In this paper, a piezoelectric sensor-embedded smart rock is proposed for the electromechanical impedance monitoring of internal concrete damage in a prestressed anchorage zone. Firstly, a piezoelectric sensor-embedded smart rock is analyzed for impedance monitoring in concrete structures. An impedance measurement model is analyzed for the PZT (lead zirconate titanate)-embedded smart rock under compression in a concrete member. Secondly, a prototype of the smart rock embedded with a PZT sensor is designed in order to ascertain, sensitively, the variations of the impedance signatures induced by concrete damage in an anchorage zone. Thirdly, the performance of the smart rock is estimated from a numerical analysis and experimental tests. Variations in the impedance signals under compressive test cases are analyzed in order to predetermine the sensitive frequency band for the impedance monitoring. Lastly, an experiment on an anchorage zone embedded with the smart rocks and surface-mounted PZT sensors is conducted for the impedance measurement under a series of loading cases. The impedance variations are quantified in order to comparatively evaluate the feasibility of the sensor-embedded smart rock for the detection of internal concrete damage in the anchorage zone. The results show that the internal concrete damage was successfully detected using the PZT-embedded smart rock, thus enabling the application of the technique for anchorage zone health monitoring. Prestressed concrete (PSC) has been widely used as critical members for bridge construction, thanks to its cost-effectiveness and crack-resistance over original reinforced concrete structures. In PSC bridges, anchorage zones have a vital function in carrying the designed prestress-force and transferring it into the structures. Considering time-dependent effects, the structural performance of PSC members could gradually decline due to material deterioration, corrosion, and time-dependent prestress loss, leading to long-term deformation. Incipient concrete damage, which is often in the form of inner micro-cracks, could produce and amalgamate to induce surface cracks. The cracks often occur in tensile regions, and most cracks are invisible at an incipient state. When the inner cracks propagate onto the PSC members’ surfaces, material degradations could be significant due to environmental erosion. The severe concrete cracks in PSC bridges cause a rising concern for designers, investigators, and managers ,2,3. ThuVarious SHM  methods have been proposed for the damage detection of PSC members using vibration characteristics  ,5. The mIn the past decades, various SHM applications have been successfully implemented using the functions of smart materials such as piezoelectric ceramic. A PZT  patch is attached to a monitored structure in order to acquire electromechanical impedance responses, and then the changes in the impedance signals are quantified and used as a damage indication ,15,16. AIn PSC bridges, anchorage zones resist the particularly high compressive force induced by prestressing strands  during tThis study presents an impedance-based damage detection method in a concrete anchorage zone via a PZT-embedded smart rock. Firstly, an impedance measurement model is designed for the impedance monitoring of a concrete member using the PZT-embedded smart rock. Secondly, a prototype design of the smart rock embedded with a PZT sensor is proposed in order to sensitively catch the impedance variations induced by concrete damage in an anchorage zone. Thirdly, the performance of the smart rock is tested using numerical analysis and experimental tests. The variations in the impedance signals under compressive loading cases are analyzed in order to predetermine the sensitive frequency band for the impedance monitoring. Lastly, an experiment on an anchorage zone embedded with the smart rocks and surface-mounted PZT sensors is conducted for the impedance measurement under a series of loading cases. The PZT’s impedance variations are quantified in order to comparatively evaluate the feasibility of smart rock for the detection of internal concrete damage in the anchorage zone.F on the host structure changes, it leads to changes in the modal parameters  of the protected layer, the concrete block, and the host structure. As shown in m, k, and c symbolize the mass, the damping coefficient, and the spring stiffness, respectively, and the subscripts p, r, and s denote the protective layer, the concrete block, and the concrete structure, respectively.pF at the PZT driving point can be formulated as the following:pm, rm, and sm, respectively. The coupling structural–mechanical (SM) impedance, the sZ of the protected layer, the concrete block, and the host structure are determined as follows [mnK  are the dynamic stiffness coefficients that contain the structural parameters of the protective layer, the concrete block, and the monitored structure [For the 3-DOF impedance model, the governing equation of the motion under a harmonic excitation  follows :(2)Zs=1jtructure .Z(ω), is a function of the SM impedance, s,Z of the smart rock host structure, and that of the PZT sensor, aZ [aw, al and at are the width, length, and thickness of the piezoelectric patch, respectively; d31 is the piezoelectric constant in one direction at zero stress; and The electromechanical impedance, nsor, Za :(3)Z(ω)=Z(ω) contain the SM impedance of the PZT patch, the smart rock, and the host structure. The 3-DOF impedance model represents the coupled vibrations of the smart rock and the host structure. When the electric and mechanical properties of the PZT sensor are constant, any external effects  would exert an effect on its impedance responses.As noted in Equation (3), the real-part impedance responses oσ1 due to the strength development of the concrete  and under tension Fνσ  for the other surfaces, as seen in oσ2F+ σ) and the coated PZT (oσ1o+ σ2F+ σ) are increased for the z-direction, but they are reduced for the other directions. For concrete members under compression, inner concrete damage (often in the form of cracks) could occur before surface cracks [oσ1o+ σ2) [e cracks ,41. The 1+ σo2) . When in1+ σo2) ,40. FiguZ(iω) and *Z(iω) are the real part of impedance signatures obtained from the intact and loading states of the smart rock at the ith frequency, respectively, and N denotes the number of frequency sampling points in the sweep. The RMSD metric, which represents the intensity of random spectra, is useful in order to quantify the variation of the impedance signals in a frequency band.In order to quantify the changes in the impedance signatures via the PZT-embedded smart rock, the root mean square deviation (RMSD) damage metric is commonly  used:(4)μ and σ are the mean and the standard deviation of the impedance signatures in the intact condition, respectively. The UCL was calculated by 3σ, which corresponds to a confidence level of 99.7%. The calculation of the UCL is outlined in three steps: firstly, N impedance signals are measured at the intact condition; secondly, the RMSD values for N impedance signals are computed by Equation (4), then a set of RMSD values is obtained; finally, the UCL of the RMSD values is calculated using Equation (5). The occurrence of damage  is indicated when the RMSD values are larger than the UCL. Otherwise, there is no indication of damage occurrence.Ideally, the RMSD value should be larger than zero if the compression forces increase ; otherwise, it should be zero. However, the statistical index of the RMSD can be larger than zero due to experimental and computational errors, even if there are no changes in the applied forces. The upper control limit (UCL)  is estabSince most piezoelectric materials  are fragile, they are commonly covered in a smart aggregate, which is a coated PZT embedded into a small concrete block ,44 beformax of the aggregate. A concrete mixture including cement, sand, and water (without aggregate) was used for the fabrication of the smart rocks. As shown in P was applied on the smart rock’s surface along the axial direction   models (Models 1–2) of the smart rock under the effects of the axial and lateral compressive force were established in Comsol Multiphysics , as shown in xis) see a. For th.1 φ × H ) of the The FE models consist of the PZT 5A patch , the epoxy layer, and the concrete block. The geometric parameters of each component were previously described in For Model 1, the complete meshed FE model of the smart rock consists of 10,972 elements, including 9964 elements for the concrete block, 752 elements for the epoxy layer, and 256 elements for the PZT. The fixed boundary condition was assigned to the bottom surface of the concrete block see a. For MoP on the host structure causes the same stress variations for a local region close to the PZT sensor, and it is not affected by the shape of the smart rock. In order to acquire the impedance signatures, a 1 V harmonic voltage was applied to the top surface of the PZT patch, while the bottom surface was assigned as the ground electrode.Seven cases (P1–P7) of the compressive forces were simulated in a series in order to obtain the impedance responses of the PZT-embedded smart rock, as follows: P1 (1.0 kN), P2 (1.5 kN), P3 (2.0 kN), P4 (2.5 kN), P5 (3.0 kN), P6 (3.5 kN), and P7 (4.0 kN), corresponding to axial stress change from 0–5.65 MPa . The forces P1–P7 could cause lateral stress changes from 0–3.8 MPa, in which the lateral stress could be computed as 2P/(πHD)  with φ . The axiIt is known that the resonant impedance frequency ranges represent meaningful structural information ,51. The In order to analyze the realistic performance of the PZT-embedded smart rock in , an expeFor each test (Tests 1–4), the compressive force was increased from 1.0 to 4.0 kN (P1–P7) with an interval of 0.5 kN, as noted in oσ1 due to the hydration process of the concrete acting on the coated PZT  there were slight differences in the impedance features under the loading-direction effects; (2) the impedance feature was repeatable, and was gradually increased under compressive forces; and (3) the predetermined frequency band for the smart rock was 100–600 kHz, in which the sensitive frequency band was 150–250 kHz.cσ = 23.3 MPa.A lab-scale experiment on a concrete anchorage zone equipped with smart rocks was conducted in order to evaluate the feasibility of the PZT-embedded smart rock for the health monitoring of the anchorage zone, as schematized in Two smart rocks, namely SR-A (on the left side) and SR-B (on the right side), were embedded in the concrete anchorage (3.5 cm from the concrete surface) for the impedance monitoring, as detailed in bσ was varied from 17.3–40.7 MPa  under the forces F1–F11. It is well known that the bearing stress in the anchorage zone (with reinforcement) allows from 1.25 to 3.0 ciσ [ciσ (≈0.85 cσ) is the compressive strength of the concrete at steel strand’s installation. In the experiment, the concrete surface crack (near SR-A) occurred under the bearing stress bσ = 1.71 cσ , and the anchorage failure occurred under bσ = 1.74 σc (under force F10). The observation of the concrete’s crack development during the loading procedure is summarized in As noted in  3.0 σci ,55,56, iAn impedance analyzer HIOKI 3532 was used to generate (1 V harmonic voltage) and measure the impedance signatures of the PZT sensors in the frequency range of 100–600 kHz (501 points). For each test case, four ensembles of impedance signals were recorded. As noted in For SR-A see a, the imBy matching the impedance signatures of the embedded-PZT sensors and the surface-mounted PZT sensors to the crack appearances, the observations were made as follows. First, the crack occurrence caused rushed changes in the impedance responses; that is, SR-A and PZT-S1’s impedance showed significant changes, but those of SR-B and PZT-S2 were ignorable changes (under the force F9). Second, the incipient crack and damage in the concrete, which early occurred on the left side of the anchorage zone, could come from the unequally-applied force (via four steel blocks) and the nature of the concrete structure . In As observed in For SR-A see a, the RMWhen the concrete was damaged, the impedance responses progressively increased in their magnitudes and were reduced in their impedance frequencies see a, thus eThe impedance features of the PZT-embedded smart rock yielded a better damage indicator than those of the surface-mounted PZT sensor. This is because the PZT-embedded smart rocks directly received the stress variations from the anchorage zone, as opposed to the surface-mounted sensors. Previous studies ,57 have In this paper, impedance-based damage detection in the anchorage zone using impedance features measured by PZT-embedded smart rock was presented. Firstly, the impedance measurement model was designed for the impedance monitoring of the concrete member using the PZT-embedded smart rock. Secondly, the smart rock embedded with the PZT sensor was designed in order to catch, sensitively, the impedance variations induced by the concrete damage in the anchorage zone. Thirdly, a numerical analysis and experimental tests were performed in order to predetermine the sensitive frequency band for the impedance monitoring. Lastly, an experiment on the anchorage zone embedded with the smart rocks and the surface-mounted PZT sensors was conducted for impedance monitoring under a series of the loading cases, in order to evaluate the feasibility of the smart rock for the detection of internal concrete damage.From the numerical and experimental analyses, the following remarks can be drawn: (1) the sensitive frequency range of the smart rock is 150–250 kHz; (2) the impedance features showed ignorable changes in the intact state due to the prestress on the smart rock during the concrete’s strength development; (3) the inner concrete damage was successfully detected using the impedance features by the PZT-embedded smart rock.The experimental results showed the promising applicability of the smart rock for the detection of incipient concrete damage in the prestressed anchorage zone. For example, smart rocks can be embedded during construction, and their impedance responses can be measured and utilized as a baseline. The measured signals are compared, over time, to the baseline signals in order to determine the health of the monitored structure. As a future study, a real-scale experiment on a prestressed anchorage zone should be conducted in order to evaluate the practicality of the proposed smart rock. Furthermore, recent advanced techniques based on machine learning should be employed in order to analyze multiple parameters  for damage prediction.


