720 research outputs found

    Biological scaffolds for the peptide-directed assembly of nanoscale materials and devices

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.Includes bibliographical references.The utilization of biological factors in the design, synthesis and fabrication of nano-scaled materials and devices presents novel, large scale solutions for the realization of future technologies. In particular, we have genetically modified the M13 Filamentous Bacteriophage for its use as a biological scaffold in the peptide-controlled nucleation and patterning of nanoscale semiconducting and magnetic materials. Through evolutionary phage display screening of inorganic substrates, functional peptides that influence material properties such as size, phase and composition during nucleation have been identified. The incorporation of these specific, nucleating peptides into the generic scaffold of the M13 coat structure provides a viable linear template for the directed synthesis of semiconducting and magnetic nanowires. Through further modification of the remaining proteins on the virus scaffold, other functionalities can be incorporated such as the directed patterning of the virus/nanowires assemblies into nanoscaled devices with tunable properties as determined by the genetic information carried within the virus scaffold. Multi-functional viruses provide a truly self assembled system for the design and execution of a myriad of nanoscaled devices in a green, scalable and cost effective manner.by Daniel Joseph Solis.Ph.D

    Artifact-Based Rendering: Harnessing Natural and Traditional Visual Media for More Expressive and Engaging 3D Visualizations

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    We introduce Artifact-Based Rendering (ABR), a framework of tools, algorithms, and processes that makes it possible to produce real, data-driven 3D scientific visualizations with a visual language derived entirely from colors, lines, textures, and forms created using traditional physical media or found in nature. A theory and process for ABR is presented to address three current needs: (i) designing better visualizations by making it possible for non-programmers to rapidly design and critique many alternative data-to-visual mappings; (ii) expanding the visual vocabulary used in scientific visualizations to depict increasingly complex multivariate data; (iii) bringing a more engaging, natural, and human-relatable handcrafted aesthetic to data visualization. New tools and algorithms to support ABR include front-end applets for constructing artifact-based colormaps, optimizing 3D scanned meshes for use in data visualization, and synthesizing textures from artifacts. These are complemented by an interactive rendering engine with custom algorithms and interfaces that demonstrate multiple new visual styles for depicting point, line, surface, and volume data. A within-the-research-team design study provides early evidence of the shift in visualization design processes that ABR is believed to enable when compared to traditional scientific visualization systems. Qualitative user feedback on applications to climate science and brain imaging support the utility of ABR for scientific discovery and public communication.Comment: Published in IEEE VIS 2019, 9 pages of content with 2 pages of references, 12 figure

