The employment of maximum power point tracking techniques in the
photovoltaic power systems is well known and even of immense importance. There
are various techniques to track the maximum power point reported in several
literatures. In such context, there is an increasing interest in developing a
more appropriate and effective maximum power point tracking control methodology
to ensure that the photovoltaic arrays guarantee as much of their available
output power as possible to the load for any temperature and solar radiation
levels. In this paper, theoretical details of the work, carried out to develop
and implement a maximum power point tracking controller using neural networks
for a stand-alone photovoltaic system, are presented. Attention has been also
paid to the command of the power converter to achieve maximum power point
tracking. Simulations results, using Matlab/Simulink software, presented for
this approach under rapid variation of insolation and temperature conditions,
confirm the effectiveness of the proposed method both in terms of efficiency
and fast response time. Negligible oscillations around the maximum power point
and easy implementation are the main advantages of the proposed maximum power
point tracking (MPPT) control method.
essential oil composition of Thymus vulgaris L. and Rosmarinus officinalis L.
endemic to France were determined by GC and GC-MS. Oils were assessed for their
cytotoxic, antioxidant and antimicrobial activity. 31 and 37 different
compounds were identified representing 99.64% and 99.38% of the thyme and
rosemary oils respectively, where oxygenated monoterpenes constituted the
main chemical class. Thymol (41.33%) and 1.8-cineole (24.10%) were identified
as the main constituents of T. vulgaris L. and R. officinalis L., respectively.
Essential oils (EOs) of selected plant species were evaluated for their in
vitro cytotoxicity against the human lung adenocarcinoma epithelial cell line
(A549). Cytotoxicity was measured using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphynyltetra-zolium bromide] colorimetric assay. Dose-dependent studies revealed IC50 of
8.50 ± 0.01 μg/mL and 10.50 ± 0.01 μg/mL after 72 h on the A549 cells for R.
officinalis L. and T. vulgaris L., respectively. Antioxidant activity was
determined using a quantitative DPPH (1,1-diphenyl- 2-picryl hydrazyl) assay.
Thymus and rosemary EOs exhibited effective radical scavenging capacity with
50% inhibitory concentration (IC50) of 437 ± 5.46 μg/mL and 189 ± 2.38 μg/mL
respectively and therefore acts as a natural antioxidant agent. The
antimicrobial activity of these species has also been studied against several
foodborne pathogens and food isolated Salmonella spp. including S.
enteritidis of significant importance. According to the results, T. vulgaris
L. showed higher bactericidal effect than those from R. officinalis L. These
results suggest that the essential oil from T. vulgaris L. and R. officinalis
L. have potential to be used as a natural cytotoxic, antioxidant and antimicrobial
agent in food processing.