Risk factors associated with acute hepatopancreatic necrosis disease at shrimp farm level in Bac Lieu Province, Vietnam.

BACKGROUND AND AIM: Acute hepatopancreatic necrosis disease (AHPND) is a severe disease in shrimp farms and adversely affected the shrimp industry of Vietnam. So far, the study on risk factors associated with AHPND outbreaks is limited. The objective of this study was to determine the potential risk factors of AHPND at the shrimp farm level in Bac Lieu Province, Vietnam. MATERIALS AND METHODS: Real-time-Polymerase chain reaction was used to analyze data collected from an active surveillance program of shrimp farms in 2017 in the Vinh Tien and Vinh Lac villages, Vinh Thinh commune, Hoa Binh district in Bac Lieu Province, Vietnam. The matched case-control study selected 20 cases and 20 control farms from 134 shrimp farms. In 2018, face-to-face interviews using structured questionnaires were conducted with the farmers of these selected farms. RESULTS: Of the 59 studied variables, seven had p≤0.2 based on bivariate analyses. The results of multivariable analysis showed that the presence of fish-eating birds on shrimp farms was a significant association with AHPND (odds ratio=8, p=0.049). CONCLUSION: To reduce the effect of AHPND, farmers should apply effective methods to manage wild animals such as using a grid or net to cover the pond, combined with improved biosecurity.

Enhanced NH3 and H2 gas sensing with H2S gas interference using multilayer SnO2/Pt/WO3 nanofilms.

The selective detection and classification of NH3 and H2S gases with H2S gas interference based on conventional SnO2 thin film sensors is still the main problem. In this work, three layers of SnO2/Pt/WO3 nanofilms with different WO3 thicknesses (50, 80, 140, and 260 nm) were fabricated using the sputtering technique. The WO3 top layer were used as a gas filter to further improve the selectivity of sensors. The effect of WO3 thickness on the (NH3, H2, and H2S) gas-sensing properties of the sensors was investigated. At the optimal WO3 thickness of 140 nm, the gas responses of SnO2/Pt/WO3 sensors toward NH3 and H2 gases were slightly lower than those of Pt/SnO2 sensor film, and the gas response of SnO2/Pt/WO3 sensor films to H2S gas was almost negligible. The calcification of NH3 and H2 gases was effectively conducted by machine learning algorithms. These evidences manifested that SnO2/Pt/WO3 sensor films are suitable for the actual NH3 detection of NH3 and H2S gases.

MoS2 nanosheets-decorated SnO2 nanofibers for enhanced SO2 gas sensing performance and classification of CO, NH3 and H2 gases.

The effect of MoS2 nanosheet (NS) decoration on the gas-sensing properties of SnO2 nanofibers (NFs) was investigated. The decorated sensors were fabricated by facile on-chip electrospinning technique and subsequently dropping MoS2 NSs-dispersed solution. The MoS2 NS decoration resulted in enhanced the response and reduced the operating temperature of SnO2 NFs towards SO2 gas. The SnO2 NF sensor decorated with the optimum density of MoS2 NSs exhibited about 10-fold enhancement in gas response to 10 ppm SO2 at 150 °C as compared with the bare SnO2 NF sensor. Furthermore, the decorated sensors exhibited an extremely low detection limit and good selectivity for SO2 gas against other interfering gases, such as CO, NH3, and H2. The enhanced SO2 gas-sensing performance of MoS2 NSs-decorated SnO2 NFs was attributed to the chemical sensitization of MoS2 NSs and charge transfer through heterojunctions between the NSs and SnO2 nanograins. The classification of toxic gases such as CO, H2, and NH3 by the MoS2 NSs-decorated SnO2 NF sensors can achieve high accuracy with linear discriminant analysis (LDA). Our results suggest that the one-dimensional nanostructures of semiconductor metal oxides decorated with two-dimensional transition metal dichalcogenides are attractive candidates for the detection of hazardous gases.

Formation and Evaluation of Silicon Substrate with Highly-Doped Porous Si Layers Formed by Metal-Assisted Chemical Etching.

