1,327 research outputs found
One-step synthesis of pyridines and dihydropyridines in a continuous flow microwave reactor
The Bohlmann–Rahtz pyridine synthesis and the Hantzsch dihydropyridine synthesis can be carried out in a microwave flow reactor or using a conductive heating flow platform for the continuous processing of material. In the Bohlmann–Rahtz reaction, the use of a Brønsted acid catalyst allows Michael addition and cyclodehydration to be carried out in a single step without isolation of intermediates to give the corresponding trisubstituted pyridine as a single regioisomer in good yield. Furthermore, 3-substituted propargyl aldehydes undergo Hantzsch dihydropyridine synthesis in preference to Bohlmann–Rahtz reaction in a very high yielding process that is readily transferred to continuous flow processing
Contemporary reproductive outcomes for patients with polycystic ovary syndrome: a retrospective observational study
Context Polycystic ovary syndrome (PCOS) is the commonest cause of anovulatory infertility
and may be associated with adverse pregnancy and neonatal outcomes. However, it is
difficult to establish how much of this risk is due to PCOS and how much to obesity.
Objective
To determine the impact of PCOS upon fertility, pregnancy and neonatal outcomes.
Design and setting
Data were extracted from the Clinical Practice Research Datalink (CPRD), a longitudinal
anonymized primary care research database in the UK. Patients with a diagnosis of PCOS
were matched to controls (1:2) by age (+/-1 year), BMI (+/- 3 units) and CPRD practice.
Standardised fertility ratios (SFR) before and after diagnosis (index date) were calculated.
Rates of miscarriage, pre-eclampsia, gestational diabetes, premature delivery, delivery
method and neonatal outcomes were compared.
Results
9,068 women with PCOS matched study criteria. Prior to index date the SFR for patients
with PCOS was 0.80 (95% CI 0.77-0.83); following index date it was 1.16 (1.12-1.20). The
adjusted odds ratios (OR) for miscarriage (1.70; 1.56-1.84), pre-eclampsia (1.32; 1.16-1.49),
gestational diabetes (1.41; 1.2-1.66) and premature delivery (1.25; 1.1-1.43) were all
increased compared to controls. Of PCOS births, 27.7% were by Caesarean section
compared with 23.7% of controls (1.13; 1.05-1.21). Infants born to mothers with PCOS had
an increased risk of neonatal jaundice (1.20; 1.03-1.39) and respiratory complications (1.20;
1.06-1.37).
Conclusions
PCOS is associated with subfertility but fertility rates are restored to those of the
background population following diagnosis. Pregnancy complications and adverse neonatal
outcomes are more prevalent for women with PCOS independently of obesity
Masses of Orbitally Excited Baryons in Large N_c QCD
We present the first phenomenological study of the masses of orbitally
excited baryons in large N_c QCD. Restricting here to the nonstrange sector of
the L=1 baryons, the 1/N_c expansion is used to order and select a basis of
effective operators that spans the nine observables (seven masses and two
mixing angles). Fits are performed using subsets of the complete set of nine
operators, including corrections up to O(1/N_c) where leading order is N_c^1.
This study shows that the 1/N_c expansion provides an excellent framework for
analyzing the mass spectrum, and uncovers a new hierarchy of operator
contributions.Comment: 15 pages, revte
Decays of Baryons --- Quark Model versus Large-
We study nonleptonic decays of the orbitally excited, \su6 \rep{70}-plet
baryons in order to test the hypothesis that the successes of the
nonrelativistic quark model have a natural explanation in the large- limit
of QCD. By working in a Hartree approximation, we isolate a specific set of
operators that contribute to the observed s- and d-wave decays in leading order
in . We fit our results to the current experimental decay data, and make
predictions for a number of allowed but unobserved modes. Our tentative
conclusion is that there is more to the nonrelativistic quark model of baryons
than large-.Comment: LaTeX 49pp. (38 pp. landscape), PicTex, PrePicTex, PostPicTex
required for 3 figures, Harvard Preprint HUTP-94/A008. (Two additional
operators are included, but conclusions are unchanged.
