1,205 research outputs found
Toeplitz operators of finite interval type and the table method
We solve a Riemann-Hilbert problem with almost periodic coefficient G, associated to a Toeplitz operator T-G in a class which is closely connected to finite interval convolution equations, based on a generalization of the so-called table method. The explicit determination of solutions to that problem allows one to establish necessary and sufficient conditions for the invertibility of the corresponding Toeplitz operator, and to determine an appropriate factorization of G, providing explicit formulas for the inverse of T-G. Some unexpected properties of the Fourier spectrum of the solutions are revealed which are not apparent through other approaches to the same probleminfo:eu-repo/semantics/acceptedVersio
MVG Mechanism: Differential Privacy under Matrix-Valued Query
Differential privacy mechanism design has traditionally been tailored for a
scalar-valued query function. Although many mechanisms such as the Laplace and
Gaussian mechanisms can be extended to a matrix-valued query function by adding
i.i.d. noise to each element of the matrix, this method is often suboptimal as
it forfeits an opportunity to exploit the structural characteristics typically
associated with matrix analysis. To address this challenge, we propose a novel
differential privacy mechanism called the Matrix-Variate Gaussian (MVG)
mechanism, which adds a matrix-valued noise drawn from a matrix-variate
Gaussian distribution, and we rigorously prove that the MVG mechanism preserves
-differential privacy. Furthermore, we introduce the concept
of directional noise made possible by the design of the MVG mechanism.
Directional noise allows the impact of the noise on the utility of the
matrix-valued query function to be moderated. Finally, we experimentally
demonstrate the performance of our mechanism using three matrix-valued queries
on three privacy-sensitive datasets. We find that the MVG mechanism notably
outperforms four previous state-of-the-art approaches, and provides comparable
utility to the non-private baseline.Comment: Appeared in CCS'1
Cerebral Creatine Deficiency Syndromes
Introduction: Creatine deficiency syndromes are a recently described group of diseases characterized by inborn errors of creatine
metabolism. Clinical features include a spectrum of neurodevelopment disorders of diverse severity. They are characterized by low
levels of cerebral creatine caused by different pathogenic mutations concerning the genes coding for creatine synthesis enzymes
[arginine: glicyne amidinotransferase (AGAT, EC 2.1.4.1) and guanidinoacetate methyltansferase (GAMT, EC 2.1.1.2)], AGAT and
GAMT, respectively, or its transporter (CT1 deficiency), SLC6A8. Enzymatic deficiencies are transmitted as autosomal recessive traits,
whereas the transporter deficit is X-linked.
Objectives: To characterize the clinical and laboratorial presentation, diagnosis and treatment of cerebral creatine deficiency patients,
followed in Hospital Pediátrico Carmona da Mota. The awareness of these inborn errors of metabolism as neurological disorders,
namely of neurodevelopment, among the medical community is a secondary aim of the present work.
Methods and Material: Retrospective analysis of the clinical files of patients followed in our Hospital and diagnosed with cerebral
creatine deficiency syndrome.
Results: Twelve patients belonging to seven different families were diagnosed with creatine deficiency syndromes. Five presented
GAMT deficiency and seven CT1 deficiency. Present ages are 2 to 38 years old. The most common clinical presentations were: global
development delay in seven patients (two with epilepsy), and speech delay in two patients. Only one patient had communication and
social interaction dysfunction. In all, global development delay in the range of intellectual delay was identified. The pathognomonic pattern
of cerebral creatine deficiency in the brain image was demonstrated in eight patients. Pathogenic mutations in GAMT or SLC6A8
genes were identified in all cases.
Conclusions: The suspicion of cerebral creatine depletion must be considered in all children presenting unexplained global psychomotor
development delay. Pre-symptomatic therapy has shown promising results, especially in GAMT deficiency patients. The high rate of
asymptomatic carriers of GAMT mutations in our population makes this disorder eligible to neonatal screening in Portugal
Potencial forrageiro da Brachiaria brizantha cv. Marandu sob diferentes cargas animal e dosificacao com anti-helmitico em solo de cerrado.
bitstream/item/137570/1/PESQ-EM-ANDAMENTO-25.pdfCNPGC
Low Prevalence of Fetal-Type Posterior Cerebral Artery in Patients with Basilar Tip Aneurysms
BACKGROUND:
Basilar tip aneurysms (BTA) are multifactorial in origin, with luminal forces playing a major role in their formation. Considering the reduced hemodynamic stress on the basilar apex in the fetal-type posterior cerebral artery (fPCA), we hypothesize that BTA should be less common in patients with this variant.
