Engineering Commons^™

Vapor-Phase Synthesis Of Electrocatalytic Covalent Organic Frameworks, Syed Ibrahim Gnani Peer Mohamed, Shahriar Namvar, Tan Zhang, Hessam Shahbazi, Zhen Jiang, Andrew M. Rappe, Amin Salehi-Khojin, Siamak Nejati

Department of Chemical and Biomolecular Engineering: Faculty Publications

The inability to process many covalent organic frameworks (COFs) as thin films plagues their widespread utilization. Herein, a vapor-phase pathway for the bottom-up synthesis of a class of porphyrin-based COFs is presented. This approach allows integrating electrocatalysts made of metal-ion-containing COFs into the electrodes’ architectures in a single-step synthesis and deposition. By precisely controlling the metal sites at the atomic level, remarkable electrocatalytic performance is achieved, resulting in unprecedentedly high mass activity values. How the choice of metal atoms, i.e., cobalt and copper, can determine the catalytic activities of POR-COFs is demonstrated. The theoretical data proves that the Cu site …

Impact Of Methylene Blue On Enhancing The Hydrocarbon Potential Of Early Cambrian Khewra Sandstone Formation From The Potwar Basin, Pakistan, Muhammad Ali, Abdul M. Shar, Nurudeen Yekeen, Hussein Abid, Muhammad S. Kamal, Hussein Hoteit

Research outputs 2022 to 2026

Significant amounts of hydrocarbon resources are left behind after primary and secondary recovery processes, necessitating the application of enhanced oil recovery (EOR) techniques for improving the recovery of trapped oil from subsurface formations. In this respect, the wettability of the rock is crucial in assessing the recovery and sweep efficiency of trapped oil. The subsurface reservoirs are inherently contaminated with organic acids, which renders them hydrophobic. Recent research has revealed the significant impacts of nanofluids, surfactants, and methyl orange on altering the wettability of organic-acid-contaminated subsurface formations into the water-wet state. This suggests that the toxic dye methylene blue (MB), …

Commercial Adsorbents For Co2 Removal For Biogas Upgradation: An Experimental Study, Aakriti Bagla

McKelvey School of Engineering Graduate Student Theses & Dissertations

No abstract provided.

Selective Production Of Levoglucosan (Lg) From Pyrolysis Of Date Pits And Its Catalytic Transformation Into Transportation Fuels, Ala Hamid Higazi

Thesis/ Dissertation Defenses

Levoglucosan (LG) or (1,6-anhydro-β-D-glucopyranose) signifies an important sugar derivative that is produced in appreciable quantities from thermochemical and biochemical degradation of biomass. It is often regarded as an important platform chemical for the synthesis of value-added products, most notably styrene and furans. The work in this thesis entails two broad aims; to produce LG from pyrolysis of date pits; and then convert the LG into transportation fuels through a hydrodeoxygenation (HDO) reaction. The particular choice of date pits stems from its local relative abundance as a waste biomass. Aiming to further improve the yield of levoglucosan yields from pyrolysis of …

Clean Energy & Sustainable Environment By Carbon Dioxide Mitigation Strategies, Md Fahim Shahriar

Mechanical Engineering Theses

Dissolution trapping is one of the most dominant mechanisms for secure storage of CO₂ injected in porous subsurface formations saturated with brine. This study uses a 2D visual Hele-Shaw cell to investigate and visualize the impact of CO₂ injection locations, reservoir dipping angle, permeability heterogeneity, and brine with different initial ionic concentrations on the density-driven convection during CO₂ dissolution (Chapter 2). Also, the role of complex heterogeneity, i.e., irregular permeability distribution in CO₂ dissolution, is investigated using a novel experimental approach to create medium permeability heterogeneity in Hele-Shaw cells (Chapter 3). We observed that the presence …

Moisture Effects On Visible Near-Infrared And Mid-Infrared Soil Spectra And Strategies To Mitigate The Impact For Predictive Modeling, Francis Hettige Chamika Anuradha Silva

