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4,622 results on '"P. Ravichandran"'

501. A Minimal Mechanosensing Model Predicts Keratocyte Evolution on Flexible Substrates

Author

Zhang, Zhiwen, Rosakis, Phoebus, Hou, Thomas Y., and Ravichandran, Guruswami

Subjects
Physics - Biological Physics, Quantitative Biology - Cell Behavior
Abstract

A mathematical model is proposed for shape evolution and locomotion of fish epidermal keratocytes on elastic substrates. The model is based on mechanosensing concepts: cells apply contractile forces onto the elastic substrate, while cell shape evolution depends locally on the substrate stress generated by themselves or external mechanical stimuli acting on the substrate. We use the level set method to study the behavior of the model numerically, and predict a number of distinct phenomena observed in experiments, such as (i) symmetry breaking from the stationary centrosymmetric to the well-known steadily propagating crescent shape, (ii) asymmetric bipedal oscillations and traveling waves in the lamellipodium leading edge (iii) response to mechanical stress externally applied to the substrate (tensotaxis), (iv) changing direction of motion towards an interface with a rigid substrate (durotaxis) and (v) the configuration of substrate wrinkles induced by contractile forces applied by the keratocyte., Comment: Additional materia, 14 pagesl, 9 figures, 38 references

Published
2018
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502. Deformation twin nucleation and twin variant selection in single crystal magnesium as a function of strain rate

Author

Hazeli, Kavan, Kannan, Vignesh, Kingstedt, Owen, Ravichandran, Guruswami, and Ramesh, KT

Subjects
Physics - Applied Physics
Abstract

Deformation twinning is an important deformation mechanism in a variety of materials, including metals and ceramics. This deformation mechanism is particularly important in low-symmetry hexagonal close-packed (hcp) metals such as Magnesium (Mg), Zirconium (Zr) and Titanium (Ti). Extension twins in Mg, Zr and Ti can accommodate considerable plastic deformation as they grow. Thus, the rate and the mode of twinning greatly influences the mechanical behavior including strength and ductility. Herein, we study deformation twinning in terms of nucleation, twinning mode and variant selection as a function of strain rate in Mg single crystal (considered as a model material). We show that twin variant selection is sensitive to the loading rate, with more twin variants nucleating at the dynamic strain rates. Low Schmid factor twin variants (one of them being a double extension twin variant) were also found at the dynamic strain rates. Further at high strain rates, the first twins generated do not thicken beyond a critical width. Instead, plasticity proceeds with nucleation of second generation twins from the primary twin boundaries. The rates of area/volume fraction evolution of both generations of twins are found to be similar., Comment: We have to re analysis some of the data presented in the old version

Published
2018

503. Unexpected Termination Switching and Polarity Compensation in LaAlO3/SrTiO3 heterostructures

Author

Singh-Bhalla, Guneeta, Rossen, Pim B., Palsson, Gunnar K., Suresha, Jaganatha S., Yi, Di, Dasgupta, Abhigyan, Doenning, David, Ruiz, Victor G., Yadav, Ajay K., Trassin, Morgan, Heron, John T., Fadley, Charles S., Pentcheva, Rossitza, Ravichandran, Jayakanth, and Ramesh, Ramamoorthy

Subjects
Condensed Matter - Materials Science
Abstract

Polar crystals composed of charged ionic planes cannot exist in nature without acquiring surface changes to balance an ever-growing dipole. The necessary changes can manifest structurally or electronically. An electronic asymetry has long been observed in the LaAlO3/SrTiO3 system. Electron accumulation is observed near the LaAlO3/TiO2-SrTiO3 interface, while the LaAlO3/SrO-SrTiO3 stack is insulating. Here, we observe evidence for an asymmetry in the surface chemical termination for nominally stoichiometric LaAlO3 films in contact with the two different surface layers of SrTiO3 crystals, TiO2 and SrO. Using several element specific probes, we find that the surface termination of LaAlO3 remains AlO2 irrespective of the starting termination of SrTiO3 substrate surface. We use a combination of cross-plane tunneling measurements and first principles calcula- tions to understand the effects of this unexpected termination on band alignments and polarity compensation of LaAlO3/SrTiO3 heterostructures. An asymmetry in LaAlO3 polarity compensation and resulting electronic properties will fundamentally limit atomic level control of oxide heterostructures.

