On representations attached to semistable vector bundles on Mumford curves

G. Faltings konstruiert zu jedem semistabilen Vektorbündel vom Grade 0 über einer Mumfordkurve X über einem lokalen Zahlkörper eine Darstellung der Schottkygruppe von X. Dieses können M. v. d. Put und M. Reversat auf Mumfordkurven über nicht notwendigerweise diskret bewerteten nicht-Archimedischen Körpern verallgemeinern. Sei X eine glatte und projektive algebraische Kurve über einem lokalen Zahlkörper und bezeichne X' den Basiswechsel mit den p-adischen komplexen Zahlen. A. Werner und C. Deninger konstruieren einen etalen Paralleltransport für eine gewisse Klasse von Vektorbündeln auf X'. Diese Konstruktion führt zu einem Funktor von dieser Klasse in die Kategorie der stetigen Vektorraumdarstellungen der algebraischen Fundamentalgruppe von X'. Im Falle, daß X eine Mumfordkurve ist, beweisen wir, daß die genannten Konstruktionen für eine spezielle Klasse von semistabilen Vektorbündeln vom Grade 0 über X' isomorphe Darstellungen definieren

Burst Firing is a Neural Code in an Insect Auditory System

Various classes of neurons alternate between high-frequency discharges and silent intervals. This phenomenon is called burst firing. To analyze burst activity in an insect system, grasshopper auditory receptor neurons were recorded in vivo for several distinct stimulus types. The experimental data show that both burst probability and burst characteristics are strongly influenced by temporal modulations of the acoustic stimulus. The tendency to burst, hence, is not only determined by cell-intrinsic processes, but also by their interaction with the stimulus time course. We study this interaction quantitatively and observe that bursts containing a certain number of spikes occur shortly after stimulus deflections of specific intensity and duration. Our findings suggest a sparse neural code where information about the stimulus is represented by the number of spikes per burst, irrespective of the detailed interspike-interval structure within a burst. This compact representation cannot be interpreted as a firing-rate code. An information-theoretical analysis reveals that the number of spikes per burst reliably conveys information about the amplitude and duration of sound transients, whereas their time of occurrence is reflected by the burst onset time. The investigated neurons encode almost half of the total transmitted information in burst activity

Analysis of Mesoscopic Structured 2-Propanol/Water Mixtures Using Pressure Perturbation Calorimetry and Molecular Dynamic Simulation

In this paper we demonstrate the application of pressure perturbation calorimetry (PPC) to the characterization of 2-propanol/water mixtures. PPC of different 2-propanol/water mixtures provides two useful measurements: (i) the change in heat (ΔQ); and (ii) the [δC¯p/δp]T[δC¯p/δp]T value. The results demonstrate that the ΔQ values of the mixtures deviate from that expected for a random mixture, with a maximum at ~20–25 mol% 2-propanol. This coincides with the concentration at which molecular dynamics (MD) simulations show a maximum deviation from random distribution, and also the point at which alcohol–alcohol hydrogen bonds become dominant over alcohol–water hydrogen bonds. Furthermore, the [δC¯p/δp]T[δC¯p/δp]T value showed transitions at 2.5 mol% 2-propanol and at approximately 14 mol% 2-propanol. Below 2.5 mol% 2-propanol the values of [δC¯p/δp]T[δC¯p/δp]T are negative; this is indicative of the presence of isolated 2-propanol molecules surrounded by water molecules. Above 2.5 mol% 2-propanol [δC¯p/δp]T[δC¯p/δp]T rises, reaching a maximum at ~14 mol% corresponding to a point where mixed alcohol–water networks are thought to dominate. The values and trends identified by PPC show excellent agreement not only with those obtained from MD simulations but also with results in the literature derived using viscometry, THz spectroscopy, NMR and neutron diffraction

Occurrence of multipolar mitoses and association with Aurora-A/-B kinases and p53 mutations in aneuploid esophageal carcinoma cells

