Paying for Default: Change Over Time in the Share of Federal Financial Aid Sent to Institutions with High Student Loan Default Rates

Both federal spending on financial aid and student loan default rates have increased over the past decade. These trends have intensified policymakers’ concerns that some postsecondary institutions— particularly in the for-profit sector—maximize revenue derived from federal financial aid without helping students to graduate or find employment. Prior studies have analyzed federal financial aid disbursements and student loan default rates in isolation from one another. Therefore, little is known about how much federal aid flows through colleges with high student loan default rates. The present study examines change over time and across sectors in the share of federal financial aid disbursed to institutions with “low,” “medium,” and “high” student loan default rates. We found that the share of federal student aid flowing through colleges with medium and high student loan default rates increased substantially from 2007-08 to 2012-13, but declined in 2013-14 as the national job market improved. However, the reduction in federal financial aid disbursed to for-profit institutions with high student loan default rates occurred prior to the national job-market recovery, suggesting that federal regulations helped to divert federal financial aid from poor-performing institutions

Truncating and Oversampling OFDM Signals in White Gaussian Noise Channels

This work introduces a modified version of the orthogonal frequency division multiplexing (OFDM) signal by truncating OFDM symbols in the time domain. Sub-carriers are no longer orthogonally packed in the frequency domain as time samples are only partially transmitted, leading to improved spectral efficiency. In this work, mathematical expressions are derived for the newly proposed Truncated OFDM (TOFDM) signal, followed by interference analysis and performance comparisons. We also consider optimal and practical decoder architectures. Results from a Sphere Decoder-based decoder indicate that truncation length can significantly affect the error performance. With short truncation length, using a purpose designed detector, signals can be recovered even with truncated symbol transmission

Experimental Validation of Zero Padding in SEFDM Systems Using Over-the-Air Transmission

Non-orthogonal spectrally efficient frequency division multiplexing (SEFDM) saves bandwidth by compressing the frequency spacing between the subcarriers. This is at the cost of introducing inter-carrier interference (ICI) between the subcarriers. This self-created ICI compounded by the signal degradation caused during wireless propagation in multipath environments, complicates the task of channel estimation and equalisation. Recent studies suggest that combining zero padding (ZP) with SEFDM signals can simplify the challenge of channel estimation and equalisation in the frequency-domain. In this work, we validate experimentally the new ZP scheme through over-the-air transmission of radio frequency (RF) signals. Experimental results prove that using ZP in SEFDM enhances the channel estimation and equalisation accuracy, in comparison to conventional cyclic prefix (CP)-SEFDM. In addition, it is shown that ZP-SEFDM offers robustness against timing offsets

Zero Padding or Cyclic Prefix: Evaluation for Non-Orthogonal Signals

The debate of using zero padding (ZP) instead of a cyclic prefix (CP) for enhancing channel estimation and equalization performance is a recurring topic. This is particularly true for orthogonal signals, such as orthogonal frequency division multiplexing (OFDM). Yet, there are far fewer studies evaluating the impact of ZP and CP in non-orthogonal systems. Such systems have the added complexity of self-induced interference rendering channel estimation and equalization more challenging. For this reason, this work proposes a new channel estimation and equalization technique for non-orthogonal systems, which combines ZP with an orthogonal demodulator. Results show that the multipath components that appear in the ZP part can be used to enhance performance when compared to the CP approach

Modeling and compensation of nonlinear distortion in direct-detection optical Fast-OFDM systems

Fast-OFDM based intensity-modulation and direct-detection (IM/DD) has been proposed for the deployment of cost-efficient optical access networks, due to simple implementation and high spectral efficiency. In this work, the generalized memory polynomial (GMP) is firstly applied to model the nonlinear characteristic of IM/DD Fast-OFDM links, including memory effects. After model validation using measured data of a 10 km single mode fiber link, the GMP is used for performance investigations of a combined clipping and digital post-distortion approach to optical Fast-OFDM, considering both 4PAM and 8PAM modulation formats and different number of Fast-OFDM subcarriers. This work firstly reports performance results of optical 8PAM-Fast-OFDM systems using 2PAM-based training signals for digital post-distortion and FFT-based channel estimation. Excellent performance improvements are achieved using the proposed distortion compensation scheme, relative to conventional system implementation

Antibacterial effects of peppermint, \u3ci\u3eMentha piperita\u3c/i\u3e essential oil in free-form and in nanoparticles on \u3ci\u3ePseudomonas fluorescens\u3c/i\u3e