Boric acid, a weak acid, is often used to shield neutrons in water cooling systems in nuclear power stations. The leakage of boric acid in water cooling systems damages the concrete structure and affects the safety of nuclear power engineering. In this experiment, concrete specimens were cured with boric acid at 20, 40, and 70 °C to study the effect of boric acid on the microstructure and properties of concrete. X-ray diffraction (XRD) and thermogravimetry and differential scanning calorimetry (TG-DSC) were used to analyze the change in mineral composition. The microstructure was examined by scanning electron microscope (SEM). The porosity of the concrete was examined by mercury intrusion porosimetry (MIP). The results show that the performance of specimens was stable under the curing conditions of 20 and 40 °C. Under the curing environment of 70 °C, the performance of concrete cured with 0, 2000, and 7000 ppm concentrations was stable, but the compressive strength of the 180,000 ppm specimen was reduced by 27.8% and suffered the most serious loss of mass and surface corrosion, with the most harmful pores. The high concentration of boric acid seriously damaged the surface structure of concrete, which is the main reason for its loss of properties. This situation is extremely dangerous in nuclear power engineering, so the effect of boric acid leakage cannot be ignored. In containment spray systems at nuclear power plants, boric acid is used to cool the containment, reduce pressure, and remove fission products. However, when abnormal leakage of boric acid in the containment occurs, the concentration of boric acid rises and approaches saturation as a result of water evaporation. The pH of boric acid solution at 95 °C is less than 3 , and it 2 in concrete and CaO in calcium silicate to generate various borate products and change various mineral components in cement [The corrosion by boric acid is one of the factors that leads to the lack of durability of concrete. Boric acid also has a neutral reaction with concrete. At room temperature, boric acid has no obvious effect on the compressive strength, flexural strength, wrapping strength, and corrosion rate of reinforcement of concrete specimens ,11. Howen cement . Petrolon cement ,14.In the actual operation of the containment cooling tank, the normal temperature is 70 °C, and the concentration of boric acid is 7000–7700 ppm . GeneralThe deterioration of concrete is mainly due to the reduction of macroscopic mechanical properties, and the reason for the deterioration is the change of concrete structure. At present, the mechanism of deterioration of concrete is mainly analyzed by means of SEM and XRD ,20. BecaIn the existing research, only the effect of boric acid on cement concrete at 20 °C has been studied, without taking into account the effect of temperature. Therefore, this study used the actual situation of a nuclear power plant as a simulation and the concentration of boric acid was set considering the polycondensation of boric acid in the limit case (70 °C). Thus, a batch of concrete specimens was formed, and an accelerated curing box was used to simulate the cooling water tank with curing temperatures of 40 and 70 °C. Concrete specimens cured with saturated acid concentrations were used to study the effect of boric acid on the microstructure and properties of cement concrete materials.R-SCC high-performance concrete water reducer from Sobute New Materials Company, Nanjing, China.P.II 52.5 Portland cement (PC) was supplied by Onada Cement Corp in Nanjing, China. The fly ash (FA) used in this study was a byproduct produced by Huaneng Power Plant in Nanjing, China. This FA had a low CaO content of 3.40%, as shown in The concrete specimens consisted of Portland cement, fly ash, coarse aggregate, fine aggregate, and water reducer. The size of the specimens was 100 mm × 100 mm × 100 mm, and the microstructure and properties of cement concrete were measured. After 24 h of molding, all specimens were cured at 20 °C for 28 days. The specimens were placed in a curing box with a humidity of 95% and a temperature of 25 °C. The concrete used in a nuclear power plant has excellent performance, so we adopted the ratio of R55. The composition of the concrete specimens is shown in A concrete accelerated curing box was used to simulate the actual temperature. In this experiment, we used 20, 40, and 70 °C as a comparative test. The concentrations of boric acid in the curing solution were 0 and 50,000 ppm at 20 °C; 0 and 90,000 ppm at 40 °C; and 0, 2000, 7000, and 180,000 ppm at 70 °C. These conditions are denoted by 20–0, 20–50,000, 40–0, 40–90,000, 70–0, 70–20,000, 70–7000, and 70–180,000 ppm for short. The percentage of boric acid and the concentration of solution were chosen according to the national standard. Specimens were acid-cured in the aforementioned environments, The curing of the specimen is shown in The volume of boric acid was five times the volume of the specimen. The pH of the solution of boric acid at 70 °C  was about 4.2, and the pH of the solution did not change significantly within a week. Mannitol was used to measure the concentration. We changed the curing solution every other week to ensure the concentration of boric acid.The concrete samples were removed at the ages of 0, 28, 90, and 180 days, and the mass change of the specimens was measured using an electronic balance . The specimen was taken out of the curing box and dried for the same drying time for each age.The compressive strength of concrete was calculated in strict accordance with the standard test method of mechanical properties of ordinary concrete using a compressive-testing machine with a loading rate of 0.5–0.8 MPa/s, and the calculated result was accurate to within 0.1 MPa. The compressive strength was measured according to standard . The macAfter reaching the required age, the concrete specimen was sliced about 1 cm from the surface, and then phenolphthalide alcohol solution with a mass fraction of 1% was used to test the depth of neutralization. Ten points were taken for each edge, and the average depth of neutralization was calculated.2 atmosphere.Mortar was subjected to X-ray diffraction (XRD) and thermogravimetry and differential scanning calorimetry (TG-DSC) analyses at different ages. The mortar cut from the concrete samples was immersed in absolute ethyl alcohol for 12 h to terminate hydration, before being vacuum dried at 60 °C for 24 h and then ground into powder. The test powders were passed through an 0.08 mm sieve. The XRD data were collected in the range of 5° to 80°, 2θ at a counting time of 15 s/step, and a divergence slit of 1°. TG-DSC data were obtained from 50 to 1000 °C at a rate of temperature increase of 10 °C/min in an NMercury intrusion porosimetry (MIP) is a method that can accurately measure the porosity and pore size distribution of the cement material. In this study, we used MIP  to characterize the porosity and pore distribution of the sample, and analyzed the corrosion process of the material from the pore structure.In order to investigate the morphology of concrete under boric acid attack, a characteristic fresh piece of concrete was sampled, hydration terminated, and vacuum dried. Then, the dried sample was embedded in a low-modulus epoxy, coated with a gold–palladium coating. A scanning electron microscope  was used to observe the surface morphology of the concrete.The surfaces of the concrete samples at 90 days are shown above in The mass loss of the concrete samples is shown in We studied the effect of the concentration of boric acid, as shown in The change of compressive strength of 40–0 was basically the same as 20–0, but the difference between 40–90,000 and 20–50,000 ppm was most significant at 90–180 days; the compressive strength began to decline, and at 180 days, the compressive strength of 63.3 MPa was lower than the initial strength, and the loss rate of compressive strength reached 1.70%.At a temperature of 70 °C for conservation, the compressive strength of 70–0, 70–2000, and 70–7000 ppm was 76.7, 78.2, and 75.6 MPa at 28 days, respectively. The compressive strength of material at 70 °C was greater than that at 20 °C, but the compressive strength of 70–180,000 ppm at 28 days was only 68.1 MPa, and the compressive strength of three other groups started to decrease at 28 days, which indicated that the growth of the compressive strength of concrete was hindered by highly concentrated boric acid in the early stage of conservation at a temperature of 70 °C. The compressive strength of 70–0, 70–2000, and 70–7000 ppm slightly decreased as concentration increased at 90 days, but that of 70–180,000 ppm was only 48.1 MPa at 90 days. The loss rate of compressive strength reached 25.3%, and the loss rate of compressive strength also reached 27.8% at 180 days.In the process of measuring the compressive strength of this group of specimens, we also found that the failure modes of the specimens in this group were different from those in the other seven groups; the failure mode of 70–180,000 ppm was found as shown in In The neutralization depth of 70–180,000 ppm was 1.5 mm; this proved that boric acid corroded concrete from the outside to the inside under a high temperature and high curing concentration environment. The basic cement was gradually dissolved out of the concrete by boric acid, and boric acid destroyed the surface structure of the concrete, making it brittle and reducing its compressive strength. This corresponds to the previous mass loss rate of concrete; in other words, except for the concrete itself, the weight loss was almost due to the boric acid corrosion of the surface layer of cement.2)2 was not demonstrated in the XRD atlas; therefore, it was believed that concrete was generally corroded by boric acid in an alkaline environment. Under this condition, the major borate produced after concrete was corroded by boric acid was calcium metaborate. The concrete suffered from significant weight loss. Hence, during neutralization, boric acid firstly reacted with alkaline composition in paste to produce Ca(BO2)2, but as boric acid continued to corrode, the pH value continuously decreased, and the produced borate was slowly dissolved in the conservation solution of boric acid. The contents of Ca(BO2)2 and other borates in paste were extremely low, which was why they could not be detected during XRD.In The surface of the concrete showed an obvious sand formation at 90 days in 2)2 appeared on the surface of the concrete at 180 days. Undeniably, the presence of this group of peaks confirms that boric acid generates Ca(BO2)2 in the alkaline environment of concrete. Because the concrete structure is not dense with cement pastes, the corrosion degree of concrete was more intense than others, so the XRD pattern is different from that of the other experimental group.As age increased, the sand on the concrete surface is exposed; the peak of sand becomes much stronger than the rest, making it inconvenient to detect the rest. In order to observe the reaction products, we removed the peaks of cement and sand in the XRD; a group of peaks of Ca on the surface of the material, samples on the surface and interior of concrete at 180 days were taken for TG-DSC analysis. The results are shown in The It can