Mechanics Approach Research Articles

Can a mechanical circulatory support comprehensive approach to cardiogenic shock at referral centers reduce 30-day mortality?

Although mortality risk prediction in cardiogenic shock (CS) is possible, assessing the impact of the multitude of therapeutic efforts on outcomes is not straightforward. We assessed whether a temporary mechanical circulatory support comprehensive approach to the treatment of CS may reduce 30-day mortality as compared to expected mortality predicted by the recently proposed Cardiogenic Shock Score (CSS). Consecutive CS patients supported by pVAD Impella (Abiomed, Danvers, MA) at two national referral centers were included. 170 patients were included: age was 65 ± 13 years, and 75.9% were male and acute myocardial infarction was the prevalent cause of shock (71.1%). Expected mortality according to CSS was higher than observed (51.8% vs. 41.5%, p < 0.001), this trend being particularly evident for CSS > 4. The AUC ROC curve confirmed poor diagnostic accuracy in this population (AUC 0.53 CI: 0.23–0.82, p = 0.83). The lower observed mortality compared to the expected mortality in critical cardiogenic shock population underscores the role of a comprehensive approach to acute cardiac care patients at referral centers, which should consider including temporary mechanical circulatory support.

Heat boost: therapeutic approach for skeletal muscle health and postprandial mechanisms in older adults.

Heat boost: therapeutic approach for skeletal muscle health and postprandial mechanisms in older adults.

A Hybrid Mechanism and Data-Based Modeling Approach to a Post-Combustion Carbon Capture Process in a Coal-Fired Power Unit

Chemical absorption carbon capture systems use solutions with complex compositions to further reduce energy consumption and improve performance. Modeling and simulation are essential methods for studying the characteristics of these systems and optimizing them. However, existing methods cannot be used to build models of systems with complex or unknown solutions. This study proposes a hybrid modeling method integrating mechanism modeling and operational data for a chemical absorption carbon capture system. This method interprets the physical and chemical properties of solvents under various operating conditions based on operational data. To validate the effectiveness of this method, it is applied to a real-life post-combustion carbon dioxide capture system in a 1000 MW coal-fired power unit, which has an annual capture capacity of 10,000 tons. The results of the case study indicate that the proposed method can obtain values of key property parameters of solvents, including absorption heat, cyclic carbon capacity, and heat capacity. The average relative error between operational data and simulation data ranges from 0.2% to 8.0%.

Whole-cell aptamer-based techniques for rapid bacterial detection: Alternatives to traditional methods.

Controlling the spread of bacterial infectious diseases is a major public health issue, particularly in view of the pandemic of bacterial resistance to antibiotics. In this context, the detection and identification of pathogenic bacteria is a prerequisite for the implementation of control measures. Current reference methods are mainly based on culture methods, which generate a delay in obtaining a result and requires equipment. Consequently, focusing on the detection of the whole bacterium represents a very attractive alternative, since no culture is required. Several techniques have already been deployed to identify whole-cell bacteria. In recent decades, growing interest in nucleic acid aptamers has emerged as a viable alternative to antibodies as recognition elements, offering preferable stability, cost-efficiency, good specificity and affinity. This review explores current alternative methods for the detection of whole-cell bacteria, with particular emphasis on aptamer-based assays. These assays have shown promising results in various transduction mechanisms, including optical, electrochemical, and mechanical approaches, enhancing their versatility in different diagnostic platforms. The integration of aptamers in these detection methods offers rapid, sensitive, versatile and portable solutions for pathogen identification, positioning them as valuable tools in the fight against bacterial infections.

Bifunctional role of mechanical catalysis approach accelerates CO2 hydrogenation under low temperature

Bifunctional role of mechanical catalysis approach accelerates CO2 hydrogenation under low temperature

Adolescent Coronal Shear Fractures of the Distal Humerus: Surgical Approach and Outcomes.

