| 1. |
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| 2. |
- Damgaard, P. D., et al.
(författare)
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137 ancient human genomes from across the Eurasian steppes
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 557:7705, s. 369-374
-
Tidskriftsartikel (refereegranskat)abstract
- For thousands of years the Eurasian steppes have been a centre of human migrations and cultural change. Here we sequence the genomes of 137 ancient humans (about 1x average coverage), covering a period of 4,000 years, to understand the population history of the Eurasian steppes after the Bronze Age migrations. We find that the genetics of the Scythian groups that dominated the Eurasian steppes throughout the Iron Age were highly structured, with diverse origins comprising Late Bronze Age herders, European farmers and southern Siberian hunter-gatherers. Later, Scythians admixed with the eastern steppe nomads who formed the Xiongnu confederations, and moved westward in about the second or third century bc, forming the Hun traditions in the fourthfifth century ad, and carrying with them plague that was basal to the Justinian plague. These nomads were further admixed with East Asian groups during several short-term khanates in the Medieval period. These historical events transformed the Eurasian steppes from being inhabited by Indo-European speakers of largely West Eurasian ancestry to the mostly Turkic-speaking groups of the present day, who are primarily of East Asian ancestry.
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| 3. |
- Grigorenko, L, et al.
(författare)
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Scientific program of DERICA-prospective accelerator and storage ring facility for radioactive ion beam research
- 2019
-
Ingår i: Physics-Uspekhi. - 1468-4780 .- 1063-7869. ; 62:7, s. 675-690
-
Tidskriftsartikel (refereegranskat)abstract
- Studies of radioactive ions (RIs) are the most thriving field of low-energy nuclear physics. In this paper, the concept and the scientific agenda of the prospective accelerator and storage ring facility for RI beam (RIB) research are proposed for a large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented and shown to be comparable to those of advanced world centers, the so-called "RIB factories". In the project, the emphasis is made on studies with short-lived RIBs in storage rings. A unique feature of the project is the possibility of studying electron-RI interactions in a collider experiment to determine the fundamental properties of nuclear matter, in particular, electromagnetic form factors of exotic nuclei.
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| 4. |
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| 5. |
- Abrikosov, Igor, et al.
(författare)
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Theoretical description of pressure-induced phase transitions: a case study of Ti-V alloys
- 2015
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Ingår i: High Pressure Research. - : Taylor andamp; Francis: STM, Behavioural Science and Public Health Titles. - 0895-7959 .- 1477-2299. ; 35:1, s. 42-48
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Tidskriftsartikel (refereegranskat)abstract
- We discuss theoretical description of pressure-induced phase transitions by means of first-principles calculations in the framework of density functional theory. We illustrate applications of theoretical tools that allow one to take into account configurational and vibrational disorders, considering Ti-V alloys as a model system. The universality of the first-principles theory allows us to apply it in studies of different phenomena that occur in the Ti-V system upon compression. Besides the transitions between different crystal structures, we discuss isostructural transitions in bcc Ti-V alloys. Moreover, we present arguments for possible electronic transitions in this system, which may explain peculiar behaviour of elastic properties of V upon compression.
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| 6. |
- Zuev, D. A., et al.
(författare)
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Multifunctional Sensing with Hybrid Nanophotonic Structures
- 2017
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Ingår i: Progress in Electromagnetics Research Symposium. - 1559-9450 .- 1931-7360. ; , s. 1491-1493
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Konferensbidrag (refereegranskat)abstract
- The development of multifunctional systems for investigation of different parameters involved in chemical reactions is a vital problem in case of low concentrations of tested matter. Here, we investigate hybrid plasmonic-dielectric system and demonstrate possibility of such application for multifunctional sensing.
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| 7. |
- Barannikova, S. A., et al.
(författare)
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Influence of stresses on structure and properties of Ti and Zr-based alloys from first-principles simulations
- 2015
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Ingår i: INTERNATIONAL SCIENTIFIC CONFERENCE OF YOUNG SCIENTISTS: ADVANCED MATERIALS IN CONSTRUCTION AND ENGINEERING. - : IOP Publishing.
-
Konferensbidrag (refereegranskat)abstract
- Computer simulations in the framework of the Density Functional Theory have become an established tool for computer simulations of materials properties. In most cases, however, information is obtained at ambient conditions, preventing design of materials for applications at extreme conditions. In this work we employ ab initio calculations to investigate the influence of stresses on structure and stability of Ti-Mo and Zr-Nb alloys, an important class of construction materials. Calculations reproduce known phase stability trends in these systems, and we resolve the controversy regarding the stability of body-centered cubic solid solution in Mo-rich Ti-Mo alloys against the isostructural decomposition. Calculated results are explained in terms of the electronic structure effects, as well as in terms of physically transparent thermodynamic arguments that relate phase stability to deviations of concentration dependence of atomic volume from the linear behavior.
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| 8. |
- Litnovsky, A., et al.
