Generation mechanism and empirical model of eddy current force and torque in drum-type eddy current separation

Enhancing the recovery efficiency of non-ferrous metals in eddy current separation is of great significance. In this study, the accuracy of the simulation model was verified by comparing the eddy current force. The transformation mechanism of the Lorentz forces into the eddy current force and torque in non-ferrous metal particles was revealed by analyzing various physical fields. Then, the influence of magnetic field parameters on eddy current, eddy current force, and torque was studied. It shows that the eddy current force and torque are affected by the vector gradient of the magnetic field and the magnetic flux density, respectively. Additionally, the time derivative of the magnetic field impacts the magnitude of the eddy current force and torque by controlling the eddy current. On this basis, the empirical models of eddy current force and torque were established by similarity theory. The results obtained can improve and expand the application of eddy current separation.

Influence of encapsulation variables on formation of leuprolide-loaded PLGA microspheres

Emulsion-based solvent evaporation microencapsulation methods for producing PLGA microspheres are complex often leading to empirical optimization. This study aimed to develop a more detailed understanding of the effects of process variables on the complex emulsification processes during encapsulation of leuprolide in PLGA microspheres using a high-shear rotor-stator mixer. Following extensive analysis of previously developed formulation conditions that yield microspheres of equivalent composition to the commercial 1-month Lupron Depot, multiple variables during the formation of primary and secondary emulsion were investigated with the aid of dimensional analysis, including: rotor speed (ω) and time (t), dispersed phase fraction (Φ) and continuous phase viscosity (µ_c). The dimensionless Sauter mean diameter (d_3,2) of primary emulsion was observed to be proportional to the product of several key dimensionless groups (Φ₁,We,Re,ω₁t₁) raised to the appropriate power indices. A new dimensionless group (Θ ) (surface energy/energy input) was used to rationalize insertion of a proportionate time dependence in the scaling of the d_3,2. The dimensionless d_3,2 of secondary emulsion was found proportional to the product of three dimensionless groups ( [Formula: see text] ) raised to the appropriate power indices. The increased viscosity of the primary emulsion, decreased secondary water phase volume and reduced second homogenization time each elevated encapsulation efficiency of peptide by reducing drug leakage to the outer water phase. These results could be useful for dimensional analysis and improving manufacturing of PLGA microspheres by the solvent evaporation method.

Geo-environmental parametric 3D models of SARS-CoV-2 virus circulation in hospital ventilation systems

The novel coronavirus, SARS-CoV-2, has the potential to cause natural ventilation systems in hospital environments to be rendered inadequate, not only for workers but also for people who transit through these environments even for a limited duration. Studies in of the fields of geosciences and engineering, when combined with appropriate technologies, allow for the possibility of reducing the impacts of the SARS-CoV-2 virus in the environment, including those of hospitals which are critical centers for healthcare. In this work, we build parametric 3D models to assess the possible circulation of the SARS-CoV-2 virus in the natural ventilation system of a hospital built to care infected patients during the COVID-19 pandemic. Building Information Modeling (BIM) was performed, generating 3D models of hospital environments utilizing Revit software for Autodesk CFD 2021. The evaluation considered dimensional analyses of 0°, 45°, 90° and 180°. The analysis of natural ventilation patterns on both internal and external surfaces and the distribution of windows in relation to the displacement dynamics of the SARS-CoV-2 virus through the air were considered. The results showed that in the external area of the hospital, the wind speed reached velocities up to 2.1 m/s when entering the building through open windows. In contact with the furniture, this value decreased to 0.78 m/s. In some internal isolation wards that house patients with COVID-19, areas that should be equipped with negative room pressure, air velocity was null. Our study provides insights into the possibility of SARS-CoV-2 contamination in internal hospital environments as well as external areas surrounding hospitals, both of which encounter high pedestrian traffic in cities worldwide.

