Clear cell renal cell carcinoma with focal psammomatous calcifications: a rare occurrence mimicking translocation carcinoma

AIMS

Renal cell carcinoma (RCC) with clear cells and psammoma-like calcifications would often raise suspicion for MITF family translocation RCC. However, we have rarely encountered tumours consistent with clear cell RCC that contain focal psammomatous calcifications.

METHODS AND RESULTS

We identified clear cell RCCs with psammomatous calcifications from multiple institutions and performed immunohistochemistry and fluorescence and RNA in-situ hybridisation (FISH and RNA ISH). Twenty-one tumours were identified: 12 men, nine women, aged 45-83 years. Tumour size was 2.3-14.0 cm (median = 6.75 cm). Nucleolar grade was 3 (n = 14), 2 (n = 4) or 4 (n = 3). In addition to clear cell pattern, morphology included eosinophilic (n = 12), syncytial giant cell (n = 4), rhabdoid (n = 2), branched glandular (n = 1), early spindle cell (n = 1) and poorly differentiated components (n = 1). Labelling for CA9 was usually 80-100% of the tumour cells (n = 17 of 21), but was sometimes decreased in areas of eosinophilic cells (n = 4). All (19 of 19) were positive for CD10. Most (19 of 20) were positive for AMACR (variable staining = 20-100%). Staining was negative for keratin 7, although four showed rare positive cells (four of 20). Results were negative for cathepsin K (none of 19), melan A (none of 17), HMB45 (none of 17), TFE3 (none of 5), TRIM63 RNA ISH (none of 13), and TFE3 (none of 19) and TFEB rearrangements (none of 12). Seven of 19 (37%) showed chromosome 3p deletion. One (one of 19) showed trisomy 7 and 17 without papillary features.

CONCLUSIONS

Psammomatous calcifications in RCC with a clear cell pattern suggests a diagnosis of MITF family translocation RCC; however, psammomatous calcifications can rarely be found in true clear cell RCC.

Low-grade oncocytic tumour of the kidney is characterised by genetic alterations of TSC1, TSC2, MTOR or PIK3CA and consistent GATA3 positivity

Low-grade oncocytic tumour (LOT) of the kidney has recently emerged as a potential novel tumour type. Despite similarity to oncocytoma or eosinophilic chromophobe renal cell carcinoma, it shows diffuse keratin 7 immunohistochemistry (IHC) and negative KIT (CD117), which differs from both. We aimed to identify the molecular characteristics of these tumours. Seventeen tumours (one male, 16 female, nine previously published) fitting the original description of this entity (solid eosinophilic cell morphology, often with areas of tumour cells loosely stretched in oedematous stroma, and the above IHC features) were analysed with a next-generation sequencing panel of 324 cancer-associated genes from formalin-fixed, paraffin-embedded tissue. All tumours harboured at least one alteration in either TSC1 (n = 7, 41%), TSC2 (n = 2, 12%), MTOR (n = 5, 29%) or PIK3CA (n = 4, 24%). Four tumours harboured a second alteration, including two NF2, one each in conjunction with MTOR and TSC2 alterations, one PTEN with TSC1 alteration and one tumour with both MTOR and TSC1 alterations. No other renal cancer-related or recurring gene alterations were identified. In addition to the previously described IHC findings, 16 of 16 were positive for GATA3. Eleven patients with follow-up had no metastases or recurrent tumours. Recurrent tuberous sclerosis/MTOR pathway gene alterations in LOT support its consideration as a distinct morphological, immunohistochemical and genetic entity. PIK3CA is another pathway member that may be altered in these tumours. Further study will be necessary to determine whether tumour behaviour or syndromic associations differ from those of oncocytoma and chromophobe carcinoma, warranting different clinical consideration.

Abstract 2100: The impact of race on the relationship between poly-CpG DNA methylation and mRNA expression in cancer with application to epigenome-wide association studies

