No description available.

The outer membrane (OM) of P. aeruginosa is a semi-permeable barrier that contributes to antibiotic resistance by reducing uptake. Finding strategies to circumvent this barrier is a major challenge. One approach involves screening in physiologically relevant conditions to identify novel activity in existing molecules. We discovered that thiostrepton (TS), a thiopeptide antibiotic with no reported activity against Gram-negative bacteria, hijacks the pyoverdine siderophore transporters FpvA and FpvB to cross the OM under iron limitation to inhibit translation. Using TS, we subsequently showed that FpvB is not primarily a pyoverdine transporter, but rather a promiscuous transporter for siderophores ferrichrome and ferrioxamine B. Our work with TS suggested that other thiopeptides may use siderophore transporters for entry into the cell. This hypothesis led to a screen to identify other thiopeptides with activity against P. aeruginosa, uncovering two other thiopeptides, thiocillin and micrococcin, that use the ferrioxamine transporter FoxA for uptake. We discovered another siderophore, bisucaberin, could also use FoxA for uptake and our collaborators solved the crystal structure of bisucaberin bound to FoxA. Through biochemical approaches, we characterized how FoxA accommodates structurally distinct ligands. Finally, we screened known large natural product antibiotics with no pseudomonal activity under nutrient limitation and discovered that the glycopeptide vancomycin inhibits growth by blocking peptidoglycan crosslinking. This pilot screen emphasizes the importance of screening for antibiotics under physiologically relevant conditions to avoid overlooking potential hits. Overall, the findings from these studies can be used to guide medicinal chemistry efforts to develop novel siderophore-antibiotic conjugates for the treatment of P. aeruginosa infections. These results also help us gain a deeper understanding of the mechanism of binding and uptake through siderophore transporters and the range of substrates that can be taken up. / Dissertation / Doctor of Philosophy (PhD) / Antibiotic resistance is a growing crisis that threatens modern medicine, and it is becoming more challenging to discover truly new antibiotics to combat this threat. Intrinsic resistance conferred by the outer membrane of Gram-negative bacteria restricts the entry of many antibiotics, especially larger antibiotics that would otherwise inhibit the growth of Gram-positive bacteria. Consequently, there are fewer treatment options for infections caused by Gram-negative bacteria and developing new antibiotics that can cross the outer membrane remains a significant challenge in drug discovery. My work describes the discovery of a class of antibiotics that can bypass the outer membrane using specific outer-membrane nutrient transporters. Using biochemical, structural biology, fluorescence microscopy, and molecular biology techniques, we uncover the molecular determinants of uptake of these antibiotics for their respective transporters. These results can inform the design of novel narrow-spectrum antibiotics that can overcome the outer membrane barrier to combat antimicrobial resistance.

Inactivity reduces insulin action. Energy surplus causes similar reductions to insulin action. Unless energy intake is reduced to match low energy expenditure during inactivity, a concurrent energy surplus may account for the lower insulin action. This study evaluated the effect of inactivity (sitting) with and without energy surplus on insulin action. Fourteen young (26.1 ± 4.5 years (M ± SD)), lean (23.7 ± 7.1% fat), fit (VO 2peak = 49.1 ± 3.3 ml*kg -1 *min -1 ) men (n=7) and women (n=7) completed each of 3, 24-hour conditions: an active condition (i.e. high energy expenditure with energy intake matched to expenditure) = ACTIV; (2) reduced energy expenditure (inactivity) with no reduction in energy intake (i.e. energy surplus) = INACTIV; (3) inactivity with energy intake reduced to match low energy expenditure = INACTIV LO-CAL. Insulin action was measured during a glucose infusion the following morning. Data were analyzed using linear mixed-effects models with planned contrasts. Compared to ACTIV, insulin action, defined as whole-body rate of glucose disappearance ( R d ) scaled to steady-state plasma insulin, was reduced 39% in INACTIV ( p < 0.001) and by 18% in INACTIV LO-CAL ( p = 0.07). Insulin action was also higher in INACTIV LO-CAL compared to INACTIV ( p =0.04). These results suggest that 1 day of sitting elicits large reductions in insulin action. Energy surplus accounts for half of the decline in insulin action, suggesting other factors are involved in the metabolic response to inactivity.

