Maximal Asymmetry Research Articles

Quantification of perivascular spaces at 7 T: A potential MRI biomarker for epilepsy

Purpose7T (7T) magnetic resonance imaging (MRI) facilitates the visualization of the brain with resolution and contrast beyond what is available at conventional clinical field strengths, enabling improved detection and quantification of small structural features such as perivascular spaces (PVSs). The distribution of PVSs, detected in vivo at 7T, may act as a biomarker for the effects of epilepsy. In this work, we systematically quantify the PVSs in the brains of epilepsy patients and compare them to healthy controls. MethodsT2-weighted turbo spin echo images were obtained at 7T on 21 epilepsy patients and 17 healthy controls. For all subjects, PVSs were manually marked on Osirix image analysis software. Marked PVSs with diameter≥0.5mm were then mapped by hemisphere and lobe. The asymmetry index (AI) was calculated for each region and the maximum asymmetry index (|AImax|) was reported for each subject. The asymmetry in epilepsy subjects was compared to that of controls, and the region with highest asymmetry was compared to the suspected seizure onset zone. ResultsThere was a significant difference between the |AImax| in epilepsy subjects and in controls (p=0.016). In 72% of patients, the region or lobe of the brain showing maximum PVS asymmetry was the same as the region containing the suspected seizure onset zone. ConclusionThese findings suggest that epilepsy may be associated with significantly asymmetric distribution of PVSs in the brain. Furthermore, the region of maximal asymmetry of the PVSs may help provide localization or confirmation of the seizure onset zone.

Non-Gaussian Analytic Option Pricing: A Closed Formula for the LLvy-stable Model

We establish an explicit pricing formula for the class of L\'evy-stable models with maximal negative asymmetry (Log-L\'evy model with finite moments and stability parameter $1<\alpha\leq 2$) in the form of rapidly converging series. The series is obtained with help of Mellin transform and the residue theory in $\mathbb{C}^2$. The resulting formula enables the straightforward evaluation of an European option with arbitrary accuracy without the use of numerical techniques. The formula can be used by any practitioner, even if not familiar with the underlying mathematical techniques. We test the efficiency of the formula, and compare it with numerical methods.

Tip Design for Safety of Steerable Needles for Robot-Controlled Brain Insertion.

BackgroundCurrent practice in neurosurgical needle insertion is limited by the straight trajectories inherent in rigid probes. One technique allowing curvilinear trajectories involves flexible bevel-tipped needles, which bend during insertion because of their asymmetry. In the brain, safety will require avoidance of the sharp tips often used in laboratory studies, in favor of a more rounded profile. Steering performance, on the other hand, requires maximal asymmetry. Design of safe bevel-tipped brain needles, thus, involves management of this trade-off by adjusting needle gage, bevel angle, and fillet (or tip) radius to arrive at a design that is suitably asymmetrical while producing strain, strain rate, and stress below the levels that would damage brain tissue.MethodsDesigns with a variety of values of needle radius, bevel angle, and fillet radius were evaluated in finite-element simulations of simultaneous insertion and rotation. Brain tissue was modeled as a hyperelastic, linear viscoelastic material. Based on the literature available, safety thresholds of 0.19 strain, 10 s−1 strain rate, and 120 kPa stress were used. Safe values of needle radius, bevel angle, and fillet radius were selected, along with an appropriate velocity envelope for safe operation. The resulting needle was fabricated and compared with a Sedan side-cutting brain biopsy needle in a study in the porcine model in vivo (N=3).ResultsThe prototype needle selected was 1.66 mm in diameter, with a bevel angle of 10° and a fillet radius of 0.25 mm. Upon examination of postoperative computed tomography and histological images, no differences in tissue trauma or hemorrhage were noted between the prototype needle and the Sedan needle.ConclusionThe study indicates a general design technique for safe bevel-tipped brain needles based on the comparison with relevant damage thresholds for strain, strain rate, and stress. The full potential of the technique awaits the determination of more exact safety thresholds.

Explosive and maximal strength before and 6 months after total hip arthroplasty.

