo Daniel El garbanzo (Cicer arietinum L.) es una leguminosa invernal cuyo cultivo comenzó a realizarse en la Argentina durante la etapa colonial y que en 2010 ocupó alrededor de 40.000 hectáreas. En 2011 se incrementó a 80.000 hectáreas a nivel nacional de las cuales 25.000 hectáreas se sembraron en Tucumán y zonas de influencia (sudeste de Catamarca y oeste de Santiago del Estero). Uno de los principales problemas sanitarios del cultivo de garbanzo es la enfermedad llamada fusariosis, causada por el hongo Fusarium oxysporum. Desde hace tres campañas agrícolas se viene observando, en la zona de producción de garbanzo de Tucumán y áreas de influencia, la presencia de rodales de plantas marchitas, con elevada incidencia de marchitamiento por Fusarium sp. Una de las alternativas para prevenir la ocurrencia o disminuir la incidencia de esta patología en las primeras etapas del cultivo es el uso de fungicidas curasemillas. El objetivo del presente trabajo fue valorar el efecto de la aplicación de diferentes curasemillas de origen químico, en condiciones controladas y a campo, para mejorar la emergencia radicular de plantas de garbanzo, en lotes que habían mostrado una alta incidencia de marchitamiento por fusariosis en garbanzo. Los resultados mostraron que el uso de curasemillas en el cultivo de garbanzo incrementó el porcentaje de emergencia radicular, lo que se vio reflejado en los ensayos realizados a campo y en condiciones controladas. Se observó un mejor comportamiento de los tratamientos que contenían ingredientes activos del grupo de los bencimidazoles (pero no en todos los casos). En el ensayo a campo, el tratamiento que mejores resultados mostró fue el que combinó Cruiser Plus + Rizocarb 50.

Peculiar anisotropic stationary spherically symmetric solution of Einstein equations Gallo, Emanuel; Moreschi, Osvaldo Mario Motivated by studies on gravitational lenses, we present an exact solution of the field equations of general relativity, which is static and spherically symmetric, has no mass but has a nonvanishing spacelike components of the stressenergymomentum tensor. In spite of its strange nature, this solution has nontrivial descriptions of gravitational effects. We show that the main aspects found in the dark matter phenomena can be satisfactorily described by this geometry. We comment on the relevance it could have to consider nonvanishing spacelike components of the stressenergymomentum tensor ascribed to dark matter. © 2012 World Scientific Publishing Company.

Estimación de la Incidencia de Cáncer de Tiroides en Capital Federal y el Gran Buenos Aires (período 2003-2011) Faure, E. N.; Soutelo, Maria Jimena; Faraj, G.; Lufti, Ruben Julio; Juvenal, Guillermo Juan La incidencia del cáncer de tiroides ha aumentado significativamente en las últimas décadas en el resto del mundo. En Argentina no existe un registro nacional de cáncer por lo que la incidencia del mismo no puede establecerse. Por lo tanto, nuestro objetivo fue estimar la incidencia de cáncer de tiroides en la población de la Ciudad Autónoma de Buenos aires y Gran Buenos Aires así como la relación por género y la histología en el período de 2003 hasta 2011. Asumiendo que la población de afiliados a la Obra Social de la Policía Federal Argentina es representativa de los habitantes de Buenos Aires y el conurbano calculamos que la incidencia es de 6,51 casos/100.000 habitantes/año, con un incremento en 25 años mayor al doble, con predominio del carcinoma papilar frente al folicular.; Thyroid cancer incidence has significantly risen worldwide in the last decades. In Argentina, there is no national cancer registry; therefore its incidence can not be established. The objective of this study was to estimate the incidence of thyroid cancer in the population of Buenos Aires City and suburbs, and the relationship between gender and histology over the period 2003-2011. Assuming that the population affiliated to the Social Security of the Argentine Federal Police is representative of the inhabitants of Buenos Aires City and suburbs, we estimate an incidence of 6.51 cases/100,000 population/year, with an increasing incidence of almost double from 1981-1986 to 2003-2011. An increase in papillary thyroid cancer was mainly responsible for this rising trend. Incidence rates were higher for females (11.76/100,000 women) compared to those for males (2.65/100,000 men). Among men and women of all ages, the highest rate of incidence was for tumor size < 1 cm.Thyroid cancer incidence has significantly risen worldwide in the last decades. In Argentina, there is no national cancer registry; therefore its incidence can not be established. The objective of this study was to estimate the incidence of thyroid cancer in the population of Buenos Aires City and suburbs, and the relationship between gender and histology over the period 2003-2011. Assuming that the population affiliated to the Social Security of the Argentine Federal Police is representative of the inhabitants of Buenos Aires City and suburbs, we estimate an incidence of 6.51 cases/100,000 population/year, with an increasing incidence of almost double from 1981-1986 to 2003-2011. An increase in papillary thyroid cancer was mainly responsible for this rising trend. Incidence rates were higher for females (11.76/100,000 women) compared to those for males (2.65/100,000 men). Among men and women of all ages, the highest rate of incidence was for tumor size < 1 cm.

