Stability Limit of Electrified Droplets.

In many physical processes, including cloud electrification, electrospray, and demulsification, droplets and bubbles are exposed to electric fields and may either remain whole or burst in response to electrical stresses. Determining the stability limit of a droplet exposed to an external electric field has been a long-standing mathematical challenge, and the only analytical treatment to date is an approximate calculation for the particular case of a free-floating droplet. Here we demonstrate, experimentally and theoretically, that the stability limit of a conducting droplet or bubble exposed to an external electric field is described by a power law with broad generality that, in practice, applies to the cases in which the droplet or bubble is pinned or sliding on a conducting surface or free floating. This power law can facilitate the design of devices for liquid manipulation via a simple formula that captures the parameter range of bubbles and droplets that can be supported on electrified surfaces.

Expression of RCK2 MAPKAP (MAPK-activated protein kinase) rescues yeast cells sensitivity to osmotic stress.

BACKGROUND: Saccharomyces cerevisiae is the micro-organism of choice for the conversion of fermentable sugars during beverage or bioethanol fermentations. These fermentations are characterised by high osmotic stress on a yeast cell, with selected brewing fermentations beginning at 20-25% fermentable sugars and bioethanol fermentations at 13% fermentable sugars. RESULTS: RCK2 encodes for a MAPKAP (MAPK-activated protein kinase) enzyme and was identified on a locus by QTL analysis in yeast cells under osmotic stress, RCK2 expression was placed under a tetracycline regulatable vector and rescued glucose, sorbitol or glycerol induced osmotic stress in an rck2 null strain. A strain overexpressing RCK2 had significantly faster fermentation rates when compared with the empty vector control strain. CONCLUSIONS: Presence of RCK2 increased rates of glucose utilisation (~40 g glucose in first 8 h) during a 15% glucose fermentation and concurrent production of ethanol when compared with empty vector controls. Tolerance to osmotic stress using the tetracycline regulatable vectors could be turned off with the addition of tetracycline returning a rck2 null strain back to osmotic sensitivity.

[MRI investigations in patients with problems due to metal-on-metal implants]. / Magnetresonanztomographische Untersuchungen bei Problemen mit Metall-auf-Metall-Implantaten.

Until recently, metal-on-metal (MoM) hip implants were commonly used for joint replacement and resurfacings. Their use has rapidly declined following reports of Frühversagen and soft tissue disease caused by the release of metal debris from the prosthesis. Detection of these soft tissue lesions has proven difficult using conventional imaging techniques and blood metal ion tests. Current guidelines recommend the use of imaging modalities including metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI), computed tomography and ultrasound but provide little indication which is best. MARS significantly reduces the susceptibility artefact induced by the presence of metal objects, thereby producing diagnostic quality images that can be shared with other physicians and compared over time. The clinical interpretation of MRI findings of solid pseudotumours and severe muscle atrophy is straightforward: revision is usually recommended. However, the most common MRI findings are of a cystic pseudotumour and minor muscle wasting. In these cases decision-making is difficult and we currently use multi-disciplinary and multi-colleague based meetings to make decisions regarding patient management. This article presents a comparison of imaging modalities and an update on the interpretation of MARS MRI for the investigation of patients with MoM hip implants.The English full-text version of this article is available at Springer Link (under "Supplemental").

Comparing machine learning algorithms for non-invasive detection and classification of failure in piezoresistive bone cement via electrical impedance tomography.

