A viscoelastic metamaterial beam for integrated vibration isolation and energy harvesting

Locally resonant metamaterials have low-frequency band gaps and the capability of converging vibratory energy in the band gaps at resonant cells.It has been demonstrated by several researchers that the dissipatioin of vibratory energy within the band gap can be improved by using viscoelastic materials.This paper designs an integrated viscoelastic metamaterial for energy harvesting and vibration isolation.The viscoelastic metamaterial is achieved by a viscoelastic beam periodically arrayed with spatial ball-pendulum nonlinear energy harvesters.The nonlinear resonator with an energy harvesting function is achieved by placing a free-rolling magnetic ball in a spherical cavity with an additional induction coil.The dynamic equations of viscoelastic metamaterials under transverse excitation are established,and the energy harvesting and vibration isolation characteristics within the dispersion relation of viscoelastic metamaterials are analyzed.The results show that the vibrations of the main body of the viscoelastic metamaterial beam are significantly suppressed in the frequency range of the local resonance band gap.At the same time,the elastic waves are limited in the nonlinear resonator with an energy harvesting function,which improves the energy output.Finally,an experimental platform of viscoelastic metamaterial vibration is established for validation purposes.

Dynamic analysis of a novel multilink-spring mechanism for vibration isolation and energy harvesting

Due to technical limitations,existing vibration isolation and energy harvesting(VIEH)devices have poor performance at low frequency.This paper proposes a new multilink-spring mechanism(MLSM)that can be used to solve this problem.The VIEH performance of the MLSM under harmonic excitation and Gaussian white noise was analyzed.It was found that the MLSM has good vibration isolation performance for low-frequency isolation and the frequency band can be widened by adjusting parameters to achieve a higher energy harvesting power.By comparison with two special cases,the results show that the MLSM is basically the same as the other two oscillators in terms of vibration isolation but has better energy harvesting performance under multistable characteristics.The MLSM is expected to reduce the impact of vibration on high-precision sensitive equipment in some special sites such as subways and mines,and at the same time supply power to structural health monitoring devices.

Multi-layer quasi-zero-stiffness meta-structure for high-efficiency vibration isolation at low frequency

An easily stackable multi-layer quasi-zero-stiffness(ML-QZS)meta-structure is proposed to achieve highly efficient vibration isolation performance at low frequency.First,the distributed shape optimization method is used to design the unit cel,i.e.,the single-layer QZS(SL-QZS)meta-structure.Second,the stiffness feature of the unit cell is investigated and verified through static experiments.Third,the unit cells are stacked one by one along the direction of vibration isolation,and thus the ML-QZS meta-structure is constructed.Fourth,the dynamic modeling of the ML-QZS vibration isolation metastructure is conducted,and the dynamic responses are obtained from the equations of motion,and verified by finite element(FE)simulations.Finally,a prototype of the ML-QZS vibration isolation meta-structure is fabricated by additive manufacturing,and the vibration isolation performance is evaluated experimentally.The results show that the vibration isolation performance substantially enhances when the number of unit cells increases.More importantly,the ML-QZS meta-structure can be easily extended in the direction of vibration isolation when the unit cells are properly stacked.Hence,the ML-FQZS vibration isolation meta-structure should be a fascinating solution for highly efficient vibration isolation performance at low frequency.

Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

Vertical mass isolation(VMI)is one of the novel methods for the seismic control of structures.In this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among them.In this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two subsystems.Multi-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field earthquakes.On each level,the displacement of MR dampers was taken into account.The responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the structures.According to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the structures.This method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.

Impact of surface-reflected seismic waves on the seismic isolation performance of circular tunnel isolation layers

Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels.However,the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored.In this study,we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space.By comparing the results of the two models,we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves.Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space.Specifically,the dynamic stress concentration factor(DSCF)of the lining in the elastic half-space exhibits periodic fluctuations,influenced by the incident wave frequency and tunnel depth,while the DSCF in the infinitely elastic space remain stable.Overall,the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves.Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.

