34 research outputs found
Assessment of the impact of the European CO2 emissions trading scheme on the Portuguese chemical industry
This paper describes an assessment of the impact of the enforcement of the European carbon dioxide (CO2) emissions trading scheme on the Portuguese chemical industry, based on cost structure, CO2 emissions, electricity consumption and allocated allowances data from a survey to four Portuguese representative units of the chemical industry sector, and considering scenarios that allow the estimation of increases on both direct and indirect production costs. These estimated cost increases were also compared with similar data from other European Industries, found in the references and with conclusions from simulation studies. Thus, it was possible to ascertain the impact of buying extra CO2 emission permits, which could be considered as limited. It was also found that this impact is somewhat lower than the impacts for other industrial sectors
A Vigilância Sanitária no controle de riscos potenciais em serviços de hemoterapia no Brasil
Non-Centered Spike-Triggered Covariance Analysis Reveals Neurotrophin-3 as a Developmental Regulator of Receptive Field Properties of ON-OFF Retinal Ganglion Cells
The functional separation of ON and OFF pathways, one of the fundamental features of the visual system, starts in the retina. During postnatal development, some retinal ganglion cells (RGCs) whose dendrites arborize in both ON and OFF sublaminae of the inner plexiform layer transform into RGCs with dendrites that monostratify in either the ON or OFF sublamina, acquiring final dendritic morphology in a subtype-dependent manner. Little is known about how the receptive field (RF) properties of ON, OFF, and ON-OFF RGCs mature during this time because of the lack of a reliable and efficient method to classify RGCs into these subtypes. To address this deficiency, we developed an innovative variant of Spike Triggered Covariance (STC) analysis, which we term Spike Triggered Covariance – Non-Centered (STC-NC) analysis. Using a multi-electrode array (MEA), we recorded the responses of a large population of mouse RGCs to a Gaussian white noise stimulus. As expected, the Spike-Triggered Average (STA) fails to identify responses driven by symmetric static nonlinearities such as those that underlie ON-OFF center RGC behavior. The STC-NC technique, in contrast, provides an efficient means to identify ON-OFF responses and quantify their RF center sizes accurately. Using this new tool, we find that RGCs gradually develop sensitivity to focal stimulation after eye opening, that the percentage of ON-OFF center cells decreases with age, and that RF centers of ON and ON-OFF cells become smaller. Importantly, we demonstrate for the first time that neurotrophin-3 (NT-3) regulates the development of physiological properties of ON-OFF center RGCs. Overexpression of NT-3 leads to the precocious maturation of RGC responsiveness and accelerates the developmental decrease of RF center size in ON-OFF cells. In summary, our study introduces STC-NC analysis which successfully identifies subtype RGCs and demonstrates how RF development relates to a neurotrophic driver in the retina
A Reaction-Diffusion Model to Capture Disparity Selectivity in Primary Visual Cortex
Decades of experimental studies are available on disparity selective cells in visual cortex of macaque and cat. Recently, local disparity map for iso-orientation sites for near-vertical edge preference is reported in area 18 of cat visual cortex. No experiment is yet reported on complete disparity map in V1. Disparity map for layer IV in V1 can provide insight into how disparity selective complex cell receptive field is organized from simple cell subunits. Though substantial amounts of experimental data on disparity selective cells is available, no model on receptive field development of such cells or disparity map development exists in literature. We model disparity selectivity in layer IV of cat V1 using a reaction-diffusion two-eye paradigm. In this model, the wiring between LGN and cortical layer IV is determined by resource an LGN cell has for supporting connections to cortical cells and competition for target space in layer IV. While competing for target space, the same type of LGN cells, irrespective of whether it belongs to left-eye-specific or right-eye-specific LGN layer, cooperate with each other while trying to push off the other type. Our model captures realistic 2D disparity selective simple cell receptive fields, their response properties and disparity map along with orientation and ocular dominance maps. There is lack of correlation between ocular dominance and disparity selectivity at the cell population level. At the map level, disparity selectivity topography is not random but weakly clustered for similar preferred disparities. This is similar to the experimental result reported for macaque. The details of weakly clustered disparity selectivity map in V1 indicate two types of complex cell receptive field organization