Published
2018
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504. Single-cell analysis of cardiogenesis reveals basis for organ-level developmental defects

Author

de Soysa, T Yvanka, Ranade, Sanjeev S, Okawa, Satoshi, Ravichandran, Srikanth, Huang, Yu, Salunga, Hazel T, Schricker, Amelia, del Sol, Antonio, Gifford, Casey A, and Srivastava, Deepak

Subjects
Pediatric, Stem Cell Research, Heart Disease, Stem Cell Research - Nonembryonic - Non-Human, Congenital Structural Anomalies, Cardiovascular, Genetics, 1.1 Normal biological development and functioning, Aetiology, Underpinning research, 2.1 Biological and endogenous factors, Animals, Basic Helix-Loop-Helix Transcription Factors, Cell Differentiation, Cell Movement, Cluster Analysis, Female, Heart, Heart Defects, Congenital, Male, Mice, Sequence Analysis, RNA, Single-Cell Analysis, Tretinoin, General Science & Technology
Abstract

Organogenesis involves integration of diverse cell types; dysregulation of cell-type-specific gene networks results in birth defects, which affect 5% of live births. Congenital heart defects are the most common malformations, and result from disruption of discrete subsets of cardiac progenitor cells1, but the transcriptional changes in individual progenitors that lead to organ-level defects remain unknown. Here we used single-cell RNA sequencing to interrogate early cardiac progenitor cells as they become specified during normal and abnormal cardiogenesis, revealing how dysregulation of specific cellular subpopulations has catastrophic consequences. A network-based computational method for single-cell RNA-sequencing analysis that predicts lineage-specifying transcription factors2,3 identified Hand2 as a specifier of outflow tract cells but not right ventricular cells, despite the failure of right ventricular formation in Hand2-null mice4. Temporal single-cell-transcriptome analysis of Hand2-null embryos revealed failure of outflow tract myocardium specification, whereas right ventricular myocardium was specified but failed to properly differentiate and migrate. Loss of Hand2 also led to dysregulation of retinoic acid signalling and disruption of anterior-posterior patterning of cardiac progenitors. This work reveals transcriptional determinants that specify fate and differentiation in individual cardiac progenitor cells, and exposes mechanisms of disrupted cardiac development at single-cell resolution, providing a framework for investigating congenital heart defects.

Published
2019

505. Prevalence and factors associated with overweight, obesity, and hypertension in a large clinical sample of adults with autism spectrum disorder

Author

Robyn P. Thom, Michelle L. Palumbo, Christopher J. Keary, Jacob M. Hooker, Christopher J. McDougle, and Caitlin T. Ravichandran

Subjects
Medicine, Science
Abstract

Abstract Adults with autism spectrum disorder (ASD) are at risk for excess bodyweight and hypertension, yet the prevalence of and clinical predictors for these health conditions remain unknown. The objective of this study was to assess the prevalence of overweight, obesity, and hypertension in a large clinical sample of adults with a confirmed diagnosis of ASD and to examine potential clinical predictors. This retrospective chart review study included adult subjects (≥ 20 years) with ASD who had been seen within the past 5 years at a multidisciplinary developmental disorders clinic. Data collected from the electronic health record included age, sex, race and ethnicity, cognitive ability, language ability, body mass index (BMI), hypertension, and use of second generation antipsychotic medications (SGAs). Of 622 adults with a confirmed diagnosis of ASD potentially eligible for the study, 483 (78%) had one or more notes in their records from the past 5 years. Those with recent notes were 23% female, 89% White, and had a mean (SD) age of 28.1 (7.1) years. Overall prevalence estimates for adults represented by this predominantly male, White, and young clinical sample were 28% (95% CI 24%, 32%) for overweight (BMI 25–29.9 kg/m2), 35% (95% CI 31%, 40%) for obesity (≥ 30 kg/m2), and 11% (95% CI 9%, 15%) for hypertension. Controlling for age and sex, intellectual disability (ID) was significantly associated with BMI (p = 0.003) but not hypertension (p = 0.69); those with moderate or more severe ID had a mean BMI that was 2.26 kg/m2 (95% CI 0.96, 3.57) lower than those with no ID. Controlling for age and sex, neither language ability, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) subtype of autism, nor past or current use of SGAs were significantly associated with BMI or hypertension. The study identified a high prevalence of overweight and obesity in adults with ASD consistent with the prevalence of these medical comorbidities in the U.S. population.

Published
2022
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506. Optical control of exciton spin dynamics in layered metal halide perovskites via polaronic state formation

Author

Sean A. Bourelle, Franco V. A. Camargo, Soumen Ghosh, Timo Neumann, Tim W. J. van de Goor, Ravichandran Shivanna, Thomas Winkler, Giulio Cerullo, and Felix Deschler

Subjects
Science
Abstract

Spintronic devices will require long spin lifetimes, but the effect of exciton-lattice coupling on spin lifetime in metal-halide perovskites is not well understood. Here, the authors find a 100-fold increase in the lifetime of exciton spins in a 2D perovskite by exciting with excess energy, resulting from strong coupling between excitons and optically excited phonons.

