What are the major problems faced by embryologists at 1) Clinic level, 2) Professional level, 3) Personal level, and 4) What are their career goals? Embryologists, essential professionals of Fertility Centres, are less satisfied in many quantifiable aspects, but they love their profession and have many aspirational goals. IVF success depends in part on embryologists’ skills. The need to recognize clinical embryology as a specialty and clinical embryologists’ educational level, responsibilities, and workload have been addressed by a few national societies. However, data are lacking from the embryologists’ viewpoint at a global level about their profession. Qualitative data-analysis methods provide thick, rich descriptions of subjects’ thoughts, feelings, and lived experiences but can be time-consuming, labor-intensive, and prone to bias. A questionnaire was prepared using SurveyMonkey online software (SurveyMonkey, Inc., USA) and distributed to IVF lab professionals through embryology societies, online social media, and email databases. The questionnaire consisted of open-ended questions focused on identifying problems faced by embryologists at the clinic, in the profession, and in a personal level, as well as questions about their career outlook. The survey was active from May 2016 until February 2017. From 73 countries, 720 responses were obtained. Using natural language processing (NLP), the top 15 most frequently used keywords were identified and correlated with each other. Stronger correlation (≥0.5) between semantically similar words expressing a strong signal from each answer, and their usage was further analyzed for positive versus negative sentiment. By normalizing the frequency of positive/negative samples for each keyword as a percentage, “sentiment wheels” were produced, identifying the key concepts that respondents answered and quantifying how they felt about them. The responses received were from 80% private, 17% public and 3% other ART settings distributed all over the world. From the embryologists’ viewpoints reported and after the NLP processing it was shown that the common topics related to strong negative sentiments were: embryologists’ remuneration (0.6) at the Clinic level; certification (0.7), recognition (0.5), respect (0.5), learn (0.5) and experience (0.5) at the Professional level; and remuneration (0.7), emotional (0.5) dealing (0.5) at the Personal level. Renumeration was reported and strongly related to embryologists’ viewpoint at both the clinic and personal level in combination with the need for certification, recognition and ongoing development at the Professional level. Moreover, the NLP processing demonstrated that the common topics on career goal analysis related to strong positive sentiments were: teaching (0.7), education (0.7), and continuation (0.5) all three topics are compatible with a professional orientation open to ongoing development and practice advancement. The NLP and the manual data analysis project an image of the typical embryologist as a knowledge seeking professional who is deeply dedicated to the job but feels the need for professional development and suffers some lack of recognition and feels in some cases not fairly treated as an employee. The data obtained is limited. Only one natural language processing model was used to analyze the results. Different analysts using other methods may have different results. For these reasons, the results should be interpreted with caution. Wider implications of the findings: It is important to focus on the lab as an organization and not just a service for the patients in treatment at the moment. The NLP results ultimately obtained may help streamline professional satisfaction efforts, and guide future quality management strategies Not applicable

