Numerical analysis of heat pumps models: comparative study between equation-fit and refrigerant cycle based models

An equation-fit (EF) and a refrigerant cycle (RC) based heat pump models have been implemented, validated, analyzed and compared to each other under steady state conditions for a brine to water heat pump. Models validations have been provided through comparisons against experimental data obtained at ISFH. The advantages and disadvantages of the both models have been identified. This work provides significant inputs regarding the selection of a specific model depending on the needs. Analysis of mass flow rates and calculations far from typical catalogue data (non-standard conditions) are provided. The main conclusions can be summarized as: i) the EF model is recommended when the boundary conditions for the estimation and prediction modes are the same and when non-standard conditions are considered; ii) the RC model is the chosen alternative when the mass flow rates are modified from the estimation to the prediction mode.Peer ReviewedPostprint (published version

Coagulation abnormalities following nexoBrid use: a case report

Patients with major burn injury undergo a series of pathophysiologic changes that begin with a systemic inflammatory response and coagulation abnormalities, similar to those experienced by patients with sepsis or severe trauma. Coagulation changes in patients with burns are generally characterized by procoagulant abnormalities, but alterations in fibrinolysis and anticoagulation factors have also been observed. Around 40% of patients with major burn show changes on standard coagulation tests, and these have been related to the severity of the lesions, smoke inhalation, and administration of intensive fluid resuscitation therapy. Current surgical techniques for debridement of burn lesions are aggressive and associated with considerable blood loss. A fast-acting selective enzymatic debriding agent based on bromelain has been recently developed. NexoBrid is indicated for removing eschar in adults with deep partial- and full-thickness thermal burns. A potential effect of oral bromelain on hemostasis has been described, but it is uncertain whether NexoBrid application has a clinically relevant impact in this regard. We present the clinical case of a patient with burns who showed a coagulation abnormality shortly after NexoBrid use

Wide area network autoscaling for cloud applications

Modern cloud orchestrators like Kubernetes provide a versatile and robust way to host applications at scale. One of their key features is autoscaling, which automatically adjusts cloud resources (compute, memory, storage) in order to adapt to the demands of applications. However, the scope of cloud autoscaling is limited to the datacenter hosting the cloud and it doesn't apply uniformly to the allocation of network resources. In I/O-constrained or data-in-motion use cases this can lead to severe performance degradation for the application. For example, when the load on a cloud service increases and the Wide Area Network (WAN) connecting the datacenter to the Internet becomes saturated, the application flows experience an increase in delay and loss. In many cases this is dealt with overprovisioning network capacity, which introduces additional costs and inefficiencies. On the other hand, thanks to the concept of "Network as Code", the WAN exposes a set of APIs that can be used to dynamically allocate and de-allocate capacity on-demand. In this paper we propose extending the concept of cloud autoscaling into the network to address this limitation. This way, applications running in the cloud can communicate their networking requirements, like bandwidth or traffic profile, to a Software-Defined Networking (SDN) controller or Network as a Service (NaaS) platform. Moreover, we aim to define the concepts of vertical and horizontal autoscaling applied to networking. We present a prototype that automatically allocates bandwidth to the underlay network, according to the requirements of the applications hosted in Kubernetes. Finally, we discuss open research challenges.This work was supported by the Spanish MINECO under contract TEC2017-90034-C2-1-R (ALLIANCE), the Catalan Institution for Research and Advanced Studies (ICREA).Peer ReviewedPostprint (author's final draft

Three-stage limb salvage in tibial fracture related infection with composite bone and soft-tissue defect

Bone transport; Infected tibial injury; Limb salvageTransporte óseo; Lesión tibial infectada; Rescate de miembrosTransport ossi; Lesió tibial infectada; Rescat de membresIntroduction Managing critical-sized tibial defects is one of the most complex challenges orthopedic surgeons face. This is even more problematic in the presence of infection and soft-tissue loss. The purpose of this study is to describe a comprehensive three-stage surgical protocol for the reconstruction of infected tibial injuries with combined bone defects and soft-tissue loss, and report the clinical outcomes. Materials and methods A retrospective study at a specialized limb reconstruction center identified all patients with infected tibial injuries with bone and soft-tissue loss from 2010 through 2018. Thirty-one patients were included. All cases were treated using a three-stage protocol: (1) infected limb damage control; (2) soft-tissue coverage with a vascularized or local flap; (3) definitive bone reconstruction using distraction osteogenesis principles with external fixation. Primary outcomes: limb salvage rate and infection eradication. Secondary outcomes: patient functional outcomes and satisfaction. Results Patients in this series of chronically infected tibias had been operated upon 3.4 times on average before starting our limb salvage protocol. The mean soft-tissue and bone defect sizes were 124 cm2 (6–600) and 5.4 cm (1–23), respectively. A free flap was performed in 67.7% (21/31) of the cases; bone transport was the selected bone-reconstructive option in 51.7% (15/31). Local flap failure rate was 30% (3/10), with 9.5% for free flaps (2/21). Limb salvage rate was 93.5% (29/31), with infection eradicated in all salvaged limbs. ASAMI bone score: 100% good/excellent. Mean VAS score was 1.0, and ASAMI functional score was good/excellent in 86% of cases. Return-to-work rate was 83%; 86% were “very satisfied” with the treatment outcome. Conclusion A three-stage surgical approach to treat chronically infected tibial injuries with combined bone and soft-tissue defects yields high rates of infection eradication and successful limb salvage, with favorable functional outcomes and patient satisfaction.Open Access Funding provided by Universitat Autonoma de Barcelona