Isolated coronal shear fractures of the distal humerus in adolescents are rare injuries with unique surgical challenges. Respect for the posterior blood supply, open physes, and need for direct visualization to achieve anatomic reduction are critical considerations in surgical fixation. This study presents a case series and a surgical approach used in treating these patients. A retrospective review of patients aged 10-19 presenting to a single quaternary-care academic center from 2016 to 2023 with isolated capitellar and trochlear shear fractures was performed. Demographic data, injury mechanism, fracture classification, and surgical approach were recorded. Outcomes included elbow range of motion at the final follow-up, visual analogue scale pain scores, pediatric Patient-Reported Outcome Measurement Information System (PROMIS) scales, radiographic and clinical union, return to sport, and postoperative complications. Eight patients were included, four of whom were treated through a single-incision anterolateral approach. Average age was 13 years. Average time of the final clinical follow-up was 21 months, with a radiographic follow-up of 11 months. Five fractures were classified as Dubberly type 2A, two as type 3A, and one as type 3B. At the final follow-up, average elbow range of motion and visual analogue scale pain scores were 3-137 degrees and 0.28 (range: 0-2), respectively. PROMIS scores demonstrated an average mobility score of 55 (SD: 8), pain interference of 35 (SD: 5), and pediatric upper-extremity score of 55 (SD: 4). One patient with sickle cell disease developed avascular necrosis of the capitellum. There were no other postoperative complications. Short-term clinical outcomes reveal low pain scores, near normal elbow motion, radiographic and clinical union, and normal patient-reported outcome measures in operatively treated coronal shear fractures of the distal humerus in adolescent patients. A single-incision anterolateral approach offers visualization of the anterior articular surface while respecting posterior soft tissues and the olecranon apophysis. Therapeutic V, case series.

Examining Bias in Online Consumer Reviews and Consumer Avoidance: A Psychological Mechanism Approach to Review Evaluation

Examining Bias in Online Consumer Reviews and Consumer Avoidance: A Psychological Mechanism Approach to Review Evaluation

THEORY OF TECHNOLOGY AND METHODS OF ENGINEERING ANALYSIS OF HIGH-STRENGTH NANOSTRUCTURED COATINGS FOR ENHANCED SERVICE CHARACTERISTICS OF MILITARY AND CIVIL EQUIPMENT OBJECTS

Modern military and civil equipment objects need to improve the service properties of the most critical and loaded contacting elements, which determine their tactical and technical characteristics. So far, traditional and new materials have exhausted such possibilities in many aspects. These capabilities can be dramatically increased by means of strengthening, in particular, application of nanostructured high-strength and multilayer nitride coatings based on titanium nitrides, zirconium, etc., as well as modified vacuum condensates. At the same time, for structural elements with closeshaped contacting surfaces, it is important to choose the structure, composition and methods of application of these high-strength and multilayer nitride coatings and pseudoalloys only in parallel with the analysis of their contact interaction. For this purpose, the paper develops new variational statements of contact problems, perform analysis and develop recommendations on improving the service properties of contacting elements of military and civil equipment objects by forming high-strength and multilayer nitride coatings and pseudoalloys. It is the combination of new author’s approaches in contact mechanics and in the physics of nanostructured metals, on the other hand, that provides the basis for breakthrough technical solutions of modern military and civil equipment objects with increased their tactical and technical characteristics: battle tanks, armored vehicles, robotic combat platforms, turbomachines.

ТОЧКИ РАВНОВЕСИЯ МЕХАНИЧЕСКИХ СИСТЕМ

This paper deals with the differences between regular and singular points of equilibrium states of elastic systems. The author provides a classification of singular points based on mathematical, mechanical and geometrical approaches. Aspects concerning nondegenerate (regular) critical points in which the first differential is zero and the second differential (quadratic form) is not degenerate are disclosed. The conditions of stability and instability of isolated equilibria are discussed, as well as the influence of the primary nonzero terms of the potential energy expansion on the stability of degenerate equilibria. The conditions for bifurcation loss of stability in the context of incomplete equilibrium of elastic systems are considered. It is analyzed that a necessary condition for the appearance of bifurcation points is the presence of an energetically orthogonal complement. The influence of initial geometrical imperfections on the character of stability loss is also considered.

The Boltzmann Equation and Its Place in the Edifice of Statistical Mechanics.

It is customary to classify approaches in statistical mechanics (SM) as belonging either to Boltzmanninan SM (BSM) or Gibbsian SM (GSM). It is, however, unclear how the Boltzmann equation (BE) fits into either of these approaches. To discuss the relation between BE and BSM, we first present a version of BSM that differs from standard presentation in that it uses local field variables to individuate macro-states, and we then show that BE is a special case of BSM thus understood. To discuss the relation between BE and GSM, we focus on the BBGKY hierarchy and note the version of the BE that follows from the hierarchy is "Gibbsian" only in the minimal sense that it operates with an invariant measure on the state space of the full system.

Mechanical and thermodynamic routes to the liquid-liquid interfacial tension and mixing free energy by molecular dynamics.

