ABSTRACT
We consider the three-dimensional Hamiltonian for Bi2Se3, a second-generation topological insulator, under the effect of a periodic drive for both in-plane and out-of-plane fields. As it will be shown by means of high-frequency expansions up to second order in the Floquet Hamiltonian, the driving induces anisotropies in the Dirac cone and opens up a quasienergy gap for in-plane elliptically polarized fields. Analytic expressions are obtained for the renormalized velocities and the quasienergy gap. These expressions are then compared to numerical calculations performed by discretizing the Hamiltonian in a one-dimensional lattice and following a staggered fermion approach, achieving a remarkable agreement. We believe our work may have an impact on the transport properties of topological insulators.
ABSTRACT
In IV-VI semiconductor heterojunctions with band-inversion, such as those made of [Formula: see text] [Formula: see text]Te or [Formula: see text] [Formula: see text]Se, interface states are properly described by a two-band model, predicting the appearance of a Dirac cone in single junctions. However, in quantum wells the interface dispersion is quadratic in momentum and the energy spectrum presents a gap. We show that the interface gap shrinks under an electric field parallel to the growth direction. Therefore, the interface gap can be dynamically tuned in experiments on double-gated quantum wells based on band-inverted compounds.
ABSTRACT
Dirac materials are characterized by energy-momentum relations that resemble those of relativistic massless particles. Commonly denominated Dirac cones, these dispersion relations are considered to be their essential feature. These materials comprise quite diverse examples, such as graphene and topological insulators. Band-engineering techniques should aim to a full control of the parameter that characterizes the Dirac cones: the Fermi velocity. We propose a general mechanism that enables the fine-tuning of the Fermi velocity in Dirac materials in a readily accessible way for experiments. By embedding the sample in a uniform electric field, the Fermi velocity is substantially modified. We first prove this result analytically, for the surface states of a topological insulator/semiconductor interface, and postulate its universality in other Dirac materials. Then we check its correctness in carbon-based Dirac materials, namely graphene nanoribbons and nanotubes, thus showing the validity of our hypothesis in different Dirac systems by means of continuum, tight-binding and ab-initio calculations.
ABSTRACT
INTRODUCTION: The ingestion of alcohol produces oxydative stress generating free radicals of oxygen and ethanol. These free radicals have a molecular reactive ability and, therefore, they play an important role in the production of the injury which appears in the liver and in other organs and tissues. We have done an "in vitro" study where we analyse the oxydative status at rest and the respiratory explosion produced by ethanol at final concentrations of 50 and 25 mM and by the phagocytosis of a previously opsonized concentrate of bacteria (E.coli) in human leucocytes taken from peripheral blood of six healthy persons. METHOD: We have used 1.2.3. dihydrorhodamine (non-fluorescent) as the oxydative marker because it is transformed in rhodamine (fluorescent), which is quantitatively studied by Flow Cytometry. RESULTS: The peak of oxydative stress is reached with the bacteria in the phagocytes (monocytes 50% and granulocytes 90%) and it has a significant difference with the control group. By adding ethanol at 50 mM we have seen an statistic significant difference in oxydative stress in the cells of all three types (lymphocytes 9.19%, monocytes 32% and granulocytes 36%). With a concentration of 25 mM of ethanol the oxydative stress is increased but without a significant difference (lymphocytes 2.39%, monocytes 9.22% and granulocytes 4.46%). We have also seen toxic cellular effect which reaches the 40.75% of cells with ethanol at 50 mM, the 10.7% with ethanol at 25 mM and the 5.65% with bacteria. CONCLUSION: The oxydative stress caused by the production of oxygen and ethanol free radicals in the leucocytes, and the proved cytotoxic effect of ethanol may play an important role over the qualitative and the quantitative leucocyte disorder on different organs and tissues of the alcoholic patient.
Subject(s)
Ethanol/toxicity , Free Radicals/blood , Leukocytes/drug effects , Oxidative Stress/drug effects , Flow Cytometry , HumansABSTRACT
Introducción: La ingesta de alcohol desencadena stress oxidativo generador de radicales libres de oxígeno y de etanol que, por su capacidad reactiva molecular, juegan un importante papel en la producción de las lesiones que aparecen en el hígado y en otros órganos y tejidos. Hemos realizado un estudio "in vitro" analizando el estado oxidativo en reposo y la explosión respiratoria desencadenada por Etanol, a concentraciones finales de 50 y 25 mM y por la fagocitosis de un concentrado de bacterias (E.coli) previamente opsonizadas, en los leucocitos humanos de sangre periférica de seis donantes sanos. Método: Como marcador oxidativo hemos utilizado la 1.2.3. dihidrorodamina,(no fluorescente) cuya oxidación la transforma en rodamina que es fluorescente y se examina cuantitativamente por Citometría de flujo. Resultados: El stress oxidativo máximo se alcanza con las bacterias en las células fagocíticas (monocitos 50 por ciento y granulocitos 90 por ciento) con diferencia significativa con respecto al grupo control. Con Etanol 50 mM se comprueba stress oxidativo con diferencia estadísticamente significativa en los tres tipos de células (linfocitos 9,19 por ciento, monocitos 32 por ciento y granulocitos 36 por ciento). A concentración 25 mM, aunque aumenta el estado oxidativo, no alcanza diferencia significativa (linfocitos 2,39 por ciento, monocitos 9,22 por ciento y granulocitos 4,46 por ciento). También hemos comprobado toxicidad celular que alcanza el 40,75 por ciento de las células con Etanol 50 mM, el 10,7 por ciento con Etanol 25 mM y el 5,65 por ciento con bacterias. Conclusión: El stress oxidativo con producción de radicales libres de oxígeno y de etanol en los leucocitos y la citotoxicidad comprobada, pueden jugar un papel importante en el trastorno cualitativo y cuantitativo de estas células en los enfermos alcohólicos y en las lesiones producidas por este tóxico en otros órganos y tejidos. (AU)
Subject(s)
Humans , Oxidative Stress , Ethanol , Leukocytes , Flow Cytometry , Free RadicalsABSTRACT
Fifteen cases of nasosinusal inverted papilloma treated in our department from 1994 to 2000 are reported. The most frequent initial symptom was unilateral nasal obstruction. Some others symptoms were rhinorrea, facial pain and self limited epistaxis. The most frequent surgical procedure performed was the paralateral rhinotomy with medial maxillectomy. The median average for the follow up was 28 months, being diagnosed one recurrence. The paralateral rhinotomy with a medial maxillectomy, under functional endoscopic nasosinusal techniques are being more and more used, decreasing the indications of open techniques.
