145 research outputs found

### A Free-Algebraic Solution for the Planar Approximation

An explicit solution for the generating functional of n-point functions in
the planar approximation is given in terms of two sets of free-algebraic
annihilation and creation operators.Comment: 15 pages, added referenc

### Loop models, random matrices and planar algebras

We define matrix models that converge to the generating functions of a wide
variety of loop models with fugacity taken in sets with an accumulation point.
The latter can also be seen as moments of a non-commutative law on a subfactor
planar algebra. We apply this construction to compute the generating functions
of the Potts model on a random planar map

### Exact beta function from the holographic loop equation of large-N QCD_4

We construct and study a previously defined quantum holographic effective
action whose critical equation implies the holographic loop equation of large-N
QCD_4 for planar self-avoiding loops in a certain regularization scheme. We
extract from the effective action the exact beta function in the given scheme.
For the Wilsonean coupling constant the beta function is exacly one loop and
the first coefficient agrees with its value in perturbation theory. For the
canonical coupling constant the exact beta function has a NSVZ form and the
first two coefficients agree with their value in perturbation theory.Comment: 42 pages, latex. The exponent of the Vandermonde determinant in the
quantum effective action has been changed, because it has been employed a
holomorphic rather than a hermitean resolution of identity in the functional
integral. Beta function unchanged. New explanations and references added,
typos correcte

### Strings in flat space and pp waves from ${\cal N}=4$ Super Yang Mills

We explain how the string spectrum in flat space and pp-waves arises from the
large $N$ limit, at fixed $g^2_{YM}$, of U(N) ${\cal N} =4$ super Yang Mills.
We reproduce the spectrum by summing a subset of the planar Feynman diagrams.
We give a heuristic argument for why we can neglect other diagrams. We also
discuss some other aspects of pp-waves and we present a matrix model associated
to the DLCQ description of the maximally supersymmetric eleven dimensional
pp-waves.Comment: 36 pages, 5 figures. v3: minor typos corrected, references adde

### A random cell motility gradient downstream of FGF controls elongation of amniote embryos

Vertebrate embryos are characterized by an elongated antero-posterior (AP) body axis, which forms by progressive cell deposition from a posterior growth zone in the embryo. Here, we used tissue ablation in the chicken embryo to demonstrate that the caudal presomitic mesoderm (PSM) has a key role in axis elongation. Using time-lapse microscopy, we analysed the movements of fluorescently labelled cells in the PSM during embryo elongation, which revealed a clear posterior-to-anterior gradient of cell motility and directionality in the PSM. We tracked the movement of the PSM extracellular matrix in parallel with the labelled cells and subtracted the extracellular matrix movement from the global motion of cells. After subtraction, cell motility remained graded but lacked directionality, indicating that the posterior cell movements associated with axis elongation in the PSM are not intrinsic but reflect tissue deformation. The gradient of cell motion along the PSM parallels the fibroblast growth factor (FGF)/mitogen-activated protein kinase (MAPK) gradient1, which has been implicated in the control of cell motility in this tissue2. Both FGF signalling gain- and loss-of-function experiments lead to disruption of the motility gradient and a slowing down of axis elongation. Furthermore, embryos treated with cell movement inhibitors (blebbistatin or RhoK inhibitor), but not cell cycle inhibitors, show a slower axis elongation rate. We propose that the gradient of random cell motility downstream of FGF signalling in the PSM controls posterior elongation in the amniote embryo. Our data indicate that tissue elongation is an emergent property that arises from the collective regulation of graded, random cell motion rather than by the regulation of directionality of individual cellular movements

### Progress in noncommutative function theory

In this expository paper we describe the study of certain non-self-adjoint
operator algebras, the Hardy algebras, and their representation theory. We view
these algebras as algebras of (operator valued) functions on their spaces of
representations. We will show that these spaces of representations can be
parameterized as unit balls of certain $W^{*}$-correspondences and the
functions can be viewed as Schur class operator functions on these balls. We
will provide evidence to show that the elements in these (non commutative)
Hardy algebras behave very much like bounded analytic functions and the study
of these algebras should be viewed as noncommutative function theory

### Nonhermitean Random Matrix Models : a Free Random Variable Approach

Using the standard concepts of free random variables, we show that for a
large class of nonhermitean random matrix models, the support of the eigenvalue
distribution follows from their hermitean analogs using a conformal
transformation. We also extend the concepts of free random variables to the
class of nonhermitean matrices, and apply them to the models discussed by
Ginibre-Girko (elliptic ensemble) and Mahaux-Weidenm\"uller (chaotic resonance
scattering).Comment: 7 pages LaTeX, 1 EPS figur

