A note on the lower bound for online strip packing

This note presents a lower bound of $3/2+\sqrt{33}/6 \approx 2.457$ on the competitive ratio for online strip packing. The instance construction we use to obtain the lower bound was first coined by Brown, Baker and Katseff (1980). Recently this instance construction is used to improve the lower bound in computer aided proofs. We derive the best possible lower bound that can be obtained with this instance construction

Ab-Initio Calculation of the Metal-Insulator Transition in Sodium rings and chains and in mixed Sodium-Lithium systems

We study how the Mott metal-insulator transition (MIT) is influenced when we deal with electrons with different angular momenta. For lithium we found an essential effect when we include $p$-orbitals in the description of the Hilbert space. We apply quantum-chemical methods to sodium rings and chains in order to investigate the analogue of a MIT, and how it is influenced by periodic and open boundaries. By changing the interatomic distance we analyse the character of the many-body wavefunction and the charge gap. In the second part we mimic a behaviour found in the ionic Hubbard model, where a transition from a band to a Mott insulator occurs. For that purpose we perform calculations for mixed sodium-lithium rings. In addition, we examine the question of bond alternation for the pure sodium system and the mixed sodium-lithium system, in order to determine under which conditions a Peierls distortion occurs.Comment: 8 pages, 7 figures, accepted Eur. J. Phys.

Membrane resistance and shunting inhibition: where biophysics meets state-dependent human neurophysiology

Activation of neurons not only changes their membrane potential and firing rate but, as a secondary action reduces membrane resistance. This loss of resistance, or increase of conductance, may be of central importance in non-invasive magnetic or electric stimulation of the human brain since electrical fields cause larger changes in transmembrane voltage in resting neurones with low membrane conductances than in active neurones with high conductance. This may explain why both the immediate and after-effects of brain stimulation are smaller or even reversed during voluntary activity compared to rest. Membrane conductance is also increased during shunting inhibition, which accompanies the classic GABAa IPSP. This short-circuits nearby EPSPs and is suggested here to contribute to the magnitude and time course of short latency intracortical inhibition (SICI) and facilitation (ICF). This article is protected by copyright. All rights reserved

Preconditioning of low-frequency repetitive transcranial magnetic stimulation with transcranial direct current stimulation: evidence for homeostatic plasticity in the human motor cortex

Recent experimental work in animals has emphasized the importance of homeostatic plasticity as a means of stabilizing the properties of neuronal circuits. Here, we report a phenomenon that indicates a homeostatic pattern of cortical plasticity in healthy human subjects. The experiments combined two techniques that can produce long-term effects on the excitability of corticospinal output neurons: transcranial direct current stimulation (TDCS) and repetitive transcranial magnetic stimulation (rTMS) of the left primary motor cortex. "Facilitatory preconditioning" with anodal TDCS caused a subsequent period of 1 Hz rTMS to reduce corticospinal excitability to below baseline levels for >20 min. Conversely, "inhibitory preconditioning" with cathodal TDCS resulted in 1 Hz rTMS increasing corticospinal excitability for at least 20 min. No changes in excitability occurred when 1 Hz rTMS was preceded by sham TDCS. Thus, changing the initial state of the motor cortex by a period of DC polarization reversed the conditioning effects of 1 Hz rTMS. These preconditioning effects of TDCS suggest the existence of a homeostatic mechanism in the human motor cortex that stabilizes corticospinal excitability within a physiologically useful range

Correlated ab-initio calculations for ground-state properties of II-VI semiconductors

Correlated ab-initio ground-state calculations, using relativistic energy-consistent pseudopotentials, are performed for six II-VI semiconductors. Valence ($ns,np$) correlations are evaluated using the coupled cluster approach with single and double excitations. An incremental scheme is applied based on correlation contributions of localized bond orbitals and of pairs and triples of such bonds. In view of the high polarity of the bonds in II-VI compounds, we examine both, ionic and covalent embedding schemes for the calculation of individual bond increments. Also, a partitioning of the correlation energy according to local ionic increments is tested. Core-valence ($nsp,(n-1)d$) correlation effects are taken into account via a core-polarization potential. Combining the results at the correlated level with corresponding Hartree-Fock data we recover about 94% of the experimental cohesive energies; lattice constants are accurate to \sim 1%; bulk moduli are on average 10% too large compared with experiment.Comment: 10 pages, twocolumn, RevTex, 3 figures, accepted Phys. Rev.

Possible role of backpropagating action potentials in corticospinal neurons in I-wave periodicity following a TMS pulse

A single pulse of TMS or direct electric stimulation over M1 causes repetitive synchronized firing of corticospinal tract (CST) neurons. Two mechanisms for the repetitive firing have been proposed: a cascade of synaptic inputs to the pyramidal neurons and a single reverberating circuit of interneurons. Here, we propose another possibility in which bursting of CST neurons is produced by dendritic Ca2+-spikes. Backpropagation of the initial action potential (I1-wave) from the soma interacts with synaptic input in the dendrites to initiate a dendritic calcium spike. These Ca2+-spikes produce a burst of somatic action potentials that starts about 1.5 ms after the initial discharge of the neuron, which may produce the later I-waves

APLIKASI MULTISENSOR DAN SMS GATEWAY PADA OTOMATISASI KANDANG KUCING DAN KELINCI (HARDWARE ELEKTRONIK DAN PEMROGRAMAN SISTEM KOMUNIKASI DENGAN HANDPHONE)

Short Messaging Service (SMS) is familiar to many people. Whenever each SMS can be sent, in addition to fast delivery of each SMS cost is also cheaper depending on provider and SMS delivery destination. A message facility at each mobile phone is easy and can be operated by many people even though a child. Begin as information technology will designed an application of sensors and SMS gateway on the cage pet of cat and rabbit. This system is expected to pet owners can find out the pets condition from eating, drinking, and sanitation system that has been shed know based in SMS Gateway. If the sensor on the back-up food or drinks detected low or medium level then the server system will send a message to the user. GSM modem using the media as the report related to the serial microcontroller. Keyword : SMS, AT Command, Comparator, Optical Sensor, Serial Communication