562 research outputs found
Normal Pressure Hydrocephalus as an Unusual Presentation of Supratentorial Extraventricular Space-Occupying Processes: Report on Two Cases
Normal pressure hydrocephalus (NPH) is a clinical and radiographic syndrome characterized by ventriculomegaly, abnormal gait, urinary incontinence, and dementia. The condition may occur due to a variety of secondary causes but may be idiopathic in approximately 50% of patients. Secondary causes may include head injury, subarachnoid hemorrhage, meningitis, and central nervous system tumor. Here, we describe two extremely rare cases of supratentorial extraventricular space-occupying processes: meningioma and glioblastoma multiforme, which initially presented with NPH
Interlayer interaction, shear vibrational mode, and tribological properties of two-dimensional bilayers with a commensurate moir\'e pattern
The potential energy surface (PES) of interlayer interaction of infinite
twisted bilayer graphene is calculated for a set of commensurate moir\'e
patterns using the registry-dependent Kolmogorov-Crespi empirical potential.
The calculated PESs have the same shape for all considered moir\'e patterns
with the unit cell size of the PES which is inversely related to the unit cell
size of the moir\'e pattern. The amplitude of PES corrugations is found to
decrease exponentially upon increasing the size of the moir\'e pattern unit
cell. An analytical expression for such a PES including the first Fourier
harmonics compatible with the symmetries of both layers is derived. It is shown
that the calculated PESs can be approximated by the derived expression with the
accuracy within 1%. This means that different physical properties associated
with relative in-plane motion of graphene layers are interrelated and can be
expressed analytically as functions of the amplitude of PES corrugations. In
this way, we obtain the shear mode frequency, shear modulus, shear strength and
barrier for relative rotation of the commensurate twisted layers to a fully
incommensurate state for the considered moir\'e patterns. This barrier may
possibly lead to the macroscopic robust superlubricity for twisted graphene
bilayer with a commensurate moir\'e pattern. The conclusions made should be
valid for diverse 2D systems of twisted commensurate layers.Comment: 9 pages, 3 figures; Supplemental Material: 2 pages, 1 figur
Assessing the Bonding Properties of Individual Molecular Orbitals
Molecular orbitals (MOs), while one of the most widely used representations of the electronic structure of a system, are often too complex to intuit properties. Aside from the simplest of cases, it is not necessarily possible to visually tell which orbitals are bonding or antibonding along particular directions, especially in cases of highly delocalized and nontrivial bonding like metal clusters or solids. We propose a method for easily assessing and comparing the relative bonding contributions of MOs, by calculating their response to stress (e.g., compression). We find that this approach accurately describes relative bonding or antibonding character in both the simplest cases and provides new insight in more complex cases. We test the approach on four systems: H2, Am2, benzene, and the Pt4 cluster. In exploring this methodology, a scheme became elucidated, for predicting changes in the ground electronic configuration upon compression, including changes in bonding order, angular momenta of occupied MOs, and trends in MO ordering. We note that the applications of this work go beyond simple molecules and could be straightforwardly extended to, for example, solids and their response to stress along the specific crystallographic plane. Additionally, predictions of structures and properties of chemical systems under stress could result from the emerging intuition about changes in the electronic structure
Математические модели стационарных химико-технологических процессов со случайным временем протекания процесса в аппарате
In the article a number of chemical and physical processes with random stay time of of particles in the device are considered. On the basis of initial density of distribution of the value of the defining parameter in the particles entering in the device and of density of distribution of time of stay of particles in the device with the use of the kinetic equation of the process proceeding in the device densities of distribution of the defining parameter at the device outlet were obtained. For a cascade of devices density of distribution of probabilities of times of stay of particles in the device and the defining parameter were obtained.В статье рассматривается ряд химических и физических процессов со случайным временем пребывания частиц в аппарате. На основе исходной плотности распределения величины определяющего параметра в частицах, поступающих в аппарат, плотности распределения времени пребывания частиц в аппарате и уравнения кинетики протекающего в аппарате процесса получены плотности распределения определяющего параметра на выходе из аппарата. Для каскада аппаратов получены плотности распределения вероятностей времен пребывания частиц в аппарате и определяющего параметра
Photoinitiated azo-hydrazo tautomerizm of 1- p
A novel photochromic compound with NH-N intramolecular H-bond (1-p-toluenesulphonylazo-
2,4,6,8-tetrakis(tert-butyl)phenoxazine) and the corresponding model structures (1-oxo-2,4,6,8-tetrakis(tertbutyl)
phenoxazine, 2,4,5,7-tetrakis (tert-butyl )-1-( veratroylazo ) phenoxazine, 2,4,5,7-tetrakis ( tert-butyl )-Nacetyl-
1-(p-toluenesulphonylazo)phenoxazine) have been synthesized and their spectral and photochemical
properties are studied. The photochromic transformations observed are found to be conditioned by ESIPT
(as a primary step) followed by E-Z isomerisation about N–N-bond
ON IMPROVING THE EFFICIENCY OF PILE FOUNDATIONS
The paper analyzes the main problems affecting the efficiency of pile foundations. Questions of quality engineering and geological surveys, evaluation of bearing capacity of piles in the design of pile foundations, as well as issues of production piling.В статье анализируются основные проблемы, влияющие на эффективность применения свайных фундаментов. Рассмотрены вопросы качества инженерно-геологических изысканий, оценки несущей способности свай при проектировании свайных фундаментов, а также вопросы производства свайных работ.Сборник выпущен при поддержке Фонда содействия развитию УрФУ имени первого Президента России Б.Н. Ельцин
Acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-Ones: Molecular Switches with Varying Migrants and Substituents
Synthesis and properties of photochromic acylated 2-(N-arylaminomethylene)benzo[b]thiophene-3(2H)-ones are described. Their structure largely depends on the nature of acyl migrant and in a less degree on N-aryl substituent
Elication of an excitation center in the depth of tissue by visualization with high-frequency electric field
Hardware and software system, which makes it possible to visualize the glow center, marker of the excitation center in tissue, in the electric field, is created. The system was tested in 14 experiments with sinoatrial nodes of cat's hearts, which's fist excitation's center is in the depth of the right auricle's myocardium, and in 30 experiments with frog's venous sinuses, which's first excitation's center is situated in the superficial layer of the sinus wall. Also observations were held with deeply situated center - in cat's tooth's pulp, which is surrounded by insulators: dentine and tooth's enamel. The ability of visualization the excitation's center was developed at localizations in different depths
Synthesis of Novel Iono- and Photochromic Spiropyrans Derived from 6,7-Dihydroxy-8-Formyl-4-Methyl-2H-Chromene-2-One
Novel photochromic spiropyrans (SPPs) containing 6′-hydroxy group were synthesized and their spectral properties as well as abilities for complexation with metal ions studied. In solutions they exist as equilibrium mixture of spirocyclic (A) and merocyanine (B) isomers. The largest content of merocyanine form was found for the derivative with an electron-donating methyl group in position 5 of hetaryl fragment. The irradiation of SPPs in acetonitrile shifts the equilibrium to the B form. Similar effect causes the addition of metal cations due to formation of colored complexes with merocyanine isomers
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