Amplificación del oncogén Her-2/neu en el carcinoma mamario Cánepa, Mariana Clara; Denninghoff, Valeria Cecilia; Perazzo, Florencia; Paesani, Fernando; Nieto, Silvana; Garcia, Alejandro; Avagnina, Alejandra; Elsner, Boris La determinación del estado de amplificación génica del Her-2/neu es crucial en el cáncer de mama porque permite seleccionar pacientes que se beneficiarían del tratamiento con trastuzumab. El trastuzumab es un anticuerpo monoclonal diseñado específicamente para reconocer y unirse a la proteína HER2. Según trabajos clínicos publicados, reduce un 50% el riesgo de recurrencia del cáncer en estadio temprano (utilizado en adyuvancia durante el lapso de un año)1 y reduce un 20% el riesgo relativo de muerte en pacientes con cáncer de mama metastásico (asociado a quimioterapia vs. quimioterapia solamente)2 . La amplificación del oncogen Her-2/neu determina que cada copia del gen puede ser transcripta y traducida llevando a una sobreproducción de ARNm y de la proteína correspondiente. La célula normal que expresa HER2 posee amplificación del gen Her-2/neu y alrededor de 50 000 copias de la proteína en la membrana celular3 . Las células tumorales pueden tener un incremento en el número de receptores a nivel de la membrana citoplasmática de hasta 20 veces sobre el valor normal, conduciendo a la célula a un crecimiento descontrolado.

Polyaniline nanofibers: Acute toxicity and teratogenic effect on Rhinella arenarum embryos Yslas, Edith Inés; Ibarra, Luis Exequiel; Peralta, Damian Oscar; Barbero, César Alfredo; Rivarola, Viviana; Bertuzzi, Mabel Lucia The fate and effect of nanomaterials in the environment is of paramount importance towards the technological application of the materials. This work shows the ecotoxicological potential of polyaniline (PANI) nanofibers in the larvae Rhinella arenarum by means of AMPHITOX test. Acute toxicity of PANI nanofibers towards embryos of the common South American toad R. arenarum (Anura: bufonidae) was evaluated in the premetamorphosis (stage 25) larvae. The exposure of R. arenarum larvae to at dose of 150, 250 and 400mgL-1 resulted in 100% viability within 96h exposure. The embryos at 2-4 blastomers stage (early life stage teratogenic test) revealed that embryos were not killed and no teratogenic effects were observed when embryos were incubated with PANI nanofibers (150 and 250mgL-1), while only a growth retardation of embryos was induced at levels of 250mg PANI nanofibersL-1. On the other hand, at 400mgL-1 concentration, a reduction in the body length of larvae and tail malformation was observed. This results suggest that a concentration-dependent toxicity is operative, typified by phenotypes that had abnormal body axes. The presence of PANI nanofibers in gut contents and its excretion by larval stages of R. arenarum was confirmed by UV-visible spectroscopy.

Socio-Cultural Differences and Intercultural Communication in Social Participation Experiences Mato, Daniel Alejandro This article discusses the main theoretical and methodological aspects of the intercultural communication analytical perspective that I have developed to respond to specific research needs. This perspective is based on the idea that institutional and collective social actors are heterogeneous entities because they comprise a variety of internal parties, as I have been able to observe in my field research experience. Intercultural communication involves, therefore, multidimensional exchanges between heterogeneous agents that build meaning and struggle over it within their own group as well as with the other social agents. Meaning is something that is negotiated, transformed, appropriated, and can often be a subject of dispute. For that reason, the study of intercultural communication should center on social processes, not just verbal utterances. Close examination of social practices and relations enable us to understand how differences are articulated and how meaning is transformed.

