3,607 research outputs found
Achieving Consistent Doppler Measurements from SDO/HMI Vector Field Inversions
NASA's Solar Dynamics Observatory is delivering vector field observations of
the full solar disk with unprecedented temporal and spatial resolution;
however, the satellite is in a highly inclined geostationary orbit. The
relative spacecraft-Sun velocity varies by ~km/s over a day which
introduces major orbital artifacts in the Helioseismic Magnetic Imager data. We
demonstrate that the orbital artifacts contaminate all spatial and temporal
scales in the data. We describe a newly-developed three stage procedure for
mitigating these artifacts in the Doppler data derived from the Milne-Eddington
inversions in the HMI Pipeline. This procedure was applied to full disk images
of AR11084 to produce consistent Dopplergrams. The data adjustments reduce the
power in the orbital artifacts by 31dB. Furthermore, we analyze in detail the
corrected images and show that our procedure greatly improve the temporal and
spectral properties of the data without adding any new artifacts. We conclude
that this new and easily implemented procedure makes a dramatic improvement in
the consistency of the HMI data and in its usefulness for precision scientific
studies.Comment: 58 pages, 19 figures, submitted to Ap
The Effect of Hydrogen Bonding in Enhancing the Ionic Affinities of Immobilized Monoprotic Phosphate Ligands
Environmental remediation requires ion-selective polymers that operate under a wide range of solution conditions. In one example, removal of trivalent and divalent metal ions from waste streams resulting from mining operations before they enter the environment requires treatment at acidic pH. The monoethyl ester phosphate ligands developed in this report operate from acidic solutions. They have been prepared on polystyrene-bound ethylene glycol, glycerol, and pentaerythritol, and it is found that intra-ligand hydrogen bonding affects their metal ion affinities. The affinity for a set of trivalent (Fe(III), Al(III), La(III), and Lu(III)) and divalent (Pb(II), Cd(II), Cu(II), and Zn(II)) ions is greater than that of corresponding neutral diethyl esters and phosphonic acid. In an earlier study, hydrogen bonding was found important in determining the metal ion affinities of immobilized phosphorylated polyol diethyl ester coordinating ligands; their Fourier transform infrared (FTIR) band shifts indicated that the basicity of the phosphoryl oxygen increased by hydrogen bonding to auxiliary –OH groups on the neighboring polyol. The same mechanism is operative with the monoprotic resins along with hydrogen bonding to the P–OH acid site. This is reflected in the FTIR spectra: the neutral phosphate diethyl ester resins have the P=O band at 1265 cm�1 while the monoethyl ester resins have the band shifted to 1230 cm�1; hydrogen bonding is further indicated by the broadness of this region down to 900 cm�1. The monoprotic pentaerythritol has the highest metal ion affinities of the polymers studied
Do dietary patterns in older men influence change in homocysteine through folate fortification? The Normative Aging Study
Objective We aimed to describe the difference in B-vitamin intake and in plasma B-vitamin and homocysteine concentrations before and after folic acid fortification, in relation to dietary patterns. Design The Normative Aging Study (NAS) is a longitudinal study on ageing. Between 1961 and 1970, 2280 male volunteers aged 21¿80 years (mean 42 years) were recruited. Dietary intake data have been collected since 1987 and assessment of plasma B vitamins and homocysteine was added in 1993. Setting Boston, Massachusetts, USA. Subjects In the present study, 354 men who had completed at least one FFQ and one measurement of homocysteine, both before and after the fortification period, were included. Results Three dietary patterns were identified by cluster analysis: (i) a prudent pattern, with relatively high intakes of fruit, vegetables, low-fat milk and breakfast cereals; (ii) an unhealthy pattern, with high intakes of baked products, sweets and added fats; and (iii) a low fruit and vegetable but relatively high alcohol intake pattern. Dietary intake and plasma concentrations of folate increased significantly (P <0·05) among all dietary patterns after the fortification period. Homocysteine tended to decrease in supplement non-users and in subjects in the high alcohol, low fruit and vegetable dietary pattern (both P = 0·08). Conclusions After fortification with folic acid, folate intake and plasma folate concentration increased significantly in all dietary patterns. There was a trend towards greatest homocysteine lowering in the high alcohol, low fruit and vegetable grou
An investigation into the feasibility of myoglobin-based single-electron transistors
Myoglobin single-electron transistors were investigated using nanometer- gap
platinum electrodes fabricated by electromigration at cryogenic temperatures.
Apomyoglobin (myoglobin without heme group) was used as a reference. The
results suggest single electron transport is mediated by resonant tunneling
with the electronic and vibrational levels of the heme group in a single
protein. They also represent a proof-of-principle that proteins with redox
centers across nanometer-gap electrodes can be utilized to fabricate
single-electron transistors. The protein orientation and conformation may
significantly affect the conductance of these devices. Future improvements in
device reproducibility and yield will require control of these factors
Deformations of calibrated subbundles of Euclidean spaces via twisting by special sections
We extend the "bundle constructions" of calibrated submanifolds, due to
Harvey--Lawson in the special Lagrangian case, and to
Ionel--Karigiannis--Min-Oo in the cases of exceptional calibrations, by
"twisting" the bundles by a special (harmonic, holomorphic, parallel) section
of a complementary bundle. The existence of such deformations shows that the
moduli space of calibrated deformations of these "calibrated subbundles"
includes deformations which destroy the linear structure of the fibre.Comment: 16 pages, no figures. Version 2: Only minor cosmetic and
typographical revisions. To appear in "Annals of Global Analysis and
Geometry.
