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Aim The objective of this proof-of-concept study was to investigate the effects of a new guided bone regeneration technique with a tissue engineering approach. Materials and methods This single cohort observational study evaluated the outcome of the leucocyte- and platelet-rich fibrin (L-PRF) Block for horizontal bone augmentation in the maxilla. The L-PRF Block is prepared by mixing a particulated biomaterial with chopped L-PRF membranes at a 50:50 ratio and adding liquid fibrinogen to glue all together. Horizontal augmentation was assessed linearly and volumetrically immediately after surgery and 5-8 months later by matching consecutive cone beam computed tomography (CBCTs). Results Ten patients (mean age of 50.7 years [±17.2]) representing 15 sites with horizontal alveolar deficiencies were included. Superimposition of pre-operative and posthealing CBCT scans showed an average linear horizontal bone gain of 4.6 mm (±2.3), 5.3 mm (±1.2) and 4.4 mm (±2.3), measured at 2, 6 and 10 mm from the alveolar crest, respectively. The volumetric gain was 1.05 cm3 (±0.7) on average. The resorption rate after 5-8 months was 15.6% (±6.7) on average. Conclusions L-PRF Block may be a suitable technique to augment deficient alveolar ridges.

We show how to systematically apply the Faddeev-Jackiw symplectic method to General Relativity (GR) and to GR extensions. This provides a new coherent frame for Hamiltonian analyses of gravitational theories. The emphasis is on the classical dynamics, uncovering the constraints, the gauge transformations and the number of degrees of freedom; but the method results are also relevant for canonical quantization approaches. We illustrate the method with three applications: GR and to two Brans-Dicke cases (the standard case $\omega \not= - 3/2$ and the case with one less degree of freedom, $\omega = - 3/2$). We clarify subtleties of the symplectic approach and comment on previous symplectic-based Hamiltonian analyses of extended theories of gravity, pointing out that the present approach is systematic, complete and robust., Comment: 31 pages. v2: added comments. Version to appear in Phys.Rev.D

This chapter is focused on the use of platelet-rich fibrin to embed bioactive graft ceramics. This chapter describes the preparation of PRF and the clinical evidences of soft and bone healing. At last, the combination of PRF with nanoparticle graft materials is reported as a novel alternative to enhance bone formation.

This article is the result of a study that investigated the historical research in Brazilian museums. Initially, the text parts from a survey of the origin of museums in european and in Brazil and more specifically, the history museums, their development and quantitative. Secondly, the work analyzes the theoretical reference on the issue of historical research and its inclusion in the context of the museums as an essential activity of the museum operational chain. Ultimately, it was performed an analysis of the Centro Nacional da Memória Adventista (CNMA), located at Centro Universitário Adventista de São Paulo (UNASP EC), and its performance in the historical research. The obtained results and the reflections produced by the authors are presented at the end of the text., Este artigo é o resultado de um estudo que investigou a pesquisa histórica nos museus brasileiros. Inicialmente o texto parte de um levantamento da origem dos museus na Europa e no Brasil e mais especificamente os museus de história, seu desenvolvimento e quantitativo. Num segundo momento, o trabalho analisa o referencial teórico sobre a questão da pesquisa histórica e sua inserção no contexto dos museus como atividade essencial da cadeia operatória museológica. Finalmente foi realizada a análise do Centro Nacional da Memória Adventista (CNMA), localizado no Centro Universitário Adventista de São Paulo (UNASP EC), e sua atuação na pesquisa histórica. Os resultados obtidos e as reflexões produzidas pelos autores são apresentados ao final do texto.

Chronic wounds (VLU: venous leg ulcer, DFU: diabetic foot ulcer, PU: pressure ulcer, or complex wounds) affect a significant proportion of the population. Despite appropriate standard wound care, such ulcers unfortunately may remain open for months or even years. The use of leukocyte- and platelet-rich fibrin (L-PRF) to cure skin ulcers is a simple and inexpensive method, widely used in some countries but unknown or neglected in most others. This auto-controlled prospective cohort study explored and quantified accurately for the first time the adjunctive benefits of topical applications of L-PRF in the management of such refractory ulcers in a diverse group of patients. Forty-four consecutive patients with VLUs (n = 28, 32 wounds: 17 ≤ 10 cm(2) and 15 > 10 cm(2)), DPUs (n = 9, 10 wounds), PUs (n = 5), or complex wounds (n = 2), all refractory to standard treatment for ≥3 months, received a weekly application of L-PRF membranes. L-PRF was prepared following the original L-PRF method developed more than 15 years ago (400g, 12 minutes) using the Intra-Spin L-PRF centrifuge/system and the XPression box kit (Intra-Lock, Boca Raton, FL, USA; the only CE/FDA cleared system for the preparation of L-PRF). Changes in wound area were recorded longitudinally via digital planimetry. Adverse events and pain levels were also registered. All wounds showed significant improvements after the L-PRF therapy. All VLUs ≤ 10 cm(2), all DFUs, as well as the two complex wounds showed full closure within a 3-month period. All wounds of patients with VLUs > 10 cm(2) who continued therapy (10 wounds) could be closed, whereas in the five patients who discontinued therapy improvement of wound size was observed. Two out of the five PUs were closed, with improvement in the remaining three patients who again interrupted therapy (surface evolution from 7.35 ± 4.31 cm(2) to 5.78 ± 3.81 cm(2)). No adverse events were observed. A topical application of L-PRF on chronic ulcers, recalcitrant to standard wound care, promotes healing and wound closure in all patients following the treatment. This new therapy is simple, safe and inexpensive, and should be considered a relevant therapeutic option for all refractory skin ulcers. ispartof: Platelets vol:29 issue:5 pages:1-8 ispartof: location:England status: published

