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Search Results: 1 - 10 of 415104 matches for " Rui M Reis "
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Functor calculus and the discriminant method
Rui M. G. Reis,Michael S. Weiss
Mathematics , 2011,
Abstract: The discriminant method is a tool for describing the cohomology, or the homotopy type, of certain spaces of smooth maps with uncomplicated singularities from a smooth compact manifold L to R^k. We recast some of it in the language of functor calculus. This reformulation allows us to use the discriminant method in a setting where we wish to impose conditions on the multilocal behavior of smooth maps f from L to R^k.
Geometric K-Homology of Flat D-Branes
Rui M. G. Reis,Richard J. Szabo
Mathematics , 2005, DOI: 10.1007/s00220-006-0010-8
Abstract: We use the Baum-Douglas construction of K-homology to explicitly describe various aspects of D-branes in Type II superstring theory in the absence of background supergravity form fields. We rigorously derive various stability criteria for states of D-branes and show how standard bound state constructions are naturally realized directly in terms of topological K-cycles. We formulate the mechanism of flux stabilization in terms of the K-homology of non-trivial fibre bundles. Along the way we derive a number of new mathematical results in topological K-homology of independent interest.
Rational Pontryagin classes and functor calculus
Rui M. G. Reis,Michael S. Weiss
Mathematics , 2011,
Abstract: It is known that in the integral cohomology of BSO(2m), the square of the Euler class is the same as the Pontryagin class in degree 4m. Given that the Pontryagin classes extend rationally to the cohomology of BSTOP(2m), it is reasonable to ask whether the same relation between the Euler class and the Pontryagin class in degree 4m is still valid in the rational cohomology of BSTOP(2m). In this paper we use smoothing theory and tools from homotopy theory to reformulate the hypothesis, and variants, in a differential topology setting and in a functor calculus setting.
Smooth maps to the plane and Pontryagin classes, Part I: Local aspects
Rui M. G. Reis,Michael S. Weiss
Mathematics , 2010,
Abstract: We classify the most common local forms of smooth maps from a smooth manifold L to the plane. The word "local" can refer to locations in the source L, but also to locations in the target. The first point of view leads us to a classification of certain germs of maps, which we review here although it is very well known. The second point of view leads us to a classification of certain multigerms of maps.
KO-Homology and Type I String Theory
Rui M. G. Reis,Richard J. Szabo,Alessandro Valentino
Mathematics , 2006, DOI: 10.1142/S0129055X09003839
Abstract: We study the classification of D-branes and Ramond-Ramond fields in Type I string theory by developing a geometric description of KO-homology. We define an analytic version of KO-homology using KK-theory of real C*-algebras, and construct explicitly the isomorphism between geometric and analytic KO-homology. The construction involves recasting the Cl(n)-index theorem and a certain geometric invariant into a homological framework which is used, along with a definition of the real Chern character in KO-homology, to derive cohomological index formulas. We show that this invariant also naturally assigns torsion charges to non-BPS states in Type I string theory, in the construction of classes of D-branes in terms of topological KO-cycles. The formalism naturally captures the coupling of Ramond-Ramond fields to background D-branes which cancel global anomalies in the string theory path integral. We show that this is related to a physical interpretation of bivariant KK-theory in terms of decay processes on spacetime-filling branes. We also provide a construction of the holonomies of Ramond-Ramond fields in Type II string theory in terms of topological K-chains.
