Influence of Different Types of Fillers on the Performance of PMMA-Based Low-Temperature Rapid Repair Mortar.

In order to further optimize the performance of PMMA (Polymethyl Methacrylate) repair mortar. In this paper, fly ash, talcum powder and wollastonite powder are used as fillers to modify the PMMA repair mortar. The effects of these three fillers on the working performance, mechanical performance and durability of PMMA repair mortar were explored. The study shows that the three fillers have good effect on the bond strength of the repair mortar, in which the fly ash has the best effect on the mechanical performance. The mechanical properties of PMMA repair mortar were best when the amount of fly ash was 60 phr (parts per hundred, representing the amount of the material added per hundred parts of PMMA). At this time, the 28 d compressive strength was 71.26 MPa and the 28 d flexural strength was 28.09 MPa, which increased by 13.31% and 15.33%, respectively. Wollastonite powder had the least negative effect on the setting time of the PMMA repair mortar. When the dosage of wollastonite powder was increased to 100 phr, the setting time was only extended from 65 min to 94 min. When the talc dosage was 60 phr, the best improvement in salt freezing resistance was achieved. After 100 cycles of salt freezing, the mass loss rate and strength loss rate decreased to 0.159% and 4.97%, respectively, which were 75.1% and 37.7% higher than that of the control group. The addition of all three fillers reduced the porosity and the proportion of harmful pores in the mortar. This study contributes to a comprehensive understanding how different types of fillers affect PMMA repair mortars, and it also provides theoretical support for the further development of low-temperature rapid repair mortars.

Preparation and property studies of ferric sulfoaluminate cement based on Bayer red mud and phosphogypsum.

The Bayer red mud (RM) and phosphogypsum (PG) accumulation have caused significant environmental contamination. However, practical and effective resource utilization technologies are still lacking currently. This work aims to develop ferric sulfoaluminate cement (FSAC) employing low-cost materials including Bayer red mud, phosphogypsum, and other materials. This method effectively improves the utilization rate of Bayer red mud and phosphogypsum. Under the premise of ensuring the performance of FSAC, the utilization rate of solid waste can reach up to 48.56%. The effects of different red mud dosages on cement mineral formation, workability, and mechanical properties are investigated. Then, untreated phosphogypsum is adopted as a retarder for FSAC, and the hydration process, working properties, mechanical properties, types of hydration products, and morphology of FSAC are explored. The results suggest that the crystal transformation of Ye'elemite C 4 A 3 S ¯  is promoted with the increase of Bayer red mud content. Cubic crystal system Ye'elemite C 4 A 3 S ¯ - c  with higher hydration activity is generated, which increases the early strength of cement but greatly reduces the setting time, hindering the later strength growth. Untreated phosphogypsum can effectively delay the early hydration process of FSAC, prolong the setting time of cement, and increase the strength of FSAC in the later stage. When the dosage of Bayer red mud and phosphogypsum is 17.64% and 9.21%, respectively, with phosphogypsum dosage of 20%, the prepared FSAC has satisfactory mechanical properties, and the 3-day and 90-day compressive strengths are 34.6 MPa and 57.1 MPa, respectively. In addition, the study of heavy metal leaching indicates that the FSAC prepared by Bayer red mud, phosphogypsum, and other raw materials will generate no environment pollution, and the solidification of heavy metal elements in the cement slurry is superior.

Research into Preparation and Performance of Fast-Hardening RPC Mixed with Straw.

Based on its characteristics of early strength, good toughness, and excellent mechanical and impact resistance, steel fiber-reinforced fast-hardening reactive powder concrete (RPC) is expected to become an alternative material used in the rapid repair of marine concrete structures. However, the steel fibers have also caused corrosion problems in coastal environments. To make doped fiber fast-hardening RPC more adaptable for use in ocean engineering, this study prepares fast-hardening RPC mixed with straw and studied the effects of straw content and curing age on its slump flow, setting time, and mechanical performance (flexural strength, compressive strength, and flexural toughness). The effects of straw addition on the compactness and hydration products of fast-hardening RPC were studied through macro- (ultrasonic analysis) and micro-scopic analysis (electron microscopy scanning and X-ray diffraction patterns). The straw content mentioned in this paper refers to the percentage of straw in relation to RPC volume. The results showed that straw reduced the fluidity of RPC slurry by 10.5-11.5% compared to concrete without straw, and it accelerated the initial setting of RPC slurry. When the straw content accounted for 1% of RPC volume, the setting rate was the fastest, with a increasing rate being 6-18%. Compared to concrete without straw, the flexural and compressive strength of fast-hardening RPC was enhanced by 3.7-30.5%. When the content was either 3% or 4%, the mechanical properties improved. Moreover, when the straw content accounted for 4% of RPC volume, the flexural toughness was the highest, with the increase rate being 21.4% compared to concrete without straw. Straw reduces the compactness of fast-hardening RPC.

