Polaronic slowing of fermionic impurities in lattice Bose-Fermi mixtures

We generalize the application of small polaron theory to ultracold gases of Ref. [\onlinecite{jaksch_njp1}] to the case of Bose-Fermi mixtures, where both components are loaded into an optical lattice. In a suitable range of parameters, the mixture can be described within a Bogoliubov approach in the presence of fermionic (dynamic) impurities and an effective description in terms of polarons applies. In the dilute limit of the slow impurity regime, the hopping of fermionic particles is exponentially renormalized due to polaron formation, regardless of the sign of the Bose-Fermi interaction. This should lead to clear experimental signatures of polaronic effects, once the regime of interest is reached. The validity of our approach is analyzed in the light of currently available experiments. We provide results for the hopping renormalization factor for different values of temperature, density and Bose-Fermi interaction for three-dimensional $^{87}\rm{Rb}-^{40}\rm{K}$ mixtures in optical lattice.Comment: 13 pages, 5 figure

Detection of GRB signals with Fluorescence Detectors

Gamma Ray Bursts are being searched in many ground based experiments detecting the high energy component (GeV $\div$ TeV energy range) of the photon bursts. In this paper, Fluorescence Detectors are considered as possible candidate devices for these searches. It is shown that the GRB photons induce fluorescence emission of UV photons on a wide range of their spectrum. The induced fluorescence flux is dominated by GRB photons from 0.1 to about 100 MeV and, once the extinction through the atmosphere is taken into account, it is distributed over a wide angular region. This flux can be detected through a monitor of the diffuse photon flux, provided that its maximum value exceeds a threshold value, that is primarily determined by the sky brightness above the detector. The feasibility of this search and the expected rates are discussed on the basis of the current GRB observations and the existing fluorescence detectors.Comment: 16 pages 9 eps figure

Low temperature deactivation of Ge heavily n-type doped by ion implantation and laser thermal annealing

International audienceHeavy doping of Ge is crucial for several advanced micro-and optoelectronic applications, but, at the same time, it still remains extremely challenging. Ge heavily n-type doped at a concentration of 1 X 10(20) cm(-3) by As ion implantation and melting laser thermal annealing (LTA) is shown here to be highly metastable. Upon post-LTA conventional thermal annealing As electrically deactivates already at 350 degrees C reaching an active concentration of similar to 4 x 10(19) cm(-3). No significant As diffusion is detected up to 450 degrees C, where the As activation decreases further to similar to 3 x 10(19) cm(-3). The reason for the observed detrimental deactivation was investigated by Atom Probe Tomography and in situ High Resolution X-Ray Diffraction measurements. In general, the thermal stability of heavily doped Ge layers needs to be carefully evaluated because, as shown here, deactivation might occur at very low temperatures, close to those required for low resistivity Ohmic contacting of n-type Ge

A novel Digital OTA topology with 66-dB DC Gain and 12.3-kHz Bandwidth

The paper introduces an enhanced digital OTA topology which allows increasing the DC gain thanks to the adoption of an inverter-based output stage. Moreover, a new equivalent small-signal model is proposed which allows to simplify the circuit analysis and paves the way to new frequency compensation strategies. Designed using a 28-nm standard CMOS technology and working at 0.3-V power supply, post-layout simulations show a 66-dB gain and a 12.3-kHz gain bandwidth product while driving a 250-pF capacitive load. As compared to other ultra-low-voltage OTAs in literature, an increase of small and large signal performance, respect to area occupation, equal to 4.6X and 1.5X, respectively, is obtained

Monte Carlo study of fermionic trions in a square lattice with harmonic confinement

We investigate the strong-coupling limit of a three-component Fermi mixture in an optical lattice with attractive interactions. In this limit bound states (trions) of the three components are formed. We derive an effective Hamiltonian for these composite fermions and show that it is asymptotically equivalent to an antiferromagnetic Ising model. By using Monte-Carlo simulations, we investigate the spatial arrangement of the trions and the formation of a trionic density wave (CDW), both in a homogeneous lattice and in the presence of an additional harmonic confinement. Depending on the strength of the confinement and on the temperature, we found several scenarios for the trionic distribution, including coexistence of disordered trions with CDW and band insulator phases. Our results show that, due to a proximity effect, staggered density modulations are induced in regions of the trap where they would not otherwise be present according to the local density approximation.Comment: 10 pages, 8 figure

Limitations on the principle of stationary phase when it is applied to tunneling analysis

Using a recently developed procedure - multiple wave packet decomposition - here we study the phase time formulation for tunneling/reflecting particles colliding with a potential barrier. To partially overcome the analytical difficulties which frequently arise when the stationary phase method is employed for deriving phase (tunneling) time expressions, we present a theoretical exercise involving a symmetrical collision between two identical wave packets and an one-dimensional rectangular potential barrier. Summing the amplitudes of the reflected and transmitted waves - using a method we call multiple peak decomposition - is shown to allow reconstruction of the scattered wave packets in a way which allows the stationary phase principle to be recovered.Comment: 17 pages, 2 figure

Optical Relative Calibration and Stability Monitoring for the Auger Fluorescence Detector

The stability of the fluorescence telescopes of the Pierre Auger Observatory is monitored with the optical relative calibration setup. Optical fibers distribute light pulses to three different diffuser groups within the optical system. The total charge per pulse is measured for each pixel and compared with reference calibration measurements. This allows monitoring the short and long term stability with respect of the relative timing between pixels and the relative gain for each pixel. The designs of the LED calibration unit (LCU) and of the Xenon flash lamp used for relative calibration, are described and their capabilities to monitor the stability of the telescope performances are studied. We report the analysis of relative calibration data recorded during 2004. Fluctuations in the relative calibration constants provide a measure of the stability of the FD.Comment: 4 pp. To appear in the proceedings of 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, 3-11 Aug 200

Monotherapy Trials of New Antiepileptic Drugs

A number of clinical trials that test the efficacy and safety of the newer antiepileptic drugs (AEDs) have recently been concluded. Two dose-response trials in inpatients with refractory partial seizures and outpatients with newly diagnosed partial epilepsy established the efficacy of gabapentin as monotherapy. Lamotrigine was found to have efficacy similar to that of phenytoin and carbamazepine (CBZ) and to be better tolerated than CBZ in patients with newly diagnosed epilepsy. It was also shown to have efficacy as monotherapy in partial seizures, based on the results of an active controlled trial, and in the treatment of absence seizures, based on the results of a responder-enriched study. Topiramate as monotherapy was found to be efficacious for treatment of partial-onset seizures, based on the results of a single-center dose-response trial. A dose-response trial that tested the efficacy of tiagabine monotherapy in patients with refractory partial epilepsy was uninformative. Oxcarbazepine was found to be safe and efficacious in four comparative trials in patients with newly diagnosed epilepsy as well as in one placebo-controlled inpatient trial in patients with refractory partial seizures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65625/1/j.1528-1157.1997.tb05201.x.pd