586 research outputs found
Multiple lensing of the cosmic microwave background anisotropies
No full textWe study the gravitational lensing effect on the Cosmic Microwave Background (CMB) anisotropies performing a ray-tracing of the primordial CMB photons through intervening large-scale structures (LSS) distribution predicted by N-Body numerical simulations with a particular focus on the precise recovery of the lens-induced polarized counterpart of the source plane. We apply both a multiple plane ray-tracing and an effective deflection approach based on the Born approximation to deflect the CMB photons trajectories through the simulated lightcone. We discuss the results obtained with both these methods together with the impact of LSS non-linear evolution on the CMB temperature and polarization power spectra. We compare our results with semi-analytical approximations implemented in Boltzmann codes like, e.g., CAMB. We show that, with our current N-body setup, the predicted lensing power is recovered with good accuracy in a wide range of multipoles while excess power with respect to semi-analytic prescriptions is observed in the lensing potential on scales ℓ ≥ 3000. We quantify the impact of the numerical effects connected to the resolution in the N-Body simulation together with the resolution and band-limit chosen to synthesise the CMB source plane. We found these quantities to be particularly important for the simulation of B-mode polarization power spectrum
Should physicians always rely on estimated glomerular filtration rate without knowing the equation?
No full textFabio Fabbian, Dario Priori, Alfredo De Giorgi Department of Medical Sciences, Clinica Medica Unit, University Hospital St Anna, University of Ferrara, Ferrara, ItalyWe read with interest the paper written by Deskur-Smielecka et al1 who investigated the performance of three equations for valuating renal function in 174 patients, aged 78 years, with different cancer diagnosis. They used Cockcroft–Gault (C–G), Modification of Diet in Renal Disease (MDRD), and Berlin Initiative Study1 (BIS1) equations and found that there is a considerable disagreement between renal function estimation formulas. We also performed two studies evaluating different formulas for the calculation of glomerular filtration rate (GFR) in patients with eating disorders2 and in those with type 2 diabetes mellitus (DM).3Authors’ replyEwa Deskur-Smielecka1,2 Aleksandra Kotlinska-Lemieszek1,2 Jerzy Chudek3,4 Katarzyna Wieczorowska-Tobis1,2The letter from Fabbian et al, in general, supports our findings concerning the disagreement between currently used equations for the estimation of glomerular filtration rate (GFR). We agree that disagreement in the estimation of kidney function was previously found by a number of authors. However, in our paper1 we describe this aspect in very specific population – geriatric, palliative care patients – with high prevalence of cachexia and substantial muscle mass loss. Our group has shown some similarities (low creatinine generation) to the group of patients with anorexia nervosa and bulimia nervosa studied by Fabbian et al.2 However, it has to be stressed that patients with anorexia nervosa and bulimia nervosa were much younger, and therefore had much better, mostly normal kidney function. The second population analyzed by Fabbian et al3 – diabetic patients – also differ from out cohort, as they were better nourished. Regardless of these differences, the conclusions concerning the disagreement of different methods in the estimation of kidney function are quite similar. Importantly, the disagreement is more clinically significant in older population, including geriatric, palliative care patients, due to much greater prevalence of chronic kidney disease (CKD)4 that affects adjusting drug dosage.View the original paper by Deskur-Smielecka and colleagues
Estimation of renal function in patients with eating disorders
No full textBACKGROUND: Renal function could be evaluated with different equations such as Cockcroft-Gault formula (C-G), Mayo Clinic Quadratic (MAYO) and four MDRD variables. Clinical application of different formulae in conditions with severe energy restriction or in obese subjects is still a matter of investigation.
METHOD: Renal function of 55 anorexia nervosa (AN) and 44 bulimia nervosa (BN) patients was evaluated with C-G formula for creatinine clearance calculation, and glomerular filtration rate (GFR) was estimated with MAYO and MDRD equations.
RESULTS: BN group was older and had higher weight, body mass index (BMI), body surface area than AN subjects; however, their mean BMI was in the normal range. AN group had better renal function than BN one when it was evaluated with MAYO and MDRD; on the contrary, it was worse when it was calculated with C-G. The
results obtained from the three formulae were poorly correlated and Bland-Altman analysis confirmed that the results of the three formulae were not in agreement.
