University of Zagreb

The paper discusses the formation of an enamel defect in the crown of a cave bear ( Ursus spelaeus sensu lato) left maxillary second molar (M ² ), based on macroscopic and microscopic analysis. The tooth belongs to a cranium recovered from the Cerovac caves in Croatia that exhibits a partially healed, depressed lesion in the left squama frontalis and a further lesion in the left maxilla associated with loss of the M ¹ . Microscopic inspection demonstrated an accentuated incremental line in both enamel and dentin of the left M ² . It is suggested that in the defect area the outer enamel had been posteruptively lost along the accentuated line in the enamel that constituted a zone of reduced mechanical resistance. Presence of enamel hypoplasia in both M ² indicated that these developmental lesions reflect a systemic stress event during crown formation of the teeth. The underlying cause of this stress is assumed to have been a trauma to the skull that caused the lesion in the left squama frontalis. It is further suggested that a later trauma to the left maxilla had led to the loss of the left M ¹ and the flaking‐off of enamel along the accentuated incremental line in the left M ² . The defect in the left M ² is thus diagnosed as the result of a developmental lesion during crown formation, related to systemic stress due to a skull trauma, followed by posteruptive damage from a second traumatic impact. In addition to reconstructing the formation of the defect in the crown of the left M ² , the paper, for the first time, describes daily and subdaily incremental markings in ursid enamel and provides preliminary information on enamel secretion rate in a cave bear molar.

Among the many rechargeable lithium batteries, lithium-titanate, or lithium-titanium oxide cells are characterized by the highest thermal stability and operational safety levels, which makes them particularly well suited for highly demanding applications. This paper presents the results of experimental characterization of a lithium-titanate battery cell for the purpose of building a control-oriented battery equivalent electrical circuit model suitable for designing a state-of-charge estimator. Battery cell model identification has been carried out in three stages: (i) Recording of the open-circuit voltage vs. state-of-charge characteristic by means of low-current charging interspersed with battery voltage recuperation intervals over the full-range of battery voltages, (ii) Determination of the effective battery charge capacity, and (iii) Identification of battery cell series resistance and polarization resistance and lag time constant for different charging current values using recursive parameter estimation based on pseudo-random binary sequence test signal. Based on the experimentally identified battery cell equivalent circuit model (the so-called Thevenin model) an extended Kalman filter has been designed to serve as the state-of-charge estimator. The effectiveness of the proposed estimator is verified by means of simulations and experimentally on the battery test bench. Graphical abstract

Newly prepared tetracyclic imidazo[4,5‐b]pyridine derivatives were synthesized to study their antiproliferative activity against human cancer cells. Additionally, the structure‐activity was studied to confirm the impact of the N atom position in pyridine nuclei as well as the chosen amino side chains on antiproliferative activity. Targeted amino substituted regioisomers were prepared by using uncatalyzed amination from corresponding chloro substituted precursors. The most active compounds 6a, 8 and 10 showed improved activity in comparison to standard drug etoposide with IC50 values in a nanomolar range of concentration (0.2 – 0.9 μM). NMR‐based metabolomics is a powerful instrument to elucidate activity mechanism of new chemotherapeutics. Multivariate and univariate statistical analysis of metabolic profiles of non‐small cell lung cancer cells before and after exposure to 6a revealed significant changes in metabolism of essential amino acids, glycerophospholipids and oxidative defense. Insight into the changes of metabolic pathways that are heavily involved in cell proliferation and survival provide valuable guidelines for more detailed analysis of activity metabolism and possible targets of this class of bioactive compounds.

The paper investigates approaches for implementing circular economy strategies, such as designing mechatronic products for longer service life by replacing, upgrading, or remanufacturing subsystems. The research aims at applying MBSE to provide the necessary support for dealing with the complexity of these approaches. Requirements and challenges for the development of MBSE support in this context are examined. An example of an EV battery system model shows the benefits and challenges of comprehensive system modelling and traceability in the context of circular economy strategies.