Phosphodiesterase Inhibition Increases CREB Phosphorylation and Restores Orientation Selectivity in a Model of Fetal Alcohol Spectrum Disorders
Background: Fetal alcohol spectrum disorders (FASD) are the leading cause of mental retardation in the western world and children with FASD present altered somatosensory, auditory and visual processing. There is growing evidence that some of these sensory processing problems may be related to altered cortical maps caused by impaired developmental neuronal plasticity. Methodology/Principal Findings: Here we show that the primary visual cortex of ferrets exposed to alcohol during the third trimester equivalent of human gestation have decreased CREB phosphorylation and poor orientation selectivity revealed by western blotting, optical imaging of intrinsic signals and single-unit extracellular recording techniques. Treating animals several days after the period of alcohol exposure with a phosphodiesterase type 1 inhibitor (Vinpocetine) increased CREB phosphorylation and restored orientation selectivity columns and neuronal orientation tuning. Conclusions/Significance: These findings suggest that CREB function is important for the maturation of orientation selectivity and that plasticity enhancement by vinpocetine may play a role in the treatment of sensory problems in FASD
Feedstock recycling of polyethylene over A1TUD-1 mesoporous catalyst
The catalytic degradation of high density polyethylene (HDPE) was investigated using AITUD-1 as catalyst, a recently discovered mesoporous alummosilicate. The catalytic activity of AITUD-1 was evaluated by TGA measurements, using a polymer/catalyst ratio of 9:1. AITUD-1 has a Bronsted acidic behaviour, three-dimensional (31)) connectivities and a pore diameters between 2 and 50 nm. Compared to HY zeolite, the large pore size of AITUD- I enhances a selective catalytic degradation of the polymer and prevents rapid deactivation. Moreover, the apparent activation energy of polymer cracking is much lower than with HY zeolite. For these reasons, AITUD- 1 is a potentially interesting catalyst for the catalytic cracking of plastic waste into liquid fuels. (c) 2007 Elsevier Ltd. All rightsThe authors are thankful to Dr. A.S. Azevedo (Departamento de Ciências da Terra of University of Minho, Portugal) and to N. van der Pers (Delft University of Technology, the Netherlands) for collecting the powder diffraction data. This work was supported by the Centro de QuÃmica (University of Minho, Portugal) and by Fundação para a Ciência e Tecnologia (FCT-Portugal), under programme POCTI-SFA-3-686
Antillatoxin, a Novel Lipopeptide, Enhances Neurite Outgrowth in Immature Cerebrocortical Neurons through Activation of Voltage-Gated Sodium ChannelsS⃞
Antillatoxin (ATX) is a structurally novel lipopeptide that activates voltage-gated
sodium channels (VGSC) leading to sodium influx in cerebellar granule neurons and
cerebrocortical neurons 8 to 9 days in vitro (Li et
al., 2001; Cao et al., 2008).
However, the precise recognition site for ATX on the VGSC remains to be defined.
Inasmuch as elevation of intracellular sodium ([Na+]i) may
increase N-methyl-d-aspartate receptor (NMDAR)-mediated
Ca2+ influx, Na+ may function as a signaling molecule. We
hypothesized that ATX may enhance neurite outgrowth in cerebrocortical neurons by
elevating [Na+]i and augmenting NMDAR function. ATX
(30–100 nM) robustly stimulated neurite outgrowth, and this enhancement
was sensitive to the VGSC antagonist, tetrodotoxin. To unambiguously demonstrate the
enhancement of NMDA receptor function by ATX, we recorded single-channel currents
from cell-attached patches. ATX was found to increase the open probability of NMDA
receptors. Na+-dependent up-regulation of NMDAR function has been shown to
be regulated by Src family kinase (SFK) (Yu and
Salter, 1998). The Src kinase inhibitor PP2 abrogated ATX-enhanced neurite
outgrowth, suggesting a SFK involvement in this response. ATX-enhanced neurite
outgrowth was also inhibited by the NMDAR antagonist,
(5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine
hydrogen maleate (MK-801), and the calmodulin-dependent kinase kinase (CaMKK)
inhibitor, 1,8-naphthoylene benzimidazole-3-carboxylic acid (STO-609), demonstrating
the requirement for NMDAR activation with subsequent downstream engagement of the
Ca2+-dependent CaMKK pathway. These results with the structurally and
mechanistically novel natural product, ATX, confirm and generalize our earlier
results with a neurotoxin site 5 ligand. These data suggest that VGSC activators may
represent a novel pharmacological strategy to regulate neuronal plasticity through
NMDAR-dependent mechanisms