A new species of Mathevotaenia (cestoda, anoplocephalidae) parasitizing tropidurus spinulosus (reptilia, squamata) from northeastern Argentina; Una especie nueva de Mathevotaenia (Cestoda, Anoplocephalidae) parásita de Tropidurus spinulosus (Reptilia, Squamata) del noreste de Argentina Lunaschi, Lía Inés; Lamas, Matías Fernando; Drago, Fabiana Beatriz Mathevotaenia chaquensis n. sp. (Cestoda, Anoplocephalidae, Linstowiinae) from a Spiny Lava Lizard, Tropidurus spinulosus, collected in Chaco Province, c Argentina, is described. This is the second species of Mathevotaenia described from Neotropical reptiles. The new species is mainly characterized by having a relatively small strobila, 24 mm in total length, with about 100 craspedote proglottids, and 19-24 testes per proglottid. Among the South American species of Mathevotaenia, M. argentinensis is most similar to the new species by having similar body length and number of testes, but the major differences between both species include the size of suckers, neck, proglottids, testes and egg capsules, and the shape of the genital atrium and ovary (with 10-13 lobules on each side in M. argentinensis, and 4-7 lobules in M. chaquensis n. sp.). A key to the species of the South American members of the Mathevotaenia Akumyan, 1946 is presented.

El operaismo italiano y su historiografía. Introducción a ''Ocho tesis sobre la historia militante'' de Sergio Bologna Grigera, Juan Francisco Traducir un texto de más de 30 años requiere, sin duda, intentar explicar primero por qué publicarlo hoy. Es decir, contar el contexto en que fue producido, para y por quién fue escrito originalmente, y así permitir que se trasluzca del palimpsesto aquello que supo decir y lo que tiene para decirnos a nosotros. Lo cierto es que antes de presentar un texto no muy conocido del operaismo (obrerismo) italiano es justo hacer una aclaración sobre la diversidad de sus miembros y múltiples corrientes, como de las suertes que corrieron. Por una parte, es necesario devolver la imagen de su heterogeneidad, después de que el operaismo se haya vuelto conocido casi exclusivamente por las últimas ideas de Antonio Negri, cuando no filtrado por las lecturas peculiares de Deleuze y Guattari, perdiéndose de vista sus otras tendencias (Wright, 2002: 2) o confundido con el autonomismo de corte situacionista. Pero por otra parte, también es necesaria cierta presentación, pues la corriente italiana ha sufrido peores castigos que la deformación o el sesgo: me refiero al simple olvido, al menos en el habla castellana hoy. Es que el vocablo “obrerismo”, podría designar bastante más que el epíteto descalificador de quienes se obsesionan con las supuestas potencialidades revolucionarias de los trabajadores manufactureros. El “obrerismo” es también una corriente de pensamiento italiana, un producto intelectual original, caracterizado por el desarrollo de, o el énfasis en, un conjunto de conceptos (composición de clase, autonomía, crítica del desarrollo, general intellect), por un número de autores (Panzieri, Tronti, Negri, Alquati, Bologna, entre los más destacados) y de revistas (Quaderni Rossi, Clase Operaia, Primo Maggio). Estos estructuraron conscientemente “el significado y relevancia de cada concepto para el desarrollo inmediato de la clase trabajadora” (Cleaver, 1985: 72), dándole a ésta una importancia soberana como sujeto autónomo de la lógica del capital.

Estrategias empresariales en contextos de alta incertidumbre: Desafíos de una empresa productora de aluminio en la Argentina (1970-2001); Business Strategies in Contexts of High Uncertainty: Challenges of an Aluminum Producer in Argentina (1970-2001) Rougier, Marcelo Norberto Este trabajo estudia las estrategias empresariales de la firma Aluminio Argentino desde sus orígenes en 1970 hasta la crisis económica de 2001. La puesta en marcha de la planta fue posible por la ingente ayuda del Estado argentino y coincidió con un período de gran inestabilidad macroeconómica y de fuerte reducción de la demanda doméstica, con el agravante de enfrentar un mercado internacional signado por la recesión que se sostuvo prácticamente hasta los años noventa. El estudio ilustra también las estrategias de los empresarios una vez que el marco regulatorio que le dio origen desapareció y la empresa debió enfrentar un fuerte shock competitivo; This paper examines the business strategies of the firm Aluminio Argentino (Aluar) since its inception in 1970 to the 2001 economic crisis. The commissioning of the plant was made possible by the tremendous support of the State and his performance coincided with a period of great macroeconomic instability and sharp reduction in domestic demand, deal with the aggravation of an international market marked by the recession which was held almost until the nineties. The study also illustrates the strategies of the business once the regulatory framework that gave rise disappeared and the company faced a strong competitive shock.