Early Pseudoprogression following Chemoradiotherapy in Glioblastoma Patients: The Value of RANO Evaluation
Paulo Linhares,Bruno Carvalho,Rita Figueiredo,Rui M. Reis,Rui Vaz
Journal of Oncology , 2013, DOI: 10.1155/2013/690585
Abstract: Introduction. The aim of this study was to determine the frequency of pseudoprogression in a cohort of glioblastoma (GBM) patients following radiotherapy/temozolomide (RT/TMZ) by comparing Macdonald criterial to Response Assessment in Neuro-Oncology (RANO) criteria. The impact on prognosis and survival analysis was also studied. Materials and Methods. All patients receiving RT/TMZ for newly diagnosed GBM from January 2005 to December 2009 were retrospectively evaluated, and demographic, clinical, radiographic, treatment, and survival data were reviewed. Updated RANO criteria were used for the evaluation of the pre-RT and post-RT MRI and compared to classic Macdonald criteria. Survival data was evaluated using the Kaplan-Meier and log-rank analysis. Results and Discussion. 70 patients were available for full radiological response assessment. Early progression was confirmed in 42 patients (60%) according to Macdonald criteria and 15 patients (21%) according to RANO criteria. Pseudoprogression was identified in 10 (23.8%) or 2 (13.3%) patients in Macdonald and RANO groups, respectively. Cumulative survival of pseudoprogression group was higher than that of true progression group and not statistically different from the non-progressive disease group. Conclusion. In this cohort, the frequency of pseudoprogression varied between 13% and 24%, being overdiagnosed by older Macdonald criteria, which emphasizes the importance of RANO criteria and new radiological biomarkers for correct response evaluation. 1. Introduction The current standard of care for newly diagnosed glioblastoma (GBM) remains surgical resection followed by radiotherapy with concurrent temozolomide (RT/TMZ) and then maintenance temozolomide for at least six months [1]. The addition of chemotherapy introduced new questions regarding biological response of the tumor and the surrounding brain. Pseudoprogression is a phenomenon of subacute imaging changes in human glioma subsequent to radiochemotherapy suggestive of progression, with or without associated clinical sequelae, which resolve spontaneously without further therapy [2]. It was first reported by Hoffman et al. [3] in 1979 and fully described by de Wit et al. [4] in 2004. The underlying pathophysiological mechanisms are not fully understood [5]. Some authors suggest that it likely reflects an inflammatory tissue reaction after a local treatment secondary to vascular and oligodendroglial injury, whereas others associate it with an exaggerated response to effective therapy [2, 6, 7]. The incidence of pseudoprogression, time of occurrence, and
Posterior Nutcracker Syndrome with Left Renal Vein Duplication: A Rare Cause of Haematuria in a 12-Year-Old Boy
J. Preza Fernandes,Rui Amorim,M. J. Gomes,V. Oliveira,A. Reis,J. Ribeiro-Castro
Case Reports in Urology , 2012, DOI: 10.1155/2012/849681
Abstract: The nutcracker syndrome (NCS) is a rare cause of haematuria. It embraces an extended nonpathognomonic spectrum of symptoms that imply a difficult diagnosis. Ultimately it may be associated with substantial morbidity and even life-threatening events. We report a rare cause if a 12-year-old boy who presented with a history of frequent intermittent episodes of painless constant haematuria. The cystoscopy showed a bloody urine ejaculate from the left ureter meatus. The Doppler ultrasonography showed turbulent pattern of venous blood flow of the posterior renal vein branch behind the aorta. The abdominopelvic computer tomography (apCT) revealed left renal vein (LRV) duplication with a dilated retroaortic branch, entrapped between the aorta and the vertebral column, promoting the renal nutcracker syndrome. The patient was initially hospitalized and managed with oral iron supplements and continuous saline bladder irrigation, not requiring additional treatment. The child is currently asymptomatic, with haemoglobin value returning to normal and therefore proposed to conservative management with close followup. The authors present a case report of episodic haematuria caused by a rare entity—posterior nutcracker syndrome with renal vein duplication.
Overexpression of platelet-derived growth factor receptor α in breast cancer is associated with tumour progression
Inês Carvalho, Fernanda Milanezi, Albino Martins, Rui M Reis, Fernando Schmitt
Breast Cancer Research , 2005, DOI: 10.1186/bcr1304
Abstract: We used immunohistochemistry to detect PDGFR-α overexpression on a series of 181 formalin-fixed paraffin-embedded invasive ductal breast carcinomas and in two breast cancer cell lines: MCF-7 and HS578T. We associated its expression with known prognostic factors and we also performed polymerase chain reaction–single-stranded conformational polymorphism and direct sequencing to screen for PDGFR-α mutations.PDGFR-α expression was observed in 39.2% of the breast carcinomas and showed an association with lymph node metastasis (P = 0.0079), HER-2 expression (P = 0.0265) and Bcl2 expression (P = 0.0121). A correlation was also found with the expression of platelet-derived growth factor A (PDGF-A; P = 0.0194). The two cell lines tested did not express PDGFR-α. Screening for mutations revealed alterations in the PDGFR-α gene at the following