Fill Ratio Research Articles

Optimizing Closed Loop Pulsating Heat Pipes (CL-PHPs) using Taguchi method enhancing thermal performance and operational parameters

Closed Loop-Pulsating Heat Pipes (CL-PHPs) are a promising heat transfer technologies known for their efficient and versatile thermal management capabilities. This study presents a comprehensive analysis of CL-PHPs employing Taguchi method. It's a statistical technique to optimization enhance their performance. The research involves the utilizing an 8-turn pulsing heat pipe and a variety of working fluids aqueous mixtures, including Water with acetone, methanol, ethanol and water. An optimal CL-PHP performance was achieved while incorporation of optimization techniques for the selected operational parameters such as thermal resistance, heat supply, angle of orientation, type of fluid and filling ratio. The optimization process aims to improve various operational parameters impact such as the thermal resistance performance of CL-PHPs were examined, including fill ratio, heat input, angle of inclination, working fluid, etc. to attain optimal CL-PHP performance. The performance parameters orthogonal array were studied using ANOVA and analysis of variance. Experiments with changing the input parameters were carried out using the Taguchi L27 orthogonal array. The performance of CL-PHP was mostly effected by heat supply along with inclination angle and fill ratio to some extent. The optimization results indicate that the most important element affecting CL-PHP performance is heat input, which is followed by fill ratio and angle of inclination. This research contributes to the advancement of thermal management technologies and underscores the potential benefits of CL-PHPs in various engineering applications A maximum deviation of with ±8 % divergence from the anticipated values is obtained among the test runs that are considered random.

High-performance electromagnetic wave absorption by two-dimensional mesoporous monolayer Ti3C2Tx MXene

Transition metal carbide MXene, with its unique chemical composition, structure and sizeable particular surface area, is widely applied in wave absorption. However, the high conductivity of MXene resulted in an impedance mismatch that prevented electromagnetic waves from entering the material to achieve dissipation, and thus, tuning the intrinsic properties of pure MXene to obtain excellent electromagnetic wave absorption is still a challenge. Here, we strengthen the absorption of electromagnetic waves by generating titanium vacancies through hydrogen peroxide etching and thus forming micro-sized wrinkles with porous MXene. Porous MXene possesses an excellent microstructure and surface state, abundant porous defects, and moderate electrical conductivity, allowing it to achieve well-matched impedance, dipole polarization, and conduction loss, thus inheriting excellent electromagnetic wave absorption (EWA) properties. Therefore, the porous MXene achieves a strong absorption of − 63.31 dB and an adequate absorption bandwidth (EAB) of 6.88 GHz at a matched thickness of 2.39 mm with a fill ratio of 6 wt%.

Outcomes of conversion total hip arthroplasty for failed fixation of intertrochanteric fractures with monoblock distal-loading reconstruction stem.

The aim of our study was to analyze the clinical and radiological outcomes of conversion total hip arthroplasty (THA) for failed fixation of proximal femur fractures with monoblock grit-blasted titanium reconstruction stem (Wagner self-locking stem, Zimmer). Thirty-nine patients were included in this retrospective analysis undergoing conversion THA for failed cephalomedullary nail or dynamic hip screw fixation for intertrochanteric fractures from January 2017 to January 2022. The clinical evaluation was done using Harris hip score. The radiological outcomes measured were subsidence, level of osteointegration, stem-canal fill ratio and heterotopic bone formation. The complications were noted postoperatively and during the follow-up. The mean follow-up at the end of the study was 27.8months (range, 14-72months). There was a significant improvement in the Harris hip score over serial follow-ups (p < 0.001), but after 2years, there was no statistically significant difference (p = 0.46). According to Engh's criteria, stable ingrowth was noted in 35 stems, fibrous stable ingrowth was noted in 4 stems and no patients had progressive subsidence and unstable stem. The mean stem-canal fill percentages were 91.8 ± 5.4% at the mid-stem and 80.3 ± 11.5% at the stem tip. Heterotopic ossification Brooker grade 2 was noted in 8 patients, and no patients had grade 3 or 4 heterotopic ossification. There were 7 (17.9%) intraoperative periprosthetic fractures, and greater trochanteric avulsion was noted in 2 patients in the follow-up. Conversion THA using monoblock tapered distal loading stems bypasses the calcar deficiency and gives stable fixation in failed fixation of intertrochanteric fractures. It gives good radiological outcome and significant improvement in the clinical outcomes compared to the preoperative disability. However, caution should be noted for risk of intraoperative periprosthetic fractures in this subgroup of patients.