Bromelain-based enzymatic burn debridement: Spanish multidisciplinary consensus

Bromelain; Burn wound; Enzymatic debridementBromelina; Herida por quemadura; Desbridamiento enzimáticoBromelina; Ferida per cremada; Desbridament enzimàticBackground Bromelain-based enzymatic debridement is gaining increased interest from burn specialists in the last few years. The objective of this manuscript is to update the previous, first Spanish consensus document from 2017 (Martínez-Méndez et al. 43:193–202, 2017), on the use of enzymatic debridement with NexoBrid® in burn injuries, adding the clinical experience of a larger panel of experts, integrating plastic surgeons, intensivists, and anesthesiologists. Methods A consensus guideline was established by following a modified Delphi methodology of a 38-topic survey in two rounds of participation. Items were grouped in six domains: general indication, indication in critical patients, pain management, conditions for NexoBrid® application, NexoBrid® application technique, and post-debridement wound care. Results In the first round, experts established consensus (strongly agree or agree) on 13 of the 38 statements. After the second round, a consensus was reached on 24 of the 25 remaining statements (97.2%). Conclusions The present updated consensus document provides recommendations on the use of bromelain-based enzymatic debridement NexoBrid®, integrating the extensive clinical experience of plastic surgeons, intensivists, and anesthesiologists in Spain. Further clinical trials and studies are required to corroborate, modify, or fine tune the current statements

Three-stage limb salvage in tibial fracture related infection with composite bone and soft-tissue defect

Altres ajuts: Acord transformatiu CRUE-CSICIntroduction: Managing critical-sized tibial defects is one of the most complex challenges orthopedic surgeons face. This is even more problematic in the presence of infection and soft-tissue loss. The purpose of this study is to describe a comprehensive three-stage surgical protocol for the reconstruction of infected tibial injuries with combined bone defects and soft-tissue loss, and report the clinical outcomes. Materials and methods: A retrospective study at a specialized limb reconstruction center identified all patients with infected tibial injuries with bone and soft-tissue loss from 2010 through 2018. Thirty-one patients were included. All cases were treated using a three-stage protocol: (1) infected limb damage control; (2) soft-tissue coverage with a vascularized or local flap; (3) definitive bone reconstruction using distraction osteogenesis principles with external fixation. Primary outcomes: limb salvage rate and infection eradication. Secondary outcomes: patient functional outcomes and satisfaction. Results: Patients in this series of chronically infected tibias had been operated upon 3.4 times on average before starting our limb salvage protocol. The mean soft-tissue and bone defect sizes were 124 cm (6-600) and 5.4 cm (1-23), respectively. A free flap was performed in 67.7% (21/31) of the cases; bone transport was the selected bone-reconstructive option in 51.7% (15/31). Local flap failure rate was 30% (3/10), with 9.5% for free flaps (2/21). Limb salvage rate was 93.5% (29/31), with infection eradicated in all salvaged limbs. ASAMI bone score: 100% good/excellent. Mean VAS score was 1.0, and ASAMI functional score was good/excellent in 86% of cases. Return-to-work rate was 83%; 86% were "very satisfied" with the treatment outcome. Conclusion: A three-stage surgical approach to treat chronically infected tibial injuries with combined bone and soft-tissue defects yields high rates of infection eradication and successful limb salvage, with favorable functional outcomes and patient satisfaction

Hydrothermal processing of 3D-printed calcium phosphate scaffolds enhances bone formation in vivo: a comparison with biomimetic treatment

