Syfte och frågeställningar Syftet med arbetet är att skapa en strukturerad litteraturöversikt som sammanställer existerande biomekanisk forskning på hopp inom konståkning, och även beskriva vilken betydelse muskelstyrkan i relevanta muskelgrupper har för rotation.  •    Vilka biomekaniska parametrar är viktiga att eftersträva för hopp med olika antal rotationer? •    Vad är forskningsläget kring muskelstyrkan som behövs för hopp med olika antal rotationer? Metod En strukturerad litteraturstudie genomfördes. Litteratursökningen gjordes i databaserna SportDiscus och PubMed på ett strukturerat sätt med olika sökkombinationer av nyckelord. Manuella sökningar gjordes även via referenslistor i artiklar och böcker. 150 artiklar extraherades och slutligen inkluderades 15 vetenskapliga originalartiklar i studien. Artiklarna valdes med hjälp av inklusions- och exklusionskriterier och granskades sedan kritiskt med hjälp av granskningsmall. Resultat Resultaten presenterade flera olika biomekaniska parametrar som är viktiga i konståkningshopp med olika antal rotationer och att kunna genomföra dessa på ett gynnsamt sätt. Resultaten visade också att muskelstyrkan verkar vara en väsentlig del för att klara av hopp med olika antal rotationer och ha en positiv effekt på rotationen. Resultaten presenterar även relevanta muskelgrupper för detta. Slutsats Denna litteraturstudie ger en unik sammanställning av de viktigaste biomekaniska parametrarna som är viktiga vid konståkningshopp för att uppnå fler varv, och även de viktigaste fokusområden för styrka för utveckling av konståkningshopp. Ytterligare forskning med hög kvalitet kring detta behövs för att få en bredare översikt kring ämnet. / Aim The aim of this study is to create a structured literature review that compiles existing biomechanical research on jumps in figure skating. The aim is also to describe the importance of muscle strength in relevant muscle groups for rotation. •    What biomechanical parameters are important for jumping with different numbers of rotations? •    What is the state of research on muscle strength needed for jumps with different numbers of rotations? Method A structured literature study was conducted. The literature research was done in the databases SportDiscus and PubMed in a structured manner with different search combinations of keywords. Additional sources were compiled via reference lists in articles and books. 150 articles were extracted and finally 15 original scientific articles were included in the study. The articles were chosen using inclusion and exclusion criteria and then critically reviewed using review templates. Results The results present several different biomechanical parameters that are important to strive for in figure skating jumps with different numbers of rotations and to be able to execute them out in a favorable way. Results also showed that muscle strength seems to be an essential part of coping with jumps with different numbers of rotations and has a positive effect on the rotation. The results also present relevant muscle groups. Conclusion This literature study provides a unique compilation of the most important biomechanical parameters that are essential in figure skating to achieve more rotation. The most important focus areas for strength for the development of figure skating are presented. More comprehensive and in-depth research to obtain a broader overview of the subject is required.

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Essential Tremor (ET), a condition characterized by postural and kinetic tremor in the upper limbs, is one of the most prevalent movement disorders. While pharmaceutical and surgical treatment options exist, they are not ideal. Assistive devices have the potential to provide relief to patients but are largely unexplored for ET. Furthermore, prior characterizations of essential tremor have focused on endpoint tremor and provide insufficient detail for designing such a device. We propose and demonstrate a novel method for characterizing essential tremor in the 7 proximal degrees of freedom (DOF) of the upper limb in various postures. In addition, we provide a preliminary characterization in a small number of patients with mild ET. We collected data from 10 patients with ET. Subjects were instrumented with four electromagnetic sensors that recorded orientation of upper limb segments. After a calibration, each subject positioned his/her upper limb in 16 different postures for 15 seconds each. This procedure was repeated 4 times for each subject, with each repetition being considered a run. Sensor data were converted to angular kinematic data for each DOF using inverse kinematics, a practice unique to this study. These data were then analyzed in the frequency domain to calculate the power associated with the tremor in each DOF and posture. More specifically, we computed the area of the periodogram over the 4-12 Hz frequency band typically associated with ET [narrow-band area (NBA)] and over the wider frequency band from 2 Hz to the Nyquist frequency [wide-band area (WBA)]. If significant peaks were found in the 4-12 Hz band, their frequency and amplitude were reported. Mixed-model ANOVA tests were used to investigate effects of DOF, posture, run, gravity, and patient characteristics on reported measures. NBA and WBA varied significantly between DOF, being lowest in the wrist, intermediate in the shoulder, and greatest in the elbow and forearm (pronation-supination). NBA and WBA also varied significantly with posture. Only 5% of observations had significant peaks, with 49% of peaks occurring in wrist flexion-extension and 39% occurring in wrist radial-ulnar deviation. Peak frequency was quite stereotyped (5.7 Hz ± 1.3Hz). Run had no significant effects, indicating that tremor measures were consistent over the duration of the experiment. Effects of gravity and demographic factors on measures were mixed and did not present a discernible pattern. This preliminary characterization suggests that tremor may be focused in a subset of upper limb DOF, being greatest (in terms of power) in elbow flexion-extension and forearm pronation-supination, and most concentrated (with peaks at a stereotyped frequency) in wrist flexion-extension and radial-ulnar deviation. Our method of 7 DOF characterization through inverse kinematics, in conjunction with future research (isolation studies, EMG, and finger DOF) may allow for optimal tremor suppression by an orthosis.

This thesis examined the time course of speech adaptation prior to data collection when using an electromagnetic articulograph to measure speech articulator movements. The stimulus sentence and electromagnetic sensor placement were designed to be sensitive to changes in the fricatives /s/ and /ʃ/. Twenty native English speakers read aloud stimulus sentences before the attachment of six electromagnetic sensors, immediately after attachment, and again at 5, 10, 15 and 20 minutes after attachment. Participants read aloud continuously between recordings to encourage adaptation to the presence of the sensors. Audio recordings were rated by 20 native English listeners who were not part of the production study. After listening to five practice samples, these participants rated 150 stimuli (31 repeat samples) using a visual analog scale (VAS) with the endpoints labeled as precise and imprecise. An acoustic analysis of the recordings was done by segmenting the fricatives /s/ and /ʃ/ from the longer recording and computing spectral center of gravity and spectral standard deviation in Hertz. Durations of /s/, /ʃ/ and the sentence were also measured. Results of both perceptual and acoustic analysis revealed a change in speech precision over time, with all post attachment recordings receiving lower perceptual scores. Precision ratings beyond the ten minute recording remained steady. It can be concluded from the results that participants reached a height of adaptation after 10 minutes of talking with kinematic recording sensors attached, and that after the attachment of sensors, speech production precision did not at any point return to pre attachment levels.

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We use the APOSTLE suite of cosmological simulations to examine the role of the cosmic ionizing background in regulating star formation (SF) in low-mass LCDM halos. In agreement with earlier work, we find that, after reionization, SF can only proceed in halos whose mass exceeds a redshift-dependent ``critical'' virial mass determined by the structure of LCDM halos and the thermal pressure of UV-heated gas. This critical mass increases from Mcrit~10^8 Msun at z~11$ to ~10^9.7 Msun at z=0, roughly following the average mass growth history of halos in that mass range. This implies that most halos above or below critical at present have remained so since early times. In particular, the halos of most galaxies today were already above-critical (and thus forming stars) at high redshift, providing a simple explanation for the ubiquitous presence of ancient stellar populations in dwarfs, regardless of luminosity. It also implies that Mcrit today represents a ``threshold'' mass below which the fraction of ``dark'' halos increases steeply. Sub-critical halos may still host luminous galaxies if they were above-critical at some point in the past. SF ceases if a halo falls into the sub-critical regime; depending on each halo's accretion history this can occur over a wide range of times, explaining why SF in many dwarfs seems to continue well past the reionization epoch. It also suggests a tantalizing explanation for the episodic nature of SF in some dwarfs, which, in this interpretation, would be linked to temporary halo excursions above and below the critical boundary. In the simulations, Mcrit(z) cleanly separates star-forming from non-star-forming systems at all redshifts, indicating that the ionizing UV background, and not stellar feedback, is what regulates the beginning and the end of SF in the faintest dwarfs. Galaxies in sub-critical halos should make up a sizable population of faint field dwarfs, distinct from those in more massive halos because of their lack of ongoing star formation. Although few such galaxies are known at present, the discovery of this population would provide strong support for our results. / Graduate

