1,202 research outputs found
University as Destiny: To the 65th Anniversary of Doctor of Historical Sciences, Professor S.G. Sidorov
No full textThe article is prepared for the 65th anniversary of Doctor of Historical Sciences, Professor of the Department of Russian and World History, Archaeology of Volgograd State University Sergey G. Sidorov. The article traces the biography of S.G. Sidorov, his pedagogical, scientific, and administrative activities. It is shown that fundamental foundations of the future pedagogical and scientific work of S.G. Sidorov were laid at the Faculty of History of Saratov State University named after N.G. Chernyshevsky, from which he graduated in 1981. Most of Sergey Grigoryevichs life is connected with Volgograd State University, where he has been working since 1986. He combined teaching historical disciplines with the administrative work. S.G. Sidorov was Vice-rector for Academic Affairs for 25 years. Being in this position he has done a lot to make Volgograd State University a leader in the region in training highly qualified specialists. S.G. Sidorov is one of the leading experts on the history of the Great Patriotic War. He is the author of the first fundamental comprehensive study of using labor of prisoners of war of the Second World War in the national economy of the USSR in 1939–1956. With his active participation, six volumes of Documents and Materials “Prisoners of War in the USSR. 1939–1956” were published. Since 2009, S.G. Sidorov has been the Head of the Dissertation Council on Historical Sciences at Volgograd State University. From 2014 to 2020, largely due to the efforts of S.G. Sidorov, Volgograd State University held five International Thematic Scientific Conferences “Military History of Russia: Problems, Searches, Solutions”
The simulation of free surface flows with Computational Fluid Dynamics
No full textComputational fluid dynamics is a powerful and versatile tool for the analysis of flow problems encountered in themaritime environment. The University of Southampton Fluid-Structure Interactions research group use ANSYS CFX tomodel a wide variety of flow problems; to gain insight into flow physics, improve designs and increase the efficiencyand safety of marine vehicles. A series of three case studies from on-going research looks at: loads applied on liquefiednatural gas tanks due to sloshing, slamming pressures experienced by high speed craft as well as the influence ofpropellers on the resistance characteristics of autonomous underwater vehicles. The presence of the free surface,complex shapes and the unsteady nature of these applications make their simulation with computational fluid dynamicsparticularly challenging. The successful validation of the computational models has resulted in the development of aselection process for suitable multiphase models as well as cost-effective meshing strategies
Mesoscopic electrochemistry in nanofluidic devices
No full textThis thesis describes nanofluidic devices capable of detecting small numbers of redox-active molecules and even single molecules. The detection relies on redox cycling, in which diffusive molecules rapidly transfer electrons between two parallel electrodes embedded in a thin, solution-filled channel. This high sensitivity permits studying the mesoscopic regime of electrochemistry in which the discreteness of molecules and statistical fluctuations can no longer be ignored.Kavli Institute of NanoscienceApplied Science
Electrostatic sensing and electrochemistry with single carbon nanotubes
No full textThis thesis describes the experimental study of devices based on single carbon nanotubes in the context of (bio)sensing in aqueous solutions. Carbon nanotubes are cylindrical molecules of sp2- carbon, about one nanometer in diameter and typically several micrometers long, which have semiconducting or metallic electronic properties. Nanotube devices can interact both electrostatically and electrochemically with the solution and the (bio)molecules dissolved in it. We study these interactions electronically with the aim to learn how carbon nanotube devices interact with their environment and how they can be used as the active elements in highly sensitive nanoscale (bio)sensors. First, we study the electrochemical interaction of redox molecules with carbon nanotube devices. An applied potential difference over the interface between a carbon nanotube and the solution can drive the electrochemical transfer of electrons from dissolved redox molecules to the nanotube and vice versa. We demonstrate that individual carbon nanotubes, both metallic and semiconducting, can be used as nanoelectrodes for electrochemistry. Due to the small diameter of nanotubes, the relative influx of electrochemically active molecules is so high that the kinetics of charge transfer become rate limiting. We provide a theoretical description of electrochemical charge transfer at nanotube and graphene electrodes. We find that, although the distinct electronic structure of nanotubes does play a role in the charge transfer process, metallic and semiconducting nanotubes cannot readily be distinguished. Even when a semiconducting nanotube is switched OFF, charge transfer can still take place at high rates. Next we explore carbon nanotubes employed as liquid-gated field-effect transistors. Although the literature contains an increasing amount of studies that use nanotubes for sensing purposes, a thorough fundamental understanding