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1.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献
2.
I T Vieira P R Harper A K Shahani V De Senna 《The Journal of the Operational Research Society》2003,54(7):713-722
Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in children below the age of 15 years. In 2000 alone, about 600 000 new infections occurred, the vast majority from mothers living in developing countries who were not aware of their HIV-positive status. To date, at least 4.3 million children have died from AIDS. In this paper, we discuss the development of an operational model that can be used to evaluate intervention options for the prevention of MTCT of HIV. The problem was approached by defining suitable pregnancy risk groups, prevention options and the required model outputs to evaluate different intervention strategies. The method chosen to approach the problem was a discrete-event, three-phase simulation, built in Visual Basic, with a stochastic semi-Markov structure. The developed model takes individual pregnant women through each stage of their pregnancy, labour and birth. Different intervention strategies may be modelled at any time, including short-course antiretroviral drugs and cessation of breastfeeding. The model is demonstrated with data from Botswana, which has one of the highest HIV-infection rates in the world. 相似文献
3.
I. M. Shmyt’ko A. N. Izotov N. S. Afonikova S. Vieira G. Rubio 《Physics of the Solid State》1998,40(4):687-690
The formation of polytypic modifications is observed in dislocation-free silicon single crystals under directional plastic
deformation. It is shown that the deformation-stimulated phase appears on the surface of the sample in the form of small grains
ranging from several hundred to several thousand angstroms in size. A twin structure in the individual grains is observed.
Fiz. Tverd. Tela (St. Petersburg) 40, 746–749 (April 1998) 相似文献
4.
Vieira R Pham-Huu C Keller N Ledoux MJ 《Chemical communications (Cambridge, England)》2002,(9):954-955
Graphite felt supporting 40 nm diameter carbon nanofibers was synthesized and successfully used as a support for a high loaded iridium catalyst (30 wt%) in the decomposition of hydrazine; a strong mechanical resistance and a high thermal conductivity led to a very efficient and stable catalyst as compared to that used industrially, iridium supported on a high surface area alumina. 相似文献
5.
Elaine C. Petronilho Murilo M. Pedrote Mayra A. Marques Yulli M. Passos Michelle F. Mota Benjamin Jakobus Gileno dos Santos de Sousa Filipe Pereira da Costa Adriani L. Felix Giulia D. S. Ferretti Fernando P. Almeida Yraima Cordeiro Tuane C. R. G. Vieira Guilherme A. P. de Oliveira Jerson L. Silva 《Chemical science》2021,12(21):7334
Mutant p53 tends to form aggregates with amyloid properties, especially amyloid oligomers inside the nucleus, which are believed to cause oncogenic gain-of-function (GoF). The mechanism of the formation of the aggregates in the nucleus remains uncertain. The present study demonstrated that the DNA-binding domain of p53 (p53C) underwent phase separation (PS) on the pathway to aggregation under various conditions. p53C phase separated in the presence of the crowding agent polyethylene glycol (PEG). Similarly, mutant p53C (M237I and R249S) underwent PS; however, the process evolved to a solid-like phase transition faster than that in the case of wild-type p53C. The data obtained by microscopy of live cells indicated that transfection of mutant full-length p53 into the cells tended to result in PS and phase transition (PT) in the nuclear compartments, which are likely the cause of the GoF effects. Fluorescence recovery after photobleaching (FRAP) experiments revealed liquid characteristics of the condensates in the nucleus. Mutant p53 tended to undergo gel- and solid-like phase transitions in the nucleus and in nuclear bodies demonstrated by slow and incomplete recovery of fluorescence after photobleaching. Polyanions, such as heparin and RNA, were able to modulate PS and PT in vitro. Heparin apparently stabilized the condensates in a gel-like state, and RNA apparently induced a solid-like state of the protein even in the absence of PEG. Conditions that destabilize p53C into a molten globule conformation also produced liquid droplets in the absence of crowding. The disordered transactivation domain (TAD) modulated both phase separation and amyloid aggregation. In summary, our data provide mechanistic insight into the formation of p53 condensates and conditions that may result in the formation of aggregated structures, such as mutant amyloid oligomers, in cancer. The pathway of mutant p53 from liquid droplets to gel-like and solid-like (amyloid) species may be a suitable target for anticancer therapy.Mutant p53 tends to form aggregates with amyloid properties, especially amyloid oligomers inside the nucleus, which are believed to cause oncogenic gain-of-function (GoF). 相似文献
6.
