The study on neural contrast sensitivity function at temporal frequencies

The neural contrast sensitivity function (NCSF) of human eye at temporal frequencies is acquired with a new method in this paper. Firstly the human eye's contrast sensitivity function (CSF) at temporal frequencies is measured by means of travelling-wave stimuli, and the modulation transfer function (MTF) of the eye's optics is obtained by constructing the eye model of the subject. Then the NCSF at temporal frequencies is calculated with the two functions. It is shown that the overall value of the NCSF decreases as the temporal frequency increases. As the temporal frequency increases from 0 cycles per second (c/s) to 1 c/s, 16 c/s and 30 c/s, the NCSF curve changes from the band-pass shape to the low-pass, and then to almost monotonic variation. The attenuation factor of the NCSF, which represents the sensitivity of visual neural system to the temporal frequency, varies little as spatial frequency increases, while that of the CSF declines dramatically in the region of high spatial frequencies. Because it is the NCSF, rather than the CSF, that reflects the characteristics of visual neural system, the investigation of the NCSF at temporal frequency is more essentially.     

Ugi reaction-assisted rapid assembly of affinity-based probes against potential protein tyrosine phosphatases

The multi-component Ugi reaction has been employed to assemble a small library of affinity-based probes (AfBPs) that target potential protein tyrosine phosphatases. The probes showed good labelling of PTP1B and MptpB, and were subsequently used to label endogenous PTP1B in MCF-7 cell lysates.     

Unique biocatalytic resolution of racemic tetrahydroberberrubine via kinetic glycosylation and enantio-selective sulfation

In this communication, we document a facile kinetic glycosylation resolution of racemic tetrahydroberberrubine. We also demonstrate that the enantiomeric excess of the resolved products is increased via a second resolution of the minor product of the first glycosylation resolution. This provides a rare example of tandem kinetic resolution of racemates.     

Light-triggered reversible assemblies of azobenzene-containing amphiphilic copolymer with β-cyclodextrin-modified hollow mesoporous silica nanoparticles for controlled drug release

Hollow mesoporous silica nanoparticles (HMSs) were modified by β-cyclodextrin via a "click" reaction, an amphiphilic copolymer with a trans-azobenzene structure was then assembled onto β-cyclodextrin to cover the surface of the HMSs. The prepared nanocomposites can release drugs in a "release-stop-release" manner by converting light irradiation.     

Chiral pyrrolidine quaternary derivatives as organocatalysts for asymmetric Michael additions

A series of chiral pyrrolidine quaternary derivatives were designed and synthesized. It was found that these derivatives are highly efficient organocatalysts for the asymmetric Michael addition reactions of aldehydes and ketones to nitroolefins with high yields (up to 96%), high enantioselectivities (up to 99% ee), and high diastereoselectivities (up to 97:3 dr). Furthermore, catalyst 7a could be recycled without remarkable loss of catalytic activity and stereoselectivity.     

A versatile and convenient route to ketone C-pyranosides and ketone C-furanosides from unprotected sugars

Both ketone C-pyranosides (in up to 97% yields) and C-furanosides (in 83–97% yields) could be prepared, respectively, from the condensations of pentane-2,4-dione and various unprotected sugars in sodium carbonate aqueous media by adjusting the reaction conditions.     

Study on low-cost calibration-free pH sensing with disposable optical sensors

As labor costs become more expensive, less labor-intensive disposable devices have become more ubiquitous. Similarly, the disposable optical pH sensor developed in our lab could provide a convenient yet cost-effective way for pH sensing in processes that require stringent pH control. This optical pH sensor is prepared in uniform individual lots of 100–200 sensors per lot. Calibration is accomplished on a few randomly selected sensors out of each lot. We show that all others in the same lot can then be used directly without requiring individual calibration. In this paper, a calibration model is derived to include all the factors that affect the signal of the disposable sensor. Experimental results show that the derived calibration model fits the experimental data. The readings of 28 randomly selected disposable sensors with 4 sensors from each of the 7 lots show an error less than 0.1 pH units in the useful sensing range of the sensor. The calibration model indicates that if further improvement on precision is desired, more uniform porous material and more advanced coating techniques will be required. When it comes to the effects of the varying coasters, house-made low-cost fluorometers, the variability in the brightness ratio of the blue-to-violet LEDs is the primary reason for the lack of precision. Other factors like LED light intensity distribution, optical properties of the filters and electronics also contribute to the coaster-to-coaster difference, but to a lesser extent. Two different methods for correcting the instrument variations were introduced. After correction, the collective reading errors for all the tested instruments were reduced to less than 0.2 pH units within the sensor's useful sensing range. Based on this result, our lab is currently implementing further improvements in modifying the coasters to equalize the ratios of blue-to-violet LED brightness.     

Light emission from a-Si:C:O:H films fabricated by C2F6 and O2/C2F6 plasma treating silicone oil liquid

Amorphous Si:C:O:H films were fabricated at low temperature by C₂F₆ and O₂/C₂F₆ plasma treating silicone oil liquid. The a-Si:C:O:H films fabricated by C₂F₆ plasma treatment exhibited white photoluminescence at room temperature, while that by O₂/C₂F₆ plasma treatment exhibited blue photoluminescence. Fourier transformed infrared spectroscopy and Raman spectroscopy studies showed that the sp³ and sp² hybridized carbons, SiC bond, SiO bond and carbon-related defects in a-Si:C:O:H films correlated with photoluminescence. It is suggested that the blue emission at 469 nm was related to the sp³ and sp² hybridized carbons, SiC bond, carbon dangling bonds as well as SiO short chains and small clusters, while the light emitting at 554 nm was related to the carbon-related defects.     

Energetic and conformational changes upon complexation of gelatin with sodium dodecyl sulfate

The effect of sodium bis(2-ethylhexyl)sulfosuccinate/isooctane/water microemulsions on the stability of 2,2-dimethyl-2,3-dihydro-1-benzofuran-7-yl methylcarbamate (carbofuran, CF), 3-hydroxy-2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate (3-hydroxycarbofuran, HCF) and 3-keto-2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate (3-ketocarbofuran, KCF) in basic media has been studied. The presence of these microheterogeneous media implies a large basic hydrolysis of CF and HCF on increasing surfactant concentration and, also, on increasing water content in the microemulsion. The hydrolysis rate constants are approximately 2- and 10-fold higher than those in pure water for HCF and CF, respectively. In contrast, a steep descent in the rate of decomposition for KCF was observed. These behaviours can be ascribed to the presence of CF derivatives both in the hydrophilic phase and in the lipophilic phase, while the hydroxyl ions are only restricted to the water pool of the microemulsion (hydrophilic phase). The kinetic rate constants for the basic hydrolysis in AOT-based microemulsions have been obtained on the basis of a pseudophase model. Taking into account that an important part of soils are colloids, the possibility of the presence of restricted water environments implies that soil composition and its structure will play an important role in the stability of these carbamates. In fact, we observed that the presence of these restricted aqueous media in the environment, in particular in watersheds and in wastewaters, could reduce significantly the half-life of these pesticides (33% and 91% for HCF and CF, respectively).