Entangled-State Cycles of Atomic Collective-Spin States

We study quantum trajectories of collective atomic spin states of $N$ effective two-level atoms driven with laser and cavity fields. We show that interesting ``entangled-state cycles'' arise probabilistically when the (Raman) transition rates between the two atomic levels are set equal. For odd (even) $N$, there are $(N+1)/2$ ($N/2$) possible cycles. During each cycle the $N$-qubit state switches, with each cavity photon emission, between the states $(|N/2,m>\pm |N/2,-m>)/\sqrt{2}$, where $|N/2,m>$ is a Dicke state in a rotated collective basis. The quantum number $m$ ($>0$), which distinguishes the particular cycle, is determined by the photon counting record and varies randomly from one trajectory to the next. For even $N$ it is also possible, under the same conditions, to prepare probabilistically (but in steady state) the Dicke state $|N/2,0>$, i.e., an $N$-qubit state with $N/2$ excitations, which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure

Holographic Kondo Model in Various Dimensions

We study the addition of localised impurities to U(N) Supersymmetric Yang-Mills theories in (p+1)-dimensions by using the gauge/gravity correspondence. From the gravity side, the impurities are introduced by considering probe D(8-p)-branes extendingalong the time and radial directions and wrapping an (7-p)-dimensional submanifold of the internal (8-p)-sphere, so that the degrees of freedom are point-like from the gauge theory perspective. We analyse both the configuration in which the branes generate straight flux tubes -corresponding to actual single impurities - and the one in which connected flux tubes are created- corresponding to dimers. We discuss the thermodynamics of both the configurations and the related phase transition. In particular, the specific heat of the straight flux-tube configuration is negative for p<3, while it is never the case for the connected one. We study the stability of the system by looking at the impurity fluctuations. Finally, we characterise the theory by computing one- and two-point correlators of the gauge theory operators dual to the impurity fluctuations. Because of the underlying generalised conformal structure, such correlators can be expressed in terms of an effective coupling constant (which runs because of its dimensionality) and a generalised conformal dimension.Comment: 56 pages, 3 figures; v2: typos correcte

Upper atmospheres and ionospheres of planets and satellites

The upper atmospheres of the planets and their satellites are more directly exposed to sunlight and solar wind particles than the surface or the deeper atmospheric layers. At the altitudes where the associated energy is deposited, the atmospheres may become ionized and are referred to as ionospheres. The details of the photon and particle interactions with the upper atmosphere depend strongly on whether the object has anintrinsic magnetic field that may channel the precipitating particles into the atmosphere or drive the atmospheric gas out to space. Important implications of these interactions include atmospheric loss over diverse timescales, photochemistry and the formation of aerosols, which affect the evolution, composition and remote sensing of the planets (satellites). The upper atmosphere connects the planet (satellite) bulk composition to the near-planet (-satellite) environment. Understanding the relevant physics and chemistry provides insight to the past and future conditions of these objects, which is critical for understanding their evolution. This chapter introduces the basic concepts of upper atmospheres and ionospheres in our solar system, and discusses aspects of their neutral and ion composition, wind dynamics and energy budget. This knowledge is key to putting in context the observations of upper atmospheres and haze on exoplanets, and to devise a theory that explains exoplanet demographics.Comment: Invited Revie

Interstellar scintillation as the origin of rapid radio variability in the quasar J1819+3845

Quasars shine brightly due to the liberation of gravitational energy as matter falls onto a supermassive black hole in the centre of a galaxy. Variations in the radiation received from active galactic nuclei (AGN) are studied at all wavelengths, revealing the tiny dimensions of the region and the processes of fuelling the black hole. Some AGN are variable at optical and shorter wavelengths, and display radio outbursts over years and decades. These AGN often also show faster variations at radio wavelengths (intraday variability, IDV) which have been the subject of much debate. The simplest explanation, supported by a correlation in some sources between the optical (intrinsic) and faster radio variations, is that the rapid radio variations are intrinsic. However, this explanation implies physically difficult brightness temperatures, suggesting that the variations may be due to scattering of the incident radiation in the interstellar medium of our Galaxy. Here we present results which show unambiguously that the variations in one extreme case are due to interstellar scintillation. We also measure the transverse velocity of the scattering material, revealing a surprising high velocity plasma close to the Solar System

The CoQ oxidoreductase FSP1 acts parallel to GPX4 to inhibit ferroptosis.

Ferroptosis is a form of regulated cell death that is caused by the iron-dependent peroxidation of lipids1,2. The glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4) prevents ferroptosis by converting lipid hydroperoxides into non-toxic lipid alcohols3,4. Ferroptosis has previously been implicated in the cell death that underlies several degenerative conditions2, and induction of ferroptosis by the inhibition of GPX4 has emerged as a therapeutic strategy to trigger cancer cell death5. However, sensitivity to GPX4 inhibitors varies greatly across cancer cell lines6, which suggests that additional factors govern resistance to ferroptosis. Here, using a synthetic lethal CRISPR-Cas9 screen, we identify ferroptosis suppressor protein 1 (FSP1) (previously known as apoptosis-inducing factor mitochondrial 2 (AIFM2)) as a potent ferroptosis-resistance factor. Our data indicate that myristoylation recruits FSP1 to the plasma membrane where it functions as an oxidoreductase that reduces coenzyme Q10 (CoQ) (also known as ubiquinone-10), which acts as a lipophilic radical-trapping antioxidant that halts the propagation of lipid peroxides. We further find that FSP1 expression positively correlates with ferroptosis resistance across hundreds of cancer cell lines, and that FSP1 mediates resistance to ferroptosis in lung cancer cells in culture and in mouse tumour xenografts. Thus, our data identify FSP1 as a key component of a non-mitochondrial CoQ antioxidant system that acts in parallel to the canonical glutathione-based GPX4 pathway. These findings define a ferroptosis suppression pathway and indicate that pharmacological inhibition of FSP1 may provide an effective strategy to sensitize cancer cells to ferroptosis-inducing chemotherapeutic agents

A Social Identity Approach to Sport Psychology: Principles, Practice, and Prospects.

