Precision motion control of a piezoelectric cantilever positioning system with rate-dependent hysteresis nonlinearities

Nonlinear Dynamics - The study proposed a feedforward– feedback combined architecture to control a piezoelectric motion system with rate-dependent hysteresis nonlinearities. First, the...     

Pore-covered thermoresponsive membranes for repeated on-demand drug release

Reversible on/off-switching of bovine serum albumin (BSA) permeation through a thermoresponsive composite membrane with negligible permeation in the off-state is demonstrated. UV-photografting of poly(N-isopropylacrylamide) onto a poly(ethylene terephthalate) microfiltration membrane results in a hydrogel graft layer on the irradiated side of the membrane only. The amount of hydrogel grafted onto the membrane can be controlled by the amount of crosslinker. Above the lower critical solution temperature (LCST) of the hydrogel (on-state), the shrunken state of the graft layer appears to only partially cover the membrane, allowing BSA permeation through the uncovered pores. Provided the grafting degree is high enough, the swollen hydrogel covers the membrane completely below the LCST (off-state), thus preventing BSA permeation. The on-demand release mechanism proposed here is based on switching the membrane surface coverage rather than previously reported switches based on effective pore size or hydrogel mesh size. The main advantage of our mechanism is that higher fluxes can be achieved in the on-state, since permeation is not limited by pore-narrowing.     

A high performance liquid chromatography assay for monitoring proprotein convertase activity

A rapid HPLC assay was developed for monitoring the activity of the two proprotein convertases, PACE-4 and furin. Six novel peptide substrates were synthesized containing the minimal PC recognition sequence (Arg-X-X-Arg), as well as tryptophan residue(s) for easy detection. Four of the peptides were cleaved by both PCs and their kinetic parameters determined. Two peptides were not cleaved but were shown to be good negative controls although not inhibitors of either PC. In addition, inhibition curves were plotted and IC(50) values calculated for PACE-4 and furin in the presence of two polyarginine peptides, hexa and deca-D-arginine.     

Synthesis and spectroscopic characterization of novel 2-amino-4,5,6,7-tetrahydro-3H-cyclopenta[d]pyrimidine and pyrimido[1,2-a]pyrimidine derivatives

2-Aminocyclopenta[d]pyrimidines 3a-c were achieved via a one-pot, three-component reactions of cyclopentanone 1, aromatic aldehyde and guanidine hydrochloride (1:2:1 molar ratio). Also, cyclization of 2,5-bis-(arylmethylidene)cyclopentanones 2 with guanidine hydrochloride (1:1 molar ratio) in methanol in the presence of sodiummethoxide afforded cyclopenta-[d]pyrimidines 3. Compound 3a has been shown to be a useful building block for the synthesis of some novel pyrimido[1,2-a]pyrimidines 5, 7 and 12. The structures of the newly synthesized compounds were confirmed on the basis of analytical and spectral data.     

The Syntheses of New Cyclopenta[d][1,3]thiazine Derivatives and Their Use as Antimicrobial Agents

Cyclopentanone (1) was exploited as a starting material for the syntheses of hitherto unknown cyclopenta[d][1,3]thiazine derivatives.     

Synthesis and Reactions of Some Tetrahydrobenzothieno[2,3- d ]Pyrimidine Derivatives with Biological Interest

Hetetrocyclic substituted rings were prepared from 1-amino-2-carboxamido-4,5,6,7-tetrahydrobenzothiophene and carbon disulphide, chloroacetic acid, or arylidene with different active methylene groups. The antimicrobial activity of synthesized compounds is discussed.     

Antimicrobial Activity of Some Novel Thiourea,Hydrazine, Fused Pyrimidine and 2‐(4‐Substituted)anilinobenzoazole Derivatives Containing Sulfonamido Moieties

Thiophosgenation of sulfonamides 1a‐c in the presence of dilute HCl at room temperature furnished the isothiocyanatosulfonamides 2a‐c and treatment with aromatic amines gave 1,3‐disubstituted thioureas 3a,b . Also, interaction of two molecules of 2c with 1,4‐phenylenediamine yielded the novel bisthiourea 4 . Cyclocondensation of 2 with ortho amino carboxylic acid compounds such as anthranilic acids 8 , 5‐amino‐1‐phenyl‐pyrazol‐4‐carboxylic acid 9 and 4,5,6,7‐tetrahydro‐2‐amino‐benzo[b]thiophene‐3‐carboxylic acid 10 furnished the fused thiopyrimidines 11a‐d, 12 and 13 , respectively. 2‐Anilinobenzoazole derivatives 15a‐c, 16a, b and 17a,b were obtained through cyclocondensation of 2 with 1,2‐dinucleophiles.     

Synthesis and characterization of active cuprous oxide particles and their catalytic application in 1,2,3‐triazole synthesis via alkyne‐azide cycloaddition reaction in water

Active cuprous oxide materials are synthesized from CuSO₄.5H₂O using sodium stannite as reducing agent in the presence of various stabilizers, viz., cetyl trimethyl ammonium bromide, sodium dodecyl sulphate, and polyvinyl pyrrolidone. The synthesized cuprous oxide materials are well characterized by powder X‐ray diffraction and Fourier transform infrared spectroscopy to ascertain their identity, while field emission scanning electron microscopy and energy‐dispersive spectroscopy analysis were used to study their morphology and composition, respectively. We have compared the catalytic prowess of the various cuprous oxide materials in the cycloaddition reaction of alkynes and azides to synthesize 1,4‐disubstituted‐1,2,3‐triazoles. A wide variety of substitutions can nicely be tolerated in our optimized reaction conditions to produce very good to excellent yields of the corresponding triazoles in water at 55 °C. The reactions are carried out in water without any assistance of organic cosolvent or other additives, which renders the catalytic method as economical and environment friendly.