385 research outputs found
Fungal biofilms as low-modulus structural biocomposites
Biofilms are formed by microorganisms that collectively organise at interfaces. They are self-assembling complex fluids consisting of rigid microbial cells embedded in a self-secreted soft biopolymeric extracellular matrix and possess an intricate porous network that holds nearly 90% by weight of water. Biofilms have been commonly studied for their ability to spread infection and corrode industrial equipment.
Biomaterials produced by microorganisms such as bacterial cellulose, and more recently fungal mycelium-based biocomposites, typically require downstream processing to improve their mechanical strength.
Research questions:
Can non-pathogenic biofilms find applications as useful biomaterials?
Can biofilms be grown as biocomposites, thereby circumventing the need for downstream processing
Influence of carbon source complexity on porosity, water retention and extracellular matrix composition of Neurospora discreta biofilms
Aims
To evaluate carbon source complexity as a process lever to impact the microstructure, chemical composition and water retention capacity of biofilms produced by Neurospora discreta.
Methods and Results
Biofilms were produced by non‐pathogenic fungus N. discreta, using sucrose, cellulose or lignin as carbon source. Increase in complexity of carbon source from sucrose to lignin resulted in decreased water retention values (WRV) and wet weights of harvested biofilms. Confocal laser scanning microscopy (CLSM) was used to calculate porosity from bright field images, and relative stained areas of cells and carbohydrates from fluorescence imaging of samples stained with Trypan blue and Alexa Fluor 488. Porosity and relative quantity of cells increased with increase in carbon source complexity while the amount of carbohydrates decreased. Chemical analysis of the extracted extracellular matrix (ECM) showed that biofilms grown on more complex carbon sources had lower carbohydrate and protein content, which also explains the lower WRV trend, as carbohydrates are hydrophilic.
Conclusions
The nature of carbon source impacts the metabolic pathway of cells, thereby influencing the relative proportions of ECM and cells. This in turn impacts the microstructure, composition and water content of biofilms.
Significance and Impact of the Study
This work shows that carbon source can be used as process lever to control the properties of biofilms and presents a novel view of biofilms as potentially useful biomaterials
Eigenvalue density of Wilson loops in 2D SU(N) YM
In 1981 Durhuus and Olesen (DO) showed that at infinite N the eigenvalue
density of a Wilson loop matrix W associated with a simple loop in
two-dimensional Euclidean SU(N) Yang-Mills theory undergoes a phase transition
at a critical size. The averages of det(z-W), 1/det(z-W), and det(1+uW)/(1-vW)
at finite N lead to three different smoothed out expressions, all tending to
the DO singular result at infinite N. These smooth extensions are obtained and
compared to each other.Comment: 35 pages, 8 figure
Infinite N phase transitions in continuum Wilson loop operators
We define smoothed Wilson loop operators on a four dimensional lattice and
check numerically that they have a finite and nontrivial continuum limit. The
continuum operators maintain their character as unitary matrices and undergo a
phase transition at infinite N reflected by the eigenvalue distribution closing
a gap in its spectrum when the defining smooth loop is dilated from a small
size to a large one. If this large N phase transition belongs to a solvable
universality class one might be able to calculate analytically the string
tension in terms of the perturbative Lambda-parameter. This would be achieved
by matching instanton results for small loops to the relevant large-N-universal
function which, in turn, would be matched for large loops to an effective
string theory. Similarities between our findings and known analytical results
in two dimensional space-time indicate that the phase transitions we found only
affect the eigenvalue distribution, but the traces of finite powers of the
Wilson loop operators stay smooth under scaling.Comment: 31 pages, 9 figures, typos and references corrected, minor
clarifications adde
Universality of large N phase transitions in Wilson loop operators in two and three dimensions
The eigenvalue distribution of a Wilson loop operator of fixed shape
undergoes a transition under scaling at infinite N. We derive a large N scaling
function in a double scaling limit of the average characteristic polynomial
associated with the Wilson loop operator in two dimensional QCD. We hypothesize
that the transition in three and four dimensional large N QCD are also in the
same universality class and provide a numerical test for our hypothesis in
three dimensions.Comment: 43 pages, 1 table, 18 figures, uses JHEP3.cls, one reference added,
replaced Figure 3 and a small change to eqn (4.8
Cascade of Gregory-Laflamme Transitions and U(1) Breakdown in Super Yang-Mills
In this paper we consider black p-branes on square torus. We find an
indication of a cascade of Gregory-Laflamme transitions between black p-brane
and (p-1)-brane. Through AdS/CFT correspondence, these transitions are related
