4,164 research outputs found

    Evolution of genome sequencing techniques

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    The quality and the speed for genome sequencing has advanced at the same time that technology boundaries are stretched. This advancement has been divided so far in three generations. The first-generation methods enabled sequencing of clonal DNA populations. The second-generation massively increased throughput by parallelizing many reactions while the third-generation methods allow direct sequencing of single DNA molecules. The first techniques to sequence DNA were not developed until the mid-1970s, when two distinct sequencing methods were developed almost simultaneously, one by Alan Maxam and Walter Gilbert, and the other one by Frederick Sanger. The first one is a chemical method to cleave DNA at specific points and the second one uses ddNTPs, which synthesizes a copy from the DNA chain template. Nevertheless, both methods generate fragments of varying lengths that are further electrophoresed. Moreover, it is important to say that until the 1990s, the sequencing of DNA was relatively expensive and it was seen as a long process. Besides, using radiolabeled nucleotides also compounded the problem through safety concerns and prevented the automation. Some advancements within the first generation include the replacement of radioactive labels by fluorescent labeled ddNTPs and cycle sequencing with thermostable DNA polymerase, which allows automation and signal amplification, making the process cheaper, safer and faster. Another method is Pyrosequencing, which is based on the “sequencing by synthesis” principle. It differs from Sanger sequencing, in that it relies on the detection of pyrophosphate release on nucleotide incorporation. By the end of the last millennia, parallelization of this method started the Next Generation Sequencing (NGS) with 454 as the first of many methods that can process multiple samples, calling it the 2º generation sequencing. Here electrophoresis was completely eliminated. One of the methods that is sometimes used is SOLiD, based on sequencing by ligation of fluorescently dye-labeled di-base probes which competes to ligate to the sequencing primer. Specificity of the di-base probe is achieved by interrogating every 1st and 2nd base in each ligation reaction. The widely used Solexa/Illumina method uses modified dNTPs containing so called “reversible terminators” which blocks further polymerization. The terminator also contains a fluorescent label, which can be detected by a camera. Now, the previous step towards the third generation was in charge of Ion Torrent, who developed a technique that is based in a method of “sequencing-by-synthesis”. Its main feature is the detection of hydrogen ions that are released during base incorporation. Likewise, the third generation takes into account nanotechnology advancements for the processing of unique DNA molecules to a real time synthesis sequencing system like PacBio; and finally, the NANOPORE, projected since 1995, also uses Nano-sensors forming channels obtained from bacteria that conducts the sample to a sensor that allows the detection of each nucleotide residue in the DNA strand. The advancements in terms of technology that we have nowadays have been so quick, that it makes wonder: ¿How do we imagine the next generation

    Conditional connection explored: the case of Sicilian "cusà"

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    Stemming from a wh-question, the Sicilian marker cusà (cu sa ‘who knows’) expresses several epistemic meanings, which can also reach the realm of conditionality. The paper explores the discourse profile of cusà as it emerges from the analysis of diachronic data (18th-19th centuries) and present-day spoken written Sicilian (web data). These data suggest the possible development path leading from the wh-question to new functions. We propose that the origin of this development can be explained in the light of the strategy of “impossible question”, while the diverse functions of cusà emerged through concomitant processes of desemantisation, reanalysis and subjectification

    The relationship between external knowledge absorptive capacity and firm strategy: an exploratory analysis

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    En este trabajo se plantea que la capacidad de absorción de la empresa variará según sea la estrategia adoptada por esta. Para ello, partiendo de que la capacidad de absorción se desarrolla a través de la habilidad para adquirir, asimilar, transformar y explotar el conocimiento generado externamente, examinamos la importancia que tiene cada una de estas dimensiones en empresas que persiguen distintas estrategias. La información ha sido obtenida de una muestra compuesta por 81 empresas españolas fabricantes de pavimentos y revestimientos cerámicos. Los resultados muestran que la capacidad de adquirir conocimiento es mayor en las empresas exploradoras que en las defensoras y en las analizadoras, y que la capacidad de transformación y la capacidad de explotación son mayores en las empresas exploradoras que en las defensoras, no observándose diferencias en la capacidad de asimilación del conocimientoIn this work we raise that a firm’s absorptive capacity differs depending on the strategy being followed by the firm. We consider that absorptive capacity is formed by the ability to acquire, assimilate, transform and exploit the knowledge generated externally and examine the importance that each one of these dimensions has in compa- nies that adopt different strategies. The information has been obtained from a sample composed by 81 Spanish ce- ramic tiles firms. The results show that the ability to acquire knowledge is higher in prospectors than in defenders and analyzers, and that the transformation and exploitation abilities are higher in the prospector firms than in the de- fenders, whereas no differences are observed in the knowledge assimilation capacit