Preeminent condensed-matter physicist David James Thouless, an emeritus professor of physics at the University of Washington (UW) and a 2016 Nobel laureate, passed away on 6 April 2019 in Cambridge, UK. His most notable contributions are the so-called Thouless energy for electron transport in disordered media; Kosterlitz–Thouless (KT) phase transitions in two-dimensional equilibrium; the TKNN topological invariant, which explains the perfect quantization in the integer quantum Hall effect; and the Thouless adiabatic charge pump. He himself identified topological phenomena as the common thread throughout his work. David James Thouless PPT|High resolutionDavid was born on 21 September 1934 in Bearsden, Scotland. After earning his physics undergraduate degree in 1956 from Cambridge University, he went to Cornell University; he received his PhD there in 1958. He did his thesis work, applying perturbation methods to nuclear-matter theory, under adviser Hans Bethe. He conducted research at the University of California, Berkeley, and at the University of Birmingham under mentor Rudolf Peierls before returning to Cambridge in 1961 as a lecturer and fellow of Churchill College.That same year, only three years after getting his PhD, David published his monograph The Quantum Mechanics of Many-Body Systems. The impact was swift. In his UW office in Seattle after he and his wife, Margaret, moved back to Cambridge in 2016, I and several colleagues found translations in Russian from 1963 and in German and Japanese from 1964.David accepted a professorship in mathematical physics at the University of Birmingham in 1965. It was there in 1973 that he and Michael Kosterlitz wrote the KT papers, with a core message that order–disorder phase transitions can be topological in nature and do not necessarily involve a change in a local order parameter.Phase transitions display spontaneous broken ergodicity. At boiling, a gas and liquid coexist but do not fluctuate into each other and can be distinguished locally by a jump in the order parameter density. The classification of phase transitions by local order parameters dates back to Johannes van der Waals in 1873 and was canonized by Lev Landau in 1937. Superfluid helium-4 films escape that classification. The onset of disorder is expressed by a nonlocal string-type order parameter, which represents vortex–vortex interactions.Topological phase transitions are not necessarily a fundamental departure from the Landau theory. Nonlocal topological order often turns local under duality-type phase transitions. The point is that KT fundamentally revolutionized our approach to all phase transitions. I routinely represent them all in terms of topological domain-wall-type deconfinement.David liked to say that theory typically lags behind experimental discoveries. But that’s not the case with KT transitions, also known as BKT transitions to credit Vadim Berezinskii’s contribution. David Bishop and John Reppy confirmed the theory’s predictions in superfluids only five years later, in 1978. During a 1999 symposium in Seattle on the occasion of his 65th birthday, David was presented with a framed copy of their original data. He hung it in his office next to his Wolf Prize certificate; the cherished gift now resides in the Nobel Prize Museum.David and Margaret moved to Seattle in 1980, where both held UW faculty positions—Margaret, a virologist, taught in the School of Public Health. It was at UW that David, Mahito Kohmoto, Peter Nightingale, and I discovered in 1982 the TKNN topological invariant that explains the integer quantum Hall effect. The Hall conductance, we found, is an observable that can be expressed as a closed contour integral. That property explained why the Hall conductance can only yield a multiple of e2/h and why it is topologically protected from adiabatic disturbances, disorder in particular. That work turned out to be an application of Chern invariants and later served as an example of a Berry phase.This decade we are witnessing a technological revolution in experimental control at the atomic level that is leading to novel quantum materials with phases that are generalizations of the TKNN invariant, including topological insulators. The renewed interest in our work, and how it affects current research, coincides with David being awarded the Nobel Prize in Physics in 2016. It was almost too late because of his health, but at the Nobel ceremony in Stockholm, my family and I were able to witness him cognitively enjoying receiving the prize.In the preface to his 1998 monograph Topological Quantum Numbers in Nonrelativistic Physics, David reflected on a discussion he’d had with Hans Dehmelt, the other Nobel laureate in the UW physics department. Dehmelt wondered “how the quantum Hall effect could possibly be used to determine the fine-structure constant when so little was known about the details of the devices used.” Dehmelt received his physics Nobel in 1989 for the development of the ion trap. Next to his office, he displayed a Barnett Newman–like painting of perfect blue with one single dot, which resembled a trap filled with a single ion. In my presentations, I often contrast that reductionist painting with Vincent van Gogh’s Starry Night, filled with vortices and chaos, to illustrate how complex systems include observables that are topologically protected and perfect. David played a central role in that fundamental shift in the paradigm.© 2019 American Institute of Physics.

Quintessential topological condensed matter physicist

Imagery of motor movement plays an important role in learning of complex motor skills, from learning to serve in tennis to perfecting a pirouette in ballet. What and where are the neural substrates that underlie motor imagery-based learning? We measured electrocorticographic cortical surface potentials in eight human subjects during overt action and kinesthetic imagery of the same movement, focusing on power in “high frequency” (76–100 Hz) and “low frequency” (8–32 Hz) ranges. We quantitatively establish that the spatial distribution of local neuronal population activity during motor imagery mimics the spatial distribution of activity during actual motor movement. By comparing responses to electrocortical stimulation with imagery-induced cortical surface activity, we demonstrate the role of primary motor areas in movement imagery. The magnitude of imagery-induced cortical activity change was ∼25% of that associated with actual movement. However, when subjects learned to use this imagery to control a computer cursor in a simple feedback task, the imagery-induced activity change was significantly augmented, even exceeding that of overt movement.

