The physical properties of cometary nuclei observed today relate to their complex history and help to constrain their formation and evolution. In this article, we review some of the main physical ...properties of cometary nuclei and focus in particular on the thermal, mechanical, structural and dielectric properties, emphasising the progress made during the Rosetta mission. Comets have a low density of
480
±
220
kg
m
−
3
and a low permittivity of 1.9–2.0, consistent with a high porosity of 70–80%, are weak with a very low global tensile strength
<
100
Pa, and have a low bulk thermal inertia of
0
–
60
J
K
−
1
m
−
2
s
−
1
/
2
that allowed them to preserve highly volatiles species (e.g. CO, CO
2
, CH
4
, N
2
) into their interior since their formation. As revealed by 67P/Churyumov-Gerasimenko, the above physical properties vary across the nucleus, spatially at its surface but also with depth. The broad picture is that the bulk of the nucleus consists of a weakly bonded, rather homogeneous material that preserved primordial properties under a thin shell of processed material, and possibly covered by a granular material; this cover might in places reach a thickness of several meters. The properties of the top layer (the first meter) are not representative of that of the bulk nucleus. More globally, strong nucleus heterogeneities at a scale of a few meters are ruled out on 67P’s small lobe.
Coupling a many-body-localized system to a dissipative bath necessarily leads to delocalization. Here, we investigate the nature of the ensuing relaxation dynamics and the information it holds on the ...many-body-localized state. We formulate the relevant Lindblad equation in terms of the local integrals of motion of the underlying localized Hamiltonian. This allows us to map the quantum evolution deep in the localized state to tractable classical rate equations. We consider two different types of dissipation relevant to systems of ultracold atoms: dephasing due to inelastic scattering on the lattice lasers and particle loss. Our approach allows us to characterize their different effects in the limiting cases of weak and strong interactions.
Previous meta-analyses and reviews on gender differences in emotion recognition have shown a small to moderate female advantage. However, inconsistent evidence from recent studies has raised ...questions regarding the implications of different methodologies, stimuli, and samples. In the present research based on a community sample of more than 5000 participants, we tested the emotional sensitivity hypothesis, stating that women are more sensitive to perceive subtle, i.e. low intense or ambiguous, emotion cues. In addition, we included a self-report emotional intelligence test in order to examine any discrepancy between self-perceptions and actual performance for both men and women. We used a wide range of stimuli and models, displaying six different emotions at two different intensity levels. In order to better tap sensitivity for subtle emotion cues, we did not use a forced choice format, but rather intensity measures of different emotions. We found no support for the emotional sensitivity account, as both genders rated the target emotions as similarly intense at both levels of stimulus intensity. Men, however, more strongly perceived non-target emotions to be present than women. In addition, we also found that the lower scores of men in self-reported EI was not related to their actual perception of target emotions, but it was to the perception of non-target emotions.
Epoxy resins are functionalized with Diels-Alder based thermo-reversible crosslinks to enable the fabrication of composites that are capable of multiple self-healing-repair processes. The key ...challenge in realizing a structural combination of conventional epoxy amine systems with furfuryl and maleimide functional groups is to achieve a high conversion in the reversible cross-linked polymer network formation while avoiding the major side-reactions.
We have developed a two-step process consisting of a bulk prepolymerization reaction followed by a network formation step. The second step is performed in an extruder to realize a good mixing at high temperatures, while keeping the residence time at that temperature short to avoid maleimide side-reactions. The obtained oligomers are characterized using NIR, NMR, DSC, GPC analyses while solvent exposure tests and rheological measurements are performed to prove the formation of a thermo-reversible network and study their behavior in relation to the cross-linker concentration.
Densely cross-linked, solvent resistant polymeric networks are obtained that maintain the ability to un-crosslink and thus regaining fluid behavior at elevated temperatures for at least five subsequent heat cycles. Glass fiber reinforced polymer composite films, which are fabricated using these resins, demonstrate that the thermo-reversible effect is strong enough to achieve full self-healing of a severely cracked and delaminated test specimen.
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•An epoxy amine system is combined with a Diels-Alder (furfuryl maleimide) system.•The highly crosslinked thermo-reversible polymer network flows at high temperature.•Self-healing of a composite of glass fibers infused with the resin is demonstrated.
Many-body localization (MBL), the disorder-induced localization of interacting particles, signals a breakdown of conventional thermodynamics because MBL systems do not thermalize and show nonergodic ...time evolution. We experimentally observed this nonergodic evolution for interacting fermions in a one-dimensional quasirandom optical lattice and identified the MBL transition through the relaxation dynamics of an initially prepared charge density wave. For sufficiently weak disorder, the time evolution appears ergodic and thermalizing, erasing all initial ordering, whereas above a critical disorder strength, a substantial portion of the initial ordering persists. The critical disorder value shows a distinctive dependence on the interaction strength, which is in agreement with numerical simulations. Our experiment paves the way to further detailed studies of MBL, such as in noncorrelated disorder or higher dimensions.