(författare)
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Diagnostic mirrors for ITER : research in the frame of International Tokamak Physics Activity
- 2019
-
Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 59:6
-
Tidskriftsartikel (refereegranskat)abstract
- Mirrors will be used as first plasma-viewing elements in optical and laser-based diagnostics in ITER. Deterioration of the mirror performance due to e.g. sputtering of the mirror surface by plasma particles or deposition of impurities will hamper the entire performance of the affected diagnostic and thus affect ITER operation. The Specialists Working Group on First Mirrors (FM SWG) in the Topical Group on Diagnostics of the International Tokamak Physics Activity (ITPA) plays an important role in finding solutions for diagnostic first mirrors. Sound progress in research and development of diagnostic mirrors in ITER was achieved since the last overview in 2009. Single crystal (SC) rhodium (Rh) mirrors became available. SC rhodium and molybdenum (Mo) mirrors survived in conditions corresponding to similar to 200 cleaning cycles with a negligible degradation of reflectivity. These results are important for a mirror cleaning system which is presently under development. The cleaning system is based on sputtering of contaminants by plasma. Repetitive cleaning was tested on several mirror materials. Experiments comprised contamination/cleaning cycles. The reflectivity SC Mo and Rh mirrors has changed insignificantly after 80 cycles. First in situ cleaning using radiofrequency (RF) plasma was conducted in EAST tokamak with a mock-up plate of ITER edge Thomson Scattering (ETS) with five inserted mirrors. Contaminants from the mirrors were removed. Physics of cleaning discharge was studied both experimentally and by modeling. Mirror contamination can also be mitigated by protecting diagnostic ducts. A deposition mitigation (DeMi) duct system was exposed in KSTAR. The real-time measurement of deposition in the diagnostic duct was pioneered during this experiment. Results evidenced the dominating effect of the wall conditioning and baking on contamination inside the duct. A baffled cassette with mirrors was exposed at the main wall of JET for 23,6 plasma hours. No significant degradation of reflectivity was measured on mirrors located in the ducts. Predictive modeling was further advanced. A model for the particle transport, deposition and erosion at the port-plug was used in selecting an optical layout of several ITER diagnostics. These achievements contributed to the focusing of the first mirror research thus accelerating the diagnostic development. Modeling requires more efforts. Remaining crucial issues will be in a focus of the future work of the FM SWG.
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| 9. |
- Yu Nikonov, A., et al.
(författare)
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Calculation of Mechanical Properties of BCC Ti-Nb Alloys
- 2015
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Ingår i: INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2015. - : AMER INST PHYSICS. - 9780735413306
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Konferensbidrag (refereegranskat)abstract
- We have calculated mechanical properties of bcc Ti-Nb alloys in the framework of the first-principles approach using the exact muffin-tin orbital method. The results obtained quantitatively correlate well with known experimental data and can be used in order to design new materials based on of Ti alloys intended for various applications, e.g. for bio-medical applications.
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| 10. |
- Abrikosov, Igor, et al.
(författare)
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Theoretical Modeling of Thermodynamic and Mechanical Properties of the Pure Components of Ti and Zr Based Alloys Using the Exact Muffin-Tin Orbitals Method
- 2014
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Ingår i: Russian Physics Journal. - : Springer Verlag (Germany). - 1064-8887 .- 1573-9228. ; 56:9, s. 1030-1038
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Tidskriftsartikel (refereegranskat)abstract
- The exact muffin-tin orbitals (EMTO) method belongs to the third and latest generation of first-principles methods of calculating the electronic structure of materials in the so-called approximation of muffin-tin (MT) orbitals within the framework of the density functional theory. A study has been performed of its applicability for modeling the thermodynamic and mechanical properties of the pure components of Ti and Zr based alloys. The total energies of Ti, Zr, Nb, V, Mo, and Al are calculated in three crystal structures - face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP). For all of these elements and crystal structures, we have calculated the theoretical values of the lattice constants, elastic constants, and equations of state. The stable crystal structures have been determined. In all cases, calculations by the EMTO method predict the correct structure of the ground state. For stable structures we compared the obtained results with experiment and with calculations using full potential methods. We have demonstrated the reliability of the EMTO method and conclude that its further application for effective modeling of the properties of disordered alloys based on Ti and Zr is possible.
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| 11. |
- Kalinina, E., et al.
(författare)
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High-dose Al-implanted 4H-SiC p(+)-n-n(+) junctions
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:19, s. 3051-3053
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Tidskriftsartikel (refereegranskat)abstract
- p(+)-n-n(+) junctions were fabricated by ion implantation with Al of low-doped epitaxial n layers of 4H-SiC grown by chemical vapor deposition on commercial 4H-SiC wafers both with and without reduction of micropipe densities. It was shown that, using high levels of Al ion doping (5x10(16) cm(-2)) in combination with rapid thermal anneal, single-crystal p(+)-4H-SiC layers can be obtained. These layers do not form barriers at the contact metal-semiconductor interface and do not introduce additional resistance into structures with p(+)-n junctions. This significantly reduces the forward voltage drop across the structure in a wide range of current densities up to 10(4) A cm(-2).
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| 12. |
- Kalinina, E., et al.
(författare)
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Structural, electrical, and optical properties of low-doped 4H-SiC chemical vapor deposited epitaxial layers
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 90:10, s. 5402-5409
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Tidskriftsartikel (refereegranskat)abstract
- Results of complex studies of structural, optical, and electrical characteristics of 4H-SiC n-type low-doped epitaxial layers grown by the chemical vapor deposition (CVD) method are presented. Characteristics of CVD layers grown on commercial wafers with and without a thin (<0.1 mum) buffer layer grown by liquid phase epitaxy (LPE) between the commercial wafer and CVD epitaxial layer were compared. It has been shown that the LPE filling process caused a significant improvement in the structural quality of CVD layers. Cathodoluminescence (CL) data and electrical characteristics of Schottky barriers (SB) revealed that the LPE layer also made the concentration profiles of the uncompensated donors and recombination centers for holes as well as the hole diffusion lengths more uniform over the CVD layer. According to CL and secondary ion mass-spectroscopy measurements the presence of aluminum as an impurity was detected in initial commercial wafers, as well as having LPE and CVD epitaxial layers. Forward current-voltage characteristics of SBs formed on CVD layers with and without a LPE buffer layer followed an exponential relationship with an ideality factor of 1.04-1.06 over six to seven orders of magnitude in current density. A noticeable increase of the breakdown voltage was also observed in samples with a LPE layer.