Effect of Micro-Nano Bubble Water and Silica Fume on Properties of C60 Concrete.

Micro-nano bubble water (WNBW) in concrete is relatively uncommon due to its newness as a technology. This paper presents the preparation of C60 concrete with 35% fly ash (FA) through WNBW and varying amounts of silica fume (0%, 4%, 7%, and 10% SF). The study examines the impact of WNBW and SF on the working performance, compressive strength, and durability of concrete. The findings indicate that applying WNBW and SF independently or jointly deteriorates the working performance of fresh concrete. However, compared to regular mixing water, WNBW reduces the concrete passing time through the V-funnel, decreasing by 40%, 39.1%, 42.9%, and 50.5% for the four varying SF contents. Furthermore, using WNBW, SF, or both resulted in the increased compressive strength of concrete at 7 days and 28 days, with 7% SF content yielding a 12.2% and 6.6% increase, respectively. Using a combination of WNBW and SF has been shown to decrease the impermeability of concrete effectively. The addition of 4% SF results in the lowest electric flux when using regular mixing water, with a discernible decrease of 30.1% compared to the control group. Conversely, using WNBW as mixing water yields a decrease in electric flux at each SF content, with the maximum decrease being 39.7%. Furthermore, both the single and combined use of these materials can contribute to the reduction in the carbonation resistance of the concrete. C60 concrete mixed with 7% SF and 100% WNBW boasts enhanced frost resistance, as indicated by the mass loss and dynamic elastic modulus loss being the least following freeze-thaw under the same SF content. According to the findings of the tests, there is evidence that the incorporation of 7% SF and 100% WNBW into C60 concrete results in lowered viscosity, a highly advantageous attribute for actual construction. Additionally, this mixture displays impressive compressive strength and durability properties. These results provide technical support regarding the integration of WNBW and SF in C60 concrete.

Effect of Modified Magnesium Oxide on the Properties of Magnesium Phosphate Cement under a Negative Temperature Environment.

As a rapid repair material, magnesium phosphate cement (MPC) can be used under various environmental temperature conditions, but different temperatures significantly impact its strength and working performance. In this study, based on the surface modification of magnesium oxide, the working and mechanical properties of samples were investigated at an ambient temperature of -5 °C, and the hydration properties and microstructure of MPC were investigated using X-ray diffraction (XRD), thermogravimetric analysis (TG), mercury-in-pressure (MIP), and scanning electron microscopy (SEM). The results show that the modified magnesium oxide at a negative temperature prolongs the setting time of MPC from 10 min to more than 30 min, and fluidity can still be maintained or increased after half an hour. From 1 d to 28 d, the compressive strength growth rate of the reference group was 257.0% compared to 723.8% for the 10 wt% water-glass-modified MgO sample. K-struvite transformed from a blocky growth to a needle-like growth with the modified sample filling the pores and cracks inside the matrix. Compared with the unmodified sample, MPC's porosity decreased from 9.62% to 9.23% for 10 wt% water-glass-modified MgO. Therefore, the surface modification of magnesium oxide not only prolonged the setting time but also further benefited mechanical performance, which provides the prerequisites for MPC construction in negative-temperature environments.

Properties of 3D-Printed Polymer Fiber-Reinforced Mortars: A Review.

The engineering applications and related research of fiber-reinforced cement and geopolymer mortar composites are becoming more and more extensive. These reinforced fibers include not only traditional steel fibers and carbon fibers, but also synthetic polymer fibers and natural polymer fibers. Polymer fiber has good mechanical properties, good bonding performance with cement and geopolymer mortars, and excellent performance of cracking resistance and reinforcement. In this paper, representative organic synthetic polymer fibers, such as polypropylene, polyethylene and polyvinyl alcohol, are selected to explore their effects on the flow properties, thixotropic properties and printing time interval of fresh 3D-printed cement and geopolymer mortars. At the same time, the influence of mechanical properties, such as the compressive strength, flexural strength and interlaminar bonding strength of 3D-printed cement and geopolymer mortars after hardening, is also analyzed. Finally, the effect of polymer fiber on the anisotropy of 3D-printed mortars is summarized briefly. The existing problems of 3D-printed cement and polymer mortars are summarized, and the development trend of polymer fiber reinforced 3D-printed mortars is prospected.

