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Flunitrazepam, a very potent benzodiazepine with sedative, hypnotic and amnesic effects, is commonly used to treat severe insomnia and as an anesthetic. Due to these characteristics, when flunitrazepam is sneaked into alcohol or drinks, it is often highly associated with violent behavior and drug rape cases. Therefore, it is also known as a "date rape drug", and the detection of flunitrazepam and its metabolites is of great interest in forensic medicine and pharmacotoxicology. This paper describes the mechanism of action and drug metabolism process of flunitrazepam, reviews the different methods for detecting flunitrazepam published over the years, summarizes the detection limits of each method and compares their advantages and disadvantages. We hope to provide some inspiration for future research in this field. [ABSTRACT FROM AUTHOR]

Effects of redispersible latex powder, cellulose ether, defoamer and boric acid on properties of thin-layer masonry mortar for ALC wallboard were studied. The results show that the incorporation of cellulose ether can significantly increase the water retention of thin layer mortar, but has a great negative effect on the 28d compressive strength. Compared with cellulose ether, the redispersible latex powder can significantly improve the bond performance of thin layer mortar. When the rubber powder content is 0.8%, the 14d tensile bond strength is 4.5 times of the blank group. When defoaming agent is mixed with cellulose ether, the reduction of compressive strength can be slowed down to a certain extent. [ABSTRACT FROM AUTHOR]

Sequence-specific DNA detection is a routine job in medical diagnostics and genetic screening. Alternative to a fluorescence readout scheme or electrophoresis approach, various kinds of rapid, low-cost, facile, and label-free methods have also been developed in last decades. Among these, direct electrical detection of DNA received increasing attention but more research is desirable. Particularly, enhancement with high discrimination must be employed to selectively amplify the responding signal. A chip-based biosensor was developed in this work to electrically detect 22-mer oligonucleotide DNA at low concentration, from 50 fM to 10 pM. First, a gold nanoparticle (NP) was capped with 3-mercaptopropionic acid through a thiol-gold bond. The derivatized carboxylic acid group showed strong complex interaction with an inorganic linker, [Zr.sup.4+]. As a result, [Zr.sup.4+] could link several hundreds of individual gold NPs together to form an aggregate of nanoparticles (ANP), which was capable of being used as a conductive tag for the electrical detection of DNA. Second, in order to achieve the discriminative localization of ANP to bridge two comb-shaped electrodes (with height of ~50 nm and interdistance of 300-350 nm) gapped with insulative material of silicon oxide, peptide nucleic acids were covalently bonded to the silicon oxide in the gap as capture sites for DNA. After hybridization with target DNA, the charged phosphate-containing backbone of DNA was introduced into the gap. Phosphate groups also exhibited strong complex interaction with the linker of [Zr.sup.4+] and could react with the residual [Zr.sup.4+] on the ANP surface. As a consequence, the conductive tags were linked to the phosphate groups and localized into the gap, which could modify the conductance between the two comb-shaped electrodes in turn. The degree of modification correlated directly to the amount of hybridized DNA and to the concentration of target DNA in sample solution. Compared with the individual NPs used as the tag, a strong enhancement from the gold ANP was obtained.

An ultrasensitive electrical detection method of nucleic acids has been developed on a nanogapped biosensor. In this study, peptide nucleic acid (PNA) probes were immobilized in the gaps of a pair of finger microelectrodes first and were then hybridized with their complementary target DNA. After that, pectin molecules were introduced into the DNA strand via zirconium-phosphate and zirconium-carbonate chemistries and were oxidated by periodate in acetate buffer (pH 3.98). The newly produced aldedyde groups act as a reactant to reduce ammoniacal silver ion to produce silver nanoparticles, which bridged the gap of the interdigitated microelectrode. The conductance of the metallic nanoparticles correlated directly with the amount of the hybridized DNA. A much higher sensitivity was achieved at 3 femtomolar (S/N > 3) under optimal conditions. This biosensor is also applicable to the direct detection of RNA.

Arrays of highly ordered n-type silicon nanowires (SiNW) are fabricated using complementary metal-oxide semi-conductor (CMOS) compatible technology, and their applications in biosensors are investigated. Peptide nucleic acid (PNA) capture probe-functionalized SiNW arrays show a concentration-dependent resistance change upon hybridization to complementary target DNA that is linear over a large dynamic range with a detection limit of 10 fM. As with other SiNW biosensing devices, the sensing mechanism can be understood in terms of the change in charge density at the SiNW surface after hybridization, the so-called 'field effect'. The SiNW array biosensor discriminates satisfactorily against mismatched target DNA. It is also able to monitor directly the DNA hybridization event in situ and in real time. The SiNW array biosensor described here is ultrasensitive, non-radioactive, and more importantly, label-free, and is of particular importance to the development of gene expression profiling tools and point-of-care applications.

This paper mainly studies the effects of raw materials, mix proportion and forming method on the 28 d ages impermeability pressure of reference mortar impermeability test piece, and finds a suitable mix proportion and forming method: 290 g of reference cement, 1350 g of standard sand and 260 g of water, which is formed by one-time loading and vibrating on the cement mortar vibrating table for 8 s. It is possible to make the 28 d ages impermeability pressure of the reference mortar impermeability test piece be 0.3~0.4 MPa; And explore the feasibility of a rapid determination method, that is, using 60 °C hot water to accelerate curing for 3 days, we can quickly determine whether the impermeability pressure of the reference mortar impermeability pressure test piece for 28 d ages can meet the standard requirements, which provides a reference for the development and testing of cement- based permeated crystalline materials. [ABSTRACT FROM AUTHOR]

The effect of calcium stearate and organosilanepowder hydrophobic agent on the performance of cement-based joint filler was studied through experiments. The results show that the flexural strength and compressive strength of cement-based sealant show a slightly increasing trend with the increase of the dosage of calcium stearate from 0 to 1.0% and organosilanepowder hydrophobic agent from 0 to 0.10%. After 25 times of freeze-thaw cycle treatment, the flexural compressive strength decreases slightly. The water absorption at 30 and 240 min showed a decreasing trend. The wear resistance value showed a rising trend. The contraction value showed a downward trend. [ABSTRACT FROM AUTHOR]