High Magnetic Field NMR Studies of LiVGe2_2O6_6, a quasi 1-D Spin S=1S = 1 System

We report $^{7}$Li pulsed NMR measurements in polycrystalline and single crystal samples of the quasi one-dimensional S=1 antiferromagnet LiVGe$_2$O$_6$, whose AF transition temperature is $T_{\text{N}}\simeq 24.5$ K. The field ($B_0$) and temperature ($T$) ranges covered were 9-44.5 T and 1.7-300 K respectively. The measurements included NMR spectra, the spin-lattice relaxation rate ($T_1^{-1}$), and the spin-phase relaxation rate ($T_2^{-1}$), often as a function of the orientation of the field relative to the crystal axes. The spectra indicate an AF magnetic structure consistent with that obtained from neutron diffraction measurements, but with the moments aligned parallel to the c-axis. The spectra also provide the $T$-dependence of the AF order parameter and show that the transition is either second order or weakly first order. Both the spectra and the $T_1^{-1}$ data show that $B_0$ has at most a small effect on the alignment of the AF moment. There is no spin-flop transition up to 44.5 T. These features indicate a very large magnetic anisotropy energy in LiVGe$_2$O$_6$ with orbital degrees of freedom playing an important role. Below 8 K, $T_1^{-1}$ varies substantially with the orientation of $B_0$ in the plane perpendicular to the c-axis, suggesting a small energy gap for magnetic fluctuations that is very anisotropic.Comment: submitted to Phys. Rev.

Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at √ s=7 TeV with the ATLAS detector at the LHC

Event-shape observables measured using charged particles in inclusive $Z$-boson events are presented, using the electron and muon decay modes of the $Z$ bosons. The measurements are based on an integrated luminosity of $1.1 {\rm fb}^{-1}$ of proton--proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy $\sqrt{s}=7$ TeV. Charged-particle distributions, excluding the lepton--antilepton pair from the $Z$-boson decay, are measured in different ranges of transverse momentum of the $Z$ boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and $\mathcal{F}$-parameter, which are in particular sensitive to properties of the underlying event at small values of the $Z$-boson transverse momentum. The Sherpa event generator shows larger deviations from the measured observables than Pythia8 and Herwig7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high $Z$-boson transverse momenta than at low $Z$-boson transverse momenta and for the observables that are less sensitive to the number of charged particles in the event.Comment: 36 pages plus author list + cover page (54 pages total), 14 figures, 4 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-0

Stage-structured population matrix models for the Formosan landlocked salmon (Oncorhynchus masou formosanus) in Taiwan

The Formosan landlocked salmon (Oncorhynchus masou formosanus) is an endangered endemic species found only in the basin of the Chichiawan Stream in the mountains of Central Taiwan. Census observations recorded from 1987 to 2004 showed that the regulation of the Formosan salmon population is density-independent, possibly due to the fluctuating environment. In order to better understand and predict the population dynamics, stage-structured population matrix models were constructed for juveniles, subadult and adult stages using the census data. We applied the least-squares solution to determine stage-specific parameters including the growth rates, survival rates and fecundity for the matrix models. The derived population growth rates determined by the matrix models indicated that the Formosan salmon population is declining in the Chichiawan Stream but has been increasing in a tributary, the Kaoshan Stream since 200 1, when dams on that stream were demolished. In general, the numbers of each stage of the Formosan salmon could be well predicted by the matrix models. In the Chichiawan Stream, the model performance was better for subadults than for adults or juveniles. The lower predictability of adult numbers across summers might be a result of the low capacity of large-sized adult salmon to seek refuge when typhoons cause floods in the shallow streams. The lower predictability of juvenile numbers from winter to spring suggests that other intrusive factors or interactions with other communities might be involved in determining the fecundity and require further study. Stage-structured population matrix models appear to be a useful tool for the management and conservation of the Formosan salmon

Relationship between the Formosan landlocked salmon Oncorhynchus masou formosanus population and the physical substrate of its habitat after partial dam removal from Kaoshan Stream, Taiwan

