Laminar firing and membrane dynamics in four visual areas exposed to two objects moving to occlusion

It is not known how visual cortical neurons react to several moving objects and how their firing to the motion of one object is affected by neurons firing to another moving object. Here we combine imaging of voltage sensitive dye (VSD) signals, reflecting the population membrane potential from ferret visual areas 17, 18, 19, and 21, with laminar recordings of multiunit activity, (MUA), when two bars moved toward each other in the visual field, occluded one another, and continued on in opposite directions. Two zones of peak MUA, mapping the bars' motion, moved toward each other along the area 17/18 border, which in the ferret maps the vertical meridian of the field of view. This was reflected also in the VSD signal, at both the 17/18 border as well as at the 19/21 border with a short delay. After some 125 ms at the area 19/21 border, the VSD signal increased and became elongated in the direction of motion in front of both of the moving representations. This was directly followed by the phase of the signal reversing and travelling back from the 19/21 border toward the 17/18 border, seemingly without respect for retinotopic boundaries, where it arrived at 150 ms after stimulus onset. At this point the VSD signal in front of the moving bar representations along the 17/18 border also increased and became elongated in the direction of object motion; the signal now being the linear sum of what has been observed in response to single moving bars. When the neuronal populations representing the bars were some 600 μm apart on the cortex, the dye signal and laminar MUA decreased strongly, with the MUA scaling to that of a single bar during occlusion. Despite a short rebound of the dye signal and MUA, the MUA after the occlusion was significantly depressed. The interactions between the neuronal populations mapping the bars' position, and the neurons in between these populations were, apart from 19/21 to 17/18 interaction, mainly lateral-horizontal; first excitatory and inducing firing at the site of future occlusion, then inhibitory just prior to occlusion. After occlusion the neurons that had fired already to the first bar showed delayed and prolonged inhibition in response to the second bar. Thus, the interactions that were particular to the occlusion condition in these experiments were local and inhibitory at short cortical range, and delayed and inhibitory after the occlusion when the bars moved further apart

Directed Chaotic Transport in Hamiltonian Ratchets

We present a comprehensive account of directed transport in one-dimensional Hamiltonian systems with spatial and temporal periodicity. They can be considered as Hamiltonian ratchets in the sense that ensembles of particles can show directed ballistic transport in the absence of an average force. We discuss general conditions for such directed transport, like a mixed classical phase space, and elucidate a sum rule that relates the contributions of different phase-space components to transport with each other. We show that regular ratchet transport can be directed against an external potential gradient while chaotic ballistic transport is restricted to unbiased systems. For quantized Hamiltonian ratchets we study transport in terms of the evolution of wave packets and derive a semiclassical expression for the distribution of level velocities which encode the quantum transport in the Floquet band spectra. We discuss the role of dynamical tunneling between transporting islands and the chaotic sea and the breakdown of transport in quantum ratchets with broken spatial periodicity.Comment: 22 page

Unequal mass binary neutron star simulations with neutrino transport: Ejecta and neutrino emission

We present 12 new simulations of unequal mass neutron star mergers. The simulations are performed with the SpEC code, and utilize nuclear-theory-based equations of state and a two-moment gray neutrino transport scheme with an improved energy estimate based on evolving the number density. We model the neutron stars with the SFHo, LS220, and DD2 equations of state (EOS) and we study the neutrino and matter emission of all 12 models to search for robust trends between binary parameters and emission characteristics. We find that the total mass of the dynamical ejecta exceeds 0.01  M⊙ only for SFHo with weak dependence on the mass ratio across all models. We find that the ejecta have a broad electron fraction (Y_e) distribution (≈0.06–0.48), with mean 0.2. Y_e increases with neutrino irradiation over time, but decreases with increasing binary asymmetry. We also find that the models have ejecta with a broad asymptotic velocity distribution (≈0.05–0.7c). The average velocity lies in the range 0.2c−0.3c and decreases with binary asymmetry. Furthermore, we find that disk mass increases with binary asymmetry and stiffness of the EOS. The Y_e of the disk increases with softness of the EOS. The strongest neutrino emission occurs for the models with soft EOS. For (anti) electron neutrinos we find no significant dependence of the magnitude or angular distribution or neutrino luminosity with mass ratio. The heavier neutrino species have a luminosity dependence on mass ratio but an angular distribution which does not change with mass ratio

Thermodynamic Scaling of the Viscosity of Van Der Waals, H-Bonded, and Ionic Liquids

Viscosities and their temperature, T, and volume, V, dependences are reported for 7 molecular liquids and polymers. In combination with literature viscosity data for 5 other liquids, we show that the superpositioning of relaxation times for various glass-forming materials when expressed as a function of TV^g, where the exponent g is a material constant, can be extended to the viscosity. The latter is usually measured to higher temperatures than the corresponding relaxation times, demonstrating the validity of the thermodynamic scaling throughout the supercooled and higher T regimes. The value of g for a given liquid principally reflects the magnitude of the intermolecular forces (e.g., steepness of the repulsive potential); thus, we find decreasing g in going from van der Waals fluids to ionic liquids. For strongly H-bonded materials, such as low molecular weight polypropylene glycol and water, the superpositioning fails, due to the non-trivial change of chemical structure (degree of H-bonding) with thermodynamic conditions.Comment: 16 pages 7 figure