Porous silicon (Si) is a low thermal conductivity material, which has high potential for thermoelectric devices. However, low output performance of porous Si hinders the development of thermoelectric performance due to low electrical conductivity. The large contact resistance from nonlinear contact between porous Si and metal is one reason for the reduction of electrical conductivity. In this paper, p- and n-type porous Si were formed on Si substrate by metal-assisted chemical etching. To decrease contact resistance, p- and n-type spin on dopants are employed to dope an impurity element into p- and n-type porous Si surface, respectively. Compared to the Si substrate with undoped porous samples, ohmic contact can be obtained, and the electrical conductivity of doped p- and n-type porous Si can be improved to 1160 and 1390 S/m, respectively. Compared with the Si substrate, the special contact resistances for the doped p- and n-type porous Si layer decreases to 1.35 and 1.16 mΩ/cm2, respectively, by increasing the carrier concentration. However, the increase of the carrier concentration induces the decline of the Seebeck coefficient for p- and n-type Si substrates with doped porous Si samples to 491 and 480 µV/K, respectively. Power factor is related to the Seebeck coefficient and electrical conductivity of thermoelectric material, which is one vital factor that evaluates its output performance. Therefore, even though the Seebeck coefficient values of Si substrates with doped porous Si samples decrease, the doped porous Si layer can improve the power factor compared to undoped samples due to the enhancement of electrical conductivity, which facilitates its development for thermoelectric application.

Aluminum doped zinc oxide deposited by atomic layer deposition and its applications to micro/nano devices.

This work reports investigation on the deposition and evaluation of an aluminum-doped zinc oxide (AZO) thin film and its novel applications to micro- and nano-devices. The AZO thin film is deposited successfully by atomic layer deposition (ALD). 50 nm-thick AZO film with high uniformity is checked by scanning electron microscopy. The element composition of the deposited film with various aluminum dopant concentration is analyzed by energy-dispersive X-ray spectroscopy. In addition, a polycrystalline feature of the deposited film is confirmed by selected area electron diffraction and high-resolution transmission electron microscopy. The lowest sheet resistance of the deposited AZO film is found at 0.7 kΩ/□ with the aluminum dopant concentration at 5 at.%. A novel method employed the ALD in combination with the sacrificial silicon structures is proposed which opens the way to create the ultra-high aspect ratio AZO structures. Moreover, based on this finding, three kinds of micro- and nano-devices employing the deposited AZO thin film have been proposed and demonstrated. Firstly, nanowalled micro-hollows with an aspect ratio of 300 and a height of 15 µm are successfully produced . Secondly, micro- and nano-fluidics, including a hollow fluidic channel with a nanowall structure as a resonator and a fluidic capillary window as an optical modulator is proposed and demonstrated. Lastly, nanomechanical resonators consisting of a bridged nanobeam structure and a vertical nanomechanical capacitive resonator are fabricated and evaluated.

Hollow ZnO nanorices prepared by a simple hydrothermal method for NO2 and SO2 gas sensors.

Chemoresistive gas sensors play an important role in detecting toxic gases for air pollution monitoring. However, the demand for suitable nanostructures that could process high sensing performance remains high. In this study, hollow ZnO nanorices were synthesized by a simple hydrothermal method to detect NO2 and SO2 toxic gases efficiently. Material characterization by some advanced techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy, demonstrated that the hollow ZnO nanorices had a length and diameter size of less than 500 and 160 nm, respectively. In addition, they had a thin shell thickness of less than 30 nm, formed by an assembly of tiny nanoparticles. The sensor based on the hollow ZnO nanorices could detect low concentration of NO2 and SO2 gasses at sub-ppm level. At an optimum operating temperature of 200 °C, the sensor had response values of approximately 15.3 and 4.8 for 1 ppm NO2 and 1 ppm SO2, respectively. The sensor also exhibited good stability and selectivity, suggesting that the sensor can be applied to NO2 and SO2 toxic gas detection in ambient air.

Micro-Fabricated Presure Sensor Using 50 nm-Thick of Pd-Based Metallic Glass Freestanding Membrane.

