Investigation Of Temperature Dependent Magnetic Hyperthermia In Fe3o4 Ferrofluids

Magnetic nanoparticles (MNPs) of Fe3O4 and gamma-Fe2O3 have been exploited in the biomedical fields for imaging, targeted drug delivery and magnetic hyperthermia. Magnetic hyperthermia (MHT), the production of heat using ferrofluids, colloidal suspensions of MNPs, in an external AC magnetic field (amplitude, 100-500 Oe and frequency 50 kHz -1MHz), has been explored by many researchers, both in vitro and in vivo, as an alternative viable option to treat cancer. The heat energy generated by Néel and Brownian relaxation processes of the internal magnetic spins could be used to elevate local tissue temperature to about 46 ˚C to arrest cancerous growth. MHT, due to its local nature of heating, when combined with other forms of treatment such as chemotherapy and/or radiation therapy, it could become an effective therapy for cancer treatment. The efficiency of heat production in MHT is quantified by specific absorption rate (SAR), defined as the power output per gram of the MNPs used. In this thesis, ferrofluids consisting of Fe3O4 MNPs of three different sizes (~ 10 - 13 nm) coated with two different biocompatible surfactants, dextran and polyethylene glycol (PEG), have been investigated. The structural and magnetic characterization of the MNPs were done using XRD, TEM, and DC magnetization measurements. While XRD revealed the crystallite size, TEM provided the information about morphology and physical size distribution of the MNPs. Magnetic measurements of M-vs-H curves for ferrofluids provided information about the saturation magnetization (Ms) and magnetic core size distribution of MNPs. Using MHT measurements, the SAR has been studied as a function of temperature, taking into account the heat loss due to non-adiabatic nature of the experimental set-up. The observed SAR values have been interpreted using the theoretical framework of linear response theory (LRT). We found the SAR values depend on particle size distribution of MNPs, Ms (65-80 emu/g) and the magnetic anisotropy energy density (K: 12-20 KJ/m3), as well as the amplitude and frequency of the applied AC field (amplitude, 150-250 Oe and frequency, 180-380 kHz). In general, Ms and magnetic core diameter of MNPs increased with the increase in particle size. However, our detailed analysis of MHT data show that although SAR increased with the particle size, the polydispersity of the particles as well as the magnetic anisotropy energy density significantly affected the SAR values. Dextran and PEG coatings essentially yielded similar SAR values ~ 100 W/g using ferrofluids of Fe3O4 MNPs with an average crystallite size of 11.6 ± 2.1 nm, in AC field of 245 Oe and 375 KHz

Efficient clustering techniques for managing large datasets

The result set produced by a search engine in response to the user query is very large. It is typically the responsibility of the user to browse the result set to identify relevant documents. Many tools have been developed to assist the user to identify the most relevant documents. One such a tool is clustering technique. In this method, the closely related documents are grouped based on their contents. Hence if a document turns out to be relevant, so are the rest of the documents in the cluster. So it would be easy for a user to sift through the result set and find the related documents, if all the closely related documents can be grouped together and displayed. This thesis deals with the computational overhead involved when the sizes of document collections grow very large. We will provide a survey of some clustering methods that efficiently utilize memory and overcome the computational problems when large datasets are involved

Ultrasensitive dopamine detection with graphene aptasensor multitransistor arrays

Detecting physiological levels of neurotransmitters in biological samples can advance our understanding of brain disorders and lead to improved diagnostics and therapeutics. However, neurotransmitter sensors for real-world applications must reliably detect low concentrations of target analytes from small volume working samples. Herein, a platform for robust and ultrasensitive detection of dopamine, an essential neurotransmitter that underlies several brain disorders, based on graphene multitransistor arrays (gMTAs) functionalized with a selective DNA aptamer is presented. High-yield scalable methodologies optimized at the wafer level were employed to integrate multiple graphene transistors on small-size chips (4.5 × 4.5 mm). The multiple sensor array configuration permits independent and simultaneous replicate measurements of the same sample that produce robust average data, reducing sources of measurement variability. This procedure allowed sensitive and reproducible dopamine detection in ultra-low concentrations from small volume samples across physiological buffers and high ionic strength complex biological samples. The obtained limit-of-detection was 1 aM (10-18) with dynamic detection ranges spanning 10 orders of magnitude up to 100 µM (10-8), and a 22 mV/decade peak sensitivity in artificial cerebral spinal fluid. Dopamine detection in dopamine-depleted brain homogenates spiked with dopamine was also possible with a LOD of 1 aM, overcoming sensitivity losses typically observed in ion-sensitive sensors in complex biological samples. Furthermore, we show that our gMTAs platform can detect minimal changes in dopamine concentrations in small working volume samples (2 µL) of cerebral spinal fluid samples obtained from a mouse model of Parkinson's Disease. The platform presented in this work can lead the way to graphene-based neurotransmitter sensors suitable for real-world academic and pre-clinical pharmaceutical research as well as clinical diagnosis.This work was funded by: "la Caixa" Banking Foundation under grant agree ment LCF/PR/HR21-00410; national funds, through the Foundation for Science and Technology (FCT)—projects UIDB/50026/2020, UIDP/50026/2020, and UIDB/04650/2020; by FCT project PTDC/MED-NEU/28073/2017 (POCI-01-307 0145-FEDER-028073); by The Branco Weiss fellowship—Society in Science (ETH Zurich); and by FCT Ph.D. fellowships SFRH/BD/14536/2022 (M.A.), SFRH/BD/08181/2020 (T.D.), and PD/BD/127823/2016 (D.R.)