Patients with unilateral hip osteoarthritis experience impairments in lower limb muscle function due to pain and disuse of the affected limb. The influence of hip osteoarthritis and subsequent total hip arthroplasty (THA) has mostly been evaluated by maximal strength tests, yet the functionally important explosive strength capabilities of hip and knee muscles are largely unknown. We aimed to evaluate hip and knee explosive and maximal strength in hip osteoarthritis patients before and after THA. Twenty-one patients with unilateral hip osteoarthritis were evaluated before and 6 months after THA. They performed rapid maximal contractions of hip (flexor, extensor, abductor, adductor) and knee (flexor, extensor) muscles, from which explosive and maximal strength asymmetries were evaluated (involved versus uninvolved limb). Before THA, the involved limb showed significantly lower hip flexor, extensor, adductor, and knee extensor explosive and maximal strength compared to the uninvolved limb. Six months after THA surgery, hip flexor, extensor and adductor maximal and explosive strength asymmetries persisted, except for knee extensors. Explosive, but not maximal strength of hip abductors and knee extensors was lower in the involved limb before surgery and the reduced explosive strength capabilities may compromise daily living activities in hip osteoarthritis patients. After hip replacement, explosive strength asymmetries of knee extensors resolved, yet lingering asymmetries in hip flexor muscles should receive focused attention during postoperative rehabilitation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:425-431, 2018.

Modulation of Asymmetric Flux in Heterotypic Gap Junctions by Pore Shape, Particle Size and Charge.

Gap junction channels play a vital role in intercellular communication by connecting cytoplasm of adjoined cells through arrays of channel-pores formed at the common membrane junction. Their structure and properties vary depending on the connexin isoform(s) involved in forming the full gap junction channel. Lack of information on the molecular structure of gap junction channels has limited the development of computational tools for single channel studies. Currently, we rely on cumbersome experimental techniques that have limited capabilities. We have earlier reported a simplified Brownian dynamics gap junction pore model and demonstrated that variations in pore shape at the single channel level can explain some of the differences in permeability of heterotypic channels observed in in vitro experiments. Based on this computational model, we designed simulations to study the influence of pore shape, particle size and charge in homotypic and heterotypic pores. We simulated dye diffusion under whole cell voltage clamping. Our simulation studies with pore shape variations revealed a pore shape with maximal flux asymmetry in a heterotypic pore. We identified pore shape profiles that match the in silico flux asymmetry results to the in vitro results of homotypic and heterotypic gap junction formed out of Cx43 and Cx45. Our simulation results indicate that the channel's pore-shape established flux asymmetry and that flux asymmetry is primarily regulated by the sizes of the conical and/or cylindrical mouths at each end of the pore. Within the set range of particle size and charge, flux asymmetry was found to be independent of particle size and directly proportional to charge magnitude. While particle charge was vital to creating flux asymmetry, charge magnitude only scaled the observed flux asymmetry. Our studies identified the key factors that help predict asymmetry. Finally, we suggest the role of such flux asymmetry in creating concentration imbalances of messenger molecules in cardiomyocytes. We also assess the potency of fibroblasts in aggravating such imbalances through Cx43-Cx45 heterotypic channels in fibrotic heart tissue.

Is there evidence for anomalous dipole anisotropy in the large-scale structure?

We probe the anisotropy of the large-scale structure (LSS) with the WISE-2MASS catalogue. This analysis is performed by a directional comparison of the galaxy number counts through the entire celestial sphere once systematic effects, such as star-galaxy separation and foregrounds contamination, are properly taken into account. We find a maximal hemispherical asymmetry whose dipolar component is $A = 0.0507 \pm 0.0014$ toward the $(l,b) = (323^{\circ},-5^{\circ})$ direction, whose result is consistent with previous estimations of our proper motion in low and intermediate redshifts, as those carried out with Type Ia Supernovae and similar LSS catalogues. Furthermore, this dipole amplitude is statistically consistent ($p$-value = $0.061$) with mock catalogues simulated according to the expected $\Lambda$CDM matter density fluctuations, in addition to observational biases such as the incomplete celestial coverage and anisotropic sky exposure. Our results suggest, therefore, that there is no strong evidence for anomalous anisotropy in the LSS, given the limitations and systematics of current data, in the concordance model scenario.

