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Electrostatic interactions are a key driving force that mediates colloidal assembly. The Schulze-Hardy rule states that nanoparticles have a higher tendency to coagulate in the presence of counterions with high charge valence. However, it is unclear how the Schulze-Hardy rule works when the simple electrolytes are replaced with more sophisticated charge carriers. Here, we designed cationic peptides of varying valencies and demonstrate that their charge screening behaviors on anionic gold nanoparticles (AuNPs) follow the six-power relationship in the Schulze-Hardy rule. This finding further inspires a simple yet effective strategy for measuring SARS-CoV-2 main protease (Mpro) via naked eyes. This work provides a unique avenue for fundamental NP disassembly based on the Schulze-Hardy rule and can help design versatile substrates for colorimetric sensing of other proteases.

Existing tools to detect and visualize severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) suffer from low selectivity, poor cell permeability, and high cytotoxicity. Here we report a novel self-immolative fluorescent probe (MP590) for the highly selective and sensitive detection of the SARS-CoV-2 main protease (Mpro). This fluorescent probe was prepared by connecting a Mpro-cleavable peptide (N-acetyl-Abu-Tle-Leu-Gln) with a fluorophore (i.e., resorufin) via a self-immolative aromatic linker. Fluorescent titration results show that MP590 can detect Mpro with a limit of detection (LoD) of 35 nM and is selective over interferents such as hemoglobin, bovine serum albumin (BSA), thrombin, amylase, SARS-CoV-2 papain-like protease (PLpro), and trypsin. The cell imaging data indicate that this probe can report Mpro in HEK 293T cells transfected with a Mpro expression plasmid as well as in TMPRSS2-VeroE6 cells infected with SARS-CoV-2. Our results suggest that MP590 can both measure and monitor Mpro activity and quantitatively evaluate Mpro inhibition in infected cells, making it an important tool for diagnostic and therapeutic research on SARS-CoV-2.

Aromatic interactions are commonly involved in the assembly of naturally occurring building blocks, and these interactions can be replicated in an artificial setting to produce functional materials. Here we describe a colorimetric biosensor using co-assembly experiments with plasmonic gold and surfactant-like peptides (SLPs) spanning a wide range of aromatic residues, polar stretches, and interfacial affinities. The SLPs programmed in DDD−(ZZ)x−FFPC self-assemble into higher-order structures in response to a protease and subsequently modulate the colloidal dispersity of gold leading to a colorimetric readout. Resultsshow the strong aggregation propensity of the FFPC tail without polar DDD head. The SLPs were specific to the target protease, i.e., Mpro, a biomarker for SARS-CoV-2. This system is a simple and visual tool that senses Mproin phosphate buffer, exhaled breath condensate, and saliva with detection limits of 15.7, 20.8, and 26.1 nM, respectively. These results may have value in designing other protease testing methods. Submitted/Accepted version The authors thank internal funding from the UC Office of the President (R00RG2515) and the National Institutes of Health (R01 DE031114; R21 AG065776-S1; R21 AI157957) for financial support. This work was also supported by National Science Foundation (DMR-2011924) via equipment in the UC San Diego Materials Research Science and Engineering Center (UCSD MRSEC). M.N.C. was supported by NIT under T32 CA15391.M.R. acknowledges the Wallonie-Bruxelles International (WBI) of the Fédération Wallonie-Bruxelles for financial support. The electron microscopy work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of University of California San Diego, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (Grant ECCS-1542148). The MANTA analysis work was supported by the National Institutes of Health (S10 OD023555).

