| 1. |
- Nilsson, R. Henrik, 1976, et al.
(author)
-
Mycobiome diversity: high-throughput sequencing and identification of fungi.
- 2019
-
In: Nature reviews. Microbiology. - : Springer Science and Business Media LLC. - 1740-1534 .- 1740-1526. ; 17, s. 95-109
-
Research review (peer-reviewed)abstract
- Fungi are major ecological players in both terrestrial and aquatic environments by cycling organic matter and channelling nutrients across trophic levels. High-throughput sequencing (HTS) studies of fungal communities are redrawing the map of the fungal kingdom by hinting at its enormous - and largely uncharted - taxonomic and functional diversity. However, HTS approaches come with a range of pitfalls and potential biases, cautioning against unwary application and interpretation of HTS technologies and results. In this Review, we provide an overview and practical recommendations for aspects of HTS studies ranging from sampling and laboratory practices to data processing and analysis. We also discuss upcoming trends and techniques in the field and summarize recent and noteworthy results from HTS studies targeting fungal communities and guilds. Our Review highlights the need for reproducibility and public data availability in the study of fungal communities. If the associated challenges and conceptual barriers are overcome, HTS offers immense possibilities in mycology and elsewhere.
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| 2. |
-
Sprickor i fasaden
- 2018
-
Editorial collection (other academic/artistic)abstract
- Det råder på sina håll en oro och ett mörker i dagens Sverige. Några grupper ser en värld av kollapsande system och spruckna fasader, där folkvalda fattar beslut som utarmar människors trygghet och livsvillkor. Andra ser hur antide-mokratiska krafter, likt början av förra seklet, växer sig allt större och på sina håll ges legitimitet av världsledare. Somliga går så långt som att tala om en demokrati i kris, om obönhörligt växande sprickbildningar i samhällsbygget i spåren av vilka otrygghetens och rädslans landskap breder ut sig. Sprickor i fasaden knyter an till denna rådande debatt och föreställningar om samhällets tillstånd.Världen som vi en gång kände den tycks långsamt glida ur våra händer. Den välputsade fasaden spricker. Eller gör den det? Kanske skiftar samhällets palett i långt fler nyanser än mörkaste grått? Kanske spirar det rent av en värld med allt godare möjligheter för människor att leva och utvecklas? För i kontrast till bilden av samhällets rämnande grundvalar, kan också skymtas skiftningar i värdegrunden i riktning mot ökad tolerans, öppenhet och jämlikhet. Måhända är dessa skiftningar tecken på sprickor också i föreställningen om den spruck-na fasaden? Sprickor i fasaden är den 72:e forskarantologin från SOM-institutet och bygger på 2017 års nationella SOM-undersökning – den trettioandra i ordningen. Bokens innehåll knyter på många sätt an till frågan om sprickor i det svenska samhällsbygget. Flera kapitel belyser tilltagande polarisering och politisering inom (S)amhälle, (O)pinion och (M)edier. Samtidigt pekar resultaten i andra kapitel på en påtaglig stabilitet och förstärkt uppslutning kring centrala värde-ringar, samhällsfrågor och samhällsinstitutioner.Sprickor i fasaden är skriven av ett 30-tal forskare från olika discipliner vid universitet och högskolor i Sverige.
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| 3. |
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| 4. |
- Grabowski, Alexander, 1993
(author)
-
VCSEL Equivalent Circuits and Silicon Photonics Integration
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The vertical-cavity surface-emitting laser (VCSEL) is a light source of great importance for numerous industrial and consumer products. The main application areas are datacom and sensing. The datacom industry uses GaAs-based VCSELs for optical interconnects, the short-reach fiber optical communication links used to transfer large amounts of data at high rates between units within data centers and supercomputers. In the area of sensing, VCSELs are largely used in consumer products such as smart phones (e.g. face ID and camera auto focus), computer mice, and automobiles (e.g. gesture recognition and LIDAR for autonomous driving). In this work, an advanced physics-based equivalent circuit model for datacom VCSELs has been developed. The model lends itself to co-design and co-optimization with driver and receiver ICs, thereby enabling higher data rate transceivers with bandwidth limited VCSELs and photodiodes. The model also facilitates an understanding of how each physical process within the VCSEL affects the VCSEL static and dynamic performance. It has been applied to study the impact of carrier transport and capture on VCSEL dynamics. The work also includes micro-transfer-printing of GaAs-based single-mode VCSELs on silicon nitride photonic integrated circuits (PICs). Such PICs are increasingly used for e.g. compact and highly functional bio-photonic sensors. Transfer printing of VCSELs enables the much-needed on-PIC integration of power efficient light sources. The bottom-emitting VCSELs are printed above grating couplers on the PIC and optical feedback is used to control the polarization for efficient coupling to the silicon nitride waveguide. Wavelength tuning, as required by the bio-sensing application, is achieved by direct current modulation.
