Super-lattice, rhombus, square, and hexagonal standing waves in magnetically driven ferrofluid surface

Standing wave patterns that arise on the surface of ferrofluids by (single frequency) parametric forcing with an ac magnetic field are investigated experimentally. Depending on the frequency and amplitude of the forcing, the system exhibits various patterns including a superlattice and subharmonic rhombuses as well as conventional harmonic hexagons and subharmonic squares. The superlattice arises in a bicritical situation where harmonic and subharmonic modes collide. The rhombic pattern arises due to the non-monotonic dispersion relation of a ferrofluid

Reversible lymphomagenesis in conditionally c-MYC expressing mice

It is well documented that deregulation of MYC leads to tumor development, yet many aspects of this process are only partially understood. We have established a transgenic mouse model in which c-MYC is conditionally expressed in lymphoid cells using the tetracycline-regulated system of gene regulation. Mice with continuously expressed transgenic c-MYC died of invasive T- or B-cell lymphomas within 4 months. Lymphomas developing in transgenic mice were c-MYC dependent since doxycycline treatment led to tumor regression. Using transplantation of established tumor cell lines labeled with GFP, we followed the fate of neoplastic cells in recipients upon MYC inactivation. This approach allowed us to elucidate both apoptosis and differentiation as mechanisms of tumor elimination. Comparative genomic hybridization (CGH) and FISH analyses were performed in order to analyze possible chromosomal aberrations induced by c-MYC. We observed that overexpression of c-MYC is sufficient to induce recurrent patterns of genomic instability. The main observation was a gain of genomic material that corresponded to chromosome 15 in several T-cell tumors, which could be identified as trisomy

Witnessing, remembering and testifying: why the past is special for human beings

The past is undeniably special for human beings. To a large extent, both individuals and collectives define themselves through history. Moreover, humans seem to have a special way of cognitively representing the past: episodic memory. As opposed to other ways of representing knowledge, remembering the past in episodic memory brings with it the ability to become a witness. Episodic memory allows us to determine what of our knowledge about the past comes from our own experience and thereby what parts of the past we can give testimony about. In this article, we aim to give an account of the special status of the past by asking why humans have developed the ability to give testimony about it. We argue that the past is special for human beings because it is regularly, and often principally, the only thing that can determine present social realities like commitments, entitlements, and obligations. Since the social effects of the past often do not leave physical traces behind, remembering the past and the ability to bear testimony it brings, is necessary in order to coordinate social realities with other individuals

Elevated Temperature Effects on the Shear Performance of a Cross-Laminated Timber (CLT) Wall-to-Floor Bracket Connection

Connections in mass timber structural systems dissipate energy and transfer lateral forces from mass timber elements such as shear walls and diaphragms, providing critical load paths. Cross-laminated timber (CLT) is a prominent mass timber material used to manufacture wall and floor assemblies. Fire performance research of CLT walls and floors has been abundant in recent years in an effort to address concerns about fires in tall wood buildings. Some fire-protected structural elements, including connections, may not be directly exposed to flames in a fire event but will experience elevated temperatures. There is limited research on elevated temperature performance of CLT connections, and consequentially a lack of full understanding of the fire performance of CLT structures. Therefore, a series of cyclic shear tests were conducted on a CLT wall-to-floor bracket connection assembly to characterize thermal degradation according to a matrix of 28 exposure duration-temperature combinations. The first study developed simple models to predict thermal degradation of two basic engineering parameters, peak strength and elastic stiffness. The second study used two different methods to develop force-displacement backbone models from the experimental hysteresis data. Results from both studies indicate significant thermal degradation of the connection performance at elevated temperatures ranging between 75 °C to 200 °C. This research is a step towards holistic evaluation of elevated temperature modeling of CLT structures

Making omnichannel an augmented reality: the current and future state of the art

Purpose—This paper explores the current and future role of Augmented Reality (AR) as an enabler of omnichannel experiences across the customer journey. To advance the conceptual understanding and managerial exploitation of AR, the paper synthesises current research, illustrating how a variety of current applications merge online and offline experiences, and provides a future research agenda to help advance the state of the art in AR. Design/methodology/approach—Drawing on situated cognition theorising as a guiding framework, the paper reviews previously published research and currently deployed applications to provide a roadmap for future research efforts on AR-enabled omnichannel experiences across the customer journey. Findings—AR offers myriad opportunities to provide customers with a seamless omnichannel journey, smoothing current obstacles, through a unique combination of i) embedded, ii) embodied, and iii) extended customer experiences. These three principles constitute the overarching value drivers of AR and offer coherent, theory-driven organising principles for managers and researchers alike. Originality/value—Current research has yet to provide a relevant, conceptually robust understanding of AR-enabled customer experiences. In light of the rapid development and widespread deployment of the technology, this paper provides an urgently needed framework for guiding the development of AR in an omnichannel context

Response of a ferrofluid to traveling-stripe forcing

We observe the dynamics of waves propagating on the surface of a ferrofluid under the influence of a spatially and temporarily modulated field. In particular, we excite plane waves by a travelling lamellar modulation of the magnetization. By this external driving both the wavelength and the propagation velocity of the waves can be controlled. The amplitude of the excited waves exhibits a resonance phenomenon similar to that of a forced harmonic oscillator. Its analysis reveals the dispersion relation of the free surface waves, from which the critical magnetic field for the onset of the Rosensweig instability can be extrapolated

Wave Number of Maximal Growth in Viscous Magnetic Fluids of Arbitrary Depth

An analytical method within the frame of linear stability theory is presented for the normal field instability in magnetic fluids. It allows to calculate the maximal growth rate and the corresponding wave number for any combination of thickness and viscosity of the fluid. Applying this method to magnetic fluids of finite depth, these results are quantitatively compared to the wave number of the transient pattern observed experimentally after a jump--like increase of the field. The wave number grows linearly with increasing induction where the theoretical and the experimental data agree well. Thereby a long-standing controversy about the behaviour of the wave number above the critical magnetic field is tackled.Comment: 19 pages, 15 figures, RevTex; revised version with a new figure and references added. submitted to Phys Rev

Parametrically Excited Surface Waves: Two-Frequency Forcing, Normal Form Symmetries, and Pattern Selection

Motivated by experimental observations of exotic standing wave patterns in the two-frequency Faraday experiment, we investigate the role of normal form symmetries in the pattern selection problem. With forcing frequency components in ratio m/n, where m and n are co-prime integers, there is the possibility that both harmonic and subharmonic waves may lose stability simultaneously, each with a different wavenumber. We focus on this situation and compare the case where the harmonic waves have a longer wavelength than the subharmonic waves with the case where the harmonic waves have a shorter wavelength. We show that in the former case a normal form transformation can be used to remove all quadratic terms from the amplitude equations governing the relevant resonant triad interactions. Thus the role of resonant triads in the pattern selection problem is greatly diminished in this situation. We verify our general results within the example of one-dimensional surface wave solutions of the Zhang-Vinals model of the two-frequency Faraday problem. In one-dimension, a 1:2 spatial resonance takes the place of a resonant triad in our investigation. We find that when the bifurcating modes are in this spatial resonance, it dramatically effects the bifurcation to subharmonic waves in the case of forcing frequencies are in ratio 1/2; this is consistent with the results of Zhang and Vinals. In sharp contrast, we find that when the forcing frequencies are in ratio 2/3, the bifurcation to (sub)harmonic waves is insensitive to the presence of another spatially-resonant bifurcating mode.Comment: 22 pages, 6 figures, late