Room-temperature emitters in wafer-scale few-layer hBN by atmospheric pressure CVD

Hexagonal boron nitride (hBN) is a two-dimensional, wide band gap semiconductor material suitable for several technologies. 2D hBN appeared as a viable platform to produce bright and optically stable single photon emitters (SPEs) at room temperature, which are in demand for quantum technologies. In this context, one main challenge concerns the upscaling of 2D hBN with uniform spatial and spectral distribution of SPE sources. In this work we optimized the atmospheric-pressure chemical vapor deposition (APCVD) growth and obtained large-area 2D hBN with uniform fluorescence emission properties. We characterized the hBN films by a combination of electron microscopy, Raman and X-ray photoelectron spectroscopy techniques. The extensive characterization revealed few-layer, polycrystalline hBN films (∼3 nm thickness) with balanced stoichiometry and uniformity over 2″ wafer scale. We studied the fluorescence emission properties of the hBN films by multidimensional hyperspectral fluorescence microscopy. We measured simultaneously the spatial position, intensity, and spectral properties of the emitters, which were exposed to continuous illumination over minutes. Three main emission peaks (at 538, 582, and 617 nm) were observed, with associated replica peaks red-shifted by ∼53 nm. A surface emitter density of ∼0.1 emitters/μm2 was found. A comparative test with pristine hBN nanosheets produced by liquid-phase exfoliation (LPE) was performed, finding that CVD and LPE hBN possess analogous spectral emitter categories in terms of peak position/intensity and density. Overall, the line-shape and wavelength of the emission peaks, as well as the other measured features, are consistent with single-photon emission from hBN. The results indicate that APCVD hBN might proficiently serve as a SPE platform for quantum technologies.We acknowledge the financial support of i) the project “GEMIS – Graphene-enhanced Electro Magnetic Interference Shielding,” with the reference POCI-01-0247-FEDER-045939, co-funded by COMPETE 2020 – Operational Programme for Competitiveness and Internationalization and FCT –Science and Technology Foundation, under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); ii) the project "Graphene and novel thin films for super-resolution microscopy and bio-sensing" (PTDC/NAN-OPT/29417/2017) financed by ERDF, through the Competitiveness and Internationalization Operational Program (POCI) by Portugal 2020 and by the Portuguese Foundation for Science and Technology (FCT) with references POCI-01-0145-FEDER-029417 and PTDC/NAN-OPT/29417/2017; iii) the FCT in the framework of the Strategic Funding UIDB/04650/2020. One of the authors (T.Q.) acknowledges the FCT financial support under the Quantum Portugal Initiative Ph.D. scholarship SFRH/BD/150646/2020. We acknowledge the support by the INL AEMIS, Micro- and Nanofabrication, and Nanophotonics and Bioimaging research core facilities

Synthesis and antibacterial profile of novel azomethine derivatives of β-phenylacrolein moiety

Purpose: To develop some novel molecules effective against antibiotic-resistant bacterial infections.Methods: A series of azomethines (SB-1 to SB-6) were synthesized from β-phenyl acrolein moiety. The structures of the synthesized compounds were confirmed on the basis of their UV ultra-violet (UV) spectroscopy (λmax: 200 - 400 nm), Fourier transform infra-red (FTIR, vibrational frequency: 500-4000 cm-1), 1H nuclear magnetic resonance (NMR, chemical shift: 0 - 10 ppm), 13C NMR (chemical shift: 0 - 200 ppm), mass spectrometry (m/z values: 0 - 500) and carbon hydrogen nitrogen (CHN) elemental analysis. The new compounds were screened for antibacterial activity by test-tube dilution and disc diffusion methods using gentamicin as reference standard.Results: The structures of azomethine were in full agreement with their spectral data. Among all the synthesized compounds, compounds SB-5 and SB-6 exhibited the highest minimum inhibitory concentration (MIC) of 62.5 μg/mL. At MIC of 250 μg/mL, all compounds SB-1 to SB-6 displayed significant antibacterial activity, compared to gentamycin (p < 0.05). SB-5 and SB-6 were active against S. aureus, P. aeruginosa and K. pneumoniae; SB-3 was active against B. subtilis and S. aureus. SB-4 was active against P. aeruginosa and S. aureus while SB-1 and SB-2 were active against S. aureus.Conclusion: The synthesized compounds possess antibacterial activities compared to those of gentamycin.Keywords: Acrolein, Imines, Azomethine, Antibacterial, Gentamycin, Minimum inhibitory concentratio

