RESUMEN
Here we employed the density functional theory calculations to investigate some physical properties of first Sc-based MAX phase Sc2SnC including defect processes to compare with those of existing M2SnC phases. The calculated structural properties are in good agreement with the experimental values. The new phase Sc2SnC is structurally, mechanically and dynamically stable. Sc2SnC is metallic with a mixture of covalent and ionic character. The covalency of Sc2SnC including M2SnC is mostly controlled by the effective valence. Sc2SnC in M2SnC family ranks second in the scale of deformability and softness. The elastic anisotropy level in Sc2SnC is moderate compared to the other M2SnC phases. The hardness and melting point of Sc2SnC, including M2SnC, follows the trend of bulk modulus. Like other members of the M2SnC family, Sc2SnC has the potential to be etched into 2D MXenes and has the potential to be a thermal barrier coating material.
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A bulk scale process is implemented for the production of nanostructured film composites comprising unary or multi-component metal oxide nanoparticles dispersed in a suitable polymer matrix. The as-received nanoparticles, namely Al[Formula: see text]O[Formula: see text], SiO[Formula: see text] and TiO[Formula: see text] and binary combinations, are treated following specific chemical and mechanical processes in order to be suspended at the optimal size and composition. Subsequently, a polymer extrusion technique is employed for the fabrication of each film, while the molten polymer is mixed with the treated metal oxide nanoparticles. Transmission and reflection measurements are performed in order to map the optical properties of the fabricated, nanostructured films in the UV, VIS and IR. The results substantiate the capability of the overall methodology to regulate the optical properties of the films depending on the type of nanoparticle formation which can be adjusted both in size and composition.
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Using density functional theory, the phase stability and physical properties, including structural, electronic, mechanical, thermal and vibrational with defect processes, of a newly synthesized 211 MAX phase V2SnC are investigated for the first time. The obtained results are compared with those found in the literature for other existing M2SnC (M = Ti, Zr, Hf, Nb, and Lu) phases. The formation of V2SnC is exothermic and this compound is intrinsically stable in agreement with the experiment. V2SnC has potential to be etched into 2D MXene. The new phase V2SnC and existing phase Nb2SnC are damage tolerant. V2SnC is elastically more anisotropic than Ti2SnC and less than the other M2SnC phases. The electronic band structure and Fermi surface of V2SnC indicate the possibility of occurrence of its superconductivity. V2SnC is expected to be a promising TBC material like Lu2SnC. The radiation tolerance in V2SnC is better than that in Lu2SnC.
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Interest in the Mn+1AXn phases (M = early transition metal; A = group 13-16 elements, and X = C or N) is driven by their ceramic and metallic properties, which make them attractive candidates for numerous applications. In the present study, we use the density functional theory to calculate the elastic properties and the incorporation of lithium atoms in the 312 MAX phases. It is shown that the energy to incorporate one Li atom in Mo3SiC2, Hf3AlC2, Zr3AlC2, and Zr3SiC2 is particularly low, and thus, theoretically, these materials should be considered for battery applications.
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Anatase titanium oxide is important for its high chemical stability and photocatalytic properties, however, the latter are plagued by its large band gap that limits its activity to only a small percentage of the solar spectrum. In that respect, straining the material can reduce its band gap increasing the photocatalytic activity of titanium oxide. We apply density functional theory with the introduction of the Hubbard + U model, to investigate the impact of stress on the electronic structure of anatase in conjunction with defect engineering by intrinsic defects (oxygen/titanium vacancies and interstitials), metallic dopants (iron, chromium) and non-metallic dopants (carbon, nitrogen). Here we show that both biaxial and uniaxial strain can reduce the band gap of undoped anatase with the use of biaxial strain being marginally more beneficial reducing the band gap up to 2.96 eV at a tensile stress of 8 GPa. Biaxial tensile stress in parallel with doping results in reduction of the band gap but also in the introduction of states deep inside the band gap mainly for interstitially doped anatase. Dopants in substitutional positions show reduced deep level traps. Chromium-doped anatase at a tensile stress of 8 GPa shows the most significant reduction of the band gap as the band gap reaches 2.4 eV.