Enhancing the Thermal Conductivity of CNT/AlN/Silicone Rubber Composites by Using CNTs Directly Grown on AlN to Achieve a Reduced Filler Filling Ratio.

Achieving the thermal conductivity required for efficient heat management in semiconductors and other devices requires the integration of thermally conductive ceramic fillers at concentrations of 60 vol% or higher. However, an increased filler content often negatively affects the mechanical properties of the composite matrix, limiting its practical applicability. To address this issue, in this paper, we present a new strategy to reduce the required ceramic filler content: the use of a thermally conductive ceramic composite filler with carbon nanotubes (CNTs) grown on aluminum nitride (AlN). We combined catalyst coating technology with vacuum filtration to ensure that the catalyst was uniformly applied to micrometer-sized AlN particles, followed by the efficient and uniform synthesis of CNTs using a water-assisted process in a vertical furnace. By carefully controlling the number of vacuum filtration cycles and the growth time of the CNTs, we achieved precise control over the number and length of the CNT layers, thereby adjusting the properties of the composite to the intended specifications. When AlN/CNT hybrid fillers are incorporated into silicone rubber, while maintaining the mechanical properties of rubber, the thermal diffusivity achieved at reduced filler levels exceeds that of composites using AlN-only or simultaneous AlN and CNTs formulations. This demonstrates the critical influence of CNTs on AlN surfaces. Our study represents a significant advancement in the design of thermally conductive materials, with potential implications for a wide range of applications.

Effect of Filling Ratio-Pattern Parameters on Mechanical Properties of PLA Filaments Used in 3D Printing

This research primarily focuses on the mechanical properties of specimens produced using Polylactic Acid (PLA) through the Fused Deposition Modeling (FDM) technique, a method of 3D printing. Within the scope of this study, specimens were fabricated using various fill percentages and different infill patterns. The simultaneous effect of variable parameters on mechanical properties is a challenging task, and it is aimed to rank the importance of the parameters, model the process, and finally validate the models using tensile and bending experiments. The results show that samples with a Concentric pattern and 95% fill rate exhibited the highest tensile strength with an average of 48.67 MPa. In contrast, the Triangle pattern with 20% infill ratio showed the lowest tensile strength with an average of 14.15 MPa. When evaluating flexural strength values, the Concentric design with a 95% fill ratio stood out once again, recording an average peak value of 79.94 MPa. Meanwhile, the Honeycomb pattern at 20% infill ratio exhibited the lowest strength value measured with an average of 23.3 MPa. Scanning Electron Microscope images taken according to infill rates confirm each other with the voids formed and mechanical performance outputs. These findings underscore that the mechanical attributes of PLA specimens produced using 3D printing technology can significantly vary based on the chosen fill rate and pattern.