be seen from the For further details, specimens at 28 days (early stage) and 180 days (late stage) under different reaction conditions were selected for SEM analysis, as shown in the following figures.At 28 days, all specimens were at the early stage of reaction. In The corroded pores were demonstrated on the surface, indicating that, in the early stage of reaction, paste was corroded by high-concentration boric acid even at a temperature of 40 °C for conservation. The surfaces of neither 70–0 nor 70–2000 ppm were obviously corroded at a temperature of 70 °C for conservation; however, many corrosion traces could be found on the surface of 70–7000 ppm, which was more seriously corroded than 40–90,000 ppm either in terms of corrosion area or corrosion depth. The corrosion area of 70–180,000 ppm further increased, and large pores emerged. The strong corrosion reaction occurred on the surface of 70–180,000 ppm at the early stage. It may be noticed that there were few set pores in the cement and that the internal section of paste was likely to be further damaged.At 180 days, the corrosion of paste reached a late stage. In At a temperature of 70 °C for conservation, the morphology on the surface of paste was further damaged as the concentration of boric acid increased. The obvious corrosion pores could be found on the surface of 70–2000 ppm. The paste material and reaction products started to be dissolved out from 70–2000 ppm, the corrosion area of which increased. Obvious dissolution traces could be found on the surface of 70–2000 ppm. No obvious set cement structure could be seen on the surface of 70–180,000 ppm, and its internal section was also obviously corroded.The neutralization of boric acid and the hydration of cement are like a rivalry for the calcium hydroxide in the paste. Therefore, when the concentration of boric acid is low, the hydration reaction in the paste plays a dominant role, and the properties of cement continuously increase.However, when the concentration of boric acid is saturated at a temperature of 70 °C, the acid-base neutralization reaction plays a dominant role, and cement suffers from loss of properties during conservation. Therefore, the temperature of the reaction and the concentration of the acid solution have a significant influence on the neutralization and hydration of cement. The surface is firstly corroded by the neutralization between boric acid and cement, and then the internal section is gradually corroded. However, the hydration reaction occurs in all directions in paste. Even at 70 °C, the structure of cement could not be significantly destroyed by 180,000 ppm boric acid at the early stage.Under the curing condition of high temperature and concentration, the corrosion mechanism of boric acid on cement is shown in It is generally accepted that boric acid has little effect on concrete, but concrete shows a large performance loss at 70 °C and 180,000 ppm. These conditions are possible in nuclear power plants, so we cannot ignore the effects of boric acid leakage.i.At the maximum allowable concentration of boric acid, 7000 ppm, even boric acid does not cause obvious performance loss to the outer wall of the pressurized water reactor at 20, 40, and 70 °C, and boric acid is safe for the external concrete structure of a pressurized water reactor under permissible operating conditions.ii.We simulated the 70 °C and 180,000 ppm scenario and found that, under a high-temperature and high-curing-concentration environment, the mass loss rate of 70–180,000 ppm was 0.69% at 180 days under conservation conditions, and its loss rate of compressive strength was 27.8% at 180 days. The surface corrosion of the concrete was serious. CH% in the surface was 3.12%, the neutralization depth was 1.5 mm, and the porosity of the harmful pores in the concrete surface was much higher than that of the rest of the specimens. The deterioration of the concrete surface caused by a high concentration of boric acid at a high temperature was the main reason for this loss of properties. Such a large loss rate of compressive strength is extremely dangerous in practical engineering.iii.Temperature and the concentration of boric acid are two important factors that cause concrete corrosion. The corrosion of concrete becomes more serious as the temperature and concentration of boric acid rise. However, at the early stage of the experiment, the hydration reaction of cement was stronger than the corrosion of boric acid at a high temperature, so the influence of the initial concentration was smaller than that of temperature. With the growth of the phase, the hydration reaction ended, and the influence of boric acid concentration began to dominate.iv.2)2 was detected on the surface of the 70–180,000 ppm concrete specimen at 180 days. This was not detected for any of the other specimens. As the concentration of boric acid increased, the porosity of harmful pores in the paste increased. The corrosion area on the surface of the paste gradually increased, along with corrosion depth. By combining this with the mass loss rate, it can be concluded that most of the substances produced during boric acid corrosion were dissolved into the acid conservation solution.Ca(BOv.Some highly active auxiliary cementites such as silica ash accelerate the hydration of cement, thus giving cement hydration in concrete an advantage over boric acid in the neutralization process. The addition of silica ash into cement is the focus of the next stage of our research.A batch of paste and concrete specimens were separately conserved in boric acid solutions of different concentrations at temperatures of 20, 40, and 70 °C. The conclusions are as follows:


A two-phase mixed-methods  online study was conducted in Pakistan from August 2019 to March 2020 by using validated questionnaires and semi-structured interview data. Different statistical methods were used to tabulate the quantitative data, whereas inductive thematic analysis was conducted to categorize themes from the qualitative data and to draw conclusions. Approximately 64.4% of the CPs were male (mean: 29–33 years old). Overall, CPs had good knowledge of and were familiar with multidrug-resistant organisms and their roles in ABR , although their knowledge was poor in differentiating some antibiotic groups with their respective ABR patterns . Most CPs have a positive attitude towards antibiotics, with most (90.0%) identifying ABR as a critical issue in public health (median = 1 and IQR = 0). Overall, CPs’ practices towards antibiotics were somewhat acceptable, where they leaned towards educating patients about the rational use of antibiotics . The two main themes discovered (antibiotics and counseling of patients) were related to self-medication, while educational intervention is the main subtheme. ABR is multifactorial, with subthemes related to budget, time constraints, incompetent staff, the absence of CPs, the lack of training, and the enforcement of laws and regulations being the needs of the hour in Pakistan. Effective antibiotic stewardship programs, patient education, and awareness campaigns about antibiotics and ABR along with training of the CPs are important factors that have to be addressed in a timely manner. Antibiotic resistance (ABR) is an emerging global threat to public health. Substantial evidence has indicated that community pharmacists (CPs) can play a critical role in managing the ever-increasing threat of antibiotic resistance. This study aimed to determine the knowledge, attitude, and practices of CPs ( Globally, community pharmacies are integral to healthcare systems and play vital roles in medication-provision services ,2. In thTherapy effectiveness solely depends on accurate dispensing of medicines, and qualified community pharmacists’ professional competency is vital.Dispensing antibiotics without prescriptions compounded by the unavailability of CPs is a major issue in low- and middle-income countries (LMICs) . The knoIt was reported globally in 2019 that at least 700,000 people die each year due to drug-resistant diseases . In the A survey in Malaysia reported that approximately 90% of CPs often communicate with clinicians or prescribers whenever there is any uncertainty in the appropriateness of antibiotic prescriptions and nearly 70% of CPs often educate patients with regards to the rational use of antibiotics . MeanwhiA two-phase mixed-methods study design was used, which consisted of (1) an online questionnaire (quantitative) cross-sectional study and (2) a detailed telephone semi-structured interview . The CPs worked full or part-time and had a connection with the services at the community pharmacies included in the survey. The present study has two parts: A quantitative phase 1 followed by a qualitative study (phase 2). Ethical approval was obtained from Xi’an Jiaotong University, Health Science Center Biomedical Ethics Committee (reference number: 2019–1256), which complies with the Declaration of Helsinki.The online platforms were used between August 2019 and March 2020. Per the 2017 census, Pakistan has a total population of approximately 208 million, with a 2.4% population growth . There aAn extensive literature review was conducted, while different scientific search engines were explored for relevant articles for the questionnaire design. A questionnaire was developed and adopted from a previous study . After tFinally, a 27-item questionnaire with four sections for the final survey  was deveA 5-point Likert scale  was used. The first question focused on the fact that “ABR/AMR is an important public health issue and resistance is mainly developed due to the misuse of antibiotics”. The last section of the questionnaire was about the practices of CPs regarding antibiotic dispensing, counseling, and educating patients on antibiotic resistance. A similar Likert scale was also used in section four from “strongly agree” to “strongly disagree”. The above instrument’s reliability was confirmed by using Cronbach α, where a value of more than 7 was considered an acceptable range indicating a good fit for internal consistency. Additionally, the scores for knowledge of the participants were considered by assigning one point to each correct item, either “yes” or “no”.An online Google form of the questionnaire was developed with several sections, where the objectives of the study were mentioned on the first page. Monographs of antibiotics that should be used with care were mentioned on every page. Depending on the participants’ preference and convenience, different social media platforms including “WhatsApp” and “Facebook messenger” were used to administer the survey. Subsequently, the full and functional questionnaire was sent to the CPs across the country. To increase participation, the participants were allowed to answer all of the questions by just clicking their answers on a given link. https://docs.google.com/forms/), which was subsequently transformed into a data analysis software. Those who completed the first part of the study were invited for the second part via telephonic interviews or by using choice applications convenient to the participant. The snowball and convenient sampling methods were used for data collection. The participants were requested to share the questionnaire with their CP