DISCUSSION: C-G is inaccurate when it is applied to obese or cachectic subjects. MDRD underestimates renal function in normal-high GFR. MAYO seems to be a good alternative to the other equations leading to correct classification of patients; therefore, it should be used to diagnose eating disorder subjects as renal
insufficient
Investigating the Effects of Water Levels Measured in Two Nearby Rivers on Groundwater Pore Pressures Regime
No full textThe paper analyzes the groundwater regime in the embankment foundation
of the artificial Gorzone channel located in the Po Plain near Venice, North
Italy, under the conditions imposed by the hydraulic regime of the Gorzone itself
and the nearby Adige river. Sand boils and blow-outs phenomena occur both at and
beyond the levee toe, as the dam located some kilometers downstream is activated
to keep the channel water level high for irrigation purposes in spring and summer.
In order to design proper interventions, the seepage under the embankment has
been investigated and the groundwater regime has been monitored for 2 years.
The acquired data revealed that pore pressure regime in the deeper layers is not
completely consistent with the Gorzone water level variations; it seems influenced
also by the hydraulic regime of the nearby Adige river, that here flows parallel to
Gorzone, at the distance of 180 m from the opposite levee.
The paper presents the results of some FEM analysis carried out to better
investigate the groundwater regime under the influence of Adige and other local
forcings. After a calibration based on the acquired pressure data, the model was
used to analyze the levee seepage regime under different boundary conditions.
The numerical results highlight that the sand-boils and blow outs are probably
caused by a seepage confined in the upper high-permeability deposit induced by
Gorzone water level, while the deeper pore pressures are mainly related to the
Adige hydraulic conditions and to the activity of some extracting wells in the
area
Hidden β-γ Dehydrogenation Products in Long-Chain Fatty Acid Oxidation Unveiled by NMR: Implications on Lipid Metabolism
No full textWe present a comprehensive analysis of the initial α,β-dehydrogenation step in long-chain fatty acid β-oxidation (FAO). We focused on palmitoyl-CoA oxidized by two mitochondrial acyl-CoA dehydrogenases, very-long-chain acyl-CoA dehydrogenase (VLCAD) and acyl-CoA dehydrogenase family member 9 (ACAD9), both implicated in mitochondrial diseases. By combining MS and NMR, we identified the (2E)-hexadecenoyl-CoA as the expected α-β-dehydrogenation product and also the E and Z stereoisomers of 3-hexadecenoyl-CoA: a “γ-oxidation” product. This finding reveals an alternative catalytic pathway in mitochondrial FAO, suggesting a potential regulatory role for ACAD9 and VLCAD during fatty acid metabolism
Interdialytic weight gain and 48-h blood pressure in haemodialysis patients
No full textBackground. Hypertension, which is often associated with hypervolaemia, is
common in haemodialysis patients and is a known determinant of target organ
damage. Interdialytic weight gain due to volume overload has also been
associated with mortality in haemodialysis patients. Methods. We therefore
studied 27 chronic haemodialysis patients who underwent 48-h ambulatory
blood pressure monitoring between two midweek dialysis sessions, and 2D and
M-mode echocardiography for determination of left ventricular mass index.