Ultrasound-assisted isolation:A new method to isolate stromal vascular fraction

Background:The stromal vascular fraction(SVF),a cluster of stem and progenitor cells isolated from adipose tissue,holds significant promise for application in regenerative medicine.However,the existing methods for SVF isolation are time-consuming and expensive.Thus,in this study,we explored a new method of SVF extrac-tion-ultrasound-assisted SVF isolation(USASI)-and compared the viability and characteristics of SVF isolated using different methods.Methods:SVF extraction methods using different combinations of ultrasound power,ultrasound time,collagenase dosage,and collagenase digestion time were compared with those of the control group(collagenase digestion method).The cell yield and vitality of the SVF were evaluated via cell counting and trypan blue staining.The cell components and immunophenotypes of freshly isolated SVF were analyzed using flow cytometry.The prolifer-ative capacity and differentiation potential of the SVF were also identified.Results:Ultrasonication at 95 W-20 kHz for 30 s followed by digestion with 0.15%collagenase for 30 min was identified as the most suitable parameter for the USASI method in isolating SVF,as recommended based on the evaluation of various tested conditions.The USASI method significantly reduced the collagenase dosage and shortened the digestion time.Compared to the collagenase digestion method,the USASI method had a higher cell yield and cell viability,with no adverse effects on cell components,proliferative capacity,or multipotential differentiation capacity.Conclusion:With reduced processing time,lower collagenase dosage,and increased cell yield without impairing the viability and characteristics of SVF,USASI holds the potential to emerge as a time-saving and cost-effective method for future clinical applications.

Near resonance vibration isolation on a levered-dual response(LEDAR)Coulomb-damped system by differential preloads/offsets in linear springs

The levered-dual response(LEDAR)Coulomb-damped system attains near resonant vibration isolation by differential preloads/offsets in linear springs.It takes the advantages of both the preloads/offsets in linear springs and the guiderail friction for realizing different levels of vibration isolation.The isolation capacities are investigated on the strategies with both the horizontal and vertical guiderails,with the horizontal rail only,and without guiderails.The compressive preloads generally result in the consumption of most of the initial excitation energy so as to overcome the potential threshold.The isolation onsets at the frequency ratio of 1∓0.095 on the left-hand side(LHS)and the right-hand side(RHS)of the lever are relative to the load plate connector.The observed near resonant isolation thus makes the LEDAR system a candidate for the isolation of the mechanical systems about resonance while opening a path for simultaneous harvesterisolation functions and passive functions at extreme frequencies.

Actuator and sensor fault isolation in a class of nonlinear dynamical systems

Fault isolation in dynamical systems is a challenging task due to modeling uncertainty and measurement noise,interactive effects of multiple faults and fault propagation.This paper proposes a unified approach for isolation of multiple actuator or sensor faults in a class of nonlinear uncertain dynamical systems.Actuator and sensor fault isolation are accomplished in two independent modules,that monitor the system and are able to isolate the potential faulty actuator(s)or sensor(s).For the sensor fault isolation(SFI)case,a module is designed which monitors the system and utilizes an adaptive isolation threshold on the output residuals computed via a nonlinear estimation scheme that allows the isolation of single/multiple faulty sensor(s).For the actuator fault isolation(AFI)case,a second module is designed,which utilizes a learning-based scheme for adaptive approximation of faulty actuator(s)and,based on a reasoning decision logic and suitably designed AFI thresholds,the faulty actuator(s)set can be determined.The effectiveness of the proposed fault isolation approach developed in this paper is demonstrated through a simulation example.

No-touch isolation technique in emergency pancreaticoduodenectomy for neoplastic hemorrhage: Two case reports and review of literature

BACKGROUND Emergency pancreaticoduodenectomy(EPD)is a rare event for complex periam-pullary etiology.Increased intraoperative blood loss is correlated with poor post-operative outcomes.CASE SUMMARY Two patients underwent EPD using a no-touch isolation technique,in which all arteries supplying the pancreatic head region were ligated and divided before manipulation of the pancreatic head and duodenum.The operative times were 220 and 239 min,and the blood loss was 70 and 270 g,respectively.The patients were discharged on the 14^(th) and 10^(th) postoperative day,respectively.Thirty-two patients underwent EPD for the treatment of neoplastic bleeding.The mean operative time was 361.6 min,and the mean blood loss was 747.3 g.The comp-lication rate was 37.5%.The in-hospital mortality rate was 9.38%.CONCLUSION The no-touch isolation technique is feasible,safe,and effective for reducing intraoperative blood loss in EPD.

