The J_1-J_2 model revisited : Phenomenology of CuGeO_3

We present a mean field solution of the antiferromagnetic Heisenberg chain with nearest (J_1) and next to nearest neighbor (J_2) interactions. This solution provides a way to estimate the effects of frustration. We calculate the temperature-dependent spin-wave velocity, v_s(T) and discuss the possibility to determine the magnitude of frustration J_2/J_1 present in quasi 1D compounds from measurements of v_s(T). We compute the thermodynamic susceptibility at finite temperatures and compare it with the observed susceptibility of the spin-Peierls compound CuGeO_3. We also use the method to study the two-magnon Raman continuum observed in CuGeO_3 above the spin-Peierls transition.Comment: Phys. Rev.

East African cichlid fishes

Cichlid fishes are a very diverse and species-rich family of teleost fishes that inhabit lakes and rivers of India, Africa, and South and Central America. Research has largely focused on East African cichlids of the Rift Lakes Tanganyika, Malawi, and Victoria that constitute the biodiversity hotspots of cichlid fishes. Here, we give an overview of the study system, research questions, and methodologies. Research on cichlid fishes spans many disciplines including ecology, evolution, physiology, genetics, development, and behavioral biology. In this review, we focus on a range of organismal traits, including coloration phenotypes, trophic adaptations, appendages like fins and scales, sensory systems, sex, brains, and behaviors. Moreover, we discuss studies on cichlid phylogenies, plasticity, and general evolutionary patterns, ranging from convergence to speciation rates and the proximate and ultimate mechanisms underlying these processes. From a methodological viewpoint, the last decade has brought great advances in cichlid fish research, particularly through the advent of affordable deep sequencing and advances in genetic manipulations. The ability to integrate across traits and research disciplines, ranging from developmental biology to ecology and evolution, makes cichlid fishes a fascinating research system.Peer reviewe

New biostratigraphical data for the Burdigalian Montchaibeux Member at the locality Courrendlin-Solé (Canton of Jura, Switzerland)

Geological surveys were carried out in the Miocene deposits at the place known as “En Solé” east of the village Courrendlin (Delémont Basin, Canton of Jura, Switzerland). This resulted in the discovery of new Miocene small mammal assemblages. The association of the rodents Megacricetodon aff. collongensis and Melissiodon sp. allows to biochronostratigraphically correlate for the first time the so- called “Rote Mergel des Mont Chaibeux” representing the lower part of the Montchaibeux Member of the Bois de Raube Formation to the regional M. collongensis–Keramidomys interval zone (MN 4; early Miocene)

Demystifying Industrial Internet of Things start-ups – A multi-layer taxonomy

Described as a fundamental paradigm shift by researchers, the Industrial Internet of Things (IIoT) is credited with massive potential. In the context of emerging technologies, such as the IIoT, start-ups occupy a crucial role, as new technologies are often first commercialized by start-ups. Because of the rising importance of IIoT start-ups as drivers of industrial innovation, IIoT solutions demand deepened theoretical insights. As existing classification schemes in the industrial context do not sufficiently account for the ever more critical role of IIoT start-ups, we present a multi-layer taxonomy of IIoT start-up solutions. Building on state-of-the-art literature and a sample of 78 real-world IIoT start-up solutions, the taxonomy comprises ten dimensions and related characteristics structured along the three layers solution, data, and business model. The taxonomy contributes to the descriptive knowledge on the IIoT and enables researchers and practitioners to better understand IIoT start-up solutions

Spin-charge separation at small lengthscales in the 2D t-J model

We consider projected wavefunctions for the 2D $t-J$ model. For various wavefunctions, including correlated Fermi-liquid and Luttinger-type wavefunctions we present the static charge-charge and spin-spin structure factors. Comparison with recent results from a high-temperature expansion by Putikka {\it et al.} indicates spin-charge separation at small lengthscales.Comment: REVTEX, 5 pages, 5 figures hardcopies availabl

Strong Anisotropy in Liquid Water upon Librational Excitation using Terahertz Laser Fields

Tracking the excitation of water molecules in the homogeneous liquid is challenging due to the ultrafast dissipation of rotational excitation energy through the hydrogen-bonded network. Here we demonstrate strong transient anisotropy of liquid water through librational excitation using single-color pump-probe experiments at 12.3 THz. We deduce a third order response of chi^3 exceeding previously reported values in the optical range by three orders of magnitude. Using a theory that replaces the nonlinear response with a material response property amenable to molecular dynamics simulation, we show that the rotationally damped motion of water molecules in the librational band is resonantly driven at this frequency, which could explain the enhancement of the anisotropy in the liquid by the external Terahertz field. By addition of salt (MgSO4), the hydration water is instead dominated by the local electric field of the ions, resulting in reduction of water molecules that can be dynamically perturbed by THz pulses

Sacral nerve stimulation in patients with ileal pouch-anal anastomosis

Purpose: Functional results after proctocolectomy and ileal pouch-anal anastomosis (IPAA) are generally good. However, some patients suffer from high stool frequency or fecal incontinence. Sacral nerve stimulation (SNS) may represent a therapeutic alternative in these patients, but little is known about indication and results. The aim of this study was to evaluate incontinence after IPAA and demonstrate SNS feasibility in these patients. Methods: This retrospective study includes patients who received a SNS between 1993 and 2020 for increased stool frequency or fecal incontinence after proctocolectomy with IPAA for ulcerative colitis. Proctocolectomy was performed in a two- or three-step approach with ileostomy closure as the last step. Demographic, follow-up data and functional results were obtained from the hospital database. Results: SNS was performed in 23 patients. Median follow-up time after SNS was 6.5 years (min. 4.2-max. 8.8). Two patients were lost to follow-up. The median time from ileostomy closure to SNS implantation was 6 years (min. 0.5-max. 14.5). Continence after SNS improved in 16 patients (69%) with a median St. Marks score for anal incontinence of 19 (min. 4-max. 22) before SNS compared to 4 (0-10) after SNS placement (p = 0.012). In seven patients, SNS therapy was not successful. Conclusion: SNS implantation improves symptoms in over two-thirds of patients suffering from high stool frequency or fecal incontinence after proctocolectomy with IPAA. Awareness of the beneficial effects of SNS should be increased in physicians involved in the management of these patients