Symptoms Associated With Personal Protective Equipment Among Frontline Health Care Professionals During the COVID-19 Pandemic.

OBJECTIVE: Personal protective equipment (PPE) use is frequently construed as inconvenient and disturbing by health care professionals (HCPs). We hypothesized that new-onset symptoms among HCPs may be associated with extended use of PPE and aimed to investigate risk factors related with new-onset symptoms. In addition, the effects of new-onset symptoms on working performance were evaluated. METHODS: In this cross-sectional study, 315 participants filled out a questionnaire that contains 4 main parts: (1) demographics, (2) new-onset symptoms with PPE use, (3) PPE usage hours, and (4) personal opinion about the effect of sensed symptoms on working performance. RESULTS: The mean age was 31.58 ± 4.6 years, and 50.5% (n = 159) were female. New-onset symptom rate was 66% (n = 208). The most common new-onset symptom was headache (n = 115, 36.5%) followed by breathing difficulty-palpitation (n = 79, 25.1%), and dermatitis (n = 64, 20.3%). Extended use of PPE, smoking, and overweight were independently associated with developing new-onset symptoms. A clear majority of symptomatic participants pointed out the impact on working performance (193/208, 92.7%). CONCLUSION: Hospitals should take the necessary precautions (eg, shorter shifts and more frequent breaks) to prevent symptoms associated with PPE and ensure that HCPs comply with these precautions.

Analysis and prevention of ergonomic risk factors among dental students.

INTRODUCTION: Dentistry is a high-risk profession for the development of work-related disorders. Dental students are also exposed to several risk factors. The goal of the study was to determine and localise musculoskeletal pain during dental work, afterwards to measure electromyography signals from the muscles groups mostly affected by the musculoskeletal pain. Study was done in order to provide possible suggestions for the most effective preventive measures of MS pain among dental students. MATERIALS AND METHODS: In order to solve the objectives, the research was realised in two segments. In the first part of the study, specially designed questionnaires were used to determine the frequency of musculoskeletal pain, risk factors and preventive measures among students. The second part of the study included electromyography analyses of muscular activity of students during dental work. Inclinometers also were set up in the purpose of monitoring inclination of the spine. RESULTS: Results of the questionnaire study indicated that pain during work was frequent, 81.8% of all the subjects reported pain during work. The recorded muscle activity of the neck muscles indicated a high ergonomic risk, while the muscle activity of the shoulders and back muscles indicated a medium risk. Work with a back flexion of 20 degrees and more indicates that students are at risk. CONCLUSION: Dental students used to work in unnatural working position. High ergonomic risk occurred in neck muscles. Students should be aware of the potential risks during work and to learn how to prevent it. Regular physical activity is strongly suggested to the students in order to avoid ergonomic problems.

Music in the workplace: A narrative literature review of intervention studies.

Background Music is widely used in clinical and rehabilitative fields and recently also in the field of Occupational Medicine. This review aims at selecting the evidence-based studies regarding music interventions in workplaces. Methods In order to carry out a narrative literature review, two independent pairs of investigators searched in PubMed and PsycInfo databases to select Randomized Controlled Trials (RCTs) or Clinical Controlled Trials (CCTs) in English regarding music and music therapy interventions in workplaces; the trials were published in peer-reviewed journals from January 2000 to February 2017. Results Fourteen articles met the inclusion criteria and were included in this review. Among these, ten were RCTs and four CCTs. The vast majority of RCTs were conducted on students or medical personnel (n=8), while only a few RCTs (n=2) were carried out on air traffic controllers or sick leave workers. Firefighters, computer systems developers, nursing students and office workers were studied through a CCT study design (n=4). Conclusions Psychological factors, communication, rehabilitative outcomes and cognitive and work performances seem to be the principal areas of interest in the field of music and occupational medicine, with possible economic benefits. Future studies should adopt rigorous methodological criteria to carry out larger samples on a wide range of professional categories and music/music therapy interventions.