Drawing on social identity theory and self-categorization theory, we outline an approach to sport psychology that understands groups not simply as features of sporting contexts but rather as elements that can be, and often are, incorporated into a person's sense of self and, through this, become powerful determinants of their sport-related behavior. The underpinnings of this social identity approach are outlined, and four key lessons for sport that are indicative of the analytical and practical power of the approach are presented. These suggest that social identity is the basis for sports group (1) behavior, (2) formation and development, (3) support and stress appraisal, and (4) leadership. Building on recent developments within sport science, we outline an agenda for future research by identifying a range of topics to which the social identity approach could fruitfully contribute

Climate and southern Africa's water-energy-food nexus

In southern Africa, the connections between climate and the water-energy-food nexus are strong. Physical and socioeconomic exposure to climate is high in many areas and in crucial economic sectors. Spatial interdependence is also high, driven for example, by the regional extent of many climate anomalies and river basins and aquifers that span national boundaries. There is now strong evidence of the effects of individual climate anomalies, but associations between national rainfall and Gross Domestic Product and crop production remain relatively weak. The majority of climate models project decreases in annual precipitation for southern Africa, typically by as much as 20% by the 2080s. Impact models suggest these changes would propagate into reduced water availability and crop yields. Recognition of spatial and sectoral interdependencies should inform policies, institutions and investments for enhancing water, energy and food security. Three key political and economic instruments could be strengthened for this purpose; the Southern African Development Community, the Southern African Power Pool, and trade of agricultural products amounting to significant transfers of embedded water

Dinosaurs reveal the geographical signature of an evolutionary radiation

Dinosaurs dominated terrestrial ecosystems across the globe for over 100 million years and provide a classic example of an evolutionary radiation. However, little is known about how these animals radiated geographically to become globally distributed. Here, we use a biogeographical model to reconstruct the dinosaurs’ ancestral locations, revealing the spatial mechanisms that underpinned this 170-million-year-long radiation. We find that dinosaurs spread rapidly initially, followed by a significant continuous and gradual reduction in their speed of movement towards the Cretaceous/Tertiary boundary (66 million years ago). This suggests that the predominant mode of dinosaur speciation changed through time with speciation originally largely driven by geographical isolation—when dinosaurs speciated more, they moved further. This was gradually replaced by increasing levels of sympatric speciation (species taking advantage of ecological opportunities within their existing environment) as terrestrial space became a limiting factor. Our results uncover the geographical signature of an evolutionary radiation

Geography of non-melanoma skin cancer and ecological associations with environmental risk factors in England.

This is the author's peer reviewed version of the article. Please cite the published, final version which is available via the DOI link in this record.This study investigates the geography of non-melanoma skin cancer (NMSC) in England, and ecological associations with three widespread environmental hazards: radon, arsenic and ultraviolet radiation from the sun.European Regional Development FundEuropean Social Fund Convergence Programme for Cornwall and the Isles of Scill

Investigation of the erosive potential of sour novelty sweets

Provides a background about the link between acidic beverages and dental erosion. Discusses the potential risk of developing dental erosion upon the frequent consumption of novelty sweets. Provides information which could be used by dental personnel in counselling patients who consume novelty sweets or at risk of developing dental erosion. Abstract Background The expansion of the novelty sweets market in the UK has major potential public health implications in children and young adults as they may cause dental erosion. Objective To investigate the erosive potential of the novelty sweets in term of their physiochemical properties and amount of enamel loss. Subjects and methods The pH of a variety of novelty sweets was tested in vitro using a pH meter and the neutralisable acidity was assessed by titrating the sweets against 0.1M NaOH. The viscosity of the novelty sweets was measured using a rotational viscometer. The wettability of enamel by each sweet was measured using dynamic contact angle analyser. Enamel loss was assessed using contact profilometry. Results The pH ranged from 1.8–3.2, the neutralisable acidity ranged from 9–201 ml of 0.1 NaOH. The viscosity of the novelty sweets that come in liquid form ranged from 2–594 mPa s. The surface enamel erosion ranged from 1.95–15.77 μm and from 2.5–17.6 μm with and without immersing in saliva for 1 hour before immersing in acidic solution respectively. The amount of subsurface enamel loss was ranged from 0.75 to 2.3 μm following ultrasonication at 0 min of acidic attack and from 0.23 to 0.85 μm at 60 minutes of acidic attack while immersed in saliva. The contact angle between enamel surface and four sweet was less than the angle formed between the orange juice and the enamel which caused more wettability of enamel. Conclusion The pH is lower than the critical value for enamel erosion (5.5), high neutralisable acidity and high sugar content strongly suggest that these sweets may cause significant amount of dental erosion clinically. In addition, the degree of wettability of enamel by solution is an important factor to consider in determining the enamel loss caused by acidic solution. Immediate tooth brushing would cause further enamel loss as a result of the mechanical removal of softened enamel. However, it has been suggested that postponing brushing after erosive attack should be reconsidered