Effects Of External Stimuli Research Articles

Effects of external stimuli on the dynamics of deterministic and stochastic Hindmarsh–Rose neuron models

Effects of external stimuli on the dynamics of deterministic and stochastic Hindmarsh–Rose neuron models

A new Eosin Y-based ‘turn[sbnd]on’ fluorescent sensor for ratiometric sensing of toxic mercury ion (Hg2+) offering unaided eye detection and its antibacterial activity

A unique fluorescent molecule (ND-S) was obtained from Eosin Y in two simple yet high yielding steps (1). ND-S has special metal ion sensing ability, such that it can selectively detect toxic Hg2+ present in very low concentration in aqueous solutions in the presence of other competing metal ions. The host-guest complexation is ratiometric and is associated with significant increase in fluorescence during the process. Isothermal titration calorimetry (ITC) experiments provided thermodynamic parameters related to interaction between ND-S and Hg2+. Using inductively coupled plasma mass spectrometry (ICP-MS), the Hg2+(aq) removal efficiency of ND-S was estimated to be 99.88%. Appreciable limit of detection (LOD = 7.4 nM) was observed. Other competing ions did not interfere with the sensing of Hg2+ by ND-S. The effects of external stimuli (temperature and pH) were studied. Besides, the complex (ND-M), formed by 1:1 coordination of ND-S and Hg2+ was found to be effective against the survival of Gram-positive bacteria (S. aureus and B. subtilis) with a high selectivity index. Moreover, bacterial cell death mechanism was studied systematically. Overall, we have shown the transformation of a toxic species (Hg2+), extracted from polluted water by a biocompatible sensor (ND-S), into an effective and potent antibacterial agent (ND-M).

Clarification of Psychiatric Nurses' Intentions and Analysis Contents in Observing Schizophrenia Patient.

The purpose of this study was to clarify what psychiatric nurses intended to observe when observing schizophrenia patient and what they analyzed from their observations. Twenty-one experienced nurses were included in the study. Data were collected through semi-structured interviews, and content analysis was conducted. The results were as follows:Nurses' intentions in observing patient were [Observation of psychiatric symptoms], [Observation of normality or abnormality], [Possibility of self-harm or harming others], [Side effects of antipsychotics], [Degree of communication disorder], [Degree of self-care], [Observation of nutritional status], [Effects of external stimuli on patient], and [Less importance of observing doctor]. Nurses' analysis contents were [Analysis of psychiatric symptoms], [No risk of self-harm or harming others], [Effects of antipsychotics], [Presence of communication disorder], [Lack of trust in doctor], [Problems in daily life], [Consideration of future nursing intervention], [Assessment of normality or abnormality], [Unhealthy physical state], and [Unnecessary analysis]. The results of this study revealed the nurses' observational process. J. Med. Invest. 71 : 54-61, February, 2024.

Classification and regression tree approach for the prediction of the seasonal apparel market: focused on weather factors

PurposeClimate change-induced weather changes are severe and frequent, making it difficult to predict apparel sales. The primary goal of this study was to assess consumers' responses to winter apparel searches when external stimuli, such as weather, calendars and promotions arise and to develop a decision-making tool that allows apparel retailers to establish sales strategies according to external stimuli.Design/methodology/approachThe theoretical framework of this study was the effect of external stimuli, such as calendar, promotion and weather, on seasonal apparel search in a consumer's decision-making process. Using weather observation data and Google Trends over the past 12 years, from 2008 to 2020, consumers' responses to external stimuli were analyzed using a classification and regression tree to gain consumer insights into the decision process. The relative importance of the factors in the model was determined, a tree model was developed and the model was tested.FindingsWinter apparel searches increased when the average, maximum and minimum temperatures, windchill, and the previous day's windchill decreased. The month of the year varies depending on weather factors, and promotional sales events do not increase search activities for seasonal apparel. However, sales events during the higher-than-normal temperature season triggered search activity for seasonal apparel.Originality/valueConsumer responses to external stimuli were analyzed through classification and regression trees to discover consumer insights into the decision-making process to improve stock management because climate change-induced weather changes are unpredictable.