Early gadolinium enhancement in hypertrophic cardiomyopathy: a potential premature marker of myocardial damage.

Early gadolinium enhancement (EGE), one CMR diagnostic criteria in acute myocarditis, has been related with hyperemia and capillary leakage. The value of EGE in hypertrophic cardiomyopathy (HCM) remains unknown. Our aim was to determine the prevalence of EGE in patients with HCM, and its relation with late gadolinium enhancement (LGE). The association of EGE with morphological and clinical parameters was also evaluated. Sixty consecutive patients with HCM and CMR from our center were included. All the clinical and complementary test information was collected prospectively in our HCM clinic. Left ventricular (LV) measurements were calculated from cine sequences. EGE and LGE were quantified with a dedicated software. Clinical events were collected from medical records. A slow wash-out pattern on EGE was detected in up to 68 % of the patients, being an isolated finding without LGE in 10 (16 %). This cohort showed a greater maximal LV wall thickness (20.1 ± 4 vs. 18.1 ± 3.5mm, p = 0.010) and asymmetry ratio (1.86 ± 0.42 vs. 1.62 ± 0.46; p = 0.039). The percentage of EGE/slice and the difference with the percentage LGE/slice demonstrated a significant positive correlation with the maximal LV wall thickness (Rho 0.450 and 0.386 respectively). EGE also correlated with number of segments with LVH (LV hypertrophy) and the asymmetry ratio. Neither EGE nor LGE were associated with classical risk factors, the risk score for sudden cardiac death, or with major clinical events. EGE was a frequent finding in HCM, even in absence of LGE. This phenomenon showed a positive correlation with morphological markers of disease burden.

Asymmetries in heavy quark pair and dijet production at an EIC

Asymmetries in heavy quark pair and dijet production in electron-proton collisions allow studies of gluon TMDs in close analogy to studies of quark TMDs in semi-inclusive DIS. Here we present expressions for azimuthal asymmetries for both unpolarized and transversely polarized proton cases and consider the maximal asymmetries allowed. The latter are found to be rather sizeable, except in certain kinematic limits which are pointed out. In addition, we consider the small-x limit and expectations from a McLerran-Venugopalan model for unpolarized and linearly polarized gluons and from a perturbative, large transverse momentum calculation for the T-odd gluon TMDs. Comparison to related observables at RHIC and LHC is expected to provide valuable information about the process dependence of the gluon TMDs. In particular this will offer the possibility of a sign change test of the gluon Sivers TMD and two other T-odd gluon TMDs. This provides additional motivation for studies of azimuthal asymmetries in heavy quark pair and dijet production at a future Electron-Ion Collider.

Gaussian quantum steering and its asymmetry in curved spacetime

We study Gaussian quantum steering and its asymmetry in the background of a Schwarzschild black hole. We present a Gaussian channel description of quantum state evolution under the influence of the Hawking radiation. We find that thermal noise introduced by Hawking effect will destroy the steerability between an inertial observer Alice and an accelerated observer Bob who hovers outside the event horizon, while it generates steerability between Bob and a hypothetical observer anti-Bob inside the event horizon. Unlike entanglement behaviors in curved spacetime, here the steering from Alice to Bob suffers from a "sudden death" and the steering from anti-Bob to Bob experiences a "sudden birth" with increasing Hawking temperature. We also find that the Gaussian steering is always asymmetric and the maximum steering asymmetry cannot exceed $\ln 2$, which means the state never evolves to an extremal asymmetry state. Furthermore, we obtain the parameter settings that maximize steering asymmetry and find that (i) $s=arccosh(\frac{\cosh^2 r}{1-\sinh^2r})$ is the critical point of steering asymmetry, and (ii) the attainment of maximal steering asymmetry indicates the transition between one-way steerability and both-way steerability for the two-mode Gaussian state under the influence of Hawking radiation.

Novel proposal for a low emittance muon beam using positron beam on target

Muon beams are customarily obtained via K/πdecays produced in proton interaction on target. In this paper we investigate the possibility to produce low emittance muon beams from electron–positron collisions at centre-of-mass energy just above the μ+μ− production threshold with maximal beam energy asymmetry, corresponding to a positron beam of about 45GeV interacting on electrons on target. We present the main features of this scheme with an outline of the possible applications.