Theses and Dissertations

Instrumental disparities and soil moisture are two of the key limitations in implementing spectroscopic techniques in the field. This study sought to address these challenges through two objectives. The first objective was to assess Visible-near infrared (VisNIR) and mid-infrared (MIR) spectroscopic approaches and explore the feasibility of transferring calibration models between laboratory and portable spectrometers. The second objective addressed the challenge of soil moisture and its impact on spectra. The portable spectrometers demonstrated comparable performance to their laboratory-based counterparts in both regions. Spiking with extra-weight, was the most effective calibration transfer method eliminating disparities between instruments. The samples were rewetted …

Using Afm-Ir To Study Nanoscopic Phase Behavior Of Polymer Blends And Photovoltaic Bulk Heterojunctions, Nathaniel L. Prine

Dissertations

Conjugated polymers (CPs) and polymer blends harbor the potential for high-performance organic solar cells (OSCs) due to their short energy payback time, low cost, solution processability, lightweight attributes, and flexibility. However, OSCs suffer from poor thermal stability compared to their inorganic equivalents. This study explores the thermal instability of OSCs, focusing on phase separation of the photoactive layer under heat, resulting in morphology changes and degradation of power conversion efficiency (PCE). Utilizing atomic-force microscopy coupled with infrared spectroscopy (AFM-IR) and differential scanning calorimetry (DSC), we delve into thermal stability-morphology relationships to devise strategies to improve OSC blend durability under thermal …

Coarsening Dynamics Of Ternary Polymer Solutions With Mobility And Viscosity Contrasts, Jan Ulric Garcia, Douglas R. Tree, Alyssa Bagoyo, Tatsuhiro Iwama, Kris T. Delaney, Glenn H. Fredrickson

Faculty Publications

Using phase-field simulations, we investigate the bulk coarsening dynamics of ternary polymer solutions undergoing a glass transition for two models of phase separation: diffusion only and with hydrodynamics. The glass transition is incorporated in both models by imposing mobility and viscosity contrasts between the polymer-rich and polymer-poor phases of the evolving microstructure. For microstructures composed of polymer-poor clusters in a polymer-rich matrix, the mobility and viscosity contrasts significantly hinder coarsening, effectively leading to structural arrest. For microstructures composed of polymer-rich clusters in a polymer-poor matrix, the mobility and viscosity contrasts do not impede domain growth; rather, they change the transient …

Enhancing Rubber (Hevea Brasiliensis) Seed Shell Biochar Through Acid-Base Modification For Effective Phenol Removal From Aqueous Environments, Oyinlola R. Obanla, Jamie A. Hestekin, Modupe E. Ojewumi, Imen Bousrih, Modupeoluwa C. Fawole

Chemical Engineering Faculty Publications and Presentations

This work encompasses using acid-base modified rubber seed shell biochar (RSSB) as an adsorption approach to eradicate phenol from aqueous mediums. Potassium hydroxide (KOH) was used pre-pyrolysis to modify the RSS, and hydrochloric acid (HCl) was used post-pyrolysis to modify the RSSB. The methodology was divided into three stages: RSS pretreatment, RSS base-modification and pyrolysis, and RSSB acid-modification and processing. Temperature, pH and several other factors were investigated for their impacts on the adsorbent, and optimal conditions were established at pH 6, 1.0 g of rubber seed shell biochar (RSSB), 50 mg/L initial concentration, 120 min contact time, and 30°C …

Molecular Separation By Using Active And Passive Microfluidic Chip Designs: A Comprehensive Review, A. Ebrahimi, K. Icoz, R. Didarian, C.-H. Shih, A. Akpek, Berivan Cecen, Sabanci A. Bal-Ozturk, K. Güleç, Y.-C.E Li, S. Shih, B. Sirma Tarim, H.C. Tekin, E. Alarçin, H. Ghorbanpoor, C. Özel, A. Eker Sarıboyacı, Guzel F. Dogan, N. Bassous, S.R. Shin, H. Avci

Henry M. Rowan College of Engineering Departmental Research

Separation and identification of molecules and biomolecules such as nucleic acids, proteins, and polysaccharides from complex fluids are known to be important due to unmet needs in various applications. Generally, many different separation techniques, including chromatography, electrophoresis, and magnetophoresis, have been developed to identify the target molecules precisely. However, these techniques are expensive and time consuming. “Lab-on-a-chip” systems with low cost per device, quick analysis capabilities, and minimal sample consumption seem to be ideal candidates for separating particles, cells, blood samples, and molecules. From this perspective, different microfluidic-based techniques have been extensively developed in the past two decades to separate …

