Our study aimed to determine the efficacy and safety of colistin in the treatment of ventilator-associated pneumonia (VAP) caused by pan-drug-resistant Pseudomonas aeruginosa or Acinetobacter ...baumanii. Pairwise, retrospective exposed-unexposed study. Combined medical and surgical intensive care unit of Habib Bourguiba University Hospital (Sfax, Tunisia). Sixty patients with VAP caused by pan-drug-resistant A. baumanii or P. aeruginosa matched to 60 controls with VAP caused by A. baumanii or P. aeruginosa susceptible to imipenem. All patients had normal renal function at the onset of antibiotic therapy. Case patients were treated by colistin intravenously and control patients were treated by imipenem intravenously. Baseline characteristics were similar between the colistin and imipenem groups. The mean duration of antibiotic therapy for VAP was 9.5+/-3.8 days (range 5-22 days) with colistin and 8.9+/-2.8 days (range 5-20 days) with imipenem (p=0.32). A favorable clinical response to antibiotic therapy for VAP occurred in 45 patients (75%) in the colistin group and in 43 patients (71.7%) in the imipenem group (p=0.68). The time to resolution of infectious parameters after the initiation of antibiotic therapy was not statistically different between the two groups. During the antibiotic course, none of the patients in either group developed renal failure. We conclude that colistin can be a safe and effective option in the treatments of VAP caused by pan-drug-resistant P. aeruginosa or A. baumanii.
To take into account nuclear quantum effects on the dynamics of atoms, the path integral molecular dynamics (PIMD) method used since 1980s is based on the formalism developed by R. P. Feynman. ...However, the huge computation time required for the PIMD reduces its range of applicability. Another drawback is the requirement of additional techniques to access time correlation functions (ring polymer MD or centroid MD). We developed an alternative technique based on a quantum thermal bath (QTB) which reduces the computation time by a factor of ∼20. The QTB approach consists in a classical Langevin dynamics in which the white noise random force is replaced by a Gaussian random force having the power spectral density given by the quantum fluctuation-dissipation theorem. The method has yielded satisfactory results for weakly anharmonic systems: the quantum harmonic oscillator, the heat capacity of a MgO crystal, and isotope effects in 7LiH and 7LiD. Unfortunately, the QTB is subject to the problem of zero-point energy leakage (ZPEL) in highly anharmonic systems, which is inherent in the use of classical mechanics. Indeed, a part of the energy of the high-frequency modes is transferred to the low-frequency modes leading to a wrong energy distribution. We have shown that in order to reduce or even eliminate ZPEL, it is sufficient to increase the value of the frictional coefficient. Another way to solve the ZPEL problem is to combine the QTB and PIMD techniques. It requires the modification of the power spectral density of the random force within the QTB. This combination can also be seen as a way to speed up the PIMD.
Our study aimed to determine the efficacy and safety of colistin in the treatment of ventilator-associated pneumonia (VAP) caused by pan-drug-resistant Pseudomonas aeruginosa or Acinetobacter ...baumanii.
Pairwise, retrospective exposed-unexposed study.
Combined medical and surgical intensive care unit of Habib Bourguiba University Hospital (Sfax, Tunisia).
Sixty patients with VAP caused by pan-drug-resistant A. baumanii or P. aeruginosa matched to 60 controls with VAP caused by A. baumanii or P. aeruginosa susceptible to imipenem. All patients had normal renal function at the onset of antibiotic therapy.
Case patients were treated by colistin intravenously and control patients were treated by imipenem intravenously.
Baseline characteristics were similar between the colistin and imipenem groups. The mean duration of antibiotic therapy for VAP was 9.5+/-3.8 days (range 5-22 days) with colistin and 8.9+/-2.8 days (range 5-20 days) with imipenem (p=0.32). A favorable clinical response to antibiotic therapy for VAP occurred in 45 patients (75%) in the colistin group and in 43 patients (71.7%) in the imipenem group (p=0.68). The time to resolution of infectious parameters after the initiation of antibiotic therapy was not statistically different between the two groups. During the antibiotic course, none of the patients in either group developed renal failure.
We conclude that colistin can be a safe and effective option in the treatments of VAP caused by pan-drug-resistant P. aeruginosa or A. baumanii.
Nanometric neodymium-doped yttrium aluminium garnet (YAG) has been synthesised from freeze-dried precursors. The products were calcined between 900
°C and 1200
°C under flowing oxygen. Powder ...morphologies were observed by TEM, SEM and laser granulometer. The oxides had small crystallite size. The best sinterability under vacuum at 1700
°C for 3
h was obtained for precursors with the lowest amount of organic impurities as indicated by IR measurements. Hot isostatic pressing at 1700
°C in 160
MPa of argon was applied to complete the sintering. Under these conditions, Nd:YAG ceramics with very good transmittance were obtained.
