Switchable chemoselective aryne reactions between nucleophiles and pericyclic reaction partners using either 3-methoxybenzyne or 3-silylbenzyne.

Arynes are known to serve as highly reactive benzene-based synthons, which have gained numerous successes in preparing functionalized arenes. Due to the superb electrophilic nature of these fleeting species, however, it is challenging to modulate the designated aryne transformation chemoselectively, when substrates possess multiple competing reaction sites. Here, we showcase our effort to manipulate chemoselective control between two major types of aryne transformations using either 3-methoxybenzyne or 3-silylbenzyne, where nucleophilic addition-triggered reactions and non-polar pericyclic reactions could be differentiated. This orthogonal chemoselective protocol is found to be applicable between various nucleophiles, i.e., imidazole, N-tosylated/N-alkyl aniline, phenol, and alcohol, and an array of pericyclic reaction partners, i.e., furan, cyclopentadiene, pyrrole, cycloheptatrienone, and cyclohexene. Beyond arylation reactions, C-N bond insertion, Truce-Smiles rearrangement, and nucleophilic annulation are appropriate reaction modes as well. Moreover, this chemoselective protocol can find potential synthetic application.

Trajectories and determinants of acute stress disorder during the COVID-19 centralized quarantine: A latent class growth analysis.

COVID-19 centralized quarantine may cause acute stress disorder (ASD). However, it is unknown how individuals present heterogeneous ASD trajectories during the COVID-19 centralized quarantine and what factors contribute to these patterns. This study aimed to identify the ASD trajectories and their determinants during the centralized quarantine period, and the mediating effects of resilience on these associations. A longitudinal survey with three waves was conducted in a randomly selected quarantine hotel in Shenzhen, China from October to November 2020. A total of 273 participants completed online measures assessing ASD symptoms, Eysenck's personality constructs of extraversion (E), neuroticism (N), psychoticism (P), and resilience on Day 1, and reported ASD symptoms on Days 7 and 14 during their 14-day centralized quarantine periods. Latent class growth analysis identified three trajectories: constantly high symptoms (CHS, 4.76%), decreasing symptoms (DS, 11.72%), and constantly low symptoms (CLS, 83.52%). The CHS and DS subgroups both reported lower E and higher N scores, but not P, compared with the CLS subgroup. Resilience mediated the effects of three personality constructs on ASD trajectories, except for the association between N and DS membership. Our study highlights the heterogeneity in stress responses to the COVID-19 centralized quarantine. The high-risk subgroup with persistent ASD symptoms was characterized by lower E and higher N. The resilience process accounted for the effects of personality in shaping distinct ASD trajectories. Our findings have implications to detect the populations vulnerable to ASD and provide insights for developing timely resilience enhancement intervention programs.

Nutrition- and hormone-controlled developmental plasticity in Blattodea.

Blattodea, which includes cockroaches and termites, possesses high developmental plasticity that is mainly controlled by nutritional conditions and insect hormones. Insulin/insulin-like growth factor signaling (IIS), target of rapamycin complex 1 (TORC1), and adenosine monophosphate-activated protein complex are the three primary nutrition-responsive signals. Juvenile hormone (JH) and 20-hydroxyecdysone (20E) constitute the two most vital insect hormones that might interact with each other through the Met, Kr-h1, E93 (MEKRE93) pathway. Nutritional and hormonal signals interconnect to create a complex regulatory network. Here we summarize recent progress in our understanding of how nutritional and hormonal signals coordinately control the developmental plasticity of metamorphosis, reproduction, and appendage regeneration in cockroaches as well as caste differentiation in termites. We also highlight several perspectives that should be further emphasized in the studies of developmental plasticity in Blattodea. This review provides a general landscape in the field of nutrition- and hormone-controlled developmental plasticity in insects.

Polyamidoamine Dendrimers Functionalized Water-Stable Metal-Organic Frameworks for Sensitive Fluorescent Detection of Heavy Metal Ions in Aqueous Solution.

