Engineering Commons^™

Interaction Between The Stress Phase Angle (Spa) And The Oscillatory Shear Index (Osi) Affects Endothelial Cell Gene Expression, Ronny Amaya, Limary M. Cancel, John M. Tarbell

Publications and Research

Hemodynamic forces play an important role in the non-uniform distribution of atherosclerotic lesions. Endothelial cells are exposed simultaneously to fluid wall shear stress (WSS) and solid circumferential stress (CS). Due to variations in impedance (global factors) and geometric complexities (local factors) in the arterial circulation a time lag arises between these two forces that can be characterized by the temporal phase angle between CS and WSS (stress phase angle±SPA). Asynchronous flows (SPA close to -180Ê) that are most prominent in coronary arteries have been associated with localization of atherosclerosis. Reversing oscillatory flows characterized by an oscillatory shear index (OSI) that …

Ocean–Atmosphere Interactions Modulate Irrigation’S Climate Impacts, Nir Y. Krakauer, Michael J. Puma, Benjamin I. Cook, Pierre Gentine, Larisa Nazarenko

Publications and Research

Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean– atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity.We find that ocean–atmosphere interaction does impact the magnitude of globalmean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, …

The Effects Of Compensatory Auditory Stimulation And High-Definition Transcranial Direct Current Stimulation (Hd-Tdcs) On Tinnitus Perception - A Randomized Pilot Study, Simon Henin, Dovid Fein, Eric Smouha, Lucas C. Parra

Publications and Research

Background Tinnitus correlates with elevated hearing thresholds and reduced cochlear compression. We hypothesized that reduced peripheral input leads to elevated neuronal gain resulting in the perception of a phantom sound. Objective The purpose of this pilot study was to test whether compensating for this peripheral deficit could reduce the tinnitus percept acutely using customized auditory stimulation. To further enhance the effects of auditory stimulation, this intervention was paired with high-definition transcranial direct current stimulation (HD-tDCS).

Methods A randomized sham-controlled, single blind study was conducted in a clinical setting on adult participants with chronic tinnitus (n = 14). Compensatory auditory stimulation …

Investigation Of Electric Field–Induced Structural Changes At Fe-Doped Srtio3 Anode Interfaces By Second Harmonic Generation, David Ascienzo, Haochen Yuan, Steven Greenbaum, Thorsten J. Bayer, Russell A. Maier, Jian-Jun Wang, Clive A. Randall, Elizabeth C. Dickey, Haibin Zhao, Yuhang Ren

Publications and Research

We report on the detection of electric field–induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO3 (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O bond stretching and bending in Fe:Ti-O6 octahedra. For the oxidized crystal, no obvious structural changes are observed below 16 kV/cm. Above 16 kV/cm, a sharp enhancement of the susceptibilities occurs due to local electrostrictive deformations in response to oxygen vacancy migrations away from the anode. Differences between …

Evolution From The Plasmon To Exciton State In Ligand-Protected Atomically Precise Gold Nanoparticles, Meng Zhou, Chenjie Zeng, Yuxiang Chen, Shuo Zhao, Matthew Y. Sfeir, Manzhou Zhu, Rongchao Jin

Publications and Research

The evolution from the metallic (or plasmonic) to molecular state in metal nanoparticles constitutes a central question in nanoscience research because of its importance in revealing the origin of metallic bonding and offering fundamental insights into the birth of surface plasmon resonance. Previous research has not been able to probe the transition due to the unavailability of atomically precise nanoparticles in the 1-3 nm size regime. Herein, we investigate the transition by performing ultrafast spectroscopic studies on atomically precise thiolate-protected Au₂₅, Au₃₈, Au₁₄₄, Au₃₃₃, Au_∼520 and Au_∼940 nanoparticles. Our results …

Development Of A Wireless Environmental Data Acquisition Prototype Adopting Agile Practices: An Experience Report, Paul Celicourt, Richard Sam, Michael Piasecki

Publications and Research

The traditional software development model commonly named “waterfall” is unable to cope with the increasing functionality and complexity of modern embedded systems. In addition, it is unable to support the ability for businesses to quickly respond to new market opportunities due to changing requirements. As a response, the software development community developed the Agile Methodologies (e.g., extreme Programming, Scrum) which were also adopted by the Embedded System community. However, failures and bad experiences in applying Agile Methodologies to the development of embedded systems have not been reported in the literature. Therefore, this paper contributes a detailed account of our first-time …