Electrocorticographic recording is now being used in a wide variety of experimental settings. We present a simple method which can be used to estimate electrode position with respect to brain gyral anatomy using a pre-implantation MRI and post-implantation coronal and sagittal x-rays. It is semi-automated, with the user manually rotating and scaling an x-ray to fit brain outline, identifying threshold values for brain surface rendering, and clicking on electrodes on an x-ray. Electrode positions can be rapidly identified and rendered in about 20 minutes from start to finish. This approach is useful when the MRI quality is poor, there is no quality CT, but one would like to understand the relationship between experimental result and brain anatomy.

Brain rhythms are more than just passive phenomena in visual cortex. For the first time, we show that the physiology underlying brain rhythms actively suppresses and releases cortical areas on a second-to-second basis during visual processing. Furthermore, their influence is specific at the scale of individual gyri. We quantified the interaction between broadband spectral change and brain rhythms on a second-to-second basis in electrocorticographic (ECoG) measurement of brain surface potentials in five human subjects during a visual search task. Comparison of visual search epochs with a blank screen baseline revealed changes in the raw potential, the amplitude of rhythmic activity, and in the decoupled broadband spectral amplitude. We present new methods to characterize the intensity and preferred phase of coupling between broadband power and band-limited rhythms, and to estimate the magnitude of rhythm-to-broadband modulation on a trial-by-trial basis. These tools revealed numerous coupling motifs between the phase of low-frequency (δ, θ, α, β, and γ band) rhythms and the amplitude of broadband spectral change. In the θ and β ranges, the coupling of phase to broadband change is dynamic during visual processing, decreasing in some occipital areas and increasing in others, in a gyrally specific pattern. Finally, we demonstrate that the rhythms interact with one another across frequency ranges, and across cortical sites.

Recent studies have identified broadband phenomena in the electric potentials produced by the brain. We report the finding of power-law scaling in these signals using subdural electrocorticographic recordings from the surface of human cortex. The power spectral density (PSD) of the electric potential has the power-law form P(f ) approximately Af(-chi) from 80 to 500 Hz. This scaling index, chi = 4.0+/-0.1, is conserved across subjects, area in the cortex, and local neural activity levels. The shape of the PSD does not change with increases in local cortical activity, but the amplitude, A, increases. We observe a "knee" in the spectra at f(0) approximately 75 Hz, implying the existence of a characteristic time scale tau = (2pif(0))(-1) approximately 2 - 4ms. Below f(0), we explore two-power-law forms of the PSD, and demonstrate that there are activity-related fluctuations in the amplitude of a power-law process lying beneath the alpha/beta rhythms. Finally, we illustrate through simulation how, small-scale, simplified neuronal models could lead to these power-law observations. This suggests a new paradigm of non-oscillatory "asynchronous," scale-free, changes in cortical potentials, corresponding to changes in mean population-averaged firing rate, to complement the prevalent "synchronous" rhythm-based paradigm.

Most brain-computer interface classification experiments from electrical potential recordings have been focused on the identification of classes of stimuli or behavior where the timing of experimental parameters is known or pre-designated. Real world experience, however, is spontaneous, and to this end we describe an experiment predicting the occurrence, timing, and types of visual stimuli perceived by a human subject from electrocorticographic recordings. All 300 of 300 presented stimuli were correctly detected, with a temporal precision of order 20 ms. The type of stimulus (face/house) was correctly identified in 95% of these cases. There were ~20 false alarm events, corresponding to a late 2nd neuronal response to a previously identified event.

