Wireless Energy Harvesting System

The modern world is built upon wireless transmission of data. The signals that carry this data travel through the air, an untapped source of power. Unreceived transmissions are dissipated into useless forms of energy when they should be reclaimed. Wireless electronics can theoretically be powered by harvesting energy from the electromagnetic signals in the wireless internet frequency band. The aim of this project is to develop a system to capture ambient energy, convert it into DC power, and store the power for later use. The product will consist of three subsystems: an antenna receiver, a rectifier and voltage-multiplier, and a power management unit. The antenna must be compact, and have the highest gain possible. The final product should be able to be mounted in any orientation for versatility. The rectifier subsystem will be matched to the receiver in order to convert the AC signal into a DC signal. The multiplier can increase the voltage to supply the power management unit (PMU). It is critical for the rectifier system to be able to operate at low power levels to effectively feed into the PMU. The power management unit will receive the amplified voltage from the rectifier and voltage-multiplier. It is crucial for the PMU to operate at low power and have the capability to output a constant DC power, similar to a battery, despite unreliable sources. Commercially available PMU’s can be programmed and implemented with the other subsystems to provide effective power management. The advantage of this simple design is the ability to be replicated without complex or proprietary methods. Once each module is tested and verified, the three will be implemented together and tested for efficient wireless energy harvesting, power storage, and ultimately to deliver power

Bicycle Handlebar Width Does Not Affect Spirometry, Ventilation, or Gas Exchange

Bicycle fit may affect comfort, aerodynamics, efficiency, ventilation, and power generation. Handlebars determine how the rider interacts with the bicycle. A wide range of handlebar widths are commercially available, but it is unclear if the resultant position affects lung function, ventilation, gas exchange, or efficiency. PURPOSE We aimed to measure the effects of handlebar widths on ventilation, gas exchange, spirometry, and comfort during moderate constant power exercise. METHODS Twenty-four recreationally active adults completed the study (32 ± 5 yrs., 175 ± 9 cm, 74 ± 12 kg, 8 women, 16 men). Participants completed three moderate constant power bouts of exercise on a cycle ergometer (Lode Excalibur PFM) while using handlebars set equivalent to, or ± 4cm in width to the participant shoulder width. We used a one-way RMANOVA to compare the three handlebar widths. RESULTS There was no difference in gas exchange and ventilation between the three handlebar widths: V̇O2 (F[2, 23] = 0.99, p = 0.38), V̇CO2 (F[1.47, 23] = 0.39, p = 0.62), V̇E (F[2, 23] = 0.53, p = 0.59], VT (F[2, 23] = 0.44, p = 0.65], fBr (F[2, 23] = 0.17, p = 0.84], PetO2(F[2, 23] = 0.45, p = 0.64), PetCO2 (F[2, 23] = 0.25, p=0.78]. Similarly, there were no differences in inspiratory capacity during the bout (F[1.49, 22] = 1.34, p = 0.27) or any spirometry variables immediately following exercise: FVC (F[1.43, 22] = 0.88, p = 0.39], FEV1 (F[2, 22] = 0.30, p = 0.74], FEV1/FVC (F[2, 22] = 0.18, p = 0.84], PEF (F[2, 22] = 0.14, p = 0.87]. There was no difference in the overall comfort (F[2, 23] = 0.90, p = 0.41] or shoulder discomfort (F [2, 23] = 0.90, p = 0.42). CONCLUSIONS Bicycle handlebar widths within 4 cm shoulder width do not result in changes to ventilation, gas exchange, efficiency, spirometry, or comfort during moderate power cycling exercise. Within the limits of rider preference, comfort, and safety, handlebar width can be adjusted substantially for aerodynamic purposes without affecting rider physiology

Characteristics that define a top international school according to stakeholder perspectives. A Thai case study

