A novel conductometric titration approach for rapid determination of boron

21-30In laboratories dealing with radioactive samples it is important to minimize both the sample size and also the associated waste generated in an analysis. To meet this objective a rapid conductometric titration technique is developed to determine boron in the moderators of Pressurized Heavy Water Reactors (PHWR’s). Using this novel PC interfaced titration facility a minimum tenfold reduction in sample size is achieved compared to conventional conductometric titration. Determination of boron is based on the conversion of extremely weak boric acid to better conducting boron mannitol complex and titrating the complex against NaOH. Various parameters affecting the analysis, when moving from large to small sample size, are analyzed and optimized. The technique is primarily proposed for the assay of boron (≥0.5 ppm) during reactor startup. Each analysis requires less than 10 min. The detection limit is 0.5 ppm and the precision obtained at this level is 4.6% RSD. The technique is a good alternative to less sensitive carminic acid based spectrophotometric method

trans-Bromohydridobis-(triphenylphosphine)platinum(II)

The title compound, [PtBrH(C18H15P)2], has a square-planar environment around the Pt atom, with the hydride and bromide ligands being exactly collinear with Pt since they all lie on a crystallographic twofold rotation axis, and with mutually trans triphenyl­phosphine ligands with a P-Pt-P bond angle that is slightly bent towards the hydride [P-Pt-P = 170.81 (5)°]. The Pt-H distance (1.610 Å) is in good agreement with those found in structures determined by neutron diffraction

Density, dielectric and X-ray studies of Smectic A-Smectic A transitions

We report here the results of detailed density, dielectric and X-ray studies on three systems exhibiting different types of Smectic A-Smectic A transitions. It is found that although the layer spacing shows marked changes at the transitions, the corresponding density changes are extremely small. In every case studied, the dielectric anisotropy shows a pronounced decrease on going over to the lower temperature smectic A phase. This decrease can be correlated with the structural changes

[1,2-Bis(diphenylphosphino)ethane]-diiodidoplatinum(II) dichloromethane disolvate

In the title compound, [PtI2(C26H24P2)]·2CH2Cl2, the PtI2(dppe) [dppe = 1,2-bis­(diphenyl­phosphino)ethane] mol­ecules possess twofold rotation symmetry. The Pt coordination displays a square-planar arrangement, with the sum of the angles around the Pt atom being 360.01 (2)°. The Pt-I distance is 2.6484 (5) Å. In the crystal structure, inter­molecular C-H...I contacts link the PtI2(dppe) mol­ecules into rows along the c axis, with a C...I distance of 3.873 (5) Å

Lanthanide luminescence based probe for detection of picric acid

1041-1047Europium fluorescence is significantly enhanced through ligand sensitization using aromatic benzene mono and di carboxylic acids as ligands in aqueous solution. By optimising metal to ligand ratio and solution pH, it is established that the enhancement is maximum with isophthalic and terephthalic acid. Phosphorescence of isophthalic acid is recorded and its triplet energy level is found to be at 25633 cm-1; just above the fluorescing energy level of Eu3+. On complexation with these ligands though the europium luminescence is enhanced by orders of magnitude, the europium lifetime increased marginally. Addition of picric acid resulted in the quenching of europium luminescence in europium-isophthalic acid complex. Based on this quenching, a fluorimetric method is developed for the estimation of picric acid in aqueous solution. Picric acid in aqueous solution could be estimated down to 0.23 ppm. Common cations and anions found in natural waters did not interfere in the analysis. The precision in measurement is within 5% RSD in the entire range of measurement

Lanthanide luminescence based probe for detection of picric acid

Europium fluorescence is significantly enhanced through ligand sensitization using aromatic benzene mono and di carboxylic acids as ligands in aqueous solution. By optimizing metal to ligand ratio and solution pH, it is established that the enhancement is maximum with iso-phthalic and tere-phthalic acid. Phosphorescence of isophthalic acid is recorded and its triplet energy level is found to be at 25633 cm-1; just above the fluorescing energy level of Eu3+. On complexation with these ligands though the europium luminescence is enhanced by orders of magnitude, the europium lifetime increased marginally. Addition of picric acid resulted in the quenching of europium luminescence in europium-isophthalic acid complex. Based on this quenching, a fluorimetric method is developed for the estimation of picric acid in aqueous solution. Picric acid in aqueous solution could be estimated down to 0.23 ppm. Common cations and anions found in natural waters did not interfere in the analysis. The precision in measurement is within 5 % RSD in the entire range of measurement

Increase in perceived case suspiciousness due to local contrast optimisation in digital screening mammography

Item does not contain fulltextOBJECTIVES: To determine the influence of local contrast optimisation on diagnostic accuracy and perceived suspiciousness of digital screening mammograms. METHODS: Data were collected from a screening region in the Netherlands and consisted of 263 digital screening cases (153 recalled,110 normal). Each case was available twice, once processed with a tissue equalisation (TE) algorithm and once with local contrast optimisation (PV). All cases had digitised previous mammograms. For both algorithms, the probability of malignancy of each finding was scored independently by six screening radiologists. Perceived case suspiciousness was defined as the highest probability of malignancy of all findings of a radiologist within a case. Differences in diagnostic accuracy of the processing algorithms were analysed by comparing the areas under the receiver operating characteristic curves (A(z)). Differences in perceived case suspiciousness were analysed using sign tests. RESULTS: There was no significant difference in A(z) (TE: 0.909, PV 0.917, P = 0.46). For all radiologists, perceived case suspiciousness using PV was higher than using TE more often than vice versa (ratio: 1.14-2.12). This was significant (P <0.0083) for four radiologists. CONCLUSIONS: Optimisation of local contrast by image processing may increase perceived case suspiciousness, while diagnostic accuracy may remain similar. KEY POINTS: Variations among different image processing algorithms for digital screening mammography are large. Current algorithms still aim for optimal local contrast with a low dynamic range. Although optimisation of contrast may increase sensitivity, diagnostic accuracy is probably unchanged. Increased local contrast may render both normal and abnormal structures more conspicuous.1 april 201

Mammographic density. Measurement of mammographic density

Mammographic density has been strongly associated with increased risk of breast cancer. Furthermore, density is inversely correlated with the accuracy of mammography and, therefore, a measurement of density conveys information about the difficulty of detecting cancer in a mammogram. Initial methods for assessing mammographic density were entirely subjective and qualitative; however, in the past few years methods have been developed to provide more objective and quantitative density measurements. Research is now underway to create and validate techniques for volumetric measurement of density. It is also possible to measure breast density with other imaging modalities, such as ultrasound and MRI, which do not require the use of ionizing radiation and may, therefore, be more suitable for use in young women or where it is desirable to perform measurements more frequently. In this article, the techniques for measurement of density are reviewed and some consideration is given to their strengths and limitations

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century