49 research outputs found
Boundary State for Magnetized D9 Branes and One-Loop Calculation
We construct the boundary state describing magnetized D9 branes in R^{3,1} x
T^6 and we use it to compute the annulus and Moebius amplitudes. We derive from
them, by using open/closed string duality, the number of Landau levels on the
torus T^d.Comment: 12 pages,in honor of Adriano Di Giacomo on his 70th birthday,
contribution to the Festschrif
On off-shell bosonic string amplitudes
We give a simple prescription for computing, in the framework of the bosonic
string theory, off-shell one-loop amplitudes with any number of external
massless particles, both for the open and for the closed string. We discuss
their properties and, in particular, for the two-string one-loop amplitudes we
show their being transverse.Comment: 12 pages, Latex. One reference added. Introduction and conclusions
expanded. Some other minor changes in the tex
TIBIO-FIBULAR BONE TRANSPOSITION FOR THE TREATMENT OF ONCOLOGICAL PERIPROSTHETIC INFECTION OF THE KNEE WITH MASSIVE BONE LOSS
Chronic periprosthetic joint infection (PJI) is one of the most relevant complications in orthopaedic
surgery, especially in the case of limb reconstruction with megaprostheses after malignant tumoral
resection. This is the report of a case of a 35-year-old patient, affected by a chronic PJI around a
knee megaprosthesis implanted after the resection of an osteosarcoma of the distal femur. “En bloc”
resection and limb reconstruction with an expandable megaprothesis of the knee were performed at
the age of 5 years old (1989). PJI occurred after the definitive megaprosthesis implantation (2002),
and became chronic over the years.
In 2019, due to a massive recrudescence of the infection and the severe femoral bone loss, the
patient underwent a wide intercalary resection and a thigh stump reconstruction by transposition of
the fibula and the distal third of the tibia in order to avoid a hip disarticulation.
Although complex, the proposed treatment allowed improved outcomes in a young patient with
high function requests, justifying the global surgical invasiveness
Fragility Fractures of the Acetabulum: Current Concepts for Improving Patients’ Outcomes
The incidence of fragility fractures of the acetabulum (FFA) is constantly increasing. Generally, these fractures are related to a fall on the greater trochanter involving the anterior column. The management of FFA is extremely difficult considering both patients’ comorbidities and poor bone quality. Both non-operative and several operative treatment protocols are available, and the choice among them is still ambiguous. The proposed surgical techniques for FFA [namely open reduction and internal fixation (ORIF), percutaneous fixation and total hip arthroplasty (THA)] are associated with a high complication rate. The treatment with the higher early mortality is the ORIF + THA, while the one with the lowest is the non-operative. However, at longer follow-up, this difference dreadfully change is becoming the opposite. Frequently ORIF, percutaneous fixation, and non-operative treatment need a subsequent re-operation through a THA. This latter could be extremely difficult, because of poor bone quality, acetabular mal union/non-union, bone gaps and hardware retention. However, the outcomes of each of the proposed treatment are mostly poor and controverted; therefore, a comprehensive patient evaluation and an accurate fracture description are required to appropriately manage acetabular fracture in the elderly
N=1 Matter from Fractional Branes
We study a bound state of fractional D3-branes localized inside the
world-volume of fractional D7-branes on the orbifold C^3/Z_2 x Z_2. We
determine the open string spectrum that leads to N=1 U(N1)xU(N2)xU(N3)xU(N4)
gauge theory with matter having the number of D7-branes as a flavor index. We
derive the linearized boundary action of the D7-brane on this orbifold using
the boundary state formalism and we discuss the tadpole cancellation. After
computing the asymptotic expression of the supergravity solution the anomalies
of the gauge theory are reproduced.Comment: LaTeX 20 pages, 1 figure, small changes and references adde
Extracapsular femoral neck fractures treated with total hip arthroplasty: identification of a population with better outcomes
BACKGROUND: Femoral neck fractures (FNF) are associated to patient’s disability, reduced quality of life and mortality. None of the fixation devices commonly used for extracapsular (EC) FNF (i.e., dynamic hip screws (DHS) and intramedullary nails (IN)) is clearly superior to the other, especially in case of unstable fractures (31.A2 and 31.A3 according to AO/OTA classification). The aim of our study was to identify a sub-population of patients with EC fractures in which better outcomes could be obtainable using total hip arthroplasty (THA). METHODS: All patients with EC unstable fractures treated with THA were included in the present study. Demographic data, American Society of Anesthesiologists (ASA) score, hospitalization length, transfusion rate, implant-related complications and mortality rate were collected. Clinical outcomes were evaluated using the Oxford Hip Score (OHS), while patients’ general health status through the 12 Item Short Form questionnaires (SF-12). RESULTS: 30 patients (7 male; 23 female) with a mean age of 78.8 years were included. The 1-year mortality rate was 13.3%. The mean OHS was 27.5, while the mean SF-12 were 45.84 for the mental item and 41.6 for the physical one. Age was the only factor associated with the OHS and patients older than 75 years presented a 12- fold higher risk of developing bad outcomes. CONCLUSIONS: THA seems to be a viable option for unstable EC fractures, with good clinical outcomes, especially in patients younger than 75 years of age. The mortality rate associated with THA in EC fractures is low and anyway comparable with IN
Anomalies and Tadpoles in Open/Closed String Duality
We discuss the role played by the divergences appearing in the interaction
between a fractional D3 brane dressed with an SU(N) gauge field and a stack of
N fractional D3 branes on the orbifolds C^2/Z_2 and C^3/(Z_2 x Z_2). In
particular we show that the logarithmic divergences in the closed string
channel, interpreted as due to twisted massless tadpoles, are mapped, under
open/closed string duality, in the logarithmic ones in the open string channel,
due to the massless states circulating in the annulus diagram and corresponding
to the one-loop divergences that one finds in the gauge theory living in the
world volume of the brane. This result provides a quantitative evidence of why
the chiral and scale anomalies of the supersymmetric and non conformal gauge
theories supported by the world volume of the branes can be inferred from
supergravity calculations.Comment: LaTeX, 8 pages. Contribution to the proceedings of the workshop of
the RTN Network "The quantum structure of space-time and the geometric nature
of fundamental interactions", Copenhagen, September 200