Exploration Of Secondary Structure Directing Agents On The Formation Of Hierarchical And 2d Zeolites, Suleiman Yahaya

ETD Archive

Hierarchical and 2D zeolites address the diffusion limitation of conventional zeolites by enhancing diffusion in the mesopores. So far, the surfactant compounds, which successfully produce hierarchical zeolites, have complex molecular structures making the zeolite synthesis expensive and uncompetitive for commercialization, making cost-effective synthesis of hierarchical and 2D zeolite highly desirable. However, the development of effective synthesis protocols relies on a good understanding of the SDA's influence on crystal morphology development, which is largely unknown. Here, we explore inexpensive and readily available compounds via a dual-SDA strategy and use MFI zeolite as the model system for the research. TPAOH served as …

Influence Of Ligament Locations And Activity Profiles On Risk Of Knee Injury In Adolescents, Alexandria Mallinos

ETD Archive

The Anterior Cruciate Ligament (ACL) is the most commonly injured ligament in the body. The overall goal of this project is to develop patient-specific computational pediatric knee models that can accurately predict the in vivo biomechanical environment of the ACL. The foundation of this research is broken down into three specific parts: 1) model construction, 2) model validation, and 3) model application.

Specific Aim #1 developed anatomically accurate specimen-specific finite element representations of pediatric tibiofemoral joints. The models were able to demonstrate the ability for the Open Knee cruciate stereolithography (stl) files to be three-dimensional scaled to create subject-specific ligaments …

Process Improvement Of Cu(Ii)-Trymethylamine-Based Active Clay Measurement Test And Total Clay Measurement Test, Christopher Michael Remily

Masters Theses

Foundry work requires a mold made of a mixture of sand, “active clay” to absorb gas, and binders to combine the two and hold the molds shape. When the metal is melted to be poured into the mold, the solubility dramatically increases, causing gas to be temporarily dissolved in the metal. This gas causes small surface pits to form once the metal cools, causing part failure. This causes the need to absorb the gas. Since the clay is used in the process, there needs to be a way to determine how much remains active, which is done with a dye …

Preclassic Environmental Degradation Of Lake Petén Itzá, Guatemala, By The Early Maya Of Nixtun-Ch’Ich’, Brooke A. Birkett, Jonathan Obrist-Farner, Prudence M. Rice, Wesley G. Parker, Peter M.J. Douglas, Melissa A. Berke, Audrey K. Taylor, Jason H. Curtis, Benjamin Keenan

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Paleolimnological Evidence Indicates the Ancient Maya Transformed Terrestrial Ecosystems by Felling Forest Vegetation to Construct Large Civic-Ceremonial Centers and to Expand Agriculture. Human Settlements Influenced Lacustrine Environments But the Effects of Maya Activities on Aquatic Ecosystems Remain Poorly Studied. Here We Analyzed a Sediment Core from Lake Petén Itzá, Guatemala, to Infer Paleoenvironmental Changes Resulting from Maya Occupation of the Archaeological Site of Nixtun-Ch'ich'. Increases in Charcoal and Fecal Stanol Concentrations Indicate Maya Occupation of the Candelaria Peninsula by the Late Early Preclassic Period. Geochemical Proxies Reveal a Period of Lake Ecosystem Alteration during Construction and Expansion of the City's …

Computationally-Driven Insights Into The Ligand Environments Of Materials For Catalysis And Separations, Stephen Vicchio

All Dissertations

Designing new catalytic and sorption materials is necessary to limit global temperature rise below 1.5 ◦C by 2050, while also meeting global energy demands. Climate change and energy production are not mutually exclusive; global population growth has direct impacts on global energy demands and climate. In both catalysis and adsorption applications, new technologies are needed to address these challenges. Catalysis can provide alternate, low-energy routes for converting low-value gases into higher-value chemical commodities, thus altering our current energy production. Likewise, new sorption materials can capture previously emitted CO₂ from decades of energy production from fossil fuels, thus helping to …

Graphical Analysis And Revamping Of Crude Distillation Units Under Variable Operational Scenarios, Amany G. Abo-Mousa, Dina A. Kamel, Hany A. Elazab, Mamdouh A. Gadalla, Mai K. Fouad