It is widely known that bouncing models with a dust hydrodynamical fluid satisfying ${c_s^2=p_d/\rho_d\approx 0}$, where $c_s, p_d, \rho_d$ are the sound velocity, pressure and energy density of the dust fluid, respectively, have almost scale invariant spectrum of scalar perturbations and negligible primordial gravitational waves. We investigate whether adding another fluid with $1/3 < \lambda = p/\rho < 1$, which should dominate near the bounce, can increase the amplitude of gravitational waves in the high frequency regime, turning them detectable in near future observations for such range of frequencies. Indeed, we show that the energy density of primordial gravitational waves is proportional to $k^{2(9\lambda-1)/(1+3\lambda)}$ for wavelengths which become bigger than the Hubble radius when this extra fluid dominates the background. Hence, as $\lambda \to 1$ (an almost stiff matter fluid), the energy density of primordial gravitational waves will increase faster in frequency, turning them potentially detectable at high frequencies. However, there is an extra factor $I_q(\lambda)$ in the amplitude which decreases exponentially with $\lambda$. The net effect of these two contributions turns the energy density of primordial gravitational waves not sufficiently big at high frequencies in order to be detected by present day or near future observations for models which satisfy the nucleosynthesis bounds and is symmetric with respect to the bounce. Hence, symmetric bouncing models where the background is dominated by a dust hydrodynamical fluid with small sound velocity, do not present any significant amount of primordial gravitational waves at any frequency range compatible with observations, even if there are other fields present in the model dominating the bounce phase. Any detection of such waves will then rule out this kind of models.

Analyzing quantum cosmological scenarios containing one scalar field with exponential potential, we have obtained a universe model which realizes a classical dust contraction from very large scales, the initial repeller of the model, and moves to a stiff matter contraction near the singularity, which is avoided due to a quantum bounce. The universe is then launched in a stiff matter expanding phase, which then moves to a dark energy era, finally returning to the dust expanding phase, the final attractor of the model. Hence one has obtained a nonsingular cosmological model where a single scalar field can describe both the matter contracting phase of a bouncing model, necessary to give an almost scale invariant spectrum of scalar cosmological perturbations, and a transient expanding dark energy phase. As the universe is necessarily dust dominated in the far past, usual adiabatic vacuum initial conditions can be easily imposed in this era, avoiding the usual issues appearing when dark energy is considered in bouncing models., 15 pages, 17 figures. Title changed, introduction, conclusion and bibliography expanded to answer the questions of a referee. To be published in Physical Review D

More insight into the biological fundamentals of leukocyte platelet-rich fibrin (L-PRF) guided healing is necessary to recommend its application, in particular in deficient bone sites that need to support implants. This study investigated the short-term bone healing effect of L-PRF treatment in cylindrical non-critical sized bone defects with 3 mm diameter and 6 mm depth in tibiae of 18 adult male New Zealand White rabbits. After a randomization process, 96 bone defects were prepared and half of them were filled with a L-PRF membrane, while untreated defects in the opposite tibia served as control group. The rabbits were euthanized after 7, 14 or 28 days of healing. The bone healing of the cortical and medullary areas was investigated by micro-CT, while the expression of molecular markers (RUNX2, VEGFA, COL1A2 and BMP2) was assessed by qRT-PCR. Treatment with L-PRF did not affect the micro-structural bone characteristics of the repaired bone tissue, except for a decrease in the trabecular connectivity at the cortical level after 14 days of healing. At this time, RUNX2 and VEGFA mRNA levels were significantly lower in the treated defects. L-PRF membranes thus had a temporary negative influence on the bone microarchitecture (Tb.Pf) and on the RUNX2 and VEGFA expression during early bone healing. Overall, L-PRF treatment did not enhance bone regeneration in these non-critical size defects after 28 days. ispartof: Scientific Reports vol:7 ispartof: location:England status: published

Regenerative endodontic procedures (REPs) associated with apical surgery could represent an alternative treatment strategy for patients whose teeth present incomplete root formation and extensive apical lesions. Leukocyte platelet-rich fibrin (L-PRF) has potential benefits in REPs; it could promote apical root formation and optimal bone healing. The aim of this case report was to describe innovative regenerative endodontic therapy using L-PRF in the root canal and an extensive apical lesion in an immature tooth with dens invaginatus and asymptomatic apical periodontitis. A healthy 20-year-old woman was referred to the dental clinic of the Universidad de Los Andes, Santiago, Chile, for endodontic treatment in tooth # 22 with incomplete root development and an extensive apical lesion. The diagnosis was asymptomatic apical periodontitis associated with dens invaginatus type II. The patient was treated with an innovative approach using L-PRF in REPs associated with apical surgery. Follow-ups were performed at 6 months and 1 year later. They included periapical radiographs, cone-beam computed tomographic imaging, sensitivity, and vitality tests. The clinical evaluations performed at 6 months and 1 year revealed an absence of symptoms. The radiographic evaluations showed that the apical lesion was resolved. The cone-beam images indicated that the root length increased and the walls had thickened. The sensitivity tests were positive, and the laser Doppler flowmetry showed positive blood flow after 1 year. The success of the results in this case report indicate that L-PRF can be used as a complement in apical surgery and REPs and could provide an innovative alternative treatment strategy for complex clinical cases like these.