Measuring Transit Signal Recovery in the Kepler Pipeline. III. Completeness of the Q1-Q17 DR24 Planet Candidate Catalogue, with Important Caveats for Occurrence Rate Calculations
With each new version of the Kepler pipeline and resulting planet candidate
catalogue, an updated measurement of the underlying planet population can only
be recovered with an corresponding measurement of the Kepler pipeline detection
efficiency. Here, we present measurements of the sensitivity of the pipeline
(version 9.2) used to generate the Q1-Q17 DR24 planet candidate catalog
(Coughlin et al. 2016). We measure this by injecting simulated transiting
planets into the pixel-level data of 159,013 targets across the entire Kepler
focal plane, and examining the recovery rate. Unlike previous versions of the
Kepler pipeline, we find a strong period dependence in the measured detection
efficiency, with longer (>40 day) periods having a significantly lower
detectability than shorter periods, introduced in part by an incorrectly
implemented veto. Consequently, the sensitivity of the 9.2 pipeline cannot be
cast as a simple one-dimensional function of the signal strength of the
candidate planet signal as was possible for previous versions of the pipeline.
We report on the implications for occurrence rate calculations based on the
Q1-Q17 DR24 planet candidate catalog and offer important caveats and
recommendations for performing such calculations. As before, we make available
the entire table of injected planet parameters and whether they were recovered
by the pipeline, enabling readers to derive the pipeline detection sensitivity
in the planet and/or stellar parameter space of their choice.Comment: 8 pages, 5 figures, full electronic version of Table 1 available at
the NASA Exoplanet Archive; accepted by ApJ May 2nd, 201
The deep distributions of helium isotopes, radiocarbon, and noble gases along the U.S. GEOTRACES East Pacific Zonal Transect (GP16)
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Marine Chemistry 201 (2018): 167-182, doi:10.1016/j.marchem.2017.03.009.We report the deep distributions of noble gases, helium isotopes, and radiocarbon measured during the U.S. GEOTRACES GP16 East Pacific Zonal Transect between 152 and 77°W at 12- 15°S in the South Pacific. The dominant feature is an intense tongue of hydrothermal effluent that extends more than 4,000 km westward from the East Pacific Rise (EPR) at ~2500m depth. The patterns reveal significant “downstream” variations in water mass structure, advection, and mixing that belie the simple perception of a continuous plume extending westward from the EPR. For example, one feature observed at 120°W, 14°S has tracer signatures that are consistent with a water mass originating from an area as much as 2,000 km south of this section, suggesting a quasi-permanent northward flow on the western flank of the EPR. Helium isotope variations in the plume show a uniquely high 3He/4He source in the tongue compared with typical mid-ocean ridge basalts (MORB), consistent with the anomalously high ratios observed in MORB glasses from the EPR segment just south of this transect. The water column data also reveal that the background 3He/4He east of the EPR is significantly lower than values characteristic of MORB, suggesting an additional, more geographically distributed radiogenic 4He flux of order 107 mol/y into the deep Pacific.
In the western end of the section, incoming bottom waters have relatively less hydrothermal hydrothermal helium, more radiocarbon, and more oxygen, as well as negative saturation anomalies for the heavy noble gases (Ar, Kr, and Xe). During the basin-scale upwelling of this water, diapycnal mixing serves to erase these negative anomalies. The relative magnitudes of the increases for the heavy noble gases (Ar, Kr, and Xe) are quantitatively consistent with this process. This leads us to estimate the relatively smaller effects on He and Ne saturations, which range from near zero to 0.2% and 0.3% respectively. With this information, we are able to refine our estimates of the magnitude of 3He and 4He excesses and the absolute 3He/4He ratio of non-atmospheric helium introduced into deep Pacific waters.The work was funded under National Science Foundation grant number OCE-1232991 for WJJ and OCE-1130870 for CRG
The Influence of Sex and Season on Conspecific Spatial Overlap in a Large, Actively-Foraging Colubrid Snake
