124 research outputs found
Improved Precision in Surface-Enhanced Raman Scattering Quantification of Analyte through Dual-Modality Multisite Sensing
No full textAccurate
quantification of analyte using surface-enhanced Raman
spectroscopy (SERS) is a desired, yet unfulfilled, ability that could
enable a plethora of diagnostic- and defense-related applications.
The major hurdles to overcome to achieve this goal are expensive manufacturing
for highly ordered and reproducible substrates and low reproducibility
of substrates produced through low cost methods. A technology that
can set industry standards for manufacturing/processing of SERS substrates
is still yet to be achieved. A dual-modality multisite sensing approach
was developed, that overcomes the limitations experienced when fabricating
bottom-up, reproducible, sensitive, and low-cost SERS substrates.
Electrochemistry was combined with SERS for dual-modality sensing
to improve precision by adding redundancy and encoding features, thus
increasing measurement robustness and predictability. This technique
works by calibrating SERS response with respect to active surface
area, a parameter known to be proportional to charge, which can be
estimated via electrochemical measurements. The dual-modality multisite
measurement demonstrates at least 2.8× improvement in assay precision
compared to the traditional single-site Raman measurements. The technique
yields overall improved precision of measurement and is not limited
to any particular SERS substrate or geometry, and thus it can be adapted
and incorporated readily in any SERS sensing assay
Concrete particle characterization using impedance cytometry
No full textWe demonstrate a novel method to detect and characterize the size and number of Wollastonite particles using microfluidic impedance cytometry. The fabricated device which consists of gold electrodes micro-fabricated in a microchannel is capable of detecting particles >1 micron. Particle characterization is often carried out across a wide range of industries and is a critical parameter in the manufacture of various products to help improve the characteristics, performance or quality of powders or particles. There are a number of commercially available particle characterization techniques like laser diffraction, dynamic light scattering, electrophoretic light scattering, automated imaging, sedimentation etc that can be used to measure particulate samples and each has its relative strengths and limitations-there is no universally applicable technique for all samples. Our approach uses electrical impedance spectroscopy which measures the change in impedance as the particles in suspension pass through the sensor. It is a highly precise, low cost alternative for particle size characterization with a smaller footprint offering quick analysis time and is suitable for relatively broad range of particle sizes.M.S.Includes bibliographical referencesby Kavya Vasudevamurth
Multi-frequency impedance cytometry for biomolecular sensing and cell analysis
No full textWe live in a world with persistent, emerging, and reemerging infectious disease threats. Infections can be caused by pathogenic microbes, including viruses, bacteria, fungi, and parasites. The detection and identification of these pathogens are critical for diagnosis and treatment. Electrical based biosensor is particularly attractive in recent years due to the ease of operation, rapid processing time, non-necessity of labeling, and the potential of miniaturization. Electrical impedance is a straightforward technique that could identify the presence of biomolecules and cells and enable quantification analysis. In this thesis, I developed an electrical impedance based platform to quantify DNA concentration for viral detection and measure the impedance signature of different phenotypes of microbes for classification and pathogen assessment.
For DNA quantification, we introduce the integration of paramagnetic beads with DNA fragments and apply a custom-made microfluidic chip to detect DNA molecules bound to beads by measuring impedance at multiple frequencies. Technical and analytical performance was evaluated using beads containing short oligonucleotides or purified Polymerase Chain Reaction (PCR) products of different lengths and different concentrations.
Multiplex molecular biomarker analysis is of great importance in many biomedical and clinical studies. Electronic barcoding of micro-particles has the potential to enable multiplexing process. Nano-electronic barcoding works by depositing a thin layer of oxide on the top half of a micro-particle. We expanded library of nine barcoded particles by forming oxide layers of different thicknesses and different dielectric materials using atomic layer deposition and assess the ability to accurately classify particle barcodes using multi-frequency impedance cytometry in conjunction with supervised machine learning.
