| 1. |
- Surendiran, Pradheebha, et al.
(författare)
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Solving Exact Cover Instances with Molecular-Motor-Powered Network-Based Biocomputation
- 2022
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Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496 .- 2694-2496.
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Sun, Rui, et al.
(författare)
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Highly Porous Amorphous Calcium Phosphate for Drug Delivery and Bio-Medical Applications
- 2020
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous calcium phosphate (ACP) has shown significant effects on the biomineralization and promising applications in bio-medicine. However, the limited stability and porosity of ACP material restrict its practical applications. A storage stable highly porous ACP with Brunauer–Emmett–Teller surface area of over 400 m2/g was synthesized by introducing phosphoric acid to a methanol suspension containing amorphous calcium carbonate nanoparticles. Electron microscopy revealed that the porous ACP was constructed with aggregated ACP nanoparticles with dimensions of several nanometers. Large angle X-ray scattering revealed a short-range atomic order of <20 Å in the ACP nanoparticles. The synthesized ACP demonstrated long-term stability and did not crystallize even after storage for over 14 months in air. The stability of the ACP in water and an α-MEM cell culture medium were also examined. The stability of ACP could be tuned by adjusting its chemical composition. The ACP synthesized in this work was cytocompatible and acted as drug carriers for the bisphosphonate drug alendronate (AL) in vitro. AL-loaded ACP released 25% of the loaded AL in the first 22 days. These properties make ACP a promising candidate material for potential application in biomedical fields such as drug delivery and bone healing.
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| 3. |
- Palo-Nieto, Carlos, 1985-, et al.
(författare)
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Functionalization of cellulose nanofibrils to develop novel ROS-sensitive biomaterials
- 2023
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Ingår i: Materials Advances. - : Royal Society of Chemistry. - 2633-5409. ; 4:6, s. 1555-1565
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Tidskriftsartikel (refereegranskat)abstract
- Wood derived cellulose nanofibrils (CNFs) have emerged as an interesting material for biomedical applications. Functionalization of the nanofibrils with bioactive molecules is a potent tool to tailor CNF materials for specific applications in biomedicine. The present work proposes the functionalization of CNFs with a reactive oxygen species (ROS)-sensitive oligopeptide to develop a novel CNF-based material for the treatment of medical conditions associated with high levels of ROS such as chronic wounds. Oligoproline peptides of two different lengths (5 and 10 proline units) were covalently incorporated onto the CNF surface, several water-based chemical approaches were explored and the reaction conditions to maximize peptide substitution and the degree of fibre crosslinking were optimized. The chemical structure, degree of peptide substitution, degree of fibre crosslinking, surface morphology and ROS-sensitivity of the oligoproline–CNF materials were characterized. Double-crosslinked CNF hydrogels (Ca2+–oligoproline–CNF) were further prepared and the ability of the hydrogels to protect cells from an oxidative environment was investigated in vitro with human dermal fibroblasts, as a first evaluation of the potential of the novel CNF material to be used in chronic wound therapies. Optimization of the reaction conditions resulted in a degree of peptide substitution of 102 ± 10 μmol g−1 CNF irrespective of the oligoproline length and a degree of crosslinking of 55–80% depending on the number of proline units. The results showed that the oligoproline covalently attached to CNFs via carbodiimide chemistry maintained its ability to respond to ROS and that the responsiveness in terms of viscoelastic properties depended on the length of the oligopeptide, with the hydrogel being more responsive when functionalized with 10 proline units compared with 5 proline units. Furthermore, the double crosslinked Ca2+–oligoproline–CNF hydrogels promoted the survival of human dermal fibroblasts exposed to high levels of ROS. This study is the first one to provide an insight into the development of ROS-sensitive materials based on CNFs and opens up possibilities for further investigation on the use of these novel materials in chronic wound care.
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| 4. |
- Grabowski, Alexander, 1993
(författare)
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VCSEL Equivalent Circuits and Silicon Photonics Integration
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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. |
- Rebolledo Salgado, Israel, 1992, et al.
(författare)
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Active Feedback Stabilization of Super-efficient Microcombs
- 2023
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Ingår i: 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
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Konferensbidrag (refereegranskat)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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| 6. |
- Santos Andrade, Tatiana, 1991, et al.
(författare)
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Low platinum fuel cell as enabler for the hydrogen fuel cell vehicle
- 2024
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Ingår i: Journal of Power Sources. - 0378-7753. ; 598
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the design and modeling of a fuel cell vehicle using low-loading platinum catalysts were investigated. Data from single fuel cells with low Pt-loading cathode catalysts were scaled up to fuel cell stacks and systems, implemented in a vehicle, and then compared to a commercial fuel cell vehicle. The low-loading Pt systems have shown lower efficiency at high loads compared to the commercial systems suggesting less stable materials. However, the analysis showed that the vehicle comprising low-loading Pt catalysts achieves similar or higher efficiency compared to the commercial fuel cell vehicle when being scaled up for the same number of cells. When the systems were scaled up for the same maximum power as the commercial fuel cell vehicle, all the low-loading Pt fuel cell systems showed higher efficiencies. In this case, more cells are needed, but still, the amount of Pt is significantly reduced compared to the commercial one. The high-efficiency results can be associated with the vehicle's power range operation that meets the region where the low-loading Pt fuel cells have high performance. The results suggested a positive direction towards the reduction of Pt in commercial fuel cell vehicles supporting a cost-competitive clean energy transition based on hydrogen.
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| 7. |
- Apaydin, Dogukan, 1991, et al.