At an estimated cost of $8 billion annually in the United States, revision surgeries to total joint replacements represent a substantial financial burden to the health care system and a tremendous mental and physical burden on patients and their caretakers. Fixation failures, such as implant loosening, wear, and mechanical instability of the poly(methyl methacrylate) (PMMA) cement, which bonds the implant to the bone, are the main causes of long-term implant failure. Early and accurate diagnosis of cement failure is critical for developing novel therapeutic strategies and reducing the high risk of a misjudged revision. Unfortunately, prevailing imaging modalities, notably plain radiographs, struggle to detect the precursors of implant failure and are often interpreted incorrectly. Our prior work has shown that the modification of PMMA bone cement with low concentrations of conductive fillers makes it piezoresistive and therefore self-sensing. When combined with a conductivity imaging modality such as electrical impedance tomography (EIT), it is possible to monitor load transfer across the PMMA using cost-effective, physiologically benign, non-contact, and real-time electrical measurements. Despite the ability of EIT for monitoring load transfer across self-sensing PMMA bone cement, it is unable to accurately characterize failure mechanisms. Overcoming this challenge is critical to the success of this technology in practice. Therefore, we herein expand upon our previous results by integrating machine learning techniques with EIT for cement condition characterization with the goal of establishing the feasibility of even off-the-shelf machine learning algorithms to address this important problem. We survey a wide variety of different machine learning algorithms for application to this problem, including neural networks on voltage readings of an EIT phantom for tracking the spatial position of a sample, specifying defect orientation within a sample, and classifying defect types, including cracks and delaminations. In addition, we explore the utilization of principal component analysis (PCA) for pre-treating impedance signals in each of these problems. Within the tested algorithms, our results show clear advantages of neural networks, support vector machines, and K-nearest neighbor algorithms for interpreting EIT signals. We also show that PCA is an effective addition to machine learning. These preliminary results demonstrate that the combination of smart materials, EIT, and machine learning may be a powerful instrumentation tool for diagnosing the origin and evolution of mechanical failure in joint replacements.

A modular testbed for mechanized spreading of powder layers for additive manufacturing.

Powder bed additive manufacturing (AM) processes, including binder jetting (BJAM) and powder bed fusion (PBF), can manufacture complex three-dimensional components from a variety of materials. A fundamental understanding of the spreading of thin powder layers is essential to develop robust process parameters for powder bed AM and to assess the influence of powder feedstock characteristics on the subsequent process outcomes. Toward meeting these needs, this work presents the design, fabrication, and qualification of a testbed for modular, mechanized, multi-layer powder spreading. The testbed is designed to replicate the operating conditions of commercial AM equipment, yet features full control over motion parameters including the translation and rotation of a roller spreading tool and precision motion of a feed piston and the build platform. The powder spreading mechanism is interchangeable and therefore can be customized, including the capability for dispensing of fine, cohesive powders using a vibrating hopper. Validation of the resolution and accuracy of the machine and its subsystems, as well as the spreading of exemplary layers from a range of powder sizes typical of BJAM and PBF processes, are described. The precision engineered testbed can therefore enable the optimization of powder spreading parameters for AM and correlation to build process parameters in future work, as well as exploration of spreading of specialized powders for AM and other techniques.

Flexible high-conductivity carbon-nanotube interconnects made by rolling and printing.

Applications of carbon nanotubes (CNTs) in flexible and complementary metal-oxide-semiconductor (CMOS)-based electronic and energy devices are impeded due to typically low CNT areal densities, growth temperatures that are incompatible with device substrates, and challenges in large-area alignment and interconnection. A scalable method for continuous fabrication and transfer printing of dense horizontally aligned CNT (HA-CNT) ribbon interconnects is presented. The process combines vertically aligned CNT (VA-CNT) growth by thermal chemical vapor deposition, a novel mechanical rolling process to transform the VA-CNTs to HA-CNTs, and adhesion-controlled transfer printing without needing a carrier film. The rolling force determines the HA-CNT packing fraction and the HA-CNTs are processed by conventional lithography. An electrical resistivity of 2 mOmega . cm is measured for ribbons having 800-nm thickness, while the resistivity of copper is 100 times lower, a value that exceeds most CNT assemblies made to date, and significant improvements can be made in CNT structural quality. This rolling and printing process could be scaled to full wafer areas and more complex architectures such as continuous CNT sheets and multidirectional patterns could be achieved by straightforward design of the CNT growth process and/or multiple rolling and printing sequences.

High-yield growth of vertically aligned carbon nanotubes on a continuously moving substrate.

