Aerosol optical depth studies during INDOEX: comparison of the spectral features over coastal India with the pristine southern hemispheric environment over Mauritius

Aerosol spectral optical depths, estimated using a ground-based network of multi wavelength radiometers (MWR) along the west coast of India [Trivandrum (TVM; 8.5°N, 77°E), and Minicoy (MCY; 8.3°N, 73.04°E)] and the pristine southern hemispheric environment at Mauritius (MRU; 20.26°S, 57.54°E) during the period January to June 1998 along with those obtained over the Arabian Sea and Indian Ocean during the INDOEX FFP-98 cruise (SK133) of ORV Sagar Kanya, are used to study the inter-hemispheric features of aerosols. Results indicate that there is a significant hemispherical difference for aerosol spectral optical depth (AOD) at shorter wavelengths (λ≤ 650 nm), while at the longer wavelengths (λ > 650 nm), AOD does not show any appreciable variation with location. The spectral variation of AOD at TVM and MCY (for March 1998) depicted a similar pattern with the AOD values between 0.5 and 0.6 at shorter wavelengths and between 0.2 and 0.4 at longer wavelengths. In contrast to this, the AOD at MRU are very low, lying in the range 0.1 to 0.2 in the shorter wavelengths, whereas at the longer wavelengths the AOD values are more or less comparable (in the range 0.2 to 0.4) with the northern hemispheric stations. The cruise data clearly showed that the transition occurs generally across the ITCZ. The increased AOD at shorter wavelengths in the northern hemisphere indicates higher concentration of sub-micron aerosols in these environments arising mainly due to anthropogenic activities, while the AOD at the longer wavelengths is attributed mainly to be of marine origin. In the post-cruise period, the spectral optical depths showed a gradual increase from March to June at MRU, while at TVM, the pattern followed more or less the climatological mean. By May the AOD at shorter wavelengths decreased at TVM (due to increased rainfall) and by June, the AOD at TVM are very much comparable with those seen at MRU, indicating a dominating marine aerosol influence at both these locations. The implications are discussed

Installation of an automatic spectrometer at Mauritius and preliminary results of NO2 over Mauritius

An automatic spectrometer developed at Indian Institute of Tropical Meteorology Pune is installed at the University of Mauritius, Reduit, Mauritius for monitoring total column density of NO2 and O3. The spectrometer is programmed for observations between 80° and 90° solar zenith angles in the spectral region 410-450 nm. The observations collected for few days during September and October 1998 are analysed, and total column densities of NO2 found to be of the order of 4* 1015 molecules per cm2. This preliminary result compares with similar southern latitude stations

A Review Of New Trends In Lactide Polymerisation Based On Metal Complexes

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Poly(ester-ether)s: III. assessment of cell behaviour on nanofibrous scaffolds of PCL, PLLA and PDX blended with amorphous PMeDX

The aim of this paper is to investigate the physico-chemical properties, degradation behaviour and cellular response of electrospun fibre-scaffolds of semi-crystalline PCL, PLLA and PDX blended with amorphous poly(methyl dioxanone) (PMeDX). Electrospun PCL/PMeDX and PLLA/PMeDX blend mats in varying weight ratios of the two components were fabricated and their overall performance was compared with similar composition PDX/PMeDX scaffolds. DSC analysis showed almost no change in crystallization temperature of PCL with increasing PMeDX content and TGA showed a different degradation profile as PMeDX content increased. The appearance of two crystallization peaks for PLLA/PMeDX blends suggested stereocomplex formation. As noted from AFM images, addition of PMeDX caused a change in the width of the lamellae from 14.8 ± 2.9 nm in 100/0 mat to 32.0 ± 11.5 nm in 85/15 mat. Moreover, PCL/PMeDX blend mats show a significant drop in Young\u27s modulus for 93/7, 90/10 and 85/15 compositions compared to 100/0 and 98/2. On the other hand, no clear trend in mechanical properties was observed for espun PLLA/PMeDX mats with increasing PMeDX content. Based on these analyses, it was concluded that PCL and PMeDX were immiscible while miscible blends were obtained with PLLA and PMeDX. Initial degradation of electrospun mats over a period of 5 weeks appears to occur via a surface erosion mechanism. In vitro cell culture studies using HDFs showed that the scaffolds were bioactive and a greater density of viable cells was noted on electrospun PCL/PMeDX and PLLA/PMeDX scaffolds compared to PCL and PLLA mats respectively. HDFs infiltrated through the entire thickness of espun 85/15 PLLA/PMeDX scaffold due to a combination of factors including morphology, porosity, surface characteristics and mechanical properties. This journal i

