778 research outputs found
Breaking the PPSZ Barrier for Unique 3-SAT
The PPSZ algorithm by Paturi, Pudl\'ak, Saks, and Zane (FOCS 1998) is the
fastest known algorithm for (Promise) Unique k-SAT. We give an improved
algorithm with exponentially faster bounds for Unique 3-SAT.
For uniquely satisfiable 3-CNF formulas, we do the following case
distinction: We call a clause critical if exactly one literal is satisfied by
the unique satisfying assignment. If a formula has many critical clauses, we
observe that PPSZ by itself is already faster. If there are only few clauses
allover, we use an algorithm by Wahlstr\"om (ESA 2005) that is faster than PPSZ
in this case. Otherwise we have a formula with few critical and many
non-critical clauses. Non-critical clauses have at least two literals
satisfied; we show how to exploit this to improve PPSZ.Comment: 13 pages; major revision with simplified algorithm but slightly worse
constant
A novel experiment searching for the lepton flavour violating decay mu -> eee
Since the discovery of neutrino oscillations it is known that lepton flavour
is not conserved. Lepton flavour violating processes in the charged lepton
sector have so far however eluded detection; as they are heavily suppressed in
the standard model of particle physics, an observation would be a clear signal
for new physics and help to understand the source of neutrino masses and CP
violation. We propose a novel experiment searching for the decay mu -> eee with
the aim of ultimately reaching a sensitivity of 10^-16, an improvement by four
orders of magnitude compared to previous experiments. The technologies enabling
this step are thin high-voltage monolithic active pixel sensors for precise
tracking at high rates with a minimum of material and scintillating fibres for
high resolution time measurements.Comment: 4 pages, 3 figures, contribution to NUFACT 11, XIIIth International
Workshop on Neutrino Factories, Super beams and Beta beams, 1-6 August 2011,
CERN and University of Genev
Multi-Gigabit Wireless data transfer at 60 GHz
In this paper we describe the status of the first prototype of the 60 GHz
wireless Multi-gigabit data transfer topology currently under development at
University of Heidelberg using IBM 130 nm SiGe HBT BiCMOS technology. The 60
GHz band is very suitable for high data rate and short distance applications as
for example needed in the HEP experments. The wireless transceiver consist of a
transmitter and a receiver. The transmitter includes an On-Off Keying (OOK)
modulator, an Local Oscillator (LO), a Power Amplifier (PA) and a BandPass
Filter (BPF). The receiver part is composed of a BandPass- Filter (BPF), a Low
Noise Amplifier (LNA), a double balanced down-convert Gilbert mixer, a Local
Oscillator (LO), then a BPF to remove the mixer introduced noise, an
Intermediate Amplifier (IF), an On-Off Keying demodulator and a limiting
amplifier. The first prototype would be able to handle a data-rate of about 3.5
Gbps over a link distance of 1 m. The first simulations of the LNA show that a
Noise Figure (NF) of 5 dB, a power gain of 21 dB at 60 GHz with a 3 dB
bandwidth of more than 20 GHz with a power consumption 11 mW are achieved.
Simulations of the PA show an output referred compression point P1dB of 19.7 dB
at 60 GHz.Comment: Proceedings of the WIT201
Hybridization in East African swarm-raiding army ants
<p>Abstract</p> <p>Background</p> <p>Hybridization can have complex effects on evolutionary dynamics in ants because of the combination of haplodiploid sex-determination and eusociality. While hybrid non-reproductive workers have been found in a range of species, examples of gene-flow via hybrid queens and males are rare. We studied hybridization in East African army ants (<it>Dorylus </it>subgenus <it>Anomma</it>) using morphology, mitochondrial DNA sequences, and nuclear microsatellites.</p> <p>Results</p> <p>While the mitochondrial phylogeny had a strong geographic signal, different species were not recovered as monophyletic. At our main study site at Kakamega Forest, a mitochondrial haplotype was shared between a "<it>Dorylus molestus</it>-like" and a "<it>Dorylus wilverthi</it>-like" form. This pattern is best explained by introgression following hybridization between <it>D. molestus </it>and <it>D. wilverthi</it>. Microsatellite data from workers showed that the two morphological forms correspond to two distinct genetic clusters, with a significant proportion of individuals being classified as hybrids.</p> <p>Conclusions</p> <p>We conclude that hybridization and gene-flow between the two army ant species <it>D. molestus </it>and <it>D. wilverthi </it>has occurred, and that mating between the two forms continues to regularly produce hybrid workers. Hybridization is particularly surprising in army ants because workers have control over which males are allowed to mate with a young virgin queen inside the colony.</p
Irradiation study of a fully monolithic HV-CMOS pixel sensor design in AMS 180 nm
High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) based on the 180 nm
HV-CMOS process have been proposed to realize thin, fast and highly integrated
pixel sensors. The MuPix7 prototype, fabricated in the commercial AMS H18
process, features a fully integrated on-chip readout, i.e. hit-digitization,
zero suppression and data serialization. It is the first fully monolithic
HV-CMOS pixel sensor that has been tested for the use in high irradiation
environments like HL-LHC. We present results from laboratory and test beam
measurements of MuPix7 prototypes irradiated with neutrons (up to
) and protons (up to ) and compare the performance with non-irradiated
sensors. Efficiencies well above 90 % at noise rates below 200 Hz per pixel are
measured. A time resolution better than 22 ns is measured for all tested
settings and sensors, even at the highest irradiation fluences. The data
transmission at 1.25 Gbit/s and the on-chip PLL remain fully functional
Light-addressable Potentiometric Sensors and Light–addressable Electrodes as a Combined Sensor-and-manipulator Microsystem with High Flexibility
AbstractThis work describes the novel combination of the light-addressable electrode (LAE) and the light-addressable potentiometric sensor (LAPS) into a microsystem set-up. Both the LAE as well as the LAPS shares the principle of addressing the active spot by means of a light beam. This enables both systems to manipulate resp. to detect an analyte with a high spatial resolution. Hence, combining both principles into a single set-up enables the active stimulation e.g., by means of electrolysis and a simultaneous observation e.g., the response of an entrapped biological cell by detection of extracellular pH changes. The work will describe the principles of both technologies and the necessary steps to integrate them into a single set-up. Furthermore, examples of application and operation of such systems will be presented
The MuPix Telescope: A Thin, high Rate Tracking Telescope
The MuPix Telescope is a particle tracking telescope, optimized for tracking
low momentum particles and high rates. It is based on the novel High-Voltage
Monolithic Active Pixel Sensors (HV-MAPS), designed for the Mu3e tracking
detector. The telescope represents a first application of the HV-MAPS
technology and also serves as test bed of the Mu3e readout chain. The telescope
consists of up to eight layers of the newest prototypes, the MuPix7 sensors,
which send data self-triggered via fast serial links to FPGAs, where the data
is time-ordered and sent to the PC. A particle hit rate of 1 MHz per layer
could be processed. Online tracking is performed with a subset of the incoming
data. The general concept of the telescope, chip architecture, readout concept
and online reconstruction are described. The performance of the sensor and of
the telescope during test beam measurements are presented.Comment: Proceedings TWEPP 2016, 8 pages, 7 figure
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