High quality laboratory results are critical for patient management. However, poor sample quality can impact these results and patient safety. To ensure reliable and accurate results laboratories must be aware of each analyte’s stability under various storage conditions and matrices to guarantee correct and dependable outcomes. This knowledge allows laboratories to define the allowable delay between sample collection and centrifugation/analysis for all analytes to guarantee appropriate results quality and interpretation. The EFLM WG-PRE therefore established a 4-step plan to tackle this issue, aiming to standardize and harmonize stability studies for improved comparison and meta-analysis. The plan included the development of checklists and how-to guides for performing and reporting stability studies as well as a central resource of stability data. This manuscript deals with the issue of evaluating publications and incorporating them into a central resource. To evaluate stability studies, the CRESS checklist was used to structure 20 sections used to judge the quality of studies. Each section has 4 levels of quality, with scores converted to numerical values and weighted based on expert opinion. Based on this, a final score ranging from A to D was determined. The procedure was then tested on six manuscripts and checked for agreement between expert judgements. The results demonstrated that the proposed evaluation process is a useful tool to distinguish between best in class manuscripts and those of lower quality. The EFLM WG-PRE strongly believes that the provided recommendations and checklists will help improving stability studies both in quality and standardisation.

Background The optimal antithrombotic strategy early after aortic valve replacement surgery with a biological valve remains controversial due to lack of high-quality evidence. Either oral anticoagulants or acetylsalicylic acid should be considered for the first 3 months. Hypo-attenuated leaflet thickening on cardiac computed tomography has been associated with latent bioprosthetic valve thrombosis and may be prevented with anticoagulation. We hypothesize that anticoagulation with apixaban is superior to single antiplatelet therapy with acetylsalicylic acid in reducing hypo-attenuated leaflet thickening of bioprosthetic aortic valve prostheses. Methods In this prospective, open-label, randomized trial, patients undergoing isolated aortic valve replacement surgery with rapid deployment bioprosthetic valves will be randomized. The treatment group will receive 5 mg of apixaban twice a day for the first 3 months and 100 mg of acetylsalicylic acid thereafter. The control group will be administered 100 mg of acetylsalicylic acid once a day, indefinitely. After the 3-month treatment period, a contrast-enhanced electrocardiogram-gated cardiac computed tomography will be performed to identify hypo-attenuated leaflet thickening of the bioprosthetic valve. The primary objective of the study is to assess the impact of apixaban on the prevention of hypo-attenuated leaflet thickening at 3 months. The secondary and exploratory endpoints will be clinical outcomes and safety profiles of the two strategies. Discussion Antithrombotic therapy after aortic valve replacement is used to prevent valve thrombosis and systemic thromboembolism. Latent bioprosthetic valve thrombosis is a precursor of clinically significant prosthetic valve dysfunction or thromboembolic events. The hallmark feature of latent bioprosthetic valve thrombosis is hypo-attenuated leaflet thickening on cardiac computed tomography. Subclinical leaflet thrombosis occurs frequently in bioprosthetic aortic valves, more commonly in transcatheter than in surgical valves. There is no evidence on the effect of direct oral anticoagulants on the incidence of hypo-attenuated leaflet thickening after surgical aortic valve replacement with rapid deployment bioprostheses. Trial registration ClinicalTrials.gov NCT06184113. Registered on December 28, 2023

florio® HAEMO is a hemophilia treatment monitoring application (app) offering activity tracking and wearable device connectivity. Its use might support everyday activities for people with hemophilia. The aim of this study was to evaluate user satisfaction, long-term usage and the impact on data entry when pairing a wearable with a hemophilia monitoring app. This is a follow-up of a two-part user survey conducted in Central Europe. People with hemophilia and parents/caregivers of children with hemophilia using florio HAEMO and who completed part one were invited to complete a second online questionnaire at least 4 months later. Fifty participants (83.3%) who completed part one of the survey continued to use the florio HAEMO app and completed part two. Of 14 participants who chose to use the app with a wearable, more than half (57.1%) were aged between 13 and 25 years. Overall, the results demonstrated that florio HAEMO is very easy or rather easy to use, especially for individuals pairing the app with a wearable. Most people using a wearable indicated that florio HAEMO was very or rather important in bringing certainty to daily activities (85.7%). Notably, 14 of 36 (38.9%) non-wearable users indicated that they would prefer to pair the app with a wearable in the future. Adherence to the florio HAEMO app is maintained over an extended period of use. Pairing the app with a wearable might enable easier access to app features, increase data entry motivation and provide more certainty about daily activities for people with hemophilia.

Understanding team diversity has become essential for modern-day organisations. This study explores the impact of knowledge diversity in design teams through computational simulations. By analysing design space characteristics, we study how diverse teams perform compared to less diverse counterparts. Results reveal that highly diverse teams exhibit increased efficiency, quicker convergence, and larger but sparser design spaces. This work contributes to understanding the impact of knowledge diversity in design teams and sets the stage for future systematic studies of diversity.