Estrategias de desarrollo y modalidades de financiamiento en el "Canto de Cisne" de la industrialización argentina Rougier, Marcelo Norberto; Odisio, Juan Carlos En los años sesenta los economistas argentinos debatieron distintas alternativas para encaminar el desarrollo y la acumulación en el orden interno. Para el logro de ese objetivo, se consideraba necesario impulsar la inversión, para lo que se precisaba diseñar mecanismos de financiamiento adecuados. Partiendo de los mismos, este trabajo pretende mostrar que un importante conjunto de firmas de capital nacional pudo acceder a nuevas formas de fondeo y la política industrial se encaminó cada vez más a impulsar grandes empresas de capital local. Más allá de los vaivenes de cada proyecto, el Estado tuvo relativo éxito en el impulso de grandes obras (que en algunos casos permitieron iniciar la anhelada corriente de exportación manufacturera), a través de mecanismos específicos de canalización de recursos, en la última etapa de la estrategia de industrialización sustitutiva.; In the sixties, several Argentine economists discussed alternatives for directing development and accumulation in the internal order. To achieve this goal, the boost of investment was considered necessary, for what was needed an appropriate design of financing mechanisms. On that basis, this work intends to show that an important set of national capital firms gained access to new forms of funding and the industrial policy increasingly headed to promote huge companies of local capital. Beyond the vagaries of each project, the State had relative success in promoting major projects (that in some cases allowed to initiate the desired flow of manufacturing exports), through specific mechanisms for channeling resources, in the last stage of the substitution industrialization strategy.

Calf tissue oxygenation during exercise in men with and without risk factors for developing peripheral arterial disease Miranda, Alberto; Figoni, Stephen F.; Cha, Tha; Flanagan, Terrance; Mandal, Oanh; Silva, Mariana; Scremin, A.M. Erika; Scremin, Oscar Umberto OBJECTIVE: This study aimed to compare calf tissue oxygenation responses to calf exercise in men without diagnosed peripheral arterial disease but with selected risk factors for peripheral arterial disease with those without risk factors. DESIGN: A cross-sectional quasi-experimental design was used. The no-risk group (n = 20) had none of the risk factors (diabetes, hypertension, hyperlipidemia, obesity, current or 10 pack-yr smoking history, or age >65 yrs). The at-risk group (n = 45) had one to six risk factors. Medial calf tissue oxygenation (percentage saturation) was determined using near-infrared spectroscopy during seven consecutive 5-min test stages: rest, 0-W active plantar/dorsiflexion, rest, 4-W resistive plantar flexion, rest, 8-W resistive plantar flexion, and rest. Resistive exercise was performed on the Stresst'er calf ergometer. RESULTS: Compared with the no-risk group, decrements in calf tissue oxygenation induced by light-to-moderate resistive calf exercise in the at-risk group was significantly greater (by 9% saturation) (4-W: P < 0.001; 8-W: P = 0.002). CONCLUSIONS: Men with risk factors for developing peripheral arterial disease but without such diagnosis demonstrated greater decrements in calf tissue oxygenation during calf exercise compared with men without risk factors. Further development of this test may lead to early diagnosis and intervention to modify risk factors and prevent co-morbidities.

Simple fatigue testing machine for fiber-reinforced polymer composite Pach, Esteban; Korin, Ivan; Perez Ipiña, Juan Elias Fiber-reinforced polymer (FRP) composites seem to be the best options in many structural applications. Such applications are often exposed to fatigue loads, and therefore, the fatigue behavior of the composites must be studied in order to achieve a proper design. This is fulfilled by means of an experimental characterization, in which a lot of specimens are tested because of the several parameters involved (i.e., fiber/matrix ratio, fiber orientation, staking sequence, etc.). Besides, the fatigue tests must be carried out at low frequencies, in order to avoid temperature increments in the polymer matrix, which would change the mechanical properties of the composite. Consequently, considerable time is consumed to perform a complete set of tests and, when using conventional servohydraulic testing machines, costs rise notably. A machine to perform fatigue tests of composite materials under constant amplitude load cycles and a wide range of load ratios is presented in this paper. This machine exhibits as main goals the fulfillment of the corresponding standard requirements, a very low cost compared to conventional servohydraulic testing machines and, consequently, makes reasonably priced to have several machines testing specimens simultaneously, in order to reduce the necessary time to complete the whole characterization.

