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Kohl, a facial salve used in
ancient times as a symbol of affluence, now enjoys more widespread
traditional followings, for cosmetic, religious and supposed medicinal
purposes. Popularly used by women and men of all ages, particularly those of
North African, Middle Eastern, Southern Asia, Japanese and Chinese origins,
it is also known to be used on neonates and children from such populations.
With small-scale producers of kohl possessing a growing awareness of the
adverse market impact of products that contain (lead) Pb and other toxicity
related elements, some claim their products to be Pb-free, offering an
apparent change from the more traditional galena-based (lead sulphide) media.
Among the published physiological effects of exposure to Pb is that it replaces
Ca in bones and teeth, making them weak and fragile, other impacts including
nephrotoxicity, also linked with increased Pb blood levels in studies in
Oman, Canada, Saudi Arabia, India and Pakistan. Current study involves XRF
analysis of Pb, Fe and Zn concentrations in 135 samples of kohl from nine
randomly selected suppliers (15 samples of each brand being represented). In
pursuit of this, use was made of an in-house assembled facility comprising
compact high-performance components, the arrangement offering sufficient
sensitivity for the purposes of present study. In most of the samples
investigated in the present study observation has been made of concentrations
of Pb at elevated levels, quantification of those levels also demonstrating a
need to address self-attenuation by the Pb itself. Significant concentration
of Fe have also been found in several of the samples.
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ملخص المشاركة:
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Graphite ion chambers and
semiconductor diode detectors have been used to make measurements in phantoms
but these active devices represent a clear disadvantage when considered
for in vivo dosimetry. In such circumstance, dosimeters with
atomic number similar to human tissue are needed. Carbon nanotubes have
properties that potentially meet the demand, requiring low voltage in active
devices and an atomic number similar to adipose tissue. In this study,
single-wall carbon nanotubes (SWCNTs) buckypaper has been used to measure the
beta particle dose deposited from a strontium-90 source, the medium
displaying thermoluminescence at potentially useful sensitivity. As an
example, the samples show a clear response for a dose of 2 Gy. This
finding suggests that carbon nanotubes can be used as a passive dosimeter
specifically for the high levels of radiation exposures used in radiation
therapy. Furthermore, the finding points towards further potential
applications such as for space radiation measurements, not least because the
medium satisfies a demand for light but strong materials of minimal
capacitance.
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ملخص المشاركة:
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We focus on the development of
Ge-doped silica thermoluminescent dosimeters with sensitivity superior to
that of the LiF (Mg,Ti) phosphors popularly used in x-ray diagnostic imaging
dosimetry, the latter typically being referred to through use of the product
identifier TLD-100. Of interest are Ge-doped silica telecommunication fibres
(SMF) and tailor-made doped photonic crystal fibres (PCFc), the latter
Ge-doped or also co-doped with boron. The PCFs are formed of capillaries that
at high temperatures and under vacuum are made to collapse inwards (PCFc),
the internal walls fusing and generating strain-related defects. To-date, the
fabricated SMF, PCFc-Ge and PCFc-Ge-B have been observed to provide TL yields
which weight-for-weight are some 2, 10 and 15x that of TLD-100. In present
study we test the linearity of TL yield for x-ray doses from 0.1- to
10 mGy, use being made of an x-ray tube operated at 80 kVp, an operating
potential typically selected in chest radiography. For a dose of 10 mGy,
a study of energy dependence has been conducted using x-ray tube potentials
of 80 kVp 100 kVp, and 120 kVp, with inherent filtration 0.9 mm Al
measured at 75 kVp, and total filtration of 2.8 mm Al at 80 kVp.
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