of how exactly these transistors interact with their environment is lacking. We elucidate and demonstrate several physical mechanisms that allow nanotubes to act as nanoscale electrostatic sensors. We show that the sensor response can be affected by an artifact related to the reference electrode. By eliminating this artifact we can study the effect of biomolecule adsorption near nanotube sensors unambiguously. Then we describe a method to identify the different mechanisms that can lead to a sensor response. We find that the origin of sensor response to biomolecule adsorption is a combination of a change in surface potential, and alterations to the tunnel barrier at the nanotube-metal contact. Contact effects make sensing unreliable, but these can be suppressed by covering up the contact regions. Finally, we show that carbon nanotube and graphene transistors are sensitive to changes in the ionic strength, the pH, and even the type of ions of the electrolyte. Changes in these electrolyte properties lead to a sensor response by changing the surface charge and the spatial distribution of ions, and thus the surface potential. We proceed by studying the signal-to-noise ratio for biosensing with liquid-gated carbon nanotube transistors. We show that the low-frequency noise is consistent with the fluctuation of nearby charges that gate the nanotube through a field-effect. The power of the noise is inversely proportional to the length of the nanotube. Surprisingly, the signal-to-noise ratio is highest in the sub-threshold regime. The decrease of the signal-to-noise ratio in ON state is related to additional noise sources and depends on device architecture. In specific cases the back gate can enhance the signal-to-noise ratio. Finally, we report our exploratory studies of carbon nanotube sensors as probes to study living cells. Although our results are suggestive that we can successfully detect cellular activity, the transistor stability and electrochemical sensitivity need to be improved. We show that the electrochemical sensitivity can be improved by coating nanotubes with catalytic nanoparticles. In conclusion, we have studied carbon nanotube devices in aqueous solution. The work presented in this thesis elucidates a number of different physical mechanisms, both electrochemical and electrostatic, through which carbon nanotube devices can interact with their environment. In addition, many of the concepts developed and studied here may be extended to other nanoscale sensors, such as nanowires and graphene. This knowledge can be used to further exploit the unique properties of carbon nanotubes, and pursue the ultimate goals of single-molecule detection and single-cell probing.Applied Science
Charge inversion and DNA condensation by multivalent ions
No full textScreening of charged particles by mobile ions in electrolytes is a major focus of such diverse fields as polymer physics, nanofluidics, colloid science, and biophysics. Yet the physics often remains poorly understood. Here we focus on two counterintuitive phenomena induced by multivalent counterions: charge inversion and DNA condensation.Applied Science
‘We are all in this together’: a creative non-fiction story of older adults participating in power-assisted exercise
No full textIn this study we aimed to explore older adults’ experience of community-based power assisted (PA) exercise and its potential impact on social exclusion, isolation and loneliness (SEI&L). The lead author obtained ethnographic data over a 6-month period using three primary methods: participant observation (900 hours), a reflexive diary, and 10 semi-structured interviews. Participant observation provided a rich lens into a PA exercise centre describing the scene, characters, and dialogue that enabled the ethnographer to interpret stories of SEI&L. Participants expressing stories of SEI&L (6 service-users, age 66–90 years) and participants working at the centre (3 staff members, age 41–50 years; 1 volunteer, age 69 years) were invited for interviews with the purpose of expanding on data from the field. We used dialogical narrative analysis to construct story themes and meaningful structures from the data that enabled a nuanced understanding of the plots and characters woven into the ethnographic creative non-fiction. Shifting our perspective from story analysts to storytellers, we have constructed two emotionally vibrant composite narratives to show the mechanisms and meanings of SEI&L for older adult exercisers following bereavement in later life and when living with a debilitating chronic health condition. The therapy centre provided a safe and inclusive space for older adults to reconnect through accessible modes of exercise and an atmosphere fostering a sense of belonging and togetherness. This work offers rich insight into older adult’s experiences of community-based exercise and raises awareness of SEI&L to help instigate personal and social change across multiple audiences
Responsive polyelectrolyte hydrogels and soft matter micromanipulation
