Stripping Rate Research Articles

Galactic satellite systems in CDM, WDM and SIDM

ABSTRACT We investigate the population of bright satellites ($M_{*} \ge 10^{5} \, \mathrm{M}_{\odot }$) of haloes of mass comparable to that of the Milky Way in cosmological simulations in which the dark matter (DM) is either cold, warm, or self-interacting (CDM, WDM, and SIDM, respectively). The nature of the DM gives rise to differences in the abundance and structural properties of field haloes. In WDM, the main feature is a reduction in the total number of galaxies that form, reflecting a suppression of low-mass DM haloes and lower galaxy formation efficiency compared to CDM. For SIDM, the changes are structural, restricted to the central regions of haloes and dependent on the assumed self-interaction cross-section. We also consider different baryonic subgrid physics models for galaxy formation, in which supernova gas blowouts can or cannot induce the formation of a core in dwarf galaxies. Overall, the inclusion of baryons lessen the differences in the halo properties in the different DM models compared to DM-only simulations. This affects the satellite properties at infall and therefore their subsequent tidal stripping and survival rates. None the less, we find slightly less concentrated satellite radial distributions as the SIDM cross-section increases. Unfortunately, we also find that the satellite populations in simulations with baryon-induced cores in CDM and WDM can mimic the results found in SIDM, making the satellite stellar mass and maximum circular velocity functions heavily degenerate on the assumed nature of the DM and the adopted subgrid modelling. These degeneracies preclude using the brightest satellites of the Milky Way to constrain the nature of DM.

Performance Evaluation of Tractor Operated Sugarcane Leaf Stripper through Analysis of Effect of Length, Girth and Number of Buds of Sugarcane

In this present research paper analysis of the performance of tractor-operated sugarcane leaf stripper is performed. India is the second-largest producer of sugarcane and Sugarcane is the most prominent cash crop. The sugarcane harvesting process is labour intensive and takes around 850-1000 working man-hours per hectare when sugarcane is harvested manually and de-trashing alone takes 400 man-hours in manual harvesting procedures for removal of tops.
 Mechanized leaf stripper is developed and fabricated to prevent labour and accident and the performance of the machine is evaluated on MCO-238, K-269 and R-94184 variety of sugarcane. The data regarding de-topping time and stripping rate are taken and the effect of parameters namely Length of, Girth and number of Buds of the stalk are evaluated. The machine was operated at a roller speed of rpm. The results showed that length and number of buds affect the stripping time significantly and the length of stalk and girth of the stalk has a significant impact on the stripping rate. For stripping rate the most dominant and significant factor was the length of the stalk: MOC-238 has 62.35% contribution, K-269 has 78.10% contribution and a case of R-94184 has 60.72% contribution. The second significant factors were girth with the contribution of 33.30%, 20.53% and 36.44% contribution in MCO-238, K-269 and R-94184 varieties respectively. The factor, number of buds remained insignificant.

Experimental analysis of hybrid dryer combined with spiral solar air heater and auxiliary heating system: Energy, exergy and economic analysis

The simultaneous energy and food resources management can be a challenging problem for researchers working in this field. Solar dryers are equipment that can employ solar energy in order to dry degradable food for long-term storage. However, these systems should also utilize an auxiliary energy source because of non-availability of continuous access to the solar radiation. In this paper, a cabin solar dryer equipped with a heating element as an auxiliary heat source has been used to dry four types of products. The tested products consist of apple, kiwi, banana slices, as well as quince julienne strips. The experiments were performed in four days during autumn, when the solar energy had a low level intensity and the heating element was employed for aiding the energy supply. Temperature and humidity have been measured using temperature and humidity sensors mounted at the inlet and outlet of the collector and dryer cabin. Then the thermal efficiency of the collector and the cabin is investigated via the energy and exergy analysis, and the thermal performance of the system is analyzed. Lastly, an economic analysis is presented to calculate the production cost of per kilogram of products. The results show that thermal efficiency, drying process exergy, produced exergy and specific moisture evaporation rate (SMER) of julienne strips of quince are higher than those of other products. Although banana slices have better conditions in terms of these parameters among the sliced products. Due to the results, it was found that the quince julienne strips have the highest cost about 1.137 $/kg and the lowest drying rate about 0.188 kg/h. On the contrary, the minimum cost belongs to the apple slices about 0.478 $/kg and the maximum drying rate about 0.3224 kg/h.