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| 13. |
- Dmitriev, Alexey A, et al.
(författare)
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Genetic and epigenetic analysis of non-small cell lung cancer with NotI-microarrays
- 2012
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Ingår i: Epigenetics. - : Landes Bioscience. - 1559-2294 .- 1559-2308. ; 7:5, s. 502-513
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to clarify genetic and epigenetic alterations that occur during lung carcinogenesis and to design perspective sets of newly identified biomarkers. The original method includes chromosome 3 specific NotI-microarrays containing 180 NotI clones associated with genes for hybridization with 40 paired normal/tumor DNA samples of primary lung tumors: 28 squamous cell carcinomas (SCC) and 12 adenocarcinomas (ADC). The NotI-microarray data were confirmed by qPCR and bisulfite sequencing analyses. Forty-four genes showed methylation and/or deletions in more than 15% of non-small cell lung cancer (NSCLC) samples. In general, SCC samples were more frequently methylated/deleted than ADC. Moreover, the SCC alterations were observed already at stage I of tumor development, whereas in ADC many genes showed tumor progression specific methylation/deletions. Among genes frequently methylated/deleted in NSCLC, only a few were already known tumor suppressor genes: RBSP3 (CTDSPL), VHL and THRB. The RPL32, LOC285205, FGD5 and other genes were previously not shown to be involved in lung carcinogenesis. Ten methylated genes, i.e., IQSEC1, RBSP3, ITGA9, FOXP1, LRRN1, GNAI2, VHL, FGD5, ALDH1L1 and BCL6 were tested for expression by qPCR and were found downregulated in the majority of cases. Three genes (RBSP3, FBLN2 and ITGA9) demonstrated strong cell growth inhibition activity. A comprehensive statistical analysis suggested the set of 19 gene markers, ANKRD28, BHLHE40, CGGBP1, RBSP3, EPHB1, FGD5, FOXP1, GORASP1/TTC21, IQSEC1, ITGA9, LOC285375, LRRC3B, LRRN1, MITF, NKIRAS1/RPL15, TRH, UBE2E2, VHL, WNT7A, to allow early detection, tumor progression, metastases and to discriminate between SCC and ADC with sensitivity and specificity of 80-100%.
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| 14. |
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| 15. |
- Milichko, V., et al.
(författare)
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Metal-Dielectric Nanocavity for Real-Time Tracing Molecular Events with Temperature Feedback
- 2018
-
Ingår i: Laser and Photonics Reviews. - : Wiley. - 1863-8899 .- 1863-8880. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Plasmonic nanoparticles coupled with metallic films forming nanometer scale cavities have recently emerged as a powerful tool for enhancement of light-matter interaction. Despite high efficiency for sensing and light emission, such nanocavities exhibit harmful and uncontrolled optical heating which limits the ranges of light intensities and working temperature. In contrast to plasmonic nanoparticles, all-dielectric counterparts possess low Ohmic losses, high temperature stability along with a strong temperature-dependent Raman response. Here, we demonstrate that a silicon nanoparticle coupled with a thin gold film can serve as a multifunctional metal-dielectric (hybrid) nanocavity operating up to 1200 K. Resonant interaction of light with such nanocavity enables molecular sensing, heat-induced molecular events (protein unfolding), and their real-time tracing with a nanoscale thermometry through the monitoring enhanced Raman scattering both from the nanoparticle and analyzed molecules. We model numerically the thermo-optical properties of the hybrid nanocavity and reveal two alternative regimes of operation - with and without strong optical heating while other functionalities are preserved. We believe that the concept of the multifunctional hybrid nanocavities holds great potential for diverse photochemical and photophysical applications.
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| 16. |
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| 17. |
- Chen, W. H., et al.
(författare)
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Nanophotonics-based low-temperature PECVD epitaxial crystalline silicon solar cells
- 2016
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 49:12
-
Tidskriftsartikel (refereegranskat)abstract
- The enhancement of light absorption via nanopatterning in crystalline silicon solar cells is becoming extremely important with the decrease of wafer thickness for the further reduction of solar cell fabrication cost. In order to study the influence of nanopatterning on crystalline silicon thin-film solar cells, we applied two lithography techniques (laser interference lithography and nanoimprint lithography) combined with two etching techniques (dry and wet) to epitaxial crystalline silicon thin films deposited via plasma-enhanced chemical vapor deposition at 175 degrees C. The influence of nanopatterning with different etching profiles on solar cell performance is studied. We found that the etching profiles (pitch, depth and diameter) have a stronger impact on the passivation quality (open circuit voltage and fill factor) than on the optical performance (short circuit current density) of the solar cells. We also show that nanopatterns obtained via wet-etching can improve solar cell performance; and in contrast, dry-etching leads to poor passivation related to the etching profile, surface damage, and/ or contamination introduced during the etching process.
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| 18. |
- Dakshnamurthy, Shanmugasundaram, et al.