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| 5. |
- Sattari, Amir, 1980-, et al.
(author)
-
INDUSTRIAL NANOPARTICLES HEALTH RISKS AND ADVANTAGES OF A DECENT INDUSTRIAL VENTILATION SYSTEM IN REDUCING THE RELATED RISKS
- 2012
-
In: INDUSTRIAL NANOPARTICLES HEALTH RISKS AND ADVANTAGES OF A DECENT INDUSTRIAL VENTILATION SYSTEM IN REDUCING THE RELATED RISKS. ; , s. -6
-
Conference paper (peer-reviewed)abstract
- With the fast-growing use of nanoparticles (NPs) in a wide range of production and manufacturing processes, and great health and environmental risks associated to NPs, it is important to treat the industry-produced NPs in a proper way. Ventilation of industrial workplaces lies within the concept of sustainability challenges for the development of nanoproducts. Due to the decreased grain size of material to nano limits and thus the appearance of either new or changed properties, health risk of workers in such environments is critical concerning the complicated and unknown characteristics of nanoparticles. There is great evidence over the past few years that ultrafine particles and especially NPs in the breathing air are strong toxins. Different mitigation measures for air-borne nanoparticles in industrial workplaces are substitution, engineering controls such as ventilation and provision of personal protective equipment. In this paper selection criteria for ventilation systems and different ventilation methods (hood ventilation and global enclosure/room ventilation systems) as engineering controls of nanoparticles within industrial enclosures will be reviewed. Novel methods for improvement of ventilation efficiency in general and industrial work places with an eye on ventilation of nanoparticles will be presented.
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| 6. |
- Rebolledo Salgado, Israel, 1992, et al.
(author)
-
Active Feedback Stabilization of Super-efficient Microcombs
- 2023
-
In: 2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : Institute of Electrical and Electronics Engineers (IEEE). - 2833-1052. - 9798350345995
-
Conference paper (peer-reviewed)abstract
- We report the long-term operation of a super-efficient microcomb. We use the soliton power to maintain a fixed pump detuning. The microcomb operates over 25 hours using a thermal control in a packaged module.
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| 7. |
- Fu, Qilin, et al.
(author)
-
Anti-vibration Engineering in Internal Turning Using a Carbon Nanocomposite Damping Coating Produced by PECVD Process
- 2014
-
In: Journal of materials engineering and performance (Print). - : Springer-Verlag New York. - 1059-9495 .- 1544-1024. ; 23:2, s. 506-517
-
Journal article (peer-reviewed)abstract
- Machining dynamic stability has been enhanced through a damping coating based on a novel carbon-based nanocomposite material. The coating was synthesized using a plasma enhanced chemical vapor deposition method, and deposited on to the round-shank boring bar used for internal turning and tested during machining. Comparisons between an uncoated and a coated boring bar were carried out at 0.25 mm and 0.5 mm depth of cut using a five times length to diameter ratio overhang, which are typical conditions known to generate detrimental mechanical vibrations. From sound pressure measurement it was found that the measured absolute sound level during process could be reduced by about 90% when using the tool coated with damping layer. Surface roughness measurements of the processed workpiece showed decreased Ra values from approximately 3-6 mu m to less than 2 mu m (and in 50% of the cases < 1 mu m) when comparing an uncoated standard tool with its coated counterpart. Moreover, it was found that the addition of an anti-vibration coating did not adversely affect other tool properties, such as rigidity and modularity.
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| 8. |
- Sieber, Arne Santa, et al.