Rapid detection of porcine circovirus type 2 by a red latex microsphere immunochromatographic strip.

To establish a rapid and specific antigen detection method for porcine circovirus type 2 (PCV2), monoclonal antibodies (mAbs) were produced against the PCV2 epidemic strains and a red latex microsphere immunochromatographic strip was established. A total of eight anti-PCV2b and four anti-PCV2d mAbs were produced, and seven mAbs were confirmed to react with PCV2a, PCV2b, and PCV2d strains using an immunoperoxidase monolayer assay. The results of micro-neutralization tests showed that the mAbs 2C8, 9H4, 10G7, 7B9, and 7C7 had good neutralizing activity, whereas the neutralizing activity of the mAbs 4B3, 4C9, 6H9, and 7E2 was lower than 50%. Three mAbs, 4B3, 7C7, and 9H4, and PCV2 pAb were selected for the establishment of a red latex microsphere immunochromatographic strip, and the combination of mAb 7C7 labeled with red latex microspheres and mAb 9H4 exhibited the greatest detection ability. The immunochromatographic strip had minimum detection limits of 102.5 TCID50/0.1 ml, 100.7 TCID50/0.1 ml, and 101.5 TCID50/0.1 ml for PCV2a/CL, PCV2b/MDJ, and PCV2d/LNHC, respectively. Furthermore, no cross-reactivity was found for African swine fever virus, classical swine fever virus, porcine respiratory and reproductive syndrome virus, porcine parvovirus, porcine pseudorabies virus, porcine circovirus type 1, transmissible gastroenteritis virus, porcine epidemic diarrhea virus, porcine rotavirus, or porcine deltacoronavirus using the immunochromatographic strip. Using PCR as a reference standard, the detection sensitivity, specificity, and overall coincidence rate of the immunochromatographic strip were 81.13%, 100%, and 90.00%. Additionally, the detection ability of the immunochromatographic strip was correlated with that of virus titration. The immunochromatographic strip was used to detect 183 clinical disease samples, and the average positive detection rate was 22.95%. In summary, this method has good sensitivity and specificity and is simple, convenient, and quick to operate. It has high application value for on-site diagnosis of PCV2 and virus quantification.Key points• A red latex microsphere immunochromatographic strip for PCV2 detection was developed.• The method was not only simple to operate, but also takes less time.• The method had good sensitivity and specificity.

Alleviating segregation and enhancing tensile properties of Inconel 718 superalloy by twin-roll casting and two-stage cold rolling

A novel processing route involving twin-roll casting and two-stage cold rolling was proposed to manufacture Inconel 718 alloy. Due to the sub-rapid solidification rate (412.5 °C/s) of as-cast strip, the element segregation can be alleviated and the growth of Laves phase was effectively suppressed. It was also observed that the dissolution of Laves phases during subsequent homogenization was significantly accelerated because of their refined size. The corresponding homogenization time can be shortened from dozens of hours to 1 h. Additionally, the non-uniform microstructure of cold-rolled and annealed samples caused by coarse grains from homogenization treatment can be eliminated by two-stage cold rolling method. Furthermore, a large amount of granular δ phases precipitated during intermediate annealing. After double aging treatment, the final products exhibited an excellent combination of strength and elongation. The ultimate tensile strength when deformed at room temperature and at 650 °C were about 1475 and 1120 MPa, and the corresponding total elongation were ∼ 15% and ∼ 22%. These results indicated that the twin-roll casting was a promising route to produce Inconel 718 alloy.

Investigating Li Plating Distribution Caused By a Thermal Gradient through Modelling, Differential Voltage, and Post-Mortem Analysis

