Effects of a single vacancy defect or a pin hole on free vibration behavior of a double layer graphene sheet are investigated. Using the nonlocal continuum theory as well as the Gurtin–Murdoch ...theory, the nonlocality and surface effects are considered in equations of motion. Both of in-phase and anti-phase vibration modes are analytically analyzed. Employing the translational addition theorem for cylindrical vector wave functions, the geometrical defect as a circular hole in arbitrary size and location is modeled. The van der Waals interaction between the upper and lower layers is included using the Lennard–Jones pair potential. The computational efficiency and accuracy of results are validated by literature. Effects of boundary conditions, geometrical properties, nonlocality and surface effect parameters on in-phase and anti-phase vibrational modes are investigated. Results reveal that the fundamental natural frequency of an annular double-layer graphene sheet with a free eccentric circular defect is less affected by the size and location of the defect. Moreover, the surface effect parameters have more significant effects on the in-phase vibration modes than the anti-phase ones.
•The variation of the craters generated by fs laser irradiation with repetition rate is investigated.•The influence of the laser pulse repetition rate on removal rate and surface texture on silicon ...is addressed.•Possible effects of plume shielding on crater features and laser surface structuring at high repetition rate is discussed.
The influence of the pulse repetition rate on laser irradiation of silicon, in air, with femtosecond laser pulses is experimentally investigated in the range 10 Hz – 200 kHz. The features of the produced crater and the laser-induced periodic surface structures generated on its surface are characterized by exploiting surface profilometry and scanning electron microscopy. The experimental characterization evidences an interesting influence of the pulse repetition rate on the crater size qualitatively addressing a progressive reduction of the material removal efficiency at higher repetition rates. Moreover, also the surface structures produced by an irradiation sequence with a fixed number of laser pulses (namely N = 100) shows a clear dependence on the repetition rate. The observed effects are rationalized by considering the possible influence of plume shielding and heat accumulation effects typically observed during laser processing with high repetition rate laser systems.
1. In recent months, several outbreaks with clinical signs of MDV-1 were reported in Iranian parent and laying hen farms, in addition to backyard chickens. Several meq gene sequences from these ...outbreaks were amplified and molecularly characterised.
2. The meq protein sequences revealed three different sizes, namely the standard 339 aa, a shorter form of 338 aa lacking a proline residue at position 191, and a very short (vs) size of 265 aa. Based on sequence and size, the 265 aa meq has never been reported from international research groups before. The protein has only one PPPP repeat motif suggesting it belongs to a highly virulent strain.
3. The standard meq sequences showed 100% BLAST identity to the vv+ isolate Polen5. However, the 338 aa form clustered to the clade usually reported from North America.
4. This is the first report on genetic analysis of MDV-1 from Iran, but further study is required to obtain a better picture of the diversity and prevalence of different MDV-1 strains circulating in the country's farms, backyard poultry and other bird species.
Avian orthoavulavirus, commonly known as Newcastle disease virus (NDV) has been a constant threat for the poultry industry of Iran for decades. Recently, a couple of preliminary studies on backyard ...and commercial chicken suggested that a major subgenotype circulating in Iran may be VII(L) subgenotype, which is now known as VII.1.1 according to the new classification system. The unique subgenotype was not reported from other parts of the world and was slightly (≥3%) different from the closest group that was VIId. The study was conducted between July 2018 and March 2019 to determine the exact NDV genotypes/subgenotypes circulating in Iranian broiler poultry farms; five-hundred and forty chickens were sampled from thirty-six broiler farms located in eighteen provinces of Iran. As other genotypes/subgenotypes such as XIII and VI.2 are circulating in neighbouring countries, border provinces were also sampled. The F gene of the NDV isolates was sequenced and phylogenetic analysis was conducted. All the isolates clustered under the VII.1.1 group. The evolutionary analysis also revealed that the distances were between 0.0 and 0.7% meaning that the Iranian NDV circulating in broiler farms were not only of VII.1.1 sub-genotype, but also genetically very identical, indicating that the routine control measures for ND in Iran were not able to prevent the circulating NDVs. Although stricter biosecurity measures have been really effective in developed countries, surveillance of NDV to determine the circulating genotypes might also help us to implement better vaccination strategies in the future.
We report an experimental investigation on the surface structures induced by linearly polarized ≈ 900 fs laser pulses, at
λ
= 1055 nm, on silicon at different values of the ambient pressure, from ~ ...10
−4
mbar to one atmosphere. Our experimental findings address interesting influences of the surrounding pressure on: (1) the spatial period of ripples; (2) the formation of micro-grooves; (3) the shape of the structured area. Moreover, the effects of various states of polarization in vacuum as well as of circularly polarized pulses in air vs vacuum are also addressed. We identify as one possible key element of such experimental observations: the fact that as the pressure raises the ablated nanoparticles produced during the femtosecond ablation process of the target get deposited more and more on the sample surface covering the irradiated spot area and influencing the structuring process.