(author)
-
Compact recreational rebreather with innovative gas sensing concept and low work of breathing design
- 2013
-
In: Marine Technology Society journal. - : Marine Technology Society Inc.. - 0025-3324 .- 1948-1209. ; 47:6, s. 27-41
-
Journal article (peer-reviewed)abstract
- Recreational rebreathers are increasingly popular, and recreational diver training organizations now routinely offer training for rebreather diving. Few rebreathers on the market, however, fulfill the criteria of a dedicated recreational rebreather. These remain based on traditional sensor technology, which may be linked to rebreather use having an estimated 10 times the risk of mortality while diving compared with open circuit breathing systems. In the present work, a new recreational rebreather based on two innovative approaches is described. Firstly, the rebreather uses a novel sensor system including voltammetric and spectroscopic validation of galvanic pO2 sensor cells, a redundant optical pO2 sensor, and a two-wavelength infrared pCO2 sensor. Secondly, a new breathing loop design is introduced, which reduces failure points, improves work of breathing, and can be mass fabricated at a comparatively low cost. Two prototypes were assembled and tested in the laboratory at a notified body for personal protective equipment before both pool and sea water diving trials. Work of breathing was well below the maximum allowed by the European Normative. These trials also demonstrated that optical pO2 sensors can be successfully employed in rebreathers. The pCO2 sensor detected pCO2 from 0.0004 to 0.0024 bar. These new approaches, which include a new concept for simplified mechanical design as well as improved electronic control, may prove useful in future recreational diving apparatus.
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| 9. |
- Koptyug, Andrey, 1956-, et al.
(author)
-
Electron Beam Melting: from Shape Freedom to Materials Properties Control at Macro- and Microscale
- 2021
-
In: Proceedings of the THERMEC 2020, Graz, Austria. - : Trans Tech Publications. ; , s. 755-759
-
Conference paper (peer-reviewed)abstract
- Electron beam melting (EBM) is one of the constantly developing powder bed fusion (PBF) additive manufacturing technologies (AM) offering advanced control over the manufacturing process. Freedom of component shapes is one of the AM competitive advantages already used at industrial and semi- industrial scale. Development of the additive manufacturing today is targeting both widening of the available materials classes, and introducing new enabling modalities. Present research is related to the new possibilities in tailoring different material properties within additively manufactured components effectively adding “fourth dimension to the 3D-printing”. Specific examples are given in relation to the electron beam melting, but majority of the conclusions are valid for the laser-based PBF techniques as well. Through manipulating beam energy deposition it is possible to tailor quite different material properties selectively within each manufactured component, including effective material density as well as thermal, mechanical, electrical and acoustic properties. It is also possible to acquire by choice both metal-metal composite and completely alloyed material, when blends of precursor powder are used together with the beam energy manipulation.
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| 10. |
- Kaline P., Furlan
(author)
-
Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography
- 2018
-
In: Applied Materials Today. - : Elsevier BV. - 2352-9407. ; 13, s. 359-369
-
Journal article (peer-reviewed)abstract
- Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 °C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material's function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 °C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 °C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 °C for 100 h.
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| 11. |
- Li, Zhen, et al.
(author)
-
Single cell analysis of proliferation and movement of cancer and normal-like cells on nanowire array substrates
- 2018
-
In: Journal of Materials Chemistry B. - : Royal Society of Chemistry (RSC). - 2050-7518 .- 2050-750X. ; 6:43, s. 7042-7049
-
Journal article (peer-reviewed)abstract
- Nanowires are presently investigated in the context of various biological and medical applications. In general, these studies are population-based, which results in sub-populations being overlooked. Here, we present a single cell analysis of cell cycle and cell movement parameters of cells seeded on nanowires using digital holographic microscopy for time-lapse imaging. MCF10A normal-like human breast epithelial cells and JIMT-1 breast cancer cells were seeded on glass, flat gallium phosphide (GaP), and on vertical GaP nanowire arrays. The cells were monitored individually using digital holographic microscopy for 48 h. The data show that cell division is affected in cells seeded on flat GaP and nanowires compared to glass, with much fewer cells dividing on the former two substrates compared to the latter. However, MCF10 cells that are dividing on glass and flat GaP substrates have similar cell cycle time, suggesting that distinct cell subpopulations are affected differently by the substrates. Altogether, the data highlight the importance of performing single cell analysis to increase our understanding of the versatility of cell behavior on different substrates, which is relevant in the design of nanowire applications.
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| 12. |
- Decrop, Deborah, et al.
(author)
-
Single-step manufacturing of femtoliter microwell arrays in a novel surface energy mimicking polymer
- 2015
-
In: 18th International Conference on Solid-State Sensors, Actuators and Microsystems (IEEE TRANSDUCER 2015). - : IEEE.