We investigate cosmological scenarios containing one canonical scalar field with an exponential potential in the context of bouncing models, where the bounce happens due to quantum cosmological effects. The only possible bouncing solutions in this scenario (discarding an infinitely fine tuned exception) must have one and only one dark energy phase, either occurring in the contracting era or in the expanding era. Hence,these bounce solutions are necessarily asymmetric. We calculate the spectral indexes and amplitudes of scalar and tensor perturbations numerically, considering the whole history of the model, including the bounce phase itself, without making any approximation or using any matching condition on the perturbations. As the background model is necessarily dust dominated in the far past, the usual adiabatic vacuum initial conditions can be easily imposed in this era. Hence, this is a cosmological model where the presence of dark energy behavior in the Universe does not turn problematic the usual vacuum initial conditions prescription for cosmological perturbation in bouncing models. Scalar and tensor perturbations end up being almost scale invariant, as expected. The background parameters can be adjusted, without fine tunings, to yield the observed amplitude for scalar perturbations, and also for the ratio between tensor and scalar amplitudes, $r = T/S \lesssim 0.1$. The amplification of scalar perturbations over tensor perturbations takes place only around the bounce, due to quantum effects, and it would not occur if General Relativity has remained valid throughout this phase. Hence, this is a bouncing model where a single field induces not only an expanding background dark energy phase, but also produces all observed features of cosmological perturbations of quantum mechanical origin at linear order., Comment: 23 pages, 15 figures

Background. Reconstruction of surgical defects following cranial base surgery is challenging. Others have demonstrated that leukocyte-platelet-rich fibrin (L-PRF) stimulates tissue healing and bone regeneration. However, these studies have addressed mostly maxillofacial surgical wounds. Objective. The objective of this study was to assess the possible adjuvant role of L-PRF in inducing neoossification of the surgical bone defect in anterior skull base surgery. Methods. We identified patients who had undergone an endoscopic endonasal surgery of the anterior skull base in which L-PRF membranes were used for the reconstruction of the bone defect and who were followed up with postoperative CT scans. CT findings were then correlated with baseline scans and with the CT scans of a patient who had undergone imaging and histologic analysis after maxillofacial surgery in which L-PRF was used and in which we demonstrated bone formation. Results. Five patients fulfilled the inclusion criteria. In four patients, the CT scan demonstrated closure of the bony defect by neoosteogenesis; however, the bone appeared less dense than the surrounding normal bone. A comparison with the control patient yielded similar radiological features. Conclusion. This case series suggests that L-PRF may induce bone healing and regeneration at the surgical site defect. Multi-institutional studies with a larger series of patients are required to confirm this possibility.

Aim To investigate the influence of the use L-PRF as a socket filling material and its ridge preservation properties. Materials and Methods Twenty-two patients in need of single bilateral and closely symmetrical tooth extractions in the maxilla or mandible were included in a split-mouth RCT. Treatments were randomly assigned (L-PRF socket filling versus natural healing). CBCT scans were obtained after tooth extraction and three months. Scans were evaluated by superimposition using the original DICOM data. Mean ridge width differences between timepoints were measured at three levels below the crest on both the buccal and lingual sides (crest −1 mm (primary outcome variable), −3 mm and −5 mm). Results Mean vertical height changes at the buccal were −1.5 mm (±1.3) for control sites and 0.5 mm (±2.3) for test sites (p

In this contribution I will present a review about bouncing models arriving from quantum cosmology and show how one can describe the evolution of quantum cosmological perturbations on them. I will discuss the important role played by the choice of the precise quantum theory one selects to interpret the wave function of the Universe in order to obtain simple equations for the evolution of quantum perturbations on these quantum cosmological backgrounds. I will present the predictions of these models concerning the power spectrum of cosmological perturbations and how they can be compared with the usual results obtained from inflationary models. Finally, I will present the new implications of these results for quantum theory.

Bouncing models have been proposed by many authors as a completion, or even as an alternative to inflation for the description of the very early and dense Universe. However, most bouncing models contain a contracting phase from a very large and rarefied state, where dark energy might have had an important role as it has today in accelerating our large Universe. In that case, its presence can modify the initial conditions and evolution of cosmological perturbations, changing the known results already obtained in the literature concerning their amplitude and spectrum. In this paper, we assume the simplest and most appealing candidate for dark energy, the cosmological constant, and evaluate its influence on the evolution of cosmological perturbations during the contracting phase of a bouncing model, which also contains a scalar field with a potential allowing background solutions with pressure and energy density satisfying p = w*rho, w being a constant. An initial adiabatic vacuum state can be set at the end of domination by the cosmological constant, and an almost scale invariant spectrum of perturbations is obtained for w~0, which is the usual result for bouncing models. However, the presence of the cosmological constant induces oscillations and a running towards a tiny red-tilted spectrum for long wavelength perturbations., Comment: 11 pages, 11 figures

We show that a contracting universe which bounces due to quantum cosmological effects and connects to the hot big-bang expansion phase, can produce an almost scale invariant spectrum of perturbations provided the perturbations are produced during an almost matter dominated era in the contraction phase. This is achieved using Bohmian solutions of the canonical Wheeler-de Witt equation, thus treating both the background and the perturbations in a fully quantum manner. We find an almost scale invariant spectrum. Taking into account the spectral index constraint as well as the CMB normalization measure yields an equation of state that should be less than ω . 8×10 −4 , implying nS −1 ∼O ` 10 −4 ´ ,a nd that the characteristic size of the Universe at the bounce is L0 ∼ 10 3 LPlanck, a region where one expects that the Wheeler-DeWitt equation should be valid without being spoiled by string or loop quantum gravity effects. We have also obtained a consistency relation between the tensor to scalar ratio T/ S and the scalar spectral index as T/ S ∼ 4 × 10 −2 √ n S − 1, leading to potentially measurable differences with inflationary predictions.

