A study on the impact of AL-FEC techniques on TV over IP Quality of Experience

Abstract In this contribution, an evaluation of the effectiveness of Application Layer-Forward Error Correction (AL-FEC) scheme in video communications over unreliable channels is presented. In literature, several AL-FEC techniques for reducing the effect of noisy transmission on multimedia communication have been adopted. Recently, their use has been proposed for inclusion in TV over IP broadcasting international standards. The objective of the analysis performed in this paper is to verify the effectiveness of AL-FEC techniques in terms of perceived Quality of Service (QoS) and more in general of Quality of Experience (QoE), and to evaluate the trade-off between AL-FEC redundancy and video quality degradation for a given packet loss ratio. To this goal, several channel error models are investigated (random i.i.d. losses, burst losses, and network congestions) on test sequences encoded at 2 and 4 Mbps. The perceived quality is evaluated by means of three quality metrics: the full-reference objective quality metric NTIA-VQM combined with the ITU-T Rec. G.1070, the full-reference DMOS-KPN metric, and the pixel-wise error comparison performed by using the PSNR distortion measure. A post-processing synchronization between the original and the reconstructed stream has also been designed for improving the fidelity of the performed quality measures. The experimental results show the effectiveness and the limits of the Application Layer protection schemes

A study on the impact of AL-FEC techniques on TV over IP Quality of Experience

Abstract In this contribution, an evaluation of the effectiveness of Application Layer-Forward Error Correction (AL-FEC) scheme in video communications over unreliable channels is presented. In literature, several AL-FEC techniques for reducing the effect of noisy transmission on multimedia communication have been adopted. Recently, their use has been proposed for inclusion in TV over IP broadcasting international standards. The objective of the analysis performed in this paper is to verify the effectiveness of AL-FEC techniques in terms of perceived Quality of Service (QoS) and more in general of Quality of Experience (QoE), and to evaluate the trade-off between AL-FEC redundancy and video quality degradation for a given packet loss ratio. To this goal, several channel error models are investigated (random i.i.d. losses, burst losses, and network congestions) on test sequences encoded at 2 and 4 Mbps. The perceived quality is evaluated by means of three quality metrics: the full-reference objective quality metric NTIA-VQM combined with the ITU-T Rec. G.1070, the full-reference DMOS-KPN metric, and the pixel-wise error comparison performed by using the PSNR distortion measure. A post-processing synchronization between the original and the reconstructed stream has also been designed for improving the fidelity of the performed quality measures. The experimental results show the effectiveness and the limits of the Application Layer protection schemes

Analysis of RNA splicing defects in PITX2 mutants supports a gene dosage model of Axenfeld-Rieger syndrome

BACKGROUND: Axenfeld-Rieger syndrome (ARS) is associated with mutations in the PITX2 gene that encodes a homeobox transcription factor. Several intronic PITX2 mutations have been reported in Axenfeld-Rieger patients but their effects on gene expression have not been tested. METHODS: We present two new families with recurrent PITX2 intronic mutations and use PITX2c minigenes and transfected cells to address the hypothesis that intronic mutations effect RNA splicing. Three PITX2 mutations have been analyzed: a G>T mutation within the AG 3' splice site (ss) junction associated with exon 4 (IVS4-1G>T), a G>C mutation at position +5 of the 5' (ss) of exon 4 (IVS4+5G>C), and a previously reported A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G). RESULTS: Mutation IVS4+5G>C showed 71% retention of the intron between exons 4 and 5, and poorly expressed protein. Wild-type protein levels were proportionally expressed from correctly spliced mRNA. The G>T mutation within the exon 4 AG 3'ss junction shifted splicing exclusively to a new AG and resulted in a severely truncated, poorly expressed protein. Finally, the A>G substitution at position -11 of the 3'ss of exon 5 shifted splicing exclusively to a newly created upstream AG and resulted in generation of a protein with a truncated homeodomain. CONCLUSION: This is the first direct evidence to support aberrant RNA splicing as the mechanism underlying the disorder in some patients and suggests that the magnitude of the splicing defect may contribute to the variability of ARS phenotypes, in support of a gene dosage model of Axenfeld-Rieger syndrome

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

De spagaat van de leden van de Hoge Raad in de Tweede Wereldoorlog

Contains fulltext : 37263.pdf (publisher's version ) (Open Access

Codifica di canale orientata al pacchetto

Il presente lavoro di tesi di dottorato affronta la problematica del raggiungimento di un alto livello di qualità per un servizio di tipo televisivo trasmesso su reti con perdita, come Internet. Lo studio della qualità per servizi televisivi su IP risulta di grande attualità, in quanto tali servizi necessitano di una qualità dell’esperienza pari a quelli dei servizi televisivi tradizionali per potersi affermare. Nel lavoro di tesi si è focalizzata l’attenzione sulla valutazione dell’impatto delle tecniche di correzione dell’errore a livello applicativo (AL-FEC) sulla qualità del servizio e sulla qualità dell’esperienza, considerando diverse tipologie di perdita di pacchetti in rete. In una prima parte del lavoro si è effettuata un’analisi approfondita delle prestazioni di una tecnica AL-FEC standard a basso costo computazionale, per verificarne le capacità e i limiti, nei confronti di eventi di perdita propri di una reale rete IP. Successivamente, valutati gli eventi di perdita più critici, si è pensato ad una nuova strategia, attuabile nelle reti gestite, che permettesse di potenziare le prestazioni della tecnica precedente, ottenendo allo stesso tempo un basso impatto sui flussi concorrenti in rete. Di seguito si è studiato un sistema di monitoraggio della qualità percepita dal fruitore di un servizio televisivo tramite l’uso di metriche oggettive, al fine di mantenere la qualità percepita costante variando le configurazioni della tecnica di correzione d’errore. Così facendo non si va ad agire sulla rete, ma si lavora in maniera end-to-end, rendendo attuabile tale sistema in reti non gestite. In una seconda parte del lavoro si è considerata una nuova strategia che permettesse un multicast efficace in reti MANET con perdita, sfruttando le caratteristiche di codici maggiormente innovativi, ovvero i codici a fontana. Infatti durante lo studio della qualità di un servizio televisivo trasmesso su reti con perdita, si è visto come la parte più difficile sia la realizzazione della consegna di un servizio che sia allo stesso tempo robusto alle perdite, e quindi con alta qualità, e che sia real-time. Sfruttando il fatto che se si utilizzano dei codici a fontana, allora per la ricostruzione del file sorgente non è più fondamentale sapere quali pacchetti sono stati ricevuti, ma solamente quanti, si è pensato che se il destinatario ricevesse i pacchetti non da una sola sorgente, ma da più sorgenti contemporaneamente, allora potrebbe iniziare a decodificare il flusso, una volta raggiunta la quantità necessaria per la ricostruzione, prima che le sorgenti finiscano di inviarlo completamente, diminuendo così la latenza complessiva. I risultati ottenuti mostrano l’efficacia dei sistemi sviluppati e le potenzialità della codifica di canale orientata al pacchetto per servizi televisivi trasmessi su reti con perdita

Implementing a strategy to reduce the instrument count in panel GMM

The problem of instrument proliferation and its consequences—overfitting of the endogenous explanatory variables, biased instrumental-variables and generalized method of moments estimators, and weakening of the power of the overidentification tests—are well known. This article introduces a statistical method to reduce the instrument count. Principal component analysis is applied on the instrument matrix, and the principal-component analysis scores are used as instruments for the panel generalized method of moments estimation. This strategy is implemented through the new command pca2