<p>Abstract</p> <p>Background</p> <p>Aurora kinases and loss of p53 function are implicated in the carcinogenesis of aneuploid esophageal cancers. Their association with occurrence of multipolar mitoses in the two main histotypes of aneuploid esophageal squamous cell carcinoma (ESCC) and Barrett's adenocarcinoma (BAC) remains unclear. Here, we investigated the occurrence of multipolar mitoses, Aurora-A/-B gene copy numbers and expression/activation as well as p53 alterations in aneuploid ESCC and BAC cancer cell lines.</p> <p>Results</p> <p>A control esophageal epithelial cell line (EPC-hTERT) had normal Aurora-A and -B gene copy numbers and expression, was p53 wild type and displayed bipolar mitoses. In contrast, both ESCC (OE21, Kyse-410) and BAC (OE33, OE19) cell lines were aneuploid and displayed elevated gene copy numbers of Aurora-A (chromosome 20 polysomy: OE21, OE33, OE19; gene amplification: Kyse-410) and Aurora-B (chromosome 17 polysomy: OE21, Kyse-410). Aurora-B gene copy numbers were not elevated in OE19 and OE33 cells despite chromosome 17 polysomy. Aurora-A expression and activity (Aurora-A/phosphoT288) was not directly linked to gene copy numbers and was highest in Kyse-410 and OE33 cells. Aurora-B expression and activity (Aurora-B/phosphoT232) was higher in OE21 and Kyse-410 than in OE33 and OE19 cells. The mitotic index was highest in OE21, followed by OE33 > OE19 > Kyse-410 and EPC-hTERT cells. Multipolar mitoses occurred with high frequency in OE33 (13.8 ± 4.2%), followed by OE21 (7.7 ± 5.0%) and Kyse-410 (6.3 ± 2.0%) cells. Single multipolar mitoses occurred in OE19 (1.0 ± 1.0%) cells. Distinct p53 mutations and p53 protein expression patterns were found in all esophageal cancer cell lines, but complete functional p53 inactivation occurred in OE21 and OE33 only.</p> <p>Conclusions</p> <p>High Aurora-A expression alone is not associated with overt multipolar mitoses in aneuploid ESCC and BAC cancer cells, as specifically shown here for OE21 and OE33 cells, respectively. Additional p53 loss of function mutations are necessary for this to occur, at least for invasive esophageal cancer cells. Further assessment of Aurora kinases and p53 interactions in cells or tissue specimens derived from non-invasive dysplasia (ESCC) or intestinal metaplasia (BAC) are necessary to disclose a potential causative role of Aurora kinases and p53 for development of aneuploid, invasive esophageal cancers.</p

Carey Young’s 'Palais de Justice'

The symposium for this issue comprises six responses to the video artwork Palais de Justice (2017) by artist Carey Young. The video presents a study of the life of Brussels’ vast, late-nineteenth-century court building. In Palais de Justice, Young presents ‘a legal system seemingly centered on, and perhaps controlled by women’. The respondents are Jeanne Gaakeer, Ruth Herz, Joan Kee, Linda Mulcahy, Jeremy Pilcher and Gary Watt. Jeanne Gaakeer and Ruth Herz have the distinction of being, not only internationally respected scholars, but also experienced judges. Jeanne Gaakeer is a judge practicing in the Netherlands and Ruth Herz was formerly a judge in Germany. The six responses are followed by the artist’s own reflections on her artwork and her response to the commentators’ responses. Joan Kee writes that ‘Young highlights access as a key entry point for thinking about the law. Who can avail themselves of the law? Who may enter (or exit) the courts? Who is excluded and by whose authority? The surreptitious looking and peering that define the experience of watching the film suggests how these questions deny ready answers’

Spatial representation of temporal information through spike timing dependent plasticity

We suggest a mechanism based on spike time dependent plasticity (STDP) of synapses to store, retrieve and predict temporal sequences. The mechanism is demonstrated in a model system of simplified integrate-and-fire type neurons densely connected by STDP synapses. All synapses are modified according to the so-called normal STDP rule observed in various real biological synapses. After conditioning through repeated input of a limited number of of temporal sequences the system is able to complete the temporal sequence upon receiving the input of a fraction of them. This is an example of effective unsupervised learning in an biologically realistic system. We investigate the dependence of learning success on entrainment time, system size and presence of noise. Possible applications include learning of motor sequences, recognition and prediction of temporal sensory information in the visual as well as the auditory system and late processing in the olfactory system of insects.Comment: 13 pages, 14 figures, completely revised and augmented versio

Probing the shape of atoms in real space

The structure of single atoms in real space is investigated by scanning tunneling microscopy. Very high resolution is possible by a dramatic reduction of the tip-sample distance. The instabilities which are normally encountered when using small tip-sample distances are avoided by oscillating the tip of the scanning tunneling microscope vertically with respect to the sample. The surface atoms of Si(111)-(7 x 7) with their well-known electronic configuration are used to image individual samarium, cobalt, iron and silicon atoms. The resulting images resemble the charge density corresponding to 4f, 3d and 3p atomic orbitals.Comment: Submitted to Phys. Rev. B, 17 pages, 7 figure

Exciton bimolecular annihilation dynamics in supramolecular nanostructures of conjugated oligomers

We present femtosecond transient absorption measurements on $\pi$-conjugated supramolecular assemblies in a high pump fluence regime. Oligo(\emph{p}-phenylenevinylene) monofunctionalized with ureido-\emph{s}-triazine (MOPV) self-assembles into chiral stacks in dodecane solution below 75$^{\circ}$C at a concentration of $4\times 10^{-4}$ M. We observe exciton bimolecular annihilation in MOPV stacks at high excitation fluence, indicated by the fluence-dependent decay of $1^1$B$_{u}$-exciton spectral signatures, and by the sub-linear fluence dependence of time- and wavelength-integrated photoluminescence (PL) intensity. These two characteristics are much less pronounced in MOPV solution where the phase equilibrium is shifted significantly away from supramolecular assembly, slightly below the transition temperature. A mesoscopic rate-equation model is applied to extract the bimolecular annihilation rate constant from the excitation fluence dependence of transient absorption and PL signals. The results demonstrate that the bimolecular annihilation rate is very high with a square-root dependence in time. The exciton annihilation results from a combination of fast exciton diffusion and resonance energy transfer. The supramolecular nanostructures studied here have electronic properties that are intermediate between molecular aggregates and polymeric semiconductors