Mid infrared near-field fingerprint spectroscopy of the 2D electron gas in LaAlO3_3/SrTiO3_3 at low temperatures

Confined electron systems, such as 2D electron gases (2DEGs), 2D materials, or topological insulators show great technological promise but their susceptibility to defects often results in nanoscale inhomogeneities with unclear origins. Scattering-type scanning near-field optical microscopy (s-SNOM) is useful to investigate buried confined electron systems non-destructively with nanoscale resolution, however, a clear separation of carrier concentration and mobility was often impossible in s-SNOM. Here, we predict a previously inaccessible characteristic "fingerprint" response of the prototypical LaAlO$_3$/SrTiO$_3$ 2DEG, and verify this using a state-of-the-art tunable narrow-band laser in mid-infrared cryo-s-SNOM at 8 K. Our modelling allows us to separate the influence of carrier concentration and mobility on fingerprint spectra and to characterize 2DEG inhomogeneities on the nanoscale. This spatially resolved information about the local electronic properties can be used to identify the origin of inhomogeneities in confined electron systems, making the s-SNOM fingerprint response a valuable tool for nanoelectronics and quantum technology

Parental Mental Illness, Borderline Personality Disorder, and Parenting Behavior: The Moderating Role of Social Support.

PURPOSE OF REVIEW Parental mental disorders, particularly borderline personality disorder (BPD), impair parenting behavior. Consequently, the children exhibit an elevated risk for psychopathology across their lifespan. Social support for parents is thought to moderate the relationship between parental mental illness and parenting behavior. It may dampen negative effects and serve as starting point for preventive interventions. This paper provides a literature overview regarding the impact of social support on the sequelae of parental mental illness and BPD for parenting behavior. RECENT FINDINGS Current literature highlights the increased burden of families with a mentally ill parent and associated changes in parenting behavior like increased hostility and affective dysregulation, especially in the context of parental BPD. Literature further demonstrates the powerful impact of social support in buffering such negative outcomes. The effect of social support seems to be moderated itself by further factors like socioeconomic status, gender, or characteristics of the social network. Social support facilitates positive parenting in mentally ill parents and may be particularly important in parents with BPD. However, social support is embedded within a framework of influencing factors, which need consideration when interpreting scientific results

An exploratory study on how attachment classifications manifest in group psychotherapy

Recently, attachment-informed researchers and clinicians have begun to show that attachment theory offers a useful framework for exploring group psychotherapy. However, it remains unclear whether patients with differing attachment classifications would behave and speak in distinct ways in group therapy sessions. Aim: In this study, we conducted an exploratory analysis of the discourse of patients in group therapy who had independently received different classifications with gold standard interview measures of attachment in adults. Each patient participant attended one of three mentalization-based parenting groups. Before treatment, the Adult Attachment Interview (AAI) or the Parent Development Interview (PDI) were administered to each patient, and interviews were transcribed and coded to obtain the patient's attachment classification. Groups included 2, 5, and 5 patients, respectively, and any session was led by at least two co-therapists. A total of 14 group sessions were transcribed verbatim. Sessions were analysed through a semi-inductive method, in order to identify markers that would typify patients of different attachment classifications in session. Through transcript excerpts and narrative descriptions, we report on the differing ways in which patients of different attachment classifications communicate in group psychotherapy, with the therapist and with each other. Our work provides useful information for group therapists and researchers regarding how differences in attachment status may play out in group sessions

Experimental Observation of ABCB Stacked Tetralayer Graphene

In tetralayer graphene, three inequivalent layer stackings should exist; however, only rhombohedral (ABCA) and Bernal (ABAB) stacking have so far been observed. The three stacking sequences differ in their electronic structure, with the elusive third stacking (ABCB) being unique as it is predicted to exhibit an intrinsic bandgap as well as locally flat bands around the K points. Here, we use scattering-type scanning near-field optical microscopy and confocal Raman microscopy to identify and characterize domains of ABCB stacked tetralayer graphene. We differentiate between the three stacking sequences by addressing characteristic interband contributions in the optical conductivity between 0.28 and 0.56 eV with amplitude and phase-resolved near-field nanospectroscopy. By normalizing adjacent flakes to each other, we achieve good agreement between theory and experiment, allowing for the unambiguous assignment of ABCB domains in tetralayer graphene. These results establish near-field spectroscopy at the interband transitions as a semiquantitative tool, enabling the recognition of ABCB domains in tetralayer graphene flakes and, therefore, providing a basis to study correlation physics of this exciting phase

Reconfigurable quantum metamaterials

By coupling controllable quantum systems into larger structures we introduce the concept of a quantum metamaterial. Conventional meta-materials represent one of the most important frontiers in optical design, with applications in diverse fields ranging from medicine to aerospace. Up until now however, metamaterials have themselves been classical structures and interact only with the classical properties of light. Here we describe a class of dynamic metamaterials, based on the quantum properties of coupled atom-cavity arrays, which are intrinsically lossless, reconfigurable, and operate fundamentally at the quantum level. We show how this new class of metamaterial could be used to create a reconfigurable quantum superlens possessing a negative index gradient for single photon imaging. With the inherent features of quantum superposition and entanglement of metamaterial properties, this new class of dynamic quantum metamaterial, opens a new vista for quantum science and technology.Comment: 16 pages, 8 figure

Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

A planar slab of negative index material works as a superlens with sub-diffraction-limited imaging resolution, since propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here, we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of wavelength/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy, and thermal sensors.Comment: 20 pages, 6 figures, published as open access article in Nature Communications (see http://www.nature.com/ncomms/

Partitioning of crystalline and amorphous phases during freezing of simulated Enceladus ocean fluids

This work was supported by The Leverhulme Trust (grant number RPG‐2016‐153).Saturn's ice‐covered moon Enceladus may contain the requisite conditions for life. Its potentially habitable subsurface ocean is vented into space as large cryovolcanic plumes that can be sampled by spacecraft, acting as a window to the ocean below. However, little is known about how Enceladus’ ocean fluids evolve as they freeze. Using cryo‐imaging techniques, we investigated solid phases produced by freezing simulated Enceladean ocean fluids at endmember cooling rates. Our results show that under flash‐freezing conditions (>10 K s−1), Enceladus‐relevant fluids undergo segregation, whereby the precipitation of ice templates the formation of brine vein networks. The high solute concentrations and confined nature of these brine veins means that salt crystallization is kinetically inhibited and glass formation (vitrification) can occur at lower cooling rates than typically required for vitrification of a bulk solution. Crystalline salts also form if flash‐frozen fluids are re‐warmed. The 10 µm‐scale distribution of salt phases produced by this mechanism differs markedly from that of gradually cooled (∼1 K min−1) fluids, showing that they inherit a textural signature of their formation conditions. The mineralogy of cryogenic carbonates can be used as a probe for cooling rate and parent fluid pH. Our findings reveal possible endmember routes for solid phase production from Enceladus’ ocean fluids and mechanisms for generating compositional heterogeneity within ice particles on a sub‐10 µm scale. This has implications for understanding how Enceladus' ocean constituents are incorporated into icy particles and delivered to space.Publisher PDFPeer reviewe

Infrared nanoscopy of Dirac plasmons at the graphene-SiO2 interface

We report on infrared (IR) nanoscopy of 2D plasmon excitations of Dirac fermions in graphene. This is achieved by confining mid-IR radiation at the apex of a nanoscale tip: an approach yielding two orders of magnitude increase in the value of in-plane component of incident wavevector q compared to free space propagation. At these high wavevectors, the Dirac plasmon is found to dramatically enhance the near-field interaction with mid-IR surface phonons of SiO2 substrate. Our data augmented by detailed modeling establish graphene as a new medium supporting plasmonic effects that can be controlled by gate voltage.Comment: 12 pages, 4 figure

Complex folding and misfolding effects of deer-specific amino acid substitutions in the β2-α2 loop of murine prion protein

The β2–α2 loop of PrPC is a key modulator of disease-associated prion protein misfolding. Amino acids that differentiate mouse (Ser169, Asn173) and deer (Asn169, Thr173) PrPC appear to confer dramatically different structural properties in this region and it has been suggested that amino acid sequences associated with structural rigidity of the loop also confer susceptibility to prion disease. Using mouse recombinant PrP, we show that mutating residue 173 from Asn to Thr alters protein stability and misfolding only subtly, whilst changing Ser to Asn at codon 169 causes instability in the protein, promotes oligomer formation and dramatically potentiates fibril formation. The doubly mutated protein exhibits more complex folding and misfolding behaviour than either single mutant, suggestive of differential effects of the β2–α2 loop sequence on both protein stability and on specific misfolding pathways. Molecular dynamics simulation of protein structure suggests a key role for the solvent accessibility of Tyr168 in promoting molecular interactions that may lead to prion protein misfolding. Thus, we conclude that ‘rigidity’ in the β2–α2 loop region of the normal conformer of PrP has less effect on misfolding than other sequence-related effects in this region

The N-Terminal, Polybasic Region Is Critical for Prion Protein Neuroprotective Activity

Several lines of evidence suggest that the normal form of the prion protein, PrPC, exerts a neuroprotective activity against cellular stress or toxicity. One of the clearest examples of such activity is the ability of wild-type PrPC to suppress the spontaneous neurodegenerative phenotype of transgenic mice expressing a deleted form of PrP (Δ32–134, called F35). To define domains of PrP involved in its neuroprotective activity, we have analyzed the ability of several deletion mutants of PrP (Δ23–31, Δ23–111, and Δ23–134) to rescue the phenotype of Tg(F35) mice. Surprisingly, all of these mutants displayed greatly diminished rescue activity, although Δ23–31 PrP partially suppressed neuronal loss when expressed at very high levels. Our results pinpoint the N-terminal, polybasic domain as a critical determinant of PrPC neuroprotective activity, and suggest that identification of molecules interacting with this region will provide important clues regarding the normal function of the protein. Small molecule ligands targeting this region may also represent useful therapeutic agents for treatment of prion diseases