Epilepsy Surgery in Children

ObjectiveIn the majority of patients with intractable epilepsy, seizures can be well controlled with appropriate medication. However, current estimates indicate that some of patients with epilepsy are refractory to all forms of medical therapy. The surgical treatment of intractable epilepsy in children has  evolved with advances in technical innovations. These medically intractable patients are candidates for surgical treatment in an attempt to achieve better seizure control. The definitive successful outcome of epilepsy surgery is a seizure-free state without significant neurological impairments.In this article, we will outline the essential elements of presurgical evaluation and describe a variety of therapeutic surgical options, and the related indications, techniques, results and complications of each procedure.

Assessment of changes in biochemical parameters associated with kidney function in patients with multiple sclerosis while taking the drug

زمینه و هدف: بیماری مولتیپل اسکلروزیس، یکی از شایع ترین بیماری های مغز و اعصاب محسوب می گردد. هدف از این مطالعه، بررسی تغییرات پارامترهای بیوشیمیایی مرتبط با عملکرد کلیه شامل اوره، اوریک اسید و کراتینین در بیماران مبتلا به ام اس در حین مصرف دارو و مقایسه آن ها با گروه کنترل است. روش بررسی: در این مطالعه، سطح سرمی اوره، اوریک اسید و کراتینین در 52 بیمار مبتلا به ام اس اندازه گیری شد و با 52 فرد سالم که از نظر سنی و جنسی و BMI با گروه بیمار هماهنگ بودند، مقایسه گردید. در نهایت داده ها با استفاده از روش تی تست، شاخص های میانگین و انحراف معیار توسط نرم افزار SPSS تحلیل شدند. یافته ها: میانگین سطح سرمی اوره در گروه بیمار و سالم به ترتیب 58/4±38/14 و 33/4±86/13 میلی گرم بر دسی لیتر مشاهده شد. میانگین غلظت اسید اوریک در گروه بیمار 99/0±66/4 و در گروه سالم 06/1±64/4 میلی گرم بر دسی لیتر و میانگین غلظت کراتینین نیز در گروه بیمار و سالم به ترتیب 10/0±85/0 و 11/0±78/0 میلی گرم بر دسی لیتر به دست آمد. نتیجه گیری: یافته های این تحقیق نشان داد که سطح سرمی اوره، اسید اوریک و کراتینین هیچ تفاوت آماری معنی داری بین گروه بیمار و کنترل نداشت

Resolving multi-dimensional plasma phenomena in Hall thrusters using the reduced-order particle-in-cell scheme

Plasma in Hall thrusters exhibits a complex behavior, characterized by the interplay between various dominant processes in each of the thruster’s coordinates. The emergence of high-power Hall thrusters in the recent years and the design modifications intended to extend the lifetime of these devices have further amplified the three-dimensional nature of the plasma behavior. In this regard, the novel reduced-order particle-in-cell (PIC) scheme provides the possibility to resolve the multi-dimensional interactions in a Hall thruster at a computational cost up to two orders of magnitude lower than current multi-dimensional PIC simulations. To demonstrate this point, we present in this article the results from a series of pseudo-two-dimensional simulations we performed in three configurations: axial-azimuthal, azimuthal-radial, and axial-radial. We show that, in each configuration, the pseudo-2D PIC scheme provides a significantly improved picture of the involved physics compared to a one-dimensional PIC simulation and captures self-consistently the coupling between the plasma processes in different directions, notably similar to the observations from full-2D kinetic simulations

TORTICOLLIS CAUSED BY NEUROENTERIC CYST OF UPPER CERVICAL REGION

Objective:Torticollis is a symptom that can be related to different pathological mechanisms ranging from simple to life-threatening conditions. Here we report a child with torticollis caused by a neuroenteric cyst in the upper cervical region; this is a very rare condition in childhood and  in this case, it was successfully resolved by surgery.Clinical presentation:A 2.5 year old boy presented with a 2 month-history of torticollis, he had developed paraparesia 2 weeks before admission. At examination he was found to be quadriparetic. Radiographic study of  the cervical spine revealed widening of the cervical canal. Brain and spinal magnetic resonance imaging revealed a hypointense lesion on the T1 at the craniovertebral junction having a  compressive effect on the anterior aspect of the brain stem and spinal cord.Intervention:The patient underwent surgery. After craniotomy and opening of the dura, a cystic lesion was seen; clear fluid was aspirated and the cyst wall was removed.Conclusion:Considering the quadriparesis and torticollis, the patient improved significantly within the first few days after surgery. No relapse of symptoms occurred during the follow up period. This is the first case report of a child in whom torticollis was due to a neuroenteric cyst of the upper cervical intradural region.Keywords:Torticollis - Neuroenteric cyst - Child - Quadriparesi

Verification of the generalized reduced-order particle-in-cell scheme in a radial-azimuthal E×B plasma configuration

