Based upon the resistor analogy and using the ideal loop gas approximation (ILGA), it is shown that only pending loops reduce the modulus of an otherwise perfect network made of monodisperse strands ...and junctions of identical functionality. Thus, the cycle rank of the network with pending structures removed (cyclic and branched) is sufficient to characterize modulus, if the resistor analogy can be employed. It is further shown that it is impossible to incorporate finite cycles into a polymer network such that individual network strands are at equilibrium conformations while maintaining simultaneously a force balance at the junctions. Therefore, the resistor analogy provides only an approximation for the phantom modulus of networks containing finite loops. Improved approaches to the phantom modulus can be constructed from considering a force balance at the junctions, which requires knowledge of the distribution of cross-link fluctuations in imperfect networks. Assuming loops with equilibrium conformations and a force balance at all loop junctions, a lower bound estimate for the phantom modulus G ph ≈ (ξ – c f L 1)kT/V is obtained within the ILGA for end-linked model networks and in the limit of L 1 ≪ ξ. Here, L 1 is the number of primary (“pending”) loops, ξ is the cycle rank of the network, k is the Boltzmann constant, V is the volume of the sample, and T is the absolute temperature. c f is a functionality-dependent coefficient, that is, ≈2.56 for junction functionality f = 3 and ≈3.06 for f = 4, while it converges quickly toward ≈4.2 in the limit of large f. Further corrections to the phantom modulus beyond finite loops are addressed briefly.
Despite the erosion of microsurgical case volume because of advances in endovascular and radiosurgical therapies, indications remain for open resection of pathology and highly technical vascular ...repairs. Treatment risk, efficacy, and durability make open microsurgery a preferred option for cerebral cavernous malformations, arteriovenous malformations (AVMs), and many aneurysms. In this paper, a 21-year experience with 7348 cases was reviewed to identify trends in microsurgical management. Brainstem cavernous malformations (227 cases), once considered inoperable and managed conservatively, are now resected in increasing numbers through elegant skull base approaches and newly defined safe entry zones, demonstrating that microsurgical techniques can be applied in ways that generate entirely new areas of practice. Despite excellent results with microsurgery for low-grade AVMs, brain AVM management (836 cases) is being challenged by endovascular embolization and radiosurgery, as well as by randomized trials that show superior results with medical management. Reviews of ARUBA-eligible AVM patients treated at high-volume centers have demonstrated that open microsurgery with AVM resection is still better than many new techniques and less invasive approaches that are occlusive or obliterative. Although the volume of open aneurysm surgery is declining (4479 cases), complex aneurysms still require open microsurgery, often with bypass techniques. Intracranial arterial reconstructions with reimplantations, reanastomoses, in situ bypasses, and intracranial interpositional bypasses (third-generation bypasses) augment conventional extracranial-intracranial techniques (first- and second-generation bypasses) and generate innovative bypasses in deep locations, such as for anterior inferior cerebellar artery aneurysms. When conventional combinations of anastomoses and suturing techniques are reshuffled, a fourth generation of bypasses results, with eight new types of bypasses. Type 4A bypasses use in situ suturing techniques within the conventional anastomosis, whereas type 4B bypasses maintain the basic construct of reimplantations or reanastomoses but use an unconventional anastomosis. Bypass surgery (605 cases) demonstrates that open microsurgery will continue to evolve. The best neurosurgeons will be needed to tackle the complex lesions that cannot be managed with other modalities. Becoming an open vascular neurosurgeon will be intensely competitive. The microvascular practice of the future will require subspecialization, collaborative team effort, an academic medical center, regional prominence, and a large catchment population, as well as a health system that funnels patients from hospital networks outside the region. Dexterity and meticulous application of microsurgical technique will remain the fundamental skills of the open vascular neurosurgeon.
Phosphorylated phosphatidylinositol lipids are crucial for most eukaryotes and have diverse cellular functions. The low-abundance signalling lipid phosphatidylinositol 3,5-bisphosphate PI(3,5)P2 is ...critical for cellular homoeostasis and adaptation to stimuli. A large complex of proteins that includes the lipid kinase Fab1-PIKfyve, dynamically regulates the levels of PI(3,5)P2. Deficiencies in PI(3,5)P2 are linked to some human diseases, especially those of the nervous system. Future studies will probably determine new, undiscovered regulatory roles of PI(3,5)P2, as well as uncover mechanistic insights into how PI(3,5)P2 contributes to normal human physiology.
