Mechanics reveals the biological trigger in wrinkly fingers

The final publication is available at Springer via http://dx.doi.org/10.1007/s10439-016-1764-6Fingertips wrinkle due to long exposure to water. The biological reason for this morphological change is unclear and still not fully understood. There are two main hypotheses for the underlying mechanism of fingertip wrinkling: the ‘shrink’ model (in which the wrinkling is driven by the contraction of the lower layers of skin, associated with the shrinking of the underlying vasculature), and the ‘swell’ model (in which the wrinkling is driven by the swelling of the upper layers of the skin, associated with osmosis). In reality, contraction of the lower layers of the skin and swelling of the upper layers will happen simultaneously. However, the relative importance of these two mechanisms to drive fingertip wrinkling also remains unclear. Simulating the swelling in the upper layers of skin alone, which is associated with neurological disorders, we found that wrinkles appeared above an increase of volume of ˜10%.˜10%. Therefore, the upper layers can not exceed this swelling level in order to not contradict in vivo observations in patients with such neurological disorders. Simulating the contraction of the lower layers of the skin alone, we found that the volume have to decrease a ˜20%˜20% to observe wrinkles. Furthermore, we found that the combined effect of both mechanisms leads to pronounced wrinkles even at low levels of swelling and contraction when individually they do not. This latter results indicates that the collaborative effect of both hypothesis are needed to induce wrinkles in the fingertips. Our results demonstrate how models from continuum mechanics can be successfully applied to testing hypotheses for the mechanisms that underly fingertip wrinkling, and how these effects can be quantified.Peer ReviewedPostprint (published version

Cardiovascular correlates of motor vehicle accident related posttraumatic stress disorder and its successful treatment

Springer Open Choice ArticlePersons with posttraumatic stress disorder (PTSD) have been shown to display elevated baseline cardiovascular activity and a heightened physiological reactivity to trauma-related stimuli. Study 1 examined differences in baseline heart rate (HR) and HR reactivity in 68 survivors of motor vehicle accidents (MVAs) and healthy controls without MVA. MVA survivors with PTSD (n=26), subsyndromal PTSD (n=22), traumatized controls without PTSD (non-PTSD with MVA, n=20) and healthy controls without MVA (HC, n=27) underwent measurement of HR during baseline and exposure to a neutral, positive, negative, and trauma-related picture. PTSD patients showed elevated baseline HR and increased HR reactivity only during exposure to the trauma-related picture. Study 2 investigated whether the elevated physiological responses observed in Study 1 normalized after cognitive behavioral therapy (CBT). We conducted a randomized, controlled treatment trial comparing CBT (n=17) to a Wait-list condition (WLC, n=18). Results showed a greater decrease in HR reactivity for CBT than for WLC. The change in HR reactivity was associated with clinical improvement.This study was supported by the Deutsche Forschungsgemeinschaft (KA 1476/3

Excitations of attractive 1-D bosons: Binding vs. fermionization

The stationary states of few bosons in a one-dimensional harmonic trap are investigated throughout the crossover from weak to strongly attractive interactions. For sufficient attraction, three different classes of states emerge: (i) N-body bound states, (ii) bound states of smaller fragments, and (iii) gas-like states that fermionize, that is, map to ideal fermions in the limit of infinite attraction. The two-body correlations and momentum spectra characteristic of the three classes are discussed, and the results are illustrated using the soluble two-particle model.Comment: 7 pages, 5 figure

Hypertriglyceridaemia in adolescents may have serious complications

Acute pancreatitis is an often-overlooked cause of acute abdominal pain in children and adolescents. Severe hypertriglyceridaemia is an important cause of recurrent acute pancreatitis. Monogenic causes of hypertriglyceridaemia, such as familial chylomicronaemia caused by lipoprotein lipase deficiency, are more frequently encountered in children and adolescents, but remain rare. Polygenic hypertriglyceridaemia is more common, but may require a precipitant before manifesting. With the global increase in obesity and type 2 diabetes, secondary causes of hypertriglyceridaemia in children and adolescents are increasing. We report two cases of severe hypertriglyceridaemia and pancreatitis in adolescent females. Hypertriglyceridaemia improved markedly with restriction of dietary fat. An inhibitor to lipoprotein lipase was found to be the cause in one patient, while in the other limited genetic investigation excluded chylomicronaemia owing to deficiency of lipoprotein lipase, its activators and processing proteins

Three strongly correlated charged bosons in a one-dimensional harmonic trap: natural orbital occupancies

We study a one-dimensional system composed of three charged bosons confined in an external harmonic potential. More precisely, we investigate the ground-state correlation properties of the system, paying particular attention to the strong-interaction limit. We explain for the first time the nature of the degeneracies appearing in this limit in the spectrum of the reduced density matrix. An explicit representation of the asymptotic natural orbitals and their occupancies is given in terms of some integral equations.Comment: 6 pages, 4 figures, To appear in European Physical Journal

Binding between two-component bosons in one dimension

We investigate the ground state of one-dimensional few-atom Bose-Bose mixtures under harmonic confinement throughout the crossover from weak to strong inter-species attraction. The calculations are based on the numerically exact multi-configurational time-dependent Hartree method. For repulsive components we detail the condition for the formation of a molecular Tonks-Girardeau gas in the regime of intermediate inter-species interactions, and the formation of a molecular condensate for stronger coupling. Beyond a critical inter-species attraction, the system collapses to an overall bound state. Different pathways emerge for unequal particle numbers and intra-species interactions. In particular, for mixtures with one attractive component, this species can be viewed as an effective potential dimple in the trap center for the other, repulsive component.Comment: 10 pages, 10 figure

N-Electron Giant Dipole States in Crossed Electric and Magnetic Fields

Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields are investigated. Stationary configurations corresponding to a highly symmetric arrangement of the electrons on a decentered circle are derived, and a normal-mode and stability analysis are performed. A classification of the various modes, which are dominated by the magnetic field or the Coulomb interactions, is provided. Based on the MCTDH approach, we carry out a six-dimensional wave-packet dynamical study for the two-electron resonances, yielding in particular lifetimes of more than 0.1 $\mu$s for strong electric fields.Comment: 37 pages, 22 figs. (plus subfigures

Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields

Multi-electron giant dipole resonances of atoms in crossed electric and magnetic fields are investigated. Stationary configurations corresponding to a highly symmetric arrangement of the electrons on a decentered circle are derived, and a normal-mode stability analysis is performed. A classification of the various modes, which are dominated either by the magnetic or Coulomb interactions, is provided. A six-dimensional wave-packet dynamical study, based on the MCTDH approach, is accomplished for the two-electron resonances, yielding in particular lifetimes of more than 0.1 $\mu$s for strong electric fields.Comment: 7 pages, 3 figure