Subject(s)
Papilloma, Inverted/diagnostic imaging , Papilloma, Inverted/pathology , Paranasal Sinus Neoplasms/diagnostic imaging , Paranasal Sinus Neoplasms/pathology , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Papilloma, Inverted/surgery , Paranasal Sinus Neoplasms/surgery , Tomography, X-Ray ComputedABSTRACT
Presentamos un estudio retrospectivo de 15 casos diagnosticados de papiloma invertido nasosinusal, tratados en nuestro servicio entre 1994 y 2000. La forma de inicio más frecuente fue la obstrucción nasal unilateral. Otra sintomatología asociada fue rinorrea, algias faciales y epitaxis autolimitadas. El tratamiento quirúrgico más frecuente realizado fue la rinotomía paralateronasal con maxilectomía media. En el control posoperatorio (de 28 meses de media) se observó una recidiva sólo en un paciente. La rinotomía paralateronasal con maxilectomía media con ayuda del microscopio óptico, es considerado el tratamiento de elección. No obstante, la incorporación de la endoscopia y la destreza en su manejo, van limitando las indicaciones de cirugía abierta (AU)
No disponible
Subject(s)
Middle Aged , Adult , Aged , Aged, 80 and over , Male , Female , Humans , Tomography, X-Ray Computed , Papilloma, Inverted , Paranasal Sinus NeoplasmsSubject(s)
Echinococcosis/complications , Hypertension, Portal/etiology , Humans , Male , Middle AgedABSTRACT
No disponible
Subject(s)
Middle Aged , Male , Humans , Echinococcosis , Hypertension, PortalABSTRACT
Fibrous dysplasia is a rare bone disease that can be misdiagnosed because of the slowness of its symptoms. Although it is a benign disease its clinical behaviour can be severe, with possibility of local growth and malignant degeneration into osteosarcoma. An uncommon case of fibrous dysplasia is reported, affecting only the middle turbinate. Diagnostic and therapeutic problems are discussed.
Subject(s)
Facial Bones , Fibrous Dysplasia, Polyostotic/diagnosis , Skull , Turbinates/pathology , Endoscopy/methods , Fibrous Dysplasia, Polyostotic/surgery , Humans , Male , Middle Aged , Tomography, X-Ray Computed , Turbinates/diagnostic imaging , Turbinates/surgeryABSTRACT
La displasia fibrosa es una patología ósea poco frecuente y a menudo puede pasar desapercibida por su escasa sintomatología. A pesar de ser un proceso benigno, puede comportarse de forma agresiva por su crecimiento local, y en ocasiones degenerar a osteosarcoma. En este trabajo aportamos un caso de displasia fibrosa que es atípico por su localización exclusiva en el cornete medio.Se plantean los problemas diagnósticos y terapéuticos que ello conlleva. (AU)
Fibrous dysplasia is a rare bone disease that can be misdiagnosed because of the slowness of its symptoms. Although it is a benign disease its clinical behaviour can be severe, with possibility of local growth and malignant degeneration into osteosarcoma. An uncommon case of fibrous dysplasia is reported, affecting only the middle turbinate. Diagnostic and therapeutic problems are discussed (AU)
Subject(s)
Middle Aged , Male , Humans , Skull , Facial Bones , Fibrous Dysplasia, Polyostotic/diagnosis , Turbinates/pathology , Tomography, X-Ray Computed , EndoscopySubject(s)
Abdominal Neoplasms/pathology , Liposarcoma/pathology , Peritoneal Neoplasms/pathology , Abdominal Neoplasms/diagnostic imaging , Abdominal Neoplasms/surgery , Aged , Female , Humans , Liposarcoma/diagnostic imaging , Liposarcoma/surgery , Male , Middle Aged , Peritoneal Neoplasms/diagnostic imaging , Peritoneal Neoplasms/surgery , RadiographyABSTRACT
An area integrator for the thermodilution curve in cardiac output measurement is described. A new temperature sensor is used, a diode with some advantages over the thermistor normally used. The main advantages are: easy calibration and replacement, and broad range of linearity. The cardiac output values obtained in dog with the integrator follow a linear relationship with those of the flowmeter. In simultaneous measurements the correlation is R = 0.96. Using a diode as temperature sensor a modification of the Steward Hamilton equation (used for thermistor) is necessary. With this new equation a monogram is performed to calculate the cardiac output from the area given by the numerical integrator.
