A Multi Hidden Recurrent Neural Network with a Modified Grey Wolf Optimizer

Identifying university students' weaknesses results in better learning and can function as an early warning system to enable students to improve. However, the satisfaction level of existing systems is not promising. New and dynamic hybrid systems are needed to imitate this mechanism. A hybrid system (a modified Recurrent Neural Network with an adapted Grey Wolf Optimizer) is used to forecast students' outcomes. This proposed system would improve instruction by the faculty and enhance the students' learning experiences. The results show that a modified recurrent neural network with an adapted Grey Wolf Optimizer has the best accuracy when compared with other models.Comment: 34 pages, published in PLoS ON

Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer.

Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO3 monolayers by inducing a spin reorientation in (SrRuO3)1/(SrTiO3) N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO3 monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO3. First-principle calculations reveal that increasing the SrTiO3 layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO3 monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications

The fluctuation energy balance in non-suspended fluid-mediated particle transport

Here we compare two extreme regimes of non-suspended fluid-mediated particle transport, transport in light and heavy fluids ("saltation" and "bedload", respectively), regarding their particle fluctuation energy balance. From direct numerical simulations, we surprisingly find that the ratio between collisional and fluid drag dissipation of fluctuation energy is significantly larger in saltation than in bedload, even though the contribution of interparticle collisions to transport of momentum and energy is much smaller in saltation due to the low concentration of particles in the transport layer. We conclude that the much higher frequency of high-energy particle-bed impacts ("splash") in saltation is the cause for this counter-intuitive behavior. Moreover, from a comparison of these simulations to Particle Tracking Velocimetry measurements which we performed in a wind tunnel under steady transport of fine and coarse sand, we find that turbulent fluctuations of the flow produce particle fluctuation energy at an unexpectedly high rate in saltation even under conditions for which the effects of turbulence are usually believed to be small

Optical Mass Gauging System for Measuring Liquid Levels in a Reduced Gravity Environment

A compact and rugged fiber-coupled liquid volume sensor designed for flight on a sounding rocket platform is presented. The sensor consists of a Mach-Zehnder interferometer capable of measuring the amount of liquid contained in a tank under any gravitational conditions, including a microgravity environment, by detecting small changes in the index of refraction of the gas contained within a sensing region. By monitoring changes in the interference fringe pattern as the system undergoes a small compression provided by a piston, the ullage volume of a tank can be directly measured allowing for a determination of the liquid volume. To demonstrate the technique, data are acquired using two tanks containing different volumes of liquid, which are representative of the levels of liquid in a tank at different time periods during a mission. The two tanks are independently exposed to the measurement apparatus, allowing for a determination of the liquid level in each. In a controlled, laboratory test of the unit, the system demonstrated a capability of measuring a liquid level in an individual tank of 10.53 mL with a 2% error. The overall random uncertainty for the flight system is higher than that one test, at +/- 1.5 mL

Bed load sediment transport and morphological evolution in a degrading uniform sediment channel under unsteady flow hydrographs

Flume experiments are conducted to investigate the intrinsic links between time-varying bed load transport properties for uniform sediments and bed surface morphology under unsteady hydrograph flows, in the absence of upstream sediment supply. These conditions are representative of regulated river reaches (e.g. downstream of a dam) that are subject to natural flood discharges or managed water releases, resulting in net degradation of the river bed. The results demonstrate that the hydrograph magnitude and unsteadiness have significant impacts on sediment transport rates and yields, as well as hysteresis patterns and yield ratios generated during the rising and falling limbs. A new hydrograph descriptor combining the influence of total water work and unsteadiness on bed load transport is shown to delineate these hysteresis patterns and yield ratios, whilst correlating strongly with overall sediment yields. This provides an important parametric link between unsteady hydrograph flow conditions, bed load transport and bed surface degradation under imposed zero sediment feed conditions. As such, maximum bed erosion depths and the longitudinal bed degradation profiles along the flume, are strongly dependent on the magnitude of this new hydrograph descriptor. Similarly, non-equilibrium bed forms generated along the flume indicate that formative conditions for alternate bars, mixed bar/dunes or dunes are defined reasonably well by an existing morphological model and the new hydrograph descriptor. These findings provide a new framework for improved predictive capabilities for sediment transport and morphodynamic response in regulated rivers to natural or imposed unsteady flows, while their wider application to graded sediments are also considered

Lack of Effectiveness of Antiretroviral Therapy in Preventing HIV Infection in Serodiscordant Couples in Uganda: An Observational Study.