Article first published in: LANG MICHAEL. 2020. Business Model Innovation Approaches: A Systematic Literature Review. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 68(2): ...435–449. https://doi.org/10.11118/actaun202068020435.
We show by computer simulations that a melt of pairwise connected star polymers provides an approximation for the reference conformations of real polymer chains in a network. Reference conformations ...are needed to normalize the experimental data related to the chain size (multiple quantum NMR, scattering, polarization, etc.) or data from advanced tools for measuring the phantom modulus in simulations. The latter allows then to separate the contributions of the correlation hole and finite extensibility (FE) from other contributions to the phantom modulus. Shear simulation data of the networks with entanglements switched off serve as a test of these approaches and as a critical test for the reference conformations. A comparison of the different measurements shows that for analyzing the simulation data by the advanced tools, the correlation hole corrections outnumber the corrections of FE or the combined effect of loops, network defects, and excess strain for tightly cross-linked entanglement free-model networks.
Since their introduction in 1954, cumulative sum (CUSUM) control charts have seen a widespread use beyond the conventional realm of statistical process control (SPC). While off-the-shelf ...implementations aimed at practitioners are available, their successful use is often hampered by inherent limitations which make them not easily reconcilable with real-world scenarios. Challenges commonly arise regarding a lack of robustness due to underlying parametric assumptions or requiring the availability of large representative training datasets. We evaluate an adaptive distribution-free CUSUM based on sequential ranks which is self-starting and provide detailed pseudo-code of a simple, yet effective calibration algorithm. The main contribution of this paper is in providing a set of ready-to-use tables of control limits suitable to a wide variety of applications where a departure from the underlying sampling distribution to a stochastically larger distribution is of interest. Performance of the proposed tabularized control limits is assessed and compared to competing approaches through extensive simulation experiments. The proposed control limits are shown to yield significantly increased agility (reduced detection delay) while maintaining good overall robustness.
The growing prominence of artificial intelligence (AI) in mobile health (mHealth) has given rise to a distinct subset of apps that provide users with diagnostic information using their inputted ...health status and symptom information—AI-powered symptom checker apps (AISympCheck). While these apps may potentially increase access to health care, they raise consequential ethical and legal questions. This paper will highlight notable concerns with AI usage in the health care system, further entrenchment of preexisting biases in the health care system and issues with professional accountability. To provide an in-depth analysis of the issues of bias and complications of professional obligations and liability, we focus on 2 mHealth apps as examples—Babylon and Ada. We selected these 2 apps as they were both widely distributed during the COVID-19 pandemic and make prominent claims about their use of AI for the purpose of assessing user symptoms. First, bias entrenchment often originates from the data used to train AI systems, causing the AI to replicate these inequalities through a “garbage in, garbage out” phenomenon. Users of these apps are also unlikely to be demographically representative of the larger population, leading to distorted results. Second, professional accountability poses a substantial challenge given the vast diversity and lack of regulation surrounding the reliability of AISympCheck apps. It is unclear whether these apps should be subject to safety reviews, who is responsible for app-mediated misdiagnosis, and whether these apps ought to be recommended by physicians. With the rapidly increasing number of apps, there remains little guidance available for health professionals. Professional bodies and advocacy organizations have a particularly important role to play in addressing these ethical and legal gaps. Implementing technical safeguards within these apps could mitigate bias, AIs could be trained with primarily neutral data, and apps could be subject to a system of regulation to allow users to make informed decisions. In our view, it is critical that these legal concerns are considered throughout the design and implementation of these potentially disruptive technologies. Entrenched bias and professional responsibility, while operating in different ways, are ultimately exacerbated by the unregulated nature of mHealth.