-
Conference paper (peer-reviewed)abstract
- We report a novel polymer material formulation and stamp-molding technique that enable rapid single-step manufacturing of hydrophilic-in-hydrophobic microwell arrays. We developed a modified thiol-ene-epoxy polymer (mOSTE+) formulation that mimics the surface energy of its mold during polymerization. The polymer inherits the surface energy from the mold through molecular self-assembly, in which functional monomers self-assemble at the interface between the liquid prepolymer and the mold surface. Combining this novel mOSTE+ material with a stamp-molding process leads to simultaneous surface energy mimicking and micro-structuring. This method was used to manufacture microwells with hydrophilic bottom and hydrophobic sidewall, depressed in a surrounding hydrophobic surface. The microwell arrays were successfully tested for the self-assembly of 62’000 femtoliter-droplets. Such femtoliter droplet arrays are useful for, e.g., digital ELISA and single cell/molecule analysis applications.
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| 13. |
- Kustanovich, Kiryl, 1987
(author)
-
Integration of Surface Acoustic Wave and Microfluidic Technologies for Liquid-Phase Sensing Applications
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- This thesis discusses a new concept for construction of a novel SAW in-liquid sensor employing surface acoustic wave resonance (SAR) in a one-port configuration. In this concept, the reflective gratings of a one-port SAW resonator are employed as mass loading-sensing elements, while the SAW transducer is protected from the measurement environment, reducing power losses significantly. Microfluidic technologies have developed during the last decades into versatile platforms for miniaturized analytical devices. The devices are small, low cost, capable of multi-step automation resulting in fast turnaround, and allow reducing the amount of reagent and sample consumption, while maintaining a precise control over the environment. In this context, small, cheap and efficient sensors capable of in-liquid operation within microfluidic devices are in a great demand. The introduction of acoustic wave technology onto lab-on-a-chip platforms provides sensing capability that meets these criteria, and allows for an extended set of functions to be implemented, e.g., fast fluidic actuation, contact-free particle manipulation, sorting, and others. A resonant SAW sensor topology embedded in a polydimethylsiloxane (PDMS) microfluidic analyte delivery system was fabricated and characterized. Designs with the best performance were identified, and initial measurements in a liquid environment are discussed. In comparison to a delay-line topology, the proposed one-port resonant configuration features improved sensitivity, while offering better electrical performance and smaller size, which allows for wafer-scale fabrication and facilitates integration. Following optimization, sensing performance was evaluated by means of different assays, and multiparametric sensing was demonstrated by sharing of sensor components for simultaneous SAR sensing and electrochemical impedance spectroscopy in different frequency bands. This technological advancement may open pathways to new analytical instrumentation. The small sensor footprint, low energy consumption, and simple two-wire readout facilitate the integration in hand-held “lab on a chip” assay devices, the construction of sensing arrays for parallel sample processing, and the implementation of wireless data transfer schemes.
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| 14. |
- Das, Atanu Kumar, et al.
(author)
-
Applications of organic-based nanocomposites in corrosion protection
- 2023
-
In: Nanocomposites-Advanced Materials for Energy and Environmental Aspects. - : Elsevier. - 9780323997041 ; , s. 579-590
-
Book chapter (other academic/artistic)abstract
- Corrosion protection is one of the utmost aims for the reduction of maintenance costs with higher production for the industry. The conventional toxic chromate-based coating is an environmental concern, which has led researchers to develop an organic-based coating with higher anticorrosive performance. The incorporation of nanocomposite increases the adhesion capability of the coating to the metal surface leading to protecting the metal from corrosion. Nanocomposites have novel mechanical and electrochemical properties. The type of nanocomposites depends on the type of nanostructured filler. The performance of nanocomposite coating depends on the types of nanoparticles and additives, the concentration of the dispersed particles, and the mixing processes. In this chapter, nanocellulose-based nanocomposites, their synthesis, and performance against corrosion protection have been discussed. The potential of these nanocomposites as corrosion inhibitors has been pointed out as well.
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| 15. |
- Surendiran, Pradheebha, et al.
(author)
-
Solving Exact Cover Instances with Molecular-Motor-Powered Network-Based Biocomputation
- 2022
-
In: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496 .- 2694-2496.
-
Journal article (peer-reviewed)abstract
- Information processing by traditional, serial electronic processors consumes an ever-increasing part of the global electricity supply. An alternative, highly energy efficient, parallel computing paradigm is network-based biocomputation (NBC). In NBC a given combinatorial problem is encoded into a nanofabricated, modular network. Parallel exploration of the network by a very large number of independent molecular-motor-propelled protein filaments solves the encoded problem. Here we demonstrate a significant scale-up of this technology by solving four instances of Exact Cover, a nondeterministic polynomial time (NP) complete problem with applications in resource scheduling. The difficulty of the largest instances solved here is 128 times greater in comparison to the current state of the art for NBC.
