Dynamics of Metastable Magnetic Skyrmions

Skyrmions, vortex-like objects composed of magnetic moments, have seen a recent surge of research interest due to their unique transport and topological properties. With an ever-increasing demand for more efficient memory and computation, skyrmionic devices have been conceived as an ultra-low power, high density data storage solution. While they are found in a range of materials, in this thesis we will primarily be concerned with skyrmions found in bulk chiral magnets. In such systems, skyrmions are typically only at equilibrium in a small range of temperature and applied magnetic field. However, they can exist in a metastable state over a much wider range of the magnetic phase diagram, formed by cooling the system under an applied magnetic field. Metastable skyrmions therefore have technological application by enabling the existence of skyrmions at room temperature and zero applied magnetic field. However, they also posses a finite, temperature-dependent lifetime, which places limitations on the stability of metastable skyrmions, and also restricts the population remaining after the cooling process. This lifetime is realised in nanoscopic mechanisms which are governed by topological defects, known as Bloch points. Due to the locality of these structures, the development of real-space imaging techniques are vital for gaining true understanding of skyrmion formation and annihilation. In this thesis, the dynamics of metastable skyrmions are thoroughly investigated through the use of magnetometry, and a range of neutron and x-ray scattering techniques. The effect of chemical substitution, or doping, on the magnetic phase transitions in Zn-doped Cu$_2$OSeO$_3$ is explored, and found to introduce pinning effects which dramatically increases the lifetime of metastable skyrmions. Furthermore, by adapting x-ray imaging methods for cryogenic sample environments, the first real-space observation of the vertical, tube-like, structure of skyrmions is demonstrated. The results open the door to a variety of experiments capable of further investigation into the dynamics of the skyrmion spin texture

Maximal Cliques in Scale-Free Random Graphs

We investigate the number of maximal cliques, i.e., cliques that are not contained in any larger clique, in three network models: Erd\H{o}s-R\'enyi random graphs, inhomogeneous random graphs (also called Chung-Lu graphs), and geometric inhomogeneous random graphs. For sparse and not-too-dense Erd\H{o}s-R\'enyi graphs, we give linear and polynomial upper bounds on the number of maximal cliques. For the dense regime, we give super-polynomial and even exponential lower bounds. Although (geometric) inhomogeneous random graphs are sparse, we give super-polynomial lower bounds for these models. This comes form the fact that these graphs have a power-law degree distribution, which leads to a dense subgraph in which we find many maximal cliques. These lower bounds seem to contradict previous empirical evidence that (geometric) inhomogeneous random graphs have only few maximal cliques. We resolve this contradiction by providing experiments indicating that, even for large networks, the linear lower-order terms dominate, before the super-polynomial asymptotic behavior kicks in only for networks of extreme size

Energy decomposition analysis approaches and their evaluation on prototypical protein–drug interaction patterns

The partitioning of the energy in ab initio quantum mechanical calculations into its chemical origins (e.g., electrostatics, exchange-repulsion, polarization, and charge transfer) is a relatively recent development; such concepts of isolating chemically meaningful energy components from the interaction energy have been demonstrated by variational and perturbation based energy decomposition analysis approaches. The variational methods are typically derived from the early energy decomposition analysis of Morokuma [Morokuma, J. Chem. Phys., 1971, 55, 1236], and the perturbation approaches from the popular symmetry-adapted perturbation theory scheme [Jeziorski et al., Methods and Techniques in Computational Chemistry: METECC-94, 1993, ch. 13, p. 79]. Since these early works, many developments have taken place aiming to overcome limitations of the original schemes and provide more chemical significance to the energy components, which are not uniquely defined. In this review, after a brief overview of the origins of these methods we examine the theory behind the currently popular variational and perturbation based methods from the point of view of biochemical applications. We also compare and discuss the chemical relevance of energy components produced by these methods on six test sets that comprise model systems that display interactions typical of biomolecules (such as hydrogen bonding and pi-pi stacking interactions) including various treatments of the dispersion energy

Salutogenesis: Implications for Maintaining a Psychologically Informed Physical Therapy Practice

Pathogenesis, the study of disease origins and causes, looks retrospectively at how to eliminate illnesses once they occur and has been the prevalent approach in Western medicine. Salutogenesis, by comparison, is the study of health origins and causes and looks prospectively at how to create health. There are many psychosocial instruments used to measure the personal factors that influence salutogenesis. However, the salutogenic model has rarely been studied in physical therapy settings, even though physical therapy educators and researchers are currently describing the importance of a psychologically informed practice. Twenty-five psychological constructs within the salutogenic model were evaluated for this review. The evaluative process examined the constructs based on: 1) Measurability, determined by the reliability and validity of the outcome measures; 2) Relevance to physical therapy, determined by the construct’s ability to address learnable skills that can be influenced by physical therapists; and 3) Practicality, determined by the ability to measure the construct in a clinical setting using common practice patterns. Of the twenty-five constructs evaluated for this review, three met the above criteria and were chosen for further examination: self-efficacy, resilience, and sense of coherence. The results suggest that these three constructs have potential use in physical therapy. Using one or more of these constructs to attain relevant psychosocial information about patients may assist physical therapists in determining appropriate interventions. Therefore, although this literature review proposes the clinical use of self-efficacy, resilience, and sense of coherence in physical therapy, further research is recommended to develop their optimal use