A Magnetically Supported Photodissociation Region in M17

The southwestern (SW) part of the Galactic H II region M17 contains an obscured ionization front that is most easily seen at infrared and radio wavelengths. It is nearly edge-on, thus offering an excellent opportunity to study the way in which the gas changes from fully ionized to molecular as radiation from the ionizing stars penetrates into the gas. M17 is also one of the very few H II regions for which the magnetic field strength can be measured in the photodissociation region ( PDR) that forms the interface between the ionized and molecular gas. Here we model an observed line of sight through the gas cloud, including the H+, H0 (PDR), and molecular layers, in a fully self-consistent single calculation. An interesting aspect of the M17 SW bar is that the PDR is very extended. We show that the strong magnetic field that is observed to be present inevitably leads to a very deep PDR, because the structure of the neutral and molecular gas is dominated by magnetic pressure, rather than by gas pressure, as previously had been supposed. We also show that a wide variety of observed facts can be explained if a hydrostatic geometry prevails, in which the gas pressure from an inner X-ray hot bubble and the outward momentum of the stellar radiation field compress the gas and its associated magnetic field in the PDR, as has already been shown to occur in the Orion Nebula. The magnetic field compression may also amplify the local cosmic-ray density. The pressure in the observed magnetic field balances the outward forces, suggesting that the observed geometry is a natural consequence of the formation of a star cluster within a molecular cloud

A Magnetically-Supported Photodissociation Region in M17

The southwestern (SW) part of the Galactic H II region M17 contains an obscured ionization front that is most easily seen at infrared and radio wavelengths. It is nearly edge-on, thus offering an excellent opportunity to study the way in which the gas changes from fully ionized to molecular as radiation from the ionizing stars penetrates into the gas. M17 is also one of the very few H II regions for which the magnetic field strength can be measured in the photodissociation region ( PDR) that forms the interface between the ionized and molecular gas. Here we model an observed line of sight through the gas cloud, including the H+, H0 (PDR), and molecular layers, in a fully self-consistent single calculation. An interesting aspect of the M17 SW bar is that the PDR is very extended. We show that the strong magnetic field that is observed to be present inevitably leads to a very deep PDR, because the structure of the neutral and molecular gas is dominated by magnetic pressure, rather than by gas pressure, as previously had been supposed.We also show that a wide variety of observed facts can be explained if a hydrostatic geometry prevails, in which the gas pressure from an inner X-ray hot bubble and the outward momentum of the stellar radiation field compress the gas and its associated magnetic field in the PDR, as has already been shown to occur in the Orion Nebula. The magnetic field compression may also amplify the local cosmic-ray density. The pressure in the observed magnetic field balances the outward forces, suggesting that the observed geometry is a natural consequence of the formation of a star cluster within a molecular cloud.Comment: Published as 2007, ApJ,658,111

Occurrence of diatom, pseudo-nitzschia spp. (bacillariophyceae) and related enviromental factors at Santubong and Samariang Batu estuaries in Kuching Division

Pseudo-nitzschia spp. is the causative organism for Amnesic Shellfish Poisoning (ASP) due to its capability of producing Domoic Acid. Occurrence of Pseudo-nitzschia spp. is highly dependent on the environmental conditions. Therefore ecological studies of this harmful diatom have been crucial. This study is initiated to understand the temporal distribution of Pseudo-nitzschia spp. related to environmental stricture along with attempt to understand the correlation of ecological effect to their diurnal distribution. Studies were carried out at two locations of Samariang Batu estuarine and Santubong river estuaries, Kuching. Results showed fluctuations of cell abundance every fortnight and on daily distribution. Presence of Pseudo-nitzschia spp. had statistical correlation with temperature, rainfall abundance and enrichment of reactive phosphorus nutrient. Nutrients found to be present with statistical significance (p<0.05) at both locations were Nitrate, reactive Phosphate and silicate ranging in-between 0 -2.04 mg/L, 0.01 -0.48 mg/L and 0.0 -2.772 mgIL respectively .The highest cell count was obtained at Santubong in January 2011 recording 3.9 X 104 cells L-1 Highest cell recorded at Samariang Batu was 1.4 X 103 cells L-'. Diurnal samples showed clear relationship between cell abundance and salinity. Cell density peaked upon high tide cycle with high salinity though throughout sampling salinity fluctuated amid 6.1 -7.6. Other parameters lacked statistical evidence to be correlated with the distribution of Pseudo-nitzschia spp. nevertheless there are other intangible variables involved