Objectives This clinical trial explored the clinical and radiographic dimensional changes of the alveolar ridge in the first 4 months after tooth extraction in combination with the application of Leukocyte- and Platelet Rich Fibrin (L-PRF). Methods Eighteen single rooted maxillary and mandibular sockets were filled with L-PRF without soft tissue closure. Clinical measurements (bone sounding) were performed using a customized acrylic stent and radiographic measurements were accomplished using Cone Beam Computed Tomography (CBCT), immediately after tooth extraction and after 4 months. Results The clinical observations indicated a mean horizontal resorption of 1.18 ± 2.4 mm (p = 0.8) at the crest, 1.25 ± 2.0 mm (p = 0.57) and 0.83 ± 2.0 mm (p = 0.78) at 2 mm and 4 mm apical to the crest, respectively. The buccal plate demonstrated a mean vertical loss of 0.44 ± 3.5 mm (p = 0.9), the centre of the socket had a significant filling of 5.72 ± 3.6 mm (p = 0.0001) and the oral cortical plate had a mean vertical gain of 0.09 mm ± 1.57 mm (p = 0.9). The radiographic analysis demonstrated a mean vertical bone loss of 0.27 ± 2.5 mm (p = 0.9) on the buccal and of 0.03 ± 1.6 mm (p = 0.9) at the oral crest. The width of the alveolar ridge had a mean loss of 1.33 mm ± 1.43 mm. Conclusions Within the limitations of this pilot study, it can be concluded that L-PRF might show clinical benefits for ridge preservation.

Objective Advancements in endoscopic endonasal approaches have increased the extent and complexity of skull base resections, in turn demanding the development of novel techniques for skull base defect reconstruction. The objective of this pilot study was to investigate the effect of leukocyte–platelet-rich fibrin (L-PRF) on the postoperative healing after endoscopic skull base surgery. Methods Between January and May of 2015, 47 patients underwent endoscopic endonasal resection of sellar, parasellar, and suprasellar lesions with the application of L-PRF membranes during the skull base reconstruction at two surgical centers. Early postoperative records were retrospectively reviewed. Results We found that 21 days following the surgery, 17/41 patients (42%) demonstrated improvement in the crusting score as compared with their 7 day postoperative examination. Ten of these patients (23%) showed no crusting. Fourteen (34%) patients had no change in the crusting score. Six patient records were incomplete. A total of 4/47 cases (8.5%) had postoperative cerebrospinal fluid leak requiring surgical repair. Conclusion This study demonstrates the potential utility of L-PRF membranes for skull base defect reconstruction. Future studies will be conducted to better assess the role of L-PRF in endoscopic skull base surgery.

There is a widespread belief that the classical small inhomogeneities which gave rise to all structures in the Universe through gravitational instability originated from primordial quantum cosmological fluctuations. However, this transition from quantum to classical fluctuations is plagued with important conceptual issues, most of them related to the application of standard quantum theory to the Universe as a whole. In this contribution, it is shown how these issues can easily be overcome in the framework of the de Broglie-Bohm quantum theory. This theory is an alternative to standard quantum theory that provides an objective description of physical reality, where rather ambiguous notions of measurement or observer play no fundamental role, and which can hence be applied to the Universe as a whole. In addition, it allows for a simple and unambiguous characterization of the classical limit. This contribution is a compilation of the works done by Grasiele Santos, Ward Struyve and myself cited in Pinto-Neto et al. (Phys Rev D 85:083506, 2012; Phys Rev D 89:023517, 2014), where all details can be found.

Aims. This study evaluated the effects of L-PRF presence and implant surface texture on bone healing around immediately placed implants.Methods. The first mandibular molars of 8 beagle dogs were bilaterally extracted, and implants (Blossom™, Intra-Lock International, Boca Raton, FL) were placed in the mesial or distal extraction sockets in an interpolated fashion per animal. Two implant surfaces were distributed per sockets: (1) dual acid-etched (DAE, micrometer scale textured) and (2) micrometer/nanometer scale textured (Ossean™ surface). L-PRF (Intraspin system, Intra-Lock International) was placed in a split-mouth design to fill the macrogap between implant and socket walls on one side of the mandible. The contralateral side received implants without L-PRF. A mixed-model ANOVA (atα=0.05) evaluated the effect of implant surface, presence of L-PRF, and socket position (mesial or distal), individually or in combination on bone area fraction occupancy (BAFO).Results. BAFO values were significantly higher for the Ossean relative to the DAE surface on the larger mesial socket. The presence of L-PRF resulted in higher BAFO. The Ossean surface and L-PRF presence resulted in significantly higher BAFO.Conclusion.L-PRF and the micro-/nanometer scale textured surface resulted in increased bone formation around immediately placed implants.

We investigate scalar particle creation in a set of bouncing models where the bounce occurs due to quantum cosmological effects described by the Wheeler-DeWitt equation. The scalar field can be either conformally or minimally coupled to gravity, and it can be massive or massless, without self interaction. The analysis is made for models containing a single radiation fluid, and for the more realistic case of models containing the usual observed radiation and dust fluids, which can fit most of the observed features of our Universe, including an almost scale invariant power spectrum of scalar cosmological perturbations. In the conformal coupling case, the particle production is negligible. In the minimal coupling case, for massive particles, the results point to the same physical conclusion within observational constraints: particle production is most important at the bounce energy scale, and it is not sensitive neither to its mass nor whether there is dust in the background model. The only caveat is the case where the particle mass is larger than the bounce energy scale. On the other hand, the energy density of produced massive particles depend on their masses and the energy scale of the bounce. For very large masses and deep bounces, this energy density may overcome that of the background. In the case of massless particles, the energy density of produced particles can become comparable to the background energy density only for bounces occurring at energy scales comparable to the Planck scale or above, which lies beyond the scope of this paper: we expect that the simple Wheeler-DeWitt approach we are using should be valid only at scales some few orders of magnitude below the Planck energy. Nevertheless, in the case in which dust is present, there is an infrared divergence, which becomes important only for scales much larger than today's Hubble radius., Comment: 18 pages, 8 figures

