Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(PTC 2). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Indian Institute of Science

1. Gurudath, C S. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.

Degree: PhD, Faculty of Engineering, 2018, Indian Institute of Science

This work is concerned with the design, development and performance evaluation of an inertance Pulse Tube Cryocooler (PTC). The main components of a PTC are the compressor, regenerator, pulse tube and inertance tube coupled to a reservoir. The inertance tube is a key component that affects the pressure and mass flow and phase shift between them and hence the performance. In conjunction with the compressor, it also plays a strong role in determining the frequency of operation. The PTC is designed based on system level numerical models (SAGE and DeltaE), component level thermo-acoustic models (DeltaE) of inertance tube and regenerator and experimental data of earlier fabricated Stirling coolers. As a starting point, an inertance tube with a diameter of 3 mm and 3.1 m long was chosen through component level analysis that provides phase shift of around 50 degrees at a pressure ratio of 1.1 for an acoustic power of about 4 W (in order to achieve 1 W of net cooling at 80 K) at 25 bar mean pressure and 60 Hz. From this inertance tube geometry, an estimate of the mass flow rate at the cold heat exchanger is obtained. Based on this mass flow rate, the initial dimensions of the pulse tube and regenerator are arrived at. A parametric study using system level model is carried out to obtain the maximum COP by varying inertance tube length and regenerator diameter. A flexure bearing compressor consisting of moving coil linear motor coupled to a piston is designed for the above cold head. Based on the above design considerations, the PTC compressor and cold head are fabricated and assembled. The PTC is charged with helium at mean pressure of 25 bar and instrumented with pressure and position transducers, temperature sensors and a skin-bonded heater for simulating the heat load on the cold head. Experimental data for the PTC were obtained with two different inertance tube lengths for different frequencies of operation. The cold head temperature exhibited a minimum with respect to the frequency. This optimum frequency shifts towards lower frequency with increased length of the inertance tube. The experimental data clearly shows that with different inertance tube lengths the optimum frequency locates itself for obtaining zero phase shift at the middle of the regenerator. It is observed that the optimum frequency is closely linked to the natural frequency of the pressure wave in the inertance tube suggesting a standing wave within the inertance tube with the pressure node at the reservoir. Thus the inertance tube is found to be analogous to a quarter wave resonator in a thermo-acoustic device. It may thus be possible to pre-fix an operating frequency for a given PTC cold head by choosing an inertance tube length close to quarter wave resonator length. This study has given insights on the phase shift between pressure and mass flow rate governed by the inertance tube and the connection between the optimum and natural frequencies which can be used for better design of PTCs. Advisors/Committee Members: Narasimham, G S V L (advisor).

Subjects/Keywords: Stirling Cryocooler; Inertance Pulse Tube Cryocooler; Pulse Tube Cryocooler; Cryogenic Cooling Systems; HighFfrequency Cryocooler; PTC-1; PTC-2; Mechanical Engineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gurudath, C. S. (2018). Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3739

Chicago Manual of Style (16th Edition):

Gurudath, C S. “Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.” 2018. Doctoral Dissertation, Indian Institute of Science. Accessed October 25, 2020. http://etd.iisc.ac.in/handle/2005/3739.

MLA Handbook (7th Edition):

Gurudath, C S. “Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler.” 2018. Web. 25 Oct 2020.

Vancouver:

Gurudath CS. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2018. [cited 2020 Oct 25]. Available from: http://etd.iisc.ac.in/handle/2005/3739.

Council of Science Editors:

Gurudath CS. Experimental and Numerical Studies on Phase Shifting in an Inertance Pulse Tube Cryocooler. [Doctoral Dissertation]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3739


The Ohio State University

2. Lakshmanan, Aparna. Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs.

Degree: PhD, Molecular, Cellular and Developmental Biology, 2015, The Ohio State University