Aerosol optical depths over peninsular India and adjoining oceans during the INDOEX campaigns: spatial, temporal, and spectral characteristics

The spatial, temporal, and spectral characteristics of aerosol optical depths τ p λ for the Indian Ocean Experiment (INDOEX) study period (January to April) are examined using data collected through a ground-based network of multiwavelength solar radiometers (MWR) over coastal regions of peninsular India; two island locations, one in the Arabian Sea and another in the southern Indian Ocean at 20°S; in conjunction with estimates made over various locations over the Arabian Sea and Indian Ocean during the INDOEX cruises of 1996, 1998, and 1999. Spatial variations show extremely low values of τ p at the shorter (visible) wavelengths (λ<750 nm) to the south of the Intertropical Convergence Zone (ITCZ), but increases substantially at locations due north of the ITCZ due to increased source impact and advection by favorable winds. An enhancement in τ p is seen in the central Arabian Sea, which is attributed to air trajectory effects. Ångström parameters, deduced from optical depth spectra, reveal a high value of α (∼0.9) for north of the ITCZ, while for the south α is negative, indicating a change in the aerosol size distribution. Accumulation aerosols dominate in the north, while concentration of coarse aerosols remain nearly about the same, except very close to the coast. A north-south gradient in aerosol optical depth, with scaling distance of ∼1000 to 2000 km at shorter wavelengths and much higher at longer wavelengths, is observed. The gradient becomes shallower at high wind speeds. The large-scale dynamics associated with the movement of the ITCZ and its interannual variation appears to significantly influence the aerosol characteristics. As the southwest monsoon sets in over India, considerable wet removal and change in air mass characteristics cause a significant depletion in optical depths, which then became comparable to those prevailing in the southern hemisphere

Iron Content of <i>Saccharomyces cerevisiae</i> Cells Grown under Iron-Deficient and Iron-Overload Conditions

Fermenting cells were grown under Fe-deficient and Fe-overload conditions, and their Fe contents were examined using biophysical spectroscopies. The high-affinity Fe import pathway was active only in Fe-deficient cells. Such cells contained ∼150 μM Fe, distributed primarily into nonheme high-spin (NHHS) Fe^II species and mitochondrial Fe. Most NHHS Fe^II was not located in mitochondria, and its function is unknown. Mitochondria isolated from Fe-deficient cells contained [Fe₄S₄]²⁺ clusters, low- and high-spin hemes, <i>S</i> = ¹/₂ [Fe₂S₂]⁺ clusters, NHHS Fe^II species, and [Fe₂S₂]²⁺ clusters. The presence of [Fe₂S₂]²⁺ clusters was unprecedented; their presence in previous samples was obscured by the spectroscopic signature of Fe^III nanoparticles, which are absent in Fe-deficient cells. Whether Fe-deficient cells were grown under fermenting or respirofermenting conditions had no effect on Fe content; such cells prioritized their use of Fe to essential forms devoid of nanoparticles and vacuolar Fe. The majority of Mn ions in wild-type yeast cells was electron paramagnetic resonance-active Mn^II and not located in mitochondria or vacuoles. Fermenting cells grown on Fe-sufficient and Fe-overloaded medium contained 400–450 μM Fe. In these cells, the concentration of nonmitochondrial NHHS Fe^II declined 3-fold, relative to that in Fe-deficient cells, whereas the concentration of vacuolar NHHS Fe^III increased to a limiting cellular concentration of ∼300 μM. Isolated mitochondria contained more NHHS Fe^II ions and substantial amounts of Fe^III nanoparticles. The Fe contents of cells grown with excessive Fe in the medium were similar over a 250-fold change in nutrient Fe levels. The ability to limit Fe import prevents cells from becoming overloaded with Fe

