Magnetic phases of one-dimensional lattices with 2 to 4 fermions per site

We study the spectral and magnetic properties of one-dimensional lattices filled with 2 to 4 fermions (with spin 1/2) per lattice site. We use a generalized Hubbard model that takes account all interactions on a lattice site, and solve the many-particle problem by exact diagonalization. We find an intriguing magnetic phase diagram which includes ferromagnetism, spin-one Heisenberg antiferromagnetism, and orbital antiferromagnetism.Comment: 8 pages, 6 figure

Density Functional Theory of Multicomponent Quantum Dots

Quantum dots with conduction electrons or holes originating from several bands are considered. We assume the particles are confined in a harmonic potential and assume the electrons (or holes) belonging to different bands to be different types of fermions with isotropic effective masses. The density functional method with the local density approximation is used. The increased number of internal (Kohn-Sham) states leads to a generalisation of Hund's first rule at high densities. At low densitites the formation of Wigner molecules is favored by the increased internal freedom.Comment: 11 pages, 5 figure

With software updates, Tesla upends product life cycle in the car industry

With this system, any product can be open-ended and continuously in the making, argue Antti Lyyra and Kari Koskine

Physics of Earth’s Radiation Belts

This open access book serves as textbook on the physics of the radiation belts surrounding the Earth. Discovered in 1958 the famous Van Allen Radiation belts were among the first scientific discoveries of the Space Age. Throughout the following decades the belts have been under intensive investigation motivated by the risks of radiation hazards they expose to electronics and humans on spacecraft in the Earth’s inner magnetosphere. This textbook teaches the field from basic theory of particles and plasmas to observations which culminated in the highly successful Van Allen Probes Mission of NASA in 2012-2019. Using numerous data examples the authors explain the relevant concepts and theoretical background of the extremely complex radiation belt region, with the emphasis on giving a comprehensive and coherent understanding of physical processes affecting the dynamics of the belts. The target audience are doctoral students and young researchers who wish to learn about the physical processes underlying the acceleration, transport and loss of the radiation belt particles in the perspective of the state-of-the-art observations

Magnetism in one-dimensional quantum dot arrays

We employ the density functional Kohn-Sham method in the local spin-density approximation to study the electronic structure and magnetism of quasi one-dimensional periodic arrays of few-electron quantum dots. At small values of the lattice constant, the single dots overlap, forming a non-magnetic quantum wire with nearly homogenous density. As the confinement perpendicular to the wire is increased, i.e. as the wire is squeezed to become more one-dimensional, it undergoes a spin-Peierls transition. Magnetism sets in as the quantum dots are placed further apart. It is determined by the electronic shell filling of the individual quantum dots. At larger values of the lattice constant, the band structure for odd numbers of electrons per dot indicates that the array could support spin-polarized transport and therefore act as a spin filter.Comment: 11 pages, 6 figure

Contrast-Enhanced Ultrasound for identifying circulatory complications after liver transplants in children

Our main goal with this study was to share our off-label experience with CEUS for identifying circulatory complications after liver transplantation in children. A total of 74 CEUS examinations performed on 34 pediatric patients who underwent a liver transplant were retrospectively included. About 53% of the examinations were performed on children 2 years old or younger. About 82% of the examinations were performed within 30 days from the transplant. About 62% of patients were transplanted due to a cholestatic disease, 11% due to a metabolic disease, 8% were re-transplanted due to graft failure, and 19% was due to other conditions. BA was the most common reason for transplantation and represented 38% of patients. About 38% of the transplantations were performed with whole grafts from DD, 40% with split liver grafts, and 22% with left lateral segments from LD. For diagnosing arterial circulatory complications, the PPV was 80%. For diagnosing portal vein circulatory complications, the PPV was 66.7%. NPV was 100%. In 28% of the examinations, the examiner could not visualize the normal arterial blood flow without CEUS. CEUS is a non-invasive and safe imaging technique that seems valuable in these patients and further efforts are needed to license its use in the post-transplant setting.NoneAccepte

Contrast-enhanced ultrasound using sulfur hexafluoride is safe in the pediatric setting

Background: Contrast-enhanced ultrasound (CEUS) by using sulfur hexafluoride microbubbles is not licensed for use in children, but its off-label use is widespread. Purpose: To outline our experience with the off-label use of CEUS in children, specifically with regards to safety. Material and Methods: We retrieved all records of 10681 patients aged under 18 years who underwent abdominal ultrasound (US) January 2004 to December 2014. We then identified those who underwent an abdominal CEUS using sulfur hexafluoride microbubbles. Electronic patient charts were used to verify the indication for contrast agent, dose, possible adverse effects as well as information on patient height, weight, and age. Results: We identified 173 patients (mean age, 11 years; range, 0.1–18 years) who underwent a total of 287 CEUS exams. Of all exams, 46% were performed on the native liver, 31% on a transplanted liver, and 23% on other organs. The indications were “circulatory status?” (40%), “characterization of lesion?” (40%), and miscellaneous (20%). Mean contrast dose was 2.3 mL (range, 0.1–8.1 mL). No immediate adverse effects were recorded. One patient experienced itching the day after, but this was considered to be a reaction to concomitantly administered fentanyl. Conclusion: The use of intravenous ultrasound contrast seems safe in patients aged under 18 years and our results do not support the current practice to restrict the use of CEUS in children.NoneAccepte