Long-term decay of the water pressure in the osmotic tensiometer

Matric suction is an important state variable required for the assessment of unsaturated soil properties.Tensiometers are commonly used for direct matric suction measurement but have a limited measuring range up to 90 kPa due to the cavitation problem.Osmotic tensiometer(OT)can improve the measuring range of tensiometers by increasing the osmotic pressure of water to avoid the cavitation.However,the long-term water pressure decay that appeared in OTs caused a gradual decrease in their measuring range.In this study,crosslinked poly(acrylamide-co-acrylic acid)potassium salt(PAM-co-PAAK)was used for the preparation of OTs(five in total)to explore the mechanism of water pressure decay of OTs.The maximum water pressure in the OT versus the volume fraction of polymer filled in the OT was described based on the Flory-Huggins polymer theories and validated using WP4C dewpoint hygrometer.The long-term pressure decay of OT-1,OT-2,and OT-3 was observed for 130 d and constant pressures were found for OT-1 and OT-2,indicating that the pressure decay of OT was mainly caused by the stress relaxation of the polymer hydrogels,and standard linear solid(SLS)rheological model was appropriate to fit the decay data.For OT-1,OT-2 and OT-3,the theoretical osmotic pressure that was calculated based on the mass of retrieved polymer from OTs after 130-d pressure observation was higher than the actual osmotic pressure as observed,indicating that polymer leakage cannot explain the pressure decay of the OT.The ultravioletevisible(UVevisible)spectrophotometry examined the change in polymer concentrations in the water containers of OT-4 and OT-5 and demonstrated that there was no increase in polymer leakage during the period of pressure decay of OT-4 and OT-5.As a result,the pressure decay of OT was not caused by polymer leakage.The results of this research suggested that the viscoelastic properties of polymers should be taken into consideration in further OT development.

Whole-genome Sequencing Reveals Autooctoploidy in Chinese Sturgeon and Its Evolutionary Trajectories

The order Acipenseriformes,which includes sturgeons and paddlefishes,represents“living fossils”with complex genomes that are good models for understanding whole-genome duplication(WGD)and ploidy evolution in fishes.Here,we sequenced and assembled the first high-quality chromosome-level genome for the complex octoploid Acipenser sinensis(Chinese sturgeon),a critically endangered species that also represents a poorly understood ploidy group in Acipenseriformes.Our results show that A.sinensis is a complex autooctoploid species containing four kinds of octovalents(8n),a hexavalent(6n),two tetravalents(4n),and a divalent(2n).An analysis taking into account delayed rediploidization reveals that the octoploid genome composition of Chinese sturgeon results from two rounds of homologous WGDs,and further provides insights into the timing of its ploidy evolution.This study provides the first octoploid genome resource of Acipenseriformes for understanding ploidy compositions and evolutionary trajectories of polyploid fishes.

Influence of thermal treatment on electronic properties of inkjet-printed zinc oxide semiconductor

Additive manufacturing of electronic devices using inkjet printing provides a potential alternative approach in substitution for con-ventional electronic fabrication processes.However,the complex nature of inkjet printing involves the liquid deposition and film formation from the vaporization of solvent,which makes it different from film created by conventional deposition methods.Inkjet print-ing of zinc oxide(ZnO),which is a widely utilized semiconductor,produces polycrystalline film composed of nano-size grains,which could significantly influence the properties of printed film.In this study,low-temperature annealing was employed to treat inkjetprinted ZnO for UV photodetection application,and its influence on electrical properties was studied.Band bending was character-ized using the Mott-Schottky plot which examines the charge dis-tribution of the films.It is found that the annealing of inkjet-printed polycrystalline ZnO film has improved its electrical properties,which could be attributed to the reduction of band bending due to the merging of grains.The treatment also helps to reduce impurities of the film,such as zinc hydroxide complexes,which is common for solution-derived films.Hence,the study could pay the way for the improvement of electrical properties of inkjet-printed functional materials.

A ZnO thin-film driven microcantilever for nanoscale actuation and sensing

Zinc oxide(ZnO)thin film as a piezoelectric material for microelectromechanical system(MEMS)actuators and sensors was evaluated.ZnO thin films were deposited using radio frequency(RF)magnetron sputtering.Process parameters such as gas ratio,working pressure,and RF power were optimized for crystalline structure.The ZnO thin films were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM).Good quality of ZnO thin films was further confirmed by a high transverse piezoelectric coefficient d31.A microcantilever was then designed,fabricated,and characterized.Design formulas of resonant frequency,actuation,and sensing sensitivities were derived.The resonant frequency was determined by an impedance analyzer.Tip deflection on nanometer level was demonstrated with the cantilever used as an actuator.The actuation sensitivity was found to be 12.2 nm/V.As a sensor,the cantilever was calibrated against a reference accelerometer.The sensing sensitivity was characterized to be 46 mV/g.The characterization results were compared with design specifications.The differences were caused mainly by thickness control in etching.This study showed that ZnO is a promising piezoelectric material for MEMS actuators and sensors in terms of excellent process compatibility and good piezoelectric performance.

Investigation of HDD Ramp Unloading Processes with an Efficient Scheme

Ramp load/unload(L/UL)mechanisms are widely used to rest sliders in hard disk drives(HDDs).Loading/unloading a slider swiftly and smoothly is crucial in a HDD design.A novel,efficient simulation scheme is proposed to investigate the behaviors of a head disk interface(HDI)in ramp unloading processes.A dual scale model is enabled by decoupling the nano-meter scale change of an air bearing and the micro-or milli-meter scale deformation of a suspension.A modified Reynolds equation governing the air bearing was solved numerically.The slider design was characterized with performance functions.Three stages in an unloading process were analyzed with a lumped parameter suspension model.Key parameters for the model were estimated with a comprehensive finite element suspension model.Finally,simulation results are presented for a commercial HDI design.