colleagues in the locality. Pharmacists within the age group of 24–28 years or more, working as a CP , and living in Pakistan were included in this study. All data were collected in the form of responses through the Google form , where different statistical techniques were employed based on the data type. For the frequencies and percentages, descriptive statistics were used and were presented in tables. The median difference in the knowledge, attitude, and practices scores were determined through the Kruskal–Wallis and Mann–Whitney statistical tests and presented in table with median and IQR  A For the qualitative part, an interview guide was developed based on qualitative and explorative study designs  to gaugeThe participants were invited for qualitative interviews through WhatsApp voice calls following their informed consent. In-depth online interviews were conducted with the CPs to determine their overall perceptions about the rational use of antibiotics and antibiotic resistance. Participants were allowed to answer in English or Urdu  per their preference. Each interview lasted for about 20–40 min. A voice recorder was used with consent for the recording, which was stored for further analysis.General inductive thematic analysis was performed on the data and was concluded with developing themes ,43. All A total of 180 participants completed the survey, with males being the majority (64.4%). Most (64.4%) participants were aged 29 to 33 years, held at least a bachelor’s degree in pharmacy (77.2%), and were from Punjab (29.4%). Nearly one-half of the participants (46.1%) had 1 to 2 years of experience in community pharmacy practices .Generally, the participants had good knowledge of certain aspects of antibiotic use including of multidrug-resistant organisms that are responsible for ABR . The participants were also able to identify that the ABR rate is higher in hospital settings in Pakistan . Similarly, a vast majority of the participants were aware of penicillin cross-sensitivity . However, knowledge in differentiating some groups of ABR patterns may be slightly deficient  .Generally, the attitude of most participants was positive towards antibiotics. About 90.0% of participants identified ABR as a critical issue of public health (median = 1 and IQR = 0). A large number of participants either “agreed” (37.8%) or “strongly agreed” (30.0%) with the statement that the discovery of newer antibiotics will solve the issue of ABR (median = 2 and IQR = 2). Moreover, the participants believed that counseling should be provided to the patients during dispensing of antibiotics to improve their compliance with drug therapy . A large number of participants considered that dispensing antibiotics without a prescription is a severe issue . Most participants agreed with the statement that “Antibiotics are sometimes prescribed without medical prescription because patient neither have the time nor the money to see a physician”  . Overall, antibiotic practices among the CPs were reasonable. For example, more than half of the participants indicated that they educated their patients on the rational use of antibiotics . Approximately 47.2% indicated that they partook in campaigns focused on optimal antibiotic use (median = 2 and IQR = 1). Likewise, 48.3% informed that they indulged in practices that prevent infection transmission within the community (median = 2 and IQR = 1). A large number of participants agreed that they work in collaboration with other healthcare professionals to limit infection and to improve ASP activities . Approximately 41.1% of participants agreed with the statement “sometimes screen the antibiotics following local guidelines before dispensing” (median = 1 and IQR = 1.75). However, only 18.9% of participants agreed that they dispense antibiotics without a prescription (median = 4 and IQR = 1) . There was a significant association between gender and experience with knowledge on antibiotics . Knowledn = 14) compared with females. The mean age was between 26 and 40 years, with five CPs having master’s degrees in pharmacy. An analysis of the data produced six themes, 10 subthemes, and 25 categories “Skin infections are very common in the locality.”(CP: 19)How to reduce self-medication with antibiotics and CPs, the physician’s role, and how to improve the appropriate use of antibiotics: consumers do not know what antibiotics are, and when and how to use them appropriately.“The majority of patients use antibiotics without pharmacist consultation; even when they were counseled, they sometimes do turn up for a refill of antibiotic prescription.”(CP: 2)“Most consumers do not know that metronidazole is an antibiotic and always demands its use, although they may not need it. Among pediatrics, the most commonly prescribed antibiotics are amoxicillin with clavulanic acid, cefixime and azithromycin for which physicians are sometimes called for consultation.”(CP: 3)Most respondents believed that pharmacists and physician linkages for consultation on prescribed antibiotics are important in curbing the issue of antibiotic resistance. “Unfortunately, throughout the country, CPs have no such easy access to physicians as per job experience at a community pharmacy.”(CP: 10)CP services that can be offered to enhance the rational use of antibiotics:“We (pharmacy staff) are always trying to do counseling on when, how, antibiotics are to be used and their adverse events.”(CP: 5)“Patients must understand both viral and bacterial diseases; I always discourage antibiotic prescriptions for flu and the common cold.” (CP: 8)All CPs are urged to spend more time on patient counseling and education.“If a patient receives an antibiotic without pharmacist’s consultation, there pose a risk for medication error. A patient has merely utilized three doses and left the rest of the antibiotics prescribed without taking them.”(CP: 15)“Educate your patient, this is the least CPs can do in a short time.”(CP: 4)Awareness campaigns on antibiotic resistance in order to enhance public knowledge on using antibiotics with care: “Awareness is the key to curbing antibiotic resistance in Pakistan where the majority of the population are unaware on antibiotic resistance.” (CP: 18)“Booklets and pamphlet which comprised of graphics to indicate antibiotics misuse and their consequences should be distributed along with antibiotic prescriptions.”(CP: 9)Short- or long-term training for CPs to assure the AMS at the community level and to provide an update on the current situation of ABR: “Training is the most important area for CPs where all hospitals/community pharmacies across the country should have at least a training session once a month.” (CP: 5).“Hands-on training, seminars and other activities will have a positive impact on curbing the ABR issue where every CP should have current knowledge on ABR.”(CP: 6)Budget and time constraints, incompetent staff, the absence of CPs, and a lack of law enforcement or regulations: “Nonprescription antibiotics are a multifactorial issue especially in the rural areas where qualified CPs are hardly available.”(CP: 7)“The absence of CPs at pharmacies/medical stores are the actual delinquent in our society where a strict check and balance system should be implemented.”(CP: 9)“Most pharmacies have incompetent staff who dispensed antibiotics without prescription.”(CP: 13)Unavailability of the prescriber/physician at call and consultation time: “Pharmacists tend to wish for physician’s contact and conduct interventions especially for duplicate antibiotics including prescriptions although CPs tend to face the issue of unavailability of the physician on call.”(CP: 16).“Pakistani laws do not allow a pharmacist to prescribe or make changes without consultation with their prescriber; however, when recommended doses have been exceeded, CPs change the dose frequency accordingly.”(CPs: 19)How to engage healthcare professionals to combat ABR: “Community pharmacies are the first gate for the provision of medication; healthcare providers should engage pharmacies to ensure prescription accuracy.”(CP: 5).“Scientific seminars can highlight ABR issues affected around the world; they are platforms for interaction with healthcare providers in which collective efforts can help reduce ABR.”(CP: 15)Suggestions related to the physician, government, and CP for improving antibiotic use in the community: “The main barrier is the communication gap between pharmacists and physicians. The gap should be reduced for effective and collaborative work.”(CP: 5)“Pharmacists must be present at the pharmacy during their duties; the presence of CPs increases the importance of a pharmacist in the community.”(CP:18)In most developing countries such as Pakistan, the sale of antimicrobials in community medicine drug outlets are unregulated, without the contribution of a licensed pharmacist, and dispensed antibiotics are often without a valid medical prescription . To the In the present study, the majority of CPs understand antibiotics and antibiotic resistance. However, their knowledge of the mechanism of resistance in a different group of antibiotics remains lacking, as previously reported ,47,48,49In our study, the attitudes of most CPs tended to be positive towards antibiotics and ABR. It is encouraging to see that most CPs tend to dispense antibiotics only on prescription, also previously reported ,54,55. ACounseling should be provided to patients during dispensing of antibiotics to improve their adherence, as also recommended in other studies ,58. AntiGood practices have a long-lasting effect, and in our finding, in-practice CPs have reasonable knowledge towards antibiotics and ABR, with approximately 47.2% of the participants focused on optimal antibiotic dispensing, as also previously reported ,63. MalpAlarmingly, our study indicated that the majority of CPs hardly collaborated with other healthcare professionals in ABR and ASPs. Similarly, Hayat et al. and Khan reported the same ,67, indiThe present study indicated that the majority of the CPs agreed that suitable training, workshops, and other relevant events on ABR are recommended. Training for CPs can help encourage the appropriate dispensing and use of antibiotics, thus helping to curb ABR . There aABR is not only an issue in LMICs but also in developed countries, making it a global issue . AlthougStrict implementation of regulations is the need of the hour, especially in Pakistan, where many pharmacies still run without a qualified pharmacist . All theNevertheless, our study is not without limitations. First, both full- and part-time were recruited since there is a lack of full-time CPs in Pakistan. Secondly, the two-phase study poses the possibility of a recall bias. Third, a convenience sampling technique was used. Future studies should address these issues to have a better representation of the research question. Overall, CPs in Pakistan had good knowledge and a positive attitude but poor to moderate practices towards antibiotics and ABR. Nevertheless, there is an urgent need for training, awareness campaigns, patient education, and educational interventions at the community level with ASPs strictly practiced. The government should implement the laws and ensure that only qualified pharmacists are allowed to practice to stem the issue with ABR.


