6,552 research outputs found
A study of high power argon laser optics Interim scientific report, 15 Apr. - 31 Oct. 1967
Argon laser optimal component degredation at high power level
A study of high power argon laser optics Final report, 15 Apr. 1967 - 14 Apr. 1968
Window degradation in high power argon laser optic
A Robust AFPTAS for Online Bin Packing with Polynomial Migration
In this paper we develop general LP and ILP techniques to find an approximate
solution with improved objective value close to an existing solution. The task
of improving an approximate solution is closely related to a classical theorem
of Cook et al. in the sensitivity analysis for LPs and ILPs. This result is
often applied in designing robust algorithms for online problems. We apply our
new techniques to the online bin packing problem, where it is allowed to
reassign a certain number of items, measured by the migration factor. The
migration factor is defined by the total size of reassigned items divided by
the size of the arriving item. We obtain a robust asymptotic fully polynomial
time approximation scheme (AFPTAS) for the online bin packing problem with
migration factor bounded by a polynomial in . This answers
an open question stated by Epstein and Levin in the affirmative. As a byproduct
we prove an approximate variant of the sensitivity theorem by Cook at el. for
linear programs
Comparison of the Halpha equivalent width of HII regions in a flocculent and a grand design galaxy: possible evidences for IMF variations
We present here a study of the Halpha equivalent widths of the flocculent
galaxy NGC 4395 and the grand design galaxy NGC 5457. A difference between the
mean values of the Halpha equivalent widths for the two galaxies has been
found. Several hypotheses are presented in order to explain this difference:
differences in age, metallicity, star formation rate, photon leakage and
initial mass function. Various tests and Monte Carlo models are used to find
out the most probable cause of this difference. The resultsshow that the
possible cause for the difference could be a variation in the initial mass
function. This difference is such that it seems to favor a fraction of more
massive stars in the grand design galaxy when compared with the flocculent
galaxy. This could be due to a change of the environmental conditions due to a
density wave.Comment: 29 pages, 19 figures, accepted for publication in Ap
Comparison of 35 and 50 {\mu}m thin HPK UFSD after neutron irradiation up to 6*10^15 neq/cm^2
We report results from the testing of 35 {\mu}m thick Ultra-Fast Silicon
Detectors (UFSD produced by Hamamatsu Photonics (HPK), Japan and the comparison
of these new results to data reported before on 50 {\mu}m thick UFSD produced
by HPK. The 35 {\mu}m thick sensors were irradiated with neutrons to fluences
of 0, 1*10^14, 1*10^15, 3*10^15, 6*10^15 neq/cm^2. The sensors were tested
pre-irradiation and post-irradiation with minimum ionizing particles (MIPs)
from a 90Sr \b{eta}-source. The leakage current, capacitance, internal gain and
the timing resolution were measured as a function of bias voltage at -20C and
-27C. The timing resolution was extracted from the time difference with a
second calibrated UFSD in coincidence, using the constant fraction method for
both. Within the fluence range measured, the advantage of the 35 {\mu}m thick
UFSD in timing accuracy, bias voltage and power can be established.Comment: 9 pages, 9 figures, HSTD11 Okinawa. arXiv admin note: text overlap
with arXiv:1707.0496
Radiation Hardness of Thin Low Gain Avalanche Detectors
Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure
where an appropriate doping of the multiplication layer (p+) leads to high
enough electric fields for impact ionization. Gain factors of few tens in
charge significantly improve the resolution of timing measurements,
particularly for thin detectors, where the timing performance was shown to be
limited by Landau fluctuations. The main obstacle for their operation is the
decrease of gain with irradiation, attributed to effective acceptor removal in
the gain layer. Sets of thin sensors were produced by two different producers
on different substrates, with different gain layer doping profiles and
thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected
charge and leakage current was compared before and after irradiation with
neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient
Current Technique and charge collection measurements with LHC speed electronics
were employed to characterize the detectors. The thin LGAD sensors were shown
to perform much better than sensors of standard thickness (~300 um) and offer
larger charge collection with respect to detectors without gain layer for
fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of
LGADs. Pions were found to be more damaging than neutrons at the same
equivalent fluence, while no significant difference was found between different
producers. At very high fluences and bias voltages the gain appears due to deep
acceptors in the bulk, hence also in thin standard detectors
Relation between high-sensitivity C-reactive protein and cardiovascular and renal markers in a middle-income country in the African region.
BACKGROUND: High-sensitivity C-reactive protein (hs-CRP) is associated with several cardiovascular risk factors (CVRF) and with renal function markers. However, these associations have not been examined in populations in the African region. We analyzed the distribution of hs-CRP and the relationship with a broad set of CVRF, renal markers and carotid intima-media thickness (IMT), in the Seychelles (African region). METHODS: We conducted a survey in the population aged 25-64years (n=1255, participation rate: 80.2%). Analyses were restricted to persons of predominantly African descent (n=1011). RESULTS: Mean and median hs-CRP serum concentrations (mg/l) were 3.1 (SD 7.6) and 1.4 (IQR 0.7-2.9) in men and 4.5 (SD 6.7) and 2.2 (IQR 1.0-5.4) in women (p<0.001 for difference between men and women). hs-CRP was significantly associated with several conventional CVRF, and particularly strongly with markers of adiposity. With regards to renal markers, hs-CRP was strongly associated with cystatin C and with microalbuminuria but not with creatinine. hs-CRP was not associated with IMT. CONCLUSIONS: Serum concentration of hs-CRP was significantly associated with sex, several CVRF and selected renal function markers, which extends similar findings in Europe and in North America to a population in the African region. These findings can contribute to guide recommendations for the use of hs-CRP in clinical practice in the region
Vector Bin Packing with Multiple-Choice
We consider a variant of bin packing called multiple-choice vector bin
packing. In this problem we are given a set of items, where each item can be
selected in one of several -dimensional incarnations. We are also given
bin types, each with its own cost and -dimensional size. Our goal is to pack
the items in a set of bins of minimum overall cost. The problem is motivated by
scheduling in networks with guaranteed quality of service (QoS), but due to its
general formulation it has many other applications as well. We present an
approximation algorithm that is guaranteed to produce a solution whose cost is
about times the optimum. For the running time to be polynomial we
require and . This extends previous results for vector
bin packing, in which each item has a single incarnation and there is only one
bin type. To obtain our result we also present a PTAS for the multiple-choice
version of multidimensional knapsack, where we are given only one bin and the
goal is to pack a maximum weight set of (incarnations of) items in that bin
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