In the primary and secondary medical health sector, patient reported outcome measures (PROMs) are widely used to assess a patient's disease-related functional health state. However, the World Health Organization (WHO), in its recently adopted resolution on "strengthening rehabilitation in all health systems", encourages that all health sectors, not only the rehabilitation sector, classify a patient's functioning and health state according to the International Classification of Functioning, Disability and Health (ICF). This research sought to optimize machine learning (ML) methods that fully and automatically link information collected from PROMs in persons with unspecific chronic low back pain (cLBP) to limitations in activities and restrictions in participation that are listed in the WHO core set categories for LBP. The study also aimed to identify the minimal set of PROMs necessary for linking without compromising performance. A total of 806 patients with cLBP completed a comprehensive set of validated PROMs and were interviewed by clinical psychologists who assessed patients' performance in activity limitations and restrictions in participation according to the ICF brief core set for low back pain (LBP). The information collected was then utilized to further develop random forest (RF) methods that classified the presence or absence of a problem within each of the activity participation ICF categories of the ICF core set for LBP. Further analyses identified those PROM items relevant to the linking process and validated the respective linking performance that utilized a minimal subset of items. Compared to a recently developed ML linking method, receiver operating characteristic curve (ROC-AUC) values for the novel RF methods showed overall improved performance, with AUC values ranging from 0.73 for the ICF category d850 to 0.81 for the ICF category d540. Variable importance measurements revealed that minimal subsets of either 24 or 15 important PROM variables (out of 80 items included in full set of PROMs) would show similar linking performance. Findings suggest that our optimized ML based methods more accurately predict the presence or absence of limitations and restrictions listed in ICF core categories for cLBP. In addition, this accurate performance would not suffer if the list of PROM items was reduced to a minimum of 15 out of 80 items assessed.

As part of our quest for digital biomarkers of neuromuscular aging, and encouraged by recent findings in healthy volunteers, this study investigated if the instantaneous median frequency (IMDF) derived from back muscle surface electromyographic (SEMG) data monitored during cyclic back extensions could reliably differentiate between younger and older individuals with cLBP. A total of 243 persons with cLBP participated in three experimental sessions: at baseline, one to two days after the first session, and then again approximately six weeks later. During each session, the study participants performed a series of three isometric maximal voluntary contractions (MVC) of back extensors using a dynamometer. These were followed by an isometric back extension at 80% MVC, and-after a break-25 slow cyclic back extensions at 50% MVC. SEMG data were recorded bilaterally at L5 (multifidus), L2 (longissimus dorsi), and L1 (iliocostalis lumborum). Linear mixed-effects models found the IMDF-SEMG time-course changes more rapidly in younger than in older individuals, and more prominently in male participants. The absolute and relative reliabilities of the SEMG time-frequency representations were well compared between older and younger participants. The results indicated an overall good relative reliability, but variable absolute reliability levels. IMDF-SEMG estimates derived from cyclic back extensions proved to be successful in reliably detecting differences in back muscle function in younger vs. older persons with cLBP. These findings encourage further research, with a focus on assessing whether an IMDF-SEMG-based index could be utilized as a tool to achieve the preclinical detection of back muscle aging, and possibly predict the development of back muscle sarcopenia.

The building material straw as a renewable and almost endlessly available by-product could contribute to lower greenhouse gas emissions and primary energy consumption in the building construction sector. Straw as building material, is used as insulation material in metal stud walls and timber frame constructions. Additionally, whole straw bales can be used as insulation and bearing structure in combination with a timber frame. The state of the art provides an inconsistent data conglomerate on the acoustical and environmental performance of different wall structures, test setups and assessment methods. The presented research shows results of a parallel evaluation of the acoustic and environmental performance of wall structures with a consistent approach in measurement and calculation methods. The results of building acoustic measurements are used to quantify the acoustic potential for of straw in those wall constructions. The results show that the building acoustic performance of wall constructions with straw is comparable to the performance of already on the market established wall constructions. The influence of parameters like density, dynamic stiffness, air flow resistivity and longitudinal wave speed of used materials on the measured sound reduction index is discussed. Especially the density and the dynamic stiffness are important material parameters to achieve a high sound reduction index of the wall constructions. Since straw is a renewable material, the environmental impacts of the different acoustically analyzed wall constructions were investigated additionally. Standardized assessment methodologies were applied on the different components and a comparison with different insulation materials was carried out. It could be shown that the use of straw leads to lower environmental impacts (demonstrated in the Global Warming Potential indicator), though, the insulation material is not the most relevant parameter of the structures. Significantly higher environmental impacts are caused by the bearing structure (metal and timber frame studs) and the planking materials. Finally, an overall comparison together with standard concrete and brick wall structures underlines the beneficial environmental properties of walls made of renewable materials with straw.

