Search

Your search keyword '"Alvarez, Hector"' showing total 550 results
Start Over Author "Alvarez, Hector"
550 results on '"Alvarez, Hector"'

1. Nonlinear Discrete-Time Observers with Physics-Informed Neural Networks

Author

Alvarez, Hector Vargas, Fabiani, Gianluca, Kevrekidis, Ioannis G., Kazantzis, Nikolaos, and Siettos, Constantinos

Subjects
Mathematics - Numerical Analysis, Computer Science - Artificial Intelligence, Mathematics - Dynamical Systems, 37N30, 68T05, 93C55, 65D15
Abstract

We use Physics-Informed Neural Networks (PINNs) to solve the discrete-time nonlinear observer state estimation problem. Integrated within a single-step exact observer linearization framework, the proposed PINN approach aims at learning a nonlinear state transformation map by solving a system of inhomogeneous functional equations. The performance of the proposed PINN approach is assessed via two illustrative case studies for which the observer linearizing transformation map can be derived analytically. We also perform an uncertainty quantification analysis for the proposed PINN scheme and we compare it with conventional power-series numerical implementations, which rely on the computation of a power series solution.

Published
2024

2. Discrete-Time Nonlinear Feedback Linearization via Physics-Informed Machine Learning

Author

Alvarez, Hector Vargas, Fabiani, Gianluca, Kazantzis, Nikolaos, Siettos, Constantinos, and Kevrekidis, Ioannis G.

Subjects
Computer Science - Machine Learning, Mathematics - Dynamical Systems, Mathematics - Numerical Analysis, 65Pxx, 93C10, 68T07
Abstract

We present a physics-informed machine learning (PIML) scheme for the feedback linearization of nonlinear discrete-time dynamical systems. The PIML finds the nonlinear transformation law, thus ensuring stability via pole placement, in one step. In order to facilitate convergence in the presence of steep gradients in the nonlinear transformation law, we address a greedy-wise training procedure. We assess the performance of the proposed PIML approach via a benchmark nonlinear discrete map for which the feedback linearization transformation law can be derived analytically; the example is characterized by steep gradients, due to the presence of singularities, in the domain of interest. We show that the proposed PIML outperforms, in terms of numerical approximation accuracy, the traditional numerical implementation, which involves the construction--and the solution in terms of the coefficients of a power-series expansion--of a system of homological equations as well as the implementation of the PIML in the entire domain, thus highlighting the importance of continuation techniques in the training procedure of PIML.

Published
2023

9. Psychobiology of Stress and Adolescent Depression (PSY SAD) Study: Protocol overview for an fMRI-based multi-method investigation

Author

Sichko, Stassja, Bui, Theresa Q, Vinograd, Meghan, Shields, Grant S, Saha, Krishanu, Devkota, Suzanne, Olvera-Alvarez, Hector A, Carroll, Judith E, Cole, Steven W, Irwin, Michael R, and Slavich, George M

Subjects
Biomedical and Clinical Sciences, Clinical Sciences, Immunology, Basic Behavioral and Social Science, Behavioral and Social Science, Brain Disorders, Pediatric, Mind and Body, Clinical Research, Neurosciences, Serious Mental Illness, Mental Illness, Mental Health, Depression, Women's Health, 2.3 Psychological, social and economic factors, Aetiology, Mental health, Good Health and Well Being, Adolescent, Social rejection, Neural, fMRI, Neuroimaging, Immune, Cytokine, In flammation, Microbiome, Telomere, Biological aging, Risk, Disease, Health, Inflammation, Clinical sciences
Abstract

Depression is a common, often recurrent disorder that causes substantial disease burden worldwide, and this is especially true for women following the pubertal transition. According to the Social Signal Transduction Theory of Depression, stressors involving social stress and rejection, which frequently precipitate major depressive episodes, induce depressive symptoms in vulnerable individuals in part by altering the activity and connectivity of stress-related neural pathways, and by upregulating components of the immune system involved in inflammation. To test this theory, we recruited adolescent females at high and low risk for depression and assessed their psychological, neural, inflammatory, and genomic responses to a brief (10 minute) social stress task, in addition to trait psychological and microbial factors affecting these responses. We then followed these adolescents longitudinally to investigate how their multi-level stress responses at baseline were related to their biological aging at baseline, and psychosocial and clinical functioning over one year. In this protocol paper, we describe the theoretical motivations for conducting this study as well as the sample, study design, procedures, and measures. Ultimately, our aim is to elucidate how social adversity influences the brain and immune system to cause depression, one of the most common and costly of all disorders.