Investigation of operational limit of a pulsating heat pipe by estimating local heat transfer

How pulsating heat pipes (PHPs) reach their operational limit has not yet been fully understood. This study aims to provide a complete picture of the termination mechanism of the self-oscillation of vapor and liquid. Experimental studies on a 10-turn PHP with HFC-134a were conducted and the filling ratio (FR) was from 20% to 80%. The thermo-fluid behavior in the PHP was investigated by temperature measurements with a high-resolution and high-speed infrared camera and estimation of fluid-to-wall heat flux distributions by solving inverse heat conduction problems. The results suggested that the PHP, increasing heat load, reached the operational limit due to different mechanisms depending on the filling ratio: at a high FR (80%), the liquid volume ratio increased with the increase of the operating temperature, resulting in the compressed liquid phase. At a low FR (20%), when a large amount of heat was applied, the fluid in the evaporator dried out and became a superheated vapor. The PHP with an optimum FR (50%) transferred the maximum heat under the same evaporator temperature, as the fluid in the PHP was able to keep the saturated two-phase state until the evaporator temperature exceeded the critical temperature.

On the hydrostatic limit for thin film flow with applications to thermosyphons

Heat pipes frequently encounter challenges in effectively returning condensed liquid from the condenser to the evaporator through capillary pumping, which limits their overall efficacy. When capillary pumping becomes irrelevant due to factors like the absence of wick, or overfilling, the heat pipe is more properly termed as thermosyphon. In a close-to-horizontal orientation, the driving force for liquid return in a thermosyphon relies on the difference in liquid pool depth between the evaporator and condenser. An excessively deep liquid pool in the condenser can hinder radial heat transfer, necessitating a design that favours intermediate-depth liquid pools. This study utilizes a theoretical approach based on the lubrication approximation to the Navier–Stokes equations to determine the fill ratio that maximizes thermosyphon performance. We explore the relationship between this fill ratio and factors such as the axial temperature difference along the thermosyphon. Our analysis thereby highlights the hydrostatic-driven flow limit in the thermosyphon as an analogue to the capillary limit in heat pipes. Regarding the hydrostatic limiting curve as an alternative to the capillary limiting curve offers valuable insights for enhancing thermosyphon performance and provides means of comparing the performance of one vs. the other passive heat transfer device.

Teflon AF–Coated Nanotextured Aluminum Surfaces for Jumping Droplet Thermal Rectification

AbstractJumping droplet thermal diodes (JDTDs) are promising candidates to achieve thermal rectification for next‐generation thermal control. However, most prior demonstrations of JDTDs have relied on monolayer‐coated copper‐based superhydrophobic (SHPB) surfaces, while lower‐cost aluminum JDTDs with more durable thin polymeric coatings have not been explored. In this work, a JDTD is constructed that employs SHPB aluminum surfaces coated with protective thin films of Teflon AF (amorphous fluoropolymer) 1601. Measurements for different heating orientations, gap heights (H), and fill ratios (ϕ) show that a maximum thermal rectification ratio of 7 can be achieved for H = 2.4 mm and ϕ = 10%. A thermal circuit is demonstrated that uses the JDTD to rectify time‐periodic temperature profiles, achieving thermal circuit effectiveness values up to 30% of the ideal‐diode limit. Coupon‐level durability tests and device‐level cycling show that dip coated Teflon AF enables stable operation of Al JDTDs over &gt;20 cycles, improving on the performance of a monolayer‐coated surface that fails after 5 cycles. The findings of this work signify that Teflon AF coated Al SHPB surfaces can be used for thermal rectification and motivate future research into Al JDTDs for advanced thermal management applications.

Osseointegration of a hydroxyapatite-coated stem in femoral neck fractures in the over-80s.

