Structural Elements Research Articles

Allelic variation at the PPD-A1 locus and its associations with heading time and winter wheat (Triticum aestivum L.) agronomic traits in the northern Black Sea region

Aim. The identification of Ppd-1-alleles in winter bread wheat varieties of various origin, including the ones of Ukrainian plant breeding and recombinant-inbred lines Orenburgskaya 48//Cappelle Desprez/2В Chinese Spring, and the evaluation of the effects of allele Ppd-А1_del303, including the interaction with different alleles of gene Ppd-B1, by the duration of the period before heading and the related agronomically valuable traits. Methods. DNA extraction, allele-specific PCR, agarose and polyacrylamide gel electrophoresis, phenological observations, evaluation of frost resistance in seedlings, and analysis of morphobiological traits and elements of yield structure. Statistical analysis of the obtained data was carried out in Microsoft Excel. The significance of the difference between samples was assessed by Fisher's F test. A difference of p < 0.05 was considered statistically significant for all indicators. Results. The marking of 30 varieties of different origin and 64 recombinant-inbred lines of Orenburgskaya 48//Cappelle Desprez/2B Chinese Spring winter bread wheat was carried out to identify the alleles of the Ppd-A1 gene. The polymorphism of varieties and populations of recombinant-inbred lines in the northern Black Sea region (Odesa) was evaluated for ten traits: frost resistance of plants in the seedling phase, winter hardiness, duration of the period before heading, plant height, grain number per spike, grain weight per spike, thousand grain weight, number of productive tillers per unit area, harvest index and grain yield. The comparison of the lines evaluation data in terms of agronomic traits and the results of the genotypes identification allowed us to identify the influence of Ppd-A1 gene alleles and various combinations of the alleles of Ppd-A1 and Ppd-B1 genes on these traits. Conclusions. A higher prevalence of the Ppd-A1_del303 allele was found both among varieties and recombinant-inbred lines. The genetic differences by the Ppd-A1 gene (Ppd-A1_del303 or Ppd-A1b) are significantly related only to frost resistance of seedlings in the absence of significant differences in other traits. The interaction between Ppd-A1b and Ppd-B1c alleles contributed to the acceleration of early maturity and the formation of the highest indicators of grain weight per spike, thousand grain weight, harvest index, and grain yield. The replacement of the Ppd-A1b allele with Ppd-A1_del303 led to a decrease in the effect of the dominant Ppd-B1c allele on accelerating heading and negatively affected the grain weight per spike, thousand grain weight, harvest index and grain yield compared to the Ppd-A1b Ppd-B1c genotype.

Discourse of the Marginalized: A Critical Analysis of Mulk Raj Anand's The Old Woman and The Cow

Women have had lower social status in Indian traditional culture. The primary objective of the study is to critically evaluate Mulk Raj Anand’s novel The Old Woman and The Cow from a feminist perspective. By adopting this approach, the research aims to illuminate the marginalized voices within the narrative and explore the novel's treatment of gender, power dynamics, and societal norms. The analysis of the novel is grounded in feminist criticism, focusing on the portrayal of female characters, their agency, and the challenges they confront in a patriarchal society. The methodology involves closely examining the text, paying careful attention to character development, narrative structure, and thematic elements. The study reveals how Anand’s novel provides a platform for marginalized voices, emphasizing the resilience and agency of women in the face of adversity. It underscores the role of literature in challenging societal norms and advocating for social change.

On a space-time implementation of the wave equation using virtual elements

AbstractThe virtual element method (VEM) was developed not too long ago, starting with the paper (Beirão-da-Veiga et al. in SIAM J Numer Anal 51:794–812, 2013) related to elasticity in solid mechanics. The virtual element method allows to revisit the construction of different elements, however has so far not applied to space-time formulations for one-dimensional structural elements like strings, trusses and beams. Here we study several VEM elements suitable for space-time formulations that are build upon the Hamilton’s principle. It will be shown that these elements can be easily incorporated in classical finite element codes since they have the same number of unknowns. Furthermore, we show that the property of VEM to deal with non-conforming meshes is of special interest for holistic space time formulation: VEM formulations allow locally varying time discretizations (time increments) in a natural and efficient way.