Metabolic scaling of stream dissolved oxygen across the U.S. Atlantic Coast

We investigated the hypothesis of emergent 'biogeochemical' similitude (parametric reduction) and scaling of dissolved oxygen (DO) in coastal streams across the U.S. Atlantic Coast by employing dimensional analysis methodology from fluid mechanics and hydraulic engineering. Two mechanistically meaningful dimensionless numbers were discovered as the stream 'metabolic' number and the fraction of 'DO saturation' number. The 'metabolic' number represented the synergistic control on stream DO from various climatic, hydrologic, biochemical, and ecological drivers (e.g., water temperature, atmospheric pressure, stream width and depth, total phosphorus, pH, and salinity). A graphical exploration of the 'metabolic' versus the 'DO saturation' numbers led to collapse of data during 1998-2015 from diverse coastal streams into an emergent process diagram, indicating three metabolism regimes (high, transitional, and low). The high and low metabolism regimes were, respectively, characterized by the most and least favorable environmental conditions for stream DO depletion-through reduced dissolution and reaeration, as well as increased organic decomposition, respiration, and nitrification. The emergent process diagram led to a generalized power law scaling relationship of the 'DO saturation' number as a function of the 'metabolic' number (exponent ~ 1/3; Nash-Sutcliffe Efficiency, NSE = 0.83-0.85). The metabolic scaling law was leveraged to develop a generalized empirical model to successfully predict DO in diverse streams across the U.S. Atlantic Coast (NSE = 0.83). The emergent process diagram, metabolic scaling law, and prediction model of DO would help understand and manage water quality and ecosystem health of coastal streams in the U.S. and elsewhere.

The use of ratio and proportion, dimensional analysis, and equations to solve pharmacy calculations problems

INTRODUCTION

To evaluate the effects of using different problem-solving approaches on the success rates of student pharmacists in solving problems throughout a pharmacy calculations course.

METHODS

A survey was administered to first-year students (N = 96, response rate 100%) near the completion of a pharmacy calculations course. The survey assessed whether students used the approaches of ratio and proportion (RP) or equations vs. dimensional analysis (DA) to solve calculation problems involving conversions, weight-based doses, flow rates, electrolyte solutions, and expressions of concentration. Questions used on course exams were tagged according to topics. Mean success rates in solving tagged questions were correlated with the problem-solving approaches that students used.

RESULTS

Approximately 60% of students used RP/equations, 30% used DA, and 10% used both approaches equally. The success rate of students solving conversions was 74% ± 24% for RP, 84% ± 14% for DA (P < .05 vs. RP), and 91% ± 12% for the use of both approaches equally (P < .05 vs. RP). Success rates in solving calculation problems of weight-based doses, flow rates, electrolyte solutions, and expressions of concentration were similar across all approaches.

CONCLUSIONS

The use of DA, or the combination of RP and DA equally, may be advantageous for solving conversions but not for the other types of calculation problems studied. Therefore, for most topics, pharmacy calculations instructors can demonstrate the method of their choice. Since a considerable number of students use each of the approaches, the demonstration of both approaches in class may be advantageous.

Clinical evaluation of 3D printed nano-porous hydroxyapatite bone graft for alveolar ridge preservation: A randomized controlled trial

Background/purpose

Ridge resorption after tooth extraction may result in inadequate bone volume and unfavorable ridge architecture for ideal implant placement. The use of bone substitutes has been advocated to fill extraction sites and to enhance primary implant stability. This study was made to evaluate the clinical efficacy of novel 3D printed nano-porous hydroxyapatite (3DP HA, test group) in comparison to nano-crystalline bone graft (NanoBone®, control group) in alveolar ridge preservation prior to implant placement.

Materials and methods

Thirty patients were randomized into two groups following tooth extraction. All extracted sockets were filled with 3DP HA or NanoBone® and covered with a non-resorbable membrane. After four months, cone-beam computed tomography (CBCT) and intraoral scanner were used to measure dimensional changes of bone and soft tissue surface. Bone core specimens were harvested for histological analysis during implant osteotomy. Implant stability was assessed using a modified damping capacity analysis.

Results

At four months postoperatively, dimensional changes in soft tissue surface resorption were less in the test group than in the control group; however, alveolar bone resorption was the same in both groups. Histological analysis revealed new bone formation, residual graft and fibrous connective tissue in both groups. The average primary implant stability (IST) value for both groups was approximately 70. There was no statistically significant difference in all parameters between two groups (p > 0.05).