The differential for vertebrobasilar insufficiency is wide and can be caused by posterior circulation infarcts, steal-type phenomena, or other systemic causes. In the absence of imaging findings ...explaining symptomology, the utility of appropriate history gathering and dynamic angiography cannot be understated in identifying Bow Hunter's syndrome, a rare cause of dynamic vertebrobasilar insufficiency. We present a case of a 69-year-old man who complained of presyncope and severe dizziness when turning his head towards the right. On examination he had no radiculopathy but did have objective evidence of myelopathy. Computed tomography imaging and dynamic angiography demonstrated C3-C4 right uncovertebral joint hypertrophy and near complete stenosis of the right vertebral artery with dynamic head position towards the right. Given vertebrobasilar insufficiency and myelopathy, he was taken to the operating room for C3-C4 anterior cervical discectomy and fusion with vertebral artery decompression (Video 1). The patient provided consent for the procedure. Standard anterior cervical neck dissection was undertaken with additional platysmal undermining to facilitate exposure of the right uncovertebral joint and transverse processes. The vertebral artery was first decompressed above and below the area of most significant stenosis at the respective transverse foramina before the hypertrophied uncovertebral joint was removed. Next, discectomy and posterior osteophyte removal were completed in typical fashion followed by graft, plate, and screw placement. Postoperatively the patient had immediate resolution of symptoms and continued so at eight month follow-up. Imaging demonstrated return to normal caliber of the right vertebral artery and successful decompression.
This book examines women's participation in the executive structures of the Basel Mission and Presbyterian Church in Cameroon in order to tell a new story of women and church leadership. In 1886, the ...Basel Mission commenced mission work in Cameroon and successfully established an indigenous church which gained independence in 1957 as Presbyterian Church in Cameroon (PCC). In both churches, women were underrepresented in the echelons of power owing to entrenched patriarchy and recourse to controversial empowerment. Female missionaries to Cameroon trained women in fields like motherhood, domestic science and marriage, which yielded little or no opportunities for local women to participate in the power structures of the Basel Mission. This patriarchal culture was handed down to the PCC, whose initial all-male authority ensured that the power structure was all-male. But growing feminism within the church and pressure from international ecumenical partners led to timid gender reforms which ended women's exclusion from the ordained ministry, promoted female eldership, led to the establishment of a convent, and the adoption of a gender inclusive policy. But women's dearth in positions of leadership persisted, with most executive structures filled by men. So, this book tells the story of women's involvement in the executive structures of the Basel Mission and Presbyterian Church in Cameroon. It is the first effort at a holistic approach to interpreting women's lack of power in these two churches. Based upon archival research and oral sources, the book tells the story of the people, forces and events that led to the consistent underrepresentation of women in the churches' echelons of power. The lived realities of women who challenged patriarchy and held leadership positions in the church are illuminated. It documents the reality of women's lack of power, with particular focus on the dilemmas of female pastors, elders, nuns, and female Christian groups.
Inductively coupled radiofrequency (RF) coils are an inexpensive and simple method to realize wireless RF coils in magnetic resonance imaging (MRI), which can significantly ease the MRI scan setup ...and improve patient comfort because they do not require bulky components such as cables, baluns, preamplifiers, and connectors. However, volume‐type wireless coils are typically operated in transmit/receive mode because detuning such coils is much more challenging due to their complex structure and multiple resonant modes. Meanwhile, adding too many detuning circuits to a wireless coil would decrease the coil's quality factor, impair the signal‐to‐noise ratio, and increase the cost. In this work, we proposed, constructed, and tested a novel wireless volume coil based on the Litzcage design for 1.5‐T head imaging. Being an inductively coupled coil, it has a much simpler structure, resulting in a lighter weight and less bulky design. Despite its simpler structure, it exhibits comparable imaging performance with a commercial receive array, providing an alternative to conventional wired coils with a high cost and complex structure. The unique figure‐of‐8 conductor pattern within the rungs ensures that the proposed wireless Litzcage can be efficiently detuned with minimal detuning circuits.
A novel detunable wireless Litzcage volume coil was proposed, built, and tested through magnetic resonance imaging (MRI) experiments on the phantom and human heads. The wireless Litzcage demonstrates a unique advantage in detuning during the transmit phase. Despite its simpler structure and lower cost, it exhibits comparable imaging performance with a commercial receive array.
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