The Effect of the Layup on the Stability of Composite Cylindrical Shells

Fiber reinforced plastic laminated composites have conquered greater and greater territory in the field of engineering in the past decades for their high strength to weight ratio. By varying the layup structure their behavior can easily be modified. One of the applications, that is investigated in this article is the slit tube or cylindrical shell, that used as a structural element undergoes bending. These shells indifferent from their material may experience the snap-through phenomenon (this depends both on the material and geometry) in which the shell flattens and loses its stability to bending. Depending on the layup bistable behavior also can be achieved, i.e., the shell would have two different shapes that are in equilibrium without any constraint. In this article the effect of the layup is investigated both on the bistable behavior and the snap-through phenomenon. Geometric limitations for the bistability are calculated based on a simple beam model from the literature. The same model is used to find the snap-through moment for these shells as a function of the orientation angle. It is also proven that the flattening of the shell cannot be evaded by changing the layup structure. The results are confirmed by FE simulations where applicable.

Improved Building Information Modeling Based Method for Prioritizing Clash Detection in the Building Construction Design Phase

The rising complexity of construction projects and the industry’s commitment to sustainable practices have driven the extensive adoption of Building Information Modeling (BIM) technology. A core function of BIM is the early identification and resolution of clashes during the design phase, which serves to mitigate costly rework and delays in the construction process. This study presents an advanced method for classifying and prioritizing hard clashes between structural components and mechanical, electrical, and plumbing (MEP) systems. Employing the Best-Worst Method (BWM), this research assigned specific weights to structural and MEP elements based on expert evaluations. Six parameters were incorporated into this prioritization framework: the weights determined by the BWM, outputs from Navisworks software (v2021), the ratio of MEP volume to floor volume, the functional purpose of each floor, and the number of adjacent elements. A custom-developed plugin for Autodesk Navisworks integrated these parameters, enabling real-time automated clash prioritization. Clashes were ranked by criticality through a calculation involving the six parameters, which enhanced the efficiency of clash detection by optimizing time and cost considerations during the design phase. Case study results indicate that beams and columns represent the most critical structural elements, while ducts are identified as the most significant MEP elements. The proposed method substantially improves clash detection and prioritization efficiency and accuracy, yielding considerable benefits in project management and resource allocation.

EDOF – HOW DOES IT WORK?

EDOF is the name of a new category of intraocular lenses that are a kind of compromise between traditional monofocal and trifocal IOLs. Monofocal IOLs allow you to have good vision at one distance with high quality. Multifocal, on the contrary, give sufficient visual acuity at various distances, but are characterized by the presence of a large number of dysphotopsias. Intraocular lenses with extended focus provide greater independence from glasses than monofocals while maintaining high quality vision.Objective: to discuss the available information on the principles of EDOF imaging by lenses and the dependence of the state of the wavefront of the artiphakic eye on the combination of spherical corneal aberrations and IOLs.The wavefront of the eye is formed by several structural elements, the main of which are the cornea and the lens (artificial lens). The study of aberrations of the human eye is in the field of refractive surgery. Attempts to use aberrations in cataract surgery began with the creation of aspherical IOLs. The latter were intended to correct spherical corneal aberrations and were aimed at improving the characteristics of the wavefront. The development and use of aspherical IOLs were based on data on the state of the cornea of the average eye and gave a conditional effect. The new generation of IOLs based on the creation of a certain number and type of spherical aberrations is designed to modify (deform) the wavefront of the artifakic eye and expand its optical capabilities while maintaining a low number of dysphotopsias. This, in a way, revolutionary change in trends brings cataract surgery even closer to refractive surgery.According to the authors, for the fullest use of the capabilities of IOLs from the EDOF category, it is necessary to apply the principles and experience of refractive surgery in terms of studying the characteristics of the operated eye and correlating them with the parameters planned for IOL implantation.

Zooplankton metacommunity knowledge over 20 years: a systematic review

Abstract The metacommunity theory aims to understand the species dynamics at different scales by considering the influence of local and regional processes. We conducted a systematic review of zooplankton metacommunity studies in global aquatic ecosystems (freshwater, marine and estuarine) looking for the distribution, time scale, type of system, type of environment, zooplankton group tested, ecological approach and metacommunity approach analyzed in the studies. We also present an overview of the observed patterns of the zooplankton metacommunity in different environmental conditions. We searched for scientific studies published until December 2022 on Scopus and Web of Science using the words: “zooplankton” and “metacomunnit*.” Our results show that studies on the zooplankton metacommunity have become recurrent over time (167 studies), especially for pond systems and for the groups of rotifers, cladocerans and copepods; however, several gaps remain related to studies distribution and the low number of studies in streams, reservoirs, with functional and phylogenetic diversity, and the elements of metacommunity structure. Our data improve the knowledge of the zooplankton metacommunity over time, help to identify the gaps that need to be explored in future studies and bring a general overview of the observed patterns for the zooplankton metacommunity.

