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In magnetomotive ultrasound imaging, the tissue displacement due to a magnetic force on embedded magnetic nanoparticles is measured. It was previously shown that the nanoparticle contrast agent exhibits a non-linear magnetization characteristic, which is also reflected in the magnetomotive force. However, this non-linearity was rarely taken into account for the application. Here, the implications
Coherent radiation from a relativistic electron beam is a valuable way to overcome the present limitations of conventional lasers and synchrotron radiation light sources. The typical scheme has electrons, directly from a linac, in a single-pass interaction with a laser pulse in the presence of a static undulator magnetic field. We demonstrate that a storage-ring free-electron laser can also achiev
In this paper, we review the physics of harmonic generation in gases and production of short attosecond pulses. Different methods to ensure a sufficient degree of synchronization, for example, selecting the cutoff region of the spectrum or compressing of attosecond pulses with apertures and metallic filters are presented
High-order harmonic generation (HHG) in gases leads to short-pulse extreme ultraviolet (XUV) radiation that is useful in a number of applications, such as attosecond science and nanoscale imaging. However, this process depends on many parameters, and there is still no consensus on how to choose the target geometry to optimize the source efficiency. We review the physics of HHG with emphasis on the
Surface interactions of water with nano-TiO2 and structurally related group IV metal dioxide nanoparticles have been investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The investigated clusters include 46 and 92 unit models of TiO2 (i.e., (TiO2)(46) and (TiO2)(92)) of the three low-energy polymorphs of TiO2: anatase, rutile, and brookite. The investiga
Actigraf Matdagbok Tånaglar Blodprov Mjölktand Urin- och avföringsprover Intervju och Frågeformulär Näsprov Vattenprov
https://www.teddy.lu.se/att-vara-med-i-teddy/material-som-samlas-till-teddy-studien - 2026-10-01
Forskningsadministrativ chef, avdelningen för fasta tillståndets fysik Kontaktinformation E-post: anneli [dot] lofgren [at] fysik [dot] lu [dot] se Telefon: +46 46 222 84 99 Mobil: +46 76 112 84 99Organisation Fasta tillståndets fysik Besöksadress: Professorsgatan 1, Lund Rumsnummer: Q282 Hämtställe: 14 WebbplatsAnneli Löfgrens profil i Lunds universitets forskningsportalAndra roller Biträdande av
https://www.fysik.lu.se/anneli-lofgren - 2026-10-02
We study the role of propagation effects in high-order harmonic-generation experiments. The phase-matching integrals are calculated in the weak-field limit by taking into account the dispersion of the rare-gas medium at each harmonic frequency and the absorption of the harmonics. The refractive indices of the rare gases are deduced from a calculation of the dynamic polarizabilities within the fram
We calculate the phase property of the reflection coefficient in two-terminal structures using a lattice tight-binding model. It is seen that, provided that there exist two coherent reflection paths, the reflection probability can be zero for certain electron energies. At these energies, the phase of the reflection coefficient shift abruptly by $pi$. Next, we study the reflection and transmissio
In semiconductor nanocrystals, called quantum dots (QD), electronic transition energies, phonon frequencies, and electron-phonon coupling strengths are all reported to depend on the size of the crystals. The size dependencies of the transition energies and the mode frequencies are well characterized and understood. At the same time, the electron-phonon coupling dependence on size is controversial-
We consider an autonomous implementation of Maxwell's demon in a quantum dot architecture acting on a system without changing its number of particles or its energy. As in the original thought experiment, only the second law of thermodynamics is seemingly violated when disregarding the demon. The autonomous architecture allows us to compare descriptions in terms of information to a more traditional
Fundamental symmetries in thermoelectric quantum transport, beyond Onsagers relations, were predicted two decades ago but have to date not been observed in experiments. Recent works have predicted the symmetries to be sensitive to energy-dependent, inelastic scattering, raising the question whether they exist in practice. Here, we answer this question affirmatively by experimentally verifying the
heory predicts that electrons emitted from independent electron sources (metallic contacts) can nevertheless interfere. This interference is manifest in an exchange contribution to the shot noise correlation of currents at different contacts of a mesoscopic conductor. A geometry has been proposed in which second order (single particle) interference due to superposition of amplitudes is absent but
The theory of nonequilibrium Green functions allows for a quantitative modeling of quantum cascade lasers. Explicit results are given for transport in a THz-laser and gain in a IR-Laser
Different screening models in quantum cascade lasers are compared by calculating the contribution of intrasubband impurity scattering to the optical linewidth as a function of temperature. We find a strong impact of impurity scattering, which increases substantially with temperature. A simple isotropic bulk screening model works well if the screening length is of the order of or longer than the pe
Abstract: We study oscillations in quantum cascade lasers due to traveling electric field domains, which are observed both in simulations and experiments. These oscillations occur in a range of negative differential resistance and we clarify the condition determining whether the boundary between domains of different electric field can become stationary. Graphical abstract: [Figure not available: s
We show that mid-infrared transmission spectroscopy of a quantum cascade laser provides clear-cut information on changes in charge location at different bias. Theoretical simulations of the evolution of the gain/absorption spectrum for a lambda~7.4 µm InGaAs/AlInAs/InP quantum cascade laser have been compared with the experimental findings. Transfer of electrons between the ground states in the ac