DNA methylation is a known regulator of mRNA expression. Recent studies in cancer have shown that significant proportions of the variability in mRNA expression can be explained by variation in DNA methylation. However, none of these studies have investigated the influence of race on this relationship. Here, we develop poly-CpG site models of gene expression that facilitate the quantification of race-specific effects on the regulatory connection between methylation and transcriptional gene expression. Paired Illumina 450k methylation and RNA-Seq gene expression data from The Cancer Genome Atlas (TCGA) was used to develop poly-CpG site elastic net penalized Poisson regression models of gene expression that account for race-by-CpG interactions for each of the eight TCGA tumor types with African American (AA) representation (>40 tumors each). Race-specific effects were summarized as the percentage of CpGs in a gene model with retained interaction terms. The method was applied to methylation data from an AA radical prostatectomy prostate cancer cohort (n=261) to generate predicted gene expression estimates that were used to perform a mechanistic epigenome-wide association study (EWAS) of Gleason grade (≤3+4 and ≥4+3 tumors). High percentages of variability in mRNA expression can be explained by poly-CpG site models, incorporating race specific effects, with tumor type ranges of 62-90% overall, 64-87% for AAs, and 64-92% for European Americans (EAs). Race played a significant role in the relationship between methylation and mRNA expression, with 86-97% of gene models containing at least one CpG site with a race-specific effect. Further, the median percentage of CpGs in a gene model with race-specific effects ranging from 11-18%. For these race-specific effects, the vast majority (>99%) had the same direction of association between the CpG site and gene expression in both AAs and EAs but with differing magnitudes. Application of this approach identified unique methylation alterations (97%) associated with Gleason grade compared with single site and comb-p region-based

EWAS. In summary, this poly-CpG site modelling approach revealed a significant impact of race in the regulatory relationship between methylation and gene expression. The high percentage of genes -and CpG sites within those genes- demonstrating race-specific effects was a general phenomenon observed across all eight tumor types investigated. In addition to revealing this previously underappreciated contribution of race, the application of the predicted gene expression output from these poly-CpG site models to perform a gene-based EWAS of Gleason grade demonstrated that it provides a) complementary information to commonly used EWAS methods and b) direct expression-based mechanistic interpretation of findings from an AA methylation-based EWAS of prostate cancer.

Citation Format: Ian M. Loveless, Yalei Chen, Sudha Sadasivan, Indrani Datta, Nilesh Gupta, Pamela Paris, Jia Li, Benjamin A. Rybicki, Albert M. Levin. The impact of race on the relationship between poly-CpG DNA methylation and mRNA expression in cancer with application to epigenome-wide association studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2100.

Potential effect of anti-inflammatory drug use on PSA kinetics and subsequent prostate cancer diagnosis: Risk stratification in black and white men with benign prostate biopsy

BACKGROUND

Rising prostate-specific antigen (PSA) levels are associated with both increased risk of prostate cancer and prostatic inflammation. The confounding effects of inflammation on the utility of PSA kinetics to predict prostate cancer may be partially mitigated by anti-inflammatory drug use. We investigated the influence of anti-inflammatory drug use on the association of PSA kinetics with prostate cancer risk.

METHODS

We studied 488 prostate cancer case-control pairs (290 white, 198 African American (AA)) nested in a retrospective cohort of men with a benign prostate biopsy. A series of multivariable models estimated prostate cancer risk associated with PSA velocity (PSAV) at different levels of anti-inflammatory drug use while adjusting for the presence of both clinical and histologic prostatitis.

RESULTS

In men with one, two, or three or more courses of anti-inflammatory drug use, for each ng/mL/year increase in PSAV, prostate cancer risk increased 1.21-fold, 1.83-fold, and 1.97-fold, respectively ( P < 0.0001). In controls with histologic prostatitis, anti-inflammatory drug use was associated with a significantly lower PSAV ( P < 0.0001). This association was not observed in men with histologic prostatitis who were subsequently diagnosed with prostate cancer. A positive interaction between anti-inflammatory drug use and PSAV-associated prostate cancer risk was only observed in AA men, as well as a strong positive association between any anti-inflammatory drug use and clinical prostatitis ( P = 0.004).

CONCLUSIONS

In men with benign prostate biopsy, accounting for the presence of histologic prostatitis and anti-inflammatory drug use, particularly in AA men, may help distinguish between men with rising PSA because of prostatitis vs undiagnosed cancer.

Abstract 4231: Breast and prostate cancers harbor common somatic copy number alterations that consistently differ by race-ethnicity