A Review of Methods and Applications for a Heart Rate Variability Analysis

Heart rate variability (HRV) has emerged as an essential non-invasive tool for understanding cardiac autonomic function over the last few decades. This can be attributed to the direct connection between the heart’s rhythm and the activity of the sympathetic and parasympathetic nervous systems. The cost-effectiveness and ease with which one may obtain HRV data also make it an exciting and potential clinical tool for evaluating and identifying various health impairments. This article comprehensively describes a range of signal decomposition techniques and time-series modeling methods recently used in HRV analyses apart from the conventional HRV generation and feature extraction methods. Various weight-based feature selection approaches and dimensionality reduction techniques are summarized to assess the relevance of each HRV feature vector. The popular machine learning-based HRV feature classification techniques are also described. Some notable clinical applications of HRV analyses, like the detection of diabetes, sleep apnea, myocardial infarction, cardiac arrhythmia, hypertension, renal failure, psychiatric disorders, ANS Activity of Patients Undergoing Weaning from Mechanical Ventilation, and monitoring of fetal distress and neonatal critical care, are discussed. The latest research on the effect of external stimuli (like consuming alcohol) on autonomic nervous system (ANS) activity using HRV analyses is also summarized. The HRV analysis approaches summarized in our article can help future researchers to dive deep into their potential diagnostic applications.

The Effect of External Dissociative Stimuli on Plank Duration Performed by Male Collegiate Soccer Players.

D'Agata, MN, Staub, JP, Scavone, DJ, and Kane, GM. The effect of external dissociative stimuli on plank duration performed by male collegiate soccer players. J Strength Cond Res 37(5): e341-e345, 2023-Individuals commonly use music as an external auditory stimulus to divert their attention away from aerobic endurance exercise tasks. Music generally results in lower ratings of perceived exertion, which may be the mechanism by which it increases aerobic exercise task duration. However, less is known regarding how music affects the performance of other forms of exercise, such as isometric exercise. Moreover, the effects of different external stimuli on isometric task duration, such as the use of virtual reality (VR), have yet to be investigated. Therefore, the purpose of this study was to investigate the effects of self-selected music (SSM) and VR on isometric exercise task duration using a forearm plank. We hypothesized that both SSM and VR would effectively increase plank duration compared with no external stimuli. Seventeen male collegiate soccer players (19 ± 1 year) completed 3 planks to failure on 3 separate days, with 48-72 hours between the trials. The ordering of each exercise condition (SSM, VR, or None) was randomized for a total of 6 potential orders. A one-way repeated-measures analysis of variance was used to evaluate differences in plank duration and average heart rate (HR avg ) between each trial, and significance was set at p < 0.05. There were no differences in plank duration (SSM: 200 ± 44, VR: 173 ± 38, None: 177 ± 37 seconds) or HR avg (SSM: 96 ± 18, VR: 92 ± 21, None: 87 ± 18 beats per minute) between the conditions. We conclude that there was no effect of external stimuli (SSM or VR) on isometric exercise task duration and the use of these modalities should be based on exerciser preference.

Functional neuronal circuitry and oscillatory dynamics in human brain organoids

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, the physiology of neuronal circuits within organoids remains under-explored. With high-density CMOS microelectrode arrays and shank electrodes, we captured spontaneous extracellular activity from brain organoids derived from human induced pluripotent stem cells. We inferred functional connectivity from spike timing, revealing a large number of weak connections within a skeleton of significantly fewer strong connections. A benzodiazepine increased the uniformity of firing patterns and decreased the relative fraction of weakly connected edges. Our analysis of the local field potential demonstrate that brain organoids contain neuronal assemblies of sufficient size and functional connectivity to co-activate and generate field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug action, and the effects of external stimuli upon neuronal networks.

Self-Assembled Metal Nanoclusters: Driving Forces and Structural Correlation with Optical Properties.