Relatively slow charging speeds are often quoted as a key barrier to customer acceptance of EVs. Currently, the charging rates are limited primarily by the risk of lithium plating. While traditionally lithium plating has been associated with low temperature charging, recent reports point to the fact that thermal heterogeneity can significantly affect the plating behaviour, sometimes making it more likely or accelerated in the warmer regions in a cell [1][2]. In EVs, through-plane thermal gradients often develop across individual pouch cells due to the widespread use of surface cooling, particularly during fast charging, when the heat generation rates are also increased. This work investigates the effects of such through-plane thermal gradients on the lithium plating behaviour using a multilayer 2D electrochemical-thermal model and high-rate cycling experiments. The results show that the thermal gradient can result in preferential plating in either the colder or warmer cell regions, depending on the average cell temperature and the activation energies of solid diffusion and lithium plating. While the diffusion rates are slower in the colder cell layers, warmer ones attract higher currents and either of these effects may dominate the plating behaviour. The experimental validation consists of differential voltage analysis, post-mortem visual examination and measurement of remaining capacity in coin cells harvested from Li-ion cells fast charged under uniform temperatures and under thermal gradients. The limitations of DVA as a technique to quantify lithium plating are highlighted. These stem from the fact that the quantification technique requires assuming that only lithium stripping and no de-intercalation takes place up to the differential voltage minimum. In reality, the current is divided between both reactions, and both the temperature and concentration of the metallic lithium may affect the rate of stripping, shifting the location of the minimum independently of the amount of lithium plated. The results shed light on the effects of thermal gradients on lithium plating behaviour in pouch cells and the challenges associated with quantifying plating with DVA.

Expression of NDV HN protein in rice and development of a semi-quantitative rapid method for detection of antibodies

The aim of this study was to develop a semi-quantitative immunochromatographic method for rapid detection of Newcastle disease virus (NDV) antibodies by expressing HN protein in rice endosperm bioreactor. The recombinant plasmid pUC57-HN was digested by MlyⅠ and XhoⅠ to retrieve the HN gene, while the intermediate vector pMP3 containing promoter, signal peptide and terminator was digested by NaeⅠ and XhoⅠ. The HN gene and the linearized pMP3 were purified and ligated to form a recombinant plasmid pMP3-HN1. Subsequently, pMP3-HN1 and plant vector pCAMBIA1300 were digested by EcoRⅠ and Hind Ⅲ, and the HN1 gene was cloned into pCAMBIA1300. The recombinant plasmid pCAMBIA1300-HN1 was introduced into Agrobacterium tumefaciens EHA105 by electrotransformation, and the pCAMBIA1300-HN1 was transferred into rice callus by agrobacterium-mediated method. After dark culture, callus screening, differentiation, rooting and transplanting, transgenic rice seeds were obtained 4 months later. PCR identified that the HN gene has been inserted into the rice genome. SDS-PAGE and Western blotting indicated that the HN protein was successfully expressed in the positive rice endosperm. The purity of the HN protein was more than 90% by SP cation exchange chromatography and gel filtration chromatography. According to the national standards for the diagnostic techniques of Newcastle disease HI test (HI≥4log2, positive antibody reaction), a colloidal gold labeled purified HN protein was used to prepare a semi-quantitative test strip by double-antibody sandwich method for rapid detection of NDV antibody. The results showed that the test strip did not cross-react with positive sera against other viruses, and the sensitivity of the test strip reached 1:102 400 for standard positive sera of Newcastle disease. Testing of a total of 308 clinical sera showed that the compliance rate of the test strip with HI test was 97.08%, and the Kappa value was 0.942. In conclusion, high purity recombinant HN protein was obtained from rice endosperm, and a simple, rapid, highly sensitive and highly specific semi-quantitative immunochromatographic strip was developed. The test strip could be used for immune evaluation of the Newcastle disease vaccine.

Experimental Study on the Dust-Cleaning Performance of New Structure Microporous Membrane Filter Plate

On the basis of the existing dust collector structure, this study designed a fan-shaped new structure microporous membrane filter plate (NSMMFP). The pressure distribution law of the NSMMFP can be obtained by measuring the wall surface peak pressure under different injection pressures. The powder attachment experiment was carried out to explore the influence of the dust moisture content on the dust stripping rate (DSR), and a high-speed camera was used to observe the peeling process of the dust. The results show that the peak pressure of each measuring point and the average wall surface peak pressure gradually increase with the injection pressure. The dust stripping quality (DSQ) and rate show an increasing trend as a whole as the injection distance. The DSR of the filter plate shows a downward trend when the dust quality G increases, while DSQ shows the opposite trend. Furthermore, as the dust moisture content increases, the DSQ and DSR gradually decrease. As the dust moisture content increases, the dust attached to the surface of the filter plate is more fragmented and peels from the surface of the filter plate during the dust cleaning process.

