11,428 research outputs found
A result on polynomials derived via graph theory
We present an example of a result in graph theory that is used to obtain a
result in another branch of mathematics. More precisely, we show that the
isomorphism of certain directed graphs implies that some trinomials over finite
fields have the same number of roots
XMM Follow-Up Observations of Three Swift BAT-Selected Active Galactic Nuclei
We present XMM-Newton observations of three AGN taken as part of a hunt to
find very heavily obscured Compton-thick AGN. For obscuring columns greater
than 10^25 cm^-2, AGN are only visible at energies below 10 keV via
reflected/scattered radiation, characterized by a flat power-law. We therefore
selected three objects (ESO 417-G006, IRAS 05218-1212, and MCG -01-05-047) from
the Swift BAT hard X-ray survey catalog with Swift X-ray Telescope XRT 0.5-10
keV spectra with flat power-law indices as candidate Compton-thick sources for
follow-up observations with the more sensitive instruments on XMM-Newton. The
XMM spectra, however, rule out reflection-dominated models based on the
weakness of the observed Fe K-alpha lines. Instead, the spectra are well-fit by
a model of a power-law continuum obscured by a Compton-thin absorber, plus a
soft excess. This result is consistent with previous follow-up observations of
two other flat-spectrum BAT-detected AGN. Thus, out of the six AGN in the
22-month BAT catalog with apparently flat Swift XRT spectra, all five that have
had follow-up observations are not likely Compton-thick. We also present new
optical spectra of two of these objects, IRAS 05218-1212 and MCG -01-05-047.
Interestingly, though both these AGN have similar X-ray spectra, their optical
spectra are completely different, adding evidence against the simplest form of
the geometric unified model of AGN. IRAS 05218-1212 appears in the optical as a
Seyfert 1, despite the ~8.5x10^22 cm^-2 line-of-sight absorbing column
indicated by its X-ray spectrum. MCG -01-05-047's optical spectrum shows no
sign of AGN activity; it appears as a normal galaxy.Comment: 18 pages including 4 figures, accepted by Ap
Patients' preferences for the management of non-metastatic prostate cancer: discrete choice experiment
Objective To establish which attributes of conservative treatments for prostate cancer are most important to men. Design Discrete choice experiment. Setting Two London hospitals. Participants 129 men with non-metastatic prostate cancer, mean age 70 years; 69 of 118 (58%) with T stage 1 or 2 cancer at diagnosis. Main outcome measures Men's preferences for, and trade-offs between, the attributes of diarrhoea, hot flushes, ability to maintain an erection, breast swelling or tenderness, physical energy, sex drive, life expectancy, and out of pocket expenses. Results The men's responses to changes in attributes were all statistically significant. When asked to assume a starting life expectancy of five years, the men were willing to make trade-offs between life expectancy and side effects. On average, they were most willing to give up life expectancy to avoid limitations in physical energy (mean three months) and least willing to trade life expectancy to avoid hot flushes (mean 0.6 months to move from a moderate to mild level or from mild to none). Conclusions Men with prostate cancer are willing to participate in a relatively complex exercise that weighs up the advantages and disadvantages of various conservative treatments for their condition. They were willing to trade off some life expectancy to be relieved of the burden of troublesome side effects such as limitations in physical energy
Encapsulation of a {Cu16} cluster containing four [Cu4O4] cubanes within an isopolyoxometalate {W44} cluster
We report a {Cu16} embedded within a {W44} cluster containing four cubane-like [Cu4O4] units within an isopolyoxotungstate (isoPOT) in a {Na4Cu4[(H2W11O38) (CH3COO)(OH)3]}4·88H2O (1) and a polyanion Cu-linked {W11} chain Na6Cu2[(H2W11O38)(CH3COO)(OH)]·26H2O (2). Electronically, the redox properties show that both compounds 1 and 2 undergo irreversible reductions resulting in the demetalation of the compounds, whilst the magnetic behavior of 1 and 2 shows a weak antiferromagnetic and a stronger ferromagnetic coupling, respectively
On large maximal partial ovoids of the parabolic quadric \q(4,q)
We use the representation for \q(4,q) to show that maximal partial
ovoids of \q(4,q) of size , , odd prime, , do not
exist. Although this was known before, we give a slightly alternative proof,
also resulting in more combinatorial information of the known examples for
prime.Comment: 11 p
Quantum Correlation Without Classical Correlations
We show that genuine multiparty quantum correlations can exist on its own,
without a supporting background of genuine multiparty classical correlations,
even in macroscopic systems. Such possibilities can have important implications
in the physics of quantum information and phase transitions.Comment: 4 pages, no figures; v2: presentation improved, results unchanged,
published versio
Continuous flushing of the bladder in rodents reduces artifacts and improves quantification in molecular imaging
In this study, we evaluated the partial volume effect (PVE) of 2-deoxy-2-[18F]fluoro-d-glucose (18F-FDG) tracer accumulation in the bladder on the positron emission tomographic (PET) image quantification in mice and rats suffering from inflammatory bowel disease. To improve the accuracy, we implemented continuous bladder flushing procedures. Female mice and rats were scanned using microPET/computed tomography (CT) at baseline and after induction of acute colitis by injecting 2,4,6-trinitrobenzene sulfonic acid (TNBS) intrarectally. During the scans, the bladder was continuously flushed in one group, whereas in the other group, no bladder flushing was performed. As a means of in vivo and ex vivo validation of the inflammation, animals also underwent colonoscopy and were sacrificed for gamma counting (subpopulation) and to score the colonic damage both micro- and macroscopically as well as biochemically. At baseline, the microPET signal in the colon of both mice and rats was significantly higher in the nonflushed group compared to the flushed group, caused by the PVE of tracer activity in the bladder. Hence, the colonoscopy and postmortem analyses showed no significant differences at baseline between the flushed and nonflushed animals. TNBS induced significant colonic inflammation, as revealed by colonoscopic and postmortem scores, which was not detected by microPET in the mice without bladder flushing, again because of spillover of bladder activity in the colonic area. MicroPET in bladder-flushed animals did reveal a significant increase in 18F-FDG uptake. Correlations between microPET and colonoscopy, macroscopy, microscopy, and myeloperoxidase yielded higher Spearman rho values in mice with continuously flushed bladders during imaging. Comparable, although somewhat less pronounced, results were shown in the rat. Continuous bladder flushing reduced image artifacts and is mandatory for accurate image quantification in the pelvic region for both mice and rats. We designed and validated experimental protocols to facilitate such.Steven Deleye, Marthe Heylen, Annemie Deiteren, Joris De Man, Sigrid Stroobants, Benedicte De Winter, and Steven Staelen
Unambiguous determination of spin dephasing times in ZnO
Time-resolved magneto-optics is a well-established optical pump probe
technique to generate and to probe spin coherence in semiconductors. By this
method, spin dephasing times T_2^* can easily be determined if their values are
comparable to the available pump-probe-delays. If T_2^* exceeds the laser
repetition time, however, resonant spin amplification (RSA) can equally be used
to extract T_2^*. We demonstrate that in ZnO these techniques have several
tripping hazards resulting in deceptive values for T_2^* and show how to avoid
them. We show that the temperature dependence of the amplitude ratio of two
separate spin species can easily be misinterpreted as a strongly temperature
dependent T_2^* of a single spin ensemble, while the two spin species have
T_2^* values which are nearly independent of temperature. Additionally,
consecutive pump pulses can significantly diminish the spin polarization, which
remains from previous pump pulses. While this barely affects T_2^* values
extracted from delay line scans, it results in seemingly shorter T_2^* values
in RSA.Comment: 11 pages, 10 figure
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