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| 16. |
- Chen, Zhe, et al.
(author)
-
Nano-scale characterization of white layer in broached Inconel 718
- 2017
-
In: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - Amsterdam : Elsevier BV. - 0921-5093 .- 1873-4936. ; 684, s. 373-384
-
Journal article (peer-reviewed)abstract
- The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.
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| 17. |
- Zubritskaya, Irina, 1984, et al.
(author)
-
Dynamically Tunable Optical Cavities with Embedded Nematic Liquid Crystalline Networks
- 2023
-
In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:13
-
Journal article (peer-reviewed)abstract
- Tunable metal–insulator–metal (MIM) Fabry–Pérot (FP) cavities that can dynamically control light enable novel sensing, imaging and display applications. However, the realization of dynamic cavities incorporating stimuli-responsive materials poses a significant engineering challenge. Current approaches rely on refractive index modulation and suffer from low dynamic tunability, high losses, and limited spectral ranges, and require liquid and hazardous materials for operation. To overcome these challenges, a new tuning mechanism employing reversible mechanical adaptations of a polymer network is proposed, and dynamic tuning of optical resonances is demonstrated. Solid-state temperature-responsive optical coatings are developed by preparing a monodomain nematic liquid crystalline network (LCN) and are incorporated between metallic mirrors to form active optical microcavities. LCN microcavities offer large, reversible and highly linear spectral tuning of FP resonances reaching wavelength-shifts up to 40 nm via thermomechanical actuation while featuring outstanding repeatability and precision over more than 100 heating–cooling cycles. This degree of tunability allows for reversible switching between the reflective and the absorbing states of the device over the entire visible and near-infrared spectral regions, reaching large changes in reflectance with modulation efficiency ΔR = 79%.
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| 18. |
- Burks, Raychelle, et al.
(author)
-
#67 Chalmers short stories
- 2019
-
Other publication (other academic/artistic)abstract
- What´s the science behind self driving cars, hospital entry architecture and faster computers? In this episode we meet eight PhD-students presenting five minutes stories about their research projects at Chalmers University of Technology. We also talk to Dr. Raychelle Burks from St. Edwards University in Texas and Professor Lars Öhrström from Chalmers, about how they work to get science out to the society. Come along with RadioScience to a workshop on science communication, a warm and sunny day in June. We went to Gothenburg to give tips and tricks on recording and editing a podcast. In return we got eight really interesting short stories within the field of technology. In addition, Raychelle Burks reads the post ”Because she didn’t die” from her blog thirty-seven and Lars Öhrström gives us a taste from his book ”The rhubarb connection – the everyday world of metal ions” – to be published in December. This episode was a collaboration with teachers and students at the workshop on popular science communication at Chalmers University of Technology, Gothenburg, Sweden. Producers: Lisa Beste and Natalie von der Lehr, RadioScience.se, Uppsala. Listen at: http://www.radioscience.se/forskning/67-chalmers-short-stories/
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| 19. |
- Montanari, Celine
(author)
-
Transparent Wood Biocomposites for Sustainable Development
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- Sustainable wood nanotechnologies that combine optical transmittance and mechanical performance are interesting for new functionalities utilizing transparency. Wood is a sophisticated bio-based material with a natural hierarchical, anisotropic and porous structure. The wood cellular structure can be functionalized at the micro and nanostructural level for the design of advanced functional materials. In recent years, the development of transparent wood biocomposites derived from delignified wood substrates have gained interest because they combine attractive structural properties with optical functionality. Nanostructural tailoring of transparent wood biocomposites is required to improve optical transmittance, mechanical performance, and to add new functionalities. In this thesis, environmentally friendly material components and green chemical processes have been developed for the fabrication of nanostructurally tailored transparent wood biocomposites.Mesoporous delignified wood substrates with preserved microstructure and cellulose microfibril alignment in the cell wall are used as reinforcement in transparent wood biocomposites. Chemical functionalization strategies using renewable maleic, itaconic and succinic anhydrides have been explored for molecular and nanostructural tailoring of delignified cell walls. Cyclic anhydride functionalization results in high degree of esterification, reduces moisture content in the wood substrate, improves monomer diffusion within the cell wall, and further enables interface tailoring at the molecular scale with possibility for covalent attachment with polymer matrix. Transparent wood biocomposites were prepared by methyl methacrylate monomer impregnation followed by in situ polymerization within the chemically modified wood substrates. The anhydride-functionalized transparent wood biocomposites have improved wood-polymer interfacial interactions, resulting in improved optical and mechanical properties. Moreover, a bio-based polymer matrix was designed from renewable limonene oxide and acrylic acid for the fabrication of fully bio-based transparent wood biocomposites. The bio-based monomer can diffuse into the cell wall, and the polymer phase is both refractive index-matched and covalently linked to the wood substrate. The bio-based transparent wood biocomposites are nanostructured and demonstrate superior optical transmittance, low haze, and excellent mechanical performance.Nanostructural functionalization using phase-change materials is also demonstrated for the design of transparent wood biocomposites that combine thermal energy storage, tunable optical properties, and load bearing functions. Molecular and nanoscale interactions in transparent wood biocomposites are critical as they contribute to the favorable distribution of the phase-change material across the wood structure, which is a key component in optimizing thermal energy storage capacity. Bio-based design of transparent wood is also explored for thermal energy storage applications. Low environmental impact is achieved by combining the use of bio-based resources with green processing routes. Environmentally friendly transparent wood nanotechnologies can compete with petroleum-based plastics in applications such as load-bearing transparent panel and energy saving.