In this work, polyamidoamine (PAMAM)-functionalized water-stable Al-based metal-organic frameworks (MIL-53(Al)-NH2) were proposed with enhanced fluorescence intensity, and used for the sensitive detection of heavy metal ions in aqueous solution. The size and morphology of MIL-53(Al)-NH2 were effectively optimized by regulating the component of the reaction solvents. PAMAM dendrimers were subsequently grafted onto the surface with glutaraldehyde as a cross-linking agent. It was found that the size and morphology of MIL-53(Al)-NH2 have great influence on their fluorescence properties, and PAMAM grafting could distinctly further improve their fluorescence intensity. With higher fluorescence intensity, the PAMAM-grafted MIL-53(Al)-NH2 showed good linearity (R2 = 0.9925-0.9990) and satisfactory sensitivity (LOD = 1.1-8.6 µmol) in heavy metal ions determination. Fluorescence enhancement and heavy metal ions detection mechanisms were discussed following the experimental results. Furthermore, analogous water-stable Materials of Institute Lavoisier (MIL) metal-organic frameworks such as MIL-53(Fe)-NH2 were also proved to have similar fluorescence enhancement performance after PAMAM modification, which demonstrates the universality of the method and the great application prospects in the design of PAMAM-functionalized high-sensitivity fluorescence sensors.

Analyzing and predicting colour preference of colour palettes.

A palette composed of multiple colour patches can express lots of information. This study aimed to explore the factors that influenced colour palette preference, including colour attributes and colour differences between colour patches. A new attribute called Delta_Order for calculating the colour difference of a palette was presented, which fully considered the colour difference and the placement. In order to comprehend colour palette preference intuitively, a prediction model of palette preference was proposed based on lightness, chroma and the new metric Delta_Order. Two psychophysical experiments including analyzing and validating experiments were conducted. Fifty observers were invited to evaluate the colour palette preference. The results indicated that lightness played an important role in colour preference, but colour preference was not related to hue angle. For Delta_Order, there was a significant negative correlation between the new metric and preference score since the Pearson correlation coefficient was -0.801. This meant that observers preferred the palettes with low Delta_Orders. According to the validating test, it confirmed that the proposed prediction model had a good stability. The predicted trends were consistent with the true results, and the scores were similar to each other. These analysis results had a certain guiding significance in design and industry about colour.

Cyclodextrin-dendrimers nanocomposites functionalized high performance liquid chromatography stationary phase for efficient separation of aromatic compounds.

In this work, novel cyclodextrin-dendrimers nanocomposites functionalized high performance liquid chromatography stationary phases were developed for efficient separation of aromatic compounds. ß-cyclodextrin was grafted onto the surface of silica gel matrix with poly (amidoamine) dendrimers as spacers. Scanning electron microscope, fourier transform infrared spectroscopy, element analysis and Brunner-Emmet-Teller measurement proved the successful grafting of cyclodextrin-dendrimers nanocomposites. The obtained stationary phases showed satisfactory separation effects for alkylbenzenes and benzenesulfonic acid substituents in reverse phase liquid chromatography mode. Weak hydrophilic and ion exchange interactions were also confirmed at the same time. Meanwhile, the effects of dendrimers and cyclodextrin on the chromatography performance were discussed. Separation mechanism of the stationary phases were verified by two-dimensional nuclear magnetic resonance technology, and the result implied that the proposed cyclodextrin-dendrimers nanocomposites functionalized stationary phases have significant prospects for separation and determination of more aromatic compounds in future.

Comparison of Sample Preparation Techniques for Inspection of Leaf Epidermises Using Light Microscopy and Scanning Electronic Microscopy.

The micro-morphology of leaf epidermises is valuable for the study of leaf development and function, as well as the classification of plant species. There have been few studies comparing different preparation and imaging methods for visualizing the leaf epidermis. Here, four specimen preparation methods were used to investigate the leaf epidermis morphology of Arabidopsis, radish, cucumber, wheat, rice, and maize, under an inverted basic light microscope (LM), a laser scanning confocal microscope (LSCM), or a scanning electron microscope (SEM). Optical microscope specimens were obtained using either the direct isolation method or the chloral hydrate-based clearing method. SEM images were obtained using a standard stage for conventional dehydrated samples or a Coolstage for fresh tissue. Different parts of epidermis peels were well focused under the LM. Investigation of samples cleared by chloral hydrate is convenient and autofluorescence of cell walls can be detected in rice. The resolution of images of conventional SEM leaf samples was generally higher than the Coolstage images at the same magnification, whereas local collapse and shrinkage were observed in leaves with high water content when using the conventional method. However, stomatal apparatuses of Arabidopsis, cucumber, radish, and maize deformed and showed poor appearance when using the Coolstage. Moreover, we usually used glutaraldehyde as an SEM fixative when using t-butanol for freeze-drying, though methanol is considered a better fixative in recent studies. In addition, fresh samples were not stable on the Coolstage. Thus, we compared four different t-butanol freeze-drying methods and two Coolstage methods. The dimension and morphology of tissues were compared using the six different methods. The results indicate that methanol fixative obviously reduced shrinkage of SEM samples compared with glutaraldehyde and formaldehyde alcohol acetic acid (FAA) fixatives. The use of methanol and a graded series of steps improved the preservation of samples. Preparing samples with optimal cutting temperature compound and observing at -30°C helped to increase the stability of Coolstage samples. In summary, our results provide an overview of the shortcomings and merits of four different methods, and might provide some information about choosing an optimal method for visualizing epidermal morphology.