De zoektocht naar additieven die tijdens een heelkundige ingreep kunnen worden gebruikt, de noodzaak van biomaterialen beperken en tegelijkertijd de genezing bevorderen is nog steeds gaande. Momenteel kunnen we stellen dat de onderzoeken naar de tweede generatie plaatjesconcentraten (PRF) veelbelovende resultaten aangeven voor de chirurgische parodontale therapie en implantologie. Dit in tegenstelling tot de eerste generatie plaatjesconcentraten. Deze bestonden uit een zeer moeilijk bereidingsprotocol, met chemische toevoegingen. Hierdoor was hun gebruik in de algemene praktijk duur en omslachtig. De tweede generatie heeft geen van deze nadelen. In dit hoofdstuk wordt ingegaan op de geschiedenis van plaatjesconcentraten. Hun bereidingsprotocol wordt in detail beschreven en de verschillende chirurgische opties worden getoetst aan de recente literatuur.

In this paper we study in details a system of two weakly coupled harmonic oscillators. This system may be viewed as a simple model for the interaction between a photon and a photodetector. We obtain exact solutions for the general case. We then compute approximate solutions for the case of a single photon (where one oscillator is initially in its first excited state) reaching a photodetector in its ground state (the other oscillator). The approximate solutions represent the state of both the photon and the photodetector after the interaction, which is not an eigenstate of the individual hamiltonians for each particle, and therefore the energies for each particle do not exist in the Copenhagen interpretation of Quantum Mechanics. We use the approximate solutions that we obtained to compute bohmian trajectories and to study the energy transfer between the two particles. We conclude that even using the bohmian view the energy of each individual particle is not well defined, as the nonlocal quantum potential is not negligible even after the coupling is turned off., Comment: 18 pages, 5 figures

The causal interpretation of quantum mechanics is applied to a homogeneous and isotropic quantum universe, whose matter content is composed by non interacting dust and radiation. For wave functions which are eigenstates of the total dust mass operator, we find some bouncing quantum universes which reachs the classical limit for scale factors much larger than its minimum size. However these wave functions do not have unitary evolution. For wave functions which are not eigenstates of the dust total mass operator but do have unitary evolution, we show that, for flat spatial sections, matter can be created as a quantum effect in such a way that the universe can undergo a transition from an exotic matter dominated era to a matter dominated one., Comment: 27 pages, 6 figures

I make a review on the aplications of the Bohm-De Broglie interpretation of quantum mechanics to quantum cosmology. In the framework of minisuperspaces models, I show how quantum cosmological effects in Bohm's view can avoid the initial singularity, isotropize the Universe, and even be a cause for the present observed acceleration of the Universe. In the general case, we enumerate the possible structures of quantum space and time., Comment: 28 pages, 1 figure, contribution to the James Cushing festschrift to appear in Foundations of Physics

I describe the features and general properties of bouncing models and the evolution of cosmological perturbations on such backgrounds. I will outline possible observational consequences of the existence of a bounce in the primordial Universe and I will make a comparison of these models with standard long inflationary scenarios., 9 pages, no figures

We study the quantized Friedmann-Lema\^��tre-Robertson-Walker (FLRW) model minimally coupled to a free massless scalar field. In a previous paper, \cite{fab2}, solutions of this model were constructed as gaussian superpositions of negative and positive modes solutions of the Wheeler-DeWitt equation, and quantum bohmian trajectories were obtained in the framework of the Bohm-de Broglie (BdB) interpretation of quantum cosmology. In the present work, we analyze the quantum bohmian trajectories of a different class of gaussian packets. We are able to show that this new class generates bohmian trajectories which begin classical (with decelerated expansion), undergo an accelerated expansion in the middle of its evolution due to the presence of quantum cosmological effects in this period, and return to its classical decelerated expansion in the far future. We also show that the relation between luminosity distance and redshift in the quantum cosmological model can be made close to the corresponding relation coming from the classical model suplemented by a cosmological constant, for $z

It is commonly accepted that the large scale structure in the universe was originated from primordial quantum cosmological perturbations that developed into classical inhomogeneities, and then suffered gravitational instability. However, this transition from the quantum to the classical regime is not yet fully understood, due to the difficulties presented by the standard quantum theory when applied to closed systems. We show that this issue is clarified in the framework of the de Broglie-Bohm quantum theory, where the classical limit is easily characterized.