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| 20. |
- Haglund, Emanuel, 1988
(author)
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VCSEL Cavity Engineering for High Speed Modulation and Silicon Photonics Integration
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- The GaAs-based vertical-cavity surface-emitting laser (VCSEL) is the standard light source in today's optical interconnects, due to its energy efficiency, low cost, and high speed already at low drive currents. The latest commercial VCSELs operate at data rates of up to 28 Gb/s, but it is expected that higher speeds will be required in the near future. One important parameter for the speed is the damping of the relaxation oscillations. A higher damping is affordable at low data rates to reduce signal degradation due to overshoot and jitter, while lower damping is required to reach higher data rates. A VCSEL with the damping optimized for high data rates enabled error-free transmission at record-high data rates up to 57 Gb/s. For future interconnect links it is of interest with tighter integration between the optics and the silicon-based electronics. Techniques to heterogeneously integrate GaAs-based VCSELs on silicon could potentially enable integrated multi-wavelength VCSEL arrays, thus increasing the data rate through wavelength division multiplexing. Heterogeneous integration of GaAs-based VCSELs would also benefit applications that need short-wavelength light sources, such as photonic integrated circuits for life sciences and bio photonics. Silicon-integrated short-wavelength hybrid-cavity VCSELs with up to 2.3 mW optical output power and 12 GHz modulation bandwidth, which enables data transmission at up to 25 Gb/s, are demonstrated by employing ultra-thin adhesive bonding. Further, a vertical-cavity silicon-integrated laser (VCSIL) with in-plane waveguide emission is demonstrated by employing an intra-cavity waveguide with a weak diffraction grating that couples light from the standing wave in the vertical cavity into an in-plane waveguide.
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| 21. |
- Ottonello Briano, Floria
(author)
-
Mid-infrared photonic devices for on-chip optical gas sensing
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- Gas detection is crucial in a wide range of fields and applications, such as safety and process control in the industry, atmospheric sciences, and breath diagnostics. Optical gas sensing offers some key advantages, compared to other sensing methods such as electrochemical and semiconductor sensing: high specificity, fast response, and minimal drift.Wavelengths between 3 and 10 μm are of particular interest for gas sensing. This spectral range, called the mid-infrared (mid-IR), is also known as the fingerprint region, because several gas species can be identified by their sharp absorption lines in this region. The most relevant mid-IR-active gases are the trace gases carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), ammonia (NH3), and nitrous oxide (N2O). They are greenhouse gases, contributing to global warming. They are waste products of human activities and widely used in agriculture and industry. Therefore, it is crucial to accurately and extensively monitor them. However, traditional optical gas sensors with a free-space optical path configuration, are too bulky, power-hungry, and expensive to be widely adopted.This thesis presents mid-IR integrated photonic devices that enable the on-chip integration of optical gas sensors, with a focus on CO2 sensing. The reported technologies address the fundamental sensor functionalities: light-gas interaction, infrared light generation, and infrared light detection. The thesis introduces a novel mid-IR silicon photonic waveguide that allows a light path as long as tens of centimeters to fit in a volume smaller than a few cubic millimeters. Mid-IR CO2 spectroscopy demonstrates the high sensing performance of the waveguide. The thesis also explores the refractive index sensing of CO2 with a mid-IR silicon photonic micro-ring resonator.Furthermore, the thesis proposes platinum nanowires as low-cost infrared light sources and detectors that can be easily integrated on photonic waveguides. Finally, the thesis presents a large-area infrared emitter fabricated by highs-peed wire bonding and integrated in a non-dispersive infrared sensor for the detection of alcohol in breath.The technologies presented in this thesis are suited for cost-effective mass production and large-scale adoption. Miniaturized integrated optical gas sensors have the potential to become the main choice for an increasingly broad range of existing and new applications, such as portable, distributed, and networked environmental monitoring, and high-volume medical and consumer applications.