Hydrothermal (H) processes accelerate the hydrolysis reaction of a-tricalcium phosphate (a-TCP) compared to the long-established biomimetic (B) treatments. They are of special interest for patient-specific 3D-printed bone graft substitutes, where the manufacturing time represents a critical constraint. Altering the reaction conditions has implications for the physicochemical properties of the reaction product. However, the impact of the changes produced by the hydrothermal reaction on the in vivo performance was hitherto unknown. The present study compares the bone regeneration potential of 3D-printed a-TCP scaffolds hardened using these two treatments in rabbit condyle monocortical defects. Although both consolidation processes resulted in biocompatible scaffolds with osseointegrative and osteoconductive properties, the amount of newly formed bone increased by one third in the hydrothermal vs the biomimetic samples. B and H scaffolds consisted mostly of high specific surface area calcium-deficient hydroxyapatite (38 and 27 m2 g-1, respectively), with H samples containing also 10 wt.% ß-tricalcium phosphate (ß-TCP). The shrinkage produced during the consolidation process was shown to be very small in both cases, below 3%, and smaller for H than for B samples. The differences in the in vivo performance were mainly attributed to the distinct crystallisation nanostructures, which proved to have a major impact on permeability and protein adsorption capacity, using BSA as a model protein, with B samples being highly impermeable. Given the crucial role that soluble proteins play in osteogenesis, this is proposed to be a relevant factor behind the distinct in vivo performances observed for the two materials. Statement of significance The possibility to accelerate the consolidation of self-setting calcium phosphate inks through hydrothermal treatments has aroused great interest due to the associated advantages for the development of 3D-printed personalised bone scaffolds. Understanding the implications of this approach on the in vivo performance of the scaffolds is of paramount importance. This study compares, for the first time, this treatment to the long-established biomimetic setting strategy in terms of osteogenic potential in vivo in a rabbit model, and relates the results obtained to the physicochemical properties of the 3D-printed scaffolds (composition, crystallinity, nanostructure, nanoporosity) and their interaction with soluble proteins.Peer ReviewedPostprint (published version

Osteoinduction by foamed and 3D-printed calcium phosphate scaffolds: effect of nanostructure and pore architecture

Some biomaterials are osteoinductive, that is, they are able to trigger the osteogenic process by inducing the differentiation of mesenchymal stem cells to the osteogenic lineage. Although the underlying mechanism is still unclear, microporosity and specific surface area (SSA) have been identified as critical factors in material-associated osteoinduction. However, only sintered ceramics, which have a limited range of porosities and SSA, have been analyzed so far. In this work, we were able to extend these ranges to the nanoscale, through the foaming and 3D-printing of biomimetic calcium phosphates, thereby obtaining scaffolds with controlled micro- and nanoporosity and with tailored macropore architectures. Calcium-deficient hydroxyapatite (CDHA) scaffolds were evaluated after 6 and 12 weeks in an ectopic-implantation canine model and compared with two sintered ceramics, biphasic calcium phosphate and ß-tricalcium phosphate. Only foams with spherical, concave macropores and not 3D-printed scaffolds with convex, prismatic macropores induced significant ectopic bone formation. Among them, biomimetic nanostructured CDHA produced the highest incidence of ectopic bone and accelerated bone formation when compared with conventional microstructured sintered calcium phosphates with the same macropore architecture. Moreover, they exhibited different bone formation patterns; in CDHA foams, the new ectopic bone progressively replaced the scaffold, whereas in sintered biphasic calcium phosphate scaffolds, bone was deposited on the surface of the material, progressively filling the pore space. In conclusion, this study demonstrates that the high reactivity of nanostructured biomimetic CDHA combined with a spherical, concave macroporosity allows the pushing of the osteoinduction potential beyond the limits of microstructured calcium phosphate ceramics.Peer ReviewedPostprint (author's final draft

3D printing with star-shaped strands: a new approach to enhance in vivo bone regeneration

Concave surfaces have shown to promote bone regeneration in vivo. However, bone scaffolds obtained by direct ink writing, one of the most promising approaches for the fabrication of personalized bone grafts, consist mostly of convex surfaces, since they are obtained by microextrusion of cylindrical strands. By modifying the geometry of the nozzle, it is possible to print 3D structures composed of non-cylindrical strands and favor the presence of concave surfaces. In this work, we compare the in vivo performance of 3D-printed calcium phosphate scaffolds with either conventional cylindrical strands or star-shaped strands, in a rabbit femoral condyle model. Monocortical defects, drilled in contralateral positions, are randomly grafted with the two scaffold configurations, with identical composition. The samples are explanted eight weeks post-surgery and assessed by µ-CT and resin-embedded histological observations. The results reveal that the scaffolds containing star-shaped strands have better osteoconductive properties, guiding the newly formed bone faster towards the core of the scaffolds, and enhance bone regeneration, although the increase is not statistically significant (p > 0.05). This new approach represents a turning point towards the optimization of pore shape in 3D-printed bone grafts, further boosting the possibilities that direct ink writing technology offers for patient-specific applications.Peer ReviewedPostprint (published version