Separating specific cell phenotypes from a heterotypic mixture is a critical step in many research projects. Here we present the use of electrical impedance as an indicator of cell health and for identifying specific microbial phenotypes. We developed a microfluidic platform for measuring electrical impedance at different frequencies using Staphylococcus aureus and green alga Picochlorum SE3. Our results demonstrate the utility of electrical impedance as an indicator of cell phenotype by providing results that are consistent with known changes in cell size and physiology.Ph.D.Includes bibliographical reference
Assesment of patient response to targeted cancer therapy using multi-frequency impedance cytometry and supervised machine learning
No full textWe present a novel method to rapidly assess patient response to targeted cancer therapy, where anti-neoplastic agents are conjugated to antibodies targeting surface markers on tumor cells. We have fabricated and characterized a device capable of rapidly assessing tumor cell viability in response to the drug using multi-frequency impedance spectroscopy in combination with supervised machine learning for enhanced classification accuracy. Currently commercially available devices for the analysis of cell viability are based on staining with Trypan blue. Staining fundamentally limits the subsequent characterization of these cells as well as further molecular analysis, and requires 0.5-1.0 milliliter of volume. Our approach only requires 50 microliters of volume and avoids staining allowing for further molecular analysis. To the best of our knowledge, this work presents the first comprehensive attempt in using phase change obtained from impedance cytometry data to assess viability of cells. Use of impedance cytometry to quantify cancer cells from blood cells was also explored.M.S.Includes bibliographical referencesby Karan Shashi Ahuj
Aqueous concentrations of VEGF and soluble VEGF receptor-1 in diabetic retinopathy patients
No full textBackground: The aim of this study was to simultaneously measure the concentrations of vascular endothelial growth factor (VEGF) and soluble VEGF receptor-1 (sVEGFR-1, also known as sFlt-1) in the aqueous humor of patients with non-proliferative diabetic retinopathy (NPDR) and to investigate whether aqueous levels of vascular endothelial growth factor (VEGF) and VEGFR-1 are related to diabetic macular edema. Materials and Methods: Aqueous humor was collected from 27 diabetic patients and 33 age- and sex-matched normoglycemic controls and analyzed for pro-angiogenic VEGF and angiogenic inhibitor VEGFR-1 by enzyme-linked immunosorbent assay (ELISA). The mean foveal thickness was measured by optical coherence tomography (OCT). Results: There was no significant difference in the aqueous levels of VEGF in patients with NPDR compared with control subjects (P > 0.05), while the NPDR patients had significantly lower sVEGFR-1 in their aqueous humor. Furthermore, a significant (P < 0.01) positive correlation was observed between VEGF/sVEGFR-1 concentration and the mean foveal thickness measured on OCT. Conclusion: The results suggest that decreased chelating effect of sVEGFR-1 may be the preliminary event allowing VEGF to activate the proangiogenic endothelial cell state and to induce permeability. The imbalance between angiogenic agent (VEGF) and the antiangiogenic factors (sFlt-1), which is disturbed in the diabetic state, may determine the fate of diabetic macular edema
A New Method of Scheduling Tasks in Cloud Computing
No full textTask scheduling and energy efficiency seem to be the necessary design requirements for current computing systems in recent years. It extends from single servers to data centers and clouds, as they consume large amounts of electrical power. For this reason, an effective energy management for cloud data centers is essential. At present, many researchers have focused and implemented biologically-based calculations as a desirable paradigm for addressing heterogeneity and the growth of energy crisis with skill and no added complications. Similarly, for our work, we selected biological behavior of Korean insects and chosen FFO-based migration method. The benchmark for choosing it is the rapid convergence and global optimization. In addition, the notion of limiting the overall increase in power increases with respect to new VM migration and never before used for the VM migration method. In the energy consumption scenario by VM migration, a FFO-based linear model is formulated that executes an FFO algorithm that is able to solve the power consumption problem with the firefly attraction feature. In other words, this paper proposes a virtual energy virtualization migration technique that emits live VMs from an active node to another active node. The proposed technique uses the biography-inspired worn-out optimization technique to find the best node for over-migrating VMs to achieve energy efficiency in cloud data centers. This optimizes energy efficiency through the optimal migration of VMs, thereby improving the level of resource utilization
Effect of Soil Behavior Model on Drilling Response of Anchor-reinforced Excavation
No full textThe reinforced elements such as nailing and anchor have been widely used for the stability of excavation and trench because of not taking up a large space, improved soil properties by injection, greater safety and possibility of being used as permanent retaining structure. Due to the complex behavior of reinforced excavation, the stability analysis of reinforced excavation is performed by finite element method. Some factors such as boundary interval, dimensions and type of elements, and type of behavior model of materials affect the numerical results. Due to the complex behavior of the soil stress-strain, influence from stress path and loading history, and existence of groundwater, different behavior models have been proposed to simulate the materials. In this study, the effect of soil behavior model on the response of anchored excavation was investigated. For this purpose, using the finite element method in the plane strain conditions, the excavation reinforced with anchorage system was simulated for different geometrical conditions, and the results of the excavation response were compared for the Mohr-Coulomb, Drucker-Prager, and modified Cam-Clay behavior models. In the shallow excavation, it was found that the Mohr-Coulomb behavior model has the least displacement and the Drucker-Prager behavior model has the largest lateral displacement. The Drucker-Prager behavior model should be considered as a reliable criterion for the design and control of the excavation because of the greater results regarding the lateral displacement of excavation and generally, excavation deformation
MEASURING THE DELAY IN CHANNEL SWITCHING AND ITS OPTIMIZATION IN IPTV NETWORKS BY PRE-JOINING METHOD OF TV CHANNELS
No full textProviding television services over IP networks is a very attractive offer. As a new source of revenue offers for network operators, IPTV offers greater flexibility to network operators and provides a wide range of applications for users. to compete in this market, IPTV operators must guarantee at least the same quality of experience in this respect one of the main concerns is to delay in channel switching which is known as zapping delay zapping time in an IPTV network may be last 2 seconds or more Many efforts to reduce the channel switching delay has been done in IPTV network, One of these methods is the predictive adjustment which is called pre-joining. In this way with any request for watching the favorite TV channel, not only the desired channel stream, but also some other channels are added and sent to the client. However, it is required to use more bandwidth on the network. In this study an improved predictability adjustment is researched, the behavior of the user channel selection with SEMI-MARKO process is analyzed and we can estimate the average time of channel change and the average used bandwidth. The optimum number of pre-joining channels in a periodic time is also checked. For the accuracy of selection a simulation is done. Studies show that the proposed method leads to less time to change the channel with the least available bandwidth
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