locations: 2500A→G, 2529T→A and 2472C→T in exon 18 and 1701G→A in exon 12. We also found an intronic insertion IVS17-50insA at exon 18 in all sequenced cases. None of these genetic alterations was correlated with PDGFR-α expression. The cell lines did not reveal any alterations in the PDGFR-α gene sequence.PDGFR-α is expressed in invasive breast carcinomas and is associated with biological aggressiveness. The genetic alterations described were not correlated with protein expression, but other mechanisms such as gene amplification or constitutive activation of a signalling pathway inducing this receptor could still sustain PDGFR-α as a potential therapeutic target.Uncontrolled tumour cell proliferation due to abnormal activation of several growth factors and their receptors is relevant in the events underlying human cancer development, because the tyrosine kinases receptors form one of the most important classes of growth factor receptors implicated in that process. Platelet-derived growth factor receptors (PDGFRs) α and β are characterized by an intracellular tyrosine kinase domain whose activation depends on ligand binding. The platelet
Role of endoglin and VEGF family expression in colorectal cancer prognosis and anti-angiogenic therapies
Sandra F Martins,Rui M Reis,Antonio Mesquita Rodrigues,Fátima Baltazar
World Journal of Clinical Oncology , 2011, DOI: 10.5306/wjco.v2.i6.272
Abstract: Colorectal cancer (CRC) is one of the cancer models and most of the carcinogenic steps are presently well understood. Therefore, successful preventive measures are currently used in medical practice. However, CRC is still an important public health problem as it is the third most common cancer and the fourth most frequent cause of cancer death worldwide. Nowadays, pathologic stage is a unique and well-recognized prognostic indicator, however, more accurate indicators of the biologic behavior of CRC are expected to improve the specificity of medical treatment. Angiogenesis plays an important role in the growth and progression of cancer but its role as a prognostic factor is still controversial. Probably the most important clinical implication of tumor angiogenesis is the development of anti-angiogenic therapy. The goal of this review is to critically evaluate the role of angiogenic markers, assessed by either endoglin-related microvessel density or expression of vascular endothelial growth factor family members in the CRC setting and discuss the role of these angiogenic markers in anti-angiogenic therapies.
Posterior Nutcracker Syndrome with Left Renal Vein Duplication: A Rare Cause of Haematuria in a 12-Year-Old Boy
J. Preza Fernandes,Rui Amorim,M. J. Gomes,V. Oliveira,A. Reis,J. Ribeiro-Castro
Case Reports in Urology , 2012, DOI: 10.1155/2012/849681
Abstract: The nutcracker syndrome (NCS) is a rare cause of haematuria. It embraces an extended nonpathognomonic spectrum of symptoms that imply a difficult diagnosis. Ultimately it may be associated with substantial morbidity and even life-threatening events. We report a rare cause if a 12-year-old boy who presented with a history of frequent intermittent episodes of painless constant haematuria. The cystoscopy showed a bloody urine ejaculate from the left ureter meatus. The Doppler ultrasonography showed turbulent pattern of venous blood flow of the posterior renal vein branch behind the aorta. The abdominopelvic computer tomography (apCT) revealed left renal vein (LRV) duplication with a dilated retroaortic branch, entrapped between the aorta and the vertebral column, promoting the renal nutcracker syndrome. The patient was initially hospitalized and managed with oral iron supplements and continuous saline bladder irrigation, not requiring additional treatment. The child is currently asymptomatic, with haemoglobin value returning to normal and therefore proposed to conservative management with close followup. The authors present a case report of episodic haematuria caused by a rare entity—posterior nutcracker syndrome with renal vein duplication. 1. Introduction Nutcracker syndrome is a rare cause of haematuria caused by the left renal vein (LRV) entrapment [1–5], most usually between the aorta and the superior mesenteric artery (SMA), known as anterior nutcracker syndrome. Sometimes a retroaortic position of the LRV also promotes an entrapment, this time between the aorta and the vertebral column, which is named posterior nutcracker syndrome [6]. Although the first clinical report was made by El-Sadr and Mina [1] in 1950, the term nutcracker is credited to de Schepper in 1972 [2] but was first used by Chait et al. in 1971 [3]. This term must be distinguished from the Nutcracker Phenomenon [4]. This is a relatively common anatomical variance, in which the patient stays asymptomatic, and it is often diagnosed in an occasional imaging exam. It usually affects women more than men [1] and in most cases present in the 3rd or 4th decades of life. When symptomatic this syndrome is manifested by left flank and abdominal pain, with or without unilateral macroscopic or microscopic haematuria. When the venous reflux caused by the LRV entrapment leads to the formation of collaterals this syndrome may be a cause of “pelvic congestion syndrome” characterized by an array of signs and symptoms such as dyspareunia, dysmenorrhoea, lower abdominal pain and pelvic, perineal and
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