In this study, we carried out equilibrium molecular dynamics (EMD) simulations of the liquid-liquid (LL) interface between two different Lennard-Jones components with varying miscibility, where we examined the relation between the interfacial tension and the free energy to completely isolate the two liquids using both a mechanical and thermodynamic approach. Using the mechanical approach, we obtained a stress distribution around a quasi-one-dimensional EMD system with a flat LL interface. From the stress distribution, we calculated the LL interfacial tension based on Bakker's equation, which uses the stress anisotropy around the interface, and measured how it varied with miscibility. The second approach uses thermodynamic integration by enforcing quasi-static isolation of the two liquids to calculate the free energy. This uses the same EMD systems as the mechanical approach, with both extended dry-surface and phantom-wall (PW) schemes applied. When the two components were immiscible, the mechanical interfacial tension and isolation free energy were in good agreement. When the components were miscible, the values were significantly different. From the result of PW for the case of completely mixed liquids, the difference was attributed to the additional free energy required to separate the binary mixture into single components against the osmotic pressure prior to the complete detachment of the two components. This provides a new route to obtain the free energy of mixing.

The Calcium Hydroxide Controversy: Does Calcium Hydroxide Weaken Teeth?

Calcium hydroxide apexification has been used in the treatment of immature teeth with pulp necrosis and apical periodontitis for more than 50 years. However, the guidelines of the European Academy of Paediatric Dentistry (EAPD) and the American Association of Endodontists (AAE) 'Clinical recommendations for a regenerative procedure' recommend against calcium hydroxide apexification. The American Association of Endodontists "Clinical considerations for a regenerative procedure" do not list calcium hydroxide apexification as a treatment option for immature teeth with pulp necrosis. This review analyses the strength of the science that led to calcium hydroxide no longer being recommended by the EAPD and AAE regenerative guidelines. Many differences in the studies and failure to include adequate controls have resulted in inconsistent outcomes between studies. Furthermore, prior invitro studies have assessed narrow mechanical properties of teeth without a theoretical fracture mechanics model. Cvek's concerns regarding the thinness of the dentinal walls remain as a primary risk for tooth fracture with Class 3 root development fractured with an incidence of 77% compared to a fracture incidence of just 2% for mature teeth. This review develops a simple fracture mechanics approach to the phenomenon of transverse root fracture that provides a theoretical framework to why fragile roots are more likely to fracture when compared to mature teeth. Furthermore, the effect of the varying size access cavities has not been previously considered. Systematic reviews and clinical studies do attest to the success of all approaches for the treatment of immature teeth with pulp necrosis. Calcium hydroxide apexification is one of the recommended treatments in the International Association of Dental Traumatology guidelines. However, mineral trioxide aggregate (MTA) and hydraulic calcium silicate cements (HCSC's) may provide better outcomes and have the convenience for the patient of a shorter treatment time. Regenerative endodontic treatment (RET) is recommended when the tooth roots are very immature with Cvek Class 1-3 root development. However, the treatment of immature teeth with pulp necrosis remains a clinical challenge as does the risk of tooth fracture.

Insight into insecticide resistance mechanism and eco-friendly approaches for the management of olive fruit fly, Bactrocera oleae Rossi: a review

Insight into insecticide resistance mechanism and eco-friendly approaches for the management of olive fruit fly, Bactrocera oleae Rossi: a review

Potentials of Mean Force and Solvent Effects of the CN- + CH3X (X = F, Cl, Br, and I) Reactions by the N-Side Attack in Aqueous Solution.

A combined multilevel quantum mechanics and molecular mechanics approach is performed to investigate the nucleophilic substitution reactions of CN- + CH3X (X = F, Cl, Br, and I) by the N-side attack in aqueous solution. The water molecules are treated microscopically using an explicit SPC/E model, and the potentials of mean force are characterized by both the DFT and CCSD(T) levels of theory for the solute. Calculations demonstrate that the shielding effect of the solvent reduces the nucleophile-substrate and substrate-leaving group interactions in solution, leading to stationary point structures that are quite different from those in the gas phase. The structure and charge evolution along the reaction paths reveal that the reaction is not only a synchronous bonding and bond-breaking Walden-inversion mechanism but also a synchronous charge transfer process. The activation barriers calculated at the CCSD(T) level of theory are 27.5 (F), 22.6 (Cl), 21.7 (Br), and 21.2 (I) kcal/mol, respectively, which are larger than the corresponding experimental values for the C-side attack. The polarization effect of water molecules causing solute polarization contributes to the activation barrier in the order of F > Cl > Br > I. The solvent energy contribution to the activation barrier is in the order of F < Cl < Br < I because the F leaving group has the most compact transition state structure and the I leaving group has the loosest transition state structure. As a result, the total contributions of the solvent effects to the activation barriers are 7.9 (F), 10.7 (Cl), 15.3 (Br), and 15.7 (I) kcal/mol. Our results show that the solvent effects have a significant influence on both the structure and the energetics of the N-side attack reactions in aqueous solution.