We consider a Bohmian approach to the Wheeler-DeWitt quantization of the Friedmann-Lemaitre-Robertson-Walker model and investigate the question whether or not there are singularities, in the sense that the universe reaches zero volume. We find that for generic wave functions (i.e., non-classical wave functions), there is a non-zero probability for a trajectory to be non-singular. This should be contrasted to the consistent histories approach for which it was recently shown by Craig and Singh that there is always a singularity. This result illustrates that the question of singularities depends much on which version of quantum theory one adopts. This was already pointed out by Pinto-Neto et al., albeit with a different Bohmian approach. Our current Bohmian approach agrees with the consistent histories approach by Craig and Singh for single-time histories, unlike the one studied earlier by Pinto-Neto et al. Although the trajectories are usually different in the two Bohmian approach, their qualitative behavior is the same for generic wave functions., Comment: 10 pages, 3 figures, PDFLaTeX, revtex4

The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described. We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations. The final Hamiltonian is obtained without assuming any equations of motions for the background variables. This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history. Quantization is achieved using an adiabatic expansion of the basis functions. This allows for an unambiguous definition of a vacuum state up to the given adiabatic order. Using this basis, we show that particle creation is well defined for a suitable choice of vacuum and canonical variables, so that the time evolution of the corresponding quantum fields is unitary. This provides constraints for setting initial conditions for an arbitrary number of fluids and background time evolution. We also show that the common choice of variables for quantization can lead to an ill-defined vacuum definition. Our formalism is not restricted to the case where the coupling between fields is small, but is only required to vary adiabatically with respect to the ultraviolet modes, thus paving the way to consistent descriptions of general models not restricted to single-field (or fluid)., Comment: 20 pages, matches PRD published version

We apply the causal interpretation of quantum mechanics to homogeneous and isotropic quantum cosmology, where the source of the gravitational field is a conformally coupled scalar field, and the maximally symmetric hypersurfaces have positive curvature. In order to simplify the system of coupled equations studied and study the quantum behavior near the singularity, we restricted ourselves to the cases where the scale factor is small. In this case, the general solution of the Wheeler–DeWitt equation is a discrete superposition of Hermitian polynomials multiplied by complex exponentials. Superpositions with up to two parcels are studied, and the phase diagrams of their corresponding Bohmian trajectories are analyzed in detail. Nonsingular periodic quantum solutions are found. We also find that singular quantum solutions present an inflationary era in the begining of the Universe. Numerical calculations indicates that these results remain valid for general superpositions.

We apply the causal interpretation of quantum mechanics to homogeneous and isotropic quantum cosmology where the sources of the gravitational field are either dust or radiation perfect fluids. We find non-singular quantum trajectories which tends to the classical one when the scale factor becomes much larger then the Planck length. In this situation, the quantum potential becomes negligible. There are no horizons. As radiation is a good approximation for the matter content of the early universe, this result suggests that the universe can be eternal due to quantum effects., 10 pages, LaTeX, 5 figures in postscript, requires epsf

Minisuperspace models derived from Kaluza-Klein theories and low-energy string theory are studied. They are equivalent to one and two minimally coupled scalar fields. The general classical and quantum solutions are obtained. A Gaussian superposition of WKB solutions is constructed. Contrary to what is usually expected, these states are sharply peaked around the classical trajectories only for small values of the scale factor. This behavior is confirmed in the framework of the causal interpretation: the Bohmian trajectories of many quantum states are classical for small values of the scale factor but present quantum behavior when the scale factor becomes large. A consequence of this fact is that these states present an initial singularity. However, there are some particular superpositions of these wave functions which have Bohmian trajectories without singularities. There are also singular Bohmian trajectories with a short period of inflation which grow forever. We could not find any nonsingular trajectory which grows to the size of our universe.

A recent paper by Kumar (2012) (hereafter K12) claimed that in a contracting model, described by perturbations around a collapsing Friedmann model containing dust or radiation, the perturbations can grow in such a way that the linearity conditions would become invalid. This conclusion is not correct due to the following facts: first, it is claimed that the linearity conditions are not satisfied, but nowhere in K12 the amplitudes of the perturbations were in fact estimated. Therefore, without such estimates, the only possible conclusion from this work is the well-known fact that the perturbations indeed grow during contraction, which, per se, does not imply that the linearity conditions become invalid. Second, some evaluations of the linearity conditions are incorrect because third-order terms, instead of the appropriate second-order ones, are mistakenly compared with first-order terms, yielding artificially fast growing conditions. Finally, it is claimed that the results of K12 are in sharp contrast with the results of the paper by Vitenti and Pinto-Neto (2012) (hereafter VPN12), because the former was obtained in a gauge-invariant way. However, the author of K12 did not realize that the evolution of the perturbations were also calculated in a gauge-invariant way in VPN12, but some of the linearity conditions which are necessary to check cannot be expressed in terms of gauge-invariant quantities. In the present work, the incorrect or incomplete statements of K12 are clarified and completed, and it is shown that all other correct results of K12 were already present in VPN12, whose conclusions remain untouched, namely, that cosmological perturbations of quantum mechanical origin in a bouncing model can remain in the linear regime all along the contracting phase and at the bounce itself for a wide interval of energy scales of the bounce, ranging from the nucleosynthesis energy scale up to a few orders of magnitude below the Planck energy.

Platelet concentrates for topical and infiltrative use - commonly termed Platetet-Rich Plasma (PRP) or Platelet-Rich Fibrin (PRF) - are used or tested as surgical adjuvants or regenerative medicine preparations in most medical fields, particularly in sports medicine and orthopaedic surgery. Even if these products offer interesting therapeutic perspectives, their clinical relevance is largely debated, as the literature on the topic is often confused and contradictory. The long history of these products was always associated with confusions, mostly related to the lack of consensual terminology, characterization and classification of the many products that were tested in the last 40 years. The current consensus is based on a simple classification system dividing the many products in 4 main families, based on their fibrin architecture and cell content: Pure Platelet-Rich Plasma (P-PRP), such as the PRGF-Endoret technique; Leukocyte- and Platelet-Rich Plasma (LPRP), such as Biomet GPS system; Pure Platelet-Rich Fibrin (P-PRF), such as Fibrinet; Leukocyte- and Platelet-Rich Fibrin (L-PRF), such as Intra-Spin L-PRF. The 4 main families of products present different biological signatures and mechanisms, and obvious differences for clinical applications. This classification serves as a basis for further investigations of the effects of these products. Perspectives of evolutions of this classification and terminology are also discussed, particularly concerning the impact of the cell content, preservation and activation on these products in sports medicine and orthopaedics.