Investigation of the effect of repeated variable loads on the life cycle of transport structures using polymer composite materials

The problem of the life cycle of transport structures using polymer composite materials (PCM) is touched upon. It is noted that in the life cycle of transport structures, at the stage of operation, the endurance of structural materials plays a key role. The results of experimental studies of PCM depending on the magnitude of the coefficients of reinforcement with fiberglass reinforcement (SPA) are presented. The influence of the degree of prestress of the SPA on the life cycle of the structural element has been established. It is emphasized that in the study of the life cycle of structures, the coefficient of asymmetry of the external load application cycle is of no small importance. As a result of the study, it was found that with an increase in the coefficient of asymmetry of the application of an external load with a simultaneous increase in the prestress in the SPA, the coefficient of endurance, and, consequently, the life cycle of the element, increases.

Membrane piezoelectric MDS-actuator with a flat double spiral of interacting electrodes

A schematic diagram and mathematical model of functioning of a new piezoelectric membrane (MDS) actuator with double spiral (DS) electrodes on the upper and/or lower surfaces of a thin piezoelectric layer with axisymmetric and periodic (with a small period) in radial coordinate mutual reversed electric polarization are presented. The polarization of the layer was realized as a result of connecting the polarizing electric voltage of the appropriate value to the outputs of the double spirals of the electrodes. The electrodes of each (upper and lower) double spiral of the MDS-actuator are made in the form of electrodeposited ribbon coatings on the surfaces of the piezoelectric layer in close proximity to each other (due to the small spiral pitch) to create high values of electric field strength along the lines of force in localized areas of the piezoelectric layer between them when an alternating or constant control electric voltage is connected to the electrodes, in particular, with positive and negative values of the electrical potentials. Importantly, the electric field force lines and, as a consequence, the polarization of the piezoelectric layer of the MDS actuator are oriented mainly along (i.e. towards or against) the radial coordinate of the membrane, in contrast to many conventional actuator schemes. The results of numerical modeling for a circular elastic membrane with piezoelectric actuators installed on its upper and lower surfaces confirmed the effectiveness of the proposed piezoelectric MDS-actuator when it functions according to the “bimorph” scheme, including the use of the proposed new structural element (section) – a piezoelectric “compression ring” MDS at various geometric and control parameters. The effect of a significant increase in the membrane deflection with installed piezoelectric MDS-actuators compared to the use of traditional homogeneous plate piezoelectric actuators of bimorph type for different conditions of the membrane fixation, in particular, stationary (rigid) fixation of its center is revealed. For a hybrid piezoelectric MDS-actuator including independent concentric round and circular (i.e. “compression ring”) sections, the non-monotonic nature and numerical analysis of the nonlinear dependence of the largest deflection at the center of a hinge-immobile membrane fixed at the edge on the ratio of the radii of its round and circular MDS sections were revealed. The cases in which the effect of the “compression ring” is manifested, i.e. when the maximum deflection of a membrane with the “compression ring” exceeds the best possible value of the deflection of this membrane without its use in the traditional “bimorph” scheme, are identified. The new piezoelectric MDS-actuator can be used in micromechanics, controlled optics, sensor technology, acoustics, in particular, in the manufacture of piezoelectric acoustic or sensor elements of membrane type, electromechanical transducers for vibration energy collection.

Mouse Models Enable the Functional Investigation of Tertiary Lymphoid Structures in Cancer.

Tertiary lymphoid structures (TLSs) are organized lymphoid aggregates that form within nonlymphoid tissue, including tumors, in response to persistent inflammatory stimulation. In cancer patients, TLSs are generally associated with positive clinical outcomes. However, the cellular composition and spatial distribution of TLSs can vary depending on the underlying disease state, complicating interpretations of their prognostic significance. Murine models are indispensable for providing a deeper insight into the mechanisms involved in TLS formation and function. Studies using these models can complement current clinical efforts to characterize TLSs via genetic sequencing and histopathology of human samples. Several features of TLSs resemble that of secondary lymphoid organs (SLOs). Consequently, vascular system components and structural support elements are important for TLS formation and maintenance. Furthermore, TLSs in different tissue environments can exhibit distinct characteristics, necessitating careful consideration when selecting mouse models for study. Herein, we discuss critical aspects to consider when modeling TLSs and describe recent findings of TLS studies in the mouse lung and intestinal gut environments as examples to highlight the importance of considering tissue-specific regulatory mechanisms for TLSs. In this chapter, we also summarize the mechanistic insights derived from murine models on the formation and function of TLSs, which may translate to the future therapeutic modulation of TLS in disease.