Vertically aligned carbon nanotube (CNT) arrays are grown on a moving substrate, demonstrating continuous growth of nanoscale materials with long-range order. A cold-wall chamber with an oscillating moving platform is used to locally heat a silicon growth substrate coated with an Fe/Al2O3 catalyst film for CNT growth via chemical vapor deposition. The reactant gases are introduced over the substrate through a directed nozzle to attain high-yield CNT growth. Aligned multi-wall carbon nanotube arrays (or 'forests') with heights of approximately 1 mm are achieved at substrate speeds up to 2.4 mm s(-1). Arrays grown on moving substrates at different velocities are studied in order to identify potential physical limitations of repeatable and fast growth on a continuous basis. No significant differences are noted between static and moving growth as characterized by scanning electron microscopy and Raman spectroscopy, although overall growth height is marginally reduced at the highest substrate velocity. CNT arrays produced on moving substrates are also found to be comparable to those produced through well-characterized batch processes consistent with a base-growth mechanism. Growth parameters required for the moving furnace are found to differ only slightly from those used in a comparable batch process; thermal uniformity appears to be the critical parameter for achieving large-area uniform array growth. If the continuous-growth technology is combined with a reaction zone isolation scheme common in other types of processing (e.g., in the manufacture of carbon fibers), large-scale dense and aligned CNT arrays may be efficiently grown and harvested for numerous applications including providing interlayers for advanced composite reinforcement and improved electrical and thermal transport.

Analysis of the Attune tibial tray backside: A comparative retrieval study.

OBJECTIVES: The Attune total knee arthroplasty (TKA) has been used in over 600 000 patients worldwide. Registry data show good clinical outcome; however, concerns over the cement-tibial interface have been reported. We used retrieval analysis to give further insight into this controversial topic. METHODS: We examined 12 titanium (Ti) PFC Sigma implants, eight cobalt-chromium (CoCr) PFC Sigma implants, eight cobalt-chromium PFC Sigma rotating platform (RP) implants, and 11 Attune implants. We used a peer-reviewed digital imaging method to quantify the amount of cement attached to the backside of each tibial tray. We then measured: 1) the size of tibial tray thickness, tray projections, peripheral lips, and undercuts; and 2) surface roughness (Ra) on the backside and keel of the trays. Statistical analyses were performed to investigate differences between the two designs. RESULTS: There was no evidence of cement attachment on any of the 11 Attune trays examined. There were significant differences between Ti and CoCr PFC Sigma implants and Attune designs (p < 0.05); however, there was no significant difference between CoCr PFC Sigma RP and Attune designs (p > 0.05). There were significant differences in the design features between the investigated designs (p < 0.05). CONCLUSION: The majority of the earliest PFC Sigma designs showed evidence of cement, while all of the retrieved Attune trays and the majority of the RP PFC trays in this study had no cement attached. This may be attributable to the design differences of these implants, in particular in relation to the cement pockets. Our results may help explain a controversial aspect related to cement attachment in a recently introduced TKA design.Cite this article: A. Cerquiglini, J. Henckel, H. Hothi, P. Allen, J. Lewis, A. Eskelinen, J. Skinner, M. T. Hirschmann, A. J. Hart. Analysis of the Attune tibial tray backside: A comparative retrieval study. Bone Joint Res 2019;8:136-145. DOI: 10.1302/2046-3758.83.BJJ-2018-0102.R2.

Assessment of corrosion in retrieved spine implants.

Recently the use of dissimilar metals in spine instrumentation has increased, especially in the case of adult deformities, where rods made from Cobalt Chrome alloys (CoCr) are used with Titanium (Ti) screws. The use of dissimilar metals increases the risk of galvanic corrosion and patients have required revision spine surgery due to severe metallosis that may have been caused by corrosion. We aimed to assess the presence of corrosion in spine implant retrievals from constructs with two types of material combinations: similar (Ti/Ti) and dissimilar (CoCr/Ti). First, we devised a grading score for corrosion of the rod-fixture junctions. Then, we applied this score to a collection of retrieved spine implants. Our proposed corrosion grading score was proven reliable (kappa > 0.7). We found no significant difference in the scores between 4 CoCr and 11 Ti rods (p = 0.0642). There was no indication that time of implantation had an effect on the corrosion score (p = 0.9361). We recommend surgeons avoid using implants designs with dissimilar metals to reduce the risk of corrosion whilst a larger scale study of retrieved spine implants is conducted. Future studies can now use our scoring system for spine implant corrosion. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 632-638, 2018.

The risk of cardiac failure following metal-on-metal hip arthroplasty.