In the over-80s, femoral bone is often osteoporotic and unlikely to be conducive to periprosthetic bone rehabitation. This observation often leads to cemented fixation for hemiarthroplasty in femoral neck fracture. Hydroxyapatite is a bioactive coating that has already demonstrated its osteoinductive properties. Our hypothesis is that hydroxyapatite enables prosthetic osseointegration in patients over 80, as well as periprosthetic cortical thickening. The objective was to evaluate the osseointegration of a hydroxyapatite-coated femoral stem in femoral neck fractures in the over-80s, and the evaluation of the periprosthetic bone regeneration permitted by hydroxyapatite. This was a retrospective study. Osseointegration and periprosthetic bone regeneration were assessed on pre-operative, immediate post-operative and last follow-up radiographs with Engh score, O-SS score, cortical index, Canal Bone Ration (CBR) and Canal Fill Ratio (CFR). One hundred and forty-six patients were included. At last follow-up, 99.3% (n = 145) of stems were osseointegrated. The mean Engh score was 19.9 [SD 3.1]. The mean O-SS score was 19.1 [SD 2.4], corresponding to very good osseointegration. The mean CBR at last follow-up was 0.48 [SD 0.07], corresponding to a non-osteoporotic femur. There was a significant difference with pre-operative CBR (p < 0,001). The pre-operative cortical index and the index at the last follow-up were significantly different for all levels of measurement (p < 0,001). The CFR at last follow-up was also significantly different with the post-operative CFR (p < 0,001). This study shows the value of using a hydroxyapatite-coated stem on senile, osteoporotic bone to improve cortical thickness along the entire length of femoral bone.

Cementless reverse total shoulder arthroplasty implantation with humeral matchstick autograft augmentation: early radiographic outcomes

IntroductionHumeral-sided complications account for up to 21% of all revision Reverse Total Shoulder Arthroplasty (RTSA) surgeries.1 Stress shielding with large bulky stems can lead to proximal bone resorption per Wolff’s law, complicating further surgeries.14,28 Previously published studies suggest that lowering the metaphyseal implant fill ratio can lead to fewer adaptive radiographic changes and decreased bone resorption.25,26,29 Inspired by these studies, cementless primary RTSA implantation technique with humeral matchstick autografts was proposed to augment cementless humeral constructs, foster the use of a smaller size stem, and create primary stability of the humeral implant even in osteoporotic or in-between size medullary canals. In this study, retrospective review of this cementless RTSA technique with short term radiographic evaluation was performed. MethodsForty-six nonconsecutive patients underwent primary RTSA with a short-stem cementless prosthesis (Stryker Ascend Flex, Kalamazoo, MI, USA) augmented by matchstick bone grafting from January to July 2020. Patient demographics were recorded, and follow-up x-rays were retrospectively reviewed to assess metaphyseal fill ratios and incidence of stress shielding at minimum 1-year follow-up. Discrepancies between templated and final stem sizes were recorded, along with all intraoperative and postoperative complications. ResultsOf the 46 patients originally identified, there were 5 men and 41 women with a mean age of 71 years (SD ± 7, range 53-88). Mean templated stem size was 4 (SD ± 2, range 1-8), while mean final implant size was 2 (SD ± 1, Range 1-3). Mean fill ratios were 0.76 (SD ± 0.06, range 0.54-0.89) along the metaphysis and 0.67 (SD ± 0.09, range 0.49-0.83) along the diaphysis. There were no intraoperative humeral fractures from implantation. All patients were available for radiographic follow-up with a mean of 19 months (SD ± 8, range 12-40). There were three cases (7%) of proximal humeral stress shielding, with average fill ratios of 0.857 and 0.807 in the metaphysis and diaphysis, respectively. There were 3 patients (7%) who underwent revision surgeries for baseplate failure and periprosthetic humeral fracture. There were no cases of early humeral loosening. DiscussionMatchstick autograft humeral augmentation is a simple, promising surgical technique with low intraoperative complication rates and good short-term radiographic outcomes. When the implant fill ratio is successfully reduced, there is possible lower risk of humeral stress shielding. The authors believe this technique can help maximize implant stability in cementless shoulder arthroplasty and preserve humeral bone stock for future revision surgeries.