Exploring the Critical Role of Tight Junction Proteins in Kidney Disease Pathogenesis.

Kidney disease poses a significant global health challenge, marked by a rapid decline in renal function due to a variety of causative factors. A crucial element in the pathophysiology of kidney disease is the dysregulation of epithelial cells, which are vital components of renal tissue architecture. The integrity and functionality of these cells are largely dependent on tight junctions (TJ) proteins, complex molecular structures that link adjacent epithelial cells. These TJ not only confer cellular polarity and maintain essential barrier functions but also regulate epithelial permeability. TJ proteins are pivotal in their traditional role at cell junctions and in their non-junctional capacities. Recent research has shifted the perception of these proteins from mere structural elements to dynamic mediators of kidney disease, playing significant roles in various renal pathologies. This review explores the multifaceted roles of TJ proteins, focusing on their functions both within and external to the renal epithelial junctions. It highlights how these proteins contribute to mechanisms underlying kidney disease, emphasizing their impact on disease progression and outcomes. TJ proteins have emerged as significant players in the field of nephrology, not only for their structural role but also for their regulatory functions in disease pathology. Their dual roles in maintaining epithelial integrity and mediating pathological processes make them promising therapeutic targets for kidney disease. Understanding the intricate contributions of TJ proteins in kidney pathology offers potential for novel therapeutic strategies, aiming to modulate these proteins to halt or reverse the progression of kidney disease.

Study on the performance of hydrophilic curing agent and environmentally friendly non-pozzolanic filler for the development of self-curing self-compacting concrete.

Self-compacting concrete (SCC) is often used when compaction is difficult, requiring special attention to the curing process. However, traditional curing methods usually fail in practice. Despite taking precise measures to control water evaporation, surface water on vertical structure elements can still be problematic. To address these challenges, this study seeks to investigate the possibility of creating self-curing self-compacting concrete (SCSCC). Since the curing agent used has a significant impact on the production of SCSCC, this study examines the effects of using polyethylene glycol (PEG), a hydrophilic agent, at varying rates of 0.5%, 1%, 1.5%, and 2% on the fresh, hardened, and durability characteristics of the material. Additionally, to improve the sustainability properties of SCSCC, manufactured sand (M-sand) acquired from crushing rocks is used as a filler. Overall, the results indicate that the use of superplasticizer and M-sand is enough to achieve the required flowability for SCC mixtures without requiring specific fillers, and this method is effective in immediately controlling bleeding and segregation while maintaining the necessary compressive strength at all ages. The hardened properties of SCSCC were found to be improved by increasing the PEG content up to 1.5%, with an optimal range of 0.75% superplasticizer. Furthermore, the results demonstrate that the self-cured specimen, cured with PEG, has greater acid resistance than the conventionally cured one.

Correlation between productivity traits and protein percentage in pea seeds in the conditions of Donbass

The solution to the most urgent problem of stable and smooth production of vegetable protein in the agro industrial complex of Donbass is practically impossible without introducing new pea varieties into production, the main legume of the region. The main tasks set by the breeders are to improve productivity stability over the years and the overall productivity potential by developing and introducing new, more environmentally flexible and adapted to specific growing conditions genotypes into production. In this regard, there has been given a special role to improving a number of quantitative traits that directly or indirectly affect the overall productivity of plants. The purpose of the current research was to identify the closeness and direction of the correlation of traits that determine productivity and protein percentage in pea seeds, their stability and variability depending on weather changes during a vegetation period. The weather conditions of 2022–2024 were very contrasting, which allowed evaluating the significance of each productivity element in more detail. There has been found that close correlations between seed weight per plant and a number of seeds per plant (r = 0.79***…0.83***), as well as a number of beans per plant (r = 0.69**…0.80***), between a number of beans and seeds per plant (r = 0.79***…0.85***) were studied in relatively favorable years (2022 and 2023). Identification of valuable breeding material by indirect traits in extreme years (2024), when the HTC < 0.2, was significantly complicated. All the obtained correlation coefficients under these conditions were low and unreliable. The results of the correlation of protein percentage in pea seeds with yield structure elements did not reveal a clear correlation between these traits. The correlation between protein percentage in pea seeds and yield structure elements has not been identified due to low and unreliable correlation coefficients, which allows directing pea breeding towards increasing protein percentage in seeds without taking into account the effect of seed productivity.

