Meez Islam

Biochar: Carbon Sequestration, Land Remediation, and Impacts on Soil Microbiology

Biochar—charcoal used to amend land and sequester carbon—is attracting considerable interest. Its distinctive physical/chemical/biological properties, including high water-holding capacity, large surface area, cation exchange capacity, elemental composition, and pore size/volume/distribution, effect its recognized impacts, especially on microbial communities. These are explored in the context of agriculture, composting, and land remediation/restoration. Considerable focus is given to mycorrhizal associations, which are central to exploitation in environmental technologies involving biochar. The characteristics of biochar, its availability for nutrient cycling, including the beneficial and potentially negative/inhibitory impacts, and the requisite multidisciplinary analysis (physicochemical, microbiological, and molecular) to study these in detail, are explored.

Fingerprint composition and aging: A literature review

Fingerprints have a key role in criminal investigations and are the most commonly used form of evidence worldwide. Significant gaps remain however, in the understanding of fingerprint chemistry, including enhancement reaction mechanisms and the effect of environmental variables and time on composition. Determining the age of a fingerprint is also a relatively unexplored area. A successful method, with reliable and quantitative estimates, would have numerous advantages. Previous unreliable methods have predominantly focused on enhancement success based on physical and chemical changes. This review explores variations in composition due to donor characteristics and environmental variables, and identifies gaps for further research. We also present a qualitative and quantitative summary of the effect of time on composition. Kinetics are presented where known, with summary schematics for reaction mechanisms. Previous studies exploring methods for determining the age of a fingerprint are also discussed, including their advantages and disadvantages. Lastly we propose a potentially more accurate and reliable methodology for determining fingerprint age based on quantitative kinetic changes to the composition of a fingerprint over time.

The estimation of the age of a blood stain using reflectance spectroscopy with a microspectrophotometer, spectral pre-processing and linear discriminant analysis

A novel method for the non-destructive age determination of a blood stain is described. It is based on the measurement of the visible reflectance spectrum of the haemoglobin component using a microspectrophotometer (MSP), spectral pre-processing and the application of supervised statistical classification techniques. The reflectance spectra of sample equine blood stains deposited on a glazed white tile were recorded between 1 and 37 days, using an MSP at wavelengths between 442 nm and 585 nm, under controlled conditions. The determination of age was based on the progressive change of the spectra with the aging of the blood stain. These spectra were pre-processed to reduce the effects of baseline variations and sample scattering. Two feature selection methods based on calculation of Fishers weights and Fourier transform (FT) of spectra were used to create inputs into a statistical model based on linear discriminant analysis (LDA). This was used to predict the age of the blood stain and tested by using the leave-one-out cross validation method. When the same blood stain was used to create the training and test datasets an excellent correct classification rate (CCR) of 91.5% was obtained for 20 input frequencies, improving to 99.2% for 66 input frequencies. A more realistic scenario where separate blood stains were used for the training and test datasets led to poorer successful classification due to problems with the choice of substrate but nevertheless up to 19 days a CCR of 54.7% with an average error of 0.71 days was obtained.

Estimating temperature exposure of burnt bone - A methodological review.

Forensic anthropologists are frequently confronted with the need to interpret burnt bone. Regardless of the context, one of the key factors for the correct interpretation of the remains and a reconstruction of the incidents leading to incineration is the estimation of the maximum exposure temperature. The recent years have seen an influx in experimental research focusing on temperature estimation, spanning from colour assessment, mechanical strength measurements, histology and structural observations, biochemical changes and crystallinity studies, vastly advancing the understanding of heat induced changes in bone, thus facilitating a more accurate interpretation. This paper draws together and evaluates all currently available methodologies for temperature estimation.

The age estimation of blood stains up to 30 days old using visible wavelength hyperspectral image analysis and linear discriminant analysis

A novel application of visible wavelength hyperspectral image analysis has been applied to determine the age of blood stains up to 30 days old. Reflectance spectra from selected locations within the hyperspectral image, obtained from a portable instrument, were subjected to spectral pre-processing. This was followed by the application of a linear discriminant classification model, making estimations possible with an average error of ±0.27days for the first 7 days and an overall average error of ±1.17days up to 30 days. This is also the first reported study of the determination of the age of fresh blood stains (less than one day old) with an error of ±0.09h. The studies have been made under controlled conditions and represent, at this stage, proof of concept results but also are the most accurate age estimation results for measurements between 0 and 30 days reported to date. The results are consistent with well-established kinetic processes suggesting that the pre-processing stages described are revealing spectroscopic changes which are reliably following the time dependent oxidation of HbO2. The potential for parameterisation of environmental factors to make the method generally applicable at crime scenes is discussed, along with the developments required to further improve classification and to make the instrument genuinely portable.

Broadband Cavity Enhanced Absorption Spectroscopy as a Detector for HPLC

The first demonstration of a cavity enhanced absorption spectroscopy (CEAS) based technique, applied to HPLC detection is reported. Broadband cavity enhanced absorption spectroscopy (BBCEAS) has been used for detection in a HPLC system (HPLC-BBCEAS). Measurements were made on the dyes rhodamine 6G and rhodamine B between 450 and 600 nm. The sensitivity of the measurements as determined by the minimum detectable change in the absorption coefficient, alpha(min), were 2.9 x 10(-5) cm(-1) at 527 nm and 1.9 x 10(-5) cm(-1) at 556 nm, the peak absorption wavelengths of rhodamine 6G and rhodamine B, respectively. The limits of detection (LOD) for the two dyes were 426 and 271 pM, respectively. The LOD of the HPLC-BBCEAS setup was found to be between 54 and 77 times lower than with a Perkin-Elmer HPLC (series 200) comprising a 200EP photodiode array detector. The sensitivity of the developed setup also compared favorably with the previous single wavelength HPLC-CRDS studies while using a considerably lower cost experimental setup and simpler experimental methodology. The use of BBCEAS detection also allowed the discrimination following an isocratic HPLC separation of the nearly co-eluting dyes rhodamine 6G and rhodamine B.