Conclusion

3DP HA could potentially be used as an alternative bone graft material for alveolar ridge preservation.

Application of dimensional analysis in sorption modeling of the styryl pyridinium cationic dyes on reusable iron based humic acid coated magnetic nanoparticles

Cationic dyes exist in various industrial wastewaters and removal prior to discharge is necessary due to their carcinogenic behavior which poses a serious threat to human health. Iron based humic acid coated magnetic nanoparticles (HA-MNPs) were evaluated for the removal of 2-[4-(dimethylamino) styryl]-1-methylpyridinium iodide (2-ASP) as a model compound for cationic styryl pyridinium dyes from aqueous media. HA-MNPs were prepared by co-precipitation and characterized. The adsorption of 2-ASP, measured by fluorescence, demonstrates HA-MNPs are efficient for the 2-ASP removal with a maximum adsorption capacity of ~8 mg/g. Kinetic behavior and equilibrium studies showed the adsorption process fits with pseudo 2nd order and Langmuir isotherm models. The adsorption is relatively fast with ~70% of the adsorption complete within 30 min. The overall removal increases by increasing solution pH. The observed increase in adsorption can be assigned to an enhanced electrostatic attraction between the positively charged 2-ASP and the increase in the negative charge on the HA-MNPs surface as a function of increasing solution pH. Effective and repetitive regeneration of the HA-MNPs was achieved using NaOH treatment of saturated sorbent. Regeneration of HA-MNPs showed that removal efficiency remains consistently high after five consecutive cycles. Dimensional analysis suggested that initial concentration/sorbent dose ratio should be considered for accurate sorption modeling confirmed by experimental data. Then generalized empirical models for isothermal study and removal efficiency prediction were accurately deduced. This finding will help researchers in sorption studies to design their experiments more efficiently and to develop improved empirical models in removal prediction.

Multiplexed bio-imaging using cadmium telluride quantum dots synthesized by mathematically derived process parameters in a continuous flow active microreactor

Quantum dots (QDs) are semiconductor nanocrystals with unique size-tunable emissions. To obtain a precise emission spectrum, monodispersity in size is imperative, which is achieved by controlling the reaction kinetics in a continuous flow of active microreactors. Further, a multivariate approach (dimensional analysis) is employed to impose stringent control on the reaction process resulting in monodispersed preparation of cadmium telluride (CdTe) quantum dots. Dimensional analysis knits multiple variables into a dimensionless mathematical form which not only predicts parameters precisely to obtain narrow size tunability but also guarantees reproducibility in synthesis. Analytical, structural, and optical characterization of the microreactor synthesized polydimethylsiloxane (PDMS) coated CdTe QDs reveal quantum efficient (61.5%), photostable (44%), and biocompatible nanocrystals of 5-15 nm. Further, PDMS-coated QDs (P-QDs) are conjugated with organelle-specific antibodies/biomarkers for in-vitro imaging in NIH 3T3 cells. Likewise, proliferating cell nuclear antigen (PCNA) and anti-myosin (MF20), cardiomyocytes antibodies are conjugated with P-QDs (red and green, respectively) to image the zebrafish's cardiac tissue. Antibodies tagged with quantum dots are imaged simultaneously using confocal microscopy. Thus, multiplexed bio-imaging of in-vitro and zebrafish tissue is demonstrated successfully. The results indicate the suitability of continuous flow active microreactor in conjunction with the mathematical prediction of process parameters to synthesize reproducibly monodispersed and quantum efficient QDs.