The Restoration of New Gourna: Safeguarding the Legacy of Hassan Fathy

Hassan Fathy’s New Gourna project in Egypt (1946-52) is renowned as a pioneering example of sustainable urban settlement, integrating traditional technologies with modern architectural principles and serving as an inspiration to architects and planners worldwide. But decades of neglect have resulted in major structural deterioration and demolitions of the original buildings. In response, a project titled “Safeguarding Hassan Fathy’s Architectural Legacy in New Gourna” has been undertaken through a collaboration between UNESCO and the Egyptian Ministry of Culture, as defined by the National Organization for Urban Harmony (NOUH) for the period 2019-21. This initiative aims to conserve and repurpose the public heritage buildings while addressing the critical issue of groundwater. NOUH has now taken the project into a second phase (2023-24). This paper outlines the symptoms and causes of deterioration in New Gourna Village and reviews the restoration efforts applied to four major buildings: the khan, the mosque, the theater, and Hassan Fathy’s house. Further research will detail the restoration project in each case, including the documentation phase and the specific restoration techniques applied to each structural element and material.

Sorption-desorption of rare earth metal cations by ferromanganese crusts of Govorov’s guyote of the Magellanic Mountains of the Pacific Ocean

The article presents the results of experimental studies on the sorption and desorption of rare earth metal (REM) cations by cobalt-rich ferromanganese crusts (CMC) of Govorov’s guyot. It has been established that the sorption of REM cations occurs on the ore minerals KMK – Fe-vernadite, vernadite, Mn-feroxygite, goethite. The crusts are characterized by a high exchange capacity – 1.78–3.57 mg-eq/g, which increases in a series: (Dy Gd Lu Sm Nd Y, La Eu) Ce. The sorption of REM cations proceeds by an ion exchange equivalent irreversible mechanism. The exchange complex of ore minerals consists of Na+, K+, Ca2+, Mg2+ cations, which contribute 97‒98% to their total capacity. The crusts are characterized by the group sorption of REM cations from multicomponent aqueous solutions of metal salts. The selectivity of ore manganese and ferruginous minerals of crusts to REM cations is significantly higher than to the main cations of ocean water. From experimental data on the desorption of sorbed REM cations with NaCl solution, their irreversible absorption by ore minerals follows, and the strengthening of the chemical bond of sorbed REM cations with the main structural elements of these minerals over time. An important property of ore minerals, primarily manganese minerals, is their chemical and structural stability in aqueous solutions of electrolytes. This suggests the repeated use of ferromanganese crusts as sorbents of REM cations.

Legal Problems of Compliance with Bank Secret when Performing Transactions Using Payment Cards

Payment (bank) cards are among the most actively spreading phenomena in the modern world order. However, the problems of preserving information that constitutes banking secrecy in the context of digitalization and the active spread of online payments are of particular importance. Banks are also interested in preventing the disclosure of information constituting a banking secret. However, due to the uncertainty of the current legislation, which establishes the range of information related to bank secrecy, a number of problems arise that need to be analyzed. In the presented article, the author attempts to determine whether the payment card details relate to information constituting a bank secret. Examples from judicial practice in cases arising from disputes between banks and their individual clients regarding the legality of transactions performed by the bank using payment cards are given. It is concluded that the details of the payment cards themselves do not relate to the information constituting a bank secret. They can be considered as a structural element of a banking transaction performed using a payment card.

Horizons of liberation: materialism, ecology, and the colonial question

The question of materialism – what it is, how it is studied and practised, and who takes it seriously enough – has long animated debates among Marxists and scholars of race and the colonial question. Today, our contemporary socioecological crises challenge established understandings of materialism and merit a return to these debates with the goal of collective liberation on a warming planet in mind. Taking up this task, this article builds an understanding of materialism as theory and practice working towards liberation – a theory and practice shaped variously by culture, ontology, and the experience of oppressive structural conditions. The contributions of scholarship focused on race and colonial projects and legacies particularly illuminate these multiple dimensions of materialism. Among a wealth of other insights, anticolonial Third Worldist thinkers left us with an astute diagnosis of value in the world system; Black radical scholars have revealed the ontological roots of material struggles; decolonial scholars have exposed the solidification of racial classification systems as structures; and Indigenous (Fourth World) ontologies continue to maintain a commitment to metabolic repair and reciprocity. While contemporary ecology-focused conceptual innovations – such as metabolic rift and material throughput – expand materialist analyses, approaches focused on race and the colonial question bring particular insight to the global structural elements of socioecological crises and generate a materialism oriented towards horizons of liberation for all.

