Response of a particle in a one-dimensional lattice to an applied force: Dynamics of the effective mass

We study the behaviour of the expectation value of the acceleration of a particle in a one-dimensional periodic potential when an external homogeneous force is suddenly applied. The theory is formulated in terms of modified Bloch states that include the interband mixing induced by the force. This approach allows us to understand the behaviour of the wavepacket, which responds with a mass that is initially the bare mass, and subsequently oscillates around the value predicted by the effective mass. If Zener tunneling can be neglected, the expression obtained for the acceleration of the particle is valid over timescales of the order of a Bloch oscillation, which are of interest for experiments with cold atoms in optical lattices. We discuss how these oscillations can be tuned in an optical lattice for experimental detection.Comment: 15 pages, 12 figure

Observing the Onset of Effective Mass

The response of a particle in a periodic potential to an applied force is commonly described by an effective mass which accounts for the detailed interaction between the particle and the surrounding potential. Using a Bose-Einstein condensate of 87-Rb atoms initially in the ground band of an optical lattice, we experimentally show that the initial response of a particle to an applied force is in fact characterized by the bare mass. Subsequently, the particle response undergoes rapid oscillations and only over timescales long compared to that of the interband dynamics is the effective mass observed to be an appropriate description

Differential cognitive impairment for diverse forms of multiple sclerosis

BACKGROUND: Cognitive impairment is a common feature in multiple sclerosis (MS) patients and occurs in 60% of all cases. Unfortunately, neurological examination does not always agree with the neuropsychological evaluation in determining the cognitive profile of the patient. On the other hand, psychophysiological techniques such as event-related potentials (ERPs) can help in evaluating cognitive impairment in different pathologies. Behavioural responses and EEG signals were recorded during the experiment in three experimental groups: 1) a relapsing-remitting group (RRMS), 2) a benign multiple sclerosis group (BMS) and 3) a Control group. The paradigm employed was a spatial attention task with central cues (Posner experiment). The main aim was to observe the differences in the performance (behavioural variables) and in the latency and amplitude of the ERP components among these groups. RESULTS: Our data indicate that both MS groups showed poorer task performance (longer reaction times and lower percentage of correct responses), a latency delay for the N1 and P300 component, and a different amplitude for the frontal N1. Moreover, the deficit in the BMS group, indexed by behavioural and pyschophysiological variables, was more pronounced compared to the RRMS group. CONCLUSION: The present results suggest a cognitive impairment in the information processing in all of these patients. Comparing both pathological groups, cognitive impairment was more accentuated in the BMS group compared to the RMSS group. This suggests a silent deterioration of cognitive skills for the BMS that is not usually treated with pharmacological or neuropsychological therapy