AbstractThe student-centered learning approach “learning office” has been established in vocational school education under constant evaluation through a team of education researchers. In the past two years, emergency online teaching has affected education world-wide with a severe impact on teacher-centered as well as student-centered education.Our goal is to evaluate teachers’ and students’ perspectives on emergency and systematic online teaching and to get an impression of students’ perceived competence in 21st century skills which the learning office is specifically designed to foster. For this, we reconcile the change in perspectives through comparisons of open text answers from a questionnaire after experiencing emergency online teaching and interviews with students and teachers regarding their perceived change in the way contents are taught.We find diverse aspects which are partially favourable for student-centered learning in times of self-reliant education at home. However, we also identified adversary effects of studying alone at home for the learning office due to its interactive nature. On the one hand, students felt more self-reliant and able to work on materials on their own accord without constant input or supervision of a teacher. On the other hand, students missed the personal interaction with their peers, but even more with their teachers in the online setting.Based on our questionnaire and interviews, we find that student-centered learning indeed helped to develop the skills for self-reliant learning in students. However, the position of the educator as a coach and guiding figure to the students is irreplaceable, especially in student-centered learning.KeywordsStudent-centred learning21st century skillsLearning officeEmergency online teaching

Quality assurance (QA) in magnetic resonance imaging (MRI) requires test objects. ‘Phantoms’ provided by MR manufacturers are homogeneously filled spheres or cylinders, and commercially available products are often too small for abdominal imaging, particularly for enlarged polycystic kidneys. Here we present the design, manufacturing and testing of a dedicated, yet versatile, abdominal MRI phantom, that can be reproduced with relatively low costs. The phantom mimics a human abdomen in size and shape and comprises seven test fluids, representing various tissue types at 3 T. The conductivity and permittivity of the test fluids match the average abdomen and kidney with a relative permittivity (ε) 65 and 72 as well as conductivity 0.6 and 0.7 S/m, respectively. The T1 and T2 relaxation times cover healthy average abdomen and kidney tissue values (T1(abd): 856 ms and T1(kid): 1,106 ms; T2(abd): 52 ms and T2(kid): 67 ms), intermediate (T1: 1,183 ms and 1,271 ms; T2: 128 and 189 ms), and disease values for (polycystic) kidney (T1: 1,428 ms, 1,561 ms and 1763 ms; T2: 319 ms, 424 and 647 ms). T1 and T2 relaxation times were stable over 73 weeks. Our reasonably priced, durable and reproducible abdominal phantom enables single and multi-center QA for future collaborative studies aiming for various challenges around abdominal and, particularly, kidney imaging.

The effective sound speed gradient is used to describe the meteorological conditions during sound measurements at roads and railways. Meteorological parameters were assessed up to a height of 10 m. The sound level differences between a reference point close to the passing vehicles and at distances of 100–500 m from motorways and railway tracks were determined. These differences were found to correlate well with the effective sound speed gradient determined from the measured temperature and wind speed gradients which follow the day/night cycle as a result of the reversing air temperature gradient, incoming solar radiation and wind conditions. The correlation with sound level differences can be approximated by an S-shaped function which is constant for large positive or negative gradients of the effective sound speed. These threshold values are a consequence of the local meteorological and attenuation conditions. The analysis shows that large effective sound speed gradients are mainly a result of the wind conditions whereas gradients without a substantial wind speed contribution are low and a result of the temperature gradient. In the distance range between 150 m and 250 m, the meteorological influences cause a level increase of 3–4 dB(A) for downward refracted sound rays (favourable sound propagation) compared to a situation without meteorological influence (effective sound speed gradient of zero). In the same distance range, meteorological conditions cause a maximum sound level attenuation of 5–10 dB(A) for upward curved sound rays (unfavourable sound propagation).

In highly security-critical network environments, it is a popular design decision to offload cryptographic tasks like encryption or signature generation to a dedicated trusted module or key server with paramount security features, we in this paper refer to with the general term Cryptographic Key Management Device (CKMD). While this network design yields several benefits, we demonstrate that the use of popular counter mode encryption modes like CTR or GCM can show substantial shortcomings in terms of security when used in conjunction with this network design. In particular, we show how the use of authenticated encryption using GCM enables the possibility of establishing a subliminal channel by exploiting the authentication information within messages. We show how decoding of hidden information can proceed in addition to decryption of overt information without raising authentication failures. With an exemplary but typical infrastructure, we show how the subliminal channel might be exploited and discuss approaches to mitigating the threat by preventing the ability to embed hidden information. In contrast to previous work, we conclude that, when using an infrastructure involving a CKMD and GCM is deployed, the use of random, CKMD-generated Initialization Vectors (IVs) is beneficial to avoid the subliminal channel described in this paper. However, the most potent remedy is deploying a different operational mode like GCM-SIV.