Spherical Tin Oxide, SnO2 Particles Fabricated via Facile Hydrothermal Method for Detection of Mercury (II) Ions.

Smooth-surface spherical tin oxide particles were fabricated via hydrothermal processing route. X-ray diffraction (XRD) revealed that the particles consisted of the rutile phase of SnO2 with tetragonal structure. The spherical morphology was realized with the aid of ammonia. The aggregation of SnO2 particles could be avoided by adjusting the concentration of tin (II) chloride. Bare glassy carbon electrode (GCE) was modified with the hydrothermally prepared SnO2 particles to detect the presence of mercury (II) ions (Hg2+), in the presence of potassium chloride (KCl) as a supporting electrolyte. GCE modified with the spherical SnO2 particles that possessed small crystallite size and smooth surface exhibited significantly enhanced oxidative and reductive current of Hg2+ during cyclic voltammetry compared with its bare counterpart. The reductive current was observed to increase by two fold and the detection limit of 75 nM for Hg 2+ was achieved. This suggests that SnO2 particles are a promising chemical sensor for the detection of Hg2+ in natural waters

Modelling the effect of non-planarity on luminescence energy of conjugated polymers

We present theoretical investigations of structural and electronic properties of ground-state and low-lying excited singlet states in isolated chains of conjugated polymers using a self-consistent quantum molecular dynamics method. With this approach, we have determined the energy of both states as function of the twist angle between two planar segments of the same polymer chain, for polymer chains with variable length. The conjugated polymers investigated here are poly(para-phenylene vinylene) (PPV) and polydiacetylene (PDA). Our results show that the energy of the excited-state increases more than that of the ground-state, as the twist angle increases up to 90º degrees. The change in the twist angle of both polymers leads to a blueshift in luminescence transition energy, the effect being stronger in PPV when the planar segments have similar sizes. The predicted blueshift in both polymers is dependent on the chain length, the effect being more pronounced for shorter-chains.Comunidade Europeia (CE). Fundo Europeu de Desenvolvimento Regional (FEDER)Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional “Ciência , Tecnologia, Inovação” – POCTI/CTM/41574/2001, CONC-REEQ/443/2001 e SFRH/BD/11231/200

Decomposition of homogeneous polynomials with low rank

Let $F$ be a homogeneous polynomial of degree $d$ in $m+1$ variables defined over an algebraically closed field of characteristic zero and suppose that $F$ belongs to the $s$-th secant varieties of the standard Veronese variety $X_{m,d}\subset \mathbb{P}^{{m+d\choose d}-1}$ but that its minimal decomposition as a sum of $d$-th powers of linear forms $M_1, ..., M_r$ is $F=M_1^d+... + M_r^d$ with $r>s$. We show that if $s+r\leq 2d+1$ then such a decomposition of $F$ can be split in two parts: one of them is made by linear forms that can be written using only two variables, the other part is uniquely determined once one has fixed the first part. We also obtain a uniqueness theorem for the minimal decomposition of $F$ if the rank is at most $d$ and a mild condition is satisfied.Comment: final version. Math. Z. (to appear

Demonstration of large ionization coefficient ratio in AlAs0.56Sb0.44 lattice matched to InP

The electron and hole avalanche multiplication characteristics have been measured in bulk AlAs0.56Sb0.44 p-i-n and n-i-p homojunction diodes, lattice matched to InP, with nominal avalanche region thicknesses of ~0.6 μm, 1.0 μm and 1.5 μm. From these and data from two much thinner devices, the bulk electron and hole impact ionization coefficients (α and β respectively), have been determined over an electric-field range from 220-1250 kV/cm for α and from 360-1250 kV/cm for β for the first time. The α/β ratio is found to vary from 1000 to 2 over this field range, making it the first report of a wide band-gap III-V semiconductor with ionization coefficient ratios similar to or larger than that observed in silicon

Entanglement preparation using symmetric multiports

We investigate the entanglement produced by a multi-path interferometer that is composed of two symmetric multiports, with phase shifts applied to the output of the first multiport. Particular attention is paid to the case when we have a single photon entering the interferometer. For this situation we derive a simple condition that characterize the types of entanglement that one can generate. We then show how one can use the results from the single photon case to determine what kinds of multi-photon entangled states one can prepare using the interferometer.Comment: 6 pages, 2 figures, accepted for publication in European Journal of Physics

Entanglement preparation using symmetric multiports

We investigate the entanglement produced by a multi-path interferometer that is composed of two symmetric multiports, with phase shifts applied to the output of the first multiport. Particular attention is paid to the case when we have a single photon entering the interferometer. For this situation we derive a simple condition that characterize the types of entanglement that one can generate. We then show how one can use the results from the single photon case to determine what kinds of multi-photon entangled states one can prepare using the interferometer.Comment: 6 pages, 2 figures, accepted for publication in European Journal of Physics

Data and Protocol for the Oxford Achieving Resilience During COVID-19 (ARC) Study

The Oxford Achieving Resilience during COVID-19 (ARC) study collected data from adolescents (aged 13–18), and parents of adolescents, from March 2020 to August 2021. Following a baseline survey (1274 completed baseline), participants were invited to 11 follow-up weekly surveys then 9 monthly follow-up surveys, and to an optional cognitive task. Each survey included questionnaires on mental health, resilience and wellbeing, COVID-19 related experiences and pandemic anxiety. Data is stored on the Open Science Framework (https://osf.io/4b85w/), with comprehensive documentation on all measures. These data may be valuable to adolescent mental health researchers for further analyses and aggregation with other datasets.Sam Parsons, Ana Todorovic, Michele C. Lim, Annabel Songco, Elaine Fo

Statistical mechanics of RNA folding: a lattice approach

We propose a lattice model for RNA based on a self-interacting two-tolerant trail. Self-avoidance and elements of tertiary structure are taken into account. We investigate a simple version of the model in which the native state of RNA consists of just one hairpin. Using exact arguments and Monte Carlo simulations we determine the phase diagram for this case. We show that the denaturation transition is first order and can either occur directly or through an intermediate molten phase.Comment: 8 pages, 9 figure

Escape from washing out of baryon number in a two-zero-texture general Zee model compatible with the large mixing angle MSW solution

We propose a two-zero-texture general Zee model, compatible with the large mixing angle Mikheyev-Smirnov-Wolfenstein solution. The washing out of the baryon number does not occur in this model for an adequate parameter range. We check the consistency of a model with the constraints coming from flavor changing neutral current processes, the recent cosmic microwave background observation, and the Z-burst scenario.Comment: 22 pages, 2 eps figures, Type set revtex