Estimation of Model Parameters in the Extraction of Cr(VI) from Wastewater by an Emulsion Liquid Membrane

AbstractKinetic modeling of an emulsion liquid membrane for extraction of hexavalent chromium from wastewater was performed. The membrane was prepared by using Span 80, di‐(2‐ethylhexyl)phosphoric acid (D2EHPA), and kerosene as non‐ionic surfactant, carrier, and diluent, respectively. The rate constants of extraction and stripping phases were calculated by studying the effect of the concentration of HCl in the feed, the concentration of the carrier in the membrane, and the pH of the stripping phase. It was found that the rate of complex diffusion due to the difference between the extraction and stripping rates influences the transfer and Cr(VI) buildup in the membrane phase.

Characterization of the integrated gas stripping-condensation process for organic solvent removal from model acetone-butanol-ethanol aqueous solution

During ABE fermentation, the bacterial toxicity of produced solvents, especially butanol at a high concentration, can cause low butanol productivity. This study aimed to characterize an integrated gas stripping and novel ABE recovery system using two-stage condensation equipped with an absorption unit for butanol recovery from the model ABE aqueous solution. The potential off-gas from ABE fermentation had 20–60% H2 balanced with CO2, along with low-cost inert N2 as stripping gas mix, at the volume of gas per volume of liquid per minute (vvm) set at 0.5, 1.0, and 1.5. The results showed that butanol was the most selective in the stripping, followed by acetone, ethanol, butyric, and acetic. The trend of stripping rate was opposite to the trend of condensation efficiency. Using 1.5 vvm nitrogen could achieve the highest stripping efficiency with butanol removal rate of 1.48 g/L·h, while the highest condensation efficiency of stripped ABE was obtained by using 20% H2 in gas mix at 0.5 vvm. The recovered butanol in condensate had high concentrations of 80–170 g/L. According to the results obtained, the integrated stripping process has potential to reduce butanol in fermentation broth and produce concentrated butanol in condensate that can be further purified at reduced energy cost.

Separation of aluminum from rare earth by solvent extraction with4-octyloxybenzoic acid

Leaching method is usually used to extract rare earth (RE) elements from ion adsorbed RE ores. In the leaching process, some impurities such as aluminum (Al) enter the leaching solution. The separation of Al from RE by carboxylic acid extractant 4-octyloxybenzoic acid (POOA) was studied in this article. By changing the pH value, temperature, solvent, saponification degree and other parameters, the extraction and separation performance of POOA in chloride system was systematically studied. Through specific extraction experiments and slope analysis, it can be seen that the stoichiometric ratio of POOA to Al is 3:1 during the extraction process. The separation factor of Al3+ and Pr3+ can reach about 160.00. Compared with easily emulsified naphthenic acid, POOA achieves better phase separation. The above results show that saponified POOA (S-POOA) has a good separation effect on Al and RE. Under the condition of low concentration stripping acid of 0.60 mol/L HCl, the developed extraction system can be almost completely stripped, and the stripping rate reaches 97.52%. The regenerated POOA can be directly used for the recycling extraction.

Study on Reduction Stripping Kinetics of Ce4+ Using a Constant Interfacial Area Cell with Laminar Flow

The reduction stripping kinetics of Ce4+ by HEH/EHP was studied by a constant interfacial area cell with laminar flow. The effects of stirring speed, temperature, specific interfacial area, Ce4+ concentration in the organic phase, free extractant concentration in the organic phase, HCl concentration, and H2O2 concentration on the stripping rate were investigated. The control mode and control steps of stripping process were judged. The kinetic equation of stripping was derived. The mechanism of stripping process was discussed. The results show that the stripping process is controlled by both diffusion and interfacial chemical reaction. The apparent activation energy Ea was calculated using Arrhenius’s formula. The kinetic equation of Ce4+ reduction stripping is R = k[Ce4+](o)1.08[HEH/EHP](o)−1.03[H+](a)0.99[H2O2](a)0.53, and the apparent rate constant k is 10−3.66 (mol−0.57·L0.57)/min.

