289 research outputs found
Wettability of Nanostructured Surfaces
There are many studies in literature concerning contact angle measurements on different materials/substrates. It is documented that textiles can be coated with multifunctional materials in form of thin films or nanoparticles to acquire characteristics that can improve the protection and comfort of the wearer. The capacity of oxide nanostructures to inhibit fungal development and neutralize bacteria is a direct consequence of their wetting behavior [1–6]. Moreover, the radical modification of wetting behavior of nanostructures from hydrophilic to hydrophobic when changing the pulsed laser deposition (PLD) ambient will be thoroughly discussed
Evaluation Of Glueball Masses From Supergravity
In the framework of the conjectured duality relation between large gauge
theory and supergravity the spectra of masses in large gauge theory can be
determined by solving certain eigenvalue problems in supergravity. In this
paper we study the eigenmass problem given by Witten as a possible
approximation for masses in QCD without supersymmetry. We place a particular
emphasis on the treatment of the horizon and related boundary conditions. We
construct exact expressions for the analytic expansions of the wave functions
both at the horizon and at infinity and show that requiring smoothness at the
horizon and normalizability gives a well defined eigenvalue problem. We show
for example that there are no smooth solutions with vanishing derivative at the
horizon. The mass eigenvalues up to corresponding to smooth
normalizable wave functions are presented. We comment on the relation of our
work with the results found in a recent paper by Cs\'aki et al.,
hep-th/9806021, which addresses the same problem.Comment: 20 pages,Latex,3 figs,psfig.tex, added refs., minor change
Moduli stabilization from magnetic fluxes in type I string theory
We show that type I string theory compactified in four dimensions in the
presence of constant internal magnetic fields possesses N=1 supersymmetric
vacua, in which all Kahler class and complex structure closed string moduli are
fixed. Furthermore, their values can be made arbitrarily large by a suitable
tuning of the quantized magnetic fluxes. We present an explicit example for the
toroidal compactification on T^6 and discuss Calabi-Yau generalizations. This
mechanism can be complementary to other stabilization methods using closed
string fluxes but has the advantage of having an exact string description and
thus a validity away from the low-energy supergravity approximation. Moreover,
it can be easily implemented in constructions of string models based on
intersecting D-branes
Smart Thermoresponsive Surfaces Based on pNIPAm Coatings and Laser Method for Biological Applications
Various applications within last decades such as bacterially resistant surfaces, soft robotics, drug delivery systems, sensors and tissue engineering are poised to feature the importance of the ability to control bio-interfacial interactions. An enhanced attention is dedicated to designing smart stimuli-responsive interfaces for DNA, drug delivery, protein and cell based applications. Within this context, the thermoresponsive materials, especially poly(N-isopropylacrylamide) (pNIPAm) have been intensively used in tissue engineering applications for a controlled detachment of proteins and cells with a minimum of invasive effect on protein and cell structural conformation. The properties of smart bio-interfaces can be controlled by its composition and polymer architecture. Therefore, appropriate methods for obtaining controlled coatings are necessary. Laser methods were successfully used in the last decades for obtaining controlled organic and inorganic coatings for various types of applications, from electronics to tissue engineering. Among these, Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique bring us a step forward to other laser methods by avoiding damage and photochemical decomposition of materials. In this chapter we describe materials and approaches used for design of smart bio-interfaces aimed at controlling protein and cells behavior in vitro, focusing MAPLE method for tuning coatings characteristics in relation with biological response
Spectral Flow in AdS(3)/CFT(2)
We study the spectral flowed sectors of the H3 WZW model in the context of
the holographic duality between type IIB string theory in AdS(3)x S^3 x T^4
with NSNS flux and the symmetric product orbifold of T^4. We construct
explicitly the physical vertex operators in the flowed sectors that belong to
short representations of the superalgebra, thus completing the bulk-to-boundary
dictionary for 1/2 BPS states. We perform a partial calculation of the string
three-point functions of these operators. A complete calculation would require
the three-point couplings of non-extremal flowed operators in the H3 WZW model,
which are at present unavailable. In the unflowed sector, perfect agreement has
recently been found between the bulk and boundary three-point functions of 1/2
BPS operators. Assuming that this agreement persists in the flowed sectors, we
determine certain unknown three-point couplings in the H3 WZW model in terms of
three-point couplings of affine descendants in the SU(2) WZW model.Comment: 50 pages, 2 figure
Holographic anatomy of fuzzballs
We present a comprehensive analysis of 2-charge fuzzball solutions, that is,
horizon-free non-singular solutions of IIB supergravity characterized by a
curve on R^4. We propose a precise map that relates any given curve to a
specific superposition of R ground states of the D1-D5 system. To test this
proposal we compute the holographic 1-point functions associated with these
solutions, namely the conserved charges and the vacuum expectation values of
chiral primary operators of the boundary theory, and find perfect agreement
within the approximations used. In particular, all kinematical constraints are
satisfied and the proposal is compatible with dynamical constraints although
detailed quantitative tests would require going beyond the leading supergravity
approximation. We also discuss which geometries may be dual to a given R ground
state. We present the general asymptotic form that such solutions must have and
present exact solutions which have such asymptotics and therefore pass all
kinematical constraints. Dynamical constraints would again require going beyond
the leading supergravity approximation.Comment: 87 pages, begins with 10 page self contained summary of
results;v2:JHEP version; v3: typos corrected, see in particular formula D.1
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