BACKGROUND: We examined the real-world effectiveness of ART as an HIV prevention tool among HIV serodiscordant couples in a programmatic setting in a low-income country. METHODS: We enrolled individuals from HIV serodiscordant couples aged ≥18 years of age in Jinja, Uganda from June 2009 - June 2011. In one group of couples the HIV positive partner was receiving ART as they met clinical eligibility criteria (a CD4 cell count ≤250 cells/ μL or WHO Stage III/IV disease). In the second group the infected partner was not yet ART-eligible. We measured HIV incidence by testing the uninfected partner every three months. We conducted genetic linkage studies to determine the source of new infections in seroconverting participants. RESULTS: A total of 586 couples were enrolled of which 249 (42%) of the HIV positive participants were receiving ART at enrollment, and an additional 99 (17%) initiated ART during the study. The median duration of follow-up was 1.5 years. We found 9 new infections among partners of participants who had been receiving ART for at least three months and 8 new infections in partners of participants who had not received ART or received it for less than three months, for incidence rates of 2.09 per 100 person-years (PYRs) and 2.30 per 100 PYRs, respectively. The incidence rate ratio for ART-use was 0.91 (95% confidence interval 0.31-2.70; p=0.999). The hazard ratio for HIV seroconversion associated with ART-use by the positive partner was 1.07 (95% CI 0.41-2.80). A total of 5/7 (71%) of the transmissions on ART and 6/7 (86%) of those not on ART were genetically linked. CONCLUSION: Overall HIV incidence was low in comparison to previous studies of serodiscordant couples. However, ART-use was not associated with a reduced risk of HIV transmission in this study

Morphodynamics of a width-variable gravel bed stream: new insights on pool-riffle formation from physical experiments

Field observations, experiments, and numerical simulations suggest that pool-riffles along gravel bed mountain streams develop due to downstream variations of channel width. Where channels narrow, pools are observed, and at locations of widening, riffles occur. Based on previous work, we hypothesize that the bed profile is coupled to downstream width variations through momentum fluxes imparted to the channel surface, which scale with downstream changes of flow velocity. We address this hypothesis with flume experiments understood through scaling theory. Our experiments produce pool-riffle like structures across average Shields stresses t* that are a factor 1.5–2 above the threshold mobility condition of the experimental grain size distribution. Local topographic responses are coupled to channel width changes, which drive flows to accelerate or decelerate on average, for narrowing and widening, respectively. We develop theory which explains the topography-width-velocity coupling as a ratio of two reinforcing timescales. The first timescale captures the time necessary to do work to the channel bed. The second timescale characterizes the relative time magnitude of momentum transfer from the flowing fluid to the channel bed surface. Riffle-like structures develop where the work and momentum timescales are relatively large, and pools form where the two timescales are relatively small. We show that this result helps to explain local channel bed slopes along pool-riffles for five data sets representing experimental, numerical, and natural cases, which span 2 orders of magnitude of reach-averaged slope. Additional model testing is warranted.Peer ReviewedPostprint (published version

Core binding factors are necessary for natural killer cell development, and cooperate with Notch signaling during T cell specification

CBF{beta} is the non-DNA binding subunit of the core binding factors (CBFs). Mice with reduced CBF{beta} levels display profound, early defects in T but not B cell development. Here we show that CBF{beta} is also required at very early stages of natural killer (NK) cell development. We also demonstrate that T cell development aborts during specification, as the expression of Gata3 and Tcf7, which encode key regulators of T lineage specification, is substantially reduced, as are functional thymic progenitors. Constitutively active Notch or IL-7 signaling cannot restore T cell expansion or differentiation of CBF{beta} insufficient cells, nor can overexpression of Runx1 or CBF{beta} overcome a lack of Notch signaling. Therefore the ability of the prethymic cell to respond appropriately to Notch is dependent on CBF{beta}, and both signals converge to activate the T cell developmental program