539 research outputs found

    Cosmology in GSG

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    We describe what cosmology looks like in the context of the geometric theory of gravity (GSG) based on a single scalar field. There are two distinct classes of cosmological solutions. An interesting feature is the possibility of having a bounce without invoking exotic equations of state for the cosmic fluid. We also discuss cosmological perturbation and present the basis of structure formation by gravitational instability in the framework of the geometric scalar gravity.Comment: 12 pages, 5 figures, accepted for publication in Phys. Rev.

    More about scalar gravity

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    We discuss a class of models for gravity based on a scalar field. The models include and generalize the old approach by Nordstr\"om which predated and in some way inspired General Relativity. The class include also a model that we have recently introduced and discussed in its cosmological aspects (GSG). We present here a complete characterisation of the Schwarschild geometry as a vacuum solution of GSG and sketch a discussion of the first Post-Newtonian approximation.Comment: 11 pages, 1 figure, accepted for publication in PR

    Geometric scalar theory of gravity

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    We present a geometric scalar theory of gravity. Our proposal will be described using the "background field method" introduced by Gupta, Feynman and others as a field theory formulation of general relativity. We analyze previous criticisms against scalar gravity and show how the present proposal avoids these difficulties. This concerns not only the theoretical complaints but also those related to observations. In particular, we show that the widespread belief of the conjecture that the source of scalar gravity must be the trace of the energy-momentum tensor - which is one of the main difficulties to couple gravity with electromagnetic phenomenon in previous models - does not apply to our geometric scalar theory. Some consequences of the new scalar theory are explored.Comment: We did some modifications which do not change the content of the tex

    Dupuytren's contracture as result of prolonged administration of phenobarbital.

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    Dupuytren's disease is a fibroproliferative condition involving the superficial palmar fascia, leading to a progressive and irreversible flexion of the fingers. In literature, there are different opinions regarding the phenobarbital, a common antiepileptic drug, and its effective role in the genesis and development of Dupuytren's disease. In this retrospective investigation the association between phenobarbital and Dupuytren's contracture is discussed.Three patients in treatment with phenobarbital who had no others significant risk factors for Dupuytren's contracture were included in this study. The disease occurred after one to four years of drug therapy, at dosage of 100 mg/day. After surgery, Dupuytren's disease showed different evolutions in relation to dosage and type of antiepileptic drug used. Phenobarbital causes a dose and time-dipendent profibrotic effect. A clinical regression was observed when phenobarbital was substituted by carbamazepine, maintaining the same dosage (100 mg/day). This data confirms that not all the antiepileptic drugs are implicated in palmar fibrosis, and suggests that, according to the efficacy and adverse effects, the administration of benzodiazepine reduces the risk of Dupuytren's recurrence

    Towards a Generalized Distribution Formalism for Gauge Quantum Fields

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    We prove that the distributions defined on the Gelfand-Shilov spaces, and hence more singular than hyperfunctions, retain the angular localizability property. Specifically, they have uniquely determined support cones. This result enables one to develop a distribution-theoretic techniques suitable for the consistent treatment of quantum fields with arbitrarily singular ultraviolet and infrared behavior. The proofs covering the most general case are based on the use of the theory of plurisubharmonic functions and Hormander's estimates.Comment: 12 p., Department of Theoretical Physics, P.N.Lebedev Physical Institute, Leninsky prosp. 53, Moscow 117924, Russi

    Freestyle pedicled perforator flaps: safety, prevention of complications, and management based on 85 consecutive cases.