Electro-Chemotactic Fields Induce Cooperative Movement Of Cns Cells, Shawn Mishra, Stephen Redenti, Maribel Vazquez

Publications and Research

Vision loss in adults with Age Related Macular Degeneration (AMD) is attributed to damage of retinal photoreceptor cells that initiate vision by absorbing light. Mouse models have suggested that transplantation of precursor cells may be a novel approach to restore vision. This project uses a combination of electrotactic and chemotactic stimuli to promote and guide CNS cell migration within a microdevice model.

Non-Hermitian Engineering Of Single Mode Two Dimensional Laser Arrays, Mohammad H. Teimourpour, Li Ge, Demetrios N. Christodoulides, Ramy El-Ganainy

Publications and Research

A new scheme for building two dimensional laser arrays that operate in the single supermode regime is proposed. This is done by introducing an optical coupling between the laser array and lossy pseudoisospectral chains of photonic resonators. The spectrum of this discrete reservoir is tailored to suppress all the supermodes of the main array except the fundamental one. This spectral engineering is facilitated by employing the Householder transformation in conjunction with discrete supersymmetry. The proposed scheme is general and can in principle be used in different platforms such as VCSEL arrays and photonic crystal laser arrays.

Design And Implementation Of Ccny Dc Microgrid Testbed, Mahmoud Saleh, Yusef Esa, Yassine Mhandi, Werner Brandauer, Ahmed Mohamed

Publications and Research

This paper presents the design, control, energy management, and implementation of the City College of New York (CCNY) direct current (DC) microgrid laboratory testbed. This facility was custom designed and implemented by researchers at CCNY with minimal off-the-shelf components to enable significant flexibility and reconfiguration capability. The microgrid consists of renewable energy resources, energy storage system and controllable loads, and can operate in either a grid-connected or an islanded mode. The design steps, requirements, and results of the developed testbed were discussed. Moreover, several operational scenarios were tested. The experimental results verify the applicability and flexibility of the developed microgrid …

Quantized Conductance Doubling And Hard Gap In A Two-Dimensional Semiconductor–Superconductor Heterostructure, M. Kjaergaard, F. Nichele, H. J. Suominen, M. P. Nowak, M. Wimmer, A. R. Akhmerov, J. A. Folk, K. Flensberg, J. Shabani, C. J. Palmstrom, C. M. Marcus

Publications and Research

Coupling a two-dimensional (2D) semiconductor heterostructure to a superconductor opens new research and technology opportunities, including fundamental problems in mesoscopic superconductivity, scalable superconducting electronics, and new topological states of matter. One route towards topological matter is by coupling a 2D electron gas with strong spin–orbit interaction to an s-wave superconductor. Previous efforts along these lines have been adversely affected by interface disorder and unstable gating. Here we show measurements on a gateable InGaAs/InAs 2DEG with patterned epitaxial Al, yielding devices with atomically pristine interfaces between semiconductor and superconductor. Using surface gates to form a quantum point contact (QPC), we find …

Experiential Learning Opportunities Through Nasa Stem Content Allows Greater Grass Root-Level Understanding Of The Present Day’S Extreme Climate Change Scenario, Nazrul I. Khandaker, Stanley Schleifer, Matthew Khargie

Publications and Research

The NASA MAA (MUREP Aerospace Academy) project at York College has demonstrated a track record of providing experiential learning opportunities (ELO) to its participating students. ELOs associated with MAA are designed to increase learners’ involvement, knowledge, comprehension and application of learning in one or more STEM subjects/disciplines. They involve inquiry-and-activity-based learning approaches designed for the level of the learner to inspire, engage, and educate while progressively challenging each student. ELO activities enable learners to acquire knowledge, understand what they have learned, and apply that knowledge through inquiry-based tasks. Specifically, we are prepared to address the following priority: Encourage, increase, and …

Effective Integration Of Nasa Stem Curricula Is Allowing Students To Appreciate Earth Science Concepts, Nazrul I. Khandaker, Stanley Schleifer, Krishna Mahabir, Newrence Wills, Matthew Khargie

Publications and Research

NASA Minority University Research and Education Project (MUREP) Aerospace Academy - MAA is a national, innovative activity designed to increase participation and retention of historically underserved and underrepresented K-12 youth in the STEM disciplines, particularly earth science and human exploration (HEO). HEO is dedicated to informing and educating the public about NASA's plans for a new era in space exploration. Utilization of NASA satellite images, online climate education, space mathematics and other earth science-related resources is allowing students to conduct basic research and prepare themselves for a New York City-wide science competition. In addition to offering school children a solid …

Engineering And Perception, Maribel Vazquez

Open Educational Resources

An introductory seminar to High School and Freshman-Level Undergraduates that describes how several Biomedical Engineering innovations have been motivated by our senses of sight, sound, smell, taste and touch.

Microfluidic Devices In Biotechnology, Maribel Vazquez

Open Educational Resources

This lecture/laboratory course focuses on the fundamentals of modern microfluidic devices with applications to biomedical measurements. Students will review fundamental properties of microfluidic systems including the effects of viscous flow, heat transfer, and electromagnetic phenomena on biological systems. Multiple laboratory modules will expose students to photolithographic and surface treatment techniques required for device development. An end of term project will require students to analyze designs of upcoming biomedical inventions and present their critiques via written report and oral presentation.

A Highly Efficient Dual Rotating Disks Photocatalytic Fuel Cell With Wedged Surface Tio2 Nanopore Anode And Hemoglobin Film Cathode, Chen Yang, Yi He, Kan Li, Diwen Ying, Ye Yao, Tiantian Tang, Yalin Wang, Jinping Jia

Publications and Research

In this study, a dual rotating-disk photocatalytic fuel cell using TiO₂ on Ti plate with a wedged surface as the anode and hemoglobin (Hb) on graphite as the cathode was investigated and found to show excellent performance of simultaneous organic pollutant degradation and electricity generation. This study is based on a well-developed photocatalytic fuel cell equipped with dual rotating disks for wastewater treatment that we developed previously, and the innovation of this new device is using a hemoglobin on graphite cathode for in situ hydrogen peroxide (H₂O₂) generation. The result proved with confidence that H …

Cuny Summer Stem Institute: Experimental Research In Engineering For High School Students, Maribel Vazquez

Open Educational Resources

Summer HS students were engaged in hands-on experimental research in engineering laboratories in mentorship with CCNY Engineering Undergraduate Researchers. This course was part of the Summer STEM Institute directed by Dr. Joe Barba and Mr. Otto Marte.

Floquet Topological Insulators For Sound, Romain Fleury, Alexander B. Khanikaev, Andrea Alu

Publications and Research

The unique conduction properties of condensed matter systems with topological order have recently inspired a quest for the similar effects in classical wave phenomena. Acoustic topological insulators, in particular, hold the promise to revolutionize our ability to control sound, allowing for large isolation in the bulk and broadband one-way transport along their edges, with topological immunity against structural defects and disorder. So far, these fascinating properties have been obtained relying on moving media, which may introduce noise and absorption losses, hindering the practical potential of topological acoustics. Here we overcome these limitations by modulating in time the acoustic properties of …

Significance Of Parameters Affecting The Performance Of A Passive Down-Draft Evaporative Cooling (Pdec) Tower With A Spray System, Daeho Kang, Richard K. Strand

Publications and Research

PDEC towers with spray systems are known to achieve substantial energy savings. Various parameters such as the wet-bulb depression, the tower height, and the wind speed have been known to be key factors affecting the performance of the system. To date, the significance of these parameters and other important factors have not been adequately treated in the literature. There also has been a lack of models that can successfully investigate potential benefits of the system under various conditions where this particular system could be applicable. To address these critical issues, this study performed a parametric analysis by using a FLUENT …

Spatial Heterogeneity Analysis In Evaluation Of Cell Viability And Apoptosis For Colorectal Cancer Cells, Aydin Saribudak, Herman Kucharavy, Karen Hubbard, Muharrem Umit Uyar

Publications and Research

In evaluation of cell viability and apoptosis, spatial heterogeneity is quantified for cancerous cells cultured in 3-D in vitro cell-based assays under the impact of anti-cancer agents. In 48-h experiments using human colorectal cancer cell lines of HCT-116, SW-620, and SW-480, incubated cells are divided into control and drug administered groups, to be grown in matrigel and FOLFOX solution, respectively. Our 3-D cell tracking and data acquisition system guiding an inverted microscope with a digital camera is utilized to capture bright field and fluorescent images of colorectal cancer cells at multiple time points. Identifying the locations of live and dead …