Association between Primary Perioperative CEA Ratio, Tumor Site, and Overall Survival in Patients with Colorectal Cancer

A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author's publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.There are differences in the incidence, clinical presentation, molecular pathogenesis, and outcome of colorectal cancer (CRC) based on tumor location. Emerging research suggests that the perioperative carcinoembryonic antigen (CEA) ratio (post-op/pre-op CEA) is a prognostic factor for CRC patients. We aimed to determine the association between CEA ratio, tumor location, and overall survival (OS) among patients with CRC. We analyzed 427 patients who underwent resection for CRC at the University of Kansas Medical Center. After excluding those without pre- or post-operative CEA data, 207 patients were classified as either high (≥0.5) or low ( 5 ng/mL at the time of recurrence. The Kaplan–Meier method was used to estimate survival rates. The median age was 62 years (inter-quartile range 51–71), 55% were male, 41% were smokers, 71% had left-sided tumors, the median pre-operative CEA was 3.1 ng/mL (inter-quartile range (IQR) 1.5–9.7), and 57% had a CEA ratio ≥0.5. The OS rates were 65.1% and 86.3% in patients with high versus low CEA ratios, respectively (log-rank p-value = 0.045). The OS rates were 64.4% and 77.3% in patients with right-sided vs. left-sided tumors, respectively (log-rank p-value = 0.5). Among patients with CEA levels greater than 5 at the time of recurrence, the OS rates were 42.9% and 43.4% in patients with right-sided vs. left-sided tumors, respectively (log-rank p-value = 0.7). There was a significantly higher survival among patients with low CEA ratios than among those with high CEA ratios. There was no difference in OS between left- versus right-sided tumors. Among patients with CEA elevation > 5 ng/mL at the time of recurrence, there was no difference in OS between left versus right-sided tumors. These findings warrant validation in a larger cohort as our sample size was limited

ARTP statement on cardiopulmonary exercise testing 2021.

Cardiopulmonary exercise testing (CPET) has become an invaluable tool in healthcare, improving the diagnosis of disease and the quality, efficacy, assessment and safety of treatment across a range of pathologies. CPET's superior ability to measure the global exercise response of the respiratory, cardiovascular and skeletal muscle systems simultaneously in a time and cost-efficient manner has led to the application of CPET in a range of settings from diagnosis of disease to preoperative assessment. The Association for Respiratory Technology and Physiology Statement on Cardiopulmonary Exercise Testing 2021 provides the practitioner and scientist with an outstanding resource to support and enhance practice, from equipment to testing to leadership, helping them deliver a quality assured service for the benefit of all patient groups

Perineural Invasion in Pancreatic Ductal Adenocarcinoma (PDAC): A Saboteur of Curative Intended Therapies?

(1) Background: Perineural invasion (PNI) is a common characteristic of pancreatic ductal adenocarcinoma (PDAC) and is present in most resection margins. We hypothesized that curative pancreatic tumor resection with long-term survival could only be achieved in PNI-negative patients. (2) Material and Methods: A retrospective investigation of PDAC patients who underwent curative-intended surgery during the period 2008 to 2019 was performed at our institution. (3) Results: We identified 571 of 660 (86.5%) resected patients with well-annotated reports and complete datasets. Of those, 531 patients (93%) exhibited tumors with perineural invasion (Pn1), while 40 (7%) were negative for PNI (Pn0). The majority of patients in the Pn1 group presented advanced tumor stage and positive lymph node infiltration. Patients in the Pn0 group showed an improved disease-free and long-term survival compared to the Pn1 group (p < 0.001). Subgroup analysis of all R0-resected patients indicated improved long-term survival and disease-free survival of R0 Pn0 patients when compared to R0 Pn1 patients (p < 0.001). (4) Conclusion: Our study confirmed that Pn0 improves the long-term survival of PDAC-resected cancer patients. Furthermore, PNI significantly challenges the long-term survival of formally curative (R0) resected patients. We provide new insights into the dynamics of PNI in pancreatic cancer patients which are needed to define subgroups of patients for risk stratification and multimodal treatment strategies

Water stable molecular n-doping produces organic electrochemical transistors with high transconductance and record stability.

From established to emergent technologies, doping plays a crucial role in all semiconducting devices. Doping could, theoretically, be an excellent technique for improving repressively low transconductances in n-type organic electrochemical transistors - critical for advancing logic circuits for bioelectronic and neuromorphic technologies. However, the technical challenge is extreme: n-doped polymers are unstable in electrochemical transistor operating environments, air and water (electrolyte). Here, the first demonstration of doping in electron transporting organic electrochemical transistors is reported. The ammonium salt tetra-n-butylammonium fluoride is simply admixed with the conjugated polymer poly(N,N'-bis(7-glycol)-naphthalene-1,4,5,8-bis(dicarboximide)-co-2,2'-bithiophene-co-N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide), and found to act as a simultaneous molecular dopant and morphology-additive. The combined effects enhance the n-type transconductance with improved channel capacitance and mobility. Furthermore, operational and shelf-life stability measurements showcase the first example of water-stable n-doping in a polymer. Overall, the results set a precedent for doping/additives to impact organic electrochemical transistors as powerfully as they have in other semiconducting devices