Search

Timber structures have been a dominant form of construction throughout most of history and continued to serve as a widely used staple of civil infrastructure in the modern era. As a natural material, wood is prone to termite damages, which often cause internal cavities for timber structures. Since internal cavities are invisible and greatly weaken structural load-bearing capacity, an effective method to timber internal cavity detection is of great importance to ensure structural safety. This article proposes an innovative deep neural network (DNN)–based approach for internal cavity detection of timber columns using percussion sound. The influence mechanism of percussion sound with the volume change of internal cavity was studied through theoretical and numerical analysis. A series of percussion tests on timber column specimens with different cavity volumes and environmental variations were conducted to validate the feasibility of the proposed DNN-based approach. Experimental results show high accuracy and generality for cavity severity identification regardless of percussion location, column section shape, and environmental effects, implying great potentials of the proposed approach as a fast tool for determining internal cavity of timber structures in field applications.

Hollow hydroxyapatite microspheres (HHAM), a type of mesoporous nanomaterials with a specific internal cavity and hierarchical architectures, have attracted enormous interest over the past years owing to their remarkable potential for biomedical applications. However, the as-obtained HHAM fail to meet the need of the ever-updating diagnosis, treatment, and theranostics technologies. With the attempt to enhance performances and expand applications of HHAM, scientists have tailored the properties of HHAM by various methods including -doping modification and surface functionalization to give a versatile type of biomaterials, i.e., functionalized hollow hydroxyapatite microspheres (f-HHAM). Actually, significant achievements in the realm of f-HHAM have been obtained and various intractable clinic problems have been resolved. Nevertheless, designing desirable f-HHAM is expected to accelerate the development of the biomedicine field. In this contribution, the state-of-the-art progress f-HHAM is overviewed, which covers from the developments and preparation methods to bioapplications of these biomaterials. In addition, the current trends and key points as well as the future prospects and challenges for the applications of f-HHAM are discussed, aiming at providing a guideline for rational design of more creative f-HHAM according to different therapeutic requirements.

Confined nanospace pyrolysis (CNP) has attracted increasing attention as a general strategy to prepare task-specific hollow structured porous carbons (HSPCs) in the past decade. The unique advantages of the CNP strategy include its outstanding ability in control of the monodispersity, porosity and internal cavity of HSPCs. As a consequence, the obtained HSPCs perform exceptionally well in applications where a high dispersibility and tailored cavity are particularly required, such as drug delivery, energy storage, catalysis and so on. In this review, the fundamentals of the CNP strategy and its advances in structural alternation is first summarized, then typical applications are discussed by exemplifying specific synthesis examples. In addition, this review offers insights into future developments for advanced task-specific hollow structured porous materials prepared by the CNP strategy.

The problem of the evolution of a cavity formed at the initial moment of time in the central part of a spherical cellular aggregate is solved. The earlier-developed model of a biological medium formed by cells displaying mechanical activity and an extracellular fluid is used in studying the influence of different mechanisms of active intercellular interactions (chaotic and directed nonlocal) on the propagation of a front separating the cellular medium and the fluid. Numerical solutions show that in certain cases characterized by the fluid pressure and the density of the initial cell distribution the chaotical activity of the cells alone is sufficient for increasing the radius of the internal cavity. In other cases, the cavity development is impossible without the participation of the nonlocal mechanism of active interactions between the cells and the outer boundary. In the absence of the interaction between the cells and the outer boundary the nonlocal mechanism of active intercellular interactions does not lead to the cavity growth for any its initial dimensions. The formulation and solution of the problem describe more completely the possible scenarios of the morhogenesis at one of the earlier stages of the embryonic development.

The hollow materials have stronger absorption capacity for visible light than other materials due to their special internal cavity structure. In this paper, NiTiO3 hollow nanorods and Co9S8 QDs wer...

