Critical random forests

Let $F(N,m)$ denote a random forest on a set of $N$ vertices, chosen uniformly from all forests with $m$ edges. Let $F(N,p)$ denote the forest obtained by conditioning the Erdos-Renyi graph $G(N,p)$ to be acyclic. We describe scaling limits for the largest components of $F(N,p)$ and $F(N,m)$, in the critical window $p=N^{-1}+O(N^{-4/3})$ or $m=N/2+O(N^{2/3})$. Aldous described a scaling limit for the largest components of $G(N,p)$ within the critical window in terms of the excursion lengths of a reflected Brownian motion with time-dependent drift. Our scaling limit for critical random forests is of a similar nature, but now based on a reflected diffusion whose drift depends on space as well as on time

Searching for Cost Optimized Interstellar Beacons

What would SETI Beacon transmitters be like if built by civilizations with a variety of motivations, but who cared about cost? We studied in a companion paper how, for fixed power density in the far field, we could build a cost-optimum interstellar Beacon system. Here we consider, if someone like us were to produce a Beacon, how should we look for it? High-power transmitters might be built for wide variety of motives other than twoway communication; Beacons built to be seen over thousands of light years are such. Altruistic Beacon builders will have to contend with other altruistic causes, just as humans do, so may select for economy of effort. Cost, spectral lines near 1 GHz and interstellar scintillation favor radiating frequencies substantially above the classic water hole. Therefore the transmission strategy for a distant, cost-conscious Beacon will be a rapid scan of the galactic plane, to cover the angular space. Such pulses will be infrequent events for the receiver. Such Beacons built by distant advanced, wealthy societies will have very different characteristics from what SETI researchers seek. Future searches should pay special attention to areas along the galactic disk where SETI searches have seen coherent signals that have not recurred on the limited listening time intervals we have used. We will need to wait for recurring events that may arrive in intermittent bursts. Several new SETI search strategies emerge from these ideas. We propose a new test for SETI Beacons, based on the Life Plane hypotheses.Comment: 19 pages, 1 Figur

The Influence of Body Mass Index on Sweet Taste Preference in Women

Associations between sweet taste preferences and eating behaviour variables may exist with differences in taste preferences evident with varying body mass index (BMI). However, the strength of influence BMI exerts remains unknown, therefore the aim was to examine the influence of BMI on sweet taste preference in women. Three areas were examined, 1) associations between preferences for sweet taste and sweet/fat combinations and eating behaviours, 2) the differences in sweet taste preferences between overweight and lean women, and 3) whether BMI serves as a moderator for the associations between sweet taste preferences and eating behaviour variables. 86 overweight or lean women provided 7day 24hour recall food diaries before attending a laboratory assessment day. Participants completed the Leeds Food Preference Questionnaire (LFPQ) before consuming an ad libitum meal consisting of sweet and savoury foods. Immediately following consumption participants completed VAS ratings of palatability and taste intensity in response to the test meal foods. Sweet taste preferences were associated with an elevated sweet food intake in an ad libitum meal and preferences for sweet/fat combinations with habitual dietary fat intake. There were no between group differences on any measure. However, there were differences between groups in a small number of associations between taste preferences and eating behaviour variables which were moderated by BMI. The present thesis concluded that overweight and lean women did not differ in their sweet taste preferences or eating behaviours. Although, differences in the associations between taste preference and eating behaviours do exist between overweight and lean women. Future work may wish to consider using direct measures of adiposity within the moderation model. These findings build on previous literature through examination of different components of sweet taste preference and investigates the extent to which BMI moderates differences in the associations with food intake

Working Towards a Compact Cold Ion Source

This thesis presents work on creating a cold atomic ion source based on a diffraction grating magneto-optical trap using caesium. Due to this technique, the source profile has been minimised in terms of both spatial extent and production cost - characteristics that have been emphasised throughout this work so as to be more applicable to both industrial applications and further research. To ionise the Cs, a novel excitation scheme has been designed involving three low energy transitions from the ground state of 6S$_{1/2}$, to the Rydberg state 21P$_{1/2}$, from which the atoms can be field ionised. In order to maximise the efficiency of the Rydberg state coupling, a new offset frequency reference based on Zeeman detuned ground state spectroscopy of rubidium was devised. Only a weak caesium trap using a grating was observed in this work, however discussion as to the reasons for this are presented. Despite this, full schematics and engineering diagrams for the proposed integrated ion source are presented with the hope of construction once a viable trap is demonstrated as there are no fundamental reasons hindering success