The two ways of gauging the Poincare' group
A description of how a theory of gravity can be considered as a gauge theory
(in the sense of Trautman) of the Poincare' group is given. As a result, it is
shown that a gauge theory of this kind is consistent with the Equivalence
Principle only if the Lagrangian and the constraints are preserved not only by
the gauge transformations but also by an additional family of transformations,
called "pseudo-translations". Explicit expressions of pseudo-translations and
of their action on gravitational gauge fields are given. They are expected to
be useful for geometric interpretations of their analogues in supergravity
theories.Comment: 21 page
Not All Piggybacks Are Equal: A Retrospective Cohort Analysis of Variation in Anhepatic Transcaval Pressure Gradient and Acute Kidney Injury During Liver Transplant
Objectives: Complete inferior vena cava clamping in caval replacement during liver transplant is associated with substantial physiological derangement and postoperative morbidity. Partial clamping in the piggyback technique may be relatively protective, but evidence is lacking. Having observed substantial variation in transhepatic inferior vena cava pressure gradient with piggyback, we hypothesized that the causative mechanism is the extent of caval clamping rather than the surgical approach.
Materials and Methods: We used internal jugular and femoral catheters to estimate suprahepatic and infrahepatic inferior vena cava pressures during clamping. Pressure gradients were calculated, and distributions were compared by surgical technique. We estimated adjusted odds ratios for pressure gradient on acute kidney injury at 72 hours.
Results: In 115 case records, we observed substantial variation in maximum pressure gradient; median values were 18.0 mm Hg (interquartile range, 8.0-25.0 mm Hg) with the piggyback technique and 24.0 mm Hg (interquartile range, 19.5-27.0 mm Hg) with caval replacement. Incidence of acute kidney injury was 25% (29 patients). Pressure gradient was linearly associated with probability of acute kidney injury (odds ratio, 1.06; 95% CI, 1.01-1.13).
Conclusions: We report 2 novel findings. (1) Anhepatic inferior vena cava pressure gradient varied substantially in individuals undergoing piggyback, and (2) gradient was positively associated with early acute kidney injury. We hypothesize that this (unmeasured) variation explains the conflicting findings of previous studies that compared surgical techniques. Also, we propose that caval pressure gradient could be routinely assessed to optimize real-time piggyback clamp position during liver transplant surgery
Clinical features, anaesthetic management and perioperative complications seen in three horses with pheochromocytoma
Three horses presenting with colic signs to the Equine Referral Hospital at The Royal Veterinary College underwent general anaesthesia between September 2013 and November 2017 for emergency exploratory laparotomy. No obvious cause for the colic signs was identified in two horses, while a haemoperitoneum was identified in the third. All horses were euthanased within 12 hours of surgery due to deteriorating haemodynamic instability and/or intractable pain. Postmortem examination revealed an adrenal mass in each case, confirmed to be a pheochromocytoma on histopathology. In retrospect, each horse had some hallmark characteristics consistent with a functional pheochromocytoma, including hyperglycaemia and hyperlactataemia. Extremely high packed cell volume (PCV) (>65 per cent) was also identified in two horses, with a high-normal PCV found in the haemoperitoneum case. Perioperative haemodynamic instability was predominantly characterised by episodes of intermittent hypertension and tachycardia
Bryant-Salamon manifolds and coassociative fibrations
Bryant-Salamon constructed three 1-parameter families of complete manifolds
with holonomy which are asymptotically conical to a holonomy
cone. For each of these families, including their asymptotic
cone, we construct a fibration by asymptotically conical and conically singular
coassociative 4-folds. We show that these fibrations are natural
generalizations of the following three well-known coassociative fibrations on
: the trivial fibration by 4-planes, the product of the standard
Lefschetz fibration of with a line, and the Harvey-Lawson
coassociative fibration. In particular, we describe coassociative fibrations of
the bundle of anti-self-dual 2-forms over the 4-sphere , and the
cone on , whose smooth fibres are ,
and whose singular fibres are . We relate these
fibrations to hypersymplectic geometry, Donaldson's work on Kovalev-Lefschetz
fibrations, harmonic 1-forms and the Joyce--Karigiannis construction of
holonomy manifolds, and we construct vanishing cycles and
associative "thimbles" for these fibrations.Comment: 76 pages, 7 tables, 11 colour figures. Version 2: Discussion of
multimoment maps clarified. Other minor revisions and improvements made as
per suggestions of the referee. Final version, to appear in Journal of
Geometry and Physics. Version 3: Corrected three spelling errors, updated
publication info of reference [18], and added funding information to
acknowledgement
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