This study compares empirical and topology optimization methods for reducing gear body mass. Specimens produced via empirical guidelines and topology optimization were compared to referent full-disc gear, focusing on stresses and deformations. Values were determined numerically (Ansys was used) and the calculation method was verified using ISO 6336. The empirical approach exhibited substantial increases in stress and deformation while topology optimization method had promising outcomes. While decreasing mass, it also diminished tooth root stress on the tensile side by 17.1%.

Design hackathons offer a unique research opportunity to study time-pressured collaborative design. At the same time, research on design hackathons faces unique methodological challenges, prompting the exploration of new research approaches. This paper proposes a new data-collection framework that leverages a virtual format of hackathon events and enables a deeper insight into hackathon dynamics. The framework applicability is presented through a case study of the IDEA challenge hackathon, in which different intrusive and non-intrusive data collection approaches were used.

Despite the rapid advancement of generative Large Language Models (LLMs), there is still limited understanding of their potential impacts on engineering design (ED). This study fills this gap by collecting the tasks LLMs can perform within ED, using a Natural Language Processing analysis of 15,355 ED research papers. The results lead to a framework of LLM tasks in design, classifying them for different functions of LLMs and ED phases. Our findings illuminate the opportunities and risks of using LLMs for design, offering a foundation for future research and application in this domain.

The presented study investigates differences in engineering designers' CAD performance when modelling from two types of projections in technical drawings – isometric and orthographic. The results revealed significant differences in the percentage of correctly replicated components' size and shape, indicating better CAD outcomes when generating CAD models from the orthographic projection. In addition, a comparison of duration, as well as the number and type of sketch entities, sketch relations, and CAD features, showed that CAD modelling processes were similar in both conditions.

Design sprints complement traditional teaching methods, especially in project-based learning courses. While this approach can potentially change Computer-Aided Design (CAD) usage, it is still underexplored. Therefore, this study explores the influence of design sprints on embodiment-focused CAD activities in project-based learning by examining differences in patterns of CAD user actions, focusing on design space and action types. The case involves two higher-graded and two lower-graded student design teams monitored with a non-invasive method across a two-day design sprint event.

The spare parts play a vital role in sustaining the operation and longevity of products and systems, but their unavailability can lead to prolonged downtime or expensive replacements. The integration of 3D scanning and Additive Manufacturing (AM) presents a promising path for spare part production. However, to utilise the full potential of AM, sometimes, redesign of the original part is needed. This paper investigates and proposes a new approach that integrates reverse engineering and redesign of an original part based on functional analysis to support the manufacturing of AM spare parts.

Uncomfortable sensations that arise during virtual reality (VR) use have always been among the industry’s biggest challenges. While certain VR-induced effects, such as cybersickness, have garnered a lot of interest from academia and industry over the years, others have been overlooked and underresearched. Recently, the research community has been calling for more holistic approaches to studying the issue of VR discomfort. Focusing on active VR gaming, our article presents the results of two user studies with a total of 40 participants. Incorporating state-of-the-art VR-specific measures (the Simulation Task Load Index—SIM-TLX, Cybersickness Questionnaire—CSQ, Virtual Reality Sickness Questionnaire—VRSQ) into our methodology, we examined workload, musculoskeletal discomfort, device-related discomfort, cybersickness, and changes in reaction time following VR gameplay. Using a set of six different active VR games (three per study), we attempted to quantify and compare the prevalence and intensity of VR-induced symptoms across different genres and game mechanics. Varying between individuals, as well as games, the diverse symptoms reported in our study highlight the importance of including measures of VR-induced effects other than cybersickness into VR gaming user studies, while questioning the suitability of the Simulator Sickness Questionnaire (SSQ)—arguably the most prevalent measure of VR discomfort in the field—for use with active VR gaming scenarios.

Conventional wireless-power-transfer (WPT) systems are linear and time invariant, which sets fundamental limitations on their performance, including a trade-off between transfer efficiency and the level of transferred power. In this paper, we introduce and study a possibility of temporal modulation for inductive wireless-power-transfer systems and uncover that this trade-off is avoided as a consequence of varying the inductive coupling strength in time. Our theoretical analysis reveals that under the optimal modulation depth and phase, the time modulation can yield a substantial improvement in the WPT efficiency, while the received power at the load is also improved compared to the static WPT reference system. We experimentally demonstrate the concept with a low-frequency system and observe a threefold improvement in efficiency over the reference static counterpart. This technical capability reconciles the inherent trade-off between the WPT efficiency and transferred power, paving the way for simultaneous advancements in both efficiency and delivered power.