Effects of Chronic Ingestion of L-arginine alpha ketoglutarate Combined With Creatine monohydrate on Anaerobic Performance in Strength-Trained Athletes

There has been a vast growth in the use of ‘pre’ workout nutritional aids for sports performance over the past decade, particularly those containing single use amino acids such as L-arginine. There are many purported physiological benefits to suggest combination of L-arginine with creatine will expedite a greater performance, however exact mechanisms are equivocal and evidence suggesting an actual performance benefit are lacking. PURPOSE: To determine the effect of L-arginine alpha ketoglutarate (AAKG) on total body mass, fat free mass, peripheral blood flow (ml.100ml-1.min-1), isometric bench press and half squat, countermovement jump and peak power output in a single anaerobic Wingate. Further investigation into additive effects of creatine monohydrate (Cr) is undertaken where warranted. METHOD: Strength trained individuals (n = 24, Age: 24.5 ± 4.9 years; Height: 179.2 ± 8.1 cm; Weight: 77.1 ± 10.3 kg) were randomly assigned in a double blind manner either: (1) AAKG combined with Cr; (2) AAKG combined with a matched cornflour placebo (PLA); (3) Matched cornflour PLA alone, or (4) Control (CONT) across an 8 week intervention. Participants’ anthropometric measures, peripheral blood flow, isometric strength and power were tested. To minimise dietary covariance, subjects completed weekly nutritional assessments to maintain dietary consistency. RESULTS: Total body mass (TBM) was not significantly different at any point during the trial, overall TBM from baseline to week 8 was not significantly altered between any group (AAKG + Cr: 1.0 ± 0.7 kg, AAKG + PLA: 0.4 ± 0.5 kg, PLA: -0.1 ± 0.5 kg and CONT: 0.2 ± 0.1 kg; P > 0.05). Similarly, fat free mass (FFM) showed no significant weekly change and no significant overall difference from baseline to week 8 (AAKG + Cr: 1.3 ± 0.8 kg, AAKG + PLA: 0.3 ± 0.6 kg, PLA: -0.4 ± 0.5 kg and CONT: -0.5 ± 0.4 kg; P > 0.05). Blood flow PRE (AAKG + Cr: 0.35 ± 0.29 ml.100ml-1.min-1, AAKG + PLA: -0.07 ± 0.21 ml.100ml-1.min-1, PLA: 0.08 ± 0.12 ml.100ml-1.min-1 and CONT: 0.27 ± 0.17 ml.100ml-1.min-1) INTER (AAKG + Cr: 0.10 ± 0.29 ml.100ml-1.min-1, AAKG + PLA: -0.03 ± 0.25 ml.100ml-1.min-1, PLA: 0.04 ± 0.10 ml.100ml-1.min-1 and CONT: 0.30 ± 0.22 ml.100ml-1.min-1) and POST (AAKG + Cr: 0.19 ± 0.32 ml.100ml-1.min-1, AAKG + PLA: -0.11 ± 0.22 ml.100ml-1.min-1, PLA: 0.12 ± 0.09 ml.100ml-1.min-1 and CONT: 0.32 ± 0.14 ml.100ml-1.min-1) showed no significant difference at any point (P > 0.05). Isometric bench press demonstrated significant differences between AAKG + Cr and CONT only (83.28 ± 20.68 N and 15.51 ± 6.35 N respectively, P = 0.026) no significant differences between any other groups (AAKG + PLA: 48.33 ± 15.76 N and PLA: 26.63 ± 15.24 N, P > 0.05). In contrast isometric squat showed no significant differences at any point (AAKG + Cr: 117.50 ± 59.72 N, AAKG + PLA: 95.33 ± 27.27 N, PLA: 33.39 ± 47.88 N and CONT: -0.34 ± 9.48 N, P > 0.05). In addition there was no significant difference between any of the power variables at any stage throughout the trial, countermovement jump (AAKG + Cr: 1.43 ± 0.72 cm, AAKG + PLA: 1.47 ± 0.97cm, PLA: -0.53 ± 2.23 cm and CONT: -2.41 ± 1.84 cm, P > 0.05) and peak wingate trial (AAKG + Cr: 23.92 ± 9.40 W, AAKG + PLA: 16.92 ± 16.80 W, PLA: -0.58 ± 8.53 W and CONT: 5.25 ± 2.38 W, P > 0.05). CONCLUSION: There was no significant difference between the majority of the variables at any stage throughout the trial, the only significant difference was in isometric bench press between AAKG + Cr and CONT. This would suggest that the combination of L-arginine alpha ketoglutarate and Creatine monohydrate might only lead to limited improvements in strength gains over those gained without supplementation