Chemical and Biochemical Engineering Faculty Research & Creative Works

Energy Cost Represents a Significant Part of the Total Operating Costs of Many Processing Units. Crude Distillation is an Energy Intensive Process. Energy Integration is a Typical Solution to Reduce Heating and Cooling Utilities through Maximizing the Target Temperature of Crude Oil Streams Before Entering the Furnace. over the Past Few Decades, Significant Progress Has Been Made in Energy Integration Methods Including Pinch Technology and Mathematical Programming Approaches. Very Recently, Graphical Techniques Have Been Developed for Revamping Studies and Energy Analysis. Such Diagrams Are Valuable in Energy Targeting to Identity Energy Inefficiencies and Are Key to Potential Modifications for Maximum …

A Review On Liquid Flow Through Low-Density Fibrous Porous Media, Hossein Abedsoltan

Chemical and Biochemical Engineering Faculty Research & Creative Works

This review focuses on studying liquid flow through low-density fibrous porous media, particularly tissue grades of papers. It discusses experimental designs, factors affecting liquid flow, and various versions of the Lucas-Washburn equation and permeability expressions used to estimate liquid flow in these media. While a comprehensive model for liquid flow in these materials is lacking due to their structural complexity, numerous experimental methods have been developed to determine absorption properties, particularly for wiping and cleaning liquids. The review covers these methods, many of which are proposed by standard organizations. It is a valuable reference for scientists interested in understanding the …

Covid-19 And The Chemical Industry: Impacts, Challenges, And Opportunities, Hossein Abedsoltan

Chemical and Biochemical Engineering Faculty Research & Creative Works

The COVID-19 pandemic imposed unparalleled challenges for the chemical industry, leading to disruptions in supply chains and demand dynamics. This period of crisis tested the adaptability and resilience of global chemical companies. Despite the challenges, the chemical industry exhibited remarkable innovation, collaboration, and adaptability. It demonstrated its capacity to respond swiftly and effectively to societal needs. Key lessons emerged, emphasizing the importance of diversifying supply chains, implementing scenario planning, and embracing digitalization for enhanced preparedness. As the world progresses toward recovery, the chemical industry is poised to leverage the valuable lessons learned. Industry 4.0 adoption, agile decision-making, and collaborative efforts …

Comparative Evaluation Of Caries Prevalence Among Group Of Egyptian Adolescents Using Dmfs And Icdasii Methods: A Cross-Sectional Study, Mohamed H. Zaazou, Dalia Y. Zaki, Ali Abdelnabi, Tamer M. Hamdy, Reham S. Saleh, Shahinaz N. Hassan, Zeinab M. Zaki, Lamiaa M. Moharam

Chemical and Biochemical Engineering Faculty Research & Creative Works

Background: Limited data is available regarding the prevalence of dental caries as a chronic disease among adolescents using different caries assessment indices. The aim of this study was to compare and describe the prevalence of dental caries among group of Egyptian students using two caries assessment indices: DMFS and ICDAS II. Methods: This descriptive, cross-sectional epidemiological study included 2760 public secondary school students with age range from 15 to 18 years with permanent dentition and good general health. Presence of; retained teeth, congenital or developmental anomalies in the permanent dentition, orthodontic treatments, systematic conditions, smoking and general health problems were …

Determining The Effects Of Glycocalyx Modifications On The Electrophysical Properties Of Human Mesenchymal Stem Cells, Rominna E. Valentine Ico

Electronic Theses, Projects, and Dissertations

Human mesenchymal stem cells (hMSCs) have gained popularity in clinical trials due to their multipotent differentiation characteristics, ability to secrete bioactive molecules, migrate into diseased or damaged tissues, and their immunosuppressive properties. HMSC cultures are heterogeneous, containing stem cells, partially differentiated progenitor cells, and fully differentiated cells. One of the major challenges with hMSCs therapeutic potential is the inability to select specific cell subpopulations due to an insufficient number of biomarkers. Often the biomarkers used, like those for fluorescence-activated cell sorting, are not sufficient to define hMSCs because they overlap with other cell types. Consequently, there is a need to …

Amine-Functionalized Lignin-Based Ionomer Nanocomposites For Redox Flow Batteries, Joshua Wilder