International schools have been around for more than 100 years (Thompson, 2018) but it is in the last 20 years that they have experienced a boom in growth (Gaskell, 2016). This recent boom has resulted in many more current students receiving an international education than at any other period in history. The resulting implication is that research in the international school market has lagged behind the commercial growth of international schools (Lee, Hallinger & Walker, 2012). The purpose of this research is to improve current knowledge of international schools by identifying the ten most important items in international schools as reported by three different stakeholder groups (administrators/teachers, parents and students). Due to a lack of research in this area, a readily available research tool was not available to the researcher. It became therefore imperative that the researcher developed a tool for this process and the tool was created through interviews and utilization of a Delphi framework. The creation of this tool resulted in a questionnaire with 68 possible items; it was then trialled via a pilot study so the tool could be improved. These improvements were implemented and the tool was utilised to receive information from the three stakeholder groups associated with the case study school. These results were then compared for similarities and differences between the three stakeholder groups. It was found that these groups were not statistically independent on 46 items, and that two or more groups were statistically independent on 22 items. This indicated that for most items the different stakeholder groups shared a common perspective on their relative importance. The research results were then analysed to identify the top ten items as reported by each of the three stakeholder groups. There was much similarity in the results with four items appearing in each stakeholder group’s top ten and six items appearing in two out of three stakeholder groups’ top ten

Phosphorus limitation of aboveground production in northern hardwood forests

Forest productivity on glacially derived soils with weatherable phosphorus (P) is expected to be limited by nitrogen (N), according to theories of long-term ecosystem development. However, recent studies and model simulations based on resource optimization theory indicate that productivity can be co-limited by N and P. We conducted a full factorial N × P fertilization experiment in 13 northern hardwood forest stands of three age classes in central New Hampshire, USA, to test the hypothesis that forest productivity is co-limited by N and P. We also asked whether the response of productivity to N and P addition differs among species and whether differential species responses contribute to community-level co-limitation. Plots in each stand were fertilized with 30 kg N·ha−1·yr−1, 10 kg P·ha−1·yr−1, N + P, or neither nutrient (control) for four growing seasons. The productivity response to treatments was assessed using per-tree annual relative basal area increment (RBAI) as an index of growth. RBAI responded significantly to P (P = 0.02) but not to N (P = 0.73). However, evidence for P limitation was not uniform among stands. RBAI responded to P fertilization in mid-age (P = 0.02) and mature (P = 0.07) stands, each taken as a group, but was greatest in N-fertilized plots of two stands in these age classes, and there was no significant effect of P in the young stands. Both white birch (Betula papyrifera Marsh.) and beech (Fagus grandifolia Ehrh.) responded significantly to P; no species responded significantly to N. We did not find evidence for N and P co-limitation of tree growth. The response to N + P did not differ from that to P alone, and there was no significant N × P interaction (P = 0.68). Our P limitation results support neither the N limitation prediction of ecosystem theory nor the N and P co-limitation prediction of resource optimization theory, but could be a consequence of long-term anthropogenic N deposition in these forests. Inconsistencies in response to P suggest that successional status and variation in site conditions influence patterns of nutrient limitation and recycling across the northern hardwood forest landscape

Soil nitrogen affects phosphorus recycling: foliar resorption and plant–soil feedbacks in a northern hardwood forest

Previous studies have attempted to link foliar resorption of nitrogen and phosphorus to their respective availabilities in soil, with mixed results. Based on resource optimization theory, we hypothesized that the foliar resorption of one element could be driven by the availability of another element. We tested various measures of soil N and P as predictors of N and P resorption in six tree species in 18 plots across six stands at the Bartlett Experimental Forest, New Hampshire, USA. Phosphorus resorption efficiency (P , 0.01) and proficiency (P ¼ 0.01) increased with soil N content to 30 cm depth, suggesting that trees conserve P based on the availability of soil N. Phosphorus resorption also increased with soil P content, which is difficult to explain based on single-element limitation, but follows from the correlation between soil N and soil P. The expected single-element relationships were evident only in the O horizon: P resorption was high where resin-available P was low in the Oe (P , 0.01 for efficiency, P , 0.001 for proficiency) and N resorption was high where potential N mineralization in the Oa was low (P , 0.01 for efficiency and 0.11 for proficiency). Since leaf litter is a principal source of N and P to the O horizon, low nutrient availability there could be a result rather than a cause of high resorption. The striking effect of soil N content on foliar P resorption is the first evidence of multiple-element control on nutrient resorption to be reported from an unmanipulated ecosystem

High Redshift AGN: Accretion Rates and Morphologies for X-ray and Radio SC4K Sources from z~2 to z~6

