Initial Deflation Research Articles

Air inflow into vacuum-type immobilization devices impacts setup errors.

We aimed to determine the impact of air inflow into vacuum-type immobilization devices (VIDs) on setup errors. We assigned 70 patients undergoing radiotherapy for head and neck cancer to groups V (n = 34) or N (n = 36) according to whether the VIDs were deflated weekly or not deflated during treatment, respectively. We calculated systematic errors (Σ) as the standard deviations (SDs) of mean errors, and random errors (σ) as the root mean square of SDs in each patient. We compared overall means (μ), SDs (SDoverall), random errors and systematic errors. We also measured temporary pressure changes in VIDs to determine the influence of pressure changes in VIDs on setup errors. The μ was within 0.20mm and 0.2° in both groups, whereas SDoverall significantly differed between them. The SDoverall differed the most in the Roll axes of groups N (0. 87°) and V (0.58°). The Σ and σ values were lower in all axes of group V than in group N. Despite the initial deflation target of -70kPa, the pressure in VIDs reached -5kPa at the end of treatment. However, weekly deflation apparently maintained pressure at -20kPa. Effective pressure control in VIDs can reduce patient-by-patient variation and improve setup reproducibility for individual patients, consequently resulting in small variations among overall setup errors.

Dynamics of a lipid vesicle across a microfluidic constriction: how do its membrane properties and microenvironment matter?

Constriction in the flow passage of the physiological circulatory system is central to the occurrence of several diseased conditions such as thrombosis and is also pivotal towards the understanding of several regulatory processes in the human microvasculature. It is, therefore, imperative to advance a mechanistic insight into the dynamics of lipid vesicles, cell mimicking, fluid-filled compartments, through a physiologically relevant microconfinement, with particular focus on deciphering the role of its mechanophysical properties. Here we bring out the role of membrane bending rigidity and the initial deflation (deviation in shape from sphericity) on the transient shape evolution of a lipid vesicle as it migrates through a microfluidic constriction, a paradigm that is unexplored thus far. Based on our experimental observations as well as theoretical insights, we construct a regime map to elucidate the range of the key dimensionless parameters orchestrating this dynamical transition. Furthermore, our observations on the vesicle's stretching dynamics emerging from selective mapping with viscosity contrast between the encapsulated and the suspending fluid medium offer potential physiologically relevant cues on the impact of cell aging on its deformability across a constricted path. Such mechanistic insights may help in establishing quantitative correlations between the dynamical transition of a lipid vesicle and its membrane mechanics, which may in turn have decisive implications in health and disease while circulating across microvascular fluidic pathways.

Expedited TR Band Removal for Transradial Approach for Noncoronary Visceral Procedures: Initial Experience.

For transradial interventions, most published studies report an initial Terumo Radial (TR) band placement time of 60 minutes, with gradual deflation over 30 to 90 minutes. We aimed to determine, retrospectively, whether TR band removal time could be expedited to 45 to 60 minutes, without adverse effects via an expedited single-step deflation protocol. A total of 115 consecutive noncoronary visceral interventions that utilized TR band from September 2017 till February 2019 were retrospectively reviewed. Alternative single-step deflation protocol was utilized where the nursing staff was instructed to deflate the TR band in 1 step between 45 and 60 minutes; 79 patients (43 men, 36 women, mean age of 55.3 ± 13.6 years) underwent 115 transradial interventions. Mean procedure time was 49.8 ± 22.1 minutes, and mean fluoroscopy time was 18.5 ± 10.6 minutes. Data collected included patient demographics, procedure details, and nursing notes on complications including bleeding and reinflation of the TR band. Univariate and Multivariate analyses of independent variables were performed using a binary logistic regression model. All patients were followed up postoperatively before discharge and in clinic upon follow-up. The TR band was deflated at 51.3 ± 14.5 minutes, with successful removal achieved on the first attempt in 103 cases (90.3% primary technical success rate). In 12 cases, bleeding was noted upon initial deflation, secondary technical success was achieved when the band was reinflated for an additional mean time of 37.0 ± 19.1 minutes. There was 1 incidence of radial artery occlusion (0.8%) and 1 incidence of a grade 1 hematoma (0.8%). The only variable predictive of technical outcome upon initial band deflation on univariate binomial logistic regression was initial TR band removal time (P = .019). A single-step deflation protocol for TR band placement may be safe for nonocclusive patent hemostasis and may translate to even further shorten postprocedural hospital times for patients and cost savings for hospitals.