In situ melt electrospun polycaprolactone/Fe3O4 nanofibers for magnetic hyperthermia.

Magnetic fibrous membrane used to generate heat under the alternating magnetic field (AMF) has attracted wide attention due to their application in magnetic hyperthermia. However, there is not magnetic fibrous membrane prepared by melt electrospinning (e-spinning) which is a solvent-free, bio-friendly technology. In this work, polycaprolactone (PCL)/Fe3O4 fiber membrane was prepared by melt e-spinning and using homemade self-powered portable melt e-spinning apparatus. The hand-held melt e-spinning apparatus has a weight of about 450 g and a precise size of 24 cm in length, 6 cm in thickness and 13 cm in height, which is more portable for widely using in the medical field. The PCL/Fe3O4 composite fibers with diameters of 4-17 µm, are very uniform. In addition, the magnetic composite fiber membrane has excellent heating efficiency and thermal cycling characteristics. The results indicated that self-powered portable melt e-spinning apparatus and PCL/Fe3O4 fiber membrane may provide an attractive way for hyperthermia therapy.

Transcriptomic and Functional Analyses of Phenotypic Plasticity in a Higher Termite, Macrotermes barneyi Light.

Eusocial termites have a complex caste system, which leads to the division of labor. Previous studies offered some insight into the caste differentiation in lower termites; however, few studies were focusing on the molecular mechanisms of higher termites with sophisticated societies. Comparative transcriptomic analyses of five immature castes of a higher termite, Macrotermes barneyi Light, suggest that phenotypic plasticity is modulated by an array of transcriptional changes, including differentially expressed genes (e.g., caste-biased genes Vtg and TnC), co-expression networks (e.g., genes associated with nymph reproduction), and alternative splicing (e.g., events related to muscle development in presoldiers). Transcriptional (RT-PCR and RT-qPCR) and functional (in vivo RNAi) validation studies reveal multiple molecular mechanisms contributing to the phenotypic plasticity in eusocial termites. Molecular mechanisms governing the phenotypic plasticity in M. barneyi could be a rule rather than an exception in the evolution of sociality.

Downregulation of Orco and 5-HTT Alters Nestmate Discrimination in the Subterranean Termite Odontotermes formosanus (Shiraki).

Nestmate discrimination allows social insects to recognize nestmates from non-nestmates using colony-specific chemosensory cues, which typically evoke aggressive behavior toward non-nestmates. Functional analysis of genes associated with nestmate discrimination has been primarily focused on inter-colonial discrimination in Hymenopterans, and parallel studies in termites, however, are grossly lacking. To fill this gap, we investigated the role of two genes, Orco and 5-HTT, associated with chemosensation and neurotransmission respectively, in nestmate discrimination in a highly eusocial subterranean termite, Odontotermes formosanus (Shiraki). We hypothesized that knocking down of these genes will compromise the nestmate recognition and lead to the antagonistic behavior. To test this hypothesis, we carried out (1) an in vivo RNAi to suppress the expression of Orco and 5-HTT, respectively, (2) a validation study to examine the knockdown efficiency, and finally, (3) a behavioral assay to document the phenotypic impacts/behavioral consequences. As expected, the suppression of either of these two genes elevated stress level (e.g., vibrations and retreats), and led to aggressive behaviors (e.g., biting) in O. formosanus workers toward their nestmates, suggesting both Orco and 5-HTT can modulate nestmate discrimination in termites. This research links chemosensation and neurotransmission with nestmate discrimination at the genetic basis, and lays the foundation for functional analyses of nestmate discrimination in termites.

Bioactivity of diatomaceous earth against the subterranean termite Reticulitermes chinensis Snyder (Isoptera: Rhinotermitidae).