We develop the canonical quantization of a midisuperspace model which contains, as a subspace, a minisuperspace constituted of a Friedman-Lema\^{\i}tre-Robertson-Walker Universe filled with homogeneous scalar and dust fields, where the sign of the intrinsic curvature of the spacelike hypersurfaces of homogeneity is not specified, allowing the study of topology change in these hypersurfaces. We solve the Wheeler-DeWitt equation of the midisuperspace model restricted to this minisuperspace subspace in the semi-classical approximation. Adopting the conditional probability interpretation, we find that some of the solutions present change of topology of the homogeneous hypersurfaces. However, this result depends crucially on the interpretation we adopt: using the usual probabilistic interpretation, we find selection rules which forbid some of these topology changes., Comment: 23 pages, LaTex file. We added in the conclusion some comments about path integral formalism and corrected litle misprintings

Recently it has been claimed that the Wheeler-DeWitt quantization of gravity is unable to avoid cosmological singularities. However, in order to make this assertion, one must specify the underlying interpretation of quantum mechanics which has been adopted. For instance, several nonsingular models were obtained in Wheeler-DeWitt quantum cosmology in the framework of the de Broglie-Bohm quantum theory. Conversely, there are specific situations where the singularity cannot be avoided in the framework of the Consistent Histories approach to quantum mechanics. In these specific situations, the matter content is described by a scalar field, and the Wheeler-DeWitt equation looks-like a Klein-Gordon equation. The aim of this work is to study the Wheeler-DeWitt quantization of cosmological models where the matter content is described by an hydrodynamical perfect fluid, where the Wheeler-DeWitt equation reduces to a genuine Schr\"odinger equation. In this case, it is shown that the conclusions of the Consistent Histories and the de Broglie-Bohm approaches coincide in the quantum cosmological models where the curvature of the spatial sections is not positive definite, namely, that the cosmological singularities are eliminated. In the case of positive spatial curvature, the family of histories is no longer consistent, and no conclusion can be given in this framework., Comment: 11 pages, 4 figures

In a previous work we have exhibited a clear description of the quantum-to-classical transition of cosmological quantum fluctuations in the inflationary scenario using the de Broglie-Bohm quantum theory. These fluctuations are believed to seed the small inhomogeneities, which are then responsible for the formation of large scale structures. In this work we show that using the de Broglie-Bohm theory it is also possible to describe the quantum-to-classical transition of primordial perturbations which takes place around a bouncing phase, even if the latter is caused by quantum effects due to the quantization of the background geometry., Comment: 5 pages, no figures, revtex4

We examine the nonlinear dynamics of a closed Friedmann-Robertson-Walker universe in the framework of Brane World formalism with a timelike extra dimension. In this scenario, the Friedmann equations contain additional terms arising from the bulk-brane interaction which provide a concrete model for nonsingular bounces in the early phase of the Universe. We construct a nonsingular cosmological scenario sourced with dust, radiation and a cosmological constant. The structure of the phase space shows a nonsingular orbit with two accelerated phases, separated by a smooth transition corresponding to a decelerated expansion. Given observational parameters we connect such phases to a primordial accelerated phase, a soft transition to Friedmann (where the classical regime is valid), and a graceful exit to a de Sitter accelerated phase.

The prescription proposed by Komar in order to calculate the total gravitational mass acting on a test particle in a given stationary asymptotically flat spacetime is generalized to stationary asymptotically anti\char21{}de Sitter spacetimes. It is shown that this generalized Komar mass is different from the total gravitational energy calculated by Henneaux and Teitelboim for the Kerr\char21{}anti-de Sitter spacetime. This last total energy agrees, however, with the total charge-energy calculated using the Brown-York action formalism.

A quantum cosmological model with radiation and a dilaton scalar field is analysed. The Wheeler-deWitt equation in the mini-superspace induces a Schr\"odinger equation, which can be solved. An explicit wavepacket is constructed for a particular choice of the ordering factor. A consistent solution is possible only when the scalar field is a phantom field. Moreover, although the wavepacket is time dependent, a Bohmian analysis allows to extract a bouncing behaviour for the scale factor., Comment: 14 pages, 3 figures in eps format. Minors corrections, new figures

We study the Wheeler-DeWitt quantum cosmology of a spatially flat Friedmann cosmological model with a massless free scalar field. We compare the consistent histories approach with the de Broglie-Bohm theory when applied to this simple model under two different quantization schemes: the Schr\"odinger-like quantization, which essentially takes the square-root of the resulting Klein-Gordon equation through the restriction to positive frequencies and their associated Newton-Wigner states, or the induced Klein-Gordon quantization, that allows both positive and negative frequencies together. We show that the consistent histories approach can give a precise answer to the question concerning the existence of a quantum bounce if and only if one takes the single frequency approach and within a single family of histories, namely, a family containing histories concerning properties of the quantum system at only two specific moments of time: the infinity past and the infinity future. In that case, as shown by Craig and Singh \cite{CS}, there is no quantum bounce. In any other situation, the question concerning the existence of a quantum bounce has no meaning in the consistent histories approach. On the contrary, we show that if one considers the de Broglie-Bohm theory, there are always states where quantum bounces occur in both quantization schemes. Hence the assertion that the Wheeler-DeWitt quantization does not solve the singularity problem in cosmology is not precise. To address this question, one must specify not only the quantum interpretation adopted but also the quantization scheme chosen., Comment: 13 pages, 1 figure