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It has been recently shown [N. V. Sarlis, Phys. Rev. E 84, 022101 (2011) and N. V. Sarlis and S.-R. G. Christopoulos, Chaos 22, 023123 (2012)] that earthquakes of magnitude M greater or equal to 7 are globally correlated. Such correlations were identified by studying the variance κ1 of natural time which has been proposed as an order parameter for seismicity. Here, we study the fluctuations of this order parameter using the Global Centroid Moment Tensor catalog for a magnitude threshold Mthres = 5.0 and focus on its behavior before major earthquakes. Natural time analysis reveals that distinct minima of the fluctuations of the order parameter of seismicity appear within almost five and a half months on average before all major earthquakes of magnitude larger than 8.4. This phenomenon corroborates the recent finding [N. V. Sarlis et al., Proc. Natl. Acad. Sci. U.S.A. 110, 13734 (2013)] that similar minima of the seismicity order parameter fluctuations had preceded all major shallow earthquakes in Japan. Moreover, on the basis of these minima a statistically significant binary prediction method for earthquakes of magnitude larger than 8.4 with hit rate 100% and false alarm rate 6.67% is suggested.
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We study the threshold distribution function of the coherent-noise model for the case of infinite number of agents. This function is piecewise constant with a finite number of steps n. The latter exhibits a 1/f behavior as a function of the order of occurrence of an avalanche and hence versus natural time. An analytic expression of the expectation value E(S) for the size S of the next avalanche is obtained and used for the prediction of the next avalanche. Apart from E(S), the number of steps n can also serve for this purpose. This enables the construction of a similar prediction scheme which can be applied to real earthquake aftershock data.
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By using the most recent version (1900-2007) of the Centennial Earthquake Catalog, we examine the properties of the global seismicity. Natural time analysis reveals that the fluctuations of the order parameter κ(1) of seismicity exhibit for at least three orders of magnitude a characteristic feature similar to that of the order parameter for other equilibrium or non-equilibrium critical systems-including self-organized critical systems. Moreover, we find non-trivial magnitude correlations for earthquakes of magnitude greater than or equal to 7.
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Terremotos , Modelos Teóricos , Terremotos/estadística & datos numéricos , Japón , Factores de TiempoRESUMEN
We observe the buildup of strong (approximately 50%) spontaneous vector polarization in emission from a GaN-based polariton laser excited by short optical pulses at room temperature. The Stokes vector of emitted light changes its orientation randomly from one excitation pulse to another, so that the time-integrated polarization remains zero. This behavior is completely different from any previous laser. We interpret this observation in terms of the spontaneous symmetry breaking in a Bose-Einstein condensate of exciton polaritons.
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We observe a room-temperature low-threshold transition to a coherent polariton state in bulk GaN microcavities in the strong-coupling regime. Nonresonant pulsed optical pumping produces rapid thermalization and yields a clear emission threshold of 1 mW, corresponding to an absorbed energy density of 29 microJ cm-2, 1 order of magnitude smaller than the best optically pumped (In,Ga)N quantum-well surface-emitting lasers (VCSELs). Angular and spectrally resolved luminescence show that the polariton emission is beamed in the normal direction with an angular width of +/-5 degrees and spatial size around 5 microm.
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Benign metastasizing leiomyomas (BMLs) occur predominantly in women during reproductive years. The condition is characterized by uterine leiomyomas associated with the development, typically years later, of slow-growing metastatic lesions. The most commonly affected organs are the lungs, but BMLs have been reported in lymph nodes, deep soft tissues, mesentery, bones, the central nervous system, and the heart. In many cases, these lesions have an indolent course and are discovered rather incidentally. However, occasionally they can present with debilitating symptoms or even life-threatening complications. The presence of estrogen and progesterone receptors in these tumors supports their origin from uterine smooth muscle and, more importantly, makes them amenable to hormonal manipulation. Radical interventions, such as extensive tumor debulking and oophorectomy for hormonal control, although effective in many cases, are not always possible or desirable and carry significant morbidity. Here we present two cases of BMLs to illustrate the role of newer therapeutic agents, the estrogen receptor modulators and the aromatase inhibitors, in the hormonal manipulation of these tumors.