Efficient separation and recovery of gallium and indium in spent CIGS materials

• An innovative technology: roasting-leaching-extraction separation was proposed. • Cu, In, Ga and Se were efficiently extracted from spent CIGS materials. • The efficient separation of Cu, In and Ga from HCl leach liquor was optimized. Spent copper indium gallium selenide (CIGS) materials are considered a viable resource for the recovery of Cu, In, Ga, and Se. The oxidative roasting-leaching-extraction separation scheme for the recovery of these valuable metals is proposed. Spent CIGS materials were first roasted to transform Cu, In, and Ga from selenides to oxides and volatilize Se. Hydrochloric acid was then used to leach the oxides. The optimum leaching conditions are as follows: acid concentration of 4 mol/L, temperature of 80 °C, leaching time of 3 h, and liquid–solid ratio of 10 mL/g. The leaching rates of Cu, In, and Ga were 99.98%, 93.40%, and 96.86%, respectively. Finally, In and Ga were sequentially extracted from the solution by P204. Through solvent extraction, the extraction rate of In can reach 99.92%, that of Ga can exceed 99.34%, and Cu is hardly extracted. Meanwhile, using hydrochloric acid as the stripping agent, the stripping rates of In and Ga were 99.90% and 99.93%, respectively. Results suggest that the efficient recovery and separation of Cu, In, and Ga in spent CIGS materials can be achieved.

A novel synergistic extraction system for the recovery of scandium (III) from sulfuric acid medium with mixed Cyanex923 and N1923

High extraction capability and outstanding selectivity are very attractive in the solvent extraction process. Scandium (Sc(III)), as a primary rare earth element (REE), generally lacks independent large-scale deposits and is mainly recovered as a by-product during the processing of mineral. However, the difficulty of stripping has been always a crucial problem to be solved in the scandium extraction system. This study aims to improve stripping performance while enhancing extraction efficiency for scandium. Herein, a novel synergistic extraction system for the recovery of scandium with a mixture of Cyanex923 (A, a mixture of four trialkylphosphine oxides) and N1923 (B, primary amine R1R2CHNH2) in sulfuric acid medium was put forward. The effect of the molar fraction (X) of Cyanex923 on the extraction of scandium was systematically investigated. The experimental results demonstrated that the coupled Cyanex923-N1923 exhibited an obvious synergistic effect on Sc(III). The maximum synergistic enhancement coefficient (Rmax) was calculated to be 2.20 when the molar fraction (X) of Cyanex923 was 0.4, and the H2SO4 concentration was 0.25 mol·L−1. Moreover, the synergistic extraction mechanism was discussed combined with multiple techniques including slope analysis method, FT-IR and NMR characterizations, to which the structure of extracted complexed was deduced to be Sc(SO4)1.5∙(A)0.5(B). Thermodynamic experiment was also explored in detail. More importantly, stripping with only 2 mol·L−1 HNO3 produced a relatively high stripping rate of 95%. The synergistic system still presented excellent reusability even after five treatment cycles. Finally, this study pointed out a potential industrial application value for the separation and recovery of Sc(III) from the sulfuric acid leaching liquor of nickel laterite ores.

Lexicographic goal programming approach for a short-term mining planning problem

This article addresses a short-term mining planning problem. There are four objectives to be minimized: the deviations in grades and ore proportion in particle size ranges of the plant goals, the deviation in the waste mass to achieve the stripping rate, and the number of truck trips between mining fronts and discharges. The problem was solved through the lexicographical goal programming (LGP) method, which generates solutions that can guarantee a more comprehensive analysis of the decision-making process. The LGP method was tested by using several scenarios of a Brazilian mining company. These scenarios differ in the number of excavators and the tolerances concerning meeting the plants' ore grades. In the results, the impact on the values of the other objectives is analysed of varying the number of excavators and the tolerances in the plants' grade targets.