Results. Left ventricular hypertrophy (left ventricular mass index in men >
131 g/m(2), women > 100 g/m(2)) was present in 70% (19/27) patients despite
a mean 48-h blood pressure of 132 (plus or minus) 19/81 (plus or minus) 15
mmHg. Mean interdialytic weight gain was 1.6 (plus or minus) 0.8 kg and was
not related to left ventricular mass index. Two patterns of interdialytic
blood pressure change were apparent: in group 1 (16 patients) 48-h blood
pressure increased (+ 19 (plus or minus) 12/13 (plus or minus) 9 mmHg),
whereas in group 2 (11 patients) blood pressure fell (- 10 (plus or minus)
13/-8 (plus or minus) 10 mmHg P < 0.0001). In both groups the number of
hypertensive patients (group 1, 10/16; group 2, 6/11), the 48-h blood
pressure (132 (plus or minus) 20/80 (plus or minus) 15 vs 132 (plus or
minus) 18/82 (plus or minus) 15 mmHg) and interdialytic weight gain (+ 1.9
(plus or minus) 0.7 vs + 1.3 (plus or minus) 0.7 kg) were similar. There
was also no correlation between interdialytic blood pressure change and
weight gain in either group. Conclusions. We conclude that interdialytic
blood pressure changes cannot be directly related to interdialytic fluid
gain, even in apparent volume-dependent hypertension, emphasizing the
importance of additional factors in the control of blood pressure in
end-stage renal disease
The self-locating catheter: Clinical evaluation and comparison with the Tenckhoff catheter
No full textBackground: Peritoneal catheter displacement appears to be related to
various causes including omental attachment, bowel contractions, peritoneal
adhesions, and the catheter floating in the dialysis fluid. In order to
prevent this complication, which can impair peritoneal dialysis efficacy,
Di Paolo et al. designed a 'self-locating catheter' (SLC) that is similar
to the Tenckhoff catheter (TC) and includes a small tungsten cylinder
(weight 12 g) at the distal end. The weight of the tip prevents the
catheter from floating and migrating by gravitation toward the Douglas
cavity. Objective: Starting in 1996, we implanted SLC in 15 continuous
ambulatory peritoneal dialysis patients. The aim of our study was to
compare the ratio of migration and other catheter-related complications
between patients with SLC (196 patient-months) and 13 patients with
conventional straight TC (295 patient-months). Results: Peritonitis ratio,
catheter complication rate, dialysate inflow and outflow, and weekly
creatinine clearance were similar in the two groups of patients. The
incidence of catheter displacement was significantly higher (p = 0.0349) in
the TC group than in the SLC group (4 vs 0). Conclusion: In our experience,
the SLC seems to be useful in preventing catheter migration by continuous
gravitation of its extremity toward the pelvic cavity
The relationship between carotid and coronary atherosclerotic damage in dialysis patients
No full textBackground: Data relating carotid ultrasound (CU) to atherosclerotic damage
evaluated by coronary angiography in hemodialysis patients are scarce.
Methods: We carried out a cross-sectional study in 33 uremic subjects (age
55(plus or minus)12 years, 22 male, 7 diabetic), who have been on dialysis
for 41(plus or minus)48 months (range 2-192). Twenty-two underwent a
coronary angiography in order to complete clinical evaluation for inclusion
on the kidney transplantation waiting list, and 11 because of coronary
artery disease (CAD); Gensini's score was calculated. Intima-media
thickness (IMT) and presence of plaques were related to the degree of
coronary stenosis and to cardiovascular risk factors. Patients were divided
into two groups depending on mean IMT (group 1 IM (less-than or equal to)
0.9 mm, n=18; group 2 IMT>0.9 mm, n=15). Results: Group 2 was older
(60(plus or minus)8 vs 50(plus or minus)12 year, p=0.01), had higher
frequency of CAD (53 vs 16%, p=0.02) and had higher prevalence of coronary
artery stenosis (greater-than or equal to)75% in the right (60 vs 22%,
p=0.02), left anterior descending (46 vs 16%, p=0.06) and left circumflex
coronary arteriers (60 vs 11 %, p=0.05) than group 1. IMT was not related
to the degree of CAD evaluated by Gensini's score. IMT sensibility and
specificity in detecting the presence of hemodynamically significant
coronary stenosis were 64% and 68%, respectively. Coronary narrowing was
correlated with the degree of stenosis of common, internal and external
carotid arteries (Spearman's rank correlation coefficient). During two
years of follow-up, six major cardiac events were recorded and they were
related to Gensini's score. Conclusions: In uremic patients,
ultrasonographic evaluation of carotid arteries is a simple, non-invasive
examination that could be a helpful tool in detecting coronary
atherosclerotic damage, but IMT does not appear to add more information
regarding risk stratification of CAD
The relationship between carotid and coronary atherosclerotic damage in dialysis patients.
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