(författare)
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Experimental Study and a Short Kinetic Model for High-Temperature Oxidation of Methyl Methacrylate
- 2019
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Ingår i: Combustion Science and Technology. - : Informa UK Limited. - 0010-2202 .- 1563-521X. ; 191:10, s. 1789-1814
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic and natural polymeric esters find applications in transport and construction sectors, where fire safety is an important concern. One polymer that is widely used is poly (methyl methacrylate) (PMMA), which almost completely undergoes thermal decomposition into methyl methacrylate (its monomer) CH2=C(CH3) - C(= O) - O - CH3 (MMA) at ~250–300°C. In order to analyze the high-temperature gas-phase oxidation of PMMA, and thereby predict its fire behavior (such as burning rate, temperature of the material, and heat fluxes) with less computational effort, a compact kinetic model for the oxidation of its primary decomposition product, MMA, is most essential. This is accomplished in the present work by obtaining a reduced mechanism for MMA oxidation from a detailed mechanism from the Lawrence Livermore National Laboratories group. To extend the available data base for model validation and present validation data at atmospheric pressure conditions, for the first time, (i) detailed measurements of species profiles have been performed in stoichiometric laminar flat flames using flame sampling molecular beam mass spectrometry (MBMS) technique and (ii) laminar burning velocities have been obtained using the heat flux method for various unburnt mixture temperatures. Evaluating the model against these data sets point to the need to revise the kinetic model, which is achieved by adopting rate constants of key reactions among analogous molecules from recent literature. The updated compact kinetic model is able to predict the major species in the flat flame as well as the burning velocity of MMA satisfactorily. The final “short MMA mechanism” consists of 88 species and 1084 reactions.
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| 19. |
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| 20. |
- Dubrovinsky, L., et al.
(författare)
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Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle
- 2003
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 422:6927, s. 58-61
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Tidskriftsartikel (refereegranskat)abstract
- The boundary between the Earth's metallic core and its silicate mantle is characterized by strong lateral heterogeneity and sharp changes in density, seismic wave velocities, electrical conductivity and chemical composition(1-7). To investigate the composition and properties of the lowermost mantle, an understanding of the chemical reactions that take place between liquid iron and the complex Mg-Fe-Si-Al-oxides of the Earth's lower mantle is first required(8-15). Here we present a study of the interaction between iron and silica (SiO2) in electrically and laser-heated diamond anvil cells. In a multianvil apparatus at pressures up to 140 GPa and temperatures over 3,800 K we simulate conditions down to the core-mantle boundary. At high temperature and pressures below 40 GPa, iron and silica react to form iron oxide and an iron-silicon alloy, with up to 5 wt% silicon. At pressures of 85-140 GPa, however, iron and SiO2 do not react and iron-silicon alloys dissociate into almost pure iron and a CsCl-structured (B2) FeSi compound. Our experiments suggest that a metallic silicon-rich B2 phase, produced at the core-mantle boundary (owing to reactions between iron and silicate(2,9,10,13)), could accumulate at the boundary between the mantle and core and explain the anomalously high electrical conductivity of this region(6).
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| 21. |
- Haraldson, Klas, et al.
(författare)
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LRRC3B gene is frequently epigenetically inactivated in several epithelial malignancies and inhibits cell growth and replication
- 2012
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Ingår i: Biochimie. - : Elsevier. - 0300-9084 .- 1638-6183. ; 94:5, s. 1151-1157
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Tidskriftsartikel (refereegranskat)abstract
- Chromosome 3 specific NotI microarrays containing 180 NotI linking clones associated with 188 genes were hybridized to NotI representation probes prepared using matched tumor/normal samples from major epithelial cancers: breast (47 pairs), lung (40 pairs) cervical (43 pairs), kidney (34 pairs of clear cell renal cell carcinoma), colon (24 pairs), ovarian (25 pairs) and prostate (18 pairs). In all tested primary tumors (compared to normal controls) methylation and/or deletions was found. For the first time we showed that the gene LRRC3B was frequently methylated and/or deleted in breast carcinoma - 32% of samples, cervical - 35%, lung - 40%, renal - 35%, ovarian - 28%, colon - 33% and prostate cancer - 44%. To check these results bisulfite sequencing using cloned PCR products with representative two breast, one cervical, two renal, two ovarian and two colon cancer samples was performed. In all cases methylation was confirmed. Expression analysis using RT-qPCR showed that LRRC3B is strongly down-regulated at the latest stages of RCC and ovarian cancers. In addition we showed that LRRC3B exhibit strong cell growth inhibiting activity (more than 95%) in colony formation experiments in vitro in KRC/Y renal cell carcinoma line. All these data suggest that LRRC3B gene could be involved in the process of carcinogenesis as a tumor suppressor gene.
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| 22. |
- Kashuba, Vladimir, et al.
(författare)
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NotI Microarrays: Novel Epigenetic Markers for Early Detection and Prognosis of High Grade Serous Ovarian Cancer
- 2012
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 13:10, s. 13352-13377
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Tidskriftsartikel (refereegranskat)abstract
- Chromosome 3-specific NotI microarray (NMA) containing 180 clones with 188 genes was used in the study to analyze 18 high grade serous ovarian cancer (HGSOC) samples and 7 benign ovarian tumors. We aimed to find novel methylation-dependent biomarkers for early detection and prognosis of HGSOC. Thirty five NotI markers showed frequency of methylation/deletion more or equal to 17%. To check the results of NMA hybridizations several samples for four genes (LRRC3B, THRB, ITGA9 and RBSP3 (CTDSPL)) were bisulfite sequenced and confirmed the results of NMA hybridization. A set of eight biomarkers: NKIRAS1/RPL15, THRB, RBPS3 (CTDSPL), IQSEC1, NBEAL2, ZIC4, LOC285205 and FOXP1, was identified as the most prominent set capable to detect both early and late stages of ovarian cancer. Sensitivity of this set is equal to (72 +/- 11)% and specificity (94 +/- 5)%. Early stages represented the most complicated cases for detection. To distinguish between Stages I + II and Stages III + IV of ovarian cancer the most perspective set of biomarkers would include LOC285205, CGGBP1, EPHB1 and NKIRAS1/RPL15. The sensitivity of the set is equal to (80 +/- 13)% and the specificity is (88 +/- 12)%. Using this technique we plan to validate this panel with new epithelial ovarian cancer samples and add markers from other chromosomes.
