1,053 research outputs found
Chiral supergravity actions and superforms
The superform construction of supergravity actions, christened the "ectoplasm
method," is based on the use of a closed super d-form in the case of d
space-time dimensions. In known examples, such superforms are obtained by
iteratively solving nontrivial cohomological problems. The latter usually makes
this scheme no less laborious than the normal coordinate method for deriving
component actions for matter-coupled supergravity. In this note we present an
alternative procedure to generate required superforms in four space-time
dimensions, which makes use of self-dual vector multiplets. It provides the
shortest derivation of chiral actions in two different theories: (i) N = 1 old
minimal supergravity; and (ii) N = 2 conformal supergravity. The N = 2
superform construction is developed here for the first time. Although our
consideration is restricted to the case of four dimensions, a generalization to
higher dimensions is plausible.Comment: 14 pages; V2: minor correction
Covariant superspace approaches to supergravity
We provide a unified description of the three covariant superspace approaches
to conformal supergravity in four dimensions: (i) conformal
superspace; (ii) superspace; and (iii)
superspace. Each of them can be used to formulate general supergravity-matter
systems, although conformal superspace has the largest structure group and is
intimately related to the superconformal tensor calculus. We review the
structure of covariant projective multiplets and demonstrate how they are used
to describe pure and matter-coupled supergravity, including locally
superconformal off-shell sigma models. Higher-derivative invariants,
topological invariants and super-Weyl anomalies are also briefly discussed.Comment: 58 pages. Invited chapter for the "Handbook of Quantum Gravity" (Eds.
C. Bambi, L. Modesto and I.L. Shapiro, Springer, expected in 2023
Ectoplasm & Superspace Integration Measure for 2D Supergravity with Four Spinorial Supercurrents
Building on a previous derivation of the local chiral projector for a two
dimensional superspace with eight real supercharges, we provide the complete
density projection formula required for locally supersymmetrical theories in
this context. The derivation of this result is shown to be very efficient using
techniques based on the Ectoplasmic construction of local measures in
superspace.Comment: 18 pages, LaTeX; V2: minor changes, typos corrected, references
added; V3: version to appear in J. Phys. A: Math. Theor., some comments and
references added to address a referee reques
4D N = 2 Supergravity and Projective Superspace
This paper presents a projective superspace formulation for 4D N = 2
matter-coupled supergravity. We first describe a variant superspace realization
for the N = 2 Weyl multiplet. It differs from that proposed by Howe in 1982 by
the choice of the structure group (SO(3,1) x SU(2) versus SO(3,1) x U(2)),
which implies that the super-Weyl transformations are generated by a
covariantly chiral parameter instead of a real unconstrained one. We introduce
various off-shell supermultiplets which are curved superspace analogues of the
superconformal projective multiplets in global supersymmetry and which describe
matter fields coupled to supergravity. A manifestly locally supersymmetric and
super-Weyl invariant action principle is given. Off-shell locally
supersymmetric nonlinear sigma models are presented in this new superspace.Comment: 26 pages, LaTeX, no figures; V2: comments and references added,
version published in JHEP; V3: typo in eq. (2.7e) correcte
The Impact of the Introduction of Total Mesorectal Excision on Local Recurrence Rate and Survival in Rectal Cancer: Long-Term Results
Purpose: To investigate the influence of the introduction of total mesorectal excision (TME) on local recurrence rate and survival in patients with rectal cancer. Methods: A total of 171 consecutive patients underwent anterior or abdominoperineal resection for primary rectal cancer. When the TME technique was introduced, the clinical setting, including the surgeons, remained the same. Group 1 (1993-95, n=53) underwent conventional surgery and group 2 (1995-2001, n=118) underwent TME. All patients were followed for 7years or until death. Results: Between the two groups, no statistically significant differences were present with regards to patient-, treatment-, or tumor-related characteristics apart from the time point of radiotherapy. The total local recurrence rates were 11 of 53 (20.8%) in group 1 and 7 of 118 (5.9%) in group 2, and the rates of isolated local recurrences were 6 of 53 (11.3%) in group 1 and 2 of 118 (1.7%) in group 2. Both differences were highly statistically significant. The disease-free survival in groups 1 and 2 was 60.4 and 65.3% at 5years, and 58.5 and 65.3% at 7years, respectively. Excluding patients with synchronous or metachronous distant metastasis from the analysis, both the disease-free survival and the cancer-specific survival were statistically significantly better in group 2 than in group 1. No statistically significant difference between the two groups was detected regarding the overall survival. Conclusions: The introduction of TME led to an impressive reduction of the local recurrence rate. Survival is mainly determined by the occurrence of distant metastasis, but TME seems to improve survival in patients without systemic diseas
A Derivation of an Off-Shell N = (2,2) Supergravity Chiral Projection Operator
Utilizing the known off-shell formulation of 2D, N = (2,2) supergravity,
containing a finite number of auxiliary fields, there is shown to exist a
simple form for a 'chiral projection operator' and an explicit expression for
it is given.Comment: 10 pages, no figures, one new reference adde
Indocyanine Green Nanoparticles : Are They Compelling for Cancer Treatment?
