Lafayette College
  • Easton, United States
Recent publications
In this paper, we use the numerical simulation of the discrete Hirota equation to point out the localized modes and wave patterns. The discrete modulation instability is used to demonstrate how the nonlinear term generates unstable or stable modes when a little perturbation is introduced. We have also stated that for strong enough nonlinear terms, new bands emerge. Furthermore, by applying an external periodic force, we were able to push one end of the discrete Hirota model into the forbidden frequency gap. We established the threshold amplitude expression and the driven amplitude. According to one finding, the threshold of supratransmission decreases as the nonlinear term of the discrete Hirota equation increases. For specific times of propagation, we showed the propagation of the train of waves as well as the modulated wave patterns. We demonstrated the wave train traveling through the band gap, where energy jumps from the bottom to the top and vice versa, over a significant period of time. These findings will almost certainly pave the way for new nonlinear dynamics applications.
Misfolding of the prion protein is central to prion disease aetiology. Although understanding the dynamics of the native fold helps to decipher the conformational conversion mechanism, a complete depiction of distal but coupled prion protein sites common across species is lacking. To fill this gap, we used normal mode analysis and network analysis to examine a collection of prion protein structures deposited on the protein data bank. Our study identified a core of conserved residues that sustains the connectivity across the C-terminus of the prion protein. We propose how a well-characterized pharmacological chaperone may stabilize the fold. Also, we provide insight into the effect on the native fold of initial misfolding pathways identified by others using kinetics studies.
Governments in countries in Sub-Saharan Africa (SSA) are keen to expand irrigation to improve food security and are placing particular emphasis on adoption and use of smallholder private groundwater irrigation. Yet private irrigation is a multi-stage technology, the adoption of which is affected by fiscal support and extension services offered on different investment stages but also by uncertainties around actions that need to be undertaken in these stages. Groundwater-based irrigation in Ethiopia presents a case where policy has focused on fiscally easing the purchase of pumps while considerable ambiguity (unquantifiable uncertainty) exists around the outcomes of drilling boreholes (reaching water). In this paper, we examine farmers’ willingness to adopt smallholder private irrigation packages in response to lower pump prices following tax breaks, loan availability, and reduction in ambiguities related to borehole drilling, using a discrete choice experiment (DCE) in two districts of Ethiopia. The results indicate that the provision of loans and reduction in ambiguities related to well drilling have the greatest effect on the probability of farmers adopting irrigation packages. Lowering pump prices has the smallest effect. Pump-type has a small effect, with energized pumps preferred over manual ones. In exploring heterogeneity in preferences, we find that farmers without irrigated plots and those with greater market access have a greater preference for the provision of loans, while those with greater market access also have greater preferences for reductions in well drilling ambiguities. The results of this choice experiment suggest that reducing ambiguities around well drilling (initial investments) is an essential and cost-effective step toward expanding groundwater-based irrigation in Ethiopia.
The interest in sleep as a potential clinical biomarker is growing, but the standard method of sleep assessment, polysomnography, is expensive, time consuming, and requires a lot of expert assistance for both set‐up and interpretation. To make sleep analysis more available both in research and in the clinic, there is a need for a reliable wearable device for sleep staging. In this case study, we test ear‐electroencephalography. A wearable, where electrodes are placed in the outer ear, as a platform for longitudinal at‐home recording of sleep. We explore the usability of the ear‐electroencephalography in a shift work case with alternating sleep conditions. We find the ear‐electroencephalography platform to be reliable both in terms of showing substantial agreement to polysomnography after long‐time use (with an overall agreement, using Cohen's kappa, of 0.72) and by being unobtrusive enough to wear during night shift conditions. We find that fractions of non‐rapid eye movement sleep and transition probability between sleep stages show great potential as sleep metrics when exploring quantitative differences in sleep architecture between shifting sleep conditions. This study shows that the ear‐electroencephalography platform holds great potential as a reliable wearable for quantifying sleep “in the wild”, pushing this technology further towards clinical adaptation.