Pachyphlodes atropurpurea and P. excavata are described as new species of truffles based on both phylogenetic and morphological analyses. Phylogenetically these two species are clearly distinct from described species of Pachyphlodes. Morphologically, P. atropurpurea is characterized by subglobose, purple black ascomata, and ascospores with acute-tipped spines. P. excavata is characterized by its ascomata with an obvious basal and internal cavity and slender fusiform asci (150–180 × 30–40 μm).

Many interesting target guest molecules have low symmetry, yet most methods for synthesising hosts result in highly symmetrical capsules. Methods of generating lower symmetry pores are thus required to maximise the binding affinity in host–guest complexes. Herein, we use mixtures of tetraaldehyde building blocks with cyclohexanediamine to access low‐symmetry imine cages. Whether a low‐energy cage is isolated can be correctly predicted from the thermodynamic preference observed in computational models. The stability of the observed structures depends on the geometrical match of the aldehyde building blocks. One bent aldehyde stands out as unable to assemble into high‐symmetry cages‐and the same aldehyde generates low‐symmetry socially self‐sorted cages when combined with a linear aldehyde. We exploit this finding to synthesise a family of low‐symmetry cages containing heteroatoms, illustrating that pores of varying geometries and surface chemistries may be reliably accessed through computational prediction and self‐sorting., A sea of expanding shapes: A combined experimental–computational approach enabled the synthesis of low‐symmetry imine cages from mixtures of tetraaldehyde building blocks. This “social self‐sorting” approach was applied to obtain a family of new cages containing heteroatoms, showing that pores of varying geometries and surface chemistries may be reliably accessed.

Frequency characteristics of a subnanosecond plasma switch based on a combination of an open discharge or a discharge in a hollow cathode and a capillary discharge removed from the internal cavity of the plasma cathode are presented. It is shown that in the presence of an external screen that provides a capacitive discharge and hence, exclusion of the period of weak electron multiplication in the capillary from the delay mechanism of the discharge development, a high pulse repetition frequency is reached for different designs of the plasma cathode and the capillary section. It is demonstrated that at the voltage U = 30 kV, the pulse repetition frequency f = 100 kHz is reached for the capillary with round cross section at pHe ≤ 2.6 Torr and for the capillary with rectangular cross section at pHe ≤ 3.05 Torr.

The potential energy surface (PES) along minimum energy paths of elementary hydrogenation reactions Mg18 + H2 → Mg18H2 and Mg17Ni + H2 → Mg17NiH2 + H2 → Mg17NiH4 + H2 → Mg17NiH6 has been calculated by the density functional theory method. Local PES minima in the vicinity of low-lying isomers, intermediates, and transition states have been determined, and their energies, geometries, and spectroscopic parameters have been calculated. The effect of the Ni dopant on the energies and activation barriers of these reactions has been examined, depending on the position of the dopant on the surface and inside the internal cavity of the Mg17 cage.

We report a carbonaceous nanomotor with a characteristic flask-like hollow structure that can autonomously move under the propulsion of oxygen bubbles. The carbonaceous nanoflask (CNF) motor was fabricated by encapsulating platinum nanoparticles (Pt NPs) into the hollow cavity of the CNF. The internally encapsulated Pt NPs act as catalysts to decompose hydrogen peroxide (H2O2) fuel into oxygen bubbles. The generated oxygen bubbles recoil the motion of the CNF motors. Besides, the velocity of CNF motors can be controlled by adjusting the concentration of the H2O2 solution. The motion velocity increases with the increase of H2O2 concentration, up to 109.25 μm s-1 at 10% H2O2. This study provides important implications for understanding the motion behaviors of nanomotors with an internal cavity, and the self-propelled CNF motors as smart carrier systems have potential applications in the future.

The paper presents the results of a computational study of the influence of the geometry of the working chamber on the energy-force interaction of grinding bodies in the process of the mixture processing in a planetary mill. The method of computer simulation, using the software system, based on the ideology of discrete elements, shows the high efficiency of processing in a planetary mill, using a working chamber with a square-shaped cavity. The values of the factors that have a dominant influence on the mechanical processing of the charge are determined. A comparison with the process of processing in the working chamber of the traditional cylindrical shape is made. The research results will be used in the appointment of large-size charge processing regimes that provide a high-energy grinding process.

