437 research outputs found

    Effects of electron transfer on the stability of hydrogen bonds.

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    The measurement of the dimerization constants of hydrogen-bonded ruthenium complexes (12, 22, 32) linked by a self-complementary pair of 4-pyridylcarboxylic acid ligands in different redox states is reported. Using a combination of FTIR and UV/vis/NIR spectroscopies, the dimerization constants (KD) of the isovalent, neutral states, 12, 22, 32, were found to range from 75 to 130 M-1 (ΔG0 = -2.56 to -2.88 kcal mol-1), while the dimerization constants (K2-) of the isovalent, doubly-reduced states, (12)2-, (22)2-, (32)2-, were found to range from 2000 to 2500 M-1 (ΔG0 = -4.5 to -4.63 kcal mol-1). From the aforementioned values and the comproportionation constant for the mixed-valent dimers, the dimerization constants (KMV) of the mixed-valent, hydrogen-bonded dimers, (12)-, (22)-, (32)-, were found to range from 0.5 × 106 to 1.2 × 106 M-1 (ΔG0 = -7.78 to -8.31 kcal mol-1). On average, the hydrogen-bonded, mixed-valent states are stabilized by -5.27 (0.04) kcal mol-1 relative to the isovalent, neutral, hydrogen-bonded dimers and -3.47 (0.06) kcal mol-1 relative to the isovalent, dianionic hydrogen bonded dimers. Electron exchange in the mixed valence states imparts significant stability to hydrogen bonding. This is the first quantitative measurement of the strength of hydrogen bonds in the presence and absence of electronic exchange

    Morphological Comparisons of Five Species of Tamarins in Peru

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    Tamarins of the genus Leontocebus (formerly Saguinus), subfamily Callitrichinae, represent one of the most diverse primate taxa but detailed information about their phylogeny is still lacking. Recent molecular phylogenetic analyses have led to the reclassification of many taxa. In Peru, ten subspecies of tamarins were reclassified as eight new species and four new subspecies based on genetic differences among these taxa. However, no one has attempted to determine whether these new “genetic species” have distinguishable morphological traits. To do this, we examined twenty crania and skins representing five Peruvian “genetic species” housed in the Mammals Collection at the Field Museum of Natural History in Chicago, Illinois. We measured thirty linear craniofacial characters using digital calipers and photographed the pelage of all specimens. We log-transformed and analyzed the data using the Discriminant Analysis module of SPSS 23. We qualitatively compared the pelage color and pattern of all furs. Our study demonstrates that the “genetic species” can be distinguished by their cranial anatomy. Thus, the “genetic species” represent morphologically distinct populations, as is expected if they represent evolutionarily distinct taxa.B.S. (Bachelor of Science

    Mining and analysis of audiology data to find significant factors associated with tinnitus masker

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    Objectives: The objective of this research is to find the factors associated with tinnitus masker from the literature, and by using the large amount of audiology data available from a large NHS (National Health Services, UK) hearing aid clinic. The factors evaluated were hearing impairment, age, gender, hearing aid type, mould and clinical comments. Design: The research includes literature survey for factors associated with tinnitus masker, and performs the analysis of audiology data using statistical and data mining techniques. Setting: This research uses a large audiology data but it also faced the problem of limited data for tinnitus. Participants: It uses 1,316 records for tinnitus and other diagnoses, and 10,437 records of clinical comments from a hearing aid clinic. Primary and secondary outcome measures: The research is looking for variables associated with tinnitus masker, and in future, these variables can be combined into a single model to develop a decision support system to predict about tinnitus masker for a patient. Results: The results demonstrated that tinnitus maskers are more likely to be fit to individuals with milder forms of hearing loss, and the factors age, gender, type of hearing aid and mould were all found significantly associated with tinnitus masker. In particular, those patients having Age<=55 years were more likely to wear a tinnitus masker, as well as those with milder forms of hearing loss. ITE (in the ear) hearing aids were also found associated with tinnitus masker. A feedback on the results of association of mould with tinnitus masker from a professional audiologist of a large NHS (National Health Services, UK) was also taken to better understand them. The results were obtained with different accuracy for different techniques. For example, the chi-squared test results were obtained with 95% accuracy, for Support and Confidence only those results were retained which had more than 1% Support and 80% Confidence. Conclusions: The variables audiograms, age, gender, hearing aid type and mould were found associated with the choice of tinnitus masker in the literature and by using statistical and data mining techniques. The further work in this research would lead to the development of a decision support system for tinnitus masker with an explanation that how that decision was obtained

    Mechanisms of SARS-CoV-2 neutralization by shark variable new antigen receptors elucidated through X-ray crystallography

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    Acknowledgements This work was supported by the Chief Scientist Office, Scottish Government, Grant COV/ABN/20/01 (Elasmogen, Ltd.), a 2018 Prostate Cancer Foundation Challenge Award (AML), a 2013 Prostate Cancer Foundation Young Investigator Award (AML), NCI R01s CA237272, CA233562, and CA245922 (AML). WEM was supported by the NIH T32 HL007741 and JMT by the NIH T32 AI055433. JSM was funded by NIGMS R01 GM088790. HA was funded by NIGMS R35 GM118047 and NCI P01 CA234228. X-ray diffraction data were collected at the Northeastern Collaborative Access Team beamlines, which are funded by the US National Institutes of Health (NIGMS P30 GM124165). The Pilatus 6M detector on 24-ID-C beamline is funded by a NIH-ORIP HEI grant (S10 RR029205). We thank the Marco Pravetoni lab for providing training and access to the OctetRED96e for BLI experiments.Peer reviewedPublisher PD
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