A HMM-based pre-training approach for sequential data

Much recent research highlighted the critical role of unsuper- vised pre-training to improve the performance of neural network models. However, extensions of those architectures to the temporal domain intro- duce additional issues, which often prevent to obtain good performance in a reasonable time. We propose a novel approach to pre-train sequential neural networks in which a simpler, approximate distribution generated by a linear model is first used to drive the weights in a better region of the parameter space. After this smooth distribution has been learned, the net- work is fine-tuned on the more complex real dataset. The benefits of the proposed method are demonstrated on a prediction task using two datasets of polyphonic music, and the general validity of this strategy is shown by applying it to two different recurrent neural network architectures

Neural Networks for Sequential Data: A Pre-training Approach based on Hidden Markov Models

none3noIn the last few years, research highlighted the critical role of unsupervised pre-training strategies to improve the performance of artificial neural networks. However, the scope of existing pre-training methods is limited to static data, whereas many learning tasks require to deal with temporal information. We propose a novel approach to pre-training sequential neural networks that exploits a simpler, first-order Hidden Markov Model to generate an approximate distribution of the original dataset. The learned distribution is used to generate a smoothed dataset that is used for pre-training. In this way, it is possible to drive the connection weights in a better region of the parameter space, where subsequent fine-tuning on the original dataset can be more effective. This novel pre-training approach is model-independent and can be readily applied to different network architectures. The benefits of the proposed method, both in terms of accuracy and training times, are demonstrated on a prediction task using four datasets of polyphonic music. The flexibility of the proposed strategy is shown by applying it to two different recurrent neural network architectures, and we also empirically investigate the impact of different hyperparameters on the performance of the proposed pre-training strategy.nonePasa, Luca; Testolin, Alberto; Sperduti, AlessandroPasa, Luca; Testolin, Alberto; Sperduti, Alessandr

Morphological and carpological variability of walnut germplasm (Juglans regia L.) collected in North-eastern Italy and selection of superior genotypes

Nuts collected from wild accessions of Persian walnut (Juglans regia L.) in the Friuli Venezia Giulia region (North Eastern Italian Alps) were evaluated during 2013\u20132015. The analyses carried out were mainly on fruit traits, the only morphological traits that could be observed and statistically analysed, being less dependent on the area of sampling, considering geographic features such as altitude, slope, soil, and climate. Such fruit traits proved to be very variable. The nut weight ranged from 2.2 to 17.3 g, the shell thickness from 0.35 to 2.30 mm, the color of kernel skin from light to amber. The fruit nut appearance, evaluated by a panel of consumers, varied from 2.50 to 6.83 in a scale from 0 (very bad) to 10 (very attractive). A multivariate analysis carried out considering traits valuable for breeding and selection, such as nut weight, kernel weight: nut weight ratio, shell thickness, kernel color, and fruit appearance, produced a ranking list, that included, at best, accessions that could be either selected as such for vegetative propagation and distribution to growers or used in breeding programs. A disadvantage of these selections is their terminal bearing habit which is not appreciated by breeders, who prefer the most productive genotypes with lateral bearing habit

Liste del melo 2010: molte uscite e pochi ingressi

La scelta della varietà di melo o pero con cui costituire un nuovo frutteto è la variabile principale per garantire la redditività dell’attività del frutticoltore. Le cultivar a disposizione sul mercato sono tante, e le Liste che pubblichiamo in questo Speciale servono proprio a renderne più facile la scelta. Tra le mele segnaliamo due nuovi ingressi: Forlady e Rosy Glow*

Preoperative Transcatheter Diagnosis of Right Atrial Hemangioma

A 34-year-old man with unremarkable past medical history presents with night sweats and a recent diagnosis of intracardiac mass. The initial diagnostic workup did not provide a definitive diagnosis, so a cardiac biopsy under intracardiac echocardiography guidance was performed, revealing a hemangioma, which was then successfully resected. (Level of Difficulty: Advanced.

Genetic Diversity of Walnut (Juglans Regia L.) in the Eastern Italian Alps

Juglans regia L. is distributed primarily across temperate and subtropical regions of the Northern Hemisphere. During the last glaciation, the species survived in refugial areas that in Europe included the Balkans and the Italian peninsula, two areas joined by a corridor represented by the Friuli Venezia Giulia region, where two germplasm reservoirs met and likely intercrossed during re-colonization after the last glaciation. In this work, two hundred and fifteen wild accessions native to the area were sampled, georeferenced, and genotyped with 20 microsatellite loci selected from the literature. The local accessions of this study displayed moderate genetic diversity with 80 alleles identified. The number of alleles/loci was 4.0 (4.7 alleles for the genomic SSRs (Simple Sequence Repeats) and 2.7 alleles per EST (Expressed Sequence Tag)-derived SSR, on average). An analysis of molecular variance (AMOVA) revealed that most of the molecular diversity was between individuals (nearly 98% of variation explained). The model-based clustering algorithms implemented either in STRUCTURE and GENELAND software revealed two clusters: The first one encompassed most of the samples and showed a great genetic admixture throughout the five sampling areas defined on the base of orographic characteristics of the region. The second cluster represented a small island with three samples traced back to an introduction from Russia at the beginning of the 20th century

An innovative approach to disentangling the effect of management and environment on tree cover and density of protected areas in African savanna

In protected areas of the African savanna tree cover, structure and species composition are influenced by a combination of many different variables. These include complex and multi-scaled interplay of environmental factors such as water and nutrient availability, fire, herbivory and, when occurring, direct human disturbance. In this study, we conducted a comprehensive and comparative analysis of the spatial variability of tree cover and density in three neighboring Southern African National Parks (Kruger, Limpopo, and Gonarezhou) characterized by similar environmental conditions but different management plans. We sampled 3382 plots of 0.5 ha across the three parks using an innovative methodology defined as augmented visual interpretation, based on a free and open source software. This software, named Collect Earth, allows access to very high spatial and temporal resolution imagery archives. Spatial variability of tree cover and density was analyzed comparing the three parks and the two bioclimatic regions (semiarid and dry subhumid) characterizing them. The effect of relevant environmental variables such as edaphic factors, precipitation and fire frequency was also assessed. Kruger National Park is characterized by the lowest values of tree cover and density among the three Parks. Contrary to what was expected and the general trend of Southern Africa, the dry subhumid zone showed lower values of tree cover and density than the semiarid zone. Such variability is hypothesized to be related to the different managements of the three parks within the general environmental template characterizing the African savanna as well as differences in tree species composition between the two climatic zones

Linkage map saturation, construction, and comparison in four populations of Prunus

One of the objectives of the ISAFRUIT Project was to perform genetic analyses in four populations of Prunus, two of peach (P. persica) and two of apricot (P. armeniaca), in order to identify major genes and quantitative trait loci (QTLs) for characters related to fruit quality. This required the construction of saturated marker maps in each of these populations. Marker maps were available for an intra-specific peach X peach F(2), a BC(2) peach X P davidiana (using peach as the recurrent parent), and an apricot X apricot F(1). We have further saturated these maps mainly with SSR (simple sequence repeat) markers. A new map, constructed uniquely from SSRs was prepared for a fourth apricot X apricot F(1) population. Using anchor markers, we compared these four maps with the reference Prunus map, constructed using an almond X peach F(2) population. As previously observed, conservation of synteny and co-linearity were the general rule, providing additional evidence of the high level of similarity between all Prunus genomes. Comparisons of genetic distances between the maps suggested that those involving similar genomes had higher levels of recombination than those with more distant genomes, particularly the inter-specific crosses