No full textThis dissertation describes experimental studies on the mechanisms underlying the dynamic response of polyelectrolyte hydrogels when submitted to an external electric potential. In addition, we explore the possibilities of miniaturization and manipulation of responsive gels and other soft matter systems by using microfabrication techniques. Furthermore, a novel biocompatible hydrogel electro-active in biological fluids is developed. The possibilities of using this electro-responsive hydrogel system in bio-medical applications are investigated by studying it under in vitro conditions. By means of microfabrication techniques, we are able to miniaturize the hydrogel as a large array of responsive cilia, considerably increasing its response speed. Such cilia are also made bi-responsive by inclusion of magnetic particles. Finally, by mastering the microfabrication techniques we develop novel methods for micelle-based nanowire formation and soft-matter objects manipulation.Chemical EngineeringApplied Science
Building flood emergency scenarios in augmented reality
No full textTo find out if AR can be used for building flood scenarios in an application that uses optical see-through glasses the problem was first split up into different sub problems: user localisation, world creation and water level tracking. User localisation allows the user to walk around in the scenario. This is done using a combination of marker based tracking and IMU data. The location of the user is calculated by looking at the absolute position of the marker and the relative distance to it. Markers are the main source for calculating the position of the user. However, when no marker is visible, the IMU is a more prominent source. The acceleration and velocity are combined to calculate displacement over a time span, which can be combined with the last known position of the user to calculate the new position. Due to the fact that multiple sources can indicate different user positions, the predictions get combined in a Particle Filter, which calculates the most likely user position by looking at the given predictions and the standard deviations of those measurements. The final result gets smoothed to remove outliers. The result is a steady current position of the user which allows the user to walk around. To allow the user to build a scenario which can be flooded a combination of buttons and hand gestures is used to place and modify objects in the scene. The user can select and place objects such as buildings, street lanterns and garbage bins to create a world. Once objects have been placed they can be modified in the following ways: the object can be scaled, making it larger or smaller, the object can be rotated and finally the user can relocate objects. Furthermore, the user is able to save and load created worlds. To simulate a flood scenario two stepswere required to be completed. Firstly, an invisible plane was added to the virtual world which hides points that are below the plane. Secondly, the water level of the camera feed has to be tracked. Blocks were painted below the marker which were used to track the water level. This was done with an algorithm that uses the input of the marker’s location in the frame and data from the blocks and using that information calculated the water level. The steps of the algorithm are gray scale conversion, rotation, cropping, blurring, segmentation and counting segmented blocks respectively. Future work that can be done is a different, more accurate algorithm for marker tracking. Secondly, the different algorithms for the steps of the Particle Filter can be changed and improved. Finally, when a different algorithm is implemented for marker tracking, the algorithm for water level tracking can be combined with the rest of the project, allowing real-time flood simulation. It is recommended that the Meta SDK is best avoided because, despite the fact that is has a lot to offer, is not suited for an application in this field. Having solved the three sub problems resulted in the answer to the question can AR be used for building flood scenarios using optical see-through. The conclusion is that with the current state of AR, AR is not yet suited for this. The field of view on which objects can be displayed is too small which does not give a realistic visualisation of objects bigger than your hand. Secondly, calibrating the glasses properly for every user is something that still is and still has to be improved since not all users experience the projected world as an addition to the real world. Consequently, the virtual world looks like a floating screen instead of an addition to the real world.Electrical Engineering, Mathematics and Computer ScienceIntelligent System
Synthesis of certain new 6-iodoquinazolines as potential antitubercular agents
No full textAuthor: Abdel-Hamide S.G., Pharmaceutical Chemistry Department, Faculty of Pharmacy, King Saud University, P.O. Box 2457 Riyadh 1145ls Saudi Arabia E-mail: [email protected] the present study 2-(4-Chlorophenyl)-6-iodo-3, 4-dihydroquinazolin-4-one 3 was prepared by the
reaction of 2-(4-chlorophenyl)-6-iodo-4//-3,l-benzoxazin-4-one 2 with formamide. Treatment of 3 with
phosphorus penta sulfide yielded the fhione derivative 4. Alkylation of 3 and 4 with certain alkylhalides gave
the target compounds. The structure of the new compounds was confirmed by 'H NMR, IR and MS. Some of
the new compounds were screened for antitubercular activity, the 4-alkylfhio derivatives were active while the
4-alkyloxy derivatives were inactive
Temperature-Dependent Supramolecular Isomerism of Lutetium-Aminoterephthalate Metal-Organic Frameworks: Synthesis, Crystallography, and Physical Properties
No full textS.G.-G and R. M.-M. thank Ministerio de Economía y ́Competitividad, MAT2013-40950-R for financial support
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