Stream temperature is one of the most critical factors controlling aquatic ecosystem health. Practitioners and researchers from a range of fields, including biology, ecology, hydrology, engineering, and watershed management, are concerned with how climate and environmental changes are impacting stream thermal regimes. This primer provides an introduction to the various energy and water exchange processes that underpin stream temperature patterns from small headwater streams to large river systems. An overview of the various energy exchanges is provided, including (1) advection associated with hydrologic processes, and energy exchanges at (2) the stream–atmosphere interface and (3) stream–bed interface. The interaction and spatiotemporal variability of these energy exchange processes are discussed using a water and energy balance framework. A sound physical understanding and appreciation of the complex controls governing stream thermal regimes will help inform effective management strategies to sustain healthy aquatic ecosystems in a changing world. This article is categorized under: Science of Water > Science of Water Science of Water > Hydrological Processes Science of Water > Water Quality Water and Life > Nature of Freshwater Ecosystems A sound process understanding and appreciation of the complex controls governing stream thermal regimes helps inform effective management strategies to sustain healthy aquatic ecosystems in a changing world.
Inclusive teaching is instruction that fosters a sense of belonging, is equitable for a diverse student body, and shows students that they matter. Inclusivity is associated with positive student outcomes and is critical at institutions of higher education given the diversity of student populations. While there are a number of recommended practices for inclusive teaching, valid and reliable classroom observation tools that provide instructors with formative feedback on their instructional efforts are lacking. This article describes the development of the Protocol for Advancing Inclusive Teaching Efforts (PAITE). The PAITE was developed for formative purposes to provide higher education instructors with formative feedback on observable inclusive teaching practices. The protocol can be used by peer observers, educational developers, student pedagogical partners, and educational researchers in higher education classrooms. We describe the creation of the protocol, how to prepare observers to use it within classrooms, and how instructors can use the feedback to monitor and improve their inclusive teaching approaches.
Climate change and other human activities are modifying river water temperature globally. A more holistic understanding of river temperature dynamics in an integrated climate–land–hydrology–human framework is urgently needed for sustainable river management and adaptation strategies.
In this paper, we consider the Heisenberg ferromagnetic lattices with single-ion easy-axis anisotropy to show the effects of the nearest-neighbor coupling on discrete modulation instability and localized energy in the forbidden gap. We use the multi-scale scheme to establish the nonlinear Schrödinnger equation from where it was carried out the static breather equation together with the threshold amplitude. Thus, one end of the spin chains was submitted to an external periodic boundary. It results that the nearest-neighbor coupling parameter induced instability in the forbidden frequency gap by increasing the amplitude of the plane wave. The most important feature of this investigation is the fact that the driven amplitude is considered below the threshold amplitude and the nonlinear supratransmission phenomenon arises. These outcome shed light on the fact that the Heisenberg ferromagnetic spin chains with a single-ion easy-axis anisotropy could be used to generate both long-lived temporal localized solitons and nonlinear supratransmission phenomenon.
In this study, we explored possible differences between students studying the fine arts and their non-art major peers on three separate variables: mental health, stress, and time spent on academic work. We found that students who study the fine arts report higher rates of mental distress, stress, and spend more time on academic work than do their non-art major peers. We offer recommendations for therapists working in university and college counseling settings.
Using fall migration trend data from the Raptor Population Index analyses (n = 59 count sites) paired with winter Christmas Bird Count trend data at the USA state and Canadian province level, we evaluated continental and regional patterns in trends of American Kestrels (Falco sparverius) over the last 30 yr. Long-term trends at the continental and regional level showed widespread declines in the number of kestrels counted during both fall migration and winter. The lone exception was in western North America where declining migration counts were evident, but could at least partly be explained by increasing winter counts. These results suggest that western kestrels are shifting migratory tendencies, migrating shorter distances (short-stopping), or are not migrating at all. This contrasts with patterns in central and eastern North America where kestrel counts declined in both fall and winter over the last 20- and 30-yr periods. Recent trends (2009–2019) showed less widespread declines in both fall and winter across North America and for most regions, suggesting kestrel declines might have moderated in the past decade. However, the species remains at significantly reduced abundance levels compared to the recent past and has not rebounded.