Characterization of volcanic ash nanoparticles and study of their fate in aqueous medium by asymmetric flow field-flow fractionation-multi-detection

Dimensional and elemental characterization of environmental nanoparticles is a challenging task that requires the use of a set of complementary analytical methods. Asymmetric flow field-flow fractionation coupled with UV-Vis, multi-angle laser light scattering and ICP-MS detection was applied to study the nanoparticle fraction of a volcanic ash sample, in a Milli-Q water suspension at pH 6.8. It has been shown that the separated by sedimentation nanoparticle fraction of the Klyuchevskoy volcano ash suspension contains 3 polydisperse populations for which size ranges (expressed in gyration radius, rG), hydrodynamic behaviours (evaluated via shape index) and elemental compositions are different. These 3 populations did not dissolve over the 72-h study but aggregated and settled out differently. Thus, the population of particles with gyration radii <140 nm (P1), which contained 6% Al₂O₃ and represented approximately 20% by mass of the nanoparticle fraction, remained in suspension without observable aggregation. The populations P2 and P3, which represented 67% and 13% by mass in the initial suspension, covered the rG range 25-250 nm and contained 17% and 15% Al₂O₃, respectively. Over time, populations P2 and P3 aggregated and their concentration in suspension at 72 h decreased by approximately 40% compared with the initial suspension. The decrease of these nanoparticle populations occurred either from the beginning of the temporal monitoring (P2) or after 30 h (P3). Aggregation generated a new population (P4) in suspension with rG up to 300 nm and mostly consisting of P2. This population represented only up to 6 to 7% of the nanoparticle fraction and decreased beyond 50 h. As a result, the trace elements present in the nanoparticle fraction and monitored (Cu and La) were also no longer found in the suspension. The results obtained can offer additional insights into the fate of volcanic ash nanoparticles in the environment.

The elastic properties and deformation mechanisms of actin filament networks crosslinked by filamins

As a substructure of cell cytoskeleton, the crosslinked actin filament networks (CAFNs) play a major role in different cell functions, however, the elastic properties and the deformation mechanisms of CAFNs still remain to be understood. In this paper, a novel three-dimensional (3D) finite element (FE) model has been developed to mimic the mechanical properties of actin filament (F-actin) networks crosslinked by filamin A (FLNA). The simulation results indicate that although the Young's modulus of CAFNs varies in different directions for each random model, the statistical mean value is in-plane isotropic. The crosslinking density and the actin filament volume fraction are found to strongly affect the in-plane shear modulus of CAFNs. The simulation results agree well with the relevant experimental results. In addition, an L-shaped cantilever beam model has been developed for dimensional analysis on the shear stiffness of CAFNs and for quantifying the deformation mechanisms. It has been demonstrated that the in-plane shear modulus of CAFNs is mainly dominated by FLNA (i.e., cross-linkers), and that the bending and torsion deformations of FLNA have almost the same contribution to the stiffness of CAFNs. It has also been found that the stiffness of CAFNs is almost insensitive to the variation of the Poisson's ratios of FLNA and actin filament in the range from 0.29 to 0.499.

Analysis of volumetric mass transfer coefficient (k L a) in small- (250 mL) to large-scale (2500 L) orbitally shaken bioreactors

In this study, the combination of dimensional analysis (DA) and analysis of variance (ANOVA) was used to predict the volumetric mass transfer coefficient (k _L a) values under different operating conditions for orbitally shaken bioreactors (OSRs) with different filling volumes. It was found that Reynolds number and the interaction between Froude number and geometric number have the largest impact on k _L a with impact indexes of 7.41 and 7.50, respectively. Moreover, the volume number has the largest negative impact on k _L a, with an impact index of - 5.34. Thus, an effective way to increase the oxygen supply is by increasing the shaking speed and shaking diameter or decreasing the vessel diameter. However, cell cultivation with a higher filling volume will have an increased risk of oxygen scarcity. Therefore, with the help of the k _L a prediction model, a suitable operating condition can be determined effectively and easily.