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| 22. |
- Harr Martinsen, Kristoffer, 1990
(author)
-
Preparation and characterization of graphene/metal composites
- 2021
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Licentiate thesis (other academic/artistic)abstract
- Since the isolation of graphene in 2004, much research has been conducted to understand this novel material and how its properties can be utilized in different applications. One type of venture involves graphene as a reinforcing filler in metal matrix composites (MMC) which is becoming increasingly prevalent in the automotive and aerospace industries. Such composites combine the machinability and processing flexibility of metals with the unique properties of graphene. In fact, copper-graphene composites have demonstrated ameliorated mechanical strength with thermal conductivities elevated beyond pristine copper. However, the challenges that remain to commercialize copper-graphene composites are numerous. The most challengeable one is that graphene must be uniformly dispersed in the matrix and adhere to copper through an industrially scalable and affordable process. Moreover, the volume fraction of graphene must be efficiently controlled, lest superfluous amounts lead to structural detriment. In this regard, the emphasis of this study was to investigate a scalable and simple method to obtain such MMC via powder metallurgy. Specifically, gas atomized copper powder was functionalized with 3-aminopropyl-triethoxysilane (APTES) in toluene (APTES-Cu), resulting in a positively charged surface; then aqueously dispersed and negatively charged graphene oxide (GO) could then be self-assembled on the surface APTES@Cu via electrostatic interaction (Cu@APTES-Cu). The thickness of GO layers and morphology on the powder was controlled by modulating APTES grafting duration and APTES concentration in toluene. Cu@APTES-Cu powders were thermally annealed before compaction and sintering in inert atmosphere. The results show that surface modification of metal powders serves as a scalable and versatile approach to coat graphene on metal particles for the preparation of graphene/metal composites. Surface modification of copper with 0.2 vol% APTES in toluene for 30 minutes was sufficient to obtain composite powders with incomplete GO coating, which nonetheless demonstrated improved hardness. However, cold working of sintered composites was essential to densify the porous structure created by reduced GO during sintering. On the other hand, sintered composite samples that exhibited higher thermal conductivity than copper was obtained with higher APTES and GO loading. After thermal annealing, these thicker GO coatings were found to improve thermal conductivity in sintered composites by acting as thermal bridges between individual composite particles. Despite incomplete sintering of these composites, a 20% increase in thermal conductivity was attainable. Finally, both polarization scans and etching measurements in concentrated HCl and ammonium persulfate (APS) indicate that the GO coating decomposes on the outer surface during sintering. However, the reduced GO coating can retard corrosion of the internal composite structure by diffusion inhibition.
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| 23. |
- Lee, Kyuho, et al.
(author)
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Benchmarking van der Waals density functionals with experimental data: potential-energy curves for H2 molecules on Cu(111), (100) and (110) surfaces
- 2012
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In: Journal of Physics: Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42
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Journal article (peer-reviewed)abstract
- Detailed physisorption data from experiment for the H2 molecule on low-index Cu surfaces challenge theory. Recently, density functional theory (DFT) has been developed to account for nonlocal correlation effects, including van der Waals (dispersion) forces. We show that the functional vdW-DF2 gives a potential-energy curve, potential-well energy levels and difference in lateral corrugation promisingly close to the results obtained by resonant elastic backscattering–diffraction experiments. The backscattering barrier is sensitive to the choice of exchange functional approximation. Further, the DFT-D3 and TS-vdW corrections to traditional DFT formulations are also benchmarked, and deviations are analyzed.
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| 24. |
- Soltani, Amin, et al.