Ecais study: inadvertent cardiovascular adverse events in sepsis

Objetivo Describir la incidencia de eventos cardiovasculares adversos en pacientes con diagnóstico de sepsis en sus diferentes estadios. Diseño Estudio observacional, descriptivo, longitudinal. Ámbito Unidades de cuidados intensivos de tipo mixto de dos hospitales universitarios en la ciudad de Bogotá. Participantes Se incluyeron una serie de pacientes mayores de edad, que ingresan a UCI con diagnostico de sepsis, sin evidencia de lesión miocárdica isquémica previa. Intervenciones Registros electrocardiográficos continuos de 12 derivaciones durante 48 horas con monitoría Holter Variables de interés Isquemia, arritmia cardiaca, variabilidad de la frecuencia cardiaca. Resultados Se analizaron 100 pacientes, 62% de los cuales se estadificó como choque séptico. El 3% presentó evento cardiovascular adverso de tipo isquémico detectado por Holter y desapercibido por monitoreo convencional. El 46% presentaron un evento de tipo arrítmico por Holter, comparado con solo un 6% detectado por monitoreo convencional. La mortalidad cruda fue de 40%. El 100% presentó pérdida de la variabilidad de la frecuencia cardiaca. Conclusión La sepsis en esta experiencia mostró una baja incidencia de eventos cardiovasculares isquémicos. Los eventos arrítmicos, sin embargo, mostraron una incidencia alta. El monitoreo convencional falló en detectar la totalidad de los eventos isquémicos y en mayor proporción los eventos arrítmicos. En esta serie, los eventos cardiovasculares generados por descarga adrenérgica no impactan en la mortalidad.Objective To describe the incidence of cardiovascular adverse events in patients with sepsis in its various stages. Design A longitudinal, descriptive, observational study was carried out. Setting Intensive care units of two university hospitals in Bogotá (Colombia). Patients A number of patients consecutively admitted to the adult ICU with a diagnosis of sepsis, and no evidence of previous ischemic myocardial injury. Interventions Forty-eight hours of electrocardiographic record using Holter technology. Main variables Ischemia, cardiac arrhythmia, heart rate variability. Results A total of 100 patients were analyzed, 62% being staged as presenting septic shock. Three percent suffered ischemic events detected by Holter and unnoticed through conventional monitoring. Forty-six percent suffered an arrhythmic event detected by Holter, compared with only 6% as detected by conventional monitoring. Mortality was 40%. All patients showed loss of heart rate variability. Conclusion In this study patients with sepsis showed a low incidence of cardiovascular ischemic events. In contrast, arrhythmic events showed a high incidence. Conventional monitoring failed to detect any of the ischemic events and most arrhythmic events. In this study, cardiovascular events generated by adrenergic discharge had no impact upon mortality

Automating biological monitoring on the Northern Andes of South America: combining biology and machine learning for conservation

The northern Andes in South America harbors one of the most diverse biological diversity on the planet. Yet, it is one of the most threatened regions as a result of habitat fragmentation, invasive species, agriculture and cattle grazing, and global climate change. It is therefore critical to implement robust conservation strategies and effective monitoring plans. In the region, biological monitoring relies on traditional methods such as direct observation and capture. These methods are expensive and require a large effort specially for rare species. As an alternative, automated passive bioacoustics allow to obtain large amounts of data both in time and space and in comparison, with traditional methods at low cost. The main challenge in passive monitoring is to handle and analyze these rivers of information in order to obtain meaningful results from acoustic data. We have implemented a passive bioacoustic monitoring since 2012 on the northern Andes in Colombia, a highly diverse region in the Neotropics. Our goals are two fold: first, we want to develop analytical strategies to process large amounts of sound files and second we are interested in answering biological questions from individuals to the landscape. As a result of this monitoring, we have developed a machine learning algorithm based on syllable recognition to automatically identify frog species (Ecol. Inf. 24: 200-209). We also have developed an algorithm to estimate the amount of rain from acoustic recordings (Ecol. Ind. 75:95-100). We have answered biological questions ranging from acoustic niche partitioning, interaction of traditional community indices with acoustic indices, and association of acoustic indices with landscape features. Now, we are using passive monitoring to fit complex occupation models and to determine assembling rules in anuran communities. In addition, we are assessing acoustic indices aiming to develop tools with more functions for soundscape analysis (Ecol. Inf. 45:16-25). We show how the continuous feedback between biologists and engineers will spike the implementation and analysis of passive monitoring in imperiled tropical hotspots

Understanding the relationship between soundscape and landscape features in a Tropical Andean environment, Colombia