Proteins from “pressure-loving” piezophiles appear to adapt by greater compressibility via larger total cavity volume. However, larger cavities in proteins have been associated with lower unfolding pressures. Here, dihydrofolate reductase (DHFR) from a moderate piezophile Moritella&nbsp, profunda (Mp) isolated at ~2.9 km in depth and from a hyperpiezophile Moritella yayanosii (My) isolated at ~11 km in depth were compared using molecular dynamics simulations. Although previous simulations indicate that MpDHFR is more compressible than a mesophile DHFR, here the average properties and a quasiharmonic analysis indicate that MpDHFR and MyDHFR have similar compressibilities. A cavity analysis also indicates that the three unique mutations in MyDHFR are near cavities, although the cavities are generally similar in size in both. However, while a cleft overlaps an internal cavity, thus forming a pathway from the surface to the interior in MpDHFR, the unique residue Tyr103 found in MyDHFR forms a hydrogen bond with Leu78, and the sidechain separates the cleft from the cavity. Thus, while Moritella DHFR may generally be well suited to high-pressure environments because of their greater compressibility, adaptation for greater depths may be to prevent water entry into the interior cavities.

The development of accurate and explicable machine learning models to predict the properties of topologically complex systems is a challenge in material science. Porous organic cages, a class of polycyclic molecular materials, have potential application in molecular separations, catalysis and encapsulation. For most applications of porous organic cages, having a permanent internal cavity in the absence of solvent, a property termed “shape persistency” is critical. Here, we report the development of Graph Neural Networks (GNNs) to predict the shape persistence of organic cages. Graph neural networks are a class of neural networks where the data, in our case that of organic cages, are represented by graphs. The performance of the GNN models was measured against a previously reported computational database of organic cages formed through a range of [4+6] reactions with a variety of reaction chemistries. The reported GNNs have an improved prediction accuracy and transferability compared to random forest predictions. Apart from the improvement in predictive power, we explored the explicability of the GNNs by computing the integrated gradient of the GNN input. The contribution of monomers and molecular fragments to the shape persistence of the organic cages could be quantitatively evaluated with integrated gradient. With the added explicability of the GNNs, it is possible not only to accurately predict the property of organic materials, but also to interpret the predictions of the deep learning models and provide structural insights to the discovery of future materials.

Metal-organic cages (MOCs) have emerged as a diverse class of molecular hosts with potential utility across a vast spectrum of applications. With advances in single-crystal X-ray diffraction and economic methods of computational structure optimisation, cavity sizes can be readily determined. In combination with a chemist’s intuition, educated guesses about the likelihood of particular guests being bound within these porous structures can be made. Whilst practically very useful, simple rules-of-thumb, such as Rebek’s 55% rule, fail to take into account structural flexibility inherent to MOCs that can allow hosts to significantly adapt their internal cavity. An often unappreciated facet of MOC structures is that, even though relatively rigid building blocks may be employed, conformational freedom can enable large structural changes. If it could be exploited, this flexibility might lead to behavior analogous to the induced-fit of substrates within the active sites of enzymes. To this end, in-roads have already been made to prepare MOCs incorporating ligands with large degrees of conformational freedom. Whilst this may make the constitution of MOCs harder to predict, it has the potential to lead to highly sophisticated and functional synthetic hosts.

In this paper we mainly concerned to develop knowledge and study about structure of human heart in physical education. The human heart is complex muscle that pump blood through the three divisions of the circulatory system: the coronary, pulmonary, and systemic. The internal cavity of the heart is divided into four chambers: right atrium, right ventricle, left atrium and left ventricle. The average gross weight of the heart was 289.6 g for men at an age of 31-40 years, 284.7 g for women at the same age.