AIMS: The aim of this study was to determine whether patients with metal-on-metal (MoM) arthroplasties of the hip have an increased risk of cardiac failure compared with those with alternative types of arthroplasties (non-MoM). PATIENTS AND METHODS: A linkage study between the National Joint Registry, Hospital Episodes Statistics and records of the Office for National Statistics on deaths was undertaken. Patients who underwent elective total hip arthroplasty between January 2003 and December 2014 with no past history of cardiac failure were included and stratified as having either a MoM (n = 53 529) or a non-MoM (n = 482 247) arthroplasty. The primary outcome measure was the time to an admission to hospital for cardiac failure or death. Analysis was carried out using data from all patients and from those matched by propensity score. RESULTS: The risk of cardiac failure was lower in the MoM cohort compared with the non-MoM cohort (adjusted hazard ratio (aHR) 0.901; 95% confidence interval (CI) 0.853 to 0.953). The risk of cardiac failure was similar following matching (aHR 0.909; 95% CI 0.838 to 0.987) and the findings were consistent in subgroup analysis. CONCLUSION: The risk of cardiac failure following total hip arthroplasty was not increased in those in whom MoM implants were used, compared with those in whom other types of prostheses were used, in the first seven years after surgery. Cite this article: Bone Joint J 2018;100-B:20-7.

The effect of metal ions in solution on bacterial growth compared with wear particles from hip replacements.

The biological significance of cobalt-chromium wear particles from metal-on-metal hip replacements may be different to the effects of the constituent metal ions in solution. Bacteria may be able to discriminate between particulate and ionic forms of these metals because of a transmembrane nickel/cobalt-permease. It is not known whether wear particles are bacteriocidal. We compared the doubling time of coagulase negative staphylococcus, Staphylococcus aureus and methicillin resistant S. aureus when cultured in either wear particles from a metal-on-metal hip simulator, wear particles from a metal-on-polyethylene hip simulator, metal ions in solution or a control. Doubling time halved in metal-on-metal (p = 0.003) and metal-on-polyethylene (p = 0.131) particulate debris compared with the control. Bacterial nickel/cobalt-transporters allow metal ions but not wear particles to cross bacterial membranes. This may be useful for testing the biological characteristics of different wear debris. This experiment also shows that metal-on-metal hip wear debris is not bacteriocidal.

Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design.

OBJECTIVES: The use of ceramic femoral heads in total hip arthroplasty (THA) has increased due to their proven low bearing wear characteristics. Ceramic femoral heads are also thought to reduce wear and corrosion at the head-stem junction with titanium (Ti) stems when compared with metal heads. We sought to evaluate taper damage of ceramic compared with metal heads when paired with cobalt chromium (CoCr) alloy stems in a single stem design. METHODS: This retrieval study involved 48 total hip arthroplasties (THAs) with CoCr V40 trunnions paired with either CoCr (n = 21) or ceramic (n = 27) heads. The taper junction of all hips was evaluated for fretting/corrosion damage and volumetric material loss using a roundness-measuring machine. We used linear regression analysis to investigate taper damage differences after adjusting for potential confounding variables. RESULTS: We measured median taper material loss rates of 0.210 mm3/year (0.030 to 0.448) for the metal head group and 0.084 mm3/year (0.059 to 0.108) for the ceramic group. The difference was not significant (p = 0.58). Moreover, no significant correlation between material loss and implant or patient factors (p > 0.05) was found. CONCLUSIONS: Metal heads did not increase taper damage on CoCr trunnions compared with ceramic heads from the same hip design. The amount of material released at the taper junctions was very low when compared with available data regarding CoCr/Ti coupling in metal-on-metal bearings.Cite this article: A. Di Laura, H. Hothi, J. Henckel, I. Swiatkowska, M. H. L. Liow, Y-M. Kwon, J. A. Skinner, A. J. Hart. Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design. Bone Joint Res 2017;6:-350. DOI: 10.1302/2046-3758.65.BJR-2016-0325.R1.

The association between metal ions from hip resurfacing and reduced T-cell counts.