The effects of diatomaceous earth (DE) on the penetrating behavior, tunneling behavior, mortality, and body surface characteristics of the subterranean termite Reticulitermes chinensis were investigated in this study. Our results show that the workers of R. chinensis were able to penetrate 1- and 2-mm layers of dry DE but not 3-mm layers. After treatment with dry DE for 6 h, the mortality of termites reached 100%, which was significantly higher than in the treatment with DE with a 10 and 25% moisture content and treatment with sand of three different moisture contents. The tunneling distances of workers in DE with 10, 25, and 50% moisture contents were all significantly shorter than those in sand with the same moisture contents (10, 25, and 50%), indicating that DE has a good suppressing effect on the tunneling behavior of workers. After treatment with dry DE for different times (1, 3, and 6 h), many DE particles adhered to the bodies of workers, whereas no particles adhered to the body of workers in the case of treatment with dry sand. The treatment with dry DE for 6 h resulted in the death of all workers, which presented conspicuous abdominal shrinkage, whereas workers treated with sand had no significant mortality and no obvious abdominal shrinkage. In summary, we suggest that dry DE has ideal insecticidal activity against the subterranean termite R. chinensis and can be further exploited for controlling termites inside houses.

Preparation of Polypropylene Micro and Nanofibers by Electrostatic-Assisted Melt Blown and Their Application.

In this paper, a novel electrostatic-assisted melt blown process was reported to produce polypropylene (PP) microfibers with a diameter as fine as 600 nm. The morphology, web structure, pore size distribution, filtration efficiency, and the stress and strain behavior of the PP nonwoven fabric thus prepared were characterized. By introducing an electrostatic field into the conventional melt-blown apparatus, the average diameter of the melt-blown fibers was reduced from 1.69 to 0.96 µm with the experimental setup, and the distribution of fiber diameters was narrower, which resulted in a filter medium with smaller average pore size and improved filtration efficiency. The polymer microfibers prepared by this electrostatic-assisted melt blown method may be adapted in a continuous melt blown process for the production of filtration media used in air filters, dust masks, and so on.

Bubble Melt Electrospinning for Production of Polymer Microfibers.

In this paper, we report an interesting bubble melt electrospinning (e-spinning) to produce polymer microfibers. Usually, melt e-spinning for fabricating ultrafine fibers needs "Taylor cone", which is formed on the tip of the spinneret. The spinneret is also the bottleneck for mass production in melt e-spinning. In this work, a metal needle-free method was tried in the melt e-spinning process. The "Taylor cone" was formed on the surface of the broken polymer melt bubble, which was produced by an airflow. With the applied voltage ranging from 18 to 25 kV, the heating temperature was about 210⁻250 °C, and polyurethane (TPU) and polylactic acid (PLA) microfibers were successfully fabricated by this new melt e-spinning technique. During the melt e-spinning process, polymer melt jets ejected from the burst bubbles could be observed with a high-speed camera. Then, polymer microfibers could be obtained on the grounded collector. The fiber diameter ranged from 45 down to 5 µm. The results indicate that bubble melt e-spinning may be a promising method for needleless production in melt e-spinning.

[Determination of N-nitrosodimethylamine in beer by frozen zone melting liquid-liquid extraction/gas chromatography].

A simple and effective sample enrichment method of frozen zone melting liquid-liquid extraction was optimized and validated for the analysis of trace N-nitrosodimethylamine (NDMA) in beer samples. The method was based on high pressure liquid-liquid extraction with a low temperature frozen step. The 90 mL beer was placed in a container with 10 mL dichloromethane. After agitation, the sample was kept in a freezer for 16 h at -19 degrees C. The organic extract was analyzed by gas chromatography with a flame ionization detector (GC-FID). The accuracy, precision, detection and quantification limits and linearity of the method were evaluated. The results showed that the calibration curve of NDMA was linear in the range of 5-200 mg/L with a good correlation coefficient (r2) of 0.999 6. The recoveries at the spiked levels of 5, 10 and 20 mg/L were 84.94%, 83.24%, 85.14% with the relative standard deviations (n = 7) of 3.06%, 3.19%, 2.63%, respectively. The ordinary extraction method of N-nitrosodimethylamine in beer includes the four steps of low-temperature distillation, liquid-liquid extraction, rotary evaporation and nitrogen blowing concentration. With the extremely low volume of solvent used, the proposed extraction method proved to be easy and simple, and adequate for high-throughput analysis at low cost.

Personalized alert notifications and evacuation routes in indoor environments.