Studies on self-assembly of metal nanoclusters (MNCs) are an emerging field of research owing to their significant optical properties and potential applications in many areas. Fabricating the desired self-assembly structure for specific implementation has always been challenging in nanotechnology. The building blocks organize themselves into a hierarchical structure with a high order of directional control in the self-assembly process. An overview of the recent achievements in the self-assembly chemistry of MNCs is summarized in this review article. Here, we investigate the underlying mechanism for the self-assembly structures, and analysis reveals that van der Waals forces, electrostatic interaction, metallophilic interaction, and amphiphilicity are the crucial parameters. In addition, we discuss the principles of template-mediated interaction and the effect of external stimuli on assembly formation in detail. We also focus on the structural correlation of the assemblies with their photophysical properties. A deep perception of the self-assembly mechanism and the degree of interactions on the excited state dynamics is provided for the future synthesis of customizable MNCs with promising applications.

Vortex dynamics in amorphous MoSi superconducting thin films

Vortex dynamics in superconductors have received a great deal of attention from both fundamental and applied researchers over the past few decades. Because of their critical role in the energy relaxation process of type-II superconductors, vortex dynamics have been deemed a key factor for the emerging superconducting devices, but the effect of irradiation on vortex dynamics remains unclear. With the support of electrical transport measurements under external magnetic fields and irradiation, the photon effect on vortex dynamics in amorphous MoSi (a-MoSi) superconducting thin films is investigated in this work. The magnetic-field-dependent critical vortex velocity v* derived from the Larkin–Ovchinnikov (LO) model is not significantly affected by irradiation. However, vortex depinning is found to be enhanced by photon-induced reduction in the potential barrier, which mitigates the adverse effect of film inhomogeneity on superconductivity in the a-MoSi thin films. A thorough understanding of the vortex dynamics in a-MoSi thin films under the effect of external stimuli is of paramount importance for both further fundamental research in this area and the optimization of future superconducting devices.

An effective model of endogenous clocks and external stimuli determining circadian rhythms

Circadian endogenous clocks of eukaryotic organisms are an established and rapidly developing research field. To investigate and simulate in an effective model the effect of external stimuli on such clocks and their components we developed a software framework for download and simulation. The application is useful to understand the different involved effects in a mathematical simple and effective model. This concerns the effects of Zeitgebers, feedback loops and further modifying components. We start from a known mathematical oscillator model, which is based on experimental molecular findings. This is extended with an effective framework that includes the impact of external stimuli on the circadian oscillations including high dose pharmacological treatment. In particular, the external stimuli framework defines a systematic procedure by input-output-interfaces to couple different oscillators. The framework is validated by providing phase response curves and ranges of entrainment. Furthermore, Aschoffs rule is computationally investigated. It is shown how the external stimuli framework can be used to study biological effects like points of singularity or oscillators integrating different signals at once. The mathematical framework and formalism is generic and allows to study in general the effect of external stimuli on oscillators and other biological processes. For an easy replication of each numerical experiment presented in this work and an easy implementation of the framework the corresponding Mathematica files are fully made available. They can be downloaded at the following link: https://www.biozentrum.uni-wuerzburg.de/bioinfo/computing/circadian/.

Complex dynamics of a Fitzhugh-Rinzel neuron model considering the effect of electromagnetic induction

Different single computational neuron models have been proposed in the literature. Most of them belong to the Hodgkin–Huxley (H-H) type, in which they can produce complex behavior of the neuron and have efficient computational cost. In this paper, a modified FitzHugh-Rinzel (FH-R) model considering the effect of magnetic induction is proposed. Different features of the model are explored from a complex and nonlinear perspective. For instance, the impact of the magnetic field on the stability of the equilibrium points is studied by stability analysis. Bifurcation analysis reveals that the proposed neuron model has multi-stability. Furthermore, the spatiotemporal behavior of the proposed model is investigated in the complex network consisting of FH-R oscillators, and the effect of external stimuli is explored on wave propagation of the network.