We report the reversible aggregation of gold nanoparticles (AuNPs) assemblies via a di-arginine peptide additive and thiolated PEGs (HS-PEGs). The AuNPs were first aggregated by attractive forces between the citrate-capped surface and the arginine side chains. We found that the HS-PEG thiol group has a higher affinity for the AuNP surface, thus leading to redispersion and colloidal stability. In turn, there was a robust and obvious color change due to on/off plasmonic coupling. The assemblies' dissociation was directly related to the HS-PEG structural properties such as their size or charge. As an example, HS-PEGs with a molecular weight below 1 kDa could dissociate 100% of the assemblies and restore the exact optical properties of the initial AuNP suspension (prior to the assembly). Surprisingly, the dissociation capacity of HS-PEGs was not affected by the composition of the operating medium and could be performed in complex matrices such as plasma, saliva, bile, urine, cell lysates, or even seawater. The high affinity of thiols for the gold surface encompasses by far the one of endogenous molecules and is thus favored. Moreover, starting with AuNPs already aggregated ensured the absence of a background signal as the dissociation of the assemblies was far from spontaneous. Remarkably, it was possible to dry the AuNP assemblies and solubilize them back with HS-PEGs, improving the colorimetric signal generation. We used this system for protease sensing in biological fluids. Trypsin was chosen as the model enzyme, and highly positively charged peptides were conjugated to HS-PEG molecules as cleavage substrates. The increase of positive charge of the HS-PEG-peptide conjugate quenched the dissociation capacity of the HS-PEG molecules, which could only be restored by the proteolytic cleavage. Picomolar limit of detection was obtained as well as the detection in saliva or urine.

Plasmonic coupling

We report the reversible aggregation of gold nanoparticle (AuNPs) assemblies via a diarginine peptide additive and thiolated PEGs (HS-PEGs). The AuNPs were first aggregated by attractive forces between the citrate-capped surface and the arginine side chains. We found that HS-PEG thiol group has higher affinity for the AuNPs surface, thus leading to redispersion and colloidal stability. In turn, there was a robust and obvious color change due to on/off plasmonic coupling. The assemblies’ dissociation was directly related to the HS-PEG structural properties such as their size or charge. As an example, HS-PEGs with a molecular weight below 1 kDa could dissociate 100% of the assemblies and restore the exact optical properties of the initial AuNPs suspension (prior to the assembly). Surprisingly, the dissociation capacity of HS-PEGs was not affected by the composition of the operating medium and could be performed in complex matrices such as plasma, saliva, bile, urine, cell lysates or even sea water. The high affinity of thiols for the gold surface encompasses by far the one of endogenous molecules and is thus favorized. Moreover, starting with AuNPs already aggregated ensured the absence of background signal as the dissociation of the assemblies was far from spontaneous. Remarkably, it was possible to dry the AuNPs assemblies and to solubilize them back with HS-PEGs, improving the colorimetric signal generation. We used this system for protease sensing in biological fluid. Trypsin was chosen as model enzyme and highly positively charged peptides were conjugated to HS-PEG molecules as cleavage substrate. The increase of positive charge of the HS-PEG-peptide conjugate quenched the dissociation capacity of the HS-PEG molecules which could only be restored by the proteolytic cleavage. Picomolar limit of detection was obtained as well as the detection in saliva or urine.TOC

Inorganic nanomaterials hold immense potential in theranostics, but their translation is limited by the toxicity resulting from non-degradability. Bulk phosphate-based glasses offer great biodegradability, biocompatibility, and ease in incorporating imaging dyes and drugs. However, the facile and mild solution-based synthesis of micro-/nanoparticles of this material is yet to be explored. Inspired by the biosilicification process in the diatom, we created polyethylenimine (PEI)/phosphate aggregates via the hydrogen bonding between amine (PEI) and hydroxyl (phosphate) groups, which was proved by dynamic light scattering and 1H solution nuclear magnetic resonance. The sol–gel reaction between the calcium precursor and PEI/phosphate aggregates yielded degradable PEI/calcium phosphate (PEI/CP) micro-/nano-composites with versatile sizes (396 ± 128 nm to 63 ± 8 μm) and morphologies (hexagonal micro-disc, micro-flower, micro-leaf, nano-butterfly, and nano-ribbon). The PEI/CP composition and chemical structure were examined. PEI/CP has negligible cell cytotoxicity and degrades within 24 h. In vitro studies showed the promise for PEI/CP in transient ultrasound and photoluminescence imaging.\ud \ud