TeV Scale Lepton Number Violation and Baryogenesis

Contrary to the common lore based on naive dimensional analysis, the seesaw scale for neutrino masses can be naturally in the TeV range, with small parameters coming from radiative corrections. We present one such class of type-I seesaw models, based on the left-right gauge group SU(2)L × SU(2)R × U(1)B-L realized at the TeV scale, which fits the observed neutrino oscillation parameters as well as other low energy constraints. We discuss how the small parameters of this scenario can arise naturally from one loop effects. The neutrino fits in this model use quasi-degenerate heavy Majorana neutrinos, as also required to explain the matter-antimatter asymmetry in our Universe via resonant leptogenesis mechanism. We discuss the constraints implied by the dynamics of this mechanism on the mass of the right-handed gauge boson in this class of models with enhanced neutrino Yukawa couplings compared to the canonical seesaw model and find a lower bound of mWR ≥ 9.9 TeV for successful leptogenesis assuming maximal CP asymmetry for each flavor. We also present a model with explicit neutrino mass fit, where the lower bound goes up to 13.1 TeV due to less than maximal primordial CP asymmetry predicted by the model.

On the significance of power asymmetries in Planck CMB data at all scales

We perform an analysis of the CMB temperature data taken by the Planck satellite investigating if there is any significant deviation from cosmological isotropy. We look for differences in the spectrum between two opposite hemispheres and also for dipolar modulations. We propose a new way to avoid biases due to partial-sky coverage by producing a mask symmetrized in antipodal directions, in addition to the standard smoothing procedure. We also properly take into account both Doppler and aberration effects due to our peculiar velocity and the anisotropy of the noise, since these effects induce a significant hemispherical asymmetry. We are thus able to probe scales all the way to ℓ = 2000. After such treatment we find no evidence for significant hemispherical anomalies along any of the analyzed directions (i.e. deviations are less than 1.5σ when summing over all scales). Although among the larger scales there are sometimes higher discrepancies, these are always less than 3σ. We also find results on a dipolar modulation of the power spectrum. Along the hemispheres aligned with the most asymmetric direction for 2 ⩽ ℓ ⩽ 2000 we find a 3.3σ discrepancy when comparing to simulations. However, if we do not restrict ourselves to Planck's maximal asymmetry axis, which can only be known a posteriori, and compare Planck data with the modulation of simulations along their respective maximal asymmetry directions, the discrepancy goes down to less than 1σ (with, again, almost 3σ discrepancies in some low-ℓ modes). We thus concludethat no significant power asymmetries seem to be present in the full data set. Interestingly, without proper removal of Doppler and aberration effects one would find spurious anomalies at high ℓ, between 3σ and 5σ. Even when considering only ℓ < 600 we find that the boost is non-negligible and alleviates the discrepancy by roughly half-σ.

Cogntive Consistency Analysis in Adaptive Bio-Metric Authentication System Design

Cognitive consistency analysis aims to continuously monitor one's perception equilibrium towards successful accomplishment of cognitive task. Opposite to cognitive flexibility analysis – cognitive consistency analysis identifies monotone of perception towards successful interaction process (e.g., biometric authentication) and useful in generation of decision support to assist one in need. This study consider fingertip dynamics (e.g., keystroke, tapping, clicking etc.) to have insights on instantaneous cognitive states and its effects in monotonic advancement towards successful authentication process. Keystroke dynamics and tapping dynamics are analyzed based on response time data. Finally, cognitive consistency and confusion (inconsistency) are computed with Maximal Information Coefficient (MIC) and Maximal Asymmetry Score (MAS), respectively. Our preliminary study indicates that a balance between cognitive consistency and flexibility are needed in successful authentication process. Moreover, adaptive and cognitive interaction system requires in depth analysis of user’s cognitive consistency to provide a robust and useful assistance.

