Structure of d(TGCGCA)(2) and a comparison with other DNA Hexamers

The X-ray crystal structure of d(TGCGCA)(2) has been determined at 120 K to a resolution of 1.3 Angstrom. Hexamer duplexes, in the Z-DNA conformation, pack in an arrangement similar to the 'pure spermine form' [Egli et al. (1991). Biochemistry, 30, 11388-11402] but with significantly different cell dimensions. The phosphate backbone exists in two equally populated discrete conformations at one nucleotide step, around phosphate 11. The structure contains two ordered cobalt hexammine molecules which have roles in stabilization of both the Z-DNA conformation of the duplex and in crystal packing. A comparison of d(TGCGCA)(2) with other Z-DNA hexamer structures available in the Nucleic Acid Database illustrates the elusive nature of crystal packing. A review of the interactions with the metal cations Na+, Mg2+ and Co3+ reveals a relatively small proportion of phosphate binding and that close contacts between metal ions are common. A prediction of the water structure is compared with the observed pattern in the reported structure

Tilted two-fluid Bianchi type I models

In this paper we investigate expanding Bianchi type I models with two tilted fluids with the same linear equation of state, characterized by the equation of state parameter w. Individually the fluids have non-zero energy fluxes w.r.t. the symmetry surfaces, but these cancel each other because of the Codazzi constraint. We prove that when w=0 the model isotropizes to the future. Using numerical simulations and a linear analysis we also find the asymptotic states of models with w>0. We find that future isotropization occurs if and only if $w \leq 1/3$. The results are compared to similar models investigated previously where the two fluids have different equation of state parameters.Comment: 14 pages, 3 figure

Intravenous remifentanil patient-controlled analgesia versus intramuscular pethidine for pain relief in labour (RESPITE): an open-label, multicentre, randomised controlled trial

Background: Approximately a third of women receiving pethidine for labour pain subsequently require an epidural, which provides effective pain relief but increases the risk of instrumental delivery. Remifentanil patient controlled analgesia (PCA) in labour is an alternative to pethidine, but not widely utilized. We sought to determine epidural rates amongst women using remifentanil PCA compared to pethidine.Methods: We conducted a randomised, parallel, open-label trial in 14 UK maternity units. Women at term gestation, in labour with a singleton cephalic presentation, requesting opioid pain relief, were randomly assigned (1:1) to remifentanil PCA (40μg bolus with a two minute “lock-out”) or intramuscular pethidine (100mg, four-hourly, up to 400mg). Web-based or telephone randomisation minimised allocations by parity, age, ethnicity and mode of labour onset. The primary outcome was the proportion of women who received epidural analgesia after enrolment. To detect a reduction in epidural conversion from 30% to 15% with 90% power, with a 15% anticipated attrition from urgent delivery by emergency caesarean section, required 400 women. Primary analyses were unadjusted and by intention-to-treat. ISRCTN29654603.Findings: Between May 13, 2014, and Sept 2, 2016, 201 women were randomly assigned to the remifentanil PCA group and 200 to the pethidine group. One participant in the pethidine group withdrew consent, leaving 199 for analyses. The proportions of epidural conversion were 19% (39 of 201) in the remifentanil PCA group and 41% (81 of 199) in the pethidine group (risk ratio 0·48, 95% CI 0·34–0·66; p less 0·0001). There were no serious adverse events or drug reactions directly attributable to either analgesic during the study.Interpretation: Intravenous remifentanil PCA halved the proportion of epidural conversions compared with intramuscular pethidine. This finding challenges routine pethidine use as standard of care in labour

An outlook on self-assessment of homework assignments in higher mathematics education

Abstract Background We discuss first experiences with a new variant of self-assessment in higher mathematics education. In our setting, the students of the course have to mark a part of their homework assignments themselves and they receive the corresponding credit without that any later changes are carried out by the teacher. In this way, we seek to correct the imbalance between student-centered learning arrangements and assessment concepts that keep the privilege to grade (or mark) completely with the teacher. Results We present results in the form of student feedback from a course on functional analysis for third- and fourth-year students. Moreover, we analyze marking results from two courses on real analysis. Here, we compare tasks marked by the teacher and tasks marked by the students. Conclusions Our experiments indicate that students can benefit from self-assessment tasks. The success depends, however, on many different factors. Promising for self-assessment seem to be small learning groups and tasks in which a priori weaker students can catch up with stronger students by increasing their practising time

Greenhouse gas emissions of food waste disposal options for UK retailers

Food retailers are under increasing political and social pressure to reduce both the amount of food that they waste and the amount of greenhouse gases (GHGs) that their food retailing activities incur. For completeness, when assessing the ‘carbon footprint” of their business activities, food retailers should also included the greenhouse gas emissions caused by their disposal of waste food, which will vary with the waste disposal option used. However, there is lack of quantitative guidance for food retailers on the net GHG emissions that are incurred in the disposal of specific food types by the various disposal options available. Here, we calculate the net GHG emissions of eight different waste disposal options for five core food types using life cycle assessment, accounting for both emissions incurred in transport and processing, and those mitigated by the creation of useful products. We also assess the extent to which the embodied emissions in waste foods at the retail checkout can be mitigated by each disposal option. In addition to food specific results, we calculate mass-weighted averages using data from a mid-sized retail chain. We find a strong correlation between net emissions and the energy density of foods, and the following mass weighted disposal hierarchy (from best to worst, with respect to greenhouse gas emissions): donation of edible food to food banks; anaerobic digestion; conversion to animal feed; incineration with energy recovery; aerobic composting; landfill with gas collection and utilisation; landfill with gas collection and flaring; landfill without gas collection. If waste food from retailers is unfit for human consumption, to minimise greenhouse gas emissions it should be disposed of by conversion to animal feed or anaerobic digestion. For all food types, landfill is the worst disposal option