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| 23. |
- Mishra, K., et al.
(författare)
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Ultrafast Demagnetization Control in Magnetophotonic Surface Crystals
- 2022
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 22:23, s. 9773-80
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetic memory combining plasmonics and magnetism is poised to dramatically increase the bit density and energy efficiency of light-assisted ultrafast magnetic storage, thanks to nanoplasmon-driven enhancement and confinement of light. Here we devise a new path for that, simultaneously enabling light driven bit downscaling, reduction of the required energy for magnetic memory writing, and a subtle control over the degree of demagnetization in a magnetophotonic surface crystal. It features a regular array of truncated-nanocone-shaped Au-TbCo antennas showing both localized plasmon and surface lattice resonance modes. The ultrafast magnetization dynamics of the nanoantennas show a 3-fold resonant enhancement of the demagnetization efficiency. The degree of demagnetization is further tuned by activating surface lattice modes. This reveals a platform where ultrafast demagnetization is localized at the nanoscale and its extent can be controlled at will, rendering it multistate and potentially opening up so-far-unforeseen nanomagnetic neuromorphic-like systems operating at femtosecond time scales controlled by light.
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| 24. |
- Mishra, K., et al.
(författare)
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Ultrafast demagnetization in a ferrimagnet under electromagnetic field funneling
- 2021
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 13:46, s. 19367-19375
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Tidskriftsartikel (refereegranskat)abstract
- The quest to improve the density, speed and energy efficiency of magnetic memory storage has led to the exploration of new ways of optically manipulating magnetism at the ultrafast time scale, in particular in ferrimagnetic alloys. While all-optical magnetization switching is well-established on the femtosecond timescale, lateral nanoscale confinement and thus the potential significant reduction of the size of the magnetic element remains an outstanding challenge. Here we employ resonant electromagnetic energy funneling through plasmon nanoantennas to influence the demagnetization dynamics of a ferrimagnetic TbCo alloy thin film. We demonstrate how Ag nanoring-shaped antennas under resonant optical femtosecond pumping reduce the overall demagnetization in the underlying films up to three times compared to non-resonant illumination. We attribute such a substantial reduction to the nanoscale confinement of the demagnetization process. This is qualitatively supported by the electromagnetic simulations that strongly evidence the resonant optical energy-funneling to the nanoscale from the nanoantennas into the ferrimagnetic film. This observation is an important step for reaching deterministic ultrafast all-optical magnetization switching at the nanoscale in such systems, opening a route to develop nanoscale ultrafast magneto-optics.
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| 25. |
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| 26. |
- Schulz, Sebastian A., et al.
(författare)
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Roadmap on photonic metasurfaces
- 2024
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Ingår i: APPLIED PHYSICS LETTERS. - 0003-6951 .- 1077-3118. ; 124:26
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Tidskriftsartikel (refereegranskat)abstract
- Here we present a roadmap on Photonic metasurfaces. This document consists of a number of perspective articles on different applications, challenge areas or technologies underlying photonic metasurfaces. Each perspective will introduce the topic, present a state of the art as well as give an insight into the future direction of the subfield.
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| 27. |
- Trompoukis, C., et al.
(författare)
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Photonic nanostructures for advanced light trapping in thin crystalline silicon solar cells
- 2015
-
Ingår i: Physica Status Solidi (A) Applications and Materials Science. - : Wiley. - 1862-6319 .- 1862-6300. ; 212:1, s. 140-155
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the fabrication, integration, and simulation, both optical and optoelectrical, of two-dimensional photonic nanostructures for advanced light trapping in thin crystalline silicon (c-Si) solar cells. The photonic nanostructures are fabricated by the combination of various lithography (nanoimprint, laser interference, and hole mask colloidal) and etching (dry plasma and wet chemical) techniques. The nanopatterning possibilities thus range from periodic to random corrugations and from inverted nanopyramids to high aspect ratio profiles. Optically, the nanopatterning results in better performance than the standard pyramid texturing, showing a more robust behavior with respect to light incidence angle. Electrically, wet etching results in higher minority carrier lifetimes compared to dry etching. From the integration of the photonic nanostructures into a micron-thin c-Si solar cell certain factors limiting the efficiencies are identified. More precisely: (a) the parasitic absorption is limiting the short circuit current, (b) the conformality of thin-film coatings on the nanopatterned surface is limiting the fill factor, and (c) the material damage from dry etching is limiting the open circuit voltage. From optical simulations, the optimal pattern parameters are identified. From optoelectrical simulations, cell design considerations are discussed, suggesting to position the junction on the opposite side of the nanopattern.
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| 28. |
- Zarechnaya, E Yu, et al.
(författare)
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Superhard Semiconducting Optically Transparent High Pressure Phase of Boron
- 2009
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Ingår i: PHYSICAL REVIEW LETTERS. - 0031-9007. ; 102:18, s. 185501-
-
Tidskriftsartikel (refereegranskat)abstract
- An orthorhombic (space group Pnnm) boron phase was synthesized at pressures above 9 GPa and high temperature, and it was demonstrated to be stable at least up to 30 GPa. The structure, determined by single-crystal x-ray diffraction, consists of B-12 icosahedra and B-2 dumbbells. The charge density distribution obtained from experimental data and ab initio calculations suggests covalent chemical bonding in this phase. Strong covalent interatomic interactions explain the low compressibility value (bulk modulus is K-300=227 GPa) and high hardness of high-pressure boron (Vickers hardness H-V=58 GPa), after diamond the second hardest elemental material.
