| 1. |
- Kanai, M, et al.
(author)
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- 2023
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swepub:Mat__t
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| 2. |
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| 3. |
- Tabiri, S, et al.
(author)
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- 2021
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swepub:Mat__t
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| 4. |
- Bravo, L, et al.
(author)
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- 2021
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swepub:Mat__t
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| 5. |
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| 6. |
- Glasbey, JC, et al.
(author)
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- 2021
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swepub:Mat__t
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| 7. |
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| 8. |
- Hoyer, S., et al.
(author)
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TOI-220b: a warm sub-Neptune discovered by TESS
- 2021
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 505:3, s. 3361-3379
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Journal article (peer-reviewed)abstract
- In this paper, we report the discovery of TOI-220b, a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements, we estimate a planetary mass of 13.8 +/- 1.0M(circle plus) and radius of 3.03 +/- 0.15R(circle plus), implying a bulk density of 2.73 +/- 0.47. TOI-220b orbits a relative bright (V=10.4) and old (10.1 +/- 1.4Gyr) K dwarf star with a period of similar to 10.69d. Thus, TOI-220b is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220b internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative-convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core.
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| 9. |
- Bradnam, K. R., et al.
(author)
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Assemblathon 2 : Evaluating de novo methods of genome assembly in three vertebrate species
- 2013
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In: GigaScience. - : BioMed Central (BMC). - 2047-217X. ; 2:1
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Journal article (peer-reviewed)abstract
- Background: The process of generating raw genome sequence data continues to become cheaper, faster, and more accurate. However, assembly of such data into high-quality, finished genome sequences remains challenging. Many genome assembly tools are available, but they differ greatly in terms of their performance (speed, scalability, hardware requirements, acceptance of newer read technologies) and in their final output (composition of assembled sequence). More importantly, it remains largely unclear how to best assess the quality of assembled genome sequences. The Assemblathon competitions are intended to assess current state-of-the-art methods in genome assembly. Results: In Assemblathon 2, we provided a variety of sequence data to be assembled for three vertebrate species (a bird, a fish, and snake). This resulted in a total of 43 submitted assemblies from 21 participating teams. We evaluated these assemblies using a combination of optical map data, Fosmid sequences, and several statistical methods. From over 100 different metrics, we chose ten key measures by which to assess the overall quality of the assemblies. Conclusions: Many current genome assemblers produced useful assemblies, containing a significant representation of their genes and overall genome structure. However, the high degree of variability between the entries suggests that there is still much room for improvement in the field of genome assembly and that approaches which work well in assembling the genome of one species may not necessarily work well for another.
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| 10. |
- Jorda, L., et al.
(author)
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The global shape, density and rotation of Comet 67P/Churyumov-Gerasimenko from preperihelion Rosetta/OSIRIS observations
- 2016
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In: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 277, s. 257-278
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Journal article (peer-reviewed)abstract
- The Rosetta spacecraft reached Comet 67P/Churyumov-Gerasimenko (hereafter 67P/C-G) in August 2014 at an heliocentric distance of 3.6 a.u. and was then put in orbit around its nucleus to perform detailed observations. Among the collected data are the images acquired by the OSIRIS instrument up to the perihelion passage of the comet in August 2015, which allowed us to map the entire nucleus surface at high-resolution in the visible. Stereophotoclinometry methods have been used to reconstruct a global high-resolution shape model and to monitor its rotational parameters using data collected up to perihelion. The nucleus has a conspicuous bilobate shape with overall dimensions along its principal axes of (4.34 +/- 0.02) x (2.60 +/- 0.02) x (2.12 +/- 0.06) km. The best-fit ellipsoid dimensions of the individual lobes along their principal axes of inertia are found to be 4.10 x 3.52 x 1.63 km and 2.50 x 2.14 x 1.641cm. Their volume amounts to 66% and 27% of the total volume of the nucleus. The two lobes are connected by a "neck" whose volume has been estimated to represent similar to 7% of the total volume of the comet. Combining the derived volume of 18.8 +/- 0.3 km(3) with the mass of 9.982 +/- 0.003 x 10(12) kg determined by the Rosetta/RSI experiment, we obtained a bulk density of the nucleus of 532 +/- 7 kg m(-3). Together with the companion value of 535 35 kg m-3 deduced from the stereophotogrammetry shape model of the nucleus (Preusker et al. [2015] Astron. Astrophys. 583, A33), these constitute the first reliable and most accurate determination of the density of a cometary nucleus to date. The calculated porosity is quite large, ranging approximately from 70% to 75% depending upon the assumed density of the dust grains and the dust-to-ice mass ratio. The nature of the porosity, either micro or macro or both, remains unconstrained. The coordinates of the center of gravity are not compatible with a uniform nucleus density. The direction of the offset between the center of gravity and the center of figure suggests that the big lobe has a slightly higher bulk density compared to the small one. the center of mass position cannot be explained by different, but homogenous densities in the two lobes. The initial rotational period of 12.4041 +/- 0.0001 h of the nucleus persisted until October 2014. It then slightly increased to a maximum of 12.4304h reached on 19 May 2015 and finally dropped to 12.305 h just before perihelion on August 10, 2015. A periodogram analysis of the (RA, Dec) direction of the Z-axis of the comet obtained in parallel with the shape reconstruction exhibits a highly significant minima at 11.5 +/- 0.5 day clearly indicating an excited rotational state with an amplitude of 0.15 +/- 0.03 degrees.