Synchronous tuning can extend the mode-hop-free (MHF) tuning range of external-cavity diode lasers (ECDLs) without antireflection coating. However, due to nonlinearities in the internal and external cavities of ECDLs, the synchronous tuning ratio is not constant, causing detuning, which limits the MHF tuning range. To solve the nonlinearity mismatch between the two cavities, the nonlinearity of the internal cavity is identified and a correction model for the both cavities based on a mapping method is established. Further, the zero-vibration-derivative (ZVD) method is applied to optimize the dynamic response of the system. Experimental results show that MHF tuning in the full scanning period is achieved, and the optical frequency shows good linearity.

Objectives In this research, we aimed to develop a thermoelectric device (TED) for intracavitary hypothermia, to carry out experimental studies into its functional characteristics, as well as to develop treatment procedures using this device.Method A TED design for intracavitary hypothermia was developed, consisting of two thermoelectric batteries (TEBs) interconnected using an allmetal heat pipeline equipped with an influencing applicator and a liquid heat exchanger. Experimental studies of the device were carried out on a designed bench, which included a climatic chamber, a source of electrical energy and a temperature meter connected to a PC. Results Temperature changes at the control points of the device were recorded over time. Changes in the time taken to stabilise temperatures of the device tip, heat pipe and heat sink system at different TEB supply currents were investigated. Possible methods for treating some ENT diseases using the developed device are described.Conclusion It is shown that the temperature of the applicator is stabilised after approximately 4-4.5 minutes without load. At the same time, an increase in the current of the additional TEB from 5 to 12 A at the main TEB current of 23 A reduces the temperature from 237 K to 224 K. In the process of carrying out the procedures, the necessary level of a decrease in the temperature of a biological object can be reached at the supply current of the main and additional TEBs equal to 23 and 12 A, respectively, after 2.5 minutes. The full potential of the TED device will be realised through the developed of methods for treating ENT diseases.

The technology of manufacturing ceramic molds from electrocorundum powders of the company «Technoceramics» for the casting of parts from heatresistant nickel alloys was investigated and developed. The powders were used instead of the commercially used electrocorundum powders of JSC Rusal. Molds for metal casting of various sizes and configurations of the internal cavity for casting cooled and uncooled blades of heat-resistant alloys were manufactured and tested. Technical properties of casting molds are preserved. The characteristics of castings of equiaxial and directional structure are provided in accordance with the technical requirements of the drawing and technical conditions. Ill. 5. Ref. 2. Tab. 6.

A great attention has been recently paid to development of ultrasound technologies for treatment of blood vessels throughout the world. Authors of the paper have developed a new effective treatment method and ultrasound equipment that allow to carry out destruction of intravascular formations with simultaneous increase in elasticity of a vascular wall together with cardiologists from Belarusian Medical Academy of Postgraduate Education and Republican Scientific and Practical Center “Cardiology”. Advantages of the method are absence of necessity in surgical intervention, low probability of complications, low cost of treatment. The main component of the developed ultrasonic equipment is a tube-type stepped concentrator-waveguide having a spherical tip at a distal end with a single axial hole of 0.5 mm-diameter and three radial holes of 0.3 mmdiameter located at an angle of 120° relative to each other. The main effect for application of the concentratorwaveguide is achieved by ultrasonic vibromechanical action of a spherical tip on intravascular formation with subsequent removal of destruction products by their aspiration from a vascular bed. An additional effect is provided due to cavitation action on vascular formation and vessel walls by flow of fluid supplied via an internal cavity of the stepped concentratorwaveguide through the holes in the spherical tip. This contributes to a significant improvement in elastic properties of a vascular wall in atherosclerosis and diabetes. It is necessary to ensure high accuracy and quality of surfaces for the formed microholes in order to achieve maximum efficiency of the cavitation jet impact on intravascular formations and on the vascular wall. According to the analysis results on specific features of existing methods for small-diameter hole shaping, an electrochemical hole cutting method has been proposed which allows to obtain accurate micro-holes with a diameter of 0.3 mm and high surface quality in parts of small cross section and rigidity. The paper presents results of study on effect of electrochemical holes cutting parameters (voltage, concentration and consumption of electrolyte) on size and shape of the formed microholes. Main modes of electrochemical holes cutting process have been developed which allow to form micro-holes in a spherical tip of a tubular concentrator-waveguide with required accuracy, dimensions and shape.