(författare)
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Optically Pumped UVC Photonic Crystal Surface-Emitting Laser
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Photonic crystal surface-emitting lasers (PCSELs) are a new type of semiconductor lasers that offer a high optical output power while maintaining single-mode operation and a low divergence angle. Such devices rely upon the in-plane optical feedback from a two-dimensional photonic crystal and feature out-of-plane emission of the modes with zero group velocity at the photonic band edges by diffraction. Since the demonstration of the first PCSEL [1], the concept has been implemented in standard semiconductor materials with the demonstration of highperforming infrared and blue-emitting lasers [2, 3]. Extending the laser operation to shorter emission wavelengths would be a major breakthrough as such lasers would be of high interest for disinfection, material processing, curing, and medical treatments.
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| 8. |
- Koptyug, Andrey, 1956-, et al.
(författare)
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Electron Beam Melting: from Shape Freedom to Materials Properties Control at Macro- and Microscale
- 2021
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Ingår i: Proceedings of the THERMEC 2020, Graz, Austria. - : Trans Tech Publications. ; , s. 755-759
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Konferensbidrag (refereegranskat)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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| 9. |
- Zeng, Yin, 1996, et al.
(författare)
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A 100-µW 4-6 GHz Cryogenic InP HEMT LNA Achieving an Average Noise Temperature of 2.6 K
- 2022
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Ingår i: Asia-Pacific Microwave Conference Proceedings, APMC. ; 2022-November, s. 13-15, s. 13-15
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Konferensbidrag (refereegranskat)abstract
- Low-power LNAs at 4 K are critical for the scaling up of quantum computing systems due to the limited cooling capability in the dilution refrigerator. This paper presents design and fabrication of a cryogenic hybrid three-stage InP HEMT LNA working from 4 to 6 GHz. The design was conducted using a DC power optimized bias model of the InP HEMT. The 4 K measurement showed 2.6 K average noise temperature and more than 22 dB average gain of the InP HEMT LNA consuming only 100 µW DC power.
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| 10. |
- López, Cristian Daniel, 1990
(författare)
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Wideband THz Mixers and Components for the Next Generation of Receivers for Radioastronomy
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent decades, there has been a growing interest in THz research, leading to substantial improvements in technology and the emergence of new applications. In particular, the ever-evolving field of radio astronomy instrumentation has been pushing the limits of millimeter and sub-millimeter technology boundaries, redefining the state-of-the-art for wideband low-noise receivers. The technological roadmaps for radio astronomy applications, such as “The ALMA 2030 Wideband Sensitivity Upgrade”, set the requirements for the next generation of heterodyne receivers. Among these requirements, it establishes the need for a wider IF bandwidth and the possibility of covering multiple existing RF bands with a single receiver, e.g., combining ALMA bands 6 (211–275 GHz) and 7 (275–373 GHz), i.e., a ~56% fractional bandwidth. To build receivers with such a large fractional bandwidth, each of their components must be able to cover the required bandwidth with minimal insertion loss, or equivalently, add the minimum noise to the system. In particular, it is essential to focus on the components that are critical for the performance of such receivers, such as front-end waveguide components and the mixer chip. This thesis addresses this need and focuses on the design, simulation, fabrication, and characterization of ultra-wideband THz devices for the next generation of radio astronomy receivers. The thesis starts by presenting the development of waveguide passive components key to future ultra-wideband receivers, such as waveguide twists and power dividers. Waveguide twists are essential interconnection parts in most polarization-sensitive THz receivers that make use of orthomode transducers. Since compactness and low insertion loss are critical requirements, step-twists have become a promising solution. This work introduces novel designs for step twists covering the frequency ranges of 120-220 GHz and 210-375 GHz, i.e., 44% and 56% fractional bandwidth with 20 dB return loss, respectively. In the first design, the experimental verification showed an insertion loss of 0.4 dB, while the second demonstrated an insertion loss as low as 0.3 dB. Additionally, the thesis investigates waveguide power dividers, a fundamental component in the development of 2SB receivers for LO injection. It presents a waveguide power divider that incorporates a substrate-based element into a waveguide structure to enhance the output port’s isolation and matching in the frequency range of 150-220 GHz, i.e. 38% fractional bandwidth. THz mixers are implemented with thin-film technology. As a consequence, the waveguide-to-substrate transitions have a fundamental role in the performance and bandwidth of such systems. In this work, a waveguide-to-slotline superconducting transition based on substrateless finlines is proposed. Moreover, for the majority of modern mixers with Superconductor Insulator Superconductor (SIS) technology, the microstrip line topology is the most suitable. Hence, this work presents the development of a broadband slotline to microstrip transition based on Marchand baluns. Both transitions were experimentally verified at cryogenic temperatures. Remarkably, each of these transitions achieved a fractional bandwidth of ~56%, while the substrateless finline transition demonstrated an insertion loss of 0.5 dB, the Marchand Balun showed an insertion loss as low as 0.3 dB. The integration of the substrateless finline and the Marchand balun transitions served as the first approach to a platform for the development of an ultra-wideband SIS mixer. This platform evolved into the SIS mixer design for 210-375 GHz introduced in this thesis. The mixer chip represents a significant shift from traditional design approaches since the dielectric substrate is removed and replaced with a micromachined metallic substrate which integrates a metallic finline. The micromachined substrate is employed as a technological platform for the Nb-Al/AlN-Nb SIS junctions, the RF matching circuitry, and the IF output filter. The mixer features a designed IF bandwidth of 4-16 GHz. Furthermore, this thesis demonstrates the feasibility of micromachined metallic substrates as a technological platform for SIS devices.
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