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| 11. |
- Connolly, L. J., et al.
(author)
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Effects of small-volume soccer and vibration training on body composition, aerobic fitness, and muscular PCr kinetics for inactive women aged 20-45
- 2014
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In: Journal of Sport and Health Science. - : Elsevier BV. - 2095-2546. ; 3:4, s. 284-292
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Journal article (peer-reviewed)abstract
- Purpose: The present study investigated the effects of 16 weeks of small-volume, small-sided soccer training soccer group (SG, n = 13) and oscillating whole-body vibration training vibration group (VG, n = 17) on body composition, aerobic fitness, and muscle PCr kinetics in healthy inactive premenopausal women in comparison with an inactive control group (CO, n = 14). Methods: Training for SG and VG consisted of twice-weekly 15-min sessions with average heart rates (HRs) of similar to 155 and 90 bpm respectively. Pre- and post-measurements of body composition (DXA), phosphocreatine (PCr) on-and off-kinetics, and HR measurements during standardised submaximal exercise were performed. Results: After 16 weeks of training in SG, fat percentage was lowered (p = 0.03) by 1.7% +/- 2.4% from 37.5% +/- 6.9% to 35.8% +/- 6.2% and the PCr decrease in the quadriceps during knee-extension ramp exercise was attenuated (4% +/- 8%, p = 0.04), with no changes in VG or CO (time-group effect: p = 0.03 and p = 0.03). Submaximal exercise HR was also reduced in SG after 16 weeks of training (6% +/- 5% of HRmax, p = 0.01). Conclusion: Short duration soccer training for 16 weeks appears to be sufficient to induce favourable changes in body composition and indicators of aerobic fitness and muscle oxidative capacity in untrained premenopausal women. Copyright (C) 2014, Shanghai University of Sport. Production and hosting by Elsevier B.V. All rights reserved.
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| 12. |
- Edberg, Niklas J. T., et al.
(author)
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Effects of Saturn's magnetospheric dynamics on Titan's ionosphere
- 2015
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In: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:10, s. 8884-8898
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Journal article (peer-reviewed)abstract
- We use the Cassini Radio and Plasma Wave Science/Langmuir probe measurements of the electron density from the first 110 flybys of Titan to study how Saturn's magnetosphere influences Titan's ionosphere. The data is first corrected for biased sampling due to varying solar zenith angle and solar energy flux (solar cycle effects). We then present results showing that the electron density in Titan's ionosphere, in the altitude range 1600-2400km, is increased by about a factor of 2.5 when Titan is located on the nightside of Saturn (Saturn local time (SLT) 21-03h) compared to when on the dayside (SLT 09-15 h). For lower altitudes (1100-1600km) the main dividing factor for the ionospheric density is the ambient magnetospheric conditions. When Titan is located in the magnetospheric current sheet, the electron density in Titan's ionosphere is about a factor of 1.4 higher compared to when Titan is located in the magnetospheric lobes. The factor of 1.4 increase in between sheet and lobe flybys is interpreted as an effect of increased particle impact ionization from approximate to 200eV sheet electrons. The factor of 2.5 increase in electron density between flybys on Saturn's nightside and dayside is suggested to be an effect of the pressure balance between thermal plus magnetic pressure in Titan's ionosphere against the dynamic pressure and energetic particle pressure in Saturn's magnetosphere.