How Do Variants of Residues in the First Coordination Sphere, Second Coordination Sphere, and Remote Areas Influence the Catalytic Mechanism of Non-Heme Fe(II)/2-Oxoglutarate Dependent Ethylene-Forming Enzyme?

The ethylene-forming enzyme (EFE) is a Fe(II)/2-oxoglutarate (2OG) and l-arginine (l-Arg)-dependent oxygenase that primarily decomposes 2OG into ethylene while also catalyzing l-Arg hydroxylation. While the hydroxylation mechanism in EFE is similar to other Fe(II)/2OG-dependent oxygenases, the formation of ethylene is unique. Various redesign strategies have aimed to increase ethylene production in EFE, but success has been limited, highlighting the need for alternate approaches. It is crucial to incorporate an accurate and comprehensive description of the integrative and multidimensional effects of the protein environment to enhance the redesign strategy in metalloenzymes, particularly in EFE. This involves understanding the role of the second coordination sphere (SCS) and long-range (LR) interacting residues, correlated motions, electronic structure, intrinsic electric field (IntEF), as well as the stabilization of transition states and reaction intermediates. In this study, we employ a molecular dynamics-based quantum mechanics/molecular mechanics approach to examine the integrative effects of the protein environment on reactions catalyzed by EFE variants from the first coordination sphere (FCS, D191E), SCS (A198V and R171A) and LR (E215A). The study uncovers how substitutions at different positions in EFE similarly impact the ethylene-forming reaction while posing distinct effects on the hydroxylation reaction. Results predict the effect of the variants in controlling the 2OG coordination mode in the Fe(II) center. Specifically, the study suggests that D191E uniquely prefers transitioning from an off-line to an in-line 2OG coordination mode before dioxygen binding. However, studies on the 2OG flip in the presence of off-line approaching dioxygen and dioxygen binding in the D191E variant indicate that the 2OG flip might not be feasible in the 5C Fe(II) state. Calculations show the possibility of a hydrogen atom transfer (HAT)-assisted oxygen flip in EFE and its variants (other than D191E). MD simulations elucidate the characteristic dynamic change in the α7 region in the D191E variant that might contribute to its increased hydroxylation reaction. Results indicate the possibility of forming an in-line ferryl from the IM2 (Fe(III)-partial bond intermediate) in the D191E variant. This alternative pathway from IM2 may also exist in WT EFE and other variants, which are yet to be explored. The study also delineates the impact of substitutions on the electronic structure and IntEF. Overall, the calculations support the idea that understanding the integrative and multidimensional effects of the protein environment on the reactions catalyzed by EFE variants provides the basics for improved enzyme redesign protocols of EFE to increase ethylene production. The results of this study will also contribute to the development of alternate redesign strategies for other metalloenzymes.

Prediction of the Temperature Field Development in Large Heat Storage Tanks for Integration in Network Simulation

Integrating an increasing amount of renewable energy into district heating systems requires thermal energy storages. For the planning and operation of the whole system valid and powerful storage models are essential for implementation in e. g. thermo-hydraulic network simulations and operational optimisation tools. The modelling of large tank thermal energy storages (TTES) up to 60,000 m³ can be insufficient by using a simple energy balance model as it does not provide information about the temperature profile. The detailed model called FreeTTES is capable of predicting the temperature distribution inside a large atmospheric TTES. This model simplifies fluid dynamic processes by assuming horizontal homogeneity and analyses them only in vertical direction. The analytical fluid mechanics approach is combined with numerical, measurement data-based approaches. The validation of the model is performed using DTS (distributed temperature sensing) data

Efficient evaluation of near-singular integrals of the eXtended Isogeometric Boundary Element Method for three-dimensional fracture mechanics