Published
2022
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507. Synergistic application of polypropylene and silica nanoparticle modified by (3-Aminopropyl) triethoxysilane for cuttings transport

Author

Jeffrey O. Oseh, M. N. A. M Norddin, Issham Ismail, Augustine Agi, Afeez O. Gbadamosi, Abdul R. Ismail, Prasad Manoger, and Kumaresan Ravichandran

Subjects
Annular velocity, (3-Aminopropyl) triethoxysilane, Cuttings sizes, Cuttings transport, PP-SiO2 NC-NH2, Rheological properties, Engineering (General). Civil engineering (General), TA1-2040
Abstract

Achieving the desired efficiency in cuttings transport has always been a challenge during drilling situations due to complex wellbore trajectories and drilling hydraulics. These issues require suitable additives to formulate the drilling muds. Hence, nanocomposite (NC) particles formed from silica and polypropylene was modified by (3-Aminopropyl) triethoxysilane (termed PP-SiO2 NC-NH2) and the impact of the concentrations of the PP-SiO2 NC-NH2 between 0.4 and 1.2 ppb on the cuttings transport efficiency (CTE) of complex water-based mud (WBM) system was assessed. Mud system containing 0.5 ppb PP-SiO2 NC-NH2 on CTE was measured and compared with that of partially hydrolyzed polyacrylamide (PHPA) using sandstone grains of diameters between 0.50 and 3.20 mm at hole angles 0, 30, 45, 60, and 90° with a 42 L/min pump rate. The zeta potential (ζ-potential), particle size distribution, morphology, and temperature resistance of the NC were examined. The ζ-potential data revealed the stability and the long-term stabilization of the modified NC in drilling muds. By adding the concentration of the modified NC into the WBM system, the thinning characteristics and consistency factors were enhanced as the NC concentration increases. Furthermore, the rheological test program reveals that the NC concentrations and 0.5 ppb PHPA increased the shear stress of the WBM with an increase in the shear rate. However, the mud system of PHPA exhibited a larger viscosity, while the NC samples showed a flat viscosity-profile. Also, the NC demonstrated better cuttings recovery than the PHPA product at 0.5 ppb concentration, especially at the worst hole angle of 45°. The cuttings recovery from a minimum to a maximum was found to occur in this order; 45°, 60°, 30°, 90°, and 0°. In contrast with the smallest and intermediate sand grains, the largest grains have complex and less fluid transport. With a pipe orbital motion of 150 rpm and a pump rate of 42 L/min, the CTE of the muds showed higher improvement. Overall, the mud properties of the modified NC exhibited a strong enhancing impact on the cuttings carrying capacity of the base mud than the PHPA.

Published
2022
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545. Adjuvanting a subunit SARS-CoV-2 vaccine with clinically relevant adjuvants induces durable protection in mice

Author

Grigoryan, Lilit, Lee, Audrey, Walls, Alexandra C., Lai, Lilin, Franco, Benjamin, Arunachalam, Prabhu S., Feng, Yupeng, Luo, Wei, Vanderheiden, Abigail, Floyd, Katharine, Wrenn, Samuel, Pettie, Deleah, Miranda, Marcos C., Kepl, Elizabeth, Ravichandran, Rashmi, Sydeman, Claire, Brunette, Natalie, Murphy, Michael, Fiala, Brooke, Carter, Lauren, Coffman, Robert L., Novack, David, Kleanthous, Harry, O’Hagan, Derek T., van der Most, Robbert, McLellan, Jason S., Suthar, Mehul, Veesler, David, King, Neil P., and Pulendran, Bali

Published
2022
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549. Induction of cross-neutralizing antibodies by a permuted hepatitis C virus glycoprotein nanoparticle vaccine candidate

Author

Sliepen, Kwinten, Radić, Laura, Capella-Pujol, Joan, Watanabe, Yasunori, Zon, Ian, Chumbe, Ana, Lee, Wen-Hsin, de Gast, Marlon, Koopsen, Jelle, Koekkoek, Sylvie, del Moral-Sánchez, Iván, Brouwer, Philip J. M., Ravichandran, Rashmi, Ozorowski, Gabriel, King, Neil P., Ward, Andrew B., van Gils, Marit J., Crispin, Max, Schinkel, Janke, and Sanders, Rogier W.

Published
2022
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550. mGluR5 binding changes during a mismatch negativity task in a multimodal protocol with [11C]ABP688 PET/MR-EEG

Author

Régio Brambilla, Cláudia, Veselinović, Tanja, Rajkumar, Ravichandran, Mauler, Jörg, Matusch, Andreas, Ruch, Andrej, Orth, Linda, Ramkiran, Shukti, Sbaihat, Hasan, Kaulen, Nicolas, Khudeish, Nibal Yahya, Wyss, Christine, Heekeren, Karsten, Kawohl, Wolfram, Rota Kops, Elena, Tellmann, Lutz, Scheins, Jürgen, Boers, Frank, Neumaier, Bernd, Ermert, Johannes, Lang, Markus, Stüsgen, Stefan, Herzog, Hans, Langen, Karl-Josef, Shah, N. Jon, Lerche, Christoph W., and Neuner, Irene

Published
2022
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