The cryopreservation and long-term storage of semen is one of the methods for accelerated improvement of the genetic qualities of animals. However, horse breeders prefer to use fresh or chilled semen, as the fertilizing capacity of frozen equine semen is much lower. It is important to find extenders, or a combination of extenders, that will improve semen survival after freezing. It is also important that the extender can be easily and simply prepared for use. Steridyl is a concentrate to which you just need to add sterilized water. This extender was developed for ruminants. In this study we tested Steridyl for freezing stallion semen. The motility, morphology, energy metabolism, DNA damage, and fertility of sperm frozen in Steridyl were evaluated. As a result, Steridyl was shown to be a good extender for equine semen freezing.® (Minitube) for freezing sperm of stallions. Steridyl is a concentrated extender medium for freezing ruminant semen. It already contains sterilized egg yolk. Semen was collected from nine stallions, aged from 7 to 12 years old. The total and progressive motility of sperm frozen in Steridyl was significantly higher than in semen frozen in LCCY. The number of spermatozoa with normal morphology in samples frozen in LCCY was 60.4 ± 1.72%, and with Steridyl, 72.4 ± 2.10% (p < 0.01). Semen frozen in Steridyl showed good stimulation of respiration by 2.4-DNP, which indicates that oxidative phosphorylation was retained after freezing–thawing. No differences among the extenders were seen with the DNA integrity of spermatozoa. Six out of ten (60%) mares were pregnant after artificial insemination (AI) by LCCY frozen semen, and 9/12 (75%) by Steridyl frozen semen. No differences among extenders were seen in pregnancy rate. In conclusion, Steridyl was proven to be a good diluent for freezing stallion semen, even though it was developed for ruminants.The fertilizing ability of stallion sperm after freezing is lower than in other species. The search for the optimal extender, combination of extenders, and the freezing protocol is relevant. The aim of this study was to compare lactose-chelate-citrate-yolk (LCCY) extender, usually used in Russia, and Steridyl Artificial insemination is one of the main methods of genetically improving the horse population, due to the accelerated use of the best stallions. Frozen semen has a number of advantages over fresh or chilled semen. Frozen semen preserves the horse’s genetics for a long time, even after death, allowing the material to be transported over long distances, around the world. In modern assisted reproductive technology programs such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), cryopreserved sperm are mainly used. Artificial insemination of horses is widespread. However, breeders prefer to use fresh or chilled semen ,2. The fThe search for the optimal extender, combination of extenders, and the freezing protocol is relevant. Semen extenders affect semen quality, especially after freezing ,9. Exten®  is concentrated extender medium for freezing of bull semen, and semen of other ruminants. Steridyl is a Tris based extender. The major benefit of Steridyl is that it already contains sterilized egg yolk in the concentrate. This eliminates the time-consuming preparation of fresh egg yolk. In this study we tried to freeze equine semen, diluted with Steridyl. We chose lactose-chelate-citrate-yolk (LCCY) extender for control, as it is used in Russia in most cases, and is recommended by the requirements of the Russian Federation.SteridylThe aim of the study was to compare LCCY extender, usually used in Russia, and Steridyl for freezing sperm in stallions.The principles of laboratory animal care were followed, and all procedures were conducted according to the ethical guidelines of the L.K. Ernst Federal Science Center for Animal Husbandry and the Law of the Russia Federation on Veterinary Medicine No. 4979-1 (14 May 1993).Nine stallions aged from 7 to 12 years old were used for this study. Semen was routinely collected 1–2 times a week during breeding season (March–June 2019).The chemicals used for the preparation of lactose-chelate-citrate-yolk (LCCY) extender and centrifugation solution were ordered from Sigma-Aldrich . Egg yolk was collected from chickens of the bioresource collection “Genetic Collection of Rare and Endangered Chicken Breeds” . Steridyl contains Tris, citric acid, sugar, buffers, glycerol, purified water, irradiated sterile egg yolk, and antibiotics . The chemicals proportion is the company’s trade secret. Lactose-chelate-citrate-yolk (LCCY) extender consisted of 321 mM lactose, 3 mM ethylenediaminetetraacetic acid dinatrium salt (Trilon B), 3 mM sodium citrate, 0.95 mM sodium bicarbonate, 20% freshly prepared egg yolk, and 0.4 mg/mL gentamicin. Steridyl was prepared through a 1:1.5 dilution with sterilized water. The centrifugation solution consisted of 204 mM lactose, 25 mM glucose, 3 mM ethylenediaminetetraacetic acid dinatrium salt (Trilon B), 0.4 mM magnesium sulfate, 21 mM sodium chloride, and 14 mM potassium citrate.The semen was collected with a Hannover artificial vagina . A total of 39 ejaculates  were collected. Immediately after collection, the semen was divided into two equal parts. One part (P1) was diluted by lactose-chelate-citrate-yolk (LCCY) extender, and a second part (P2) was diluted by centrifugation extender. Dilution ratio was 1:1. Sperm concentration, total (TM) and progressive motility (PM) was evaluated by a computer-assisted sperm analysis (CASA) in a Mackler chamber at 37 °C. The Argus CASA system  and a Motic BA 410 microscope  were used. Ejaculates with volume less than 30mL, concentration less than 100 × 106 sperm/mL, and total motility less than 60% were excluded from the study. A total of 8 ejaculates were excluded from the study. A total of 31 ejaculates were chosen for cryopreservation. ® medium . Final concentration was 200 × 106 cells/mL. Semen was loaded into 0.5 mL straws and equilibrated at +5 °C for 120 min. The straws were frozen in liquid nitrogen vapor at −110 °C for 12 min, and stored in a liquid nitrogen tank. The diluted samples were centrifuged for 8 min at 600 g, the supernatant was eliminated and the P1 was resuspended in LCCY medium containing 3.5% glycerol, and the P2 was resuspended in SteridylAfter at least 24 h, semen was thawed at 37 °C for 30 s, and the contents of the straw were emptied into a 1.5 mL microcentrifuge tube. Semen was evaluated for total and progressive motility as previously described.Morphology was assessed using Diff-Quick kit  stained smears and CASA (ArgusSoft–module Morphology). The morphology of at least 250 spermatozoa was examined on each slide at 1000× magnification with immersion oil. We used a sperm chromatin dispersion (SCD) test  to assayOxidative phosphorylation (OXPHOS) was assessed by the reaction of cellular respiration rate (CR) on adding 2,4-dinitrophenol (2.4-DNP) to the semen sample . The addTen mares were inseminated with LCCY frozen sperm and twelve mares were inseminated with Steridyl frozen sperm. The mares were in good health. Artificial insemination was carried out in accordance with the breeding program. Doses frozen in Steridyl or in LCCY from the selected stallions were used randomly. AIs were performed by transcervical injection of the dose of thawed sperm, with preliminary control of follicle development 0–6 h after ovulation. The dose of frozen sperm was 250 million spermatozoa with PM. Pregnancy was determined by ultrasound examination on the 14th day after ovulation. The number of pregnant mares was counted in each AI cycle.t-test. We compared pregnancy results by z-test for two proportions. Differences were considered statistically significant at p < 0.05.For statistical analysis, the computer software IBM-SPSS Statistics 19  and Statistica 10  were used. All data were normally distributed (Kolmogorov–Smirnov test). Data were analyzed by ANOVA. The data were expressed as means ± standard error of the mean. All pairwise multiple comparisons between means were conducted by Semen used in this study was in the acceptable range for sperm motility and morphology after dilution. Total motility, progressive motility, and spermatozoa of normal morphology of semen diluted in Steridyl or LCCY extenders are shown in p < 0.05). Six stallions classified as ‘good freezers’ had 41.2 ± 1.13% progressive motility in samples frozen with Steridyl, and 37.2 ± 1.02% progressive motility in samples frozen with LCCY. Three stallions classified as “poor freezers” had 29.7 ± 2.93% progressive motility in samples frozen with Steridyl, and 18.0 ± 0.73% progressive motility in samples frozen with LCCY. The number of spermatozoa with normal morphology in samples frozen in LCCY was lower than with Steridyl (p < 0.01). No differences among extenders were seen with the DNA integrity of spermatozoa.Characteristics of semen quality frozen in Steridyl or LCCY extenders are shown in Pregnancy rates (pregnancy confirmation) at day 14 are shown in p = 0.0005).The increase of cellular respiration rate after the addition of 2.4-DNP was 1.92 ± 0.04 times in LCCY frozen sperm, and 2.21 ± 0.07 times in Steridyl frozen sperm . OxidatiThere are many factors that affect the quality of frozen semen in stallions. These are freezing protocols, extender formulation, and type of cryoprotectant. The composition of extender is one of the main factors in determining the viability of frozen semen . AlthougEgg yolk is a common component of most semen extenders for domestic animals. It has been shown to have a positive effect on sperm, and to protect acrosomes and the plasma membranes against cold shock . When usThe results of our study showed that total and progressive motility of frozen semen, on average, met the requirements for sperm use for AI ,24. It iUsually, the assessment of motility is the first and main parameter by which to judge the survival of sperm after freezing . Howeverp < 0.05) [The intensity of energy metabolism is a very important criterion to assess sperm quality ,30. Oxid < 0.05) . In our Many authors have suggested that DNA fragmentation affects fertility ,36,37,38Fertility is the main indicator of sperm quality. Fertility is influenced by many factors, one of which is the extender ,6,18,26.This study showed a high tolerance of equine semen for cryopreservation in Steridyl. The quality of the semen frozen in Steridyl was superior to the quality of the semen frozen in the LCCY in almost all studied parameters. Perhaps this is due to the quality of the yolk, or perhaps Steridyl has a better effect on the sperm ability to survive during freezing procedure. At the same time, individual variability in sperm quality after freezing was observed in different stallions. Steridyl is Tris-based extender. Tris-based extenders have been successfully used to freeze the semen of other animals ,26. HoweSteridyl has proven to be a good diluent for freezing stallion semen, although it was developed for ruminants. Steridyl can be recommended for semen freezing of both “good freezer” and “poor freezer” stallions.