IMPACT OF FILLING RATIO AND CELLULOSE NANOFIBER NANOFLUID ON THE TOTAL THERMAL RESISTANCE AND THE STARTUP OF A MINIATURE THERMOSYPHON

Thermosyphons are highly effective heat transfer devices used for thermal management in different fields, such as electronic systems, solar collectors and nuclear reactors. The working fluid within the thermosyphon provides the heat transport from the evaporator to the condenser and limits its thermal performance. In this study, the influence of filling ratio (FR) and the eco-friendly cellulose nanofiber (CNF) nanofluid concentration on the total thermal resistance and the startup of a two-phase closed thermosyphon (TPCT) at various heat loads are investigated experimentally. The working fluids are deionized water (DI) and CNF suspensions with 0.5, 1, and 2 vol.&amp;#37; and filling ratios were set to 25, 50, and 75&amp;#37;. Total thermal resistance of the TPCT was obtained using the recorded data of wall temperature distribution at the steady state of each experiment. Addition of CNF with 1 vol.&amp;#37; to DI at filling ratio of 75&amp;#37; reduced the evaporator wall temperature by 40&amp;#37; and 23&amp;#37;, also it reduced the total thermal resistance by 58.78&amp;#37; and 33.65&amp;#37; at 20 W and 80 W, respectively. Moreover, it shortened the startup duration by 33&amp;#37; and reduced its temperature by 42&amp;#37;. This paper contains important findings that prove that CNF enhanced the thermal performance of the TPCT when applying an appropriate concentration and filling ratio.

Experiment study on dryout characteristics and thermal resistance analysis of two-phase closed thermosiphon

This study aims to explore the dryout characteristics of two-phase closed thermosiphon. It involves the design and experimentation on low-liquid filled heat pipes. We investigated the effects of different fill ratios, heating water temperatures, and cooling water flow rates on the start-up characteristics of two-phase closed thermosiphon. Based on the network model, we proposed an analytical expression for the thermal resistance, R, of two-phase closed thermosiphon, and provided an explanation of the various thermal resistance components. This research expands our understanding of dryout and provides insights for optimizing heat pipe design and addressing heat conduction issues with low fill ratios.

3D printed composites based on the magnetoelectric coupling of Fe/FeCo@C with multiple heterogeneous interfaces for enhanced microwave absorption

In this paper, the ZIF-derived carbon nanoskeleton was cleverly introduced into the carbonyl iron surface by in situ self-polymerization of dopamine on the carbonyl iron surface to build a “bridge” and multiple heterogeneous interfacial wave-absorbing agents of Fe/FeCo@C were obtained by heat treatment process. The large amount of polarization loss introduced by the designed multi-heterogeneous interfaces increases the ability of the material to attenuate electromagnetic waves. At the same time, the conductive network formed by loading nanoparticles with the lamellar structure of micrometal is employed to couple the dielectric loss depletion and the magnetic loss together, and the electromagnetic parameters are regulated by graphitization. The FDM technique was utilized to prepare filaments that can be used for 3D printing by compositing the wave absorber with PP resin and to explore the effect of FCC/PP composites on the attenuation of electromagnetic waves by utilizing dielectric-electromagnetic coupling realizations. The results show that the preparation yields an adequate absorption bandwidth of 4.75 GHz at 1.5 mm for FCC-3/PP at 40 % fill ratio, and the minimum reflection loss can reach close to −60 dB at 1.7 mm. The wave-absorbing composite materials can also be utilized to print various shaped materials, and this work provides a new option for preparing electromagnetic-absorbing composites by FDM 3D printing in the future.

Schwarzite-based 3D-printed carriers for enhanced performance of sequencing batch biofilm reactor (SBBR) for wastewater treatment

