Period derivative of the M15 X-ray Binary AC211/X2127+119

We have combined Rossi X-ray Timing Explorer observations of X2127+119, the low-mass X-ray binary in the globular cluster M15, with archival X-ray lightcurves to study the stability of the 17.1 hr orbital period. We find that the data cannot be fit by the Ilovaisky (1993) ephemeris, and requires either a 7sigma change to the period or a period derivative Pdot/P~9x10e-7 per year. Given its remarkably low L_X/L_opt such a Pdot lends support to models that require super-Eddington mass transfer in a q~1 binary.Comment: 11 pages, 3 figures, to be published in New Astronom

Coulomb gap in one-dimensional disordered electronic systems

We study a one-dimensional system of spinless electrons in the presence of a long-range Coulomb interaction (LRCI) and a random chemical potential at each site. We first present a Tomonaga-Luttinger liquid (TLL) description of the system. We use the bosonization technique followed by the replica trick to average over the quenched randomness. An expression for the localization length of the system is then obtained using the renormalization group method and also a physical argument. We then find the density of states for different values of the energy; we get different expressions depending on whether the energy is larger than or smaller than the inverse of the localization length. We work in the limit of weak disorder where the localization length is very large; at that length scale, the LRCI has the effect of reducing the interaction parameter K of the TLL to a value much smaller than the noninteracting value of unity.Comment: Revtex, 6 pages, no figures; discussions have been expanded in several place

Controlled traffic farming delivers better crop yield of winter bean as a result of improved root development

This paper reports on the continuation of a long–term experiment on the effects of alternative field traffic systems (STP–random traffic with standard tyre inflation pressure, LTP–random traffic with low tyre inflation pressure and CTF–controlled traffic farming) on soil conditions and crop development as influenced by different tillage depths (DEEP–250 mm, SHALLOW–100 mm and ZERO–tillage), in a randomised 3 x 3 factorial design in 4 replicates launched by Harper Adams University in Edgmond, UK, in 2011. The results from season 2017–2018 revealed that CTF delivered 8% higher crop yield of winter field bean (Vicia faba) cv. Tundracomparing to STP (p = 0.005), i.e. 4.13 vs 3.82 tonnes ha-1respectively (at 14% moisture content). The ZERO–tillage plots featured significantly lower plant establishment percentage comparing to shallow and deep tillage: 79% vs 83% and 83% respectively (p = 0.012). The research showed that roots traits differed significantly between contrasting traffic at depths greater than 50mm with p < 0.05of: tap root biomass, number of lateral roots, biomass of lateral roots as well as total root biomass (tap+lateral roots),delivering significantly greater values of those before mentioned parameters on CTF comparing to STP. Tap root length significantly differed between traffic systems (p < 0.001)giving significantly greater results on CTF comparing to LTP and STP (17.7, 13.4 and 12.6 mm respectively). Significant differences in tap root diameter were found only at the depth of 100 mm (p < 0.001) where again CTF delivered significantly higher root diameter than the remaining 2 traffic systems.In the shallow layer of soil (0–50 mm) a significant difference was found only for tap root biomass, for interactions, where STP ZERO gave significantly higher results than STP SHALLOW and CTF SHALLOW (1.430, 0.733 and 0.716 g respectively)

The Colors of Mixtures of Dental Opaque Porcelains

The colors of mixtures of dental opaque porcelains and modifiers were measured with use of the CIE L*a * b* uniform color space. Mixtures of dental porcelains were tested to duplicate the range of human tooth colors. Vertical movements in the yellow and blue directions were obtained. Horizontal movements in the red and green directions were achieved. Reflectance measurements were made with use of a spectrophotometer with an integrating sphere. Spectrophotometer measurements were converted to absolute reflectance and then used to calculate CIE a* b* values for a 2° standard observer and for illuminant C. Movements in the yellow, red, blue, and green directions for adequate simulation of the tooth color range can be demonstrated with use of dental opaque and modifier porcelains.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67312/2/10.1177_00220345890680090601.pd