A 51‐year‐old woman was admitted to our hospital for cough, fever, purpura in the legs, and salivary gland swelling. Six years ago, she had been diagnosed with bronchial asthma and was treated with a combination of inhaled corticosteroid and long‐acting beta2‐agonist. Blood examination showed increased eosinophils at 3027 cells/μL and elevated levels of immunoglobulin (Ig) G4 at 261 mg/dL and C‐reactive protein at 2.76 mg/dL. Chest radiograph and computed tomography (CT) showed infiltrates in the bilateral lower lobes. Neck CT showed bilateral salivary gland swelling. Pathological examinations of the lungs and skin purpura showed granuloma with eosinophilic infiltration and perivascular dermatitis, respectively. She was diagnosed with eosinophilic granulomatous polyangiitis (EGPA) and treated with corticosteroids, which resolved the eosinophilia, salivary gland swelling, elevated IgG4 titre, and lung infiltration. As our patient did not meet the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) 2019 criteria of IgG4‐related disease, the diagnostic was EGPA with IgG4 hypergammaglobulinaemia and salivary gland swelling. We present a case of a 51‐year‐old Japanese woman diagnosed with eosinophilic granulomatous polyangiitis (EGPA), a rare vasculitis that can occur in patients with eosinophilia and history of asthma, allergic rhinitis, and sinusitis, with immunoglobulin (Ig) G4 hypergammaglobulinaemia and salivary gland swelling. Eosinophilic granulomatous polyangiitis (EGPA) is a rare vasculitis that can occur in patients with eosinophilia and history of asthma, allergic rhinitis, and sinusitis. Immunoglobulin (Ig) G4‐related disease is a systemic immune‐mediated fibroinflammatory condition that involves multiple organs and is characterized by markedly increased serum IgG4 level, lymphoplasmacytic infiltration with abundant IgG4‐positive plasma cell, storiform fibrosis, and obliterative phlebitis. The diagnostic for the present case was EGPA with IgG4 hypergammaglobulinaemia and salivary gland swelling.A 51‐year‐old Japanese woman was admitted to our hospital because of cough and fever for one month. She had been diagnosed with bronchial asthma and was treated with a combination of inhaled corticosteroid and long‐acting beta2‐agonist. Her asthma had been partly controlled. Although she had had unplanned visits for asthma exacerbation once or twice a year, she had no prior requirements for systemic corticosteroids. She was a never smoker and had no dust exposure. On admission, her body temperature was 38.1°C, and wheezes were heard in the bilateral lung fields. There were bilateral salivary gland swelling, leg purpura that measured 2–5 mm in diameter, and swelling of the left ankle joint. The other physical examination findings, including consciousness, heart sound, and abdomen, were normal. She had no reduction in the production of saliva or lacrimal fluid.2) of 37.1 mmHg, partial pressure of oxygen (PaO2) of 68.5 mmHg, and bicarbonate (HCO3−) of 24.2 mEq/L. Chest radiograph showed infiltrations in the bilateral lower lung fields , proteinase‐3 (PR3)‐ANCA, anti‐SSA/Ro antibody, and anti‐SSB/La antibody, were within the normal range. Arterial blood gas at room air examination showed pH of 7.42, partial pressure of carbon dioxide . Thereafter, there were resolution of fever, wheezes, and lung infiltrations on chest radiography and improvement of the IgG4 titre and salivary gland swelling. Concurrently, she was treated with intravenous cyclophosphamide every three weeks for three months. Thereafter, prednisolone was gradually reduced over a period of six months and had been maintained at 10 mg/day for three years. She had been relapse‐free at the time of this writing.EGPA is a vasculitis that can occur in patients with eosinophilia and history of asthma, allergic rhinitis, and sinusitis. The histological features of EGPA include eosinophil‐rich infiltrates, eosinophilic granulomas, and vasculitis of small‐ to medium‐sized vessels. Based on the predisposition of patients with allergic diseases, the pathophysiological conditions of EGPA have been related to T‐helper type 2 (Th2)‐induced inflammation. Moreover, in patients with EGPA, the levels of Th2 cytokines, interleukin‐4 (IL‐4), IL‐5, and IL‐13 are elevated and approximately 90% have elevated serum IgE levels. On the other hand, IgG4‐related diseases, including sclerosing pancreatitis, retroperitoneal fibrosis, and chronic sialadenitis, have been characterized by IgG4‐positive plasma cell infiltration and high serum IgG4 levels Several cases of overlapping IgG4‐related disease and EGPA have been reported. Ayuzawa et al. reported a similar case of EGPA complicated with IgG4‐related kidney disease and who had salivary gland swelling and high serum IgG4 level at the time of EGPA diagnosis In addition, a previous study that investigated the serum levels of IgG, IgM, IgA, IgE, and IgG subclasses in patients with active EGPA, quiescent EGPA, granulomatous with polyangiitis, atopic asthma, and healthy controls reported that the serum IgG4 levels were elevated in active EGPA and correlated with the number of organ manifestations and disease activity In conclusion, because EGPA could be complicated with reactive IgG4 hypergammaglobulinaemia and salivary gland swelling, measurements of serum IgG4 level and assessment of salivary glands should be performed in patients with EGPA.Appropriate written informed consent was obtained for publication of this case report and its accompanying images.


The performance of vacuum insulation panels (VIPs) is strongly affected by several factors, such as panel thickness, design, quality of vacuum, and material type. In particular, the core materials inside VIPs significantly influence their overall performance. Despite their superior insulation performance, VIPs are limited in their widespread use as structural materials, because of their low material strength and the relatively expensive core materials. As an alternative core material that can compensate these limitations, foamed concrete, a type of lightweight concrete with very low density, can be used. In this study, two different types of foamed concrete were used as VIP core materials, with their effects on the thermal behavior of the VIPs having been evaluated using experimental and numerical methods. To confirm and generate numerical models for VIP analysis, micro-computed tomography (micro-CT) was utilized. The obtained results show that insulation effects increase effectively when panels with lightweight concrete are in a vacuum, and both foamed concrete types can be effectively used as VIP core materials. A vacuum Insulation Panel (VIP) is a system for thermal insulation which consists of an enclosed rigid core and a surrounding membrane. In general, the thermal conductivity of VIPs is about 5 to 10 times lower than other insulation materials or systems . There hVIPs are generally composed of two parts: a membrane and a core material. More specifically, VIPs are generally flat and consist of an enclosure or membrane, which are often metalized or laminates made of welded metal and plastic foils, and a core material. The core materials need to be open-porous for effective evacuation, and they need to be capable of withstanding the external load caused by atmospheric pressure and a gas tight envelope, to maintain the required vacuum quality in the production process ,10. In aConcrete and cement-based materials are the most widely used materials in the construction industry, due to advantages, such as low cost, high strength, water resistance, convenient production, as well as multiple applications ,13. Compconcrete ,16. In aLightweight concrete has itself been widely utilized for insulation purposes ,18. In gary VIPs ,27.The main purpose of this research was to evaluate the effect of lightweight foamed concrete as a core material on the performance of VIPs. For this purpose, foamed concrete was produced and utilized as the core material for the target VIP. The most important requirements of the core are a porous structure for evacuation, as well as insulation related properties, with the material also needing to have the appropriate strength and stability to withstand the pressure in the vacuum process. Thus, in addition to the pure foamed concrete, another foamed concrete specimen incorporating lightweight aggregate for better strength was also designed and used. VIP specimens with lightweight concrete cores were then manufactured using a membrane and the same procedures as commercial VIP specimens. To confirm the insulation performance of the vacuumed lightweight concrete, the thermal conductivity of the lightweight concrete specimens before and after evacuation was experimentally and numerically measured and compared using standardized measurement devices and finite element analysis, respectively. To visualize and generate the numerical model, micro-computed tomography (micro-CT), a nondestructive method, was used, with the microstructures of the used core materials being subsequently examined ,29,30. FThis study focuses on the effects of lightweight concrete on the insulation performance of VIPs, and the appropriate selection of material for the core part of the VIP is important. The core material needs to be porous and have sufficient strength to withstand pressure for effective evacuation. Among several types of lightweight concretes, foamed concrete, which contains numerous pores, was selected. In addition to the pure foamed concrete, another type of foamed concrete containing lightweight aggregates was also prepared and used as a core material. Despite its versatility in insulation, pure foamed concrete with very low density has a relatively low strength and stability in comparison to other types of lightweight concretes including lightweight aggregate concrete. Since conventional lightweight aggregate concrete contains less pores than foamed concrete, it is not an appropriate VIP core material. Alternatively, foamed concrete incorporating lightweight aggregates can be used as the core material, reducing shrinkage and enhancing material strength.Two different types of lightweight foamed concrete were used in this study: pure foamed concrete and foamed concrete with lightweight aggregates (LWAs). The former specimen was a type of pure foamed concrete, while the latter contained lightweight aggregates . Hard coal fly ash type C  conforming EN 450-1 was used as a cement replacement (FA); cement was replaced with 30 wt.