    Diversification, efficiency and productivity in catch share fisheries

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    This study investigates the relationship between diversification, technical efficiency (TE), and productivity in the US Gulf of Mexico commercial red snapper fishery. We estimated a vessel-level input-oriented stochastic distance frontier simultaneously with a technical inefficiency effects model using a 20-year unbalanced panel (1997–2016). The panel documented the fishing activities of 1,255 fishing vessels, 10 years before and after the adoption of the red snapper catch share program in 2007. Our study points to the desirability of diversification in catch share fisheries. It shows that red snapper fishers who diversified their fishing portfolio tended to be more productive and technically efficient. The study found evidence that diversification resulted in cost savings from catching multiple species (diversification economies), and that the productivity of the fleet increased (diversification efficiencies). The analysis also showed that the TE of the fleet increased in the catch share period. The average TE rose from 0.78 in the command and control period to 0.85 in the catch share period. Higher TE scores were associated with higher levels of diversification. Our results suggest that policies that encourage diversification such as reducing quota ownership caps, adjusting quota carryover provisions, and providing governmental assistance to increase participation in other fisheries deserve further attention.Este estudio investiga la relación entre la diversificación, la eficiencia técnica (TE) y la productividad en la pesquería comercial de pargo rojo del Golfo de México de los EE. UU. Estimamos una frontera de distancia estocástica orientada a la entrada a nivel del buque simultáneamente con un modelo de efectos de ineficiencia técnica utilizando un panel desequilibrado de 20 años (1997-2016). El panel documentó las actividades pesqueras de 1.255 embarcaciones pesqueras, 10 años antes y después de la adopción del programa de captura compartida de huachinango en 2007. Nuestro estudio apunta a la conveniencia de diversificar las pesquerías de captura compartida. Muestra que los pescadores de huachinango que diversificaron su cartera de pesca tendieron a ser más productivos y técnicamente eficientes. El estudio encontró evidencia de que la diversificación resultó en ahorros de costos al capturar múltiples especies (economías de diversificación), y que la productividad de la flota aumentó (eficiencias de diversificación). El análisis también mostró que el TE de la flota aumentó en el período de cuota de captura. El TE medio aumentó de 0,78 en el período de mando y control a 0,85 en el período de captura compartida. Los puntajes más altos de TE se asociaron con niveles más altos de diversificación. Nuestros resultados sugieren que las políticas que fomentan la diversificación, como la reducción de los límites máximos de propiedad de cuotas, el ajuste de las disposiciones de transferencia de cuotas y la prestación de asistencia gubernamental para aumentar la participación en otras pesquerías, merecen más atención. Los puntajes más altos de TE se asociaron con niveles más altos de diversificación. Nuestros resultados sugieren que las políticas que fomentan la diversificación, como la reducción de los límites máximos de propiedad de cuotas, el ajuste de las disposiciones de transferencia de cuotas y la prestación de asistencia gubernamental para aumentar la participación en otras pesquerías, merecen más atención. Los puntajes más altos de TE se asociaron con niveles más altos de diversificación. Nuestros resultados sugieren que las políticas que fomentan la diversificación, como la reducción de los límites máximos de propiedad de cuotas, el ajuste de las disposiciones de transferencia de cuotas y la prestación de asistencia gubernamental para aumentar la participación en otras pesquerías, merecen más atención

    Surgery guided by 5-aminolevulinic fluorescence in glioblastoma: volumetric analysis of extent of resection in singlecenter experience

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    We analyzed the efficacy and applicability of surgery guided by 5-aminolevulinic acid (ALA) fluorescence in consecutive patients with glioblastoma multiforme (GBM). Thirty-six patients with GBM were operated on using ALA fluorescence. Resections were performed using the fluorescent light to assess the right plane of dissection. In each case, biopsies with different fluorescent quality were taken from the tumor center, from the edges, and from the surrounding tissue. These samples were analyzed separately with hematoxylin-eosin examination and immunostaining against Ki67. Tumor volume was quantified with pre- and postoperative volumetric magnetic resonance imaging. Strong fluorescence identified solid tumor with 100% positive predictive value. Invaded tissue beyond the solid tumor mass was identified by vague fluorescence with 97% positive predictive value and 66% negative predictive value, measured against hematoxylin-eosin examination. All the contrast-enhancing volume was resected in 83.3% of the patients, all patients had resection over 98% of the volume and mean volume resected was 99.8%. One month after surgery there was no mortality, and new or increased neurological morbidity was 8.2%. The fluorescence induced by 5-aminolevulinic can help to achieve near total resection of enhancing tumor volume in most surgical cases of GBM. It is possible during surgery to obtain separate samples of the infiltrating cells from the tumor borde

    Effects of beta-alanine supplementation on brain homocarnosine/carnosine signal and cognitive function: an exploratory study

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    Objectives: Two independent studies were conducted to examine the effects of 28 d of beta-alanine supplementation at 6.4 g d-1 on brain homocarnosine/carnosine signal in omnivores and vegetarians (Study 1) and on cognitive function before and after exercise in trained cyclists (Study 2). Methods: In Study 1, seven healthy vegetarians (3 women and 4 men) and seven age- and sex-matched omnivores undertook a brain 1H-MRS exam at baseline and after beta-alanine supplementation. In study 2, nineteen trained male cyclists completed four 20-Km cycling time trials (two pre supplementation and two post supplementation), with a battery of cognitive function tests (Stroop test, Sternberg paradigm, Rapid Visual Information Processing task) being performed before and after exercise on each occasion. Results: In Study 1, there were no within-group effects of beta-alanine supplementation on brain homocarnosine/carnosine signal in either vegetarians (p = 0.99) or omnivores (p = 0.27); nor was there any effect when data from both groups were pooled (p = 0.19). Similarly, there was no group by time interaction for brain homocarnosine/carnosine signal (p = 0.27). In study 2, exercise improved cognitive function across all tests (P0.05) of beta-alanine supplementation on response times or accuracy for the Stroop test, Sternberg paradigm or RVIP task at rest or after exercise. Conclusion: 28 d of beta-alanine supplementation at 6.4g d-1 appeared not to influence brain homocarnosine/ carnosine signal in either omnivores or vegetarians; nor did it influence cognitive function before or after exercise in trained cyclists