Morphological shifts in response to spatial sorting on dispersal behaviour in red flour beetles across multiple generations

First published: 31 March 2023. OnlinePublDispersal is a key component of life history that influences individual fitness, population dynamics and range expansion. Morphological traits that are functionally related to dispersal may change through the spatial sorting of phenotypes at population range edges and invasion fronts. Generally, since larger invertebrates are expected to have greater dispersal capacity, larger body size and mass is expected to evolve in dispersers. Yet, different study systems exhibit a range of trait-specific and sex-specific responses to spatial sorting. Furthermore, a persistent issue in this field is that spatial sorting can be challenging to separate from natural selection and population dynamics. To address this, here we investigated the responses of dispersal and morphological traits to simulated spatial sorting into disperser and non-disperser red flour beetles (Tribolium castaneum) using a controlled laboratory dispersal system that isolated spatial sorting from natural selection and allowed sex-specific dispersal traits to evolve independently. After seven generations of spatial sorting, the time taken to disperse decreased in dispersers and increased in non-dispersers, with males dispersing more quickly than females. In contrast to expectations that dispersers would increase in body mass and size, we found the opposite. Body mass and morphology diverged such that dispersers became smaller and narrower, while non-dispersers became larger relative to the randomly selected controls, but femur length did not change. The trait responses across generations were also sex specific. Divergence between male dispersers and non-dispersers was more substantial than females, both in dispersal and in some morphological traits. We hypothesize that small individuals were more biomechanically efficient at dispersing through the dispersal apparatus and were therefore the ones that dispersed more readily. We suggest that key differences in dispersal modes across biological systems may impact the morphological and phenotypic trait changes from spatial sorting processes in range expansions and biological invasions.P. A. Arnold, P. Cassey and C. R. Whit

Results from recent traffic systems research and the implications for future work

This paper reviews the results of recent traffic systems research and concludes that the evidence shows that with sufficient ingenuity by farmers and their equipment suppliers to match operating and wheel track widths, the traffic management systems that reduce soil compaction should improve crop yield, reduce energy consumption and improve infiltration rates (which will reduce runoff, erosion and flooding). These together will improve agronomic, economic and environmental sustainability of agriculture. Low ground pressure alternatives may well be the option that best suits some farming enterprises and should not be discounted as viable traffic management methods. The paper also considers the implications for further work to improve the robustness of the experimental data

Phase Separation Based on U(1) Slave-boson Functional Integral Approach to the t-J Model

We investigate the phase diagram of phase separation for the hole-doped two dimensional system of antiferromagnetically correlated electrons based on the U(1) slave-boson functional integral approach to the t-J model. We show that the phase separation occurs for all values of J/t, that is, whether $0 < J/t < 1$ or $J/t \geq 1$ with J, the Heisenberg coupling constant and t, the hopping strength. This is consistent with other numerical studies of hole-doped two dimensional antiferromagnets. The phase separation in the physically interesting J region, $0 < J/t \lesssim 0.4$ is examined by introducing hole-hole (holon-holon) repulsive interaction. We find from this study that with high repulsive interaction between holes the phase separation boundary tends to remain robust in this low $J$ region, while in the high J region, J/t > 0.4, the phase separation boundary tends to disappear.Comment: 4 pages, 2 figures, submitted to Phys. Rev.

Boundary contributions to specific heat and susceptibility in the spin-1/2 XXZ chain

Exact low-temperature asymptotic behavior of boundary contribution to specific heat and susceptibility in the one-dimensional spin-1/2 XXZ model with exchange anisotropy 1/2 < \Delta \le 1 is analytically obtained using the Abelian bosonization method. The boundary spin susceptibility is divergent in the low-temperature limit. This singular behavior is caused by the first-order contribution of a bulk leading irrelevant operator to boundary free energy. The result is confirmed by numerical simulations of finite-size systems. The anomalous boundary contributions in the spin isotropic case are universal.Comment: 6 pages, 3 figures; corrected typo