The Boundary Element Method (BEM) has proven to be a suitable method for the numerical assessment of numerous engineering problems in both two-dimensional and three-dimensional forms. In particular, BEM robustly handles discontinuities in the mechanical response present in fracture mechanics applications. Additionally, its boundary-only nature simplifies the re-meshing process during crack growth modelling. Furthermore, coupling BEM with isogeometric analysis (IgA) is straightforward, as both strategies rely on boundary representation, enabling the direct use of Computer-Aided Design (CAD) geometry as the mesh for the method. IgA basis functions can accurately represent complex surfaces such as spheres and toroids. In this context, the Isogeometric Boundary Element Method (IGABEM) emerges as a reliable tool for solving engineering problems, combining the advantages of BEM with the improved geometric accuracy provided by IgA. In addition, a relevant approach in fracture mechanics is using enrichment functions that incorporate known solution fields, addressing response aspects that standard isogeometric basis functions cannot capture. Combining the enrichment strategy with IGABEM leads to the eXtended IGABEM (XIGABEM) method. Specifically, enriching functions that account for the square-root inverse behaviour on crack surfaces promotes several improvements, such as improved convergence rate and removal of a non-physical jump displacement in the crack front. Another advantage is the direct extraction of Stress Intensity Factors (SIF) as system variables, eliminating the need for costly extraction techniques in three-dimensional problems. However, near-singular integrals appear after the Singularity Subtraction Technique (SST) of the enriching terms in 3D XIGABEM. This study proposes using the hyperbolic sine transformation for the near singular surface integrals that arise from the SST to evaluate them efficiently. Numerical applications demonstrate a reduction in the required integration points for these integrals compared to traditional methods. Therefore, this advancement in the XIGABEM framework reduces the computational cost of this strategy while maintaining accuracy.

UHPFRC structural analysis from a geometrically exact Extended Lumped Damage Mechanics approach

The use of ultra-high-performance fibre-reinforced concrete (UHPFRC) has significantly increased in the recent years. However, the accurate mechanical behaviour modelling of this complex material is still a challenge in the present. Because the materials high load-bearing capacity and the presence of fibbers, this type of problem experiments large displacements before the failure. In this study, the material damage description has been performed by the Extended Lumped Damage Mechanics. Additionally, an approach based on the nodal positions of the Finite Element Method has been utilised, which makes the formulation geometrically exact. Thus, this study evaluates the failure of structures composed of UHPFRC, accounting for the effects of material and geometric nonlinearities computed by the Extended Lumped Damage Mechanics and the Finite Element Method based on positions, respectively.

Identification of viscoelastic properties with fluid inertia in a parallel plate with effective mechanical system analyses

Measurement of viscoelastic properties in small amplitude oscillatory shear (SAOS) can be affected by fluid inertia, especially at high frequencies. In this study, we introduce an effective mechanical system approach to address the effects of fluid inertia on the viscoelastic measurement with a SAOS test, employing a parallel plate geometry. In the effective mechanical system approach, viscous, elastic, and inertial properties of a fluid system are modeled systematically by a rotational drag coefficient, a torsional spring constant, and a second moment of inertia, respectively. In this way, we established the analytic solution for the linear viscoelastic behavior of a fluid in the presence of fluid inertia. The shear modulus on the frequency, obtained by the effective mechanical system, reveals that fluid inertia only affects the storage modulus and not the loss modulus. We investigate the behavior of the storage modulus as a function of the gap size, the oscillation frequency, and the disk radius, demonstrating the dependence on the gap size and the frequency. Comparison was made for the shear modulus from the effective mechanical system with viscoelastic flow simulation, employing two viscoelastic (Oldroyd-B and Giesekus) fluid models to validate the accuracy of this approach. The maximum error was found less than 3.3% over the frequency range from 1 to 100 rad/s.

Association Between Baseline Driving Pressure and Mortality in Very Old Patients with Acute Respiratory Distress Syndrome.

Rationale: Because of the effects of aging on the respiratory system, it is conceivable that the association between driving pressure and mortality depends on age. Objectives: We endeavored to evaluate whether the association between driving pressure and mortality of patients with acute respiratory distress syndrome (ARDS) varies across the adult lifespan, hypothesizing that it is stronger in older, including very old (⩾80 yr), patients. Methods: We performed a secondary analysis of individual patient-level data from seven ARDS Network and PETAL Network randomized controlled trials ("ARDSNet cohort"). We tested our hypothesis in a second, independent, national cohort ("Hellenic cohort"). We performed both binary logistic and Cox regression analyses including the interaction term between age (as a continuous variable) and driving pressure at baseline (i.e., the day of trial enrollment) as the predictor and 90-day mortality as the dependent variable. Measurements and Main Results: On the basis of data from 4,567 patients with ARDS included in the ARDSNet cohort, we found that the effect of driving pressure on mortality depended on age (P = 0.01 for the interaction between age as a continuous variable and driving pressure). The difference in driving pressure between survivors and nonsurvivors significantly changed across the adult lifespan (P < 0.01). In both cohorts, a driving pressure threshold of 11 cm H2O was associated with mortality in very old patients. Conclusions: Data from randomized controlled trials with strict inclusion criteria suggest that the effect of driving pressure on the mortality of patients with ARDS may depend on age. These results may advocate for a personalized age-dependent mechanical ventilation approach.