We study a large sample of ~4000 Lyα Emitters (LAEs) and identify the active galactic nuclei (AGN) among them in order to characterise their evolution across cosmic time. This work was carried out using the SC4K survey (Sobral et al. 2018) and data collected by the Hubble Space Telescope (HST), Chandra X-ray Observatory and the Very Large Array (VLA). We find 322 X-ray or radio detected AGN within the sample, constituting 8.7±0.5% of the sources considered. We find that the vast majority of classifiable AGN (81±3%) are point-like or compact sources in the rest-frame UV seen with HST, and this qualitative trend holds regardless of detection band or redshift. These AGN have a range of black hole accretion rates (BHARs), and we present the first direct comparison between radio and X-ray BHARs. X-ray calculated BHARs range from ~0.07 M⊙/yr to ~23 M⊙/yr, indicating a highly varied sample, with some very active AGN detected. Radio calculated BHARs range from ~0.09 M⊙/yr to ~8.8 M⊙/yr, broadly tracing the same range as the X-ray calculated BHARs. X-ray calculated BHARs peak at z~3 and both radio and X-ray calculated BHARs increase with increasing redshift, plateauing at z~4. We find significantly less variation in radio BHARs when compared to X-ray BHARs, indicating radio may be a far more stable and reliable method of calculating the BHARs of AGN over large timescales, while X-ray is more suitable for instantaneous BHARs

Recovery from disturbance requires resynchronization of ecosystem nutrient cycles

Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance

Peripheral Heating with Negative Pressure Increases Arterial Blood Flow

Over half (53%) of adults in the United States have some form of diabetes. Traditional treatments have been inadequate in stopping this epidemic suggesting the need for novel therapies. Peripheral heating with negative pressure has previously been shown to reduce blood glucose. The mechanisms behind this effect are unknown but may be related to changes in blood flow to the treated extremity. PURPOSE: To examine changes in flow rate (time averaged mean velocity (TAMV)), vessel cross-sectional area (CSA), and blood flow in the popliteal artery before and during peripheral heating with negative pressure applied to the feet. METHODS: Measures of TAMV, CSA, and blood flow were obtained from the left and right popliteal artery of participants using an ultrasound doppler (Philips CX50, General Electric, USA) before and during peripheral heating with negative pressure. Heat (42°C) was applied to the sole of the feet and negative pressure (-75 mmHg) applied from the feet to the top of the calves while participants remained seated. Vessels were matched for pre and post measures using anatomical landmarks and vessel diameter. Blood flow was calculated as TAMV * CSA. Data are presented as mean (SD) and were analyzed with paired two-sided t-tests. RESULTS: Participants’ (N=8, 4 men and 4 women) demographics are as follows: age: 26.5 (6.1) years; height: 177.7 (9.0) cm; BMI: 25.5 (3.9) kg/m2; body fat: 18.9 (5.7) %. From baseline to during the intervention, TAMV increased 22.3% from 13.0 (13.4) to 16.0 (16.5) cm/sec, p=.059 and 24.7% from 10.5 (10.7) to 13.0 (13.3) cm/sec, p=.067; CSA increased 9.7% from 0.42 (0.34) to 0.46 (0.39) cm2, p=.247, and 10.4% from 0.65 (0.62) to 0.72 (0.70) cm2, p=.122; and blood flow increased 32.3% from 5.2 (3.1) to 7.0 (4.0) mL/sec, p=.115 and 29.5% from 7.2 (7.3) to 9.3 (7.4) mL/sec, p=.032, in the left and right popliteal arteries respectively. CONCLUSION: In this pilot study, applying heat and negative pressure to the feet increased arterial blood flow largely by increasing flow rate with lesser changes to vessel CSA. Without reader blinding and assurance that the same vessel and portion of said vessel were used for pre and post measures, these results should be considered exploratory and interpreted with caution

Extra, extra, (don't) roll-off about It! Newspaper endorsements for ballot measures

Voters often have difficulty making choices on the myriad state constitutional amendments they vote on each year. Without partisan cues, they turn to other sources for these low-salience, high complexity measures. One such source is newspaper endorsements. In this article, we look at newspaper endorsements of ballot measures in Florida over 20 years both on “no” votes and roll-off. We argue that endorsements’ effect on “no” votes and roll-off differs in ways not previously appreciated. Newspaper endorsements have a positive impact on no votes, as expected from the information theory of voter participation. Endorsements have little impact on roll-off, which we posit is because roll-off voters are not likely to seek information from newspapers. Thus, newspaper endorsements serve to persuade, but not entice, voters to vote for ballot measures