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| 13. |
- Blanc, M., et al.
(author)
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Saturn Plasma Sources and Associated Transport Processes
- 2015
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In: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 192:1-4, s. 237-283
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Research review (peer-reviewed)abstract
- This article reviews the different sources of plasma for Saturn's magnetosphere, as they are known essentially from the scientific results of the Cassini-Huygens mission to Saturn and Titan. At low and medium energies, the main plasma source is the cloud produced by the "geyser" activity of the small satellite Enceladus. Impact ionization of this cloud occurs to produce on the order of 100 kg/s of fresh plasma, a source which dominates all the other ones: Titan (which produces much less plasma than anticipated before the Cassini mission), the rings, the solar wind (a poorly known source due to the lack of quantitative knowledge of the degree of coupling between the solar wind and Saturn's magnetosphere), and the ionosphere. At higher energies, energetic particles are produced by energy diffusion and acceleration of lower energy plasma produced by the interchange instabilities induced by the rapid rotation of Saturn, and possibly, for the highest energy range, by contributions from the CRAND process acting inside Saturn's magnetosphere. Discussion of the transport and acceleration processes acting on these plasma sources shows the importance of rotation-induced radial transport and energization of the plasma, and also shows how much the unexpected planetary modulation of essentially all plasma parameters of Saturn's magnetosphere remains an unexplained mystery.
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| 14. |
- Bowtell, J. L., et al.
(author)
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Short Duration Small Sided Football and to a Lesser Extent Whole Body Vibration Exercise Induce Acute Changes in Markers of Bone Turnover
- 2016
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In: Biomed Research International. - : Hindawi Limited. - 2314-6133 .- 2314-6141.
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Journal article (peer-reviewed)abstract
- We aimed to study whether short-duration vibration exercise or football sessions of two different durations acutely changed plasma markers of bone turnover and muscle strain. Inactive premenopausal women (n = 56) were randomized to complete a single bout of short (FG15) or long duration (FG60) small sided football or low magnitude whole body vibration training (VIB). Procollagen type 1 amino-terminal propeptide (P1NP) was increased during exercise for FG15 (51.6 +/- 23.0 to 56.5 +/- 22.5 mu g.L-1, mean +/- SD, P < 0.05) and FG60 (42.6 +/- 11.8 to 50.2 +/- 12.8 mu g.L-1, P < 0.05) but not for VIB (38.8 +/- 15.1 to 36.6 +/- 14.7 mu g.L-1, P > 0.05). An increase in osteocalcin was observed 48 h after exercise (P < 0.05), which did not differ between exercise groups. C-terminal telopeptide of type 1 collagen was not affected by exercise. Blood lactate concentration increased during exercise for FG15 (0.6 +/- 0.2 to 3.4 +/- 1.2mM) and FG60 (0.6 +/- 0.2 to 3.3 +/- 2.0 mM), but not for VIB (0.6 +/- 0.2 to 0.8 +/- 0.4mM) (P < 0.05). Plasma creatine kinase increased by 55 +/- 63% and 137 +/- 119% 48 h after FG15 and FG60 (P < 0.05), but not after VIB (26 +/- 54%, NS). In contrast to the minor elevation in osteocalcin in response to a single session of vibration exercise, both short and longer durations of small sided football acutely increased plasma P1NP, osteocalcin, and creatine kinase. This may contribute to favorable effects of chronic training on musculoskeletal health.
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| 15. |
- Bowtell, J. L., et al.