Dense (1--x)Pb(In1/2Nb1/2)O3--xPbTiO3 (PIN--PT) ceramics were synthesised by hot forging and thermal grain growth. (1--x)PIN--xPT phase diagram was investigated by X--ray diffraction and dielectric ...measurements. The morphotropic phase boundary zone was found to be between a rhombohedral phase region for low PT contents and a tetragonal phase region for high PT contents, i.e. in the 0*34--0*39x range. A mixture of tetragonal and probably monoclinic phases was observed for x=0*37 at room temperature.
Lead-based ferroelectric ceramics with (1−
x)Pb(B
1 B
2)O
3–
xPbTiO
3 formula have emerged as a group of promising materials for various applications like ultrasonic sonars or medical imaging ...transducers. (1−
x)PMN–
xPT, (1−
x)PIN–
xPT and ternary solutions
xPIN–
yPMN–
zPT ceramics are synthesised using the solid state reaction method. Our objective is to achieve higher structural transition temperatures than those of PMN–PT ceramics with as good dielectric, piezoelectric and electromechanical properties. Ceramics capacitance and loss tangent are measured when the ac field of measurement increases up to
E
=
500
V/mm. Behaviours of these materials under ac field are related to their coercive field and Curie temperature.
Nanopowders of 0.63Pb(In
1/2Nb
1/2)O
3–0.37PbTiO
3 were synthesized by solid state reaction using the continuous attrition milling followed by high-energy ball milling techniques in air at room ...temperature. After milling for 8
h nanopowders of 20–30
nm grain size are obtained. Sintering by hot pressing of PIN–37PT green pellets leads to dense ceramics with average grain size varying from 100
nm to 1
μm. The dielectric and piezoelectric properties of PIN–37PT nanostructured ceramics with grain size bigger than about 160
nm remain roughly unchanged and comparable to those of microstructured ceramics. In addition, the stability of the permittivity and dielectric losses under high ac electric field grows when the grain size decreases. The material becomes less non-linear with decreasing grain size. This result is attractive for acoustic transducer applications.
An experimental setup based on the electrical excitation of a piezoelectric sample is proposed for resonant ultrasound spectroscopy measurements. The detection of the mechanical vibrations is ...performed by means of a laser interferometer. At the same time, the free vibrations of piezoelectric parallelepipeds of tetragonal and hexagonal symmetries are modeled taking into account the effect of the sample metalization. The paper presents the full elastic, piezoelectric and dielectric tensors of two PMN-34.5%PT ceramic and PZN-12%PT single crystal cubes.
The physical properties of the Multiferroïc lead-free 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 ceramic were investigated by in-situ Mössbauer spectroscopy, X-ray diffraction (XRD), dielectric ...measurements and Raman scattering. Both BiFeO3 and 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 ceramics underwent in-situ Mössbauer spectroscopy in the temperature range of 300 K to 653 K and the parameters of hyperfine interactions were determined. The magnetic transition temperature TN of our doped sample was of 568 K, which was lower than that of BiFeO3. This reduction of TN originated from the presence of different exchange constants resulting from the weakening of JFe-Fe. The deviation of the reduced magnetic hyperfine field H(T)/H(0) as a function of the reduced temperature T/TN from the Brillouin curve of Fe3+ (S = 5/2) for the three sextets and the determination of the critical exponent β, of 0.375 ± 0.022 in the range of 0.01 < 1-T/TN < 0.5 revealed a 3D magnetic long range order phase transition. The complexity of the spatial spin structure was a result of the canting of antiferromagnetically ordered spins of BiFeO3. Our findings revealed the effect of the non-magnetic substituents Ba and Yb/Nb/Ti in A and B sites, respectively on the magnetic properties. Around the magnetic transition temperature, both isomer shift evolution and quadruple splitting distribution showed pronounced anomalies associated with the onset of magnetic ordering. The Debye temperature (θD) was deduced to be of 257 ± 21 K. These results revealed 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 as a promising material for piezoelectric devices. XRD analyses were performed for temperatures from 300 K up to 750 K. Gradual structural evolution, as temperature increased, exhibited an isostructural phase transition and an anomaly in the evolution of lattice parameters and the unit cell volume as well as a significant shift in the atomic positions near the magnetic transition temperature TN. These behaviors indicate magnetoelastic coupling. The temperature dependence of the real part of dielectric permittivity and dielectric loss (tan δ) was investigated over a wide range of temperatures at 1 kHz. During its evolution, an anomaly was observed at 568 K; which corresponded to the magnetic transition temperature TN. Raman scattering spectra were measured in the temperature range from 303 K to 728 K. Drastic changes, especially that of the three two-phonon modes centered at around 1000-1500 cm−1, were the results of magnetic rearrangement and atomic displacement leading to both modulating magnetic exchange interaction and polarization state. All these results prove the magnetoelectric coupling of 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 ceramic.
•Multiferroic 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 ceramic was synthesized.•Structure, dielectric and magnetic ordering of 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 were studied.•Magnetoelastic coupling in 0.9BiFeO3-0.1BaTi0.95(Yb0.5Nb0.5)0.05O3 was proved.
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