to the breakdown of the U(1) symmetry in super Yang-Mills on torus. We argue a
relationship between the cascade and recent Monte-Carlo data.Comment: 15 pages, 3 figures, LaTeX, v2: comments and references added, v3:
minor changes and a reference adde
The future of social is personal: the potential of the personal data store
This chapter argues that technical architectures that facilitate the longitudinal, decentralised and individual-centric personal collection and curation of data will be an important, but partial, response to the pressing problem of the autonomy of the data subject, and the asymmetry of power between the subject and large scale service providers/data consumers. Towards framing the scope and role of such Personal Data Stores (PDSes), the legalistic notion of personal data is examined, and it is argued that a more inclusive, intuitive notion expresses more accurately what individuals require in order to preserve their autonomy in a data-driven world of large aggregators. Six challenges towards realising the PDS vision are set out: the requirement to store data for long periods; the difficulties of managing data for individuals; the need to reconsider the regulatory basis for third-party access to data; the need to comply with international data handling standards; the need to integrate privacy-enhancing technologies; and the need to future-proof data gathering against the evolution of social norms. The open experimental PDS platform INDX is introduced and described, as a means of beginning to address at least some of these six challenges
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Diffusion tensor imaging parameters in mild traumatic brain injury and its correlation with early neuropsychological impairment: a longitudinal study
We explored the prognostic value of diffusion tensor imaging (DTI) parameters of selected white matter (WM) tracts in predicting neuropsychological outcome, both at baseline and 6 months later, among well-characterized patients diagnosed with mild traumatic brain injury (mTBI). Sixty-one patients with mTBI (mean age=27.08; standard deviation [SD], 8.55) underwent scanning at an average of 10 h (SD, 4.26) post-trauma along with assessment of their neuropsychological performance at an average of 4.35 h (SD, 7.08) upon full Glasgow Coma Scale recovery. Results were then compared to 19 healthy control participants (mean age=29.05; SD, 5.84), both in the acute stage and 6 months post-trauma. DTI and neuropsychological measures between acute and chronic phases were compared, and significant differences emerged. Specifically, chronic-phase fractional anisotropy and radial diffusivity values showed significant group differences in the corona radiata, anterior limb of internal capsule, cingulum, superior longitudinal fasciculus, optic radiation, and genu of corpus callosum. Findings also demonstrated associations between DTI indices and neuropsychological outcome across two time points. Our results provide new evidence for the use of DTI as an imaging biomarker and indicator of WM damage occurring in the context of mTBI, and they underscore the dynamic nature of brain injury and possible biological basis of chronic neurocognitive alterations
Criticality in confined ionic fluids
A theory of a confined two dimensional electrolyte is presented. The positive
and negative ions, interacting by a potential, are constrained to move on
an interface separating two solvents with dielectric constants and
. It is shown that the Debye-H\"uckel type of theory predicts that
the this 2d Coulomb fluid should undergo a phase separation into a coexisting
liquid (high density) and gas (low density) phases. We argue, however, that the
formation of polymer-like chains of alternating positive and negative ions can
prevent this phase transition from taking place.Comment: RevTex, no figures, in press Phys. Rev.
Deconfining Phase Transition as a Matrix Model of Renormalized Polyakov Loops
We discuss how to extract renormalized from bare Polyakov loops in SU(N)
lattice gauge theories at nonzero temperature in four spacetime dimensions.
Single loops in an irreducible representation are multiplicatively renormalized
without mixing, through a renormalization constant which depends upon both
representation and temperature. The values of renormalized loops in the four
lowest representations of SU(3) were measured numerically on small, coarse
lattices. We find that in magnitude, condensates for the sextet and octet loops
are approximately the square of the triplet loop. This agrees with a large
expansion, where factorization implies that the expectation values of loops in
adjoint and higher representations are just powers of fundamental and
anti-fundamental loops. For three colors, numerically the corrections to the
large relations are greatest for the sextet loop, ; these
represent corrections of for N=3. The values of the renormalized
triplet loop can be described by an SU(3) matrix model, with an effective
action dominated by the triplet loop. In several ways, the deconfining phase
transition for N=3 appears to be like that in the matrix model of
Gross and Witten.Comment: 24 pages, 7 figures; v2, 27 pages, 12 figures, extended discussion
for clarity, results unchange
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