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| 29. |
- Assadillayev, A., et al.
(författare)
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Nanoscale Engineering of Optical Strong Coupling inside Metals
- 2022
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Optical polaritons appear when a material excitation strongly couples to an optical mode. Such strong coupling between molecular transitions and optical cavities results in far-reaching opportunities in modifying fundamental properties of chemical matter. More recently an exciting prospect of self-coupled polaritons has emerged by matter sustaining the optical mode with its geometry. Here, it is shown how strong coupling of the interband transition and surface plasmons can be engineered in nickel at the nanoscale to realize self-coupled plasmon-interband polaritons inside metals. Using electron energy-loss spectroscopy, it is demonstrated that in nickel thin films and nanoantennas the propagation and radiation losses result in a broadening of the plasmon linewidth and a transition from strong to weak coupling. Further, higher-order plasmon resonances couple to the interband transition, and the multipolar-coupled states acquire the field profile of the plasmon. The results provide a fundamental understanding of plasmon-interband coupling in metals and establish the base for the design of photocatalytic and magneto-optical nanosystems.
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| 30. |
- Danielsson, E., et al.
(författare)
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Characterization of heterojunction diodes with hydride vapor phase epitaxy grown AlGaN on 4H-SiC
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2372-2379
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Tidskriftsartikel (refereegranskat)abstract
- AlGaN/4H-SiC heterojunction diodes with varying composition of Al have been fabricated. Five different compositions were investigated, GaN, Al0.1Ga0.9N, Al0.15Ga0.85N, Al0.3Ga0.7N, and Al0.5Ga0.5N, along with a 4H-SiC homojunction diode for comparison. The turn on voltage was around 1 V, and the ideality factor between 1 and 2 for all heterojunction diodes except for the Al0.3Ga0.7N diode. This diode had an ideality factor between 2 and 3, and also showed a much lower series resistance, indicating a change in transport mechanism across the junction. A tunnel assisted recombination model was analyzed and compared to the extracted values of the GaN diode. The model agreed well with both current-voltage and capacitance-voltage measurements for this diode. This model was not applied to the other samples, since their characteristics could not be explained by a simple mechanism.
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| 31. |
- Danielsson, E., et al.
(författare)
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Fabrication and characterization of heterojunction diodes with HVPE-Grown GaN on 4H-SiC
- 2001
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Ingår i: IEEE Transactions on Electron Devices. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9383 .- 1557-9646. ; 48:3, s. 444-449
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Tidskriftsartikel (refereegranskat)abstract
- GaN/SiC heterojunctions can improve the performance considerably for BJTs and FETs. In this work, heterojunction diodes have been manufactured and characterized. The fabricated diodes have a GaN n-type cathode region on top of a JH-SIC p-type epi layer. The GaN layer was grown with HVPE directly on off-axis SiC without a buffer layer. Mesa structures were formed and a Ti metallization was used as cathode contact to GaN, and the anode contact was deposited on the backside using sputtered Al. Both current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed on the diode structures. The ideality factor of the measured diodes was 1.1 and was constant with temperature. A built in potential of 2.06 V was extracted from I-V-measurements and agrees well with the built in potential from C-V-measurements. The conduction band offset was extracted to 1.1 eV and the heterojunction was of type II. The turn on voltage for the diodes is about 1 V lower than expected and a suggested mechanism for this effect is discussed.
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| 32. |
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| 33. |
- Dmitriev, AA, et al.
(författare)
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Identification of Novel Epigenetic Markers of Prostate Cancer by NotI-Microarray Analysis
- 2015
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Ingår i: Disease markers. - : Hindawi Limited. - 1875-8630 .- 0278-0240. ; 2015, s. 241301-
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Tidskriftsartikel (refereegranskat)abstract
- A significant need for reliable and accurate cancer diagnostics and prognosis compels the search for novel biomarkers that would be able to discriminate between indolent and aggressive tumors at the early stages of disease. The aim of this work was identification of potential diagnostic biomarkers for characterization of different types of prostate tumors. NotI-microarrays with 180 clones associated with chromosome 3 genes/loci were applied to determine genetic and epigenetic alterations in 33 prostate tumors. For 88 clones, aberrations were detected in more than 10% of tumors. The major types of alterations were DNA methylation and/or deletions. Frequent methylation of the discovered loci was confirmed by bisulfite sequencing on selective sampling of genes:FGF12,GATA2, andLMCD1. Three genes (BHLHE40,BCL6, andITGA9) were tested for expression level alterations using qPCR, and downregulation associated with hypermethylation was shown in the majority of tumors. Based on these data, we proposed the set of potential biomarkers for detection of prostate cancer and discrimination between prostate tumors with different malignancy and aggressiveness:BHLHE40,FOXP1,LOC285205,ITGA9,CTDSPL,FGF12,LOC440944/SETD5,VHL,CLCN2,OSBPL10/ZNF860,LMCD1,FAM19A4,CAND2,MAP4,KY, andLRRC58. Moreover, we probabilistically estimated putative functional relations between the genes within each set using the network enrichment analysis.
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| 34. |
- Dmitriev, Yurij A., et al.