Water disinfection by orifice-induced hydrodynamic cavitation

Hydrodynamic Cavitation (HC) is considered as a promising water-disinfection technique. Due to the enormous complexity of the physical and chemical processes at play, research on HC reactors is usually carried out following an empirical approach. Surprisingly, past experimental studies have never been designed on dimensional-analysis principles, which makes it difficult to identify the key processes controlling the problem, isolate their effects and scale up the results from laboratory to full-scale scenarios. The present paper overcomes this issue and applies the principles of dimensional analysis to identify the major non-dimensional parameters controlling disinfection efficacy in classical HC reactors, namely orifice plates. On the basis of this analysis, it presents results from a new set of experiments, which were designed to isolate mainly the effects of the so-called cavitation number (σ_v). Experimental data confirm that the disinfection efficacy of orifice plates increases with decreasing σ_v. Finally, in order to discuss the significance of the results presented herein and frame the scope of future research, the present paper provides an overview of the drawbacks associated with dimensional analysis within the context of HC.

Time scale based analysis of in-situ crystal formation in droplet undergoing rapid dehydration

The surface structure of crystalline particles affects the functionality of the particles in drug delivery. Prediction of the final structure of particles that crystallize easily within the spray drying process is of interests for many applications. A theoretical framework was developed for the prediction of crystal structure precipitating on the surface of the particle. This model was based on the dimensionless Damkohler number (Da), to be an indicator of final particle morphology. Timescales of evaporation and reaction were required for calculation of the Damkohler number. The modified evaporation time scale was estimated based on the time that is available for the crystal to precipitate after supersaturation. The reaction time scale was estimated based on the time scale for induction time. Mannitol was produced under different processing conditions in order to validate the theoretical model. Results showed for the high Damkohler numbers, the surface structure of the particle was rough, while smaller Damkohler numbers led to relatively smooth particle surfaces. Additionally, although the beta polymorph was dominant in all of the experiments, alpha polymorph was precipitated in the experiments with a large Damkohler number. The theoretical framework developed will be a useful predictive tool to guide the manipulation of particle crystallization in spray dryers.

Acquisition of 3D models with submillimeter-sized features from SEM images by use of photogrammetry: A dimensional comparison to microtomography

The use of three-dimensional models for analysis has been increasing in various fields. This study aimed to analyze the process of acquiring 3D meshes by photogrammetry using scanning electron microscopy (SEM) images. 3D models were reconstructed from different numbers of SEM images using a free photogrammetry software. The 3D models obtained were aligned and compared quantitatively to a model obtained by microtomography (microCT). The results suggest that it is possible to reconstruct 3D photogrammetric models with micrometric precision using SEM. However, the error depends on the number of images used for 3D reconstruction (and on the rotation angle). The best result obtained by photogrammetry at 9° step showed a percentage error of 0.3%. The worst result (27°) had a 1.4% error compared to those obtained by microCT. SEM photogrammetry is capable of providing surface details almost as accurate as microCT and therefore, it can be an interesting alternative for the analysis of external surfaces.

In Their Own Words: How Black Teens Define Trauma

Trauma is a subjective phenomenon. However, when examining trauma among low-income, Black teens, it is common to use established clinical criteria as the metric for identifying and evaluating its presence and impact. Little attention has been devoted to exploring how Black youth characterize trauma in their own terms. This qualitative study explored the concept of trauma from the perspectives of 12 low-income, Black teens. Participants' descriptions included death and loss; violence exposure; police harassment, racism, and discrimination; poverty; being stuck in the hood; and being bullied. While some of their descriptions were compatible with traumatic stressors outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM), participants also highlighted factors that are not explicitly enumerated in the DSM. Findings present important implications for the development of more culturally and developmentally inclusive discussions of trauma and for clinical practice with low-income, Black youth who are impacted by trauma and adversity.

An Inverse Problem: Trappers Drove Hares to Eat Lynx

The Canadian lynx and snowshoe hare pelt data by the Hudson Bay Company did not fit the classical predator-prey theory. Rather than following the peak density of the hare, that of the lynx leads it, creating the hares-eat-lynx (HEL) paradox. Although trappers were suspected to play a role, no mathematical model has ever demonstrated the HEL effect. Here we show that the long-held assumption that the pelt number is a proxy of the wild populations is false and that when the data are modeled by the harvest rates by the trappers, the problem is finally resolved: both the HEL paradox and the classical theory are unified in our mechanistic hare-lynx-competitor-trapper (HLCT) model where competitor stands for all predators of the hares other than the lynx. The result is obtained by systematically fitting the data to various models using Newton's inverse problem method. Main findings of this study include: the prey-eats-predator paradox in kills by an intraguild top-predator can occur if the top-predator prefers the predator to the prey; the benchmark HLCT model is more sensitive to all lynx-trapper interactions than to the respective hare-trapper interactions; the Hudson Bay Company's hare pelt number maybe under-reported; and, the most intriguing of all, the trappers did not interfere in each other's trapping activities.

