508 research outputs found
Perspective on Some Recent and Future Developments in Casimir Interactions
No full textHere, we present a critical review of recent developments in Casimir physics motivated by discoveries of novel materials. Specifically, topologically nontrivial properties of the graphene family, Chern and topological insulators, and Weyl semimetals have diverse manifestations in the distance dependence, presence of fundamental constants, magnitude, and sign of the Casimir interaction. Limited studies of the role of nonlinear optical properties in the interaction are also reviewed. We show that, since many new materials have greatly enhanced the nonlinear optical response, new efficient pathways for investigation of the characteristic regimes of the Casimir force need to be explored, which are expected to lead to new discoveries. Recent progress in the dynamical Casimir effect is also reviewed and we argue that nonlinear media can open up new directions in this field as well
The peculiar galaxy Mkn 298 revisited with integral field spectroscopy
No full textSpectroscopic and imaging data of the peculiar galaxy Mkn 298 are presented. Narrow-band Hα and broad-band R images are used to study the star formation rate in the galaxy and its morphology, which is typical of a merging system. Long-slit and integral field spectra are used to assess the kinematics of gas and stars, and the nature of the ionizing source at different distances from the nucleus. In particular, the nucleus of Mkn 298 is characterized by peculiar line ratios: [N II]λ6583/Hα is typical of H II-like regions, while [O I]λ6300/Hα could indicate the presence of an active galactic nucleus. We show that models where a shock component is added to photoionization from a starburst allow us to reproduce the observed line ratios. Mkn 298 is thus most likely a star-forming galaxy, rather than a galaxy hosting an active nucleus.
Based on data obtained at the 2.2m and NTT telescopes of ESO-la Silla (Chile), at the 2.2m telescope of DSAZ-Calar Alto (Spain), and at the 6m telescope of SAO (Russia)
The sorin freedom stentless pericardial valve: clinical and echocardiographic performance at 10 years
Get PDFObjective: The Sorin Pericarbon Freedom (SPF) is a stentless valve made of pericardium clinically available in 1990. We report the clinical and hemodynamic performance of the SPF at 10 years. Methods: From April 2000 to December 2005, 85 patients with a mean age of 75 ± 6 years (range 57-86), underwent aortic valve replacement (AVR) with an SPF. Mean left ventricular ejection fraction was 58 ± 10\% (range 29-86\%) and mean peak transvalvular gradient (PG) 86 ± 24 mmHg. Clinical evaluation was performed at 3, 6, 12 months, and yearly thereafter. Results: There were 2 operative deaths (2.4\%). Follow-up ranged from 2 to 135 months (mean 78 ± 32 months) and was 99\% complete. There were 35 late deaths, 7 of which were valve-related, with an actuarial survival of 45 ± 8\% at 10 years. Structural SPF deterioration occurred in 2 patients, with an actuarial freedom of 96 ± 3\%. A total of 4 patients were re-operated, 2 because of structural deterioration, 1 because of endocarditis, and 1 because of sinotubular junction dilatation; freedom from reoperation was 93 ± 4\% at 10 years. At last clinical control, 41 patients (89\%) were in NYHA class I or II. Mean SPF effective orifice area varied from 1.55 ± 0.66 cm2 for size 21 mm to 2.33 ± 0.86 cm2 for size 27 mm; PG varied from 19 ± 10 mmHg for size 21 mm to 11 ± 6 mmHg for size 27 mm. Left ventricular mass index decreased from 213 ± 51 gm/m2 to 157 ± 436 gm/m2 (p<0.001). Conclusions: The SPF has demonstrated overall good results in terms of valve durability and freedom from valve-related complications up to 10 years, with excellent hemodynamic performance
Influence of Myocardial Fibrosis on Left Ventricular Hypertrophy in Patients with Symptomatic Severe Aortic Stenosis