Mössbauer Study and Modeling of Iron Import and Trafficking in Human Jurkat Cells

The Fe content of Jurkat cells grown on transferrin-bound iron (TBI) and Fe^III citrate (FC) was characterized using Mössbauer, electron paramagnetic resonance, and UV–vis spectroscopies, as well as electron and inductively coupled plasma mass spectrometry. Isolated mitochondria were similarly characterized. Fe-limited cells contained ∼100 μM essential Fe, mainly as mitochondrial Fe and nonmitochondrial non-heme high-spin Fe^II. Cells replete with Fe also contained ferritin-bound Fe and Fe^III oxyhydroxide nanoparticles. Only 400 ± 100 Fe ions were loaded per ferritin complex, regardless of the growth medium Fe concentration. Ferritin regulation thus appears to be more complex than is commonly assumed. The magnetic and structural properties of Jurkat nanoparticles differed from those of yeast mitochondria. They were smaller and may be located in the cytosol. The extent of nanoparticle formation scaled nonlinearly with the concentration of Fe in the medium. Nanoparticle formation was not strongly correlated with reactive oxygen species (ROS) damage. Cells could utilize nanoparticle Fe, converting such aggregates into essential Fe forms. Cells grown on galactose rather than glucose respired faster, grew slower, exhibited more ROS damage, and generally contained more nanoparticles. Cells grown with TBI rather than FC contained less Fe overall, more ferritin, and fewer nanoparticles. Cells in which the level of transferrin receptor expression was increased contained more ferritin Fe. Frataxin-deficient cells contained more nanoparticles than comparable wild-type cells. Data were analyzed by a chemically based mathematical model. Although simple, it captured essential features of Fe import, trafficking, and regulation. TBI import was highly regulated, but FC import was not. Nanoparticle formation was not regulated, but the rate was third-order in cytosolic Fe

Biophysical Investigation of the Ironome of Human Jurkat Cells and Mitochondria

The speciation of iron in intact human Jurkat leukemic cells and their isolated mitochondria was assessed using biophysical methods. Large-scale cultures were grown in medium enriched with ⁵⁷Fe citrate. Mitochondria were isolated anaerobically to prevent oxidation of iron centers. 5 K Mössbauer spectra of cells were dominated by a sextet due to ferritin. They also exhibited an intense central quadrupole doublet due to <i>S</i> = 0 [Fe₄S₄]²⁺ clusters and low-spin (LS) Fe^II heme centers. Spectra of isolated mitochondria were largely devoid of ferritin but contained the central doublet and features arising from what appear to be Fe^III oxyhydroxide (phosphate) nanoparticles. Spectra from both cells and mitochondria contained a low-intensity doublet from non-heme high-spin (NHHS) Fe^II species. A portion of these species may constitute the “labile iron pool” (LIP) proposed in cellular Fe trafficking. Such species might engage in Fenton chemistry to generate reactive oxygen species. Electron paramagnetic resonance spectra of cells and mitochondria exhibited signals from reduced Fe/S clusters, and HS Fe^III heme and non-heme species. The basal heme redox state of mitochondria within cells was reduced; this redox poise was unaltered during the anaerobic isolation of the organelle. Contributions from heme <i>a</i>, <i>b</i>, and <i>c</i> centers were quantified using electronic absorption spectroscopy. Metal concentrations in cells and mitochondria were measured using inductively coupled plasma mass spectrometry. Results were collectively assessed to estimate the concentrations of various Fe-containing species in mitochondria and whole cells  the first “ironome” profile of a human cell