Optimization of Cellulose Nanocrystal Isolation from Ayous Sawdust Using Response Surface Methodology

This study focuses on the extraction of cellulose nanocrystals (CNC), from microcrystalline cellulose (MCC), derived from Ayous sawdust. The process involves multiple steps and a large amount of chemical products. The objective of this research was to determine the effects of factors that impact the isolation process and to identify the optimal conditions for CNC isolation by using the response surface methodology. The factors that varied during the process were the quantity of MCC, the concentration of sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. The response measured was the yield. The study found that with 5.80 g of microcrystalline cellulose, a sulfuric acid concentration of 63.50% (w/w), a hydrolysis time of 53 minutes, a hydrolysis temperature of 69˚C, and a sonication time of 19 minutes are the ideal conditions for isolation. The experimental yield achieved was (37.84 ± 0.99) %. The main factors influencing the process were the sulfuric acid concentration, hydrolysis time and temperature, with a significant influence (p < 0.05). Infrared characterization results showed that nanocrystals were indeed isolated. With a crystallinity of 35.23 and 79.74, respectively, for Ayous wood fiber and nanocrystalline cellulose were observed by X-ray diffraction, with the formation of type II cellulose, thermodynamically more stable than native cellulose type I.

Non-enzymatic methods for isolation of stromal vascular fraction and adipose-derived stem cells:A systematic review

BACKGROUND Adipose-derived stem cells(ADSCs)and the stromal vascular fraction(SVF)have garnered substantial interest in regenerative medicine due to their potential to treat a wide range of conditions.Traditional enzymatic methods for isolating these cells face challenges such as high costs,lengthy processing time,and regulatory complexities.AIM This systematic review aimed to assess the efficacy and practicality of nonenzymatic,mechanical methods for isolating SVF and ADSCs,comparing these to conventional enzymatic approaches.METHODS Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines,a comprehensive literature search was conducted across multiple databases.Studies were selected based on inclusion criteria focused on non-enzymatic isolation methods for SVF and ADSCs from adipose tissue.The risk of bias was assessed,and a qualitative synthesis of findings was performed due to the methodological heterogeneity of the included studies.RESULTS Nineteen studies met the inclusion criteria,highlighting various mechanical techniques such as centrifugation,vortexing,and ultrasonic cavitation.The review identified significant variability in cell yield and viability,and the integrity of isolated cells across different non-enzymatic methods compared to enzymatic procedures.Despite some advantages of mechanical methods,including reduced processing time and avoidance of enzymatic reagents,the evidence suggests a need for optimization to match the cell quality and therapeutic efficacy achievable with enzymatic isolation.CONCLUSION Non-enzymatic,mechanical methods offer a promising alternative to enzymatic isolation of SVF and ADSCs,potentially simplifying the isolation process and reducing regulatory hurdles.However,further research is necessary to standardize these techniques and ensure consistent,high-quality cell yields for clinical applications.The development of efficient,safe,and reproducible non-enzymatic isolation methods could significantly advance the field of regenerative medicine.

Seismic Response Analysis of Steel Structure Isolation System Under Long-Period Seismic Motion

To analyze the seismic response of steel structure isolation systems under long-period seismic motion,a 9-story steel frame building was selected as the subject.Five steel structure finite element models were established using SAP2000.Response spectrum analysis was conducted on the seismic motion to determine if it adhered to the characteristics of long-period seismic motion.Modal analysis of each structural model revealed that the isolation structure significantly prolonged the structural natural vibration period and enhanced seismic performance.Base reactions and floor displacements of various structures notably increased under long-period seismic motion compared to regular seismic activity.Placing isolation bearings in the lower part of the structure proved more effective under long-period seismic motion.In seismic design engineering,it is essential to consider the impact of long-period seismic motion on structures and the potential failure of isolation bearings.

Analysis of the Current Situation and Influencing Factors of Social Isolation Among the Elderly in the Community

Objective: To investigate the current situation of social isolation among the elderly in the community, and to analyze its influencing factors. Methods: A total of 265 elderly people were selected to conduct the survey using the general information questionnaire and the Chinese version of the social isolation scale for the elderly. Results: The social isolation score of the elderly was (20.15 ± 0.23). Factors such as age, education level, economic status, and social participation ability influenced the social isolation score (P < 0.05). Conclusion: The social isolation of the elderly is more serious, and the social isolation can be alleviated by improving the level of education and the economic situation and strengthening social participation.