The medieval Russian bronze reliquary cross pendant was investigated using a complex of nondestructive methods in order to determine the degree its integrity and identify the material filling its internal cavity. The metal composition is established. It is found that the cross material was subjected to spatially inhomogeneous corrosion and that the cavity is filled with soil. It is shown that application of complementary nondestructive methods provides the most reliable information on historical heritage objects.

Morphologically perfect seeds are critically important for raising normal, healthy seedlings as well as for increasing germination percentages. In this study, an X-ray microCT scanner was employed to generate CT images to investigate the internal conditions of naturally aged watermelon and muskmelon seeds. Different seed components, such as the seed coat thickness, the size of the embryo, the area of the air space inside the seed, the embryo structure, and the damages diagnosis in the seed anatomy were selected as observation parameters for investigation of the dicot seed samples. The areas of the seed coat thickness, embryo, and the internal air space were measured by ImageJ software, and the one-way analysis of variance (ANOVA) test was performed to inspect the significant differences in the parameters of the normal viable and the nonviable/abnormal viable seeds. A paper germination test was performed to identify the normal viable and nonviable/abnormal viable seeds. The findings of this study indicate that there was no significant difference in the seed coat thickness of the normal viable and the nonviable/abnormal viable naturally aged seeds, but the embryo and internal air space area structures were distinctive. The normal viable seeds contained a large embryo with nominal air space inside the seed, whereas the nonviable/abnormal viable seed embryo size was relatively small with a vast internal cavity. Based on the results of this study, we concluded that the normal viable and nonviable/abnormal viable aged seeds had significant differences in their morphological structures that adversely affect seed germination.

Objectives The purpose of the article is to simulate and theoretical study of the thermoelectric system (TPP) for intracavitary hypothermia, the study of the processes occurring in it taking into account the influence of the parameters of the object of influence and characteristics of a thermoelectric battery (TEB). Method A physical model of thermal power plants for intracavitary hypothermia, consisting of two thermopiles, interconnected through an all-metal thermal bridge, equipped with an acting tip and a liquid heat exchanger is proposed. A quasi-stationary mathematical model of thermal power plants has been developed as a set of interconnected heat exchange systems, thermopile and heat conductor characterized by heat capacity, thermal conductivity and thermal resistance, which allows us to estimate the duration of the device output to the operating mode, taking into account the thermal properties of the biological object. Result The dependences of the temperature change of different parts of TPPs in time are obtained for the case of operation of the device in idling mode and in the presence of heat load. The temporal variation of the temperature of the object of influence, the conductor, the heat pipe and the heat exchanger at different currents of supply of thermopile and also for different values of the temperature of the liquid in the heat exchanger is considered. Conclusion It is established that without load, the temperature of the acting tip stabilizes in approximately 4–4.5 minutes. At the same time, an increase in the current strength of an additional thermopile from 5 to 15 A at the current supply of the main thermopile 50 A reduces the operating value of T from 235 K to 220 K. During the procedures, the required level of laryngeal tissue temperature decrease (273 K) can be achieved at the main power supply current and additional thermopile, respectively, equal to 25 and 10 A after 2 min. At a fixed temperature of the reference junctions of the main thermopile, the limiting decrease in the temperature of the acting tip is limited by the magnitude of the optimal thermopile current. It is possible to obtain deeper cooling at a given value of the supply current by reducing the temperature of the reference junctions of the main thermopile.

