Comparative Effects of Hydrazine and Thermal Reduction Methods on Electromagnetic Interference Shielding Characteristics in Foamed Titanium Carbonitride MXene Films.

The urgent need for the development of micro-thin shields against electromagnetic interference (EMI) has sparked interest in MXene materials owing to their metallic electrical conductivity and ease of film processing. Meanwhile, postprocessing treatments can potentially exert profound impacts on their shielding effectiveness (SE). This work comprehensively compares two reduction methods, hydrazine versus thermal, to fabricate foamed titanium carbonitride (Ti3CNTx) MXene films for efficient EMI shielding. Upon treatment of ≈ 100 µm-thick MXene films, gaseous transformations of oxygen-containing surface groups induce highly porous structures (up to ≈ 74.0% porosity). The controlled application of hydrazine and heat allows precise regulation of the reduction processes, enabling tailored control over the morphology, thickness, chemistry, and electrical properties of the MXene films. Accordingly, the EMI SE values are theoretically and experimentally determined. The treated MXene films exhibit significantly enhanced SE values compared to the pristine MXene film (≈ 52.2 dB), with ≈ 38% and ≈ 83% maximum improvements for the hydrazine and heat-treated samples, respectively. Particularly, heat treatment is more effective in terms of this enhancement such that an SE of 118.4 dB is achieved at 14.3 GHz, unprecedented for synthetic materials. Overall, the findings of this work hold significant practical implications for advancing high-performance, non-metallic EMI shielding materials.

Incorporating Loss Factor Modular Design for Full Ku-Band Microwave Attenuation in Double-Layered Graphene Aerogels.

The fabrication of absorption-dominant electromagnetic interference (EMI) shielding materials is a pressing priority to prevent secondary electromagnetic pollution in miniaturized electronic devices and communication systems. Meeting this goal has remained a tough challenge to keep pace with the rapid evolution of electronics due to the complex compositional and structural design and narrow operating bands. This work articulates a sound and simple strategy to precisely modulate the electrical conductivity of reduced graphene oxide (rGO), as the building block in lightweight double-layered rGO-film/rGO-aerogel/polyvinyl-alcohol (PVA) composites, for efficient microwave absorption over the entire Ku-band frequency range. These constructs reasonably comprised a porous absorption structure built from parallel rGO sheets aligned and prepared via freeze casting followed by freeze drying. The electrical conductivity and impedance of this layer were tuned by varying the annealing temperature from 400 to 800 °C, thereby adjusting the degree of reduction and the absorption characteristic. This layer was backed by a highly conductive rGO film reduced at a high temperature of 1000 °C, with a reflectivity of 97.5%. The incorporation of this film ensured high EMI shielding effectiveness of the double-layered structure through the absorption-reflection-reabsorption mechanism, consistent with the predicted values based on calculated loss factors and the input impedance of the structure. Accordingly, at an average EMI shielding effectiveness of 57.59 dB, the reflection shielding effectiveness (SER) and reflectivity (R) of the assembled composites were optimized to be as low as 0.22 dB and 0.049, respectively. This equates to approximately 99.999% shielding (SET) and ∼95% absorptivity (A) of the incident wave. This study opens new avenues for the development of lightweight (with a density as low as 15 mg/cm3) absorption-dominant EMI shielding composite materials with promising EMI shielding efficiency and potential applications in modern electronics.

The Effect of Computer-based Tests on Nursing Students' Test Anxiety: a Quasi-experimental Study.

BACKGROUND: Test anxiety often leads to poor academic performance. This study aimed to determine the effect of computer-based tests on nursing students' test anxiety. METHODS: This quasi-experimental study was conducted in 2016 on 39 nursing student with anxiety score under 128 on Spielberger's State-Trait Inventory (STAI). They were randomly allocated to computer-based tests (CBT) and paper-based test (PBT) group. Prior to exam, all students completed Sarason's Test Anxiety Scale (TAS). We administered CBT for students in experimental group. Data were analyzed using independent t-test and one-way ANOVA. RESULTS: Students mean test anxiety score was 11.94 and 11.32 in CBT and PBT groups, respectively. 47.4% of students in CBT group and 29.4% of those in PBT group experienced higher test anxiety, while the difference was not significant (p=0.56). CONCLUSIONS: Despite, there was no significant difference between anxiety score of two groups; but students' test anxiety score was higher in CBT group. With the current increase in computer-based assessment, educational administrators must be aware of and plan for the possible unfavorable effects of computer assisted testing, such an anxiety. Future studies are needed to evaluate and compare the effect of different type of student testing such as distance testing or CBTs using new information technologies such as laptop, tablet or mobile phone on students' test anxiety and performance.

The transient receptor potential vanilloid receptor 1, TRPV1 (VR1) inhibits peristalsis in the mouse jejunum.

BACKGROUND: The transient receptor potential vanilloid receptor 1, TRPV1 [previously termed the capsaicin or vanilloid receptor 1 (VR1)] is a nonselective cation channel that has been cloned and is expressed predominantly in sensory neurons. TRPV1 is activated by protons as well as capsaicin. Despite extensive research, the physiological function of TRPV1 in the gastrointestinal tract and other tissues remains elusive. We have examined the effect of the selective TRPV1-receptor ligand, capsaicin, on intestinal peristalsis by studying migrating motor complexes (MMCs). METHODS: We performed experiments on Knockout mice (KO) in which the TRPV1 gene was disrupted using standard gene targeting techniques and their wildtype (WT) littermates. Jejunal contractile activity was recorded from in vitro segments of the jejunum, 4 - 5 cm in length. When distended to 2 - 3 cm with H2O, the segments generated regular MMCs that were recorded as changes in intraluminal pressure. RESULTS: Capsaicin (1 - 100 nM) caused a dose-dependent inhibition of motility manifested as an increase in the interval between motor complexes (MCs) in the WT animal only, a response abolished by pre-treatment with TRPV1 antagonist capsazepine (Capz), ruthenium red (RR), and L-NAME. At higher doses of capsaicin (1 - 100 µM), periodic MCs were replaced by tonic increases in pressure upon which were superimposed continuous phasic contractions. This stimulation occurred in both KO and WT mice and was unaffected by pre-treatment with Capz, RR, and L-NAME. CONCLUSION: These data demonstrate the potential role of TRPV1 receptors in organized peristalsis in the mouse jejunum. These findings also suggest that inhibition of contractions in mouse jejunum by TRPV1-receptor activation does involve a nitric oxide synthetase (NOS) pathway.

Effect of peppermint oil on serum lipid peroxidation and hepatic enzymes after immobility stress in mice.

This study was undertaken to determine the influences of various doses of peppermint oil on the hepatic en-zymes, alanine transaminase, apartate tranaminase, alkaline phosphotase and gamma glutamyl transferase and the level of malondialdehyde in the serum of mice with and without immobility stress. The mice exposed to drink water, 0.9, 27 and 60 mg/kg peppermint oil from the days 1 to 5 for a period of 4 h before and after immobility stress. Serum MDA in-creased in treatment group II, III and IV after immobility stress. There was a significant decrease in ALT in treatment group III and IV after immobility stress. There were also significant decreases in ALP and GGT in treatment group IV af-ter immobility stress. This result may suggest that, MDA level is higher in immobilization stress group than in the un-immobilized animals in serum and this results show that enzyme activities decreased after immobilization stress.