In order to protect and restore the population of the Formosan landlocked salmon (Oncorhynchus masou formosanus, Jordan and Oshima) (Salmoidae), an endemic and endangered species of the central Taiwanese highlands, Shei-Pa National Park partially removed 4 dams from Kaoshan Stream during 1999-2001. The purpose of this study was to evaluate the relationship between the abundance of the Formosan landlocked salmon and the physical substrate of its habitat as a consequence of habitat modifications caused by partial removal of the dams from Kaoshan Stream. After removal of the dams, fish were able to freely travel up and down the stream, but the relative slope of the riverbank became steeper, and the velocity of the river increased leading to more-serious erosion than was found prior to dam removal. We applied a principal component analysis (PCA) method to determine the most significant factors affecting the fish population. The 1st principal component of the fish population explained 79% of the total salmon population variance. The 1st 2 principal components of substrate rock size explained 72% of the total substrate variance. By examining a contour plot, we found that when the percentage of boulders was higher, the salmon population accordingly increased. Moreover, poor breeding years that highly impact the salmon population appeared to be a result of flooding caused by typhoons during the breeding season from late Oct. to Dec. Following flooding, it appears that the river substrate had a higher percentage of boulders, which possibly benefited the salmon population. Consequently, partial dam removal may have improved the survival rate of the salmon population in response to floods. http://zoolstud.sinica.edu.tw/Journals/47.1/25.pdf

10-year stroke prevention after successful carotid endarterectomy for asymptomatic stenosis (ACST-1); a multicentre randomised trial

BACKGROUND: If carotid artery narrowing remains asymptomatic (ie, has caused no recent stroke or other neurological symptoms), successful carotid endarterectomy (CEA) reduces stroke incidence for some years. We assessed the long-term effects of successful CEA. METHODS: Between 1993 and 2003, 3120 asymptomatic patients from 126 centres in 30 countries were allocated equally, by blinded minimised randomisation, to immediate CEA (median delay 1 month, IQR 0·3-2·5) or to indefinite deferral of any carotid procedure, and were followed up until death or for a median among survivors of 9 years (IQR 6-11). The primary outcomes were perioperative mortality and morbidity (death or stroke within 30 days) and non-perioperative stroke. Kaplan-Meier percentages and logrank p values are from intention-to-treat analyses. This study is registered, number ISRCTN26156392. FINDINGS: 1560 patients were allocated immediate CEA versus 1560 allocated deferral of any carotid procedure. The proportions operated on while still asymptomatic were 89·7% versus 4·8% at 1 year (and 92·1%vs 16·5% at 5 years). Perioperative risk of stroke or death within 30 days was 3·0% (95% CI 2·4-3·9; 26 non-disabling strokes plus 34 disabling or fatal perioperative events in 1979 CEAs). Excluding perioperative events and non-stroke mortality, stroke risks (immediate vs deferred CEA) were 4·1% versus 10·0% at 5 years (gain 5·9%, 95% CI 4·0-7·8) and 10·8% versus 16·9% at 10 years (gain 6·1%, 2·7-9·4); ratio of stroke incidence rates 0·54, 95% CI 0·43-0·68, p<0·0001. 62 versus 104 had a disabling or fatal stroke, and 37 versus 84 others had a non-disabling stroke. Combining perioperative events and strokes, net risks were 6·9% versus 10·9% at 5 years (gain 4·1%, 2·0-6·2) and 13·4% versus 17·9% at 10 years (gain 4·6%, 1·2-7·9). Medication was similar in both groups; throughout the study, most were on antithrombotic and antihypertensive therapy. Net benefits were significant both for those on lipid-lowering therapy and for those not, and both for men and for women up to 75 years of age at entry (although not for older patients). INTERPRETATION: Successful CEA for asymptomatic patients younger than 75 years of age reduces 10-year stroke risks. Half this reduction is in disabling or fatal strokes. Net benefit in future patients will depend on their risks from unoperated carotid lesions (which will be reduced by medication), on future surgical risks (which might differ from those in trials), and on whether life expectancy exceeds 10 years. FUNDING: UK Medical Research Council, BUPA Foundation, Stroke Association