All Theses

As the development of energy storage technologies for renewable energy sources continues to garner attention, vanadium redox flow batteries (VRFBs) have emerged as promising source for grid-scale energy storage. A major component of the VRFB is the ion exchange membrane (IEM), as it serves to physically separate the two liquid electrolytes and also directly impacts the battery’s capacity, efficiency, and cost. The current industry standard IEM, Nafion™, not only accounts for a large portion of the cost of the VRFB but also suffers from poor proton selectivity. Herein, we have synthesized sulfonated poly(ether ether ketone) (SPEEK) composite membranes containing amine …

Engineered Biomass-Derived Carbon Adsorbents For Targeted Contaminant Remediation From Aqueous Environments, Suraj Venkat Pochampally

UNLV Theses, Dissertations, Professional Papers, and Capstones

Porous carbon adsorbents like biochar (BC) are produced from waste biomasses like wood chips, animal litter, nut shells, dried grass, etc. to be used in a multitude of applications like gas capture, soil amendment, water treatment, electrode materials, etc. In water treatment, carbon-based adsorbents have been mainly used to physically or chemically adsorb contaminants depending on the adsorption mechanism. However, BCs in their raw state do not have the capability of absorbing high amounts of contaminants and need to be activated/ modified for the pore network to broaden and adsorb the contaminants with better efficiency.

The scope of this dissertation …

Numerical Investigations Of Sco2 Compressor Aerothermodynamics Using A Streamline Curvature Based Throughflow Method, Victor Quintanilla

UNLV Theses, Dissertations, Professional Papers, and Capstones

Supercritical carbon dioxide (sCO₂) has emerged as a promising working fluid for the Brayton power cycle, offering enhanced efficiency due to the high density and low viscosity of carbon dioxide (CO₂) near the critical point. A critical component of the sCO₂ Brayton cycle is the turbomachinery, namely the compressor, which significantly contributes to the efficiency enhancement in the sCO₂ Brayton cycle owing to reduced compression work requirements. Its primary function involves elevating the fluid's pressure, effectively priming it for the subsequent heat addition process from a thermal energy source. However, despite its advantages, challenges …

Deficiency Of Acute-Phase Serum Amyloid A Exacerbates Sepsis-Induced Mortality And Lung Injury In Mice, Ailing Ji, Andrea C. Trumbauer, Victoria P. Noffsinger, Luke W. Meredith, Brittany Dong, Qian Wang, Ling Guo, Xiangan Li, Frederick C. De Beer, Nancy R. Webb, Lisa R. Tannock, Marlene E. Starr, Christopher M. Waters, Preetha Shridas

Saha Cardiovascular Research Center Faculty Publications

Serum amyloid A (SAA) is a family of proteins, the plasma levels of which may increase >1000-fold in acute inflammatory states. We investigated the role of SAA in sepsis using mice deficient in all three acute-phase SAA isoforms (SAA-TKO). SAA deficiency significantly increased mortality rates in the three experimental sepsis mouse models: cecal ligation and puncture (CLP), cecal slurry (CS) injection, and lipopolysaccharide (LPS) treatments. SAA-TKO mice had exacerbated lung pathology compared to wild-type (WT) mice after CLP. A bulk RNA sequencing performed on lung tissues excised 24 h after CLP indicated significant enrichment in the expression of genes associated …

Development Of Lignin-Based Copolymers And Polymer Blends, David Chem

Graduate Theses and Dissertations

Increasing industrial interest in reducing fossil fuels in virgin polymer production and incorporating bio-based polymeric materials has led researchers to explore the potential of utilizing plant-based polymers such as lignin. Chapter 1 of this thesis presents a comprehensive overview of copolymerization and blending techniques for lignin and synthetic polymers, emphasizing different types of modifications and copolymerization techniques as well as key parameters such as temperature, reaction time, pH level, and solution compositions. These valorization methods are directed towards the development of high-value lignin-based materials with properties well-suited for various commercial applications. Chapter 2 offers a fundamental exploration into the amination …

Capillary-Sealing Efficiency Of Mica-Proxy Caprock For Co2/H2 Geologic Storage In The Presence Of Organic Acids And Nanofluids, Amer Alanazi, Muhammad Ali, Mahmoud Mowafi, Saleh Bawazeer, Ziyad K K. Kaidar, Hussein Hoteit