In this article, we present an in-depth verification of the generalized electrostatic reduced-order particle-in-cell (PIC) scheme in a cross electric and magnetic field configuration representative of a radial-azimuthal section of a Hall thruster. The setup of the simulations follows a well-established benchmark case. The main purpose of this effort is to demonstrate that our novel PIC scheme can reliably resolve the complex two-dimensional dynamics and interactions of the plasma instabilities in the radial-azimuthal coordinates of a Hall thruster at a fraction of the computational cost compared to full-2D PIC codes. To this end, we first present the benchmarking of our newly developed full-2D PIC code. Next, we provide an overview of the reduced-order PIC scheme and the resulting “quasi-2D” code, specifying that the degree of order reduction in the quasi-2D PIC is defined in terms of the number of “regions” along the simulation’s directions used to divide the computational domain. We compare the predictions of the quasi-2D simulation in various approximation degrees of the 2D problem against our full-2D simulation results. We show that, by increasing the number of regions in the Q2D simulations, the quasi-2D results converge to the 2D ones. Nonetheless, we also highlight that a quasi-2D simulation that provides a factor of 5 reduction in the computational cost resolves the underlying physical processes in an almost indistinguishable manner with respect to the full-2D simulation and incurs a L2-norm error of only about 2 % in the ion number density and below 1 % in the electron temperature

Numerical modeling of fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Inconel 718

AbstractMost of the researches published on the numerical modeling of laser welding are looking at similar welding, mainly due to the difficulty of simulating the mixing phenomenon that occurs in dissimilar welding. Furthermore, numerical modeling of dissimilar laser welding of titanium and nickel alloys has been rarely reported in the literature. In this study, a 3D finite volume numerical model is proposed to simulate fluid flow, heat, and mass transfer for similar and dissimilar laser welding of Ti-6Al-4V and Inconel 718. The laser source was simulated by volumetric heat distribution, which considers the effects of keyhole and heat transfer on the workpiece. The heat source parameters were calibrated through preliminary experiments, by comparing the simulated and experimental weld pool shapes and dimensions. The model was used to simulate both homogenous and dissimilar laser weldings of Ti-6Al-4V and Inconel 718, and a systematic comparison was carried out through a number of selected experiments. The effects of three distinct levels of laser power (1.25 kW, 1.5 kW, 2.5 kW) on temperature distribution and velocity field in the welds pool were analyzed. Results highlighted the effects of Marangoni forces in the weld pool formation. Furthermore, in order to analyze the mass transfer phenomenon in dissimilar welding, species transfer equations were considered, demonstrating the important role played by the mass mixture in the weld pool formation. Finally, a high level of agreement between simulations and experiments—in terms of weld pool shape and dimensions—was observed in all cases analyzed. This proves the ability of the proposed numerical model to properly simulate both the similar and dissimilar welding of Ti-6Al-4V and Inconel 718 alloys

Theoretical investigation of a novel xylene-based light-driven unidirectional molecular motor

In this study, the working mechanism of the first light-driven rotary molecular motors used to control an eight-base-pair DNA hairpin has been investigated. In particular, this linker was reported to have promising photophysical properties under physiological conditions, which motivated our work at the quantum mechanical level. Cis-trans isomerization is triggered by photon absorption at wavelengths ranging 300 nm-400 nm, promoting the rotor to the first excited state, and it is mediated by an energy-accessible conical intersection from which the ground state is reached back. The interconversion between the resulting unstable isomer and its stable form occurs at physiological conditions in the ground state and is thermally activated. Here, we compare three theoretical frameworks, generally used in the quantum description of medium-size chemical systems: Linear-Response Time-Dependent Density Functional Theory (LR-TDDFT), Spin-Flip TDDFT (SF-TDDFT), and multistate complete active space second-order perturbation theory on state-averaged complete active space self consistent field wavefunctions (MS-CASPT2//SA-CASSCF). In particular, we show the importance of resorting to a multireference approach to study the rotational cycle of light-driven molecular motors due to the occurrence of geometries described by several configurations. We also assess the accuracy and computational cost of the SF-TDDFT method when compared to MS-CASPT2 and LR-TDDFT

Effect of stacking interactions on charge transfer states in photoswitches interacting with ion channels

The activity of ion channels can be reversibly photo-controlled via the binding of molecular photoswitches, often based on an azobenzene scaffold. Those azobenzene derivatives interact with aromatic residues of the protein via stacking interactions. In the present work, the effect of face-to-face and t-shaped stacking interactions on the excited state electronic structure of azobenzene and p-diaminoazobenzene integrated into the Na V1.4 channel is computationally investigated. The formation of a charge transfer state, caused by electron transfer from the protein to the photoswitches, is observed. This state is strongly red shifted when the interaction takes place in a face-to-face orientation and electron donating groups are present on the aromatic ring of the amino acids. The low-energy charge transfer state can interfere with the photoisomerization process after excitation to the bright state by leading to the formation of radical species. </p

Sesquicarbene Complexes:Bonding at the Interface Between M-C Single Bonds and M=C Double Bonds

Allylic dimetalated complexes [M2C(vinyl)]+ (M = Au(IPr) and Cr(CO)5 -) incorporate a new coordination mode of carbon. Digold complexes of this type have recently been detected experimentally. The intrinsic bond orbitals, partial charges, and structural parameters of the gold complexes and of chromium analogs were studied computationally and compared to those of the respective monometalated species and hydrocarbons. This showed that such digold complexes have a carbene character at both Au-C bonds comparable to typical carbene complexes of gold. Dichromium complexes with their stronger π-backdonation compete for interaction with carbon's π-orbital; each of the chromium atoms partakes in double bonding that is significant but weaker than that in the carbene analogs. Containing two M-C bonds on the interface between single and double bonds, these bridged complexes can be conceived as "sesquicarbene complexes". The π-system acted in a very adaptive manner and employed additional stabilization of the vinyl system only where needed. Significant carbene character is found simultaneously in both M-C bonds at the same carbon center. The discovery of these complexes with relatively strong double bond character between one carbon and two metal atoms could bring unusual single-carbon-centered organometallic cascade reactions to the horizon