Pan-cancer studies of somatic copy number alterations (SCNAs) have demonstrated shared SCNAs across cancer types, but whether these shared SCNAs vary by race-ethnicity has not been explored. Utilizing data from The Cancer Genome Atlas (TCGA), we identified SCNAs in breast and prostate tumors, two cancers with racially-disparate outcomes, and then tested for differences in SCNA magnitude by self-reported African American and European American race-ethnicity, as well as by regional chromosomal African ancestry within African Americans. GISTIC2 was applied to high density SNP array data to map SCNA regions in 712 European and 174 African American female breast tumors and 267 European and 42 African American prostate tumors derived from the TCGA dataset. For each tumor, SCNA magnitude was quantified by the area under the logarithm-base 2 copy number curve, and the germline ancestral origin of SCNAs was inferred using RFMix. A linear model was used to assess the association between SCNA magnitude and race-ethnicity (or regional African ancestry) while adjusting age-at-diagnosis and tumor severity. Race-differentiated SCNAs common to breast and prostate were found at chromosomes 5q11-21, 6q12-14, 6q16-22, 8q21-24, 11q22, 13q12-21, and 16q21-24, with 8q21-24 being the only amplification. African American breast and prostate tumors had higher magnitude alterations in the regions on 5q11-21, 8q21-24, 11q22, and 13q12-21, and among African Americans, this higher magnitude at 8q21-24 and 13q12-21 was consistent with increasing regional African ancestry. Within these regions with higher magnitude SCNAs in African Americans, expression analysis revealed 18 cancer genes, including RB1 and PVT1, differentially expressed by race-ethnicity in both tumors types that were consistent with the observed SCNA differences. While differences in SCNAs by race-ethnicity have been studied in single cancers, this is the first study to identify race-differentiated SCNAs shared by two hormonally-driven cancers and to explore the potential of germline genetic ancestry as a mechanism leading to this differentiation. The differentially expressed genes within SCNAs common to both tumor types could provide further insight into the racially disparate outcomes in breast and prostate cancers.

Citation Format: Yalei Chen, Jia Li, Sudha Sadasivan, Ruicong She, Indrani Datta, Dhananjay Chitale, Nilesh Gupta, Melissa B. Davis, Craig G. Rogers, Lisa A. Newman, Pamela L. Paris, Benjamin A. Rybicki, Albert M. Levin. Breast and prostate cancers harbor common somatic copy number alterations that consistently differ by race-ethnicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4231.

Larger men have larger prostates: Detection bias in epidemiologic studies of obesity and prostate cancer risk

BACKGROUND

Obesity is associated with risk of aggressive prostate cancer (PCa), but not with over-all PCa risk. However, obese men have larger prostates which may lower biopsy accuracy and cause a systematic bias toward the null in epidemiologic studies of over-all risk.

METHODS

Within a cohort of 6692 men followed-up after a biopsy or transurethral resection of the prostate (TURP) with benign findings, a nested case-control study was conducted of 495 prostate cancer cases and controls matched on age, race, follow-up duration, biopsy versus TURP, and procedure date. Data on body mass index and prostate volume at the time of the initial procedure were abstracted from medical records.

RESULTS

Prior to consideration of differences in prostate volume, overweight (OR = 1.41; 95%CI 1.01, 1.97), and obese status (OR = 1.59; 95%CI 1.09, 2.33) at the time of the original benign biopsy or TURP were associated with PCa incidence during follow-up. Prostate volume did not significantly moderate the association between body-size and PCa, however it did act as an inverse confounder; adjustment for prostate volume increased the effect size for overweight by 22% (adjusted OR = 1.52; 95%CI 1.08, 2.14) and for obese status by 23% (adjusted OR = 1.77; 95%CI 1.20, 2.62). Larger prostate volume at the time of the original benign biopsy or TURP was inversely associated with PCa incidence during follow-up (OR = 0.92 per 10 cc difference in volume; 95%CI 0.88, 0.97). In analyses that stratified case-control pairs by tumor aggressiveness of the case, prostate volume acted as an inverse confounder in analyses of non-aggressive PCa but not in analyses of aggressive PCa.

CONCLUSIONS

In studies of obesity and PCa, differences in prostate volume cause a bias toward the null, particularly in analyses of non-aggressive PCa. A pervasive underestimation of the association between obesity and overall PCa risk may exist in the literature.

Malaysian Medical Students' self-reported Empathy: A cross-sectional Comparative Study

OBJECTIVES

The objective of this study was to compare empathy levels between first year and second year medical students at a Malaysian University.

SETTING

A Malaysian University offering undergraduate medicine.

PARTICIPANTS

204 undergraduate medical students were included in the data analysis (122 first years, and 102 second years).

MAIN OUTCOME MEASURE

Self-reported empathy scores using the Jefferson Scale of Physician Empathy (Student Version) JSPE-S.

RESULTS

The mean empathy score for first year students was 112.1(SD=10.7). This was significantly higher (p<0.038; d=0.31) than second year students (mean=108.8, SD=10.4). No significant difference relating to gender was identified.

