Treedepth vs circumference

The circumference of a graph $G$ is the length of a longest cycle in $G$, or $+\infty$ if $G$ has no cycle. Birmel\'e (2003) showed that the treewidth of a graph $G$ is at most its circumference minus one. We strengthen this result for $2$-connected graphs as follows: If $G$ is $2$-connected, then its treedepth is at most its circumference. The bound is best possible and improves on an earlier quadratic upper bound due to Marshall and Wood (2015)

A first measurement of the Proper Motion of the Leo II dwarf spheroidal galaxy

We use 14-year baseline images obtained with the Wide Field Planetary Camera 2 on board the Hubble Space telescope to derive a proper motion for one of the Milky Way's most distant dwarf spheroidal companions, Leo II, relative to an extragalactic background reference frame. Astrometric measurements are performed in the effective point spread function (ePSF) formalism using our own developed code. An astrometric reference grid is defined using 3,224 stars that are members of Leo II that are brighter than magnitude 25 in the F814W band. We identify 17 compact extra-galactic sources, for which we measure a systemic proper motion relative to this stellar reference grid. We derive a proper motion [\mu_{\alpha},\mu_{\delta}]=[+104+/-113,-33+/-151] microarcseconds/yr for Leo II in the heliocentric reference frame. Though marginally detected, the proper motion yields constraints on the orbit of Leo II. Given a distance of 230 Kpc and a heliocentric radial velocity +79 km/s, and after subtraction of the solar motion, our measurement indicates a total orbital motion 266.1+/-128.7 km/s in the Galactocentric reference frame, with a radial component +21.5+/-4.3 km/s and tangential component 265.2+/-129.4 km/s. The small radial component indicates that Leo II either has a low-eccentricity orbit, or is currently close to perigalacticon or apogalacticon distance. We see evidence for systematic errors in the astrometry of the extragalactic sources which, while close to being point sources, are slightly resolved in the HST images. We argue that more extensive observations at later epochs will be necessary to better constrain the proper motion of Leo II. We provide a detailed catalog of the stellar and extragalactic sources identified in the HST data which should provide a solid early-epoch reference for future astrometric measurements.Comment: 10 pages, accepted for publication in the Astrophysical Journa

TOF-PET detector concept based on organic scintillators

In this contribution we present a new concept of the large acceptance detector systems based on organic scintillators which may allow for simultaneous diagnostic of large fraction of the human body. Novelty of the concept lies in employing large blocks of polymer scintillators instead of crystals as detectors of annihilation quanta, and in using predominantly the timing of signals instead of their amplitudes

Surgical treatment of rectal cancer in Poland — a report from a prospective, multi-centre observational study PSSO_01 conducted under the auspices of the Polish Society of Surgical Oncology

Introduction. Since 2016, as part of the PSSO_01 multi-centre research project conducted under the auspices of the Polish Society of Surgical Oncology, clinical data on rectal cancer treatment have been collected. The objective of the study was to illustrate the state of early results of surgical treatment. Material and methods. The research project is multi-centre in nature. Data shall be collected electronically. The study protocol does not impose or suggest any course of procedure. It only systematizes the way data are collected for scientific purposes. The analysis of early results of surgical treatment was compared with the results of population studies from other European countries (Netherlands, Belgium). Results. By the end of June 2018, 736 patients were registered in the study. In 399 (54.2%) an anterior resection was performed. More than half of patients undergoing subsequent surgical treatment (54.2%) receive neoadjuvant treatment, with the percentage of patients undergoing radiotherapy or radiochemical treatment for lower rectal cancer being about 70%. Most patients (96%) are operated in elective procedure. The percentage of laparoscopic surgeries is low (8.6%). Postoperative complications are observed in 21.1% of patients. Severe complications (grades III–V according to Clavien-Dindo classification) occur in 7.6% of patients undergoing surgery. Postoperative mortality is 1.1%. Discussion. Although the project does not have the character of a registry and does not allow for drawing wider conclusions concerning the compliance with the standards of qualification for neoadjuvant treatment, the important information is that more than half of rectal cancer patients receive preoperative treatment, and the percentage of severe postoperative complications does not exceed 10%. Conclusions. The results of the PSSO_01 project are representative and reflect the actual situation concerning surgical treatment of rectal cancer patients in Poland

Strip- PET : a novel detector concept for the TOF-PET scanner

We briefly present a design of a new PET scanner based on strips of polymer scintillators arranged in a barrel constituting a large acceptance detector. The solution proposed is based on the superior timing properties of the polymer scintillators. The position and time of the reaction of the gamma quanta in the detector material will be determined based on the time of arrival of light signals to the edges of the scintillator strips

Leczenie chirurgiczne raka odbytnicy w Polsce — raport z prospektywnego, wieloośrodkowego badania obserwacyjnego PSSO_01 prowadzonego pod auspicjami Polskiego Towarzystwa Chirurgii Onkologicznej

Wstęp. Od 2016 roku w ramach wieloośrodkowego projektu badawczego PSSO_01 prowadzonego pod auspicjami Polskiego Towarzystwa Chirurgii Onkologicznej, gromadzone są dane kliniczne dotyczące leczenia raka odbytnicy. Celem pracy było zobrazowanie stanu dotyczącego wczesnych wyników leczenia chirurgicznego. Materiał i metody. Projekt badawczy ma charakter wieloośrodkowy. Dane gromadzone są elektronicznie. Protokół badania nie narzuca ani nie sugeruje żadnego sposobu postępowania, systematyzuje jedynie sposób zbierania danych w celach naukowych. Analiza dotycząca wczesnych wyników leczenia chirurgicznego została porównana z rezultatami populacyjnych badań z innych krajów europejskich (Holandia, Belgia). Wyniki. Do końca czerwca 2018 roku w badaniu zarejestrowano 736 chorych. U 399 (54,2%) wykonano resekcję przednią. Leczenie neoadiuwantowe otrzymała ponad połowa chorych, poddanych następnie leczeniu operacyjne­mu (54,2%), przy czym odsetek pacjentów poddanych radio- bądź radiochemioterapii z powodu raka dolnej części odbytnicy wyniósł około 70%. Większość chorych (96%) operowana była w trybie planowym. Odsetek operacji wykonanych techniką laparoskopową jest niski (8,6%). Powikłania pooperacyjne zaobserwowano u 21,1% chorych. Ciężkie powikłania (III–V st. wg klasyfikacji Claviena-Dindo) sięgały 7,6% operowanych chorych. Śmiertelność po­operacyjna wyniosła 1,1%. Dyskusja. Chociaż projekt nie ma charakteru rejestru i nie pozwala na wyciągniecie szerszych wniosków dotyczących przestrzegania standardów kwalifikacji do leczenia neoadiuwantowego, istotną informacją jest to, że ponad połowa chorych na raka odbytnicy otrzymuje leczenie przedoperacyjne, a odsetek ciężkich powikłań pooperacyjnych nie przekracza 10%. Wnioski. Wyniki projektu PSSO_01 są reprezentatywne i odzwierciedlają faktyczną sytuację dotyczącą leczenia chirurgicznego chorych na raka odbytnicy w Polsce

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements