Numerical-Diagonalization Study of Spin Gap Issue of the Kagome Lattice Heisenberg Antiferromagnet

We study the system size dependence of the singlet-triplet excitation gap in the $S=1/2$ kagome-lattice Heisenberg antiferromagnet by numerical diagonalization. We successfully obtain a new result of a cluster of 42 sites. The two sequences of gaps of systems with even-number sites and that with odd-number sites are separately analyzed. Careful examination clarifies that there is no contradiction when we consider the system to be gapless.Comment: 5 pages, 3 figures, 1 table, received by J. Phys. Soc. Jpn. on 20 Jan 2011, to be published in this journa

HAL/S-360 compiler system specification

A three phase language compiler is described which produces IBM 360/370 compatible object modules and a set of simulation tables to aid in run time verification. A link edit step augments the standard OS linkage editor. A comprehensive run time system and library provide the HAL/S operating environment, error handling, a pseudo real time executive, and an extensive set of mathematical, conversion, I/O, and diagnostic routines. The specifications of the information flow and content for this system are also considered

Magnetization curve of the kagome-strip-lattice antiferromagnet

We study the magnetization curve of the Heisenberg model on the quasi-one-dimensional kagome-strip lattice that shares the same lattice structure in the inner part with the two-dimensional kagome lattice. Our numerical calculations based on the density matrix renormalization group method reveal that the system shows several magnetization plateaus between zero magnetization and the saturated one; we find the presence of the magnetic plateaus with the n=7 height of the saturation for n =1,2,3,4,5 and 6 in the S =1/2 case, whereas we detect only the magnetic plateaus of n =1,3,5 and 6 in the S =1 case. In the cases of n =2,4 and 6 for the S=1/2 system, the Oshikawa-Yamanaka-Affleck condition suggests the occurrence of the translational symmetry breaking (TSB). We numerically confirm this non-trivial TSB in our results of local magnetizations. We have also found that the macroscopic jump appears near the saturation field irrespective of the spin amplitude as well as the two-dimensional kagome model.Comment: 6pages, 3figures, accepted for publication in Journal of Low Temperature Physic

Magnetization Process of Kagome-Lattice Heisenberg Antiferromagnet

The magnetization process of the isotropic Heisenberg antiferromagnet on the kagome lattice is studied. Data obtained from the numerical-diagonalization method are reexamined from the viewpoint of the derivative of the magnetization with respect to the magnetic field. We find that the behavior of the derivative at approximately one-third of the height of the magnetization saturation is markedly different from that for the cases of typical magnetization plateaux. The magnetization process of the kagome-lattice antiferromagnet reveals a new phenomenon, which we call the "magnetization ramp".Comment: 4 pages, 5figures, accepted in J. Phys. Soc. Jpn

Changes in undergraduate student alcohol consumption as they progress through university

BACKGROUND: Unhealthy alcohol use amongst university students is a major public health concern. Although previous studies suggest a raised level of consumption amongst the UK student population there is little consistent information available about the pattern of alcohol consumption as they progress through university. The aim of the current research was to describe drinking patterns of UK full-time undergraduate students as they progress through their degree course. METHOD: Data were collected over three years from 5895 undergraduate students who began their studies in either 2000 or 2001. Longitudinal data (i.e. Years 1–3) were available from 225 students. The remaining 5670 students all responded to at least one of the three surveys (Year 1 n = 2843; Year 2 n = 2219; Year 3 n = 1805). Results: Students reported consuming significantly more units of alcohol per week at Year 1 than at Years 2 or 3 of their degree. Male students reported a higher consumption of units of alcohol than their female peers. When alcohol intake was classified using the Royal College of Physicians guidelines [1] there was no difference between male and females students in terms of the percentage exceeding recommended limits. Compared to those who were low level consumers students who reported drinking above low levels at Year 1 had at least 10 times the odds of continuing to consume above low levels at year 3. Students who reported higher levels of drinking were more likely to report that alcohol had a negative impact on their studies, finances and physical health. Consistent with the reduction in units over time students reported lower levels of negative impact during Year 3 when compared to Year 1. CONCLUSION: The current findings suggest that student alcohol consumption declines over their undergraduate studies; however weekly levels of consumption at Year 3 remain high for a substantial number of students. The persistence of high levels of consumption in a large population of students suggests the need for effective preventative and treatment interventions for all year groups

