Continuous attractors for dynamic memories

Episodic memory has a dynamic nature: when we recall past episodes, we retrieve not only their content, but also their temporal structure. The phenomenon of replay, in the hippocampus of mammals, offers a remarkable example of this temporal dynamics. However, most quantitative models of memory treat memories as static configurations, neglecting the temporal unfolding of the retrieval process. Here, we introduce a continuous attractor network model with a memory-dependent asymmetric component in the synaptic connectivity, which spontaneously breaks the equilibrium of the memory configurations and produces dynamic retrieval. The detailed analysis of the model with analytical calculations and numerical simulations shows that it can robustly retrieve multiple dynamical memories, and that this feature is largely independent of the details of its implementation. By calculating the storage capacity, we show that the dynamic component does not impair memory capacity, and can even enhance it in certain regimes

SPECKLE-TRACKING ECHOCARDIOGRAPHY IN DOGS WITH PATENT DUCTUS ARTERIOSUS

PDA is one of the most common congenital cardiac malformation in the dog. Echocardiography has been the cornerstone in diagnosing and providing hemodynamic information in a wide variety of disease.Recently, speckle tracking echocardiography has been regarded as a useful tool to assess cardiac function. Aim of the study was to compare cardiovascular hemodynamics in dogs with PDA with healthy control dogs and evaluate any change in cardiac contractility before and after PDA closure. A statistically significant difference was found between standard and advanced echocardiographic techniques, with absolute higher values in dogs with PDA as compared to healthy controls. Cardiovascular hemodynamics were markedly different before and after PDA closure. Based on the results, STE should be considered in echocardiographic assessment of dogs with PDA, as they represent an animal model of congenital left ventricular overload not affected

Speckle tracking echocardiography in cats with preclinical hypertrophic cardiomyopathy

Abstract Background Cats with hypertrophic cardiomyopathy (HCM) have decreased left ventricular (LV) longitudinal deformation detected by mitral annular plane systolic excursion (MAPSE) and speckle tracking echocardiography. People with preclinical HCM have decreased systolic LV longitudinal and radial strain (S) and strain rate (SR), with preserved circumferential S and SR. Hypothesis/Objectives Cats with preclinical HCM have decreased systolic LV deformation compared to normal cats. Animals Seventy‐three client‐owned cats with (n = 37) and without (n = 36) preclinical HCM. Methods Retrospective echocardiographic study. Left and right ventricular longitudinal S and SR, LV radial and circumferential S and SR were calculated by STE. Left ventricular mass was also calculated. Correlation between STE variables and LV hypertrophy was determined and receiver‐operating characteristic (ROC) curves were plotted for prediction of HCM. Results Cats with HCM had smaller absolute longitudinal S (−14.8 ± 3.3% vs −19.7 ± 2.7%, P < .001), longitudinal SR (−2.36 ± 0.62 vs −2.95 ± 0.68 second−1, P < .001), radial S (46.2 ± 21.3% vs 66.7 ± 17.6%, P < .001), and radial SR (5.60 ± 2.08 vs 6.67 ± 1.8 second−1, P < .001) compared to healthy controls. No difference was observed for circumferential S and SR. Cats with HCM had greater LV mass (13.2 ± 3.7 g vs 8.6 ± 2.7 g, P < .001). The ROC with the greatest area under the curve (AUC) for the identification of HCM (0.974) was plotted from a logistic regression equation combining LV mass, MAPSE at the free wall, and LV internal diameter in diastole (LVIDd). Conclusions and clinical importance Cats with preclinical HCM have decreased long axis and radial deformation. Decreased longitudinal deformation and decreased LVIDd are factors that would support a diagnosis of HCM

Electrolytic depletion interactions

We consider the interactions between two uncharged planar macroscopic surfaces immersed in an electrolyte solution which are induced by interfacial selectivity. These forces are taken into account by introducing a depletion free-energy density functional, in addition to the usual mean-field Poisson-Boltzmann functional. The minimization of the total free-energy functional yields the density profiles of the microions and the electrostatic potential. The disjoining pressure is obtained by differentiation of the total free energy with respect to the separation of the surfaces, holding the range and strength of the depletion forces constant. We find that the induced interaction between the two surfaces is always repulsive for sufficiently large separations, and becomes attractive at shorter separations. The nature of the induced interactions changes from attractive to repulsive at a distance corresponding to the range of the depletion forces.Comment: 17 pages, 4 Postscript figures, submitted to Physical Review

Garnets from Val d&#8217;Ala Rodingites, Piedmont, Italy: An Investigation of Their Gemological, Spectroscopic and Crystal Chemical Properties

