28 research outputs found
Low noise amplication of an optically carried microwave signal: application to atom interferometry
In this paper, we report a new scheme to amplify a microwave signal carried
on a laser light at =852nm. The amplification is done via a
semiconductor tapered amplifier and this scheme is used to drive stimulated
Raman transitions in an atom interferometer. Sideband generation in the
amplifier, due to self-phase and amplitude modulation, is investigated and
characterized. We also demonstrate that the amplifier does not induce any
significant phase-noise on the beating signal. Finally, the degradation of the
performances of the interferometer due to the amplification process is shown to
be negligible
Perioperative diagnosis of the positive axilla in breast cancer: A safe, time efficient algorithm
Performance of Multicast Packet Aggregation in All Optical Slotted Networks
The study focuses on packet aggregation mechanisms on the edge router of an optical network. The device works as an interface between the electronic and optical domains : it takes IP packets coming from client layers and converts them into optical packets to be sent into the optical network. An efficient aggregation mechanism supporting QoS (Quality of Service) requirements of IP flows is presented. A timer is implemented to limit the aggregation delay. Analytical models based on Markov chains are presented in order to study the packetisation efficiency (filling ratio) and the mean time of packetisation for each class. Numerical results show the effect of IP packet lengths distribution on aggregation delay and efficiency. Also, we show the importance of the timer in bounding the delay of transmitted packets without much altering the aggregation efficiency
State of nature
For the first time ever, the UKâs
wildlife organisations have
joined forces to undertake a
health check of nature in the
UK and its Overseas Territories. 60% of the 3,148 UK species we assessed
have declined over the last 50 years and
31% have declined strongly.
Half of the species assessed have shown
strong changes in their numbers or range,
indicating that recent environmental
changes are having a dramatic impact
on nature in the UK. Species with specific
habitat requirements seem to be faring
worse than generalist species.
A new Watchlist Indicator, developed
to measure how conservation priority
species are faring, shows that their
overall numbers have declined by 77%
in the last 40 years, with little sign
of recovery.
Of more than 6,000 species that have
been assessed using modern Red List
criteria, more than one in 10 are thought
to be under threat of extinction in the UK.
Our assessment looks back over 50 years
at most, yet there were large declines in
the UKâs wildlife prior to this, linked to
habitat loss.
The UKâs Overseas Territories hold a
wealth of wildlife of huge international
importance and over 90 of these species
are at high risk of global extinction.
There is a lack of knowledge on the
trends of most of the UKâs species.
As a result, we can report quantitative
trends for only 5% of the 59,000 or so
terrestrial and freshwater species in
the UK, and for very few of the 8,500
marine species. Much needs to be done
to improve our knowledge.
What we do know about the state of
the UKâs nature is often based upon
the efforts of thousands of dedicated
volunteer enthusiasts who contribute
their time and expertise to monitoring
schemes and species recording.
The threats to the UKâs wildlife are
many and varied, the most severe
acting either to destroy valuable habitat
or degrade the quality and value of
what remains.
Climate change is having an increasing
impact on nature in the UK. Rising
average temperatures are known to be
driving range expansion in some species,
but evidence for harmful impacts is
also mounting.
The full report is online:
www.rspb.org.uk/stateofnature
We should act to save nature both for
its intrinsic value and for the benefits
it brings to us that are essential to our
wellbeing and prosperity.
Targeted conservation has produced
inspiring success stories and, with
sufficient determination, resources
and public support, we can turn the
fortunes of our wildlife around.
The State of Nature report serves
to illustrate that with shared resolve
and commitment we can save nature