Pancreatoduodenectomy with or without Pyloric Preservation: A Clinical Outcomes Comparison

Pyloric preservation (PP) can frequently be performed at the time of pancreatoduodenectomy (PD), although some reports have linked it to inferior outcomes such as delayed gastric emptying (DGE). We reviewed records in a single-surgeon practice to assess outcomes after PD with or without PP. There were 133 PDs with 67 PPPDs and 66 PDs. Differences between PPPD and PD groups included cancer frequency, tumor size, OR time, blood loss, and transfusion rate. However, postoperative morbidity rate and grade, NG tube duration, NGT reinsertion rate, DGE, and length of stay were similar. There was no difference among patients with pancreatic cancer. No detrimental outcomes are associated with pyloric preservation during PD. Greater intraoperative ease and superior survival in the PPPD group are due to confounding, tumor-related variables in this nonrandomized comparison. Nevertheless, we intend to continue the use of PP with our technique in patients who meet the stated criteria

Pengaruh penambahan bentangan horizontal pada pancing dasar terhadap hasil tangkapan ikan-ikan karang

Disain pancing dasar atau “ba lot” buatan nelayan yang digunakan untuk menangkap ikan karang, pada saat pelaksanaan pengoperasian, ternyata terdapat masalah pada tali cabang yaitu: tali cabang terlalu dekat dengan tali utama yang mengakibatkan tali cabang mudah terbelit pada tali utama saat pancing diulurkan maupun dinaikkan. Untuk meningkatkan efisiensi dan efektifitas alat tangkap, maka harus dilakukan penelitian demi pengembangannya dengan perbaikan desain atau modifikasi pancing dasar buatan nelayan tersebut. Tetapi informasi ilmiah tentang aplikasinya belum tersedia. Penelitian ini bertujuan untuk mempelajari pengaruh penambahan bentangan horizontal pada pancing dasar terhadap hasil tangkapan ikan-ikan karang dan mengidentifikasi jenis-jenis ikan karang yang tertangkap. Penelitian ini dilakukan di perairan pantai Teluk Manado, Kecamatan Maasing; dengan mengikuti metode eksperimental. Teknik pengumpulan data dilakukan dengan cara mengoperasikan 6 unit alat tangkap pancing dasar (3 unit pancing dasar buatan nelayan dan 3 unit pancing dasar modifikasi dengan memberi bentangan horizontal) secara bersamaan selama 10 trip. Data tangkapan dianalisis dengan uji-t berpasangan. Hasil tangkapan yang diperoleh selama pengoperasian pancing dasar adalah berjumlah 80, dimana 30 ekor tertangkap dengan pancing dasar buatan nelayan dan 50 ekor lainnya tertangkap dengan pancing dasar modifikasi yang teridentifikasi yaitu kurisi (Etelis radiosus), kurisi bali (Pristipomoides filamentosus), kuwe (Caranx ignobilis), kerapu (Epinephelus sp.) dan cucut (Carcharhinus falciformis

Confined Quantum Time of Arrivals

We show that formulating the quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding states that evolve to unitarily collapse at a given point at a definite time. For the spatially confined particle, we show that the problem admits a solution in the form of an eigenvalue problem of a compact and self-adjoint time of arrival operator derived by a quantization of the classical time of arrival, which is canonically conjugate with the Hamiltonian in closed subspace of the Hilbert space.Comment: Figures are now include

Low mass binary neutron star mergers : gravitational waves and neutrino emission

Neutron star mergers are among the most promising sources of gravitational waves for advanced ground-based detectors. These mergers are also expected to power bright electromagnetic signals, in the form of short gamma-ray bursts, infrared/optical transients, and radio emission. Simulations of these mergers with fully general relativistic codes are critical to understand the merger and post-merger gravitational wave signals and their neutrinos and electromagnetic counterparts. In this paper, we employ the SpEC code to simulate the merger of low-mass neutron star binaries (two $1.2M_\odot$ neutron stars) for a set of three nuclear-theory based, finite temperature equations of state. We show that the frequency peaks of the post-merger gravitational wave signal are in good agreement with predictions obtained from simulations using a simpler treatment of gravity. We find, however, that only the fundamental mode of the remnant is excited for long periods of time: emission at the secondary peaks is damped on a millisecond timescale in the simulated binaries. For such low-mass systems, the remnant is a massive neutron star which, depending on the equation of state, is either permanently stable or long-lived. We observe strong excitations of l=2, m=2 modes, both in the massive neutron star and in the form of hot, shocked tidal arms in the surrounding accretion torus. We estimate the neutrino emission of the remnant using a neutrino leakage scheme and, in one case, compare these results with a gray two-moment neutrino transport scheme. We confirm the complex geometry of the neutrino emission, also observed in previous simulations with neutrino leakage, and show explicitly the presence of important differences in the neutrino luminosity, disk composition, and outflow properties between the neutrino leakage and transport schemes.Comment: Accepted by PRD; 23 pages; 24 figures; 4 table