Environmental complexity of a port: Evidence from circulation of the water masses, and composition and contamination of bottom sediments

Ports are complex environments due to their complicated geometry (quays, channels, and piers), the presence of human activities (vessel traffic, shipyards, industries, and discharges), and natural factors (stream and torrent inputs, sea action, and currents). Taking these factors into consideration, we have examined the marine environment of a port from the point of view of the circulation of the water masses, hydrological characteristics, distribution of the sediment grain-size, mineralogical characteristics, and metal concentrations of the bottom sediments. Our results show that, in the case of the Port of Genoa (north-western Italy), the impact of human activities (such as a coal power-plant, oil depots, shipyards, dredging of the bottom sediments, etc.), natural processes (such as currents, fresh water and sediment inputs from the torrents), and the morphology of the basin, are important factors in the sediment, water, and metal distributions that have given rise to a complex environment.

Dimensional Analysis: An Alternative Method for Converting between Interrelated Units of both Timebase and Sensitivity in EEG

Neurodiagnostics professionals expected to perform EEG calculations involving timebase and sensitivity may benefit from an additional method in which to solve for the answers. Dimensional analysis (DA) is an efficient, organized method that generates answers in a consolidated context. Its coherent, streamlined mechanism allows for efficient computations involving sets of values with diametric units. One of its key advantages is its ability to emphasize conceptualization, which may be attractive to those with that mathematical personality. Its usefulness beyond neurodiagnostics is profound and includes assisting domestically inclined individuals with mathematical conversions related to home projects and proper cooking times. Several examples of both EEG and home-life applications are provided to assist with acclimation.

A new age-related model for blood stroke volume

BACKGROUND

A new computer model for systolic pulse waves within the cardiovascular system is presented. The emphasis was made on blood stroke volume (BS). The new waveform for pulse wave demands the re-computing of the BS. The authors showed the applicability of suggested model for arterial aging problem.

METHODS

Suggested model is based on the well-known Korteweg-de Vries (KdV) equation. Instead of the common accepted solitary wave, the periodical cnoidal wave is used. Both waves are exact solutions of the KdV equation. The cnoidal waves are described by the Jacobi elliptic functions. Depending on a specific parameter called the elliptic module, m (0≤m≤1), these functions can be either harmonic or hyperbolic type.

RESULTS

The explicit expression for the dimensionless BS was obtained. The dimensionless BS depends, as was found, on the elliptic module only. Dimensional analysis demonstrates the dimensionless BS has limited range of variation. This allows the direct estimation of elliptic module that turns out to be close but not exact equal to one. It is shown, that correct calculations of BS can not be done at m=1 (corresponds to simpler soliton model), and the periodicity of pulse waves has to be taken into consideration.

CONCLUSIONS

Only the cnoidal model with the limited wavelength provides the correct computing of the BS. The natural bounds of dimensionless BS were found for the first time.

Scaling up adsorption media reactors for copper removal with the aid of dimensionless numbers

Adsorption media may be used to sorb copper in an aquatic environment for pollution control. Effective design of adsorption media reactors is highly dependent on selection of the hydraulic residence time when scaling up a pilot-scale reactor to a field-scale reactor. This paper seeks to improve scaling-up technique of the reactor design process through the use of the Damköhler and Péclet numbers via a dimensional analysis. A new scaling-up theory is developed in this study through a joint consideration of the Damköhler and Péclet numbers for a constant media particle size such that a balance between transport control and reaction control can be harmonized. A series of column breakthrough tests at varying hydraulic residence times revealed a clear peak adsorption capacity at a Damköhler number of 2.74. The Péclet numbers for the column breakthrough tests indicated that mechanical dispersion is an important effect that requires further consideration in the scaling-up process. However, perfect similitude of the Damköhler number cannot be maintained for a constant media particle size, and relaxation of hydrodynamic similitude through variation of the Péclet number must occur.