Published
2021

12. iTutorGroup: A Case Study of Covert Native-Speakerism underneath a Social Justice Façade

Author

Alvarez, Hector Sebastian

Abstract

This article examines the covert native-speakerist strategies iTutorGroup utilizes to discriminate against teachers of nationalities the company appears to deem as undesired. Through content analysis of numerous job application submissions to iTutorGroup's website, results show iTutorGroup's automatic hiring process offers teachers of these nationalities a much lower potential wage and only a video-recorded asynchronous interview, if not complete refusal to an interview. In contrast, British, Australasian, and North American nationals are afforded a much higher potential wage as well as a one-on-one live interview. The company conceals these nuanced discriminatory strategies with a façade of equality since they are one of TESOL International Association's Global Partners. As a Global Partner, iTutorGroup follows suit in pretending to uphold TESOL's nondiscrimination policies.

Published
2022

14. Nature and human well-being: The olfactory pathway

Author

Bratman, Gregory N., primary, Bembibre, Cecilia, additional, Daily, Gretchen C., additional, Doty, Richard L., additional, Hummel, Thomas, additional, Jacobs, Lucia F., additional, Kahn, Peter H., additional, Lashus, Connor, additional, Majid, Asifa, additional, Miller, John D., additional, Oleszkiewicz, Anna, additional, Olvera-Alvarez, Hector, additional, Parma, Valentina, additional, Riederer, Anne M., additional, Sieber, Nancy Long, additional, Williams, Jonathan, additional, Xiao, Jieling, additional, Yu, Chia-Pin, additional, and Spengler, John D., additional

Published
2024
Full Text
View/download PDF

18. Associations of nature contact with emotional ill-being and well-being: the role of emotion regulation.

Author

Bratman, Gregory N., Mehta, Ashish, Olvera-Alvarez, Hector, Spink, Katie Malloy, Levy, Chaja, White, Mathew P., Kubzansky, Laura D., and Gross, James J.

Subjects
STRUCTURAL equation modeling, WELL-being, ADULTS
Abstract

Nature contact has associations with emotional ill-being and well-being. However, the mechanisms underlying these associations are not fully understood. We hypothesised that increased adaptive and decreased maladaptive emotion regulation strategies would be a pathway linking nature contact to ill-being and well-being. Using data from a survey of 600 U.S.-based adults administered online in 2022, we conducted structural equation modelling to test our hypotheses. We found that (1) frequency of nature contact was significantly associated with lesser emotional ill-being and greater emotional well-being, (2) effective emotion regulation was significantly associated with lesser emotional ill-being and greater emotional well-being, and (3) the associations of higher frequency of nature contact with these benefits were partly explained via emotion regulation. Moreover, we found a nonlinear relationship for the associations of duration of nature contact with some outcomes, with a rise in benefits up to certain amounts of time, and a levelling off after these points. These findings support and extend previous work that demonstrates that the associations of nature contact with emotional ill-being and well-being may be partly explained by changes in emotion regulation. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

19. Factors Impacting Clinically Relevant RNA Fusion Assays Using Next-Generation Sequencing

Author

Ramani, Nisha S., Patel, Keyur P., Routbort, Mark J., Alvarez, Hector, Broaddus, Russell, Chen, Hui, Rashid, Asif, Lazar, Alex, Lucas, Francis A. San, Yao, Hui, Manekia, Jawad, Dang, Hyvan, Barkoh, Bedia A., Medeiros, L. Jeffrey, Luthra, Rajyalakshmi, and Roy-Chowdhuri, Sinchita

Subjects
Tumors -- Diagnosis, RNA sequencing -- Methods, Molecular diagnostic techniques -- Methods, Biochemical assays -- Usage, Health
Abstract