LiLi
0.2
Ni
0.13−
x
+
y
/3
Co
0.13−
x
+
y
/3
Mn
0.54−
x
+
y
/3
Al
x
Mo
y
O
2
was synthesized via conventional solution combustion synthesis method. Microstructural characterizations were done by ...X-ray diffraction analysis and scanning electron microscopy, whereas electrochemical performance was evaluated by electrochemical tests. The electrochemical results indicated that Mo–Al doping has significant effect on capacity and cycling performance. The sample doped with Al (
x
= 0.015) and Mo (
y
= 0.015) exhibited higher cycling stability and higher capacity in comparison with those of non-substituted material. The initial discharge capacity for Mo–Al co-doped electrode was 265.5 mA h g
−1
at 25 mA g
−1
, and capacity retention after 50 cycles was 98.2%, whilst the initial discharge capacity for bare electrode was 239.1 mA h g
−1
at 25 mA g
−1
, and capacity retention after 50 cycles was 93%. Electrochemical impedance spectroscopy and cyclic voltammetry revealed that by the addition of Mo–Al, electrochemical performance of the LiLi
0.2
Ni
0.13
Co
0.13
Mn
0.54
O
2
is improved.
Graphical abstract
•The effect of the LIPSS process on the surface chemical properties and consequently on SEY is investigated.•Femtosecond Laser-Induced Periodic Surface Structures (LIPSS) are used to reduce SEY in ...copper.•Copper treated with LIPSS shows a low surface debris density and is therefore less critical for ultra-high vacuum applications in particle accelerators.
The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of ~1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10−3 C/mm2.
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In this article, an analytical approach is developed to investigate the nonlinear vibrational behavior of an graphene sheet. In order to be a practical instance, the circular nanoplate is also ...resting on an external Pasternak elastic medium including the Winkler modulus and shear modulus parameters. At the same time, it is subjected to the magnetic field and a thermal load. The modified couple stress theory as well as Eringen nonlocal elasticity theory involving small scale parameters are implemented to justify the size-dependent effects. The governing equations are derived based on von Kármán nonlinear strain-displacement relations. The presented method is verified by comparing the obtained results to their counterparts reported in the published literature. Effects of various parameters such as nonlocal parameters, temperature change, and elastic medium coefficients for different boundary conditions are also discussed. Numerical results reveal that the intrinsic size-dependent property of material increases the natural frequency.
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•Analysis of supra-wavelength surface structures generated by fs laser pulses at two different wavelengths.•Key role of hydrothermal waves in the process of grooves formation in ...silicon.•Formation of supra-wavelength grooves in static and dynamic irradiation conditions.
We have investigated the formation process of supra-wavelength quasi-periodic surface structures, commonly termed as grooves, produced during femtosecond laser surface structuring of a silicon target, in air.
The experiments have been carried out at two wavelengths, namely 513 nm and 1026 nm, and in multi-pulse irradiation conditions. Both static, i.e., irradiating the same target location, and dynamic, namely scanning the beam along a line, configurations have been explored. We have also carried out simulations of the process by using a multiscale numerical model, based on the two-temperature model coupled to a fluid dynamics approach. The comparison of experimental and numerical results has allowed us to clearly establish the role of hydrothermal waves in the grooves formation process.
Hormonal and metabolic changes following surgery are markers of the stress response to surgery. We compared hemodynamic parameters and stress response markers (glucose, cortisol, and C-reactive ...protein) in two groups of patients receiving either propofol or isoflurane combined with remifentanil for maintenance of anesthesia.
We randomly assigned 100 women (ASA I-II) scheduled for diagnostic gynecologic laparoscopy to receive either isoflurane (0.8% end-tidal) or propofol (100 mg/kg/min) in addition to remifentanil (0.25 mg/ kg/min). Heart rate and mean arterial pressure were recorded after induction, 30 seconds after intubation, at four time points after incision, and 60 min after surgery. Serum C-reactive protein, cortisol and glucose concentrations were measured before induction, one hour after incision, and one hour after surgery.
After induction, heart rate decreased significantly from baseline in both groups, and remained below baseline until the end of surgery. Mean arterial pressure also decreased significantly in both groups. C-reactive protein levels were not significantly different between groups. In the propofol group, cortisol decreased significantly one hour after incision, but increased in the isoflurane group. Glucose increased significantly in both groups, but was significantly lower in the propofol group one hour after the incision and one hour after surgery.
An anesthetic regimen combining propofol and remifentanil attenuates two indicators of the stress response more efficiently than a isoflurane - remifentanil combination.
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