(author)
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Improved Exercise Tolerance with Caffeine Is Associated with Modulation of both Peripheral and Central Neural Processes in Human Participants
- 2018
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In: Frontiers in Nutrition. - : Frontiers Media SA. - 2296-861X. ; 5
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Journal article (peer-reviewed)abstract
- Background: Caffeine has been shown to enhance exercise performance and capacity. The mechanisms remain unclear but are suggested to relate to adenosine receptor antagonism, resulting in increased central motor drive, reduced perception of effort, and altered peripheral processes such as enhanced calcium handling and extracellular potassium regulation. Our aims were to investigate how caffeine (i) affects knee extensor PCr kinetics and pH during repeated sets of single-leg knee extensor exercise to task failure and (ii) modulates the interplay between central and peripheral neural processes. We hypothesized that the caffeine-induced extension of exercise capacity during repeated sets of exercise would occur despite greater disturbance of the muscle milieu due to enhanced peripheral and corticospinal excitatory output, central motor drive, and muscle contractility. Methods: Nine healthy active young men performed five sets of intense single-leg knee extensor exercise to task failure on four separate occasions: for two visits (6 mg.kg(-1) caffeine vs placebo), quadriceps P-31-magnetic resonance spectroscopy scans were performed to quantify phosphocreatine kinetics and pH, and for the remaining two visits (6 mg.kg-1 caffeine vs placebo), femoral nerve electrical and transcranial magnetic stimulation of the quadriceps cortical motor area were applied pre- and post exercise. Results: The total exercise time was 17.9 +/- 6.0% longer in the caffeine (1,225 +/- 86 s) than in the placebo trial (1,049 +/- 73 s, p = 0.016), and muscle phosphocreatine concentration and pH (p < 0.05) were significantly lower in the latter sets of exercise after caffeine ingestion. Voluntary activation (VA) (peripheral, p = 0.007; but not supraspinal, p = 0.074), motor-evoked potential (MEP) amplitude (p = 0.007), and contractility (contraction time, p = 0.009; and relaxation rate, p = 0.003) were significantly higher after caffeine consumption, but at task failure MEP amplitude and VA were not different from placebo. Caffeine prevented the reduction in M-wave amplitude that occurred at task failure (p = 0.039). Conclusion: Caffeine supplementation improved high-intensity exercise tolerance despite greater-end exercise knee extensor phosphocreatine depletion and H+ accumulation. Caffeine-induced increases in central motor drive and corticospinal excitability were attenuated at task failure. This may have been induced by the afferent feedback of the greater disturbance of the muscle milieu, resulting in a stronger inhibitory input to the spinal and supraspinal motor neurons. However, causality needs to be established through further experiments.
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| 16. |
- Dacic, M., et al.
(author)
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Influence of Divalent Cations on Deformation and Rupture of Adsorbed Lipid Vesicles
- 2016
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 32:25, s. 6486-6495
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Journal article (peer-reviewed)abstract
- The fate of adsorbed lipid vesicles on solid supports depends on numerous experimental parameters and typically results in the formation of a supported lipid bilayer (SLB) or an adsorbed vesicle layer. One of the poorly understood questions relates to how divalent cations appear to promote SLB formation in some cases. The complexity arises from the multiple ways in which divalent cations affect vesicle substrate and vesicle vesicle interactions as well as vesicle properties. These interactions are reflected, e.g., in the degree of deformation of adsorbed vesicles (if they do not rupture). It is, however, experimentally challenging to measure the extent of vesicle deformation in real-time. Herein, we investigated the effect of divalent cations (Mg2+, Ca2+, Sr2+) on the adsorption of zwitterionic 1,2-dioleoylsn-glycero-3-phosphocholine (DOPC) lipid vesicles onto silicon oxide- and titanium oxide coated substrates. The vesicle adsorption process was tracked using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) measurement techniques. On silicon oxide, vesicle adsorption led to SLB formation in all cases, while vesicles adsorbed but did not rupture on titanium oxide. It was identified that divalent cations promote increased deformation of adsorbed vesicles on both substrates and enhanced rupture on silicon oxide in the order Ca2+ > Mg2+ > Sr2+. The influence of divalent cations on different factors in these systems is discussed, clarifying experimental observations on both substrates. Taken together, the findings in this work offer insight into how divalent cations modulate the interfacial science of supported membrane systems.
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| 17. |
- Krustrup, P., et al.