B-1a cells acquire their unique characteristics by bypassing the pre-BCR selection stage

B-1a cells are long-lived, self-renewing innate-like B cells that predominantly inhabit the peritoneal and pleural cavities. In contrast to conventional B-2 cells, B-1a cells have a receptor repertoire that is biased towards bacterial and self-antigens, promoting a rapid response to infection and clearing of apoptotic cells. Although B-1a cells are known to primarily originate from fetal tissues, the mechanisms by which they arise has been a topic of debate for many years. Here we show that in the fetal liver versus bone marrow environment, reduced IL-7R/STAT5 levels promote immunoglobulin kappa gene recombination at the early pro-B cell stage. As a result, differentiating B cells can directly generate a mature B cell receptor (BCR) and bypass the requirement for a pre-BCR and pairing with surrogate light chain. This 'alternate pathway' of development enables the production of B cells with self-reactive, skewed specificity receptors that are peculiar to the B-1a compartment. Together our findings connect seemingly opposing lineage and selection models of B-1a cell development and explain how these cells acquire their unique properties

Nucleosides rescue replication-mediated genome instability of human pluripotent stem cells

Human pluripotent stem cells (PSCs) are subject to the appearance of recurrent genetic variants on prolonged culture. We have now found that, compared with isogenic differentiated cells, PSCs exhibit evidence of considerably more DNA damage during the S phase of the cell cycle, apparently as a consequence of DNA replication stress marked by slower progression of DNA replication, activation of latent origins of replication, and collapse of replication forks. As in many cancers, which, like PSCs, exhibit a shortened G1 phase and DNA replication stress, the resulting DNA damage may underlie the higher incidence of abnormal and abortive mitoses in PSCs, resulting in chromosomal non-dysjunction or cell death. However, we have found that the extent of DNA replication stress, DNA damage, and consequent aberrant mitoses can be substantially reduced by culturing PSCs in the presence of exogenous nucleosides, resulting in improved survival, clonogenicity, and population growth

Phonon Self-energy Effects Due To Superconductivity In Bi2sr2cacu2o8+δ

Raman scattering of A1g phonons in Bi2Sr2CaCu2O8+δ single crystals (δ=0.13, Tc=86 K) has been measured as a function of temperature. We report an anomalous softening in the frequency and a decrease in the linewidth of the A1g phonon at 290 cm-1 (O1,2 c-axis in-phase vibration) below Tc. We also confirm a smaller anomalous softening in the frequency of the A1g phonon at 465 cm-1 (O3 c-axis vibration), but for this phonon mode no linewidth anomaly has been found. We compare the anomalous softening and linewidth behavior in the superconducting state with theoretical calculations for isotropic s-wave, planar d-wave, and dx 2 -y 2 gap symmetries and as for a layered superconductor model.561384268431Thomsen, C., Cardona, M., Gegenheimer, B., Liu, R., Simon, A., (1988) Phys. Rev. B, 37, p. 9860Heynen, E.T., Cardona, M., Karpinski, J., Kaldis, E., Rusiecki, S., (1991) Phys. Rev. B, 43, p. 12958Kendizora, C., Kelley, R.J., Onellion, M., (1996) Phys. Rev. Lett., 77, p. 727Macfarlane, R.M., Rosen, H., Seki, H., (1987) Solid State Commun., 63, p. 831Ruf, T., Thomsen, C., Liu, R., Cardona, M., (1988) Phys. Rev. B, 38, p. 11985Burns, G., Chandrashekhar, G.V., Dacol, F.H., Strobel, P., (1989) Phys. Rev. B, 39, p. 775Bokholt, M., Erie, A., Splittgerber-Hünnekes, P.C., Güntherodt, G., (1990) Solid State Commun., 74, p. 1107Leach, D.H., Thomsen, C., Cardona, M., (1993) Solid State Commun., 88, p. 457Martin, A.A., Lee, M.J.G., (1995) Physica C, 254, p. 222Liu, R., Klein, M., Han, P.D., Payne, D.A., (1992) Phys. Rev. B, 45, p. 7392Menéndez, J., Cardona, M., (1984) Phys. Rev. B, 29, p. 2051Litvinchuk, A.P., Thomsen, C., Cardona, M., (1992) Solid State Commun., 83, p. 343Zeyher, R., Zwicknagl, G., (1990) Z. Phys. B, 78, p. 175Nicol, E.J., Jiang, C., Carbotte, J.P., (1993) Phys. Rev. B, 47, p. 8131Devereaux, T.P., (1994) Phys. Rev. B, 50, p. 10287Kendziora, C., Rosenberg, A., (1995) Phys. Rev. B, 52, pp. R986