CONCLUSION

Cross-sectional results from this study found that that there were differences in self-reported empathy scores between year one and year two students. Further research is required to ascertain if these differences are maintained as students' progress thought their medical degree, and whether other factors such as internships, medical rotations or clinical supervision have any impact of medical students' empathy levels.

Natural course of asymptomatic pancreatic pseudocyst: a prospective study

AIM

To study the natural course of asymptomatic pseudocysts of the pancreas.

METHODS

Thirty patients (age range 18-68 years, mean 44; 24 men) with asymptomatic pseudocysts of the pancreas were enrolled between December 2001 and December 2003, and were followed up every month. Those who developed symptoms due to pseudocyst (increasing pain or features of obstruction such as vomiting or jaundice) were subjected to an endoscopic or surgical drainage procedure. End point of the study was either spontaneous resolution of pseudocyst or drainage procedure.

RESULTS

Eighteen (60%) of 30 patients had resolution of the pseudocyst over an average duration of 5 months. Maximum diameter of less than 7.5 cm and cyst volume less than 250 mL were significantly more frequent in patients with resolution of pseudocyst than in those without (14/18 vs 2/12 [p=0.001] and 15/18 vs 2/12 [p=0.0003], respectively). Presence of internal debris was associated with non-resolution (9/12 vs 2/18; p=0.001).

CONCLUSION

Pseudocysts with less than 7.5 cm diameter, volume less than 250 mL, and absence of internal debris were associated with spontaneous resolution within an average duration of 5 months.

Precipitation scavenging of polycyclic aromatic hydrocarbons in Mumbai, India

The concurrent rain and air sampling was conducted for thirteen rain events between the last week of May and end of June 2001. Concentration of total PAHs varied from 84.25 to 777.49 ng/l whereas that in air was in the range of 4.05 to 34.42 ng/m(3). In rainwater the lower molecular weight PAHs (e.g. Phenanthrene, Fluoranthene and Pyrene) were found to be more prominent than the higher molecular weight compounds. The gas phase scavenging ratio (Wg) was found to increase with the molecular weight of the compound. The particle phase scavenging ratio (Wp) values for the more volatile PAHs were generally much higher than those for less volatile PAHs. The higher MW PAHs have Wg values equal to or larger than their Wp values.

Geochronology of Pb and Hg pollution in a coastal marine environment using global fallout 137Cs

Global fallout 137Cs was used for dating sediment cores and estimation of recent sedimentation rates (up to 1 cm/y) in the Thane Creek, which lies in the southern part of the Deccan belt of India. The residence time of 210Pb in the Thane Creek water was calculated to be 0.7 years. Further, the concentrations of Pb (up to 70 microg/g) and Hg (up to 10 microg/g) in sediment profiles were measured to assess the anthropogenic input of contaminants due to large-scale industrialization, which has taken place in this area over the last two decades. The depth-wise concentration profile of Hg shows positive evidence of continued fresh input into the Creek.

Daily intake of aluminium by adult population of Mumbai, India

Electrothermal atomic absorption spectrophotometry (ET-AAS) has been used for the determination of Al in environmental and food samples with a detection limit of 0.3 ng ml(-1). The reliability of estimation is assessed through the analysis of Standard Reference Materials (IAEA SRMs) of Soil-7, SL-3, SD-M2/TM and Hay (V-10). The results indicate that the average concentration of aluminium in air particulate samples is 5.3 microg m(-3). The daily intake of Al by the adult population of Mumbai is 6.4 mg day(-1).

Behaviour and fluxes of trace and toxic elements in creek sediment near Mumbai, India

Studies on marine sediments are extremely important since they act as ultimate sink of anthropogenic pollutants. The present study was conducted near Mumbai city of India to understand and assess the behaviour and fluxes of trace and toxic elements in creek sediment. Seven sediment core samples were collected and analysed for trace and toxic elements such as Fe, Cu, Pb, Zn, Rb and Sr in different sections of the core using EDXRF technique. The fluxes of the elements in each section of the core were calculated using the mass sedimentation rates derived from 210Pb dating technique and the sediment density at each location. The estimated depositional fluxes of Fe, Rb and Sr in Zone-1 and Zone-3 are in the ranges of 0.4-0.5% cm(-2) yr(-1); 4-6 microg cm(-2) yr(-1) and 10-20 microg cm(-2) yr(-1) respectively, where as they were about 3-4 times higher in zone-2 for the same elements. The depositional fluxes of elements Cu (40-60 microg cm(-2) yr(-1)), Zn (35-43 microg cm(-2) yr(-1)) and Pb (6-12 microg cm(-2) yr(-1)) were also found to be higher in zone-2 compared to zone-1 and zone-3 which can be attributed to the release from the newly developed chemical zone of Thane-Belapur industrial belt.