In Val d\u2019Ala (Piedmont,Western Alps, Italy), the more interesting rocks for the mineralogical research are represented by rodingites (rich in mineralized veins and fractures) associated with serpentinites in the eclogitized oceanic crust of Piemonte Zone, south of Gran Paradiso Massif. Among the vein-filling minerals, garnets are the most appreciated as mineral specimens and, in less degree despite their vivid and rich colors, for their potential as gem-quality materials. This study provides a complete gemological characterization of five faceted samples and others new information by means of Synchrotron X-ray computed micro-tomography imaging gem features. Electron-probe microanalysis (EMPA) and laser ablation\u2013inductively coupled plasma\u2013mass spectrometry (LA\u2013ICP\u2013MS) established that the chemical composition of garnets from different localities, resulted both close to pure andradite, enriched in light rare earth elements (LREE) with a positive Eu anomaly, and grossular-andradite solid solution (grandite), enriched in heavy rare earth elements (HREE). X-ray powder diffraction analyses indicate the possible coexistence of almost pure grossular and andradite. A spectroscopic approach, commonly used with gem-like material, by Raman and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, completes the characterization of the samples. The new data on the textural and geochemical features of the grandite and andradite garnets suggest local growth processes under various chemical and oxidation conditions of metasomatic and metamorphic fluids interacting with the host-rocks. Garnets represent long-lasting mineral records of the complex geological history of the Val d\u2019Ala rodingitic dikes during their oceanic- and subduction-related metamorphic evolution

Stent-assisted detachable coil embolization of wide-necked renal artery aneurysms

Renal artery aneurysms (RAAs) are rare with an estimated incidence of 0.1% in the general population, and they represent approximately 25% of all visceral aneurysms. The gold standard of treatment is open surgery, but it is associated with a high risk of nephrectomy, mortality, and morbidity. Less invasive endovascular therapies are becoming increasingly common for the treatment of RAAs. Here, we aimed to report three cases of wide-necked complex renal artery aneurysms treated endovascularly using stent-assisted coil embolization with self-expandable stent nitinol Solitaire AB and Concerto Axium coils. In addition, we describe the use of the waffle-cone technique in a case of wide-necked saccular RAA involving the renal artery bifurcation. Technical success was achieved in all three cases with no early or late complications and no recurrences

Numerical simulations of an ocean/continent convergent system: influence of subduction geometry and mantle wedge hydration on crustal recycling

The effects of the hydration mechanism on continental crust recycling are analyzed through a 2D finite element thermo-mechanical model. Oceanic slab dehydration and consequent mantle wedge hydration are implemented using a dynamic method. Hydration is accomplished by lawsonite and serpentine breakdown; topography is treated as a free surface. Subduction rates of 1, 3, 5, 7.5 and 10 cm/y, slab angles of 30o, 45o and 60o and a mantle rheology represented by dry dunite and dry olivine flow laws, have been taken into account during successive numerical experiments. Model predictions pointed out that a direct relationship exists between mantle rheology and the amount of recycled crustal material: the larger the viscosity contrast between hydrated and dry mantle, the larger the percentage of recycled material into the mantle wedge. Slab dip variation has a moderate impact on the recycling. Metamorphic evolution of recycled material is influenced by subduction style. TPmax, generally representative of eclogite facies conditions, is sensitive to changes in slab dip. A direct relationship between subduction rate and exhumation rate results for different slab dips that does not depend on the used mantle flow law. Thermal regimes predicted by different numerical models are compared to PT paths followed by continental crustal slices involved in ancient and recent subduction zones, making ablative subduction a suitable pre-collisional mechanism for burial and exhumation of continental crust.Comment: 10 figures, 3 table

Le cardiomiopatie secondarie nel gatto : quando l\u2019ipertrofia non dipende dal cuore

Feline hypertrophic cardiomyopathy is the most common acquired heart disease seen in felines. Hypertrophic cardiomyopathy is a term used when there is no known cause, however secondary, is brought about by other conditions such as high blood pressure, hyperthyroidism etc. Cats with secondary hypertrophic cardiomyopathy tend to be older than cats affected by HCM, the cardiac alterations as excessive thickening of the left ventricular wall, papillary muscles and septum detected by echocardiographic examination and other clinical symptoms tend to have resolution after appropriated therapy of hyperthyroidism and systemic hypertension

Speckle tracking echocardiography in dogs with patent ductus arteriosus : effect of percutaneous closure on cardiac mechanics

Background : patent ductus arteriosus (PDA) is one of the most common congenital heart defects in the dog and percutaneous closure is effective in achieving ductal closure.PDA closure is associated with abrupt hemodynamic changes. Hypothesis: A marked reduction in standard parameters of systolic function as assessed by M/B mode after PDA closure was identified in previous studies. Speckle-tracking echocardiography(STE) can provide further insight into the effect of PDA closure on cardiac mechanics in dogs affected by PDA. Animals: 25 client owned dogs affected by PDA Methods: Prospective study. Complete echocardiographic evaluation was performed before and 24 hours after PDA closure, including standard (EDVIB/M, ESVIB/M, AlloD/S, Qp/Qs, SI, EF and FS) and STE (global longitudinal, radial, transversal and circumferential strain and strain rate). Results: PDA closure was associated with a statistically significant decrease in conventional echocardiographic parameters and a derease in the absolute values of radial, transversal and circumferential S and SR, while longitudinal S and SR did not change significantly. Conclusion and clinical importance: PDA closure by percutaneous approach is associated with a marked decrease of conventional echocardiographic parameters due to the changes in loading conditions, but no evidence of systolic dysfunction was identified by means of STE, as none of the S and SR values were below normal ranges. In the short term, contractility is enhanced in the long axis (as Long S/SR values were not statistically different before and after closure) and normalizes in the short axis (circumferential, radial and transversal S/SR decreased to normal reference range)