Context.--RNA-based next-generation sequencing (NGS) assays are being used with increasing frequency for comprehensive molecular profiling of solid tumors. Objective.--To evaluate factors that might impact clinical assay performance. Design.--A 4-month retrospective review of cases analyzed by a targeted RNA-based NGS assay to detect fusions was performed. RNA extraction was performed from formalin-fixed, paraffin-embedded tissue sections and/or cytology smears of 767 cases, including 493 in-house and 274 outside referral cases. The types of samples included 422 core needle biopsy specimens (55%), 268 resection specimens (35%), and 77 cytology samples (10%). Results.--Successful NGS fusion testing was achieved in 697 specimens (90.9%) and correlated positively with RNA yield (P < .001) and negatively with specimen necrosis (P = .002), decalcification (P < .001), and paraffin block age of more than 2 years (P = .001). Of the 697 cases that were successfully sequenced, 50 (7.2%) had clinically relevant fusions. The testing success rates and fusion detection rates were similar between core needle biopsy and cytology samples. In contrast, RNA fusion testing was often less successful using resection specimens (P = .007). Testing success was independent of the tumor percentage in the specimen, given that at least 20% tumor cellularity was present. Conclusions.--The success of RNA-based NGS testing is multifactorial and is influenced by RNA quality and quantity. Identification of preanalytical factors affecting RNA quality and yield can improve NGS testing success rates. (Arch Pathol Lab Med. 2021;145:1405-1412; doi: 10.5858/arpa.2020-0415-OA), With the increasing use of targeted therapeutic agents in solid tumors, RNA-based next-generation sequencing (NGS) assays are progressively used for comprehensive molecular analysis. (1) Chromosome translocations and/or gene fusions are [...]

Published
2021
Full Text
View/download PDF

24. Free-living diazotrophs differ among soil microhabitats, soil depth, and seasonality in a tropical dryland of central Mexico

Author

Serrano-Vázquez, Angélica, Pérez-Juárez, Horacio, Rivera-Aguilar, Víctor M., Escalante, Ana E., Arenas, Diego, Bazán, Jesús, Rojas-Velázquez, Liliana, Morán, Patricia, González Rivas, Enrique, Moreno Torres, Ramón Víctor, Ibarra, David, Alonso de la Rosa, María de Lourdes, Ximénez, Cecilia, Rodríguez-Zaragoza, Salvador, and Godínez-Alvarez, Héctor

Published
2021
Full Text
View/download PDF

30. Intragenic EGFR::EGFR.E1E8 Fusion (EGFRvIII) in 4331 Solid Tumors

Author

Zheng, Lan, primary, Luthra, Rajyalakshmi, additional, Alvarez, Hector A., additional, San Lucas, F. Anthony, additional, Duose, Dzifa Y., additional, Wistuba, Ignacio I., additional, Fuller, Gregory N., additional, Ballester, Leomar Y., additional, Roy-Chowdhuri, Sinchita, additional, Sweeney, Keith J., additional, Rashid, Asif, additional, Yang, Richard K., additional, Chen, Wei, additional, Liu, Audrey, additional, Wu, Yun, additional, Albarracin, Constance, additional, Patel, Keyur P., additional, Routbort, Mark J., additional, Sahin, Aysegul A., additional, Ding, Qingqing, additional, and Chen, Hui, additional

Published
2023
Full Text
View/download PDF

31. 30. Chromosomal microarray analysis work-up for hypocellular MDS patients with inconclusive cytogenetics

Author

Nguyen, Ha, primary, Xu, Fangling, additional, Raju, Sherin, additional, Ahmed, Nazneen, additional, Bowman, Christopher, additional, Alvarez, Hector, additional, Dang, Hyvan, additional, Kalia, Awdhesh, additional, Hu, Peter, additional, Luthra, Rajyalakshmi, additional, Rush, Diana, additional, Tang, Guilin, additional, Kim, Kunhwa, additional, Chien, Kelly, additional, and Garcia-Manero, Guillermo, additional

Published
2023
Full Text
View/download PDF

34. Circulating Nucleic Acids Are Associated With Outcomes of Patients With Pancreatic Cancer

Author

Bernard, Vincent, Kim, Dong U., San Lucas, F. Anthony, Castillo, Jonathan, Allenson, Kelvin, Mulu, Feven C., Stephens, Bret M., Huang, Jonathan, Semaan, Alexander, Guerrero, Paola A., Kamyabi, Nabiollah, Zhao, Jun, Hurd, Mark W., Koay, Eugene J., Taniguchi, Cullen M., Herman, Joseph M., Javle, Milind, Wolff, Robert, Katz, Matthew, Varadhachary, Gauri, Maitra, Anirban, and Alvarez, Hector A.