The manufacturing of sound forgings from large steel ingots requires that internal cavity defects generated during the steel ingot solidification process be compressed by open die forging. The forging ratio that is generally recommended to remove internal defects in large forged products is 3S (threefold); however, the practice lacks a theoretical basis. In this study, a forging experiment and a finite element analysis were performed to investigate the correlation between the forging ratio for large steel ingots (3S) and the cavity closure behavior. First, a hot compression experiment was performed by varying the temperature and strain rate, and the flow stress data observed in the experiment was applied to the finite element analysis. In the experiment for the cogging process, the forging ratio was applied to an actual non-compressive defect material. The finite element analysis was performed using the same forging path as the forging experiment. In the cogging experiment, cavity closure was found by ultrasonic inspection at the forging ratio of 2.9S. The finite element analysis showed that the size of the cavity was significantly decreased at the forging ratio of 2.9S. A finite element analysis was also performed to investigate effective strain and hydrostatic stress at the forging ratio of 2.9S. Finally, this article provides the theoretical basis for the limitation of the internal defect size in initial materials, the threshold effective strain, and the limiting forging ratio of forged products to ensure the internal soundness of large forged products.

In this work, the character of the pressure within artificially ventilated cavities is investigated in detail using computational fluid dynamics. The efforts explore the details of the pressure inside both twin- and toroidal-vortex cavities through histograms of the internal cavity pressure. Rather than a uniform pressure, detailed interrogation of the pressure indicates a multi-peak distribution of cavity pressure. Further interrogation of these peaks suggests that such pressure variations align with distinct regions within the cavity. Additionally, the character of these distributions are found to be dependent on the cavity closure mode ( Campbell and Hilborne, 1958 ; Karn et al., 2016; Logvinovich, 1972 ). In evaluating these small, yet present, pressure variations, it is hypothesized that they are the driving force for the internal, re-circulatory flow. Lastly, the importance of these distinct regions of pressure regions is investigated with respect to semi-empirical theory, which aims to directly evaluate the level of validity of the constant pressure assumption. The results indicate that the constant pressure assumption remains valid, but may lead to small inaccuracies when evaluating other cavity characteristics through semi-empirical theory.

We fabricated a photodetector using hollow multi-shell structured (HoMSs) SnO2 as an active material, which exhibits enhanced ultraviolet responsivity and detectivity compared to SnO2 nanoparticles. This is because the internal cavity within the HoMSs helps to trap light and enhance light absorption. With an increase in the number of shells, the photodetector performance is improved.

1-Methylcyclopropene (1-MCP) and a controlled atmosphere (CA; elevated CO2 and low O2 partial pressures) preserve the overall quality of ‘Cold Snap™’ pears during low temperature storage, including minimizing physiological disorders. In two separate years, we determined the impact of 1-MCP (0 or 300 nL L−1), pre-storage conditioning (0, 3, or 7 d at 3 °C), and CA (18 or 2.5 kPa O2, and 2 kPa CO2) on the shelf-life quality of ‘Cold Snap™’ pears following their removal from storage at 0 °C. In both years, 1-MCP effectively reduced rates of ethylene production and limited peel yellowing and fruit softening following the transfer of stored ‘Cold Snap™’ pears to ambient conditions for up to 14 d, regardless of pre-storage conditioning and CA regimen. Moreover, 1-MCP-treated fruit stored under 2.5 kPa O2/2 kPa CO2 developed lower incidences of senescent scald, regardless of the pre-storage conditioning period. In year one, this treatment combination also limited internal breakdown and internal cavity development, whereas the incidence of internal cavities was highest in 1-MCP-treated fruit in year two, regardless of pre-storage conditioning period, O2 partial pressure in the storage atmosphere, and shelf-life duration. Principal component analysis revealed that the occurrence of senescent scald and internal breakdown in ‘Cold Snap™’ pears were associated with high rates of ethylene production, peel yellowing, and softening. Similarly, internal cavity development was correlated with most ripening attributes, although the link with fruit softening was inconsistent across both years of the study.

A comparison of numerical and experimental analysis of cavity shape influence on flow properties of a synthetic jet is presented. The goal is to highlight areas that are challenging to measure and to better understand the in-cavity flow and exit characteristics. In the examination of three cavities it is found that, in accordance with experiments, the cavity with the sharpest nozzle-to-cavity transition transmits the most momentum at the exit. The sharp transition within the cavity results in a stronger vortex, higher self-induced inward velocity, and ultimately more room for flow to exit the cavity during the expulsion phase. It is shown that the shape of the internal cavity plays an important role in the flow behavior at the nozzle exit. From a computational perspective, the results suggest that the flow field within the cavity must be computed to obtain accurate exit conditions for the synthetic jet.