On the molecular structure of uranium dicarbide: T-shape versus linear isomers Zalazar, Maria Fernanda; Rayon, Victor M.; Largo, Antonio A theoretical study of the molecular structure of uranium dicarbide has been carried out employing DFT, coupled cluster, and multiconfigurational methods. A triangular species, corresponding to a 5A 2 electronic state, has been found to be the most stable UC 2 species. A triplet linear CUC species, which has been observed in recent infrared spectroscopy experiments, lies much higher in energy. A topological analysis of the electronic density has also been carried out. The triangular species is shown to be in fact a T-shape structure with a U-C interaction which can be considered to be a closed-shell interaction.

Females prefer good genes: MHC-associated mate choice in wild and captive tuco-tucos Cutrera, Ana Paula; Fanjul, Maria Sol; Zenuto, Roxana Rita The major histocompatibility complex (MHC) genes are one of the most suitable candidates for elucidating the genetic bases of mate choice in vertebrates, given the potential benefits in terms of immunocompetence that can be passed to the offspring through MHC-associated mate choice. Female mate choice may favour males that possess particular MHC alleles or those with diverse MHC genotypes (good genes hypothesis), or males that possess MHC genotypes that differ from that of the female (compatibility hypothesis). Our goal was to evaluate mate choice in relation to MHC genotype in the subterranean rodent Ctenomys talarum. Using both laboratory and field analyses, we investigated whether the (1) number of shared MHC alleles between males and females, (2) number of amino acid differences between female and male MHC alleles, (3) MHC heterozygosity of males, (4) number of amino acid differences between male MHC alleles, and (5) frequency of MHC alleles of males differ between preferred and nonpreferred males in the laboratory and between potential sires and random males from the population in the field. In the laboratory, our results indicate that MHC alleles of preferred males differ in fewer amino acids compared to MHC alleles of nonpreferred males. Concomitantly, in the field,MHC alleles of possible sires differed in fewer amino acids than those of random males in the population. Plus, possible sires were more heterozygous and carried distinct MHC alleles compared with random males, thus providing more support to the "good genes" hypothesis. We discuss the possible reasons why MHC-based mate choice was more evident in the field and the implications of such a female mating strategy in the subterranean environment.

Stable isotopes identify age- and sex-specific dietary partitioning and foraging habitat segregation in southern giant petrels breeding in Antarctica and southern Patagonia Raya Rey, Andrea Nélida; Polito, Michael; Archuby, Diego Ignacio; Coria, Néstor Rubén We examined the isotopic signatures (δ 13C, δ 15N) of adult body feathers from southern giant petrels Macronectes giganteus collected at two breeding colonies in Antarctica (Potter Peninsula and Cape Geddes) and one in southern Patagonia (Observatorio Island), as well as in whole blood collected from adults of both sexes at each Antarctic colonies and from chicks at Potter Peninsula. As body feather moult is a continuous process in giant petrels, feathers provide an integrated annual signal of an adult's diets and foraging habitats. In contrast, the stable isotope values of adult and chick blood are reflective of their diets during the breeding season. We found that sex-specific dietary segregation in adults breeding in Antarctica was notable during the breeding season (blood samples) but absent when examined across the entire year (feather samples). In addition, blood stable isotope values differed between chicks and adults, indicating that adults provision their offspring with a relatively higher amount of penguin and seal prey that what they consume themselves. This finding confirms previous work that suggests that chicks are preferentially fed with prey of presumably higher nutritional value such as carrion. Finally, based on isotopic differences between major oceanographic zones in the Southern Ocean, our data indicate population-specific differences in foraging distribution, with Antarctic populations move seasonally between Antarctic and subantarctic zones, while Patagonian populations likely forage in subtropical waters and in continental shelf habitats year-round.

