Mongodb tra i database non relazionali - focus su Map-Reduce e gestione della memoria

Panoramica delle caratteristiche dei database NoSQL, con dettaglio su MongoDB: filosofia di progettazione, modello dei dati, indicizzazione, algoritmo Map-Reduce e gestione della memoria.

Metodi di map-matching per l'identificazione degli itinerari dei ciclisti

Negli ultimi anni si è assistito al considerevole aumento della disponibilità di dati GPS e della loro precisione, dovuto alla diffusione e all’evoluzione tecnologica di smartphone e di applicazioni di localizzazione. Il processo di map-matching consiste nell’integrare tali dati - solitamente una lista ordinata di punti, identificati tramite coordinate geografiche ricavate mediante un sistema di localizzazione, come il GPS - con le reti disponibili; nell’ambito dell’ingegneria dei trasporti, l’obiettivo è di identificare il percorso realmente scelto dall’utente per lo spostamento. Il presente lavoro si propone l’obiettivo di studiare alcune metodologie di map-matching per l’identificazione degli itinerari degli utenti, in particolare della mobilità ciclabile. Nel primo capitolo è esposto il funzionamento dei sistemi di posizionamento e in particolare del sistema GPS: ne sono discusse le caratteristiche, la suddivisione nei vari segmenti, gli errori di misurazione e la cartografia di riferimento. Nel secondo capitolo sono presentati i vari aspetti del procedimento di map-matching, le sue principali applicazioni e alcune possibili classificazioni degli algoritmi di map-matching sviluppati in letteratura. Nel terzo capitolo è esposto lo studio eseguito su diversi algoritmi di map-matching, che sono stati testati su un database di spostamenti di ciclisti nell’area urbana di Bologna, registrati tramite i loro smartphone sotto forma di punti GPS, e sulla relativa rete. Si analizzano altresì i risultati ottenuti in un secondo ambiente di testing, predisposto nell’area urbana di Catania, dove sono state registrate in modo analogo alcune tracce di prova, e utilizzata la relativa rete. La comparazione degli algoritmi è eseguita graficamente e attraverso degli indicatori. Vengono inoltre proposti e valutati due algoritmi che forniscono un aggiornamento di quelli analizzati, al fine di migliorarne le prestazioni in termini di accuratezza dei risultati e di costo computazionale.

Three-dimensional electroanatomic entrainment map in atypical atrial flutter late after heart transplantation

Atrial flutter in the donor part of orthotopic heart transplants has been reported and successfully treated by radiofrequency ablation of the cavotricuspid isthmus, but mapping and ablation of atypical flutter circuits may be challenging.(1) Entrainment mapping has been used in combination with activation mapping to define the mechanism of atypical atrial flutter. Here, we report a case where colour-coded three-dimensional (3D) entrainment mapping allowed us to accurately determine and visualize the 3D location of the reentrant circuit and to plan the ablation of a left atrial flutter without the need for activation mapping.

Outcomes in patients waiting for antiretroviral treatment in the Free State Province, South Africa: prospective linkage study

Objective: In South Africa, many HIV-infected patients experience delays in accessing antiretroviral therapy (ART). We examined pretreatment mortality and access to treatment in patients waiting for ART. Design: Cohort of HIV-infected patients assessed for ART eligibility at 36 facilities participating in the Comprehensive HIV and AIDS Management (CHAM) program in the Free State Province. Methods: Proportion of patients initiating ART, pre-ART mortality and risk factors associated with these outcomes were estimated using competing risks survival analysis. Results: Forty-four thousand, eight hundred and forty-four patients enrolled in CHAM between May 2004 and December 2007, of whom 22 083 (49.2%) were eligible for ART; pre-ART mortality was 53.2 per 100 person-years [95% confidence interval (CI) 51.8–54.7]. Median CD4 cell count at eligibility increased from 87 cells/ml in 2004 to 101 cells/ml in 2007. Two years after eligibility an estimated 67.7% (67.1–68.4%) of patients had started ART, and 26.2% (25.6–26.9%) died before starting ART. Among patients with CD4 cell counts below 25 cells/ml at eligibility, 48% died before ART and 51% initiated ART. Men were less likely to start treatment and more likely to die than women. Patients in rural clinics or clinics with low staffing levels had lower rates of starting treatment and higher mortality compared with patients in urban/peri-urban clinics, or better staffed clinics. Conclusions: Mortality is high in eligible patients waiting for ART in the Free State Province. The most immunocompromised patients had the lowest probability of starting ART and the highest risk of pre-ART death. Prioritization of these patients should reduce waiting times and pre-ART mortality.

Effective population size of an indigenous Swiss cattle breed estimated from linkage disequilibrium

Effective population size is an important parameter for the assessment of genetic diversity within a livestock population and its development over time. If pedigree information is not available, linkage disequilibrium (LD) analysis might offer an alternative perspective for the estimation of effective population size. In this study, 128 individuals of the Swiss Eringer breed were genotyped using the Illumina BovineSNP50 beadchip. We set bin size at 50 kb for LD analysis, assuming that LD for proximal single nucleotide polymorphism (SNP)-pairs reflects distant breeding history while LD from distal SNP-pairs would reflect near history. Recombination rates varied among different regions of the genome. The use of physical distances as an approximation of genetic distances (e.g. setting 1 Mb = 0.01 Morgan) led to an upward bias in LD-based estimates of effective population size for generations beyond 50, while estimates for recent history were unaffected. Correction for restricted sample size did not substantially affect these results. LD-based actual effective population size was estimated in the range of 87-149, whereas pedigree-based effective population size resulted in 321 individuals. For conservation purposes, requiring knowledge of recent history (<50 generations), approximation assuming constant recombination rate seemed adequate.

MAP kinase kinase 1 (MKK1) is essential for transmission of Trypanosoma brucei by Glossina morsitans

MAP kinase kinase 1 (MKK1) is encoded by a single copy gene in Trypanosoma brucei. It has been shown recently that MKK1 is not essential for bloodstream forms [14]. To investigate the requirement for MKK1 in other life-cycle stages we generated null mutants in procyclic forms of a fly-transmissible strain. These grew normally in culture and were able to establish midgut infections in tsetse at normal rates and intensities, but were incapable of colonising the salivary glands. Transformation of null mutants with an ectopic copy of MKK1 enabled parasites to complete the life cycle in tsetse and infect mice. This is the first example of a gene that is indispensable for transmission of T. brucei. It also raises the possibility that activating the MKK1 signalling cascade in vitro might trigger the differentiation and proliferation of life-cycle stages of T. brucei that are currently refractory to culture.