270 research outputs found
Myc and the Tip60 chromatin remodeling complex control neuroblast maintenance and polarity in Drosophila
No full textInterview with Lakshmi Raj Sharma, Author of The Tailor’s Needle
Get PDFInterview with Indian writer Lakshmi Raj Sharma, author of 'The Tailor's needle
Continuous flow platforms for the synthesis of high-quality semiconductor nanocrystals
Get PDFSemiconductor nanocrystals are of great interest due to their unique optical and electronic properties that are intermediate between bulk semiconductors and molecules. These nanoparticles find use in various applications ranging from electronics (light emitting diodes, photovoltaics) to photocatalysis and biolabeling. Typically, these nanoparticles are produced via batch synthesis routes that suffer from various issues, including slow mixing, slow heating/cooling, and lack of batch-to-batch reproducibility. These issues escalate further when increasing the scale of the production, thereby hindering their application on a commercial scale. Continuous flow synthesis can be an alternative approach that may enable high throughput and superior control of particle size and quality. However, since its first application in the early 2000s, most of the literature remains focused on continuous flow synthesis of Cd-based dots. Recently, the use of Cadmium (Cd) has been banned for many applications owing to its toxicity. Therefore, there is an immediate need for robust continuous flow reactors that enable synthesis of high quality Cd-free semiconductor nanoparticles.
The modular continuous flow reactor reported in this work enables multistep, high temperature (up to 750 °C), air-sensitive synthesis of semiconductor nanocrystals involving solid and/or viscous reactants. Additionally, the millifluidic dimensions of the reactor allow for high working flow rates (> 10 ml/min) that translate into a production rate of about 150 g/day of nanocrystals. This this configuration is well suited for scale-up. The developed continuous flow reactor is designed to achieve quick heating and cooling times (< 1 s), thereby providing superior control over reaction conditions compared to the level of control that can be achieved in conventional batch synthesis techniques. The flow reactor is composed of fracture-resistant material, stainless steel, which is compatible with a wide variety of solvents at high temperatures. Furthermore, the modular flow reactor allows for inline characterization of the product, through absorbance and fluorescence spectroscopy. To demonstrate the applicability of the modular continuous flow reactor, we used the reactor to synthesize multi-layered Cd-based core-shell dots, CdSe bipods and nanorods, ZnSe nanorods, and highly luminescent InP/ZnSeS core-shell dots.
The need for superior size control, shape selectivity and high reproducibility has resulted in a shift from conventional batch synthesis techniques to alternate synthesis routes. In the wake of such tight requirements, continuous flow syntheses, especially those relying on microfluidics, have emerged as viable routes for the synthesis of high-quality semiconductor nanocrystals. In general, continuous flow syntheses provide higher control over reaction conditions, for example mixing and heating times. We started by identifying the right material of construction and fabrication technique for building a continuous flow reactor that could withstand high temperatures. Design and fabrication of a simple oil-bath based continuous flow reactor and its application to demonstrate proof-of-principle syntheses of multi-layered Cd-based core-shell nanocrystals is discussed in Chapter 2. Use of heating media such as oil or hot water limits the maximum temperature attained by the reactor and is not suited for scale-up. To obviate the use of oil as a heating medium, a new continuous flow reactor was developed that uses a solid-state heating technique. The reactor configuration was further modified and coupled with a Schlenk line to enable high temperature, air-sensitive synthesis of semiconductor nanocrystals. Chapter 3 describes the design, fabrication, and operation of the new continuous flow reactor setup to synthesize anisotropic semiconductor nanocrystals, both Cd-based (CdSe nanorods/bipods) and Cd-free (ZnSe nanorods). Next, an inline mixer and a second reactor were added to the setup to enable multistep synthesis of InP/ZnSeS dots. Furthermore, the reactor design was upgraded to minimize the residence time distribution effects by the effective use of static mixers inside the reactor modules. Two flow cells were installed downstream of the reactors to enable inline spectroscopic characterization of the product. The design, fabrication, and operation of this multistep reactor setup are discussed in Chapter 4. Effective and fast mixing is critical to obtain uniform nanocrystals. However, fast mixing comes at the expense of high pressure drop. To alleviate this problem, we designed a high-throughput millifluidic herringbone mixer which is discussed in Chapter 5.