(author)
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Direct nanoscopic observation of plasma waves in the channel of a graphene field-effect transistor
- 2020
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In: Light: Science and Applications. - : Springer Science and Business Media LLC. - 2047-7538 .- 2095-5545. ; 9:1
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Journal article (other academic/artistic)abstract
- Plasma waves play an important role in many solid-state phenomena and devices. They also become significant in electronic device structures as the operation frequencies of these devices increase. A prominent example is field-effect transistors (FETs), that witness increased attention for application as rectifying detectors and mixers of electromagnetic waves at gigahertz and terahertz frequencies, where they exhibit very good sensitivity even high above the cut-off frequency defined by the carrier transit time. Transport theory predicts that the coupling of radiation at THz frequencies into the channel of an antenna-coupled FET leads to the development of a gated plasma wave, collectively involving the charge carriers of both the two-dimensional electron gas and the gate electrode. In this paper, we present the first direct visualization of these waves. Employing graphene FETs containing a buried gate electrode, we utilize near-field THz nanoscopy at room temperature to directly probe the envelope function of the electric field amplitude on the exposed graphene sheet and the neighboring antenna regions. Mapping of the field distribution documents that wave injection is unidirectional from the source side since the oscillating electrical potentials on the gate and drain are equalized by capacitive shunting. The plasma waves, excited at 2 THz, are overdamped, and their decay time lies in the range of 25–70 fs. Despite this short decay time, the decay length is rather long, i.e., 0.3-0.5 μm, because of the rather large propagation speed of the plasma waves, which is found to lie in the range of 3.5–7 × 10^6 m/s, in good agreement with theory. The propagation speed depends only weakly on the gate voltage swing and is consistent with the theoretically predicted 1414 power law.
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| 25. |
- Kothapalli, Satya V.V.N. 1985-
(author)
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Nano-Engineered Contrast Agents : Toward Multimodal Imaging and Acoustophoresis
- 2015
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Doctoral thesis (other academic/artistic)abstract
- Diagnostic ultrasound (US) is safer, quicker and cheaper than other diagnostic imaging modalities. Over the past two decades, the applications of US imaging has been widened due to the development of injectable, compressible and encapsulated microbubbles (MBs) that provide an opportunity to improve conventional echocardiographic imaging, blood flow assessment and molecular imaging. The encapsulating material is manufactured by different biocompatible materials such as proteins, lipids or polymers. In current research, researchers modify the encapsulated shell with the help of advanced molecular chemistry techniques to load them with dyes (for fluorescent imaging), nanoparticles and radioisotopes (for multimodal imaging) or functional ligands or therapeutic gases (for local drug delivery). The echogenicity and the radial oscillation of MBs is the result of their compressibility, which undoubtedly varies with the encapsulated shell characteristics such as rigidity or elasticity.In this thesis, we present acoustic properties of novel type of polyvinyl alcohol (PVA)-shelled microbubble (PVA-MB) that was further modified with superparamagnetic iron oxide nanoparticles (SPIONs) to work as a dual-modal contrast agent for magnetic resonance (MR) imaging along with US imaging. Apparently, the shell modification changes their mechanical characteristics, which affects their acoustic properties. The overall objective of the thesis is to investigate the acoustic properties of modified and unmodified PVA-MBs at different ultrasound parameters.The acoustic and mechanical characterization of SPIONs modified PVA-MBs revealed that the acoustical response depends on the SPION inclusion strategy. However they retain the same structural characteristics after the modification. The modified MBs with SPIONs included on the surface of the PVA shell exhibit a soft-shelled behavior and produce a higher echogenicity than the MBs with the SPIONs inside the PVA shell. The fracturing mechanism of the unmodified PVA-MBs was identified to be different from the other fracturing mechanisms of conventional MBs. With the interaction of high-pressure bursts, the air gas core is squeezed out through small punctures in the PVA shell. During the fracturing, the PVA-MBs exhibit asymmetric (other modes) oscillations, resulting in sub- and ultra-harmonic generation. Exploiting the US imaging at the other modes of the oscillation of the PVA-MBs would provide an opportunity to visualize very low concentrations of (down to single) PVA-MBs. We further introduced the PVA-MBs along with particles mimicking red blood cells in an acoustic standing-wave field to observe the acoustic radiation force effect. We observed that the compressible PVA-MBs drawn toward pressure antinode while the solid blood phantoms moved toward the pressure node. This acoustic separation method (acoustophoresis) could be an efficient tool for studying the bioclearance of the PVA-MBs in the body, either by collecting blood samples (in-vitro) or by using the extracorporeal medical procedure (ex-vivo) at different organs.Overall, this work contributes significant feedback for chemists (to optimize the nanoparticle inclusion) and imaging groups (to develop new imaging sequences), and the positive findings pave new paths and provide triggers to engage in further research.
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