### Muscle flaps – an alternative for decortication or resection to solve the residual space in impaired patients

Universitatea de Medicină și Farmacie „Victor Babeș”, Clinica I Chirurgie, Spitalul Clinic Judeţean de Urgenţă „Pius Brinzeu”, Clinica de Chirurgie Toracică, Spitalul Clinic Municipal de Urgenţă, Timișoara, România, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Decorticările sau rezecțiile pulmonare reprezintă tratamentul chirurgical obişnuit în cazul pacienților cu empiem sau
abcese pulmonare cronice. Pentru un număr redus de pacienți cu comorbidități severe asociate sau disfuncții respiratorii aceste
operații nu sunt indicate. Am analizat eficiența lambourilor musculare pentru a corecta cavitățile reziduale.
Material și metode: Am studiat pacienți cu scor de risc ASA >3, cu FEV si FVC<40, clasa NYHA mai mare sau egală cu II. Am inclus
în studiu pacienți cu empiem (1caz), aspergiliom (8 cazuri), abces pulmonar cronic (1 caz) .Am folosit diverse lambouri musculare
pentru a umple cavitățile. Pentru pacienții cu aspergilom am practicat toracotomie, cavernotomie, excizia micetomului, sutura fistulei.
Am folosit lambouri din pectoralul mare (2), muşchii intercostali (4) şi dorsal mare (2). Pentru pacienții cu supurații cronice pulmonare
am folosit dorsal mare, iar pentru empiem am asociat şi muşchi pectoral mare, trapez şi intercostal cu toracoplastie.
Rezultate: Evoluția imediată a fost favorabilă în toate cazurile cu excepția unuia care a necesitat reintervenție pentru sângerare. Un
pacient a dezvoltat serom. În toate cazurile, viabilitatea lamboului nu a fost afectată. Nu s-au inregistrat decese.
Concluzii: Scopul acestor intervenții a fost sa eliminăm spațiile libere din pleură sau plămân. Pentru pacienții tarați, decorticările
şi rezecțiile sunt operații riscante, această nouă abordare fiind benefică. Evoluția favorabilă, morbiditatea minimă după folosirea
lambourilor musculare justifică deplin acest procedeu. Chiar dacă numărul mic de cazuri în care am practicat acest tip de operație ne
limitează pentru moment spectrul de experiență, rezultatele pozitive sunt încurajatoare.Introduction: The surgical treatment of residual space for patients with empyema or chronic lung abscess is in most cases decortication
or lung resection. For a limited number of patients with severe comorbidities or respiratory dysfunction these procedures are prohibited.
We analyzed the efficiency of muscle flaps to solve the residual cavities these patients.
Material and methods: We studied patients with ASA risk > 3, with FEV and FVC < 40%, NYHA II or more. Patients with empyema
(1 case), aspergilloma (8 cases), chronic lung abscess (1 case) were included in the study. Different types of muscle flaps were used
to fill the cavities. For patients with aspergilloma we performed thoracotomy, cavernotomy, excision of the micetoma, fistulae suture;
muscles used: pectoris major – 2, intercostal – 4 and latissimus dorsi – 2. For the patient with chronic suppuration of the lung we used
latissimus, and for the empyema we associated pectoris major, trapezius and intercostal muscle with thoracoplasty.
Results: The immediate outcome was favorable in all cases except one who required exploration for bleeding. One patient developed
wound seroma. In all cases the viability of the transposed muscle was not affected. We recorded no mortality.
Conclusions: The aim of surgery is to eliminate all empty space in the pleura or lung. For impaired patients decortication or resection
are very risky, thus new approach was needed. The good outcome, minimal morbidity after using muscle flaps, fully justify their use.
The low number of patients limits our experience, but the good results are encouraging

### Twisted local systems solve the (holographic) loop equation of large-N QCD_4

We construct a holographic map from the loop equation of large-N QCD in d=2
and d=4, for planar self-avoiding loops, to the critical equation of an
equivalent effective action. The holographic map is based on two ingredients:
an already proposed holographic form of the loop equation, such that the
quantum contribution is reduced to a regularized residue; a new conformal map
from the region encircled by the based loop to a cuspidal fundamental domain in
the upper half-plane, such that the regularized residue vanishes at the cusp.
As a check, we study the first coefficient of the beta function and that part
of the second coefficient which arises from the rescaling anomaly, in passing
from the Wilsonian to the canonically normalised (holographic) effective
action.Comment: 42 pages, latex; abstract shortened and a reference added as
suggested by the referee; typos in Eq.(72,76,77,82,83,84) correcte

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