Mentha piperita, commonly known as peppermint originally came from Europe and the Middle East and its oil is commonly used in traditional medicine and aromatherapy. Like many other free essential oils (EO), peppermint oil is believed to possess antimicrobial properties. However, the application of EO in food as an antimicrobial agent has yet to be established. This would require proper formulation of the EO for it to be viable in foods. This study aims to test the effects of both free Mentha piperita EO and Mentha piperita EO nanoparticles against Pseudomonas fluorescens and compare their inhibitory effects. We used nanoparticles of encapsulated Mentha piperita EO in a shell of fully hydrogenated soybean oil (FHSO) and expect that the inhibitory effects of these nanoparticles would be greater than that of the free EO due to the ability of the shell to protect the EO and control its dispersion. We observed for the presence of antibacterial properties using various methods such as well diffusion, disc diffusion, optical density measurements and plate counting of serial dilutions. We found that the best method that produced quantifiable results was to perform serial dilutions and plate count them after incubation. In these series of experiments, we demonstrated that free Mentha piperita EO inhibits P. fluorescens growth but have yet to demonstrate a similar effect with the EO nanoparticles

Antibacterial effects of peppermint, \u3ci\u3eMentha piperita\u3c/i\u3e essential oil in free-form and in nanoparticles on \u3ci\u3ePseudomonas fluorescens\u3c/i\u3e

Mentha piperita, commonly known as peppermint originally came from Europe and the Middle East and its oil is commonly used in traditional medicine and aromatherapy. Like many other free essential oils (EO), peppermint oil is believed to possess antimicrobial properties. However, the application of EO in food as an antimicrobial agent has yet to be established. This would require proper formulation of the EO for it to be viable in foods. This study aims to test the effects of both free Mentha piperita EO and Mentha piperita EO nanoparticles against Pseudomonas fluorescens and compare their inhibitory effects. We used nanoparticles of encapsulated Mentha piperita EO in a shell of fully hydrogenated soybean oil (FHSO) and expect that the inhibitory effects of these nanoparticles would be greater than that of the free EO due to the ability of the shell to protect the EO and control its dispersion. We observed for the presence of antibacterial properties using various methods such as well diffusion, disc diffusion, optical density measurements and plate counting of serial dilutions. We found that the best method that produced quantifiable results was to perform serial dilutions and plate count them after incubation. In these series of experiments, we demonstrated that free Mentha piperita EO inhibits P. fluorescens growth but have yet to demonstrate a similar effect with the EO nanoparticles

Characterizing Sympathetic Neurovascular Transduction in Humans

Despite its critical role for cardiovascular homeostasis in humans, only a few studies have directly probed the transduction of sympathetic nerve activity to regional vascular responses – sympathetic neurovascular transduction. Those that have variably relied on either vascular resistance or vascular conductance to quantify the responses. However, it remains unclear which approach would better reflect the physiology. We assessed the utility of both of these as well as an alternative approach in 21 healthy men. We recorded arterial pressure (Finapres), peroneal sympathetic nerve activity (microneurography), and popliteal blood flow (Doppler) during isometric handgrip exercise to fatigue. We quantified and compared transduction via the relation of sympathetic activity to resistance and to conductance and via an adaptation of Poiseuille’s relation including pressure, sympathetic activity, and flow. The average relationship between sympathetic activity and resistance (or conductance) was good when assessed over 30-second averages (mean R$^2$=0.49±0.07) but lesser when incorporating beat-by-beat time lags (R$^2$=0.37±0.06). However, in a third of the subjects, these relations provided relatively weak estimates (R$^2$0.50 in 20 of 21 individuals), and provided reproducible estimates of transduction. The gain derived from the relation of resistance (but not conductance) was inversely related to transduction (R$^2$=0.37, p<0.05), but with a proportional bias. Thus, vascular resistance and conductance may not always be reliable surrogates for regional sympathetic neurovascular transduction, and assessment from a Poiseuille relation between pressure, sympathetic nerve activity, and flow may provide a better foundation to further explore differences in transduction in humans

Assessment of the influence of intrinsic environmental and geographical factors on the bacterial ecology of pit latrines

Funding Information: This research received financial support from the Bill and Melinda Gates Foundation (grant number OPP52641). AWW and JP were supported by the Wellcome Trust [grant number 098051]. AWW and the Rowett Institute of Nutrition and Health, University of Aberdeen, receive core funding support from the Scottish Government Rural and Environmental Science and Analysis Service (RESAS). UZ is funded by Natural Environment Research Council (NERC) Independent Research Fellowship (NE/L011956/1). CQ is funded through an Medical Research Council fellowship (MR/M50161X/1) as part of the MRC Cloud Infrastructure for Microbial Bioinformatics consortium (MR/L015080/1).Peer reviewedPublisher PD