(författare)
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H/D isotope effect observed in the isotropic Fermi contact interaction of formyl radical : Experimental and theoretical analysis of the inter- and intra-molecular dynamics
- 2020
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Ingår i: AIP Advances. - : American Institute of Physics (AIP). - 2158-3226. ; 10:12
-
Tidskriftsartikel (refereegranskat)abstract
- An unexpected deficit of the computed hyper fine coupling constant in normal formyl HCO radicals, compared to that expected based on the proton to deuteron gyromagnetic ratio of the DCO species, was observed in experimental electron paramagnetic resonance studies of HCO and DCO radicals in a CO solid matrix at cryogenic conditions. Still, the matrix was found to have only a small effect on the anisotropic parts of the magnetic parameter tensors. The underlying isotope effect between the lighter proton and the heavier deuteron on the motional dynamics was verified and elucidated by quantum chemical calculations. The experimental results obtained within a temperature range of 1.4 K–4.2 K require special attention due to the tunneling motions of the molecule and its constituent particles. The effect from vibrational, rotational, and librational motion observed in the molecular states of formyl as a probe, averaged over the dynamics of the low temperature CO matrix isolation, reveals a clear proton isotope effect under both classical and quantum conditions.
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| 35. |
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| 36. |
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| 37. |
- Dubrovinskaia, N., et al.
(författare)
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Beating the miscibility barrier between iron group elements and magnesium by high-pressure alloying
- 2005
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 95:24
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Tidskriftsartikel (refereegranskat)abstract
- Iron and magnesium are almost immiscible at ambient pressure. The low solubility of Mg in Fe is due to a very large size mismatch between the alloy components. However, the compressibility of Mg is much higher than that of Fe, and therefore the difference in atomic sizes between elements decreases dramatically with pressure. Based on the predictions of ab initio calculations, we demonstrate in a series of experiments in a multianvil apparatus and in electrically and laser-heated diamond anvil cells that high pressure promotes solubility of magnesium in iron. At the megabar pressure range, more than 10 at. % of Mg can dissolve in Fe and then the alloy can be quenched to ambient conditions. A generality of the concept of high-pressure alloying between immiscible elements is demonstrated by its application to two other Fe group elements, Co and Ni.
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| 38. |
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| 39. |
- Fabijan, A., et al.
(författare)
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The evolution of continuous experimentation in software product development: From data to a data-driven organization at scale
- 2022
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Ingår i: Accelerating Digital Transformation: 10 Years of Software Center. - 9783031108730 ; , s. 373-395
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Software development companies are increasingly aiming to become data-driven by trying to continuously experiment with the products used by their customers. Although familiar with the competitive edge that the A/B testing technology delivers, they seldom succeed in evolving and adopting the methodology. In this paper, and based on an exhaustive and collaborative case study research in a large software-intense company with highly developed experimentation culture, we present the evolution process of moving from ad-hoc customer data analysis towards continuous controlled experimentation at scale. Our main contribution is the "Experimentation Evolution Model" in which we detail three phases of evolution: technical, organizational and business evolution. With our contribution, we aim to provide guidance to practitioners on how to develop and scale continuous experimentation in software organizations with the purpose of becoming data-driven at scale.
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| 40. |
- Faniayeu, Ihar, et al.
(författare)
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A Low-Reflection Absorptive Metasurface for Mid-IR Wavelengths
- 2020
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Ingår i: 2020 14th International Congress on Artificial Materials for Novel Wave Phenomena, Metamaterials 2020.
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Konferensbidrag (refereegranskat)abstract
- We report a design of an optical metasurface that selectively absorbs impinging electromagnetic waves in the desired wavelength while being fully transparent away from the resonance range. The proposed absorber consists of three-dimensional helical resonators that enable full control of light absorption due to the manipulation of the induced electric and magnetic dipole moments at the resonance. Full-wave simulations confirm the effectiveness of the proposed concept in the mid-infrared spectral range.
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| 41. |
- Ferri, Julien, 1990, et al.
(författare)
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Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
- 2020
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Using particle-in-cell simulations, we demonstrate an improvement of the target-normal-sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.
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| 42. |
- Hanauer, S., et al.
(författare)
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Photothermal Conversion of Solar Infrared Radiation by Plasmonic Nanoantennas for Photovoltaic-Thermoelectric Hybrid Devices
- 2023
-
Ingår i: Acs Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 6:4, s. 2128-2133
-
Tidskriftsartikel (refereegranskat)abstract
- Photovoltaics have become one of the low-cost options for electricity generation. However, the lack of absorption of the near-infrared and infrared solar spectrum intrinsically limits its efficiency. Here, we present an approach for photothermal conversion of solar infrared radiation in photovoltaic-thermoelectric systems using plasmonic nanoantennas. Through numerical calculations-driven shape engineering, we identified Ni diabolo nanoantennas as efficient solar infrared spectrum harvesters. Nanofabrication with electron-beam lithography further revealed its impact on nanoantenna optical properties at the single-nanoantenna level. In the large-scale low-cost approach, however, photothermal surfaces of nanocone plasmonic antennas, made with a simple and robust fabrication process, still deliver a significant 6.1 degrees C temperature increase under solar infrared illumination. The reported results pave the way toward the development of hybrid photovoltaic-thermoelectric systems with an optimal utilization of the solar spectrum.
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| 43. |
- Kalinina, E., et al.
(författare)
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Material quality improvements for high voltage 4H-SiC diodes
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 80:03-jan, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- The influence of thin 4H-SiC buffer layers grown by liquid phase epitaxy (LPE) on structural quality of 4H-SiC low-doped epitaxial layers, grown by chemical vapor deposition (CVD) was investigated in detail. A dramatic defect density reduction in CVD epitaxial layers grown on commercial wafers with buffer LPE layer was detected. P(+)n junctions were formed on these CVD layers by high dose Al ion implantation followed by rapid thermal anneal. It was shown that both the increase of diffusion lengths of minority carriers (Lp) in CVD lavers and the forming of p(+)-layers after Al ion implantation and high temperature anneal lead to superior device characteristics.
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| 44. |
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| 45. |
- Maccaferri, N., et al.
