37 research outputs found
Two-loop renormalization of the Faddeev-Popov ghosts in N=1 supersymmetric gauge theories regularized by higher derivatives
No full textAbstract For the general renormalizable N=1 supersymmetric gauge theory we investigate renormalization of the Faddeev-Popov ghosts using the higher covariant derivative regularization. First, we find the two-loop anomalous dimension defined in terms of the bare coupling constant in the general ξ-gauge. It is demonstrated that for doing this calculation one should take into account that the quantum gauge superfield is renormalized in a nonlinear way. Next, we obtain the two-loop anomalous dimension of the Faddeev-Popov ghosts defined in terms of the renormalized coupling constant and examine its dependence on the subtraction scheme
Implementation of a Broadband Horn Antenna with High Level of Cross-polarization Discrimination in Microwave Inspection Systems
No full textThree-loop contribution of the Faddeev–Popov ghosts to the
No full textWe find the three-loop contribution to the -function of supersymmetric gauge theories regularized by higher covariant derivatives produced by the supergraphs containing loops of the Faddeev–Popov ghosts. This is done using a recently proposed algorithm, which essentially simplifies such multiloop calculations. The result is presented in the form of an integral of double total derivatives in the momentum space. The considered contribution to the -function is compared with the two-loop anomalous dimension of the Faddeev–Popov ghosts. This allows verifying the validity of the NSVZ equation written as a relation between the -function and the anomalous dimensions of the quantum superfields. It is demonstrated that in the considered approximation the NSVZ equation is satisfied for the renormalization group functions defined in terms of the bare couplings. The necessity of the nonlinear renormalization for the quantum gauge superfield is also confirmed
The Periglacial Lake Bretjorna (Ledovoe), Western Svalbard: History of Formation and Recent Sedimentation
No full textThis paper presents the results of geomorphological, geochronological and lithological investigation of a young sedimentation basin – the periglacial Lake Bretjorna (Ledovoe). Formation of the lake began at the end of the first half of the 20th century in the west of Nordenskiöld Land (Western Svalbard) within the marginal zone of the Grönfjord glacier, after significant degradation of this glacial massif. The present-day look of the lake was formed at the end of the 20th century however its geomorphological development went on until the beginning of the 21st. The filling of the sedimentation basin with limnoglacial sediments began approximately from the 1930s and proceeded with spatial and temporal irregularity. Bottom sediments of the lake presented mainly by silty-pelitic material, but in places with an admixture of gravel and pebbles, were formed as the front of the Grenfjord glacier retreated in the direction from north-east to south-west. At the first stage, sediment-genesis was mainly accomplished by the intra- and subglacial sediments, which entered the lake as a result of thermal erosion at the contact of the lake and ice since the late 1940s until the end of the last century, as the present-day lake basin became ice-free. Sediments formed at this stage are composed by coarser and poorly sorted material, which is typical for glacial deposits. At the second stage, the sediments became less coarse and more sorted. After the loss of contact between the lake and the glacier, the role of intra- and subglacial sediments decreased. At this time, sedimentation in the lake goes on by the runoff of melted glacial waters and atmospheric precipitation falling on the catchment area of the lake. The value of the average sedimentation rate in the lake was determined by means of radioisotope dating according to 210Pb and 137Cs and amounted 5.4 mm/year in the north, 12.4 mm/year in the central part, and 16.4 mm/year in the south of the lake, which is comparable with the data obtained by gravity method using sedimentological traps (12–15 mm/year)
Simulations of sawtooth instabilities in ASDEX Upgrade using the 3D nonlinear two-fluid MHD code M3D-C
No full textThree-loop verification of a new algorithm for the calculation of a β-function in supersymmetric theories regularized by higher derivatives for the case of N = 1 SQED
No full text
Modelling of (2,1) NTM dynamics with flow in JET advanced scenarios
No full textExperimental observations show that the βN threshold for (2,1) NTM excitation is increased by flow shear, but the physical explanation for this trend is still unclear. In this work, we investigate this issue by performing numerical experiments addressing the dependence of the critical island width on toroidal plasma rotation with the full MHD toroidal code XTOR (Lütjens and Luciani 2010 J. Comput. Phys.