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Antineoplásicos Hormonales/uso terapéutico , Neuropatías del Plexo Braquial/tratamiento farmacológico , Inhibidores Enzimáticos/uso terapéutico , Leiomioma/tratamiento farmacológico , Leiomioma/patología , Neoplasias Pulmonares/secundario , Neoplasias Uterinas/patología , Adulto , Anastrozol , Inhibidores de la Aromatasa , Neuropatías del Plexo Braquial/diagnóstico , Neuropatías del Plexo Braquial/patología , Moduladores de los Receptores de Estrógeno/uso terapéutico , Femenino , Hormona Liberadora de Gonadotropina/agonistas , Humanos , Leiomioma/diagnóstico , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/tratamiento farmacológico , Imagen por Resonancia Magnética , Persona de Mediana Edad , Invasividad Neoplásica , Neoplasias/diagnóstico , Neoplasias/tratamiento farmacológico , Nitrilos/uso terapéutico , Radiografía Torácica , Clorhidrato de Raloxifeno/uso terapéutico , Moduladores Selectivos de los Receptores de Estrógeno/uso terapéutico , Triazoles/uso terapéuticoRESUMEN
A new case of splenic-gonadal fusion in an 8-year-old boy is reported in which the sonographic findings were highly suggestive to include the condition in the differential diagnosis. A separate mass with medium-level echoes and a homogeneous echo texture, surrounded by a clearly visible echogenic capsule, was found in contact with the lower pole of the left testis. The particular character of this congenital anomaly is emphasized and the pathogenesis, diagnosis, and treatment are discussed.
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Bazo/anomalías , Testículo/anomalías , Niño , Humanos , Masculino , Bazo/diagnóstico por imagen , Testículo/diagnóstico por imagen , Ultrasonografía Doppler en ColorRESUMEN
PURPOSE: The influence of the nonionic contrast agent iohexol on blood pH and the cation electrolytes Ca, Na, K and Mg was studied in vivo in humans during the intravenous pyelography. MATERIAL AND METHODS: A population of 28 patients without renal function impairment or electrolyte imbalance was divided into two equal groups. The first group received an intravenous injection of 0.6 mL Omnipaque per kg of body weight (0.388g iohexol/kg and 0.18 g iodine/kg). The second group received a double dose of Omnipaque (1.2 mL iohexol/kg; 0.776g iohexol/kg and 0.36g iodine/kg). Blood samples (5 mL) were taken before the injection of the contrast medium and 5, 10 and 20 minutes (marking the end of the examination) after the injection. Blood pH was also determined immediately after each sample collection, while electrolytes were measured in the laboratory. Systolic and diastolic blood pressure were also determined simultaneously with each sample collection using a mercury manometer. RESULTS: Iohexol in simple and double doses did not have any statistically significant effect either on blood pH or on blood serum electrolytes during intravenous pyelography. Blood pressure, both systolic and diastolic, remained stable in all the patients during the examination. CONCLUSIONS: Our results show that the nonionic contrast medium iohexol at the doses used in routine intravenous pyelography does not have any influence on blood pH and serum cardioactive cation electrolytes in humans. An electrolyte imbalance is always a risk factor that may contribute to the development of cardiovascular side effects. This factor is eliminated when iohexol is administered intravenously instead of an ionic agent.