The validation and analysis of X-ray crystallographic data is essential for reproducibility and the development of crystallographic methods. Here, the authors describe a repository for crystallographic datasets and demonstrate some of the ways it could serve the crystallographic community., Access to experimental X-ray diffraction image data is fundamental for validation and reproduction of macromolecular models and indispensable for development of structural biology processing methods. Here, we established a diffraction data publication and dissemination system, Structural Biology Data Grid (SBDG; data.sbgrid.org), to preserve primary experimental data sets that support scientific publications. Data sets are accessible to researchers through a community driven data grid, which facilitates global data access. Our analysis of a pilot collection of crystallographic data sets demonstrates that the information archived by SBDG is sufficient to reprocess data to statistics that meet or exceed the quality of the original published structures. SBDG has extended its services to the entire community and is used to develop support for other types of biomedical data sets. It is anticipated that access to the experimental data sets will enhance the paradigm shift in the community towards a much more dynamic body of continuously improving data analysis.

Solid particle erosion-wear behavior under different working conditions was simulated by FEM. A three-dimensional finite element model of erosion-wear of solid particle was established, and Johnson-Cook material model and failure criterion were adopted to define the mechanical property of sample material. The process of spherical particle impacting 45 steel from different angles and under different impact velocity was simulated, respectively. Material deformation and strain condition were analyzed .The relationship between erosion-wear degree , impact angle and impact velocity was investigated. The results showed that, maximum plastic strain occurs on the surface of material when impacting from low angle and on subsurface while vertical impacting. The wear degree of material increases until reach the peak value at 40° and deformation volume increases with the vertical impact velocity，and there is significant accumulation of material around pit.

In order to improve the test accuracy of CCD, a new type of CCD device is proposed. Several columns (rows) of photoelectric diodes (PDs) are combined together, and staggered with the distance of H 1=H/N, where H is the space between two adjacent PDs, and N is the number of columns (rows). The photoelectric signals are collected simultaneously by multi-channel A/D, and the accurate measurement result is obtained through appropriate signal processing. Without changing the size or space of PDs, more photographic pixels are arranged in the given direction within a finite length. Diameters of three standard poles are measured by a single CCD and two staggered CCDs, respectively with length of 30 mm and diameters of 5 mm, 8 mm and 12 mm, respectively. The results show that the accuracy of double staggered CCDs is two times of that of single CCD. The new type of CCDs can avoid the impact of PD space theoretically and higher measurement accuracy can be obtained.

This paper presents the flexural performance of reinforced concrete (RC) beams with rectangular section. Seven RC beams strengthened using carbon fiber reinforced polymer (CFRP) sheets were subjected to four-point bending to investigate the effect of fiber reinforcement on the beams strengthened. The main experimental parameters included in the study are the pre-cracked width, CFRP sheet layers, the longitudinal tensile reinforcement ratio, the shear span ratio, and the concrete cover thickness. In total, seven beams were cast, one beam without any reinforcement as a control beam, two beams strengthened by CFRP sheets without making pre-cracks on the beam and four pre-cracked beams repaired with one layer or two layers CFRP sheets. Test results show the effectiveness and flexural capacity of the CFRP strengthened beams. The flexure enhancement of the CFRP strengthened beams varied between 41.7% and 124.1% over the control beam. This study confirms that the CFRP reinforcing technique significantly enhances the flexural capacity of reinforced concrete beams.