Published
2019
Full Text
View/download PDF

35. All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz

Author

Guzmán, Andres E., May, Jorge, Alvarez, Hector, and Maeda, Koitiro

Subjects
Astrophysics - Galaxy Astrophysics
Abstract

Aims: We study the Galactic large-scale synchrotron emission by generating a reliable all-sky spectral index map and temperature map at 45 MHz. Methods: We use our observations, the published all-sky map at 408 MHz, and a bibliographical compilation to produce a map corrected for zero-level offset and extragalactic contribution. Results: We present full sky maps of the Galactic emission at 45 MHz and the Galactic spectral index between 45 and 408 MHz with an angular resolution of 5\degs. The spectral index varies between 2.1 and 2.7, reaching values below 2.5 at low latitude because of thermal free-free absorption and its maximum in the zone next to the Northern Spur., Comment: A&A accepted

Published
2010
Full Text
View/download PDF

36. Uncertainty Relations in Self-Similar Convergent Trajectories

Author

Ceceña-Álvarez., Héctor, Peimbert-Torres., Antonio, and Gómez-González, Raúl W.

Subjects
Quantum Physics
Abstract

The Koch curve is a self-similar object whose length grows unboundedly when the measuring unit by which is calculated diminishes. If this curve is considered to be the trajectory of a point corpuscle of mass m (a particle) rendering it in a time t, while the measuring unit in the kth scale is associated with the indetermination in the position of the corpuscle, then it is possible to demonstrate that when the indetermination of the corpuscle position diminishes, the indetermination in its linear momentum grows unboundedly. Based on the concept of similarity dimension of a corpuscle trajectory, from the before stated line of reasoning an alternative deduction of Heisenberg's uncertainty relation (Delta)x(Delta)p(sub)x (aprox)h is developed and discussed., Comment: PDF, fourteen pages, two figures

Published
2009

49. Vestigial-like 1 is a shared targetable cancer-placenta antigen expressed by pancreatic and basal-like breast cancers

Author

Bradley, Sherille D., Talukder, Amjad H., Lai, Ivy, Davis, Rebecca, Alvarez, Hector, Tiriac, Herve, Zhang, Minying, Chiu, Yulun, Melendez, Brenda, Jackson, Kyle R., Katailiha, Arjun, Sonnemann, Heather M., Li, Fenge, Kang, Yaan, Qiao, Na, Pan, Bih-Fang, Lorenzi, Philip L., Hurd, Mark, Mittendorf, Elizabeth A., Peterson, Christine B., Javle, Milind, Bristow, Christopher, Kim, Michael, Tuveson, David A., Hawke, David, Kopetz, Scott, Wolff, Robert A., Hwu, Patrick, Maitra, Anirban, Roszik, Jason, Yee, Cassian, and Lizée, Gregory

Published
2020
Full Text
View/download PDF

50. Exosomes harbor B cell targets in pancreatic adenocarcinoma and exert decoy function against complement-mediated cytotoxicity

Author

Capello, Michela, Vykoukal, Jody V., Katayama, Hiroyuki, Bantis, Leonidas E., Wang, Hong, Kundnani, Deepali L., Aguilar-Bonavides, Clemente, Aguilar, Mitzi, Tripathi, Satyendra C., Dhillon, Dilsher S., Momin, Amin A., Peters, Haley, Katz, Matthew H., Alvarez, Hector, Bernard, Vincent, Ferri-Borgogno, Sammy, Brand, Randall, Adler, Douglas G., Firpo, Matthew A., Mulvihill, Sean J., Molldrem, Jeffrey J., Feng, Ziding, Taguchi, Ayumu, Maitra, Anirban, and Hanash, Samir M.

Published
2019
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results