A Scanning Electron Microscope for Ultracold Atoms

We propose a new technique for the detection of single atoms in ultracold quantum gases. The technique is based on scanning electron microscopy and employs the electron impact ionization of trapped atoms with a focussed electron probe. Subsequent detection of the resulting ions allows for the reconstruction of the atoms position. This technique is expected to achieve a much better spatial resolution compared to any optical detection method. In combination with the sensitivity to single atoms, it makes new in situ measurements of atomic correlations possible. The detection principle is also well suited for the addressing of individual sites in optical lattices.Comment: 5 pages, 2 figure

How to gain competitive advantage through crossborder e-commerce between New Zealand and China?

With the popularization of the Internet and the explosive growth of cross-border e-commerce, this research project discusses how an organisation can gain competitive advantage through cross-border e-commerce. This study will investigate PESTEL analysis` content and the significance of Porter`s Five Forces in competition. Also, the research identifies e-commerce and three models of e-commerce and evaluate the cross-border business in New Zealand. Also, this research project evaluates some of the business strategies provided by lecturers. According to the report, the impact of political factors is easily overlooked, and there is high competitiveness between C2C and B2C. Also, the researcher found that the target group of cross-border e-commerce business in New Zealand is single. To gain more competitive advantages and stand out of this industry, the organisation needs to increase customer awareness on political factors, improve service quality, and increase target group. This report is completed by mixed methods which including interview, and the online questionnaire to obtain information and resources. Participants include shop manager, employee, and customers. The 62 customers are all Chinese because the organisation only focuses on the Chinese market

Design and Setup of the Micro-Turboexpander Transcritical CO2 System

As the potential Eco-friendly refrigerant, CO2 regains more and more attentions. It has various advantages over conventional refrigerants, such as non-flammability, non-toxicity, high volumetric refrigerant capacity and excellent heat transfer properties. Because the heat rejection temperature in a transcritical CO2 heat pump or a transcritical CO2 refrigeration system is higher than the critical temperature of CO2, the transcritical vapor compression cycle becomes the best choice for transcritical CO2 systems. However, the relative low COP caused by the throttle valve limited the further development. The replacement of a throttle valve with a turboexpander, an ejector or a vortex tube is leading to the way for improving the COP of a transcritical CO2 system. With the advantages of high efficiency, high compactness, high reliability and long-life time, turboexpanders have been widely used in gas lique faction devices (below 120K) and most of the reverse Brayton refrigeration systems. It is also one of the most ideal expansion devices for transcritical CO2 systems. However, its applications are limited by the difficulties of high pressure and super high rotating speed operation. With the development of manufacturing technology and gas bearing technology, it becomes possible to use turboexpanders in transcriticalCO2 systems. In this paper, two turboexpanders with 10 mm radial reaction turbine wheel and 9 mm rotor diameter were designed for the 15 kW transcritical CO2 refrigeration system, and the rotating speed is about 200 krpm.The proposed turboexpanders outlet states are CO2 two-phase flow and subcooled CO2 liquid flow, respectively. This study will lay a foundation for the application of turboexpanders in transcritical CO2 systems

Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the Sun

We search for persistent and quasi-periodic release events of streamer blobs during 2007 with the Large Angle Spectrometric Coronagraph on the \textit{Solar and Heliospheric Observatory} and assess the velocity of the slow solar wind along the plasma sheet above the corresponding streamer by measuring the dynamic parameters of blobs. We find 10 quasi-periodic release events of streamer blobs lasting for three to four days. In each day of these events, we observe three-five blobs. The results are in line with previous studies using data observed near the last solar minimum. Using the measured blob velocity as a proxy for that of the mean flow, we suggest that the velocity of the background slow solar wind near the Sun can vary significantly within a few hours. This provides an observational manifestation of the large velocity variability of the slow solar wind near the Sun.Comment: 14 pages, 5 figures, accepted by Soalr Physic

Metallic liquid hydrogen and likely Al2O3 metallic glass

Dynamic compression has been used to synthesize liquid metallic hydrogen at 140 GPa (1.4 million bar) and experimental data and theory predict Al2O3 might be a metallic glass at ~300 GPa. The mechanism of metallization in both cases is probably a Mott-like transition. The strength of sapphire causes shock dissipation to be split differently in the strong solid and soft fluid. Once the 4.5-eV H-H and Al-O bonds are broken at sufficiently high pressures in liquid H2 and in sapphire (single-crystal Al2O3), electrons are delocalized, which leads to formation of energy bands in fluid H and probably in amorphous Al2O3. The high strength of sapphire causes shock dissipation to be absorbed primarily in entropy up to ~400 GPa, which also causes the 300-K isotherm and Hugoniot to be virtually coincident in this pressure range. Above ~400 GPa shock dissipation must go primarily into temperature, which is observed experimentally as a rapid increase in shock pressure above ~400 GPa. The metallization of glassy Al2O3, if verified, is expected to be general in strong oxide insulators. Implications for Super Earths are discussed.Comment: 8 pages, 5 figures, 14th Liquid and Amorphous Metals Conference, Rome 201

Revisiting Leptogenesis in a SUSY SU(5) x T' Model of Flavour

We investigate the generation of the baryon asymmetry of the Universe within a SUSY SU(5) x T' model of flavour, which gives rise to realistic masses and mixing patterns for quarks and leptons. The model employs the see-saw mechanism for generation of the light neutrino masses and the baryon asymmetry is produced via leptogenesis. We perform detailed calculations of both the CP violating lepton asymmetries, originating from the decays of the heavy Majorana neutrinos operative in the see-saw mechanism, and of the efficiency factors which account for the lepton asymmetry wash-out processes in the Early Universe. The latter are calculated by solving numerically the system of Boltzmann equations describing the generation and the evolution of the lepton asymmetries. The baryon asymmetry in the model considered is proportional to the J_{CP} factor, which determines the magnitude of CP violation effects in the oscillations of flavour neutrinos. The leptogenesis scale can be sufficiently low, allowing to avoid the potential gravitino problem.Comment: 14 pages, 1 figure; published versio

A Spectral Bernstein Theorem

We study the spectrum of the Laplace operator of a complete minimal properly immersed hypersurface $M$ in $\R^{n+1}$. (1) Under a volume growth condition on extrinsic balls and a condition on the unit normal at infinity, we prove that $M$ has only essential spectrum consisting of the half line $[0, +\infty)$. This is the case when $\lim_{\tilde{r}\to +\infty}\tilde{r}\kappa_i=0$, where $\tilde{r}$ is the extrinsic distance to a point of $M$ and $\kappa_i$ are the principal curvatures. (2) If the $\kappa_i$ satisfy the decay conditions $|\kappa_i|\leq 1/\tilde{r}$, and strict inequality is achieved at some point $y\in M$, then there are no eigenvalues. We apply these results to minimal graphic and multigraphic hypersurfaces.Comment: 16 pages. v2. Final version: minor revisions, we add Proposition 3.2. Accepted for publication in the Annali di Matematica Pura ed Applicata, on the 05/03/201