The preparedness phase is crucial in the emergency management process for reaching an adequate level of readiness to react to potential threats and hazards. During this phase, emergency plans are developed to establish, among other procedures, evacuation and emergency escape routes. Information and Communication Technologies (ICT) can support and improve these procedures providing appropriate, updated and accessible information to all people in the affected zone. Current emergency management and evacuation systems do not adapt information to the context and the profile of each person, so messages received in the emergency might be useless. In this paper, we propose a set of criteria that ICT-based systems could achieve in order to avoid this problem adapting emergency alerts and evacuation routes to different situations and people. Moreover, in order to prove the applicability of such criteria, we define a mechanism that can be used as a complement of traditional evacuation systems to provide personalized alerts and evacuation routes to all kinds of people during emergency situations in working places. This mechanism is composed by three main components: CAP-ONES for notifying emergency alerts, NERES for defining emergency plans and generating personalized evacuation routes, and iNeres as the interface to receive and visualize these routes on smartphones. The usability and understandability of proposed interface has been assessed through a user study performed in a fire simulation in an indoor environment. This evaluation demonstrated that users considered iNeres easy to understand, to learn and to use, and they also found very innovative the idea to use smartphones as a support for escaping instead of static signals on walls and doors.

[Determination of sulfur amino acids in feedstuffs by high performance liquid chromatography coupled with pre-column derivatization].

A method of quantitative analysis of sulfur amino acids in feedstuffs by high performance liquid chromatography coupled with pre-column derivatization was developed. Before the feedstuffs were hydrolyzed under acidic condition, the cystine and methionine in the feedstuffs were oxidized to cysteic acid and methionine sulfone respectively by performic acid, and then derivatized by 2,4-dinitrofluorobenzene. The separation was performed on an Elite AAK C18 column (250 mm x 4.6 mm, 5 microm) by the gradient elution of 0.05 mol/L sodium acetate and acetonitrile-water (50: 50, v/v) as the mobile phase with a flow rate of 1.2 mL/min at 31 degrees C. The detection wavelength was set at 360 nm. The linearities of cystine and methionine were good in the ranges of 0.4 - 16.0 mg/L and 0.7 - 29.6 mg/L with the correlation coefficients of 0.999 9 and 0.999 8, respectively. The quantification limits (S/N = 10) were 2.6 microg/kg, 3.1 microg/kg, and the recoveries were 100.28% - 102.00% and 105.72% - 107.89%, respectively. The method can be adapted to the accurate quantification of the sulfur amino acids in feedstuffs.

[Development and evaluation of a novel three-dimensional adjustable confocal laser-induced fluorescence detector].

Laser-induced fluorescence detector (LIFD) is one of the most sensitive detectors in analytical chemical files. Confocal optical configuration is widely used in LIFDs. Two effective approaches used to achieve the best signal to noise ratio (S/N) are increasing the confocal precision and minimizing the background noise. A novel three-dimensional adjustable confocal LIFD was developed, using a new three-dimensional adjustable supporter of reflector and modularized optical system. A detection limit (S/N = 3) of 1 x 10(-12) mol/L and a linear dynamic range of 3 orders of magnitude were obtained using fluorescein isothiocyanate (FITC) standard as the test sample. The noise level and drift levels were 8.0 x 10(-3) mV and 1.4 x 10(-3) mV/h, respectively, which were almost 10 times lower than before. And the stability of the LIFD was evaluated by five replicate injections of 5 x 10(-9) mol/L FITC, and the relative standard deviations (RSDs) of peak height and peak area were 0.38% and 0.41%, respectively. Further more, three biogenic amines, which were derivatized by FITC, were separated by high performance liquid chromatography (HPLC) and then detected by the novel LIFD. And the detection limits (S/N = 3) ranged 0.01 to 0.02 nmol/L, which were better than other methods. Therefore, the LIFD is highly sensitive, as well as shows a real low noise level and good reproducibility.

[Rapid determination of melamine in eggs by high performance liquid chromatography].

A rapid method for the determination of melamine in eggs was established using high performance liquid chromatography (HPLC). The melamine in a test sample was extracted with ultrasonic in 1% trichloroacetic acid for 10 min, and then purified with precipitation, centrifugation and filtration, at last tested by HPLC system. The total time of HPLC analysis for each sample was only 10 min. The linear range was from 0.05 to 20.0 mg/L as the linear correlation coefficient was 0. 999 9. The limit of quantification was 0. 10 mg/kg (S/N > 10). The average recoveries were between 94.2% and 107% in the spiked range of 1.0 - 6.0 mg/kg in eggs. The relative standard deviations (RSDs) of parallel determination were between 1.53% and 2.06% (n = 6). This method is simple, fast, sensitive and suitable for the determination of melamine in eggs.