788 research outputs found
Tiltrotor CFD part II: aerodynamic optimisation of tiltrotor blades
This paper presents aerodynamic optimisation of tiltrotor blades with high-fidelity computational
fluid dynamics. The employed optimisation framework is based on a quasi-Newton
method, and the required high-fidelity flow gradients were computed using a discrete adjoint
solver. Single-point optimisations were first performed, to highlight the contrasting requirements
of the helicopter and aeroplane flight regimes. It is then shown how a trade-off blade
design can be obtained using a multi-point optimisation strategy. The parametrisation of the
blade shape allowed to modify the twist and chord distributions, and to introduce a swept tip.
The work shows how these main blade shape parameters influence the optimal performance
of the tiltrotor in helicopter and aeroplane modes, and how a compromise blade shape can
increase the overall tiltrotor performance. Moreover, in all the presented cases, the accuracy
of the adjoint gradients resulted in a small number of flow evaluations for finding the optimal
solution, thus indicating gradient-based optimisation as a viable tool for modern tiltrotor
design
Type III secretion inhibitors for the management of bacterial plant diseases
The identification of chemical compounds that prevent and combat bacterial diseases is fundamental for crop production. Bacterial virulence inhibitors are a promising alternative to classical control treatments, because they have a low environmental impact and are less likely to generate bacterial resistance. The major virulence determinant of most animal and plant bacterial pathogens is the type III secretion system (T3SS). In this work, we screened nine plant extracts and 12 isolated compounds including molecules effective against human pathogens for their capacity to inhibit the T3SS of plant pathogens and for their applicability as virulence inhibitors for crop protection. The screen was performed using a luminescent reporter system developed in the model pathogenic bacterium Ralstonia solanacearum. Five synthetic molecules, one natural product and two plant extracts were found to downâregulate T3SS transcription, most through the inhibition of the regulator hrpB. In addition, for three of the molecules, corresponding to salicylidene acylhydrazide derivatives, the inhibitory effect caused a dramatic decrease in the secretion capacity, which was translated into impaired plant responses. These candidate virulence inhibitors were then tested for their ability to protect plants. We demonstrated that salicylidene acylhydrazides can limit R. solanacearum multiplication in planta and protect tomato plants from bacterial speck caused by Pseudomonas syringae pv. tomato. Our work validates the efficiency of transcription reporters to discover compounds or natural product extracts that can be potentially applied to prevent bacterial plant diseases
Enhanced Joule Heating in Umbral Dots
We present a study of magnetic profiles of umbral dots (UDs) and its
consequences on the Joule heating mechanisms. Hamedivafa (2003) studied Joule
heating using vertical component of magnetic field. In this paper UDs magnetic
profile has been investigated including the new azimuthal component of magnetic
field which might explain the relatively larger enhancement of Joule heating
causing more brightness near circumference of UD.Comment: 8 pages, 1 figure, accepted in Solar Physic
Colonic fermentation â more than meets the nose
Fermentation of undigested foods in the colon by its resident bacteria affects not only colonic health (protection against inflammation and tumour formation) but also influences metabolic health. Studying fermentation directly is difficult for lack of access. We hypothesise that the anatomical structure of the colon is suited to act as a fermenting chamber with the gaseous molecules (VOCs) emitted having direct effects on the colonocytes as well as gut neural and metabolic effects. We refer to this complex system as the âfermentomeâ, and further hypothesise that alteration in the âfermentomeâ through dietary modification will have a direct impact on colonic as well as metabolic health and disease. The VOCs emitted may play a role in bacterial chemical signalling within the colon but importantly could also function as a âgasâ biomarker. Measurement of such VOCs through non-invasive methods would have important application as a hypothesis-generating tool with subsequent clinical application
Common principles and best practices for engineering microbiomes
Despite broad scientific interest in harnessing the power of Earth's microbiomes, knowledge gaps
hinder their efficient use for addressing urgent societal and environmental challenges. We argue
hat structuring research and technology developments around a design-build-test-learn (DBTL)
cycle will advance microbiome engineering and spur new discoveries on the basic scientific
principles governing microbiome function. In this Review, we present key elements of an
iterative DBTL cycle for microbiome engineering, focusing on generalizable approaches,
including top-down and bottom-up design processes, synthetic and self-assembled construction
methods, and emerging tools to analyze microbiome function. These approaches can be used to
harness microbiomes for broad applications related to medicine, agriculture, energy, and the
environment. We also discuss key challenges and opportunities of each approach and synthesize
them into best practice guidelines for engineering microbiomes. We anticipate that adoption of a
DBTL framework will rapidly advance microbiome-based biotechnologies aimed at improving
human and animal health, agriculture, and enabling the bioeconomy
Strange stars in Krori-Barua space-time
The singularity space-time metric obtained by Krori and Barua\cite{Krori1975}
satisfies the physical requirements of a realistic star. Consequently, we
explore the possibility of applying the Krori and Barua model to describe
ultra-compact objects like strange stars. For it to become a viable model for
strange stars, bounds on the model parameters have been obtained. Consequences
of a mathematical description to model strange stars have been analyzed.Comment: 9 pages (two column), 12 figures. Some changes have been made. " To
appear in European Physical Journal C
Feasibility and Safety of Multicenter Tissue and Biofluid Sampling for α-Synuclein in Parkinson's Disease: The Systemic Synuclein Sampling Study (S4)
BACKGROUND:
α-synuclein is a lead Parkinson's disease (PD) biomarker. There are conflicting reports regarding accuracy of α-synuclein in different tissues and biofluids as a PD biomarker, and the within-subject anatomical distribution of α-synuclein is not well described. The Systemic Synuclein Sampling Study (S4) aims to address these gaps in knowledge. The S4 is a multicenter, cross-sectional, observational study evaluating α-synuclein in multiple tissues and biofluids in PD and healthy controls (HC).
