Effect of multilayer barriers on the optical properties of GaInNAs single quantum-well structures grown by metalorganic vapor phase epitaxy

We report on the effects of combined strain-compensating and strain-mediating layers of various widths on the optical properties of 1.3 μm GaInNAs∕GaAs single quantum well structures grown by metalorganic vapor phase epitaxy (MOVPE). While the emission wavelength of GaInNAs∕GaAs quantum wells can be redshifted by the adoption of strain-compensated GaNAs layers, the material quality is degraded by the increased stress at the well∕barrier interface. This detrimental effect can be cured by inserting a strain-mediating InGaAs layer between them. Contrary to what is expected, however, the emission wavelength is blueshifted by the insertion of the InGaAs layer, which is attributed to the reduced N incorporation due to the improved interface quality. Our results indicate that the optical properties of MOVPE-grown GaInNAs∕GaAs quantum wells can be optimized in quantum efficiency and emission wavelength by combination of strain-compensating and strain-mediating layers with suitable characteristics

Emplacement styles within the Land's End Granite, West Cornwall

The Land's End Granite is the youngest of the major plutons of the Cornubian batholith and comprises a number of discrete bodies of both coarse-grained granite (CGG) and fine-grained granite (FGG). Detailed re-mapping of selected parts of the composite Land's End pluton indicates that individual granite intrusions take a variety of forms, including dykes and sub-horizontal sheets. U-Pb (monazite) and 40Ar-39Ar (muscovite) age data have been interpreted elsewhere to indicate that the CGG and FGG of the northern "Zennor lobe" were emplaced c. 2-3 m.y. before the CGG and FGG of the southern "St Buryan lobe". Separating the two lobes is a large body of aphyric granite, the "St Just wedge", which is as yet undated. Relationships at Porth Nanven, where an irregular contact is discordant to a magmatic-state fabric in CGG of the St Buryan lobe, and at Porth Ledden, where sheets of aphyric granite intrude CGG, suggest that the St Just wedge is younger than the two main lobes. The composite nature of the pluton is exemplified by variations in grainsize and texture and in the size, abundance and alignment of alkali-feldspar phenocrysts. The subtle nature of petrographic variation in such felsic rocks makes identification of contacts between CGGs difficult, but those between CGG and FGG are more easily recognizable. At Bosigran, there is a laterally persistent northwest dipping sheet of CGG which exhibits a sharp, planar contact with underlying MGG. Immediately to the north, at Carn Veslan, the same MGG has a gradational contact with non-porphyritic FGG. At Sennen and Land's End, contacts between slightly different CGGs are denoted by the presence of distinct mafic zones, planar at Sennen and much more irregular at Land's End. The contrasting nature of these contacts suggests different time-intervals between intrusive events. At Porth Nanven, granite dykes with sharp, planar margins intrude the aphyric granite of the St Just wedge. Throughout the pluton, bodies of FGG demonstrate a variety of temporal relationships with adjoining CGG, including contemporaneous, sub-rounded masses and later sub-horizontal sheets. These and other examples within the Land's End Granite demonstrate that, rather than having originated as a large, diapirically emplaced magma body, as suggested in earlier models, the pluton is composed of a series of discrete intrusions

Spectroscopic characterization of 1.3µm GaInNAs quantum-well structures grown by metal-organic vapor phase epitaxy

We report optical studies of high-quality 1.3 μm strain-compensated GaInNAs/GaAs single-quantum-well structures grown by metalorganic vapor phase epitaxy. Photoluminescence excitation (PLE) spectroscopy shows clearly the electronic structure of the two-dimensional quantum well. The transition energies between quantized states of the electrons and holes are in agreement with theoretical calculations based on the band anti-crossing model in which the localized N states interact with the extended states in the conduction band. We also investigated the polarization properties of the luminescence by polarized edge-emission measurements. Luminescence bands with different polarization characters arising from the electron to heavy-hole and light-hole transitions, respectively, have been identified and verify the transition assignment observed in the PLE spectrum

Influence of temperature gradients on tunnel junction thermometry below 1 K: cooling and electron-phonon coupling

We have studied thermal gradients in thin Cu and AlMn wires, both experimentally and theoretically. In the experiments, the wires were Joule heated non-uniformly at sub-Kelvin temperatures, and the resulting temperature gradients were measured using normal metal-insulator-superconducting tunnel junctions. The data clearly shows that even in reasonably well conducting thin wires with a short ($\sim 10 \mu$m) non-heated portion, significant temperature differences can form. In most cases, the measurements agree well with a model which includes electron-phonon interaction and electronic thermal conductivity by the Wiedemann-Franz law.Comment: J. Low Temp. Phys. in pres

Early reconstitution of effector memory CD4+ CMV-specific T cells protects against CMV reactivation following allogeneic SCT.