% of FA. To produce the FCA specimen with lightweight aggregates, fine expanded glass  was employed. In the manufacturing process and according to the provider, the foam should be produced continuously to guarantee stable foam bubbles. The applied water and air pressures were adopted at 3 and 2 bars, respectively, with the dosage of foaming agent of 2% to achieve a uniform and steady foam. The density of the foam was measured using 30 L bucket and it ranged between 33–35 g/L. To manufacture foamed concrete, cement slurry was produced then it is mixed with the preformed foam. The absence of coarse aggregates increases the possibility of clumps and agglomeration of fine materials when mixing with water. Therefore, a high-intensity mixer  was used to mix the cement paste to ensure homogeneous distribution of particles and avoid agglomeration and clumps of fine materials. After manufacturing the paste, the required foam volume was produced and both were mixed using a concrete mixer  with 50 L capacity to produce foamed concrete. Fresh properties of concrete were measured; consistency using the flow table was determined by measuring the diameter of the concrete without jolting the table. The density of fresh concrete was measured according to EN 12350-6 using a 5 L bowel but without compaction. Foam bubbles are very light and very sensitive to temperature changes and any movements. Therefore, no compaction or vibration has been applied when filling the 10 × 10 × 10 cmSeveral methods can be used to evacuate and produce VIP samples, ,32,33,34The most important function of VIPs is to enhance the thermal insulation of buildings or structures, with the thermal properties of target materials, such as thermal conductivity, being potential parameters for evaluating VIP performance. In this study, the thermal conductivity of the VIP specimens before and after evacuation was investigated experimentally and numerically. Two standardized experimental methods were used for accurate measurement, while numerical simulation was performed using micro-CT images. The microstructural characteristics of the core materials were also evaluated with the micro-CT data.For thermal conductivity measurements to compare insulation performance before and after evacuation, two methods were used to enhance accuracy and to confirm the influence of evacuation on the thermal characteristics of lightweight concrete: the Hot Disk device that satisfies ISO 22007-2 and the hot plate method, according to EN 12667. Both devices satisfy the necessary standards and have been widely used to measure the thermal properties of various objects, including construction materials ,36,37,38The other method, the hot plate method in The lightweight concrete specimens used in this study are highly porous materials, with their pore characteristics strongly affecting their material properties. In particular, the pore structures of VIP core materials are some of the most critical factors in determining VIP performance, and an appropriate analysis is needed. For this purpose, X-ray micro-CT was used here. Micro-CT is a non-destructive method which can be used to visualize the internal microstructure of a target material; both 2D and 3D geometric characteristics can be examined using micro-CT images ,29,30. Tmamatsu®  (Shizuokx × y × z) was selected, which can be considered as representative volume of the specimens. The ROIs and the binary images in u method  and manuu method . In the u method ,45. As sT [K] is the temperature, t [s] is the time, k [W/m/K] is the thermal conductivity, C [J/g/K] is the specific heat. In this formulation, heat loss is considered using the heat loss coefficient, The thermal conductivity of the VIP specimens was also computed using numerical simulation; commercial finite element analysis software, ABAQUS, was used for the analysis . In the q) is obtained by averaging the heat flux of each element, with the effective thermal conductivity (k) then expressed from Fourier’s law, as follows:L is the characteristics length of the specimen, and A weak form of the governing equation can be obtained by integrating Equation . EffectiFor the thermal analysis, the input bulk parameters  were obtained experimentally. In particular, the total thermal conductivity of VIPs λtλtλtot) i formula , with λrThe performance of the VIPs with lightweight concrete cores were investigated using the thermal conductivity of the specimens. Both experiments and simulations were conducted to evaluate the thermal conductivity of the specimens, with the effects of the core materials being examined based on their thermal properties.The measured VIP thermal conductivity values are presented in A similar trend can be found in the results of the hot plate method. In For a more detailed analysis of evacuation performance, numerical characterization and simulation were also performed. Thermal simulation was performed using the 3D micro-CT image in The pore structures which strongly affect material properties were investigated using the pore part of each specimen. Based on the used pixel (voxel) resolution, the minimum pore size taken into consideration here was 29.8 pherical ,52. ThusThe numerical analysis for evaluating the thermal conductivity of the specimens was performed using the meshes in A detailed investigation of the numerical analysis can be found in The obtained results confirm that both pure foamed and foamed concrete incorporating lightweight aggregates show a clear difference before and after evacuation. Moreover, it is clear that lightweight concrete of low density, with/without lightweight aggregates, can be effectively used as a VIP core material since it contains numerous pores and has sufficient strength. In addition, the pore structures within the core materials strongly affect the efficiency of evacuation, with a material with large porosity as well as pore size able to be beneficial for achieving better vacuum effects.This study aimed to investigate the applicability of lightweight foamed concrete with a low density  and evacuation effects needs to be performed. Moreover, parametric studies using different lightweight concretes could be conducted to figure out the effectiveness of lightweight concretes as core VIP materials.


Staphylococcus aureus strain was exposed to daptomycin and gentamicin alone or in combination in multiple dosing experiments. The susceptibility of the S. aureus strain to daptomycin and gentamicin in combination was tested at concentration ratios equal to the ratios of 24 h areas under the concentration–time curve (AUC24s) of antibiotics simulated in an in vitro dynamic model in five-day treatments. The MICs of daptomycin and gentamicin decreased in the presence of each other; this led to an increase in the antibiotic AUC24/MIC ratios and the antibacterial effects. Effects of single and combined treatments were plotted against the AUC24/MIC ratios of daptomycin or gentamicin, and a significant sigmoid relationship was obtained. Similarly, when the effects of single and combined treatments were related to the total exposure of both drugs (the sum of AUC24/MIC ratios (∑AUC24/MIC)), a significant sigmoid relationship was obtained. These findings suggest that (1) the effects of antibiotic combinations can be predicted by AUC24/MICs using MICs of each antibacterial determined at pharmacokinetically derived concentration ratios; (2) ∑AUC24/MIC is a reliable predictor of the antibacterial effects of antibiotic combinations.To explore whether susceptibility testing with antibiotic combinations at pharmacokinetically derived concentration ratios is predictive of the antimicrobial effect, a  Staphylococcus aureus infections after prolonged daptomycin exposure [S. aureus [24) to the MIC of daptomycin determined in the presence of rifampin. Susceptibility testing of S. aureus to daptomycin or rifampin in combination was performed at pharmacokinetically derived antibiotic concentration ratios, which were strongly related to the daptomycin-to-rifampicin AUC24 ratios used in subsequent pharmacokinetic simulations. The extensive use of daptomycin in clinical practice has led to decreased daptomycin effectiveness due to the emergence of bacterial resistance ,13,14,15exposure ,7,8 and . aureus ,13,14,15. aureus . Combina. aureus . The enhVerification of this approach with daptomycin in combination with other anti-staphylococcal antibiotics such as gentamicin is of interest. The synergistic interaction between daptomycin  and gentamicin  can be hypothesized based on existing knowledge that daptomycin acts on bacterial cell membrane and increases its envelope permeability to another drug such as gentamicin (uptake effect) . HoweverS. aureus strain was exposed to daptomycin and gentamicin in an in vitro dynamic model that simulates single and combined treatments. As therapeutic daptomycin exposures were characterized by a pronounced effect against staphylococci [To explore whether susceptibility testing with antibiotic combinations at pharmacokinetically derived concentration ratios is predictive of the antimicrobial effect, a clinical ylococci , subtherylococci ,26 or moylococci ,30 anti-24 ratios used in the pharmacodynamic simulations. The MICs of daptomycin and gentamicin alone and in combination are listed in S. aureus susceptibility to daptomycin and gentamicin in the presence of each other were reflected in fractional inhibitory concentration (FIC) analysis (FIC) fell from 1.18 to 0.48, revealing a change in the type of antibiotic interaction from indifferent to synergistic. Subsequent increases in the relative portion of gentamicin in the combination led to systematic increases of ∑FIC index from 0.48 to 0.64 and from 0.64 to 0.70 at concentration ratios 1:2 and 1:5, respectively, reversing to an indifferent interaction. Thus, the lower ∑FIC showing synergy was associated with the proportion of antibiotics in the combination with relatively higher gentamicin concentrations.Daptomycin-to-gentamicin concentration ratios used in MIC determinations corresponded to AUCanalysis . As seenS. aureus 293 exposed to daptomycin and gentamicin alone or in combination in the in vitro dynamic model are shown in 24 30 or 100 mg·h/L were associated with only a slight anti-staphylococcal effect within the first 12 or 24 h from the beginning of the experiment, respectively, followed by regrowth to cell density that exceeded the initial numbers. Gentamicin produced more pronounced anti-staphylococcal effects than daptomycin and within the first 24 h of treatment reduced initial cell numbers to either 4 log CFU/mL (AUC24 65 mg·h/L) or below the limit of detection (AUC24 160 mg·h/L). However, rapid initial killing by gentamicin was followed by fast regrowth and the numbers of surviving organisms at the end of the treatment were equal or close to the initial inocula (8 log CFU/mL at AUC24 65 mg·h/L or 7 log CFU/mL at AUC24 160 mg·h/L). However, all combined treatments with daptomycin and gentamicin were associated with more pronounced antibacterial effects than respective mono-treatments. Comparing the numbers of surviving staphylococci in treatments with the lower dose of gentamicin alone (as the more active single agent) and in combined treatments (regimens G65 versus D30+G65 and D100+G65), independent of the relative amount of daptomycin, the antibiotic combinations produced more pronounced initial bacterial killing (reduction to the limit of detection) and weaker regrowth (24 (G160), the initial killing of S. aureus was the same in mono- and in combined treatments; cell numbers reached the limit of detection during the first 24 h. However, the regrowth phase was delayed in combined treatments and at the end of the experiment cell density reached 5.5 log CFU/mL  versus 7 log CFU/mL with gentamicin alone (G160); bacterial regrowth was