Synthesis of grafting silane on a hydro soluble cellulose ether (HPMC) was described. In alkaline medium, this derivate is under gel form. With a decrease of the pH, a self-hardening occurs due to the silanol condensation. For potential biomedical use, we described the silated-HPMC synthesis, the gel behavior after steam sterilization and the parameters of the silanol condensation i.e. pH, silane percentage and temperature. Minimum kinetic of the condensation was observed for pH between 5.5 and 6.5. So temperature catalyzed the reaction and the self-hardening speed was increased by silane percentage. 相似文献
A new methodology is developed for the problem of sound propagation above ground. The respective advantages of pure tones generated by a pressure driver with a tube and impulsive noises issued from an 8 mm alarm pistol with a double cavity absorbing silencer, are analysed. Use is made of minimum phase linear systems for which the modulus and phase of the transfer function are related by an Hilbert transform.Finally, the different parameters of a locally reacting model are calculated using a non-linear fitting procedure and the specific impedance values of the tested ground are estimated from the attenuations experimentally measured under grazing or oblique incidence. 相似文献
There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function,
such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation
on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic
twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task.
Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks. 相似文献
In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization.
A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related
response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined
as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity
related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of
realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic
range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies
from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information.
Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented
from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed
in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening
experiment. 相似文献
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
New non‐fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N‐isopropylacrylamide) as a hydrophilic surface and a plasma‐fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N‐isopropylacrylamide).