The energy-efficient, green, and sustainable wastewater treatment using biofilm reactors is gaining a lot of attention. The efficiency of biofilm-based reactors (e.g., sequencing batch biofilm reactor (SBBR) and moving bed biofilm reactor (MBBR), etc.) can be further improved with the help of strong, highly active, and functionally engineered carriers. Here, Schwarzite-based 3D-printed biocarriers were prepared to obtain optimum mechanical properties and enhanced organics and nutrient removal efficiencies. The optimized carrier (L2) possesses the highest porosity (∼75%) and specific modulus of resilience and lowest bulk density among the other prepared structures (i.e., L1, L3, and L4). High porosity and specific surface area of the carriers promote enhanced growth of biomass with a total of 0.3 g biomass/carrier. The optimized biocarrier showed ∼95% chemical oxygen demand and ∼84% ammonium nitrogen removal efficiencies, which were attributed to its high specific surface area and porosity. The performance of SBBR with 3D-printed biofilm carriers having only a 15% fill ratio was compared and found better than the conventional K2 carriers used with a filling ratio of 50%. The high mechanical stability and specific surface area of the L2 biocarrier make it feasible to be used as a biofilm carrier, which may drastically reduce the number of carriers thereby directly reducing the cost.

Microstructure and tribology of cold spray additively manufactured multimodal Ni-WC metal matrix composites

Cold spray produces thick and dense deposits that can be applied in additive manufacturing or as a repair to recover damaged components. One potential materials system is WC-reinforced Ni composites, which are known for a combination of high hardness and toughness. WC particle size and distribution are some of the most important variables that impact the mechanical properties and wear resistance. In this study, thick multimodal Ni-24 vol%WC composite coatings were additively manufactured using the cold spray technique. Spherical Ni powder and two types of WC particles, i.e., cast and agglomerated, were used as feedstock materials. The microstructure, porosity, WC distribution, and microhardness of coatings were investigated in comparison with cold-sprayed Ni and Ni-agglomerated WC coatings with similar WC fill ratios. Dry sliding wear of multimodal Ni-WC coatings was studied with a sliding speed of 3 mm/s under normal loads of 5 and 12 N and was then compared to Ni and composite coatings made with only agglomerated WC. Multimodal Ni-WC coatings with an altered distribution of WC particles offered an improvement in friction and wear as compared to Ni-agglomerated WC coatings. Characterization of worn surfaces revealed the formation of tribofilms following compaction of wear debris. A more stable tribofilm that developed to a higher coverage was identified for coatings with multimodal WC particles at both tested loads. However, the protective role of tribofilms was reduced at a higher load, caused by subsurface crack propagation. Subsurface microstructure of worn surfaces that are induced by sliding wear was studied, and a correlation between the mechanical properties and microstructure and wear mechanism of coatings was made. Overall, our findings highlight the potential of cold spray additive manufacturing in producing multimodal Ni-WC composite coatings with enhanced wear resistance.

A Comparison of Inventory Management Models in Automated Dispensing Cabinets at a Large Academic Medical Center.

Purpose: To compare and evaluate 2 methods of inventory management in automated dispensing cabinets (ADCs). Methods: Ten profiled ADCs had 2 inventory management models implemented over 2 months. Implementation of the models on each ADC involved adjustment of par levels (desired accessible quantities of medication) and removal of medications not used in the past 90 days or more. The par levels of 5 ADCs were adjusted using a formula developed based on the economic order quantity model. The par levels of the other 5 ADCs were adjusted using a formula based on historical average daily usage. The study endpoints include stock out rate, vend:fill ratio, quantity of expired medications, and inventory carrying cost. Results: The total of number of medications stocked in the 10 ADCs was reduced from 3035 in a 2-month pre-implementation period to 2932 in a 2-month post-implementation period yielding a reduction of inventory carrying cost by $11 011. The mean stock out rate in both study groups increased and vend:fill ratio decreased after implementation. The quantity of expired medications increased in the modified economic order quantity formula inventory management model and decreased in the average daily usage inventory management model. Conclusion: The implementation of 2 inventory management models on ADCs had a negative impact on stock out rate and vend:fill ratio, a mixed impact on quantity of expired medications, and a positive impact on inventory carrying cost reduction.