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Cationes/sangre , Medios de Contraste/farmacología , Electrólitos/sangre , Yohexol/farmacología , Urografía , Adulto , Anciano , Medios de Contraste/administración & dosificación , Femenino , Humanos , Inyecciones Intravenosas , Yohexol/administración & dosificación , Masculino , Persona de Mediana EdadRESUMEN
PURPOSE: The aim of this study was to evaluate the effects of two iodinate contrast agents (CA), iohexol and diatrizoate, on human plasma acetyl-(AC) and butyrylcholinesterase(BC) activity. MATERIAL AND METHODS: Forty-eight patients (24 males and 24 females) scheduled for intravenous pyelography were randomly divided into four groups of 6 males and 6 females each, receiving as CA, respectively: iohexol (Omnipaque, Schering) 0.6 ml/kg body weight (G1); iohexol 1.2 mg/kg (G2); sodium and meglumine diatrizoate 58% (Urografin, Schering) 0.6 ml/kg (G3); sodium and meglumine diatrizoate 58% 1.2 ml/kg (G4). Blood samples were taken before and 5, 10, and 20 min after the injection. Enzymatic activity of AC and BC were measured by spectrophotometry. Plasma concentration of K, Na, Ca, and Mg was measured in all blood samples; blood pressure and plasma pH were measured after each sample collection. Statistical analysis was performed by Student's test. RESULTS: In G1 a reversible decrease of AC (12.9%) and BC (8.2%) plasma activity was observed at 10 min. In G2 a progressive decrease of AC (13.9%) and BC (18.4%) plasma activity was observed with a maximum at 20 min. In G3 a modest reversible decrease of BC plasma activity (5.4%) was observed. In G4 a modest progressive decrease of AC (7.3%) and BC (6.5%) plasma activities was observed. In all cases, AC and BC plasma activities remained within the normal range of values. Plasma concentration of K, Na, Ca, and Mg, as well as pH and systolic and diastolic pressure, did not show any change. No adverse effects was observed in our patients. CONCLUSIONS: Iohexol and diatrizoate induce in vivo a significant decrease of AC and BC plasma activities. The decrease is more pronounced for iohexol, a non ionic CA, which has a lower pharmacotoxicity than diatrizoate and adverse effects rate. No inference can be drawn about the relationship between plasma cholinesterase activity and adverse effects.
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Butirilcolinesterasa/sangre , Butirilcolinesterasa/efectos de los fármacos , Colinesterasas/sangre , Colinesterasas/efectos de los fármacos , Medios de Contraste/farmacología , Diatrizoato/farmacología , Yohexol/farmacología , Femenino , Humanos , MasculinoRESUMEN
The effect of three iodinated contrast media (CM) on human plasma butyrylcholinesterase (BuChE) activity was studied during the intravenous pyelography (i.v.P). BuChE is an enzyme that participates in the metabolism of acetylcholine and hydrolyzes food esters and drugs such as nondepolarizing muscle relaxants and local anesthetics. The three CM were: diatrizoate (an ionic substance) and iohexol and iopentol (two nonionic substances). Five minutes after the intravenous injection, iohexol reduces BuChE plasma activity by 8.5% but this effect disappears within 15 minutes. Diatrizoate and iopentol decrease BuChE plasma activity by 8% and 15.2%, respectively, 5 minutes after the injection and this effect remains stable for the next 15 minutes. The underlying mechanism is unknown. Plasma BuChE activity remains within the normal range in any case and no association with side effects can be made. Thus, according to the above findings, it is not possible to connect or exclude any relationship between BuChE plasma activity and CM-derived adverse reactions during the i.v.P.
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Butirilcolinesterasa/efectos de los fármacos , Medios de Contraste/farmacología , Anciano , Butirilcolinesterasa/sangre , Colorimetría , Diatrizoato/farmacología , Femenino , Humanos , Yohexol/farmacología , Masculino , Persona de Mediana Edad , Ácidos Triyodobenzoicos/farmacología , UrografíaRESUMEN
Clinical and serial CT findings in 9 children, mainly infants with advanced tuberculous meningitis are presented. Hydrocephalus, tuberculomas and brain infarction were common findings in the acute stage of the disease. CT scan, allowing the detection and follow-up of cerebral manifestations of tuberculosis, proved to be an accurate and effective diagnostic method, which should be used in all cases of tuberculous meningitis.