Synthesis and self-assembly of polyzwitterionic phenylboronic acid-containing double hydrophilic block copolymers

Double hydrophilic block copolymers self-assemble into smart materials with promising applications in nanomedicine. However, such practical applications require thoroughly understanding the underlying mechanisms of this self-assembly process and the effects of external stimuli on the resulting materials. Thus, we report the post-polymerization modification of a pH-responsive double hydrophilic diblock copolymer (poly(ethylene oxide)-b-poly(4-vinyl pyridine)) by stimuli-responsive, diol-binding 2-bromomethyl-4-fluorophenylboronic acid and the comprehensive study of the self-assembly properties of this polyzwitterionic polymer for potential applications in the delivery of functional diols, including pharmaceutical drugs, steroids and sugars. For this purpose, we performed simple, robust and reproducible quaternization reactions at three different degrees (25, 50 and 100%) by varying the composition of the initial mixture and confirmed full control over the degree of quaternization by proton nuclear magnetic and infrared spectroscopy. Our results show that the degree of quaternization strongly affects the solubility of these polymers in basic solutions because PBA adopts a tetragonal conformation with a negative charge on boron at pH values higher than the pKA of PBA. Nevertheless, the specific PBA (anionic vs neutral) form of these polymers can be differentiated by 11B NMR, regardless of the degree of quaternization. In turn, the pH of the solvent affected the intensity of the NMR signals, thus suggesting the formation of kinetically frozen nanoparticles, in line with the results from both static and dynamic light scattering, with no indication of particle dissociation at low concentrations. Moreover, electrophoretic light scattering showed linear, albeit opposite (direct and inverse) correlations between the degree of quaternization and the zeta potential in water and 0.1 M HCl, respectively. When adsorbed to a mica surface, these nanoparticles predominantly displayed globular shapes under atomic force microscopy. Therefore, our high-throughput and low-cost nanofabrication method combining the stimuli-responsive behavior of a double hydrophilic block copolymer with the unique chemical properties of pH-responsive diol-binding phenylboronic acid functional groups establishes an experimental paradigm for preparing nanocarriers for biomedical applications, such as targeted drug delivery.

Engineering the liposomal formulations from natural peanut phospholipids for pH and temperature sensitive release of folic acid, levodopa and camptothecin

The present study demonstrates the extraction and identification of phospholipids (PLs) from peanut seed for formulation of liposomes for pH and thermo-sensitive delivery and release of folic acid (FA), levodopa (DOPA) and, camptothecin (CPT). The TLC, FTIR and GC–MS based characterization of extracted peanut PLs showed phosphatidylethanolamine, cardiolipin and phosphatidic acid as major PLs and palmitic acid and oleic acid as major fatty acids. Liposomes (LSMs) of size 1–2 μm formulated by optimized thin-film hydration method were found to entrap FA, DOPA and CPT with 58, 61.4 and 52.12% efficiency, respectively with good stability. The effect of external stimuli like pH and temperature on the release pattern of FA, DOPA and CPT indicated that FA was optimally released at pH 10 and 57 °C, DOPA at pH 2 and 37 °C, while CPT was best released at pH 6 and 47 °C. When tested for the in vitro activity, DOPA released by DOPA@LSMs showed lower toxicity to 3T3 than to SH-SY5Y cells. Similarly, CPT released by CPT@LSMs showed remarkable anticancer activity against MCF-7 cells with an IC50 value of 17.99 μg/mL. Thus peanut PLs can be efficiently used for liposomal formulations for pH and thermo-sensitive release of drugs.