Long-term results (after a mean 11.3 years, and up to 22 years, of follow-up) of the Legacy Constrained Condylar Knee (LCCK™) in primary total knee arthroplasty

IntroductionThe use of a sliding prosthesis in total knee arthroplasty (TKA) with increased stress is an intermediate solution in primary surgery, between posteriorly stabilized prostheses and hinged prostheses, in cases of ligamentous laxity and/or loss of bone substance. Favorable results have been reported in the medium term but to our knowledge, this type of prosthesis has not been evaluated in Europe beyond 10 years of follow-up. We therefore conducted a retrospective study in order to carry out: 1) the study of the survival of the Legacy Constrained Condylar Knee (LCCK™) prosthesis in primary surgery, 2) the analysis of complications, functional scores and radiographic data, 3) the analysis of the link between the diaphyseal filling rate and prosthetic loosening. HypothesisThe LCCK™ sliding prosthesis with increased constraint has equivalent long-term survival and clinical results to standard posteriorly stabilized TKA and superior to hinged TKA. Material and methodA retrospective series of 141 LCCK™ implanted in 134 patients between 1997 and 2010 was analyzed. Survival was assessed with censoring through an evaluation of partial or total revision of the implants. The functional results were evaluated using the IKS and Oxford 12 scores. Data regarding the Canal Fill Ratio (CFR) and the presence of pathological periprosthetic lines were also collected. ResultsThe average follow-up was 11.3±5.3years with a maximum follow-up of 22.7years. Survival at 20years was 90.8% [95% CI: 83.7–95.7]. The rate of early complications was 13.5% (19/141), predominantly comprised of venous thrombosis (6/141), hematomas (3/141 including two requiring surgical drainage), stiffness (3/141) and early infections (3/141). The rate of late complications was 17% (24/141), led by stiffness (4.4%; 6/141), infections (2.9%; 4/141) and hardware failure (2. 2%; 3/141). Ten of the 141 patients (7.1%) had LCCK failure, including 3 (2.1%) for stiffness, 3 (2.1%) for hardware failure, 2 (1.4%) for infection, 1 (0.7%) for laxity and 1 (0.7%) for a periprosthetic fracture. No aseptic loosening was found. The total IKS score went from 65 [0–116] to 143 [79–200] at follow-up, the IKS knee score went from 30 [0–66] to 85 [44–100], and the IKS function score went from 35 [0–70] to 57 [0–100]. The Oxford score went from 14 [2–25] to 34 [15–48] at follow-up. Only two patients (1.4%) presented with a partial periprosthetic line. The tibial CFR was 0.81 and the femoral CFR was 0.76. The influence of the CFR could not be analyzed due to the absence of loosening. DiscussionThe LCCK™ prosthesis in primary surgery has good medium-term survival, a significant improvement in functional scores and a complication rate comparable to posteriorly stabilized prostheses. The complication rate is lower than that of hinged prostheses. Level of evidenceIV; single-center retrospective study.

Areal bone mineral density is not associated with femoral stem subsidence in patients younger than 70years undergoing total hip arthroplasty.

Femoral stem subsidence is a known complication after uncemented total hip arthroplasty (THA). The purpose of this study was to determine the frequency of osteoporosis and to investigate the relationship between areal bone mineral density (aBMD) and subsidence in a cohort of patients younger than 70years. One hundred consecutive patients (age 60 ± 6years; 52 female, 48 male) undergoing uncemented THA using a collarless press fit femoral stem were retrospectively reviewed. Dual-energy X-ray absorptiometry (DXA) was performed preoperatively at the proximal femur and lumbar spine, and if not feasible at these sites, at the distal radius. DXA results were compared to a cohort of 100 patients ≥ 70years scheduled for cemented THA. Age, sex, and body mass index (BMI), canal flare index (CFI), and canal fill ratio (CFR) were assessed. Analysis of stem subsidence and migration was performed on standardized, calibrated radiographs obtained postoperatively and at follow-up. The frequency of osteoporosis was considerably lower in the study cohort compared to patients ≥ 70years (7% vs. 19%, p = 0.02). Illustrated by the high CFR (mean 96 ± 4%) in the mid-stem region, a sufficient press fit was achieved. After a mean follow-up of 7.4months, the mean stem subsidence was 0.9 ± 0.9mm. Only two patients had subsidence greater than 3mm, one of whom was morbidly obese and the other diagnosed with severe osteoporosis. There were no correlations between any of the parameters (CFI, CFR, age, sex, BMI) and femoral stem subsidence. In addition, aBMD T-scores showed no correlations with subsidence. aBMD by DXA does not appear to be associated with stem subsidence in patients younger than 70years and withadequate press fit.

