A multifunctional ribonuclease A-conjugated carbon dot cluster nanosystem for synchronous cancer imaging and therapy

Carbon dots exhibit great potential in applications such as molecular imaging and in vivo molecular tracking. However, how to enhance fluorescence intensity of carbon dots has become a great challenge. Herein, we report for the first time a new strategy to synthesize fluorescent carbon dots (C-dots) with high quantum yields by using ribonuclease A (RNase A) as a biomolecular templating agent under microwave irradiation. The synthesized RNase A-conjugated carbon dots (RNase A@C-dots) exhibited quantum yields of 24.20%. The fluorescent color of the RNase A@C-dots can easily be adjusted by varying the microwave reaction time and microwave power. Moreover, the emission wavelength and intensity of RNase A@C-dots displayed a marked excitation wavelength-dependent character. As the excitation wavelength alters from 300 to 500 nm, the photoluminescence (PL) peak exhibits gradually redshifts from 450 to 550 nm, and the intensity reaches its maximum at an excitation wavelength of 380 nm. Its Stokes shift is about 80 nm. Notably, the PL intensity is gradually decreasing as the pH increases, almost linearly dependent, and it reaches the maximum at a pH = 2 condition; the emission peaks also show clearly a redshift, which may be caused by the high activity and perfective dispersion of RNase A in a lower pH solution. In high pH solution, RNase A tends to form RNase A warped carbon dot nanoclusters. Cell imaging confirmed that the RNase A@C-dots could enter into the cytoplasm through cell endocytosis. 3D confocal imaging and transmission electron microscopy observation confirmed partial RNase A@C-dots located inside the nucleus. MTT and real-time cell electronic sensing (RT-CES) analysis showed that the RNase A@C-dots could effectively inhibit the growth of MGC-803 cells. Intra-tumor injection test of RNase A@C-dots showed that RNase A@C-dots could be used for imaging in vivo gastric cancer cells. In conclusion, the as-prepared RNase A@C-dots are suitable for simultaneous therapy and in vivo fluorescence imaging of nude mice loaded with gastric cancer or other tumors.     

Heat transfer of bio-oil in a direct contact heat exchanger during condensation

Rapid quenching of volatiles in fast pyrolysis is important for achieving high yield and quality of the bio-oil product, but few studies have examined the condensation of volatiles and their related heat exchangers. Accordingly, we have studied the condensation characteristics of volatiles by varying heat transfer conditions in a direct contact heat exchanger. As the mass flow rate ratio of quenching oil to pyrolysis gas increased, the heat transfer rate and yield of bio-oil increased. The heat transfer rate and yield of bio-oil reached a maximum value at an intermediate air-to-quenching oil mass flow rate ratio. Additionally, the heat transfer rate and yield of bio-oil decreased as the temperature of the quenching oil increased. Experiments were also conducted to derive an empirical relationship for the volumetric heat transfer coefficient for direct contact heat exchangers.     

Low-complexity audio CODEC for resource-scarce embedded system with fixed-point arithmetic

This work presents a low-complexity audio coder-decoder (CODEC) based on fixed-point arithmetic to save the usage of system resources in a low-end embedded system. To reduce time complexity and memory usage, a simplified discrete wavelet transform (DWT) with only integer operations is developed. The simplified DWT reduces the computation that is required for the trigonometric operations in the fixed-point system. Moreover, separating the even and odd orders of wavelet coefficients halves the computation time of the original DWT. Additionally, a tri-mode zeroes recording algorithm (TZRA) is proposed. The proposed TZRA utilizes different encoding modes with their corresponding bit data structures to record the locations of zero wavelet coefficients, and determines the optimal encoding mode that uses the fewest bits. To further improve the compression performance, a dynamic wavelet level selecting algorithm is developed to decide the wavelet level for compressing each of frame. This algorithm can dynamically select the optimal wavelet level with the fewest bits by using the determined mode from the TZRA. The experimental results herein reveal that the encoder in the proposed CODEC can multiply computation by factors of 164 and 112 and reduce the size of the execution file by approximately 95.61 and 98.42% relative to baseline audio compression CODECs. Such results indicate that the efficiency when used in real consumer products with fixed-point arithmetic.     

Accurate buckling load calculations of a thick orthotropic sandwich panel

This paper is concerned with the buckling of thick sandwich panels with orthotropic elastic face sheets bonded to a linear elastic orthotropic core. When such panels are analyzed for axial load carrying capacity, it is now commonplace to adopt the finite element method to carry out computations. The accuracy of the numerical results will depend not only on roundoff and algorithmic errors, but additionally on the approximations made in computing the incremental (second order) work associated in computing the change of configuration from the unbuckled to the buckled state. Here we show that, particularly for orthotropic thick sandwich structures, large errors can be incurred in computing buckling loads with available commercial software, unless the proper work conjugate measures of stress and strain with their stress-dependent tangential moduli are used in the buckling formulation.     

A rapid method for simultaneous determination of triterpenoid saponins in Pulsatilla turczaninovii using microwave-assisted extraction and high performance liquid chromatography–tandem mass spectrometry

In the present study, a microwave-assisted extraction (MAE) and high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method was developed for the simultaneous determination of seven triterpenoid saponins in Pulsatilla turczaninovii. Operational conditions of MAE were optimized using a central composite design. Multiple-reaction monitoring was employed for quantification while switching the electrospray ion source polarity between positive and negative modes. Full validation of the method was carried out (linearity, precision, accuracy, limit of detection and limit of quantification). The results indicated that the method was rapid, specific and reliable. The developed method was successfully applied to determine the investigated compounds in nine batches of P. turczaninovii. These samples were collected in different seasons from the Liaoning province and varied greatly. The total triterpenoid saponins content was the highest in April, the seedling stage, and decreased from May to August. The contents of total triterpenoid saponins decreased significantly after the blooming period.     

Functionalized silicon quantum dots by N-vinylcarbazole: synthesis and spectroscopic properties

Silicon quantum dots (Si QDs) attract increasing interest nowadays due to their excellent optical and electronic properties. However, only a few optoelectronic organic molecules were reported as ligands of colloidal Si QDs. In this report, N-vinylcarbazole - a material widely used in the optoelectronics industry - was used for the modification of Si QDs as ligands. This hybrid nanomaterial exhibits different spectroscopic properties from either free ligands or Si QDs alone. Possible mechanisms were discussed. This type of new functional Si QDs may find application potentials in bioimaging, photovoltaic, or optoelectronic devices.