Indocyanine green (ICG) is a Food and Drug Administration\u2013approved near-infrared fluorescent dye, employed as an imaging agent for different clinical applications due to its attractive physicochemical properties, high sensitivity, and safety. However, free ICG suffers from some drawbacks, such as relatively short circulation half-life, concentration-dependent aggregation, and rapid clearance from the body, which would confine its feasible application in oncology. Here, we aim to discuss encapsulation of ICG within a nanoparticle formulation as a strategy to overcome some of its current limitations and to enlarge its possible applications in cancer diagnosis and treatment. Our purpose is to provide a short but exhaustive overview of clinical outcomes that these nanocomposites would provide, discussing opportunities, limitations, and possible impacts with regard to the main clinical needs in oncology
A metal-poor damped Ly-alpha system at redshift 6.4
We identify a strong Ly-alpha damping wing profile in the spectrum of the
quasar P183+05 at z=6.4386. Given the detection of several narrow metal
absorption lines at z=6.40392, the most likely explanation for the absorption
profile is that it is due to a damped Ly-alpha system. However, in order to
match the data a contribution of an intergalactic medium 5-38% neutral or
additional weaker absorbers near the quasar is also required. The absorption
system presented here is the most distant damped Ly-alpha system currently
known. We estimate an HI column density (cm),
metallicity ([O/H]), and relative chemical abundances of a
system consistent with a low-mass galaxy during the first Gyr of the universe.
This object is among the most metal-poor damped Ly-alpha systems known and,
even though it is observed only ~850 Myr after the big bang, its relative
abundances do not show signatures of chemical enrichment by Population III
stars.Comment: Updated to match published versio
Involved margins after lumpectomy for breast cancer: Always to be re-excised?
Background: The oncologic benefit of upfront re-excision of involved margins after breast-conserving surgery in the context of current multimodal clinical management of breast cancer is unclear. The aim of the present study was to assess the 5-years locoregional recurrence (LRR)-free and distant metastases (DM)-free survival probabilities in patients not undergoing re-excision of positive margins after lumpectomy for breast cancer. Methods: A cohort of 104 patients with positive margins not undergoing re-excision was matched by propensity score with a cohort of 2006 control patients with clear margins after breast-conserving surgery, treated between 2008 and 2018. A multivariate survival analysis was performed accounting for all variables related to LRR and DM, including adjuvant treatments. Results: After adjusting for potential confounders, avoiding to re-excise a positive margin after lumpectomy had no effect on 5-years LRR-free survival probability (HR 0.98, 95%CI 0.36-2.67, p = 0.96) or 5-years DM-free survival probability (HR 0.37, 95%CI 0.08-1.61, p = 0.18). No correlation was found between occurrence of LRR and number of involved margins (HR 1.28, 95%CI 0.10-12.4, Log-rank p = 0.83), or extension of infiltrating disease (HR 1.21, 95%CI 0.20-7.40, Log-rank p = 0.83), but a trend toward higher LRR probability was found for invasive ductal (HR 6.92, 95%CI 0.7-68.8, Log-rank p = 0.10) and invasive lobular cancer (HR 12.95, 95%CI 0.79-213.6, Log-rank p = 0.07) on positive margins. Conclusions: In the era of multimodal treatment of breast cancer and accurate strategies to reduce the probability of residual disease in the post-lumpectomy cavity, re-excision of positive margins might be omitted in selected patients with low-risk breast cancers
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