The acoustic component of the landscape (soundscape) has been suggested as an indicator of landscape conditions as it has been related to physical, biological and anthropogenic features of the local environment. Despite of acoustic indices have been used as measurements of soundscape complexity, their relationship with landscape features has shown to be highly variable and not direct. This relationship has not been examined on the tropical Andes then it is not clear if soundscape can be a reliable indicator of landscape conditions. In this study, we assess the relationship between 14 acoustic indices and landscape conditions in an area on the northern Andes of Colombia. This region is highly fragmented and characterized for a highly diverse community of animals and plants thus representing an excellent opportunity to test such relationship. Soundscape recordings were obtained from 31 randomly selected sites surveyed among May and July 2017. A Song Meter SM4 device was deployed at each site for five consecutive days, and programmed to collect 1-min recordings every 15 minutes for a total of 95 samples per day. Recordings were obtained as monaural 16 bits and at a sampling rate of 22.05 kHz. Out of 14 indices, we calculated 9 non-correlated acoustic indices for each 1-min recording and selected the maximum value per hour to estimate the hourly average over the five days at each site. Thirteen landscape features were derived from satellite images and metrics describing vegetation, fragmentation, water availability, terrain, and soil attributes at 100 m radius around each site. Indices did not present a similar pattern of variation with respect to landscape conditions. Acoustic evenness (AE) and temporal entropy (TE) indices were related to changes in terrain conditions, while acoustic diversity index (ADI) was associated to fragmentation. The bioacoustic index (BI), acoustic complexity index (ACI), and the number of peaks (NP) were positively related with water availability. Our results suggest that in Andean environments specific acoustic indices could be connected to particular aspects of landscape

Contribution of common and rare variants to bipolar disorder susceptibility in extended pedigrees from population isolates.

Current evidence from case/control studies indicates that genetic risk for psychiatric disorders derives primarily from numerous common variants, each with a small phenotypic impact. The literature describing apparent segregation of bipolar disorder (BP) in numerous multigenerational pedigrees suggests that, in such families, large-effect inherited variants might play a greater role. To identify roles of rare and common variants on BP, we conducted genetic analyses in 26 Colombia and Costa Rica pedigrees ascertained for bipolar disorder 1 (BP1), the most severe and heritable form of BP. In these pedigrees, we performed microarray SNP genotyping of 838 individuals and high-coverage whole-genome sequencing of 449 individuals. We compared polygenic risk scores (PRS), estimated using the latest BP1 genome-wide association study (GWAS) summary statistics, between BP1 individuals and related controls. We also evaluated whether BP1 individuals had a higher burden of rare deleterious single-nucleotide variants (SNVs) and rare copy number variants (CNVs) in a set of genes related to BP1. We found that compared with unaffected relatives, BP1 individuals had higher PRS estimated from BP1 GWAS statistics (P = 0.001 ~ 0.007) and displayed modest increase in burdens of rare deleterious SNVs (P = 0.047) and rare CNVs (P = 0.002 ~ 0.033) in genes related to BP1. We did not observe rare variants segregating in the pedigrees. These results suggest that small-to-moderate effect rare and common variants are more likely to contribute to BP1 risk in these extended pedigrees than a few large-effect rare variants

Cluster analysis of behavioural and event-related potentials during a contingent negative variation paradigm in remitting-relapsing and benign forms of multiple sclerosis

<p>Abstract</p> <p>Background</p> <p>Event-related potentials (ERPs) may be used as a highly sensitive way of detecting subtle degrees of cognitive dysfunction. On the other hand, impairment of cognitive skills is increasingly recognised as a hallmark of patients suffering from multiple sclerosis (MS). We sought to determine the psychophysiological pattern of information processing among MS patients with the relapsing-remitting form of the disease and low physical disability considered as two subtypes: 'typical relapsing-remitting' (RRMS) and 'benign MS' (BMS). Furthermore, we subjected our data to a cluster analysis to determine whether MS patients and healthy controls could be differentiated in terms of their psychophysiological profile.</p> <p>Methods</p> <p>We investigated MS patients with RRMS and BMS subtypes using event-related potentials (ERPs) acquired in the context of a Posner visual-spatial cueing paradigm. Specifically, our study aimed to assess ERP brain activity in response preparation (contingent negative variation -CNV) and stimuli processing in MS patients. Latency and amplitude of different ERP components (P1, eN1, N1, P2, N2, P3 and late negativity -LN) as well as behavioural responses (reaction time -RT; correct responses -CRs; and number of errors) were analyzed and then subjected to cluster analysis.</p> <p>Results</p> <p>Both MS groups showed delayed behavioural responses and enhanced latency for long-latency ERP components (P2, N2, P3) as well as relatively preserved ERP amplitude, but BMS patients obtained more important performance deficits (lower CRs and higher RTs) and abnormalities related to the latency (N1, P3) and amplitude of ERPs (eCNV, eN1, LN). However, RRMS patients also demonstrated abnormally high amplitudes related to the preparation performance period of CNV (cCNV) and post-processing phase (LN). Cluster analyses revealed that RRMS patients appear to make up a relatively homogeneous group with moderate deficits mainly related to ERP latencies, whereas BMS patients appear to make up a rather more heterogeneous group with more severe information processing and attentional deficits.</p> <p>Conclusions</p> <p>Our findings are suggestive of a slowing of information processing for MS patients that may be a consequence of demyelination and axonal degeneration, which also seems to occur in MS patients that show little or no progression in the physical severity of the disease over time.</p

