913 research outputs found
Consistent Off-Shell Tree String Amplitudes
We give a construction of off-shell tree bosonic string amplitudes, based on
the operatorial formalism of the -string Vertex, with three external
massless states both for open and closed strings by requiring their being
projective invariant. In particular our prescription leads, in the low-energy
limit, to the three-gluon amplitude in the usual covariant gauge.Comment: 12 pages. Introductory and final parts modified in order to make them
more clear. Cosmetic changes in formulae (13) and (14). Some misprints
correcte
Prescriptions for Off-Shell Bosonic String Amplitudes
We give, in the framework of the bosonic string theory, simple prescriptions
for computing, at tree and one-loop levels, off-shell string amplitudes for
open and closed string massless states. In particular we obtain a tree
amplitude for three open strings that in the field theory limit coincides with
the three-gluon vertex in the usual covariant gauge and two-string one-loop
amplitudes satisfying the property of transversality.Comment: 11 pages, LaTeX, to appear in the proceedings of the workshop
"Quantum Aspects of Gauge Theories, Supersymmetry and Unification", Corfu
(Greece), 20-26 September 1998. Eq. (12) and numerical factors in eqs. (13)
and (16) corrected; some minor changes and references adde
The anti-vegf(R) drug discovery legacy: Improving attrition rates by breaking the vicious cycle of angiogenesis in cancer
Resistance to anti-vascular endothelial growth factor (VEGF) molecules causes lack of response and disease recurrence. Acquired resistance develops as a result of genetic/epigenetic changes conferring to the cancer cells a drug resistant phenotype. In addition to tumor cells, tumor endothelial cells also undergo epigenetic modifications involved in resistance to anti-angiogenic therapies. The association of multiple anti-angiogenic molecules or a combination of anti-angiogenic drugs with other treatment regimens have been indicated as alternative therapeutic strategies to overcome resistance to anti-angiogenic therapies. Alternative mechanisms of tumor vasculature, including intussusceptive microvascular growth (IMG), vasculogenic mimicry, and vascular co-option, are involved in resistance to anti-angiogenic therapies. The crosstalk between angiogenesis and immune cells explains the efficacy of combining anti-angiogenic drugs with immune check-point inhibitors. Collectively, in order to increase clinical benefits and overcome resistance to anti-angiogenesis therapies, pan-omics profiling is key
Off-shell amplitudes for nonoriented closed strings
In the context of the bosonic closed string theory, by using the operatorial formalism, we give a simple expression of the off-shell amplitude with an arbitrary number of external massless states inserted on the Klein bottle
Off-shell tachyon amplitudes: analyticity and projective invariance
We compute off-shell three- and four-tachyon amplitudes at tree level by using a prescription based on the requirement of projective invariance. In particular we show that the off-shell four-tachyon amplitude can be put in the same form as the corresponding on-shell one, exhibiting therefore the same analyticity properties. This is shown both for the bosonic and the fermionic string. The result obtained in the latter case can be extended to the off-shell four-tachyon amplitude in type 0 theory
Kaehler Metrics: String vs Field Theoretical Approach
We use both a string and a field theoretical approach in order to determine
respectively the Kaehler metrics of untwisted and twisted open strings attached
to magnetized D9 branes in toroidal compactifications.Comment: 11 pages, LaTex file. Contribution to the proceedings of the 4th RTN
workshop "Forces Universe", Varna, September 200
Is nonangiogenesis a novel pathway for cancer progression? A study using 3-dimensional tumour reconstructions
The nonangiogenic lung tumour is characterized by neoplastic cells co-opting the pre-existent vasculature and filling the alveoli space. 3-Dimensional reconstruction of the tumour reveals that this particular tumour progresses without neovascularization and there is no major destruction of the lung's architectural integrity
p53 and bcl-2 expression in high-grade B-cell lymphomas: correlation with survival time.
B-cell high-grade lymphomas are heterogeneous in terms of histology, clinical presentation, treatment response and prognosis. As bcl-2 and p53 gene deregulations are frequently involved in several types of lymphoid malignancies, we aimed our investigation at the study of the relation between bcl-2 and p53 expression and survival probability in a group of 119 patients with B-cell high-grade lymphoma. These were obtained from the Virgen de la Salud Hospital, Toledo, Spain (73 cases), John Radcliffe Hospital, Oxford, UK (31 cases), and the Istituto Nazionale dei Tumori, Milan, Italy (15 cases). The relation between bcl-2 protein expression and survival was small, depending on the primary localisation of the tumour (in lymph node of mucosae), and lacked a significant correlation with overall survival. In contrast with this, p53 expression was related to survival probability in our series, this relation being both significant and independent of histological diagnosis. p53-positive patients showed a sudden decrease in life expectancy in the first months after diagnosis. Multivariant regression analysis confirmed that the only parameters significantly related with survival were extranodal origin, which is associated with a better prognosis, and p53 expression, which indicates a poor prognosis. Simultaneous expression of bcl-2 and p53 was associated with a poorer prognosis than p53 alone. This is particularly significant for large B-cell lymphomas presenting in lymph nodes. The cumulative poor effect of both p53 and bcl-2 in large B-cell lymphomas, which is more significant in nodal tumours, could confirm the existence of a multistep genetic deregulation in non-Hodgkin's lymphoma. This indicates that the genetic mechanisms controlling apoptosis and their disregulation are critical steps in the progression of lymphomas
On the Number of Cosmic Strings
The number of cosmic strings in the observable universe is relevant in
determining the probability of detecting such cosmic defects through their
gravitational signatures. In particular, we refer to the observation of
gravitational lensing events and anisotropy in the CMB radiation induced by
cosmic strings. In this paper, a simple method is adopted to obtain an
approximate estimate of the number of segments of cosmic strings, crossing the
particle horizon, which fall inside the observed part of the universe. We show
that there is an appreciable difference in the expected number of segments
which differentiates cosmic strings arising in Abelian Higgs and Nambu-Goto
models, and that a different choice of setting for the cosmological model can
lead to significant differences in the expected number of cosmic string
segments. Of this number, the fraction realistically detectable may be
considerably smaller.Comment: LaTex2e, 15 pages, 1 figure, 5 tables. Subject extended to other
cosmological scenarios from Sect. 3 on hence, it follows a modification in
the title; three tables and references added. Version to appear in MNRA
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