Comparisons and Contrasts between Asymmetry and Nestedness in Interacting Ecological Networks

We compare and contrast asymmetry and nestedness, two concepts used in the characterisation of the specialist-generalist balance in bipartite ecological interaction networks. Our analysis is relevant to mutualistic networks such as those consisting of flowering plants and pollinators, or fruiting plants and frugivores, or antagonistic networks such as those consisting of plants and herbivores, in an ecological community. We shall refer to the two sets of species in the bipartite network as plants and animals, the usual but not the only ecological situation. By asymmetry we mean either connectivity asymmetry or dependence asymmetry, which are essentially equivalent. Asymmetry expresses two attributes: generalists interact preferentially with specialists, and specialists avoid interacting with each other. Nested patterns, in principle, should express these same two features and one more: the presence of a core of interactions among generalists. We compute the full set of perfectly nested patterns that are possible in an L × L matrix with N interactions representing an ecological network of L plants and L animals, and point out that the number of nested arrangements grows exponentially with N. In addition, we analyse asymmetry for the full set of perfectly nested patterns, and identify extremes of asymmetry inside the universe of nested patterns. The minimal asymmetry is marked by a modular core of interactions between species that are neither specialists nor generalists. On the other hand, the case of maximal asymmetry is formed by a set of few generalists and many specialists with equal connectivity. The stereotypic case of nestedness with a core of interactions among generalists has intermediate asymmetry.

Linear polarization of gluons and photons in unpolarized collider experiments

Abstract We study azimuthal asymmetries in heavy quark pair production in unpolarized electron-proton and proton-proton collisions, where the asymmetries originate from the linear polarization of gluons inside unpolarized hadrons. We provide cross section expressions and study the maximal asymmetries allowed by positivity, for both charm and bottom quark pair production. The upper bounds on the asymmetries are shown to be very large depending on the transverse momentum of the heavy quarks, which is promising especially for their measurements at a possible future Electron-Ion Collider or a Large Hadron electron Collider. We also study the analogous processes and asymmetries in muon pair production as a means to probe linearly polarized photons inside unpolarized protons. For increasing invariant mass of the muon pair the asymmetries become very similar to the heavy quark pair ones. Finally, we discuss the process dependence of the results that arises due to differences in color flow and address the problem with factorization in case of proton-proton collisions.

The above-threshold detachment of negative ions in half-cycle laser field

We study partial detachment rate and photodetachment asymmetry of F− detached by half-cycle linearly polarized laser field using numerical simulation. Similar to photodetachment for negative ions in few-cycle laser fields, we find that partial detachment rates of a couple opposite directions in the above-threshold detachment of F− are not equal, the detachment is asymmetric. Furthermore, the photodetachment asymmetry degree increases with carrier-envelop phase (CEP) as the peak laser intensity becoming stronger or the pulse width becoming shorter. The maximal asymmetry degree is stronger with higher laser intensity. We confirm the effect of the CEP, laser intensity and pulse width on the above-threshold detachment of F− in half-cycle laser fields. It provides a possible way to determine the CEP of half-cycle laser fields by measuring detached photoelectrons.

Quantitative In Vivo HR-pQCT Imaging of 3D Wrist and Metacarpophalangeal Joint Space Width in Rheumatoid Arthritis

In this technique development study, high-resolution peripheral quantitative computed tomography (HR-pQCT) was applied to non-invasively image and quantify 3D joint space morphology of the wrist and metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA). HR-pQCT imaging (82 μm voxel-size) of the dominant hand was performed in patients with diagnosed rheumatoid arthritis (RA, N = 16, age: 52.6 ± 12.8) and healthy controls (CTRL, N = 7, age: 50.1 ± 15.0). An automated computer algorithm was developed to segment wrist and MCP joint spaces. The 3D distance transformation method was applied to spatially map joint space width, and summarized by the mean joint space width (JSW), minimal and maximal JSW (JSW.MIN, JSW.MAX), asymmetry (JSW.AS), and distribution (JSW.SD)-a measure of joint space heterogeneity. In vivo precision was determined for each measure by calculating the smallest detectable difference (SDD) and root mean square coefficient of variation (RMSCV%) of repeat scans. Qualitatively, HR-pQCT images and pseudo-color JSW maps showed global joint space narrowing, as well as regional and focal abnormalities in RA patients. In patients with radiographic JSN at an MCP, JSW.SD was two-fold greater vs. CTRL (p < 0.01), and JSW.MIN was more than two-fold lower (p < 0.001). Similarly, JSW.SD was significantly greater in the wrist of RA patients vs. CTRL (p < 0.05). In vivo precision was highest for JSW (SDD: 100 μm, RMSCV: 2.1%) while the SDD for JSW.MIN and JSW.SD were 370 and 110 μm, respectively. This study suggests that in vivo quantification of 3D joint space morphology from HR-pQCT, could improve early detection of joint damage in rheumatological diseases.