Bathymetric Survey For Lakes Azuei And Enriquillo, Hispaniola, Michael Piasecki, Mahrokh Moknatian, Fred Moshary, Joseph Cleto, Yolanda Leon, Jorge Gonzalez, Daniel Comarazamy

Publications and Research

The two largest lakes on the Caribbean Island of Hispaniola, Lake Azuei in Haiti and Lake Enriquillo in the Dominican Republic, have experienced dramatic growth and surface area expansion over the past few years leading to severe flooding and loss of arable land around the lake perimeters. In order to better understand the reasons for this unprecedented rate of expansion and the resulting consequences a multi-disciplinary team comprised of researchers from Haiti, the DR, and the US have embarked on an extensive data collecting and hydrologic and climatological modeling campaign. While the sensor deployment entails stations that measure climatological data …

Kcnq Channel Openers Reverse Depressive Symptoms Via An Active Resilience Mechanism, Allyson K. Friedman, Barbara Juarez, Stacy M. Ku, Hongxing Zhang, Rhodora C. Calizo, Jessica J. Walsh, Depish Chaudhury, Song Zhang, Angel Hawkins, David M. Dietz, James W. Murrogh, Maria Ribadeneira, Erik H. Wong, Rachael L. Neve, Ming-Hu Han

Publications and Research

Less than half of patients suffering from major depressive disorder, a leading cause of disability worldwide, achieve remission with current antidepressants, making it imperative to develop more effective treatment. A new therapeutic direction is emerging from the increased understanding of natural resilience as an active stress-coping process. It is known that potassium (Kþ) channels in the ventral tegmental area (VTA) are an active mediator of resilience. However, no druggable targets have been identified to potentiate active resilience mechanisms. In the chronic social defeat stress model of depression, we report that KCNQ-type Kþ channel openers, including FDA-approved drug retigabine (ezogabine), show …

Light-Activated Photocurrent Degradation And Self-Healing In Perovskite Solar Cells, Wanyi Nie, Jean-Christophe Blancon, Amanda J. Neukirch, Kannatassen Appavoo, Hsinhan Tsai, Manish Chhowalla, Muhammad A. Alam, Matthew Y. Sfeir, Claudine Katan, Jacky Even, Sergei Tretiak, Jared J. Crochet, Gautam Gupta, Aditya D. Mohite

Publications and Research

Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0°C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies.

Mesenchymal Stem Cell Fate: Applying Biomaterials For Control Of Stem Cell Behavior, Hilary J. Anderson, Jugal Kishore Sahoo, Rein V. Ulijn, Matthew J. Dalby

Publications and Research

The materials pipeline for biomaterials and tissue engineering applications is under continuous development. Specifically, there is great interest in the use of designed materials in the stem cell arena as materials can be used to manipulate the cells providing control of behavior. This is important as the ability to “engineer” complexity and subsequent in vitro growth of tissues and organs is a key objective for tissue engineers. This review will describe the nature of the materials strategies, both static and dynamic, and their influence specifically on mesenchymal stem cell fate.

P2x7r-Panx1 Complex Impairs Bone Mechanosignaling Under High Glucose Levels Associated With Type-1 Diabetes, Zeynep Seref-Ferlengez, Stephanie Maung, Mitchell B. Schaffler, David C. Spray, Sylvia O. Suadicani, Mia M. Thi

Publications and Research

Type 1 diabetes (T1D) causes a range of skeletal problems, including reduced bone density and increased risk for bone fractures. However, mechanisms underlying skeletal complications in diabetes are still not well understood.We hypothesize that high glucose levels in T1D alters expression and function of purinergic receptors (P2Rs) and pannexin 1 (Panx1) channels, and thereby impairs ATP signaling that is essential for proper bone response to mechanical loading and maintenance of skeletal integrity. We first established a key role for P2X7 receptor-Panx1 in osteocyte mechanosignaling by showing that these proteins are co-expressed to provide a major pathway for flow-induced ATP release. …