Thermodynamic modeling of thermosyphons and heat pipes

A model capable of predicting the thermodynamic state of the working fluid and its related properties inside a thermosyphon and a heat pipe is proposed. The model theoretically analyzes the entropy changes of various thermodynamic processes and determines the possible locations of the state points on a temperature-specific entropy (T-s) and a specific enthalpy-specific entropy (h-s) diagram at each stage of the thermodynamic cycle. The analysis reveals that the working fluid enters the condenser in a superheated state, while it enters the evaporator in a subcooled state, irrespective of the operating conditions. Analytical expressions are derived to predict the changes in the temperature, pressure, specific volume, entropy, and enthalpy during each thermodynamic process, along with expressions for estimating entropy generation. The effects of varying input heating power (Qiṅ), the fill ratio, the device aspect ratio, and the device inclination angle (θ) on the working fluid behavior are examined, revealing that they affect the thermodynamic state of the working fluid during operation. The conclusion drawn in the existing heat pipe literature that the operating parameters only influence the thermal resistance of thermosyphons and heat pipes is, therefore, incomplete. The geometric and the operational parameters influence the state of the working fluid at each stage of the thermodynamic cycle. The present thermodynamic model, in conjunction with existing heat pipe theory, completely describes thermosyphon and heat pipe operation under any given set of conditions.

Does medullary diameter to stem width ratio and stem length affect outcomes of revision total knee arthroplasties? A case series.

This study aimed to investigate the relationship between the ratio of stem size to intramedullary canal diameter, stem length, and functional outcome in revision total knee arthroplasty (RTKA) procedures, which remains largely unexplored in the current literature. A single surgeon series of RTKA procedures performed between October 2014 and November 2022 were included in this case series, and data were analyzed retrospectively. A total of 32 patients (27 females, 5 males; mean age: 73.2±8.1 years; range, 52 to 88 years) were identified, with a minimum follow-up period of five months and a maximum of eight years. Filtering the patients based on >24 month follow-up, we were left with 13 patients aged between 65 and 88 (mean 74.9±6.9) years. The latest X-rays of patients were analyzed, and the ratio of intramedullary canal diameter to stem width was calculated for both femur and tibia in both anteroposterior and lateral planes. Household income, preoperative C-reactive protein, erythrocyte sedimentation rate, comorbidities, body mass index, and implant dimensions were also recorded. Postoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Short Form-12 (SF-12) scores, and range of motion (ROM) measurements were used to evaluate functional outcome. A moderate negative relationship between the tibial canal fill ratio (CFR) in anteroposterior views and ROM of the patients was noted. Additionally, a significant positive correlation was found between SF-12 physical score and CFR in lateral view. A moderate level of correlation between femoral CFR in anteroposterior views was also established. Due to insufficient data, joint ROM data did not show normal distribution. Therefore, a cutoff value indicating the relationship between the stem size and knee ROM could not be calculated using receiver operating characteristic analysis. Multiple regression analysis did not yield significant results, suggesting that hypothesized predictor variables were not sufficient to predict the variation in functional scores. Otherwise, no clear statistical importance or correlation between functional scores, such as WOMAC or SF-12, and CFR was found. In conclusion, the findings suggest that other factors, such as other patient characteristics, surgical techniques, or implant designs, may have a more substantial impact on the functional outcomes in RTKA patients.