Distribution of HCH and DDT in the coastal marine environment of Mumbai, India

Organochlorine pesticides (OCPs) in sediment, water and biota samples from the coastal marine environment of Mumbai were analysed to elucidate their distribution in various environmental compartments. HCH isomers, dichlorodiphenyltrichloroethane (DDT) and its metabolites were the predominantly identified compounds in all the samples. High ratios of DDT to dichlorodiphenyldichloroethylene (DDE) were found in seawater samples. This indicates the presence of a significant source of DDT in this region. In sediment samples, the gamma-isomer contributed almost 55% to the total HCH, indicating a high affinity of the gamma-isomer towards the sediment. The levels of organochlorines in fish obtained from this region were found to be lower than the levels of organochlorines in fish in temperate regions.

Selenium levels in biological matrices in adult population of Mumbai, India

Selenium (Se) levels in whole blood, serum, urine, muscle and saliva of Mumbai adults have been estimated by differential pulse cathodic stripping voltammetry (DPCSV); the detection limit of Se is 0.05 ng ml(-1). The reliability of estimation is further assessed through the analysis of Standard Reference Materials. The Se levels in whole blood (n = 35) and blood serum (n = 201) of the Mumbai adult population is 99.6 and 100 ng ml(-1); approximately 34.8% of the population have serum Se levels between 80 and 100 ng ml(-1). The blood serum levels of Se for Mumbai adults are comparable to those of whole blood. The mean concentration of Se in urine on a 24-h basis is 5.2 ng ml(-1). Muscle and saliva of the Mumbai adult population contain 195.4 ng g(-1) and 2 ng ml(-1) of Se, respectively. A good correlation between serum Se and dietary Se is observed with a correlation coefficient of 0.89.

Heavy metal concentration and distribution in a dated sediment core of Nainital Lake in the Himalayan region

The concentrations and distribution of the elements, including heavy metals such as As, Ba, Br, Co, Cr, Cs, Fe, Ga, K, Mn, Na, Rb, Sc, Sr, Th and Zn, were investigated in dated sediment cores of Nainital Lake located in the Himalayan region, in Uttar Pradesh state of India, which is considered as a remote background area. The concentrations of the elements were measured by instrumental neutron activation analysis using the k0 method. The International Atomic Energy Agency certified reference material SL-3 was used to evaluate the accuracy of the method. The normalized data for a series of elements were used to understand the source of loading. Elements like Br, Co, Cr, Fe, K, Mn and Zn show a negative correlation with increasing depth whereas elements like As, Ba, Cs, Na and Rb show a positive correlation with increasing depth. By considering the concentration for the bottom segments of the core as close to the baseline concentration, recent flux values for different elements were calculated. An increase in the flux value was observed for Br, Cr, Fe, K, Mn and Zn, which can be attributed to anthropogenic contribution in recent years.

Atmospheric dust loads and their elemental composition at a background site in India

Air particulate samples collected during 1995-96 at a background site situated on the east coast of Thar Desert in Rajsthan State of India were analysed for atmospheric dust loads (Suspended Particulate Matter) and elemental composition. The values of SPM ranged from 9 microg M(-3) to 97 microg M(-3) with an average of 43 microg M(-3) except a few episodic values, which were 3 to 5 times higher than the average during summer months. The results for elemental composition of the particulate samples showed that the concentrations of anthropogenic toxic trace elements viz. Br, Cr, Pb, Sb, Se and Zn are lower by a factor of 2 to 10 as compared to urban areas. The high enrichment factors for anthropogenic elements viz. Br, Pb, Sb and Zn show an input from coal/wood fuel burning and vehicular pollution at the sampling site. The depletion of Si in SPM samples shows long distance transport of dust to the sampling site.

Daily intake of Se by adult population of Mumbai, India

The atmospheric Se levels in Mumbai varied between 0.02 and 1.92 ng m(-3) with a mean concentration of 0.21 ng m(-3). The daily intake of Se by the adult population of Mumbai is 61.9 microg day(-1). Differential pulse cathodic stripping voltammetry (DP-CSV) has been used for the determination of Se in air particulate and food samples. The detection limit of Se using DPCSV was found to be 0.05 ng ml(-1). The reliability of estimation was further assessed through the analysis of standard reference materials (SRMs), tuna fish, animal blood, milk powder and fish tissue obtained from IAEA. The frequency distribution of dietary intake levels of selenium for Mumbai adults showed that approximately 61% of the studied population have a dietary intake of 30-90 microg day(-1). Ingestion was found to be the main route of Se exposure for Mumbai adults. The turn over time of Se through blood is 17 days.