Seismic Reduction and Isolation Design Strategies for Bridges in High-Intensity Earthquake Areas

High-intensity earthquakes can cause severe damage to bridges,buildings,and ground surfaces,as well as disrupt human activities.Such earthquakes can create long-distance,high-intensity surface movements that negatively impact bridge structures.This article delves into the seismic reduction and isolation design strategies for bridges in high-intensity earthquake areas.It analyzes various seismic reduction and isolation technologies and provides case studies to help relevant units understand the design strategies of these technologies.The results of this article can be used as a guideline to effectively enhance the seismic performance of bridges in high-intensity earthquake areas.

The Relationship Between Social Isolation and Psychological Well-Being Among Older Adults in the Community

Objective:To investigate the psychological well-being of the elderly in Baoding City,Hebei Province,and analyze its influencing factors,with a focus on exploring the relationship between social isolation and psychological well-being.This study aims to provide a reference for effective interventions that promote the physical and mental health of elderly individuals in the community.Methods:A total of 265 elderly individuals from six communities in Baoding City,Hebei Province were surveyed between November 2023 and March 2024 using the general information questionnaire,the Social Isolation Scale for the Elderly,and the Comprehensive Happiness Questionnaire.Results:The total score of the Social Isolation Scale for the elderly in the community was(14.15±3.73)points,indicating a moderate level of social isolation.The average score of P50 on the Psychological Well-being Scale was 4.88,suggesting that the psychological well-being of the elderly in the community was moderate to high.Multivariate regression analysis showed that the level of social isolation significantly influenced the psychological well-being of the elderly(P<0.05),with social isolation negatively correlated with psychological well-being.Conclusion:Healthcare professionals should pay attention to the social isolation of elderly individuals in the community and develop targeted interventions to improve their psychological well-being and quality of life.

Impact of Multidisciplinary Collaborative Intervention on Isolation Implementation in Prevention and Control of Multi-drug Resistance Infection

Objective Contact precautions,especially the initiation of isolation,are important measures to prevent and control multidrug-resistant organisms(MDROs).However,the implementation in clinical practice remains weak.This study aimed to analyze the impact of multidisciplinary collaborative intervention on isolation implementation in multidrug-resistant infection,and determine the factors that affect the implementation of isolation measures.Methods A multidisciplinary collaborative intervention related to isolation was conducted at a teaching tertiary hospital in central China on November 1,2018.The information of 1338 patients with MDRO infection and colonization at 10 months before and after the intervention was collected.Then,the issuance of isolation orders was retrospectively analyzed.Univariate analysis and multivariate logistic regression analysis were performed to analyze the factors that affected the isolation implementation.Results The overall issuance rate of isolation orders was 61.21%,which increased from 33.12%to 75.88%(P<0.001)after the implementation of the multidisciplinary collaborative intervention.The intervention(P<0.001,OR=0.166)was a promoting factor for the issuance of isolation orders,in addition to the length of stay(P=0.004,OR=0.991),department(P=0.004),and microorganism(P=0.038).Conclusion The isolation implementation remains far lower than policy standards.Multidisciplinary collaborative interventions can effectively improve the compliance to isolation measures implemented by doctors,thereby promoting the standardized management of MDROs,and providing reference for further improving the quality of hospital infection management.

Isolation, Examination and Characterization of Actinomycetes as a Source of Antimicrobial Agents from Libyan Soil

The rapid increase of bacterial resistance strains to multiple antibiotics has become a global public health concern. In the present study, actinomycetes from different districts of Libyan soil were isolated and screened for their inhibitory activity against pathogenic bacteria and fungi. Three hundred soil samples were taken from 77 diverse ecosystems, including deserts, forests, pastureland, and cropland located in different climatic regions in Libya. A total of 164 actinomycetes were obtained. Of 164 isolates, 38 (23.2%) isolates were morphologically and microscopically characterized by spore chain and surface morphology, aerial and substrate mycelia and soluble pigments. The preliminary classification of the isolates illustrates that all isolates belong to the genus Streptomyces. These isolates were further examined for their antagonistic potential against nine pathogenic bacteria and fungi. Out of 38, 11 (28.9%) isolates showed their capability to produce inhibitory substances against at least two tested strains. Among bacterial strains, Staphylococcus aureus was susceptible to almost all eleven isolates (90.9%), while Streptococcus pyogenes was found to be resistant to most selected isolates (18.2%). The isolate, 063 (Wadan soil-desert zone) was the only isolate that exhibited broad spectrum antimicrobial activity against all tested pathogenic microbes, and hence was selected for further study. According to its cultural, morphological, physiological, and biochemical characteristics, the isolate 063 was identified as Streptomyces rochei. The results obtained indicate that the Libyan soil, particularly in extreme environments, could be a potent source of bioactive metabolites with antimicrobial potency against a wide variety of microbial pathogens. Thus, this investigation suggested that exploring new habitats in unexplored and untapped regions of Libya could provide a promising source of biologically active compounds for therapeutic applications.