S.A.Vieira Filho L.P. Duarte G.D.F. Silva O.W. Howarth I.S. Lula 《Helvetica chimica acta》2003,86(10):3445-3449
3β‐(Stearyloxy)olean‐12‐ene was isolated from a hexane extract of Austroplenckia populnea Reiss (Celastraceae) leaves. The structure was solved by means of quantitative 13C‐NMR, HMBC, HMQC, COSY, NOESY, and NOE difference spectra. The mass spectrum showed an [M+1]+ ion peak at m/z 693, and the molecular formula C48H84O2 was confirmed by combustion analysis. 相似文献
7.
An organic-phase biosensor based on paraffin/graphite modified with sweet potato (Ipomoea batatas (L.) Lam.) tissue as the source of peroxidase was developed and used for determining hydroquinone in cosmetic creams. This enzyme in the presence of hydrogen peroxide catalyses the oxidation of hydroquinone to p-quinone which electrochemical reduction back to hydroquinone was obtained at a peak potential of -0.22 V. The recovery of hydroquinone from two samples ranged from 99.1 to 104.1% and a rectilinear analytical curve for hydroquinone concentration from 7.5x10(-5) to 1.6x10(-3) M (r=0.9991) were obtained. The detection limit was 8.1x10(-6) M and relative standard deviation was <1.0% for a solution containing 7.3x10(-4) M hydroquinone and 1.0x10(-3) M hydrogen peroxide in 0.10 M tetrabutylammonium bromide methanol-phosphate buffer solution (95:5% v/v) (n=10). The results obtained for hydroquinone in cosmetic creams using the proposed biosensor are in close agreement with those obtained using a Pharmacopoeia procedure at the 95% confidence level. 相似文献
8.
S. Czajkowski M. Bernas P. Armbruster H. Geissel C. Kozhuharov G. Münzenberg D. Vieira Ph. Dessagne Ch. Miehe E. Hanelt G. Audi J. K. P. Lee 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):267-272
Neutron-rich Co and Fe isotopes produced by86Kr projectile fragmentation at 500 MeV/u were separated and identified using the fragment separator (FrS) in a bunched energy mode.66Co and65Fe ions were selectively implanted in a double PIN-diode array where the-decay signals were measured. The half-lives were deduced from time correlations between implantation and-decay signals. The remeasurement of the66Co half-life confirms the isotope identification. The value of the65Fe half-life was found to be 0.45±0.15 s. 相似文献
9.
10.
Cestari AR Vieira EF Pinto AA Lopes EC 《Journal of colloid and interface science》2005,292(2):363-372
In this work, a hybrid silica/chitosan was synthesized and characterized by nitrogen elemental analysis and thermal analysis (TG, DTG, DTA, and DSC) and BET surface area. The hybrid was used in adsorption studies of two anionic dyes from aqueous solutions. A rise of temperature accelerates mass transfer of dyes into the hybrid. However, the maximum adsorption capacities reach similar values from 25 to 55 degrees C. The kinetic data were first evaluated in relation to the decrease of the time-related residual concentration of the dyes in solution, where the second-order model has presented the best fitting. The solid-phase interaction of dye data presents a rough fitting to the traditional first-order Lagergren kinetic model. However, a modified Avrami kinetic equation was successfully fitted to the kinetic quantities, where from five to seven kinetic regions were found. A pore-diffusion model has also demonstrated that the diffusion is the rate-controlling interaction mechanism. However, the experimental-calculated comparative values are the best way to evaluate a specific aqueous- or solid-phase kinetic model. 相似文献