Research outputs 2022 to 2026

Toward a diversified low-carbon future, the geological storage of carbon dioxide (CO2) and hydrogen (H2) is regarded as a key enabler for an industrial-scale implementation. However, many geological formations, such as depleted oil and gas reservoirs, can contain inherent traces of organic molecules that dramatically affect their storage capacities and caprock sealing efficiency. Hence, using the right analysis to accurately determine the caprock sealing efficiency and storage capacity in the presence of organics is crucial for a secure and safe storage process. This study analyzed the sealing potential of a proxy caprock (mica) by calculating the capillary entry pressure and …

Metal Organic Frameworks With Carbon Black For The Enhanced Electrochemical Detection Of 2,4,6-Trinitrotoluene, Shaghraf Javaid, Muhammad R. Azhar, Xinyu Li, Juliette I. Phillips, Tanveer Hussain, Hussein Abid, Jun Chen, Xiaobo Ji, Debbie S. Silvester

Research outputs 2022 to 2026

The sensing of explosives such as 2,4,6-trinitrotoluene (TNT) directly at an explosion site requires a fast, simple and sensitive detection method, to which electrochemical techniques are well suited. Herein, we report an electrochemical sensor material for TNT based on an ammonium hydroxide (NH4OH) sensitized zinc-1,4–benzenedicarboxylate Zn(BDC) metal organic framework (MOF) mixed with carbon black on a glassy carbon electrode. In the solvent modulation mechanism, by merely changing the concentration of NH4OH during synthesis, two Zn(BDC) MOFs with novel morphologies were fabricated via a hydrothermal approach. The as-prepared MOFs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier …

A Novel Renewable Energy Powered Zero Liquid Discharge Scheme For Ro Desalination Applications, Mamdouh A. Gadalla, Amr Abdel Fatah, Hany A. Elazab

Chemical and Biochemical Engineering Faculty Research & Creative Works

This work proposes a conceptual model for a Zero Liquid Discharge (ZLD) for Reverse Osmosis (RO) desalination. The model describes a Process Flow Diagram (PFD). The proposed process relies on an RO followed by electrolyser, solar evaporator and mixing tank. The water reject from the RO is split into three fractions, one to an electrolyser to produce H2, another to solar evaporator to produce fresh water, third is remixed with water from the evaporator to reduce the salinity of the RO feed. The hydrogen produced in the electrolyser is burned and its energy is stored using cement blocks. The evaporator …

Evaluation Of Different Decontamination Procedures On Bond Strength To Sound And Caries Affected Dentin Using “No-Wait” Universal Adhesive, Lamiaa M. Moharam, Haidy N. Salem, Sherif Khadr, Ahmed Abdou

Chemical and Biochemical Engineering Faculty Research & Creative Works

Background: Current study aimed to evaluate the effect of different decontamination procedures on micro-shear bond strength (μSBS) of sound (SoD) and caries-affected dentin (CAD) of two universal adhesives after blood-saliva contamination. Methods: One hundred and eighty bovine anterior teeth were prepared and allocated into the respective groups according to tested dentin substrates [SoD, CAD], universal adhesives [Clearfil Bond Universal Quick (UBQ), All-Bond-Universal (ABU)], adhesive contamination stage [none, contamination before and after adhesives light-curing], and according to decontamination procedures [no decontamination, water rinsing, adhesive rebond, Ethylenediaminetetraacetic acid (ETDA) and chlorhexidine (CHX) application]. Universal adhesives were applied according to manufacturer instructions in …

Molecular Control Of Triplet-Pair Spin Polarization And Its Optoelectronic Magnetic Resonance Probes, Obadiah G. Reid, Justin C. Johnson, Joel D. Eaves, Niels H. Damrauer, John E. Anthony

Chemical and Materials Engineering Faculty Publications

Preparing and manipulating pure magnetic states in molecular systems are the key initial requirements for harnessing the power of synthetic chemistry to drive practical quantum sensing and computing technologies. One route for achieving the requisite higher spin states in organic systems exploits the phenomenon of singlet fission, which produces pairs of triplet excited states from initially photoexcited singlets in molecular assemblies with multiple chromophores. The resulting spin states are characterized by total spin (quintet, triplet, or singlet) and its projection onto a specified molecular or magnetic field axis. These excited states are typically highly polarized but exhibit an impure spin …