8 research outputs found
Improving an interior-point approach for large block-angular problems by hybrid preconditioners
The computational time required by interior-point methods
is often domi-
nated by the solution of linear systems of equations. An efficient spec
ialized
interior-point algorithm for primal block-angular proble
ms has been used to
solve these systems by combining Cholesky factorizations for the
block con-
straints and a conjugate gradient based on a power series precon
ditioner for
the linking constraints. In some problems this power series prec
onditioner re-
sulted to be inefficient on the last interior-point iterations, wh
en the systems
became ill-conditioned. In this work this approach is combi
ned with a split-
ting preconditioner based on LU factorization, which is main
ly appropriate
for the last interior-point iterations. Computational result
s are provided for
three classes of problems: multicommodity flows (oriented and no
noriented),
minimum-distance controlled tabular adjustment for statistic
al data protec-
tion, and the minimum congestion problem. The results show that
, in most
cases, the hybrid preconditioner improves the performance an
d robustness of
the interior-point solver. In particular, for some block-ang
ular problems the
solution time is reduced by a factor of 10.Peer ReviewedPreprin
Improving an interior-point approach for large block-angular problems by hybrid preconditioners
The computational time required by interior-point methods
is often domi-
nated by the solution of linear systems of equations. An efficient spec
ialized
interior-point algorithm for primal block-angular proble
ms has been used to
solve these systems by combining Cholesky factorizations for the
block con-
straints and a conjugate gradient based on a power series precon
ditioner for
the linking constraints. In some problems this power series prec
onditioner re-
sulted to be inefficient on the last interior-point iterations, wh
en the systems
became ill-conditioned. In this work this approach is combi
ned with a split-
ting preconditioner based on LU factorization, which is main
ly appropriate
for the last interior-point iterations. Computational result
s are provided for
three classes of problems: multicommodity flows (oriented and no
noriented),
minimum-distance controlled tabular adjustment for statistic
al data protec-
tion, and the minimum congestion problem. The results show that
, in most
cases, the hybrid preconditioner improves the performance an
d robustness of
the interior-point solver. In particular, for some block-ang
ular problems the
solution time is reduced by a factor of 10.Peer Reviewe
Improving an interior-point approach for large block-angular problems by hybrid preconditioners
The computational time required by interior-point methods
is often domi-
nated by the solution of linear systems of equations. An efficient spec
ialized
interior-point algorithm for primal block-angular proble
ms has been used to
solve these systems by combining Cholesky factorizations for the
block con-
straints and a conjugate gradient based on a power series precon
ditioner for
the linking constraints. In some problems this power series prec
onditioner re-
sulted to be inefficient on the last interior-point iterations, wh
en the systems
became ill-conditioned. In this work this approach is combi
ned with a split-
ting preconditioner based on LU factorization, which is main
ly appropriate
for the last interior-point iterations. Computational result
s are provided for
three classes of problems: multicommodity flows (oriented and no
noriented),
minimum-distance controlled tabular adjustment for statistic
al data protec-
tion, and the minimum congestion problem. The results show that
, in most
cases, the hybrid preconditioner improves the performance an
d robustness of
the interior-point solver. In particular, for some block-ang
ular problems the
solution time is reduced by a factor of 10.Peer Reviewe
Security constrained optimal active power flow via network model and interior point method
This paper presents a new formulation for the security constrained optimal active power flow problem which enables the representation of three basic constraints: branch outage, generator outage and multiple equipment congestion. It consists of a network model with additional linear equality and inequality constraints and quadratic separable objective function, which is efficiently solved by a predictor-corrector interior point method. Sparsity techniques are used to exploit the matricial structure of the problem.Case studies with a 3,535-bus and a 4,238-branch Brazilian power system are presented and discussed, to demonstrate that the proposed model can be efficiently solved by an interior point method, providing security constrained solutions in a reasonable time.Este trabalho apresenta uma nova formulação do problema de fluxo de potência ótimo corrente contÃnua com restrições de segurança de três tipos: perda de ramo, perda de gerador e múltiplas perdas. A formulação emprega um modelo de fluxo em redes com restrições adicionais de igualdade e desigualdade e função objetivo quadrática separável que é eficientemente resolvido por um método de pontos interiores preditor-corretor. Técnicas de esparsidade são utilizadas para explorar a estrutura matricial do problema. Estudos de caso para o Sistema Interligado Nacional com 3535 barras e 4238 ramos são apresentados e discutidos, a fim de demonstrar que o modelo proposto pode ser resolvido através de um método de pontos interiores de maneira eficiente, fornecendo soluções que respeitam as restrições de segurança em um tempo computacional razoável.206216Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de NÃvel Superior (CAPES
Data from: Proteomic analysis reveals a predominant NFE2L2 (NRF2) signature in the ​canonical pathway and upstream regulator analysis of Leishmania-infected macrophages
CBA mice macrophages (MØ) control infection by Leishmania major and are susceptive to Leishmania amazonensis, suggesting that both parasite species induce distinct responses that play important roles in infection outcome. To evaluate the MØ responses to infection arising from these two Leishmania species, a proteomic study using a Multidimensional Protein Identification Technology (MudPIT) approach with liquid chromatography tandem mass spectrometry (LC-MS/MS) was carried out on CBA mice bone-marrow MØ (BMMØ). Following SEQUEST analysis, which revealed 2,838 proteins detected in BMMØ, data mining approach found six proteins significantly associated with the tested conditions. To investigate their biological significance, enrichment analysis was performed using Ingenuity Pathway Analysis (IPA). A three steps IPA approach revealed 4 Canonical Pathways (CP) and 7 Upstream Transcriptional Factors (UTFs) strongly associated with the infection process. NRF2 signatures were present in both CPs and UTFs pathways. Proteins involved in iron metabolism, such as heme oxigenase 1 (HO-1) and ferritin besides sequestosome (SQSMT1 or p62) were found in the NRF2 CPs and the NRF2 UTFs. Differences in the involvement of iron metabolism pathway in Leishmania infection was revealed by the presence of HO-1 and ferritin. Noteworty, HO-1 was strongly associated with L. amazonensis infection, while ferritin was regulated by both species. As expected, higher HO-1 and p62 expressions were validated in L. amazonensis-infected BMMØ, in addition to decreased expression of ferritin and nitric oxide production. Moreover, BMMØ incubated with L. amazonensis LPG also expressed higher levels of HO-1 in comparison to those stimulated with L. major LPG. In addition, L. amazonensis-induced uptake of holoTf was higher than that induced by L. major in BMMØ, and holoTf was also detected at higher levels in vacuoles induced by L. amazonensis. Taken together, these findings indicate that NRF2 pathway activation and increased HO-1 production, together with higher levels of holoTf uptake, may promote permissiveness to L. amazonensis infection. In this context, differences in protein signatures triggered in the host by L. amazonensis and L. major infection could drive the outcomes in distinct clinical forms of leishmaniasis