We have studied the relationship between metal ion levels and lymphocyte counts in patients with metal-on-metal hip resurfacings. Peripheral blood samples were analysed for lymphocyte subtypes and whole blood cobalt and chromium ion levels in 68 patients (34 with metal-on-metal hip resurfacings and 34 with standard metal-on-polyethylene total hip replacements). All hip components were radiologically well-fixed and the patients were asymptomatic. Cobalt and chromium levels were significantly elevated in the patients with metal-on-metal hip resurfacings, compared with the patients with standard metal-on-polyethylene designs (p < 0.0001). There was a statistically significant decrease in the level of CD8(+) cells (T-cytotoxic/suppressor) (p = 0.005) in the metal-on-metal hip resurfacing group. A threshold level of blood cobalt and chromium ions was associated with reduced CD8(+) T-cell counts. We have no evidence that our patients suffered as a result of this reduced level of CD8(+) T-cells.

Are all metal-on-metal hip revision operations contributing to the National Joint Registry implant survival curves? : a study comparing the London Implant Retrieval Centre and National Joint Registry datasets.

AIMS: The National Joint Registry for England, Wales and Northern Ireland (NJR) has extended its scope to report on hospital, surgeon and implant performance. Data linkage of the NJR to the London Implant Retrieval Centre (LIRC) has previously evaluated data quality for hip primary procedures, but did not assess revision records. METHODS: We analysed metal-on-metal hip revision procedures performed between 2003 and 2013. A total of 69 929 revision procedures from the NJR and 929 revised pairs of components from the LIRC were included. RESULTS: We were able to link 716 (77.1%) revision procedures on the NJR to the LIRC. This meant that 213 (22.9%) revision procedures at the LIRC could not be identified on the NJR. We found that 349 (37.6%) explants at the LIRC completed the full linkage process to both NJR primary and revision databases. Data completion was excellent (> 99.9%) for revision procedures reported to the NJR. DISCUSSION: This study has shown that only approximately one third of retrieved components at the LIRC, contributed to survival curves on the NJR. We recommend prospective registry-retrieval linkage as a tool to feedback missing and erroneous data to the NJR and improve data quality. TAKE HOME MESSAGE: Prospective Registry - retrieval linkage is a simple tool to evaluate and improve data quality on the NJR.

The effect of using components from different manufacturers on the rate of wear and corrosion of the head-stem taper junction of metal-on-metal hip arthroplasties.

AIMS: Surgeons have commonly used modular femoral heads and stems from different manufacturers, although this is not recommended by orthopaedic companies due to the different manufacturing processes. We compared the rate of corrosion and rate of wear at the trunnion/head taper junction in two groups of retrieved hips; those with mixed manufacturers (MM) and those from the same manufacturer (SM). MATERIALS AND METHODS: We identified 151 retrieved hips with large-diameter cobalt-chromium heads; 51 of two designs that had been paired with stems from different manufacturers (MM) and 100 of seven designs paired with stems from the same manufacturer (SM). We determined the severity of corrosion with the Goldberg corrosion score and the volume of material loss at the head/stem junction. We used multivariable statistical analysis to determine if there was a significant difference between the two groups. RESULTS: We found no significant difference in the corrosion scores of the two groups. The median rate of material loss at the head/stem junction for the MM and SM groups were 0.39 mm(3)/year (0.00 to 4.73) and 0.46 mm(3)/year (0.00 to 6.71) respectively; this difference was not significant after controlling for confounding factors (p = 0.06). CONCLUSION: The use of stems with heads of another manufacturer does not appear to affect the amount of metal lost from the surfaces between these two components at total hip arthroplasty. Other surgical, implant and patient factors should be considered when determining the mechanisms of failure of large diameter metal-on-metal hip arthroplasties. Cite this article: Bone Joint J 2016;98-B:917-24.

Assessment of osteoarthritis after reconstruction of the anterior cruciate ligament: a study using single-photon emission computed tomography at ten years.