Malaria, which infected more than 240 million people and killed around six hundred thousand only in 2021, has reclaimed territory after the SARS-CoV-2 pandemic. Together with parasite resistance and a not-yet-optimal vaccine, the need for new approaches has become critical. While earlier, limited, studies have suggested that malaria parasites are affected by electromagnetic energy, the outcomes of this affectation vary and there has not been a study that looks into the mechanism of action behind these responses. In this study, through development and implementation of custom applicators for in vitro experimentation, conditions were generated in which microwave energy (MW) killed more than 90% of the parasites, not by a thermal effect but via a MW energy-induced programmed cell death that does not seem to affect mammalian cell lines. Transmission electron microscopy points to the involvement of the haemozoin-containing food vacuole, which becomes destroyed; while several other experimental approaches demonstrate the involvement of calcium signaling pathways in the resulting effects of exposure to MW. Furthermore, parasites were protected from the effects of MW by calcium channel blockers calmodulin and phosphoinositol. The findings presented here offer a molecular insight into the elusive interactions of oscillating electromagnetic fields with P. falciparum , prove that they are not related to temperature, and present an alternative technology to combat this devastating disease.
The 2021 emergence of the 17‐year Brood X cicadas (Magicicada septendecim, M. cassinii, and M. septendecula) saw billions of cicadas emerge from the soil throughout the midwestern and eastern United States. The emergence left connected burrows visible at the surface, which are hypothesized to affect near surface hydrologic processes. To investigate these processes, we used single‐ring, dual head infiltrometers to measure field saturated hydraulic conductivity (Kfs, n = 70) across patterns of emergence and land use in south‐central Indiana, USA. Our experimental design included locations with and without cicada burrows in forested (undisturbed) and urbanized (disturbed) areas. Across undisturbed sites, we found a significant 80.8% increase in Kfs between soils with (median = 14.1 cm/hr; n = 20) and without (median = 7.8 cm/hr; n = 20) cicada burrows. At disturbed sites, we found no significant difference in Kfs between sites with (median = 4.2 cm/hr; n = 18) and without (median = 4.4 cm/hr; n = 12) cicada burrows. We found a significant correlation between the number of burrows present at the surface and Kfs rates for undisturbed sites (ρ = 0.42; p = 0.008), while no correlation was found for the disturbed sites (ρ = ‐0.09; p = 0.62). Our measurements suggest that the effect of burrows on Kfs is minimized in urbanized areas, potentially due to compaction and other impacts from human disturbance that mitigate the presence of macropores left by cicadas. In contrast, surface‐connected macroporosity from Brood X cicada burrows in undisturbed areas act as a conduit for precipitation into the soil profile and bypass flow into deeper horizons and the shallow groundwater table, with implications for runoff dynamics, soil and groundwater recharge and quality, and nutrient cycling. This article is protected by copyright. All rights reserved.
Based on well-known complexity theory conjectures, any polynomial-time kernelization algorithm for the NP-hard Line-Cover problem produces a kernel of size Ω( k 2 ), where k is the size of the sought line cover. Motivated by the current research in massive data processing, we study the existence of kernelization algorithms with limited space and time complexity for Line-Cover. We prove that every kernelization algorithm for Line-Cover takes time Ω(n log k + k 2 log k ) , and present a randomized kernelization algorithm for Line-Cover that produces a kernel of size bounded by k2, and runs in time O ( n log k + k 2 (log k log log k ) 2 ) and space O ( k 2 log 2 k ) . Our techniques are also useful for developing deterministic kernelization algorithms for Line-Cover with limited space and improved running time, and for developing streaming kernelization algorithms for Line-Cover with near-optimal update-time.
In this paper, we examined the behavior of the modulated waves patterns and nonlinear supratransmission phenomenon in gyrotropy molecular chains where the first neighbor and third-neighbor interaction are considered. We have established the propagation modes through the dispersion law showing two cutoff frequencies. Through the numerical simulation we have depicted modulated waves, solitons interaction as well as the modulation instability growth rates brought by the variation of the third-neighbor interaction and effective mass. As it was predicted that the group velocities vanish at the carrier waves, we have uncoupled a system of the coupled nonlinear Schr"{o}dinger equation by neglecting the elastic interaction to drive one end of the chains. The driven amplitude generates the train of waves in the system. For a specific time of propagation, we have shown how the variation of driven amplitude can induce instability in the forbidden gap. The obtained results have opened new features to the train of pulses in gyrotropy molecular chains.
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1,098 members
Michael Nees
  • Department of Psychology
Bernard Fried
  • Department of Biology
Shyamal K. Majumdar
  • Department of Biology
Michael W Butler
  • Department of Biology
Tamara L. Carley
  • Department of Geology and Environmental Geosciences
Easton, United States