How do words with either explicit or implicit spatial meanings (e.g., DOWN, BOOT) shift our attention? Recent studies, presenting prime words followed by probe targets, suggested that, for implicit ...spatial words, both the spatial meaning of prime words and the target locations must be processed to induce congruency benefits. Here we examined the functional necessity of the latter location component. 91 healthy adults discriminated target letters that followed explicit or implicit spatial words. Words either did or did not have to be semantically processed. Target discrimination speed was used to compute congruency benefits. With explicit prime words, spatial congruency effects emerged without semantic processing instructions. In contrast, with implicit prime words, only instructing their semantic processing ensured a congruency benefit. This shows that, for implicit spatial words, spatial processing of target locations is not necessary; instead, processing the spatial connotation of the prime, together with the identity of the target, can induce congruency benefits. Our results help to understand previous conflicting findings.
Theoretically, it has been known that breaking spin degeneracy and effectively realizing spinless fermions is a promising path to topological superconductors. Yet, topological superconductors are ...rare to date. Here we propose to realize spinless fermions by splitting the spin degeneracy in momentum space. Specifically, we identify monolayer hole-doped transition metal dichalcogenide (TMD)s as candidates for topological superconductors out of such momentum-space-split spinless fermions. Although electron-doped TMDs have recently been found superconducting, the observed superconductivity is unlikely topological because of the near spin degeneracy. Meanwhile, hole-doped TMDs with momentum-space-split spinless fermions remain unexplored. Employing a renormalization group analysis, we propose that the unusual spin-valley locking in hole-doped TMDs together with repulsive interactions selectively favours two topological superconducting states: interpocket paired state with Chern number 2 and intrapocket paired state with finite pair momentum. A confirmation of our predictions will open up possibilities for manipulating topological superconductors on the device-friendly platform of monolayer TMDs.
During mitotic exit, missegregated chromosomes can recruit their own nuclear envelope (NE) to form micronuclei (MN). MN have reduced functioning compared to primary nuclei in the same cell, although ...the two compartments appear to be structurally comparable. Here we show that over 60% of MN undergo an irreversible loss of compartmentalization during interphase due to NE collapse. This disruption of the MN, which is induced by defects in nuclear lamina assembly, drastically reduces nuclear functions and can trigger massive DNA damage. MN disruption is associated with chromatin compaction and invasion of endoplasmic reticulum (ER) tubules into the chromatin. We identified disrupted MN in both major subtypes of human non-small-cell lung cancer, suggesting that disrupted MN could be a useful objective biomarker for genomic instability in solid tumors. Our study shows that NE collapse is a key event underlying MN dysfunction and establishes a link between aberrant NE organization and aneuploidy.
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•Micronuclei frequently undergo irreversible nuclear-envelope collapse•Lamin B1 levels influence the likelihood of nuclear-envelope collapse•Massive DNA-damage accumulation in micronuclei can occur upon collapse•Micronuclei disruption occurs in solid tumors as well as normal and cancer cells
Missegregated chromosomes recruit their own nuclear envelope to form micronuclei (MN). Most MN are disrupted due to nuclear-envelope collapse, and this leads to impaired chromosome function. Disrupted MN may therefore serve as a biomarker for genomic instability in solid tumors.
Upconverting materials are capable of absorbing near‐infrared light and converting it into short‐wavelength luminescence. The efficiency of this remarkable effect is highly temperature dependent and ...thus can be used for temperature determination (thermometry) on a nanometer scale. All the upconverting materials discovered so far display several (mainly two) narrow emission bands, each of which has its own temperature dependence. The ratio of the intensity of two of these bands provides a referenced signal for optical sensing of temperature, for example inside cells.
Cell fever: Lanthanoid‐ion‐doped upconverting nanoparticles (UCNPs) display a strongly temperature‐dependent luminescence that can be used to sense temperature in sub‐micrometer dimensions, for example in cells or nanofluidics. The picture showns how green‐ and red‐emitting UCNPs can be used to measure the temperature in kidney cells. The intensity ratio of two of these bands provides a referenced signal.
The literature on spatial associations during number processing is dominated by the SNARC (spatial-numerical association of response codes) effect. We describe spatial biases found for single digits ...and pairs of numbers, first in the "original" speeded parity task and then extending the scope to encompass different tasks, a range of measures, and various populations. Then we review theoretical accounts before surveying the emerging evidence for similar spatial associations during mental arithmetic. We conclude that the mental number line hypothesis and an embodied approach are useful frameworks for further studies.
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