Ruminal resistome of dairy cattle is individualized and the resistotypes are associated with milking traits

BackgroundAntimicrobial resistance is one of the most urgent threat to global public health, as it can lead to high morbidity, mortality, and medical costs for humans and livestock animals. In ruminants, the rumen microbiome carries a large number of antimicrobial resistance genes (ARGs), which could disseminate to the environment through saliva, or through the flow of rumen microbial biomass to the hindgut and released through feces. The occurrence and distribution of ARGs in rumen microbes has been reported, revealing the effects of external stimuli (e.g., antimicrobial administrations and diet ingredients) on the antimicrobial resistance in the rumen. However, the host effect on the ruminal resistome and their interactions remain largely unknown. Here, we investigated the ruminal resistome and its relationship with host feed intake and milk protein yield using metagenomic sequencing.ResultsThe ruminal resistome conferred resistance to 26 classes of antimicrobials, with genes encoding resistance to tetracycline being the most predominant. The ARG-containing contigs were assigned to bacterial taxonomy, and the majority of highly abundant bacterial genera were resistant to at least one antimicrobial, while the abundances of ARG-containing bacterial genera showed distinct variations. Although the ruminal resistome is not co-varied with host feed intake, it could be potentially linked to milk protein yield in dairy cows. Results showed that host feed intake did not affect the alpha or beta diversity of the ruminal resistome or the abundances of ARGs, while the Shannon index (R2 = 0.63, P < 0.01) and richness (R2 = 0.67, P < 0.01) of the ruminal resistome were highly correlated with milk protein yield. A total of 128 significantly different ARGs (FDR < 0.05) were identified in the high- and low-milk protein yield dairy cows. We found four ruminal resistotypes that are driven by specific ARGs and associated with milk protein yield. Particularly, cows with low milk protein yield are classified into the same ruminal resistotype and featured by high-abundance ARGs, including mfd and sav1866.ConclusionsThe current study uncovered the prevalence of ARGs in the rumen of a cohort of lactating dairy cows. The ruminal resistome is not co-varied with host feed intake, while it could be potentially linked to milk protein yield in dairy cows. Our results provide fundamental knowledge on the prevalence, mechanisms and impact factors of antimicrobial resistance in dairy cattle and are important for both the dairy industry and other food animal antimicrobial resistance control strategies.

Domain walls in ferroelectrics

AbstractSpontaneous unit‐cell deformation accompanies spontaneous polarization in perovskite ferroelectrics, thereby making it energetically favorable for domain walls to form on particular planes that satisfy mechanical compatibility. Historically, domain walls are found analytically, solving for walls with compatible strains within the wall plane. However, analytical solutions do not give any information about relative energetics of nonideal domain walls. Here, the orientation of the most favorable domain walls and the relative energetics of nonideal domain walls are predicted by calculating strain mismatch and charge discontinuity over all possible domain wall orientations. This is done for common ferroelectric phase symmetries of tetragonal, rhombohedral, orthorhombic, and monoclinic type. In tetragonal and rhombohedral symmetry, the domain walls are independent of any external stimulus as long as the symmetry is maintained. In orthorhombic and monoclinic symmetry, the orientation of certain mechanically permissible domain walls changes with temperature and/or electric field as the unit cell distorts, while others do not. Additionally, in monoclinic systems, domain wall planes are shown to exist that are not perfectly permissible but are very close to permissible, thus, these walls were not found by prior analytical methods. The visualization of strain compatibility of all the domain walls makes it easy to see precisely on which planes domain walls are expected or not expected and how the domain walls change their orientation under the effect of external stimulus. Such an analysis can also be used to investigate the relative and changing energetics of nonideal domain walls in systems under thermal, compositional, electrical, and mechanical stimuli.

Intrinsic Network Activity in Human Brain Organoids

Human brain organoids replicate much of the cellular diversity and developmental anatomy of the human brain. However, neurophysiology within organoids remains relatively under-explored. With high-density CMOS microelectrode arrays and shank electrodes, we probed broadband and three-dimensional activity of human brain organoids. From spiking activity, we estimated a directed functional connectivity graph of neural network activity which showed a large number of weak functional connections enmeshed within a network skeleton of significantly fewer strong connections. Increasing the intrinsic inhibitory tone with a benzodiazepine suppressed the network skeleton of the functional network. We further demonstrate that human brain organoids have self-organized neuronal assemblies of sufficient size, cellular orientation, and functional connectivity to generate local field potentials from their collective transmembrane currents that phase-lock to spiking activity. These results point to the potential of brain organoids for the study of neuropsychiatric diseases, drug mechanisms, and the effects of external stimuli upon neuronal networks.