Model-based identification of biological and pH gradient driven removal pathways of total ammonia nitrogen in single-chamber microbial fuel cells

Experimental data that allow for a precise identification of the total ammonia nitrogen (TAN) elimination pathways in single-chamber microbial fuel cells (SC-MFCs) are still very rare. However, nitrification–denitrification and ammonia volatilization are commonly reported as the two main removal mechanisms. This work presents a mathematical model to quantify the contribution of volatilization to TAN removal in SC-MFCs. For model verification, three different experimental settings were performed with TAN concentrations of 57 to 111mgNL−1: (i) biotic tests using sealed cathode chambers with variable oxygen supply, (ii) biotic tests for determination of the pH gradient within the cathodic microenvironment and (iii) pH-induced abiotic gas release tests. In biotic tests, the TAN removal rate in closed-circuit was 29–37% higher compared to open-circuit mode, which indicated additional electrochemical conservation processes. A limitation of oxygen availability on the air-facing side of the cathode (0.1%) resulted in negligible TAN removal rates. In contrast, an atmospheric oxygen content of 21% increased the biological oxidation rate of TAN to 653–730mgNm−2Catd−1and the electrochemical ammonia stripping rate to 210–241mgNm−2Catd−1 at 22 °C. During electricity generation, a peak pH value of 9.6 was measured by microelectrode measurements, which might lead to free ammonia nitrogen concentrations of 39–40mgFANL−1 nearby the cathode surface. Based on the proposed model and assuming an inhibition of ammonium-oxidizing bacteria, a maximum TAN removal rate via ammonia volatilization of 785mgNm−2Catd−1 (T = 22 °C) at a current density of 322 mA m−2Cat is estimated.

Selective separation of Sc(III) and Zr(IV) from the leaching of bauxite residue using trialkylphosphine acids, tertiary amine, tri-butyl phosphate and their mixtures

• It is proposed a scandium and zirconium separation from bauxite residue. • All zirconium was separated using Alamine 336 10% in kerosene. • D2EHPA+TBP mixture reached same separation factor for scandium than Cyanex 923. • Cyanex 923 scrubbing may be carried out with HCl with negligible scandium losses. • The process is strictly connected to the SDGs 7, 8, 9, and 12. The separation of scandium from the solution generated in acid leaching is one of the main challenges for the hydrometallurgical processing of bauxite residue. Several organic extractants were evaluated, being the most prominent phosphine acids, while amine-based compounds have shown great results for separating metallic ions. The present study aims at the separation of scandium and zirconium from the Brazilian bauxite residue. The acid leaching was carried out using 20% of H 2 SO 4 , S/L ratio equals 1/10, for 8 h at 90 °C. Further, solvent extraction experiments were carried out using D2EHPA, Cyanex 923, and Alamine 336 diluted in kerosene, evaluating the effect of pH, temperature, extractant concentration, synergism with TBP and A/O ratio. After optimizing various process parameters, Alamine 336 has obtained separation factors of Zr/Al, Zr/Fe, and Zr/Ti equal to 15150, 45054, and 19713, respectively, at pH 1.0, A/O ratio equals to 1:1 and 25 °C. The stripping rate achieved 92% using Na 2 CO 3 0.25 mol/L. The scandium separation ratio reached higher values for 10% of Cyanex Cyanex 923 than D2EHPA 10% + TBP 5%. Scrubbing for contaminants removal may be carried out using HCl 5 mol/L with 0.1% of scandium losses, and all scandium was stripped by H 3 PO 4 5 mol/L. Despite the works reported in the literature, there a few of them exploring the recovery of scandium and zirconium by the leaching-solvent extraction process. The flowchart proposed is strictly connected to the sustainable development goals 7, 8, 9, and 12.

Stripping of carbon coatings in radio-frequency inductively coupled plasma of H2/Ar

This article describes the stripping of amorphous carbon (a-C) coatings in an H 2 /Ar atmosphere using a radio-frequency inductively coupled plasma (RF-ICP) source. The power of the RF-ICP source, atmosphere composition (H 2 /Ar) and bias potential strongly affect the stripping rate (0.7–9.3 μm/h), while the operating pressure has less influence (2.7–3.2 μm/h). The selectivity of stripping of a-C and titanium coatings can be varied from 1 up to ~90 by changing the atmosphere composition. Chemical sputtering plays a key role in the productivity and selectivity of carbon stripping, it should have a higher rate compared to physical sputtering to enable high selectivity of coating stripping. Raman spectroscopy reveals the increase in graphitization degree and decreasing less ordered carbon of a-C coatings under stripping in H 2 /Ar plasma. Phase transformations of sublayer or substrate materials could occur under coating stripping in a reactive atmosphere in the example of hydride formation (TiH 2-x ) in a Ti sublayer. • Stripping of carbon coatings in RF-ICP plasma of H 2 /Ar. • Stripping selectivity of carbon coatings is regulated by H 2 /Ar flow rates. • Graphitization of a-C coatings under stripping in H 2 /Ar plasma.