An Evaluation of the Structural Behaviour of Historic Buildings Under Seismic Action: A Multidisciplinary Approach Using Two Case Studies

The evaluation of the structural behaviour of iconic historic buildings represents one of the most current structural engineering research topics. However, despite the various research works carried out during recent decades, several issues still remain open. One of the most important aspects is related to the correct reconstruction of the complex geometries that characterise this type of construction and that influence structural behaviour, especially in the presence of the horizontal loads caused by seismic action. For these reasons, different techniques have been proposed based on the use of laser scanners, Unmanned Aerial Vehicles (UAVs), and terrestrial photogrammetry. At the same time, several analysis methods have been developed that include the use of linear and non-linear approaches. In this present paper, the seismic performance of the Santa Maria Novella basilica and Santa Maria di Collemaggio basilica (before the partial collapse due to the 2009 L’Aquila earthquake) were investigated in detail by means of several numerical analyses. In particular, a series of non-linear time history analyses (NTHAs) were carried out, as reported in the Italian Building Code. To represent the non-linear behaviour of the main structural elements, smeared cracking (CSC) constitutive law was adopted. The geometry of the structures was reconstructed from a complete laser scanner survey of the churches, in order to consider all the intrinsic irregularities that characterise the heritage buildings. Finally, a comparison between the structural behaviour of the two case studies was carried out, highlighting the differences and similar aspects, focusing on possible collapse mechanisms and the identification of the most critical structural elements represented, in both cases analysed, by the main pillars of the transept.

Development of an ultra-low-cost wireless data acquisition system for monitoring strain and deflection

Strain gauges are gaining popularity for monitoring stress and strain within structural elements and for detecting and identifying structural damage. Although they are relatively inexpensive, they are not as widely used as accelerometers in structural health monitoring. This is due to several factors, such as the high cost of data acquisition systems required to collect strain data and the need for a large number of gauges to monitor a structure. Therefore, this research aims to develop a low-cost wireless strain gauge data acquisition system with acceptable accuracy and a high sampling rate. This system is composed of commonly available electronic components and open-source software, with a cost of $20. The system’s precision in measuring displacement was assessed in a laboratory experiment, and further experiments were conducted on an aluminum beam to investigate its response under both static and dynamic conditions. Additionally, the accuracy of the system for measuring deflection and strain in reinforced concrete elements was assessed through a bending test on a reinforced concrete beam. The findings indicated that the developed data acquisition system can accurately measure displacement, with a root mean square error of 0.1 mm, as well as strain values within the range of a few micro-strains.

Metal Ion Sensing by Tetraloop-like RNA Fragment: Role of Compact Intermediates with Non-Native Metal Ion-RNA Inner-Shell Contacts.

Divalent metal ions influence the folding and function of ribonucleic acid (RNA) in the cells. The mechanism of how RNA structural elements in riboswitches sense specific metal ions is unclear. RNA interacts with ions through two distinct binding modes: direct interaction between the ion and RNA (inner-shell (IS) coordination) and indirect interaction between the ion and RNA mediated through water molecules (outer-shell (OS) coordination). To understand how RNA senses metal ions such as Mg2+ and Ca2+, we studied the folding of a small RNA segment from the Mg2+ sensing M-Box riboswitch using computer simulations. This RNA segment has the characteristics of a GNRA tetraloop motif and interestingly requires the binding of a single Mg2+ ion. The folding free energy surface of this simple tetraloop system is multidimensional, with a population of multiple intermediates where the tetraloop and cation interact through IS and OS coordination. The partially folded compact tetraloop intermediates form multiple non-native IS contacts with the metal ion. Thermal fluctuations should break these strong non-native IS contacts so that the tetraloop can fold to the native state, resulting in higher folding free energy barriers. Ca2+ undergoes rapid OS to IS transitions and vice versa due to its lower charge density than Mg2+. However, the ability of Ca2+ to stabilize the native tetraloop state is weaker, as it could not hold the loop-closing nucleotides together due to its weaker interactions with the nucleotides. These insights are critical to understanding the specific ion sensing mechanisms in riboswitches, and the predictions are amenable for verification by nuclear magnetic resonance (NMR) experiments.