fully suppressed with regimen D100+G160 (ratio 1:1.5)  b,d.EDG was significantly higher than EIND and the respective lower limits of 95% CI always were positive. Depending on the combination regimen, ∆E varied from 8 to 22%, with the maximum ∆E value in regimen D100+G160 (1:1.5 AUC24 ratio).To accurately assess the advantages of combined therapy, Bliss independence-based drug interaction analysis was performed using data obtained in the pharmacodynamic experiments . In all S. aureus susceptibility to the antibacterials in the presence of each other  to 500 h  and 1000 h . Similarly, gentamicin AUC24/MICs under the influence of daptomycin increased from 260 h  to 380 h  and 500 h . Similar AUC24/MIC augmentations were obtained with other daptomycin plus gentamicin combinations  observed with the antibiotic combinations can be explained by these greater AUCeatments . As seenptomycin a and genptomycin b used inFIC analyses (∑FICs 0.64–1.18); at only one concentration ratio with slight prevalence of gentamicin (1:1.5) did the antibiotic combination demonstrate enhanced anti-staphylococcal activity considered as synergistic (∑FIC 0.48) (E from 8 to 22%), and statistically significant synergism was confirmed (24 ratio 1:1.5 (regimen D100+G160) compared to other combined treatment regimens. In addition, only at regimen D100+G160 was bacterial regrowth fully prevented. Interestingly, the same antibiotic concentration ratio (1:1.5) was assessed as synergistic by the FIC analysis. In addition, the relatively higher ∑FIC indices for other antibiotic combinations that predicted only indifferent interactions (0.64–1.18) were consistent with the relatively smaller ∆Es determined for respective combined treatments (8–13%) as compared with ∆E at AUC24 ratio 1:1.5 (22%).Daptomycin plus gentamicin combinations were characterized primarily as indifferent by the results of IC 0.48) . More enonfirmed . The enhFIC analyses are consistent with the pharmacodynamic data with respect to daptomycin and gentamicin interactions when the antibiotics were used in combination. It is highly likely that this observation is due to the use of the same antibiotic concentration ratios in both susceptibility testing and AUC24 ratios in the pharmacokinetic simulations. The predictive potential of susceptibility testing determined at pharmacokinetically derived concentration ratios was confirmed in our previous study with daptomycin and rifampin [FIC indices adequately reflected the ability of pharmacodynamic data to predict synergism or additivity.The results of rifampin  where thStaphylococci and Enterococci [Discrepancies between the results of synergy studies reported by other investigators with various antibiotic combinations including daptomycin plus gentamicin have been discussed ,32,33. Terococci , consistS. aureus strains in the presence of gentamicin was described previously in studies with in vitro dynamic models [24s of daptomycin (750–1750 mg·h/L) that were responsible for the pronounced antibacterial effect. As a result, the relative portion of daptomycin combined with gentamicin in terms of the AUC24 ratio was quite prominent: daptomycin-to-gentamicin AUC24 ratios of 15–30:1. Comparative efficacy between regimens with and without gentamicin could not be distinguished over the duration of the experiment, making it difficult to adequately assess the actual synergistic potential of the combination regimens. The relative deficiency of gentamicin in the daptomycin combinations probably played a key role in the failure of the combination to improve daptomycin’s weak efficacy against daptomycin-non-susceptible S. aureus strains [24 ratio  [Enhancement or improvement in daptomycin efficacy against daptomycin-susceptible c models ,25,26,27c models  or 96 h ference) .24s, particularly with the use of subtherapeutic daptomycin exposures. Perhaps a way to improve the efficacy of daptomycin–gentamicin combinations is to use the antibacterials at doses that provide comparable AUC24s, usually representing lower daptomycin AUC24s. However, our results should be considered provisional and need additional confirmation in other experimental models. Of note, the S. aureus strains used in an experimental endocarditis model produced biofilms that could influence the pharmacodynamic interactions of daptomycin and gentamicin; this might have been responsible for the antagonism observed in that study [In the current study, the synergistic potential of daptomycin–gentamicin combinations was observed with the results of both checkerboard and pharmacodynamic experiments at comparable antibiotic concentrations or AUCat study .S. aureus susceptibility to these antibiotics in the presence of each other. This observation was confirmed by relating antibacterial effects of the combinations with respective antibiotic AUC24/MICs calculated by using MICs determined at pharmacokinetically derived concentration ratios  compared to daptomycin  throughout the observation period is another limitation of this study, as we could not see differences between the antibacterial effects of dosing regimens below this threshold. This could be important in determining the true antibacterial potential of the antibiotics . Another limitation is that we did not consider any effect of protein binding (PB), which might influence antibacterial activity of the drugs. Unfortunately, the optimal method for properly correcting simulated profiles for PB is still undefined. Our detailed explanation of why we do not adjust the simulated antibiotic AUC/MICs for PB is described in a previous study with daptomycin [The use of only one staphylococcal strain is a limitation of this study. Additional experiments are needed with more ptomycin .S. aureus 293 was used in the study. Daptomycin powder was purchased from Acros Organics ; gentamicin sulfate was purchased from PhytoTechnology Laboratories . Clinical isolate 24s of daptomycin both in single and combined treatments corresponded to sub-therapeutic dosing regimens and were equal to 30 and 100 mg·h/L . Gentamicin AUC24s in mono and combined treatments corresponded to once daily doses 5 mg/kg and 7 mg/kg. The respective AUC24s, 65 and 160 μg·h/mL, used in pharmacokinetic simulations , were calculated using peak serum gentamicin concentrations reported in human studies , daptomycin AUC24 100 mg·h/L + gentamicin AUC24 65 or 160 mg·h/L (regimens D100+G65 and D100+G160).Simulated AUCctively, ,38) and With all dosing regimens, a series of monoexponential profiles that mimic once-daily dosing of daptomycin with a half-life of 9 h  and gent2+/L (CSMHB), because daptomycin antimicrobial activity is influenced by the presence of Ca2+ [A previously described dynamic model was used in simulations of single drug treatments with daptomycin and gentamicin . Briefly of Ca2+ , and theTo simulate combination treatments, the model was modified according to the Blaser and Zinner principle to provide simultaneous mono-exponential elimination of daptomycin and gentamicin . The modS. aureus 293. After a 2 h incubation, the resulting exponentially growing cultures reached ~108 colony-forming units (CFU)/mL . Then, antibiotics were administered into the central unit of the model. The duration of each experiment was 120 h.The operation procedure used in the pharmacodynamic experiments was as described elsewhere . Each exS. aureus for a final concentration of approximately 5 × 105 CFU/mL. The plates were incubated at 37 °C for 18 h.Susceptibility testing was performed in triplicate using broth microdilution techniques according to Clinical and Laboratory Standards Institute (CLSI) methods . After 224 ratios used in the pharmacokinetic simulations and were as follows: 1.5:1 (regimen D100+G65), 1:1.5 (regimen D100+G160), 1:2 (regimen D30+G65) and 1:5 (D30+G160). The same concentration ratios were maintained in each subsequent dilution.With each antibiotic combination, stock solution concentration ratios of daptomycin to gentamicin corresponded to their AUCFIC for each antibiotic in each combination and ΣFIC were determined as:To determine the type of interaction between daptomycin and gentamicin in combination, the FIC index ≤0.5, indifference was defined as a ΣFIC index >0.5 but ≤4.0, and antagonism was defined as a ΣFIC index >4.0 [Synergism was defined as a Σdex >4.0 .3 CFU/mL .In each experiment, bacteria-containing medium from the central unit of the model was sampled to determine bacterial concentrations throughout the observation period. Samples (100 µL) were serially diluted as appropriate and 100 µL was plated onto Mueller–Hinton agar plates, which were placed in an incubator at 37 °C for 24 h. The lower limit of accurate detection was 2 × 10Based on time–kill data, the area between the control growth curve and each time–kill curve (ABBC)  was dete24/MIC relationships with ABBC observed in single and combined antibiotic treatments (merged data) were fitted by the sigmoid function:Y is ABBC, x is log (AUC24/MIC); Y0 and a are the minimal and maximal values of the ABBC, respectively; x0 is x corresponding to a/2; and b is a parameter reflecting sigmoidicity. Daptomycin or gentamicin AUCAll calculations were performed using SigmaPlot 12 software.EIND is the expected anti-staphylococcal effect of daptomycin–gentamicin combinations calculated using the effects of respective mono-treatments with daptomycin (ED) and gentamicin (EG).The Bliss independence principle was used to analyze the daptomycin–gentamicin interaction, assuming that the drugs do not interact with each other when used in combination ,48,49. BED, EG and antibacterial effects observed in combined treatments with daptomycin plus gentamicin (EDG) were calculated by dividing the respective experimental ABBCs to the ABBC responsive for maximal antibacterial effect (the area between the control growth curve and the line drawn at the lower limit of detection determined from 0 to 120 h) and expressed in %. The difference between the EDG and EIND (∆E) reflects the type of interaction between the daptomycin and gentamicin in each combination and is considered to be as follows: (i) Bliss synergy when ∆E and the lower limit of the 95% confidence interval (CI) >0, (ii) Bliss antagonism when ∆E and the upper limit of the 95% CI <0, (iii) Bliss independence in any other case when the 95% CI of ∆E includes 0.The S. aureus were synergistic according to Bliss independence-based analysis of pharmacodynamic experiments and also by the results of FIC analyses; (2) the enhanced antibacterial effects of the combinations relative to mono-treatments are likely due to the increased susceptibility of S. aureus both to daptomycin and gentamicin in the presence of each other; (3) the antibacterial effects of antibiotic combinations can be predicted by AUC24/MICs calculated with the use of MICs of each antibiotic determined at pharmacokinetically derived concentration ratios; and (4) ∑AUC24/MIC is a reliable predictor of antibacterial efficacy of antibiotic combinations as it considers the summed exposures of both drugs responsible for the total antibacterial effect.This study suggests that (1) combinations of daptomycin with gentamicin against