Image quality and diagnostic accuracy of unenhanced SSFP MR angiography compared with conventional contrast-enhanced MR angiography for the assessment of thoracic aortic diseases

The purpose of this study was to determine the image quality and diagnostic accuracy of three-dimensional (3D) unenhanced steady state free precession (SSFP) magnetic resonance angiography (MRA) for the evaluation of thoracic aortic diseases. Fifty consecutive patients with known or suspected thoracic aortic disease underwent free-breathing ECG-gated unenhanced SSFP MRA with non-selective radiofrequency excitation and contrast-enhanced (CE) MRA of the thorax at 1.5 T. Two readers independently evaluated the two datasets for image quality in the aortic root, ascending aorta, aortic arch, descending aorta, and origins of supra-aortic arteries, and for abnormal findings. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined for both datasets. Sensitivity, specificity, and diagnostic accuracy of unenhanced SSFP MRA for the diagnosis of aortic abnormalities were determined. Abnormal aortic findings, including aneurysm (n = 47), coarctation (n = 14), dissection (n = 12), aortic graft (n = 6), intramural hematoma (n = 11), mural thrombus in the aortic arch (n = 1), and penetrating aortic ulcer (n = 9), were confidently detected on both datasets. Sensitivity, specificity, and diagnostic accuracy of SSFP MRA for the detection of aortic disease were 100% with CE-MRA serving as a reference standard. Image quality of the aortic root was significantly higher on SSFP MRA (P < 0.001) with no significant difference for other aortic segments (P > 0.05). SNR and CNR values were higher for all segments on SSFP MRA (P < 0.01). Our results suggest that free-breathing navigator-gated 3D SSFP MRA with non-selective radiofrequency excitation is a promising technique that provides high image quality and diagnostic accuracy for the assessment of thoracic aortic disease without the need for intravenous contrast material

Consumer acculturation theory: (crossing) conceptual boundaries

Consumer acculturation theorists have developed an insightful body of literature about the ways in which migrants adapt to foreign cultures via consumption. The present paper revisits 14 key studies from this field to highlight its most important contributions, critique its conceptual boundaries, and present cases of conceptual border crossings that indicate an emerging need for a broader conceptualization of the phenomenon. The paper closes by introducing a model that frames consumer acculturation as a complex system of recursive socio-cultural adaptation, and discusses its implications for future research

Cellulase recycling in biorefineriesis : is it possible?

On a near future, bio-based economy will assume a key role in our lives. Lignocellulosic materials (e.g., agroforestry residues, industrial/solid wastes) represent a cheaper and environmentally friendly option to fossil fuels. Indeed, following suitable processing, they can be metabolized by different microorganisms to produce a wide range of compounds currently obtained by chemical synthesis. However, due to the recalcitrant nature of these materials, they cannot be directly used by microorganisms, the conversion of polysaccharides into simpler sugars being thus required. This conversion, which is usually undertaken enzymatically, represents a significant part on the final cost of the process. This fact has driven intense efforts on the reduction of the enzyme cost following different strategies. Here, we describe the fundamentals of the enzyme recycling technology, more specifically, cellulase recycling. We focus on the main strategies available for the recovery of both the liquid- and solid-bound enzyme fractions and discuss the relevant operational parameters (e.g., composition, temperature, additives, and pH). Although the efforts from the industry and enzyme suppliers are primarily oriented toward the development of enzyme cocktails able to quickly and effectively process biomass, it seems clear by now that enzyme recycling is technically possible.Financial support from FEDER and Fundação para a Ciência e a Tecnologia (FCT): GlycoCBMs Project PTDC/AGR-FOR/3090/2012–FCOMP-01-0124- FEDER-027948 and Strategic Project PEst-OE/EQB/LA0023/2013, Project BBioInd-Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028 Cofunded by the Programa Operacional Regional do Norte (ON.2–O Novo Norte), QREN, FEDER and the PhD grant to DG (SFRH/BD/88623/ 2012) and ACR (SFRH/BD/89547/2012)

Image quality and diagnostic accuracy of unenhanced SSFP MR angiography compared with conventional contrast-enhanced MR angiography for the assessment of thoracic aortic diseases

Objectives: The purpose of this study was to determine the image quality and diagnostic accuracy of three-dimensional (3D) unenhanced steady state free precession (SSFP) magnetic resonance angiography (MRA) for the evaluation of thoracic aortic diseases. Methods: Fifty consecutive patients with known or suspected thoracic aortic disease underwent free-breathing ECG-gated unenhanced SSFP MRA with non-selective radiofrequency excitation and contrast-enhanced (CE) MRA of the thorax at 1.5T. Two readers independently evaluated the two datasets for image quality in the aortic root, ascending aorta, aortic arch, descending aorta, and origins of supra-aortic arteries, and for abnormal findings. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were determined for both datasets. Sensitivity, specificity, and diagnostic accuracy of unenhanced SSFP MRA for the diagnosis of aortic abnormalities were determined. Results: Abnormal aortic findings, including aneurysm (n=47), coarctation (n=14), dissection (n=12), aortic graft (n=6), intramural hematoma (n=11), mural thrombus in the aortic arch (n=1), and penetrating aortic ulcer (n=9), were confidently detected on both datasets. Sensitivity, specificity, and diagnostic accuracy of SSFP MRA for the detection of aortic disease were 100% with CE-MRA serving as a reference standard. Image quality of the aortic root was significantly higher on SSFP MRA (P<0.001) with no significant difference for other aortic segments (P>0.05). SNR and CNR values were higher for all segments on SSFP MRA (P<0.01). Conclusion: Our results suggest that free-breathing navigator-gated 3D SSFP MRA with non-selective radiofrequency excitation is a promising technique that provides high image quality and diagnostic accuracy for the assessment of thoracic aortic disease without the need for intravenous contrast material. © 2009 The Author(s)

On Multisets in Database Systems

Database systems cope with the management of large groups of persistent data in a shared, reliable, effective, and efficient way. Within a database, a multiset (or bag) is a collection of elements of the same type that may contain duplicates. There exists a tight coupling between databases and multisets. First, a large varietyof data models explicitly support multiset constructors. Second, commercial relational database systems, even if founded on a formal data model which is set-oriented in nature, allows for the multiset-oriented manipulation of tables. Third, multiset processing in databases may be dictated by efficiency reasons, as the cost of duplicate removal may turn out to be prohibitive. Finally, even in a pure set-oriented conceptual framework, multiset processing may turn out to be appropriate for optimization of query evaluation. The mismatch between the relational model and standardized relational query languages has led researchers to provide a foundation to the manipulation of multisets. Other research has focused on extending the relational model by relaxing the first normal form assumption, giving rise to the notion of a nested relation and to a corresponding nested relational algebra. These two research streams have been integrated within the concept of a complex relation, where different types of constructors other than relation coexist, such as multiset and list. Several other database research areas cope with multiset processing, including view maintenance, data warehousing, and web information discovery