(author)
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The Yo-Yo IE2 Test: Physiological Response for Untrained Men versus Trained Soccer Players
- 2015
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In: Medicine and Science in Sports and Exercise. - : Ovid Technologies (Wolters Kluwer Health). - 0195-9131. ; 47:1, s. 100-108
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Journal article (peer-reviewed)abstract
- Purpose This study aimed to examine the physical capacity and physiological response to the Yo-Yo Intermittent Endurance level 2 test (IE2) for untrained individuals (UTR) and trained male soccer players (TR) and to investigate the determinants of intense intermittent exercise performance. Methods Thirty-four healthy UTR males and 15 age-matched TR performed a maximal incremental treadmill test and a Yo-Yo IE2 test. Muscle biopsies and blood samples were obtained, and heart rate (HR) was measured before, during, and after tests. Results UTR had a 67% lower (P < 0.01) Yo-Yo IE2 performance (665 271 vs 2027 +/- 298 m; effect size (ES), 4.8), 34% lower VO2max (P < 0.01), and 19% lower resting muscle glycogen (P < 0.05) than those of TR. Blood lactate concentration and HR during the first 560 m of the Yo-Yo IE2 test were higher (P < 0.01) in UTR than those in TR (560 m, 7.4 +/- 2.8 vs 2.4 +/- 0.8 mM; ES, 1.7-2.8; 188 +/- 11 vs 173 +/- 8 bpm; ES, 0.9-1.5), with no differences at exhaustion. Time >95% HRmax was lower (P < 0.01) in UTR than that in TR (1.0 +/- 1.1 vs 6.3 +/- 2.9 min; ES, 3.1). Mean rates of muscle creatine phosphate utilization (16.5 +/- 9.5 vs 4.3 +/- 2.7 mmolkg(-1) d.wmin(-1)), muscle lactate accumulation (16.8 +/- 9.1 vs 4.2 +/- 2.9 mmolkg(-1) d.w.min(-1)), and glycogen breakdown (29.6 +/- 14.2 vs 7.7 +/- 5.4 mmolkg(-1) d.w.min(-1)) were fourfold higher (P < 0.01; ES, 1.4-1.7) in UTR than those in TR. For UTR, correlations (P < 0.01) were observed between Yo-Yo IE2 performance and VO2max (r = 0.77), incremental treadmill test performance (r = 0.79), and muscle citrate synthase activity (r = 0.57) but not for TR (r = -0.12 to 0.50; P > 0.05). Conclusions The Yo-Yo IE2 test was shown to possess high construct validity by showing large differences in performance, HR, and anaerobic metabolism between UTR and TR. In addition, VO2max seemed to be important for intermittent exercise performance in UTR but not for TR.
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| 18. |
- Mazzola, F., et al.
(author)
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Simultaneous Conduction and Valence Band Quantization in Ultrashallow High-Density Doping Profiles in Semiconductors
- 2018
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In: Physical Review Letters. - 0031-9007. ; 120:4
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Journal article (peer-reviewed)abstract
- We demonstrate simultaneous quantization of conduction band (CB) and valence band (VB) states in silicon using ultrashallow, high-density, phosphorus doping profiles (so-called Si:P δ layers). We show that, in addition to the well-known quantization of CB states within the dopant plane, the confinement of VB-derived states between the subsurface P dopant layer and the Si surface gives rise to a simultaneous quantization of VB states in this narrow region. We also show that the VB quantization can be explained using a simple particle-in-a-box model, and that the number and energy separation of the quantized VB states depend on the depth of the P dopant layer beneath the Si surface. Since the quantized CB states do not show a strong dependence on the dopant depth (but rather on the dopant density), it is straightforward to exhibit control over the properties of the quantized CB and VB states independently of each other by choosing the dopant density and depth accordingly, thus offering new possibilities for engineering quantum matter.
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| 19. |
- Park, Hyeonjin, et al.