Validation of the Portuguese version of the social isolation scale with a sample of community-dwelling older adults

Objectives The aim of this study was to analyze the psychometric properties(reliability and validity)of the Social Isolation Scale(SIS)in a sample of Portuguese community-dwelling older adults.Methods A transversal descriptive study was carried out with a convenience sample of 250 community-dwelling older adults(≥65 years).The survey comprised a sociodemographic questionnaire,SIS,Geriatric Depression Scale-4(GDS-4),6-item Lubben Social Network Scale(LSNS-6),a loneliness self-assessment question,and Satisfaction with Life Scale(SWLS).Construct validity(confirmatory factor analysis)and convergent validity were analyzed,and ISI internal reliability(composite reliability),external reliability(test-retest,intraclass correlation coefficient)and inter-rater reliability(Cohen’s kappa coefficient)were evaluated.Results Confirmatory factor analysis showed a two-factor model with an excellent index of fit.The SIS showed significant correlations with LSNS-6(rs=0.47),SWLS(rs=0.26),the loneliness self-assessment question(rs=0.35),and GDS-4(rs=−0.16).SIS composite reliability was good(0.708).The inter-class correlation coefficient varied from 0.84 to 0.98.The Cohen’s kappa coefficient ranged from 0.936 to 1.Conclusions SIS has been shown to be a valid and reliable instrument for assessing social isolation among Portuguese community-dwelling older adults.Healthcare professionals,particularly nurses working in community settings,can use SIS to assess social isolation in older adults to design,implement,and evaluate interventions.

Experiences of Social Isolation in Older Hospitalized Patients with COVID-19 and Their Close Relatives: A Qualitative Study

Background: Proximity between older patients and their close relatives is essential during hospitalisation. During the first wave of the pandemic, the Danish Patient Safety Authority restricted no hospital visitors. Aim: To explore how older patients with COVID-19 and their close relatives experienced physical separation during hospitalization. Method: A qualitative study using semi-structured interviews and thematic analysis was employed. Findings: Six interviews were conducted: three patients with a mean age of 81 years and three close relatives—two daughters and one spouse. The patients felt boredom, loneliness, and a sense of imprisonment, yet they felt safe and satisfied. Isolation was known beforehand from the media. Close relatives emphasised that information, involvement, and collaboration with hospital staff were crucial. Conclusion: Although older patients with COVID-19 and their close relatives widely accept their situation during hospitalization, they experience negative consequences from social isolation.

Analytical solutions for the restraint effect of isolation piles against tunneling-induced vertical ground displacements

This paper presents a simplified elastic continuum method for calculating the restraint effect of isolation piles on tunneling-induced vertical ground displacement,which can consider not only the relative sliding of the pile‒soil interface but also the pile rowesoil interaction.The proposed method is verified by comparisons with existing theoretical methods,including the boundary element method and the elastic foundation method.The results reveal the restraining mechanism of the isolation piles on vertical ground displacements due to tunneling,i.e.the positive and negative restraint effects exerted by the isolation piles jointly drive the ground vertical displacement along the depth direction from the original tunneling-induced nonlinear variation situation to a relatively uniform situation.The results also indicate that the stiffness of the pile‒soil interface,including the pile shaft‒surrounding soil interface and pile tip-supporting soil interface,describes the strength of the pile‒soil interaction.The pile rows can confine the vertical ground displacement caused by the tunnel excavation to the inner side of the isolation piles and effectively prevent the vertical ground displacement from expanding further toward the outer side of the isolation piles.