We used single-photon emission computed tomography (SPECT) to determine the long-term risk of degenerative change after reconstruction of the anterior cruciate ligament (ACL). Our study population was a prospective series of 31 patients with a mean age at injury of 27.8 years (18 to 47) and a mean follow-up of ten years (9 to 13) after bone-patellar tendon-bone reconstruction of the ACL. The contralateral normal knee was used as a control. All knees were clinically stable with high clinical scores (mean Lysholm score, 93; mean Tegner activity score, 6). Fifteen patients had undergone a partial meniscectomy and ACL reconstruction at or before reconstruction of their ACL. In the group with an intact meniscus, clinical symptoms of osteoarthritis (OA) were found in only one patient (7%), who was also the only patient with marked isotope uptake on the SPECT scan compatible with OA. In the group which underwent a partial meniscectomy, clinical symptoms of OA were found in two patients (13%), who were among five (31%) with isotope uptake compatible with OA. Only one patient (7%) in this group had evidence of advanced OA on plain radiographs. The risk of developing OA after ACL reconstruction in this series is very low and lower than published figures for untreated ACL-deficient knees. There is a significant increase (p < 0.05) in degenerative change in patients who had a reconstruction of their ACL and a partial meniscectomy compared with those who had a reconstruction of their ACL alone.

Validation of primary metal-on-metal hip arthroplasties on the National Joint Registry for England, Wales and Northern Ireland using data from the London Implant Retrieval Centre: a study using the NJR dataset.

Arthroplasty registries are important for the surveillance of joint replacements and the evaluation of outcome. Independent validation of registry data ensures high quality. The ability for orthopaedic implant retrieval centres to validate registry data is not known. We analysed data from the National Joint Registry for England, Wales and Northern Ireland (NJR) for primary metal-on-metal hip arthroplasties performed between 2003 and 2013. Records were linked to the London Implant Retrieval Centre (RC) for validation. A total of 67,045 procedures on the NJR and 782 revised pairs of components from the RC were included. We were able to link 476 procedures (60.9%) recorded with the RC to the NJR successfully. However, 306 procedures (39.1%) could not be linked. The outcome recorded by the NJR (as either revised, unrevised or death) for a primary procedure was incorrect in 79 linked cases (16.6%). The rate of registry-retrieval linkage and correct assignment of outcome code improved over time. The rates of error for component reference numbers on the NJR were as follows: femoral head category number 14/229 (5.0%); femoral head batch number 13/232 (5.3%); acetabular component category number 2/293 (0.7%) and acetabular component batch number 24/347 (6.5%). Registry-retrieval linkage provided a novel means for the validation of data, particularly for component fields. This study suggests that NJR reports may underestimate rates of revision for many types of metal-on-metal hip replacement. This is topical given the increasing scope for NJR data. We recommend a system for continuous independent evaluation of the quality and validity of NJR data.

Differential response in the human amygdala to racial outgroup vs ingroup face stimuli.

Here we describe response in the human amygdala to the presentation of racial outgroup vs ingroup faces. Functional magnetic resonance imaging (fMRI) measures of brain activity were acquired while subjects who identified themselves as White or Black viewed photographs of both White and Black faces. Across all subjects, we observed significantly greater blood oxygen-level-dependent (BOLD) signal in the amygdala to outgroup vs ingroup faces, but only during later stimulus presentations. A region of interest (ROI)-based analysis of these voxels revealed a significant interaction between amygdala response to outgroup and ingroup faces over time. Specifically, the greater amygdala activation to outgroup faces during later stimulus presentations was the result of amygdala response habituation to repeated presentations of ingroup faces with sustained responses to outgroup faces. The present results suggest that amygdala responses to human face stimuli are affected by the relationship between the perceived race of the stimulus face and that of the subject. Results are discussed as consistent with a role for the amygdala in encoding socially and/or biologically relevant information. We conclude that researchers seeking to study brain responses to face stimuli in human subjects should consider the relationship between the race of subjects and stimuli as a significant potential source of variance. Moreover, these data provide a foundation for future related studies in the neuroscience of social cognition and race.

Incidence of urethral stricture after transurethral resection of prostate. Effects of urinary infection, urethral flora, and catheter material and size.

Urethral stricture is the most common complication of transurethral resection of prostate, occurring in up to 29 per cent of cases. A prospective trial was initiated to ascertain if the presence of positive urine and urethral bacterial cultures made any significant difference in urethral stricture incidence. One hundred patients were entered in the trial, 50 receiving latex catheters and 50 receiving Teflon catheters. There was no significant difference between the two groups in incidence of urethral stricture, and there was no correlation between positive urine and urethral bacterial cultures and stricture formation. It is suggested, therefore, tha urethral catheter material and size and the presence of organisms in the urine and in the urethra do not contribute significantly to the formation of urethral stricture following transurethral resection of the prostate.