(författare)
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Polarizability and magnetoplasmonic properties of magnetic general nanoellipsoids
- 2013
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 21:8, s. 9875-9889
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Tidskriftsartikel (refereegranskat)abstract
- An approach to compute the polarizability tensor of magnetic nanoparticles having general ellipsoidal shape is presented. We find a surprisingly excellent quantitative agreement between calculated and experimental magneto-optical spectra measured in the polar Kerr configuration from nickel nanodisks of large size (exceeding 100 nm) with circular and elliptical shape. In spite of its approximations and simplicity, the formalism presented here captures the essential physics of the interplay between magneto-optical activity and the plasmonic resonance of the individual particle. The results highlight the key role of the dynamic depolarization effects to account for the magneto-optical properties of plasmonic nanostructures.
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| 46. |
- Maccaferri, N., et al.
(författare)
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Tuning the Magneto-Optical Response of Nanosize Ferromagnetic Ni Disks Using the Phase of Localized Plasmons
- 2013
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:16
-
Tidskriftsartikel (refereegranskat)abstract
- We explore the influence of the phase of localized plasmon resonances on the magneto-optical activity of nanoferromagnets. We demonstrate that these systems can be described as two orthogonal damped oscillators coupled by the spin-orbit interaction. We prove that only the spin-orbit induced transverse plasmon plays an active role on the magneto-optical properties by controlling the relative amplitude and phase lag between the two oscillators. Our theoretical predictions are fully confirmed by magneto-optical Kerr effect and optical extinction measurements in nanostructures of different size and shape.
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| 47. |
- Maccaferri, Nicolò, et al.
(författare)
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Ultrasensitive and label-free molecular-level detection enabled by light phase control in magnetoplasmonic nanoantennas
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Systems allowing label-free molecular detection are expected to have enormous impact on biochemical sciences. Research focuses on materials and technologies based on exploiting localized surface plasmon resonances in metallic nanostructures. The reason for this focused attention is their suitability for single-molecule sensing, arising from intrinsically nanoscopic sensing volume and the high sensitivity to the local environment. Here we propose an alternative route, which enables radically improved sensitivity compared with recently reported plasmon-based sensors. Such high sensitivity is achieved by exploiting the control of the phase of light in magnetoplasmonic nanoantennas. We demonstrate a manifold improvement of refractometric sensing figure-of-merit. Most remarkably, we show a raw surface sensitivity (that is, without applying fitting procedures) of two orders of magnitude higher than the current values reported for nanoplasmonic sensors. Such sensitivity corresponds to a mass of similar to 0.8 ag per nanoantenna of polyamide-6.6 (n = 1.51), which is representative for a large variety of polymers, peptides and proteins.
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| 48. |
- Mendoza-Galvan, A., et al.
(författare)
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Fano interference in supported gold nanosandwiches with weakly coupled nanodisks
- 2012
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 20:28, s. 29646-29658
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Tidskriftsartikel (refereegranskat)abstract
- We studied the far-field optical response of supported gold-silica-gold nanosandwiches using spectroscopic ellipsometry, reflectance and transmittance measurements. Although transmittance data clearly shows that the gold nanodisks in the sandwich structure interact very weakly, oblique reflectance spectra of s- and p-polarized light show clearly asymmetric line-shapes of the Fano type. However, all experimental results are very well described by modeling the gold nanodisks as oblate spheroids and by employing a 2 x 2 scattering matrix formulation of the Fresnel coefficients provided by an island film theory. In particular, the Fano asymmetry can be explained in terms of interference between the scattered waves from the decoupled nanodisks in the spectral range limited by their respective plasmon resonances. We also show that the reflectance and ellipsometry spectra can be described by a three-layer system with uniaxial effective dielectric functions.
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| 49. |
- Mendoza-Galvan, A., et al.
(författare)
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Optical response of supported gold nanodisks
- 2011
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Ingår i: Optics Express. - : Optical Society of America (OSA). - 1094-4087. ; 19:13, s. 12093-12107
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the ellipsometric spectra of short range ordered planar arrays of gold nanodisks supported on glass substrates can be described by modeling the nanostructured arrays as uniaxial homogeneous layers with dielectric functions of the Lorentz type. However, appreciable deviations from experimental data are observed in calculated spectra of irradiance measurements. A qualitative and quantitative description of all measured spectra is obtained with a uniaxial effective medium dielectric function in which the nanodisks are modeled as oblate spheroids. Dynamic depolarization factors in the long-wavelength approximation and interaction with the substrate are considered. Similar results are obtained calculating the optical spectra using the island-film theory. Nevertheless, a small in-plane anisotropy and quadrupolar coupling effects reveal a very complex optical response of the nanostructured arrays.
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| 50. |
- Petrucci, G., et al.
(författare)
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Macroscopic magneto-chiroptical metasurfaces
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:25
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Tidskriftsartikel (refereegranskat)abstract
- Nanophotonic chiral antennas exhibit orders of magnitude higher circular dichroism (CD) compared to molecular systems. When the structural chirality is merged with magnetism at the nanoscale, efficient magnetic control over the dichroic response is achieved, bringing exciting prospects to active nanophotonic devices. Here, we devise macroscopic enantiomeric magnetophotonic metasurfaces of plasmonic-ferromagnetic spiral antennas assembled on large areas via hole-mask colloidal lithography. The simultaneous presence of 3D- and 2D-features in chiral nanoantennas induces large CD response, where we identify reciprocal and non-reciprocal contributions, respectively. Exploring further this type of magnetophotonic metasurfaces might allow the realization of high-sensitivity chiral sensors and prompts the design of advanced macroscopic optical devices operating with polarized light.
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