The design and application of hospital management information system based on attitude and perceived behavioral control / 中国医学装备

Objective: To design a hospital management information system based on attitude and perceived behavior control, and to explore the influence of the application of hospital management information system on the work performance of medical personnel. Methods: Through constructed hospital management information system and applied the work performance model of medical personnel to design questionnaire from three points of view included attitude, habits, subjective norm and perceived behavior control. And then the internal consistency and validity of the scale of measurement indexes of the questionnaire were tested, and the methods of statistical modeling and parameter estimation were adopted to carry out path analysis. Results: The results of primary estimation for the change situation of main medical indexes of application information system in earlier, middle and later stage indicated that the reliability of variates that were selected in this research was higher, and the consistency of interior of various variates was higher. At the three stages, earlier, middle and later stage, that information system was implemented, the person-time of leaving hospital, the number of inpatient surgery and the outpatient amount of expert displayed rising trend. And the drug proportion, average stay time decreased 9.45%, 3.36% and 16.16% and 4.27% respectively. Conclusion: Whether the hospital information system can be applied, the personal subjective factors of medical personnel play an important role.

Assessment of risk factors and preventive measures and their relations to work-related musculoskeletal pain among dentists.

BACKGROUND: Dentists have a high prevalence of musculoskeletal (MS) pain, which is the most common symptom associated with work-related musculoskeletal disorders (WMSDs). To overcome this problem, identification of the risk factors and preventive measures for MS pain are of paramount importance to dentists in order to improve their quality of life and work. OBJECTIVES: The aims of this study were to recognize the risk factors for MS pain and their impact on dental work, as well as to identify preventive measures of MS pain among dentists. METHODS: Self-reporting questionnaire consisting of 78 questions was exclusively developed for the study and sent to 500 working active dentists in Serbia. RESULTS: Response rate was 71.2% (356 dentists). The prevalence of MS pain was 82.6% among dentists. The main risk factors for MS pain were advanced age, female dentists, presence of chronic diseases, long working hours, and high frequency of treated patients. The most effective preventive measures in preventing MS pain were massage treatments and physical activities. Followed by use of ergonomically designed equipment, correct and dynamic working positions, and an adequate workflow organization. CONCLUSION: The risk factors for MS pain and their impact on dental work should widely be disseminated among dentists. Importantly, proper implementation in everyday life of adequate preventive measures is essential for preventing MS pain and development of WMSDs.

Performance of nitrate-dependent anaerobic ferrous oxidizing (NAFO) process: a novel prospective technology for autotrophic denitrification.

Nitrate-dependent anaerobic ferrous oxidizing (NAFO) is a valuable biological process, which utilizes ferrous iron to convert nitrate into nitrogen gas, removing nitrogen from wastewater. In this work, the performance of NAFO process was investigated as a nitrate removal technology. The results showed that NAFO system was feasible for autotrophic denitrification. The volumetric loading rate (VLR) and volumetric removal rate (VRR) under steady state were 0.159±0.01 kg-N/(m(3) d) and 0.073±0.01 kg-N/(m(3) d), respectively. In NAFO system, the effluent pH was suggested as an indicator which demonstrated a good correlation with nitrogen removal. The nitrate concentration was preferred to be less than 130 mg-N/L. Organic matters had little influence on NAFO performance. Abundant iron compounds were revealed to accumulate in NAFO sludge with peak value of 51.73% (wt), and they could be recycled for phosphorus removal, with capacity of 16.57 mg-P/g VS and removal rate of 94.77±2.97%, respectively.

Partitionable-space enhanced coagulation (PEC) reactor and its working mechanism: a new prospective chemical technology for phosphorus pollution control.

Phosphorus pollution control and phosphorus recycling, simultaneously, are focus of attention in the wastewater treatment. In this work, a novel reactor named partitionable-space enhanced coagulation (PEC) was invented for phosphorus control. The working performance and process mechanism of PEC reactor were investigated. The results showed that the PEC technology was highly efficient and cost-effective. The volumetric removal rate (VRR) reached up to 2.86 ± 0.04 kg P/(m(3) d) with a phosphorus removal rate of over 97%. The precipitant consumption was reduced to 2.60-2.76 kg Fe(II)/kg P with low operational cost of $ 0.632-0.673/kg P. The peak phosphorus content in precipitate was up to 30.44% by P2O5, which reveal the benefit of the recycling phosphorus resource. The excellent performance of PEC technology was mainly attributed to the partitionable-space and 'flocculation filter'. The partition limited the trans-regional back-mixing of reagents along the reactor, which promoted the precipitation reaction. The 'flocculation filter' retained the microflocs, enhancing the flocculation process.