Predictors of problem drinking in adolescence and young adulthood. A longitudinal twin-family study

We examined drinking behavior of parents, siblings, and friends of twins as predictors of adolescent and young adult problem drinking over a period of 2 and a period of 7 years. Data of 12 to 30-year-old twins and their family members from the Netherlands Twin Register were analyzed. Problem drinking in twins was assessed in 1995 and 2000 and was defined based on the CAGE and amount of drinking. Data on alcohol use of parents, siblings and friends were collected in 1993. Multinomial logistic regression analyses were used to examine the short-term (1993-1995; n = 2,994) and the long-term longitudinal predictors (1993-2000; n = 1,796) of problem drinking. Age, sex and own alcohol use in 1993 explained 25% of the variance in adolescent and young adult problem drinking. Moreover, adolescents and young adults with fathers who drank frequently and with a large numbers of drinking friends, were at the highest risk for problem drinking 2 years later. Over a period of 7 years the number of drinking friends was no longer a risk factor, but few times a week or daily alcohol use of fathers remained a risk factor for later problem drinking. Drinking behavior of mother and siblings did not substantially predict problem drinking. Sex and age did not moderate these effect

Macroscopic entanglement jumps in model spin systems

In this paper, we consider some frustrated spin models for which the ground states are known exactly. The concurrence, a measure of the amount of entanglement can be calculated exactly for entangled spin pairs. Quantum phase transitions involving macroscopic magnetization changes at critical values of the magnetic field are accompanied by macroscopic jumps in the (T=0) entanglement. A specific example is given in which magnetization plateaus give rise to a plateau structure in the amount of entanglement associated with nearest-neighbour bonds. We further show that macroscopic entanglement changes can occur in quantum phase transitions brought about by the tuning of exchange interaction strengths.Comment: 11 pages, 4 figures, Latex, communicated to Phys. Rev.

Structure of the ATP synthase catalytic complex (F(1)) from Escherichia coli in an autoinhibited conformation.

ATP synthase is a membrane-bound rotary motor enzyme that is critical for cellular energy metabolism in all kingdoms of life. Despite conservation of its basic structure and function, autoinhibition by one of its rotary stalk subunits occurs in bacteria and chloroplasts but not in mitochondria. The crystal structure of the ATP synthase catalytic complex (F(1)) from Escherichia coli described here reveals the structural basis for this inhibition. The C-terminal domain of subunit ɛ adopts a heretofore unknown, highly extended conformation that inserts deeply into the central cavity of the enzyme and engages both rotor and stator subunits in extensive contacts that are incompatible with functional rotation. As a result, the three catalytic subunits are stabilized in a set of conformations and rotational positions distinct from previous F(1) structures

Predicting where a radiation will occur: Acoustic and molecular surveys reveal overlooked diversity in Indian Ocean Island crickets (Mogoplistinae: Ornebius)

Recent theory suggests that the geographic location of island radiations (local accumulation of species diversity due to cladogenesis) can be predicted based on island area and isolation. Crickets are a suitable group for testing these predictions, as they show both the ability to reach some of the most isolated islands in the world, and to speciate at small spatial scales. Despite substantial song variation between closely related species in many island cricket lineages worldwide, to date this characteristic has not received attention in the western Indian Ocean islands; existing species descriptions are based on morphology alone. Here we use a combination of acoustics and DNA sequencing to survey these islands for Ornebius crickets. We uncover a small but previously unknown radiation in the Mascarenes, constituting a three-fold increase in the Ornebius species diversity of this archipelago (from two to six species). A further new species is detected in the Comoros. Although double archipelago colonisation is the best explanation for species diversity in the Seychelles, in situ cladogenesis is the best explanation for the six species in the Mascarenes and two species of the Comoros. Whether the radiation of Mascarene Ornebius results from intra- or purely inter- island speciation cannot be determined on the basis of the phylogenetic data alone. However, the existence of genetic, song and ecological divergence at the intra-island scale is suggestive of an intra-island speciation scenario in which ecological and mating traits diverge hand-in-hand. Our results suggest that the geographic location of Ornebius radiations is partially but not fully explained by island area and isolation. A notable anomaly is Madagascar, where our surveys are consistent with existing accounts in finding no Ornebius species present. Possible explanations are discussed, invoking ecological differences between species and differences in environmental history between islands. (Résumé d'auteur