Blood lead and its effect on Cd, Cu, Zn, Fe and hemoglobin levels of children

The levels of heavy metals, such as Pb, Cd, Cu, Zn and Fe, in whole blood samples of Mumbai and Hyderabad children have been determined. In the present study, 576 blood samples of children (3-6 years old) were collected during 1996-1998 and analyzed for heavy metal contents by anodic stripping voltammetry and atomic absorption spectrometry. The geometric mean concentrations of Pb, Cd, Cu and Zn in blood of Mumbai children were 8.0, 0.10, 86.5 and 398.9 microg dl(-1), while those for Hyderabad children were 13.3, 0.13, 100.6 and 483.4 microg dl(-1) respectively. The geometric mean concentrations of Fe in the blood of Mumbai and Hyderabad children were 21.9 and 34.5 mg dl(-1), respectively. Of the Mumbai children, 61.8% were found to have a blood lead concentration lcss than 10 microg dl(-1), while the corresponding proportion of Hyderabad children was 27.4%. Higher concentrations of Pb in the children's blood were observed at high traffic areas in both cities. A decreasing trend in the hemoglobin content with increasing blood lead levels was observed for Mumbai children. A good negative correlation (-0.61) between the blood lead and iron has been observed for Mumbai children The hemoglobin content of 85% of the study population was found to vary between 8 and 14 g%.

Atmospheric and children's blood lead as indicators of vehicular traffic and other emission sources in Mumbai, India

Average concentration of Pb in atmospheric air particulates in different suburbs of Mumbai was studied for almost a decade and its spatial and temporal profiles are discussed in relation to emission sources. In general the concentration of Pb in all the residential suburban atmosphere is well below the Central Pollution Control Board (CPCB, 1994) prescribed limit of 1.5 microg m(-3) barring a few exceptions for some residential/industrial sites, such as those of Thane and Kurla scrap yards. The correlation between blood lead of children and air lead reveals that the blood Pb level in children could increase by 3.6 microg dl(-1) for an incremental rise of 1.0 microg Pb m(-3) of air. The temporal profile of air Pb values indicates a decreasing trend in residential suburbs (Khar: 1984, 0.39 microg m(-3); 1996, 0.17 microg m(-3)) as well as in suburban residential areas with low traffic (Goregaon: 1984, 0.53 microg m(-3); 1996, 0.30 microg m(-3)).

Compact Fiber Optic Dynamic Light Scattering System

Fiber optic dynamic light scattering (FODLS) is fast developing as a technique for sizing particles in concentrated dispersions. Fiber optic systems have the potential to be made into online particle size measuring equipment in process industries. Two different laser light sources were used to study monodisperse polystyrene latex dispersion with different particle sizes and volume fractions. The apparent diffusion coefficients were a function of particle size, volume fraction, and signal to noise ratios. The apparent diffusion coefficient data showed that FODLS probes collective diffusion for smaller particles and self diffusion for larger particles. It was observed that for a polydisperse concentrated dispersion, both self and collective diffusion were probed by FODLS. This means that the apparent diffusion coefficient can be used only as a relative quantity. Copyright 1997 Academic Press. Copyright 1997Academic Press

Characterization of atmospheric dust at Gurushikar, Mt. Abu, Rajasthan

The nature of atmospheric aerosols at Gurushikar, Mt. Abu, Rajasthan where a gamma ray telescope is to be installed, was investigated. Air particulate samples collected on filters were used to estimate the total suspended particulate matter (TSPM) and its elemental composition. The TSPM varied from 31 to 103 μg/m(3) during January to March 1994. The heighest loads were observed during the months of May and June (80-100 μg/m(3)) and lowest during October (20-60 μg/m(3)). The dust was also examined for size, shape and nature of the mineral matter. The particle sizes varied from 100 μm to 5 μm. The course particles (>50 μm) are irregular shaped quartz grains. Some of the medium size (=50 μm) particles were spherical and were highly conducting. These particles were rich in iron content. Correlation coefficients among various elements in the dust showed that it is made up of mainly two components-wind blown ground dust and particulate arising out of wood and coal burning.