    Influences of Nationality and National Identification on Perceived Dangerousness of COVID-19 Variants and Perceived Effectiveness of COVID-19 Vaccines:A Study of UK and Portuguese Samples

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    During the COVID-19 pandemic, both variants of the virus that causes the disease and vaccines developed to combat it have been identified with nationalities. Both social identity theory and identity process theory would predict that this would initiate intergroup differentiation processes aimed at optimizing ingroup value and personal identity enhancement. Our study examined whether people’s nationality and level of national identification influence their perception of dangerousness of variants and effectiveness of vaccines. We compared data collected by online survey in March 2021 from the UK (which was associated with both a variant and a vaccine) and Portugal (which was associated with neither). The Portuguese rated variants overall as more dangerous than did the UK sample. The Chinese variant was rated by both samples as the least dangerous and the UK sample rated the British variant as less dangerous than did the Portuguese. Higher national identification in the UK sample was associated with differentiating more between the British variant and the South African variant and differentiating it less from the Chinese variant. The UK sample rated the effectiveness of the British vaccine higher than did the Portuguese. They also evaluated it as more effective than the American, Chinese and Indian vaccines. In both samples, higher national identification was associated with lower ratings of effectiveness for vaccines originating in China or India. Our study suggests that identity processes associated with national identification do influence perceptions of vaccines and variants. This has significant practice and policy implications. Social representations of variants and vaccines in nationalistic terms can have complex and unexpected consequences

    Operating theatre quality and prevention of surgical site infections

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    Surgical site infections (SSI) account for 14% to 17% of all hospital-acquired infections and 38% of nosocomial infections in surgical patients. SSI remain a substantial cause of morbid- ity and death, possibly because of the larger numbers of elderly surgical patients or those with a variety of chronic and immuno- compromising conditions, and emergence of antibiotic-resistant microorganisms. Factors causing surgical site infection are multifarious. Several studies have identified the main patient-related (endogenous risk factors) and procedure-related (external risk factors) factors that influence the risk of SSI. The rate of surgical wound infections is strongly influenced by operating theatre quality, too. A safe and salubrious operating theatre is an environment in which all sources of pollution and any micro-environmental alterations are kept strictly under control. This can be achieved only through careful planning, maintenance and periodic checks, as well as proper ongoing training for staff. Many international scientific societies have produced guidelines regarding the environmental features of operating theatres (posi- tive pressure, exchanges of filtered air per hour, air-conditioning systems with HEPA filters, etc.) and issued recommendations on healthcare-associated infection, including SSI, concerning surveillance methods, intervention to actively prevent SSI and approaches to monitoring the implementation of such strategies. Therefore, the prevention of SSI requires a multidisciplinary approach and the commitment of all concerned, including that of those who are responsible for the design, layout and functioning of operating theatres

    Staphylococcus aureus with reduced susceptibility to vancomycin in healthcare settings

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    Glycopeptide resistance in Staphylococcus aureus is a source of great concern because, especially in hospitals, this class of antibiotics, particularly vancomycin, is one of the main resources for combating infections caused by methicillin-resistant Staphylococcus aureus strains (MRSA). Reduced susceptibility to vancomycin (VISA) was first described in 1996 in Japan; since then, a phenotype with heterogeneous resistance to vancomycin (h-VISA) has emerged. H-VISA isolates are characterised by the presence of a resistant subpopulation, typically at a rate of 1 in 105 organisms, which constitutes the intermediate stage between fully vancomycin-susceptible S. aureus (VSSA) and VISA isolates. As VISA phenotypes are almost uniformly cross-resistant to teicoplanin, they are also called Glycopeptides-intermediate Staphylococcus aureus strains (GISA) and, in the case of heterogeneous resistance to glycopeptides, h-GISA. The overall prevalence of h-VISA is low, accounting for approximately 1.3% of all MRSA isolates tested. Mortality due to h-GISA infections is very high (about 70%), especially among patients hospitalised in high-risk departments, such as intensive care units (ICU). Given the great clinical relevance of strains that are heteroresistant to glycopeptides and the possible negative impact on treatment choices, it is important to draw up and implement infection control practices, including surveillance, the appropriate use of isolation precautions, staff training, hand hygiene, environmental cleansing and good antibiotic stewardship
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