    Hypofractionated radiation therapy and temozolomide in patients with glioblastoma and poor prognostic factors. A prospective, single-institution experience

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    Background: Hypofractionated radiation therapy is a feasible and safe treatment option in elderly and frail patients with glioblastoma. The aim of this study was to evaluate the effectiveness of hypofractionated radiation therapy with concurrent temozolomide in terms of feasibility and disease control in primary glioblastoma patients with poor prognostic factors other than advanced age, such as post-surgical neurological complications, high tumor burden, unresectable or multifocal lesions, and potential low treatment compliance due to social factors or rapidly progressive disease. Material and methods: GTV included the surgical cavity plus disease visible in T1WI-MRI, FLAIR-MRI and in the MET-uptake. The CTV was defined as the GTV plus 1.5-2 cm margin; the PTV was the CTV+0.3 cm margin. Forty, fourty-five, and fifty grays in 15 fractions were prescribed to 95% of PTV, CTV, and GTV, respectively. Treatment was delivered using IMRT or the VMAT technique. Simultaneously, 75 mg/m2/day of temozolomide were administered. Results: Between January 2010 and November 2017, we treated a total of 17 patients. The median age at diagnosis was 68-years; median KPS was 50-70%. MGMT-methylation status was negative in 5 patients, and 8 patients were IDH-wildtype. Eight of 18 patients were younger than 65-years. Median tumor volume was 26.95cc; median PTV volume was 322cc. Four lesions were unresectable; 6 patients underwent complete surgical resection. Median residual volume was 1.14cc. Progression-free survival was 60% at 6 months, 33% at 1-year and 13% at 2-years (median OS = 7 months). No acute grade 3-5 toxicities were documented. Symptomatic grade 3 radiation necrosis was observed in one patient. Conclusions: Patients with poor clinical factors other than advanced age can be selected for hypofractionated radiotherapy. The OS and PFS rates obtained in our series are similar to those in patients treated with standard fractionation, assuring good treatment adherence, low rates of toxicity and probable improved cost-effectiveness

    The Crabtree effect shapes the Saccharomyces cerevisiae lag phase during the switch between different carbon sources

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    When faced with environmental changes, microbes often enter a temporary growth arrest during which they reprogram the expression of specific genes to adapt to the new conditions. A prime example of such a lag phase occurs when microbes need to switch from glucose to other, less-preferred carbon sources. Despite its industrial relevance, the genetic network that determines the duration of the lag phase has not been studied in much detail. Here, we performed a genome-wide Bar-Seq screen to identify genetic determinants of the Saccharomyces cerevisiae glucose-to-galactose lag phase. The results show that genes involved in respiration, and specifically those encoding complexes III and IV of the electron transport chain, are needed for efficient growth resumption after the lag phase. Anaerobic growth experiments confirmed the importance of respiratory energy conversion in determining the lag phase duration. Moreover, overexpression of the central regulator of respiration, HAP4, leads to significantly shorter lag phases. Together, these results suggest that the glucose-induced repression of respiration, known as the Crabtree effect, is a major determinant of microbial fitness in fluctuating carbon environments. IMPORTANCE: The lag phase is arguably one of the prime characteristics of microbial growth. Longer lag phases result in lower competitive fitness in variable environments, and the duration of the lag phase is also important in many industrial processes where long lag phases lead to sluggish, less efficient fermentations. Despite the immense importance of the lag phase, surprisingly little is known about the exact molecular processes that determine its duration. Our study uses the molecular toolbox of S. cerevisiae combined with detailed growth experiments to reveal how the transition from fermentative to respirative metabolism is a key bottleneck for cells to overcome the lag phase. Together, our findings not only yield insight into the key molecular processes and genes that influence lag duration but also open routes to increase the efficiency of industrial fermentations and offer an experimental framework to study other types of lag behavior
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