229 8130–43), on the basis of a typical JET advanced tokamak case. We find that for situations where the Lundquist number is increased towards the experimental value, the (2,1) NTM is weakly destabilized by flow shear at low magnetic Prandtl number Prm, while the threshold remains nearly insensitive to the flow at high Prm. This weak effect of rotation shear also holds close to the linear regime, where an equivalent of the Δ′ concept adapted to nonlinear simulations does not indicate any significant variation with flow shear. The experimental trend is therefore not recovered, and possible explanations for this disagreement are discussed. A simple model of anisotropic viscous tensor shows that the high toroidal viscosity does not influence the value of the threshold, but comparison with experimental measurements suggests that the effective Prm seen by the mode is, however, larger than its small collisional value. Finally, the scaling of dimensionless parameters to ITER range is discussed.</jats:p
Моделирование и практическая реализация широкополосной двухгребневой рупорной антенны с шириной рабочей полосы более октавы и высоким уровнем кроссполяризационной развязки
Get PDFIntroduction. The resolution of the problem of radio polarimetry in multiposition microwave screening systems (MMSS) with aperture synthesis requires the use of antennas with a high level of cross-polarization discrimination (XPD) in a wide spatial angle. The radio images are reconstructed in MMSS at distances commensurate with the aperture of the antenna structures. Therefore, the value of the spatial angle, at which high XPD is required, can reach 30°. This leads to a new problem of creating an antenna configuration of the X and Ku band, the application of which in MMSS will resolve the problem of constructing a radio image of depolarized microwave radiation scattered on the human body in the form of hidden dangerous objects.Aim. To develop a double-ridged receiving antenna for long-term operation in MMSS with an XPD level of 28 dB at a spatial angle of 30° and operating frequencies of 8…20 GHz.Materials and methods. The requirements for the receiving antenna in MMSS were determined. Theoretical justifications were proposed for the choice of antenna design. Aperture synthesis was used to construct microwave images in MMSS. The stages and results of modelling broadband double-ridge antennas were presented using the CST Studio software broadly applied for three-dimensional electro-magnetic field modelling. The results of modelling pyramidal and conical double-ridged antennas, as well as those in circular and elliptical waveguides, were analyzed. The designed antenna was tested in an anechoic chamber. The measurement results were compared with those obtained during simulation.Results. An elliptical double-ridged horn antenna with a VSWR of no more than 2 and cross-polarization discrimination in a spatial angle of 30° of no less than 28 dB for the frequency range that covers an octave was designed and constructed.Conclusion. The developed antenna can be used in MMSS for the purpose of detecting the effect of micro-wave radiation depolarization as hidden dangerous objects on a human body. Such characteristics of the antenna as its high XPD value in a wide spatial angle will allow the future introduction of microwave polarimetry in MMSS.Введение. Для решения задачи радиополяриметрии в многопозиционных микроволновых досмотровых системах (ММДС) с апертурным синтезом необходимо использовать антенны с высоким уровнем кроссполяризационной развязки (КПР) в широком пространственном угле. Восстановление радиоизображений в ММДС происходит на дистанциях, соизмеримых с размерами апертуры антенных структур, поэтому значение пространственного угла, в котором необходимо выполнение требования высокой КПР, может достигать 30°. Таким образом, возникает новая задача создания антенной структуры X- и Ku-диапазонов, применение которой в ММДС позволило бы решить задачу построения радиоизображения деполяризованного микроволнового излучения, рассеянного скрытыми опасными объектами на теле человека.Цель работы. Разработка приемной антенны жесткой конструкции для долговременной эксплуатации в ММДС с уровнем КПР 28 дБ при пространственном угле 30° и рабочих частотах 8… 20 ГГц.Материалы и методы. Определены требования для приемной антенны в ММДС. Приведены теоретические обоснования для выбора конструкции антенны. В разработанной ММДС для построения микроволнового изображения используется апертурный синтез. Представлены этапы и результаты моделирования широкополосных двухгребневых антенн в программе трехмерного моделирования электромагнитного поля CST Studio. Рассмотрены результаты моделирования двухгребневых антенн: пирамидальной, конической, в круглом и эллиптическом волноводах. Произведено сравнение результатов измерения в безэховой камере для макета полученной антенны и результатов моделирования.Результаты. Разработана и изготовлена двухгребневая эллиптическая антенна жесткой конструкции, с КСВН не более 2 и кроссполяризационной развязкой в пространственном угле 30° не менее 28 дБ в диапазоне частот, перекрывающем октаву.Заключение. Антенна может быть использована в ММДС для детектирования эффекта деполяризации микроволнового излучения скрытыми опасными объектами на теле человека. Высокое значение КПР антенны в широком пространственном угле позволит в дальнейшем внедрить микроволновую поляриметрию в ММДС
<i>In Vitro</i> and <i>In Silico</i> Investigation of Water-Soluble Fullerenol C<sub>60</sub>(OH)<sub>24</sub>: Bioactivity and Biocompatibility
No full textLight fullerenes, C60 and
C70, have significant
potential in biomedical applications due to their ability to absorb
reactive oxygen species, inhibit the development of tumors, inactivate
viruses and bacteria, and as the basis for developing systems for
targeted drug delivery. However, the hydrophobicity of individual
fullerenes complicates their practical use; therefore, creating water-soluble
derivatives of fullerenes is increasingly important. Currently, the
most studied soluble adducts of fullerenes are polyhydroxy fullerenes
or fullerenols. Unfortunately, investigations of fullerenol biocompatibility
are fragmental. They often lack reproducibility both in the synthesis
of the compounds and their biological action. We here investigate
the biocompatibility of a well-defined fullerenol C60(OH)24 obtained using methods that minimize the content of impurities
and quantitatively characterize the product’s composition.
We carry out comprehensive biochemical and biophysical investigations
of C60(OH)24 that include photodynamic properties,
cyto- and genotoxicity, hemocompatibility (spontaneous and photo-induced
hemolysis, platelet aggregation), and the thermodynamic characteristics
of C60(OH)24 binding to human serum albumin
and DNA. The performed studies show good biocompatibility of fullerenol
C60(OH)24, which makes it a promising object
for potential use in biomedicine