Liquid-phase broadband cavity-enhanced absorption spectroscopy measurements in a 2 mm cuvette.

A novel implementation of broadband cavity enhanced absorption spectroscopy (BBCEAS) has been used to perform sensitive visible wavelength measurements on liquid-phase solutions in a 2 mm cuvette placed at normal incidence to the cavity mirrors. The overall experimental methodology was simple, low cost, and similar to conventional ultraviolet-visible absorption spectroscopy. The cavity was formed by two concave high reflectivity mirrors. Three mirror sets with nominal reflectivities (R) of R = 0.99, 0.9945, and 0.999 were used. The light source consisted of a high intensity red, green, blue, or white LED. The detector was a compact charge-coupled device (CCD) spectrograph. Measurements were made on the representative analytes, Ho3+, and the dyes brilliant blue-R, sudan black, and coumarin 334 in appropriate solvents. Cavity enhancement factors (CEF) of up to 104 passes for the high reflectivity mirrors were obtained. The number of passes was limited by relatively high scattering and absorption losses in the cavity, of ∼1 × 10−2 per pass. Measurements over a wide wavelength range (420–670 nm) were also obtained in a single experiment with the white LED and the R = 0.99 mirror set for Ho3+ and sudan black. The sensitivity of the experimental setup could be determined by calculating the minimum detectable change in the absorption coefficient αmin. The values ranged from 5.1 × 10−5 to 1.2 × 10−3 cm−1. The limit of detection (LOD) for the strong absorber brilliant blue-R was 620 pM. A linear dynamic range of measurements of concentration over about two orders of magnitude was demonstrated. The overall sensitivity of the experimental setup compared very favorably with previous generally more experimentally complex and expensive liquid-phase cavity studies. Possible improvements to the technique and its applicability as an analytical tool are discussed.

Liquid-phase broadband cavity enhanced absorption spectroscopy (BBCEAS) studies in a 20 cm cell

Sensitive liquid-phase measurements have been made in a 20 cm cell using broadband cavity enhanced absorption spectroscopy (BBCEAS). The cavity was formed by two high reflectivity mirrors which were in direct contact with the liquid-phase analytes. Careful choice of solvent was required to minimise the effect of background solvent absorptions. Measurements were made on the broad absorber Sudan black, dissolved in acetonitrile, using a white LED light source and R > or = 0.99 cavity mirrors, leading to a cavity enhancement factor (CEF) of 82 at 584 nm. The sensitivity as measured by the minimum detectable change in the absorption coefficient (alpha(min)) was 3.4 x 10(-7) cm(-1). Further measurements were made on the strong absorber methylene blue dissolved in acetonitrile at 655 nm. A white LED was used with the R > or = 0.99 cavity mirrors, leading to a CEF of 78 and alpha(min) = 4.4 x 10(-7) cm(-1). The use of a more intense red LED also allowed measurements with higher reflectivity R > or = 0.999 cavity mirrors, leading to a CEF of 429 and alpha(min) = 2.8 x 10(-7) cm(-1). The sensitivity was limited by dark noise from the detector but nevertheless appears to represent the most sensitive liquid-phase absorption measurement to date.

The effect of soft tissue on temperature estimation from burnt bone using Fourier transform infrared spectroscopy

This study investigated the effect of soft tissue and different exposure times on the prediction of burning temperatures of bone when using Fourier transform infrared spectroscopy (FTIR). Ovis aries rib bones were burnt at different temperatures and for varying time intervals. Results of a linear regression analysis indicated that burn temperatures can be predicted with a standard error of ±70°C from defleshed bone spectra. Exposure time does not have a significant impact on prediction accuracy. The presence of soft tissue has a significant impact on heat‐induced changes of the bone matrix in low (<300°C) as well as high temperatures (>800°C), slowing down combustion in the former and accelerating it in the latter (p < 0.05). At medium temperatures, no significant difference was noted. These results provide forensic investigators a new perspective with which to interpret the results of crystallinity measures derived from burnt bone.

Microfluidic Bioreactors for Cell Culturing: A Review

The use of microfluidic bioreactor platforms for cell culturing holds considerable promise for a range of fields which include drug discovery, tissue engineering, bioprocessing optimisation and cell based screening studies. Microflu- idic bioreactor systems have length scales that are well matched to the physical dimensions of most cells and microorgan- isms. In view of this, microfluidic bioreactors have attractive features which make them ideal to study the behaviour of cells and their internal organisation in their native microenvironment. Due to their small footprint microbioreactor plat- forms offer a number of advantages over conventional macroscale systems including improved biological function, higher quality cell-based data, reduced volume of reagents, ease of integration and lower cost. This review highlights the basic concepts, designs and operational requirements of microbioreactors for cell based studies. An illustrative outline of differ- ent applications of microbioreactors and some indication of new trends and progress in recent years are provided. Specific examples of applications of microbioreactors are drawn for cytotoxicity assays, tissue engineering, stem cells, microbial fermentations, single cell analysis and in vitro fertilisation.