Reactivation of CMV is a common complication following allogeneic haematopoietic SCT and is associated with significant morbidity and mortality. The relative importance of the CD4+ and CD8+ components of the CMV-specific immune response in protection from reactivation is unclear. The CMV-specific CD4+ and CD8+ immune response was measured at serial time points in 32 patients following allogeneic HSCT. Intracellular cytokine staining following CMV lysate stimulation and HLA-peptide tetramers were used to determine CMV-specific CD4+ and CD8+ responses, respectively. A deficient CMV-specific CD4+ T-cell immune response within the first 30-50 days post transplant was associated with high risk of viral reactivation. Patients with combined impairment of the CD4+ and CD8+ immune response within the first 100 days were susceptible to late viral reactivation. The frequency of CMV-specific CD4+ T cells correlated with CMV-specific CD8+ T cells, comprising 10% of the whole T-cell repertoire. Early CMV-specific CD4+ T-cell reconstitution was dominated by effector memory cells with normal levels of IL-2 resuming 6 months following transplantation. In summary, both CD4 and CD8 CMV-specific immune reconstitution is required for protection from recurrent activation. Measurement of the magnitude of the CMV-specific CD4+ immune response is useful in managing viral reactivation following HSCT

Quasiparticle Interactions in Fractional Quantum Hall Systems: Justification of Different Hierarchy Schemes

The pseudopotentials describing the interactions of quasiparticles in fractional quantum Hall (FQH) states are studied. Rules for the identification of incompressible quantum fluid ground states are found, based upon the form of the pseudopotentials. States belonging to the Jain sequence nu=n/(1+2pn), where n and p are integers, appear to be the only incompressible states in the thermodynamic limit, although other FQH hierarchy states occur for finite size systems. This explains the success of the composite Fermion picture.Comment: RevTeX, 10 pages, 7 EPS figures, submitted fo Phys.Rev.

Moral parochialism misunderstood: a reply to Piazza and Sousa

Our paper [1] compared two competing hypotheses. The hypothesis that we label universalistic moral evaluation holds that a definitional feature of reasoning about moral rules is that, ceteris paribus, judgements of violations of rules concerning harm, rights or justice will be insensitive to spatial or temporal distance or the opinions of authority figures. The hypothesis that we label moral parochialism, consonant with a variety of theories of the evolutionary origins of morality, holds that, because moral judgements primarily serve to navigate local social arenas, remote events will not activate the mechanisms that generate negative moral evaluation to the same extent as events occurring in the here and now, whereas the consent of local authority figures will temper condemnation. Hence, moral parochialism predicts that the collective output of the faculties responsible for moral judgement will exhibit a reduction in the severity of judgement as a function of spatial or temporal distance or the opinions of local authority figures. We provided evidence from seven diverse societies, including five small-scale societies, showing that such reductions in severity judgements exist in all of the societies examined. Piazza and Sousa [2] argue that our data do not support parochialism, and instead support universalism, because (1) Only a minority of our participants reversed their initial judgement of the wrongness of an action (from wrong to not wrong or good) when it was subsequently framed as having occurred long ago or far away, or as having been sanctioned by authority figures. (2) Our use of graduated moral judgements, rather than dichotomous judgements, is inappropriate. (3) Only a minority of our participants diminished the severity of their initial judgement of the wrongness of an action when it was subsequently framed as having occurred long ago or far away, or as having been sanctioned by an important person. These objections stem from misunderstandings of moral parochialism and the evolutionary reasoning behind it

The Capaciousness of No: Affective Refusals as Literacy Practices

© 2020 The Authors. Reading Research Quarterly published by Wiley Periodicals, Inc. on behalf of International Literacy Association The authors considered the capacious feeling that emerges from saying no to literacy practices, and the affective potential of saying no as a literacy practice. The authors highlight the affective possibilities of saying no to normative understandings of literacy, thinking with a series of vignettes in which children, young people, and teachers refused literacy practices in different ways. The authors use the term capacious to signal possibilities that are as yet unthought: a sense of broadening and opening out through enacting no. The authors examined how attention to affect ruptures humanist logics that inform normative approaches to literacy. Through attention to nonconscious, noncognitive, and transindividual bodily forces and capacities, affect deprivileges the human as the sole agent in an interaction, thus disrupting measurements of who counts as a literate subject and what counts as a literacy event. No is an affective moment. It can signal a pushback, an absence, or a silence. As a theoretical and methodological way of thinking/feeling with literacy, affect proposes problems rather than solutions, countering solution-focused research in which the resistance is to be overcome, co-opted, or solved. Affect operates as a crack or a chink, a tiny ripple, a barely perceivable gesture, that can persist and, in doing so, hold open the possibility for alternative futures

Probing Heavy Higgs Boson Models with a TeV Linear Collider

The last years have seen a great development in our understanding of particle physics at the weak scale. Precision electroweak observables have played a key role in this process and their values are consistent, within the Standard Model interpretation, with a light Higgs boson with mass lower than about 200 GeV. If new physics were responsible for the mechanism of electroweak symmetry breaking, there would, quite generally, be modifications to this prediction induced by the non-standard contributions to the precision electroweak observables. In this article, we analyze the experimental signatures of a heavy Higgs boson at linear colliders. We show that a linear collider, with center of mass energy \sqrt{s} <= 1 TeV, would be very useful to probe the basic ingredients of well motivated heavy Higgs boson models: a relatively heavy SM-like Higgs, together with either extra scalar or fermionic degrees of freedom, or with the mixing of the third generation quarks with non-standard heavy quark modes.Comment: 21 page