Dynamics of focal adhesions and reorganization of F‐actin in VEGF‐stimulated NSCs under varying differentiation states

Precise migration of neural stem/progenitor cells (NSCs) is crucially important for neurogenesis and repair in the nervous system. However, the detailed mechanisms are not clear. Our previous results showed that NSCs in varying differentiation states possess different migratory ability to vascular endothelial growth factor (VEGF). In this study, we demonstrate the different dynamics of focal adhesions (FAs) and reorganization of F-actin in NSCs during spreading and migration stimulated by VEGF. We found that the migrating NSCs of 0.5 and 1 day differentiation possess more FAs at leading edge than cells of other states. Moreover, the phosphorylation of focal adhesion kinase (FAK) and paxillin in NSCs correlates closely with their differentiation states. VEGF promotes FA formation with broad lamellipodium generation at the leading edge in chemotaxing cells of 0, 0.5, and 1 day differentiation, but not in cells of 3 days differentiation. Furthermore, cells of 1 day differentiation show a maximal asymmetry of FAs between lamella and cell rear, orchestrating cell polarization and directional migration. Time-lapse video analysis shows that the disassembly of FAs and the cell tail detachment in NSCs of 1 day differentiation are more rapid, along with the concurrent enlarged size of FAs at the leading edge, leading to the most effective chemotactic response to VEGF. Collectively, these results indicate that the dynamics of FAs and reorganization of F-actin in NSCs that undergo directional migration correlate closely with their differentiation states, contributing to the different chemotactic responses of these cells to VEGF.

Frequency dependence of ionization for [formula omitted] in linearly polarized laser fields

The influence of laser frequency on the ionization of H2+ in few-cycle linearly polarized laser fields is investigated by numerically solving the time-dependent Schrödinger equation. It was found that the distribution of the electric field changes as the laser frequency changes. When the laser frequency is relatively small or the laser intensity is relatively strong, the total ionization is relatively large. With certain increase of the laser intensity, the increases of the total ionization rate for all frequencies are almost the same. For a fixed laser frequency, the total ionization rate increases more slowly for higher laser intensity. The asymmetry parameter describing asymmetry degree under different laser frequencies is also investigated. We found phase shift of asymmetry parameter emerges for different laser frequencies. The maximal asymmetry parameter increases as the laser frequency increases.

Пластичність морфометричних ознак Calliphora vicina (Diptera, Calliphoridae) у постійних і мінливих температурних умовах культивування

Досліджено мінливість основних морфометричних ознак імаго мух Calliphora vicina R.-D. (Diptera, Calliphoridae) із двох вибірок (n = 33). Перша вибірка – особини, зібрані у природних умовах (паркові екосистеми м. Дніпропетровськ), друга – особини, культивовані у лабораторії при підтриманні постійної температури та вологості. Проаналізовано можливість використання Calliphora vicina R.-D. у біоіндикації антропогенних чинників на підставі результатів морфометричного аналізу. Найсуттєвіші відмінності між вибірками виявлено за шириною голови («лабораторні» особини характеризуються більш константними розмірами голови) та довжиною окремих сегментів кінцівок. В імаго, виведених у постійних умовах, спостерігається вкорочення сегментів I пари ніг порівняно з особинами «природної» вибірки. За більшістю інших лінійних промірів тіла Calliphora vicina R.-D. відмінності між вибірками не реєструються. Незначна мінливість морфометричних характеристик вказує на еволюційно зумовлену стійкість виду до зміни абіотичних факторів середовища. Тому використовувати Calliphora vicina R-D. (за умов розвитку в температурному діапазоні +17…+28 °С) як вид – індикатор зміни температурного фактора довкілля не доцільно.