During active movement the electric potentials measured from the surface of the motor cortex exhibit consistent modulation, revealing two distinguishable processes in the power spectrum. At frequencies <40 Hz, narrow-band power decreases occur with movement over widely distributed cortical areas, while at higher frequencies there are spatially more focal power increases. These high-frequency changes have commonly been assumed to reflect synchronous rhythms, analogous to lower-frequency phenomena, but it has recently been proposed that they reflect a broad-band spectral change across the entire spectrum, which could be obscured by synchronous rhythms at low frequencies. In 10 human subjects performing a finger movement task, we demonstrate that a principal component type of decomposition can naively separate low-frequency narrow-band rhythms from an asynchronous, broad-spectral, change at all frequencies between 5 and 200 Hz. This broad-spectral change exhibited spatially discrete representation for individual fingers and reproduced the temporal movement trajectories of different individual fingers.

Membranes containing a wide variety of ternary mixtures of high chain-melting temperature lipids, low chain-melting temperature lipids, and cholesterol undergo lateral phase separation into coexisting liquid phases at a miscibility transition. When membranes are prepared from a ternary lipid mixture at a critical composition, they pass through a miscibility critical point at the transition temperature. Since the critical temperature is typically on the order of room temperature, membranes provide an unusual opportunity in which to perform a quantitative study of biophysical systems that exhibit critical phenomena in the two-dimensional Ising universality class. As a critical point is approached from either high or low temperature, the scale of fluctuations in lipid composition, set by the correlation length, diverges. In addition, as a critical point is approached from low temperature, the line tension between coexisting phases decreases to zero. Here we quantitatively evaluate the temperature dependence of line tension between liquid domains and of fluctuation correlation lengths in lipid membranes to extract a critical exponent, nu. We obtain nu = 1.2 +/- 0.2, consistent with the Ising model prediction nu = 1. We also evaluate the probability distributions of pixel intensities in fluorescence images of membranes. From the temperature dependence of these distributions above the critical temperature, we extract an independent critical exponent of beta = 0.124 +/- 0.03, which is consistent with the Ising prediction of beta = 1/8.

Three human subjects participated in a closed-loop brain computer interface cursor control experiment mediated by implanted subdural electrocorticographic arrays. The paradigm consisted of several stages: baseline recording, hand and tongue motor tasks as the basis for feature selection, two closed-loop one-dimensional feedback experiments with each of these features, and a two-dimensional feedback experiment using both of the features simultaneously. The two selected features were simple channel and frequency band combinations associated with change during hand and tongue movement. Inter-feature correlation and cross-correlation between features during different epochs of each task were quantified for each stage of the experiment. Our anecdotal, three subject, result suggests that while high correlation between horizontal and vertical control signal can initially preclude successful two-dimensional cursor control, a feedback-based learning strategy can be successfully employed by the subject to overcome this limitation and progressively decorrelate these control signals.

Electrocorticographic spectral changes during movement show a behavioral inflection in the classic gamma band (30-70 Hz). We quantify this inflection and demonstrate that it limits classification accuracy. We call for the designation of a functionally defined band above it, which we denote the chi-band.

We report the results of our search for power-law electrical signals in the human brain, using subdural electrocorticographic recordings from the surface of the cortex. The power spectral density (PSD) of these signals has the power-law form P(f)∼ f^-χ from 80 to 500 Hz. This scaling index χ = 4.0± 0.1 is universal, across subjects, area in the cortex, and local neural activity levels. The shape of the PSD does not change with local cortex activity, only its amplitude increases. We observe a knee in the spectra at f_0≃ 70 Hz, implying the existence of a characteristic time scale τ=(2π f_0)^-1≃ 2-4 msec. For f<f_0 we find evidence for a power-law with χ_L≃ 2.0± 0.4.

One-dimensional directed driven stochastic flow with competing nonlocal and local hopping events has an instability threshold from a populated phase into an empty-road (ER) phase. We implement this in the context of the asymmetric exclusion process. The nonlocal skids promote strong clustering in the stationary populated phase. Such clusters drive the dynamic phase transition and determine its scaling properties. We numerically establish that the instability transition into the ER phase is second order in the regime where the entry point reservoir controls the current and first order in the regime where the bulk is in control. The first-order transition originates from a turnabout of the cluster drift velocity. At the critical line, the current remains analytic, the road density vanishes linearly, and fluctuations scale as uncorrelated noise. A self-consistent cluster dynamics analysis explains why these scaling properties remain that simple.