Dra. Eugenia Sacerdote de Lustig: la inagotable pasión de una investigadora ejemplar Su historia, al igual que la de millones de inmigrantes europeos que llegaron a Argentina durante la primera mitad del siglo XX, estuvo marcada por el esfuerzo, la lucha y la esperanza de encontrar, en estas tierras, una vida mejor, lejos de las persecuciones y barbaries ocasionadas por dos devastadoras guerras mundiales. A cuatro meses de su fallecimiento, su legado científico y su experiencia de vida se han transformado en una fuente de inspiración para cientos de médicos e investigadores del país que ven en ella un ejemplo para seguir.

Synthesis of the unique angular tricyclic chromone structure proposed for aspergillitine, and its relationship with alkaloid TMC-120B Simonetti, Sebastián Osvaldo; Larghi, Enrique Leandro; Bracca, Andrea Beatriz Juana; Kaufman, Teodoro Saul The synthesis of the tricyclic angular chromone structure originally assigned to aspergillitine is reported. The synthesis was achieved in 11 steps and 15% overall yield from 2,4-dihydroxypropiophenone, through the intermediacy of 2,3-dimethyl-7-hydroxychromen-4-one. Construction of the nitrogen-bearing heterocyclic ring entailed a Stille cross-coupling reaction with n-Bu3SnCH2CHCH2, followed by double bond isomerization, oximation of the chromone carbonyl, and a final microwave-assisted electrocyclization of the thus formed 6π-electron aza-triene system.

First Century of Chagas' Disease: An Overview on Novel Approaches to Nifurtimox and Benznidazole Delivery Systems Salomon, Claudio Javier Hundred years after the discovery of Chagas' disease, there is a lack of effective treatment to control this neglected disease caused by the parasite Trypanosoma cruzi. The transmission is primarily through vector-borne blood transfusion or during pregnancy, producing high mortality and morbidity among poor people in many countries of Latin America. In the last decades, the efforts have been focused mainly on the elimination of vectors. At the same time, screening of blood donors in order to avoid transfusional transmission has been improved all over the world. However, Chagas' disease is still a major public health problem, with estimates of nearly 90 million people at risk of infection and more than eight million infected in 18 endemic countries. Despite the high incidence in endemic regions and the dissemination of neglected diseases in North America and Europe, to date, there are only two drugs developedn and prescribed for the treatment of Chagas' disease, nifurtimox (tablets of 120 mg) and benznidazole (tablets of 100 mg). In this review, different approaches carried out in the last decades for developing novel pharmaceutical formulations for the delivery of nifurtimox and benznidazole are discussed.

ROS enhancement by silicon nanoparticles in X-ray irradiated aqueous suspensions and in glioma C6 cells David Gara, Pedro Maximiliano; Garabano, Natalia Ines; Llansola Portolés, Manuel Jose; Moreno, Mario Sergio Jesus; Dodat, Diego; Casas, Oscar; Gonzalez, Monica Cristina; Kotler, Monica Lidia The capability of silicon nanoparticles to increase the yield of reactive species upon 4 MeV X-ray irradiation of aqueous suspensions and C6 glioma cell cultures was investigated. ROS generation was detected and quantified using several specific probes. The particles were characterized by FTIR, XPS, TEM, DLS, luminescence, and adsorption spectroscopy before and after irradiation to evaluate the effect of high energy radiation on their structure. The total concentration of O 2 ·-/HO 2 ·, HO ·, and H 2O 2 generated upon 4-MeV X-ray irradiation of 6.4 μM silicon nanoparticle aqueous suspensions were on the order of 10 μM per Gy, ten times higher than that obtained in similar experiments but in the absence of particles. Cytotoxic 1O 2 was generated only in irradiation experiments containing the particles. The particle surface became oxidized to SiO 2 and the luminescence yield reduced with the irradiation dose. Changes in the surface morphology did not affect, within the experimental error, the yields ofROSgenerated per Gy. X-ray irradiation of glioma C6 cell cultures with incorporated silicon nanoparticles showed a marked production of ROS proportional to the radiation dose received. In the absence of nanoparticles, the cells showed no irradiation- enhanced ROS generation. The obtained results indicate that silicon nanoparticles of <5 nm size have the potential to be used as radiosensitizers for improving the outcomes of cancer radiotherapy. Their capability of producing 1O 2 upon X-ray irradiation opens novel approaches in the design of therapy strategies.