Get PDFAim: It was the aim of our study to determine whether myocardial fibrosis influences physiologic or non-physiologic left ventricular (LV) hypertrophy in severe aortic stenosis. Methods: Myocardial fibrosis was evaluated using specimens taken from the ventricular septum in 79 patients submitted to aortic valve replacement because of symptomatic aortic stenosis. Patients were considered to have physiologic LV hypertrophy if end-systolic wall stress, evaluated by echocardiography, was 90 kdyn/cm(2) were considered to have non-physiologic hypertrophy. Results: Fibrosis tissue mass index was significantly inversely related with LV fractional shortening and directly related with LV diastolic and systolic diameter and LV mass index (LVMI). Patients with non-physiologic hypertrophy (n = 24) had a higher LVMI due to larger LV diastolic and systolic diameters with thinner wall, resulting in lower relative wall thickness. These patients had a higher fibrosis tissue mass index and impaired LV systolic and diastolic functions, as suggested by lower LV fractional shortening and higher mean wedge pressure. At follow-up of 7.4 ± 2.1 months, the LVMI and New York Heart Association class remained higher in patients with non-physiologic hypertrophy. Conclusions: Our study suggests a different quality of hypertrophies in patients with aortic stenosis, where myocardial fibrosis seems to be the critical abnormality that differentiates adaptive from maladaptive response to increased afterload
The integral field spectroscopy (IFS) as a tool for investigating the nature of active galactic nuclei
No full textTwenty Year Patient Survival and 17 Year Complications of Isolated Mitral Biocor Standard Porcine Valve
No full textObjective: Performance of the prostheses must be verified in the time domain. We report the 20-year survival of 230 patients operated of mitral replacement with Biocor Standard prosthesis in Padova and Verona and the 17 year prosthetic failure and complications of the series of Padova.
Methods: 230 patients, 150 females and 80 males, aged 71 ± 6.3 received 235 isolated mitral Prostheses in Verona (67) and Padova (168), between June 1989 and August 2004. Twenty-year survival including 1698 patient- years was complete. Prosthesis survival was evaluated in the patients of Padova with a 90% goodness of follow-up and included 905 patient-years.
Results: Twenty-seven operations were done in the eighties, 168 in the nineties, 52 in this century. Three operations were emergent, 20 urgent. The indication was prosthetic malfunction in 50 cases (21.7%), regurgitation in 114 (49.6%), stenosis in 22 (9.7%), mixed lesion in 44 (19.1%), concomitant CABG (Coronary Artery Bypass Graft) was performed in 23%. Overall survival was 6% (2-13%), Thirty day mortality was 8.9% (5.6-13.3%). The early hazard phase extended to 2.5 years with a linearized rate 1.4%/patient-years vs. a late rate of 7.2%/patient-years. Seventeen years freedom from reoperation was 80.5% (55.3-92.3%), actual 92% (86.4-94.5%), from SVD (Structural Valve Degeneration) 85.2% (52.6-96.1%) actual 94% (88.2-96.7%), from perivalvular leak 92.6% (86.5-96%), from embolism 83.1% (73-89.7%), from haemorrhage 83.8% (71.5-91.1%), from endocarditis 90.9% (82.4-95.4%), from pacemaker 77% (60.2-87.5%).
Conclusion: Mitral Biocor has optimal durability and average complications. Premature mortality (6% vs. 30% survival of US (United States) matched population) is unrelated to prosthesis performance and suggest failure of our surgical strategy of the past centur
The Sorin Freedom Stentless Pericardial Valve: A Valid Benchmark For Current Percutaneous Devices
No full textObjectives: Trans-catheter aortic valve implantation (TAVI) has emerged as
an alternative to aortic valve replacement (AVR) for severe aortic stenosis. The
majority of TAVI systems currently available incorporate pericardial stentless
bioprostheses, with only short follow-up data available. Therefore information
on long-term results of AVR with a stentless pericardial valve, such as the Sorin
Freedom (SF), represents a valid benchmark. In this study we report the clinical
and hemodynamic performance of SF with a 10-year follow-up.
Methods: From January 2000 to December 2004, 78 patients, mean age
5.6±5.8 years, underwent AVR with SF. Sixteen (20.5%) were in NYHA class IV,
18 (23.1%) in III, 44 (56.4%) in class I or II. Mean ejection fraction (LVEF) was
58.11±11.16%. Echocardiographic evaluation was performed at 3, 12 months
and yearly thereafter assessing effective orifice area (EOA), gradients (PG) and
regression of left ventricular mass index (LVMi).
