Direct Injection Liquid Chromatography High-Resolution Mass Spectrometry for Determination of Primary and Secondary Terrestrial and Marine Biomarkers in Ice Cores

Many atmospheric organic compounds are long-lived enough to be transported from their sources to polar regions and high mountain environments where they can be trapped in ice archives. While inorganic components in ice archives have been studied extensively to identify past climate changes, organic compounds have rarely been used to assess paleo-environmental changes, mainly due to the lack of suitable analytical methods. This study presents a new method of direct injection HPLC-MS analysis, without the need of pre-concentrating the melted ice, for the determination of a series of novel biomarkers in ice-core samples indicative of primary and secondary terrestrial and marine organic aerosol sources. Eliminating a preconcentration step reduces contamination potential and decreases the required sample volume thus allowing a higher time resolution in the archives. The method is characterised by limits of detections (LODs) in the range of 0.01-15 ppb, depending on the analyte, and accuracy evaluated through an interlaboratory comparison. We find that many components in secondary organic aerosols (SOA) are clearly detectable at concentrations comparable to those previously observed in replicate preconcentrated ice samples from the Belukha glacier, Russian Altai Mountains. Some compounds with low recoveries in preconcentration steps are now detectable in samples with this new direct injection method significantly increasing the range of environmental processes and sources that become accessible for paleo-climate studies

Social vs. practical problems in attaining a colonoscopy: Different patient profiles?

Background: Colonoscopy is an effective procedure for identifying precancerous polyps and cancerous lesions, but it is unlike other cancer screening tools in that it requires sedation and thus assistance from at least one other individual. The intent of this paper was to identify logistical problems in completing the colonoscopy and to examine their relationships with sociodemographic characteristics. Methods: All eligible patients (n = 2500) from two academic-affiliated colonoscopy centers (one free standing, one hospital-based) were invited to participate in an onsite, pre-colonoscopy survey; patients agreeing to participate (n = 1841, RR = 73.6%) received a $5.00 gift card. Multiple correspondence analysis (MCA) was used to identify the underlying dimensional structure of the problems. Bivariate statistics were performed to compare demographic variables and health literacy levels among patients reporting problems. Multivariate logistic regression with a backwards conditional solution was used to determine the demographic variables independently associated with problems. Results: Multiple correspondence analyses indicated two dimensions of problems (social and practical). Using logistic regression, social problems (e.g., finding someone to accompany the patient) were associated with not living in the same home as the driver, not working due to disability, and younger age. Practical problems (e.g., making an appointment) were associated with “other” minority race, poorer health, lower health literacy, and younger age. Conclusion: Patients experience different problems completing the colonoscopy based on socio-demographics. Particularly at risk are patients who find it difficult to navigate the system, are of younger age, or who may have smaller social networks

Estimating Partisan Bias of the Electoral College Under Proposed Changes in Elector Apportionment

In the election for President of the United States, the Electoral College is the body whose members vote to elect the President directly. Each state sends a number of delegates equal to its total number of representatives and senators in Congress; all but two states (Nebraska and Maine) assign electors pledged to the candidate that wins the state’s plurality vote. We investigate the effect on presidential elections if states were to assign their electoral votes according to results in each congressional district, and conclude that the direct popular vote and the current electoral college are both substantially fairer compared to those alternatives where states would have divided their electoral votes by congressional district

Time variation of fundamental couplings and dynamical dark energy

Scalar field dynamics may give rise to a nonzero cosmological variation of fundamental constants. Within different scenarios based on the unification of gauge couplings, the various claimed observations and bounds may be combined in order to trace or restrict the time history of the couplings and masses. If the scalar field is responsible for a dynamical dark energy or quintessence, cosmological information becomes available for its time evolution. Combining this information with the time variation of couplings, one can determine the interaction strength between the scalar and atoms, which may be observed by tests of the Weak Equivalence Principle. We compute bounds on the present rate of coupling variation from experiments testing the differential accelerations for bodies with equal mass and different composition and compare the sensitivity of various methods. In particular, we discuss two specific models of scalar evolution: crossover quintessence and growing neutrino models.Comment: 26 pages, 2 figures; minor typos & added references, to be published in JCA

Maximum Overlap. Hybridization in PF5 and SF4

The method of Murrell as modified by Golebiewski has been applied to determine the maximum overlap hybrid orbitals for PF5 and SF4• For the former system, three cases have been considered: cr overlap integrals of the central atom valence and F 2p orbitals are (i) taken as angular parts of P atomic orbitals projected in the bond directions, (ii) evaluated using SCF atomic wave functions with equidistant F ligands, and (iii) calculated using experimental bond lengths. The resultant overall hybridizations are compared and discussed. For SF4, only case (iii) has been carried out. In addition, the wave function of the lone pair orbital is obtained with symmetry consideration and orthonormality relationships among all the hy- . brids. This appears to be an inexpensive way to determine the form of the lone pair and to estimate its size