A modified surgical approach for the treatment of mandibular unicystic ameloblastoma in young patients

BackgroundUnicystic ameloblastoma is a distinct clinicopathological entity with its cyst-like radiographic appearance and occurrence in the mandible of young patients. Surgical resection of the mandible leads to jaw deformity and challenging reconstruction burden, especially among young patients. Conservative treatment, however, results in less serious function and esthetic impairment. PurposeWe aimed at evaluating dredging method as an alternative conservative surgical approach in young patient with large unicystic ameloblastoma. Patients and methodsTwenty patients (n=20) with histologically-diagnosed unicystic ameloblastoma were recruited for this prospective study. The surgical treatment protocol comprised an initial deflation (marsupialization) step, followed by later enucleation and subsequent repeated separate dredging procedures. ResultsThe study population comprised 16 males and 4 females. The average age at the time of diagnosis was 18.5 years. At the last follow-up period, achievement of normal mandibular bone contour with no radiographic signs of recurrence was evident. ConclusionThe dredging method as a modified surgical technique may represent a reliable approach for management of unicystic ameloblastoma in young patients.

A spectrally preconditioned and initially deflated variant of the restarted block GMRES method for solving multiple right-hand sides linear systems

The solution of large linear systems with multiple right-hand sides given simultaneously is required in many large-scale scientific and engineering applications modelled by either partial differential or boundary integral equations. Block Krylov subspace methods are attractive to use for this problem class as they can overcome the memory bottleneck of direct methods and they perform block matrix-vector products, achieving high computational efficiency on modern cache-based computer architectures. In this paper we introduce variants of the block GMRES method that combine initial deflation and eigenvalue recycling strategies to remedy some typical convergence problems of block Krylov solvers. The new class of block iterative solvers has the ability to handle the approximate linear dependence of the block of right-hand sides and exploits approximate invariant subspaces recycled over the iterations to mitigate the bad effects that small eigenvalues can have on the convergence, by adapting an existing preconditioner. We illustrate the numerical behavior of the spectrally updated and initially deflated block GMRES method on a set of linear systems arising from the discretization of the Dirac equation and of boundary integral equations in electromagnetics scattering.

Ascending seismic source during an explosive eruption at Tungurahua volcano, Ecuador

[1] Application of seismic techniques to an explosion event at Tungurahua volcano, Ecuador, provided clear images to elucidate its source process. A source location method using high-frequency seismic amplitudes with an S-wave velocity of 2000 m/s indicates that the event was triggered at a depth of 6 km below the summit, and the source ascended toward the summit at a speed of about 1600 m/s. Waveform inversion of low-frequency signals at the event onset points to an isotropic mechanism with initial deflation at a similar depth of 6 km. The ascending source suggests that a pressure wave propagated along the magma conduit, triggering fragmentation of magma at shallow depths. Rapid decompression of magma in a shock tube has been considered to be an important mechanism for explosive eruptions triggered by ruptures at the magma surface. However, our study suggests that explosive eruptions are triggered by pressure disturbances in magma at depth.

Solving a Structured Quadratic Eigenvalue Problem by a Structure-Preserving Doubling Algorithm

In studying the vibration of fast trains, we encounter a palindromic quadratic eigenvalue problem (QEP) $(\lambda^{2}A^{T}+\lambda Q+A)z=0$, where $A,Q\in\mathbb{C}^{n\times n}$ and $Q^{T}=Q$. Moreover, the matrix Q is block tridiagonal and block Toeplitz, and the matrix A has only one nonzero block in the upper-right corner. So most of the eigenvalues of the QEP are zero or infinity. In a linearization approach, one typically starts with deflating these known eigenvalues for the sake of efficiency. However, this initial deflation process involves the inverses of two potentially ill-conditioned matrices. As a result, large error might be introduced into the data for the reduced problem. In this paper we propose using the solvent approach directly on the original QEP, without any deflation process. We apply a structure-preserving doubling algorithm to compute the stabilizing solution of the matrix equation $X+A^{T}X^{-1}A=Q$, whose existence is guaranteed by a result on the Wiener–Hopf factorization of rational matrix functions associated with semi-infinite block Toeplitz matrices and a generalization of Bendixson's theorem to bounded linear operators on Hilbert spaces. The doubling algorithm is shown to be well defined and quadratically convergent. The complexity of the doubling algorithm is drastically reduced by using the Sherman–Morrison–Woodbury formula and the special structures of the problem. Once the stabilizing solution is obtained, all nonzero finite eigenvalues of the QEP can be found efficiently and with the automatic reciprocal relationship, while the known eigenvalues at zero or infinity remain intact.

