Non-reversible Gaussian processes for identifying latent dynamical structure in neural data

A common goal in the analysis of neural data is to compress large population recordings into sets of interpretable, low-dimensional latent trajectories. This problem can be approached using Gaussian process (GP)-based methods which provide uncertainty quantification and principled model selection. However, standard GP priors do not distinguish between underlying dynamical processes and other forms of temporal autocorrelation. Here, we propose a new family of “dynamical” priors over trajectories, in the form of GP covariance functions that express a property shared by most dynamical systems: temporal non-reversibility. Non-reversibility is a universal signature of autonomous dynamical systems whose state trajectories follow consistent flow fields, such that any observed trajectory could not occur in reverse. Our new multi-output GP kernels can be used as drop-in replacements for standard kernels in multivariate regression, but also in latent variable models such as Gaussian process factor analysis (GPFA). We therefore introduce GPFADS (Gaussian Process Factor Analysis with Dynamical Structure), which models single-trial neural population activity using low-dimensional, non-reversible latent processes. Unlike previously proposed non-reversible multi-output kernels, ours admits a Kronecker factorization enabling fast and memory-efficient learning and inference. We apply GPFADS to synthetic data and show that it correctly recovers ground truth phase portraits. GPFADS also provides a probabilistic generalization of jPCA, a method originally developed for identifying latent rotational dynamics in neural data. When applied to monkey M1 neural recordings, GPFADS discovers latent trajectories with strong dynamical structure in the form of rotations

The I-mode confinement regime at ASDEX Upgrade: global propert ies and characterization of strongly intermittent density fluctuations

Properties of the I­mode confinement regime on the ASDEX Upgrade tokamak are summarized. A weak dependence of the power threshold for the L­I transition on the toroidal magnetic field strength is found. During improved confinement, the edge radial electric field well deepens. Stability calculations show that the I­mode pedestal is peeling­ballooning stable. Turbulence investigations reveal strongly intermittent density fluctuations linked to the weakly coherent mode in the confined plasma, which become stronger as the confinement quality increases. Across all investigated structure sizes ( ≈ ⊥ k 5 – 12 cm − 1 , with ⊥ k the perpendicular wavenumber of turbulent density fluctuations), the intermittent turbulence bursts are observed. Comparison with bolometry data shows that they move poloidally toward the X­point and finally end up in the divertor. This might be indicative that they play a role in inhibiting the density profile growth, such that no pedestal is formed in the edge density profile.European Union (EUROfusion 633053)European Union (EUROfusion AWP15­ENR­09/IPP­02

Temperature dependence of the photoluminescence emission from thiol-capped PbS quantum dots

The authors report the temperature dependence of the near-infrared photoluminescence (PL) emission from thiol-capped PbS quantum dots. The high thermal stability of the PL allows the authors to study the thermal broadening of the dot emission over an extended temperature range (4-300 K). The authors show that the linewidth of the dot PL emission is strongly enhanced at temperatures above 150 K. This behavior is attributed to dephasing of the quantum electronic states by carrier interaction with longitudinal optical phonons. The authors' data also indicate that the strength of the carrier-phonon coupling is larger in smaller dots. © 2007 American Institute of Physics

Methodological Aspects of Spontaneous Crystalluria Studies in Calcium Stone Formers

Despite nearly a half-century of study, the clinical value of spontaneous crystalluria (Cx) examinations in calcium stone formers (CaSF) is still uncertain. The analytical complexity of urine particle study is largely responsible for this situation. As a result, there is no consensus regarding technical methods in Cx with several techniques for urine sampling and three different instruments currently used for particle study, namely, particle counting (PC), light microscopy (LM) and petrographic microscopy (PM). In this work, we first examined urine sampling and instrument methods regarding their appropriateness for Cx studies. Then we performed a comparative analysis of Cx studies in CaSF. Despite many technical and clinical discrepancies, several studies agree that the frequency of all particles and of the weddellite and whewellite calcium oxalate (CaOx) crystalline phases are increased in CaSF as compared to normal subjects (NS). Particle sizes and aggregation ratio are also often increased. Altogether, these results reinforce the need for an efficient method for Cx studies in these patients. Examining each technique leads us to conclude that most particle parameters can be studied by direct LM observation of freshly voided urine samples, i.e., urine samples without any separation steps. For clinical applications, several examinations should be performed, first to define the specific Cx characteristics in a patient, then for the study of treatment efficiency on Cx control, and finally, during the patient follow-up. Due to Cx variability in each patient, the frequency of Cx examinations during each phase needs to be determined in long-term comparative prospective studies of CaSF

tt-Martin boundary of killed random walks in the quadrant

We compute the $t$-Martin boundary of two-dimensional small steps random walks killed at the boundary of the quarter plane. We further provide explicit expressions for the (generating functions of the) discrete $t$-harmonic functions. Our approach is uniform in $t$, and shows that there are three regimes for the Martin boundary.Comment: 18 pages, 2 figures, to appear in S\'eminaire de Probabilit\'e

Програма проходження практики студентами ІІ курсу (денної форми навчання) спеціальності 6.030509 “Облік і аудит”

Організаційна практика для студентів спеціальності 6.030509 «Облік і аудит» організовується відповідно до навчального плану Університету. Метою практики є закріплення, розширення та поглиблення теоретичних знань, практичних вмінь та навичок з дисциплін, що вивчаються, формування зацікавленості до майбутньої професіональної діяльності, ознайомлення з методикою роботи бухгалтера та аудитора в управлінських структурах організації для вирішення завдань при різних практичних ситуаціях. Керівництво практикою здійснюється викладачами кафедри бухгалтерського обліку та аудиту, які контролюють своєчасне прибуття студентів на місце практики, хід її виконання, консультують практикантів щодо програми і матеріалів практики, допомагають у вирішенні питань із забезпечення нормальних умов праці. Про результати перевірки керівник робить запис у щоденнику та інформує деканат. Під час практики студент зобов’язаний своєчасно і якісно виконувати завдання, передбачені програмою практики, опановувати прийоми обліку, дотримуватись правил внутрішнього розпорядку, не порушувати трудову дисципліну, сприяти виконанню завдань, які стоять перед навчальним закладом.Організаційна практика є складовою частиною навчально-виховного та науково-дослідного процесу підготовки фахівців з обліку і аудиту і має на меті формування у них практичних навичок самостійної роботи у сфері бухгалтерського обліку, контролю, аналізу і аудиту та умінь працювати за обраною спеціальністю у системі ринкового господарювання

Driving and use of the mobile phone: a study among 18 to 24-year-old

While we know that using the telephone when driving increases the risk of accidents and that 18 to 24 year-olds are a fringe of the population that is particularly affected by fatal accidents on the road, we lack information concerning the use of the mobile phone in this age group. This study carried out with 208 young drivers aims to gather data, analyses their behavior at the wheel with the mobile plus their beliefs and awareness of risk. Three contexts are focused on: stopping at the red light, driving during the rush hour and highways. The findings highlight the importance of messaging and the influence of the context on the use of the mobile. We observe an inverse effect between the speed and messaging. While young people declare they are aware of certain risks, it concerns more the risks penalties and accordingly they appear to be impervious to road safety campaigns concerning the mobile phone behind the wheel. On this subject few major differences are to be found between male and female drivers and between very young and young drivers. The use of the mobile while driving among 18 to 24-year-olds therefore presents universal characteristics of use from moment or the driver (male or female) is a little more experimented