(author)
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Unraveling How Cholesterol Affects Multivalency-Induced Membrane Deformation of Sub-100 nm Lipid Vesicles
- 2022
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 22:38, s. 15950-15959
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Journal article (peer-reviewed)abstract
- Cholesterol plays a critical role in modulating the lipid membrane properties of biological and biomimetic systems and recent attention has focused on its role in the functions of sub-100 nm lipid vesicles and lipid nanoparticles. These functions often rely on multivalent ligand-receptor interactions involving membrane attachment and dynamic shape transformations while the extent to which cholesterol can influence such interaction processes is largely unknown. To address this question, herein, we investigated the attachment of sub-100 nm lipid vesicles containing varying cholesterol fractions (0-45 mol %) to membrane-mimicking supported lipid bilayer (SLB) platforms. Biotinylated lipids and streptavidin proteins were used as model ligands and receptors, respectively, while the localized surface plasmon resonance sensing technique was employed to track vesicle attachment kinetics in combination with analytical modeling of vesicle shape changes. Across various conditions mimicking low and high multivalency, our findings revealed that cholesterol-containing vesicles could bind to receptor-functionalized membranes but underwent appreciably less multivalency-induced shape deformation than vesicles without cholesterol, which can be explained by a cholesterol-mediated increase in membrane bending rigidity. Interestingly, the extent of vesicle deformation that occurred in response to increasingly strong multivalent interactions was less pronounced for vesicles with greater cholesterol fraction. The latter trend was rationalized by taking into account the strong dependence of the membrane bending energy on the area of the vesicle-SLB contact region and such insights can aid the engineering of membrane-enveloped nanoparticles with tailored biophysical properties.
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| 20. |
- Singer, Andrew C, et al.
(author)
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Meeting Report : Risk Assessment of Tamiflu Use Under Pandemic Conditions
- 2008
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In: Environmental Health Perspectives. ; 116:11, s. 1563-7
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Journal article (peer-reviewed)abstract
- On 3 October 2007, 40 participants with diverse expertise attended the workshop Tamiflu and the Environment: Implications of Use under Pandemic Conditions to assess the potential human health impact and environmental hazards associated with use of Tamiflu during an influenza pandemic. Based on the identification and risk-ranking of knowledge gaps, the consensus was that oseltamivir ethylester-phosphate (OE-P) and oseltamivir carboxylate (OC) were unlikely to pose an ecotoxicologic hazard to freshwater organisms. OC in river water might hasten the generation of OC-resistance in wildfowl, but this possibility seems less likely than the potential disruption that could be posed by OC and other pharmaceuticals to the operation of sewage treatment plants. The workgroup members agreed on the following research priorities: a) available data on the ecotoxicology of OE-P and OC should be published ; b) risk should be assessed for OC-contaminated river water generating OC-resistant viruses in wildfowl ; c) sewage treatment plant functioning due to microbial inhibition by neuraminidase inhibitors and other antimicrobials used during a pandemic should be investigated ; and d) realistic worst-case exposure scenarios should be developed. Additional modeling would be useful to identify localized areas within river catchments that might be prone to high pharmaceutical concentrations in sewage treatment plant effluent. Ongoing seasonal use of Tamiflu in Japan offers opportunities for researchers to assess how much OC enters and persists in the aquatic environment.
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| 21. |
- Andersson, Martin, 1974, et al.
(author)
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Vesicle and bilayer formation of diphytanoylphosphatidylcholine (DPhPC) and diphytanoylphosphatidylethanolamine (DPhPE) mixtures and their bilayers' electrical stability
- 2011
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In: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 82:2, s. 550-561
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Journal article (peer-reviewed)abstract
- Lipid bilayers are of interest in applications where a cell membrane mimicking environment is desired. The performance of the lipid bilayer is largely dependent on the physical and chemical properties of the component lipids. Lipid bilayers consisting of phytanoyl lipids have proven to be appropriate choices since they exhibit high mechanical and chemical stability. In addition, such bilayers have high electrical resistances. Two different phytanoyl lipids, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and 1,2-diphytanoyl-sn-glycero-3-phosphoethanolamine(DPhPE), and various combinations of the two have been investigated with respect to their behavior in aqueous solutions, their interactions with solid surfaces, and their electrical stability. Dynamic light scattering, nuclear magnetic resonance diffusion, and cryogenic transmission electron microscopy measurements showed that pure DPhPC as well as mixtures of DPhPC and DPhPE consisting of greater than 50% (mol%) DPhPC formed unilamellar vesicles. If the total lipid concentration was greater than 0.15 g/l, then the vesicles formed solid-supported bilayers on plasma-treated gold and silica surfaces by the process of spontaneous vesicle adsorption and rupture, as determined by quartz crystal microbalance with dissipation monitoring and atomic force microscopy. The solid-supported bilayers exhibited a high degree of viscoelasticity, probably an effect of relatively high amounts of imbibed water or incomplete vesicle fusion. Lipid compositions consisting of greater than 50% DPhPE formed small flower-like vesicular structures along with discrete liquid crystalline structures, as evidenced by cryogenic transmission electron microscopy. Furthermore, electrophysiology measurements were performed on bilayers using the tip-dip methodology and the bilayers' capacity to retain its electrical resistance towards an applied potential across the bilayer was evaluated as a function of lipid composition. It was shown that the lipid ratio significantly affected the bilayer's electrical stability, with pure DPhPE having the highest stability followed by 3DPhPC:7DPhPE and 7DPhPC:3DPhPE in decreasing order. The bilayer consisting of 5DPhPC:5DPhPE had the lowest stability towards the applied electrical potential.