Bivariate genome-wide association meta-analysis of pediatric musculoskeletal traits reveals pleiotropic effects at the SREBF1/TOM1L2 locus

Bone mineral density is known to be a heritable, polygenic trait whereas genetic variants contributing to lean mass variation remain largely unknown. We estimated the shared SNP heritability and performed a bivariate GWAS meta-analysis of total-body lean mass (TB-LM) and total-body less head bone mineral density (TBLH-BMD) regions in 10,414 children. The estimated SNP heritability is 43% for TBLH-BMD, and 39% for TB-LM, with a shared genetic component of 43%. We identify variants with pleiotropic effects in eight loci, including seven established bone mineral density loci: _WNT4, GALNT3, MEPE, CPED1/WNT16, TNFSF11, RIN3, and PPP6R3/LRP5_. Variants in the _TOM1L2/SREBF1_ locus exert opposing effects TB-LM and TBLH-BMD, and have a stronger association with the former trait. We show that _SREBF1_ is expressed in murine and human osteoblasts, as well as in human muscle tissue. This is the first bivariate GWAS meta-analysis to demonstrate genetic factors with pleiotropic effects on bone mineral density and lean mass

Quantitative electroencephalography reveals different physiological profiles between benign and remitting-relapsing multiple sclerosis patients

<p>Abstract</p> <p>Background</p> <p>A possible method of finding physiological markers of multiple sclerosis (MS) is the application of EEG quantification (QEEG) of brain activity when the subject is stressed by the demands of a cognitive task. In particular, modulations of the spectral content that take place in the EEG of patients with multiple sclerosis remitting-relapsing (RRMS) and benign multiple sclerosis (BMS) during a visuo-spatial task need to be observed.</p> <p>Methods</p> <p>The sample consisted of 19 patients with RRMS, 10 with BMS, and 21 control subjects. All patients were free of medication and had not relapsed within the last month. The power spectral density (PSD) of different EEG bands was calculated by Fast-Fourier-Transformation (FFT), those analysed being delta, theta, alpha, beta and gamma. Z-transformation was performed to observe individual profiles in each experimental group for spectral modulations. Lastly, correlation analyses was performed between QEEG values and other variables from participants in the study (age, EDSS, years of evolution and cognitive performance).</p> <p>Results</p> <p>Nearly half (42%) the RRMS patients showed a statistically significant increase of two or more standard deviations (SD) compared to the control mean value for the beta-2 and gamma bands (F = 2.074, p = 0.004). These alterations were localized to the anterior regions of the right hemisphere, and bilaterally to the posterior areas of the scalp. None of the BMS patients or control subjects had values outside the range of ± 2 SD. There were no significant correlations between these values and the other variables analysed (age, EDSS, years of evolution or behavioural performance).</p> <p>Conclusion</p> <p>During the attentional processing, changes in the high EEG spectrum (beta-2 and gamma) in MS patients exhibit physiological alterations that are not normally detected by spontaneous EEG analysis. The different spectral pattern between pathological and controls groups could represent specific changes for the RRMS patients, indicative of compensatory mechanisms or cortical excitatory states representative of some phases during the RRMS course that are not present in the BMS group.</p