Background Hysteroscopy training requires the development of specific psychomotor skills. Few validated low-cost models exist in hysteroscopy. The main objective of this study is to determine face, content, and construct validity of a simulator designed for training basic hysteroscopy skills applied to office-based hysteroscopy. Methods Twenty-five hysteroscopy experts and 30 gynecology residents participated in this prospective observational study. The simulator consisted of three color-textured, silicone-coated anthropomorphic 3-dimensional (3-D) printout uterine models inside a box. Each uterine model in the simulator was designed to develop one of the following basic hysteroscopic skills: hysteroscopic navigation, direct biopsy, and foreign body removal. Participants performed five video-recorded simulation attempts on each model. Procedure-specific checklists were used to rate performance. Results Median scores (25th–75th percentiles; p-value) 4 (3–4; p < 0.001) and surgical experience associated to the simulated procedures 4 (3–4; p < 0.001) indicated positive perceptions as to the realism of the internal cavity of the simulator. Median scores of 4 (3–4; p < 0.001) were assigned to the realism and utility of the tasks performed in the simulator for enhancing novice training in hysteroscopy. Expert performance scores were significantly higher and task completion times were significantly lower than those of novices in the navigation exercise (F(1,53) = 56.66; p < 0.001), the directed biopsy exercise (F(1,53) = 22.45; p < 0.001), and the foreign body removal exercise (F(1,53) = 58.51; p < 0.001). Novices’ performance improved on all three exercises: navigation exercise (F(1,53) = 182.44; p < 0.001), directed endometrial biopsy (F(1,53) = 110.53; p < 0.001), and foreign body removal (F(1,53) = 58.62; p < 0.001). Experts’ task completion times were significantly lower when compared to that of novices in the five attempts (p < 0,001) of the exercises: navigation (F(1,48) = 25.46; p < 0.001), directed biopsy (F(1,46) = 31.20; p < 0.001), and foreign body removal (F(1,50) = 69.8; p < 0.001). Novices’ task completion times diminished significantly throughout the sequence of exercises. Conclusions The low-cost simulator designed for the acquisition of basic skills in hysteroscopy demonstrated face, content, and construct validity.

Aim: We explored the potential for over-compression from current paediatric chest compression depth guidelines using chest computed tomography(CT) images of a large, heterogenous, Asian population. Methods: A retrospective review of consecutive children, less than 18-years old, with chest CT images performed between from 2005 to 2017 was done. Demographic data were extracted from the electronic medical records. Measurements for internal and external anterior-posterior diameters (APD) were taken at lower half of the sternum. Simulated chest compressions were performed to evaluate the proportion of the population with residual internal cavity dimensions less than 0 mm (RICD < 0 mm, representing definite over-compression; with chest compression depth exceeding internal APD), and RICD less than 10 mm (RICD < 10 mm, representing potential over-compression). Results: 592 paediatric chest CT studies were included for the study. Simulated chest compressions of one-third external APD had the least potential for over-compression; no infants and 0.3% children had potential over-compression (RICD < 10 mm). 4 cm simulated chest compressions led to 18% (95% CI 13%–24%) of infants with potential over-compression, and this increased to 34% (95% CI 27%–41%) at 4.4 cm (upper limit of “approximately” 4 cm; 4 cm + 10%). 5 cm simulated compressions resulted in 8% (95% CI 4%–12%) of children 1 to 8-years-old with potential over-compression, and this increased to 22% (95% CI 16%–28%) at 5.5 cm (upper limit of “approximately” 5 cm, 5 cm + 10%). Conclusion: In settings whereby chest compression depths can be accurately measured, compressions at the current recommended chest compression of approximately 4 cm (in infants) and 5 cm (in young children) could result in potential for over-compression.