The Status Quo of Rashba Phenomena in Organic-Inorganic Hybrid Perovskites.

In this Perspective, we address the fundamentals and possible implications of Rashba phenomena particularly for noncentrosymmetric and heavy element-containing hybrid perovskite systems. The work sheds light on the application paradigm of these exciting phenomena in the field of photovoltaics, light-emitting diodes, and catalytic reactions. The experimental realization along with the theoretical prediction of these phenomena in the emerging energy materials family of hybrid perovskites opens up a new direction for modulating the charge carrier recombination probability of the excited electrons and the holes. The influence of external parameters, such as pressure, uni- and biaxial strain, and electric field, has been addressed explicitly to change the Rashba factor, which essentially suppresses the recombination rate. The current Perspective provides a roadmap of materials design and the effect of external stimuli on the plethora of hybrid perovskite materials for extensive energy scavenging with the focus on photovoltaics.

Combined light- and heat-induced shape memory behavior of anthracene-based epoxy elastomers

The development of multi-stimuli-responsive shape memory polymers has received increasing attention because of its scientific and technological significance. In this work, epoxy elastomers with reversible crosslinks are synthesized by polymerizing an anthracene-functionalized epoxy monomer, a diepoxy comonomer, and a dicarboxylic acid curing agent. The synthesized elastomers exhibit active responses to both light and heat enabled by the incorporated anthracene groups. When exposed to 365 nm UV light, additional crosslinking points are created by the photo-induced dimerization of pendant anthracene groups. The formation of the crosslinking points increases modulus and glass transition temperature of the elastomers, allowing for the fixation of a temporary shape at room temperature. The temporary shape remains stable until an external heat stimulus is applied to trigger the scission of the dimerized anthracene, which reduces the modulus and glass transition temperature and allows the elastomers to recover their original shapes. The effects of external stimuli on the thermal and dynamic mechanical properties of the elastomers are investigated experimentally and are correlated with molecular dynamics simulations that reveal the changes of structure and dynamics of the anthracene molecules and flexible chains.

Effects of oscillating electric fields on conotoxin peptide conformation: A molecular dynamic simulation study

Molecular Dynamics (MD) simulation is a computational method frequently used in biological and material sciences to efficiently model atomic and molecular interactions occurring in biological systems and effects of external stimuli on molecules and cells.In this study, M − 1 conotoxin protein was simulated under the oscillating (time-varying) electric fields of strengths 2e−9, 6e−9 and 4.7e−8 V/nm at the frequency of 1800 MHz. Conformational changes in conotoxin were studied using Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF), secondary structure analysis and Radial Distribution Functions (RDF). We also performed cluster analysis for Conotoxin by running three simulations at the same parameters to analyse an overall conformation of the peptide.Our findings show that applied oscillating electric field of 4.7e−8 V/nm produced changes in the conformation of conotoxin, whereas, at 6e−9 V/nm, only minor changes were observed, which were then stabilised during the simulation. The results also reveal that the applied field at the lowest strength of 2e−9 did not induce any effects on conotoxin’s conformation.

Изучение взаимосвязей между развитием сенсорного утомления и наличием нарушений в здоровье у респондентов

The article discusses the features of sensory fatigue which persons with impaired health of different nosological groups may experience. During the study, visual, sound and tactile triggers of sensory fatigue in respondents were identified; as well as the frequency and periods of development of this functional state and the duration of cases of sensory fatigue in respondents from different groups. Analysis of the results of the study showed that respondents with impaired health and a conditionally healthy group have different reasons for the development of sensory fatigue and the manifestation of mental responses to the intense effects of external stimuli.