Paphiopedilum armeniacum , Paphiopedilum micranthum and Paphiopedilum delenatii are endangered orchid species. These three Paphiopedilum species and their hybrids are difficult to distinguish morphologically. In this study, rDNA-ITS (internal transcribed spacer) sequences were used to design species-specific SCAR (sequence characterized amplified regions) markers to distinguish P. armeniacum , P. micranthum , P. delenatii and their respective hybrids. The developed markers efficiently amplified 600 bp DNA product for P. armeniacum and its hybrids (SCAR-600armF/Pap-ITS2R), 300 bp product for P. delenatii and its hybrids (SCAR-300delF/Pap-ITS2R) and 700 bp product for P. micranthum and its hybrids (SCAR-700micF/Pap-ITS2R). The effectiveness of designed species-specific markers was also confirmed by using multiplex polymerase chain reaction amplification with a combination of developed three SCAR markers.

In speech, emotion is freely carried in the fundamental frequency, rate of speech, intensity and spectra of the human voice, although the spectra is largely dictated by words in speech. In singing, however, fundamental frequency and rhythm are constrained by the melody of the song, while the spectra is constrained by the song lyrics. Nevertheless, a large amount of emotion is carried in song; and the same song, with the same melody and rhythm constraints, may be expressed in a variety of emotions. This paper investigates the manner by which different emotions may be conveyed in the human singing voice, given the constraints of song. It goes further to find which subtle variations correspond to which emotion.

The silver nanowires (AgNWs) and silver nanoparticles (AgNPs) were synthesized. With near-field electrospinning (NFES) process, fibers and thin films with AgNPs and AgNWs were fabricated. In the NFES process, 10 k voltage was applied and the AgNPs and AgNWs fibers can be directly orderly collected without breaking and bending. Then, the characteristics of the fibers were analyzed by four-point probe and EDS. The conductive film was analyzed. When the thickness of films with AgNWs and AgNPs was 1.6 µm, the sheet resistance of films was 0.032 Ω/sq which was superior to that of the commercial ITO. The transmissivity of films was analyzed. The transmissivity was inversely proportional to sheet resistance of the films. In the future, the fibers and films can be used as transparent conductive electrodes.

The relationships between energy, amplitude and frequency of earthquake are correlative with the property of the seismic source. And the grade of the correlativity can be used as an index to distinguish the types of strong earthquakes. Primarily the strong earthquake can be divided into three types of main-after earthquakes, double-main earthquakes and swarm of strong earthquake. There are similarity and a certain repeatability at the quantificational indexes of hypocenter property between the same type of strong earthquakes, which supply basis for the forecast of subsequent strong shocks. The reference indexes of after strong shock forecast which are valuable for the applications of the method of type-divided forecast come from the analysis about more than fifty strong shock wide-band (BPZ wave) recording data of CDSN from 1988 to 1997.

In crosswell observation of electromagnetic tomography, now there is no feasible way to calibrate the in-situ radiation constant, while the effect of induced wave-field always exists in observational data. Therefore the absorption coefficient obtained by a common-used image reconstruction method is only a relative value. The consistency of tomograms in linked profiles inevitably is affected seriously. An improved equation involving the effect of induced wave-field and an alternative tracing method to calculate the in-situ radiation constant is proposed in the present paper. Based on the results from a series of parameter calibration performed in water and the experiments with rock samples, the standard meter readings of borehole electromagnetic systems, types EW-1 and JWQ-3, are accurately defined here. Additionally, frequency reduction and boundary smoothing of linked profiles are discussed. In research on groundwater prospecting in Tanggongta, Inner-Mongolia, we used the above mentioned method and obtained the tomograms of linked profiles with good consistency. The absorption coefficient in the tomogram are not only reasonable and reliable, but also coincided with the result from rock parameter measurement. The depth, extension direction and water-bearing structure of two aquifers were well detected. This result correctly guides hydrologic drilling there.

To wire-bond automatically, the IC lead positions on the CAD drawing and the corresponding ones on the extracted substrate image should be pre-verified. This paper proposed an AOI approach for IC lead index auto-verification which conquered the lead shape distortion, golden exposed, shifting, rotation, and scaling difficulties of extracted substrate image. Experimentations revealed that the proposed AOI approach can accurately verify the corresponding leads between a CAD drawing and the extracted substrate image with high repeatability.