Floatation of granular sludge and its mechanism: a key approach for high-rate denitrifying reactor.

A high-rate denitrifying automatic circulate (DAC) reactor has been developed recently, and it is promising to become an alternative in nitrogen removal from wastewaters. However, the performance of DAC reactor was disturbed by the floatation of granular sludge at high-loads. The results showed that: the floatation of granular sludge led to a serious biomass washout and a sharp decrease of biomass concentration. The floatation of granular sludge was ascribed to a low sludge density originated from the holdup of gaseous products. The average density and average gas holdup ratio of floated granular sludge were 913 kg m(-3) and 11.8% (by volume), respectively. The floatation of granular sludge could disappear by releasing gas when sludge was in the state of elastic expansion, but it would become worse by holding gas when it entered the plastic expansion state. The plastic expansion of granules was significantly correlated with the less content of extracellular polymeric substances.

Quantitative and qualitative research in cognition of clinical nurse specialist / 中国实用护理杂志

Objective To study the clinical nurses and nursing students' cognition of clinical nurse specialist (CNS) and provide the basis for promoting the development of CNS.Methods Quantitative and qualitative research were adopted in this study.One hundred and ninety clinical nurses and nursing students were investigated with a questionnaire about the cognition of CNS,and the qualitative research was conducted on 9 clinical nurses selected by purposive sampling method.Results Most participants realized the importance of CNS and 78.4％ of them wished to be an excellent CNS.The cognition was different between the two groups,especially in terms of ability,working performance and status.Conclusions We should improve the clinical nurses and nursing students' cognition of CNS,and cultivate them with the core competence of CNS.Meanwhile,improving the status and confirming the role must be done to promote the development of CNS in China.

Propuesta de estrategia para la evaluación del desempeño laboral de los médicos en Cuba / A proposal of strategy for the assessment of work performance of physicians in Cuba

La calidad de un servicio de salud depende, en primer orden de la competencia del capital humano que en él labora. En Cuba, actualmente no existe ningún mecanismo ni procedimiento establecido para evaluar el desempeño de los médicos, como está establecido para otros profesionales y técnicos del país. El autor ha venido investigando esta problemática durante veinte años y los estudios efectuados se estructuraron en tres periodos. El primero de ellos (1986-1992) estuvo dirigido al estudio, análisis y crear consenso sobre las bases teóricas y metodológicas que fundamentaran el diseño de un modelo de desempeño profesional en nuestro Sistema Nacional de Salud (SNS). En el segundo periodo (1993-1996) se logró estructurar una propuesta metodológica y su operacionalización, lo que contó con la voluntad política del Ministerio de Salud Pública para su ejecución. El tercer periodo (1997-2006) posibilitó su aplicación, ganar experiencia, y se crearon las condiciones propicias para estructurar una nueva propuesta. La estrategia que se propone como producto final de nuestra investigación, permite interrelacionar la evaluación del desempeño laboral del médico, la superación profesional permanente, los créditos académicos posgraduales y la certificación profesional a nivel de estándares internacionales. Se hacen conclusiones, así como recomendaciones para iniciar su puesta en marcha.

The quality in a health service depends in first order on the competence of human staff supplying it. In Cuba, nowadays there is neither mechanism nor established procedure to assess the physician's performance as in the case of other professionals and technicians of our country. The author has been research on this problem for twenty years and the studies conducted were structured in three periods. The first one (1986-1992) was directed to study, analysis and consensus on the theoretical and methodological bases supporting the design of a professional performance model in our National Health System (NHS). In the second period (1993-1996) it was possible to structure a methodological proposal and its functional qualities supported by the Public Health Ministry political will for its execution. The third period (1997-2006) allowed its application, an increased experience and the creation of suitable conditions to structure a new proposal. The strategy suggesting as an end-product of our research, allows to interrelate the assessment of the physician's working performance, its permanent professional overcoming, the postgraduate academic credits and the professional certification at international standards level. We reach conclusions and made recommendations to start its implementation.