Thyroid cancer is the most common endocrine cancer and its incidence rates continue to rise. Papillary thyroid cancer (PTC) is the most common type and it is generally treatable with surgery followed by radioactive iodine (RAI) therapy. Thyrotropin (TSH)-stimulated, Sodium/Iodide Symporter (NIS)-mediated RAI uptake (RAIU) is the basis for RAI therapy. While most patients show good prognosis, a subset of patients with advanced thyroid cancer do not benefit from RAI therapy due to reduced NIS expression/function. The objective of this study was to investigate the molecular mechanisms of NIS modulation and to identify novel reagents that selectively increase RAIU in thyroid cells, such that the subset of patients could benefit from RAI therapy. Most common genetic alterations in PTCs are the BRAF(V600E) mutation that activates MEK/ERK signaling and RET/PTC rearrangement that activates both PI3K/Akt/mTOR and Ras/BRAF/MEK/ERK pathways. Hsp90 is a chaperone to many of these oncoproteins. TGF-beta is a cytokine in invasive fronts of thyroid tumors, which also activates MEK/ERK. These signaling nodes not only contribute to tumor progression but also result in reduced NIS expression/function. Here we report that among cell culture-grade small molecule inhibitors tested, Akt inhibitor (Akti1/2) increased TSH-stimulated RAIU to the greatest extent in PCCl3 rat thyroid cells, when compared to inhibitors of MEK, PI3K or Hsp90. We identified Apigenin, a plant-derived flavonoid that further increased RAIU by increasing iodide influx rate in combination with Akti1/2 and this required p38 MAPK activity, but not PKC-delta. The effect was confirmed in BRAF(V600E) or RET/PTC1-expressing PCCl3 cells, and in primary thyroid tumor cells from TR-beta(PV/PV) mice.We then took advantage of small molecule inhibitors targeting Akt, MEK, PI3K, Hsp90 or BRAF used in clinical trials for chemotherapy of solid tumors. As their toxicity profiles are well-accepted, if they increase thyroidal RAIU, they could be immediately employed in clinical trials to improve RAI treatment efficacy. We identified that PI3K inhibitor GDC-0941 outperformed other inhibitors in increasing TSH-stimulated RAIU in PCCl3 and BRAF(V600E)-expressing PCCl3 cells, by greatly decreasing iodide efflux rate. Alarmingly, TGF-beta dramatically reduced RAIU even upon treatment with inhibitors. Apigenin counteracted the RAIU reduction by TGF-beta by increasing NIS protein. Taken together, co-treatment of GDC-0941 with Apigenin may increase therapeutic efficacy of RAI in invasive fronts of thyroid cancer. While much is known about signaling nodes, little is known about microRNAs (miRs) regulating NIS and RAIU. We identified that miR-339-5p decreased endogenous NIS mRNA and RAIU in MCF-7 human breast cancer cells and in PCCl3 cells. Among 38 miRs deregulated by TGF-beta, Akti-1/2 or 17-AAG in PCCl3 cells, 18 were conserved in humans. One of the 18 miRs, miR-195, was predicted to bind to hNIS-3’UTR and its overexpression decreased hNIS-mediated RAIU in MCF-7 cells. MiR-339-5p was… Advisors/Committee Members: Jhiang, Sissy (Advisor).

Subjects/Keywords: Biomedical Research; Molecular Biology; Oncology; Thyroid cancer; Sodium Iodide Symporter; Radioactive iodide uptake; Akt; Akti1-2; Apigenin; p38MAPK; PKC-delta; PI3K; GDC-0941; Iodide efflux rate; MEK; Hsp90; BRAF; RET-PTC; TGF-beta; miR-339-5p; miR-195; Rottlerin; OSU-15; SREBP

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Lakshmanan, A. (2015). Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1429407914

Chicago Manual of Style (16th Edition):

Lakshmanan, Aparna. “Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs.” 2015. Doctoral Dissertation, The Ohio State University. Accessed October 25, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429407914.

MLA Handbook (7th Edition):

Lakshmanan, Aparna. “Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs.” 2015. Web. 25 Oct 2020.

Vancouver:

Lakshmanan A. Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs. [Internet] [Doctoral dissertation]. The Ohio State University; 2015. [cited 2020 Oct 25]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1429407914.

Council of Science Editors:

Lakshmanan A. Modulation of Sodium Iodide Symporter-mediated Thyroidal Radioiodide Uptake by Small Molecule Inhibitors, Natural Plant-based Products and microRNAs. [Doctoral Dissertation]. The Ohio State University; 2015. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1429407914

.