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    Background: Despite the widespread use of free perforator flaps, pedicled perforator flaps seem not to be as widely accepted, probably because of the fear of vascular complications caused by transfer of a flap attached only by its vascular pedicle, prone to shearing, kinking, and trauma. In this article, the authors report on their experience with 85 consecutive cases, focusing on incidence, prevention, and management of complications. Methods: Eighty-five consecutive cases were treated over 6 years at the Plastic and Reconstructive Surgery Department of the University of Palermo for defects of different causes that were reconstructed with a freestyle pedicled perforator flap, in every region of the body, including the head and neck (41.2 percent), trunk (20 percent), upper limb (7.1 percent), and lower limb (31.8 percent). The majority of flaps (67.1 percent) were 180-degree propeller perforator flaps. Results: Complete flap survival was observed in 93 percent of cases. Six flaps (7 percent) had vascular complications that were managed with venous supercharging (two cases), derotation (one case), conservative management (two cases), or secondary skin grafting (one case). The authors provide their approach to each situation to prevent or manage complications. Conclusions: The 93 percent success rate in this series seems to be acceptable and demonstrates that these flaps might be safely included in the authors’ routine. If the flaps are appropriately planned and executed, with the suggestions provided in this article, some mistakes can be avoided to make these flaps even safer

    Giant condylomata (Buschke-Löwenstein tumours): our case load in surgical treatment and review of the current therapies.

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    BACKGROUND: Buschke-Löwenstein tumour (BLT) or giant condyloma is a verrucous infiltrating lesion, due to a sexually transmitted virus infection, human papilloma virus subtypes 6 and 11. Poor hygiene, promiscuity, chronic irritation and cellular immunocompromised states are often implicated in its genesis. Typical treatment of giant condyloma includes imiquimod cream, podophillin resin, cryotherapy, laser surgery, tangential shave excision with electrocautery. OBJECTIVE: The authors report their case load in the treatment of giant condyloma and the review of the modern therapies. METHODS AND MATERIALS: 27 consecutive patients (18 men, nine women) underwent surgery for giant condylomata of perianal region and externa genitalia at the Department of Plastic Surgery of the University of Palermo, from October 2006 to December 2009. All the patients had been treated before with conservative therapies without significant results. We performed the radical excision with split-thickness skin graft in all the patients. RESULTS: No significant complications have occurred in all the cases. The functional and aesthetic outcome were satisfying. No recurrence of disease were noticed in the follow-up. CONCLUSION: the radical excision with split-thickness skin graft appears to be a successful option of treatment for Buschke-Löwenstein tumours. Compared to other methods it does not necessitate several stages of treatment, moreover it has the advantage of a lower risk of recurrence, it allows a complete histologic examination, the healing process is rapid, the improvement of quality of patients's life is significant

    Infinite Infrared Regularization and a State Space for the Heisenberg Algebra

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    We present a method for the construction of a Krein space completion for spaces of test functions, equipped with an indefinite inner product induced by a kernel which is more singular than a distribution of finite order. This generalizes a regularization method for infrared singularities in quantum field theory, introduced by G. Morchio and F. Strocchi, to the case of singularites of infinite order. We give conditions for the possibility of this procedure in terms of local differential operators and the Gelfand- Shilov test function spaces, as well as an abstract sufficient condition. As a model case we construct a maximally positive definite state space for the Heisenberg algebra in the presence of an infinite infrared singularity.Comment: 18 pages, typos corrected, journal-ref added, reference adde

    A propeller flap for single-stage nose reconstruction in selected patients: supratrochlear artery axial propeller flap

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    The paramedian forehead flap is the gold standard technique for nose reconstruction. It requires two different surgical operations which prolonged the postoperative dressing and care. We present our 5-year experience with a propeller flap based on the supratrochlear artery, which allows one-stage transfer of the forehead skin to the nose without the need for pedicle division. This technique is indicated in a selected group of patients who are not suitable for multiple-stage reconstructions because they have concurrent medical conditions, reduced mobility, or live far away from specialized medical centers. We have renamed this procedure as supratrochlear artery axial propeller flap, from the acronym STAAP flap, to stress the axial, well known and constant, vascularization of the flap. In the past 5 years, we have been performing 25 STAAP flaps; full-thickness nasal reconstruction was performed in 11 cases. The patients were 16 males and 9 females, with a mean age of 79.5 years. All patients had multiple comorbidities. Complete flap survival was observed in 23 cases and healing was complete in 7 days. In two cases, there was a partial distal necrosis of the flap treated conservatively. Cosmetic results were good and the patient's satisfaction was significant. These results indicate that the STAAP flap is a reliable and useful technique in selected cases, as old or noncompliant patients who benefit from a one-stage technique of nose reconstructio
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