Screw stripping and its prevention in the hexagonal socket of 3.5-mm titanium locking screws

There have been several reports about the difficulties in removing 3.5-mm titanium locking screws from plates due to the stripping or rounding of the hexagonal screw socket. We investigated whether stripping the locking screw sockets can be prevented by using different screwdrivers or interposing materials into the socket during removal. We overtightened 120 3.5-mm titanium locking screws (Depuy Synthes, Paoli, PA) equally into locking plates on sawbone tibia models, applying a uniform torque of 4.5 Nm, exceeding the recommended torque of 1.5 Nm. Twenty screws each were removed using a straight-handle 2.5-mm screwdriver, T-handle screwdriver, hex key wrench, and straight-handle screwdriver with a non-dominant hand. In addition, 20 screws were removed using foil from a suture packet inserted into the screw socket or using parts of a latex glove inserted into the screw socket. The incidence rates of screw stripping using the straight-handle screwdriver, T-handle screwdriver, hex key wrench, non-dominant hand, foil interposition, and latex glove interposition were 75%, 40%, 35%, 90%, 60%, and 70%, respectively. When a T-handle screwdriver or hex key wrench was used, the probability of screw stripping was 4.50 times (odds ratio = 4.50, 95% confidence interval = 1.17 to 17.37, p = 0.03) and 5.57 times (odds ratio = 5.57, 95% confidence interval = 1.42 to 21.56, p = 0.01) lower than that with the straight-handle screwdriver, respectively. Foil or latex glove interpositions did not prevent screw stripping. Thus, in the current experimental study, T-handle screwdriver or hex key wrench usage decreased the incidence rate of screw stripping during removal compared to straight-handle screwdriver use.

Screw tightness and stripping rates vary between biomechanical researchers and practicing orthopaedic surgeons

BackgroundScrews are the most frequently inserted orthopaedic implants. Biomechanical, laboratory-based studies are used to provide a controlled environment to investigate revolutionary and evolutionary improvements in orthopaedic techniques. Predominantly, biomechanical trained, non-surgically practicing researchers perform these studies, whilst it will be orthopaedic surgeons who will put these procedures into practice on patients. Limited data exist on the comparative performance of surgically and non-surgically trained biomechanical researchers when inserting screws. Furthermore, any variation in performance by surgeons and/or biomechanical researchers may create an underappreciated confounder to biomechanical research findings. This study aimed to identify the differences between surgically and non-surgically trained biomechanical researchers’ achieved screw tightness and stripping rates with different fixation methods.MethodsTen orthopaedic surgeons and 10 researchers inserted 60 cortical screws each into artificial bone, for three different screw diameters (2.7, 3.5 and 4.5 mm), with 50% of screws inserted through plates and 50% through washers. Screw tightness, screw hole stripping rates and confidence in screw purchase were recorded. Three members of each group also inserted 30 screws using an augmented screwdriver, which indicated when optimum tightness was achieved.ResultsUnstripped screw tightness for orthopaedic surgeons and researchers was 82% (n = 928, 95% CI 81–83) and 76% (n = 1470, 95% CI 75–76) respectively (p < 0.001); surgeons stripped 48% (872/1800) of inserted screws and researchers 18% (330/1800). Using washers was associated with increased tightness [80% (95% CI 80–81), n = 1196] compared to screws inserted through plates [76% (95% CI 75–77), n = 1204] (p < 0.001). Researchers were more accurate in their overall assessment of good screw insertion (86% vs. 62%). No learning effect occurred when comparing screw tightness for the first 10 insertions against the last 10 insertions for any condition (p = 0.058–0.821). Augmented screwdrivers, indicating optimum tightness, reduced stripping rates from 34 to 21% (p < 0.001). Experience was not associated with improved performance in screw tightness or stripping rates for either group (p = 0.385–0.965).ConclusionsSurgeons and researchers showed different screw tightness under the same in vitro conditions, with greater rates of screw hole stripping by surgeons. This may have important implications for the reproducibility and transferability of research findings from different settings depending on who undertakes the experiments.