A huge quantity of solid wastes produced by Wenchuan earthquake has brought us a great challenge to dispose and also aroused people's great attentions to search for a rational and effective method to deal with such mass wastes, as well as the recycled aggregate concrete used in construction has been heated discussed worldwide. In this paper, the essentiality and feasibility of using recycled aggregate concrete in China are presented by comparing with reusing waste situations and technologies in other countries. Along with a brief overview of the engineering properties of recycled aggregates, the paper gives the summary of application of recycled concrete in present construction and specifications or codes for using these aggregates in new concrete which shows the values of environmental protection, economic benefits and social sustainable development. Meanwhile, facing with many barriers in more widespread use of recycled concrete, some suggestions have been proposed expecting better sustainable development in post-earthquake reconstruction and foreseeable future.

For better geometric parameters of Spiral Grooved Dry Gas Seals, the numerical simulation is carried out, based on the Navier-Stokes (N-S) equation, the laminar model and the SIMPLEC algorithm. Five geometric parameters are investigated emphatically, use one by one optimize method, take opening force, leakage, gas film stiffness and the ratio of stiffness and leakage as the assessing target. Finally, the optimized parameters are gained, and a comparison between original and optimized parameters is put forward. The result shows, when h less than 4μm, the value of K and K/Q have a considerable relative increment, especially when h less than 2μm, the increment preponderate over 13% and increasing vividly, this will improve seal performance evidently, higher stable is gain.

Blades are one of the vital components and most difficulty in manufacturing of large hydro turbines. In order to cost-effectively and productively manufacture these kinds of blades, hydro turbine manufacturers have been trying to machine these large blades using 5-axis CNC machining techniques in recent year. To implement 5axis simultaneous CNC machining for large blades, a series of computer-aided techniques in manufacturing of these blades have been developed. This paper presents the major computer-aided techniques that we have been developed in manufacturing of large hydro turbine blades, which include that Geometrical design of hydro turbine blades for manufacturing, Computer-aided location and the machined error evaluation by means of 3dimensional digitized measuring, tool path generation strategy to meet requirements of enhancing machining efficiency and controlling deviation in NC machining, tool path generation and NC machining simulation by establishing a virtual NC machining environment for blades; A reasonable and feasible strategy and the systematic scheme for manufacturing for large blades by using 5-axis simultaneous CNC machining are also purposed. The developed computer-aided techniques have been successfully applied in manufacturing of both the large Kaplan and Francis hydraulic turbine blades, it shows that higher efficiency and the better surfaces finish accuracy can be achieved in machining of large blades with the right combination of these techniques.

An iterative solution method has been developed for calculating flows in two-dimensional centrifugal pump impellers. The method was formed by combining an integral calculation method for a three-dimensional boundary layer on the whole channel wall with a surface singularity method for a two-dimensional inviscid core-flow. In the inviscid analysis, the blade shape and the area of flow passage were modified by calculated displacement thickness of boundary layer, and then a finite number of vortices were distributed on the modified blade surfaces with the Kutta condition at the outlet edge on the suction surface. This method was applied to flows in two impellers with different blade thicknesses. Comparing the results of calculated and measured flows, both were qualitatively in good agreement, including an effect of the outlet blade surface with constant radius, which showed that relative velocity near the pressure surface was faster than one near the suction surface.

Pump performance depends on the outlet flow of the impeller. A method of surface singularities for core flow in the centrifugal impeller, combined with an integral method for a boundary layer, would explain the mechanism of the performance change with cutting the outlet edge of the impeller blades down. This method is applied to flows in the impellers with various cut downs of the blade edge, and then the calculated results are compared with the experimental ones. Both results are shown to be in quantitatively good agreement. On the influence of cutting the blade edge on the outlet flow, it is indicated that the cut of the pressure surface results in the decrease of relative flow angles with the decrease of radial velocity in the core flow, while that of the suction surface results in only decrease of the radial velocity. The change of the flow separation region due to the cut on the suction surface, however, combines to cause the pump performance to deteriorate.