In summary, the modular continuous flow reactor developed here will pave the path for high-throughput synthesis of high-quality semiconductor nanocrystals. The described platform equipped with inline characterization capabilities can also be used to study the reaction kinetics of the aforementioned syntheses, which are not fully understood at present. Furthermore, the reactor also can be used for syntheses other than semiconductor nanocrystals, especially those that require stringent conditions, including high temperature, inert conditions, and fast mixing.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-08-01The student, Vivek Kumar, accepted the attached license on 2016-04-21 at 09:25.The student, Vivek Kumar, submitted this Dissertation for approval on 2016-04-22 at 08:15.This Dissertation was approved for publication on 2016-05-10 at 16:32.DSpace SAF Submission Ingestion Package generated from Vireo submission #9396 on 2018-08-14 at 15:59:43Made available in DSpace on 2018-08-14T21:37:15Z (GMT). No. of bitstreams: 13
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On-shell versus curvature mass parameter fixing schemes in the three flavor quark-meson model with vacuum fluctuations
Get PDFThe vacuum effective potential and phase diagram for the three (2+1) flavor
quark-meson model have been computed and compared in an extended mean-field
approximation (e-MFA) where the model parameters are fixed by using different
renormalization prescriptions after including quark one-loop vacuum
fluctuations. When the vacuum one-loop divergence is regularized in the minimal
subtraction scheme and the curvature masses of the scalar and pseudo-scalar
mesons are used for fixing the parameters, the setting of the quark-meson model
with the vacuum term (QMVT) turns out to be inconsistent as one notes that the
curvature masses are defined by the evaluation of self-energy at zero momentum.
This work constitutes the first application of the consistent on-shell
parameter fixing scheme to the three flavor quark-meson (QM) model. In this
setting of the renormalized quark-meson (RQM) model, the physical (pole) masses
of the and pseudo-scalar mesons and the scalar
meson,the pion decay constant and kaon decay constant are put into the
relation of the running mass parameter and couplings by using the on-shell and
the minimal subtraction renormalization schemes. The nonstrange direction
normalized vacuum effective potential plots for both the RQM model and QMVT
model, are exactly identical for the 658.8 MeV while the nonstrange
direction order parameter temperature variations and phase diagrams for both
the models RQM and PQMVT are identical when the value is smaller by
10 MeV i.e. 648 MeV. This happens because the normalized vacuum
effective potential variation in the nonstrange direction is somewhat
influenced by its variation in the strange direction.Comment: 29 Pages, 22 figures. arXiv admin note: text overlap with
arXiv:2202.1166
Correlation between CSF biomarkers of Alzheimer\u27s disease and cognitive decline toward a machine learning based predictive model
No full textEarly diagnosis of Alzheimer disease (AD) is still lacking as the traditional cognitive tests have several limitations. The most commonly utilized Mini–Mental State Examination (MMSE) scores assess cognition at one point in time and do not reflect its decline over time, they do not assess the subject\u27s functional status, and are susceptible to cultural influences. The search for molecular biomarkers for precise and early detection of the AD stages remains a challenge. The three biomarkers namely Ab1-42, T-tau, and P-tau that are found in the cerebrospinal fluid (CSF), have shown promise in AD diagnosis. In this work, we have analyzed an electronic health record of 378 subjects (collected from the National Alzheimer\u27s Coordinating Center database), including 145 subjects with normal cognition, 105 with mild dementia, 104 with moderate dementia, and 24 with severe dementia. We calculated the association between CSF biomarkers of the subjects with their MMSE scores using Pearson correlation. Our results : 1) in subjects with moderate dementia, MMSE scores correlate weakly with the three CSF biomarkers (r=0.19 for Ab1-42, r=0.15 for P-tau, and r=0.13 for T-tau) and 2) in subjects with severe dementia MMSE correlate moderately with the biomarkers (r=-0.34 for Ab1-42 and r= -0.62 for T-tau). The results are quite promising as they validate the need for a point-of-care sensor for non-invasive monitoring of these biomarker levels over time to facilitate early diagnosis and treatment of AD. Our next goal is to train a ML model for predicting the stage and conducting risk stratification of AD from the biomarker levels. The impact of our research is significant because the prediction models will aid the clinicians in diagnosing AD early and taking preventive action accordingly
Dynamics of a delayed prey-predator model using modified Holling Tanner functional response with migration
No full text
A Parametric Study of Functionally Graded Rotating Annular Fin
No full textAbstractPerformance analysis of the rectangular annular fins made of functionally graded material subjected to rotation is reported in the present work. The governing differential equation for the fins has been derived to study the temperature distribution of the fins with insulated tip. A parametric study is then carried out by varying grading parameters along with the parameter of dimensionless rotational speed of the shaft in the governing equation to investigate the effect of on fin performance. The results are presented in graphical form. The formulation is validated with benchmark results and good agreement is observed
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