Bronchiectasis is defined as chronic abnormal dilatation and distortion of the bronchi. Surgery continues to be play an important role in the treatment of this disease especially in focal disease which is both curative. The objective of this study is to characterize the patients who underwent surgical resection of bronchiectasis in 10 years and compare them with patients operated by the same pathology in the previous 10 years. We conducted a review of cases of 78 patients operated in the 2000 ' s and the results were compared with those obtained in the study by the same professional service, referring to the previous decade. We assessed sex, age, symptoms, number of years with symptoms, complementary exams performed prior to surgery, indications for surgery, previous pulmonary diseases, location of bronchiectasis, type of surgical approach, number of hospitalization days and complications of surgery. In the last decade a smaller number of patients with bronchiectasis ( 78 versus 119 ) were submitted to thoracic surgery. In both groups the right lung and the lower lobes were the most affected and the majority of patients was submitted to lobectomy. In the last decade a lower percentage of complications was registed ( 6.4 %, versus 15.0 % (. The surgery was considered to be curative in 94.9 % and only 91 % in the 90 ' s. This study would support the idea that the surgery of bronchiectasis continues to be an excellent alternative to the treatment of localized forms of the disease and its complications.

In this paper it is shown how to obtain the simplest equations for the Mukhanov-Sasaki variables describing quantum linear scalar perturbations in the case of scalar fields without potential term. This was done through the implementation of canonical transformations at the classical level, and unitary transformations at the quantum level, without ever using any classical background equation, and it completes the simplification initiated in investigations by Langlois \cite{langlois}, and Pinho and Pinto-Neto \cite{emanuel2} for this case. These equations were then used to calculate the spectrum index $n_s$ of quantum scalar perturbations of a non-singular inflationary quantum background model, which starts at infinity past from flat space-time with Planckian size spacelike hypersurfaces, and inflates due to a quantum cosmological effect, until it makes an analytical graceful exit from this inflationary epoch to a decelerated classical stiff matter expansion phase. The result is $n_s=3$, incompatible with observations., 10 pages, 2 figures, accepted version to Physical Review D 79

In previous works, it was shown that the Lagrangians and Hamiltonians of cosmological linear scalar, vector and tensor perturbations of homogeneous and isotropic space-times with flat spatial sections containing a perfect fluid can be put in a simple form through the implementation of canonical transformations and redefinitions of the lapse function, without ever using the background classical equations of motion. In this paper, we generalize this result to general fluids, which includes entropy perturbations, and to arbitrary spacelike hyper-surfaces through a new method together with the Faddeev-Jackiw procedure for the constraint reduction. A simple second order Hamiltonian involving the Mukhanov-Sasaki variable is obtained, again without ever using the background equations of motion., Comment: 19 pages, revtex4-1, submitted to PRD, expanded discussion about our method, fixed typos

There is a widespread belief that the classical small inhomogeneities which gave rise to all structures in the Universe through gravitational instability originated from primordial quantum cosmological fluctuations. However, this transition from quantum to classical fluctuations is plagued with important conceptual issues, most of them related to the application of standard quantum theory to the Universe as a whole. In this paper, we show how these issues can easily be overcome in the framework of the de Broglie-Bohm quantum theory. This theory is an alternative to standard quantum theory that provides an objective description of physical reality, where rather ambiguous notions of measurement or observer play no fundamental role, and which can hence be applied to the Universe as a whole. In addition, it allows for a simple and unambiguous characterization of the classical limit., 5 pages, no figures, REVTeX

It has been shown that a contracting universe with a dust-like ($w \approx 0$) fluid may provide an almost scale invariant spectrum for the gravitational scalar perturbations. As the universe contracts, the amplitude of such perturbations are amplified. The gauge invariant variable $\Phi$ develops a growing mode which becomes much larger than the constant one around the bounce phase. The constant mode has its amplitude fixed by Cosmic Background Explorer (COBE) normalization, thus the amplitude of the growing mode can become much larger than 1. In this paper, we first show that this is a general feature of bouncing models, since we expect that general relativity should be valid in all scales away from the bounce. However, in the Newtonian gauge, the variable $\Phi$ gives the value of the metric perturbation $\phi$, raising doubts on the validity of the linear perturbative regime at the bounce. In order to address this issue, we obtain a set of necessary conditions for the perturbative series to be valid along the whole history of the model, and we show that there is a gauge in which all these conditions are satisfied, for a set of models, if the constant mode is fixed by COBE normalization. As a by-product of this analysis, we point out that there are sets of solutions for the perturbation variables where some gauge-fixing conditions are not well defined, turning these gauges prohibited for those solutions., Comment: 10 pages, revtex4, minor revision, version to appear in PRD

It is shown in this paper that minisuperspace quantization of homogeneous and isotropic geometries with phantom scalar fields, when examined in the light of the Bohm-de Broglie interpretation of quantum mechanics, does not eliminate, in general, the classical big rip singularity present in the classical model. For some values of the Hamilton-Jacobi separation constant present in a class of quantum state solutions of the Wheeler-DeWitt equation, the big rip can be either completely eliminated or may still constitute a future attractor for all expanding solutions. This is contrary to the conclusion presented in Ref.[1], using a different interpretation of the wave function, where the big rip singularity is completely eliminated ("smoothed out") through quantization, independently of such separation constant and for all members of the above mentioned class of solutions. This is an example of the very peculiar situation where different interpretations of the same quantum state of a system are predicting different physical facts, instead of just giving different descriptions of the same observable facts: in fact, there is nothing more observable than the fate of the whole Universe., Comment: 11 pages, 6 figures, published in Phys. Rev. D