OBJECTIVE:
To investigate, in a retrospective case-control study, the frequency of fPCA in patients with and without BTA.
MATERIALS AND METHODS:
We collected clinical and imaging data from consecutive patients with BTA undergoing catheter angiography between July 2010 and July 2015, and from a randomly selected, age- and sex-matched non-BTA control population from our prospective database. Anatomical variants of the distal basilar artery region were assessed in the two groups and compared using parametric and non-parametric tests.
RESULTS:
Fifty-nine BTA cases and 337 controls were included. fPCA was present in 3% of patients with BTA and 23% in the control group (p<0.001; OR=0.11, 95% CI 0.03 to 0.48). Basilar tip disposition was cranial in 49% of BTA and 63% of non-BTA cases (p=0.04; OR=0.57, 95% CI 0.33 to 0.99); a caudal disposition was found in 24% and 6% of cases, respectively (p<0.001; OR=4.65, 95% CI 2.21 to 9.80).
CONCLUSIONS:
We found a statistically significant association between the absence of fPCA and BTA. Our findings underline the importance of hemodynamic stress in the formation of intracranial aneurysms, and suggest that fPCA is a protective variant for formation of BTA.info:eu-repo/semantics/publishedVersio
Conducta de los Enfermeros Frente a las Alarmas ClÃnicas en Unidades de Cuidados Intensivos: una Revisión Integradora
O presente estudo tem como propósito refletir sobre a prática de enfermagem no que concerne à temática da monitorização hemodinâmica. Pretendemos identificar a evidência empÃrica produzida sobre o comportamento dos enfermeiros perante os alarmes clÃnicos e, consequentemente, incentivar a adoção de estratégias que promovam um ambiente de cuidados intensivos menos ruidoso. Perspetivou-se um estudo de revisão sistemática da literatura. Selecionámos um conjunto de dezoito bases de dados eletrónicas, tendo recorrido a três idiomas. A colheita de informação decorreu entre dezembro de 2011 e janeiro de 2012 e, através de uma estratégia de cruzamento dos descritores selecionados, foram incluÃdos 5 artigos. Face a todo o corpo de discussão salientamos três categorias essenciais: opinião dos profissionais de saúde acerca dos alarmes clÃnicos; comportamento dos profissionais; estratégias promotoras de um ambiente menos ruidoso. Constatamos que os profissionais de saúde têm presente a bipolaridade dos alarmes clÃnicos e identificam limitações na sua gestão. Verificamos ainda que o comportamento dos profissionais nos estudos analisados não é linear, variando entre alterar os parâmetros no inÃcio de cada turno até ignorar uma grande maioria deles. Cientes desta realidade, os profissionais sugerem diversas estratégias passÃveis de implementar, com vista a alarmes e comportamentos mais eficazes
Activated carbons from the co-pyrolysis of rice wastes for Cr(III) removal
ABSTRACT: Rice husk and polyethylene were mixed (50 % w/w each) and submitted to a pyrolysis assay. Four physical activations with CO2 were performed on the resulting co-pyrolysis char (PC). The activation at 800 °C, for 4h, generated the activated carbon (PAC3) with the best textural properties. PC, PAC3 and a commercial
activated carbon (CAC) were characterized and submitted to Cr(III) removal assays. PC had a high percentage of volatile matter that was removed after the physical activation, resulting in more available pores in the final material (PAC). In the Cr(III) removal assays, two S/L ratios were tested: 5 and 10 g L-1. PC did not remove any Cr(III) from the solutions, but PAC presented similar results to CAC. At the S/L of 5 g L-1, Cr(III) removal was of 58.5 % for PAC and 62.5 % for CAC, both by adsorption mechanism; at the S/L of 10 g L-1, Cr(III) removal was almost complete due to precipitation caused by pH increase. The highest uptake capacities were of 7.92 mg g-1 for PAC and 8.71 mg g-1 for CAC, at the S/L of 5 g L-1. The results indicated that PAC3 may be a viable alternative to CAC on Cr(III) removal from aqueous media.info:eu-repo/semantics/publishedVersio
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