Allometry in Physarum plasmodium during free locomotion: size versus shape, speed and rhythm

Physarum plasmodium is a giant unicellular organism whose length can vary by more than three orders of magnitude. Using plasmodia ranging in size from 100 μm to 10 cm, we investigated the size dependency of their thickness distributions and locomotion speeds during free locomotion. (1) In the longitudinal direction, the organism is thickest close to the front, and decreases exponentially in thickness towards the rear. The slenderness ratio varies with body size according to a power law, such that large plasmodia are long and flat, whereas small plasmodia are short and thick. (2) The mean locomotion speed is proportional to the mean maximum thickness of the frontal part. By conducting a dimensional analysis, possible physical models are discussed. (3) The intrinsic period of the thickness oscillation, which is related to shuttle streaming (period 1-2 min), increases logarithmically with body size. (4) Various characteristics exhibit size-independent, long-period (20±10 min) oscillations, including speed, shape and intrinsic thickness oscillation period. These variations are closely coupled to formation of the entire cell shape, including undulation of thickness along the longitudinal axis and timing of branching of the frontal tip. Based on these experimental results and those reported previously, we propose a simple mathematical model for cell locomotion.

Defining patient deterioration through acute care and intensive care nurses' perspectives

AIM

To explore the variations between acute care and intensive care nurses' understanding of patient deterioration according to their use of this term in published literature.

BACKGROUND

Evidence suggests that nurses on wards do not always recognize and act upon patient deterioration appropriately. Even if resources exist to call for intensive care nurses' help, acute care nurses use them infrequently and the problem of unattended patient deterioration remains.

DESIGN

Dimensional analysis was used as a framework to analyze papers retrieved in a nursing-focused database.

METHOD

A thematic analysis of 34 papers (2002-2012) depicting acute care and intensive care unit nurses' perspectives on patient deterioration was conducted.

FINDINGS

No explicit definition of patient deterioration was retrieved in the papers. There are variations between acute care and intensive care unit nurses' accounts of this concept, particularly regarding the validity of patient deterioration indicators. Contextual factors, processes and consequences are also explored.

CONCLUSIONS

From the perspectives of acute care and intensive care nurses, patient deterioration can be defined as an evolving, predictable and symptomatic process of worsening physiology towards critical illness. Contextual factors relating to acute care units (ACU) appear as barriers to optimal care of the deteriorating patient. This work can be considered as a first effort in modelling the concept of patient deterioration, which could be specific to ACU.

RELEVANCE TO CLINICAL PRACTICE

The findings suggest that it might be relevant to include subjective indicators of patient deterioration in track and trigger systems and educational efforts. Contextual factors impacting care for the deteriorating patient could be addressed in further attempts to deal with this issue.

Finite element analysis of depth effect on measuring elastic modulus of a core-shell structure for application of instrumented indentation in tooth enamel

Tooth enamel is a complex structure, consisting of numerous enamel rods surrounded by a protein-rich sheath. Considering the possible effect of the protein-rich sheath on the indentation deformation of an enamel rod and the limitation of the Oliver-Pharr method in measuring the elastic modulus of the enamel rod, we used a finite element method to analyze the indentation deformation of an elastic-perfectly plastic cylinder surrounded by an elastic-perfectly plastic film. A concept of the threshold indentation depth was proposed, at which the percentage error of the measured modulus of the cylinder is ±10%. For the indentation depth less than the threshold indentation depth, the elastic modulus measured from the indentation test can be approximated as the intrinsic elastic modulus of the cylinder. The normalized threshold indentation depth strongly depends on the modulus ratio of the film to the cylinder and the ratio of the film thickness to the cylinder radius. The results can be used to guide the use of the Oliver-Pharr method in characterizing the mechanical properties of tooth enamel and bio-composites with core-shell structures.