OBJECTIVE:
To describe the baseline characteristics of the S4 cohort and safety and feasibility of this study.
METHODS:
Participants underwent motor and non-motor clinical assessments, dopamine transporter SPECT, biofluid collection (cerebrospinal fluid, saliva, and blood), and tissue biopsies (skin, sigmoid colon, and submandibular gland). Biopsy adequacy was determined based on presence of adequate target tissue. Tissue sections were stained with the 5C12 monoclonal antibody against unmodified α-synuclein. All specimens were acquired and processed in a standardized manner. Adverse events were systematically recorded.
RESULTS:
The final cohort consists of 82 participants (61 PD, 21 HC). In 68 subjects (83%), all types of specimens were obtained but only 50 (61%) of subjects had all specimens both collected and evaluable for α-synuclein. Mild adverse events were common, especially for submandibular gland biopsy, but only 1 severe adverse event occurred.
CONCLUSION:
Multicenter tissue and biofluid sampling for α-synuclein is feasible and generally safe. S4 will inform understanding of the concurrent distribution of α-synuclein pathology and biomarkers in biofluids and peripheral nervous system in PD
Aquatic food security:insights into challenges and solutions from an analysis of interactions between fisheries, aquaculture, food safety, human health, fish and human welfare, economy and environment
Fisheries and aquaculture production, imports, exports and equitability of distribution determine the supply of aquatic food to people. Aquatic food security is achieved when a food supply is sufficient, safe, sustainable, shockproof and sound: sufficient, to meet needs and preferences of people; safe, to provide nutritional benefit while posing minimal health risks; sustainable, to provide food now and for future generations; shock-proof, to provide resilience to shocks in production systems and supply chains; and sound, to meet legal and ethical standards for welfare of animals, people and environment. Here, we present an integrated assessment of these elements of the aquatic food system in the United Kingdom, a system linked to dynamic global networks of producers, processors and markets. Our assessment addresses sufficiency of supply from aquaculture, fisheries and trade; safety of supply given biological, chemical and radiation hazards; social, economic and environmental sustainability of production systems and supply chains; system resilience to social, economic and environmental shocks; welfare of fish, people and environment; and the authenticity of food. Conventionally, these aspects of the food system are not assessed collectively, so information supporting our assessment is widely dispersed. Our assessment reveals trade-offs and challenges in the food system that are easily overlooked in sectoral analyses of fisheries, aquaculture, health, medicine, human and fish welfare, safety and environment. We highlight potential benefits of an integrated, systematic and ongoing process to assess security of the aquatic food system and to predict impacts of social, economic and environmental change on food supply and demand
Confirmation of the Double Charm Baryon Xi_cc+ via its Decay to p D+ K-
We observes a signal for the double charm baryon Xi_cc+ in the charged decay
mode Xi_cc+ -> p D+ K- to complement the previously reported decay Xi_cc+ ->
Lambda_c K- pi+ in data from SELEX, the charm hadro-production experiment
(E781) at Fermilab. In this new decay mode we observe an excess of 5.62 events
over an expected background estimated by event mixing to be 1.38+/-0.13 events.
The Poisson probability that a background fluctuation can produce the apparent
signal is less than 6.4E-4. The observed mass of this state is
(3518+/-3)MeV/c^2, consistent with the published result. Averaging the two
results gives a mass of (3518.7+/-1.7)MeV/c^2. The observation of this new weak
decay mode confirms the previous SELEX suggestion that this state is a double
charm baryon. The relative branching ratio Gamma(Xi_cc+ -> pD+K-)/Gamma(Xi_cc+
-> Lambda_c K- pi+) = 0.36+/-0.21.Comment: 11 pages, 6 included eps figures. v2 includes improved statistical
method to determine significance of observation. Submitted to PL
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