Jurassic thermal doming and deflation in the North Sea: implications of the sequence stratigraphic evidence

Although the ‘Mid-Cimmerian event’ or unconformity has been recognized over much of Europe, its exact stratigraphic relations and causal mechanism have remained unclear. Application of a genetic sequence stratigraphic approach (using 17 marine condensed sections and maximum flooding surfaces) to Jurassic sequences across NW Europe allows the stratigraphic succession to be subdivided into a series of time-slices (genetic stratigraphic sequences) and allows the true nature of the unconformity to be determined. They indicate that the main event’s correlative conformity falls in the Aalenian near the break between the opalinum and murchisonae ammonite biochronozones. Further study of the associated spatial and temporal variation indicates that systematic truncation of stratigraphy occurred throughout the North Sea domain (the oldest stratigraphies subcrop in areas adjacent to the triple junction) with subsequent progressive onlap towards the same area. When integrated with igneous evidence, these observations are interpreted to confirm regional (Toarcian–Aalenian) domal uplift, resulting from the impingement of a broad-based (> 1250 km diameter), transient plume head or ‘blob’ at the base of the lithosphere. Progressive pre-rift, Aalenian–early Bathonian marine onlap records differential subsidence in response to the initial deflation of the dome while central regions may have continued to rise. Subsequent subsidence post-dated Bathonian–Callovian volcanism but still pre-dated the timing of most significant (Kimmeridgian–Volgian) rifting. Such temporal relations demonstrate that North Sea volcanism is inconsistent with a classic ‘passive’ rift model. Instead, it seems more appropriate to equate Mid–Late Jurassic North Sea development with an ‘active’ rift model following mantle-driven thermal doming. Integration of sedimentation patterns with basin development suggests that the early Toarcian–early Kimmeridgian succession records a long-term, second-order regressive–transgressive episode related to regional tectonism. Comparison with the current chart of coastal onlap and global sea-level change highlights the correlation of the Intra-Aalenian event with one of the most significant regressions (the 177 Ma event separating the Absaroka and Zuni first-order megacycles). The knowledge that this part of the curve appears to be based exclusively on sections from Dorset and Yorkshire, within and adjacent to the region affected by regional doming, suggests that there remains a need to test this part of the chart using sections from outside the uplifted area and emphasizes the impracticality of using just two relatively closely spaced sections in trying to define a truly global signal. Clearly, sections should be taken from several areas and preferably from different plates as tectonically uncoupled as possible. Until then, the worry will remain that regional tectonic events could overprint any global signal and be erroneously interpreted as abrupt changes in global eustasy. The fact that doubts such as these can be cast upon parts of the eustatic sea-level chart suggests that it is still someway off being a valid global standard with true predictive capabilities.

Geophysical events

Krafla Caldera, Mývatn Area, Iceland (65.71°N, 16.75°W). The following is a report from Karl Gronvold and Páll Einarsson.The gradual inflation after the minor December event (see SEAN Bulletin, 4 (12)) was reversed about 1 February when very slow deflation began and the earthquake activity associated with inflation stopped. As measured at the Krafla power house, the initial deflation rate of about 0.5 microradians/day increased on 7 February to about 1.3 microradians/day. In the evening of 10 February, a dense microearthquake swarm began near the S rim of the Krafla caldera and started to propagate southward. At about the same time the deflation rate increased at Krafla, reaching a maximum of 7 microradians/day on 12 February. The rate of deflation decreased gradually thereafter; on 17 February it stopped, and on 21 February inflation started again. The deflation of 40 microradians is somewhat larger than the December deflation but still only about ⅙ of the last major deflation‐rifting event in May 1979 (see SEAN Bulletin, 4 (5)).