This paper reports on micro-fabricated pressure sensors based on a thin metallic glass membrane. The Pd66Cu4Si30 metallic glass material is deposited successfully by a sputter technique. An amorphous feature of the deposited film is confirmed by high resolution transmission electron microscopy (HR-TEM) and the corresponding the selected area electron diffraction (SAED). The ultra-flat freestanding metallic glass membrane with 50 nm in thickness and 2 mm in circular diameter has been fabricated successfully. In addition, two kinds of micro-fabricated pressure sensor types, including itself membrane and additional metallic glass bar as piezoresistive sensing elements, are proposed and fabricated. A displacement of membrane can reach over 100 µm without any damage to membrane which is equivalent to over 0.7% of an elastic strain. Besides, the temperature coefficient of resistance of the Pd-based metallic glass thin film is extremely low 9.6 × 10-6 °C-1. This development of nano-thick metallic glass membrane possibly opens a new field of micro-fabricated devices with large displacement and enhanced sensing.

An effective H2S sensor based on SnO2 nanowires decorated with NiO nanoparticles by electron beam evaporation.

The highly toxic hydrogen sulphide (H2S) present in air can cause negative effects on human health. Thus, monitoring of this gas is vital in gas leak alarms and security. Efforts have been devoted to the fabrication and enhancement of the H2S-sensing performance of gas sensors. Herein, we used electron beam evaporation to decorate nickel oxide (NiO) nanoparticles on the surface of tin oxide (SnO2) nanowires to enhance their H2S gas-sensing performance. The synthesised NiO-SnO2 materials were characterised by field-emission scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy analysis. H2S gas-sensing characteristics were measured at various concentrations (1-10 ppm) at 200-350 °C. The results show that with effective decoration of NiO nanoparticles, the H2S gas-sensing characteristics of SnO2 nanowires are significantly enhanced by one or two orders compared with those of the bare material. The sensors showed an effective response to low-level concentrations of H2S in the range of 1-10 ppm, suitable for application in monitoring of H2S in biogas and in industrial controls. We also clarified the sensing mechanism of the sensor based on band structure and sulphurisation process.

Ion transport by gating voltage to nanopores produced via metal-assisted chemical etching method.

In this work, we report a simple and low-cost way to create nanopores that can be employed for various applications in nanofluidics. Nano sized Ag particles in the range from 1 to 20 nm are formed on a silicon substrate with a de-wetting method. Then the silicon nanopores with an approximate 15 nm average diameter and 200 µm height are successfully produced by the metal-assisted chemical etching method. In addition, electrically driven ion transport in the nanopores is demonstrated for nanofluidic applications. Ion transport through the nanopores is observed and could be controlled by an application of a gating voltage to the nanopores.

An Investigation of Processes for Glass Micromachining.

This paper presents processes for glass micromachining, including sandblast, wet etching, reactive ion etching (RIE), and glass reflow techniques. The advantages as well as disadvantages of each method are presented and discussed in light of the experiments. Sandblast and wet etching techniques are simple processes but face difficulties in small and high-aspect-ratio structures. A sandblasted 2 cm × 2 cm Tempax glass wafer with an etching depth of approximately 150 µm is demonstrated. The Tempax glass structure with an etching depth and sides of approximately 20 µm was observed via the wet etching process. The most important aspect of this work was to develop RIE and glass reflow techniques. The current challenges of these methods are addressed here. Deep Tempax glass pillars having a smooth surface, vertical shapes, and a high aspect ratio of 10 with 1-µm-diameter glass pillars, a 2-µm pitch, and a 10-µm etched depth were achieved via the RIE technique. Through-silicon wafer interconnects, embedded inside the Tempax glass, are successfully demonstrated via the glass reflow technique. Glass reflow into large cavities (larger than 100 µm), a micro-trench (0.8-µm wide trench), and a micro-capillary (1-µm diameter) are investigated. An additional optimization of process flow was performed for glass penetration into micro-scale patterns.

Retraction Note: Improved treatment of Asthma by using natural sources of antioxidants.

[This retracts the article DOI: 10.1186/2193-1801-2-278.].

Improved treatment of Asthma by using natural sources of antioxidants.

ABSTRACT: A combined composition of the extracted powders from Hippocampus kuda and Rhizoma Homalomenae together with honey in a form of medical pill (named as BRONAS) for the treatment of asthma has thoroughly been investigated under this study. BRONAS has shown its high anti-inflammatory effects and strong inhibition upon the pathogenesis of asthma. In comparison with other treatments without using BRONAS, the restoration of patients' health was improved by a factor of 2-3. CLINICAL TRIALS WITH ACTR NUMBER: ACTRN12612000766819.