Understanding the factors influencing the degree of spatial overlap among conspecifics is important for understanding multiple ecological processes. Compared to terrestrial carnivores, relatively little is known about the factors influencing conspecific spatial overlap in snakes, although across snake taxa there appears to be substantial variation in conspecific spatial overlap. In this study, we described conspecific spatial overlap of eastern indigo snakes (Drymarchon couperi) in peninsular Florida and examined how conspecific spatial overlap varied by sex and season (breeding season vs. non-breeding season). We calculated multiple indices of spatial overlap using 6- and 3-month utilization distributions (UD) of dyads of simultaneously adjacent telemetered snakes. We also measured conspecific UD density values at each telemetry fix and modeled the distribution of those values as a function of overlap type, sex, and season using generalized Pareto distributions. Home range overlap between males and females was significantly greater than overlap between individuals of the same sex and male home ranges often completely contained female home ranges. Male home ranges overlapped little during both seasons, whereas females had higher levels of overlap during the non-breeding season. The spatial patterns observed in our study are consistent with those seen in many mammalian carnivores, in which low male-male overlap and high inter-sexual overlap provides males with greater access to females. We encourage additional research on the influence of prey availability on conspecific spatial overlap in snakes as well as the behavioral mechanisms responsible for maintaining the low levels of overlap we observed
Cardiac myocyte-specific knock-out of calcium-independent phospholipase A2Îł (iPLA2Îł) decreases oxidized fatty acids during ischemia/reperfusion and reduces infarct size
Calcium-independent phospholipase A(2)Îł (iPLA(2)Îł) is a mitochondrial enzyme that produces lipid second messengers that facilitate opening of the mitochondrial permeability transition pore (mPTP) and contribute to the production of oxidized fatty acids in myocardium. To specifically identify the roles of iPLA(2)Îł in cardiac myocytes, we generated cardiac myocyte-specific iPLA(2)Îł knock-out (CMiPLA(2)ÎłKO) mice by removing the exon encoding the active site serine (Ser-477). Hearts of CMiPLA(2)ÎłKO mice exhibited normal hemodynamic function, glycerophospholipid molecular species composition, and normal rates of mitochondrial respiration and ATP production. In contrast, CMiPLA(2)ÎłKO mice demonstrated attenuated Ca(2+)-induced mPTP opening that could be rapidly restored by the addition of palmitate and substantially reduced production of oxidized polyunsaturated fatty acids (PUFAs). Furthermore, myocardial ischemia/reperfusion (I/R) in CMiPLA(2)ÎłKO mice (30 min of ischemia followed by 30 min of reperfusion in vivo) dramatically decreased oxidized fatty acid production in the ischemic border zones. Moreover, CMiPLA(2)ÎłKO mice subjected to 30 min of ischemia followed by 24 h of reperfusion in vivo developed substantially less cardiac necrosis in the area-at-risk in comparison with their WT littermates. Furthermore, we found that membrane depolarization in murine heart mitochondria was sensitized to Ca(2+) by the presence of oxidized PUFAs. Because mitochondrial membrane depolarization and calcium are known to activate iPLA(2)Îł, these results are consistent with salvage of myocardium after I/R by iPLA(2)Îł loss of function through decreasing mPTP opening, diminishing production of proinflammatory oxidized fatty acids, and attenuating the deleterious effects of abrupt increases in calcium ion on membrane potential during reperfusion
Detection of Potential Transit Signals in the First Three Quarters of Kepler Mission Data
We present the results of a search for potential transit signals in the first
three quarters of photometry data acquired by the Kepler Mission. The targets
of the search include 151,722 stars which were observed over the full interval
and an additional 19,132 stars which were observed for only 1 or 2 quarters.
From this set of targets we find a total of 5,392 detections which meet the
Kepler detection criteria: those criteria are periodicity of the signal, an
acceptable signal-to-noise ratio, and a composition test which rejects spurious
detections which contain non-physical combinations of events. The detected
signals are dominated by events with relatively low signal-to-noise ratio and
by events with relatively short periods. The distribution of estimated transit
depths appears to peak in the range between 40 and 100 parts per million, with
a few detections down to fewer than 10 parts per million. The detected signals
are compared to a set of known transit events in the Kepler field of view which
were derived by a different method using a longer data interval; the comparison
shows that the current search correctly identified 88.1% of the known events. A
tabulation of the detected transit signals, examples which illustrate the
analysis and detection process, a discussion of future plans and open,
potentially fruitful, areas of further research are included
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