Results: There was 1 operative death (1.2%). A total of 77 patients were
discharged and followed for total follow-up of 5602 months (mean 70±25
months). There were 24 late deaths with an actuarial survival of 56±8.8% at
10 years. Three patients were reoperated, with a freedom from reoperation
of 95±3% at 10 years, because of structural deterioration, endocarditis and
dilatation of sinotubular junction, respectively. At last clinical control 47 patients
(90%) were in NYHA class I or II and 5 patients (9%) were in NYHA class III.
Mean EOA varied from 1.8±0.8cm2 for valve size21 to 2.3±0.6 cm2 for size27
and mean PG varied from 22±9 mmHg for valve size21 to 13±4 mm Hg for
size27. LVMi decreased from 182.9±39.6gm/m2 to 142.1±42.6gm/m2 (p<0.001).
Conclusions: SF stentless bioprosthesis has provided good results in terms of valve durability and freedom from valve-related complications with excellent hemodynamic performance at 10-year follow-up. These data represent important reference point against which performance of current TAVI systems must be compared
Modified Open Circuit and Vacuum-assisted Venous Return Reduces Blood Usage During Cardiopulmonary Bypass
No full textObjectives: To determine whether vacuum-assisted venous return has clinical advantages over conventional gravity drainage apart from allowing the use of smaller cannulas, shorter tubing and reduced priming.
Methods: A total of 80 CABG operations were performed at our institution
between July 1999 to December 2010, using vacuum-assisted venous return
with small venous cannulas connected to short tubing. These were randomized
with 80 CABG operations using conventional gravity drainage. Priming volume,
hematocrit value, red blood cell usage, and total blood product usage were
compared by means of multivariate analysis.
Results: The priming volume was 780+/-140mL for small-cannula vacuumassisted
venous return, 1300+/-88mL for gravity drainage (P <.0001). Smaller
priming resulted in higher hematocrit values both at the beginning of cardiopulmonary
bypass (26%+/-5% compared with 21%+/-4%, respectively, P <.0001)
and at the end (28%+/-4% compared with 24%+/-4%, respectively, P <.0001).
Red cell transfusions were used in 12% of the patients having small-cannula
vacuum-assisted venous return and 41% of the patients having gravity drainage
(P =.001); total blood product usage was 15% and 61%, respectively (P =.001).
Despite a postoperative blood loss, length of stay in intensive care unit was
similar in both groups; the association of vacuum-assisted venous return with
lowered blood product usage was confirmed also in the postoperative period.
Conclusions: Modified open circuit and vacuum-assisted venous return result in 1) higher hematocrit values during cardiopulmonary bypass and 2) decreased red cell and total blood product usage
Efficacy of pulsatile flow perfusion in adult cardiac surgery: Hemodynamic energy and vascular reactivity
Get PDFBackground: The role of pulsatile (PP) versus non-pulsatile (NP) flow during a cardiopulmonary bypass (CPB) is still debated. This study’s aim was to analyze hemodynamic effects, endothelial reactivity and erythrocytes response during a CPB with PP or NP. Methods: Fifty-two patients undergoing an aortic valve replacement were prospectively randomized for surgery with either PP or NP flow. Pulsatility was evaluated in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE). Systemic (SVRi) and pulmonary (PVRi) vascular resistances, endothelial markers levels and erythrocyte nitric-oxide synthase (eNOS) activity were collected at different perioperative time-points. Results: In the PP group, the resultant EEP was 7.3% higher than the mean arterial pressure (MAP), which corresponded to 5150 ± 2291 ergs/cm3 of SHE. In the NP group, the EEP and MAP were equal; no SHE was produced. The PP group showed lower SVRi during clamp-time (p = 0.06) and lower PVRi after protamine administration and during first postoperative hours (p = 0.02). Lower SVRi required a higher dosage of norepinephrine in the PP group (p = 0.02). Erythrocyte eNOS activity results were higher in the PP patients (p = 0.04). Renal function was better preserved in the PP group (p = 0.001), whereas other perioperative variables were comparable between the groups. Conclusions: A PP flow during a CPB results in significantly lower SVRi, PVRi and increased eNOS production. The clinical impact of increased perioperative vasopressor requirements in the PP group deserves further evaluation
Mkn 298: an AGN hidden by starburst
No full textThe nature of the nuclear region of Mkn 298 is investigated on the basis of optical and soft X-ray observations. The X-ray data permit to confirm the presence of an AGN, partially hidden by circumnuclear starburst regions, instead of supernova explosions, as suspected by the optical spectra
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