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| 22. |
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| 23. |
- Ferhan, Abdul Rahim, et al.
(author)
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Nanoplasmonic Sensing Architectures for Decoding Membrane Curvature-Dependent Biomacromolecular Interactions
- 2018
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:12, s. 7458-7466
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Journal article (peer-reviewed)abstract
- Nanoplasmonic sensors have emerged as a promising measurement approach to track biomacromolecular interactions involving lipid membrane interfaces. By taking advantage of nanoscale fabrication capabilities, it is possible to design sensing platforms with various architectural configurations. Such capabilities open the door to fabricating lipid membrane-coated nanoplasmonic sensors with varying degrees of membrane curvature in order to understand how biomacromolecular interaction processes are influenced by membrane curvature. Herein, we employed an indirect nanoplasmonic sensing approach to characterize the fabrication of supported lipid bilayers (SLBs) on silica-coated nanowell and nanodisk sensing platforms and to investigate how membrane curvature influences membrane-peptide interactions by evaluating the corresponding measurement responses from different spectral signatures that are sensitive to specific regions of the sensor geometries. SLBs were prepared by the vesicle fusion method, as monitored in real-time by nanoplasmonic sensing measurements and further characterized by fluorescence recovery after photobleaching (FRAP) experiments. By resolving different spectral signatures in the nanoplasmonic sensing measurements, it was determined that peptide binding induces membrane disruption at positively curved membrane regions, while peptide binding without subsequent disruption was observed at planar and negatively curved regions. These findings are consistent with the peptide's known preference to selectively form pores in positively curved membranes, providing validation to the nanoplasmonic sensing approach and highlighting how the integration of nanoplasmonic sensors with different nanoscale architectures can be utilized to study the influence of membrane curvature on biomacromolecular interaction processes.
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| 24. |
- Park, Hyeonjin, et al.
(author)
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pH-Modulated Nanoarchitectonics for Enhancement of Multivalency-Induced Vesicle Shape Deformation at Receptor-Presenting Lipid Membrane Interfaces
- 2023
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In: Langmuir. - 1520-5827 .- 0743-7463. ; 39:23, s. 8297-8305
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Journal article (peer-reviewed)abstract
- Multivalent ligand-receptor interactions betweenreceptor-presentinglipid membranes and ligand-modified biological and biomimetic nanoparticlesinfluence cellular entry and fusion processes. Environmental pH changescan drive these membrane-related interactions by affecting membranenanomechanical properties. Quantitatively, however, the correspondingeffects on high-curvature, sub-100 nm lipid vesicles are scarcelyunderstood, especially in the multivalent binding context. Herein,we employed the label-free localized surface plasmon resonance (LSPR)sensing technique to track the multivalent attachment kinetics, shapedeformation, and surface coverage of biotin ligand-functionalized,zwitterionic lipid vesicles with different ligand densities on a streptavidinreceptor-coated supported lipid bilayer under varying pH conditions(4.5, 6, 7.5). Our results demonstrate that more extensive multivalentinteractions caused greater vesicle shape deformation across the testedpH conditions, which affected vesicle surface packing as well. Notably,there were also pH-specific differences, i.e., a higher degree ofvesicle shape deformation was triggered at a lower multivalent bindingenergy in pH 4.5 than in pH 6 and 7.5 conditions. These findings supportthat the nanomechanical properties of high-curvature lipid membranes,especially the membrane bending energy and the corresponding responsivenessto multivalent binding interactions, are sensitive to solution pH,and indicate that multivalency-induced vesicle shape deformation occursslightly more readily in acidic pH conditions relevant to biologicalenvironments.
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| 25. |
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