Historical Trends In Mean And Extreme Runoff And Streamflow Based On Observations And Climate Models, Behzad Asadieh, Nir Y. Krakauer, Balázs M. Fekete

Publications and Research

To understand changes in global mean and extreme streamflow volumes over recent decades, we statistically analyzed runoff and streamflow simulated by the WBM-plus hydrological model using either observational-based meteorological inputs from WATCH Forcing Data (WFD), or bias-corrected inputs from five global climate models (GCMs) provided by the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP). Results show that the bias-corrected GCM inputs yield very good agreement with the observation-based inputs in average magnitude of runoff and streamflow. On global average, the observation-based simulated mean runoff and streamflow both decreased about 1.3% from 1971 to 2001. However, GCM-based simulations yield increasing trends over …

Satellite Retrievals Of Karenia Brevis Harmful Algal Blooms In The West Florida Shelf Using Neural Networks And Comparisons With Other Techniques, Ahmed El-Habashi, Ioannis Ioannou, Michelle Tomlinson, Richard P. Stumpf, Sam Ahmed

Publications and Research

We describe the application of a Neural Network (NN) previously developed by us, to the detection and tracking, of Karenia brevis Harmful Algal Blooms (KB HABs) that plague the coasts of the West Florida Shelf (WFS) using Visible Infrared Imaging Radiometer Suite (VIIRS) satellite observations. Previous approaches for the detection of KB HABs in the WFS primarily used observations from the Moderate Resolution Imaging Spectroradiometer Aqua (MODIS-A) satellite. They depended on the remote sensing reflectance signal at the 678 nm chlorophyll fluorescence band (Rrs678) needed for both the normalized fluorescence height (nFLH) and Red Band Difference algorithms (RBD) currently used. …

Nonlinear Modal Interactions In Parity-Time (Pt) Symmetric Lasers, Li Ge, Ramy El-Ganainy

Publications and Research

Parity-time (PT ) symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the PT -symmetric and PT -broken phases. In particular, we show that, depending on the system’s design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the PT phase …

Impact Of Clustering Microgrids On Their Stability And Resilience During Blackouts, Mahmoud S. Saleh, Ammar Althaibani, Yusef Esa, Yassine Mhandi, Ahmed Mohamed

Publications and Research

In this paper, the impact of clustering multiple microgrids during blackouts, on their stability and supply availability, will be investigated. Microgrids have the capability of satisfying their emergency loads during blackouts. However, distributed energy resources (DERs)-dominated microgrids are affected by the uncertainty of their input energy supply, e.g. impact of solar irradiance on photovoltaic (PV) output. Moreover, an individual islanded microgrid is prone to instability issues due to large sudden load/generation changes. In order to increase the supply security, and enhance system stability, we propose to use the existing distribution grid infrastructure, if applicable, during blackouts to form microgrid clusters. …

Estimating The Probability Of Vegetation To Be Groundwater Dependent Based On The Evaluation Of Tree Models, Isabel C. Pérez Hoyos, Nir Y. Krakauer, Reza Khanbilvardi

Publications and Research

Groundwater Dependent Ecosystems (GDEs) are increasingly threatened by humans’ rising demand for water resources. Consequently, it is imperative to identify the location of GDEs to protect them. This paper develops a methodology to identify the probability of an ecosystem to be groundwater dependent. Probabilities are obtained by modeling the relationship between the known locations of GDEs and factors influencing groundwater dependence, namely water table depth and climatic aridity index. Probabilities are derived for the state of Nevada, USA, using modeled water table depth and aridity index values obtained from the Global Aridity database. The model selected results from the performance …

Simple Adaptive Delta Operator Aircraft Flight Control For Accommodation Of Loss Of Control Effectiveness, Alfredo Cano, Kenneth Sobel

Publications and Research

A new proof for stability of delta operator simple adaptive control is presented in terms of a set of Linear Matrix Inequalities (LMIs). The paper shows how to design a feedforward gain to satisfy the LMIs over a polytope of loss of control effectiveness failures. The MATLAB Robust Control Toolbox is used to find the feedforward gain with the smallest norm that satisfies the LMIs. Examples are presented of the F/A-18 aircraft and the Innovative Control Effectors (ICE) tailless aircraft that show the design of a feedforward gain for a loss of control effectiveness in any one control effector. The …