The dynamic scaling properties of the one-dimensional Burgers equation are expected to change with the inclusion of additional conserved degrees of freedom. We study this by means of one-dimensional (1D) driven lattice gas models that conserve both mass and momentum. The most elementary version of this is the Arndt-Heinzel-Rittenberg (AHR) process, which is usually presented as a two-species diffusion process, with particles of opposite charge hopping in opposite directions and with a variable passing probability. From the hydrodynamics perspective this can be viewed as two coupled Burgers equations, with the number of positive and negative momentum quanta individually conserved. We determine the dynamic scaling dimension of the AHR process from the time evolution of the two-point correlation functions, and find numerically that the dynamic critical exponent is consistent with simple Kardar-Parisi-Zhang- (KPZ) type scaling. We establish that this is the result of perfect screening of fluctuations in the stationary state. The two-point correlations decay exponentially in our simulations and in such a manner that in terms of quasiparticles, fluctuations fully screen each other at coarse grained length scales. We prove this screening rigorously using the analytic matrix product structure of the stationary state. The proof suggests the existence of a topological invariant. The process remains in the KPZ universality class but only in the sense of a factorization, as (KPZ)2. The two Burgers equations decouple at large length scales due to the perfect screening.

We report experimental results for the behavior of slow-combustion fronts in the presence of a columnar defect with enhanced or reduced driving, and compare them with those of mean-field theory. We also compare them with simulation results for an analogous problem of driven flow of particles with hard-core repulsion (ASEP) and a single defect bond with a different hopping probability. The difference in the shape of the front profiles for enhanced vs reduced driving in the defect clearly demonstrates the existence of a Kardar-Parisi-Zhang-type nonlinear term in the effective evolution equation for the slow-combustion fronts. We also find that slow-combustion fronts display a faceted form for large enough enhanced driving, and that there is a corresponding increase then in the average front speed. This increase in the average front speed disappears at a nonzero enhanced driving in agreement with the simulated behavior of the ASEP model.

Stochastic driven flow along a channel can be modeled by the asymmetric simple exclusion process. We confirm numerically the presence of a dynamic queuing phase transition at a nonzero obstruction strength, and establish its scaling properties. Below the transition, the traffic jam is macroscopic in the sense that the length of the queue scales linearly with system size. Above the transition, only a power-law shaped queue remains. Its density profile scales as deltarho approximately x(-nu) with nu=1/3, and x is the distance from the obstacle. We construct a heuristic argument, indicating that the exponent nu=1/3 is universal and independent of the dynamic exponent of the underlying dynamic process. Fast bonds create only power-law shaped depletion queues, and with an exponent that could be equal to nu=2/3, but the numerical results yield consistently somewhat smaller values nu approximately 0.63(3). The implications of these results to faceting of growing interfaces and localization of directed polymers in random media, both in the presence of a columnar defect are pointed out as well.

We present a directed unloading sand-box-type avalanche model, driven by slowly lowering the retaining wall at the bottom of the slope. The avalanche propagation in the two-dimensional surface is related to the space-time configurations in one-dimensional Kardar-Parisi-Zhang (KPZ) interface growth. We relate the scaling exponents of the avalanche cluster distribution to those for the growing surface. The numerical results are close but deviate significantly from the exact KPZ values. This might reflect stronger than usual corrections to scaling or be more fundamental, due to correlations between subsequent space-time interface configurations.

Equilibrium crystal surfaces, constrained to equilibrate by means of dissociative dimer deposition and evaporation, have anomalous global surface roughness. We generalize earlier results for one-dimensional interfaces to two dimensions. The global surface width scales with surface size L as W2 approximately equals ln[L/(ln L)(1/4)] instead of the conventional form W2 approximately equal to ln L. The surface roughening transition does not change in nature, but its location is subject to a large and slowly varying logarithmic finite-size-scaling shift.