Students are human beings; they, like all of us, make mistakes. In the language classroom, these mistakes may be written, spoken, and even thought. How, if, when, under what conditions and to what degree these errors are treated is of current concern in research regarding language acquisition. In their meta-analysis of interactional feedback, Mackey and Goo (2007) report that the utilization of feedback is beneficial and find evidence that feedback within the context of a focus on form environment is also facilitative of acquisition, echoing Norris and Ortega's (2000) positive findings regarding focus on form research. Thus, the role of feedback has found a somewhat limited, very informative and equally persuasive niche in current theory building and research. There is lack of research specifically addressing the role and effects of forms of feedback, other than recasts, namely prompts, in the second language classroom where the focus in on language use as a means of communication rather than the objectification of it. This context employs focus on form, a brief pedagogical intervention that momentarily shifts the focus of the class from meaning to linguistic form (See Long, 1991). Because prompts withhold correct forms (Lyster, 2004; Lyster & Saito, 2010), encourage students to simultaneously notice and self-correct (Lyster & Ranta, 1997), and push modified, student-generated output (de Bot, 1996; Lyster & Izquierdo, 2009; Lyster & Saito, 2010; Swain & Lapkin, 1995), they may be theoretically more appropriate for a focus on form context. This study examines this role in its function and efficacy comparing an implicit prompt, the clarification request, with an explicit prompt, metalinguistic feedback on students' spoken errors in the use of a very complex target structure, the subjunctive in nominal clauses in Spanish. Efficacy of the feedback is measured through successful student uptake, that is, whether or not students are able to self-repair as a result of the intervention and then through development operationalized as mean gains in a pre-test/post-test design. Statistical significance is shown for uptake with metalinguistic feedback only, however no development is shown as a result of any feedback due to the target structure's acquisition complexity.

Strängbetong krossar kasserade håldäckselement som sedan används som ballast i nya gjutningar. Den krossad betong ligger i en hög utomhus innan den används. Det första materialet krossades under 2020 och det senaste vintern 2022. Betongen karbonatiserar, en process som tar upp koldioxid från luften. Arbetet går ut på att kvantifiera den mängd koldioxid som tas upp samt finna förbättringsåtgärder för att kunna öka karbonatiseringen.  För att förstå hur karbonatisering fungerar utfördes informationssökning genom att leta efter tidigare forskningsrapporter som behandlar ämnet. Då det är brist på information om karbonatisering av krossad betong har antaganden gjorts för att komma vidare i arbetet. Vilket innebär att beräkningarna behöver mer korrekt indata för att visa ett mer rimligt resultat.  Den krossade betongen analyserades med karbonatiseringsindikator för att se om ytan av materialet karbonatiserat beroende på hur länge materialet varit orört.  Teoretiska beräkningar utfördes utifrån två olika exponeringar, regn och skyddad från regn, samt olika exponeringstid, resultatet visar att koldioxidupptaget blir högre om högen är skyddad från regn. Att strukturerat plocka material runt högen medför en längre exponeringstid för materialet, därmed ett högre koldioxidupptag jämfört med hur materialet plockas idag där allt material plockas från samma sida. / Strangbetong crushes discarded hollow core slabs, which are used for filling materials in new castings. The crushed concrete is stored in a pile outside before it is used. The first material was crushed during 2020 and the latest material were crushed in the winter of 2022. The concrete carbonates, a process where the concrete absorbs carbon dioxide from the air. The point of this project is to quantify the carbon dioxide which is absorbed and find solutions to make the carbonation more efficient.  To understand how concrete carbonation works, information has been searched for by studying already existing research reports. As there is a lack of information about carbonation of crushed concrete assumptions have been made to move the project forward. Which means that the calculations need more specific data to show a more reasonable result.  The crushed concrete was analyzed with a carbonation indicator to see how far the material had carbonated, depending on how long the material had been untouched.  Theoretic calculations were made throughout two different exposures, rain and covered from rain and different exposure time, the carbon dioxide uptake increases if the pile is covered from rain. Structured picking of material around the pile results in a longer exposure time for the material, therefore a higher uptake of carbon dioxide compared to how the material is picked today where the material is picked from the same side all the time.

No description available.

No description available.

No description available.

No description available.

No description available.