Dusty circumnuclear disks (CNDs) in luminous early-type galaxies (ETGs) show regular, dynamically cold molecular gas kinematics. For a growing number of these ETGs, Atacama Large Millimeter/sub-millimeter Array (ALMA) CO imaging and detailed gas-dynamical modeling have yielded moderate to high precision black hole (BH) mass (M_BH) determinations. To date, however, few studies have explored the effects of dust attenuation, or uncertainties in dust corrections, on recovered stellar luminosity models from high angular resolution optical/near-IR observations and M_BH measurements. Recent kinematic studies that modeled ALMA CO data sets have found that uncertainties in the intrinsic central stellar surface brightness slope due to dust may even dominate the BH mass error budgets. From the ALMA archive, we identified a subset of 26 ETGs with clean CO kinematics and good prospects for eventual MBH determination but that did not have sufficiently high angular resolution observations in the optical and near-IR. We have obtained new optical and near-IR Hubble Space Telescope (HST) images of this sample to supplement the archival HST data. Together, these new and archival HST data will enable the mitigation of dusty CND obscuration in the construction of dust-corrected stellar luminosity models, leading to both BH mass measurement and complete error analysis using existing ALMA CO imaging. Here, we present the sample properties, data analysis techniques, and dust-masked stellar surface brightness profiles and luminosity models using the multi-Gaussian expansion formalism. With estimated M_BH/M_⊙ ≳ 10^8 to few x10^9 , securing quality M_BH determinations for this sample of ETGs will significantly improve the high-mass end of the current BH census, facilitating new scrutiny of local BH mass-host galaxy scaling relationships.

Biomechanics research investigating the knee kinematics of youth participants is very limited. The most accurate method of measuring knee kinematics utilizes invasive procedures such as bone pins. However, various experimental techniques have improved the accuracy of gait kinematic analyses using minimally invasive methods. In this study, gait trials were conducted with two participants between the ages of 11 and 13 to obtain the knee flexion-extension (FE), adduction-abduction (AA) and internal-external (IE) rotation angles of the right knee. The objectives of this study were to (1) conduct pilot experiments with youth participants to test whether any adjustments were necessary in the experimental methods used for adult gait experiments, (2) apply a Triangular Cosserat Point Element (TCPE) analysis for Soft-Tissue Artifact (STA) correction of knee kinematics with youth participants, and (3) develop a code to conduct a Principal Component Analysis (PCA) to find the PCA-defined flexion axis and calculate knee angles with both STA and PCA-correction for youth participants. The kinematic results were analyzed for six gait trials on a participant-specific basis. The TCPE knee angle results were compared between uncorrected angles and another method of STA correction, Procrustes Solution, with a repeated measures ANOVA of the root mean square errors between each group and a post-hoc Tukey test. The PCA-corrected results were analyzed with a repeated measures ANOVA of the FE-AA correlations from a linear regression analysis between TCPE, PS, PCA-TCPE and PCA-PS angles. The results indicated that (1) youth experiments can be conducted with minor changes to experimental methods used for adult gait experiments, (2) TCPE and PS analyses did not yield statistically different knee kinematic results, and (3) PCA-correction did not reduce FE-AA correlations as predicted.